Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 17

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  84.40.-x
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

3D Imaging of Water Behavior at Millimeter Wavelength

100%
Sayinti A., Kaya A., Vertiy A.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
467-469
EN
During the transmission of electromagnetic radiation through a medium containing water molecules, portions of the electromagnetic spectrum are absorbed by water molecules. This water absorption occurs preferentially at certain characteristic wavelengths while the balance of the spectrum is transmitted with minimal effects. This characteristic of water provides advantages but also some disadvantages in science and engineering applications. Especially in remote sensing applications, it may cause to produce incorrect information. So identification of behavior of electromagnetic wave in water is significantly important. Some of the studies based on electromagnetic wave behavior in water are bio-medical researches, sensors, transmitters, accumulators, organic-inorganic materials, and microwave ovens. In this paper, based on the water's absorption of electronic wave property, a plastic cup as half-full of water is imaged using near field microwave system. After being processed with 3D-DLL algorithm it is imaged as 3D with IRIS software. A robotic system is used for data collection process. Transmission and reflection measurements of system are done with N5230A network analyzer.
2
Content available remote

Yearly, Seasonal and Daily Variations of Radio Refractivity

63%
Žilinskas M., Tamošiūnas S., Tamošiūnaitė M., Tamošiūnienė M.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 4
533-536
EN
Yearly, seasonal and daily variations of radio refractivity have been analyzed. The method proposed in the recommendation of International Telecommunication Union ITU has been used. The local meteorological data have been used in calculation of radio refractivity. The highest values of the radio refractivity have been observed in Klaipėda (in Seacoast) in the year 2009. In July, the values of the radio refractivity were highest in all localities investigated here and over all the time of the day in the year 2009. In the continental part of Lithuania (in Vilnius and Kaunas), analysis of radio refractivity has been made by using the meteorological data of longer period (starting from April 2005 up to July 2010). Five-year meteorological data collected in February, April, July and October have been used. It was obtained that the values of refractivity in the year 2010 are much higher than ones obtained in all the years of the period investigated here.
3
Publication available in full text mode
Content available

Submicrometric Heavily Doped n-GaAs Structures for Microwave Detection

63%
Ašmontas S., Gradauskas J., Kozič A., Shtrikmann H., Sužiedėlis A.
Acta Physica Polonica A
|
2005
|
vol. 107
|
issue 1
147-150
EN
Strong coupling between electrons and phonons in heavily doped semiconductors impedes, in general, investigation of hot carrier phenomena in the material. Investigations of hot electron electromotive force arising in symmetrically and asymmetrically shaped structures of heavily doped n-GaAs under microwave radiation are presented in this paper. Mesas of MBE grown n-GaAs layers with neck shaped down to submicron dimensions revealed strong dependence of voltage sensitivity of the structure on the size of the neck. Slight frequency dependence of voltage sensitivity of the microwave diodes with both symmetrically and asymmetrically shaped n-n^+ junctions was observed experimentally in K_a frequency range, which coincides well with theoretical predictions.
4
Content available remote

Wide Stopband Microstrip Bandpass Filter Based on a Compact Slotted Ground Structure

63%
Challal M., Dehmas M., Azrar A., Aksas R., Trabelsi M.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-71-B-72
EN
A new concept for implementing a bandpass filter by employing a discontinuity in the feed microstrip line in the upper layer and modified dumbbell-shaped slots etched in the ground plane is proposed. The effect of the slot area on the bandpass filter performance is examined. The proposed bandpass filter showed wide stopband and low insertion loss. To further verify the new concept, the structure is implemented and the measurement results are found to be in good agreement with the simulation ones. The proposed structure can be used in various microwave circuits.
5
Content available remote

Characterization of a Schottky Diode Rectenna for Millimeter Wave Power Beaming Using High Power Radiation Sources

51%
Etinger A., Pilossof M., Litvak B., Hardon D., Einat M., Kapilevich B., Pinhasi Y.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 5
1280-1284
EN
Two principal elements play a role in a wireless power beaming system: a high power radiation source as the transmitter and a rectifying antenna (rectenna) as an RF to DC converter at the receiving site. A millimeter wave power transmission is analyzed using transmission system and a W-band rectenna based on a low-barrier Schottky diode. A quasi-optical approach is presented here, using free-space Gaussian propagation and optical ABCD matrices for lenses. Experiments are made to estimate the optimal load resistance and power handling capability of a single rectifier. A low power W-band tunable solid-state source delivering 0.4 W CW power equipped by the focusing lenses is used to characterize the responsivity of the rectenna. A pulsed power gyrotron is used to identify the diode breakdown point. It was found that the RF-to-DC conversion efficiency corresponding to the optimal load of 200 Ω is about 20.5% while the maximum DC power converted by the diode with optimal load is about 15 mW before breakdown.
6
Content available remote

A System of B-C-N-O: Synthesis, Characterization and Determination of Unit Cell Parameters

51%
Gül G., Kurtuluş F.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 1
36-38
EN
Boron-rich solids are good candidates to apply instead of diamond. Boron has a unique crystal structure and compounds of it are resistant to heat treatment. These structures have light density, high hardness, and chemically inertness. Also, boron compounds display thermal and electronic properties as a thermoelectric power at high temperatures. A boron, carbon, nitrogen, and oxygen containing compound was synthesized for the first time by classical microwave method using elemental amorphous boron, active carbon, and urea with 1:1:1 molar ratio. The compound is crystallized in monoclinic system with unit cell parameters a=12.9575 Å, b=9.3264 Å, c=9.6529 Å, β =113.277° which are calculated by POWD indexing program. The X-ray diffraction, POWD, the Fourier transform infrared, scanning electron microscopy/energy X-ray diffraction spectroscopy and thermogravimetric/different thermal analysis were achieved.
7
Publication available in full text mode
Content available

High Power Microwave Detection in Asymmetrically Shaped n-Al_xGa_{1-x}As Structures

51%
Ašmontas S., Čerškus A., Gradauskas J., Kundrotas J., Lučun A., Petkun V., Sužiedėlis A., Šilėnas A.
Acta Physica Polonica A
|
2005
|
vol. 107
|
issue 2
315-318
EN
Investigations of detection of high power microwaves in planar asymmetrically shaped microwave diodes on the basis of Al_xGa_{1-x}As ternary semiconductors with various AlAs mole fraction are presented. The principle of operation of the microwave diodes is based on carrier heating phenomena in asymmetrically shaped homogeneous semiconductor structure due to different distribution of the electric field strength along the sample. Experimental results of microwave detection on the barrier-less asymmetrically shaped diodes are presented paying special attention to the homogeneity of Al_xGa_{1-x}As which was monitored by photoluminescence technique.
8
Content available remote

On Current and Prospective Use of Binary Thin Multilayers in Radar Absorbing Structures

51%
Kapelewski J.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 3
451-455
EN
The main objective of the paper is to overview of the actual and potential capabilities of some complex multilayers to enhance, and control the microwave absorption. Going through available literature data we emphasize the role of interphase coupling, and material resonances in enhancing phenomena of importance for internal scattering, diffusions, and intrinsic material absorption of propagating EM wave, especially in microwave and mm wave ranges. The theoretical background is consequently formulated in terms of transmissions line approach.
9
Content available remote

Microwave-Assisted Synthesis of CeVO_4 in the Mild Conditions, Characterization and Investigation of Luminescent Properties

51%
Çelik G., Kurtuluş F.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
357-358
EN
CeVO_4 (ICDD: 12-757) was synthesized by microwave-assisted method by using cerium sulphate and vanadium (V) oxide in an appropriate molar ratio. Characterizations were done by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet spectrophotometry and thermogravimetric/differential thermal analysis. The material is crystallized in tetragonal system with unit cell parameters a = 7.399 Å and c = 6.496 Å and space group I41/amd(141).
10
Content available remote

Optical mm-Wave Synthesizer Using Semiconductor Ring Laser (a Review)

51%
Memon M., Siraj M., Fathallah H.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1274-1276
EN
Millimeter wave (mm-wave) technology is significant for military needs and applications due to its numerous advantages, such as huge bandwidth, deploying small antenna and high radar resolution. Due to atmospheric influence, mm-wave is important in short-range applications such as fire control radar. Similarly for the next-generation communication and military applications, high-speed radio over fiber networks are very crucial. In this paper, a review of the generation and modulation of millimeter-wave signal optically using semiconductor ring laser (SRL) has been done. The phenomena of optical injection locking and four-wave mixing are exploited in SRL to generate radio frequency (RF) optical signals. The signals with huge data rate can be transferred directly from an intensity modulated optical signal onto a RF optical signal with RF frequency tunable in steps of the free spectrum range (FSR) of SRL. They can be converted with flexible RF modulation formats over the optical carrier.
11
Content available remote

Collapse of the Nonlinear Spin Dipole Wave Pulses of the Millimeter Wave Range in the YIG Films

45%
Grimalsky V., Koshevaya S., Kolokoltsev O.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 4
528-532
EN
The spatiotemporal collapse of the spin-dipole wave pulses of the millimeter wave range is investigated theoretically. The dispersion and the diffraction coefficients of spin-dipole wave have been calculated, when the retardation has been taken into account. It is demonstrated that YIG films are suitable for observing the wave collapse in the millimeter wave range, due to low dissipation and quite high values of dispersion and diffraction coefficients. In the hexaferrite films, despite the higher values of the dispersion and the diffraction coefficients, the dissipation prevents the formation of the spatiotemporal collapse. The additional focusing of the pulse can increase the nonlinear pulse compression. The numerical simulations have confirmed this result.
12
Content available remote

The Effect of Earth's Magnetic Field on the HF Radio Wave Modes at the Heated Subionosphere

45%
Canyilmaz M., Atici R., Guzel E.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 4
786-790
EN
In this study, the effect of the actual geometry of the magnetic field on the electron temperature has been investigated daily and seasonally for the electromagnetic wave travelling at subionosphere. The electron energy balance equation has been obtained by using the ideal gas approximation. The results show that there are notable differences between the two situations (B ∥ k ∥ z and B real, ∥ z). According to our theoretical study, the maximum changes are shown at L- and R-mode, small effect on X-mode and no variation on O-mode due to the real geometry of the magnetic field. Besides, the heights of the maximum points are changeable daily and seasonally for all modes at the subionosphere.
13
Content available remote

From Acoustic Waves to Microwaves

38%
Mendes Pacheco G., Salvi Sakamoto J., Kitano C.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 1
25-28
EN
We present here some results of our research related to the optoelectronics and photonics and show all the experimental setups used. Starting with a discussion on the importance of the waves, we demonstrate our achievements based on employment of acoustic, optical, and microwaves and their technological use. The results concern the acousto-optic and electro-optic effects. The generalized analysis of the electro-optic effect reveals a new high induced birefringence in lithium niobate. A patented optical fiber microphone is presented, and its applications to the measurements of acoustic wave velocity in gases and in the laser ultrasound non-destructive evaluation system are discussed. Finally, the generation of microwaves by an optical method with substantial cost reduction is presented.
14
Publication available in full text mode
Content available

Aspects of the Scattering and Impedance Properties of Chaotic Microwave Cavities

38%
Hemmady S., Zheng X., Antonsen T., Ott E., Anlage S.
Acta Physica Polonica A
|
2006
|
vol. 109
|
issue 1
65-71
EN
We consider the statistics of the impedance Z of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental Z data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized impedance whose probability density function is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We find that impedance fluctuations decrease with increasing loss. The results apply to scattering measurements on any wave chaotic system.
15
Content available remote

Transverse magnetic scattering of two incident plane waves by a dielectric coated cylindrical reflector

32%
Mushref M.
Open Physics
|
2005
|
vol. 3
|
issue 2
229-246
EN
Scattering characteristics of two plane waves are investigated for a circular cylinder covered by a dielectric substance. Fields are assumed to be transverse magnetic (TM) and represented in an exponential series form. The diffracted radiations are found by applying the boundary conditions to the wave functions. The wave transformation method and the orthogonality of the exponential functions are respectively employed to obtain an infinite series in the solution. Numerical results are evaluated by reducing the infinite series to a finite number of terms and comparing estimates with the single plane wave scattering situation.
16
Content available remote

Novel Route to Prepare Magnetic Material Co_3V_2O_8 and Structural Characterization

32%
Celik G., Kurtulus F., Guler H.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 1
203-204
EN
Co_3V_2O_8 is a member of kagomé staircase oxides, represented by general formula M_3V_2O_8 (M = Ni, Co, Mn). It attracted great attention due to strong magnetic anisotropy, magnetic phase transition, genuine macroscopic quantum effects, strong quantum fluctuations, low-temperature ferroelectricity, field-induced magnetic transitions, complicated phase diagram and displays long-range magnetic order because of geometrical frustration. Different routes to prepare the frustrated magnetic material was reported such as floating zone technique and conventional high temperature method. Co_3V_2O_8 (International Centre for Diffraction Data (ICDD): 16-675) was synthesized with Co_3O_4 (ICDD: 80-1536) as binary phase by microwave assisted preparation using Co(NO_3)_2 ·6H_2O and NH_4VO_3. The synthesized material was characterization by powder X-ray diffraction, the Fourier transform infrared spectroscopy, and thermogravimetric-differential thermal analysis.
17
Content available remote

Numerical Analysis of Metal-Cylinder-Based Microwave Plasma Module

26%
Sobański M., Jasiński M., Mizeraczyk J.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 6
1309-1312
EN
We present optimization of energy transfer in the waveguide-supplied metal-cylinder-based microwave plasma module with an inner cylindrical quartz tube. The construction of microwave plasma module is based on a WR 340 waveguide standard. Presented microwave plasma module operates at atmospheric pressure and frequency of 2.45 GHz. There is a reduced height section waveguide in microwave plasma module which provides local increase of the electric field in the plasma region. Microwave plasma module is terminated with a movable plunger which plays the role of the tuning element. Tuning characteristics of microwave plasma module are defined as the dependence of the P_{R}/P_{I} on the position l_{s} of the movable plunger, where P_{R} and P_{I} are the microwave power reflected and power incident, respectively. The powers P_{R} and P_{I} are measured in the input plane of microwave plasma module. The purpose of the presented optimization is to achieve P_{R} lower than 5% of P_{I} in widest range of position of movable plunger l_{s}. We used Comsol Multiphysics software to make numerical analysis which allows to optimize the parameters of microwave plasma module. Results of numerical analysis show that P_{R}/P_{I} is lower than 0.05 in a wide range of movable plunger position l_{s}.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.