Showing papers by "University of Electro-Communications published in 1987"
145 citations
130 citations
TL;DR: In this paper, a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator were integrated by three-step vapor phase epitaxy (VPE).
Abstract: Monolithic integration of a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator was studied. The difference between the lasing photon energy and the bandgap energy of the modulator waveguide was designed to be 30-40 meV, taking into account the linewidth-enhancement factor and the zero-bias absorption loss. The integrated devices were grown by three-step vapor phase epitaxy (VPE). The CW threshold current at 20°C of the DFB laser part with a buried heterostructure was 30-60 mA and the breakdown voltage of the modulator part with a strip-loaded stripe geometry was 20-40 V, and these values indicated satisfactory crystal quality in the VPE epitaxial layers. The operating voltage of the modulator to give on:off ratios of 10:1 and 100:1 was 1.5- 4 V and 2.5-6.5 V, respectively, depending on the length in the range 200-500 \mu m. A 3-dB bandwidth of about 2.5 GHz and a linewidth-enhancement factor of about 1.6 were obtained for the integrated modulator.
108 citations
TL;DR: Traduction anglaise d'un article en japonais publie en Aout 1970 dans la serie Kokyuroku Vol-91 (pp 82-118) as discussed by the authors.
91 citations
TL;DR: The effectiveness of well-tempered Gaussian basis sets has been tested for the atoms He-Ar, Ag, and Xe in this paper, and it has been found that orbital exponents optimized through the welltempered scheme for non-relativistic atoms can be carried over to relativistic calculations to produce wavefunctions close to the Hartree-Fock limit.
58 citations
TL;DR: In this article, a two-layer traveling-wave type electrooptic modulator structure was proposed to maximize the modulation bandwidth from transmission line aspects, which can satisfy the velocity matching and impedance matching condition simultaneously.
Abstract: This paper proposes a two-layer traveling-wave type electrooptic modulator structure to maximize modulation bandwidth from transmission line aspects. This structure can be designed to satisfy the velocity matching and impedance matching condition simultaneously. A design method for this structure is discussed.
39 citations
TL;DR: In this paper, the occurrence distributions of narrow-banded ELF emissions over the southern polar region have been studied statistically and it was found that emissions mostly occurred in the evening 17-24 M.L.T. sector and in the region of 65°-75° invariant latitude associated with V-shaped VLF hiss emissions.
30 citations
TL;DR: In this paper, the results of experiments into the use of a field shaper for the bulging of a tube are presented and the major factors determining the final profile of the tube and the capability of the control of forming to achieve the desired profile are discussed.
28 citations
TL;DR: In this paper, the properties of a GaAs-oxide interface formed by recently proposed photochemical oxidation in water were studied, and remarkable photoluminescence intensity enhancement was observed after oxidation which previously was interpreted as "unpinning" of the Fermi level.
Abstract: The properties of a GaAs–oxide interface formed by recently proposed photochemical oxidation in water were studied. Remarkable photoluminescence intensity enhancement was observed after oxidation which previously was interpreted as "unpinning" of the Fermi level. However, the surface current transport and capacitance-voltage measurements consistently indicated a strong Fermi level pinning with an increased surface depletion. These apparently contradictory results can be explained by a new model in which photochemical oxidation does not unpin, but shifts the pinning position of the Fermi level towards the valence band edge.
19 citations
TL;DR: In this article, a neon atomic beam in the 1s5 (J=2) metastable level is cooled by a counterpropagating laser beam using 1s 5-2p9 transition.
Abstract: A neon atomic beam in the 1s5 (J=2) metastable level is cooled by a counterpropagating laser beam using 1s5-2p9 transition. By transferring the 1s5 population to the 1s3 (J=0) metastable level using the optical pumping through 2p2, a cooled 1s3 beam is also generated.
17 citations
TL;DR: A new transformation technique based on partial parametrization and fully lazy evaluation for eliminating multiple traversais of data structures is described, which uses no particular mechanisms in functional programming and transforms a wider class of programs into efficient ones than that proposed so far.
Abstract: The use of higher order functions in functional programming opens up the possibility of defining functions by partial parametrization, and lazy evaluation brings out a new approach in programming methodology. This paper describes a new transformation technique based on partial parametrization and fully lazy evaluation for eliminating multiple traversais of data structures. It uses no particular mechanisms in functional programming, whereas it transforms a wider class of programs into efficient ones than that proposed so far.
TL;DR: In this article, the Gilbert equation is solved numerically to obtain detailed structures of two-dimensional vertical Bloch lines, and the instability associated to the equation is suppressed completely by discretizing the equation according to the backward Euler method.
Abstract: The Gilbert equation is solved numerically to obtain detailed structures of two-dimensional vertical Bloch lines. To avoid situations in which magnetization aligns parallel to the polar axis, the computing region is divided into three subregions, and two kinds of coordinates systems are used depending on the orientation of the magnetization in each subregion. The instability associated to the equation is suppressed completely by discretizing the equation according to the backward Euler method. The paper formulates the method of calculation, describes the derived structure of a plane-like wall with periodically-spaced VBL's, and makes comparison with the results of simulations based on various modelings developed so far.
TL;DR: In this paper, the authors present formulas for molecular nuclear attraction integrals over Gaussian-type functions, which indicate that the homogeneously charged sphere model can be adopted in molecular calculations.
TL;DR: In this article, a mixture of methane (1%)/hydrogen with a pressure to 400 Pa was flown at a rate of 150 cc/min and was discharged by applying 200 W, 2.45 GHz microwave power.
Abstract: Growth of filmy diamond crystals has been strongly desired, and the plasma CVD is expected as one of the growth techniques which provide high quality crystalline diamond films. This study deals with the growth of uniform crystalline diamond films by means of the plasma CVD. The main stress was laid on the effects of the surface treatments of the silicon substrate and the substrate potential on composition of deposited materials as well as on the morphology of diamond crystals grown on the substrate. A mixture of methane (1%)/hydrogen with a pressure to 400 Pa was flown at a rate of 150 cc/min and was discharged by applying 200 W, 2.45 GHz microwave power. The Si substrates were heated to 850 ° C. Nuclei for the diamond crystal growth were preferentially generated on the defect sites caused by the surface treatments. With increasing the substrate potential in the negative direction, the growth of silicon carbide was observed to increase. When the substrate was positively biased, filmy diamond layers were found to be deposited.
TL;DR: In this paper, anisotropy of electron temperature was measured by means of planar probes on Japan's ninth scientific satellite OHZORA, which was carried out simultaneously both along and vertical to the geomagnetic line of force.
Abstract: Electron temperature was measured by means of planar probes on Japan's ninth scientific satellite OHZORA. The measurement, which was carried out simultaneously both along and vertical to the geomagnetic line of force, showed anisotropy of electron temperature. The temperature of the electrons along the geomagnetic field, T∥, is very often higher than the temperature of electrons collected by the electrode whose normal is perpendicular to the geomagnetic field, T⟂. Anisotropy increases as we move to higher geomagnetic latitudes. Anisotropy occurs more often in the early morning than at any other time of day. There is also a tendency for anisotropy to occur more often at lower altitudes.
It is suggested that the existence of anisotropy of electron temperature can explain some puzzling phenomena that have previously not been explained.
TL;DR: In this paper, the effect of the contraction of the transition is reasonably treated as the pressure effect and the calculated temperature dependence of the effective magnetic moment for various dopant concentrations reproduces the essential features of the two types of observed results.
Abstract: Hendrickson et al. (Inorg. Chem. 20 (1981) 131) showed that the transition temperature for the high-spin\(\rightleftarrows\)low-spin transition in the spin crossover compound [Fe x Cr 1- x (3–OCH 3 –SalEen) 2 ]PF 6 decreases with increasing the Cr concentration, whereas the transition temperature in [Fe x Co 1- x (3–OCH 3 –SalEen) 2 ]PF 6 increases with increasing Co concentration. These dilution effects on the high-spin\(\rightleftarrows\)low-spin transitions is studied on the basis of the ligand field theory by taking account of the coupling between d electrons of iron and a lattice strain. The present model clarifies the origins of the two kinds of dilution effects. In the latter case, the lattice contraction is induced by the Co ions. The effect of the contraction of the transition is reasonably treated as the pressure effect. The calculated temperature dependence of the effective magnetic moment for various dopant concentrations reproduces the essential features of the two types of observed results.
TL;DR: In this paper, the multichannel maximum entropy method (MULMEN) was applied to the study of medium-scale traveling ionospheric disturbances (MS-TID) detected with an array of HF Doppler receivers in central Japan during MAP period.
Abstract: This paper briefly describes the application of the cross-spectrum analysis technique by multichannel maximum entropy method (MULMEN) to the study of medium-scale traveling ionospheric disturbances (MS-TID) detected with an array of HF Doppler receivers in central Japan during MAP period.Experiments with artificial data have shown that the MULMEM technique provides by far better spectral estimates than the traditional technique of Blackman-Tukey using FFT algorithm. Several fundamental wave parameters of the TID were then calculated as a function of time by the MULMEM technique. We find that the dynamical (spectral peak traced) multiplet structure of the wave parameters can be well resolved. It is exemplified that such resolution is utilized not only to estimate the number of simultaneous excitation sources but also to detect on occasion the temporal variation in the velocity dispersion of the MS-TID.
TL;DR: In this article, the surface diffusion of adsorbates and the formation of an ordered phase are investigated in a Monte Carlo simulation using the lattice gas model, and the relation between the nearest neighbor correlation and the long-range order is investigated in the quasi-chemical approximation.
TL;DR: In this paper, the Weibull distribution of Ni and Np was investigated for rotating bending fatigue tests for Ni-Cr-Mo-V steel, using for a large-sized turbine rotor shaft.
01 Mar 1987
TL;DR: In this article, arc-shaped turbulence promoters along the circular tube inside surface which have capability of cleaning down tube fouling by sponge balls are proposed for enhancing the heat transfer performance.
Abstract: Arc-shaped turbulence promoters along the circular tube inside surface which have capability of cleaning down tube fouling by sponge balls are proposed for enhancing the heat transfer performance First, flow characteristics and heat transfer performance of air flow in a rectangular channel for several promoters were investigated The arc-shaped promoter was found to have the lowest pressure loss Secondly, turbulence structures of water flow by the arc-shaped promoters in a circular tube were measured by use of a newly developed two-color LDV The local heat transfer coefficient was shown to be well correlated to the Reynolds stress and the existence of the optimum height of the promoter as elucidated Lastly, performances of thermoelectric power generation by using cascade arc-shaped promoters for OTEC were measured and the optimum condition was investigated
TL;DR: In this paper, the transition frequency and dominant-pole frequency are derived from a relaxation or harmonic oscillator in which the OA under test is used as an element of the circuit.
Abstract: New simple and easy methods measuring the parameters of operational amplifiers (OA's) are presented with newly constructed testing circuits and setups. Firstly, it is shown that the transition frequency and dominant-pole frequency are derived from a relaxation or harmonic oscillator in which the OA under test is used as an element of the circuit. Secondly, it is shown that other parameters such as the open-loop gain, the input and output resistance, the input offset voltage, the input bias current, and the input offset current are obtained easily from the new circuits.
TL;DR: In this article, the theoretical probabilities for a number of hole-electron pairs are derived for the dark-current and signal multiplication noises in avalanche photodiodes (APD) and the optimum gain characteristics are analyzed for the detection systems which include the multiplication noises, the thermal noise of load resistance, and the following amplifier's noise.
Abstract: Theoretical probabilities for a number of hole-electron pairs are derived for the dark-current and signal multiplication noises in avalanche photodiodes (APD). The excess noise factors for the dark-current multiplication noises are given in forms similar to the signal multiplication noise. The error probabilities influenced by the multiplication noises are calculated, and it is pointed out that the error probabilities basically have no dependency on the ratio of the ionization coefficients k when APD has no dark-current source. The optimum gain characteristics are analyzed for the detection systems which include the multiplication noises, the thermal noise of load resistance, and the following amplifier's noise.
11 Mar 1987
TL;DR: In this paper, the authors used the charcteristics of strongly saturated amplifier with a 100ns electron beam excitation to determine the small signal gain, non-saturable absorption, and saturation intensity from 6% Kr to 95% Kr in Ar diluent.
Abstract: The charcteristics of strongly saturated amplifier with a 100ns electron beam excitation are studied to determine the small signal gain, non-saturable absorption, and saturation intensity from 6% Kr to 95% Kr in Ar diluent. The pumping rates are maintained constant by adjusting the total pressure of gas mixtures to conpensate the different stopping power of Ar and Kr. Non-saturable absorption coefficients are measured at a full saturated amplifier between the zero gain intensity to 80MW/cm2. The small signal gain of 12.9%/cm and non-saturable absorption coefficient of 1.32%/cm2 are obtained for 95% Kr mixture. The saturation intensity, 2.2MW/cm2 for 6% Kr and 2.9MW/cm2 for 95% Kr mixture, derived from the zero gain intensity is in good agreement with the prediction of our computer model. Highest intrinsic efficiency of 12.2% is measured at high Kr concentration where the Extraction power density of 6.8MW/cm2 is obtained by the probe laser beam between 5-6MW/cm2. The formation efficiency for a wide range of Kr concentrations agrees with the theoretical prediction excellently as a function of Kr concentration. The details of the important parameters, gain , absorption, saturation intensity, maximum output, intrinsic efficiency, extraction efficiency, and formation efficiency will be discussed in this paper.
TL;DR: In this paper, the concept of one-directionality was introduced, which includes both cases of location (and scale) parameter and selection parameter and also other cases, and established some theorems for shapr lower bounds and for the existence of zero variance unbiased estimator for this class of non-regular distributions.
Abstract: In this paper we introduce the concept of one-directionality which includes both cases of location (and scale) parameter and selection parameter and also other cases, and establish some theorems for shapr lower bounds and for the existence of zero variance unbiased estimator for this class of non-regular distributions.
TL;DR: In this paper, photo-acoustic signals induced by Kr F laser irradiations on to the optical thin layers have been measured to detect the small absorptions and the damage thresholds of dielectric coatings.
Abstract: Photo-acoustic (PA) signals induced by Kr F laser irradiations on to the optical thin layers have been measured to detect the small absorptions and the damage thresholds of dielectric coatings. Extremely low absorption with the extinction coefficient of 10-4 is detectable for the single-layer coatings with optical thickness of 1.5 wavelength at 248nm. The pre-damage detections have been studied with the assistance of laser scattering damage detection techniques. Thechanges of the slope and the variation of the PA signals have been observed at the irradiation of Kr F laser of lower fluence compared with the damage thresholdsby microscopic measurements. The pre-damage thresholds detected by the PA signaldetection agreed well with the laser scattering method for low index fluoridecoatings. Typical features of the laser induced damages related to the linear absorption and the refractive index will be discussed about the coating materials forshort wavelength lasers.
TL;DR: In this paper, the E-symmetry amplitudon was observed at about 8 cm-1 with an intensity proportional to the square of the order parameter of the Raman spectra.
17 Aug 1987
TL;DR: In this article, the authors present the quantitative analysis on the clutter effect of a radar homing system using a program named SAMS, which is a hierarchical and generalized version of the SLAM (Statistical linearization Adjoint Method).
Abstract: When the target Doppler frequency in a radar homing missile crosses the main lobe clutter spectrum at the terminal phase of its flight, a large miss distance is induced. This paper presents the quantitative analysis on this clutter effect using a program named SAMS (Statistical Assessment of Missile Systems), which is a hierarchical and generalized version of the SLAM (Statistical Linearization Adjoint Method). A homing missile is represented by triple time constants, a limiter, a second-order missile airframe, and proportional navigation. The main lobe clutter is imposed on to this system along with the target random maneuver, glint, fading, and receiver noise. By processing the covariance propagation of the system equation and the adjoint system, the miss distance and the contribution of each noise are calculated. The results reveal that the clutter effect is maximized if the target Doppler frequency begins to cross the main lobe clutter spectrum 2 s prior to the terminal time, and it is largely enhanced if the target random maneuver is combined. These effects are reduced, however, if the missile lateral acceleration capability is increased or the target lateral acceleration decreased. The radome effect is also analyzed by adding the related feedforward loop to the original system, which makes a considerable change in the miss distance.
TL;DR: In this paper, two direct search approaches to obtain the SCF solution for a true maximum of the self-repulsion energy with energy-localized orbitals are proposed: an approach based on the level-shifted second-order method and a scaling of the orbital transformation vector to obtain an approximate solution for the true maximum.
TL;DR: In this article, the dynamic treatment of a one-dimensional transient coupled-thermoelastic problem of heat conduction is made for a layered plate which is exposed to a uniform sudden heating or cooling.