Web服务降级替换的一致性问题及量化研究

在开放的网络环境下,软件系统的可信性受到了更大的挑战,软件系统的降级替换是提高其可信性的方法之一。基于进程代数研究了Web服务的降级替换问题。在原有进程代数的基础上,添加了超时处理算子和延时处理算子,给出了Web服务降级替换一致性条件,从而保证了合成Web服务中降级替换的正确性。进一步地,从量化角度对Web服务的降级替换进行了研究。     

RFID系统安全分析

无线射频识别（RFID）技术与条形码技术等识别技术相比,具有防水防磁、读取距离远、存储数据多、数据可加密等优点,目前已做广泛应用于交通、物流、医疗、食品安全等领域。但作为物联网重要的感知设备因其缺乏有效的安全机制影响到物联网的应用与推广。本文从物理安全、通信安全和信息安全三个角度分析RFID系统安全问题及其解决方法。     

Design and implementation of light-weight mobile multicast for fast MIPv6

Mobile multicast is a research hotspot and can provide many applications. Some mobile multicast schemes have been proposed, but most of them introduce new entities and study construction algorithms of the dynamic multicast delivery structure which is heavyweight for wireless devices. In this paper, we propose a light-weight mobile multicast (LMM) scheme for Fast Mobile IPv6 which reduces the redundant operational overhead by simplifying multicast listener discovery (MLD) proxying. The LMM scheme implements simplified MLD proxying function on home agent to reduce the complicated multicast routing protocol and modifies MLD host part function on mobile node to reduce the multicast membership messages interaction. In order to solve the tunnel convergence problem, LMM also introduces a multicast tunnel combination and reconstruction algorithm. We set up a test-bed to evaluate the performance of LMM, and compare it with other mobile multicast schemes. The experimental results show that LMM reduces the multicast disruption time at handover. Based on the experimental results, we analyze the cost of LMM, and the results show that it has lower protocol cost than other schemes.     

Multisensor based security robot system for intelligent building

Intelligent building can provide safety, convenience, efficiency and entertainment for life in the 21st century. The most importance role of the intelligent building is the security system. We develop a multi sensor-based intelligent security robot (ISR) that is widely employed in intelligent buildings. The intelligent security robot can detect abnormal and dangerous situations and notify users. The robot has the shape of cylinder and its diameter, height, and weight are 50 cm, 130 cm and 100 kg respectively. The function of the ISR contains six parts. There is the software development system; avoiding obstacle and motion planning system, image system, sensor system, remote supervise system and other systems. We develop a multi sensor-based sensor system in the ISR. We use multiple multisensor fusion algorithms to get an exact decision in the detection subsystem of the sensor system. There is an adaptive fusion method, a rule based method, and a statistical signal method. We demonstrate the remote supervisory system to control the ISR using a direct control mode and a behavior control mode. We think that the man–machine interface in a security robot system must have mobility and convenience. Therefore, we use a touch screen to display the system state, and design a general user interface (GUI) to service the user and visitors. The user can remotely control the appliance using a cell phone through a GSM modem, too. The appliance module can feedback reaction results to the user through a cell phone. Finally, we implement the fire detection system in the intelligent security robot (Chung-Cheng-I). If a fire occurs, the intelligent security robot can find out the fire source using the fire detection system. In intruder detection, we program the same scenario to detect the intruder using the intelligent security robot. The intelligent security robot transmits the message of the detection result to the user using a GSM modem for a fire event or intruder, and transmits the detection result to a client computer through the internet.     

多电子元件及芯片组布局的热分析

针对电子线路板上多电子元件及芯片组的不同布局所产生的热场分布问题,分析了分布元件的热产生、热传导、对流和辐射过程,采用有限元理论分析方法和ANSYS软件,对线路板上多芯片组件的热场分布进行仿真.结果表明:电子元件的不同布局将导致线路板热点的温度存在差别,在有限空间内合理布置元件可明显降低设备的热失效率.     

Ultrathin MoSSe alloy nanosheets anchored on carbon nanotubes as advanced catalysts for hydrogen evolution

The activity of transition metal dichalcogenides (TMD) toward hydrogen evolution reaction (HER) derives from the active sites at the edges, but the basal surface still remain catalytic insert. Herein, ultrathin MoSSe alloy nanosheets array on multiwalled carbon nanotubes (MWCNTs) to form a core shell structure via a simple solvothermal process. These three-dimensional (3D) MoSSe hybrids show a high activity in hydrogen evolution reaction (HER) with a small Tafel slope of 38 mV dec⁻¹ and a low overpotential of 102 mV at 10 mA cm⁻². In addition, their HER activity remains remarkably stable without significant decay after 100 h polarization. Such superior catalytic HER activity springs from the 3D hierarchical heterostructure, which is abundant of catalytic edge sites, and the alloy effect between S and Se, which will create huge defects and strain to form vacancy sites on the basal plane. This strategy may open a new avenue toward the development of nonprecious high-performance HER catalysts.     

Free carrier absorption in self-activated PbWO4 and Ce-doped Y3(Al0.25Ga0.75)3O12 and Gd3Al2Ga3O12 garnet scintillators

Nonequilibrium carrier dynamics in the scintillators prospective for fast timing in high energy physics and medical imaging applications was studied. The time-resolved free carrier absorption investigation was carried out to study the dynamics of nonequilibrium carriers in wide-band-gap scintillation materials: self-activated led tungstate (PbWO₄, PWO) ant two garnet crystals, GAGG:Ce and YAGG:Ce. It was shown that free electrons appear in the conduction band of PWO and YAGG:Ce crystals within a sub-picosecond time scale, while the free holes in GAGG:Ce appear due to delocalization from Gd³⁺ ground states to the valence band within a few picoseconds after short-pulse excitation. The influence of Gd ions on the nonequilibrium carrier dynamics is discussed on the base of comparison the results of the free carrier absorption in GAGG:Ce containing gadolinium and in YAGG without Gd in the host lattice.     

Graphene nanosheets as counter electrode with phenoxazine dye for efficient dye sensitized solar cell

Efficient dye sensitized solar cells (DSSCs) are developed using phenoxazine (POZ) based organic dye (WS5) and graphene nanosheets (GNs) counter electrode (CE). Being organic, both these materials are used together to explore compatibility of organic materials in current DSSCs. Organic dye with POZ moiety is synthesized and graphene oxide nanosheets (GONs) are spin coated on FTO glass and thermally reduced afterwards. To increase the performance of WS5 through decreased dye aggregation, deoxycholic acid (DCA) is added to it. The results of adding DCA are observed and compared using UV–Vis spectroscopy, external quantum efficiency (EQE), electrochemical impedance spectroscopy (EIS) and photovoltaic conversion efficiency (PCE). Prepared organic dye based DSSC cell results in a high PCE of 6.61%. The optimized WS5 dye and GNs CE, shows PCE of 5.77% and the GNs CE compared to Pt CE results in almost identical charge transfer resistance value at the CE/electrolyte interface. Low cost of this designed organic dye and GNs and the PCE results indicate that this combination may result in the reduction of cost of current DSSCs and the realization that expensive and rare inorganic materials can be replaced with organic ones in future.     

Emerging technology enabled energy-efficient GPGPUs register file

Modern Graphics Processing Units (GPGPUs) employ the fine-grained multi-threading among thousands of active threads, leading to the sizable register file (RF) with massive energy consumption. In this study, we explore the emerging technology (i.e., Tunnel FET (TFET)) enabled energy-efficient GPGPUs RF. TFET is much more energy-efficient than CMOS at the low voltage operations, but always using TFET at the low voltage (so that low frequency) causes significant performance degradation. In this study, we first design the hybrid CMOS-TFET based register file, and propose the memory-contention-aware TFET register allocation (MEM_RA). MEM_RA allocates TFET-based registers to threads whose execution progress can be delayed to some degree to avoid the memory contentions with other threads, and the CMOS-based registers are still used for threads requiring normal execution speed. We further observe the insufficient TFET register resources for the memory-intensive benchmarks when applying the MEM_RA technique. We then develop the TFET-register-utilization-aware block allocation (TUBA) and TFET-regsiter-request-aware warp scheduling (TRWS) mechanisms to effectively utilize the limited TFET registers and achieve the maximal energy savings. Our experimental results show that the proposed techniques achieve 40% energy (including both dynamic and leakage) reduction in GPGPUs register file with negligible performance overhead.     

Automatic characterisation method for statistical evaluation of tin whisker growth

In this paper, an automatic method was developed to characterise whisker growth quantitatively in SEM images. The key step of the automatic methods in this case is the determination of the optimal threshold value for image segmentation, i.e. separation of the objects (whiskers) from the background (substrate). A thresholding method was developed for this purpose and was compared to manual and to general purpose automatic methods as references. As it was proven in previous studies the vacuum deposited tin layers on copper substrates can produce numerous tin whiskers in various shapes and lengths in a short time. This layer deposition technology was therefore chosen for the comparison of the thresholding methods. Images of the produced whiskers were captured by a FEI Inspect S50 Scanning Electron Microscope. By executing the automatic methods in the captured images, the area density of the whiskers, and the maximum and the mean length of the whiskers were measured. Based on the results of area density, the automatic methods were compared to manual counting and the Mean Absolute Percentage Error (MAPE) was determined. Finally, the reference automatic methods were compared to the self-developed method from the maximum and mean length of whiskers point of view.