Search Results

The demands for high-performance power electronics systems are rapidly surpassing the power density, efficiency, and reliability limitations defined by the intrinsic properties of silicon (Si)-based semiconductors. The advantages of silicon carbide (SiC) are well known, including high temperature operation, high voltage blocking capability, high speed switching, and high energy efficiency. These advantages, however, are severely limited by conventional power packages, particularly at temperatures higher than 175°C and ≻100 kHz switching speeds. Here, APEI, Inc., presents the design process and testing data of its newly developed high performance HT-2000 SiC power module for extreme environment systems and applications.

A new environmental friendly method to supply metalworking fluid called Oil on Water Drop is proposed. In this study, the obtained results using this new method are compared to the dry cutting one in the machining of oil grooves in engine bearings. Conventional machining of engine bearings is carried out in the dry cutting condition; however, it was found that using the new Oil on Water Drop method the machining performances were greatly improved. In terms of machining tool life, a twofold increase was obtained, while an improvement in the machining error led to a considerable reduction in the rejection of parts made in the production line.

Plants utilize photons at wavelengths between 400 and 700 nm. These photons, called photosynthetically active radiation (PAR), represent only a part of the total solar spectral energy. The optical waveguide solar plant lighting system has the potential to generate electric power while providing plant lighting. Recently, Physical Sciences Inc. (PSI) demonstrated simultaneous PAR transmission and photovoltaic (PV) power generation at its solar facility. In this paper, we will discuss the results of our work pertaining to feasibility of simultaneous plant lighting and electric power generation.

In this paper we discuss the results of theoretical and experimental study of key components of the optical waveguide (OW) solar plant lighting system. In this system, solar radiation is collected by the concentrator which transfers the concentrated solar radiation to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the selective beam splitter where the solar spectra is divided into two components: plant lighting spectra (400 nm < λ < 700 nm) and power generation spectra (λ > 700 nm). The plant lighting spectra are transmitted to the plant growth chamber where the solar radiation from the optical fibers is de-focused for optimum intensity for plant growing. The power generation spectra are transmitted to the photovoltaic (PV) power generator for power generation.

Hybrid solar and electric lighting (HYSEL) systems constitute the latest generation of lighting systems for advanced life support, exhibiting continued potential for reducing the significant electrical power demand of current bioregenerative life support systems (BLSS). Two experimental HYSEL systems were developed: one employing xenon-metal halide (XMH) lamps and the other adopting light-emitting diodes (LEDs) as the electric-lighting components, and both using a mirror-based, fiberoptic-based solar collection system. The results showed that both the XMH and LED HYSEL systems effected reduced effective plant growing volume, indicating potential for a compact plant hardware design. The apparent electrical conversion efficiency of the LED HYSEL system exceeded that of the XMH HYSEL system by five-fold. Both the XMH and LED HYSEL systems provided reasonably acceptable spectral quality and lighting uniformity.

The Hybrid Solar and Artificial Lighting (HYSAL) system used in this study consisted of a mirror-based Optical Waveguide (OW) Solar Lighting System as the solar component and four 60-W xenon-metal halide illuminators as the artificial-light component. A reference (or control) system consisted of a conventional 250-W high pressure sodium (HPS) lamp. Solar irradiance was harnessed whenever available for the HYSAL treatment. During the course of the 30-day growth period for lettuce (Lactuca sativa), the HYSAL's solar PPF varied with the natural fluctuations of terrestrial solar irradiance, which changed dramatically within each day and between days. When averaged over the entire growth period, the average instantaneous solar PPF for the HYSAL treatment turned out to be 322 μmol m−2 s−1 for an average daily photoperiod of only 3.86 hours owing to numerous cloudy days.

The long-term supplemental terrestrial solar lighting made available to the Biomass Production Chamber (BPC) located in the Subterranean Plant Growth Facility (SPGF) at The University of Arizona was determined for two cases where two types of Solar Irradiance Collection, Transmission and Distribution System (SICTDS) were used for the facility. Databases for hourly solar irradiance incident upon Tucson, AZ compiled over a 12-year period from 1987 through 1998 were used to calculate the projected average instantaneous PPF within the BPC per hour and per day throughout the year. The results showed that replacing the available solar irradiance within the BPC as delivered by the Himawari SICTDS in June would require either 97.7 W m−2 of HPS lighting or 185.9 W m−2 of CWF lighting supplied continuously for 450 hrs. In energy terms, these would be equivalent to 44.0 kW-hr m−2 for the HPS lamp and 83.7 kW-hr m−2 for the CWF lamp.

This paper summarizes the results of a program to develop key components for the Optical Waveguide (OW) Solar Plant Lighting System. In the OW solar lighting system, solar radiation is collected by the concentrator which transfers the photosynthetically active radiation (PAR) to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the plant growing units where the PAR component of the radiation is directed to the plants. The non-PAR components of the solar radiation is directed to the energy conversion device for non-plant lighting applications. This program, conducted by Physical Sciences Inc.

The evolution of lighting systems for Bioregenerative Space Life Support (BLSS) has been brought about by two major challenges confronting current BLSS models: (1) the extensive use of highly energy-intensive artificial lamps; and (2) the substantial energy wastes incurred through heat dissipations by these lamps, frequently dictating unnecessarily large, and costly, physical volumes for the plant growing structures. The results of our studies showed that Solar Irradiance Collection, Transmission and Distribution Systems (SICTDS) should be used to augment artificial lighting for growing plants in a BLSS to constitute a reliable, energy-efficient and mass-optimized Hybrid Solar and Artificial Lighting (HYSAL) system for a BLSS.

A geometrically nonlinear finite element analysis of flexural edge waves for the composite jet engine fan blade model is presented. For the transient response problem of the composite fan blade subjected to local impact loading with foreign objects, existence of flexural edge wave in the region of the leading edge and the trailing edge was confirmed for the first time in computer simulation. Amplitudes of edge wave decrease exponentially with distance from the edge. These waves have dispersive characteristic even at low frequencies and are important in the region of the leading edge and the trailing edge of composite blade structures. It was found that delaminations of the leading edge in experimental results for ATP (Advanced TurboProp) blade model presented in the literature were related to this edge wave propagation along the free boundary. And also it was clear that just after the impact, higher order flexural waves are generated owing to local deformations.