Diastereo‐ and Enantioselective Synthesis of Chiral Pyrrolidine‐Fused Spirooxindoles via Organocatalytic [3+2] 1,3‐Dipolar Cycloaddition of Azomethine Ylides with Maleimides

In the presence of a Cinchona alkaloid‐based squaramide organocatalyst, the [3+2] cycloaddition of isatin‐derived azomethine ylides with maleimides proceeded readily, thus delivering the desired pyrrolidine‐fused spirooxindoles in 61–89% yields with >20:1 dr and 12 to >99 % ee. The absolute configuration of 5‐chloro‐1,5′‐dimethyl‐3′‐phenyl‐3′,3a′‐dihydro‐2′H‐spiro[indoline‐3,1′‐pyrrolo[3,4‐c]pyrrole]‐2,4′,6′(5′H,6a′H)‐trione was unambiguously determined by means of X‐ray single crystal structure analysis. The reaction mechanism was hypothesized to account for the enantioselective formation of 5‐chloro‐1,5′‐dimethyl‐3′‐phenyl‐3′,3a′‐dihydro‐2′H‐spiro[indoline‐3,1′‐pyrrolo[3,4‐c]pyrrole]‐2,4′,6′(5′H,6a′H)‐trione.

     

Porous sheet-like and sphere-like nano-architectures of SnO2 nanoparticles via a solvent-thermal approach and their gas-sensing performances

Porous sheet-like and sphere-like nano-architectures of SnO₂ nanoparticles have been prepared via a solvent-thermal approach in the absence of any surfactant or polymer templates by simply changing the volume ratio of DMF to water. The nano-materials have been characterized by FESEM, XRD, IR, TEM and BET. A mechanism for the formation of nano-architectures is also proposed based on the assembly behaviors of DMF in water. The gas sensors constructed with porous sphere-like SnO₂ nano-architectures exhibit much higher sensitivity to the reduce vapors tested, compared to those from porous sheet-like SnO₂ materials, while the sheet-like materials show better selectivity to ethanol. The nano-architectures fabricated with the facile method are promising candidates for building chemical sensors with tunable performances.     

A formal model of the Semantic Web Service Ontology (WSMO)

Semantic Web Service, one of the most significant research areas within the Semantic Web vision, has attracted increasing attention from both the research community and industry. The Web Service Modelling Ontology (WSMO) has been proposed as an enabling framework for the total/partial automation of the tasks (e.g., discovery, selection, composition, mediation, execution, monitoring, etc.) involved in both intra- and inter-enterprise integration of Web services. To support the standardisation and tool support of WSMO, a formal model of the language is highly desirable. As several variants of WSMO have been proposed by the WSMO community, which are still under development, the syntax and semantics of WSMO should be formally defined to facilitate easy reuse and future development. In this paper, we present a formal Object-Z formal model of WSMO, where different aspects of the language have been precisely defined within one unified framework. This model not only provides a formal unambiguous model which can be used to develop tools and facilitate future development, but as demonstrated in this paper, can be used to identify and eliminate errors present in existing documentation.     

Surface microstructuring of aluminum alloy 2024 using femtosecondexcimer laser irradiation

Surface microstructuring and modification of aluminum alloy 2024-T3 were investigated using a femtosecond pulse laser irradiation. The surface micrographs of the scanning electron microscopy were characterized as a function of incident laser fluence. The surface features ranging from submicrometer to micrometers were developed through the variation in laser fluence and laser pulse count. Results indicated that surface patterns were uniquely constructed in a controlled use of pulsed laser parameters for the ablation. Two ablation regimes were found in the logarithmic dependence of the ablated depth on laser fluence and two components were attributed to the optical and energy penetration. A thermal dynamic model was adopted to analyze the ablation processes, and the theoretical analysis agreed well with the experimental results     

00Cr18Ni10N不锈钢点焊工艺参数的正交优化

应用正交试验方法对00Cr18Ni10N不锈钢电阻点焊工艺参数进行优化,确定了其点焊工艺参数的合理规范带为:焊接电流5800-6300A,电极压力5.1～6.0kN,焊接时间6～9cyc.研究发现,焊接时间对点焊接头单点抗剪力影响最显著,焊接电流和电极压力次之.     

基质细胞衍生因子－１介入治疗股骨头坏死的实验研究

目的探讨基质细胞衍生因子－１（SDF－１）治疗股骨头坏死的机制和疗效。方法选用日本大耳白兔３０只，制成激素性股骨头坏死模型后，随机分为３组。A组为对照组；B组为髓心减压＋生理盐水治疗组；C组为髓心减压＋SDF－１治疗组。各组动物均于治疗后８周处死，处死后分别进行股骨头骨密度测定及组织病理观察。结果SDF－１治疗后８周，骨密度明显增高，病理组织学表现血管数目增多，空骨陷窝减少。SDF－１治疗后显示股骨头修复效果明显。结论髓芯减压SDF－１移植治疗股骨头缺血性坏死效果明显，具有较广的临床应用前景。     

Comparison and analysis of bare soil evaporation models combined with ASTER data in Heihe River Basin

Based on ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) remote sensing data, bare soil evaporation was estimated with the Penman-Monteith model, the Priestley-Taylor model, and the aerodynamics model. Evaporation estimated by each of the three models was compared with actual evaporation, and error sources of the three models were analyzed. The mean absolute relative error was 9% for the Penman-Monteith model, 14% for the Priestley-Taylor model, and 32% for the aerodynamics model; the Penman-Monteith model was the best of these three models for estimating bare soil evaporation. The error source of the Penman-Monteith model is the neglect of the advection estimation. The error source of the Priestley-Taylor model is the simplification of the component of aerodynamics as 0.72 times the net radiation. The error source of the aerodynamics model is the difference of vapor pressure and neglect of the radiometric component. The spatial distribution of bare soil evaporation is evident, and its main factors are soil water content and elevation.     

Remarkable enhancement of the photocatalytic activity of ZnO nanorod array by utilizing energy transfer between Eosin Y and Rose Bengal for visible light-driven hydrogen evolution

In this work, we suggested that an efficient ZnO-based photocatalyst can be prepared utilizing energy transfer among organic dyes for visible light-driven hydrogen evolution. Followed this idea, a photocatalytic system containing Eosin Y, Rose Bengal, ZnO nanorod array and Pt was fabricated. Meanwhile, photocatalytic H₂ evolution over the as-prepared photocatalytic system was explored. The results indicate that the visible photocatalytic activity of ZnO nanorod array can be obviously enhanced utilizing the energy transfer between Eosin Y and Rose Bengal. This photocatalytic system possesses high activity for visible light-driven H₂ evolution. A rate of H₂ evolution of approximate 0.52 L m^?2 h^?1 was achieved under optimal condition, which is 130% and 58% higher than those of the photocatalytic systems containing individual dye, respectively. The present results may reveal a new strategy for preparation of efficient visible photocatalyst.     

Research on heat dissipation performance and flow characteristics of air‐cooled battery pack

With the depletion of fossil fuels and the aggravation of environmental pollution, the research and development speed of electric vehicles has been accelerating, and the thermal management of battery pack has become increasingly important. This paper selects the electric vehicle battery pack with natural air cooling as the study subject, conducts simulation analysis of the heat dissipation performance of battery packs with and without vents. Then this paper researches on the influence of internal flow field and external flow field. Field synergy principle is used to analyze the effect of velocity field and temperature field amplitude. The results show the following: it is found that the maximum temperature rise and the internal maximum temperature difference of the battery pack with vents are reduced by about 23.1% and 19.9%, raising speed value can improve the heat dissipation performance, and raising temperature value can decrease the heat dissipation performance. Reasonable design of the vents can make the inner and outer flow field work synergistically to achieve the best cooling effect. Then the reference basis for the air cooling heat dissipation performance analysis of electric vehicle, battery pack structure arrangement, and air‐inlet and air‐outlet pattern choosing are offered.