• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.110-123
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• 2005

This paper proposes an intelligent method for the optimal load distribution of two cooperating robots(TCRs) using fuzzy logic. The proposed scheme requires the knowledge of the robots' dynamics, which in turn depend upon the characteristics of large flat panel displays(LFPDs) carried by the TCRs. However, the dynamic properties of the LFPD are not known exactly, so that the dynamics of the robots, and hence the required joint torque, must be calculated for nominal set of the LFPD characteristics. The force of the TCRs is an important factor in carrying the LFPD. It is divided into external force and internal force. In general , the effects of the internal force of the TCRs are not considered in performing the load distribution in terms of optimal time, but they are essential in optimal trajectory planning: if they are not taken into consideration, the optimal scheme is no longer fitting. To alleviate this deficiency, we present an algorithm for finding the internal-force factors for the TCRs in terms of optimal time. The effectiveness of the proposed system is demonstrated by computer simulations using two three-joint planner robot manipulators.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.233-245
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• 2007

Previous finite element studies have shown that AASHTO Standard load distribution factor (LDF) equations appear to be conservative for longer spans and larger girder spacing, but too permissible for short spans and girder spacing. AASHTO LRFD specification defines the distribution factor equation for girder spacing, span length, slab thickness, and longitudinal stiffness. However, this equation requires an iterative procedure to correctly determine the LDF value due to an initially unknown longitudinal stiffness parameter. This study presents a simplified LDF equation for interior and exterior girders of two-span continuous I-girder bridges that does not require an iterative design procedure. The finite element method was used to investigate the effect of girder spacing, span length, slab thickness, slab width, and spacing and size of bracing. The computer program, GTSTRUDL, was used to idealize the bridge superstructures as the eccentric beam model, the concrete slab by quadrilateral shell elements, steel girders by space frame members, and the composite action between these elements by rigid links. The distribution factors obtained from these analyses were compared with those from the AASHTO Standard and LRFD methods. It was observed through the parametric studies that girder spacing, span length, and slab thickness were the dominant parameters compared with others. The LRFD distribution factor for the interior girder was found to be conservative in most cases, whereas the factor for the exterior girder to be unconservative in longer spans. Furthermore, a regression analysis was performed to develop simplified LDF formulas. The formulas developed in this study produced LDF values that are always conservative to those from the finite element method and are generally smaller than the LDF values obtained from the AASHTO LRFD specification. The proposed simplified equation will assist bridge engineers in predicting the actual LDF in two-span continuous I-girder bridges.

• Journal of Distribution Science
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• v.19 no.12
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• pp.15-22
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• 2021

Purpose: There is still lack of guidance for merchants toward price discount presentations (absolute/relative), especially for consumers in different purchase contexts. Based on the general evaluability theory, this study investigates consumers' preferences for the presentation of discounts in various contexts through experiments. Research design, data and methodology: The relationship between discount presentation and consumers' preference is investigated in Study 1 using a two-factor between-subject design of 2 (purchase type: material vs. experiential) ×2 (discount type: absolute vs. relative). The Moderating effect of thinking mode has been examined in Study 2 via a multi-factor intergroup design of 2 (purchase type: material vs. experiential) ×2 (discount type: absolute vs. relative) ×2 (cognitive load: high vs. low). One-way ANOVA and planned contrast have been performed for analysis. Results: Experiment 1 reveals that consumers prefer absolute discounts rather than relative discounts when in material purchases. However, when in experiential purchases, they are willing to choose relative discounts. Experiment 2 verifies the boundary conditions of matching effect and illustrates the generation of matching effect is determined by thinking mode. Conclusions: Our study enriches the theories of purchase type and thinking mode. Simultaneously, the results provide practical guidance for merchants to formulate the discount presentation and distribution pricing strategies.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.311-313
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• 2006

전력계통의 안정적 운용을 위한 EMS(Energy Management System)에서 현재 운용중인 계통의 상태를 추정하는 상태추정기는 매우 중요한 역할을 지닌다. 그러나 간혹 측정된 데이터가 잘못된 정보이거나, 데이터가 전송되지 않는 경우 가관측성이 확보되지 않게 될 수 있는데 이때는 의사측정값(pseudo measurements)을 이용하여 가관측성을 확보해 주어야 한다. 본 연구에서는 상태추정의 부하 데이터의 부재시사용하기 위한 모선별 부하분포계수(Bus Load Distribution Factor)에 관하여 소개하며, 그 오차를 최소한으로 줄이기 위해 사용하는 평활법에 대해 소개한다.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.199-207
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• 2006

Before getting to the actual study of the load distribution factor in various excavating methods, this research is preliminarily focused on the comparison of two different excavation methods, CD cut method and Ringcut method. Especially, the purpose of this research is to study the behavioral mechanism of two tunnels which share the same construction environment but different excavating method. Two numerical analysis models with the same tunnel section and material properties are compared in this study, and they are analyzed by 3D Finite Element Analysis. In each model, face stability, crown displacement, ground settlement, and shotcrete-lining stress are computed. Thus, the general behavior of CD cut method and Ringcut method are studied, and it certified what should be considered for the calculation of the load distribution factor.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.51-57
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• 1998

It is common to assume identical allowable safety factors in static strength defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety (actors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and a normal distribution. The calculation of fatigue reliability fur limited life is discussed with example.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.236-243
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• 2005

Nonlinear static analysis is used to quantify the resistance of the structure to lateral deformation and to gauge the mode of deformation and intensity of local demands. A simple method for the nonlinear static analysis of complex building structures subjected to monotonically increasing horizontal loading(pushover analysis) is presented. The method is designed to be a part of new methodologies for the seismic design and evaluation of structures. A variety of existing pushover analysis procedures are currently being consolidated under programs such as ATC 40 and FEMA 273. And various techniques have been recommended, including the use of constant lateral force profiles and the use of adaptive and multimodal approaches. In this paper a modal pushover analysis using design response spectra of UBC 97 is proposed. Proposed method is compared against the method in FEMA 273 and ATC 40, and results of time history analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.35-40
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• 2019

The objective of this paper is to identify the fatigue properties of carbon-fiber composite which is widely applied for the development of aircraft structures and obtain data for full-scale fatigue test. The durability and damage tolerance evaluation of composite structures is achieved by fatigue tests and parameters such as fatigue life factor and load enhancement factor. The specimens are made with carbon-fiber/epoxy UD tape and fabric prepreg. Fatigue tests are performed with several stress ratios and lay-up patterns. The Weibull shape parameters are analyzed by Sendeckyj model and individual fatigue lives with Weibull distribution. And the fatigue life factor and load enhancement factor considering reliability are evaluated.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.9-14
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• 2008

In the case of horizontally curved bridges, the use of curved composite box girder bridges are increased due to its functionality and for aesthetical reason. As it compared with the open section, the steel box girder bridges have advantages to resistant of distortion and corrosion. In practice the grid analysis is conducted by utilizing only the cross beam. Since the stiffness of the concrete slab is not included in the grid analysis, the cross beam is induced the distribution of the live load. In this study the affects of the radius of curvature, the number of diaphragm and cross beam to the load distribution of the curved steel box girder bridge was investigated by applying the finite element method. The results indicate that the curvature of curved bridge had a large affect of the load distribution and as the curvature was increased the load distribution factor was increased. A single diaphragm at the center of girder is important role for the load distribution effects and structural stability, but additional diaphragm did not affect it as much. The affects of the cross beam to the load distribution were investigated and its influence was minor. It can be safely concluded that the addition of cross beam does not aid the purpose of the live load distribution. And the stiffness of concrete slab for the load distribution effects should be concerned in the design of curved steel box girder bridges.

• Steel and Composite Structures
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• v.51 no.2
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• pp.203-223
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• 2024

This study shows functionally graded material structural topology optimization under buckling constraints. The SIMP (Solid Isotropic Material with Penalization) material model is used and a method of moving asymptotes is also employed to update topology design variables. In this study, the quadrilateral element is applied to compute buckling load factors. Instead of artificial density properties, functionally graded materials are newly assigned to distribute optimal topology materials depending on the buckling load factors in a given design domain. Buckling load factor formulations are derived and confirmed by the resistance of functionally graded material properties. However, buckling constraints for functionally graded material topology optimization have not been dealt with in single material. Therefore, this study aims to find the minimum compliance topology optimization and the buckling load factor in designing the structures under buckling constraints and generate the functionally graded material distribution with asymmetric stiffness properties that minimize the compliance. Numerical examples verify the superiority and reliability of the present method.