• 한국수학교육학회지시리즈B:순수및응용수학
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• 제21권4호
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• pp.307-316
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• 2014

We prove the existence of the risk-efficient options proposed by Xu [7]. The proof is given by both indirect and direct ways. Schied [6] showed the existence of the optimal solution of equation (2.1). The one is to use the Schied's result. The other one is to find the sequences converging to the risk-efficient option.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권1호
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• pp.61-74
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• 2014

This paper presents accurate and efficient numerical methods for calculating the sensitivities of two-asset European options, the Greeks. The Greeks are important financial instruments in management of economic value at risk due to changing market conditions. The option pricing model is based on the Black-Scholes partial differential equation. The model is discretized by using a finite difference method and resulting discrete equations are solved by means of an operator splitting method. For Delta, Gamma, and Theta, we investigate the effect of high-order discretizations. For Rho and Vega, we develop an accurate and robust automatic algorithm for finding an optimal value. A cash-or-nothing option is taken to demonstrate the performance of the proposed algorithm for calculating the Greeks. The results show that the new treatment gives automatic and robust calculations for the Greeks.

• 해양환경안전학회지
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• 제24권3호
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• pp.302-310
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• 2018

Despite the accident rate for fishing vessels accounts for 70% of all maritime accidents, few studies on such accidents have been done and most of the them mainly focus on causes and mitigation policies to reduce that accident rate. Thus, this risk analysis on sea accidents is the first to be performed for the successful and efficient implementation of accident reducing measures. In risk analysis, risk is calculated based on the combination of frequency and the consequence of an accident, and is usually expressed as a single number. However, there exists uncertainty in the risk calculation process if one uses a limited number of data for analysis. Therefore, in the study we propose a probabilistic simulation method to forecast risk not as a single number, but in a range of possible risk values. For the capability of the proposed method, using the criteria with the ALARP region, we show the possible risk values spanning across the different risk regions, whereas the single risk value calculated from the existing method lies in one of the risk regions. Therefore, a decision maker could employ appropriate risk mitigation options to handle the risks lying in different regions. For this study, we used fishing vessel accident data from 1988 to 2016.

• 한국안전학회지
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• 제38권3호
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• pp.102-109
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• 2023

Following the accident at Fukushima, the true impact of multi-unit accidents came to light. Accordingly, research related to multi-unit accident effect analysis, risk evaluation, and accident prevention/prevention technology has been conducted. Specific examples are mobile/fixed equipment such as multi-barrier accident coping strategy (MACST) and diverse and flexible coping strategies (FLEX), which have been introduced and installed in multi-units for preventing and mitigating multi-unit accidents. These strategies are useful for enhancing the safety of nuclear power plants (NPPs); however, a more efficient strategy is required in terms of the costs of physical and human resources. To effectively and efficiently mitigate an increase in multi-unit accidents, it is necessary to not only to utilize mobile/fixed equipment but to also use crosstie options with resources that already exist at NPPs. Therefore, we analyzed the current international and domestic status of crosstie systems technology and propose a method to evaluate feasibility alongside risk based on a multi-unit probabilistic safety assessment (PSA). To analyze the international and domestic status of crosstie systems technology, actual cases and related research were studied, and a list of potential crosstie safety resources was derived. Additionally, a case study was performed on crosstie cases of two systems within the assumed six units on-site under a multi-unit accident, and a multi-unit PSA-based risk evaluation method is proposed.

• Journal of Information Processing Systems
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• 제18권5호
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• pp.637-649
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• 2022

Investors aim to increase their profitability by investing in the stock market. An adroit strategy for minimizing related risk lies through diversifying portfolio operationalization. In this paper, we propose a six-step stocks portfolio selection model. This model is based on data mining clustering techniques that reflect the ensuing impact of the political, economic, legal, and corporate governance in Mongolia. As a dataset, we have selected stock exchange trading price, financial statements, and operational reports of top-20 highly capitalized stocks that were traded at the Mongolian Stock Exchange from 2013 to 2017. In order to cluster the stock returns and risks, we have used k-means clustering techniques. We have combined both k-means clustering with Markowitz's portfolio theory to create an optimal and efficient portfolio. We constructed an efficient frontier, creating 15 portfolios, and computed the weight of stocks in each portfolio. From these portfolio options, the investor is given a choice to choose any one option.

• Journal of Chest Surgery
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• 제31권7호
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• pp.697-702
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• 1998

손바닥, 액와부의 다한증은 많은 사람에서 생활의 질에 강한 부정적인 영향을 준다. 기존의 비수술적 치료방법은 이상적이지 못하고 확실한 치료는 상흉부 교감신경절(T2-4) 절제로 얻을 수 있다. 과거에는 전통적인 흉부개방창에 의한 수술이 주요한 방법이었으나 최근에 흉강내시경을 이용해 교감신경절제술을 시행하고 있다. 1995년 1월부터 1997년 8월까지 흉강내시경을 이용해 양측 교감신경절제술을 40명의 환자에서 시행하여서 사망이나 생명을 위협하는 합병증은 없었고 유일한 부작용은 보상성 다한증이었으나 모든 환자에서 만족스러운 증세의 호전을 얻을 수 있었다. 결론적으로 흉강내시경하 제 2, 3, 4 흉부 교감신경절제술은 수장부, 액와부의 다한증 치료에 있어서 효과적이고 안전하며, 경제적인 최소한의 침습성 수술방법이다.

• 한국환경농학회:학술대회논문집
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• 한국환경농학회 2009년도 정기총회 및 국제심포지엄
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• pp.93-115
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• 2009

There are growing public concerns over crop and food safeties due to the elevated levels of heavy metals grown in contaminated soil. Heavy metals are classified as the chemical harmful risks for crop and food safety. With implementation of GAP, crop safety is controlled by many regulatory options for soil, irrigation water and fertilizers. Any attempt to retard the metal uptake by crops may be the best protocol to secure crop and food safety. This article reviews the management strategies for heavy metals in view of crop safety in Korea and demonstrates results from the field experiments to retard metal translocation from soil to crops by using chemical amendments and soil layer management methods. Major source of soil pollution by heavy metals has been related with mining activities. Risk assessment revealed that rice consumption and groundwater ingestion in the abandoned mining areas were the major exposure pathways for metals to human and the heavy metal showed the toxic effects on human health. Chemical amendments such as lime and slag retarded Cd uptake by rice (Oryza sativa L.) by increasing soil pH, lowering the phytoavailable Cd concentration in soil solution, immobilizing Cd in soil and converting the available Cd fractions into non-available fractions. The soil layer management methods decreased the Cd uptake by 76% and Pb by 60%. Either reversing the surface layer with subsurface layer or immobilization of metals with layer mixing with lime was considered to be the practical option for the in-situ remediation of the contaminated paddy soils. Combination of chemical soil amendments and layer management methods was efficient to retard the metal bioavailability and thus to secure crop safety for heavy metals. This protocol seems to be cheap, relatively easy to practice and practical in the agricultural fields. However, a long term monitoring work should be followed to verify the efficiency of this protocol.

• Asian Pacific Journal of Cancer Prevention
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• 제14권1호
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• pp.511-514
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• 2013

Background: A small but significant proportion of cases with atypical squamous cells of undetermined significance (ASCUS) may harbour CIN 2-3, or even invasive carcinoma. Although immediate colposcopy, HPV-DNA testing or expectant management are three recommended options in ASCUS triage, a consensus does not currently exist on which one of these approaches is the most efficient. In this study, we aimed to compare the performance and cost of immediate colposcopy and colposcopy based on the human papillomavirus (HPV) testing for detecting histologically confirmed high-grade cervical intraepithelial neoplasia (CIN) in women with ASCUS. Materials and Methods: Records of 594 women with an index Papanicolaou smear showing ASCUS were retrospectively analyzed. Women in the immediate colposcopy arm were referred directly to colposcopy (immediate colposcopy group, n=255) and those in the HPV triage arm were proceeded to colposcopy if the high-risk HPV (hrHPV) test was positive (HPV triage group, n=339). High grade CIN (CIN2+) detection rate and treatment costs were compared between the groups. Results: The detected rate of CIN2+ was higher in the HPV triage group compared to immediate colposcopy group (8% vs. 1.6%, p=0.011). In the HPV triage group, the total cost, cost per patient, and the cost for detecting one case of high grade CIN were higher than the immediate colposcopy group (p<0.001). Conclusions: In women with ASCUS cytology, HPV DNA testing followed by colposcopy is more costly than immediate colposcopy, but this approach is associated with a higher rate of CIN2+ detection. This findings suggest that HPV DNA testing combined with cervical cytology could reduce the referral rate to colposcopy.