Composite Optical Bend Loss Sensor for Pressure and Shear Measurement

A composite optical bend loss sensor for measuring 3-D forces has been developed. The sensor is composed of two optic fiber meshes which are embedded into a polydimethylsiloxane (PDMS) slab. The sensor consists of an array of optical fibers lying in perpendicular rows and columns sandwiched inside an elastomeric pad. A map of normal and shear stress is constructed based on observed macrobending through the intensity attenuation from physical deformation of two adjacent perpendicular fibers. Due to the new addition of the composite design and acrylic holder, the stability of the present sensor is found to be significantly better than our previously reported microfabricated optical bend loss sensor. In this paper, we will report the results of an optical bend loss simulation using the beam propagation method based on a series of images captured by a CCD camera on the fiber's bending curvatures. The result from the simulation will be compared with the results obtained from the experiment. Other results include vertical force and shear measurements at a single pressure point of the sensor. A force image algorithm is used to map the force distribution detected by the sensor. Here, we will present the results of six different shape patterns and two force magnitudes on each shape using a neural network system. We will also present a radio frequency sensor module, which we developed for the composite optical bend loss sensor for remote sensing.     

Performance evaluation of a new BPSK-OFDM timing estimation algorithm

Previously, the timing estimation in OFDM system employs cyclic prefix has been presented with the assumption of independent identified distributed OFDM symbol. The information used to find the symbol synchronization depends on the length of cyclic prefix. Actually, the data in the BPSK-OFDM modulated symbol, transferred by inverse fast Fourier transform, is with a complex symmetry character. With this character, more information from the whole OFDM symbol could be provided for the symbol timing. In this paper, the proposed algorithm uses the autocorrelation of the received signal to obtain the symbol timing. The simulation of Beek’s algorithm and the proposed scheme are presented. The performances of these algorithms are evaluated based on the missing symbol probability and the estimator mean square error. The simulation results show that the proposed algorithm is suitable to achieve a better symbol synchronization.     

基于CCP的AMT电控单元标定系统开发

为方便、快捷、稳定地对AMT电控系统进行标定,采用基于CCP协议的通讯标准,以某AMT系统为平台,开发了AMT电控系统标定仪。试验证明,所设计的标定仪能较好的实现预期功能且性能稳定。     

Solving the master equation for extremely long time scale calculations

The dynamics of magnetic reversal process plays an important role in the design of the magnetic recording devices in the long time scale limit. In addition to long time scale, microscopic effects such as the entropic effect become important in magnetic nano-scale systems. Many advanced simulation methods have been developed, but few have the ability to simulate the long time scale limit and to accurately model the microscopic effects of nano-scale systems at the same time. We develop a new Monte Carlo method for calculating the dynamics of magnetic reversal at arbitrary long time. For example, actual calculations were performed up to 10⁵⁰ Monte Carlo steps. This method is based on microscopic interactions of many constituents and the master equation for magnetic probability distribution function is solved symbolically.     

A Web‐based and Group Learning Environment for Introductory Environmental Engineering

The use of computer‐based technology is becoming more prevalent in the classroom. As a part of an educational research project sponsored by the GE Foundation, strategies for augmenting a course, Introduction to Environmental Engineering (CE 280), were investigated including cross‐disciplinary experiences in teamwork, design, and the use of advanced teaching technologies such as the web. Interactive tools to assist student learning were developed and refined. Efforts have focused on developing an extensive website, web‐based quizzes and homework assignments, and tutorials. Base groups were used to provide both intellectual and emotional support to students. This paper summarizes the development of this course and the impact of rapid feedback on the progression of student understanding.     

“制器尚象”造物思想对当代陶艺的价值研究

目的研究"制器尚象"造物思想对当代陶瓷艺术设计的价值和意义。方法分析当今中国陶艺创作的思想与工艺技术的现状与问题,将"象"之要义从象形、象理、象德进行解析,在外形、材质、巧工、情感传递4个方面解读"制器尚象"的美学特征、造物哲理和蕴涵在古人造物过程中的哲匠精神。结论当代陶瓷艺术创作应注重"制器尚象"造物思想的传承创新和工艺技术的精湛用心,以执着追求的匠心精神创造出具有时代审美需求和民族特色的陶艺精品。     

集束实验针孔成像与仿真分析北大核心CSCD

在激光装置实验中,通过小孔成像原理可获取黑腔靶中发射的X光图像的时间积分。提出一种3倍放大的新型成像设备用于集束实验,通过在与靶轴线夹角30°方向安装带多层镜选能的成像设备从而获取低能和高能段的X光时间积分图像,观察腔壁的再辐射现象。开展了用于集束实验针孔相机的研制工作,包括光路设计与结构设计,通过离线进行测试,在线实验进行打靶考核。进行成像光路仿真,模拟计算了两种镜子的选能效果,并通过光路仿真得到了多层镜、滤片和谱分布对成像结果的影响。采用FLASH对实验辐射场分布进行仿真,作为成像仿真的输入。最后,将此设备获取的成像结果与仿真计算得到的结果进行比较,实验结果与仿真结果基本一致,得到了X光信号强度的分布情况,获取了理想的实验数据,加深了对内部物理现象的理解。由此,建立了针孔成像的仿真能力,能够对成像结果进行预判,指导针孔相机的设计。     

Software Reliability Analysis and Measurement Using Finite and Infinite Server Queueing Models

Software reliability is often defined as the probability of failure-free software operation for a specified period of time in a specified environment. During the past 30 years, many software reliability growth models (SRGM) have been proposed for estimating the reliability growth of software. In practice, effective debugging is not easy because the fault may not be immediately obvious. Software engineers need time to read, and analyze the collected failure data. The time delayed by the fault detection & correction processes should not be negligible. Experience shows that the software debugging process can be described, and modeled using queueing system. In this paper, we will use both finite, and infinite server queueing models to predict software reliability. We will also investigate the problem of imperfect debugging, where fixing one bug creates another. Numerical examples based on two sets of real failure data are presented, and discussed in detail. Experimental results show that the proposed framework incorporating both fault detection, and correction processes for SRGM has a fairly accurate prediction capability.     

关于单相异步电机定子绕组接线与转向问题探讨

介绍了单相异步电机定子接线与转向的问题进行了探讨,对转子的转向和转动的方向与合成磁场进行了分析,阐述了两绕组流过的情况可做其合成磁场为逆时针方向。     

KT178型取心钻具在共和干热岩钻井中的应用

青海共和盆地干热岩资源富集于花岗岩地层,硬度高,研磨性强,部分层段裂隙发育,取心困难.针对干热岩地层和取心需求特点,研制了一套KT178型取心钻具,并配套设计了孕镶金刚石取心钻头.该钻具为单动双管取心钻具,可配套井底动力钻具使用,设计中注重对钻具外管、卡簧等关键部件的强度校核.在GH-01井和GH-02井中,经过两轮试验和优化,钻具逐渐成熟,获取了较完整的岩心样本,满足干热岩勘探取心要求,具备了向页岩气、水资源勘察等具有间断取心需求的同类工程推广应用的条件.