• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.10
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• pp.996-1002
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• 2009

Elimination of squeal noise occurred during brake application is an important task for the improvement of comforts in an industrial forklift. In this paper, a test rig was developed which was possible for testing of brake noise and an experimental measurement on squeal noise was performed. The causes of the brake noise are identified by experimenting how the factors such as automatic transmission fluid and rpm of drive axle affect the squeal. In order to identify the squeal characteristics, the signal analyses for noise are performed by using frequency spectrums. Also, brake test using a forklift was carried out to confirm the reliability of test results by using a test rig comparing with the occurrence of squeal noise. Experimental results showed that the tendencies of occurrence of squeal noise are well agreed at two test methods by using the test rig and forklift.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.37.1-37.1
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• 2017

Since the seminal work of Perrin, physicists have understood in the context of kinetic theory how ink slowly diffuses in a glass of water. The fluctuations of the stochastic forces acting on water molecules drive the diffusion of the ink in the fluid. This is the archetype of a process described by the so-called fluctuation-dissipation theorem, which universally relates the rate of diffusion to the power spectrum of the fluctuating forces. For stars in galaxies, a similar process occurs but with two significant differences, due to the long-range nature of the gravitational interaction: (i) for the diffusion to be effective, stars need to resonate, i.e. present commensurable frequencies, otherwise they only follow the orbit imposed by their mean field; (ii) the amplitudes of the induced fluctuating forces are significantly boosted by collective effects, i.e. by the fact that, because of self-gravity, each star generates a wake in its neighbours. In the expanding universe, an overdense perturbation passing a critical threshold will collapse onto itself and, through violent relaxation and mergers, rapidly converge towards a stationary, phase-mixed and highly symmetric state, with a partially frozen orbital structure. The object is then locked in a quasi-stationary state imposed by its mean gravitational field. Of particular interests are strongly responsive colder systems which, given time and kicks, find the opportunity to significantly reshuffle their orbital structure towards more likely configurations. This presentation aims to explain this long-term reshuffling called gravity-driven secular evolution on cosmic timescales, described by extended kinetic theory. I will illustrate this with radial migration, disc thickening and the stellar cluster in the galactic centre.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.1997-2003
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• 2003

Recently, there have been many researches and developments in optical disc drive by high density of track and high access speed. Therefore, the optical pick-up should guarantee highly accurate dynamic characteristics for the wide bandwidth in order to cope with this trend. These demands for optical pick-up actuator can be solved by improvements of lens-holder through the following methods. The first way is the analysis of the sensitivity matrix of design variables for vibration modes after appropriate design parameters are selected like shapes and local dimensions of a lens-holder. The second way is the optimization of design variables by calculating sequential linear programming after the problem of extending bandwidth are converted to problem of minimizing adequate objective function. In the result, modified FE model is obtained through several iterations by finite difference scheme(FDS). While results of the first way show better convergence of the target frequency, the second result shows better reduction of mass increase.

• Transactions of the Society of Information Storage Systems
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• v.10 no.2
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• pp.32-38
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• 2014

Heat emission from the laser diode used in the optical disc drive and the defects from the increased temperature at the system have attracted attentions from the field of the information storage device. Thermoelectric refrigerator is one of the fine solutions to solve these thermal problems. The refrigeration performance of thermoelectric device is dependent on the thermoelectric material's figure-of-merit. Meanwhile, high electrical contact resistivity between metal electrode and p- and n-type thermoelectric materials in the device would lead increased total electrical resistance resulting in the degeneracy in performance. This paper represents the manufacturing process of the PbTe-based material which has one of the highest figure-of-merit at medium-high-temperature, ~ 600K to 900 K, and the nickel contact layer for reduced electrical contact resistance at once, and the results showing the decent contact structure and figure-of-merit even after the long-term operation environment.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.191-195
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• 2007

The optical disc drive has used a high NA objective lens and a shorter wavelength laser diode for high recording density. But high NA and shorter wavelength cause several margins to become short. Focusing and tracking servo has to be more accurate and active tilt compensation mechanism is also needed for coma aberration compensation. In this paper, we proposed 3-axis moving magnet type actuator. For 3-DOF motion, moving coil actuator has to be equipped with 6 wires for supplying 3 independent signals. However, moving magnet type actuator doesn't need to change the configuration of wires because coils are in stator. So, we added a tilt mechanism to the 2-axis moving magnet actuator which is designed in previous research. Addition of the tilt mechanism cuts down the focus sensitivity. So, maximization the tilting sensitivity and securing the focusing sensitivity are objectivities of this research. DOE (design of experiments) procedures of electromagnetic circuit are performed for parameter study and the optimization is also performed to maximize the tilt sensitivity. And then the final design is suggested and its performance is verified by FE simulation.

• Journal of Drive and Control
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• v.11 no.3
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• pp.47-54
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• 2014

Clutches are an integral part of the automatic transmission for changing gears. Modern automatic transmissions make extensive use of wet multiple-disc clutches employing hydraulic actuation mechanism with electronic control. Although nowadays, highly advanced shifting algorithm implements the superior shift quality and transmission efficiency, its performance should be based on smooth, reliable engagement with a reasonably durable friction material as well as stable clutch piston dynamics. Particularly, clutch filling control is the crucial part of shifting process because only the open-loop control is available due to the lack of measurement. In this paper, the effect of clutch-fill control parameters on clutch piston dynamics is experimentally investigated by using clutch piston test equipment which enables the clutch piston to actuate similar to real shifting conditions. The experimental analysis results can be expected to be utilized for the calibration of proportional solenoid valve as reference current profile data in vehicle test.

• Journal of Drive and Control
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• v.14 no.4
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• pp.71-78
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• 2017

The power train of hydro-mechanical continuously variable transmission (HMCVT) for 8-ton class forklift includes hydro-static units, hydraulic multi-wet disc brake & clutches and complex helical & planetary gears. The helical & planetary gears are key components of HMCVT's power train wherein strength problems are the main concerns including gear bending stress, gear compressive stress, and scoring failure. Many failures in power train gears of HMCVT are due to the insufficient gear strength and resonance problems caused by major excitation forces, such as gear transmission error of mating gear fair in the transmission. In this study, wherein excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate the power train gears' critical speeds. Mode shapes and natural frequencies of the power train gears are calculated by CATIA V5. These are used to predict resonance failures by comparing the actual working speed range with the critical speeds due to the gear transmission errors of HMCVT's power train gears.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.113-122
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• 2021

This study begins on the basis of Jacques Lacan's article 『Logical Time and Assertions of Preemptive Certainty: A New Sophism』 published in the reissue of 『Art Note Les Cahiers d'Art』 in March 1945. In this paper, a guard presents an esoteric problem to three prisoners. If the problem is solved, the prisoner is released. A condition is given to solve a problem. Conversation between prisoners is prohibited, and the disc behind them cannot be seen. In this time and space, prisoners place themselves in logical time through the 'time of understanding' in order to become the chosen ones. We always live in logical time. We will argue the point at which Lacan destroys logical time in psychoanalysis. Time in Lacanian psychoanalysis transcends time divisions of the past, present, and future. Our time is always the past in the present. In Lacanian psychoanalysis, logical time is the time in the Other. The transcendence of the Lacanian psychoanalysis concept of time shows the deviation of logical time. In this text, We try to prove how Lacan contrasts psychoanalysis and the problem of time with time in the other. First, we will examine how logical time and impulse are related in psychoanalysis. Second, the postmortemity of the signifient (signifier) will be discussed. Third, Lacan psychoanalysis will present the transcendence of time. In conclusion, We will present the view that the time of Lacan psychoanalysis is flowing backwards. In Lacanian psychoanalysis, we try to prove that logical time is in the territory of the Other and is infinite time.