• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.200-203
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• 2000

The application of the ultrasonic nozzle has been extended because it is possible atomization of liquid material. In this study, the characteristics of the ultrasonic nozzle and ceramic oscillator were investigated. The oscillator for the ultrasonic nozzle were made piezoelectric ceramic of Pb[($Sb_{1/2}$ $Nb_{1/2}$)$_{0.035}$-($Mn_{1/3}$$Nb_{2/3}$)$_{0.065}$-($Zr_{0.49}$$Ti_{0.51}$)$_{0.90}$]$O_3$. The electromechanical coupling factor($k_p$) and mechanical quality factor(Qm) showed the values of 0.555, 1, 214 respectively when the Zr/Ti ratio was 49/51. Moreover, this oscillator will have the temperature stability because it's curie temperature is 322[$^{\circ}C$]. The driving current of ultrasonic nozzle showed the value of 80[mA] when the driving time was lO[min.]. Also, The surface temperature of ceramic oscillator showed 80[$^{\circ}C$] at driving time lO[min.] We knew that the ultrasonic nozzle had stabile driving above 10[min.].

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.77-84
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• 2014

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.246-253
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• 2002

This paper describes the development and the field application of the ultrasonic gas flowmeter for accurate measurement of the volumetric flow rate of gases in a harsh environmental conditions in iron & steel making company. This ultrasonic flowmeter is especially suited for measuring LDG, COG, BFG gases produced in iron & steel making process. This is a transit time type ultrasonic flowmeter. We have developed the transmitting & receiving algorithm of ultrasonic wave and the ultrasonic signal processing algorithm to develope a transit time type ultrasonic flowmeter. We have evaluated the performance of ultrasonic flowmeter by the calibration system with Venturi type standard flowmeter. We has confirmed its reliability by extensive field tests for a year in POSCO, iron & steel making company. Now we have developed the commercial model of ultrasonic flowmeter and applied to the POSCO gas line.

• Journal of Information Processing Systems
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• v.15 no.5
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• pp.1131-1140
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• 2019

Characteristics of fruit tree canopies are important target information for adjusting the pesticide application rate in variable rate spraying in orchards. Therefore, the target detection of the canopy characteristics is very important. In this study, a canopy volume measurement method for peach trees was presented and a variable rate spraying system based on canopy volume measurement was developed using the ultrasonic sensing, one of the most effective target detection method. Ten ultrasonic sensors and two flow control units were mounted on the orchard air-assisted sprayer. The ultrasonic sensors were used to detect the canopy diameters and the flow controls were used to modify the flow rate of the nozzles in real time. Two treatments were established: a constant application rate of $300Lha^{-1}$ was set as the control treatment for the comparison with the variable rate application at a $0.095Lm^{-3}$ canopy. The tracer deposition at different parts of peach trees and the tracer losses to the ground (between rows and within rows) were analyzed in detail under constant rate and variable rate application. The results showed that there were no significant differences between two treatments in the liquid distribution and the capability to reach the inner parts of the crop canopies.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.25-36
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• 1989

This essay is a general review of the application of ultrasonic NDE techniques to the performance assessment and characterization of composite materials. A brief review of ultrasonic input-output characterization of a composite plate by shear waves is presented. A theoretical development of ultrasonic wave propagation in isotropic and anisotropic media excited, respectively, by a circular transducer and an oscillatory point source is summarized. Some experimental results are described in which ultrasonic velocity and attenuation measurements give insight into material degradation of fatigued composite laminates. Ultrasonic determination of the elastic constants of a composite plate and an experimental attempt at ultrasonic testing of an isotropic plate containing a crack are also included. A recent effort for the characterization of viscoelastic materials using the ultrasonic NDE technique is outlined. Finally, the reliability of ultrasonic NDE is briefly touched upon.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.231-234
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric and hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $\textrm{Al}_2\textrm{O}_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.

• Korean Journal of Dental Materials
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• v.43 no.1
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• pp.17-28
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• 2016

The aim of this study was to evaluate the changes in dentinal permeability after application of dentin desensitizer on exposed dentin immediately after ultrasonic scaling to teeth with non-carious cervical lesions. Thirty caries-free extracted molars were fixed to slide glasses after horizontally being sectioned at 5 mm below the cemento- enamel junction (CEJ). The prepared specimen was connected to a fluid flow measuring device (nano-Flow), and a V-shaped cavity was formed at the CEJ to imitate the non-carious cervical lesion. After no fluid leakage was confirmed in the connected system with specimen, tooth surface was treated ultrasonic cleaning with piezoelectric ultrasonic scalers until dentinal tubules were exposed. And 6 different desensitizers were applied on exposed dentin. Real-time measurements of dentinal fluid flow were performed during ultrasonic scaling and application of dentin desensitizer. To evaluate the occlusion of exposed dentinal tubules, tooth surface was examined by SEM. Following results were observed. After ultrasonic scaling, more dentinal tubules were exposed on the tooth with non-carious cervical lesions compared to tooth without lesions. The rate of fluid flow measured with nano-Flow system had correlation with the degree of dentin occlusion observed with SEM after application of desensitizers on exposed dentin. Desensitizers with glutaraldehyde and HEMA did not decrease the rate of fluid flow and did not show dentin occlusion. Desensitizers with oxalate showed the limited effects on the rate of fluid flow and dentinal tubule occlusion. Desensitizer with resin monomer showed the significant effect on the rate of fluid flow and dentin occlusion.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.225-233
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• 2002

This study was aimed to evaluate the effects of ultrasonic vibration on margin types and cements by comparing bond strength of cemented crown. In this study, margins of each metal die, which were chamfer, shoulder and shoulder with bevel, were prepared using computer milling machine. Specimens were cemented with zinc phosphate cement or resin cement. The specimens were divided by the finish line and cement used, ultrasonic vibration. I made total 84 specimens. All specimens were divided into two groups. One group was not vibrated, the other group was subjected to ultrasonic vibration for 12 minutes. Tensile bond strength was measured using Universial testing machine. The changes of bond strength in groups were statistically analyzed by t-test or One-way ANOVA. The results were as follows : 1. Ultrasonic instrumentation diminished the bond strength of crown cemented with zinc phosphate cement and resin cement after 12 minutes application. 2. In case of zinc phosphate cement, the bond strength of a vibrated group was showed significantly decreased(p<0.05). In vibrated groups with zinc phosphate cement, shoulder with bevel exhibit a significant difference to chamfer and shoulder(p<0.05) 3. Resin cement was more resistant to ultrasonic vibration than zinc phosphate cement and showed no significant differences according to ultrasonic vibration and margin type. In conclusion, These results revealed that zinc phosphate cement was most affected and resin cement was the least affected by ultrasonic vibration. Especially shoulder with bevel design was most affected in zinc phosphate cement groups. we should consider these results and be taken in the application of ultrasonic vibration to any teeth restored with crowns.

• Smart Structures and Systems
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• v.17 no.1
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• pp.17-29
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• 2016

Ultrasonic tomography is a powerful tool for identifying defects within an object or structure. But practical application of ultrasonic tomography to solids is often limited by time consuming transducer coupling. Air-coupled ultrasonic measurements may eliminate the coupling problem and allow for more rapid data collection and tomographic image construction. This research aims to integrate recent developments in air-coupled ultrasonic measurements with current tomography reconstruction routines to improve testing capability. The goal is to identify low velocity inclusions (air-filled voids and notches) within solids using constructed velocity images. Finite element analysis is used to simulate the experiment in order to determine efficient data collection schemes. Comparable air-coupled ultrasonic signals are then collected through homogeneous and isotropic solid (PVC polymer) samples. Volumetric (void) and planar (notch) inclusions within the samples are identified in the constructed velocity tomograms for a variety of transducer configurations. Although there is some distortion of the inclusions, the experimentally obtained tomograms accurately indicate their size and location. Reconstruction error values, defined as misidentification of the inclusion size and position, were in the range of 1.5-1.7%. Part 2 of this paper set will describe the application of this imaging technique to concrete that contains inclusions.

• Environmental Engineering Research
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• v.11 no.2
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• pp.99-105
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• 2006

A digital ultrasonic image construction system was developed for the nondestructive detection of cracks in water distribution pipes. The system consists of PC based ultrasonic testing system and a scanning device. The PC based ultrasonic system has an ultrasonic pulse/receive board for the generation and reception of ultrasonic signals, an analogue to digital conversion board for the digitization of the received ultrasonic signals, and transducers for the ultrasonic sensors. Using this system, the digitized ultrasonic signals were properly constructed in accordance with the position information obtained by scanning device that moves an ultrasonic transducer along the outer surface of pipes. In the construction of the ultrasonic signals, signal processing concepts, such as spatial average and array concept, were considered to enhance the resolution of ultrasonic images of pipe wall. Using the developed system, crack detection experiments were performed in both laboratory and field, which shows promise for crack detection in the water distribution system.