• Tribology and Lubricants
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• v.19 no.2
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• pp.85-93
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• 2003

In this study, a multigrid multi-integration method has been used to solve the steady-state, elastohydrodynamic lubrication (EHL) point contact problem of a ball joint mechanism used in small reciprocating compressors. Pressure and film thickness profiles have been calculated at minimum and maximum Moes M parameter conditions during one revolution of crankshaft. The effects of various lubricant viscosities, loads, ball velocities, elastic modulli, and radii of curvature on the calculated pressure distribution and film thicknesses have been investigated. The results indicate that the viscosity of lubricant, the sliding velocity of ball, and the reduced radius of curvature have considerable effects on the minimum and central film thicknesses. Solutions obtained with the multigrid analysis are compared with results calculated according to the Hamrock ＆ Dowson relations for the minimum and central film thicknesses.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.133.1-133
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• 2001

When the signals from satellite vehicles are blocked, it is impossible to provide positioning information. Integrating CDGPS with INS, the performances of output can be greatly improved. In the CDGPS/INS integrated system, the error growth in INS can be efficiently suppressed due to CDGPS. On the contrary, the search range of integer ambiguities can be reduced with the aids of INS. Furthermore, cycle slips in carrier phase measurements can be easily detected using INS. The paper presents a CDGPS/INS integrated system that utilizes CDGPS aided with INS. Using the outputs of CDGPS/INS integration filter, a method to reduce search range of integer ambiguities is proposed. A method to detect cycle slips in carrier phase measurements is ...

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.602-609
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• 2001

This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zeroenergy mode of the element. The analysis includes an inflation analysis and a lateral analysis of an air spring for the deformed shape and the spring load with respect to the vertical and l ateral deflection. Numerical results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force with respect to the inflation pressure and the lateral deflection.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.274-279
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• 2000

This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zero-energy modes of the element. An inflation analysis and a lateral deformation analysis of an air spring are carried out. Numerical analysis results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.60-68
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• 2005

For study on the unsteady wall interference effect, flows around a forced oscillating airfoil in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The Spalart-Allmaras one-equation model is employed for the turbulence effect. The computed results of the oscillating airfoil having a thin wake showed that the lift curve slope is increased and the magnitude of hysteresis loop is reduced by the interference effects. Since the vortex around the airfoil is generated and convected downstream faster than the free-air condition, the phase of lift, drag and pitching moment coefficients was shifted. The pressure on the test section wall shows harmonic terms having the oscillating frequency contained in the wail effect.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.682-687
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• 2000

In this paper, the simulation methods using transmission lines are studied and realized, which are necessary in design and analysis of hydraulic control systems. The basic idea of this method is that system components are separated by transmission line element for simulation. The PI-controller can keep inductance level as low as desired. It can also handle nonlinearities and discontinuities without flag signal when restarting integration. Parallel hydraulic circuits are simulated using parallel processing algorithm. To shoe that using variable timestep size in each subsystem, simulation time can be reduced. Performance of the simulation results is compared with that of Runge Kutta method.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.296-301
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• 2012

This paper describes an analytic method for infrared thermography to detect surface cracks in thin plates. Traditional thermographic method uses the spatial contrast of a thermal field, which is often corrupted by noise in the experiment induced mainly by emissivity variations of target surfaces. This study developed a robust analytic approach to crack detection for thermography using the holomorphic function of a temperature field in thin plate under steady-state thermal conditions. The holomorphic function of a simple temperature field was derived for 2-D heat flow in the plate from Cauchy-Riemann conditions, and applied to define a contour integral that varies depending on the existence and strength of singularity in the domain of integration. It was found that the contour integral at each point of thermal image reduced the noise and temperature variation due to heat conduction, so that it provided a clearer image of the singularity such as cracks.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.3
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• pp.125-131
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• 2018

STT-RAM is attracting as a next generation Non-volatile memory for replacing cache memory with low leakage energy, high integration and memory access performance similar to SRAM. However, there is problem of write operations as the other Non_volatile memory. Hybrid cache memory using SRAM and STT-RAM is attracting attention as a cache memory structure with lowe power consumption. Despite this, reducing the leakage energy consumption by the STT-RAM is still lacking access to the Dynamic energy. In this paper, we proposed as energy management method such as a way-selection approach for hybrid L2 cache fo SRAM and STT-RAM and memory selection method of write/read operation. According to the simulation results, the proposed hybrid cache memory reduced the average energy consumption by 40% on SPEC CPU 2006, compared with SRAM cache memory.

• Journal of IKEEE
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• v.19 no.2
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• pp.219-224
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• 2015

Electrical impedance tomography is an imaging technique to reconstruct the internal conductivity distribution based on applied currents and measured voltages in a domain of interest. In this paper, a modified Gauss-Newton method is proposed for conductivity image reconstruction. In the proposed method, the dimension of the inverse term is reduced by replacing the number of elements with the number of measurement data in the conductivity updating equation of the conventional Gauss-Newton method. Therefore, the computation time is greatly reduced as compared to the conventional Gauss-Newton method. Moreover, the regularization parameter is selected by computing the minimum-maximum from the diagonal components of the Jacobian matrix at every iteration. The numerical experiments with several scenarios were carried out to evaluate the reconstruction performance of the proposed method.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4350-4356
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• 2023

Radiation detection systems working at high count rates suffer from the overlapping of their output electric pulses, known as pulse pile-up phenomenon, resulting in spectrum distortion and degradation of the energy resolution. Pulse tail extrapolation is a pile-up correction method which tries to restore the shifted baseline of a piled-up pulse by extrapolating the overlapped part of its preceding pulse. This needs a mathematical model which is almost always nonlinear, fitted usually by a nonlinear least squares (NLS) technique. NLS is an iterative, potentially time-consuming method. The main idea of the present study is to replace the NLS technique by an integration-based non-iterative method (NIM) for pulse tail extrapolation by an exponential model. The idea of linear extrapolation, as another non-iterative method, is also investigated. Analysis of experimental data of a NaI(Tl) radiation detector shows that the proposed non-iterative method is able to provide a corrected spectrum quite similar with the NLS method, with a dramatically reduced computation time and complexity of the algorithm. The linear extrapolation approach suffers from a poor energy resolution and throughput rate in comparison with NIM and NLS techniques, but provides the shortest computation time.