bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating angle of arrival with non‐uniformly spaced array
Authors: Nakazawa Toshiyuki , Takahashi Masaharu , Abe Minoru 
Published: August 2002

AbstractThe present direction‐finding equipment has insufficient accuracy and resolution, so that accurate evaluation of the direction of arrival and the position cannot be carried out. Although each radar signal has a narrow bandwidth, the entire bandwidth for various radars used exceeds four octaves. In order to search all of these, equipment for each bandwidth is used at present so that the entire frequency range is covered. However, it is more effective from the standpoint of equipment size and cost to cover the entire spectrum with a single kind of equipment. It is desirable to realize high‐accuracy high‐resolution direction finding over a broad bandwidth. In realization, broadband antennas are used, and high‐gain antennas are also needed in a low‐S/N environment. Since the dimensions of high‐gain and broadband antennas are large, an array configuration with a half‐wave spacing may not physically be possible. Thus, the array spacing becomes more than a half‐wavelength. If the range of direction estimation is −90 to +90°, the phase difference exceeds 360° so that ambiguity occurs. As a method to resolve this ambiguity problem, a nonuniformly spaced array is effective. In this paper, the array conditions for a nonuniformly spaced array are determined in the case of one arriving wave. Next, the case of several arriving waves is discussed and the array conditions for several arriving waves are derived. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(3): 1–8, 2002
Detecting Each Position of Residual Reflections Using a Radiation Pattern Measurement Method for Eliminating Reflections by Distance Changing Technique
Authors: Nishizawa Kazushi , Konishi Yoshihiko , Makino Shigeru , Katagi Takashi 
Published: August 2002

AbstractIn order to carry out high‐precision measurement of the radiation characteristics of antennas and to evaluate the reflection characteristics of microwave anechoic chamber used for antenna measurement, it is important to recognize the location and intensity of the unwanted reflection sources caused by the ambient environment. In this paper, the radiation pattern measurement proposed by the authors is applied for estimating the location of the reflection sources and their effects on the radiation pattern. In the proposed radiation pattern measurement method, the reflected waves are eliminated by the Fourier transform of the measured reflected electric field data obtained on varying the measurement distance. First, a method for estimating the locations of the reflected wave sources and their effects is theoretically shown from the radiation pattern of the reflected wave. This pattern is obtained after the direct radiation pattern obtained from the radiation pattern with the reflected wave suppressed is eliminated from the measured radiation pattern. From a verification experiment using a standard L‐band horn, the effectiveness of the method is verified. Second, a window function is applied to the measurement distance range so that the sidelobes of the Fourier transform spectrum are reduced. From the radiation pattern of the reflected wave obtained by applying a gating process to this Fourier spectrum at each angle, the effect of several reflection sources is estimated individually. From the results of computer simulation, the effectiveness of the proposed method is verified. Further, the range of applicability of the method is discussed. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(4): 33–43, 2002
An Approximate Method for Minimizing Communications Cost and Time for Replication Update of Distributed Databases
Authors: Wakahara Yasushi 
Published: August 2002

AbstractIn distributed databases, oriented toward general business software such as groupware, the asynchronous update method is widely used in order to align the databases. In this method, each database has replicas of the other databases, and the replicas are updated at the same time according to a predetermined replica routing schedule. This paper discusses an approximate method for minimizing the communication cost and time needed for updating the replicas in such a distributed database. More precisely, the case in which the communication cost is proportional to the amount of transferred data is considered, and an optimization problem is formulated in which the replication routing schedule minimizing the time for the replica update is to be determined from those minimizing the communication cost for the replica update. An approximate solution for the formulated problem is presented. Then the result of evaluation of the approximate replication routing schedule obtained as the approximate solution is discussed, and it is shown that the communication cost for replica update is minimized and that the time for the replica update is at most 1.2 times the minimum value if the number of distributed databases is at most 7. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(4): 61–70, 2002
Analysis of door seal structure of microwave oven with consideration of higher modes by the FDTD method
Authors: Kusama Yuusuke , Hashimoto Osamu , Makida Minoru 
Published: August 2002

AbstractThis paper focuses on the choke structure, which is generally used in suppressing the leakage wave from the door gap of microwave ovens. A choke structure which simulates the interdigital periodic choke structure for mass‐produced microwave ovens is considered, and the shielding effect is examined by the FDTD method for leaky waves (hybrid waves) including the higher modes, as a situation very close to practice. As an application of such an analysis to the optimal design of the choke groove, the shielding effect is examined as a function of the angle of the metal plates composing the choke groove. It is shown that the proposed method of analysis is effective for such a complex structure. © 2002 Scripta Technica, Electron Comm Jpn Pt 2, 85(3): 50–57, 2002
The quantum‐classical correspondence for the degree of freedom in 2D irregular sound fields
Authors: Fujisaka Yoh‐ichi , Tohyama Mikio , Sugimura Akira 
Published: August 2002

AbstractIn the area of research on quantum chaos, the correspondence between the quantum and classical theories on the chaos is a problem. In the billiard problem of a stadium type in a classical system (to be replaced with the acoustic line tracing the acoustics), it is known that the acoustic line locus exhibits a chaotic behavior. However, no chaos exists in the wave phenomena in a quantum system as a linear wave field. Where in the linear wave field a chaotic behavior exists and how the linear wave field is related to the chaotic nature of the classical system have been research topics. The objective of the present research is to search the correspondence between the classical and quantum theories on the chaos from the point of view of indoor acoustics. The authors define semistadium boundaries with higher‐order curves of more than second order and calculate the degrees of freedom in the wave system and classical system. From the point of view of degrees of freedom in the system, the correspondence is analyzed on the chaos between the wave and classical theories. It is found that the correspondence between the chaotic nature of the acoustic line propagation and the wave nature depends on the degrees of freedom of the system. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 85(3): 61–68, 2002
Performance of M‐ary/SSMA using soft decision Viterbi decoding
Authors: Ito Katsuyuki , Hamamura Masanori , Tachikawa Shin'ichi 
Published: August 2002

AbstractIn this paper, we discuss the performance of M‐ary/SSMA and M‐ary/SSMA systems using convolutional code and co‐channel interference (CCI) cancellation techniques. First, we show a proposed system model and describe a soft decision method of M‐ary/SS which can operate soft decision Viterbi decoding. Next, we evaluate the system performance in an AWGN environment and a Rayleigh fading environment by computer simulations. As a result, spectral efficiency of the system using convolutional code is improved in both environments, though its effects depend on the coding rate. Finally, we discuss the systems using CCI cancellation and convolutional code. As a result, when the spreading factor becomes large, its performance becomes inferior to that of the system which applies no convolutional code in an AWGN environment. However, under a Rayleigh fading environment, a considerable improvement of the performance can be obtained. © 2002 Scripta Technica, Electron Comm Jpn Pt 3, 85(6): 11–20, 2002
Growth of thick and low‐doped 4H‐SiC epitaxial layers in a vertical radiant‐heating VPE reactor
Authors: Tsuchida Hidekazu , Kamata Isaho , Jikimoto Tamotsu , Izumi Kunikazu 
Published: August 2002

AbstractA new vertical radiant‐heating reactor has been designed and constructed for thick SiC vapor‐phase epitaxy (VPE). Growth of 4H‐SiC epitaxial layers is performed under a reduced pressure as low as 6.7 × 103 Pa. A high growth rate exceeding 16 µm/h has been achieved in the reactor. Smooth surface is obtained by controlling the input C/Si ratio of source gases, and we have demonstrated growth of very thick layers over 160 µm with a mirrorlike morphology. Low‐background doping in the 1013 cm−3 range (n‐type) and intentional n‐type doping in a range from low 1015 to low 1019 cm−3 have also been demonstrated. We have performed photoluminescence spectroscopy and deep level transient spectroscopy to check impurities and intrinsic defects in the epitaxial layers, and the spectra show that the layers have a good purity and quality. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 18–25, 2002; DOI 10.1002/eej.1134
Novel development of an inductively coupled thermal plasma with pulse amplitude modulation of electromagnetic field
Authors: Sakuta Tadahiro , Tanaka Yasunori , Hashimoto Yoshifumi , Katsuki Makoto 
Published: August 2002

AbstractA novel system of an inductively coupled thermal plasma with a fundamental frequency of 450 kHz has been developed. This system has a capability of modulating the amplitude of the coil current periodically with a cycle on the order of 10 ms, including an inverter power supply rated with a power of 50 kW, an induction plasma torch with a 10‐turn coil, and vacuum chamber. The controlled modulation of the coil current can lead the plasma to be under various transient states intentionally. A pulse‐modulated inductively coupled plasma of Ar‐H2 plasma was successfully generated at a plasma power of 30 kW under the atmospheric pressure condition. The on‐time and off‐time of the pulsation were set to 10 and 5 ms, respectively, for a stable pulse‐modulated plasma establishment, and the ratio of minimum to maximum of the amplitude of the coil current can be set down to 61.7%. In order to investigate the transient behavior of the plasma dynamics in such a pulsing mode, spectroscopic observations of an argon atomic spectral line at a wavelength of 751 nm were made. It was found that the pulse‐modulated plasma has a characteristic time on the order of 2 to 5 ms to rise or to decrease. The excitation temperature of the Ar atom was estimated from the spectroscopic measurement by the Boltzmann plot method, and it was found to change periodically from 5000 to 10,000 K with the pulse modulation of the amplitude of the coil current. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 26–33, 2002; DOI 10.1002/eej.1135
Characteristic performance of radio‐frequency (RF) plasma heating using inverter RF power supplies
Authors: Imai Takahiro , Sawada Hiroyuki , Hattori Norifumi , Uesugi Yoshihiko , Takamura Shuichi 
Published: August 2002

AbstractHigh‐heat‐flux plasmas are produced by high‐power (∼14 kW) ICRF heating using inverter power supplies in the linear diverter simulator NAGDIS‐II. The power flow of radiated RF power is investigated by a calorimetric method. From conventional power calculation using antenna voltage and current, about 70% of the RF power is radiated into the plasma. But the increase of the plasma heat load along the magnetic field by RF heating is about 10% of the RF power. Through this experiment, we find that about half of the RF power is lost at the antenna surface through the formation of RF‐induced sheath, and about 30% of the power is lost into the wall of the vacuum vessel through the charge exchange and elastic collision of ions with neutrals. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 34–41, 2002; DOI 10.1002/eej.1136
Genetic toxicology testing of the antimalarial drugs chloroquine and a new analog, AQ‐13
Authors: Riccio Edward S. , Lee Pamela S. , Winegar Richard A. , Krogstad Donald J. , De Dibyendu , Mirsalis Jon C. 
Published: August 2002

AbstractAQ‐13 ([N1‐(7‐chloro‐quinolin‐4yl)‐3‐(N3,N3‐diethylamino)propylamine] dihydrochloride trihydrate) is an aminoquinoline antimalarial drug that is effective against chloroquine‐resistant strains of Plasmodium falciparum. It is structurally similar to the widely used chloroquine diphosphate (CQ). We evaluated these drugs in the three assays currently recommended by the International Conference on Harmonization (ICH): bacterial mutagenesis in Salmonella typhimurium and Escherichia coli, mammalian cell mutagenesis in L5178Y mouse lymphoma cells, and micronucleus induction in rat bone marrow. A small but statistically significant increase in revertant colonies was produced by CQ with Salmonella tester strain TA98 without metabolic activation (MA) and by AQ‐13 with strain TA1537 both with and without MA. In L5178Y cells, testing of CQ and AQ‐13 up to cytotoxic concentrations with and without MA produced no increase in mutant colonies and no increase in the numbers of small colonies. Slight decreases in the ratio of polychromatic erythrocytes (PCE) to red blood cells (RBC) were observed in male and female rats treated with CQ and in females only treated with AQ‐13; however, none of these changes was statistically significant. No increases in the frequency of micronucleated PCE were observed at any dose level of CQ or AQ‐13. Although both CQ and AQ‐13 showed weak bacterial mutagenicity, this mutagenic effect was not confirmed in either the mouse lymphoma mutagenesis assay or the micronucleus assay. These results indicate that CQ and AQ‐13 should pose minimal risk of genotoxic damage in human populations being administered these drugs. Environ. Mol. Mutagen. 38:69–79, 2001 © 2001 Wiley‐Liss, Inc.
Tangential‐projection algorithm for manifold representation in unidentifiable model updating problems
Authors: Katafygiotis Lambros S. , Lam Heung‐Fai 
Published: August 2002

AbstractThe problem of updating a structural model and its associated uncertainties by utilizing structural response data is addressed. In an identifiable case, the posterior probability density function (PDF) of the uncertain model parameters for given measured data can be approximated by a weighted sum of Gaussian distributions centered at a number of discrete optimal values of the parameters at which some positive measure‐of‐fit function is minimized. The present paper focuses on the problem of model updating in the general unidentifiable case for which certain simplifying assumptions available for identifiable cases are not valid. In this case, the PDF is distributed in the neighbourhood of an extended and usually highly complex manifold of the parameter space that cannot be calculated explicitly. The computational difficulties associated with calculating the highly complex posterior PDF are discussed and a new adaptive algorithm, referred to as the tangential‐projection (TP) algorithm, allowing for an efficient approximate representation of the above manifold and the posterior PDF is presented. Using this approximation, expressions for calculating the uncertain predictive response are established. A numerical example involving noisy data is presented to demonstrate the proposed method. Copyright © 2002 John Wiley & Sons, Ltd.
Inelastic deformation response of SDOF systems subjected to earthquakes
Authors: Riddell Rafael , Garcia Jaime E. , Garces Eugenio 
Published: August 2002

AbstractPerformance‐based seismic design requires reliable methods to predict earthquake demands on structures, and particularly inelastic deformations, to ensure that specific damage‐based criteria are met. Several methods based on the response of equivalent linear single‐degree‐of‐freedom (SDOF) systems have been proposed to estimate the response of multi‐degree‐of‐freedom structures. These methods do not offer advantages over the traditional Veletsos–Newmark–Hall (VNH) procedure, indeed, they have been shown to be inaccurate. In this study, the VNH method is revised, considering the inelastic response of elastoplastic, bilinear, and stiffness‐degrading systems with 5% damping subjected to two sets of earthquake ground motions. One is an ensemble of 51 earthquake records in the Circumpacific Belt, and the other is a group of 44 records in California. A statistical analysis of the response data provides factors for constructing VNH inelastic spectra. Such factors show that the ‘equal‐displacement’ and ‘equal‐energy’ rules to relate elastic and inelastic responses are unconservative for high ductilities in the acceleration‐ and velocity‐sensitive regions of the spectrum. It is also shown that, on average, the effect of the type of force–deformation relationship of non‐linear systems is not significant, and responses can be conservatively predicted using the simple elastoplastic model. Copyright © 2001 John Wiley & Sons, Ltd.
Duration of strong ground motion during Mexican earthquakes in terms of magnitude, distance to the rupture area and dominant site period
Authors: Reinoso Eduardo , Ordaz Mario 
Published: August 2002

AbstractA study of the duration of strong ground motion using accelerometric data of subduction and normal‐faulting Mexican earthquakes is presented. Duration is obtained based on the time between 2.5 and 97.5 per cent of the Arias intensity. An expression to predict this duration in terms of the magnitude, distance to the rupture area and site period is proposed and compared with predictions available in the literature. The effect of large duration for very distant sites and the contribution of soft soils to the duration of strong ground motion are widely discussed. We have found that large magnitude not only yields long duration at the source, but also proportionally longer duration with distance and with dominant site period compared to small magnitude. The duration obtained from the regression is used as a parameter to obtain input and hysteretic energy and on the use of damage models available in the literature. Finally, duration is used together with the random vibration theory to predict response spectra. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal control of linear buildings under seismic excitations
Authors: Aldemir U. , Bakioglu M. , Akhiev S. S. 
Published: August 2002

AbstractConsiderable effort has been devoted to develop optimal control methods for reducing structural response under seismic forces. In this study analytical solution of the linear regulator problem applied widely to the control of earthquake‐excited structures is obtained by using the sufficient conditions of optimality even though almost all of the optimal controls proposed previously for structural control are based on the necessary conditions of optimality. Since the resulting optimal closed–open‐loop control cannot be implemented for civil structures exposed to earthquake forces, the solution of the optimal closed–open‐loop control is carried out approximately based on the prediction of the seismic acceleration values in the near future. Upon obtaining the relation between the exact optimal solution and future values of seismic accelerations, it is shown numerically that the solution of the optimal closed–open‐loop control problem can be performed approximately by using only the first few predicted seismic acceleration values if a given norm criteria is satisfied. Calculated performance measures indicate that the suggested approximate solution is better than the closed‐loop control and as we predict the future values of the excitation more accurately, it will approach the optimal solution. Copyright © 2001 John Wiley & Sons, Ltd.
Hysteretic energy spectrum and damage control
Authors: Riddell Rafael , Garcia Jaime E. 
Published: August 2002

AbstractThe inelastic response of single‐degree‐of‐freedom (SDOF) systems subjected to earthquake motions is studied and a method to derive hysteretic energy dissipation spectra is proposed. The amount of energy dissipated through inelastic deformation combined with other response parameters allow the estimation of the required deformation capacity to avoid collapse for a given design earthquake. In the first part of the study, a detailed analysis of correlation between energy and ground motion intensity indices is carried out to identify the indices to be used as scaling parameters and base line of the energy dissipation spectrum. The response of elastoplastic, bilinear, and stiffness degrading systems with 5 per cent damping, subjected to a world‐wide ensemble of 52 earthquake records is considered. The statistical analysis of the response data provides the factors for constructing the energy dissipation spectrum as well as the Newmark–Hall inelastic spectra. The combination of these spectra allows the estimation of the ultimate deformation capacity required to survive the design earthquake, capacity that can also be presented in spectral form as an example shows. Copyright © 2001 John Wiley & Sons, Ltd.
Computational fluid dynamics modelling of boundary roughness in gravel‐bed rivers: an investigation of the effects of random variability in bed elevation
Authors: Nicholas A.P. 
Published: August 2002

AbstractResults from a series of numerical simulations of two‐dimensional open‐channel flow, conducted using the computational fluid dynamics (CFD) code FLUENT, are compared with data quantifying the mean and turbulent characteristics of open‐channel flow over two contrasting gravel beds. Boundary roughness effects are represented using both the conventional wall function approach and a random elevation model that simulates the effects of supra‐grid‐scale roughness elements (e.g. particle clusters and small bedforms). Results obtained using the random elevation model are characterized by a peak in turbulent kinetic energy located well above the bed (typically at y/h = 0·1–0·3). This is consistent with the field data and in contrast to the results obtained using the wall function approach for which maximum turbulent kinetic energy levels occur at the bed. Use of the random elevation model to represent supra‐grid‐scale roughness also allows a reduction in the height of the near‐bed mesh cell and therefore offers some potential to overcome problems experienced by the wall function approach in flows characterized by high relative roughness. Despite these benefits, the results of simulations conducted using the random elevation model are sensitive to the horizontal and vertical mesh resolution. Increasing the horizontal mesh resolution results in an increase in the near‐bed velocity gradient and turbulent kinetic energy, effectively roughening the bed. Varying the vertical resolution of the mesh has little effect on simulated mean velocity profiles, but results in substantial changes to the shape of the turbulent kinetic energy profile. These findings have significant implications for the application of CFD within natural gravel‐bed channels, particularly with regard to issues of topographic data collection, roughness parameterization and the derivation of mesh‐independent solutions. Copyright © 2001 John Wiley & Sons, Ltd.