The main contribution of this work is to propose energy-efficient randomized initialization protocols for ad-hoc radio networks (ARN, for short). First, we show that if the number n of stations is known beforehand, the single-channel ARN can be initialized by a protocol that terminates, with high probability, in O(n) time slots with no station being awake for more than O(log n) time slots. We then go on to address the case where the number n of stations in the ARN is not known beforehand. We begin by discussing, an elegant protocol that provides a tight approximation of n. Interestingly, this protocol terminates, with high probability, in O((log n)2) time slots and no station has to be awake for more than O(log n) time slots. We use this protocol to design an energy-efficient initialization protocol that terminates, with high probability, in O(n) time slots with no station being awake for more than O(log n) time slots. Finally, we design an energy-efficient initialization protocol for the k-channel ARN that terminates, with high probability, in O(n/k+log n) time slots, with no station being awake for more than O(log n) time slots.

To accomplish an efficient test pattern generation, the isomorphism identification algorithm and the pseudo dominator identification algorithm are developed which are used to identify redundant faults efficiently. Results show that test pattern generation using these algorithms is very efficient.

The application of subsurface radar using electromagnetic waves in the VHF band is wide and includes surveying voids under the ground and archaeological prospecting. To achieve a wider application range, the survey depth must be deeper. In this paper, a method of pulse compression using a chirp signal as one of the methods to fulfill this requirement is described, and its advantages and problems are discussed. First, a delay correlation method is proposed as a processing method of pulse compression. It converts RF band chirp signal directly into a pulse. Moreover, the method improves the S/N ratio by over 40 dB compared with conventional pulse radar. Therefore, it has the same detection ability as conventional pulse radar even though it uses less transmitting power. Next, the influences of RF amplifier saturation and underground propagation characteristics on the chirp signal are discussed; both are shown to have little influence on the detection ability of the method.

Most of current codesign tools or methodologies only support validation in the form of cosimulation and testing of design alternatives. The results of hardware-software codesign of a distributed system are often not verified, because they are not easily verifiable. In this paper, we propose a new formal coverification approach based on linear hybrid automata, and an algorithm for automatically converting codesign results to the linear hybrid automata framework. Our coverification approach allows automatic verification of real-time constraints such as hard deadlines. Another advantage is that the proposed approach is suitable for verifying distributed systems with arbitrary communication patterns and system architecture. The feasibility of our approach is demonstrated through several application examples. The proposed approach has also been successfully used in verifying deadline violations when there are inter-task communications between tasks with different period lengths.

This paper presents a novel competitive learning algorithm for the design of variable-rate vector quantizers (VQs). The algorithm, termed variable-rate competitive learning (VRCL) algorithm, designs a VQ having minimum average distortion subject to a rate constraint. The VRCL performs the weight vector training in the wavelet domain so that required training time is short. In addition, the algorithm enjoys a better rate-distortion performance than that of other existing VQ design algorithms and competitive learning algorithms. The learning algorithm is also more insensitive to the selection of initial codewords as compared with existing design algorithms. Therefore, the VRCL algorithm can be an effective alternative to the existing variable-rate VQ design algorithms for the applications of signal compression.

In this paper, some properties of domain tree languages of top-down pushdown tree transducers (domain(t-PDTT) or t-PDTTD) are shown. It is shown that (1) for any L1, L2 in context-free language (CFL), L1L2yielde(t-PDTTD) (where yielde is an extended yield), (2) yielde(t-PDTTε0DF) is closed under homomorphisms, where t-PDTTε0 is a t-PDTT which can not proceed generations after reading a constant symbol σ and t-PDTTε0DF denotes a domain tree language of t-PDTTε0 with a final state translation, and (3) yielde(t-PDTTε0DF) is the class of recursively enumerable languages, and consequently yielde(t-PDTTD) is the class of recursively enumerable languages.

Triple-layer CoCrPt magnetic thin films with different bias configurations were fabricated by DC magnetron sputtering on CrV and glass substrate. In-plane coercivity (Hc) showed an increase for those films with bias sputtered CoCrPt layer. The in-plane coercivity (Hc) was optimized in NB-B-NB type film prepared with substrate heating at 300C (NB: no bias and B: rf bias applied in sputtering). Better in-plane crystal texture was observed in NB-B-NB type film by XRD and this is believed to be the main reason for the coercivity improvement. The other resource for the coercivity improvement was due to the decoupling of intergrain magnetic interactions. This was discussed accordingly to the results obtained from TEM, MFM and SIMS depth profiling.

Natural language interface systems can accept more unrestricted queries from users than other systems, however it is impossible to understand erroneous sentences which include the syntax errors, unknown words and misspelling. In order to realize the superior natural language interface, the automatic error correction for erroneous sentences is one of problems to be solved. The method to apply the LR parsing strategies is one of the famous approaches as the robust error recovery scheme. This method is able to obtain a high correction accuracy, however it takes a great deal of time to parse the sentence, such that it becomes a very important task to improve the time-cost. In this paper, we propose the method to improve the time efficiency, keeping the correction accuracy of the traditional method. This method makes use of a new parsing table that denotes the states to be transited after accepting each symbol. By using this table, the symbol which is allocated just after the error position can be utilized for selecting correction symbols, as a result, the number of candidates produced on the correction process is reduced, and fast system can be realized. The experiment results, using 1,050 sentences including error characters, show that this method can correct error points 69 times faster than the traditional method, also keep the same correction accuracy as the traditional method.

A tunable optical Fabry-Perrot filter was designed by setting a single-mode optical fiber normal to the diaphragm of a capacitive pressure sensor. The silicon diaphragm is deflected by the electrostatic force generated by applying a voltage to the capacitive electrodes. According to the movement of the diaphragm, the peak wavelength changed from 1546 to 1551 nm when applied voltage was increased from 20 to 50 V. The relationship of the wavelength change to the applied voltage was derived from the silicon diaphragm deflection theory. That measured change of the wavelength agrees well with the wavelength change calculated from this relationship. The commercial pressure sensors are expected to be able to be used as a tunable optical filter.

Magnetic layer thickness dependences of magnetic properties are investigated for Co-Cr-Pt polycrystalline thin films with different Cr-alloy underlayers (Cr-Ti, Cr-W, Cr-Mo, Cr-V, Cr-Mo-V). The specimens with Cr-Ti, Cr-V, and Cr-Mo-V underlayers show higher coercivities by about 30% and lower activation magnetic moments than those with Cr-Mo underlayer. The effective diameter of activation volume increases by 10-20% when the magnetic layer thickness is decreased from 12 to 8 nm. Temperature dependences of magnetic properties are also determined and discussed by referring to the data obtained using single crystal magnetic thin films with similar composition.

Program slicing is a technique for statically analyzing a program and extracting an executable sub-program, which is called a program slice, from the original program. This technique has been widely applied to program testing, debugging and maintenance. This paper presents a slicing method for extracting program slices from a program that calls library functions, which are provided as object code. The method this paper presents analyzes dependence relationships between library functions using global data that are referred to by the library functions but not explicitly declared in a program. In this method, before slicing a program with respect to a slicing criterion, a Def-Slice-Use table will be generated that stores slice information for each function in the program by slicing these functions in advance, and then the program can be efficiently sliced using this table. The paper also illustrates some examples of program slicing using a program slicer LibSlicer that implements this method.

Several packaging methods for athermalization of Fiber Bragg Grating (FBG), which is equipped with negative expansion substrates, have been proposed. However, those methods have some deficiency resulted from the substrates such as complex structure or poor thermal expansion characteristics. In order to provide a suitable substrate for the athermalization of FBG, the authors have developed a Negative Expansion Ceramic Substrate (NECS) which has simple structure and suitable thermal expansion characteristics. NECS consists of polycrystalline β-quartz solid solution (Li2O-Al2O3-nSiO2, n>2), and has thermal expansion coefficient of about -65 to -85 10-7/C, which is sufficient large enough for total compensation of the Bragg wavelength shift. No difference in the thermal expansion was observed between the specimen as prepared and the one on which an epoxy adhesive was applied. NECS is produced by means of a sintering method, which enables flexible design of the chemical composition. It was found that the hysteresis in thermal expansion of the NECS depends upon the chemical composition and crystalline structure. We decreased thermal expansion hysteresis by controlling the SiO2 ratio in the composition and the crystal grain size. We confirmed that the temperature dependence of the FBG mounted on the NECS with an epoxy adhesive was decreased to -2.3 10-3 nm/C from 10.0 10-3 nm/C, in good agreement with the calculated value of -2.6 10-3 nm/C. The hysteresis in Bragg wavelength shift was less than 0.03 nm, that is sufficiently small enough for practical use. It was confirmed that NECS has suitable thermal expansion characteristics for the athermalization of FBG.

Aiming at lower cost and further miniaturization, we developed a new optical coupling system for use as an optical interface of a parallel optical interconnect module, called ParaBIT-1. It consists of a new-structure 24-fiber bare fiber (BF) connector whose main parts are made of molded plastic and a 24-channel optical coupling component using new polymeric optical waveguide film. To prevent bare fibers from breaking, the BF connector plug has a fiber protector. This BF connector can be joined by direct physical contact between bare fibers in fiber guide holes with a 250-µm pitch. The buckling forces of the fibers themselves secure the physical contacts. The average measured insertion loss of the 24-fiber BF connector was 0.05 dB, and the return losses were over 35 dB. The optical coupling components are composed of a 24-ch polymeric optical waveguide film with 45 mirrors and the 24-fiber BF connector interface, and can be assembled by passive alignment. The high thermal stability of the film allows soldering, and the film is fabricated by direct photo patterning. The average insertion losses of the components for transmitter and receiver modules were 1.28 and 1.35 dB, respectively.

We investigate traffic performance of CBWL schemes with multimedia services on non-homogeneous cellular network in which cut-off priority is given to handoff calls. Two generic routing schemes are analyzed: one is the randomized routing and the other is the least loaded routing. The performance measures that we focus on are the new call blocking probabilities and the handoff failure probabilities. To evaluate blocking probabilities of interest, we construct a generalized access network whose blocking probabilities are same as ones for CBWL systems. For analysis of generalized access network, we apply the reduced load approximation. The computational complexity and memory requirements of proposed algorithm are linear so that we can use this algorithm to approximate blocking probabilities of CBWL systems of large size. The proposed approximations are tested on a number of simple examples. Numerical results for 12 cells and 36 cells networks are given. The comparison between approximation and simulation results shows that the proposed approximation method is quite accurate.

In Optimistic Two-Phase Locking (O2PL), when a transaction requests a commit, the transaction can not be committed until all requested locks are obtained. By this reason, O2PL leads to unnecessary waits and operations even though it adopts an optimistic approach. This paper suggests an efficient optimistic cache consistency protocol that provides serializability of committed transactions. Our cache consistency scheme, called PCP (Preemptive Cache Protocol), decides whether to commit or abort without waiting when transactions request commits. In PCP, some transactions that read stale data items can not be aborted, because it adopts a re-ordering scheme to enhance the performance. In addition, for re-ordering, PCP stores only one version of each data item. This paper presents a simulation-based analysis on the performance of PCP with other protocols such as O2PL, Optimistic Concurrency Control and Caching Two-Phase Locking. The simulation experiments show that PCP performs as well as or better than other schemes with low overhead.

This paper concentrates on the model useful for analyzing the error performance of M-estimators of a single unknown signal parameter: that is the error intensity model. We develop the point process representation for the estimation error, the conditional distribution of the estimator, and the distribution of error candidate point process. Then the error intensity function is defined as the probability density of the estimate and the general form of the error intensity function is derived. We compute the explicit form of the intensity functions based on the local maxima model of the error generating point process. While the methods described in this paper are applicable to any estimation problem with continuous parameters, our main application will be time delay estimation. Specifically, we will consider the case where coherent impulsive interference is involved in addition to the Gaussian noise. Based on numerical simulation results, we compare each of the error intensity model in terms of the accuracy of both error probability and mean squared error (MSE) predictions, and the issue of extendibility to multiple parameter estimation is also discussed.

The purpose of this letter is to modify the correlation least mean squares algorithm using a sum of the lagged squared errors as the cost function and extend the modified CLMS algorithm to two-dimensional domain. The effectiveness of the proposed algorithm is shown by the computer simulation.

This paper investigates an obstructed radio channel by foliage for LMDS (local multipoint distribution services) where a relative evaluation of attenuation characteristics of foliage at 29.5 and 5 GHz is performed. Results show that the attenuation in dB should be treated statistically as Rician distribution. It is also found that swaying foliage in wind causes a significant channel fading at 29.5 GHz, ranging over 10 dB, while the fading depth at 5 GHz is approximately 2 dB.

The interconnect analysis of on- and off-chips is very important in the design of high-speed signal processing, digital communication, and microwave electronic systems. When the interconnects are characterized by sampled data via electromagnetic analysis, the circuit-level simulation of the network requires rational approximation of the sampled data. Since the frequency band of the sampled data is more than 10 GHz, the rational function must fit into it at many frequency points. The rational function is approximated using the orthogonal least-squares method. With an increase in the number of the fitting data, the least-squares method suffers from a singularity problem. To avoid this, the sampled data are hierarchically approximated in this paper. Moreover, to reduce the computational cost of the circuit-level simulation, the parameter matrix of the interconnects is approximated by a rational matrix with one common denominator polynomial, and the selective orthogonalization procedure is presented.

At the sliding contact of brush and rotating slip-ring or commutator, it has been recognized that the brush wear is influenced by brush pressure, current density and atmosphere nearby contact part. However, little is known about the relation between brush wear and atmosphere condition in detail. In this paper, the experiments are carried out with a great attention to the effect of surrounding temperature and humidity on brush wear. The sliding part of brush and slip-ring is put on the sealed box and the atmosphere in the sealed box is kept on the specified condition by temperature and humidity control system. The brush wear, contact voltage drop and slip-ring surface morphology are observed after the sliding test. From these results, in both cases of the high humidity (nearby 80%) and low humidity (nearby 20%), the brush wear are large. And the brush wear rate is the lowest around 60% relative humidity. However, the characteristics of brush wear under the 15C is not similar to others. When the surrounding temperature is changed, in case of the 20% humidity, the brush wear increases with increasing surrounding temperature. On the other hand, in case of 80% humidity, the brush wear increases with decreasing surrounding temperature. Consequently, the results clearly shows that the temperature and humidity not only affect the brush wear but also change the condition of the film formation on slip-ring.