• Korean Journal of Metals and Materials
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• 제48권12호
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• pp.1056-1063
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• 2010

We present a new joining method for Pd-Cu membrane foils used as permeation tubes to collect $CO_2$. Since foils have poor mechanical strength, joining should be done at low temperatures to reduce residual stresses and without joining pressure. This contradicts the well known conditions for good contact between base materials that determines joint qualities. We selected Sn-Ag-Cu alloys that are highly reactive with Pd and Cu as a filler metal. As the filler melts at joining temperatures as low as $220{\sim}280^{\circ}C$, Pd and Cu are dissolved into the melt and react with the filler elements, which raises the melting temperature of the filler based on eutectic structures among the elements. Then, isothermal solidification progresses for the rest of the joining time. Intermetallic compounds (IMC) in the joints, one of the main factors for brittle joints, are inevitably formed. However, by optimizing both joining time and temperature, we balanced the wettability with IMC. Sealing test results confirmed that the joints are mechanically reliable during operation.

• Journal of the Korean Society of Propulsion Engineers
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• 제16권4호
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• pp.9-15
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• 2012

In this paper, the bearing strengths and fracture behaviors of the pin-jointed carbon fiber/epoxy composites were investigated through pin loading test with acoustic emission technique. The composites were fabricated by a filament winding process, and three types of laminated patterns were considered. Type 1 was fabricated with stitch, Type 2 was fabricated without stitich and Type 3 was fabricated with prepregs. According to the results, bearing strength of Type 1 was 3.3% lower than that of Type 2 and that of Type 3 was highest. Type 1 and Type 2 revealed a net-tension failure mode, respectively, whereas Type 3 pattern exhibited a bearing failure mode. Also, acoustic emission energy of the Type 3 was higher than that of the Type 1 and Type 2. Therefore, the Type 3 was found to be structurally safer than the Type 1 and Type 2.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.339-364
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• 2010

Following a joint OECD/NEA-IAEA-sponsored meeting to define the current role and future perspectives of the application of Computational Fluid Dynamics (CFD) to nuclear reactor safety problems, three Writing Groups were created, under the auspices of the NEA working group WGAMA, to produce state-of-the-art reports on different aspects of the subject. The work of the second group, WG2, was to document the existing assessment databases for CFD simulation in the context of Nuclear Reactor Safety (NRS) analysis, to gain a measure of the degree of quality and trust in CFD as a numerical analysis tool, and to take initiatives to extend the existing databases. The group worked over the period of 2003-2007 and produced a final state-of-the-art report. The present paper summarises the material gathered during the study, illustrating the points with a few highlights. A total of 22 safety issues were identified for which the application of CFD was considered to potentially bring real benefits in terms of better understanding and increased safety. A list of the existing databases was drawn up and synthesised, both from the nuclear area and from other parallel, non-nuclear, industrial activities. The gaps in the technology base were also identified and discussed. In order to initiate new ways of bringing experimentalists and numerical analysts together, an international workshop -- CFD4NRS (the first in a series) -- was organised, a new blind benchmark activity was set up based on turbulent mixing in T-junctions, and a Wiki-type web portal was created to offer online access to the material put together by the group giving the reader the opportunity to update and extend the contents to keep the information source topical and dynamic.

• Economic and Environmental Geology
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• 제52권1호
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• pp.81-90
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• 2019

In this study, the effects of fracture tensor component and first invariant on block hydraulic behaviors are evaluated in the 2-D DFN(discrete fracture network) systems. A series of regression analysis is performed between connected fracture tensor components and block hydraulic conductivities estimated at every $30^{\circ}$ hydraulic gradient directions for a total of 36 DFN systems having various joint density and size distribution. The directional block hydraulic conductivity seems to have strong relation with the fracture tensor component estimated in direction perpendicular to it. It is found that an equivalent continuum approach could be acceptable for the 2-D DFN systems under condition that the first invariant of fracture tensor is more than 2.0~2.5. The first invariant of fracture tensor seems highly correlated with average block hydraulic conductivity and can be used to evaluate hydraulic characteristics of the 2-D DFN systems. Also, a possibility of upscaling using the first invariant of fracture tensor for the DFN system is addressed through this study.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• 제25권1호
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• pp.71-76
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• 2019

Background: An 8-year-old girl had severe neck pain and stiffness after trauma. CT scan showed atlantoaxial rotatory subluxation (AARS). She had conservative treatment because she did not have neurological symptoms and spinal basilar artery dysfunction. Conservative therapy was halter traction twice for 4 weeks. However, pain and stiffness persisted. She had been recommended to have surgery from her physician, but she received manual therapy for non-surgical procedures. Methods: The joint mobilization, muscle energy technique, motor control exercise, and deep neck flexor (DNF) endurance exercise were applied as manual therapy and 10 session for 2weeks. Results: Clinical outcomes were measured at initial baseline, after 2 weeks, and after 6weeks. Active range of motion was completely restored after 6weeks and numeric pain rating scale was completely reduced after 2 weeks. The strength of neck flexor muscle recovered to normal after 2 weeks, and the DNF endurance was improved to 25 seconds after 2 weeks and to 42 seconds after 6weeks. Motor control capacity recovered to 30 ㎜Hg after 2 weeks. Conclusions: This case report describes the immediate and short-term clinical outcomes for a patient presenting with symptoms of neck pain following AARS. Clinical rationale and patient preference aided the decision to incorporate manual therapy as a treatment for this patient. Manual therapy has shown a successful recovery in AARS patients, more research is needed to validate the inference of this case report.

• Tunnel and Underground Space
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• 제31권1호
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• pp.66-81
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• 2021

The effects of directional fracture tensor components and first invariant of fracture tensor on deformation moduli and shear moduli of fractured rock masses is analyzed based on regression analysis performed between 3-D fracture tensor parameters and deformability of DFN blocks. Using one or two deterministic joint sets, a total of 224 3-D discrete fracture network (DFN) cube blocks were generated with various configurations of deterministic density and probabilistic size distribution. The fracture tensor parameters were calculated for each generated DFN systems. Also, deformability moduli with respect to three perpendicular direction of the DFN cube blocks were estimated based on distinct element method. The larger the first invariant of fracture tensor, the smaller the values for the deformability moduli of the DFN blocks. These deformability properties present an asymptotic pattern above the certain threshold. It is found that power-law function describes the relationship between the directional deformability moduli and the corresponding fracture tensor components estimated in same direction.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.281-292
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• 2022

This study aimed to analyze the dynamic punching shear performance of slab-column joints under cyclic loads with the use of double-hooked end (5D) steel fibers. Structural systems such as slab-column joints are widely found in infrastructures. The susceptibility to collapse of such structures when submitted to seismic loads is highly dependent on the structural performance of the slab-column connections. For this reason, the punching capacity of reinforced concrete (RC) structures has been the subject of a great number of studies. Steel fibers are used to achieve a certain degree of ductility under seismic loads. In this context, 5D steel hooked fibers provide high levels of fiber anchoring, tensile strength and ductility. However, only limited research has been carried out on the performance under cyclic loads of concrete structural members containing steel fibers. This study covers this gap with experimental testing of five different full-scale subassemblies of RC slab-column joints: one without punching reinforcement, one with conventional punching reinforcement and three with 5D steel fibers. The subassemblies were tested under cyclic loading, which consisted of applying increasing lateral displacement cycles, such as in seismic situations, with a constant axial load on the column. This set of cycles was repeated for increasing axial loads on the column until failure. The results showed that 5D steel fiber subassemblies: i) had a greater capacity to dissipate energy, ii) improved punching shear strength and stiffness degradation under cyclic loads; and iii) increased cyclic loading capacity.

• Journal of the Korean Orthopaedic Association
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• 제56권4호
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• pp.361-365
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• 2021

Pelvic fractures are high-energy injuries, often accompanied by damage to the adjacent tissues and organs. For patients with pelvic trauma, active treatment is required early in the injury, because mortality can increase if appropriate treatment is not provided. In most cases, however, minimally invasive surgery is considered because extensive surgery cannot be performed due to the patient's condition. Percutaneous fixation of the pubis has been introduced because it can be applied easily to achieve the stability of the anterior part of the pelvis. Although many studies introduced percutaneous fixation of pubic bone fractures, most describe screw fixation for nondisplaced fractures. When treating displaced fractures with percutaneous screw fixation, it is difficult for the guide pin or drill bit to avoid the joint surface. Using a bent guide pin could allow easy insertion of the cannulated screw while avoiding the articular surface.

• Asia-Pacific Journal of Business
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• 제12권4호
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• pp.107-134
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• 2021

Purpose - Korean firms have entered the Mongolia, the world's top 10 resource rich country with huge market potential, since the diplomatic relations between Korea and Mongolia were established in 1990, but little is known about Korean firms' entry strategy in the Mongolian market. With this background, this study aims to investigate the seven cases of Korean firms doing business in Mongolia (SK Telecom, Samsung S1, T-Money, E1 Energy, Cafe Bene, E-Mart, and CU). Methodology - this study is based on numerous primary and secondary data about the Mongolian market, as well as Korean firms in Mongolia. Findings - the following three implications were derived from our case analysis: first, when entering into Mongolia, a thorough analysis of political and social risks and a good understanding of institutional voids should be preceded. Second, for this reason, entering through cooperation with local partners, such as joint ventures or franchising, is expected to increase the possibility of success. Third, unlike in the early days of Korean firms in Mongolia, the business environment in Mongolia has become more stable and predictable, and a friendly atmosphere for Koreans and Korean firms is forming, increasing the possibility of success and settlement of Korean firms. Research implications - this study contributes to extant literature by providing more systematic research on Korean firms in Mongolia and by presenting practical implications through the analysis of success and failure cases of Korean firms in the Mongolian market.

• Journal of Advanced Navigation Technology
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• 제27권1호
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• pp.146-153
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• 2023

In accordance with the industrial convergence regulation sandbox decision promoted by the Ministry of Trade, Industry and Energy, the "machine tool sharing service in the factory" applied for by MyMaker Co., Ltd., an industry-academia cooperation company, was granted a demonstration exception. While implementing this, in a situation where the ordering service part had to be developed as software, the company's domain problems were identified and analyzed, procedures were established, and a system was designed that met the related requirements. As a joint research and development project to solve the difficulties of the LINC+ industry, the order-to-order system was finally developed for shared factory services. In accordance with the procedure and requirements analysis, the planning, design, prototyping, and implementation production stages were carried out. Finally, it was confirmed that the final development contents were well implemented according to the requirements, and the resolution of the difficulties was confirmed through functional verification demonstrations.