• 대한치과의사협회지
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• 제11권2호
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• pp.123-129
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• 1973

The authors measured orthodontic force using the orthodontic materials of the Rocky Mountain Products Company. The results were as follows : ① Use latex of wide diameter in long distance, and when the latex of wide diameter activated by four or five times, we obtained a optimal force. ② The authors obtained canine retractions with sectional arch. Activation of sectional arch began at 1mm and had to do not activations of 3mm more. ③ The leveling started from .014 green round wire and finished to. 0.16" green Elgiloy round wire. Permit only a mild force in ideal arch form, in rectangular wire. ④ Fundamentaly, elastic thread obtained maximum force by activating as two times. ⑤ Coil spring obtained more heavy force from short distance than long distance.

• 아태비즈니스연구
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• 제15권1호
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• pp.335-352
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• 2024

Purpose - Low fertility rate is a serious problem, and this study analyzes factors affecting total fertility rate using panel data from 16 metropolitan cities and provinces in Korea from 2000 to 2022. Design/methodology/approach - Estimating the SAR model considering the weak cross-sectional dependence that exists in variables related to the regional total fertility rate, and using the DKSE estimation method considering the strong cross-sectional dependence. Findings - Estimation results considering weak and strong cross-sectional dependence were similar, confirming the robustness of the results. Female labor force participation rate has a positive effect on total fertility rate, and employment rate has no effect. However, the interaction term is a negative (-) sign. Crude marriage rate has a positive effect on total fertility rate, and apartment price has a slightly positive effect. Environmental factor has no effect, and policy factor has a negative effect. Research implications or Originality - In order for an increase in the female labor force participation rate to lead to an increase in the total fertility rate, qualitative improvements in female employment must be made. Financial investment policies for childbirth must increase their effectiveness. The problem of low fertility rate requires not only population policy but also social, economic, cultural, environmental, and policy conditions to be considered.

• 한국농공학회지
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• 제34권1호
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• pp.57-65
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• 1992

The main purpose of this paper is to present both the natural frequencies and mode shapes of tapered beams under tensile axial force. The differential equation governing planar free vibration for tapered beams under tensile axial force is derived as nondimensional form. The three kinds of cross sectional shape are considered in differential equation. The Runge-Kutta method and Determinant Search method are used to perform the integration of the differential equation and to determine the natural frequencies, respectively. The hinged-hinged, hinged-clamped, clamped-clamped and constraints are applied in numerical examples. The lowest four nondimensional natural frequencies are reported as the function of nondimensional tensile axial force. The fundamental natural frequencies are presented when section ratios and nondimensional axial forces are varied. The effects of cross sectional shapes are reported and some typical mode shapes are also presented.

• 대한토목학회논문집
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• 제31권3A호
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• pp.145-152
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• 2011

일반적으로 교량의 교대 날개벽 설계를 위한 해석은 날개벽을 4개의 구역으로 나누고 이를 1차원 캔틸레버 구조로 간략화하여 단면력을 산정하는 방법이 실무에서 관례적으로 사용되고 있다. 이러한 간편법은 수계산에 의존하던 때에 만들어진 일본 규정으로 국내 도로교설계기준에 채택되어 개정없이 계속 사용되어지고 있다. 본 연구에서는 불합리한 교대 날개벽의 단면력 산정법을 개선하기 위해서 날개벽을 단순 캔틸레버 해석이 아닌 실제에 가까운 2변 고정 판구조로 해석하여 현 도로교설계기준의 단면력과 비교 분석을 실시하였다. 또한 해외의 날개벽 단면력 산정법을 조사 분석하여 국내의 규정과 비교하였다. 본 연구에서 제시한 날개벽의 가용 매개변수 범위 내에서 유한요소 해석을 실시한 결과, 현 도로교설계기준의 간편법에 의한 단면력은 날개벽 형상에 따라 때로는 안전측이지만 때로는 비안전측인 결과를 나타내고 있어 실제의 단면력을 반영하지 못하는 것으로 분석되었다.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.251-259
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• 2003

본 논문은 매립형 SRC기둥의 축력과 변형능력과의 관계를 찾아내기 위하여 해석적인 연구를 수행하였다. 해석 모델은 캔틸레버기둥으로 한정하였으며 SRC 기둥의 비탄성 거동에 영향을 미치는 변수들인 철골비, 매립철골형상과 전단스팬과 춤과의 비에 대하여 검토하였다. 일정회전각하에 축력과 반복수평력을 받는 SRC기둥의 안정적 거동을 보장하기 위한 최대한계축력이 있다는 것을 해석결과들은 보여 주고 있다. 반복 횡하중을 받는 기둥이 저항할 수 있는 최대축력은 소요회전각을 보장하는 안정한계축력으로서 정의된다. 해석결과에 따르면 안정한 계축력비는 강재의 강도가 증가함에 따라 콘크리트의 강도가 감소함에 따라 증가하는 것으로 나타났다. 또한 I형 단면이 매립형 철골로 사용될때 철골 단면적이 증가함에 따라 안정한계 축력비는 증가하며, 십자형 단면이 사용되는 경우에는 단면적에 의한 영향이 거의 없었다.

• 한국해양공학회지
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• 제15권2호
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• pp.66-71
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• 2001

A sectional analysis of trunk-lid carried out by using the equilibrium approach based on the force balance together with geometric relations and plasticity theory. In computing a force balance equation, it is required to define a geometric curve approximating the shape of sheet metal at any step of deformation from the interaction between the die and the deformed sheet. The trunk-lid panel material is assumed to possess normal anisotropy and to obey Hill's new yield criterion. Deformation of each section of trunk-lid panel is simulated and composed to get the three-dimensional shape by using CAD technique. It was shown that the three-dimensional shape composition of the two-dimensional analysis.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.39-52
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• 2003

A computer program has been developed for the optimum design of prestressed concrete beams under flexure. Optimum values of prestressing force, tendon configuration, and cross-sectional dimensions are determined subject to constraints on the design variables and stresses. 28 constraints have been used including flexural stresses, cover requirement, the aspect ratios for top and bottom flanges and web part of a beam and ultimate moment. The objective function contains cost of concrete, prestressing force and formwork. Using this function, it is possible to obtain minimum cost design, minimum weight or cross-sectional area of concrete design and minimum prestressing force design. Besides the idealized I-shaped cross-section, which is widely used in literature, a general I-shaped cross-section with eight geometrical design variables are used here. Four examples, one of which is available in the literature and the others are modified form of it, have been solved for minimum cost and minimum cross-sectional area designs and the results are compared. The computer program, which employs modified grid search optimization method, can assist a designer in producing efficient designs rapidly and easily. Considerable savings in computational work are thus made possible.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.187-193
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• 1999

As the slenderness ratio increases, it is necessary to examine the increased sectional area of member by means of increasing buckling strength because the sectional area of compressive member is designed in accordance with buckling. In this reason tn reinforce insufficient strength it don not have to reinforce the whole sectional area of member. Force of member can be increased in a way to restrict buckling mode by means of the partially increased sectional area of member. Therefore, in this study, we put emphasis on compressive members among many members that constitute space frame and try to get basic data about the reinforcement of space frame by means of investigating the bucking characteristic according to the size and length of partially increased sectional area of member.

• Wind and Structures
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• 제12권1호
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• pp.63-76
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• 2009

The vortex-induced vibration of an ${\sqcap}$-shaped bridge deck sectional model is studied in this paper via the wind tunnel experiment. The vibratory behavior of the model shows that there is a transition of the predominant vibration mode from the vertical to the rotational degree of freedom as the wind speed increases gradually or vice versa as the wind speed decreases gradually. The vertical vibration is, however, much weaker in the latter case than in the former. This is a phenomenon which is difficult to model by existing parametric models for vortex-induced vibrations. In order to characterize the aeroelastic property of the ${\sqcap}$-shaped sectional model, a time domain force identification scheme is proposed to identify the time history of the aeroelastic forces. After the application of the proposed method, the resultant fluid forces are re-sampled in dimensionless time domain so that reduced frequency response function (RFRF) can be obtained to explore the properties of the vortex-induced wind forces in reduced frequency domain. The RFRF model is proven effective to characterize the correlation between the wind forces and bridge deck motions, thus can explain the aeroelastic behavior of the ${\sqcap}$-shaped sectional model.

• Tribology and Lubricants
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• 제29권3호
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• pp.149-159
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• 2013

In this research, the lubrication characteristics of spool valves with various cross-sectional groove shapes were studied. The validity of using the Reynolds equation for the analysis of spool valves with various groove shapes was also investigated. The cross-sectional shapes for the grooves included a triangle, square, and U shape. The characteristics of the flow in the groove were investigated using streamlines. When the number of grooves was increased, the difference between the results obtained from the Reynolds equation and those obtained from the Navier-Stokes equation increased according to the groove shape. Thus, it was found that the Navier-Stokes equation should be used to investigate the lubrication characteristics of the spool valves in those cases. Moreover, in the case where the cross section of the groove was U-shaped, the groove prevented the small eddy current from occurring in the groove. Therefore, the lateral force and friction force of the spool valve with the U-shaped groove were lower than those of the spool valves with other groove shapes.