Showing papers by "University of Electro-Communications published in 1995"
TL;DR: In this paper, the symmetry properties of carbon nanotubes for both symmorphic and non-symmorphic tubules which have screw-axis symmetry are discussed. And the implications of symmetry on the vibrational and electronic structure of 1D carbon nanite systems are considered.
1,061 citations
TL;DR: In this article, microfracturing electrification is discussed as a possible explanation of ULF electromagnetic emissions observed before and after earthquakes, using a space-time simple model of micro-fracture progression, it is possible to compare theoretical results and observed results with special reference to the intensity, spectrum, and temporal development of the magnetic field variations.
Abstract: Microfracturing electrification is discussed as a possible explanation of ULF electromagnetic emissions observed before and after earthquakes. Using a space-time simple model of microfracture progression, it is possible to compare theoretical results and observed results with special reference to the intensity, spectrum, and temporal development of ULF magnetic field variations.
221 citations
TL;DR: In this article, the characteristics of high temperature flow curves and evolution of new grain structures under conditions of dynamic recrystallization (DRX) are reviewed, together with the associated development of dislocation substructures.
184 citations
TL;DR: In this article, a statistical parameter estimation theory for quantum pure state models is presented, based on symmetric logarithmic derivatives, and clarified the differences between pure-state models and strictly positive models.
155 citations
TL;DR: In this article, the scaling law for stationary states and the governing equation of morphology were considered and a possible rigorous approach was presented to stability and morphological selection problems for them. But this approach is restricted to the case where the steady patterns become finer and finer in the scaling limit due to their mesoscopic nature.
149 citations
TL;DR: Frequency detuning as a result of self-phase modulation that exceeds by four times the primary laser frequency is demonstrated.
Abstract: Frequency detuning as a result of self-phase modulation that exceeds by four times the primary laser frequency is demonstrated. The white light, ranging from the IR to 150 nm, was generated by a self-trapped femtosecond Ti:Al2O3 laser pulse in atmospheric-pressure rare gases. Spectral intensities in the UV and the visible regions are 100 MW/nm and 1 GW/nm, respectively. The beam divergence was measured to be 1 mrad.
88 citations
TL;DR: A decoding algorithm for algebraic-geometric codes from regular plane curves, in particular the Hermitian curve, which corrects all error patterns of weight less than d*/2 with low complexity is presented.
Abstract: We present a decoding algorithm for algebraic-geometric codes from regular plane curves, in particular the Hermitian curve, which corrects all error patterns of weight less than d*/2 with low complexity. The algorithm is based on the majority scheme of Feng and Rao (1993) and uses a modified version of Sakata's (1988) generalization of the Berlekamp-Massey algorithm.
88 citations
TL;DR: A new method for information display based on fractal theory is proposed, which provides fisheye-like views which integrate local details around the focal point and major landmarks further away and can be set flexibly.
Abstract: Computer users often must view large amounts of information through video displays which are physically limited in size. Although some methods, which automatically display/erase information units based on their degrees of importance, have been proposed, they lack an ability to keep the total amount of displayed information nearly constant. We propose a new method for information display based on fractal theory. By regarding the information structures used in computers as complex objects, we can abstract these objects as well as control their amount. Using our method, (1) the total amount of information is kept nearly constant even when users change their focuses of attention and (2) this amount can be set flexibly. Through mathematical analysis, we show our method's ability to control the amount. An application to program display is also shown. When this method is applied to the display of structured programs, it provides fisheye-like views which integrate local details around the focal point and major landmarks further away.
67 citations
TL;DR: In this paper, an ab initio calculation of the ionization cross section of atomic hydrogen near threshold with precision that compares excellently with the Shah-Elliot-Gilbody experiment was presented.
Abstract: We present an ab initio calculation of the ionization cross section of atomic hydrogen near threshold with precision that compares excellently with the Shah-Elliot-Gilbody experiment [J. Phys. B 20, 3501 (1987)]. This fills the gap between theory and experiment down to 0.1 a.u. above threshold, complementing the recent spectacular work of Bray and Stelbovics [Phys. Rev. Lett. 70, 746 (1993)]. The angular momentum distributions of the secondary electron display an evolution in correlation patterns toward the threshold.
64 citations
TL;DR: In this paper, a Relativistic Gaussian basis set of neutral atoms Rn-Pu and ions Th+4, U+3 and Pu+3 in the configurations of average energies is presented.
Abstract: Relativistic Gaussian basis sets of neutral atoms Rn-Pu and ions Th+4, U+3 and Pu+3 in the configurations of average energies are presented. The exponent parameters of the basis sets are determined by least-squares fitting to the numerical Dirac-Fock wave functions. The total energies obtained are within 0.155 a.u. of the Dirac-Fock limits and the qualities of the basis sets are between double-zeta and triple-zeta in the valence parts. Using the exponent parameters the Breit interaction energies have been calculated by perturbation theory and the self-consistent field treatment.
51 citations
TL;DR: This paper gives a nesessary and sufficient condition for a Choquet integral model to be decomposable into an equivalent hierarchical Choquet Integral model constructed by hierarchical combinations of some ordinary Choquetintegral models.
Abstract: In this paper we give a nesessary and sufficient condition for a Choquet integral model to be decomposable into an equivalent hierarchical Choquet integral model constructed by hierarchical combinations of some ordinary Choquet integral models. The condition is obtained by Inclution-Exclusion Covering (IEC). Moreover we show some properties on the set of IECs.
TL;DR: In this paper, the authors describe the accurate measurement of ultralow loss in a high-finesse Fabry-Perot interferometer using a diode-pumped Nd:YAG laser locked to the longitudinal mode with an active frequency-stabilization technique.
Abstract: We describe the accurate measurement of ultralow loss in a high-finesse Fabry-Perot interferometer using a diode-pumped Nd:YAG laser locked to the longitudinal mode with an active frequency-stabilization technique. By measuring the resonance full width and the free spectral range with the frequency response functions, and by measuring the transmission efficiency on resonance, the finesse and the loss at 1064 nm are accurately measured to be 78100 ± 1200 (reflectance of 99.99598 ± 0.00006%) and 1 5.9 ±2.0 × 10−6 (15.9 ± 2.0 ppm), respectively.
TL;DR: This paper presents a learning algorithm that learns any SDA M in the limit from positive data, satisfying the properties that (i) the time for updating a conjecture is at most O(lm), and (ii) the number of implicit prediction errors is at least O(ln), where l is the maximum length of all positive data provided.
Abstract: This paper deals with the polynomial-time learnability of a language class in the limit from positive data, and discusses the learning problem of a subclass of deterministic finite automata (DFAs), called strictly deterministic automata (SDAs), in the framework of learning in the limit from positive data. We first discuss the difficulty of Pitt's definition in the framework of learning in the limit from positive data, by showing that any class of languages with an infinite descending chain property is not polynomial-time learnable in the limit from positive data. We then propose new definitions for polynomial-time learnability in the limit from positive data. We show in our new definitions that the class of SDAs is iteratively, consistently polynomial-time learnable in the limit from positive data. In particular, we present a learning algorithm that learns any SDA M in the limit from positive data, satisfying the properties that (i) the time for updating a conjecture is at most O(lm), (ii) the number of implicit prediction errors is at most O(ln), where l is the maximum length of all positive data provided, m is the alphabet size of M and n is the size of M, (iii) each conjecture is computed from only the previous conjecture and the current example, and (iv) at any stage the conjecture is consistent with the sample set seen so far. This is in marked contrast to the fact that the class of DFAs is neither learnable in the limit from positive data nor polynomial-time learnable in the limit.
TL;DR: The stable formation of PurR hinge helices requires PurR dimerization, which brings the hinge regions proximal to each other, which is likely to be controlled by the CBDDimerization interface, but is induced by specific-DNA binding.
TL;DR: In this paper, the efficient Raman scattering in two tetragonal laser crystalline hosts with disordered structure has been studied by Q-switched infrared laser pulse excitation and it was shown that such disordered crystals have larger cross sections than those of typical ordered crystals.
Abstract: The efficient Raman scattering in two tetragonal laser crystalline hosts with disordered structure has been studied by Q-switched infrared laser pulse excitation. Raman spectra show that such disordered crystals have larger cross sections than those of typical ordered crystals. The effective Raman gain coefficients were estimated as (9±4) cm/GW for NaBi(MoO4)2 (across c-axis) and as (8±4) cm/GW for NaBi(WO4)2.
TL;DR: The spectrum at low electron energies less than 1 eV clearly shows structures even in the energy region of the order of 1 meV, which agrees well with the theoretical calculations based on a multichannel quantum defect theory including rotational motions and off-the-energy-shell effects.
Abstract: Dissociative recombination of ${\mathrm{HD}}^{+}$ was studied with an adiabatically expanded low-temperature electron beam in a cooler ring TARN II. Measurements were performed over a wide energy range from 0 to 40 eV in the center of mass system. The spectrum at low electron energies less than 1 eV clearly shows structures even in the energy region of the order of 1 meV. The results agree well with the theoretical calculations based on a multichannel quantum defect theory including rotational motions and off-the-energy-shell effects.
TL;DR: To the authors' knowledge, the loss is the lowest obtained at 1064 nm, and this result coincides with that of the response function within accuracies cited above.
Abstract: We describe an ultralow-loss and high-reflectance mirror at 1064 nm. A Fabry-Perot cavity is fabricated with two mirrors to measure the finesse and the transmission efficiency on resonance. The finesse was cross checked by two different methods: measurements of the cavity decay time and of the frequency-response function. As a result, a loss of 6 +/- 6 x 10(-6) (6 +/- 6 parts in 10(6), scatter and absorption) and a finesse of 2236 +/- 54 were measured during the cavity decay time. This result coincides with that of the response function within accuracies cited above. To our knowledge, the loss is the lowest obtained at 1064 nm.
TL;DR: In this article, the influence of changing of the magnetic field and skin depth on the forming tube, the magnetic pressure is deviated, and the effects of changing the working conditions such as the capacity of capacitor bank, the length of solenoidal coil were analyzed and experimentally investigated for the electromagnetic forming process and the forming efficiency.
TL;DR: A formula for the characteristic polynomial of the derived graph covering of a graph with voltages in any finite group is given.
01 Jan 1995
TL;DR: In this article, a triplet structure (g, ∇(e), ∇ (m) on S via the specified covariance is introduced, where g is a Riemannian metric and ∇ and m are affine connections.
Abstract: In this article, we treat the space S of finite-dimensional positive density operators (quantum states) in a differential geometrical viewpoint. We suppose that a generalized covariance for arbitrary two observables (Hermitian operators) is specified at each state in S, which includes the symmetrized inner product and the Bogoliubov inner product as special (but important) cases, and introduce a triplet structure (g, ∇(e), ∇(m) on S via the specified covariance, where g is a Riemannian metric and ∇(e) and ∇(m) are affine connections. The structure (g, ∇(e), ∇(m) is regarded as a quantum analogue of the triplet of Fisher metric, exponential connection and mixture connection on a space of probability densities introduced in the information geometry by S. Amari ([1]). Some aspects relating to the quantum state estimation and the relative entropy are treated in terms of the differential geometry, where the theory of dual connections developed by Nagaoka and Amari ([4] [1]) plays an essential role.
TL;DR: Optimal static routing problems in open BCMP queueing networks with state-independent arrival and service rates are studied and it is shown that the utilization of each service center is uniquely determined by the overall optimal policy.
TL;DR: In this article, the supertransferred hyperfine magnetic field at 55 Mn from each neighboring Co 2+ ion is found to be +5.0 kOe, which is considerably smaller than that of Ni 2+ in a similar oxide system La(Ni 1- x Mg x ) 0.5 Mn 0.4 O 3.
Abstract: Magnetic properties and the hyperfine magnetic fields at 55 Mn in ferromagnetic oxides La(Co 2+ 1- x Mg x 2+ ) 0.5 Mn 0.5 4+ O 3 (0≤ x ≤0.4) are studied. The exchange integral, J , for the superexchange interaction between neighboring Mn 4+ and Co 2+ ions is found to be +15.3 K in magnitude. 55 Mn NMR spectra, composed of several equidistantly separated peaks, are interpreted as each peak being the signal associated with Mn 4+ surrounded by a specific number of Co 2+ ions. The supertransferred hyperfine magnetic field, H STHF , at 55 Mn from each neighboring Co 2+ ion is found to be +5.0 kOe, which is considerably smaller than that (+6.3 kOe) from Ni 2+ in a similar oxide system La(Ni 1- x Mg x ) 0.5 Mn 0.5 O 3 . On the other hand, the hyperfine magnetic field (-296 kOe) originating from 3 d magnetic moment of Mn 4+ is virtually the same in both systems. The values of J and H STHF are discussed in relation with the spin density in 2 p σ orbitals of the oxygen ions.
TL;DR: A novel side-pumping configuration of the virtual-point-source diode-array-pumped Nd:YAG laser with 32 cw 10-W laser diodes with optically thin gain medium is described.
Abstract: We describe a novel side-pumping configuration of the virtual-point-source diode-array-pumped Nd:YAG laser with 32 cw 10-W laser diodes. A new concept of the virtual point source and an image-relay system are proposed for the generation of a Gaussian-like pumping profile with an optically thin gain medium. A cw linearly polarized TEM00-mode, 26.5-W output was obtained at a diode pump power of 171 W. The M2 values at the x and y axes were measured to be Mx2=1.03 and My2=1.20, respectively.
TL;DR: In this paper, an analysis on the heating of electrons in the lower ionosphere due to the electromagnetic radiation from vertical and horizontal lightning discharges is performed, and the association of this analysis to some other related phenomena is finally discussed.
Abstract: An analysis is performed on the heating of electrons in the lower ionosphere due to the electromagnetic radiation from vertical and horizontal lightning discharges. Disturbances of the electron temperature in the daytime ionosphere may exceed 50° K for vertical strokes and 100° K for horizontal lightning discharges. The association of this analysis to some other related phenomena, is finally discussed.
TL;DR: In this paper, the factors responsible for temporal variation of the detected frequency in an FT ion cyclotron resonance (ICR) spectrometer are analysed. And the influence of the Coulomb interaction on the signal and the spectral peak shape is studied by a computer simulation using a highly parallel computer.
TL;DR: In this paper, the phase spectrum of the Earth-ionosphere waveguide is approximated with a model function of two main parameters: the ionospheric height and the distance to the source, in the frequency range between the: first and second cutoff frequencies.
18 Oct 1995
TL;DR: The results obtained are essentially related to the closure property of concept classes under infinite intersections (or infinite unions) and there exist some interesting example concept classes with such properties by which an upper-best approximation of any concept can be identifiable in the limit from positive data.
Abstract: In this paper, we introduce various kinds of approximations of a concept and propose a framework of approximate learning in case that a target concept could be outside the hypothesis space. We present some characterization theorems for approximately identifiability. In particular, we show a remarkable result that the upper-best approximate identifiability from complete data is collapsed into the upper-best approximate identifiability from positive data. Further, some other characterizations for approximate identifiability from positive data are presented, where we establish a relationship between approximate identifiability and some important notions in quasi-order theory and topology theory. The results obtained in this paper are essentially related to the closure property of concept classes under infinite intersections (or infinite unions). We also show that there exist some interesting example concept classes with such properties (including specialized EFS's) by which an upper-best approximation of any concept can be identifiable in the limit from positive data.
25 Apr 1995
TL;DR: Simulation results show that both adaptive and static policies improve performance dramatically, and that the performance provided by static policies is not much inferior to that provided by adaptive policies.
Abstract: This paper focuses on using simulation to compare the performances of adaptive and static load balancing policies in a heterogeneous distributed system model. All the hosts (nodes) an the system are assumed to have the same function but possibly different processing capacities. The overheads and the delays for both job transfer and system state-information exchange are assumed to be nonnegligible. Simulation results show that both adaptive and static policies improve performance dramatically, and that the performance provided by static policies is not much inferior to that provided by adaptive policies. They also show that when overheads are nonnegligibly high at heavy system loads, static policies can provide performance more stable and better than that provided by adaptive policies. >
TL;DR: In this article, a new method of estimating the propagation distance and ionospheric reflection height by using sophisticated signal processing for the dispersive tails of tweek sferics near the cutoff frequencies is presented.
17 Sep 1995
TL;DR: The modified log-star function is introduced to reveal the existance of better prefix codes than the Elias omega code and other known codes, including the Bentley-Yao search tree.
Abstract: In this paper we study universal coding problems for the integers, in particular, establish rather tight lower and upper bounds for the Elias omega code and other codes. In these bounds, the so-called log-star function plays a central role. Furthermore, we investigate unbounded search trees induced by these codes, including the Bentley-Yao search tree. We will reveal beautiful recursion structures latent in these search trees as well as in these codes. Finally, we introduce the modified log-star function to reveal the existance of better prefix codes than the Elias omega code and other known codes.