Key Engineering Materials Vols. 321-323

Abstract: NDE (Nondestructive Evaluation) of wood was performed using X-ray CT technique in order to determine the applicability of this technology to ancient wooden buildings in the field. Two main objectives were studied to consider applicability as well as accuracy. First, the most suitable number of radiographs for reconstructing proper X-ray CT images was determined. Secondly, X-ray CT images using SIRT were reconstructed using various numbers of radiographs in order to consider the possible effects of absent projection data in field applications. As a result of this study, 9 radiographs were determined to be the most suitable number for this application. Brown-rotted part in wood was also detected by X-ray CT images using 9 radiographs. It was concluded that even there exists some absent projection data, CT images can be reconstructed with high accuracy.

Abstract: This research was carried out to grasp the factors influencing to the ultrasonic velocity to improve the efficiency of the ultrasonic wave test using as the method of NDE of wood. However, it was difficult to detect the defect of wood accurately, because ultrasonic velocity is influenced by various factors. So, some effect factors, which were not concerned with decay, were confirmed at first. Therefore, in this research, we tried to find the factors which affect on the natural characters and the ultrasonic velocity at decayed wood, additionally, we tried an anatomic experiment and analyze. As a result of research, the velocity at radial direction was faster than that at tangential direction and the ultrasonic velocity at immature wood and reaction wood was slower than that at normal wood. And the ultrasonic velocity was more the slower at bigger the length of decay and reduction of weight.

Abstract: Recently, a new ultrasonic CT system has been developed as the NDE method suitable for wood. In this system, several characteristics related to the ultrasound traveling in the woods such as the anisotropy of woods, existence of immature woods and ultrasound diffraction in the woods are considered during image composition process. In this study, we inspected the system that had been newly developed for the decayed wood specimen. We performed the ultrasound measurements to reconstruct the CT image. And then, we verified the distributions of each characteristic in the section by measuring the moisture content, specific gravity and compressive strength after cutting the measured specimen by small specimen again. The acquired results are compared with the CT image acquired in the same section. As a result, it is determined that it is possible to detect the locations and sizes of decayed parts in the wood by using the developed ultrasound CT system. In particular, the results show that the initial decays that the weight loss rate is less than 10% and the strength loss rate is less than 30% are also detectable.

Abstract: This paper presents a machine vision method to inspect the maturity of pineapples that ripe naturally. Unlike previous methods, the proposed technique can be categorized as a real-time non destructive testing (Real-Time NDT) approach. It consists of two phases, learning and recognition phases. In the learning phase, the system constructs a library of reference pineappleskin- color models. In the recognition phase, the same process is performed to build a pineappleskin- color model of the testing subject. The model is then compared with each of the reference in the library by a method called region-segmented histogram intersection. The subject is then labeled with the grade of the best match. The system achieved a high performance and speed (3 frames/sec.) in our experiment. The system also includes weighing machine on belt transmission for weight prediction.

Abstract: This study was conducted to analyze the ultrasonic transmitted signal for apple using wavelet transform. Fruit consists of non-linear visco-elastic properties such as flesh, an ovary and rind and hence most ultrasonic wave is attenuated and its frequency is shifted during passing the fruit. Thus it was not easy to evaluate the internal quality of the fruit using typical ultrasonic parameters such as wave velocity, attenuation, and frequency spectrum. The discrete wavelet transform was applied to the ultrasonic transmitted signal for apple. The magnitude of the first peak frequency of the wavelet basis from the ultrasonic transmitted signal showed a close correlation to the storage time of apple.

Abstract: In this study, microwave free-space transmission technique was applied to measure the moisture content of powdered food (wheat flour, milk powder, and coffee powder). In frequency range from 1 to 15 GHz, the microwave attenuation and phase shift due to moisture content of food samples were measured and analyzed using vector network analyzer, double rigid horn antennas, and sample holder filled with moist food samples. To estimate the relationship between moisture density of powdered food and the attenuation and phase shift, correlation analysis was performed. The correlation coefficients at each food sample were greater than 0.91. The calibration equation for moisture content measurement having attenuation and phase shift as independent variables at 15 GHz was developed and evaluated. The coefficient of determination and root mean square for all food samples were 0.974 and 0.328 % respectively.

Abstract: This study was conducted to develop an accurate quality evaluation system based on optimized factors such as light source array and light power, which are used in non-destructive fruit sorter to obtain the internal quality information of fruits using the near infrared transmittance spectra. It is necessary to provide the proper design guide for the light source part in the existing non-destructive fruit sorters for apples and pears, and to measure the real-time near infrared transmittance spectrum without the leakage of light. The near infrared transmittance spectrum detection system was developed with the light source part which has the power-controllable 12 halogen lamps (100W/12V) with gold coating, light detection part, and transfer line. By using the accurate control of the voltage and current (maximum power is 1.2kW) in light power control part, it is concluded that the minimum power for the internal quality evaluation of apples and pears was over 0.5 kW. To prevent the leakage of light, the array of light source was rearranged and tested. Without changing the tray structure, it is concluded that the leakage of light can be prevented by the proper array of light source and power. For the irradiation for the moving apples and pears, 2 upper lamps and 4 lower lamps combination did not have leakage of light and the correlation coefficient of this combination shows the 0.90 for apples and 0.96 for pears.

Abstract: This study was aimed at developing a new quality evaluation system for classifying the cucumber based on its length and curvature, and removing the taper and dumbbell shaped cucumbers using the thickness changes. Especially machine vision technique was used in carrying out field application. The cucumber image was obtained from a frame grabber, and the image was improved by minimizing the nonuniform illumination and image blurring due to line movement. From the obtained image, background was separated from the original image, and cucumber length and curvature was calculated after thinning and post-processing operation. After thinning operation, cucumber region was sliced and the thickness was calculated. From the thickness calculation, cucumber can be classified as straight, cudgel and dumbbell shape. The classification rate for bowing was close to 100%. The overall average recognition rate for good, dumbbell and cudgel cucumber fruits was 90.7%

Abstract: Watermelons are usually sorted by theirs weight and internal quality. Some automated watermelon weight sorters have been developed and operated in watermelon production areas. However, inspection of internal quality of watermelon is still performed by manually. Principal method of identifying internal defect of watermelon is analyzing the percussion sound of watermelon by human experts. Development of non-destructive evaluation technique for internal quality of watermelon is required to reduce human decision errors. The objective of this study was to develop a non-destructive sorting system which can detect internal defect of watermelons. The internal defect evaluation system has a constant-force hitting hammer to generate the acoustic sound, a multi-point sound signal acquiring system, a noise removal circuit, and a signal processing and quality evaluation program. An internal quality prediction model by PLSR (Partial Least Square Regression) was developed by analyzing the percussion sound of watermelons. Using the developed model, the prediction result shows that the overall prediction accuracy was 90.1%, and severely defected watermelons were identified perfectly.

Abstract: Precision agriculture, also called as site-specific crop (or field) management, is a recent trend in crop production that uses field information collected at different within-field locations to optimize amount, timing, and location of agricultural inputs according to the site-specific requirements. Recent development of soil property sensors has facilitated sensor-based data collection for SSCM in many countries around the world. In this study, commercial soil strength, electrical conductivity, and water content and temperature sensors were applied to a Korean rice (Oriza Sativa L) field and spatial and non-spatial statistical techniques were used to assess soil conditions and the variability, and investigate optimum sampling intensity. Results of the study would be useful for establishment of data collection schemes and better application of soil property sensors to Korean paddy fields for successful precision agriculture.