摘要:
A low noise imaging apparatus for producing Magnetic Resonance (MR) images of a subject and for substantially minimizing acoustic noise generated during imaging is provided. The imaging apparatus comprises a magnet assembly, a gradient coil assembly, and a rf coil assembly, wherein at least one of the magnet assembly, the gradient coil assembly and the rf coil assembly are configured to reduce the generation and transmission of acoustic noise.
摘要:
Power semiconductor device structures and assemblies with improved heat dissipation characteristics and low impedance interconnections include a thermally-conductive dielectric layer, such as diamondlike carbon (DLC) overlying at least portions of the active major surface of a semiconductor chip, with vias formed in the dielectric layer in alignment with contact pads on the active major surface. A patterned metallization layer is formed over the thermally-conductive dielectric layer, with portions of the metallization layer extending through the vias into electrical contact with the chip contact pads. A metal structure is electrically and thermally coupled to selected areas of the patterned metallization, such as by solder bonding or by a eutectic bonding process. In different embodiments, the metal structure may comprise a metal conductor bonded to the opposite major surface of another power semiconductor device structure, a heat-dissipating device-mounting structure, or simply a low-impedance lead.
摘要:
A wireless network is provided, that may comprise wireless sensor units organized in chains of wireless sensor units. Each wireless sensor unit may comprise plural sensors and at least a wireless transceiver connected to communicate by wires or wirelessly with the plural sensors. Each chain of wireless sensor units may include a terminal wireless sensor unit and intermediate wireless sensor units, each intermediate wireless sensor unit being configured to relay data along the chain of intermediate wireless sensor units towards the terminal wireless sensor unit. The terminal wireless sensor unit in each chain of wireless sensor units is adapted to communicate wirelessly with at least one backhaul unit of plural backhaul units; and the backhaul units are adapted to communicate with a central computer.
摘要:
An amalgam is accurately placed and retained in an optimized location in the exhaust tube of an electrodeless SEF lamp for operation at a mercury vapor pressure in the optimum range from approximately four to seven millitorr by forming a dimple in the exhaust tube and using a dose locating member to locate and retain the amalgam on the side of the dimple away from the core of the lamp after filling the lamp. As an alternative, two dimples may be situated on opposite sides of the exhaust tube for performing the same function as, but with less depth than, the single dimple. In another alternative embodiment, first and second dimple configurations are formed in the exhaust tube after tip-off thereof, each dimple configuration including either one or two dimples. The second dimple configuration is spaced apart from the first dimple configuration along the length of the exhaust tube. In this way, the amalgam may be initially positioned farther from the tip-off region, thereby avoiding problems during tipping off of the exhaust tube, such as loss of mercury from the lamp, or quenching of the tip which could cause stress cracks. After tip-off, the second dimple configuration allows for placement of the amalgam closer to, or preferably in contact with, the tip of the sealed exhaust tube, i.e., the coolest location in the exhaust tube.
摘要:
An electrically controllable variable capacitor includes the interelectrode capacitance of at least one power MOSFET, a capacitance connected in series with the MOSFET and having one terminal connected to the drain or source thereof (the series capacitance), and bias control circuitry for controlling the bias voltage applied to the MOSFET. The voltage rating of the MOSFET, the peak amplitude of the applied ac signal, and the value of the series capacitance determine the range of dc bias voltages over which the MOSFET can be operated, and hence the capacitance range of the variable capacitor. Such a variable capacitance is useful as a tuning capacitor in an electrodeless HID lamp ballast.
摘要:
An electrodeless lamp (e.g., an electrodeless fluorescent lamp) includes a dielectric housing shaped to conform to a portion of a lamp envelope, which housed portion is opposite to a portion through which light is emitted. The dielectric housing includes a continuous conductor, i.e., a shorted turn, situated between the dielectric housing and the lamp envelope which conforms to at least a portion of the dielectric housing. The configuration of the shorted turn, in terms of the location and amount of surface area occupied thereby, is optimized to minimize interaction between the excitation coil and any metallic fixture and to avoid interfering with lamp starting and light output.
摘要:
All the magnetic functions required in a ballast for a fluorescent lamp are integrated in a single, standard magnetic core which provides isolation, voltage step-up, ballasting, power factor correction and cathode heat for multiple lamps operating multiple lamps in an isolated-series configuration. In a three-legged transformer core embodiment, the primary winding is continuously wound on all three legs, while secondary windings are included on two of the legs. Ballasting inductance is provided by winding the primary on the third leg. The number of primary turns N.sub.p necessary to avoid saturation of the transformer for any specific input voltage and core material, the number of primary windings N.sub.p1 on the secondary legs and the number of primary windings N.sub.p2 on the third leg are determined according to the equation 2N.sub.p1 =N.sub.p -N.sub.p2.
摘要:
System and method for retrieving data from distributed nodes using radio. Data is transmitted through a mesh of nodes to aggregators, and may be transmitted through a mesh of aggregators to higher level aggregators. High level aggregators are arranged in pipelines and configured to transmit and receive simultaneously to maximize information relaying capacity.
摘要:
A method of collecting data from wireless sensor units arranged in a network. The method may comprise the steps of initiating distribution of control signals to the wireless sensor units, acquiring data with the wireless sensor units by sensing one or more physical parameters, each of the wireless sensor units transmitting the acquired data in response to the control signals; and each of the wireless sensor units transmitting of at least a portion of the acquired data according to a prioritizing algorithm associated with each respective wireless sensor unit.
摘要:
A quadrature coil suitable for use with an open frame MRI system provides crossing pairs of arrays of parallel conductor elements, respectively. Compact configuration is provided through use of an isolating circuit for incorporating parasitic capacitances at the resonance frequency of the coil into a blocking parallel resonance. Termination of the parallel conductor elements may be accomplished by equal impedance node connectors formed from branching pairs of conductors or a triangular least resistance connection form. RF shields are provided by pairs of conductive sheets containing eddy current reducing slots aligned with the parallel conductors elements of the coil.