基于动态优先级的实时Java垃圾回收策略

针对通用平台下Java虚拟机垃圾回收器（GC）的不定期启动问题,提出了一个周期性提升GC优先级、提前调度GC的解决方案.该方案把优先级按任务的重要程度分两个等级：关键线程和非关键线程,通过计算垃圾回收的时机即计算出垃圾回收的周期上限T_GC,在任务运行最长不超过T_GC的时间内提升GC的优先级为非关键线程的最大值,从而使GC在不影响关键线程的情况下能提前回收内存中的垃圾,使虚拟机的内存处于非饱和状态.理论分析和实验结果表明,该方法可以提高通用环境下Java关键线程的实时性及执行的可预测性.     

气体作冷却润滑剂的绿色切削试验

为实现绿色切削,研究了无污染、无危害的冷却润滑技术.采用氮气、氧气、二氧化碳气、氩气及过热水蒸气作冷却润滑剂,进行了单因素切削试验.试验结果表明,这些气体冷却润滑剂可以减小切削变形、切削力,降低切削温度,改善加工表面形貌.根据试验结果和冷却润滑作用机理分析可知,气体在切削中具有一定的冷却润滑作用,同时具有来源广泛、无毒害和污染、不用回收处理等绿色特点,故气体具备绿色切削的潜力.     

Facile synthesis of thin coating C/ZnO composites with strong electromagnetic wave absorption

C/ZnO composites with increased electromagnetic (EM) wave absorbing features have been synthesized through a simple one-pot hydrothermal process and subsequent high temperature carbonization under the protection of argon. The results depict that the maximum absorption of C/ZnO composites synthesized with the optimal molar ratio of zinc acetate to glucose is ?50.43?dB at 15.77?GHz. The 1.16-mm-thick coating shows a wide effective absorption bandwidth (3.52?GHz) of EM wave (RL≤?10?dB). The thin coating thickness of the C/ZnO composites is desirable for decreasing the absorber weight in EM wave absorption. And there are no other reagents used throughout the synthesis process except for the green glucose and zinc acetate. Thus, C/ZnO composites would be highly promising lightweight EM wave absorbing materials.     

Highly electrocatalytic activity Ruddlesden−Popper type electrode materials for solid oxide fuel cells

To promote the viability of commercial solid oxide fuel cell (SOFC), developing novel oxygen electrodes with high electrochemical activity is essential. Herein, a series Ruddlesden-Popper oxides, Sr_3?xLa_xFe₂O_7?δ (SLFx), are successfully synthesized and evaluated as potential cathode materials for SOFC. The oxygen desorption behavior, electrochemical activity and oxygen reduction reaction (ORR) kinetics of the SLFx cathodes are systematically discussed. The Sr_2.9La_0.1Fe₂O_7?δ (SLF10) cathode exhibits highest oxygen vacancy concentration and excellent electrocatalytic performance, as evidenced by a low polarization resistance of 0.14 Ω cm² and high maximum power density of 0.77 W cm^?2 at 700 °C. From electrochemical impedance spectra and distribution of relaxation times analysis, the oxygen adsorption/desorption process is the rate-limiting step toward ORR at the cathode interface. Furthermore, SLF10 shows considerable polarization overpotentials in both SOFC and solid oxide electrolysis cell (SOEC) modes, indicating that SLF10 is a promising bifunctional electrode for electrocatalytic oxygen reaction.     

Insight into the vacancy effects on mechanical and electronic properties of Tantalum Silicide

The effects of the vacancies on the structural stability, elastic constants, elastic moduli, brittle-to-ductile transition and electronic properties of Tantalum Silicide (TaSi₂) are investigated in detail by first-principles calculations. The values of vacancy formation energy confirm that the perfect TaSi₂ and TaSi₂ with different atomic vacancies can exhibit the structural stability at ground state. It is found that Ta atom vacancies are more stable than Si atom vacancies in TaSi₂ with vacancies. The elastic constants and elastic moduli describe the mechanical behavior for TaSi₂ and TaSi₂ with vacancies. The different atomic vacancies weaken the elastic stiffness for TaSi₂. But the values of B/G confirm that the brittle-to-ductile transition occurs with different atomic vacancies for TaSi₂. Although these vacancies make the shear and volume deformation resistance of TaSi₂ weaker, they obviously improve the brittle behavior of TaSi₂. The difference charge density and electronic structures are calculated to discuss and analyze the structural stability and mechanical properties for the perfect TaSi₂ and TaSi₂ with vacancies.     

Fe-Cr-C-B-N系堆焊合金的显微组织及耐磨性

在低碳钢表面采用明弧堆焊的方法制备了不同氮含量的Fe-Cr-C-B-N系堆焊合金.借助X射线衍射仪（XRD）、光学显微镜（OM）、扫描电子显微镜（SEM）、洛氏硬度计和湿砂磨损试验机对堆焊层的组织和性能进行分析.结果表明,堆焊层的显微组织为马氏体+奥氏体+BN+M₂₃（C, B）₆+M₃（C, B）+M₂B.随着氮添加量的增多,组织中有BN生成,初生奥氏体向针状马氏体转变,枝晶间共晶组织的数量减少;堆焊层硬度增加,磨损量出现先减少后增加的趋势.当堆焊层中氮的含量为0.17%时,基体组织与硬质相之间匹配良好,堆焊层的综合性能达到最佳,其硬度值为62.7 HRC,而磨损量仅为0.054 2 g.     

Hydrothermal synthesis and tuning of size and morphology of α-Co(OH)2 and α-Co2(OH)3Cl nanostructures as precursors for nanosized Co3O4

This study aims to investigate the hydrothermally synthesized cobalt(II) hydroxide-based materials, which will be thermally converted to generate Co₃O₄ nanostructures; an important class of materials characterized by good electrochemical, catalytic and optical properties. First, cobalt(II) hydroxide nanostructures were prepared via hydrothermal hydrolysis of two different precursors (cobalt(II) chloride salt and dichlorobis(thiourea)cobalt(II) complex) exposure to an ammonia atmosphere, and then the obtained α-Co(OH)₂ and α-Co₂(OH)₃Cl nanostructures were calcined to produce Co₃O₄ nanostructures that were characterized by FT-IR, XRD, UV–vis DRS and SEM techniques. The effects of the nature of the precursor, its concentration, and of the temperature and reaction time on size and morphology of the product were also investigated.     

Unidirectional wavelength filtering characteristics of the two-dimensional triangular-lattice photonic crystal structures with elliptical defects

The unidirectional wavelength filtering characters of the two-dimensional triangular-lattice photonic crystal structures consisting of two waveguides and an elliptic defect are theoretically studied by the finite-difference time-domain method. Through designing the coupling regions between the elliptical defect and the adjacent waveguides, the unidirectional wavelength filtering is achieved owing to the modes’ match and mismatch between the elliptical defect and waveguides, which converts the incident fundamental even-symmetric modes to the higher order odd modes. Based on the abundant defective modes with different symmetries supported by the elliptical defect, this kind of wavelength filters can allow the unidirectional light propagation with inverse forward directions, and the bidirectional propagation through the same structure at different wavelengths.     

基于组合特征和SVM的视频中人体行为识别算法

针对复杂场景中的人体行为识别困难的问题,提出了一种基于组合特征和SVM的行为识别算法.该算法使用光流特征、HOG特征、重心特征和3D SIFT特征构成的组合特征来描述人体的各种行为;使用一对一的方式训练SVM分类器对提取出的特征进行分类,并以投票的方式得到具体的行为类别.使用包含4个场景的KTH数据集进行仿真.结果表明,所提出的算法能适应各种复杂环境,且相比只采用单一特征的识别算法具有更高的分类精度.