• Steel and Composite Structures
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• v.48 no.5
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• pp.565-582
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• 2023

The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (>5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift >3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.727-735
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• 2005

Statement of problem. Platform switching in implant prosthesis has been used for esthetic and biological purpose. But there are few reports for this concept. Purpose. The purpose of this study is evaluation of platform switching in wide implant by three dimensional finite element analysis. Materials and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for Osstem implant system. Three-dimensional finite element models were developed for (1) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with wide cemented abutment, titanium alloy abutment screw, and prosthesis (2) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with regular cemented abutment, titanium alloy abutment screw and prosthesis(platform switching) was made for finite element analysis. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized to 650N, and round and flat type prostheses were loaded to 200 N. Four loading offset point (0, 2, 4, 6 mm from the center of the implants) were evaluated. Models were processed by the software programs HyperMesh and ANSA. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView were used for post processing. Results. The results from experiment were as follows; 1. von Mises stress value is increased in order of bone, abutment, implant and abutment screw. 2. von Mises stress of abutment screw is lower when platform switching. 3. von Mises stress of implant is lower when platform switching until loading offset 4 mm. 4. von Mises stress of abutment is similar between each other. 5. von Mises stress of bone is slightly higher when platform switching. Conclusion. The von Mises stress pattern of implant components is favor when platform switch ing but slightly higher in bone stress distribution than use of wide abutment. The research about stress distribution is essential for investigation of the cortical bone loss.

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.234-240
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• 2016

The effect of initial electrolyte loading (IEL) on cell performance in a coin-type molten carbonate fuel cell (MCFC) was investigated in this work. Since the material of MCFC depends on the manufacturer, optimisation requires experimental investigation. In total, four IEL values, 1.5, 2.0, 3.0, and 4.0 g, were used, corresponding to a pore filling ratio (PFR) of 38, 51, 77, and 102%, respectively. The cell performance with respect to the PFR was analysed via steady-state polarisation, step-chronopotentiomtery, and impedance methods. The electrochemical analyses revealed that internal resistance and overpotential of the cell decreased with increasing PFR, and a large overpotential was observed when the PFR was 102%, probably due to the flooding phenomenon. After operation, cross-section of the cell was analysed via surface analysis of SEM and EDS methods, and the remaining electrolyte was estimated by dissolution of the cell in 10 wt% acetic acid. A linear relationship between IEL and the weight reduction ratio by dissolution was obtained. Thus, the remaining amount of electrolyte could be measured after operation. The results of SEM and EDS showed that a PFR of 38 and 102% showed a lack and flooding of electrolytes at the cell, respectively, which led to a large overpotential. This work reports that MCFC performance is allowed only in the narrow range of PFR.

• The Korean Journal of Air & Space Law and Policy
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• v.32 no.2
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• pp.101-127
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• 2017

Even with the most advanced aviation technology benefits, aircraft accidents are constantly occurring while air passenger transportation volume is expected to double in the next 15 years. Since it is not possible to secure aviation safety only by the post aircraft accident safety action of accident investigations, it has been recognized and consensus has been formed that proactive and predictive prevention measures are necessary. In this sense, the aviation safety management system (SMS) was introduced in 2008 and has been carried out in earnest since 2011. SMS is a proactive and predictive aircraft accident preventive measure, which is a mechanism to eliminate the fundamental risk factors by approaching organizational factors beyond technological factors and human factors related to aviation safety. The methodology is to collect hazards in all the sites required for aircraft operations, to build a database, to analyze the risks, and through managing risks, to keep the risks acceptable or below. Therefore, the improper implementation of SMS indicates that the aircraft accident prevention is insufficient and it is to be directly connected with the aircraft accident. Reports of duty performance related hazards including their own errors are essential and most important in SMS. Under the policy of just culture for voluntary reporting, the guarantee of information providers' anonymity, non-punishment and non-blame should be basically secured, but to this end, under-reporting is stagnant due to lack of trust in their own organizations. It is necessary for the accountable executive(CEO) and senior management to take a leading role to foster the safety culture initiating from just culture with the safety consciousness, balancing between safety and profit for the organization. Though a Ministry of Land, Infrastructure and Transport's order, "Guidance on SMS Implementation" states the training required for the accountable executive(CEO) and senior management, it is not legally binding. Thus it is suggested that the SMS training completion certificates of accountable executive(CEO) and senior management be included in SMS approval application form that is legally required by "Korea Aviation Safety Program" in addition to other required documents such as a copy of SMS manual. Also, SMS related items are missing in the aircraft accident investigation, so that organizational factors in association with safety culture and risk management are not being investigated. This hinders from preventing future accidents, as the root cause cannot be identified. The Aircraft Accident Investigation Manuals issued by ICAO contain the SMS investigation wheres it is not included in the final report form of Annex 13 to the Convention on International Civil Aviation. In addition, the US National Transportation Safety Board(NTSB) that has been a substantial example of the aircraft accident investigation for the other accident investigation agencies worldwide does not appear to expand the scope of investigation activities further to SMS. For these reasons, it is believed that investigation agencies conducting their investigations under Annex 13 do not include SMS in the investigation items, and the aircraft accident investigators are hardly exposed to SMS investigation methods or techniques. In this respect, it is necessary to include the SMS investigation in the organization and management information of the final report format of Annex 13. In Korea as well, in the same manner, SMS item should be added to the final report format of the Operating Regulation of the Aircraft and Railway Accident Investigation Board. If such legal and institutional improvement methods are complemented, SMS will serve the purpose of aircraft accident prevention effectively and contribute to the improvement of aviation safety in the future.

• Journal of Wetlands Research
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• v.10 no.1
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• pp.59-68
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• 2008

Three phases of development in construction projects (i.e. pre-development, construction and post construction) diversely effect the environment, hydraulics and ecosystem. Currently, the domestic environmental policy is in control of the various environmental hazards produced after completion of development operations. Nevertheless, with the enforcement of water pollution total amount management system, improving the water quality; also the water and ecosystem preservation law recommends enforcing the sediment management for development operations in order to lessen the negative impacts to the environment. Recently, the country is experiencing difficulties in various development project locations due to insufficiency of interpreting the fundamental data for sediment loss and miscalculation of soil loss unit loads of sediment. This research utilizes data from 2000 to 2005 discussing a total of 1,036 environment impact assessment projects gathered from various ministries and offices namely Ministry of Environment (MOE), Ministry of Agriculture, the Office of Forestry, and Ministry of Construction and Transportation. Moreover, quantity of sediment from high land agriculture reports involving contaminant discharge characteristic investigation previously did concerning old land agriculture and So-Yang lake non-point pollution source management area as well as management measured data from MOE. The findings of this study reveal that the highest soil loss rate occurred from mountain district for pre-development and post construction and sports facility during construction.

• Journal of Intelligence and Information Systems
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• v.17 no.4
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• pp.37-58
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• 2011

In general, testing DB applications is much more difficult than testing other types of software. The fact that the DB states as much as the input data influence and determine the procedures and results of program testing is one of the decisive reasons for the difficulties. In order to create and maintain proper DB states for testing, it not only takes a lot of time and efforts, but also requires extensive IT expertise and business knowledge. Despite the difficulties, there are not enough research and tools for the needed help. This article reports the result of research on automatic creation and maintenance of DB states for testing DB applications. As its core, this investigation develops an automation tool which collects relevant information from a variety of sources such as log, schema, tables and messages, combines collected information intelligently, and creates pre- and post-Images of database tables proper for application tests. The proposed procedures and tool are expected to be greatly helpful for overcoming inefficiencies and difficulties in not just unit and integration tests but including regression tests. Practically, the tool and procedures proposed in this research allows developers to improve their productivity by reducing time and effort required for creating and maintaining appropriate DB sates, and enhances the quality of DB applications since they are conducive to a wider variety of test cases and support regression tests. Academically, this research deepens our understanding and introduces new approach to testing enterprise systems by analyzing patterns of SQL usages and defining a grammar to express and process the patterns.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.21-28
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• 2007

It is very difficult to forecast accurately a damage from the natural disaster which occurs frequently due to the climate change. When the significant weather event is forecast, it will be able to minimize a damage with the suitable prevention action. But 2000's our country meterological disaster damage is a several trillion won. Therefore, this paper analyzes Korea Meterological Administration, Japan Meterological Agency, television and newspaper have reported, information substance, transmission system, an ex post facto valuation about typhoon Nabi between september $5{\sim}7$ in 2005 and heavy rainfall in 1998 at Japan. Through the investigation, we want to present basic data order to rises the application effect of disaster prevention meterological information. We think KMA must present many information report to promote a people's understanding about the meterological information and the serious disaster situation. Also the disaster damage estimation model development is necessary, which forecasts the accurate damage scale due to the weather event, such as typhoon, heavy rainfall, strong wind. And also we think the KMA, National Emergency Management Agency, related agency, television and newspaper must positive reports the contents which is suitable to disaster response phases and an ex post facto examination. Then it grasps the problem of disaster prevention meterological information and must improve effectively.

• Journal of Korean Elementary Science Education
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• v.43 no.1
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• pp.108-121
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• 2024

In this study, we developed a sustainability education program employing a project-based learning strategy for prospective teachers and investigated its effectiveness. A total of 23 senior students from a university of education participated in the study. The investigation involved a pretest on their pro-environmental behavior and attitudes, followed by a five-week implementation of the program, during which students individually engaged in energy-saving projects. Following the program, a post-test, which used the same questionnaire as the pretest, was administered. In addition, we conducted individual interviews with nine students who actively engaged in the projects. We analyzed the interview contents, portfolios, and reports; identified sub-concepts related to the program's effectiveness and its causes; and then organized them into subcategories. Then, we extracted recurring relationships among the subcategories to formulate a tentative explanatory model. The results indicate that the program positively impacted students' pro-environmental behavior and values/attitudes. Notably, the students' "sense of achievement gained through success" emerged as a significant factor influencing their pro-environmental behavior. Furthermore, some causes were found to indirectly affect pro-environmental behavior through pro-environmental values and attitudes.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.177-186
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• 2021

For disaster management and mitigation of earthquakes in Korea Peninsula, active fault investigation has been conducted for the past 5 years. In particular, investigation of sediment-covered active faults integrates geomorphological analysis on airborne LiDAR data, surface geological survey, and geophysical exploration, and unearths subsurface active faults by trench survey. However, the fault traces revealed by trench surveys are only available for investigation during a limited time and restored to the previous condition. Thus, the geological data describing the fault trench sites remain as the qualitative data in terms of research articles and reports. To extend the limitations due to temporal nature of geological studies, we utilized a terrestrial LiDAR to produce 3D point clouds for the fault trench sites and restored them in a digital space. The terrestrial LiDAR scanning was conducted at two trench sites located near the Yangsan Fault and acquired amplitude and reflectance from the surveyed area as well as color information by combining photogrammetry with the LiDAR system. The scanned data were merged to form the 3D point clouds having the average geometric error of 0.003 m, which exhibited the sufficient accuracy to restore the details of the surveyed trench sites. However, we found more post-processing on the scanned data would be necessary because the amplitudes and reflectances of the point clouds varied depending on the scan positions and the colors of the trench surfaces were captured differently depending on the light exposures available at the time. Such point clouds are pretty large in size and visualized through a limited set of softwares, which limits data sharing among researchers. As an alternative, we suggested Potree, an open-source web-based platform, to visualize the point clouds of the trench sites. In this study, as a result, we identified that terrestrial LiDAR data can be practical to increase reproducibility of geological field studies and easily accessible by researchers and students in Earth Sciences.

• Journal of Chest Surgery
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• v.42 no.4
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• pp.456-463
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• 2009

Background: Although the reports on re-operative coronary revascularization (redo-CABG) have increased, there are only limited reports on redo-CABG using arterial grafts. The aim of this study was to analyze the safety and feasibility of using various arterial grafts for redo-CABG. Material and Method: A consecutive series of patients who underwent 33 redo-CABGs from March 2001 to July 2008 were retrospectively reviewed. We performed conventional CABG in 17 patients, on-pump beating CABG in 7, off-pump CABG in 7 and minimally invasive direct coronary artery bypass in 2. The grafted that were used included 34 internal thoracic arteries (ITA), 14 radial arteries, 14 right gastroepiploic arteries and others. Arterial composite grafts were constructed in 26 patients. Of these, a previously patent in-situ left ITA was re-used as the in-flow of a composite graft in 10 patients. Result: No hospital deaths or major wound problems occurred. The post-operative complications included 2 myocardial infarctions (6%), 1 intra-aortic balloon pump insertion (3%), 5 cases of atrial fibrillation (15.1 %) and 3 neurologic complications (9.1%). The meanfollow-up duration was 31.1$\pm$22.7 months and the 3 year survival rate was 86.4%. There were 4 late deaths (2 cardiac deaths) and no recurrent angina during the follow-up period. Conclusion: Redo-CABG with using various arterial grafts is currently a safe, feasible procedure, but further investigation and long term follow-up are needed.