空间太阳电池槽式聚光热电联供系统特性分析

建立了空间太阳电池的热电联供系统在槽式聚光条件下的热电性能模型, 并与实验进行了对比.理论计算与实验结果吻合较好, 最大误差在5.1%以内, 证明了该数学模型的正确性.通过此数学模型, 从聚光镜面的光学效率与焦线宽度、导热胶的导热系数、金属平板光照面的吸收率等内部特性参数及风速、太阳直辐射等外部特性参数出发, 对所设计制造的空间太阳电池槽式聚光热电联供系统进行分析.较为全面而系统地分析了这些参数的改变对其系统的热电效率、总效率及火用效率等性能指标的影响, 其中聚光镜面的光学效率影响最大, 光学效率从0.5增加至0.95, 系统的总效率和火用效率分别增加0.9倍和0.5倍, 其余参数对性能也有较强影响.研究结果为新一轮系统装置的制作提供了优化设计基础.     

Seasonal variation of 129I species in the Baltic Proper

Iodine speciation plays a significant role in iodine volatilizing into atmosphere from the seas, as well as serving as a biological indicator. Despite this importance, the data on iodine species revealed inconclusive evidence of what factors controlling speciation transformation. We here present new data on profiles of ¹²⁹I speciation in the Baltic Proper during November 2009. Along with the two earlier investigations (August 2006 and April 2007), an assessment of seasonal variation of ¹²⁹I species is presented. The results show that, due to the anoxic nature of Baltic Proper, presence of ¹²⁹IO₃ ^? in the Baltic Proper does not follow an obvious seasonal cycle, as the case with ¹²⁹I^?. Concentrations of ¹²⁹I^? in the Baltic Proper exhibit higher values in summer than the other two seasons (spring and winter), which might be associated with degrading of organic matter and release from sediment to water column that is more pronounced during summer. ¹²⁹I^? in surface water from the three seasons does not reflect the release function from the reprocessing facilities during the period April 2007 to November 2009. Consequently variability of ¹²⁹I^? in surface seawater of the Baltic Proper depends, to some extent, on local physical as well as biochemical conditions.     

Intrinsic properties of active sites for hydrogen production from alcohols without coke formation

The detailed reaction pathway and coke formation mechanism over Pt/metal oxide nanoparticles during the steam reforming of ethanol（SRE） at 300℃were studied.The catalysts were prepared by incipient wetness impregnation method and were characterized with CO pulse chemisorption, BET surface measurement,oxygen adsorption,ethanol-TPD,NH₃-TPD,and TPO.The SRE activity of the catalysts with steam/ethanol molar ratio of 3/1 was tested using a continuous fixed-bed reactor.Strong interaction between Pt and supports causes lower H₂ production temperatures and no C₂H₄ formation,while weak interaction leads to C₂H₄ formation and strong bonded CO on Pt particles during ethanol-TPD. H₂ production over Pt-based catalysts is mainly resulted from the decomposition and dehydrogenation of ethanol,and decarbonylation of acetaldehyde.Meanwhile,coke can be formed from acetaldehyde,acetone,C₂H₄ and CO.However,when the interaction between Pt and supports is weak,more coke is formed especially from acetone,C₂H₄ and CO.When the interaction is strong,no coke formation is observed due to high oxygen storage capacity of the catalyst.     

Facile one‐pot method of initiator fixation for surface‐initiated atom transfer radical polymerization on carbon hard spheres

An efficient and novel one‐pot process is developed to immobilize the atom transfer radical polymerization (ATRP) initiators onto the surface of fully pyrolyzed carbon hard spheres (CHSs) via a radical trapping process from the in situ thermal decomposition of bis(bromomethylbenzoyl)peroxide. The CHSs do not require any additional preparative treatment prior to the initiator immobilization. Styrene and methyl methacrylate are polymerized onto initiator‐immobilized CHSs by surface‐initiated atomic transfer radical polymerization (SI‐ATRP). Samples are characterized using Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. These methods of characterization confirmed that all the CHSs are coated with a uniform layer of grafted polymer. This efficient, one‐pot immobilization of ATRP‐initiators represents an exceptionally simple route for the rapid preparation of various polymer‐coated carbon‐based nanomaterials using SI‐ATRP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3314–3322     

Effect of Vacancy Defects on the Young's Modulus and Fracture Strength of Graphene: A Molecular Dynamics Study

The Young's modulus of graphene with various rectangular and circular vacancy defects is investigated by molecular dynamics simulation. By comparing with the results calculated from an effective spring model, it is demonstrated that the Young's modulus of graphene is largely correlated to the size of vacancy defects perpendicular to the stretching direction. And a linear reduction of Young's modulus with the increasing concentration of mono‐atomic‐vacancy defects (i.e., the slope of ?0.03) is also observed. The fracture behavior of graphene, including the fracture strength, crack initiation and propagation are then studied by the molecular dynamics simulation, the effective spring model, and the quantized fracture mechanics. The blunting effect of vacancy edges is demonstrated, and the characterized crack tip radius of 4.44 Å is observed.     

Biological evaluation of novel selenazole‐based compounds as potential thioredoxin reductase inhibitors

Recently, thioredoxin reductase as a target for treatment of tumors has attracted the attention of scientists. 1,2‐[Bis(1,2‐benzisoselenazolone‐3(2 H)‐ketone)]ethane (ethaselen, BBSKE, PCT: CN02/00412), designed and synthesized previously, is an effective thioredoxin reductase inhibitor; presently it is in phase II clinical trials, targeting gastric cancer, lung cancer and colon cancer. To seek more novel and effective anticancer drugs, we have developed many selenazole‐based compounds. Evaluation of the thioredoxin reductase inhibitory effect and investigation of the mechanism of anticancer drugs require abundant thioredoxin reductase, but since commercial thioredoxin reductase is expensive its use is often limited. Therefore, the preparation of thioredoxin reductase is necessary. Base on the above investigation, in this work we have prepared thioredoxin reductase and evaluated selenazole‐based compounds, and found that 44 compounds have high inhibitory effect on thioredoxin reductase with IC₅₀ < 10 µ m , of which 16 compounds have IC₅₀ values below 1 µ m . This is helpful in investigating and elucidating the mechanism of this kind of compound. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of alkoxide in catalytic transfer hydrogenation of unsaturated nitrogen compounds

Alcoholate was utilized in catalytic transfer hydrogenation of unsaturated nitrogen compounds. In the reduction of nitro compounds, oximes and imines, alkoxide was used as the promoter, with alcohol as the hydrogen source, while in the reduction of nitriles, alkoxide was used as the hydrogen source.     

Homogenization of layered elastoplastic composites: Theoretical results

Exact closed-form solutions are derived that completely characterize the effective behavior of a composite material made of elastic-perfectly plastic parallel plane layers perfectly bonded together. The derivation is framed within a rigorous theory of homogenization for elastoplastic composites, and based on the fundamental fact that the in-plane part of the strain tensor and the out-of-plane part of the stress tensor are uniform throughout the composite provided no free-edge effects occur. The obtained expressions are coordinate-free and valid in the general anisotropic case. As an example, a layered composite material with isotropic constituents is examined in detail.