• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.231-234
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• 2009

Based on combined continuum-fracture mechanics, fracture criterion was utilized to predict impact performance of advanced high-strength steel sheets: 340R and TWIP940. The macro-crack propagation behavior at high stress triaxiality was characterized by V-notch tests while deformation behavior at high strain rate was characterized by simple tension tests with various cross head speeds. The characterized mechanical properties were incorporated into the FE program ABAQUS/Explicit to simulate the charpy impact tests, which showed good agreement with experiments.

• Journal of Advanced Research in Ocean Engineering
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• 제3권4호
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• pp.174-183
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• 2017

Numerical simulations were performed about the green water problem of a FPSO. Three regular waves in head sea were tested. A rectangular box-shaped FPSO was considered and it is assumed there is a vertical wall on the deck. For the numerical simulations, an open-source CFD code, OpenFOAM, was applied to solve the present problems. Focus is on wave fields around the FPSO, water flows and impact pressures on the deck. For the validation, the present calculation results were compared with the existing experimental of Lee et al. (2012) and Changwon university in KTTC Cooperative Study Report (2015). The statistical values and spatial distribution of the peak pressures are directly compared with the experimental data. Some discussions are made on the effects of the domain breadth on the Green water impact pressure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.917-917
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• 2003

The auditory experiments based on the subjective annoyance responses were undertaken for the establishment of the adverb modifiers of the heavy-weight impact noises. The standard heavy weight impact noise, impact ball noise and adult walking noise were recorded by dummy head at a newly-built apartment and were presented to the subjects by headphones. The levels of the three impact noises were varied from 30 to 60㏈(A) and the subjects matched one of the adverb modifiers to each level of the noise sources. As a result, seven scale modifiers were established and the intervals between the modifiers were found as equal. In addition, it was found that the lower annoyance noise limits for the heavyweight impact, impact ball and walking were 40-45㏈ (L$\sub$I, Fmax. AW), which is 6㏈ lower than in the previous study. The background noise level was as low as 21㏈(A) in the test booth, therefore, the testing conditions need to be concerned for evaluation of floor impact noise.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1773-1795
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• 2020

Unmanned aerial vehicles (UAVs) network are a very vibrant research area nowadays. They have many military and civil applications. Limited bandwidth, the high mobility and secure communication of micro UAVs represent their three main problems. In this paper, we try to address these problems by means of secure clustering, and a security clustering algorithm based on integrated trust value for UAVs network is proposed. First, an improved the k-means++ algorithm is presented to determine the optimal number of clusters by the network bandwidth parameter, which ensures the optimal use of network bandwidth. Second, we considered variables representing the link expiration time to improve node clustering, and used the integrated trust value to rapidly detect malicious nodes and establish a head list. Node clustering reduce impact of high mobility and head list enhance the security of clustering algorithm. Finally, combined the remaining energy ratio, relative mobility, and the relative degrees of the nodes to select the best cluster head. The results of a simulation showed that the proposed clustering algorithm incurred a smaller computational load and higher network security.

• The Journal of Korean Physical Therapy
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• 제25권6호
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• pp.386-392
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• 2013

Purpose: This study aimed to verify the impact of the time that the sitting posture is maintained on changes in muscle performance and head alignment. Methods: The subjects of this study were healthy adults aged between 20 and 30 years. Ninety-three subjects participated in this study (male: 57, female: 36). The subjects were divided into a one-hour group, a two-hour group, and a three-hour group. All the subjects adjusted the height of their chair to a comfortable position and then seat for one, two, or over three hours. Both prior to and after the experiment, the muscle performance (muscle strength, endurance, and flexibility) of the subjects was measured. Results: In the 2-hours and 3-hour group, muscle strength, flexibility and endurance reduced significantly before and after the study, and the head alignment significantly changed. Conclusion: Thease findings showed that sitting continuously for longer than two hours decreases muscle strength, endurance, and flexibility. A flexed posture affects the muscle performance of the lumbar region and may result in problematic postures, such as a forward head position.

• 한국운동역학회지
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• 제19권2호
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• pp.287-296
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• 2009

본 연구는 숙련자 4명과 3년 이내의 골프전공 학생 4명을 대상으로 아이언 클럽(3, 4, 5, 6, 7, 8, 9) 간의 기초샷 정보와 체중이동 정보를 분석하기 위하여 RD-TEC사의 샷분석기와 체중판을 이용하여 분석하였다. 본 연구의 목적은 기존 연구에서 다루어지지 않았던 전체 아이언 클럽간의 샷분석의 차이와 체중이동의 변화를 고찰하는데 그 목적이 있다. 실험대상자(숙련자 4명과 비숙련자 4명) 모두 헤드스피드와 볼스피드에서 롱아이언과 숏아이언의 차이는 통계적으로 유의하게 나타났으나, 3, 4, 5번 아이언에서는 에서 통계적으로 유의한 차이가 나타나지 않았다. 숙련자는 비숙련자보다 헤드스피드, 볼스피드, 방항성, 타출각에서 높은 결과를 나타냈다. 그리고 체중이동의 분석에서는 백스윙 톱에서는 비숙련자가 더 많은 체중이동(65.36%)을 하였고, 숙련자는 임팩트시에서 70.21%정도의 체중이 왼발에 있었다. 숙련자 그룹은 체중이동을 통하여 보다 효과적으로 파워를 내는 것으로 나타났다.

• Imaging Science in Dentistry
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• 제50권1호
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• pp.31-36
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• 2020

Purpose: The purpose of this study was to investigate the impact of radiotherapy on mandibular bone tissue in head and neck cancer patients through an analysis of pixel intensity and fractal dimension values on digital panoramic radiographs. Materials and Methods: Thirty patients with radiographic records from before and after 3-dimensional (3D) conformational radiotherapy were selected. A single examiner carried out digital analyses of pixel intensity values and fractal dimensions, with the areas of interest unilaterally located in the right angle medullary region of the mandible below the mandibular canal and posterior to the molar region. Results: Statistically significant decreases were observed in the mean pixel intensity (P=0.0368) and fractal dimension (P=0.0495) values after radiotherapy. Conclusion: The results suggest that 3D conformational radiotherapy for head and neck cancer negatively affected the trabecular microarchitecture and mandibular bone mass.

• 대한통합의학회지
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• 제2권4호
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• pp.9-17
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• 2014

Purpose : The purpose of this study was to ascertain the effects of air-pressure cervical traction on the tension headache in the adults. Method : All subjects were treated with air-pressure cervical traction while 15 minutes a day, 3 times per week, for 4 weeks. The effects of air-pressure cervical traction were evaluated by HIT-6(headache impact test), VAS, and flexion, extension, left right flexion, left right rotation of cervical ROM. The measured data were analyzed by using repeated ANOVA. Especially in order to investigate the effect of air-pressure cervical traction. The comparison with among three measurement time. Results : The results of this study were as follows; 1) Prior and two weeks measurement did not show significant differences. The head forward posture than before the experiment, each experimental group was significantly increased(p<.05). 2) Prior and two weeks measurement did not show significant differences. The experimental group than ever cervical ROM of the movable range increased significantly(p<.05). 3) The experimental group was significantly lower than before the VAS(p<.05). 4) HIT score of the experimental group was significantly lower than before(p<.05). Conclusion : These findings suggest that air-pressure cervical traction had effect on the tension headache in the adults.

• 한국정밀공학회지
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• 제24권11호
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• pp.116-125
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• 2007

Human muscle skeletal model was developed for biomechanical study. The human model was consists with 19 bone-skeleton and 122 muscles. Muscle number of upper limb, trunk and lower limb part are 28, 60, 34 respectively. Bone was modeled with 3D beam element and muscle was modeled with spar element. For upper limb muscle modelling, rectus abdominis, trapezius, deltoideus, biceps brachii, triceps brachii muscle and other main muscles were considered. Lower limb muscle was modeled with gastrocenemius, gluteus maximus, gluteus medius and related muscles. The biomechanical stress and strain analysis of human was conducted by proposed finite element analysis model under Kumdo head hitting motion. In this study structural analysis has been performed in order to investigate the human body impact by Kumdo head hitting motion. As the results, the analytical displacement, stress and strain of human body are presented.

• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.365-369
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• 2006

According to the IIHS (Insurance Institute fur Highway Safety), side impacts are made up 30% of all accidents (reported 1998). In the case of auto accidents, head and neck injuries were most common as 58%, injuries to the body's trunk equaled 32%, and injuries to the abdomen were 21%. Therefore in this study, injury of wheelchair occupant in frontal and side impact of wheelchair loaded vehicle was analyzed using computer simulation method. The occupant was restrained at the rear of wheelchair by the lap belt. The detailed fixation and restrain conditions of the wheelchair occupant are referred to SAR J2249's recommendation. We estimated HIC(Head Injury Criteria) and HNIC (Head and Neck Injury Criteria) based on measured data.