浅谈车载视频监控系统解决方案的发展

传统固定点车载视频监控仅将车辆的视频进行录像保存,在2G网络环境（GPRS／EDGE／CDMA）下,只有部分厂家尝试进行图片、视频的即时网传。图片网传对网络的占用率较低,一般10秒左右可将照片网传回中心;视频网传则对网络要求较高,2G网络环境只能传输低帧率的视频图像。     

数字电影高帧率技术推广应用需尽快制定压缩码率标准

自2011年CinemaCon展会提出高帧率摄制与放映话题之后,业内对此开展了广泛讨论,不少专家进行了相关试验。研究表明,播放帧速率在60帧/秒以上的图像序列能够显著提升观影感受,而48帧/秒并不能显著提升观影感受。发明休斯坎(Showscan)系统的道格.特朗布尔认为,50     

怎样提高焦平面帘幕式快门X闪光同步速度

引言广大摄影爱好者可能都知道，目前国外先进的焦平面钢片快门的X闪光最高同步速度可达1／250秒，一般的焦平面帘幕式快门也都能达到1／60秒。但是爱好者们不一定都知道，找国自行设计DF系列照相机的焦平面帘幕式快门的X闪光最高同步速度只有1／45秒。这项指标一直延用了二十多年。本文将就明佳S－201M型相机在这项性能上的改进经验，谈谈体会。一、问题的引出X闪光同步（X－synchronisation）是一种闪光同步法，系在中心快门叶片开启到最大光栏面积的80－100％范围或焦平面快门的像幅被全部开启至开始关闭前0．5毫秒范围内接触点火来…     

具有双极性的非相干OCDMA系统性能分析

提出了一种可减少多址干扰的非相干OCDMA编解码方案，该方案利用光开关控制2个单极性编码器和1个具有平衡互补结构的解码器，在1个光学信道上实现了双极性OCDMA信号传输；分析了电光编码、传输、解码、光电转换等环节的信号变化，推导出系统的噪声和误码率公式；与其它CDMA方案比较表明本方案在误码率方面可达到电域双极性CDMA系统的水平。     

输电线路危险点远程视频监测系统

为了解决巡视周期真空期不能及时掌握线路走廊外力变化,极易在下一个巡视未到之前由于缺乏监测发生线路事故等原因,提出依靠公网无线3G/GPRS/EDGE/CDMA1X的数据通道为传输手段,对输电线路环境通道环境、周围施工情况、杆塔倾斜等进行实时监测,提供线路异常状况的预警。     

基于低复杂度自适应帧的WVSN视频编码方法

针对WVSN视频节点资源受限与视频编码方法复杂度高等问题,提出一种基于低复杂度自适应帧的视频编码方法。由"隔块-对角线"差异值计算方法求得差异值,建立自适应帧传输机制,避免逐帧判断,减少计算量。帧内图像采用多边形DCT裁剪JPEG压缩,减少二维DCT计算复杂度。实验结果表明,该方法在保证视频质量前提下,能有效降低视频编码复杂度,与无裁剪JPEG图像压缩相比,当前帧、差分帧JPEG压缩DCT计算量分别减少9.4%、56.3%;与M-JPEG视频编码相比,平均PSNR减少3.1%情况下,平均文件大小显著减少55.0%。     

论高帧率电影前景

传统的24帧电影无疑在今天将面临越来越多高新技术的挑战和洗礼,而采用每秒48帧画面频率拍摄的影像就是这众多革新中的一次突破,它带来更加完美的影像效果和逼真的画面还原。更重要的是目前越来越多的影院都已逐步具备播放高帧率电影的能力,而越来越多的影片也加入到高帧率拍摄的阵营中来。本文从技术、市场及神经学科等方面阐述了对高帧率电影前景及发展的态度和看法。     

异种帧的相关性对MPEG-2视频源建模的影响

MPEG编码标准通常使用I、P、B三种帧类型。由于P，B帧利用基于I帧的运动补偿技术进行编码，因此同一GOP内不同类型帧之间存在较强的相关性。考虑场景并用二阶自回归模型为I帧建模：（1）对P，B帧采用相地于I帧的一阶合成回归模型建模；（2）分别对P，B帧采用二阶自回归模型建模。实验结果表明，考虑同一GOP内不同帧之间的相关性的模型，比较准确地反映了视频源的统计特征与排队性能。     

检修玛米亚（Mamiya）ZM型单镜头反光照相机

玛米亚（Mamiya）ZM型照相机是石英电子控制式35mm钢片快门单镜头反光照相机。这个相机在国内使用量很大。该照相机的摄影方式有两种：一种是光圈优先式AE（自动曝光）摄影；另一种是手动曝光控制摄影（！。ED双重显示）方式。玛米亚ZM照相机配套的镜头是FZ／50mm标准镜头，此外还可配E系列和EF系列镜头。玛米亚ZM照相机采用石英电子控制纵走式焦平面钢片快门。“A”档自动曝光摄影时，快门速度有4秒到1／1000秒；手动摄影时，有2秒、1秒、1／2、1／8、1／4、1／15、1／30、1／60、1／125、1／250、1／500、1／1000秒及B门，快门释…     

问题解决 达能吹响胜利的号角

在达能美国俄亥俄州的工厂中不存在设备问题的复评。公司的双照相视频系统能以最快1/128,000秒的快门速度以及最快达60帧/秒的帧速记录下发生的故障,大大推进了包装生产线的效率。     

40Gbps甚短距离并行光传输系统接收电路的设计与实现

给出了符合OIF-VSR5规范的40Gbps甚短距离光传输系统接收电路的设计与实现。该接收电路实现简单,由一片转换芯片及光接收模块构成。其特点是充分利用现场可编程门阵列(FPGA)内嵌的高速收发器成功实现了16×2.488Gbps和12×3.318Gbps信号的发送和接收,并且在一片FPGA上实现了诸如时钟数据恢复、串/并转换、帧同步、通道对齐、12-16路映射等全部功能。基于二分查找法的帧同步电路则大大提高了转换芯片的工作速度。Signaltap Ⅱ逻辑分析仪的测试结果表明接收电路工作正常,性能良好。在此基础上,给出了VSR5实验系统的点到点测试方法,通过12通道垂直腔面发射激光器并行接收模块和7m 12芯多模带状光纤,将发送电路与接收电路相连,实现了OC768/STM-256 40Gbps的点到点测试,测试结果表明系统误码率小于10~(-12)。     

宽带CDMA无线多媒体接入系统的研究

提出了可变传输速率的宽带CDMA扩频调制方法、非平衡功率控制算法以及自适应接入速率的无线接入方法。基于上述技术,给出了由基站和多媒体终端组成的实验系统参数。该系统实现了舆速率分别为8kbp和144skbps的语音和数据通信。     

High rate material behaviour at hot forming conditions

Modern processes of hot forming use very high strain rates and large, mostly incrementally applied strains. For the simulation of such forming processes relevant material data are needed, which have to be recorded under accordant forming conditions. This places extraordinary demands on the experimental technique, because high temperatures, high strain rates and large strains have to be implemented simultaneously. In the following contribution such an aligned experimental technique is introduced. In order to apply a very large range of strain rate, compression tests are performed using different technical equipment up to a drop tower and Hopkinson pressure bar. To reach large plastic strains, a hot torsion test was developed, which allowed true plastic shear strains up to 10 at strain rates in the order of 100 1/s at hot forming temperatures.     

爆破模拟地震动下框架抗震性能试验分析

通过爆破试验模拟天然地震,进行了地震动条件下中核厂区七层框架结构模型的动力响应现场试验,对所取得的试验数据进行统计回归分析,给出了能够预测适合本场地和本次爆破方式条件下爆破振动烈度的经验公式,并分析了土与结构动力相互作用对基础的影响,可为结构的基础设计提供参考。试验结果显示,该七层框架结构模型在地震烈度Ⅶ度下结构安全,故该结构在未来可能遭遇地震动条件下,抗震性能良好,可为框架结构抗振设计提供依据。     

Ratcheting and fatigue properties of the high-nitrogen steel X13CrMnMoN18-14-3 under cyclic loading

High-nitrogen steel X13CrMnMoN18-14-3 has been used in manufacturing expanding metallic stents with 0.1 mm diameter, and such medical implant is subjected to complicated and asymmetrical cyclic loading during service. But there is no test data published for the thin wire of the material under cyclic loading. In this study, a series of tests were conducted on X13CrMnMoN18-14-3 stainless steel under uniaxial cyclic loading with mean tensile stress. The yield stress and ultimate strength were higher than that of large size specimen with diameters of 5 mm and 7 mm. The effects of stress amplitude, mean stress, loading history and stress rate on the ratcheting behavior of high-nitrogen steel were analyzed, respectively. It can be concluded that the ratcheting strain amplitude and ratcheting strain rate of X13CrMnMoN18-14-3 steel increases with increasing stress amplitude or mean stress correspondingly. At the meantime, experimental results reveal that the material exhibits a strong memory of the previous loading history, the stress cycling with higher stress amplitude or mean stress greatly restrains the ratcheting of subsequent stress cycling with lower ones. The ratcheting strain rate was very sensitive to the applied cyclic stress rate, and the accumulation of ratcheting strain under stress rate of 21.2 MPa/s is much faster than that under stress rate of 106 MPa/s. In addition, comparison of the fatigue life between bulk specimen and thin wire indicates that the size effect has significant influence on fatigue properties of the material. In the case of the test conducted under stress amplitude of 400 MPa, the fatigue life of small specimen is approximately ten times longer than that of bulk specimen under the same loading conditions.     

Performance analysis of multipath transmission over 802.11-based multihop ad hoc networks: a cross-layer perspective

Data transmission in ad hoc networks involves interactions between medium access control (MAC)-layer protocols and data forwarding along network-layer paths. These interactions have been shown to have a significant impact on the performance of a system. This impact on multipath data transmission over multihop IEEE 802.11 MAC-based ad hoc networks is assessed; analysis is from a cross-layer perspective. Both MAC layer protocols and network-layer data forwarding are taken into account in the system models. The frame service time at source in a 802.11 MAC-based multipath data transmission system under unsaturated conditions is studied. Analytical models are developed for two packet generation schemes (round robin and batch) with a Poisson frame arrival process. Moreover, an analytical model is developed to investigate the throughput of a multipath transmission system in 802.11-based multihop wireless networks. Two methods are proposed to estimate the impact of cross-layer interactions on the frame service time in such a system. Two bounds of the system throughput are obtained based on these estimation methods. These models are validated by means of simulation under various scenarios.     

钢筋混凝土异形柱空间框架抗倒塌试验研究

预知结构在偶然荷载作用下的失效机理和提供新荷载路径是异形柱框架结构抗倒塌设计的重要内容。进行1/3比例的两层3×2跨的底层边柱、角柱的突然失效试验及拟静力倒塌试验。分析钢筋混凝土异形柱空间框架的试验现象、裂缝分布、破坏过程及荷载-位移等,进行异形柱空间框架受力过程分析,研究异形柱空间框架结构的受力机制转换过程。研究结果表明：动力效应对异形柱空间框架的影响效果并不显著。试验中没有出现钢筋被拔出现象,裂缝主要集中在竖向构件支座处;异形柱空间框架的边柱、角柱倒塌破坏过程均经历了弹性阶段、弹塑性阶段、塑性阶段和悬链线阶段,边柱表现的悬链线效应远大于角柱的;楼板及梁的钢筋产生的悬链线效应在异形柱空间框架抗倒塌中发挥重要作用。     

Use of modulated excitation signals in medical ultrasound. Part III: High frame rate imaging

This paper, the last from a series of three papers on the application of coded excitation signals in medical ultrasound, investigates the possibility of increasing the frame rate in ultrasound imaging by using modulated excitation signals. Linear array-coded imaging and sparse synthetic transmit aperture imaging are considered, and the trade-offs between frame rate, image quality, and SNR are discussed. It is shown that FM codes can be used to increase the frame rate by a factor of two without a degradation in image quality and by a factor of 5, if a slight decrease in image quality can be accepted. The use of synthetic transmit aperture imaging is also considered, and it is here shown that Hadamard spatial encoding in transmit with FM emission signals can be used to increase the frame rate by 12 to 25 times with either a slight or no reduction in signal-to-noise ratio and image quality. By using these techniques a complete ultrasound-phased array image can be created using only two emissions.     

12路40Gb/s甚短距离并行光传输信号转换器研究

基于OIF-VSR5-01.0规范,分析了12路并行40Gb/s甚短距离(VSR)光传输转换器模块的实现原理.采用top-down分析方法,使用硬件描述语言verilog,在可编程逻辑器件上完成了时钟数据恢复、基于字节对齐方案的帧同步、信道去斜移、比特间差奇偶校验(BIP)等功能模块的程序设计,实现了SFI-5与OIF-VSR5-01.0电信号格式的相互转换,并在Altera的Stratix II GX 系列的高速现场可编程门阵列(FPGA)上对功能模块进行了功能验证和联合仿真.结果表明所设计的各个功能模块满足系统应用要求,为下一步将系统设计转换为专用集成电路(ASIC)奠定了基础.