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Tytuł:
Dose sensitivity enhancement on polymer gel with suspended gold particles
Autorzy:
Afonso, L. C.
Schöfer, F.
Hoeschen, Ch.
Caldas, L. V. E.
Powiązania:
https://bibliotekanauki.pl/articles/146797.pdf
Data publikacji:
2012
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
polymer gel
dose enhancement
radiation therapy
X-rays
Opis:
The presence of high Z material adjacent to soft tissue, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such an effect occurs due to the outscattering of photoelectrons from the high Z material. Polymer gel (PG) dosimeters were used to investigate this effect. Analytic calculations to estimate the dose enhancement were performed. Samples containing a polymer gel with 0.005 gAu/gPG and a pure polymer gel were irradiated using an X-ray beam produced by 150 kV, filtered with 4 mm Al and 5 mm Cu, which resulted in an approximately 20% greater absorbed dose in the samples with gold in comparison to those with the pure polymer gel. The analytic calculations resulted in a dose enhancement factor of approximately 30% for the gold concentration of 0.005 gAu/gPG.
Źródło:
Nukleonika; 2012, 57, 4; 467-472
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of linewidth enhancement factor (LEF) on routes to chaos in optically injected semiconductor lasers
Autorzy:
Al-Hosiny, N. M.
Powiązania:
https://bibliotekanauki.pl/articles/2033881.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
injection locking
chaos
linewidth enhancement factor
routes to chaos
Opis:
The effect of the linewidth enhancement factor (LEF) or α-factor on two common routes to chaos (mainly period-doubling and quasi-periodic routes) in optically injected semiconductor laser is theoretically investigated using bifurcation diagrams. The value of the LEF is slightly modified to examine the sensitivity of routes to chaos to any variation in the LEF. Despite the fact that LEF enhances chaos in the system, both routes are found to be highly insensitive to the variation in the LEF.
Źródło:
Optica Applicata; 2021, 51, 4; 621-632
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Contrast enhancement of scanning electron microscopy images using a noncomplex multiphase algorithm
Autorzy:
Alsaygh, Zaid
Al-Ameen, Zohair
Powiązania:
https://bibliotekanauki.pl/articles/2097436.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Promocji Wiedzy
Tematy:
image enhancement
SEM images
statistical approaches
contrast enhancement
Opis:
Microscopic technology has recently flourished, allowing unparalleled viewing of microscopic elements invisible to the normal eye. Still, the existence of unavoidable constraints led on many occasions to have low contrast scanning electron microscopic (SEM) images. Thus, a noncomplex multiphase (NM) algorithm is proposed in this study to provide better contrast for various SEM images. The developed algorithm contains the following stages: first, the intensities of the degraded image are modified using a two-step regularization procedure. Next, a gamma-corrected cumulative distribution function of the logarithmic uniform distribution approach is applied for contrast enhancement. Finally, an automated histogram expansion technique is used to redistribute the pixels of the image properly. The NM algorithm is applied to natural-contrast distorted SEM images, as well as its results are compared with six algorithms with different processing notions. To assess the quality of images, three modern metrics are utilized, in that each metric measures the quality based on unique aspects. Extensive appraisals revealed the adequate processing abilities of the NM algorithm, as it can process many images suitably and its performances outperformed many available contrast enhancement algorithms in different aspects.
Źródło:
Applied Computer Science; 2022, 18, 2; 28--42
1895-3735
Pojawia się w:
Applied Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of protrusions on the initiation of partial discharges in XLPE high voltage cables
Autorzy:
AlShaikh Saleh, Mohammad
Refaat, Shady S.
Olesz, Marek
Abu-Rub, Haitham
Guziński, Jarosław
Powiązania:
https://bibliotekanauki.pl/articles/2173562.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
FEA
finite elements analysis
protrusions
XLPE
water trees
partial discharge
void
space charge
stress enhancement factor
analiza elementów skończonych
kable XLPE
polietylen kablowy
polietylen sieciowany
wyładowanie niezupełne
ładunek przestrzenny
Opis:
This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; art. no. e136037
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of protrusions on the initiation of partial discharges in XLPE high voltage cables
Autorzy:
AlShaikh Saleh, Mohammad
Refaat, Shady S.
Olesz, Marek
Abu-Rub, Haitham
Guziński, Jarosław
Powiązania:
https://bibliotekanauki.pl/articles/2090691.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
FEA
finite elements analysis
protrusions
XLPE
water trees
partial discharge
void
space charge
stress enhancement factor
analiza elementów skończonych
kable XLPE
polietylen kablowy
polietylen sieciowany
wyładowanie niezupełne
ładunek przestrzenny
Opis:
This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; e136037, 1--9
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Beyond instructed L2 grammar acquisition: Theoretical insights and pedagogical considerations about the role of prior language knowledge
Autorzy:
Angelovska, Tanja
Powiązania:
https://bibliotekanauki.pl/articles/780551.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
prior language knowledge
input
practice
output
enhancement
grammar instruction
Opis:
The prior language knowledge of learners for whom the target language is not the first foreign language poses a different starting learning situation that should merit pedagogical attention. The present paper seeks to contribute to the question of which pedagogical considerations can be made in regard to the role of prior language knowledge beyond instructed L2 grammar acquisition. Moreover, it fills a significant gap expanding the limited existing pedagogical options that instructors have at their disposal when it comes to teaching in classrooms where one foreign language is simultaneously chronologically first to some and second to others. Starting with (combinations of) existing theoretical accounts and associated pedagogical aspects (such as explicit information, negative evidence, metalinguistic explanations, grammar consciousness raising, and input enhancement), a recently developed method (Hahn & Angelovska, 2017) is discussed. The method acknowledges equally the three phases of input, practice and output and is applicable in instructed L2 grammar acquisition and beyond.
Źródło:
Studies in Second Language Learning and Teaching; 2017, 7, 3; 397-417
2083-5205
2084-1965
Pojawia się w:
Studies in Second Language Learning and Teaching
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bandwidth Enhancement for Half Mode Substrate Integrated Waveguide Antenna using Defected Ground Structures
Autorzy:
Astuti, Dian Widi
Rivayanto
Muslim
Simanjuntak, Imelda
Firmansyah, Teguh
Cahyasiwi, Dwi Astuti
Natali, Yus
Powiązania:
https://bibliotekanauki.pl/articles/27311970.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
Bandwidth enhancement
dual cavity
half modesubstrate integrated waveguide
defected ground structure
U-slot
Opis:
The SIW antenna suffers from the narrow bandwidth for a single cavity and single resonant. Defected ground structure (DGS) with a dual cavity was the solution to solve narrow bandwidth by resulting in hybrid resonance. The hybrid resonance with 14.83% impedance bandwidth is proposed in this antenna design. The first resonance resulted from the combination of the TE101 modes from inner and outer HMSIW cavities while the second resonance resulted from the combination of the strong TE101 and the weak TE102 mode from the inner HMSIW cavity and the addition of the weak TE101 from the outer HMSIW cavity. The measurement antenna design has a broadband antenna with a 14.31% (5.71 – 6.59 GHz) impedance bandwidth by using substrate Rogers RO 5880.
Źródło:
International Journal of Electronics and Telecommunications; 2023, 69, 3; 449--454
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Systematic Review of Theoretical Foundations for Pedagogical Strategies to Promote Positive Behavior
Autorzy:
Awang, Mohd Mahzan
Snape, Divya-Jindal
Barber, Terry
Powiązania:
https://bibliotekanauki.pl/articles/1967524.pdf
Data publikacji:
2019-12-31
Wydawca:
Wydawnictwo Adam Marszałek
Tematy:
positive behaviour enhancement
pedagogical strategies
systematic review
theories
Opis:
This study analysed the theoretical foundations utilised by past empirical research in order to understand the pedagogical strategies used in schools for promoting positive behaviour. The analyses also include how pedagogical theories underpinned past research on positive behaviour enhancement. Samples for this study were academic papers obtained from four main databases: the Australian Education Index, British Education Index, ERIC (Educational Research Information Centre) and Scopus. By using a systematic review technique, a total number of 143 papers were found to be relevant for further analysis. Results revealed that four theoretical models dominate the studies examined, namely Applied Behavioural Analysis, Social Capital theory, Culturally Responsive Classroom Management, and Ecological Systems theory. This study recommends understanding of those theories is important in designing modules for positive behaviour enhancement in schools.
Źródło:
The New Educational Review; 2019, 58; 133-143
1732-6729
Pojawia się w:
The New Educational Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Foundations of the Navier-Stokes boundary conditions in fluid mechanics
Autorzy:
Badur, J.
Karcz, M.
Lemański, M.
Nastałek, L.
Powiązania:
https://bibliotekanauki.pl/articles/175407.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
enhancement
slip
Navier number
Navier-Stokes
nanoflow
Opis:
Until recently it was believed that Navier’s boundary condition could be given as a rigorous foundation for slip phenomena. Due to the latest measurements in the mass flow rate of a gas flowing through nano- and microchannels, several discrepancies in the mathematical modelling have been found. Thus, in the literature, the opinion persists for the Navier slip condition to be correct only under certain circumstances, particularly those restricted to the first order boundary conditions. One of many ways to eliminate this discrepancy, which is extensively employed in the contemporary literature, is to develop a variety of the so-called second order boundary conditions. This path, however, seems incorrect since it lacks consistency between the bulk stress tensor and its boundary representation. In the paper we propose to replace the classical Navier slip condition with the new, more general Navier-Stokes slip boundary condition. Instead of the usual method of consideration, the boundary condition is presented as following from the mass and momentum balances within a thin, shell-like moving layer. Owing to this, the problem of consistency between the internal and external friction in a viscous fluid is solved within the framework of new layer balances, and a proper form of constitutive relations for friction and mobility forces. Finally, the common features of the Navier, Stokes, Maxwell and Reynolds concepts of a boundary slip layer are compared and revalorized. The classifications of different mobility mechanisms, important for flows in nano-, microchannels are also discussed.
Źródło:
Transactions of the Institute of Fluid-Flow Machinery; 2011, 123; 3-55
0079-3205
Pojawia się w:
Transactions of the Institute of Fluid-Flow Machinery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Monte Carlo study on dose enhancement and photon contamination production by various nanoparticles in electron mode of a medical linac
Autorzy:
Bahreyni Toossi, M. T.
Ghorbani, M.
Sobhkhiz Sabet, L.
Akbari, F.
Mehrpouyan, M.
Powiązania:
https://bibliotekanauki.pl/articles/146518.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
dose enhancement
electron mode
Monte Carlo
nanoparticles
photon contamination
Opis:
The aim of this study is the evaluation of electron dose enhancement and photon contamination production by various nanoparticles in the electron mode of a medical linac. MCNPX Monte Carlo code was used for simulation of Siemens Primus linac as well as a phantom and a tumor loaded with nanoparticles. Electron dose enhancement by Au, Ag, I and Fe2O3 nanoparticles of 7, 18 and 30 mg/ml concentrations for 8, 12 and 14 MeV electrons was calculated. The increase in photon contamination due to the presence of the nanoparticles was evaluated as well. The above effects were evaluated for 500 keV and 10 keV energy cut-offs defined for electrons and photons. For 500 keV energy cut-off, there was no significant electron dose enhancement. However, for 10 keV energy cut-off, a maximum electron dose enhancement factor of 1.08 was observed for 30 mg/ml of gold nanoparticles with 8 MeV electrons. An increase in photon contamination due to nanoparticles was also observed which existed mainly inside the tumor. A maximum photon dose increase factor of 1.07 was observed inside the tumor with Au nanoparticles. Nanoparticles can be used for the enhancement of electron dose in the electron mode of a linac. Lower energy electron beams, and nanoparticles with higher atomic number, can be of greater benefi t in this field. Photons originating from nanoparticles will increase the photon dose inside the tumor, and will be an additional advantage of the use of nanoparticles in radiotherapy with electron beams.
Źródło:
Nukleonika; 2015, 60, No. 3, part 1; 489-496
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Porównanie wybranych metod oceny kontrastu achromatycznych obrazów cyfrowych
Comparison of selected gray-level image contrast evaluation methods
Autorzy:
Bal, A.
Powiązania:
https://bibliotekanauki.pl/articles/154187.pdf
Data publikacji:
2009
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
wstępne przetwarzanie obrazów
poprawa kontrastu
globalne i lokalne metody poprawy kontrastu
ocena kontrastu obrazu
image preprocessing
contrast enhancement
global and local image contrast enhancement methods
image contrast evaluation
Opis:
Praca dotyczy zagadnienia oceny kontrastu achromatycznych obrazów cyfrowych. Przedstawiono i porównano znane z literatury metody oceny kontrastu obrazów, a także zaproponowano nowe rozwiązania bazujące na określeniu różnic poziomów szarości sąsiadujących ze sobą pikseli. Ocena przydatności poszczególnych metod została dokonana na przykładzie zadania wyboru najlepszej wersji obrazu pod kątem jego dalszej analizy. Przeprowadzona analiza wyników oceny kontrastu obrazów wskazuje, że dla przyjętych warunków porównania najlepszą metodą oceny kontrastu jest jedna z nowych metod.
This paper deals with the gray-level image contrast evaluation problem. In the paper some methods of contrast evaluation are considered, namely: (1) and (2) - two methods based on Weber-Fechner law ((2) is a Michelson contrast), next two methods (3) and (4) are based on variance of gray-level values in the image, and the last two (5) and (6) are new methods in which the difference between gray-level values of neighbouring pixels is used for calculating the image contrast ratio. The evaluation of the described methods has been made for one of the standard usage cases of the contrast evaluation method, i.e. evaluation of images after contrast enhancement for choosing the best of them for its visual analysis. The investigations have been performed on the example of aerial image AERIAL (Fig. 1). The contrast enhancement of this image gives the set of test images (a)-(j) (Fig. 1). Table 1 presents the contrast enhancement methods and their parameters used for obtaining test images. The contrasts evaluation values of the test images obtained by use of the methods (1)-(6) are given in Table 2. Table 3 shows the ranking of the images (a)-(j) obtained by sorting in descending order the contrast ratio of test images independently for each evaluation method. It is difficult to indicate the best evaluation method but it seems that, basing on the comparison, the new method (5) is the best image contrast evaluation method
Źródło:
Pomiary Automatyka Kontrola; 2009, R. 55, nr 7, 7; 501-503
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Porównanie wybranych miar kontrastu obrazów achromatycznych
Comparison of selected contrast evaluation methods of gray level images
Autorzy:
Bal, A.
Powiązania:
https://bibliotekanauki.pl/articles/152934.pdf
Data publikacji:
2010
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
wstępne przetwarzanie obrazów
poprawa kontrastu
globalne i lokalne metody poprawy kontrastu
ocena kontrastu obrazu
image preprocessing
contrast enhancement
global and local image contrast enhancement methods
image contrast evaluation
Opis:
W pracy poruszono zagadnienie oceny kontrastu achromatycznych obrazów cyfrowych. Przedstawiono porównanie wyników oceny kontrastu obrazów przy wykorzystaniu, zarówno znanych z literatury jak i nowych, miar kontrastu. Zaproponowane nowe miary bazują na lokalnej realizacji pewnych znanych z literatury globalnych miar kontrastu. Badania przeprowadzono dla kilkudziesięciu obrazów testowych. Przedstawiono także problemy związane z doborem miar kontrastu do danego zastosowania.
The paper deals with the problem of gray level image contrast evaluation. Comparison of several, both known from the literature and new, image contras evaluation methods are presented. Methods taken into consideration are: (1) and (2)-two methods based on Weber-Fechner law, (3) and (4)-variance based methods, method (5) with its modifications-based on difference between gray-level values of neighboring pixels, (6)-image energy based method, (7)- method based on Shannon entropy information theory, (8)-(11)-group of new methods based on the idea of aggregating of local contrast evaluation value obtained for neighborhood of pixel for all pixels in image. The comparison was performed on the set of 48 test images obtained as a result of contrast enhancement of 8 images (Fig. 1) using 5 contrast enhancement methods. The results of contrast evaluation of all images are given in Table 1. In order to compare the numerical contrast evaluation with visual judgment, two subsets of test images are presented (Figs. 2 and 3) together with charts of the contrast values (Fig. 4). The obtained results are analysed in Section 4, where on the example of two different applications of contrast enhancement the difficulties with contrast evaluation and selection of the best contrast evaluation method are discussed. It is not possible to choose the best contrast evaluation method basing on the obtained results and taking into consideration different purposes of image contrast enhancement. Because of this, a contrast evaluation method should be chosen for each application individually.
Źródło:
Pomiary Automatyka Kontrola; 2010, R. 56, nr 11, 11; 1359-1353
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Posthuman – Postnature? Transhumanism and Environmental Ethics
Autorzy:
Bardziński, Filip
Powiązania:
https://bibliotekanauki.pl/articles/903495.pdf
Data publikacji:
2015-12-30
Wydawca:
Akademia Pedagogiki Specjalnej im. Marii Grzegorzewskiej. Wydawnictwo APS
Tematy:
environmental ethics
transhumanism
human enhancement
ethics of respect for nature
Paul W. Taylor
Nick Bostrom
Julian Savulescu
Opis:
The author proposes a set of possible objections and amendments to the notion of transhumanism that can be made from the standpoint of environmental ethics. The transhumanist movement, as it is developed by such researchers as Nick Bostrom, Ingmar Persson, Julian or Savulescu, is devoted to identifying the best ways and measures of utilizing the scientific knowledge of human biology in order to allow people overcoming the limits of their current biological condition. However, such project raises several moral, ethical, political, and economical issues. It is worthwhile – in the author’s opinion – to broaden the discussion over transhumanism by including environmental issues, raised by such thinkers as Aldo Leopold or Paul W. Taylor. The author argues for a radical concept of enhancement – in opposition to Nicholas Agar’s “moderate enhancement”. The author believes that by introducing the Taylorian concept of “respect for nature”, it is possible to ameliorate the transhumanist program by – on one hand – identifying its possible shortcomings, but also by ensuring the care or the best possible ecological conditions for future generations.
Źródło:
Studies in Global Ethics and Global Education; 2015, 4; 18-33
2392-0890
Pojawia się w:
Studies in Global Ethics and Global Education
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Artificial Magnetic Conductor-based Millimeter Wave Microstrip Patch Antenna for Gain Enhancement
Autorzy:
Belabbas, Khadidja
Khedrouche, Djamel
Hocini, Abdesselam
Powiązania:
https://bibliotekanauki.pl/articles/1839467.pdf
Data publikacji:
2021
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
artificial magnetic conductor
gain enhancement
microstrip patch antenna
millimeter wave
reection phase
Opis:
In this paper, a small (20 × 20 × 2.4 mm) loaded microstrip patch antenna (MPA) with an asymmetric artificial magnetic conductor (AMC) as a ground plane is designed for millimeter wave applications. Two AMC structures are proposed; one has the property of a 0 ◦ reflection phase around 28.4 GHz, with a symmetric geometry, which makes the reflection phase insensitive to variations in both polarization and incident angle. This symmetric AMC structure ensures angular stability which is considered as a major requirement when periodic structures are used as antenna ground planes. The other structure is characterized by an asymmetric geometry and shows an interesting behavior around 28.6 GHz, where a discontinuity in the reflection phase appeared due to the fact that surface impedance nature changed from purely capacitive to purely inductive. This paper studies the effects of the two proposed AMC structures on the performance of MPAs, by using an array of 8 × 8 unit cell elements as an artificial ground plane. Simulation results show that an MPA with a symmetric AMC ground plane offers better impedance matching and a wider bandwidth. Compared with conventional MPAs, gain is enhanced and directivity is improved as well. As far as an MPA with an asymmetric AMC ground plane is concerned, its performance in terms of gain and directivity is higher than that of the conventional solution.
Źródło:
Journal of Telecommunications and Information Technology; 2021, 1; 56-63
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Artificial Magnetic Conductor-based Millimeter Wave Microstrip Patch Antenna for Gain Enhancement
Autorzy:
Belabbas, Khadidja
Khedrouche, Djamel
Hocini, Abdesselam
Powiązania:
https://bibliotekanauki.pl/articles/1839484.pdf
Data publikacji:
2021
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
artificial magnetic conductor
gain enhancement
microstrip patch antenna
millimeter wave
reection phase
Opis:
In this paper, a small (20 × 20 × 2.4 mm) loaded microstrip patch antenna (MPA) with an asymmetric artificial magnetic conductor (AMC) as a ground plane is designed for millimeter wave applications. Two AMC structures are proposed; one has the property of a 0 ◦ reflection phase around 28.4 GHz, with a symmetric geometry, which makes the reflection phase insensitive to variations in both polarization and incident angle. This symmetric AMC structure ensures angular stability which is considered as a major requirement when periodic structures are used as antenna ground planes. The other structure is characterized by an asymmetric geometry and shows an interesting behavior around 28.6 GHz, where a discontinuity in the reflection phase appeared due to the fact that surface impedance nature changed from purely capacitive to purely inductive. This paper studies the effects of the two proposed AMC structures on the performance of MPAs, by using an array of 8 × 8 unit cell elements as an artificial ground plane. Simulation results show that an MPA with a symmetric AMC ground plane offers better impedance matching and a wider bandwidth. Compared with conventional MPAs, gain is enhanced and directivity is improved as well. As far as an MPA with an asymmetric AMC ground plane is concerned, its performance in terms of gain and directivity is higher than that of the conventional solution.
Źródło:
Journal of Telecommunications and Information Technology; 2021, 1; 56-63
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
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