国外水电站调压室采用予应力混凝土结构的概况

水电站的调压室为大型贮水结构,要承受较大的内水压力和有较高的不透水性要求。国外从70年代开始在多座水电站上采用予应力混凝土结构的调压室。本文将几个主要技术问题做简要介绍。     

Neuroradiology workstation reading in an inter-hospital environment: a nineteen month study

Two workstations (WS) each with two, 2500 line display monitors were installed in the in-patient and the out-patient neuroradiology reading areas for inter-hospital workstation readings. These WSs are part of the display component of a hospital-integrated picture archiving and communication system (PACS). Direct digital neuro images from 10 CT and MR scanners located at various buildings from two medical centers are first transmitted to the PACS database and then distributed to these two WSs automatically. This paper attempts to answer two questions. First, do the WSs facilitate neuroradiology operation? Second, does it cost less for preparing WS reading than that for the traditional film reading? Two parameters, the "time required before images become available for reading after the examination" and a "workstation utilization index" were derived as a means for answering these two questions. Nineteen months of clinical data were collected and analyzed. The results demonstrate that the workstation utilization index goes up from 40% in September 1994 when the WS was first introduced to over 80% in March 1996. This upward trend substantiates the hypothesis that these WSs do facilitate the neuroradiology operation. The derived results also exhibit that it costs much less to prepare images for WS reading than for film reading. Other indirect results derived from this study including the WS utilization hours, WS functions used, and the time duration of each WS session are also presented.     

Development of an algorithm for the calculation of the scattering properties of agglomerates

A new, improved, and more efficient algorithm for calculation of the scattering, extinction, and absorption characteristics of agglomerates consisting of Rayleigh-size primary particles is presented. The computer code is based on a new formulation of the light scattering for such agglomerates and is more than 10 times faster than the codes based on previous formulations. The computational times required by the old and the new algorithms, run on VAX 7000, IBM 3090, and UNIX RS6000 mainframe computers, are compared for different agglomerate configurations, such as straight chains, clusters, and randomly branched chains. A distributed-parallel-computing scheme was used to run the new algorithm on four UNIX RS6000 processors concurrently, resulting in computational times 47 times faster than required for the calculations. Furthermore, the robustness and convenience of the algorithm are assessed.     

TE On o -to- mode transducer designmode transducer design

This paper gives a structure on the mode converter from TE _0n ^O mode of gyrotron output to the main mode of the circular groove guide. The design consists of two parts: the first part is to convert TE _0n ^O to TE ₀₁ ^O using an advanced periodic wall perturbation technology, the second part is to convert TE ₀₁ ^O to mode basing on the method of gradually changing the wave guide cross section. An example at 37.5Ghz is given. For the first part, the efficiency is 94.71%, the length is 1.868m. For the second part, the theoretic figure of reflectance coefficient vs. frequency is given.     

The Trapped Charges at Grain Boundaries in Perovskite Solar Cells

The performance of perovskite solar cells is greatly affected by the crystallization of the perovskite active layer. Perovskite crystal grains should neatly arrange and penetrate the entire active layer for an ideal perovskite crystallization. These kinds of crystallized perovskite films exhibit fewer defects and longer carrier lifetime, which is beneficial to enhance the performance of perovskite solar cells. Here, by testing the residual charge of perovskite solar cells with different crystallization conditions, it is demonstrated that the residual charge exists widely at the grain boundary, which is parallel to the device, and the residual charge is related to the performance of the perovskite solar cells. Single crystal grains neatly arranged and penetrate the entire active layer can generate less residual charge and improve device performance of the perovskite solar cells. The results also show that the long decay time of open-circuit voltage comes from the detrapping of trapped carriers. The residual charge testing technology provides a new idea for the investigation of carrier trap and detrap characteristics in photovoltaic devices.     

Non‐Noble‐Metal‐Based Electrocatalysts toward the Oxygen Evolution Reaction

The development of low‐cost, high‐efficiency, and robust electrocatalysts for the oxygen evolution reaction (OER) is urgently needed to address the energy crisis. In recent years, non‐noble‐metal‐based OER electrocatalysts have attracted tremendous research attention. Beginning with the introduction of some evaluation criteria for the OER, the current OER electrocatalysts are reviewed, with the classification of metals/alloys, oxides, hydroxides, chalcogenides, phosphides, phosphates/borates, and other compounds, along with their advantages and shortcomings. The current knowledge of the reaction mechanisms and practical applications of the OER is also summarized for developing more efficient OER electrocatalysts. Finally, the current states, challenges, and some perspectives for non‐noble‐metal‐based OER electrocatalysts are discussed.     

基于电容传感器的纸张计数器设计

本文利用电容式传感器FDC2214设计制作了一个纸张计数器。待计数的纸张放置并被压紧于平行板电容器的两金属极板间,电容值随板间距(纸张厚度)变化,从而引起计数器前端谐振回路谐振频率变化。该传感器将感测到的谐振频率变化数字化,并送处理器进行中值平均滤波以降低噪声影响。系统将采样值与前期校准学习预存数据进行比对匹配,从而得到纸张计数值,并对计数结果进行液晶显示和语音播报输出。     

FFT复数处理器设计与FPGA验证

本文介绍了一种基于现场可编程门阵列(FPGA)的快速傅里叶变换(FFT)复数处理器设计,可进行1024点复数计算。采用按时间抽取的基-4算法和基于RAM的蝶形结构。同时对最后一级旋转因子进行了优化,减少了存储器的资源占用。使用流水线的处理结构,控制器简单。最后定点matlab建模与Synopsys的仿真器VCS仿真结果进行了对比,功能正确。完成整个运算仅用了2064个周期。最后用Altera公司的Cyclone IV E系列EP4CE10E22C8芯片完成原型验证,在时钟频率为50MHz时,完成1024点复数FFT仅用41.28μs。     

Measurement method of asphalt pavement mean texture depth based on multi-line laser and binocular vision

A new measuring method of mean texture depth of asphalt pavement is proposed based on the technology of multi-line laser and binocular vision. The developed method is incorporated with the profile method and the digital image technology. A three-dimensional mathematical model is established based on the triangulation measuring principle in order to implement the three-dimensional reconstruction of asphalt surface profile. Image processing technology helps locate the exact coordinates of each point on the model. In addition, the techniques of multi-line laser pairing and epipolar restriction are introduced for the image matching between multi-line laser and binocular vision. Through the model and the spatial equations obtained, the values of the mean profile depth of asphalt pavement can be figured out. According to the profile method, an integrated calculation procedure of texture depth is established. A set of sand patch field tests are implemented to verify the reliability of the developed method.