• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.344-348
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• 2002

As microelectronics technology continues to progress, there is also a continuous demand on highly integration and miniaturization of systems. For example, it is desirable to package several integrated circuits together in multilayer structure, such as multichip modules, to achieve higher levels of compactness and higher performance. Passive components (i.e., capacitors, resistors, and inductors) are very important fort many MCM applications. In addition, the low-temperature co-fired ceramic (LTCC) process has considerable potential for embedding passive components in a small area at a low cost. In this paper, we investigate a method of statistically modeling integrated passive devices from just a small number of test structures. A set of LTCC inductors is fabricated and their scattering parameters (s-parameters) are measured for a range of frequencies from 50MHz to 5GHz. An accurate model for each test structure is obtained by using a building block based modeling methodology and circuit parameter optimization using the HSPICE circuit simulator.

• 한국정밀공학회지
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• 제11권6호
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• pp.168-178
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• 1994

This paper presents an optical surface roughness sensor developed for intermediate- process measurement on the machine. The light scattering method is adopted for the sensor, which is designed conpact and flexible enough to apply to 'on the machine' measurement of surface roughness. The developed sensor has special features such that it makes use, as the measurement parameter, of the ratio between fluxes of the incident light, and the specularly and partly diffusely reflected light, and that it can adjust the incident light angle. The experimental investigation reveals not only the sensor has good performance as a surface roughness sensor but the sensor is very robust so as to be useful in in-process measurement.

• Fibers and Polymers
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• 제2권2호
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• pp.98-107
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• 2001

The phase transition behavior isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering(SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147$\pm$$2^{\circ}$, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the inveriant growth rate. By extrapolating the inveriant growth rate to zero, a transition temperature of about 145$\pm$$\pm$$2^{\circ}$ was obtained.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.75.1-75.1
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• 2010

Dye sensitized solar cells(DSSCs) have been extensively studied due to their various advantages such as low production cost, colorful design, and eco-friendly process. Long optical path length is one of the most effective method to improve light harvest efficiency for DSSCs. Multi-layered $TiO_2$ nano-structured film with scattering layer has been studied to generate scattering effect by many researchers. It was expected that the difference of refractive index between $TiO_2$ particles and glass frit would generate the light scattering effect and provide the long optical path length. Therefore, to enhance the scattering effect, the frits of $Bi_2O_3-B_2O_3$-ZnO glass system that has the different refractive index were added to $TiO_2$ pastes in this study. First of all, the absorbance and haze factor of $TiO_2$ electrode with dyes and the refractive index of glass frit and $TiO_2$ were measured, respectively. To study the effect of frits, the efficiencies of DSSCs added glass frit and without glass frit were compared. Our results showed slightly higher efficiency with the different absorbance and haze factor of $TiO_2$ and glass frit. It was considered that the light scattering effect would be improved with adding frits to $TiO_2$ paste. Our preliminary studies will be useful for increasing efficiency of DSSCs.

• 천문학회지
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• 제48권3호
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• pp.195-202
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• 2015

Star forming galaxies found in the early universe exhibit asymmetric Lyα emission line that results from multiple scattering in a neutral thick medium surrounding the Lyα emission source. It is expected that emergent Lyα will be significantly polarized through a large number of resonance scattering events followed by a number of successive wing scatterings. In this study we adopt a Monte Carlo method to calculate the polarization of Lyα transferred in a very thick static slab of H_I. Resonantly scattered radiation associated with transitions between is only weakly polarized and therefore linear polarization of the emergent Lyα is mainly dependent on the number of off-resonant wing scattering events. The number of wing scattering events just before escape from the slab is determined by the product of the Doppler parameter a and the line center optical depth τ₀, which, in turn, determines the behavior of the linear polarization of Lyα. This result is analogous to the study of polarized radiative transfer of Thomson scattered photons in an electron slab, where the emergent photons are polarized in the direction perpendicular to the slab when the scattering optical depth is small and polarized in the parallel direction when the slab is optically thick. Our simulated spectropolarimetry of Lyα shows that the line center is negligibly polarized, the near wing parts polarized in the direction parallel to the slab and the far wing parts are polarized in the direction perpendicular to the slab. We emphasize that the flip of polarization direction in the wing parts of Lyα naturally reflects the diffusive nature of the Lyα transfer process in thick neutral media.

• 한국게임학회 논문지
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• 제9권5호
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• pp.137-144
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• 2009

이 논문은 피하산란의 정도가 다를 것으로 예상되는 얼굴의 6개의 부위를 촬영하여 각각의 산란특성을 추출하고 렌더링에 반영하여 얼굴의 사실감 있는 표현이 가능한 방법을 제안한다. 각 부위별 산란이미지는 프로젝터로부터 피부에 입사된 단위광선이 내부 산란을 거쳐 밖으로 드러나는 모양을 여러 노출로 촬영하여 HDR 이미지로 합성하고, 비선형 최소제곱합의 해법 중 Sequential Quadratic Programming을 이용하여 광선의 입사지점을 지나는 단면이 이루는 곡선에 '가우스 함수의 선형결합'을 적합한다. 가우스 함수는 산란곡선을 잘 근사하면서 필터로서 적용이 쉬운 장점을 가진다. 우리는 최소제곱합의 해가 지역 해에 빠지는 않도록 유전알고리듬을 이용해 초기 값을 설정한다. 근사된 식의 각 가우스 항은 얼굴에 입사되는 복사조도를 렌더링한 텍스처에 가우스 필터로 적용되어 피하산란효과를 표현. 이 논문에서는 최대 12회의 가우스 필터링을 효율적으로 처리하기 위해 쿠다의 병렬처리능력를 활용하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제43권5호
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 추계종합학술대회
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• pp.552-554
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• 1999

포논산란과 임팩트이온화 모델은 풀밴드 모델과 페르미 황금법칙을 이용한 고에너지 영역에서 hot carrier 전송을 해석하기 위해서 제시되어 왔다. 본 연구에서는 77K와 300k에서 실제에너지 밴드 구조를 이용한 Si의 임팩트이온화 과정에 대해서 온도 의존성을 조사했다. 풀밴드 모델은 local form factors을 이용한 의사포텐셜방법에서 얻어지고, 산란율 계산에 이용된다. 정확한 임팩트이온화율 계산은 파동벡터와 주파수에 의존하는 유전함수를 필요로 한다. 포논 산란율은 상태밀도에 선형적으로 의존하기 때문에 포논산란율과 상태밀도의 비에 대한 선형함수 유도에 의해서 구해진다 임팩트이온화율 $P_{ii}$ 는 first principle's theory로부터 계산되어지고, 수정된 Keldysh 공식에 의해서 최적화되었다.

• Journal of Magnetics
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• 제13권2호
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• pp.43-52
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• 2008

The objective of this paper is to review the magnetic and magneto-transport properties of Co/$Co_2TiSn$ consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/$Co_2TiSn$ system, which has a $Co_2$TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/$Co_2TiSn$ thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/$Co_2TiSn$ films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.

• 한국화재소방학회논문지
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• 제23권2호
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• pp.96-100
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• 2009

우리나라는 최근 숲이 우거져 있어 산불이 발생하면 대형화 위험성이 증대하고, 인력접근이 제한되어 항공기에 의한 진화율이 90% 이상이 된다. 그러므로 항공기 특히 헬기의 산불진화 활용성은 점차 증대 될 전망이다. 아울러 산불진화의 전 과정에 있어서 헬기 물 살포 기술은 안전한 헬기운항과 효율적인 산불진화의 성공요인으로서 특히, 표준화된 물 살포 기술은 매우 필요하다. 그러나 아직 헬기 물 살포 기술이 표준화 되지 않으므로 인하여 산불진화의 효율성과 안전성이 떨어지고 있다. 따라서 본 연구에서는 산불 현장 공중진화 경험을 바탕으로 11개의 헬기 물 살포 유형을 제안하였다.