• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.697-702
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• 2012

In this study, unidirectional and plain woven carbon fiber reinforced magnesium matrix composite laminates were fabricated by the liquid pressing infiltration process, and evolutions of the microstructure and compressive strength of the composite laminates under corrosion were investigated by static immersion tests. In the case of the unidirectional composite laminate, the main microstructural damage during immersion appeared as a form of corrosion induced cracks, which were formed at both CF/Mg interfaces and the interfaces between layers. On the otherhand, wrap/fill interface cracks were mainly formed in the plain woven composite laminate, without any cracks at the CF/Mg interface. The formation of these cracks was considered to be associated with internal thermal residual stress, which was generated during cooling after the fabrication process of these materials. As a consequence of the corrosion induced cracks, the thickness of both laminates increased in directions vertical to the fibers with increasing immersion time. With increasing immersion time, the compressive strengths of both composite laminates also decreased continuously. It was found that the plain woven composite laminates have superior corrosion resistance and stability under a corrosive condition than unidirectional laminates.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.6
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• pp.1271-1282
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• 2012

Recently, security incidents occur continuously, resulting in the leakages of a large amount of the company's confidential and private information. For these reasons, the security technologies such as the authentication and the access control in order to prevent the information leakage are attracting attention. In particular, location-based authentication that utilizes the user's current location information which is used an authentication factor. And it provides more powerful authentication by controlling the users who attempt to access and blocks internal information leakage path. However, location information must be handled safely since it is the personal information. The location based authentication scheme proposed in this paper enhances the stability of the process location information compared with existing relevant location-based authentication protocol. Also it strengthens the end-user authentication by using one-time password. In addition, the proposed scheme provides authentication to prevent information leakage and employs the concept of the user's physical access control. Resultingly, the proposed scheme can provide higher security than the previous studies, while guarantee to low communication cost.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.35-43
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• 2020

Currently, cofferdams of circular cross section are widely applied as temporary facilities for the installation of bridge foundations in river/sea bridge construction in Korea. Existing caisson, sheet pile, and cell type cofferdam are widely used, but these methods take a lot of time and cost for installation and dismantling. In the case of the existing sheet pile construction method, attention is needed to secure internal and external stability because of the damage to the sheet pile due to ground penetration and difficulty in connecting element members. In this study, penetration design of circular steel pipes using suction pressure was performed on the soft ground of the west coast, and it was confirmed that penetration construction using suction pressure was possible through field tests. It was confirmed that applying the ground analysis results using the cone penetration test (CPT) to the design rather than the standard penetration test (N value) results more similar to the field test results. In addition, it was confirmed that local failure of the inside of the cofferdam was induced when a suction pressure higher than the upper limit suction pressure was applied in the silty sand.

• Journal of the Korean Society for Library and Information Science
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• v.55 no.1
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• pp.343-364
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• 2021

In this study, as examples of domestic libraries currently using the cloud-based library system, the main characteristics and issues that appeared in the experience of use divided into the processes of introduction, conversion, and operation of each system were investigated, and the results are as follows. First, it is said that new systems were introduced as alternatives to problems caused by the operation of the existing system, and the current products were selected because they were cost-effective. Second, the main issues in the conversion process were data migration work, implementation of existing service functions, and linking problems of internal and external systems in the library. Third, the main advantages identified in the operation process were cost reduction, simple installation and automatic management and maintenance, and convenient use in mobile devices. The main drawbacks were the difficulty of customizing that reflects the characteristics of the library, and the need for stability of the network. The disappeared role of the information technology librarian is the regular system inspection and maintenance support, and various new roles have been suggested. The responses of librarians and users to the new system were generally satisfied rather than dissatisfied.

• Journal of Korean Library and Information Science Society
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• v.52 no.4
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• pp.153-177
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• 2021

The revision of the Korean Cataloging Rules (KCR) is in progress in order to conform IFLA LRM conceptual model and to strengthen its internal stability. Religious works, along with musical works and legal works, have been treated as special and important in cataloging rules. This trend continues in the new cataloging rules that seek a bibliographic model that interconnects related materials. However since KCR2(1966), there are no rules for access points or specific rules on religious works. Under the circumstances, this study analyzed (1) the contents of religious works in the recently revised cataloging rules, (2) the access points and their functions for religious works implemented in online catalogs and authority system, and finally (3) the direction and scope of KCR revision. As a result of the study, this study suggested that it is necessary to prepare detailed rules for preferred title and authorized access points for various religious works in KCR. In conclusion, some issues for further discussion were summarized.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.100-106
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• 2022

Ships are built according to the purpose and operated with individual goals. Operational goals are reflected in the design of the ships and become the main criterion for determining the required ship ability. In general, cargo ships and passenger ships are objectively evaluated in terms of the operation part of the ship and the capacity part of the cargo or passenger, centering on their transportation ability. In consideration of the required ship ability, the built ship can expect effects such as economic feasibility and eco-friendliness in addition to basic characteristics such as stability. Accordingly, the concept of ship ability is expected to be effectively used in the field of training-only ship management by each institution, which plays a pivotal role in training ship-officers. In this study, the basic direction was verified for the ship ability evaluation criteria of training-only ships through the analysis of the internal space of two training-only ships of the Korea Institute of Maritime and Fisheries Technology, which were recently built with a time lag. In the process of building training-only ship or general-purpose training ship, the possibility of using the ship ability standards in securing budget and designing was derived.

• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.343-350
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• 2021

PURPOSE. The success of an implant-prosthetic rehabilitation is influenced by good implant health and an excellent implant-prosthetic coupling. The stability of implant-prosthetic connection is influenced by the rotational tolerance between anti-rotational features on the implant and those on the prosthetic component. The aim of this study is to investigate the rotational tolerance of a conical connection implant system and its titanium abutment counterpart, in various conditions. MATERIAL AND METHODS. 10 preparable titanium abutments, having zero-degree angulation (MegaGen, Daegu, Korea) with an internal 5-degree conical connection, and 10 implants (MegaGen, Daegu, Korea) were used. Rotational tolerance between the connection of implant and titanium abutments was measured through the use of a tridimensional optics measuring system (Quick Scope QS250Z, Mitutoyo, Kawasaki, Japan) in the as-received condition (Time 0), after securing with a titanium screw tightening at 35 Ncm (Time 1), after tightening 4 times at 35 Ncm (Time 2), after tightening one more time at 45 Ncm (Time 3), and after tightening another 4 times at 45 Ncm (Time 4). RESULTS. The group "Time 0" had the lowest values of rotational freedom (0.22 ± 0.76 degrees), followed by the group Time 1 (0.46 ± 0.83 degrees), the group Time 2 (1.01 ± 0.20 degrees), the group Time 3 (1.30 ± 0.85 degrees), and the group Time 4 (1.49 ± 0.17 degrees). CONCLUSION. The rotational tolerance of a conical connection is low in the "as received" condition but increases with repetitive tightening and with application of a torque greater than 35 Ncm.

• Journal of the Korean Geotechnical Society
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• v.38 no.4
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• pp.5-20
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• 2022

To analyze the flow and density variations in debris flows, a two-phase finite volume model simplified with momentum equations was constructed in this study. The Hershel-Buckley rheology model was employed in this model to account for the internal and basal friction of debris flows and was utilized to analyze complex topography and entrainments of basal soil beds. In order to numerically solve the debris flow analysis model, a finite volume model with the Harten-Lax-van Leer-Contact method was used to solve the conservation equation for the debris flow interface. Case studies of circular dam failure, non-Newtonian fluid dam failure, and multiple debris flows were analyzed using the proposed model to evaluate shock absorption capacity, numerical isotropy, model accuracy, and mass conservation. The numerical stability and correctness of the debris flow analysis of this analysis model were proven by the analysis results. Additionally, the rate of debris flow with various rheological properties was systematically simulated, and the effect of debris flow rheological properties on behavior was analyzed.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.4
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• pp.95-102
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• 2021

PURPOSE: This study examined the muscle activity of the abdominal muscle when lifting with abdominal hollowing with visual feedback and lifting with a pelvic compression belt. This study suggests how to lift an object safely in the workplace for people who bend their backs repeatedly. METHODS: The study was conducted on healthy men in their 20s and 30s. When lifting a 7kg object, lifting with abdominal hollowing with visual feedback, and lifting an object with a pelvic compression belt were performed three times in random order. The muscle activities were measured rectus abdominis (RA), external oblique (EO), internal oblique/transverse abdominis (IO/TrA) muscles, and abdominal hollowing exercises, and box lifting exercises were carried out in advance before the experiment. One-way ANOVA was used to compare muscle activities, and a Tukey HSD was used for post-analysis. The level of significance was set to .05. RESULTS: According to the study, there was no significant difference in muscle activity of the RA muscle depending on the lifting method (p > .05). There were significant differences between the EO and IO/TrA muscle (p < .05). The IO/TrA muscle activity showed the largest increase in lifting an abdominal hollowing with visual feedback (p < .05). The EO muscle activity increased in pelvic compression belt lifting (p < .05). The muscle activity was increased in RA, but there was no significant difference (p < .05). CONCLUSION: Abdominal hollowing lifting with visual feedback increases the muscle activity of the IO/TrA muscle, which is higher than normal, and affects the core stability of the body.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.78-89
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• 2022

ANODE-free Li-metal batteries (AFLMBs) operating with Li of cathode material have attracted enormous attention due to their exceptional energy density originating from anode-free structure in the confined cell volume. However, uncontrolled dendritic growth of lithium on a copper current collector can limit its practical application as it causes fatal issues for stable cycling such as dead Li formation, unstable solid electrolyte interphase, electrolyte exhaustion, and internal short-circuit. To overcome this limitation, here, we report a novel dual-salt electrolyte comprising of 0.2 M LiPF₆ + 3.8 M lithium bis(fluorosulfonyl)imide in a carbonate/ester co-solvent with 5 wt% fluoroethylene carbonate, 2 wt% vinylene carbonate, and 0.2 wt% LiNO₃ additives. Because the dual-salt electrolyte facilitates uniform/dense Li deposition on the current collector and can form robust/ionic conductive LiF-based SEI layer on the deposited Li, a Li/Li symmetrical cell exhibits improved cycling performance and low polarization for over 200 h operation. Furthermore, the anode-free LiFePO₄/Cu cells in the carbonate electrolyte shows significantly enhanced cycling stability compared to the counterparts consisting of different salt ratios. This study shows an importance of electrolyte design guiding uniform Li deposition and forming stable SEI layer for AFLMBs.