导弹防御中指挥控制通信系统效能评估方法

采用系统学中由上而下的分析方法,将目标弹看作时间敏感性目标,对弹道导弹的拦截概率进行建模.在分析弹道导弹时间特性的基础上,提出了基于拦截概率的指挥控制通信系统效能评估方法,建立了指挥控制通信系统的效能评估模型,并利用该模型对指挥控制通信系统的效能进行分析.仿真算例表明基于拦截概率的效能评估方法是有效可行的.     

空间信息系统在弹道导弹防御中的效能评估框架

针对空间信息系统在弹道导弹防御(BMD)中的效能评估问题,从系统整体性和复杂性角度提出了空间信息系统在BMD中的效能评估框架.该框架主要包括整体性分析、综合集成以及结果分析3个部分.在整体性分析中,通过系统学模型确定导弹防御的边界、要素集和关系集.在综合集成中,应用基于Agent的建模与仿真方法对系统要素进行建模,并对...     

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。     

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.     

双离子束溅射镀膜机的维修性分配和预计

分析了双离子束溅射镀膜机的设备原理、功能层次,参照《GJB/Z57维修性分配与预计手册》中的相关要求,根据各部件的故障率和维修经验数据,对双离子束溅射镀膜机进行维修性分配与预计。     

Compact SC frequency tuning circuit for continuous-time Gm–C filters

A novel automatic frequency tuning circuit for continuous-time filters is presented. Based on the switched-capacitor technique, the circuit offers an advantage in terms of simplicity resulting from the use of only two matched current sources, an operational amplifier with relaxed specifications and a transconductor that is a replica of the filter transconductors. Despite the simplicity of the scheme, the accuracy of the system is less than 1 % of frequency error. The circuit has been designed in a 0.5 μm CMOS technology with a 3.3 V power supply and simulation results confirm the suitability of the proposed approach.     

盲均衡技术的研究及发展

盲均衡技术是一种新兴的均衡技术,不需要发送训练序列就能在接收端恢复出发送序列。本文着重介绍了盲均衡技术的原理及其算法,并对盲均衡技术的新研究进行了展望。盲均衡技术能有效地克服码间干扰,对于提高通信质量具有十分重要的意义。     

用MOCVD方法在GaAs衬底上低温生长ZnO薄膜

采用二乙基锌(DEZn)和水(H2O)作为生长源,利用金属有机化学气相沉积(MOCVD)的方法,在100～400℃低温范围内,在GaAs(001)衬底上制备了ZnO薄膜.利用X射线衍射(XRD),室温PL,AFM,SEM研究了薄膜的晶体结构特性、发光特性及表面形貌特性.XRD分析表明ZnO薄膜具有很强的c轴取向,(002)峰的FWHM平均值为0.3°.当生长温度达到400℃时从SEM测量结果可以观察到薄膜表面呈六角状结晶.随着生长温度的升高,薄膜的晶粒尺寸变大,结晶质量得到提高但同时表面变粗糙.室温PL测量显示薄膜在370nm附近有强的近带边发射,没有观测到深能级发射峰.     

Integration of Stiff Graphene and Tough Silk for the Design and Fabrication of Versatile Electronic Materials

The production of structural and functional materials with enhanced mechanical properties through the integration of soft and hard components is a common approach to Nature's material design. However, directly mimicking these optimized design routes in the lab for practical applications remains challenging. For example, graphene and silk are two materials with complementary mechanical properties that feature ultrahigh stiffness and toughness, respectively. Yet, no simple and controllable approach is developed to homogeneously integrate these two components into functional composites, mainly due to the hydrophobicity and chemical inertness of graphene. In this study, well‐dispersed and highly stable graphene/silk fibroin (SF) suspension systems are developed, which are suitable for processing to fabricate polymorphic materials, such as films, fibers, and coatings. The obtained graphene/SF nanocomposites maintain the electronic advantages of graphene, and they also allow tailorable mechanical performance to form including ultrahigh stretchable (with a strain to failure to 611 ± 85%), or high strength (339 MPa) and high stiffness (7.4 GPa) material systems. More remarkably, the electrical resistances of these graphene/SF materials are sensitive to material deformation, body movement, as well as humidity and chemical environmental changes. These unique features promise their utility as wearable sensors, smart textiles, intelligent skins, and human–machine interfaces.     

更换旧蓄电池组应注意的安全问题

先期使用的大批阀控式密封铅酸蓄电池(VRLA电池),及固定型防酸隔爆式铅酸蓄电池(GGF电池)由于各种原因容量下降,不能保证其正常使用需进行更换。本文对如何安全可靠进行新旧蓄电池组的更换割接提出建议。