A disruptive technology for thermal to electrical energy conversion

A disruptive approach to thermal energy harvesting is presented. The new technique can be used for powering ultra-low power electronics. We propose a two-step conversion of heat into electricity: thermal to mechanical accomplished with thermal bimetals and mechanical to electrical accomplished with piezoelectrics. Devices can work in a wide range of temperatures: from −40 °C to 300 °C and the available mechanical power density is in the order of 1 mW/cm². The first electrical results and the first prototype built on a flexible substrate are presented in this work. We evidenced that one of the keys to improve the generated power density is downscaling of individual devices. To demonstrate this point, laws modeling downscaling have been established and show that the miniaturization of the devices by a factor k increases the generated power density by the same factor, due to the higher heat transfer rate. The path followed in order to establish the laws is given in this paper.     

煤矿机电设备中变频节能技术的应用分析

近几年我国加大了对环境的保护力度,利用进口煤矿代替国内开发的趋势越来越明显,对于国内煤矿开采企业来说,必须降低开发成本,才能够在国内煤炭市场的激烈竞争中获得发展的利润.而煤矿开采过程中机电设备是必不可少的,电机本身需要消耗大量的电能,控制好机电设备的能耗对于降低开发成本有着巨大的作用.     

Cryosurgical monitoring using bioimpedance measurements--a feasibility study for electrical impedance tomography

The effectiveness of cryosurgery in treating tumors is highly dependent on knowledge of freezing extent, and therefore relies heavily on real-time imaging techniques for monitoring. Electrical impedance tomography (EIT), which utilizes tissue impedance variation to construct an image, is very well suited to cryosurgery since frozen tissue impedance is much higher than that of unfrozen tissue. In this study, we explore cryosurgical monitoring as a previously uninvestigated application for EIT. The feasibility of bio-impedance measurements to detect ice front propagation is demonstrated by freezing planar tissue samples one-dimensionally while measuring impedance along a linear array. The experimental results compare favorably to a simple finite element model designed to provide an electrical field visualization tool.     

A feasibility study for electrical impedance tomography as a means to monitor tissue electroporation for molecular medicine

Molecular medicine involves the introduction of macromolecules, such as drugs or gene constructs, into specific cells of the body. Electroporation, which uses electric pulses to permeate cell membranes, is a method for achieving this. However, as with other molecular medicine procedures, it lacks a real-time mechanism to detect and control which cells have been affected. We propose and demonstrate, via computer simulation, that electrical impedance tomography has the potential for detecting and imaging electroporation of cells in tissue in real-time, thereby providing feedback for controlling electroporation.     

Varying mechanical compliance benefits energy efficiency of a knee joint actuator

In the field of wearable robots, actuator efficiency and user safety are frequently addressed by intentionally adding compliance to the actuation unit. However, the implications compliance has on the actuator’s overall performance in different conditions and activities are not fully understood, largely due to single task-focused experimental evaluations of these devices. To overcome this, our paper analyzes the effects that changing mechanical compliance has on the actuator’s overall performance in different ideal conditions in an experimental test setup. The torque performance and electrical energy consumption of an orthotic, adjustable-compliance knee joint actuator are evaluated during emulated walking and sit-to-stand-to-sit movements. Furthermore, the feasibility of combined operation of a dual mechanical compliance configuration during walking is investigated, and its outcomes reported in this work. The results demonstrate that varying mechanical compliance can lead up to 50% energy savings compared to a no-compliance configuration and show that, in general, changing compliance level leads to either energy-optimal or power-optimal actuator performance, but not both.     

An electrical model with junction temperature for light-emitting diodes and the impact on conversion efficiency

We present an electrical model for quantum-well light-emitting diodes (LEDs) with a current-spreading layer. The LEDs studied have a multiquantum well (MQW) between p-GaN and the n-GaN grown on sapphire. The model consists of a diode connected with a series resistor resulting from the combined resistance of the p-n junction, contacts, and current spreader. Based upon this model, the I-V curve of the diode itself without the series resistance is extracted from the measured LED I-V curve. The model also includes an empirical diode current equation which was sought by matching the extracted I-V curve. In the seeking process, junction temperature (T/sub j/) rather than case temperature (T/sub c/) was used in the equation. The diode model allows one to calculate the reduction on conversion efficiency caused by the series resistor. Results show that the current-spreading layer causes 20% of the efficiency reduction at T/sub j/=107/spl deg/C.     

胎儿膝关节半月板超微结构的扫描电镜观察

目的：进一步探讨膝关节半月板超微结构，为防治半月板损伤提供一定的实验依据，方法：采用扫描电镜了4、6、8月龄 胎儿膝关节半月板的超微形态结构。结果：4、6月龄胎儿半月板表面可见条状隆起，沟和圆形成卵圆形细胞样突起；8月龄半月板条状隆起和沟更明显，且基本平行排列，偶见细胞样突起，同时在各月龄组半月板表面可见微细的小孔或空隙区，在胎儿增龄过程孔径未见显著性改变（P＞0．05），半月板切面上软骨细胞呈椭圆形，位于软骨隐窝内，以4月龄多见，随着胎龄增加有所减少。     

An algorithm for polygon conversion to boxes for VLSI layouts

We develop an algorithm for covering polygons by rectangles. The algorithm achieves a minimum number of rectangles in most cases and in a short time. The algorithm is suitable for use in generating masks for microcircuits, design rule checking of VLSI layouts, graphical editors, etc.     

乏汽余热回收利用电气工程的可行性探究

本项目乏汽余热回收利用以节能减排为目标、以解决供热的民生问题为出发点,回收电厂发电后的大量乏汽余热用于城市采暖供热,该项目在不增加一次能源消耗的情况下,加大了城市供热面积、减少了大量投资,所以探讨乏汽余热回收利用的电气工程(包括厂用电系统、控制系统等)很有必要。     

An experimental feasibility study on applying SDN technology to disaster-resilient wide area networks

The Internet may get catastrophic impacts when unexpected disasters such as earthquakes, tsunami, etc. happen. Therefore, it is necessary to equip resilient technologies for the Internet backbones in order to face challenges (e.g., link, device failures, rerouting traffic, etc.) in the disasters. The emerging software-defined networking (SDN) technology, which logically centralizes network function on a controller and remotely manages distributed SDN devices, shows a lot of potential. This paper presents an experimental feasibility study on applying SDN to wide area backbones for the disaster-resilient purpose. To show the efficiency of SDN technology in responding fast to the network situation changes, we conduct three evaluations on real SDN devices and large-scale SDN-based wide area networks (WANs) assuming disaster scenarios. In the first evaluation, we explore the proactive recovery mechanism using the fast failover on SDN devices. In the second one, we investigate the communication latency between controllers and SDN devices, which is one of the most important factors in the reactive recovery in the software-defined backbone. In the last one, we experiment the fast end-to-end reactive recovery behavior of a TCP flow in a disaster scenario. The evaluation results clearly indicate that the SDN-based WAN is technically feasible and effective for fast recovery from disasters.     

An assessment of ocean thermal energy conversion as an advancedelectric generation methodology

The history of ocean thermal energy conversion (OTEC), a process that employs the temperature difference between surface and deep ocean water to alternately evaporate and condense a working fluid, is reviewed. In the open-cycle OTEC configuration, the working fluid is seawater. In the closed-cycle configuration, a working fluid such as propane is used. OTEC is assessed for its practical merits for electric power generation. Because rather large amounts of seawater and working fluid are required, the energy requirements for pumping them may be greater than the energy recovered from the OTEC engine itself. The concept of net power production is discussed. The components of a typical OTEC plant are described with emphasis on the evaporator heat exchanger. Operation of an OTEC electric generating station is discussed, including transient operation. Recent experiments and efforts at the National Energy Laboratory-Hawaii (NELH) are summarized. Remarks are made on bottlenecks and the future of OTEC as an advanced electric generation methodology     

全息波带片用于太阳能转换

目前,在太阳电池发电中,迫切需要解决的问题是降低半导体材料的成本和提高能量转换效率。人们对此已经做了大量的研究工作。人们研究用全息光学元件聚集太阳能,并探讨基于这种全息光学元件组成集热器或光生伏打发生器。本文介绍一种适用于太阳电池聚光发电的全息方法。光电转换器的主要组成部分是体积位相全息波带片和半导体太阳电池。利用体积位相全息波带     

Conversion of thermal to electrical energy with ferroelectric materials

The subject is reviewed and recent experimental and theoretical results are presented. It is shown that materials with high polarization and high dielectric strength can yield good conversion efficiencies. Very high specific outputs are calculated for the conversion of uncollected solar radiation by a spinning space vehicle. Such high specific outputs require suitable thin ferroelectric films of high thermal shock resistance. These requirements can not be met in present experimental converters. Approaches for the improvement of insulation resistance and polarization are given.     

An electromechanical model of the heart for image analysis and simulation

This paper presents a new three-dimensional electromechanical model of the two cardiac ventricles designed both for the simulation of their electrical and mechanical activity, and for the segmentation of time series of medical images. First, we present the volumetric biomechanical models built. Then the transmembrane potential propagation is simulated, based on FitzHugh-Nagumo reaction-diffusion equations. The myocardium contraction is modeled through a constitutive law including an electromechanical coupling. Simulation of a cardiac cycle, with boundary conditions representing blood pressure and volume constraints, leads to the correct estimation of global and local parameters of the cardiac function. This model enables the introduction of pathologies and the simulation of electrophysiology interventions. Moreover, it can be used for cardiac image analysis. A new proactive deformable model of the heart is introduced to segment the two ventricles in time series of cardiac images. Preliminary results indicate that this proactive model, which integrates a priori knowledge on the cardiac anatomy and on its dynamical behavior, can improve the accuracy and robustness of the extraction of functional parameters from cardiac images even in the presence of noisy or sparse data. Such a model also allows the simulation of cardiovascular pathologies in order to test therapy strategies and to plan interventions.     

An economic feasibility study for a broadband virtual pathSONET/ATM self-healing ring architecture

A ring architecture that uses the asynchronous transfer mode (ATM) virtual path (VP) concept to reduce the SONET ring cost in terms of bandwidth management is discussed. The add-drop multiplexer (ADM) proposed for VP ring architectures can evolve from existing SONET ADMs by replacing the STS-3 termination cards by the ATM STS-3c line cards. Existing standard self-healing schemes and protocol SONET rings can be applied to proposed ATM/SONET VP rings. A case study based on a BCC (Bellcore client company) ring network and the sensitivity analysis suggests that the proposed ATM VP ring architecture may be a cost-effective option for implementing the distributed ring grooming system at the DS 1 level. The proposed VP self-healing rings are not only used to carry existing DS 1 and DS 3 service, but can also be used to more cost-effectively consolidate switches for public-switched services and for SMDS, frame relay, and FDDI in metropolitan areas     

电气自动化的节能设计技术分析

无论是在工业还是人们日常生活当中,节能都成为国家和人们关注的焦点之一。就工业行业来讲,电气是其中的重要的节能领域之一,做好电气节能是所有电气行业的从业者都应该关注的课题。做好电气节能工作,不仅可以保护环境、节约资源,还可以提高工业的生产效益,推动工业的进步。因此,本文简要分析了电气自动化领域的节能设计技术的基本原则,并提出了一些可能的策略和做法。     

Phantom-based multimodal interactions for medical education and training: the Munich knee joint simulator

Simulation environments based on virtual reality technologies can support medical education and training. In this paper, the novel approach of an "interactive phantom" is presented that allows a realistic display of haptic contact information typically generated when touching and moving human organs or segments. The key idea of the haptic interface is to attach passive phantom objects to a mechanical actuator. The phantoms look and feel as real anatomical objects. Additional visualization of internal anatomical and physiological information and sound generated during the interaction with the phantom yield a multimodal approach that can increase performance, didactic value, and immersion into the virtual environment. Compared to classical approaches, this multimodal display is convenient to use, provides realistic tactile properties, and can be partly adjusted to different, e.g., pathological properties. The interactive phantom is exemplified by a virtual human knee joint that can support orthopedic education, especially for the training of clinical knee joint evaluation. It is suggested that the technical principle can be transferred to many other fields of medical education and training such as obstetrics and dentistry.     

A parallel framework for the FE-based simulation of knee joint motion

We present an object-oriented framework for the finite-element (FE)-based simulation of the human knee joint motion. The FE model of the knee joint is acquired from the patients in vivo by using magnetic resonance imaging. The MRI images are converted into a three-dimensional model and finally an all-hexahedral mesh for the FE analysis is generated. The simulation environment uses nonlinear finite-element analysis (FEA) and is capable of handling contact of the model to handle the complex rolling/sliding motion of the knee joint. The software strictly follows object-oriented concepts of software engineering in order to guarantee maximum extensibility and maintainability. The final goal of this work-in-progress is the creation of a computer-based biomechanical model of the knee joint which can be used in a variety of applications, ranging from prosthesis design and treatment planning (e.g., optimal reconstruction of ruptured ligaments) over surgical simulation to impact computations in crashworthiness simulations.     

An energy efficient joint localization and synchronization solution for wireless sensor networks using unmanned aerial vehicle

Localization and synchronization are fundamental services for many applications in wireless sensor networks (WSNs), since it is often required to know the sensor nodes’ position and global time to relate a given event detection to a specific location and time. However, the localization and synchronization tasks are often performed after the sensor nodes’ deployment on the sensor field. Since manual configuration of sensor nodes is usually an impractical activity, it is necessary to rely on specific algorithms to solve both localization and clock synchronization problems of sensor nodes. With this in mind, in this work we propose a joint solution for the problem of 3D localization and time synchronization in WSNs using an unmanned aerial vehicle (UAV). A UAV equipped with GPS flies over the sensor field broadcasting its geographical position. Therefore, sensor nodes are able to estimate their geographical position and global time without the need of equipping them with a GPS device. Through simulation experiments, we show that our proposed joint solution reduces time synchronization and localization errors as well as energy consumption when compared to solutions found in the literature.     

An electrical study of SIMOX material by a quick-turn-around approach

Circuits built on silicon-on-insulator (SOI) substrates, have different requirements for material quality, depending on the intended application. Thus, the need exists for a detailed characterization of the electrical properties of the silicon and buried oxide layers. In this paper, we study the effects of processing on the electrical characteristics of SOI wafers formed by the implantation of oxygen (SIMOX). To facilitate this investigation, we developed a quick-turn-around (QT) approach, based on C-V and C-t measurements on a capacitor formed with the buried oxide as the capacitor dielectric. A simple process is used to isolate silicon islands in the film layer, thus delineating the capacitor. The measurements allow one to determine the fixed oxide charge and interface trap densities of both buried oxide interfaces, and the minority carrier generation time of both the film and substrate. The QT approach is used to study the effects of changing the post-implant anneal time and temperature, and of using a screen oxide during the oxygen implant.