• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.39-45
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• 2024

Seismic safety of expansion joints for piping systems has been underscored by water pipe ruptures and leaks resulting from the Gyeongju and Pohang earthquakes. Metal bellows in piping systems are applied to prevent damage from earthquakes and road subsidence in soft ground. Designed with a series of corrugated segments called convolutions, metal bellows exhibit flexibility to accommodate displacements. Several studies have examined variations in convolution shapes and layers based on the intended performance to be evaluated. Nonetheless, the research on the seismic performance of complex bellows having multiple corrugation heights is limited. In this study, monotonic loading tests, cyclic loading tests, and fatigue tests were conducted to evaluate the shear performance in seismic conditions, of metal bellows with variable convolution heights. Single- and triple-layer bellows were considered for the experimentation. The results reveal that triple-layer bellows exhibit larger maximum deformation and fatigue life than single-layer bellows. However, the high stiffness of triple-layer bellows in resisting internal pressure poses certain disadvantages. The convolutions are less flexible at lower displacements and experience leakage at a rate related to the variable height of the convolutions in certain conditions. At lower deformation rates, the fatigue life is rated higher as the number of layers increase. It converges to a similar fatigue life at higher deformation rates.

• Journal of The Korean Association For Science Education
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• v.43 no.1
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• pp.17-28
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• 2023

In line with the entry into the digital-based intelligent information society, the science curriculum emphasizes the cultivation of scientific competencies, and computer-based test (CBT) is drawing attention for assessment of competencies. CBT has advantages to develop items that have high fidelity, and to establish a feedback system by accumulating results into the database. However, it is necessary to solve the problems of improving validity of assessment results, lowering measurement efficiency, and increasing management factors. To examine students' responses to the introduction of the new assessment tools in the process of transitioning from paper-based test (PBT) to CBT, in this study, we analyzed the results of the PBT and the CBT conducted in 2021 National Assessment of Educational Achievement (NAEA). In particular, we sought to find the effects on student achievement when only the mode of assessment was changed without change of items, and the effect on student achievement when the items were composed including technology enhanced features that take advantage of CBT. This study is derived through the analysis of the results of 7,137 third-grade middle school students taking one among the three kinds of assessments, which were the PBT or two kinds of CBT. After the assessment, the percentage of correct answers and the item discriminations were collected for each group, and expert opinions on characteristics of response were collected through the expert council involving 8 science teachers with experience in NAEA. According to the results, there was no significant difference between students' achievement results in the PBT and the CBT-M, which means simple mode conversion type of CBT, so it could be explained that the mode effect did not appear. However, it was confirmed that the percentage of correct answers for the construct response items was somewhat high in the CBT, and this result was analyzed to be related to the convenience of the response. On the other hand, there were the items with a difference of more than 10%p from the correct answer rate of similar items, among the items to which technology enhanced functions were applied following the introduction of CBT. According to the analysis of response rate of options, these results could be explained that the students' level of understanding could be more closely grasped through the innovative items developed through the technology enhanced function. Based on the results, we discussed some guidance to be considered when introducing CBT and developing items through CBT, and presented implications.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.197-206
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• 2003

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid and hollow hemispherical shells of revolution of arbitrary wall thickness having arbitrary constraints on their boundaries. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components μ/sub Φ/, μ/sub z/, and μ/sub θ/ in the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the Φ and z directions. Potential (strain) and kinetic energies of the hemispherical shells are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for solid and hollow hemispheres with linear thickness variation. The effect on frequencies of a small axial conical hole is also discussed. Comparisons are made for the frequencies of completely free, thick hemispherical shells with uniform thickness from the present 3-D Ritz solutions and other 3-D finite element ones.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.100-107
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• 2018

The material and geometrical nonlinear finite elment analysis of UHPFRC 50M composite box girder was carried out. Constitute law in tension and compressive region of UHPFRC and HPC were modeled based on specimen test. The accuracy of nonlinear FEM analysis was verified by the experimental result of UHPFRC 50M composite girder. The UHPFRC 50M segmental composite box girder which has 1.5% steel fiber of volume fraction, 135MPa compressive strength and 18MPa tensile strength was tested. The post-tensioned UHPFRC composite girder consisted of three segment UHPFRC U-girder and High Strength Concrete reinforced slab. The parts of UHPFRC girder were modeled by 8nodes hexahedron elements and reinforcement bars and tendons were built by 2nodes linear elements by Midas FEA software. The constitutive laws of concrete materials were selected Multi-linear model both of tension and compression function under total strain crack model, which was included in classifying of smeared crack model. The nonlinearity of reinforcement elements and tendon was simulated by Von Mises criteria. The nonlinear static analysis was applied by incremental-iteration method with convergence criteria of Newton-Raphson. The validation of numerical analysis was verified by comparison with experimental result and numerical analysis result of load-deflection response, neutral axis coordinate change, and cracking pattern of girder. The load-deflection response was fitted very well with comparison to the experimental result. The finite element analysis is seen to satisfactorily predict flexural behavioral responses of post-tensioned, reinforced UHPFRC composite box girder.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.24 no.2
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• pp.49-69
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• 2013

The purpose of this study is to analyze status of information service and to suggest its activation strategies after establishing its category in the school library. As a result of establishing scope and contents of information service, materials of information offering and guide are converged on reading education and information literacy curriculum integrated subjects. But the arrival rate of information service is very low like 48.2% under the 2012 Korean Libraries' Management Evaluation. It is especially poor to raise self resilience and school participation of students with information service involved in the affective domain such as readers' advisory service and bibliotherapy. In order to activate its information service, there is an urgent need for systems improvement in placement of the teacher librarian. It is also necessary to reinforce the status of information literacy instruction under the nation-level curriculum and continuous base expansion as a core information service of the school library. Service development for readers' advisory service and bibliotherapy is also needed to contribute to solving problem and stress situation of the student. The school library has to make an effort to connect its information service with local communities for the school community.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.19-31
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• 2007

When estimating the benefits from an investment project in the transportation sector, errors caused by many factors may exist. This study focuses on user equilibrium traffic assignment methods and stopping criteria. According to previous studies, when using a user equilibrium assignment model, the benefits of travel time savings can be effected by the relative gap value. As the stopping criteria decreases, the time needed for traffic assignment increases, so that lowering the criteria cannot be the best solution. Therefore, an effort is necessary to reduce this change rate and thus improve reliability. This paper considers three methods: reducing the links subject to benefit calculation, extracting sub-area O/D tables and networks, and applying the mean value of successive traffic assignment results. The results of the analysis show that the method using the mean value of five results is more proper than the other methods. Using the sub-area analysis method, if the study area is small the benefits of a project might be over- or under-estimated. This paper used a nationwide O/D table and network at peak time as a case study. The resulting patterns can differ according to basic data to be used in analysis. So further analysis using the data from metropolitan areas are needed.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.1-17
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• 2016

Recently, although many government agencies, including the Korea Tourism Organization, have been operating two-way interactive online idea proposal communities in order to reflect the various ideas of citizens in business, the utilization rate is still extremely low due to the lack of public's understandings and management's commitments. Therefore, based on previous studies on the characteristics of information quality, this research (1) derives key factors constituting idea quality in the context of online idea proposal communities, (2) classifies them into the content cues (value-added, relevancy, originality, and completeness) and the non-content cue (amount of writing) according to the heuristic-systematic model, and (3) finally validates how these content/non-content cues influence the knowledge adoption of administrators in an online idea proposal community. The findings of the structural equation modeling analysis with all of the 240 completed idea proposals in the 'Tourism Idea Bank' of Korea Tourism Organization reveal that, among content cues, value-added, relevancy, and originality have a significant effect on knowledge adoption. Moreover, it is also found that amount of writing as a non-content cue has a positive moderation effect on the relationships between originality and knowledge adoption.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.421-430
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• 1997

In this study, the static and the fatigue tests were performed with high tension bolted joints, of which the surfaces were spread with inorganic zinc-primer after shot-blast, and milling surface, and steel-natural surface, difference of friction surface condition were examined by comparing the esults of tests. From the result of synthetical investigation of this study. it is proper that using the torque management method in order to introduce design axial force to blots, and the provision of specifications that initial axial forces must be 110% of design axial forces is proper. Decreasing ratio of axial forces to initial force is proportional to common lorgarithms of time progress, it converge constant value after 20 hours, and decreasing ratio is little related to the roughness of friction surface. Sliding coefficient of milling, spreading inorganic zinc-primer, just producting is great in order and sliding forces are dependent on the applied axial forces, but if the applied axial forces are great, sliding coefficient become small by a loss of roughness. So it is confirmed that relation between the applied axial forces and the sliding forces are not proportional linearly. From the result of estimation on fatigue strength, all specimens satisfy the specifications with B-grade and milling surface is lower than the others about 14% in fatigue strength because in milling surface lose the function of friction-types joints at lower number of cycles. From the result of eximination for the distribution area of compressive force, friction area near to inside bolt is wider in the direction of stress than near to outside. It is guessed that this situation occurs because outside bolts firstly change from the friction connection to the bearing connection.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.423-435
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• 2010

The number of professionals in the science and engineering fields decreases all over the world. Especially in Korea, the declining rate of both the laborable and economically active population, aging of the population at the fastest level, and the declining birth rate make it tougher to secure the core brains of the future. After speculation of all programs above, some common factors have been derived and every program appeared to have the support for each level of inducing, caring, and utilizing. And the means of support could be categorized into the financial, legal, and social aspects. Lastly, a logical tool called Systems Thinking has been applied to the FLS Conditions and the Brain Internalization Process to assure the efficacy and applicability of the models. This is to minimize any de facto side effects by analyzing all 'feedback loops' stemming from the models. And the 'causal loop diagrams' have been utilized to come with the complementary measures. Such series of verification could convince the virtue of the models. Governments and universities can make use of the FLS Conditions and the Brain Internalization Process so the policies or plans about the foreign brains can be built in a uniformized and consistent framework. I hope, as a result, the international competency of Korea to induce and utilize the foreign brains be raised with the constant and standardized formality.

• Journal of Korean Library and Information Science Society
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• v.51 no.1
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• pp.227-253
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• 2020

The purpose of this study is to establish a mid-to-long-term comprehensive development plan for the Gimpo library, and to lay out the overall system of the library scattered by region in Gimpo, and to present Gimpo library's unique vision and strategy to differentiate it from other regions. As a research, surveys and interviews were conducted for the residents of Gimpo-si (library users and beneficiaries) and library personnel. As a result, first, all libraries in Gimpo-si have a user-centered multicultural space service with differentiated concepts and themes of each library based on the functions and roles of data collection, information services, and various programs as public libraries. Seems to be oriented. Second, with regard to Gimpo library collections, it is necessary to first collect books with high usage rate by library and expand them to the needs of consumers. Third, in order to provide the services of the Gimpo library, it is necessary to develop a service that can raise satisfaction by using the citizens' participation and utilizing them in order to derive the service by analyzing other local library programs or services.