Adaptable Center Detection of a Laser Line with a Normalization Approach using Hessian-matrix Eigenvalues

Guan Xu,Lina Sun,Jian Su,Zhaobing Hao,Xue Lu,Xiaotao Li 한국광학회 2014 Current Optics and Photonics Vol.18 No.4

In vision measurement systems based on structured light, the key point of detection precision is to determine accurately the central position of the projected laser line in the image. The purpose of this research is to extract laser line centers based on a decision function generated to distinguish the real centers from candidate points with a high recognition rate. First, preprocessing of an image adopting a difference image method is conducted to realize image segmentation of the laser line. Second, the feature points in an integral pixel level are selected as the initiating light line centers by the eigenvalues of the Hessian matrix. Third, according to the light intensity distribution of a laser line obeying a Gaussian distribution in transverse section and a constant distribution in longitudinal section, a normalized model of Hessian matrix eigenvalues for the candidate centers of the laser line is presented to balance reasonably the two eigenvalues that indicate the variation tendencies of the second-order partial derivatives of the Gaussian function and constant function, respectively. The proposed model integrates a Gaussian recognition function and a sinusoidal recognition function. The Gaussian recognition function estimates the characteristic that one eigenvalue approaches zero, and enhances the sensitivity of the decision function to that characteristic, which corresponds to the longitudinal direction of the laser line. The sinusoidal recognition function evaluates the feature that the other eigenvalue is negative with a large absolute value, making the decision function more sensitive to that feature, which is related to the transverse direction of the laser line. In the proposed model the decision function is weighted for higher values to the real centers synthetically, considering the properties in the longitudinal and transverse directions of the laser line. Moreover, this method provides a decision value from 0 to 1 for arbitrary candidate centers, which yields a normalized measure for different laser lines in different images. The normalized results of pixels close to 1 are determined to be the real centers by progressive scanning of the image columns. Finally, the zero point of a second-order Taylor expansion in the eigenvector’s direction is employed to refine further the extraction results of the central points at the subpixel level. The experimental results show that the method based on this normalization model accurately extracts the coordinates of laser line centers and obtains a higher recognition rate in two group experiments.

Three Degrees of Freedom Global Calibration Method for Measurement Systems with Binocular Vision

Guan Xu,Xinyuan Zhang,Xiaotao Li,Jian Su,Xue Lu,Huanping Liu,Zhaobing Hao 한국광학회 2016 Current Optics and Photonics Vol.20 No.1

We develop a new method to globally calibrate the feature points that are derived from the binocularsystems at different positions. A three-DOF (degree of freedom) global calibration system is establishedto move and rotate the 3D calibration board to an arbitrary position. A three-DOF global calibration modelis constructed for the binocular systems at different positions. The three-DOF calibration model unifiesthe 3D coordinates of the feature points from different binocular systems into a unique world coordinatesystem that is determined by the initial position of the calibration board. Experiments are conducted onthe binocular systems at the coaxial and diagonal positions. The experimental root-mean-square errorsbetween the true and reconstructed 3D coordinates of the feature points are 0.573 mm, 0.520 mm and0.528 mm at the coaxial positions. The experimental root-mean-square errors between the true andreconstructed 3D coordinates of the feature points are 0.495 mm, 0.556 mm and 0.627 mm at the diagonalpositions. This method provides a global and accurate calibration to unity the measurement points ofdifferent binocular vision systems into the same world coordinate system.

Precision Evaluation of Three-dimensional Feature Points Measurement by Binocular Vision

Guan Xu,Xiaotao Lin,Jian Su,Hongda Pan,Guangdong Tian 한국광학회 2011 Current Optics and Photonics Vol.15 No.1

Binocular-pair images obtained from two cameras can be used to calculate the three-dimensional (3D) world coordinate of a feature point. However, to apply this method, measurement accuracy of binocular vision depends on some structure factors. This paper presents an experimental study of measurement distance, baseline distance, and baseline direction. Their effects on camera reconstruction accuracy are investigated. The testing set for the binocular model consists of a series of feature points in stereo-pair images and corresponding 3D world coordinates. This paper discusses a method to increase the baseline distance of two cameras for enhancing the accuracy of a binocular vision system. Moreover, there is an inflexion point of the value and distribution of measurement errors when the baseline distance is increased. The accuracy benefit from increasing the baseline distance is not obvious, since the baseline distance exceeds 1000 mm in this experiment. Furthermore, it is observed that the direction errors deduced from the set-up are lower when the main measurement direction is similar to the baseline direction.

Method of stress field and stability analysis of bedding rock slope considering excavation unloading

Hui Qin,Xiaotao Yin,Hua Tang,Xu Cheng,Hao Yuan 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

The stress state of a slope and its analytical solution are prerequisites for stability analysis. Currently, the limit equilibrium method cannot consider the stress state of slopes, and the solution of bedding slope stress remains in numerical simulations for a long time. In this paper, based on the theory of the elastic stress solution of the wedge top under a concentrated load, the analytical solution of the stress field was obtained using Matlab programming. Unloading stress analysis method (USAM) for determining the sliding surface of the bedding rock slope, safety factor (Fs), and reinforcement forces (Fr) were proposed. The USAM is compared with the Limit Equilibrium Method (LEM) and Finite Element Method (FEM) in terms of the Fs, Fr, sliding surface position, and sliding surface stress. The results show: 1) The analytical stress of the slope can be obtained quickly and conveniently using the USAM, while subsequent programming helps in faster completion of the stability evaluation of the bedding rock slope. Fs, Fr, sliding surface position, and sliding surface stress are all close to the results obtained by the FEM. 2) The USAM is more suitable for analyzing slopes when the angle between the slope surface and structural plane is greater than 20° (θ > 20o) and the slope angle is greater than 45o (β > 45o). 3) Through the analysis of specific engineering cases, the safety factor calculated by USAM are 0.06 and 0.02 larger than those obtained by LEM and FEM, respectively, and the required reinforcement force for the slope is closer to that obtained by FEM. The novel stress and stability analysis method allows for the rapid evaluation and optimal engineering design of bedding rock slope.

A new device for restraining rail vibration of ballastless track and its effect study

Zhenxing He,Xu Zhang,Xiaotao Wang,Hualong Zhou,Quanbao Feng,Qingchao Chen,Junxia Chen,Yanbo Bai,Runxi Zhang,Nengneng Bao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

A new type of rail vibration damping device (NTRVDV), which is arranged between the bottom of the rail and track bed, is proposed in this paper. The finite element model of the rail system with the NTRVDV and tuned rail damper (TRD) was established, respectively. The impact load was applied to the finite element model, and comparison of the set of existing TRD and NTRVDV on the dynamic response of rail and rail vibration decay rate. The effect of the stiffness change of the elastic layer of the NTRVDV on the rail vibration was studied, and a hammering test verified the theoretical research results. The research results show that compared with the traditional TRD, the NTRVDV has a more obvious suppression effect on rail vibration acceleration. The rail vibration decay rate is significantly improved, especially in the low-frequency stage. With the increase of the stiffness of the elastic layer of the vibration suppression device, the vibration suppression effect of the NTRVDV on the rail is improved. The change of the elastic layer stiffness significantly impacts the rail’s vibration suppression effect in the range of 0-7 kN/mm.

Structural Conservation and Food Habit-related Liver Expression of Uncoupling Protein 2 Gene in Five Major Chinese Carps

Liao, Wan-Qin,Liang, Xu-Fang,Wang, Lin,Fang, Ling,Lin, Xiaotao,Bai, Junjie,Jian, Qing Korean Society for Biochemistry and Molecular Biol 2006 Journal of biochemistry and molecular biology Vol.39 No.4

The full-length cDNA of grass carp (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) uncoupling protein 2 (UCP2) was obtained from liver. The grass carp UCP2 cDNA was determined to be 1152 bp in length with an open reading frame that encodes 310 amino acids. Five introns (Intron 3, 4, 5, 6 and 7) in the translated region, and partial sequence of Intron 2 in the untranslated region of grass carp UCP2 gene were also obtained. Gene structure comparison between grass carp and mammalian (human and mouse) UCP2 gene shows that, the UCP2 gene structure of grass carp is much similar to that of human and mouse. Partial UCP2 cDNA sequences of bighead carp (Aristichthys nobilis) and mud carp (Cirrhinus molitorella), were further determined. Together with the common carp (Cyprinus carpio) UCP2 sequence from GenBank (AJ243486), multiple alignment result shows that the nucleotide and amino acid sequences of the UCP2 gene, were highly conserved among the five major Chinese carps that belong to four subfamilies. Using beta-actin as control, the ratio UCP2/beta-actin mRNA (%) was determined to be $149.4{\pm}15.6$ (common carp), $127.4{\pm}22.1$ (mud carp), $96.7{\pm}12.7$ (silver carp), $94.1{\pm}26.8$ (bighead carp) and $63.7{\pm}16.2$ (grass carp). The relative liver UCP2 expression of the five major Chinese carps, shows a close relationship with their food habit: benthos and detrituseating fish (common carp and mud carp) > planktivorious fish (silver carp and bighead carp) > herbivorious fish (grass carp). We suggest that liver UCP2 might be important for Chinese carps to detoxify cyanotoxins and bacteria in debris and plankton food.

Association between Retinal Vascular Geometric Changes and Cognitive Impairment: A Systematic Review and Meta-Analysis

Huiqun Wu,Chendong Wang,Cong Chen,Xiaotao Xu,Yi Zhu,Aimin Sang,Kui Jiang,Jiancheng Dong 대한신경과학회 2020 Journal of Clinical Neurology Vol.16 No.1

Background and Purpose Previous studies have explored the association between retinal vascular changes and cognitive impairment. The retinal vasculature shares some characteristics with the cerebral vasculature, and quantitative changes in it could indicate cognitive impairment. Hence, a comprehensive meta-analysis was performed to clarify the potential relationship between retinal vascular geometric changes and cognitive impairment. Methods Relevant databases were scrupulously and systematically searched for retinal vascular geometric changes including caliber, tortuosity, and fractal dimension (FD), and for cognitive impairment. The Newcastle-Ottawa Scale was used to evaluate the methodological quality of included studies. RevMan was used to perform the meta-analysis and detect publication bias. Sensitivity analyses were also performed. Results Five studies that involved 2,343 subjects were finally included in the meta-analysis. The results showed that there was no significant association between central retinal artery equivalents (Z=1.17) or central retinal venular equivalents (Z=1.74) and cognitive impairment (both p>0.05). Similarly, no significant difference was detected in retinal arteriolar tortuosity (Z=0.91) and venular tortuosity (Z=1.31) (both p>0.05). However, the retinal arteriolar FD (mean difference: -0.03, 95% CI: -0.05, -0.01) and venular FD (mean difference: -0.03, 95% CI: -0.05, -0.02) were associated with cognitive impairment. Conclusions A smaller retinal microvascular FD might be associated with cognitive impairment. Further large-sample and well-controlled original studies are required to confirm the present findings.