• Advances in aircraft and spacecraft science
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• 제9권4호
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• pp.319-333
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• 2022

This work presents a numerical investigation of the aerodynamics and aero acoustics of the HVAB rotor in hover conditions. Two fully turbulent models are employed, the one-equation Spalart-Allmaras model and the two-equation k-ω SST model. Transition effects are investigated as well using the Langtry-Menter γ-Re θt transition transport model. The noise generation and propagation are being investigated using the Ffows-Williams Hawking model for far-field noise and the broadband model for near-field noise. Comparisons with other numerical solvers and with the PSP rotor test data are presented. The results are presented in terms of thrust and power coefficients, the figure of merit, surface pressure distribution, and Sound pressure level. Velocity, pressure, and vortex structures generated by the rotor are also shown in this work. In addition, this work investigates the contribution of different blade regions to the overall noise levels and emphasizes the importance of considering specific areas for future improvements.

• 대한지하수환경학회지
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• 제2권1호
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• pp.14-21
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• 1995

지하수에 콜로이드가 있을 경우 지체계수 감소로인한 오염물의 가속이송이 일어난다. 세균은 콜로이드 크기이며, 비중이 물과 비슷하고. 또 특유의 표면조건으로 인하여 오염물을 가속이송시킬 수 있다. 유동 세균이 지하수에 있으면 그 system 은 액상, 고상, 그리고 입상의 3 상 (phase) 으로 해석되어야 한다. 본 연구에서는 물질수지에 기초한 수학적 모델을 개발하여 다공매질에서의 오염물의 이동을 예측했다. 세균과 오염물의 각 상사이의 분배는 평형분배 모델을 이용했다. 모델결과를 일반화하기 위하여 무차원화 기법이 사용되었다. 모델의 해는 수치해법이 사용되었고, 문헌상의 실험결과와 비교되었다. 유동 세균이 존재하므로써 오염물이 가속이송되었고, 오염물을 섭취하므로써 그 농도를 낮출 수 있었다.

• Korean Chemical Engineering Research
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• 제58권2호
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• pp.319-324
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• 2020

전기와류 불안정성은 전기투석 장치, 갈바니 전지, 전해 전지 등의 이온-선택성 이동 현상계에서 발견되는 비선형 이동 현상이다. 이 불안정성은 이온-선택성 표면 근처 공간 전하층의 요동에 의해 발생하며, 불안정성의 발현은 물질 전달 속도를 증가시켜 준다. 따라서 전기와류 불안정성은 물질 전달 측면에서 중요한 의미를 가진다. 최근의 실험적 기법들이 불안정성의 직접적 가시화를 가능하게 해주었으나, 실험적 한계점에 의해 불안정성의 원론적 연구는 제한된 영역에서만 이루어지고 있다. 본 연구에서는 일정 전위 모드에서의 전기와류 불안정성에 대한 수치 해석을 진행하여 전류-시간 곡선과 불안정성의 거동 간의 상관관계를 밝히고자 하였다. 시간-분해 해석을 통하여, 불안정성의 발달 거동을 SCL 형성 - 전기와류 불안정성의 성장 - 정상 상태 도달로 구분 지었다. 더불어, 인가 전위에 따른 전이 시간들의 크기 법칙 또한 수치적으로 유도하였다.

• 항공우주정책ㆍ법학회지
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• 제23권1호
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• pp.3-32
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• 2008

In proportion to recent developments in aviation technology and growth of the air transport market, the risk of damages to third parties caused by aircrafts and the likelihood of unlawful interference on an aircraft in flight has grown larger. The war risk insurance market was paralyzed by the 9/11 terror event. And if another event on the scale of 9/11 occurs, compensations for third party damages will be impossible. Recognizing the need to modernize the existing legal framework and the absence of a globally accepted authority that deals with third party liability and compensation for catastrophic damage caused by acts of unlawful interference, the ICAO and various countries have discussed a liability and compensation system that can protect both third party victims and the aviation industry for the 7 years. In conclusion, in order to provide adequate protection for victims and the appropriate protection for air transport systems including air carriers, work on modernizing the Rome Convention should be continued and the new Convention should be finalized in the near future. Korea has not ratified the relevant international treaties, i.e. Rome Convention 1933, 1952 and 1978, and has no local laws which regulate the damage caused by aircraft to third parties on land. Consequently, it has to depend on the domestic civil tort laws. Most of the advanced countries in aviation such as the United States, England, Germany, France and even China, have incorporated the International Conventions to their national air law and governed carriers third party liability within their jurisdiction. The Ministry of Justice organized the Special Enactment Committee for Air Transport chapter under Commercial Law. The Air Transport chapter, which currently includes third party liability, is in the process of instituting new legislation. In conclusion, to settle such problems through local law, it is necessary to enact as soon as possible domestic legislation on the civil liability of the air carrier which has been connected with third party liability and aviation insurance.

• 한국컴퓨터정보학회논문지
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• 제27권1호
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• pp.157-166
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• 2022

본 연구는 철로 복합화물 운송 시 환적 작업으로 인해 발생하는 소요 시간과 비용을 줄이고 운송속도 향상이 가능한 피기백시스템의 도입 타당성을 분석하는 것을 목표로 한다. 이를 위해 국내외 문헌검토를 통해 타당성 분석방법론을 검토한다. 타당성 분석 값을 정량적으로 도출하기 위해 교통 데이터베이스를 적용하여 운송거리가 200KM이상인 주요 화물 운송 O-D 노선에 화물 운송 시뮬레이션 모델과 운송 수단별 화물 수요 예측 모델을 개발하였다. 2025년 주요 화물 운송 O-D 노선에 피기백시스템이 도입된다는 전제로 분석기간을 15년으로 설정하여 경제적 타당성을 분석한 결과 NPV 값이 양수이고 B/C값이 1.18로 도출되어 피기백시스템이 경제성이 있는 것으로 나타났다. 제안된 연구 방법은 철도운송의 경쟁력을 향상할 수 있는 교통 정책 수립에 유의미한 자료가 될 수 있다.

• Safety and Health at Work
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• 제13권1호
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• pp.117-125
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• 2022

Background: External-cause mortality is an important public health issue worldwide. Considering its significance to workers' health and inequalities across industries, we aimed to describe the state of external-cause mortality and investigate its difference by industry in Republic of Korea based on data for 2018. Methods: Data obtained from the Statistics Korea and Korean Employment Information System were used. External causes of death were divided into three categories (suicide, transport accident, and others), and death occurred during employment period or within 90 days after unemployment was regarded as workers' death. We calculated age- and sex-standardized mortalities per 100,000, standardized mortality ratios (SMRs) compared to the general population and total workers, and mortality rate ratios (RRs) across industries using information and communication as a reference. Correlation analyses between income, education, and mortality were conducted. Results: Age- and sex-standardized external-cause mortality per 100,000 in all workers was 29.4 (suicide: 16.2, transport accident: 6.6, others: 6.6). Compared to the general population, all external-cause and suicide SMRs were significantly lower; however, there was no significant difference in transport accidents. When compared to total workers, wholesale, transportation, and business facilities management showed higher SMR for suicide, and agriculture, forestry, and fishing, mining and quarrying, construction, transportation and storage, and public administration and defense showed higher SMR for transport accidents. A moderate to strong negative correlation was observed between education level and mortality (both age- and sex-standardized mortality rates and SMR compared to the general population). Conclusion: Inequalities in external-cause mortalities from suicide, transport accidents, and other causes were found. For reducing the differences, improved policies are needed for industries with higher mortalities.

• 한국ITS학회 논문지
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• 제19권2호
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• pp.48-61
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• 2020

본 연구는 2개 차로 중 1개 차로를 차단하고 공사를 시행하는 고속도로 공사구간의 중차량비에 따른 도로 용량을 추정하는 것을 목적으로 한다. 이를 위해 영동고속도로와 중부내륙고속도로 공사구간의 CCTV 영상자료를 수집하고, 고속도로 상류부 지점의 정체를 관찰하였다. 상류부 정체 이후 차로차단으로 인해 생성되는 병목구간의 통과 교통량을 측정하는 방법을 활용하여 고속도로 하류부 지점의 통과 교통량을 분석하였다. 공사구간의 도로 용량 추정을 위해 관찰된 차두간격을 활용하여 이론적인 차종별 차두간격의 확률분포를 추정하고 적합성 검정을 통해 도로 용량을 산정하였다. 이를 통해 공사구간을 통과하는 중차량 비에 따라 적합한 용량 값과 추정식을 제시하였다. 추정된 도로 용량은 영동고속도로의 경우 중차량의 비에 따라 1,181~1,422pcphpl, 중부내륙고속도로의 경우 1,475~1,589pcphpl로 산정되었으며 중차량의 비가 증가할수록 도로 용량이 점차 감소하는 것을 확인하였다. 이러한 연구 결과는 편도 2차로 차단 공사를 수행하는 공사구간에 대한 적합한 도로 용량 추정과 효율적인 교통운영 및 관리에 기여할 수 있다.

• 한국항만학회지
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• 제7권1호
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• pp.43-58
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• 1993

There has been fast progress in economy in Korea derived by a consecutive five-year plan program for economic development started in the early 1960's. In the field of transportation, rapid changes in the technological environment of transportation and communication have brought a revolution of the transport system, of which inter-modal transportation through containerisation is typical. Because of the rapidly growing traffic volumes of cargo, especially container traffic, and lack of investment into transport infrastructure in the past, both road and railway are beyond their capacity. As a result, the public-road network has suffered a serious congestion problem. For instance, in relation to the corridor between Seoul and Pusan, today, it takes about 14 hours for the journey of container trailer through Kyongbu Expressway, for which it used to take only 7 hours in 1986. For the railway, though the congestion problem is not very serious compared with the road sector, a shortage of capacity on certain main lines has emerged as a problem as railway traffic has increased. Furthermore, the further expansion of the system in near future is difficult due to burden of higher construction the cost. Unlike these two modes, coastal shipping, which has been paid relatively less attention for commodity transport in Korea, shows no constraint in this respect. In addition, it is the most cost efficient mode of transport. This work therefore aims to make a proposal for the alternative inland transportation mode, which is to promote the coastal transport of container. Three obstructing factors for the promotion of the coastal transport are investigated and some solutions for those are suggested as follows : First, it appears to be essential to provide exclusive ports for the coastal shipping, that comply with simplification, specialization and rationalization. The optimum size of berths on the exclusive ports in Pusan port is estimated as 16-20. We found that it needs periodical study and publicity on the advantages from the adoption of the coastal mode. Inducing competition in the coastal shipping market is also necessary. For the supply of the fleet in the coastal shipping, chartering of the surplus ships in the oversea shipping is found to be more desirable than new shipbuilding. Second, to solve the fragmentation of the companies which wish to participate in the coastal transport, government has to implement the subsidy policy. The encouragement of participation of the shipping lines engaging in Korea-Japan run and Korea-East South Asia run, into coastal shipping also needs to be considered cautiously. Third, simplification of the document for entry in ports is needed for rational coastal shipping management. We can use B/L (Bill of Lading) for coastal shipping as a prerequisite to get the indemnity by P & I Club. The reduction of the government controls on entering and leaving the ports also needs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.351.2-351.2
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• 2014

Indium tin oxide (ITO) has a lot of variations of its properties because it is basically in an amorphous state. Therefore, the differences in composition ratio of ITO can result in alteration of electrical properties. Normally, ITO is considered as transparent conductive oxide (TCO), possessing excellent properties for the optical and electrical devices. Quantitatively, TCO has transparency over 80 percent within the range of 380nm to 780nm, which is visible light although its specific resistance is less than $10-3{\Omega}/cm$. Thus, the solar cell is the best example for which ITO has perfectly matching profile. In addition, when ITO is used as transparent conductive electrode, this material essentially has to have a proper work function with contact materials. For instance, heterojunction with intrinsic thin layer (HIT) solar cell could have both front ITO and backside ITO. Because each side of ITO films has different type of contact materials, p-type amorphous silicon and n-type amorphous silicon, work function of ITO has to be modified to transport carrier with low built-in potential and Schottky barrier, and approximately requires variation from 3 eV to 5 eV. In this study, we examine the change of work function for different sputtering conditions using ultraviolet photoelectron spectroscopy (UPS). Structure of ITO films was investigated by spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM). Optical transmittance of the films was evaluated by using an ultraviolet-visible (UV-Vis) spectrophotometer

• Safety and Health at Work
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• 제5권3호
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• pp.140-146
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• 2014

Background: Young male and female workers are over-represented in statistics concerning negative outcomes of poor work environment and risky work. Young workers often have low awareness of risk, a lack of safety training, and inadequate introduction to the work. The aim of this study was to identify the knowledge and experiences of pupils of vocational schools concerning potential work environment risks in their future work. Methods: The study design was a dual one, and included a questionnaire and focus group interviews. The study group consisted of 239 pupils from 10 upper secondary schools, who were graduating pupils in four vocational programs: the Industrial Technology Programme, the Restaurant Management and Food Programme, the Transport Programme, and the Handicraft Programme (in which students specialize in wood products). The upper secondary schools were located in the central region of Sweden. Results: The pupils had limited knowledge that employers must, by law, conduct risk analyses and prevent risks. Many felt that they themselves are mainly responsible for performing their tasks safely. Pupils in all programs mentioned acute risk as the greatest risk at work. The theoretical education about safety at work was provided in the $1^{st}$ year of the 3-year vocational programs. Conclusion: A systematic approach to pupils' training in work environment, which is a basis for a safe and healthy workplace, is lacking. The study findings indicate that pupils are offered knowledge far from that intended by laws and by state-of-the-art occupational health risk research.