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基于马氏距离和Canopy改进K-means的交通聚类算法
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作者 徐文进 马越 杜咏慧 《计算机与数字工程》 2024年第6期1630-1635,1649,共7页
在对交通数据的研究中经常会使用到聚类算法,且不同的聚类算法有不同的特性。K-means作为其中的一种聚类算法,具有较高的准确性和实用性,但其准确性易受主观选取K值和确定初始聚类中心的影响。为了优化聚类中心和K值的选取问题,提出MC-K... 在对交通数据的研究中经常会使用到聚类算法,且不同的聚类算法有不同的特性。K-means作为其中的一种聚类算法,具有较高的准确性和实用性,但其准确性易受主观选取K值和确定初始聚类中心的影响。为了优化聚类中心和K值的选取问题,提出MC-Kmeans算法。在所提方法中,首先通过Canopy算法选取K值,然后依据马氏距离的计算准则来确定初始聚类中心,最后将K值和聚类中心的值作为K-means的参数进行聚类。将MC-Kmeans算法应用到某时间段的纽约出租车交通数据中进行实际的验证。结果表明,与K-means算法比较,所提方法准确度更高,与实际交通情况更加相匹配,更能反映区域内的交通热点情况。 展开更多
关键词 K-MEANS canopy算法 马氏距离 交通
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基于信息熵和Canopy-K-Means算法的货车驾驶风格识别
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作者 李浩 王肇飞 李微 《交通工程》 2024年第7期123-128,共6页
为识别货车的激进驾驶行为,保障货车行车安全,提出1种基于信息熵和Canopy-K-Means算法的货车驾驶风格识别方法。首先,从货车自然驾驶数据中提取出604个驾驶片段,根据信息熵理论计算各个驾驶片段的速度熵值、横向加速度熵值和纵向加速度... 为识别货车的激进驾驶行为,保障货车行车安全,提出1种基于信息熵和Canopy-K-Means算法的货车驾驶风格识别方法。首先,从货车自然驾驶数据中提取出604个驾驶片段,根据信息熵理论计算各个驾驶片段的速度熵值、横向加速度熵值和纵向加速度熵值,构成货车驾驶风格表征指标集;其次,针对K-Means算法的聚类数量主观选取、初始聚类中心随机选取的问题,使用Canopy算法改进K-Means算法(Canopy-K-Means算法);最后,分别使用K-Means算法和Canopy-K-Means算法对货车驾驶风格进行识别。研究结果显示,Canopy-K-Means算法的轮廓系数和Calinski-Harabasz指数均大于K-Means算法,表现出更优的聚类性能。根据Canopy-K-Means算法,可将货车驾驶风格分为沉稳型、常规型和激进型3类,其中激进型货车驾驶风格的指标熵值和极差均较大,存在较高的安全隐患,需要引起相关部门的高度重视。 展开更多
关键词 交通工程 驾驶风格 canopy-K-Means算法 信息熵 货车
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基于改进的Canopy-k-means的大跨屋盖表面风荷载分区方法
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作者 李玉学 纪君 董阳 《河北科技大学学报》 CAS 北大核心 2024年第5期530-538,共9页
针对k-means聚类算法在大跨屋盖结构表面风荷载分区计算中,聚类数k值随机选取容易导致结果不稳定和计算效率低等问题,提出改进的Canopy-k-means聚类算法。首先,引入Canopy算法并对其初始阈值和聚类中心的选取方式进行改进,减少初始值选... 针对k-means聚类算法在大跨屋盖结构表面风荷载分区计算中,聚类数k值随机选取容易导致结果不稳定和计算效率低等问题,提出改进的Canopy-k-means聚类算法。首先,引入Canopy算法并对其初始阈值和聚类中心的选取方式进行改进,减少初始值选取的盲目性,以提高风荷载分区结果的可靠性;其次,通过改进Canopy算法对风荷载数据集进行预处理,快速准确地确定聚类数k值;第三,将改进Canopy算法与k-means结合使用,实现最优分类数k值的精准识别,使得改进的Canopy-k-means聚类算法进行大跨屋盖结构表面风荷载分区时能够快速准确地得到分区结果;最后,以一大跨柱面屋盖干煤棚结构为例,基于风洞试验所得结构表面风荷载数据测试结果,采用所提改进的Canopy-k-means聚类算法对其表面风荷载进行分区计算。结果表明,采用改进的Canopy-k-means聚类算法,将0°、50°和90°风向角时大跨屋盖表面风荷载划分为了3个不同的分区,其对应的SD值分别为2.36、3.51和2.52,较传统k-means聚类算法所得对应值明显降低,类内紧凑性和类间分散性明显提升。所提改进Canopy-k-means聚类算法能够快速准确地得到最优分区结果,对大跨屋盖表面风荷载分区具有工程参考价值。 展开更多
关键词 薄壳结构 风荷载测压 风荷载分区 K-MEANS聚类算法 canopy算法
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核电站控制棒驱动机构Canopy焊缝焊接温度场和应力-应变场模拟
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作者 米大为 沈天阔 +4 位作者 宿希慧 郭宝超 邹小平 孙广 吴超平 《精密成形工程》 北大核心 2024年第2期182-189,共8页
目的研究机加工和拉拔2种成形方式下得到的填充环对Canopy焊缝的影响,获取焊接焊缝成形、焊接残余应力和变形的相关数据,以指导Canopy焊缝焊接工艺。方法采用数值模拟的方法,建立Canopy焊缝焊接数值分析模型,模拟焊接温度场、焊接残余... 目的研究机加工和拉拔2种成形方式下得到的填充环对Canopy焊缝的影响,获取焊接焊缝成形、焊接残余应力和变形的相关数据,以指导Canopy焊缝焊接工艺。方法采用数值模拟的方法,建立Canopy焊缝焊接数值分析模型,模拟焊接温度场、焊接残余应力和焊接残余变形。结果拉拔成形环焊接熔池高度为9 mm,机加工成形环焊接熔池高度为8.3 mm;机加工成形环焊接最大残余应力为255.6 MPa,而拉拔成形环焊接最大残余应力为277.8 MPa,均出现在管座紧贴焊缝的位置;机加工成形环焊接残余变形为0.19 mm,拉拔成形环焊接残余变形为0.186 mm,最大残余变形均出现在焊接起始位置附近,在焊缝与管座交接的位置。结论熔池形貌直接影响了热影响区域的大小,拉拔Y型环焊接熔池高度更大,焊接的热影响区域更大;拉拔Y型环焊接残余应力略大于机加工Y型环焊接残余应力;机加工成形环和拉拔成形环焊接残余变形相近。 展开更多
关键词 焊接模拟 焊接温度场 焊接应力 焊接变形 canopy焊缝
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Rice canopy temperature is affected by nitrogen fertilizer
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作者 Min Jiang Zhang Chen +3 位作者 Yuan Li Xiaomin Huang Lifen Huang Zhongyang Huo 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2024年第3期824-835,共12页
Canopy temperature strongly influences crop yield formation and is closely related to plant physiological traits.However, the effects of nitrogen treatment on canopy temperature and rice growth have yet to be comprehe... Canopy temperature strongly influences crop yield formation and is closely related to plant physiological traits.However, the effects of nitrogen treatment on canopy temperature and rice growth have yet to be comprehensively examined. We conducted a two-year field experiment with three rice varieties(HD-5, NJ-9108, and YJ-805) and three nitrogen treatments(zero-N control(CK), 200 kg ha~(–1)(MN), and 300 kg ha~(–1)(HN)). We measured canopy temperature using a drone equipped with a high-precision camera at the six stages of the growth period. Generally,canopy temperature was significantly higher for CK than for MN and HN during the tillering, jointing, booting, and heading stages. The temperature was not significantly different among the nitrogen treatments between the milky and waxy stages. The canopy temperature of different rice varieties was found to follow the order: HD-5>NJ-9108>YJ-805, but the difference was not significant. The canopy temperature of rice was mainly related to plant traits, such as shoot fresh weight(correlation coefficient r=–0.895), plant water content(–0.912), net photosynthesis(–0.84), stomatal conductance(–0.91), transpiration rate(–0.90), and leaf stomatal area(–0.83). A structural equation model(SEM) showed that nitrogen fertilizer was an important factor affecting the rice canopy temperature.Our study revealed:(1) A suite of plant traits was associated with the nitrogen effects on canopy temperature,(2) the heading stage was the best time to observe rice canopy temperature, and(3) at that stage, canopy temperature was negatively correlated with rice yield, panicle number, and grain number per panicle. This study suggests that canopy temperature can be a convenient and accurate indicator of rice growth and yield prediction. 展开更多
关键词 canopy temperature RICE physiological and biochemical characteristics YIELD
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Drought events influence nutrient canopy exchanges and green leaf partitioning during senescence in a deciduous forest
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作者 J.Touche C.Calvaruso +1 位作者 P.De Donato M.-P.Turpault 《Forest Ecosystems》 SCIE CSCD 2024年第1期110-119,共10页
The increase in the frequency and intensity of drought events expected in the coming decades in Western Europe may disturb forest biogeochemical cycles and create nutrient deficiencies in trees.One possible origin of ... The increase in the frequency and intensity of drought events expected in the coming decades in Western Europe may disturb forest biogeochemical cycles and create nutrient deficiencies in trees.One possible origin of nutrient deficiency is the disturbance of the partitioning of the green leaf pool during the leaf senescence period between resorption,foliar leaching and senesced leaves.However,the effects of drought events on this partitioning and the consequences for the maintenance of tree nutrition are poorly documented.An experiment in a beech forest in Meuse(France)was conducted to assess the effect of drought events on nutrient canopy exchanges and on the partitioning of the green leaf pool during the leaf senescence period.The aim was to identify potential nutritional consequences of droughts for trees.Monitoring nutrient dynamics,including resorption,chemistry of green and senesced leaves,foliar absorption and leaching in mature beech stands from 2012 to 2019 allowed us to compare the nutrient exchanges for three nondry and three dry years(i.e.,with an intense drought event during the growing season).During dry years,we observed a decrease by almost a third of the potassium(K)partitioning to resorption(i.e.resorption efficiency),thus reducing the K reserve in trees for the next growing season.This result suggests that with the increased drought frequency and intensity expected for the coming decades,there will be a risk of potassium deficiency in trees,as already observed in a rainfall exclusion experiment on the same study site.Reduced foliar leaching and higher parititioning to the senesced leaves for K and phosphorus(P)were also observed.In addition,a slight increase in nitrogen(N)resorption efficiency occurred during dry years which is more likely to improve tree nutrition.The calcium(Ca)negative resorption decreased,with no apparent consequence in our study site.Our results show that nutrient exchanges in the canopy and the partitioning of the green leaf pool can be modified by drought events,and may have consequences on tree nutrition. 展开更多
关键词 Natural drought Beech forest canopy RESORPTION Foliar leaching Senesced leaves NUTRITION
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Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain
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作者 F.Animah C.Keles +1 位作者 W.R.Reed E.Sarver 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第3期86-101,共16页
Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effective... Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly. 展开更多
关键词 Respirable dust Dust control SEM–EDX SCRUBBER canopy air curtain SILICA
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The influences of canopy temperature measuring on the derived crop water stress index
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作者 WANG Hongxi LI Fei +4 位作者 SHEN Hongtao LI Mengyu YIN Gongchao FANG Qin SHAO Liwei 《中国生态农业学报(中英文)》 CAS CSCD 北大核心 2024年第9期1503-1519,共17页
Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the... Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the influences of atmospheric conditions,settled height,view angle of infrared thermography,and investigating time of temperature measuring on the performance of the CWSI.Three irrigation treatments were used to create different soil water conditions during the 2020-2021 and 2021-2022 winter wheat-growing seasons.The CWSI was calculated using the CWSI-E(an empirical approach)and CWSI-T(a theoretical approach)based on the T_(c).Weather conditions were recorded continuously throughout the experimental period.The results showed that atmospheric conditions influenced the estimation of the CWSI;when the vapor pressure deficit(VPD)was>2000 Pa,the estimated CWSI was related to soil water conditions.The height of the installed infrared thermograph influenced the T_(c)values,and the differences among the T_(c)values measured at height of 3,5,and 10 m was smaller in the afternoon than in the morning.However,the lens of the thermometer facing south recorded a higher T_(c)than those facing east or north,especially at a low height,indicating that the direction of the thermometer had a significant influence on T_(c).There was a large variation in CWSI derived at different times of the day,and the midday measurements(12:00-15:00)were the most reliable for estimating CWSI.Negative linear relationships were found between the transpiration rate and CWSI-E(R^(2)of 0.3646-0.5725)and CWSI-T(R^(2)of 0.5407-0.7213).The relations between fraction of available soil water(FASW)with CWSI-T was higher than that with CWSI-E,indicating CWSI-T was more accurate for predicting crop water status.In addition,The R^(2)between CWSI-T and FASW at 14:00 was higher than that at other times,indicating that 14:00 was the optimal time for using the CWSI for crop water status monitoring.Relative higher yield of winter wheat was obtained with average seasonal values of CWSI-E and CWSI-T around 0.23 and 0.25-0.26,respectively.The CWSI-E values were more easily influenced by meteorological factors and the timing of the measurements,and using the theoretical approach to derive the CWSI was recommended for precise irrigation water management. 展开更多
关键词 canopy temperature Measuring time Measuring height and direction Crop water stress index
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Fuzzy C-Means Algorithm Based on Density Canopy and Manifold Learning
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作者 Jili Chen Hailan Wang Xiaolan Xie 《Computer Systems Science & Engineering》 2024年第3期645-663,共19页
Fuzzy C-Means(FCM)is an effective and widely used clustering algorithm,but there are still some problems.considering the number of clusters must be determined manually,the local optimal solutions is easily influenced ... Fuzzy C-Means(FCM)is an effective and widely used clustering algorithm,but there are still some problems.considering the number of clusters must be determined manually,the local optimal solutions is easily influenced by the random selection of initial cluster centers,and the performance of Euclid distance in complex high-dimensional data is poor.To solve the above problems,the improved FCM clustering algorithm based on density Canopy and Manifold learning(DM-FCM)is proposed.First,a density Canopy algorithm based on improved local density is proposed to automatically deter-mine the number of clusters and initial cluster centers,which improves the self-adaptability and stability of the algorithm.Then,considering that high-dimensional data often present a nonlinear structure,the manifold learning method is applied to construct a manifold spatial structure,which preserves the global geometric properties of complex high-dimensional data and improves the clustering effect of the algorithm on complex high-dimensional datasets.Fowlkes-Mallows Index(FMI),the weighted average of homogeneity and completeness(V-measure),Adjusted Mutual Information(AMI),and Adjusted Rand Index(ARI)are used as performance measures of clustering algorithms.The experimental results show that the manifold learning method is the superior distance measure,and the algorithm improves the clustering accuracy and performs superiorly in the clustering of low-dimensional and complex high-dimensional data. 展开更多
关键词 Fuzzy C-Means(FCM) cluster center density canopy ISOMAP clustering
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Analysis on the Application and Improvement of Canopy without Sunshade Curtain
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作者 Yi Bengang Wang Kai +5 位作者 Tian Hongsheng Ye Zihan Qing Minghao Zhao Mingguo Qiu Shoufa Wang Dan 《汽车文摘》 2024年第11期24-32,共9页
Nowadays,in order to expand the roof view to bring passengers closer to nature,more and more new energy vehicles are opting for canopy designs without sunshades.However,after removing traditional sunshades,new solutio... Nowadays,in order to expand the roof view to bring passengers closer to nature,more and more new energy vehicles are opting for canopy designs without sunshades.However,after removing traditional sunshades,new solutions must be sought to address issues such as heat insulation,glaring sunlight,and interior reflections from the roof glass during the summer months.This paper conducts an in-depth analysis of the technical advantages and shortcomings of sunshade-free canopy in terms of heat insulation and interior reflections during summer,from both theoretical analysis and experimental comparison perspectives,and proposes improvement strategies.The research results indicate that although the panoramic roof enhances the vehicle's interior view and technological appeal,it still has shortcomings in terms of heat insulation and the problem of interior reflections caused by direct sunlight.The proposed improvement strategies can effectively mitigate these issues,and offers consumers more comfortable and intelligent driving experiences. 展开更多
关键词 canopy Heat-insulated glass Dimmable glass In-vehicle reflection
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不同Y形环应用于核电站控制棒驱动机构Canopy焊缝焊接工艺及焊缝性能的研究
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作者 沈天阔 邵善家 +9 位作者 郭宝超 邹小平 邱振生 邢会平 米大为 卜佳炜 陈宝洪 潘长建 郑兵德 熊丹丹 《金属加工(热加工)》 2024年第2期42-46,共5页
试验采用两种机械加工Y形环和一种拉拔Y形环应用于核电站控制棒驱动机构Canopy焊缝,研究不同Y形环对Canopy焊缝焊接工艺及焊缝性能的影响。结果表明:机械加工Y形环为整圈环,相比拉拔Y形环,更有利于定位焊;机械加工Y形环(控公差)与拉拔Y... 试验采用两种机械加工Y形环和一种拉拔Y形环应用于核电站控制棒驱动机构Canopy焊缝,研究不同Y形环对Canopy焊缝焊接工艺及焊缝性能的影响。结果表明:机械加工Y形环为整圈环,相比拉拔Y形环,更有利于定位焊;机械加工Y形环(控公差)与拉拔Y形环装配间隙范围相当,比机械加工Y形环装配间隙范围大,更有利于工程应用;3种Y形环熔成的Canopy焊缝组织主要由铁素体和柱状奥氏体组成,无明显差异;3种Y形环熔成的Canopy焊缝经23.1~23.3MPa水压试验,焊缝表面均无渗漏,无可见变形。该研究为机械加工Y形环应用于核电站控制棒驱动机构Canopy焊缝提供了宝贵的经验。 展开更多
关键词 Y形环 canopy焊缝 焊接工艺
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核电站控制棒驱动机构Canopy焊缝组织和性能研究
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作者 沈天阔 邵善家 +8 位作者 邹小平 郭宝超 孙广 蒋恩 卜佳炜 施誉 卫晓春 黄文惠 陈宝洪 《金属加工(热加工)》 2024年第1期43-46,共4页
试验采用专用自动TIG焊机焊接核电站控制棒驱动机构Canopy焊缝,选用机械加工Y形环作为填充材料,研究Canopy焊缝组织和性能。结果表明:通过自动TIG焊,机械加工Y形环熔成的Canopy焊缝,成形良好,宽度适中,焊缝与母材冶金熔合良好;焊缝组织... 试验采用专用自动TIG焊机焊接核电站控制棒驱动机构Canopy焊缝,选用机械加工Y形环作为填充材料,研究Canopy焊缝组织和性能。结果表明:通过自动TIG焊,机械加工Y形环熔成的Canopy焊缝,成形良好,宽度适中,焊缝与母材冶金熔合良好;焊缝组织主要由板条状或骨架状铁素体与快速凝固的柱状奥氏体组成;经23.1~23.3MPa水压试验,Canopy焊缝表面无渗漏,无可见变形;维氏硬度结果表明:焊缝硬度在210HV左右,焊缝硬度分布均匀。该研究为核电站控制棒驱动机构Canopy焊缝用机械加工Y形环提供了宝贵的经验。 展开更多
关键词 控制棒驱动机构 canopy焊缝 TIG焊 焊接工艺
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屏蔽主泵Canopy密封环自动焊接技术研究
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作者 闫国华 陈树 +2 位作者 章济 施国龙 陶泽勇 《热加工工艺》 北大核心 2023年第9期115-117,114,共4页
为了降低作业人员在AP1000机组屏蔽主泵在役检修拆装过程中的辐照剂量,研究了与实际作业工序相同的Canopy密封环自动焊接工艺,开发了可远程控制、对称施焊的自动焊接装置,并在模拟体上进行了焊接试验。试验结果表明,在优化的焊接参数下,... 为了降低作业人员在AP1000机组屏蔽主泵在役检修拆装过程中的辐照剂量,研究了与实际作业工序相同的Canopy密封环自动焊接工艺,开发了可远程控制、对称施焊的自动焊接装置,并在模拟体上进行了焊接试验。试验结果表明,在优化的焊接参数下,Canopy密封环打底焊成形良好,多层多道焊缝无层间未熔合等缺陷,起弧、收弧过渡良好。该自动焊接装置结构紧凑,可实现模拟件的稳定焊接,焊接质量良好,能够满足屏蔽主泵在役检修更换时的自动焊接需求。 展开更多
关键词 屏蔽主泵 canopy密封环 在役检修 自动焊接
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基于加权密度Canopy的K-means文本聚类 被引量:2
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作者 宋健 李岩芳 陈占芳 《中南民族大学学报(自然科学版)》 CAS 北大核心 2023年第5期636-642,共7页
针对现有文本聚类性能不高的问题,提出了一种改进质心初始化的K-means文本聚类算法.该算法首先利用Canopy算法进行文本预聚类,并且对Canopy算法的阈值选取策略进行改进,定义加权密度进行Canopy中心的选取,得到更准确的聚类数以及初始聚... 针对现有文本聚类性能不高的问题,提出了一种改进质心初始化的K-means文本聚类算法.该算法首先利用Canopy算法进行文本预聚类,并且对Canopy算法的阈值选取策略进行改进,定义加权密度进行Canopy中心的选取,得到更准确的聚类数以及初始聚类中心;然后将所得结果作为K-means算法的初始化参数进行后续迭代聚类,有效解决了传统算法因随机选取初始聚类中心而陷入局部最优解的问题,减少了算法的迭代次数,提高了聚类准确性.实验结果表明:与其他同类型算法相比,该算法在文本聚类分析中更具优势. 展开更多
关键词 文本聚类 K-MEANS算法 加权密度 canopy算法
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A double-layer model for improving the estimation of wheat canopy nitrogen content from unmanned aerial vehicle multispectral imagery 被引量:1
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作者 LIAO Zhen-qi DAI Yu-long +5 位作者 WANG Han Quirine M.KETTERINGS LU Jun-sheng ZHANG Fu-cang LI Zhi-jun FAN Jun-liang 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2023年第7期2248-2270,共23页
The accurate and rapid estimation of canopy nitrogen content(CNC)in crops is the key to optimizing in-season nitrogen fertilizer application in precision agriculture.However,the determination of CNC from field samplin... The accurate and rapid estimation of canopy nitrogen content(CNC)in crops is the key to optimizing in-season nitrogen fertilizer application in precision agriculture.However,the determination of CNC from field sampling data for leaf area index(LAI),canopy photosynthetic pigments(CPP;including chlorophyll a,chlorophyll b and carotenoids)and leaf nitrogen concentration(LNC)can be time-consuming and costly.Here we evaluated the use of high-precision unmanned aerial vehicle(UAV)multispectral imagery for estimating the LAI,CPP and CNC of winter wheat over the whole growth period.A total of 23 spectral features(SFs;five original spectrum bands,17 vegetation indices and the gray scale of the RGB image)and eight texture features(TFs;contrast,entropy,variance,mean,homogeneity,dissimilarity,second moment,and correlation)were selected as inputs for the models.Six machine learning methods,i.e.,multiple stepwise regression(MSR),support vector regression(SVR),gradient boosting decision tree(GBDT),Gaussian process regression(GPR),back propagation neural network(BPNN)and radial basis function neural network(RBFNN),were compared for the retrieval of winter wheat LAI,CPP and CNC values,and a double-layer model was proposed for estimating CNC based on LAI and CPP.The results showed that the inversion of winter wheat LAI,CPP and CNC by the combination of SFs+TFs greatly improved the estimation accuracy compared with that by using only the SFs.The RBFNN and BPNN models outperformed the other machine learning models in estimating winter wheat LAI,CPP and CNC.The proposed double-layer models(R^(2)=0.67-0.89,RMSE=13.63-23.71 mg g^(-1),MAE=10.75-17.59 mg g^(-1))performed better than the direct inversion models(R^(2)=0.61-0.80,RMSE=18.01-25.12 mg g^(-1),MAE=12.96-18.88 mg g^(-1))in estimating winter wheat CNC.The best winter wheat CNC accuracy was obtained by the double-layer RBFNN model with SFs+TFs as inputs(R^(2)=0.89,RMSE=13.63 mg g^(-1),MAE=10.75 mg g^(-1)).The results of this study can provide guidance for the accurate and rapid determination of winter wheat canopy nitrogen content in the field. 展开更多
关键词 UAV multispectral imagery spectral features texture features canopy photosynthetic pigment content canopy nitrogen content
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Effect of the L-D_(1)alleles on leaf morphology,canopy structure and photosynthetic productivity in upland cotton(Gossypium hirsutum L.) 被引量:1
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作者 JIANG Hui GAO Ming-wei +7 位作者 CHEN Ying ZHANG Chao WANG Jia-bao CHAI Qi-chao WANG Yong-cui ZHENG Jin-xiu WANG Xiu-li ZHAO Jun-sheng 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2023年第1期108-119,共12页
One of the most important objectives for breeders is to develop high-yield cultivars.The increase in crop yield has met with bottlenecks after the first green revolution,and more recent efforts have been focusing on a... One of the most important objectives for breeders is to develop high-yield cultivars.The increase in crop yield has met with bottlenecks after the first green revolution,and more recent efforts have been focusing on achieving high photosynthetic efficiency traits in order to enhance the yield.Leaf shape is a significant agronomic trait of upland cotton that affects plant and canopy architecture,yield,and other production attributes.The major leaf shape types,including normal,sub-okra,okra,and super-okra,with varying levels of lobe severity,are controlled by a multiple allelic series of the D-genome locus L-D_(1).To analyze the effects of L-D_(1)alleles on leaf morphology,photosynthetic related traits and yield of cotton,two sets of near isogenic lines(NILs)with different alleles were constructed in Lumianyan 22(LMY22)and Lumianyan 28(LMY28)backgrounds.The analysis of morphological parameters and the results of virus-induced gene silencing(VIGS)showed that the regulation of leaf shape by L-D_(1)alleles was similar to a gene-dosage effect.Compared with the normal leaf,deeper lobes of the sub-okra leaf improved plant canopy structure by decreasing the leaf area index(LAI)and increasing the light transmittance rate(LTR),and the mid-range LAI of sub-okra leaf also guaranteed the accumulation of cotton biomass.Although the chlorophyll content(SPAD)of sub-okra leaf was lower than those of the other two leaf shapes,the net photosynthetic rate(Pn)of sub-okra leaf was higher than those of okra leaf and normal leaf at most stages.Thus,the improvements in canopy structure,as well as photosynthetic and physiological characteristics,contributed to optimizing the light environment,thereby increasing the total biomass and yield in the lines with a sub-okra leaf shape.Our results suggest that the sub-okra leaf may have practical application in cultivating varieties,and could enhance sustainable and profitable cotton production. 展开更多
关键词 PHOTOSYNTHESIS canopy structure YIELD BIOMASS sub-okra leaf shape
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Visual rating and the use of image analysis for assessing canopy density in a pecan provenance collection during leaf fall
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作者 Cristina Pisani Clive H.Bock Jennifer Randall 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第6期1843-1854,共12页
A collection representing the native range of pecan was planted at the US DA-ARS Southeastern Fruit and Tree Nut Research Station,Byron,GA.The collection(867 trees)is a valuable genetic resource for characterizing imp... A collection representing the native range of pecan was planted at the US DA-ARS Southeastern Fruit and Tree Nut Research Station,Byron,GA.The collection(867 trees)is a valuable genetic resource for characterizing important horticultural traits.Canopy density during leaf fall is important as the seasonal canopy dynamics provides insights to environmental cues and breeding potential of germplasm.The ability of visual raters to estimate canopy density on a subset of the provenance collection(76 trees)as an indicator of leaf shed during autumn along with image analysis values was explored.Mean canopy density using the image analysis software was less compared to visual estimates(11.9%vs 18.4%,respectively).At higher canopy densities,the raters overestimated foliage density,but overall agreement between raters and measured values was good(ρc=0.849 to 0.915),and inter-rater reliability was high(R^(2)=0.910 to 0.953).The provenance from Missouri(MOL),the northernmost provenance,had the lowest canopy density in November,and results show that the higher the latitude of the provenance,the lower the canopy density.Based on regression,the source provenance latitude explained 0.609 of the variation using image analysis,and0.551 to 0.640 when based on the rater estimates of canopy density.Visual assessment of pecan canopy density due to late season leaf fall for comparing pecan genotypes provides accurate and reliable estimates and could be used in future studies of the whole provenance collection. 展开更多
关键词 Carya illinoinensis Accuracy Reliability canopy Foliage density Leaf area density Leaf area index
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Remote sensing of subtropical tree diversity:The underappreciated roles of the practical definition of forest canopy and phenological variation
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作者 Yongchao Liu Ruyun Zhang +11 位作者 Chen-Feng Lin Zhaochen Zhang Ran Zhang Kankan Shang Mingshui Zhao Jingyue Huang Xiaoning Wang You Li Yulin Zeng Yun-Peng Zhao Jian Zhang Dingliang Xing 《Forest Ecosystems》 SCIE CSCD 2023年第3期378-386,共9页
Tree species diversity is vital for maintaining ecosystem functions,yet our ability to map the distribution of tree diversity is limited due to difficulties in traditional field-based approaches.Recent developments in... Tree species diversity is vital for maintaining ecosystem functions,yet our ability to map the distribution of tree diversity is limited due to difficulties in traditional field-based approaches.Recent developments in spaceborne remote sensing provide unprecedented opportunities to map and monitor tree diversity more efficiently.Here we built partial least squares regression models using the multispectral surface reflectance acquired by Sentinel-2 satellites and the inventory data from 74 subtropical forest plots to predict canopy tree diversity in a national natural reserve in eastern China.In particular,we evaluated the underappreciated roles of the practical definition of forest canopy and phenological variation in predicting tree diversity by testing three different definitions of canopy trees and comparing models built using satellite imagery of different seasons.Our best models explained 42%–63%variations in observed diversities in cross-validation tests,with higher explanation power for diversity indices that are more sensitive to abundant species.The models built using imageries from early spring and late autumn showed consistently better fits than those built using data from other seasons,highlighting the significant role of transitional phenology in remotely sensing plant diversity.Our results suggested that the cumulative diameter(60%–80%)of the biggest trees is a better way to define the canopy layer than using the subjective fixeddiameter-threshold(5–12 cm)or the cumulative basal area(90%–95%)of the biggest trees.Remarkably,these approaches resulted in contrasting diversity maps that call attention to canopy structure in remote sensing of tree diversity.This study demonstrates the potential of mapping and monitoring tree diversity using the Sentinal-2 data in species-rich forests. 展开更多
关键词 canopy structure Multispectral remote sensing Seasonal phenology Subtropical forest Tree species diversity
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Assessing the severity of cotton Verticillium wilt disease from in situ canopy images and spectra using convolutional neural networks
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作者 Xiaoyan Kang Changping Huang +3 位作者 Lifu Zhang Mi Yang Ze Zhang Xin Lyu 《The Crop Journal》 SCIE CSCD 2023年第3期933-940,共8页
Verticillium wilt(VW)is a common soilborne disease of cotton.It occurs mainly in the seedling and bollopening stages and severely impairs the yield and quality of the fiber.Rapid and accurate identification and evalua... Verticillium wilt(VW)is a common soilborne disease of cotton.It occurs mainly in the seedling and bollopening stages and severely impairs the yield and quality of the fiber.Rapid and accurate identification and evaluation of VW severity(VWS)forms the basis of field cotton VW control,which has great significance to cotton production.Cotton VWS values are conventionally measured using in-field observations and laboratory test diagnoses,which require abundant time and professional expertise.Remote and proximal sensing using imagery and spectrometry have great potential for this purpose.In this study,we performed in situ investigations at three experimental sites in 2019 and 2021 and collected VWS values,in situ images,and spectra of 361 cotton canopies.To estimate cotton VWS values at the canopy scale,we developed two deep learning approaches that use in situ images and spectra,respectively.For the imagery-based method,given the high complexity of the in situ environment,we first transformed the task of healthy and diseased leaf recognition to the task of cotton field scene classification and then built a cotton field scenes(CFS)dataset with over 1000 images for each scene-unit type.We performed pretrained convolutional neural networks(CNNs)training and validation using the CFS dataset and then used the networks after training to classify scene units for each canopy.The results showed that the Dark Net-19 model achieved satisfactory performance in CFS classification and VWS values estimation(R^(2)=0.91,root-mean-square error(RMSE)=6.35%).For the spectroscopy-based method,we first designed a one-dimensional regression network(1D CNN)with four convolutional layers.After dimensionality reduction by sensitive-band selection and principal component analysis,we fitted the 1D CNN with varying numbers of principal components(PCs).The 1D CNN model with the top 20 PCs performed best(R^(2)=0.93,RMSE=5.77%).These deep learning-driven approaches offer the potential of assessing crop disease severity from spatial and spectral perspectives. 展开更多
关键词 canopy scale Cotton verticillium wilt Deep learning Disease assessment In situ imagery In situ spectrometry
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铁皮石斛仿野生栽培研究 被引量:1
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作者 李桂琳 姚志军 +4 位作者 贾敏 罗凯 周侯光 董蓉娇 李泽生 《热带农业科技》 2024年第4期37-41,共5页
以铁皮石斛为试验材料,开展种苗选择、种植时间、相对湿度、荫蔽度、附生树种、固定材料、固定部位、种植密度、采收时间等仿野生栽培试验。结果表明:仿野生种植铁皮石斛应选用驯化组培苗或者扦插苗,在1月或9月,在相对湿度大于50%,荫蔽... 以铁皮石斛为试验材料,开展种苗选择、种植时间、相对湿度、荫蔽度、附生树种、固定材料、固定部位、种植密度、采收时间等仿野生栽培试验。结果表明:仿野生种植铁皮石斛应选用驯化组培苗或者扦插苗,在1月或9月,在相对湿度大于50%,荫蔽度60%~70%的林地,选用梨树、澳洲坚果树、龙眼树等树皮粗糙、多纵沟纹、不易脱落且径围>10 cm的树种,用棕绳将铁皮石斛种苗按6~8株/丛,丛距×层距10 cm×20 cm,根系朝上,茎叶朝下,螺旋式将铁皮石斛捆绑在附生树种上。生长期每天喷雾2次,每月喷叶面肥1次,种植24个月后即可采收铁皮石斛封顶的鲜茎。 展开更多
关键词 铁皮石斛 仿野生栽培 林下 澳洲坚果
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