谈谈我国水利科学研究的现状—对《水利学报》的论文,引文及作者的统计分析

本文通过对《水利学报》１９８０－１９９３年间发表的论文、引文及作者的统计分析。展示了我国水利科学的研究水平和科技成果，提示了水利科学研究者的现状和地区、系统分布的特点和规律，从中了解水利科技人员利用文献的一些基本特点和规律，确定了该刊核心作者、活跃作者群的数量及比例，肯定了该刊作为我国自然科学的核心期刊的合理性。     

红山水电站采用爆破膜装置取代调压塔

红山水电站装有４台１６００ｋＷ机组，属长压力引水管，多岔管和机组型号不一的电站，甩负荷时水击波在多岔管中的反射与传递情况比较复杂，曾考虑过调压塔及水阻器方案，因投资大，施工困难或动作不灵达不到预期效果而放弃。采用爆破膜装置，投资少结构简单，运行维护方便，且已有运行经验，红山水电站最终采用爆破膜装置。     

紫色土丘陵区小流域地面侵蚀量预报

 针对长江上游紫色土丘陵区小流域面积侵蚀及泥沙输移特征以及现有资料的可利用性，用演绎法建立了小流域地面侵蚀的预报模型及相应的输沙预报模型。模型参数求取简便，经研究区的典型小流域实测资料检验，预报精度较高，可用于研究区资料短缺小流域的地面侵蚀量和输沙量的估算。     

面向自然人机交互的力触觉再现方法综述

力触觉再现技术借助力触觉人机接口设备,提供了操作者与虚拟环境之间的力触觉交互,使得操作者能够主动地触摸、感知和操纵虚拟物体,从而有效增强了虚拟现实等系统的真实感和沉浸感,进一步拓展了虚拟现实等技术的应用领域。传统的穿戴式、力反馈操纵杆式力触觉再现设备在便携性、操作空间等方面存在局限性,随着计算机技术与消费电子的快速发展,面向自然交互的力触觉再现方法受到广泛的关注。评述了传统的穿戴式、力反馈操纵杆式力触觉再现设备后,重点阐述了非固定式和非接触式的两类面向自然交互的力触觉再现方法。在对比分析不同的力触觉再现方法之间的差异后,探讨了面向自然交互的力触觉再现方法的未来发展方向。     

基于固态变压器的大功率逆变技术研究

固态变压器结合了电力电子变换技术和高频电能变换技术,实现将电能从一种电力特征的转变为另一种电力特征。逆变器作为固态变压器中能量转换的装置,技术已经很成熟,但是在大功率逆变器运行的设计上还有许多问题有待解决。逆变器并联运行控制技术是实现模块化、高可靠性冗余逆变电源系统的基础。分析了逆变器并联运行时环流的产生原因,总结了目前已有的逆变器并联方案。又根据组合式逆变器运行原理,用仿真实验验证了三相组合式逆变器用于固态变压器的优越性和可行性。     

优化传输栅下电势分布改善四管像素的电荷转移效率

提出了一种通过优化传输栅下沿电荷转移路径的电势分布来提高电荷转移效率的方法。通过使用非均匀掺杂传输管沟道,形成了传输管沟道内部的电势分布梯度。通过对R1区与传输栅的交叠长度,R1区的掺杂剂量,防穿通注入（APT）与传输栅交叠长度的调整,减小了传输管沟道与箝位光电二极管（PPD）连接区域的电子势垒与电子势阱,增强了二者的电势连接。仿真结果显示,剩余电荷占总电荷的比例由1/104减小至1/107,转移时间由500 ns缩短为110 ns。这意味电荷转移效率得到了提高。     

A new adaptive switching filter with directional impulse detection

A novel adaptive switching filter （ASF） based on directional detection is proposed for denoising the images that are highly corrupted by impulse noise. The proposed algorithm employs an efficient noise detection mechanism. It first employs an efficient method to estimate the differences between the current pixel and its neighbors aligned with 28 directions. The current noise pixel is replaced by a median or a mean value within an adaptive filter window with respect to different noise densities. Experimental results show that the proposed approach can not only achieve very low miss-detection ratio and false-alarm ratio even up to high noise corruption, but also preserve the detailed information of an image very well.     

Optimal Hankel-norm approximation of continuous-time linear systems

A problem on optimal approximation of continuous-time linear systems is studied. The performance measure (error) is chosen to be the spectral norm of the difference between the Hankel operators associated with the original system and the approximant. It is shown that the Hankel operators associated with continuous-time systems and the Hankel matrices associated with discrete-time systems are related by an interesting correspondence property via bilinear transforms. This fact is then used to derive the continuous-time results (theory and algorithms) from the established discrete-time ones. Some simple examples are presented.This research was supported by the Army Research Office under Grant No. DAAG 29-79-C-0054, and by the National Science Foundation Grant No. ENG-7908673, and by the Office of Naval Research under Contract No. N000-14-81-K-0191.Formerly with the Department of Electrical Engineering-Systems, University of Southern California, Los Angeles, California 90007, USA     

An ADPCM Receiver for NTSC Composite Video Signals

An ADPCM codec for carrying one broadcast quality NTSC color TV channel at a bit rate of 42.9 Mb/s has been proposed. The system uses 3 fsc sampling, adaptive intrafield contour prediction, adaptive quantization., 4/8-bit dual length coding, and horizontal blanking interval suppression techniques. The receiver of.the video codec is designed and implemented in ECL for recovery of the original signal. The receiver accepts.a 42.9 Mb/s serial data stream with a synchronous clock from the transmitter. The receiver detects the line synchronization code, demultiplexes the audio signal and video signal, and generates the horizontal blanking patterns which have been removed at the transmitter side. The 4/8-bit dual length code is decoded and fed to the ADPCM reconstruction loop to obtain the reconstructed active video signal. The generated horizontal blanking pattern is multiplexed with the reconstructed video=signal and sent through a D/A converter to form the reconstructed analog NTSC composite video signal.     

Copolymerization of tetrahydrofuran and propylene oxide

Summary Copolymerization of tetrahydrofuran and propylene oxide catalyzed by modified H₂SO₄.SO₃ system has been studied. Sodium perchloride was used to replace perchloric acid as co-catalyst. The copolymerization rate was obviously accelerated when using the new H₂SO₄.SO₃–NAClO₄ catalyst system. The reaction became less sensitive to the moisture.