• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.689-692
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• 2005

In this paper, we have developed a retrodirective active array operating in the 2 GHz LS band. The retrodirective array has the property of re-directing any electromagnetic wave back to the incoming direction without any priory informations. The system is consisted of frequency mixers and antenna array. The mixer is acting as a phase conjugator. In this research, 2-port gate mixers using pHEMT and 1${\times}$4 monopole array have been used. The retrodirective array developed in this research can be applied in the base station facilities for the wireless mobile communications and RFID transponders.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.212-218
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• 2011

The effect of composite reinforcing bars on surface electrical resistivity of concrete was investigated through experimental program. The resistivity was measured by Wenner method using an equipment with 4 probe. Ordinary steel, GFRP, and CFRP reinforcing bars produced domestically were used and a specimen with no reinforcement was tested for the comparison. This investigation is motivated from the fact that measured value of resistivity of concrete is significantly affected by details of steel reinforcements, such as location, depth and direction of the internal steel reinforcement. These results could be valuable data for evaluation of corrosion degree of concrete structures reinforced or strengthened by the composite reinforcing bars.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.95-102
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• 1996

The skewness of near-bottom velocity distribution caused by the nonlinear interaction of the second order waves proposed by Wells (1967) has been re-evaluated. The direction of cross-shore sediment transport was related to the sign of the third moment (skewness) of velocity distribution, and a new concept of neutral depth which can explain the recovery of beach equilibrium after a disturbance is suggested. The seasonal change of beach profile due to the change of wave condition (storm-swell profile) is interpreted in terms of nonlinear interaction of the waves rather than the conventional wave steepness. The beach is eroded (storm profile) when the nonlinear interaction of the waves is strong (storm wave), whereas the beach is accreted (swell profile) when the nonlinear interaction is weak (swell wave).

• Physical Therapy Rehabilitation Science
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• v.10 no.4
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• pp.463-469
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• 2021

Objective: If non-surgical treatment fails, arthroscopic rotator cuff repair (ARCR) is recommended, and ARCR considers graft augmentation in consideration of size, direction, and re-tear. It is reported to have potential benefits by improving the healing rate as it can fill the gaps that have been left behind. The purpose of this study is to investigate the effect of structural changes observed after ARCR on muscle action through magnetic resonance imaging and to investigate the effect of appropriate physical therapy required for graft augmentation in the general ARCR rehabilitation protocol. Case presentation: A 47-year-old male hospitalized for postoperative rehabilitation following ARCR participated in a 5-week physical therapy intervention. The postoperative day was 6 months, but due to shooting pain and shoulder dysfunction,and the movement of the shoulder was compensatory motion, not normal motion. Physical agents, manual therapy, and supervised exercise for 110 minutes per session were performed 3 times a week, and pain intensity, range of motion, function, and strength were evaluated. Results: As a result of the study, the patient showed positive improvement in pain intensity, range of motion, function, and strength. In addition, normal scapulohumeral rhythm movement was observed. Conclusions: According to the results of this case, appropriate physical therapy according to the compensatory motion shown in the structural changes after ARCR can positively improve the pain intensity, range of motion, function, and strength of ARCR patients.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.665-675
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• 2019

The wire-wrapped fuel bundle is an assembly design in a sodium-cooled fast reactor. A wire spacer is used to maintain a constant gap between rods and to enhance the mixing of coolants. The wire makes the flow complicated by creating a sweeping flow and vortex flow. The vortex affects the flow field and heat transfer inside the subchannels. However, studies on vortices in this geometry are limited. The purpose of this research is to investigate the vortex flow created in the wire-wrapped fuel bundle. For analysis, a RANS-based numerical analysis was conducted for a 37-pin geometry. The sensitivity study shows that simulation with the shear stress transport model is appropriate. For the case of Re of 37,100, the mechanisms of onset, periodicity, and rotational direction were analyzed. The vortex structures were reconstructed in a three-dimensional space. Vortices were periodically created in the interior subchannel three times for one wire rotation. In the edge subchannel, the largest vortex occurred. This large vortex structure blocked the swirl flow in the peripheral region. The small vortex formed in the corner subchannel was negligible. The results can help in understanding the flow field inside subchannels with sweeping flow and vortex structures.

• Wind and Structures
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• v.29 no.1
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• pp.43-53
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• 2019

Vortex-induced vibration of three circular cylinders (each of diameter D) in an equilateral triangular arrangement is investigated using the immersed boundary method. The cylinders, with one placed upstream and the other two side-by-side downstream, are free to vibrate in the cross-flow direction. The cylinder center-to-center spacing L is adopted as L/D = 2.0. Other parameters include the Reynolds number Re = 100, mass ratio $m^*=2.0$, reduced velocity $U_r=2{\sim}15$ and damping ratio ${\zeta}=0$. Cylinder vibration responses are dependent on $U_r$ and classified into five regimes, i.e. Regime I ($U_r{\leq}3.2$), Regime II ($3.2<U_r{\leq}5.0$), Regime III ($5.0<U_r{\leq}6.4$), Regime IV ($6.4<U_r{\leq}9.2$) and Regime V ($U_r>9.2$). Different facets of vibration amplitude, hydrodynamic forces, wake patterns and displacement spectra are extracted and presented in detail for each regime.

• Journal of the Korea Society of Computer and Information
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• v.23 no.11
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• pp.167-173
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• 2018

The Korean government announced its goal of commercializing autonomous vehicle by year 2020. With such changes, it is expecting to decrease car accident mortality by half. To commercialize autonomous car, not only worries on safety of autonomous vehicle has to be solved but at the same time, institutional system has to be clear to distinguish legal responsibilities in case of accident. This paper will present the legal improvement direction of the introduction of autonomous vehicles as follows. First, it is necessary to re-establish concept of 'driver' institutionally. Second, it is appropriate to focus on Level 3 autonomous vehicle which is about to be commercialized in year 2020 and organize legal responsibility. Third, we should have a clear understanding on how level 3 autonomous vehicle will be commercialized in the future. Fourth, it is necessary to revise The Traffic Law, Act on Special Cases concerning the Settlement of Traffic Accident, and Automobile Accident Compensation Security Law in line with level 3 autonomous vehicle. Fifth, it is necessary to review present car insurance system. Sixth, present Product Liability Law is limited to movable products (Article 2), however, it is necessary to include intangible product which is software. Seventh, we should review on making special law related to autonomous car including civil, criminal, administrative, and insurance perspectives.

• Journal of the Korea Society of Computer and Information
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• v.24 no.5
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• pp.139-147
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• 2019

This study is conducted to analyze how Social Media characteristics of restaurant franchise affect customer decision making and redelivery intention and find out how to do Social Media marketing which is getting important. Through this study, we will understand the direction of Social Media management. In this study, we had 220 users to respond questionnaires who looked up about restaurant franchise through Social Media. In the previous research, we classified the Social Media characteristics about the restaurant franchise into the fields of liveliness, agreement, reliability, communication, accuracy, and entertainment. In order to verify the hypothesis, we conducted single regression analysis and multiple regression analysis and verified the relationship between variables. First, we found that Social Media characteristics of restaurant franchise has a positive relationship with favorability. Second, Social Media characteristics of restaurant franchise has a positive relationship with satisfaction. Third, favorability has a positive effect on satisfaction. Fourth, favorability has a positive effect on the intention of re-inquiry and redeliver. Fifth, satisfaction has a positive effect on the revisit and intention to redirect. As a result of the study, we found that restaurant franchise will gain trust of customers if they take into account the characteristics of Social Media of restaurant franchise and conduct customized marketing according to the head office of restaurant franchise and perform continuous feedback and management in order to improve customer's favorability and loyalty.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.1
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• pp.37-46
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• 2019

In order to present the enhancement direction for the military administrative facilities, that can satisfy the user demands and achieve cost-effectiveness the goal of public projects, this research analyzes the features of functional spaces using Analytical Hierarchy Process(AHP). Basically, the scope is selected to four facilities commander office, private office, public office, and meeting room, because they have an effect on military administrative facilities. Since the space is established by a combination of their own functions, this research begins with an analysis of functional spaces of military administrative facilities, which is verified through literature review and interview with expert. Thereafter, an AHP survey is conducted to military personnel to analyze the priority of functional spaces and to re-classify the functional spaces of each Military administrative facilities. Resultingly, the difference of functional spaces preference according to ranks and facility type are identified. Even though the same military facilities, it means that user satisfaction is different. Therefore, user satisfaction should be considered for each facility at the construction plan. It can minimize overlapped and unused spaces, which can help ensure cost-effectiveness. Consequently, this research suggested the methodology and the process that can take user satisfaction and can support the enhancement of military facilities standards.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.852-857
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• 2018

Vortex Generators are used in heat exchanger to enhance the heat transfer of air side. 3-D numerical analysis is performed on heat transfer characteristics of a channel with trapezoidal vortex generator. We investigate the effects of vortex generators with two different inclined angles to flow direction which are forward and backward vortex generators. The thermal hydraulic performance such as Nu and pressure drop, is compared quantitatively. The results show that vortex generator enhances the heat transfer by developing boundary layers and secondary flow in the downstream. The downwash flow region corresponds to the maximum Nu, while the upwash flow region corresponds to Nu minimum. In the view of the heat transfer characteristics, FVG is better than BVG. However, when flow is turbulent as Re increases, the pressure drop for FVG is higher than that for BVG.