bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross‐Sections, Rate Constants and Transport Coefficients in Silane Plasma Chemistry
Authors: Perrin J. , Leroy O. , Bordage M. C.
Published: July 2007

This paper presents a critical review of the basic data concerning the physics and chemistry of low pressure SiH4 glow discharges used to deposit hydrogenated amorphous silicon films (a‐Si:H). Starting with an updated table of thermochemical data, we analyze the gas‐phase elementary processes consisting of i) electron‐molecule collisions, ii) ion‐molecule collisions, iii) neutral‐neutral collisions, iv) other electron and ion collisions involving electron‐ion and ion‐ion recombination, electron attachment on radicals and detachment of anions, and v) cluster growth kinetics in dusty plasmas. Experimental data or theoretical estimates are given and discussed in terms of cross‐sections, collision and reaction rate constants, and transport coefficients. We also analyze the surface processes and reaction probabilities of ions, radicals and molecules.
Particle simulation of the plasma‐wall transition in presence of drifts perpendicular to the wall
Authors: Bergmann A. , Chodura R.
Published: July 2007

The flow of a non‐uniform collisionless plasma towards an absorbing wall is modelled with one‐ and two‐dimensional particle simulations. The influence on the plasma flow of the E × B and diamagnetic drift motion perpendicular to the wall is studied.
Power Balance in the ITER Plasma and Divertor
Authors: Post D. E. , Braams B. , Mandrekas J. , Stacey W. , Putvinskaya N.
Published: July 2007

It is planned to use atomic processes to spread out most of the heating power over the first wall and side walls to reduce the heat loads on the plasma facing components in ITER to ∼ 50 MW. Calculations indicate that there will be 100 MW in bremstrahlung radiation from the plasma center, 50 MW of radiation from the plasma edge inside the separatrix and 100 MW of radiation from the scrape‐off layer and divertor plasma, leaving 50 MW of power to be deposited on the divertor plates. The radiation losses are enhanced by the injection of impurities such as Neon or Argon at acceptably low levels (∼0.1 % Argon, etc.)
Particle in Cell Simulation on Thermoelectron Emission from Hot Target Plate
Authors: Ohno Noriyasu , Shimizu Eri , Takamura Shuichi
Published: July 2007

A space charge effect on thermoelectron emission current from an electron‐emissive target plate in plasmas has been investigated by using a self‐consistent particle in cell simulation code. Comparison between the conventional Child‐Langmuir's formula for the space charge limited current and the simulation results shows that we should employ αλD (λD : Debye length; α ∼ 2.6 in helium plasma, α ∼ 2.0 in hydrogen plasma) as the effective sheath thickness in the Child‐Langmuir's formula. The sheath voltage is found to be constant, independent of plasma density in the space charge limited condition. This can be clearly explained by the Stangeby's formula for a sheath voltage including the thermoelectron emission current determined by the above‐mentioned modified Child‐Langmuir's formula.
Bifurcation and Relaxation Oscillations in Divertor Plasmas
Authors: Bachmann P. , Sünder D. , Wenzel U.
Published: July 2007

This paper presents a contribution to bifurcation phenomena in scrape‐off layer modelling. The bifurcations are caused by the non‐monotonic temperature behaviour of the radiation characteristics of plasma impurities. Low‐frequency relaxation oscillations observed in divertor plasmas of the ASDEX Upgrade tokamak are analyzed and computed using a simple model for the dynamics of the impurity density and the electron temperature. The corresponding model equations are a special case of a general system of transport equations whose stability is analyzed. Bifurcations are calculated by solving autonomous and parametrically driven model equations.
Alfvén Waves in Non‐Stationary and Non‐Uniform Media: An Exactly Solvable Model
Authors: Stenflo L. , Shvartsburg A. B. , Weiland J.
Published: July 2007

The modulation of Alfvén waves interacting with a non‐uniform and non‐stationary plasma is considered. The waveforms are allowed to change rapidly. We examine our phenomena by means of exact analytical solutions of the MHD equations in the presence of large amplitude disturbances of the magnetic field and plasma density. In contrast to the WKB approach, we do not have to use limiting assumptions regarding the variations of the background medium. We show that the large amplitude time and space disturbances lead to a new cut‐off frequency for Alfvén wave propagation. A rapid reshaping of the Alfvén waveform can also obstruct the resonant interactions between the waves and the plasma particles.
A Linear Model for the Interpretation of Optical Emission Spectroscopy Measurements in Low Pressure DC Magnetron Sputtering
Authors: Schulte J. , Sobe G. , Reiss G.
Published: July 2007

For a balanced dc magnetron discharge a linear model for the formation of excited and ionized species is presented. The consideration is based on collisional kinetic theory and a correlation of discharge current with ionization rates, and leads to normalized rate coefficients. The electron energy distribution changes according to the determining external parameters, but needs neither to be known in detail nor to be of Maxwellian type. The model calculations are consistent with measurements done by optical emission spectroscopy (OES) on the magnetron sputtering of aluminium in argon discharges. The dependences of optical emission intensities on discharge current and on argon pressure show that both, excited argon atoms as well as excited argon ions, are generated from neutral argon by direct, fast electron impact. It is additionally shown that at least for low argon pressure the excitation of aluminium atoms is also caused by direct electron impact.
Advanced Divertor Concepts for Helical Devices
Authors: Ohyabu N. , Renner H.
Published: July 2007

Two large helical devices/ stellarators, LHD and W7X are under construction, equipped with divertor system. The divertor concepts in these devices are briefly reviewed.
Stochastic Magnetic Field Structure in the Edge Region of W7‐X
Authors: Strumberger E.
Published: July 2007

The topology of stochastic magnetic fields in the edge region of Wendelstein 7‐X (W7‐X) is investigated for fields with volume‐averaged β‐values of 〈β〉 = 0. 2 and 4% inside the last closed magnetic surface (LCMS) and rotational transform values of i > 1 in the edge region. The Kolmogorov lengths of flux tubes are determined and compared with the corresponding connection lengths to an outer limiting surface.
Finite Beta Electro‐Magnetic Effects at the Edge and the Role of the Scrape‐off Layer in the L‐H Transition
Authors: Chankin A. V. , Matthews G. F.
Published: July 2007

Magnetic induction becomes important when the skin‐depth equals the wavelength of the electrostatic drift turbulence: \documentclass{article}\pagestyle{empty}\begin{document}$ C/\sqrt 4 \pi \sigma \omega = K_ \bot ^{ - 1} $ \end{document}. It is predicted that this suppresses the longwave perturbations responsible for the bulk of the turbulent transport, providing an explanation for the L‐H transition. Since k⟂ρs ≪ 1 at the edge (ρs ‐ ion Larmor radius), this may occur at rather low β, typical of the separatrix parameters. The above equality is used to derive thresholds for the L‐H transition: β ≈ (k⟂ρs)2(me/mi)in the collisionless skin‐depth limit of very low density plasmas and \documentclass{article}\pagestyle{empty}\begin{document}$ T^3 _e \sim B^2 L_ \bot Z_{eff} /\sqrt m $\end{document} (L⟂‐perpendicular decay length) in the collisional skin‐depth limit of medium to high density plasmas. The latter is in a broad agreement with experiment, pointing to a possible role of low temperature collisional plasma (which is in the SOL) in the physics of the L‐H transition.
Long Mean Free Path Modifications of Electron Heat Conduction
Authors: Catto Peter J. , Yeoh Kim‐Ee
Published: July 2007

The Spitzer‐Härm parallel electron heat conductivity begins to fail even at surprisingly large values of collisionality because the energy squared dependence of the mean free path results in contributions from electrons not satisfying the short mean free path expansion. Self‐similar solutions of model problems are employed to demonstrate that exponentially small, non‐expandable modifications that cannot be retained in conventional treatments are the cause of the departure of heat transport from its Spitzer‐Härm value.
Hot Spot Formation on different Tokamak Wall Materials
Authors: Nedospasov A. V. , Bezlyudny I. V.
Published: July 2007

The thermal contraction phenomenon and generation of ‘hot spots’ due to thermoemission were described in [1–3]. The paper consider non‐linear stages of heat contraction on the graphite, beryllium, tungsten and vanadium wall. It is shown that on the beryllium surface hot spot can't appear due to strong cooling by sublimation. For other materials the conditions of hot spot appearance due to local superheating of the wall have been calculated and their parameters were found: critical surface temperature, size of spots and their temperature profiles, heat fluxes from plasma to the spots. It have been calculated fluxes of sublimating materials from spots to the plasma. It is noticed that nominal temperature of the grafite divertor plate, accepted in ITER's project to being equal 1500°C, is lower then critical temperature of the development heat contraction due to thermoemission.
One‐Particle Spectral Function of Electrons in a Hot and Dense Plasma
Authors: Wierling A. , Röpke G.
Published: July 2007

A self‐consistent determination of the spectral function and the self‐energy of electrons in a hot and dense plasma is reported. The self‐energy is determined within the approximation of the screened potential (GW approximation). The rigorous self‐consistent calculation of the spectral function is compared with the quasi‐particle approximation. Results are presented for the solar core plasma as well as for ICF plasmas. It is shown, that the quasi‐particle concept is not an adequate concept for these plasmas. For the sake of comparison an effective quasi‐particle picture is introduced.
Time ‐ Dependent Multi ‐ Term Treatment of Plasma Electrons Acted upon by RF Electric Fields
Authors: Loffhagen D. , Braglia G. L. , Winkler R.
Published: July 2007

Using a new method for solving the time‐dependent electron Boltzmann equation in higher order accuracy, studies of the temporal behaviour of electrons in weakly ionized, collision‐dominated plasmas under the action of rf fields have been performed. The method is based upon a multi‐term approximation of the Legendre polynomial expansion of electron velocity distribution function and is applied to investigate the established periodic behaviour of the electron velocity distribution in helium, argon and CO plasmas.

The results obtained in various approximation orders are discussed. The analysis has shown that the simplified treatment using only two terms of the velocity distribution expansion can fail in several conditions. In general, the four‐term approximation gives already a good representation of the convergent solution of the electron Boltzmann equation at each instant of the rf period. The discrepancies between two‐term and convergent results are found to depend sensitively on the specific atomic data, in particular on the magnitude of the various electron collision cross sections involved.

Furthermore, the results obtained in the multi‐term approximation are compared with corresponding ones obtained by accurate Monte Carlo simulations. Very good agreement between convergent eight‐term Boltzmann and Monte Carlo calculations is found.
Nonlinear Ion‐Acoustic Solitary Waves and Double Layers in Multicomponent Plasmas
Authors: Das G. C. , Talukdar Madhuri , Sarma Jnanjyoti
Published: July 2007

In sequel to earlier observations on soliton dynamics in the plasmas, a few more features on solitons and double layers have been studied in a nonisothermal plasma conceiving multi‐temperature electrons. The basic equations governing the plasma dynamics, based on quasipotential analysis, are first reduced to an energy integral equation known as Sagdeev potential equation, to elucidates the salient features plasma of acoustic modes associating to those furthered in laboratory and space plasmas. The Sagdeev potential equation, under small amplitude approximation derives various kinds of Korteweg de Vries (K‐dV) equations in nonisothermal plasma and is solved by employing a modified approach of simple wave solution technique called as tanh‐method. The analyses show, under certain conditions, the remarkable properties of soliton propagation and double layers of compressive and rarefactive nature in the plasmas. The outcome of the observations could be of interest further in understanding the features of various plasma acoustic waves in laboratory and space plasmas.
Quasiparticle Boltzmann Equation for Nonlocal Binary Collisons
Authors: Morawetz K. , Špička V. , Lipavský P.
Published: July 2007

Virial corrections to the Boltzmann equation for quasiparticles are obtained from non‐equilibrium Green's functions. These corrections are expressed in terms of shifts in space and time that characterize non‐locality of scattering integrals. The space shifts parallel finite‐diameter corrections to collisions of hard spheres. The time shift is identified as the collision delay. All shifts are given by derivatives of the phase shift in a binary collision.
Stopping Power of Proton Beam in a Weakly Non‐ideal Xenon Plasma
Authors: Mintsev V. , Gryaznov V. , Kulish M. , Filimonov A. , Fortov V. , Sharkov B. , Golubev A. , Fertman A. , Turtikov V. , Vishnevskiy A. , Kozodaev A. , Hoffmann D. H. H. , Funk U. , Stoewe S. , Geisel M. , Jacoby J. , Gardes D. , Chabot M.
Published: July 2007

Experimental equipment for the investigations of stopping power of proton beam in explosively driven plasma is described. A 3 MeV 60 μs duration proton beam pulses delivered by 148.5 MHz ISTRA‐36 RFQ linac at ITEP and compact metallic vacuum pumped chamber for explosions up to 150 g TNT were the main unit of this set‐up. Differential pumping and fast valves proved to be sufficient for the protection of high vacuum beam line from the high pressure detonation products. Compact explosively driven cumulative shock tubes were worked out to generate uniform plasma slug behind powerful shock waves with the velocities of 10 km/s at the initial pressure of Xenon 50‐200 kPa. Plasma parameters were: pressure 15–100 MPa, electron concentration 1E+19 ‐ 1E+20 1/cc, nonideality parameter 0.2–0.5. Stopping power of proton beam was defined by the displacement of the position of the spot image of the beam on the scintillator screen after it's passing through the analyzing magnet and by time of flight method. The measured values of proton beam energy losses were 100–300 keV in dependence on plasma parameters. Comparison of the experimental data with the theoretical models was carried out.
A Semirelativistic Equation of State for Stellar Interiors
Authors: Stolzmann W. , Blöcker T.
Published: July 2007

Using the technique of Padé Approximants for the correlation contributions of charged particles we are able to reproduce complex mathematical expressions by simple algebraic formulas. The Padé formulas are analytical expressions, which interpolate between certain density‐temperature regions and are characterized by exact asymptotics. We present a semi‐relativistic description of the thermodynamics applicable for stellar interiors. Comparisons with equation‐of‐state data obtained by other calculational schemes are presented.
Clusters Ions Fragmentation in Dense Target
Authors: Deutsch C.
Published: July 2007

The basics issues encountered in the expansion of microplasmas due to fragmentation of large n‐clusters when interacting with femtosecond laser pulses, or when accelerated toward cold matter and dense plasmas, are timely reviewed.
Electrical Conductivity of Fully‐Ionized Multicomponent Real and Model Plasmas
Authors: Tkachenko I. M. , De Córdoba P. Fernández
Published: July 2007

A self‐consistent field theory of transport properties of strongly coupled, fully ionized, multicomponent plasmas is successfully applied to real and model plasmas. In addition, a soft interpolation is found between the Monte‐Carlo OCP equation of state and the low‐density exact expansion by Abe.
Landau and Collisional Damping in Nonideal Plasmas
Authors: Kaklyugin A. S.
Published: July 2007

Taking into account collisional damping as a diffusion of nonuniformity of space distribution of the charges allows to present plasma polarization as a regular integral. Estimates of permittivity can be drawn from the proposed regular integral for both large and small frequences compared to wave number multiplied by thermal velocity of charges. It is shown that in nonideal plasmas: (1) plasma wave decrement decreases as nonideality grows, (2) negative dispersion appears for large wave number, (3) ion‐sound waves appear to be possible even in isothermal plasmas and their frequency turns out to be greater than the standard value about 1.5 times.
The Influences of the Magnetic Field Strength on the Magnetic Confinement of Primary Electrons in an Ion Source
Authors: Sandonato G. M. , Lima P. E. , Maciel H. S. , Otani C.
Published: July 2007

This paper deals with the simulation of trajectories of energetic electrons under the influence of a multi‐cusp magnetic field produced by a permanent magnet assembly in a ring cusp geometry which is designed for supporting a plasma based ion source. The primary electrons are assumed as being emitted from a cathode located coaxially with the cylindrical discharge chamber. The volume of the region occupied by the electron trajectories and the magnetic trapping time were evaluated and plots are presented showing the effects of the surface magnetic field strength of the magnets on the volume and the mean confinement time of primary electrons in the ion source.
Dielectric Function and Diffusivity of Nonideal Plasmas
Authors: Röpke G. , Redmer R. , Wierling A. , Reinholz H.
Published: July 2007

The dielectric function for a two‐component (hydrogen) plasma at arbitrary degeneracies is considered in the entire (k, w)‐space. Collisions are treated in Born approximation leading to a (k, w)‐dependent collision integral. Two possible limits are considered: (1) k → 0 (first), w → 0 (second) leading to the dc conductivity σ. (2) w → 0 (first), k → 0 (second) leading to the diffusivity D. The relation between σ and D is discussed.
Some Basic Physics Results for Plasma Spectroscopy and Modelling
Authors: Behringer K. , Fantz U.
Published: July 2007

Spectroscopic diagnostics and modelling of technical or divertor plasmas require many results from basic physics research. Reasonable simplifications must be introduced and information is necessary about atomic and molecular processes in the plasma volume and at the walls. As a first approximation, the corona model is presented, which is applicable for excitation and ionisation at low densities. This model requires cross sections and rate coefficients for electron impact. Many of these can be found in the literature, but it is also shown, how they can be estimated from the optical f‐values. Consideration of competing processes is often required, as e.g. dissociative excitation, excitation transfer, charge exchange or quenching. Some examples are reported. At higher electron densities, collisional‐radiative models must be used, which are available for electron impact collisions. Redistribution by neutral particles can present a major problem in low density discharges and many questions are still open. Heavy particle reaction rates are published in the literature, but must sometimes be taken with caution. The optical thickness of resonance lines is discussed, which may considerably affect line emission also in the visible spectral range. Models and programs are described for taking into account opacity and the results are shown. In addition to reaction cross sections, the electron energy distribution function must be known, which is often non‐Maxwellian. It is demonstrated, how deviations can be recognised in spectroscopic criteria with different energy thresholds and how the high‐energy tail may be reconstructed for further use in diagnostics or modelling. Eventually, a self‐consistent model of these plasmas is highly desirable calculating electrical and magnetic fields, all chemical reaction rates and the consequent distribution functions.
Modern Applications of Plasma Etching and Patterning in Silicon Process Technology
Authors: Engelhardt M.
Published: July 2007

Besides plasma etching of through‐wafer interconnects in wafer stacks for vertical integration of chips, fabrication of platinum (Pt) electrodes with non‐tapered sidewalls for the storage node in modern memories (DRAMs and FeRAMs) is one of the most challenging tasks of plasma process technology today.

This paper describes the achievement of vertical integration of chips by plasma etching of high aspect ratio interchip vias. The etching processes for dielectrics, single crystal silicon, and the organic glue layer were all optimized for minimum reactive ion etching (RIE) lag i.e. for minimum decrease of etch rate with increasing etch depth.

Furthermore the fabrication of perfect Pt electrodes for modern DRAMs and FeRAMs is reported. Vertical Pt profiles were achieved by plasma processing with resist mask. In this novel approach, the build‐up of thin redepositions of Pt onto the sidewalls of the resist, obtained as a result of processing in pure Ar plasmas, is utilized to achieve a sidewall steepness of the patterned Pt film which is determined by the steepness of the pre‐etch resist profile. After pattern transfer and resist stripping, the portion of the redepositions protruding above the fabricated storage node was completely removed by chemical mechanical polishing.
A time and wavelength division fiber loop distribution system with acousto‐optic tunable filters
Authors: Shimazu Yoshihiro , Kikuchi Shiro
Published: July 2007

A time and wavelength division fiber loop distribution system with acousto‐optic tunable filters is proposed. This system can provide a large number of 150 Mb/s HDTV channels with a reliable technology. A theoretical analysis by Gaussian beam approximation shows that one system can distribute 320 HDTV channels to 256 subscribers with a minimum wavelength spacing of 2 nm. An experimental 12 channel (4 time division × 3 wavelength division) system with a wavelength spacing of 20 nm in the 1.3 μm region demonstrates a data rate of 1.2 Gb/s with only −4dB loss and −20 dB crosstalk at the tunable filter. The experimental loss and crosstalk characteristics agree well with the theoretical analysis.
Professional viewpoint
Authors: Schaffer Bernhard
Published: July 2007

An invited contribution from a member of the editorial board, or another respected figure in the profession, in which a particular viewpoint is put forward giving an informed, but not necessarily conventional, opinion on a major topic in the field of communication systems.
Traffic characteristics and a congestion control scheme for an ATM network
Authors: Hirano Miki , Watanabe Naoya
Published: July 2007

In this paper, the cell loss rate and delay time of a cell multiplexer handling bursty input traffic are analysed, and the relation between these characteristics and burstiness is shown. Then, a buffer design guideline when input traffic characteristics are given is introduced for determining the queue size which satisfies permissible loss rate and delay time. Next, input traffic management and congestion control are discussed. For a congestion control, the marking method, which marks cells exceeding the bandwidth, allocated when the call is established, at a user/network interface, and discards those marked cells only at congested nodes, is evaluated. Simulation results show that the marking method can improve service quality and network throughput by allowing cells exceeding the allocated bandwidth into the network instead of discarding them.
Prototyping an ATM adaptation layer in a multimedia terminal
Authors: Armitage G. J. , Adams K. M.
Published: July 2007

This paper describes the implementation of a prototype ATM adaptation layer (AAL) within the kernels of two machines running Sun Operating System 4.1.1. The implementation is achieved by using the STREAMS paradigm and an Ethernet link between the two machines as a surrogate optical fibre link. The flexibility of the STREAMS facility for building layered protocols, and the real‐time performance limitations of the STREAMS scheduling system are identified. STREAMS is shown to be no less susceptible to naïve buffer utilization than earlier paradigms. It is necessary to minimize message passing and copying of data to achieve high throughput. This study has clarified several key issues in the functional design of AALs.
The JAK/STAT pathway regulates proximo‐distal patterning in Drosophila
Authors: Ayala‐Camargo Aidee , Ekas Laura A. , Flaherty Maria Sol , Baeg Gyeong‐Hun , Bach Erika A.
Published: July 2007

JAK/STAT signaling is thought to control growth and proliferation. However, here we show a novel role for this pathway in the patterning of Drosophila appendages. Loss of Stat92E function results mainly in ventralizations and multiplications of the proximo‐distal axis in leg and antenna, primarily through the ectopic misexpression of wingless. We also show that the pathway ligand Unpaired is expressed in two domains in leg and antenna that abuts those of wingless and decapentaplegic. We report that JAK/STAT signaling represses both wingless and decapentaplegic, restricting them to their respective domains in leg and antenna. In a reciprocal manner, we show that wingless and decapentaplegic restrict unpaired to its two domains. Thus, a main function of the JAK/STAT pathway in leg and antennal development is to promote the formation of a single proximo‐distal axis per disc by constraining the intersection of wingless and decapentaplegic to the center of the disc. Developmental Dynamics 236:2721–2730, 2007. © 2007 Wiley‐Liss, Inc.
A method of estimating the irregularity of scattering medium using characteristics of ultrasonic speckle
Authors: Ohya Akihisa , Kashioka Junji , Nakajima Masato
Published: July 2007

When examining a random group of scatterers, random granular patterns called speckle appear on echograms obtained by pulse echo ultrasonic diagnostic equipment. In living body organs such as the liver, there is a profound connection between the irregularity of the tissue structure and the severity of the disease. Therefore, if the degree of the irregularity can be estimated through analysis of the echogram, the possibility exists that the properties of the tissues can be diagnosed quantitatively.

This paper considers a medium that grouped scatterers as the model of the object and investigates the relationship between the statistics of interference pattern such as the speckle that appears on the ultrasonic echogram and the irregularity of the scattering medium. Also examined is the possibility of estimating the degree of irregularity of the medium from the echogram.

From the results of a computer simulation, it is found that if the density of the scatterers is known, the degree of irregularity of the medium can be determined from the value of the signal‐to‐noise ratio (SNR) statistic of the echogram. In addition, it is learned that by using the SNR as the statistics together with the skewness of the brightness histogram of the image, it is possible to estimate the degree of irregularity and the density of the scatterers.
A generalized principal component analysis for mixed measurement level data
Authors: Yaguchi Hiroyuki , Ichino Manabu
Published: July 2007

The principal component analysis is well known as a method to summarize the phenomenon described by the quantitative features. The quantification theory III is known as a method to summarize the phenomenon described by the mixed qualitative and quantitative features. However, several problems are pointed out in the quantification theory III, e.g., the manipulation containing an arbitrariness to divide the quantitative feature into intervals or the increase of the number of features due to the use of the dummy variables.

This paper proposes a generalization of the principal component analysis for the mixed qualitative and quantitative data. A model is considered which can handle the mixed qualitative and quantitative data, and the quantification of the information is executed on the model using the distance function. Then the principal component analysis is applied. The proposed method is a natural extension of the ordinary principal component analysis and has the advantages that the resolution for the score is high, the number of features is less, and the interpretation of the result of analysis is easy. Using two simple examples, the proposed method is compared to the quantification theory III and the effectiveness of the proposed method is demonstrated.
A method of selecting HDTV test pictures for subjective quality assessments
Authors: Tachi Takeshi , Iai Satoru , Kitawaki Nobuhiko
Published: July 2007

This paper presents a quantitative selection method for still images for use in assessment tests to obtain reasonable assessment results for high‐quality images in subjective assessment tests of high‐definition television (HDTV) signals. First, based on the selection criterion which is to select images that exhibit the characteristic of high quality, it was clarified that the three elementary psychological factors of vividness, comfortableness, and sharpness constituted the characteristics of high‐quality images and that the amplitudes of these psychological factors could be quantified by means of the statistics of the HVC signal distribution in the Munsell color space of the image.

Next, based on the selection criterion where images can be evaluated accurately even when slightly degraded, subjective assessment tests were performed for random additive noise, high‐frequency cutoff, and adaptive DCT coding distortion. The results showed clearly that images suited for use in the assessment test of each degradation could be selected based on the statistics of the image HVC signal distribution. By performing assessment tests using the smallest possible number of images selected by the guidelines presented here, assessment results can easily be obtained efficiently and reliably.
Stability analysis of periodic solutions in nonautonomous systems with hysteretic elements
Authors: Matsuo Tetsuji , Kishima Akira
Published: July 2007

This paper considers the case where hysteresis is given by the Preisach model and discusses the stability analysis for the periodic solution in the nonautonomous system containing hysteretic elements. The behavior of the system containing hysteretic elements is affected by the history of the system until it arrives at the steady state.

In this paper, it is shown first that even periodic solutions with the same hysteretic loop may have different variational systems for the steady‐state solution if the histories until arriving at the steady state are different. Next, two kinds of stability criteria are considered based on the difference of the history up to the steady state and the stability against the external disturbance is investigated. The dependence of the stability of the solution on the bifurcation of the periodic solution also is discussed. Finally, examples of numerical analysis are presented to verify the result of discussions.
Synchronized quasi‐periodic oscillations in a ring of coupled oscillators with hard characteristics
Authors: Yoshinaga Tetsuya , Kawakami Hiroshi
Published: July 2007

This paper considers properties of quasi‐periodic oscillations in a ring of mutually coupled oscillators and investigates phenomena such that envelopes of wave‐forms observed in the oscillators are synchronized dynamically.

Several properties derived from analysis using a perturbation method are discussed, and the following results are obtained: It is necessary for the stability of double‐mode oscillations that oscillators have hard characteristic nonlinearity; phase relations among envelopes depend on oscillatory mode combinations; and so on. It is shown that all quasi‐periodic oscillations, whose stability is suggested by the theoretical analysis, are observed numerically in up to four‐coupled oscillators. Moreover, the system parameter regions in which quasi‐periodic oscillations exist are given for two‐coupled oscillators and it is shown that an out‐of‐phase synchronization of envelopes can be explained by using the bifurcation theory of periodic oscillations.
An effective weighting method for hopfield neural networks
Authors: Mizutani Hikaru
Published: July 2007

The Hopfield neural network is considered to be promising as a means to solve the paired association problem, which is to recall complete information from incomplete information by realizing the highly parallel system. However, the neural network has problems in that the already memorized basic memory (complete information) which is the closest to the input, may not be recalled or a solution other than the basic memory may be recalled. When, for example, the neural network is weighted using the sum of the autocorrelation matrices, solutions other than the basic memory are produced as the outputs for more than half of the possible input incomplete information.

This paper aims to remedy these problems and proposes a new weighting method for the Hopfield neural network. In the proposed method, the evaluation function for the weighting is defined and the weights are determined so that the evaluation function is optimized.

To determine the weights by the proposed method, a fairly complex algorithm must be executed, compared to the calculation of the sum of the autocorrelation matrices. However, the weighting process is required only once in the design of the neural network and the neural network designed by this method is expected to exhibit a better performance than the traditional network.
Two‐route flows in an undirected flow network
Authors: Kishimoto Wataru , Takeuchi Masashi , Kishi Genya
Published: July 2007

This paper defines anew the maximum two‐route flow as a measure to represent the relation between two vertices in the flow network. The maximum two‐route flow corresponds to the maximum number of communication channels that are composed of two‐route paths between two terminals in a communication network. The ℱ‐rings that can be composed simultaneously, containing the considered two vertices, is defined as the maximum two‐route flow between those two vertices.

It is shown in this paper that a theorem exists for the maximum two‐route flow similar to the max‐flow min‐cut theorem for the ordinary flow.
A code to correct synchronization errors
Authors: Iwamura Keiichi , Imai Hideki
Published: July 2007

Until now, no code has been reported which can algebraically correct errors consisting in bit deletions or insertions (synchronization errors) and errors by bit inversion (inversion errors) when they occur simultaneously. This paper proposes a code that can algebraically correct simultaneously occurring synchronization and inversion errors as long as they occur within the range of a single byte. The proposed code is practical, involving very simple operations, and can correct synchronization and inversion errors in an information sequence of k bytes, where 1 byte consists of q bits, when the errors occur within a single byte. The redundancy and effectiveness of the code also are discussed.
An information‐theoretical approach and its application to optimal problems
Authors: Ohya Masanori , Mizu Masanori
Published: July 2007

There have been a large number of approaches to the optimal value problem but only a few from the information‐theoretical viewpoint. In particular, no measure to represent the easiness in solving the optimal value problem has been presented.

From such a viewpoint, this paper represents the object function which is the object of the optimization in the form of the Boltzmann distribution and the properties of the object function are represented quantitatively using the entropy S(pβ) ≡ − Σ pβ(x)log pβ(x) of the Boltzmann distribution.

It is noted that the optimal solution is difficult to obtain in the actual computation for the optimization problem taking discrete values. For this problem, a measure is introduced for the easiness of the problem (object function) to be optimized, apart from the algorithm to arrive at the optimal solution.
Bifurcations of equilibria and periodic solutions in a nonlinear autonomous system with symmetry
Authors: Katsuta Yuuji , Kawakami Hiroshi
Published: July 2007

In the engineering and physical systems described by a lumped‐constant system, sometimes a certain kind of symmetry is observed in the structure of the system or the nonlinear characteristics of the element. In such a system the symmetry is reflected on the state equation and the equation becomes invariant under the symmetrical transformation of the state variable.

It may happen in the state equation with a symmetry that there exists an equilibrium point or a periodic solution, and the solution bifurcates into the solution without a symmetry when the system parameter changes. This phenomenon is called symmetry‐breaking bifurcation.

This paper discusses the symmetry concerning the equilibrium point and the periodic solution of the autonomous system and presents the condition for the symmetry‐breaking bifurcation and the method to calculate the bifurcation parameters. It is pointed out that the symmetry‐breaking bifurcation is, in general, a degenerate bifurcation and the bifurcation parameters cannot be determined by the ordinary method. It is shown that, by considering the symmetry, the calculation is made possible and is simplified.
Characteristics and the present status of SAW materials in Japanese industries
Authors: Shimizu Yasutaka
Published: July 2007

Surface acoustic wave (SAW) devices have been used for filters, delay lines, resonators and oscillators. Since the characteristics of SAW devices are determined by the piezoelectric substrate, SAW devices must be selected for appropriate material.

This paper examines first the characteristics of SAW propagating through several kinds of piezoelectric substrates. Next, using the reports from companies involved with SAW devices, the application and development of piezoelectric materials and the present status of SAW devices will be summarized. The future of SAW materials will also be described.
Equivalent circuit consideration on null signals in a piezoelectric vibratory gyroscope
Authors: Sugawara Sumio , Konno Masashi , Kudo Subaru , Yoshida Tomio
Published: July 2007

An equivalent circuit analysis on a spurious component of the force factor, an input‐output electrostatic coupling and a mechanical coupling in a piezoelectric vibratory gyroscope is carried out. These factors cause leakage output. It is found quantitatively that the spurious component of the force factor and the input‐output electrostatic coupling generate a leakage output and provide a lateral shift in the characteristic of the synchronous detection output versus the applied angular rate of the vibratory gyroscope. It is found also that a large mechanical coupling not only generates a leakage output but also reduction of the sensitivity; and, hence, it is not desirable. Further, a method for reduction of these factors is presented and a design guideline of a vibratory gyroscope is summarized.
Error control technique for parallel combinatory spread spectrum communication system
Authors: Sasaki Shigenobu , Zhu Jinkang , Marubayashi Gen
Published: July 2007

This paper discusses the application of the error control technique for parallel combinatory spread spectrum (PC‐SS) communication system proposed previously by the authors. This paper considers the case where &‐bit information is transmitted in the spreading sequences and considers the following two coding methods as suited to PC‐SS systems: 1) to use 2k‐ary Reed‐Solomon code; and 2) to use the constant‐weight code by Chung et al. in the transmitter, converting the data into the combinatory spreading sequences, and to suppress the error in the receiver by taking the double correlation. The bit‐error rate performance is examined for the two methods and the effectiveness is discussed.

It is shown as a result that both methods are useful in improving the bit‐error rate of the PC‐SS system. In the latter method, the number of spreading sequences needed per user is reduced to approximately one‐fourth compared to the conventional PC‐SS system with nearly the same bit‐error rate.
Finite‐element analysis of SAW reflection from a metallic grating with an arbitrary angle of incidence
Authors: Ohbuchi Kazuhiro , Koshiba Masanori
Published: July 2007

With a view to developing a method enabling accurate derivation of the reflection characteristics for an oblique incidence of the surface acoustic wave (SAW) into a metallic grating which is a fundamental constituent element of an SAW device, an analysis method is formulated based on the finite‐element method (FEM). The FEM can easily be applied to an anisotropic and piezo‐electric substrate. It is possible to carry out an analysis taking into account the electrical perturbation, mechanical perturbation, and the energy storage effect by a nonradiating bulk wave at the reflection end.

In this paper, from the information on the stopband computed by the FEM, the amount of reflection per reflecting strip in the reflector and the shift of the center frequency of the stopband are computed. These quantities are actually computed for gratings on a Bi12GeO20 substrate and an ST‐cut quartz substrate so that the validity and usefulness of the present analysis method are presented.
Synchronization of nonlinear coupled oscillators
Authors: Hirai Kazumasa , Ohnishi Ryouta
Published: July 2007

This paper studies the synchronization phenomenon of frequency and phase of two coupled limit cycle oscillators. This problem is fundamental for many subsystems coupled to each other to behave autonomously.

A nonlinear coupled system becomes the gradient system if its coupling factors are chosen appropriately and then a potential function can be determined. Moreover, conditions for the potential function to have the minimum point are investigated and, from this condition, the synchronization conditions of frequency and phase of two coupled oscillators are studied. It is shown that the simulation results agree quite well with the theoretical ones.
Multilevel run‐length‐limited modulation codes for optical disk recording system
Authors: Honguh Yoshinori , Murakami Teruo
Published: July 2007

A generalization of the run‐length‐limited (RLL) code has been studied for multilevel recording systems where more than one kind of mark is used to record information. The run‐length constraints have been generalized to include the spacing in addition to the minimum and maximum run‐length constraints. The ratic of the minimum run length to the detection window has become arbitrarily adjustable. This provides the flexibility to design the modulation codes which match with the resolution and jitter characteristics of the recording system.

The method of the calculus of variations has been applied to the asymptotic behavior of the amount of information stored in a sufficiently long code sequence. The formulation has been obtained for the code characteristics, which include the maximum density ratio, the maximum amount of information contained in the detection window, the average rate of appearance for individual run lengths, etc.

The effect of the multilevel recording scheme depends on the number of the levels, the minimum and maximum run length, and the spacing. The optimum selection of these parameters can realize a large recording capacity close to the intrinsic potential of the multilevel recording system.
A model for multiple‐choice problem selection
Authors: Ueno Maomi , Nagaoka Keizo
Published: July 2007

This paper proposes a new model for the alternative selection process for multiple‐choice test items. The model has the following features in the description: (1) it can cope with the real‐time data, and (2) it is based on the entropy model. The feature of each selection item can be represented using the estimated parameters. Furthermore, using the indices derived from the model parameters, the extent of “illusion” among the test items can be represented quantitatively. The method is applied to the actual data and the following points are discussed: (1) validity of the model, (2) analysis of the characteristics of the selection item, and (3) characteristics analysis of alternative selection process. The effectiveness of the method is demonstrated.
A configuration methodology for high‐speed, bi‐level image codec LSI
Authors: Sato Fumitaka , Murayama Masayoshi
Published: July 2007

Earlier, the authors proposed a processing scheme for expansion of the MR/MMR code to improve the performance close to the limit of the method. This paper proposes the processing scheme for MR/MMR encoding (compression) which can suitably be combined with the previously proposed expansion processing scheme. The two schemes are combined to form a CODEC, which is implemented as an LSI;, and the result of evaluation is reported here. This kind of LSI will frequently be used in image retrieval‐type applications, and it is important to reduce the time for expansion processing.

In this study, the hardware needed in the proposed high‐performance expansion scheme is determined first and then the functions needed in the compression are mapped on the architecture. The length of the machine cycle is optimized from the viewpoint of expansion. When the delay in the compression circuit exceeds the machine cycle time, the function is divided into two cycles.

It is shown that the priority order of pass mode and V mode recommended by T.4/T.6 of CCITT desirably should be reversed from the viewpoint of design, in the case of compression processing. The effect of this reversal is examined. Based on those ideas, CODEC is designed and constructed. It is verified that the functions and performances are realized as are designed. The processing time is mostly proportional to the amount of images. The image data flow almost at a constant rate, which is convenient in the design of the pipeline structure.
Estimation of the system state of a non‐gaussian stochastic system based on the time transitions of moment and probability function—establishment of digital filter and experiment
Authors: Ikuta Akira , Ohta Mitsuo
Published: July 2007

The specific signal in the actual sound environment shows complex distribution forms apart from the standard Gaussian distribution, which is due to a variety of causes. Furthermore, the observed data are often contaminated by additional external noise with an arbitrary distribution type. In this paper, a digital filter for estimating recursively the state variable of a specific signal based on the observation data contaminated by non‐Gaussian type external noise is proposed. More concretely, two types of state estimation methods are derived by adopting respectively (i) a time series regression model and (ii) the entire conditional probability density function, as the state transition model (i.e., system equation). The effectiveness of the proposed method is experimentally confirmed by applying it to the actual data of an acoustic environment.