• The Journal of the Acoustical Society of Korea
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• v.18 no.1E
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• pp.20-26
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• 1999

Although the radiation impedance of a transducer with a regular square surface has been studied by many researchers, the formulas are still very complicated, which results in long computation time and low accuracy. In this paper, we propose a new algorithm for the calculation of acoustic radiation impedance in which the regular square vibrating surface of a transducer is divided into small elements and duplicate calculations are eliminated in the process of calculating mutual effects of the elements. Using this algorithm, shorter computation time and higher accuracy of results can be obtained. As a demonstration, the self and the mutual radiation impedance of transducers with a regular square surface are calculated and the accuracy of the results is evaluated.

• Journal of Biomedical Engineering Research
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• v.11 no.2
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• pp.257-268
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• 1990

A system has been developed for monitoring the effect of neuromuscular blocking frugs and the neuromuscular function during anesthesia and surgery. This system is composed of software and hardware, the latter are nerve stimulator, force transducer, interface board(preamplifier, filter, peripheral input/output) and personal computer (apple ll) , the former are programmed in ASSEMBLY and BASIC language. The nerve stimulator which is controlled by personal computer is capable of delivering single shocks at o.)Hz, train of four at 2Hz and tetanic stimulation at 30, 100, 200Hz. The response, adduction of the thumb, is sensed by the force transducer. The output of the force transducer Is amplified, filtered, converted digital signal and then processed by the per- sonal computer. The personal computer quantia4es twitch and traln of four tesponse and calculates the 74 ratio (Ta/Tl )between the first and fourth response of train of four. This ratio is used to estimate the level of the neuromuscular block. This system has reaserch potential for determining the effect of newer neuromuscular blocking drugs for comparlsion with presently used drugs of alternatively, for delerminig the effects of blocking drugs in altered physilogical states.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1200-1209
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• 2010

The main subject of this paper is to develop analytic method with which output power or sensitivity variations of a magnetostrictive ultrasonic transducer can be estimated with no aid of experiments. After the bias magnetic field deployed over the patch is calculated using finite element analysis for magnetostatics, the representative value is extracted by averaging these field values. The operating point on the characteristic curve for magnetostriction is identified by this value and then the output performance is calculated from it. It is verified that the results from this simple model match well with those of its experimental version and some limits of this modeling technique are also considered.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.241-262
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• 2012

Some applications require structural health monitoring in inaccessible components. This paper presents a technique useful for Structural Health Monitoring of double wall structures, such as double wall steam pipes and double wall pressure vessels separated from an ultrasonic transducer by three layers. Detection has been demonstrated at distances in excess of one meter for a fixed transducer. The case presented here is for one of the layers, the middle layer, being a fluid. For certain transducer configurations the wave propagating in the fluid is a wave with low velocity and attenuation. The paper presents a model based on wave theory and finite element simulation; the experimental set-up and observations, and comparison between theory and experiment. The results provide a description of the technique, understanding of the phenomenon and its possible applications in Structural Health Monitoring.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.30-33
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• 1995

By using X-ray double crystal diffraction technique the multilayer structure composed of glass membrane, platinum film and $\alpha Al_2O_3$ substrate has been studied. It is found the stress is produced in the film by thermal mismatch within multilayer materials. The measuring results of thin film platinum resistors show that the stress were induce resistance change of device and different stress status will produce add resistance in different direction. Selecting proper glass material can make opposite stress in Pt film and opposite add resistance due to thermal mismatch. The reliability of Pt resistor has been improved with method of this stress compensation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.10
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• pp.780-787
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• 2014

This paper experimentally deals with the vibration characteristics of flat ring transducers used for ultrasonic sensors and actuators. Radial vibration mode, which is the fundamental mode of a thin piezoelectric transducer, was measured by a laser in-plane vibrometer. An impedance analyzer was used to measure natural frequencies. The results measured by experiments verified theoretical predictions. The vibration characteristics of ring transducers were identified according to the outer diameter size. The shape of the fundamental mode is almost uniform but slightly decreases from the inner to the outer circumferential surfaces. The natural frequency of the fundamental mode decreases as the outer diameter increases. It appears that the ring type transducer is suitable to excite uniformly distributed vibration on a flat surface.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.96-103
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• 2005

One of the major problems limiting the accuracy of piezoelectric transducers fur cylinder pressure measurements in an internal combustion (IC) engine is the thermal shock. Thermal shock is generated from the temperature variation during the cycle. This temperature variation results in contraction and expansion of the diaphragm and consequently changes the force acting on the quartz in the pressure transducer An empirical equation for compensation of the thermal shock error was derived from consideration of the diaphragm thermal deformation and actual pressure data. The result indicate that the thermal shock equation provides reliable correction based on known surface temperature swing.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.75-85
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• 1996

The gas pressure acting on the rings in internal combustion engine influences the friction, wear and HC emission. In order to understand their characteristics, it is necessary to measure the interring gas pressure during engine operations. In this study, miniature type pressure transducer was developed to measure inter-ring gas pressure. And measurements of cylinder and inter-ring gas pressure were made on a gasoline engine running at full and part load conditions. Finally the characteristics of inter-ring gas pressure variation during engine operation were obtained form analysis of measured date.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.6
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• pp.39-47
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• 1988

A disk photo sensor system was constructed and installed on engine for the crank angle measurement. Statically measured TDC crank angle data were compared with those obtained from engine motoring. Two groups of cylinder pressure data were compared each other, one measured by pressure transducer mounted flush on the combustion chamber and the other obtained with the help of spark plug type adaptor. A simple analysis on the gas flow in the spark plug type pressure transducer displayed reasonably good agreement with those from engine motoring tests. In various firing tests, the IMERs obtained from the spark plug type pressure transducer turned out to be higher than those from the flush mounted one at low engine speed while those two were nearly the same at high engine speed. As the engine load decreased the relative difference in IMEP measurement between the two types tended to be enlarged.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.292-295
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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 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. In this paper, elliptical trajectory of transducer was analyzed by employing the finite element method.