P-RBAC:一种门户环境下的访问控制模型

门户能够有效地实现异构信息之间的集成与协作,并为用户提供可定制、统一且遵循规范的访问服务.然而,由于门户所具有的这些不同于普通Web应用的特性,也使得传统访问控制模型无法在门户中直接使用.提出了一种面向门户系统的访问控制模型p-RBAC.P-RBAC扩展了传统的基于角色访问控制模型,并根据行为状态进一步分为静态模型和动态模型.P-RBAC给出了静态模型和动态模型上的行为规则,提出了具体的动态权限指派和角色组织策略,从而有效地解决了门户的访问控制问题.实际的应用案例证明,P-RBAC模型能够适用于门户的访问控制,并较之传统访问控制模型更高效可行.

Microcalorimetric studies of the iridium catalyst for hydrazine decomposition reaction

Microcalorimetric studies of H-2, NH3 and O-2 adsorption, as well as the NH3 decomposition activities evaluation were used to characterize the iridium catalysts for hydrazine decomposition with different supports (Al2O3, SiO,) and iridium contents (1.8, 10.8 and 22.1%). The higher H-2 chemisorption amounts on Ir/Al2O3 catalysts than those on the corresponding Ir/SiO2 counterparts revealed that the strong interaction of iridium and Al2O3 led to higher dispersion of iridium on Ir/Al2O3 catalysts than on Ir/SiO2 catalysts. The larger increase in strong H-2 adsorption sites on highly loaded Ir/Al2O3 than the corresponding Ir/SiO2 ones could be attributed to the interaction not only between iridium atoms but also between iridium and Al2O3. The microcalorimetric results for NH3 adsorption showed that no apparent chemisorption of NH3 existed on Ir/SiO2 catalysts while NH3 chemisorption amounts increased on Ir/Al2O3 catalysts with iridium loadings, which arose from the interaction of the catalysts support of Al2O3 With chloride anion. Both highly dispersed iridium active sites and chloride anion on Ir/Al2O3 catalysts could be beneficial to the intermediate NH3 decomposition in N2H4 decomposition. The similar O-2 plots of differential heat versus normalized coverage on Ir/Al2O3 and Ir/SiO2 catalysts could not be due to the metal-support interaction, but to the formation of strong Ir-O bond. (C) 2005 Elsevier B.V. All rights reserved.

Shear Strength Measurements in LY-12 Aluminium Alloy During Shock Loading

Lateral stress of LY-12 alummium alloy under plate impact shock loading was measured. Based on the measured data, the Hugoniot relation and shear strength were obtained. The result has demonstrated that the shear strenath of the tested material increases remarkably with the increasing longitudinal stress. This means that the assumption of constant shear strength usually adopted in shock stress calculation is not suitable for the present material.

The Evolution of Fatigue bocks in Aluminum Alloy LY-12 under Shock beading

对LY12铝合金在低周疲劳条件下的裂纹情况和随后进行的动态拉伸条件下裂纹的发展给予了观察和统计分析。发现裂纹的累积数密度分布在损伤演化过程中保持指数形式,用NAG模型对实验结果进行分析,得出该材料裂纹演化发展方程的各种参数。

LY-12铝高温凝聚态动力学性质研究——高温冲塞剪切破坏强度的测量

本文介绍Ly-12铝合金从常温到400℃高温下,动态冲塞剪切破坏强度的测试及研究结果,并给出了该种材料静态压剪破坏强度的测量结果。在上述温度范围内,Ly-12铝的动态冲塞剪切破坏强度与其静态结果之比为1.3∶1～4∶1,表明随着温度的升高,动态的强度远大于同温度的静态结果。

LY-12铝高温凝聚态动力学性质研究——高温弹性模量的测定

金属材料的高温动态力学性能是材料科学领域中的重要方面。本文介绍LY-12合金铝在常温至450℃的温度区间内和动载下(应变率为 10~3/秒),材料弹性模量的研究。此项研究采用的试验装置为一维Hopkinson压杆及管式高温炉。应用一维弹性应力波传播理论,测得LY-12铝试件在不同温度T条件下的声速c(T),按照c(T)=[E(T)/ρ(T)]~(1/2),获得杨氏模量E(T)随温度的变化曲线。

结构弛豫对Zr_(64.13)Cu_(15.75)Ni_(10.12)Al_(10)块体非晶合金硬度和剪切带特征的影响

通过接近玻璃转变温度的等温退火获得不同弛豫状态的Zr64.13Cu15.75Ni10.12Al10块体非晶合金样品。利用维氏显微硬度计和洛氏硬度计研究结构弛豫对合金硬度和压痕周围剪切带特征的影响规律。结果表明:在590K等温退火处理使Zr64.13Cu15.75Ni10.12Al10块体非晶合金发生焓弛豫行为,其维氏显微硬度随退火时间的延长较快增加后趋于稳定,而大载荷洛氏硬度对结构弛豫不敏感。通过洛氏压痕周围剪切带特征的研究,定量比较了结构弛豫对剪切带间距、数量的影响规律。

On a fiber grating sensor system with the capacity of cross-sensitivity discrimination

A novel fiber Bragg grating (FBG) sensor system based on an interrogating technique by two parallel matched gratings was designed and theoretically discussed. With an interrogation grating playing the role of temperature compensation grating simultaneously, the wavelength drifts induced by temperature and strain were discriminated. Additionally, the expressions of temperature and strain were deduced for our solution, and dual-value problem and cross sensitivity were solved synchronously through data processing. The influence of the FBG's parameters on the dynamic range and precision was discussed. Besides, the change of environment temperature cannot influence the dynamic range of the sensor system through temperature tuning. The system proposed in this paper will be of great significance to accelerate the real engineering applications of FBG sensing techniques. (c) 2007 Elsevier GmbH. All rights reserved.

Nd：Y3Sc（1．5）Al（3．5）O（12）透明陶瓷的光谱性能以及激光输出

采用燃烧法制备了Nd：YSAG粉体,经过成型、素烧,最终在氢气气氛中烧结制备了Nd：YSAG透明陶瓷.测试结果表明,Nd：YSAG透明陶瓷具有荧光谱线较宽,荧光寿命较长的特点.激光实验得到的激光输出,斜率效率为23.6%,输出功率为0.36W,输出激光的谱线分布较宽.

Dual-wavelength competitive output in Nd:Y3Sc1.5Al3.5O12 ceramic disk laser

In this paper, we demonstrated a dual-wavelength competitive output in Nd:Y3SC1.5Al3.5O12 ceramic disk laser. Different dual-wavelength output behaviors for Nd:YSAG and Nd:YAG ceramic disk laser were investigated and discussed. By applying the energy transfer model, we suggested the reasonable explanation for this new phenomenon as the disordered replacing of Al3+ ions by Sc3+ ions. The main advantage of the dual-wavelength ceramic laser is the possibility to serve as the seed source to generate Terahertz radiation. (C) 2008 Elsevier B.V. All rights reserved.

Generation of 1.5-12 ns width-tunable 532 nm pulses by adopting laser-induced plasma shutter technique

The pulse-shaping technique has found widespread applications in nonlinear optics and material processing. Experimental research on laser-induced plasma shutter to control the 532 nm pulse width is conducted. The impacts of the total pulse output energy on pulse compression are investigated, and a useful conclusion can be drawn that there exists an optimal value of pulse energy at which the shortest output pulse of 3.23 ns can be obtained without a device for delay-time. Once the device for delay-time is employed to change the optical differences between two laser paths, the pulse width can be further shortened to 1.51 ns. In short, the 1.5-12 ns width-tunable 532 nm laser pulses have been obtained by adopting the laser-induced plasma shutter technique. (C) 2007 Elsevier GmbH. All rights reserved.

Yb∶Y3Al5O12晶体晶格振动光谱的研究

采用提拉法生长Y3Al5O12(YAG)晶体和Yb3+掺杂原子数分数分别为5%, 10%, 15%, 20%, 25%, 50%和100%的Yb∶Y3Al5O12(Yb∶YAG)晶体。系统表征和分析了Yb3+掺杂浓度对拉曼光谱的影响。随着Yb3+掺杂浓度的增加,晶体的振动模式没有明显的变化,晶体结构没有改变;在370 cm-1和785 cm-1附近,振动吸收峰的半峰全宽逐渐增大。分析得出,Yb3+掺杂浓度对晶体的晶格、对称性、荧光寿命均有影响,从而可能影响到晶体的光谱和激光性能。

Yb∶Y_3Al_5O_(12)/Y_3Al_5O_(12)复合晶体的制作和光谱性能

采用热键合技术,制作中运用不同的工艺参量制作出12片Yb∶Y3Al5O12/Y3Al5O12(Yb∶YAG/YAG)复合晶体。利用偏光显微镜对其键合界面进行了观察,研究了样品的透射光谱,从而确定出复合晶体合适的制作工艺。通过透射光谱的形状和透射率来表征复合晶体键合界面的质量。研究表明Yb∶YAG/YAG复合晶体键合质量较好,可实现一体化。

Effects of gamma-irradiation and air annealing on Yb-doped Y3Al5O12 single crystal

The effects of gamma-irradiation on the air-annealed 10 at.% Yb:Y3Al5O12 (YAG) and air annealing on the gamma-irradiated 10at.% Yb:YAG have been studied by the difference absorption spectra before and after treatment. The gamma-irradiation and air annealing led to opposite changes of the absorption properties of the Yb:YAG crystal. After air annealing, the gamma-irradiation induced centers were totally removed and the concentration of Fe3+ and Yb3+ were lightly increased. For the first time, the gamma-irradiation induced valence changes between Yb3+ and Yb2+ ions in Yb:YAG crystals have been observed. (C) 2007 Elsevier B.V. All rights reserved.