基于信捷PLC对细石混凝土泵电气系统的设计

为了推进细石混凝土泵的国产化,在保证产品性能的前提下,降低其电气系统的生产成本,采用以国产信捷PLC(Programmable Logic Controller)为主的控制元件对细石混凝土泵电气系统进行了设计。在保证细石混凝土泵使用稳定性的同时,降低了其电气系统的制造成本,提高了适用性。所设计电气系统经菏泽永安机械制造有限公司检验使用,实际应用情况良好。     

Performance Evaluation of IEEE 802.15.4 CSMA/CA Scheme Adopting a Modified LIB Model

Since the successful release of the IEEE 802.15.4 standard, a great convenience is offered to applications in low-power and low-rate wireless sensor networks (WSNs) which almost touch upon all aspects in our surrounding circumstances. For time-critical applications, we use a modified Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism called Linear Increase Backoff (LIB) to enhance the performance of packet delay, but not compromise the metrics of energy efficiency and throughput. An accurate and comprehensive Markov model is used to analyze the characteristics of our LIB scheme predicting packet delay, energy consumption and throughput of unsaturated, unacknowledged IEEE 802.15.4 networks in which the unsaturated state is dependent on the traffic condition rather than the depiction by a predetermined length. Simulation results are consistent with the predictions of this model. We also compare the performance of LIB with that of several mechanisms according to the optimal parameters selected from operating point, and find that packet delay is obviously superior to that of other schemes, while energy efficiency and throughput are superior to others for large number of nodes and high traffic arrivals.     

我国固定网本地环路分拆问题的探讨

我国电信业新的竞争格局和宽带接入需求的增长推动了固定本地网领域的竞争。本地环路分拆有助于促进竞争同时减少重复建设。本文介绍了本地环路分拆的概念，对我国实施本地环路分拆的必要性进行了论述，并借鉴其他国家的实施经验，对我国实施本地环路分拆的监管政策提出了建议。     

585nm脉冲染料激光治疗皮肤血管性疾病所致的副作用

目的:观察585nm脉冲染料激光治疗血管性疾病所致的副作用。方法:分析500例经585nm脉冲染料激光治疗后的副反应。结果:500例接受治疗的患者中发生副反应者89例。其中色素沉着35例、色素减退12例、萎缩性瘢痕40例、增生性瘢痕2例。出现副反应与疾病种类、治疗能量无关,与治疗次数有关。结论:585nm脉冲染料激光治疗血管性疾病无连续激光治疗后所致的增生性瘢痕、持续性色素沉着等副作用,用于治疗血管性疾病是比较安全的。     

Single‐Crystalline Dodecahedral and Octodecahedralα‐Fe2O3 Particles Synthesized by a Fluoride Anion–Assisted Hydrothermal Method

Despite significant advances in iron oxide nanoparticles, it is still a challenge to synthesize regular polyhedral single‐crystalline α‐Fe₂O₃ particles because the surface energies of several low‐index planes are fairly similar. In the work presented here, well‐dispersed and single‐crystalline dodecahedral and octodecahedral α‐Fe₂O₃ particles are synthesized by a facile hydrothermal method with the aid of F^? anions. The crystalline structure of the polyhedral particles is disclosed by various characterization techniques. The dodecahedral particles are of hexagonal bipyramidal shape and enclosed by twelve equivalent (101) planes. The octodecahedral particles are formed by adding six equivalent (111) planes on the two tips of a dodecahedral particle, that is, they are enclosed by twelve (101) planes and six (111) planes. The existence of F^? anions plays a crucial role in the control of polyhedral particle shape. The function of F^? anions in the shape formation of the polyhedral particles is proposed as follows: 1) A high concentration of exposed Fe³⁺ cations induces preferential adsorption of F^? anions on the (100) plane and leads to the slowest growth along the [100] direction. When the concentration of F^? anions is higher than 24 mM , a stable speed ratio of growth along the [001] and [100] directions results in the exposure of (101) planes. 2) With a lower concentration of F^? anions, six symmetrical (111) planes with low concentration of exposed Fe³⁺ cations are present at the tops of a dodecahedral particle to form an octodecahedron. Furthermore, the dodecahedral and octodecahedral α‐Fe₂O₃ particles show much stronger magnetism than the previously reported α‐Fe₂O₃ nanostructures, having coercivities of 4986 Oe and 6512 Oe, respectively. Such high coercivities are attributed to a large local magnetic anisotropy, which might be induced by the polyhedron with equivalent crystallographic planes and/or the presence of F^? anions.     

基于PLC、触摸屏、电子模块的蔬菜大棚监控系统

以DVP-SS-11R型PLC为蔬菜大棚温湿度控制中心,利用DOP-B07S201型触摸屏显示,设定温湿度值以及报警的上下限值,使用电子模块DVP-04PT、DVP-04AD以及温度传感器PT100和湿度传感器HM1500对蔬菜大棚的温湿度进行检测,实现对蔬菜大棚温度和湿度的控制。     

Performance Analysis of Multiuser Diversity in MIMO Systems with Antenna Selection

In this paper, a framework is presented to analyze the performance of multiuser diversity (MUD) in multiuser point-to-multipoint (PMP) MIMO systems with antenna selection. Based on this framework, the tight closed-form expressions of outage capacity and average symbol error rate are derived for the multiuser transmit antenna selection with maximal-ratio combining (TAS/MRC) system, by which we show how and with what characteristics antenna selection gains, MIMO antenna configurations and fading gains impact on the system performance, with an emphasis on the study of multiuser diversity influence. From both theoretical and simulation results, our study shows that in multiuser PMP TAS/MRC systems an diversity order equals to the product of the number of transmit antennas, number of receive antennas and number of users can be achieved; what's more, users plays a key role in the system performance and can be viewed as equivalent 'virtual" transmit antennas, which is the source of the multiuser diversity inherent exists in the multiuser system. This kind of diversity can be efficiently extracted in the design of multiantenna systems.     

蜂箱内多点温度检测系统

介绍了基于AT89C52单片机的蜂箱内多点温度检测系统软、硬件结构设计。详细介绍了PN结温度传感器的工作原理以及在温度采集系统中的应用;AD0809在A/D转换中的应用;最后给出了软件设计的主流程图。该系统对蜂箱内温度变化规律的研究具有重要的现实意义。     

基于SOPC的双目视频采集及显示系统设计

针对双目视频传输数据量大、实时性及同步性要求严的问题,给出了一种以SOPC为核心的双目同步视频采集及显示系统设计实例.采用软硬件协同设计的方法,将视频采集控制器、视频输出控制器及DMA控制器集组成数据传输快速通道集成在SOPC中,并结合OpenCV开发上位机应用软件.结果证明,该设计方法在保证双目视频数据同步性和实时性的同时,极大的提升了系统集成度,并降低了设计复杂度,具有较高的实用价值.