• Title/Summary/Keyword: 개구면

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Comparison of GMTI Performance Using DPCA for Various Clutters (DPCA를 이용한 지상 이동 표적 탐지에서 클러터 종류에 따른 성능 비교)

  • Lee, Myung-Jun;Lee, Seung-Jae;Kang, Byung-Soo;Ryu, Bo-Hyun;Lim, Byoung-Gyun;Oh, Tae-Bong;Kim, Kyung-Tae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.6
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    • pp.487-496
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    • 2017
  • Ground moving target indicator(GMTI) using syntheticaperture radar(SAR) used for finding moving targets on wide background clutter in short time is one of good ways to monitor a traffic situation or an enemy's threat. Although displaced phase center antenna (DPCA) is a real time method with low computational complexity, there have been few studies about its performance against various ground clutters. Thus, we need to analyze GMTI performance for various ground clutters in order to design a suitable DPCA detector. In this paper, simulation results show that the conventional DPCA detector produces different performance in terms of detection rate and false alarm rate. In particular, the false alarm rate of heterogeneous or extremely heterogeneous clutter from urban area is higher than one of homogeneous clutter from natural area.

A Design of Dual-band Microstrip Antennas using Stacked Inverted-L-shaped Parasitic Elements for GPS Applications (GPS용 역 L형 기생소자를 이용한 이중대역 마이크로스트립 안테나 설계)

  • Kim, Jun-Won;Woo, Jong-Myung
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.14 no.3
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    • pp.31-37
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    • 2015
  • In this paper, newly proposed dual-band microstrip antennas using stacked inverted-L-shaped parasitic elements are presented for GPS $L_1(1.575GHz)$ and $L_2(1.227GHz)$ bands. For making dual band which has large interval, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements were stacked at both side of radiation apertures on the half-wavelength($L_2$ band) patch antennas. The resonance in the parasitic elements occurs through coupling to the patch. Next, due to using circular polarization at GPS, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements was stacked using sequential rotation technique on the patch and both side of the diagonal corners of the antenna were eliminated to make dual-band circular polarization. The designed circular polarized antenna's dimensions are $0.43{\lambda}L{\times}0.43{\lambda}L{\times}0.06{\lambda}L$ (${\lambda}L$ is the free-space wavelength at 1.227 GHz). Measured -10 dB bandwidths was 120 MHz(7.6%) and 82.5 MHz(6.7%) at GPS $L_1$ and $L_2$ bands. and 3 dB axial ration bandwidths are 172 MHz(10.9%) and 25 MHz(2.03%), respectively. All of these cover the respective required system bandwidths. Within each of the designed bands, broadside radiation patterns were observed.

SH Wave Scattering from Cracks: Comparisons of Approximate and Exact Solutions (SH파의 균열 산란장 해석: 근사해와 엄밀해의 비교)

  • Jeong, Hyun-Jo;Park, Moon-Cheol;Song, Sung-Jin;Schmerr, L.W.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.4
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    • pp.354-361
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    • 2004
  • This Paper describes a crack scattering model for SH wave based on the boundary integral equation(BIE) method, where the fundamental unknown is crack opening displacement(COD). When a time harmonic plane wave was incident on a 2-D isolated crack (slit) of width 2a, the COD distributions were numerically calculated as a function of ka. The calculated COD agreed well with results obtained with other methods. The far-field scattering amplitude, which completely characterizes the flaw response, was calculated in two ways. The Kirchhoff approximation and the BIE-COD exact formulation were compared in terms of incidence angle and frequency ka in a pulse-echo mode. Maximum response was obtained for both methods at the specular reflection direction. Away from the specular direction, the Kirchhoff approximation becomes less accurate. The time domain crack response was also calculated using a band-limited spectrum of center frequency 10 MHz. At oblique incidence to the crack both methods show the existence of an antisymmetric flash points occurring from the crack edge. The Kirchhoff approximation provides an exact time interval between flash points, although it unrealistically gives the same amplitude.

Miniaturized λ/4 Folded Microstrip Antenna for Parking Monitoring Base Station System (주차장관리 시스템 기지국용 소형 λ/4 폴디드 마이크로스트립 안테나)

  • Keum, Jae-Min;Ko, Dong-Ok;Jeong, Jae-Yeop;Woo, Jong-Myung
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.15 no.2
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    • pp.95-101
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    • 2016
  • In this paper, miniaturized ${\lambda}/4$ folded microstrip antennas is presented for parking monitoring base station system. The proposed antenna reduced a width of the radiating element for miniaturizing a size and we changed an aperture such as folded shape for reducing a length of the antenna by the pertubation effect by reducing a width of the antenna. Finally, the ${\lambda}/2$ length of the folded microstrip antenna to ${\lambda}/4$ folded microstrip antenna was miniaturized by reducing the length. The proposed antenna was designed to receive 425 MHz of center frequency that can be used without permission. Dimensions are $134mm{\times}143.85mm{\times}20.1mm$($0.19{\lambda}{\times}0.2{\lambda}{\times}0.028{\lambda}$, ${\lambda}$ is wavelength at 425 MHz) that are compared with basic microstrip patch antenna miniaturized 97.2%. Also, Measured -10 dB bandwidth was 2.44 MHz(0.57%). On the other hand, measured radiation patterns was 1.82 dBi at E-plane $15^{\circ}$.

Verification of Radiation and Beam-Steering Characteristics for Planar-Phased Array Radars Using Near-Field Beam Focusing (근전계 빔 집속 시험 기법을 활용한 평면위상배열레이다 시스템 복사 및 빔 조향 특성 검증)

  • Kim, Young-Wan;Lee, Jaemin;Jung, Chae-Hyun;Park, Jongkuk;Lee, Yuri;Kim, Jong-Phil;Kim, Sunju
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.2
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    • pp.160-168
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    • 2019
  • In this study, we propose a verification method for a planar-phased array radar system using a near-field beam focusing(NFBF) test method. We then confirmed the validity of the results. The proposed method can be used to verify a radar system in the near-field range of twice the antenna aperture size, and this is done in the same manner as the field system performance test conducted in a non-outdoor electromagnetic anechoic chamber. The test configuration and procedure for verifying the NFBF using near-field energies were reviewed. In addition, the phase compensation values of additional individual channels were quantified through mathematical verification of the beam-steered NFBF test. Based on a theoretical verification, the actual NFBF test was performed and the validity of the test method was confirmed through comparison with ideal analytical results.

A Study on Flash Over Delay Effects on Applied Plate-Fire Spread Prevention Method at Sandwich Panels Structure (샌드위치패널 건축물 플래시오버 지연을 위한 화재확산방지플레이트 시공방법 연구)

  • Kim, Do-hyun;Cho, Nam-Wook
    • Fire Science and Engineering
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    • v.31 no.3
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    • pp.79-87
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    • 2017
  • Sandwich panels which are having the both sides are bonded with a heat insulating material with an iron plate are used as factories, warehouse structures as advantages of convenience in construction at economic efficiency of material cost. However, in a panel structure constructed by continuous joining of sandwich panels, a joint portion where a panel and a panel are connected is generated. The joint part is a part which is easily vulnerable to fire because flames easily flow into the melting and deformation of the iron plate during fire. The flames flowing into the panel induce diffusion of fire by rapid burning, causing damage of human life and property. In this research, we developed a flame spread prevention plate to prevent spreading of sandwich panel. This is an improvement of the workability by the anti-spreading construction method of the existing previous research, it can be applied independently to the connecting part where the panel and the panel are coupled, designed to prevent inflow and spreading of flame did. The actual fire test of the test method of KS F ISO 13784-1 of the sandwich panel specimen was conducted and the burning behavior corresponding to the presence or absence of application of the flame spread prevention plate was grasped at the panel connection part and its effect was measured. Inserting a fire spreading plate into the test result panel connecting part is measured by delaying the flashover, prevention of collapse of the specimen, and temperature rise of the opening, effectively improving the fire safety of the panel structure It was confirmed as a method that can be secured. It is judged that panel structure will contribute to ensuring fire safety by applying the fire spread prevention construction method of various methods ensuring the workability and economy of panel connection vulnerable to fire.

Fundamentals of Ultrasonic Welding (초음파 용접의 기초)

  • ;Jeong, H. S.
    • Journal of Welding and Joining
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    • v.15 no.6
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    • pp.24-31
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    • 1997
  • 2매의 금속을 맞대어 그 한 쪽에 접촉면과 평행하게 고주파진동을 가하면 단 시간에 접합된다. 이공정을 초음파 용접이라고 하며 그 물리적인 본질은 아직 불분명 하지만, 첫째로는 강한 마찰에 의해 금속 자유면의 산화물층이 제거되기 때문이라는 점과 둘째로는 마찰에 의해 금속 표면이 강하게 가열되어 이에 따른 연화에 의해 접합 이 된다고 하는 점이다. 그러나 이와 같이 가열된다고 하더라도 가열은 표면부에만 국한되고 다른 부분은 가열되지 않는다. 따라서 초음파용접은 냉간접합이라고도 한다. 또 가압력과 진동에 의한 힘이 동시에 작용하기 때문에 용접할 면을 미리 청정하게 할 필요는 없고 용접전의 단계에서 자연적으로 청정화가 이루어진다고 하는 사실이 간접 적으로 증명되고 있다. 초음파 용접(Ultrasonic welding)의 특징을 요약하면 고상용접 의 일종으로서 용접중에 국부적으로 고주파 진동에너지와 압력을 가하여 용접하는 방법이다. 이 때 모재를 용융시키지 않고 건전한 야금학적 결합부가 얻어진다는 데에 큰 특징이 있다. 또한 초음파용접은 다른 용접법에 비해 경제성이 매우 높고, 초음파 용접에 필요한 출력이 전기아크 용접에 필요한 출력의 5 - 10%로 충분한 경우가 많다. 초음파 용접은 통상의 방법으로는 용접하기 어려운 동종 금속이나 이종 금속의 용접에 널리 사용된다. 이 용접법은 반도체, 미세회로, 전기 접점의 형성에 대한 생산기술 로서 사용되고 있는데 소형 모터, 알루미늄 박의 가공, 알루미늄 합금의 조립 등에 이용되고 있다. 한편 최근에는 자동차, 우주항공산업 분야의 구조제 용접용으로도 채용되고 있다.출함이 바람직하다.분비되는 배설-분비 항원의 자극과 깊은 관계가 있음을 알 수 있었다.넌트 명세서를 대한 XML DTD(Document Type Definition)를 정의하고, HTML 기반 검색 방법과 XML 기반 검색 방법에 대한 컴포넌트 검색 성능을 비교한다.따라 NO 생산 및 세포독성이 증가하였고. NO 생산을 저하시키는 약제들은 활성화된 복강 대식세포 및 RAW264.7 세포에 의한 질편모충에 대한 세포독성을 현저히 감소시키는 것으로 보아 NO는 질편모충에 대한 대식세포의 숙주 방어기전에서 중요한 역할을 감당할 것으로 생각된다.nction index) 와 최대개구시 동통의 정도는 시술전과 시술 4주후간에 유의한 차이가 관찰되었다.피부온도는 검사자간에는 특정부위에 따라 다소 차이가 있을 수 있으나 일반적으로 높은 재현성을 보여줌으로서 향후 교근 및 측두근의 임상연구 평가에 피부온도조사는 도움이 되리라 사료된다. lactobacilli의 양은 peroxidase system을 함유하거나(p < 0.01) 함유하지 않은(p < 0.05) 치약을 사용한 군 모두에서 양치전에 비해 유의성있게 감소하였다. 6. 양치후 30분에 채취한 구강건조증 환자의 자극성 전타액내 S. mutans 양은 peroxida system을 함유한 세치제를 사용한 군에서 대조군에 비해 유의성있게 낮았다(p < 0.05). 7. 양치후 30분에 채취한 구강건조증 환자의 자극성 전타액내 lactobacilli양은 peroxidase system을 함유한 세치제를 사용한 군에서 대조군에 비해 상대적으로 낮게 나타났으나(p = 0.067)

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One dimensional inhomogeneous aperture modulation effects on the MTF of optical system II (일차원적 비균일 개구변조시 광학계의 최적상면 MTF에 미치는 영향)

  • 홍경희
    • Korean Journal of Optics and Photonics
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    • v.9 no.5
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    • pp.277-281
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    • 1998
  • One dimensional inhomogeneous aperture modulation effects on the MTF of optical system was investigated. The lens under test was a doublet made in Korea. It has 10 mm effective diameter, 87.8 mm effective focal length. The ray-fans and spot diagrams were calculated and presented on the picture for on-axis and off-axis (field of view, $1^{\circ}$ and $2^{\circ}$). Aperture modulation was carried out by positioning a aperture modulator close contacter with the lens under test. We bought two modulators from Edmud Company in U.S.A. One was linear type and the other was stepped type. The MTFs were measured on the best of focus for each modulated aperture where the MTF has the highest value for 60 line/mm and were compared with one another. For on-axis, the MTFs of some modulated apertures had higher values than the MTF of unmodulated aperture in the high frequency region. In the case of off-axis, at the field of view $1^{\circ}$, the MTF values of some modulated aperture are improved prominently and some other one are disimproved. At the field of view $2^{\circ}$ most of the MTFs of modulated apertures had lower values than the MTF of unmodulated aperture except the MTFs of linear and inverse linear type aperture in the high frequency area. But the values of MTFs in high frequency region were too low for actual use.

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Surface ultrastructures of the third-stage larvae of Gnathostoma hispidum (돼지악구충(Gnuhostoma hispidum) 제3기 유충의 표면 미세구조)

  • 손운목;이진하
    • Parasites, Hosts and Diseases
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    • v.34 no.3
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    • pp.169-176
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    • 1996
  • A scanning electron microscopic study was performed to observe the surface ultrastructures of the third-stage larvae of Gnathostoma hispidun. The early third-stage larvae (EL3) were collected from the viscera of Chinese loaches by the artificial digestion method . The advanced third-stage larvae (AdL3) were recovered from mice experimentally infected with EL3. Both larval worms were fixed with 2.5% glutaraldehyde, dehydrated in graded alcohol. dryad in critical point dryer, and coated with gold. The specimens were observed with a SEM (DS- l30C). On the head bulb of both larval stage, the mouth had a pair of lateral lips of equal size and of half moon shape. Each lip had a couple of labial papillae and a small amphid located between the two papillae. The hooklets on the head bulb had single-pointed tips and curved posteriorly. The cuticular spines of EL3 were larger and more densely distributed in the anterior area (about 1.8 Mm in length) and gradually decreased in size and number posteriorly. The cuticular spines in the anterior area of AdL3 were sharp-pointed and about 4.5 Mm in length, and those in the middle area were about 1.75 Mm. The velvety cuticular folds and dot-like cuticular spines were distributed in the posterior area. A cervical papilla was located between the 7th and 8th transverse striations. A dome-like body papilla was located at the posterior 1/4 of body. An ellipsoidal excretory pore was located between the 17th and 18th striations. From the above results, it is suggested that the characteristic SEM findings obtained from this study may be helpful on the species identification of larval Gncthostomn.

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Effect of conservative therapy and Mandibular condylar bone change on Adolescents with osteoarthritis of TMJ (청소년 측두하악관절 골관절염의 보존적 치료효과 및 관절면의 변화 비교)

  • Jeon, Hye-Mi;Kim, Kyung-Hee;Ok, Soo-Min;Heo, Jun-Young;Jeong, Sung-Hee;Ko, Myung-Yun;Ahn, Young-Woo
    • Journal of Oral Medicine and Pain
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    • v.38 no.4
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    • pp.357-366
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    • 2013
  • This study is designed to evaluate the treatment outcome of occlusal stabilizing splint and to assess follow-up study of condylar bony changes using cone beam computed tomography(CBCT) in adolescents patients (12-19 years) with TMJ osteoarthritis(OA). 167 eroded condyles in 149 subjects were chosen among the patients who presented to the Department of Oral Medicine of Pasan National University Hospital, diagnosed as TMJ osteoarthritis by clinical exam, x-ray and CBCT from 2009 to 2012. They were treated conservatively with physical therapy, medication, behavioral therapy and occlusal stabilizing splint therapy. After average 9 months, CBCT was retaken and subjective symptoms and clinical findings were investigated. Condyle bony changes were classified by unchanged, less severe and more severe. The obtained results were as follow: 1. Pain, Noise, LOM(Limitation of motion) and MCO(Maximum comfortable opening) measurement of TMJ OA patients were markedly improved after conservative treatment. 2. In the occlusal stabilizing splint therapy group, Pain and LOM were statistically significant improved than non-occlusal stabilizing splint therapy group. 3. In the acute occlusal stabilizing splint therapy group, Pain and LOM were remarkably improved. 4. In comparison of CBCT1 and CBCT2 images, the transition of bone changes to lesser severe was most commonly in joint with erosive change. 5. In the non-occlusal stabilizing splint therapy group, the transition of condylar bone changes from erosion to more severe was many than occlusal stabilizing splint therapy group.