RELATIONSHIP BETWEEN CREEP PROPERTIES AND STRUCTURE OF STEEL 20Cr11MoVNbNB

Studies were made of the creep properties and structure change of steet 20Cr11MoVNbNB at550-650℃.It is found that at 550℃ when creep stress>180 MPa there exists linear rela-tion with two different slopes β_1 and β-2 between transitional creep strain ε_β and creeptime t~(1/3),and β_1(in initiol period)>β_2(in later period).The Creep rate of stable stage at550℃ can be expressed by =Aσ exp(-Q_ /RT),where,n=4.7.A exp(-Q_ /RT)=5.37×10~(-16).Apparent creep activation energy Q_ =430 kJ/mol at 550-650℃,which ismuch higher than the self-diffusion activation energy of atoms for matrix Fe.In creepprocess,as the creep stress and time increase,the total weight of precipitated phases and rela-tive weight of Cr,Mo and V increase,but those of Fe and Nb decrease in precipitated phases,     

TC11钛合金表面电弧离子镀TiAlN涂层防护性能的研究

利用电弧离子镀技术在TC11钛合金基体上沉积TiAlN涂层。采用扫描电子显微镜（SEM）、X射线衍射仪（XRD）等方法对比分析了钛合金基体和涂层氧化前后的表面形貌、物相结构。采用X射线光电子能谱仪（XPS）对TiAlN涂层性能进行了分析，研究了基体和镀膜的耐磨性。结果表明，TiAlN涂层显著改善了钛合金的粘着磨损性及高温抗氧化性，在空气中650℃静态氧化100h后，TiAlN涂层依然保持良好的状态和抗磨损性能。     

Effect of NiAl Microcrystalline Coating on the High-Temperature Oxidation Behavior of NiAl–28Cr–5Mo–1Hf

The effect of an NiAl microcrystalline coating prepared by magnetron sputtering on the high-temperature oxidation behavior of NiAl–28Cr–5Mo–1Hf was investigated in static air at 1000–1150°C. The additions of Cr, Mo, and Hf changed the single 11gq7454214v154/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-phase structure into a multiphase structure [11gq7454214v154/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-NiAl, 11gq7454214v154/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Cr(Mo), and Heusler phase]. The NiAl–28Cr–5Mo–1Hf alloy formed a nonprotective mixed scale of Al₂O₃+Cr₂O₃+HfO₂ and exhibited relatively large weight gains. The large weight gains were attributed to extensive internal oxidation. The sputtered NiAl microcrystalline coating remarkably improved the oxidation resistance of NiAl–28Cr–5Mo–1Hf due to the formation of a compact and adherent Al₂O₃ scale at all test temperatures. It was found that the 11gq7454214v154/xxlarge952.gif" alt="theta" align="BASELINE" BORDER="0">-11gq7454214v154/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Al₂O₃ transformation caused the anomalous behavior of the oxidation–kinetics curves of the NiAl microcrystalline coating in the temperature range 1000–1150°C. A change in the morphology of scales occurred with the transformation.     

使用PKCS#11标准实现OpenVPN硬件加密算法

随着企业对使用互联网的安全需求大幅提高,VPN技术成为重要的解决方案。OpenVPN作为Linux下开源VPN的先锋,得到了广泛研究和应用。采用PKCS#11标准将硬件加密设备(KEY,一种智能密码钥匙)接入OpenVPN,使身份验证所需的数字证书能够通过硬件读写、存储,并且使VPN加密算法及加密/解密过程能够通过硬件实现,从而进一步提高OpenVPN的安全性能。     

State feedback control of continuous-time T-S fuzzy systems via switched fuzzy controllers

This paper studies the problem of state feedback control of continuous-time T-S fuzzy systems. Switched fuzzy controllers are exploited in the control design, which are switched based on the values of membership functions, and the control scheme is an extension of the parallel distributed compensation (PDC) scheme. Sufficient conditions for designing switched state feedback controllers are obtained with meeting an H_∞ norm bound requirement and quadratic D stability constraints. It is shown that the new control design method provides less conservative results than the corresponding ones via the parallel distributed compensation (PDC) scheme. A numerical example is given to illustrate the effectiveness of the proposed method.     

基于JAVA平台的移动代码安全性探讨

该文对Java平台中Applet安全性方面的问题,从1.0版本至今的发展过程进行了讨论。详细讨论了Java2平台对移动代码安全性的解决方案及Java6.0平台安全性的增强,对于在java平台下进行移动代码开发有一定指导意义。     

基于一类新的强化缓冲算子的GM(1,1)预测精度研究

根据灰色系统理论中新息优先利用原理,在对缓冲算子和已有强化缓冲算子研究的基础上,构造了一类新的强化缓冲算子,有效解决了冲击扰动数据序列在建模预测过程中常常出现的定量预测结果与定性分析结论不符的问题.实例分析结果表明,这类新的强化缓冲算子能显著提高GM(1,1)模型的预测精度.     

Controller synthesis with guaranteed closed-loop phase constraints

In this paper, we present an analysis and synthesis approach for guaranteeing that the phase of a single-input, single-output closed-loop transfer function is contained in the interval [−α,α] for a given α>0 at all frequencies. Specifically, we first derive a sufficient condition involving a frequency domain inequality for guaranteeing a given phase constraint. Next, we use the Kalman–Yakubovich–Popov theorem to derive an equivalent time domain condition. In the case where , we show that frequency and time domain sufficient conditions specialize to the positivity theorem. Furthermore, using linear matrix inequalities, we develop a controller synthesis approach for guaranteeing a phase constraint on the closed-loop transfer function. Finally, we extend this synthesis approach to address mixed gain and phase constraints on the closed-loop transfer function.     

Phase Separation Derived Core/Shell Structured Cu11V6O26/V2O5 Microspheres: First Synthesis and Excellent Lithium‐Ion Anode Performance with Outstanding Capacity Self‐Restoration

Novel amorphous vanadium oxide coated copper vanadium oxide (Cu₁₁V₆O₂₆/V₂O₅) microspheres with 3D hierarchical architecture have been successfully prepared via a microwave‐assisted solution method and subsequent annealing induced phase separation process. Pure Cu₁₁V₆O₂₆ microspheres without V₂O₅ coating are also obtained by an H₂O₂ solution dissolving treatment. When evaluated as an anode material for lithium‐ion batteries (LIBs), the as‐synthesized hybrid exhibits large reversible capacity, excellent rate capability, and outstanding capacity self‐recovery. Under the condition of high current density of 1 A g^?1, the 3D hierarchical Cu₁₁V₆O₂₆/V₂O₅ hybrid maintains a reversible capacity of ≈1110 mA h g^?1. Combined electrochemical analysis and high‐resolution transmission electron microscopy observation during cycling reveals that the amorphous V₂O₅ coating plays an important role on enhancing the electrochemical performances and capacity self‐recovery, which provides an active amorphous protective layer and abundant grain interfaces for efficient inserting and extracting of Li‐ion. As a result, this new copper vanadium oxide hybrid is proposed as a promising anode material for LIBs.     

固溶处理对TC11钛合金棒材组织和性能的影响

通过场发射扫描电镜及拉伸性能测试,研究了TC11钛合金棒材3种固溶处理时间和2种固溶方式对显微组织及力学性能的影响。结果表明:TC11钛合金在经过3 h的固溶后,组织中局部的亚稳定β晶体位相发生偏转,β转变组织中的次生α相变的粗大,经过后续时效后的β转变基体发生更为充分的分解和析出,在片层的β边界出现连续的更细小的次生α相。由于固溶时间延长,发生了过固溶,析出的次生相逐渐细小,导致裂纹扩展阻力降低,引起屈服强度的降低,分开各1 h的固溶时效性能低于连续2 h的固溶时效性能。