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An Overview of Wideband Immittance Measurements Techniques and Terminology: You Say Absorbance, I Say Reflectance
Rosowski, John J.1; Stenfelt, Stefan2; Lilly, David3
Ear and Hearing: July 2013 - Volume 34 - Issue - p 9s–16s
doi: 10.1097/AUD.0b013e31829d5a14
This article reviews the relationships among different acoustic measurements of the mobility of the tympanic membrane, including impedance, admittance, reflectance, and absorbance, which the authors group under the rubric of immittance measures. Each of these quantities is defined and related to the others. The relationship is most easily grasped in terms of a straight rigid ear canal of uniform area terminated by a uniform middle ear immittance placed perpendicular to the long axis of the ear canal. Complications due to variations from this geometry are discussed. Different methods for measuring these quantities are described, and the assumptions inherent within each method are made explicit. The benefits of wideband measurements of these quantities are described, as are the benefits and limitations of different components of immittance and reflectance/absorbance. While power reflectance (the square of the magnitude of pressure reflectance) is relatively invariant along the length of the ear canal, it has the disadvantage that it ignores phase information that may be useful in assessing the presence of acoustic leaks in ear-canal measurements and identifying other potential error sources. A combination of reflectance and impedance magnitude and angle give a more complete description of the middle ear from measurements in the ear canal.
1Department of Otology and Laryngology, Harvard Medical School and Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary Boston, Massachusetts, USA; 2Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden; and 3National Center for Rehabilitative Auditory Research, Portland Veterans Affairs Medical Center, Portland, Oregon, USA.
ACKNOWLEDGMENTS: The authors declare no conflict of interest.
Address for correspondence: John J. Rosowski, Eaton-Peabody Laboratory, 243 Charles Street, Boston, MA 02114, USA. E-mail: john_rosowski@meei.harvard.edu
Received January 21, 2013
THE DEFINITION OF ACOUSTIC IMPEDANCE AND ADMITTANCE
WAVES IN TUBES
ACOUSTIC REFLECTANCE AND ABSORBANCE
MEASUREMENTS IN EAR CANALS
WIDEBAND MEASUREMENTS
COMPLICATIONS IN THE MEASUREMENT OF IMMITTANCE/REFLECTANCE
Variations in Canal Cross-Section
Nonuniformities in the Sound Field Within a Given Cross-Sec...
Variation in the Rigidity of the Ear-Canal Walls
The Effect of Viscosity
Power Reflectance ℜ(f) Versus Pressure Reflectance R(f,x)
APPENDIX A: DETERMINATION OF THE SOURCE CHARACTERISTICS APP...
Multiple acoustic techniques and devices have been used to measure the average motion of the tympanic membrane (TM) in response to sound, where the basic task is to figure out what is the relationship between sound pressure as a function of time, p(t), and the rate of alternating volume displacement, u(t), (usually called the volume velocity) of the TM (Fig. 1). If the stimulus is a sinusoid of frequency f, that is, p(t) = P cos(2πft + θP), with an amplitude P and a phase argument θP (which specifies the value of the cosine function when time equals 0), and the sound intensity is within the range where themiddle ear is linear (sound levels less than 120 dB SPL, (Guinan & Peake 1967; Goode et al. 1994; Dalhoff et al. 2007), then the volume velocity at the TM is also a sinusoid at the stimulus frequency u(t) = U(f) cos(2πft + θU(f)), with a frequency-dependent magnitude U(f) and a phase θU(f)*. From these relationships we can define a frequency-dependent acoustic impedance Z(f), where Z is a complex number with a magnitude equal to the ratio of the magnitudes of the pressure and volume velocity at each stimulus frequency, |Z(f)| = P/U(f), and a phase angle ∠Z(f) that equals the difference between the phases of p(t) and u(t), that is, ∠Z(f) = θP − θU(f). (Note that while the sound pressure and volume velocity vary with time, the magnitude and phase angle of the impedance do not. All symbols are summarized and defined in Appendix B.)
Alternatively, we can use measurements of u(t) and p(t) to define an acoustic admittance Y(f), where the admittance magnitude |Y(f)|, is the ratio of U(f)/P, and its phase angle is the phase of the volume velocity relative to the phase of the sound pressure, that is, ∠Y(f) = θU(f) − θP. In terms of complex numbers †Z(f) = 1/Y(f). The simple relationship between Z(f) and Y(f) makes them effectively interchangeable; a fact that leads to the use of the term immittance to describe Z(f) and Y(f) collectively. The two quantities have different but related units. The Système International unit of acoustic impedance is the acoustic ohm: one acoustic ohm = 1 Pa-s-m−3. The unit of acoustic admittance is the acoustic siemen: one acoustic siemen = 1 m3-s−1-Pa−1. The pascal (Pa) is the Système International unit of pressure, where 1 Pa = 1 kg-m−1-s−2.
The techniques used to measure immittance in the ear canal are tabulated in Table 1, and include: (a) the combination of sound pressure measurements with the volume velocity output from a well-characterized sound source (determination of the equivalent source characteristics—as described in Appendix A—is required because it is difficult to measure directly volume velocity), (b) acoustic bridges that estimate Z(f) or Y(f) from direct comparisons of the sound pressures produced in unknown acoustic immittance and known acoustic immittances, (c) wave tubes that quantify the variation in sound pressure magnitude and phase angle along the length of a uniform tube coupled to a structure of unknown Z(f) or Y(f), and (d) wave tube methods that use sound pressure measurements along the length of the ear canal. Methods (1), and (2) are direct measurements of acoustic immittance determined from the measurement of sound pressure produced by a volume velocity source. Methods (3) and (4) actually measure acoustic reflectance within tubes and ear canals from which the immittance at the termination of the tube can be calculated.
A long narrow rigid-walled tube of constant cross-section S acts like a one-dimensional acoustic device. The sound pressure varies along the long axis of the tube (the x axis) in the form of forward (p+) and backward (p−) traveling waves:
, where
, and
ω = 2πf, and k = ω/c.Figure 2 schematizes the presence of a forward and a backward wave traveling in a rigid tube of uniform cross-section. The tube is terminated on the right-hand side with an unknown acoustic immittance. The forward wave is initiated by a sound source on the left-hand side. The backward wave is initiated by reflection of the foward wave at the tube's terminal end.
When discussing acoustic reflectance, we need to distinguish between pressure reflectance and power or energy reflectance. Lets start with the more basic quantity. Acoustic pressure reflectance R(f, x) compares the complex sound pressure (magnitude and phase) in a sinusoidal wave that propagates toward a terminal boundary (the incident or forward wave) within the tube with the sound pressure of the reflected (backward traveling) wave that originates at the tubes terminal boundary. More specifically, R(f, x) is the ratio of the complex amplitude of the reflected and incident waves with a magnitude |R(f, x)| equal to the ratio of the magnitudes of the reflected and incident pressures wave and an angle ∠R(f, x) (which varies with distance from the source of the reflection) equal to the difference in phase angle between the reflected and incident waves at the measurement location. In terms of the description of the forward and backward waves of Eq. (1), the magnitude of the pressure reflection coefficient is:
and the phase of the pressure reflection coefficient is:
Reflectance is most easily understood and determined in a well-controlled system such as a wave tube (e.g., Fig. 2). A wave tube is a long cylindrical tube of constant (uniform) cross-sectional area with rigid walls. A sound source is placed at one end of the long tube, and an object with unknown immittance is used to terminate the other end of the tube. The tube construction includes some mechanism enabling measurements of sound pressure at varied x locations along the length of the tube, where the sound pressure at any x equals the sum of the forward going "incident" pressure wave and the backward "reflected" wave at the measurement location [Eq. (1)]. The relative magnitude of the backward and forward going waves depends on the magnitude of the acoustic immittance that terminates the tube. The relative phase angle of the two waves at position x depends on the phase angle of the waves at the termination and the distance between the measurement location and the termination. If the measurement tube walls are rigid, the tube is of uniform or slowly (variations in cross-section that are much smaller than a wavelength) and regularly (the derivative of the area with x is continuous and of a single sign) varying cross-section, and effects of the viscosity of air are small (a reasonable assumption for many circumstances), then |R(f,x)| is constant throughout the tube, and the phase angle of the reflectance ∠R(f,x) varies regularly with position along the tube [Eq. (2)]. Local maxima in sound pressure occur at positions in the tube where the phase angles of the incident and reflected waves are equal. Local minima occur at positions where the two waves are 180° out-of-phase. The ratio of the magnitude of the pressures at the local maxima and minima can be used to define the magnitude of the pressure reflectance |R(f,x)| within the tube produced by the termination, and the location of the minima together with the speed of sound and the frequency of the tonal signal defines the phase angle of the pressure reflectance ∠R(f,0) at the termination (Kinsler et al. 1982; Stinson et al. 1982).
The pressure reflectance at the termination (at position x = 0 in Fig. 2) can be quantified in terms of the acoustic impedance of the termination ZT(f) = Z(f, 0) and the characteristic impedance of the air-filled measurement tube Z0, where Z0 depends on the density of air ρ0, the speed of sound in air c, and the cross-sectional area of the tube S (Z0= ρ0c/S), such that:
You can also determine the pressure reflectance in the tube at any distance x away from the termination by comparing the impedance measured at that distance with Z0 based on the cross-sectional area at location x.:
At the terminal boundary, when the magnitude of ZT(f) is much larger than Z0, R(f, 0) is approximately 1, that is, the reflected pressure magnitude approximates the incident pressure magnitude, and the phase of the incident and reflected waves at the terminal boundary are nearly equal. When the magnitude of ZT(f) is much smaller than Z0, R(f, 0) is approximately −1, and the reflected pressure magnitude also approximates the incident pressure magnitude, but the phases of the incident and reflected waves are opposite (i.e., they differ by 180°). When the magnitude of ZT(f) equals Z0, the magnitude of the reflected wave is zero and R(f, 0) = 0. As noted in Eq. (2a), for a rigid-walled air-filled tube of uniform or slowly and regularly varying cross-section, the magnitude of the pressure reflectance along the tube is constant and equals the magnitude of the pressure reflectance at the termination where x = 0, that is, |R(f, x)|= |R(f, 0)|. The angle of the pressure reflectance measured along the tube equals the angle of the reflectance at the termination plus a factor related to the round trip travel time of the pressure wave between the measurement point and the termination [Eq. (2b)], that is, ∠R(f, x) = ∠R(f,0) +4π x/λ, where λ is the wavelength of sound at the stimulus frequency f and is equal to c/f. We can also express the right-hand term on the right side of the equation (4π x /λ) in terms of wave number (2kx) [e.g., Eq. (2b)].
The power reflectance ℜ describes the ratio of the power or energy in the reflected wave to the power or energy in the incident wave. Power reflectance (sometimes called energy reflectance) equals the square of the magnitude of the pressure reflectance: ℜ(f) =|R(f)|2. Note that the power reflectance is a real number and contains no phase information. Again, within an air-filled rigid tube of uniform or regularly varying cross-section, the terminating acoustic impedance and the tube's cross-sectional area at the termination determine the power reflectance. This reflectance is constant along the tubes length, as long as losses are negligible.
While reflectance quantifies the amount of sound pressure or power reflected from the termination of the wave tube, absorbance defines the sound power that is absorbed by the termination. The absorbance is A(f) = 1 − ℜ(f). In some cases, it is useful to quantify the absorbance as a decibel value‡ where the absorbance level in decibels is 10 log10(A). This quantity has also been called transmittance (Allen et al. 2005).
Modern techniques of estimating impedance and reflectance use measurements of sound pressure at a point x in the ear canal along with a completely characterized sound source to compute the impedance at the point of measured pressure Z(f, x). If power reflectance at the TM is the desired final measurement, Eq. (4) is used along with an estimate of the cross-sectional area of the ear canal at the measurement point (necessary to define Z0 at that point) to calculate the pressure reflectance R(f, x) at the measurement point and the power reflectance at the TM is assumed to equal the square of the magnitude of the pressure reflectance ℜ(f) =|R(f,x)|2. The accuracy of the measured ℜ(f), therefore, depends on the accuracy of the estimate of reflectance at the measurement point and the approximations that (1) the viscosity of air is negligible and (2) that the ear canal is a rigid-walled tube of constant or slowly and regularly varying cross-section. Figure 3 illustrates some schematic representations of the human ear canal that demonstrate that the ear canal is only approximated by a uniform tube, and that the assumption of a slowly and regularly varying cross-section is not accurate everywhere within the canal: near the eardrum termination, the cross-section of the canal doubles within a significant fraction (>10%) of the wavelength of a moderate- to high-frequency sound; and half-way down the length of the canal, there is a local minimum in the cross-sectional area (Farmer-Fedor & Rabbitt 2002).
One major advantage of using the reflectance is that as long as the approximations of slow, regular variations in cross-section and low-viscosity hold, the power reflectance at the point of measurement in the ear canal is a good approximation of the power reflectance at the TM. This is not the case with measurements of immittance in the ear canal, where the immittance magnitude and angle varies regularly with position in the canal. This variation occurs because the immittance measured at any point in the ear canal is influenced not only by the immittance at the TM (the middle ear input immittance) but also by the immittance of the air space between the TM and the measurement point (Moller 1960; Zwislocki 1962; Rabinowitz 1981). At frequencies where the length of the remaining canal lEC is less than a 10th of the sound wavelength, the air space in the canal acts like an acoustic compliance in parallel with the immittance of the TM such that
; with
where the average cross-sectional area of the ear canal is S, lEC × S is the volume of the residual ear-canal space, and 1.4 × 105 Pa is the compressibility of air at one atmosphere of static pressure and 20°C. The parallel arrangement of the compliance and the TM immittance makes it convenient to use admittances in the calculation of Eq. (5). At frequencies where the length of the remaining canal is more than 0.1 λ, more complicated and less certain descriptions of the effect of the immittance of the intervening canal (Rabinowitz 1981; Lynch et al. 1994; Huang et al. 2000) can be used to estimate ZTM from the impedance measured at a location in the ear canal Z(f, lEC). Some of these techniques rely on measurements of the phase of the pressure reflectance to help determine the length of the canal between the measurement location and the TM (Keefe 2007; Voss et al. 2012).
One of the benefits of modern signal generation and averaging techniques is the ability to quickly measure the acoustic response of tubes and ears over a wide frequency range. These techniques rely on the use of wideband stimuli that are the sum of many sinusoidal waves of varied frequencies. Averaging the sound pressures produced by such wideband stimuli allows a fairly rapid computation of the immittance or reflectance over a wide frequency range (e.g., 0.2 to 6 kHz) with a relatively fine frequency resolution (e.g., a point every 100 Hz). The combination of fine resolution and wide bandwidth produces a more detailed look at the immittance and reflectance. Later articles in this volume will demonstrate that (1) finer frequency resolution can help detect variations in reflectance due to ossicular interruption and superior canal dehiscence (Nakajima et al. this issue, pp. 48S–53S) and (2) that the reflectance in the higher frequency range (1 to 4 kHz) can be a useful indicator of the presence of fluid-related conductive hearing loss in infants (Prieve et al. this issue, pp. 54S–59S).
The wideband immittance and reflectance at the TM can be readily and accurately estimated from measurements made in a rigid ear canal of uniform cross-section. However, the ear-canal cross-section is not uniform along its length; the canal geometry (Fig. 3) includes local constrictions and expansions as well as bends and curves, and significant tapering of the canal near the TM (Johansen 1975; DiMaio & Tonndorf 1978; Stinson & Lawton 1989). Local constrictions and expansions in area are particularly critical for the generation of nonuniformities in the sound field (Farmer-Fedor & Rabbitt 2002). The significance of these deviations from uniformity increases with stimulus frequency.
One reflectance measurement technique that is less affected by the variations in canal cross-section along its length is based on finely spaced measurements of sound pressure within the ear canal (Stinson et al. 1982; Stinson 1990; Farmer-Fedor & Rabbitt 2002). Such reflectance estimates for the human TM can be readily calculated at frequencies as high as 20 kHz, and the fine spatial deviations in sound pressure observed in such studies are the best evidence for the significance of variations in canal cross-section.
Nonuniformities in the Sound Field Within a Given Cross-Section
The impedance and reflectance techniques that depend on the measurement of the sound pressure at a single point in the ear canal also assume that the pressure measured at that point describes the sound pressure throughout the canal cross-section (Fig. 2). This "uniform plane wave" assumption is common in describing sound flow in tubes, but it can break down in the presence of spatial variations in tubal cross-sections. Sudden or irregular variations in ear-canal area actually generate nonuniformities in sound pressure across a canal cross-section (Farmer-Fedor & Rabbitt 2002). Such nonuniform pressure waves generally only propagate short distances in the ear canal before dying out (this is true in the adult human ear canal at sound frequencies less than about 20 kHz), but they can be large enough to affect measurements at a single point. It is the effect of such nonuniformities on single-point sound pressure measurements within the ear canal that are the likely root of uncertainties in the reflectance and immittance at frequencies above 5 to 6 kHz in adult human ear canals (Farmer-Fedor & Rabbitt 2002).
The walls of the adult human ear canal are not perfectly rigid. This is especially true of the cartilage and other soft tissues that compose the walls of the outer half of the ear canal. However, for the most part, the deviations from rigidity are small compared with the compliance of the air in the canal and can be ignored. The same cannot be said for newborn and infant ear canals in which the deviations from wall rigidity are even larger. Indeed, the increased compliance of the newborn and infant ear canal is known to play a significant role in tympanometric measurements where the compliance of the ear-canal walls can add to the measured compliance in both the static and pressurized conditions. Tympanometry depends on the response to both acoustic and static pressures, and the utility of such measurements in the infant and newborn population has been questioned (Holte et al. 1991; Prieve et al. this issue, pp. 54S–59S; Hunter et al. this issue, pp. 36S–42S). While the tissues of the canal wall are less stiff in infants and newborns, as sound frequency increases, it is the density of these tissues that determines the degree of their rigidity, and the effect of density increases as sound frequency increases. Experimental results suggest that at 1000 Hz and higher, the walls of the infant and newborn ear canals are significantly more rigid than the air in the canal. Acoustic measurements made at these higher frequencies are less affected by the ear canal and better reflect the acoustics and mechanics of the TM and middle ear (Prieve et al. this issue, pp. 54S–59S; Hunter et al. this issue, pp. 36S–42S).
The viscosity of air is small and generally negligible; however, there are circumstances in which it can play a small role in measurements of immittance and reflectance. An area where its effect is minor is in the estimation of reflectance magnitude at the TM from measurements made in the ear canal. While viscous interactions between the air in the ear canal and the stationary walls of the canal will cause sound power to be absorbed as sound travels between the reflector and the measurement location, over dimensions relevant to measurements in humans, the losses involved are small (Huang et al. 2000; Voss et al. 2008; Keefe et al. 2010).
An area where the effect of viscosity is also small but more significant is in the calibration procedure used to describe the acoustic source in the first immittance measurement technique listed in Table 1. That method (Appendix A) uses measurements of sound pressure at the entrance of well-defined acoustic loads to characterize the output pressure and impedance of the sound source. The loads used are tubes of varied length. The fitting procedure used in the calculation works better if viscous looses (which are most significant at the resonant and antiresonant frequencies of the tube impedances) and "heat" losses (which are most significant at frequencies below 100 Hz) are included in the description of the calibration loads (Lynch et al. 1994).
Descriptions of the power reflectance at the TM based on ear-canal measurements, by themselves, have advantages and disadvantages. The primary advantage of power reflectance (and the closely related absorbance A(f)) is that both are relatively independent of the measurement position within the ear canal, and they provide a simple frequency-dependent measure of the power transfer at the TM. A significant disadvantage is that power reflectance and absorbance depend only on the magnitude of the pressure reflectance and ignore significant information in the phase angle of the pressure reflectance and terminating immittance. Eqs. (2), (3), and (4) document that the terminating impedance of the ear canal ZT(f) and the associated pressure reflectance R(f,x) can be calculated from each other if one knows the diameter and the length of the intervening ear canal. However, the loss of the pressure reflectance phase information in the transformation to power reflectance makes it impossible to derive ZT(f) from ℜ(f) or A(f). This loss of information can be significant. For example, attempts to determine whether a low-power reflectance reading at low frequencies results from a leak of sound pressure out of the ear canal are greatly aided by inspection of the immittance phase (Voss et al. this issue, pp. 60S–64S; Huang et al. 2000; Voss et al. 2008; Keefe et al. 2010).
This article details the close theoretical relationship between acoustic immittance (impedance or admittance) and pressure and power reflectance. The relationship is strongest in cases of pressure reflectance at the termination of a uniform rigid ear-canal tube; the pressure reflectance in the canal depends only on the immittance at the TM, the canal cross-sectional area, and the distance between the TM and the measurements location within the canal. The power reflectance is simpler and only depends on the immittance at the TM and the cross-sectional area. This simplicity comes at a cost in that the power reflectance, by itself, does not completely describe the mechanics and acoustics at the TM.
A major advantage of power reflectance, or pressure reflectance magnitude, is that these measures are relatively independent of position within a canal with slowly and regularly varying cross-section. However, the pressure reflectance phase angle and the magnitude and angle of the immittance measured in the canal vary significantly at different locations within the ear canal. Indeed, measurements of immittance within the ear canal include effects of the canal space between the measurement location and the TM. The effect of this space on the measured immittance can be removed at frequencies where the space is small compared with a wavelength; such compensation is easiest and most accurate when the ear canal acts like a rigid uniform tube. Nonuniformities in the cross-section of the ear canal and other complications in ear-canal geometry can generate nonuniform sound pressure variations in the ear canal that complicate the measurement of reflectance and impedance with sound frequencies above 4 to 5 kHz when the single-point techniques is used. Reflectance and impedance estimated from measurements at multiple locations in the ear canal are less affected by such nonuniformities.
The ear-canal sound pressure, by itself, is not a sufficient descriptor of the sound drive to the ear canal and middle ear. A more complete description includes a measurement of sound volume velocity, where knowledge of both volume velocity and sound pressure is needed to define the acoustic immittance and calculate reflectance. To estimate the immittance and reflectance of the middle ear, from a measurement at a single location in the ear canal, the sound delivery system needs to be completely defined. A common characterization is to describe the source by its Norton or Thévenin equivalent circuit (Rabinowitz 1981; Allen 1986; Keefe et al. 1992; Lynch et al. 1994). The measurement of the sound pressure magnitude and angle (PL) at the entrance to the acoustic load (ZL) is illustrated in Figure A1 along with a Thévenin equivalent description of the sound source.
Fig. A1
The source is described by an ideal sound pressure generator (PS) in series with a source impedance (ZS), which is in series with ZL. The impedances are complex and of the form Z = a + jb, where j is the imaginary number
. The volume velocity output from the source is the ratio of the pressure difference and the source impedance: (PS − PL) / ZS. The relation between PS and PL is also described by Eq. (A1):
Measurements of PL in two different loads (ZA and ZB) allow the calculation of the two equivalent circuit descriptors for the source (PS and ZS) (e.g., Rabinowitz 1981). Specifically, ZS can be directly estimated from the pressures measured at the entrance of the two loads (A and B):
and PS can then be determined from Eq. (A1) (Lynch et al. 1994).
The most common method to determine the equivalent source pressure and source impedance is by measurements in closed tubes of different lengths. The impedance at the entrance of a lossless tube with a closed ending is given in Eq. (A3).
Again, ρ0 is the density of the air, c is the speed of sound, S is the cross-section area, f the frequency, l is the length of the tube, and j is the imaginary number (Stevens 1998). The tubes are of a hard and smooth material consistent with the lossless approximation, and the cross-sectional area is chosen to be similar to the ear-canal cross-section area. We show the lossless equation for simplicity, the lossy versions are well described in the literature (e.g., Egolf 1977). The inclusion of losses becomes important at very low frequencies (∠100 Hz), where heat losses can be significant, and at the frequencies near the peaks and valleys in the cotangent function, where viscous losses dominate the impedance.
Examples of the calculated lossless impedance at the entrance of three tubes of different lengths (15, 25, and 40 mm) and a diameter of 8 mm are illustrated in Figure A2A; note the sudden and sharp phase transitions that occur at the frequencies with extremely sharp variations in magnitude. The calculated lossy impedances in the same three tubes are illustrated in Figure A2B; note the more rounded phase transitions and magnitude maxima and minima.
The parameters PS and ZS are often determined by measurements in more than two tubes, resulting in an overdetermined system. One way to estimate the source components in an overdetermined equation system is by using a least-squares approach. If the number of tubes for the determination of the source generator and source impedance is n, there are n measurements of PL. If Eq. (A1) is written in matrix form, the equation for the n measurements is
where A is the column array containing n rows of the product of the measured pressure in each load and the load impedance, B is the two-column array of n rows of the load impedance and −1 times the measured pressure, and C is a two-element column array with the elements PS and ZS. The estimated least-square values for the source,
is then
where B−1 is the inverse of B and BT is the transpose of the matrix B.
APPENDIX A: DETERMINATION OF THE SOURCE CHARACTERISTICS APPENDIX B: LIST OF SYMBOLS
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Stinson M. R., Shaw E. A., Lawton B. W.. Estimation of acoustical energy reflectance at the eardrum from measurements of pressure distribution in the human ear canal. J Acoust Soc Am. (1982);72:766–773
Tröger J.. Die Schallaufnahme durch die aüssere Ohr. Phys Zeits. (1930);31:26–47
Voss S. E., Horton N. J., Woodbury R. R., et al. Sources of variability in reflectance measurements on normal cadaver ears. Ear Hear. (2008);29:651–665
Voss S. E., Merchant G. R., Horton N. J.. Effects of middle-ear disorders on power reflectance measured in cadaveric ear canals. Ear Hear. (2012);33:195–208
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* The frequency dependence of the volume velocity magnitude and phase angle results from the interaction of the controlled stimulus sound pressure and the mechanics and acoustics of the system that is opposing the sound pressure.
Complex numbers can be written as numbers that contain a real and an imaginary component or a magnitude and phase (polar coordinates). For example, if A= a+jb, where we use the electrical engineering convention that j =
, then the magnitude of the complex number is calculated via the Pythagorean theorem
, and the phase angle is the inverse tangent of the imaginary part of the complex number over the real part
. The mathematics of complex numbers are reviewed by Keefe and Feeney (2009). In this article, bold–italic symbols are used to represent complex values that have both a magnitude and an angle. Matrix symbols are bold.
‡ Absorbance is a measure of sound power and, therefore, we multiply the log10 of the absorbance by 10, not 20, to compute absorbance level.
© 2013 by Lippincott Williams & Wilkins
THE DEFINITION OF ACOUSTIC IMPEDANCE AND ADMITTAN...
COMPLICATIONS IN THE MEASUREMENT OF IMMITTANCE/RE...
Nonuniformities in the Sound Field Within a Given...
Power Reflectance ℜ(f) Versus Pressure Reflectanc...
APPENDIX A: DETERMINATION OF THE SOURCE CHARACTER...
Ear and Hearing34:9s-16s, July 2013.
Articles in PubMed by John J. Rosowski
Articles in Google Scholar by John J. Rosowski
Other articles in this journal by John J. Rosowski
Wideband Acoustic Immittance Measurements of the Middle Ear: Introduction and Some Historical Antecedents
Wideband Acoustic Immittance Normative Data: Ethnicity, Gender, Aging, and Instrumentation
Wideband Acoustic Immittance Measures: Developmental Characteristics (0 to 12 Months)
Wideband Acoustic Immittance: Tympanometric Measures
Pediatric Applications of Wideband Acoustic Immittance Measures


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Research Wish List
African Wildcat Breeding & Release Program
Previously listed as endangered, the African Wildcat has recently been "down listed" to species "unknown", simply because little information exists on these animals, particularly in a savannah system. The greatest threat to these cats is loss of habitat and hybridisation with domestic cats. As a result, it is feared that few "pure" Wildcats remain in the wild. As the true African Wildcat resembles the domestic cat, the only accurate method of distinguishing the two is by DNA testing. The primary objective of this project was to release the offspring of DNA tested African Wildcat breeding pairs back into their natural environment where they could breed with those cats already on the reserve, thereby enhancing the genetic variability. To date, 10 offspring have been successfully reintroduced into the Greater Makalali Private Game Reserve. Makalali aims to engage in a long-term monitoring program to acquire data on the ranging, foraging and reproductive behaviour of these animals in a savannah environment.
Predicting Grazer Distribution
PREDICTING GRAZER DISTRIBUTION WITH GRASS QUALITY AND QUANTITY PARAMETERS
Maarten van Strien, MSc
Wageningen University, The Netherlands
Predicting species distribution is an important part of ecology. There are numerous factors influencing the distribution of herbivores in an ecosystem. The distribution of food resources within an ecosystem is an important explanatory factor for herbivore distribution. Hence, the distribution of grass quality and quantity parameters (GQQPs) could explain grazer distribution. The goal of this study is to (i) explore the possibility of predicting grazer distribution with grass quality and quantity parameters, making use of new statistical modeling techniques, (ii) explore which parameters have most influence on grazer distribution in the wet and the dry season and (iii) create resource maps for grazer species for practical purposes. The study area is the Greater Makalali Private Game Reserve (GMPGR), South Africa. Maps of GQQPs (grass species abundance, herbaceous biomass, grass species richness and herbaceous coverage) are created by relating field measurements with Landsat ETM+ bands and variables derived from a digital elevation model using Generalized Additive Modeling (GAM). The accuracy of the GQQP maps was not very high, which could be caused by the date the Landsat ETM+ image was taken. The GAM method proved to be a flexible and empirical method. In 2005 and 2006 sighting locations of grazers were recorded throughout the GMPGR. The maps of the GQQPs are used to predict zebra (Equus burchelli) and wildebeest (Connochaetes taurinus) distribution in the wet and the dry season making use of Ecological Niche Factor Analysis (ENFA).
By applying a quantile reclassification to the values of the GQQP maps, so that the GQQP values have a uniform distribution, the grazer distribution was reliably predicted for the wet season. Predicting grazer distribution in the dry season wasn't successful, which could be because other factors than the GQQPs determine the distribution in the dry season, or be a result of the sampling method of the grazer locations, or be caused by a possible change in the values of the GQQPs in the dry season. From the results of the ENFA, 'resource maps' were calculated that mapped the habitat suitability for the grazers. One of the findings is that the only factors positively influencing the distribution of both zebra and wildebeest in the wet season, is a high abundance of Urochloa mossambicensis and in lesser extent a high herbaceous biomass. All other GQQPs had a negative influence on grazer distribution, which could be because the environment a certain grass species grows in is of more influence on grazer distribution than the grazing value of the grass species. This study describes a method that is suited to obtain grazer resource preference in a specific area, but is less suited for studying the universal resource preference of a certain grazer. For wildlife and range management this method provides detailed information on the food selection of grazers within a certain area. The method simultaneously gives insight into grazer food preference and the spatial distribution of the preferred food resources in the area.
Bird & Mammal Release Site
The Greater Makalali Private Game Reserve (GMPGR) acts as a release site for rehabilitated birds of prey. After rehabilitation, the birds are relocated and released on the Conservancy. To date, over 40 barn owls and a green pigeon have been released.
Similarly, a number of small rehabilitated mammals have been released onto the Conservancy including small spotted genets, caracal, serval and duiker. In order to give these mammals a second chance, they undergo an extensive period of rehabilitation. Thereafter, the process of integrating them back into the wild begins. In some cases, this takes months.
Once released, the small cats are monitored and all sightings are recorded religiously. To further aid in monitoring and to assess the success of reintroduction, some of the cats are fitted with telemetry collars. This allows us to follow the cats for long periods post release and to determine the animal's ranging and feeding patterns.
Another female caracal will be relocated to GMPGR by end May 2009. We require a telemetry collar to assist us with her monitoring post release. As the Trust is a non-profit organisation, it is dependent on donations to continue its work. If you would like to make a donation for a telemetry collar please contact Audrey Delsink for further details.
Invertebrate Diversity
The invertebrate diversity study encompassed an investigation into the factors influencing invertebrate diversity in the Greater Makalali Conservancy. In addition to vegetation monitoring, it serves as an alternative method for monitoring the health of the environment as the invertebrate biomass forms approximately 70% of the total faunal biomass. This type of information is generally lacking for Southern African animals, but is very important for effective biodiversity conservation. The small-scale Geographic Information System (GIS) of the GMPGR allows us to study various factors, which influence diversity and distribution. The project included the sampling for specific invertebrate groups and the mapping of distribution ranges and diversity indices of species onto a GIS model. The invertebrate study targeted millipede, centipede, scorpion and spider diversity with GMPGR. Three undescribed millipede and one centipede species was found and a new distribution record for a scorpion species was documented. The spider sampling revealed 14 potentially new species, 8 endemic and 2 new genus records for South Africa and 1 new family record for South Africa. Refer to www.ukzn.ac.za/
Ground Hornbills
Over the years, a substantial database has been compiled which illustrates the bird diversity that exists within the GMPGR. This is invaluable in the managing of endangered species e.g. Ground hornbills and Lappet-faced vultures. The monitoring has revealed that a resident group of Ground hornbills continue to forage on GMPGR, and have successfully nested and fledged two chicks in the last 3 years. Sadly, the last chick to be fledged is not present with the group in early 2009 and is presumed to have died. However, the birds have produced a healthy chick in the 2008/2009 season. The birds have used the same nest for a number of years.
One of the greatest threats these birds face in the wild is a lack of suitable nesting sites. Together with the help of Scott Ronaldson of the Endangered Wildlife Trust, a number of artificial nests have been erected within the birds ranging area to facilitate nesting. Birds are recognised as good indicator species for biodiversity monitoring and thus monitoring is essential in the long-term preservation of a healthy ecosystem.
The effects of savanna trees on grass
The effects of savanna trees on grass: possible consequences for grazing herbivores in the Greater Makalali Conservancy, South Africa
Frank A. Looringh van Beeck
The savanna biome is characterized by a dynamic balance between trees and grasses. This study was performed to give an insight into the effects of savanna trees on grass quality and quantity, and what the possible consequences are for grazing herbivores. Also a small study was performed to analyze the impact of elephants on trees. To determine the role of trees on quality and quantity of grass in subtropical savannas, grass and soil samples were taken inside and outside the canopy area of Acacia nigrescens (nitrogen-fixing) and Sclerocarya birrea (non-nitrogen-fixing) trees in three different tree densities in the Greater Makalali Conservancy, Limpopo Province, South Africa. Grass selection of blue wildebeest (Connochaetes taurinus), Burchell's zebra (Equus burchelli), warthog (Phacochoerus africanus) and impala (Aepyceros melampus) was recorded to determine whether the grass resource selection was related to the difference in grass quality. Finally, the impact of elephants (Loxodonta africana) on trees was observed to determine the indirect effects that elephants may have on the grass resource.
Soil nutrient contents, for both nitrogen and phosphorous, were higher in soil under the canopy compared to soil outside the canopy. Tree density did not significantly alter soil nutrient concentrations. The canopy seemed to increase soil nutrients in open, moderate and dense tree density areas. Trees with nitrogen fixing capabilities did not significantly change the concentration of soil nutrients. The above ground biomass was not significantly different inside the canopy compared to outside. In areas with high tree density the above ground dry grass biomass was about three times lower (103±9 g m -2 ) than in the open areas (304±35 g m -2) or in areas with moderate tree density (282±38 g m -2 ). Both the stem-to-leaf ratio and green-to-dead ratio were reduced with increasing tree density. The percentage alive grass was significant higher inside the canopy compared to outside. The tree canopy increased nitrogen and therefore the crude protein (CP) oncentrations in grass. Grass in areas with high tree density had a lower CP-content. CP-content in grass was higher around N-fixating trees. The phosphorous content in grass was reduced by increasing tree density. On the other hand, fibre content (%NDF) increased with tree density and was also lower under N-fixing trees. High nutritional grass species had a CP- and P-content of respectively 2.5 and 3.3 times higher than low nutritional grass species (range CP-content in grass species: 6.46-16.50%; P-content: 0.07-0.23%), and a lower %NDF (range: 62.9-73.9%).
The relative number of zebra observations was significantly higher in open woodland than expected. The relative grazing activity of both zebra and wildebeest seems to be higher in the open woodlands than in closed woodlands. This study showed that grass quality was higher in the areas with low tree density. This might indicate that resource selection of large grazing herbivores is influenced by grass quality, in particular by phosphorous content in grass. The impact of elephants on trees seems to be very low, 65 of the 347 recorded trees were utilized by elephants, and only 14 trees were utilized and dead. Tree utilization by elephants was mainly characterised by the breaking of main branches.
This study clearly shows that savanna trees have an effect on grass, and are therefore able to affect the resource of grazing herbivores. The most important factor is tree density, grass quality and quantity reduces with increasing tree density. This is possibly due to resource (nutrient, light and water) competition between trees and grasses which reduces the nutrient uptake and grass biomass production. The tree crown also plays a role by increasing the nitrogen availability in the soil which results in higher crude protein content in grass, and therefore a higher grass quality.
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Watch: Plane dumps fuel over school kids in during emergency landing
Planes dumps fuel on elementary school kids Photograph:( Reuters )
A mist of fuel was sprayed in two lines and has adversely affected 60 people in which most of them were students.
Elementary school kids of Park Avenue elementary school in Cudahy California were doused by an aeroplane's fuel during its emergency landing to Los Angeles International Airport (LAX) on Tuesday.
Delta flight 89 which was a Boeing 777, was en route to Shanghai and had taken off from Los Angeles Airport with 149 passengers on board.
Watch | 60 injured after flight dumped fuel on school playground
Plane was enroute emergency landing@nischitav explains pic.twitter.com/tytcXuZj9x
— WION (@WIONews) January 15, 2020
But it was turned around due to an engine issue.A mist of fuel was sprayed in two lines and has adversely affected 60 people in which most of them were students.
A video of the plane on the verge of emergency landing was shot by a 16-year-old outside his house.First response emergency units were witnessed almost immediately.
The evacuation of students and meeting their parents and caretakers at the school gate can be seen in the aerial video.According to the fire department, the firefighters needed to treat ''multiple'' children after they complained of skin and lung irritation by the fuel.
Some hit by the fuel decontaminated themselves with soap and water from the strong vapour.
According to Cudahy mayor's, Elizabeth Alcantar "during the afternoon today, a delta airlines flight dumped fuel over park avenue elementary school in the city of Cudahy as well as surrounding communities.''
''There were other 14 schools affected by this incident with our school here in the city having the biggest impact. We have been advised that 22 children and 11 adults reported minor injuries of skin irritation and have been cleared. But none were transported to the hospital," she also added.
''This afternoon at approximately 12:12 pm, your Los Angeles county fire department was dispatched to a hazardous materials incident here at park avenue elementary school. Upon the first arriving units they found 31 patients who were contacted with the jet fuel. They were all treated and released at the scene here to their parents or their guardians," said battalion chief Jason Robertson, Los Angeles county fire department.
Tulsi Gabbard sues Hillary Clinton for defamation, seeks $50 mn over 'Russian asset' comment
Auburn Police released a CCTV footage on Facebook of a ceiling thief
125 Tweets in a day — Donald Trump floods Twitter with impeachment proceedings


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Where have I been? It's been over a month since I posted. I'd wish I could say I've merely been enjoying the first springtime in Maine I've witnessed in the dozen or so years I've lived here. But, in actuality I've been working – consulting, chatting with architects and lead technologists, writing, reading, tinkering and thinking. It's the last one (thinking) combined with a period of silence that used to simultaneously intrigue and frighten my old (awesome) team at LLB. It was hard to predict the outcome of such a cycle, but it was bound to be interesting! At the moment, even I'm not sure what will transpire, so I'll refrain from wasting more space on that here (for now).
In the meantime, I want to share some information and insights I've collected over the last month. Instead of dumping everything into one post, I thought I'd start with an excerpt from the Observations from the Field: SOA report I just wrote for PSGroup.
In this excerpt, I share the "Hard Part of SOA" as identified by enterprise practitioners and lead thinkers/technologists (not marketers) at application infrastructure vendors.
The illustration I've included is one I first drew for a SOA workshop gig in 2004. I'd be curious if readers see the relationship between re-use and granularity differently.
Since real-world insights are invaluable, I invite enterprises to share their SOA tips, concerns, and stories with me. In turn, I'll share that information back to the broader community. Together, we can cut through the hype, and develop pragmatic practices for SOA success.
Enterprise architects and technical leaders consistently state the hardest part of SOA isn't the technology. Rather, the real work is in service definition, semantics, and establishing a SOA program.
Many enterprises find it difficult to determine the correct bounds (job and tasks) and granularity (collaborations) of business services. Correctness is viewed in terms of both re-use and agility. Business services should be reusable (shared) within a line of business, across lines, and in some cases, at the enterprise level. Business services should be easily changeable (replace, augment, compose) to meet business demands.
Enterprises have erred equally on creating services at too fine a grain, and too large a grain. Erring on the fine-grained side still allows for re-use, through service collaboration, but creates performance inefficiencies to perform actual work (bounds). Erring on the large-grained side creates application- or use-specific services, rather than common business services.
This illustration shows the general relationship between granularity and service re-use. As service granularity increases, the opportunity for re-use of the resulting service decreases. However, what's important to note is the reliance on collaborators when creating a large-grained service. A large-grained service, such as a process-oriented service, should be composed of multiple function and information-oriented services. The proper use of appropriately bounded (defined) collaborators is the re-use payoff.
Industry Specifications. Architects most confident in their business service definition have been able to leverage industry-specific specifications, such as the Open Travel Alliance (OTA). OTA specifications include schemas and WSDL implementation guidelines for common travel-related interactions, such as Request Rail Availability.
service definition practices from SOA technology and/or solution providers, or adopting best practices from experience, gut feel, and a wide range of published methods, including PSGroup's Service Discovery.
What's missing—and desperately needed—is a publicly available, cohesive, services definition methodology. Cohesive doesn't refer to degree of documentation. [I believe a methodology should contain the right amount of methodology to accomplish the task, no more, no less.] Rather, with the word "cohesive", I am referring to the service definition activities that span business modeling, analysis, and design. You find a service (and the need for it) during business modeling. You define and refine the service during analysis. You further refine and provision the service during design.
In such, the business definition of a service is derived independent of technology implementation—current or future. As notation and tooling are used to transition the business service definition to technical implementation, the business intent must be retained.
Since the emergence of a good methodology happens over time, from real-world experience, I encourage practitioners to share their tips and challenges publicly, and join or create practitioner-led forums to advance real-world SOA.
For humans, machines, and the combination, semantics has always been a challenge. While it is relatively easy to receive information (conversation, message, data exchange) it is not always easy to discern the sender's true meaning. For example, when the word "customer" is used, does it mean end consumer, prospect, or purchaser?
As information exchange between applications and businesses became prevalent, industry and company dialects were defined to assign common terms, syntax and meaning to information elements. Given the initial purpose (technical integration) of these terms, the definition and administration has largely been the purview of technologists (geeks). As such, many of the terms are cryptic, derived from the application and information sources, rather than a true business dialect.
With SOA, the need for semantic understanding becomes even more pronounced, because of the multitude of service interactions, and the self-describing nature of service-oriented languages for service descriptions, contracts, policies, and orchestrations.
Similar to the service definition (above), semantics must be expressed in business terms. These terms must be recognized and understood by both business and technology professionals and machines, within an enterprise, and often between enterprises.
Most architects are approaching the challenge of semantics incrementally. A first priority is to achieve a common language between human parties in the enterprise, to enable proper business service definition.
Another is to adopt a common XML dialect to enable semantic interoperability between services.
A common practice is to describe interfaces and message payloads with a common XML dialect, and leave the underlying providers (applications, data stores) in their current formats.
The adoption of industry standard dialects varies by enterprise. Some enterprises adopt industry standards such as ACORD for insurance, throughout the enterprise. Others limit the adoption to customer- and partner-facing services. A common complaint from architects is the industry dialects are overly complex. And the problem worsens as functional dialects (human resources, banking) are added to the mix.
Vendors agree. The semantics problem is very difficult to resolve. While most offer support for industry dialects in their SOA products, none have tackled the big semantic problem. Although the problem is difficult, it can't be ignored. To ease your way, be sure to define and/or adopt a common business lexicon for semantic compatibility of services, applications, events, processes, information stores, and of course, people.
The mission of an SOA program is to articulate and execute an SOA strategy that makes sense for your business. Common activities include evangelizing SOA, setting and enforcing standards (technical, methods), selecting application infrastructure and tooling, building out common (system-oriented) services, finding and conducting pilot projects, and stewarding the service catalog.
Architects, technical leaders, and business solution project leaders say the biggest challenge in developing a SOA program is balancing the natural tension of executing business projects (today, on-time, on-budget) with the need for architectural integrity.
Obviously, the simplest thing to do is give your architecture team a head start. Fund, staff, and start the SOA program three to six months ahead of the first business project that needs it. The shorter the head start, the less critical that first business project should be.
Plan and deliver your SOA environment—practices, tools, technology, and infrastructure—incrementally. Plot your plan to balance business project delivery and architecture delivery. Better to build an incremental architecture, than a bottleneck, or bypass route.
For tolerant re-use and incremental architecture, you must plan and allocate time and resources to refactor and re-release code/assets.
Trust your architect instincts. Think about the standards, technology, and products you need in a service-oriented manner, and then map options to them. Don't buy a box of SOA. Leverage tools and practices you have in place today.
nice post — i discovered you from O'Reilly Radar.
Good to see you back and posting!
This was a well thought out post…both practical and pragmatic.
(1) If you have taken the steps to adopt SOA but have a large portfolio (and therein partial bene's) and are looking to take it to the next level…what challenges do you see for architects supporting that scenario?
(2) Who owns the taxonomy for "Business Terms"? Business? Architecture? Both?
I've seen the industry standards you mention result in a lot of challenges. I think that a Canonical Message Format is very important to success in SOA/EDA.
The trick is to keep it simple – there is a sweet spot.
I posted some more details on my blog.
Good read. I was particularly interested in point number 2, semantic understanding. This begins to touch on the concept of something that my company, Xcalia, calls a "service metadata repository" (SMR). We have a product that leverages our version of an SMR to enable the truly dynamic composition of both traditional databases as well as services (web and otherwise).
Your article focuses on the identification, partitioning, and creation of services, which is obviously very important. The industry, however, is largely overlooking another issue in SOA — the consumption of services, especially when those services run the gamut from today's web services back to EJB session beans, CORBA services, and even mainframes.
tools like ours can be used to completely encapsulate a composite application from the underlying services that are used in the application's course of execution, instead being built only against the object model that comes directly from the business lexicon.
I'd like to discuss it further with you — please drop me a line if you're interested. I think it would be well worth your time.
Thanks for the stimulating reading!
(1) Canonicals by themselves won't scale SOA's if you don't have tooling to manage their complete lifecyle. Manual governance and universal consensus surrounding the definition and versioning of canonicals won't scale. All that's been done is move the reconciliations to the edge and disconnected from any sort of end-end impact analysis.
(2) EAI tooling can't do this. They are essentially point-point mapping and transform tools and don't manage the abstraction needed in a many-many architecture.
(3) The very abstraction we find in the business process (BPM's) and the transport layers (ESB's) needs to occur in the semantic tier. A sort of semantic broker without the proprietary server or single point of failure.
(4) Industry taxonomies are coming to the fore as they have grown in richness and abstraction. The consequence of this development, is however, that the models are getting more complex and hard to handle. Advanced tooling is going to be essential to govern and operationalize them.
I'm glad this post has generated a lot of interest. Here's my quick attempt to answer comments to date.
Anjan: Thanks for the feedback.
(1) This one deserves a long answer. But for now, (IMO) the short answer is "portfolio management". With the "composable architectures" (SOA, EDA, etc) it's critical that Application Portfolio owners and Project Managers think about what they are producing at the asset, deliverable (project, application) and portfolio levels. Folks need to start considering the value of the individual assets. Are those assets valuable beyond the current initiative? What is the value relative to other portfolio assets? How might that change design and implementation decisions?
Too often a project or application is a labeled "quick and dirty" and then all assets are treated that way. Same on the other side. Just because a project or application is a "strategic enterprise whatever" it doesn't mean every asset needs to be "enterprise class".
The architect will be critical to this shift… portfolio planning, rationalization, valuation, refresh/replace, and release planning. This is one of my "business-driven architecture" soapbox items. I'll clarify and augment this in a future post. Hopefully, the gist comes through.
(2) I think the business is responsible for the definition (terms, meaning), architecture is responsible for the management, and business and architecture are jointly responsible for the communication and adoption.
Mike: Thanks. Good Post. Consistent with the folks I spoke with.
Matthew: Sounds interesting. To date, the practitioners I speak with are doing "discovery" at design time, rather than run-time. I'd be interested in hearing your story.
Pano: Good to hear from you. I'll take a look at your blog.
How about the data architecture???
Personally I'm fairly comfortable with levels of granularity, defining cononical forms, and communicating domain models and symantics.
The huge unknow for me is how exactly the data architecture _really_ works.
When your business functions are represented as services (instead of monolithic applications), what happens to your data integration? Do you really have to throw out centralised databases and use EII/ data gateways to access all of your data?
IMHO the realities of volumes/ performance and transactional complexities make this a pie in the sky approach.
-throw away our traditional reporting tools (crystal/ actuate) and build reports manually, calling web services?
There is a lot of hand wavy marketing material floating around talking about how EII / data gateways are going to solve all these problems, but the detail is lacking and I find myself seriously doubting that this problem space is well understood (let alone resolved).
I've done a lot of SOA based on pub sub in the past (which I believe is vastly superior to point-to-point models). I've always had to compromise with the data architecture. In some cases the data is sourced from a service, which is elegant. In other cases (high volume or reporting), I've had to tightly couple services to a shared database schema.
In large environments, OLAP is required, but comes with a loss of agility, and high operational/ maintenance costs.


"I'd like to thank you for coming today. It has been great to spend time with you this morning.
"As the next door MP I know how much Pudsey needs a Labour MP. Someone who puts you first, not the millionaires or the city bankers, but decent hardworking people trying to do the right thing for their families. People I came into politics to serve and I know that's what motivates Jamie.
"I want to talk to you today about the choice the British people face at the next election. And how it affects social security; one of the largest areas of public spending, and something that is vital to the lives of millions of people across the U.K.
"An economy based on low paid and insecure jobs, with failing programmes and waste driving up social security spending under the Tories.
"Or Labour's long-term reforms to make work pay and get social security spending under control.
"In 2010 the Tories promised a new approach to social security. But after four years their record is one of failure and waste.
"And the costs of failing Tory policies are mounting.
"It's now clear that the fall in wages under David Cameron is record-breaking. As Ed Balls said last week, we haven't seen such a sustained decline in living standards since the 1870s.
"I think that if someone goes out and works hard, leaving home early, often doing two or three jobs they deserve a fair deal.
"The deal was that people work hard, play by the rules and do the right thing might have opportunities to buy a home, have some security and their kids would have opportunities that their parents didn't.
"But that deal seems to have been broken for too many people.
"I want to restore that deal again.
"And that fall in wages isn't only felt in people's pockets, but in the public finances. The Tories promised to get a grip on the social security budget.
"But they overshot their own plans for spending on social security this Parliament by over £13 billion.
"And their failure to tackle low pay, rising job insecurity, zero hour contracts and the cost-of-living crisis has meant millions of people are working harder for less. And as a result are relying on housing benefit and tax credits to stay afloat.
"Today we're publishing shocking new numbers which shows the cost of the Tories' failure to build an economy which works for working people.
"Analysis by the House of Commons library has found the number of working people claiming housing benefit is set to double between 2010 and 2018 costing a staggering £12.9 billion or £488 for every British household.
"The Tories seem to be content with a low wage, zero hours culture where people are working harder for less, adding billions to Britain's benefits bill. Labour is not.
"But the Tory record isn't just one of spiralling social security costs. Since 2010 the Government's record has been characterised by crisis, chaos and waste.
"And there's no bigger crisis in the Department for Work and Pensions than the Government's £12.8 billion flagship Universal Credit programme which was supposed to merge six benefits into one.
"Iain Duncan Smith promised a million people would be on Universal Credit by April 2014. But the latest figures show less than 6,000 people are claiming.
"At the current rate of progress it will take 1,222 years for Universal Credit to be rolled out across the country. That means Universal Credit will finally be rolled out in 3236.
"There is little sign that Ministers have a grip on Universal Credit. On 23rd June Iain Duncan Smith said in the House of Commons that, 'there are, at the moment, around 11,000 people making those claims on universal credit.' But three weeks later the Department for Work and Pensions published monthly claimant figures for Universal Credit which said 5,880 people were claiming the new benefit.
"And it's not just the delays with Universal Credit, it's the waste. The Government have spent a staggering £100,000 for each person who is on Universal Credit. And they have wasted over £130million on IT.
"Today I want to make a direct appeal to David Cameron and Iain Duncan Smith. Labour wants Universal Credit to work. But we won't accept more taxpayer's money being written off and wasted.
"In June I announced a Labour Government would take steps to enable us to decide if Universal Credit can be saved and to ensure the programme delivers value for money by ordering a three-month pause for a thorough review of Universal Credit and calling in the National Audit Office.
"But I don't want to wait another nine months for this to happen. Universal Credit is in crisis and needs urgent action now. If the Government acts on the proposals Labour made in June we will support them because it's the right thing for the country.
"Look at what's happened with the introduction of the new Personal Independence Payment. These are vital payments made to people who need our support – people affected by terminal illnesses, blindness, and other disabilities which we all know mean that they face extra costs in their day-to-day lives, often but not always unable to work.
"But in February 2014 the National Audit Office said the chaotic rollout of Personal Independence Payment had led to the loss of £140 million to taxpayers. And the backlog of assessments has grown so much that it will take a staggering 42 years to clear at the current rate.
"And what about the Work Programme? Tory ministers promised to 'tackle endemic worklessness'. Once again the National Audit office has had to point out the failures that Tory ministers won't admit. In a report last month they were clear that the Work Programme has underperformed, with more people returning to the Jobcentre than finding a job after two years on the programme.
"The National Audit Office also found £11 million of Work Programme funding had already been wasted and a further £25 million is at risk. It's clear that the Work Programme isn't working.
"And with every week that goes by we discover more examples of the DWP's carelessness with public money. The latest is £27 million poured down the drain on a project called My Benefits Online.
"18 months ago the DWP announced it was launching a website for people to check details about their benefits. But earlier this year the website was scrapped and the project joined the long list of failed schemes which have cost taxpayers hundreds of millions of pounds.
"So what would another five years of the Tories mean for Britain and our social security system?
"More people stuck in low paid jobs relying on housing benefit and tax credits to make ends meet racking up a huge bill for taxpayers and a huge injustice to those who aren't earning enough to live on.
"Not to mention thousands of people hit by the cruel and unfair Bedroom Tax.
"So the choice today is between a Tory economy that doesn't work for working people and adds billions to the social security bill, and a Labour Government that would take a different approach, to make work pay and to get a grip of the chaos and waste facing the DWP.
"We believe it is only by getting more people into work and creating better paid and more secure jobs, that we'll tackle the drivers of rising benefits bills and ensure the system is sustainable for the long-term while ensuing dignity fo0r those with illness, disability or caring responsibilities who can't work.
Raising the National Minimum Wage and to ensure it gets closer to average earnings in the next Parliament.
Introducing Living Wage Contracts, so that firms which sign up to paying the Living Wage at the start of the Parliament will benefit from a 12 month tax rebate of up to £1,000 for every low paid worker who gets a pay rise.
Bearing down on the culture of waste under the Tories which has cost taxpayers millions and will ensure taxpayers money is spent responsibly.
And scrapping the cruel, costly and unfair Bedroom Tax that is sending people in Pudsey and across the country to food banks.
"The social security system was created so that you paid in when in work and drew on support if you were out of work, ill or old.
"And as Ed Miliband set out in June, we want to go further to make sure our system is based on what you have paid in over time, meaning that those who have lived and worked here for years get more than those who have only recently joined the workforce.
"Rebuilding the 'something for something' principle that is at the heart of our welfare system, but that too many people feel has been eroded over time.
"So we want to change Jobseeker's Allowance so that someone who has been working for many years gets more help if they lose their job than someone who has been working for a short time or not at all.
"A step on the route to creating a benefit system that is fair and decent, and rewards those who do the right thing.
"And as I've said before, to make sure that the system is fair and seen to be fair we must clamp down on the scandal of child benefit being sent abroad. It's not right that people are able to claim child benefits for children who don't live in this country. The Government should be negotiating now to bear down on this abuse of our system and to ensure people who come to the UK come to contribute and not just to claim benefits.
"Or a Labour future with reforms to make work pay and get social security spending under control.


text:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using TMPro;

/// <summary>
/// Displays the current game info.  Takes two targets and tweens to the endTarget.
/// </summary>
public class LauncherGameInfo : Tweenable {

    public LauncherController controller;
    public TextMeshProUGUI text;

    public Vector3 endTarget;
    public Vector3 startTarget;
    public float tweenTime;

    public void Start()
    {
        endTarget = transform.localPosition;

        //Hook in the delegate so Trigger fires each time the UI is refreshed
        controller.refreshLauncherUI += Trigger;

        ResetPosition();
    }

    public void Trigger()
    {
        ResetPosition();
        CompileString();
        TweenLocalPosition(endTarget, tweenTime, false);
    }

    private void ResetPosition()
    {
        transform.localPosition = startTarget;
    }

    private void CompileString()
    {
        var info = "";
        var game = controller.GetCurrentGame();

        if (game == null)
            return;

        if (game.Author.Length > 2) info += "Developed by: " + game.Author + "\n";
        if (game.Description.Length > 4) info += game.Description + "\n";

        text.text = info;
    }
}

redpajama_set_name: RedPajamaGithub


text:
Feature film based on the multi-award winning thriller novel from the Australian "queen of psychological thrillers."
YOU'VE KILLED ME
Feature length documentary on the incredible true story of a murder that took place from a teenage charoom in the UK.
ONCE IS NEVER
A thriller/action feature film that puts some of the best Parkour and Free Runners in Sydney up against a gang of drug dealers.
Feature length documentary on our rapid acceleration towards peak population, and what can do done?
EVILDOER
Remake of a French horror film. Prisoners trying to escape discover an ancient book in the wall. Prison is now the least of their worries.
THE UNBORN
Remake of a 60's Hollywood horror film. When a retired genetic scientist hits a dog in his car one evening, he decides to try his skills once more.
DARK HORSE - FILM
DARK HORSE FILMS
© 2015 Dark Horse Films


Anyone else have a weird craving for popcorn?
I will not speak to how others must treat this murderous cult.
I have offered all the leaders I have met a chance to throw down arms and turn themselves over to the Justice of Kormyre for their crimes. They have all refused. I have no wish to waste breath or the common folk's tax coins attempting to make depraved degenerates, who play about in offal and filth while singing hymns, to see reason. I will burn them out.
I will however make the same offer of surrender and compliance to their minions. It will not be an exchange of sophistry. Once they have been deescalated and disarmed, then we can begin their penance and reeducation. I will endeavor not to repeat myself.


text:
Lautertal (Vogelsberg) è un comune tedesco di 2.611 abitanti, situato nel land dell'Assia.

Le sue tre frazioni di Engelrod, Hörgenau e Hopfmannsfeld sono attraversate dalla Lauter, un affluente del fiume Schlitz.

Altri progetti

Collegamenti esterni

Comuni del circondario del Vogelsberg

redpajama_set_name: RedPajamaWikipedia


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We'll help you take care of what's under the hood, but also what keeps you on the road: your tires. Investing in the best car or truck tires can be one of the top ways to help keep it driving smoothly for years to come. Whether you need all-season truck tires or high-performance car tires, we've got the right tire selection for your climate, budget, driving style, and vehicle type. And if your TPMS light comes on or you need flat tire repair? Just point your dash in our direction. Explore tires online or in-store and visit a Firestone Complete Auto Care near 38545 to help make sure your ride stays safe and smooth, no matter the season. We've been a leading tire provider in Bloomington Spri for years.
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From transmission work to batteries to pothole damage repair, head to a Firestone Complete Auto Care near you for your automotive service needs. We're your local car care center, tire store, and automotive shop combined into one. That's convenience! Our highly qualified technicians believe in truly complete auto care. Bring your truck or car to us for maintenance and we will strive to make your visit satisfying. Learn more below and book your auto repair or service near 38545 today.


text:
const CGFloat YOSRefreshFastAnimationDuration = 0.25;
const CGFloat YOSRefreshTopBottomHeight = 64;
const CGFloat YOSRefreshLeftRightWidth = 64;

NSString *const YOSRefreshContentOffset = @"contentOffset";
NSString *const YOSRefreshContentSize = @"contentSize";


text:
Q: nginx/sites-available issue with subdomain from a different host I have a domain on bluehost. I am trying to subdomain a flask app on Digital Ocean. Everything works great up until this point with the nginx/sites-available/webApp:
server {
listen 80;
server_name therapist.vrifyhealth.com www.therapist.vrifyhealth.com;

location / {
    include proxy_params;
    proxy_pass http://unix:/root/webApp/webApp.sock;
}
}

I have looked here and here and this fails to help because I'm trying to run a flask application. Is there a way to run a flask app with server blocks? I have my BH subdomain pointing to the IP of this droplet. Could I just deploy the site as a standalone IP? Any advice?
--I'm running through the root because my user on the site was having issues with running tensorflow--

A: Make sure that you have forward the new ip to the correct address with the subdomain appended! Then once the hosting provider completes pushing the ip to the new address, this should work!

redpajama_set_name: RedPajamaStackExchange


Volosatova K.I. , Markovskaia E.I.
This article investigates the capital structure by the example of airline companies in Russia. The relevance of the topic depends on the relationship between the decisions about the capital structure and the value of the company. The purpose of the work is to identify patterns in making decisions about the capital structure by the example of Russian air companies, as well as the analysis of these relationships in terms of classical theories. First the Russian airline market was identified, next, the study methodology was formulated. After that, the collected data were outlined, the model, which demonstrates an impact of the determinants on the financial leverage, was conducted. The choice of determinants of capital structure, which were included in the model in the empirical part of the work, was based on the conclusions of the classical theories that are presented in the work. A methodology for studying the structure of capital was formulated, a detailed description of the selected factors and proxy variables for them was presented. Hypotheses were formulated and a model was built for analysis. The model included fixed effects for companies. After an econometric analysis, the final model showed that the company's growth was a significant factor. In addition, the obtained results were compared with the provisions of classical theories and the author's hypotheses. The survey found the regularities in determining the capital structure by management. It was shown that these patterns are only partially explained by classical theories. The obtained results can be applied to make a decision about financing by start-ups.
Keywords: factor analysis of airlines, capital structure of airlines, financial leverage, trade-off theory, agency theory, pecking order theory.