• Journal of Mechanical Science and Technology
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• v.14 no.7
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• pp.764-772
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• 2000

In this paper, an engine-CVT integrated control algorithm is suggested by considering the inertia torque and the CVT ratio change response lag in acceleration. In order to compensate for drive torque time delay due to CVT response lag, two algorithms are presented: (1) an optimal engine torque compensation algorithm, and (2) an optimal engine speed compensation algorithm. Simulation results show that the optimal engine speed compensation algorithm gives better engine operation around the optimal operation point compared to the optimal torque compensation while showing nearly the same acceleration response. The performance of the proposed engine-CVT integrated control algorithms are compared with those of conventional CVT control, and It is found that optimal engine operation can be achieved by using integrated control during acceleration, and improved fuel economy can be expected while also satisfying the driver's demands.

• Journal of The Korean Astronomical Society
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• v.34 no.4
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• pp.293-295
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• 2001

A numerical scheme that incorporates a self-consistent cosmic-ray (CR, hereafter) injection model into the combined gas dynamics and CR diffusion-convection code has been developed. The hydro/CR code can follow in a very cos-effective way the evolution of CR modified shocks by adopting subzone shock-tracking and multi-level Adaptive Mesh Refinement techniques. The injection model is based on interactions of the suprathermal particles with self-generated MHD waves in quasi-parallel shocks. The particle injection is followed numerically by filtering the diffusive flux of suprathermal particles across the shock to upstream region according to a velocity-dependent transparency function, which represents the fraction of leaking suprathermal particles. In the strong shock limit of Mach numbers $\ge$20, significant physical processes such as the injection and acceleration seem to become independent of M, while they are sensitively dependent on M for M < 10. Although some particles injected early in the evolution continue to be accelerated to higher energies, the postshock CR pressure reaches a time asymptotic value due to balance between acceleration and diffusion of the CR particles.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.250-258
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• 2002

This Paper is to apply the well-established coarse mesh finite difference(CMFD) method to the method of characteristics(MOC) transport calculation as an acceleration scheme. The CMFD problem is first formulated at the pin-cell level with the multi-group structure To solve the cell- based multi-group CMFD problem efficiently, a two-group CMFD formulation is also derived from the multi-group CMFD formulation. The performance of the CMFD acceleration is examined for three test problems with different sizes including a realistic quarter core PWR problem. The CMFD formulation provides a significant reduction in the number of ray tracings and thus only about 9 ray tracing iterations are enough for the realistic problem. In computing time, the CMFD accelerated case is about two or three times faster than the coarse-mesh rebalancing(CMR) accelerated case.

• International Journal of Railway
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• v.1 no.3
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• pp.122-127
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• 2008

Rubber components are widely used in many application such as vibration isolators, damping, ride quality. Rubber spring is used in primary suspension system for railway vehicle. Characteristics and useful life prediction of rubber spring was very important in design procedure to assure the safety and reliability. Non-linear properties of rubber material which are described as strain energy function are important parameter to design and evaluate of rubber spring. These are determined by physical tests which are uniaxial tension, equi-biaxial tension and pure shear test. The computer simulation was executed to predict and evaluate the load capacity and stiffness for rubber spring. In order to investigate the useful life, the acceleration test were carried out. Acceleration test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the acceleration test, several useful life prediction for rubber spring were proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1097-1104
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• 2008

Working condition is one of the most important factors in precision working. In this study, we optimized the vibration acceleration of working progress direction using RSM(response surface methodology) by table of orthogonal array. RSM was well adapted to make analytic model for minimizing vibration acceleration, created the objective function and saved a great deal of computational time. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of working condition. The experimental results of the surface roughness and vibration acceleration showed the validity of the proposed working condition of side wall end-milling as it can be observed.

• The Journal of the Korean dental association
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• v.52 no.12
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• pp.734-743
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• 2014

Objectives: By introduced reciprocation motion file in dentistry, dentists benefit simple canal shaping procedure and time-saving. But, reciprocation motion generates uncomfortable vibration to doctors and patients. Because there was no study about this consideration, this study compared vibration pattern and power generated from reciprocation motion motor and conventional rotary motor. Materials & Methods: One conventional rotary motor; X-Smart (Dentsply Maillefer, Ballaigues, Switzerland); and two reciprocating motors; WaveOne Motor (Dentsply Maillefer, Ballaigues, Switzerland) and X-SMART PLUS (Dentsply Maillefer, Ballaigues, Switzerland); were used in this study. Triaxial $ICP^{(R)}$ Accelerometer (Model 356A12, PCB piezotronics, New York, USA) was attached on motor's handpiece head, and was measured tri-axial vibratory acceleration with NI Sound and Vibration Assistant 2009 software (National Instruments, Texas, USA). Mean vibratory acceleration and maximum vibratory acceleration was measured on fixed position and handed position. The results of vibratory acceleration were statistically analyzed using ANOVA and multiple comparisons are made using Turkey's test at p<0.05 level. Results: Reciprocating motors showed higher mean vibratory acceleration and maximum vibratory acceleration than conventional rotary motor (p<0.05). Between reciprocating motors, X-SMART PLUS had lower mean vibratory acceleration and maximum vibratory acceleration than WaveOne Motor (p<0.05). Conclusion: Reciprocating motors generate more vibration than conventional rotary motor. Further study about effect of vibration to dentist and patient is needed. And it seems to be necessary to make a standard about vibration level in endodontic motors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.52-63
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• 1998

The impact programmer for impact test was designed and the impact analysis was conducted. The effects of the material and geometric parameters on the impact force and pulse shape were investigated. The impact characteristics were examined by experimental and finite element method. The impact test was conducted with free drop impact tester. The ABAQUS/Explicit 5.5 version was used for finite element analysis. The geometric parameters of the conical and dome type impact programmer were analyzed. The polyurethane impact programmers were fabricated and tested. The effects of the hardness and thickness of the impact programmer were studied. The peak acceleration and time duration of impact programmer have close correlation with the hardness, impact energy and thickness of the impactor. The experiment was good agreement with analytical predictions. The impact pulse shape generated with polyurethane impact programmer was half sine shape. The maximum impact force was proportional to impact energy. The impact acceleration was decreased with thickness of impact programmer. The maximum impact time duration level was about 2 msec.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.33-40
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• 2010

In this paper, we consider three macroscopic traffic flow monitoring indices, Travel Time Index(TTI), Acceleration Noise(AN) and Two Fluid(TF) and investigate how to determine a proper rate of probe cars for producing reliable values of these indices. For the analysis, we use classical sampling theories and provide numbers of probe rates using simulation data.

• Journal of Korean Society for Quality Management
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• v.41 no.4
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• pp.659-672
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• 2013

Purpose: The purpose of this study was to estimate life time of halogen lamps and acceleration factors using accelerated life test. Methods: Voltage was selected as an accelerating variable through the technical review about failure mechanism. The test was performed at 14.5V, 15.5V and 16.5 for 4,471 hours. It was assumed that the lifetime of Halogen lamps follow Weibull distribution and the inverse power life-stress relationship models. Results: Mean lifetimes of pin and screw types were 19,477 hours and 6,056 hours, respectively. In addition, acceleration factor of two items are calculated as 4.8 and 2.2 based on 15.5V, respectively. Conclusion: The life-stress relationship, acceleration factor, and MTTF at design condition are estimated by analyzing the accelerated life test data. These results suggest that voltage was very important factor to accelerate life time in the case of halogen lamps and the life time of pin type is three times longer than screw type lamps.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.513-528
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• 2013

A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.