• 한국자동차공학회논문집
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• 제2권1호
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• pp.1-8
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• 1994

This study carried out to investigate the spray characteristics of diesel oil through out ultrasonic fuel supply system in comparison with conventional. Size of the droplets comprising diesel spray was measured by immersed liquid method at different positions along the spray axis. Droplets distribution diagram was ploted and Sauter Mean Diameter(SMD) was also calculated. The effects of the ultrasonic vibration and injection pressure on the droplet size distribution and SMD were investigated. As the ultrasonic vibration supply SMD decreases on the same injection pressure conditions with conventional injector's. But the effect of ultrasonic vibration decreases with injection pressure increasing.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.122-123
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• 2014

Measurement of the strength of concrete is an important indicator of the safety of the fresh as well as old concrete structures. It is possible to evaluate the strength of the concrete by means of an ultrasonic velocity method which is a kind of non-destructive inspection method for safety diagnostic evaluation of the building structures with aging. Steel embedded in the concrete and age of the concrete may affect ultrasonic pulse velocity. In order to accurately assess the strength of the concrete, it is necessary to understand rebar embedded in the concrete, steel shapes in various forms which effect ultrasonic pulse velocity. In this study, by measuring the velocity of ultrasonic waves generated when the waves pass through the ultrasonic pulse in a direction perpendicular to the reinforcing bars embedded in concrete, the effect of reinforcing bars on ultrasonic velocity accurately was verified and used to estimate the strength of the concrete.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.245-248
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• 1997

The distilled water is used for the ultrasonic wave propagating material in the measurements of broadband ultrasonic attenuation (BUA) that is applied in industrial and medical applications, The acoustic impedance of water is significantly changed with its temperature. Therefore, the quantitative evaluation of BUA with temperature and the ultrasonic wave propagating distance is highly needed. In this study, we evaluated the variation of attenuation with change in temperature. To measure the variation of BUA in the low frequency region at the temperatures, 27$^{\circ}C$, 29$^{\circ}C$, and 31$^{\circ}C$, we tested the Plyethylene, Teflon, MC-Nylon, Urethane specimens and analyzed the center frequency, frequency bandwidth, spectral peak amplitude. The results showed that BUA value appeared to be lower with increasing temperature. This may be due to the fact that the frequency feature of ultrasonic wave is affected by not only the specific gravity, acoustic impedence, but material crystalline, porosity, the distance of ultrasonic wave propagation in water.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.369-374
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• 2000

This study has been achieved on the characteristics of ultrasonic wave in 2.25Cr-1Mo steel to evaluate the feasibility of ultrasonic nondestructive technique on the assessment of aging degradation. The measured values were used find a relationship between the ultrasonic propagation properties and degradation such as coarsening of carbides and precipitates. The ultrasonic attenuation coefficient was mainly affected by the grain size of prior austenitic phase as well as degradation. In this results, degradation and grain size in 2.25Cr-1Mo steel was able to cope with the changes in ultrasonic wave properties by applying the nondestructive evaluation method

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.344-353
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• 1996

A fundamental study was conducted to obtain the basic data involved in nondestructive quality evaluation of the fruit and vegetables. An experimental equipment for ultrasonic propagation characteristics of the fruit and vegetables such as radish , carrot , potato, and apple was set up and also power spectrum analysis system of an ultrasonic wave through the fruit and vegetables was set up. The velocity and attenuation of ultrasonic wave through the tissue specimens from the fruit and vegetables were measured and analyzed. The elastic modulus and density by the mechanical method currently used were compared with those using by ultrasonic method. The ultrasonic tranit time was almost linearly increased with the length of the specimens and attenuation of ultrasonic was mainly affected by the internal flbrous structure of the products. The regression equation was derived from the highly correlated experimental variables.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2421-2423
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• 2002

A global ultrasonic sensor system for self-localization of an indoor mobile robot is proposed in this paper. By the global ultrasonic sensor system, it is meant several ultrasonic transmitters fixed at some positions in the world coordinate and the receiver in the moving coordinate of a mobile robot. In order to achieve the synchronization between an ultrasonic transmitter and receiver and to avoid the crosstalk among the ultrasonic transmitters, simple radio frequency transmitters and receivers are adopted. Experiments are carried out to verify the effectiveness of the proposed ultrasonic sensor system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1702-1704
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• 1998

In order to establish the usefulness of ultrasonic techniques for detecting corona discharges in high-voltage power apparatus, it is first necessary to determine the relationship between electrical and ultrasonic signals of corona discharges in air. In this paper, various characteristics of ultrasonic signal detection for point-to-plane corona discharges using a 200[kHz] ultrasonic sensor are examined. In regard to the attenuation and directivity of ultrasonic signals, the signals were inversely proportional to the distance between corona sources and ultrasonic receiving sensors, and half attenuation angles were approximately 7.0 degree. Ultrasonic signals of positive polarities were first obserbed at corona inception voltages. and the signals were increased with increasing the applied voltages.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1203-1210
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• 2003

Emission of ultrasonic vibration to turbulent flow promotes the turbulence generation due to the resonantly oscillating pressure field and thereby induced cavitation. In addition, ultrasonic vibration is well transmitted through water and not dissipated easily so that the micro-bubbles involved in the fluid induce the gaseous cavitation if the bubbles are resonated with the ultrasonic field. In the present study, we found through LDV measurement that the gaseous cavitation induced by ultrasonic vibration to CO$_2$saturated water flow in the rectangular cross-sectioned straight duct enhances turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation. We also found that the fluctuating velocity component induced by emitting the ultrasonic vibration in normal direction of a rectangular channel flow can be redistributed to stream-wise component by the agitation of gaseous cavitation.

• 한국생산제조학회지
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• 제19권3호
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• pp.402-406
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• 2010

Conventionally, the machined surface roughness in nano-second(ns) laser machining is damaged and rough due to thermal effects. To obtain the improved surface finish, the ultrasonic vibration is applied to ns-laser machining. The ultrasonic vibration jig is developed to apply the ultrasonic high precision motion to workpieces. And then the ns-laser machining is conducted to compare the effects of the ultrasonic vibration. The results show that the surface roughness with ultrasonic vibration is smoother than that without the vibration. The phenomenon could be explained as enhancement of heat transfer by ultrasonic vibration.

• Journal of Forest and Environmental Science
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• 제23권2호
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• pp.73-78
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• 2007

Ultrasonic deinkings of white ledger were carried out to confirm whether the ink removal efficiency and pulp qualities can be improved by the ultrasonic deinking. The effects of conventional pulping and ultrasonic treatment of white ledger on the ink particle size distribution and ink removal coefficient were compared. The physical properties of paper, energy consumption and effluent qualities were measured. The ultrasonic treatment of white ledger resulted in the ink particle size distribution suitable for flotation. The ink removal efficiency, brightness, breaking length and effluent quality were improved by the ultrasonic deinking. It is expected that the competitiveness of ultrasonic deinking system can be improved by the optimization of treatment condition.