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Applying feedback control to a flyback converter in discontinuous conduction mode causes instability by virtue of a jump phenomenon under some snubber circuit conditions. In this paper, we clarify this jump phenomenon, analyze stability, and discuss circuit constants to avoid the phenomenon. We propose current-mode control without relying on circuit constants. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 21–29, 1999 [ABSTRACT FROM AUTHOR]

Extensive research has been carried out on transform coding using the discrete cosine transform (DCT) for compression of digital video data. Improvement of the video quality has been brought about by an increased number of pixels, such that a reduction of the time required for coding per pixel is highly desirable. When the multiplier coefficients in the coding operation or the values of the basis coefficients of the DCT are expressed as binary numbers, it is possible to reduce the operating time and simplify the process by using as few bits as possible. It is necessary to consider the constraint that the picture quality of the reconstructed video image should not be degraded by the reduction of the number of bits. In this paper, it is shown that the number of bits of the basis coefficients can be reduced under this constraint if quantization of the transform coefficients is taken into account. Also, the limiting value of the decrease of the number of bits in specific coding examples such as JPEG is determined. Finally, it is confirmed that the quality of the reconstructed video image changes very little even if the basis coefficients are represented by fewer bits than in previous schemes, provided that the reduction is within the limit presented in this paper. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(8): 81–91, 1997 [ABSTRACT FROM AUTHOR]

The antennas for mobile communication handsets have become smaller in shape, which has degraded their electrical performance significantly. To obtain a small but high-performance handset, it is important to increase the antenna efficiency. The important parameter for such a purpose is the radiation efficiency which can be measured easily by the. Wheeler method. This method is carried out based assumption that the input power is equal to power loss if the antenna is covered with a cap of a size on the order of a radian sphere. However, unless this assumption holds, the computed Wheeler efficiency does not give accurate raditon efficiency. When the raditon the radition efficiency is actually measured by the Wheeler method, the measured values often have a dip from the theoretical value. In this paper, the cap is approximated by wire grids and the Wheeler method is simulated on a computer. It is confirmed that the dip is not cause derives from the invalidness of the presumption of the Wheeler method that the internal reactive electromagnetic field not changed when a cap is sleep. It is shown also that the Wheeler method can be used sufficiently even if the size of the cap is larger than the radian sphere. The limit of application is studied. [ABSTRACT FROM AUTHOR]

This paper proposes an N X N input-output buffer switch model which switch several kinds of packet emphasizing the real-time property as well as packet emphasizing the secure transmission. The model corresponds to the Poisson and Bernoulli traffic switching system. Such performances as the average systems queueing delay and the loss probability for the packet emphasizing the real-time transmission are analyzed. Nonpreemptive priority discipline is applied on the input side where the circuit configuration is relatively simple. On the output side, the first-come/first-served (FCFS) process is applied without considering the priority service. In the proposed model, the out buffer size is assumed as finited and the input buffer size is assumed as infinited. For the two kinds of switching systems which serve the Poisson arrival packets and the Bermouli arrival packets, respectively, the means system queueing delay for the priority class is analyzed. For the case where the input buffer size is limited for the packet with a high priority emphasizing the real-time transmission, the relation between the loss probability for the packet with a high priority and the sizes of the input and output buffers is investigated by a computer simulation for the case of two classes. The adequate input buffer size for the packet with a high priority is determined. [ABSTRACT FROM AUTHOR]

The conflict alert system was development for air traffic control to detect and warn of the danger of aircraft collisions. This paper presents a configuration for air traffic control data tables that increases the efficiency of the conflict alert system, which was devised to predict what instructions to give for preventing collisions. Air traffic control data tables are constructed mainly from air rout data and aircraft data. The aircraft are controlled by the air route unit, and all data as well as the relationship between the data (i.e, between aircraft and air routes,etc.) are updated continually in real time for the data tables in question. As a result;(1) the relationship between the aircraft and the air route can instantly be grasped, thereby improving the accurancy of the course prediction for the aircraft; and (2) when judgeing if two aircraft are possibly in conflict, the efficiency of the conflict detection process can be improved by rapidly being able to grasp the relative relationship of aircraft on adjacent air routes and the relationship between the leading and last aircraft on the same course. The feasibility of the point (1) and (2) is demonstrated through computer simulation. [ABSTRACT FROM AUTHOR]

In the frequency agility radar in which the transmit frequency of the radar can be changed at an ultrahigh speed, not only is excellent electronic counter counter-measure (ECCM) performance obtained but also improvement of the detection probability of the object with a fluctuating reflection cross section is expected. However, in the conventional-type radar, the frequency is modified at a high speed so as to change the entire pulse. However, the standard Doppler process is not possible. In this paper, in order to add a Doppler processing function to a frequency agility radar, the clutter is suppressed with one pulse and the obtained object signal is integrated coherently. The method and the simulation results are presented. [ABSTRACT FROM AUTHOR]

This paper describes a theoretical model of the power spectrum density (PSD) for a field-merges frame signal and compares the efficiency between the field-based coding and frame-based coding which uses the field-merged signal. The field- merged signal has also been used recently as an signal to the spatial coding process for the coding of interlaced-scammed television signals. However, the nature of PSD, witch is an important basis for high-efficiency coding, is not sufficiently understood in the area of field-merged signal. For instance, optimality of the conventional techniques applied to the field-merged signal is not assured. A theoretical PSD model for the field-merged signal has been introduces and its properties have been clarified in relation to the motion of the image. The performance of frame based-coding is calculated using this model. [ABSTRACT FROM AUTHOR]

Lightning surge which is induced on a telecommunication cable may damage telecommunication equipment. This paper proposes a design method for a lightning surge generator which can accurately predict reliability for the lightning surges in telecommunication equipment and the quality of the lightning surge genetor development based on this method is described. First, the characteristics of the lightning surge which is fed to the equipment are determined from such factors as the lightning surge inducing mechanism. Next, the testing surge waveform desing method is determined in which evaluations of the lightning surge proof of equipment by the peak voltage, steepness (peak voltage/ front time) and energy of the lightning surge can be performed in one test. The testing surge waveform then is determined based on this design method. A method is described for realizing the lightning surge characteristics and the testing surge waveform using a basic impulse voltage generator circuit which consist of an LRC circuit with few circuit elements. Experimental results demonstrate that the developed lightning surge generator based on the proposed designed method can predict the malfunction rate accurately. It is shown also that it is highly practical because its size and cost are about one-tenth that of a conventional testing device. [ABSTRACT FROM AUTHOR]

A new clutter suppression method is proposed for a multibeam radar with which the profile of the input signal can be estimated with a statistically high accurancy. In this method, the suppression filter is selected adaptively from discrete filter bank on the basic of the estimated clutter bandwidth. As the selection method, the concept of selection probability linked to the bandwidth estimation accurancy in introduced so that the selection algorithm is derived. To evaluate the performance of the system based on this algorithm, the conventional improvement factor is improved by defining the performance function taking into consideration the filter selection probability and the desired detection probability. Based these factors, a configuration example of a notch filter bank is presented for the model radar. The system performance is evaluated by the figure of merit (FOM) defined here. The results obtained are:(1) there exist an optimum maximizing the FOM in the clutter bandwidth estimation accurancy and the filter distribution spacing; and (2) if the estimation accurancy is increased in reduced. [ABSTRACT FROM AUTHOR]

As a small antenna for mobile communication, a circular patch antenna miniaturized with a shorting post is proposed. These shorting post as placed near the feed post. The circular patch antenna miniaturized by offset is excited by a hybrids of the coaxial TM01>/sub> mode and the TM11 Mode. Hence, the antenna has directivities in several polarization planes so that a low gain pattern not realizable with an antenna with a monopole mode is attained. The theorectical analysis of the antenna is carried out by a cavity model in which an impedance boundary is assumed at the edge of the element. Since the conventional procedure cannot be applied to the coaxial TM01 mode that is the fundamental mode of the antenna, an approximate formulation based on the equivalent circuit containing the feed post and the shorting post as the current sources is proposed. It is confirmed that the numerical results of the input impedance and the experimental results agree well, From the numerical analysis, the modal amplitude characteristics of the magnetic current contributing the radiation and the resonant frequency characteristics of the antenna are discussed from the relationship to the method. [ABSTRACT FROM AUTHOR]

This paper discusses fundamental characteristics in reachability analysis of communication service specifications defined by means of production rules. In the conventional service specifications, reachability has been analyzed within a finite number of communication processes. However, it is necessary to deal with infinite processes to verify state reachbility of the global transition description of the production rules. If the reachability state as a reachable subglobal state constructed with a number of processes is defined, the size of the reachability states set depends on the number of processes at the initial state. In general, the system is analyzed on the assumption of an infinitive number of processes to verify reachability. This paper presents the relationship between the size of the reachable set and the number of processes in the systems. It also shows the existence of the upper bound of the reachable state set and a method to obtain the minimum number of processes that gives the upper bound of the reachable set. This study makes it possible to analyze the reachability of an infinite number of processes by a reachability problem of finite number of processes [ABSTRACT FROM AUTHOR]

There is increasing demand for a system that supports various multipoint activities such as a conference and education using multimedia information. This paper consider the situation where such a multimedia remote presentation system is to be constructed and discusses the condition for maintaining the synchronization among the media in the information at each node. In this paper, first, the synchronization semantics is defined based on the information presentation timing between the media information taken out from the storage information source and the live media information such as the user's voice. Then a computation procedure is shown for the buffer size needed in each node in order to satisfy the sematics. Based on those reasonings, the design condition is presented for the buffer size and the command response time. [ABSTRACT FROM AUTHOR]

We propose presents a model for a token ring system using jump-type stochastic differential equations. We model waiting frames as a queueing system whose mechanism is different from those of convertion queueing systems. In addition, we assume that frame interarrival time obeys an exponential distribution, and we show that the number of waiting frames has the same law as M/M/-queue. For this case, we obtain stationary distribution, mean cycle time, and mean system time. We also compare these results with simulation. [ABSTRACT FROM AUTHOR]

The spatial distribution method using orthogonal transformation of signal is proposed and studied for its effectiveness in a new digital communication system having high immunity to impulse interferences. This method is based on the time domain consideration that spatially spread information can be recovered even if part of the information is destroyed by a pulselike disturbance. Computational investigations on the application of the distributed signal transmission method to the baseband digital signal transmission when discrete Fourier transform (DFT), discrete cosine transform (DCT), and Walsh-Hadamard transform (WHT) are used as the signal distributor are covered in this research. It is also shown that the estimation of an erased symbol at the receiver is possible using an estimation method. [ABSTRACT FROM AUTHOR]

This paper proposes a staggered superposed transmission scheme of narrow bandlimited spread spectrum multiple access (SSMA) signals and multicarrier high-speed signals. To lessen degradation due to mutual interference between SSMA signals and multicarrier high-speed signals, SSMA signals are set between two high-speed signal channels. Moreover, a band-limitation filter in the transmission side and an interference-suppression filter in the receiving side whose bandwidths are narrower than Nyquist bandwidth of spreading code chip-rate are employed. The proposed scheme decreases SSMA signal transmission power and increases the number of SSMA channels. [ABSTRACT FROM AUTHOR]

The longitudinal lightning surge appearing on the telecom cable between the pair of conductors and ground is changed into the transverse lightning surge between the conductors due to conversion characteristics of the system. The transverse lightning surge overlaps the signal voltage and causes bit errors. In this paper, the longitudinal and transverse lightning surges are determined. Using these lightning surges, a new method of estimating bit-error rate by simulation (numerical calculation) is proposed. Time domain and frequency domain parameters obtained by actual measurement of lightning surge are used in the simulation. Using this method, bit-error rate due to lightning surge can be evaluated easily. Moreover, it can cope with the changes in the telecom system and is superior to the conventional method of evaluating the bit-error rate using actual lightning surges. [ABSTRACT FROM AUTHOR]

When a processing gain of a direct sequence spread spectrum (DS/SS) system is too small to suppress narrowband interferences and the interference power is much higher than that of the desired signal, an adaptive filter cannot compensate for the uncorrelated interference signals because the filter coefficients cannot be updated. In this case, if the interfered bands are known, a notch or bandpass filtering is useful. However, such frequency domain filtering in the receiver may suppress not only the interfering signals but also the desired one. Prefiltering in the transmitter cannot achieve the same performance as DS/SS systems without a bandpass-filter in the absence of interference. This paper proposes and investigates a scheme of controlling the transmission bandwidth and its power spectral density using two spreading sequences in order to improve the performance in the presence or absence of high-power periodical partial-band interference. Two concrete systems also are proposed: a spreading sequence serial transmission system using different spreading sequences; and a spreading sequence selectable ARQ system. In the former system, the transmitter does not consider the phase of the periodical partial-band interference in the receiver. Therefore, the system is realized easily because of the rather loose timing control requirement on the penalty of bit rate and because it does not require backward channels. On the other hand, in the latter system, 75 percent of the transmitted data are not degraded by the interference because of the more careful channel state selection at the transmitter than the former system. [ABSTRACT FROM AUTHOR]

With the severe traffic situation in recent years as the background, there are intensive studies on the intervehicle communication system, aiming at the safety improvement of the road traffic system and the smooth control of the traffic flow. The spread-spectrum communication is very useful in the realization of such a system since the data for the distance between vehicles are obtained, which is very important in driving the vehicle, as well as the communication. This paper considers the intervehicle communication network using the spread-spectrum system and proposes the medium access control (MAC) protocol for the autonomous distributed access control. To evaluate the performance of the proposed system, a computer simulation is executed for the environment where the vehicles run freely on a highway. It is shown that stable information exchange can be realized with vehicles running in nearby positions. [ABSTRACT FROM AUTHOR]

To resolve the propagation characteristics of low-frequency (LF) radio waves in the low latitude magnetosphere, the navigation radio signal (transmitting frequency of 85.725 kHz, 12 kW CW) from Biei Decca station in Hokkaido (geographical latitude: 43.60°N, geographical longitude: 142.45°E, magnetic latitude: 37.20°N) was observed at Birdsville, Australia (geographical latitude: 25.83°S, geographical longitude: 13933°E, magnetic longitude: 37.08°S), which is the magnetic conjugate point. From the analysis of the intensity, Doppler spectrum and polarization of the magnetospheric propagation wave, the following characteristics were obtained. (1) The magnetospheric wave, which is below the detectable level during daytime, appeared around sunset and disappeared immediately after sunrise, (2) at sunset, the width of the Doppler spectrum spreading is rather narrow and the polarization is a right-handed elliptical one. This suggests a propagation in a few ducts. (3) During the night, the width of the Doppler spectrum spreading is rather wide and the polarization is a right-handed elliptical one close to linear. The intensity is higher when the sustaining duration of the magnetospheric propagation wave is longer. This suggests a propagation within several chamber-type ducts, which are repeatedly generated and eliminated within a rather short period. From the calculation of the loss of the ionospheric transmission, difference is suggested in the duct emission mechanism of the magnetospheric duct propagation at the sunset and at night. [ABSTRACT FROM AUTHOR]

It is often not possible to operate a microstrip antenna with a probe feed with a zero reactance at the designed frequency because the self-inductance of the probe is added to the input impedance. It is proposed that by means of matching stubs added on the periphery of the patch, this excess reactance is cancelled. Few examples exist on the analytical studies of the operating principle of such a proposal. In the present paper, it is noticed that this matching stub resembles by shape the metal piece added for separating the degeneracy in the design of a circularly polarized annular microstrip antenna with a one-point feed. Then the effects of these two metal pieces and the feed pin are analyzed by the eigenfunction expansion method and the perturbation method. It is found that the excitation amplitude ratio of the two principal modes can be varied and the phase of the input impedance can be controlled by adding the matching stubs. Further, the design of areas and locations of the two metal pieces are investigated for generation of a circular polarization. [ABSTRACT FROM AUTHOR]

An approximate numerical analysis to evaluate the mean waiting time and the blocking probability of the packet switch under first-in/first-out (FIFO) policy with speedup factor is performed. The improved input buffer control policy with speedup factor C is proposed to achieve small mean waiting time by computer simulation and compare the performance with conventional FIFO policy and longest queue policy. Under the proposed model, there are N/2 pairs of input buffers; if one input buffer is empty, the second packet in the queue of the other buffer is transferred to the other empty buffer. It is shown that speedup factor and proposed input buffer control policy can reduce the waiting time compared with conventional FIFO policy and longest queue policy. [ABSTRACT FROM AUTHOR]

One of the main factors preventing the increase of the input power of optical fibers is the saturation of the input power by stimulated Brillouin scattering (SBS). In this paper, theoretical and experimental investigations are performed of three methods for suppressing SBS. The first method is to enlarge the optical fiber Brillouin gain bandwidth by applying a periodic strain distribution in the longitudinal direction of an optical fiber using the structure of the optical fiber cables. The second method is to shift the frequency of the Brillouin gain spectrum by connecting fibers with different core dopant concentrations. The third method is the combination of the two methods described above. In the cable described in this paper, a sinusoidal strain distribution was induced in the fibers with a maximum strain amplitude of 0.4 percent and a pitch of 600 mm by using a double-stranded structure. By doing so, the Brillouin gain bandwidth could be enlarged up to 400 MHz. Also, a frequency difference of 580 MHz is induced by connecting fibers with a dopant difference of a maximum of 4.4 percent between each fiber. It is shown that the SBS can be suppressed up to a CW optical input power of +17.4 dBm by widening the bandwidth and connecting optical fibers with shifted bandwidths. Therefore, it is concluded that the proposed method is effective and practical for SBS suppression. [ABSTRACT FROM AUTHOR]

Optical noise enhanced by the nonlinear refractive index of optical fibers is one of the major factors limiting the system performance of in-line amplifier transmission. This paper derives an analytical expression of noise enhancement taking into account group-velocity dispersion of optical fibers. Evolution of the in-phase and quadrature-phase noise field components is expressed by a simple matrix describing the transmission characteristics of optical noise through the basic section composed of an optical amplifier and a transmission fiber. This enables minute investigation of noise evolution in in-line amplifier systems; approximate characteristics can be learned as well. A noise increase proportional to the third power of a number of amplifiers is verified in the normal dispersion regime while an exponentially rising noise peak is found in the anomalous dispersion regime. Based on these results, signal-to-noise ratios at the receiver and allowable transmission distances are discussed in terms of the dispersion parameter and the amplifier number. From the noise evolution point of view, the longest transmission distance is achieved in the normal dispersion regime. [ABSTRACT FROM AUTHOR]

No detailed analysis has been available on the return loss characteristics of a pyramidal electromagnetic wave absorber. Therefore, an approximate analysis method for the pyramidal absorber has not been established in a rigorous sense. In this paper, the return loss characteristics for the normal incident on the pyramidal absorber are derived by the numerical simulation based on the spatial network method. Also, as an approximate method for the wave absorber that can approximate the obtained results well, a method called the synthesized capacitance model is proposed. By comparison of the numerical results by the two methods, it is found that the approximate results by the synthesized capacitance model provide more accurate results than those by the previous approximate models. Further, by means of the synthesized capacitance model for the normal incidence, the oblique incidence characteristics of the TE wave were computed and the results agreed well with the measured data. [ABSTRACT FROM AUTHOR]

The authors have developed the tracking control system of astronomical objects in the Nobeyama millimeter array. A system was studied which can accomplish sufficient tracking accuracy for an interferometer, such as delay tracking, phase tracking, and fine delay correction. It was found that the location error of an astronomical object can be made less than 1 percent of the maxi- mum spatial resolution on a synthesized map and the radio intensity degradation less than 0.1 percent if the phase tracking is executed at an interval of about 10 s and the fine delay correction at 1 - 2 s. Further, from the actual observation results, it was confirmed that this system has realized an extremely high tracking accuracy. [ABSTRACT FROM AUTHOR]

When we shape reflector surfaces of an offset dual reflector antenna for a given desired aperture distribution, we create a phenomenon in which the direction of the reflected ray by the shaped surfaces and an assumed direction of radiation by geometric optics do not coincide. Hence, the characteristics of cross-polarized waves are degraded. If we shape the surfaces at a tilt angle of the main dish with respect to the direction of the main radiation pattern, we found that the directional errors become extremely small between the direction of the actually reflected ray and that of the assumed direction of radiation by geometric optics for an optimum tilt angle. At this tilt angle, we can shape the reflector surfaces satisfying almost all of the conditions imposed by geometric optics. When we shape the surfaces at the optimum tilt angle, we obtain continuous surfaces which generate a desired axisymmetric aperture distribution along the radial direction. We can design an offset dual reflector antenna with low sidelobes and favorable characteristics for cross-polarized waves. Based on this theory, we built an experimental offset Gregorian-type antenna with aperture diameter of about 50 λ. Measured results revealed excellent characteristics for cross-polarized waves and those for sidelobes. Thus, we confirmed the validity of the theory of shaping reflector surfaces. [ABSTRACT FROM AUTHOR]

In conventional rule-based speech recognition, the rules have been constructed in a heuristic way. In that method, the rules with high accuracy have been difficult to construct when the recognition algorithm is complex, as in the case of consonant recognition. To cope with this problem, this paper presents a method for automatically constructing the recognition algorithm in the form of a set of rules. The method is a compromise between the transparency of the algorithmic representation by rule-based representation and the high accuracy by the optimization of the automatic construction. The unit of the rule is represented by if (condition), then (branch 1), and else (branch 2). The condition is a threshold logic using the discrimination parameter with clear meaning. The set of rules is constructed by the iterative procedure of selecting the optimum discrimination parameter and the threshold, for partitioning the consonant training samples into two sets. By connecting the constructed rules, a binary decision tree is formed. The consonant is recognized by iterating binary decisions on the tree and examining upon each which terminating node is arrived at. By constructing the rules depending upon each succeeding vowel, a set of rules with a higher accuracy can be obtained. By the evaluation experiment, it was seen that transparent rules with higher accuracies can be constructed. The obtained rules are in agreement with the empirical rules of phonology. Furthermore, using the rules, the consonant recognition rate in 1O0 city succeeding vowel-dependent names uttered by 50 subjects was improved from 72.4 to 80.0 percent. [ABSTRACT FROM AUTHOR]

Most of the studies in the past on the hierarchical control have been concerned with the computational allotment between higher and lower levels, or among lower levels. In the actual system with a hierarchical structure, however, it often happens that the functional allotment is made between higher and lower levels. From such a viewpoint, the following scheme is considered in this paper. Consider a hierarchical control scheme with a functional allotment between higher and lower levels. The higher-level controller views the whole system by n macroscopic view, and makes decisions so that the system is optimized from a wide range of viewpoints. Then the instruction is issued toward the lower-level controller. The lower-level controller views his own subsystem in detail and makes finer decisions so that the subsystem is optimized, while observing the instruction from the higher level as far as possible. The problem is formulated for the hierarchical control with functional allotment, considering the controllable linear discrete-time stochastic system with a quadratic cost function. Then a situation in assumed where the information concerning the state estimation and the control input can be exchanged at each time between the higher and lower levels, and an algorithm is derived which can successively determine the control input at each time far the higher- and lower-level controllers. Furthermore, it is shown by a numerical example that the intention of the higher-level controller is reflected on the actual control by the lower level, by a suitable definition of the cost function of the higher-level controller. [ABSTRACT FROM AUTHOR]

Among methods for deriving a symbolic reliability expression between two specified vertices (s, t) in a network, a tree-expansion method proposed herein generates an expression in summation form with fewer product terms and computes it very fast. The tree-expansion method has a fundamental operation to enumerate s - t paths (u1, u2, ..., um) and generates a rooted tree (reference tree) from subpaths of paths uj (j = 1, 2, ..., i -1) having their initial and terminal vertices on a path uj and then derives a symbolic reliability expression directly from its subtree (implicant tree). This method has a disadvantage in that the number of product terms depends heavily on the order of paths obtained by a depth-first search. In this paper for each vertex in a network we define its weight as the number of edges with terminal vertices having small weights and apply the tree-expansion method according to the generation order, then we can reduce the number of product terms (this is called the modified tree-expansion method). Also, we show by computer experiments that the modified tree-expansion method can reduce the number of product terms and its running time. [ABSTRACT FROM AUTHOR]

A problem inherent in discussing the antenna radiation mechanism is that the electromagnetic energy flux density can not be deterministically defined. The practice has been to interpret the Poynting vector as the flux density vector and to use it to explain the various phenomena. In this paper, as the equivalent of the Poynting vector, the Nukiyama vector derived from the energy theorem is interpreted as the flux density vector. This interpretation is applied to the radiation mechanism of a perfectly conducting antenna, and it is shown that the radiation can be explained as "an exchange of energy between the electromagnetic wave radiated into space and the conductor on which the power is impressed, with the energy exchange taking place as the energy transverses the conductor." It is also shown that the new concept of locally-stored energy derived from Nukiyama's vector for use in this exposition is a broad concept which also encompasses the representation of observable stored energy as defined by Rhodes. [ABSTRACT FROM AUTHOR]

In analyzing inhomogeneous waveguides, this paper derives an analytical method that is effective even for the radiation mode light. Also, the propagation characteristic of intersecting waveguides is studied by using this method. In this analysis, considering virtual waveguides that include the real waveguide completely, the propagating light is expressed by the Fourier transform with virtual modes set up in the virtual waveguides. Moreover, using the concept of the power flow equation, the Helmholtz equation is transformed into a difference equation of Fourier coefficients, where weak coupling and parallel rays are assumed. Applying this method to intersecting waveguides having inhomogeneous index gradients, we study the dependency of the propagation characteristics of the intersecting angle and the index gradient difference. From these results, light propagation in branching waveguides is found for low intersecting angles. This phenomenon is explained successfully by a model which combines TM0 and TM1 modes. Furthermore, the propagation characteristics of inhomogeneous waveguides are simulated and their dependency on the index gradient is studied. [ABSTRACT FROM AUTHOR]

This paper proposes &Rtilde;(t), an approximation for the auto-covariance function of virtual waiting time in an M/G/1. Calculation by &Rtilde;(t) is much easier and faster than the exact formula R(t). By the use of this approximation, not only the computation for arbitrary model becomes possible, but also the computation time can be reduced below 10-3 time even for the model which can be calculated by the exact formula, such as M/M/1. Comparisons between &Rtilde;(t) and R(t) for several models show that &Rtilde;(t) approximates R(t) closely enough for practical use. We have applied &Rtilde;(t) to the accuracy estimation of waiting time measurement by test calls (test call method) and obtained several important results for waiting time measurement. They are: i) the accuracy is improved as the interval of test calls is set shorter, but is hardly improved even if the interval is set shorter than ten times the mean waiting time (saturation characteristic); ii) better measurement accuracy is obtained by the test call method if the interval of test calls is properly set than by the real call method; and iii) the coefficient of variation of service time distribution greatly affects the measurement accuracy. [ABSTRACT FROM AUTHOR]