• Structural Engineering and Mechanics
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• 제42권3호
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• pp.291-311
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• 2012

The multi-span suspension bridge having double main cables in the vertical plane is investigated regarding endurance of live load distribution in the case of non-displaced pylon and pylon displacement. The coefficient formula of live load distribution described as the ratio of live load on the bottom cable to the top cable is obtained. Based on this formula, some function in respect of this bridge are derived and used to analyze its characteristics. This analysis targets the cable force, the cable sag and the horizontal displacement at the pylon top under live load etc. The results clarified that the performance of the live load distribution and the horizontal force of cables in the case of non-deformed pylon has a similar tendency to those in the case of deformed pylon, and the increase of pylon rigidity can increase live load distributed to the bottom cable and slightly raise the cable horizontal force under live load. However, effect on the vertical rigidity of bridge and the horizontal force increment of cables caused by live load is different in the case of non-deformed pylon and deformed pylon.

• 한국기계가공학회지
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• 제19권11호
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• pp.70-77
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• 2020

Vibratory bowl feeders are widely utilized to align and feed the parts stacked inside the bowl of a feeder. The electro-magnetic force of the electromagnet in a bowl feeder generates the excitation force for the bowl to vibrate in both the horizontal and vertical directions to continuously feed the parts on the track. The feed rate of the part depends on the associated displacement in each direction during the vibration. Therefore, the excitation force induced by the electromagnet should be estimated in advance to ensure the suitable design of the bowl feeder. In this study, a theoretical solution was developed to calculate the electro-magnetic force of the electromagnet for a bowl feeder. Using the proposed solution, the electro-magnetic forces corresponding to a variation in the input parameters of the electromagnet, such as the voltage, frequency, and air gap, could be obtained. The force values obtained using the theoretical solution exhibited a satisfactory agreement with the results obtained using the finite element method, thereby demonstrating the validity of the approach. Subsequently, the bowl displacements were analyzed using the motion equation for the bowl feeder when the theoretically obtained excitation force were applied to vibrate the feeder. The correlation between the vertical displacements of the bowl and input parameters of the electromagnet could be obtained.

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.231-243
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• 2021

In this paper, a dynamic response mapping model of the wheel-rail system is established by using the support vector regression (SVR) method, and the hierarchical safety thresholds of the subgrade void are proposed based on the reliability theory. Firstly, the vehicle-track coupling dynamic model considering the subgrade void is constructed. Secondly, the subgrade void area, the subgrade compaction index K30 and the fastener stiffness are selected as random variables, and the mapping model between these three random parameters and the dynamic response of the wheel-rail system is built by using the orthogonal test and the SVR. The sensitivity analysis is carried out by the range analysis method. Finally, the hierarchical safety thresholds for the subgrade void are proposed. The results show that the subgrade void has the most significant influence on the carbody vertical acceleration, the rail vertical displacement, the vertical displacement and the slab tensile stress. From the range analysis, the subgrade void area has the largest effect on the dynamic response of the wheel-rail system, followed by the fastener stiffness and the subgrade compaction index K30. The recommended safety thresholds for the subgrade void of level I, II and III are 4.01㎡, 6.81㎡ and 9.79㎡, respectively.

• 한국지진공학회논문집
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• 제20권6호
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• pp.413-424
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• 2016

The vertical design spectrum for Korea, which is known to belong to an intra-plate region, is developed from the ground motion records of the earthquakes occurred in Korea and overseas intra-plate regions. From the statistical analysis of the vertical response spectra, a mean plus one standard deviation spectrum in lognormal distribution is obtained. Regression analysis is performed on this curve to determine the shape of spectrum including transition periods. The developed design spectrum is valid for the estimation both spectral acceleration and displacement. The ratio of vertical to horizontal response spectrum for each record is calculated. Statistical analysis of the ratios rendered the vertical to horizontal ratio (V/H ratio). Subsequently the ratio between the peak vertical ground acceleration to the horizontal one is obtained.

• 한국산학기술학회논문지
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• 제14권10호
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• pp.5268-5273
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• 2013

진동타입기에 의해 시공되는 말뚝 해석을 위해 해석기법을 개발하고 진동타입기의 사하중 크기 변화에 따른 해석결과를 분석하였다. 주면마찰에 대한 하중전이곡선은 사하중이 감소함에 따라 연직하향으로 이동하는 결과를 보였다. 사하중이 감소함에 따라 주면마찰에 대한 하중전이곡선의 형상은 점점 뚜렷한 코일 형상을 띄었다. 선단저항의 크기는 사하중의 크기에 큰 영향을 받지 않음을 알 수 있었으며 선단저항에 대한 하중전이곡선의 형상은 주면마찰에 대한 하중전이곡선에서와 마찬가지로 사하중이 감소함에 따라 점점 뚜렷한 코일 형상을 띔을 알 수 있었다. 사하중이 증가함에 따라 연직변위도 크게 계산되었으며 시간에 따른 연직변위의 형상에 있어서는 사하중이 감소함에 따라 마루와 골이 점점 뚜렷해지는 파형을 보였다.

• 대한토목학회논문집
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• 제12권2호
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• pp.205-215
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• 1992

본문은 점토지반에 기초를 통해 하중이 전달 될 경우 기초의구조(강성기초 및 요성기초), Geotextile, Sand Mat, 다층구조의 지반 등이 점토 기초지반에 어떤 거동을 일으키는가를 모형재하시험을 통해 관찰하고 수치계산을 시도한 것이다. 총 14개의 시험을 통해 수직, 수평변위를 기초형태별, 기초처리별, 강성차이별로 고찰하고 이들 변형을 예측하는 프로그램을 통해 변형과 응력을 예측하였다. 그 결과는 지반지지력은 강성기초가 유리하지만 이보다는 지반 강성이 큰 다층 구조지반이 가장 유리하며 수평, 수직, 변위에 대해서는 G/T, S/M의 병용공법이 가장 유리하고 S/M 공법만 단독으로 이용할 경우는 연직변위 억제 효과가 탁월하다. 그리고 강성이 큰 다층구조 지반은 이를 G/T와 S/M의 병용공법과 같은 효과가 있다. 본 연구결과는 강성이 큰 지반(여기서는 Rubber층)이 상층에 있고, 두께 또한 두꺼울수록 지반의 침하가 크게 억제되는 것을 확인하였다. 측방변위에서도 강성차이도 중요하지만, 이보다는 강성지반의 두께에 더 깊은 관계가 있다. 모형 토조실험을 통한 실측치와 수치해석 결과가 연직변위에 대해서는 서로 좋은 결과를 나타내 다층토 지반의 침하예측이 가능하다.

• 한국운동역학회지
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• 제16권1호
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• pp.109-117
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• 2006

The purpose of this study was done in order to investigate the Kinematical variables of the Rybalko motion on the Horizontal bar using the 3-dimensional cinematographic method. For this study, three excellent athletes take part in a 2003 Daegue universid game were chosen. The subject,s Rybalko motion was filmed with S-VHS camera at the speed of 60 fields per second and digitized the each fields. And the Kwon3D 3.1 version program was employed to obtain 3-dimensional data. As a result of this study. 1. A total time spent for performing Rybalko skill was Mean $2.52{\pm}0.13sec$. From starting down swing to releasing right hand the Mean $0.84{\pm}0.24sec$ was taken. 2. In the event 3 of Rybalko motion, that is, the moment which the right-hand is released on the bar, the center of mass must is employed at the position above the horizontal line of bar. In this research, the average vertical displacement(z axe) of center of mass shows $47.87{\pm}3.14cm$. 3. In the event 5, that is, the moment which the right-hand is catched again on the bar, the center of mass is employed at the position before the vertical line of bar. In this research, the average horizontal displacement(z axe) of center of mass shows $47.87{\pm}3.14cm$. 4. It has been seen that, at the moment of release of right-hand, lateral variation of center of mass is 13.395cm, vertical variation of center of mass is 7.41cm Thus, it is concluded that lateral variation of center of mass should be reduced for high grade to be acquired. 5. It has been founded that high speed of down swing influences speed of up swing, and that, in the motion of twist, the horizontal speed is little changed.

• 대한치과교정학회지
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• 제43권1호
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• pp.3-14
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• 2013

Objective: To evaluate the factors that affect torque control during anterior retraction when utilizing the C-retractor with a palatal miniplate as an exclusive source of anchorage without posterior appliances. Methods: The C-retractor was modeled using a 3-dimensional beam element (0.9-mm-diameter stainless-steel wire) attached to mesh bonding pads. Various vertical heights and 2 attachment positions for the lingual anterior retraction hooks (LARHs) were evaluated. A force of 200 g was applied from each side hook of the miniplate to the splinted segment of 6 or 8 anterior teeth. Results: During anterior retraction, an increase in the LARH vertical height increased the amount of lingual root torque and intrusion of the incisors. In particular, with increasing vertical height, the tooth displacement pattern changed from controlled tipping to bodily displacement and then to lingual root displacement. The effects were enhanced when the LARH was located between the central and lateral incisors, as compared to when the LARH was located between the lateral incisors and canines. Conclusions: Three-dimensional lingual anterior retraction of the 6 or 8 anterior teeth can be accomplished using the palatal miniplate as the only anchorage source. Using LARHs at different heights or positions affects the quality of torque and intrusion.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.263-267
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• 2006

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a significant deflection with relatively small temperature rise. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. Additionally, we can achieve response time of 14.6 ms, resonance frequency of 12 Hz, and reliability ability of $10^5$ cycles. The proposed actuator can find applications where a large vertical displacement is needed while maintaining compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1286-1289
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• 2004

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene(PVDF-TrFE). The large difference of coefficient of thermal expansion(CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a large deflection with relatively small temperature rising. Compared to the most conventional micro actuators based on MEMS(micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. The proposed actuator can find applications where a large vertical displacement is needed while keeping compact overall device size, such as a micro zooming lens.