In order to reduce the threshold current of GaInAsP/InP surface emitting (SE) laser, we introduce a flat surface circular buried heterostructure (FCBH), which has merits of both planar buried heterostructure (PBH) and buried heterostructure with a SiO2 mask (BH), into GaInAsP/InP SE laser. Its minimum threshold current was 20 mA at 77 K, which provide better result than previous PBH-SE lasers or BH-SE lasers grown with a SiO2 mask.

Light amplifiers are very important devices for optical fiber communication and all-optical signal processing. Waveguide-type laser amplifiers are proposed to be constructed in 1 at.% Nd doped Yittrium Gallium Garnet crystalline thin films deposited on Yittrium Aluminium Garnet substrates. The amplifiers are classified into a traveling wave (TW)type and a Fabry-Perot(FP)cavity-type. Numerical calculations of gains, SN ratios and pulse response of the optical signal for both amplifiers are carried out using the rate equations for a four-level system of Nd ions in the garnet thin-film with a thickness of about 2.5 µm. For the TW-type amplifier, the net gain and SN ratio are about 10 dB and 20 dB at the signal power of 10-6 W and the pumping power of 210-4W. For the FP-type amplifier, the net gain at the signal power of 10-7W and the pumping power of 10-4W is twice that for the TW-type amplifier. The net gain and SN ratio are 6 dB and 8 dB. Numerical calculations of the pulse response of the optical signals are carried out. The rise and fall times of the output pulse for the TW- and FP-type amplifiers are about 0.01 ns and 1 ns, respectively.

The higher a social mission of computer systems becomes, the more important developing highly reliable computer softwares becomes. During the testing phase in the software development, a developed software is repeatedly tested with a lot of test cases to remove latent software errors. Using the observed test data, it is of great interest to evaluate reliability for the developed software. In this paper, we propose and investigate a software reliability growth model for software error detection phenomena in the software testing. The useful software reliability measures are derived from the model. Using the number of test runs as the unit of software error detection period, the model is described by a nonhomogeneous Poisson process in which the random variable is the cumulative number of software errors detected by the testing. The model proposed here considers that the testing efficiency is geometrically decreasing with the progress of software testing. We apply this model to a set of actual software error data and illustrate the statistical inferences based on a method of maximum likelihood. Finally, an optimum software release problem using software reliability index is discussed as a practical application of the model.

This letter derives frequency dependent Lyapunov equations for the 2-D observability and controllability Gramians which are the most important matrices in the study on the structural property of 2-D systems. These equations provide a new and efficient method to compute the 2-D Gramians.

In this paper we propose a new model for real-time programs. In the model a set of concurrent processes executed by a time-shared single processor interacts with a set of input tapes and a set of output tapes representing their environment. Processes access their tapes through reading heads and writing heads. The distinctive feature of our model is the way the movement of heads is controlled. Their movement is not controlled by programs. Instead, they move unidirectionally scanning the tapes according to the flow of time. Stimuli for a process (responses by a process) are modeled as a sequence of symbols, representing data, interspersed with sequences of the special symbol representing time intervals separating successive stimuli (responses). Next, for the model, we define important properties of real-time programs including data overrun, deadlock and correctness, and show an example of verification of these properties for a small and typical real-time program.

In the present paper, procedures for extracting nucleoli from leukocyte images are proposed. Main processed procedures consist of the filtering operation in the frequency domain, the edge preserving smoothing, the extraction of the nuclear region, the edge detection and the decision of nucleolar regions. By applying proposed procedures, nucleoli can be extracted easily and precisely from the nucleus if we can clearly see nucleoli with human eyes. We were able to achieve the correct discrimination of 82 percent of nucleoli in immature leukocytes.

There has been a rapid traffic volume increase in packet switched networks due to the recent data communication growth. Consequently, the ease with which networks are capable of expanding to keep pace with this increase has become an important consideration. In this paper, a comparison is made of the hierarchical and non-hierarchical network configurations which may serve as possible methods for readily accommodating this increasing network expansion. A special developed simulation providing essential simulation analyses confirms that the hierarchical network offers the most promising approach to this problem from the viewpoints of cost effectiveness and network maintenance.

This paper presents a method for implementing the testing and realization of three-valued majority functions by using properties of 02-complete monotonicity which is an extended concept of complete monotonicity in binary logic. It is shown that reduced functions of three-valued majority functions are 02-completely monotonic, and all 7 or less variable three-valued logical functions satisfying the M(1) majority condition are three-valued majority functions if two-valued input three-valued output functions obtained by taking out only output values for 02-input vectors are 02-completely monotonic. For the realization of majority functions, m-variable inequalities are defined from 02-complete monotonicity. The weight vector is determined by solving weight inequalities derived from m-variable inequalities, and then thresholds are obtained. The overall algorithm of the method is given along with an example.

A new dynamic image processing technique is proposed for measuring the velocity-field of the translational motion of crowded particles. The local velocity at a target pixel-site is estimated by mutual-correlation analysis between the temporal brightness change of the target pixel and that of neighbouring pixels. The next-nearest 16 pixels are selected as the neighbouring pixels in this study. The direction and the speed of the particle motion are evaluated by the mutual-correlation function having maximum value and the lag time of the function, respectively. The usefulness of the proposed technique is examined by a simulation experiment (unidirectional motion) and an actual scene analysis (vortex motion). Obtained velocity-field of these motions are visualized with orientated lines, and the resulting fields are consistent with expected fields.

In this coding scheme for delta modulation of color still pictures, either of two reference regions is selected on a pel by pel. In comparison with fixed region scheme, average color differences can be decreased by approximately 30% in exchange for about 0.5 bit/pel overhead caused by selecting codes.

A segmentation-free learning recognition system for binary signals has been constructed by using a cellular automaton array, known as a max-product cellular automaton array. Each cellular automaton has transition functions concerning activities, similarities, and inner states. Learning is carried out by the linearly reinforcement method of the inner states. The activity is transferred from the left neighbor cells to the right neighbor cells. Terminal decisions for categories are given by outputs of categories in the case that the activity of the output cell has the maximum value. Also, another system for analogue signals has been constructed. A coefficient of separation is introduced in order to separate analogue signals. Experiments by computer simulation gave good results for both systems.

This paper gives a hierarchical property on the number of reversals of real-time counter machines. That is, we show that for any k1, a real-time counter machine with 2k+1 reversals is more powerful than one with k reversals.

A simple method is proposed for estimating the orders of ARMA processes for which the autocorrelations are given. Main efforts are made to estimate the AR order by applying the fast algorithm to solve non-symmetric Toeplitz equations. Numerical examples show the advantages of the method.

This paper discusses the response time problem for concurrent processes sharing resources which are granted according to an FCFS strategy. The problem is shown to be NP-hard, but when less than four resources are shared, a restricted case is shown to be solvable in linear time.

Natural quartz jacketed fibers showed a larger OH loss increase due to diffused H2 than synthesized silica jecketed fibers. This additional OH loss increased with an increase in the drawing temperature and a decrease in the drawing speed in the former, although it was not changed by the drawing conditions in the latter. From this result, it was estimated that impurities which diffused from the natural quartz into the core glass during the drawing process were related to the large OH loss increase.

GaInAs/InP MOSFETs were fabricated by organometallic vapor phase epitaxy (OMVPE) for the first time to obtain an effective channel mobility of 900 cm2/Vs comparable to the best data by other growth techniques. For the MOS structure, a native oxide layer was formed by low-temperature (220) oxidation technique using water. Due to potentially high uniformity, OMVPE MOSFET technique could be very attractive in the optoelectronic integrated circuits(OEIC) for optical communication.

In this letter, an economical VLSI switch MWS is proposed. MWS is constructed using a large amount of normal speed RAM and provdies sufficient switching capacity without high speed devices or technology.

A simple power spectral calculation formula for a digitally modulated carrier signal is derived by modifying the method for a baseband signal previously proposed by Yasuda and Inose. Some computed examples based on the proposed formula are presented to show its effectiveness.

A new switching gate called a kinetic momentum quantum transition device is proposed. The device is composed of two SQUIDs; one is a guantum flux generator and the other is a flux detector. The two SQUIDs are magnetically coupled with each other. The principle of operation is based on the quantized effective flux generated by the SQUID with a small inductance (LI0φ0) and detected by the other SQUID. The device operations were demonstrated experimentally using the fabricated coupled SQUIDs having lead-alloy Josephson junctions. The experimental results were analysed quantitatively using the proposed model for devices. The input-output chracteristics of the device showed step-function-like nonlinearity resulting in a very high current gain. The input and output are well separated from each other. Because of the small necessary inductances, the device-size is one tenth smaller than usual SQUID gates.

The construction method for ladder filters employing piezoelectric ceramic resonators, widely used in consumer radio communication equipments, is investigated with the object of obtaining low-cost high-performance filters. For the presented method, the resonant or antiresonant frequencies of the resonators included in a filter are staggered one after another, perceiving that a small difference in these frequencies between electrically adjacent resonators can be tolerated. The allowable frequency limits for this filter are about four times as great as those for a usual filter, designed using the image parameter or near-image parameter method. The filter can exhibit performances equal to the usual filter. The frequency adjustment process for resonators is able to be fairly well curtailed. Filters based on this construction method include ceramic filters for CB transceiver and pocket-bell receiver, which were designed and trially produced. As a result, low-ripple filters with rough frequency adjustment at most were obtained.