静电放电次数与半导体器件潜在性失效的关系

为研究硅双极晶体管中由ESD注入引起的潜在性失效与放电次数间的关系,对微波低噪声小功率硅双极器件进行了同一电压不同次数的人体模型ESD注入实验.注入电压为1.50 kV.注入管脚为器件对ESD最敏感的端对.器件分组注入不同次数的ESD后,将注入和未注入过ESD的器件同时进行加速寿命实验.通过比较各组器件损伤率的大小来反映器件使用寿命的变化.经统计分析与计算发现:开始时,随放电次数的增加,器件出现潜在性失效的概率增大,当概率达到一定极限值后,又会随放电次数的增大而减小,说明ESD的注入不仅可能在部分硅器件内部造成潜在性失效,也可能提高另外一部分器件的可靠性.     

数字时代图书馆员素质探析

分析了数字时代图书馆信息服务的变化,指出图书馆员应具备良好的职业道德、广阔的知识面、熟练的业务技能和健康的心理素质等,并提出提高馆员素质的具体措施。     

论网络时代的图书馆创新文化

探讨了网络时代图书馆创新文化的意义,论述了网络时代图书馆创新文化的特征,提出了网络时代图书馆创新文化的举措。     

基于开放式遗传算法的图像阈值选取

引入了开放式遗传算法的理论,使种群在一个开放的环境中进化,增加了种群的多样性。同时对交叉、变异操作进行了改进,避免了进化过程中种群的退化现象,从而有效克服了遗传算法的早熟问题又提高了遗传算法的收敛性能。文章以最小误差法为例,对比了本文算法和简单遗传算法在阈值处理中的性能,并用实验证明了本文算法的可行性。     

Solid state phase transitions characterized by ESR and XAS

Measurements of the relaxation time, τ of electron systems to a disturbance, by two different spectroscopic methods are examined in detail, with the purpose to establish how the presence of fluctuations near a solid state phase transition are made evident in insulators, conductors and superconductors. The absolute temperature and the relaxation time determine the thermodynamic stability of the electronic system near a phase transition by the Uncertainty Principle. At a given temperature T, Landau and Lifshitz obtain the stability from the lower limit of the uncertainty in entropy in units of the Boltzmann constant, ΔS/k_B<<1 when T τ>>3.82 K ps. Magnetic resonance can measure τ>>10⁻¹⁰ s, when v=9 GHz. X-ray spectroscopy can measure τ<10⁻¹⁶s for hv>5 keV. The results extract information about phenomena that occur at the phase transition by following the evolution of spectral features versus T and crystal orientation. Electron spin resonance identifies the phase transition by the evolution of doublet, triplet and antiferromagnetic resonance, and energy loss. Analysis of the X-ray absorption near an element edge determines one, the relative valence: V(Cu in chains)−V(Cu in planes) ≈1 in YBa₂Cu₃O_7−δ, two, the appearance of allowed Cu K pre-edge quadrupole transitions at T_c, three, the enhancement of Ba L3,2 edge transitions by an order of magnitude, just above T_c, at a crystal orientation of the c-axis to the X-ray polarization vector of 8 π/18, and four, difference X-ray absorption spectra, relative to the transition temperature, identify the bonds as well as the atoms involved in the transition. The figure abstract shows the changes in electron density obtained by temperature difference X-ray absorption near the Y K-edge in YBa₂Cu₃O_7−δ below T_c.     

Analysis of Off-Axial Optical Systems (2)

The extended 4×4 Gaussian bracket matrix Gij represents the lowest order quantity of “aberration coefficient tensor quantities” which are defined to as the peculiarity of off-axial optical systems and are independent of azimuths. We newly confirmed this extended 4×4 Gaussian bracket matrix of deflection (refraction or reflection), transmission and “twisting.” The result determined by use of a new representative method of asymmetrical surfaces and a method of paraxial expansion along the folded reference axis shows that the 4×4 Gaussian bracket matrix is the extended form of the 2x2 Gaussian bracket matrix which is used in co-axial rotational symmetric optical systems. Furthermore, we analyze and formalize the crossterm effects, which are the most serious problem in optical systems having multiple off-axial surfaces, using the concept of a chain of “optical systems divided into former and latter” and the vector-tensor analysis method. The result of this analysis reveals the structure of the cross-term effects and proves the usefulness of the vector-tensor analysis method in general image analysis.     

The impact of a heavy-tailed service-time distribution upon the M/GI/s waiting-time distribution

By exploiting an infinite-server-model lower bound, we show that the tails of the steady-state and transient waiting-time distributions in the M/GI/s queue with unlimited waiting room and the first-come first-served discipline are bounded below by tails of Poisson distributions. As a consequence, the tail of the steady-state waiting-time distribution is bounded below by a constant times the sth power of the tail of the service-time stationary-excess distribution. We apply that bound to show that the steady-state waiting-time distribution has a heavy tail (with appropriate definition) whenever the service-time distribution does. We also establish additional results that enable us to nearly capture the full asymptotics in both light and heavy traffic. The difference between the asymptotic behavior in these two regions shows that the actual asymptotic form must be quite complicated. This revised version was published online in June 2006 with corrections to the Cover Date.     

信息时代图书馆数字化建设新探

根据数字化图书馆的特征,阐述了建设数字化图书馆的必要性、具体措施以及建设数字化图书馆中应重视的问题。     

信息时代档案工作者必须具备的职业意识

从档案工作的现实出发,指出了档案工作者必须具备的现代档案职业意识。     

Thermoelectric Properties of Czochralski GeSi Crystal

In order to discuss the application possibility of SiGe crystal in thermoelectric materials,we investigated the thermoelectric properties of several silicon-germanium alloys with different content,orientation and electric conductive type. As discussed in the experiment result,the absolute value of Seebeck coefficient fluctuates from 300 to 600 μV/K in the whole temperature range. In the present paper,the relationship of Seebeck coefficient against content,orientation and electric conductive type is summarized in detail. The Seebeck coefficient of the sample with <111> orientation is smaller than that in <100> at the same temperature. Absolute value of P-type is larger than that of N-type except pure Ge. But as the temperature increases,the absolute value of pure Ge decreases many times as quickly as that of other specimens. In addition,the specimens of bulk GeSi alloy crystals for experiment were grown by the Czochralski method through varying the pulling rate during the growing process.