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排序方式: 共有431条查询结果,搜索用时 31 毫秒
1.
Binbo Jiang Jincheng Dai Jingyuan Sun Jian Ye Meijuan Chen Guodong Han Jingdai Wang Jian Yang Yongrong Yang 《Polymer Engineering and Science》2020,60(8):1998-2007
The diffusion behavior of ethylene in polyethylene is of great importance for the polymerization and degassing of polyethylene (PE) industry. Based on the gravimetric sorption and desorption measurement approach, an intelligent gravimetric analyzer is applied to obtain the solubility and diffusion coefficients of ethylene in solid low-density PE (LDPE) with different melt indices at 30°C to 70°C, 0 to 4 atm and in molten LDPE at 160°C to 230°C, 0 to 4 atm, respectively. Results indicate that both the solubility and diffusion coefficients of ethylene in solid LDPE are smaller than those in molten LDPE, while the dissolution enthalpy and diffusion activation energy of ethylene in solid LDPE are higher. In addition, one- and two-dimensional diffusion models are built and the effects of particle size, polymer properties, and operation conditions are systematically investigated on the diffusion behaviors of ethylene in solid and molten LDPE. 相似文献
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Se-Jin Joo Hee-Jung Park Ji-Hae Park Jin-Gyeong Cho Ji-Hyun Kang Tae-Sook Jeong Hee Cheol Kang Dae-Young Lee Hack-Soo Kim Sang-Yo Byun Nam-In Baek 《International journal of molecular sciences》2014,15(9):16418-16429
Stems of Machilus japonica were extracted with 80% aqueous methanol (MeOH) and the concentrated extract was successively extracted with ethyl acetate (EtOAc), normal butanol (n-BuOH), and water. Six flavonoids were isolated from the EtOAc fraction: (+)-taxifolin, afzelin, (−)-epicatechin, 5,3''-di-O-methyl-(−)-epicatechin, 5,7,3''-tri-O-methyl-(−)-epicatechin, and 5,7-di-O-methyl-3'',4''-methylenedioxyflavan-3-ol. The chemical structures were identified using spectroscopic data including NMR, mass spectrometry and infrared spectroscopy. This is the first report of isolation of these six compounds from M. japonica. The compounds were evaluated for their diphenyl picryl hydrazinyl scavenging activity and inhibitory effects on low-density lipoprotein oxidation. Compounds 1 and 3–6 exhibited DPPH antioxidant activity equivalent with that of ascorbic acid, with half maximal inhibitory concentration (IC50) values of 0.16, 0.21, 0.17, 0.15 and 0.07 mM, respectively. The activity of compound 1 was similar to the positive control butylated hydroxytoluene, which had an IC50 value of 1.9 µM, while compounds 3 and 5 showed little activity. Compounds 1, 3, and 5 exhibited LDL antioxidant activity with IC50 values of 2.8, 7.1, and 4.6 µM, respectively. 相似文献
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结合具体工程实例,探讨了彩云星城的设计思想,介绍了该项目的总体布局和绿地环境,详细分析了小区建设的户型设计、立面设计和节能设计,指出该项目是一个高层与多层相结合的低密度经典实例,是对高层与多层建筑创新性的完善演绎。 相似文献
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住宅平面设计多为直觉和感性设计,由此产生的设计方案往往在住宅的朝向、采光及节能等方面存在着不足,从而造成住宅使用功能方面的问题,这种现象在低密度住宅的设计中尤为突出。针对独院式、并联式、联排式等低密度住宅的平面布局特点,提出住宅内不同位置处依据朝向、自然采光及节能保温等因素的“优势度”概念,并根据房间不同朝向,自然光源数量及不同围护内墙数量等因素,分别为每一个区域赋于优势度分值。建议平面设计以各区域综合优势度排序为依据。该方法有助于建筑师将直觉和感性设计转为理性设计。具体案例应用表明了方法的适用性。 相似文献
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Loop distribution of Tanner graph affects the BER performance of low-density parity-check codes(LDPC) decoding.To count short cycles in the Tanner graph efficiently,a side by side recursion algorithm based on matrix computation was proposed.Firstly,5 basic graph structures were defined to realize recursive calculate in the implementation process.Compared with previous works,the algorithm provided many methods for counting the same length of cycles.The same result confirmed the correctness of the algorithm.The new algorithm could not only calculate the total number of cycles,but also gave the number each edge participating in fixed-length cycles.Its complexity was proportional to the product of D and square of N,where D was the average degree of variable nodes,and N denoted the code length.For LDPC codes,D was far less than N.For most of the LDPC codes,the calculation for numbers of cycle-length g、g+2、g+4 was only several seconds. 相似文献
9.
Alexander N. Orekhov Yuri V. Bobryshev Igor A. Sobenin Alexandra A. Melnichenko Dimitry A. Chistiakov 《International journal of molecular sciences》2014,15(7):12807-12841
In atherosclerosis; blood low-density lipoproteins (LDL) are subjected to multiple enzymatic and non-enzymatic modifications that increase their atherogenicity and induce immunogenicity. Modified LDL are capable of inducing vascular inflammation through activation of innate immunity; thus, contributing to the progression of atherogenesis. The immunogenicity of modified LDL results in induction of self-antibodies specific to a certain type of modified LDL. The antibodies react with modified LDL forming circulating immune complexes. Circulating immune complexes exhibit prominent immunomodulatory properties that influence atherosclerotic inflammation. Compared to freely circulating modified LDL; modified LDL associated with the immune complexes have a more robust atherogenic and proinflammatory potential. Various lipid components of the immune complexes may serve not only as diagnostic but also as essential predictive markers of cardiovascular events in atherosclerosis. Accumulating evidence indicates that LDL-containing immune complexes can also serve as biomarker for macrovascular disease in type 1 diabetes. 相似文献
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《国际聚合物材料杂志》2012,61(14):1091-1101
The melt flow behavior and thermal properties of low-density polyethylene (LDPE)/palm kernel shell (PKS) composites were studied. Polyethylene acrylic acid (PEAA) was used as a compatibilizer in the composites. The results showed that the increasing of PKS loading had decreased MFI values of LDPE/PKS composites. The presence of PEAA increased the MFI values of the LDPE/PKS composites. The apparent viscosity of the composites was found to exhibit a linear relationship with the reciprocal of the temperature. Thermal properties showed that higher filler loading tended to reduce the onset temperature as the PKS possessed lower degradation temperature compared to the LDPE. The presence of the PKS in the LDPE polymeric matrix improved the thermal stability of the composites. The addition of PEAA into the composites provided better interfacial bonding between the LDPE matrix and PKS filler, while higher onset temperature and lower total weight loss were observed of LDPE/PKS composites. The activation energy of the LDPE/PKS composites was increased with increasing filler loading. At similar filler loading, the presence of PEAA increased the activation energy of the LDPE/PKS composites. 相似文献