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s: Arc detection is difficult for processing, assembly and testing of industrial production because of limitations of detection methods, algorithms and instruments. The least-squares algorithm is used to fit data in circle detection. The application of conventional least-squares algorithm is limited, as roundness error is bigger, precision is lower. For detecting arc with data points of non-uniform distribution, improved least-squares algorithm, developed an analysis algorithm for assessing the minimum zone roundness error. Center and radius can be solved, without iteration and truncation error. Using the discrete data instances verified different roundness error evaluation methods. Visual measurements have been carried out using the proposed methods. Calculated results using the four kinds of roundness error evaluation methods (Figure 7-10). Ball diameter errors are-0.0245mm、0.0176mm、-0.1052mm and 0.302mm, roundness errors are 0.07mm、0.063mm、0.078mm and 0.146mm. The improved least-squares algorithm and the minimum zone algorithm are suitable for distributed data of all kinds situations, particularly suitable for the realization of machine vision inspection system, fast speed, high precision, wide application.

This paper describes the importance of increasing control of technology and quality of road bridge construction and puts forwards effective measures to control the proposed road bridge construction technology and quality. Road bridge engineering is a basic livelihood projects while also ensuring economic and social development, but in recent years the reports about the quality of bridge construction repeatedly appeared in press which highlighting the poor construction quality control.

s.The least-squares algorithm is usually used to fit data in circle detection. The application of the conventional least-squares algorithm is limited, its’ roundness error is bigger, and precision is lower. For detecting circle with data points of non-uniform distribution, developed an analysis algorithm for assessing the minimum zone roundness error. Center and radius can be accurately solved, without iteration, without truncation error. Visual measurements have been carried out for known diameter D=2.564mm tooth shape chain board’s aperture using the proposed methods, calculated results (Table 1) using four kinds of roundness error evaluation methods. Tooth shape chain board’s aperture diameter errors are 0.0157mm、0.0126mm、0.0117 mm and 0.0218mm, roundness errors are 0.0251 mm、0.0225mm、0.0228mm and 0.0244mm respectively. The minimum zone algorithm are suitable for distributed data of all kinds situation, particularly suitable for the realization of machine vision inspection system, fast speed for high precision, wide range of application.

In the automatic assembly of locks system the pins’ selection depends on depth of key’s groove. Although the kinds of groove’s depth are fixed, the arrangements are random and they can’t be unpredictable. The difference in depth of key’s groove is very small, so it can’t be judged by eyes accurately. To solve the problem that the pins assembly is tried frequently, the depth of keys’ groove can be measured accurately by the machine vision. So the problem of the serious influence production efficiency is solved successfully. This kind lock is widely used and machine’s cost is very low by allocation. The experiments show that this method fully met the locks automatic assembly system requirements from the assembly precision, real time performance and robustness and other aspects, solving the problems encountered in the lock assembly.

This paper proposes a new kind of detection method based on CCD to measure geometry sizes and roundness error of chain board of roller chain. Image is collected, and is input into computer, then is processed by a series of steps such as grey level transformation, image smoothness, lower filtration, and threshold value selection, etc. The measurement of the geometric parameters and the roundness error relies on the image contour. Roundness error is evaluated by Minimum Region Law. The diameter of the holes and the distance between the axes of two holes are calculated and measured by self-developed program. Roundness error of chain board is less than 8μm, and the distance error between the axes of two holes is 9μm. The diameters of the holes are 4.467mm and 4.461mm respectively. The reasons of measurement error are also analyzed. Theory analyses and experiment show that it is feasible to measure the geometric sizes and roundness error of roller chain by this method, which is both efficient and practicable.

Background Family influence plays an important role in a child’s physical activity (PA). This study aimed to describe the level of moderate to vigorous intensity physical activity (MVPA) and sedentary behaviours among Chinese junior high school students and examine the associations between different types of family influence and MVPA or sedentary behaviours. Methods Participants of two independent cross-sectional surveys, conducted in 2009 and 2011, were students in Grade 7 and 9 from all junior high schools in Hangzhou, China. The daily duration and frequency of MVPA, amount of sedentary time and frequency of family support were self-reported. Multi-level mixed-effects logistic regression was used to examine the associations between different types or levels of family influence and MVPA or sedentary behaviours. Results A total of 7286 students were analysed finally. Overall, only 9.0% of the students participated in MVPA at least 60 minutes/day; 63.9% spent no more than 2 hours/day in sedentary behaviours. Frequent verbal encouragement and watching were associated with less leisure-time sedentary behaviours. The multivariate-adjusted odds ratios (ORs) for verbal encouragement and watching were 1.29 (95% CI, 1.08 to 1.55) and 1.19 (95% CI, 0.97 to 1.45) for 5-7 days per week. The involvement of family in the children’s activity in most days of the week was associated with both higher level of MVPA and less leisure-time sedentary behaviours. The respective ORs among students who reported familial support 5-7 days per week, were 1.50 (95% CI, 1.21 to 1.86) for engaging in seven days of MVPA per week, 1.67 (95% CI, 1.19 to 2.32) for at least 60 minutes of MVPA daily, and 1.48 (95% CI, 1.19 to 1.84) for no more than 2 hours of leisure-time sedentary behaviours daily. Conclusions This study found that less than 10.0% of urban Chinese adolescents engaged in MVPA at least 60 minutes/day. Family involving themselves in the children’s activity exerted the most significant influence on children’s behaviours as compared with verbally encouraging and observing children’s activity. Any type of familial support including verbally encouraging, watching, and involving had effects on reducing leisure-time sedentary behaviours. Electronic supplementary material The online version of this article (doi:10.1186/s12889-015-1593-9) contains supplementary material, which is available to authorized users.

Discussed ordinary image processing technology of inverted tooth chain board, including noise reduction, image segmentation, edge detection and contour extraction etc.. Put forward a new kind of sub-pixel arithmetic for edge orientation of circle. The arithmetic first did edge detection to image by Canny arithmetic, so as to enhance primary orientation precision of edge, then calculated gradient direction, and then interpolated gradient image (image that was detected by Sobel arithmetic) along gradient direction, last obtained sub-pixel orientation of edge. Performed two kinds of least-square fitting methods for line edge to getting its sub-pixel orientation, from analysis and experiments, the orientation error of improved least-square linear fitting method was one quarter of ordinary least-square linear fitting error under small difference of orientation time. The sub-pixel orientation of circle made resolution of CCD increase 42 tines, which enhanced greatly orientation precision of image edge. For the need of quick on-line inspection next step, integrated the whole environment containing image preprocess, Hough conversion of line, setting orientation & direction of image, sub-pixel orientation of line and circle, output of calculation result. The whole quick processing course performed without operator, processing tine of single part is less than 0.3 second. The sub-pixel orientation method this paper posed fits precision orientation of image, and integration calculation method ensure requirement of quick inspection, and lays the foundations for on-line precision visual measurement of image.