• Journal of Oral Medicine and Pain
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• v.30 no.1
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• pp.45-55
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• 2005

As people prefer to use right or left hand, some have preferred chewing side while others do not. Totally, 82 volunteers composed of students and staffs from Dental Hospital College of Dentistry Yonsei University participated in this study for the investigation of influence of preferred chewing habit, that has lasted for more than a year, on electromyographic(EMG) activity of masticatory muscles and bite force. Among the 82 volunteers, 46 had preferred chewing habit while the other 36 did not. Prior to the investigation, those with factors that could affect the study, such as, general disease, irregular dentition and malocclusion, were screened and excluded by questionnaire and clinical examination. The results were as follows: 1. There was no significant difference in EMG activities between chewing side and non-chewing side of preferred chewing subjects at rest as well as maximal voluntary contraction(MCV)(p>0.05). 2. Asymmetrical coefficient of temporal and masseter muscle EMG activities between preferred chewing subjects and non-preferred chewing subjects at rest was not significantly different(p>0.05). 3. Asymmetrical coefficient of masseter EMG activity was significantly higher(p<0.05) than that of non-preferred chewing subjects at MCV, whereas that of anterior temporal muscle showed no difference(p<0.05). 4. In preferred chewing subjects, there was no significant difference in average bite force and occlusal contact area between chewing side and non-chewing side(p>0.05). 5. There was no significant difference in Asymmetrical coefficients of average bite force and occlusal contact area between preferred chewing subjects and non-preferred chewing subjects (p>0.05). Consequently, preferred chewing habit can be considered as physiological asymmetry with normal function rather than to have influence on EMG muscle activity of masticatory muscles, average bite force and occlusal contact area. Objective standardization to differentiate preferred chewing subjects and non-preferred chewing subjects should be established in the further study.

• Journal of Oral Medicine and Pain
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• v.33 no.3
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• pp.279-294
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• 2008

This study aimed to make an analysis of the occlusion in the state of muscle fatigue produced by excessive mouth opening and clenching during the dental treatment to control the dental pain and to evaluate the sensory nerve in the muscle pain state. Most of the reasons why patients visit the dental office result in pain-either conceivably the dental origin pain or the non-dental origin pain. The dental offices have many therapeutic actions to produce the masticatory muscle fatigue for the treatment. Dental treatment with long minutes of mouth opening can cause some headaches, masticatory muscle pain and mouth opening difficulties. Patients with mastication problems who visits a dental office to alleviate pain run against another unexpected pain with other aspects. This study uses T-scan II system(Tekscan Co., USA) for the evaluation on the occlusal pattern in the experimental muscle fatigue after clenching, opening the mouth excessively and chewing gum. The occlusal contact pattern is analyzed by the contact timing, namely first, intercuspal, maximum and end point of contact. This inspection was performed at frequencies of 2000Hz, 250 Hz and 5 Hz before and after each experimental muscle pain was produced to 24 subjects who had normal occlusion without the orthodontic treatment or a wide range of the prosthesis by using $neurometer^{\circledR}$ CPT/C(Neurotron, Inc. Baltimore, Maryland, USA). The measuring sites were mandibular nerve experimental muscle fatigue respectively. This study could obtain the following results after the assessment of occlusion and sensory nerve of the experimental muscle fatigue. 1. There were the fastest expression after the excessive mouth opening in muscle fatigue and after tooth clenching in muscle pain. In the visual analog scale that records the subjective level, there was the highest scale after the clenching in the muscle fatigue in jumping off the point of pain. 2. Tooth contact time, contact force, relative contact force on the point of the first contact had no difference, and there were decreases in the contact force after the excessive mouth opening on intercuspal position point, after the excessive mouth opening and the gum chewing on the point of the maximum, and in the contact time after all the experimental muscle fatigue state on the point of the end contact. 3. There was no statistic significance in the current perception threshold before and after the experimental muscle fatigue. 4. There was no significant difference in the contact number, the maximal contact number on the point of the first contact, and the contact number after the mouth opening and gum chewing on the point of the intercuspal position and the contact number after the experimental muscle fatigue on the maximum point, and showed significant decreases. In conclusion, it was found that the occlusal pattern can cause the changes on the case of the clinical muscle weakness by intra-external oral events. It was important that the sedulous attention to details is required during dental treatment in case of excessive mouth opening, mastication and clenching.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.827-833
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• 2011

In this study, a simulation model to estimate the current-collection performance of a high-speed train was developed by using a commercial finite element analysis software, SAMCEF. A three-dimensional springDdamperDmass model of a pantograph was created, and its reliability was validated by comparing the receptance of the model to that of the actual pantograph. The wave propagation speed of the catenary model was compared with the analytical wave propagation speed of the catenary system presented in the UIC 799 OR standard. The length of the droppers was controlled, and the pre-sag of the contact wire due to gravity was considered. The catenary and the pantograph were connected by using a contact element, and the contact force variation when the pantograph was moved at velocities of 300 km/h and 370 km/h was obtained. The average, standard deviation, maximum, and minimum values of the contact force were analyzed, and the effectiveness of the developed simulation model was examined.

• Journal of Korean Society of Transportation
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• v.23 no.8 s.86
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• pp.101-111
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• 2005

Various urban transport policies have an effect on urban transit riderships and accessibility. This study reports variations of metropolitan subway travel patterns affected by an enormous change in bus routes and transfer discount fare policy between subway and bus mode conducted by Seoul city in July 1st of 2004. In an effort to see the difference between the before and the after policies, two data sets are prepared. Firstly, on a daily bassis. an origin-destination trip table of May of 2004 is used. Secondly, on a daily bassis, an origin-destination trip table of August-September of 2004 is used as a counter measure. Even if seasonal variation was not considered, Seoul metropolitan area have experienced increasing riderships and accessibility. Finally, the effects of accessibility in spatial interaction model by rall service changes such as random shocks were scrutinized and interpreted in detail.

• Korean Journal of Culture and Social Issue
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• v.25 no.2
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• pp.119-135
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• 2019

There have been many efforts to reduce prejudice and discrimination against people with mental illness in our community. Studies have shown that the threat to people with mental illness is a important factor. In this study, we focused on contact experience and sense of community that are believed to influence both realistic and symbolic threat We looked the differences in threat depending on the type of contact(family, friends/coworker, public places, no contact) with people with mental illness. Next, if there is contact experience, we questioned that the quality of the experience could influence the threats in all types of contact. Finally, could contact experience and sense of community affect the threats? The total of 465 respondents were surveyed in this study. The result showed that the realistic threat were not different depending on the types of contact, but that the symbolic threat were more higher people with no-contact experience than people with contact experience. The quality of experience had a significant effect on both threats, except in the case of the family contact on realistic threat. Lastly, sense of community was analyzed as a significant variable for both realistic and symbolic threats. Based on these results, we discussed the impact of contact and sense of community and implications of this study.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.369-378
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• 2018

The purpose of this study was to investigate the relationship between elderly people's consciousness of discrimination, elderly contact experience, grandparents' bonding, recognition of filial piety in College 190 Students and descriptive research study to identify factors affecting the sense of discrimination of the elderly. The questionnaire was collected from May 28 to June 15, 2018. The results of this study are as follows: First, the elderly's perception of the elderly was related to the elderly's contact experience (r = -. 353, p <.01), grandparent relationship with grandparents (r =. 01) were statistically significan. The influence factors of the elderly discrimination consciousness of college students are recognition of filial piety (${\beta}=-.354$, p<.001) and knowledge of the elderly (${\beta}=.281$, p <.001), the elderly contact experience and grandparents' bonding. The total explanatory power of the variables was 29.1%.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.249-263
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• 2017

The expansion behavior of inflatable steel pipe rockbolt shows geometric nonlinearity due to its ${\Omega}-shaped$ section. Previous studies on the anchoring behavior of inflatable steel pipe rockbolt were mainly performed using theoretical method. However, those studies oversimplified the actual behavior by assuming isotropic expansion of inflatable steel pipe rockbolt. In this study, the anchoring behavior of the inflatable steel pipe rockbolt were investigated by the numerical method considering the irregularity of pipe expansion and other influencing factors. The expansion of inflatable steel pipe rockbolt, the contact stress distribution and the change of the average contact stress and the contact area during installation were analyzed. The contact stresses were developed differently depending on the constitutive behavior of rocks. Small contact stresses occurred in steel pipes installed in elasto-plastic rock compared to steel pipes installed in elastic rock. Also, the anchoring behaviors of the inflatable steel pipe rockbolt were different according to the stiffness of the rock. The steel pipe was completely unfolded in the case of the stiffness smaller than 0.5 GPa, but it was not fully unfolded in the case of the stiffness larger than 0.5 GPa for the given analysis condition. When the steel pipe is completely unfolded, the contact stress increases as the rock stiffness increases. However, the contact stress decreases as the rock stiffness increases when the steel pipe is not fully expanded.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.953-959
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• 2013

In this study, a multibody dynamic model of the cervical spine was developed for a virtual in-vitro cadaveric experiment. The dynamic cervical spine model was reconstructed based on Korean CT images and the material properties of joints and soft tissue obtained from in-vitro experimental literature. The model was validated by comparing the inter-segmental rotation, multi-segmental rotations, load-displacement behavior, ligament force, and facet contact force with the published in-vitro experimental data. The results from the model were similar to published experimental data. The developed dynamic model of the cervical spine can be useful for injury analysis to predict the loads and deformations of the individual soft-tissue elements as well as for virtual in-vitro cadaveric experiments.

• 전기의세계
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• v.39 no.5
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• pp.68-75
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• 1990

급속한 경제발전과 이에 대응한 교통인구의 증가로 운송시스템의 속도 경쟁은 날로 심화되고 있다. 그러나, 기존의 차륜구동 시스템은 본질적으로 궤도와 차륜의 마찰에 의하여 추진력을 얻기 때문에 평균 최대속도 250Km/h(상한 최대속도 350Km/h)수준이며 소음, 진동 등의 많은 문제점이 있다. 이러한 단점을 극복하기 위하여 선진 외국에서는 부상식 열차의 개발에 관심을 표명하여 1960년대 후반부터 열차와 공기부상식 열차에 대한 연구를 병행하였다. 1970년대 중반까지 프랑스, 영국, 미국 등에서 개발이 진행된 공기 부상식 열차는 고속 주행 및 환경 문제 등에 문제점이 많아 실용화에는 이루지 못하고 신교통 시스템에 부분적으로 적용되고 있는 실정이다. 그러나 자기부상 열차는 Power Electronics 및 자기관련 기술의 급속한 발전에 힘입어 현재 실용화 단계에 이르고 있다. 특히 자기부상(Magnetic Levitation : Maglev) 시스템은 레일과의 마찰력에 의해 추진하는 방식이 아니기 때문에 본질적으로 고속성, 무공해, 안정성, 신뢰성, 경제성 그리고 승차감이 뛰어나다. Maglev는 레일 표면에서 자력을 이용해서 약 1.0cm 또는 10cm 가량 부상한 상태에서 주행하기 때문에 외부와의 물리적인 접촉이 필요 없어 마찰에 의한 소음, 공해, 마모 등이 없는 대단히 이상적인 미래의 운송 수단으로 각광을 받고 있다.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.37-46
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• 2001

Pile load tests were carried out to investigate the contribution of the pile cap to the carrying capacity of a pile group and load transfer characteristics of piles in the group. A group of 24 piles$(4 \times6 array)$ of 92.5mm diameter steel pipe were installed to the depth of 3m fron the ground surface, the top of weathered rock. A maximum load of 320ton was applied to the pile cap, $1.5\times2.3m$, in contact with the ground surface. At the maximum load of 320ton, the pile cap has carried 22% of the total load. Average ultimate capacity of pile in the pile group was estimated to be 16.4ton, substantially higher than that of single pile, installed at the corner and tested before pile cap construction. For the same magnitude of settlement, the pile in the center carried less load than the pile at the perimeter due to strain superposition effect. Piles in the group showed almost constant contribution(approx. 60%) of side friction to the total capacity for all of the loading stages, while that of single pile decreased from 82% to 65%.