• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.30-34
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• 1993

기계구조물이 고속화, 경량화 됨에 따라 더 정밀한 구조물의 설계 및 해석이 요구되어지고 있고, 이에 따라 단속적모형 보다 한 단계 더 나아가 분포변수 모형으로 구조물을 모형화하게 된다. 특히 나선형 스프링은 기계구조물에서 가장 널리 사용되는 일반적인 요소로서, 그 형상이 공간상의 굽은 봉 형상이 므로 연성된 편미분방정식 형태로 지배방정식이 기술된다. 나선형 스프링 해 석은 Michell(1890)과 Love(1899)의 정적해석을 시작으로 Phillips와 Costello [1]의 'SimpleTheory' 및 Wittrick [3]의 지배방정식등 매우 복잡한 연성된 편미분방정식 형태를 지니고 있다. 그러나 이와 같은 편미분방정식은 해석하 기가 매우 어려워 수치해법으로도 간단한 경우에 한해서만 해석하여 왔다. 본 연구에서는 이와 같은 연성된 편미분방정식을 해석하기 위하여 보다 구 조진동문제에 적합한 수치해법을 제안하고, 이를 이용하여 나선형 스프링의 강제과도진동 응답을 정확하고 효율적으로 구하였다.

• The Journal of Korean Association of Computer Education
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• v.14 no.2
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• pp.13-22
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• 2011

The importance of algorithm education has been emphasized for creative problem-solving capability. Especially, algorithm teaching materials related with mathematics and science are under development to enhance logical thinking. However, there are not enough teaching-learning models applicable in the field of education. Therefore, this paper proposed a teaching-learning model for effective algorithm education. The teaching-learning model reflects two characteristics : an algorithm learning process is spiral, and algorithm education is based on logical thinking. Furthermore, a survey was conducted for students' satisfaction, and the result was a mixed teaching-learning model with PBL, SDL, and peer tutoring. Based on the proposed model, examples of classes for mathematics and science are suggested to show the feasibility of effective algorithm education.

• Journal of Engineering Education Research
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• v.11 no.3
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• pp.54-62
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• 2008

This paper presents the process of developing, applying and increasingly updating curriculums to reinforce education in IT field through cooperation of industry and academy by the invention of government. In particular, the curriculums are developed and refined in order to satisfy both industry as users and academy as suppliers, using a spiral model, which was originally proposed for software development by Boehm. The result and the assessment are described where the developed curriculums have been applied at the universities in a national-wide base through a project by government. The basic principles of this model are general enough to be applied to curriculum development in various areas of college education.

• Journal of Digital Contents Society
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• v.15 no.3
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• pp.327-338
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• 2014

This study proposes the evolution model of emerging media platform including smart media (M-IPTV, Smart TV) and IPTV, through a spiral evolution model based on the theory of the exploration & the exploitation. Authors suppose that the IP media evolved from IPTV technology, evolution of which has come through the development model of serial circular process. For explanation of this evolution, we propose the research model integrating the spiral model and the exploration & exploitation theory. Researchers define the smart media as the evolved media from IPTV, through this proposed model. We expect this model to be the theoretical base of media regulation and setting direction of future media service. Thus, this research are summed up as follows. To begin with, we classify the evolutionary stage of IPTV from the view points of service feature, regulation frame and technological characters. Secondly, we organize and confirm the research model of IPTV evolution through case analysis of the 3 cycles of each evolutionary stage. As a result, discussion of this study helps understanding mobile IP media and smart media as a post IPTV and leads the solution of various regulation issues and the development of the innovative media service and content. In addition, it can guide the government for the evolutionary direction to promote the media and the content industry.

• Journal of the Korean Society of Radiology
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• v.7 no.2
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• pp.137-143
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• 2013

This study presents comparison results between axial and spiral scanning in the head and chest region with 64 MDCT to evaluate organ doses in infants and toddlers, who are more radiosensitive to radiation than adults and rise in the number of CT examinations, during CT scanning. Organ doses were significantly lower in spiral scanning than axial scanning regardless of scanned regions. The average organ dose for the chest scan using pitch of 1.355 was found to be significantly higher(average -12.03%) than for the other two pitch settings(0.525 and 0.988) in the spiral scanning mode compared with the axial one. Organ doses in the spiral scanning mode were lower by average 20.54% than the axial scanning mode. The results of the study that evaluated organ doses with an anthropomorphic phantom will help to demonstrate the result values of Monte Carlo simulations and make a contribution to more accurate evaluations of organ doses in toddlers undergoing a CT examination.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.567-575
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• 2018

This study examined a pile foundation using a spiral pile. To maintain the structural safely, a foundation for connecting the ground and the ground structure is needed. On the other hand, noise and vibration, etc. cause problems when constructing a foundation on adjacent structures or urban areas. A study of the spiral foundation of a new shape with low vibration and noise was carried out to solve these problems. A study of pile foundations was carried out on a scaled model test and compared with the results of Meyerhof's bearing capacity theory. The scaled model test results showed that the bearing capacity increases with increasing pitch angle and length of the spiral pile. To verify the measured bearing capacity in a test with theoretical results, the bearing capacity of the actual spiral pile and scaled model pile were examined and compared. The ultimate bearing capacity of the spiral pile can be increased by increasing the foundation length and pitch angle. This study complements existing foundation construction problems and contributes to a better effect and safety.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.905-910
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• 2013

The flow analysis has been made by applying the turbulent models in the helically coiled tubes of heat transfer. The k-${\varepsilon}$ and Spalart-Allmaras turbulent models are used in which the structured grid is applied for the simulation. The velocity vector, the pressure contour, the change of residuals along the iteration number and the friction factors are simulated by solving the Navier-Stokes equations to make clear the Reynolds number effect. The helical tube increases the centrifugal forces by which the wall shear stress become larger on the outer side of the tube. The centrifugal force makes the heat transfer rate locally larger due to the increase of the flow energy, which finds out the close relationship between the pressure drop and friction factor in the internal flow. The present numerical results are compared with others, for example, in the value of friction factor for validation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.95-103
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• 2016

In this paper, aeroelastic instability and aerodynamic damping ratio of a helical $180^{\circ}$ model which shows better aerodynamic behavior in both along-wind and crosswind responses on a super tall building was investigated by an aeroelastic model test, and the aerodynamic damping ratio was evaluated from the wind-induced responses of the model by using Random Decrement Technique. Aerodynamic damping ratios evaluated in this study were verified through comparison with previous results obtained by quasi-steady theory. As a result, the aeroelastic instability of the helical $180^{\circ}$ model in crosswind direction were not occurred for any conditions with increasing the reduced wind velocity while the square model generally encounters aeroinstability due to the vortex shedding. The aerodynamic damping in along-wind direction for the helical $180^{\circ}$ and the square model increased monotonically both with reduced wind velocity, i.e., there is no relation with modifications of building shapes. On the other hand, in crosswind direction, the characteristics of aerodynamic damping ratio with reduced wind velocity for helical $180^{\circ}$ model were quit different from those of the square model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.9-17
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• 2017

Characteristics of aerodynamic damping ratios of a helical $180^{\circ}$ model which shows better aerodynamic behavior in both along-wind and across-wind responses on a super tall building was investigated by an aeroelastic model test. The aerodynamic damping ratio was evaluated from the wind-induced responses of the model by using Random Decrement (RD) technique. Further, various triggering levels in evaluation of aerodynamic damping ratios using RD technique were also examined. As a result, it was found that when at least 2000 segments were used for evaluating aerodynamic damping ratio for ensemble averaging, the aerodynamic damping ratio can be obtained more consistently with lower irregular fluctuations. This is good agreement with those of previous studies. Another notable observation was that for square and helical $180^{\circ}$ models, the aerodynamic damping ratios in along-wind direction showed similar linear trends with reduced wind speeds regarding of building shapes. On the other hand, for the helical $180^{\circ}$ model, the aerodynamic damping ratio in across-wind direction showed quite different trends with those of the square model. In addition, the aerodynamic damping ratios of the helical $180^{\circ}$ model showed very similar trends with respect to the change of wind direction, and showed gradually increasing trends having small fluctuations with reduced wind speeds. Another observation was that in definition of triggering levels in RD technique on aerodynamic damping ratios, it may be possible to adopt the triggering levels of "standard deviation" or "${\sqrt{2}}$ times of the standard deviation" of the response time history if RD functions have a large number of triggering points. Further, these triggering levels may result in similar values and distributions with reduced wind speeds and either may be acceptable.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.173-177
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• 2011

만곡도가 높은 하천의 경우 수위가 상승하게 될 때 만곡부에서의 흐름 회전 방향이 나선형 흐름으로 바뀌어 하류방향으로 주 흐름에 중첩하여 발생하는 이차류로 인해 하도가 불안정해지고 내 외측의 수위차가 발생하는 편수위가 발생하면서 하도 바깥쪽으로 수위가 상승하는 현상이 나타나게 된다. 이와 같은 만곡부의 외측부에서 발생하는 수위상승은 제방의 월류 피해와 이차류로 인한 침식 피해를 유발하게 된다. 하천에서의 만곡은 보편적인 현상이며, 흐름의 물리적인 현상으로 인해 발생하는 자연현상이다. 본 연구에서는 만곡수로의 내 외측부에서 발생하는 유속과 편수위 현상과 같은 수리학적 특성을 규명하기 위해 $90^{\circ}$ 하도와 $180^{\circ}$ Sharp 하도와 같은 만곡 실험하도를 대상으로 SMS 모형, RAMS 모형 그리고 CCHE2D 모형과 같은 3개의 2차원 모형을 적용하고 그 결과를 실측자료와 비교함으로써 만곡부에서의 2차원 수리 특성을 살펴보았다. 또한 과거에 개발된 편수위 산정공식들의 적용성을 살펴보기 위해 주요 지점의 실측자료와 2차원 모형의 모의자료를 이용하여 만곡부의 편수위를 산정하여 비교 검토하였다.