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Influences of local factors on permafrost occurrence and their implications for Qinghai-Xizang Railway design 被引量:27
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作者 CHENG Guodong 《Science China Earth Sciences》 SCIE EI CAS 2004年第8期704-709,共6页
The construction of the Qinghai-Xizang Railway is facing some challenges posed by the presence of warm and ice-rich permafrost and predicted climate warming. To resolve these issues and ensure the railway a success, a... The construction of the Qinghai-Xizang Railway is facing some challenges posed by the presence of warm and ice-rich permafrost and predicted climate warming. To resolve these issues and ensure the railway a success, adjustments will have to be made in design strategies and principles. This paper presents several examples of permafrost-distribution anomaly caused by site-specific conditions. It analyzes the mechanism through which these local factors influence the occurrence and preservation of permafrost by modifying the heat convection and conduction patterns, and the amount of solar radiation received by the ground surface. A good understanding of these anomalies in permafrost occurrence is significant as it may provide some hints on the techniques and measures we can use to artificially simulate similar effects. A number of measures can be taken to lower ground temperature and to counter the effect of cli-mate warming. These measures include use of proper roadbed material and configuration, in order to adjust solar radiation, heat convection and conduction patterns. It is recommended that a new proactive approach be adopted in the railway design. This approach emphasizes the use of all the above-mentioned measures to cool down the roadbed. This is different from previous methods of preventing permafrost from thawing by utilizing more thermal resistant materials. 展开更多
关键词 local factor anomaly in PERMAFROST occurrence cooled roadbed Qinghai-Xizang Railway climate warming.
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Three-dimensional stability of landslides based on local safety factor 被引量:4
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作者 YANG Tao Man-chu Ronald YEUNG +2 位作者 YANG Bing LIU Yong-jiang YANG Yan-xin 《Journal of Mountain Science》 SCIE CSCD 2016年第9期1515-1526,共12页
Unlike the limit equilibrium method(LEM), with which only the global safety factor of the landslide can be calculated, a local safety factor(LSF) method is proposed to evaluate the stability of different sections of a... Unlike the limit equilibrium method(LEM), with which only the global safety factor of the landslide can be calculated, a local safety factor(LSF) method is proposed to evaluate the stability of different sections of a landslide in this paper. Based on three-dimensional(3D) numerical simulation results, the local safety factor is defined as the ratio of the shear strength of the soil at an element on the slip zone to the shear stress parallel to the sliding direction at that element. The global safety factor of the landslide is defined as the weighted average of all local safety factors based on the area of the slip surface. Some example analyses show that the results computed by the LSF method agree well with those calculated by the General Limit Equilibrium(GLE) method in two-dimensional(2D) models and the distribution of the LSF in the 3D slip zone is consistent with that indicated by the observed deformation pattern of an actual landslide in China. 展开更多
关键词 Landslide stability local safety factor Stability analysis method Slip mechanism
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Obtaining Profiles Based on Localized Non-negative Matrix Factorization 被引量:2
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作者 JIANGJi-xiang XUBao-wen +1 位作者 LUJian-jiang ZhouXiao-yu 《Wuhan University Journal of Natural Sciences》 EI CAS 2004年第5期580-584,共5页
Nonnegative matrix factorization (NMF) is a method to get parts-based features of information and form the typical profiles. But the basis vectors NMF gets are not orthogonal so that parts-based features of informatio... Nonnegative matrix factorization (NMF) is a method to get parts-based features of information and form the typical profiles. But the basis vectors NMF gets are not orthogonal so that parts-based features of information are usually redundancy. In this paper, we propose two different approaches based on localized non-negative matrix factorization (LNMF) to obtain the typical user session profiles and typical semantic profiles of junk mails. The LNMF get basis vectors as orthogonal as possible so that it can get accurate profiles. The experiments show that the approach based on LNMF can obtain better profiles than the approach based on NMF. Key words localized non-negative matrix factorization - profile - log mining - mail filtering CLC number TP 391 Foundation item: Supported by the National Natural Science Foundation of China (60373066, 60303024), National Grand Fundamental Research 973 Program of China (2002CB312000), National Research Foundation for the Doctoral Program of Higher Education of China (20020286004).Biography: Jiang Ji-xiang (1980-), male, Master candidate, research direction: data mining, knowledge representation on the Web. 展开更多
关键词 localized non-negative matrix factorization PROFILE log mining mail filtering
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Anomaly IoT Node Detection Based on Local Outlier Factor and Time Series 被引量:2
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作者 Fang Wang Zhe Wei Xu Zuo 《Computers, Materials & Continua》 SCIE EI 2020年第8期1063-1073,共11页
The heterogeneous nodes in the Internet of Things(IoT)are relatively weak in the computing power and storage capacity.Therefore,traditional algorithms of network security are not suitable for the IoT.Once these nodes ... The heterogeneous nodes in the Internet of Things(IoT)are relatively weak in the computing power and storage capacity.Therefore,traditional algorithms of network security are not suitable for the IoT.Once these nodes alternate between normal behavior and anomaly behavior,it is difficult to identify and isolate them by the network system in a short time,thus the data transmission accuracy and the integrity of the network function will be affected negatively.Based on the characteristics of IoT,a lightweight local outlier factor detection method is used for node detection.In order to further determine whether the nodes are an anomaly or not,the varying behavior of those nodes in terms of time is considered in this research,and a time series method is used to make the system respond to the randomness and selectiveness of anomaly behavior nodes effectively in a short period of time.Simulation results show that the proposed method can improve the accuracy of the data transmitted by the network and achieve better performance. 展开更多
关键词 local outlier factor time series Internet of Things anomaly node detection
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Anomalous Cell Detection with Kernel Density-Based Local Outlier Factor 被引量:2
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作者 Miao Dandan Qin Xiaowei Wang Weidong 《China Communications》 SCIE CSCD 2015年第9期64-75,共12页
Since data services are penetrating into our daily life rapidly, the mobile network becomes more complicated, and the amount of data transmission is more and more increasing. In this case, the traditional statistical ... Since data services are penetrating into our daily life rapidly, the mobile network becomes more complicated, and the amount of data transmission is more and more increasing. In this case, the traditional statistical methods for anomalous cell detection cannot adapt to the evolution of networks, and data mining becomes the mainstream. In this paper, we propose a novel kernel density-based local outlier factor(KLOF) to assign a degree of being an outlier to each object. Firstly, the notion of KLOF is introduced, which captures exactly the relative degree of isolation. Then, by analyzing its properties, including the tightness of upper and lower bounds, sensitivity of density perturbation, we find that KLOF is much greater than 1 for outliers. Lastly, KLOFis applied on a real-world dataset to detect anomalous cells with abnormal key performance indicators(KPIs) to verify its reliability. The experiment shows that KLOF can find outliers efficiently. It can be a guideline for the operators to perform faster and more efficient trouble shooting. 展开更多
关键词 data mining key performance indicators kernel density-based local outlier factor density perturbation anomalous cell detection
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Evaluate the Role of Socio-cultural Factors in the Global Localization of TNC Activity
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作者 关静雯 《中山大学研究生学刊(自然科学与医学版)》 2010年第2期66-72,共7页
As an increasing number of firms are exercising transnational operations to occupy markets and exploit location-specific factors,some scholars claimed that 'the world is flat' and the local particularities no ... As an increasing number of firms are exercising transnational operations to occupy markets and exploit location-specific factors,some scholars claimed that 'the world is flat' and the local particularities no longer matter for the 'invincible' transnational corporations(TNC).But I argue that there exist some socio-cultural factors in the host countries influencing the actions of TNCs.I point out six local factors which include social norms,local attitudes,class formation,family structure, religion,and consumption pattern.Social norms are regulating TNCs' activities and local attitudes in varying contexts are encouraging or resisting against the transnational operators.Class formation generates new demands benefiting TNCs ' expansion. Religion structure and family value are reshaping TNCs' operational practices in production as well as distribution spheres.The location-specific consumption patterns are transforming TNCs' operations,deepening their territorial embeddedness,or even exposing them to the danger of overlocalization. 展开更多
关键词 摘要 编辑部 编辑工作 读者
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A comprehensive factor model of growth velocity of green algae and diatoms in local lake area
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作者 Zhihong WANG Fuyi CUI +1 位作者 Jie JIA Wenxuan CHEN 《Chinese Journal Of Geochemistry》 EI CAS 2006年第B08期163-163,共1页
关键词 藻类 速度模型 生长速度 盐度
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Encoding of rat working memory by power of multi-channel local field potentials via sparse non-negative matrix factorization 被引量:1
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作者 Xu Liu Tiao-Tiao Liu +3 位作者 Wen-Wen Bai Hu Yi Shuang-Yan Li Xin Tian 《Neuroscience Bulletin》 SCIE CAS CSCD 2013年第3期279-286,共8页
Working memory plays an important role in human cognition. This study investigated how working memory was encoded by the power of multichannel local field potentials (LFPs) based on sparse non negative matrix factor... Working memory plays an important role in human cognition. This study investigated how working memory was encoded by the power of multichannel local field potentials (LFPs) based on sparse non negative matrix factorization (SNMF). SNMF was used to extract features from LFPs recorded from the prefrontal cortex of four SpragueDawley rats during a memory task in a Y maze, with 10 trials for each rat. Then the powerincreased LFP components were selected as working memoryrelated features and the other components were removed. After that, the inverse operation of SNMF was used to study the encoding of working memory in the time frequency domain. We demonstrated that theta and gamma power increased significantly during the working memory task. The results suggested that postsynaptic activity was simulated well by the sparse activity model. The theta and gamma bands were meaningful for encoding working memory. 展开更多
关键词 sparse non-negative matrix factorization multi-channel local field potentials working memory prefrontal cortex
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Risk factors for local recurrence and appropriate surveillance interval after endoscopic resection 被引量:7
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作者 Yoriaki Komeda Tomohiro Watanabe +10 位作者 Toshiharu Sakurai Masashi Kono Kazuki Okamoto Tomoyuki Nagai Mamoru Takenaka Satoru Hagiwara Shigenaga Matsui Naoshi Nishida Naoko Tsuji Hiroshi Kashida Masatoshi Kudo 《World Journal of Gastroenterology》 SCIE CAS 2019年第12期1502-1512,共11页
BACKGROUND Risk factors for local recurrence after polypectomy, endoscopic mucosal resection(EMR), and endoscopic submucosal dissection(ESD) have not been identified.Additionally, the appropriate interval for endoscop... BACKGROUND Risk factors for local recurrence after polypectomy, endoscopic mucosal resection(EMR), and endoscopic submucosal dissection(ESD) have not been identified.Additionally, the appropriate interval for endoscopic surveillance of colorectal tumors at high-risk of local recurrence has not been established.AIM To clarify the clinicopathological characteristics of recurrent lesions after endoscopic colorectal tumor resection and determine the appropriate interval.METHODS Three hundred and sixty patients(1412 colorectal tumors) who underwent polypectomy, EMR, or ESD and received endoscopic surveillance subsequently for more than one year to detect local recurrence were enrolled in this study. The clinicopathological factors associated with local recurrence were determined via univariate and multivariate analyses.RESULTS Local recurrence was observed in 31 of 360(8.6%) patients [31 of 1412(2.2%)lesions] after colorectal tumor resection. Piecemeal resection, tumor size of more than 2 cm, and the presence of villous components were associated with colorectal tumor recurrence after endoscopic resection. Of these three factors, the piecemeal resection procedure was identified as an independent risk factor for recurrence. Colorectal tumors resected into more than five pieces were associated with a high risk of recurrence since the average period from resection torecurrence in these cases was approximately 3 mo. The period to recurrence in cases resected into more than 5 pieces was much shorter than that in those resected into less than 4 pieces(3.8 ± 1.9 mo vs 7.9 ± 5.0 mo, P < 0.05).CONCLUSION Local recurrence of endoscopically treated colorectal tumors depends upon the outcome of first endoscopic procedure. Piecemeal resection was the only significant risk factor associated with local recurrence after endoscopic resection. 展开更多
关键词 local RECURRENCE COLORECTAL tumor ENDOSCOPIC SURVEILLANCE Piecemeal RESECTION Risk factors
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THE FACTORS AND TREATMENT OF LOCAL RECURRENCE AFTER RADICAL RESECTION RESERVING THE ANUS IN THE PATIENTS WITH RECTAL CANCER
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作者 单吉贤 陈峻青 +1 位作者 张文范 齐春莲 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 1989年第4期73-76,共4页
Of seventy-one patients with rectal cancer after radical resection retaining the anus, 15 developed local recurrence with a recurrence rate of 21.1%. Local recurrence was correlated with improper safety margin from th... Of seventy-one patients with rectal cancer after radical resection retaining the anus, 15 developed local recurrence with a recurrence rate of 21.1%. Local recurrence was correlated with improper safety margin from the lower edge of cancer to the anal end. There was statistical significant difference between 3 cm or more and 2 cm or less. The local recurrence was also related to the pathologic stage, histologic differentiation and implant of free cancer cells. It is suggested that the surgical indication of saving the anus be strict and without stretching, the safety margin from the lower edge of cancer to the anal end should not be less than 2 cm in early rectal cancer and not less than 4 cm in advanced lesions. During the operation, no touching tumor technique, thorough rinsing of the peritoneal cavity and pre- or post-operative radiotherapy are important for prevention of local recurrence. Early local recurrent rectal cancer can be detected by periodic examinations. 展开更多
关键词 THE factorS AND TREATMENT OF local RECURRENCE AFTER RADICAL RESECTION RESERVING THE ANUS IN THE PATIENTS WITH RECTAL CANCER
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Fast parallel factor decomposition technique for coherently distributed source localization 被引量:2
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作者 CHENG Qianlin ZHANG Xiaofei CAO Renzheng 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2018年第4期667-675,共9页
This paper links parallel factor(PARAFAC) analysis to the problem of nominal direction-of-arrival(DOA) estimation for coherently distributed(CD) sources and proposes a fast PARAFACbased algorithm by establishing... This paper links parallel factor(PARAFAC) analysis to the problem of nominal direction-of-arrival(DOA) estimation for coherently distributed(CD) sources and proposes a fast PARAFACbased algorithm by establishing the trilinear PARAFAC model.Relying on the uniqueness of the low-rank three-way array decomposition and the trilinear alternating least squares regression, the proposed algorithm achieves nominal DOA estimation and outperforms the conventional estimation of signal parameter via rotational technique CD(ESPRIT-CD) and propagator method CD(PM-CD)methods in terms of estimation accuracy. Furthermore, by means of the initialization via the propagator method, this paper accelerates the convergence procedure of the proposed algorithm with no estimation performance degradation. In addition, the proposed algorithm can be directly applied to the multiple-source scenario,where sources have different angular distribution shapes. Numerical simulation results corroborate the effectiveness and superiority of the proposed fast PARAFAC-based algorithm. 展开更多
关键词 source localization coherently distributed (CD)source parallel factor analysis propagator method (PM) trilin-ear decomposition
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Influencing factors on the accuracy of local geoid model
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作者 Shazad Jamal Jalal Tajul Ariffin Musa +3 位作者 Ami Hassan Md Din Wan Anom Wan Aris WenBin Shen Muhammad Faiz Pa’suya 《Geodesy and Geodynamics》 2019年第6期439-445,共7页
Different modification methods and software programs were developed to obtain accurate local geoid models in the past two decades.The quantitative effect of the main factors on the accuracy of local geoid modeling is ... Different modification methods and software programs were developed to obtain accurate local geoid models in the past two decades.The quantitative effect of the main factors on the accuracy of local geoid modeling is still ambiguous and has not been clearly diagnosed yet.This study presents efforts to find the most influential factors on the accuracy of the local geoid model,as well as the amount of each factor’s effect quantitatively.The methodology covers extracting the quantitative characteristics of 16 articles regarding local geoid models of different countries.The Statistical Package of Social Sciences(SPSS)software formulated a strong multiple regression model of correlation coefficient r = 0.999 with a high significance coefficient of determination R^2 = 0.997 and adjusted R^2 = 0,98 for the required effective factors.Then,factor analysis is utilized to extract the dominant factors which include:accuracy of gravity data(40%),the density of gravity data(25%)(total gravity factors is 65%),the Digital Elevation Model(DEM)resolution(16%),the accuracy of GPS/leveling points(10%)and the area of the terrain of the country/state under the study(9%).These results of this study will assist in developing more accurate local geoid models. 展开更多
关键词 ACCURACY of local GEOID MODEL MULTIPLE regression MODEL Influence factorS
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Local HIV/AIDS NGOs and Client Satisfaction: Dimensions and Explanatory Factors through a Multilevel Regression Analysis 被引量:1
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作者 Maurice T. Agonnoude François Champagne Nicole Leduc 《Open Journal of Epidemiology》 2020年第3期303-322,共20页
<strong>Background:</strong> HIV/AIDS Non-governmental organizations (NGOs) in Benin can use evaluations (including client satisfaction surveys) as tools to improve the effectiveness of their interventions... <strong>Background:</strong> HIV/AIDS Non-governmental organizations (NGOs) in Benin can use evaluations (including client satisfaction surveys) as tools to improve the effectiveness of their interventions. <strong>Objective:</strong> It is to identify the dimensions of NGO clients’ satisfaction and their associated factors. <strong>Methods:</strong> We conducted a cross-sectional survey of 2413 clients receiving both preventive and curative services from 31 NGOs working in HIV/AIDS prevention-screening and providing care to persons living with HIV. <strong>Results:</strong> We identified four dimensions of satisfaction relevant to our setting: reception and humane attitude, accessibility of care and resources, staff availability and competence and continuity of care. Individual factors [(age positively and gender (men negatively)] statistically significantly influenced global satisfaction and three of its four dimensions but the strength of these associations was too weak. Concerning organizational factors, involvement in evaluation had a negative effect on reception and humane attitude. A local source as principal source of funding was associated with greater satisfaction with accessibility of care and resources, while foreign partners as the principal source of funding were associated with greater satisfaction in terms of both global satisfaction and its dimensions, except for continuity of care. Organizational factors explain from 12.5% to 15.6% of the variance of global satisfaction and its dimensions (except for continuity of care). <strong>Conclusion:</strong> These information on the global satisfaction and its dimensions as well as the influencing factors are important for NGOs and their partners as these can help them to plan and implement actions to improve performance. 展开更多
关键词 local NGO HIV/AIDS Client Satisfaction Individual and Organizational factors BENIN
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基于目标扰动的本地化差分隐私矩阵分解推荐算法 被引量:2
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作者 王永 罗陈红 +1 位作者 邓江洲 高明星 《计算机学报》 北大核心 2025年第2期451-462,共12页
推荐系统作为有效应对信息过载的工具被广泛应用在电子商务、社交媒体和新闻资讯等领域中。矩阵分解具有泛化能力强和计算效率高的优点,是构建推荐系统的主流算法之一。为提高推荐质量,推荐服务器需要收集大量用户数据用于推荐模型的训... 推荐系统作为有效应对信息过载的工具被广泛应用在电子商务、社交媒体和新闻资讯等领域中。矩阵分解具有泛化能力强和计算效率高的优点,是构建推荐系统的主流算法之一。为提高推荐质量,推荐服务器需要收集大量用户数据用于推荐模型的训练。由于推荐服务器不是完全可信的,向服务器共享用户数据会对用户隐私构成极大的威胁。如何构建一个在保护用户隐私的同时,还能确保推荐质量和准确性的系统,成为了一个热门的研究话题。本地化差分隐私是一种分布式的隐私保护机制,它从中心化差分隐私中发展而来,旨在解决服务器不可信场景下的数据的安全收集和分析。这种框架通过精确的数学证明来确保隐私保护的强度。目前,已经有研究工作将本地化差分隐私引入推荐系统,目的是在推荐效果可接受的情况下,确保用户隐私数据的安全。然而,这些研究还面临一些挑战。首先,隐私保护的范围有限。目前的方法大多只关注显式数据的具体数值,认为这是用户的隐私信息。事实上,攻击者可以通过检查数据是否包含在数据集中,来推测用户的隐私信息。其次,推荐质量较低。本地化差分隐私通过引入扰动来保护用户隐私,但这种方法会导致扰动幅度过大和误差累积,进而影响推荐质量。在推荐服务器不可信场景下,本文提出一种基于本地化差分隐私的矩阵分解推荐算法。首先,该算法将评分数值和评分存在性同时作为隐私保护的对象,为用户提供全面的隐私保护。其次,本算法采用目标扰动方法,添加的噪声量不会随着迭代次数增加而增加,有效避免模型训练过程中噪声累积的问题,保证模型训练的有效性。最后,针对分布式场景下多轮迭代导致的中间参数泄露问题,以无放回方式将采样的模型梯度元素发送给推荐服务器,用于模型训练。本文从理论上证明了所提算法满足本地化差分隐私。对所提算法的效用分析证明本文算法在保证有效的推荐质量的同时,能够实现对用户隐私数据的保护。实验结果表明本文算法极大地提高了隐私保护推荐算法的性能,本文算法在公开数据集上的误差下降幅度平均可达18%,在推荐领域数据隐私保护中展现出良好的应用价值。 展开更多
关键词 矩阵分解 本地化差分隐私 目标扰动 推荐算法 隐私保护
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基于局部离群因子与隔离森林的激光超声缺陷检测
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作者 李阳 朱文博 +4 位作者 静丰羽 叶中飞 马云瑞 周洋 邹云 《郑州大学学报(工学版)》 CAS 北大核心 2025年第1期105-112,共8页
针对激光超声(LU)缺陷检测中最大振幅图存在伪像的问题,结合主成分分析(PCA)和两种无监督的机器学习算法局部离群因子(LOF)与隔离森林(IF),以实现对LU数据的无监督异常检测。首先,利用PCA算法对LU数据进行降维处理,减轻了LU数据的复杂度... 针对激光超声(LU)缺陷检测中最大振幅图存在伪像的问题,结合主成分分析(PCA)和两种无监督的机器学习算法局部离群因子(LOF)与隔离森林(IF),以实现对LU数据的无监督异常检测。首先,利用PCA算法对LU数据进行降维处理,减轻了LU数据的复杂度;其次,利用LOF算法和IF算法进行了数据异常值的识别分析,并利用累积分布函数和核密度估计确定异常值的阈值大小;最后,对比了LOF算法、IF算法以及最大振幅图的检测结果。结果表明:LOF算法有更优的缺陷识别精度和更低的误判率。 展开更多
关键词 激光超声 缺陷检测 主成分分析 局部离群因子 隔离森林 铝合金
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气层减阻系统输气管路设计及评估方法研究
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作者 陈少峰 王兴 +3 位作者 高丽瑾 张晓嵩 严周广 黄红波 《中国造船》 北大核心 2025年第3期198-208,共11页
船用气层减阻系统通过向船体底部输入气体,形成隔离船底和水的气层,达到降低摩擦阻力、节能减阻的效果。论文建立了输气管路总阻力和各支管局部阻抗计算方法,在管路输气效率和各支管间气量平衡分配评估的基础上进行输气管路的优化设计,... 船用气层减阻系统通过向船体底部输入气体,形成隔离船底和水的气层,达到降低摩擦阻力、节能减阻的效果。论文建立了输气管路总阻力和各支管局部阻抗计算方法,在管路输气效率和各支管间气量平衡分配评估的基础上进行输气管路的优化设计,提高了气层减阻系统的节能效果。以某超大型油船为对象,进行气层减阻系统的管路评估和支管间气量平衡分配方案研究及CFD验证。研究结果表明:实船装载姿态变化导致的支管间气量分配不平衡,可通过调节支管阀门开度来保持气量的平衡分配,提升气层减阻的节能效果。 展开更多
关键词 气层减阻系统 管路设计 局部阻力系数 沿程阻力系数
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多源数据融合的焊接质量监测技术 被引量:1
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作者 张发平 孙昊 +1 位作者 魏剑峰 宋紫阳 《北京理工大学学报》 北大核心 2025年第5期471-481,共11页
针对焊接质量的图像信息检测方法难以发现隐性焊接缺陷的问题,提出基于多源数据融合的焊接隐性异常检测和识别方法,以期增加缺陷检测的种类和提高精度.首先,对采集的焊接过程中的声音、电压、光谱、温度等多维度信息进行特征值计算,并... 针对焊接质量的图像信息检测方法难以发现隐性焊接缺陷的问题,提出基于多源数据融合的焊接隐性异常检测和识别方法,以期增加缺陷检测的种类和提高精度.首先,对采集的焊接过程中的声音、电压、光谱、温度等多维度信息进行特征值计算,并将这些特征值与焊接的熔池图像特征值结合,构成焊接质量的原始特征空间;然后采用线性判别方法,降维形成焊接信息的低维特征空间;最后,使用孤立森林法筛选邻域搜索空间,并将该邻域搜索空间中的焊接数据点划分为多个重叠子集.采用局部离群因子法对新数据点在多个重叠子集中进行邻域搜索,对焊接过程进行异常检测,该方法充分考虑了焊接质量数据的全局特征并且计算复杂度大为降低.最后,采用基于人工蜂群算法优化的概率神经网络进行焊接质量数据的精确细分和异常的精准识别,该方法增强了全局搜索能力,同时避免陷入局部最优.试验验证结果显示所提方法都焊接异常的检测精度可达97.44%,对综合焊接异常的识别精度可达96.03%,证明了方法的有效性. 展开更多
关键词 隐性焊接异常 多源数据 局部离群因子 概率神经网络 线性判别方法 人工蜂群算法
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肿瘤局部因素和放疗剂量对临床T1-4N0M0期食管鳞癌患者预后的影响
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作者 孔雁 董倩 +4 位作者 李曙光 许金蕊 赵小涵 邓文钊 沈文斌 《肿瘤防治研究》 2025年第3期225-232,共8页
目的探讨不同放疗剂量对接受根治性放(化)疗的cT1-4N0M0期食管鳞癌患者不同肿瘤局部因素亚组人群预后的影响。方法对256例临床无转移食管鳞癌患者进行回顾性分析,明确肿瘤局部因素指标预测患者预后的最佳截断值,分析近期疗效与肿瘤局部... 目的探讨不同放疗剂量对接受根治性放(化)疗的cT1-4N0M0期食管鳞癌患者不同肿瘤局部因素亚组人群预后的影响。方法对256例临床无转移食管鳞癌患者进行回顾性分析,明确肿瘤局部因素指标预测患者预后的最佳截断值,分析近期疗效与肿瘤局部因素相关指标的关系,多因素分析影响患者OS的独立性指标,最后进行亚组分析,确定从不同放疗剂量中获益的亚组人群。结果食管肿瘤病变X线长度越短、食管管壁厚度和GTV越小,患者近期疗效越好(χ^(2)=9.066、10.310、15.661,P=0.011、0.006、<0.001)。多因素分析结果显示,食管GTV(P<0.001)、放疗剂量(P=0.038)和近期疗效(P<0.001)等3项指标为影响患者OS的独立性指标,后两项指标亦为影响患者PFS预后的独立性指标(P=0.033、P<0.001)。亚组分析结果显示放疗剂量较大(≥60 Gy)时,可使管壁最大厚度≤3.7 cm组、食管病变GTV≤37.34 cm3组和未接收同步化疗组患者OS(χ^(2)=5.040、4.588、5.400,P=0.025、0.032、0.020)和PFS(χ^(2)=6.089、4.353、6.459,P=0.014、0.037、0.011)均获益。结论肿瘤局部因素指标为影响接受根治性放(化)疗食管鳞癌患者的重要预后因素;病变食管壁厚度和肿瘤体积较小的患者可能更能从较高的剂量(≥60 Gy)照射中获益。 展开更多
关键词 食管鳞癌 临床无转移 肿瘤局部因素 放疗剂量 亚组 预后
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基于改进ALTRO的果园机器人实时局部轨迹优化算法
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作者 李天博 郭奕 +2 位作者 刘慧 沈跃 沈亚运 《农业工程学报》 北大核心 2025年第9期1-10,共10页
实时局部轨迹优化是果园机器人安全、稳定自主运行的重要保障。针对原始增广拉格朗日轨迹优化器算法存在迭代效率低下、易陷入数值病态及权重难以平衡等问题,该研究提出了一种基于改进ALTRO(augmented lagrangiantrajectory optimizer)... 实时局部轨迹优化是果园机器人安全、稳定自主运行的重要保障。针对原始增广拉格朗日轨迹优化器算法存在迭代效率低下、易陷入数值病态及权重难以平衡等问题,该研究提出了一种基于改进ALTRO(augmented lagrangiantrajectory optimizer)的果园机器人实时局部轨迹优化算法。在获得机器人全局参考轨迹的前提下,首先采用加速增广拉格朗日算法,改进ALTRO算法中的乘子迭代策略,实现算法的加速收敛;其次,加入乘子可行域投影,保证每次迭代更新得到的乘子都在可行域范围内,避免迭代次数较多导致的算法数值病态现象,提高算法的稳定性。最后,引入基于轨迹时间步长的自适应缩放因子,调整原算法中的终点权重,保证算法具有更好的局部障碍响应能力。基于相同参考路径及配置参数,在多障碍仿真场景中本文算法相较于原始ALTRO算法的运算时间减少32.76%,而在实物试验中,该研究算法运算耗时相较原算法降低67.80%,且该算法优化轨迹的曲率最大值、平均曲率及曲率标准差相较原算法分别下降了10.59%、2.98%及10.17%,航向角、前轮转角、线速度和前轮角速度的最大变化率、平均变化率和变化率标准差上,改进算法相较原算法分别下降了14.19%、3.61%及10.69%,轨迹的曲率表现和控制量变化都更加平滑,能够为机器人提供良好的运行参考。 展开更多
关键词 机器人 算法 ALTRO 果园 缩放因子 局部轨迹优化
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基于异常检测的图像特征匹配算法
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作者 肖剑 武亮亮 +1 位作者 何昕泽 胡欣 《浙江大学学报(工学版)》 北大核心 2025年第6期1140-1147,共8页
基于预定义参数化模型的特征匹配方法通用性较低,为此提出基于异常检测的特征匹配算法(RFM-AD).根据假定特征匹配构建异常检测样本,将特征匹配问题转换为异常样本点检测问题,引入局部异常因子(LOF)算法作为异常检测的基础.针对LOF算法... 基于预定义参数化模型的特征匹配方法通用性较低,为此提出基于异常检测的特征匹配算法(RFM-AD).根据假定特征匹配构建异常检测样本,将特征匹配问题转换为异常样本点检测问题,引入局部异常因子(LOF)算法作为异常检测的基础.针对LOF算法不能有效检测低密度样本的缺陷,引入并改进基于连通性的异常检测方法(COF),并基于引导匹配策略对COF算法和LOF算法进行融合.在随机选取的30幅涉及不同变换模型和噪声干扰的图像对上测试算法的参数设置,确定全局最优的关键参数.在4个公开数据集上进行实验,结果表明,本研究算法在面对大量异常值时具有良好的鲁棒性和匹配性能;在保证较高匹配准确率的情况下,本研究算法相比于RANSAC、LPM、RFM-SCAN等先进算法取得了较高的召回率;在内点率最低的Retina数据集上,本研究算法的F分数较高. 展开更多
关键词 特征匹配 异常检测 局部异常因子 误匹配剔除 图像配准
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