• 제목/요약/키워드: SET/SEM

검색결과 398건 처리시간 0.025초

The empirical corner stiffness for right-angle frames of rectangular and H-type cross-sections

  • Kwon, Young-Doo;Kwon, Soon-Bum;Gil, Hyuck-Moon;Cho, Hui-Jeong
    • Structural Engineering and Mechanics
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    • 제51권3호
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    • pp.471-485
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    • 2014
  • Until now, the finite corner stiffness of the right-angle frames used as horizontal girders in a bonnet, have not been considered during the design process to result in not a precise result. This paper presents a design equation set for right-angle frames used as horizontal girders in a bonnet assuming rigid corner stiffness. By comparing the center stresses of the right-angle frame according to the design equation set with the results of the finite element method, the master curves for the empirical corner stiffness can be determined as a function of slenderness ratio. A second design equation set for a right-angle frame assuming finite corner stiffness was derived and compared with the first equation set. The master curves for the corner stiffness and the second design equation set can be used to determine the design moments at the centers of the girder so that the bending stresses can be analyzed more precisely.

취업스트레스, 외모인식, 재무스트레스, 정부신뢰도, 내외통제성이 대학생의 행복에 미치는 영향 (The Effects of Job-Seeking Stress, Appearance Recognition, Financial Distress, Trust in Government, and Locus of Control on University Students' Happiness)

  • 김민구;이경근;이석용;전준하;한용희
    • 산업경영시스템학회지
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    • 제40권4호
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    • pp.171-182
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    • 2017
  • Most people seek a happy life and happiness positively affects sentiment, satisfaction with life, creativity, human relationship, business productivity, and even health and life extension. However, according to a survey in 2013, subjective happiness of adolescents (including university students) was very low compared to other age groups in Korea. Therefore this paper examined the effects of job-seeking stress, appearance recognition, financial situation, trust in government, and locus of control on university students' happiness using SEM (structural equation modeling). 207 university students in Seoul, Korea have been surveyed. At first, an initial experimental SEM model among these variables has been set up and reliability analysis has been conducted. Then multiple regression analyses on job-seeking stress and happiness as well as SEM analysis have been conducted. As a result of these analyses, the SEM model has been revised two times. The final SEM model passed the goodness-of-fit test (using RMR, GFI, NFI, CFI, and IFI indices). The final SEM model showed the followings. First, Higher job-seeking stress (especially sentimental part, rather than environment or action related parts) negatively affects happiness. Second, Trust in government also affects happiness both directly and indirectly. Third, Locus of control is affected both by trust in government and financial situation. Fourth, appearance recognition heavily affects job-seeking stress. In addition, appearance importance is higher than appearance interest, meaning that students who are not very interested in appearance usually recognize the importance of appearance. Finally, happiness is affected neither financial situation nor appearance recognition. Therefore, even either they are in a poor financial situation or not happy with their appearance, they can be happy if they have firm locus of control.

국내 MIS 연구에서 구조방정식모형 활용에 관한 메타분석 (A Meta Analysis of Using Structural Equation Model on the Korean MIS Research)

  • 김종기;전진환
    • Asia pacific journal of information systems
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    • 제19권4호
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    • pp.47-75
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    • 2009
  • Recently, researches on Management Information Systems (MIS) have laid out theoretical foundation and academic paradigms by introducing diverse theories, themes, and methodologies. Especially, academic paradigms of MIS encourage a user-friendly approach by developing the technologies from the users' perspectives, which reflects the existence of strong causal relationships between information systems and user's behavior. As in other areas in social science the use of structural equation modeling (SEM) has rapidly increased in recent years especially in the MIS area. The SEM technique is important because it provides powerful ways to address key IS research problems. It also has a unique ability to simultaneously examine a series of casual relationships while analyzing multiple independent and dependent variables all at the same time. In spite of providing many benefits to the MIS researchers, there are some potential pitfalls with the analytical technique. The research objective of this study is to provide some guidelines for an appropriate use of SEM based on the assessment of current practice of using SEM in the MIS research. This study focuses on several statistical issues related to the use of SEM in the MIS research. Selected articles are assessed in three parts through the meta analysis. The first part is related to the initial specification of theoretical model of interest. The second is about data screening prior to model estimation and testing. And the last part concerns estimation and testing of theoretical models based on empirical data. This study reviewed the use of SEM in 164 empirical research articles published in four major MIS journals in Korea (APJIS, ISR, JIS and JITAM) from 1991 to 2007. APJIS, ISR, JIS and JITAM accounted for 73, 17, 58, and 16 of the total number of applications, respectively. The number of published applications has been increased over time. LISREL was the most frequently used SEM software among MIS researchers (97 studies (59.15%)), followed by AMOS (45 studies (27.44%)). In the first part, regarding issues related to the initial specification of theoretical model of interest, all of the studies have used cross-sectional data. The studies that use cross-sectional data may be able to better explain their structural model as a set of relationships. Most of SEM studies, meanwhile, have employed. confirmatory-type analysis (146 articles (89%)). For the model specification issue about model formulation, 159 (96.9%) of the studies were the full structural equation model. For only 5 researches, SEM was used for the measurement model with a set of observed variables. The average sample size for all models was 365.41, with some models retaining a sample as small as 50 and as large as 500. The second part of the issue is related to data screening prior to model estimation and testing. Data screening is important for researchers particularly in defining how they deal with missing values. Overall, discussion of data screening was reported in 118 (71.95%) of the studies while there was no study discussing evidence of multivariate normality for the models. On the third part, issues related to the estimation and testing of theoretical models on empirical data, assessing model fit is one of most important issues because it provides adequate statistical power for research models. There were multiple fit indices used in the SEM applications. The test was reported in the most of studies (146 (89%)), whereas normed-test was reported less frequently (65 studies (39.64%)). It is important that normed- of 3 or lower is required for adequate model fit. The most popular model fit indices were GFI (109 (66.46%)), AGFI (84 (51.22%)), NFI (44 (47.56%)), RMR (42 (25.61%)), CFI (59 (35.98%)), RMSEA (62 (37.80)), and NNFI (48 (29.27%)). Regarding the test of construct validity, convergent validity has been examined in 109 studies (66.46%) and discriminant validity in 98 (59.76%). 81 studies (49.39%) have reported the average variance extracted (AVE). However, there was little discussion of direct (47 (28.66%)), indirect, and total effect in the SEM models. Based on these findings, we suggest general guidelines for the use of SEM and propose some recommendations on concerning issues of latent variables models, raw data, sample size, data screening, reporting parameter estimated, model fit statistics, multivariate normality, confirmatory factor analysis, reliabilities and the decomposition of effects.

VR 특성이 이용자 만족과 지속이용의도에 미치는 영향에 관한 연구 -VR 프레즌스, 이용자 특성, VR 멀미를 중심으로- (Study on the Influence of VR Characteristics on User Satisfaction and Intention to Use Continuously -Focusing on VR Presence, User Characteristics, and VR Sickness-)

  • 장형준;김광호
    • 한국콘텐츠학회논문지
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    • 제18권5호
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    • pp.420-431
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    • 2018
  • 본 연구는 가상현실(VR)을 주제로 이용자 관점에서 프레즌스를 기반으로 만족과 지속 이용 의도에 관한 주제로 접근하였다. 설문조사 기관을 통해 의뢰한 569명의 남녀 이용자들이 느끼는 만족과 이를 매개로 한 지속 이용 의도에 대한 연구를 진행하였다. 연구 내용에서는 독립변수인 VR 프레즌스의 구성 요인을 사실감이나 몰입감, 상호작용으로 설정 하였다. 이용자 특성은 개인의 혁신적 성향이나 몰입의 정도, VR 이용 경험으로 설정 하였다. VR 프레즌스와 이용자 특성 그리고 어지러움이나 시각적 피로도로 대표되는 VR 멀미가 콘텐츠 만족과 시스템 만족에 미치는 관계와 지속 이용 의도에 대해 연구 문제와 모델을 제시하였다. 구조방정식(SEM) 모델을 적용한 연구 문제의 해석으로는 8개의 가설이 모두 채택되었다. 결론에서 VR 콘텐츠의 만족을 높이는 요인과 지속적 이용 의도에 가장 큰 영향력으로 작용하는 콘텐츠 만족이 본 연구가 제시하는 핵심 시사점으로 나타났다.

A study of hydroxyapatite coating on Ti-6Al-4V alloy with different surface treatments using a sol-gel derived precursor

  • Balakrishnan Avinash;Kim Yun-Jong;Lee Seung-Woo;Kim Taik-Nam
    • 공학논문집
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    • 제6권1호
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    • pp.161-168
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    • 2004
  • In the present study, a simple method was successfully used for hydroxyapatite coatings on Ti-6AL-4V substrates deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coating the samples were micropolished (0.1 micron) and divided into three sets. The first set, were the micropolished samples kept as such. The second set were coated with titania sol and the third set was treated with 5M NaOH. After three repetitions of hydroxyapatite coating procedures on each set and heat treatment at $600^{\circ}C$, the formation of hydroxyapatite has been confirmed by XRD analyses and the substrate material was found to be oxidized with negligible amount of CaO in the coating. The SEM studies revealed surface morphology. Hydroxyapatite, calcined at $600^{\circ}C$, displaying a porous structure arisen from heating of the bulk

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Sol-Gel 성형체에 의해 다르게 표면 처리된 치과 Implant용 Ti-6Al-4V합금의 Hydroxyapatite 코팅에 관한 연구 (A study of hydroxyapatite coating on Ti-6Al-4V dental implant alloy with different surface treatments using a sol-gel derived precursor)

  • 한석윤
    • 대한치과기공학회지
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    • 제26권1호
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    • pp.139-144
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    • 2004
  • In the present study, a simple method was successfully used for hydroxyapatite coatings on Ti-6Al-4V substrates deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coating the samples were micropolished (0.1 micron) and divided into three sets. The first set,were the micropolished samples kept as such. The second set were coated with titania sol and the third set was treated with 5M NaOH. After three repetitions of hydroxyapatite coating procedures on each set and heat treatment at 600 $^{\circ}\Delta C$, the formation of hydroxyapatite has been confirmed by XRD analyses and the substrate material was found to be oxidized with negligible amount of CaO in the coating. The SEM studies revealed surface morphology. Hydroxyapatite, calcined at 600$^{\circ}\Delta C$, displaying a porous structure arisen from heating of the bulk. But, it is very meaningful in trying to approach morale management plans with an object of dental technicians. It is necessary that dental technicians should make efforts to control themselves.

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Rapid S-N type life estimation for low cycle fatigue of high-strength steels at a low ambient temperature

  • Feng, Liuyang;Qian, Xudong
    • Steel and Composite Structures
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    • 제33권6호
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    • pp.777-792
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    • 2019
  • This paper presents a new efficient approach to estimate the S-N type fatigue life assessment curve for S550 high strength steels under low-cycle actions at -60℃. The proposed approach combines a single set of monotonic tension test and one set of fatigue tests to determine the key material damage parameters in the continuum damage mechanics framework. The experimental program in this study examines both the material response under low-cycle actions. The microstructural mechanisms revealed by the Scanning Electron Microscopy (SEM) at the low temperature, furthermore, characterizes the effect due to different strain ratios and low temperature on the low-cycle fatigue life of S550 steels. Anchored on the experimental results, this study validates the S-N curve determined from the proposed approach. The S-N type curve determined from one set of fatigue tests and one set of monotonic tension tests estimates the fatigue life of all specimens under different strain ratios satisfactorily.

Tensile and fracture characterization using a simplified digital image correlation test set-up

  • Kumar, Abhishek;Vishnuvardhan, S.;Murthy, A. Ramachandra;Raghava, G.
    • Structural Engineering and Mechanics
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    • 제69권4호
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    • pp.467-477
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    • 2019
  • Digital image correlation (DIC) is now a popular and extensively used full-field metrology technique. In general, DIC is performed by using a turnkey solution offered by various manufacturers of DIC. In this paper, a simple and economical set-up for DIC is proposed which uses easily accessible digital single-lens reflex (DSLR) camera rather than industrial couple-charged device (CCD) cameras. The paper gives a description of aspects of carrying a DIC experiment which includes experimental set-up, specimen preparation, image acquisition and analysis. The details provided here will be helpful to carry DIC experiments without specialized DIC testing rig. To validate the responses obtained from proposed DIC set-up, tension and fatigue tests on specimens made of IS 2062 Gr. E300 steel are determined. Tensile parameters for a flat specimen and stress intensity factor for an eccentrically-loaded single edge notch tension specimen are evaluated from results of DIC experiment. Results obtained from proposed DIC experiments are compared with those obtained from conventional methods and are found to be in close agreement. It is also noted that the high resolution of DSLR allows the use of proposed approach for fracture characterization which could not be carried out with a typical turnkey DIC solution employing a camera of 2MP resolution.

승용차 운전자에 대한 사용성 평가 구조 모형 개발 (Development of a Usability Evaluation Structural Model on Car Driver)

  • 박준수;박성준;임영재;정의승
    • 대한인간공학회지
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    • 제29권6호
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    • pp.843-851
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    • 2010
  • This study aims to systematically develop a usability evaluation model using the Structural Equation Model (SEM) from experiment of usability on using vehicle. Vehicle developers have been adding many functions for enhance the user satisfaction. But it will be made the trade-off problem of usability and design elements of vehicle interior from attempt to make best usability satisfaction in a restricted space. To solve the trade-off problem, we set a new solution criterion from usability evaluation model. The usability experiment is based on major activity pool from derived user's acts pattern in vehicle for make more accurate usability evaluation model. And this model was built with twenty-nine measurement variables for the evaluation of usability of vehicle user. As a result, the proposed SEM model showed statistical significance as well as a high level of R Square (0.7144). This model shows the relationships of detailed usability and design elements. According to the result, this study introduces the criterion to secure the best satisfaction of usability and design elements.

미세구조 분석방법을 활용한 서로 다른 밀도를 가진 기포콘크리트 특성 분석 (Investigation of Microstructural Characteristics of Foamed Concrete with Different Densities)

  • 정상엽;조수성;오서은
    • 대한토목학회논문집
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    • 제43권1호
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    • pp.1-7
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    • 2023
  • 서로 다른 밀도를 가진 기포콘크리트 시편을 생성하고, 각 시편의 특성을 SEM, micro-CT 등의 미세구조 분석 방법을 활용하여 분석하였다. 서로 다른 재령 일자에 대한 기포콘크리트 시편의 공극과 고체 구조를 분석함으로써, 재령 기간이 재료 특성 변화에 미치는 영향을 살펴보았다. 각 기포콘크리트 시편의 압축강도와 열전도도를 측정하여, 재료 물성과 미세구조적 특성 간의 상관관계에 대하여 분석하였으며, 결과를 통해 밀도와 재령 기간이 재료 강도에 미치는 영향을 확인하였다.