三端双向晶闸管的功耗计算和Tjmax预测

三端双向晶闸管用于控制AC电源负载。在大多数应用中,三端双向晶闸管会消耗大量电能,因而需要考虑散热。同时必须计算散热器的大小并预测最高结点温度Tjmax。散热设计和分析是设计和开发过程的基本部分。散热设计需要几个计算阶段,涉及到功率、热阻和温度升高。本文介绍的便是这些计算。     

Overexpression of cyclin D1 and cdk4 in tumorigenesis of sporadic hepatoblastomas

We have shown previously that normal B cells share, with Epstein-Barr virus-transformed and malignant B cells, the ability to activate the alternative pathway (AP) of complement in vitro, resulting in the deposition of C3 fragments on the cell surface. Complement receptor type 2 (CR2, CD21) has been implicated directly as the site for formation of an AP convertase, which provides nascent C3b for deposition at secondary sites on the B-cell surface. In the present study, we have examined C3 fragment deposition in vitro in more detail by (1) assessing the importance of locally generated C3b for the deposition process, (2) investigating whether CR2 is the sole requirement for conferring AP activation capacity on a cell, and (3) determining whether CR2's function, as an AP activator, has different structural requirements from ligand binding. Increasing the availability of native C3, by increasing the serum (NHS) concentration, resulted in enhanced C3 fragment deposition on the B cells, whereas use of factor 1-depleted NHS, which showed massive fluid phase C3 conversion during the incubation, diminished the deposition. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting of untreated and hydroxylamine-treated lysates from B cells, after in vitro activation, revealed that the majority of C3 fragments (primarily iC3b and C3dg) had been covalently bound to the cell surface. Transfection of COS cells with wild-type CR2 or a deletion mutant lacking 11 of the molecule's 15 homologous domains, but retaining the ligand-binding site, revealed that expression of intact CR2 conferred a 12-fold increase in AP-activating capacity on these cells, while no increase in AP activity was apparent on cells transfected with the mutant CR2.     

Buttockectomy as a limbsaving procedure for locally advanced soft tissue sarcoma of the buttock region

Cord blood was obtained from 164 neonates at birth and investigated for the presence of aflatoxins. 14 of the samples were neonates without jaundice and 150 from neonates with jaundice. There was significant reduction (P > 0.05) in birth weight of jaundiced neonates with aflatoxin. Neonates with jaundice have high mean concentration of aflatoxin B1 (32.3 ng/ml and 35.6 ng/ml). Aflatoxin G1 was not detected in any of the groups. The rate of detection was higher in wet (81.8%) than dry season (50.0%). These findings show that neonates are exposed to aflatoxin prenatally and that high incidence of jaundice occurred in the wet warm months.     

Stress and "storm and stress" in early adolescence: The relationship of negative events with dysphoric affect.

The theory that adolescence is universally a time of emotional turmoil has been disproved, yet research indicates higher rates of negative affect among adolescents than preadolescents. This study evaluates the relationship of distressed affect in early adolescence to the experience of stressful life events. 483 5th–9th graders provided experience sampling reports on their daily emotional states; data on recent major events in the child's life were obtained from the child and a parent. Findings indicate that older students in this age range encountered more negative events than younger ones, including more peer, school, and family events, and that experience of multiple negative events had a stronger association with daily negative affect among the older students. These findings suggest that the higher rates of daily distress experienced in adolescence may be partly attributable to the greater number of negative life events encountered by some youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Pneumatic Biped “Lucy” Actuated with Pleated Pneumatic Artificial Muscles

This paper reports on the bipedal robot Lucy which is actuated by pleated pneumatic artificial muscles. This novel actuator is very suitable to be used in machines which move by means of legs. Besides its high power to weight ratio the actuator has an adaptable passive behavior, meaning the stiffness of the actuator can be changed on-line. This allows to change the natural frequency of the system while controlling angular joint positions. The main control concept intended for Lucy is joint trajectory control while selecting appropriate actuator compliance characteristics in order to reduce control efforts and energy consumption which is of great importance towards the autonomy of legged robots. Presently Lucy has made her first steps with the implementation of basic control strategies.The pleated pneumatic artificial muscle and its characteristics will be discussed briefly and the design of Lucy which is made modular on mechanical as well as electronic hardware level will be described in detail. To pressurize the muscles, a lightweight valve system has been developed which will be presented together with the fundamental control aspects of a joint actuated with two antagonistically setup artificial muscles. Additionally the first experimental results will be shown and briefly discussed.Björn Verrelst (1972) Study of Mechanical Engineering at the Vrije Universiteit Brussel, graduated in 1996. Since 1998 researcher and teaching assistant at the Vrije Universiteit Brussel. The focus of his research is the use of pneumatic artificial muscles in the walking biped Lucy for dynamically balanced walking.Ronald Van Ham (1976) Study of Electro-Mechanical Engineering at the Vrije Universiteit Brussel, graduated in 1999. Since 1999 researcher and teaching assistant at the Vrije Universiteit Brussel. The focus of his research is the use of adaptable compliance of pneumatic artificial muscles in the walking biped Lucy.Bram Vanderborght (1980) Study of Mechanical Engineeringat the Vrije Universiteit Brussel, graduated in 2003. Since 2003 researcher at the Vrije Universiteit Brussel, supported by the Fund for Scientific Research Flanders (Belgium). The focus of his research is the use of adaptable compliance of pneumatic artificial muscles in the dynamically balanced biped Lucy.Frank Daerden (1966) Study of Mechanical Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 1999. Research and teaching assistant at the Vrije Universiteit Brussel, 1991–1999. Doctor-Assistant at the dept. of Mechanical Engineering, Vrije Universiteit Brussel since 1999, visiting Professor since 2003.Dirk Lefeber (1956) Study of Civil Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 1986. Professor at the dept. of Mechanical Engineering, head of the Multibody Mechanics Research Group, Vrije Universiteit Brussel.Jimmy Vermeulen (1973) Study of Mechanical Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 2004. Research and teaching assistant at the Vrije Universiteit Brussel, 1996–2004. Post-Doctoral researcher at the dept. of Mechanical Engineering, Vrije Universiteit Brussel since 2004. The focus of his research is trajectory generation and control of dynamically balanced legged robots.     

Palladium sintering: Shrinkage kinetics for a sponge powder

Pellets pressed from sponge palladium powder were sintered both isothermally and with constant heating rates using a precision low force dilatometer. Computer analysis of the data is used to determine shrinkage and shrinkage rate behavior during the sintering operation. The data are used in conjunction with metallographic examination to correlate the shrinkage phenomena to the change in grain size and pore morphology. The results show a characteristic shrinkage rate behavior associated with grain growth during sintering which can effectively halt densification.     

A semi-active milling procedure in view of preparing implantation beds in robot-assisted orthopaedic surgery

Bone cutting in total joint reconstructions requires a high accuracy to obtain a well-functioning and long-lasting prosthesis. Hence robot assistance can be useful to increase the precision of the surgical actions. A drawback of current robot systems is that they autonomously machine the bone, in that way ignoring the surgeon's experience and introducing a safety risk. This paper presents a semi-active milling procedure to overcome that drawback. In this procedure the surgeon controls robot motion by exerting forces on a force-controlled lever that is attached to the robot end effector. Meanwhile the robot constrains tool motion to the planned motion and generates a tool feed determined by the feed force that the surgeon executes. As a case study the presented milling procedure has been implemented on a laboratory set-up for robot-assisted preparation of the acetabulum in total hip arthroplasty. Two machining methods have been considered. In the first method the surgeon determines both milling trajectory and feed by the forces that he/she executes on the force-controlled lever. In the second method the cavity is machined contour by contour, and the surgeon only provides the feed. Machining experiments have shown that the first method results in large surface irregularities and is not useful. The second method, however, results in accurate cavity preparation and has therefore potential to be implemented in future robot systems.     

AB9: A neural processor for inference acceleration

We present AB9, a neural processor for inference acceleration. AB9 consists of a systolic tensor core (STC) neural network accelerator designed to accelerate artificial intelligence applications by exploiting the data reuse and parallelism characteristics inherent in neural networks while providing fast access to large on‐chip memory. Complementing the hardware is an intuitive and user‐friendly development environment that includes a simulator and an implementation flow that provides a high degree of programmability with a short development time. Along with a 40‐TFLOP STC that includes 32k arithmetic units and over 36 MB of on‐chip SRAM, our baseline implementation of AB9 consists of a 1‐GHz quad‐core setup with other various industry‐standard peripheral intellectual properties. The acceleration performance and power efficiency were evaluated using YOLOv2, and the results show that AB9 has superior performance and power efficiency to that of a general‐purpose graphics processing unit implementation. AB9 has been taped out in the TSMC 28‐nm process with a chip size of 17 × 23 mm². Delivery is expected later this year.     

Atomic Layer Deposition‐Assisted Fabrication of Co‐Nanoparticle/N‐Doped Carbon Nanotube Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction

Transition metal (TM)‐based carbon hybrids have numerous applications in the field of regenerative electrochemical energy. The synergetic effects of high conductivity of carbon supports and abundant catalytic active sites in TMs make these hybrids promising oxygen evolution reaction (OER) electrocatalysts. However, strategies for modulating the catalytic active species in the above hybrids are limited despite being highly sought after. Furthermore, the exact roles of chemical species in the hybrids (e.g., N, C, or TM) mainly responsible for this high OER performance remain unknown. Herein, an innovative approach based on atomic layer deposition is developed to tune the true active species in Co nanoparticle/N‐doped carbon nanotube (Co/N‐CNT) hybrids. Specifically, the configuration predominantly promoting water oxidation in an alkaline medium is identified as pyridinic N–Co–C. Furthermore, a physicochemical intact interface between metallic Co nanoparticles and conductive N‐CNTs is demonstrated to induce synergetic effects for accelerating charge transfer and enhancing electrocatalytic activity as well as stability in the hybrid catalysts. The optimized hybrid catalyst is revealed to exhibit outstanding alkaline OER activity and stability, outperforming RuO₂, a benchmark novel OER electrocatalyst.     

Information Theoretic Weighted Fuzzy Clustering Ensemble

In order to improve performance and robustness of clustering, it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique. Fuzzy clustering ensemble approaches attempt to improve the performance of fuzzy clustering tasks. However, in these approaches, cluster (or clustering) reliability has not paid much attention to. Ignoring cluster (or clustering) reliability makes these approaches weak in dealing with low-quality base clustering methods. In this paper, we have utilized cluster unreliability estimation and local weighting strategy to propose a new fuzzy clustering ensemble method which has introduced Reliability Based weighted co-association matrix Fuzzy C-Means (RBFCM), Reliability Based Graph Partitioning (RBGP) and Reliability Based Hyper Clustering (RBHC) as three new fuzzy clustering consensus functions. Our fuzzy clustering ensemble approach works based on fuzzy cluster unreliability estimation. Cluster unreliability is estimated according to an entropic criterion using the cluster labels in the entire ensemble. To do so, the new metric is defined to estimate the fuzzy cluster unreliability; then, the reliability value of any cluster is determined using a Reliability Driven Cluster Indicator (RDCI). The time complexities of RBHC and RBGP are linearly proportional with the number of data objects. Performance and robustness of the proposed method are experimentally evaluated for some benchmark datasets. The experimental results demonstrate efficiency and suitability of the proposed method.