This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillati...This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction of the bubble reentrant jet was towards the aperture or away from it respectively when the normalized aperture size was smaller or greater than a certain critical value. In addition, a toroidal vortex ring was observed to form, which rotated inwards as it moved away from the aperture. It was also found that if the bubble was incepted at a distance sufficiently away from a supercritical size aperture a single droplet could be produced. In the case of a bub- ble initiated in the middle of a circular aperture submerged just beneath the water free surface, the bubble was found to take the shape of an ellipsoid during its expansion. Then a reentrant jet was initiated and pierced the bubble from its top side.展开更多
医学影像学是临床医学中一门实践性极强辅助学科,同时也是发展迅猛,日新月异的学科,在现代医疗中扮演着越来越重要的角色。文章通过对影像医学教学的基本要求、教学目标和目的进行说明,采用影像存储和传输系统(picture archiving and co...医学影像学是临床医学中一门实践性极强辅助学科,同时也是发展迅猛,日新月异的学科,在现代医疗中扮演着越来越重要的角色。文章通过对影像医学教学的基本要求、教学目标和目的进行说明,采用影像存储和传输系统(picture archiving and communication system,PACS)结合以问题为基础的教学法(problem-based learning,PBL)及以案例为基础的教学法(case-based learning,CBL)教学法进行实践。针对非影像专业学员学习时间短、学习任务重,学员影像基础和需求迥异,部分非影像专业学员自身对医学影像学的重视不足以及放射基地重视不足等问题。文章阐述了PACS与PBL、CBL教学法、钉钉、微信及SPARK学习平台等学习沟通平台相结合,并增加专职人员对基地管理、带教老师一对一指导,以及不断加强科室建设、安排名师上课来提高科室影响力等多种混合教学模式的解决对策,来唤起学员学习影像相关知识的内驱力,达到提高学员轮转学习效果的目的。展开更多
针对大数据环境下并行深度森林算法中存在不相关及冗余特征过多、多粒度扫描不平衡、分类性能不足以及并行化效率低等问题,提出了基于互信息和融合加权的并行深度森林算法(parallel deep forest algorithm based on mutual information ...针对大数据环境下并行深度森林算法中存在不相关及冗余特征过多、多粒度扫描不平衡、分类性能不足以及并行化效率低等问题,提出了基于互信息和融合加权的并行深度森林算法(parallel deep forest algorithm based on mutual information and mixed weighting,PDF-MIMW)。首先,在特征降维阶段提出了基于互信息的特征提取策略(feature extraction strategy based on mutual information,FE-MI),结合特征重要性、交互性和冗余性度量过滤原始特征,剔除过多的不相关和冗余特征;接着,在多粒度扫描阶段提出了基于填充的改进多粒度扫描策略(improved multi-granularity scanning strategy based on padding,IMGS-P),对精简后的特征进行填充并对窗口扫描后的子序列进行随机采样,保证多粒度扫描的平衡;其次,在级联森林构建阶段提出了并行子森林构建策略(sub-forest construction strategy based on mixed weighting,SFC-MW),结合Spark框架并行构建加权子森林,提升模型的分类性能;最后,在类向量合并阶段提出基于混合粒子群算法的负载均衡策略(load balancing strategy based on hybrid particle swarm optimization algorithm,LB-HPSO),优化Spark框架中任务节点的负载分配,降低类向量合并时的等待时长,提高模型的并行化效率。实验表明,PDF-MIMW算法的分类效果更佳,同时在大数据环境下的训练效率更高。展开更多
文摘This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction of the bubble reentrant jet was towards the aperture or away from it respectively when the normalized aperture size was smaller or greater than a certain critical value. In addition, a toroidal vortex ring was observed to form, which rotated inwards as it moved away from the aperture. It was also found that if the bubble was incepted at a distance sufficiently away from a supercritical size aperture a single droplet could be produced. In the case of a bub- ble initiated in the middle of a circular aperture submerged just beneath the water free surface, the bubble was found to take the shape of an ellipsoid during its expansion. Then a reentrant jet was initiated and pierced the bubble from its top side.
文摘医学影像学是临床医学中一门实践性极强辅助学科,同时也是发展迅猛,日新月异的学科,在现代医疗中扮演着越来越重要的角色。文章通过对影像医学教学的基本要求、教学目标和目的进行说明,采用影像存储和传输系统(picture archiving and communication system,PACS)结合以问题为基础的教学法(problem-based learning,PBL)及以案例为基础的教学法(case-based learning,CBL)教学法进行实践。针对非影像专业学员学习时间短、学习任务重,学员影像基础和需求迥异,部分非影像专业学员自身对医学影像学的重视不足以及放射基地重视不足等问题。文章阐述了PACS与PBL、CBL教学法、钉钉、微信及SPARK学习平台等学习沟通平台相结合,并增加专职人员对基地管理、带教老师一对一指导,以及不断加强科室建设、安排名师上课来提高科室影响力等多种混合教学模式的解决对策,来唤起学员学习影像相关知识的内驱力,达到提高学员轮转学习效果的目的。
文摘针对大数据环境下并行深度森林算法中存在不相关及冗余特征过多、多粒度扫描不平衡、分类性能不足以及并行化效率低等问题,提出了基于互信息和融合加权的并行深度森林算法(parallel deep forest algorithm based on mutual information and mixed weighting,PDF-MIMW)。首先,在特征降维阶段提出了基于互信息的特征提取策略(feature extraction strategy based on mutual information,FE-MI),结合特征重要性、交互性和冗余性度量过滤原始特征,剔除过多的不相关和冗余特征;接着,在多粒度扫描阶段提出了基于填充的改进多粒度扫描策略(improved multi-granularity scanning strategy based on padding,IMGS-P),对精简后的特征进行填充并对窗口扫描后的子序列进行随机采样,保证多粒度扫描的平衡;其次,在级联森林构建阶段提出了并行子森林构建策略(sub-forest construction strategy based on mixed weighting,SFC-MW),结合Spark框架并行构建加权子森林,提升模型的分类性能;最后,在类向量合并阶段提出基于混合粒子群算法的负载均衡策略(load balancing strategy based on hybrid particle swarm optimization algorithm,LB-HPSO),优化Spark框架中任务节点的负载分配,降低类向量合并时的等待时长,提高模型的并行化效率。实验表明,PDF-MIMW算法的分类效果更佳,同时在大数据环境下的训练效率更高。
