• 한국해양공학회지
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• 제29권4호
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• pp.322-330
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• 2015

As a new technical approach, a hydraulic and magnetic clamp device was developed to realize a magnetic clamp crane system by simultaneously actuating eight individual hydraulic cylinders. In this approach, an Sr-type of ferritic permanent magnet (SrO· 6Fe₂O₃), rather than the previous electromagnet, was utilized for the purpose of lifting and transporting the large curved steel plates used for manufacturing ships. This study had the goal of developing and manufacturing a hydraulic, magnetic clamp prototype composed of three main parts, including the base frame, cylinder joint, and magnet joint, in order to safely transport curved steel plates. Furthermore, this research included a performance evaluation of the manufactured prototype and acquired the purposed quantity value in the performance test. The most significant item, the magnetic adhesive force (G), was evaluated in a performance test, which utilized a ferritic permanent magnet (Sr type) with 3700~4000 G of residual induction (Br) and 2640/2770 Oe of coercive force (Hc). In particular, relevant items such as the hoist tension (kN), transportation time (s), and applied load (Kgf) on the hydraulic cylinders were also evaluated in order to determine the optimum values.

• 한국해양공학회지
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• 제25권5호
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• pp.15-20
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• 2011

This study carried out a series of experiments involving impact tests (Drop Weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditiAn experimental study was carried out to study the solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. The lift forces acting on a fluidized particle play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport, the cleaning of particles from surfaces, etc. In this study a clear acrylic pipe was used to observe the movement of solid particles. Annular velocities varied from 0.4 to 1.2 m/s. The effect of the annulus inclination and drill pipe rotation on the carrying capacity of a drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully-developed flows of water and aqueous solutions of CMC (sodium carboxymethyl cellulose) and bentonite. The rotation of the inner cylinder was efficient at carrying particles to some degree. For a higher particle volume concentration, the hydraulic pressure loss of the mixture flow increased because of the friction between the wall and solids or between solids.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2006년도 총회 및 춘계학술발표회
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• pp.216-219
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• 2006

Water retention curve (WRC), one of soil hydraulic properties, is often approximated by property-transfer models (PTMs). Using the PTMs, we can estimate the WRCs from other physical properties such as particle-size distribution (PSD). The objective of this work was to investigate the performance of two PTMs with different origins for numerical simulations on transport of Benzo[a]pyrene in a soil. To do this, we chose both PTMs with different origins, i.e., (1) the lognormal distribution model (L anti NL models), and (2) the modified $Kov\'{a}cs$ model (MK model). The MK model showed tile worse performance in estimation of the WRCs. When transport of B[a]P was simulated, the MK model predicted to move farther than the L and NL models did, indicating that transport of B[a]P in a soil can be greatly influenced by the choice of PTMs.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권5호
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• pp.31-39
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• 2012

Chemical and isotopic variations of snowmelt provide important clues for understanding snowmelt processes and the timing and contribution of snowmelt to catchment or watershed in spring. The newly developed model includes a hydraulic exchange between mobile and immobile water (${\omega}$), and isotopic exchanges between both mobile water and ice ($f_1$) and immobile water and ice ($f_2$). Since the new model is based on the mobile-immobile water conceptualization, which is widely used for describing chemical tracer transport in snow, it allows simultaneous calculations of chemical as well as isotopic variations in snowpack discharge. We compare the model results with a study of solute transport and isotopic evolution of snowmelt in snow, using artificial rain-on-snow experiments with conservative anion ($Br^-$). These observations are used to test the newly developed model and to better understand physical processes in a seasonal snowpack where our model simulates the chemical and isotopic variations.

• 대한지하수환경학회지
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• 제2권1호
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• pp.30-37
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• 1995

조석의 영향을 받는 감조구역의 대수층은 감조 하천의 수위에 따라 지하수 수두의 변화가 예상된다. 지하수 수두가 주기적으로 변화하는 대수층에서 지하수를 이용하거나 구조물을 시공하기 위해서는 지하수 수두의 거동을 고려해야 한다. 감조구역에서 지하수 수두에 영향을 미치는 조석의 진폭과 투수계수 등의 변수에 대해서 수치실험을 수행하였다. 수치실험을 위해 1차원 유한차분 모형을 이용하였다. 우선 수치모형의 안정성을 검토하기 위해 해석해와 비교하였다. 그리고 조석의 진폭과 투수계수가 지하수 수두에 미치는 영향에 대해 고찰하고 이 때 지하수의 수리경사가 존재하는 경우와 없는 경우에 대해 수치실험하였다. 또한 감조구역 내에서 양수를 하는 경우에 지하수 수두의 변화 양상을 고찰하기 위해 수치실험을 수행하였다. 본 논문에서 사용된 변수값을 이용하면 영향권은 약 60 m정도인데 이는 한 파장(equation omitted) 내에서 영향권이 설정된다. 조석의 영향을 받는 대수층과 영향을 받지 앎은 대수층에서 일정한 율로 양수하였다. 영향권 내에서 조석의 영향을 받는 대수층의 수두가 크기 때문에 상대적으로 양정고는 작아져 동력비의 절감을 가져올 수 있음을 알았다 그리고 이들의 결과를 이용하면 감조구역에서 오염원의 추적, 지하수의 효율적인 이용, 구조물을 시공할 때 구조물의 안정성과 안전성을 검토하는데 도움이 될 것이다.

• 한국수소및신에너지학회논문집
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• 제31권4호
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• pp.387-394
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• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.

• 한국습지학회지
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• 제19권2호
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• pp.181-192
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• 2017

침식 및 퇴적과 관련된 수치모형을 이용한 분석은 하천에 존재하는 보와 같은 수리구조물들의 유사이송을 연구하는데 중요한 요소이다. 본 연구에서는 다기능보들의 효과적인 운영을 위하여 낙동강수계에 위치해 있는 강정고령보를 대상으로 하상변동을 예측하였다. 2차원 모형은 CCHE2D를 이용하여 유사이송이 지배적으로 발생하는 다기능보 상 하류 구간 25km를 대상으로 침식과 퇴적에 대한 모의를 수행하였다. 2006년 태풍 "에위니아"사상을 대상으로 모형을 검 보정 하였으며, 모의결과와 관측값의 비교를 통하여 전체 모의구간에서 신뢰성 있는 결과가 도출되었다. 강정고령보가 건설된 이후 태풍사상에 의한 하상변동은 가동보 구간에서 상당히 증가하는 것으로 나타났고 하상변동은 유사의 재분배를 야기하였다.

• 한국수자원학회논문집
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• 제46권7호
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• pp.707-717
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• 2013

충적하천에서 발생하는 하천의 침식과 퇴적은 흐름을 통해 발생하는 자연적인 현상이다. 침식 및 퇴적과 관련된 수치모형을 이용한 분석은 하천에 존재하는 보와 같은 수리구조물들의 유사이송을 연구하는데 중요한 요소이다. 본 연구에서는 다기능보들의 효과적인 운영을 위하여 낙동강수계에 위치해 있는 창녕함안보를 대상으로 하상변동을 예측하였다. 2차원 모형은 CCHE2D를 이용하여 유사이송이 지배적으로 발생하는 다기능보 상 하류 구간 12 km를 대상으로 침식과 퇴적에 대한 모의를 수행하였다. 2003년 태풍 "매미"사상을 대상으로 모형을 검 보정 하였으며, 모의결과와 관측값의 비교를 통하여 전체 모의구간에서 신뢰성 있는 결과가 도출되었다. 함안창녕보가 건설된 이후 태풍사상에 의한 하상변동은 상당히 증가하는 것으로 나타났고 하상변동은 유사의 재분배를 야기하였다. 보와 같은 수리구조물들은 하도내 흐름과 유속을 변화시키기 때문에 세굴과 퇴적 문제를 심화시켰다.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.581-588
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• 2013

This paper deals with the Safety Analysis for $CANDU^{(R)}$ 6 nuclear reactors as affected by main Heat Transport System (HTS) aging. Operational and aging related changes of the HTS throughout its lifetime may lead to restrictions in certain safety system settings and hence some restriction in performance under certain conditions. A step in confirming safe reactor operation is the tracking of relevant data and their corresponding interpretation by the use of appropriate thermal-hydraulic analytic models. Safety analyses ranging from the assessment of safety limits associated with the prevention of intermittent fuel sheath dryout for a slow Loss of Regulation (LOR) analysis and fission gas release after a fuel failure are summarized. Specifically for fission gas release, the thermal-hydraulic analysis for a fresh core and an 11 Effective Full Power Years (EFPY) aged core was summarized, leading to the most severe stagnation break sizes for the inlet feeder break and the channel failure time. Associated coolant conditions provide the input data for fuel analyses. Based on the thermal-hydraulic data, the fission product inventory under normal operating conditions may be calculated for both fresh and aged cores, and the fission gas release may be evaluated during the transient. This analysis plays a major role in determining possible radiation doses to the public after postulated accidents have occurred.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.223-226
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• 2009

This paper presents three-dimensional flow analysis for a mixed-flow pump which consists of a rotor and a stator. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved by the commercial CFD code CFX 11.0. Structured grid system is constructed in the computational domain, which has O-type grids near the blade surfaces and H-type grids in other regions. Validation of the numerical results was performed with experimental data for head coefficients and hydraulic efficiencies at different flow coefficients. This paper shows that the pump characteristics can be predicted effectively by numerical analysis.