Coupled mechanical and chemical processes in engineered geothermal reservoirs with dynamic permeability

A model is developed to represent mechanical strain, stress-enhanced dissolution, and shear dilation as innately hysteretic and interlinked processes in rough contacting fractures. The model is incorporated into a numerical simulator designed to examine permeability change and thermal exchange in chemically active and deformable fractured reservoirs. A candidate engineered geothermal reservoir system (EGS) is targeted. The mechanistic model is able to distinguish differences between the evolution of fluid transmission characteristics of (1) small scale, closely spaced fractures, and (2) large-scale, more widely spaced fractures. Alternate realizations of fracture frequency and scale, exhibiting identical initial bulk permeability, lead to significantly different conclusions regarding permeability evolution and thermal drawdown within the reservoir. Reactivation, primarily through mechanical shear, of pervasive, large-scale fractures is shown capable of causing both hydraulic and thermal short circuiting. Small variations in fracture scale impact the balance between the efficiency of thermal transfer and the rate of fluid circulation. Stress-enhanced chemical dissolution, initially at equilibrium within the reservoir, may be reactivated as fractures are forced out of equilibrium during hydraulic fracturing. At the conditions examined (250 °C reservoir with 70 °C injection), however, shear dilation exerts dominant control over changes to permeability. Heterogeneity in permeability, generated from a normal distribution of fracture spacing, impacts thermal breakthrough times at the withdrawal well, as well as withdrawal rates. For the given conditions, spatial variability over ～1 order of magnitude leads to a reduction of ～10% in withdrawal rates compared to a spatially uniform system. Permeability is a strongly dynamic property and at geothermal conditions is influenced by the full suite of THMC interactions.     

Colossal magnetodielectric effect caused by magnetoelectric effect under low magnetic field

The colossal magnetodielectric effect is reported in Pb(Zr,Ti)O₃/Terfenol-D laminate composite under low magnetic field. When the composite is placed in an external a.c. magnetic field, magnetoelectric effect is produced, as a result, the dielectric properties of the Pb(Zr,Ti)O₃ is changed, i.e. magnetodielectric effect. Both the amplitude and resonance frequency change with the external magnetic field. The colossal magnetodielectric coefficient of 5 × 10⁴% at low magnetic field of 20 Oe is achieved near the electromechanical resonance frequency.     

面向公共安全数据处理的浪涌模型研究应用

近年来,随着平安城市和智慧城市项目的建设和发展,视频监控系统已经成为公安机关治安管控、打击犯罪、预防应急突发事件的有效手段。随着网络通信技术的迅速发展以及移动智能终端(如智能手机、平板电脑等)的快速普及,智能终端已经普遍携带视频监控、音频、加速传感器等感知设备。部分高端智能终端所能携带的视频设备已经超过部分低端的视频监控设备。智能终端的大量普及使得构建以人为中心的感知与计算网络成为可能。对不同信息空间的信息进行有效融合,可以加强对于公共安全事件的有效感知与检测。针对公共安全事件多源信息的融合问题,提出了数据浪涌模型,并对该模型进行了定义。同时利用该模型对人证合一系统进行了实例验证。开发的人证合一系统已经应用于北京市的多个长途车站与火车站。     

GNSS软件接收机的框架结构及原型系统开发

介绍全球导航卫星系统软件接收机的基本结构和优点,系统地实现了GPS软件接收机。该结构的硬件部分实现中频信号采样模块,软件部分实现可设置12通道的中频信号处理模块、信号捕获和跟踪、导航电文存储及转换,并针对伪距定位算法部分实现了单点静态定位,考虑的误差源主要包括卫星钟误差、对流层误差、电离层误差和地球自转引起的偏差。定位数据水平精度基本达到15 m(95%),几何精度因子(GDOP)值较好的数据可达10 m。     

浅论软件技术发展

本文以软件基本模型的发展为主线,对软件技术的历史和现状进行了回顾;分析了Internet的基本特征及其对软件技术带来的需求和挑战;总结提炼出Internet环境下软件的新形态--网构软件(Internetware),探讨了其不同于传统软件的主要特性和主要研究方向.     

Online approach to feature interaction problems in middleware based system

As a popular infrastructure for distributed systems running on the Internet, middleware has to support much more diverse and complex interactions for coping with the drastically increasing demand on information technology and the extremely open and dynamic nature of the Internet. These supporting mechanisms facilitate the development, deployment, and integration of distributed systems, as well as increase the occasions for distributed systems to interact in an undesired way. The undesired interactions may cause serious problems, such as quality violation, function loss, and even system crash. In this paper, the problem is studied from the perspective of the feature interaction problem （FIP） in telecom, and an online approach to the detection and solution on runtime systems is proposed. Based on a classification of middleware enabled interactions, the existence of FIP in middleware based systems is illustrated by four real cases and a conceptual comparison between middleware based systems and telecom systems. After that, runtime software architecture is employed to facilitate the online detection and solution of FIP. The approach is demonstrated on J2EE （Java 2 Platform Enterprise Edition） and applied to detect and resolve all of the four real cases.     

Piezoresistive TiB2/silicone rubber composites for circuit breakers

Piezoresistive composites with high hardness and conductivity are required for circuit breakers for multi-cycle operation under large current flow. Based on the simulation results for the mechanical behavior of piezoresistive composites, we developed piezoresistive composites with conductive TiB₂ ceramic materials and silicone rubber. TiB₂ up to 70 vol.% was embedded into the polymer matrix without any mechanical deterioration while the electrical resistance was decreased with increasing TiB₂ content. Piezoresistive composites with 70 vol.% TiB₂ particles exhibited a resistance of 1.7 Ω at a pressure of 1.1 MPa. A circuit breaker with the fabricated piezoresistive composites acted as a switch with a response time of around 2 ms.     

Functional no-flow events and their identification in the Lower Yellow River

Based on the understandings of the relationship between the river runoff and the primary functions of the Yellow River, this paper advances the concept of functional no-flow event that is different from the zero-discharge event occurring in the river. Factors reflecting the characteristics of functional no-flow events were analyzed and the criteria describing severity levels of the events were given from the cluster analysis with the measured data from 1950 to 1999. The results show that the severity level is subject to the critical water demand for river ecosystem protection. Using two critical water use demand scenarios for the Yellow River proposed by the authors and the Yellow River Water Conservancy Commission, different severity levels of functional no-flow events are identified. In addition, the differences between the zero-discharge and the functional no-flow events are discussed.     

对表面势为基础的MOSFET片电荷模型的基本检验

本文完成了对多种表面势为基础的MOSFET片电荷(charge-sheet)模型反型层电荷和沟道电流计算的基本检验.相对于以基本的MOSFET器件物理为基础的Pao-Sah模型结果,大多数片电荷模型在不同的工作区域内都会出现不同程度的反型层电荷计算误差.为了模拟沟道电流,MOSFET片电荷模型必须使用一个半经验的沟道电流方程.这个近似会导致沟道电流方程和反型层电荷方程之间物理上的不自恰,从而使计算的沟道电流结果与Pao-Sah模型相比有近10%的误差.这些基本的检验结果表明:为了保持基本的MOSFET器件物理内容和Pao-Sah模型的高精度,以表面势为基础的片电荷模型还需要一些根本的器件物理改进和进一步的模型精度提高.