• Journal of Oral Medicine and Pain
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• v.24 no.2
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• pp.189-206
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• 1999

This study was performed to investigate the factors affecting muscle activity and cephalometric variables according to change of head postures. For this study, 150 patients with temporomandibular disorders and 80 dental students without any signs and symptoms of temporomandibular disorders were selected as the patients group and as the normal group, respectively. Head position to body-midline in frontal plane and upper quarter posture to body plumb line in sagittal plane were observed clinically and electromyographic(EMG) activity of anterior temporalis, masseter, sternocleidomastoideus, and trapezius on clenching were recorded with $BioEMG^{(R)}$ in four head postures, which were natural head posture(NHP), forward head posture(FHP), $20^{\circ}$ upward head posture(UHP), and $20^{\circ}$ downward head posture(DHP). Cephaloradiographs were also taken in the same head postures as in EMG taking, but that was taken only in NHP for the patient group. Cephalometric variables measured were SN angle, CVT angle, atlas inclination angle, occlusal plane angle, Me-C2 angle, pharyngeal width, occiput~axis distance, area of pharyngeal space, and cervical curvature. The data were analyzed by SAS statistical program. The results of this study were as follows : 1. Between the patient and the normal group, there were significant difference in distance from plumb line to acromion, eye-tragus angle, electromyographic activity of the four muscles, and cephalometric variables of linear measurement. 2. There was no consistent pattern of correlation between upper quarter posture, EMG activity and cephalometric variables in any case without relation to cervical curvature and head position in frontal plane. 3. Sternocleidomastoid muscle only showed variation of electromyographic activty with changes of head postures, but all the muscles did show correlation with head postures. 4. All the cephalometric variables measured in this study showed difference of mean value by head posture, and CVT angle, pharyngeal width, occiput-atlas distance, and area of pharyngeal space showed correlation between these variables with change from NHP to FHP, and from NHP to UHP.

• Food Science of Animal Resources
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• v.20 no.1
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• pp.44-55
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• 2000

신선한 품질의 식품에 대한 수요가 증가함에 따라 열처리의 대체수단으로 이용하기 위한 고압기술의 전망이 밝다. 압력을 이용하여 가공된 과일 쥬스와 잼이 이미 일본시장에 출시되고 있다. 전세계적으로 다른 식품의 안전을 위해서도 이 기술에 대한 개발노력이 진행중이다. 압력과 열, 시간의 복합효과에 대한 이해는 식품의 안정성에 대한 이 기술의 이용 가능성을 더해준다. 효소의 비활성화와 미생물의 사멸을 위한 압력과 시간의 의존도에 대한 상세한 연구는 식품저장에 초고압기술을 활용하는데 있어 매우 중요하다. 에너지 비용을 절감하기 위한 설계의 개선과 여러 식품성분의 변화에 대한 이해는 이 기술의 응용에 큰 도움이 될 것이다. 안전성과 저장성이 높은 신선한 식품을 생산할 수 있는 초고압 기술은 곧 광범위하게 이용될 전망이다.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.763-764
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• 2008

3D displays requires multiplexing of left and right pictures on the same screen so that they can be viewed independently by the view using various schemes, including LCD shutters, polarizers, narrow band filters, and lenticular lenses on the screen. All these methods reduce the effective screen brightness by as much as 10X. The eye responses to the lower brightness are analyzed and found to compensate partially giving a lower perceived brightness. This paper presents such eye response analysis and a low cost approach to increasing brightness in a RPTV using the long life DPR system, increasing the screen brightness by over 2.5 times, while maintaining acceptable lamp lifetime.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.541-544
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• 2002

The reflective liquid crystal(LC) imager in one panel Liquid Crystal on Silicon(LCoS) System must have the properties such as fast response time, high contrast ratio(C/R) and voltage holding ratio(VHR) which are more related to the lifetime of imager than the others. As the high-output light including a short wavelength from UHP lamp is exposed to LCoS imager, the indium metal impurities, which decrease the C/R and VHR, are diffused from ITO thin film on glass. To ensure the high reliable LCoS imager for HD projection TV, we have studied the effects of the plasma treatment on ITO film to reduce impurities in imager.

• Journal of Oral Medicine and Pain
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• v.25 no.2
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• pp.173-189
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• 2000

The purpose of this study was to evaluate the effect of specific head positions on the mandibular rotational torque movements in maximum mouth opening, protrusion and lateral excursion. Thirty dental students without any sign or symptom of temporomandibular disorders(TMDs) were included as a control group and 90 patients with TMDs were selected and examined by routine diagnostic procedure for TMDs including radiographs and were classified into 3 subgroups : disc displacement with reduction, disc displacement without reduction, and degenerative joint disease. Mandibular rotational torque movements were observed in four head postures: upright head posture(NHP), upward head posture(UHP), downward head posture(DHP), and forward head posture(FHP). For UHP, the head was inclined 30 degrees upward: for DHP, the head was inclined 30 degrees downward: for FHP, the head was positioned 4cm forward. These positions were adjusted with the use of cervical range-of-motion instrumentation(CROM, Performance Attainment Inc., St. Paul, U.S.A.). Mandibular rotational torque movements were monitored with the Rotate program of BioPAK system (Bioresearch Inc., WI, U.S.A.). The rotational torque movements in frontal and horizontal plane during mandibular border movement were recorded with two parameters: frontal rotational torque angle and horizontal rotational torque angle. The data obtained was analyzed by the SAS/Stat program. The obtained results were as follows : 1. The control group showed significantly larger mandibular rotational angles in UHP than those in DHP and FHP during maximum mouth opening in both frontal and horizontal planes. Disc displacement with reduction group showed significantly larger mandibular rotational angles in DHP and FHP than those in NHP during lateral excursion to the affected and non-affected sides in both frontal and horizontal planes(p<0.05). 2. Disc displacement without reduction group showed significantly larger mandibular rotational angles in FHP than those in any other head postures during maximum mouth opening as well as lateral excursion to the affected and non-affected sides in both frontal and horizontal planes. Degenerative joint disease group showed significantly larger mandibular rotational angles in FHP than those in any other head postures during maximum mouth opening, protrusion and lateral excursion in both frontal and horizontal planes(p<0.05). 3. In NHP, mandibular rotational angle of the control group was significantly larger than that of any other patient subgroups. Mandibular rotational angle of disc displacement with reduction group was significantly larger than that of disc displacement without reduction group during maximum mouth opening in the frontal plane. Mandibular rotational angle of disc displacement without reduction group was significantly larger than that of disc displacement with reduction group or degenerative joint disease group during maximum mouth opening in the horizontal plane(p<0.05). 4. In NHP, mandibular rotational angles of disc displacement without reduction group were significantly larger than those of the control group or disc displacement with reduction group during lateral excursion to the affected side in both frontal and horizontal planes. Mandibular rotational angle of disc displacement without reduction group was significantly smaller than that of the control group during lateral excursion to the non-affected side in frontal plane. Mandibular rotational angle of disc displacement without reduction group was significantly larger than that of disc displacement with reduction group during lateral excursion to the non-affected side in the horizontal plane(p<0.05). 5. In NHP, mandibular rotational angle of the control group was significantly smaller than that of disc displacement with reduction group or disc displacement without reduction group during protrusion in the frontal plane. Mandibular rotational angle of disc displacement without reduction group was significantly larger than that of the disc displacement with reduction group or degenerative joint disease group during protrusion in the horizontal plane. Mandibular rotational angle of the control group was significantly smaller than that of disc displacement without reduction group or degenerative joint disease group during protrusion in the horizontal plane(p<0.05). 6. In NHP, disc displacement without reduction group and degenerative joint disease group showed significantly larger mandibular rotational angles during lateral excursion to the affected side than during lateral excursion to the non-affected side in both frontal and horizontal planes(p<0.05). The findings indicate that changes in head posture can influence mandibular rotational torque movements. The more advanced state is a progressive stage of TMDs, the more influenced by FHP are mandibular rotational torque movements of the patients with TMDs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.629-634
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• 2017

In the case of the UHP (Ultra high performance) tire that the demand has increased rapidly, compared with the commonly used tire, severe deformation has been observed because of the low aspect ratio. When repeated deformations are applied to the sidewall rubber, accumulated fatigue damage may cause fatigue failure. Thus, the evaluation of the durability of the tire sidewall rubber has become a very important issue to prevent accidents that occur while the vehicle is running. However, the research and design criteria for the durability performance of the tire sidewall rubber hardly exist. In this study, we suggest a lifetime prediction formula using strain energy density obtained by performing tensile tests and fatigue tests on two different kinds of the tire sidewall compounds. Additionally, the applicability of our findings for low fuel consumption tires was reviewed by converting the fatigue life of the sidewall rubber into the expected mileage of the tire.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.622-628
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• 2013

Due to the development of compounding technology, there is a considerable increase in the number of high performance rubbers in the world. Accordingly, there are rapid growing requests about high performance tires such as UHP tire and Run-flat tire. However, it is extremely difficult to investigate the friction coefficient of tire tread rubbers. An alternative solution must be developed with the reliability of high-speed linear friction test machines. The use of friction test machines can be expected to improve rubber friction researches. In this paper, we propose a new kind of high-speed linear friction test machine. We have designed and manufactured various mechanisms for friction tests. The final goals are to design and manufacture friction test machines that can investigate friction coefficients efficiently and rapidly. The performance of the proposed high-speed linear friction test machine is evaluated experimentally; however additional study should be necessary for safer and more reliable experimentation.

• Elastomers and Composites
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• v.52 no.3
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• pp.167-172
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• 2017

Ultra-high performance (UHP) tires, for which demand has recently surged, are subject to severe strain conditions due to the low aspect ratio of their sidewalls. It is important to ensure sidewall material durability, since a sudden tire sidewall breakage during vehicle operation is likely to cause a major accident. In the automotive application of rubber parts, cracking is defined as a failure because when cracks occur, the mechanical properties of rubber change. According to Mars, Andre et al., strain and strain energy density (SED) are mainly used as a failure parameters and the SED is generally used as a fatigue damage parameter. In this study, the fatigue life curves of sidewall rubber of tires were determined by using the SED as fatigue damage parameter while the effect of aging on fatigue life was evaluated after obtaining the SED-Nf curves according to aging condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.57-60
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• 2005

The objective of this paper is to investigate and analyze the behaviour of prestressed I section structural members constructed with ultra high perfomance steel fiber reinforced cementitious concrete (SFR-UHPC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The parameters of test specimens were span to depth ratio, prestressing force, prestressing wire placement and web width. Most influential parameter to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone should be redefined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

• Journal of Oral Medicine and Pain
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• v.23 no.4
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• pp.457-473
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• 1998

This study was performed to investigate the morophological and positional correlation between the upper cervical vertebra, the oral structures and the pharyngeal tissues, and the correlation of these anatomical structures with dental features, such as teeth wear area nad tooth contact status, etc. Seventy patients with temporamandibular disorders and sixty three dental students without any signs and symptoms in head and neck region were selected for this study. All they had natural dentition without any fixed and removable protheses. Teeth wear area and arch width wre measured from the upper dental cast, tooth contact status were observed by T-Scan system$^\textregistered$ and four cephaloradiograpohs were taken from four head postures, namely, natural(NHP), forward(FHP), upward(UHP), and downward head postiure(DHP). 22 cephalometric items were measured on the films and the data were processed with SAS statistical program. The result of this study were as follows : 1. In normal group, angle of cervical vertebra tangent and of between hard and soft palate were broader in female subjects than those in male subjacets, but distance from subocciput to axis, size of soft palate, and pharyngeal space width were larger in male subjects. 2. In normal group with natural head posture, the items correlated each others from the three anatomical regions were distance between first nad second vertebra in posterior part, distance from the lingual surface of lower anterior teeth to anterior surface of soft palate, and distance from the hyoid bone to third vertebra. 3. Three set of items showed significant correlation each other in the four head postures in normal group. First set was the angle between hard and soft palate and the idstance from subocciput to posterior arch of first vertebra, second set was the distance between first and second vertebra in posterior part and the teeth wear area, third set was number and force of tooth contact and length of soft palate and distance from anterior tip of hyoid bone to mandibular plane.