• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.103-106
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• 2003

The microscopic quantum Langevin equations for two-level atom electric dipole systems are derived. starting from the microscopic interaction Hamiltonian of the systems. By averaging those microscopic equations over a macroscopic region, the macroscopic quantum Langevin equations are derived and the effect of local-field corrections on the two-level systems is investigated.

• Nonlinear Functional Analysis and Applications
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• v.26 no.5
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• pp.1021-1034
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• 2021

This paper deals with a nonlinear Langevin equation involving two fractional orders with three-point boundary conditions. Our aim is to find the existence of solutions for the proposed Langevin equation by using the Banach contraction mapping principle and the Krasnoselskii's fixed point theorem. Three examples are also given to show the significance of our results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.275-276
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• 2010

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.627-630
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• 2004

Transducer for linear ultrasonic motor with symmetric and anil anti-symmetric modes was studied. The transducer was composed of two Langevin-type vibrators that cross at right angles with each other at tip. In order to excite two vibration modes, two Langevin-type vibrators must have 90-degree phase difference with each other. As a result, tip of transducers moves in elliptical motion. Elliptical trajectoric of transducer was analyzed by employing the finite element method. From these results, the ultrasonic motor was fabricated and was measured for characteristics. In this paper compared an ANSYS analysis with an experiment results. The no-road maximum speed was 113.1[cm/s].

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.612-617
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• 2000

The vibrational characteristics of Langevin-type piezoelectric torsional transducers have been studied theoretically and experimentally in this paper. The differential equations of piezoelectric torsional motion have been derived in terms of the circumferential displacement and the electric potential. Solutions of the boundary-value problem have yielded the natural frequencies and mode shapes of the transducers. The theoretical solutions have been verified by comparing the numerical results with experimental ones.

• 전기의세계
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• v.30 no.1
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• pp.47-54
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• 1981

The fabrication of Langevin type vibrators producing relatively high sonic and ultrasonic energy is described. The dependence of the acoustic output and the frequency characteristics on the thickness of the steel plates and the pressure at the ceramics are investigated. As results, the acoustic output of Langevin type vibrators are relatively high, and the resonant frequency is decreassed by thickening the steel plates and lowering the pressure at the ceramics. Using these results, sonic and ultrasonic vibrator whose resonant frequency is determined can be designed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.634-637
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• 2002

Transducer for linear ultrasonic motor with symmetric and anti-symmetric modes was studied. The transducer was composed of two Langevin-type vibrators. In order to excite two vibration modes, Two Langevin-type vibrators must have 90-degree phase difference with each other. As result, tip of transducers moves in elliptical motion. In this paper, vibration shape of transducer was simulated and The resonant frequency and maximum displacement were calculated using the FEA (Finite Element Analysis).

• Kyungpook Mathematical Journal
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• v.63 no.3
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• pp.437-450
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• 2023

In this paper, we present a sufficient condition for the unique existence of solutions for a coupled system of nonlinear fractional Langevin equations with a new class of multipoint and nonlocal integral boundary conditions. We define a 𝓩^*_λ-contraction mapping and present the sufficient condition by identifying the problem with an equivalent fixed point problem in the context of b-metric spaces. Finally, some numerical examples are given to validate our main results.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.422-427
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• 2018

The purpose of this study is to investigate the effect of acoustic radiation force on the standing wave acoustic levitation phenomenon, which is the levitation of small objects near the pressure node of the standing wave, using the Bernoulli principle. The source and scheme of the acoustic radiation force, which is the cause of the levitation, are conceptually explained through comparison with the graph of the acoustic radiation force versus the distance from the transducer. A series of experiments supporting this explanation was performed with a BLT(Bolt-clamped Langevin Type) ultrasonic transducer to confirm that the objects are floating near the pressure nodes and that it satisfies the condition for the standing wave formation when the object is levitating. Furthermore, the vertical alignment of floating objects, which is a characteristic of standing wave acoustic levitation phenomenon, could be explained.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.3
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• pp.123-127
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• 2004

Mode conversion type ultrasonic rotary motor using bolt tightened Langevin type vibrator was studied. Driving frequency of the motor, displacements and elliptical trajectories at tip of the coupler were simulated by finite element analysis program (ANSYS). Speed and torque of the fabricated motor were measured as functions of input voltage and load. As results, from FEA the driving frequency of 40.8[kHz] and useful elliptical trajectories were found. Fabricated motor rotated clockwise at frequency of 38.2[kHz]. Speed and torque of the motor were increased when the input voltage was increased. Maximum speed, torque and efficiency were 75[rpm], 0.14[Nm] and 6.28[％], respectively.