• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.498-502
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• 2004

In a link-motion mechanism, numerous links are interconnected and each link executes a constrained motion at a high speed. Due to the complicated constrained motions of the constituent links, dynamic unbalance forces and moments are generated and transmitted to the main frame. Therefore unwanted vibration is produced. This degrades productivity and precise work. Based on constrained multi-body dynamics, the kinematic analysis is carried out to enable design changes to be made. This will provide the fundamental information for significantly reducing dynamic unbalance forces and moments which are transmitted to the main frame. In this work, a link-motion punch press is selected as an example of a link-motion mechanism. To calculate the mass and inertia properties of every link comprising a link-motion punch press, 3-dimensional CAD software is utilized. The main issue in this work is to eliminate the first-order unbalance force and moment in a link-motion punch press. The mass, moment of inertia link length, location of the mass center in each link have a great impact on the degree of dynamic balancing which can be achieved maximally. Achieving good dynamic balancing in a link motion punch press is quite essential fur reliable operation at high speed.

• Journal of KSNVE
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• v.7 no.1
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• pp.91-97
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• 1997

An analysis is presented on the stability of an elastic cantilever column having the elastic restraints at its free end, carrying an added tip mass, and subjected to uniformly distributed follower forces. The elastic restraints are formed by both a translational spring and a rotatory spring. For this purpose, the governing equations and boundary conditions are derived by using Hamilton's principle, and the critical flutter loads and frequencies are obtained from the numerical evaluation of the eigenvalue functions of this elastic system. The added tip mass increases as a whole the critical flutter load of the elastic cantilever column, but the presence of its moment of inertia of mass has a destabilizing effect. The existence of the translational and rotatory springs at the free end increases the critical flutter load of the elastic cantilever column. Nevertheless, their effects on the critical flutter load are not uniform because of their coupling. The translational spring restraining the free end of the cantilever column decreases the critical flutter load by coupling with a large value of tip mass, while by coupling with the moment of inertia of tip pass its effect on the critical flutter load is contrary. The rotatory spring restraining the free end of the cantilever column increases the critical flutter load by coupling with the tip mass, but decreases it by coupling with the moment of inertia of the tip mass.

• Journal of Biosystems Engineering
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• v.31 no.4 s.117
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• pp.323-333
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• 2006

Introduction of a direct engine-PTO driveline to agricultural tractors has reduced production cost and increased transmission efficiency of the PTO driveline. However, this type of PTO driveline has caused a severe rattle noise in the PTO gearbox under idle conditions. This study was conducted to investigate the causes of the rattle noise and the effects of driveline parameters on it. A mathematical model was developed for a direct engine-PTO driveline. The model was proved experimentally to be accurate enough to simulate the dynamic characteristics of the PTO driveline motions. The simulation study showed that the rattle noise was caused by collisions between the driving and driven gears in the PTO gearbox due to velocity variation of the gears, which was induced by torque fluctuations from the engine. It was also found that the rattle noise decreased with the drag torque and mass moment of inertia of the engine flywheel. Smaller mass moment of inertia of the driven gears and backlash also reduced the rattle noise. However, increasing the drag torque and mass moment of the engine flywheel or decreasing the backlash and mass moment of inertia of the driven gears were limited practically by their detrimental effects on transmission efficiency, gear strength and smooth meshing of the gears.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.156-162
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• 2013

Moments of inertia of limb segments are essential to calculate parameters related to the segmental rotation. To analyze the human motion accurately and specifically, moments of inertia obtained from the individual are required. In this study, a simple method to determine a subject-specific moment of segmental inertia using a dynamometer is introduced. In order to evaluate the method, one male participated to test for his forearm plus hand on a commercial dynamometer. Three passive speeds, i.e. 240, 270, and $300^{\circ}/s$, were chosen to confirm whether the moment of inertia values at each speed approach to a fixed value. The same procedure was repeated on the day after to evaluate whether the method is reproducible. As the results, there were no significant differences among the speeds and between the days. The value of the moment of the forearm inertia was 0.216 $kg{\cdot}m^2$ that is apparently higher compared to values by previous models. Nonetheless, it seems to be acceptable based on our body mass index analysis using reported subject height and mass in each previous study. According to our results, the developed method could be useful to determine the segmental moment of inertia of an individual, showing no significant differences among the speeds and between the days. Thus, we believe that our results are reliable according to two appropriate evaluation procedures. This finding would be helpful to calculate segmental rotation related parameters of an individual.

• Bulletin of the Society of Naval Architects of Korea
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• v.11 no.2
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• pp.41-44
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• 1974

A calculation of the two dimensional added mass moment of inertia for the Kim's chine form sections is made with a special consideration of a location of a axis of rotation. The results are compared with those of Lewis form section equivalent to the above chine form sections calculated by Kumai.

• Journal of Astronomy and Space Sciences
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• v.39 no.2
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• pp.59-65
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• 2022

In this paper we propose a new perspective for explaining galaxy rotation curves. We conjecture that there is a gravitational moment of inertia which, together with gravitational mass, contributes to the gravitational potential. We substantiate a formula for the potential created by the moment of inertia. We validate our model by computing orbital rotation velocities for several galaxies and showing that computed rotation velocities correspond to the observed ones. Our proposed approach is capable of accounting for constant gas velocities outside of a galactic disc without relying on the dark matter hypothesis. Furthermore, it addresses several problems faced by the application of the dark matter hypothesis, e.g., the absence of inward collapse of dark matter into a galaxy, the spherical distribution of dark matter around galaxies, and absence of traces of the effect of dark matter in two ultra-diffuse galaxies, NGC 1052-DF2, and NGC 1052-DF4.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.167-172
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• 1996

A Dual Mass Flywheel system is a evolution to the reduction of torsional vibration and impact noise occuring in powertrain when a vehicle is eit-her moving or idling. The name already explains what it is : The mass of the conventional single mass flywheel is divided. One section continues to belong to the mass moment of inertia of the engine-side. The ot-her section increass the mass moment of inertia of the transmission-side. The two masses are connected via a spring /damping system. This reduces the speed at which the dreaded resonance occurs to below idle speed. Since 1984 Dual Mass Flywheel has been de-veloped again and again. But the prosidures of de-velopment of D.M.F system didn't have had differe-nce from conventional clutch system's trial and err-or This paper presents the method for systematical design of D.M.F system with demensionless design variables of D.M.F system mass ratio between two flywheels λ. natual frequency rate of two flywheel s, ${\gamma}$and viscosity coefficient ζ. And experimental re-sults are used to prove these theoretical results.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.49-58
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• 1998

On the stability of the Timoshenko cantilever column subjected of a compressive follower force, the influences of the moment of inertia of the tip mass at the free end and the characteristics of a translational spring at the free end of the column are studied. The equations of motion and boundary conditions of system are estabilished by using the d'Alembert virtual work of principle. On the evaluation of stability of the column, the effect of the shear deformation and rotatory inertia is considered in calculation. The moment of inertia of the tip mass at the free end of the column is changed by adjusting the distance c, from the free end of the column to the tip mass center. The free end of the column is supported elastically by a translational spring. For the maintenance of the good stability of the column, it is also proved that the constant of the translational spring at the free end must be very large for the case without a tip mass while it must be small for the case with a tip mass. Therefore, it is found that the shape of the tip mass and the characteristic of the spring at the free end are very effective elements for the stability of the column when the columns subjected to a compressive follower force are designed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1575-1582
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• 1992

This study describes the response performances of actual engine speed, turbocharger speed, air mass flow rate through engine, boost pressure ratio, exhaust temperature and combustion efficiency for a six-cylinder four-stroke turbocharged diesel engine during the change in operating conditions by using the computer simulation with test bed. In order to obtain the transient conditions, a suddenly large load was applied to the simulation engine with the several kinds of inertia moment in turbocharger and engine, and engine set speed. From the results of this study, the following conclusions were summarized The inferior response performances was mainly caused by turbocharger lag, and air mass flow rate and boost pressure ratio were closely related to the turbocharger speed. A reduced moment of turbocharger inertia resulted in less transient speed drop and much faster recovery to the steady state of the engine. The increase of moment of engine inertia reduced cyclic variation of engine speed. When a large load was applied to the engine at high speed, the engine could be fastly recovered. However, when the same load was applied to the engine at low speed, the engine was stalled.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.3-12
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• 1998

On the stability of the cantilever beam subjected to a follower force at the free end, the influences of the translational spring and the moment of inertia of a tip mass at the free end have been studied by numerical methods. The centroid of a tip mass is offset from the free end of a Beam and is located along its extended axis to vary the value of moment of inertia of a tip mass. It is proved that as the constants of a spring supporting the free end are augmented, the critical flutter loads of the above system decrease, whereas they increase without a tip mass.