一种新型宽频带正交线极化馈源设计

本文介绍一种适用于散射通讯用的前馈抛物面宽频带正交器双线极化馈源设计,该馈源工作于0.8GHz频段。实践证明,该馈源在20％的工作带宽内基本上具有近似于旋转对称的波束,且系统VSWR<1.3。因此,对工作于较低频段的天线,该馈源是很好的选型。     

用于多种组装技术的厚膜导体复合结构

厚膜导体Ｐｄ－Ａｇ／Ａｕ、Ｐｔ－Ｐｄ－Ａｕ／Ａｕ平面复合结构，Ｐｄ－Ａｇ／Ａｕ立体复合结构可使多种组装技术相互兼容。立体复合结构还可有效地降低导体线电阻，减少线损耗。而且，其超声键合性尤佳     

直接基于灰度图象的多尺度角点检测方法

在计算机视觉领域中角点特征的提取具有相当重要的地位，因为角点包含了丰富的信息。本文提出了一种新的利用微分几何和小波变换的多尺度角点检测方法，它具有以下特点：一是无须提取边缘图象，而是直接在灰度图象上提取角点。二是由于利用了小波变换技术从多个尺度上进行角点的提取，所以它既较为有效的抑制了由于噪音等原因造成的诸多错误角点位置的出现，又能得到较为精确的有用角点位置。最后通过实验证明了本算法有效性。     

野外观测系统的检验与校正

在地震资料处理中常常发现野外观测系统不准,其后果极为严重。为了避免重复施工,改善处理效果,笔者在IBM3081系统上编制了利用初至波对野外观测系统进行检验和校正的程序。文中介绍了两种校正方法:其一是只作炮检距校正。根据工区的小折射、井口时间、反射记录等资料提供一条或几条比较准确的初至时距曲线,作为标准曲线,然后将从实际共炮点道集中拾取的初至曲线与标准初至时距曲线相比较,确定出实际初至曲线所对应的炮检距,并对各个地震道的空间属性进行修改。对某三维工区的处理结果表明,该方法的效果良好。其二是先用迭代方法加误差约束条件计算炮点和检波点的坐标,然后计算炮检距,再进行校正。这种校正处理的效果也是明显的。但实验表明,对于观测系统误差较大的数据,不宜作坐标计算,只作炮检距校正尚可完成部分校正。处理中要根据数据的性质选取校正方法。     

Analysis of the detectivity for triple-layer heterojunction GaSb/GaInAsSb infrared detectors

In this paper, the detectivity is calculated and analyzed with the front-or backside illuminated case for both N-GaSb/p₂-Ga_0.8In_0.2As_0.19Sb_0.81/p₁-Ga_0.9In_0.1As_0.09Sb_0.91 and N₁-GaSb/n₂-Ga_0.9In_0.1As_0.09Sb_0.91/p-Ga_0.8In_0.2As_0.19Sb_0.81 infrared photovoltaic detectors, respectively. The analysis results show that the main absorption appears in the p-type Ga_0.8In_0.2As_0.19Sb_0.81 material with either front- or backside illuminated case for above two structures. In each structure, the carrier concentration obviously affects the detectivity. The carrier concentration in the wide-bandgap material for the isotype heterojunction should be reduced as low as possible to reduce the tunneling rate at the isotype heterointerface. Moreover, the change of the detectivity with the p-side surface recombination velocity for the N₁-n₂-p structure is more sensitive than that with the p₁-side surface recombination velocity for the N-p₂-p₁ structure. In the N-p₂-p₁ structure with the incident light from the p₁-side surface, two-color detection is achieved.     

Flood frequency and routing processes at a confluence of the middle Yellow River in China

Floods cause environmental hazards and influence on socio‐economic activities. In this study, we evaluated the historic flood frequency at a confluence in the middle Yellow River, China. A non‐parametric, multivariate, empirical, orthogonal function matrix model, which consists of time correlation coefficients of flood discharge at different gauge stations and flood events was used for the analysis of flood frequency. The model addresses the characteristics of confluent floods such as frequency and the probability in multiple tributary rivers. Flood frequency analysis is often coupled with studies of hydrological routing processes that reduce the flood capacity of the rivers. Flood routing to the confluence were simulated using kinematic wave theory. Results of this flood frequency analysis showed that flooding frequency has intensified in the past 500 years, especially during the 19th century. Flooding in streams above the confluence was more frequent than in streams below the confluence. Over the last 2000 years, concurrent flooding in multiple tributary rivers accounted for 67.5% of the total flooding in the middle Yellow River. Simulation of flood routing processes shows that the decreased flooding capacity and elevated river bed of the shrunken main channel leads to an increased flood wave propagation time (24–52.3 h) in the study area after 1995. The model indicates that human activities, such as constructions of the Sanmenxia Dam, have changed flood routing boundary conditions and have contributed to the increased flood frequency at the confluence. Copyright © 2007 John Wiley & Sons, Ltd.     

奥氏体耐热钢21-4N碳化物析出行为研究

通过对奥氏体耐热钢21-4N碳化物析出行为的研究,探讨了对性能的影响,提出了改善其综合性能的措施和方法.     

Densitometry determination of dioxins using gold nanoparticlemodified dioxin response element probes

This study aims to develop a rapid and sensitive densitometry bioassay of dioxins. It is known that dioxin ligand can bind heterodimeric aryl hydrocarbon receptor (AhR) and trigger the formation of the complex of dioxin-AhR, AhR nuclear translocator (Arnt), and dioxin-responsive element (DRE). We have established a rapid and sensitive method using nanoparticle-modified DRE probes based on dioxin-dependent binding of DRE to AhR complex. Dioxins can trigger the binding of nanoparticle-modified DRE probe to AhR complex. The nanoparticle-modified DRE probes in the dioxin-AhR-Arnt-DRE complexes immobilized on the microplates were detected by measuring optical density after silver enhancement. Results showed that as little as 0.01 pM of TCDD could be detected. Dioxins could be quantified accurately with the linear range from 1 nM to 0.01 pM. The coefficient of variation was 5≈8% in this bioassay. The optical density of nanoparticle-based silver enhancement was produced in a dose- and time- dependent manner. The dioxin concentrations in fly ash samples determined by this bioassay were comparable with that by the standard HRGC/HRMS. Thus this bioassay is a sensitive and convenient cell-free bioassay of dioxin that is suitable for screening of dioxins in environmental or food matrices.     

现代模具技术及其进展

论述了现代模具种类和学科特点、模具工业特点、模具领域新技术、模具CAD/CAM集成化技术的发展及展望。     

填充料细度对水工沥青混凝土性能的影响

近年来沥青混凝土作为防渗材料，在我国水工建筑中得到了广泛应用。与道路工程的沥青混凝土不同的是，水工沥青混凝土具有良好的粘弹性及抗渗性。目前，国家规范对填充料的细度尚无明确规定，通过调整沥青混凝土的填充料细工，对沥青混凝土的各项性能进行了系统的试验和分析，研究表明：适宜的填充料细度及掺量，能有效地改善沥青混凝土性能，提高其抗渗性。