• Structural Engineering and Mechanics
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• 제22권5호
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• pp.563-574
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• 2006

This paper studies mechanical behavior of the superelastic shape memory alloy (SMA) rods in terms of local deformations and time via tensile loading-unloading cycles for both ends fixed end constraints. Besides the unique stress induced martensitic transformation (SIMT), SMA's time dependent behavior when it is in mixed-phase condition upon loading and unloading, also need careful attention with a view of investigating the local deformation of the structural elements made of the same material. With this perspective, the so-called stress-relaxation tests have been performed to demonstrate and investigate the local strains-total strains relationships with time, particularly, during the forward SIMT. Some remarkable phenomena have been observed pertaining to SIMT, which are absent in traditional materials and those unique phenomena have been explained qualitatively. For example, at the stopped loading conditions the two ends (fixed end and moving end of the tensile testing machine) were in fixed positions. So that there was no axial overall deformation of the specimen but some notable increase in the axial local deformation was shown by the extensometer placed at the middle of the SMA specimen. It should be noted that this peculiar behavior termed as 'inertia driven SIMT' occurs only when the loading was stopped at mixed phase condition. Besides this relaxation test for the SMA specimens, the same is performed for the mild steel (MS) specimens under similar test conditions. The MS specimens, however, show no unusual increase of local strains during the stress relaxation tests.

• 한국지구과학회지
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• 제25권3호
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• pp.142-151
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• 2004

This study was designed to determine whether visitor behavior at science museums differs across various exhibit styles and between Family and Non Family groups. Eight exhibits in the natural history sections of the national science museum located in Daejeon were identified to have distinctive characteristics and styles. At each selected exhibit, visitor behavior was observed for an hour. An average of eighty people stopped by each exhibit. Descriptive analyses of visitors behaviors showed that: 1) families spent more time than non-family visitors; 2) families paid more attention to exhibits, for instance, they talked and commented about the exhibits; 3) exhibit characteristics related to holding power and attention span; 4) families more frequently visited exhibits related to school curriculum rather than ones that looked attractive, fun or novel. Visitors did not play with sensory simulation types of exhibits as much as expected. This implicates that exhibit style does not guarantee long visitors holding time and attracting power. Non-significant results are explained in terms of environmental and exhibit-related factors. Several potential factors including visitor factors, setting factors, and exhibit factors are discussed and explored with topics proposed for future study.

• Geomechanics and Engineering
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• 제6권6호
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• pp.531-544
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• 2014

Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Nonlinear behavior of soils during a seismic event has a predominant role in current site response analysis approaches. Common approaches to ground response analysis include linear, equivalent linear and nonlinear methods. These methods of ground response analysis may also be categorized into time domain and frequency domain concepts. Simplicity in developing analytical relations and accuracy in considering soils' dynamic properties dependency to loading frequency are benefits of frequency domain analysis. On the other hand, nonlinear methods are complicated and time consuming mainly because of their step by step integrations in time intervals. In part Ι of this paper, governing equations for seismic response analysis of surcharged and layered soils were developed using fundamental of wave propagation theory based on transfer function and boundary conditions. In this part, nonlinear seismic ground response is analyzed using extended HFTD method. The extended HFTD method benefits Newton-Raphson procedure which applies regular iterations and follows soils' fundamental stress-strain curve until convergence is achieved. The nonlinear HFTD approach developed here are applied to some examples presented in this part of the paper. Case studies are carried in which effects of some influencing parameters on the response are investigated. Results show that the current approach is sufficiently accurate, efficient, and fast converging. Discussions on the results obtained are presented throughout this part of the paper.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.988-1003
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• 2021

Existing elastic analysis methods cannot be adhered to in order to assess the structural integrity of a reactor vessel and internals for a beyond design basis earthquake. Elasto-plastic analysis methods are required, and the factors that affect the elasto-plastic behavior of reactor materials should be taken into account. In this study, a material behavior model was developed that considers the irradiation embrittlement effect, which affects the elasto-plastic behavior of the reactor material. This was used to perform the elasto-plastic time history analyses of the reactor vessel and its internals for beyond design basis earthquake. For this investigation, appropriate beyond design basis earthquakes and reliable finite element models were used. Based on the analysis results, consideration was given to the load reduction effect and the margin change. These were transferred to the internals due to the plastic deformation of the reactor vessel.

• 한국기계기술학회지
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• 제20권6호
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• pp.745-750
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• 2018

In this study, the thermal behavior of adaptor housing was analyzed by the numerical method. The boundary conditions used to die casting process were the temperature of molten metal and injection time. As the temperature of the molten metal increased, the tensile strength of the product decreased by the blow hole generated in the molten metal, and the decreasing tendency was gradually decreased. As the injection time of the molten metal increased, the heat flux rose, but the degree of the increase was very small. So, the injection time of the molten metal had little effect on the thermal behavior and diffusion of the adapter housing. As a result, the heat of the molten metal was transferred into the housing and the thermal behavior spread widely.

• Design & Manufacturing
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• 제17권1호
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• pp.1-5
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• 2023

In multi-material injection molding, since two or more materials with different process conditions are used, it is essential to maximize process efficiency by operating the cooling or heating system to a minimum. In this study, Liquid silicone rubber (LSR) that can be cured at a low temperature suitable for the multi-material injection molding was selected and the cure behavior according to the process conditions was analyzed through differential scanning calorimetry (DSC). Dynamic measurement results of DSC with different heating rate were obtained, and through this, the total heat of reaction when the LSR was completely cured was calculated. Isothermal measurement results of DSC were derived for 60 minutes at each temperature from 80 ℃ to 110 ℃ at 10 ℃ intervals, and the final degree of cure at each temperature was calculated based on the total heat of reaction identified from the Dynamic DSC measurement results. As the result, it was found that when the temperature is lowered, the curing start time and the time required for the curing reaction increase, but at a temperature of 90 ℃ or higher, LSR can secure a degree of cure of 80% or more. However, at 80 ℃., it was found that not only had a relatively low degree of curing of about 60%, but also significantly increased the curing start time. In addition, in the case of 110 ℃, the parameters were derived from experimental result using the Kamal kinetic model.

• Structural Engineering and Mechanics
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• 제90권2호
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• pp.189-208
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• 2024

Artificial intelligence is one of the efficient methods that can be developed to simulate nonlinear behavior and predict the response of building structures. In this regard, an adaptive method based on optimization algorithms is used to train the TSK model of the fuzzy inference system to estimate the seismic behavior of building structures based on analytical data. The optimization algorithm is implemented to determine the parameters of the TSK model based on the minimization of prediction error for the training data set. The adaptive training is designed on the feedback of the results of previous time steps, in which three training cases of 2, 5, and 10 previous time steps were used. The training data is collected from the results of nonlinear time history analysis under 100 ground motion records with different seismic properties. Also, 10 records were used to test the inference system. The performance of the proposed inference system is evaluated on two 3 and 20-story models of nonlinear steel moment frame. The results show that the inference system of the TSK model by combining the optimization method is an efficient computational method for predicting the response of nonlinear structures. Meanwhile, the multi-vers optimization (MVO) algorithm is more accurate in determining the optimal parameters of the TSK model. Also, the accuracy of the results increases significantly with increasing the number of previous steps.

• 한국심리학회지 : 문화 및 사회문제
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• 제14권2호
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• pp.63-81
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• 2008

서두름 행동은 행동의 속도를 높여 최적의 목표를 달성하는 것을 말한다. 따라서 현재 하고 있는 행동의 속도를 높이면서 목표달성을 위해 최적의 방법을 사용하는 특성을 가진다. 서두름 행동은 전적으로 좋다 혹은 나쁘다고 단정질 수 없으며, 자신의 목표를 빨리 달성하고자 하는 의지는 성취동기를 반영한다. 그러나 동시에 이러한 의지는 어떤 행동을 생략함으로써 오류행동을 발생시킬 수도 있다. 서두름 행동의 심리적 구조 및 그 특성을 살펴보고자 191명을 대상으로 서두름 행동 질문지와 성취동기척도, 성격 5요인 검사를 실시하였으며, 결측치가 많은 응답자를 제외한 188명의 자료를 분석하였다. 서두름 행동 문항을 분석한 결과, 서두름 행동은 불편함, 시간압력, 고립, 지루함, 보상기대라는 5개의 상황 요인 아래에서 발생하는 것으로 밝혀졌다. 서두름 행동을 구성하는 5요인들의 상관분석 및 서두름 행동과 성취동기의 관계를 분석한 결과, 서두름 행동은 크게 속도를 높임으로써 발생하는 '확인생략행동'과 자신의 과업을 잘하려고 하는 '성취욕구'로 이루어져 있었다. 그리고 서두름 행동을 구성하는 5요인 가운데 시간압력이 '확인생략행동'과 '성취욕구'에 공통으로 작용하고 있었다. 서두름 행동의 특성을 살펴보고자 서두름 행동의 2개 영역과 성격 5요인의 관계를 분석하였다. 그 결과, '확인생략행동'은 성격 5요인의 신경증과 정적 상관이 있는데 반해, 성실성과는 부적 상관이 있었다. 한편, '성취욕구'는 성격 5요인의 외향성과 정적 상관을 보였다.

• 대한간호학회지
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• 제35권1호
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• pp.5-15
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• 2005

Purpose: This study was conducted to develop a behavioral checklist to predict an autistic disorder and to identify the earliest detecting time. Method: One hundred and fifty eight children including normal, autistic, institutionalized normal, and retarded were assessed using critical interaction behavioral markers from literature review. Data was collected by semi-structured mother-child interaction by videotape recording and analyzed byfactor analysis, Cronbach a, Kappa, $x^2$, and Duncan. Result: Ten behavioral markers were sorted into 2 factors; joint-attention and synchronized behavior. Autistic children were impaired in pretend play, odeclarative pointing, proimperative pointing, gaze-monitoring, referential looking, showing, joint-attention, rhythmical vocal exchange, and synchronized laughing. The sychronized behavior was also a critical marker to predict the autistic disorder. However, it was difficult to differentiate autistic disorder from mental retardation. In addition, the appropriate detecting time was around 18 months after birth. Conclusion: This checklist should be behavior markers to predict autistic disorder and could be useful as educational material at children's clinics, parents class, and for caregivers in the health center. In addition, early detection should lead to treatment being started as soon after 18 months of age as possible.

• 콘크리트학회논문집
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• 제13권1호
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• pp.77-85
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• 2001

CFT 기둥은 뛰어난 구조적 성능으로 사용이 증가하고 있는 추세이다. 하지만 CFT 기둥을 사용하여 건설된 구조물도 내부콘크리트의 시간의존적 변형으로 사용상태에 이상 응력집중이나 과다 처짐 등의 구조적 문제를 초래할 수 있다. 따라서 이에 대한 연구가 필요하다. 본 논문에서는 CFT 기둥에 하중이 가해지는 시점에서의 해석법과 이를 기초로 한 장기거동 해석법을 제안하였다. 또한 이에 대한 실험을 실시하여 해석결과와 비교.분석하였다. 이를 통해 제안된 해석법을 검증하고 아울러 해석에 적용된 부착강도 모델식의 정확성 또한 평가하였다.