Force curves obtained from an elastic contact theory are shown and compared with experimental results. In the elastic contact theory, a pin-on-disk contact is assumed and the following interaction are taken into consideration; (i) elastic deformation, (ii) the specific energy of adhesion in the area of the contact, which is expressed as the difference between the surface energies and the interface energy, (iii) the long-range interaction outside the area of contact, assuming the additivity of the Lennard-Jones type potential, and (iv) another elastic term for the measurement system such as the cantilever stiffness of an atomic force microscope (AFM). In the limit when the stiffness is infinite, the theory conforms to Muller-Yushchenko-Derjaguin (MYD) theory. In the limit when the surface-surface interaction is negligible, the theory conforms to the analytical theory by Takahashi-Mizuno-Onzawa. In the limit when the stiffness is infinite and the long-range interaction outside the area of contact is negligible, the theory conforms to Johnson-Kendall-Roberts (JKR) theory. All parameters and all equations are normalized and the normalized force curve is obtained as the functional of only two parameters; (1) the normalized stiffness of the measurement system, and (2) the normalized distance which is used in the expression of the Lennard-Jones potential. The force-displacement plots are converted into force-penetration plots.

This paper describes the fabrication of micro-pipes and their applications to splicing parts and optical switches using single-mode fibers. Micro-pipes having almost the same inner diameter of bare fiber (125 µm) and lengths of around 5 mm are successfully mass-produced by using micromachining technology. We fabricate various kinds of metal pipes such as Au, Cu, Ni, and an FeNi alloy by selecting the appropriate electro-plating bath. We use an Au micro-pipe having a small slitted portion running along its axis (slitted micro-pipe) to splice single-mode fibers. We also use an FeNi alloy micro-pipe to construct a single-mode fiber switch. These new single-mode fiber devices employing micro-pipes show excellent optical and mechanical characteristics. Splicing losses are in the range of 0.2-0.4 dB. The developed 1 2 latching type single-mode fiber switches exhibit a low insertion loss of 0.35 dB, a minimum switching speed of 2 ms with a driving power of 9 mW, and stable operation for more than 108 switchings without damage. A practical application of the developed switch for testing optical devices is also demonstrated.

Digital-switching noise coupled into sensitive analog circuits is a critical problem in large-scale integration of mixed analog and digital circuits. This paper describes noise coupling of this kind, especially, through the substrate in CMOS integrated circuits, and reviews recent technical solutions to this noise problem. Simplified models have been developed to simulate the substrate coupling rapidly and accurately. A method using a CMOS comparator was proposed for measuring the effects of substrate noise, and equivalent waveforms of actual substrate noise were obtained. A circuit tecnique, called active guard band filtering, that controls the noise source is a new approach to substrate noise decoupling. CAD methods for handling substrate-coupled switching noise are making design verification possible for practical mixed-signal LSIs.

This study proposes an amplitude limiting type spread spectrum communication to be applied to extremely low power radio wave communicaion and evaluates capability of the code division multiplex. First, changes in output from the correlation device, maximum power, and in allowable noise power are compared by computer simulation for the case where the number of multiplex channels is increased. Second, possible relationship between noise intensity and error rate is measured by actual loading experiments using a device developed for trial purpose. Third, majority decision logic is proposed for the said device to realize amplitude limiting type code division multiplex easily. When the amplitude is limited, the maximum power can be controlled at about 2 dB, and channels with more than half of the number of spread sign can be used. It is revealed that, in the spread spectrum, alteration of the number of multiplex channels is made easy by application of this method.

A formal system-level synthesis model for the concurrent object-oriented design of parallel computer systems, called Multi-token Object-oriented Bi-directional net (MOBnet), is proposed. The MOBnet model extends the standard Petri net by defining (1) multiple tokens to represent different kinds of synthesis control information, (2) object-oriented nodes (places) to denote the system parts under synthesis, and (3) bi-directional arcs to model the design completion check and synthesis rollback operations. In this paper, we first show that MOBnet can serve as a pre-fabrication design methodology analysis tool in ways such as class hierarchy construction, design specification comparison, reachability analysis, and concurrent process management and analysis. We then formally prove MOBnet to be a valid model for concurrent synthesis and give experimental application examples to verify. Finally, solution schemes for the design completion check and synthesis rollback problems are formally validated by analyzing the dynamic behavior of MOBnet, and experimentally illustrated through examples.

In the information engineering learning environment, there may be more than one solution to any given problem. We have developed CAMELOT using the Nominal Group Technique for group problem solving. This paper describes the collaborative learning system on the Internet using discussion model, the effectiveness of collaborative learning in modeling the entity-relationship diagram within the field of information engineering, and how to apply AI technologies such as rule-based reasoning and case-based reasoning to the pedagogical strategy. By using CAMELOT, each learner learns how to analyze through case studies and how to collaborate with his or her group in problem solving. As a result. We have found evidence for the effectiveness of collaborative learning, such as getting a deeper understanding by using CAMELOT than by individual learning, because they can reach better solutions through discussion, tips from other learners, examination of one another's individual solutions, and understanding alternative solutions using case-based reasoning.

This paper discusses the problems in designing virtual-path (VP) networks and underlying transmission-path (TP) networks using the "self-sizing" capability. Self-sizing implies an autonomous adjustment mechanism for VP bandwidths based on traffic conditions observed in real time. The notion of "bandwidth demand" has been introduced to overcome some of the problems with VP bandwidth sizing, e.g., complex traffic statistics and diverse quality of service requirements. Using the bandwidth demand concept, a VP-bandwidth-sizing procedure is proposed in which real-time estimates of VP bandwidth demand and successive VP bandwidth allocation are jointly utilized. Next, TP bandwidth demand, including extra capacity to cover single-link failures, is defined and used to measure the congestion level of the TP. Finally, a TP provisioning method is proposed that uses TP "lifetime" analysis.

The majority of independent locomotion microrobots pack batteries as their energy source. However, because the energy that can be stored in a battery is proportional to its volume, the operating time becomes shorter as the robot becomes smaller. To solve this problem the energy must be supplied from outside by wireless transmission. We propose a microwave energy transmission system for microrobots in metal piping. Because microwave is rectified and converted in the form of electric energy in this system, we developed a receiving antenna for microrobots in piping and a microwave rectifying circuit to generate high voltage. These were loaded on a microrobot, tested to drive a locomotive mechanism, and the efficiency of the proposed system was confirmed.

Photovoltaic devices capable of generating more than 200 volts with an area of 1 cm2 have been developed for directly driving microactuators such as piezoelectric or electrostatic actuators. The micro-devices interconnect 285 micro cells (unit cell size: about 0.5 mm 2.0 mm) in series, and have an open circuit voltage (Voc) of 207 volts, a short circuit current (Isc) of 36.6 µA, a maximum output power (Pmax) of 4.65 mW and a fill factor (F.F.) of 0.615 under AM (Air Mass) 1.5 and 100 mW/cm2 illumination. This voltage is the highest in the world for the area of 1 cm2. The series connection is precisely processed by a focused laser beam, thereby significantly reducing the area needed for device connections. It has been confirmed that a piezoelectric polymer can be directly driven by the electrical output in evaluating the potential of the devices to be used as a microactuator's power source.

Fiber physical contact (FPC) is proposed and demonstrated as a new method designed to enable fibers to be connected easily with a small structure while maintaining high optical performance. FPC is performed by mating two bare optical fibers in a micro sleeve and fixing them to a holder while they are buckled. Buckling is a phenomenon whereby a long column is bent by compression along its length. PC connection is realized by the buckling force of the fibers themselves and does not require any springs. Optical fiber buckling is studied both theoretically and experimentally. The buckling force, which is determined by an initial span between the optical fiber holding points, remains constant when the span is changed and is useful as the PC force. The buckling amplitude which is determined by the span reduction must be so small that it does not cause excess radiation loss. A suitable span is about 7 mm. This generates a 0.7 N. The allowed span reduction is 0.1 mm. This results in a buckling amplitude of 0.64 mm which prevents radiation losses of above 0.1 dB for 1.31 µm light. Based on a study of fiber buckling, we demonstrate the optical performance for FPC connection with a 0.126 mm diameter micro sleeve in which optical fibers are mated and with polished fiber end faces. The insertion loss is under 0.3 dB and the average return loss is 50 dB for 1.31 µm light. These values are stable in the 20 to 70 temperature range. We confirm that FPC connection realizes high optical performance with a small simple structure.

A 2.7-V Si-bipolar quadrature modulator with a 90 phase shifter consisting of a frequency doubler and a master-slave flip-flop is described. The modulator operates over a wide bandwidth (0.95 to 1.88 GHz) without any tuning or adjustments. It is implemented using 20-GHz Si-bipolar technology and dissipates 97 mW at 2.7 V. An image ratio of less than -40 dBc is obtained between 1.1 and 1.8 GHz. Moreover, third-order harmonic products are less than -40 dBc and carrier leakage is less than -30 dBc.

This paper discusses the development of a design tool which supports a process for constructing PVC-based, ATM networks. Because of mathematical complexities, a heuristic approach has been adopted to find an optimal network configuration. Through a GUI, users define a physical network, and PVC networks which are logically constructed within the physical network. Based on the defined network configurations and user traffic demand, the tool evaluates performance measures. In response to the results of the evaluation, network designers can modify the network configuration to improve the performance. With the aid of this tool, they can repeat this interactive process until the estimated performance measures meet a desired quality. The tool has been applied to the design of several private ATM networks which will be constructed in the near future. The response time of this design tool is so fast that wait time can be negligible.

This paper presents a novel approach to a soft-output equalizer, which makes a symbol-by-symbol soft-decision based on a posteriori probabilities (APP's) criterion in the presence of intersymbol interference. The authors propose a soft-output Viterbi equalizer (SOVE) employing expanded memory length in a trellis of the Viterbi algorithm with small arithmetic complexity. The proposed equalizer gives suboptimum soft-decision closer to that of a equalizer with the maximum a posteriori probabilities (MAP) algorithm than the conventional SOVE.

Partial capture effect for multi-carrier radio packet communication network is evaluated in frequency selective fading channel. In multi-carrier modulation (MCM) network where each terminal uses several sub-carriers for transmission,the terminals have different instantaneous frequency responses because of its location, fading pattern, and other various factors. This generates the difference of received power in frequency domain, then partial capture effect can be considered at each sub-carrier. Moreover these partially captured packets are not damaged by inter symbol interference (ISI) caused by frequency selective fading, which seriously degrades single-carrier modulation (SCM) network. From this point of view we present the partial capture effect for the MCM network in the frequency selective fading environment. The results show that the MCM network with partial capture has more advantages than the MCM network without partial capture in terms of the throughput and the average number of transmissions.

The use of existing metallic local line facilities is being studied for the provision of high-speed digital transmission services. Local line characteristics have to be modeled in the form of the objective requirements that should be met by DSL for estimating the feasibility of the service provision in the actual network. This paper presents the results of a study that models the metallic media characteristics of NTT's local network. First, the line lenghts determined by the existing local line deployment rule and the cable types used in the networks are introduced. Second, the values of crosstalk characteristics, the most significant factors in limiting DSL range, are given by classifying essential line conditioning states of each cable. The values of crosstalk characteristics are newly computed by taking into account detailed cable pair-binding (cabling) structures, and the worst case values among all possible combinations of multiple inter-pair interfering-interfered relationships within a cable are given though a previous study approximated cable pair-binding structures. The crosstalk characteristics of NTT's and American local networks are also compared. A modified approximate equation of line propagation characteristics is also proposed for representative local lines, and its precision is verified by comparing simulation results to actual measurements in both frequency and time domains.

The Virtual Path (VP) concept is one of the versatile features of ATM/B-ISDN. Using the VP concept, a bundle of virtual circuits can be grouped together between any two switching nodes in the network. Further, the VP bandwidth and routing can be dynamic. Building on this idea, a dynamically reconfigurable, dynamic call routing wide area (backbone) broadband network concept is proposed. Specifically, this provides dynamism at two levels: at the VP level and at the connection level. For an incoming connection request, at most two logical virtual path connections (VPCs) are allowed between the origin and the destination; these logical VPCs are defined by setting virtual paths links (VPLs) which are, in turn, physically mapped to the transmission network. Based on the traffic pattern during the day, the bandwidth of such VPCs and their routing, as well as call routing, changes so that the maximum number of connection requests can be granted while maintaining acceptable quality of service (QoS) for various services. Within this framework, we present a mathematical model for network design (dimensioning) taking into account the variation of traffic during the day in a heterogeneous multi-service environment. We present computational results for various cost parameter values to show the effectiveness of such networks compared to static-VP based networks in terms of network cost.

Weakness of a block cipher, which has provable immunity against linear cryptanalysis, is investigated. To this end, the round transformation used in MISTY, which is a data encryption algorithm recently proposed by M. Matsui from Mitsubishi Electric Corporation, is compared to the round transformation of DES from the point of view of pseudrandom generation. An important property of the MISTY cipher is that, in terms of theoretically provable resistance against linear and differential cryptanalysis, which are the most powerful cryptanalytic attacks known to date, it is more robust than the Data Encryption Standard or DES. This property can be attributed to the application of a new round transform in the MISTY cipher, which is obtained by changing the location of the basic round-function in a transform used in DES. Cryptograohic roles of the transform used in the MISTY cipher are the main focus of this paper. Our research reveals that when used for constructiong pseudorandom permutations, the transform employed by the MISTY cipher is inferior to the transform in DES, though the former is superior to the latter in terms of strength against linear and differential attacks. More specifically, we show that a 3-round (4-round, respectively) concatenation of transforms used in the MISTY cipher is not a pseudorandom (super pseudorandom, respectively) permutation.

This paper investigates the accepting powers of multi-inkdot two-way alternating pushdown automata (Turing machines) with sublogarithmic space and constant leaf-size. For each k1, and each m0, let weak-ASPACEm [L(n),k] denote the class of languages accepted by simultaneously weakly L(n) space-bounded and k leaf-bounded m-inkdot two-way alternating Turing machines, and let strong-2APDAm[L(n),k] denote the class of languages accepted by simultaneously strongly L(n) space-bounded and k leaf-bounded m-inkdot two-way alternating pushdown automata. We show that(1) strong-2APDAm [log log n,k+1]weak-ASPACEm[o(log n),k]φfor each k1 and each m1, and(2) strong-2APDA(m+1) [log log n,k]weak-ASPACEm[o(log n),k]φfor each k1 and each m0.

In this paper, we evaluate the throughput performance of CDMA Slotted ALOHA systems. To improve the throughput performance, we employ the Quasi-synchronous sequences and the Modified Channel Load Sensing Protocol as an access control procedure. As a result, we found a good throughput by the QS-sequences. By employing MCLSP, we can keep the maximum throughput even in high offered load and in the presence of a long access timing delay, which is one of the issue in satellite packet communication systems.

In this paper, we propose a practical and secure electronic voting scheme which meets the requirements of large scale general elections. This scheme involves voters, the administrator or so called the government and some scrutineers. In our scheme, a voter only has to communicate with the administrator three times and it ensures independence among voters without the need of any global computation. This scheme uses the threshold cryptosystem to guarantee the fairness among the candidate's campaign and to provide mechanism for achieving the function that any voter can make an open objection to the tally if his vote has not been published. This scheme preserves the privacy of a voter against the administrator, scrutineers, and other voters. Completeness, robustness, and verifiability of the voting process are ensured and hence no one can produce a false tally, corrupt or disrupt the election.