• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.85-89
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• 2002

This paper used the Laser Speckle Interferometry to present the strain analysis of Nd:YAG Laser welding zone. Previous TIG welding to sheet plate, which welds only high-skilled engineer, produces residual stress nearby welding zone due to thermal effect. However, Laser welding makes sheet pate welding easy and thermal effect minimum. Thermal effect zone is measured by strain analysis of the laser-welding zone by ESPI under tensile testing of sheet plate welded by Nd:YAG laser. The ESPI results, which compared with strain gage method, are agreed within error 3 %.

• 설비공학논문집
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• 제27권11호
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• pp.574-580
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• 2015

Climatic zone in building code is an administrative district classification reflecting regional climatic characteristics. Use of Degree-Days is a fundamental method that can be used in various building design codes, analysis of building energy performance, and establishment of minimum thermal transmittance of building envelopes. Many foreign countries, such as the USA, the EU, Australia, Italy, India, China, etc., have already adapted climatic zone classification with degree-days, precipitation or amount of water vapor based on the characteristics of their own country's climate. In Korea, however, the minimum requirements for regional thermal transmittance are classified separately for the Jungbu area, Nambu area and Jeju Island with no definite criterion. In this study, degree-days of 255 Korean cities were used for climatic zone classification. Outdoor dry-bulb temperature data from the Korea Meteorological Administration for 1981~2010 was used to calculate degree-days. ArcGIS and the calculated degree-days were utilized to analyze and visualize climatic zone classification. As a result, depending on the distribution and distinctive differences in degree-days, four climatic zones were derived : 1) Central area, 2) Mountain area of Gyeonggi and Gangwon provinces, 3) Southern area, and 4) Jeju Island. The climatic zones were suggested per administrative district for easy public understanding and utilization.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.565-573
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• 2004

This study is to present explicit analytical expressions for calculating bearing capacity factor $N_{\gamma}$, to provide results of the numerical computation instead of the graphical method. In this study, $N_{\gamma}$ is proposed in the critical failure surface on assumption that the center of log spiral in the radial shear zone can be located at the any points of around footing. The critical failure surface is one which yields minimum passive pressure $P_{\gamma}$ on the radial shear zone from the family of log spirals accoding to change of the center of log spiral. This study adoptes Terzaghi's bearing capacity principle(e.g., Prandtl's mechanism, limit equilibrium equation, superposition principle) but the soil wedge in an elastic zone makes angle $45^{\circ}+{\phi}/2$ with the horizontal and the location of the log spiral's center.

• 한국해안해양공학회지
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• 제13권3호
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• pp.245-253
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• 2001

속초 하수종말처리장에서의 하·폐수 해양방류에 따른 혼합구역 특성을 파악하기 위해 Huang et al.(1996)의 분석방법을 활용하여 혼합구역 모형을 수립하였다. 겨울철인 11월 하순부터 1월까지 약 2개월 동안 속초 해양방류수역에서 매시간 연속 관측된 해류, 해수 밀도의 성층자료, 그리고 하수 방류량자료를 입력한 모형모의를 통해 속초 해양방류수역에서 하수농도의 분포변화를 계산하였으며, 동일 기간에 관측된 조석자료를 토대로 약 15일 간격으로 구분한 기간 동안에 대해 평균한 농도분포를 제시하였다. 이 결과에 의하면 겨울철동안 평균된 최소희석률은 130으로 방류 하수의 혼합·의석이 대체로 양호했다. 그러나 해안에 평행한 연안류와 조류의 주 방향에 따라 방류하수의 혼합구역이 외해보다는 해변 쪽으로 확장되고 있어 인근 해수욕장의 수질악화에 큰 영향을 미칠 것으로 판단된다.

• 터널과지하공간
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• 제7권2호
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• pp.136-142
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• 1997

The behaviour of ground movement during the construction of two parallel tunnels in weathered zone and soft rock has been investigated. All the influencing factors for the behaviour of twin tunnel such as tunnel size, ground conditions, tunnel depth, pillar width and initial state of ground stresses were examined The results of FEM nonlinear analysis were compared with some of model test results in weathered zone to verify the numerical method. It was found that minimum interference was obtained in the parallel construction case when the twin tunnel distance (pillar width) is just over the twice of tunnel diameter. Guide line for the interference of twin tunnelling has been introduced for the ground of weathered zone and soft rock.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.411-414
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• 2005

In this study, 8 Landsat(TM/ETM+) satellite images acquired from 1984 to 2002 were used to investigate the growth of Chuncheon city, Kangwon-do, Korea. The images were geocoded and classified using training set collected from field survey. Four land-use types were classified such as urban area, green zone, agricultural land and water body. It also showed rapid increase of urban area in the past two decades from 1166ha in 1984 to 3358ha in 2002. About 2182ha of agricultural land and green zone have been changed to urban area. Agricultural land was newly formed from the green zone.

• 설비공학논문집
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• 제11권1호
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• pp.117-124
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• 1999

In this study, three different supply diffuser types(desktop, floor and ceiling) are compared in view of their ability to distribute supply air to the workstation breathing zone. The measurements on the age of air and the air change effectiveness using the tracer gas method are carried out to analyze the ventilation performance for provision of fresh air between the diffusers. The desktop diffuser type could deliver air directly to the occupants breathing zone with a high degree of effectiveness. The measured local air change effectiveness of the desktop diffuser in the breathing zone was usually 1.13 to 1.23 times greater than that of ceiling and floor diffusers. When the minimum outside air change rate as specified using ASHRAE Standard 62R is supplied with a desktop diffuser type, the volume of outside air can be reduced 13 to 23%, resulting in a commensurate in ventilation energy use.

• 한국환경복원기술학회지
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• 제22권6호
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• pp.115-124
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• 2019

In a climate change environment where heat damage and drought occur during a rainy season such as in 2018, a vegetation-based LID system that enables disaster prevention as well as environment improvement is suggested in lieu of an installation-type LID system that is limited to the prevention of floods. However, the quantification of its performance as against construction cost is limited. This study aims to present an experiment environment and evaluation method on quantitative performance, which is required in order to disseminate the vegetation-based LID system. To this end, a 3^rd quartile huff time distribution mass curve was generated for 20-year frequency, 60-minute probable rainfall of 68mm/hr in Cheonan, and effluent was analyzed by recreating artificial rainfall. In order to assess the reliability of the rainfall event simulator, 10 repeat tests were conducted at one-minute intervals for 20 minutes with minimum rainfall intensity of 22.29mm/hr and the maximum rainfall intensity of 140.69mm/hr from the calculated probable rainfall. Effective rainfall as against influent flow was 21.83mm/hr (sd=0.17~1.36, n=20) on average at the minimum rainfall intensity and 142.27mm/hr (sd=1.02~3.25, n=20) on average at the maximum rainfall intensity. In artificial rainfall recreation experiments repeated for three times, the most frequent quartile was found to be the third quartile, which is around 40 minutes after beginning the experiment. The peak flow was observed 70 minutes after beginning the experiment in the experiment zone and after 50 minutes in the control zone. While the control zone recorded the maximum runoff intensity of 2.26mm/min(sd=0.25) 50 minutes after beginning the experiment, the experiment zone recorded the maximum runoff intensity of 0.77mm/min (sd=0.15) 70 minutes after beginning the experiment, which is 20 minutes later than the control zone. Also, the maximum runoff intensity of the experiment zone was 79.6% lower than that of the control zone, which confirmed that vegetation unit-type LID system had rainfall runoff reduction and delay effects. Based on the above findings, the reliability of a lab-level rainfall simulator for monitoring the vegetation-based LID system was reviewed, and maximum runoff intensity reduction and runoff time delay were confirmed. As a result, the study presented a performance evaluation method that can be applied to the pre-design of the vegetation-based LID system for rainfall events on a location before construction.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1061-1066
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• 2002

This study proposes an analytic method that determines an optimal arrangement of absorptive materials on an enclosure surface. Under the optimal arrangement, a quiet zone in the enclosure has the minimum $\varepsilon$$\sub$p/ (acoustic potential energy density). The proposed method has been implemented by using a BEM simulation and a genetic algorithm. The BEM simulation evaluates the $\varepsilon$$\sub$p/ under the prescribed arrangement of the absorptive materials. The genetic algorithm searches the optimal arrangement by referring the ep evaluated from the BEM simulation. In the BEM simulation, the absorptive material arrangement is expressed as a vector, which is denoted as in absorptive material arrangement (AMA) vector. Besides, an admittance vector of which elements are admittances of available absorptive materials and an AMA matrix that transforms the admittance vector into the AMA vector are defined. The AMA matrix is also used as a chromosome in the genetic algorithm so that it functions to relate the BEM simulation to the genetic algorithm. As a verification example, the proposed method is applied to make the quiet zone in a parallelepiped enclosure.

• Journal of Power Electronics
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• 제19권5호
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• pp.1315-1325
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• 2019

Aiming at the negative sequence and harmonic problems in the operation of railway static power conditioners, an optimization compensation strategy for negative sequence and harmonics is studied in this paper. First, the hybrid RPC topology and compensation principle are analyzed to obtain different compensation zone states and current capacities. Second, in order to optimize the RPC capacity configuration, the minimum RPC compensation capacity is calculated according to constraint conditions, and the optimal compensation coefficient and compensation angle are obtained. In addition, the voltage unbalance ${\varepsilon}_U$ and power factor requirements are satisfied. A PSO (Particle Swarm Optimization) algorithm is used to calculate the three indexes for minimum compensating energy. The proposed method can precisely calculate the optimal compensation capacity in real time. Finally, MATLAB simulations and an experimental platform verify the effectiveness and economics of the proposed algorithm.