• 한국항공우주학회지
• /
• 제36권9호
• /
• pp.874-883
• /
• 2008

본 논문에서는 위성발사체의 폐루프 유도방식중 하나인 Powered Explicit Guidance에 대해서 연구하였다. 반복계산 과정이 없도록 변형시킨 알고리듬을 사용했으며, 추력변화가 큰 엔진 모델에 적용가능 하도록 단일 목표궤도에 대한 알고리듬에 대해서 기술하였다. 정상 및 비정상 비행조건에 대해서 6-자유도 컴퓨터 모의시험을 통해 얻어진 유도 알고리듬의 궤도 투입 정밀도 분석을 하였다.

• Computers and Concrete
• /
• 제18권1호
• /
• pp.17-37
• /
• 2016

This paper compares the arc-length and explicit dynamic solution methods for nonlinear finite element analysis of prestressed concrete members subjected to monotonically increasing loads. The investigations have been conducted using an L-shaped, prestressed concrete spandrel beam, selected as a highly nonlinear problem from the literature to give insight into the advantages and disadvantages of these two solution methods. Convergence problems, computational effort, and quality of the results were investigated using the commercial finite element package ABAQUS. The work in this paper demonstrates that a static analysis procedure, based on the arc-length method, provides more accurate results if it is able to converge on the solution. However, it experiences convergence problems depending upon the choice of mesh configuration and the selection of concrete post-cracking response parameters. The explicit dynamic solution procedure appears to be more robust than the arc-length method in the sense that it provides acceptable solutions in cases when the arc-length approach fails, however solution accuracy may be slightly lower and computational effort may be significantly larger. Furthermore, prestressing forces must be introduced into the finite element model in different ways for the explicit dynamic and arc-length solution procedures.

• 아동학회지
• /
• 제19권2호
• /
• pp.147-157
• /
• 1998

The purpose of this study was to investigate children's ideas about self-regulation in such situational variables as the presence of explicit rules and the domains of social rules. The subjects were 6-, 9-, and 12-year-old children (344). To assess children's ideas about self-regulation, a procedure was devised in which children were presented with stories portraying a protagonist in a conflict between an implicit or an explicit rule and a personal desire. The children were asked to make a choice for the protagonist and to give reasons for their choice. Major findings as follows: (1) There was significant difference in children's self-regulation depending on the presence of explicit rules. (2) There was significant difference in children's self-regulation depending on the domains of social rules. In situations that involved no explicit rules for behaviors, there were significant differences depending on the domains. In situations that involved explicit rules for behaviors, for 6- and 9-year-old children, there was no significant difference depending on the domains. (3) Children's use of justifications for their choice of action varied as a function of the characteristics of the social rules.

• Journal of Communications and Networks
• /
• 제7권3호
• /
• pp.294-306
• /
• 2005

Group oriented multicast applications are becoming increasingly popular in mobile ad hoc networks (MANETs). Due to dynamic topology of MANETs, stateless multicast protocols are finding increased acceptance since they do not require maintenance of state information at intermediate nodes. Recently, several multicast schemes have been proposed which scale better' with the number of multicast sessions than traditional multicast strategies. These schemes are also known as explicit multicast (Xcast; explicit list of destinations in the packet header) or small group multicast (SGM). In this paper, we propose a new scheme for small group' multicast in MANETs named extended explicit multicast (E2M), which is implemented on top of Xcast and introduces mechanisms to make it scalable with number of group members for a given multicast session. Unlike other schemes, E2M does not make any assumptions related to network topology or node location. It is based on the novel concept of dynamic selection of Xcast forwarders (XFs) between a source and its potential destinations. The XF selection is based on group membership and the processing overhead involved in supporting the Xcast protocol at a given node. If the number of members in a given session is small, E2M behaves just like the basic Xcast scheme with no intermediate XFs. As group membership increases, nodes may dynamically decide to become an XF. This scheme, which can work with few E2M aware nodes in the network, provides transparency of stateless multicast, reduces header processing overhead, minimizes Xcast control traffic, and makes Xcast scalable with the number of group members.

• 한국초등과학교육학회지:초등과학교육
• /
• 제29권3호
• /
• pp.277-291
• /
• 2010

In this study, we investigated the effects of explicit instruction about nature of science by elementary school students' cognitive level. Participants were six classes, 187 sixth graders at elementary schools in Daegu. Three classes were assigned to control groups and the other classes to treatment groups. Control groups were provided normal instructions and treatment groups were provided instructions integrated with nature of science about chapter 'electromagnet' for 9 class periods. The results of this study were as follow. Both low-cognitive level students and high-cognitive level students in the treatment groups are improved in understanding about nature of science by the explicit instructions about nature of science. Especially, the high-cognitive level students had more improvement than the low-cognitive level students in understanding about nature of science by the explicit instructions about nature of science. There were no significant differences between the test scores of the two groups in the science interest sub-domain of the science-related affective domain. But, there were significant differences between the test scores of the two groups in curiosity and open-mindedness of the scientific attitudes sub-domain of the science-related affective domain.

• 한국정밀공학회지
• /
• 제19권9호
• /
• pp.74-81
• /
• 2002

Recently tube hydroforming has been widely applied to the automotive industries due to its several advantages over conventional methods. In this paper, attention is paid to comparison of an implicit and an explicit finite element method widely used for numerical simulation of a hydroforming process. For an explicit FEM, a huge amount of computational time is required because of the very small time increment to solve a quasi-static problem. Hence, when an explicit FEM is used fDr a hydroforming process, it is general to convert the real problem to a virtual problem with a different processing time and mass density by appropriate scaling factor. However it is difficult to figure out how large the scaling should be adopted enough to ignore the dynamic effects and maintain the desired accuracy. In this paper, the comparison of the results obtained from both methods focus on the accuracy of the predicted geometrical shape and the stress with various scaling factors which are applied to analyze hydroforming process of an automobile lower arm.

• 한국자기학회지
• /
• 제8권2호
• /
• pp.49-56
• /
• 1998

본 연구에서는 비등방성 에너지가 Ksin2$\theta$로 표현되는 일축 비등방성 자성체의 자기행동을 기술하는 닫힌형태 (closed-form)의 양함수들 (explicit functions)을 구하였다. 인가 자기마당, 포화 자기화량, 비등방성 에너지뿐만아니라, 자기화역전 기구에도 의존하는 돌림형, 자기화방향, 자기화갑수율을 나타내는 닫인형태의 양함수들과 결정하였다. 개발된 단힌형태의 양함수들과 실험적으로 측정 가능한 물리량들에 대한 그들의 편미분 함수들은 최소제곱맞춤법에 의한 포화 자기화량 및 비등방성 측정법의 개발, 자성 집합체의 분산된 자기적 특성 측정법의 개발 뿐만 아니라, 자기이론 계산에도 큰 기여를 하리라 사료된다.

• 한국어교육
• /
• 제25권1호
• /
• pp.115-144
• /
• 2014

The purpose of this paper is to compare the two different instruction methods for Korean learners of academic purposes in learning request expression. Participants were divided into two groups, explicit and implicit group. Both groups viewed several scenes from the drama that involved native speakers interacting in different situations. The instructional treatment for the explicit group included metapragmatic information while the treatment for the implicit group did not. On the other hand, the treatment for the implicit group followed implicit techniques, which were repetition of the video presentation and a script reading activity. This study was made up of a pre-test, a post-test, and a delayed-test. The pre-test was conducted prior to the instructional treatment. The post-test was administered a day after the last instruction and the delayed-test was conducted five weeks after the treatments. Two types of tests, speaking and writing, were used in this study to examine subjects' knowledge of Korean request. The result of this research reveals that implicit treatment was more effective than explicit treatment in Korean learners' request acquisition. This results might have been due to the operationalization of the implicit condition in this study. Implicit instruction may help language learners make rules by themselves through tasks.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권3호
• /
• pp.792-812
• /
• 2022

Multi-agent systems often need to achieve the goal of learning more effectively for a task through coordination. Although the introduction of deep learning has addressed the state space problems, multi-agent learning remains infeasible because of the joint action spaces. Large-scale joint action spaces can be sparse according to implicit or explicit coordination structure, which can ensure reasonable coordination action through the coordination structure. In general, the multi-agent system is dynamic, which makes the relations among agents and the coordination structure are dynamic. Therefore, the explicit coordination structure can better represent the coordinative relationship among agents and achieve better coordination between agents. Inspired by the maximization of social group utility, we dynamically construct a factor graph as an explicit coordination structure to express the coordinative relationship according to the utility among agents and estimate the joint action values based on the local utility transfer among factor graphs. We present the application of such techniques in the scenario of multiple intelligent vehicle systems, where state space and action space are a problem and have too many interactions among agents. The results on the multiple intelligent vehicle systems demonstrate the efficiency and effectiveness of our proposed methods.

• 한국정밀공학회지
• /
• 제12권12호
• /
• pp.53-63
• /
• 1995

In the analysis of metal forming problems, the explicit time integration finite element method, which does not have convergence problems, is frequently used. The present work is to assess the applicability of the explicit time integration finite element method to quasi-static metal forming problems. Compressing analyses of thin-walled tubes and solid cylinders are performed with different loading velocities. The computed buckled profiles of thin walled tubes are compared with the theoretical and experimental ones and it is found that at sufficiently low loading velocity, the explicit time integration finite element method accurately predict quasi-static buckled profiles. When loading volocity is increased, the computed buckled profiles of thin-walled tubes are very sensitive to loading velocity however the computed profiles of solid cylinders are less sensitive to loading velocity. In orther words, the geometrically self-constrained specimens like solid cylinders are less sensitive to loading velocity than the geometrically unconstrained specimens like thin-walled tubes. As a result, it is found that the geometrically self-constrained problems which include the greater part of metal forming problems can be efficiently analyzed with loading velocity control technique.