bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methods for reducing the fresnel reflection in an optical‐fiber connector with index matching material
Authors: Sankawa Izumi , Satake Toshiaki , Kashima Norio , Nagasawa Shinji 
Published: July 2007

AbstractIf there is a discontinuity of the refractive index in optical fibers connected with an optical connector, the light is reflected from this part to the light source, creating a problem in its light transmission characteristic. The main causes of the discontinuity are: (1) the gap between the endfaces of the optical fibers; and (2) the change of the refractive index at the end‐face of the fibers due to their polishing. Solutions to these problems are investigated in this paper, using silica‐based graded index multimode optical fibers. For (l), a refractive‐index matching material is employed, and the method for selecting the central value of the refractive index and the temperature coefficient from the reflected light in the visual‐light wavelength region is investigated. It has been confirmed that the refractive‐index matching material made of silicone resin and chosen by this method can obtain the required reflection loss greater than 40 dB, in each of the transmission wavelengths of 0.85 pm and 1.3 μm, and in the temperature range of −30°C to +60°C. For (2), the relationship between the polishing conditions and the reflected light power was investigated. It has been found that the refractive index of the endface of an optical fiber changes slightly when polished. The conditions of polishing for suppressing this change have been determined, and the property of the polished endface has been clarified.
A study on hybrid switch architecture using hierarchical memory system
Authors: Ishikawa Hiroshi , Kosuge Yasuharu , Miyaho Noriharu 
Published: July 2007

AbstractOn the premise that flexibility in communication is a primary objective for future digital networks providing various services, it is highly desirable to integrate circuit switching (CS) and packet switching (PS) functions into a single switching node. This paper proposes a hybrid switching system where PS and CS switching functions are integrated by making use of a hierarchical memory system in which the CS and PS switching buffers and program buffers reside in the same memory area, and the high‐speed memory in the hierarchy can be accessed both by transmission lines and processors. The design concept which adopts a new architecture necessary to meet the above requirement and the evaluation of its call processing capacity using traffic simulation and theoretical analysis are described.
Comparison of error rate computations on optical communication systems
Authors: Ohta Shinji , Takahara Mikio 
Published: July 2007

AbstractError rate is an important factor in evaluation of data transmission over an optical fiber communication system. Accurate amplitude distribution of system noise must be used in the calculation of error rate. Noise in optical fiber systems consists of shot noise, signal dependent multiplicative noise created by avalanche photo diode (APD), and thermal noise. It is quite difficult to obtain an accurate amplitude distribution of the system noise. Therefore, the error rate is usually derived by approximation.This paper studies the error rate of optical fiber communication system using an integrator‐and‐dump (ID) type receiver. The error rates are computed using four different methods: the exact method based on the exact equation introduced by McIntyre, and three other approximation methods [1]. The results are compared and the adequacies of these methods are discussed.
Linear‐combined multichannel adaptive digital filters
Authors: Fujii Tetsurou , Shimada Shouji 
Published: July 2007

AbstractThe fundamental structure of linear‐combined multichannel adaptive digital filters which can process a multiple‐input single‐output time series, and their tapcoefficient correction algorithms with fast convergence are described. These are fundamental circuits required for multichannel echo‐cancellers, and echo‐cancellers with noise‐cancelling facilities. The structure of linear‐combined multichannel adaptive digital filters using the learning identification (LI) was introduced, and their characteristics were analyzed. Adaptive algorithms using the per‐channel normalization of power were proposed to improve the convergence speed. With a minor increase in the amount of computations, this method is a significant improvement of the convergence speed which, inherently, is degraded by the differences of average powers among channels in a linear‐combined multichannel adaptive filter. For further improvement in the convergence speed, another tap‐coefficient correction equation (the projection method) also was introduced. In the tap‐coefficient equation using the projection algorithms, the convergence speed can also be improved significantly by applying the per‐channel power normalization.
A method of high‐precision frequency detection with FFT
Authors: Tabei Makoto , Ueda Mistuhiro 
Published: July 2007

AbstractExcept for the nonlinear complex method such as MEM, there has not been known a method to determine the frequency with a high accuracy from the short wave train. Generally, it is considered that the frequency resolution in FFT is of the order of the step in the frequency. This paper attempts to derive a correction formula for FFT results by which the frequency, amplitude and phase of the arbitrary input signal with discrete frequencies can be calculated easily and with a high accuracy. The effect of the noise on the accuracy is discussed in the practical measurement condition, and it is shown by theory and numerical experiment for the case of white noise that the accuracy is linearly dependent on the noise ratio.
Estimation formula of vhf/uhf band field strength for mobile communications in suburban area
Authors: Morita Kazuo , Kojima Osamu , Nakano Toshio , Nonmembers Toshimi Haida, 
Published: July 2007

AbstractIn designing a mobile communication system in suburban areas, it is necessary to estimate electric field strengths in open and suburban areas. We measured field strengths in the 150/900‐MHz band in open desert areas and in the 900‐MHz band in suburban areas in the Middle East region, and open and suburban areas in Kumamoto and Okayama prefectures in the 280‐MHz band.Using these results, this paper discusses the relationship between the median values of the field strengths and distances and their frequency characteristics. As a result, it was found that the average values of measured field strengths at various sites were smaller than the theoretical values of a flat earth model. The field strengths decreased with the squares of distance. This trend agreed generally with the similar relation for the flat earth model.An empirical equation was derived for the correction factor of the electric field strength which is to be multiplied by the theoretical equation of the flat earth model. Quasi‐theoretical and quasi‐experimental equations were obtained for the estimation of the median values of the field strength of long intervals in the VHF/UHF band for flat open areas and suburban zones. With these equations we can estimate the median values of the field strengths of long intervals in open areas (desert, grassy lands and vegetated regions) and suburban areas with scattered buildings and trees, using frequency, the antenna height of the transmitter and distance as parameters.
A structure of multiband agc equalizer for digital subscriber transmission
Authors: Miki Noriki , Tamaki Norio 
Published: July 2007

AbstractThe metal subscriber transmission cable is a cascade connection of cables with different core radius and line length. To realize a digital subscriber transmission equalizer with a high accuracy requires an equalizer which does not produce an equalization error because of differences of core radius or cable length.This paper presents a multiband AGC equalizer to absorb the difference of core radius and line length whereby the filter coefficients are determined so that the equalization is optimized at several frequencies. Also, its construction, control by DFT and the design for parameters based on linear programming are presented. Based on the results of those investigations, an equalizer is constructed. By a transmission experiment using the actual transmission line, the equalization ability was verified.
Stability and throughput analysis for csma/cd system
Authors: Fujiwara Chikato , Yasuda Chikara , Okumoto Takaaki 
Published: July 2007

AbstractThis study considers the 1‐persistent CSMA/CD system and Ether‐type CSMA/CD system using binary exponential back‐off algorithm. The formula is derived for the average drift of the number of back‐logged terminals, and the stability is discussed.As a result, it is shown that the stability of 1‐persistent CSMA/CD system is related closely to the retransmission rate. An instability may result when the retransmission rate is high. It is verified for the stable case that the number of backlogged terminals at the stable point, where the average drift is 0, is strictly the same as the average number of back‐logged terminals obtained by a strict analysis or a simulation.The average back‐logs can easily be obtained based on the average drift. Utilizing this property, a kind of equilibrium analysis is presented, assuming that the number of back‐logged terminals remains at the average value. The approximation of the proposed analysis is not very good for low traffic. Compared with the conventional analysis, it has the feature that it is simple and the accuracy is improved for high traffic.In general, the performance for low traffic is not affected greatly by the system structure. Consequently, the proposed analysis has a great merit in that the stability of the system as well as the performance for high traffic can easily be examined.
Performance of a decision feedback equalizer under frequency‐selective fading in land mobile communications
Authors: Nakajima Makito , Sampei Seiichi 
Published: July 2007

AbstractSome means to cope with frequency‐selective fading is indispensable to the realization of a wideband digital mobile communication, and various investigations have been made to this end. For example, the decision feedback equalizer (DFE) is considered promising, since it requires smaller‐scale equipment and is versatile in applications.The application of DFE to mobile communication requires tracking to the time‐varying channel as well as the fast initial adaptation. Thus, comprehensive investigations, including the construction of the equalizer and tap‐updating algorithm are needed.The Kalman algorithm is employed as the tap‐updating algorithm. By introducing the memory factor into the algorithm, the tracking performance to the time‐varying channel is improved as well as the speed of the initial adaptation.A computer simulation is made for the proposed method based on the model of 256 kbit/s TDMA system with QPSK modulation. It is verified that DFE is useful in compensating for the frequency‐selective fading in mobile communication.
Objective picture quality scale by neural networks (PQS‐NN)
Authors: Kotani Kazunori , Miyahara Makoto 
Published: July 2007

AbstractThe scale for evaluating the picture quality of coded pictures objectively becomes very important because some high‐efficiency coding techniques (e.g., DCT and VQ) are applied to the practical stage. An objective picture quality scale (PQS) has been proposed which approximates well the mean opinion score (MOS) by analyzing the perceptual properties of image distortions and using multiple regression analysis (MRA) to construct a linear combination of the essential factors of distortions extracted from the fundamental distortions by principal component analysis (PCA).In this paper, a new objective picture quality scale (PQS) is obtained by three‐layered neural networks feeding the coded error images to the input layer and giving the mean opinion scores as a target. No knowledge of visual perception is given to neural networks.After learning that the mean opinion score of open test images (out of learning) is approximated well by neural networks, it is shown that neural networks (or NN) estimate MOS well with two hidden units and that the estimate performance is improved with an increase in the number of learning images. A very interesting fact is clarified, i.e., NN learned the same functions as visual perceptions. An objective picture quality scale, with considerable precision in estimating test images without professional knowledge about perceptual properties, can be obtained by using this new objective picture quality scale PQS‐NN.
A packet‐switched networks optimization method with a different kind of channel rate for each link and the fairness on grade of service
Authors: Liu Xiao‐Ming , Igarashi Jin , Miyamoto Hikaru 
Published: July 2007

AbstractThe capacity assignment problem of the packet‐switched network is to determine each link capacity (channel rate and number of channels) to minimize the total cost of the network, based on the given network topology and the link traffic, and under the constraint for service quality. Most past designs have discussed the simple network model in which the cost and the channel rate are in linear relation, and the channel rate can be set as an arbitrary value.Recently, several studies have been made considering the discreteness of the channel rate, but most of them consider only a single kind of channel. This paper proposes a link design method for the packet‐switched network which considers different kinds of channels, with the average delay of the packet for each destination in the network as the constraint. More precisely, the design procedure is divided into three parts and modified into the general nonlinear optimization problem to optimize the network. Through numerical examples, the accuracy and the effectiveness of the proposed method are demonstrated.
Majority logic combination sequences using m‐sequences for rapid acquisition in direct sequence/spread spectrum communication systems
Authors: Tachikawa Shin‐Ichi , Marubayashi Gen 
Published: July 2007

AbstractRapid acquisition is an important problem in the direct sequence spread spectrum communication system, especially when code length is long. This paper proposes a novel code construction method of making rapid acquisition, in which majority logic combination sequences constructed from M‐sequences mutually of prime length (hereafter M‐MAJ sequences) are used. By tacking cross‐correlation of incoming M‐MAJ sequence with component M‐sequences at the receiver, acquisition time can be reduced considerably. Calculated results of the average acquisition time and comparisons with conventional code construction methods (JPL sequence, concatenated sequence) are shown.
Focusing properties of leaky‐microwave from equiangular spiral slotted rectangular waveguide
Authors: Ohtera Isao , Ujiie Hiroshi 
Published: July 2007

AbstractPreviously, the authors proposed an equiangular spiral slotted rectangular waveguide (SSW).The present paper examines various unique characteristics in the fields near the focus such as phase anomalies, focal shifts, behavior of Poynting vectors, etc., and the frequency dependency of focusing properties with respect to changes of the excitation frequency. As a result, it was found that SSW had similar various characteristics near the focus for an ordinary axisymmetric optical system. It was clarified that SSW also had additional unique asymmetric properties arising from structural asymmetry and its operation as a two‐dimensional focusing system.
Prioritized resolvable‐contention‐ring access control scheme
Authors: Sittichivapak Suvepon , Okada Hiromi , Tezuka Yoshikazu , Maekawa Sadao 
Published: July 2007

AbstractThis paper proposes a prioritized resolvable‐contention‐ring scheme for high‐speed optical communication networks and investigates its performance. The priority mechanism is based on the time‐token control scheme. This mechanism attempts to guarantee the frame delay of time‐critical traffic by controlling the frame transmission of noncritical traffic. The noncritical frame can be transmitted only if token rotation time is faster than target rotation time.This paper examines the priority mechanism in the case of two priority levels and also in the case of four priority levels. System performance is studied using a computer simulation method with a time‐continuous simulator.The validity of the priority mechanism is demonstrated in a comparison with a fiber distributed data interface (FDDI) and the nonprioritized resolvable‐contention ring. Efficient operation of the priority mechanism is investigated by considering the buffer overflow rate of each priority class. The proposed scheme performs effectively. Moreover, the performance of FDDI is comparatively degraded because of long token waiting time and large token capture time.
Radio propagation characteristics in navigation experiment using ETS—V satellite
Authors: Migaki Mitsuhiko 
Published: July 2007

AbstractThis paper describes the results of the radio propagation experiment between an aircraft or a ship and a ground earth station by means of the Engineering Test Satellite V (ETS‐V) as a part of the navigation experiment program which is aimed at developing the technology for utilizing a satellite for navigation assistance by a ship and for control of an aircraft of the ocean.First, the antenna on a moving vehicle is summarized. Next, the experimental results with each moving vehicle are described with regard to the magnitude and the periodicity of the received signal level. The results were analyzed and the cause of the level variation was found in some cases.The magnitude of the variation of the signal level (fading range) was about 6 dB at the maximum for the elevation angle of the satellite from 45° to less than 10° in the case of the experiment with an aircraft. In the case of a ship, the magnitude increased with a decreasing satellite elevation angle. In the case of a one‐element antenna with a gain of 6 dBi, the magnitude of variation was more than 10 dB at an elevation angle of 10°. The periodicity of the variation was investigated by deriving the frequency components by means of the Fourier transform.In most cases for an aircraft, no remarkable frequency characteristic was observed and the spectrum was flat at the frequency range of less than 25 Hz. On the other hand, in the case of a ship, the components less than 1 Hz are predominant at a low satellite elevation angle. Hence, it is clear that the nature of the reflection is different in the aircraft and the ship. For the latter, the reflection from the ocean surface is predominant.
Monitoring of the sediment dynamics along a sandy shoreline by means of airborne hyperspectral remote sensing and LIDAR: a case study in Belgium
Authors: Deronde B. , Houthuys R. , Henriet J.‐P. , Lancker V. Van 
Published: July 2007

AbstractAirborne hyperspectral data and airborne laserscan or LIDAR data were applied to analyse the sediment transport and the beach morphodynamics along the Belgian shoreline. Between 2000 and 2004, four airborne acquisitions were performed with both types of sensor. The hyperspectral data were classified into seven sand type classes following a supervised classification approach, in which feature selection served to reduce the number of bands in the hyperspectral data. The seven classes allowed us to analyse the spatial dynamics of specific sediment volumes. The technique made it possible to distinguish the sand used for berm replenishment works or for beach nourishments from the sand naturally found on the backshore and the foreshore. Subtracting sequential DTMs (digital terrain models) resulted in height difference maps indicating the erosion and accretion zones. The combination of both data types, hyperspectral data and LIDAR data, provides a powerful tool, suited to analyse the dynamics of sandy shorelines. The technique was demonstrated on three sites along the Belgian shoreline: Koksijde, located on the West Coast and characterized by wide accretional beaches, influenced by dry berm replenishment works and the construction of groins; Zeebrugge, on the Middle Coast, where a beach nourishment was executed one year before the acquisitions started and where the dams of the harbour of Zeebrugge are responsible for the formation of a large accretional beach, and Knokke‐Heist, located on the East Coast and characterized by narrow, locally reflective, beaches, heavily influenced by nourishment activities. The methodology applied allowed retrieval of the main sediment transport directions as well as the amount of sediment transported. It proved to be specifically suited to follow up the redistribution and the re‐sorting of the fill in beach nourishment areas. Copyright © 2007 John Wiley & Sons, Ltd.
Optimization of mechanical structures under special consideration of materials
Authors: Vietor Thomas , van den Akker Simon 
Published: July 2007

AbstractStructural and Mechanical Optimization Problems are well distributed and described in literature. A high number of applications from different industry fields are publicated. Due to increasing demands for performance improvement together with reduced weight and costs the specific consideration of material laws and uncertainties into optimization problems in mechanical engineering is required. This paper presents an overview about Stochastic Structural Optimization as far as required to consider specific material laws. The application of structural stochastic optimization with specific material laws is illustrated at different test and industrial examples:• Ten‐Bar System as standard test application with elastic material law and scattering material parameters• Ceramic Mirror with brittle ceramic materials• Powertrain Mounting System with nonlinear rubber material• Large scale Vehicle Body Structure with plastic material. Here the application will be presented and one of the commercial software systems. The details of this example will be publicated in the future. The numerical evaluation of this example is very expensive and time consuming. This is the one reason why stochastic optimization is not well distributed already.The presented examples are results of different projects the authors has worked at in the last 12 years at university and industry. About a decade ago stochastic optimization routines were still programmed in small working groups at universities. To increase the application to different industry branches, commercial software has to be used. There are a number of software packages on the market claiming the capability of stochastic optimization as well. In the next time these packages will be tested at different applications. This will be part of the planned publication in the future. The Vehicle Body Structure example in this paper will outline the task without going into the details. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sesquiterpenoids from Ligularia dentata
Authors: Baba Hitomi , Yaoita Yasunori , Kikuchi Masao 
Published: July 2007

AbstractFive new compounds were isolated from the roots of Ligularia dentata, including four bisabolane‐type sesquiterpenoids, 1–4, as well a new eudesmane, 5. The previously isolated 3α,6α,9‐tris(angeloyloxy)‐2α,4β‐dihydroxy‐7,11‐epoxybisabol‐10(15)‐en‐5‐one (6), when left as an oil in a refrigerator over nine months, gave rise to a mixture of two positional isomers, 7 and 8. Their formation is rationalized by means of epoxide ring opening and shift of an angeloyl (Ang) group. The structures of compounds 1–5, 7, and 8 were established by in‐depth spectroscopic (UV, CD, IR, 1D‐ and 2D‐NMR) as well as mass‐spectrometric methods.