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991.
Chien Hwa Chong Chung Lim Law Michael Cloke Luqman Chuah Abdullah Wan Ramli Wan Daud 《Drying Technology》2013,31(10):1286-1293
Sun drying of chempedak (Artocarpus integer) was carried out on different sample sizes to investigate the effects on product quality. Fick's second law model was used to determine the effective diffusivities of sun–dried chempedak slabs based on the drying rate versus moisture content plots. In addition, texture degradation and total color changes were investigated. The texture and color changes of dried chempedak were relatively significant (p < 0.05) compared to fresh chempedak. There was an increase in dried fruit hardness and chewiness but a decrease in springiness and cohesiveness during drying. 相似文献
992.
Shu‐Kai Yeh Chien‐Hsiung Huang Chi‐Chun Su Kuo‐Chung Cheng Tsu‐Huang Chuang Wen‐Jeng Guo Sea‐Fue Wang 《Polymer Engineering and Science》2013,53(10):2061-2072
In this study, polystyrene/nanographite nanocomposite foams were made by different compounding methods, such as direct compounding, pulverized sonication compounding, and in situ polymerization, to understand the effect of the process variables on the morphology of the nanocomposites and their foam. The foam was made by batch foaming using CO2 as the blowing agent. Various foaming pressures and temperatures were studied. The results indicated that the cell size decreased and the cell morphology was improved with the advanced dispersion of the nanoparticles. Among the three methods, the in situ polymerization method provided the best dispersion and the resulting nanocomposite foam had the finest cell size and the highest cell density. In addition, adding nanoparticles as a nucleating agent can make foams of similar cell size and cell density at a much lower foaming pressure. This result can be explained by the classical nucleation theory. This discovery could open up a newroute to produce microcellular foams at a low foaming pressure. POLYM. ENG. SCI., 53:2061–2072, 2013. © 2013 Society of Plastics Engineers 相似文献
993.
Seon Mi Kong Rong Fan Sung Hee Jung Chee Won Chung 《Journal of Industrial and Engineering Chemistry》2013,19(4):1320-1324
Cu(In1?xGax)Se2 (CIGS) thin films were prepared using a single quaternary target by RF magnetron sputtering. The effects of deposition parameters on the structural, compositional and electrical properties of the films were examined in order to develop the deposition process without post-deposition selenization. From X-ray diffraction analysis, as the substrate temperature and Ar pressure increased and RF power decreased, the crystallinity of the films improved. The scanning electron microscopy revealed that the grains became uniform and circular shape with columnar structure with increasing the substrate temperature and Ar pressure, and decreasing the RF power. The carrier concentration of CIGS films deposited at the substrate temperature of 500 °C was 2.1 × 1017 cm?3 and the resistivity was 27 Ω cm. At the substrate temperature above 500 °C, In and Se contents in CIGS films decreased due to the evaporation and it led to the deterioration of crystallinity. It was confirmed that CIGS thin films deposited at optimal condition had similar atomic ratio to the target value even without post-deposition selenization process. 相似文献
994.
Three ultrafiltration membranes in series with molar mass cutoffs of 130,000, 15,000, and 5,000 Da, respectively were used to pretreat Kraft pulp bleach plant effluent prior to biological treatment. The TOC (total organic carbon), COD (chemical oxygen demand) and AOX (adsorbable organic halogen) reductions for the permeate were 65, 70 and 85%, respectively with no significant change of toxicity. Treatment of the ultrafiltration permeate using tighter ultrafiltration (UF) and nanofiltration (NF) membranes with molar mass cutoffs less than 1,500 Da, yielded TOC and AOX reductions of 90 and 99%, respectively with a permeate Microtox EC50 level of 100%. 相似文献
995.
996.
Hyun Ju Park Young-Kwon Park Jong-In Dong Joo-Sik Kim Jong-Ki Jeon Seung-Soo Kim Jinsoo Kim Byungho Song Junhong Park Kyung-Jin Lee 《Fuel Processing Technology》2009
The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil. 相似文献
997.
Min-Ah Song Sung-In Ha Dea-Young Park Cheol-Hwi Ryu An-Soo Kang Sang-Bong Moon Jang-Hoon Chung 《International Journal of Hydrogen Energy》2013
Covalently cross-linked SPEEK/Cs-TPA/CeO2 composite membrane was prepared for the polymer electrolyte membrane water electrolysis. Tungstophosphoric acid (TPA) with a cesium was added to the SPEEK to increase proton conductivity. CeO2 was used to scavenge free radicals which attack the membrane in the water electrolysis and to improve the durability of the membrane. The composite membrane featured the electrochemical characteristics, such as 0.130 S/cm of proton conductivity at 80 °C, and 2.324 meq./g-dry-memb. of ion-exchange capacity. Pt(NH3)4Cl2, Pd(NH3)4Cl2, RhCl3 and Co(NH6)4Cl3 were used to prepare a variety of the membrane electrode assemblies (MEAs) as electrocatalytic precursors. Electrochemical activity surface area (ESA) of the Pt–Pd electrode prepared with 2 mM Pt(NH3)4Cl2 and 2 mM Pd(NH3)4Cl2 showed the best properties of 26.2 m2/g with CL-SPEEK/Cs-TPA/CeO2 membrane. In water electrolysis performance, the cell voltage of Pd/PEM/Pt–Pd MEA with CL-SPEEK/Cs-TPA/CeO2(1%) composite membrane showed cell property of 1.82 V at 1 A cm−2 and 80 °C. 相似文献
998.
A numerical procedure for the deformation and solidification of a metal droplet impinging on a flat surface is developed and a sample calculation is presented. A previously derived second-order ordinary differential equation (ODE) that approximates the splat as a cylinder and describes the droplet size evolution based on the mechanical energy equation in conjunction with kinematic and geometrical compatibility is used. The thermal energy equations for the liquid and solid regions of the splat and the substrate are separately solved coupled by boundary conditions such as contact resistance and undercooling in a regularized calculation domain produced by algebraic grid generation. The solidified layer thickness is calculated by solving a hyperbolic partial differential equation (PDE) resulting from the interface energy equation at the phase change boundary. Physical processes such as convective heat loss, substrate heat loss, viscous dissipation, and surface tension are modeled through appropriate nondimensional parameters. 相似文献
999.
Haisheng Di Xin He Peng Zhang Zhi Wang Margaret S. Wooldridge Chung K. Law Cuiping Wang Shijin Shuai Jianxin Wang 《Combustion and Flame》2014
Experimental and numerical studies have been performed on the thermal and chemical effects of buffer gas composition on low temperature ignition of iso-octane and n-heptane. Experiments were conducted using a recently developed rapid compression machine in the temperature range of 600–850 K. Three buffer gases were studied including nitrogen (N2), argon (Ar), and a mixture of Ar and carbon dioxide (CO2) at a mole ratio of 65.1%/34.9%. Iso-octane was studied at 20 bar, ? = 1, and a dilution level of buffer gas to O2 of 3.76:1 (mole ratio). n-Heptane was studied at 9 bar, ? = 1, and a dilution level of buffer gas to O2 of 5.63:1 (mole ratio). For experiments where two-stage ignition was observed, the buffer gas composition had no impact on the first-stage ignition time but, as expected, it caused differences in the total heat release, pressure and temperature rise after the first-stage ignition. As a consequence, significant differences were observed for the total ignition delay time as a function of the buffer gas composition, with up to 40% and 42.5% faster total ignition time for iso-octane and n-heptane, respectively, by using Ar instead of N2. The chemical effects of the buffer gas composition were studied experimentally by comparing the results of the N2 and Ar/CO2 (65.1%/34.9%) mixtures, recognizing that while the Ar/CO2 mixture has the same heat capacity as N2, its predicted combined third-body collision efficiency is about 76% higher than N2. The experimental results showed negligible chemical effects on the first-stage and total ignition delay times. Numerical simulations were carried out over a wider range of temperatures for pure N2, Ar, and CO2 as buffer gases. Results showed that thermal effects are very pronounced and dominated at the negative temperature coefficient and two-stage ignition conditions, which is consistent with the experimental results and previous studies in the literature. However, the simulation results also showed at temperatures higher than 850 K, the chemical effects of CO2 became more important than the thermal effects. 相似文献
1000.
This study presents a designed and tested integrated miniature tubular quartz-made reactor for hydrogen (H2) production. This reactor is composed of two concentric tubes with an overall length of 60 mm and a diameter of 17 mm. The inner tube was designed as the combustor using Pt/Al2O3 as the catalyst. The gap between the inner and outer tubes is divided into three sections: a liquid methanol-water vaporizer, a methanol-steam reformer using RP-60 as the catalyst and a carbon monoxide (CO) methanator using Ru/Al2O3 as the catalyst. The experimental measurements indicated that this integrated reactor works properly as designed. The methanol conversion, hydrogen production rate and CO concentration were found to increase with an increasing methanol/air flow rate in the combustor and decreases with an increasing methanol/water feed rate to the reformer. The methanator experimental results indicated that the CO conversion and H2 consumption can be enhanced by increasing the Ru loading. It was also found that the CO methanation depends greatly on the reaction temperature. With a higher reaction temperature, the CO methanation, carbon dioxide (CO2) methanation, and reversed water gas shift reactions took place simultaneously. CO conversion was found to decrease while H2 consumption was found to increase. At a lower reaction temperature both the CO conversion and H2 consumption were found to increase indicating that only CO methanation took place. From the experimental results the maximum methanol conversion, hydrogen yield, and CO conversion achieved were 97%, 2.38, and 70%, respectively. The actual lowest CO concentration and maximum power density based on the reactor volume were 90 ppm and 0.8 kW/L, respectively. 相似文献