• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.392-392
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• 2022

세계적 규모의 팬데믹 감염병의 출현은 전 세계적으로 경제적, 문화적, 사회적 파급효과가 매우 강력하며 전 인류를 위협하고 있다. 최근에 발병한 중증급성 호흡기질환 코로나바이러스 2(Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2)는 2019년 12월 중국 우한에서 첫 보고 되었고 2022년 현재까지 종식되지 않고 있으며 바이러스의 전파력과 치명률이 높고 무증상 감염상태일 때에도 전염이 가능하여 현재 역학조사의 사후적 대응에 대한 한계가 있어 선제적 대응을 위한 수단이 필수 불가결해지고 있는 실정이다. 하수기반역학(Waste Based Epidemiology, WBE)이란 하수처리장으로 유입되기 전의 하수를 분석하여 하수 집수구역 내 도시민의 생활상을 예측하는 것으로 하수로 배출된 감염자의 분비물 및 배설물 속 바이러스를 하수관로에서 신속하게 검출함으로써 특정지역의 감염성 질환 전파 정도와 유행하는 타입(변이)등을 분석하고 기존 역학조사의 문제점을 극복할 수 있으며 선제적인 대응이 가능하다. 현재 COVID-19의 대유행과 관련하여 WBE를 기반으로 한 다양한 연구가 진행되고 있으며 실제 환자의 발생과 상관관계가 있음이 확인되고 있고 백신 접종과 새롭게 발생한 변이바이러스의 관계 속에서 발생하는 변수를 고려한 모델이 없다는 점을 들어 새로운 감염병 확산 예측 모델에 대한 필요성 또한 커지고 있다. 본 연구에서는 병원에서부터 하수처리장까지의 하수관거와 하수처리장에서의 SARS-CoV-2 검출농도 및 거동을 파악하는 것을 목적으로 하고 있으며 COVID-19의 감염규모 확산에 관한 방법론에서 수학적모델 (Euler Method, RK4 Method, Gillespie Algorithm)과 딥러닝 기반의 Nowcasting model과 Fore casting model을 살펴보고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.347-349
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• 2014

Model verification and validation (V&V) is a current research topic to build computational models with high predictive capability by addressing the general concepts, processes and statistical techniques. The hypothesis test for validity check is one of the model validation techniques and gives a guideline to evaluate the validity of a computational model when limited experimental data only exist due to restricted test resources (e.g., time and budget). The hypothesis test for validity check mainly employ Type I error, the risk of rejecting the valid computational model, for the validity evaluation since quantification of Type II error is not feasible for model validation. However, Type II error, the risk of accepting invalid computational model, should be importantly considered for an engineered products having high risk on predicted results. This paper proposes a technique named as the response-adaptive experimental design to reduce Type II error by adaptively designing experimental conditions for the validation experiment. A tire tread block problem and a numerical example are employed to show the effectiveness of the response-adaptive experimental design for the validity evaluation.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.380-387
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• 2011

In this paper, we considered the authoritative representation of Command and Fire Control System(CFCS) for the surface ship that was the engineering level model to develop system specifications and to analyze operational concepts on the concept design phase and to analyze military requirements, effectiveness and performance for the system. The engineering level model of CFCS can be used in simulation independently of the surface ship's type, and also it takes reuse, interoperability, and extension into consideration. The detailed sub-models, internal and external data interface, data flow among each sub-model, sensor and weapon models about the engineering level model of CFCS was defined. It was verified via engineering level simulations according to the V&V process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.132-132
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• 2009

A 2D-simulation using a quantum model of silicon nanowire (SiNW) field-effect transistors (FETs) have been performed by the effective mass theory. We have investigated very close for real device analysis, so we used to the non-equilibrium Green's function (NEGF) and the density gradient of quantum model. We investigated I-V characteristics curve and C-V characteristics curve of the channel thickness from 5nm to 200nm. As a result of simulation, even higher drain current in SiNW using a quantum model was observed than in SiNW using a non-quantum model. The reason of higher drain current can be explained by the quantum confinement effect.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.4
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• pp.275-283
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• 2007

This study aims at the calculation of a variation of flow characteristics of main channel for tributary inflow in river junction. So this study was analyzed the variation of flow depth and velocity in main channel for a change of inflow degree. For this purpose, FLDWAV model are carried out for variations of $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$ tributary inflow at junction. Results show that velocity ratio(V1/V3) increases and flow depth ratio(H1/H3) decreases for discharge ratio(Q1/Q3) of upstream and downstream when degree increases in junction. And FLDWAV model was applied at a real river junctions. Selected area is a junction of Gumho river and Sin stream. Results show that pattern is similar to a virtual channel.

• Bulletin of the Korean Mathematical Society
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• v.47 no.6
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• pp.1131-1138
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• 2010

In the present paper, we evaluate an analytic formula as a solution of Susceptible Infective (SI) model problem for communicable disease in which the daily contact rate (C(N)) is supposed to be varied linearly with population size N(t) that is large so that it is considered as a continuous variable of time t. Again, we introduce some Lie group of operators to make an extension of above analytic formula of the determin-istic epidemics model problem. Finally, we discuss some of its particular cases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.865-870
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• 2008

The effects of exhaust gas recirculation (ECR) on smoke emissions in heavy duty diesel engine are numerically studied by using KIVA-3V CFD code. For the analysis, RNG k-$\varepsilon$ turbulence model was given as a governing equation, and mathematical models of Tab, Wave, Watkins-Park, Nagle-Strikland were applied to describe physical process of droplet breakup, atomization, wall impingement and smoke respectively.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.112-119
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• 1996

Impact ionization model in GaAs has been presented by modified keldysh formula with two sets of power exponent of 7.8 and 5.6 in study. Impact ionization rate is derived from fermil's golden rule and ful lenergy band stucture based on empirical pseudopotential method. Impact ionization rates show anisotropic property in low energy region (<3eV), but isotropic in high energy region (3>eV). Full band monte calo simulator is coded for investigating the validity of the GaAs impact ionization model, and validity is checked by comparing impact ionization coefficients with experimental values and ones in anisotropic model. Valley transitions to energy alteration are explained by investigating electron motion in brillouin zone for full band model to electric field variation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.676-682
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• 2012

To review application of HVDC (High Voltage Direct Current) transmission line to HVAC T/L in operation, reduced-scale model was designed and manufactured. The arms of model were designed to change height and interval of conductors. Electrical environmental interferences were estimated by various configuration of AC 345kV and DC 250kV T/L. The interferences such as electric field intensity and ion current density were measured and converted reduced-scale factor to full-scaled. Additionally, effects between AC and DC T/L were studied.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.249-253
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• 2011

This paper describes the fabrication and characteristics of vibration-driven electromagnetic energy harvester without spring to use at low frequency like a human body motion. The implemented energy harvester consists of NdFeB magnets, copper coil. The optimization of induced voltage was done by the various widths of coil, number of the turns, size of fixed and moving magnets and thicknesses of the cylinder. The fabricated energy harvester is capable of producing up to 15.0 $V_{pp}$ for basic model and 28.80 $V_{pp}$ for improved model at 5.0 Hz resonance frequency and 0.75 g acceleration level. The basic model and improved model are provided a maximum power of 6.375 mWand 25.831 mW at 1 KHz of load resistance in rectifier circuit.