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مرکز اطلاعات علمی SID1
اسکوپوس
مرکز اطلاعات علمی SID
ریسرچگیت
strs
Issue Info: 
  • Year: 

    2015
  • Volume: 

    4
  • Issue: 

    1
  • Pages: 

    67-75
Measures: 
  • Citations: 

    0
  • Views: 

    36782
  • Downloads: 

    45857
Abstract: 

This paper presents a new approach for design of the log-periodic DIPOLE ARRAY antenna (LPDA) based on using of different design parameters in the LPDA elements to control the antenna behavior. In the proposed procedure, the design parameters can control the value of forward gain over the operating frequency range, and also adjust the gain flatness. Furthermore, this design procedure can decrease the LPDA dimensions in comparison to the conventional design. Based on the proposed design method, several LPDA antennas are designed and simulated numerically by the method of moment. The simulation results show that this LPDA design procedure can be a good candidate for design of optimized antenna in different frequency bands.

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Author(s): 

Valipour m. | FARHANG M.

Issue Info: 
  • Year: 

    2020
  • Volume: 

    19
  • Issue: 

    4
  • Pages: 

    795-801
Measures: 
  • Citations: 

    0
  • Views: 

    368
  • Downloads: 

    188
Abstract: 

DIPOLE asymmetry is among the most important anomalies in the cosmic microwave background (CMB). A DIPOLE, if primordial, would challenge the isotropy of the Universe. In this work, we propose a novel method to find the direction of the DIPOLE and its amplitude and assess its significance. The method is based on the comparison of annular variances on the sphere. We find the direction on the sphere around which the difference of the annular variances on the two hemispheres is maximized. By applying this algorithm on symmetric CMB simulations we get the distribution of the measured DIPOLE amplitude for these null cases, providing us with the baseline for quantifying the significance of DIPOLE amplitude of any other CMB maps. In particular, we find the statistical significance of the observed Planck DIPOLE to be 1. 6σ . Our simulations show that although the proposed method is not more powerful in detecting the DIPOLE compared to other algorithms, its relatively low computational cost (performed in the pixel-space) is its advantage. This paves the way for a straightforward upgrade of the method which uses spherical caps instead of rings and thus, by increasing the number of pixels used in calculating the variance, improves the results significantly.

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Issue Info: 
  • Year: 

    2020
  • Volume: 

    16
  • Issue: 

    4
  • Pages: 

    27-33
Measures: 
  • Citations: 

    0
  • Views: 

    438
  • Downloads: 

    309
Abstract: 

In this paper, a novel ultra-wideband DIPOLE antenna with a simple structure and low cost is presented. The impedance bandwidth (S11≤ 10 dB) of the proposed antenna is (1. 2_4. 55GHz) 116%. The whole of S-band frequency (2_4GHz) is covered completely and a part of L, C frequency bands are enveloped. The minimum and maximum gains in operation bandwidth are 2. 48dBi and 7. 48dBi respectively. The 50-ohm coaxial cable is utilized for feeding the antenna. To eliminate the backflow of the antenna and impedance matching with the coaxial transmission line, a Bazooka balun is adopted. Analysis of the current distribution and electric and magnetic fields on the DIPOLE element have been conducted. A prototype of the antenna is fabricated and return loss, gain and radiation pattern are simulated and measured. The simulation and measurement parameters are suitable agreement.

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گارگاه ها آموزشی
Issue Info: 
  • Year: 

    2020
  • Volume: 

    6
  • Issue: 

    1
  • Pages: 

    13-23
Measures: 
  • Citations: 

    0
  • Views: 

    865
  • Downloads: 

    333
Abstract: 

Sharifabad copper deposit is located on the Cenozoic volcanic belt in the northwest of Bardeskan, Khorasan Razavi Province. The host rocks of the mineralization are pyroxene andesite, tuff, agglomerate, limestone, sandstone, and micro conglomerate of the volcanic rocks of Eocene and Oligocene age. Alteration includes propylitic, silica and carbonate materials. Mineralization is restricted to the veins and veinlets and is controlled by the local faults. Mineralization mainly consists of chalcosite, magnetite, hematite, pyrite and malachite that occur in the cavities and fractures of the host rocks. Geophysical surveys using resistivity (Res) and induced polarization (IP) methods have been carried out along 5 survey lines. The results indicate high resistivity and IP values in the depth levels of 0-25 and 32-49 meters, and thus, relevant highly resistant horizons are identified. On the basis of the geological and geophysical studies in the area, eight locations for drilling exploration boreholes are proposed that probably contain highly concentrated copper mineralization. Introduction The Sharifabad copper deposit is situated in the Sabzevar zone and Eastern Iran Cenozoic volcanic rocks. The area is covered by a detailed exploration program, which includes preparation of the geological map of the area at 1: 5, 000 scale, and drilling several hundred meters of trenches. This study focuses on the copper bearing veins system and determination of subsurface mineralization by conducting geological and geophysical operations. For carrying out geophysical operations, 5 survey lines have been designed, and then, surveyed in the area. In this paper, the results of modeling and interpretation of geophysical data acquired along two survey lines DD1 and DD2 have been presented. The geophysical data include IP-Res measurements at 460 points along these two survey lines using DIPOLE-DIPOLE ARRAY with the electrode intervals of 20 meters that have been conducted by Omid Geological Engineering and Geo-Science Company. Methodology and Approaches The raw field geophysical data along the two survey lines DD1 and DD2 have been modeled using two-dimensional (2D) smooth Inversion by RES2DINV and ZONDRES2D software packages. The 2D model sections are displayed in threedimensional (3D) form using RockWorks software. The inverse modeling results and geological studies lead to the recognition of the copper mineralization zones and local faults in Sharifabad area. Results and Conclusions The results of geophysics studies in Sharifabad area show high resistivity and IP values in two depth levels 0 to 25 m and 32-49 m. On the basis of the geological and geophysical studies, eight locations for drilling exploration boreholes are proposed, and as a result, three boreholes have been drilled up to a depth ranging 33-40 m. Drilling studies confirm copper mineralization with high copper values in the depth of about 39m. These studies have also led to the identification of four local faults near the mineralization zones.

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    12
  • Issue: 

    2
  • Pages: 

    69-74
Measures: 
  • Citations: 

    0
  • Views: 

    20185
  • Downloads: 

    18189
Abstract: 

In this paper, thin DIPOLE is investigated in the 3.1-10.6 GHz Ultra-Wide Band frequency range. The study includes the design of half wave DIPOLE antenna with different DIPOLE radii to improve the antenna characteristics. Antenna parameters including return loss, Voltage Standing Wave Ratio, -10 dB bandwidth and radiation pattern are examined according to Federal Communication Commission regulations and Ultra-Wide Band system requirements in this frequency range. Additionally, two optimization techniques, Genetic Algorithm and Particle Swarm Optimization are applied to obtain the best DIPOLE radius. CST Microwave Studio, an electromagnetic simulation program, is used for the design of the antenna structure and the simulation purposes. The simulation is performed in transient mode. The results show that the antenna performance can be improved by selecting the suitable antenna dimensions. Additionally, Genetic Algorithm and Particle Swarm Optimization techniques are compared in terms of time consumption to obtain the best VSWR and return loss values. The results also depict that Genetic Algorithm yields better results for the proposed structure.

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Author(s): 

FALLAHI V. | KHALEDI NASAB ALI

Issue Info: 
  • Year: 

    2013
  • Volume: 

    3
  • Issue: 

    2
  • Pages: 

    131-135
Measures: 
  • Citations: 

    0
  • Views: 

    50403
  • Downloads: 

    19390
Abstract: 

In this paper, the interaction between an oscillating DIPOLE moment and a Silver nanoparticle has been studied. Our calculations are based on Mie scattering theory and discrete DIPOLE approximation (DDA) method. At first, the resonance frequency due to excitingthe localized surface plasmons has been obtained using Mie scattering theory and then by exciting a DIPOLE moment in theclose proximity of the nanoparticle, the induced charge distribution on the nanoparticle surface has been calculated. In our calculations, we have exploited the experimental data obtained by Johnson and Christy for dielectric function.

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strs
Author(s): 

RAMZI H.R. | KATIBEH H. | KEYVANI S.

Issue Info: 
  • Year: 

    2008
  • Volume: 

    29
  • Issue: 

    3 (GEOLOGY)
  • Pages: 

    157-168
Measures: 
  • Citations: 

    0
  • Views: 

    1096
  • Downloads: 

    288
Abstract: 

This paper is devoted to application of integrated geophysical methods in the investigation of Nazloo dam site, located in 27 km NW of Orumieh city. In this study, a combination of shallow seismic refraction profiling and resistivity sounding and DIPOLE-DIPOLE profiling methods were applied. The goals of study were the determination of alluvium properties such as thickness and grain-size, preparation of iso-depth map of the bed rock, iso-thickness map of alluvium in the dam foundation and rock mass quality in the dam embankments. The results lead to identify three layers in the alluvium with resistivity of 100, 300, and 1000 W m and P-wave velocities of 2000, 1000, and 500 m/sec from depth to surface respectively. Maximum thickness of the alluvium was found to be about 70 meter below the dam axis.

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    3
  • Issue: 

    2
  • Pages: 

    135-142
Measures: 
  • Citations: 

    778
  • Views: 

    82076
  • Downloads: 

    38028
Abstract: 

This paper presents a numerical method for analysis of electromagnetic radiation from thin wire DIPOLE antenna. For modeling of such structure, an appropriate form of Fredholm integral equation of the first kind is used, in which the unknown function is the current distribution on the surface of the antenna. An efficient collocation method is formulated for the solution of this integral equation whose main advantage is the use of entire domain basis functions. Finally, the radiation patterns for the antenna are given.

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Issue Info: 
  • Year: 

    2000
  • Volume: 

    11
  • Issue: 

    4
  • Pages: 

    39-50
Measures: 
  • Citations: 

    0
  • Views: 

    474
  • Downloads: 

    118
Keywords: 
Abstract: 

Nowadays mental disorders and body diseases is diagnosed using recorded scalp, deep and cortical electrical potentials. In this paper a novel method is presented to estimate the deep potential of the brain based on DLM technique using surface electrodes. The simulated results show while using this method and moving into depth we will be able to distinct different sources of activities inside the brain with high resolution, which is impossible by other general procedures.Increasing the number of scalp electrodes improves the accuracy of this method.

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Author(s): 

Azarian Abbas

Issue Info: 
  • Year: 

    2019
  • Volume: 

    14
  • Issue: 

    38
  • Pages: 

    61-67
Measures: 
  • Citations: 

    0
  • Views: 

    200
  • Downloads: 

    174
Abstract: 

In this article, the optical properties of Graphene/Au nanocubes have been studied for the different number of graphene layers on 1 or 2 faces of cubes. The extinction efficiency factor has been calculated in the near and far-field regime by the discrete DIPOLE approximation (DDA) method. Our results show that the height of extinction's peak decreases significantly, by increases number of graphene layers on nanocube. Moreover, the wavelength of surface plasmon resonance peak redshifts from 516 to 700 nm (this peak is due to DIPOLE formed alonge the polarisation direction), although the wavelength of the another peak stays constant about 230 nm(this peak is due to DIPOLE formed perpendicular to the polarisation). In addition, with increasing size of nanocubes, the height of peaks decrease, the width of them increase and wavelength of plasmon peaks don't show any shifts for a constant thickness of graphene. The results of this study may be used for fabrication of biological sensors at vis wavelength.

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