• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.35-35
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• 2023

The main reason for its instability is sediment scouring downstream of hydraulic structures. Both physical and numerical models have been used to investigate the influence of soil properties on scour hole geometry. Nevertheless, no research has been conducted on resistance parameters that affect sedimentation and erosion. In addition, auxiliary structures like wing walls, which are prevalent in many real-world applications, have rarely been studied for their impact on morphology. The hydraulic characteristics of steady flow through a boxed culvert are calibrated using a 3D Computational Fluid Dynamics model compared with experimental data in this study, which shows a good agreement between water depth, velocity, and pressure profiles. Test cases showed that 0.015 m grid cells had the lowest NRMSE and MAE values. It is also possible to quantify sediment scour numerically by testing roughness/d₅₀ ratios (c_s) and diversion walls at a meander flume outlet. According to the findings, c_s = 2.5 indicates a close agreement between numerical and analytical results of maximum scour depth after the culvert; four types of wing walls influence geometrical deformation of the meander flume outlet, resulting in erosion at the concave bank and deposition at the convex bank; two short headwalls are the most appropriate solution for accounting for small changes in morphology. A numerical model can be used to estimate sediment scour at the meander exit channel of hydraulic structures based on the roughness parameter of soil material and headwall type.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2002.05a
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• pp.125-130
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• 2002

우리의 언어생활을 비추어 볼 때 한자어 정보처리는 많은 연구가 이루어야 함에도 불구하고 고유어 언구에 비해 소흘해 다루어져 왔다. 본 연구는 단일 한자어를 구성하는 각 음절이 단어의 재인에 어떤 영향을 미치는지 점화과제를 통하여 알아보았다. 본 실험은 기존의 한자어 연구에 빈도특성과 고유어와 외래어의 글자특성까지 고려하여 종합적으로 살펴보았다. 먼저 실험1의 어휘판단관제에서는 고유어와 한자어의 양상이 비슷하며 외래어는 다른 처리를 하는 것으로 드러났다. 고유어와 한자어는 빈도에 따라 영향을 받지만 외래어는 빈도의 영향에 변함없이 일정하게 나타났다. 이런 결과는 한국인은 고유어와 한자어를 동일한 양상으로 처리하며 이런 이유는 외래어의 한국어와는 다른 음운규칙이나 음절규칙의 영향으로 해석할 수 있겠다. 실험 2에서는 한자어 형태소와 의미적으로 유사한 조건(강도-강력)과 철자적 유사 조건(강도-강변), 고유어 유사 조건(강도-강정)조건을 점화과제를 이용하여 어휘판단을 하게 하였다. 실험 결과 모든 조건이 통제조건에 비하여 빠르게 나왔다. 그리고 의미적 유사 조건이 촉진적 점화효과를 일으키고, 철자적 유사조건은 억제 효과를 일으켰으며 고유어는 특이하게도 판단시간이 빠르게 나와 한자어와는 다른 처리과정이 있음을 보여주고 있다. 이런 결과는 지연조건에서도 동일하게 일어나고 있다. 이런 결과는 한자어는 어휘접근 이후에도 실험의 과제 특성상 한자어 형태소는 단어 수준 아래 위치하기는 힘든 반면, 고유어는 단어 수준 아래에 존재한다고 할 수 있다. 결국 한자어와 고유어는 기본적으로 외래어와 다른 처리를 보이면 한자어와 고유어 내에서도 한자어는 단어접근 전에 의미접근의 단계를 거쳐야 하지만 고유어는 각 음절이 형태소가 아니기 때문에 바로 어휘에 접근하는 것이라고 할 수 있겠다.ulic geometry and sediment transport has been applied to: (1) gravel-bed transport measurements in a cobble-bed stream at Little Granite Creek, Wyoming; (2) sand and gravel transport by size fraction in the sharp meander bends of Fall River, Colorado; (3) changes in sand dune geometry and resistance to flow during major floods of the Rhine River in the Netherlands; (4) changes in hydraulic geometry of the Rio Grande downstream of Cochiti Dam, New Mexico; and (5) analysis of the influence of water temperature and the Coriolis force on flow velocity and sediment transport of the Lower Mississippi River in Louisiana. Recent developments also include two textbooks on "Erosion and Sedimentation" and "River Mechanics" by the author and state-of-the-art papers in the ASCE Journal of Hydraulic Engineering.rk on is diversified, the importance of skills are diversified in each field of jobs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.231-237
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• 2007

The torque ripple of the hydraulic pumps for the Electro-hydrostatic Actuators can disturb the cylinder position control under slewing speed operation condition. In principle, the periodic change of the reaction torque generated by a piston type pump is highly dependent on the waveform of its cylinder chamber pressure. In case of uni-directional pumps operating at constant speed, the transient overshoot and rising slope of the cylinder pressure can be adjusted by the precompression angle and notch shape of their valve plates. Therefore, the influence of the valve plate geometry on the torque ripple magnitude of a bent-axis type piston pump for EHA application was investigated in this study. The results showed that any improvement of the torque ripple of such a bi-directional pump can not be achieved by modifying the valve plate geometry, regardless of its operation speed.

• Tunnel and Underground Space
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• v.27 no.2
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• pp.100-108
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• 2017

As a measure of the combined effect of fracture geometry, the fabric tensor parameters could quantify the status of the connected fluid flow paths in discrete fracture network (DFN). The correlation analysis between fabric tensor parameters and hydraulic properties of the 2-D DFN was performed in this study. It is found that there exists a strong nonlinear relationship between the directional conductivity and the fabric tensor component estimated in the direction normal to the direction of hydraulic conductivity. The circular radial plots without significant variation of the first invariant ($F_0$) of fabric tensor for different sized 2-D DFN block are a necessary condition for treating representative element volume (REV) of a fractured rock mass. The relative error (ER) between the numerically calculated directional hydraulic conductivity and the theoretical directional hydraulic conductivity decreases with the increase in $F_0$. A strong functional relation seems to exist between the $F_0$ and the average block hydraulic conductivity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.237-240
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• 1997

The casing oscillator is a construction equipment to clamp, oscillate and push a casing for foundation work. In case that the casing oscillator is operated on the slant ground, if another construction heavy equipment is not used, it is impossible to insert the casing in ground using only casing oscillator. So in this paper, we present the new casing oscillator that need not to level the ground for work of casing insertion. This mechanism can execute 4 DOF motion by actuating 5 single - rod hydraulic cylinders. The forward kinematics analysis of the casrng oscillator by tetrahedron geometry is performed so predict workspace, direction and poison of casing oscillatoer.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.50-55
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• 1986

Characteristics of the flow and heat transfer in a channel of 37 rods are investigated numerically. The flow is taken to be a fully developed incompressible laminar flow and it has an uniform temperature profile at the inlet and flows down through the channel of constant wall temperature. A boundary-fitted coordinate system is used for the complex geometry. Calculation is initiated by calculating the developed flow profile and then proceeds to temperature development. Through the calculation the details of the flow and temperature distribution characteristics are found, and discussion is made on the mechanism of the transport phenomena in the complex geometry in terms of wall shear stress distribution, non-dimensionalized velocity, friction factor, Nusselt number distribution, Reynolds number, and porosity. Also the effects of the eccentricity in rod configuration are analyzed and its importance is emphasized.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.789-795
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• 2005

This study proposes a modified bifurcation model with a computational fluid analysis according to variation of a bifurcation geometry. FLUENT is used for a calculation of the head losses in case of a generation and a pumping. The pressure, velocity field and turbulent intensity are simulated in a bifurcation. With consideration about these flow properties, we propose the modified model to improve a flow efficiency and reduce a sound. The proposed model is able to cut down a head loss by 45% when a generation and 36% when a pumping.

• The KSFM Journal of Fluid Machinery
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• v.10 no.1 s.40
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• pp.7-13
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• 2007

This study proposes a modified bifurcation model with a computational fluid analysis according to variation of a bifurcation geometry. FLUENT is used for a calculation of the head losses in case of a generation and a pumping. The pressure, velocity field and turbulent intensity are simulated in a bifurcation. With consideration about these flow properties, we propose the modified model to improve a flow efficiency and reduce a sound. The proposed model is able to cut down a head loss by 45% when a generation and 36% when a pumping.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.177-184
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• 2001

For two kinds of the multi-stage centrifugal pump with diffuser vanes and return channel vanes the meanline performance prediction is applied to get information of hydraulic performance at each internal flow station, because only flange-to-flange test curves are available. As a first step of redesign fur higher efficiency, the impeller geometry is numerically investigated in the present study. Quasi-3D inviscid loading distributions are obtained, for the two impellers, using the state-of-the-art method of impeller 3D design, which provides a guide to optimal redesign. Full 3D turbulent flow fields are thereafter analyzed, using the specialized CFD code, to confirm the redesign results. The inherent limitation of the traditional graphic method of impeller design, which most of domestic pump manufacturers are now employing, is found.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.69-72
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• 2004

The performance of the centrifugal fan in a vacuum cleaner is affected by the hydraulic loss, such as the friction loss, the recirculation loss and the impact loss etc., Those losses depend on the rotational speed of the impeller, the inlet and exit widths, the relative flow angles to the blade, the number of the blades and the geometry of the shroud and the diffuser. These parameters are complicatedly interrelated, so the experimental means in analyzing the fans are rather limited. In the present study, the flow analysis are done numerically by changing the relevant fan parameters. A commercial code, STAR-CD, is used for the calculations. It is seen from the analyses that the computational results agree well with the experimental results. The results obtained can be used for the basic design of a centrifugal fan.