日盲型紫外探测系统的探测距离模型及实验研究

日盲区的存在,给近地探测240～280 nm范围的紫外辐射提供了良好的背景.本文设计了一套成像型日盲紫外探测实验系统.从辐射能量传递的角度出发,借鉴凝视型红外搜索跟踪系统的分析方法,推导了紫外探测系统的探测距离模型.以氘灯为探测目标,在三种典型天气条件下对实验系统进行了探测距离实验.结果表明,采用探测距离模型的计算值和实验测量值有较好的吻合,为紫外探测系统的设计和性能评估提供了重要的理论和实验基础.     

日盲紫外电晕探测系统定标

日盲紫外电晕探测是电力设备检修与维护的主要手段之一.为了提供更为准确和客观的评价依据,需要对日盲紫外电晕探测系统进行辐亮度定标,从而确定目标辐亮度与增益控制电压、系统输出灰度值之间的关系.为此构建了由高稳定氘灯光源、积分球、光纤光谱仪等组成的定标装置.采用可溯源美国NIST的紫外标准氘灯对光纤光谱仪进行光谱辐照度标定,并以光纤光谱仪作为标准探测器对电晕探测系统进行定标.通过实验拟合出ICCD增益控制电压与系统增益之间的关系曲线,并给出了系统的标定方程.随后进行了三组不同增益的验证实验,实验结果表明在线性区内辐亮度推算值与测量值之间的最大相对误差为6.11%,均方根为3.22%.经分析,文中所采用的系统定标方案的不确定度为9.1%,基本可以满足了日盲紫外电晕探测系统的需求.此外,不同增益条件下的系统响应特性可以为电晕探测过程中进行自动增益调整算法的设计提供参考依据.     

高量子效率碲化铯紫外日盲阴极研制

碲化铯(Cs2Te)阴极是紫外探测器的重要组成部分,其研究的时间较早,在某些紫外探测领域得到了良好应用。但是,同时具有高量子效率及良好日盲特性的阴极制备工艺还需要进一步探索。本文采用电子束蒸发镀膜在石英窗上制备金属Ni膜作为Cs2Te阴极的导电基底,用四探针测试仪、高阻计和分光光度计研究了薄膜的方块电阻和透过率关系。在超高真空系统中进行Cs2Te阴极制备,研究Te膜厚度对阴极量子效率的影响关系。用X光能量色散谱分析Cs2Te光电阴极的组分,研究Cs量与阴极日盲特性的影响关系。结果表明,最佳Ni膜厚度为1.0 nm,其电阻为107Ω/□左右,其紫外波段透过率高达80%;Cs2Te阴极的Te膜厚度为2.0nm时,光电阴极量子效率达12%;当Cs2Te阴极中Cs过量,其波长响应向长波方向延伸,Cs欠量,阴极量子效率降低。     

非晶氧化镓基日盲紫外探测器的研究进展

日盲紫外探测在空间安全通信、臭氧空洞监测、导弹来袭告警等民用与军事领域有着广阔的应用场景和特定的市场价值。氧化镓(Ga₂O₃)具有超宽的带隙(4.4~5.3 eV),几乎覆盖整个日盲波段,被认为是构筑日盲紫外探测器的理想材料之一。相较于单晶和外延氧化镓材料,非晶氧化镓(a-Ga₂O₃)的制备温度更低,工艺相对简单,且衬底的适用范围更广,因此近些年成为Ga₂O₃基日盲紫外探测领域新的研究热点。本文旨在对a-Ga₂O₃基日盲紫外探测器的研究进展与现状进行介绍。首先介绍了a-Ga₂O₃的基本特性以及几种常见的制备方法,进而介绍了各种适用的器件类型、结构及性能。目前,a-Ga₂O₃基日盲紫外探测器主要分为MSM型、结型、TFT型和阵列型等几大类,通过器件结构优化,进一步提升探测性能。其中,MSM型器件结构简单,响应度高,应用最为广泛;结型器件通过构建肖特基结和异质结等,具有响应速度快、暗电流低和自供电的特点;TFT型器件能够在抑制暗电流的同时放大增益,且可以通过施加栅压脉冲来提升响应速度;阵列型器件主要用于大面积成像。最后,本文对a-Ga₂O₃日盲紫外探测器未来的发展趋势进行了总结和展望。

     

CsI／Ni／LiF半透明真空紫外光阴极“日盲”效应的验证

ＣｓＩ／Ｎｉ／ＬｉＦ半透明真空紫外光阴极，ＣｓＩ的长波阈值为２００ｎｍ，即有很好的“日盲”效应。通过对照测试，得到验证。用氢看空紫外辐射源作检测光源，在专用的真空紫外光电发射特性测试系统中，测得ＣｓＩ／Ｎｉ／ＬｉＦ半透明真空紫外光阴极在１０５－１６５ｎｍ波长范围内平无题子产额为０．１６－０．２１电子／入射光子，而在２００－３６５ｎｍ紫外辐射下，其量子产额俟为１０＾－６－－１０＾－５电子／入射光子。     

宽禁带半导体Ga2O3基日盲紫外探测器的研究进展

β-Ga₂O₃是一种超宽禁带半导体材料,对应太阳光谱的深紫外波段,可用于制备日盲紫外探测器。日盲紫外探测器抗干扰能力强、探测灵敏度高、背景噪声低,在军事和航空航天领域具有极大的应用前景。本文主要介绍Ga₂O₃材料的基本性质,包括不同的晶相结构及其制备方法,并总结不同结构的Ga₂O₃器件在日盲紫外探测领域的研究进展。其中,金属-半导体-金属(MSM)结构的Ga₂O₃器件最为普遍,特别是基于薄膜材料的器件已具备了商业化参数,有望实现产业化应用。基于Ga₂O₃的异质结和肖特基结日盲紫外探测器也表现出优异的性能,并呈现出自供电特性。此外,薄膜晶体管结构Ga₂O₃器件结合MSM结构和晶体管结构的工作机制,可获得更大的光增益,适用于微弱信号的探测,成为一种极具潜力的日盲紫外探测器件。     

TiO2-NTAs/ZnO异质结的制备及紫外探测性能研究

利用电子束蒸发技术、阳极氧化法和磁控溅射技术在ITO玻璃衬底上制备了二氧化钛纳米管阵列/氧化锌(TiO2-NTAs/ZnO)异质结,利用SEM、EDS Mapping、XRD、Raman、分光光度计和电化学工作站等对样品的微观形貌、元素成分、晶体结构、透过率和紫外探测性能进行表征.结果表明,TiO2-NTAs的表面结构...     

石英晶体振荡器日频率波动的测量及不确定度分析

本文介绍了电子测量仪器内石英晶体振荡器的日频率波动的测量方法并分析了测量值的不确定度。     

MgZnO nanowires based deep ultraviolet heterojunction light emitting diodes

Vertically aligned Mg alloyed ZnO nanowires were successfully grown by Chemical Vapor deposition method in a tube furnace. Structural analysis found that the MgZnO nanowires are with single crystalline without phase separations. The atomic ratio of Mg/O in the nanowire was determined to be approximately 15%. Photoluminescence spectra show that the band gap of ZnO nanowire was tuned to approximately 3.6 eV due to Mg incorporation. N-type MgZnO nanowires/p-type GaN was used for heterojunctional light emitting diode fabrication. Electroluminescence measurement yielded ultraviolet emission peaks, which includes a deep ultraviolet at approximately 340 nm. The results suggest that successful Mg alloying in ZnO nanowires was achieved and is promising for deep ultraviolet devices.     

Preparation and performance analysis of barium dispenser cathodes

The intercorrelation of aluminate properties, such as structure, component and metal Os film coating with electron emission capability and longevity of Ba dispenser cathodes, has been investigated. It is shown that reactants react completely and the percentage of tribarium aluminates is larger in the normal environment, and that at 1723 K the pulse of cathode impregnated in the above aluminates is larger. Aluminates sintered under the normal environment constitute the multiphase formation, but aluminates sintered under the special environment with Ar gas injection compose the single-phase formation by means of X-ray diffraction (XRD). Both the surface and the fracture surface of cathode are full of aluminates evenly distributed by using Sirion 200 superhigh resolving power field emission scanning electron microscope (SEM). The emission current density of cathode-impregnated aluminates sintered in the special environment with Ar gas injection is larger than that in the common environment by the analysis of diode experiments. The emission capability of Os-coated cathode prepared by laser ablation deposition (LAD), which has good characteristics of low temperature is higher, than that without metal film coating cathodes.     

Anchor-free localisation algorithm and performance analysis in wireless sensor networks

A hybrid anchor-free localisation scheme for multihop wireless sensor networks is presented. First, a relatively dense group of nodes is selected as a base, which are localised by using the multidimensional scaling method. Secondly, the robust quads (RQ) method is employed to localise other nodes, following which the robust triangle and radio range (RTRR) approach is used to perform the localisation task. The RQ and the RTRR methods are used alternately until no more nodes can be localised by the two approaches. Simulation results demonstrate that the proposed hybrid localisation algorithm performs well in terms of both accuracy and the success rate of localisation. To evaluate the accuracy of anchor-free localisation algorithms, the authors derive two different accuracy measures: the Cramer-Rao lower bound (CRLB) to benchmark the coordinate estimation errors and the approximate lower bound to benchmark the distance errors. Simulation results demonstrate that both the CRLB and the distance error lower bound provide references for the accuracy of the location algorithms.     

Optimality properties and performance analysis of co-operative time-reversal communication in wireless sensor networks

The properties and performance of a technique, called time reversal, for co-operative communication on power-constrained wireless sensor networks are studied. A brief discussion of the optimality properties of this approach is presented, and performance is studied experimentally via a simulated indoor environment containing multiple wireless sensors. Using numerical simulation, the behaviour of the peak power received at a target sensor as a function of the number of co-operating transmitting sensors as well as the level of transmitted signal distortion and timing synchronisation errors, is studied. The simulation results demonstrate that, subject to some rather stringent synchronisation requirements, time reversal is an effective generalisation of beamforming that provides an efficient basis for co-operative communication on broadband multipath channels     

光引发剂接枝星型SBS的合成及其UV改性压敏胶的研究

探索了一种光引发剂接枝型的苯乙烯类热塑性弹性压敏胶的制备方法.具体实验步骤是:以马来酸酐(MAH)和四氨基二苯甲酮(4-ABP)为单体合成4-马来酰亚胺基二苯甲酮(MBP);然后在过氧化二苯甲酰(BPO)的催化作用下,合成MBP接枝星型SBS的聚合物,采用NMR、FTIR分别对MBP和SBS-g-MBP的结构进行了表征,并通过测量紫外光固化后交联体系的凝胶含量对交联程度进行分析;再用SBS-g-MBP、增粘树脂、软化剂和防老剂配制成溶剂型UV固化胶粘剂,在牛皮纸上进行了粘结性能测试,压敏胶粘性能符合国家标准的牛皮纸压敏胶粘带的技术要求(HG/T2480-92.     

立方相MgZnO纳米线的制备和表征

利用热蒸发方法,在硅衬底上制备出立方MgZnO纳米线。以Mg粉为源材料,所制备的为立方相MgO纳米线。以Mg粉和Zn粉混合物为源材料,可以制备出立方相MgZnO纳米线,Zn含量7%,直径200～300nm,具有单晶结构;同时产物中还包括六方相ZnO纳米线,直径30nm左右。MgZnO纳米线中Zn含量远低于源材料中的Zn含量,这可能是ZnO和Zn的蒸汽压远大于MgO和Mg的缘故。     

Preparation and thermal performance analysis of novel multilayer cladding structure composites

With regard to the adiabatic principle of insulation, a novel multilayer cladding structure composites (MCSC) with vacuum inside was put forward, which could be used in high temperature insulation field. In the composites, SiO₂ was used to fill the microcracks and protect the carbon matrix from oxidizing. This novel material was composed of two parts, one was the core material consisted of SiC foam ceramic, the other was the flawless outer shell consisted of carbon fiber reinforced composites with vacuum inside that produced by Chemical Vapor Infiltration (CVI) Pyrolytic Carbon (PyC) and silicasol-infiltration–sintering methods. Material density was 0.81 g/cm³. The effective thermal conductivity of MCSC ranged from 0.193 W/m · K to 0.721 W/m · K within the temperature from 303 K to 703 K, which was 13.5–23.3% lower than the value of SiC ceramic foam core materials. However, at 1473 K, the measured data of MCSC and SiC foam were 1.815 W/m · K and 1.911 W/m · K, respectively. It was only 5.02% lower than that of SiC foam.     

新型高灵敏度GLV光学电流传感器设计与性能分析

本文结合GLV技术设计了一种适于检测高压交流电的新型光学电流传感器.这一设计具有温度稳定性好、大电流下灵敏度高、频率响应范围宽等特点,且测量芯片制作工艺简单、成本低廉.通过有限元分析和数值计算对器件的模态、工作性能、热膨胀特性等进行了分析模拟,结果表明:测量芯片量程达500A～2000A,并可通过改变设计参数灵活调整;一阶固有频率接近60kHz,大电流下灵敏度接近0.2dB/A,外界温度变化±50K时传感器测试误差在0.7%以内.