bluuebunny/crossref_metadata_2025 huggingface dataset:
A Fuzzy Logic Knowledge-Based Approach for Finite Element Mesh Generation and Analysis
Authors: Kwok W. , Haghighi K.
Published: November 2005

A fuzzy logic knowledge-based approach, FUZZYMESH, for finite element mesh generation and analysis is presented. The proposed approach initiates the adaptive process with a high quality initial mesh that is more refined around the critical points/regions in the problem domain. In order to create high quality initial meshes, the heuristic knowledge, past experience, common sense, and ad hoc methods of finite element specialists are incorporated into the knowledge base of the fuzzy system. Using the linguistic variable concept and approximate reasoning techniques, the fuzzy system makes expert decisions about the initial mesh design by considering the geometric information, as well as the boundary and loading conditions. The decision process includes the determination of priority of critical points/regions and the prediction of mesh sizes for them. According to the mesh size information, a near-optimal initial mesh is created with an automatic mesh generator that is based on the advancing front mesh generation technique. The performance of the proposed approach was measured and evaluated in terms of efficiency and accuracy. The evaluation included comparison between the results of a code based on the proposed fuzzy logic knowledge-based approach, FUZZYMESH, and the conventional approach, which starts the finite element analysis with different meshes, by solving various problems. The global as well as local errors of different solutions were examined and compared. The CPU times for different approaches to achieve a particular accuracy were also measured and compared. The results showed that due to better quality of initial meshes, FUZZYMESH results in lower levels and more accurate error estimates. In turn, the proposed approach is able to solve the problem with a more accurate solution at less cost.
Inverse Pre-deformation of Finite Element Mesh for Large Deformation Analysis
Authors: Dheeravongkit Arbtip , Shimada Kenji
Published: November 2005

The process of finite element analysis that deals with large deformation often produces distorted elements in the later stages of the analysis. These distorted elements lead to analysis problems, such as inaccurate solutions, slow convergence, and premature termination of the analysis. This paper proposes a new mesh generation algorithm to mesh the input part for pure Lagrangian analysis, where our goal is to improve the shape quality of the elements along the analysis process to reduce the number of inverted elements at the later stage, and to decrease the possibility of premature termination of the analysis. One pre-analysis is required to collect geometric and stress information in the analysis. The proposed method then uses the deformed-shape boundary known from the pre-analysis, finds the optimal node locations, considers the stress information to control the mesh sizes, as well as control the mesh directionality, generates meshes on the deformed boundary, and finally, maps the elements back to the undeformed boundary using inverse bilinear mapping. The proposed method has been tested on two forging example problems. The results indicate that the method can improve the shape quality of the elements at the later stage of the analysis, and consequently extend the life of the analysis, thereby reducing the chance of premature analysis termination.
High-Quality and Property Controlled Finite Element Mesh Generation From Triangular Meshes using the Multiresolution Technique
Authors: Date Hiroaki , Kanai Satoshi , Kishinami Takeshi , Nishigaki Ichiro , Dohi Takayuki
Published: November 2005

In this paper, we propose a new triangular finite element mesh generation scheme from various kinds of triangular meshes using the multiresolution technique. The proposed scheme consists of two methods: a mesh quality improvement method and a mesh property control method. The basic strategy of these methods is a combination of the mesh subdivision and simplification. Given mesh is first subdivided to obtain enough degree of freedom for a property change, then by simplification using edge collapse for the resulting mesh to change the mesh properties, we can easily improve and control the mesh properties required for finite element analysis.
Optimal Boundary Triangulations of an Interpolating Ruled
Surface
Authors: Wang Charlie C. L. , Tang Kai
Published: November 2005

We investigate how to define a triangulated ruled surface interpolating two polygonal directrices that will meet a variety of optimization objectives which originate from many CAD/CAM and geometric modeling applications. This optimal triangulation problem is formulated as a combinatorial search problem whose search space however has the size tightly factorial to the numbers of points on the two directrices. To tackle this bound, we introduce a novel computational tool called multilayer directed graph and establish an equivalence between the optimal triangulation and the single-source shortest path problem on the graph. Well known graph search algorithms such as the Dijkstra’s are then employed to solve the single-source shortest path problem, which effectively solves the optimal triangulation problem in O(mn) time, where n and m are the numbers of vertices on the two directrices respectively. Numerous experimental examples are provided to demonstrate the usefulness of the proposed optimal triangulation problem in a variety of engineering applications.
Radiocarbon Variability in the Western North Atlantic During the Last Deglaciation
Authors: Robinson Laura F. , Adkins Jess F. , Keigwin Lloyd D. , Southon John , Fernandez Diego P. , Wang S-L , Scheirer Daniel S.
Published: November 2005

We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles.
GTF2IRD1 in Craniofacial Development of Humans and Mice
Authors: Tassabehji May , Hammond Peter , Karmiloff-Smith Annette , Thompson Pamela , Thorgeirsson Snorri S. , Durkin Marian E. , Popescu Nicholas C. , Hutton Timothy , Metcalfe Kay , Rucka Agnes , Stewart Helen , Read Andrew P. , Maconochie Mark , Donnai Dian
Published: November 2005

Craniofacial abnormalities account for about one-third of all human congenital defects, but our understanding of the genetic mechanisms governing craniofacial development is incomplete. We show that
GTF2IRD1
is a genetic determinant of mammalian craniofacial and cognitive development, and we implicate another member of the TFII-I transcription factor family,
GTF2I
, in both aspects.
Gtf2ird1
-null mice exhibit phenotypic abnormalities reminiscent of the human microdeletion disorder Williams-Beuren syndrome (WBS); craniofacial imaging reveals abnormalities in both skull and jaws that may arise through misregulation of
goosecoid
, a downstream target of
Gtf2ird1
. In humans, a rare WBS individual with an atypical deletion, including
GTF2IRD1
, shows facial dysmorphism and cognitive deficits that differ from those of classic WBS cases. We propose a mechanism of cumulative dosage effects of duplicated and diverged genes applicable to other human chromosomal disorders.
Pragmatic, observational study of bupropion treatment for smoking cessation in general practice
Authors: Wilkes S , Evans A , Henderson M , Gibson J
Published: November 2005

Background

Cigarette smoking remains the single largest cause of premature death in the United Kingdom. As part of the government’s national service framework for coronary heart disease, smoking cessation forms a key part of the strategy.

Objectives

To determine the effectiveness of bupropion treatment for smoking cessation in a general practice setting, measuring continuous abstinence from smoking, from 8 weeks to 52 weeks.

Design

Prospective observational study.

Setting

One general practice (six whole time equivalent doctors, 11 070 patients) in rural Northumberland.

Subjects

Of the 243 patients who presented to the practice over a one year period for smoking cessation, a total of 227 motivated people, who were appropriate for bupropion treatment as a pharmacological aid for smoking cessation, entered the study. Continuous smoking cessation at one year was validated by an exhaled carbon monoxide level of 10 ppm or less.

Results

Fifty patients successfully gave up smoking, giving a one year smoking cessation prevalence with bupropion of 22% (95% confidence intervals (CI) 17% to 28%). There was no difference in success rate for sex, number of cigarettes smoked, the number of years smoking, or whether there were other smokers in the household or not.

Conclusion

Bupropion treatment in this general practice helped 22% of motivated people to quit and remain stopped smoking at one year. Mainly nurses, whose prescribing rights are restricted and currently exclude bupropion, deliver smoking cessation services in primary care.
CLASSIFICATIONS OF AMINO ACIDS IN PROTEINS BY THE SELF-ORGANIZING MAP
Authors: CHEON MOOKYUNG , HEO MUYOUNG , CHANG IKSOO , KIM CHOONGRAK
Published: November 2005

We present the clustering properties of amino acids, which are building blocks of proteins, according to their physico-chemical characters. To classify the 20 kinds of amino acids, we employ a Self-Organizing Map (SOM) analysis for the Miyazawa-Jernigan (MJ) pairwise-contact matrix, the Environment-dependent One-body energy Parameters (EOP) and the one-body energy parameters incorporating the Ramachandran angle information (EOPR) over the EOP in proteins. We provide the new result of the SOM clustering for amino acids based on the EOPR and compare that with those from the MJ and the EOP matrix. All three kinds of energy parameters capture the leading role played by the hydrophobicity and the hydrophilicity of amino acids in protein folding. Our SOM analysis generally illustrates that both the EOP and the EOPR can provide the collective clustering of amino acids by the side chain characteristics and the secondary structure information. However, EOP is better at classifying amino acids according to their side chain characteristics whereas EOPR is better with secondary structure. We show that the EOP and the EOPR matrix manifests more detailed physico-chemical classification of amino acids than those from the MJ matrix, which does not contain a local environmental information of amino acids in the protein structures.
SOME CONSEQUENCES OF DARK ENERGY DENSITY VARYING EXPONENTIALLY WITH SCALE FACTOR
Authors: UNNIKRISHNAN SANIL , SESHADRI T. R.
Published: November 2005

In this paper we have explored the consequences of a model of dark energy with its energy density varying exponentially with the scale factor. We first consider the model with ρϕ∝eκa, where κ is a constant. This is a kind of generalization of the cosmological constant model with κ=0. We show that such an exponentially varying dark energy density with the scale factor naturally leads to an equivalent phantom field. We also consider a model with ρϕ∝eκ/a and show that this also naturally leads to an equivalent phantom field.
MOTION OF A VECTOR PARTICLE IN A CURVED SPACETIME. II: FIRST-ORDER CORRECTION TO A GEODESIC IN A SCHWARZSCHILD BACKGROUND
Authors: TURAKULOV ZAFAR , SAFONOVA MARGARITA
Published: November 2005

The influence of spin on a photon's motion in a Schwarzschild and FRW spacetimes is studied. The first-order correction to the geodesic motion is found. It is shown that unlike the worldlines of spinless particles, the photons worldlines do not lie in a plane.
4D GRAVITY ON A BRANE FROM BULK HIGHER-CURVATURE TERMS
Authors: CORRADINI OLINDO
Published: November 2005

We study a gravity model where a tensionful codimension-one three-brane is embedded in a bulk with infinite transverse length. We find that 4D gravity is induced on the brane already at the classical level if we include higher-curvature (Gauss–Bonnet) terms in the bulk. Consistency conditions appear to require a negative brane tension as well as a negative coupling for the higher-curvature terms.
RANK-BASED METHODS AS A NON-PARAMETRIC ALTERNATIVE OF THE T-STATISTIC FOR THE ANALYSIS OF BIOLOGICAL MICROARRAY DATA
Authors: BREITLING RAINER , HERZYK PAWEL
Published: November 2005

We have recently introduced a rank-based test statistic, RankProducts (RP), as a new non-parametric method for detecting differentially expressed genes in microarray experiments. It has been shown to generate surprisingly good results with biological datasets. The basis for this performance and the limits of the method are, however, little understood. Here we explore the performance of such rank-based approaches under a variety of conditions using simulated microarray data, and compare it with classical Wilcoxon rank sums and t-statistics, which form the basis of most alternative differential gene expression detection techniques.

We show that for realistic simulated microarray datasets, RP is more powerful and accurate for sorting genes by differential expression than t-statistics or Wilcoxon rank sums — in particular for replicate numbers below 10, which are most commonly used in biological experiments.

Its relative performance is particularly strong when the data are contaminated by non-normal random noise or when the samples are very inhomogenous, e.g. because they come from different time points or contain a mixture of affected and unaffected cells.

However, RP assumes equal measurement variance for all genes and tends to give overly optimistic p-values when this assumption is violated. It is therefore essential that proper variance stabilizing normalization is performed on the data before calculating the RP values. Where this is impossible, another rank-based variant of RP (average ranks) provides a useful alternative with very similar overall performance.

The Perl scripts implementing the simulation and evaluation are available upon request. Implementations of the RP method are available for download from the authors website ().
MINING TIME-DEPENDENT GENE FEATURES
Authors: CAPOBIANCO ENRICO
Published: November 2005

This paper presents an application of the Independent Component Analysis (ICA) method to genomic data. In particular, experimentally produced perturbation effects over the E.coli bacterium are monitored through the changes of gene expression values observed at regular times, and until steady state has been reached. The aim is to control the response of the SOS system to DNA damage. We might assume that only part of the genetic regulatory network is affected directly by the perturbation conditions, as indirect cascade effects might also be present, and some genes may change just because of randomness. ICA decomposes the gene matrix and identifies groups of genes belonging to a certain estimated component by virtue of co-expression; it is of course of interest to establish co-regulation dynamics, which might underlie the captured correlation. Stronger forms of dependence, like Mutual Information, are thus computed and compared with linear correlation in order to validate the results and establish the role of the identified components in determining the network dynamics.
A HYBRID GENETIC ALGORITHM AND EXPECTATION MAXIMIZATION METHOD FOR GLOBAL GENE TRAJECTORY CLUSTERING
Authors: CHAN ZEKE S. H. , KASABOV N. , COLLINS LESLEY
Published: November 2005

Clustering time-course gene expression data (gene trajectories) is an important step towards solving the complex problem of gene regulatory network modeling and discovery as it significantly reduces the dimensionality of the gene space required for analysis. Traditional clustering methods that perform hill-climbing from randomly initialized cluster centers are prone to produce inconsistent and sub-optimal cluster solutions over different runs. This paper introduces a novel method that hybridizes genetic algorithm (GA) and expectation maximization algorithms (EM) for clustering gene trajectories with the mixtures of multiple linear regression models (MLRs), with the objective of improving the global optimality and consistency of the clustering performance.

The proposed method is applied to cluster the human fibroblasts and the yeast time-course gene expression data based on their trajectory similarities. It outperforms the standard EM method significantly in terms of both clustering accuracy and consistency. The biological implications of the improved clustering performance are demonstrated.
ACTIVE SITE DRIVEN LIGAND DESIGN: AN EVOLUTIONARY APPROACH
Authors: BANDYOPADHYAY SANGHAMITRA , BAGCHI ANGSHUMAN , MAULIK UJJWAL
Published: November 2005

An evolutionary approach for designing a ligand molecule that can bind to the active site of a target protein is described in this article. An earlier attempt in this regard assumed a fixed tree structure of the ligand on both sides of the pharmacophore, and used a genetic algorithm for optimizing the van der Waals energy. However, it is evident that knowledge about the size of the tree is difficult to obtain an a priori. Moreover, it will also change from one active site to another. This limitation is overcome in the present article by using variable string length genetic algorithm (VGA) for evolving an appropriate arrangement of the basic functional units of the molecule to be designed, whose size may now vary. The crossover and mutation operators are appropriately redesigned in order to tackle the concept of variable length chromosomes. Once the geometry of the molecule is obtained, the possible three-dimensional structure and its docking energy is determined. Results are demonstrated for five different target proteins both numerically and pictorially. It is found that not only does the molecule designed using variable length representation, in general, have lower energy values, the docking energies are also lower, as compared to the molecule evolved using fixed size representation.
A STATISTICAL FRAMEWORK FOR HAPLOTYPE BLOCK INFERENCE
Authors: YUAN AO , CHEN GUANJIE , ROTIMI CHARLES , BONNEY GEORGE E.
Published: November 2005

The existence of haplotype blocks transmitted from parents to offspring has been suggested recently. This has created an interest in the inference of the block structure and length. The motivation is that haplotype blocks that are characterized well will make it relatively easier to quickly map all the genes carrying human diseases. To study the inference of haplotype block systematically, we propose a statistical framework. In this framework, the optimal haplotype block partitioning is formulated as the problem of statistical model selection; missing data can be handled in a standard statistical way; population strata can be implemented; block structure inference/hypothesis testing can be performed; prior knowledge, if present, can be incorporated to perform a Bayesian inference. The algorithm is linear in the number of loci, instead of NP-hard for many such algorithms. We illustrate the applications of our method to both simulated and real data sets.
Normalized Buchdahl's Aberration Coefficients of the 5th Order
Authors: Miyamoto Kenro
Published: November 2005

Buchdahl's aberration coefficients are normalized with respect to the numerical aperture and the field angle by the use of the normalized object-entrance pupil coordinates. The aberration Δ
Y' in the Gaussian image plane is given by

ΔY'/L
= ρ3
I
3(cos
θ, sin
θ)
+ ρ2(-n
1tan
α)I
I
3(1+2cos
2θ, 2cos
θsin
θ)
+ ···
+ ρ5
I
5(cos
θ, sin
θ)
+ ρ4(-n
1tan
α)(I
I
5'+I
I
5cos
2θ, I
I
5cos
θsin
θ)
+ ···

where (ρcos
θ, ρsin
θ) are the coordinates of a ray on the entrance pupil and tan
α is used to specify the incident angle of the principal ray. The calculation formulae for the coefficients of both spherical and aspherical systems are rearranged for the convenience of using an electronic computer. Numerical examples for Tessar, Sonnar and Gauss types are given and compared with the results obtained by ray-tracing.
Dislocations in Silicon Single Crystals
Authors: Furuoya Takashi
Published: November 2005

Dislocations and layer structures in silicon single crystals pulled by the Czockralski method are investigated by means of copper decoration as well as of etching with Dash's etchant. In the seeding process, a dislocation network is formed in the neighborhood of the interface between the seed and the grown crystal. Some of the dislocations propagate from the network into the grown crystal, their density being reduced under a favorable circumstance of crystal growth. Two types of layer structures are observed, one in dislocation free crystals and the other in crystals containing dislocation networks. These structures are ascertained to be caused by stratified accumulation of oxygen atoms in the form of clusters for dislocation free crystals and by stratified precipitation of oxygen atoms on the nodes of dislocation network for crystals containing many dislocations. Some interesting phenomena concerning the slips of the dislocations are discussed.
Effects of Vacuum-Drying on the Surface Properties of Germanium Transistor
Authors: Furusho Katsuhisa , Ono Kazumasa
Published: November 2005

It was investigated how the characteristics of germanium transistors, especially the ground-emitter current-amplification factor, h

f
e
, depend upon the process of vacuum-drying. It was found that the dominant factor was the adsorption and the desorption of water on the Ge surface. The surface contamination due to oil vapor from the mechanical vacuum pump also showed a great effect.
Improved Penetrometer for the Routine Test of Asphaltic Bitumens
Authors: Hirose Hidenori , Wada Yasaku
Published: November 2005

For the purpose of routine test of the asphaltic bitumen which in general exhibits both elasticity and viscosity, evaluation of the viscosity is of the first importance, because the retardation time is closely related to the viscosity. Other parameters which define the instantaneous and retarded elasticity of bitumen do not vary so much from bitumen to bitumen.
Unsuitableness of the conventional penetrometer to this purpose is clarified from both experimental and theoretical considerations. An improved type of penetrometer which exactly indicates the viscosity of a wide variety of bitumens is described. By the use of this instrument one can also measure approximately the shear creep compliance as a function of time.
Microplasmas in Silicon p-n Junctions
Authors: Maeda Keiji , Suzuki Katuhisa
Published: November 2005

Experiments are made on the microplasma pulses at the onset of avalanche breakdown in silicon p-n junctions. Critical experiments show that the carrier multiplication process is the most important in the turn-on probabilities, which are determined to vary exponentially with the applied voltage. The turn-off probability is qualitatively explainable by McIntyre's theory. The dimension and other characteristics of a microplasma region are also discussed.
Rates of variation of the breakdown voltage with temperature and pressure are calculated under the assumption that hot electrons are predominantly scattered by optical phonons. The calculated results agree well with observations.
High-Voltage Photovoltaic Effect in Evaporated CdTe Films
Authors: Kamiyama Masahide , Haradome Miyoshi , Kukimoto Hiroshi
Published: November 2005

The properties of CdTe films vacuum-evaporated at an oblique angle of incidence onto a substrate of glass, which are known to exhibit unusually high photovoltages, are experimentally studied. (1) The angular distribution of the intensity of light scattered by the film is asymmetric. (2) The (111) planes of the crystallites do not lie parallel to the substrate surface, as they do in the case of normal incidence. The incline of the (111) planes is determined in the main by the angle of incidence of vapor θ. (3) The photovoltage V exhibits a peculiar dependence on θ. It changes its sign at a certain value of θ, which in turn is determined by the substrate temperature.
A model is proposed for the structure of the film, which will explain the experimental results.
Study of the Lattice Defect in Martensite by X-Ray Diffraction (I)
Authors: Sato Shin'ichi
Published: November 2005

The profiles of Debye-Scherrer lines of martensite crystals in Fe-27%Ni alloy were measured by an X-ray diffractometer and analysed by Fourier method. As a reference the same experiment was made for filed iron. The results show that there is a large distortion in the martensite and that the widths of the lines have a strong index-dependence. The latter fact is interpreted by the existence of lattice strains and stacking faults (deformation faults or twin faults). These facts are discussed in comparison with the previous results by electron microscopy.
Domain Wall Caught in Dislocations in Ferroelectric Glycine Sulfate Crystals
Authors: Nakamura Terutaro , Nakamura Hanako
Published: November 2005

Simultaneous observation of both dislocation etch pits and ferroelectric domain walls was made on b-face of ferroelectric glycine sulfate crystals by etching technique with water. Negative end of the domain is pebbled while positive end is smooth. The dislocation etch pits are well discernible from the “pebbles” on the etched face. It was revealed that under applications of a d.c. electric field of about 30 v/cm a domain wall is caught in dislocations during the domain wall motion resulting in zig-zag shape. Evidences were obtained that also in as-grown crystals domain walls were caught in dislocations. It is assumed that dislocations in which a domain wall is caught are edge dislocations emerging out of b-face.
Turnover Phenomena in Plate Rectifiers
Authors: Numata Tadasi
Published: November 2005

On the application of short voltage pulse to selenium photocells, selenium rectifiers, and cuprous oxide rectifiers in the reverse direction, turnover phenomena are observed. The turnover behaviour of photocells is sensitive to light and the photo-breakdown occurs when the intensity of illumination exceeds a certain value.
Mechanical Dispersion and Molecular Motion in Crystals of Polyethylene and Other Polymers
Authors: Tsuge Kenji , Enjoji Hideo , Terada Hiroshi , Ozawa Yoshiyuki , Wada Yasuku
Published: November 2005

Dynamic mechanical loss of solution-grown polyethylene crystals is measured by the suspension method as a function of temperature and the crystalline dispersion (α dispersion) is observed above 40°C in just the same manner as in melt-grown polyethylene. In the temperature range of this dispersion, the ratio of crystal lattice constants b/a progressively changes toward that of a higher symmetry hexagonal form with increasing temperature. NMR line width of the broad component becomes gradually narrow with rising temperature in this temperature range. It is concluded from these reasons that the α dispersion of polyethylene should be ascribed to the rotational vibration of chain molecules in crystalline phase about c-axis. Similar behavior of low molecular weight paraffin crystals below the rotational transition point affords an additional confirmation of the above conclusion. Crystalline dispersions of other polymers are briefly discussed.
Tin-Tellurium Phase Diagram in the Vicinity of Stannous Telluride SnTe
Authors: Umeda Jun-ichi , Jeong Manu , Okada Toshihiro
Published: November 2005

A phase diagram of the Sn-Te system above 760°C is investigated by using thermal analysis and a controlled solidification technique. Stannous telluride contains 50.94 at.% Te, which correspond to SnTe1.038, at the melting point 804°C and forms no extended solid solutions with Sn or Te above 780°C. The deviation from the stoichiometric composition SnTe is of the same order as is estimated from the Hall coefficient. This non-stoichiometry may be responsible for the semi-metallic behaviours.
Die Wirkung der Kapazitäts- und Induktanzkomponente auf die Aktivierung des Gemisches bei der Funkenzündung in Gasen
Authors: Terao Kunio
Published: November 2005

The induction time to the beginning of ignition of n-hexane-air mixture by electric discharge was measured, in order to get the probabilities of ignition from its fluctuation. From these ignition probabilities the exciting energies of the spark were calculated and discussed upon the effect of two components, namely capacity component and inductance component, on the ignition.
Diffusion of Boron in Silicon through Oxide Layer
Authors: Horiuchi Shiro , Yamaguchi Jiro
Published: November 2005

The diffusion of boron into silicon through thermally grown oxide layers has been studied by an open tube diffusion technique. The experimental data are interpreted by a two boundary diffusion model, and diffusion constant of boron in silicon oxide is determined at several temperatures. The diffusion constant obtained at 1150°C is 1.2×10-16cm2/sec with an activation energy of ΔH=78 kcal/mol.
An anomalous diffusion is observed at a high impurity vapour pressure and a series of experimental results suggests conversion of silicon oxide into a “glassy layer” of unknown composition.
Microplasmas in Alloyed Germanium P-N Junctions
Authors: Tokuyama Takashi
Published: November 2005

Effect of dislocations present in the base crystal upon the electrical breakdown characteristics is studied for the case of germanium alloyed p
+-n junctions. Microplasmas are observed at liquid nitrogen temperature. Their number seems to be approximately equal to the number of dislocations traversing the p-n boundary of the sample. Such localized breakdown is considered to be due to large saturation currents and high multiplication factor at these spots where dislocations intersect the junction. The current instability may be explained on the basis of the statistical fluctuation of the saturation currents. As to the origin of the strong electric field intensity in the vicinity of a dislocation, geometrical unevenness of the p-n boundary could be assumed. But this assumption was not successfully verified experimentally.
Study of Field Emission Cathode by Field Ion Microscopy
Authors: Sugata Eizi , Nakamura Shogo
Published: November 2005

A blunting and build-up phenomena for field emission cathode of tungsten tip have been observed with the field ion microscope operated by hydrogen gas.
The change of the radius on each crystal plane of tungsten tip during the heat treatment is estimated from the voltage applied to obtain the fine field ion image. The diffusion constant of migration of tungsten atoms in blunting process is represented by D=D
0exp
(-Q/K
T) and the diffusion energy Q:2.3 eV and diffusivity constant D
0:3.6×10-3 cm2/sec are obtained from the change of radius of tip for various temperature.
Several kinds of build-up form are obtained by different electric field strength and temperature. The build-up surface of tip is easily reformed by heat-treatment and the rate of reformation coincides with the theoretical value estimated from Herring's theory on the simple model, using the diffusion constant obtained from our experimental value of blunting rate.
The recrystallization by heat-treatment on tungsten tip torn off by high electric field and on the tip with the polyhedral shape etched electrolytically are observed. The apex of the hemi-spherical surface of tungsten tip always coincides with (011) plane after heat-treatment.
A New Apparatus for Measuring Dynamic Viscoelastic Properties of Polymers
Authors: Fukuda Eiichi , Date Munehiro
Published: November 2005

The film-shaped specimen is subjected to a longitudinal forced vibration by an electromagnetic transducer. The displacement and force are detected electrically by two strain gauges connected to the clamped ends of specimen. These voltages are introduced to a specially devised circuit by which the values of dynamic elastic modulus and loss factor can be measured directly from the reading of dial in potentiometer and of output meter. The time required for measurement is only a few seconds. The observation of Lissajous' figure is also utilized at frequencies below 5c/s. The applicability of apparatus covers frequencies from 0.01 to 20c/s, temperatures from 20 to 180°C and magnitudes of elastic modulus from about 107 to 1011 dyne/cm2. The experimental results on some graft copolymers are exemplified.
Impedance Changes Induced by Photoconductive Effect in ZnS:Cu, Cl Phosphors
Authors: Uchida Ichizô
Published: November 2005

The photoconductivity of ZnS:Cu, Cl phosphors having green or blue emission is indirectly estimated from the capacitance changes induced by light. Under the irradiation of 365 mµ the photoconductive effect is remarkable in the green phosphors and is very small in the blue phosphors. This indicates that the electronic transition emitting green fluorescence is accompanied by a photoconductive process but the transition emitting blue fluorescence is not. In order to interprete the experimental results, three models are proposed for the emission mechanism in ZnS:Cu, Cl phosphors. An infrared photoconductive effect at 1.25 µ induced by previous irradiation of 365 mµ is observed with the green phosphors.
Measurement of the Stress and Strain on Specimens in an Electron Microscope
Authors: Saka Hiroyasu , Imura Toru , Yukawa Natsuo
Published: November 2005

A tensile device is developed which enables one to determine the stress-strain relationship of a specimen being extended during electron microscopic observation. The minimum detectable increment of load is about 0.01 g and the minimum detectable elongation is about 0.1%. Yield points of foils of Al and other metals are observable by 500 kV electron microscopy along the stress-strain curves.
Galvanomagnetic Effects in Silicon Surface Inversion Layers
Authors: Sakaki Hiroyuki , Sugano Takuo
Published: November 2005

In this paper a theory on the galvanomagnetic effect of two-dimensional electron gas in silicon surface inversion layers is presented together with experimental results on the (111) surface of silicon. The calculation takes into account two-dimensional many-valley energy band structure and energy-dependent relaxation time. An expression for the ratio of Hall mobility to conductivity mobility is obtained and the ratio is found to depend on crystal orientations, scattering mechanisms and carrier concentrations.
The theory of magnetoresistance is compared with experimental results measured on the (111) surface of silicon at 300°K and 77°K. Validity of the two-dimensional electron gas model for electrons in silicon surface inversion layers is evaluated and it is found that electrons behave neither as two-dimensional nor as three-dimensional gas but as the mixture of them at room temperature.
A Study of Thermally Oxidized SiO2 Films by Transmission Electron Micrographs
Authors: Yamazaki Shumpei , Kagawa Ichiro
Published: November 2005

The film structure of thermally oxidized SiO2 films close to the Si–SiO2 interface have been studied. When the (111) face silicon substrates were oxidized in dry oxygen, circular white spots are observed. The density and diameter of white spots were 78–101×108 cm-2 and 595–l360Å respectively when the substrates were oxidized at 1200°C for 6 hours. The activation energy derived from the relationship between the white spot density and the oxidation temperature was 58 kcal/mol. The dark spots surrounded by the circular white spots suggest that the excess silicon close to the interface localizes and forms excess silicon lumps. The dark and white spots were not observed when the (100) face silicon substrates are oxidized in dry oxygen at 1000–1200°C, and when the steam oxide specis were applied to the oxidation of both the (111) and (100) faces of silicon substrates at 1000–1200°C.
Theory of a Multimode Ring Laser
Authors: Miyashita Toyokatsu , Mori Hakuro , Ikenoue Jun-ichi
Published: November 2005

Amplitude and phase determining equations for a gaseous multimode ring laser are derived to the third-order approximation in the Doppler limit on the basis of Lamb's theory. Two kinds of self-phase locking phenomena are analyzed from those equations.
In the unidirectional three-mode ring laser, “0-type” or “π-type” locking occurs, unlike in the normal laser, according as the mode spacing is larger or smaller than a certain value which depends upon the decay constants of the active medium and the oscillation intensity.
In the bidirectional ring laser, there exists another kind of self-phase locking. It locks the phases of the oppositely traveling waves. According as the mode spacing is larger or smaller than the recovery rate of the population inversion, the oppositely traveling wave packets encounter at, or pass alternately through, the center of the active medium.
Stark Voltmeter as an Electromotive Force Reference
Authors: Hara Ko , Kobayashi Takeshi , Matsui Toshimi , Nakase Takahiro , Yonezaki Genta
Published: November 2005

An experimental study on a voltmeter application of the Stark effect in molecular rotational transitions aiming at an atomic voltage standard is described. A spectrometer using a Fabry-Perot resonator type Stark cell is built and the transitions J=2←1, Δ
M=±1 of s-trioxane C3H6O3 in the ground vibrational state at 21 GHz were observed. Preliminary values of the rotational constant B and µ/h (µ: dipole moment) are found to be 5273.2503±0.0006 MHz and (3.11536±0.00024)×108 esu, respectively. The estimated reproducibility of the voltmeter is 80 ppm at about 350 V/cm. Effects of three factors, Q-pulling of the cell, rf leakage field coupling in an external circuit and a frequency pulling by satellite lines, on the accuracy of the frequency measurement of spectra are discussed. The Stark cell is particularly devised for this study so as to establish an extremely uniform dc electric field and desired electrode separation. Performance of each part of the voltmeter is also reviewed.
Experimental Determination of Depth Distribution Function of Carbon Kα-Rays
Authors: Furuno Shigemi , Izui Kazuhiko
Published: November 2005

The depth distribution functions ϕ(ρx) of carbonKα-rays are determined by the experiment using carbon films of stepwise shape deposited on several kinds of substrates with atomic numbers close to that of carbon. Some results are presented for both ϕ(ρx) and X-ray intensity functionf(χ) at accelerating voltages of 5, 10 and 15 kV. It is found that Philibert's formula forf(χ) fits the present results by using suitable combinations of parameters involved.
Joule Heating in JFT-2
Authors: Takeda Tatsuoki , Itoh Satoshi
Published: November 2005

The time evolution of the spatially averaged values of the plasma parameters in JFT–2 are investigated numerically. The calculations are carried out by solving the simultaneous differential equations composed of the circuit equations and the plasma energy balance equations. Current which carries in the liner is calculated and the necessary one-turn resistance of the liner is estimated. The dependence of the ion temperature and the thermal conduction time on the plasma parameters are also obtained under several assumptions.
Some Improvements in a Neutron Time-of-Flight Spectrometer for D+T Neutrons
Authors: Hyakutake Mikio , Matoba Masaru , Tawara Hiroyuki , Wakuta Yoshihisa , Katase Akira , Sonoda Masateru
Published: November 2005

Some improvements in a neutron time-of-flight spectrometer using the associated particle method are described. A simple circuit is devised to compensate the dependence of the flight-time of neutrons of a given energy on the pulse height of the output signals of the neutron detector. By the use of this circuit in the time-of-flight spectrometer having been used in this laboratory a time resolution of 1.2 nsec (f.w.h.m.) is obtained for direct neutrons from the D+T source. The spectrometer system is also so improved that two neutron detectors operate together with a single set of circuits for n-γ discrimination and time-to-pulse height conversion. The effects of the shadow bar and detector shielding on the background level are studied. The background is reduced by an order of magnitude by the use of a suitable shadow bar and detector shield.
Purification of Bismuth by the Floating Zone Refining
Authors: Otake Shuichi , Matsuno Naoshi
Published: November 2005

In order to obtain extreme pure bismuth, the floating zone refining method is adopted in addition to the ordinary horizontal zone refining. Thereafter, single crystals of the desired orientations are grown by using seed crystals. The value of residual resistance ratio R
293$°$K/R
4.2$°$K which is measured along the binary axis is obtained as 738 at the largest. This is the highest value of purity when compared to the other published values.
Thermodynamic Analysis of Vapor Transport of GaP in the PCl3-Ga-H2 Reaction System
Authors: Hara Tohru , Asao Ichiro
Published: November 2005

A new approach to the thermodynamic analysis of the chemical transport reaction of the PCl3–Ga–H2 system is made. In this approach, the chemical reactions in reaction zone and deposition zone are analyzed individually. The result suggests that the Ga–P stoichiometry condition does not hold in their gas phase components and that the amount of gallium in gas phase in deposition zone is about 2.3 times as large as that of phosphorus. Growth rate of GaP was obtained from the calculated result as a function of temperature for various PCl3 to H2 feed ratios. A maximum growth rate occurs at around 730° and this temperature rises with increasing of PCl3 to H2 feed ratio. GaAs growth rate in the AsCl3–Ga–H2 reaction system is also obtained.
Equilibrium Concentration of Vacancies in Titanium Monoxide under High Pressure
Authors: Iwasaki Hiroshi
Published: November 2005

A simple statistical thermodynamical calculation is made to estimate an equilibrium concentration of vacancies under high pressure in titanium monoxide which contains an abnormally large number of vacancies in both titanium and oxygen lattice sites. Work necessary to create a vacancy, interaction energies between vacancies and entropy of mixing is taken into account in deriving Gibbs free energy of a titanium monoxide crystal. The contribution to the free energy from thermal vibration is also considered. The result of calculation shows that the concentration of vacancies, that is 14.5% at 1 bar, decreases to 10–14% under the pressure as high as 100 kbar, the amount of decrease being dependent on the parameters chosen. Discussion is given in terms of this theoretical prediction on the results of recent high pressure experiments made on titanium monoxides.
Build-up Phenomenon of Tungsten Cathode for FEM
Authors: Mun Dopyong , Sugata Eizi
Published: November 2005

The activation energy for migration of surface atoms is measured for the (111) or (130) plane of clean tungsten tip and for the (111) plane in the presence of oxygen. Values of the activation energy for (111) and (130) plane of the clean tungsten tip are 2.36±0.05 eV/atom and 2.10±0.05 eV/atom, respectively. When the oxygen pressure is relatively low (about 10-9 torr), the build-up phenomenon on the (111) planes occurred in twice with the lapse of time and the values of activation energy are 0.72±0.02 ev/atom and 1.10±0.05 eV/atom in each case. When the oxygen pressure is about 10-8 torr, the activation energy is 0.90±0.05 eV/atom. The decrease of activation energy due to polarization of an atom on clean surface by electrostatic field is about 0.4 eV/atom for the (111) or (130) plane, but when the oxygen is on the surface, the decrease for the (111) plane is only 0.1 eV/atom.
Properties of GaP Red-Emitting Diodes Grown by Liquid-Phase Epitaxy III. Effect of Holding Time at Growth Temperature
Authors: Kasami Akinobu , Naito Makoto , Toyama Masaharu
Published: November 2005

Effect of holding time after covering the substrate with epitaxy solution in n-on-p liquid-phase epitaxy of GaP red-emitting diodes is investigated. Emission efficiency increases sharply with increasing the holding time, reaches a maximum at 15–25 min. and then decreases. From measurements of the diodes photocurrent, this variation is shown to be due to the variation of Zn-O luminescent center concentration in the light-emitting region, and is explained by two competing processes. At a short holding time, the etching rate of the substrate surface in slightly unsaturated epitaxy solution is faster than the out-diffusion rate of zinc from the substrate surface. The surface layer deteriorated by preheating is then removed faster than it extends inward, and hence zinc and Zn-O pair concentrations in the active region increase with holding time. At a long holding time, the etching rate becomes slower than the diffusion rate, and zinc and Zn-O pair concentrations decrease.
Generalized Small Signal Admittances of Solid State Diodes
Authors: Hariu Takashi , Ono Shoichi , Shibata Yukio
Published: November 2005

A generalized expression of small signal admittances of solid state diodes with arbitrary field dependent carrier injection from the cathode is presented, which is characterized by an injection-controlling complex frequency ω
f
=[∂J

i
/∂E]
E=E
0/ε
and the dielectric relaxation frequency. The field dependent injection has considerable effects: positive mobility diodes have negative conductance similar to the monotron (cf., the metal-insulator-metal transit time effect diode), and the negative conductance of the negative mobility diode is made nearly independent of the transit angle (cf., the Schottky barrier contact Gunn diode). The Read diode is the case that ω
f
is pure imaginary and the emitter controlled negative conductance triode is the case that ω
f
is zero.
Calculations of Image Lag in Vidicon-Type Camera Tubes. II Image Lag for Moving Object: Dynamic Image Lag
Authors: Yoshida Okio
Published: November 2005

Image lags with delayed timing where the change of target illumination on a particular element occurs at a somewhat delayed time after the passing of the scanning electron beam are analyzed in vidicon-type camera tubes. Calculated image lags by varying the delayed time are rearranged into spatial order corresponding to the position of picture elements to obtain the dynamic image lags which reveal the pictures of moving objects displayed on a TV monitoring screen. The leading edges of moving bright objects are shown in the smooth rising curve, while their trailing edge are not shown in the smooth decaying curve, but the curves appear in waves, contrary to expectation. This will make the decay lag more objectionable than the rise lag in vidicon performance.
Low Frequency Noise in Unlocked Multimode He-Ne Lasers
Authors: Suzuki Takeo , Ieiri Shogo
Published: November 2005

The properties of the low frequency noise which appeared in unlocked multimode He-Ne lasers are investigated experimentally. It is found that the intensity of a mode fluctuated with opposite phase with respect to the adjacent modes. This behavior is discussed from the points of view of the mode competition and combination tones based on Lamb's theory.
Rotational Relaxation and Self-Trapping Threshold of Ultra-Short Pulses
Authors: Saikan Seishiro , Takuma Hiroshi
Published: November 2005

Self-trapping thresholds of 7 psec to 40 psec ruby laser pulses are measured in carbon disulphide, nitrobenzene, benzene, acetone, methanol, and water. The result indicates that Kerr effect is the dominant cause of self-trapping in those liquids. Temperature dependence measurement of the threshold in nitrobenzene shows that the contribution of Kerr effect is appreciable even if the pulse width is less than the relaxation time. The anti-Stokes rings are also observed in all of the liquids, and the emission angle measurement indicates that the filament size is independent of the pulse width.