Gap Phenomenon Research Articles

Effect of isolation mode and surface condition of an insulating barrier on the performance of a non-uniform field electrode system under positive DC voltage

The aim of this paper is the study of the effect of the isolation and the surface condition of an insulating barrier on the performance of a non-uniform field electrode system. The study is carried out under positive DC voltage. The dielectric properties of the material were measured using the Schering bridge. The effect of the material isolation mode in the point-plane air gap system on the optimisation of its performance was analyzed. Moreover we present findings of experiments which allow quantifying the effects of the clean or polluted atmosphere and the contamination severity level on the electric strength of the air gap system. Finally, this investigation has been supported by laboratory observations of the discharge phenomena in the air gap from inception to full flashover in all cases using a video camera system. The results from this study show that there is a distance limit of the isolation barrier beyond which its performance is optimal. In addition, a limit level of pollution, from which its minimal electric strength is equivalent to that of a conducting barrier, has been detected.

MODEL PENINGKATAN KINERJA UKM BERBASIS ORIENTASI ENTREPRENEUR

This study aims to examine how the model variables cover innovation entrepreneur orientation, learning orientation, initiative, commitment, adaptability and organizational performance based on the research gap and SMEs phenomena that exists in Semarang. The method used in this research is quantitative method. The data were collected through interviews by conducting the focus group disscusion (FGD), study documentation, and participant observation. The respondents of this research is 135 managers of SMEs in Semarang. The analysis techniques for this study is Structural Equation Model (SEM) with AMOS software. The study result shows that the increase of SMEs performance in Semarang is influenced by the ability of adaptability which is built by the commitment on consensus.

Fabrication of two-dimensional elliptic photonic lattices in photorefractive crystal by optical induction method

We fabricate two-dimensional elliptic photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time with optical induction method. The experimental setup of our method is very simple and flexible without complicated optical adjustment system. We analyze and verify the two-dimensional elliptic photonic lattices by plane wave guiding, far field diffraction pattern imaging, and Brillouin-zone spectroscopy. Induced elliptic photonic lattices can stably exist for a long time in the iron-doped lithium niobate crystal. The induced two-dimensional elliptic photonic lattices might offer an easy method to study generic band gap phenomena in anisotropic periodic structures.

Influence of Gap Phenomenon on Various Kinds of Powder-Suspended EDM

Powder-suspended Electrical Discharge Machining (EDM) produces a mirror-like finish due to the electrical discharge dispersed using powder-suspended fluid. Machined surface roughness differed, however, when several powders are mixed, so the influence of the gap phenomenon was not apparent. To vary the gap phenomenon in powder-suspended EDM, the gap region is observed using a high-speed camera. This report describes observation results in powdersuspended EDM.

Creating Structural Analysis Model from IFC-Based Structural Model

In recent years, with the rapid development of the complex building structures, the lack of collaborative work platform for the information exchange between different disciplines results in the phenomenon of information gap and information isolated island. Realizing such a demand, a software was developed for supporting information transformation from IFC-format data model to structural model. In this paper, A case study was implemented to illustrate the method of structural model transformation, The results show that the software can extract the information of IFC structural model and form a corresponding structural model.

Theoretical and Experimental Study of Locally Resonant and Bragg Band Gaps in Flexural Beams Carrying Periodic Arrays of Beam-Like Resonators

In this paper, we present a design of locally resonant (LR) beams using periodic arrays of beam-like resonators (or beam-like vibration absorbers) attached to a thin homogeneous beam. The main purpose of this work is twofold: (i) providing a theoretical characterization of the proposed LR beams, including the band gap behavior of infinite systems and the vibration transmittance of finite structures, and (ii) providing experimental evidence of the associated band gap properties, especially the coexistence of LR and Bragg band gaps, and their evolution with tuned local resonance. For the first purpose, an analytical method based on the spectral element formulations is presented, and then an in-depth numerical study is performed to examine the band gap effects. In particular, explicit formulas are provided to enable an exact calculation of band gaps and an approximate prediction of band gap edges. For the second purpose, we fabricate several LR beam specimens by mounting 16 equally spaced resonators onto a free-free host beam. These specimens use the same host beam, but the resonance frequencies of the resonators on each beam are different. We further measure the vibration transmittances of these specimens, which give evidence of three interesting band gap phenomena: (i) transition between LR and Bragg band gaps; (ii) near-coupling effect of the local resonance and Bragg scattering; and (iii) resonance frequency of local resonators outside of the LR band gap.

症例 房室結節のtriple pathwaysおよびHis-Purkinje系のdual pathwaysの関与する多種のgap現象を呈した症例

症例 房室結節のtriple pathwaysおよびHis-Purkinje系のdual pathwaysの関与する多種のgap現象を呈した症例

Theoretical analysis of transient wave propagation in the band gap of phononic system

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

Multiscale Modeling of Sinking-EDM with Gaussian Heat Flux via user Subroutine

The EDM gap phenomena in the microscale time and space domains are very complex and challenging to analyze experimentally. However, the gap phenomena are critical to produce optimal surface integrity for superior performance of EDMed components. Nevertheless, the highly nonlinear transient dynamic process involving time/space-dependent plasma and heat flux has not been well understood. This work presents a multiscale finite element modeling for single discharging of ASP2023 tool steel to incorporate the plasma-induced time/space-dependent Gaussian heat flux via a user subroutine. The long-standing numerical singularity of heat flux in EDM modeling is solved using the innovative functions of discharge current. The effects of discharge duration and current on temperature profiles, crater formation, and dimensions are investigated. The basic mechanisms of superheating and melting can be successfully predicted. In addition, melting front recedes at long discharge duration, while melting front advances at high discharge current.

High-Speed Imaging of EDM Gap Phenomena using Transparent Electrodes

In electrical discharge machining (EDM), discharge occurs with a high frequency in a narrow gap space between parallel plane electrodes filled with a dielectric fluid thus making direct observation of electrical discharge phenomena extremely difficult. On the other hand, SiC single crystals are electrica lly conductive and optically transparent. This paper describes observation of the EDM gap phenomena through the transparent electrode from the direction normal to the discharge surface using a high speed camera. In consecutive pulse discharges, distribution of discharge locations and volume fraction of bubbles in the working gap were clarified.

Gaussian and critical fluctuations in the electrical conductivity of YBa2Cu3O7-δ with chemically introduced disorder

We have studied experimentally by electrical magnetoconductivity measurements the influence of the site disorder, introduced by chemical doping, on the superconducting paring transition of the YBa2Cu3O7-δ superconductor. The measurements were performed in YBa2Cu3O7-δ and YBa1.9Sr0.1Cu3O7-δ single crystals with low magnetic fields applied either parallel or perpendicular to the superconducting Cu-O atomic planes. The in-plane electrical conductivity results show the systematic occurrence of tree-dimensional Gaussian (3D), tree-dimensional XY (3DXY) and beyond tree-dimensional XY fluctuation regimes, as the temperature is decreasing toward to the Tc of our samples. We propose that the observed beyond tree-dimensional XY fluctuation regime is precursory to a weak first-order superconducting transition driven by antiferromagnetic excitations related to the pseudo gap phenomenon. The experimental results shows that chemical introduced disorder, by Sr doping, does not hardly affect the stability of the beyond tree-dimensional XY fluctuation regimes in the YBa2Cu3O7-δ superconductor when H ≤ 600Oe are applied.

The gap phenomenon in the dimension study of finite type systems

Abstract Several examples of gaps (lacunes) between dimensions of maximal and submaximal symmetric models are considered, which include investigation of number of independent linear and quadratic integrals of metrics and counting the symmetries of geometric structures and differential equations. A general result clarifying this effect in the case when the structure is associated to a vector distribution, is proposed.

Gendered education in a gendered world: looking beyond cosmetic solutions to the gender gap in science

Young people in countries considered to be at the forefront of gender equity still tend to choose very traditional science subjects and careers. This is particularly the case in science, technology, engineering and mathematics subjects (STEM), which are largely male dominated. This article uses feminist critiques of science and science education to explore the underlying gendered assumptions of a research project aiming to contribute to improving recruitment, retention and gender equity patterns in STEM educations and careers. Much research has been carried out to understand this gender gap phenomenon as well as to suggest measures to reduce its occurrence. A significant portion of this research has focused on detecting the typical “female” and “male” interest in science and has consequently suggested that adjustments be made to science education to cater for these interests. This article argues that adjusting science subjects to match perceived typical girls’ and boys’ interests risks being ineffective, as it contributes to the imposition of stereotyped gender identity formation thereby also imposing the gender differences that these adjustments were intended to overcome. This article also argues that different ways of addressing gender issues in science education themselves reflects different notions of gender and science. Thus in order to reduce gender inequities in science these implicit notions of gender and science have to be made explicit. The article begins with an overview of the current situation regarding gender equity in some so- called gender equal countries. We then present three perspectives from feminist critiques of science on how gender can be seen to impact on science and science education. Thereafter we analyze recommendations from a contemporary research project to explore which of these perspectives is most prevalent.

Bounding the First Dirichlet Eigenvalue of a Tube Around a Complex Submanifold of ℂP n (λ) in Terms of the Degrees of the Polynomials Defining It

We obtain upper bounds for the first Dirichlet eigenvalue of a tube around a complex submanifold P of ℂPn(λ) which depends only on the radius of the tube, the degrees of the polynomials defining P, and the first eigenvalue of the tube around some model centers. The bounds are sharp on these models. Moreover, when the models used are ℂPq(λ) or Qn−1(λ) these bounds also provide gap phenomena and comparison results.

QUASI-BIENNIAL MODULATION OF GALACTIC COSMIC RAYS

The time variability of the cosmic-ray (CR) intensity at three different rigidities has been analyzed through the empirical mode decomposition technique for the period 1964-2004. Apart from the {approx}11 yr cycle, quasi-biennial oscillations (QBOs) have been detected as a prominent scale of variability in CR data, as well as in the heliomagnetic field magnitude at 1 AU and in the sunspot area. The superposition of the {approx}11 yr and QBO contributions reproduces the general features of the CR modulation, such as most of the step-like decreases and the Gnevyshev Gap phenomenon. A significant correlation has also been found between QBOs of the heliospheric magnetic field and the CR intensity during even solar activity cycles, suggesting that the former are responsible for step-like decreases in CR modulation, probably dominated by the particle diffusion/convection in such periods. In contrast, during odd-numbered cycles, no significant correlation is found. This could be explained with an enhanced drift effect also during the solar maximum or a greater influence of merged interaction regions at great heliocentric distances during odd cycles. Moreover, the QBOs of CR data are delayed with respect to sunspot activity, the lag being shorter for A > 0 periods of even cycles ({approx}1-4more » months) than for A < 0 periods of odd cycles ({approx}7-9 months); we suggest that solar QBOs also affect the recovery of the CR intensity after the solar activity maximum.« less

Estimation of partial discharge inception voltage of magnet wires under inverter surge voltage by volume-time theory

This paper discusses a novel estimation method for partial discharge inception voltage (PDIV) of magnet wire under inverter surge voltage application. We focused on the generation probability of initial electrons, which induce PD under high electric field and short rise time of surge voltage, by means of Volume-Time theory. We applied the Volume-Time theory to PD inception phenomena in a wedge-shaped air gap of twisted pair samples composed of enameled wires, and estimated PDIV in consideration of initial electron generation probability with temporal and spatial change in electric field distribution. We could estimate PDIV under different waveforms of applied surge voltage for different specifications of enameled wires. PDIV estimated by the extended Volume-Time theory agreed well with the measured PDIV. The estimated PDIV decreased with the increase in the rise time of applied voltage waveform, which corresponded to the V-t characteristics in the time range of inverter surge voltage.

Workpiece debris deposition on tool electrodes and secondary discharge phenomena in micro-EDM

During electrical discharge machining (EDM), ablated workpiece material is rapidly solidified upon ejection into the dielectric and thought not to become reattached to the electrode surfaces. This work furthers the understanding of the little understood discharge gap phenomena by investigating the attachment of machined material back onto the tool electrode surface and explains the mechanism of this attachment. After the machining of high-aspect ratio slots, SEM and EDS techniques along with single discharge and cross-sectional analysis were used to explain that debris reattachment onto the tool electrode does not occur randomly but is dependent on its remelting in the dielectric by the secondary discharge process. The subsequently bonded material is present mainly in the centre of the discharge crater, with no attachment occurring outside of discharge affected regions. The surfaces of electrodes subject to intense secondary sparking are therefore liable to transient surface properties dependent on the composition of the deposited material. It is also observed that the deposited material on the tool electrode can offer a protective effect against wear from further secondary discharges and so potentially enhancing tool life.

New Insights on Cosmic Ray Modulation through a Joint Use of Nonstationary Data-Processing Methods

The time variability of the cosmic ray (CR) intensity, recorded by the Climax neutron monitor and covering the period 1953–2004, has been analyzed by the joint application of the wavelet and the empirical mode decomposition (EMD) analyses. Dominant time scales of variability are found at~11 yr,~22 yr,~6 yr and in the range of the quasi-biennial oscillations (QBOs). The combination of the 11 yr cycle and QBOs explains the Gnevychev Gap (GG) phenomenon and many step-like decreases characterizing the CR modulation. The additional scales of variability at~22 yr and~6 yr are responsible for other features of the long-term CR trend, such as the intensity flat-topped profile, following the maxima of even-numbered cycles during positive polarity state of the heliosphere (). Comparison with basic time scales of variability derived from the sunspot area (SA) allows the association of the 11 yr cycle and QBOs with solar activity variations, whereas the other two modes with the drift effects govern the CR entrance in the heliosphere.

Acquiring Knowledge From the Media in the Internet Age

Democratic foundations rest on public support and a reasonably broad distribution of knowledge. The media have traditionally been assigned responsibility for providing much of that knowledge, but they do not inform all citizens equally; and communication scholars have, thus, studied the threat represented by the knowledge gap phenomenon. This study examines several factors on which the knowledge gap perspective is based in the online environment, including knowledge about international affairs, the local community, and the Internet. Results confirm gaps in all 3 knowledge types by education and income groups, including positive relationships between several media use and knowledge measures.

Does prior coronary artery bypass surgery alter the gender gap in patients presenting with acute coronary syndrome? A 20-year retrospective cohort study

ObjectivesPrevious studies demonstrated women presenting with acute coronary syndrome (ACS) have poor outcomes when compared with men ‘the gender gap phenomenon’. The impact of prior coronary artery bypass graft (CABG)...