摘要:

AbstractOften, in a system with a network structure, such as the communication network, traffic network and social relationships, the centrality of a point is discussed. The centrality of a point is usually measured by its relation to other points, and the distance has been used as a measure for the relation. Recently, a method based on the capacity has also been proposed. In contrast to the past theory of centrality function, which discriminated the cases into the relation between points into the distance and the capacity, this paper presents a unified theory by introducing the concept of modification of the space with respect to a point. Based on the modification of the space, the axiomatic system concerning the centrality and semi‐centrality functions are newly defined, extracting the properties shared by the past centrality functions. The characterization of the real‐valued function defined on a point is made based on the proposed axiomatic system, and it is shown that the proposed theory includes the past major results concerning the centrality function. Finally, the theory is applied to the network, where the weight is assigned to the point, and the length and capacity are assigned to the edge. Thus, the theory is a generalization of the centrality function which is applicable to the network, where weight is assigned to the point and the length and capacity are assigned to the e

ISSN:8756-6621    

DOI:10.1002/ecja.4410700501

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA new method of designing a vector quantizer is presented for bandwidth compression of speech signals, and some experimental results are shown. In this method, spectral parameters are extracted first from the DFT spectrum of input speech signals using a psychological frequency scale‐the so‐called Mel scale. This parameter is called the Mel‐scaled spectrum. The number of Mel‐scaled spectrum is reduced and the cepstrum of this parameter is calculated. Then this Mel‐scaled cepstrum is vector quantized and the codebook‐vector of the vector quantizer is determined by the algorithm using principal component analysis. With this algorithm, codebook‐vectors can be designed considering the statistical characteristics of the Mel‐scaled cepstrum. Also, the reduction of parameters by Mel‐scale can decrease the size of the codebook memory without greatly degrading the synthesized speech quality.Using the forementioned method two codebooks are designed: one contains 256 vectors, and the other contains 2048 vectors. The quantization error is compared with those designed by the well‐known LBG algorithm. The simulation results show that the codebooks designed by the proposed method present less quantization error and degradation of synthesized speech quality than those design

ISSN:8756-6621    

DOI:10.1002/ecja.4410700502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractWhen a coherent light is passed through an ultrasonic field of finite amplitude, the diffraction spectrum has an asymmetrical form around the Oth order component due to the harmonic generation corresponding to the waveform distortion in the propagation of ultrasound. This paper demonstrates that the asymmetry depends on the phase relationships among the harmonic components of the ultrasound. A method is proposed which can reconstruct the original ultrasonic waveform by a simple measurement and calculation. The method is to separate the symmetric and antimetric components of the diffracted light by calculating the sum and difference of the positive‐ and negative‐order components, and to determine the amplitude and phase from the sum and the difference, respectively. Using the proposed method, the CT techniques are applied to the optically measured data which are a line‐integral of the ultrasonic pressure. The ultrasonic field distribution is visualized for arbitrary cross section for each harmonic component, making it possible to observe the two‐dimensional distribution of the harmonic generation accompanying the propagation of finite amplitude ult

ISSN:8756-6621    

DOI:10.1002/ecja.4410700503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper discusses the approximate solution of Fredholm's integral equation of the first kind, using the trial function containing unknown parameters. The unknown parameters are determined from the observed data and the estimated values using the least‐square method. The method is applied to the remote sensing problem, where the method can be applied withouta prioriknowledge about the true solution, even if few observed data are available to estimate the correct change of the physical variable (true solution). A method is demonstrated which can examine the adequateness of the chosen trial function. Discussions are made for the accuracy of the approximate solution and the error of the physical variable which is estimated from the approximate solutio

ISSN:8756-6621    

DOI:10.1002/ecja.4410700504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractSome of the analyses which are important in practice are: the analysis of induction noise between lines on the printed board; and the analysis of extraordinary phenomena in the multiline transmission system. These problems can be reduced to the transient analysis of the transmission‐line network composed of a number of transmission‐lines with different phases, their branches and junctions, as well as a number of lumped‐constant elements. By the analysis in thes‐domain through Laplace transform, the general solution for the basic equation for the transmission‐line is obtained containing arbitrary constants, and the arbitrary constants can be determined from the system of linear equations derived from the boundary conditions. This paper presents a method of deriving this system of linear equations for the case with only lumped sources and for the case with distributed sources. By determining the arbitrary constants, the solution is obtained in the operator domain, and the time‐solution is obtained by the inverse transform. The solution in the time‐domain is obtained by the numerical inverse Laplace transform, and the computation is performed by substituting a sequence of complex values intos. The effectiveness of the proposed method is verified by applying the method to sev

ISSN:8756-6621    

DOI:10.1002/ecja.4410700505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractEqualizers which compensate the transmission characteristics of the transmission channels are important for ensuring the quality of data transmission and are inevitable especially in the data transmission using telephone networks.This paper describes a method of applying the parallel architecture (PA) which we have already proposed to an adaptive equalizer which utilizes the recursvie least square (RLS) method. The RLS method which is used to estimate and update the parameters of equalizers, is attractive as an effective algorithm because of its fast conversion. However, the complexity of its computation makes this method less popular than the least mean square (LMS) method, especially for adaptive equalizers which require the fast update of the parameters.Utilizing the parallel architecture with the method described herein it is able to execute the RLS method with the same amount of calculation time as that of the LMS method. The parallel architecture is expected to be applicable in practice because it has an architecture of regular structures and localized interconnections which are suitable for implementation in VLSIs.

ISSN:8756-6621    

DOI:10.1002/ecja.4410700506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractIt is well known that rubber sheets mixed with carbon particles or carbon fiber usually exhibit large surface anisotropy due to the rolling process employed in fabrication. The use of such materials for special microwave applications requires measurement of the complex permittivity tensors. However, no reliable method for this purpose in such lossy anisotropic materials has been established. In this paper the reflection loss of anisotropic sheet materials is measured and a method for obtaining complex permittivity tensors from the experimental results is given. That is, the frequency characteristics of the reflection loss are measured for various polarization directions of incident waves at the sheet materials and each element of the tensors including nondiagonal ones can be estimated by the least squares method using these data. As a result of study of the principal direction of the sheet using measured values of this tensor, it is found that the real and imaginary parts differ largely in the principal direction for some of the rubber sheets with carbon used for this measurement.

ISSN:8756-6621    

DOI:10.1002/ecja.4410700507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe multi‐channel CSMA/CD (M‐CSMA/CD) is a multiple‐access protocol which is suitable for broadband bus local area networks consisting of parallel channels. This protocol can achieve such good characteristics as a large capacity and a high degree of adaptability. Most of the CSMA/CD and M‐CSMA/CD protocols have been analyzed by slotted models in the past. There is one customer at a terminal (finite source) and he sends and/or receives data by the M‐CSMA/ CD protocol. The time required for the transmission start to be detected by another terminal within the same network is approximated by an exponential distribution, resulting in an irreducible Markov model. This paper presents a method of analyzing this protocol using a non‐slotted model. Numerical results are compared with computer simulation results and the approximation accuracy is discussed. The difference of the numerical results for non‐slotted models from those for slotted models is a

ISSN:8756-6621    

DOI:10.1002/ecja.4410700508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe phenomena of scattering from an object buried in the ground have been analyzed in the case where the frequency is a few kHz. In such cases the displacement current is negligibly small and the scattering object is sufficiently smaller than the wavelength. On the other hand, recently a ground radar using an RF signal of several hundred MHz has been studied. At such high frequencies the scattering body to be detected is located at a relatively shallow depth and has a size of the order of wave‐lengths because the attenuation is significant. For low‐frequency applications Green's function for the structure with a ground surface does not cause numerical problems. For high‐frequency cases the computation time increases significantly. The integrand for Green's function varies substantially depending on the relative locations of the source, scattering object and observation point. In the present paper the computation time is reduced significantly by deformation of the integration path. When both the source and the observation point are close to the ground surface, the maximum value of the scattered wave computed with consideration of the effect of the ground surface is about (1 +R) times that with this effect neglected ifRis the reflection coefficient of the ground to air. The effect of higher‐order scattering is found to b

ISSN:8756-6621    

DOI:10.1002/ecja.4410700509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractIn hyperthermia which has recently been considered as a promising cancer therapy, heating of tissue is produced by dielectric heating by microwave energy. On the other hand, owing to the substantial attenuation of electromagnetic waves within a biological body, it is not possible to heat a cancer located deep inside the body. The authors have proposed an antenna (applicator) for electromagnetic irradiation of the biological body with a converging effect in the magnetic field plane (H‐plane). In this paper, a new applicator is proposed which has a converging effect in the electric field plane (E‐plane) in addition to the previous effect in the H‐plane. Such an E‐ and H‐plane converging lens applicator has been fabricated. In addition to the theoretical analysis, a heating experiment has been performed for a phantom model of human muscle. The theoretical and experimental results agree well. If a surface cooling device is added in the applicator, the depth of the maximum temperature point is found to be more than twice that of the conventional waveguide with an identical aperture size. A similar theory has been used at 2450 MHz in the simulation of heating of a biological model considering the presence of cancer. Although the skin depth of the muscle layer at this frequency is 17 mm, the range of heating in the hyperthermia reached more than 30 mm (about twice the surface skin depth), indicating the effectiveness of the applicator devel

ISSN:8756-6621    

DOI:10.1002/ecja.4410700510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY