用能量守恒定律消除高压变频室内负压

高压变频设备在我厂投运以来节能效果显著,但由于变频设备采用的室内外空气交换散热方式而产生的负压等一系列问题,不仅严重影响着生产的安全稳定运行,也危及着人身安全。我公司技术人员通过自主创新,采用能量守恒定律对变频设备的散热方式进行了改变,无需投资,见效快,投运一年来收到了良好的运行效果。     

Scaling and technological limitations of 1/f noise and oscillator phase noise in SiGe HBTs

This paper examines the impact of SiGe HBT scaling on 1/f noise and phase noise of oscillators and frequency synthesizers. The increase of transistor speed with scaling is shown to significantly increase the sensitivity of oscillation frequency to 1/f noise and, thus, degrade close-in phase noise, but decrease the sensitivity of oscillation frequency to base current shot noise and base resistance thermal noises. The results show that corner offset frequency defined by the intersect of the 1/f³ and 1/f² phase noise has little to do with the traditional 1/f corner frequency. The relative importance of individual noise sources in determining phase noise is examined as a function of technology scaling, device sizing, and oscillation frequency. The collector current shot noise and base resistance noise are shown to set the fundamental limits of phase noise reduction. A methodology to identify the maximum tolerable 1/f K factor is established and demonstrated for the HBTs used     

表面等离子激元脉冲整流产生太赫兹电动势

为了深入地研究表面等离子(Surface Plasmon,SP)在传播方向上的太赫兹(THz)电动势,采用了在纳米线结构上对表面等离子激元(Surface Plasmon Polariton,SPP)的脉冲中电子进行整流的方法,分析了SP感应引力的整流作用,讨论了SPP横向模式在长脉冲和短脉冲情况下的电动势模型。研究结果表明,脉冲整流会产生一个幅值较大的电动势,该电动势可达10 V。由于受纳米等离子的限制,在放大过程几乎是非共振的,考虑强纳米等离子限制和纵向SPP波局域条件下,整流作用在金属表面会产生更高的局域THz电场ER,其最大强度EmR=105~106V/cm。整流后SPP脉冲表现为快速,THz场频率,带宽5~20 THz的特性。SPP脉冲中THz电动势的分析对纳米级飞秒光学场的探测,半导体设备的纳米等离子激元耦合,以及非线性THz光谱研究都具有重要意义。     

Regulation and Reconstruction of Cell Phenotype Gradients Along the Tendon-Bone Interface

Tendon–bone interface is prevalent in the human body. It is divided into four zones: tendon (soft tissue), unmineralized fibrocartilage, mineralized fibrocartilage, and bone (hard tissue). Tendon–bone interface is characterized by a cell phenotype gradient that appears in the different zones. The cell phenotype gradients at the tendon–bone interface are orchestrated by specific intracellular molecular mechanisms, extracellular factors, immune signals, and neurovascular factors. These features have inspired scientists to design systems that mimic natural cell phenotype gradients. These biomimetic systems include the construction of cell sheets, regulation of cellular microenvironments, and the design of gradient functional scaffolds. Exploration of methods to mimic cell phenotype gradients is instructional for future clinical applications in reconstituting the tendon–bone interface. The present review elucidates the gradient composition of the tendon–bone interface. The associated regulatory mechanisms and applications are discussed, with the anticipation of creating a mise en scène for future research in interface tissue engineering.     

Cooperative and opportunistic transmission for wireless ad hoc networks

Moving toward 4G, wireless ad hoc networks receive growing interest due to users' provisioning of mobility, usability of services, and seamless communications. In ad hoc networks fading environments provide the opportunity to exploit variations in channel conditions, and transmit to the user with the currently "best" channel. In this article two types of opportunistic transmission, which leverage time diversity and multi-user diversity, respectively, are studied. Considering the co-channel interference and lack of a central controller in ad hoc networks, the "cooperative and opportunistic transmission" concept is promoted. For opportunistic transmission that exploits time diversity, it is observed that the inequality in channel contention due to the hidden terminal phenomenon tends to result in energy inefficiency. Under this design philosophy, we propose a distributed cooperative rate adaptation (CRA) scheme to reduce overall system power consumption. Taking advantage of the time-varying channel among different users/receivers and being aware of the potential contention among neighboring transmissions, we propose a QoS-aware cooperative and opportunistic scheduling (COS) scheme to improve system performance while satisfying QoS requirements of individual flows. Simulation results show that by leveraging node cooperation, our proposed schemes, CRA and COS, achieve higher network throughput and provide better QoS support than existing work     

Self‐Powered Trajectory,Velocity, and Acceleration Tracking of a Moving Object/Body using a Triboelectric Sensor

Motion tracking is of great importance in a wide range of fields such as automation, robotics, security, sports and entertainment. Here, a self‐powered, single‐electrode‐based triboelectric sensor (TES) is reported to accurately detect the movement of a moving object/body in two dimensions. Based on the coupling of triboelectric effect and electrostatic induction, the movement of an object on the top surface of a polytetrafluoroethylene (PTFE) layer induces changes in the electrical potential of the patterned aluminum electrodes underneath. From the measurements of the output performance (open‐circuit voltage and short‐circuit current), the motion information about the object, such as trajectory, velocity, and acceleration is derived in conformity with the preset values. Moreover, the TES can detect motions of more than one objects moving at the same time. In addition, applications of the TES are demonstrated by using LED illuminations as real‐time indicators to visualize the movement of a sliding object and the walking steps of a person.     

静电除尘用脉冲电源拓扑研究

对一种静电除尘用脉冲电源高压拓扑进行了研究,通过模态分析谐振状态及谐振后的震荡转态,研究耦合电感、耦合系数及谐振腔电阻对静电除尘器电源输出电压的影响,优化设计耦合电感及耦合系数。通过理论分析,推导出各部分激励对负载的传递函数表达式,并绘制三维变参数曲面图进行系统参数分析,最后搭建1.5 k V的脉冲电源系统,验证静电除尘器电源拓扑的工作原理及理论分析设计的正确性。     

CMMB地面覆盖方案探讨

介绍了中国移动多媒体广播CMMB基本情况,对CMMB地面覆盖进行了初步探讨,对CMMB单频网的组建方式、建网要求等作了简要论述。     

GaAs基GaSb体材料及InAs/GaSb超晶格材料的MBE生长

采用分子束外延方法在GaAs(100)衬底上生长GaSb体材料,以此GaSb为缓冲层生长了不同InAs厚度的InAs/GaSb超晶格,其10K光致发光谱峰值波长在2.0～2.6 μm.高分辨透射电子显微镜观察证实超晶格界面清晰,周期完整.     

大视场星敏感器光学系统畸变校正方法

针对大视场星敏感器光学系统畸变较大,严重影响角距测量精度的问题,采用多项式拟合算法,对研制的星敏感器进行了畸变校正,校正后的平均角度测量误差小于1″。