Higher-dimensional virtual diagonals and ideal cohomology for triangular algebras

We investigate the cohomology of non-self-adjoint algebras using virtual diagonals and their higher-dimensional generalizations. We show that infinite dimensional nest algebras always have non-zero second cohomology by showing that they cannot possess 2-virtual diagonals. In the case of the upper triangular atomic nest algebra we exhibit concrete modules for non-vanishing cohomology.

     

HyperproⅠ：面向对象的超媒体结构研究

本文对ＨｙｐｅｒｐｒｏⅠ──一个运用面向对象方法，采用簇丛结构的超媒体信息管理系统模型进行了分析和研究．在Ｗｉｎｄｏｗｓ系统的基础上实现了面向对象方法的一般特征．通过提供结点、链和簇（模式）三种类模板建立对象结构，采用簇丛（模式）结构作为系统中表达结点组逻辑关系的一种实体，使ＨｙｐｅｒｐｒｏⅠ具有既能管理结点内容又能管理结点之间关系的功能．本文还介绍了ＨｙｐｅｒｐｒｏⅠ的结构和功能以及它的服务、查询、浏览、界面设计     

APPLEⅡ微机的多点自动测试系统

本文介绍一种个人计算机控制的新型多点自动测试系统。该系统采用了自行设计的接口仪器。新型接口包括有应变放大器和由微机程控的多路自动转换器。文中讨论了采用该系统进行应变梁的弯曲实验以及复合应力下主应力测试的实例。 本文提出的测试系统方便、价廉、可靠。     

A pulse stacker for time-resolved laser plasma diagnostics

A passive splitter array is described which allows time-resolved plasma diagnostic measurements to be performed on a single shot basis. The advantage of this stacker is that it has high efficiency, is simple, easy to adjust, and can be inserted into an optical beam path without disturbance to alignment.     

Chiral approach to nuclear matter: role of two-pion exchange with virtual delta-isobar excitation

We extend a recent three-loop calculation of nuclear matter by including the effects from two-pion exchange with single and double virtual Δ(1232)-isobar excitation. Regularization dependent short-range contributions from pion-loops are encoded in a few NN-contact coupling constants. The empirical saturation point of isospin-symmetric nuclear matter, , ρ₀=0.16 fm⁻³, can be well reproduced by adjusting the strength of a two-body term linear in density (and tuning an emerging three-body term quadratic in density). The nuclear matter compressibility comes out as K=304 MeV. The real single-particle potential U(p,k_f0) is substantially improved by the inclusion of the chiral πNΔ-dynamics: it grows now monotonically with the nucleon momentum p. The effective nucleon mass at the Fermi surface takes on a realistic value of M^*(k_f0)=0.88M. As a consequence of these features, the critical temperature of the liquid-gas phase transition gets lowered to the value T_c15 MeV. In this work we continue the complex-valued single-particle potential U(p,k_f)+iW(p,k_f) into the region above the Fermi surface p>k_f. The effects of 2π-exchange with virtual Δ-excitation on the nuclear energy density functional are also investigated. The effective nucleon mass associated with the kinetic energy density is . Furthermore, we find that the isospin properties of nuclear matter get significantly improved by including the chiral πNΔ-dynamics. Instead of bending downward above ρ₀ as in previous calculations, the energy per particle of pure neutron matter and the asymmetry energy A(k_f) now grow monotonically with density. In the density regime ρ=2ρ_n<0.2 fm⁻³ relevant for conventional nuclear physics our results agree well with sophisticated many-body calculations and (semi)-empirical values.     

A self-compensating optical delay stage

Using a retro-reflecting prism and a mirror to form a two-fold optical delay yields very useful characteristics: long optical delay, self-compensation for deviations of the motion of the delay stage, easy adjustment and no influence on polarization of the beam. Such a delay stage is described, and the advantages of the set-up explained.     

光栅传感器在弹簧测试仪中的应用

用弹簧测试仪对弹簧的特性进行测试和控制是保证产品质量的重要措施。弹簧测试仪由测试工作台和测试系统组成,工作台采用组合式结构,测试系统采用主从式结构,主机和从机之间通过RS-232串口实现通讯。采用应变式力传感器和光栅传感器分别对弹簧力和弹簧变形进行了测量。应用虚拟仪器技术对系统进行了设计,采用了多种软、硬件相结合的抗干扰措施。结果表明,研制的弹簧测试仪具有操作方便、人机交互友好、速度快、测试精度高、性能稳定等特点。     

Some structural properties of a Markovian storage/production system

We consider a storage/production system with state-dependent production rate and state-dependent demand arrival rate. Every arriving demand gives rise to a 'peak' in the trajectory of the content process. We characterize the processes N ₀(x)and N₁(x), defined as the number of peaks and the number of record peaks, respectively, before the content reaches the level x. The results are applied to the virtual waiting time process W(t) of a M/G/1 queue. Assuming that W(0)= x₀, M(x) is defined to be the number of arrivals before the virtual waiting time drops from x₀ to x₀-x(0⩽ x ⩽ x₀) ; in particular, Mx₀)is the number of customers arriving during the first busy period. It is shown that (M(x))(0⩽ x ⩽ x₀)is a compound Poisson process, and its jump size distribution is derived in closed form. This revised version was published online in June 2006 with corrections to the Cover Date.     

Evaluation of the capacitive force between an atomic force microscopy tip and a metallic surface

We propose a very simple method to determine the electrical tip-surface force in Atomic Force Microscopes used to study the electrical properties of metallic or insulating materials; the analysis of the measurements as well as determination of the appropriate experimental procedures requiring an analytical model of the tip-surface capacitance. The comparison of force expressions obtained by this method with those obtained by exact derivation in the case of the sphere-infinite plane system shows very good agreement. This method is then applied to determine the tip-surface force, the real shape of the tip being introduced in the derivation. The obtained expression is compared to experimental and numerical data. We emphasize that this method is very general and can be applied to any axially symmetric capacitor. Received: 17 June 1997 / Received: 16 September 1997 / Accepted: 7 November 1997     

VMware虚拟机技术在Windows软路由实验中的应用

介绍了使用VMware虚拟机技术在单机环境下实现Windows软路由实验的方法及步骤。该方法无需架设实际的局域网环境,也无需专门的网络实验室,利用虚拟机构建的虚拟网络及利用Windows2000的“路由和远程访问”服务达成路由器的功能,可以实现不同网络地址段的互联通信。