A simulation model for natural convection was developed for determining the surface temperature distribution in base plates with rectangular vertical fins in communication equipment. An estimated velocity derived from the buoyancy and pressure drop equations in a duct was used for laminar forced convection cooling simulations in parallel plates. Temperature distributions in finned plates were calculated by numerical integration of the heat conduction equation. An experimental study was also performed, to check these simulation results, by changing the height of fins, the pitch of fins, and the heat generation conditions. Experimental results and analytical results were found to agree well. Also, this simulation method was extended to analyze natural convection cooling in vertical base plates with inclined parallel fins. We placed alternately on the plates the sections without fins and the sections with fins on the plates. Using the inclined fins, air flow rate between fins was large and fresh air flew into the fins from the side of the plates. The natural convective heat-transfer rate for inclined fins was found to be 14% higher than that for vertical fins.

In this paper, a new variable length code transmission technique utilizing multicode DS/SS is proposed. A common problem associated with the use of variable length codes over wireless channels is loss of synchronization due to bit inversion caused by channel noise. The loss of synchronization produces burst errors in the received source symbols. The proposed system assigns multiple spreading codes to a single user to transmit variable length codes. The number of the spreading codes is equal to the maximum bit length of the codewords. All the bits of the codeword are spread and transmitted at one time by utilizing the assigned multiple spreading codes. Therefore no synchronization of the codeword is required. This paper evaluates the performance of the proposed technique over an AWGN channel and a Rayleigh fading channel. Our results show that the proposed technique improves the symbol error rate (SER) performance by 2-3 dB on the AWGN channel and 10-20 dB on the Rayleigh fading channel as compared with a conventional transmission technique. The source-channel coding suitable for the proposed technique improves the performance by another 15 dB on the Rayleigh fading channel. The proposed transmission technique works even in a low Es/No region.

This paper introduces a new analytic method that uses modified state equations to evaluate the performance of PCSD (Packet Channel Sharing protocol for DCA systems) with the goal of increasing the spectrum efficiency of DCA systems by realizing channel sharing between circuit-switched calls and packets. The results of this analysis show that PCSD is more suitable for microcellular systems than cellular systems, and that PCSD system performance improves as the average holding time of circuit-switched calls increases. Moreover, this paper proposes a novel scheme to determine the optimum release delay time of packet channels in order to achieve high throughput for packets as well as high channel capacity for circuit-switched calls. The proposed scheme shows that the optimum release delay time for PHS (Personal Handy-phone System) is greater than 60 frames and less than 100 frames.

A new learning method is proposed to enhance the performances of the fuzzy ARTMAP neural network in the noisy environment. It combines the average learning and slow learning for the weight vectors in the fuzzy ARTMAP. It effectively reduces a category proliferation problem and enhances recognition performance for noisy input patterns.

Contact recording systems have been studied for future magnetic recording disks with a high recording density. Tribological key technologies for ultra-low spacing and high wear performance are required for the contact systems. Particularly, a liquid lubrication system plays an important roll for reducing a mechanical spacing and improving wear performances. However, a lubrication design concept for contact recording systems is not established. In this study, molecular design of lubricants for contact systems will be discussed from a viewpoint of bouncing and wear behaviors. As a result, a minimum bouncing height of 3 nm and a high wear performance were obtained for ion-etched contact sliders by the optimization of design parameters, i. e. pad design and lubricant material.

We discussed on relationship between the width of slit ray and the accuracy of the measurement system for surface profile of electric contact. To obtain resolution of 10 [µm], we designed the mechanism which keeps constant the focal length between the object and the lens. As a result, the width of slit ray was clear in the whole surface. A section image could measured exactly and enhanced the resolution.

Time series prediction is very important technology in a wide variety of fields. The actual time series contains both linear and nonlinear properties. The amplitude of the time series to be predicted is usually continuous value. For these reasons, we combine nonlinear and linear predictors in a cascade form. The nonlinear prediction problem is reduced to a pattern classification. A set of the past samples x(n-1),. . . ,x(n-N) is transformed into the output, which is the prediction of the next coming sample x(n). So, we employ a multi-layer neural network with a sigmoidal hidden layer and a single linear output neuron for the nonlinear prediction. It is called a Nonlinear Sub-Predictor (NSP). The NSP is trained by the supervised learning algorithm using the sample x(n) as a target. However, it is rather difficult to generate the continuous amplitude and to predict linear property. So, we employ a linear predictor after the NSP. An FIR filter is used for this purpose, which is called a Linear Sub-Predictor (LSP). The LSP is trained by the supervised learning algorithm using also x(n) as a target. In order to estimate the minimum size of the proposed predictor, we analyze the nonlinearity of the time series of interest. The prediction is equal to mapping a set of past samples to the next coming sample. The multi-layer neural network is good for this kind of pattern mapping. Still, difficult mappings may exist when several sets of very similar patterns are mapped onto very different samples. The degree of difficulty of the mapping is closely related to the nonlinearity. The necessary number of the past samples used for prediction is determined by this nonlinearity. The difficult mapping requires a large number of the past samples. Computer simulations using the sunspot data and the artificially generated discrete amplitude data have demonstrated the efficiency of the proposed predictor and the nonlinearity analysis.

We developed a glass ferrule fiber optic connector. During development, we also studied wear-resistant coating technology for preventing scratches on the surface of a glass ferrule. The method of coating was sputtering, and the material was alumina. We confirmed that a thin uniform coating could be formed on the ferrule surface to improve the durability of glass ferrule connectors.

In the floorplan design problem, soft blocks can take various rectilinear shapes. The conventional floorplanning methods, however, restrict their shapes only to rectangle. As a result, waste area often remains in the layout. Some floorplanning methods have been developed to handle rectilinear hard blocks, however, no floorplanning methods have been developed to optimize rectilinear soft blocks. In this paper, we propose a floorplanning method which places rectilinear soft blocks. The advantages of the method are reducing both waste area and wire length. We present Separate-Rejoin method which efficiently forms rectilinear shapes for soft blocks. The result is obtained quickly because the method is based on the slicing structure in spite of handling rectilinear block. Thus, our method is suitable for practical use in terms of layout area, wire length and processing time. We applied our method to a benchmark example and an industrial data. For the benchmark example, our method reduces waste area by 25% and wire length by 13% in comparison with the conventional rectangular soft block approach.

This paper describes the design and performance of a high-speed 6-bit ADC using SiGe HBT for measuring-instrument applications. We show that the Gummel-Poon model suffices for SiGe HBT modeling and then we describe that the folding/interpolation architecture as well as simple, differential circuit design are suitable for ADC design with SiGe HBT. Measured results show that the nonlinearity of the ADC is within 1/2 LSB, and the effective bits are 5. 2 bits at an input frequency of 100 MHz and 4. 2 bits at 200 MHz with 768 MS/s. We also describe some design issues for folding/interpolation ADC.

Penumbral imaging is a technique which uses the facts that spatial information can be recovered from the shadow or penumbra that an unknown source casts through a simple large circular aperture. The technique is based on a linear deconvolution. In this paper, a two-step method is proposed for decoding penumbral images. First a local-statistic filter based on adaptive windowing is applied to smooth the noise; then, followed by the conventional linear deconvolution. The simulation results show that the reconstructed image is dramatically improved in comparison to that without the noise-smoothing filtering, and the proposed method is also applied to real experimental X-ray imaging.

The structure of bidirectional syndrome decoding for binary rate (n-1)/n convolutional codes is investigated. It is shown that for backward decoding based on the trellis of a syndrome former HT, the syndrome sequence must be generated in time-reversed order using an extra syndrome former H*T, where H* is a generator matrix of the reciprocal dual code of the original code. It is also shown that if the syndrome bits are generated once and only once using HT and H*T, then the corresponding two error sequences have the intersection of n error symbols, where is the memory length of HT.

In this paper, we compare the performance of evolutionary digital filters (EDFs) for IIR adaptive digital filters (ADFs) in terms of convergence behavior and stability, and discuss their advantages. The authors have already proposed the EDF which is controlled by adaptive algorithm based on the evolutionary strategies of living things. This adaptive algorithm of the EDF controls and changes the coefficients of inner digital filters using the cloning method or the mating method. Thus, the adaptive algorithm of the EDF is of a non-gradient and multi-point search type. Numerical examples are given to demonstrate the effectiveness and features of the EDF such that (1) they can work as adaptive filters as expected, (2) they can adopt various error functions such as the mean square error, the absolute sum error, and the maximum error functions, and (3) the EDF using IIR filters (IIR-EDF) has a higher convergence rate and smaller adaptation noise than the LMS adaptive digital filter (LMS-ADF) and the adaptive digital filter based on the simple genetic algorithm (SGA-ADF) on a multiple-peak surface.

In this paper, we study bifurcations of equilibrium points and periodic solutions observed in a resistively coupled oscillator with voltage ports. We classify equilibrium points and periodic solutions into four and eight different types, respectively, according to their symmetrical properties. By calculating D-type of branching sets (symmetry-breaking bifurcations) of equilibrium points and periodic solutions, we show that all types of equilibrium points and periodic solutions are systematically found. Possible oscillations in two coupled oscillators are presented by calculating Hopf bifurcation sets of equilibrium points. A parameter region in which chaotic oscillations exist is also shown by obtaining a cascade of period-doubling bifurcation sets.

An image recognition system using NEURO4, a programmable parallel processor, is described. Optical flow is the velocity field that an observer detects on a two-dimensional image and gives useful information, such as edges, about moving objects. The processing time for detecting optical flow on the NEURO4 system was analyzed. Owing to the parallel computation scheme, the processing time on the NEURO4 system is proportional to the square root of the size of images, while conventional sequential computers need time in proportion to the size. This analysis was verified by experiments using the NEURO4 system. When the size of an image is 84 84, the NEURO4 system can detect optical flow in less than 10 seconds. In this case the NEURO4 system is 23 times faster than a workstation, Sparc Station 20 (SS20). The larger the size of images becomes, the faster the NEURO4 system can detect optical flow than conventional sequential computers like SS20. Furthermore, the paralleling effect increases in proportion to the number of connected NEURO4 chips by a ring expansion scheme. Therefore, the NEURO4 system is useful for developing moving image recognition algorithms which require a large amount of processing time.

We present an experimental and theoretical study of multiple diffraction rings of a cw Ar+ laser beam from a nitrobenzene solution of BDN (bis-(4-dimethylaminodithiobenzil)-nickel) caused by the spatial self-phase modulation. We examine in detail the effect of the intensity and phase shift profiles of the beam in the nonlinear medium by comparing the measured ring patterns with the theoretical results based on the Fraunhofer diffraction. Although the thickness of the sample is only 180 µm in our experiment, it is found that the intensity and phase shift profiles are broadened owing to the self-defocusing effect. It is also found that the phase shift profile is further broadened by the thermal diffusion. These two effects become remarkable when the focused beam is used.

Vehicular speed response phase locked loop (VSR-PLL) is a novel circuit to remove a steady-state frequency offset which arises in the receiver with directive antenna. In this paper, the circuit is applied to Ricean fading environment. For the application of VSR-PLL to Ricean statistics channel, the Doppler shift information of direct wave must be obtained because the self-oscillation frequency of VCO is controlled by using the information. This paper describes an estimation method for the Doppler shift of the direct wave, and shows the several results of the performance analysis for the estimation method and proposed VSR-PLL with the method. As a result, we found that the proposed VSR-PLL could reduce the irreducible bit-error rate for QPSK system from about 10-2 to 10-3 on several conditions.

Digital signal processors (DSPs) usually employ indirect addressing using an address register (AR) to indicate their memory addresses, which often introduces overhead codes in AR updates for next memory accesses. In this paper, AR update scheme is extended such that address can be efficiently modified by 2 in addition to conventional 1 updates. An automatic address allocation method of program variables for this new addressing model is presented. The method formulates program variables and AR modifications by a graph, and extracts a maximum chained triangle graph, which is accessed only by AR 1 and 2 operations, so that the estimated number of overhead codes is minimized. The proposed methods are applied to a DSP compiler, and memory allocations derived for several examples are compared with memory allocations by other methods.

Estimating the deadline of a real-time task is a necessary prerequisite to the applications that have strict timing constraints, such as real-time systems design. This paper shows how Monte-Carlo simulation can be used as a space-efficient way of analyzing Timed Petri nets to predict whether the system specified can satisfy its real-time deadlines. For the purpose, Extended Timed Petri Net (XTPN), an extension of conventional Timed Petri net, and its execution rule, using Monte-Carlo technique, are newly defined. A simple simulation scheme with less memory space is presented as a way of estimating the deadline of a real-time task modeled in XTPN. And the comparison between the analytical and simulation results is given. The problem addressed here is to find the probabilities of meeting given deadlines.

This paper presents novel multimedia ATM networks which are capable of transmitting voice data efficiently and unify the switching methods among heterogeneous traffic. Fully ATMized multimedia networks are using fellow cell switches. The proposed assembly method can pack plural calls which have different virtual channel connection (VCC) into one cell. Every call in cells is able to be dynamically rearranged by the fellow cell switch to achieve an efficient use of network resources. The switching functions are supported by shared virtual channel identifier (VCI) cells and fellow cells in it. The fellow cell switch for 622 Mbps links is integrated into a single chip. The multimedia ATM networks including voice transmission can be constructed by the fellow cell switches being attached to the standard ATM switches.