• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2016-2024
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• 2005

In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the cross section stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.

• 대한공간정보학회지
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• 제16권3호
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• pp.105-110
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• 2008

하천의 수리/수문 모델링에 활용하는 하천 지형자료는 하천정비기본계획을 위한 횡단측량을 통하여 취득된 하천단면 자료를 활용하고 있으나 취득되는 단면간의 거리가 다소 커 모델링 과정 중 보다 조밀한 간격의 단면형상을 필요로 하는 경우에도 단면자료를 취득할 수 없을 뿐만 아니라 관측점간의 직선거리를 고려하는 보간기법들의 특성에 의하여 현실적인 하천의 형상을 반영하지 못하는 문제점이 있다. 본 연구에서는 대표적인 수체부 하천 지형자료라 할 수 있는 하천정비기본계획상의 하천단면자료를 이용하여 하천의 형상을 효율적으로 추정하고자 하였으며 관측된 하천단면자료들 사이의 임의 단면을 생성하는 알고리즘을 제시함으로써 GIS 자료를 이용한 수리/수문 모델링에서 쉽게 활용이 가능하도록 하였다.

• 수산해양기술연구
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• 제44권2호
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• pp.120-128
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• 2008

Estimation of the gear shape and cross section of sweep at mouth of a bottom trawl net was described and applied to the field experiments obtained with the Scanmar system. The shape of the trawl net from wingend to the beginning of codend was assumed to be part of an elliptic cone of which the cross section was ellipse, and that of the float rope be of form $y_f=a_fx^{bf}$. In case of a bottom trawl with warp 180m long, the radius of ellipse, the cross section of sweep at mouth, the eccentricity of the ellipse, the inclination angle of float rope and the contribution of the side panel to net height were estimated in accordance with towing speed. The horizontal radius of the upper ellipse increased with increasing towing speed, the eccentricity of it became slightly bigger as increasing the towing speed which meant the shape of it being flat. And the inclination angle of the float rope was about between 7 and 12 degrees in case of the above bottom trawl.

• 대한산업공학회지
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• 제20권2호
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• pp.77-90
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• 1994

Curve-net interpolation surface is one of the most popular method in engineering design. Therefore it is supported with many commercial CAD/CAM system. However, construction algorithm of curve-net interpolation surfaces is rarely opened to the public because of its copy-right. In this paper we establish a construction algorithm of curve-net interpolation surface so called sweeping surface which especially concentrates on trajectory of cross-section curve. We also show the method which can construct sweeping surfaces as NURB or Bezier mathematical models. Surfaces having the form of standard mathematical models are very useful for the application of joining, trimming, blending etc. The proposed surface interpolation scheme consists of four steps; (1) preparation of guide curves and section curves, (2) remeshing guide curves and section curves, (3) blending section curves after deformation, and (4) determination of control points for sweeping surface using gordon method. The proposed method guarantee $G^1$-continuety, and construct the surface salifying given section curves and trajectory of section curves.

• 한국산림과학회지
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• 제63권1호
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• pp.35-41
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• 1984

우리나라 남부(南部) 해안선(海岸線)을 따라 천연분포(天然分布)되어 있는 해송(Pinus thunbergii)에 대(對)하여 침엽형질상(針葉形質上)으로 본 지역간(地域間), 지역내(地域內)의 집단간(集團間), 집단내(集團內)의 개체간(個體間)에 변이(變異)를 분석(分析)하였던 바 그 결과(結果)는 다음과 같다. 거치밀도(鋸齒密度), 침엽체적(針葉體積)의 형질(形質)은 다른 형질(形質)보다 변이개체(變異係體)가 비교적(比較的) 높게 나타났고 각(各) 집단내(集團內)의 개체간(個體間)에 있어서 영광(靈光)의 침엽횡단면형상비(針葉橫斷面形狀比)를 제외(除外)하고는 집단(集團) 모두 개체간(個體間)에 1% 수준(水準)의 유의성(有意性)을 인정(認定)할 수 있었다. 지역내(地域內)의 집단간(集團間)에 있어서는 동안형지역(東岸型地域)의 경우, 거치밀도(鋸齒密度), 침엽횡단면적(針葉橫斷面積)은 5% 수준(水準), 침엽체적(針葉體積)은 1% 수준(水準)에서 유의성(有意性)을 인정(認定)할 수 있었다. 서안형지역(西岸型地域)의 집단간(集團間)에 있어서 침엽횡단면형상비(針葉橫斷面形狀比), 침엽종단면형상비(針葉縱斷面形狀比)는 1% 수준(水準)의 유의성(有意性)이 있었고 남해안형지역(南海岸型地域)에서는 침엽체적(針葉體積)에서만 5% 수준(水準)에서 유의성(有意性)이 있었다. 지역간(地域問)에 있어서 침엽횡단면형상비(針葉橫斷面形狀比), 침엽횡단면적(針葉橫斷面積)은 5% 수준(水準)에서 유의성(有意性)을 인정(認定)할 수 있었으며 이들 형질(形質)은 동안형지역(東岸型地域)이 다른 지역(地域)과 유의차(有意差)가 있었다. 이상(以上)의 결과(結果)에서 우리나라 남부(南部) 해안(悔岸)에 분포(分布)되고 있는 해송은 침엽일부(針葉一部)의 형질(形質)에서 지역적(地域的)으로 분화(分化)가 이루워지고 있음을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제3권6호
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• pp.555-567
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• 1995

Design curves have been prepared for prestressed rectangular beam section based on BS 8110, for determining area of steel for any given cross section, for stresses in concrete and steel and for the design moment. The design moment and the area of steel have been expressed in dimensionless form in terms of cross sectional dimensions and the characteristic strength of concrete. The choice and combination of design parameters result in considerably less number of curves as aid for design of rectangular prestressed beam sections, than those reported in CP 110 (Part 3).

• Steel and Composite Structures
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• 제13권1호
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• pp.71-89
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• 2012

The paper investigates beam lateral buckling stability according to linear and non-linear models. Closed form solutions for single-symmetric cross sections are first derived according to a non-linear model considering flexural-torsional coupling and pre-buckling deformation effects. The closed form solutions are compared to a beam finite element developed in large torsion. Effects of pre-buckling deflection and gradient moment on beam stability are not well known in the literature. The strength of singly symmetric I-beams under gradient moments is particularly investigated. Beams with T and I cross-sections are considered in the study. It is concluded that pre-buckling deflections effects are important for I-section with large flanges and analytical solutions are possible. For beams with T-sections, lateral buckling resistance depends not only on pre-buckling deflection but also on cross section shape, load distribution and buckling modes. Effects of pre-buckling deflections are important only when the largest flange is under compressive stresses and positive gradient moments. For negative gradient moments, all available solutions fail and overestimate the beam strength. Numerical solutions are more powerful. Other load cases are investigated as the stability of continuous beams. Under arbitrary loads, all available solutions fail, and recourse to finite element simulation is more efficient.

• 한국소음진동공학회논문집
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• 제23권4호
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• pp.338-346
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• 2013

Equations of motion of a rotating blade considering pre-twist angle, cross section taper and a concentrated mass are derived using the hybrid deformation variable modeling method. For the modeling of a concentrated mass which is located at an arbitrary position of the blade, a Dirac delta function is employed for the mass density function. The final equations for the vibration analysis are transformed into a dimensionless form using several dimensionless parameters. The effects of the dimensionless parameters on the vibration characteristics of the rotating blade are investigated through numerical analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.639-642
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• 1999

Pullout test known as Lok test among the test methods to evaluate concrete strength strength is a test method which is used to decide the form removal time by assessing the early strength of concrete in a new construction, or to control the quality of newly placed concrete. This method has inconvenience to place inserts on the form work in advance, however, the placing work is quite simple and it has advantage that the strength can be measured at field as long as the inserts are placed. In this study, the first step is to investigate the properties of test method itself, by performing the laboratory test which covers deviation of the method and factors affecting the results, etc. The second step is to correlate the result with cylinder strength and other NDT methods such as rebound hammer, ultrasonic method, etc. And that, the results are compared with foreign results to find the differences between the two. In this research, new factors such as moisture content, area of aggregate failure cross section and area of aggregate separation cross section, etc as well as wate-cement ratio and age are investigated.

• 펄프종이기술
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• 제30권2호
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• pp.62-73
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• 1998

The aim of this work was to investigate the effects of pigment composition on the calendering response and structure of the coated paper. Calendering response of the coated paper was determined from the gloss values of the uncalendered and calendered coated papers, and the relationship between gloss and coating structure was discussed. The surface and cross section of the coating layer was observed using a scanning electron microscope to examine the coating structure. Coating layers were hardened in epoxy resin and polished with carbimet paper disc for preparing SEM samples. Maximum calendering response was obtained for the coated paper prepared from 80pph of clay and 20pph of ground calcium carbonate (GCC) as pigments. Photomicrographs of the surface and cross section of the coating layer show that clay tends to form dense coating structure, while GCC tends to form bulky coating layer.