• 한국산림과학회지
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• 제86권1호
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• pp.17-24
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• 1997

지구(地球)의 잠재자연식생분포(潛在自然植生分布)를 추정(推定)하기 위한 첫단계로서 자연식생분포(自然植生分布)와 밀접(密接)한 관계가 있는 기온(氣溫)과 강수량(降水量)에 대한 최적구면보간방법(最適球面補間方法)을 개발하기 위해, Light Climatic Dataset로 명명(命名)한 전세계에 분포(分布)된 1,060점의 측후소(測候所)의 실측자료(實測資料)를 보간용(補間用)과 검정용(檢定用)으로 무작위(無作爲) 2등분(等分)하고, 검정용(檢定用) 측후소(測候所)에 있어서 관측치(觀測値)와 보간용(補間用)에 의한 추정치(推定値)와의 오차(誤差)를 보간방법(補間方法)과 파라메타가 틀린 조합(組合)에 대해 상호비교(相互比較)하였다. 보간용(補間用)에 의한 추정치(推定値)는, 측후소(測候所)의 선택법(選擇法)으로 전점(全点), 정점(定点), 안반경(安半徑)의 3가지 방법, 거리에 대한 하중(荷重)으로 n승 반비례(反比例), 부(負)의 지수함수(指數函數)의 2가지 방법, 방위(方位)에 관한 하중(荷重)으로 타원하중법(楕圓荷重法), 각각에대해 상호조합(相互組合)하여 산출(算出)되었다. 그 결과, 측후소(測候所)의 선택법(選擇法)은 정반경법(定半徑法), 거리(距離)에 관한 하중식(荷重式)은 부(負)의 지수함수(指數函數), 방위(方位)에 관한 하중법(荷重法)은 타원하중법(楕圓荷重法)을 조합(組合)하는 것이 기온(氣溫)과 강수량(降水量)의 보간(補間)에 적합(適合)하였으며, 그에 관한 파라메타 값은 기온(氣溫)에 있어서 정반경(定半徑) $30^{\circ}$, -0.78의 지수함수(指數函數), 타원하중(楕圓荷重) 0.4로, 강수량(降水量)에 있어서는 각각 $35^{\circ}$, -0.53, 1.2로 나타났다.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.59-65
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• 1993

In a spark ignition engine, in order to make research on flame propagation, attentive concentration should be paid on initial combustion stage about the formation and development of flame. In addition, the initial stage of combustion governs overall combustion period in a spark ignition engine. With the increase of the size of flame kernel, it could reach initial flame stage easily, and the mixture could proceed to the combustion of stabilized state. Therefore, we must study the theoretical calculation of minimum flame kernel radius which effects on the formation and development of kernel. To calculate the minimum flame kernel radius, we must know the thermal conductivity, flame temperature, laminar burning velocity and etc. The thermal conductivity is derived from the molecular kinetic theory, the flame temperature from the chemical reaction equations and the laminar burning velocity from the D.K.Kuehl's formula. In order to estimate the correctness of the theoretically calculated minimum flame kernel radius, the researcheres compared it with the RMaly's experimental values.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.737-746
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• 2016

This article describes a comparison on laminar burning velocity measured by Bunsen and spherical flame methods of synthetic natural gas (SNG) with various composition of hydrogen. In this study, the laminar burning velocity measurements were employed by Bunsen burner and cylindrical constant combustor at which flame images were captured by Schlieren system. These results were also compared with numerical based on CHEMKIN package with GRI 3.0, USC-II and UC Sandiego mechanism. In case of spherical flames, the suitable flame radius range and theoretical models were verified using the well-known previous results in methane/air flames. As an experimental condition, hydrogen content of SNG was adjusted 0% to 11%. Equivalence ratios of Bunsen flames were adjusted from 0.8 to 1.6. On the other hand, those of spherical flames were adjusted from 0.6 to 1.4, relatively. From results of this study, the both laminar burning velocities measured in Bunsen and spherical flame methods were resulted in similar tendency. As the hydrogen content increased, the laminar burning velocity also increased collectively. Laminar burning velocity of measured SNG-air flames was best coincided with GRI 3.0 mechanism by comparison of reaction mechanisms.

• 한국농공학회지
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• 제40권5호
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• pp.91-99
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• 1998

The widespread use of thin shell structures has created a need for a systematic method of analysis which can adequately account for arbitrary geometric form and boundary conditions as well as arbitrary general type of loading. Therefore, the stress and analysis of thin shell has been one of the more challenging areas of structural mechanics. A wide variety of numerical methods have been applied to the governing differential equations for spherical and cylindrical structures with a few results applicable to practice. The analysis of axisymmetric spherical shell is almost an every day occurrence in many industrial applications. A reliable and accurate finite element analysis procedure for such structures was needed. Dynamic loading of structures often causes excursions of stresses well into the inelastic range and the influence of geometry changes on the response is also significant in many cases. Therefore both material and geometric nonlinear effects should be considered. In general, the shell structures designed according to quasi-static analysis may fail under conditions of dynamic loading. For a more realistic prediction on the load carrying capacity of these shell, in addition to the dynamic effect, consideration should also include other factors such as nonlinearities in both material and geometry since these factors, in different manner, may also affect the magnitude of this capacity. The objective of this paper is to demonstrate the dynamic characteristics of spherical shell. For these purposes, the spherical shell subjected to uniformly distributed step load was analyzed for its large displacements elasto-viscoplastic static and dynamic response. Geometrically nonlinear behaviour is taken into account using a Total Lagrangian formulation and the material behaviour is assumed to elasto-viscoplastic model highly corresponding to the real behaviour of the material. The results for the dynamic characteristics of spherical shell in the cases under various conditions of base-radius/central height(a/H) and thickness/shell radius(t/R) were summarized as follows : The dynamic characteristics with a/H. 1) AS the a/H increases, the amplitude of displacement in creased. 2) The values of displacement dynamic magnification factor (DMF) were ranges from 2.9 to 6.3 in the crown of shell and the values of factor in the mid-point of shell were ranged from 1.8 to 2.6. 3) As the a/H increases, the values of DMF in the crown of shell is decreased rapidly but the values of DMF in mid-point shell is increased gradually. 4) The values of DMF of hoop-stresses were range from 3.6 to 6.8 in the crown of shell and the values of factor in the mid-point of shell were ranged from 2.3 to 2.6, and the values of DMF of stress were larger than that of displacement. The dynamic characteristics with t/R. 5) With the thickness of shell decreases, the amplitude of the displacement and the period increased. 6) The values of DMF of the displacement were ranged from 2.8 to 3.6 in the crown of shell and the values of factor in the mid-point of shell were ranged from 2.1 to 2.2.

• 한국농공학회지
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• 제40권3호
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• pp.113-121
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• 1998

The widespread use of thin shell structures has created a need for a systematic method of analysis which can adequately account for arbitrary geometric form. Therefore, the stress analysis of thin shell has been one of the more challenging areas of structural mechanics. The analysis of axisymmetric spherical shell is almost an every day occurrence in many industrial applications. A reliable and accurate finite element analysis procedure for such structures was needed. In general, the shell structures designed according to quasi-static analysis may fail under conditions of dynamic loading. For a more realistic prediction on the load carrying capacity of these shell, in addition to the dynamic effect, consideration should also include other factors such as nonlinearities in both material and geometry since these factors, in different manner, may also affect the magnitude of this capacity. The objective of this paper is to demonstrate the dynamic characteristics of spherical Shell. For these purpose, the spherical shell subjected to uniformly distributed step load was analyzed for its large displacements elasto-viscoplastic dynamic response. The results for the dynamic characteristics of spherical shell in the cases under various conditions of base-radius/central height(a/H) and thickness/shell radius(t/R) were summarized as follows: 1. The dynamic characteristics with a/H, 1) As the a/H increases, the amplitude of displacement increased. 2) The values of displacement Dynamic Magnification Factor (DMF) range from 2.9 to 6.3 in the crown of shell and the values of factor in the mid-point of shell range from 1.8 to 2.6. 3) As the a/H increases, the values of DMF in the crown of shell is decreased rapidly but the values of DMF in mid-point of shell is increased gradually. 4) The values of DMF of hoop-stresses range from 3.6 to 6.8 in the crown of shell and the values of factor in the mid-point of shell range from 2.3 to 2.6, the values of DMF of stress were larger than that of displacement. 2. The dynamic characteristics with t/R, 1) With the decrease of thickness of shell decreses, the amplitude of the displacement and the period increased. 2) The values of DMF of the displacement were range from 2.8 to 3.6 in the crown of shell and the values of factor in the mid-point of shell were range from 2.1 to 2.2.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1466-1469
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• 2004

Micro spherical lens mold processing method based on mechanical one completes a spherical shape by setting a diamond tool of hundreds $\mu$m radius on spins with high speed and then using Z-axis vertical feeding motion like the fabrication of micro drilling. In this method, we can see unprocessed parts shaped like cylinder and cone and check increasing chatter marks and burrs by setting errors of the central axis of rotation on the edge of the tool. That is why this method doesn't suit for the optical lens mold. In this paper presents unprocessed parts are disappeared and chatter marks and burrs are decreased from centre of the lens after using Run-out measuring and setting system on run-out occurred from setting tool. Also the fabrication characteristics of 6：4 Brass, A1601, PMMA are compared and analyzed, establishing the optimum machining condition on each material.

• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.73-86
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• 2007

The general stereographic projection which maps a point on a sphere with arbitrary radius to a point on a plane stereographically and its inverse projection have the pythagorean-hodograph (PH) preserving property in the sense that they map a PH curve to another PH curve. Upon this fact, for given spatial $C^1$ Hermite data, we construct a spatial PH curve on a sphere that is a $C^1$ Hermite interpolant of the given data as follows: First, we solve $C^1$ Hermite interpolation problem for the stereographically projected planar data of the given data in $\mathbb{R}^3$ with planar PH curves expressed in the complex representation. Second, we construct spherical PH curves which are interpolants for the given data in $\mathbb{R}^3$ using the inverse general stereographic projection.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.162-163
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• 2003

• 한국음향학회지
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• 제21권8호
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• pp.757-765
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• 2002

본 논문은 해석과 실험을 통하여 구형 압전 변환기의 점대칭 방사모드 진동 특성을 규명하는 것을 목적으로 한다. 반경 방향 좌표와 시간의 함수인 반경 방향 변위와 전기 퍼텐셜로 표현되는 지배방정식을 구성한다. 역학적 경계조건과 전기적 경계조건을 적용하여 방사 진동의 특성방정식을 유도한다. 이 식을 이용하여 압전 고유진동수를 계산하고, 그 결과를 측정 결과와 비교한다. 수치계산을 통하여 압전 공진과 탄성 공진의 차이, 구형 압전체의 반경 및 두께에 따른 고유진동수 등을 고찰한다. 그 결과 1차 방사모드의 고유진동수 크기는 압전현상으로 인해 작아지며 구형의 곡률 반지름이 커짐에 따라 지수함수적으로 작아지는 것을 알게 되었다.

• 디지털융복합연구
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• 제14권11호
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• pp.435-440
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• 2016

양안 굴절이상 차이에 의한 안광학상수 변화도 분석을 통한 양안 굴절이상 차이의 특성을 이해 할 수 있는 기초자료를 제공하고자 하였다. 20-59세의 건강한 성인 100명을 대상으로 KR-8800을 이용하여 등가구면 굴절력과 각막곡률 반경을, IOL Master를 사용하여 안축장길이와 전방깊이를 측정하였으며, 측정값의 차이는 우안 측정값-좌안 측정값의 차이값에 절대 값을 구하여 사용하였다. 전체 대상자의 등가구면 굴절력은 $-1.83{\pm}2.17D$이고, 안축장길이는 23.00~24.99mm, 각막곡률반경은 7.50~7.89mm, 전방깊이는 3.60~4.09mm의 범위에서 가장 많았다. 양안 등가구면 굴절력 차이에 따른 양안 안축장길이 차이와 양안 전방깊이의 차이가 유의한 상관관계가 있었다. 또한, 양안 굴절력 차이에 의한 양안 안축장 길이 차이가 가장 크고, 가장 높은 상관성이 있었다. 양안 굴절력 차이는 안광학 상수와 밀접한 관계가 있고, 양안 굴절력 차이에 의하여 여러 가지 시기능 문제가 발생 할 수 있으므로, 양안 굴절이상 차이에 따른 요인별 분류를 통한 융복합 연구가 필요하다.