• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.35 no.1
• /
• pp.13-21
• /
• 2023

As problems such as difficulties in securing stable energy resources and global warming due to the emission of greenhouse gases due to the use of fossil fuels have emerged, interest in the development of renewable energy is increasing. Since the tidal phenomenon has a regularity that occurs regularly with a certain period, it is possible to predict accurately in advance, which has a advantage in terms of energy recovery. Therefore, various methods have been devised to utilize the tide as an energy source. Tidal power using barrages is a representative method that is widely operated, but the promotion of tidal power generation projects is being delayed or stopped due to the decrease in the level of water in the tidal basin, changes in water quality and in the ecosystem. In this study, a field experiment was conducted to develop and verify the performance of a tidal power device applicable to sea areas where dykes are already installed. As a result of carrying out four cases of experiments using two water tanks, pipe lines, open channels, weirs, and water turbine and generator, the possibility of developing a power generation system capable of 10 kW output or more and 60% efficiency or more was confirmed. These research results can be used for small-scale tidal power by utilizing the existing dykes.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3D
• /
• pp.247-254
• /
• 2010

The positive effects of the air quality improvement policy have revealed sufficiently such as 3.3 trillion won of social benefits under the Environmental Zone in five years(K. Choi, 2009). In case of low-income freight truck owner, however, could be burdened with the requirement likes emission decreasing equipment. Eventually, restraint of running in the Environmental Zone would be affected their livelihood seriously. After estimating the scale of low-income freight truck owner for three alternatives with Road Freight Transport Center data, this study calculates decreased VKT to estimate the scale of monetary loss. In the result, decreased income amount of low-income freight truck owner under the restricted running estimated 6.1 trillion won during 5 years, quite exceeding 3.3 trillion won of the positive benefits as improving air quality, which means the necessity of immediate countermeasure. In other words, even though the governmental policy aimed benefits for the majority, the result implies that the total monetary losses of the minority could be exceed against the positives, therefore analysis should be considered carefully before the policy becomes effective.

• Information Systems Review
• /
• v.25 no.4
• /
• pp.183-204
• /
• 2023

Due to the COVID-19 pandemic, lots of occasions need to be held in online environment. This is the reason why "Metaverse" gets lots of attention in 2021. A number of companies made announcements on Metaverse, and this situation also boomed stock market. This paper investigates the relationship between Metaverse initiatives and business value of the firm (i.e., stock prices). We examine this relationship by using event study method with Lexis-Nexis News data from 2019 to 2021. The results indicate that Metaverse initiatives significantly impact positive influence on firm's value. In the technological perspective, technical factors affect more positive market returns, including Metaverse enablers (e.g., NFT, VR devices, digital twin) and common infrastructure (e.g., semiconductor, AI, cloud), and especially virtual environment was emphasized. Additionally, in the strategical perspective, radical innovation (e.g., pivoting, acquisition) impact more positive market return rather than incremental innovation (e.g., partnership, investment). Also, firms from non-service industries can achieve benefits from Metaverse initiatives rather than service industry in some degree.

• Korean Journal of Construction Engineering and Management
• /
• v.9 no.1
• /
• pp.55-65
• /
• 2008

It is increasingly recognized that the construction equipment play an important role as resources in construction process. The number of registered construction equipment in korea is over 320,000 according to the statistics. It is obvious that the machine-intensive construction method achieves productivity and quality improvement as well as safety. The main objective of this paper is to propose improvement plans for construction equipment management system in terms of scope, registration, inspection, rental business, operating licenses, and etc., which are the major issues described in the Construction Equipment Management Law. In order to satisfy the objective, this research conduct survey and interview with experts, and literature review on domestic and overseas related laws and regulations. The results of the research are about 20 issues for improvement plans for the better management system, so the further in-depth study on each issue will be recommended for the practical application to the law.

• Journal of Aerospace System Engineering
• /
• v.13 no.6
• /
• pp.60-69
• /
• 2019

Companies around the world are actively developing Personal Air Vehicle (PAV) to solve the serious social problem of traffic jams. Airworthiness certification for PAV is required, since it is a manned vehicle. As with aircraft, the critical threat to the safe operation of PAV is lightning strike with strong thermal load and magnetic fields. Lightning certification issue also remains important for PAV, since there are still insufficient development of PAV-related lightning certification technologies, guidelines, and requirements. In this study, the SAE Aerospace Recommended Practice (ARP), an international standard certification guideline recognized by the Federal Aviation Administration (FAA), was analyzed. In addition, the guideline of lightning certification was applied to a PAV. The impact of lightning on PAV was also analyzed through computational software. Finally, the basis for the establishment of the PAV lightning certification guidance was presented.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.6
• /
• pp.699-705
• /
• 2011

High-maneuver missile is a projectile which demands a strong momentum at short time. To produce a necessary thrust for the flight, the gas of high temperature and pressure is generated through explosive combustion of solid propellant, and a great thrust can be obtained by expanding this high temperature and pressure gas. Although the operating time of a rocket motor is less than a few seconds, a failure of part or ablation near the throat of nozzle may take place during the expansion of high temperature and pressure gas for great thrust. In other words, for the precise control of a missile an exact stress analysis considering both, the thermal stress caused by the heat transfer between combustion gas and wall, and the mechanical stress caused by the pressure change in the flow, should be considered first. In this connection, this study investigated the safety, as a point of view of stress and melting point of the material, of the pre-designed thrust generating structure which is subjected to high temperature and pressure as a function of motor operating time.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2010.04a
• /
• pp.143-144
• /
• 2010

Recently, IALA has introduced AIS AtoN and standardized Aids to Navigation communication system and the World-wide IALA-Net has announced plans to build the system. Systematic beacon network may offer opportunities to make infrastructure for information service and upgrade AtoN service performance. This paper proposes Aids to Navigation information service network for e-NAV. Network based on AIS is consist of AIS AtoN channels as Real, Synthetic or Virtual AIS AtoN. And inner network is consist of Wireless networks as AIS, WCDMA, WIFI, WlBRO, USN or VSAT. Introducing of various network systems can lead to combine and design among land, beacon and service network infrastructures.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.27 no.2
• /
• pp.1-12
• /
• 1990

Interactions between a propeller and vortex system contained in a ship stern flow is treated theoretically. A new formulation to determine the effective velocity distributions is developed, which may be immediately applicable to the design and analysis of compound propulsors under the influence of severe vortical cross-flows around ship stern. An axisymmetric shear flow is represented by a system of ring vortices and the axial variation of the stream lines due to the action of propeller is represented by a cubic function. The strengths of ring vortices, which are varying along the stream lines, are determined by the conservation of angular momentum. Two simplified effective velocity models are proposed to confirm the theory. Sample calculations using the simplified models are made to compare with the results by other investigators.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.26 no.2
• /
• pp.13-24
• /
• 1989

The geometrical characteristics of sculls which are in use for propulsion of Korean traditional row boats were briefly surveyed. A typical dimension of the scull was selected and prototype for test was prepared. Angular displacements and the force components at handle and pivoting point were measured when the scull was operated in moored condition by skilled fisherman. Time histories and trajectories of motion were analyzed with the force generated at the scull blade. It was found out that the thrust of the scull was generated mainly by reaction force. The direction of improvement for better rowing motion could be also suggested. Continued study on this topic in a self-propulsion condition will provide us another interesting informations and prepare a possibility of application in evaluating rowing motion of oar.

• KDI Journal of Economic Policy
• /
• v.17 no.1
• /
• pp.145-176
• /
• 1995

우리나라 생명보험산업(生命保險産業)은 과거 40여년간의 비약적인 외형성장(外形成長)에도 불구하고 내적(內的)으로는 인위적(人爲的)으로 조성되어 온 과점적(寡占的) 시장체제하(市場體制下)에서 여러가지 문제점이 노정되고 있어, 금융(金融)의 자율화(自律化) 개방화(開放化) 국제화(國際化) 시대(時代)를 맞이하여 대외경쟁력(對外競爭力) 강화(强化)와 내부효율성(內部效率性) 제고(提高)를 위한 본격적인 연구(硏究)가 시급히 이루어져야 할 시점에 섰다. 본(本) 연구(硏究)는 계량적(計量的)인 기법(技法)을 활용함으로써 우리나라 생명보험산업(生命保險産業)의 효율성(效率性)에 관한 실증분석(實證分析)을 시도하여, 내재(內在)하고 있는 문제점(問題點)을 파악하고 이에 대한 발전방안(發展方案)을 제시하고자 하는 데 목적(目的)을 두고 있다. 규모(規模)의 경제성(經濟性)(economies of scale) 분석결과 생명보험회사들이 영업인원(營業人員)에 대한 과다(過多)한 투자(投資)에 상응하는 규모확대(規模擴大)나 효과적인 경비절감(經費節減)을 이루지 못하여 내부적으로 과다인력(過多人力)의 사용으로 인한 경영(經營)의 비효율화(非效率化)가 초래되고 있으며, 대리점(代理店)을 통한 점포정책(店鋪政策)에서도 규모(規模)의 비경제성(非經濟性)이 존재하고 있음을 알 수 있다. 범위(範圍)의 경제성(經濟性)(economies of scope)과 관련해서는 주업무(主業務)인 보험영업업무(保險營業業務)와 부대업무(附帶業務)인 자산운용업무(資産運用業務)간에 비용보완성(費用補完性)(cost complementarity)이 존재하고 있는 것으로 나타나, 자산업무에 대한 적극적(積極的)인 투자(投資)와 효율적(效率的)인 관리(管理)로 업무다변화(業務多邊化)를 추진하여 범위의 경제성을 높이는 것이 바람직하다고 사료된다. 이 밖에 本(본) 논문(論文)의 분석(分析)을 통하여 도출된 우리나라 생명보험산업의 문제점으로 낮은 수익력(收益力), 저생산성(低生産性), 재무구조(財務構造)의 부건전성(不健全性), 비효율적(非效率的)인 자산운용(資産運用), 소비자보호장치(消費者保護裝置)의 미비(未備) 등을 들 수 있으며, 본 논문에서는 이에 대한 업무(業務) 및 제도개선(制度改善)의 구체적인 방향을 제시하고 있다.