Half-bridge inverter using 4H-SiC gate turn-off thyristors

This paper reports on the first demonstration of a half-bridge power inverter constructed from silicon carbide gate turn-off thyristors (GTOs) operated in the conventional GTO mode. This circuit was characterized with input bus voltages of up to 600 VDC and 2 A (peak current density of 540 A/cm²) with resistive loads using a pulse-width modulated switching frequency of 2 kHz. We discuss the implications of the thyristor's electrical characteristics and the circuit topology on the overall operation of the half-bridge circuit. This work has determined the conservative critical rate of rise value of the off-state voltage to be 200 V/μs in these devices     

用广播与选择型OADM实现低成本透明光传输

互联网业务和数据业务的不断增长，使长途骨干网中的业务传送模式发生了显著变化。目前，互联网业务流比传统的话音业务流的传送距离远得多。研究表明，从2000年到2005年，北美地区的互联网业务流的平均传输距离将从目前的740公里增长到2700公里。业务传送模式的根本性变化，要求网络设计与运营模式也作相应的更新。今后，网络节点必须能提供更多的带宽和更长的电路连接。如果采用不透明的光网络，所有的信号都必须在每个中间节点进行再生，对于60%的传输距离不超过600公里的话音业务而言是不成问题的；但对于60%的传输距离超过3000公里的互…     

Current concepts in dentin bonding: focusing on dentinal adhesion factors

With greater need for treating root surface lesions, dentinal adhesives are more in demand. For successful treatment, all factors--dentin, tooth, patient and materials--must be considered.     

Inductive switching of 4H-SiC gate turn-off thyristors

The high-temperature operation of a silicon carbide gate turn-off thyristor is evaluated for use in inductively loaded switching circuits. Compared to purely resistive load elements, inductive loads subject the switching device to higher internal power dissipation. The ability of silicon carbide components to operate at elevated temperatures and high power dissipations are important factors for their use in future power conversion/control systems. In this work, a maximum current density of 540 A/cm² at 600 V was switched at a frequency of 2 kHz and at several case temperatures up to 150°C. The turn-off and turn-on characteristics of the thyristor are discussed     

The days ahead

How are government controls affecting healthcare foodservices?Are growing elderly & outpatient populations changing foodservices' missions. What are the hottest trends? As members of the American Society for Hospital Food Service Administrators prepared for their annual meeting in Orlando, FM queried 11 Southeastern directors to learn their most pressing concerns & how they are positioning their departments for the future.     

Cyberspatial mechanics.

In support of a generalization of systems theory, this paper introduces a new approach in modeling complex distributed systems. It offers an analytic framework for describing the behavior of interactive cyberphysical systems (CPSs), which are networked stationary or mobile information systems responsible for the real-time governance of physical processes whose behaviors unfold in cyberspace. The framework is predicated on a cyberspace-time reference model comprising three spatial dimensions plus time. The spatial domains include geospatial, infospatial, and sociospatial references, the latter describing relationships among sovereign enterprises (rational agents) that choose voluntarily to organize and interoperate for individual and mutual benefit through geospatial (physical) and infospatial (logical) transactions. Of particular relevance to CPSs are notions of timeliness and value, particularly as they relate to the real-time governance of physical processes and engagements with other cooperating CPS. Our overarching interest, as with celestial mechanics, is in the formation and evolution of clusters of cyberspatial objects and the federated systems they form.     

3D-FEA of osseointegration percentages and patterns on implant-bone interfacial stresses

The aim of this study was to investigate the expression and distribution patterns of the inducible isoform of nitric oxide synthase (iNOS) in rat placenta during gestation and term labour. The expression of iNOS isoform was assessed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting with monoclonal antibodies. Two specific bands were detected corresponding to 135 and 124 kDa in all placenta samples. The upper band (135 kDa) was identified as iNOS due to its correspondence with the band obtained with mouse macrophages (positive control). Compared with its concentrations on day 16, iNOS decreased steadily toward the end of gestation to approximately 37% on day 20, 20% on day 22 before labour and 12% during labour (p < 0.01). The lower band (124 kDa) drastically increased (to almost double) from day 16 to day 18 but returned to initial values on day 22, during delivery. Immunohistochemical staining of placentae at day 16 and 22 using rabbit polyclonal anti-iNOS antibody revealed labelling specifically concentrated in the trophospongial cell layer, at the fetal-maternal interface. The most conspicuous iNOS staining was associated with islands of cells referred to as vacuolated 'glycogen cells'. Staining was greatly decreased during labour. The changes in placental iNOS expression suggest a 'paracrine' role for NO in regulating uterine contractility, blood flow and immunosuppression required for pregnancy maintenance. NO withdrawal at term may also be involved in the initiation of labour.