Vertical Current Components Research Articles

Broad axial ratio bandwidth circularly polarized with wide angle coverage planar monopole antenna

A G-shaped circularly polarized broad axial ratio bandwidth (ARBW) and high gain monopole antenna is proposed. The proposed design is imprinted on low cost, lossy FR4 substrate with relative permittivity 4.4 and loss tangent 0.025. The physical dimension of the proposed antenna is 0.36λ0×0.39λ0×0.02λ0. The G-shaped patch is developed by modifying conventional monopole radiator to create circular polarization (CP) for strong horizontal and vertical current components. The stubs, L – shaped, and T-shaped parasitic strips (PSs) are loaded at the finest positions on the ground layer of the antenna to improve the performance of ARBW and gain. The achieved percentage impedance bandwidth (IBW), ARBW, angle coverage and gain are 106%, 97%, 102° (3 dB axial ratio beam width from −46° to + 56° in XZ – plane) at 4.26 GHz and 5 dBic respectively. The fabricated antenna is reliable for IEEE standard WLAN and broadband wireless communication system.

Observed Suspended Sediment Dynamics during a Tidal Cycle above Submerged Asymmetric Compound Sand Waves

The data from Acoustic Doppler Current Profiler (ADCP) of the three-dimensional current-field, echo intensity, modulation of Suspended Sediment Concentration (SSC), and related water levels and wind velocities have been analyzed as a function of water depth above submerged asymmetric compound sand waves during a tidal cycle in the Lister Tief of the German Bight in the North Sea. Signatures of vertical current component, echo intensities and calculated SSC modulations in the water column depend strongly on wind and current velocity. Bursts of vertical current component and echo intensity are triggered by sand waves itself as well as by superimposed megaripples due to current wave interaction at high current 1.0 ms-1 and wind speeds 10.0 ms-1, preferably of opposite directions, measured at high spatial resolution. The magnitude of currents and SSC modulations during ebb and flood tidal current phases are only weakly time dependent, whereas the local magnitudes of these parameters are variable in space above the sand waves. Some hydrodynamic parameters are further investigated and analyzed, showing a consistence of ADCP measurements in the applied theory.

Piezoresistive CMOS sensor for out-of-plane normal stress

A piezoresistive sensor for measuring the temperature compensated sum (σxx+σyy)/2−βσzz of the three mechanical normal stress components, where σxx+σyy, σzz, and β denote the in-plane normal stress sum, the out-of-plane normal stress, and a numerical factor close to 1 is presented. The device is based on CMOS-compatible diffusions and exploits the piezoresistive effect acting on vertical current components. The sensor signal and resulting possibilities to extract mechanical stress components are analyzed. Experimental results illustrate the influence of design parameters and operating conditions on the sensor performance and are compared to a simple analytical sensor model. A second-order cross-sensitivity to in-plane shear stresses is discussed and determined experimentally. The temperature compensation is demonstrated by a force measurement with a deviation between the numerically expected and the experimentally extracted value smaller than 15% over the temperature range from 10°C to 60°C.

Improvement of the Light Extraction Efficiency in n-ZnO:Ga/p-Si Heterojunction Light Emitting Diodes by a SiO2 Current-Blocking Layer

We studied the role of a patterned SiO2 current-blocking layer (CBL) on the output power in polycrystal n-type ZnO:Ga/p-Si heterojunction light emitting diodes (LEDs). The introduction of a CBL considerably improved the light extraction efficiency by about 200%, despite the increased series resistance. It suppressed the vertical current with a low extraction efficiency by opaque metals and allowed the spreading current component to be enhanced, in contrast to conventional n-ZnO/p-Si LEDs operated only a vertical current component due to the grain boundaries in the ZnO films. This result suggests that the use of CBL is profitable method in the emitter application using the film with the polycrystal structure.

Improving the solution accuracy of thin dielectric approximation with a vertical electric field component

AbstractThe traditional thin dielectric sheet approximation (TDS) method models the electromagnetic scattering by thin dielectric sheet using surface integral equation. In this approximation, only the tangential current within the dielectric sheet is considered, and the vertical component is ignored. This article proposes a method that uses the volume integral equation solution to predict the vertical volume current and hence to improve the overall solution accuracy. The formulation is based on the hybrid surface (SIE) and volume integration equation (VIE) in which, the thin dielectric is modeled with SIE, and the thin layers are modeled by VIE. It is shown that the inclusion of the vertical current component does not increase memory and solution time. Numerical examples will be provided to demonstrate the effectiveness of this approach. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1978–1982, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23518

Patterns of summer vertical and horizontal currents in coastal waters of the northern Gulf of Aqaba, Red Sea

This study was focused on analysis of the horizontal and vertical current components with correspondence to tide variation, heat flux, seiches and relative backscatter intensity in coastal waters of the northern Gulf of Aqaba during the summers of 2001–2004. Spectrum analysis has shown eight distinguishable peaks of the tide measurements. In addition to semidiurnal and diurnal barotropic tides, signal periods of 8.13, 5.89–6.32 and 4.06 h were related to shallow water compound and overtides of the principal solar and lunar constituent and to seiches (second and third mode) generated in the Red Sea, whereas seiches of the first mode might enhance the semidiurnal tide signal. The shortest periods of 1.02–1.05, 0.50 and 0.36 h were related to seiches (first, second and third mode, respectively) generated in the Gulf of Aqaba. The spectrum analysis and cross-correlation tests of the horizontal and vertical current components and relative backscatter intensity suggested that the vertical motion at the diurnal period was either due to migration of zooplankton or to water convection. Both of which were of the same order as vertical motion induced by horizontal motions of water particles projected parallel on the bottom gradient line. On the other hand, semidiurnal and diurnal periods detected in the vertical currents were caused by the strong signal in the cross-shore current component, first mode seiches generated from the Red Sea and tide. This could be considered as an indicator of the dominant force influencing the currents, such as winds, thermocline depth, seiches and tidal forcing. A permanent convection during summer is likely to occur in the shallow coastal waters due to relatively high inclined bottom, high evaporation and blowing of dry air, as well as the observed dominance of the downward vertical currents in coastal waters.

Comparison of p-channel lateral insulated-gate bipolar transistors with and without collector shorts

The performances of p-channel lateral insulated-gate bipolar transistors (LIGBTs) with and without collector shorts on n/sup -/ epi/n/sup +/ substrates are compared. The collector-shorted devices have a 4* improvement in turn-off time but about 1-V higher forward drop, due to a substantially reduced vertical current component. The addition of a buried layer on the emitter side increases the forward drop and reduces the turn-off time slightly for both types of LIGBTs. The presence of the collector shorts significantly improves the breakdown voltage but increases the percentage of the lateral current component, leading to a lower maximum gate controllable current.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Current components of inversely operated vertical transistors for I 2L logic circuits

Computations have been carried out for the vertical current components of Integrated Injection and Substrate Fed Logic structures, incorporating heavy doping bandgap narrowing effects and dependence of mobility on doping level. The dependence of the current gain in the conventional I 2L on surface recombination velocity at n-n + interface is discussed. Computed results for the variation of current gain in different SFL structures, namely, ohmic base, Schottky base and double-diffused SFL structures, are presented.

Vertical current components in integrated injection logic

Analytic expressions representing a double diffused transistor impurity profile are used to calculate the current components in IIL structures. The expression for the hole current is given for IIL structures with the epitaxial layer grown on a wide n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> substrate and for buried layer structures. It was found that an equivalent recombination velocity at the n-n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> interface, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S_{nn+}</tex> , is of order 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> higher in buried layer structures than in structures with the epitaxial layer grown on a wide n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> substrate for comparable doping levels. Results obtained using the analytic expressions are compared with those obtained using a computer program which includes heavy doping effects and doping level mobility dependence. Both calculated and computed results are also compared with measured currents for a given IIL structure with the epitaxial layer grown on a wide n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> substrate. The calculated and the computed results are in good agreement with the experimental results.

Amplitude and Phase Fluctuations in Shallow Water

When an acoustic wave propagates through a turbulent medium, such as the ocean, the amplitude and phase of the incident wave experience fluctuations due to the variations of the acoustic index of refraction of the medium. Time series of experimental data of both the amplitude and phase fluctuations, the index of refraction, and the horizontal and vertical current components were obtained for a nearshore environment off Southern California. The acoustic signal output from a fixed narrow-beam ultrasonic source radiating in the CW pulse mode at 80, 90, and 100 Hz was received by a fixed directional receiver 25 m away. The vertical displacement between the two transducers was 17 m, and a sampling interval of 0.25 sec was used. This exercise was conducted in the presence of a strong seasonal thermocline separating water masses of different acoustical properties. The thermocline undergoes time- and space-dependent vertical motions related to internal waves. The projector was situated above and the receiver below the thermocline. Herein the line-of-sight propagation problem is considered and attention is given to the correlation functions and variances of the amplitude and phase fluctuations of the acoustic wave and their relation to the variation of the index of refraction along the path of wave propagation. It is shown that the turbulence near the transmitter has more effect on the fluctuation than the turbulence near the receiver.

The alteration of the magnetic field of transient variations by an axisymmetric island in a large ocean

It is shown how the density of electric currents flowing in a horizontal conducting slab (the sea) may be calculated by B.G. Galerkin's method of moments, when a uniform electric field acts in the slab. The slab is uniform except for a hole, symmetrical about a vertical axis (an island). The cross-section of the hole may be arbitrary. Electric current streamlines are drawn for an island whose shape is a frustum of a cone. The magnetic field of the disturbing currents is numerically computed using successive over-relaxation. These results are compared with a two dimensional model which is a modification of the model due to Ashour and Chapman (1965). It is shown that introducing the vertical current component in the sea affects the magnetic field at the surface of the island by only a few per cent of the total magnetic field. The computer model is applied to the study of the island effect on Oshima and Jarvis Islands. The computed results for Oshima Island explain the observed enhancement of Zat some points and the reversal, in fact, of Z at other points on the island.