期刊文献+
共找到458篇文章
< 1 2 23 >
每页显示 20 50 100
Anterior segment changes after pharmacologic mydriasis using Pentacam and optical coherence tomography in angle closure suspects 被引量:4
1
作者 Jing-Min Guo Mu Li +2 位作者 Xiao-Lan Xu Hong Zhang Jun-Ming Wang 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2015年第5期980-984,共5页
AIM: To compare the dynamic changes of anterior segment parameters especially iris morphology induced by pharmacologic mydriasis between angle closure suspects and normal controls. METHODS: The study group comprised 1... AIM: To compare the dynamic changes of anterior segment parameters especially iris morphology induced by pharmacologic mydriasis between angle closure suspects and normal controls. METHODS: The study group comprised 19 eyes of 19 angle closure suspects and 19 eyes of 19 age- and sexmatched normal open-angle eyes. Pentacam and optical coherence tomography measurements before and 30min after instillation of compound tropicamide eye drop were performed and compared. Biometric evaluations of iris tomography and anterior chamber angle were estimated by a customized image-processing software. RESULTS: Baseline axial length, iris cross sectional area and volume did not differ significantly between angle closure suspects and normal controls. Angle closure suspects had smaller pupil size, narrower anterior segment dimension and axial length, thinner iris with greater curve in comparison with normal controls. Pharmacologic mydriasis led to significant increments in iris thickness at 750 mu m, anterior chamber depth and volume, whereas significant decrements in iris curve, cross sectional area and volume in both groups. Angle opening distance at 500 mu M was increased significantly in normal controls (from 0.465 +/- 0.115 mm to 0.539 +/- 0.167 mm, P=0.009), but not in angle closure suspects (from 0.125 0.100 mm to 0.145 +/- 0.131 mm, P=0.326). Iris volume change per millimeter of pupil dilation (Delta IV/Delta PD) decreased significantly less in angle closure suspects than normal controls (-2.47 +/- 1.33 mm(2) vs -3.63 +/- 1.58 mm(2), P=0.019). Linear regression analysis showed that the change of angle opening distance at 500 mu M was associated most with the change of central anterior chamber depth (beta= 0.841, P=0.002) and Delta IV/Delta PD (beta=0.028, P=0.002), followed by gender (beta=0. 062, P=0.032). CONCLUSION: Smaller iris volume decrement per millimeter of pupil dilation is related significantly with the less anterior angle opening in angle closure suspects after pharmacologic mydriasis. Dynamic iris change may be as a prospective indicator of iris compressibility and angle closure glaucoma. 展开更多
关键词 pharmacologic mydriasis primary angle closure suspects anterior segment change iris volume
下载PDF
Unsupervised Time Series Segmentation: A Survey on Recent Advances
2
作者 Chengyu Wang Xionglve Li +1 位作者 Tongqing Zhou Zhiping Cai 《Computers, Materials & Continua》 SCIE EI 2024年第8期2657-2673,共17页
Time series segmentation has attracted more interests in recent years,which aims to segment time series into different segments,each reflects a state of the monitored objects.Although there have been many surveys on t... Time series segmentation has attracted more interests in recent years,which aims to segment time series into different segments,each reflects a state of the monitored objects.Although there have been many surveys on time series segmentation,most of them focus more on change point detection(CPD)methods and overlook the advances in boundary detection(BD)and state detection(SD)methods.In this paper,we categorize time series segmentation methods into CPD,BD,and SD methods,with a specific focus on recent advances in BD and SD methods.Within the scope of BD and SD,we subdivide the methods based on their underlying models/techniques and focus on the milestones that have shaped the development trajectory of each category.As a conclusion,we found that:(1)Existing methods failed to provide sufficient support for online working,with only a few methods supporting online deployment;(2)Most existing methods require the specification of parameters,which hinders their ability to work adaptively;(3)Existing SD methods do not attach importance to accurate detection of boundary points in evaluation,which may lead to limitations in boundary point detection.We highlight the ability to working online and adaptively as important attributes of segmentation methods,the boundary detection accuracy as a neglected metrics for SD methods. 展开更多
关键词 Time series segmentation time series state detection boundary detection change point detection
下载PDF
Semantic Segmentation of the Intertidal Zone of an Estuary—In Search of the Best Solution
3
作者 Maria da Conceição Proença Ricardo Nogueira Mendes Ricardo Melo 《Journal of Geoscience and Environment Protection》 2024年第7期1-13,共13页
An aerial photographic coverage acquired on two consecutive days in October 2021 with a ground resolution of 20 cm and a spectral resolution of 4 bands (red, green, blue and near infrared), allowed to distinguish most... An aerial photographic coverage acquired on two consecutive days in October 2021 with a ground resolution of 20 cm and a spectral resolution of 4 bands (red, green, blue and near infrared), allowed to distinguish most of the classes of interest present in the intertidal zone of the Sado estuary. We explored the possibilities of thematic classification in the powerful and complex software ArcGIS Pro;we presented the methodology used in a detailed way that allows others with minimal knowledge of GIS to reproduce the classification process without having to decipher the specifics of the software. The classification implemented used ground truth from four classes related to the macro-occupations of the area. In a first phase we explore the standard algorithms with object-based capabilities, like K-Nearest Neighbor, Random Trees Forest and Support Vector Machine, and in a second phase we proceed to test three deep learning classifiers that provide semantic segmentation: a U-Net configuration, a Pyramid Scene Parsing Network and DeepLabV3. The resulting classifications were quantitatively evaluated with a set of 500 control points in a test area of 37,500 × 12,500 pixels, using confusion matrices and resorting to Cohen’s kappa statistic and the concept of global accuracy, achieving a Kappa in the range [0.72, 0.81] and a global accuracy between 88.9% and 92.9%;the option U-Net had the most interesting results. This work establishes a methodology to provide a baseline for assessing future changes in the distribution of Sado estuarine habitats, which can be replicated in other wetland ecosystems for conservation and management purposes. 展开更多
关键词 ESTUARY Intertidal Zone ArcGIS Pro segmentATION Global changes
下载PDF
Millennial-centennial Scales Climate Changes of Holocene Indicated by Magnetic Susceptibility of High-resolution Section in Salawusu River Valley, China 被引量:20
4
作者 LU Yingxia LI Baosheng +4 位作者 WEN Xiaohao QIU Shifan WANG Fengnian NIU Dongfeng LI Zhiwen 《Chinese Geographical Science》 SCIE CSCD 2010年第3期243-251,共9页
The upmost segment (Holocene series) of the Milanggouwan stratigraphic section (MGS1) in the Salawusu River valley shows 11 sedimentary cycles of dune sands and fluvio-lacustrine facies, or dune sands and paleosols. T... The upmost segment (Holocene series) of the Milanggouwan stratigraphic section (MGS1) in the Salawusu River valley shows 11 sedimentary cycles of dune sands and fluvio-lacustrine facies, or dune sands and paleosols. The analysis of the magnetic susceptibility of this segment suggests that there are 11 magnetic susceptibility cycles with the value alternating from low to high, in which the layers of the dune sands correspond to the lower value of the magnetic susceptibility and the layers of fluvio-lacustrine facies and paleosols correspond to the higher peaks. The study reveals that the low and high magnetic susceptibility values indicate the climate dominated by cold-arid winter monsoon and warm-humid summer monsoon of East Asia, respectively, and the study area has experienced at least 22 times of millennial-centennial scales climate alternation from the cold-arid to the warm-humid during the Holocene. In terms of the time and the climate nature, the variations basically correspond to those of the North Atlantic and some records of cold-warm changes in China as well. They might be caused by the alternation of winter and summer monsoons in the Mu Us Desert induced by global climate fluctuations in the Holocene. 展开更多
关键词 萨拉乌苏河流域 气候变化 磁化率 全新世 高分辨率 百年尺度 中国 夏季季风
下载PDF
超声心动图探测在心电图无明显ST-T改变的冠心病中诊断意义:基于冠脉血流速度联合室壁运动 被引量:5
5
作者 宿海峰 甘丰 +2 位作者 裴娟慧 魏士刚 郝晓燕 《分子影像学杂志》 2023年第2期267-270,共4页
目的研究超声心动图检测患者冠状动脉相关血流速度联合节段性室壁运动对经心电图检测ST-T段未见明显改变的冠状动脉粥样硬化性心脏病中的诊断意义。方法回顾性分析2020年1月~2021年6月在我院心内科住院的经冠脉造影证实为冠心病且血管... 目的研究超声心动图检测患者冠状动脉相关血流速度联合节段性室壁运动对经心电图检测ST-T段未见明显改变的冠状动脉粥样硬化性心脏病中的诊断意义。方法回顾性分析2020年1月~2021年6月在我院心内科住院的经冠脉造影证实为冠心病且血管狭窄大于50%但未完全闭塞的患者并进行心电图检查,将其中无明显ST-T段改变的患者40例作为冠心病组;同时选取冠状动脉造影证实血管狭窄小于50%的患者30例作为对照组,所有的患者均在入院期间进行超声心动图检查,观察冠状动脉血流及室壁运动情况。结果冠心病组中冠脉舒张期血流速度高于对照组,差异有统计学意义(P<0.05)。超声心动图显示舒张期节段性血流峰值流速对诊断冠心病的准确性为92.3%,敏感度为82.4%,特异性为90%,临界值为94.5 cm/s;节段性室壁运动诊断冠心病的敏感度为55.9%,特异性为86.7%,二者联合诊断冠心病的敏感度为84.2%,特异性为92.5%。结论超声心动图对冠状动脉血流速度联合节段性室壁运动情况可以明显提高无明显ST-T改变的冠心病患者的诊断率,有利于减少临床上对冠心病患者的误诊率。 展开更多
关键词 超声心动图 节段性室壁运动 心电图无明显st-t改变 冠心病 冠脉血流速度
下载PDF
Co-seismic Coulomb stress changes on the northern Tanlu fault zone caused by the Tohoku-Oki M_(W)9.0 earthquake 被引量:1
6
作者 Fei Chen Tai Liu +2 位作者 Yawen She Xing Huang Guangyu Fu 《Earthquake Science》 2020年第1期11-22,共12页
Based on the spherical earth dislocation theory and a fault slip model of the Tohoku-Oki M_(W)9.0 earthquake,the co-seismic Coulomb failure stress changes(ΔCFS)on the northern Tanlu fault zone at depths of 0–40 km a... Based on the spherical earth dislocation theory and a fault slip model of the Tohoku-Oki M_(W)9.0 earthquake,the co-seismic Coulomb failure stress changes(ΔCFS)on the northern Tanlu fault zone at depths of 0–40 km are calculated.By comparing two sets of results from the spherical earth dislocation theory and the semi-infinite space one,the effect of earth curvature on the calculation results is analyzed quantitatively.First,we systematically summarize previous researches related to the northern Tanlu fault zone,divide the fault zone as detailed as possible,give the geometric parameters of each segment,and establish a segmented structural model of the northern Tanlu fault zone.Second,we calculate the Coulomb stress changes on the northern Tanlu fault zone by using the spherical earth dislocation theory.The result shows the Coulomb stress changes are no more than 0.003 MPa,which proves the great earthquake did not significantly change the stress state of the fault zone.Finally,we quantitatively analyze the disparities between the results of semi-infinite space dislocation theory and the spherical earth one.The average disparity between them is about 7.7%on the northern Tanlu fault zone and is 16.8%on the Fangzheng graben,the maximum disparity on this graben reaches up to 25.5%.It indicates that the effect of earth curvature can not be ignored.So it’s necessary to use the spherical earth dislocation theory instead of the semi-infinite space one to study the Coulomb stress change in the far field. 展开更多
关键词 the northern Tanlu fault zone segmented structural model spherical earth dislocation theory the Tohoku-Oki M_(W)9.0 earthquake co-seismic Coulomb stress change(△CFS)
下载PDF
动态心电瀑布图结合ST段趋势图诊断冠心病缺血性ST-T改变 被引量:1
7
作者 石衍梅 魏元杰 +3 位作者 李洁 魏希进 胡有权 高华 《吉林医学》 CAS 2023年第9期2400-2404,共5页
目的:论证动态心电瀑布图结合ST段趋势图可“快、准、全”地诊断动态变化的ST-T改变。方法:搜集冠心病常见的5种ST-T改变,逐一说明如何运用瀑布图结合ST段趋势图进行诊断。结果:在ST段趋势图上ST段抬高可见“细柱”或“峰型”突出,ST段... 目的:论证动态心电瀑布图结合ST段趋势图可“快、准、全”地诊断动态变化的ST-T改变。方法:搜集冠心病常见的5种ST-T改变,逐一说明如何运用瀑布图结合ST段趋势图进行诊断。结果:在ST段趋势图上ST段抬高可见“细柱”或“峰型”突出,ST段下移则为“细柱”或“峰型”凹陷;瀑布图ST-T改变体现在色谱变化上,ST-T高于基线,色谱变化为:黄色→红色;ST-T低于基线,色谱变化为:深蓝色→黑色。结论:瀑布图加ST段趋势图可实现精准、快速、全面地找出缺血性ST-T动态改变,提高心电图对冠心病的诊断率。 展开更多
关键词 冠心病 动态心电图 st-t动态改变 ST段趋势图 瀑布图
下载PDF
Transition from minimal change disease to focal segmental glomerulosclerosis related to occupational exposure:A case report
8
作者 Long Tang Zhen Cai +1 位作者 Su-Xia Wang Wen-Jing Zhao 《World Journal of Clinical Cases》 SCIE 2022年第17期5861-5868,共8页
BACKGROUND Although minimal change disease(MCD)and focal segmental glomerulosclerosis(FSGS)have been described as two separate forms of nephrotic syndrome(NS),they are not completely independent.We report a case of a ... BACKGROUND Although minimal change disease(MCD)and focal segmental glomerulosclerosis(FSGS)have been described as two separate forms of nephrotic syndrome(NS),they are not completely independent.We report a case of a patient transitioning from MCD to FSGS,review the literature,and explore the relationship between the two diseases.CASE SUMMARY A 42-year-old male welder,presenting with lower extremity edema and elevated serum creatinine,was diagnosed with NS and end-stage kidney disease(ESKD)based on laboratory test results.The patient had undergone a kidney biopsy for NS 20 years previously,which indicated MCD,and a second recent kidney biopsy suggested FSGS.The patient was an electric welder with excessive levels of cadmium and lead in his blood.Consequently,we suspect that his aggravated pathology and occurrence of ESKD were related to metal nephrotoxicity.The patient eventually received kidney replacement therapy and quit his job which involved long-term exposure to metals.During the 1-year follow-up period,the patient was negative for metal elements in the blood and urine and recovered partial kidney function.CONCLUSION MCD and FSGS may be different stages of the same disease.The transition from MCD to FSGS in this case indicates disease progression,which may be related to excessive metal contaminants caused by the patient’s occupation. 展开更多
关键词 Minimal change disease Focal segmental glomerulosclerosis Occupational exposure CADMIUM LEAD Case report
下载PDF
A Novel Audio Segmentation Method Based on Changing Trend of Distance between Audio Scenes
9
作者 YongchengWang Jiqing Han Haifeng Li Tieran Zheng 《通讯和计算机(中英文版)》 2006年第7期22-30,共9页
关键词 贝叶斯信息标准 音频分类 音频流分割 音视频特征
下载PDF
9号道岔区铺设减振垫浮置板的行车安全性及舒适性研究 被引量:1
10
作者 曾志平 曾强 +4 位作者 郭无极 王卫东 李秋义 何永春 岑尧 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第3期1015-1024,共10页
地铁道岔区在基本轨、尖轨处以及道岔钢轨接头处存在大量钢轨不连续地段,轮轨相互作用强烈,轨道系统振动明显,减振垫浮置板轨道作为一种高等减振措施已应用于地铁线路道岔区。为探究减振垫浮置板应用于9号道岔的适用性,并作为减振地段... 地铁道岔区在基本轨、尖轨处以及道岔钢轨接头处存在大量钢轨不连续地段,轮轨相互作用强烈,轨道系统振动明显,减振垫浮置板轨道作为一种高等减振措施已应用于地铁线路道岔区。为探究减振垫浮置板应用于9号道岔的适用性,并作为减振地段与普通无砟轨道的过渡段的可行性,以某地铁高架9号道岔为研究对象,建立桥上道岔三维有限元模型,仿真分析地铁B型车在120 km/h直向过岔和30 km/h侧向过岔的情况下,列车的行车安全性、舒适性以及轨下结构形变。对比在9号单开道岔区域设置的2种刚度过渡方式的优劣及其减振效果,较为系统地论证了在9号道岔区域铺设减振垫浮置板的可行性。研究结果表明:1)列车通过铺设减振垫浮置板的9号道岔区域时,浮置板位移极值出现在转辙区域和心轨区域,最大位移出现在尖轨位置,可增大尖轨处单板橡胶垫支承刚度,以保证轨道结构变形均匀;2)列车逆向侧向通过设置过渡段的减振垫浮置板道岔区时,2级过渡方式的车体最大垂向加速度、最大横向加速度、最大脱轨系数、最大轮重减载率、轨道刚度变化率以及减振效果等指标均优于1级过渡方式;3)在道岔区铺设减振垫浮置板,列车直向和侧向通过时的行车安全性和舒适性均能满足相关评价指标,且2级过渡方式更优。研究结果可为后续道岔区减振设计研究提供一定的理论参考。 展开更多
关键词 减振垫浮置板 道岔 过渡段 车辆-轨道耦合动力学 轨道刚度变化率
下载PDF
地方政府考核目标转变的经济效率与福利效应研究
11
作者 王文甫 方也 《四川大学学报(哲学社会科学版)》 北大核心 2024年第3期42-57,207,208,共18页
构建一个合理且科学的考核体系,并引导地方政府更科学关注经济发展质量,是学术界亟须解决的重要问题之一。基于新开放宏观模型,通过构建一个包含地区竞争、市场分割及营商环境的动态随机一般均衡模型,从经济效率和经济福利两个维度来考... 构建一个合理且科学的考核体系,并引导地方政府更科学关注经济发展质量,是学术界亟须解决的重要问题之一。基于新开放宏观模型,通过构建一个包含地区竞争、市场分割及营商环境的动态随机一般均衡模型,从经济效率和经济福利两个维度来考察地方政府考核目标转变对经济发展质量的影响。研究发现:第一,传统考核机制会阻碍经济效率、经济福利水平的提升,地区竞争程度越大、市场分割程度越高、为优化营商环境努力程度越低,所引起的阻碍作用越明显;第二,在多元化考核机制下,地方政府短期目标导向能够缓解经济发展质量的负面影响,其中营商环境的优化有利于经济高质量的发展,但由于地区竞争与市场分割的存在,缓解作用并不能得到很好地释放。在经济高质量发展不断推进阶段,应尽快落实多元化考核机制,引导地方政府优化营商环境,并在一定程度上消除地区竞争与市场分割,以保证经济可持续发展。 展开更多
关键词 考核目标转变 地区竞争 市场分割 营商环境 经济效率与福利
下载PDF
南川页岩气水平段轨迹控制技术分析
12
作者 王恒 何谦 +1 位作者 潘通 陈雅辉 《化工设计通讯》 CAS 2024年第4期24-26,44,共4页
重庆南川区块页岩气开发早期水平段使用旋导及近钻头技术,但随着区块开发力度的加大,为进一步降本提效,开始逐步推广使用单弯螺杆钻具+LWD组合进行施工。但受制于LWD仪器零长、螺杆等原因,导致伽马曲线数据滞后,调整轨迹段较长,从而频... 重庆南川区块页岩气开发早期水平段使用旋导及近钻头技术,但随着区块开发力度的加大,为进一步降本提效,开始逐步推广使用单弯螺杆钻具+LWD组合进行施工。但受制于LWD仪器零长、螺杆等原因,导致伽马曲线数据滞后,调整轨迹段较长,从而频繁穿层追层,易引起井下复杂,使得目的层钻遇率低。为此,通过从目的层岩性、钻井参数分析、工具及地层增降斜趋势、伽马曲线等四个方面出发,总结分析四者参数与地层层位变化时的对应关系,从而达到提升层位判断准确性的目的,减少仪器零长盲区而造成的误差,对提高南川区块页岩气水平段钻遇率有一定的借鉴意义。 展开更多
关键词 页岩气 水平段 LWD 参数变化 层位判断
下载PDF
一种融合多尺度混合注意力的建筑物变化检测模型
13
作者 于海洋 滑志华 +2 位作者 宋草原 谢赛飞 景鹏 《测绘工程》 2024年第1期47-56,共10页
针对高分辨率遥感图像非真实变化所引起的错误检测问题,提出一种新颖的轻量化孪生神经网络建筑物变化检测模型。其中轻量化的特征提取模块可以获取不同尺度的局部上下文信息,使其充分学习局部和全局特征。由通道和空间注意力组成的混合... 针对高分辨率遥感图像非真实变化所引起的错误检测问题,提出一种新颖的轻量化孪生神经网络建筑物变化检测模型。其中轻量化的特征提取模块可以获取不同尺度的局部上下文信息,使其充分学习局部和全局特征。由通道和空间注意力组成的混合注意力模块可以充分利用周围丰富的时空语义信息,以实现变化建筑物的准确提取。针对变化建筑物尺度跨度较大,容易导致建筑物边缘细节提取粗糙、小尺度建筑物漏检等问题,引入多尺度概念,将提取到的特征图划分为多个子区域,并分别引入混合注意力模块,最终将不同尺度的输出特征进行加权融合,以加强边缘细节提取能力。模型在WHU-CD、LEVIR-CD公开数据集进行实验,并分别取得87.8%和88.1%的F 1值,相较于6种对比模型具有更高的变化检测精度。 展开更多
关键词 建筑物变化检测 混合注意力机制 多尺度分割 轻量化孪生神经网络 高分辨率遥感图像
下载PDF
时间序列上的变化查询的高效处理算法
14
作者 施文俊 王鹏 汪卫 《计算机应用与软件》 北大核心 2024年第7期25-33,共9页
时间序列数据的值的变化往往代表着事件的发生。时间序列数据上的变化查询,即查找在一定长度内,满足增长或减少一定阈值的子序列,可以挖掘事件,有重要实际意义。现有方法无法高效解决该问题。为此,一种基于分段并构建分段关系图的方法... 时间序列数据的值的变化往往代表着事件的发生。时间序列数据上的变化查询,即查找在一定长度内,满足增长或减少一定阈值的子序列,可以挖掘事件,有重要实际意义。现有方法无法高效解决该问题。为此,一种基于分段并构建分段关系图的方法被提出。实验表明,该方法在百万长度的时间序列下仍可在百毫秒内返回结果,且分段关系图的存储开销也较小。对于波动较少的数据集,存储大小可达到原数据集大小的30%以下。且进一步提出了两种优化手段,可在原有基础上再减少约50%的存储开销,同时不过多影响查询效率。 展开更多
关键词 时间序列 变化查询 子序列查询 分段
下载PDF
全国名老中医药专家常小荣基于“经脉-脏腑相关”理论辨治脾胃病特色探骊
15
作者 张汝涵 曹思慧 +8 位作者 罗坚 肖逸 罗容 刘未艾 熊暑霖 刘琼 常小荣 钟欢 刘密 《湖南中医药大学学报》 CAS 2024年第8期1422-1426,共5页
常小荣教授认为“经脉-脏腑相关”是经络学说的核心理论,对临床工作有重要指导意义。总结常小荣教授基于“经脉-脏腑相关”理论辨治脾胃病的学术经验,在临床诊治脾胃病过程中注重经脉辨证与脏腑辨证相结合,治则以调畅中焦、调和五脏气... 常小荣教授认为“经脉-脏腑相关”是经络学说的核心理论,对临床工作有重要指导意义。总结常小荣教授基于“经脉-脏腑相关”理论辨治脾胃病的学术经验,在临床诊治脾胃病过程中注重经脉辨证与脏腑辨证相结合,治则以调畅中焦、调和五脏气机为要,辨证严谨,选穴精准,以四白、梁门、足三里为治疗脾胃病的基础用穴,并注重灸法的运用。常小荣教授提倡学习经典与继承创新,坚持研究与临床相结合,为传承发展“经脉-脏腑相关”理论作出了重大贡献。 展开更多
关键词 经脉-脏腑相关 脾胃病 三段取穴 灸法 名医经验 常小荣
下载PDF
基于激光视觉的光照变化图像分割研究
16
作者 邓舟舟 冯祥 赵继平 《激光杂志》 CAS 北大核心 2024年第1期136-141,共6页
光照变化图像在分割过程中,若不能有效抑制图像中的噪声,会直接影响图像的分割精度,为提升图像的分割效果,提出基于激光视觉的光照变化图像分割方法。将图像输入至激光视觉系统中实施去噪、目标增强等处理,过程中通过该系统中的控制传感... 光照变化图像在分割过程中,若不能有效抑制图像中的噪声,会直接影响图像的分割精度,为提升图像的分割效果,提出基于激光视觉的光照变化图像分割方法。将图像输入至激光视觉系统中实施去噪、目标增强等处理,过程中通过该系统中的控制传感器,严密跟踪图像处理流程,提升图像的处理效果;获取图像直方图,根据直方图的平滑结果确定光照变换图像灰度直方图阈值选取范围,对图像实施区域划分获取对应的阈值,根据确定的阈值完成光照图像的精准分割。实验结果表明,使用该方法开展图像分割时,有效去除了图像噪声,分割效果较好,能够实现对图像目标的高效、准确分割。 展开更多
关键词 激光视觉系统 光照变化图像 图像去噪 灰度化处理 图像分割
下载PDF
Hydraulic properties and drought response of a tropical bamboo (Cephalostachyum pergracile)
17
作者 Wanwalee Kongjarat Lu Han +10 位作者 Amy Ny Aina Aritsara Shu-Bin Zhang Gao-Juan Zhao Yong-Jiang Zhang Phisamai Maenpuen Ying-Mei Li Yi-Ke Zou Ming-Yi Li Xue-Nan Li Lian-Bin Tao Ya-Jun Chen 《Plant Diversity》 SCIE CAS CSCD 2024年第3期406-415,共10页
Bamboo plants are an essential component of tropical ecosystems,yet their vulnerability to climate extremes,such as drought,is poorly understood due to limited knowledge of their hydraulic properties.Cephalostachyum p... Bamboo plants are an essential component of tropical ecosystems,yet their vulnerability to climate extremes,such as drought,is poorly understood due to limited knowledge of their hydraulic properties.Cephalostachyum pergracile,a commonly used tropical bamboo species,exhibited a substantially higher mortality rate than other co-occurring bamboos during a severe drought event in 2019,but the underlying mechanisms remain unclear.This study investigated the leaf and stem hydraulic traits related to drought responses,including leaf-stem embolism resistance(P50leaf;P50stem) estimated using optical and X-ray microtomography methods,leaf pressure-volume and water-releasing curves.Additionally,we investigated the seasonal water potentials,native embolism level(PLC) and xylem water source using stable isotope.We found that C.pergracile exhibited strong resistance to embolism,showing low P50leaf,P50stem,and turgor loss point,despite its rapid leaf water loss.Interestingly,its leaves displayed greater resistance to embolism than its stem,suggesting a lack of effective hydraulic vulnerability segmentation(HVS) to protect the stem from excessive xylem tension.During the dry season,approximately 49% of the water was absorbed from the upper 20-cm-deep soil layer.Consequently,significant diurnal variation in leaf water potentials and an increase in midday PLC from 5.87±2.33% in the wet season to 12.87±4.09%in the dry season were observed.In summary,this study demonstrated that the rapid leaf water loss,high reliance on surface water,and a lack of effective HVS in C.pergracile accelerated water depletion and increased xylem embolism even in the typical dry season,which may explain its high mortality rate during extreme drought events in 2019. 展开更多
关键词 Climate change DROUGHT Hydraulic safety Hydraulic vulnerability segmentation Stable isotope Tree mortality
下载PDF
面板数据中方差的共同变点估计
18
作者 赵军辉 董翠玲 《新疆师范大学学报(自然科学版)》 2024年第1期22-32,共11页
文章对面板数据中方差的共同变点提出了一个含有调节参数的CUSUM(Cumulative Sum)型估计量,证明了变点估计量的相合性,并结合二元分割法将其推广到多个方差共同变点的情形。蒙特卡洛模拟发现,调节参数(γ≠0)下CUSUM型估计量的精确度要... 文章对面板数据中方差的共同变点提出了一个含有调节参数的CUSUM(Cumulative Sum)型估计量,证明了变点估计量的相合性,并结合二元分割法将其推广到多个方差共同变点的情形。蒙特卡洛模拟发现,调节参数(γ≠0)下CUSUM型估计量的精确度要高于无调节参数(γ=0)下CUSUM型估计量的精确度。应用外汇汇率进行实证分析,结果也表明调节参数(γ≠0)下CUSUM型估计方法是有效的。 展开更多
关键词 面板数据 方差变点 CUSUM 调节参数 二元分割法
下载PDF
心电图ST-T段改变在冠心病早期诊断中的价值 被引量:5
19
作者 姜桂艳 《中国卫生标准管理》 2019年第24期65-67,共3页
目的评价心电图ST-T段改变用于冠心病患者早期诊断中的价值,了解冠心病患者检查特征,为冠心病患者临床诊断工作的判断提供参考。方法选择我院2017年6月-2019年6月收治入院检查治疗的冠心病患者,总计100例,作为此次的试验组。另外,选择... 目的评价心电图ST-T段改变用于冠心病患者早期诊断中的价值,了解冠心病患者检查特征,为冠心病患者临床诊断工作的判断提供参考。方法选择我院2017年6月-2019年6月收治入院检查治疗的冠心病患者,总计100例,作为此次的试验组。另外,选择同期进行体检的非冠心病患者,总计100例,作为对照组。对比2组受试人员组间ST-T段改变率以及试验组冠心病患者单支病变、多支病变ST-T段改变率情况。结果试验组冠心病患者ST-T段改变率明显高于对照组非冠心病人群,ST-T段改变率(62%vs 40%)比较,χ^2=9.6839,P=0.0018。冠心病患者单支/多支病变心电图ST-T段改变率(70%vs 66%)比较,χ^2=0.1838,P=0.6681。结论心电图ST-T段改变在冠心病患者早期诊断中价值显著,但是为了确保诊断的准确性需早期配合实施冠脉造影检查,以确保为患者早期治疗工作提供参考。 展开更多
关键词 心电图 st-t段改变 冠心病 早期诊断 诊断价值 冠脉造影
下载PDF
市场分割对制造业出口技术复杂度的影响——基于产业聚集和技术变革视角
20
作者 刘宏楠 陈光春 杨景院 《经济与管理》 北大核心 2024年第1期53-64,共12页
基于建设全国统一大市场的背景,从理论上探析建立国内统一大市场进程中出现的市场分割扭曲现象与制造业出口技术复杂度的关系,并实证检验国内市场分割对制造业出口技术复杂度的影响机制及空间溢出效应。研究发现:国内市场分割显著抑制... 基于建设全国统一大市场的背景,从理论上探析建立国内统一大市场进程中出现的市场分割扭曲现象与制造业出口技术复杂度的关系,并实证检验国内市场分割对制造业出口技术复杂度的影响机制及空间溢出效应。研究发现:国内市场分割显著抑制了中国制造业出口技术复杂度,在考虑内生性问题及稳健性检验后依然成立;且不同时间阶段、不同地理区位,市场分割对制造业出口技术复杂度的影响有所不同;影响机制检验表明,市场分割主要通过阻碍产业聚集和技术变革进程两种渠道抑制制造业出口技术复杂度;进一步研究发现,当制造业出口技术复杂度跨越一定的门槛后,市场分割对制造业出口技术复杂度的负面影响会边际递减;考虑空间溢出效应后,市场分割对制造业出口技术复杂度产生了显著的负向空间溢出效应。因此,打破市场分割不仅是促进“制造强国”目标实现的国内市场保障,而且是对中国式现代化方法统筹“有为政府”和“有效市场”所进行的积极探索。 展开更多
关键词 市场分割 产业聚集 技术变革 出口技术复杂度
下载PDF
上一页 1 2 23 下一页 到第
使用帮助 返回顶部