• Journal of the Korean Geotechnical Society
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• v.37 no.2
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• pp.19-31
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• 2021

Micropiles are cast-in-place piles with small diameters. The advantage of micropile is low construction expense and simple procedures, so it is widely applied to existing buildings and structures for the reinforcement of foundation and seismic performances. The base expansion structure has been developed following the original mechanism of horizontal expansion steps under compressive loading. This kind of structure can be installed at the pile end to improve the bearing capacity by tip area enlargement and horizontal force increment to the pile surface area. However, 'Micropile with base expansion structure' cannot be put into practical use, because detailed verification for the developed technique has not been conducted so far. In this research, 3-D numerical analysis was conducted to figure out the bearing mechanism of base expansion micropile and to verify the bearing capacity improvement compared to the general micropiles. 3-D modelling of micropile with base expansion structure was carried out and input parameter was determined. Bearing mechanism induced by base expansion structure was analyzed by lab-scale modelling, and bearing capacity improvement was verified by field-scale analysis.

• Journal of the Korean GEO-environmental Society
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• v.22 no.3
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• pp.45-51
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• 2021

The evaluation of the degree of compaction of the embankment area, which accounts for most of highway earthworks, is generally performed by a flat plate loading test. The plate loading test is a traditional test method and has high reliability in the field. However, as reaction force equipment must be carried out and it takes about 40 minutes per site during the test, there may be limitations in managing the entire expanse of earthworks. Meanwhile, in order to overcome this, the Ministry of Land, Infrastructure and Transport proposed a simple method of evaluating the level of compactness in the provisional guidelines for compaction management of the packaging infrastructure in 2010. However, it has not been utilized at the highway construction site until now, 10 years later. Therefore, this study attempted to verify the utility of the compaction evaluation method using LFWD (Light Falling Weight Deflectometer) of the impact loading method among the test methods suggested in the provisional guideline. To this end, the correlation was derived by conducting a plate loading test and an LFWD test for each site property and compaction degree. As a result of the test, there was no consistency of test data in the ground with a relative compaction of 80% or less. However, it was confirmed that the correlation has a tendency to increase beyond that. If the test method or test equipment is improved to ensure the consistency of the test values of the impact loading method in the future, it will play a big role in solving the blind spot for compaction management in the earthworks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.45-52
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• 2020

An open-spandrel arch bridges, which consists of slab deck, arch rib, and vertical members, shows a various level of moment and axial forces according to the supporting boundary condition of arch rib and vehicle speeds. Also, the definition of impact factor accepts any kind of response parameters, not only displacement response at slab deck. The present study considers concrete open-spandrel arch bridges constrained with fixed conditions at the ends of arch rib and investigates the impact factor variation due to moving load speeds, response parameters, measuring locations, and vertical member spacing ratio of the bridges. The results of Reference model show that the impact factor is biggest when the reactive moment resulted at the vehicle-inducing opposite end of the arch rib is applied. The peak impact factor is a similar level obtained for the middle of the span adjacent to the slab deck center, but it is 19% higher than the peak impact factor calculated using the axial force developed at the same location. Reducing the spacing ratio of the vertical members as half as the reference model whose ratio is 1/9.375 produces a similar level of the moment-based peak impact factor compared to the reference model. However, when the spacing ratio is doubled, the peak impact factor is 4.4 times greater than the reference model.

• Convergence Security Journal
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• v.20 no.4
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• pp.227-236
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• 2020

Peacekeeping operations (PKO), which were based mainly on military operations in the Cold War era, have become diverse in the post-Cold War era. The history of the PKO of Korean police began in 1994 as two policemen were deployed to Somalia for rebuilding law and order in this country, but the role of Korean police in PKO has been limited so far, compared to that of Korean military. At this point when global conflicts escalate does the UN urge its 193 member states to conduct diverse PKO. In particular, maintaining law and order as the primary duty of police is required strictly for law enforcement while the warring country is being rebuilt. In this regard, some member states such as US, China, and Germany have deployed police force in order to play its role in a direct or indirect manner. On the contrary, the extent of the contribution of Korean police in PKO is too insignificant to measure. To this end, here in the present study were analyzed first the trend of global conflicts and the circumstance of law and order in the conflict regions. Then the PKO of police from countries including Republic of Korea, US, China, and Germany were compared, and so was the chronological change of PKO. Last, a measure to expand the capacity of Korean police and for its active role in PKO was proposed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.648-656
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• 2022

As environmental regulations such as the International Maritime Organization (IMO)'s strategy to reduce greenhouse gases(GHG) are strengthened, technology development such as eco-friendly ships and alternative fuels is expanding. As part of this, ship propulsion technology using energy reduction and wind propulsion technology is emerging, especially in shipping companies and shipbuilders. By securing wind propulsion technology and introducing empirical research into shipbuilding and shipping, a high value-added market using eco-friendly technology can be created. Moreover, by reducing the fuel consumption rate of operating ships, GHG can be reduced by 6-8%. Rotor Sail (RS) technology is to generate a hydrodynamic lift in the vertical direction of the cylinder when the circular cylinder rotates at a constant speed and passes through the fluid. This is called the Magnus effect, and this study attempted to propose a plan to increase propulsion efficiency through a numerical analysis study on turbulence flow characteristics around RS, a wind power assistance propulsion system installed on a ship. Therefore, C_L and C_D values according to SR and AR changes were derived as parameters that affect the aerodynamic force of the RS, and the flow characteristics around the rotor sail were compared according to EP application.

• Economic Analysis
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• v.26 no.3
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• pp.71-133
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• 2020

The Bank of Korea began its operation on June 12, 1950, with the Bank of Korea Act established a month or so earlier. Thus was first introduced to Korea modern central banking in the real sense of the word. The Bloomfield Mission, consisting of A. Bloomfield and J. Jensen of the Federal Reserve Bank of New York, spent about six months drafting a bill, which finally became the Bank of Korea Act. Little has been known yet about the process leading to the creation of the Mission and the historical context surrounding it, except that F. Tamagna of the Federal Reserve Board made in his capacity of the ECA's representative the offer of technical assistance to the Korean government. This paper attempts to dig deeper into relevant historical records and literature to fill these gaps. As it happened, the confrontation between the US and the USSR was accelerating towards the end of 1940s. The paper's new findings include that the Bloomfield Mission was, together with the ECA Mission to Korea, a product of the then US foreign policy (Cold War policy) and that the former Mission's technical assistance was conceived and provided all along as part of the inflation stabilization program pursued by the latter Mission. The Bloomfield Mission was after all a historical necessity. Next, the paper examines the changes added to the bill during its journey to becoming the Bank of Korea Act enacted in May 1950, presenting a review of the Act. The paper further evaluates the Act in terms of legal persistence, finding that the revised Act currently in force still substantially resembles the Act enacted 70 years ago from now. Finally in order is a brief discussion on those factors which seem to have contributed much to such persistence and thus apparent excellence of the Act enacted.

• Journal of Space Technology and Applications
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• v.3 no.2
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• pp.101-117
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• 2023

Active debris removal, a technology that approaches and removes space debris in orbit, and the on-orbit service, a technology for extending the mission life of satellites by fuel charging or by exchanging the battery, are gaining interest with the growth of the space community. SaTReC plans to develop a satellite capable of capturing and removing Korean satellites orbiting in space after the end of their missions. In contrast to the previously launched satellites by Korea, which were mainly intended to observe Earth and the space environment, rendezvous/docking technologies, as required in the future during, for instance, space exploration missions, will be implemented and demonstrated. In this paper, an orbital transition method for next-generation small satellites that will capture and remove space debris will be introduced. It is assumed that a small satellite with a mass of approximately 200 kg will be injected into the mission orbit through Korea Space Launch Vehicle-II in 2027. Because the satellite must access the target using a minimum amount of fuel, an approaching technology using Earth's J2 perturbation force has been developed. This method is expected to enable space debris removal missions for relatively lightweight satellites and to serve as the basis for carrying out a new type of space exploration in what is termed the 'Newspace' era.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.707-717
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• 2006

As an alternative to conventional prestressed concrete (PSC) girders, various types of PSC girders are either under development or have already been applied in bridge structures. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these new types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the dynamic interaction between bridge superstructures and passing trains is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate modal parameters of newly designed bridges before doing dynamic analyses. In the present paper, a 25 meters long full scale PSC girder was fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios at every prestressing stage. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied, in order to obtain precise frequency response functions and the modal parameters are evaluated varying with construction stages. Prestressed force effects on changes of modal parameters are analyzed at every incremental prestressing stage. With the application of reliable properties from modal experiments, estimation of dynamic performances of PSC girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of moving train. Dynamic displacements, impact factor, acceleration of the slab, end rotation of the girder, and other important dynamic performance parameters are checked with various speeds of the train.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.34 no.4
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• pp.331-350
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• 2023

The purpose of this study is to investigate the academic librarians' perception of the current status and establishment of the development plans of domestic university libraries to suggest ways to increase usefulness of development plans. And this study sought ways to establish the academic library development plan that reflected the key components of the development plan. To this end, a survey was conducted on academic library librarians, and in-depth interviews were conducted with the persons in charge of the academic library development plan to supplement the limitations of survey. The results are as follows. First, the establishment of academic library development plans tend to be formal and passive, and has limitation in eliciting cooperation between external organizations and academic libraries. Second, most academic libraries do not disclose their development plans on their websites. Third, the awareness of the leaders of the academic library organization needs to be preceded, and a task force needs to be formed to establish development plan. As a result of the study, it is suggested that 'active changes in the perceptions and operation method within academic libraries', 'external disclosure of development plans and strengthening cooperation', and 'strengthening the initiative and role of librarians' are needed as improvement measures.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.267-275
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• 2023

To obtain better esthetic results when immediately placing a dental implant, the soft tissue surrounding the implant must be conditioned during healing of the extraction socket. To this end, the emergence profile can be customized through immediate restoration of the provisional prosthesis, and good clinical results can be obtained at the time of definitive restoration in the future, resulting in high patient satisfaction. In this case, horizontal root fracture occurred after trauma to both maxillary central incisors. Immediate implant placement and loading was planned considering aesthetics and alveolar bone condition. By taking an impression using a digital intraoral scanner, a digital diagnostic wax-up was performed to make a more aesthetic prosthesis without applying external force to the traumatized teeth. Based on this, the ideal placement location was determined and immediate implant placement was performed using a 3D printed surgical guide. The provisional prosthesis was restored 5 days after placement, and the definitive zirconia crown was restored through soft tissue conditioning and customization using the shape of the provisional prosthesis for 3 months.