• 한국멀티미디어학회논문지
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• 제12권1호
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• pp.147-155
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• 2009

교합력 측정과 분석은 힘의 관계를 분석하여 치아의 역학적 관계를 진단하는 방법이다. 본 연구에서는 새로운 교합력 측정 및 분석 시스템 개발의 기초 연구로써 측정 소프트웨어를 설계 및 구현하고 유용성을 평가한다. 이를 위해 교합력의 정상, 비정상을 효과적으로 측정할 수 있는 다양한 도구들을 개발하였다. 첫째, 치아에 작용하는 힘의 중심 변화를 나타내는 표지의 경로와 14개로 나뉜 치아 영역별 교합력 분포를 정량적인 수치와 함께 가시화 하였으며, 둘째, 교합력이 어느 치아의 특정한 영역으로 치우쳐서 작용하는가를 판단할 수 있도록 하기 위해 좌 우 치아 영역의 힘의 균형을 비율로 측정할 수 있는 도구를 구현하였다. 또한 0.5초 단위로 측정된 교합력의 변화를 소프트웨어 상에서 기록할 수 있도록 하였다. 센서 시트 방식의 측정 하드웨어와 연동하여 테스트한 결과, 힘의 분포와 균형을 효과적으로 확인할 수 있었다.

• 한국전산구조공학회논문집
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• 제23권4호
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• pp.435-443
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• 2010

본 연구에서는 MR(Magneto-Reological)제어기가 설치된 단자유도 구조물의 응답을 예측하기 위하여 구조물의 운동방정식을 해석적으로 분석하고 주요변수를 파악하였다. MR제어기의 수치 모델로는 마찰 및 점성감쇠로 단순모델한 Bingham모델을 사용하였다. 자유진동과 조화진동일때의 응답감쇠를 결정짓는 주요변수가 각각 마찰력과 최대정적복원력의 비 $R_f$, 마찰력과 최대조화가진력의 비 $R_h$ 임을 파악하였다. 비선형 미분방정식을 등가의 선형 미분방정식으로 변환하기 위하여 마찰력에 의한 에너지 소산을 등가의 점성에너지로 치환하여 등가점성감쇠와 등가점성감쇠비를 유도하였다. 마지막으로 등가선형화과정을 검증하기 위하여 실제 지진에 대한 구조물의 응답을 비선형 미분방정식의 해와 비교하였다.

• 한국공간구조학회논문집
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• 제5권4호
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• pp.101-108
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• 2005

고층건물의 진동응답을 저감시키기 위한 다양한 방법들이 연구되고 있다. 이들 진동응답의 저감 연구는 건물의 외관을 병화 시키는 방법과 건물에 부가감쇠장치를 설치하는 방법들이 있는데 본 논문에서는 고층 건물의 형태의 변화에 다른 진동변위응답의 특성을 파악하고자 한다. 고층건물의 형태변화 중에서도 외관에 테이퍼를 수는 방법을 사용하였다. 기류의 특성은 도심 및 교외지역을 중심으로 풍동실험을 실시하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4144-4165
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• 2018

Software-defined networking (SDN) has emerged as a promising technology for network programmability and experiments. In this work, we focus on virtual network embedding in multiple controllers SDN network. In SDN virtualization environment, virtual SDN networks (vSDNs) operate on the shared substrate network and managed by their each controller, the placement and load of controllers affect vSDN embedding process. We consider controller placement, vSDN embedding, controller adjustment as a joint problem, together considering different quality of service (QoS) requirement for users, formulate the problem into mathematical models to minimize the average time delay of control paths, the load imbalance degree of controllers and embedding cost. We propose a heuristic method which places controllers and partitions control domains according to substrate SDN network, embeds different QoS constraint vSDN requests by corresponding algorithms, and migrates switches between control domains to realize load balance of controllers. The simulation results show that the proposed method can satisfy different QoS requirement of tenants, keep load balance between controllers, and work well in the acceptance ratio and revenue to cost ratio for vSDN embedding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1845-1865
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• 2019

Current Internet is designed by lots of service providers with different objects and policies which make the direct deployment of radically new architecture and protocols on Internet nearly impossible without reaching a consensus among almost all of them. Network virtualization is proposed to fend off this ossification of Internet architecture and add diversity to the future Internet. As an important part of network virtualization, virtual network embedding (VNE) problem has received more and more attention. In order to solve the problems of large embedding cost, low acceptance ratio (AR) and environmental adaptability in VNE algorithms, cognitive method is introduced to improve the adaptability to the changing environment and a cognitive virtual network embedding algorithm based on weighted relative entropy (WRE-CVNE) is proposed in this paper. At first, the weighted relative entropy (WRE) method is proposed to select the suitable substrate nodes and paths in VNE. In WRE method, the ranking indicators and their weighting coefficients are selected to calculate the node importance and path importance. It is the basic of the WRE-CVNE. In virtual node embedding stage, the WRE method and breadth first search (BFS) algorithm are both used, and the node proximity is introduced into substrate node ranking to achieve the joint topology awareness. Finally, in virtual link embedding stage, the CPU resource balance degree, bandwidth resource balance degree and path hop counts are taken into account. The path importance is calculated based on the WRE method and the suitable substrate path is selected to reduce the resource fragmentation. Simulation results show that the proposed algorithm can significantly improve AR and the long-term average revenue to cost ratio (LTAR/CR) by adjusting the weighting coefficients in VNE stage according to the network environment. We also analyze the impact of weighting coefficient on the performance of the WRE-CVNE. In addition, the adaptability of the WRE-CVNE is researched in three different scenarios and the effectiveness and efficiency of the WRE-CVNE are demonstrated.

• 천문학회지
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• 제46권6호
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• pp.261-268
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• 2013

Magnetohydrostatic equilibria, in which the Lorentz force, the plasma pressure force and the gravitational force balance out to zero, are widely adopted as the zeroth order states of many astrophysical plasma structures. A magnetic flux-current surface is a surface, in which both magnetic field lines and current lines lie. We for the first time derive the necessary and sufficient condition for existence of magnetic flux-current surfaces in magnetohydrostatic equilibria. It is also shown that the existence of flux-current surfaces is a necessary (but not sufficient) condition for the ratio of gravity-aligned components of current density and magnetic field to be constant along each field line. However, its necessary and sufficient condition is found to be very restrictive. This finding gives a significant constraint in modeling solar coronal magnetic fields as force-free fields using photospheric magnetic field observations.

• Steel and Composite Structures
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• 제13권6호
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• pp.501-519
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• 2012

As an alternative to current conventional force-based assessment methods, the energy-based seismic performance of a code-designed 20-storey high-rise steel building is evaluated in this paper. Using 3D nonlinear dynamic time-history method with consideration of additional material damping effect, the influences of different restoring force models and P-${\Delta}/{\delta}$ effects on energy components are investigated. By combining equivalent viscous damping and hysteretic damping ratios of the structure subjected to strong ground motions, a new damping model, which is amplitude-dependent, is discussed in detail. According to the analytical results, all energy components are affected to various extents by P-${\Delta}/{\delta}$ effects and a difference of less than 10% is observed; the energy values of the structure without consideration of P-${\Delta}/{\delta}$ effects are larger, while the restoring force models have a minor effect on seismic input energy with a difference of less than 5%, but they have a certain effect on both viscous damping energy and hysteretic energy with a difference of about 5~15%. The paper shows that the use of the hysteretic energy at its ultimate state as a seismic design parameter has more advantages than seismic input energy since it presents a more stable value. The total damping ratio of a structure consists of viscous damping ratio and hysteretic damping ratio and it is found that the equivalent viscous damping ratio is a constant for the structure, while the equivalent hysteretic damping ratio approximately increases linearly with structural response in elasto-plastic stage.

• Structural Engineering and Mechanics
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• 제63권4호
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• pp.509-519
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• 2017

Wind field in mountainous regions demonstrates unique distribution characteristic as compared with the wind field of the flat area, wind load and wind effect are the key considerations in structural design of television towers situated in mountainous regions. The television tower to be constructed is located at the top of Xiushan Mountain in Nanjing, China. In order to investigate the impact of terrain factors of hilltops on wind loads, firstly a wind tunnel test was performed for the mountainous area within 800m from the television tower. Then the tower basal forces such as bending moments and shear strength were obtained based on high frequency force balance (HFFB) test. Based on the experiments, the improved method for determining the load combinations was applied to extract the response distribution patterns of foundation internal force and peak acceleration of the tower top, then the equivalent static wind loads were computed under different wind angles, load conditions and equivalent goals. The impact of terrain factors, damping ratio and equivalent goals on the wind load distribution of a television tower was discussed. Finally the equivalent static wind loads of the television tower under the 5 most adverse wind angles and 5 most adverse load conditions were computed. The experimental method, computations and research findings provide important references for the anti-wind design of high-rise structure built on hilltops.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.76-81
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• 2002

The dramatic increase in the depth of a weld bead penetration has been demonstrated by welding a stainless steel in GTA (Gas-Tungsten-Arc) process with activating flux which consists of oxides and halides. However, there is no commonly agreed mechanism fer the effect of flux on the process. In order to make clear the mechanism, each behavior of the arc md the weld pool in GTA process with activating flux is observed in comparison with a conventional GTA process. A constricted anode root is shown in GTA process with the activating flux, whereas a diffuse anode root is shown in the conventional process. These anode roots are related strongly to metal vapor from the weld pool and the metal vapor is also related to temperature distributions on the weld pool surface. Furthermore, it is suggested that a balance between the Marangoni force and the drag force of the cathode jet should dominate the direction of re-circulatory flow in the weld pool. The electromagnetic force encourages the inward re-circulatory flow due to the constricted anode root in the case with flux. The difference in flow direction in the weld pool changes the geometry or depth/width ratio of weld bead penetration.

• 한국운동역학회지
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• 제17권4호
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• pp.27-36
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• 2007

The purpose of this study was to investigate the effect of the upper body in order to increase a propulsive force in the old's walking. The subjects were each 10 males, the latter term of the aged and former term of the aged. There were three walking speeds of slow(about 5km/h), medium(about 6km/h), and maximum speed(about 7km/h). The subjects walking 11m were filmed the 5m section (from 3m to 8m) by 2-video cameras using three dimensional cinematography. And we computed different mechanical quantities and especially computed the relative momentum in order to achieve this study's aim. In this study, we was able to acquire some knowledge. The step length and step frequency increased in proportion to the walking speed, and the faster walking speed, the shorter ratio of supporting time( both legs supporting time/one step length time). When it was one leg support phase, the torso was indicated to generate the momentum in order to produce the propulsive force of walking. The upper and lower body had a cooperative relation for walking such as keeping step rate with the arms to legs and maintaining the body balance. The opposition phase for upward-and-downward direction of the torso and arms in walking was functioned to prevent the increase rapidly toward vertical direction of the center of gravity. The arms had contributed to coordinate the tempo of legs and the posture maintenance of the upper body. And by absorbing the relative momentum from the upper torso with arms to the lower torso, it had the rhythmical movement on upward-and-downward direction reducing the vertical reaction force. On account of the relations of absorption and generation of the propulsive force and the production of vertical impulse in the lower torso when walking by maximum speed, it was showed that the function of lower torso was come up as important problem for the mechanical posture stability and propulsive force coordination.