Materials Literature
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Abstract Changes of the water content in drawn silk during drying were investigated by thermal analysis and 1 H pulse NMR. Water in liquid silk by drawing extruded from the inside of the silk filament into ambient air. The water contents in the drawn silk decreased with drying time. Assuming the nonfreezing water has…
The prospects for ultracapacitors for use in electric and hybrid vehicles in the near-term (within five years) are discussed based on the present status of the technology world-wide and the characteristics of devices that are available for purchase or in an advanced state-of-development and thus nearly ready to be mar…
This paper deals with fundamental investigations on the electric strength of liquid impregnated insulating papers namely aramid paper and cellulosic paper. These investigations point out that the breakdown voltage at 20/spl deg/C of the two papers does not differ significantly. However their electric strength differs…
This paper presents a power transformer model to evaluate differential element performance. The paper analyzes transformer energization, overexcitation, external fault and internal fault conditions with this model. Test results with an actual transformer validate the model. The paper includes a guide for properly sele…
Nowadays, the use of inverters for speed variation of low voltage motors has become more and more common. The most common technology for this kind of apparatus uses pulse width modulation (PWM). It is characterized by a square voltage shape with short rise and fall times. In order to insure the quality of turn to grou…
A new, substantial improvement of the hysteresis current control method for voltage source power converters is presented. A simple and fast prediction of the hysteresis band is added to a linearized version of the phase-locked-loop control, thus ensuring constant switching frequency and tight control of the position o…
Due to the increase of electromagnetic and electromechanical devices supplied by static converters, the classification and evaluation of energetic behaviour of soft magnetic materials, with nonsinusoidal supply, is becoming mandatory. In this paper the possibility of defining a standard methodology for the specific ir…
In gas-insulated systems (GIS) defects such as free metallic particles, protrusions from the electrodes and defects associated with insulators can lead to partial discharges (PD) and, ultimately, to electrical breakdown. Of the various diagnostic techniques used in monitoring GIS, electrical and acoustical methods of…
This paper presents a review of the experimental and theoretical investigations conducted by the author and his associates on the problems of noise produced by rotating electrical machines. After discussing the nature of the problems and the mechanism of production of acoustic noise, a detailed description of the vibr…
This paper presents the results of a research project considering 13.8 kV distribution line and 88 kV transmission line insulators, exposed to marine and industrial pollution, respectively. Leakage current measurements were performed in the field. Tests were performed in the laboratory and registration instruments wer…
A wound potential transformer failed catastrophically on the Manitoba Hydro system. The failure was attributed to excessive current flow in the primary winding due to a sustained ferroresonance between the circuit breaker grading capacitance and nonlinear magnetizing inductance of the potential transformer. In order t…
Many high power electronic devices, such as power amplifies and multiprocessors, operate at high temperatures close to or at the edge of their reliability, which could severely impact performance and operating lifetime. These devices thus need cooling to improve performance and reliability. Conventional thermal manage…
Abstract A fumed hydrophilic nano‐silica‐filled polypropylene (PP) composite was blended with a liquid‐crystalline polymer (LCP; Rodrun LC5000). The preblended polymer blend was extruded through a capillary die; this was followed by a series of rheological and morphological characterizations. The viscosity of the PP m…
Abstract Branched nanofibers of conducting polyaniline (PANI) buried in the crystals of camphor sulfonic acid (CSA) were prepared from an m ‐cresol solution of PANI and excessive CSA. After the excessive CSA was dissolved through ultrasonication in deionized water, networks of PANI nanofibers with spherical nodes, nan…
This paper discuses the design, materials, fabrication and measurements of a novel integrated decoupling capacitor for MCM-L-based substrates. Based on modeling using the SLA Roadmap, it has been estimated that 13-72 nF/cm/sup 2/ of specific decoupling capacitance will be required for the next decade. The capacitor in…
Abstract The main transitions of cellulose fatty esters with different degrees of substitution (DSs) were investigated with dynamic mechanical thermal analysis. Two distinct main relaxations were observed in partially substituted cellulose esters (PSCEs). They were attributed to the glass‐transition temperature and to…
Large ferrite cores used in high-power, high-frequency applications can experience dimensional effects that limit the bandwidth of the device and cause losses higher than those predicted by manufacturer's datasheets. This paper examines such effects in Mn-Zn cores of various sizes and presents corroborating measuremen…
Abstract Our results from structural investigations of transition metal complex ion pairs in solution by homonuclear and heteronuclear 1D‐ and 2D‐NOE NMR spectroscopy are reviewed. Both model ( A ) and catalytically active ( B ) complexes have been taken into account; their general formulas are: trans ‐[ML 2 (N,X)(Y)(…
Infrared microscopy has been used to measure the thermal conductivity K of printed wiring boards with embedded layers of Cu, for heat flow perpendicular (K/sub /spl perp//) to the plane of the board. The technique provides the thermal conductivities of the individual glass-epoxy layers and the thermal resistance at ea…
In many power electronic applications, ferrite cores of magnetic components are biased with a DC or low-frequency premagnetization. Usually however, the influence of the bias on the losses and permeability is not considered in the component design. This paper describes a precise measurement setup to determine the powe…