脉冲激光焊接钛合金薄板的熔池深度预测

激光焊接过程产生的焊斑熔深直接影响焊接质量。激光焊接过程复杂,影响因素众多,许多参数难以量化。以TC4钛合金薄板为实验样品进行脉冲激光焊接实验。通过声波频谱减法对采样的声频信号进行降噪处理,并分析了声频信号的时域和频域特征,找到了声频信号和焊斑熔深的关系。采用径向基函数神经网络对钛合金薄板焊接过程的焊斑熔深进行预测。神经网络以声压强偏差、频带功率、激光功率和焊接速度作为输入。实验证明,在不同激光功率下该方法可准确预测焊斑熔深。     

机载激光水深测量精度分析

分析了机载激光水深测量系统中的深度反演方法，着重讨论波浪潮汐改正法和利用动态全球定位系统-相位模糊度解算技术(KGPS-OTF)所测参量进行归算的方法(无修正法)。综合分析影响机载激光测深精度的各项参量，并利用机载激光雷达的技术参数，定量估算了两种方法的水深提取精度。结果表明，波浪潮汐改正法的精度略高于无修正法，但是无修正方法更加简单明了，数据后处理的计算量也可大大减小。     

基于高时空分辨率卫星数据的气溶胶光学厚度反演系统

卫星遥感技术是研究大气气溶胶时空变化规律的重要手段之一。高分四号卫星(GF-4)作为新一代静止卫星,不仅具备更多的可见-近红外波段,而且具有超高时空分辨率的特点,可以执行对固定区域连续观测或凝视扫描覆盖观测,为气溶胶光学厚度定量反演提供了有利条件。基于GF-4静止卫星超高时空分辨率卫星数据,在深入了解卫星观测模式及传感器波段对气溶胶反演敏感性基础上,基于地气时变差异核心思路,开发了针对GF-4超高时空分辨率数据气溶胶光学厚度反演算法;设计并实现了具备业务化反演气溶胶光学厚度能力的软件系统,软件系统具备多线程、全自动运行能力,满足卫星数据处理业务化需求。利用该系统对GF-4数据进行了处理和分析,通过地基仪器实测的气溶胶光学厚度进行了验证,取得了初步结果。结果表明,该系统具有良好的可靠性和稳定性,可以服务于大气颗粒物时空变化遥感监测。     

Model-guided measurement-side control for quantized block compressive sensing

To progressively provide the competitive rate-distortion performance for aerial imagery,a quantized block compressive sensing(QBCS) framework is presented,which incorporates two measurement-side control parameters:measurement subrate(S) and quantization depth(D).By learning how different parameter combinations may affect the quality-bitrate characteristics of aerial images,two parameter allocation models are derived between a bitrate budget and its appropriate parameters.Based on the corresponding allocation models,a model-guided image coding method is proposed to pre-determine the appropriate(S,D) combination for acquiring an aerial image via QBCS.The data-driven experimental results show that the proposed method can achieve near-optimal quality-bitrate performance under the QBCS framework.     

一款800V VDMOS终端结构的设计

设计了一款800 V VDMOS终端结构,采用场限环(FLR)与场板(FP)相结合的方式,在场限环上添加多晶硅场板与金属场板,有效地降低了表面电场峰值。通过调整终端结构,在135μm的有效终端长度上实现了848 V的击穿电压,最大表面电场为2.34×105 V/cm,小于工业界判断器件击穿场强标准(2.5×105 V/cm),且电场分布比较均匀,终端结构的稳定性和可靠性高。     

新型机载激光测深系统及其飞行实验结果

新研制的机载激光测深系统与第一代机载激光测深系统相比,在探测信号采集率、浅水测量能力、测点定位精度和系统的自动化方面都有较大的提高。新系统采用1000 Hz激光器以提高测量密度,分设深水浅水双通道接收回波信号以提高浅水探测能力,装配高精度的惯性导航系统(IMU)和全球定位系统(GPS)提高了测点的定位精度和深度精度,数据后处理进行了潮汐改正和波浪改正提高深度测量的精度。系统在某海域进行了多次飞行实验,实验数据经过分析和处理,得到了比较满意的结果,表明该激光测深系统在测深精度和测量效率等方面,已经接近实用化。     

关于五类线直放站的应用模式探讨

随着移动网络规模的不断发展,网络覆盖重点已由广覆盖向深度覆盖转变。由于室分天线入户困难,导致室内信号覆盖效果无法保证,已建室分系统的导频污染等问题较难解决。针对这一问题,通过具体的案例介绍了五类线直放站,并对五类线直放站的技术亮点和应用模文进行了探讨。     

用光谱辐射计测量大气光学厚度的研究

本文给出了用光谱辐射计VF921-256测量大气光学厚度的实验结果，并对其与太阳辐射计DTF-1的同步测量结果进行了比对。实验结果表明：在比较好的大气条件以及对VF921-256测量中所应用的参考板的非朗伯特性进行校正后，两种方法的测量结果符合得较好。因此，在一定的误差范围内，VF921-256可以用于辐射校正中对大气光学厚度的同步测量。最后，本文对上面两种方法各自的测量误差也进行了进一步的分析讨论。     

Disparity field and depth map coding for multiview 3D image generation

In the present paper techniques are examined for the coding of the depth map and disparity fields for stereo or multiview image communication applications. It is assumed that both the left and right channels of the multiview image sequence are coded using block- or object-based methods. A dynamic programming algorithm is used to estimate a disparity field between each stereo image pair. Depth is then estimated and occlusions are optionally detected, based on the estimated disparity fields. Spatial interpolation techniques are examined based on the disparity/depth information and the detection of occluded regions using either stereoscopic or trinocular camera configurations. It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver. Various disparity field and depth map coding techniques are then proposed and evaluated, with emphasis given to the quality of the resulting intermediate images at the receiver site. Block-based and wireframe modeling techniques are examined for the coding of isolated depth or disparity map information. Further, 2D and 3D motion compensation techniques are evaluated for the coding of sequences of depth or disparity maps. The motion fields needed may be available as a byproduct of block-based or object-based coding of the intensity images. Experimental results are given for the evaluation of the performance of the proposed coding and spatial interpolation methods.     

Bearing capacity of isolated square footing resting on contaminated sandy soil with crude oil

The main objective of this paper is the evaluation of bearing capacity of isolated square footing resting on clean and oil-contaminated sand. The study is aimed at determining the effect of percentage of oil content in sand and the depth of the contaminated sand layer under the footing on the bearing capacity of footing. A series of routine laboratory tests were carried out on sand to obtain the physical, mechanical, and chemical properties. Crude oil is used as a contamination material. The research-included the completion of experimental work that consists of a series of loading tests carried on model of isolated square footing resting on clean and oil-contaminated sand. The contaminated sand layers were prepared by mixing the sand with crude oil at percent (10 and 20) % by weight of dry sand to simulate the field conditions. The depth of contaminated sand layer (d) under the footing was chosen depending on the footing width (B) as expressed by (d/B) ratio and varied as (0.5, 1, 1.5 and 2) to simulate the field conditions. The results showed that the contamination influences the load-settlement curves and leads to a reduction in its bearing capacity. The bearing capacity of the footing decreases significantly with increasing both the percentage of oil content and the depth of the contaminated sand layer. The results also showed that the presence of oil in sand changes the mode of shear failure in sand under the footing from local shear failure to the punching shear failure.