A simple uniaxial oedometric system is developed to test the elastic modulus of granular materials. The stress- strain relationship is first measured under conditions of uniaxial compression with additional lateral st...A simple uniaxial oedometric system is developed to test the elastic modulus of granular materials. The stress- strain relationship is first measured under conditions of uniaxial compression with additional lateral stress and strain, then the elastic modulus of the material is determined by the linear fitting method. It is found that the modulus is positively correlated to the grain size and negatively correlated to the container size. Arching and dragging are revealed to be the mechanism of such correlations by using the digital image correlation method and the pressure film technology based on the statistical method.展开更多
In recent years, cloud sync（hronization） services such as GoogleDrive and Dropbox have provided Internet users with convenient and reliable data storing/sharing functionality. The cloud synchronization mechanism （i...In recent years, cloud sync（hronization） services such as GoogleDrive and Dropbox have provided Internet users with convenient and reliable data storing/sharing functionality. The cloud synchronization mechanism （in particular, how to deliver the user-side data updates to the cloud） plays a critical role in cloud sync services because it greatly affects the cloud operation cost （in terms of sync traffic） and user experience （in terms of sync delay）. By comprehensively measuring tens of popular cloud sync services, we find that their cloud sync mechanisms differ greatly in sync performance and design granularity. Quite surprisingly, some very popular services （like GoogleDrive and 115 SyncDisk） utilize a quite coarse-grained cloud sync mechanism that may lead to severe traffic overuse. For example, updating 1-MB data may sometimes result in 260-MB sync traffic. In this paper, we conduct a comparative study of various cloud sync mechanisms by analyzing their respective pros and cons under different situations, unravel the pathological processes for their traffic overuse problems, and finally provide insights/solutions for better choosing/designing a cloud sync service.展开更多
Industrial mixers for powders and granular materials operate with no effective control of mixture quality and lack scientific design. The last twenty years have seen growth in understanding of mixing and mixers. Howev...Industrial mixers for powders and granular materials operate with no effective control of mixture quality and lack scientific design. The last twenty years have seen growth in understanding of mixing and mixers. However, research falls far short of what is needed for on-line characterisation of mixture quality. Secondly, although theoretical descriptions of a few mixer types have been reported, these fall far short of what is needed for equipment design. Two thrusts could revolutionise this situation. One is a scientific characterisation of mixer structure applicable to industrial scale as well as laboratory scale equipment; this is now within our grasp using digital imaging. The other is the development of ideas to overcome the restricted number of particles that can be used in the Distinct Element Method （DEM） for mixers. The goal should be to take the designer through a sequence of steps to the most appropriate mixer size, configuration and operating conditions for a given process duty.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11372038 and 11402023
文摘A simple uniaxial oedometric system is developed to test the elastic modulus of granular materials. The stress- strain relationship is first measured under conditions of uniaxial compression with additional lateral stress and strain, then the elastic modulus of the material is determined by the linear fitting method. It is found that the modulus is positively correlated to the grain size and negatively correlated to the container size. Arching and dragging are revealed to be the mechanism of such correlations by using the digital image correlation method and the pressure film technology based on the statistical method.
基金supported in part by the National Natural Science Foundation of China (No. 61073015)the National Key Basic Research and Development (973) Program of China (No. 2011CB302305)National Key Projects of Science and Technology of China (No.2010ZX03004-001-03)
文摘In recent years, cloud sync（hronization） services such as GoogleDrive and Dropbox have provided Internet users with convenient and reliable data storing/sharing functionality. The cloud synchronization mechanism （in particular, how to deliver the user-side data updates to the cloud） plays a critical role in cloud sync services because it greatly affects the cloud operation cost （in terms of sync traffic） and user experience （in terms of sync delay）. By comprehensively measuring tens of popular cloud sync services, we find that their cloud sync mechanisms differ greatly in sync performance and design granularity. Quite surprisingly, some very popular services （like GoogleDrive and 115 SyncDisk） utilize a quite coarse-grained cloud sync mechanism that may lead to severe traffic overuse. For example, updating 1-MB data may sometimes result in 260-MB sync traffic. In this paper, we conduct a comparative study of various cloud sync mechanisms by analyzing their respective pros and cons under different situations, unravel the pathological processes for their traffic overuse problems, and finally provide insights/solutions for better choosing/designing a cloud sync service.
文摘Industrial mixers for powders and granular materials operate with no effective control of mixture quality and lack scientific design. The last twenty years have seen growth in understanding of mixing and mixers. However, research falls far short of what is needed for on-line characterisation of mixture quality. Secondly, although theoretical descriptions of a few mixer types have been reported, these fall far short of what is needed for equipment design. Two thrusts could revolutionise this situation. One is a scientific characterisation of mixer structure applicable to industrial scale as well as laboratory scale equipment; this is now within our grasp using digital imaging. The other is the development of ideas to overcome the restricted number of particles that can be used in the Distinct Element Method （DEM） for mixers. The goal should be to take the designer through a sequence of steps to the most appropriate mixer size, configuration and operating conditions for a given process duty.
