• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.636-642
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• 1997

Laminar vortex shedding behind a circular cylinder with and without splitter plates attached to the circular cylinder at low Reynolds numbers are simulated by solving the unsteady incompressible Navier-Strokes equations. The Strouhal number, lift and drag rapidly change with the splitter plate. Far-field noise from the vortex shedding behind the cylinder is computed using the Lighthill acoustic analogy and the Curle's solution for the Lighthill equation. The acoustic source functions are obtained from the computed near-field velocity and pressure. Numerical results show that the volume quadrupole noise is small at low Mach numbers, compared with the surface dipole noise. Also the amplitude and frequency of the acoustic density fluctuations are varied with the length of splitter plates. The scattering effects at the edge of a splitter plate are considered by using the half-plane Green's function.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.567-571
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• 2004

The 2-dimensional unsteady flows on and around the cambered airfoils were computed by applying LES with the deductive dynamic SGS model. The unsteady flow field were used as inputs to compute the far-field sounds and directivity patterns from rotating blades by a hybrid approach that exploits Farassat's formula. The BEM (Boundary Element Method) was applied to predict the frequency characteristics from the rotating blades for the cases of even- and uneven-pitched fans. The BEM results suggested that the unevenly pitched fan have less pronounced discrete peaks at BEF frequencies, which was confirmed by the experiment.

• Progress in Superconductivity
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• 제5권2호
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• pp.128-131
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• 2004

The resistive superconducting fault current limiters (SFCLs) are very attractive devices for the electric power network. But they have some serious problems when the YBCO thin films were used for the current limiting materials due to the in homogeneities caused by manufacturing process. When the YBCO films have some inhomogeneities, simultaneous quenches are difficult to achieve when the fault current limiting units are connected in series for increasing operating voltage ratings. Magnetic field application is one of the prospective way of inducing simultaneous quenches far the series-connected resistive FCL components. Magnetic field was typically generated by the fault current thorough a coil, which is connected to components of the fault current limiter in series, leaving the problem, which provides significant inductance to the power line and suppresses critical current density of the superconducting components. In this article we investigated the possible application of the protective current transformer (p-CT), which is available current source to the magnetic coil. This system inductively coupled to the circuit, therefore, remarkably reducing impedance to the circuit. The current by the protective current transformer was directly fed to the coil, generating magnetic field large enough to reduce critical current density of the components. This successfully induced simultaneous quenches of the series-connected resistive FCL components.

• 한국음향학회지
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• 제24권7호
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• pp.423-430
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• 2005

본 논문에서는 차량환경에서 잔향과 근접장 효과에 의해 발생하는 목적 음성 신호의 왜곡을 감소시킬 수 있는 마이크로폰 어레이 빔형성 기법을 제안하였다. 온라인으로 추정하기 어려운 소스와 마이크간의 전달함수 대신 상대적으로 추정이 용이한 기준 마이크와 다른 마이크간의 상대전달함수를 조향 벡터로 이용함으로써, 원격장 모델의 조향 벡터를 이용한 빔형성기에 비해 목적 음성 신호의 왜곡을 감소시킬 수 있는 준최적 빔형성 기법을 제안하였다. 제안된 방법의 성능을 검증하기 위해, 실제 차량에서 녹음된 음성 DB를 구축하고, 이를 이용하여 HTK를 통한 음성인식 실험을 수행하였다. 음성인식 실험 결과 원격장 모델을 이용한 방법보다 인식률이 최대 $15\%$까지 향상됨을 확인하였다.

• 한국전자파학회논문지
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• 제11권2호
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• pp.313-321
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• 2000

본 논문은 등방성 상반 매질과 단축 이방성 하반 매질의 경계변에 위치하는 수평 미세 전류원이 시간 영역에 서 충격적으로 가해칠 때, 경계변에 발생하는 수평 전기장을 구하는 반공간 경계면 문제를 다룬다. 경계변 전기 장에 대해 Cagniard -de- Hoop 법을 변형 적용함으로써. 이 전기장에 대한 명시적 해를 얻는다 또한' 경계변상 에서 퍼져 나가는 Dirac $\delta$- 함수 형태의 충격 성분에 대한 방사 특성에 대해서 논의하는데, 이 충격 성분은 원 방 경계장 특성을 이해하는데 있어서 중요하다. 한편, 단축 이방성은 등방성보다 일반화된 개념이므로 이 논문 에서 구한 전기장 해에서 이방성을 제거하면 등방성 매칠에 대한 해로 환원된다

• Progress in Superconductivity
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• 제8권2호
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• pp.158-163
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• 2007

YBCO do superconducting quantum interference device (SQUID) magnetometers based on bicrystal junctions have been fabricated for magnetocardiograph (MCG) measurements. We could fabricate YBCO SQUID magnetometers having magnetic field noise of about $20fT/Hz^{1/2}$ at white noise region. We have developed an MCG system employing the high performance SQUID magnetometers. The lightweight MCG system, requiring liquid nitrogen as a coolant, consists of 6-channel SQUID sensors, an adjustable patient bed with sliding motion, and data analyses software. The MCG system could record quite clear MCG signals in a room with moderate magnetic shielding. In normal operation with multi-position MCG measurements, we could obtain clear 48-point mappings of magnetic field map and current source map with high enough signal qualities far clinical trials.

• Current Applied Physics
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• 제18권11호
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• pp.1381-1387
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• 2018

One dimensional (1D) grating has been fabricated (using focused ion beam) on 50 nm gold (Au) film deposited on higher refractive index Gallium phosphate (GaP) substrate. The sub-wavelength periodic metal nano structuring enable to couple photon to couple with the surface plasmons (SPs) excited by them. These grating devices provide the efficient control on the SPs which propagate on the interface of noble metal and dielectric whose frequency is dependent on the bulk electron plasma frequency of the metal. For a fixed periodicity (${\Lambda}=700 nm$) and slit width (w = 100 nm) in the grating device, the efficiency of SPP excitation is about 40% compared to the transmission in the near-field. Efficient coupling of SPs with photon in dielectric provide field localisation on sub-wavelength scale which is needed in Heat Assisted Magnetic recording (HAMR) systems. The GaP is also used to emulate Vertical Cavity Surface emitting laser (VCSEL) in order to provide cheaper alternative of light source being used in HAMR technology. In order to understand the underlying physics, far-and near-field results has been compared with the modelling results which are obtained using COMSOL RF module. Apart from this, grating devices of smaller periodicity (${\Lambda}=280nm$) and slit width (w = 22 nm) has been fabricated on GaP substrate which is photoluminescence material to observe amplified spontaneous emission of the SPs at wavelength of 805 nm when the grating device was excited with 532 nm laser light. This observation is unique and can have direct application in light emitting diodes (LEDs).

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.340-343
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• 2006

Remote sensing science is a rapidly growing field of Earth sciences. Since emergence and to present day, an extensive literature has evolved which traces the wide application of remote sensing in human activities. According to the ISI Web of Science in the 1975-2005 time span more then 20,000 papers were published on remote sensing. The number of papers grew exponentially with doubling period of about 6 years. Notwithstanding all specialized proceedings, there is a lot more remote sensing papers published in a vast list of source titles (up to 350 proceedings). Only 25% of retrieved papers are published in 10 proceedings which ISI assigns to subject category of remote sensing. In 2005 all these proceedings published 1291 articles and received cca 24,000 citations. Average impact factor of the proceedings is equal to 1.181 and average cited half-life is 7.1. It means that an average paper in remote sensing proceedings is cited more then once per year and half of citations the paper receive within the next 7 years after publication. The time line of remote sensing periodicals issued in 1927-1995 shows an exponential growth with doubling period about 15 years. After 1995 there is a prominent deviation from the exponential curve which shows the demand saturation for specialized proceedings. The features revealed are discussed in terms of dynamics and impact of remote sensing in current Earth sciences development.

• 한국항공우주법학회:학술대회논문집
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• 한국항공우주법학회 2008년도 제40회 국제학술발표대회
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• pp.185-215
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• 2008

The exploitation of the natural resources of the Moon and other celestial bodies represents one of the most exiting future developments in the field of space law as well as a unique occasion for the economic and social growth of mankind as a whole. The large number of benefits that are expected to be generated from the exploitation of these resources, indeed, not only will contribute to the betterment of conditions of people on Earth but also will allow mankind to face and likely solve one of the biggest problems currently affecting our planet, namely the exhaustion of the stocks of raw materials and other source of energy, such as fossil fuels. The exploitation of the natural resources of the Moon and other celestial bodies, however, has been prevented so far by the absence of dedicated space law rules allowing its orderly and peaceful development and clarifying the rights and duties of the parties involved in it. Due to the uncertainty generated by the absence of these rules, indeed, States as well as private operators have refrained from investing in the exploitation of space resources so far. The time to change this situation and to allow the exploitation of extraterrestrial resources to begin has finally come. This paper aims at fulfilling this purpose by proposing a legal regime containing specific and detailed rules to regulate the exploitation of the natural resources of the Moon and other celestial bodies.

• 항공우주정책ㆍ법학회지
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• 제23권1호
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• pp.131-168
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• 2008

The exploitation of the natural resources of the Moon and other celestial bodies represents one of the most exiting future developments in the field of space law as well as a unique occasion for the economic and social growth of mankind as a whole. The large number of benefits that are expected to be generated from the exploitation of these resources, indeed, not only will contribute to the betterment of conditions of people on Earth but also will allow mankind to face and likely solve one of the biggest problems currently affecting our planet, namely the exhaustion of the stocks of raw materials and other source of energy, such as fossil fuels. The exploitation of the natural resources of the Moon and other celestial bodies, however, has been prevented so far by the absence of dedicated space law rules allowing its orderly and peaceful development and clarifying the rights and duties of the parties involved in it. Due to the uncertainty generated by the absence of these rules, indeed, States as well as private operators have refrained from investing in the exploitation of space resources so far. The time to change this situation and to allow the exploitation of extraterrestrial resources to begin has finally come. This paper aims at fulfilling this purpose by proposing a legal regime containing specific and detailed rules to regulate the exploitation of the natural resources of the Moon and other celestial bodies.