• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.161-166
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• 2002

As offshore oil fields move towards the deep ocean, the oil production systems such as FPSO are being built these days. Generally, the FPSO is moored by turret mooring lines to keep the position of FPSO. Thus nonlinear motion analysis of moored FPSO must be carried out in the initial design stage because sea environments affect motion of it. In this paper the mathematical model is based on the slow motion maneuvering equations in the horizontal plane considering wave, current and wind forces. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical model of MMG. The turret mooring forces are quasi-statically evaluated by using the catenary equation. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A. The nonlinear motions of FPSO are simulated under external forces due to wave, current, wind including mooring forces in time domain.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.151-154
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• 2002

The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee's total variation diminishing (TVD) scheme is used to solve the unsteady, two-dimensional, compressible, Euler equations. The Mach number $M_{s}$, of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two parallel tubes, the peak pressure produced by the twin-impulse waves and its location strongly depend upon the distance between two parallel tubes, L/d and the incident shock Mach number, $M_{s}$. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

• 한국전자파학회논문지
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• 제16권12호
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• pp.1246-1254
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• 2005

등방성 상반 매질과 수직 단축성 하반 매질의 경계면에서 $VV{\cdot}HV{\cdot}VH$ 문제에 대해, 임펄스 점전류원에 의해 발생하는 전자장을 이론적으로 고찰한다. 이들 문제에서의 전기장은 Fourier-Laplace 영역의 이상파 성분과만 관련이 있다. 각각의 문제에 대해서 Cagniard-de Hoop 해석법을 응용하여 시간 영역의 전자장 해를 얻는다. VV 문제의 전자장은 적분이 포함되지 않은 명시적인 형태로 구할 수 있다. $HV{\cdot}VH$ 문제의 해에서는 적분을 없앨 수 없지만, 적분해에 내재 된 주요 특이 성분들은 해석적으로 추출된다. 주파수 영역의 계면 원방 전자장은 시간영역의 특이 성분에 의해 결정된다.

• 한국안전학회지
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• 제36권4호
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• pp.20-28
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• 2021

With an increase in the commercialization of electricity, and the development of advanced and large electric devices and various wireless radio wave services, concerns over the effects of electromagnetic fields on human health have increased. Accordingly, the World Health Organization encouraged the development of international standards by establishing the 'International Electromagnetic Fields Project' in 1996 based on studies on the harmful effects of electromagnetic fields on the human body. Moreover, the National Institute of Environmental Health Sciences (NIEHS) classified electromagnetic fields as possible carcinogens under Group 2B category, even though they have been found to have a weak correlation with those effects on human health. Mid-to-large-sized electric facilities used at industrial sites mostly adopt a commercial frequency of 60 Hz, and workers handling these facilities are exposed to such extremely low frequency (ELF) fields for a long time. A previous study suggested that exposure to ELF electromagnetic fields with frequency ranges from 0 to 300 Hz, even for a short time, at densities higher than 100 μT may have harmful effects on human body as it affects the activation of nerve cells in the central nervous system by inducing an electric field and current and stimulating muscles and the nervous system in the body. Such studies, however, focused on home appliances used by ordinary people, and research on facilities utilizing high-capacity current and operated by workers at industrial sites is lacking. Therefore, in this study, a 3000 kilowatt generator, which is a high-capacity electric facility employed at industrial sites, was investigated, and the size of the magnetic fields generated during its no-load and high-load operations per distance to produce a map was measured to reveal spots deemed hazardous according to domestic and international exposure standards. The findings of this study is expected to alleviate workers' anxiety about the harmful effects of magnetic fields on their body and to minimize the level of exposure during operations.

• 전자공학회논문지D
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• 제35D권1호
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• pp.8-15
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• 1998

An analysis of the microstripline is started as an assumption of the axial & transveral current distribution. Applying the boundary conditions to the scalar wave equations of a electric & magnetic potential, the two simultaneous coupled integral equations are produced. The electronmagnetic fields in microstrip line can be obtained by solving these two coupled integral equaltion. In general, either a numerical analysis method or a Galerkin method was used to solve them. In this paper, a residue theorem is proposed to solve them. The electromagnetic fields are expressed as integral equations for LSE and LSM mode in the spectral domain. Applying a residue theorem to the Fourier transformed equation and Fourier inverse transformed equation which is necessary for interchanging the space domain and the spectral domain, the electromagnetic fields are expressed as algebraic equations whichare relatively easier to handle. the distributions of the electromagnetic field are shown at the range of -5w/2.leq.x.leq.5w/2, 0.lep.y.leq.4h for z=0. It agrees well with the results of the Quasi-TEM mode analysis.

• Journal of Plant Biology
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• 제29권1호
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• pp.1-10
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• 1986

Intra- and inter-specific protoplast fusion of tobacco (Nicotiana tabacum cv. Virginia 115) and pea (Pisum sativum cv. Sparkle) were carried out in highly inhomogeneous alternating electric fields. Under the electric field of alternating current (AC, sine wave), 600 V/cm and 800 kHz for tobacco protoplast, and 600 V/cm and 700 kHz for pea protoplasts, the protoplasts were aggregated in pearl chains. Intra-specific protoplast fusions were most effectively induced within the aggregates of tobacco and pea, respectively, by the additional application of a single high field pulse of direct current (DC, square wave) at 1 kV/cm for 50 $mutextrm{s}$. Inter-specific fusions between protoplasts of the two plants were most effectively induced in the electric field of 600 V/cm and 700 kHz, and square wave pulse at 1 kV/cm for 50 $mutextrm{s}$. The duration of the pulse over the electrical breakdown voltages was simulated from 1 to 100 $mutextrm{s}$ in both tobacco and pea protoplast. The yield of the electrofusion products was significantly high (above 60%), compared with that (20%) of the standard fusion method by polyethylene glycol (PEG) 4,000, and the viability of electrofused protoplasts was above 70%, but that of PEG-fused protoplasts 8~16%, when determined by Evan's blue staining method.

• Advances in nano research
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• 제13권3호
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• pp.297-312
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• 2022

Coughing and breath shortness are common symptoms of nano (small) cell lung cancer. Smoking is main factor in causing such cancers. The cancer cells form on the soft tissues of lung. Deformation behavior and wave vibration of lung affected when cancer cells exist. Therefore, in the current work, phase velocity behavior of the small cell lung cancer as a main part of the body via an exact size-dependent theory is presented. Regarding this problem, displacement fields of small cell lung cancer are obtained using first-order shear deformation theory with five parameters. Besides, the size-dependent small cell lung cancer is modeled via nonlocal stress/strain gradient theory (NSGT). An analytical method is applied for solving the governing equations of the small cell lung cancer structure. The novelty of the current study is the consideration of the five-parameter of displacement for curved panel, and porosity as well as NSGT are employed and solved using the analytical method. For more verification, the outcomes of this reports are compared with the predictions of deep neural network (DNN) with adaptive optimization method. A thorough parametric investigation is conducted on the effect of NSGT parameters, porosity and geometry on the phase velocity behavior of the small cell lung cancer structure.

• 한국해안·해양공학회논문집
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• 제32권2호
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• pp.122-134
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• 2020

최근 동해안을 비롯한 많은 해안에서 심각한 해안침식과 인접한 해안도로 유실 등과 같은 연안재해가 발생되고 있는 것은 널리 알려진 사실이다. 이에 대한 대안으로 유럽을 비롯한 해외에서는 저마루구조물(LCS, Low-Crested Structure)에 의한 연안재해 저감법이 활발하게 연구되고 있다. 본 연구에서는 선행연구를 바탕으로 투과성의 LCS 및 그의 주변 파동장에 olaFlow 모델을 적용하여 불규칙파동장 하의 3차원 수치해석을 수행한다. 이로부터 H_rms, 해빈류 및 평균난류운동에너지를 수치적으로 검토하며, 해빈류의 패턴과 평균난류운동에너지의 공간분포에 관해서는 불규칙파동장 하 잠제의 경우와 비교하였다. 이로부터 해빈류의 양상이 잠제의 경우와는 상반되게 나타나는 등의 중요한 결과를 얻을 수 있었다.

• 한국해안·해양공학회논문집
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• 제30권4호
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• pp.153-165
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• 2018

본 연구는 olaFlow을 이용하여 먼저 소스에 의한 불규칙파의 조파에서 목표주파수스펙트럼과 조파된 파랑의 주파수스펙트럼과의 비교 검토로부터 olaFlow의 타당성을 검증하였다. 이로부터 불규칙파랑 하 3차원투과성잠제를 대상으로 잠제 주변에서 형성되는 파고분포와 같은 수면변동의 특성과 설상사주의 주요외력으로 작용하는 평균유속, 연안류 및 난류운동에너지 등을 포함한 유속장의 특성을 수치적으로 검토하였다. 수치해석결과에 따르면 잠제 사이의 개구폭이 감소할수록 개구부 중앙에서는 자승평균평방근파고가 증가하지만 개구부 배후에서는 자승평균 평방근파고가 감소하며, 잠제의 개구폭이 넓을수록 강한 연안류가 형성됨과 동시에 수송유량이 증가되는 것을 확인할 수 있었다. 이로부터 잠제 배후에 형성되는 설상사주의 형성원인을 파악할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.179-187
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• 2013

Floating production storage and offloading (FPSO) facilities are used at most of the offshore oil fields worldwide. FPSO usage is expected to grow as oil fields move to deeper water, thus requiring the reliability and stability of mooring wires and risers in extreme environmental conditions. Except for the case of predictable attack angles of external loadings, FPSO facilities with turret single point mooring (SPM) systems are in general use. There are two types of turret systems: permanent systems and disconnectable turret mooring systems. Extreme environment criteria for permanent moorings are usually based on a 100-year return period event. It is common to use two or three environments including the 100-year wave with associated wind and current, and the 100-year wind with associated waves and current. When fitted with a disconnectable turret mooring system, FPSOs can be used in areas where it is desirable to remove the production unit from the field temporarily to prevent exposure to extreme events such as cyclones or large icebergs. Static and dynamic mooring analyses were performed to evaluate the stability of a spider buoy after disconnection from a turret during cyclone environmental conditions.