• KIEE International Transactions on Power Engineering
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• 제5A권1호
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• pp.85-92
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• 2005

In this paper, Nash equilibriums of generation markets are investigated using a game theory application for simplified competitive electricity markets. We analyze the characteristics of equilibrium states in N-company spot markets modeled by uniform pricing auctions and propose a new method for obtaining Nash equilibriums of the auction. We assume that spot markets are operated as uniform pricing auctions and that each generation company submits its bids into the auction in the form of a seal-bid. Depending on the bids of generation companies, market demands are allocated to each company accordingly. The uniform pricing auction in this analysis can be formulated as a non-cooperative and static game in which generation companies correspond to players of the game. The coefficient of the bidding function of company-n is the strategy of player-n (company-n) and the payoff of player-n is defined as its profit from the uniform price auction. The solution of this game can be obtained using the concept of the non-cooperative equilibrium originating from the Nash idea. Based on the so called residual demand curve, we can derive the best response function of each generation company in the uniform pricing auction with N companies, analytically. Finally, we present an efficient means to obtain all the possible equilibrium set pairs and to examine their feasibilities as Nash equilibriums. A simple numerical example with three generation companies is demonstrated to illustrate the basic idea of the proposed methodology. From this, we can see the applicability of the proposed method to the real-world problem, even though further future analysis is required.

• 한국정보전자통신기술학회논문지
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• 제13권5호
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• pp.397-402
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• 2020

타입 1 콜라겐 단백질은 인체 내에서 가장 많이 존재하는 단백질이다. 이 단백질은 점탄성 거동을 보이며 이는 힘줄에서도 찾아볼 수 있다. 분자동역학 시뮬레이션 방법에는 rescaling 방법과 reassignment 방법으로 온도를 조절할 수 있다. rescaling 방법은 온도를 주어진 온도로 책정하는 방법이고, reassignment 방법은 원하는 온도로 맥스웰 분포를 이용하여서 온도를 책정하는 방법이다. 우리는 reassignment 방법에서 콜라겐 단백질의 거동이 시간에 따라서 변화하는 현상을 찾아내었다. 반면에 rescaling 방법에서는 시간에 무관하게 거동하였다. 콜라겐에 다른 속도로 인장을 가하였을 경우, 예를 들어 0.5, 1, 2, 5 Å/ps의 속도로 40 Å까지 힘을 가했을 경우, rescaling 방법에서는 속도에 따른 변화가 거의 없었던 반면, reassignment 방법의 경우 대략 80nm, 100nm, 130nm, 180nm까지 인장이 되었음을 보여준다. 이 현상에 대한 물리학적 의미를 명확하게 규명하지는 못하였지만, 단백질에 관한 시뮬레이션을 실행하는데 있어서 주의를 기울여 수행하여야 한다는 점에서 이 논문의 가치가 있다고 생각한다.

• 한국지반공학회논문집
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• 제36권6호
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• pp.35-46
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• 2020

액상화 구성모델의 입력변수는 실내외 실험 등을 통해 지반 및 하중 조건에 적합한 값을 결정하는 것이 중요하지만, 설계 실무에서는 시험수행의 어려움 등으로 입력변수의 결정 및 해석결과의 검증이 어려웠다. 본 연구에서는 반복 직접전단시험에 대한 수치모델링을 수행하여 액상화 구성모델 중 Finn 모델과 PM4Sand 모델의 적용성을 분석하였다. 그 결과, Finn 모델은 과잉간극수압의 최대값 도달시점은 모사할 수 있었지만 항복 이후의 과잉간극수압 응답 및 응력-변형률 거동을 모사하는데 한계가 있었다. 이에 반해, PM4Sand 모델은 액상화 도달시점 및 및 액상화 이후의 응력-변형률 거동을 잘 모사할 수 있었다. 최종적으로, 설계조건에 맞는 액상화 저항전단응력비 CRR을 모사할 수 있는 액상화 모델의 입력변수 산정절차를 제안하고 PM4Sand 모델의 입력변수를 산정하는 간편식을 제안하였다.

• Coupled systems mechanics
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• 제4권4호
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• pp.297-316
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• 2015

The use of fragility curves in the design of bridges is becoming common these days. In this study, experimental data have been used to develop fragility curves for the potential of girder unseating of a three-segment bridge and a bridge-abutment system including the influence of spatially varying ground motions, pounding, and abutment movement. The ground excitations were simulated based on the design spectra for different soil conditions. The Newmarket Viaduct replacement bridge in Auckland was used as the prototype bridge. These fragility curves were also applied to the 2010 Darfield and 2011 Christchurch earthquakes. The study showed that for bridges with similar characteristics as the chosen prototype and with similar fundamental frequencies, pounding could increase the probability of girder unseating by up to 35% and 30% based on the AASHTO and NZTA seating length requirements, respectively. The assumption of uniform ground excitations in many design practices, such as the NZTA requirements, could potentially be disastrous as girders might have a very good chance of unseating (as much as 53% higher chances when considering spatial variation of ground motions) even when they are designed not to. In the case of superstructures with dissimilar frequencies, the assumption of fixed abutments could significantly overestimate the girder unseating potential when pounding was ignored and underestimate the chances when pounding was considered. Bridges subjected to spatially varying ground excitations simulated based on the New Zealand design spectra for soft soil conditions with weak correlation shows the highest chances of girders falling off, of up to 65% greater than for shallow soil excitations.

• 한국자기학회지
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• 제8권6호
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• pp.388-394
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• 1998

자성물질의 자기이방성을 측정하기 위해 개선된 구조의 null-type 토크마그네토미터를 설계, 제작하였다. 제작된 토크마그네토미터의 측정범위는 $0~{\pm}15\;dyne.cm$이며 조절이 가능하다. 이 범위내에서 분해능은 약 0.0005 dyne.cm 정도이며, 1회 측정시 잡음수준은 ~0.01 dyne.cm, 10회 반복측정한 경우 ~0.004 dyne.cm 이하였으며, 반복재현시 나타나는 오차는 0.5% 이하였다. 본 연구에서 제작된 토크마그네토미터는 종전의 null-type 토크마그네토미터와는 달리 영구자석을 내부에, 헬름홀쯔 코일을 외부에 위치시킨 구조의 토크미터를 포함하고 있다. 이로 인하여, 기하학적으로 등방적인 모양으로 토크미터를 설계할 수 있었으며, 헬름헬쯔 코일의 입력전선과 출력전선의 역학적 및 전기적 임피던스에 으히나 토크곡선의 왜곡을 방지할 수 있었고, 샘플막대의 관성모멘트를 줄일 수 있었다. 그 결과 토크에 대하 보다 민감하면서도 반응속도가 빠르며 토크곡선의 왜곡요인이 적은 토크마그네토미터를 제작할 수 있었다.

• 한국광학회지
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• 제19권4호
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• pp.249-254
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• 2008

새 구조의 액정 엑스선 감지기를 만들었다. 이것은 액정판을 만들고 유리판을 얇게 식각한 다음, 그 유리판 위에 반사막과 광전도층을 연속하여 입힌 구조이다. 새 구조의 액정엑스선 감지기는 공정의 안정성, 대면적화, 감도 등에서 이미 상품화된 엑스선 감지기와도 충분히 경쟁할 수 있으며, 따라서 성공적으로 상용화 할 수 있음을 확인했다.

• Genomics & Informatics
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• 제19권1호
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• pp.11.1-11.8
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• 2021

For the novel coronavirus disease 2019 (COVID-19), predictive modeling, in the literature, uses broadly susceptible exposed infected recoverd (SEIR)/SIR, agent-based, curve-fitting models. Governments and legislative bodies rely on insights from prediction models to suggest new policies and to assess the effectiveness of enforced policies. Therefore, access to accurate outbreak prediction models is essential to obtain insights into the likely spread and consequences of infectious diseases. The objective of this study is to predict the future COVID-19 situation of Korea. Here, we employed 5 models for this analysis; SEIR, local linear regression (LLR), negative binomial (NB) regression, segment Poisson, deep-learning based long short-term memory models (LSTM) and tree based gradient boosting machine (GBM). After prediction, model performance comparison was evelauated using relative mean squared errors (RMSE) for two sets of train (January 20, 2020-December 31, 2020 and January 20, 2020-January 31, 2021) and testing data (January 1, 2021-February 28, 2021 and February 1, 2021-February 28, 2021) . Except for segmented Poisson model, the other models predicted a decline in the daily confirmed cases in the country for the coming future. RMSE values' comparison showed that LLR, GBM, SEIR, NB, and LSTM respectively, performed well in the forecasting of the pandemic situation of the country. A good understanding of the epidemic dynamics would greatly enhance the control and prevention of COVID-19 and other infectious diseases. Therefore, with increasing daily confirmed cases since this year, these results could help in the pandemic response by informing decisions about planning, resource allocation, and decision concerning social distancing policies.

• Nutrition Research and Practice
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• 제13권1호
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• pp.11-16
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• 2019

BACKGROUND/OBJECTIVES: Fasting and postprandial hyperglycemia should be controlled to avoid complications of diabetes mellitus. This study investigated the effects of autumn olive (Elaeagnus umbellata Thunb.) berry (AOB) on fasting and postprandial hyperglycemia in mice. MATERIALS/METHODS: In vitro ${\alpha}$-glucosidase inhibitory effect of AOB was determined. Maltose solution (2 g/kg) with and without AOB extract at 500 mg/kg or acarbose at 50 mg/kg was orally administered to normal mice after overnight fasting and glucose levels were measured. To study the effects of chronic consumption of AOB, db/db mice received the basal diet or a diet containing AOB extract at 0.4% or 0.8%, or acarbose at 0.04% for 7 weeks. Blood glycated hemoglobin and serum glucose and insulin levels were measured. Expression of adiponectin protein in epididymal white adipose tissue was determined by Western blotting. RESULTS: In vitro inhibitory effect of AOB extract on ${\alpha}$-glucosidase was 92% as strong as that of acarbose. The AOB extract (500 mg/kg) or acarbose (50 mg/kg) significantly suppressed the postprandial rise of blood glucose after maltose challenge and the area under the glycemic response curve in normal mice. The AOB extract at 0.4% or 0.8% of diet or acarbose at 0.04% of diet significantly lowered levels of serum glucose and blood glycated hemoglobin and homeostasis model assessment for insulin resistance values in db/db mice. The expression of adiponectin protein in adipose tissue was significantly elevated by the consumption of AOB at 0.8% of diet. CONCLUSIONS: Autumn olive (E. umbellata Thunb.) berry may reduce postprandial hyperglycemia by inhibiting ${\alpha}$-glucosidase in normal mice. Chronic consumption of AOB may alleviate fasting hyperglycemia in db/db mice partly by inhibiting ${\alpha}$-glucosidase and upregulating adiponectin expression.

• 정보보호학회논문지
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• 제28권6호
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• pp.1329-1342
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• 2018

최근 양자 컴퓨터에 대한 개발이 활발히 진행되면서, 기존에 널리 사용되고 있는 RSA와 타원곡선 암호 알고리즘의 안전성에 대한 문제가 제기되고 있다. 이에 대응하기 위하여 미국 표준기술연구원(NIST)은 양자 컴퓨팅 환경에서도 안전한 공개키 암호 기법에 대한 표준화 작업을 진행하고 있다. 대표적인 포스트 양자 암호(post-quantum cryptography, PQC) 기법으로는 격자기반 암호(lattice-based cryptography)가 있으며, NIST의 PQC 표준화 공모에도 다양한 격자기반 암호 기법들이 제안되었다. 이 중 EMBLEM은 기존의 LWE (learning with errors) 가정을 기반으로 하여 설계된 암호 기법들과는 달리, 더 직관적이고 효율적으로 암/복호화가 가능한 새로운 다중 비트 암호화 방법을 제안하였다. 본 논문에서는 LWR(learning with rounding) 가정을 추가적으로 사용하여 더 효율적으로 동작하는 다중 비트 암호화 기법을 제안한다. 그리고 제안하는 기법의 안전성을 증명하고, EMBLEM 및 R.EMBLEM과의 비교를 통해 효율성을 분석한다.

• 한국재료학회지
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• 제29권7호
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• pp.456-462
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• 2019

ZnO thin-films are grown on a p-Si(111) substrate by RF sputtering. The effects of growth temperature and $O_2$ mixture ratio on the ZnO films are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and room-temperature photoluminescence (PL) measurements. All the grown ZnO thin films show a strong preferred orientation along the c-axis, with an intense ultraviolet emission centered at 377 nm. However, when $O_2$ is mixed with the sputtering gas, the half width at half maximum (FWHM) of the XRD peak increases and the deep-level defect-related emission PL band becomes pronounced. In addition, an n-ZnO/p-Si heterojunction diode is fabricated by photolithographic processes and characterized using its current-voltage (I-V) characteristic curve and photoresponsivity. The fabricated n-ZnO/p-Si heterojunction diode exhibits typical rectifying I-V characteristics, with turn-on voltage of about 1.1 V and ideality factor of 1.7. The ratio of current density at ${\pm}3V$ of the reverse and forward bias voltage is about $5.8{\times}10^3$, which demonstrates the switching performance of the fabricated diode. The photoresponse of the diode under illumination of chopped with 40 Hz white light source shows fast response time and recovery time of 0.5 msec and 0.4 msec, respectively.