High-efficiency Silicon Solar Cells: A Review

Over the past few decades, crystalline silicon solar cells have been extensively studied due to their high efficiency, high reliability, and low cost. In addition, these types of cells lead the industry and account for more than half of the market. For the foreseeable future, Si will still be a critical material for photovoltaic devices in the solar cell industry. In this paper, we discuss key issues, cell concepts, and the status of recent high-efficiency crystalline silicon solar cells.     

Decay Rate Kinetics of Ozone Gas in Rice Grains

The present study was carried out to evaluate the effects of ozone on rice grains for the following three conditions: saturation time, decay rate, and half-life of ozone. Experiments were performed in different bed thicknesses (5 and 10 cm) and moisture content (11.4 and 14.2% wb) at atmospheric conditions. The lowest saturation time of ozone was 119 min, with the concentration of 516 ppm for rice grains ozonated at 5-cm bed thickness with 11.4% (wb) moisture content. The decay rate kinetics of ozone obtained were consistent with a first-order model. Regarding the half-life of ozone, the lowest value obtained was 6.78 min for rice grains ozonated at 10-cm bed thickness with 14.2% (wb) moisture content.     

Energy management for commercial servers

Servers: high-end, multiprocessor systems running commercial workloads, have typically included extensive cooling systems and resided in custom-built rooms for high-power delivery. Recently, as transistor density and demand for computing resources have rapidly increased, even these high-end systems face energy-use constraints. Commercial-server energy management now focuses on conserving power in the memory and microprocessor subsystems. Because their workloads are typically structured as multiple application programs, system-wide approaches are more applicable to multiprocessor environments in commercial servers than techniques that primarily apply to single-application environments, such as those based on compiler optimizations.     

Exploiting ILP, TLP, and DLP with the polymorphous trips architecture

The Tera-op reliable intelligently adaptive processing system (TRIPS) architecture seeks to deliver system-level configurability to applications and runtime systems. It does so by employing the concept of polymorphism, which permits the runtime system to configure the hardware execution resources to match the mode of execution and demands of the compiler and application.     

Travelling-wave photodetectors with 172-GHz bandwidth and 76-GHzbandwidth-efficiency product

Results of the first fabrication and measurement of travelling-wave photodetectors are reported. The devices have bandwidths as high as 172 GHz, the highest reported for a p-i-n photodetector, and bandwidth-efficiency products as large as 76 GHz, the largest reported for any photodetector without gain. Comparisons with vertically illuminated and waveguide photodetectors fabricated on the same wafer establish the superior performance of travelling-wave photodetectors. Microwave loss on the travelling-wave photodetector structure is identified as a bandwidth limitation     

Study of Magnetic and Electrical Properties of Poly(o-phenylenediamine)/Manganese Substituted ZnFe2O4 Nanocomposites

Journal of Inorganic and Organometallic Polymers and Materials - Different concentrations of ZnFe2O4 and manganese substituted ZnFe2O4 nanoparticles (10%, 20% and 30%) dispersed...     

Observations on the role of oxide scales in high-temperature erosion-corrosion of alloys

The results are presented of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial high-temperature alloys. Analysis of the kinetic and morphological data suggested that the high-temperature oxidation behavior of a given alloy plays a very important role in determining its erosion-corrosion behavior under the conditions studied. In terms of relative behavior, alloys which are weak but ductile at temperature, and which form tenacious oxide scales, exhibited the highest resistance to high-temperature erosion-corrosion. Simple models were developed to describe the expected interaction between high-temperature oxidation and erosion.     

Corrosion of Fe-10Al-Cr alloys by coal char

Corrosion of iron-base alloys at 982°C (1800°F) by coal char is observed and the phase morphologies are discussed. No sulfidation was observed at 50 hr exposure. After 100 hr internal aluminum-rich sulfides were observed along with thick outer scales of iron oxide. The species causing the hightemperature-induced corrosion are probably sulfides and sulfates, present in most coal chars. Possible mechanisms for the corrosion are also discussed.Department of Materials Science and Mineral Engineering.     

Structure of polyurethane elastomers. X-ray diffraction and conformational analysis of MDI-propandiol and MDI-ethylene glycol hard segments

X-ray diffraction and conformational analysis have been used to investigate the structure of polyurethane hard segments prepared from diphenylmethane 4,4′-diisocyanate (MDI) with propandiol (PDO) and ethylene glycol (EDO) as chain extenders. The results are compared with those obtained previously for MDI-butandiol (BDO) hard segments. In the latter system, the poly(MDI-BDO) chains are fully extended with an all-trans conformation for the O(CH₂)₄O unit, and a monomer repeat of 18.95 Å. The unit cell is triclinic with a tilted base plane such that adjacent chains are staggered along the fibre axis. In contrast both poly(MDI-PDO) and poly(MDI-EDO) adopt unstaggered structures, i.e. the chains are in register and the unit cell base planes are perpendicular to the chain axis. The monomer repeats of 16.2 Å for poly(MDI-PDO) and 15.0 Å for poly(MDI-EDO) are shorter than the predicted repeats for fully-extended chains, indicating that these polymers have contracted conformations containing some gauche CH₂ groups. Conformational analysis shows that the 16.2 Å repeat for poly(MDI-PDO) can be achieved with the O(CH₂)₃O unit in the trans-gauche⁺-gauche⁺-trans or gauche⁺-trans-trans-gauche⁺ conformations. Similarly the 15.0 Å repeat for poly(MDI-EDO) is predicted for the gauche⁺-trans-gauche^? conformation for the O(CH₂)₂O unit. These conformations are of higher energy than the all-trans fully-extended chains. This may explain the higher crystalline perfection of the poly(MDI-BDO) hard segments, for which crystallization in the all-trans form will probably provide a greater driving force for phase separation.