• 한국대기환경학회지
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• 제13권4호
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• pp.285-296
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• 1997

The suspended particulate matters had been collected on quartz fiber fiters by a cascade impactor having 9 size stages for 4 years (Sep. 1991 to Dec. 1995) in Kyung Hee University-Suwon Campus. Membrane filters were used to collected the particulate matters on each stage. The weight concentration on each stage was obtained by a microbalance and further chemical element levels were determined by an x-ray fluorescence system. Based on these chemical information, our study focused on applying the target transformation factor analysis (TTFA), a receptor model, to identify aerosol sources and to apportion quantitatively their mass contribution. There are total of 63 ambient data sets. Each data set consists of the 8 size-ranged subdata sets characterized by 16 elemental variables. By the results, four to five sources were extracted from each size range and some sources reappeared in other size ranges. Then total of 8 source profiles were statistically generated from all the ranges, such as oil burning source, soil source, field burning source, gasoline related source, coal burning source, marine source, glass related source, and unknown sources. Apportioning aerosol mass to each source was intensively examined by investigating emission inventories near the study area. The results showed that soil particle source was the most significant contributor. However, coal and oil burning sources were the major anthropogenic ones. The study finally proposed some air quality control strategies to achieve the clean air quality in Suwon area.

• 대한전자공학회논문지
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• 제9권2호
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• pp.1-16
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• 1972

본논문은 특성임퍼이던스가 선형적으로 변화하는 단일 Strip선로의 특성파라미터를 이용하여, 우선 even-mode 및 odd-mode임피이던스가 모두 선형적으로 변화하는 비대칭형인 결합Strip선로의 특성파라미터를 구하였다. 다음에는 상기한 비대칭결합Strip선로를 종속연결한 대칭형결합Strip선로를 구성하고, 선로단자조건에 따라서 결합Strip선로가 갖는 여파특성을 고찰하였다. 선형 결합Strip선로의 특성을 해석한 결과, 선형결합Strip선로는 균일Strip선로를 사용하는 경우에 비하여 몇가지 점에서 좋은 여파특성을 갖고 있음을 명시하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권2호
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• pp.125-131
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• 2002

This paper presents MMIC drive and power amplifiers covering 6-18 ㎓. For simple wideband impedance matching and less sensitivity to fabrication variation, modified distributed topologies are employed in the both amplifiers. Cascade amplifiers with a self-biasing circuit through feedback resistors are used as unit gain blocks in the drive amplifier, resulting in high gain, high stability, and compact chip size. Self impedance matching and high-pass, low-pass impedance matching networks are used in the power amplifier. In measured results, the drive amplifier showed good return losses ($S_11,{\;}S_{22}{\;}<{\;}-10.5{\;}dB$), gain flatness ($S_{21}={\;}16{\;}{\pm}0.6{\;}dB$), and $P_{1dB}{\;}>{\;}22{\;}dBm$ over 6-18 GHz. The power amplifier showed $P_{1dB}{\;}>{\;}28.8{\;}dBm$ and $P_{sat}{\;}{\approx}{\;}30.0{\;}dBm$ with good small signal characteristics ($S_{11}<-10{\;}dB,{\;}S_{22}{\;}<{\;}-6{\;}dB,{\;}and{\;}S_{21}={\;}18.5{\;}{\pm}{\;}1.25{\;}dB$) over 6-18 GHz.

• 대한전자공학회논문지SP
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• 제43권3호
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• pp.54-60
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• 2006

본 논문에서는 EVRC와 G.729A 음성부호화기를 위한 상호부호화 알고리듬을 제안한다. 다른 음성 표준을 사용하는 통신망간에 음성신호를 연동시키는 가장 간단한 방법은 이중 부/복호화 (tandem coding) 방법이다. 이 방법은 두 번의 부/복호화 과정을 거치기 때문에 많은 계산량이 요구되며 아울러 음성 지연이 발생하게 된다. 이러한 문제점들을 개선하기 위하여 상호부호화를 사용한다. 상호부호화는 LSP (Line Spectral Pair) 변환과 피치 지연 변환 그리고 지연 시간 단축 알고리듬을 통하여 수행한다. 제안된 알고리듬은 $18{\sim}22%$의 적은 계산량과 $5{\sim}10ms$의 짧은 지연으로 상호 부/복호화에 상응하는 음성 품질을 제공함을 실험을 통해 확인할 수 있다.

• 전자공학회논문지CI
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• 제41권6호
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• pp.91-99
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• 2004

본 논문은 H.264와 MPEG-4 간의 원활한 통신을 하기위한 두 가지 트랜스코딩 방법을 제안한다. 같은 공간적 시간적 해상도(spatio-temporal resolution)를 유지하는 트랜스코팅 방법과 공간적 해상도(temporal resolution)를 줄이는 트랜스코팅 방법을 제안한다. H.264 비트스트림(bitstream)이 MPEG-4 비트스트림으로 변환 시 H.264 블록형태를 MPEG-4에서 사용 할 수 있는 블록형태로 변환 시켜야 하며, 4×4 블록단위의 움직임 벡터도 8×8 블록단위의 움직임 벡터로 조정하여야 한다. 두 가지 제안된 트랜스코딩 방법은 직렬 화소영역 트랜스코팅 방법(cascade pixel-domain transcoding) 보다 MPEG-4 부호화기 측에서 4.1~5.1배 부호화 속도가 빠를 뿐만 아니라 영상의 화질 저하는 최고 0.3dB정도 밖에 떨어 지지 않는다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.853-856
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• 2004

Monolayers of lipids on a water surface have attracted much interest as models of biological membranes but also as precursors of multilayer systems promising many technical applications. Until now, many methodologies have been developed in order to gain a better understand. Photoisomerization in monolayers of a novel azobenzene compound, azobenzene dendrimer, was investigated for the first time by means of the absorption spectrum and Maxwell displacement current (MDC) technique. Dendrimers are well-defined macromolecules exhibiting a tree-like structure, first derived by the cascade molecule approach. According to the absorption spectrum, trans-to-cis conversion ratio was estimated to the third generation of azobenzene dendrimer deposited onto a glass substrate. Temperature-dependent induced charge with trans-cis isomerization was also measured by means of MDC technique.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.153-156
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• 2006

A turbine stage consists of a stator and rotor. A stator provides the required inlet flow conditions so that a rotor can produce the necessary power. Passing wakes generated at the trailing edge of a stator make an interaction with a rotor. In the present study, this interaction flow mechanism is investigated using the numerical analysis. In case of the large gap distance between the stator and rotor, the stator and rotor flow analysis can be separated. First, only the stator flow field is solved. Second, the rotor flow field is solved including the passing wake information from the stator analysis. The passing wake experiences the shearing as it approaches to the rotor leading edge. And it is chopped when it strikes the rotor body. After that, the chopped wakes becomes the prolongation as it goes downstream. Also, the aerodynamic characteristics with the variation of the gap distance between a stator and rotor was investigated. Pressure jumps due to the passing wakes result in the pressure and lift loss and it gets stronger with the closer gap distance. This unsteady effect proves to be directly related to the fatigue and noise in turbomachinery and this study would be helpful to investigate such fields.

• 대한전자공학회논문지
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• 제21권6호
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• pp.42-50
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• 1984

배분증폭기의 각 증폭소자에 귀환 루우프를 이용하여 배역폭을 증가시킬 수 있는 방법을 제시한 것이다. 즉, 낮은 주파수 영역에서는 귀환이 걸리지 않고, 높은 주파수에서는 정귀환이 되도록 각 증폭소자에 귀환 루우프를 걸어주면 대역폭이 증가한다. 이 설계방법에서는 각 증폭소자를 단향성으록 간주하고 주기적 구조전송선로이론을 택하였으며, 실제의 컴퓨터 해석은 정확한 결과를 얻기 위하여 K. B. Nicals의 방법을 택하여 4 -포오트 이론으로 수행하였다. 여기서 이론적으로 얻은 결과는 샘플로 택한 FET로서 귀환 루우프가 없을때, 대역폭은 16[GHz] 정도였으나, 귀환 루우프를 걸었을 때는 약 20[GHz] 정도로 중가하였다.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.11-20
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• 2009

Radiation effects on materials are inherently multiscale phenomena in view of the fact that various processes spanning a broad range of time and length scales are involved. A multiscale modeling approach to embrittlement of pressure vessel steels is presented here. The approach includes an investigation of the mechanisms of defect accumulation, microstructure evolution and the corresponding effects on mechanical properties. An understanding of these phenomena is required to predict the behavior of structural materials under irradiation. We used molecular dynamics (MD) simulations at an atomic scale to study the evolution of high-energy displacement cascade reactions. The MD simulations yield quantitative information on primary damage. Using a database of displacement cascades generated by the MD simulations, we can estimate the accumulation of defects over diffusional length and time scales by applying kinetic Monte Carlo simulations. The evolution of the local microstructure under irradiation is responsible for changes in the physical and mechanical properties of materials. Mechanical property changes in irradiated materials are modeled by dislocation dynamics simulations, which simulate a collective motion of dislocations that interact with the defects. In this paper, we present a multi scale modeling methodology that describes reactor pressure vessel embrittlement in a light water reactor environment.

• Molecular & Cellular Toxicology
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• 제4권4호
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• pp.267-277
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• 2008

Benzene and ethylbenzene (BE), the volatile organic compounds (VOCs) are common constituents of cleaning and degreasing agents, paints, pesticides, personal care products, gasoline and solvents. VOCs are evaporated at room temperature and most of them exhibit acute and chronic toxicity to human. Chronic exposure of benzene is responsible for myeloid leukemia and also ethylbenzene is also recognized as a possible carcinogen. To evaluate the BE effect on human, whole human genome 35 K oligonucleotide microarray were screened for the identification of the differential expression profiling. We identified 280 up-regulated and 201 down-regulated genes changed by more than 1.5 fold by BE exposure. Functional analysis was carried out by using DAVID bioinformatics software. Clustering of these differentially expressed genes were associated with immune response, cytokine-cytokine receptor interaction, toll-like signaling pathway, small cell lung cancer, immune response, apoptosis, p53 signaling pathway and MAPKKK cascade possibly constituting alternative or subordinate pathways of hematotoxicity and immune toxicity. Gene ontology analysis methods including biological process, cellular components, molecular function and KEGG pathway thus provide a fundamental basis of the molecular pathways through BEs exposure in human lymphoma cells. This may provides a valuable information to do further analysis to explore the mechanism of BE induced hematotoxicity.