Group 3 error-free facsimile terminal for analog cellular networks

A Group 3 error-free facsimile terminal for use in an analog cellular network has been developed. This facsimile terminal is provided with the International Telecommunication Union (ITU-T, formerly CCITT) T.30 recommendation protocol and an adaptive error control scheme (AECS) for Group 3 communication and error-free communication. The AECS monitors the channel conditions and selects the optimum error correction code. The ITU-T V.27ter is used as the modulation method and the transmission rate is 4800 bps. This system is compatible with the modified Huffman (MH), modified READ (MR), and modified modified READ (MMR) image data compression codes. The average communication time of this facsimile terminal is 40 s per page while moving through the analog cellular network     

Efficient third-harmonic generation of a picosecond laser pulsewith time delay

A new configuration based on the polarization-mismatching scheme with time delay for efficient frequency tripling conversion is proposed in this paper. The calculated results showed that the requirement for the efficient frequency tripling conversion of a 1-ps laser pulse is not only the optimization of peak intensity of the second-harmonic pulse, but also the optimization of the pulse duration ratio and temporal difference between the o-polarization second-harmonic pulse and the e-polarization first-harmonic pulse due to group-velocity mismatch among the interacting pulses. With the proposed scheme the group velocity mismatch can be compensated. Overall energy conversion efficiency increases from 55% to 75% under the optimized conditions at the intensity of 6 GW/cm². The temporal shape of the third-harmonic pulse with 1 ps pulse duration has no subpulses. The optimization of the efficient frequency tripling conversion for intensities of over 75 GW/cm² is also described. The results showed that the maximum tripling energy conversion efficiency is close to 80% with the optimized doubler and tripler     

Nitric oxide decomposition in air by using nonthermal plasmaprocessing with additives and catalyst

Catalyst (copper-coated zeolite catalyst, i.e., Cu-ZSM-5) was used to enhance NO_x removal plasma chemical reactions. Two kinds of hydrocarbons (2-propane-1-ol, 2-propanol) were added to the synthesized flue gas before the nonthermal plasma process, and their effects on NO_x removal characteristics were investigated. Enhancement effects of NO_x removal by the nonthermal plasma process with hydrocarbons as the additives were confirmed. Usually, the catalyst's working temperature is much higher than the room temperature. A catalytic reactor was installed after the plasma reactor. Catalytic effects on NO_x removal characteristics disappeared when the synthesized flue gas temperature was increased (~250°C). When the synthesized flue gas temperature was at room temperature, about 90% NO _x removal efficiency was realized with a combination of hydrocarbons, the catalytic reactor, and the pulsed discharge plasma     

Silica-based planar lightwave circuits

Silica-based planar lightwave circuits (PLC) provide various important devices for both optical wavelength-division-multiplexing networks and optical access network. This paper is an overview of recent progress in PLC technology including optical power splitters, arrayed-waveguide gratings, thermooptic switches, and hybrid integrated PLC's     

A 286 mm2 256 Mb DRAM with ×32 both-ends DQ

This paper describes a 256 Mb DRAM chip architecture which provides up to ×32 wide organization. In order to minimize the die size, three new techniques: an exchangeable hierarchical data line structure, an irregular sense amp layout, and a split address bus with local redrive scheme in the both-ends DQ were introduced. A chip has been developed based on the architecture with 0.25 μm CMOS technology. The chip measures 13.25 mm×21.55 mm, which is the smallest 256 Mb DRAM ever reported. A row address strobe (RAS) access time of 26 ns was obtained under 2.8 V power supply and 85°C. In addition, a 100 MHz×32 page mode operation, namely 400 M byte/s data rate, in the standard extended data output (EDO) cycle has been successfully demonstrated     

Wide-wavelength polarization-independent optical modulator based on tensile-strained quantum well with mass-dependent width

We have fabricated a multiple-quantum-well (MQW) waveguide optical modulator incorporating tensile strain and quantum well with mass-dependent width (QWMDW) for the first time. The structure was built on a strain relief InAlGaAs buffer layer grown on a GaAs substrate. Polarization-independent modulation with more than -10 dB extinction (at 8 V reverse voltage) was achieved over a very wide operating range, from 858 to 886 nm wavelength.     

Resonance bands and resonating pairs: theoretical fundamentals ofresonant tunneling

Resonant tunneling through one-dimensional quantum-mechanical systems such as multibarrier structures and superlattices has been studied in order to solidify the foundation of exact and comprehensive treatment of it. For general systems with piecewise continuous potential and effective-mass profiles, it is proven that allowable energy levels for resonant tunneling comprise a band structure-i.e., resonance bands which are distinct, in general, from the so-called subbands. One can see a resonance is attained by adjusting external parameters to match with a real resonating pair of the objective section (internal structure). In a series connection of two or more subsections (or a heterostructure with two or more layers), resonant tunneling is shown to be caused, this time, by a matching of generally complex resonating pairs of each couple of succeeding subsections. Two particular kinds of structures, i.e., imaginal-iteration and simple-iteration structures, are investigated in detail with regard to the matching between subsections at each resonant energy level. Thus, the possibility of resonance can be seen not directly related with resonance bands of the subsections. The overall argument will provide insight into the mechanism of resonant tunneling     

Application of a chemical heat pump to a cogeneration system

The feasibility of a proposed system that combines a magnesium oxide/water chemical heat pump and a diesel engine as a cogeneration system is discussed based on experimental results. The combined system is intended to utilize the waste heat discharge from the engine by means of the chemical heat pump and to level the heat supply load of the engine, allowing enhanced energy utilization. The thermal performance of the chemical heat pump in the cogeneration system is estimated based on the results of a packed‐bed experiment. The estimation indicates that by storing the waste heat from the engine during low demand periods, the cogeneration system can produce more than several times the standard thermal output of the diesel engine during peak demand periods. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermal performance of a packed bed reactor for a high‐temperature chemical heat pump

The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high‐temperature heat above 800°C, is studied experimentally. The thermal performance of a packed‐bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high‐temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high‐temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high‐temperature process is proposed for high‐efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd.     

A life-cycle analysis on thin-film CdS/CdTe PV modules

Authors have evaluated the life cycle of a thin-film CdS/CdTe PV module to estimate the energy payback time (EPT) and the life-cycle CO₂ emissions of a residential rooftop PV system using the CdS/CdTe PV modules. The primary energy requirement for producing 1 m² of the CdS/CdTe PV module was similar to a-Si PV module at annual production scale of 100 MW. EPT was calculated at 1.7–1.1 yr, which was much shorter than the lifetime of the PV system and similar to that of a-Si PV modules. The life-cycle CO₂ emissions were also estimated at 14–9 g-C/kWh, which was less than that of electricity generated by utility companies.