• Journal of Educational Research in Mathematics
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• v.21 no.3
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• pp.221-237
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• 2011

This paper focused on three drawbacks exposed in subject matter related to solid figures in elementary school math textbook. First, general solid figure are introduced before rectangular parallelepiped and cube in fifth grade math textbook, and prism and pyramid in sixth grade math textbook are introduced. Second, the process of abstraction from concrete objects to solid figures is insufficient in sixth grade math textbook. Third, some definitions in subject matter related to solid figures are inconsistent and ambiguous. The following four suggestions can be put forward as a conclusion based on these results. First, subject matter in textbooks must be correspond with that in curriculum. Second, it is necessary to inform teachers of range of subject matter through teachers guide book and manual for curriculum definitely. Third, each grade subject matter in math textbooks must be reexamined. Fourth, regular modification of math textbooks must be possible institutionally.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.108-115
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• 2014

Mechanical properties of GFRP rebars significantly decrease due to high temperature as well as alkalinity of concrete. This study focuses on the long-term reduction of inter-laminar shear strength of pre-damaged GFRP rebars by high temperature. For this investigation, bare GFRP rebar specimens were exposed to $270^{\circ}C$ for 1hour and then immerged in alkali solution for several months and tested in shear. No thermally conditioned specimens were immerged and tested for the comparisons. In results, the reduction of thermally damaged GFRP rebars was greater than that of no thermally damaged ones. Based on the accelerated experimental test data, an polynomial equation is presented for prediction of long-term residual inter-laminar shear strength of GFRP rebars previously damaged by high temperature.

• Smart Structures and Systems
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• v.6 no.3
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• pp.277-290
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• 2010

Internationally the load carrying capacity of bridges is decreasing due to material deterioration while at the same time increasing live loads mean that they are often exposed to stresses for which they were not designed. However there are limited resources available to ensure that these bridges are fit for purpose, meaning that new approaches to bridge maintenance are required that optimize both their service lives as well as maintenance costs. Wireless sensor networks (WSNs) provide a tool that could support such an optimized maintenance program. In many situations WSNs have advantages over conventional wired monitoring systems in terms of installation time and cost. In order to evaluate the potential of these systems two WSNs were installed starting in July 2007 on the Humber Bridge and on a nearby approach bridge. As part of a corrosion prevention strategy, a relative humidity and temperature monitoring system was installed in the north anchorage chambers of the main suspension bridge where the main cables of the bridge are anchored into the foundation. This system allows the Bridgemaster to check whether the maximum relative humidity threshold, above which corrosion of the steel wires might occur, is not crossed. A second WSN which monitors aspects of deterioration on a reinforced concrete bridge located on the approach to the main suspension bridge was also installed. Though both systems have provided useful data to the owners, there are still challenges that must be overcome in terms of monitoring corrosion of steel, measuring live loading and data management before WSNs can become an effective tool for bridge managers.

• Journal of Korean Society of Archives and Records Management
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• v.18 no.3
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• pp.49-70
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• 2018

This paper proposes a cloud system model for incorporating the existing Records Management System (RMS), Archives Management System (AMS), and Central Archives Management System (CAMS) into a cloud-based national records management system. To do this, research on concrete and stepwise ways to transform AMS, including CAMS, into a cloud computing environment was carried out. This study developed a cloud system design strategy and goal model to integrate national records-related systems into a single cloud system to share and utilize information resources, manage them efficiently, and reduce costs. In particular, this study analyzed technical security and operational security that are exposed in the cloud environment and suggested measures to solve them. As a result, cloud computing technology can be applied to achieve low-cost and high-efficiency effects.

• Journal of the Korea Safety Management & Science
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• v.16 no.2
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• pp.203-210
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• 2014

The purpose of this study is to understand the meaning and essence of concrete and practical experience on a series of debates to reveal factors that could be exposed when middle or old-aged people are in the process of re-employment process when they were unemployed by exploring the phenomenon of experience on the courses for the unemployed focusing on middle or old-aged people for employment support program. Depth consultation interviews were conducted and the structure of this phenomenon was revealed and described by applying Giorgi's phenomenology technical as a procedure for analyzing participants' statements by concentrating on the essence of the experience in this study. The meaning of the experience of the unemployed re-employment process structure as a result of analysis on the nature of re-employment experience on the basis of research participants and the information stated through this study showed respectively such as , , , , , and "Reemployment Success Factors>. It is a significant meaning that middle and old-aged people were able to confirm that they experienced Dynamic pursuit of hopes and dreams and got the chance to participate in society Toward a new life By strengthening employ ability skills by undertaking vocational training, obtaining licenses, and regaining confidence and employment determination, and a lot of desire using the card for learning tomorrow, government support system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.141-147
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• 2010

The rate of carbonation is usually low in the natural environment due to the low $CO_2$ concentration in the atmosphere. Therefore, investigation of carbonation is usually conducted under accelerated testing conditions so as to speed up the process. This study is to predict carbonation progress by mathematical model, based on the diffusions of $CO_2$ and its reaction with $Ca(OH)_2$ in carbonation progressing region, in the atmosphere. To predict of carbonation progress in the atmosphere, we adopted a diffusion coefficient of $CO_2$ that agreed well the experimental value obtained by the accelerated carbonation test. Consequently the model can predict the rate of carbonation of concrete exposed in the atmosphere regardless of finishing materials.

• Journal of the Korea Convergence Society
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• v.12 no.9
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• pp.261-271
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• 2021

Recent accidents in school environment involving violence, and bullying indicate that school safety is exposed to a serious threat to community well-being. Such incidents come as big problem because various policies and programs have widely long been implemented in order to protect the school environment. Thus, it is critical for the local community and goverment to develop measures for prevention. However, some of the incidents are misrepresented because school environment still remains as one of the safest settings. The current study discusses successful case studies of education, policies and projects regarding school violence and safety that are enforced in many other nations. One of the most practical and concrete means of pursuing an improved level of school safety is for the local community to be actively involved in the process. And one of the key factors for the success of international programs was that it was very much an integrative approach involving a joint effort with the local communities, accompanying a strong tie between the school and its surrounding context.

• Explosives and Blasting
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• v.37 no.1
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• pp.34-47
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• 2019

This case study is concerned with the project of the explosive demolition for the DCRE Incheon plant located in Hakik district in Incheon city. The building was severely aging due to the high temperature and sea winds of hundreds of degrees emitted by chimney-shaped steel structures inside the building. Due to this, the concrete of the column and the beam fell off and rusted rebar were exposed, and some of the slabs were severely damaged, making it difficult for workers to access the structure. Therefore, it is not possible to apply a mechanical demolition method in which heavy equipment enters the interior of the building, and an explosive demolition method was applied to allow the building to be demolished without dismantling the internal facilities of the building. The order of blasting proceeded in the order of (1) building ${\rightarrow}$ (2) chimney 2 ${\rightarrow}$ (3) chimney 1. A total of 406 electronic detonators (Unitronic 600) was used to sequentially initiate the explosives installed at appropriate in building and chimneys.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.30-36
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• 2019

In order to evaluate service life of RC (Reinforced Concrete) structures exposed to chloride attack, chloride penetration analysis is required referred to the chloride diffusion coefficient from the actual mix proportions. In this work, accelerated diffusion coefficients are obtained from NT BUILD 492 and ASTM C 1202 and the related apparent diffusion coefficients are derived via the previously proposed relationship for RC structures near to sea shore. Considering the properties of the mix proportions and the most conservative analysis conditions like critical and surface chloride contents, service lifes in column and exterior wall member are evaluated through conventional program LIFE 365 ver.2. The different built-up period of 10 and 15 years has no significant effect on service life. The results from mix proportions with slag show longer than 75 years of service life with the help of higher time dependent parameter and lower initial diffusion coefficient.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.266-286
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• 2022

Public key encryption with keyword search (PEKS) allows a user to make search on ciphertexts without disclosing the information of encrypted messages and keywords. In practice, cryptographic operations often occur on insecure devices or mobile devices. But, these devices face the risk of being lost or stolen. Therefore, the secret keys stored on these devices are likely to be exposed. To handle the key exposure problem in PEKS, the notion of key-updatable PEKS (KU-PEKS) was proposed recently. In KU-PEKS, the users' keys can be updated as the system runs. Nevertheless, the existing KU-PEKS framework has some weaknesses. Firstly, it can't update the keyword ciphertexts on the storage server without leaking keyword information. Secondly, it needs to send the search tokens to the storage server by secure channels. Thirdly, it does not consider the search token security. In this work, a new PEKS framework named key-updatable and ciphertext-sharable PEKS (KU-CS-PEKS) is devised. This novel framework effectively overcomes the weaknesses in KU-PEKS and has the ciphertext sharing function which is not supported by KU-PEKS. The security notions for KU-CS-PEKS are formally defined and then a concrete KU-CS-PEKS scheme is proposed. The security proofs demonstrate that the KU-CS-PEKS scheme guarantees both the keyword ciphertext privacy and the search token privacy. The experimental results and comparisons bear out that the proposed scheme is practicable.