Sepic直流稳压器的设计

设计了一种输入交流电压范围为130~300 V,输出12 V/8 A、工作频率为100 k Hz的Sepic直流稳压器,阐述了主电路的拓扑结构,并设计了输入保护电路、辅助电源电路、PWM控制电路、光耦隔离驱动电路与输出过压、过流保护电路,应用反馈手段和脉宽调制技术实现电压、电流的稳定。     

基于1394b总线仿真设备的WDM驱动开发

基于解决1394b和PCI的跨速率条件下通信数据易丢失,软硬件交互产生误码的目的。本文采用WDM(波分复用)驱动的串行处理操作来保护硬件;采用内核态线程保证数据传输的确定性;采用DMA(直接内存存取)保证数据的实时性;采用循环队列的模式保证数据传输的可靠性;采用乒乓原理保证硬件和软件交互的准确性等。通过实验验证,该驱动程序实现了软硬件的协调工作、提高了软件对硬件操作的操作安全性、提高了传输数据的可靠性以及实时性等。     

Effect of enhanced interfacial reaction on the microstructure,phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites

This study investigated the microstructure, phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites with a strong interfacial reaction between the particles and the matrix. The strong interfacial reaction was related to the large surface area and energy per unit volume of the flaky shape Ni–Mn–Ga particles that favors the reaction between the particles and matrix. The martensitic transformation behavior was largely weakened due to the interfacial reactions and thus the reduced volume fraction of Ni–Mn–Ga particles. The composites exhibited a much improved compressive strength and ductility in comparison with that of the Ni–Mn–Ga alloy. The compressive plasticity of the composites was decreased when the Ni–Mn–Ga particle content exceeded 40 wt%. In comparison with the Mg-composites with large size Ni–Mn–Ga particles, the composites with small size particles would have a much stronger interfacial reactions, which was detrimental to the phase transformation and mechanical ductility of the composites. The investigation results in this article could provide a reference for the design and preparation of the particles reinforced metal matrix functional composites.     

Probabilistic modeling of hybrid transition structures

Within lightweight structures, often Fiber Reinforced Plastics (FRP) are used in combination with metallic materials. Most of these hybrid structures are manufactured by established methods like riveting, bolting or adhesive bonding. In order to avoid disadvantages like drilled FRP or large bond areas, the development of hybrid transition structures compatible to loads and material properties is required. To fulfill the requirements for enhanced lightweight design, novel, integral joint concepts are currently designed, dimensioned and produced by using textile, welding and casting techniques.Three concepts are under investigation which consist of different materials (titanium and Ti-alloys, glass fibers), manufacturing methods (casting, welding, textile techniques) and geometries.Various phase boundaries, materials and influences of the manufacturing processes have to be investigated that influence the structural behavior and its failure. Based on the results of Finite Element Models on the meso scale, further modeling is performed to include effects like material uncertainties and/or process influences.In this paper, a probabilistic computation procedure based on local survival probabilities and distribution functions is proposed and investigated. This approach allows to model the complex global failure behavior for each component or its interfaces as well as the whole hybrid transition zone. It also shows the interactions and consequences of certain component changes within the hybrid transition zone. First computations are carried out and compared with experiments.     

铜粉添加量对铜酚醛树脂导电油墨性能的影响

以微米级铜粉为导电填料、酚醛树脂为粘接剂制备了导电油墨,并将该油墨以聚酰亚胺薄膜为基底,采用丝网印刷技术制备导电涂层。研究了铜粉添加量对铜酚醛树脂导电油墨的黏度、固含量以及导电涂层的微观形貌、电阻率和附着力的影响。研究表明,当铜粉添加量质量分数为70%时,制备的铜酚醛树脂导电油墨具有良好的性能,该导电油墨经丝网印刷得到的导电铜膜经低温固化后具有良好的电性能,其电阻率最低可以达到53.865×10–3Ω·cm。     

基于气候特征的屋顶绿化效果分析及推广策略探讨

基于地域特点和气候因素,我国南、北方地区推广应用屋顶绿化差异较大。在北方地区推广应用屋顶绿化时,应注重节水、采用轻型屋顶绿化技术、注意植物的选择以及制定地方性鼓励政策,方可收到屋顶节能的效果。     

谈设计阶段造价控制措施

分析了设计阶段中各子项目阶段的主要任务,针对设计阶段现存的问题,探讨了方案设计阶段投资控制的具体措施和优化设计的必要性及积极作用,指出应在现有法律法规及相关管理制度基础上,从设计阶段就落实投资控制。     

Influences of SiC infiltration and coating on compressive mechanical behaviours of 2D C/SiC composites up to 1600 °C at wide-ranging strain rates

The influences of the SiC infiltration and coating on the compressive mechanical behaviours of 2D C/SiC composites were determined up to 1600 °C at 0.001 and 1000/s strain rates in argon and air. In addition, the failure mechanisms responsible for the compressive mechanical behaviours were elucidated through in-situ observation and micro-analysis-based methods. The 2D C/SiC composite compressive strength was highly sensitive to temperature, loading rate, and oxidation, and was enhanced by the change in the thermal residual stress and decreased by oxidation. In argon, because of the extra infiltrated SiC matrix, SiC treated 2D C/SiC specimens exhibited higher compressive strengths and lower strain rate sensitivity factors than SiC untreated 2D C/SiC specimens. The SiC coating effectively improved the oxidation resistance of the 2D C/SiC composites in air, regardless of the temperature, strain rate, and oxidative damage-which depends on SiC coating, strain rate, and temperature.     

Fusion welding of refractory metals and ZrB2-SiC-ZrC ceramics

Molybdenum and a molybdenum alloy were fusion welded to ZrB₂-based ceramics to determine if the electrical and thermal properties of the metals and ceramics affected their weldability. Commercial ceramic powders were hot pressed, machined into coupons, and preheated to 1600 °C before joining the ceramics to commercial metals using plasma arc welding. Weldability varied as indicated by the range of porosity observed within the fusion zones. Measured thermal and electrical properties appeared to have little to no effect on the weldability of metal-ceramic welds despite the large range of values measured across each property. Differences in melting temperatures between metal and ceramic coupons did affect weldability by changing the weld penetration depth into ceramic coupons. Future studies on metal-ceramic welds are suggested to investigate the effect that work function, melt viscosity, wetting, or other properties have on weldability.