• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.54-62
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• 2008

A new solution method was developed to solve the free surface flow around a hull and named as 'Variable Free Surface Panel Method'. In the method the non-linearity of the free surface boundary conditions was fully taken into account and the raised panel method was employed to effectively solve the problem. The transom stern flow was also considered and the panel on the hull was generated using the panel cutting method. Numerical calculations were performed for KCS(KRISO Container Ship) hull form and compared with the experimental data to confirm the validity of the method. The comparison with the conventional free surface panel method was also accomplished. It is confirmed that new method gives more reliable results than the conventional method.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.101-105
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• 2002

Many malfunction take place in container crane spreader due to impact. So we designed a 2 DOF hydraulic impact absorbing equipment to absorb the impact and we studied the change of damping coefficient with respect to the variation of dimensions of oil-Cylinder wail. When we design the dimension of hydraulic cylinder wall considering the displacement on the wall, the value of it over 20m didn't affect the damping coefficient.

• The Journal of the Convergence on Culture Technology
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• v.2 no.1
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• pp.45-51
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• 2016

Aristotle said 'Poet is that from who can give happiness, therapeutic effects to the reader.' He say to 'mimoumenon' it means a native Image restored. However, Kant said that Aesthetic is requested not only reappearance but freedom. This result is that between joyful freedom and reason of the judgement of tasted feeling. Because Art ever created is the spirit of the moral ideals, and those who combine the best of the joy. I think need to more communication and joy than their theories. For poet is replaced to be communicated and joyful for our happiness and freedom.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.2
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.

• Journal of Ocean Engineering and Technology
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• v.31 no.1
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• pp.8-13
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• 2017

Cavitation is used in various fields. This study examined the drag reduction of an underwater vehicle using cavitation. In this study, the natural partial cavitation analysis results were verified using CFD code with the Navier-Stokes equation based on a mixture model. The momentum and continuity equations in the mixture phase were separately solved in the liquid and vapor phases. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The results of a computational analysis showed good agreement with the experiment. A computational analysis was also performed on the supercavity. The study investigated the cavity characteristics and drag of an underwater vehicle and studied the speed required to achieve a supercavity. Finally, a 1DOF analysis was carried out to investigate the thrust system for a supercavity. As a result, one of the methods for determining a suitable thrust system for a supercavitating underwater vehicle was presented.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.349-353
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• 2013

공동주위의 유동에 대한 연구결과를 보면 개방형 공동(L/D<10)과 밀폐형 공동(L/D>13)으로 구별하는 데 개방형 공동은 앞전에서 발생한 자유전단층이 뒷전 부근에 재부착하여 공동을 완전히 연결하므로, 자유전단층과 외부유동과의 상호작용으로 발생하는 심한 압력변화에 의해 진동현상이 나타나게 된다. 이것은 큰 소음을 유발하고, 구조물의 고장 혹은 파괴의 원인이 되기도 하고, 공력 성능 및 안정성에 해를 주고 민감한 계기를 손상 시킬 수도 있다. 본 논문에서는 공동을 연구하기 위해 EDISON_CFD를 사용하여 공동의 시뮬레이션하기 위해 격자를 구성하고 세장비를 각각 1/5, 1/3, 1/2, 1, 2, 5 로 변화를 주어 M=1.5 일 때 밀도, 압력, 마하수와 유동구조를 세장비에 따라 결과를 비교, 분석한다.

• The Korea Swine Journal
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• v.10 no.11 s.111
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• pp.44-47
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• 1988

양돈업의 제1단계로서 농가호당 300두(비육돈) 까지는 자유조정에 맡기고, 300-3,000두까지는 등록제, 3,000두 초과 규모는 허가제로 하고 1만두를 넘는 대규모 양돈농가의 규모는 1만두 규모로 축소조정토록 법이 아닌 시행령으로 규정해야 한다.

• Korean Journal of Childcare and Education
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• v.12 no.1
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• pp.57-81
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• 2016

The purpose of this study was to find out the feature of children's play according to a player number restriction rule in the free choice activities. And it is expected that the result of this study will contribute to improving the management of free choice activities. The participants of this study were a homeroom teacher, professor as a co-researcher and 25 4-year-old children of a private kindergarten. The data were collected by observation, children interview and reflective journal of the teacher from July to October in 2014. The results indicated that the children were stressed out with using name cards for presenting center selection, showed overcompetitive behaviors, and frequently violated the rules. The researchers found that the restriction rule had some dysfunctions, which were interferences of moral development, social-emotional development, self-regulation development, preventing safety-accident and free choice behavior. The researcher as a teacher abandoned the player number restriction rule, and observed the children's play. As a result, children's self-regulation abilities on physical space, play and conflicts improved and the teacher changed her strategy when managing free choice activities. Based on the results, the needs of various restriction rules and appropriate methods for applying the rules in free choice activities were further discussed.

• Journal of The Korean Association For Science Education
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• v.32 no.4
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• pp.686-702
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• 2012

This study investigated the impact of grouping methods on free inquiry implementation through the use of mixed research methods. Some 113 7th graders and 2 science teachers in two middle schools participated in this study. The 113 students who participated in this study were grouped by homogeneity and heterogeneity according to scientific inquiry skills and personality types respectively, and performed free inquiry activities on the same subject for three weeks. Data were collected by means of a test on science inquiry skills and from focus group interviews with 36 students and in-depth interviews with 2 teachers. The quantitative results of this study showed that homogeneous grouping was more effective than heterogeneous grouping in improvement of scientific inquiry skills. Meanwhile, the qualitative results revealed both the students and teachers perceived that it was effective to compose a small group according to their affective quality than their cognitive quality. Particularly, most of the students preferred the method of small group from the personality types. Some students and both teachers proposed that it is necessary to collect enough information on students and to use them in mixture with the method of small group according to the affective quality.

• Journal of Korean Society of Transportation
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• v.19 no.3
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• pp.7-18
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• 2001

The pedestrian signal systems operating presently could provide more time for the pedestrian to cross the street than the previous system, but it would increase the cycle length and cause longer delays at the signalized intersections. For instance, more than 80% of traffic signals would have to have the cycle length increased by 10sec in Daegu Metropolitan areas. Therefore. the purpose of this study is to propose a pedestrian traffic signal time that not only maintains the safety of the pedestrian but also reduces the traffic cycle length. The proposed pedestrian signal time is set to enable enough time for the elderly to cross and the flashing time is set low enough to deter the ordinary person. This new pedestrian signal time can reduce the traffic cycle length at intersections and prevent the Pedestrian crossing during flashing time. In addition to the flashing green should be changed to flashing red to warn the pedestrian he should not begin crossing as opposed to the flashing green which suggest he could cross. In this study, the speed of 1.1m/sec and 0.85m/sec are applied to the new proposed signal time for normal and elderly person respectively after analyzing data collected at Daegu Metropolitan area.