Key words: DC CT detection technology; Resistivity inversion; Cylindrical structure; Curve correction
China Library Classification Number: S758. 1 Document Identification Number: A.
Article number:1672-1098 (2012) 02-0059-04.
Date of receipt: 20 12-0 1-06
About the author: Yu Zhong (1987-), male, from Zaozhuang, Shandong Province, is studying for a master's degree, and his research direction is engineering geophysical exploration technology.
Detection of tree cell structure based on DC ct technology
Yu Zhong, Zhang Pingsong, Fu Maoru, Cheng Gang
(School of Earth Science and Environmental Engineering, Anhui University of Science and Technology, Huainan, Anhui 23200 1, China)
Abstract: In order to study the imaging results of the internal structure of trees, DC ct technology was used to detect different tree species. At first, the network parallel electrical prospecting system is used to collect data, and then the curvature correction is carried out to correct the electrical parameters, and the ideal resistivity distribution profile is obtained. By comparison, it can be concluded that the resistivity of the three kinds of trees varies greatly. In addition, the electrical distribution inside the trunk is that the resistivity of the trunk section is high inside and low outside. The distribution characteristics of resistivity can provide relevant technical parameters for the diagnosis of tree health symptoms.
Key words: DC ct technology; Resistivity inversion; Cylindrical structure; Curve correction
In recent years, it is a new application direction to detect forest health by geophysical methods, among which stress wave method [1], ultrasonic method [2-5], X-ray method [3,5] and vibration detection [6] are widely used and have achieved good detection results. Stress wave, ultrasonic detection and vibration detection methods use the first arrival of picked waves (that is, the arrival of the first wave) to analyze the propagation speed or spectral characteristics of the wave field to determine the internal structural characteristics of the forest; ? x？ X-ray detection is to test the attenuation of field strength after radiation penetrates the medium, and to evaluate the density, moisture content and defects of wood and wood composites by using absorption coefficient. Limited by the tree structure, the data acquisition and observation system will have a certain impact on the detection resolution and imaging effect. Because the electrical parameters of trees are obviously different in internal structure, the author's research group has carried out corresponding detection experiments by DC method.
Direct current method is a mature detection method, which has the characteristics of high intelligence of data acquisition and high imaging accuracy, and is widely used in engineering detection field [7-9]. A circle of electrodes was arranged on the cut trunk by electrical method to monitor its internal apparent resistivity, and a two-dimensional resistivity distribution image of a single section of the trunk was obtained by finite element method. The results show that the resistivity distribution of the trunk of healthy people presents a series of concentric circles, which decreases from the center to the outside in the radial direction. It can be inferred that there is a close negative correlation between the moisture distribution and the resistivity distribution in the trunk section [10-1]. Researchers in China used high-density resistivity imaging to detect the resistivity changes of healthy trees, and discussed the migration characteristics of water in the trunk. In this paper, a correction method of cylinder electrical detection data is proposed, which solves the problem of cylinder resistivity calculation and applies this method to trunk resistivity [12] 2? . In this paper, the parallel microelectrode system is used to collect data efficiently, and the observation experiments of different tree species are carried out, and the corresponding understanding is obtained.
1 DC CT detection technology
Geophysical conditions of 1. 1 tree exploration
The physical and chemical structure of wood determines that it contains almost no free ions with good conductivity, but it is ionized under the action of electric field. It is generally believed that the weak conductivity of wood is caused by ions, which are related to the ionic groups of polymers that make up wood, or are produced by impurities contained in inorganic components of wood [13]. The different electrical differences among normal media such as phloem, xylem and pith of healthy trees provide a good test premise for DC detection. By arranging test electrodes on the surface of the trunk, according to a certain data processing method, the resistivity distribution characteristics of any test section of the trunk can be calculated, so as to diagnose the internal structure of the tree, and at the same time, it can provide reference for further analysis and research on the accuracy of electrical CT imaging of columnar structures.