为了深入揭示国际瑜伽研究发展状况,以美国Web of science(WOS)TM核心合集数据库为数据源,通过关键词检索,获取1985-2014年相关数据。运用Cite Space软件对数据进行计量分析,绘制知识图谱。结合内容分析与数据挖掘,对国际瑜伽研究演进...为了深入揭示国际瑜伽研究发展状况,以美国Web of science(WOS)TM核心合集数据库为数据源,通过关键词检索,获取1985-2014年相关数据。运用Cite Space软件对数据进行计量分析,绘制知识图谱。结合内容分析与数据挖掘,对国际瑜伽研究演进脉络与前沿动态展开体育竞争情报分析。研究结果认为,30年来,国际上对瑜伽的科研数量不断上升,研究领域涉及13个学科门类的109个研究方向,热点研究领域主要集中在医学、教育学、工学、体育学等方面。美国位居国际瑜伽研究领域的发文量之首,其次为印度、加拿大、英国、德国、澳大利亚,中国也是瑜伽研究的活跃国家。印度的研究力量以专门的瑜伽科研机构为主,欧、美国家则以高校和医学研究委员会的科研人员为主力军,各自形成了国际化的研究团队。我国研究团队的集聚性和整合程度相对不足,国际间的合作与交流仍需加强。国际瑜伽研究以运动、冥想、身体活动、替代疗法为主要内容,以女性和老年人为主要研究对象,并逐渐涉及到男性群体。以瑜伽干预作为医学辅助治疗方法,对腰背部疼痛、心血管疾病、抑郁、失眠、哮喘、情绪和骨骼肌力量等的积极影响是当前国际瑜伽领域研究的前沿热点。并在近年来有将瑜伽引入运动训练和竞赛,把其作为体能训练、运动后疲劳消除和赛前运动员心理调节方法手段等的趋势,这可能会演化为今后体育领域瑜伽科研一个新的前沿热点。展开更多
为了解决室内动态环境下移动机器人的准确定位问题,提出了一种融合运动检测算法的半直接法RGB-D视觉SLAM(同时定位与地图创建)算法,它由运动检测、相机位姿估计、基于TSDF (truncated signed distance function)模型的稠密地图构建3个...为了解决室内动态环境下移动机器人的准确定位问题,提出了一种融合运动检测算法的半直接法RGB-D视觉SLAM(同时定位与地图创建)算法,它由运动检测、相机位姿估计、基于TSDF (truncated signed distance function)模型的稠密地图构建3个步骤组成.首先,通过最小化图像光度误差,利用稀疏图像对齐算法实现对相机位姿的初步估计.然后,使用视觉里程计的位姿估计对图像进行运动补偿,建立基于图像块实时更新的高斯模型,依据方差变化分割出图像中的运动物体,进而剔除投影在图像运动区域的局部地图点,通过最小化重投影误差对相机位姿进行进一步优化,提升相机位姿估计精度.最后,使用相机位姿和RGB-D相机图像信息构建TSDF稠密地图,利用图像运动检测结果和地图体素块的颜色变化,完成地图在动态环境下的实时更新.实验结果表明,在室内动态环境下,本文算法能够有效提高相机位姿估计精度,实现稠密地图的实时更新,在提升系统鲁棒性的同时也提升了环境重构的准确性.展开更多
This study presented a quantitative investigation of deformation behavior and dynamic recrystallization of low-alloy high- strength Ni-Cr-Mo-V steels during hot deformation. A series of isothermal compression experime...This study presented a quantitative investigation of deformation behavior and dynamic recrystallization of low-alloy high- strength Ni-Cr-Mo-V steels during hot deformation. A series of isothermal compression experiments were performed at temperatures ranging from 800 to 1200 ℃ and strain rates from 0.01 to 10 s^-1 with a height reduction of 60%. A complete Arrhenius constitutive model and processing maps were developed. The results showed that the constitutive model had the ability to predict the flow stress with an average absolute relative error of 〈 5.7%. The processing maps constructed at strains of 0.2, 0.4, and 0.8 showed that flow instability was prone to occur at higher strain. Dynamic recrystallization tended to take place at higher temperatures （900-1200 ℃） and lower strain rates （0.01^-1 s^-1）. The critical strain for the onset of dynamic recrystallization was determined, and a kinetics model was developed. The predicted results for recrystaUization volume fraction and flow stress were compared with the experimental data, which indicated that the model was accurate and reliable.展开更多
The hot deformation behavior of beta C titanium alloy in β phase field was investigated by isothermal compression testson a Gleeble？3800 thermomechanical simulator. The constitutive equation describing the hot defor...The hot deformation behavior of beta C titanium alloy in β phase field was investigated by isothermal compression testson a Gleeble？3800 thermomechanical simulator. The constitutive equation describing the hot deformation behavior was obtained anda processing map was established at the true strain of 0.7. The microstructure was characterized by optical microscopy （OM）,scanning electron microscopy （SEM） and electron back-scattered diffraction （EBSD） technique. The results show that the flow stressincreases with increasing strain rates, and decreases with increasing experimental temperatures. The calculated apparent activationenergy （167 kJ/mol） is close to that of self-diffusion in β titanium. The processing map and microstructure observation exhibit adynamic recrystallization domain in the temperature range of 900-1000 ℃ and strain rate range of 0.1-1 s^-1. An instability regionexists when the strain rate is higher than 1.7 s^-1. The microstructure of beta C titanium alloy can be optimized by proper heattreatments after the deformation in the dynamic recrystallization domain.展开更多
文摘为了深入揭示国际瑜伽研究发展状况,以美国Web of science(WOS)TM核心合集数据库为数据源,通过关键词检索,获取1985-2014年相关数据。运用Cite Space软件对数据进行计量分析,绘制知识图谱。结合内容分析与数据挖掘,对国际瑜伽研究演进脉络与前沿动态展开体育竞争情报分析。研究结果认为,30年来,国际上对瑜伽的科研数量不断上升,研究领域涉及13个学科门类的109个研究方向,热点研究领域主要集中在医学、教育学、工学、体育学等方面。美国位居国际瑜伽研究领域的发文量之首,其次为印度、加拿大、英国、德国、澳大利亚,中国也是瑜伽研究的活跃国家。印度的研究力量以专门的瑜伽科研机构为主,欧、美国家则以高校和医学研究委员会的科研人员为主力军,各自形成了国际化的研究团队。我国研究团队的集聚性和整合程度相对不足,国际间的合作与交流仍需加强。国际瑜伽研究以运动、冥想、身体活动、替代疗法为主要内容,以女性和老年人为主要研究对象,并逐渐涉及到男性群体。以瑜伽干预作为医学辅助治疗方法,对腰背部疼痛、心血管疾病、抑郁、失眠、哮喘、情绪和骨骼肌力量等的积极影响是当前国际瑜伽领域研究的前沿热点。并在近年来有将瑜伽引入运动训练和竞赛,把其作为体能训练、运动后疲劳消除和赛前运动员心理调节方法手段等的趋势,这可能会演化为今后体育领域瑜伽科研一个新的前沿热点。
文摘为了解决室内动态环境下移动机器人的准确定位问题,提出了一种融合运动检测算法的半直接法RGB-D视觉SLAM(同时定位与地图创建)算法,它由运动检测、相机位姿估计、基于TSDF (truncated signed distance function)模型的稠密地图构建3个步骤组成.首先,通过最小化图像光度误差,利用稀疏图像对齐算法实现对相机位姿的初步估计.然后,使用视觉里程计的位姿估计对图像进行运动补偿,建立基于图像块实时更新的高斯模型,依据方差变化分割出图像中的运动物体,进而剔除投影在图像运动区域的局部地图点,通过最小化重投影误差对相机位姿进行进一步优化,提升相机位姿估计精度.最后,使用相机位姿和RGB-D相机图像信息构建TSDF稠密地图,利用图像运动检测结果和地图体素块的颜色变化,完成地图在动态环境下的实时更新.实验结果表明,在室内动态环境下,本文算法能够有效提高相机位姿估计精度,实现稠密地图的实时更新,在提升系统鲁棒性的同时也提升了环境重构的准确性.
基金supported financially by the Scientific Research Foundation of Tianjin University of Technology and Education (No.KYQD1801)the National Natural Science Foundation of Tianjin City (No.13JCYBJC38900)
文摘This study presented a quantitative investigation of deformation behavior and dynamic recrystallization of low-alloy high- strength Ni-Cr-Mo-V steels during hot deformation. A series of isothermal compression experiments were performed at temperatures ranging from 800 to 1200 ℃ and strain rates from 0.01 to 10 s^-1 with a height reduction of 60%. A complete Arrhenius constitutive model and processing maps were developed. The results showed that the constitutive model had the ability to predict the flow stress with an average absolute relative error of 〈 5.7%. The processing maps constructed at strains of 0.2, 0.4, and 0.8 showed that flow instability was prone to occur at higher strain. Dynamic recrystallization tended to take place at higher temperatures （900-1200 ℃） and lower strain rates （0.01^-1 s^-1）. The critical strain for the onset of dynamic recrystallization was determined, and a kinetics model was developed. The predicted results for recrystaUization volume fraction and flow stress were compared with the experimental data, which indicated that the model was accurate and reliable.
文摘The hot deformation behavior of beta C titanium alloy in β phase field was investigated by isothermal compression testson a Gleeble？3800 thermomechanical simulator. The constitutive equation describing the hot deformation behavior was obtained anda processing map was established at the true strain of 0.7. The microstructure was characterized by optical microscopy （OM）,scanning electron microscopy （SEM） and electron back-scattered diffraction （EBSD） technique. The results show that the flow stressincreases with increasing strain rates, and decreases with increasing experimental temperatures. The calculated apparent activationenergy （167 kJ/mol） is close to that of self-diffusion in β titanium. The processing map and microstructure observation exhibit adynamic recrystallization domain in the temperature range of 900-1000 ℃ and strain rate range of 0.1-1 s^-1. An instability regionexists when the strain rate is higher than 1.7 s^-1. The microstructure of beta C titanium alloy can be optimized by proper heattreatments after the deformation in the dynamic recrystallization domain.
