Design and optimization of an integrated MEMS gas chamber with high transmissivity

Non-Dispersive InfraRed (NDIR) gas sensor is widely used for gas detection in collieries and the gas chemical industry, etc. The performance of the NDIR gas sensor depends on the volume, optical length and transmittance of the gas chamber. However, the existing gas sensor products have problems of large volume, high cost and incapable of integration, which need to develop towards the miniaturized sensor. This paper first presents the theoretical background of the NDIR gas sensor and the novel structure of a fully integrated infrared gas sensor and its micro-machined gas chamber structure. Then, the light structure and the gas flow of the gas chamber are optimized on Tracepro software and Ansys workbench, respectively, and the technological process for preparing the Micro-Electro-Mechanical System (MEMS) gas chamber is designed. Finally, we produce a gas chamber with a small volume and good transmissivity, which would be the most important part of producing the miniaturized NDIR gas sensor.     

指针技术在SDH中的应用

SDH（Synchronous Digital Hierarchy）设备是一种在通信传输领域得到广泛应用的设备。在SDH技术中,指针技术是一项重要的部分。丈中详细介绍了其基础知识以及这一技术在SDH中的具体应用。     

MIMO系统中STBC与STTC的性能分析

在下一代无线通信中,由于Internet和多媒体的综合应用,使得对可靠的高速数据传输业务的需求快速增长.多输入多输出(MIMO)信道模型在收发端采用了多天线阵列方式,通过空时编码技术实现了一定的空间和时间分集,在大大增加了系统容量,提高频谱利用率的同时改善了传输可靠性.文中对空时格码和空时分组码进行了基本的理论分析,并在此基础上应用到不同天线阵列的MIMO系统中,对系统的误码率和误帧率进行了仿真分析.     

2D DOA estimation for noncircular sources using L-shaped sparse array

We present an algorithm for two-dimensional (2D) direction-of-arrival (DOA) estimation of noncircular sources using an L-shaped sparse array. An L-shaped sparse array consisting of two co-prime arrays is firstly introduced. Then, the fourth-order-cumulants (FOCs) of received data are used to construct a FOC matrix (FOCM), by which we can get the estimations of elevation angles. With the estimated elevation angles, the azimuth angles can be estimated by a low-complexity signal separation algorithm. During the procedure used for estimating azimuth angles, no any eigenvalue decomposition (EVD), peak search and pair-matching procedure need to be implemented. Although the aperture is extended significantly, the computation complexity of proposed algorithm still is acceptable. Compared with some analogous algorithms, our approach shows more attractive estimation performance. A lot of simulation results prove the advantages of proposed DOA estimation technology.     

Aperture collimation correction and maximum-likelihood image reconstruction for near-field coded aperture imaging of single photon emission computerized tomography

Coded aperture (CA) imaging originally developed in X-ray astronomy has not been widely used in nuclear medicine due to the decoding complexity of near-field CA images. In this paper, we present a near-field CA imaging technique and image reconstruction method for high sensitivity and high resolution single photon emission computerized tomography (SPECT). Our approach makes three contributions. First, a correction method for the aperture collimation effect is used to eliminate the near-field artifacts without dual acquisitions of mask and anti-mask images. Second, a maximum-likelihood expectation-maximization (MLEM) deconvolution method is used to restore CA images. Finally, a new MLEM-based algorithm is used to partially reconstruct three-dimensional (3-D) objects from a single projection of CA images. Experiments conducted using a dual-head SPECT system equipped with a parallel-hole collimator and a CA module show a tenfold increase in count sensitivity and significant improvement in image resolution with CA collimation as compared to parallel-hole collimation. Experiments conducted using the same dual-head SPECT system equipped with a pinhole collimator show that when the object is closer to the pinhole collimator the CA image resolution is only slightly inferior to the pinhole collimated image. We found that the MLEM deconvolution method provides an inherent nonnegativity constraint on pixel values and remarkably reduces background activities of CA images. The MLEM reconstruction algorithm for CA images is capable of reconstructing 3-D objects from a single projection and can be potentially extended to full 3-D SPECT reconstruction for CA images.     

Energy enhancement of dispersion-managed solitons in optical fibertransmission systems with lumped amplifiers

We simulated dispersion-managed soliton propagation in optical fiber transmission systems with lumped amplifiers and loss. The energy enhancement of dispersion-managed solitons can be more or less than in the lossless case, depending delicately on the amplifiers arrangement. In all cases, there is a maximum enhancement factor beyond which the dispersion-managed soliton no longer exists and which also depends delicately on the arrangement     

中心局搬迁中SDH传输网的割接组网方案

本文介绍了某中心局搬迁中SDH传输网的割接组网方案.     

Improving MANET performance by a hop‐aware and energy‐based buffer management scheme

A hop‐aware and energy‐based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real‐time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real‐time and non‐real‐time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end‐to‐end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop‐aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end‐to‐end delays for real‐time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.     

一种改进的多模数字下变频结构及其FPGA实现

针对目前多种通信模式的共存和发展趋势,对传统DDC结构进行改进,以适用于多模系统。提出了多模数字下变频改进结构与参数设计,完成了各模块Verilog代码编写和Modelsim仿真,并对Modelsim仿真结果进行分析和验证,验证了改进数字下变频的可行性;最后将代码移植到FPGA,并结合ETTUS射频板、自主设计的中频板以及友晶TR4 FPGA开发板多模硬件平台进行了板级调试,验证了多模功能的可行性,充分证明该结构能兼容WCDMA和TD-LTE两种模式,具有较高的实用性和通用性。     

Photothermal Modulation of Depression-Related Ion Channel Function through Conjugated Polymer Nanoparticles

Considering recent breakthroughs in the field of optogenetics, a powerful tool is established in the present study to modulate the activities of target neurons through the application of light-based methods. Near-infrared (NIR) light enables the penetration of deep-tissue. As a result, it can be used to modulate the functions of proteins/cells. Herein, it is aimed to develop a NIR light-sensitive drug delivery system to spatially and temporally control the activation of the loaded drug at the stimulation sites through its release from a nanoparticle sensitive to NIR. Owing to their excellent photothermal effect under NIR irradiation, the nanoparticles are found to penetrate the blood-brain barrier effectively, ultimately reaching neurons. Furthermore, by loading fasudil, a selective activator of the Kv7.4 potassium channel, into the precisely designed and synthesized NIR light-sensitive nanoparticles, the firing frequency of dopaminergic neurons in the ventral tegmental area is found to be remarkably reduced upon NIR light irradiation. Such findings shed light on a new concept that can be used for developing more selective drug therapies for the treatment of diseases, such as major depression.