Variations In Material Composition Research Articles

E-Brachy: New dosimetry package for electronic brachytherapy sources.

Large reported variability in the material composition and geometrical components of the Xoft electronic high-dose-rate brachytherapy Causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of thesources. This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetricproperties. E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by themanufacturer. The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles , reaching a peak at cm and . The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller values, but at higher polar angles, they increased to 300%. A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations ofTG-56.

Stochastic Nanoroughness Inhibits and Reverses Glial Scarring In Vitro and In Vivo via a Mechanobiology Paradigm Involving Piezo‐1

AbstractPhysical insult to the central nervous system (CNS) such as during electrode insertion leads to reactive astrogliosis which in turn contributes to glial scarring (GS). To date, reducing GS in these settings has focused on pharmacological agents and variations in electrode material composition or implantation procedures, and the role of electrode surface topography has remained unexplored. Since proteoglycans, a major component of GS tissue, possesses very well‐defined (nano) topography, a role for stochastic nanoroughness in glial scar formation is theorized. Using an in vitro system, we provide proof of concept that on substrates possessing stochastic nanoroughness corresponding to that of healthy astrocytes, glial scar formation is significantly inhibited, and more importantly, can be even reversed, and it involves signaling via the stretch‐activated cation channel Piezo‐1. In vivo studies reveal an absence of astrocytes aggregation along the electrode track of chronically implanted electrodes modified with stochastic surface nanoroughness, compared to non‐modified electrodes, while signal detection within the superior colliculus remains unaffected. These findings shedlight on the crucial role of stochastic biophysical cues in modulating GS formation; and offer a promising non‐chemical approach for engineering neural biomaterials interface for the CNS.

Biomechanical Evaluation of a Locally Manufactured Modular External Fixator for Tibial Shaft Fractures

Background: Modular external fixations used in the Philippines are manufactured abroad, leading to high costs and limited availability, making them unaffordable for most Filipino patients. The reliability of some external fixators is limited because not all have undergone biomechanical testing. Objective: This study aims to determine the biomechanical stability of locally manufactured modular external fixator clamps (iFIX) versus commercially available fixators (Roger-Anderson) for tibial shaft fractures. Methodology: The biomechanical stability (stiffness, yield, ultimate strength) under loading of the local prototypes compared with the commercially available fixators. Result: No slippage was observed in all rods, pins, and clamps in all groups. No bending occurred in any rods or pins in all groups. There was also no apparent deformation of the internal threading of the pins within the tibial analogs. The commercial fixator group’s ultimate load to failure up was double (110.57% difference) that of the local prototype. Conclusion: The differences in the biomechanical performance between the iFIX and Roger-Anderson clamps may be attributed to variations in clamp material composition. The iFIX fixator exhibited lower stiffness but did not display deformation under axial loading, component displaced slippage, or thread loosening, making it comparable to the commercial fixator.

Pembuatan Briket Biomassa Berbahan Baku Kulit Pisang Kepok dan Kulit Pisang Raja dengan Aditif Tempurung Kelapa

Energy sources that promise to replace our dependence on fossil fuels include biomass waste sources. This study studied the characteristics of biobriquettes from variations of kapok banana peels plus coconut shells and variations of plantain peels added coconut shells with variations in the addition of tapioca adhesive. This study was designed with fixed variables of variation in raw material composition with a sample of 90:10; 80:20; 70:30 (grams) and tapioca adhesive composition 10; 20; 30; 40; 50 (%). Banana peels that have dried naturally are then carbonized with a temperature of 300°C -350°C for 3 hours. The process of making biobriquettes begins with the crushing of charcoal and filtering charcoal grains so that a grain size of 60 mesh is obtained. Then the charcoal is mixed between kapok banana peel charcoal and plantain with coconut shell charcoal with a variation of 90:10; 80:20; 70:30 (grams) then the variation of the charcoal mixture is mixed with tapioca flour as an adhesive with variation 10; 20; 30; 40; 50 (%). Then formed biobriquette dough, then molded with a pressure of 100 kg / cm2 and dried under the hot sun. Furthermore, the charcoal is characterized by 5 parameters, namely moisture content, ash content, bound carbon content and calorific value test and compressive test. The best results for banana kepok obtained from this study were in a sample of a mixture variation of 70:30 grams with a variation of a 20% tapioca adhesive mixture. With a moisture content value of 6.95%, ash content of 16.6%, bound carbon content of 60.45%, calorific value of 6,539.04 cal/g and a compressive test value of 86.98 kg/cm2. The best results for plantains obtained from this study were in samples of mixed variations of 70:30 grams with variations of tapioca adhesive mixtures of 50%. With a moisture content value of 7.09%, ash content of 15.8%, bound carbon content of 62.31%, calorific value of 5,415.14 cal/g and a compressive test value of 89.69 kg/cm2. The results obtained in this study for water content, ash content and bound carbon content have not met, then for calorific values and compressive tests have met SNI 01-6235-2000 standards, which are ≥ 5,000 cal / g.

Characterization on the mesostructural properties of asphalt mixtures based on meso-element equivalence method

The randomness and variation of material composition at the meso-scale lead to some limitations in the application of asphalt mixture. When all features are taken into account, the computational effort increases significantly. Therefore, the relationship can be established using the meso-element equivalence method (MEEM). In this paper, the effects of aggregate-asphalt interface, initial void defects and material damage were introduced and MEEM of asphalt mixture was established based on industrial computed tomography (ICT) and finite element method (FEM). The rationality of the model was verified by laboratory performance tests, and the effects of aggregate type, mixture gradation and mesostructural parameters on the mechanical response of MEEM were compared and analyzed. The results showed that the MEEM model captures the mechanical behavior of asphalt mixtures well, the input of visco-elastic material parameters is an important step of MEEM simulation accuracy. The aggregate type, the discrete degree of the skeleton structure and the distribution characteristics of mesostructural parameters are important factors affecting the mechanical properties of asphalt mixture in MEEM.

The Hirshfeld topological surfaces, volumes, and their voids charge density interplay on radiation shielding properties: A case study of carbide-based ceramics

Transition metal carbides (TMCs) are explored for their potential as radiation shielding materials, with a focus on their γ-ray attenuation properties. These high-density materials, including WC, TaC, HfC, NbC, and VC, are evaluated across an energy range of 0.015–15.0 MeV. Notably, at low incoming photon energy (0.0150 MeV), these TMCs exhibit mass attenuation coefficients (MAC) (TMC, MAC (g/cm2)): (WC, 130.417), (TaC, 125.730), (HfC, 120.873), (NbC, 23.751), and (VC, 32.377) and effective atomic numbers (Zeff) from 22.69 to 73.68. These values surpass those of silicon dioxide (SiO2), highlighting the superior γ-ray attenuation capabilities of TMCs. TMCs exhibit a distinct trend in MAC values, with tungsten carbide (WC) consistently demonstrating the highest MAC values, making it the most efficient γ-ray attenuator. Hafnium carbide (HfC) closely follows, with tantalum carbide (TaC) exhibiting lower MAC values, while niobium carbide (NbC) and vanadium carbide (VC) display the lowest values. These differences can be attributed to variations in material composition and structure. Furthermore, the study delves into the impact of charge density within Hirshfeld voids on LAC values, revealing that as X⁴⁺ … C interactions increase due to higher charge density, LAC values rise. This fine-tuning of topological and charge density distributions within the crystal's voids offers a promising avenue to optimize these materials for enhanced radiation shielding effectiveness. Overall, this research contributes to the understanding of the potential utility of TMCs in radiation shielding applications, showcasing the interplay between crystal structure, composition, and charge distribution as key factors in determining their radiation attenuation capabilities.

The Casimir, Van der Waals, and electrostatic forces’ effects on the response of magneto-electro-elastic nanosensor/switch beams under thermal environment

This study investigates the impact of Casimir, Van der Waals, and electrostatic forces on nanomechanical switches’ thermomechanical and free vibration behavior. The analysis is conducted using a novel higher-order beam theory and the nonlocal strain gradient elasticity. The motion equations of the nanosensor/switch beam are derived using Hamilton’s principle and solved using Navier’s method for general boundary conditions. The nanoswitch is composed of electroelastic barium-titanate (BaTiO3) and magnetostrictive cobalt-ferrite (CoFe2O4) materials, which are modeled using a power-law approach to account for functionally graded material property variations across the beam’s thickness. The impact of different parameters, such as Casimir, Vander Waals, electrostatic forces, and variations in material composition, size parameters, and gap distance, on a nanoswitch system’s bucking and free vibration is comprehensively examined. With the intermolecular and electrostatic forces, the temperature dependency of barium-titanate and cobalt-ferrite nanoswitch materials, which have not been extensively studied in any previous research, is considered in the modeling of free vibration, and the buckling behavior of a nanoswitch for the first time. This research represents the first comprehensive analysis of these factors. Considering the investigated parameters, the study’s findings can provide helpful insights into developing micro/nano-electromechanical systems, including switches, sensors, and actuators.

Rapid Climate Links Between High Northern Latitudes and Tropical Southeast Asia Over the Last 40 ka

AbstractThe climate response of tropical Southeast Asia to abrupt climate change originating from high northern latitudes remains poorly understood. Here, marine sediments recovered from the Northwest Borneo Trough are analyzed to trace variations in terrigenous material composition associated with sea level and palaeoflood activities over the past 40 ka. We describe for the first time the influence of sea level change on terrigenous deposition from a tropical island with small mountainous rivers surrounded by narrow continental shelves and the coupling between North Atlantic dynamics and climate feedbacks in tropical Southeast Asia during the Dansgaard‐Oeschger stadials. This study demonstrates that climate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia through the functions of sea level, the East Asian winter monsoon and the Intertropical Convergence Zone. Such information is fundamental to correctly assessing future sea level rise and flood risks in tropical Southeast Asia.

Reservoir Characteristics and Controlling Factors of Large-Scale Mono-Block Gas Field Developed in Delta-Front Sandstone—A Case Study from Zhongqiu 1 Gas Field in the Tarim Basin

Taking the Zhongqiu 1 Gas Field in the Tarim Basin as an example, the heterogeneity of large-scale mono-block gas fields and their primary controlling factors have been analyzed. Based on drilling core data, well log data, scanning electron microscopy, thin-section analysis, and mercury injection experiments, combining sedimentological interpretation, research on the reservoir characteristics and variability was carried out. The results showed that: (1) The lithologic characteristics showed obvious variations among wells in the Zhongqiu 1 gas field. Specifically, the main lithology developed in the Zhongqiu 1 well is feldspar lithic sandstone, while the remaining wells predominantly consist of lithic feldspar sandstone. These differences in rock composition maturity reveal that a higher proportion of stable mineral components leads to poorer reservoir properties; (2) the main factors controlling oil and gas productivity include the variations in petrology, mineralogy, and diagenetic process characteristics. The high content of unstable mineral components and constructive diagenesis could increase reservoir porosity together. (3) Sedimentary facies of the Bashijiqike Formation in the Zhongqiu 1 Gas Field played a dominant role in the reservoir distribution. The division of sedimentary facies zones reflects variations in material composition and grain size, serving as the main material basis for reservoirs. Differences in mineral composition reflect the sedimentary environment of the reservoir. Additionally, mineral composition indicates the relationship between diagenetic processes and reservoir evolution. The high feldspar content in well ZQ1 corresponded to relatively favorable reservoir properties. The dominant feldspar type was plagioclase, suggesting that early-stage chemical weathering had undergone significant alteration. The above conclusions provided a microscopic perspective to explain the differences in oil and gas production capacity of large delta-front gas fields, serving as a geological basis for the exploration and exploitation of similar fields.

Accuracy of thermal microsensors embedded in orthodontic retainers of different material composition and thickness: An in vitro study

Abstract Objectives: The present research aimed to assess the accuracy and precision of the TheraMon® microsensor embedded in different thicknesses of Hawley retainers (HR) for comparison with vacuum formed retainers (VFR). Methods: Thirty microsensors contained within different thicknesses and composition of retainers were divided into three equal groups: Group A thick coverage HR (3 mm), Group B thin coverage HR (1 mm), and Group C VFR (1 mm). The microsensors were immersed in thermostatic water at a controlled temperature of 35°C, which corresponds to the average intra-oral temperature. After 1 week, data were gathered using the TheraMon® client software and analysed using ANOVA and Turkey’s HSD tests. Results: All TheraMon® microsensors were functional and produced uninterrupted recordings during the 1-week test period. Thermal detection differed between the three removable retainer groups. A near accurate thermostatic water detection was noticed with the thin HR with a mean temperature of 34.81 ± 0.04°C, followed by VFR 34.77 ± 0.09°C, and finally the thick HR 34.73 ± 0.05°C (ANOVA p-value = 0.025). A between-group comparison showed a significant mean difference (MD) between the thin and thick HR groups (MD: 0.08, p-value = 0.01). However, there were no significant differences between VFR and neither the thick Hawley (MD: 0.04, p-value = 0.27) nor the thin Hawley group (MD: -0.03, p-value = 0.39). Conclusion: A removable retainer’s variation in material thickness and composition could induce small but detectable changes in the precision of thermal detection by TheraMon® microsensors.

Machine Learning for Parametrical Analysis of Friction Stir Welded Aluminum Metal Matrix Composites

The research focuses on the behaviour and process parametric influence on friction stir welded Al metal matrix composites reinforced with varied percentages of SiC, B4C, and Mg. The experimentation involves fabrication of Al metal matrix composites followed by friction stir welding and, subsequently, evaluation of the joint properties in terms of mechanical strength, microstructural integrity, and quality. In comparison to other joints with varied base material compositions, the weld exhibits refined grains and uniform distribution of hybrid particles in the joint region, resulting in increased strength. Higher SiC composition adds to greater strength, better wear characteristics, and harness, whereas B4C percentage is linked to hardness. The maximum ultimate tensile stress for a particular sample was determined to be around 160MPa, while the maximum percentage elongation was found to be around 165 for 10% SiC and 3% B4C. As the amount of SiC declines and that of B4C rises, the percentage elongation decreases. In samples with a B4C weight percentage of 10%, the greatest hardness measured was around 103Hv. For a load of 30N, the wear rate was as high as 12gm/s with a SiC weight percentage of 10. For lower load values and a higher percentage of B4C, the wear rate often decreased. Chemical properties are barely changed. Therefore, the materials keep their original qualities after welding. During the non-destructive testing process, no large cracks, pores, or clusters of pores are found, indicating that the weld is of good quality. To achieve a satisfactory weld, optimal ranges based on analysis using machine learning of rotary tool speed, tool linear velocity, transverse speed are maintained. Linear Regression algorithm, Random Forest algorithm and Lasso Regression algorithms are being used and the results are also compared. This work covers a wide range of topics, and the results are found to have improved significantly in most cases and is in good agreement with data previously presented in the literatures.

Impact of zirconia slurry in steel powder on melt pool characteristics in laser powder bed fusion

Purposedding dopants to a powder bed could be a cost-effective method for spatially varying the material properties in laser powder bed fusion (LPBF) or for evaluating new materials and processing relationships. However, these additions may impact the selection of processing parameters. Furthermore, these impacts may be different when depositing nanoparticles into the powder bed than when the same composition is incorporated into the powder particles as by ball milling of powders or mixing similarly sized powders. This study aims to measure the changes in the single bead characteristics with laser power, laser scan speed, laser spot size and quantity of zirconia nanoparticle dopant added to SS 316 L powder.Design/methodology/approachA zirconia slurry was inkjet-printed into a single layer of 316 SS powder and dried. Single bead experiments were conducted on the composite powder. The line type (continuous vs balling) and the melt pool geometry were compared at various levels of zirconia doping.FindingsThe balling regime expands dramatically with the zirconia dopant to both higher and lower energy density values indicating the presence of multiple physical mechanisms that influence the resulting melt track morphology. However, the energy density required for continuous tracks was not impacted as significantly by zirconia addition. These results suggest that the addition of dopants may alter the process parameter ranges suitable for the fabrication of high-quality parts.Originality/valueThis work provides new insight into the potential impact of material doping on the ranges of energy density values that form continuous lines in single bead tests. It also illustrates a potential method for spatially varying material composition for process development or even part optimization in powder bed fusion without producing a mixed powder that cannot be recycled.

An Approach for Automated Disassembly of Lithium-Ion Battery Packs and High-Quality Recycling Using Computer Vision, Labeling, and Material Characterization

A large number of battery pack returns from electric vehicles (EV) is expected for the next years, which requires economically efficient disassembly capacities. This cannot be met through purely manual processing and, therefore, needs to be automated. The variance of different battery pack designs in terms of (non-) solvable fitting technology and superstructures complicate this. In order to realize an automated disassembly, a computer vision pipeline is proposed. The approach of instance segmentation and point cloud registration is applied and validated within a demonstrator grasping busbars from the battery pack. To improve the sorting of the battery pack components to achieve high-quality recycling after the disassembly, a labeling system containing the relevant data (e.g., cathode chemistry) about the battery pack is proposed. In addition, the use of sensor-based sorting technologies for peripheral components of the battery pack is evaluated. For this purpose, components such as battery pack and module housings of multiple manufacturers were investigated for their variation in material composition. At the current stage, these components are usually produced as composites, so that, for a high-quality recycling, a pre-treatment may be necessary.

Performance study of fibre reinforced functionally graded concrete pipes

The focus of the study is to develop Functionally Graded Concrete (FGC) and examine its performance in concrete pipes. FGC is concrete produced with variation in material and structure composition leading to changes in the overall behaviour of structures. In this study, functional gradation is created using micro steel fibre and basalt fibre. The FGC was prepared by varying the fibre content in concrete. The proposed functionally graded concrete consists of two-layer. One layer with fibre reinforced concrete and conventional concrete of M30 on the other side. The study has two major stages. The earlier stage is adopted to study the mechanical performance of the fibre reinforced concrete with 0.25%, 0.5%,0.75% and 1% addition of volumetric fraction to the conventional concrete mix. Compressive strength, split tensile strength, and flexural strength are taken as the mechanical parameters for consideration. FGC with a volumetric fraction of 0.75% with 0.75 h/H, where h/H ratio is the thickness of FGC to overall thickness, proved to be efficient. In the second stage, the optimum FGC is utilised to cast the Functionally graded concrete pipes (FGCP). This stage involves studying the performance of FGCP using three edge bearing tests and post crack studies. In the initial stage, Micro steel fibre reinforced concrete shows higher mechanical performance than basalt fibre, and basalt fibre shows better performance in post crack behaviour. The pipe testing indicates that micro steel fibre has higher strength aspects. Basalt fibre shows higher ductility in post crack behaviour. The micro steel fibre FGCP in strength perspective in both mechanical and post crack strength is higher than conventional concrete and Basalt FGCP.

Pengaruh Komposisi dan Temperatur Material Biokomposit Terhadap Kinerja Kampas Rem Non Asbestos

This research is focused on developing and evaluating the performance of brake pads made of biocomposite from teak wood, coconut shell charcoal, aluminum and polyurethane resin. Asbestos material which is widely used in brake pads friction material is carcinogenic which is harmful to health. Nine specimens with different material compositions were made to analyze their mechanical properties as brake lining friction materials. The results obtained in this study hardness will increase at higher specimen numbers. Specimen 10 as a comparison has a hardness level that is not much different from specimens number 6, 7, and 8. Wear of specimens with variations in material composition has a lower level of wear on specimens with higher hardness levels. Meanwhile, the effect of temperature and the interaction of the two variables has no significant effect on the level of wear.

Numerical Modeling and a Parametric Study of Various Mass Flows Based on a Multi-Phase Computational Framework

Gravity-driven mass flows are typically large-scale complex multi-phase phenomena involving multiple interacting phases. Various types of mass flows usually exhibit distinct behaviors in their formation, propagation and deposition. In such large-scale geological systems, many uncertainties may arise from the variations in material composition and phase behavior. The present study aims to investigate the important characteristics of some common types of mass flows including debris flows, mudflows and earth flows, based on a recently developed multi-phase computational framework, r.avaflow for flow simulation. Fractions of different phases are varied to reflect different characteristics of material composition of various mass flows and simulate the resulting flow behavior. The evolution of the critical entities during the flow motion, such as velocity, peak discharge, flow height, kinetic energy, run-out distance and deposition is examined; considerable differences among various flows are identified and discussed. Overall, the simulated mudflow cases develop higher velocity, peak discharge, kinetic energy, and longer run-out distance than the debris flow cases. The fluid fraction has a significant influence on the flow dynamics; a higher fluid fraction often leads to higher velocities and long run-out distances, but lower kinetic energy, and it also affects the final deposition and deposition pattern considerably. The present study shows promising potential of a quantitative approach to the physics and mechanics of mass flows that may assist in the risk assessment of such large-scale destructive geological hazards or disasters.

Differences in accumulation patterns of low-rank coalbed methane in China under the control of the first coalification jump

The considerable variations in coalbed methane (CBM) production in different low-rank basins have attracted widespread attention. Moreover, the occurrence of the “first coalification jump” (FCJ) has increased the uncertainty in the accumulation law. Following systematic sample collections of different ranks and lithotypes, the variation of material composition, methane source, reservoir properties, occurrence state, and enrichment rule under FCJ control was studied. Low-rank CBM is mainly obtained from microbial gases abundantly found in lignite and subbituminous coal. The microbial methane of lignite and sub-bituminous coal accounted for about 86.46% and 77.83%, respectively. As its maturity increases, thermogenic gas can provide a supplement to methane in subbituminous coal. Lignite has a low degree of coalification and retains a large amount of primary plant tissue structure. It is characterized by high porosity and a high proportion of macropores. The low adsorption capacity and high porosity result in a substantially higher proportion of free gas in lignite reservoirs than in subbituminous coal reservoirs. The free gases in lignite reservoirs have stronger mobility and are easily enriched in the structural culmination. Owing to coalification, the subbituminous coal’s porosity is considerably reduced. Thus, micropores and transition pores dominate subbituminous coal. The methane adsorbed in subbituminous coal is primarily concentrated in the stagnant area in the syncline and mixed “thermogenic/microbial” genetic areas. It is difficult to use a unified model to explain the gas distribution. Therefore, taking typical types of basins (foreland, craton, and fault subsidence basins) as examples, we summarize the differences in low-rank CBM enrichment patterns under FCJ control and provide a basis for detailed exploration and efficient development of CBM.

Process optimization and optimal tolerancing to improve dimensional accuracy of vat-photopolymerized functionally graded hydrogels

Functionally graded hydrogels with variation in material composition are useful for a variety of applications in domains like biomedical engineering and soft robotics. Recent developments in 3D printing have enabled the production of such graded hydrogels. However, the variation in the composition of these hydrogels layer-wise can be challenging in terms of selecting optimal 3D printing process parameters and maintaining geometrical accuracy. Unless corrective measures are taken, the variations in material composition can cause a loss in print fidelity and lead to dimensional deviations in the printed samples. In-depth studies have not been reported to address these challenges in the 3D printing of functionally graded hydrogels, and guidelines are not available for correcting the geometric deviations so produced. In this work, we study the deviations in lateral dimensions in functionally graded polyethylene glycol diacrylate (PEGDA) hydrogels produced using digital light processing (DLP) 3D printer and present a method to correct these deviations. The methodology involves specification of optimal printer parameters for each material composition and giving appropriate tolerances on the CAD model. The lateral dimensions of the printed part depend on PEGDA concentration, exposure time, layer thickness and print time. For obtaining accurate samples after printing and swelling, the printer parameters must be changed whenever a change in material composition occurs. Further, the printer parameters have to be chosen such that swelling induced cracking is reduced while maintaining good print fidelity. The tolerance on the CAD model has to consider the lateral deviation that occurs at the edges due to printing and the bulk increase that occurs due to swelling. We demonstrate this method by printing functionally graded PEGDA samples with good print fidelity and dimensional accuracy.

Mechanical Properties of Coconut Particle Board with Variation of Material Composition

The research carried out is a laboratory experimental research withmake particle board from coconut coir, with variations in the composition of fibers and powders used are 100 % - 0%, 90 % - 10 %, 80 % - 20 %, and 70 % - 30 % using urea formaldehyde adhesive in order to determine the mechanical properties, and find a good composition of coconut coir particle board. Sampling was carried out at the Forestry Laboratory of the Muhammadiyah University of West Sumatra. The tests were carried out at the Civil Polytechnic Laboratory of Unand, and at the Agricultural Product Technology Laboratory of Unand. The independent variables in this study were thickness and composition variation. The dependent variable is density, flexural strength or MOR. Control variables are temperature, adhesive content, particleboard thickness, compression pressure, and drying time. Data were taken by repeated measurements of 5 samples. Based on the results of the research that has been carried out, it was found that the use of coconut coir powder particles as an outer coating for particleboard at different percentages has an influence on the mechanical properties of the particle board. From the results of the study, it was found that particleboard with a composition between fiber and coconut coir powder (90% - 10%) was the best result because the less powder used resulted in good mechanical properties with a density of 0.52 g/cm3 and flexural strength or MOR 159, 43 Kg/cm2.

A new mixing equation for bed material composition in bed form dominant conditions

Vertical mixing beneath the bed surface and its effect on sediment composition has long been underestimated. This paper proposes a mixing equation to illustrate the temporal and spatial variations of bed material composition for bed form dominant rivers. A continuous mass conservation equation for elevation-specific nonuniform bed material composition is initially presented. A vertical mixing equation is finally derived as a diffusion-type partial differential equation with a source term characterized by a vertical diffusion coefficient and the geometric dimensions of bed forms. Coupled with boundary conditions, this equation is further developed in a vertical mixing model at the scale of bed forms, in which the variations of bed material composition are clearly illustrated. The equation accounts for vertical exchange fluxes driven by bed form migration and their effect on bed material composition, which helps elucidate the mixing mechanism. In application to riverbed degradation, the proposed equation is capable to describe armoring development in consideration of the interior mixing, which provides more satisfying predictions for bed surface materials. The new mixing equation helps gain insight into predicting the variations of bed material composition during morphological changes.