• Earthquakes and Structures
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• 제14권6호
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• pp.525-535
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• 2018

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

• 유통과학연구
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• 제21권2호
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• pp.35-43
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• 2023

Purpose: As Thailand seeks to become a regional startup hub, Thai startups have been acquiring growth and scalability in the last ten years. Hence, this paper examines influential factors in Thailand's growth of logistics tech startups. The conceptual framework incorporates sensing user needs, sensing technological options, conceptualizing, scaling, and stretching, co-producing, and orchestrating, business strategy, strategic flexibility, and startup growth. Research design, data, and methodology: The quantitative method was applied to distribute the questionnaire to 500 managers and above in logistics tech startups in Thailand. The sampling techniques involve judgmental, convenience, and snowball samplings. Before the data collection, The Item Objective Congruence (IOC) Index and pilot test (n=45) were employed for content validity and reliability. The data were mainly analyzed by Confirmatory Factor Analysis (CFA) and Structural Equation Model (SEM). Results: The findings revealed that sensing technological options, scaling, and stretching, co-producing, and orchestrating, and business strategy significantly influence the growth of startups in Thailand. Nevertheless, sensing user needs, conceptualizing, and strategic flexibility have no significant relationship with startup growth. Conclusions: For Thailand to accelerate its digital economy driven by tech startups, firms must emphasize influential factors to accelerate growth by providing the right tech solutions for people's lives.

• 유통과학연구
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• 제22권4호
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• pp.69-77
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• 2024

Purpose: This paper aims to tackle the challenges and opportunities of cities' response to COVID-19 and provide cities with policy implications for better adapting to the post-pandemic era. Cities around the world are facing new challenges and have had to adapt to maintain social distancing measures while also addressing equity and social inclusion issues. Research design, data and methodology: The research methodology relies on an examination of existing literature, coupled with trend analysis employing discourse analysis to investigate post-pandemic urban resilience. The article also attempts to employ the concepts of adaptive urbanism and spatial flexibility and their potential to address these challenges not only in response to the pandemic, but also in the long-term. Results: The article explores the impact of COVID-19 on urban spatial structure through a public health lens and proposes actions that cities are able to take to enhance their resilience in the aftermath of the pandemic. Conclusions: It underscores the significance of reconstructing with improved distribution dynamics and provides valuable guidance for companies and policymakers on navigating these challenges. Ultimately, it also suggests that the pandemic has initiated a worldwide restructuring of urban planning, potentially leading to the emergence of smart cities grounded in science and technology.

• Structural Engineering and Mechanics
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• 제71권4호
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• pp.391-405
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• 2019

Compared to the ambient vibration test mainly identifying the structural modal parameters, such as frequency, damping and mode shapes, the impact testing, which benefits from measuring both impacting forces and structural responses, has the merit to identify not only the structural modal parameters but also more detailed structural parameters, in particular flexibility. However, in traditional impact tests, an impacting hammer or artificial excitation device is employed, which restricts the efficiency of tests on various bridge structures. To resolve this problem, we propose a new method whereby a moving vehicle is taken as a continuous exciter and develop a corresponding flexibility identification theory, in which the continuous wheel forces induced by the moving vehicle is considered as structural input and the acceleration response of the bridge as the output, thus a structural flexibility matrix can be identified and then structural deflections of the bridge under arbitrary static loads can be predicted. The proposed method is more convenient, time-saving and cost-effective compared with traditional impact tests. However, because the proposed test produces a spatially continuous force while classical impact forces are spatially discrete, a new flexibility identification theory is required, and a novel structural identification method involving with equivalent load distribution, the enhanced Frequency Response Function (eFRFs) construction and modal scaling factor identification is proposed to make use of the continuous excitation force to identify the basic modal parameters as well as the structural flexibility. Laboratory and numerical examples are given, which validate the effectiveness of the proposed method. Furthermore, parametric analysis including road roughness, vehicle speed, vehicle weight, vehicle's stiffness and damping are conducted and the results obtained demonstrate that the developed method has strong robustness except that the relative error increases with the increase of measurement noise.

• 한국공간구조학회논문집
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• 제11권2호
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• pp.111-118
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• 2011

단층 래티스 돔과 같은 스페이스 프레임 구조물은 대공간을 확보하기 위하여 강접합으로 설계함으로써 경제성과 심미성 등의 장점을 확보할 수 있다. 그러나 실제 구조물의 접합상태는 완전한 강접합도, 완전한 핀접합도 아닌 접합부 상세에 따라 중간적인 특성을 나타내는 반강접합이 일반적이다. 본 연구에서는 저자 등에 의해 제안된 Step-Up Erection 공법을 적용하여 단층 라멜라 돔의 접합부 강성에 따른 시공 중의 좌굴 특성을 해석적으로 규명하였다. 얻어진 결과는 시공 Step이 증가할수록 그리고 접합부 휨강성이 핀접합에 가까울수록 좌굴내력은 감소하였으며, 좌굴모드는 시공 Step이 증가할수록, 접합부 휨강성이 강접합에 가까울수록 돔의 정점 부근에서 뜀좌굴 현상에 의한 절점좌굴이 발생하였다. 또한, 시공 Step이 낮을 경우 저면 경계부의 원주방향 부재에서 큰 인장응력 분포를 나타내었으며, 시공 Step이 증가할수록 정점 중앙부에서 큰 압축응력 분포를 보였다. 완성돔을 제외한 시공 중 Step에서는 Step이 증가할수록, 접합부 휨강성이 핀접합에 가까울수록 저면부 경선방향 부재에서 큰 인장응력 분포를 나타내었다.

• 기술혁신학회지
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• 제1권3호
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• pp.374-385
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• 1998

This study is estimates telephone service demand based on empirical studies of telecommunication service demand model. First, the telephone charge(call price index) by each location and subscription fee bring about a negative effect to telephone distribution rate: while the other explanatory variables bring about a positive effect. Second, the flexibility of telephone charge in A location(relevant location) and the flexibility between the distance of A location and B location are negative values, while the flexibility of other explanatory variables is represented in a positive value. This means that the long distance call numbers from A location to B location are in inverse proportion against the phone charge(call price index) of A location and against the distance between A location and the distance of other locations except A location, while they are in direct proportion with an average call number per minute from A location to other locations except A location, and also with subscription numbers of A location, other subscribers in locations other than A location, and the total expenditures of A location.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.189-199
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• 2020

Researchers have elaborated several accurate methods to calculate member-end rotations or moments, directly, for bridge-type structures. Recently, the concept of rotation and moment propagation (RMP) has been presented considering bending flexibility, only. Through which, in spite of moment distribution method, all joints are free resulting in rotation and moment emit throughout the structure similar to wave motion. This paper proposes a new set of closed-form equations to calculate member-end rotation or moment, directly, comprising both shear and bending flexibility. Furthermore, the authors program the algorithm of Timoshenko beam theory cooperated with the finite element. Several numerical examples, conducted on the procedures, show that the method is superior in not only the dominant algorithm but also the preciseness of results.

• 산업경영시스템학회지
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• 제24권65호
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• pp.81-88
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• 2001

In logistics decision making, Key elements in the design of any physical distribution are the location of depots and the distribution of goods from the depots to the customers. Considering open and close the depots, This paper presents a flexible analysis on the combined location-routing problem(LRP) the case for variation capacity of vehicle and customers demands each. The scenario examples are given the use of heuristic(Saving-Drop) in LRP types. The results is useful in apply to the logistics environment changes.

• Communications for Statistical Applications and Methods
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• 제21권2호
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• pp.147-160
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• 2014

In this paper, we introduce the exponentiated Weibull-geometric (EWG) distribution which generalizes two-parameter exponentiated Weibull (EW) distribution introduced by Mudholkar et al. (1995). This proposed distribution is obtained by compounding the exponentiated Weibull with geometric distribution. We derive its cumulative distribution function (CDF), hazard function and the density of the order statistics and calculate expressions for its moments and the moments of the order statistics. The hazard function of the EWG distribution can be decreasing, increasing or bathtub-shaped among others. Also, we give expressions for the Renyi and Shannon entropies. The maximum likelihood estimation is obtained by using EM-algorithm (Dempster et al., 1977; McLachlan and Krishnan, 1997). We can obtain the Bayesian estimation by using Gibbs sampler with Metropolis-Hastings algorithm. Also, we give application with real data set to show the flexibility of the EWG distribution. Finally, summary and discussion are mentioned.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.778-785
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• 2006

In this paper, two possible ways for mode shape expansion are proposed and opened for discussion for future use. The first method minimizes the modal flexibility error between the experimental and analytical mode shapes corresponding to the measured DOFs to find the multiplication matrix which can be treated as the least-squares minimization problem. In the second method, Normalized Modal Difference (NMD) is used to calculate multiplication matrix using the analytical DOFs corresponding to measured DOfs. This matrix is then used to expand the measured mode shape to unmeasured DOFs. A simulated simply supported beam is used to demonstrate the performance of the methods. These methods are then compared with two most promising existing methods namely Kidder dynamic expansion and Modal expansion methods. It is observed that the performance of the modal flexibility method is comparable with existing methods. NMD also have the potential to expand the mode shapes though it is seen more sensitive to the distribution of error between FEM and actual test data.