In this paper, we will report on a fiber optic oxygen sensor using fluorescence and its application to clinical examinations. It is based on fluorescence quenching. The quenching ratio of fluorescence is proportional to oxygen partial pressure by Stern-Volmer's formula in which oxygen concentration is estimated from measured emission intensity. We fabricated a microscopic luminous probe using a Solvent Green 5 doped plastic optical fiber coupler. The probes were demonstrated to have certain advantages for example they can be operated in both liquid and gas phases. And also, they are stable to pH and flow velocities. As a clinical application, the probe can reliably measure oxygen concentrations of whole blood in vivo. Moreover, we have clarified various characteristics of this probe.

Given a Petri net N=(P, T, E), a siphon is a set S of places such that the set of input transitions to S is included in the set of output transitions from S. Concerning extraction of one or more minimal siphons containing a given specified set Q of places, the paper shows several results on polynomial time solvability and NP-completeness, mainly for the case |Q| 1.

An evolutionary algorithm is used to evolve a digital circuit which computes a simple hash function mapping a 16-bit address space into an 8-bit one. The target technology is FPGA, where the search space of the algorithm is made of the combinational functions computed by cells and of the interconnections among cells. The evolutionary technique has been applied to five different interconnection topologies, specified by neighbourhood graphs. This circuit is readily applicable to the design of set-associative cache memories. Possible use of the evolutionary approach presented in the paper for on-line tuning of the function during cache operation is also discussed.

This paper presents a new approach to designing arithmetic circuits by using a graph-based evolutionary optimization technique called Evolutionary Graph Generation (EGG). The key idea of the proposed method is to introduce a higher level of abstraction for arithmetic algorithms, in which arithmetic circuit structures are modeled as data-flow graphs associated with specific number representation systems. The EGG system employs evolutionary operations to transform the structure of graphs directly, which makes it possible to generate the desired circuit structure efficiently. The potential capability of EGG is demonstrated through an experiment of generating constant-coefficient multipliers.

Various I/O interface technologies in today's PC platform are classified into four categories, (1) ASIC (memory Controller) from / to Main Memory, (2) MPU from /to ASIC (Memory Controller), (3) ASIC (Memory Controller) from / to ASIC (Graphic Controller) and (4) ASIC from / to Peripherals. As to Category 1, effectiveness of SSTL is shown in DIMM application of SDRAM and DDR SDRAM over 100 MHz frequency. Furthermore a comparison is made between SLDRAM and D- RDRAM from the technology point of view. Concerning Categories 2 through 4, several interfaces such as PCI, AGP, GTL, HSTL and LVDS are reviewed. Interface technologies will keep playing an important role since computer systems require higher and higher speeds.

The Conjugate Residual method, one of the iterative methods for solving linear systems, is applied to the problems with a dense coefficient matrix on distributed memory parallel computers. Based on an assumption on the computation and communication times of the proposed algorithm for parallel computers, it is shown that the optimal number of processing elements is proportional to the problem size N. The validity of the prediction is confirmed through numerical experiments on Hitachi SR2201.

For advanced data-oriented applications in distributed environments, effective information is frequently obtained by integrating or merging various autonomous information sources. There are many problems: how to search information sources, how to resolve their heterogeneity, how to merge or integrate target sources, how to represent information sources with a common protocol, and how to process queries. We have proposed a new language, QUIK, as an extension of a deductive object-oriented database (DOOD) language, QUIXOTE, and extend typical mediator systems. In this paper, we discuss various features of QUIK: programming capabilities as integrating an exchange model and mediator specifications, merging subsumption relations for maintaining consistency, searching alternative information sources by hypothesis generation, and identifying objects.

In a DC 50 V/3.3 A circuit, the spatial distributions of the spectral intensities of breaking arcs near the cathode for silver contacts were measured on the contact surfaces of three different shapes: flat and spherical (1 mm radius and 2 mm radius) and the arc temperature and the metal-vapor quantity were calculated from the spectral intensities. The influence of the contact shape on the arc temperature and the metal-vapor quantity were also examined, as well as the arc tracks on the contact surfaces and the gain and loss of the contacts. Findings show the distributions of spectral intensities are non-symmetrical from the beginning to the extinction of the breaking arc for the flat contact: However, they are symmetrical in the latter half of the breaking in spite of the number of breaking arcs and the shape of contact surface for the spherical contact. The relationship between the area of the arc tracks on the cathode and the shape of contact surface is the same as the relationship between the existent areas of measured spectra and the shape of the contact surface. For the spherical contacts, the arc temperature and the metal-vapor quantity are affected a little by the radius of the curved of contact surface and the number of breaking arcs. However, the longer the arc duration, the higher the metal-vapor quantity is in the latter period of the breaking arc. For the flat contacts, the metal-vapor quantity is lower than those for the spherical contacts. The gain and loss of the contacts are less and the arc duration is shorter for the flat contact than for the spherical contact.

The distributions of a spectral intensity of the breaking arc between silver contacts in DC 45-66 V/2.5-5.0 A circuits have been measured using a high-speed color video. As a result, a cathode brightening spot, which has a high spectral intensity, exists near the cathode surface. The cathode brightening spot expands with the increase of the contact gap, but its length expands until about 18µm. When the contact gap spreads over about 180 µm, a dark positive column appears and grows between the cathode brightening spot and the anode surface. The higher the interrupted current is, the larger the diameter of the cathode brightening spot will be. The maximum diameter of cathode brightening spot is 500 µm under these experiments.

The field profile and effective index of a rib waveguide are calculated using an improved semivectorial beam-propagation method using the imaginary-distance procedure. Convergence behavior of the effective index is compared with that obtained by the conventional Crank-Nicholson scheme and with that derived from a Bierwirth-type formula, demonstrating the effectiveness of the present method. Field discontinuities at the interface between different materials are clearly displayed.

Mechanical prosthetic cardiac valves generate not only the widely recognized audible closing clicks but also ultrasonic closing clicks, as previously reported by us. A personal-computer-based measurement and analysis system with the bandwidth of 625 kHz has been developed to clarify the characteristics of these ultrasonic closing clicks. Fifty cases in total were assessed clinically, including cases with tilting disk valves, bileaflet valves, and flat disk valves. The ultrasonic closing clicks are damped vibrations continuing for about two milliseconds, and their frequency range was confirmed to be from 8 kHz to 625 kHz, while that of the audible click was up to 8 kHz. Although the sensitivity of the sensor decreased by approximately 30 dB at 625 kHz, effective power of the ultrasonic closing click was confirmed at this frequency. Moreover, it was shown that, surprisingly, the signal power at 625 kHz was still at the same level as that at around 100 kHz. Those wide bandwidth signal components exist independent of the type of mechanical valve, but the spectral pattern shows some dependence on the valve type.

We have developed a half-duplex spread spectrum-direct sequence (SS-DS) 2. 4 GHz band transceiver (T/R) unit having a smaller size and lower power consumption. A highly efficient elastic SAW convolver with chirp interdigital transducers (IDTs) has been used in the correlation circuit of receiver unit. The code shift keying (CSK) modulation is used in the T/R unit. The size of T/R unit is 90 50 11 mm and the weight is 75 grams. The power consumption of T/R unit is 1. 4 watts. We found that the bit error rate (BER) was less than 10-6 over the range of 0-150 m outdoors and 0-80 m indoors without a digital error detection and correction method. In this case, the data rate was 102 kbps and the transmit RF power was 2. 5 mW/MHz. The electrical characteristics, anti-interference and anti-multipath fading were also evaluated.

The development of a far-infrared imaging system based on ultrafast THz time-domain spectroscopy has opened a new field of applications of femtosecond technology. We describe the principle of this new imaging technique and report recent progress to augment the possibilities of "T-ray" imaging. These include sub-wavelength-resolution near-field imaging and three-dimensional tomographic reconstruction of a samples refractive index profile.

It is well known that M-ary/spread spectrum (M-ary/SS) system is superior to direct-sequence spread spectrum system under AWGN, and can achieve high spectral efficiency. On the other hand, however, the main drawback of this system is that the synchronization acquisition is difficult. In this paper, we propose a new synchronization acquisition method of M-ary/SS system. This method acquires the code synchronization by introducing a symmetrical property in spreading sequences, and detecting this property with the differential decoding technique. As spreading sequences, a set of orthogonal sequences and a set of non-orthogonal sequences are considered. The strong features of proposed systems are that the systems can acquire the code synchronization in carrier band and can reduce the complexity of calculation greatly. Among the comparison results of the systems with newly proposed orthogonal and some specific non-orthogonal spreading sequences, it is especially noted that the latter can reduce the mean acquisition time and calculation complexity much greater than the former.

This paper presents a 4-valued content-addressable memory (CAM) for fully parallel template-matching operations in real-time cellular logic image processing with fixed templates. A universal literal is essential to perform a multiple-valued template-matching operation. It is decomposed of a pair of a threshold operation in a CAM cell and a logic-value conversion shared by CAM cells in the same column of a CAM cellular array, which makes a CAM cell function simple. Since a threshold operation together with a 4-valued storage element can be designed by using a single floating-gate MOS transistor, a high-density 4-valued universal-literal CAM with a single-transistor cell can be implemented by using a multi-layer interconnection technology. It is demonstrated that the performance of the proposed CAM is much superior to that of conventional CAMs under the same function.

In a fully depleted (FD) CMOS/SIMOX device, the threshold voltage can be reduced by 0.1 V while keeping the same off current as that of bulk CMOS. This enhances gate speed at low supply voltage so that lowering supply voltage reduces both active and static power consumption without additional circuits. An LSI architecture featuring a low supply voltage for internal gates and an LVTTL interface is proposed. However, to implement the architecture with FD-CMOS/SIMOX devices, there were problems which were low drain-breakdown voltage and half electrostatic discharge (ESD) hardness compared with that of bulk CMOS devices. An LVTTL-compatible output buffer circuit is developed to overcome the low drain-breakdown voltage. Cascade circuits are applied at an output stage and a voltage converter with cross-coupled PMOS is used for reducing the applied voltage from 3.3 V to 2.2 V or less. Using this output buffer together with an LVTTL-compatible input buffer, external 3.3 V signal can be converted from/to 2.0-1.2 V signal with little static current. The cascade circuit, however, weakens the already low ESD hardness of the CMOS/SIMOX circuit. The new ESD protection circuit provides robust LVTTL compatible I/O circuits. It features lateral diodes working as drain-well-diodes in bulk CMOS and protection devices for dual power supplies. A diode/MOS merged layout pattern is used for both to dissipate heat and save area. The CMOS/SIMOX ESD protection circuit is the first one to meet the MIL standard. Using 120 kgate test LSIs made on 300 kgate array with 0.25-µm CMOS/SIMOX, 0.25-µm bulk CMOS and 0.5-µm bulk CMOS, power consumptions are compared. The 0.25-µm CMOS/SIMOX LSI can operate at an internal voltage of 1.2 V at the same frequency as the 0.5-µm LSI operating at 3.3 V. The internal supply voltage reduction scheme reduces LSI power consumption to 3% of that of 0.5-µm bulk LVTTL-LSI.

A 2.4 GHz band direct sequence (DS) spread spectrum (SS) radio frequency modem with a wide bandwidth of 26 MHz in half-duplex system has been newly developed using the small size (832 mm) and highly-efficient (-57 dBm) elastic type of surface acoustic wave (SAW) convolver. The size of SS modem is 905011 mm and the weight is 75 g. The power consumption of SS modem is 1.5 W and data rate is 206 kbps with 63 chips of PN code. Electrical characteristics measurements were made to evaluate the SS modem performance.

Silver is a fundamental material for electrical contact application. In spite of high electrical conductivity and economical advantage, silver surface is corroded easily by environment contained sulfide. A corrosion product as Ag2S deteriorates the property of contact reliability. In order to examine contact reliability, the acceleration tests have been accepted widely in industries. In the present study, the acceleration factor of the contact reliability for the sulfide film on the surface of silver contact which was subject to the tarnish acceleration test was clarified in comparison with the film grown in a normal office environment. The accelerated environment based on the Japan Electric Industry Development Association (JEIDA) standard No.25 was adopted. This environment is consisted of air contained 3 ppm H2S gas under 40, 85-95% RH. The growth rate of the sulfide film (Ag2S) was evaluated by applying the ellipsometry analysis. In the results, it was found that growth of Ag2S film of 500 in thickness in the normal office environment required corrosion time of 3103 h. This thickness of 500 caused increase in contact resistance of 0.1-1.0 (Ω). However, in the accelerated environment, corrosion time decreased to 1.7 h for same thickness. Therefore, the acceleration factor was obtained by comparison of these time as 1.8103 for the standard test of JEIDA.

In this paper, we discuss computational methods for obtaining the bifurcation points and the branch directions at branching points of solution curves for the nonlinear resistive circuits. There are many kinds of the bifurcation points such as limit point, branch point and isolated point. At these points, the Jacobian matrix of circuit equation becomes singular so that we cannot directly apply the usual numerical techniques such as Newton-Raphson method. Therefore, we propose a simple modification technique such that the Newton-Raphson method can be also applied to the modified equations. On the other hand, a curve tracing algorithm can continuously trace the solution curves having the limit points and/or branching points. In this case, we can see whether the curve has passed through a bifurcation point or not by checking the sign of determinant of the Jacobian matrix. We also propose two different methods for calculating the directions of branches at branching point. Combining these algorithms, complicated solution curves will be easily traced by the curve tracing method. We show the example of a Hopfield network in Sect.5.

Numerical simulations for the (3+1)-dimensional optical-field dynamics of nonstationary pulsed beams that propagate down Kerr-like nonlinear channel waveguides are carried out for what is to our knowledge the first time. Time-resolved intrapulse switching due to spontaneous symmetry breaking of optical fields from a quasilinear symmetric field to a nonlinear asymmetric field is analyzed. A novel instability phenomenon triggered by the symmetry breakdown is found.