Failure characteristic and fracture evolution law of overburden of thick coal in fully mechanized sub-level caving mining

In mining process, the height of water flowing fractured zone is important significance to prevent mine of water and gas, in order to further research the failure characteristic of the overlying strata. Taking certain coal mine with 5.82 m mining height as the experimental face, by using the equipment which is sealed two ends by capsules in borehole, affused measurable water between the two capsules and borehole televiewer system, ground penetrating radar, microseismic monitoring system in underground coal mine, the height of water flowing fractured zone of fully-mechanized top caving are monitored, a numerical simulation experiment on the failure process was conducted, a similarity simulation experiment on the cracks evolution was conducted, at the same time, empirical formula of traditional was modified, The results showed that the height of caving and fractured zones were respectively 43.1 and 86.7 m in fully mechanized sub-level caving mining. The data difference of each test method of caving, fractured and water flowing fractured zones were respectively less than 4.5%, 7.1% and 9.0%. The degree of fracture development was low before mining, the number of fissures was obviously increased after mining, the degree of fracture development increased. The fractures cluster region mainly focuses near the coal wall. The fractures density distribution curves of overlying strata like sanke-shapes. The new and adapt to certain coal mine geological conditions empirical formula of water flowing fractured zone height is proposed

Effects of different intrusion patterns during anterior teeth retraction using clear aligners in extraction cases: an iterative finite element analysis

BackgroundOvertreatment design of clear aligner treatment (CAT) in extraction cases is currently primarily based on the clinical experience of orthodontists and is not supported by robust evidence on the underlying biomechanics. This study aimed to investigate the biomechanical effects of overtreatment strategies involving different maxillary anterior teeth intrusion patterns during anterior teeth retraction by CAT in extraction cases.Materials and methodsA finite element model of the maxillary dentition with the first premolar extracted was constructed. A loading method of clear aligners (CAs) based on the initial state field was proposed. The iterative method was used to simulate the long-term orthodontic tooth movement under the mechanical load exerted by the CAs. Three groups of CAs were utilized for anterior teeth retraction (G0: control group; G1: incisors intrusion group; G2: anterior teeth intrusion group). Tooth displacement and occlusal plane rotation tendency were analyzed.ResultsIn G0, CAT caused lingual tipping and extrusion of the incisors, distal tipping and extrusion of the canines, mesial tipping, and intrusion of the posterior teeth. In G1, the incisors showed minimal extrusion, whereas the canines showed increased extrusion and distal tipping tendency. G2 showed the smallest degree of posterior occlusal plane angle rotation, while the inclination tendency of the canines and second premolars decreased.Conclusion1. In CAT, tooth displacement tendency may change with increased wear time. 2. During anterior teeth retraction, the incisor intrusion pattern can provide effective vertical control for the lateral incisors but has little effect on the central incisors. Anterior teeth intrusion patterns can alleviate the inclination of canines and second premolars, resulting in partial relief of the roller-coaster effect

Fractal characteristics of reservoir structural fracture: a case study of Xujiahe Formation in central Yuanba area, Sichuan Basin

The reservoir structural fractures have excellent fractal characteristics, as well as self-similarities. Based on the fractal theory, the surface fractal characteristics of faults and the fractal characteristic of fractures in the core of the Xujiahe Formation in the Fault-Fold Belt of the central Yuanba area were studied, and a quantitative relationship was set up between them. Based on the fractal characteristics of faults, predictions were made of the favorable fracture zone, which provides a new idea for the research of fracture, as well as offers theoretical references for exploring the fracture development zone during oil-gas exploration. The results show the following: the seismic value of reflection fault fractal dimension of the Xujiahe Formation is 1.5284; the correlation coefficient R2 is bigger than 0.9901; the capacity dimension linear regression correlation coefficient of the fracture in core of the Xujiahe Formation is bigger than 0.98; the fractal dimension D can well reflect the fault and fracture development degree, as well as the complexity of the fracture system; it can quantitatively calculate the density of the fracture of the reservoir in the area; the areas of capacity dimension bigger than 1.45 are the fracture development zones in the Fault-Fold Belt of the central Yuanba area; the oil and gas enrichment degree is high; the areas with the fractal dimension value between 0.95 and 1.45 are the fracture relatively-developed zones; the fractal dimension with values smaller than 0.95 are the lack of fracture areas.Las fracturas estructurales de yacimientos tienes excelentes características fractales y autosimilares. Basados en la teoría fractal, se estudiaron las características fractales superficiales de las fallas y las características fractales de las fracturas en el núcleo del Cinturón Falla-Pliegue de la Formación Xujiahe, área central de Yuanba (China). Luego se estableció una relación cuantitativa para estas relaciones. Según las características fractales de las fallas, se predijo la zona favorable de fractura, lo que ofrece una nueva idea para el conocimiento de esta y a la vez brinda referencias teóricas para la exploración de la zona de desarrollo de la fractura durante la exploración de petróleo y gas. Los resultados muestran lo siguiente: el valor sísmico de la dimensión fractual de la falla en la Formación Xujiahe es de 1.5284; el coeficiente de correlación R2 es mayor a 0.99901; la dimensión del coeficiente de correlación de regresión lineal en el núcleo de la fractura de la Formación Xujiahe es mayor a 0.98; la dimensión fractal D puede reflejar la falla y el grado de desarrollo de la fractura, al igual que la complejidad del sistema de fractura; también puede calcular cuantitativamente la densidad de la fractura del yacimiento en el área; las áreas con capacidad mayor a 1.45 son las zonas de desarrollo de la fractura en el Cinturón Falla-Pliegue del área central de Yuanba; el grado de enriquecimiento de petróleo y gas es alta; las áreas con valor de dimensión fractal entre 0.95 y 1.45 son las zonas de fractura de desarrollo relativo; la dimensión fractal con valores menos a 0.95 son las áreas que carecen de fracturas

Fractures in Volcanic Reservoir: a case study of Zhongguai uplift in Northwestern Margin of Junggar Basin, China

Fractures in Carboniferous volcanic rocks located at Zhongguai Area (China) highly influence the accumulation and productivity of oil and gas. As such, the study of development periods and genetic mechanisms of tectonic fractures could throw useful information regarding the evaluation and development of that reservoir. Their tectonic origins caused high-angle and oblique shear fractures. The primary orientation of those fractures appears close to EW (270°±10°), NW (300°±15°), NE (45°±15°), and SN (0°±10°). At least four fracture generations can be found in Carboniferous volcanic rocks at Zhongguai Area. Combined with a tectonic evolution, they are based on the segmentation relationship of the fracture fillings, the thermometry measurement of the fracture filling inclusion, and the acoustic emission, as well. Affected by a new horizontal principal stress, the opening and permeability of nearly EW fractures are the best. In this way, a priority in the development of well's patterns should be considered close to EW fractures. The pressure change in the process of exploitation may damage the reservoir permeability of fractured volcano rocks severely. Accordingly, well patterns should be adjusted to dynamic changes of permeability happened during the oilfield development since some differences have been detected in distinct fracture sets

Comprehensive prediction of fractures distribution: A case study of Badaowan Formation of Baka Oilfield, Turban-Hami Basin, China

2042-2048Development of fractures have important influence on migration and accumulation of the hydrocarbon. Taking the Badaowan Formation of Baka Oilfield, Turban-Hami Basin as an example, Comprehensive prediction of fractures by weighting assessment was performed based on three fracture prediction method. Fractures are influenced by two tectonic movements. The main orientation of fractures lie in NWW (280°±10°), NNE (20°±10°) and NNW (330°±10°). Fractures of NWW and NNE are better validity because of its consistence or seam at small angles with present maximum principal stress, less filled degree and larger aperture. Comprehensive prediction of the fractures distribution shows that the fractures are mainly developed in Ke20~Ke23 well area, the high point of the footwall of the KEKEYA fault, Ke22 ~Ke19 well area, Ke34 well area, the area of south of Ke21,the area of west of Ke26, Ke32 well area and Ke24 well area. The comprehensive prediction technology effectively improves the accuracy and reliability of fracture distribution

Reforming intellectual property rights and the Bt cotton seed industry in China: Who benefits from policy reform?

China has been one of the leaders in agricultural biotechnology research and the adoption of transgenic plants. Despite this, critics argue that China's biotechnology policies could be improved to provide more benefits to farmers. The objective of the paper is to examine if policy changes could improve the welfare of farmers in the cotton industry. The paper first reviews recent changes in laws and policies that affect China's plant biotechnology sector--with a focus on IPR legislation and seed industry reform. Next, using a primary data set collected from 1661 plots from a sample of farmers in northern China in 1999, 2000 and 2001, we econometrically estimate the effect of changes to intellectual property rights (IPR) and seed industry reform on farmer pesticide use and yields. Our results are consistent with a conclusion that improvements to the IPR environment and greater commercialization of the seed industry can increase the benefits that farmers derive from new cotton technology.Biotechnology Intellectual property rights Seed industry China

Reforming intellectual property rights and the Bt cotton seed industry in China: Who benefits from policy reform?

China has been one of the leaders in agricultural biotechnology research and the adoption of transgenic plants. Despite this, critics argue that China's biotechnology policies could be improved to provide more benefits to farmers. The objective of the paper is to examine if policy changes could improve the welfare of farmers in the cotton industry. The paper first reviews recent changes in laws and policies that affect China's plant biotechnology sector-with a focus on IPR legislation and seed industry reform. Next, using a primary data set collected from 1661 plots from a sample of farmers in northern China in 1999, 2000 and 2001, we econometrically estimate the effect of changes to intellectual property rights (IPR) and seed industry reform on farmer pesticide use and yields. Our results are consistent with a conclusion that improvements to the IPR environment and greater commercialization of the seed industry can increase the benefits that farmers derive from new cotton technology. © 2008 Elsevier B.V

Fractal characteristics of reservoir structural fracture: a case study of Xujiahe Formation in central Yuanba area, Sichuan Basin

The reservoir structural fractures have excellent fractal characteristics, as well as self-similarities. Based on the fractal theory, the surface fractal characteristics of faults and the fractal characteristic of fractures in the core of the Xujiahe Formation in the Fault-Fold Belt of the central Yuanba area were studied, and a quantitative relationship was set up between them. Based on the fractal characteristics of faults, predictions were made of the favorable fracture zone, which provides a new idea for the research of fracture, as well as offers theoretical references for exploring the fracture development zone during oil-gas exploration. The results show the following: the seismic value of reflection fault fractal dimension of the Xujiahe Formation is 1.5284; the correlation coefficient R2 is bigger than 0.9901; the capacity dimension linear regression correlation coefficient of the fracture in core of the Xujiahe Formation is bigger than 0.98; the fractal dimension D can well reflect the fault and fracture development degree, as well as the complexity of the fracture system; it can quantitatively calculate the density of the fracture of the reservoir in the area; the areas of capacity dimension bigger than 1.45 are the fracture development zones in the Fault-Fold Belt of the central Yuanba area; the oil and gas enrichment degree is high; the areas with the fractal dimension value between 0.95 and 1.45 are the fracture relatively-developed zones; the fractal dimension with values smaller than 0.95 are the lack of fracture areas