Bell Siphon Guide – Japan Aquaponics – DIY Aquaponics Guide for Bell Siphons & Loop Siphons. In the case of the bell siphon then we would add a straight piece of plumbing pipe into this bulkhead to form what is known as the standpipe. The height of the standpipe will be adjusted to determine the maximum height of the water in the growbed.
How to Make an Indoor Aquaponics System. Aquaponics is a method by which you grow plants and nurture aquatic animals together in a system that recirculates the nutrients produced, to the benefit of both plants and animals.. The bell siphon is a very effective method of slowly flooding the.
How to aquaponics indoor Update: The owner of Sherrill's Aqua Vita Farms said today the aquaponics business is running out of money. that invested its time shepherding this effort to fruition." Doherty began his indoor.How to start aquaponic seedlings Tower Design The single-face design is a result of scientific research on the effects of light depletion rates. By ensuring high reflectivity with a white, single-faced design ZipGrow towers reduce light extinction significantly and maximize yields in small spaces.
Home / Shop / Build Your System / AquaParts Plumbing Kits / AquaParts 12Bell Siphon with Media Guard AquaParts 12Bell Siphon with Media Guard An Aquaponics Bell Siphon is an elegant way to drain your grow bed in a flood and drain aquaponics system without using a timer to turn your pump on and off.
Is aquaponic grown algae safe to eat "They've put on about half a kilo in the year and that's just from being in the good sweet waters of the Clyde eating as much algae as they could. "The big oysters are Pacifics which are only grown.
Apparent (APD) and true (TPD) protein digestibility and apparent (AAAA) and true (TAAA) amino acid availability of fish meal and plant protein ingredients utilized in the South African animal feed.
Are aquaponic vegetables healthy I think you will find that an aquaponics system. with all its benefits of small space requirements, high production of healthy organic vegetables and fruits, and a reliable source of fresh fish will be a great addition to your family. A couple of the best aquaponics systems for beginners are reviewed on this website.
a bell siphon (or auto-siphon) is placed in the grow bed to automatically regulate the ebb and flow of water, So, you are ready to make your aquaponics plans. designing an effective system will require buying the essential components.
Make a Bell Siphon Step 1: Parts and Tools. Step 2: Preparing the Dome and Guard. I created a guide that you can use to make clean. Step 3: Building the Siphon. Follow the bell siphon diagram to put the siphon together. Step 4: Test the Bell Siphon. After you have your bell siphon put together.
Where to buy tilapia for aquaponics How deep should aquaponic beds be How to set up aquaponics aquarium An Aquaponics Setup for Your Aquarium: I wanted to build a cheap and easy aquaponics system to place in my existing 10 gallon aquarium. All parts were purchased from the nearest home depot except for the pump which came from Amazon.- DWC systems should optimally be around 40-50cm deep. – The deeper water, a more stable thermal mass is achieved, i.e slower to heat up/cool down. – aeration should be no more than 1m apart, for long beds, and two per bed for small beds.How much does aquaponics cost I live in a country where the sun shows it's immense power. So much power, yet that energy is consistently ignored by most people, it should be our first priority to use that power FIRST in a system purporting to be sustainable So when you speak of feeding fish at minimal cost, does time, land and electricity figure into the cost? Yes it does.


If a "game" is defined as a simulation that gives the player a goal to work toward and a "toy" as one that just gives the player stuff to tinker around with, DAN-BALL's Powder Game is definitely the latter. Specifically, one of the "sandbox" variety. I mean that literally, as it's a clear descendent of d_of_i's World of Sand browser game. What Powder Game, also playable in a browser, adds to the formula is fluid dynamics.
This sandbox contains a variety of elements which the player can scatter at a mouse-click. Ice, water, fire, the titular "powder" (which serves as the sand). The heart of Powder Game is the way these elements interact. Water that touches ice will freeze. Ice that touches fire will melt. Drop a seed onto some powder and a plant will sprout. Water the plant and it will grow. Touch a flame to it and it will catch fire and burn.
The other key element that defines Powder Game is wind. Powder stacks in neat piles, but a click of the mouse (a right click by default, but this can be changed) sends it spiralling into the air. Currents coalesce, rub against each other, create eddies in the air. Fire creates wind, as does exploding gunpowder. Wind turns ice into snow, creates rivers of particles in the air. When the background effect is set to "BG-shade," it becomes entrancing to watch.
Powder Game is not for players looking for direction. To get the most out of Powder Game, one has to be comfortable creating one's own entertainment. Players who are willing to tinker will find a lot to tinker with. Here are some things to try: create a fountain by positioning fans over a pool of water. Make a sculpture with ice and bubbles (which turn into whatever they touch). Build an arena and populate it with fighters – tiny pixel people who jump and flip around, trying to kick each other. Set the background effect to "BG-shade" and paint a curtain of SuperBalls.
Powder Game is Java-built and playable in a web browser. It's neat to tinker with, mesmerizing to watch, and totally free. Similiar and similiarly worth playing is DAN-BALL's earlier project, Liquid Webtoy – one of a surprisingly few webtoys to simulate the phenomenon of precipitation.
Subscribe to comments with RSS or TrackBack to 'Fluid Dynamics in a Particle Sandbox'.
Excellent toy, what's the music?
This game is awesome! I think that it is very similar to the Falling Sand Game (www.fallngsandgame.com), Yet this one has better physics and most of all, wind! Your game reviews get better and better as time goes on! This game deserves a flat 5!
the music is "lyhytaallosta" by circle.
This is better than garry's mod?! I never thought t could be possible.
I think that one of the main reasons that this got better than garry's mod in the votes is because it's free.
It's still a great game either way.
My personal favorite from this genre was always Burning Sand.
It doesn't have the cool wind effect and it is less physical and more "Game of Life" like. But there are more than 30 elements (plus, with a little bit of determination you can design and "program" your own particles) and it can be played offline.
A neat toy yes but by no stretch of the imagination comparable to Gmod.
Okay now its third and as usual, GMod is in first. I love this game. It is the only game I ever wanna play online.
1. It's not that hard to figure out how to make them grow.
fun motion just hired a bunch of new people. WHY HAS THE TOPIC FLOW GONE EVEN SLOWER!!!
Yeah, sorry about that–it's been a busy week. I was out for town for a few days (vacation in the mountains), we're moving to a new office space soon at work, lot of deadlines coming up, etc etc.
The real problem is I still have to prepare the Flash videos for posting. My goal is to set up a few technically-minded reviewers so they can directly post.
World of Sand has the general advantage of being easier to use than this, however.
I don't understand why this game ranks so high… Compared to the other games this feels so lack-luster. Sure it's an oddity for a few minutes of fun, but it's not really a game and it just seems completely overrated.


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Prison Memoir of a Kurdish Revolutionary
Sakine Cansiz
(with free eBook)
The second instalment of the iconic memoirs of one of the first female fighters of the PKK
The second instalment in a gripping memoir by Sakine Cansiz (codenamed 'Sara') chronicles the Kurdish revolutionary's harrowing years in a Turkish prison, following her arrest in 1979 at the age of 21. Jailed for more than a decade for her activities as a founder and leader of the Kurdish freedom movement, she faced brutal conditions and was subjected to interrogation and torture.
Remarkably, the story she tells here is foremost one of resistance, with courageous episodes of collective struggle behind bars including hunger strikes and attempts at escape. Along the way she also presents vivid portraits of her fellow prisoners and militants, a snapshot of the Turkish left in the 1980s, a scathing indictment of Turkey's war on Kurdish people - and even an unlikely love story.
The first prison memoir by a Kurdish woman to be published in English, this is an extraordinary document of an extraordinary life.
Translated by Janet Biehl.
Sakine Cansiz was a Kurdish revolutionary, who was a leading member of the PKK, present at its first congress of 1978. She was imprisoned between 1980 and 1991 for her membership of the PKK. A close associate of Abdullah Ocalan, she was murdered in Paris in 2013.
'Diyarbakir Military Prison was the main site of Kurdish resistance during the early 1980s and as a senior member of the PKK, Sakine Cansiz played a leading role in it. This book is an excellent resource for understanding this historic period in Kurdish politics' - Cengiz Gunes, author of 'The Kurdish National Movement in Turkey: From Protest to Resistance' (Routledge, 2012).
'This memoir advances our knowledge of human endurance and allows the reader a closer look into the world of state violence. This is a compelling story of fear, hope, tensions, despair, joy, but mostly a dream of liberation' - Shahrzad Mojab, co-author of 'Revolutionary Learning: Marxism, Feminism and Knowledge'
'This second volume of memoirs covers the 11 years Sakine Cansiz spent in Turkish prisons from 1979 until 1990. With tremendous lucidity and power Cansiz tells a story of struggle against dehumanisation and an unshakeable belief in freedom. This is a deeply moving documentation of the origins of the Kurdish women's movement. A most important book - beautifully written and urgent' - Estella Schmid, Peace in Kurdistan Campaign
'Sakine shows not only Kurdish women, but all women that the most beautiful way to live is to embrace life with more strength. Sakine never gave up her love for freedom, despite the heavy sacrifices she had to bear. In a country where it is forbidden to live in freedom as human beings, she knew that the only way to survive was to fight. Every woman who longs for freedom will find a voice in Sakine's struggle' - Gönül Tepe, Kurdish Women's Liberation Movement
Translator-editor's Preface
List of Political Names and Acronyms
Published by Pluto Press in Aug 2019
Paperback ISBN: 9780745339832
Hardcover ISBN: 9780745339849
eBook ISBN: 9781786804938

redpajama_set_name: RedPajamaCommonCrawl


text:
Strategy May Help ER Docs Spot Heart Attacks Within an Hour
Cardiac enzyme data may enhance diagnosis, but some experts say more study is needed
MONDAY, Aug. 13, 2012 (HealthDay News) -- A test based on certain cardiac enzymes could help emergency department staff spot heart attacks in incoming patients within an hour, a new study finds.
The test, called high-sensitivity cardiac troponin (hs-cTn), would be used along with electrocardiography and physical exams to improve the early diagnosis of heart attacks for patients coming to the ER complaining of chest pain, the Swiss researchers said.
As one expert not connected to the study explained, cardiac enzymes called troponins can point to heart attack.
"Cardiac troponins are highly specific for the presence of myocardial cell necrosis (death of heart muscle)," said Dr. Hal Chadow, co-director of the Division of Cardiology at Brookdale University Hospital and Medical Center in New York City. Although troponins are most often elevated in people who have suffered a heart attack, he said, they also can be linked to other conditions such a heart failure, pulmonary embolisms (clots in the lungs) and stroke.
Chadow said accurate, rapid means of confirming heart attacks in the ER are needed.
"Approximately 5.5 million patients are seen in [U.S.] emergency departments annually for chest pain," he said, and "rapid diagnosis and early risk stratification are important goals."
Cardiac troponin measurement may be a key ingredient to this process, he added, since "previous studies have demonstrated very low 30-day event rates in patients with no elevation in cardiac troponin."
The new study was led by Dr. Tobias Reichlin of University Hospital Basel in Switzerland and published Aug. 13 in the journal Archives of Internal Medicine. Reichlin's team tracked nearly 900 patients with severe chest pain who visited the emergency room, including almost 150 for whom heart attack was confirmed as the final diagnosis.
About half of all patients were assessed using the new method.
The new formula gauged the patients' troponin value upon arrival and then tracked changes in troponin over the next hour.
Using the method, the researchers ruled out heart attack in 60 percent of the patients, found evidence of heart attack in 17 percent and put the other 23 percent into a group to be "observed" over the next hour.
The 30-day survival rate was 99.8 percent among the patients who did not have a heart attack, 98.6 percent among those who were placed under observation and 95.3 percent in the patients who had a heart attack.
"The use of this [formula] seems to be safe, significantly shortens the time needed for rule-out and rule-in of [heart attack], and may obviate the need for prolonged monitoring and serial blood sampling in three of four patients with chest pain," the authors concluded.
Still, experts cautioned that more study may be needed before this approach becomes routine.
Since troponin-based tests can point to a wide range of cardiac conditions, using them for spotting heart attack alone may not be advised, said Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City.
"It is important to realize that high-sensitivity troponins are not just a test to 'rule in' or 'rule out' [heart attack]," he said. "Instead, they are a valuable tool to risk-stratify patients with chest pain who may have a number of potentially lethal [conditions]."
Glatter noted that troponin tests might miss other potentially lethal heart conditions "where there may be no troponin elevation."
"If these high-sensitivity troponin assays are widely embraced, it will likely prolong the emergency department length of stay and may potentially worsen the crowding in our nation's emergency departments," Glatter said. "They cannot be seen as the answer to our dilemma of triaging high-risk chest-pain patients when they ultimately lead to more doubt and questions down the line."
For his part, Chadow said that although the troponin-based test may be "an important addition to our armamentarium in evaluating chest-pain patients in the ER, I agree that more studies are needed in a larger number of patients to confirm these findings."
The study was funded by research grants from the Swiss National Science Foundation; the Swiss Heart Foundation; medical technology companies Abbott, Roche and Siemens; and the Department of Internal Medicine at University Hospital Basel.
The U.S. National Heart, Lung, and Blood Institute provides more information on heart attacks.
SOURCE: Archives of Internal Medicine, news release, Aug. 13, 2012
Consumer News Language Emergencies / First Aid Heart / Stroke-Related: Heart Attack News types Topics Products English News


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Home All issues Volume 4 (2017) Manufacturing Rev., 4 (2017) 1 Full HTML
2. Experimental details
Production and 3D printing processing of bio-based thermoplastic filament
Eleni Gkartzou, Elias P. Koumoulos and Costas A. Charitidis*
Research Unit of Advanced, Composite, Nano Materials & Nanotechnology, National Technical University of Athens, School of Chemical Engineering, 9 Heroon Polytechniou St., Zographos, Athens 15780, Greece
In this work, an extrusion-based 3D printing technique was employed for processing of biobased blends of Poly(Lactic Acid) (PLA) with low-cost kraft lignin. In Fused Filament Fabrication (FFF) 3D printing process, objects are built in a layer-by-layer fashion by melting, extruding and selectively depositing thermoplastic fibers on a platform. These fibers are used as building blocks for more complex structures with defined microarchitecture, in an automated, cost-effective process, with minimum material waste. A sustainable material consisting of lignin biopolymer blended with poly(lactic acid) was examined for its physical properties and for its melt processability during the FFF process. Samples with different PLA/lignin weight ratios were prepared and their mechanical (tensile testing), thermal (Differential Scanning Calorimetry analysis) and morphological (optical and scanning electron microscopy, SEM) properties were studied. The composition with optimum properties was selected for the production of 3D-printing filament. Three process parameters, which contribute to shear rate and stress imposed on the melt, were examined: extrusion temperature, printing speed and fiber's width varied and their effect on extrudates' morphology was evaluated. The mechanical properties of 3D printed specimens were assessed with tensile testing and SEM fractography.
Key words: 3D Printing processability assessment / Fused filament fabrication / Additive manufacturing / Biobased 3D printing filament
© E. Gkartzou et al., Published by EDP Sciences, 2017
In the last decade, issues concerning environmental pollution and the increasing awareness of limited resources, have motivated the scientific community to study and optimize renewable alternatives to traditional petroleum-derived plastics, like biobased composite materials that are sourced from carbon-neutral feedstocks [1]. Lignin is a highly aromatic biopolymer, abundantly found in the fibrous part of various plants and extracted as a byproduct of wood pulping industries. Kraft lignin (sulfate lignin) is isolated in the so-called delignification process, from black liquor by precipitation and neutralization with an acid solution (pH = 1–2), and subsequently dried to a solid form [2]. It is estimated that only 2% of the industrially extracted lignin is exploited for low-volume, niche applications, while the rest is often relegated to a low efficiency energy recovery via combustion or as a natural component of animal feeds [3]. Thus, the development of ways to convert lignin to new high-value products is an active area of research, dealing with the main drawbacks of lignin usage regarding the low-purity standards, heterogeneity, smell and color problems of the existing commercial lignins. It is recognized that blending lignin with polymers is a convenient and inexpensive method to create new materials with tailored properties, such as hydrophobicity, stiffness, crystallinity, thermal stability, Ultraviolet (UV) blocking ability and to reduce the overall cost of the material [4, 5].
The ecosystem of 3D printing plastic market consists of numerous research and development activities and is projected to reach USD 692.2 Million by 2020, at a Compound Annual Growth Rate (CAGR) of 25.7% from 2015 to 2020 [6]. Among the various commercially available specialty filaments for Fused Filament Fabrication (FFF) processing, materials mimicking wood texture and properties are a separate category, because of their ability to create objects with the tactile feel of wood without any need for specialized woodworking tools. Furthermore, they require less maintenance and preservatives, since they are more resistant to organic decomposition, while maintaining their biodegradability. PLA/Lignin (poly(lactic acid)/Lignin) 3D printing filaments are an alternative option for lignin exploitation and filament cost reduction and can be used in rapid prototyping, presentation models and consumer products, among others. Poly(lactic acid) is a biodegradable thermoplastic, which is produced via fermentation or chemical synthesis from a bio-derived monomer, lactic acid (2-hydroxy propionic acid) [7]. The carbon in PLA originates from atmospheric carbon dioxide, which is immobilized in glucose by photosynthesis; therefore, its impact on the environment during production and disposal (carbon footprint) is low compared to other petro-based polymers. PLA is widely used in 3D printing applications, since it is one of the most user-friendly materials that can be easily processed with FFF, without emitting toxic fumes. However, its low thermal stability, high degradation rate during processing and brittle behavior have to be addressed. It has been suggested that the presence of lignin increases thermal stability and flammability under oxidative and nonoxidative conditions, due to the formation of char, which acts as a protective layer preventing oxygen diffusion [8].
Extrusion-based 3D printing techniques use temperature as a way of controlling the material state, for the successful extrusion and deposition of semi-molten thermoplastic fibers, on a flat surface. In a typical FFF process, a filament feedstock is supplied to the system by an electric motor-controlled pinch roller mechanism [9, 10]. Material is liquefied inside a reservoir, contained in a heated metal block with a machined channel, so that it can flow through the print head's nozzle and fuse with adjacent material before solidifying. This approach is similar to conventional polymer extrusion processes, except the extruder is vertically mounted on a plotting system (print head) rather than remaining in a fixed horizontal position [10]. After its deposition, the solidifying material is referred to as a fiber or road. The part is produced by superimposing a specified number of layers, where each of them is generated by a specific pattern of fibers. The formation of bonds among individual fibers in the FFF process consists of complicated heat and mass transfer phenomena coupled with thermal and mechanical stress accumulation and phase changes. The strength of these bonds depends on the growth of the neck formed between adjacent fibers and on the molecular diffusion and randomization at the interface [11]. As a natural consequence of this manufacturing approach, the part's internal microstructure consists of fibers with partial bonding among them and voids [12] and can be assimilated to a composite two-phase material with inherently orthotropic properties [13]. Individual fibers are significantly stronger in the axial direction and resemble the fibers in a composite; however, the structure shows weaker behavior in the direction where stresses need to be carried through fiber-to-fiber or layer-to-layer adhesion [12].
Three dimensional printers employing the FFF technology are Computer Numerical Control (CNC) machines, whose function is defined by a program containing coded alphanumeric data (G-code). G-code sets of commands are typically generated by Computer-Aided Manufacturing (CAM) software, which uses topological information from 3D Computer-Aided Design (CAD) data along with user-defined processing and toolpath parameters, to create virtual slices of the object to be manufactured and to calculate the toolpath and the material's Volumetric Flow Rate (VFR), in order to form the successive cross sections of the physical part. In most CAM programs for lower end FFF 3D printers, VFR is a function of the linear feed velocity of the filament and of several design parameters related to the toolpath (e.g. the width and height of individual fibers, defined by extrusion width and layer height parameters) [14]. The pressure-driven mass flow of the non-Newtonian polymeric melt through the nozzle is mainly related to nozzle geometry, pressure drop and melt's apparent viscosity. This flow can be described as a fully developed, laminar flow through a capillary die with a circular cross section [14, 15]. The necessary pressure for fiber extrusion is applied by the solid portion of the 3D printing filament which acts as a piston, as it is pushed by a pinch-roller feed mechanism into a melting reservoir, placed on the upper part of the nozzle. Volumetric flow rate along with extrusion temperature are two material-dependent factors which contribute on the shear rate and stresses imposed on the melt during extrusion. In the case of composite 3D printing materials, these factors are significantly influenced and limited by the filler's dispersion and agglomeration [16].
This study is divided in two main sections; the first section involves the preparation and characterization of bulk samples of the composite material with increasing lignin content and 3D printing filament production. The second section concerns the selection of suitable toolpath and process parameters based on the produced filament's response during FFF processing, focusing on extrusion temperature, print head's velocity and extrusion width. By understanding the relationship between processing conditions and physical phenomena involved in the material's extrusion and deposition, suitable bounds for these parameters were derived. The optimum velocity and temperature values were used for the fabrication of tensile specimens with 100% nominal density and three different extrusion widths, produced by three brass nozzles with different diameter (0.2, 0.3 and 0.4 mm), in order to measure the tensile properties of the finished parts and to compare them with the properties of the bulk material. Pure PLA filament was produced and processed under the same conditions, to be used for comparison. Fractographic analysis of tensile failure was carried out with Scanning Electron Microscopy (SEM). Also, a qualitative assessment of the filler's dispersion and agglomeration into the polymeric matrix, as well as its effect on surface morphology and diameter of individual fibers was made with optical microscopy.
2.1. Materials
Commercial PLA pellets under the grade name "INGEO 2003D" were supplied by Natureworks LLC, with number average molecular weight Mn (g/mol) = 114.317, weight average molecular weight Mw (g/mol) = 181.744 and 4.3 wt.% D‐isomer content [17]. A purified form of kraft pine lignin (Indulin AT) was supplied by MWV Specialty Chemicals, in the form of free-flowing powder with a wide distribution of particle diameter, as depicted in the SEM micrographs of Figure 1. Both materials were used without chemical treatment for the preparation of the blends. Prior to processing, the components were vacuum-dried at 50 °C for 24 h and weighted in a high precision scale.
SEM micrographs of kraft lignin (Indulin AT) particles (a) ×800 and (b) ×1.600 magnification.
2.2. Blending
Firstly, 40 g samples of PLA/Lignin blends with different lignin concentrations (5, 10, 15, 20% percentage by weight on the dry polymer – Table 1) were prepared by melt mixing in a twin-screw Brabender internal mixer. Mixing time for each sample varied from 10 to 13 min, at 35 rpm rotating speed of the screws and mixing temperature between 180–190 °C (depending on lignin content). To remove residual stresses and air bubbles caused by the blending process, the semi-molten material was collected from the mixing chamber and placed in an aluminum mold, which was inserted in a Dake thermopress to form a 15 × 60 × 1 mm plate. The plates of the thermopress were heated at 120 °C and heating was switched off when maximum load was applied on the mold. All samples used for the bulk material's characterization were cut from the aforementioned plates and kept under room temperature in a glass desiccator, to prevent moisture absorption.
Sample composition.
2.3. Characterization
The effect of increasing lignin content on the bulk material's thermal and mechanical properties was evaluated with Differential Scanning Calorimetry (DSC) and tensile testing. The phase morphology of the samples was examined with an Axio Imager A2m optical microscope and AxioCam ICc5 CCD camera (Carl Zeiss, Oberkochen, Germany) and SEM micrographs were taken with Nova NanoSEM 230 scanning electron microscope (FEI Company) with an acceleration voltage of 5 kV. Samples for optical inspection were cut with a rotating saw and embedded in cold mounting epoxy resin. The embedded samples' surface was grinded with fine silicon carbide abrasives to remove defects introduced by sectioning. Tensile specimens were directly cut from the thermopressed plates of the compounded material with a dumbbell-shaped specimen cutting die, with a 18 × 3 × 1 mm reduced gage section. Measurements of mechanical properties of specimens were performed at room temperature with a Zwick tensile tester, model 1120 equipped with a 2000 N load cell. Both Young's modulus and elongation measurements were made at a constant crosshead speed of 2 mm/min. Each value of mechanical properties reported is an average of five specimens. DSC analyses were performed with DSC Q200 TA Instruments (New Castle, DE, USA). The thermal history of samples was erased by a preliminary heating cycle, followed by a cooling cycle from 200 to 0 °C and a second heating cycle from 0 to 200 °C. Both cooling and heating rates were set at 10 °C/min. The samples' mass ranged from 6.90 to 8.36 mg and they were encapsulated in aluminum pans. An empty pan was used as reference. The glass transition temperature (Tg) cold crystallization temperature (Tcc), double melting peak temperatures (Tm1,2), cold crystallization enthalpy (ΔHcc) and melting enthalpy (ΔHm) were determined from heating scans. Thermogravimetric Analysis (TGA) of softwood kraft lignin was carried out based on global mass loss with a Netzsch 409 EP analyzer, from which lignin's decomposition pattern can be derived. The analysis was conducted under nitrogen atmosphere with a heating rate of 10 °C/min. The characterization of 3D printed fibers and tensile specimens involved optical microscopy and tensile testing. Brightfield illumination was used to observe the surface roughness of PLA/Lignin fibers. Also, by exploiting PLA's transparency and alterations in the incident light's state of polarization during its interaction with lignin, a qualitative evaluation of the dispersion of lignin's agglomerates in the fibers' bulk volume was conducted. AxioVisio digital image processing software was used to measure the diameter of the fibers from the micrographs captured by the CCD camera. Since no special standard exists for the characterization of FFF parts, tensile specimens based on a scaled down version of ASTM D638 Type I with a 36 × 8 × 2 mm gauge section, were 3D printed using Zmorph 2.0 S, a commercial FFF Cartesian XZ system (Zmorph LLC, Wroclaw, Poland). Tensile testing was carried out under the same conditions as the bulk material specimens, with the same crosshead speed of 2 mm/min. Both pure PLA and composite PLA/Lignin filaments were used as raw materials. The 3D printed specimens had 100% infill density in order to make a comparison with the tensile properties of the bulk material and to eliminate errors from G-code generation. Divergence from the nominal dimensions of the tensile specimens introduced by the fabrication process, was measured for each specimen with a high precision digital caliper and the average of 10 measured values for each dimension was used for stress calculations. Fractographic analysis of tensile failure was carried out with scanning electron microscopy. The fractured samples were sputter-coated with a thin layer of gold before observation.
2.4. Production of 3D printing filament
The 3D printing filament needs to be able to provide and sustain the pressure needed to drive the extrusion process. Failure to do this results in filament buckling, which occurs when the extrusion pressure is higher than the critical buckling load that the filament can support [10, 14, 18]. The filament's elastic modulus determines its load carrying ability and melt viscosity determines the resistance to extrusion (or extrusion pressure). As a result, the composition with 5 wt.% lignin content was selected for the production of 3D printing filament with 1.75 mm nominal diameter, which is compatible with the 3D printer's feeding system. Subsequently, a Boston-Mathews single-screw extruder with an L:D ratio of 25:1 with a 1.8 mm diameter extrusion die was used to obtain PLA/Lignin filament and several combinations of process parameters were tested in order to achieve enhanced filler dispersion and constant filament diameter. A processing temperature profile of 185–195–205–205–195 °C from feed section to die was selected along with a fixed screw speed at 16 rpm. The extrudate was collected by a conveyor belt equipped with cooling fans, whose speed was matched to the extrusion speed in order to control the diameter of the filament. The composite filament and pure PLA filament (processed under a 180–190–200–200–190 °C temperature profile) were used to obtain 3D printed specimens and individual fibers. The produced filament was conditioned in room temperature inside sealed plastic bags, in the presence of silica gel, to avoid moisture absorption. Filament sections with tight tolerances were selected for specimen fabrication. Each section's diameter was measured every 1 cm with a high precision digital caliper and average diameter and standard deviation were calculated. From Figure 2 it can be seen that the measured filament diameters are normally distributed around the mean value, with 0.02 mm standard deviation, meaning that 95% of the filament used has a ±0.04 tolerance. A tight diameter tolerance is important during the material melting and deposition process. The heating of the filament inside the print head's liquefier can be considered as a two-dimensional, axisymmetric, steady-state, advection-conduction heat transfer process [19]. Gaps between the filament and the wall of the liquefier, caused by the filament's diameter inconsistency can be expected to hinder heat transfer and result in irregular viscous behavior of the melt on the upper part of the liquefier. Diameter inconsistencies have adverse effects on the material feeding mechanism as well, since mismatches between the roller and filament surfaces may lead to filament slipping. Furthermore, the filament's mean diameter is used by the Computer Aided Manufacturing (CAM) program, which automatically calculates the material's feed velocity in the 3D printer's extruder. As a result, the diameter's standard deviation is related to volumetric flow rate fluctuations during the 3D printing process, which can alter the distance between adjacent fibers, causing insufficient bonding or fiber overlapping and thus reducing the physical object's dimensional accuracy and structural integrity.
Diameter distribution of filament sections used for specimen fabrication.
2.5. Computer aided manufacturing – toolpath and process parameters
Computer aided manufacturing software typically enables control of several design and process parameters related to fused filament fabrication. Design parameters define the toolpath followed by the nozzle's tip and include individual fibers' width and height (commonly referred to as "road/extrusion width" and "layer's height/thickness", respectively), as well as various deposition strategies to form and fill the successive cross sections of the part. A common deposition strategy is to separately deposit one or more continuous contours of all boundary 2D surfaces included in a given cross section and to fill the space between them, (corresponding to the part's interior), with specific infill patterns. Part orientation in relation to infill orientation and to the system's main axes of movement (XYZ for cartesian 3D printers) plays an important role in surface finish, dimensional accuracy, cost and mechanical behavior [20, 21]. In the simple case of rectilinear infill pattern (Figure 3), each layer is filled with a raster of parallel roads and adjacent layers have a fixed 90° raster angle between them. By adjusting infill density, which is expressed as a percentage of occupied space, more sparse or dense parts can be produced with bigger or smaller distances among contiguous fibers of the same layer (raster to raster distance, dr). A slightly negative dr, corresponding to fiber overlapping, has been reported to reduce void density and increase contact area among fibers and thus resulting in stronger fiber-to-fiber bonds [22, 23]. However, the excessive material buildup at the layer's perimeter significantly affects dimensional accuracy on the XY plane. As individual fibers are deposited on the previously solidified layer of the material, heat exchanges by conduction develop on contact surfaces between adjacent fibers and by convection and radiation with the surroundings. Upon the deposition of new layers, new physical contacts are generated; hence, several heat transfer modes change and heat transfer with air entrapped between contiguous filaments may also develop. Toolpath and G-code generation have a significant effect on thermal stress accumulation in fibers and layers and thus different CAM programs with the same input values, produce parts with different responses to external stresses. In this study, an open-source G-code generating program (Slic3r 1.2) was used for specimen fabrication. A second G-code generating program (Voxelizer 1.4), with a different generating algorithm, was used with the same input values of toolpath and process parameters, in order to estimate the effect of different CAM programs on the mechanical properties of the final part.
Illustrations of toolpath for rectilinear infill pattern with 90° raster angle generation and cross sections of the produced pattern and individual roads, where Wr is the extrusion width, Hr is layer height and dr is raster-to-raster distance.
As far as process parameters are concerned, they include extrusion temperature, chamber temperature, cooling rate, filament feed velocity and volumetric flow rate, among others. The extrusion process does not have a considerable influence on the strength and modulus of the material, but notably affects the maximum strain, since during extrusion through the nozzle, polymer chains are submitted to stress-induced orientation, which reduces the elongation characteristics of the material [12]. The rate at which the filament is fed to the liquefier (feed velocity) is dynamically controlled and connected to velocity changes of the print head, in order to maintain a constant volumetric flow rate. The amount of melt which is present in the reservoir, the temperature of the melt, and consequently, the viscosity and surface energy of the melt, vary with feed rate [14]. In the case of constant linear movement of the print head, the extruder motor speed is proportionate to printing speed, so an indirect control of feed speed can be achieved varying printing speed for the same toolpath characteristics. Extrusion temperature and deposition rate are identified as the major parameters influencing inter- and intra-layer bonding [24].
User-defined processing parameters for G-code generation and specimen fabrication are listed in Table 2, which resulted from temperature and printing speed optimization, as well as adjustments on the standard processing profile for PLA recommended by the manufacturer. A constant layer thickness of 0.1 mm was used for all specimens and extrusion widths were determined by nozzle diameter. Three nozzles with the same design characteristics and 0.2, 0.3, 0.4 mm openings were tested and extrusion width was set equal to the respective nozzle diameter. Nozzle diameter, along with the viscosity of the melt, determine the pressure drop during extrusion and thus the force required from the feed mechanism. Pressure drop increases as nozzle diameter increases, or as feed velocity increases. Furthermore, in the vicinity of the nozzle, the polymer melt is under stress and part of the deformation energy stored elastically leads to radial expansion of the fiber after extrusion. Individual fibers were extruded from each nozzle at three print speeds (20, 40 and 60 mm/s). Surface morphology and diameter were studied at the center of the fibers, in order to avoid errors related to print head acceleration and deceleration. Since no standard test specimens exists for characterization of parts processed with FFF, tensile specimens were fabricated based on a 3D model of ASTM D638 Standard Test Method for Tensile Properties of Plastics, Type I specimen, designed with Autodesk Fusion 360 CAD and extracted in fine quality Stereolithography (STL) format. The original specimen was scaled down by ×0.6 to avoid fabrication errors near the boarders of the available working volume. To ensure the repeatability of the fabrication process, all tensile specimens were fabricated separately, with their wide surface parallel to the XY plane and gauge section parallel to X axis, at the same position near the center of the build platform. Toolpath simulation generated by G-code generating software is depicted in Figure 4. Before the fabrication of each specimen, a touch probe sensor (by Zmorph LLC) was used for precise leveling of the build platform and the nozzle's distance from surface (0.1 mm) was verified at four points within the surface of specimen fabrication.
Toolpath simulation for tensile specimen fabrication with three contours and rectilinear infill pattern with 100% nominal density. Specimens consist of alternating Type A and Type B layers.
Fused filament fabrication toolpath and process parameters.
3.1. Bulk material characterization
3.1.1. Reflected light microscopy
The morphological analysis of binary PLA/Lignin blends was performed with reflected light microscopy and scanning electron microscopy. In general, the morphology is defined by the complex thermomechanical history experienced by the different constituents during processing [25]. All samples formed heterogeneous systems, due to the low compatibility between PLA matrix and the unmodified kraft lignin, which has been previously reported [24–28]. At 5 wt.% lignin content, the morphology mainly consists of a uniform dispersion of lignin aggregates of small size (<20 μm) in homogeneous surrounding matrix of PLA/Lignin, as it can be seen at Figures 5a and 5b. At higher lignin content, there is an increase in aggregates' concentration, which remained uniformly dispersed. At 20% lignin, particle size increases because of coalescence phenomena.
(a–b) Reflected light (brightfield and polarized illumination) micrographs of PLA/Lignin with 5% lignin (magnification ×100 and ×500). (c–d) Closer examination (×4000 and ×8000 magnification) of the morphology of lignin aggregation with SEM, from the tensile-fractured surface of sample with 15% lignin.
A closer examination of lignin aggregation at smaller scales can be achieved from SEM analysis of the fractured surface of the samples (Figures 5c and 5d). Prior to examination, sample surfaces were covered with gold sputter coating. It can be seen that lignin aggregates consist of smaller lignin domains of fairly circular shape, closely packed in specific regions of the PLA matrix. Interfacial separation and sliding between lignin's aggregates and the surrounding matrix are indicative of very weak secondary interactions between the two polymers.
3.1.2. Tensile testing
The type of morphology and the phase dimensions determine the mechanical and physical properties of the blend at large, which is influenced by intermolecular lignin-lignin, PLA-PLA and PLA-lignin interactions. Consequently, the observed immiscibility between the two constituents results in minor effective stress transfer between lignin's aggregates and PLA matrix and increases PLA's brittleness, which is shown as a significant reduction in the plastic region of stress-strain curves and disappearance of yield point. However, lignin has no adverse effect on Young's modulus of elasticity, as it can be seen in Figure 6 and Table 3. Samples with 5 and 10 wt.% lignin displayed a 40% and 49% reduction in elongation at break respectively. The relative change in PLA's Young's modulus of Elasticity (E), Ultimate Tensile Strength (UTS) and Elongation at Break (el) with increasing lignin content is presented in Figure 7. For samples LPLA10 and LPLA15, UTS is equal to breaking strength (absence of yield point), while the breaking strength of pure PLA and PLA with 5 wt.% lignin is slightly smaller than UTS, at 48.1 and 47.6 MPa, respectively. The sample with 20 wt.% lignin content was too brittle for tensile specimens to be cut.
Engineering stress-strain curves of the PLA/Lignin blends with 0, 5, 10 and 15 wt.% lignin content.
Percentage change of PLA's mechanical properties (ultimate tensile strength, Young's modulus of elasticity and elongation at break) with increasing lignin content.
Tensile properties of PLA/Lignin composites.
3.1.3. Thermal characterization
The DSC thermograms recorded during cooling and second heating of PLA composites are reported in Figure 8. A single glass transition temperature (Tg) registered for all blends, but no deduction can be made for the miscibility of the ingredients, since lignin's content is low and its Tg is possibly overlapped by PLA's melting peaks. At the chosen cooling rate (10 °C/min), the material did not develop a significant crystalline component and no crystallization peaks were recorded during cooling cycle both for pure PLA and PLA/Lignin composites. Therefore, a highly amorphous structure is obtained with thermodynamic instability, which can form local ordered structure during annealing below glass transition temperature due to the enthalpic relaxation of the polymeric chains [29, 30], the melting of which is manifested as a small endothermic peak during the heating cycle after the glass transition process (Figure 8). When annealed between glass transition temperature (Tg) and melting temperature (Tm), the mobility of chain segments of glassy polymers increases gradually and cold crystallization occurs [31]. Lignin appears to promote PLA's double melting behavior, which is attributed to the melting of two populations of lamellae. The lower temperature peak is connected to the melting of small lamellae produced by secondary crystallization, while the higher temperature peak originates from the melting of major crystals formed in the primary crystallization process. As part of the ongoing research related to crystalline behavior of semi-crystalline polymers, it has been suggested that the primary crystals are first formed, followed by the formation of secondary crystals and simultaneous thickening of the primary crystals [32]. Other authors have explained double melting behavior with a melt-recrystallization model, where the low-temperature and high-temperature peaks in the DSC curve are attributed to the melting of some amount of the original crystals and to the melting of crystals formed through a melt-recrystallization process during the heating scan, respectively [33]. As lignin content increases, there is a greater contribution from the melting of major crystals to the specific melting enthalpy of the sample or from crystals formed through a melt-recrystallization process, which is implied by the increase in the higher temperature melting peak in Figure 8. Therefore, for the given heating rate lignin affects nucleation and crystal growth, possibly encouraging recrystallization or the formation of thicker crystalline structures during the cold crystallization process.
(a) DSC thermographs of PLA/lignin bulk composites. (b) DSC thermograph of sample with 5 wt.% lignin. Quantities for characterization of the glass transition of sample containing 5 wt.% lignin: extrapolated onset temperature (Tge), half-step temperature (Tg1/2), change of the normalized heat capacity during transition (ΔCp), initial (Tgi) and final (Tgf) temperatures of the glass transition.
Basic quantities which characterize the samples' glass transition, cold crystallization and melting process were derived from DSC thermographs and are listed in Table 4. No significant changes were observed for the initial (Tgi), final (Tgf), extrapolated onset (Tge) and half-step (Tg1/2) glass transition temperature and for the associated change in heat capacity (ΔCp) before and after glass transition. The peak temperature for cold crystallization (Tcc), low melting peak (Tm1), high melting peak (Tm2) and the related cold crystallization and melting enthalpies also seem to be independent from lignin content, with very small variations. As a result, no special intermolecular interaction between PLA and lignin can be confirmed, in accordance to the observed phase morphology. Furthermore, since the FFF process involves melt quenching at higher cooling rates and instant solidification of the material after its deposition, it can be deducted that the material's crystallinity during and after FFF processing will mainly be defined by stress-induced crystallization.
Transition temperatures and associated changes in heat capacity, enthalpy and crystallinity of PLA/Lignin composites.
The Thermogravimetry (TG) (in weight loss percentage) and Derivative Thermogravimetry (DTG) (in weight loss percentage per °C) curves of Indulin AT kraft lignin, obtained at 10 °C/min heating rate under nitrogen atmosphere, are plotted in Figure 9. Thermal degradation data indicates weight loss and the first derivative (DTG) indicates the corresponding rate of weight loss. The peak of DTG can be presented as a measure of thermal decomposition and can be used as a means to compare thermal stability characteristics of different materials. As it can be seen in Figure 10, thermal decomposition occurred over a wide temperature range, starting at approximately 216 °C (To). Lignin's weight loss percentages for various characteristic decomposition temperatures are summarized in Table 5, where To is initial decomposition temperature, Tend is terminal decomposition temperature, T1 and T2 are attributed to the evolution of humidity and chemically bound water respectively, T3,max is maximum decomposition temperature corresponding to DTG peak and T5%, T30%, T50% are temperatures of 5, 10, 30 and 50% weight loss due to degradation.
TGA plot of Indulin AT kraft lignin and the derivative TGA curve, obtained under nitrogen atmosphere at 10 °C/min heating rate.
Macrographs of temperature calibration specimen captured with Sony SLT-A57 SAL-1855, depicting changes on surface roughness caused by thermal degradation (in black/white contrasted images, from darker to brighter images.
Characteristic decomposition temperatures of Indulin AT kraft lignin.
3.2. Fused filament fabrication process optimization
3.2.1. Extrusion temperature
A temperature calibration specimen, consisting of a 20 × 20 × 80 mm hollow rectangular cuboid with 0.8 cell thickness, was modeled in Autodesk Fusion 360 CAD program and extracted in STL file format, in order to assess the impact of liquefier temperature on surface finish (Figure 10). Extrusion temperature varied from 230 to 190 °C, with 5 °C steps every 1 cm across Z axis (10 layers with 0.1 mm height). A brass nozzle with 0.4 mm diameter was used for specimen fabrication and the rest of the user-defined input values for the CAM program are listed in Table 2. It has been observed that the 3D printing extrusion temperature is generally higher than that needed for filament extrusion [34], due to the material's short residence time in the liquefier's reservoir and the limited power of the feeding system's stepper motor (NEMA 17), compared to the single-screw extruder. Also, the liquefier temperature set on CAM program reflects the temperature of the melt reservoir on the upper part of the nozzle, close to the print head's temperature sensor. The correct deposition temperature is expected to be lower, since the tip of the brass nozzle itself is not heated and insulated [35]. From the images of Figure 10, it can be seen that surface roughness is directly connected to the material's thermal stability. At temperatures higher than 215 °C, the anisotropy of surface's topography increases, in accordance to lignin's thermal decomposition pattern (Figure 9). At 190 °C, the melt's viscosity is significantly higher, and lignin's agglomerates hinder material flow, resulting in nozzle clogging. The optimum combination of surface roughness and material flow was achieved at 205 °C.
3.2.2. Extrusion of individual fibers and infill inspection
Both PLA and PLA with 5 wt.% lignin fibers with 15 cm length were individually extruded from the FFF system at 205 °C, using nozzles with different openings (0.4, 0.3, 0.2 mm). From Figures 11 and 12, it is evident that lignin causes a severe increase in fibers' surface roughness (in comparison with pure PLA fibers) and the actual extrusion width is mainly defined by the size and distribution of lignin aggregates. Phase separation is more intense in filament as opposed to the bulk material with the same lignin content, due to the dispersive mixing limitations of the single-screw system used for filament production, as to the twin-screw internal compounder used for sample preparation. For the tested print velocities (20, 40 and 60 mm/s), no nozzle clogging occurred. However, as nozzle diameter decreases and becomes comparable with the size of lignin's aggregates, diameter inconsistencies become more prominent at higher speeds, as it can be seen in Figures 11c and 11d, where the local diameter increases by 30%. Therefore, 20 mm/s speed was selected as a common printing speed for all nozzles. A cylindrical specimen with 1 cm radius and 1 cm height, with 3 contours and rectilinear infill pattern (50% nominal density) was fabricated with 0.4 mm extrusion width for infill inspection. Uneven distribution of lignin phases of various sizes is depicted at Figure 12, along with a case of over-extrusion dew to volumetric flow fluctuations during the extrusion of the contour of the specimen.
Individual fibers extruded from 0.2 mm nozzle (a–b) 20 mm/s printing speed and (c–d) 60 mm/s, where lignin aggregation causes up to 30% increase in fiber's diameter, respectively.
Reflected light (brightfield and polarized illumination) micrographs of specimen with 50% rectilinear infill density and three successive contours, for inspection of lignin dispersion, surface texture and volumetric flow fluctuations.
3.2.3. Tensile properties of 3D printed specimens
As it has been noted by other studies [12, 13], small variations of the processing conditions can strongly affect specimens mechanical properties. The reported values and standard deviations are the average of five specimens, which failed within the specimen's gauge section. The effect of different extrusion widths is presented in Figure 13a and Table 6. As it has been mentioned, extrusion through different nozzles negatively affects specimen's maximum strain (and increases its standard deviation from average value), because of the imponderable effect of the increased stress-induced orientation of polymer chains [12, 21]. The 0.4 mm diameter nozzle resulted in specimens with maximum elongation at break similar to that exhibited by bulk material. Ultimate tensile strength and Young's modulus of elasticity have similar values for different road widths and are 18% and 6% reduced respectively, compared to bulk material. Figure 13b and Table 7 present the tensile properties of representative specimens fabricated with two different G-code generation programs and the same user-defined process and toolpath parameters. Two characteristic responses to tensile stresses appeared in both sets of tensile specimens, indicating that specimens fabricated under the same conditions can exhibit different fracture behaviors, because of premature inter- and intra-laminar failures related to over- or under-extrusion or weak bonds among individual fibers, especially at the fusion points between the infill and the internal contour. This can be also observed with SEM analysis of the fractured surfaces of tensile specimens fabricated with different CAM programs (Figure 14 – 1a–1c and 2a–2c). The stress around which premature failure occurs is approximately half of the corresponding ultimate tensile strength and is noted as Spf in Table 7. Elpf is the strain region corresponding to negative slope of stress-strain curve.
(a) Effect of different nozzle diameter on specimen's tensile properties. Comparison with the tensile properties of bulk material with the same (5 wt.%) lignin content. (b) Effect of different CAM programs on tensile properties of specimens with the same toolpath and process parameters. Representative examples with and without premature internal failure. (c) Tensile properties of specimens produced from pure PLA and PLA/Lignin filament for two different nozzle diameters.
SEM micrographs of the fractured surface of 3D printed tensile specimens. The upper/lower corners of gauge region cross section consist of three successive contours. PLA/Lignin a and PLA/Lignin b, which were fabricated with different CAM programs, exhibit different fracture morphologies.
Tensile properties PLA/Lignin 3D printed specimens with various extrusion widths – comparison with the bulk material.
Tensile properties of representative PLA with 5 wt.% lignin specimens, with and without premature failure, exhibited for both CAM programs used for fabrication.
Figure 13c and Table 8 present a comparison of tensile properties among identical specimens fabricated from pure PLA and PLA/lignin filaments. As the tensile stress increases, the failure will begin at the weakest raster and next weakest raster will break, in sequence, until total failure of the sample [36]. As expected, lignin addition mainly reduces elongation at break and increases PLA's brittle behavior, which can be also deducted by comparing the characteristics of PLA's fractured surface (Figure 14 – 3a–3c) with PLA/Lignin specimens. PLA's interlayer fusion at the infill region appears to be improved every two layers, which is caused by toolpath variation (Figure 4), since the fabrication of Type-A layers has a reduced time between successive depositions of fibers and temperature at the bonding site remains higher for a longer period of time, improving neck formation and growth with the preceding layer [37, 38]. Interestingly, this effect is limited in PLA/Lignin specimens, where all layers seem to have similar bond quality, with more complex fracture mechanisms. The non-selective trans-layer and trans-fiber crack propagation is indicative of improved bond quality, which could be explained by the adhesion-enhancing effect of lignin addition, caused by the increase in surface roughness of individual fibers [38]. As it has been mentioned, crack initiation and propagation is more probable to occur in specimen's upper/lower corners and more specifically in contour region, where void density is higher, or at the infill-contour fusion points. For the chosen process and toolpath parameters, very good adhesion among contiguous fibers and successive layers was achieved.
Tensile properties of specimens fabricated from pure PLA and PLA/Lignin filament.
In this study, the properties of biobased PLA/Lignin blends were examined and correlated to processing conditions with fused filament fabrication and tensile properties of the produced parts. Samples with different PLA/lignin weight ratios were prepared and their phase morphology as well as mechanical and thermal properties were examined. It was found that all samples formed heterogeneous systems, where interfacial separation and sliding between lignin's aggregates and the surrounding PLA matrix are indicative of very weak secondary interactions between the two polymers. Phase separation also results in minor effective stress transfer between lignin's aggregates and PLA matrix, which increases PLA's brittleness and causes a significant reduction in the plastic deformation region of stress-strain curves and disappearance of yield point. However, lignin has no adverse effect on Young's modulus of elasticity. Furthermore, the material's slow crystallization rate (at 10 °C/min cooling rate no crystallization peaks were recorded), suggests that its crystallinity during and after FFF processing will mainly be defined by stress-induced crystallization. Lignin appears to promote PLA's double melting behavior and affects nucleation and crystal growth, possibly encouraging recrystallization or the formation of thicker crystalline structures during the cold crystallization process. Thermogravimetric analysis of kraft lignin indicates that its thermal decomposition occurred over a wide temperature range, starting at approximately 216 °C. Since increasing lignin content results in severe agglomeration and increase in the material's brittleness and melt's apparent viscosity during extrusion, the composition with 5 wt.% lignin content was selected for the production of 3D printing filament and segments of 1.78 ± 0.04 mm diameter were used for extrusion of individual fibers and fabrication of tensile specimens. The addition of lignin causes a severe increase in fibers' surface roughness (in comparison with pure PLA fibers) and the actual extrusion width is mainly defined by the size and uneven distribution of lignin aggregates. Based on the material's response during processing, the optimum extrusion temperature (205 °C) and printing speed (20 mm/s) for extrusion through nozzles with different diameters (0.2, 0.3 and 0.4 mm) were used for tensile specimen fabrication. Extrusion through different nozzles negatively affects specimen's maximum strain (and increases its standard deviation from average value), because of the imponderable effect of the increased stress-induced orientation of polymer chains. The 0.4 mm diameter nozzle resulted in specimens with maximum elongation at break similar to that exhibited by bulk material. Ultimate tensile strength and Young's modulus of elasticity have similar values for different road widths and are 18% and 6% reduced respectively, compared to bulk material. It was also found that specimens fabricated under the same conditions can exhibit different fracture behaviors, because of premature inter- and intra-laminar failures related to over- or under-extrusion or weak bonds among individual fibers, especially at the fusion points between the infill and the internal contour. The non-selective trans-layer and trans-fiber crack propagation observed in SEM micrographs of the fractured surface is indicative of improved bond quality, which could be explained by the adhesion-enhancing effect caused by the increase in surface roughness of individual PLA/Lignin fibers compared to pure PLA. Additionally, specimens fabricated with different CAM programs with the same input values for basic toolpath and processing parameters, exhibit different fracture morphologies, which implies that G-code generation algorithms also affect the final part's mechanical properties.
Future studies will focus on employing Design Of Experiment (DOE) techniques for systematic analysis and determination of the relation among basic toolpath and processing parameters and output measures, aiming for an overall material-based optimization of the FFF process. As far as the raw material is concerned, various methods for improving PLA compatibility with kraft lignin will be tested (addition of plasticizers and compatibilizing agents, use of lignin fractions with lower polydispersity indices, lignin chemical treatment) and their effect on the material's dynamic rheological properties will be examined. Also, thermal stability under oxidative and nonoxidative conditions, as well as thermal degradation during processing will be investigated.
This work has partially received funding from the European Union's Horizon 2020 research and innovation program MODCOMP under grant agreement No 685844 and EU FP7 Project "Functionalized Innovative Carbon Fibres Developed from Novel Precursors with Cost Efficiency and Tailored Properties" (FIBRALSPEC) under Grant Agreement No. 604248.
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Thermal mechanical characterization of copolyester for additive manufacturing using FDM
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Fire investigators are trying to determine the cause of a fire that gutted an East Farmingdale commercial building Tuesday morning, officials said.
The two-story building, which housed three companies including an audio installation company and an equipment supply company, is located at 280 Route 109 across from Republic Airport. The building and nearby businesses were evacuated after the fire broke out, fire officials said.
An employee of Audio Unlimited, the audio installation company, called to report the fire at 7:28 a.m., fire officials said. The fire was under control by 10:30 a.m.
Paul Lichtenberg, an audio-visual technician, said he had been at work since 7 a.m. when he noticed smoke around 7:20 a.m. as he worked at the back of the building.
"I could see flames through the window," said Lichtenberg, 31, of Baldwin.
He called 911 and he and four co-workers made sure everyone was out of the building, Lichtenberg said.
James Giordano, owner of Advanced Business Equipment, said he was inside his office, unaware of the fire until he saw the flames spreading through the building.
"I lost everything. But I'm fortunate to get out," said Giordano, 30, of Lindenhurst.
Around 170 firefighters from seven fire departments from Nassau and Suffolk counties responded to the scene with at least 25 units, fire officials said.
The fire shut down all lanes of Route 109 in both directions.
Assistant Chief Michael Killbridge of the East Farmingdale Fire Department said that the fire may have started in the rear of the building.
The Suffolk County arson squad was at the building as a precaution, Killbridge said.


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text:
<?php
/**
 * WC_Report_Customers
 *
 * @author      WooThemes
 * @category    Admin
 * @package     WooCommerce/Admin/Reports
 * @version     2.1.0
 */
class WC_Report_Customers extends WC_Admin_Report {

	public $chart_colours = array();
	public $customers = array();

	/**
	 * Get the legend for the main chart sidebar
	 *
	 * @return array
	 */
	public function get_chart_legend() {
		$legend   = array();

		$legend[] = array(
			'title' => sprintf( __( '%s signups in this period', 'woocommerce' ), '' . sizeof( $this->customers ) . '' ),
			'color' => $this->chart_colours['signups'],
			'highlight_series' => 2
		);

		return $legend;
	}

	/**
	 * [get_chart_widgets description]
	 *
	 * @return array
	 */
	public function get_chart_widgets() {
		$widgets = array();

		$widgets[] = array(
			'title'    => '',
			'callback' => array( $this, 'customers_vs_guests' )
		);

		return $widgets;
	}

	/**
	 * customers_vs_guests
	 */
	public function customers_vs_guests() {

		$customer_order_totals = $this->get_order_report_data( array(
			'data' => array(
				'ID' => array(
					'type'     => 'post_data',
					'function' => 'COUNT',
					'name'     => 'total_orders'
				)
			),
			'where_meta' => array(
				array(
					'meta_key'   => '_customer_user',
					'meta_value' => '0',
					'operator'   => '>'
				)
			),
			'filter_range' => true
		) );

		$guest_order_totals = $this->get_order_report_data( array(
			'data' => array(
				'ID' => array(
					'type'     => 'post_data',
					'function' => 'COUNT',
					'name'     => 'total_orders'
				)
			),
			'where_meta' => array(
				array(
					'meta_key'   => '_customer_user',
					'meta_value' => '0',
					'operator'   => '='
				)
			),
			'filter_range' => true
		) );
		?>

				<li style="border-color: <?php echo $this->chart_colours['customers']; ?>"><?php _e( 'Customer Sales', 'woocommerce' ); ?>

				<li style="border-color: <?php echo $this->chart_colours['guests']; ?>"><?php _e( 'Guest Sales', 'woocommerce' ); ?>

		<?php
	}

	/**
	 * Output the report
	 */
	public function output_report() {

		$ranges = array(
			'year'         => __( 'Year', 'woocommerce' ),
			'last_month'   => __( 'Last Month', 'woocommerce' ),
			'month'        => __( 'This Month', 'woocommerce' ),
			'7day'         => __( 'Last 7 Days', 'woocommerce' )
		);

		$this->chart_colours = array(
			'signups'   => '#3498db',
			'customers' => '#1abc9c',
			'guests'    => '#8fdece'
		);

		$current_range = ! empty( $_GET['range'] ) ? sanitize_text_field( $_GET['range'] ) : '7day';

		if ( ! in_array( $current_range, array( 'custom', 'year', 'last_month', 'month', '7day' ) ) ) {
			$current_range = '7day';
		}

		$this->calculate_current_range( $current_range );

		$admin_users = new WP_User_Query(
			array(
				'role'   => 'administrator',
				'fields' => 'ID'
			)
		);

		$manager_users = new WP_User_Query(
			array(
				'role'   => 'shop_manager',
				'fields' => 'ID'
			)
		);

		$users_query = new WP_User_Query(
			array(
				'fields'  => array( 'user_registered' ),
				'exclude' => array_merge( $admin_users->get_results(), $manager_users->get_results() )
			)
		);

		$this->customers = $users_query->get_results();

		foreach ( $this->customers as $key => $customer ) {
			if ( strtotime( $customer->user_registered ) < $this->start_date || strtotime( $customer->user_registered ) > $this->end_date ) {
				unset( $this->customers[ $key ] );
			}
		}

		include( WC()->plugin_path() . '/includes/admin/views/html-report-by-date.php' );
	}

	/**
	 * Output an export link
	 */
	public function get_export_button() {

		$current_range = ! empty( $_GET['range'] ) ? sanitize_text_field( $_GET['range'] ) : '7day';
		?>
		<a
			href="#"
			download="report-<?php echo esc_attr( $current_range ); ?>-<?php echo date_i18n( 'Y-m-d', current_time('timestamp') ); ?>.csv"
			class="export_csv"
			data-export="chart"
			data-xaxes="<?php esc_attr_e( 'Date', 'woocommerce' ); ?>"
			data-groupby="<?php echo $this->chart_groupby; ?>"
		>
			<?php _e( 'Export CSV', 'woocommerce' ); ?>

		<?php
	}

	/**
	 * Get the main chart
	 *
	 * @return string
	 */
	public function get_main_chart() {
		global $wp_locale;

		$customer_orders = $this->get_order_report_data( array(
			'data' => array(
				'ID' => array(
					'type'     => 'post_data',
					'function' => 'COUNT',
					'name'     => 'total_orders'
				),
				'post_date' => array(
					'type'     => 'post_data',
					'function' => '',
					'name'     => 'post_date'
				),
			),
			'where_meta' => array(
				array(
					'meta_key'   => '_customer_user',
					'meta_value' => '0',
					'operator'   => '>'
				)
			),
			'group_by'     => $this->group_by_query,
			'order_by'     => 'post_date ASC',
			'query_type'   => 'get_results',
			'filter_range' => true
		) );

		$guest_orders = $this->get_order_report_data( array(
			'data' => array(
				'ID' => array(
					'type'     => 'post_data',
					'function' => 'COUNT',
					'name'     => 'total_orders'
				),
				'post_date' => array(
					'type'     => 'post_data',
					'function' => '',
					'name'     => 'post_date'
				),
			),
			'where_meta' => array(
				array(
					'meta_key'   => '_customer_user',
					'meta_value' => '0',
					'operator'   => '='
				)
			),
			'group_by'     => $this->group_by_query,
			'order_by'     => 'post_date ASC',
			'query_type'   => 'get_results',
			'filter_range' => true
		) );

		$signups         = $this->prepare_chart_data( $this->customers, 'user_registered', '', $this->chart_interval, $this->start_date, $this->chart_groupby );
		$customer_orders = $this->prepare_chart_data( $customer_orders, 'post_date', 'total_orders', $this->chart_interval, $this->start_date, $this->chart_groupby );
		$guest_orders    = $this->prepare_chart_data( $guest_orders, 'post_date', 'total_orders', $this->chart_interval, $this->start_date, $this->chart_groupby );

		// Encode in json format
		$chart_data = json_encode( array(
			'signups'         => array_values( $signups ),
			'customer_orders' => array_values( $customer_orders ),
			'guest_orders'    => array_values( $guest_orders )
		) );
		?>

		<?php
	}
}

redpajama_set_name: RedPajamaGithub


text:
Review: Unsettling Truths: The Ongoing Dehumanizing Legacy of the Doctrine of Discovery by Mark Charles and Soong-Chan Rah
[1] In 2016, the ELCA Churchwide Assembly overwhelmingly passed a "Repudiation of the Doctrine of Discovery." [1] Yet in the intervening years I have noticed that most people I come across have no idea what the Doctrine of Discovery is, or how it affects not only the lives of Native Americans, but also the lives of everyone in the Americas. Mark Charles and Soong-Chan Rah have written a powerful and accessible book that explores the impact of the 15th century papal bull that mixed imperialism, greed and racism with toxic theology.
[2] It is not that Lutherans in the US have not addressed injustices towards the original peoples of the land. In the 1970's, the National Indian Lutheran Board (NILB) was active, especially in the upper Midwest, and collaborated with other Native American advocacy groups. The legacy of NILB is told in a video produced by the ELCA in 2008–"Native Nations: Standing Together for Civil Rights." [2]
[3] In 2017, the Journal of Lutheran Ethics did a whole issue on the Repudiation of the Doctrine of Discovery, [3] including an introduction by editor Carmelo Santos, a lengthy article by the legendary scholar Tink Tinker, and a reflection on the ELCA's action (or inaction) by activist Vance Blackfox. Unfortunately, these resources have not reached the vast majority of non-Indian Lutherans in the pews or in the pulpits. And the church's efforts against racism have until now largely been tone deaf to the issues faced by Native Americans.
[4] Charles and Rah offer an antidote to our cultural blindness about the ongoing damage done by the Doctrine of Discovery. They document not only how the Doctrine of Discovery has permanently damaged native peoples, but also how it has infected and corrupted Christian theology.
[5] Chapter 1 begins with a truth that ought to be self-evident. "You cannot discover lands already inhabited."[4] Describing his encounter with some Columbus re-enactors on Columbus Day in Washington, D.C., Charles reports being told by a white man, "You are not welcome here." [5] He concludes: "The fact that America calls what Columbus did 'discovery' reveals the implicit racial bias of the country–that Native Americans are not fully human." [6]
[6] The papal bulls that became the Doctrine of Discovery were established in 1452 and 1454, as a way to mediate among European powers competing to conquer non-European lands. But it did far more than mediate–it justified the European self-understanding of superiority, and gave it a theological blessing.
[7] "The Doctrine of Discovery, first directed towards Portugal, then directed towards Spain, affirmed the imperial ambitions of these two European powers. It gave theological permission for the European body and mind to view themselves as superior to the non-European bodies and minds. The doctrine created an insider perception for the Europeans while generating an outsider, other identity for non-Europeans. It created an identity for African bodies as inferior and only worthy of subjugation; it also relegated the identity of the original inhabitants of the land 'discovered' to become outsiders, now unwelcome in their own land." [7]
[8] Contemporary Lutheran readers may wonder why we even have to worry about a 15th century papal bull. After all, didn't Luther and his successors free us from the tyranny of Rome? The answer is that while Lutherans may not have been in the first wave of European invaders, like all Europeans, Lutherans benefitted from the Doctrine of Discovery. Lutherans moved into and still occupy lands taken from the original inhabitants because of the Doctrine of Discovery. Lutherans owned slaves and benefitted from a system that privileged whites and dehumanized people of color.
[9] The Doctrine of Discovery is not simply an archaic church doctrine that has had ongoing unexpected consequences. The Doctrine of Discovery has actually become part of United States law, most notoriously with the 1823 Supreme Court decision in Johnson v. M'Intosh. Charles and Rah write: "Not only did the 1823 Supreme Court led by Chief Justice John Marshall, and subsequent Supreme Court judicial interpretations, perpetuate the dehumanizing worldview of the Doctrine of Discovery, but they transformed the discovery doctrine into a modern-day legal instrument that has become the bedrock of the legal principle for land titles in the United States." [8]
[10] Since that 1823 decision numerous injustices against Native Americans can be traced to the Doctrine of Discovery. They include, but are not limited to the Indian Removal Act of 1830, the Trail of Tears (1838-9), the Indian Indenture Act (1850); the Hanging of the 38 Dakota in 1862; the Massacre at Sand Creek (1864); Wounded Knee (1890) and more recently the 2005 decision against the Oneida Nation (written by Ruth Bader Ginsburg). Referring to state-sanctioned actions as well as individual acts, Charles and Rah write: "The history of violence against Native peoples reveals how a dysfunctional theological imagination results in broken expressions of violence and injustice," [9] The authors conclude: "The implicit bias of white supremacy is alive and well in the United States of America, and is a bipartisan value that is perpetuated by nearly every US citizen (or at least every US citizen who owns or hopes to own land.") [10]
[11] What distinguishes this book from the many other books written about the Doctrine of Discovery is that this book is directed towards the church. Like Lenny Duncan, who writes with both love and sorrow in his lament, Dear Church, [11] Charles and Rah write to a church that they know and love. Both Christian Reformed in background, they are clear about why they write: "Our connection stems from our mutual love for Jesus and our mutual passion for justice, both of which have found expression in our mutual lament for the church." [12] They see their work as both education and lament, critiquing "dysfunctional theology and broken history."[13]
[12] Time and again they contrast the development of post-Constantinian Christianity with the biblical experience of Jesus. "The idea of Christendom, an earthly Christian empire, is an extra-biblical concept that is not aligned with the teachings of Jesus." [14] "The creation of a Christian empire forced a paradigm on the church that was never imagined at its beginning." [15] "The Christian imagination shifted from a mindset of suffering to a mindset of exceptionalism and triumphalism." [16]
[13] In the chapter, "Genocide, the Impact of a Dysfunctional Theology," Charles and Chan use the "I-thou" relationship to illustrate the problems inherent in the Doctrine of Discovery. "The positioning of the other as less than–as asserted by the Doctrine of Discovery–breaks the community that God had intended." [17]
[14] The authors take historical trauma seriously and address white fragility as well, noting "White America could not perpetrate 500 years of de-humanizing injustice without traumatizing itself." [18] "In treating white people as a traumatized people, people of color have the authority to maintain their own agency and humanity in a way that has not been accessible before. Oftentimes, in conversations on race, whites are viewed as those with power who should initiate the seeking of forgiveness and initiate the process of reconciliation and healing. Instead, by treating white Americans as a traumatized people, we are called to an equality in our mutual brokenness and trauma." [19]
[15] To be clear, nothing that Charles and Rah write about white people should be taken as advocating an "all lives matter" position. They do not absolve the beneficiaries of the Doctrine of Discovery because they, too, are broken. Rather, as Christians, they confess the brokenness of all humanity. They do not let white Christians off the hook of accountability.
[16] The authors are critical of contemporary Christian efforts to apologize to aggrieved peoples without offering any remedy. Citing an ecumenical gathering at Standing Rock during the Dakota Access Pipeline Crisis in 2016, Charles noted that none of the representatives of primarily white denominations had given back land, nor had they promised not to fight lawsuits over land. Their public repudiation of the Doctrine of Discovery, therefore, was little more than a photo op, with no teeth. [20]
[17] Charles and Rah outline additional challenges to the white American church: Reconciliation without conciliation; American Christians' failure to see themselves as part of a global body of Christ; individualism; confession without consequences; false security; American exceptionalism and triumphalism. Charles and Rah challenge the church: "If the American church were to confess the sin of stolen lands, broken treaties, slavery, genocide, mass incarceration, Jim Crow laws, internment camps, nuclear weapons, the New Jim Crow, and all the social sins justified by the acceptance of the heresy of Christendom, the trauma of such a confession would compel a people unable to cope with trauma to immediately seek out a form of hope." [21] They discuss the healing power of lament, and describe hope. "The hope for America does not come from a land covenant with God–it comes from the character of God. And the character of God is not accessed by our exceptionalism but through a humility that emerges from the spiritual practice of lament." [22]
[18] This book is timely as American Christians formulate their responses to the many social issues that result from the Doctrine of Discovery. In 2019, churches and others noted the 400th anniversary of bringing enslaved Africans to the Americas. Slavery and the ongoing racism and injustice are a direct result of the Doctrine of Discovery. In 2020, the death of George Floyd at the hands of police set off widespread awareness of racism, not only towards African Americans, but also towards Native Americans. The belated efforts of some professional sports teams were among the actions. Some religious institutions are beginning to consider reparations for descendants of enslaved persons. Some are arranging to return small, symbolic pieces of land to the original inhabitants.
[19] A second contemporary issue in church and society is immigration. Charles describes a conversation with a Navajo sheepherder about immigration. It became clear that the conversation was not about the 14 million undocumented people that most people talk about, but rather about the "300 million undocumented immigrants who had been pouring into this continent since 1492." [23] Maintaining that most immigration reformers, whether conservative or liberal, get it wrong, the authors state: "What most Americans miss regarding immigration reform is that without Natives at the table, the United States of America is incapable of comprehensively or justly reforming immigration law. Without Natives at the table, a generation of undocumented immigrants is trying to decide what to do with another generation of undocumented immigrants. There is no integrity in the dialogue. It does not matter if your plan is to build a wall to keep people out or if you are working to open the gate to let people in. Neither of those decisions is yours to make alone." [24]
[20] The book concludes with a challenge and a metaphor. The challenge: "The United States of America needs a national dialogue on race, gender and class. A conversation on par with the Truth and Reconciliation Commissions that took place in South Africa, Rwanda, and Canada. It must be an inclusive dialogue, not one that takes place in specific silos. And the church must be involved. But because the American church has so broadly accepted the heresy of Christian empire and because the Western church wrote the Doctrine of Discovery, the church is currently incapable of leading this dialogue. It needs to participate, but it cannot lead." [25]
[21] The metaphor: based on the book of Hosea [26]
"Jesus is the prophet.
The Western/American church is Gomer.
Our adultery is with the empire.
And our only path to healing is through lament and learning how to accept some very unsettling truths."
[22] I commend this book to Christians who want to dive deeper into how our church is part of the complex history of the ongoing harm from the Doctrine of Discovery.
[1] www.elca.org/RepudiationDoctrineOfDiscoverySPR2016pdf
[2] "Native Nations: Standing Together for Civil Rights" ELCA, 2008. https://www.youtube.com/watch?v=XPkq8vbzYas
[3] https://learn.elca.org/jle/issue/march-2017
[4] Mark Charles and Soong-Chan Rah, Unsettling Truths: The Ongoing Dehumanizing Legacy of the Doctrine of Discovery (Downers' Grove, IL, Intervarsity Press, 2019) 13.
[5] Ibid., 14.
[8] Ibid.,109.
[9] Ibid., 119.
[10] Ibid., 128.
[11] Lenny Duncan, Dear Church: A Love Letter from a Black Preacher to the Whitest Denomination in the United States (Fortress Press, 2019).
[12] Charles and Rah, Ibid., 4.
[13] Ibid., 13.
[21] Ibid., 186-187.
Jessica Crist
Journal of Lutheran Ethics April 2021: Lutheran Ethicists' Gathering Part 1 (Volume 21 Issue 2)
Native American/American Indian