• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.1-6
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• 2013

A SIM card socket is used for a cell phone to fix an USIM card and a push-push mechanism is typically employed in the SIM card socket for a user convenience. A SIM card is inserted with locking when a user pushes the card once and a SIM card is removed with unlocking when a user pushes the card again. A push-push mechanism is operated by a heart-cam structure and a main spring. A cam slider and a cam stick consisting a push-push mechanism may be broken because of the main spring. So, dynamic stress at a cam slider and a cam stick which is generated by a main spring during operating should be analyzed and considered in the push-push mechanism design. In this paper, a flexible multibody model of a push-push mechanism was developed to analyze dynamic stress at a cam slider and a cam stick.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.368-376
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• 1999

This paper predicts the changes in the spring constant, the resonant frequency, the electrostatic force, and the displacement of a resonant structure due to non-ideal anisotropic RIE etching process. First, a $6\;{\mu}m$ thick polysilicon was etched by RIE and the anisotropy of the etched structure was measured as a function of a RF power, a $Cl_2$ flow rate and a chamber pressure. In the experimental results, an anisotropy was decreased as the RF power, the $Cl_2$ flow rate, or the chamber pressure was increased. A comb actuator's operation characteristic was predicted depending on the anisotropy variations in RIE etching. Comb actuators with three different support beam structures were investigated : fixed-fixed, crab-leg, and double crab-leg. As the RIE etch anisotropy becomes non-ideal, i.e. the cross section becomes rather a trapezoidal than a rectangular shape, it decreases spring constant, resonant frequency and electrostatic force of a comb actuator but it increases the displacement of the mass. Among the three structures, the comb actuator with double crab-leg support beams is more influenced by anisotropy variation in RIE etch than other two.

• The korean journal of orthodontics
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• v.30 no.1 s.78
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• pp.9-17
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• 2000

This study was performed to compare and analyze the mode of tooth movement according to the timing of orthodontic force application alter extraction. The upper right and left third incisors were carefully extracted at three-week interval in lout adult dogs. Both canines were used as an anchorage for the bodily movement of the upper second incisors. Orthodontic forte of 100 gm was simultaneously applied at one week after extraction on one side and four weeks after extraction on the other side using NiTi closed coil spring. While orthodontic force was applied for twelve weeks, the amount of tooth movement was measured at every second week with digital calipers. The animals were sacrificed at twelve weeks and histologic examination was executed to reveal any difference between both sides. The results were obtained as follows. 1. The tooth movement was likely to be faster in lout-week side 4han one-week side for the first two weeks while faster in one-week side during next two weeks 2. The rate of tooth movement was fastest during four to six weeks period, then decreased gradually. 3. The total amount of tooth movement was likely to be larger in one-week side compared to four-week side. 4. Any damage to tooth and periodontal tissue could not be seen in the histologic section of one-week side. These results suggest that earlier application of orthodontic force is better than later after extraction In terms of the rate of tooth movement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.86-92
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• 1993

자동차의 현가장치에 대한 능동제어연구는 국내외적으로 활발히 진행되어 왔다. 수동식현가장치는 단순히 스프링과 감쇠기로 차체의 진동을 수동 제어 하므로 성능 향상에 한계가 존재하게 된다. 수동식 현가장치가 강성계수와 감쇠계수를 조절함으로써 차체로 들어오는 진동을 억제하는 반면, 능동식제 어는 보통 유압을 이용하여 효율적으로 차체에 들어오는 진동을 억제시키게 된다. 일반적으로 자동차가 능동현가장치 설계시 요구되는 사항은 탑승자의 승차감, 조종성, 현가장치의 공간확보 문제, 경제성(제어력), 실제적으로 자동 차에 적용할 수 있는 능동제어기법인가 하는 문제이다. 자동차 능동식 현가 장치는 보통 1/4 car (2자유도계), Full-car 모델 (7자유도계) 등으로 모델링 을 하여 능동제어기를 설계한다. 1/4 car 모델의 특징은 해석이 비교적 단순 하고 현가장치의 동적거동을 이해하는데 유용하고 실험을 하거나 실제 자동 차에 적용하기 쉬운 반면에 Full-car 모델에 비해 제어력의 효율이 떨어진다 는 단점이 있다. 그 이유는 1/4 car 모델은 차체의 동역학적 특성을 고려하 여 설계하지 않았기 때문에 4개의 독립현가차축에서는 오직 그 현가축방향 으로 발생하는 수직방향의 진동만을 제어하기 때문이다. 따라서 동역학적 역 성에 기인하는 운동을 제어하는 비효율적인 제어력이 공급된다는 단점을 갖 는다. 이에 비해 full-car 모델은 주행모드(수직, 롤링, 피칭운동)간의 연성을 고려하여 제어기를 설계할 수 있기 때문에 1/4 car 모델에 비해 제어력의 효 율이 높다는 장점이 있는 반면에 모델이 수학적으로 복잡하므로 제어력을 구하는데 계산량이 많고, 실제 자동차에 적용하기에 복잡하다는 단점을 갖고 있다. 따라서 본 논문에서는 쉽게 실험할 수 있고, 실용화할 수 있는 1/4 car 모델에 대하여 능동제어기를 설계하여 실제자동차에 능동제어기를 적용할 때 참고가 될 수 있도록 하였다. 자동차는 저주파영역의 밴드통과필터 역할 을 하므로 저주파에서의 성능, 특히 탑승자가 민감하게 느끼는 0.5Hz - 10Hz 부근의 주파수성능은 승차감, 조종성에 상당히 중요하다. 이에 본 논문 에서는 0.5Hz - 10Hz 부근의 승차감, 조종성의 향상에 초점을 두고 차체의 속도를 출력변수로 한 LQG/LTR 제어기를 설계하였다. LQG/LTR 설계기법 은 안정도-강인성이 좋은 체계적인 설계기법으로서 전 상태를 측정할 필요 가 없으므로 실제 적용시 효과적이다. 또한 자동차의 제원의 변화에 대한 고 유치의 민감도해석과 새로운 개념으로 안정도-강인성(Robustness)해석을 하 여 수동시스템과 능동시스템의 강인성을 비교하였다.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.374-374
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• 2011

Recently the construction of railway sections passing the central area of cities and stations under railway lines are increasing, and then it is urgently required to take the countermeasures against the railway vibration and the second-phase noise radiated from it. The most efficient countermeasure, out of technologies developed up to now, is the floating slab track which is the track system isolated from the sub-structure by springs. In other countries, the source technologies for anti-vibration design and vibration isolator - one of key components - have been developed and many installation experiences have been accumulated. However, in Korea, since the system design technology and technologies for key components are not yet developed, the foreign system are being introduced without any adjustment, and the key component, vibration isolator, depends on imports. In this study, based on the results of previous studies of the dust-control device installation using the slab and go through time after lifting impressive when stepped on power generated by the cross-section of the slab and shear connection re-examined the structural stability.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.214-214
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• 2011

최근 국내 연안역에는 관광의 활성화 등의 목적으로 잔교가 많이 가설되고 있다. 그러나 잔교의 설계에 대한 규정이 없어 현재는 항만 및 어항설계기준을 준용하여 설계하고 있는 실정이며, 또한 지역적 특성을 반영하지 못하고 건설되어 과다한 단면을 사용하는 경우가 많고, 경제성이나 경관성을 갖추지 못한 경우가 많은 실정이다. 본 연구에서는 합리적인 잔교용 설계기준을 마련하기 위한 기초적인 연구로써 지반조건을 고려한 잔교의 거동특성을 분석하고자 하였다. 이를 위하여 해석모델을 개발하고, 다양한 해석조건에 대한 해석을 수행하여 그 특성을 정리하고자 하였다. 이를 통하여 잔교의 합리적인 구조시스템을 개발하고, 설계기준을 정리하는데 이바지 하고자 한다. 이 연구에서는 서해안의 연약지반을 고려하기 위해 지반스프링을 이용한 해석모델을 개발하고, 다양한 해석조건에 대한 해석을 수행하여 그 특성을 파악하고자 하였다. 조립식 잔교는 Capbeam, Wood Deck, ㄱ형강, Pile로 네 가지의 구성으로 이루어지고, 이 네 가지 요소의 재료는 강재로 사용하였으며, 하중에 대해서는 항만 및 어항설계기준을 준용하여 군중하중 $5kN/m^2$, 월파력 $20.1kN/m^2$을 사용하였고, 풍하중은 도로교 설계기준을 이용하여 산정한 $3.309kN/m^2$을 사용하였다. 재하하중 및 하중에 대한 최적단면에 대한 연구를 활용하여 본 연구에서는 지반조건의 영향, Capbeam과 Pile의 크기변화, 사항 등의 영향을 고려하였을 때 각 구성요소에서 발생하는 단면력의 변화와 축력, 접합부 모멘트 등의 외력과 내력을 정리하여 잔교의 거동특성을 파악하고자 하였다. 다양한 변수해석을 수행하기 위하여 지반조건을 고려한 2D 해석모델을 개발하였으며, 본 연구에서 고려한 군중하중, 풍하중, 월파력의 설계하중 중에서는 월파력이 지배적인 것을 알 수 있었다. Pier의 지름이 증가 하면 작용하는 월파력이 커지고 따라서 단면력이 증가하는 것을 알 수 있었다. 그러므로 합리적인 Pier의 크기 결정이 경제적이고 경관이 우수한 잔교 건설에 중요 요인임을 알 수 있다. 본 연구는 잔교의 설계기준 정립에 기초자료로 활용할 수 있을 것으로 판단되나, 보다 합리적인 잔교의 설계와 시공을 위해서는 지속적인 연구가 필요한 것으로 판단된다.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.397-404
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• 2011

In this paper, a research for the dynamic wheel loads of a 3D vehicle model, which relates to a tire-enveloping model, is carried out. A single truck with four axles is modeled as a 10-D.O.F. vehicle by modeling both contact length of tires and pitching of tandem spring axles. The dynamic equations of the vehicle are obtained using the Lagrange's equation, the solution of the equations is calculated by Newmark-${\beta}$ method. The validity of the developed 3D vehicle model is demonstrated by comparing results obtained from the proposed method with those from experimental data. The maximum impact factors of tire force are evaluated according to the various step bumps on which a 24-ton dump truck is running.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.95-104
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• 2002

In this paper, research for dynamic wheel loads of 3-D vehicle model considering tire enveloping model is carried out. Heavy trucks with 2-axles and 3-axles are modeled by 7-d.o.f. and 8-d.o.f., in which contact length of tire and pitching of tandem spring axles is considered. Dynamic equations of vehicle are derived by using the Lagrange's equation and solution of the equation is calculated by 5th Runge-Kutter method. The validity of the developed 3-D vehicle model is demonstrated by comparing the results obtained by the present method and experimental data by Whittemore. The maximum impact factors of tire force are calculated when vehicle models of 8ton and 15ton dump truck are running on the different class roads with 1.0km and on the various step bump.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.13-30
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• 2016

This paper concerns the development of an optimized TBM segmental lining design system for a subsea tunnel. The subsea tunnel is normally laid down under the sea water and submarine ground which consists of soil or rock. The design system is the series of process which can predict segmental lining member forces by ANN (artificial neural network system), analyze suitable section for the designated ground, construction and tunnel conditions. Finally, this lining design system aims to be connected with a BIM system for designing the subsea tunnel automatically. The lining member forces are predicted based on the ANN which was calculated by a FEM (finite element analysis) and it helps designers determine its segmental lining dimension easily without any further FE calculations.

• 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.