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.

We show that under some conditions an attacker can break the public-key cryptosystem proposed by J. Schwenk and J. Eisfeld at Eurocrypt '96 which is based on the difficulty of factoring over the ring Z/nZ [x], even though its security is as intractable as the difficulty of factoring a rational integer. We apply attacks previously reported against RSA-type cryptosystems with a low exponent to the Schwenk-Eisfeld cryptosystem and show a method of breaking the Schwenk-Eisfeld signature with a low exponent.

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.

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.

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.

The showering arc waveforms generated when contact is being separate have poor reproducibility whose causes are not sufficiently clear. This paper describes that the contact surface conditions which change with the number of contact operations are deeply related to the showering arc waveforms. First, it is experimentally shown that the contacts' surface roughness increases with the number of contact operations, and the growth model of contact surface roughness is proposed based on the change of contact resistance for the number of contact operations. Second, the growth model of molten metal bridge is proposed based on the fact that the showering arc waveforms change with the number of contact operations and the evaluation indexes of showering arc are proposed.

This paper presents a design approach for developing MU-type single-mode miniature optical connectors featuring 1. 25 mm diameter zirconia ferrules. They are smaller and have a higher packaging density than conventional optical connectors. The ferrule pitch is 1/2, the plug volume 2/5 and the cross-sectional area 2/5 that of the SC connector. The aim of our approach is to reduce the ferrule size and to realize durable connectors. With 10/125 SM fibers, these MU connectors produced an average insertion loss of 0. 07 dB and an average return loss of 49. 4 dB, and there was no degradation during or after mechanical and environmental tests.

The alloy of Ag (40wt%)-Pd(60wt%) has been used in the electrical contacts of electromechanical devices due to its superior contact properties. There is currently, an increasing trend to decrease the size of electromechanical devices. However, it has been difficult to obtain a high contact force and the high restoring force of contacts, and these problems cause contact failures such as high contact resistance. In response to this problem, the alloy is overlaid with an Au layer which is not affected by oxide films. However, when the contacts are subjected to an unacceptable amount of mechanical shock, adhesion of the Au overlay occurs easily. In order to solve these difficulties, it can be proposed to cover the contact surface with high electric conductive oxide films. With this concept, the Au overlay should be unnecessary. In the present study, to reduce the high contact resistance of the Ag-Pd alloy contaminated with an oxide film, very small amounts of Mg and Cr were used in separate doping trials to the alloy. The improvement of contact resistance characteristics is the focus of the present study. Specimens of Ag (40wt%)-Pd(60wt%), Ag-Pd-Mg(0.1, 0.5 and 1.0wt%), and Ag-Pd-Cr(0.1 and 0.5wt%) were oxidized at elevated temperatures to accelerate the process of oxidation, and the growth kinetic law of oxide films grown on the surfaces were evaluated by ellipsometry. The effect of the oxide film on the contact resistance characteristics were then clarified. A marked improvement of the contact resistance caused by the oxide film was found for the Ag-Pd alloy with a Mg doping agent. However, for the Cr doping agent, a low contact resistance was not obtained as same as the Ag-Pd alloy itself.

Gold on connector contacts is superior in environmental resistance. However, pores existing gold film are source to trigger the corrosion reaction between gold and base metal. For examination of the contacts, it has been popular to apply "Salt Spray Test" and "Sulfur Dioxide Test. " There are some differences of the corrosion products between two tests. Main metal forming the product in Salt Spray is Copper, and main metal in Sulfur Dioxide is Nickel. To investigate the reason, we tried to employ an electro-chemical method. As a result, it was found that there was the difference between the respective galvanic cell combinations generated through pores.

The tape deformation due to such particles as wear debris and dust in the head/tape contact region is one of the main causes of the signal quality deterioration in magnetic tape devices. Thus it is significant to make clear the tape deformation due to a particle for realizing higher recording densities. This paper investigates the tape deformation profile generated by a particle through an interferometric experiment and a simulation using a point loaded tape model. A rather good agreement between them is obtained, thereby the simulation is verified appropriate to estimate the tape deformation due to a particle. This paper also describes the relationship between the spacing loss and the particle height, considering the tape deformation profile obtained from the simulation. In addition, the influence of the particle height on the width of the tape deformed area is estimated, which can make a basis of the design of error correction code.

It is well known that the existence of electrically resistive film layers formed on contact surfaces increases contact resistance and it causes a nonlinear relationship between voltage and current observed in a contact layer. Nonlinear distortion voltages can be detected by our sensitive detection system based on the dual frequency method when a thin film exists on the surface. In this study, multilayer films of polyimide (PI) was used as an ideal material of ultra thin film, because of electrically good insulator with simple molecular structure, to study non-linearity through metal-insulator-metal contact. The number of deposited layers between one and twenty one were formed on three types of substrates; (a) evaporated gold on a glass plate, (b) gold plate and (c) evaporated gold on gold plate, to obtain good insulating film. Where each layer of PI film has 0. 4 nanometer thickness. A pin contact was made by pressing a bent gold wire on the PI film. It is concluded that [1]; the second-order distortion voltage increases exponentially as the film thickness increases, [2]; polarity of the surface potential of PI depends on the film thickness, and that I-V characteristic depends on the polarity of the surface potential.

Given a binary picture represented by a region quadtree, it is desirable to identify the amount of (rightward and downward) shifts of the foreground components such that it gives the minimum number of nodes of its quadtree. This problem is called "quadtree normalization. " For this problem, it is unknown whether there exists a linear time algorithm with respect to the size of given images (i. e. , the number of pixels). In this study, we investigate the "one-dimensional version" of the quadtree normalization problem, i. e. , given a binary string represented by a regional binary tree, the task is to identify the amount of (rightward) shift of the foreground components such that it gives the minimum number of nodes of its binary tree. We show that there exists a linear time algorithm for this version.

We introduce a subclass of context-free languages, called pure context-free (PCF) languages, which is generated by context-free grammars with only one type of symbol (i. e. , terminals and nonterminals are not distinguished), and consider the problem of identifying paralleled even monogenic pure context-free (pem-PCF) languages, PCF languages with restricted and enhanced features, from positive data only. In this paper we show that the ploblem of identifying the class of pem-PCF languages is reduced to the ploblem of identifying the class of monogenic PCF (mono-PCF), by decomposing each string of pem-PCF languages. Then, with its result, we show that the class of pem-PCF languages is polynomial time identifiable in the limit from positive data. Further, we refer to properties of its identification algorithm.

Geometric region method is one of the techniques to handle real-time systems which have potentially infinite state spaces. However, the original geometric region method gives incorrect results for the CTL model checking of time Petri nets. In this paper, we discuss the sufficient condition for the geometric region graphs to be correct with respect to the CTL model checking of time Petri nets, and then propose a technique to partition given geometric regions so that the graphs satisfy the sufficient condition. Finally, we implement the proposed algorithm, and compare it with the other methods by using small examples.

An acoustic diagnosis technique for the blower by wavelet transform and neural networks is described. It is important for this diagnosis to detect surging phenomena, which lead to the destruction of the blower. Dyadic wavelet transform is used as the pre-processing method. A multi-layered neural network is used as the discrimination method. Experiment is performed for a blower. The results show that the neural network with wavelet transform can detect surging sound well.

As expert system technology gains wider acceptance in digital system design, the need to build and maintain a large scale knowledge base will assume greater importance. However, how to build a correct and efficient rule base is even a hard part in the knowledge-based system development. In this paper, we develop FARHDL (Frame-And-Rule-based Hardware Description Language) to form a knowledge base. The FARHDL is simple but powerful to specify the hardware requirements and can be directly simulated by PROLOG. Through the knowledge base transformed from FARHDL, a formal method can be developed to design, implement, and validate the digital hardware systems. Furthermore, behavioral properties, anomaly properties, structural properties, and timing properties are applied to analyze the requirements specification. The purposes of those properties are used to detect explicit/implicit incorrect specification clauses and to capture some desired requirements, such as completeness and consistency. Finally, the analysis results can be a useful tool for finding obscure problems in tricky digital system designs and can also aid in the development of formal specifications.

Surface damage of the electrical contact is a primary cause of failure in many electronic devices which use sliding contacts. Therefore, the quantitative observation of the contact surface is one of the most important subjects for improvement of contact reliability. In this study, in order to clarify the relationship between the contact resistance and the damage on the contact surface, a digital image measuring system (DIMS) was developed. A shadow image processing technique (SIPT) was applied to the damage analysis on the sliding contact surface. The damage width on the contact surface and the damaged image could be obtained with a 3-D graphic image by applying both DIMS and SIPT. Part of the relationship between the damage on the contact surface and the contact resistance could be obtained in the case when Cu is used for the moving contact and Cu and Ni are used for the static contact.

Noise cancelation and system identification have been studied for many years, and adaptive filters have proved to be a good means for solving such problems. Some neural networks can be treated as nonlinear adaptive filters, and are thus expected to be more powerful than traditional adaptive filters when dealing with nonlinear system problems. In this paper, two new heterogeneous recurrent neural network (HRNN) architectures will be proposed to identify some nonlinear systems and to extract a fetal electrocardiogram (ECG), which is corrupted by a much larger noise signal, Mother's ECG. The main difference between a heterogeneous recurrent neural network (HRNN) and a recurrent neural network (RNN) is that a complete neural network is used for the feedback path along with an error back-propagation (BP) neural network as the feedforward one. Different feedback neural networks can be used to provide different feedback capabilities. In this paper, a BP neural network is used as the feedback network in the architecture we proposed. And a self-organizing feature mapping (SOFM) network is used next as an alternative feedback network to form another heterogeneous recurrent neural network (HRNN). The heterogeneous recurrent neural networks (HRNN) successfully solve these two problems and prove their superiority to traditional adaptive filters and BP neural networks.

This letter newly proposes the polarity-reversing type photonic receiving scheme based on bipolar correlation for optical CDMA signal in radio highway. The proposed scheme can more improve the limitation of the number of radio base stations connected to radio highway and more reduce the peak laser power at the radio base station than the conventional unipolar type receiving scheme using prime codes.

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.