• 대한기계학회논문집A
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• 제29권1호
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• pp.115-123
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• 2005

This paper presents the development of an algorithm for position control of feed drives in machine tools. The algorithm is constructed through an experimental method based on proportional control with a ramp input. In the first step of designing, a tracking-error curve is generated with the proportional control, and then an error model is decided to reduce the tracking error, Next, the output signal of the error model is added to the current error signal to yield the actuating error signal. The effectiveness of the proposed scheme is confirmed through simulation and experiments.

• 한국식품영양과학회지
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• 제19권3호
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• pp.215-218
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• 1990

포화성장모델을 이용하여 반응시간에 따른 생성물의 양을 예측하였다. 수용성 기질-수용성 효소간의 반응뿐만 아니라 비수용성 기질-수용성 효소간의 반응 결과에도 이 모델은 뛰어난 예측성을 나타내었다. 그외에도 측정치의 정확도도 이 모델로 대략 평가할 수 있었다. 사용자가 편리하도록 컴퓨터 프로그램을 BASIC 언어를 사용하여 제시하였고 이 프로그램을 이용하여 Pmax와 K 상수 값을 결정하고 상대오차의 평균값도 계산하였다.

• Advances in concrete construction
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• 제10권2호
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• pp.151-159
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• 2020

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

• 한국지진공학회논문집
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• 제26권2호
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• pp.59-69
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• 2022

The use of dampers is being considered a means to improve the seismic performance of buildings. It may take considerable time and effort to find an optimal design solution since repeated three-dimensional nonlinear time history analyses are required. Therefore, a preliminary design procedure for seismic retrofit using hysteretic dampers was proposed in this study. In the proposed procedure, the amount of retrofit (required number of dampers) is estimated from the capacity curve of the building before retrofit and allowable story drift of the building. In combining the capacity curves of the building and the dampers, the deformation demand for the dampers can be easily checked against their deformation capacity. The equations to transform the device displacement to roof displacement for the combination of capacity curves are developed. The proposed procedure was applied to the seismic retrofit design of sample buildings. The study found that the estimated capacity curve was very close to the actual capacity curve obtained from the pushover analysis, which can determine an appropriate configuration to meet the required seismic performance.

• 한국항행학회논문지
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• 제20권5호
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• pp.401-407
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• 2016

본 논문에서는 태양광 장기체공 무인기의 전력모델을 포함한 3차원 경로계획과 유도에 대하여 기술한다. 본 논문에서 사용한 Dubins curve는 계산속도가 빨라 경로계획에 곧바로 적용이 가능하다는 장점이 있다. 하지만 Dubins curve의 경로생성 문제는 2차원 평면에서 정의되기 때문에 실제 항공기의 경로계획을 위해 Randal W. Beard에 의해 수행된 비행 경로각의 한계를 고려하여, 고도 차이에 따라 선회경로를 추가하는 방식의 3차원 Dubins 경로생성 알고리즘을 활용하였다. 본 논문에서 사용한 항공기 모델은 Aileron이 없기 때문에 Rudder를 사용하여 횡축 방향 제어기를 설계하였으며, 비선형 경로추종 유도기법을 사용하여 경로추종 시뮬레이션을 수행하였다. 고도조건에 따른 예제를 생성하였으며, 시뮬레이션 결과 생성된 경로를 잘 추종하는 것을 확인하였다. 마지막으로 태양에너지 수율에 대한 계산식을 통해 태양광 장기체공 무인기의 전력 시스템을 모델링하여 48시간 연속비행 시뮬레이션을 실시하였고, 이에 대한 시뮬레이션 결과를 제시하였다.

• 한국산림과학회지
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• 제57권1호
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• pp.1-7
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• 1982

원래 인구증가곡선(人口增加曲線)으로 알려진 단순(單純) logistic 곡선(曲線)은 초본식물(草本植物)의 성장표현(成長表現)에도 이용(利用)되어 왔다. 초본(草本)의 경우 이론치(理論値)와 실측치(實測値) 사이의 적합도(適合度)는 만족(滿足)스러운 것으로 알려져 있다. 그러나 초본(草本)과는 특성(特性)이 상이(相異)한 목본식물(木本植物)의 성장(成長)에 단순(單純) logistic 곡선(曲線)이 적용(適用)된 예는 극히 드물다. 따라서 그에 대한 적합성(適合性) 여부는 아직 의문시 되고 있다. 본연구(本硏究)에서는 임분밀도관리(林分密度管理)의 기초(基礎)가 되고 있는 단순(單純) logistic 곡선(曲線)의 적합성(適合性)을 조사하기 위하여 이것을 소나무임분(林分)에 적용(適用)시켜 보았다. 적합성검정(適合性檢定)을 위해서는 Chi-square test가 채용되었다.

• Steel and Composite Structures
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• 제3권4호
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• pp.231-242
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• 2003

This paper deals with the formulation and development of fracture criteria for high-strength structural members containing surface damage in the form of notches (i.e., blunt defects). The important role of the yield strength of the material and its strain hardening capacity (evaluated by means of the constitutive law or stress-strain curve) is analysed in depth by considering the fracture performance of notched samples taken from high-strength steels with different levels of cold drawing (the most heavily drawn steel being commercial prestressing steel used in prestressed concrete). The final aim of the paper is to establish fracture-based design criteria for structural members made of steels with distinct yield strength and containing very different kinds of notch-shape surface damage.

• 대한기계학회논문집A
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• 제27권6호
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• pp.914-922
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• 2003

In this paper, the strain localization of voided ductile material has been analyzed by nonlocal plasticity formulation in which the yield strength not only depends on an equivalent plastic strain measure (hardening parameter), but also on the Laplacian thereof. The gradient terms in yield criterion show an important role on modeling strain-softening phenomena of material. The influence of the mesh size on the elastic -plastic deformation behavior and the effect of the characteristic length parameter for localization prediction are also investigated. The proposed nonlocal plasticity shows that the load -strain curves converge to one curve. Results using nonlocal plasticity also exhibit the dependence of mesh size is much less sensitivity than that for a corresponding local plasticity formulation.

• KCI Concrete Journal
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• 제13권1호
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• pp.35-41
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• 2001

This paper investigated rheological properties of binder pastes for self-compacting high performance concrete. Six mixtures of self-compacting concrete were initially prepared and tested to estimate self-compacting property. Then, the binder pastes used in self-compacting concrete were tested for rheological properties using a rotary type rheometer. Binder pastes with different water-binder ratios arid flow values were also examined to evaluate their rheological characteristics. The binders were composed of ordinary Portland cement, fly ash, two types of pulverized blast-furnace slag, and limestone powder. The flow curves of binder pastes were obtained by a rotary type rheometer with shear rate control. Slump flow, O-funnel time, box, and L-flow teats were carried out to estimate self-compacting property of concrete. The flow curves of binder pastes for self-compacting concrete had negligible yield stresses and showed an approximately linear behavior at higher shear rates beyond a certain limit. Test results also indicated that the binders incorporating fly ash are more appropriate than the other types of binders in quality control of self-compacting concrete.

• 소성∙가공
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• 제1권1호
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• pp.33-41
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• 1992

Sintered P/M connecting rod is forged to increase density and to satisfy dimensional specifications. Flow of the materials is different form that of wrought materials due to pores in the preform. The Mises yield function was modified to. include the first invariant of stress tensor, and the associated flow rule was derived by applying the normality rule to the yield function. Axisymmetric and plane-strain finite element analyes were carried out for the ring and beam portions of the connecting rod, respectively. The flow of the preform and density change of the analysis are presented in this paper. A load-stroke curve was also presented by superimposing analysis results for the ring and beam portions.