• Journal of computational fluids engineering
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• v.18 no.1
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• pp.28-35
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• 2013

Behavior of the side force generated at high angles of attack by two ogive-cylinder bodies of revolution with nose fineness ratio of 2.3 (B1) and 3.5 (B2) and the effect of a strip placed close the nose tip of each body (B1S and B2S) are analyzed through the wind tunnel test at ReD=200,000 and a=42~60 deg. The side force generated by B1 is increased by placing a strip. The side force generated by B2 is in the starboard direction and its magnitude is higher than that of the B1S. The effect of the strips with various dimensions placed on B2 is investigated. It is found that the 4-layer strip placed on the starboard reversed the direction of the side force into port direction. It is confirmed by numerical simulations that the strip promotes the flow separation and increases the average pressure on the side where it is placed and consequently produces the side force in the corresponding direction.

• Steel and Composite Structures
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• v.25 no.1
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• pp.19-34
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• 2017

The widespread damage to steel Moment Resisting Frames (MRFs) in past major earthquakes have underscored the need to understand the nonlinear inelastic behaviour of such systems. To assess the seismic performance of steel MRF, it is essential to model the nonlinear force-deformation behaviour of beam to column joints. To determine the extent of inelasticity in a beam to column joint, nonlinear finite element analysis is generally carried out, which is computationally involved and demanding. In order to obviate the need of such elaborate analyses, a simplistic method to predict the force-deformation behaviour is required. In this study, a simple, mechanics driven, hand calculation method is proposed to obtain the forcedeformation behaviour of strong axis beam to column moment joints. The force-deformation behaviour for twenty-five interior and exterior beam to column joints, having column to beam strength ratios ranging from 1.2 to 10.99 and 2.4 to 22, respectively, have been obtained. The force-deformation behaviour predicted using the proposed method is compared with the results of finite element analyses. The results show that the proposed method predicts the force-deformation behaviour fairly accurately, with much lesser computational effort. Further the proposed method has been used to conduct Nonlinear Dynamic Time History Analyses of two benchmark frames; close correspondence of results obtained with published results establishes the usefulness and computational accuracy of the method.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.453-459
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• 1998

The dental implants for edentulous Patients have been used for more than 20 years. After the introduction of osseointegration by $Br{\aa}nemark$, the commercially pure titanium implants were accepted by most practitioners. Recently dental implants are used for orthodontic anchorages as well as prosthetic abutment. Many researchers have reported implants as a good orthodontic anchorage through basic research and clinical evaluation. But previous researches were done after the healing time for osseointegration of inserted implants. If dental implants are to be used for prosthetic abutment the healing time for osseointegration is necessary, but orthodontic forces to implants are different from bite force regarding its amount of force, duration and direction. The authors evaluated the effect of orthopedic force to implants on bone tissue before osseointegration. 48 implants were placed at 12 rabbits. 2 implants into left side and 2 implants into right side were inserted along the long axis of femur respectively 2 weeks (2 weeks group), 4 weeks (4 weeks group) and 6 weeks (6 weeks group) after implants placement, 300g force had been applied to the implants at left side femur by Ni-Ti close coil spring for 4 weeks (experimental group) and no force applied to implants at right side femur (control group). After the force application for 4weeks, rabbits were sacrificed and microscopic evaluation was done by hematoxylin-eosin stain and Masson trichrome stain. The result3 were followed. 1. All implants in experimental group remained rigid after the force application for 4 weeks. 2. More fibrous tissue between bone and implants were noticed at 2 weeks experimental group than 2 weeks control group 3. More bone remodeling was noticed at 4weeks group than 2 weeks group and it was difficult to find out fibrous tissue between bone and implants at both experimental and control group of 4 weeks group. 4. It was hard to distinguish experimental group from control group at 6 weeks group. Therefore if initial stability can be obtained on implant insertion, it can be possible to use implants as a orthodontic anchorage before the healing time for osseointegration.

• Journal of Korean Association for Spatial Structures
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• v.14 no.1
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• pp.77-84
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• 2014

Simple 3, 10, and 30-story buildings with a nonstructural element which is located at roof or near the middle of the building height are selected. Based on 2009 Korean Building Code, the seismic design force applied at the nonstructural element is evaluated. Response spectrum analysis is conducted with the design response acceleration spectrum of 2009 Korean Building Code and the analytical response is compared with the seismic design force from the Code. Furthermore, an artificial earthquake based on Korean design response acceleration spectrum and the 50% intensity of El Centro earthquake, which can be considered as the maximum future earthquake possibly occurring in Korea, are selected to conduct time history analysis. When the period of the nonstructural element is shorter than 0.06 second or longer than that of the 1st period of each building, the Code equations of seismic design force for nonstructural element seems to be appropriate. However, the period of the nonstructural element is close to the one of the building's higher mode periods including the 1st period, seismic force of the nonstructural element might exceed the Code specified seismic design force.

• Journal of the Korean Magnetic Resonance Society
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• v.18 no.1
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• pp.24-29
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• 2014

Atomistic molecular dynamics (MD) simulation has become mature enabling close approximation of the real behaviors of biomolecules. In biomolecular NMR field, atomistic MD simulation coupled with generalized implicit solvent model (GBIS) has contributed to improving the qualities of NMR structures in the refinement stage with experimental restraints. Here all-atom force fields play important roles in defining the optimal positions between atoms and angles, resulting in more precise and accurate structures. Despite successful applications in refining NMR structure, however, the research that has studied the influence of force fields in GBIS is limited. In this study, we compared the qualities of NMR structures of two model proteins, ubiquitin and GB1, under a series of AMBER force fields-ff99SB, ff99SB-ILDN, ff99SB-NMR, ff12SB, and ff13-with experimental restraints. The root mean square deviations of backbone atoms and packing scores that reflect the apparent structural qualities were almost indistinguishable except ff13. Qualitative comparison of parameters, however, indicates that ff99SB-ILDN is more recommendable, at least in the cases of ubiquitin and GB1.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.395_396
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• 2009

This paper handles with effect of electromagnetic force on the cables by fault current accompanied by accident of underground transmission cable. Even though underground transmission cable is an essential transmission method to supply stable power for downtown and population center, interaction of electromagnetic force from fault current is very large comparing to overhead transmission line due to restricted installation space such as tunnel, etc. and close consideration is required for it. This paper describes the effect of electromagnetic force through results of three phase short-circuit test and electromagnetic force analysis using theoretical calculations and electrical evaluation test after three phase short-circuit test, which will be utilized as basic materials for improvement and development of cleat, hanger, etc. to reduce and release effect of electromagnetic force in the future.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.67-76
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• 1997

In this paper we developed a tactile feedback device using repulsive force of magnets. The force of the tactile feedback device was derived from the Maxwell's stress method by using the concept of magnetic charge. Magnetic repulsive force is linear function with respect to current and nonlinear to displacement. Experimental data shows these characteristics. To compensate the fact that the presented tactile feedback device can not be controlled by close loop control, we developed a simulation model which predicts output displacement and force by using Runge-Kutta method. And, this paper evaluated the presented tactile feedback device and compared it with commercial tactile feedback devices.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.251-260
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• 2004

As a basic experiment for robot hand for transplanting plug seedling, the experimental robot hand system which moves up and downward vertically, and allows hand blade to open and close was made. The system was constructed with the robot hand mechanism, the tray, the plug seedling, and the measuring equipments. The penetrating force and holding efficiency were analyzed according to the soil moisture and the variation of hand blade angle. The highest holding efficiency could be obtained at the penetrating angle of approximately from 0 to 0.36 degree and at the moisture content of soil from 71% to 75%. The external force acted on the robot hand should maximum force when the robot hand was penetrated to soil, minimum of approximately 30.4 N when the penetrating angle was 0$^{\circ}$ and moisture content was 66-70%. It was increased with increasing or decreasing the Penetrating angle from 0 degree and also with increasing or decreasing the moisture content of soil from 66-70%. For optimal design of the robot hand and manipulator, the external force acted on robot hand had to be based on the returning force of soil, when the robot hand was penetrated to the soil. In consideration of safety ratio, the appropriate external force seemed to be 39-49 N.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.945-956
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• 1999

This work reports a set of approximate analytical solutions describing the initial transient process of close-contact melting between a rectangular parallelepiped solid and a flat plate on which either constant temperature or constant heat flux is imposed. Not only relative motion of the solid block tangential to the heating plate, but also the density difference between the solid and liquid phase is incorporated in the model. The thin film approximation reduces the force balance between the solid weight and liquid pressure, and the energy balance at the melting front into a simultaneous ordinary differential equation system. The normalized model equations admit compactly expressed analytical solutions which include the already approved two-dimensional solutions as a subset. In particular, the normalized liquid film thickness is independent of all pertinent parameters, thereby facilitating to define the transition period of close-contact melting. A unique behavior of the solid descending velocity due to the density difference is also resolved by the present solution. A new geometric function which alone represents the three-dimensional effect is introduced, and its properties are clarified. One of the representative results is that heat transfer is at least enhanced at the expense of the increase in friction as the cross-sectional shape deviates from the square under the same contact area.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1259-1265
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• 2007

This paper presents nonlinear vibration characteristics of a vertical passive zero stiffness isolator. The passive isolator can achieve zero stiffness through buckling of notched flexure caused by a compressive force. First, a simulation model of the isolator was built based on elastic beam theory. As increasing the compression force, time and frequency responses of the isolator were simulated. In addition, further nonlinear vibration characteristics were investigated through a bifurcation diagram and a Poincare's map, which shows that even chaostic vibration could happen. The simulations show that as the compressive force increases, the stiffness goes close to zero and the nonlinear characteristic becomes stronger to have a great effect on the isolation performance.