• 한국소음진동공학회논문집
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• 제13권10호
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• pp.821-827
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method requires no interpolation functions. no integration Procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is involved, compared with FEM and BEM. In order to explain tile reason why spurious eigenvalues are generated when the NDIF method is applied to free plates, the NDIF method has been considered for free vibration analysis of both a fixed string and a free beam. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by an exact method or a numerical method (ANSYS).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1004-1008
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• 1990

This research focuses on developing a new and computationally efficient algorithm for free space structuring and planning collision free paths for an autonomous mobile robot working in an environment populated with polygonal obstacles. The algorithm constructs the available free space between obstacles in terms of free convex area. A collision free path can be efficiently generated based on a graph constructed using the midpoints of common free links between free convex area as passing points. These points correspond to nodes in a graph and the connection between them within each convex area as arcs in this graph. The complexity of the search for collision free path is greatly reduced by minimizing the size of the graph to be searched concerning the number of nodes and the number of arcs connecting them. The analysis of the proposed algorithm shows its efficiency in terms of computation ability, safety and optimality.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.115-116
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• 2016

Numerous of free-form buildings come up with external appearances using various types of free-form panels. If the panel types produced, transport and installation order and maintenance history are not properly managed, it is difficult to complete a given project successfully. For free-form building projects that satisfy 5 factors (proper time, place, price, product and quantity), a supply chain management technique is applied for distribution management of free-form concrete panels. In addition, the study listed the whole production process of free-form concrete panels and any necessary information, and suggested a basic model for the management. The study result will be a great help in effective distribution management of free-form panels for free-form building projects.

• 한국해양공학회지
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• 제29권6호
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• pp.427-435
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• 2015

This paper provides the numerical results of a simulation of the flow around a propeller working beneath the free surface. A finite volume method is used to solve the unsteady Reynolds averaged Navier-Stokes (URANS) equations, where the wave-making problem is solved using a volume-of-fluid (VOF) method. The numerical analysis focuses on the propeller wake structure affected by the free surface, where we consider another free surface boundary condition that treats the free surface as a rigid wall surface. The propeller wake under the effect of these two free surface conditions shows a reduction in the magnitude of the longitudinal and vertical flow velocities, and its vortical structures strongly interact with the free surface. The thrust and torque coefficient under the free surface effect decrease about 3.7% and 3.1%, respectively. Finally, the present numerical results show a reasonable agreement with the available experimental data.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.126-127
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• 2015

New technologies using a CNC machine to reduce the production cost of free-form buildings are being developed. To produce free-form members with such technologies, a vast free form building should be first divided into multiple panels that can be produced. Considering the curved surface of free-form buildings, the shape and size of divided freeform panels vary, which will lead to a great deal of errors. Currently, the engineers and designers complete the panelizing work through trials and errors even in large-scale projects, which results in increased construction duration and cost. Thus, it is necessary to develop a freeform panelizing technology to maximize the economic effects of free-form concrete member production technology. The purpose of the study is to analyze influence factors on panelizing of free-form buildings, which is a preceding research for development of a panelizing technology. The influence factors drawn will provide a core basis for development of panelizing technologies for free-form buildings.

• 한국소음진동공학회논문집
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• 제17권3호
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• pp.220-225
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• 2007

Free vibration analysis using the method of NDIF (non-dimensional dynamic influence function), which was developed by the author, is extended to arbitrarily shaped polygonal plates with free edges. Local Cartesian coordinate systems are employed to apply the free boundary condition to nodes distributed along the edges of the plate of interest. Furthermore, a new way for applying the free boundary condition to nodes located at corners of the plate is for the first time introduced by considering the phenomenon of stress concentration at the corners. Two case studies show that the proposed method is valid and accurate when the eigenvalues by the proposed method are compared to those by FEM(ANSYS).

• 영어어문교육
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• 제17권3호
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• pp.119-139
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• 2011

Free-talking in Korea has recently been emphasized as a way of improving students' speaking ability outside of the classroom. The purpose of this study is to examine perceptions of free-talking, to understand what type of roles were played by or allotted between Korean students and international professors (IPs) and to look for effective speaking strategies for utilizing free-talking. Participants of this study were 68 university students and 23 IPs. The data collected through a survey type of questionnaire were analyzed by this researcher and the main findings indicate that students and IPs have somewhat different viewpoints about their concepts of free-talking. Students expressed varying viewpoints depending on their experience and class (year). In terms of the benefits, usefulness, and satisfaction of free-talking, students and IPs seem to be in more agreement with each other although the two groups have conflicting perceptions in the particular operation of free-talking, especially in terms of preparation and feedback. Students stated that they feel anxious, nervous, and that they struggle with peer pressure while free-talking. However, they feel that through free-talking they build up confidence and increase their speaking ability. Regarding roles, most professors play a helpful role as a guide or facilitator while students want professors to provide more suitable materials and to tutor them by means of appropriate feedback and strategies as well-prepared teachers like a prompter, participant or tutor in the timely manner. Finally, this paper proffers a few practical suggestions for activating free-talking and a discussion of the pedagogical implications.

• 한국생산제조학회지
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• 제21권5호
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• pp.720-725
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• 2012

Sodium hypochlorite is used worldwide as a water disinfectant and in bleaching agent. Sodium hypochlorite applied to water initially undergoes hydrolysis to form free chlorine consisting of hypochlorous acid(HOCl) and hypochlorite ion($OCl^-$). For free chlorine determination, an electrochemical method is simple due to the electroactivity of free chlorine; it measures current and is free of most reagents. Amperometric free chlorine sensor has been developed with gold (Au)-based electrode. The 3-electrode free chlorine sensor whose working and counter electrodes were Pt exhibited excellent response to HClO at +400mV vs. Ag/AgCl/sat. KCl. In addition, the use of a pH error correction algorithm provided a reliable measurement of residual free chlorine in water sample without any pretreatment in the normal pH range(pH 6~8) of municipal water supply. The free chlorine sensor installed in on-line monitoring system could be used to continually monitor the level of residual free chlorine in real samples.

• Journal of Trauma and Injury
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• 제23권2호
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• pp.157-162
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• 2010

Purpose: Free flap reconstruction in the pediatric population is difficult. However, microsurgery has had remarkable success rates in children. The aim of study is to present our clinical experience using free flap for reconstruction of soft tissue defects in children and to describe long-term follow-up results. Methods: Between June 2002 and July 2010, 30 cases of pediatric reconstruction were performed with free flap. The authors analyzed several items, such as the kind of flap, associated complications, and growth problems. Results: Among the 30 cases, 21 cases were due to traffic accidents, 5 to cancer, and 4 to falls and other soft tissue defects. The lower leg and foot were the most common sites of the lesion. In the free flap operations we have done, 20 cases involved an anterolateral thigh perforator free flap, 6 a superficial circumflex iliac perforator free flap, and 4 an upper medial thigh perforator free flap. In early postoperative complications, partial necrosis was seen in 2 cases, infection in 1 case, and the hematoma in 1 case. A satisfactory success rate and functional results were achieved. Conclusion: Free flap reconstruction in children allows satisfactory function with no significant effect on growth. Free flaps are regarded as the primary choice for selective pediatric reconstructive cases.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.166-167
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• 2016

Unlike the past, supported by the development of digital technologies, free-form buildings are frequently designed with creative thoughts of architectural designers. However, there are some difficulties preventing successfully completion of projects, like reduced productivity and increased construction duration and cost upon the process of producing and installing concrete panels for free-form structures. In particular, there are active studies on the CNC machine for production of free-form concrete panels. Yet, it is difficult to effectively and easily come up with information on production and installation of free-form, curve-surfaced panels which are difficult to be mathematically defined. This requires a lot of manpower and time to implement the curved surfaces of free-form buildings as intended by architects. Accordingly, it needs a model that can effectively create production-installation data of free-form concrete panels for successful free-form building projects. Thus, the purpose of the study is to suggest data estimation model of production-installation using mathematical algorithm in free-form concrete panels. The study results will realize effective production and installation of free-form concrete members, allowing improved productivity of projects, reduced cost and shortened construction duration.