In the paper a referral system to assist the medical experts in the screening/referral of diabetic retinopathy is suggested. The system has been developed by a sequential use of different existing mathematical techniq...In the paper a referral system to assist the medical experts in the screening/referral of diabetic retinopathy is suggested. The system has been developed by a sequential use of different existing mathematical techniques. These techniques involve speeded up robust features（SURF）, K-means clustering and visual dictionaries（VD）. Three databases are mixed to test the working of the system when the sources are dissimilar. When experiments were performed an area under the curve（AUC） of 0.9343 was attained. The results acquired from the system are promising.展开更多
The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structu...The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.展开更多
It is illegal to spread and transmit pornographic images over internet,either in real or in artificial format.The traditional methods are designed to identify real pornographic images and they are less efficient in de...It is illegal to spread and transmit pornographic images over internet,either in real or in artificial format.The traditional methods are designed to identify real pornographic images and they are less efficient in dealing with artificial images.Therefore,criminals turn to release artificial pornographic images in some specific scenes,e.g.,in social networks.To efficiently identify artificial pornographic images,a novel bag-of-visual-words based approach is proposed in the work.In the bag-of-words(Bo W)framework,speeded-up robust feature(SURF)is adopted for feature extraction at first,then a visual vocabulary is constructed through K-means clustering and images are represented by an improved Bo W encoding method,and finally the visual words are fed into a learning machine for training and classification.Different from the traditional BoW method,the proposed method sets a weight on each visual word according to the number of features that each cluster contains.Moreover,a non-binary encoding method and cross-matching strategy are utilized to improve the discriminative power of the visual words.Experimental results indicate that the proposed method outperforms the traditional method.展开更多
海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备...海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备采集眨眼频率、单位时间内人眼闭合时间所占比例(percentage of eye closure over the pupil per unit time,PERCLOS)、隧道坡度、车速等数据。利用偏相关性分析得出海底隧道坡度、曲率与驾驶人眨眼频率、PERCLOS、车速的相关性及显著性,采用Ploy 2D非线性曲面拟合方法,分别建立眨眼频率、PERCLOS、车速与坡度-曲率的数学模型,量化分析眨眼频率、PERCLOS及车速与海底隧道平纵线形之间的关系,进而反映出海底隧道不同平纵线形组合对驾驶人的精神状态及行车状态的影响。结果表明:坡度1.3%和圆曲线半径4348 m的海底隧道平纵线形组合方式下,驾驶人的眨眼频率最大,精神最放松,适当增加上坡坡度值、减小圆曲线半径可以提高驾驶人的紧张感;坡度3.05%和圆曲线半径3521 m的海底隧道平纵线形组合方式下,驾驶人的PERCLOS最大,疲劳程度最高,适当增加下坡坡度值、减小圆曲线半径可以缓解驾驶人的疲劳;坡度1.78%和圆曲线半径2433 m的海底隧道平纵线形组合方式下,车速最快,适当增加上坡坡度值和圆曲线半径,可以降低车速。本文构建的视觉特征及车速模型,可以反映驾驶人的精神及行车状态随平纵线形的变化,为海底隧道平纵线形安全设计与运营管理提供理论支撑。展开更多
文摘In the paper a referral system to assist the medical experts in the screening/referral of diabetic retinopathy is suggested. The system has been developed by a sequential use of different existing mathematical techniques. These techniques involve speeded up robust features（SURF）, K-means clustering and visual dictionaries（VD）. Three databases are mixed to test the working of the system when the sources are dissimilar. When experiments were performed an area under the curve（AUC） of 0.9343 was attained. The results acquired from the system are promising.
基金The project supported by the National Natural Science Foundation of China (19672070)
文摘The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.
基金Projects(41001260,61173122,61573380) supported by the National Natural Science Foundation of ChinaProject(11JJ5044) supported by the Hunan Provincial Natural Science Foundation of China
文摘It is illegal to spread and transmit pornographic images over internet,either in real or in artificial format.The traditional methods are designed to identify real pornographic images and they are less efficient in dealing with artificial images.Therefore,criminals turn to release artificial pornographic images in some specific scenes,e.g.,in social networks.To efficiently identify artificial pornographic images,a novel bag-of-visual-words based approach is proposed in the work.In the bag-of-words(Bo W)framework,speeded-up robust feature(SURF)is adopted for feature extraction at first,then a visual vocabulary is constructed through K-means clustering and images are represented by an improved Bo W encoding method,and finally the visual words are fed into a learning machine for training and classification.Different from the traditional BoW method,the proposed method sets a weight on each visual word according to the number of features that each cluster contains.Moreover,a non-binary encoding method and cross-matching strategy are utilized to improve the discriminative power of the visual words.Experimental results indicate that the proposed method outperforms the traditional method.
文摘海底隧道平纵线形组合方式复杂多样,容易导致驾驶人产生分心、疲劳等不良反应。为此,采集了30名驾驶人的实车数据,量化分析了海底隧道平纵线形对驾驶人视觉特征及车速的影响。运用Facelab眼动仪、GPS X10车载坡度计、行车记录仪等设备采集眨眼频率、单位时间内人眼闭合时间所占比例(percentage of eye closure over the pupil per unit time,PERCLOS)、隧道坡度、车速等数据。利用偏相关性分析得出海底隧道坡度、曲率与驾驶人眨眼频率、PERCLOS、车速的相关性及显著性,采用Ploy 2D非线性曲面拟合方法,分别建立眨眼频率、PERCLOS、车速与坡度-曲率的数学模型,量化分析眨眼频率、PERCLOS及车速与海底隧道平纵线形之间的关系,进而反映出海底隧道不同平纵线形组合对驾驶人的精神状态及行车状态的影响。结果表明:坡度1.3%和圆曲线半径4348 m的海底隧道平纵线形组合方式下,驾驶人的眨眼频率最大,精神最放松,适当增加上坡坡度值、减小圆曲线半径可以提高驾驶人的紧张感;坡度3.05%和圆曲线半径3521 m的海底隧道平纵线形组合方式下,驾驶人的PERCLOS最大,疲劳程度最高,适当增加下坡坡度值、减小圆曲线半径可以缓解驾驶人的疲劳;坡度1.78%和圆曲线半径2433 m的海底隧道平纵线形组合方式下,车速最快,适当增加上坡坡度值和圆曲线半径,可以降低车速。本文构建的视觉特征及车速模型,可以反映驾驶人的精神及行车状态随平纵线形的变化,为海底隧道平纵线形安全设计与运营管理提供理论支撑。
