Wind speed variability across the UK between 1957 and 2011

By using surface data from 57 UK meteorological stations, a national [British Atmospheric Data Centre (BADC)‐57] and regional wind index for the UK has been calculated for the period 1983–2011. For a subset of seven stations, an additional national index (BADC‐7) has been calculated for the period 1957–2011. The indices show an annual variability of 4% over their respective periods, corresponding to a variation in typical wind turbine capacity factor of 7%. These indices are compared with indices calculated from other sources, namely an index generated using a gridded dataset of observed values interpolated across the UK, an index calculated from an area bounding the UK using the ERA‐40 re‐analysis dataset, indices calculated from bilinear interpolation of the ERA‐40 re‐analysis dataset to the 57 and 7 stations and another independent UK wind index. The indices show variation in trends, with all showing some level of decline with the exception of that generated using the ERA‐40 re‐analysis dataset averaged over the UK, which shows a significant increase. The various indices show varying degrees of agreement with correlation coefficients, after trends are removed, ranging between 0.611 and 0.979. The effect of changes in site exposure, instrument bias and measuring height was considered for the BADC‐7 and BADC‐57 indices. The change in instrument measurement height appears to have a significant biasing effect, and it is likely that this along with changes in exposure at urban sites has caused the decline in annual wind speeds observed for some of the indices. There does not appear to be evidence for significant changes in large‐area (mesoscale) surface roughness. The correlation between annual mean wind speeds at the seven surface station sites used to calculate the BADC‐7 index is seen to be quite weak, indicating very localized variations in inter‐annual variability. When regional differences in the index are investigated, it is seen that wind speeds show a very slight decline across the UK in all regions except the south‐east, which shows a slight increase. The greatest decrease is seen in the north‐west. These changes are in the same direction as the tentative predictions given by climate models for future changes in wind speed across the UK, although the uncertainty is large given the large degree of inter‐annual variation. Copyright © 2013 John Wiley & Sons, Ltd.     

基于图像处理的二维条码技术的应用

本文针对陕西省边防检查机关验放旅客由人工处理信息的现状,提出了基于二维条码技术的自动识别与传输方案,设计并实现了条码技术在出入境人员申报系统中的应用。本系统极大地简化了边检工作流程、提升了服务水平,是实现电子政务建设的一次有力推动。     

用于高分辨率光谱仪的离轴三反射镜光学系统的设计

面对空间遥感,尤其在目标特性的精细化识别中,要求成像光谱仪具有高灵敏度、高光谱分辨率与高能量通过力等优点．在同轴三反射光学系统的基础上,采用视场离轴方式,设计了一个三镜无遮拦全反射光学系统．次镜和光阑重合,无中间像,实现了高分辨率、大视场、长焦距的要求．光学系统的基本参数为：焦距f’=1600mm,视场角为2w=18°×0．148°,相对孔径为1／10,3个反射面均为二次曲面．设计结果表明,成像质量接近衍射极限,用此方法设计的光学系统在航天遥感领域具有很好的应用前景．     

Au线键合中"塌线"问题的研究

目前,在半导体闪存多芯片的金线键合工艺中,为满足堆叠芯片不断增加等结构需要,键合线弧要求更低、更长,制造工艺变得相对更加复杂。针对生产过程中常遇到的塌线问题,通过对金线键合工艺中线弧形成动作的过程分析,以金线弹动现象为线索,探究了生产过程中塌线问题产生的原因,并给出了相应解决方案。经过此研究,长线键合的生产工艺能力得到加强,其成果对新封装产品的研发及基板设计具有有益的参考价值。     

一种面向多媒体SOC的微状态低功耗设计方法

针对目前移动多媒体SOC设计中日益突出的功耗问题,结合传统的动态功率管理和动态频率调整中的负载预测和反馈控制两种方法,同时利用系统中各类IP和设计模块的可配置特性,提出了一种基于微状态的面向多媒体应用SOC的系统级低功耗设计方法。该方法以F-ARIMA过程作为负载预测模型,以最后期限缺失率作为反馈控制信号来实现系统实时动态在微状态之间进行切换,从而尽可能使得负载能均匀分布于运行期间。该方法在保证多媒体服务质量(QOS)的同时,有效降低了系统功耗。     

长距离磁路传输电能系统之磁路分析

提出一种新的传输电能的系统,即长距离磁路传输电能系统,长距离磁路是指距离在400km以上的闭合磁路。通过磁路分析的第一类方法及第二类方法对该系统的磁路结构及系统参数进行了分析,验证了该新的系统的合理性,为电能传输方式提供新的思路并进行了有益的探索。但还有诸如恒定磁场如何取电的问题有待进一步研究。     

车路通信环境下TD-LTE无线资源调度建模与仿真

为了改善现有车路通信方式覆盖范围小、交付时延大和传输速率低的现状,将TD-LTE技术引入车路通信接入系统。提出了基于TD-LTE的车路通信接入系统无线资源调度模型;构建了车路通信仿真场景,对比例公平算法、指数比例公平算法和改进的最大权重时延优先算法进行性能分析。仿真结果表明:车辆低速移动场景下,系统负载较低时指数比例公平算法性能较好,系统负载较高时改进的最大权重时延优先算法表现更优,比例公平算法不适合车路通信多媒体业务流调度;车辆高速移动场景下,三者都不适合车路通信多媒体业务流调度。     

From Long Infrared to Very Long Infrared Wavelength Focal Plane Arrays Made with HgCdTe n + n ?/ p Ion Implantation Technology

This paper aims at studying the feasibility of very long infrared wavelength (VLWIR) (12–18 μm) focal plane arrays using n-on-p planar ion-implanted technology. To explore and analyze the feasibility of such VLWIR detectors, a set of four Cd _x Hg_1−x Te LPE layers with an 18 μ cutoff at 50 K has been processed at Defir (LETI/LIR–Sofradir joint laboratory), using both our “standard” n-on-p process and our improved low dark current process. Several 320 × 256 arrays, 30-μm pitch, have been hybridized on standard Sofradir readout circuits and tested. Small dimension test arrays characterization is also presented. Measured photonic currents with a 20°C black body suggest an internal quantum efficiency above 50%. Typical I(V) curves and thermal evolution of the saturation current are discussed, showing that standard photodiodes remain diffusion limited at low biases for temperatures down to 30 K. Moreover, the dark current gain brought by the improved process is clearly visible for temperatures higher than 40 K. Noise measurements are also discussed showing that a very large majority of detectors appeared background limited under usual illumination and biases. In our opinion, such results demonstrate the feasibility of high-performance complex focal plane arrays in the VLWIR range at medium term.     

一种平滑的可变步长算法

本文从长时相关性(LRD)和突发性两个方面,阐明图像组(GOP)时间尺度上的流量能够体现原有视频帧序列的流量特性。并在固定步长自适应算法(FSSA)和可变步长自适应算法(VSSA)的基础上提出了一种新的平滑的可变步长自适应算法(S-VSSA),这种算法可以在GOP所表示的大时间尺度上预测MPEG-4视频流量。仿真实验结果显示:该算法收敛速度快,预测误差低,可以明显改善预测性能。     

大尺寸气孔微结构光纤在光纤光栅中的应用

将微结构光纤分为光子晶体光纤和大尺寸气孔微结构光纤两种。详细介绍了大尺寸气孔微结构光纤。其包层的气孔硅结构（或者聚合物硅结构）影响了包层模式的空间分布以及包层模式的有效折射率，使其表现出与传统光纤不同的光学特性。基于这种微结构光纤的光纤光栅对外部折射率的变化显示了很好的稳定性。偏振特性（对长周期光纤光栅）可以大大加强。基于聚合物硅包层的长周期光纤光栅显示了优良的温度调谐性能。