• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1916-1924
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• 2017

Fossil oil, as the main energy of transportation, is destined to be exhausted. The electrification of transportation is a sustainable solution to the energy crisis, since electric power could be acquired from the inexhaustible sun, wind and water. Among all the problems that hinder the development of Electric Vehicle (EV) industry, charging issue might be the most prominent one. In this paper, the service process of a charging station with Battery Energy Storage System (BESS) is analyzed by means of $Cram{\acute{e}}r$ - Lundberg model which has been intensively utilized in ruin theory. The service quality is proposed in two dimensions: the service efficiency and the service reliability. The arrival rate and State of Charge (SOC) upon arrival are derived from 2009 National Household Travel Survey (NHTS). The simulations are performed to show how the service quality is determined by the system parameters such as the number of servers, the service rate, the initial capacity, the charge rate and the maximum waiting time. At last, the economic analysis of the system is conducted and the best combination of the system parameters are given.

• 해양환경안전학회지
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• 제23권1호
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• pp.56-66
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• 2017

본 연구에서는 상선과 어선의 해기사, 해군의 함정장교 양성기관의 해기교육 시스템을 비교분석 함으로써 해양력 확보를 위한 해기교육 상황을 파악하였다. 분석결과 상선의 해기사 양성과정을 제외하고는 선박운영에 관한 교육과정이 상대적으로 낮은 비중을 차지하고 있었다. 선박운영에 필수적인 해기교육의 강화는 해양력 확보에 필수적이지만 인력공급이 어려운 선원직의 특수성이 교육과정에 반영된 것으로 보인다. 우수한 선원의 확보와 해기교육 문제를 해결하기 위해서는 국가차원의 관심과 지원방안이 마련되어야 할 것이다.

• 환경영향평가
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• 제23권1호
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• pp.1-9
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• 2014

This study, focusing on the area expansion of limestone mines, identifies the problems of Environmental Impact Assessment(EIA) and what impact the current problems exert on another mines developing process. The legal relations analysis reveals that the Management of Mountainous Districts Act and other related laws effect on EIA process, especially the case of area expansion of limestone mines excluded from EIA. However, these problems can create mismatch with the policy goal of EIA system and have a negative impact on the environment in the future. A series of indepth interviews with managers in related agencies found that those agencies have been unaware of the seriousness of the problem. Without any strategy, negative result made by development activities would get more serious and sustainable development may not be possible at all. In order to solve these problems, government should modify the current interdependent legal provision and create the incentive structure to participate actively related agency in the EIA system.

• 한국재료학회지
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• 제32권10호
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• pp.429-434
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• 2022

There is ongoing research to develop lithium ion batteries as sustainable energy sources. Because of safety problems, solid state batteries, where electrolytes are replaced with solids, are attracting attention. Sulfide electrolytes, with a high ion conductivity of 10^-3 S/cm or more, have the highest potential performance, but the price of the main materials is high. This study investigated lithium hydride materials, which offer economic advantages and low density. To analyze the change in ion conductivity in polymer electrolyte composites, PVDF, a representative polymer substance was used at a certain mass ratio. XRD, SEM, and BET were performed for metallurgical analyses of the materials, and ion conductivity was calculated through the EIS method. In addition, thermal conductivity was measured to analyze thermal stability, which is a major parameter of lithium ion batteries. As a result, the ion conductivity of LiH was found to be 10^-6 S/cm, and the ion conductivity further decreased as the PVDF ratio increased when the composite was formed.

• Structural Engineering and Mechanics
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• 제88권4호
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• pp.323-334
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• 2023

The submerged floating tunnel (SFT) infrastructure has been regarded as an emerging technology that efficiently and safely connects land and islands. The SFT route problem is an essential part of the SFT planning and design phase, with significant impacts on the surrounding environment. This study aims to develop an optimization model considering transportation and structure factors. The SFT routing problem was optimized based on two objective functions, i.e., minimizing total travel time and cumulative strains, using NSGA-II. The proposed model was applied to the section from Mokpo to Jeju Island using road network and wave observation data. As a result of the proposed model, a Pareto optimum curve was obtained, showing a negative correlation between the total travel time and cumulative strain. Based on the inflection points on the Pareto optimum curve, four optimal SFT routes were selected and compared to identify the pros and cons. The travel time savings of the four selected alternatives were estimated to range from 9.9% to 10.5% compared to the non-implemented scenario. In terms of demand, there was a substantial shift in the number of travel and freight trips from airways to railways and roadways. Cumulative strain, calculated based on SFT distance, support structure, and wave energy, was found to be low when the route passed through small islands. The proposed model helps decision-making in the planning and design phases of SFT projects, ultimately contributing to the progress of a safe, efficient, and sustainable SFT infrastructure.

• 한국해양공학회지
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• 제38권3호
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• pp.137-147
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• 2024

Green hydrogen presents a sustainable and environmentally friendly solution for clean energy production and transportation. This study aims to identify the optimal profile of green hydrogen transportation risers originating from a floating offshore wind turbine (FOWT) integrated with a hydrogen production facility. Employing the Cummins equation, a fully coupled dynamic analysis for FOWT with a flexible riser was conducted, with the tower, mooring lines, and risers described using a lumped mass line model. Initially, motion response amplitude operators (RAOs) were compared with openly published results to validate the numerical model for the FOWT. Subsequently, a parametric study was conducted on the length of the buoyancy module section and the upper bare section of the riser by comparing the riser's tension and bending moment. The results indicated that as the length of the buoyancy module increases, the maximum tension of the riser decreases, while it increases with the lengthening of the bare section. Furthermore, shorter buoyancy modules are expected to experience less fatigue damage, with the length of the bare section having a relatively minor impact on this phenomenon. Consequently, to ensure safety under extreme environmental conditions, both the upper bare section and the buoyancy module section should be relatively short.

• 대한교통학회지
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• 제29권2호
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• pp.47-58
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• 2011

최근 OECD 국가에서는 공공투자사업과 정책의 성과를 감사행정을 통해 적극 평가함에 따라 본 연구에서는 국내 교통투자사업 및 정책의 성과를 사전적으로 평가 점검할 수 있는 교통계획 분야의 성과감사 평가기준 및 방법론을 개발하였다. 또한 국내 교통분야 감사 실태를 조사하여 중요도분석(IPA)을 수행하였으며, 분석결과 교통행정분야(계획-건설-운영관리-기타) 중 교통계획 분야의 감사가 부족하였고 특히 민자, 항공 및 물류 분야는 감사빈도 및 접근 방법의 변경 등 성과감사 방법론의 개선이 필요한 분야로 나타났다. 따라서 본 연구에서는 주요국 감사원의 교통계획 분야 감사사례를 분석하여 성과감사 평가기준 및 감사방법론을 고찰한 후 주요국의 교통계획 분야 성과감사 평가기준 및 성과감사 방법론을 도출하였다. 먼저 성과감사 평가기준으로 영국 PPG13의 교통계획 지침, 미국의 3C 교통계획수립 지침 등 영 미의 교통계획의 수립원칙과 영 미 감사원의 교통계획 분야 성과감사 평가기준을 고찰한 후 교통계획의 정책성과(형평성, 환경적 지속가능성), 정책수단(인과성), 행정절차(일관성, 협조성, 종합성)를 점검할 수 있는 5Es+4Cs 기준을 정립하였다. 그리고 향후 교통계획 분야 성과감사 시 적용 가능한 교통계획 분야 성과감사 방법론을 정립하기 위한 주요국의 교통계획 분야 감사 초점과 분석지표를 체크리스트 형태로 제시하였으며, 국내 교통계획 분야 전문가 설문조사를 통해 각 체크리스트에 대한 중요도를 순위로 제시 활용토록 하였다. 향후 과제로 교통 및 물류분야의 정책 및 사업이 지속가능한 성과를 달성하기 위해 서는 성과감사 평가기준 및 방법론을 지속적으로 보완 정비하여 나가야할 필요가 있다고 판단된다.

• 한국철도학회논문집
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• 제17권2호
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• pp.94-99
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• 2014

최근의 신 교통시스템 개발 동향은 주로 지속가능하고 친환경적인 교통수단을 제공하는데 초점이 맞춰져 있다. 그 중에서도, 수요응답형 순환교통(PRT: Personal Rapid Transit) 시스템은 그 가능성 때문에 주목을 받고 있으며, 첨단 전기 자동차(EV) 개발 기술과의 융합을 통해서 경쟁력은 보다 향상되고 있다. 하지만 전기 배터리에 의해 구동되는 차량의 경우 안정적이고 효율적인 운영의 측면에서 기술적인 어려움에 직면하고 있다. 본 논문에서는, 기술적인 난제를 극복하고 전기에너지를 기반으로 한 교통수단의 보급을 증대하기 위하여 태양전지에 의한 보조 전력 공급을 위한 설계적 접근방법에 대해서 모형실험을 통해서 논한다. 그 결과, 실제 차량에 적용했을 시 보조 전원 공급장치로서 일부 서비스 기기에 소요되는 전력량의 대략 11% 정도를 감당할 수 있을 것으로 예측되었다. 특히, 유연소재 태양전지의 장점은 저렴하고 가벼우며 디자인 의도를 최대한 살릴 수 있다는 데 있다. 무엇보다도 유연함과 용이한 부착성은 다양한 분야에서의 확대 적용 가능성을 보여준다.

• 한국환경보건학회지
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• 제50권2호
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• pp.157-167
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• 2024

Background: Several previous studies have shown that commuting is a source of stress for undergraduate students. However, few studies have investigated the effect of commuting on academic stress among undergraduate students, and there has been little awareness of the environmental impact of commuting. Objectives: To evaluate the associations between commute type and/or time and academic stress among undergraduate students in South Korea, focusing on environmental sustainability. Methods: We conducted an online survey and obtained information on commute types, commute times, and academic stress from 510 undergraduate students aged ≥19 years. Academic stress was comprised of five sub-categories of stress, and total academic stress ranged from 5 to 25 points. Multiple linear regression analysis was used to analyze the associations between commute type and commute time and academic stress. Furthermore, the students were grouped into 21 categories based on their transportation mode for commuting. CO₂ emission factors per each commuting category were calculated using the transportation type's CO₂ emission data from previous studies. Spearman's correlation analysis was used to confirm the correlation between CO₂ emission factors and total academic stress. Results: Students using home-to-school transportation without transfers (vs. walking) showed a significantly higher total academic stress of 2.19 points (95% CI: 0.58, 3.80). In contrast, students using school-to-home transportation without transfers (vs. walking) showed a significantly lower total academic stress of 1.96 points (95% CI: -3.55, -0.38). Moreover, students using transportation with lower CO₂ emission factors had lower academic stress scores (home-to-school: correlation coefficient = 0.507, p<0.001; school-to-home: correlation coefficient = 0.491, p<0.001). Conclusions: Our findings suggest that both commute type and time are significantly associated with academic stress among South Korean undergraduate students. When students select environmentally-friendly transportation, they may not only improve their mental health but also improve climate resilience.

• 대한토목학회논문집
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• 제34권4호
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• pp.1241-1249
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• 2014

본 연구는 수원 시민들을 대상으로 카쉐어링 선호도 요인을 분석하여 제시하였다. 시민의 약 60% 정도가 카쉐어링 이용을 고려하고 있으며, 남자가 여자보다, 젊은 층이 장년층보다, 단독주택과 오피스텔이 아파트와 연립주택보다, 대중교통 이용이 불편한 시민이, 차량 미소유자가, 자동차를 일주일 1~3회 이용하는 통행자들의 카쉐어링 선호도가 높은 것으로 나타났다. 특히 주거 밀집지역과 대중교통 역 주변에서의 카쉐어링 잠재수요가 가장 높은 것으로 나타났다. 요금체계는 시간당 지불방식을 가장 선호하였으며, 시간당 7,967원의 지불용의가 있는 것으로 조사되었다. 통행목적에서는 업무 쇼핑 여가 레저 통행에서 카쉐어링 선호도가 택시 및 렌터카보다 높은 것으로 확인되었다. 본 연구결과는 카쉐어링 사업 시행의 정책방향 결정에 기여하며, 카쉐어링의 활성화에 도움이 될 것으로 기대된다.