一种宽带反射超表面设计

本文提出一种"[]"形单元,当改变单元的尺寸时,可以改变电磁波的反射相位。通过优化之后选取了10个不同尺寸的单元,以此来组成超表面。在TE波垂直入射的条件下,可在该频点处观察到反射波偏折-30°的异常反射现象。同时也观察了X波段其他几个频点处的反射波,也存在明显的异常反射现象,说明所设计的超表面具有宽带特性。随后,本文给出一种在X、Y轴均具有相位梯度的超表面,从仿真结果中可以看出,反射波沿-X、-Y轴方向均偏折了30°。最后观察了超表面的背向RCS,可以看到所设计的超表面均比相同尺寸金属板的RCS低5~10dB,具有低散射特性。     

Nonlinear interferometers with correlated photons: toward spectroscopy and imaging with quantum light

A nonlinear optical interferometer based on crystal superlattices has been demonstrated for the first time in a cascade of up to five crystals. The enhanced sen...     

Magnetic velocity sensors

There are two types of low-cost velocity sensors based on magnetic principles, variable-reluctance sensors, and galvanomagnetic semiconductor (Hall effect or magnetoresistive) sensors. Variable-reluctance devices sense variations in flux linkage while semiconductors read variations in local flux density. The paper shows how recognizing this fundamental difference leads to markedly different sensor design approaches, and proposes new configurations with improved performance. The analysis of the sensors is based on a general theory specifically developed for these sensors. The magnetic field computations use the finite-element method, which is particularly well suited to this problem involving complex airgap configurations and a need for the calculation of local flux densities and flux linkages. Experiments were carried out to validate the models and confirm the predicted sensitivity improvements of the new sensor structures     

Large momentum beamsplitting in atom interferometry

Large momentum transfer (LMT) beamsplitting in atom interferometry is reviewed, focusing on the use of Bloch Oscillations to achieve high momentum separation without loss of visibility. Phase sensitivity with a fringe visibility of 7% is observed in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of 80?k between its arms. In addition, a 510?k beamsplitter is demonstrated.     

Wearable sensors and telerehabilitation

The article summarizes ongoing research on both mobile interfaces and therapies related to rehabilitation with special focus on emerging possibilities for home therapy programs for two areas of special interest to our group: stroke and cardiac. Both are areas where considerable scientific evidence suggesting the need for new therapeutic strategies has not significantly impacted clinical practice, and where home-based programs may be the answer. The article covers two aspects of the design of the mobile intelligent telerehabilitation assistant (ITA), a long-term project intended to provide an alternative for 21st-century rehabilitative telecare, and describes the interactive, mobile ITA interfaces and telecommunications infrastructure, which was motivated by the need identified by participants at the Home Care Technologies Workshop for user-centered interactive systems. We also discuss an approach for addressing the top recommendation of the Workshop: the critical need for intelligent interpretation and management of healthcare data. With the addition of wearable systems and telehealth tools, embedded intelligence takes added significance. We also address the challenge of extracting expert knowledge.     

MEMS-based microheaters integrated gas sensors

Abstract

In the present work efforts have been made to develop microheater integrated gas sensors with low power consumption. The design and simulation of a single-cell microheater is carried out using ANSYS. Low power consumption (<35?mW) platinum micro-heater has been fabricated using bulk micromachining technique on silicon dioxide membrane (1.5?μm thin), which provided improved thermal isolation of the active area of 250?×?250?μm². The micro-heater has achieved a maximum temperature of ～950?°C at an applied dc voltage of 2.5 V. Fabricated mircro-heater has been integrated with SnO₂ based gas sensors for the efficient detection of H₂ and NO₂ gases. The developed sensors were found to yield the maximum sensing response of ～184 and ～2.1 with low power consumption of 29.18 and 34.53?mW towards the detection of 1?ppm of NO₂ gas and 500?ppm of H₂ gas, respectively.     

门磁开关产品UL试验点滴

门磁开关产品主要应用在安防系统中,UL试验是国际上认可的考核其性能是否可靠的有效方式.本篇文章依据UL1054标准,说明BS门磁开关的UL试验要求及方法,并配有详细的试验数据和试验问题探讨.     

Cylindrical geometry electroquasistatic dielectrometry sensors

Semianalytical models are used to simulate the response of periodic-field electroquasistatic dielectrometry sensors. Due to the periodic structure of the sensors it is possible to use Fourier transform methods in combination with collocation point numerical techniques to generate accurate sensor simulations much more efficiently than with the more general finite-element methods. The models previously developed for Cartesian geometry sensors have been extended to sensors with cylindrical geometry. This enables the design of families of circularly symmetric dielectrometers with the "model-based" methodology, which requires close agreement between actual sensor response and simulated response. These kinds of sensors are needed in applications where the components being tested have circular symmetry, or if it is important to be insensitive to sensor orientation, in cases where a property shows some anisotropy. It is possible to extend the Fourier Series Cartesian geometry models to this case with the use of Fourier-Bessel Series over a radius large compared to the sensor dimensions. The validity of the cylindrical geometry model is confirmed experimentally, where the combined response of two circularly symmetric dielectric sensors with different depths of sensitivity is used to simultaneously measure the permittivity of a dielectric plate and its lift-off from the electrode surface     

Neural networks with quantum architecture and quantum learning

A method is proposed for solving the two key problems facing quantum neural networks: introduction of nonlinearity in the neuron operation and efficient use of quantum superposition in the learning algorithm. The former is indirectly solved by using suitable Boolean functions. The latter is based on the use of a suitable nonlinear quantum circuit. The resulting learning procedure does not apply any optimization method. The optimal neural network is obtained by applying an exhaustive search among all the possible solutions. The exhaustive search is carried out by the proposed quantum circuit composed of both linear and nonlinear components. Copyright © 2009 John Wiley & Sons, Ltd.     

原子干涉重力仪集成光源系统综述

高精度重力测量是进行惯性导航、大地测量、空间科学、海洋探测、基础物理研究的重要观测手段,高精度的重力仪一直是科学研究追求的目标。原子干涉重力仪能够提供uGal量级的绝对重力加速度值,是获取高精度重力信息的重要仪器之一,其集成光源系统的设计及实现对其实用化和商业化具有重要意义。首先介绍原子干涉重力仪激光系统的输出需求,然后对国内外典型集成光源系统的相关研究发展进行综述,分别介绍了基于自由空间和光纤传输的两种光源系统的实现方案和发展现状,重点阐述了其稳频、跳频、稳功率等关键技术。最后,对原子干涉重力仪集成光源系统的进行了总结与展望。     

Applying sensors to automatic assembly systems

The author describes the classes of sensors that are available to the automatic assembly machine designer. Examples of each class of sensor along with a discussion of their specific benefits and problems are included. Guidelines that will aid a machine designer in the selection and application of sensors for automatic assembly systems are provided. The necessity of providing methods in the automation for verifying the sensors' accuracy is discussed     

High-speed advanced sensors for bioterror weapons

"Biological weapons" include bacteria, viruses, and toxins that are spread deliberately in air, food, or water to cause disease or death to humans, animals, or plants. This discourse addresses specifically the applicability of integrated sensors and the use of technologies (both information technologies and biological/pharmaceutical technologies) in a concerted threat identification and avoidance paradigm designed to alert, to muster, and to deploy assets in counterterrorist efforts, specifically: Do we work to identify threats far enough in advance to allow proper response? What more needs to be done? What is the worth (value) of we can do now; what do we hope to do in the future?     

An introduction to Bragg diffraction-based cold atom interferometry gravimeter

This paper presents a new type of cold atom interferometry gravimeter based on Bragg diffraction, which is able to increase the gravity measurement sensitivity and stability of common Raman atom gravimeters significantly. By comparing with Raman transition, the principles and advantages of Bragg diffraction-based atom gravimeters have been introduced. The theoretical model for a time-domain Bragg atom gravimeter with atomic incident direction parallels to the wave vector of Bragg lasers has been constructed. Some key technical requirements for an nth-order Bragg diffraction-based atom gravimeter have been deduced, including the temperature of atom cloud, the diameter, curvature radius, frequency, intensity, and timing sequence of Bragg lasers, etc. The analysis results were verified by the existing experimental data in discussion. The present study provides a good reference for the understanding and construction of a Bragg atom gravimeter.     

Intra-vascular oxygen sensors for neonatal monitoring

The following topics are discussed: clinical background; catheter-tip sensors; transport of O₂ in blood; principles and construction of O₂ sensors; electrochemical O₂ measurement; mass spectrometer probes; optical O₂ sensors; in vivo use; clinical experience; problems of sensors in clinical use; hemocompatibility (blood-polymer interactions); future prospects     

Optical sensors based on active microcavities

We propose an active optical sensor based on a microcavity with gain. Greatly improved sensitivity can be achieved in active microcavities as compared with passive high-Q microcavities. We show that an active sensor using a gain-doped microsphere can provide 10/sup 4/-fold narrower resonance linewidth than does a passive microcavity in the transmission spectrum. Such highly sensitive microcavity optical sensors can be used to detect low concentrations of chemicals or biomolecules in their surroundings. Our analysis shows that this type of compact active microcavity is sensitive to an effective refractive index change of the order of 10/sup -9/.     

Microcomputer-based fault detection using redundant sensors

The design of a prototype device that implements a redundancy management scheme for online detection and isolation of faulty sensors in strategic facilities such as nuclear reactors, hazardous chemical plants, and advanced aircraft is presented. Such a device can potentially reduce the number of display devices in the control room and relieve the plant operator(s) from the tasks of assimilation and analysis of redundant sensor data as well as enhance the processing capabilities of the main computer. The device can be used as an integral part of intelligent instrumentation systems. It was built using an 8-bit microcomputer system and commercially available electronic hardware. The software is completely portable. The operation of a prototype has been successfully demonstrated for real-time validation of sensor data at the MITR-II nuclear research reactor     

Fabricating biomedical sensors with thin-film technology

Reviews some of the different chemical and physical sensor structures that have been fabricated using thin- and thick-film technology. Individual reports referenced in this article describe the details of the sensor designs and give calibration characteristics and applications. This article illustrates the wide variety of sensors that are possible using thin- and thick-film microelectronic technology. It by no means exhausts the possibilities of what can be done, since only a few materials and applications have been considered. It does, however, point out the great versatility of this type of processing, and sensors fabricated using these microelectronic processes require far less capital expenditure than when full silicon technology is employed     

Micromachined piezoelectric structures for high-temperature sensors

The availability of large size langasite (La₃Ga₅SiO₁₄) wafers enables micromachining of this high-temperature stable piezoelectric material which has been shown to exhibit bulk oscillations at temperatures of up to at least 1400 °C. In particular, the realization of miniaturized resonant sensors becomes feasible. Such resonators are operated far above their dielectric relaxation frequency leading to relatively low losses. Our specific research is focused on the development of monolithic structures to overcome problems originating from thermal stress. The concept includes the local doping of langasite by niobium, strontium and praseodymium. Their chemical diffusion coefficients were determined and found to be fairly small. Field enhanced diffusion results in an increased doping depth and concentration as demonstrated for niobium. The effect is governed by local heating of the sample. Optimized process conditions lead potentially to a pronounced drift of the dopants. Strontium doping increases the conductivity of langasite by three to four orders in magnitude and enables the formation of monolithic electrodes for high-temperature resonators as demonstrated by operation of such devices at temperatures as high as 800 °C. Micromachined functional structures including planar and biconvex membranes, as well as cantilevers, are prepared and demonstrated to be operational up to 930 °C. The analysis of their resonance behavior shows high resonator quality factors, e.g. 190 for a 60 MHz bulk acoustic resonator at the above-mentioned temperature.