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Technical papers on QUANTACHROME particle analysis techniques
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1 PARTICLE WORLD Technical papers on QUANTACHROME particle analysis techniques 1 st English issue Dear Reader, with our first English Particle World we want to inform you about newest developments in the field of Characterization of Fine and Porous Systems, but also about relevant analysis methods, results, potential problems and their solutions. We, as QUANTACHROME in Germany offer sales, service and support for four product lines of innovative analysis instruments around the world of particles. We have experience with CILAS laser granulometers for particle sizing and with QUANTACHROME analytical instruments for characterization of fine and porous particles for more than 15 years. In 1999 we started as the EUROPEAN DISTRIBUTOR for DISPERSION TECHNO- LOGY scientific instruments to determine particle size and zeta potential of concentrated liquid dispersions. Since 2005 we are distributor for FORMULACTION, the innovative company for characterization of stability of dispersions in original concentration and without the need to change the sample. FORMULACTION started in 2006 with a worldwide new principle HORUS, the analytical tool for characterization of drying processes of thin film layers. A complete PARTICLE CHARACTERI- ZATION LAB is available for your test and contract analyses! Please mark this on the fax answer sheet to get more information. As business manager in Germany as well as member of the German DIN norm group for surface and pore characterization I look forward to maintain contacts with you. Please, feel invited to visit us at www. quantachrome.de or the manufacturers of the excellent particle characterization equipments at their homepages. Especially the fax answer of this Particle World could be the starting point for further information, discussions and cooperation. Don t hesitate to contact us! Yours sincerely Dr. Dietmar Klank QUANTACHROME Application Lab for characterization of fine and porous systems: Excellent results, reliable and fast reports and professional information QUANTACHROME particle analysis technique does not only offer analysis methods and the instruments themselves but also an excellent application lab. The QUANTACHROME Particle Characterization Lab provides not only test analysis of samples to search out the adequate analysis method but also the service for contract analysis in case that your number of necessary measurements should not be substantial enough to make the use of own instruments economic. Our support is also very valuable in case that you have only single samples or if you want to see if special analysis methods and the resulting parameters respectively could be the methods to solve your applications in your lab. The QUANTACHROME Particle Characterization Lab has all instruments of four product lines around the characterization of fine and porous systems available and sends excellent reports with comments and explanations to understand the determined parameters and the methods themselves. The QUANTACHROME Particle Characterization Lab is acknowledged for particle size measurements, surface and pore characterization methods and other analyses around the particle, respectively for results according to international and/or national norms and new developed innovative methods: Particle size in liquid and dry mode with laser diffraction (ISO 13320) Particle shape Particle size in concentrated dispersions from 5 nanometers Zeta potential in concentrated dispersions BET surface area (ISO 9277 / DIN 66131) Surface and pore characterization: - Micropores (DIN 66135) - Mesopores (ISO / DIN and ISO / DIN 66134) - Macropores (ISO / DIN 66133) Chemisorption (DIN 66136) and TPD/TPR/TPO Density of solids (DIN 66137) Tap-Density of Powders (DIN 53194, ISO 3953) Open/Closed cell content of rigid foams (ISO 4590) Sorption of water vapour and other vapours (draft DIN 66138) Stability of liquid dispersions Characterization of drying processes of thin film layers The QUANTACHROME Particle Characterization Lab has the equipment and the experienced staff to take representative samples respectively to divide the samples into representative small samples and to find out and propose specific preparation and measurement conditions according to your application. We are capable to measure your single sample as exact as periodic samples or large numbers of samples in really short period. You can load the necessary sample forms directly from our Homepage and can fill the deadline according the need when you should have the results via , fax or letter. If necessary you can clarify to get results overnight or as express service respectively. For more information about all the possible measurements please use the fax answer sheet. Articles in this issue Page 2 40 years CILAS Experts in Laser Particle Size and Shape Analysis for 40 years Page 4 Surface and pore characterization by means of gas adsorption and mercury porosimetry (Part 1) Page 5 Determination of particle size and zeta potential of concentrated ceramic slurries Please read furthermore Page 1 QUANTACHROME Particle Characterization Lab, News on page 10 and 11, Fax answer sheet to copy on page 12
2 40 Years Cilas Experts in Laser Particle Size and Shape Analysis for 40 years In the last decades, the laser diffraction has persisted against more traditional measurement methods in particle sizing. Influential reasons are considerable time saving, wider measurement ranges, higher flexibility and no need to know about parameters of the material or material mixtures in the framework of the Fraunhofer approach. For the evaluation of the measurement method, the ISO can give support. Nevertheless there are again and again new challenges and questions, which have to be evaluated and solved: a wide measurement range of a laser granulometer says nothing about the sensitivity of the special measurement equipment or the quality of the dispersion unit. Very often only a practical test gives an explanation about the automation and operation of hard- and software. The micrometer range is a typical domain of many powders and dispersed systems which were developed in several branches of industry. The particle size analysis is an elemental tool to characterize powders, suspensions and emulsions. This concept is often reduced by the main measurement process which builds the primary base of measurement results. In the following the perception of particle size analysis is expanded to a wider meaning. In practice we have to estimate single measurements which were performed by ourselves or from which we only get a report. It is important to get an overview of the hole process: starting from sampling to the dispersing conditions and to the main measurement. Sampling and sample separation Not always sampling and sample separation takes place in particle size analysis. It is strongly recommended in ISO that samples has to be representative and has to be prepared with sample separation, for example with a rotary MICRORIFFLER. By means of this instrument, several samples get separated to receive representative charges of samples for particle analysis. Figure 1 shows the importance of representative sampling to the particle size results and the need of sample divider. Dispersing Conditions Any dispersing method has advantages and disadvantages. The treatment authoritatively depends on the nature of samples, the particle size range and also on analysis tasks. If samples are soluble in common liquids and no dispersing problems are expected, a dry dispersing treatment could be favourable. Different dispersing units give caution of the limited field of applications. The liquid dispersing treatment has the advantage, that several parameters can be adjusted. These are ultrasonic time and intensity, type and nature of dispersing agents and of course the nature of solvent itself. Figure 2 shows this principle for dispersing agents. Particles are agglomerated (left/right) with/without using additives, with additives and by use of ultrasonic agglomerates they are separated and stabilized to primary particles (middle). The amount of dispersing agent should be not to low and not to high in order to have a good dispersion of the product in the carrier liquid. Figure 2 Dispersing situation depending on concentration of dispersing agents. Dispersing agents are often used in water based liquid media. For several hydrophobic samples, like carbons, carbon black or pharmaceutical products a tenside is a suitable agent to disperse such samples in water. Other (hydrophilic) samples also show excellent results of measurements without using any agent. In many cases, for example in cement industry, the use of additives could be saved by using isopropyl alcohol as liquid. Also the risk of manually dispersing errors could be prevented. The following measurements were done in isopropyl alcohol by using a CILAS 1064L adapted with an alcohol recycling unit ARU (figure 3). Figure 3 Consumption of liquid is minimized to 3 % by use of A.R.U. (Alcohol Recycling Unit). The ARU is not only suitable with alcohols, but solvents of silicon oil or aqueous solutions are additive applications. Independent from the nature of solvent: thousands of single measurements by using only 40 litres of liquid are impressive for many users of CILAS laser granulometer for particle sizing. Figure 1 CILAS 1180L Particle size analysis of feldspar without sample separation (28 measurements, left) and after use of QUANTACHROME MICRORIFFLER (28 measurements, right). Measurement principle The particle size analysis of laser diffraction is based on the theories of FRAUNHOFER
3 or the MIE approach. By sending monochromatic light through the sample, particles diffract light as illustrated in figure 4. The interaction of light with a single particle results in a specific angle depending on the light spectrum. Figure 4 Principle of laser diffraction. The diffraction pattern depends on laser wavelength, particle sizes and the optical properties of the sample. The location of minima and maxima is caused by interference. Different particle diameters result in specific diffraction patterns (figure 5). Figure 5 Diffraction patterns of large (left above), smaller (left below) and the overlay of both spectra. The diffraction pattern of mono dispersed particles is known. The pattern of different particle sizes is an overlay of all single spectra. So the particle size distribution of an experimental diffraction pattern can be calculated by parts of theoretical curves. Figure 6 Optical bench of CILAS 1180 Granulometer. The patented three laser technology provides a particle size range from 0.04 to 2500 µm in one measurement. The change from liquid to dry mode takes exactly one mouseclick only! Figure 6 shows the technical conversion of CILAS Particle Size Analysers. For different measurement ranges CILAS provides several instruments with exactly that range for your needs and applications. The basic instrument CILAS 930e has one Laser (Laser 1) which gives results from 0.2 µm to 500 µm. To explore better at the sub-micrometer range the CILAS 1064 Granulometer provides a second Laser (Laser 2) in a 45 disposition. The particle size range is increased to 0.04 to 500 µm. The hole range of particle size from 0.04 to 2500 µm is realized with the patented Three Laser Technology of the CILAS The size distribution of large particles is determined by Laser 3 and a CCD camera within a digital signal processor. This arrangement enables a very short optical bench for a large measurement range without changing or moving any optical parts or further adjustments. Analyses by use of superior CILAS laser technique If the sampling is done and optimal dispersing conditions are known or tested, the main measurement takes place. We demand reproducible measurements of well dispersed primary particles. The results strongly depend on the optical system and the arrangement of dispersing unit integrated in the instrument. The design of pumps, ultrasonic and stirring unit enables air bubble free measurements, especially in the large micrometer range. CILAS offers an instrument configuration with the way of ultrasound dispersion during the measurement! In this way the particles cannot agglomerate during the measurement, this is a very useful feature for testing unknown and special suspensions, for instance in case of magnetic products! Ultrasound dispersion during the measurement works by use of up-to-date CILAS instrument version CILAS 920, CILAS 930e, CILAS 1064 and CILAS 1180 without air bubbles in case of measurements of water based suspensions. Another excellent feature of CILAS granulometers is the dispersion of particles with high density in liquid mode! In this way, users of CILAS laser diffraction instruments are able to measure not only particles with densities of 4, 7 or 10 g/cm 3, but also tungsten or gold powders with densities of 19 g/cm 3 because of the sophisticated liquid dispersion unit with both integrated, special designed ultrasonic bath and also special designed pump with stirrer system. Figure 7 Experiments with CILAS 1064L from left to right: titanium dioxide (20 repeats), limestone (20), cement (100) and silica (20). In figure 7 and 8 the particle size distributions of several different materials are displayed. Figure 7 shows also the investigation of reproducibility of several materials, each time 20 measurements of titanium dioxide, limestone and silica and 100 measurements of a cement sample. Figure 8 Experiments with CILAS 1064L from left to right: zinc oxide, graphite, lactose, milk powder. Figure 8 shows how non-mineral powders can excellently be analysed in isopropyl alcohol without any dispersing agent. From particle size distributions, specific surfaces can also be calculated. The comparison of the particle size distributions of very different powders with the geometrical surface area and with the BET surface area, measured by use of the QUANTACHROME NOVA 2200e surface area analyser, will be discussed in our next Particle World. Conclusion The laser diffraction method is the standard method for the micrometer range. The first commercial laser granulometer worldwide was produced by CILAS in 1968, a special development for building materials at that time. The laser diffraction method has been developed to the most popular and superior method for the micrometer particle size range since then. The state-of-the-art CILAS analysis instruments can characterize particle size distributions in the fine range downwards up to 0.04 µm and in the large range up to 2.5 mm with implemented additional information about particle shape. If your interest is to be prepared for dispersion of simple but also of special samples: CILAS laser diffraction analysers offer solutions as to use ultrasound during the measurement or to analyse powders with high density in liquid dispersion! While the sieving method is often used in the higher millimetre range, there are other analysis methods especially for the nanometer range. How even particle size distributions in concentrated dispersions can be analysed, you can read in article on characterization of concentrated ceramic slurries on page 7 of this issue.
4 Surface- and Pore characterization by means of gas adsorption and mercury porosimetry Mercury porosimetry for pore characterization up to 950 µm (Part 1) In this series we will discuss different aspects related to surface and pore characterization. We will describe the different measurement methods as well as the instrumental possibilities. We also explain the potential problems related to this, including the technical solutions for them. Pore analysis by means of mercury porosimetry Surfaces and pores play an important role for certain applications and materials, independent of the fact whether the pores are wanted or not wanted. Therefore, the characterization of (porous) materials is often necessary, to understand the behavior of materials or to quantify its behavior. Also for production control and in the research, for developing new materials, people need to characterize the materials. This also implies the development of new instruments. Advantage of mercury porosimetry If surface area is the important issue, and/ or related with pore characteristics of pores smaller than 0.2 µm, then gas adsorption is the method to use. For an extended pore structure analysis however, mercury porosimetry is often needed, especially when the pore diameters are in the micrometer range. The main advantage of mercury porosimetry for pore characterization is the large range of pore diameters that can be covered with the measurements. The measuring range of this method, by use of the QUANTA- CHROME POREMASTER, is between 3 nanometers up to 950 micrometers, so it will cover more than 5 decades. Washburn-Equation which gives a direct relation between pore diameter D (µm) and pressure (p). Typically one measures the amount of mercury intruded in the pores as a function of pressure, the intrusion curve. With the aid of the Washburn-Equation these data result in a function of intruded mercury volume vs. pore diameter (see figure 1). From that curve, one can calculate the pore volumes as well as the pore size distribution. An estimation of the specific surface area can be given, assuming that all pores are cylindrical or have a predefined structure. Experimental The following results are obtained using the mercury porosimeter POREMASTER 60 (QUANTACHROME) with pressures up to 4000 bar. The samples are automatically evacuated, before starting the analysis, and automatically measured. Two porous materials, alumina (granulates) and silica gel (powder), are analyzed as well as predefined mixtures of those materials. Mixtures of silica gel/alumina are analyzed, containing 33, 50 and 75 weight percent silica respectively. Additional gas adsorption measurements are performed using the AUTOSORB-1 (QUANTACHROME) as well as a particle size distribution analysis, using the laser granulometer CILAS 1064L. Interparticle voids in powders What happens when loose powders are analyzed? The interparticle voids as well as the real pore structure is being measured. Be referred to figure 1, where the intrusion curves obtained with the POREMASTER 60 are displayed. The lower intrusion curve is related to the alumina, and the upper intrusion curve is related to the pure silica gel. In between are the mixtures as mentioned above. Three intrusion steps are clearly seen (left to right): µm, µm and µm. Those steps are explainable. In this case it is an advantage to have more information about the samples. Gas adsorption for measuring BET surface area as well as characterization of smaller pores is highly recommendable. For powders, the particle size distribution can be used for interpreting the results. Compartmentation between pore volume and interparticle voids Clearly seen is an intrusion step with an increasing amount of silica gel at 100 µm, and especially at pore diameters between 40 and 20 µm. The particle size distribution of the silica powder, measured with the CILAS 1064 L, gives an average particle diameter of 90 µm, whereas still 10 % of the volume distribution is represented by particles bet- The measuring technique can be realized with the use of the POREMASTER series, manufactured by QUANTACHROME Instruments. The method is based on the fact that mercury is a non-wetting liquid, and therefore can enter the pores of materials, without changing the solid s physical characteristics nor losing its own properties. These measurements give a correlation between pressure, applied for filling the pores, and the pore diameter of the pore which is being filled. This correlation is expressed in the Figure 1 Intrusion curves of silica gel (upper curve), alumina (lower curve) and their mixtures.
5 Amount Intrusion Surface area calculated amount calculated amount silica (%) Volume (cc/g) (m 2 /g) silica (%) silica (%) (from intrusion volume) (from surface area) 100 0,045 22,43 100,0 100,0 75 0,202 91,58 75,8 76,7 50 0, ,58 50,8 50,1 33 0, ,79 33,2 31,5 0 0, ,30 0,0 0,0 Table 1 Evaluation of silica gel/alumina mixtures for pores smaller than 0.1 µm. ween 3 µm and 50 µm. This significant amount of small particles in the silica gel powders do give interparticle voids between µm, in the pure silica gel powder as well as in the mixtures. This is clearly seen in the curves shown in figure 1, where there is an intrusion between µm for all samples. The real pore filling of the silica gel starts at pores of 0.04 µm, and of the alumina at about 0.1 µm. The curves in figure 1 show those phenomena of the mixtures. For the pore analysis of powder samples, not the complete curve may be used. For calculation of the average pore size, the interparticle voids should be eliminated. The POREMASTER software opens the way to exclude a certain range. This will result in compartmentation of pore volume and/or interparticle voids. Shown in table 1 is the separate examination of the pores from the used alumina (pores below 0.01 µm). Taking the calculation models into account, it is shown that the pore volumes of the mixtures are directly an indication of the concentration of the mixtures. The calculated and measured concentrations do match very well. This is also shown in figure 2, where the plots of the pore size distributions are overlaid. With an increasing amount of alumina, the peak at the pore size distribution shifts. Figure 2 Pore size distributions of pores smaller than 0.01 µm. Figure 3 Mercury intrusion curve of silica gel. There are more difficult samples, where the interparticle voids and pore filling is not as clear as in the described example. This is especially the case where the interparticle voids and pores have an overlap, how it is seen in figure 3. The intrusion curve of silica gel shows a fraction at 1.5 µm and an amount of pores smaller than 0.3 µm. The latter one can be confirmed using an AUTOSORB gas adsorption measurement. On the other hand this is a sample with a high BET surface area, which indicates a large porous system inside the material. For the silica a particle size distribution between 2 and 20 µm was measured with the laser granulometer CILAS 1064L. For such samples, interparticle voids in the micrometer range are likely, but in the nanometer range such interparticle voids are normally not possible. After examination of the data for silica gel one can say: no significant pores below 0.3 µm, interparticle voids are above 1.5 µm, and the pore range of the silica is between µm. Summary Mercury porosimetry is extremely useful for the characterization of pores over a wide range. Powder samples are showing at low pressures the interparticle voids, and at higher pressures the pore filling is shown. Those two processes are sometimes well shown, but sometimes it is more difficult to interpret the data. In the difficult cases additional techniques are needed in order to properly explain the data. The use of the gas adsorption technique (for BET surface area and small pores characterization) as well as particle size measurements can be very useful. There are not such problems with granulate or porous pieces, e.g. from building materials. For such samples you can especially use the full pore size range of the POREMASTER up to more than 950 µm.
6 Determination of particle size and zeta potential of concentrated ceramic slurries The extensive characterization of ceramic slurries is one of the most important tasks and challenges in the ceramic industry. It is important for fields like research and development as well as quality control. The particle size distribution and the zeta potential of a ceramic slurry are of key importance in slurry characterization and in optimizing performance. The size of the particles is closely related to inhomogeneities, which in turn relate to fracture origins as well as shape distortion/cracking during drying, pyrolysis and sintering. Moreover, the zeta potential of the slurry particulates can be used as a tool for optimizing chemical dosage to achieve the desired colloid stability and size distribution. Traditional measurements of particle size and zeta potential usually involve light scattering or sedimentation techniques and therefore require extreme dilution of the ceramic slip along with other sample preparation steps. Depending on the measurement technique employed, this sample preparation might include adding surfactants, sonication, and stirring. Although the samples prepared this way may yield reproducible data, the results may be meaningless in terms of understanding the complex nature of the original ceramic slip. The sample preparation unavoidably changes both the size distribution and zeta potential of the sample, thereby distorting the very information being sought. Characterizing the concentrated sample, as is, would allow us to realistically judge the true agglomeration status of the slip and to optimize the dosage of various chemical additives in situ. In contrast, measurements of the diluted samples with traditional methods often reveal only the primary size of the raw materials since the sample preparation steps may have destroyed most of the useful information about the original slurry. spectroscopy for particle size measurements and Electroacoustic spectroscopy to measure the zeta potential of the slurry [1]. In both methods the interaction of sound with the dispersed particles provides useful information. However, the driving force and measured parameters are different in each case. Acoustic Spectroscopy for Particle Size Characterization For acoustic spectroscopy pulses of sound are applied to the test ceramic slurries. The pulses are transmitted through the sample. The acoustic part of the instrument measures the attenuation and propagation velocity of the sound over a wide range of ultrasonic frequencies. The typical frequency range is 1 to 100 MHz. A transmitter generates acoustic pulses of certain frequency and length. These ultrasound pulses pass through the concentrated slurry. The acoustic sensor measures energy losses. Simply put: sound in sound out (see figure 1). The most important part of the energy loss occurs while the ultrasound pulse propagates through the slurry and interacts with the particles and the liquid, but one part of the loss comes from the components of an instrument. However, an acoustic instrument can measure independently the losses in electro- nics and losses in transducer. In this way the colloid loss can be calculated from the total loss and can be used to calculate the particle size distribution. The rate of change in the signal level with gap (distance from transducer to the sensor), expressed in db/cm, corresponds to the attenuation due to losses in the colloid. It is convenient to normalize the attenuation by frequency. The experimental output of the acoustic sensor is the attenuation frequency spectra in db/cm/mhz. The colloid losses arise from several sources or mechanisms including the main mechanisms for the acoustic method to characterize ceramic slurries: 1. scattering, 2. viscous, 3. thermal, and 4. intrinsic loss. For dispersions with large differences between density of the particles and density of the liquid, as in the case of ceramic slurries, the viscous dissipation mainly cause the attenuation to calculate particle sizes. On the basis of the most well known acoustic theory for heterogeneous systems by Epstein and Carhart, Allegra and Hawley (ECAH theory) one can calculate the particle size distribution from an attenuation spectra. A key part of the acoustic method is a predictive theory which allows to calculate the expected attenuation for a given size distribution, taking into account all of the Ultrasound can propagate through samples that are not transparent for light, which open up many new applications. Two complementary ultrasonic techniques have been developed that allow such neat measurement of ceramic slurries, without sample preparation or dilution: Acoustic Figure 1 Block Diagram of Acoustic Spectrometer: The transmitting transducer (left) converts electrical pulsed RF signal to ultrasound and launches acoustic wave pulse into slurry. The receiving sensor (right) converts the acoustic wave that passes through the slurry back into an electrical pulse. The attenuation is measured from the decrease in the received signal with increasing gap (length L).
7 various loss mechanisms. The particle size distribution is computed by finding that particular distribution that minimizes the difference between the experimental spectrum and that predicted by theory. The fitting error between theory and experiment provides a confidence factor for the final result. One very attractive feature of this acoustic technique is that the colloid attenuation depends only on the rate of change of signal with changes in the gap and is independent of the actual magnitude of the signal. As a result, acoustic spectroscopy, unlike optical methods, is inherently very robust and not sensitive to fouling or contamination of the transducers and therefore very suitable for online production monitoring and control. Electroacoustic Spectroscopy for Zeta Potential Measurements Electroacoustic spectroscopy measures the interaction of electric and acoustic fields from which the zeta potential can be determined. It probes the interaction between acoustic and electric fields. There are two ways to do this. In the first case, the slurry is excited with pulses of ultrasound. Ultrasound induces a motion of particles relative to the liquid. The small fluid displacements produced by this sound wave causes small periodic displacements of the electrical doublelayer surrounding each charged particle. This displacement of the ionic cloud with respect to the particle surface creates a dipole moment. The sum of these dipole moments over many particles creates an electric field, which can be sensed by an antenna immersed in the slurry to record the short circuit colloid vibration current (CVI). Such an electroacoustic sensor has also two parts: a piezoelectric transducer and an electroacoustic antenna. Another design is an electroacoustic probe where the antenna is placed on the transducer. Simply put: sound in electrical signal out. In principle, one can do the reverse experiment, i.e. excite the slurry with an electric field, which then interacts with the particles to create an acoustic response. This reverse technique is often referred to as Electrokinetic Sonic Amplitude (ESA). Simply put: electrical signal in sound out. Combination of both methods for ceramic slurry characterization The measured electroacoustic spectrum for a given slurry contains information about both the particle size and zeta potential. At first blush, it would appear that the electroacoustic spectra would be very attractive for providing simultaneous measurement of both size and zeta potential. In practice, however, there are several disadvantages to using only electroacoustic data for such complex particle characterization. First, the electroacoustic spectra can only be measured for charged particles. Second, the desired particle size distribution and zeta potential information can only be deduced from this spectra for a limited range of conductivity and only if one makes some rather restrictive assumptions about the nature of the double layer surrounding the particle. Third, the uncertainties in the model and the underlying theory makes it most difficult to obtain any more detailed information than a simple lognormal approximation to the actual distribution. In contrast, the acoustic spectra for a given slurry is unaffected by either the slurry conductivity or the charge on the particles. On the down side, it is not possible to obtain zeta potential from the acoustic spectra. On the bright side, however, we can obtain size data for any conductivity, and even for uncharged particles. The acoustic spectra depend only on the size distribution and the slurry concentration. Therefore, one might reasonably expect that the particle size derived from acoustic spectroscopy to be more accurate than that obtained from the electroacoustic spectra. In practice, one finds that the most reliable and versatile measurements are obtained by incorporating results from both acoustic and electroacoustic spectra. The particle size is best derived from the acoustic spectra. This size data is valid for any conductivity, whether the particles are charged or not. The electroacoustic spectra is then used primarily for calculating the zeta potential, however, a particle size determined from this data can be used as a consistency test to see how well the actual colloid fits the assumptions of the model. This high degree of crosschecking between the two independent techniques provides a high confidence in the quality of the data. Such confidence checks are often missing in some black box instruments, which do not have the advantage of redundant sources of data. Experimental A combined acoustic and electroacoustic spectrometer DT-1200 developed by Dispersion Technology Inc. was used. The DT-1200 is a combination of the acoustic spectrometer DT-100 and the electroacoustic spectrometer DT-300 (2) and has separate sensors for measuring acoustic and electroacoustic signals. Both sensors use a pulse technique. The gap between the transmitting and receiving transducer of the DT-1200 is variable in steps from 0.15 to 20 mm and computer controlled by means of a stepping motor. The signal level at the output transducer is measured for a set of discrete frequencies and gaps. The resulting attenuation spectra are used by the DT-software to calculate the particle size distribution over a range from to 1000 micrometers. The acoustic sensor also measures the sound speed at one chosen frequency. For measurement of zeta potential we used the DT-1200 design of the electroacoustic sensor where the antenna is placed on the transducer. This zetaprobe is very flexible to measure the zeta potential in an external experiment, online or from small samples (see figure 2). Although the normal and reverse methods appear similar, the theory for the more conventional forward CVI technique has been more extensively developed and is valid for concentrations up to 50 volume % without empirical corrections (1). Figure 2A and B, Acoustic and electroacoustic parts of the DT-1200: Acoustic transducer (left), acoustic sensor (right), zeta potential probe (in front), smaller sensors are for temperature and conductivity measurement and for titration. The zeta potential probe can be used for external experiments, like special titrations or online-monitoring.
8 In just minutes, both methods provide an accuracy and precision of a few percent. The total volume of samples required is about 100 ml, measurements of zeta potential are already possible with sample volume of 5 ml. We used the automated titration equipment of the DT-1200 to invoke changes in agglomeration as a function of ph or dispersant dosage, which allows also the ceramics manufacturer to optimize performance at minimum chemical cost and operate the process under the best conditions. A quite unique feature of the technique is the ability to determine separate particle size distributions for individual components in mixed systems such as alumina/ zirconia slurries. Although much of the experimental method is new, the overall approach is based on a well-established scientific background (1,2). Ceramic Applications Acoustic and Electroacoustic spectroscopy can be used in ceramic industry and research from the very beginning to the very end of the ceramic manufacturing process. Typical applications are quality control of raw materials, control and manipulation of grinding processes (3.4), optimizing stability and performance of ceramic slurries at minimum chemical cost, operating the process under the best conditions, characterizing of non aqueous slurries e.g. for electrophoretic deposition processes, finding the optimum of flocculant dosage in ceramic waste water treatment. Figure 3A and B Acoustic Spectra for four aluminas fit precisely with theoretical curve based on output particle size distribution (weight fraction 17 % (black and red sample) and 33 % (brown and blue sample). The measured particle size distributions for same four Sumitomo aluminas demonstrate the wide particle size range capability of acoustic spectroscopy. possibility. Examples are given in figures 3 and 4. When these measurements do not correspond with dilute measurements one needs to examine whether the chemical formulation is adequate. For some applications it is important to recognize particle size sub-populations in the final slurry. Such bimodal distributions might result from agglomeration of primary particles caused by non-optimum dispersant addition, or perhaps from intentional addition of a second size fraction. For other ceramic applications the ceramic slip is actually a mixture of more than one solid component. Traditional optical or sedimentation techniques cannot provide correct interpretation of such mixtures and typically assume that all particles have a common set of physical properties. Today acoustic method is able to solve such applications. The commercially available software for acoustic spectroscopy has evolved to the point that allows the specification of at least two classes of disperse particles. Furthermore latest developments in ceramic manufacturing like electrophoretic deposition require characterization of high concentrated non-aqueous slurries. One example is given in figure 5. It is not always appreciated that the particle size distribution of a slurry is not simply a function of the primary size of the constituent ingredients, but instead is a result of many complex chemical and mechanical operations on the system. The zeta potential of the system is one parameter that can be used to investigate this complex relationship. Acoustics and Electroacoustics provide accurate particle size and zeta potential data for ceramic slips, neat, without any dilution or sample preparation. In some cases these acoustic techniques may agree with more traditional measurements on the diluted samples, particularly when care is taken in formulating the concentrated dispersion with an optimum level of surfactant to insure good dispersion of the primary particles. However, in many real-world cases, the final dispersant dose may have been simply extrapolated from dilute measurements and one may obtain a larger particle size in the actual slurry than predicted from these dilute measurements. It is always better to characterize the particle size and zeta potential of the actual slurry. Acoustics and electroacoustics offer this Figure 4 Versatility of acoustic method and the ability to provide quality control of a wide range of raw materials is illustrated by particle size distributions for a variety of ceramic materials.
9 In the real world, the situation is sometimes even more complex. The particle size and zeta potential is not just a function of the final chemical state of the system, but may depend also on the history of how the system reached this state. In other words, the complete history of the sample may be important (figure 8). Figure 5 Particle Size distribution of a 10% alumina in Methyethylketone (MEK) used for electrophoretic depositions. Figure 6 Slurry isoelectric point suggests optimum ph for achieving stability. Poor stability normally occurs if absolute value of zeta potential is less than mv. Titration curve for alumina slurry suggests avoiding the range ph 9-10, whereas titania curve suggests avoiding the range ph 3-4. The ph at which the zeta potential goes to zero is referred to as the isoelectric ph. Different materials may have quite different isoelectric points (see figure 6). If we desire good stability, then we need to operate far enough from the isoelectric point to achieve a zeta potential in excess of perhaps mv, either plus or minus. This complex relationship between zeta potential and particle size distribution can be easily understood using acoustic spectroscopy (see figure 7). Zeta potentials far enough from the isoelectric point can be also reached by adding chemicals like ligninsulfonate (plastifisizer). Optimum dosage of these chemicals can be determined by zeta potential! Figure 7A and B Particle size distribution of slurry depends on chemical environment. Alumina slurry at ph 4 with zeta potential of +40 mv gives unimodal distribution corresponding to the primary size of raw material. Bimodal distribution results from aggregation of unstable alumina slurry at ph 9 having a zeta potential of only +5 mv. Figure 8 Case History. Slurry stability depends not only on chemical state but how one reaches this state. Laboratory titration of production silicon nitride slurry to low ph indicates high zeta potential and good stability at ph 7-8. However, process engineers found that this ph did not provide good operating performance. Actual process included an acid wash of slurry. Subsequent back-titration to alkaline conditions shows dramatic shift in isoelectric point that required shift in plant operating conditions. The explanation for this shift in isoelectric point is quite interesting. The initial slurry had a very small level of contamination, which was insignificant in terms of the overall zeta potential and stability of the system. However, under acid conditions this minor component dissolved. Upon subsequent change to more alkaline conditions, this dissolved material then re-precipitated on the surface of the bulk of the silicon nitride surface. This minor component, although present in seemingly insignificant quantity, nevertheless finally dominated the surface chemistry of the silicon nitride material. By realizing that the final state is dependent on the history of the sample the process could be modified to accommodate this change. However, it can be also appreciated to work with unstable slurries near the isoelectric point. This becomes important in the case of filtration or flocculation. In many ceramic plants it becomes more and more important to recycle the process water. Waste water treatment is usually performed by flocculation. If recycling the process water the optimum dosage of flocculants is crucial. If amount of flocculant is too low particles will remain in the water. On the other hand side overdosing leads to remaining flocculant in the process water having a devastating effect during the production process. Optimum dosage of flocculant is given by the isoelectric point and can therefore be measured by zeta potential (figure 9, next page).
10 Figure 9 Determination of optimum flocculant dosage in ceramic waste water treatment. In this example a 10% (w/w) clay slurry was titrated with flocculant Prestol from Stockhausen. The titration was performed with an automated titration equipment. Isoelectric point (IEP). is reached after adding 2 ml of this flocculant to 1 liter of the slurry. At IEP optimum flocculation is observed, as electroacoustic works excellent at high particle concentration typical for ceramic waste water. Thus flocculation can be controlled online by measuring zeta potential. Summary In summary, acoustic and electroacoustic spectroscopy offer an unique tool to characterize concentrated slurries as they turn up in ceramic production and research. These methods provide not only a means for characterizing the final aggregative state of a ceramic slip, but more significantly gives us tools to understand, optimize, and control this state. These techniques will clearly become more and more important as users understand the benefits of supplementing data on diluted samples with measurements of the final concentrated product. References 1. Dukhin, A. S., Goetz, P. J.: Ultrasound for Characterizing Colloids Particle Sizing, Zeta Potential, Rheology, Amsterdam 2002, Elsevier S. Mende, J. Schwedes, F. Stenger, W. Peukert: Mechanical production and stabilisation of submicron particles in stirred media mills, 10 th Europ. Symp. Comminution, Heidelberg, Germany, September 2002, Proc. 4. Stenger F., Peukert W.: Nanomilling The influence of suspension stability, Proc. World Congress on Particle Technology 4, Sydney, Australia, July 2002 Gas Adsorption: QUADRASORB SI with KR/MP option The QUADRASORB SI Automatic Surface Area and Pore Size Analyzer is a four sample station, bench-top, fully automated, vacuum volumetric gas sorption system. The QUADRASORB SI is a high-throughput, cost-effective system featuring four separate and independent measurement ports allowing for simultaneous analysis of four samples. New samples may be added at each port as soon as previous measurements are completed thereby providing an analytical platform for many samples or multiple users. The QUADRASORB SI is available with two versions. The standard QUADRASORB SI is excellent for determination of BET surface area, micropore and total pore volume and mesopore size distribution. QUADRASORB SI KR/MP has an additional implemented krypton option for very small specific surface areas and micropore option for more information Quadrasorb SI-KR/MP about adsorption in the lower relative pressure range! This option includes a patented oil-free turbomolecular vacuum system and a low pressure 10 Torr sensor for low surface area measurement with Krypton and low pressure adsorption data for more complete micropore characterization. QUADRASORB SI is supplied complete with QUADRAWin software for instrument control, report generation and file management, and full set of standard parts and accessories. The instrument is suitable for operation with nitrogen, argon, carbon dioxide, krypton and other non-corrosive gases for a wide range of applications. The QUADRASORB SI is configured as standard or as 21 CFR Part 11 compliant BET Surface Area and Pore Size Analyzer system according to the regulatory requirements for electronic records within the pharmaceutical industry. N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S Water Vapor Sorption: HYDROSORB 1000 The HYDROSORB 1000 is a fully automated, high speed water sorption analyzer that performs measurements of adsorption and desorption isotherms for the study of water sorption properties of solids. Accurate determination of water sorption is assured by a unique high temperature oven that maintains all critical components at elevated temperature and the use of the patented NOVA (No Void Analysis) sorption method. The standard HYDROSORB 1000 offers the analysis temperature range from 12 C to 47 C. This model is upgradeable to the HYDROSORB 1000 HT, which expands the analysis temperature range to 85 C. Controlled by a built-in microprocessor, the HYDROSORB is a self-contained instrument requiring no external PC support. Graphical and tabular data reports are generated directly by the HYDROSORB to an external printer and a RS232 port provides for download of data (in ASCII format) to other software applications (HydroWin). Built-in color graphical display and keyboard provide for convenient operation. Hydrosorb 1000 HT 10
11 Density Measurements: Ultrapycnometer 1000T The redesigned Ultrapycnometer 1000T Automated Gas Pycnometer is utilized for measurement of true volume and density of solids. The Ultrapycnometer 1000T features automatic repeat measurement mode until results fall within a user-specified tolerance or achieve a user-specified maximum number of runs. In addition, the instrument features a printer port, RS-232 port, and balance input port. Designed with the ability to be connected to an optional recirculating water bath for temperature control to enable measurements at temperatures other than ambient. The reports include density and volume results with statistics. Complete with three interchangeable sample cells (10, 50 and 135 cc) and full set of calibration spheres. Appropriate expansion volumes automatically chosen by microprocessor according to sample cell selected. One measurement cycle takes less than one minute, sample preparation is possible in user selectable continuous flow or purge mode programmable by time and number respectively. 40 years CILAS: Excellent laser technique for particle sizing and a special offer for our customers Particle size from 0.04 to 2500 µm with a CILAS laser granulometer exactly according to your application and budget: CILAS 930e CILAS 1064 CILAS 1180 (0.2 to 500 µm) with optional Particle Shape (0.04 to 500 µm) with optional Particle Shape (0.04 to 2500 µm) including Particle Shape Optional accessories as Alcohol Recycling Unit (A.R.U.), dry dispersion unit (DJD), Small Volume Cell etc. Before you choose another pycnometer: Contact us for a side-by-side test of the ULTRA- PYCNOMETER 1000T to compare the stability and accuracy during the measurements of your samples! Most modern CILAS laser granulometers of 40 years history: CILAS 930, 1064 and 1180 Please contact us e.g. with to in case of interest to use our special particle size instrument offer regarding 40 years anniversary of CILAS! Mercury Porosimetry: POREMASTER for pore size analysis with horizontal filling, cold trap and wide range up to 950 µm! The PoreMaster-60 Automated Mercury Porosimeter performs pore size distribution measurements from 950 to µm pore diameter (in standard mode and without special expensive sample cells!) by continuous or stepwise pressure generation from vacuum to 60,000 psia. There are different models of POREMASTER available, please contact us to find out the model according your application and sample throughput. The POREMASTER is the tool for determination of total pore volume, pore volume distribution, pore surface area and its distribution, pore number distribution and envelope or particle density, tortuosity, fractality and other parameters. A mercury porosimeter is not only working with mercury but also with vacuum for sample degassing and as starting point for the measurement. By use of a cold trap QUANTACHROME prevents that mercury vapor can flow to the vacuum pump! Another important feature of the POREMASTER is the horizontal filling of the sample cells to prevent a hydrostatic pressure of the mercury itself which would fill large pores already before the measurement. POREMASTER 60 GT N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S N E W S 11
12 Fax No Fax answer Please copy this page and use the copy as fax sheet to get more information. I would like to have information only in English only in German in English and German concerning the following subjects: PARTICLE WORLD Technical papers on QUANTACHROME particle analysis techniques 1st English Issue Quantachrome Rudolf-Diesel-Str. 12 D Odelzhausen phone fax Particle Size: (and Particle Shape) Pore Size: BET Surface Area Zeta Potential Sample Dividing Micrometer Range ( µm) Nanometer Range (> 5 nm) Gas Adsorption ( nm) Mercury Porosimetry ( µm ) Density Chemisorption, TPD, TPR, TPO Water vapor sorption Editorial Dr. Dietmar Klank Pictures Quantachrome Time of going to press 02. September 2006 Characterization of drying processes or formation of films Characterization of stability of liquid dispersions Particle Characterization Lab Last name, First name, Title Company Department Street Country/Zip Code/City Phone/Fax 12


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Our manuals are arranged by product type. If you have a 15 to 25 gallon sprayer from 2 or more years ago and are looking for a manual, then click on the "Old Tank Style Sprayers" expandable box. For all current sprayers, just find what type of sprayer it is, i.e. a 15 gallon spot sprayer, and click on that corresponding expandable box.
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spray gun udor hose reel *by pass hose (soft hose) agitation hose suction hose ball valve suction hose udor large area 16 mesh strainer udor diaphragm pump saver valve udor diaphragm pump basic diaphragm pump plumbing diagram for a typical lawn care pest control sprayer *by pass hoses must be open and unrestricted at all times.


So, you've decided to try your luck at "You are Meg",huh? Fair deal. Lemme explain how this whole thing works. Remember when you first saw Hercules ? Suuuure you do. This little "Game" is for all those times when you looked something that Meg did and gone, "I wouldn't have done that!" Well, now's your chance to right all of her wrongs.
You're walking through the streets of Thebes with your loving boyfriend, when a giant building starts to crumble above you. You grab your boyfriend's hand and start to run from the falling rubble, when a giant rock falls and smushes him. He's not dead yet, but he's fading fast. All of a sudden, Hades appears, "You know," He says, "I could save him, if you sell me your soul."


Today marks it- the FOURTH YEAR, to the date that I've been hanging out with this guy right here: (as in, four years ago today we had our first date, which was the first time we really ever met each other!) And I COULD NOT be more happier about it. FOUR years ago on November… Continue reading FOUR? FOUR YEARS!


The centre of Seville, with all its corners and plazas that seem to be filled with magic, will infuse your fun night with a very special charm.
You might as, "But where was this bar?", "Where did that nightclub come from?" Yes, the biggest historical centre in Spain is also full of amazing corners for your leisure and fun.
There are tablaos in Seville where you can enjoy flamenco in all its splendour. But this vital code is embedded in Seville's nocturnal DNA, so you can enjoy the party with a Flamenco soul in the secret spaces of Santa Cruz.
The Sevillian night is a good time to be filled with the soul of flamenco.
Looking for sophisticated happenings? In the Plaza Nueva area, there are elegant options with good atmospheres starting in the afternoon.
There are also different spaces where you can enjoy incredible views of the city, both day and night. Many hotel terraces have been adapted to this perfect combination of leisure and historic skyline.
And more alternative styles? In Alfalfa, we also have a multitude of small cocktail bars where you can enjoy all sorts of options: from flamenco to electronic music. The area is filled with a multitude of students from around the world who feel like enjoying the Sevillian night.
1. Seville's historic centre is the largest in Spain and the third largest in Europe.
2. If you get lost in its streets, don't worry, just ask: we love to help.
3. At night, the centre of Seville has a very special dreamlike atmosphere. Enjoy it! And pinch yourself if necessary!


text:
Home/lineup
Ken Ngo 2 weeks ago
Lightning in a Bottle Announced Special 2023 Edition Lineup
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The Lineup of Electric Zoo 3.0 is Phenomenal
Electric Zoo is this year's most evolved festival yet, as they recently announced the new 3.0 theme that shows the festival joining the…
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Love Machine Has a Stacked Lineup That Will Excite Everyone
Love Machine is a restorative musical and wellness getaway in the sun-bathed and boulder-strewn mountains of Jacumba, California. The best…
Ken Ngo July 13, 2021
CRSSD Festival Will Return to Waterfront Park in San Diego
The CRSSD Festival will make its long-awaited return to San Diego's Waterfront Park on the weekend of September 25-26, 2021.…
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Insomniac's All-Star Lineup for EDC Las Vegas 2021
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redpajama_set_name: RedPajamaCommonCrawl


Get on I-75 North take exit number 320 LaFayette/Resaca, turn (left) and go West on Hwy. 136 towards LaFayette, GA. Drive six miles until the road ends, turn right and continue on Hwy. 136, six more miles. The school and sign will be on the right.
1. From the hotel, get on I-75 going north. Get off at the next exit #335, Rocky Face. Turn left and go back under the interstate. Go approximately 3 miles and turn left onto Hwy 201. Follow Hwy 201 and 12 miles to Villanow. At the intersection in Villanow, you will see a Favorite Market on the left. Turn left onto Hwy 136. We are one mile up on the left.
Cross over I-75 and proceed up Dug Gap Mountain. At the base of Dug Gap Mountain, bear right onto Hurricane Road. Follow this road to the T junction. At the T junction, turn left. Follow this road all the way out to the major State Highway. This road is Tibbs Road and will turn into Joe Robeson Road. When you come to the State Highway 201, turn left. Follow Hwy 201 until you come to the intersection at Villanow. A Favorite Market will be on the left. Turn left onto Hwy 136. We are one mile up on the left.
From our drive turn right onto Hwy 136 and travel to the Villanow intersection. Favorite Market will be on the right. Turn right onto Highway 201. Follow Hwy 201 until it ends at the T Junction at Rocky Face. Turn right. Follow the four lane highway until you come to the I-75 South exit. Go I-75 south for one exit. Get off at the Dalton exit #333. Turn left and cross back over I-75. America's Best Inn will be on the right.
Out of the FNRC, turn right onto Hwy. 136.
Travel one mile to Villanow at the intersection of Hwy 201 at the Favorite Market.
Just past the New Beginnings Baptist Church, turn right onto Joe Robeson Road.
Stay on the main road and travel about 5 miles to Hurricane Road. Watch for a brick church on the right and Hurricane Road is on the corner. Turn right onto Hurricane Road. Follow this very curvy road a short distance until you can bear left onto Dug Gap Mountain Road. (You will have the right-of-way to bear left or go straight.) Travel up and over the mountain. At the base of the mountain you will come to the I-75 entrance. Cross over I-75 and America's Best Inns will be on the right.


Then-president Obama's Iran Nuclear Deal was widely condemned on the right and by Israeli Prime Minister Benjamin Netanyahu who referred to the deal as a "bad" and "very bad deal.
The Green Arrow appears to be losing his leading lady, with Arrow star Emily Bett Rickards announcing that she will depart the superhero drama ahead of its eighth and final season.
BERLIN (Reuters) – German Foreign Minister Heiko Maas said on Thursday that it would be better to delay Britain's departure from the European Union than to have a disorderly Brexit.
Ever since the MacGyver reboot started up in September of 2016, George Eads has been a beloved part of the show as Jack Dalton, who is the titular character's partner in the field.
It's not yet clear why White House Communications Director Bill Shine cleared out his desk and left Friday. But it is plain his departure, like his hiring, was sudden and unexpected.
After eight years of holding the Gallagher family together, Emmy Rossum announced in August she was leaving "Shameless." Her final episode, the Season 9 finale, airs on Mar.
TOKYO (Reuters) – Bank of Japan Governor Haruhiko Kuroda said on Monday the central bank would debate and communicate at an appropriate timing an exit plan from its ultra-loose monetary policy.


Public Art – Why and to Whom?
A survey in Finland shows that a large part of citizens strongly support the idea of art in public spaces. A considerable part is even willing to pay more for an apartment in a location where the percent-for-art principle has been implemented. The seminar held in Tallinn introduced the experience of public art in Estonia, Sweden and Finland.


text: COMMON MUSHROOMS OF THE UNITED STATES 415 Photograph by A. G. and B. Leeper THE GIANT PUFF-BALL (Calvatia gigantea) The best-known of all puff-balls. A single specimen will suffice for the largest family. Diameter often fourteen inches and over. As children, we have all squeezed the puff-ball to make it "puff," little realizing that in doing this we were liberating billions of spores, which-if everything went well with them would produce in turn billions of puff-balls. But there is "many a slip" in the life of a puff ball spore. Were this not so, the whole country at the proper season, would be paved with puff-balls. A recent investigator, Professor Buller, computing the number of spores in a single good-sized specimen of the giant puff-ball, found that it contained about seven trillions (7,000,000,000,000); and yet this species is by no means as common as those who know its delicious flavor would like it to be. One is inclined to ask-as we do about the fate of pins what becomes of them all? . . . The plant grows in grassy places, in August and Sep tember, sometimes in "fairy-rings." It is not very common, we regret to say. To escape acceptance of the theory of the spontaneous generation of life, it has been suggested that extraordinarily minute organisms (bacteria, for example), or their spores, propelled alive through space, might be capable of carrying life to planets. When it is con sidered that the vitality of some spores remains unimpaired after prolonged exposure to liquid air and even liquid hydrogen, the suggestion seems plausible. See also pages 392 and 402.


The specific electric motor problems experienced by Oregon State University solar vehicle team while detailing the troubleshooting process.
The Oregon State University Solar Vehicle Team (OSUSVT) is a group of students, staff, and faculty members working together to design, build, and race solar-electric vehicles. The team competes in two international races hosted by the Innovators Education Foundation to prove the viability of these vehicles.
The team's third solar vehicle, the Phoenix, uses an NGM SMC150 3-phase permanent magnet AC hub motor designed specifically for solar vehicle use. With this motor, the Phoenix can reach a top speed of 135 km/h and sustain speeds of around 56 – 72 km/h while consuming about the same power as a domestic toaster.
The motor is controlled by an NGM EVC402 motor controller. This motor controller is responsible for interpreting input from the pedals and for controlling the power output to the motor.
braking (2) and high torque demand (3).
Hall-effect sensors inside the motor are used as magnetic encoders to identify the rotor's current position.
In 2013, the team's motor developed problems with commutation and torque production. When high torque was commanded by the accelerator, the motor would have mechanical torque pulsations and highly audible vibrations. This also happened when reverse torque was demanded during regenerative braking.
A Tektronix MSO2024 oscilloscope was used to determine that the fault occurred during high motor current events when noise began to affect the Hall-effect signals used for commutation (see Fig. 1). Channels 1 – 3 measure the current in the power line of each phase.
To narrow down potential issues, the team's MSO2024 was set up to measure the Hall-effects' voltages and the motor's current. The coupling was set to DC and the attenuation of the scope was set to 10 X for voltage probes and 1 X for current. The team had two test setups, one to check behaviour under no-load and another to test the behaviour in normal driving conditions.
For the first setup, the vehicle was elevated so that the back wheel, with the motor attached, was not touching the ground as it spun. During these tests, the team looked at the Hall-effect signals, examined the motor's back EMF and checked for shorts in the stator windings.
The second setup used the scope during normal driving conditions. This setup focused on examining the behaviour of the Hall-effect signals. Auxiliary power packs were used to power the oscilloscope to eliminate a ground feedback loop that caused the noise in the initial tests (see Fig. 2).
Fig. 2: Block diagram of Hall-effect signal testing setup.
The first step was to identify situations that induce an event. During the first test setup, with the vehicle elevated, the team noticed that pushing the pedal past a certain point caused an event. However, if the pedal was depressed to just before this point, the motor would accelerate normally up to maximum speed no matter how quickly the pedal position changed.
This led the team to the conclusion that speed was not a factor, but perhaps torque was. To test this theory, the team reprogrammed the motor controller to request a flat 50% torque across all pedal compressions. At this point, the motor would work perfectly. Further experimentation with the motor controller allowed the team to determine that anything above 78% torque would cause an event.
To rule out mechanical issues, the motor was disassembled, physically examined and the bearings replaced. After this, the team tested the motor's back EMF. To do this, they detached the motor from the motor controller and connected voltage probes to the power line of each phase.
The motor was then spun manually to induce a magnetic field in the stator which, in turn, produced voltage waveforms that could be read by the oscilloscope (see Fig. 3). The resulting waveforms shown in Fig. 4 indicated that the permanent magnets were good and that this was not a mechanical issue.
Fig. 3: Typical setup used during tests checking back EMF and motor current.
Next, the team examined the motor phase currents to check for hard shorts in the stator windings. However, normal current waveforms ruled out that possibility (see Fig. 5).
With mechanical issues ruled out, the team moved on to examine the Hall-effect signals which serve as magnetic encoders for commutation. Testing under normal driving conditions showed that the Hall-effect waveforms would deform radically during motor events.
To determine whether there was an issue with the Hall-effect sensors themselves, the team examined each Hall-effect output signal as the motor was spun manually. The Hall-effect waveforms were formed perfectly even at relatively high speeds, indicating that the Hall-effect issue was a symptom, not a cause.
To gain a close-up look at the observed behaviour, the team used the oscilloscope's ability to capture data over a relatively large time interval and to zoom in to timespans of 0,2 seconds.
Comparing the waveforms while the motor was being spun manually and while the motor was being powered respectively revealed significant noise in the Hall-effect sensor output during normal operation.
Fig. 4: Normal back EMF. Probes 1 – 3 measure the voltage between each phase (V AB, V BC, and V AC).
The team prototyped a low-pass filter and placed it on the Hall-effect output to reduce the noise.
The low pass filter attenuated the excess noise which improved the motor's operation noticeably. However, the filter introduced an undesirable side-effect. The time delay caused by the charging capacitors caused the motor to behave erratically and ultimately rendered the solution ineffective.
With the promising results from the low-pass filter, it was suspected that there may be noise on the Hall-effect power input. To test this theory, decoupling capacitors were installed on each Hall-effect power line to filter the DC power signal and to attenuate the noise while avoiding issues caused by an in-series filter. Further testing showed a marked improvement with only small capacitor values, and additional parallel capacitance solved the issue entirely.
Fig. 5: Normal motor current. Probes 1 – 3 are connected to each motor phase.
The motor's problems with commutation and torque production were caused by noise on the power lines for the motor's Hall-effect sensors. This problem was clearly visible using the MSO2024 oscilloscope and the team would not have been able to solve this issue without it.
The oscilloscope allowed them to rule out mechanical failure as a source of the problem, and saved the motor from being sent in for refurbishment. By examining the Hall-effect signals, the team was able to observe what was happening inside the motor during each period of violent shuddering and narrow-in on the electromagnetic noise that was the culprit.


I'm going to be straight with you. The title of this post is not accurate.
But I'll tell you why later.
If you do it right, email marketing is the most powerful tool in your sales armoury.
Once someone has gobbled up your fantastic lead generation report in exchange for their email address, they are open to a continual warming up via email.
The sole purpose of your follow-up email marketing campaign is to reinforce the message in your lead generation report, reminding your prospect of the problem they face and building the feeling in their mind that you are the solution to that problem.
So your email marketing campaign must be absolutely spot-on. This means considering some key components very carefully. The decisions you make around these areas will be the difference between success or failure in skyrocketing your conversion rate.
The Pareto principle, otherwise known as the 80/20 rule, can be applied in many situations. In online marketing, it means that 80% of your profit will be generated by 20% of your customers.
This principle is important when considering the frequency with which you email your prospects.
The "safe" frequency often advised is three times per week. Others will recommend twice per week, still others will say just once per week.
Then there are those who say email your prospects every single day.
So what frequency should you actually be using?
Ultimately that will depend on you and the testing you do. However there is one important consideration to bear in mind which relates to the Pareto principle.
If you're trying to be safe, minimising the amount of people who unsubscribe, you could be harming your conversion rate in favour of maintaining a higher subscription rate.
Let's look at hitting them with a daily email. Yes a lot of people will unsubscribe. Not everyone will like your style or your content, nor ultimately want what you have to offer.
But by ruthlessly weeding out those who are not ever going to be committed to the sale, you leave yourself with a massively motivated list of people. This will allow you to speak directly at those people, through highly targeted language which you know stands a good chance of working, rather than using a broader brush to try and encompass everyone.
Alternatively, you could decide a long slow warm up could convert people who at the time of subscribing had no intention of buying from you.
Frequency is a big issue. Consider it carefully and test, test, test.
A subject line telling people you are running a "20% off special offer for three days only" the day they download your free report will usually turn them off. People hate being marketed to directly these days, especially hard and fast.
You need to "hook" people in. This means using a captivating statement or question, to make them click to open and read your email, then take action to learn more and build desire.
Obviously this subject line will be closely tied to the content within the email and the outcome you want from the reader.
3. Linking the theme throughout.
For an auto responder follow-up sequence, a tight topical link between each email is essential.
If your subjects bounce all over the place, people will get confused and lose their focus.
At all times look at why that person read your lead generation report. Keep in mind what they are looking for and make sure your emails weave together an ongoing theme or story, as well as making an individual point within each one.
Let's use the cheesy old example of Star Wars.
Although each film is a self-contained story, there is a larger story which runs through all of the films.
That story is about the Skywalker family and the twists and turns of the battle within it.
This is the approach you need to take with your follow-up email sequence. Look at each email as a self-contained piece, a post in your fence, but ensure there is a bigger story that is ongoing, the linked chain.
4. Length of each email.
Just like frequency of sending, this is a topic around which you will find much debate and no clear answers.
Some people will tell you long copy works, some people tell you short copy works. There is a lot of research out there however which suggests anything more than 300 words will be skimmed over.
So ultimately it's your call. But it should be your call taken solely on information you see through your subscription, read and unsubscribe rates.
Should you personalise each email? The answer has to be yes...if you can and if you feel it's important.
You see, it mostlt depends on if you have that information the first place. Ultimately, there is a trade-off between making subscription as quick as possible, against information you gather during that process.
A lot of marketing landing pages literally just ask for an email address, making it impossible to address someone by name anyway.
Consider your audience. Are they likely to supply a real name? Is getting a name more important than them thinking "long form, bye bye." and clicking away?
6. How should you structure each email?
As well as making each one a self-contained piece, with the ongoing major story running through it, you need to think about the format of each email.
There are many ways you construct your emails, but my advice would be to mix things up to keep it fresh.
For example, a question and answer email can be great. Using a popular appeal story to hook people in can work, using motivational quotes or videos is great. A provocative question or seeking answers can work.
However you structure your campaign, the aim has to be to keep people interested, engaged and increasing momentum towards a purchase.
Okay, now it's time for me to tell you why the title of this post is not accurate.
There are only six key things you must include in your follow-up email marketing campaign.
Sorry about that. But there is a seventh thing you need to consider and it's the most important.
7. Do not ever directly sell in an email.
Yes, that's right, the seventh key thing is a don't ever do.
And it really is that simple. Making blatant pitch after pitch in your emails will drive people away from you, not towards you.
You are warming people up, provoking them to make their own decision, increasing their desire to solve the problem, making them feel valued and in control.
The better you do this, the more you will sell to them, more often.
So have I missed anything? I'd love to hear about the successes and failures you had with your own email marketing campaigns, so let's talk in the comments.
If you'd like to talk to us about creating a "24/7 Marketing Machine" in your business click here now.


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Partnership continues to equip students with digital skills
We're excited to have renewed our partnership with the Digital Greenhouse in Guernsey for the second year, to deliver the Digital Innovator Programme.
The scheme, which began in 2018, provides a range of exciting opportunities for young people, enabling students to get involved in hackathons, workshops and events to develop their digital skills through hands-on learning.
John Davison, our Chief Information Officer, said: "Talented individuals are highly sought after in the technology sector and it's great to see the partnership helping develop tomorrow's technology disrupters and superstars.
"We've supported the Digital Innovator Programme since day one. We have a talented team and it's great to see them devoting time to the scheme, providing guidance and support to those eyeing up a career in technology."
Lucy Kirby, Head of Digital at the Digital Greenhouse, said: "We want young people to build digital skills that give them the brightest future. Working with First Central is key to doing that, their team is full of experts who can bring real-life examples to the subjects we're teaching."
More than 140 young people took part in the programme's debut year and it continues to have a positive impact on young people. Find out more about upcoming events for young people in Guernsey.
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text:
A man, as an ordinary guest, came to Imam 'Ali's ('a) house. He was his holiness' guest for several days, but not ordinary invited, having something in his heart that he had not divulged it at first.
As a matter of fact, this man had a dispute with someone else, waiting for the person to come in the presence of Imam 'Ali ('a) so that he can take an action against him. One day he unveiled the case and raised the petition.
'Ali ('a) asked: "Then, for the time being, you are a petitioner. Aren't you?"
The man said in reply: "Yes, O leader of the believers."
The Imam ('a) said: "I beg your pardon! From today onwards, I cannot welcome you at my home as a guest. Because the Holy Prophet (S) says: "When a complaint is lodged before a judge, the judge has no right to invite one of the two belligerents, unless both adversaries were present at invitation."1
1. Wasa'il. v. 3. p. 395.
‹ Story 100: Ibn Siyabah
Story 102: Grocer's Words ›


On behalf of the dedicated men and women of the Boulder Police Department, I welcome you to our website. I hope you find the information valuable. Our goal is to exceed our community's expectations for public service. We continually strive for excellence and always welcome your suggestions on how we might serve you better.
Community Soccer from City of Boulder on Vimeo .


Ran is teaching a three-week summer course at the New England Conservatory on the music of jazz giants Louis Armstrong and Ella Fitzgerald (see poster above). Composer/conductor and former NEC President Gunther Schuller will be the course's keynote speaker.
Music Inn, a documentary on The Lenox School of Jazz, where Ran studied and performed at the start of his career, screens twice in Massachusetts in late April.
The first showing is Monday, April 27 at 5 p.m. at Amherst College. The free screening is at Pruyne Lecture Hall in the Fayerweather Building as part of the Faultlines Series.
The second screening is Tuesday, April 28 at 6 p.m. at the Boston Public Library.The free screening is part of Jazz Week events at the library. The library is located in Copley Square at 700 Boylston St, and the film screens in BPL's Rabb Lecture Hall.
At both screenings co-producer George Schuller will introduce the film and lead a panel afterward. Ran (who also appears in the film) is on the panel at the screening at the Boston Public Library, along with Gunther Schuller, Ted Casher, and Joe Hunt.
The Lenox School of Jazz operated at the Music Inn in Lenox during summers from 1957 to 1960. Faculty and guests included Gunther Schuller, Dizzy Gillespie, Kenny Dorham, the Modern Jazz Quartet, Dave Brubeck, Bill Evans, Oscar Peterson, Willis Laurence James and Jimmy Giuffre. Ran attended all four years and looks back on it as one of the highlights of his life.
NPR's Morning Edition aired an in-depth profile of Ran on April 13. Titled "Pianist Ran Blake Takes His Cues From Film Noir," the 7-minute piece featured interviews with Ran, New York Times music critic Ben Ratliff, and several students, as well as samples from Ran's new Driftwoods album.
Andrea Shea, a reporter for NPR-affiliate WBUR in Boston, put together the segment, which does an outstanding job highlighting Ran's life and creative process, as well as capturing his personality. If you missed it, you can stream or download it here and read the text here.
If you haven't ordered your copy of Driftwoods yet, you can do so through ranblake.com, Amazon, Tompkins Square, and other retailers. You can also download it from iTunes. The album has received strong reviews from the The New York Times, The Boston Globe and many other sources. Read the February and March issues of Ran's newsletter to see some of these reviews.
A recording of Ran and vocalist Jeanne Lee from 1966 titled Free Standards that includes pop and jazz standards such as the Beatles' "A Hard Day's" Night and Duke Ellington's "Take the A Train," as well as several original compositions, has surfaced on a jazz blog.
Details on the recording are sketchy. Apparently it was made in 1966 in Stockholm at a friend of Ran's house. Ran remembers the session but isn't sure whether an album was officially released. The title doesn't show up on Amazon or other official outlets, so it's possible the album circulates a bootleg.
Fans of Ran and Jeanne's groundbreaking 1962 album, The Newest Sound Around (currently out of print) will no doubt find the recording of interest. If you're curious and internet savvy, for the moment you can check out MP3s of the recordings here.
If any readers know further details about this album or own a copy, please e-mail Ran.


text:
Heinrich "Heinz" Alef (* 31. Oktober 1897 in Impekoven; † 29. September 1966 bei Unna) war in der Zeit des Nationalsozialismus von 1933 bis 1945 Bürgermeister von Bad Godesberg.

Leben
Heinrich Alef wurde als Sohn eines Landwirts geboren, er besuchte in Impekoven die Volksschule und in Bonn das Gymnasium. Anschließend wurde er 1916 Soldat. Nach dem Kriegsende arbeitete Alef für eine Bonner Baumaterialhandlung, 1921/22 als Niederlassungsleiter in Weißenthurm. Danach machte er sich in dieser Branche sowie mit einer Versicherungsagentur und einer Steuerberatung selbständig. 1925 heiratete Alef und wurde Vater einer Tochter.

"Kampfzeit" und nationalsozialistische Diktatur

Alef trat bereits zum 1. August 1930 der NSDAP bei (Mitgliedsnummer 283.186). Er wurde zwischen 1932 und 1934 Ortsgruppenleiter in Witterschlick/Duisdorf und in Mehlem sowie Kreisamtsleiter der NSDAP für Kommunalpolitik und hatte auch einen Sitz im Kreisausschuss des Kreistages Bonn-Land.

Am 14. März 1933 wurde Alef als Nachfolger des abgesetzten Bürgermeisters Josef Zander (Zentrum) Staatskommissar für Bad Godesberg und am 21. April in Abwesenheit der Stadtvertreter von SPD und KPD zum Bürgermeister gewählt. Seine Amtsführung wurde nach dem Zweiten Weltkrieg zwar zwiespältig beurteilt – er führte aber im Ergebnis konsequent die Politik der NSDAP in Bad Godesberg aus. Eine gewisse Bürgernähe nutzte er dazu, in Einzelfällen Gefälligkeiten zu erweisen. Der Bad Godesberger Entnazifizierungsausschuss vermerkt 1949 dazu: "Nach den von Alef vorgelegten Gutachten hat er in einzelnen Fällen aus gewissen Gründen eine Ausnahme gemacht; aber die in Godesberg alteingesessenen jüdischen Familien sind alle restlos ausgerottet worden und kein Alef hat sich darum gekümmert."
Er nutzte die bekannte Vorliebe Adolf Hitlers für Bad Godesberg aus, um für sich und die Stadt Freiheiten und Vorteile zu erringen. Stets sorgte er bei Besuchen seines "Führers" für ein angemessen applaudierendes Publikum in der Stadt und sonnte sich im Glanz der Prominenz, die in der Regel im Rheinhotel Dreesen abstieg. Gelegentliche Höhenflüge wurden ihm von den übergeordneten Behörden nachsichtig verziehen.

Alef übte das Bürgermeisteramt bis zum 6. März 1945 aus, als er sich vor dem Einmarsch amerikanischer Truppen wie sein Bonner Kollege Ludwig Rickert auf das rechte Rheinufer flüchtete.

Entnazifizierung
Noch am Tag vor Inkrafttreten der bedingungslosen Kapitulation der Wehrmacht am 8. Mai 1945 wurde Alef in amerikanische Internierungshaft genommen. Nach Streitigkeiten zwischen amerikanischen und britischen Strafverfolgern über die Bewertung seiner NS-Vergangenheit und Zwischenstationen in den Lagern Kornwestheim und Dachau folgte am 9. Dezember 1947 das Verfahren vor der Spruchkammer Benefeld-Bomlitz in der Britischen Besatzungszone wegen Mitgliedschaft in der Kreisleitung der NSDAP und Kenntnis der nationalsozialistischen Verbrechen.

Alef wurde zu einem Jahr Gefängnis verurteilt, das durch die Internierung als verbüßt galt, und freigelassen. Auf die folgend von ihm eingelegte Revision hin hob der Oberste Spruchgerichtshof in Hamm 1948 das Urteil auf, der Freispruch folgte Anfang 1949. Einen Rechtsstreit mit der Stadt Bad Godesberg über seine Pensionsansprüche aus der Zeit als Bürgermeister verlor Alef letztinstanzlich 1956. Das Oberverwaltungsgericht Münster stellte dazu fest, dass er in erster Linie nicht wegen seiner Befähigung, sondern deshalb Bürgermeister wurde, weil er Nationalsozialist war.
Der ehemalige Rektor der Bad Godesberger Burgschule, Schieffer, war nach dem Krieg als Leiter des Entnazifizierungsausschusses für den Landkreis Bonn zuständig und schrieb in seinem Bericht vom 23. Oktober 1948:

Im zivilen Leben nach 1950
In den 1950er Jahren war Alef wirtschaftlich mit der Wiederverwertung alter Bahnschienen wieder erfolgreich. Politisch und in der Öffentlichkeit wurde er als Mitglied des Bundes der Heimatvertriebenen bekannt. So kandidierte er 1953 für den GB/BHE zum Deutschen Bundestag, sein Listenplatz reichte aber nicht zum Einzug in das Parlament. Später war er in der FDP im Landkreis Altena aktiv und Kreistagsmitglied in Meinerzhagen.
Heinrich Alef starb am 29. September 1966 bei einem Autounfall in der Nähe von Unna.

Quellen
 Horst-Pierre Bothien: Das braune Bonn. Personen und Ereignisse (1925–1939). Mit zwei Beiträgen von Ansgar Sebastian Klein (= Forum Geschichte. Band 5). Klartext, Essen 2005, ISBN 3-89861-419-0.
 Bonner Geschichtswerkstatt e.V. (Hrsg.) / Red. Sabine Harling, Andrea Lummert, Erhard Stang: Wie herrlich duftet es hier nach Eau de Cologne! Bad Godesberg – ein historisches Lesebuch. Bonn 2008, ISBN 978-3-9806609-3-8, auswertend und zitierend:
 Bundesarchiv Berlin: Personalakte Alef
 Bundesarchiv Koblenz: Z 42 IV 6888
 Stadtarchiv Bonn: Go PA 2736
 Archiv des Rhein-Sieg-Kreises Siegburg: Personalakte Alef
 Dietrich Jung: 8. März 1945 – Kriegsende für Bad Godesberg. In: Godesberger Heimatblätter 23, 1985, S. 13–23.
 kultur-in-bonn.de

 taz.de

Einzelnachweise

Bürgermeister (Bad Godesberg)
Politiker (Deutsches Reich, 1933–1945)
NSDAP-Mitglied
GB/BHE-Mitglied
Deutscher
Mann
Geboren 1897
Gestorben 1966

redpajama_set_name: RedPajamaWikipedia


text:
Josh Duggar Thanks Dad As Wife Anna Calls Josh 'Awesome,' But '19 Kids' Duggars Family Admits Scandal 'Mess Up' [Video]
Joanne Eglash
Josh Duggar posted a video saying thanks to his dad on Father's Day. Josh's message to Jim Bob Duggar follows weeks of silence that the oldest son of the 19 Kids And Counting Duggars family has maintained since the child molestation scandal news broke, reported the New York Daily News.
"Happy Father's Day, pops," said Josh's wife Anna, who is pregnant.
"We're so grateful for you. Happy Father's Day," added her 27-year-old husband.
In the video, Josh discussed positive memories, ranging from riding in a truck to getting the inside scoop on business.
"Then later on when we built a house together and we spent three and a half years learning about construction and all the joys and sorrows of all that," recalled Josh.
And Anna expressed her thanks.
"Thank you for raising such an awesome husband," said Josh's wife to her father-in-law Jim Bob.
In the video, Josh made no mention of the issues that have piled up since it became news that he had molested five underage girls as a teenager.
Jill Dillard and Jessa Seewald, two of the sisters who Duggar molested, spoke up in Josh's defense in an interview on Fox News with Megyn Kelly.
"He made some bad choices, but really the extent of it was mild, inappropriate touching, on fully clothed victims, most of it while girls were sleeping," said Jessa. "We've never claimed to be a perfect family."
Since the 19 Kids And Counting child molestation broke, Josh has opted out of the opportunity appear in public and speak at a Christian event, as the Inquisitr reported.
Although the ALIVE Christian Music Festival Web site indicated that both Josh and pregnant wife Anna were scheduled to make appearances. The festival's manager stated that neither Anna nor Josh will attend, which is confirmed by the official schedule.
However, both Jessa and Jill recently appeared at the the ALIVE Christian music fest in Ohio, reported Extra.
"Hey, we're not a perfect family," said Jill, echoing Jessa's words.
"We mess up. Imagine what life is like with a family with two or three kids and multiply that about 10 times over and that's what you get."
But many have asked what Josh's wife Anna Duggar knew before the scandal broke, as the Inquisitr reported.
Anna revealed that she was aware of the details two years prior to his proposal.
"I was surprised at his openness and humility and at the same time didn't know why he was sharing it. For Josh, he wanted not just me but my parents to know who he really was – even very difficult past mistakes," she revealed.
[Image Via Josh And Anna Duggar Facebook Page]
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text:
Author Daniel Handler on a series of fortunate events: marriage and writing
By Daniel Handler Oct. 9, 2019
Author Daniel Handler on a series of fortunate events:...
1of2Lisa Brown and author Daniel Handler at their wedding about 20 years ago.Photo: Courtesy Lisa Brown and Daniel Handler
2of2"Bottle Grove," by Daniel Handler.Photo: Bloomsbury Publishing
Around the time "Bottle Grove," my new novel about marriage, is being published, I'm hitting two big anniversaries: 20 years being married and 20 years publishing books. Like many landmarks, these are more or less randomly constructed — I fooled around with books and Lisa Brown for quite a few years before we made it official — but still, it feels like something.
We spent part of our honeymoon in a borrowed Paris apartment proofreading my first novel. We were living in New York City, but hoping to find some situation that would allow us to return to San Francisco, where I'd grown up and where Lisa Brown and I had nailed down our relationship. It was cheaper here, back then. I'd just landed a contract for some children's books, and Lisa Brown worked for a print magazine about the internet. Her gig was the surer bet at the time.
The novel is called "Bottle Grove" and it follows two couples through the landscapes of their marriages, watched over by a shape-shifting fox. Twenty years ago I would have told you that there weren't any foxes in San Francisco, but now I see them all the time, along with coyotes and other creatures displaced by all of the new construction in a changing San Francisco.
"Changing" is a word applied so readily to "San Francisco" nowadays that it sounds like the town changed its name: I grew up in San Francisco, but I now live in Changing San Francisco.
By Peter Hartlaub
'San Francisco is rotting' story is wrong: City is...
A day that lives in infamy: Wine comes to Candlestick Park in...
Twenty years ago, when it was just San Francisco and Lisa Brown was just my girlfriend, we didn't see any wild animals around our apartment. Probably the wildest thing in our neighborhood was a sex club called Eros. We never visited it, and it was nondescript from the outside, but there'd been some articles about it, or maybe a piece on the radio, so people always asked us about it. "We live right near it," we used to tell them. "It's near our video store."
Nowadays, though, in Changing San Francisco, everyone asks about the tech industry. The tech industry is the presumed source of all changes in Changing San Francisco, from traffic to homeless encampments, from the new businesses that are springing up to the old ones closing their doors.
My novel has the tech industry in it, if only because it would be impossible to write about San Francisco without mentioning it, the way it would be impossible to write about Paris without mentioning food, or Mumbai without mentioning colonialism, and like food or colonialism or any other knotty topic, I'm not always sure what I'm talking about. I never hear the latest news or buy the latest gadget, but, like everyone else, I'm now guided on road trips by a talking map, even to places I've been countless times. If I'm on foot and I want to go home, I can summon a stranger who will drive me there and I don't even have to talk to them. I give them all five stars, the highest rating.
Author Daniel Handler, who has published children's books under the name Lemony Snicket and whose novel 'Bottle Grove' was published in August 2019, and his wife, Lisa Brown.
Photo: Meredith Heuer
I don't have the bona fide know-how to chart the tech industry's influence, but I know it's having an effect on San Francisco, or taking a toll is maybe what I mean. We now have a culture of tech bros in my city, although "tech bro," as with "hipster" or "yuppie" before that, is a term only applied to other people.
"I hate tech bros," is something I've heard from more than one person who makes what any reasonable person would call a ton of money working for an internet site everyone uses. Twenty years ago, nobody said this, although, of course, people spouting nonsense is not a new phenomenon in San Francisco, or anywhere else.
Still, I know San Francisco is changing. An early cover of "Bottle Grove" had a photograph of the city skyline, but the image was outdated. Trouble is, the publisher told me, if they used a more recent one, with all of the new buildings that have popped up lately, people wouldn't know it was San Francisco.
I know the feeling. I look at old photographs of my wife and me and I can't believe it's us. It's not just that we're younger; it's that I can't quite grasp what it was we were doing.
We ate a lot of black beans because they were cheap, and I remember, for instance, being very busy on weekend afternoons, but we had no children or anything else to be responsible about, so I can't figure out what we were busy doing. We lived, mostly, in tiny apartments, which sometimes got on our nerves. Now we live in a house that could likely fit all of our previous apartments inside, and yet we still manage, on occasion, to drive each other bonkers.
We've been in love this entire time, Lisa Brown and me, cracking each other up through good times and bad, but when I think of a plate with nothing but black beans on it, answering questions about a sex club, I wonder if we're even the same people.
We've changed a lot, along with the city that's our home. Eros is still around; it's the video stores, of course, that are all gone. Other personal landmarks in San Francisco have vanished, too — let's pause and light a candle for Aardvark Books, Streetlight Records and Josie's Cabaret and Juice Joint — while the homeless population has grown, and, after a parade of mayors promising a parade of changes, seems tragically settled in. Many artist friends have been priced out of the city, but the alarming thing to me isn't just that artists aren't able to afford the city, but that the idea of artists affording the city seems somehow outdated. It's hard to chart the specific changes in my city, because everything is changing, and San Francisco is a part of everything.
"Bottle Grove" came from my wondering what marriages are made of, conceived at a time when a changing definition of marriage was the subject of national debate, and as I hit the age when friends started getting divorced, revealing portraits of relationships that were sometimes vastly different, or eerily identical, to my own. You marry one person, but you stay married to another; a city becomes a different city, whether you stay or leave.
After 20 years, I can't say I'm truly nostalgic for the vanished video store — it's more for a time in my life when my girlfriend and I would watch two movies, right in a row, on a Saturday afternoon. I worry about my city's affordability, and our culture's increasing disregard for the arts. I don't need to return to a time when a sex club, rather than marriage, was the institution most welcoming of my queer fellow citizens. I'm leery of the tech industry, but I want these crucial conversations to happen, across boundaries geographical and social, with the speed and ease that tech has made possible.
Sometimes people ask Lisa Brown and me how we make our marriage work, and the truth is we have no idea. We were young when we started; we changed together and here we are. I'm crazier about her now than when we wed, and I don't know what could change or overturn that, just as I don't know what could change or disappear that would truly wreck San Francisco.
An anniversary is supposed to be a time to look back, but that's not where my interest lies. I'm more excited about my new book than old work, and I'm eager to see what will happen in my city, rather than yearning for how it was. I want to stay here another 20 years at least, married to Lisa Brown, watching all this and writing it down.
Daniel Handler is the author of seven novels, including "Bottle Grove," published August 2019. Under the name Lemony Snicket, he is also the author of children's books "A Series of Unfortunate Events" and "All the Wrong Questions." Email: culture@sfchronicle.com
Fire Season