This letter considers a subclass of t-symmetric error correcting/all unidirectional error detecting (t-SyEC/AUED) codes in which the information is represented in an m-out-of-k coded form, which thus can be regarded as virtually systematic for practical purposes. For t3, previous researchers proposed methods for constructing codes of this subclass which are either optimal or of asymptotically optimal order. This letter proposes a new method for constructing, for any values of t, m and k, codes that are either optimal or of asymptotically optimal order. The redundancy of the obtained code is of the order tlog2k bits when mt.

A laser/microwave method using two lasers of different wavelengths for carrier excitation is proposed to evaluate Si surfaces. These constitute a He-Ne laser (wavelength=633 nm, penetration depth=3 µm) and a YAG laser (wavelength=1060 nm, penetration depth=500 µm). Using a microwave probe, the amount of excited carriers can be detected. The carrier concentration is mainly dependent on the condition of the surface when carriers are excited by the He-Ne laser, as well as on the condition of the bulk region when carriers are excited by the YAG laser. Microwave intensities detected under the He-Ne and the YAG lasers illumination are referred to as the surface-recombination-velocity-related microwave intensity (SRMI) and the bulk-related microwave intensity (BRMI), respectively. The difference between SRMI and BRMI is called relateve SRMI (R-SRMI), and is closely related to the condition of the surface and surface active region. We evaluate the surfaces of the samples after plasma and wet etching to remove the photoresist layer. And we evaluate the surfaces of the samples after heat or HF treatment which is done to recover the damage introduced by plasma etching. It was found that the R-SRMI method is better suited to surface evaluation than conventional lifetime measurements.

Isotope dilution secondary ion mass spectroscopy (ID-SIMS) using 30Si as a spike is investigated as a quantitative analysis method for trace amounts of Si. For a standard solution of Si, the relateve standard deviation of results using this method is 5% for 0.2 µg Si, and the determination lower limit is 18 ng. Using this method, the amount of Si deposited on the Ge(100) surface by the self-limited adsorption of SiH2Cl2 is determined to be about 1.00.2 monolayer.

Surface damage to n-type silicon wafers induced by Reactive Ion Etching (RIE) with CF4 gas was evaluated using X-ray photoelectron spectroscopy (XPS) and the current-voltage (I-V) characteristics of Au/n-Si Schottky diodes fabricated on the damaged surface. The reaction products (SiF, SiF2, and SiF3) in the damaged layer were detected by XPS. Assuming the surface damage on a silicon wafer induced by RIE acts as a donor, the donor density was found to be about 21019 cm-3. The distribution of SiF3 and the donor density in the depth direction were almost equal. The thickness of the damaged layer was about 15 nm. These findings suggest that the donor in the damaged layer on a silicon surface induced by RIE may be SiF3.

Diffusion of phosphorus impurities from a polycrystalline silicon films into a silicon substrate was investigated as a function of the mean concentration of phosphorus in a polycrystalline silicon film at the first diffusion stage. We presented that good control of the redistribution of implanted phosphorus impurities was possible by optimizing the normalized dose, which is the value: [the total dose of phosphorus impurities]/[the polycrystalline silicon film thickness], in the case of samples both with and without an arsenic doped layers. In the range where the normalized dose was less than 1.52.51020 cm-3, deeper junctions were formed in samples with an arsenic doped layer. In the range where the normalized dose was more than 1.52.51020 cm-3, however, deeper junctions were formed in samples without any arsenic doped layer rather than in samples with an arsenic doped layer. These results mean that formation of the junction in the device structure where a high concentration phosphorus doped polysilicon layer is stacked on to the high concentration arsenic layer embeded at the surface of the substrate can be restricted by optimizing the normalized dose. Moreover, a trade-off relationship between suppressing phosphorus diffusion and maintaining low contact resistance against normalized doses was also observed.

Runlength-limited block codes are investigated. These codes are useful for storing data in storage devices. Since most devices are not noiselss, the codes are often required to have some error-control capability. We consider runlength-limited codes that can correct or detect unidirectional byte errors. Some constructions of such codes are presented.

A specification formalism for business application software is presented. Our approach is to investigate specification documents which are actually used in development projects of business applications in banking, insurance, and government systems. Since the specification documents are prepared mainly for users' review for the developing software, the representation of the documents is designed to be easy to understand for users, only in business terminology without losing a certain level of formality. Also, to avoid redundancy of the specification, there are some implicit assumptions in the specification. We have analyzed some commonality of these assumptions hidden in specification documents and are trying to construct a language by formalizing the underlying system model.

A novel harmonic retrieval algorithm is proposed in this paper based on Hopfield's neural network. Frequencies can be retrieved with high accuracy and high resolution under low signal to noise ratio (SNR). Amplitudes and phases in harmonic signals can also be estimated roughly by an energy constrained linear projection approach as proposed in the algorithm. Only no less than 2q neurons are necessary in order to detect harmonic siglnals with q different frequencies, where q denotes the number of different frequencies in harmonic signals. Experimental simulations show fast convergence and stable solution in spite of low signal to noise ratio can be obtained using the proposed algorithm.

This paper describes a new metric for evaluating the cost effectiveness of software reviews. The proposed metric is based on the degree to which costs needed for detecting all faults from software are reduced by software reviews in a project. The metric can be interpreted as combining two conventional metrics proposed by Fagan (1976) and Collofello and Woodfield (1989). As the proposed metric is normalized by virtual testing cost, we can compare the values of it among any different kind of projects. Using an experimental evaluation of the conventional metrics and the proposed metric for data collected in an industrial environment, we show the validity and usefulness of the proposed metric. In addition, we present a method to estimate a value of the proposed metric by using only the values which can be computed during the software reviews.

A hybrid integrated optical module composed of a silica-based planar lightwave circuit (PLC), a laser diode with an integrated monitor-photodiode, and a pin-photodiode is fabricated for use in high-performance, compact and cost-effective fiber optic subscriber systems. Its applicability to a wavelength-division-multiplex (WDM) system with a 1.3-µm bi-directional signal and a 1.5-µm one-way signal is demonstrated. The PLC was fabricated by a combination of flame hydrolysis deposition (FHD) and reactive ion etching (RIE), and it simultaneously achieved 1.3-µm/1.5-µm multi/demultiplexing and 1.3-µm Y-branching functions. The optical module exhibited insertion losses of 4.1dB at 1.31µm (including a Y-branch circuit loss of 3dB) and 0.5dB at 1.53µm. An optical output power of more than -4dBm was obtained from the optical module and the crosstalk was sufficiently low at less than -20dB between wavelengths of 1.3µm and 1.5µm. Temperature cycle tests on the optical module showed reliable and stable operation with an optical power fluctuation of less than 0.3dB for 500 cycles.

We study the most appropriate network architecture for constructing FTTH (Fiber To The Home) networks. We conclude that the Single Star network is the most advantageous for supporting the various services required by subscribers who use broadband signal such as B-ISDN (Broadband-Integrated Services Digital Network). We also study high fiber count cable and low-loss connector which are needed for this network and clarify their requirements. We also show the cable structure, connector structure and connection loss reduction method, which satisfy these requirements. We describe a 4,000-fiber cable with a new structure, a 1,000-fiber one-touch connector, a 40-fiber unit connector and TEC-fiber (Thermally-diffused Expanded Core fiber) which reduces connection loss.

This paper first discusses the software reusability-based development process in a lifecycle and reusable objects modification process called differentiation. Next, the supporting environment is described. Both the method and the environment allow developers to carry out requirement definitions, specification and implementation in a reusable way. Some quantitative evaluations are given about how productivity and quality have been improved by using this method and environment, based on a number of case studies made on development projects. Reusability has been largely improved by differential specification, and adjustment method and a direct transformation capability.

Fiber-optic subscriber loops are beginning to be constructed worldwide as an infrastructure for the 21st century. Making the most of the superior transmission capabilities of optical fiber cable, high-speed and broadband services such as so-called Broadband-ISDN (B-ISDN) services are expected to be achieved. We review current trends in fiber-optic systems and discuss how fiber-optic subscriber loops should be implemented from the points of view of services and technology. First, prospective services offered over fiber-optic subscriber loops and resulting requirements for such loops are presented. Various kinds of services produced through fiber-optic subscriber loops will further develop the information-oriented society and have a major influence not only on the industrial world but on family life as well. Next, basic concepts of totally fiber-optic subscriber loops and proposals for shifting from the existing metallic cable network to totally fiber-optic subscriber loops are discussed. In this regard, we must consider the advantages of optical fiber cables and improve upon the disadvantages of the existing metallic cable network. In particular, a Digital Loop Carrier (DLC) system or a Passive Double Star (PDS) have been proposed to shift from the existing metallic cable network to totally fiber-optic subscriber loops effectively and economically. Finally, line configuration topology and latest fiber-optic technologies such as high-count cable, construction techniques and operation systems for use in achieving totally fiber optic subscriber loops are shown. We believe a single star configuration is the most appropriate for totally fiber-optic subscriber loops.

We report on 1N branching devices for fiber-optic networks. A novel Y-pattern mask for loss reduction in branching waveguide has been investigated based on simulation. 18 branching waveguides fabricated by ion-exchange proved that the scattering loss at the branching region made with novel Y-pattern is reduced considerably. Pigtailing technique has been developed using glass fiber arrays (FAs). The fibers in FA are aligned precisely, so that all fibers can be easily and precisely put into alignment with the output ports in a branching waveguide chip at the same time. A glass plate is used for reinforcement which improves mechanical and thermal stability of the device. Reliability of packaged devices is being strongly demanded. Various reliability tests have been performed with packaged 18 branching devices and those results are presented.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.

In this paper, a new M-estimation technique for the linear prediction analysis of speech is proposed. Since in the conventional linear prediction (CLP) method the obtained estimates are very much affected by the large amplitude residual parts, in the proposed method we use a loss function which assigns large weighting factor for small amplitude residuals and small weighting factor for large amplitude residuals which is for instance caused by the pitch excitations. The loss function is based on the assumption that the residual signal has an independent and identical t-distribution t(α) with α degrees of freedom. The efficiency of this new estimator depends on α. When α=, we get the CLP method. When the proposed method with small α is applied to the problems of estimating the formant frequencies and bandwidths of the synthetic speech by finding the roots of the prediction polynomial, we can achieve a more accurate and a smaller standard deviation (SD) estimate than that with large α. When the signal is very spiky, the proposed method can ahieve more efficient and accurate estimates than that with robust linear prediction (RBLP) method. The loss function is modified in the similar manner as the autocorrelation method. The solution is calculated by the Newton-Raphson iteration technique. The simulation results show that only few iterations are needed to reach a stationary point, the stationary point is always a local minimum and the obtained prediction filter is always minimum phase. Preliminary experiments on the human speech data indicate that the obtained results are insensitive to the placement of the analysis window and a higher spectral resolution than the CLP and RBLP method can be achieved.

This paper describes on the transmission properties of the superconducting coplanar waveguide on LiNbO3 (LN) substrates, fabricated by YBa2Cu3Oy (YBCO) superconducting films. The films have been prepared by the reactive co-evaporation method and patterned by a wet etching process. The surface resistance of the obtained film was 0.04 Ω at 18 GHz and 77 K. It was confirmed from X-ray diffraction (XRD) that these films were highly oriented to the direction of c-axis without a secondary phase. The microwave transmission properties of these YBCO coplanar waveguides were investigated at frequencies up to 20 GHz and compared with that of the aluminum coplanar waveguide. The characteristic impedances of both coplanar waveguides were designed to be 50 Ω. It was found that the attenuation constants of these samples at 77 K were less than that of the aluminum coplanar waveguide for frequencies below 18 GHz.

We have fabricated superconducting microwave passive components such as resonators, bandpass filters and delay lines with YBCO thin film conductors deposited on MgO substrates. Considerably high unloaded Q values of 12000 at 5.5 GHz was obtained with the YBCO microstrip resonator at 77 K, which indicated that the surface resistance of the YBCO thin film was 0.79 mΩ at that frequency and temperature. Excellent microwave properties were also demonstrated with the bandpass filter and the delay line. Considerably low insertion loss of about 1 dB was obtained with the 10 GHz YBCO bandpass filters at 77 K which have a various bandwidth from 0.5% to 10%. Also excellent microwave propagation was obtained with a 1.3 nsec YBCO coplanar delay line. Its insertion loss was less than 1 dB for the frequencies up to 4 GHz.

Low temperature experiments have been made to demonstrate the operation of LiNbO3 optical modulator with superconducting electrodes. The operation of the modulator for applied dc signals as well as microwave signals in the frequency range between 8 GHz and 12 GHz has been observed at temparatures as low as 4.2 K. The present results indicate a possibility of realizing high performance LiNbO3 optical modulators employing superconducting electrodes.

Thin-film YBCO Josephson junctions were successfully fabricated by a pulsed excimer laser ablation, and the mixing experiments in the microwave region (820 GHz) were carried out at the temperature of 77 K. The IF output maximum was obtained at the bias voltage midway between the zero and the first Shapiro steps for the fundamental mixing. For the 2nd harmocic mixing, the IF output maximum was obtained at a zero bias voltage, and the conversion efficiency was -14 dB at the microwave frequency of 18 GHz. These results strongly suggest that the fabricated thin-film Josephson junctions work well at the temperature of 77 K as detectors and mixers in the microwave regions (820 GHz).