• 한국전자파학회지:전자파기술
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• 제6권2호
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• pp.19-26
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• 1995

광대역용 박판 전파흡수체의 설계에는 자성재료가 많이 사용되며, 주로 자성재료 박판의 이면에 금속판을 접착하여 만든다. 이 경우,6개의 변수를 포함하는 한개의 이론식에 의해 무반사 또는 보다 실용적인 99% 이상의 흡수(20dB 전파감소)가 가능한 전파흡수체의 형상과 재료 및 전자파 상수가 정의된다. 2여B 전파감소에 해당 하는 정합 경제값을 계산하기 위하여 Secant법을 적용하였으며, 전파흡수체 설계시 허용 가능한 재료 상수값의 범위를 구하기 위하여 Secant볍을 응용한 search algorithm을 개발하였다. 6개의 변수 모두에게 적용할 수 있 는 이 수치해석 방법에 의해 최소의 반복 계산으로 정확한 값을 효율적으로 구할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제23권3호
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• pp.77-82
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• 2023

본 논문에서는 접지된 2중 유전체층 사이의 저항띠 격자구조에 의한 TM(tranverse magnetic) 전자파 산란문제를 전자파 수치해석방법으로 알려진 FGMM(fourier galerkin moment method)과 PMM(point matching method)을 이용하여 해석하였다. 경계조건들은 미지의 계수를 구하기 위하여 이용하였으며, 저항띠의 해석을 위해 저항경계조건을 적용하였다. 전반적으로 저항율이 작으면 저항띠에 유도되는 전류밀도의 크기가 증가하였고, 반사전력도 증가하였다. 또한, 유전체층의 두께와 비유전율의 값이 증가하면 전반적으로 반사전력은 증가하였다. 본 논문의 제안된 구조에 대해 FGMM과 PMM의 수치해석 방법을 적용한 수치결과들은 매우 잘 일치하였다.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4112-4119
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• 2023

This study employs the microshear test method to examine the local mechanical properties of narrow-gap welded joints, revealing the mechanical inhomogeneity by evaluating the microshear strength, stress-strain curves, and failure strain. On this basis, the influence of weld joints micromechanical inhomogeneity on the crack tip opening displacement (CTOD) fracture toughness is investigated. From the root weld layer to the cover weld layer, the fracture toughness at the center of the weld seam demonstrates an increasing trend, with the experimental and calculated CTOD values showing a good correspondence. The microproperties of the welded joints significantly impact the load-bearing capacity and fracture toughness. During the deformation process of the "low-matching" microregions, the plastic zone expansion is hindered by the surrounding microregion strength constraints, thus reducing the fracture toughness. In contrast, during the deformation of the "high-matching" microregions, the surrounding microregions absorb some of the loading energy, partially releasing the concentrated stress at the crack tip, which in turn increases the fracture toughness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1594-1617
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• 2018

In this paper, we consider a spectrum access scenario which consists of two groups of users, namely Primary Users (PUs) and Secondary Users (SUs) in Cooperative Cognitive Radio Networks (CCRNs). SUs cooperatively relay PUs messages based on Amplify-and-Forward (AF) and Decode-and-Forward (DF) cooperative techniques, in exchange for accessing some of the spectrum for their secondary communications. From the literatures, we found that the Conventional Distributed Algorithm (CDA) and Pragmatic Distributed Algorithm (PDA) aim to maximize the PU sum-rate resulting in a lower sum-rate for the SU. In this contribution, we have investigated a suit of distributed matching algorithms. More specifically, we investigated SU-based CDA (CDA-SU) and SU-based PDA (PDA-SU) that maximize the SU sum-rate. We have also proposed the All User-based PDA (PDA-ALL), for maximizing the sum-rates of both PU and SU groups. A comparative study of CDA, PDA, CDA-SU, PDA-SU and PDA-ALL is conducted, and the strength of each scheme is highlighted. Different schemes may be suitable for different applications. All schemes are investigated under the idealistic scenario involving perfect coding and perfect modulation, as well as under practical scenario involving actual coding and actual modulation. Explicitly, our practical scenario considers the adaptive coded modulation based DF schemes for transmission flexibility and efficiency. More specifically, we have considered the Self-Concatenated Convolutional Code (SECCC), which exhibits low complexity, since it invokes only a single encoder and a single decoder. Furthermore, puncturing has been employed for enhancing the bandwidth efficiency of SECCC. As another enhancement, physical layer security has been applied to our system by introducing a unique Advanced Encryption Standard (AES) based puncturing to our SECCC scheme.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.359-359
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• 2014

In this study, surface plasmon resonance structures for the selective and the enhanced transmission of infrared light were designed. In order to relieve the large discontinuity of refractive index between air and metal hole array, $Si_3N_4$ was used as the impedance matching layer. Experimental parameter were calculated and determined in advance by the rigorous coupled wave analysis (RCWA) simulation, and then the experiment was carried out. A 2-dimensional metal hole array structures were patterned on the size of $1{\times}1cm^2$ GaAs substrate using photolithography process, and 5 nm thick Ti, 50 nm thick Au were deposited by E-beam evaporator, respectively. Subsequently, $Si_3N_4$ films with various thicknesses (150, 350, 550, and 750 nm) were deposited by plasma enhanced chemical vapor deposition (PECVD). For the comparison, transmittance of specimens with and without $Si_3N_4$ was measured using Fourier transform infrared spectroscopy (FTIR) in the range of $2.5-15{\mu}m$. Furthermore, the surface and the cross-sectional images were collected from the specimens by scanning electron microscopy (SEM). From the results, it was demonstrated that the transmittance was enhanced up to 80% by the deposition of 750 nm $Si_3N_4$ at $6.23{\mu}m$. It has advantage of enhanced transmission despite the simple fabrication process.

• 대한조선학회논문집
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• 제52권2호
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• pp.135-142
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• 2015

The Anti-Rolling Tank(ART) has an advantage over the other roll stabilizing devices, when ship is staying and working at one site of sea. An important design point of ART is the tank tuning, that is, matching the tank natural period to the ship's roll natural period. Since the load condition and consequently the roll natural period of ship is to be changed widely, the natural period of ART also has to be changed widely. In case of the existing U-tube type ART with a single layer duct, the tank natural period can be changed in a relatively narrow range. This paper suggests a new U-tube type ART system using a double layer duct to enable wide change of ART natural period. Through the roll experiments performed in regular beam waves for a box-type model ship, it is shown that the double layer duct ART has about two times wider period range and a better reducing effect of roll magnitude than the single layer duct ART.

• 한국측량학회지
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• 제30권4호
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• pp.379-388
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• 2012

2011년부터 본격적으로 도로명주소 체계가 시행 및 활용되고 있으나, 가장 대표적인 국가기본도인 수치지도는 현재 도로명주소 체계와 관련된 정보를 포함하지 않고 있는 관계로 도로명주소 체계하에서의 활용이 원활하게 이루어지기 어렵다. 본 논문에서는 수치지도 객체의 속성정보에 도로명주소 관련 정보를 추가하여 확장형 수치지도를 생성할 수 있는 방법론을 연구하였다. 먼저 도로명주소 지도의 도로구간 레이어와 수치지도 도로중심선 레이어와의 중첩 분석을 통하여 두 레이어의 객체간 매칭 관계를 도출였으며, 두 레이어의 속성항목 분석을 통하여 도로명주소 지도에서 수치지도로 추가할 속성항목을 추출하였다. 도출된 결과를 이용하여 도로명주소 지도의 도로명주소 관련 속성정보들을 수치지도 도로중심선 데이터로 전달하였다. 이러한 과정을 거쳐 속성 확장된 수치지도 도로중심선 레이어는 도로명주소 체계에 따른 도로명 정보를 속성으로 갖게 되며, 이에 따라 수치지도 활용시에 도로명주소 체계에 따른 위치참조가 가능하게 된다.

• 한국전기전자재료학회논문지
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• 제21권6호
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• pp.509-516
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• 2008

Multi-layer circuit card for semiconductor inspection was fabricated by LTCC technology. After a proper impedance design without electrical interference, ceramic tapes with the composition of $CaO-Al_2O_3-SiO_2-B_2O_3$ glass and $Al_2O_3$ were prepared. The electrode with silver paste printed on the tape. Printed ceramic sheets were then laminated and sintered. Densities and dielectric properties were measured. The microstructure, fracture surface of the region of via and matching state of substrate-electrode were observed. The durability of plated outside electrode were examined by hardness and scratch test.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.95-98
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• 2003

To provide high-quality media streaming service over the best-effort Internet, an efficient streaming system with a network-adaptive transport is essential. By adopting FEC-based adaptive transport and by matching it to the priority of media packets, in this paper, an enhanced MPEG-4 streaming system is implemented. The implemented adaptive transport can complement the existing MPEG-4 streaming server with components such as elementary stream provider, sync layer and DMIF layer. Sync layer packets of each MPEG-4 elementary stream are prioritized and then selectively dropped at the sender to match the currently available bandwidth. Also, with the proposed adaptive transport module, the level of FEC protection is dynamically adjusted based on the underlying network condition. With preliminary verification over the emulated network testbed, it is shown that the proposed implementation can mitigate the impact of network fluctuation and thus improve the quality of streaming.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.914-917
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• 2002

We have obtained high performance and low voltage driving OCB panel by reducing the critical voltage and retardation matching between liquid crystal layer and compensation films. The critical voltage in the panel has been minimized by flattening color filter layer and optimizing a rubbing process. In addition, an appropriate retardation of the film and LC layer has scanned to achieve low driving voltage and high transmission. The proto-type 17" WXGA OCB panel has demonstrated with less than 5V drive and over 80 degree for all viewing direction except for rubbing direction with over 90% of TN light efficiency.