bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric study of polar configurations around binaries
Authors: Giuppone C. A. , Cuello N.
Published: November 2019

Dynamical studies suggest that most of the circumbinary discs (CBDs) should be coplanar. However, under certain initial conditions, the CBD can evolve toward polar orientation. Here we extend the parametric study of polar configurations around detached close-in binaries through N-body simulations. For polar configurations around binaries with mass ratios q below 0.7, the nominal location of the mean motion resonance (MMR) 1 : 4 predicts the limit of stability for eB > 0.1. Alternatively, for eB < 0.1 or q ∼ 1, the nominal location of the MMR 1 : 3 is the closest stable region. The presence of a giant planet increases the region of forbidden polar configurations around low mass ratio binaries with eccentricities eB∼ 0.4 with respect to rocky earth-like planets. For equal mass stars, the eccentricity excitation Δβ of polar orbits smoothly increases with decreasing distance to the binary. For q < 1, Δβ can reach values as high as 0.4. Finally, we studied polar configurations around HD 98800BaBb and show that the region of stability is strongly affected by the relative positions of the nodes. The most stable configurations in the system correspond to polar particles, which are not expected to survive on longer time-scales due to the presence of the external perturber HD 98800AaAb.
Adhesive-free joining and application for flexible devices - a review
Authors: Taga Yasunori , Nishimura Keisuke , Hisamatsu Yuri
Published: November 2019

Interface has been recognized for a long time as a part of materials such as surface and grain boundary in bulk in spite of the fact that interface gives decisive influences on the performance and durability of devices in practical use. Interface is also well known to have four principal performances and roles such as mechanical, electrical, magnetic and optical properties. Here, I will at first review the interface behavior with special emphasis on materials science and then introduce typical examples of case study. Mechanical behavior of interface can be attributed to joining of different materials in particularly at low temperature and intrinsic defects introduced in the process of joining caused by difference in thermal expansion. Defects thus introduced is known to result in work hardening of interface. Recently, an epoch-making method of joining to utilize water gas adsorption layer as an adhesive agent. This gas adsorption joining (GAJ) was demonstrated in cycloolefin polymer (COP) film and borosilicate glass system. Both surfaces were first modified by atmospheric pressure plasma, followed by close lamination to reaction distance and heated at about 100°C to result in the formation of a strong covalent bond for joining. Durability thus formed system was found to remain unchanged even after weathering test in 60°C, 95%RH for 2000 hrs. Joining mechanism can be explained in terms of an increase in density of functional molecules at the interface, followed by dehydration. Thickness of joining layer was confirmed by X-ray photoelectron spectroscopy and STEM and EELS to be 1∼2nm. Sealing performance of GAJ was examined by measuring Water Vapor Transmission Rate (WVTR) by MOCON system using joined PET films on which high barrier layer was coated. The WVTR of line sealing with 1 mm width and 1-2 nm thick was found to be better than 5 x 10−4 g/m2/day. Practical applications of thus developed GAJ for joining and sealing are now in progress for flexible film devices such as OLED display, solar cells, and healthcare devices. Finally, roles of interface in materials science in future will be critically discussed.
Texture and structure formation of low-carbon low-alloy pipe steel after TMCP and heat treatment
Authors: Danilov Sergey , Semkina Iana , Pyshmintsev Igor , Lobanov Mikhail
Published: November 2019

The structure and texture of low-carbon low-alloy pipe steel after Thermo-Mechanical Controlled Processing (TMCP) and subsequent isothermal quenching were studied by the method of Electron Backscatter Diffraction (EBSD) analysis. The texture, obtained after TMCP, was formed mainly by two strong scattered orientations from {112}<110> and two weaker scattered orientations from {110}<223> and one weak orientation (001)[110]. Complex multicomponent textures were observed after heat treatment. The regions with “ferrite” and martensitic structures were identified and analyzed using Oxford Instruments HKL software. Orientations, constituting textures for both selected areas types, are associated with the basic orientations of the initial deformed austenite grains, formed during the hot deformation by orientation relationships (OR), transitory between Kurdjumov-Sachs OR and Nishiyami-Wasserman OR.
Engineered composite polymer sheets with enhanced thermal conductivity
Authors: Der Oguzhan , Edwardson Stuart , Marengo Marco , Bertola Volfango
Published: November 2019

An innovative type of engineered composite polymer sheet with enhanced thermal conductivity is described and tested. The concept is to sandwich a closed-loop serpentine channel, cut out in a polypropylene sheet and containing a self-propelled liquid-vapour mixture, between two sheets of the same material bonded by selective laser welding. Polymer materials are widely used to replace metals in different applications, however sometimes this is not possible because of their poor thermal conductivity. Thin, flexible and low-weight polymer sheets can be advantageous in various aerospace, aircraft and portable electronic applications where the device weight and its mechanical flexibility are crucial. The transient and steady-state thermal response of a prototype engineered polymer sheet was characterised for different heat power levels and spatial orientations. The equivalent thermal conductance, calculated from the surface temperatures at opposite ends of the sheet, increases four to six times in comparison with a composite polypropylene sheet without working fluid.
Elastic, Electronic, and Optical properties of NaSnX (X=Sb, Bi, As): First principle calculations
Authors: Koc Husnu , Mamedov Amirullah M , Ozbay Ekmel
Published: November 2019

In the present work, the structural, mechanical, electronic and optical properties of NaSnX (X=Sb, B, As) compounds have been investigated by means of first principles calculations. The generalized gradient approximation has been used for modeling the exchange-correlation effects. It has been observed that the calculated lattice parameters are in good agreement with the experimental and theoretical lattice parameters. Bulk modulus, shear modulus, Young’s modulus Poisson’s ratio, sound velocities and the Debye temperatures using the calculated elastic constants for NaSnSb, NaSnBi and NaSnAs compounds have been obtained. The electronic band structure and the projected density of states corresponding to the electronic band structure have calculated.and interpreted. The obtained electronic band structure for NaSnSb and NaSnBi compounds are metallic in nature, and the NaSnAs compound is also a narrow semiconductor. Based on the obtained electronic structures, we further calculated the frequency-dependent dielectric function, the energy-loss function, optical conductivity, and reflection along the x-and z-axes.
The Diagnostics of Optical and Thermal Characteristics of Semitransparent Media at Modeling Phase Influence of Oscillating Convection and Thermoradiation
Authors: Zagumennov Fedor A. , Merzlikin Vladimir G. , Bystrov Andrey V.
Published: November 2019

The paper suggests diagnostics method of non-stationary combined regime heating of semitransparent materials base on an evaluation of the interconnected complex of optical parameters (extinction – brad
, scattering-σ and absorption κ indices) and thermophysical (thermal diffusivity aT
and conductivity coefs) ones using simulation the general temperature field

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including the additive terms due to the convective and radiation fluxes with a phase shift

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within the external oscillating (frequency ω ) heat load.A one-dimensional problem of finding the temperature for a semitransparent material in the absence of aggregative transitions, neglecting long wavelength re-emission was considered in the analytic representation. The classical solution (of the homogeneous heat equation) and the particular one (of the inhomogeneous one with an internal thermal radiant source) defined summable terms with independent phases

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The obtained formulas for specific temperature distributions allow you to use them to estimate values of optical and thermal parameters of a semitransparent material from experimentally recorded phase jumps of the temperature field during the action of alternate impact of initial phased convective and radiation components of the external heat flux. The results of the study can be used both for experimental diagnostics and to select the heat regimes for combined radial and convective processing of semitransparent ceramics, composites, and biomaterials.
Effect of composition and heat treatment on porosity and microstructures of technical ceramics made from kaolin and IG-017 additive
Authors: Kurovics Emese , Gömze László A. , Ibrahim Jamal Eldin F. M. , Gömze Ludmila N.
Published: November 2019

Based on conventional kaolinite and IG-017 bio-original additives of IGREX Ltd. the authors have developed new ceramic composite materials for different industrial purposes. In this work, different powder mixtures of kaolinite and IG-017 bio-original additive were milled and uniaxially pressed at different compaction pressures into cylindrical discs, after compaction, the discs were sintered in electric kiln under oxidation atmosphere and in oxygen-free atmosphere. Using the oxygen-free sintering process, new high porosity ceramic materials were created. Through the examination of the microstructure of the produced specimens the authors have found that the ceramic structure is reinforced with carbon nanofibers.
Computer Modeling of the Stress-Strain State of the Cervical Spine Segment
Authors: Rikun Yu A , Сhaikovskaya(Kolmakova) T V , Kulkov S N
Published: November 2019

The article presents the results of the calculation of the stress-strain state of the C3-C4 segment of the cervical spine at flexion forward. The results of the calculations showed that there is the change in the deformation behavior of the segment and the change in the localization areas of the largest tensile and compression stresses at the increase in the elastic modulus of the intervertebral disk.
Unique microstructural and mechanical properties of Al-Zn alloys processed by high-pressure torsion
Authors: Chinh Nguyen Q. , Kovács Zsolt
Published: November 2019

Al-Zn alloys with different Zn concentrations between 2 and 30 wt.% were processed by high-pressure torsion (HPT) to produce ultrafine-grained (UFG) materials. Microstructural and mechanical and properties of these UFG alloys were then investigated using depth-sensing indentations (DSI), focused ion beam (FIB), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Emphasis was placed on the decomposition due to the HPT process, as well as on its effects on the mechanical properties of the UFG alloys. For low Zn contents, HPT gave strengthening due to grain refinement while for the highest Zn concentration the decomposition of the microstructure yielded an abnormal softening at room temperature. The microstructure decomposition led also to the formation of a Zn-rich phase, which wets the Al/Al grain boundaries and enhanced the role of grain boundary sliding with unusually high strain rate sensitivity. The occurrence of intensive sliding in these UFG alloys at room temperature is demonstrated by deforming micro-pillars, illustrating a potential for the effective application of these UFG materials in micro-devices
Corrosion of glass used for radioactive waste disposal influenced by iron corrosion products
Authors: Dabbas Ali AL , Kopecskó Katalin
Published: November 2019

Iron corrosion products of the steel canister in the nuclear waste container are highly silica sorptive materials and very much expected to delay formation of the protective layer (gel) on the nuclear glass interface. This study is focusing on the role of the iron carbonates (ankerite), which is probably one of iron corrosion products and already exists in the clay structure of the disposal depth. Simulating nuclear borosilicate glass samples (alternative to the R7T7-type) samples are planned to leach in different series of experimental models with dissimilar quantities of ankerite. Batch experiments all will be cultivated in synthetic groundwater; where different pH (4-9) values and temperatures (35, 50, 90 °C) are considered. In this paper the state of the art of the radioactive waste glass corrosion in the circumstances of deep geological disposal will focus on the role of ankerite as one of the iron corrosion products and clarify how it is expected to show delay in achieving the Si saturation status and accelerate glass alterations.
Time evolution of ZnO-CNT photoluminescence under variable ambient and temperature conditions
Authors: Rauwel P , Galeckas A , Rauwel E
Published: November 2019

ZnO-CNT hybrid materials were prepared by non-aqueous sol-gel routes at 240ºC. The morphology and defects have been studied by transmission electron microscopy and photoluminescence spectroscopy. The hybrid nanostructures manifest a broad luminescence emission covering the visible spectrum. Variations in photoluminescence with time are observed for the ZnO-CNT hybrid structures exposed to different ambient and temperatures. The studies show that photoluminescence from adsorbed oxygen dominates the emission emanating from other intrinsic defects and also affects the stability of the latter over time.
Formation of iron sulfide photocatalytic colloidal dispersion via pulsed laser ablation in liquids
Authors: Vála Lukáš , Vavruňková Veronika , Jandová Věra , Pola Michal , Křenek Tomáš
Published: November 2019

Pulsed laser irradiation of iron sulfide in water and ethanol allows laser ablation and generation of FeS nano/micro particles. Measurement of the size distribution reveals 100, 1000 and 5000 nm sized particles in water and 180 nm sized particles in ethanol. The values of zeta potential: 13.2 mV for colloid in water confirm incipient stability and tendency for coagulation whereas the value: -40.6 mV shows good stability of ablatively achieved nanoparticles in ethanol. SEM analyses of particles obtained by evaporation of solvents on Ta substrate revealed shapeless, roundshape and sheet-like morphology of agglomerates whose size span from units up to tens of µm. Also spherical particles sized around tens of nm were detected. EDX shows Fe/S ratio ∼3.25 and ∼ 1.2 for particles ablated in water and ethanol respectively. Raman spectroscopy indicates the formation of mackinawite (Fe1+xS) and pyrrhotite (Fe1-xS) phase. The photocatalytic effect of prepared water colloid was tested in methylene blue (MB) degradation under the daylight.
The Effect of Heat Input Parameters on Residual Stress Distribution by Numerical Simulation
Authors: Hasan Alhafadhi Mahmood , Krallics Gyorgy
Published: November 2019

This paper deals with Numerical Simulation to analyze the behavior of residual stresses in the plate. The residual stresses at the surface of some weld specimen by using the finite element technique. The results of the numerical simulation analysis were compared with three cases data to evaluate the accuracy of Goldak model (double ellipsoidal heat distribution model). Based on this study, a modeling procedure with reasonable accuracy was investigated. The developed finite element modeling was used to investigate the effects of welding heat input on magnitude and distribution of welding residual stresses in a welded plate made of steel. The different directions of residual stresses in the surface of the plate of 25 mm thick for V-groove shape were studied. It is shown that the welding heat input parameters have a significant effect on the magnitude and distribution of residual stresses.
Local mechanical properties of advanced skutterudites processed by various routes
Authors: Buršík Jirí , Buršíková Vilma , Rogl Gerda , Rogl Peter
Published: November 2019

Skutterudites are an important class of thermoelectric p- and n-type materials and they have already achieved fair efficiencies for the conversion of heat to electricity. Nevertheless researchers try to further enhance the figure of merit, ZT, by various ways. In this work we compare the microstructure and mechanical properties of an industrial p-type DDyFe3CoSb12 skutterudite powder processed by several routes containing various combinations of ball milling, hot pressing, cold pressing and high pressure torsion. Details of the resulting microstructure are studied by means of analytical electron microscopy as well as by means of local mechanical testing.
The effect of the synthetic fibre reinforcement on the fracture energy of the concrete
Authors: Juhász K P
Published: November 2019

Fibre reinforced concrete belongs to the group of composite materials, where matrix means the concrete, and fibres mean the various shaped (straight, hooked, wavy, etc.) and material (steel, polypropylene, glass, etc.) fibres, which are short compared to the size of concrete elements. Fibres are mixed in fresh concrete which supposedly provides a perfect and uniform mix. Although material of the fibres can be different (steel and synthetic polypropylene are the most widespread), material models in literature are primarily for steel fibres. Elastic modulus of steel and synthetic fibres differs from each other in terms of scale (steel 210 GPa, synthetic 8-12 GPa), despite this, however, similar results are received frequently at bending beam tests. The different result lies in the energy absorption of the fibres pulling out from the concrete matrix. In the present paper, this different behaviour is examined and a suggested material model for fibre reinforced concrete is presented. This material model is based on the modification of the fracture energy.
Synthesis and Powder Properties of Cerium Phosphate White Pigments
Authors: Onoda Hiroaki , Muraki Haruka
Published: November 2019

Catalytically active cerium dioxide is used as light reflection materials for cosmetic applications. Herein, as novel white pigments for use in cosmetics, cerium phosphates were prepared under various conditions. The chemical composition, powder properties, photocatalytic and oxidation catalytic activities, color phase, and smoothness of the cerium phosphates were evaluated. Samples prepared from cerium (+III) nitrate solution indicated XRD pattern of cerium phosphate hydrate. All samples prepared in this work had large particles and no specified shape. The obtained cerium phosphates exhibit little photocatalytic activity and no oxidation catalytic activity. These samples exhibit a little low reflectance within the range of visible light and 71-78 in L* value.
Porous geopolymers: processing routes and properties
Authors: Kovárík Tomáš , Hájek Jirí
Published: November 2019

Cellular ceramics constitute a specific class of materials containing a high level of porosity, greater than 60 vol%, which are characterized by the presence of three-dimensionally arranged open and/or closed cells. Because of their structure, cellular ceramics exhibit a unique combination of properties such as low density, low thermal conductivity, low thermal mass, high permeability, high thermal shock resistance and high specific surface area, making them essential for various engineering application. Nowadays, porous geopolymers have been the focus of promising research in the field of porous inorganic materials because of their unique combination of good thermal stability and excellent mechanical properties. An interesting technological feature is that their solidification kinetics is easily adjustable and thanks to ceramic-like structure they have significant structural stability at elevated temperatures. The processing methods used for the fabrication of porous geopolymers can be divided into various approaches. Many methods have been explored to synthesize reproducible porous sponges or foams from geopolymer systems, such as gaseous method, rapid solidification, foaming, freeze-casting and/or combination of them. Concerning the macro/micro-structure of cells, the processing can be strongly influenced by various characteristics as a chemical composition, rheological behaviour of the slurries, kinetics of pore formation and hardening behaviour. This study presents methods of processing and manufacturing approaches with respect to types of porous materials and experimental results in this field.
Detection technique of the optical and thermoradiative characteristics with compensation effect of reflection and transmittance indicatrices for the semitransparent materials with high subsurface scattering
Authors: Merzlikin Vladimir G. , Bystrov Andrey V. , Smirnov Sergey V.
Published: November 2019

The experimental set-up is developed for detection of reflection and transparence coefficients of semitransparent materials within visible and IR radiation diapasons. The peculiarity of the set-up is using the spectral photometric integrating spheres for effect compensation of reflection indicatrices of tested materials with fixed wavelengths 0.63 µm 1.15 µm (near IR), 2.79 µm and 3.39 µm (middle infrared) of probing laser radiation. In the first case the integrating sphere is a photometric ball which made from porous fluoroplastic with high reflectivity up to 97-99%. For the second range an aluminum sphere (sand blasting) was used. The application of the photometric sphere reduced the measurement error, connected with different sensitivity of photosensors to beam slope angle of detected radiation reflected (transmitted) for flat material samples with different indicatrices of reflection (transmission). The proposed method of experimental measurements of spectral photometric characteristics of reflection and transparent improve the accuracy of theoretical estimations of the optical (thermoradiation) parameters (absorption and scattering indexes), as well as the functions of a thermal radiation heat source for the calculation of temperature fields in semitransparent materials. For the first time, a computational and experimental estimation of scattering and absorption indexes (with an accuracy not less than 1%) were carried out for semitransparent materials with high scattering (porous ceramics based on stabilized zirconium dioxide) in the middle infrared range of wavelengths which is most problematic for optical measurements.
The Properties of Bolus Material using Silicone Rubber
Authors: Sutanto Heri , Marhaendrajaya Indras , Jaya Gede Wiratma , Hidayanto Eko , Supratman Astri Suppa , Astuti Santi Yuli , Budiono Tris , Firmansyah Muhammad Agus
Published: November 2019

Bolus is a material equivalent to tissue and used in radiotherapy process to increase a dose surface using electron beam. The bolus synthesis from a material equivalent to tissue is not easy, one of the alternative materials used is silicone rubber (SR). In this research bolus was synthesized with dimension of length x width x thickness is (17 x 17 x 1) cm3. Bolus has been characterized by CT-Scan to find relative electron density (RED) and linear accelerator (LINAC) to investigate percentage of surface dose (PSD) with two energy (8 MeV and 10 MeV). The RED value for bolus is 1.176, these results show the RED value for bolus between soft tissue and solid tissue. The PSD value at 8 MeV and 10 MeV are 102.32% and 101.32%, respectively. These results indicate that the silicone rubber material can be used as an alternative bolus material because it corresponds to the bolus function in radiotherapy.
Metamaterial Antenna on Electro-Optic Modulator for Wireless Terra-Hertz Detection Through Radio-Over-Fibre Technology
Authors: Wijayanto Yusuf Nur , Fathnan Ashif Aminulloh , Kanno Atsushi , Mahmudin Dadin , Daud Pamungkas
Published: November 2019

We propose a new metamaterial antenna on electro-optic (EO) modulator for wireless terra-hertz detection through radio-over-fibre (ROF) technology. By wireless terra-hertz signal irradiation to the proposed device, strong terra-hertz electric field can be induced on the electric- LC metamaterial resonator. The induced terra-hertz electric field can be used for optical modulation through EO effects when a light-wave propagates into an optical waveguide located under the capacitive gap which the strongest induced terra-hertz electric field. Analysis of optical modulation is presented in details for operational frequency of 0.1 THz. The device fabrication process and the results of its measured characteristics are also reported.
Effect of Sodium Dodecylbenzene Sulfonate as Anionic Surfactant on Water based Carbon Nanofluid Performance as Quench Medium in Heat Treatment
Authors: Oktavio L , Ramadhani C A , Rakhman D , Harjanto S , Putra W N
Published: November 2019

Quenching is performed as part of steel heat-treatment to enhance mechanical properties, by rapid cooling. Factors that affect the selection of quench medium are hardenability of material, geometry, and dimensions of the component. In recent developments, nanofluids are used to improve heat transfer capacity. In this research, nanofluids were synthesized using the two-step method. Milling of particles was done using a high energy ball mill for 15 hours at 500 rpm. Observation of particle size, material composition, and morphology of particle, and surface changes of the particle were measured by Field-Emission Scanning Electron Microscope (FE- SEM), and Energy Dispersive X-Ray Spectroscopy (EDX). Water-based nanofluids with a volume of 100ml were produced using the two-step method, with carbon concentrations of 0.1%, and 0.5% and Sodium Dodecylbenzene Sulfonate concentrations of 0%, 1%, 3%, and 5%. Samples of S45C steels were austenized at 1000°C for 60 minutes. Hardness testing results correspond to the severity of the quenching mediums, with peak hardness of 845 HV for 0.1% Carbon with 1% SDBS, and 878 HV for 0.5% carbon with 3% SDBS. Hardness testing results show a significant improvement over results without SDBS addition. Excess surfactant addition yields a lower hardness due to the re-agglomeration of particles.
Effect of Particle Size Distribution on the Preparation of Bonded NdFeB Permanent Magnet
Authors: Kurniawan C. , Wahyuni S. , Ramlan  , Setiadi E. A. , Sebayang P.
Published: November 2019

In this paper, the effect of particle size distribution on the preparation of bonded NdFeB isotropic permanent magnets was investigated. Different particle size distribution of NdFeB powders was prepared by sieving method using standard test sieves of #100, #200, and #325 meshes. Varied distribution of particle size was mixed with 3 wt% of epoxy binder and compacted by uniaxial hydraulic pressing machine to produce bonded isotropic green body. Bonded NdFeB green body was cured by vacuum drying machine under temperature 100 °C for 4 hours with vacuum pressure of 10 mbar. The characterization performed were bulk density measurement, particle size analysis, microhardness Vickers, SEM image and hysteresis curve. We find that the hardness of bonded NdFeB magnets decreased as the particle size decreases. Contrary to common belief that the finer powder with sharply particle size distribution not always give the highest product characteristics. The optimum characteristics of bonded NdFeB was obtained by the mixture of #100+#200 meshes powders with bulk density, hardness, magnetic remanence, coercivity, and energy product of 5.87 g/cm3, 88 HV, 6.5 kG, 11.15 kOe, and 9.4 MGOe, respectively. Therefore, the middle range of particle size distribution is effective to obtain high quality bonded NdFeB permanent magnets.
Synthesis of Magnetite Nanoparticles via Co-precipitation Method
Authors: Fadli Ahmad , Komalasari  , Adnan Arisman , Iwantono  , Rahimah  , Addabsi Adela Shofia
Published: November 2019

Magnetite (Fe3O4) nanoparticles becomes a new innovation that gets attention of biomedicine scientists. Magnetite can be applied to cancer treatment as a drug carrier because it’s good biocompatibility and very low toxicity. The purpose of this study was to determine the effect of temperature and stirring rate on the magnetite particle characteristics prepared by co-precipitation method. Firstly, FeCl3 and FeCl2 with 2:1 mole ratio were reacted with 10% NH4OH at 40 - 80°C temperatures and stirring speed of 300 - 500 rpm in a beaker glass. Subsequently, the precipitate was separated using filter paper and it dried into air oven at 100°C. The properties of obtained magnetite powder were determined using XRD and SEM. From XRD pattern indicates that magnetite formed at all temperatures with crystallite diameter in the range of 10-12 nm. The SEM results indicate the agglomeration of the magnetite particles with size in the range of 2.7 to 3.3 μm. In the other hand, the higher of temperature and stirring rate of agitation will make the agglomeration of the particles become more uniform. The increasing of temperature and the stirring rate will increase the magnetite crystallinity level.
The Role of Nano-SiC on Characteristics of Mg-Al-Sr/Nano-SiC Composites Produced by Stir Casting Route
Authors: Sartika Vioni Dwi , Syahrial Anne Zulfia
Published: November 2019

Magnesium composite with Mg-Al-Sr matrix reinforced by nano-SiC has successfully fabricated by stir casting process. Addition of nano-SiC into magnesium matrix varies by 0.05; 0.10; 0.15; 0.20; and 0.25 in percent of volume fraction (Vf-%). The optimum mechanical properties are found in composition of 0.15 Vf-% nano-SiC. The number of hardness, impact toughness, and wear rate of this composition are 68.4 BHN, 0.065 Joule/mm2, 1.03310−5mm3/mm respectively. Addition of 0.15 Vf-% nano-SiC enhances the hardness by 26%, impact toughness by 23.57%, and wear resistance by 38.40% respectively. Furthermore, the existence of nano-SiC in Mg-Al-Sr matrix modify the microstructure of composite by dispersing the intermetallic compounds. However, it is observed that higher nano-SiC content tends to agglomerate thus the strengthen mechanism cannot effectively occur. Microstructure analysis using OM and SEM reveals that the addition of nano-SiC transforms the dendritic matrix to globular equiaxed. EDX result predicts the phases formed are α-Mg, Al4Sr, Mg17Al12, MgAlSr, and XRD analysis finds the existence of SiC, SiO2.
Polyetherimide nanofiltration membranes modified by interfacial polymerization for treatment of textile dyes wastewater
Authors: Febrianto Gabriel , Karisma Doni , Mangindaan Dave
Published: November 2019

Azo dyes are the major type of textile dye in the world, owing to their stability to light, microbial degradation, and physical degradation due to washing. However, these properties also lead to problematic removal or degradation of azo dyes that pollute the water body. In this research, nanofiltration (NF) thin film composite (TFC) membranes based on polyetherimide (PEI) polymer are utilized to remove an azo-based dye from a simulated textile wastewater, namely Reactive Black 5 (RB5). PEI is firstly dissolved by using N-methyl-2 pyrollidone (NMP) as solvent, combined with acetone as a non-solvent, and converted to be membranes via phase inversion method. The created membrane will be further modified by interfacial polymerization (IP) method using trimesoyl chloride (TMC) and m-phenylene diamine (MPD) as precursors of acyl chloride and amine, immersed in two immiscible liquids of hexane and water, respectively. This method fabricates a new selective layer composed of tightly-packed nylon-like polyamide layer that might improve the separation performance. Membranes from polymeric dope solution of PEI/acetone/NMP 15/65/20 (w/w) were employed due to acceptable flux and rejection, compared to other formulations. They were then modified by using IP method (0.05% TMC in hexane and 1.5% MPD in water) to create PEI-TFC membranes. The PEI-TFC membranes exhibited fluxes around 0.01 L m−2 h−1 psi−1, with rejection of RB5 dyes up to 90%, which suggested the successful IP method on the PEI membranes. SEM and FTIR were carried out for comprehending the reasons behind the improved separation performance, and they revealed that the TFC nylon-like selective layer was successfully developed, from both physical and chemical perspectives, respectively. The fabrication of NF TFC membranes might open some new roads for environmental application of membranes in Indonesia.
On The Application of Diffusion Magnetic Resonance Imaging for Study of Agarose
Authors: Dwihapsari Yanurita , Zakiah Salma Niatu , Darminto
Published: November 2019

The precise and accurate measurements of material properties are needed in biomaterial and tissue engineering study to better describe the properties of material and ensure the product quality Diffusion Magnetic Resonance Imaging (MRI) is used in biomaterial study as a biomarker for composition and structure of biomaterial and a tool to observe mechanical properties of materials. The previous study predicted the mechanical properties of polyvinyl alcohol (PVA)-based material for biomedical phantom using diffusion MRI. The measurement was performed based on water diffusion inside gel and the method only worked for a certain concentration of PVA. In this study, Diffusion MRI was used to observe water diffusion of agarose as a potential hydrogel material for phantom development and tissue-mimicking materials.
Simulation of Feed Modulation on Dynamic Fixed-Bed Reactor for CO Methanation over Ni-based Catalyst
Authors: Nuravifah Utari , Putri Sarah Eka , Wibisono Yogi , Budhi  , Rizkiana Jenny
Published: November 2019

The hydrogénation of CO to produce synthetic natural gas (SNG) is highly exothermic and usually catalyzed by nickel as an active site. These reactions are typically conducted under elevated pressures and low temperatures to shift the reversible reactions to the products. However, conducting reaction under such low temperature is kinetically limited. An alternative method that can be applied to ameliorate this limitation is by conducting a dynamic operation. This study focused on model development and reactor approach for dynamic fixed-bed operation intended for CO methanation. One dimensional pseudo-homogeneous reactor model was developed for a typical laboratory scale by neglecting internal and external diffusion based on Weisz-Prater, Anderson, and Mears criteria. The gas phase model was governed for compounds in the bulk phase. The model consisted of the dynamic term, convective term, diffusive term, and source term. The design criteria involving pressure drop, ratio of the height of catalyst bed to particle diameter (LB/dp), ratio of reactor diameter to particle diameter (dr/dp), ratio of bed length to reactor diameter (LB/dr) and axial dispersion were taken into consideration. A kinetic model to complement the simulation was taken from literature. The reactor model was simulated for steady-state and unsteady-state operation with optimum feed composition. The result of steady-state model simulation was considered as a base case and comparison to judge the reactor performance under unsteady-state operation. Modulating the value of the inlet CO fraction in step function was introduced to the unsteady-state model in order to enhance methane production. The simulation results showed that the highest methane production could be achieved by modulating CO inlet fraction between 0.45 and 0.4 with the overall switching time of 25 s.
Spin Current Generation in One – Dimension Spin – Chain Model of Insulating Magnetic Interface
Authors: Cahaya Adam B. , Majidi M. A.
Published: November 2019

In a system of a thin ferromagnetic layer sandwiched by non-magnetic metals, the precession of magnetization of the ferromagnetic layer has been shown to generate spin current in the adjacent non-magnetic metals. The spin current arises from the spin-dependent scattering that is originated by the exchange interaction between the magnetic moment and the spin of adjacent normal metal’s electron. While the theory was originally studied in magnetic multilayer that consists of a thin ferromagnet sandwiched by non-magnetic materials, to be able to describe a more realistic ferromagnetic layer, we need to study how magnetic moments far from the interface can influence the spin current generation. We use a simple model one dimension ferromagnetic spin chain to show the criteria in which the collective movements of the spin moments can enhance the spin current generation.
The Ion Transport Characteristics of Chitosan Composite Membranes ‘Ch-AgNP’ with Emphasis on the Amount of Filler
Authors: Rupiasih Ni Nyoman , Suharta W. G. , Sumadiyasa Made , Ketut Putra I , Mega Trisnayani Putri Ni Made Ayu
Published: November 2019

In this study, we report about the characteristics of ion transport of chitosan composite membranes “chitosan-silver nanoparticle”. The chitosan composite membranes were prepared by a casting method using chitosan as a matrix, silver nanoparticle (AgNP) as filler, and acetic acid 1% as a solvent. The various amount of filler added e.g. 10, 100, 250, 500, 750, and 1000 μg. These membranes called chitosan composite membrane Ch-AgNP10, Ch-AgNP100, Ch-AgNP250, Ch-AgNP500, Ch-AgNP750, and Ch-AgNP1000. A membrane without AgNP has also been prepared named chitosan membrane (Ch membrane) as a comparison. The ion transport experiments conducted by using a cell model consisting of two chambers, chamber 1 and 2, and the area of the membrane was 9.616 cm2. The driving force used is a gradient concentration (dC/dx). The electrolyte solutions used were KCl and CaCl2 with concentrations of 0.1, 1, 10, 100, 250, 500, 750, and 1000 mM. The voltage difference (V) is measured using Ag/AgCl electrodes which connected to a voltmeter. All measurements were done at room temperature, 28.1°C. The result showed that the obtained Jdiff -V curves of chitosan composite membranes are similar to Jdiff -V curves of Ch membrane, where the diffusion current densities of chitosan composite membranes increased with increasing the concentration gradient of solution. It also depends on the electrolyte solutions. The diffusion current density of chitosan composite membranes had affected by the amount of AgNP added that is increased as increasing the mass of AgNP added.
Influence of Inorganic Binder Composition on the Structure-Property Relationship of Monolithic Dye-sensitized Solar Cells with Carbon-based Counter Electrode
Authors: Nursam N M , Shobih  , Rosa E S , Hidayat J , Mubarak Z
Published: November 2019

In order to fabricate a low-cost dye-sensitized solar cell (DSSC), carbon has become a highly preferred catalytic material as counter-electrode, particularly for DSSC with monolithic structure. This paper presents novel synthesis method of carbon-based composite pastes using two types of carbon material, i.e. carbon nanopowder and activated carbon. The concentrations of the inorganic binder added to the composite pastes were varied to investigate their effect on the physical properties of the counter electrode and the electronic properties of the constructed monolithic DSSC. The inorganic binder used in this work was titanium dioxide nanoparticles, Evonik P25. After optimization, power conversion efficiency of 0.221% was achieved by the monolithic DSSC with counter electrode composite comprising activated carbon and titanium dioxide with weight concentration of 0.5 g and 0.25 g, respectively. Characterizations using gas sorption technique showed that the shape of the hysteresis curves obtained for all composites resembled the isotherm curve Type II and H3, indicating the presence of micropores. Furthermore, higher concentration of titanium dioxide nanoparticles as binder led to counter electrode with lower surface area. The solar cell efficiency, however, was found to be not only correlated to the surface area or the binder composition, but it was also determined by the type of the carbon material.
Synthesis of Geopolymer from Blends of Tropical Biomass Ashes
Authors: Samadhi Tjokorde Walmiki , Wulandari Winny , Suroto Afiana , Agung Dendi Satriya
Published: November 2019

Thermal conversion of biomass to produce energy inevitably generates ash as residual matter. Therefore, sustainable utilization of biomass should also consider reuse measures for the ash. This research examines the conversion of locally available biomass ashes in Indonesia into geopolymer. This is an environmentally more benign alkali-aluminosilicate alternative to the ordinary Portland cement produced by low-temperature reactions between aluminosilicates and concentrated alkali solution. Biomass ash sources in this study are corn stover, coconut shell, and sugarcane bagasse. Biomass ash blends are prepared according to a ternary simplex centroid mixture experiment design. These blends are reacted with activator solutions containing NaOH and Na-silicate and blended with sand aggregate to produce geopolymer mortar specimens. Early compressive strengths of geopolymer mortars range from 7.2 to 10.4 MPa, which surpasses the SNI 15-2049-2004 national standard for Portland cement with low heat of hydration. Statistical analysis of the experimental data indicates that the early strength as a function of biomass ash blend formulation is represented by a quadratic mixture model. Bagasse ash produces the highest strength. The quadratic terms consist of bagasse-corn and bagasse-coconut antagonistic blending terms. Morphology of the geopolymer mortar fracture surface indicates good bonding with the sand aggregate. Extensive acicular crystal growth within the amorphous geopolymer gel phase is observed in lower-strength formulations, which points to the formation of zeolite-like phase in the geopolymerization process. While the correlation of biomass ash type to the structure of the resulting geopolymer is yet to be established, this work has clearly identified the technical feasibility of producing geopolymer with satisfactory strength from tropical biomass ashes.
𝐾-theory and 0-cycles on schemes
Authors: Gupta Rahul , Krishna Amalendu
Published: November 2019

We prove Bloch’s formula for 0-cycles on affine schemes over algebraically closed fields. We prove this formula also for projective schemes over algebraically closed fields which are regular in codimension one. Several applications, including Bloch’s formula for 0-cycles with modulus, are derived.
Analgesic Efficacy of Nerve Blocks After Abdominoplasty: A Systematic Review
Authors: Vonu Peter M , Campbell Paul , Prince Noah , Mast Bruce A
Published: November 2019

Background

A variety of regional nerve blocks have been utilized in abdominoplasty procedures, including transversus abdominis plane (TAP), intercostal, rectus sheath (RS), pararectus + ilioinguinal/iliohypogastric, quadratus lumborum, and paravertebral blocks. No consensus exists regarding the most effective nerve block modality in optimizing postprocedural comfort levels.

Objectives

The purpose of this systematic review was to explore the efficacy of the various abdominal nerve blocks employed in abdominoplasty surgery and to draw attention to any modality that may be superior in regards to effectiveness and/or administration.

Methods

Utilizing Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic review was performed to identify studies that have employed regional nerve blocks in abdominoplasty procedures. Opioid consumption, pain scores, time to ambulation, time in the recovery room, and time to first analgesia request were extracted when available.

Results

A total of 191 articles were reviewed, of which 8 met inclusion criteria. The nerve blocks represented included TAP, RS, pararectus + ilioinguinal/iliohypogastric, intercostal, and quadratus lumborum. All modalities were effective in reducing opioid consumption except quadratus lumborum.

Conclusions

TAP, RS, pararectus + ilioinguinal/iliohypogastric, and intercostal regional nerve blocks have been shown to optimize postoperative pain management in abdominoplasty procedures. The existing literature suggests that when studied against one another, TAP is more efficacious than RS and pararectus + ilioinguinal/iliohypogastric. When ultrasound guidance is unavailable, consideration should be given to TAP employing the direct visualization approach.

Level of Evidence: 2
Does vegetation change over 28 years affect habitat use and reproductive success?
Authors: Fierro-Calderón Karolina , Martin Thomas E
Published: November 2019

Individuals should prefer and use habitats that confer high fitness, but habitat use is not always adaptive. Vegetation in natural landscapes changes gradually and the ability of species to adaptively adjust their habitat use to long-term changes is largely unstudied. We studied nest patch and territory use over 28 yr in Orange-crowned Warblers (Oreothlypis celata) in a system that has undergone natural long-term changes in vegetation. Abundance of maple (Acer grandidentatum), its preferred nesting habitat, gradually declined from 1987 to 2015. We examined whether habitat use and its fitness consequences changed as the availability of preferred habitat decreased. We used resource selection function models to determine changes over time in the probability of using a nest patch given available patches, and the probability of using a territory given available territories. We estimated nest survival to evaluate changes over time in the fitness consequences of nest patch use. We also compared habitat use (nest patch and territory) and fitness (nest survival) between areas with naturally reduced abundance of maple and experimentally increased abundance of maple (fenced areas). Nest patch use depended on maple abundance and did not change drastically across 28 yr, even though the availability of preferred maple patches decreased over time. In contrast, nest survival tended to decrease over time. We did not see differences in nest patch use and nest survival between unfenced and fenced areas, unlike territory use, which increased with the abundance of maple in fenced areas and decreased in unfenced areas. Our study depicts one example of relatively unchanged habitat use in the face of decreased availability of preferred vegetation across years, with a resulting decrease in reproductive success. Investigating changes in habitat use and fitness consequences for animals exposed to long-term habitat change is necessary to understand adaptive behavioral responses.