600 A IGBT开关电路及其散热系统设计

采用IGBT开关电路，对大功率电阻带进行直流脉宽调制控制，实现了内燃机车大功率直流发电机负载实验中的负载大小的连续调节。为了避免在实验过程中IGBT器件的温度过高，采用独特的双管IGBT结构和双向强迫风冷的散热系统。实验表明该电路运行稳定、可靠。     

小块气藏早期动态特征综合评价

应用试井方法，提出一套比较切合实际的小块气藏动态特征综合评价方法，推导出水驱气藏水侵量的计算公式，编制了天然气高压物性参数计算和气藏稳产年限预测等程序软件。     

SJ—YⅡ—5型高爆速高威力水胶炸药的研制

文章简要分析了我国目前在中硬岩石爆破中工业炸药的使用情况，介绍了山西兴安化学材料厂新研制的一种适用于硬岩爆破的高爆速、高威力水胶炸药新品种，对其性能、爆破效果、经济实用性和安全性等进行了阐述。     

普通门机改为高架门机的关键性工艺

普通门机改装为高架门机的技术，在大中型水电工程岩滩水电站和百龙滩水电站相继得到应用．改装1台仅需22万元，且由于其结构简单，拆迁容易，维护方便，易于操作，运转台班费低，产量高等特点，因此，在贵港工程改装2台，深受施工单位欢迎．由于门架加高22m后重心升高，安全成了头等重要大事，为了确保门机安全，就要从安装时抓起，机手要经过培训，严格执行持证上岗，严格执行操作规程，切实做好维修保养．本文主要叙述将普通门机改装为高架门机时应采取的质量控制标准，以及遇到的问题时所采用的处理方法．1将10／30rl机改装为高架门机需…     

Analysis of the time response of multiconductor transmission lineswith frequency-dependent losses by the method ofconvolution-characteristics

A new method for analysis of the time response of multiconductor transmission lines with frequency-dependent losses is presented. This method can solve the time response of various kinds of transmission lines with arbitrary terminal networks. Particularly, it can analyze nonuniform lines with frequency-dependent losses, for which no effective method for analyzing their time response exists. This method starts from the frequency-domain telegrapher's equations. After decoupling and inversely Fourier transforming, then a set of decoupled time-domain equations including convolutions are given. These equations can be solved with the characteristic method. The results obtained with this method are stable and accurate. Two examples are given to illustrate the application of this method to various multiconductor transmission lines     

带隔板底水油藏油井临界产量计算公式

本给出了带隔板底水油藏油井的监界产量计算公式，它适用于所有带隔板底水油藏的油井。     

The correlation of texture and magnetic properties in Co-Cr films

This investigation focuses on the correlation between the crystallographic orientation of grains with respect to magnetic properties in Co-Cr films. Based on a distribution measured for the (0002) crystallographic pole densities, modified formulae describing the texture were used to calculate the coercivity Hc, the squareness ratio Rs (Mr⊥/TMs) and the anisotropy field Ha for Co-Cr films. In general, calculated values for the coercive force He agreed well with the measured values. The calculated Rs⊥. values were much larger than the measured ones, however, indicating that the influence of the demagnetizing field and the magnetostriction on the orientation of the magnetization cannot be neglected. On leave from Institute of Computing Technology, Academia Sinica, P.O.Box 2704-6, Beijing, P.R. China.     

A hybrid spreading/despreading function with good SNR performancefor band-limited DS-CDMA

Code-division multiple-access (CDMA) implemented with direct-sequence spread spectrum (DS/SS) signaling is a promising multiplexing technique for cellular telecommunications services. The efficiency of a direct-sequence spread-spectrum code-division multiple-access (DS-CDMA) system depends heavily on the shape of the spectrum of the spread signal. Maximum efficiency is obtained with an ideal brick-wall bandpass spectrum. There are two approaches toward achieving such a spectrum. One is to use a simple spreader that produces a broad spectrum and then follow it with a precise, high order filter to band limit the spectrum. A second approach, which is the approach taken in this paper, is to use a spreader that produces a spectrum close to the ideal spectrum and then employ a simple filter to control the out-of-band power. The proposed spreader/despreader is based on a simple hybrid function and can be easily implemented. An analysis provides a compact expression for the signal-to-noise ratio (SNR) of a RAKE receiver. The expression includes the effects of baseband, intermediate frequency (IF) and RF filtering as well as the effects of the spectral densities of the spreading/despreading functions. The analysis shows that the proposed spreader/despreader yields superior performance over a conventional pseudo noise (PN) spreading/despreading mechanism     

云南丽江旅游的发展与大研古镇的发展方向问题

一、发展过程与现状 (一)古城和雪山完美地结合,特点突出,古镇拉动效应明显 丽江有丰富的旅游资源,如独特的东巴文化、古城、雪山等等。经过一段时间发展,丽江旅游产品也形成几个比较突出的亮点,如古城-雪山产品,古城如此完整,雪山的风貌如此突出,而且古城和雪山在不大的地理范围内集中到一起,这在国内是很难得的。古城被评为世界文化遗产后还形成了一个显著的市场拉动效应。