• Structural Engineering and Mechanics
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• v.76 no.2
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• pp.163-173
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• 2020

As a vehicle moves on multiple equal-span beams at constant speed, the running vehicle would be subjected to repetitive excitations from the beam vibrations under it. Once the exciting frequency caused by the vibrating beams coincides with any of the vehicle's frequencies, resonance would take place on the vehicle. A similar resonance phenomenon occurs on a beam subject to sequential moving loads with identical axle-intervals. To reduce both resonant phenomena of a vehicle moving on guideway girders, this study proposed an additional feedback controller based the condensed virtual dynamic absorber (C-VDA) scheme. This condensation scheme has the following advantages: (1) the feedback tuning gains required to adapt the control currents or voltages are directly obtained from the tuning forces of the VDA; (2) the condensed VDA scheme does not need additional DoFs of the absorber to control the vibration of the maglev-vehicle/guideway system. By decomposing the maglev vehicle-guideway coupling system into two sub-systems (the moving vehicle and the supporting girders), an incremental-iterative procedure associated with the Newmark method is presented to solve the two sets of sub-system equations. From the present studies, the proposed C-VDA scheme is a feasible approach to suppress the interaction response for a maglev vehicle in resonance moving on a series of guideway girders.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.121-138
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• 2004

The design of soccer studs is important for providing friction on a variety of surfaces. We hypothesized that a certain type of soccer studs could improve performance due to high rotational friction. Thus, this study was conducted to determine the relationship between the frictional characteristics and different soccer stud design. Twelve recreational soccer players were recruited. Rotational friction data from the force plate was collected for all subjects during normal walking with 180 degree rotation. Walking speed was controlled at 1.2m/s (${\pm}\;0.1\;m/s$) with timing lights on infilled artificial turf. Three different types of soccer studs and one running shoe were tested. Repeated measures ANOVA was used to determine significance. Significant differences were found in rotational friction with four different shoes. Trx and World studs tended to have greater maximum rotational friction than the running shoe (Nova) and traditional soccer shoe(Copa Mondial). The results were as follow : world(25.95Nm) > trx(25.74Nm) > copa(22.50Nm) > nova(16.36Nm). The difference may be due to the number, location, size, and shape of studs. We concluded that stud design influences rotational friction between the shoe and surface during movement. Based on studs design and contact area, Trx with blade type studs are recommended since it showed high rotational friction for performance as well as enough contact area for stability. However, differences due to the mechanical properties of soccer studs are still being investigated.

• Interaction and multiscale mechanics
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• v.3 no.4
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• pp.309-320
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• 2010

With taking the geometric nonlinearity of bridge structure into account, a framework is presented for predicting the dynamic responses of a long-span suspension bridge subjected to running train and turbulent wind. The nonlinear dynamic equations of the coupled train-bridge-wind system are established, and solved with the Newmark numerical integration and direct interactive method. The corresponding linear and nonlinear processes for solving the system equation are described, and the corresponding computer codes are written. The proposed framework is then applied to a schemed long-span suspension bridge with the main span of 1120 m. The whole histories of the train passing through the bridge under turbulent wind are simulated, and the dynamic responses of the bridge are obtained. The results demonstrate that the geometric nonlinearity does not influence the variation tendency of the bridge displacement histories, but the maximum responses will be changed obviously; the lateral displacement of bridge are more sensitive to the wind than the vertical ones; compared with wind velocity, train speed affects the vertical maximum responses a little more clearly.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.732-738
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• 2006

This research provides a scheme for Highly Accelerated Stress Test that is necessary to demonstrate reliability prediction of Korean Rapid Transit Railway Train Control System sub-equipment, which is calculated by a relevant standard for failure rate prediction of electronic products. Although determining failure information generated in the process of trial running by statistic analysis is widely accepted as a measure of confirmation for reliability prediction, this research suggests the modeling for System Life Test determined by accelerating stress factors as a measure of confirmation for reliability prediction of sub-equipment unit that is generated ahead of a trial running in System Life Cycle. Consequently, the research demonstrates sub-equipment unit reliability test, which is based on the model derived from Accelerated Stress Test, according to accuracy level and the number of samples, and conducts an official experiment by making out a reliability test procedure sheet based on test time as well.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.335-342
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• 2009

Motion characteristics of a planing craft are sensitively changed according to its weight and longitudinal center of gravity. In this paper, planing craft model tests were performed in calm water for various test conditions and Froude numbers. Sinkage and trim were measured to analyze the relations between the attitudes of a planing craft and the weight and center of gravity of it. Theoretical formula for the prediction of the attitudes of a prismatic planing hull was modified so that it can be applied to the prediction of the attitudes of a non-prismatic planing hull, and the calculation results by the modified formula were in good agreements with the experimental data.

• The Korean Journal of Physiology
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• v.11 no.1
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• pp.33-36
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• 1977

The object of the present study is to examine the effect of physical training during early growth of life on body weight gain and physical performance. Early weaned (2 weeks after birth) male mice were divided into control and training group-and experimental period was divided into growing period (from 1st week to 6th weeks after weaning) and adult period (from 7th weeks to 9th weeks after weaning). Physical training was. given on a small animal treadmill with a speed of 34.3m/min and $19^{\circ}C$ slope and both groups of body weight gain and maximal running time on the treadmill were determined. The results obtained are summarized as follows; 1. Body weight gain was lesser in training group than control group and the difference was. statistically significant at 1, 2.5, 5.7 weeks of training period. 2. Maximal running time of training group was found to be longer than that of control group at 6th (p<0.01), 8th (p<0.001) and 9th weeks. (p<0.01). From the above results, it may be concluded that if physical training is started in early growth of life, there might be an improvement of physical performance.

• Journal of the Korean Society for Railway
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• v.14 no.6
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• pp.562-568
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• 2011

Superimposition of horizontal and vertical curves occurs frequently owing to geographical conditions. It may hamper train ride comfort and running safety and inflate maintenance costs. In this study, when the horizontal and vertical curves are superimposed, in order to analyze the effects of the compensation cant, the analytical study for running safety, ride comfort and track forces was performed in high speed line. From the analysis results, it was found that it is better to apply the compensation cant at superimposition part.

• Journal of The Korea Institute of Healthcare Architecture
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• v.14 no.4
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• pp.39-46
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• 2008

Construction and operation of Germ Free Pigs' facilities are very expensive because pigs' rooms and other major rooms of the facility require germfree environments. Especially, running the HVAC system of aseptic facilities requires a lot of expenses. However, proper location and efficient shape of outlets/inlets for the ventilation of the room can reduce the excessive running cost. In order to do that, this study proposes alternative location and shape of ventilation outlets/inlets to the existing design pattern in germfree pigs' room. The design condition of this study is the maintenance of adequate temperature(24$^{\circ}C$, $NH_3$concentration level(below 1.5 ppm), and air stream speed(below .25m/sec) in the pigs' room for the summer and the winter together. As the Software Program, FLUENT(Ver. 6.2) has been used for the analysis of proposed ventilation patterns. In conclusion, wall inlets and ceiling inlet/outlet are advisable in summer, wall inlets and ceiling outlets is advisable in winter. As far as the shape is concerned, diffuser type for the ceiling outlet is desirable.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.539-542
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• 2006

Many researches about next generation vehicles are trending toward HEV which has better fuel economy than an internal-combustion engine. But existing HEV has some defects at specific running states(eg. highway running It is possible that dual-mode hybrid system overcomes that defects. Mode change parameter, ${\gamma}$ helps to analyse the mode changing of dual mode hybrid and is applied at a numerical analysis on testing the performance. There is an additional constraint when vehicles drive on engine mode. No power assistance of battery applies on engine mode. Because vehicles must be sustained by only engine power while vehicle drives on constant speed mode. At the conclusion of this paper, graphs show the ability of motors that satisfy the equilibrium of the lever system. Designers can roughly determine capacities of the motors, parameters of the lever system by this analysing method.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.47-58
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• 2012

Dynamic behaviors of a corrugated steel plate tunnel lining system are examined under wind loads due to passing vehicles. Applied wind loads are simulated by applying the time functions as a vehicle moves through the tunnel. Wind loads are described by the pressure and suction as a vehicle arrives and leaves target positions in the tunnel. The tunnel lining is modeled using the simplified shell elements that retain the characteristics of the corrugated shapes. The displacements of the tunnel lining are evaluated under various conditions regarding wind velocity and the passing vehicles. The responses are found to increase as the vehicle velocity and wind velocity increase. A maximum displacement of 25mm occurs when two vehicles are crossing at the speed of 120km/h. A row of vehicles running consecutively minimally affects the dynamic responses with less than 2.5% of the dynamic responses enlarged and attributed to one running vehicle. It should be noted that the dynamic responses of the tunnel lining should be considered when there is no shotcrete applied.