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Records with Subject: Materials
Showing records 1 to 25 of 81. [First] Page: 1 2 3 4 Last
Efficiency Evaluation of the Ejector Cooling Cycle using a New Generation of HFO/HCFO Refrigerant as a R134a Replacement
Bartosz Gil, Jacek Kasperski
September 21, 2018 (v1)
Subject: Materials
Keywords: ejector, entrainment ratio, HFO-1234yf, HFO-1243zf, HFO-R1234ze(E), hydrofluoolefins
Theoretical investigations of the ejector refrigeration system using hydrofluoroolefins (HFOs) and hydrochlorofluoroolefin (HCFO) refrigerants are presented and discussed. A comparative study for eight olefins and R134a as the reference fluid was made on the basis of a one-dimensional model. To facilitate and extend the possibility of comparing our results, three different levels of evaporation and condensation temperature were adopted. The generator temperature for each refrigerant was changed in the range from 60 °C to the critical temperature for a given substance. The performed analysis shown that hydrofluoroolefins obtain a high efficiency of the ejector system at low primary vapor temperatures. For the three analyzed sets of evaporation and condensation temperatures (te and tc equal to 0 °C/25 °C, 6 °C/30 °C, and 9 °C/40 °C) the maximum Coefficient of Performance (COP) was 0.35, 0.365, and 0.22, respectively. The best performance was received for HFO-1243zf and HFO-1234ze(E). How... [more]
The Effect of Thermal Shocking with Nitrogen Gas on the Porosities, Permeabilities, and Rock Mechanical Properties of Unconventional Reservoirs
Khalid Elwegaa, Hossein Emadi
September 21, 2018 (v1)
Subject: Materials
Keywords: brittleness ratio, cryogenic fracturing, fracability index, nitrogen gas, P-wave velocity, permeability, porosity, rock mechanical properties, thermal shock, unconventional reservoirs
Cryogenic fracturing is a type of thermal shocking in which a cold liquid or gas is injected into a hot formation to create fractures. Research has shown that like traditional hydraulic fracturing, cryogenic fracturing could improve oil/gas recovery from unconventional reservoirs. Research has also shown, though, that, unlike traditional hydraulic fracturing, which uses water-based fluids, cryogenic fracturing limits and can even heal damage that is near the wellbore. Previous studies on thermal shocking, however, have generally examined only a few parameters at a time. To provide a more complete overview of the process, this study examines the effects of thermal shocking with low-temperature nitrogen gas on the porosities, permeabilities, and rock mechanical properties of unconventional reservoirs. Three cycles of thermal shocking were applied to a core sample and an outcrop sample from an unconventional reservoir. Each sample was heated at 82 °C for 1 h, and then nitrogen at −18 °C w... [more]
Synthesis of the ZnO@ZnS Nanorod for Lithium-Ion Batteries
Haipeng Li, Jiayi Wang, Yan Zhao, Taizhe Tan
September 21, 2018 (v1)
Subject: Materials
Keywords: anode, electrochemical performance, lithium ion battery, ZnO@ZnS nanorod
The ZnO@ZnS nanorod is synthesized by solvothermal method as an anode material for lithium ion batteries. ZnS is deposited on ZnO and assembles in nanorod geometry successfully. The nanosized rod structure supports ion diffusion by substantially reducing the ion channel. The close-linking of ZnS and ZnO improves the synergetic effect. ZnS is in the middle of the ZnO core and the external environment, which would greatly relieve the volume change of the ZnO core during the Li⁺ intercalation/de-intercalation processes; therefore, the ZnO@ZnS nanorod is helpful in maintaining excellent cycle stability. The ZnO@ZnS nanorod shows a high discharge capacity of 513.4 mAh g−1 at a current density of 200 mA g−1 after 100 cycles, while a reversible capacity of 385.6 mAh g−1 is achieved at 1000 mA g−1.
Thermally Induced Mechanical Stress in the Stator Windings of Electrical Machines
Bishal Silwal, Peter Sergeant
September 21, 2018 (v1)
Subject: Materials
Keywords: electrical machines, mechanical stress, stress, switched reluctance machines, temperature, thermal analysis
The lifetime of an electrical machine mainly depends on the thermal overloading. Modern day applications of electrical machines on one hand require compact machines with high power density, while on the other hand force electrical machines to undergo frequent temperature cycling. Until recently, in the case of electrical machines, the main factor related to the degradation of the winding insulation was thought to be the thermal oxidization of the insulation materials. It has now been revealed that thermal overloading can also induce mechanical stress in the windings of electrical machines, which over time could lead to fatigue and degradation. In this paper, a comprehensive study of the thermally induced mechanical stress in the windings of an electrical machine is presented. The study is performed using combined thermo-mechanical models. The numerical results are validated by experiments on a segmented stator winding set-up.
Design and Prototyping Medium-Frequency Transformers Featuring a Nanocrystalline Core for DC⁻DC Converters
Dante Ruiz-Robles, Vicente Venegas-Rebollar, Adolfo Anaya-Ruiz, Edgar L. Moreno-Goytia, Juan R. Rodríguez-Rodríguez
September 21, 2018 (v1)
Subject: Materials
Keywords: DAB, design methodology, medium frequency transformer, nanocrystalline core
Medium frequency transformers (MFTs) are a key component of DC⁻DC dual active bridge (DAB)-type converters. These technologies are becoming a quintessential part of renewable energy solutions, such as photovoltaic systems and wind energy power plants, as well as in modern power grid interfaces functioning as solid-state transformers in smart-grid environments. The weight and physical dimensions of an MFT are key data for the design of these devices. The size of an MFT is reduced by increasing its operating frequency. This reduction implicates higher power density through the transformer windings, as well as other design requirements distinct to those used for conventional 60/50 Hz transformers; therefore, new MFT design procedures are needed. This paper introduces a novel methodology for designing MFTs, using nanocrystalline cores, and tests it using an MFT⁻DAB lab prototype. Different to other MFT design procedures, this new design approach uses a modified version of the area-product... [more]
Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids
Mauricio Aljure, Marley Becerra, Mattias E. Karlsson
September 21, 2018 (v1)
Subject: Materials
Keywords: electric discharges, mineral oil, nanofluids, streamer inception
Positive and negative streamer inception voltages from ultra-sharp needle tips (with tip radii below 0.5 μm) are measured in TiO₂, SiO₂, Al₂O₃, ZnO and C60 nanofluids. The experiments are performed at several concentrations of nanoparticles dispersed in mineral oil. It is found that nanoparticles influence positive and negative streamers in different ways. TiO₂, SiO₂ and Al₂O₃ nanoparticles increase the positive streamer inception voltage only, whilst ZnO and C60 nanoparticles augment the streamer inception voltages in both polarities. Using these results, the main hypotheses explaining the improvement in the dielectric strength of the host oil due to the presence of nanoparticles are analyzed. It is found that the water adsorption hypothesis of nanoparticles is consistent with the increments in the reported positive streamer inception voltages. It is also shown that the hypothesis of nanoparticles reducing the electron velocity by hopping transport mechanisms fails to explain the resu... [more]
Instability Analysis of Supercritical CO₂ during Transportation and Injection in Carbon Capture and Storage Systems
Il Hong Min, Seong-Gil Kang, Cheol Huh
September 21, 2018 (v1)
Subject: Materials
Keywords: carbon capture and storage (CCS), CO2 pipeline, flow instability, stability map, supercritical CO2
Captured CO₂ is in a subcritical state, whereas CO₂ deep underground is in a supercritical state because of the high geothermal heat and pressure. The properties of CO₂ can change rapidly at the critical point and in the near-critical region during the transportation and injection process. This study aims to identify the instabilities in the CO₂ flow in these regions, along with the causes and effects, during the transportation and injection process, and propose relevant design specifications. Thus, the critical points and near-critical region of CO₂ flow were numerically analyzed. The unstable region is presented in terms of temperature and pressure ranges, and the changes in the CO₂ properties in this region were analyzed. In the unstable region, the sudden change in density was similar to the density wave oscillation of a two-phase flow. The CO₂ stability map we obtained and the stability map of supercritical water show similar trends. Flow instability was also found to occur in sta... [more]
An Experimental Investigation of Thermal Characteristics of Phase Change Material Applied to Improve the Isothermal Operation of a Refrigerator
Seok-Joon Lee, Seul-Hyun Park
September 21, 2018 (v1)
Subject: Materials
Keywords: eutectic molten salt compounds, functional duct unit, phase change material, T-history method, thermal properties
We investigated the thermal performance of a refrigerator with a functional duct unit (FDU) which was charged with a phase change material (PCM) and designed to replace the existing expandable polystyrene (EPS) duct unit. Since the performance of the FDU is dependent upon the thermal characteristics of the PCM, the eutectic water⁻salt solution as the PCM was prepared and tested to optimize the thermal characteristics. The thermal properties of the PCM were examined by the T-history method. When the PCM contained 1 wt.% eutectic molten salt compounds, the phase change temperature was approximately −0.5 °C, the supercooling temperature was approximately −2.9 °C, and the latent heat was 304.9 kJ/kg. Compared with other PCMs of different eutectic molten salt concentrations, this PCM was found to have the most appropriate thermal properties for the FDU. Therefore, the PCM with 1 wt.% eutectic molten salt compounds was used in the FDU, which was installed in a 200 L top-mounted freezer (TMF)... [more]
Effect of Sodium Chloride and Thiourea on Pollutant Formation during Combustion of Plastics
María E. Iñiguez, Juan A. Conesa, Andrés Fullana
September 21, 2018 (v1)
Subject: Materials
Keywords: catalyzed medium, ClBzs, inhibition, NaCl, PAHs, plastic mixture
Thermal decomposition of different samples containing a mixture of plastics (polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and nylon) combined with NaCl and metal oxides (Fe₂O₃, CuO) was studied under an air atmosphere at 850 °C using a reactor, followed by analysis of the evolved products. Combustion runs were performed to study how the presence of such compounds influences the production of pollutants. Here, we report the analyses of the emissions of the main gases, as well as volatiles and semivolatiles, including polyaromatic hydrocarbons (PAHs), polychlorinated benzenes and phenols, and polybrominated phenols. Results show that the production of chlorinated pollutants did not increase in the presence of NaCl, but the presence of other metals during the decomposition led to the production of a great amount of pollutants. In this regard, the emission of chlorinated phenols increased from 110 to ca. 250 mg/kg when the sample included a small quantity of a t... [more]
Estimation of Energy Requirement of Jatropha Curcas L. Seedcake Briquettes under Compression Loading
Tatiana Ivanova, Abraham Kabutey, David Herák, Cimen Demirel
September 21, 2018 (v1)
Subject: Materials
Keywords: briquettes compaction, economic value, energy consumption, force-deformation curve, jatropha seedcake
The energy requirement of Jatropha curcas L. seedcake of different dimensions (4.5, 5.6, 6.7, 8 and 10 mm) for briquette compaction was investigated under compression loading (100, 200, 300 and 400 kN) using the universal compression-testing machine. The parameters measured and/or calculated were the deformation, thickness, numerical energy and theoretical energy. The statistical analysis results show that compression forces had a significant effect (P-value < 0.05) on the amounts of deformation and thickness, while that of the dimensions of the sample did not. The increase in compression forces increased the numerical energy while that of samples dimensions caused a decrease. Using the tangent curve mathematical model; the force coefficient of mechanical behaviour (kN), the deformation coefficient of mechanical behaviour and the fitting curve function exponent were determined for describing the experimental dependency between the force and deformation curves as well as the numerica... [more]
Evaluation on Tensile Behavior Characteristics of Undisturbed Loess
Shixin He, Haibo Bai, Zhiwei Xu
September 21, 2018 (v1)
Subject: Materials
Keywords: constitutive relation, fracture, loess, tensile strength, test apparatus, water content
Tensile strength is one significant parameter involved in tensile fracture in soil mechanics. In this paper, a stress-controlled, uniaxial, direct-tension test apparatus was developed to investigate the tensile properties of soils. A limited number of investigations have examined the impact of anisotropy and loading interval on the tensile strength of undisturbed loess. The deformation and strains generated were also examined during the tests. It was revealed that anisotropy was an important factor affecting tensile strength of undisturbed loess, and the effect of loading interval on tensile strength significantly depended on water content. It was negligible while the water content was below the plastic limit. However, when the water content was above the plastic limit, the loading interval not only affected the tensile strength, but also the failure displacement and stiffness response of the soil. Two patterns of tensile fracture were summarized and discussed. Moreover, an empirical c... [more]
Lightning Impulse Withstand of Natural Ester Liquid
Stephanie Haegele, Farzaneh Vahidi, Stefan Tenbohlen, Kevin J. Rapp, Alan Sbravati
September 21, 2018 (v1)
Subject: Materials
Keywords: dielectric breakdown voltage, dielectric liquids, natural ester liquids vs. mineral oil, power transformers, vegetable oils
Due to the low biodegradability of mineral oil, intense research is conducted to define alternative liquids with comparable dielectric properties. Natural ester liquids are an alternative in focus; they are used increasingly as insulating liquid in distribution and power transformers. The main advantages of natural ester liquids compared to mineral oil are their good biodegradability and mainly high flash and fire points providing better fire safety. The dielectric strength of natural ester liquids is comparable to conventional mineral oil for homogeneous field arrangements. However, many studies showed a reduced dielectric strength for highly inhomogeneous field arrangements. This study investigates at which degree of inhomogeneity differences in breakdown voltage between the two insulating liquids occur. Investigations use lightning impulses with different electrode arrangements representing different field inhomogeneity factors and different gap distances. To ensure comparisons with... [more]
Dual-Temperature Evaluation of a High-Temperature Insulation System for Liquid-Immersed Transformer
Xiaojing Zhang, Lu Ren, Haichuan Yu, Yang Xu, Qingquan Lei, Xin Li, Baojia Han
September 21, 2018 (v1)
Subject: Materials
Keywords: dual-temperature, liquid-immersed transformer, natural ester, Nomex T910, thermal aging
A high-temperature oil⁻paper insulation system offers an opportunity to improve the overloading capability of distribution transformers facing seasonal load variation. A high-temperature electrical insulation system (EIS) was chosen due to thermal calculation based on a typical loading curve on the China Southern Power Grid. In order to evaluate candidate high-temperature insulation systems, Nomex® T910 (aramid-enhanced cellulose) immersed in FR3 (natural ester) was investigated by a dual-temperature thermal aging test compared with a conventional insulation system, Kraft paper impregnated with mineral oil. Throughout the thermal aging test, mechanical, chemical, and dielectric parameters of both paper and insulating oil were investigated in each aging cycle. The thermal aging results determined that the thermal class of the FR3-T910 insulation system meets the request of overloading transformer needs.
Electro-Insulating Nanofluids Based on Synthetic Ester and TiO₂ or C60 Nanoparticles in Power Transformer
Zbigniew Nadolny, Grzegorz Dombek
September 20, 2018 (v1)
Subject: Materials
Keywords: dielectrics, fullerene, insulation system, nanofluids, power transformer, synthetic ester, thermal properties, titanium dioxide
The article discusses thermal properties of synthetic ester admixed with nanoparticles. The analyzed thermal properties were: thermal conductivity λ, kinematic viscosity υ, density ρ, specific heat cp, and the thermal expansion factor β- all obtained by means of measurements. On the basis of these, the authors calculated the heat transfer factor α, which determines the ability of the liquid to heat transport. The authors used nanoparticles of fullerene C60 and titanium oxide TiO₂. The analysis of the thermal properties was done for the temperatures of 25, 40, 60 and 80 °C. The authors analyzed the impact of nanoparticles C60 and TiO₂ on thermal properties of synthetic ester. They proved that fullerene C60 in principle had no influence on heat transfer factor α of the ester, while titanium oxide TiO₂ had some positive influence on the factor, the value of which increased about 1⁻3%.
Extremely Pure Mg₂FeH₆ as a Negative Electrode for Lithium Batteries
Sergio Brutti, Luca Farina, Francesco Trequattrini, Oriele Palumbo, Priscilla Reale, Laura Silvestri, Stefania Panero, Annalisa Paolone
September 20, 2018 (v1)
Subject: Materials
Keywords: discharge capacity, high temperature hydrogenation, Mg2FeH6, pressure-composition isotherms, reactive ball milling
Nanocrystalline samples of Mg-Fe-H were synthesized by mixing of MgH₂ and Fe in a 2:1 molar ratio by hand grinding (MIX) or by reactive ball milling (RBM) in a high-pressure vial. Hydrogenation procedures were performed at various temperatures in order to promote the full conversion to Mg₂FeH₆. Pure Mg₂FeH₆ was obtained only for the RBM material cycled at 485 °C. This extremely pure Mg₂FeH₆ sample was investigated as an anode for lithium batteries. The reversible electrochemical lithium incorporation and de-incorporation reactions were analyzed in view of thermodynamic evaluations, potentiodynamic cycling with galvanostatic acceleration (PCGA), and ex situ X-ray Diffraction (XRD) tests. The Mg₂FeH₆ phase underwent a conversion reaction; the Mg metal produced in this reaction was alloyed upon further reduction. The back conversion reaction in a lithium cell was here demonstrated for the first time in a stoichiometric extremely pure Mg₂FeH₆ phase: the reversibility of the overall convers... [more]
Extraction of Junction Temperature of SiC MOSFET Module Based on Turn-On dIDS/dt
Delei Huang, Guojun Tan, Chengfei Geng, Jingwei Zhang, Chang Liu
September 20, 2018 (v1)
Subject: Materials
Keywords: junction temperature extraction, silicon carbide, switching transients, thermo-sensitive electrical parameter
In this paper, a method of extracting the junction temperature based on the turn-on current switching rate (dIDS/dt) of silicon carbide (SiC) metal-oxide semiconductor field effect transistors (MOSFETs) is proposed. The temperature dependence of dIDS/dt is analyzed theoretically, and experimentally to show that dIDS/dt increases with the rising junction temperature. In addition, other factors affecting dIDS/dt are also discussed by using the fundamental device physics equations and experiments. The result shows that the increase of the DC-link voltage VDC, the external gate resistance RG-ext, and the decrease of the driving voltage VGG can increase the temperature sensitivity of the dIDS/dt. A PCB (printed circuit board) Rogowski coil measuring circuit based on the fact that the SiC MOSFET chip temperature and dIDS/dt is estimated in a linear way is designed to obtain the junction temperature. The experimental results demonstrate that the proposed junction temperature extracting is eff... [more]
Investigation of Injection Strategy of Branched-Preformed Particle Gel/Polymer/Surfactant for Enhanced Oil Recovery after Polymer Flooding in Heterogeneous Reservoirs
Hong He, Jingyu Fu, Baofeng Hou, Fuqing Yuan, Lanlei Guo, Zongyang Li, Qing You
September 20, 2018 (v1)
Subject: Materials
Keywords: branched-preformed particle gel, enhanced oil recovery, heterogeneous phase combination flooding, heterogeneous reservoirs, injection strategy
The heterogeneous phase combination flooding (HPCF) system which is composed of a branched-preformed particle gel (B-PPG), polymer, and surfactant has been proposed to enhance oil recovery after polymer flooding in heterogeneous reservoirs by mobility control and reducing oil⁻water interfacial tension. However, the high cost of chemicals can make this process economically challenging in an era of low oil prices. Thus, in an era of low oil prices, it is becoming even more essential to optimize the heterogeneous phase combination flooding design. In order to optimize the HPCF process, the injection strategy has been designed such that the incremental oil recovery can be maximized using the corresponding combination of the B-PPG, polymer, and surfactant, thereby ensuring a more economically-viable recovery process. Different HPCF injection strategies including simultaneous injection and alternation injection were investigated by conducting parallel sand pack flooding experiments and large... [more]
ZnS/SiO₂ Passivation Layer for High-Performance of TiO₂/CuInS₂ Quantum Dot Sensitized Solar Cells
Hee-Je Kim, Jin-Ho Bae, Hyunwoong Seo, Masaharu Shiratani, Chandu Venkata Veera Muralee Gopi
September 19, 2018 (v1)
Subject: Materials
Keywords: Charge recombination, Passivation layer, QDSSCs, ZnS/SiO2
Suppressing the charge recombination at the interface of photoanode/electrolyte is the crucial way to improve the quantum dot sensitized solar cells (QDSSCs) performance. In this scenario, ZnS/SiO₂ blocking layer was deposited on TiO₂/CuInS₂ QDs to inhibit the charge recombination at photoanode/electrolyte interface. As a result, the TiO₂/CuInS₂/ZnS/SiO₂ based QDSSCs delivers a power conversion efficiency (η) value of 4.63%, which is much higher than the TiO₂/CuInS₂ (2.15%) and TiO₂/CuInS₂/ZnS (3.23%) based QDSSCs. Impedance spectroscopy and open circuit voltage decay analyses indicate that ZnS/SiO₂ passivation layer on TiO₂/CuInS₂ suppress the charge recombination at the interface of photoanode/electrolyte and enhance the electron lifetime.
Three-Dimensional Numerical Investigation of Coupled Flow-Stress-Damage Failure Process in Heterogeneous Poroelastic Rocks
Shikuo Chen, Chenhui Wei, Tianhong Yang, Wancheng Zhu, Honglei Liu, Pathegama Gamage Ranjith
September 19, 2018 (v1)
Subject: Materials
Keywords: coupled flow-stress-damage model, failure progress, heterogeneous, numerical investigation, permeability evolution
The failure mechanism of heterogeneous rocks (geological materials), especially under hydraulic conditions, is important in geological engineering. The coupled mechanism of flow-stress-damage should be determined for the stability of rock mass engineering under triaxial stress states. Based on poroelasticity and damage theory, a three-dimensional coupled model of the flow-stress-damage failure process is studied, focusing mainly on the coupled characteristics of permeability evolution and damage in nonhomogeneous rocks. The influences of numerous mesoscale mechanical and hydraulic properties, including homogeneity, residual strength coefficient, loading rates, and strength criteria, on the macro mechanical response are analyzed. Results reveal that the stress sensitive factor and damage coefficient are key variables for controlling the progress of permeability evolution, and these can reflect the hydraulic properties under pre-peak and post-peak separately. Moreover, several experiment... [more]
Experimental Study on the Reinforcement Mechanism of Segmented Split Grouting in a Soft Filling Medium
Zhipeng Li, Shucai Li, Haojie Liu, Qingsong Zhang, Yanan Liu
August 28, 2018 (v1)
Subject: Materials
Keywords: model experiment, reinforcement mechanism, rock-soil mechanics, segmented grouting, soft filling medium, split grouting
Subsection split grouting technology can effectively improve the grouting efficiency and homogeneity of grouting in a target reinforcement area. It is therefore necessary to clarify the reinforcement mechanism and characteristics of the soft filling medium under the condition of split grouting. A three-dimensional grouting simulation test of segmented split grouting in a soft filling medium was conducted. The distribution characteristics and thicknesses of the grouting veins were obtained under the condition of segmented grouting. The mechanical mechanism of segmented split grouting reinforcement, based on the distribution characteristics of different grouting veins, was revealed. After grouting, a uniaxial compression test and an indoor permeation test were conducted. Based on the method of the region-weighted average, the corresponding permeability coefficient and the elastic modulus of each splitting-compaction region were obtained. The quantitative relationship between the mechanic... [more]
Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water
Lina Liao, Peng Zhang
August 28, 2018 (v1)
Subject: Materials
Keywords: coagulant, low turbidity, polyaluminum titanium silicate chloride, zeta potential
Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of 50 °C, and n(Ti)/n(Al), n(-OH)/n(Ti+Al), and n(Si)/n(Ti+Al) were 0.3, 0.2, and 1.0, respectively. The species distribution and the transformation of PATC showed that the interaction between titanium tetrachloride, sodium silicate, and the hydrolysate of Al influenced the morphology distribution of Al. Temperature and -OH greatly affected the distribution of Alb in PATC. The analysis of infrared spectra and X-ray diffraction indicated that both titanium tetrachloride and sodium silicate had complex chemical reactions with aluminum chloride. Si-O-Ti and Si-O-Al pro... [more]
Deformation and Hydraulic Conductivity of Compacted Clay under Waste Differential Settlement
Sifa Xu, Cuifeng Li, Jizhuang Liu, Mengdan Bian, Weiwei Wei, Hao Zhang, Zhe Wang
August 28, 2018 (v1)
Subject: Materials
Keywords: bentonite-sand mixtures, crack, deformation, differential settlement, geogrid, hydraulic conductivity
Landfill is still the most important process to dispose of municipal solid waste in China, while landfill closure aims for pollution control, security control, and better land reuse. However, uneven settlement of landfill cover system is very likely to cause deformation and cracking. The objective of this paper is to examine the effects of geogrid reinforcement on the deformation behaviour and hydraulic conductivity of the bentonite-sand mixtures that are subjected to differential settlement. The laboratory model tests were performed on bentonite-sand mixtures with and without the inclusion of geogrid reinforcement. By maintaining the type and location of the geogrid within the liner systems as constant, the thickness of the bentonite-sand mixtures is varied. The performation of the liner systems with and without the inclusion of geogrid reinforcement was assessed by using jack to control differential settlement. Un-reinforced bentonite-sand mixtures of 100 mm and 200 mm thickness were... [more]
Technology for the Remediation of Water Pollution: A Review on the Fabrication of Metal Organic Frameworks
Yongning Bian, Nana Xiong, Guocheng Zhu
August 28, 2018 (v1)
Subject: Materials
Keywords: Adsorption, metal organic frameworks, remediation, water pollution
The ineffective control of the release of pollutants into water has led to serious water pollution. Compared with conditions in the past, the polluting components in aquatic environments have become increasingly complex. Some emerging substances have led to a new threat to the safety of water. Therefore, developing cost-effective technologies for the remediation of water pollution is urgently needed. Adsorption has been considered the most effective operational unit in water treatment processes and thus adsorption materials have gained wide attention. Among them, metal organic frameworks (denoted as MOFs) have been rapidly developed in recent years due to their unique physicochemical performance. They are characterized by larger porosity and larger specific surface area, easier pore structure designing, and comfortable structural modification. In many fields such as adsorption, separation, storage, and transportation, MOFs show a better performance than conventional adsorption material... [more]
Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed
Sung Won Kim
August 28, 2018 (v1)
Subject: Materials
Keywords: aggregates, carbon nanotube, fluidized bed, laser sheet technique, particle size
Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (dp = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidit... [more]
Effects of Pulse Interval and Dosing Flux on Cells Varying the Relative Velocity of Micro Droplets and Culture Solution
Zhanwei Wang, Kun Liu, Jiuxin Ning, Shulei Chen, Ming Hao, Dongyang Wang, Qi Mei, Yaoshuai Ba, Dechun Ba
August 28, 2018 (v1)
Subject: Materials
Keywords: cell dosing, convective diffusion, interdiffusion, microdroplet, numerical simulation
Microdroplet dosing to cell on a chip could meet the demand of narrow diffusion distance, controllable pulse dosing and less impact to cells. In this work, we studied the diffusion process of microdroplet cell pulse dosing in the three-layer sandwich structure of PDMS (polydimethylsiloxane)/PCTE (polycarbonate) microporous membrane/PDMS chip. The mathematical model is established to solve the diffusion process and the process of rhodamine transfer to micro-traps is simulated. The rhodamine mass fraction distribution, pressure field and velocity field around the microdroplet and cell surfaces are analyzed for further study of interdiffusion and convective diffusion effect. The cell pulse dosing time and drug delivery efficiency could be controlled by adjusting microdroplet and culture solution velocity without impairing cells at micro-traps. Furthermore, the accuracy and controllability of the cell dosing pulse time and maximum drug mass fraction on cell surfaces are achieved and the dr... [more]
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