Showing papers by "University of Electro-Communications published in 1997"
247 citations
TL;DR: In this paper, experimental evidence of superlubricity, the state of vanishing friction, is obtained by examining systems of sliding atomically clean surfaces by using ultrahigh vacuum scanning tunneling microscopy.
Abstract: Experimental evidence of superlubricity, the state of vanishing friction, is obtained by examining systems of sliding atomically clean surfaces by using ultrahigh vacuum scanning tunneling microscopy. The experimental results agree with theoretical predictions: Friction is not observed in the superlubricity regime in measurements capable of resolving a friction force of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\mathrm{N}$, whereas friction of $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\mathrm{N}$, which is comparable to theoretical values, is observed in the friction regime.
234 citations
TL;DR: The performance of Fourier-transform profilometry is enhanced by a new technique that is based on spatial frequency multiplexing combined with the Gushov-Solodkin phase unwrapping algorithm, which permits the three-dimensional shape measurement of objects that have discontinuous height steps and/or spatially isolated surfaces.
Abstract: The performance of Fourier-transform profilometry is enhanced by a
new technique that is based on spatial frequency multiplexing
combined with the Gushov–Solodkin phase unwrapping algorithm.
The technique permits the three-dimensional shape measurement of
objects that have discontinuous height steps and/or spatially
isolated surfaces, which has not been possible by conventional
Fourier-transform profilometry. An important feature of the technique
is that it requires only a single fringe pattern; the single-shot
recording makes possible the instantaneous three-dimensional shape
measurement of discontinuous objects in fast motion. Experimental
results are presented that demonstrate the validity of the
principle.
224 citations
TL;DR: An efficient and very simple algorithm based on the successive refinement of partitions of the unit interval (0, 1), which is called the interval algorithm, is proposed and a fairly tight evaluation on the efficiency is given.
Abstract: The problem of generating a random number with an arbitrary probability distribution by using a general biased M-coin is studied. An efficient and very simple algorithm based on the successive refinement of partitions of the unit interval (0, 1), which we call the interval algorithm, is proposed. A fairly tight evaluation on the efficiency is given. Generalizations of the interval algorithm to the following cases are investigated: (1) output sequence is independent and identically distributed (i.i.d.); (2) output sequence is Markov; (3) input sequence is Markov; (4) input sequence and output sequence are both subject to arbitrary stochastic processes.
149 citations
TL;DR: The purpose of the present study was to investigate the changes in superoxide dismutase (SOD) isoenzyme activities, contents and mRNA expressions in rat skeletal muscle during endurance training and a single bout of exercise.
Abstract: SUMMARY
1. The purpose of the present study was to investigate the changes in superoxide dismutase (SOD) isoenzyme (Mn2+-SOD and Cu2+, Zn2+-SOD) activities, contents and mRNA expressions in rat skeletal muscle during endurance training and a single bout of exercise.
2. Thirty-eight male Wistar rats were divided into untrained (U) and trained (T) groups. The T group rats were treadmill-trained for 9 weeks. The activity, content and mRNA expression of Mn2+-SOD and Cu2+, Zn2+-SOD were determined in the soleus muscle of each rat.
3. Mn2+-SOD activity and content in the T group were significantly higher than in the U group, both at rest (22 and 21%, respectively) and after exercise (24 and 46%, respectively), while a single bout of exercise affected neither the activity nor content of Mn2+-SOD in either group.
4. The content of Cu2+, Zn2+-SOD in both groups was not different at rest and after exercise, although its activity at rest was significantly higher in the T group than in the U group (by 29%).
5. After exercise, the expression of Mn2+-SOD mRNA was markedly attenuated only in the U group (49%); the expression of Cu2+, Zn2+-SOD mRNA was not influenced by exercise.
6. Our results suggest that adequate endurance training increases both the activity and content of Mn2+-SOD and that untrained rats are rather susceptible to oxidative stress during physical exercise. It thus appears that Mn2+-SOD provides a reliable index of physical training.
7. The results obtained in the present study also suggest that muscle has the capacity of responding to training in such a manner as to reduce the potential harm arising from the accumulation of oxygen free radicals resulting from enhanced metabolic activity.
112 citations
TL;DR: The Shioura and Tamura algorithm is optimal in the sense of both time and space complexities because it decreases the space complexity from O(VE) to O(V + E) while preserving the time complexity.
Abstract: Let G be an undirected graph with V vertices and E edges. Many algorithms have been developed for enumerating all spanning trees in G. Most of the early algorithms use a technique called "backtracking." Recently, several algorithms using a different technique have been proposed by Kapoor and Ramesh (1992), Matsui (1993), and Shioura and Tamura (1993). They find a new spanning tree by exchanging one edge of a current one. This technique has the merit of enabling us to compress the whole output of all spanning trees by outputting only relative changes of edges. Kapoor and Ramesh first proposed an O(N + V + E)-time algorithm by adopting such a "compact" output, where N is the number of spanning trees. Another algorithm with the same time complexity was constructed by Shioura and Tamura. These are optimal in the sense of time complexity but not in terms of space complexity because they take O(VE) space. We refine Shioura and Tamura's algorithm and decrease the space complexity from O(VE) to O(V + E) while preserving the time complexity. Therefore, our algorithm is optimal in the sense of both time and space complexities.
111 citations
TL;DR: In this paper, a collision avoidance method for 5-axis control machining is presented, which avoids collision by producing the direction of collision avoidance based on the 2-dimensional configuration space (C-space) defined by two parameters which determine the tool attitude.
Abstract: This study deals with the method of collision avoidance in the automatic tool path generation for 5-axis control machining. Five-axis NC machining offers the potential for efficient and accurate machining, but collisions between the tool and surrounding objects are still a severe problem. The method devised in this study avoids collision by producing the direction of collision avoidance, based on the 2-dimensional configuration space (C-space) defined by two parameters which determine the tool attitude. This method allows a test workpiece with overhanging parts to be milled without collisions. As a result, the validity of the method has been experimentally confirmed.
108 citations
TL;DR: The analysis shows that the basic principle to design a compact interpolation of variables at the cell edges is to prevent it from crossing the discontinuous data, such that the accuracy analysis based on Taylor series expanding is valid over all grid points.
108 citations
TL;DR: In this article, the position localization of a polarized atom interacting with an off-resonant quantized standing-wave field was investigated and it was shown that a coherent cavity field achieves a higher resolution than a classical field.
Abstract: We investigate the position localization of a polarized atom interacting with an off-resonant quantized standing-wave field. We show that a coherent cavity field achieves a higher resolution than a classical field. An almost perfect localization is possible when the atom passes through several identically prepared cavities.
95 citations
29 Jun 1997
TL;DR: An algorithm is presented which can relax the upper bound for sampling in some wavelet subspaces by using scaling functions and which can estimate a proper upper bound of sup/sub /spl kappa//|/spl delta//sub / spl kappa| such that the irregularly sampled signals can be recovered.
Abstract: From the Paley-Wiener 1/4-theorem, the finite energy signal f(t) can be reconstructed from its irregularly sampled values f(k+/spl delta//sub /spl kappa//) if f(t) is band-limited and sup/sub /spl kappa//|/spl delta//sub /spl kappa//|<1/4. We consider the signals in wavelet subspaces and wish to recover the signals from its irregular samples by using scaling functions. Then the method of estimating the upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//| such that the irregularly sampled signals can be recovered is very important. Following the work done by Liu and Walter (see J. Fourier Anal. Appl., vol.2, no.2, p.181-9, 1995), we present an algorithm which can estimate a proper upper bound of sup/sub /spl kappa//|/spl delta//sub /spl kappa//|. Compared to Paley-Wiener 1/4-theorem, this theorem can relax the upper bound for sampling in some wavelet subspaces.
86 citations
TL;DR: In this article, rare-earth complexes were used as photovoltaic precursors, and the conversion efficiency of solar cells were improved by applying rare earth complexes as photoprocessors.
TL;DR: In this article, it was shown that phase matching in a parametric process can be self-induced without the stringent restriction of the medium, and that the phase matching can be achieved by strong coupling between radiation fields and medium spontaneously established through the stimulated Raman scattering process.
Abstract: We show through the experiments of parametric anti-Stokes stimulated Raman scattering for solid hydrogen that the phase matching in a parametric process can be self-induced without the stringent restriction of the medium. We explain this self-induced phase matching as a consequence of strong coupling between radiation fields and medium spontaneously established through the stimulated Raman scattering process.
20 Apr 1997
TL;DR: The system can automatically generate a spraying path for the air spray gun on the basis of CAD date of the workpiece, and change the spraying path into robot control commands, and was found to be effective in painting bumpers of a car with uniform paint thickness.
Abstract: The study deals with the automatic spray-painting by a 6-DOF industrial robot equipped with an air spray gun. Since the conventional robot control command generation for the spray-painting is manually performed by skilled workers using a teaching-playback function of a robot controller, it is a time consuming and experience required process. The study aims at generating the robot control commands without any special knowledge on spray-painting, in the case of bumpers of a car as an example of sculptured surfaces. The system can automatically generate a spraying path for the air spray gun on the basis of CAD date of the workpiece, and change the spraying path into robot control commands. From experimental results, the system was found to be effective in painting bumpers of a car with uniform paint thickness.
TL;DR: In this article, the authors calculate the optimized geometry and corresponding electronic structure of Li ions doped in a small graphite cluster with dangling bonds or hydrogen terminations at the edge surrounding the cluster.
Abstract: We calculate the optimized geometry and the corresponding electronic structure of Li ions doped in a small graphite cluster with dangling bonds or hydrogen terminations at the edge surrounding the cluster. The calculations imply both covalent and ionic bonds of Li ions to carbon atoms, which may be relevant to explaining the broad signal of the 7Li NMR Knight shift spectra. Li intercalation, in particular, is possible even at the hydrogen-terminated edges. Because of the finite size effect of the cluster, the ionicity of intercalated Li ions has a large distribution of values, ranging from positive values close to that in graphite intercalation compounds to even slightly negative values, depending on the bonding geometry. We propose that the cluster edge surface plays a special role in accommodating excess Li ions in the disordered graphite system.
TL;DR: In this paper, the relationship between the number of reversals of a fine magnetic particle and the material parameters is investigated, and an experimental formula, p = 60α/(1 + α2)exp((−kuv0.979)/(kT)) is obtained for the transition probability due to the thermal fluctuation after-effect.
TL;DR: In this article, the time-domain and frequency-domain responses of non-uniform and uniform transmission lines excited by incident electromagnetic waves are studied and the load currents induced at terminal loads are derived.
Abstract: We study time-domain and frequency-domain responses of nonuniform and uniform transmission lines excited by incident electromagnetic waves. Externally excited uniform transmission lines permit closed-form solutions in terms of inverse chain matrix, whereas nonuniform lines cannot be analytically solved, in general. We adopt a method of equivalent cascaded network chain as the method of solving the latter situation. Useful and compact expressions for the load currents induced at terminal loads are derived. To confirm the validity of this method and the forcing terms, theoretical and experimental results of coupling calculations for a few typical (uniform/nonuniform) line geometries, relevant in the EMC field, are presented and discussed.
TL;DR: A new Electron Beam Ion Trap has recently been completed in Tokyo as mentioned in this paper, and the general features of the apparatus, design and operation are given, as well as the planned and ongoing experimental program.
Abstract: A new Electron Beam Ion Trap has recently been completed in Tokyo. The general features of the apparatus, design and operation are given. This paper also surveys the planned and ongoing experimental program.
TL;DR: In this paper, a new Electron Beam Ion Trap (EBIT) was constructed, and the performance of this EBIT was illustrated by illustrating the results of experiments with the EBIT.
Abstract: We have constructed a new Electron Beam Ion Trap (EBIT). Over recent months, we have operated this device and obtained some experimental results. In this paper, we show the performance of this EBIT by illustrating these results.
TL;DR: A variety of novel genes were noted, including two ORFs, which were homologous to the putative genes encoding xanthine dehydrogenase in the fly and a protein responsible for axonal guidance and outgrowth of the rat, mouse and nematode.
Abstract: The contiguous 874.423 base pair sequence corresponding to the 50.0-68.8 min region on the genetic map of the Escherichia coli K-12 (W3110) was constructed by the determination of DNA sequences in the 50.0-57.9 min region (360 kb) and two large (100 kb in all) and five short gaps in the 57.9-68.8 min region whose sequences had been registered in the DNA databases. We analyzed its sequence features and found that this region contained at least 894 potential open reading frames (ORFs), of which 346 (38.7%) were previously reported, 158 (17.7%) were homologous to other known genes, 232 (26.0%) were identical or similar to hypothetical genes registered in databases, and the remaining 158 (17.7%) showed no significant similarity to any other genes. A homology search of the ORFs also identified several new gene clusters. Those include two clusters of fimbrial genes, a gene cluster of three genes encoding homologues of the human long chain fatty acid degradation enzyme complex in the mitochondrial membrane, a cluster of at least nine genes involved in the utilization of ethanolamine, a cluster of the secondary set of 11 hyc genes participating in the formate hydrogenlyase reaction and a cluster of five genes coding for the homologues of degradation enzymes for aromatic hydrocarbons in Pseudomonas putida. We also noted a variety of novel genes, including two ORFs, which were homologous to the putative genes encoding xanthine dehydrogenase in the fly and a protein responsible for axonal guidance and outgrowth of the rat, mouse and nematode. An isoleucine tRNA gene, designated ileY, was also newly identified at 60.0 min.
TL;DR: In this paper, the magnetic properties of pyrimidine-bridged Cu(hfac)2 and Cu(ClO4)2 complexes were investigated, and the results showed that the P2P2Cu(NO3)2·(H2O)2 complex showed para-and antiferromagnetic behavior.
TL;DR: In this paper, the authors measured the acoustic radiation force on micrometer-sized polystyrene spheres through observation of the sphere movement in a 500 kHz ultrasonic standing wave and verified the correlation between the sphere velocity and the force.
Abstract: The acoustic radiation force on micrometer-sized polystyrene spheres was measured through observation of the sphere movement in a 500 kHz ultrasonic standing wave. The known spatial distribution of the force allowed verification of the correlation between the sphere velocity and the force. It was found that the linear dependency of the force on the cube of the sphere radius, as predicted by Yosioka, began to fail when the sphere radius was below 5 μm. This can be accounted for by the presence of a shell layer surrounding the sphere, which increased the effective radius of the sphere. This may point to applications of the acoustic radiation force in the handling of moicrospheres smaller than hitherto thought possible.
TL;DR: In this article, the nonlinear optical properties of a ferroelectric and ferroelastic β′-Gd2(MoO4)3 laser crystal-host were studied by second harmonic generation (SHG) and stimulated Raman scattering (SRS) experiments using different laser sources for excitation.
30 Aug 1997-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
Abstract: Hot deformation of an unrecrystallized 7075 aluminum alloy was studied by means of 2-step tensile testing and metallographic observations. Typical superplasticity took place accompanied with the evolution of new fine grains in the medium region of strain rate. Grain boundary sliding (GBS) operated just after yielding even in the unrecrystallized coarse grained structure. It is concluded from the mechanical and metallographic results that GBS can play a key role in the evolution of fine grains as well as the appearance of superplasticity.
13 Apr 1997
TL;DR: It is shown that there effectively exists a universal circular H system which can simulate any circular H systems with the same terminal alphabet, which strongly suggests a feasible design for a DNA computer based on circular splicing.
Abstract: From a biological motivation of the interactions between linear and circular DNA sequences, we propose a new type of splicing model called "circular H systems" and show that they have the same computational power as Turing machines. It is also shown that there effectively exists a universal circular H system which can simulate any circular H system with the same terminal alphabet, which strongly suggests a feasible design for a DNA computer based on circular splicing.
20 Apr 1997
TL;DR: This paper suggests the collision-free tool path generation for 5-axis control rough cutting, taking account of efficiency and accuracy, and the devised method allows an impeller-like shape to be actually milled with Efficiency and accuracy.
Abstract: This study deals with how to generate 5-axis control rough cutting NC data. The 5-axis control machining offers the potential of efficient and accurate machining. However, present CAM systems for 5-axis control are lacking in generality and functions for the tool path generation. Although the rough cutting is the most important process influencing the machining time and the condition in the following finishing process, a lot of difficulties arise to perform 5-axis control rough cutting. Especially, the collision between a tool and surrounding objects is still a severe problem. This paper suggests the collision-free tool path generation for 5-axis control rough cutting, taking account of efficiency and accuracy. The devised method allows an impeller-like shape to be actually milled with efficiency and accuracy. As a result, the validity of the method is experimentally confirmed.
TL;DR: In this paper, the influence of extrusion parameters on the microstructures and the mechanical properties of SiC particles reinforced Al Li composite was described, and the reduction ratio of 20:1 was superior in the mechanical property of extruded Al Li/10vol%SiCp composite under all conditions.
20 Apr 1997
TL;DR: The system gain characteristic at the antiresonance frequency is introduced to evaluate the vibratory behavior of the control system and a position control system considering the trade-off between vibration suppression and disturbance rejection is presented.
Abstract: This paper is basic study on vibration control, disturbance rejection and friction compensation in robots with flexible driving systems. Firstly, the system gain characteristic at the antiresonance frequency is introduced to evaluate the vibratory behavior of the control system. Secondly, the joint torque negative feedback which has a good effect on vibration suppression is discussed, while it is shown that the property of disturbance rejection is easily deteriorated when using high-gain joint torque feedback. Based on the assignment of pole-distribution, the relations between the vibration suppression and the disturbance rejection are analyzed. Thirdly, a feedforward compensation control based on a friction observer is proposed, it is shown that the tracking error is effectively decreased by this friction compensation. Lastly, a position control system considering the trade-off between vibration suppression and disturbance rejection is presented, and experimental results are also given.
TL;DR: In this paper, the thermal fluctuation in magnetization of longitudinal and perpendicular magnetic recording media was calculated using a Monte Carlo simulation method, and it was shown that longitudinal recording is superior to perpendicular recording when the grain size is larger than the thickness.
TL;DR: The value of Cl- concentration through the cell is fairly lower than 120 mM that was suggested from reversal potential of tail component of the olfactory response in the low Cl- bath solution, which indicates opening of the Cl- channels may serve as a booster for the depolarizing odor-response.
TL;DR: It is shown that Angluin's learning algorithm for the class of k-reversible languages can be readily adopted for the approximate identification of regular languages from positive data.