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Simulation of Electrical Discharge Initiated by a Nanometer-Sized Probe in Atmospheric Conditions

Plasma Science and Technology 2013年第9期15卷 845-851页

作者：陈然陈池来刘友江王焕钦马源 michael cada Jrgen BRUGGER 孔德义 Department of physics University of Science and Technology of China State Key Laboratory of Transducer Technology Hefei Institute of Intelligent MachinesChinese Academy of Sciences Department of Electrical and Computer Engineering Dalhousie University Ecole polytechnique f'ed'erale de Lausanne(EPFL)

In this paper, a two-dimensional nanometer scale tip-plate discharge model has been employed to study nanoscale electrical discharge in atmospheric conditions. The field strength dis- tributions in a nanometer scale tip-to-plate electrode arrangement were calculated using the finite element analysis （FEA） method, and the influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of effective discharge range （EDR） on the plate were also investigated and discussed. The simulation results show that the probe with a wide tip will cause a larger effective discharge range on the plate; the field strength in the gap is notably higher than that induced by the sharp tip probe; the effective discharge range will increase linearly with the rise of excitation voltage, and decrease nonlinearly with the rise of gap length. In addition, probe dimension, especially the width/height ratio, affects the effective discharge range in different manners. With the width/height ratio rising from 1 ： 1 to 1 ： 10, the effective discharge range will maintain stable when the excitation voltage is around 50 V. This will increase when the excitation voltage gets higher and decrease as the excitation voltage gets lower. Fhrthermore, when the gap length is 5 nm and the excitation voltage is below 20 V, the diameter of EDR in our simulation is about 150 nm, which is consistent with the experiment results reported by other research groups. Our work provides a preliminary understanding of nanometer scale discharges and establishes a predictive structure-behavior relationship.

关键词： nanodischarge nanoscale AFM probe Peek's formula modified Paschencurve effective discharge range probe based data storage nanometer-sized ion source

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Linear Prolate Functions for Signal Extrapolation with Time Shift

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Applied Mathematics 2017年第4期8卷 417-427页

作者： Daniela Valente michael cada Jacek Ilow Department of Electrical and Computer Engineering Dalhousie University Halifax Canada

We propose a low complexity iterative algorithm for band limited signal extrapolation. The extrapolation method is based on the decomposition of finite segments of the signal via truncated series of real-valued linear prolate functions. Our theoretical derivation shows that given a truncated series (up to a selectable value) of prolate functions, it is possible to extrapolate the band limited function elsewhere if each extrapolated portion of the function is subject only to moderate truncation errors that we quantify in this paper. The effects of different sources of errors have been analyzed via extensive simulations. We have investigated a property of the signal decomposition formula based on linear prolate functions whereby the integration interval does not need to be symmetric with respect to the origin while time-shifted prolate functions are used in the series.

关键词： Real-Valued Band Limited Eigenvectors Signal Decomposition Signal Extrapolation

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Analysis and Design of Different Methods to Reach Optimum Power in Butler Matrix

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International Journal of Communications, Network and System Sciences 2019年第2期12卷 19-35页

作者： Shahideh Kiehbadroudinezhad Jean-Francois Bousquet michael cada Adib Shahabi Mohammad Ali Kiehbadroudinezhad Department of Electrical and Computer Engineering Dalhousie UniversityHalifaxCanada Department of Mechanic of Biosystems University of TehranTehranIran

With the increasing demand for high speed reliable communications, smart antennas, such as the Butler Matrix array, can be used to develop a system that increases the performance of a wireless system. The Butler matrix is a switched beam array system which can produce orthogonal uniform beams. The main objective is to improve the efficiency of the power in a 90-degree bend. Also, the double-mitered bend is particularly interesting since it provides a substantially lower reflection coefficient and a lower value of S12 at a frequency of 2.4 GHz compared to an unmitered one. Therefore, this paper describes an optimum design using a double-mitered method with a 2 × 2 and a 4 × 4 Butler Matrix array, operating at 2.4 GHz which is used in wireless systems with an FR4 substrate.

关键词： Butler Matrix Beam Forming Phase Shifter Micro Strip

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Expansion of a Y-Shaped Antenna Array and Optimization of the Future Antenna Array in Malaysia for Astronomical Applications

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Journal of Modern Physics 2019年第8期10卷 888-908页

作者： Shahideh Kiehbadroudinezhad Jean-Francois Bousquet michael cada C.Ian Short Adib Shahabi Samiramis Kiehbadroudinezhad Department of Electrical and Computer Engineering Faculty of EngineeringDalhousie UniversityHalifaxCanada Department of Astronomy and Physics Saint Mary’s UniversityHalifaxCanada Department of Physics Eberhard-Karls-Universitat TübingenTübingenGermany Department of Astronomy Institute of Astronomy and AstrophysicsTübingenGermany

To achieve high quality images from the sky by extending an existing interferometric array, in this work, the Geometrical Method (GM), Genetic Algorithm (GA), and Division Algorithm (DA) are compared. These methods are each applied independently to an interferometer array starting from the same initial conditions. Using the GM method, the spiral configuration is suggested as an optimum arrangement that provides the desired u-v coverage with low side lobe levels (SLLs). Using the GA method, as the number of generations is increased, the unsampled cells are reduced, enhancing the imaging quality. As such, the algorithm improves the overlapped samples as it works with a greater number of generations. Moreover, the GA is able to suppress the SLL. Finally, the DA is applied to such an array. Results show that the DA is able to process the sampled data with less overlapping of the data in the snapshot observations, in comparison to the other discussed configurations in this paper;effectively the DA reduces the overlapped samples, such that it is more efficient than the GA. The configuration of antennas that arrives by applying the DA method can achieve a certain image quality with less overlapping, as compared to the configuration arriving by applying the GA method. The calculated SLLs for the DA configuration are used to demonstrate that the efficiency of the DA is potentially better than that of the GA. Moreover, the GA and DA algorithms discussed in this study are applied to an array of 10 antennas with coordinates that represent the antennas deployed in Malaysia. Results show that the DA can reduce the overlapping of the samples more efficiently than the GA for a 6-hour tracking observation and in terms of unsampled cells the DA has the same efficiency of the GA.

关键词： Interferometers Telescopes Genetic Algorithm Array of Antennas

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