• 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.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.670-676
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• 2014

The objective of this research is to utilize the ultrasonic method to analyze the property of partial discharge (PD) which is generated by the winding of the insulation stator in the generator. Therefore, a PD measurement system is built based on ultrasonic and virtual instruments. Three types of PD models (internal PD model, surface PD model and slot PD model) have been constructed. With the analysis of these experimental results, this research has identified the ultrasonic signals of the discharges which were produced by three types of PD models. This analysis shows the different features among these PD types. Both the time domain and frequency domain of the ultrasonic signals are obviously different. In addition, an experiment based on a large rotating machine has been done to analyze ultrasonic noises. The result indicates that the ultrasonic noises can be wiped off by the filters and algorithms. The application of this system is convenient for the detection of early signs of insulation failure, which is an effective method for diagnosis of insulation faults.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.60-65
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• 1998

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of Ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon

• 비파괴검사학회지
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• 제35권6호
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• pp.407-413
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• 2015

Ultrasonic infrared thermography is an active thermography methods. In this method, mechanical energy is introduced to a structure, it is converted into heat energy at the defects, and an infrared camera detects the heat for inspection. The heat generation mechanisms are dependent on many factors such as structure characteristics, defect type, excitation method and contact condition, which make it difficult to predict heat distribution in ultrasonic infrared thermography. In this paper, a method to simulate frictional heating, known to be one of the main heat generation mechanisms at the closed defects in metal structures, is proposed for ultrasonic infrared thermography. This method uses linear vibration analysis results without considering the contact boundary condition at the defect so that it is intuitive and simple to implement. Its advantages and disadvantages are also discussed. The simulation results show good agreement with the modal analysis and experiment result.

• 한국자동차공학회논문집
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• 제7권5호
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• pp.31-39
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• 1999

A good atomization in uniform size brings the elevation of thermal efficiency in spray combustion, the beautiful painting on surfaces, and the economical sprinkling of chemicals. Ultrasonic atomization has been expected as a good uniform atomization mechanism due to its uniform size distribution. Influx, load, and physical properties of liquids are the effecting factors to atomize liquids. In this study, distilled water and city water are selected as reference liquids and gasoline, kerosene, and petroleum as fuel liquids. Characteristics and affinity to get the maximum effect for the ultrasonic atomization are observed by using the two ultrasonic transducers with 28kHz and 2MHz. Results show that the size distributions of liquid spray dorplet by the direct vibration method prevail over those by the aerosol method in uniform droplet size and as a whole, sizes of spray liquid droplets are increased slightly according to increasing influx in the direct vibration method and quantities of spray droplets in the aerosol method decreasing according to increasing liquid load h.

• 한국해양공학회지
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• 제14권4호
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• pp.68-72
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• 2000

The ultrasonic method, which is well known as nondestructive test method, is widely used to evaluate the material damage due to degradation. However, this method is just used for measuring the crack size and the thickness loss of the tube. The purpose of this study is to investigate the application of the ultrasonic technique for the evaluation of marine diesel engine exhaust valve and to suggest the correlation between the ultrasonic characteristics and valve degradation. From the evaluation of the results obtained, the technique of using the ultrasonic property was founds to be a efficient method to degree of marine diesel engine exhaust valve by nondestructive test.

• 한국축산식품학회지
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• 제21권2호
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• pp.126-132
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• 2001

This study was carried out to investigate the effect of ultrasonic treatment on physicochemical and sensory properties of cooked chicken meat. Moisture content of ultrasonic treated breast meat was higher than that of control, fat content of control of breast and leg meat were higher than that of ultrasonic treatment, and protein of control of breast meat was higher than that of ultrasonic treatment. Hunters L(lightness)-and a(redness)-value were not different between cooking methods, L-value of breast meat and a-value of leg meat were higher without regard to cooking method. Hunterb (yellowness)-value was not different among cooking chicken meats. Cooking yield was not different between cooking methods, pH of ultrasonic treated chicken meats were higher than that of control. Water holding capacity and salt soluble protein extractability of ultrasonic treated breast meat were greater than that of control. Water soluble protein extractability of ultrasonic treated leg meat was higher than that of control, and shear force value was not different between cooking methods. Hardness, cohesiveness and gumminess were not different between cooking methods and parts of muscle. Springiness of ultrasonic treated leg meat was greater than that of control and chewiness of breast meat was higher than that of leg meat. Aroma, texture, juiciness and overall acceptability were not different between cooking methods, taste of ultrasonic treated leg meat was higher than that of control. In addition, the sensory scores of parts of muscle were affected greater than that of cooking methods.

• 동력기계공학회지
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• 제13권3호
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• pp.40-46
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• 2009

This study on the bolt elongation and torque measuring method by ultrasonic nod-destructive method. In the past, The dial gage was used for the elongation measurement of gas turbine bolts. The purpose of this study is to improve the traditional bolt elongation measurement method. The old method using dial gage measures the elongation of the gas turbine bolt. If the length differences among the loading bolts are within the required range, The loading torques of bolts consider as acceptable. But this method can not give the information about torque differences among the loading bolts. It could bring out vibration of turbine due to loading torque differences among the bolts. So the elongation and torque must be measured simultaneously. The new technology using ultrasonic non-destructive method can give the information about bolt elongation and torque. The ultrasonic method basically measures the speed in the bolt material for the calculation the bolt elongation. But the ultrasonic speed varies according to temperature and loading torque of bolts. So the factors of temperature and loading power were investigated and reflected to the calculation of bolt elongation and torque. The results of this study shows the big difference among the bolts torque in the old method and the torque differences among the bolts can be adjusted by reflecting the result of this study. And this torque adjusting method can decrease gas turbine vibration problem due to torque difference among the bolts. So this paper shows ultrasonic method is better than old method for the measurement of bolt elongation and torque.

• 소성∙가공
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• 제22권1호
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• pp.36-41
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• 2013

The present study examines the micro-pattern replication on a plastic film using ultrasonic imprinting. Ultrasonic imprinting uses ultrasonic waves to generate repetitive microscale deformation in the polymer film. The resulting deformation heat on the surface of the film causes the surface region to soften sufficiently so that a replication of the micro-pattern can be obtained. To successfully replicate the micro-pattern on a large area of polymer film, a high replication ratio is needed as well as good uniformity over the entire region. In this study, a horn design is investigated by finite element analysis and is optimized through a response surface analysis. In the ultrasonic imprinting experiments, the response surface method was also used to determine the optimal processing conditions for better replication characteristics.

• 비파괴검사학회지
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• 제7권1호
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• pp.32-41
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• 1987

As a new device of stress monitoring method, ultrasonic backscattering method has been used to aluminium samples with various grain sizes at rayleigh critical angle in order to observe the relationships between applied stress and ultrasonic backscattered energy. It was found that the ultrasonic backscattered energy was observed to decrease as the grain size increased at the given applied stress. At the same grain size, the ule ultrasonic backscattered energy increased with increasing the applies stress. Through this study, we provided some possibility to evaluate stresses in materials under loads nondestructively, and this method is expected to be used as a new stress monitoring device.