• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.35-40
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• 2015

A gas spring provides support force for lifting, positioning, lowering, and counterbalancing weights. It offers a wide range of reaction force with a flat force characteristic, simple mounting, compact size, speed controlled damping, and cushioned end motion. The most common usage is as a support on a horizontally hinged automotive tail gate. However, its versatility and ease of use has been applied in many other industrial applications ranging from office equipment to off-road vehicles. The cylinder of a gas spring is filled with compressed nitrogen gas, which is applied with equal pressure on both sides of the piston. The surface area of the rod side of the piston is smaller than the opposite side, producing a pushing force. The magnitude of the reaction force is determined by the cross-sectional area of the piston rod and the internal pressure inside the cylinder. The reaction force is influenced by many design parameters such as initial chamber volume, diameter ratio, etc. In this paper, we investigated the reaction force characteristics and carried out parameter sensitivity analysis for the design parameters of a gas spring.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.101-104
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• 2006

This study aims at verifying characteristics of torsional fluctuating moment coefficient and power spectral density, which is needed to estimate torsional response of tall buildings. In order to estimate characteristics, the wind tunnel tests have been conducted on 52 types aero-elastic model of the rectangular prisms with various aspects ratios, side ratios and surface roughness in turbulent boundary layer flows. In this paper, characteristics of torsional fluctuating wind force are briefly discussed and then these results were mainly analyzed as a function of the aspects ratios and side ratios of buildings.

• 한국기계가공학회지
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• 제11권3호
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• pp.98-103
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• 2012

One of the problems in the grinding process using the machining center(MC) with a small diametric wheels is machining error due to decrease of the quill diameter. In this thesis, side-cut grinding is performed with a vitrified bonded CBN wheel on the machining center to establish the basis of the grinding using MC. The grinding force and machining error are investigated experimentally for the change of the machining condition. It is possible to estimate the machining performance by the ratio of the setting depth of cut and actual depth of cut. In addition, the relation between normal grinding force and machining error is presented by the experimental formula.

• 한국기계가공학회지
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• 제12권5호
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• pp.36-41
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• 2013

One of the problems in grinding process using a machining center(MC) with a small diametric wheels is machining error due to decrease of the quill diameter. In this study, side-cut grinding is performed with a vitrified bonded CBN wheel on the machining center. Grinding experiments are performed at various grinding conditions including quill length, quill diameter and depth of cut. The effect on the grinding force, machining error and surface roughness due to the change of the quill rigidity are investigated experimentally. The slenderness ratio of the quill is significant factor to analyse the change of the grinding force and machining error.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1997년도 제9회 학술강연회논문집
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• pp.3-3
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• 1997

미사일 수직발사 시스템은 공간을 작게 차지하고 간편하여 각국이 선호하고 있다. 그러나 수직발사 초기에는 매우 낮은 속도로 상승하므로 Fin의 공력이 발생하지 않기 때문에 추력방향을 직접제어하지 않으면 안된다. 추력방향 제어장치는 Gimbal, Jet Vane, Jet Tab, Secondary Injection 등 여러 방식이 있으나 Jet Vane Type의 추력 방향 제어장치는 응답이 빠르고 경량화가 가능하며 후방 Fin과의 연동 및 작동 후 분리가 가능하다는 장점으로 인해 수직발사 미사일의 초기 방향제어에 주로 사용한다. 이 장치는 Vane이 화염 속에서 직접 구동되므로 고내열성 재료의 기술이 필요하며 미사일의 전체 System에 요구되는 Side Force를 발생시키기 위한 Vane의 최대 받음각 및 회전속도를 결정해야 한다. 따라서 초음속 유동해석을 통해서 Vane의 받음각에 대한 Side Force와 Torque를 계산하며, 구조해석을 통해 Side Force가 가해지는 동안의 Housing의 굽힘, 비틀림 하중 등을 계산하였다. 또한 Controller는 기존의 유압방식보다도 소형이며 복잡하지 않고 가격이 싼 DC Motor와 감속기를 이용하여 빠른 응답성에 부합토록 설계하였다. 본론에서는 성능과 관련된 초기 요구조건에 대한 최적설계의 변수들을 해석하고. 그에 따른 개발사양, 개발 과정, 구조, 시험방법 등에 대해 고찰하고자 한다.

• 대한치과교정학회지
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• 제30권1호
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• pp.9-17
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• 2000

본 연구는 발치 후 인접치 이동을 위한 교정력 적용 시 적용 시기에 따른 치아이동 양상을 비교$\cdot$분석하기 위하여 시행되었다. 성견을 실험대상으로 상악 좌우 제 3절치를 3주 간격으로 각각 발거 하고, 양 견치 를 고정 원으로 제 2절치의 치체이동을 위한 장치를 장착하였다. 100 gm의 지속적인 힘을 내는 견인 스프링을 사용하여 발치 후 4주와 1주부터 좌우 제 2절치를 각각 12주간 동시에 견인하였다. 2주 간격으로 디지털 캘리퍼스를 이용하여 이동거리를 측정$\cdot$비교하고 실험에 사용된 좌우 제 2절치의 조직소견을 관찰하여 다음과 같은 결론을 얻었다. 1. 교정력 적용 후 처음 2주간에는 발치 후 4주에 견인한 치아가, 그 다음 2주간에는 발치 후 1주에 견인한 치아가 빠르게 이동하는 양상을 보였다. 2. 12주간의 실험기간 동안 견인 4주와 6주 사이에 가장 빠르게 이동하는 경향을, 이 후에는 이동 속도가 감소하는 양상을 보였다. 3. 실험기간 동안 이동한 전체 거리는 발치 후 4주에 비해 1주에 견인한 경우에서 크게 나타나는 경향을 보였다. 4. 발치 후 4주에 견인한 경우에 비하여 1주에 견인한 경우에서 유해한 조직소견이 나타나지 않았다. 이상의 결과는 발치 후 교정력 부여 시 조기 적용이 유리함을 시사하였다.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.867-878
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• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using three-dimensional Euler equations. Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. Numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, length and the existence of a tunnel on the crossing event. Unsteady aerodynamic loads-a side force and a drag force-acting on the train during the crossing are numerically predicted and analyzed. The side force mainly depends on the nose-shape, and the drag force depends on tunnel existence. Also. a push-pull (i.e.impluse force) force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary to evaluate the stability of high speed multi-car trains. The results also indicate the effectiveness of the present numerical method for simulating the unsteady flow fields induced by bodies in relative motion.

• 대한치과보철학회지
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• 제33권2호
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• pp.281-299
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• 1995

The purpose of this study was to evaluate the degree of occlusal contact under the fixed implant prosthesis of partially edentulous patients which was hased on occlusal concept of implant prosthesis. From the patients who have free-standing implant supported prosthesis of unilateral partially edentulous area, occlusal and occlusal contact point of th enatural tooth side and implant side of light closure and heavy closure were analyzed by T-scan system throuht pre-and post-adjustment and the degree of occlusal contact was estimated by Shimstock. The following results were obtained : 1. The occlusal force of natural tooth side(NF) from mid-sagittal axis was relatively constant at light and heavy closure through pre-and post-adjustment, but the occlusal force of implant side(IF) was decreased significantly at light closure(P<0.01) and heavy closure(P<0.05) of post-adjustment. 2. Natural tooth side-implant side moment(MIMoment) fo occlusal force from mid-sagittal axis was significant(p<0.05) through pre-and post-adjustment and the deviation from mid-sagittal axis was increased at light closure of post-adjustment, but was decreased at heavy closure of post-adjustment. 3. Comparing the NF and IF, IF was greater at heavy closure of pre-adjustment, and NF was greater at light closure of post-adjustment, and the NF and IF was relatively equally distributed at light closure of pre-adjustment and at heavy closure of post-adjustment. 4. The number of occlusal contact point of natural tooth side(NC) was relatively constant through pre-and post-adjustment, but the number of occlusal contact point of implant side(IC) was significantly decreased(P<0.05) at light closure of post-adjustment, and was not significant but was lesser at heavy closure of post-adjustment. 5. Difference of the NC and IC was greater at light closure of post-adjustment, but it was less at heavy closure of post-adjustment, and therefore occlusal contact point of natural tooth side and implant side was relatively equally distributed at heavy closure of postadjustment. 6. When bilaterally distribution of occlusal force and occlusal contact point was established, degree of occlusal contact of implant suporoted prosthesis with opoosing teeth at light clousre was $34.13{\pm}21.69{\mu}m$.

• 대한치과교정학회지
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• 제23권2호
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• pp.199-216
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• 1993

The purpose of this study was to quantify the biologic effects of the tensile forces from helical springs across the maxillary incisors on the periodontal tissues of rats. 39 Sprague-Dawlely rats were divided into a control group(3 rats) and three experimental groups(36 rats)-group 1, pressured with a light force(50-75g), group 2, with a heavy force(250-300g) and group 3, with a hen force(250-300g) plus laser irradiation. Autoradiographic and histopathologic observations were performed in 12, 24, 48 and 96 hours after force application. The result were as follow : 1. Hyalinized zone of periodontal ligament began to appear at pressure side in 12 hours in group 2 and group 3 ; all decreased in 96 hours except in group 2. 2. Alveolar bone resorption began to appear in 12 hours in group 2 and group 3 ; Group 2 showed more resorption than group 1 and no difference to group 3. 3. Tearing of periodontal ligament and vascular dilatation began to appear at tension side in 12 hours in all groups ; Group 2 showed more changes than group 1 and no difference to group 3 ; Decrease began to appear in 96 hours. 4. New bone formation began to appear at tension side in 12 hours and increased more and more ; No differences were shown of groups 5. New capillary proliferation began to appear at pressure side in 12 hours ; The changes were the greatest in group 3, group 2, group 1, in that order. 6. Positive reaction of cells to $[^3H]-thymidine$ was the greatest in 24 hours of all groups and decreased with times i Group 2 showed more reaction than group 1 and no difference to group 3.

• Steel and Composite Structures
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• 제44권3호
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• pp.437-450
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• 2022

When the vertical load-bearing members in high-rise structures fail locally, the beam-column joints play an important role in the redistribution of the internal forces. In this paper, a static laboratory test of three full-scale flush flange beam-reinforced connections with side and cover plates (CP-FBSP connection) with double half-span steel beams and single L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) was conducted. The influence of the side plate width and cover plate thickness on the progressive collapse resistance of the substructure was thoroughly analyzed. The failure mode, vertical force-displacement curves, strain variation, reaction force of the pin support and development of internal force in the section with the assumed plastic hinge were discussed. Then, through the verified finite element model, the corresponding analyses of the thickness and length of the side plates, the connecting length between the steel beam flange and cover plate, and the vertical-force eccentricity were carried out. The results show that the failure of all the specimens occurred through the cracking of the beam flange or the cover plate, and the beam chord rotations measured by the test were all greater than 0.085 rad. Increasing the length, thickness and width of the side plates slightly reduced the progressive collapse resistance of the substructures. The vertical-force eccentricity along the beam length reduced the progressive collapse resistance of the substructure. An increase in the connecting length between the beam flange and cover plate can significantly improve the progressive collapse resistance of substructures.