皂河闸小水电存在问题及改造探讨

针对皂河闸水电站因长期运行造成的机电设备老化、机组效率较低等问题,对3号机进行技术改造。经过调研分析,提出改造方案,并对改造前后的经济效益进行对比分析。表3个。     

Silicon power MOSFET at low temperatures: A two-dimensional computer simulation study

Understanding how the structure of the unit-cell affects the cryogenic performance of a Si power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is an important step toward optimizing of the device for cryogenic operations. In this paper, numerical simulations of the Si power Double Diffused MOSFET’ (DMOS) are performed at room temperature and cryogenic temperatures. Physically based models for temperature dependent silicon properties are employed in the simulations. The performances of power DMOS’ with various unit-cell structures are compared at both room temperature and low temperatures. The effect of the cell structure on the on-resistance and breakdown voltage of the device are analyzed. The simulation results suggest that the device optimized for room temperature operation can be further optimized at cryogenic temperatures.     

Direct evaluation of singular integrals in elastoplastic analysis by the boundary element method

This paper presents a new method for the direct and accurate evaluation of strongly singular integrals in the sense of Cauchy principal values and weakly singular integrals over quadratic boundary elements in three-dimensional stress analysis and quadratic internal cells in two-dimensional elastoplastic analysis by the boundary element method. A quadratic triangle polar co-ordinate transformation technique is applied to reduce the order of singularity of the singular integrals. Next, a form of Stokes' theorem is introduced in order to remove the singularity in the Cauchy principal value integrals; therefore, the evaluation of these integrals can be carried out by standard Gaussian quadrature. Numerical examples of 2-D elastoplastic problems and a 3-D elastic problem show the effectiveness and efficiency of the method.     

β放射性气体浓度计的新分度方法

本文介绍β放射性气体浓度计的一种新的分度方法——泄漏元件排气法。其特点是一只元件可分度放射性气体浓度计的许多读出数(甚至是几个量程),操作方便。     

Improved coupled-mode theory of anisotropic optical waveguides

A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D₂ is about 0.1 μm     

VILOFT织物的染整工艺

新型VILOFT粘胶纤维织物具有独特的扁平截面，导湿透气，蓬松保暖。本文探讨该纤维织物的前处理，染色，整理工艺，优化并给出了具体工艺参数，对实际生产有一定的参考价值。     

大同煤矿集团公司供水处局域网的开发和应用

介绍了大同煤矿集团公司供水处处级局域网的设计原则及开发过程，对外级局域网1年来取得的管理效果、经济效益、社会效益进行了简明的阐述。     

Iterative receivers for space-time block-coded OFDM systems indispersive fading channels

We consider the design of iterative receivers for space-time block-coded orthogonal frequency-division multiplexing (STBC-OFDM) systems in unknown wireless dispersive fading channels, with or without outer channel coding. First, we propose a maximum-likelihood (ML) receiver for STBC-OFDM systems based on the expectation-maximization (EM) algorithm. By assuming that the fading processes remain constant over the duration of one STBC code word and by exploiting the orthogonality property of the STBC as well as the OFDM modulation, we show that the EM-based receiver has a very low computational complexity and that the initialization of the EM receiver is based on the linear minimum mean square error (MMSE) channel estimate for both the pilot and the data transmission. Since the actual fading processes may vary within one STBC code word, we also analyze the effect of a modeling mismatch on the receiver performance and show both analytically and through simulations that the performance degradation due to such a mismatch is negligible for practical Doppler frequencies. We further propose a turbo receiver based on the maximum a posteriori-EM algorithm for STBC-OFDM systems with outer channel coding. Compared with the previous noniterative receiver employing a decision-directed linear channel estimator, the iterative receivers proposed here significantly improve the receiver performance and can approach the ML performance in typical wireless channels with very fast fading, at a reasonable computational complexity well suited for real-time implementations     

普鲁士蓝加速人体内铯排出效果的观察

本文介绍6例在苏联切尔诺贝利核电站事故期间受到放射性铯内污染的我国驻外人员,在本实验室接受活体测量和服用普鲁士蓝促排的观察结果。6例内污染者分两组分别于受污染后的第114天和第272天开始用药,在大约一个月期间,每人共服药54g(给药方式:每次服1g,每日3次,6天为一个疗程,间隔6天,共用药3个疗程)。观测结果表明,在促排期间,6例内污染者体内铯的生物半排期均明显缩短,~(131)Cs 的生物半排期由对照期(用药前)的54—123d 缩短到28—65d,~(134)Cs 由对照期的42—117d 缩短到23—69d;6例体内放射性铯的累积活度相对于同期未用药条件下的累积活度减少2—21%。