Flexible resonant tank for a combined converter to achieve an HPS and LED compatible driver

High pressure sodium (HPS) lamp has been widely used in street lighting applications because of its maturity, relia-bility, high lighting efficiency, long life-time, and low cost. Light emitting diode ...     

Corrosion Resistance of High Performance Weathering Steel for Bridge Building Applications

 The mechanical properties, corrosion resistance and microstructures of high performance steel (HPS) was investigated by tensile testing machine, Charpy V-Notch (CVN) testing machine, cyclic immersion corrosion tester, XRD, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe micro-analyzer (EPMA). The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was composed of α-FeOOH phase and denser than that on PCS that was a mixture of α-FeOOH and Fe3O4. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS enrich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.     

Evaluation and Enhanced Use of Light Emitting Diodes for Hydroponics

Hydroponic farming is a viable and economical farming method, which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost. It is essential to provide supplemental lighting for crops grown in greenhouses to meet the daily light requirement, Daily Light Integral (DLI). The present paper investigates how effectively and efficiently LEDs can be used as a light source in hydroponics. It is important for a hydroponic grower to assess the requirement of photosynthetically active radiation (PAR) or the Photosynthetic Photon Flux Density (PPFD), in a greenhouse, and adjust the quality and quantity of supplemental lighting accordingly. A Quantum sensor (or PAR sensor) can measure PAR more accurately than a digital light meter, which measures the light intensity or illuminance in the SI unit Lux, but a PAR sensor is relatively expensive and normally not affordable by an ordinary farmer. Therefore, based on the present investigation and experimental results, a very simple way to convert light intensity measured with a Lux meter into PAR is proposed, using a simple conversion factor (41.75 according to the present work). This allows a small-scale hydroponic farmer to use a simple and inexpensive technique to assess the day to day DLI values of PAR in a greenhouse accurately using just an inexpensive light meter. The present paper also proposes a more efficient way of using LED light panels in a hydroponic system. By moving the LED light panels closer to the crop, LED light source can use a fewer number of LEDs to produce the same required daily light requirement and can increase the efficiency of the power usage to more than 80%. Specifically, the present work has determined that it is important to design more efficient vertically movable LED light panels with capabilities of switching individual LEDs on and off, for the use in greenhouses. This allows a user to control the number of LEDs that can be lit at a particular time, as required. By doing so it is possible to increase the efficiency of a LED lighting system by reducing its cost of the electricity usage.     

液压动力转向车辆的蛇行试验与仿真

汽车的操纵稳定性决定了汽车的操控性、行驶安全性和抗外界干扰能力,而转向系统与汽车操纵稳定性关系最为密切。为研究液压动力转向车辆的操纵稳定性,利用Matlab/Simulink建立了液压动力转向系统以及整车三自由度状态方程的仿真模型,在使用试验数据验证仿真模型正确性的基础上,对模型进行了蛇行试验的操纵稳定性仿真,分析了液压动力转向系统的系统结构参数对蛇行试验的影响,仿真结果的分析为动力转向系统的设计和提高车辆操纵稳定性提供了依据。     

铌对美标桥梁结构钢板性能的影响

通过向桥梁结构钢板HPS70W中添加不同含量的Nb元素,研究了合金元素Nb对桥梁结构钢板的力学性能、金相组织和第二相粒子析出的影响。试验结果表明,合金元素Nb对桥梁结构钢板HPS70W低温韧性、强度和塑性有显著影响。     

Multivariable optimization of thermal cracking severity

The changing market forces are driving olefin producers to operate their steam crackers at high operating rates and optimum production performances. These require the use of an optimizer for assessment of viable operational strategies. Most of the optimizers currently employed in this area make use of the coil outlet temperature to determine an improved severity. In rare cases only, a multivariable optimization is performed on the furnace operational conditions. This kind of optimization is implemented in PyroFur for optimizing both the furnace operation and the reaction severity using a set of first-principles mathematical models in which the coil outlet temperature, the total feed flow rate and the steam/hydrocarbon ratio are altered. The suggested procedure was applied as a case study for a typical liquid furnace. Typical improvements obtained from the optimizing control strategy proposed in this article include about 1.4% increased profitability per year per furnace. Effect of a change in the prices or the feed composition is also presented.     

K/G:一种网格的使用模式体系结构及应用

传统的客户端／服务器模式通过请求/响应的数据交换方式为用户服务，网格系统的目的是让用户更加方便和高效地共享和使用广域的资源，这可能需要改变现有的计算机系统使用模式和评价方法，基于对网格的特性分析，提出一种K／G(grid key/grid)的网格使用模式体系结构，其关键特点是，用户将网格钥匙(grid key)接入连接网格的终端设备时，网格端的服务和数据实时地动态部署到网格终端为用户服务，还分析了这种使用模式体系结构如何体现网格的动态开放功能特征和高生产率服务的性能特征。     

基于LCC谐振网络的高压钠灯电子镇流器启动方法的研究

HPS灯的启动是一个复杂的物理过程。本文通过对LCC谐振网络传输特性的分析,根据滑频软启动的工作原理,提出一种新型变频带滑频的启动方法。该方法可以减小启动过程对元器件的冲击,延长HPS灯的使用寿命,并且具有很好的自适应性。     

基于电荷泵功率因数校正技术的小功率高压钠灯用电子镇流器

本文研究了输入电流连续型电荷泵功率因数校正(CIC-CPPFC)技术在电子镇流器中的应用,采用CIC-CPPEC技术实现的电子镇流器,与传统的双功率级电子镇流器相比,结构简单、电压应力低、功率密度高、成本低。本文成功设计出了一台适合50W高压钠灯用电子镇流器。实验表明,这种单功率级电子镇流器不仅能实现高压钠灯变频软启动,而且能保证在输入电网电压大范围变化时实现恒功率运行。它具有完善的多重保护功能,功率因数大于0.98,THD值小于15%。