• Journal of electromagnetic engineering and science
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• 제15권4호
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• pp.199-205
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• 2015

An electromagnetic band gap (EBG) metamaterial construction is presented. A construction of a multipath mitigating ground plane, based on the EBG metamaterial is described. A method of the ground plane application and installation, which provides the multipath mitigating without spoiling antenna element phase center stability, is suggested and explained. A designed construction of GNSS antenna module, which contains the multipath mitigating ground plane, made from the presented EBG metamaterial and installed in the described way is shown and parameters of the antenna module are provided.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.119-125
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• 2011

In this paper, we have studied about minimizing the Energy Storage System (ESS) capacity for mitigating the fluctuation of Wind Turbine Generation System (WTGS) by using Electric Double Layer Capacitor (EDLC) and Battery Energy Storage System (BESS). In this case, they have some different characteristics: The EDLC has the ability of generating the output power at high frequency. Thus, it is able to reduce the fluctuation of WTGS in spite of high cost. The BESS, by using Li-Ion battery, takes the advantage of high energy density, however it is limited to use at low frequency response. To verify the effectiveness of the proposed method, simulations are carried out with the actual data of 2MW WTGS in case of worst fluctuation of WTGS is happened. By comparing simulation results, this method shows the excellent performance. Therefore, it is very useful for understanding and minimizing the ESS capacity for mitigating the fluctuation of WTGS.

• 대한전기학회논문지:전력기술부문A
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• 제49권11호
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• pp.558-565
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• 2000

In this paper, we propose a method for mitigating for mitigating the effect of voltage of voltage sag in radial power distribution systems using load transfer switching (LTS). The term of LTS is defined that the weakness load points for voltage sag transfer to the alternative source during the fault clearing practices. The sequenced of proposed LTS method is divided into the search of weakness points for voltage sag using the risk assessment model and transfer behavior of weakness points. The search of weakness point is carried out using the risk assessment model of voltage sag and Monte Carlo simulation method and the historical reliability data in Korea Electric Power Corporation (KEPCO) are also used. Through the case studies, we verify the effectiveness of proposed LTS method and present the searching method of effective application points of LTS method using the risk assessment model.

• 전기학회논문지
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• 제64권1호
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• pp.29-34
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• 2015

This paper presents a method to select optimal device for mitigating voltage sags. The method is based on economic evaluation and voltage sag assessment involving sag duration as well as magnitude. The economic evaluation is performed by using the operation cost and economic benefit of the mitigation devices. The optimal device can be determined from the values of NPV (net present value) which is widely accepted in cost-benefit analysis. The proposed method can help sensitive customers to select optimal mitigation device. In this paper, the case study considering two sensitive customers was performed by using the proposed method.

• 대한토목학회논문집
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• 제37권2호
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• pp.379-387
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• 2017

최근 고속철도 평균 좌석이용률이 98% 수준에 이르면서 고속철도 차량 내 혼잡이 발생하는 문제가 나타났고, 이러한 배경에서 본 연구는 고속철도 차량 내 혼잡도 완화에 따른 고속철도 이용자들의 편익을 추정하기 위하여 이용자들의 지불 용의액을 산정하였다. 진술선호자료에 근간한 조건부 가치측정법과 토빗(Tobit) 모형을 통해 지불 용의액을 추정한 결과, 지불 용의액은 소득 수준 및 혼잡도 수준과 비례하는 것으로 나타났으며, 남성, 특실이용자, 자유석 및 정기권 이용자의 지불 용의액이 높고, 주말 이용자, 주부, 통근목적이나 여가목적 이용자들은 지불 용의액이 낮은 것으로 나타났다. 본 연구에서 산정된 지불 용의액은 철도운영자들의 좌석공급 확대를 위한 노력에 대하여 정부의 지원근거나 사회적 편익을 계량화할 수 있는 근거를 제공하였다는 점에서 의의가 있다고 하겠다.

• 대한전기학회논문지
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• 제43권4호
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• pp.594-600
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• 1994

The maximum charge accumulation in transformers caused by streaming electrification is commonly observed on the bottom area of transformer winding(i.e.the oil inlet of transformer winding). It is because turbulent flows occur in this portion of transformers. Consequently, if we are to reduce the maximum charge accumulation of transformers, it is important that we should have a good understanding of the conditions of the occurence of partial turbulent flows in the oil inlet of transformer winding. With this point in mind, a simple flow model was designed in this study in order to simulate oil flow in the insulation ducts of power transformers. As a method for mitigating charge accummulation, attention was given to (a) a flow path design for the improvement of flow conditions, and (b) the charge tendency of the material used this design. The results of this study show that the above method is useful for mitigating charge accumulation.

• 한방안이비인후피부과학회지
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• 제33권4호
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• pp.1-15
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• 2020

Objectives : To investigate aggravating and mitigating factors of atopic dermatitis and to utilize the outcome in treatment planning. Methods : The research has a cross-sectional study design. Patients' SCORing Atopic Dermatitis (SCORAD) Index, demographic, physical characteristics, social history, serologic index and skin related instrumental measurements were analyzed with correlation and regression analysis method. Results : 48 patients in total were enrolled in the study. Skin Surface Hydration (SSH) and sex were found to be statistically significant aggravating and mitigating factors. As SSH increased, Total SCORAD (tSCORAD) and Objective SCORAD (oSCORAD) increased as well. As SSH decreased, tSCORAD and oSCORAD decreased as well. Female patient had a higher probability of suffering from severer subjective symptoms than that of male. Age, body mass index (BMI), alcohol consumption and smoking, transepidermal water loss (TEWL), IgE, IL-4, IL-5, IL-6, IFN-γ were found not to be statistically significant. There was no correlation between Subjective SCORAD (sSCORAD) and oSCORAD neither with Eczema Area and Severity Index (EASI). Conclusions : Increasing cutaneous moisture should be included in the treatment plan of atopic dermatitis. More emphasis should be put on alleviating subjective discomforts of female patients than that of male. Establishing separate strategies of managing objective eczema status and subjective discomforts respectively should be considered.

• 대한기계학회논문집B
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• 제21권5호
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• pp.670-678
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• 1997

A method to mitigate the thermal stratification phenomenon of pressurizer surge line is proposed by heating bottom outside of horizontal pipe. Unsteady two dimensional model has been used to numerically investigate an effect of heating the bottom of pipe. The dimensionless governing equations are solved by using the control volume formulation and SIMPLE algorithm. Temperature and streamline profiles of fluids and pipe walls with time are compared with the previous study result. The numerical result of this study shows that the outside heating can relaxate the thermal stratification flow of the pressurizer surge line. Maximum dimensionless temperature difference between hot and cold sections of the pipe inner wall which causes thermal stratification was reduced from 0.514 to 0.424 at dimensionless time 1, 632 and 1, 500 respectively.

• 국제초고층학회논문집
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• 제8권4호
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• pp.291-302
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• 2019

We performed calculations combining optimization technologies and Computational Fluid Dynamics (CFD) aimed at reducing wind forces and mitigating wind environments (local strong winds) around buildings. However, the Reynolds Averaged Navier-stokes Simulation (RANS), which seems somewhat inaccurate, needs to be used to create a realistic CFD optimization tool. Therefore, in this study we explored the possibilities of optimizing calculations using RANS. We were able to demonstrate that building configurations advantageous to wind forces could be predicted even with RANS. We also demonstrated that building layouts was more effective than building configurations in mitigating local strong winds around tall buildings. Additionally, we used the Convolutional Neural Network (CNN) as an airflow prediction method alternative to CFD in order to increase the speed of optimization calculations, and validated its prediction accuracy.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 추계학술대회
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• pp.152-155
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• 2018

지난 몇 년간, 링크 플러딩 공격이라는 새로운 형태의 분산 서비스 공격 (DDoS) 이 제안되었다. 링크 플러딩 공격은 기존 DDoS 공격과는 다르게 선택적으로 라우터 간 코어 링크를 혼잡 시킴으로써 보다 넓은 범위에 지대한 영향을 끼친다는 점에서 큰 차이가 있다. 기존 네트워크 구조에서는 링크 플러딩 공격을 완화하는 것이 어려운데, 이는 공격자가 traceroute를 이용하여 취약한 링크를 사전에 파악하고 링크맵을 구축할 수 있는 원인에 기인한다. 기존에 링크 플러딩 공격을 감지하여 대응하기 위한 여러 연구가 제안되었으나 이들은 모두 목표 링크에 실제 공격이 발생한 직후에 이를 완화하는, 즉 사후 조치를 한다는 한계점이 존재한다. 본 논문에서는 링크 플러딩 공격 시나리오에서 공격자가 링크맵을 구축할 수 있다는 점에 주목하고 이를 사전에 방지하고자 하는 접근법을 제안한다. 소프트웨어 정의 네트워크의 장점을 활용하여 취약한 링크를 사전에 파악하고, 주변에 허니팟을 배치함으로써 중요한 링크를 공격자로부터 은닉하는 시스템인 SDHoneyNet을 보인다.