• 설비공학논문집
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• 제9권4호
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• pp.561-571
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• 1997

In this paper, the fundamental equations are developed for the pulsatile laminar flow generated by changing the oscillatory flow with $0{\leq}f{\leq}48Hz$ into a steady one with $0{\leq}Re{\leq}2500$ in a rigid circular pipe. Analytical solutions for the wave propagation factor k, the axial distributions of cross-sectional mean velocity $u_m$ and pressure p are schematically derived and confirmed experimentally. The axial distributions of centerline velocity and pressure were measured by using Pitot-static tubes and strain gauge type pressure transducers, respectively. The cross-sectional mean velocity was calculated from the centerline velocity by applying the parabolic distribution of the laminar flow and it was confirmed by using the ultrasonic flowmeter. It was found that the axial distributions of cross-sectional mean velocity and pressure agree well with theoretical ones and depend only on the Reynolds number Re and angular velocity $\omega$.

• 대한조선학회논문집
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• 제30권2호
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• pp.24-29
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• 1993

초기 선형을 생성하는 과정은 대개 3가지로서 유사선으로 부터 얻는 법, 계열시험 결과로 부터 얻는 법, 주어진 조건을 만족하도록 처음부터 선형을 생성하는 법 등으로 생각할 수 있다. 본 연구에서는 마지막 방법을 택하여 초기 선형을 선형 설계자에게 익숙한 형상계수들을 이용하여 얻고자 하였다. 즉 최소화한 몇 가지의 형상계수를 이용하여 기본 곡선등을 전산기 화면에서 생성하고 이를 제어함으로 선형을 생성하거나 수정하고자 하였다. 곡선을 수학적으로 표시하기 위하여 다항식과 B-Spline 곡선을 사용하였다. 먼저 정면도를 얻기 위하여 5가지의 기본 곡선을 정의하고 이를 얻는 과정을 보였다. Centerline Contour는 B-Spline을 이용하여 생성하였고 정면도와 결합하여 수선(Water Line)을 생성하는 과정을 설명하였다. 이 과정에서 좀더 순정된 결과를 얻기 위해 2가지의 곡선이 제안되었으며 실선에 적용한 결과를 보이고 있다.

• Water Engineering Research
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• 제3권3호
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• pp.163-176
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• 2002

In this study, laboratory experiments have been performed to investigate characteristics of the velocity fields and turbulence for non-buoyant plane jet in the vicinity of the jet nozzle using PIV system. The experimental results show that, in the transition region, the lateral velocity profile is in good agreement with Gaussian distribution. However, the coefficient of Gaussian distribution, $\K_{u,}$, decreases with longitudinal distance in the transition region. The existing theoretical equation for the centerline velocity tends to overestimate the measured data in the transition region. A new equation for the centerline velocity derived by incorporating varying $k_{u}$ gives better agreement with the measured data than the previous equation. The results of the turbulence characteristics show peak values are concentrated on the shear layers. The Reynolds shear stress profile shows the positive peak in the upper layer and negative peak in the lower layer. The turbulent kinetic energy also provides double peaks at the shear layers. The peak of the Reynolds shear stress and the turbulent kinetic energy increases until x/B=8, and then it decreases afterwards.s.

• 소성∙가공
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• 제12권5호
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• pp.440-448
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• 2003

Sheet or plate bending is one of the most important industrial metal forming processes. Considerable attention has been focused on gaining a better understanding of bending characteristics. One of defaults in bending process is the springback. In this study, the springback characteristics of tailor-welded strips in U-bending process was investigated. Furthermore, effect of the process variables such as the geometry of the tools, thickness combination of workpiece, and welding prcoessing on springback were experimentally clarified. First, tailor-welded strips are joined by the laser welding process and consisted of two types of thickness combinations of the SCPl sheet, $0.8t{\times}1.2t$ and $0.8t{\times}1.6t$ to investigate the effect of different thickness combination on the springback. Secondly, two different directionly welded strips, one was welded along the centerline of the strip-width and the other was along the centerline of strip-length, were adopted to compare the effects of the location of weld line on the springback. Some cases of the experimental results were compared to the results simulated by using a commercial FEM code, PAM-STAMP and the theoretical results using the springback formula as well.

• 대한원격탐사학회지
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• 제20권1호
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• pp.57-64
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• 2004

In GIS-based network analysis, topological measure of network structure can be considered as one of important factors in the urban transportation analysis. Related to this measure, it is known that the connectivity indices such as alpha index and gamma index, which mean degree of network connectivity and complexity on a graph or a circuit, provide fundamental information. On the other hand, shimbel index is one of GIS-based spatial metrics to characterize degree of network concentration. However, the approach using these quantitative indices has not been widely used in practical level yet. In this study, an application program, in complied as extension, running on ArcView- GIS is implemented and demonstrated case examples using basic layers such as road centerline and administrative boundary. In this approach, geo-spatial imagery can be effectively used to actual applications to determine the analysis zone, which is composed of networks to extract these indices. As the results of the implementation and the case examples, it is notified that alpha and gamma indices as well as shimbel index can be used as referential data or auxiliary information for urban planning and transportation planning.

• Tribology and Lubricants
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• 제35권4호
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• pp.215-221
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• 2019

A gerotor set consists of two elements, an inner rotor and an outer rotor. The outer rotor has one more tooth than the inner rotor and has its centerline positioned at a fixed eccentricity from the centerline of the inner rotor. Although gerotors come in a variety of geometric configurations, all gerotor sets share the basic principle of having generated tooth profiles that provide continuous tight sealing during operation. The size of the gerotor is proportional to the number of teeth and the amount of eccentricity. The interior of an inner rotor with a large number of teeth has an enough space to include other machine elements. In this paper, the double gerotor mechanism, constructed by putting a small gerotor in the interior of a large inner rotor, is conceptualized. The double gerotor set is composed of an inner rotor, a planetary rotor, and an outer rotor. The inside profile of the planetary rotor corresponds to the outer rotor profile of the small gerotor, and the outside profile is the inner rotor profile of the large gerotor. In the double gerotor, the centers of the inner and the outer rotor are coincident because the eccentricities of two gerotors are balanced. The operation of a double gerotor is examined by analyzing the planetary motion, and a feasibility study for application of the double gerotor for hydraulic motors and pumps is performed. The double gerotor set has much application potential as a component of hydraulic systems.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.354-366
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• 2020

This work mainly focuses on determination of the fully plastic J-integral solutions for welded center cracked plates subjected to remote tension loading. Detailed three-dimensional elasticeplastic Finite Element Analyses (FEA) were implemented to compute the fully plastic J-integral along the crack front for a wide range of crack geometries, material properties and weld strength mismatch ratios for 900 cases. According to the database generated from FEA, Back-propagation Neural Network (BPNN) model was proposed to predict the values and distributions of fully plastic J-integral along crack front based on the variables used in FEA. The determination coefficient R2 is greater than 0.99, indicating the robustness and goodness of fit of the developed BPNN model. The network model can accurately and efficiently predict the elastic-plastic J-integral for weld centerline crack, which can be used to perform fracture analyses and safety assessment for welded center cracked plates with varying strength mismatch conditions under uniaxial loading.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3860-3865
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• 2023

A metallic microcell UO₂ pellet has a microstructure where a metal wall is connected to overcome the low thermal conductivity of the UO₂ fuel pellet. It has been verified that metallic microcell fuel pellets provide an impressive reduction of the fuel centerline temperature through a Halden irradiation test. However, it is difficult to predict the effective thermal conductivity of these pellets and researchers have had to rely on measurement and use of the finite element method. In this study, we designed a unit microcell model using a thermal resistance circuit to calculate the effective thermal conductivity on the basis of the microstructure characteristics by using the aspect ratio and compared the results with those of reported metallic UO₂ microcell pellets. In particular, using the thermal conductivity calculated by our model, the fuel centerline temperature of Cr microcell pellets on the 5th day of the Halden irradiation test was predicted within 6% error from the measured value.

• 한국측량학회지
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• 제30권4호
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• pp.379-388
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• 2012

2011년부터 본격적으로 도로명주소 체계가 시행 및 활용되고 있으나, 가장 대표적인 국가기본도인 수치지도는 현재 도로명주소 체계와 관련된 정보를 포함하지 않고 있는 관계로 도로명주소 체계하에서의 활용이 원활하게 이루어지기 어렵다. 본 논문에서는 수치지도 객체의 속성정보에 도로명주소 관련 정보를 추가하여 확장형 수치지도를 생성할 수 있는 방법론을 연구하였다. 먼저 도로명주소 지도의 도로구간 레이어와 수치지도 도로중심선 레이어와의 중첩 분석을 통하여 두 레이어의 객체간 매칭 관계를 도출였으며, 두 레이어의 속성항목 분석을 통하여 도로명주소 지도에서 수치지도로 추가할 속성항목을 추출하였다. 도출된 결과를 이용하여 도로명주소 지도의 도로명주소 관련 속성정보들을 수치지도 도로중심선 데이터로 전달하였다. 이러한 과정을 거쳐 속성 확장된 수치지도 도로중심선 레이어는 도로명주소 체계에 따른 도로명 정보를 속성으로 갖게 되며, 이에 따라 수치지도 활용시에 도로명주소 체계에 따른 위치참조가 가능하게 된다.

• 한국대기환경학회지
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• 제11권3호
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• pp.299-302
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• 1995

Many air quality models have been used for Environmental impact assessments. Miller-Holzworth model suggested by Holzworth is a simple air quality model is frequently used for air quality assessments in korea. Miller-Holzworth model suggested by Holzworth is a simple air quality model for the ground-level area source, The model estimates the pollutants concentration averaged over the wind centerline. An error involved in the Miller-Holzworth model was first indentified by Calder in 1977. But the model has been used without correction for unsuitable cases in Korea. This paper corrected that error and modified model formulation for application to urban and rural areas.