bluuebunny/crossref_metadata_2025 huggingface dataset:
DPCM variable length coding system for image using bifix‐free pattern
Authors: Saito Tadao , Inose Hiroshi , Yanaka Kazuhisa
Published: July 2007

In the past, variable length DPCM coding of gray scale image utilized block coding such as Hoffman coding scheme. However, if the midriser quantizer is used, the two levels close to zero level will occur with high probability. In such a case, the Huffman coding without extending the information source still results in a considerable level of redundancy. This is because the codewords can exist only at the tips of the branches of the coding‐tree, which is the constraint for the instantaneously decodable block code. This paper proposes a coding scheme which applies a technique similar to that used for transparency acquisition in the HDLC scheme, to insert a dummy bit into the non‐blocked codewords. In principle, it uses the properties of the bifix‐free pattern. When the two quantized levels close to zero occur with high probability, the proposed coding scheme yields a higher compression factor than does the Huffman code. Furthermore, the coding parameters can be varied adaptively depending on the properties of the image. Both the theoretical aspect of the proposed scheme and the simulation based on the standard test images are discussed in this paper.
Display methods of laser radar data using a computer system
Authors: Shimizu Hiroshi , Sasano Yasuhiro , Yasuoka Yoshihumi , Matsudo Osamu , Takeuchi Nobuo , Okuda Michio
Published: July 2007

In the computerized laser radar data processing, it is important to utilize effective data‐display techniques. This paper examines two‐dimensional data display methods using the computer peripheral systems. Five methods (color level slicing, grey level slicing, dot density, contour and perspective methods) are selected and their advantages and disadvantages are examined. According to the quantitative examination on the output efficiency, the number of data per one display, etc., the density method is the best among all methods.
Realization of open‐input type second‐order active RC filters using two operational amplifiers
Authors: Arai Ikuo , Suzuki Tsutomu
Published: July 2007

One of the active RC circuit realization methods is the inductance simulation method. Conventionally, the modeling of the floating inductance is aimed at the bi‐directional inductance L. In this paper, the authors consider the case where realization of the “unilateral” inductance is simpler than the bidirectional inductance and perform the realization using two operational amplifiers. It is shown also that the unilateral FDNR can be realized by the same procedures. These unilateral L and FDNR are applied in the realization of the open‐input type (∞‐0 type) second‐order filters which are new circuit types. Moreover, it is shown that the ∞‐0 type second‐order filters can also be derived from the ∞‐0 type for the realization of the open‐input/voltage source‐output circuits. In either circuit type, all the second‐order transfer functions are realized in the ∞‐0 type filters by using the L and FDNR circuits. The second‐order filter groups proposed in this paper have advantages in that the number of elements is less and the sensitivity is lower than in the ∞‐0 type filters. As an experimental example, the measured and calculated values are shown for the frequency characteristics of the ∞‐0 type second‐order low‐pass filters. Their operations are then verified.
A periodically sampled queuing system with load regulation
Authors: Yoshida Makoto
Published: July 2007

In connection with the periodical registration processing systems, which is uniquely applied to real‐time processing systems, analysis and evaluation are conducted for a system that has load regulation by restricting registration to finite central processor buffers and CP systems. Under the conditions of a single processor, a constant period T, Poisson arrival calls and holding times (average value h) with negative exponential distribution, the author formulates the population function representation of calls in systems immediately after a certain period, and, based on this, calculates the overflow rate and the maximum traffic to be carried per period. Next, using the above distribution, the average number of waiting calls in the CP buffers and outside the CP system at any time are formulated and the average waiting time is calculated by using Little's formula. The continuity of various characteristics in the above nonsaturated state are then examined based on analysis of the saturation states where there always exist waiting calls in the queue outside the CP system. Finally, numerical computations show that as certain evaluation measures such as the number of CP buffers n vary and saturate at about n = 30 if T/h < 30, then at n greater than T/h, T/h < 30. From the above it can be concluded that load regulation has some effect without decreasing the maximum traffic a0 on the conditions that as many CP buffers as economically possible are installed and the period T (T/h) is kept large enough within the allowable range of the average waiting time.
Characteristics of the dominant mode in a dielectric tape line
Authors: Wakabayashi Toshio , Mihara Yoshio
Published: July 2007

A dielectric tape line consists of a dielectric material of rectangular or semi‐elliptical cross section having a small thickness‐to‐width ratio and placed on a conducting plane. Analysis is here conducted by using an elliptical coordinate system. Because of the use of new field functions in the interior of the tape line, convergence of the solution of the characteristic equation is much faster than other cases. In this paper, we study theoretically and experimentally the characteristics of the dominant mode. First, the analytical results are outlined. Next, the formula for the attenuation is derived and the attenuation mechanism is explained from numerical examples. The relative strength of the electric field in the horizontal and vertical directions is computed outside the tape and the results are given. We also study the relative intensity distribution of the interior electric field, the ratio of the power carried inside the tape to the total power transmitted, and the spread of the electromagnetic field. Analytical results of the attenuation characteristics and the relative intensity distribution of the external field agree very well with experimental results.
Scattering of a plane electromagnetic wave by a conducting circular cylinder of finite length
Authors: Kinoshita Teruhiro , Sekiguchi Toshio
Published: July 2007

This paper presents an exact solution for scattering of a plane EM move (TM mode) by a perfect conducting circular hollow cylinder having no end caps. The scattered field is evaluated in the Fourier domain using the Wiener‐Hopf technique. The scattered field is divided into the IPO (improved physical optics) field, TE and TM modes in the cylinder and the diffracted fields at two edges. The range of the scattering angle where the IPO field gives good approximation is almost independent of the cylinder length if the cylinder length is larger than several wavelengths.
Traffic analysis of an alternate routing method for store‐and‐forward switching network
Authors: Kawashima Konosuke
Published: July 2007

In a packet switching type of store‐and‐forward switching network, one of the important problems is that of routing. Traffic analysis of networks has hitherto been done mainly by simulation. This paper, however, studies the problem analytically and gives a basic theory for traffic design. When the queue length of the output channel of the 1st‐choice group is full, the arriving call (packet, message, etc.) is routed to the 2nd‐choice group by means of an alternate routing scheme.

In the case of a telephone network (instantaneous network), the alternate relay theory has already been established. Based on this theory, a similar queueing system is described here. First, the properties (moment) of overflow calls from a multiple line system having finite waiting room size is gradually determined. Next, the overflow call process is approximated by the interrupted Poisson process and the mean waiting time of an overflow call routed to the 2nd‐choice group is determined. On the other hand, considering both the 1st‐ and 2nd‐choice groups simultaneously, the exact mean waiting time is determined. By comparing the numerical values of the two, it is shown that the interrupted Poisson process approximation of the overflow call process is more or less accurate. Finally, as an application of this approximation, a single‐channel system with finite waiting buffer fed from two sources‐Poisson and interrupted Poisson (overflow traffic)—is analyzed and it is clearly shown that the properties of the overflow call traffic becomes worse than those for the Poisson call traffic.
Simultaneous approximation for two kinds of system characteristics using descent method
Authors: Kiranon Wimat , Machida Toichi , Yoneyama Masao
Published: July 2007

The descent method is applied for simultaneous approximation for system characteristics with two different characteristic requirements. With given initial parameters, the descent directional vectors which derease two performance functions simultaneously are determined from the gradient vector of the performance function of each characteristic and the successive approximation is made from approximated parameters. In the algorithm, both performance functions always decrease at each step under given conditions. Next with newly defined weighting coefficients, both performance functions are decreased simultaneously at a given rate. The convergence limit of this simultaneous approximation is made clear. The effectiveness of the present method and examples of weighting coefficients are discussed.
Adaptive detection of unknown signal in colored noise of unknown parameters
Authors: Miki Shigehiko , Yoshida Kunihiko , Kaneku Seiko
Published: July 2007

This paper describes the adaptive detection of an unknown signal in colored noise. Given the statistical parameters of the observed noise, the Gremlin machine is well known as a learning scheme for the signal pattern. When this scheme is extended to unknown noise parameters, the correlation of observations based on noise poses a problem.

Here, additive colored noise is modelled by a self‐recursive process of Gaussian type of past‐dependent width k and the dispersion of its random component is unknown. Its coefficient group is taken as one of the elements of a known finite collection. Further, k does not exceed the observation space width, etc. Based on these premises, first an optimal supervised learning scheme is derived using a Bayesian scheme. Next, the theoretical convergence is studied for this learning scheme and it is shown that, under certain conditions, the detection scheme converges to that for all known parameters. Further, for a special case, the theoretical error probability of a case with assumed estimated noise parameters is computed. The importance of study of correlation between observations is pointed out at the same time the case in which the true values of the noise parameters are not included in the known finite collection is also studied. Thus, the effectiveness of the present learning scheme is clearly shown. Finally, characteristics of the learning scheme are also studied by computer simulation.
Speech quality of adaptive delta modulation (ADM) codec with syllabic companding
Authors: Itoh Kenzo , Kitawaki Nobuhiko , Kakehi Kazuhiko , Hayashi Shinji
Published: July 2007

Delta modulation with syllabic companding is one of the voice digitalization systems for which experimental studies have been conducted to evaluate speech quality. First, appropriate circuit constants are provided by use of the objective evaluation measure S/NO for the experiments and then studies are made on the features of the quantization noise in the system. Second, the cepstrum distance measure obtained from linear prediction analysis is introduced as an objective evaluation measure and its relationship to subjective evaluation is also studied. The following conclusions are made. (1) Lowering the sampling frequency to 32 kHz has little effect on articulation and can provide fair or better than fair quality if appropriate signal input levels and received speech volumes are maintained. (2) The effect of circuit noise at about 2.0 mV at the encoder input on voice articulation is deemed to be equivalent to having the same circuit noise at the decoder output. (3) The detectability threshold of transmission errors is about 2.4 × 10−4, which proves that the system is less prone to code errors than the log‐PCM system. In addition, the coincidence of the cepstrum distance measure with the subjective evaluation value is better than that of the segmental SNR.
Analysis of monopole antenna erected on circular conductor
Authors: Iwashige Jiro
Published: July 2007

A vertical monopole antenna erected on the base of a circular cone is analyzed by the equivalent edge current (EEC) and the geometrical theory of diffraction (GTD). The cone may be converted into a disk, column or truncated cone. The current distribution and input impedance are calculated by the moment method. The multiple diffraction on the circular plane is considered in the calculation of radiation patterns by the EEC method (or GTD). The experimental results agree approximately with the calculation.
Hierarchical structure of telecommunication network with independent transversal trunks
Authors: Akiyama Minoru , Tanaka Yoshiaki , Yamashita Mikio , Iio Makoto
Published: July 2007

The main objective of setting up the hierarchical structure for telecommunication network is to concentrate the traffic in order to increase the efficiency of transmission lines, thereby reducing the total cost of the network. The optimum structure of the network is determined by such factors as traffic, its flow pattern, the costs of transmission line and switching equipment. The costs of components of the switching network change rather rapidly due to recent technological development. The change of cost and the role of transversal trunks in handling traffic calls have made the reconsideration of installing transversal trunks worthwhile. This paper presents a geometrical model for the Japanese public telephone network. The optimization of the hierarchical structure of the network is performed taken into consideration such parameters as costs of transmission lines, switching facility, and traffic threshold for transversal trunk. It is concluded that the three‐stage network with end offices, toll centers, and district centers seems appropriate in the near future. The district center of this network should be about the same scale as the existing regional center. The traffic threshold for installing the transversal trunk should be almost several tens of erlangs.
Theoretical method for the analysis of queueing system with overflow traffic
Authors: Matsumoto Jun , Watanabe Yu
Published: July 2007

The theoretical analysis and design of queueing systems with overflow traffic are presented. The non‐random traffic is approximated by an interrupted Poisson process with which the 3‐moment matching method is used for obtaining the average, variance and the 3rd‐order moment. The analysis of a queueing system with finite capacity with overflow traffic can be considered to be a G/M/1 type queueing matrix to which the interrupted Poisson process and known equations apply. For analysis, the overflow traffic moments and formulas for the overflow probability and average waiting time of the finite‐capacity queueing system with overflow traffic are so derived that they can be used in their practical forms very easily. In the case of finite‐capacity queueing systems, the theoretical overflow probability and average waiting time are derived for single‐ and multiple‐overflow traffic models, overflow and random traffic models as well as the two‐stage overflow traffic model. From comparison with the simulated experimental values, the accuracy of the theoretical approximations is shown to be excellent.
Simultaneous realization of some system matrices by networks containing switches
Authors: Nishi Tetsuo , Iwasaki Kazuto
Published: July 2007

This paper discusses simultaneous realization of some system matrices Fi defined by x‐y =f1 x‐y where × is an n‐dimensional state vector, by a network composed of resistors, capacitors, amplifiers and switches. Based on a weak assumption, we obtain the following results: (1) The minimum number of switches required for realization of F1 and F2 (or F1, F2 and F3) equals r(F1 − F2) (the minimum value of r(H1) + r(H2) + r(H3) where r(A) denotes the rank of a matrix A and Hi (i = 1, 2, 3) satisfies F1 − F2 = H1 + H2 and F1 − F3 = H1 + H3; (2) At most (n + 1) amplifiers are required; (3) There is an example in which (n + 1) amplifiers are required.
Nonreciprocal devices in open‐boundary structures for millimeter‐wave integrated circuits
Authors: Muraguchi Masahiro , Naito Yoshiyuki
Published: July 2007

Although a number of components for millimeter‐wave integrated circuits based on an open dielectric waveguide have been proposed, little has been reported on nonreciprocal devices and no significant results have been obtained. In this paper we discuss experimental verification of nonreciprocal propagation phenomena in an open ferrite waveguide and their application to open nonreciprocal devices. Based on the results, we propose a circulator of directional coupler type which makes use of nonreciprocal propagation phenomena in an open ferrite waveguide. We also propose a pillbox resonator type circulator and a junction type circulator using the nonreciprocal resonance of an open cylindrical ferrite. Circulators of the directional coupler type and the pillbox type do not need any conductor in principle. The radiation loss can be reduced without significant increase of the conductor loss if a conductor shield is used in the E‐plane of the junction circulator. A junction circulator with practical characteristics is developed for millimeter‐wave integrated circuits.
Considerations of a multi‐address message delivery system consisting of multiple centers
Authors: Takenaka Toyofumi , Yoshida Yutaka , Saito Joichi , Watanabe Naoya
Published: July 2007

The multi‐address message delivery system is a communication technique for sending identical messages to plural addresses and is applicable to various information such as in data transmission, facsimile or even voice. It is promising as one of the important communication techniques for office automation. In this report, we take up a multi‐address message delivery scheme in which there are plural multi‐address message centers in a network. We compare two message delivery systems from centers to addressed terminals. One is the source center delivery system by which direct transmission is made at a source center to which a multiaddress delivery has requested. The other is the destination center delivery scheme by which transmission is made from a destination center via the source center. It is concluded that the source center delivery scheme is preferable with respect to the costs of processing and storage in the center, while the destination center delivery scheme is prefereable with respect to the cost of transmission between service areas. Further, the network cost, which is the total of both, depends on various conditions and, accordingly, their application regions are shown.
A light intensity modulator using p‐n junction
Authors: Ohke Shigeaki , Kusunoki Akira , Cho Yoshio , Matsuo Yukito
Published: July 2007

This paper investigates the basic operation of a new type of cut‐off optical modulator using a GaAlAs layer on a GaAs substrate as waveguide whose p*nn* structure is suitable for monolithic optical devices. A new numerical solution for the field in the depletion layer of a reverse‐biased pn junction diode is presented. This method is applied to the above‐mentioned cut‐off type optical modulator for calculation of the field in the two‐dimensional layer as the modulation space. For the modulator a three‐layer slab structure is assumed and the modulation is analyzed with respect to the applied voltage by the method of eigenmode expansion from the waveguide viewpoint. Results show that for a modulator with length of several mm modulation of 90% and above can be achieved.
On pair relationships in time‐division switching network
Authors: Saito Tadao , Ogino Nagao , Goto Fumihiro , Inose Hiroshi
Published: July 2007

Since a PCM transmission path can carry voice signals in one direction, the time‐division switching network at any PCM telephone exchanges employs a four‐wire configuration. Therefore, a pair of paths is required to form one connection. A general way of preparing such pairs is to establish the pair relationships between switches or links in the switching networks and to create paths automatically based upon those relationships. Having implemented these pair relationships, the blocking probability, the amount of path hunting and the required amount of control hardware for switching networks can be reduced considerably. Pair relationships are quite important in the efficient composition of time‐division switching networks. However, no general theory exists yet for the pair relationships. This report presents an overall study on the pair relationships in time‐division switching networks. First, we define the pair relationships and classify them into several forms and then present practical examples. We then describe how to compose the more important pair relationships and briefly review the connection patterns that are produced by forming the pair relationships and modifying link connection patterns. Finally, we explain how to compose favorable pair relationships based on the above study conclusions.
New doubly orthogonal functions and their application to pattern synthesis
Authors: Tokumaru Shinobu , Nakahara Masatoshi , Yamamoto Shigeru
Published: July 2007

The double orthogonality of spheroidal wave functions has been used in pattern synthesis. However, because of difficulty in calculating spheroidal wave functions and in determining double orthogonality, its application to pattern synthesis is limited. In this paper, a new eigenintegral equation is derived to obtain general doubly orthogonal function systems in which the integral section and weighting functions can be determined freely. The new doubly orthogonal functions are applied for pattern synthesis under constraints.
Application of bifurcation theory to nerve excitations
Authors: Toko Kiyoshi , Nitta Junsaku , Urahama Ki‐Ichi , Yamafuji Kaoru
Published: July 2007

An expression for the amplitude of stable steady self‐oscillatory solutions for the inverted bifurcation is obtained by applying bifurcation theory to the BVP equation, which is a model describing nerve excitations. Up to the fifth‐power term with respect to the amplitude is included in the calculation, assuming that the amplitude of the steady self‐oscillatory solution is of small order. The obtained expression for the inverted‐bifurcation can continuously be transformed, leading to an expression for the normal‐bifurcation by merely varying one parameter. Further, utilizing that expression and employing the reductive perturbation method in which the amplitude is regarded as an infinitesimal parameter, an expression describing the relaxation phenomenon in the neighborhood of the stable steady solution is derived for the inverted‐bifurcation as well as for the normal‐bifurcation, the nature of which is close to that of the inverted‐bi‐furcation. Since this expression has the form of the usual time‐dependent Ginzburg‐Landau(TDGL) equation and an additional term, the behavior of those bifurcations which considerably differ from the usual normal‐bifurcation can well be described by the derived expression.
An integral equation for electromagnetic wave scattering from a dielectric cylinder
Authors: Chiba Michitane , Ishiai Teizo
Published: July 2007

This paper describes an analysis of the problem of electromagnetic scattering by a dielectric cylinder with an arbitrary cross section by means of an integral equation a‐long the boundary. The integral equation used by Wu and Tsai for two‐dimensional boundaries for TM‐wave scattering from biological bodies is superior in simplicity to Muller's integral equation. However, the solution to the former has the disadvantage that it is susceptible to resonance of the interior region. To remove such resonance, it is effective if the boundary conditions are extended so that additional equations are included which ensure that the field inside the scatterer is zero. However, a basis for selecting the interior points is not clarified. On the other hand, for problems involving conductors, it is well known that mixing of the resonant solutions occurs in the process of solving the integral equation on the boundary. A number of methods have been reported on the construction of integral equations unaffected by the interior resonance. From this point of view, an integral equation is derived which satisfies all the boundary conditions from the integral equation by Wu and Tsai. By means of numerical calculations, it is confirmed that this integral equation is not affected by the interior resonance.
Surface fields excited by a vertical electric point source located on a conducting concave spherical surface
Authors: Inami Kazuyoshi , Sawaya Kunio , Mushiake Yasuto
Published: July 2007

With the appearance of dome antenna in recent years, the necessity for analyzing the electromagnetic fields produced by a wave source placed on the concave side of a solid conducting surface has arisen. Some research on this problem for a conducting concave cylindrical surface has beem reported. However, no research which is of practical importance, has been conducted on the concave sphere. This paper describes the result of an analysis of the surface magnetic field produced by an electric point source placed on the concave side of an open conducting sphere. The analytical technique is based on the case of a concave cylindrical surface. First, a wave component traveling along the boundary is obtained from a representation of the field inside a closed conducting sphere and the field representation for an open sphere is derived. Next, the surface magnetic field for the case where the radius of the sphere is sufficiently large compared to the wavelength is represented in the form of the fields of geometrical optics and integrals. As in the cylindrical case, the result of concrete calculation shows that the resulting field agrees with the field near the wave source in the case of a vertical electric point source placed on an infinite ground plane and that a complicated interfering pattern is produced at a distance far from the wave source. Also, the appropriateness of this analytical result is confirmed through an experimental study.
Modeling and analysis of an intersection on AGT
Authors: Hamamatsu Yoshio , Nakada Katsuhiro , Kaji Ikuo , Doi Osamu
Published: July 2007

A model for automated guideway transit (AGT) is proposed, formulating the behavior of traffic at an intersection using the Markov chain technique. It is assumed that the intersection is composed of overpasses and underpasses and the traffic from the sub‐line to the main line goes through an offline. The vehicles coming from the subline must form a queue in order to avoid colliding with the vehicles through the main line, but the queue cannot be made indefinitely long, considering its effect on the following traffic. Two kinds of restrictions on the queue on the subline are considered, which are (1) restriction on the number of vehicles in the queue (model I), and (2) restrictions on the number of vehicles in the queue and the waiting times (change of MT) of the top vehicle (model II). The relation between the incoming vehicles in the main line and subline and the behavior of traffic at the intersection (average number of vehicles in the queue and the derouting rate) are discussed.
Spatial decay properties of L‐type horizontal cell response in the retina
Authors: Fukurotani Kenkichi
Published: July 2007

This paper discusses the propagation of potentials in the receptor field of horizontal cells in the retina and the linearity of response of horizontal cells with respect to the photoreceptor input. A microelectrode is inserted into the L‐type horizontal cells of carp and, by stimulating various portions of the retina by a small light spot, the response potential of L‐type horizontal cells is measured. As a result, the amplitude of the response potential exhibits a decay depending only on the distance between the horizontal cell and the point of stimulus, without any directivity in the propagation of potential. In other words, it is shown that the receptor field of the L‐type horizontal cells is spatially uniform with respect to the propagation of potential. On the other hand, when the input from the photoreceptor, is increased by increasing the light spot intensity or by using a wavelength of higher sensitivity, the spatial decay of the response potential of L‐type horizontal cells decreases. This result seems to indicate that L‐type horizontal cells have a saturating nonlinearity in regard to the input from the photoreceptor. The response characteristics of the horizontal cells in this paper are essential in the analysis of color information processing or picture information processing in the retina.
Idle signal multiple‐access (ISMA) scheme for terrestrial packet radio networks
Authors: Mukumoto Kaiji , Fukuda Akira
Published: July 2007

This report proposes a new random‐access packet communication system which is appropriately applied to terrestrial radio and called the idle signal multiple‐access (ISMA) scheme. The characteristics of the system and its realization are studied. In this field, the CSMA system has received particular attention as a system with large channel capacity which can substitute for the ALOHA system. However, an assumption for this system is that all terminal pairs can observe each other's transmitted signals, thus imposing a severe requirement on a centralized system, which does not take into account direct communication between terminals. To cope with this problem, the BTMA system was proposed, but the ISMA system proposed herein shows its superiority to the BTMA system (a frequency‐division method) in such aspects as channel capacity and structural simplicity because the entire frequency band can be used owing to the application of time division to the transmitted control signals. The channel capacity of the ISMA system is generally close to that of the CSMA system and it can be applied to a system operating with dynamic time division of channels for calls in both directions, upward and downward.
Conditions for invariant polarization in a single‐mode optical fiber in pulse wave transmission
Authors: Kusano Kiyonobu , Nishida Shigeo
Published: July 2007

Conditions are determined for maintaining polarization when pulse waves propagate in a single‐mode fiber in which both non‐uniformity in distribution of the core dielectric constant and cross sectional deformation exist. The coupling coefficient between the waves with left‐ and right‐handed circular polarizations is denoted by β( = β1 − β2). Deformation of the core cross section from a perfect circle and deviation from uniform dielectric distribution can always be expanded into circumferential Fourier series. The values of β1 and β2 are determined by the second‐order Fourier coefficients. The condition of invariant polarization in the fiber is β1 = β2 = 0. The condition for time‐invariance of the plane of polarization is frequency independency of β1 and β2. We also study the effect of twisting of fibers satisfying these condtions. Denoting the rigidity by G, the optoacoustic constant by C and the index of refraction by N, we show that if G·C/N is frequency‐independent, the degree of polarization is maintained in the fiber with invariant polarization although the plane of polarization rotates. When a fiber time‐invariant polarization plane time is twisted, the characteristics remain unchanged. We show several examples of core cross‐sectional shapes and dielectric distributions needed for maintaining the polarization.
Resolution improvement in an analog‐to‐digital converter by the superposed dither signal
Authors: Shimizu Hiroshi , Iikura Yoshikazu , Sasano Yasuhiro , Takeuchi Nobuo
Published: July 2007

This paper discusses a method to improve the resolution of an analog‐to‐digital (A‐D) converter to detect differences less than 1 LSB (least significant bit) in the input signal. Resolution is improved by superposing dither on the input signal and averaging over many measurements. The theory and experimental verification for this method are described.

This analysis calculates numerically the expectation value of the result of A‐D conversion and the expectation value of the variance, with the dither superposed on the input signal. The results show that for larger amplitude of dither, the expectation value of A‐D conversion comes closer to the real value, and the expectation value of the variance becomes larger.

The relation between the amplitude of dither and the improvement of resolution is calculated as a function of the number of measurements. For example, when the number of measurements is 100 and the amplitude of dither is 0.4 LSB, the resolution can be improved to 0.05 LSB.

This analysis is verified experimentally by using a white noise generator as a dither source, dc voltage standard as a signal source, and a transient recorder as an A‐D converter.
Synthesis of sliding discrete fourier transform and sliding hadamard transform circuits
Authors: Fujii Tetsurou , Harashima Hiroshi , Miyakawa Hiroshi
Published: July 2007

The sliding DFT algorithm is a technique for determining the DFT coefficients for time‐series samples. The conventional sliding DFT circuit used in the frequency‐sampling filter, however, is recursive and has an instability problem because of the accumulation of errors in the feedback path. A new sliding DFT circuit is proposed which is also of recursive type but does not accumulate errors. Its behavior is analyzed in detail. The circuit proposed is relatively simple and can easily be translated into hardware. It is also shown that a sliding Hadamard transform circuit is easily constructed, and the design of a sequence sampling filter is shown.
Possibility of the reduction of the electromagnetic noise of the shinkansen (bullet train) by installing conducting nets
Authors: Amemiya Yoshifumi , Yamaguchi Takashi
Published: July 2007

Electromagnetic (EM) noise is radiated when electric trains run along the Shinkansen and the VHF content causes TV receiver jamming. Currently a shared receiving method is put into practice for anti‐jamming. The jammed area extends several hundred meters to each side of the railroad, but if the noise can be reduced by 6 dB the area will be narrowed by a factor of 3 to 4. Earlier noise reduction methods were: improvement of pantograph structure, change of rubbing plate material and use of ferrite in key parts of the pantograph. However the problem on both sides of the railroad remains difficult to solve. In this paper we propose that conducting nets be installed on the supporting poles of the trolley wires. With a net three meters in width, calculation shows that the noise at 150 MHz can be reduced by 6 dB. In the calculation the noise source is taken to be a point source and the field is determined by superposing the waves diffracted from the upper and lower edges of the nets. The calculated results have been verified by experiments with a 1/70 reduced scale model.
Minimally realizable two‐dimensional transfer functions
Authors: Haratani Naomi , Takahashi Shin‐Ichi
Published: July 2007

The minimal realization problem of two‐dimensional transfer functions remains unsolved despite numerous efforts to solve it. Most conventional approaches have taken the form of seeking real number solutions for nonlinear equations that have system coefficients as their unknown variables and are therefore not amenable to realization. This paper presents sufficient conditions by which the possibility of minimal realization can be judged without necessarily solving nonlinear equations from the coefficients of optimally given two‐dimensional transfer functions. The sufficient conditions presented here are broad ones that include the well‐known types of separable‐denominator and separable‐numerator. We also introduce the canonical forms of state space representation for the separable denominator type and separable‐numerator type, which are very useful in practical applications, and additionally show that there are cases where realization dimensions can be reduced even for the general transfer function, which is difficult in finding the minimal realization.
Design and performance of optical fiber cord and optical cord cable
Authors: Tanaka Chihaya , Katsuyama Yutaka , Ishida Yukinori , Waki Takao , Ishihara Koushi
Published: July 2007

This paper describes the optical cord and stranded cable used in cable transmission systems, stations or relays. The allowable stress, bending radius and lateral load of the fiber core are explained first, and then component designs are presented that ensure these characteristics. Tensile strength requirements on the optical cable necessitate using a cord of more than 5,500 denier and a central steel wire with 1‐mm radius. On the basis of the deformation of the PVC sheath due to lateral load, the standard outer diameter of the cable is determined to be 3 mm. The buckling phenomenon of nylon pipe is discussed as it applies to a tube‐type cord, and it is shown that the Young's modulus of the pipe must be below 70 Kg/mm2. The transmission properties, strain, tensile and bending properties of cords and cables, fabricated on the basis of the above‐described design satisfy the desired objectives, confirming the effectiveness of the design.
Self‐complementary monopole‐notch array antennas
Authors: Yamamoto Katsuhiro , Sawaya Kunio , Ishizone Takayuki , Mushiake Yasuto
Published: July 2007

The constant impedance characteristics of self‐complementary antennas are theoretically established; however, the wideband nature of their radiation patterns is not in general assured. A number of works have been published in which widebanding of radiation patterns is attempted by creating axially symmetric self‐complementary monopole‐notch array antennas on the edge of a conductor. However, for the most part these studies are based on experimental procedures. In this paper the radiation characteristics of the self‐complementary monopole‐notch antenna are analyzed theoretically and the array structure with wideband constant gain characteristics is discussed. A monopole‐notch antenna created on the edge of an ideal semiinfinite conducting plane is first analyzed and found to possess wideband radiation characteristics. A more practical monopolenotch antenna created on a finite conducting plate is then analyzed by the induced e.m.f. method. The results show that the gain is higher for the structure with a longer edge in the main beam direction. It is also found that an antenna with constant impedance and constant gain characteristic can be obtained by setting up a monopole‐notch array on a triangular conducting plate. The validity of the theoretical analysis is experimentally confirmed and the limitation of the induced e.m.f. method is evaluated.
A method of designing multielectrode‐pair monolithic filters on high‐coupling piezoelectric plates
Authors: Watanabe Hiroshi , Shimizu Hiroshi
Published: July 2007

In the design of monolithic filters using multiple energy‐trapped resonators on a piezoelectric plate, the conventional method uses operating parameter theory in lumped‐element equivalent circuits. This method cannot, however, be used for designing wideband monolithic filters employing high‐coupling piezoelectric plates such as piezo‐electromagnetic material and LiTaO3 because the error introduced by the lumpedelement equivalent circuit is large. Therefore, this paper proposes a new method using the distributed‐element equivalent circuit, which is suitable for image parameter design theory. First, it is pointed out that in the design of monolithic filters based on the image parameter method which is adopted for designing multimode filters, the resonant and antiresonant arrangement method is difficult to apply to high‐coupling piezoelectric plates. Next, we point out that in order to deal with this problem a new resonant and antiresonant frequency arrangement method is suitable for high‐coupling plate filters and thus good filter properties can be obtained.
Analysis of frequency measurement of power signals with varied amplitudes
Authors: Min Y. , Ding R. J. , Song Y. H.
Published: July 2007

Frequency is one of the most important operating parameters of a power system. Thus accurate frequency measurement plays a key role in understanding the system performance and developing effective control strategies. So far various approaches have been proposed. However, one important area, which has been neglected, is what is the effect of varied signal amplitudes on these approaches. Starting with the traditional definition of frequency, this paper analyses the basic requirements for frequency measurement, and presents new concepts for various frequency definitions. The difference between actual frequency and measured frequency by various approaches is discussed in detail. Postprocessing approach is proposed to improve the accuracy of the measurement.
Impact of decentralized wind generation in power systems reliability. Variable speed wind turbines
Authors: Morales A. B. , Trecat J. , Crappe M.
Published: July 2007

Electricity supply is challenged from deregulation and third party access to the network. In consequence of this, dispersed generation from Independent Power Producers based on co‐generation units, renewable energies or other conventional sources increase in all countries. Wind Energy Converters is one of the different technologies in use and development. Most utility‐scale wind turbines are operated at constant speed, but there is an increasing interest in variable speed ones. In this paper, a variable speed, stall regulated wind turbine has been simulated, evaluated and compared to a fixed speed wind turbine to study the impact in power systems reliability, on the basis of classic indices and risk base capacity benefit factors, as adequacy indices. Conclusions about the maximum level of penetration are illustrated using a small test system.
Comprehensive analysis and comparative study of several sensorless control systems of asynchronous motors
Authors: Abu‐Rub H. , Hashlamoun W.
Published: July 2007

The aim of this work is to present a novel and inexpensive method to develop and assess sensorless control schemes of induction motors. The proposed systems operate without speed and motor voltage sensors; the rotor angular speed is calculated in different ways. The stator voltage may be determined from measured DC link voltage with information of the pulse width modulation algorithm. A voltage source inverter feeds the induction motor with hysteresis current controllers using amplitude and angular frequency of the stator current as input commands. A comprehensive analysis and comparative study of several relationships of rotor angular speed is presented. The presented idea may be treated as an improvement on the principle of nonlinear control of induction motors. Simulation results have been performed using the proposed control systems. A set of criteria to assign “figures of merit” can be used to choose the proper scheme, depending on the specific application.
Effect of injected charge on the electrification of oil flowing past the surface of composite polymers
Authors: Metwally I. A.
Published: July 2007

The factors affecting oil‐flow electrification (OFE) in large forced oil‐cooled electric power apparatus are experimentally investigated using a closed cycle model, and a coaxial test section comprising a charge injector. The streaming and leakage currents are measured to investigate the impact of injected charge on OFE interfaced with composite polymers. The results reveal that the magnitude and polarity of the injected charge, and the type of composite polymer and its impregnation resin, if it exits, cause evident qualitative as well as quantitative changes in the measured currents. Cellulose‐based materials give the highest leakage current. For other composite polymers, the higher the number of ketonic carbonyls and/or delocalized states in the aromatic moieties, the higher is the leakage current, and hence the lower is the streaming current. Under flow conditions, the leakage current is lower than that under a stationary condition, but the trend is reversed at high temperature, especially for the HVDC case. Under HVAC, the streaming current shows polarity reversal from negative to positive on increasing the oil temperature and/or voltage. For HVDC application, the streaming current is significantly reduced by calendering the outermost layer of the composite polymer, using fine glass as a backing material instead of using glass fabric, and impregnating the composite polymer with highly dipolar epoxy resin.
Compensation of semi‐periodic currents
Authors: Czarnecki L. S. , Chen G.
Published: July 2007

Before power electronics were developed, non‐periodic currents used to occur in distribution systems, apart from arc furnaces supply, mainly during switching and faults. Now, such currents are produced at normal operation of some power electronics equipment. Power electronics enables very fast control of processes and energy flow. Non‐periodic currents are by‐products of such a fast control. Non‐periodic currents in electrical power systems occur as an effect of deformation or conversion of periodic, usually sinusoidal voltage and the periodic component of the supply current is crucial for permanent transfer of energy from generators to loads. Such non‐periodic current, with a periodic or quasi‐periodic components are referred to as semi‐periodic currents in this paper. The paper provides fundamentals of semi‐periodic current compensation and discusses a control algorithm of such a compensator.
Performance of sequence directional elements on MOV protected series compensated transmission lines
Authors: Funk A. T. , Malik O. P.
Published: July 2007

Performance of positive and negative sequence directional elements applied to MOV (metal oxide varistor) protected series compensated transmission lines with the relay voltages measured at the line side of the capacitors is investigated in this paper. Both elements basically measure the negative of the equivalent impedance behind the relay for forward faults and the line impedance plus the impedance of the remote source for reverse faults. During faults, the equivalent impedance of MOV/series capacitor combination is generally different for each of the three phases, causing mutual coupling of the sequence components, which may affect accurate impedance measurement. Simulation results indicate that mutual coupling in the sequence domain does not significantly affect the performance of the sequence directional elements on loaded systems.
Evolving artificial neural network models for voltage contingency ranking
Authors: Singh S. N. , Srivastava K. N.
Published: July 2007

This paper presents four different models of artificial neural network (ANN), namely Multi‐layer feed‐forward (BP) model, Modular neural network (MNN), Hybrid neural network (HNN), and Cascade neural network (CNN) for fast voltage contingency screening and ranking. The effectiveness of the proposed method is demonstrated for contingency screening and ranking at different loading conditions on two sample power systems. One of the proposed neural networks, CNN provides fast and accurate screening and ranking for unknown patterns and would be suitable for on‐line applications at energy management center.