Microscale crack propagation in shale samples using focused ion beam scanning electron microscopy and three-dimensional numerical modeling

Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources.Complex fracture networks need to be artificially created to employ deep shale oil and gas reserves.Randomly distributed minerals and heterogeneities in shales significantly affect mechanical properties and fracturing behaviors in oil and gas exploitation.Describing the actual microstructure and associated heterogeneities in shales constitutes a significant challenge.The RFPA3D(rock failure process analysis parallel computing program)-based modeling approach is a promising numerical technique due to its unique capability to simulate the fracturing behavior of rocks.To improve traditional numerical technology and study crack propagation in shale on the microscopic scale,a combination of high-precision internal structure detection technology with the RFPA^(3D) numerical simulation method was developed to construct a real mineral structure-based modeling method.First,an improved digital image processing technique was developed to incorporate actual shale microstructures(focused ion beam scanning electron microscopy was used to capture shale microstructure images that reflect the distri-butions of different minerals)into the numerical model.Second,the effect of mineral inhomogeneity was considered by integrating the mineral statistical model obtained from the mineral nanoindentation experiments into the numerical model.By simulating a shale numerical model in which pyrite particles are wrapped by organic matter,the effects of shale microstructure and applied stress state on microcrack behavior and mechanical properties were investigated and analyzed.In this study,the effect of pyrite particles on fracture propagation was systematically analyzed and summarized for the first time.The results indicate that the distribution of minerals and initial defects dominated the fracture evolution and the failure mode.Cracks are generally initiated and propagated along the boundaries of hard mineral particles such as pyrite or in soft minerals such as organic matter.Locations with collections of hard minerals are more likely to produce complex fractures.This study provides a valuable method for un-derstanding the microfracture behavior of shales.

Online application of automatic surface quality inspection system to finishing line of cold rolled strips

An automatic surface quality inspection system installed on a finishing lineof cold rolled strips is introduced. The system is able to detect surface defects on cold rolledstrips, such as scratches, coil breaks, rusts, roll imprints, and so on. Multiple CCD area scancameras were equipped to capture images of strip surface simultaneously. Defects were detectedthrough 'Dark-field illumination' which is generated by LED illuminators. Parallel computationtechnique and fast processing algorithms were developed for real-time data processing. Theapplication to the production line shows that the system is able to detect defects effectively.

Digitizer of astronomical plates at Shanghai Astronomical Observatory and its performance test

Before CCD detectors were widely employed in observational astronomy, the main method of detection was the use of glass astrophotographic plates. Astronomical plates have been used to record information on the position and activity of celestial bodies for more than 100 years. There are about 30 000 astronomical plates in China, and the digitization of astronomical plates is of great significance for permanent preservation and to make full use of these valuable observation data. A digitizer with high precision and high measuring speed is a key piece of equipment for carrying out the task of dig- itizing these astronomical plates. A digitizer for glass astrophotographic plates was developed jointly by Shanghai Astronomical Observatory and Nishimura Co., Ltd of Japan. The digitizer＇s hardware was manufactured by Nishimura Co., Ltd, and the performance test, error corrections as well as image pro- cessing of the digitizer were carried out by Shanghai Astronomical Observatory. The main structure and working mode of the digitizer are introduced in this paper. A performance test shows that brightness uniformity of illumination within the measuring area is better than 0.15%, the repeatability of digitized positions is better than 0.2 μm and the repeatability of digitized brightness is better than 0.01 instrumen- tal magnitude. The systematic factors affecting digitized positions, such as lens distortion, the actual optical resolution, non-linearity of guide rails, non-uniformity of linear motors in the mobile platform, deviation of the image mosaic, and non-orthogonality between the direction of scanning and camera lin- ear array, are calibrated and evaluated. Based on an astronomical plate with a size of 300 mm × 300 mm, which was digitized at different angles, the conversion residuals of positions of common stars on dif- ferent images were investigated. The results show that the standard deviations of the residuals are better than 0.9μm and the residual distribution is almost random, which demonstrates the digitizer has a higher precision for digitization.

Matching CCD images to a stellar catalog using locality-sensitive hashing

The usage of a subset of observed stars in a CCD image to find their corresponding matched stars in a stellar catalog is an important issue in astronomical research. Subgraph isomorphic-based algorithms are the most widely used methods in star catalog matching. When more subgraph features are provided, the CCD images are recognized better. However, when the navigation feature database is large, the method requires more time to match the observing model. To solve this problem, this study investigates further and improves subgraph isomorphic matching algorithms. We present an algorithm based on a locality-sensitive hashing technique, which allocates quadrilateral models in the navigation feature database into different hash buckets and reduces the search range to the bucket in which the observed quadrilateral model is located. Experimental results indicate the effectivity of our method.

NUV Star Catalog from the Lunar-based Ultraviolet Telescope Survey: First Release

We present a star catalog extracted from the Lunar-based Ultraviolet Telescope （LUT） survey program. LUT＇s observable sky area is a circular belt around the Moon＇s north pole, and the survey program covers a preferred area of about 2400 deg2 which includes a region of the Galactic plane. The data are processed with an automatic pipeline which copes with stray light contamination, artificial sources, cosmic rays, flat field calibration, photometry and so on. In the first release version, the catalog provides high confidence sources which have been cross-identified with the Tycho-2 catalog. All the sources have signalto-noise ratio larger than 5, and the corresponding magnitude limit is typically 14.4 mag, but can be as deep as -16 mag if stray light contamination is at the lowest level. A total of 86 467 stars are recorded in the catalog. The full catalog in electronic form is available online.

THE APPLICATION OF FOURIER TRANSFORM IN REGULARIZED SPECKLE PHOTOGRAPHY

Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can be calculated by using the Fouriertransform. The expression of displacement field is deduced fornon-uniform displacement, and as an example, a rotatanle disc istested for illustration. The re- sults prove that the present methodis promising.

Visual object tracking- classical and contemporary approaches

Visual object tracking （VOT） is an important sub- field of computer vision. It has widespread application do- mains, and has been considered as an important part of surveillance and security system. VOA facilitates finding the position of target in image coordinates of video frames. While doing this, VOA also faces many challenges such as noise, clutter, occlusion, rapid change in object appearances, highly maneuvered （complex） object motion, illumination changes. In recent years, VOT has made significant progress due to availability of low-cost high-quality video cameras as well as fast computational resources, and many modern techniques have been proposed to handle the challenges faced by VOT. This article introduces the readers to 1） VOT and its applica- tions in other domains, 2） different issues which arise in it, 3） various classical as well as contemporary approaches for object tracking, 4） evaluation methodologies for VOT, and 5） online resources, i.e., annotated datasets and source code available for various tracking techniques.