• 한국기계연구소 소보
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• s.15
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• pp.75-87
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• 1985

A review was performed on fatigue life prediction and strength evaluation of shot peened parts. Fatigue strength of machine parts can be improved by shot peening due to compressive residual stresses on such parts. Compressive residual stress cannot be uniquely define by peening intensity. Several measuring methods of residual stress and the principle of hole drilling method are presented. Exploratory measurement of residual stress was performed on the shot peened SM35C plate with the hole drilling method. Fatigue life and failure location of shot peened parts under bending load can be predicted by a damage parameter which is incorporated with material properties, residual stress, and applied stress conditions. Some method are presented to predict the fatigue strength of shot peened parts at any given life. Shot peening gives its full benefit to the notched machine parts of high strength steels.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1078-1081
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• 2002

In microcell or picocell mobile communication using cellular method, we suggested propagation prediction model which can accurately and rapidly interpret mobile communication propagation environment in urban, when subscriber service is done based on the main road in urban. Further, we simulated suggested propagation prediction model under the hypothesis of urban propagation environment of PCS mobile communication, analyzed receiving field strength by area within a cell, and finally suggested the optimal transmitting power and location condition of microcell or picocell mobile communication base station

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.889-894
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• 2001

In this study, the performances of various turbulence closure models are evaluated in the calculation of a transonic flow over axisymmetric bump. k-$\varepsilon$, explicit algebraic stress, and two Reynolds stress models, i.e., GL model proposed by Gibson & Launder and SSG model proposed by Speziale, Sarkar and Gatski, are chosen as turbulence closure models. SSG Reynolds stress model gives best predictions for pressure coefficients and the location of shock. The results with GL model also show quite accurate prediction of pressure coefficients down-stream of shock wave. However, in the predictions of mean velocities and turbulent stresses, the results are not so satisfactory as in the prediction of pressure coefficients.

• Journal of KSNVE
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• v.10 no.4
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• pp.686-691
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• 2000

In this paper a computer aided analysis method is proposed for durability assessment in the early design stages using dynamic analysis, stress analysis and fatigue life prediction method. From dynamic analysis of a vehicle suspension system, dynamic load time histories of a suspension component are calculated. From the dynamic load time histories and the stress of the suspension component, a dynamic stress time history at the critical location is produced using the superposition principle. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The predicted fatigue life cycle is verified by experimental durability tests.

• Journal of Ship and Ocean Technology
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• v.4 no.1
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• pp.1-10
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• 2000

A low-order potential based boundary element method is applied for the prediction of the performance of flapped rudders as well as all-movable rudders in steady inflow. In order to obtain a reasonable solution at large angles of attack, the location of the trailing wake sheet is determined by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap of a flapped rudder is modeled as Couette flow and its effect is introduced into the kinematic boundary conditions for flux at both the inlet and the outlet of the gap. In order to validate the present method, the method is applied for a series of rudders and the computational results on forces and moments are compared with experimental data. The effect of the gap size on the forces and moments is also presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4950-4966
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• 2015

Cloud providers now face the problem of estimating the amount of computing resources required to satisfy a future workload. In this paper, a virtual machine provisioning (VMP) mechanism is designed to adapt workload fluctuation. The arrival rate of forthcoming jobs is predicted for acquiring the proper service rate by adopting an exponential smoothing (ES) method. The proper service rate is estimated to guarantee the service level agreement (SLA) constraints by using a diffusion approximation statistical model. The VMP problem is formulated as a facility location problem. Furthermore, it is characterized as the maximization of submodular function subject to the matroid constraints. A greedy-based VMP algorithm is designed to obtain the optimal virtual machine provision pattern. Simulation results illustrate that the proposed mechanism could increase the average profit efficiently without incurring significant quality of service (QoS) violations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1883-1888
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• 2000

In this paper a computer aided analysis method is proposed for durability assessment in the early design stages using dynamic analysis, stress analysis and fatigue life prediction method. From dynamic analysis of a vehicle suspension system, dynamic load time histories of a suspension component are calculated. From the dynamic load time histories and the stress of the suspension component, a dynamic stress time history at the critical location is produced using the superposition principle. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The predicted fatigue life cycle is verified by experimental durability tests.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.422-428
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• 2005

In this paper, the contact force between two colliding bodies is modeled by using Hertz's force-displacement law and nonlinear damping function. In order to verify the appropriateness of the proposed contact force model, the drop type impact test is carried out for different impact velocities and different materials of the impacting body, such as rubber, plastic and steel. In the drop type impact experiment, six photo interrupters in series close to the collision location are installed to measure the velocity before impact more accurately. The characteristics of contact force model are investigated through experiments. The parameters of the contact force model are estimated using the optimization technique. Finally the estimated parameters are used to predict the impact force between two colliding bodies in opening action of the magnetic contactor, a kind of switch mechanism for switching electric circuits.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.50-52
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• 2007

In the present paper, some difficulties encountered in predicting airfoil characteristics are described and solutions for those problems are discussed Since drag is determined by the amounts of pressure and, especially, shear stress, accurate estimation of shear stress is very crucial. However shear stress computation is dependent on the grid density and turbulence model, it should be consistent in preparing grid and turbulence model. When the transition from laminar to turbulent happen at the middle of airfoil, CFD solver should divide the region into laminar and turbulent region based on the transition location.

• Journal of ILASS-Korea
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• v.20 no.4
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• pp.241-246
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• 2015

The objective of the current study is to develop an 1D thermoacoustic model for predicting basic characteristics of combustion instability and to investigate effects of key parameters on the instabilities such as effects of flame geometry and acoustic boundary conditions. Another focus of the paper is placed on limit cycle prediction. In order to improve the model accuracy, the 1D model was modified considering the actual flame location and flame length (i.e. distribution of time delay). As a result, it is found that the reflection coefficients have a great effect on the growth rate of the instabilities. In addition, instability characteristics are shown to be strongly dependent upon the fuel compositions.