智能功率模块用于汽车高压辅助电机负载应用

集成的智能功率模块(IPM)将在汽车功能电子化中发挥关键作用,促成新一代紧凑的、高能效和高可靠性的电机驱动器,实现在内燃机中省去耗能的机械式驱动负荷.IPM的主要促成元素有场截止沟槽IGBT、STEALTH二极管、HVIC、LVIC和DBC技术等.     

Isothermal vapor-liquid equilibria for the binary system of dimethyl ether (CH<Subscript>3</Subscript>OCH<Subscript>3</Subscript>)+ methanol (CH<Subscript>3</Subscript>OH)

Isothermal vapor-liquid equilibrium data for the binary mixture of dimethyl ether (CH₃OCH₃)+methanol (CH₃OH) were measured within the temperature range of 308.15–328.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS) using the Wong-Sandler mixing rules combined with the NRTL excess Gibbs free energy model. The values calculated by the PR-EOS with the W-S mixing rules show good agreement with our experimental data.     

Transient inter-production scheduling based on Petri nets and constraint programming

In this article, we focus on the transient inter-production scheduling problem between two cyclic productions in the framework of flexible manufacturing systems. This problem is first formulated as a reachability problem in timed Petri nets (TPN), then solved using a methodology based on constraint programming. Our work is based on the controlled executions proposed by Chretienne to model the sequence of transition firing dates. Our methodology is based on a preliminary resolution of the state equation between initial and final states in the underlying non-TPN. Then, we choose a duration T _max corresponding to the maximal duration time of the scheduling. For each solution S of the state equation, we build a controlled execution from the sequence of firings in S. After the propagation of firing date constraints and reachability constraints in the TPN, we use constraint programming to enumerate the set of feasible controlled executions.     

Effect of tip clearance on the cooling performance of a microchannel heat sink

In this paper, the effect of tip clearance on the cooling performance of the microchannel heat sink is presented under the fixed pumping power condition. The thermal resistance of a microchannel heat sink is defined for evaluating its cooling performance. The effect of tip clearance is numerically investigated by increasing tip clearance from zero under the fixed pumping power condition. From the numerical results, the optimized tip clearance is determined, for which the thermal resistance has a minimum value. Finally, we show that the presence of tip clearance can improve the cooling performance of a microchannel heat sink when tip clearance is smaller than a channel width.     

Improvements of resonance characteristics due to thermal annealing of Bragg reflectors in ZnO-based FBAR devices

The effects of thermal annealing of W/SiO/sub 2/ multilayer Bragg reflectors on the resonance characteristics of ZnO-based film bulk acoustic resonator (FBAR) devices are presented for the first time. The resonance characteristics could be significantly improved due to thermal annealing. FBAR devices with Bragg reflectors annealed at 400/spl deg/C/30 min show excellent resonance characteristics in terms of return loss and Q-factor.     

Studies of the mechanical and electrical properties of lead-free solder joints

The mechanical and electrical properties of several Pb-free solder joints have been investigated including the interfacial reactions, namely, the thickness and morphology of the intermetallic layers, which are correlated with the shear strength of the solder joint as well as its electrical resistance. A model joint was made by joining two “L-shaped” copper coupons with three Pb-free solders, Sn-3.5Ag (SA), Sn-3.8Ag-0.7Cu (SAC), and Sn-3.5Ag-3Bi (SAB) (all in wt.%), and combined with two surface finishes, Cu and Ni(P)/Au. The thickness and morphology of the intermetallic compounds (IMCs) formed at the interface were affected by solder composition, solder volume, and surface finish. The mechanical and electrical properties of Pb-free solder joints were evaluated and correlated with their interfacial reactions. The microstructure of the solder joints was also investigated to understand the electrical and mechanical characteristics of the Pb-free solder joints.     

Intraoperative "direct" LIMA angiography for beating heart operations

The importance of the angiographic assessment of coronary bypass grafts performed on the beating heart has been recognized. We describe a simple technique for intraoperative angiography of left internal mammary artery to left anterior descending coronary artery grafts that does not require selective left internal mammary artery catheterization. This method allows immediate appraisal of the graft, hence enabling the surgeon to revise any graft or anastomosis abnormality immediately and to verify optimal results of beating heart operations.     

An Efficient Fault Tolerance Protocol with Backup Foreign Agents in a Hierarchical Local Registration Mobile IP

A Mobile IP allows IP hosts to move between different networks without changing their IP addresses. Mobile IP systems supporting local registration were introduced to reduce the number of times a home registration with the remotely located home agent was needed. The local registration Mobile IP scheme enhanced performance by processing registration requests of mobile nodes at a local agent. The local registration approach may affect other aspects of the Mobile IP systems such as fault tolerance. In this paper, we briefly review previous solutions for supporting fault tolerance in local registration Mobile IP systems and propose a fault tolerance protocol with a backup foreign agent in a hierarchical local registration mobile IP to enhance the efficiency of such systems against foreign agent failures. We also describe the specification of the proposed protocol using LOTOS and perform its validation using MiniLite. Finally, we analyze the performance of our proposed fault tolerance protocol through simulation.     

Use of 20 cm or longer interposition vein grafts in free flap reconstruction of the trunk

Between January of 1993 and September of 1995, six microsurgical free tissue transplants were performed using saphenous vein grafts ranging from 20 to 39 cm in length. All six free flaps survived. Two wounds were caused by radiation injury and two by tumor resection. The remaining two free flaps were performed for contour deformity and spinal cord coverage. All of the recipient sites were located on the trunk. In each case, an arteriovenous loop was created before the microvascular anastomosis to the free flap. There was one arterial thrombosis requiring thrombectomy and revision of the anastomosis. Three patients developed minor wound complications that responded to local wound care. Each of the flaps successfully provided wound coverage, and in two cases the flaps tolerated further radiation results. Long interposition vein grafts can be used for difficult microsurgical reconstructive procedures with reliable results when no local recipient vessels are available. Versatility is therefore afforded in placement of the flap and the choice of recipient vessels, making this option a useful one in the treatment of complex wounds of the trunk.     

A study on material damping of 0° laminated composite sandwich cantilever beams with a viscoelastic layer

The damping behavior of a 0° laminated sandwich composite beam inserted with a viscoelastic layer is investigated. A quantitative analysis of damping in the sandwich laminated composite beam has been conducted through the theoretical method. Results showed that the viscoelastic core thickness in the sandwich beam and the length of the beam have a great effect on the damping loss factor. They also demonstrate the great capability of laminated sandwich composites with embedded viscoelastic layer to considerably enhance structural damping. It is shown that the extended Ni–Adams’ theory can be efficiently used to identify the damping characteristics of the laminated sandwich composite beam.