传统的以数据为中心的路由协议,往往会导致传感网中出现在大量的"能量空洞"或"热点"现象。为了克服上述现象,借助雾计算理论模型,提出了一种基于雾计算跨层感知分簇路由协议(A Cross-layer-sensing Clustering Rout...传统的以数据为中心的路由协议,往往会导致传感网中出现在大量的"能量空洞"或"热点"现象。为了克服上述现象,借助雾计算理论模型,提出了一种基于雾计算跨层感知分簇路由协议(A Cross-layer-sensing Clustering Routing Protocol Based on Fog Computing,CCRP)。该协议通过跨层映射原理,利用感知事件驱动机制将雾节点映射到传感层,构成功能强大的虚拟控制节点,将传感网分簇路由协议的控制过程上传至雾层,通过雾计算实现事件域节点分布式成簇路由汇聚中心,从而建立以映射雾节点为中心的优化数据聚合路由,取代传感网底层路由中的数据,进一步平衡并减少网络负载。在路由协议优化阶段,利用粒子群优化算法(Particle Swarm Optimizations,PSO)采用无竞争开销方式选举一组最佳节点担任簇首,能有效地均衡全网能量的开销,抑制传感器节点能量的快速消耗,延长了网络生存周期。仿真实验表明,CCRP协议能够有效抑制网络开销的同时还可以高效完成对数据的优化过程。展开更多
Following the recent proposal by Briegel et al. [Phys. Rev. Lett. 86 （2001） 910], a procedure is proposed for one-step realizing quantum control phase gates with two trapped ions in thermal motion. It is shown that ...Following the recent proposal by Briegel et al. [Phys. Rev. Lett. 86 （2001） 910], a procedure is proposed for one-step realizing quantum control phase gates with two trapped ions in thermal motion. It is shown that the scheme can also be used to create a new special type of entangled states, i.e., cluster states of many trapped ions. In the scheme the two-trapped ions are simultaneously excited by a single laser beam and the frequency of the laser beam is slightly off resonance with the first lower vibration sideband of the trapped ions. The distinct advantage of the scheme is that it does not use the vibrational mode as the data bus. Furthermore, our scheme is insensitive to both the initial motional state and heating （or decay） as long as the system remains in the Lamb-Dicke regime.展开更多
Airborne transmission is an important mechanism of spread for both viruses and bacteria in hospitals,with nosocomial infections putting a great burden on public health.In this study,we designed and manufactured a bed ...Airborne transmission is an important mechanism of spread for both viruses and bacteria in hospitals,with nosocomial infections putting a great burden on public health.In this study,we designed and manufactured a bed for pediatric clinic consultation rooms providing air isolation to protect patients and medical personnel from pathogen transmission.The pediatric isolation bed has several primary efficiency filters and a high-efficiency particulate air filter in the bedside unit.The air circulation between inlet and outlet forms negative pressure to remove the patient's exhaled air timeously and effectively.A computational fluid dynamics model was used to calculate the speed of the airflow and the angle of sampler.Following this,we conducted purification experiments using cigarette smoke,Staphylococcus albus(S.albus)and human adenovirus type 5(HAdV-5)to demonstrate the isolation efficacy.The results showed that the patient's head should be placed as close to the air inlet hood as possible,and an air intake wind speed of 0.86 m/s was effective.The isolation efficacy of the pediatric isolation bed was demonstrated by computational fluid dynamics technology.The isolation efficiency against cigarette smoke exceeded 91.8%,and against S.albus was greater than 99.8%,while the isolation efficiency against HAdV-5 was 100%.The pediatric isolation bed could be used where isolation wards are unavailable,such as in intensive care units and primary clinical settings,to control hospital acquired infections.展开更多
In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical obj...In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical objects: circles and spheres for two-dimensional and three-dimensional cases, respectively. The mechanism of interaction between the liquid particles on a binary level and on the level of the n-cluster is formulated. This mechanism has previously been found by the author as part of the mathematical modeling of turbulent fluid motion. In the turbulence model was derived and investigated the potential interaction of pairs of liquid particles, which contained a singularity of the branch point. Exactly, this is possible to build in this article discrete stochastic-deterministic model of an ideal fluid. The results of computational experiment to simulate various kinds of flows in two-dimensional and three-dimensional ensembles of liquid particles are presented. Modeling was carried out in the areas of quadratic or cubic form. On boundary of a region satisfies the condition of elastic reflection liquid particles. The flows with spontaneous separation of particles in a region, various kinds of eddy streams, with the quite unexpected statistical properties of an ensemble of particles characteristic for the Fermi-Pasta-Ulam effect were found. We build and study the flow in which the velocity of the particles is calibrated. It was possible using the appropriate flows of liquid particles of the ensemble to demonstrate the possibility to reproduce any prescribed image by manipulating the parameters of the interaction. Calculations of the flows were performed with using MATLAB software package according to the algorithms presented in this article.展开更多
An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole.Therefore,suitable simulation models are necessary to eval...An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole.Therefore,suitable simulation models are necessary to evaluate new tool designs and optimize drilling processes.In this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed microscopy.Micro particles are added to the cutting fluid circuit bya developed high-pressure mixing vessel.After the evaluation of suitable particle size,particle concentration and coolant pressure,a computational fluid dynamics(CFD)simulation is validated with the experimental results.The comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57%between simulation and experiment.The simulation considers the kinematic viscosity of the fluid.The results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between theguidechamfers.Theflow velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or lubrication.With the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is achieved.Based on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.展开更多
目的探讨在低剂量CT(100m A)引导下^(125)I粒子植入治疗恶性肿瘤的临床应用价值。方法收集2010年1月至2015年5月恶性肿瘤及转移病例29例,分为低剂量CT(100 m A)定位引导下治疗组(13例)及常规剂量CT引导下(250 m A)^(125)I放射性粒子植...目的探讨在低剂量CT(100m A)引导下^(125)I粒子植入治疗恶性肿瘤的临床应用价值。方法收集2010年1月至2015年5月恶性肿瘤及转移病例29例,分为低剂量CT(100 m A)定位引导下治疗组(13例)及常规剂量CT引导下(250 m A)^(125)I放射性粒子植入治疗恶性肿瘤治疗组(16例)。术前采用肿瘤治疗计划系统(Treatment Planning System,TPS)重建恶性肿瘤的三维立体图像,计算出所需粒子数目及总活度。单个病灶植入粒子数目5~76粒,平均粒子数36粒。单个粒子活度为0.5~0.9 m Ci,粒子间距为0.5~1.0 cm。常规消毒麻醉,在CT引导下选择合适穿刺点、进针角度及路径后行肿瘤病灶内^(125)I放射性粒子植入。记录CT扫描仪自动显示扫描加权容积CT剂量指数(weighted CT dose index volume,CTDIvol)、剂量长度乘积(dose-length product,DLP)并计算有效剂量(effective dose,ED),比较两种不同剂量下CT扫描在有效剂量(ED)、图像质量、穿刺植入成功率及近期疗效方面有何差异。结果低剂量CT引导植入治疗组的CTDlvol中位值为7.3 m Gy,DLP中位值为423 m Gy.cm,ED中位值为7.191 m Sv;常规剂量组CTDlvol中位值为18.3 m Gy,DLP中位值为1 089.6 m Gy.cm,ED中位值为18.52 m Sv;统计学结果示2组患者的辐射量差异有统计学意义(t=21.903,P<0.001);但在图像质量可接受性方面,2组患者的图像均为100%(评分均>2分);关于穿刺成功率及患者的近期疗效,低剂量组与常规剂量组相比差异无统计学意义(P>0.05)。结论低剂量CT(100 m A)扫描在减低患者辐射上意义显著,同时又保证了图像质量满足穿刺植入要求,由于采用了低剂量扫描,降低了CT机器的消耗,增加了机器的使用寿命,因此值得在临床上普遍开展。展开更多
The formation of a filter cake during the filtration of a suspension with non-spherical particles is studied using a multi-sphere model in a simulation that couples the discrete element method with computational fluid...The formation of a filter cake during the filtration of a suspension with non-spherical particles is studied using a multi-sphere model in a simulation that couples the discrete element method with computational fluid dynamics.The implementation of the coupling with a drag model that considers orientation,sphericity,and the presence of surrounding particles for non-spherical particles is tested for single particles and suspensions by comparing the terminal velocities with empirical results.Phenomena predicted in the simulations,such as the presence or absence of initial oscillations and changes in the orientation of a particle,are consistent with experimental observations reported in the literature.The variation in the void fraction of a filter cake with respect to the particle sphericity is obtained and compared with experimental trends reported in the literature.Furthermore,complex interdependencies of the particle sphericity,void fraction,and pressure drop of a filter cake for a wide range of fluid conditions are investigated.展开更多
Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells a...Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （CFD） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.展开更多
A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay.The aim of this testing program is to better understand the anisotropic deformation during the excavati...A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay.The aim of this testing program is to better understand the anisotropic deformation during the excavation.The testing conditions are similar to those to be experienced by host rocks around disposal galleries for radioactive waste.X-ray computed tomography is performed at different steps for each test with the samples remaining inside the loading cell.Initial analysis of the tomography images allows of the observation of the deformation of the central hole.In addition,particles manual tracking and 3D volumetric digital image correlation processing methods are considered being used to analyze the particles displacements and the boundary deformation of the sample quantitatively.An unsymmetrical damaged zone is induced around the hole,with a reverse deformation trend being found at the boundary after unloading,which indicates that the significant anisotropic deformation of boom clay can be induced by mechanical unloading.展开更多
Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle,...Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.展开更多
为实现占据多个流体网格的大颗粒在流场中运动的仿真,基于计算流体力学和离散单元法耦合(computational fluid dy namics-discrete element mothod,CFD-DEM),提出了一种新的数值方法。使用黏结颗粒模型将大颗粒近似表示为多个小球形颗...为实现占据多个流体网格的大颗粒在流场中运动的仿真,基于计算流体力学和离散单元法耦合(computational fluid dy namics-discrete element mothod,CFD-DEM),提出了一种新的数值方法。使用黏结颗粒模型将大颗粒近似表示为多个小球形颗粒黏结而成,基于非解析CFD-DEM方法计算流体对每个小球颗粒的作用力,将所有小球颗粒运动参数的平均值用于描述整个黏结颗粒的运动状态。通过黏性流体中球形大颗粒的沉降运动模拟,比较仿真结果与相关实验数据,结果表明:该方法不仅能准确模拟球形大颗粒的沉降运动,而且与浸没边界法相比计算效率更高。与传统的解析CFD-DEM方法相比,此方法还可以方便且准确地模拟三维情况下非球形大颗粒在流场中的运动。展开更多
In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian meth...In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian method. A modified structure-based drag model was developed based on our previous work. Other drag models including the Parker and Wen-Yo-Ergon drag models were also employed to investigate the effects of drag models on the simulation results. Although the modified structure-based drag model better predicts the gas-solid flow dynamics of a baffle-free bubbling fluidized bed in comparison with the experimental data, none of these drag models predict the gas-solid flow in a baffled bobbling floidized bed sufficiently well because of the treatment of baffles in the Barracuda software. To improve the simulation accuracy, future versions of Barracuda should address the challenges of incorporating the bed height and the baffles.展开更多
文摘传统的以数据为中心的路由协议,往往会导致传感网中出现在大量的"能量空洞"或"热点"现象。为了克服上述现象,借助雾计算理论模型,提出了一种基于雾计算跨层感知分簇路由协议(A Cross-layer-sensing Clustering Routing Protocol Based on Fog Computing,CCRP)。该协议通过跨层映射原理,利用感知事件驱动机制将雾节点映射到传感层,构成功能强大的虚拟控制节点,将传感网分簇路由协议的控制过程上传至雾层,通过雾计算实现事件域节点分布式成簇路由汇聚中心,从而建立以映射雾节点为中心的优化数据聚合路由,取代传感网底层路由中的数据,进一步平衡并减少网络负载。在路由协议优化阶段,利用粒子群优化算法(Particle Swarm Optimizations,PSO)采用无竞争开销方式选举一组最佳节点担任簇首,能有效地均衡全网能量的开销,抑制传感器节点能量的快速消耗,延长了网络生存周期。仿真实验表明,CCRP协议能够有效抑制网络开销的同时还可以高效完成对数据的优化过程。
基金Supported by the National Natural Science Foundation of China under Grant Nos 60478029, 90503010 and 10575040.
文摘Following the recent proposal by Briegel et al. [Phys. Rev. Lett. 86 （2001） 910], a procedure is proposed for one-step realizing quantum control phase gates with two trapped ions in thermal motion. It is shown that the scheme can also be used to create a new special type of entangled states, i.e., cluster states of many trapped ions. In the scheme the two-trapped ions are simultaneously excited by a single laser beam and the frequency of the laser beam is slightly off resonance with the first lower vibration sideband of the trapped ions. The distinct advantage of the scheme is that it does not use the vibrational mode as the data bus. Furthermore, our scheme is insensitive to both the initial motional state and heating （or decay） as long as the system remains in the Lamb-Dicke regime.
基金supported by grants from the National Key Research and Development Program of China(2018YFC1200100,2018YFC1200103)Guangdong Medical Science and Technology Research Center Project(A2019460)+5 种基金Entrepreneurship Leadership Project in Guangzhou Development Zone of China(CY2018-003)Guangzhou Science and Technology Project(202008040002)Scientific Research Project of Guangdong Province Traditional Chinese Medicine Bureau(20201191)Innovative and Strong School Project of Guangdong Provincial Department of Education(2020KZDZX1122)Guangdong Science and Technology Project(2020B111106001)Foshan Science and Technology Innovation Project(2020001000416).
文摘Airborne transmission is an important mechanism of spread for both viruses and bacteria in hospitals,with nosocomial infections putting a great burden on public health.In this study,we designed and manufactured a bed for pediatric clinic consultation rooms providing air isolation to protect patients and medical personnel from pathogen transmission.The pediatric isolation bed has several primary efficiency filters and a high-efficiency particulate air filter in the bedside unit.The air circulation between inlet and outlet forms negative pressure to remove the patient's exhaled air timeously and effectively.A computational fluid dynamics model was used to calculate the speed of the airflow and the angle of sampler.Following this,we conducted purification experiments using cigarette smoke,Staphylococcus albus(S.albus)and human adenovirus type 5(HAdV-5)to demonstrate the isolation efficacy.The results showed that the patient's head should be placed as close to the air inlet hood as possible,and an air intake wind speed of 0.86 m/s was effective.The isolation efficacy of the pediatric isolation bed was demonstrated by computational fluid dynamics technology.The isolation efficiency against cigarette smoke exceeded 91.8%,and against S.albus was greater than 99.8%,while the isolation efficiency against HAdV-5 was 100%.The pediatric isolation bed could be used where isolation wards are unavailable,such as in intensive care units and primary clinical settings,to control hospital acquired infections.
文摘In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical objects: circles and spheres for two-dimensional and three-dimensional cases, respectively. The mechanism of interaction between the liquid particles on a binary level and on the level of the n-cluster is formulated. This mechanism has previously been found by the author as part of the mathematical modeling of turbulent fluid motion. In the turbulence model was derived and investigated the potential interaction of pairs of liquid particles, which contained a singularity of the branch point. Exactly, this is possible to build in this article discrete stochastic-deterministic model of an ideal fluid. The results of computational experiment to simulate various kinds of flows in two-dimensional and three-dimensional ensembles of liquid particles are presented. Modeling was carried out in the areas of quadratic or cubic form. On boundary of a region satisfies the condition of elastic reflection liquid particles. The flows with spontaneous separation of particles in a region, various kinds of eddy streams, with the quite unexpected statistical properties of an ensemble of particles characteristic for the Fermi-Pasta-Ulam effect were found. We build and study the flow in which the velocity of the particles is calibrated. It was possible using the appropriate flows of liquid particles of the ensemble to demonstrate the possibility to reproduce any prescribed image by manipulating the parameters of the interaction. Calculations of the flows were performed with using MATLAB software package according to the algorithms presented in this article.
文摘An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole.Therefore,suitable simulation models are necessary to evaluate new tool designs and optimize drilling processes.In this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed microscopy.Micro particles are added to the cutting fluid circuit bya developed high-pressure mixing vessel.After the evaluation of suitable particle size,particle concentration and coolant pressure,a computational fluid dynamics(CFD)simulation is validated with the experimental results.The comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57%between simulation and experiment.The simulation considers the kinematic viscosity of the fluid.The results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between theguidechamfers.Theflow velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or lubrication.With the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is achieved.Based on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.
文摘目的探讨在低剂量CT(100m A)引导下^(125)I粒子植入治疗恶性肿瘤的临床应用价值。方法收集2010年1月至2015年5月恶性肿瘤及转移病例29例,分为低剂量CT(100 m A)定位引导下治疗组(13例)及常规剂量CT引导下(250 m A)^(125)I放射性粒子植入治疗恶性肿瘤治疗组(16例)。术前采用肿瘤治疗计划系统(Treatment Planning System,TPS)重建恶性肿瘤的三维立体图像,计算出所需粒子数目及总活度。单个病灶植入粒子数目5~76粒,平均粒子数36粒。单个粒子活度为0.5~0.9 m Ci,粒子间距为0.5~1.0 cm。常规消毒麻醉,在CT引导下选择合适穿刺点、进针角度及路径后行肿瘤病灶内^(125)I放射性粒子植入。记录CT扫描仪自动显示扫描加权容积CT剂量指数(weighted CT dose index volume,CTDIvol)、剂量长度乘积(dose-length product,DLP)并计算有效剂量(effective dose,ED),比较两种不同剂量下CT扫描在有效剂量(ED)、图像质量、穿刺植入成功率及近期疗效方面有何差异。结果低剂量CT引导植入治疗组的CTDlvol中位值为7.3 m Gy,DLP中位值为423 m Gy.cm,ED中位值为7.191 m Sv;常规剂量组CTDlvol中位值为18.3 m Gy,DLP中位值为1 089.6 m Gy.cm,ED中位值为18.52 m Sv;统计学结果示2组患者的辐射量差异有统计学意义(t=21.903,P<0.001);但在图像质量可接受性方面,2组患者的图像均为100%(评分均>2分);关于穿刺成功率及患者的近期疗效,低剂量组与常规剂量组相比差异无统计学意义(P>0.05)。结论低剂量CT(100 m A)扫描在减低患者辐射上意义显著,同时又保证了图像质量满足穿刺植入要求,由于采用了低剂量扫描,降低了CT机器的消耗,增加了机器的使用寿命,因此值得在临床上普遍开展。
基金The authors acknowledge financial support provided by Leistungszentrums for"Simulations und Softwarebasierte Innovation"through the SMART MODELS Einsatz Lernender Verfahren Zur Optimierung Von Produkten Und Produktionsprozessen project and The Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-Project-ID AN 782/6-2.
文摘The formation of a filter cake during the filtration of a suspension with non-spherical particles is studied using a multi-sphere model in a simulation that couples the discrete element method with computational fluid dynamics.The implementation of the coupling with a drag model that considers orientation,sphericity,and the presence of surrounding particles for non-spherical particles is tested for single particles and suspensions by comparing the terminal velocities with empirical results.Phenomena predicted in the simulations,such as the presence or absence of initial oscillations and changes in the orientation of a particle,are consistent with experimental observations reported in the literature.The variation in the void fraction of a filter cake with respect to the particle sphericity is obtained and compared with experimental trends reported in the literature.Furthermore,complex interdependencies of the particle sphericity,void fraction,and pressure drop of a filter cake for a wide range of fluid conditions are investigated.
文摘Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （CFD） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.
基金supported by Fundamental Research Funds for the Central Universities (No.FRF-TP-14-033A1)TIMODAZ project as part of the sixth EURATOM framework programme for nuclear research and training activities (2002–2006)The Department of Diagnostic and Interventional Radiology of the CHUV and the collaboration with Laboratoire 3S-R,Grenoble are gratefully acknowledged
文摘A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay.The aim of this testing program is to better understand the anisotropic deformation during the excavation.The testing conditions are similar to those to be experienced by host rocks around disposal galleries for radioactive waste.X-ray computed tomography is performed at different steps for each test with the samples remaining inside the loading cell.Initial analysis of the tomography images allows of the observation of the deformation of the central hole.In addition,particles manual tracking and 3D volumetric digital image correlation processing methods are considered being used to analyze the particles displacements and the boundary deformation of the sample quantitatively.An unsymmetrical damaged zone is induced around the hole,with a reverse deformation trend being found at the boundary after unloading,which indicates that the significant anisotropic deformation of boom clay can be induced by mechanical unloading.
基金financially supported by the National Natural Science Foundation of China(No.51304076)the Natural Science Foundation of Hunan Province,China(No.14JJ4064)
文摘Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.
文摘为实现占据多个流体网格的大颗粒在流场中运动的仿真,基于计算流体力学和离散单元法耦合(computational fluid dy namics-discrete element mothod,CFD-DEM),提出了一种新的数值方法。使用黏结颗粒模型将大颗粒近似表示为多个小球形颗粒黏结而成,基于非解析CFD-DEM方法计算流体对每个小球颗粒的作用力,将所有小球颗粒运动参数的平均值用于描述整个黏结颗粒的运动状态。通过黏性流体中球形大颗粒的沉降运动模拟,比较仿真结果与相关实验数据,结果表明:该方法不仅能准确模拟球形大颗粒的沉降运动,而且与浸没边界法相比计算效率更高。与传统的解析CFD-DEM方法相比,此方法还可以方便且准确地模拟三维情况下非球形大颗粒在流场中的运动。
文摘In this study, the flow characteristics of Geldart A particles in a bobbling fluidized bed with and without perforated plates were simulated by the multiphase particle-in-cell （MP-PlC）-based Eolerian-Lagrangian method. A modified structure-based drag model was developed based on our previous work. Other drag models including the Parker and Wen-Yo-Ergon drag models were also employed to investigate the effects of drag models on the simulation results. Although the modified structure-based drag model better predicts the gas-solid flow dynamics of a baffle-free bubbling fluidized bed in comparison with the experimental data, none of these drag models predict the gas-solid flow in a baffled bobbling floidized bed sufficiently well because of the treatment of baffles in the Barracuda software. To improve the simulation accuracy, future versions of Barracuda should address the challenges of incorporating the bed height and the baffles.
