多路徑超音波斷面影像技術評估柳杉人造孔洞之研究

Evaluation of Artificial Holes in Cryptomeria japonica by Ultrasonic Tomography Technique

高毓謙(Yu-Chien Kao) ； 林振榮(Cheng-Jung Lin) ； 林達德(Ta-Te Lin) ； 蔡明哲(Ming-Jer Tsai)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 19卷3期 (2005/09) Pp. 239-250

https://doi.org/10.6542/EFNTU.200509_19(3).0006

摘要

The purpose of this study was to investigate artificial holes in the cross section of Cryptomeria japonica by using ultrasonic tomography technique. The ultrasonic instrument SYLVATEST-DUO(superscript ®) and the trunk section of Cryptomeria japonica were employed. In order to simulate different degrees of the core decay, chiseling on the central area of trunk section was done by hand and then the ultrasonic velocities of various measured directions were investigated. The relationships among different values of ultrasonic velocities, the relative velocity drop, and the diameter of the diameter of the chiseled hole were analyzed. Moreover, we discussed the relationships among the ratio of propagation time in the 90° direction to radial (180°) direction, the average velocity of ultrasonic tomography, the ratio of the hole/section diameter, the ratio of the hole remnant, and the ratio of the hole/section area. The highest correlation coefficient was found between the ratio of central hole remnant and the ultrasonic velocity in route D (two adjacent measured points) with R^2 value up to 0.94. The order according to correlation coefficient was as followed: route C (two-point interval between two measured points), route B (one-point interval between two measured points), and route A (two measured point are adjacent to each other). It was also found that the location and the size of the hole in the tree trunk section could be detected by the ultrasonic tomography. The color difference between hole area and its surrounding area was obvious after ultrasonic tomography analysis. When the ratio of hole area to section area was above 2.7%, the hole was able to be detected by ultrasonic tomography. The results could be applied for the evaluation of trunk core decay, and could be used as a basis for the visual tree assessment.

關鍵字

多路徑超音波斷面影像技術 ； 人造孔洞 ； 傳遞時間

並列摘要

The purpose of this study was to investigate artificial holes in the cross section of Cryptomeria japonica by using ultrasonic tomography technique. The ultrasonic instrument SYLVATEST-DUO(superscript ®) and the trunk section of Cryptomeria japonica were employed. In order to simulate different degrees of the core decay, chiseling on the central area of trunk section was done by hand and then the ultrasonic velocities of various measured directions were investigated. The relationships among different values of ultrasonic velocities, the relative velocity drop, and the diameter of the diameter of the chiseled hole were analyzed. Moreover, we discussed the relationships among the ratio of propagation time in the 90° direction to radial (180°) direction, the average velocity of ultrasonic tomography, the ratio of the hole/section diameter, the ratio of the hole remnant, and the ratio of the hole/section area. The highest correlation coefficient was found between the ratio of central hole remnant and the ultrasonic velocity in route D (two adjacent measured points) with R^2 value up to 0.94. The order according to correlation coefficient was as followed: route C (two-point interval between two measured points), route B (one-point interval between two measured points), and route A (two measured point are adjacent to each other). It was also found that the location and the size of the hole in the tree trunk section could be detected by the ultrasonic tomography. The color difference between hole area and its surrounding area was obvious after ultrasonic tomography analysis. When the ratio of hole area to section area was above 2.7%, the hole was able to be detected by ultrasonic tomography. The results could be applied for the evaluation of trunk core decay, and could be used as a basis for the visual tree assessment.

並列關鍵字

Ultrasonic tomography technique ； Artificial hole ； Propagation time