• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.124-127
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• 2006

In this paper, noise and vibration reduction of double-resiliently mounted pump-like machinery is studied. SBN(Structure-borne noise) reduction through upper and lower mount is analyzed by assuming that the system is modeled as a mass-spring system. In addition, the impedance of the floor is included in the prediction. The comparison of the SBN difference through upper mount show that the effect of impedance is negligible, while the measurement differs significantly from the prediction for high frequency range. It is found that the assumption of point mass-spring system leads to the disagreement between prediction and measurements.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.1-13
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• 1995

In order to investigate the effect of liquid balancer in washing machine, we identify the vibration characteristics of suspension system of washing machine and formulate the 4 D. O. F. system dynamic equations. As the washing machine rotates higher speed, it is emphasized to reduce the ecentric force due to unbalanced mass. Nowadays, the most effective cancelling method of eccentric force is known as the usage of liquid balancer. To determine the liquid distribution in liquid balancer, the fluid statics is considered. The system dynamic equations are solved by Runge-Kutta method and represent the good characteristics of real washing machine in X-Y plane. The accuracy of the numerical solution was examined by experiments. The simulation results show that the unbalanced mass has so much influence on vibration magnitude and the rotating shape of spin-basket. But the effect of mass reduction due to the dehydration of the spin-basket has little influence on transient vibration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.582-585
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• 2006

Attempts have been applied to reduce the vibration of slab. There are several method in the vibration control of slab from a traditional method such as increment of mass or stiffness of slab to a innovative method augmenting damping of slab. In this study, a attempt has been made to increase the effective damping in slab using the Multi Tuned Mass Damper. we evaluate the reduction effect of the slab selected through numerical simulation and optimization process by applying it to a FEM model. The numerical simulation shows that the effective damping is increased as the number of bean is increased and the vibration control effect is very high.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.699-712
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• 2019

A cable-stayed bridge (CSB) is one of the most complicated structures, especially when subjected to earthquakes and taking into consideration the effect of soil-structure-interaction (SSI). A CSB of a 500 m mid-span was modeled by the SAP2000 software and was subjected to four different earthquakes. To mitigate the harmful effect of the vibration generated from each earthquake, four mitigation schemes were used and compared with the non-mitigation model to determine the effectiveness of each scheme, when applying on the SSI or fixed CSB models. For earthquake mitigation, tuned mass damper (TMD) systems and spring dampers with different placements were used to help reduce the seismic response of the CBS model. The pylons, the mid-span of the deck and the pylon-deck connections are the best TMDs and spring dampers placements to achieve an effective reduction of the earthquake response on such bridges.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.126-132
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• 1999

The paper presents the modeling and optimal control for the reduction of transverse vibration of simply supported beam under a moving mass. The equations of motion are derived by using assumed mode method. The coriolis and centripetal accelerations are accommodated in the equations of motion to account for the dynamic effect of the traveling mass. In order to reduce the transverse vibration of the beam, an optimal controller with full state feedback is designed based on the linearized equations of motion. The optimal actuator locations are determined with the evaluation of an optimal cost functional defined by the worst initial condition with the trade-off of controlled mode performance. Numerical simulations are performed with respect to various velocities and different traveling masses. Even if the velocity of the traveling mass reaches to the critical speed which can cause the resonance of the beam, the controller with two piezoelectric actuators shows the excellent performance under severe time-varying disturbances of the system.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.22-29
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• 2001

The present study investigates the effects of various rib arrangements and rotating on heat/mass transfer in the cooling passage of gas turbine blades. The cooling passage has very complex flow structure, because of the rib turbulator and rotating effect. Experiments and numerical calculation are conducted to investigate the complex flow structures and heat transfer characteristics; the numerical computation is performed using a commercial code, FLUENT ver.5, to calculate the flow structures and the experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. For the rotating duct tests, the test duct, which is the cross section of is $20mm\times40mm$ (the hydraulic diameter, $D_h$, of 26.7 mm, has two-pass with $180^{\circ}$ turning and the rectangular ribs on the wall. The rib angle of attack is $70^{\circ}$ and the maximum radius of rotation is $21.63D_h$. The partition wall has 10 mm thickness, which is 0.5 times to the channel width, and the distance between the tip of the partition wall and the outer wall of the turning region is 26.7 mm $(1D_h)$. The turning effect of duct flow makes the very complex flow structure including Dean type vortex and high turbulence, so that the heat/mass transfer increases in the turning region and at the entrance of the second pass. The Coriolis effect deflects the flow to the trailing surface, resulting in enhancement of the heat/mass transfer on the trailing surface and reduction on the leading surface in the first pass. However, the opposite phenomena are observed in the second pass. The each rib arrangement makes different secondary flow patterns. The complex heat/mass transfer characteristics are observed by the combined effects of the rib arrangements, duct rotation and flow turning.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.304-310
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• 2009

Recently, manganese nodule has been focused on alternative resources because of its high grade of noble metallic elements such as Co, Ni, and Cu etc. From the viewpoint of an optimization the operating variables for energy efficiency of smelting reduction process, thermodynamic model for smelting reduction process of Manganese nodule was developed by using energy and material balance concept. This model provided that specific consumption of pure oxygen and coke was strongly depended on post combustion ratio (PCR) and heat transfer efficiency (HTE). The dressing and dehydrating process of low grade manganese can be proposed an essential process to minimize the specific energy consumption with decreasing slag volume. The effect of electricity coal base smelting reduction process was also discussed from the energy optimizing point of view.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.423-426
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• 2007

In this paper, vibration reduction of resiliently mounted machinery and effect of the foundation impedance is studied. SBN (Structure-borne noise) reduction through the mount is analyzed by assuming that the system is modeled as a mass-spring system, while the impedance of the floor is included in the prediction. The comparison of the SBN difference through the mount between predictions and measurements show that the slopes are similar in the case of single-mount system, while the measurements differs significantly from the predictions in the case of the double-resilient system.

• Korean Journal of Exercise Nutrition
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• v.17 no.2
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• pp.43-48
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• 2013

This study aims to investigate changes in plasma lipid concentrations and appetite-regulating hormone levels after a 4% body fat reduction using a 9-week intervention involving aerobic exercise, a fat-oxidizing agent, and diet limitation. After the 9-week intervention, the aerobic exercise plus hydroxycitric acid (EX+HCA), exercise (EX), and diet limitation (DIET) groups achieved the target 4% body fat reduction from the baseline value. None of the plasma lipid indicators showed significant intergroup differences, indicating that plasma lipid levels are not influenced by body weight regulation. With regard to appetite-regulating hormones, no significant intergroup differences were observed in glucose, insulin, or glucagon-like peptide-1 levels, unlike ghrelin and leptin. Ghrelin levels in particular tended to decrease in the DIET group and increase in the HCA+EX and EX groups. Leptin levels significantly decreased in the HCA+EX and EX groups, whereas no differences were observed in the DIET group. Such results indicate that exercise alone without the administration of obesity diet supplements induces elevation in ghrelin levels and reduction in leptin levels, but that diet restriction alone does not influence changes in leptin levels. Taken together, we could not confirm any synergic effects arising from the use of a fat-oxidizing agent during an exercise program to control body weight. Furthermore, diet limitation unsupported by exercise had no effect on muscle mass reduction or appetite-regulating hormone levels; thus, it is not recommended as an effective body weight control method.

• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.382-395
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• 2002

An experimental study on transient critical heat flux (CHF) under flow coastdown has been performed for the water flow in a non-uniformly heated vertical annulus under low flow and a wide range of pressure conditions. The objectives of this study are to systematically investigate the effect of the flow transient on the CHF and to compare the transient CHF with steady-state CHF The transient CHF experiments have been performed for three kinds of flow transient modes based on the coastdown data of a nuclear power plant reactor coolant pump. At the same inlet subcooling, system pressure and heat flux, the effect of the initial mass flux on the critical mass flux can be negligible. However, the effect of the initial mass flux on the time-to- CHF becomes large as the heat flux decreases. The critical mass flux has the largest value for slow flow reduction rate. There is a pressure effect on the ratio of the transient CHF data to steady-state CHF data. Except under low system pressure conditions, the flow transient CHF was revealed to be conservative compared with the steady-state CHF data. Bowling CHF correlation and thermal hydraulic system code MARS show promising results for the prediction of CHF occurrence .