Dependence of Threshold Switching Power on the Control-Light Wavelength in a Nonlinear Distributed-Feedback GaInAsP Waveguide

We demonstrate all-optical bistable switching by using orthogonally and parallelly polarized control light in a nonlinear distributed feedback GaInAsP waveguide. When the control light that is orthogonally polarized to the signal light is within its stopband, it is possible to extract the signal without using any external devices. Also, we investigate theoretically and experimentally the dependence of threshold switching power on the wavelength and polarization of control light.     

241Am as a metabolic tracer for inhaled plutonium nitrate in external chest counting

The plutonium (Pu) treated in the nuclear fuel cycle is usually accompanied by 241Am produced from 241Pu by beta disintegration, which emits gamma rays of 60 keV with the emission rate of 0.36, being more penetrating than the L X rays from Pu. The 241Am could imprve the detection limit of chest counting of Pu, if it was being used as a metabolic tracer for Pu in lungs. Young adult male Wistar rats were exposed to polydisperse aerosols of Pu(NO3)4 with 0.6 microm in activity median aerodynamic diameter. They were periodically killed and the radioactivity of 241Am was cleared from the lungs at almost the same rate as the Pu at least for half a year post-inhalation, which proved the validity of 241Am as a metabolic tracer for inhaled Pu nitrate in external chest counting.     

Improvement of treatment efficiency of thermophilic oxic process for highly concentrated lipid wastes by nutrient supplementation

The biodegradation of highly concentrated lipid wastes was conducted by a thermophilic oxic process (TOP). In order to improve the treatment efficiency of TOP, the stimulatory effect of nutrient supplementation was examined. A model nutrient supplement that satisfied the essential components necessary to promote degradation of lipid wastes was developed. The importance of balanced nutrient supplement consisting of organic and inorganic components was demonstrated. Regardless of the source of either vegetable oil or animal fat, the combination of 1.5 g of yeast extract, 1 g of urea and 60 ml of trace-element solution was effective to stimulate the degradation of 15 g of lipids by TOP. With this combination, degradation efficiencies of 68% and 77% in a 120-h treatment were attained for salad oil and lard, respectively. The conversion ratio of degraded lipid materials to CO2 was 0.91, confirming the advantage of TOP, i.e., very low excess sludge generation. The effectiveness of the model nutrient supplement for stimulating the degradation of lipid materials by TOP was also confirmed when tested on three kinds of actual highly concentrated lipid wastes. A constant degradation efficiency of around 60% in a 120-h treatment was attained for all lipid wastes although further improvement of degradation efficiency was possible by some nutrient addition into the model supplement combination. Based on the model nutrient supplement, the essential components for stimulating oil degradation by TOP and the possible alternative materials for the model nutrient supplement were discussed. The results demonstrated the possibility of employing TOP (stimulated by nutrient supplement) as a new biological treatment strategy for highly concentrated lipid wastes.     

Expression of a gene encoding chitinase (pCA 8 ORF) from Aeromonas sp. no. 10S-24 in Escherichia coli and enzyme characterization

A gene encoding chitinase from Aeromonas sp. no. 10S-24 was expressed using pTrc99A in Escherichia coli JM 105 which yielded a 5-fold higher activity than when pUC19 was used. Three different truncated enzymes (SA-1, SA-2 and SA-3) were obtained after purification. Their isoelectric points were 7.0, 6.9, and 6.7, respectively. The enzymes showed two optimum pHs, 4.0 and 7.0, when incubated with ethylene glycol chitin as the substrate, and were stable over a wide pH range (3.0-9.0). The optimum temperature was 60 degrees C and the enzymes were stable up to 50 degrees C. The chitinases exhibited wide substrate specificities for chitin-related compounds.     

Optical Burst Switching Router With 40-,10-Gb/s Bit-Rate Transparent Contention Resolution

We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O₃ ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks     

Analysis of Polarization Splitters Composed of Multilayer Thin-Film Waveguides Using the Beam-Propagation Method Based on Yee's Mesh

Multilayer thin-film waveguides (MTFWs) are analyzed using the beam-propagation method based on Yee's mesh. The birefringence properties of the MTFW are demonstrated by the eigenmode analysis based on the imaginary-distance procedure. Taking advantage of the birefringence, a polarization splitter composed of two parallel MTFWs is proposed. Calculation shows that a short device length of 270 mum is obtainable with crosstalks of -33.5 dB for the quasi-transverse-electric mode and -20.7 dB for the quasi-transverse-magnetic mode. A crossing-type polarization splitter is also developed, and the device length is further reduced to 120 mum.     

Performance Improvement of Current Source Inverter-Fed Induction Motor Drives

A high performance variable speed drive system using current source inverter fed induction motor is described. The principle of the drive control is based on the field-orientation method, where the stator current is used as the vector quantity. To improve the system response and to operate smoothly at low speed, a current pulsewidth modulation (PWM) control is provided by means of a feedback loop. This system operates stably and shows a high dynamic performance in a wide range, from zero to rated speed. Dual current source inverter is applied to this drive system which results in a remarkably low copper loss of the motor, even in PWM operation.     

Design principle of micromechanical probe with an electrostatic actuator for friction force microscopy

It is important to understand friction force in micro/nano mechanical devices both at high sliding speed and with high lateral resolution. Dual-axis friction force microscopes that can provide high lateral resolution and accuracy have been proposed; however, the sliding speed is limited by the probe scan speed. While a micro mechanical probe (MMP) with an electrostatic actuator can overcome this problem, details of probe design have not been established yet. This paper presents the principle of the mechanical design for an MMP with high force sensitivity and sufficient drive force. The dimensions of the double cantilever beam control the spring constants, resonant frequencies, and drive force. The use of an actuated MMP enables accurate friction force microscopy at high sliding speeds, which is required for the design of micro/nano mechanical devices.     

GaInAsP-InP distributed feedback waveguides for all-opticalswitching

All-optical switching characteristics of waveguide devices having a nonlinear distributed feedback structure are reported theoretically and experimentally. These devices were composed of a strip-loaded GaInAsP-InP waveguide and a Bragg reflector, which were suitable for optical integrated circuit. In the experiments, all-optical and gate operation and set-reset operation for two output ports were successfully demonstrated     

Identification of physical parameters of a flexible structure from noisy measurement data

We focus on an inverse problem for identifying physical parameters such as Young's modulus and air and structural damping coefficients in the mathematical model of cantilevered beams subject to random disturbance, using dynamic noisy data measured on its vibration taken in a nondestructive manner. First, we describe mathematical models of the cantilevered beam by an Euler-Bernoulli type partial differential equation including parameters to be identified and the measurement equation, taking vibration data including the observation noise. Second, the identification problem using random dynamic data is divided into an estimation problem obtaining the (modal) state estimate and a least-squares problem determining unknown parameters, and then the unknown parameters are determined recursively by using the pair of algorithms alternately. Finally, in order to verify the efficacy of the proposed identification algorithm, simulation studies and experiments are shown.