• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.607-620
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• 2023

The classical optimal control (COC) method has been widely used for linear quadratic regulator (LQR) problems of structural control. However, the equation of motion of the structure is incorporated into the optimization model as the constraint condition for the LQR problem, which needs to be solved through the Riccati equation under certain assumptions. In this study, an explicit optimal control (EOC) method is proposed based on the explicit time-domain method (ETDM). By use of the explicit formulation of structural responses, the LQR problem with the constraint of equation of motion can be transformed into an unconstrained optimization problem, and therefore the control law can be derived directly without solving the Riccati equation. To further optimize the weighting parameters adopted in the control law using the gradient-based optimization algorithm, the sensitivities of structural responses and control forces with respect to the weighting parameters are derived analytically based on the explicit expressions of dynamic responses of the controlled structure. Two numerical examples are investigated to demonstrate the feasibility of the EOC method and the optimization scheme for weighting parameters involved in the control law.

• Coupled systems mechanics
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• v.12 no.1
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• pp.1-20
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• 2023

On the basis of the explicit time-domain method, an investigation is performed on the influence of the rotational stiffness and rotational damping of the vehicle body and front-rear bogies on the dynamic responses of the vehicle-bridge coupled systems. The equation of motion for the vehicle subsystem is derived employing rigid dynamical theories without considering the rotational stiffness and rotational damping of the vehicle body, as well as the front-rear bogies. The explicit expressions for the dynamic responses of the vehicle and bridge subsystems to contact forces are generated utilizing the explicit time-domain method. Due to the compact wheel-rail model, which reflects the compatibility requirement of the two subsystems, the explicit expression of the evolutionary statistical moment for the contact forces may be performed with relative ease. Then, the evolutionary statistical moments for the respective responses of the two subsystems can be determined. The numerical results indicate that the simplification of vehicle model has little effect on the responses of the bridge subsystem and the vehicle body, except for the responses of the rotational degrees of freedom for the vehicle subsystem, regardless of whether deterministic or random analyses are performed.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.86-98
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• 1996

An combined implicit/explicit scheme for the analysis of sheet forming problems has been proposed in this work. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme dmploys a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explict scheme the problem of convergency is elimented at thecost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implici/explicit scheme has been developed. In the present work, the rigid-plastic finite element method using bending energy augmented membraneelements(BEAM)(1) is employed for computation. Computations are carried out for some typical sheet forming examples by implicit, combined implicit/explicit schemes including deep drawing of an oil pan, front fender and fuel tank. From the comparison between the methods the advantages and disadvantages of the methods are discussed.

• Journal of The Korean Association For Science Education
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• v.31 no.4
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• pp.641-662
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• 2011

In this study, explicit Teaching and Learning strategy for middle school students were developed to improve basic science process skills. After applying these strategy in an actual class, the effects of Teaching and Learning strategy and change of students were analyzed. Explicit Teaching and Learning strategy to improve basic science process skills are developed based on analyzing preceding research. The use of application criteria for class of basic science process skills combined with explicit Teaching and Learning strategy, it is sought for the explicit instructional procedures of said skills. After analyzing the class in which explicit Teaching and Learning strategy were demonstrated, students reported that they were able to comprehend basic science process skills more effectively through the stages of explicit explaining and independent practice. The showing demonstration stage was heavily emphasized by the teacher in this class. Analysis of students' understanding degree about basic science process skills, most of them show positive outcome. Another analysis of ripple effect on daily life and other subjects, it is found that students could have the attitude to make use of science process skills for themselves. Through the result of study, it is found that explicit Teaching and Learning strategy that are developed from this study are an effective way to comprehension students' basic science process skills. Thus, continued study is needed to develop and spread explicit Teaching and Learning strategy of science process skills to be applicable in actual classes in secondary schools.

• Korean Journal of Culture and Social Issue
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• v.21 no.1
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• pp.97-118
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• 2015

The aim of the present study was to examine moderating effects of self-esteem on perceived transgression wrongness and forgiveness defined as Worthington and Scherer's (2004) emotional forgiveness and decisional forgiveness when receiving apologies. Data collected from 861(486 males, 375 females) Korean college students were analyzed with hierarchical multiple regression analysis. The results were as follows. First, on emotional forgiveness, the two-way interaction effect of perceived transgression wrongness and explicit self-esteem was significant. And on decisional forgiveness, the two-way interaction effect of perceived transgression wrongness and explicit self-esteem was significant. The effect of perceived transgression wrongness on emotional and decisional forgiveness for individuals with high explicit self-esteem is stronger than its impact for individuals with low self-esteem. These findings show that explicit self-esteem may play an important role in forgiveness in college students through interactions with perceived transgression wrongness. Second, on emotional forgiveness, the three-way interaction effect of perceived transgression wrongness, explicit self-esteem, and implicit self-esteem was significant. The effect of perceived transgression wrongness on emotional forgiveness for individuals with high explicit self-esteem having high implicit self-esteem is stronger than its impact for individuals with low explicit self-esteem having high implicit self-esteem. These findings show that discrepancies between implicit and explicit self-esteem are detrimental to emotional forgiveness. But, on decisional forgiveness, the three-way interaction effect of perceived transgression wrongness, explicit self-esteem, and implicit self-esteem was not significant. Implications and limitations of this study were discussed.

• Korean Journal of Culture and Social Issue
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• v.15 no.1
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• pp.49-79
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• 2009

This study examined how the explicit and implicit race attitudes differ according to age and gender from the developmental perspective in Korean elementary students. The study also investigated the efficacy of a multi-cultural education program on explicit and implicit attitude change in elementary school students. This thesis consists of two parts. In Study 1, elementary school students(first grade:117, fourth grade:117) completed Explicit Attitudes Rating Scales, Explicit Preference Test, and Child Implicit Association Tests (Korean-White/Korean-Black/ Korean-Southeast Asian IATs). The effects of age and gender on explicit and implicit attitudes toward Korean/White/Black/Southeast Asian were examined with two-way MANOVA. The results demonstrated that as age increases, in-group preference/out-group bias decrease on the explicit level. In contrast, on the implicit level, as age increases, in-group preference/out-group bias do not decrease. Rather, prejudiced attitudes toward blacks increase. Study 2 was performed to investigate the effect of a multi-cultural education program on explicit and implicit attitude change toward races in elementary school students. The program conveying an anti-bias message consists of three sessions, and the procedures are as follows; watching video clips, confirming contents and short discussion. Two classes in the program and two classes in comparative groups on the first and fourth grade of elementary school were assessed. The results showed that black preference significantly increased both in the first and the fourth grade elementary students on the explicit attitude level, but not on the implicit level. The theoretical and practical implications of these findings were discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.88-99
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• 1996

The explicit scheme for finite element analysis of sheet metal forming problems has been widely used for providing practical solutions since it improves the convergency problem, memory size and computational time especially for the case of complicated geometry and large element number. The explicit schemes in general use are based on the elastic-plastic modeling of material requiring large computataion time. In the present work, a basic formulation for rigid-plastic explicit finite element analysis of plain strain sheet metal forming problems has been proposed. The effect of some basic parameters involved in the dynamic analysis has been studied in detail. Thus, the effective ranges of parameters have been proposed for numerical simultion by the rigid-plastic explicit finite element method. A direct trial-and-error method is introduced to treat contact and friction. In computation, sheet material is assumed to possess normal anisotropy and rigid-plastic workhardening characteristics. In order to show the validity and effectiveness of the proposed explicit scheme, computations are carried out for cylindrical punch stretching and the computational results are compared with those by the implicit scheme as well as with a commercial code. The proposed rigid-plastic exlicit finite element method can be used as a robust and efficient computational method for analysis of sheet metal forming.

• Korean Journal of Community Nutrition
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• v.28 no.2
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• pp.114-123
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• 2023

Objectives: Current social norms in the United States do not favor breastfeeding in public. This study examined associations between college students' explicit and implicit emotions of breastfeeding in public and their intention to support public breastfeeding. Methods: Twenty-two student participants viewed images of a breastfeeding woman with a fully-covered, fully-exposed, or partially-exposed breast in a public setting. After viewing each image, participants' explicit emotions (self-reported) of the image were measured using a questionnaire and their implicit emotions (facial expression) were measured using FaceReader technology. We examined if a relationship exists between both emotions [toward images] and intention to support breastfeeding in public using correlation techniques. We determined the relative influence of two emotions on the intention to support breastfeeding in public using regression analyses. Results: The nursing images depicting a fully-covered breast (r = 0.425, P = 0.049 vs. r = 0.271, P = 0.222) and fully-exposed breast (r = 0.437, P = 0.042 vs. r = 0.317, P = 0.150) had stronger associations with explicit emotions and intention to support breastfeeding in public compared to implicit emotions and intention. Breastfeeding knowledge was associated with a positive explicit emotion for images with partial- (β = 0.60, P = 0.003) and full-breast exposure (β = 0.65, P = 0.002). Conclusions: Explicit emotions appear to drive stated intentions to support public breastfeeding. Further research is needed to understand the disconnect between explicit and implicit emotions, the factors that influence these emotions, and whether stated intentions lead to consistent behavior.

• Journal of Gifted/Talented Education
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• v.23 no.6
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• pp.1077-1098
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• 2013

Science gifted students enrolled in a program, where classes had either explicit or implicit instruction about self-directed learning, were asked to write what was satisfying after each class. This process was part of the evaluation of the program. Students' descriptions related to self-directed learning are compared in these two classes, one with explicit instruction and the other with implicit instruction. First, most of the components related to self-directed learning, which were reported in the previous research articles, were mentioned in students evaluation. If there was any specific description regarding what was satisfying, there were components of self-directed learning. Students descriptions were consistent with list of self-directed learning components, which was constructed based on the previous research. Therefore it may be concluded that students recognized most of the reported self-directed learning components and satisfied with them. Second, There were differences in the evaluation of two types of classes. The evaluation of class with explicit instruction contained more self-directed learning components more frequently. For example, students worked in small groups in both classes. However more students mentioned small groups in classes with explicit instruction. As a result the explicit instruction appears to be more effective for students to recognize the self-directed learning components. However some of the components mentioned in classes with implicit instruction were not mentioned in the classes with explicit instruction. Therefore classes with explicit and implicit instructions are complimentary with each other and both instructions are necessary.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.16-25
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• 1996

In the present work a rigid-plastic finite element formulation using dynamic explicit time integration scheme is proposed for numerical analysis of auto-body panel stamping processes. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. A damping scheme is proposed in order to achieve a stable solution procedure in dynamic sheet forming problems. In order to improve the drawbacks of the conventional membrane elements, BEAM(abbreviated from Bending Energy Augmented Membrane) elements are employed. Rotational damping and spring about the drilling direction are introduced to prevent a zero energy mode. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and the direct trial-and-error method. Computations are carried out for analysis of complicated auto-body panel stamping processes such as forming of an oilpan, a fuel tank and a front fender. The numerical results of explicit analysis are compared with the implicit results with good agreements and it is shown that the explicit scheme requires much shorter computational time, especially when the problem becomes more complicated. It is thus shown that the proposed dynamic explicit rigid-plastic finite element method enables an effective computation for complicated autobody panel stamping processes.