• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1086-1093
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• 2004

The modal characteristics of constrained multibody systems undergoing constant accelerated motions are investigated in this paper. Relative coordinates are employed to derive the equations of motion, which are generally nonlinear in terms of the coordinates. The dynamic equilibrium position of a constrained multibody system needs to be obtained from the nonlinear equations of motion, which are then linearized at the dynamic equilibrium position. The mass and the stiffness matrices for the modal analysis can be obtained from the linearized equations of motion. To verify the effectiveness and the accuracy of the proposed method, two numerical examples are solved and the results obtained by using the proposed method are compared with those obtained by analytical and other numerical methods. The proposed method is found to be accurate as well as effective in predicting the modal characteristics of constrained multibody systems undergoing constant accelerated motions.

• Journal of Korean Society for Quality Management
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• v.26 no.1
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• pp.74-87
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• 1998

This study considers optimal design of accelerated life tests under constant stress using that the first passage time to cross a critical boundary through amount of accumulated degradation has an inverse Gaussian distribution when the degradation process follows to a Brownian motion with positive drift of log linear function of stress. Optimum plans for Type I censoring are derived by minimizing the asymptotic variance of estimated quantiles at the use stress. Sensitivity analyses are also conducted to see how sensitive the optimality criterion is with respect to the uncertainties involved in the guessed values.

• Advances in aircraft and spacecraft science
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• v.7 no.1
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• pp.53-78
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• 2020

Automatic trajectory planning is an important task that will have to be performed by truly autonomous vehicles. The main method proposed, for unmanned airplanes to do this, consists in concatenating elementary segments of trajectories such as rectilinear, circular and helical segments. It is argued here that because these cannot be expected to all be flyable at a same constant speed, it is necessary to consider segments on which the airplane accelerates or decelerates. In order to preserve the planning advantages that result from having the speed constant, it is proposed to do all speed changes at maximum deceleration or acceleration, so that they are as brief as possible. The constraints on the load factor, the lift and the power required for the motion are derived. The equation of motion for such accelerated motions is solved numerically. New results are obtained concerning the value of the angle and the speed for which the longest distance and the longest duration glides happen, and then for which the steepest, the fastest and the most fuel economical climbs happen. The values obtained differ from those found in most airplane dynamics textbooks. Example of tables are produced that show how general speed changes can be effected efficiently; showing the time required for the changes, the horizontal distance traveled and the amount of fuel required. The results obtained apply to all internal combustion engine-propeller driven airplanes.

• Journal of Biosystems Engineering
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• v.25 no.6
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• pp.445-456
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• 2000

A can type high-speed transplanting mechanism was developed. The mechanism consists of a cam and an epicycle gear train with one sun gear in the middle and four planet gears in a row but symmetric with respect to the sun gear. Two planting knives are pivoted on the two outer gears. When sun gear rotates with a constant velocity the planting knife rotates also with a constant velocity. This constant motion of the transplanting knife is accelerated partially by a cam fixed in the gear housing so that the locus of the planting knife becomes similar to that generated by a crank-type transplanting mechanism. This cam-type transplanting mechanism can solve the problems associated with the rotary-type transplanting mechanisms. The mechanism was designed with an aid of computer simulation and proved applicable to high speed transplanters by its mock-up model. The design process of the mechanism was presented and dynamic analysis was also carried out to show the advantages of the mechanism over the rotary type high-speed planting mechanism.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.736-749
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• 2019

This paper employs computational tools to investigate the diffraction effects in regular head waves on the added resistance and wake on the propeller plane. The objective ships are a 66,000 DWT bulk carrier and a 3,600 TEU container ship. Fixed and free to heave and pitch conditions at design speed have been taken into account. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using the finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free surface is obtained by solving a VOF equation. The computations are carried out at the same scale of the model tests. Grid and numerical wave damping zones are applied to remove unwanted wave reflection at the boundaries. The computational results are analyzed using the Fourier series. The added resistances in waves at the free condition are higher than those at the fixed condition, which are nearly constant for all wavelengths. The wake velocity in waves is higher than that in calm water, and is accelerated where the wave crest locates on the propeller plane. When the vertical motion at the stern goes upward, the wake velocity also accelerated.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.864-870
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• 2001

Flame propagation along vortex tube was experimentally investigated. The vortex tube was generated by the ejection of propane from a nozzle through a single stroke motion of a speaker and the ignition was induced from a single pulse laser. Non-reactive flow fields were visualized using shadow technique. From these images, vortex ring size and translational velocity were measured in order to determine the ignition time and position. Flame structure and flame speed were measured using high speed CCD camera. Flame speed was accelerated during the initial stage of flame kernel growth, and reached near constant value during steady propagation period. Near the completion of propagation, flame speed was decelerated and then extinguished. Flame speed along the non-premixed vortex tube was found to be linearly proportional to circulation, which was similar to that of the flame propagation along premixed vortex ring. Ignition position minimally affects the propagation characteristics. These imply that flame is propagating along the maximum speed locus expected to be along stoichiometric contour and also support the existence of tribrachial flames.

• Journal of Electrical Engineering and information Science
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• v.2 no.4
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• pp.66-71
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• 1997

The dielectrophoretic(DEP) force acting on a cell in an electric field is experimentally determined. A cell is accelerated by the DEP force in an electric field generated between micro planar electrodes. the position of the cell is measured and the velocity and acceleration of the cell are calculated based on the measured position data. The DE force is determined from the motion equation of a moving cell in suspension. The electrode structure is fabricated by micromachining technology and the height of electrodes is 1 $\mu\textrm{m}$. Radish cell and yeast are used in th experiments. In the case of radish cell, the DEP force increases as voltage or frequency(1MHz∼3MHz) increases. The voltage dependence can be explained that the DEP force increases when ▽│E│$^2$increases. The frequency dependence means that Re[x\ulcorner] of radish cell is maximized in a certain frequency. In the case of yeast, the DEP force increases only as voltage increases. The reason for the voltage dependence is the same with the case of radish. The DEP force increases only as voltage increases. The reason for the voltage dependence is the same with the case of radish. The DEP force on a yeast does not vary when the frequency varies from 1MHz to 3MHz. This result coincides with the fact that the value of calculated Re[x\ulcorner] is constant in the test frequency range.