Selective lasing of InGaAs quantum-wire array on a V-grooved GaAssubstrate by distributed optical feedback

Distributed-feedback (DFB) lasers were fabricated by using strained InGaAs quantum-wire (QWR) arrays on V-grooved GaAs substrates as an active grating. After characterizing the luminescence from the QWRs and parasitic quantum wells (QWLs), a DFB laser cavity incorporating such a QWR array with its emission wavelength matched to the Bragg wavelength was designed and fabricated. The wavelength selectivity of the DFB cavity was found to strongly support the QWR emission, and DFB lasing from QWR gain up to 145 K has been achieved under pulsed current. The emission from the parasitic QWLs was suppressed by the DFB filtering and the loss induced by coupling to radiation modes. The DFB cavity was shown to be essential for obtaining lasing from QWRs on V-grooved substrates     

Basic investigation for life assessment technology of modified 9Cr–1Mo steel

In order to develop life assessment techniques for aged components made of modified 9Cr–1Mo steel, specimens were artificially deteriorated by aging, creep and fatigue tests at elevated temperatures, and associated changes in the microstructure and mechanical properties were examined. It was observed that aging resulted in formation of Laves phase causing a decrease in toughness. The creep damage in base metal could be correlated with decrease in hardness, while creep damage in weldments could be correlated with the area fraction and density of creep voids. Creep rupture in weldments occurred in the fine-grained heat affected zone by the formation and growth of creep voids. The fatigue damage in base metal correlated to the maximum length of a crack among micro-cracks initiated during fatigue cycles.     

Growth and characterization of new oxide and fluoride crystals for optical applications

High quality oxide and fluoride single crystals for optical applications have been grown by the Czochralski technique. Lattice parameter investigation of grown Gd₃Yb _x Ga_5−x O₁₂ suggested that this crystal will be a superior material as substrate for optical isolators with large Faraday effect. Growth conditions of (La,Sr)(Al,Ta)O₃ single crystals are discussed. These crystals have excellent lattice matching with GaN, a promising material for optoelectronic devices. Ce-doped fluoride single crystals—LiCaAIF₆, LiYF₄ and BaLiF₃—have been grown for solid state UV laser applications. Growth results and optical characterization are discussed.     

A monolithically sculpted van der Waals nano-opto-electro-mechanical coupler

The nano-opto-electro-mechanical systems (NOEMS) are a class of hybrid solid devices that hold promises in both classical and quantum manipulations of the inter...     

Cloning and sequence analysis of hydroxyquinol 1,2-dioxygenase gene in 2,4,6-trichlorophenol-degrading Ralstonia pickettii DTP0602 and characterization of its product

A gene encoding hydroxyquinol 1,2-dioxygenase was cloned from 2,4,6-trichlorophenol-degrading Ralstonia (Pseudomonas) pickettii strain DTP0602. Cell-free extracts of Escherichia coli containing a cloned 1.4-kb StuI-XhoI DNA fragment of R. pickettii DTP0602 hydroxyquinol 1,2-dioxygenase converted hydroxyquinol into maleylacetate and also degraded 6-chlorohydroxyquinol. The 1.4-kb DNA fragment contained one open reading frame (designated hadC) composed of 948 nucleotides. The molecular mass of 34,591 deduced from the gene product (HadC) was in agreement with the size (35 kDa) of the purified HadC protein determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid sequence of HadC exhibited high homology to that of the hydroxyquinol 1,2-dioxygenase of 2,4,5-trichlorophenoxyacetic acid-degrading Burkholderia cepacia AC1100 (Daubaras, D. L. et al., Appl. Environ. Microbiol., 61, 1279-1289, 1995). The active enzyme had a molecular mass of 68 kDa, suggesting that it is functional as a homodimer. The enzyme also catalyzed the oxidation of pyrogallol and 3-methylcatechol, possible intermediates in the degradation of 2,4,6-trichlorophenol, in addition to 6-chlorohydroxyquinol and hydroxyquinol. The dioxygenase catalyzed both ortho- and meta-cleavage of 3-methylcatechol.     

Reduction of second- and third-order harmonic distortion bynonlinear absorption in gain-coupled distributed-feedback laser diodes

We have calculated the characteristics of second- and third-order harmonic distortion in gain-coupled distributed feedback (DFB) lasers using a set of three rate equations. In these calculations, the relaxation oscillation, nonlinear gain compression, and nonlinear loss compression are taken into account. We have found that modulation distortion due to nonlinear gain compression is reduced significantly in the gain-coupled DFB laser of absorptive-grating type. This improvement occurs because gain compression is compensated by loss compression within the grating     

一种N阶电流型有源滤波器的综合法

首先分析了一种由Ｎ对零极子和２Ｎ个导纳构成的基本电路。从分析结果中推导出实现Ｎ阶电流传递函数的条件。把零极子用电流舆器取代后,构成了Ｎ阶低通或高通电流型滤波电路。Ｎ阶电路使用Ｎ＋１个ＣＣⅡ器件,所有ＲＣ元件接地,使电路得以稳定地工作。     

An investigation into the molecular orientation of sheared liquid crystalline boundary films

The molecular orientation of a nematic liquid crystal (4‐pentyl‐4′‐cyanobiphenyl, 5CB) in a shear flow between parallel plates was examined using infrared absorption spectroscopy; surface anchoring, film thickness, sliding velocity, and voltage between the parallel plates were independently investigated. Infrared absorbance of the C‐N stretch vibration was measured at the point where the direction of the vibration coincided with the long axis of each 5CB molecule. The molecular orientation depended on the product of the sliding velocity U and the film thickness D, i. e., UD. The effects of surface anchoring appeared to be stronger for lower UD. Calculated results for absorbance, based on a continuum theory, agreed well with experimental ones. The effective viscosity under the same conditions was also calculated, and was increased by a low voltage for lower UD with parallel orientation surfaces. This indicated the possibility of active control of the friction coefficient. With perpendicular orientation surfaces, even without any voltage, the effective viscosity increased with a decrease of UD, which indicated the possibility of a ‘smart lubricant’ the viscosity of which could be adequately controlled by varying the operating parameters of the mating surfaces.     

Online tuning method of stator and rotor resistances in both motoring and regenerating operations for vector‐controlled induction machines

The vector control of induction motors is widely used. This method needs accurate motor parameter but the stator and rotor resistance vary due to motor temperature variation. If the value of resistance in the controller can be set up accurately at first, there must be a difference between the reference and real value of torque because of drift of the resistance. It is necessary to adapt the resistance value. The indirect field‐oriented control of an induction motor requires the value of rotor resistance only, but the direct field‐oriented control method with rotor flux observer requires the value of not only rotor resistance but also stator resistance in the controller. Consequently, it is necessary to adapt both stator resistance and rotor resistance. A parameter adaptation scheme has previously been proposed for the direct field‐oriented control method with rotor flux observer, but this method cannot be used when the motor is in regenerating operation. In this paper, a new stator and rotor resistance adaptation scheme is proposed, which can be applied when the motor is in regenerating operation. The usefulness of the proposed adaptation scheme is confirmed by simulation. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 56–64, 2001     

Experimental study on laboratory scale Totalized Hydrogen Energy Utilization System using wind power data

The renewable energy source like wind energy generates electric power with intermittent nature. Hydrogen energy system can help to solve the fluctuation problem of the wind power. Totalized Hydrogen Energy Utilization System (THEUS) consists of a Unitized Reversible Fuel Cell (URFC), a hydrogen storage tank, and other auxiliary components. Wind power is inherently variable; the URFC will be subjected to a dynamic input power profile in water electrolyzer mode operation. This paper describes the THEUS operation and performance at different variations in intermittent wind power. The performance of the THEUS was evaluated in water electrolyzer and fuel cell mode operation. The stack efficiency, system efficiency, and system efficiency including heat output from the URFC were presented at each operation. The total efficiency of the URFC and THEUS were also investigated. The maximum total efficiency of the URFC and THEUS were 53% and 66%, respectively.