提高继电器小负载条件下接触可靠性的方法

探讨继电器小负载条件下的失效原因和工作特点,并推荐在DCS/PLC/SIS等系统中通过选择合适的继电器、完善检测电路设计方法予以解决。

小负载双缸液压同步系统的设计与实现

介绍了一种针对小负载的双缸液压同步系统。根据安装空间较小,行程长的特点,采用两级伸缩套筒式液压缸作为执行机构;通过对几种成本较低,同步精度较高的同步方式进行比较,采用同步马达作为同步措施;针对同步马达回路产生的累积误差,设计液压回路进行消除。该系统经过安装试验,工作稳定,同步精度较高,满足系统工作要求。

小负载液压缸活塞杆漂移故障分析

本文利用AMESim软件对不同的液压系统建立了小负载液压缸仿真模型,根据实际产品参数对液压缸模型进行配置。由于液压缸的内泄漏特性,当活塞杆完全回收、换向阀回到中位后,在一定的时间内出现活塞杆漂移现象,本文针对某型液压缸从内漏量、工作压力、系统背压、静摩擦力4个方面对内泄漏特性的影响开展了研究。结果表明:活塞杆自动伸出的行程取决于伸出时负载和密封圈静摩擦力的大小,完全伸出所需要的时间取决于内泄漏量的大小。最终提出了防止液压缸由于内泄漏特性导致活塞杆漂移故障的措施。

智能小型断路器典型小负载电气特性分析

随着负载的多样性与复杂性,智能小型断路器作为电压、电流测量与控制保护器件,传统的单一有效值计算方法不能满足其电气特性分析与电能质量精准化管理需求。实测了多种典型小负载的运行数据,基于实测数据进行了有效值和谐波计算分析,总结了典型小负载的电气特性,对提高智能小型断路器的测量分析和计算精度,推进多样化小负载特性下的电能质量精准化管理具有积极的意义。

Non-Point-Source Nitrogen and Phosphorus Loadings from a Small Watershed in the Three Gorges Reservoir Area

Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir(TGR);however,nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring.A representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen(N) and phosphorous(P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings.Results show that the non-point-source nitrogen and phosphorus comes mainly from the storm runoff from residential areas,citrus orchards and sloping croplands,which contributes up to 76% of the loadings in this watershed.Thus,a crucial measure for controlling non-point-source pollution is to intercept storm runoff from the three sources.Paddy fields provide a sink for non-point-source N and P by intercepting the runoff and sediment along with their different forms of nitrogen and phosphorus.The N and P removal efficiency by paddy fields from residential areas is within the range of 56% to 98%.Paddy fields are an important land-use option for reducing the non-point-source loading of N and P in the TGR area.

Improved wavelet neural network combined with particle swarm optimization algorithm and its application

An improved wavelet neural network algorithm which combines with particle swarm optimization was proposed to avoid encountering the curse of dimensionality and overcome the shortage in the responding speed and learning ability brought about by the traditional models. Based on the operational data provided by a regional power grid in the south of China, the method was used in the actual short term load forecasting. The results show that the average time cost of the proposed method in the experiment process is reduced by 12.2 s, and the precision of the proposed method is increased by 3.43% compared to the traditional wavelet network. Consequently, the improved wavelet neural network forecasting model is better than the traditional wavelet neural network forecasting model in both forecasting effect and network function.

Least-mean-square routing with load-balancing for wireless ad hoc networks

Routing algorithm is a challenge for a mobile ad hoc network （MANET）, but current routing protocols for MANETs consider the path with minimum number of hops as the optimal path to a given destination. This strategy does not balance the traffic load over a MANET, and may result in some disadvantages such as creating congested area, depleting power faster and enlarging time delay in the nodes with heavy duties. In this paper, we propose a routing scheme that balances the load over the network by selecting a path based on its mean load-square, the proposed routing metric can reflect not only the load of the path, but also the load distribution along the path. Simulation results show effectiveness of this routing scheme on balancing the load over all nodes in the network.

Solar-Powered Direct-Current Loads in Small Buildings

Traditional light bulbs （e.g., incandescent, fluorescent） use too much electricity, convert very little energy into light of sufficient quality and in their production use toxic contaminants. During the last few years, a new type of light source, LED （light emitting diode） bulb, has gained increasing popularity and its costs are set to plunge even further. LED bulbs offer many advantages over traditional sources, and they can be used as a direct replacement to existing lighting. This paper will use a spreadsheet-based analysis with hourly solar data supplied by Ecotect to show that, the efficiency of LED installations can be increased when used in conjunction with photovoltaic modules, as the two generate （and use） DC （direct-current） electricity, thereby eliminating intermediate-level losses in the electronic circuitry. If a storage battery is included, the solar panels generate electricity during the times when the occupants are not necessarily using the lighting, but the stored electricity can be used to power the lighting when the energy is required. The latest results demonstrate that, a slight reduction in the required floor area to be lit allows the solar-battery-LED system to be implemented in small buildings using a storage battery size that is within the range of present commercial devices.

Hierarchical power control for OFDM based LTE system

3 GPP LTE has approved uplink intra-cell power control and defined overload indicator （OI） for uplink inter-cell power contrQ1 to mitigate the inter-cell interference （ICI）, respectively. In this pa- per, we propose a hierarchical power control （ HPC ） scheme where intra-eell and inter-cell power controls interact with each other. The inter-cell power control eommand is generated by radio re- source management （RRM） entity according to the ICI-load model together with the current ICI and served load information. This ICI-load model is proposed as a guideline for coordination among cells to enable the system to approach its system specific interference over thermal noise （IoT） work area. Simulation results show that for HPC scheme, the system＇ s IoT is well controlled to fit its pre-de- fined work area and the power efficiency is improved significantly. Our proposed scheme is also ro- bust to different settings of its inter-cell power control period.

从2001年高考语文试卷谈起 万万不可抛弃“诚信”

去年高考作文是阅读一则寓言,寓言说的是有一个年轻人跋涉在漫长的人生路上,到了一个渡口的时候,他已经拥有了"健康"、"美貌"、"诚信"、"机敏"、"才学"、"金钱"、"荣誉"7个背囊。渡船开出时风平浪静,说不清过了多久,风起浪涌,小船上下颠簸,险象环生。艄公说:"船小负载重,客官须丢弃一个背囊方可安度难关。"看年轻人哪一个都舍不得丢,艄公又说:"有弃有取,

无线电通信

Y2000-62075-1542 0009827可靠多媒体无线网络的发展(含8篇论文)=SessionS39:advances in reliable multimedia wireless networks[会,英]//2000 IEEE International Conference on Com-munications Vol.3 of 3.—1542～1582(HC)本部分8篇论文的内容有:单速率有损网络最小负载多点扩播路由选择的性能分析,基于 OSI

Experimental research on reasonable lubricant quantity for transmission gears used in high-speed train

The transmission efficiency, bulk temperature, integrate temperature, and scuffing load of test gears were investigated by a modified FZG rig. These values were measured in four different oil immersion depths with one kind of potential oil that may be used to replace the current synthetic oil in order to find the reasonable lubricant quantity that meets not only the need of transmission performance but also the need of scuffing resistance for high-speed train gears. For the purpose of evaluating the efficiency of the test gears, there were two sensors added to measure the output torque of testing gears and the compensation torque of motor. The minimum lubrication film thickness at the pitch point was gained through an EHL model. The ratio of the film thickness A was used to identify the friction status when scuffing occurred at different oil levels. The results demonstrated that no matter what kind of the immersion depth was, the minimum film thickness on the pitch point was about 0.1 ~m and the ratio of film thickness was about 1.5 when scuffing occurred. According to the relationship of contact pressure and ratio of film thickness at the pitch point, it was found that the immersion depth of pinion should not be less than one module of the gear when the contact pressure of high-speed train gear at pitch point was about 580 MPa, which was the actual pressure at start-up stage.

Construction and evaluation of nitric oxide generating vascular graft material loaded with organoselenium catalyst via layer-by-layer self-assembly

A new biomimetic material for artificial blood vessel with in situ catalytic generation of nitric oxide(NO) was prepared in this study. Organoselenium immobilized polyethyleneimine as NO donor catalyst and sodium alginate were alternately loaded onto the surface of electrospun polycaprolactone matrix via electrostatic layer-by-layer self-assembly. This material revealed significant NO generation when contacting NO donor S-nitrosoglutathione(GSNO). Adhesion and spreading of smooth muscle cells were inhibited on this material in the presence of GSNO, while proliferation of endothelial cells was promoted. In vitro platelet adhesion and arteriovenous shunt experiments demonstrated good antithrombotic properties of this material, with inhibited platelet activation and aggregation, and prevention of acute thrombosis. This study may provide a new method of improving cellular function and antithrombotic property of vascular grafts.

Stress concentration in a finite functionally graded material plate

This paper is to study the two-dimensional stress distribution of a finite functionally graded material (FGM) plate with a circular hole under arbitrary constant loads. Using the method of piece-wise homogeneous layers, the stress analysis of the finite FGM plate having radial arbitrary elastic properties is made based on the complex variable method combined with the least square boundary collocation technique. Numerical results of stress distribution around the hole are then presented for different loading conditions, different material properties and different plate sizes, respectively. It is shown that the stress concentration in the finite plate is generally enhanced compared with the case of an infinite plate, but it can be significantly reduced by choosing proper change ways of the radial elastic modulus.