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.     

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.     

The numerical analysis of the radial sleeve bearing with combined surface slip

In order to improve the carrying capacity and reduce the temperature rise in high speed and precise spindle systems, a combined surface radial sleeve bearing using the interfacial slip technique was discussed. An extended Reynolds equation was derived based on the modified slip length model considering the limiting shear stress. By means of the finite differential methods, the characteristic analysis and optimization of the slip region of the combined surface sleeve bearing were carried out, and it has been proved that there is still a considerable large load support in a parallel sliding gap. Comparing with the general journal bearing, the load capacity and end leakage rate of the combined surface sleeve bearing can be increased greatly and the load capacity can be increased by 1.75 times. The attitude angle, friction drag, temperature rise of the combined bearing can be decreased distinctly and the temperature rise can be decreased by 92.4%.     

Effect of denucleating glass composition on undercooling of Fe83Ga17 alloy melts

Adopting glass fluxing combined with superheating cycling method, the undercooling and its stability of Fe₈₃Ga₁₇ alloy melts were investigated using different kinds of denucleating glass: B₂O₃, 90% NaSiCa + 10% B₂O₃ (simplified as Na–Si–Ca–Al–B) and 70% Na–Si–Ca–Al–B + 30% Na₂B₇O₄. The results showed that different glass has different denucleating mechanism. The purification of B₂O₃ glass is only a physical process, by which the stable bulk undercooling cannot be obtained during superheating–cooling cycles. While taking Na–Si–Ca–Al–B glass as purifying agent, its denucleating mechanism is a comprehensively physicochemical process. But the stability of undercooling is still undesirable because of the separation between melt and glass during cooling process in superheating cycling. A stable bulk undercooling can be obtained by physicochemical denucleating process in the case of 70% Na–Si–Ca–Al–B + 30% Na₂B₇O₄ molten glass owing to its suitable viscosity.     

Boosting the antimicrobial and Azo dye mineralization activities of ZnO ceramics by enhancing the light-harvesting and charge transport properties

Herein, we report the wet-chemical synthesis of a ferromagnetic nickel-doped ZnO (Zn_1-xNi_xO) nanocatalyst as a novel and visible-light-driven photocatalyst. Through X-ray diffraction, UV/Vis absorption, electronic studies, and current-voltage experiments, the effect of the ferromagnetic nickel dopant on the structural, optical, morphological, and electrical properties of the synthesized Zn_1-xNi_xO nanocatalyst was studied. The Ni-doping introduced the structural variation in the Zn_1-xNi_xO nanocatalyst, exhibiting a visible light-triggered optical band gap of 2.96 eV and an excellent current conductivity of 6.3 × 10⁻⁴ Sm⁻¹. Moreover, the synthesis of the Zn_1-xNi_xO catalyst at the nanoscale enhanced its surface energy, showing a robust affinity to stick with the dye and pathogenic microbes. The synergistic effects of all the mentioned features enable our Zn_1-xNi_xO nanocatalyst to efficiently generate and transport reactive oxygen species (ROS) under visible light illumination. Regarding antibacterial action, the as-synthesized Zn_1-xNi_xO nanocatalyst showed 1.7% higher activity against E. coli than that of the drug Ciprofloxacin. In addition, doped nanocatalysts mineralize almost 97% of the Allura red dye in just 80 min with a constant rate value of 0.036 min⁻¹. The impedance study and post-application XRD proposed that our Zn_1-xNi_xO nanocatalyst has good conductivity and structural stability. Applications studies show the unusual photocatalytic activity of as-synthesized Zn_1-xNi_xO nanocatalysts, which makes it a suitable candidate for industrial discharge treatment applications at the expense of solar light.