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1.
针对单一预测模型都存在各自优缺点的问题,本文提出时序回归GM-SVM模型,以达到最优的变形预测效果。首先对灰色模型中的灰参数导致的时间序列残差进行研究,形成时间序列模型,根据时间序列模型对其残差进行最优化设计,获取时间序列估计模型,并将该模型与支持向量机进行无缝融合以建立新的预测模型,然后根据该预测模型对观测的大坝变形影响因子进行训练和预测,并将预测结果与实际的变形值进行对比分析,经过实例分析确定该模型的预测结果更加接近实际观测值,说明该模型更加适用于基于大坝变形影响因子的变形分析。  相似文献   

2.
根据Kolmogorov连续性定理,本文建立了混沌—神经网络(C-ANN)预测模型;提出了基于遗传算法和神经网络的混沌预测模型与方法(C-ANN-GA混合预测方法);解决了混沌时间序列的非解析式预测问题;使混沌时间序列预测方法得到了新的改进和发展。  相似文献   

3.
【目的/意义】自然界中时间序列信号具有非线性、非稳定变化的特点。对时间序列信号实现准确预测,不 仅能够提高风电机组的输出功率,并且有助于调控风电场的运行维护,保障电力系统的安全运行。【方法/过程】本 文基于集合经验模式分解和变分模态分解两种时间序列分解的方法,并将其与RBF神经网络相结合提出RBF直 接预测模型和EEMD-RBF 和VMD-RBF 两种组合预测模型。利用某风电场的原始风速时间序列信息,通过 MATLAB 软件进行编程,进行案例分析。【结果/结论】预测结果表明组合预测模型优于RBF 直接预测模型,且 VMD-RBF组合预测模型的预测结果最为精确。  相似文献   

4.
【目的/意义】针对多组时间序列的海量数据集和以预测为目标的信息分析方法,提出了基于数据挖掘技术 的预测模型,在大数据环境下,提高了预测精度,以期在其他领域的信息分析和情报预测能有所借鉴。【方法/过程】 以集装箱海运价格预测为例,提出集装箱海运价格预测模型,设计自适应的网格搜索策略,高效准确地确定数据挖 掘算法中的超参数组合,提出基于时间序列留出法的评估方法,降低了集装箱运价这种多组时间序列数据集在数 据挖掘结果上的泛化误差,针对海量运价信息,对GBDT算法进行并行计算设计和预排序后的损失函数迭代计算 优化策略,提高了算法在大数据环境下的计算效率。【结果/结论】模型和算法运行结果仿真显示:对于传统的时间 序列问题,基于数据挖掘方法的预测模型取得了比传统时间序列方法更优的结果。  相似文献   

5.
本文主要研究了基于改进指数平滑算法的气温预测问题。首先引入时间序列模型概念,对常用气温预测模型进行简要分析,另外对一阶指数平滑算法进行相关推导,同时提出了自适应指数平滑算法;其次,结合广西容县近30年月均气温实测数据,分别建立BP神经网络预测模型、传统指数平滑算法预测模型以及改进后的基于自适应指数平滑算法的预测模型,对2016年气温数据进行预测并分析模型优势;最后,将改进模型用于预测2017年和2018年中未知月份的月平均气温值,并针对实验结果进行数据分析修正。通过对不同预测模型的比较和仿真实验,结果表明基于自适应指数平滑算法的气温预测模型预测精度较高,实用性强,具有一定的推广性。  相似文献   

6.
线性回归与时间序列加法预测模型   总被引:6,自引:0,他引:6  
葛新权 《预测》2000,19(1):50-50,44
线性回归和时间序列预测模型各有千秋,本文将它们结合起来,提出了一种线性回归与时间序列加法预测模型,它提高了拟合度和预测能力。  相似文献   

7.
基于灰色预测模型GM(1,1)的人才需求分析   总被引:16,自引:2,他引:14  
闵惜琳 《科技管理研究》2005,25(6):72-74,77
本文以灰色系统理论为依据,构建了广东省科技人才需求量灰色预测模型,为人才决策提供了科学的预测方法。并且,还将灰色预测模型与基于时间序列及主因子GDP回归等模型的应用结果进行了对照分析。  相似文献   

8.
应用相空间重构技术对时间序列进行分割,将原序列映射到多维的数据空间中。将期望最大化(EM)聚类算法和神经网络相结合,提出了一种基于相空间重构技术的EM聚类模糊神经网络预测模型。在股票市场上进行了应用,结果表明该预测模型降低了预测误差,提高了系统的性能。  相似文献   

9.
水质的时间变化趋势预测是进行水环境管理的前提,预测模型在很大程度上决定了预测精度的高低,如何选取有效的时间序列水质预测模型是目前的研究热点之一。以平西湖为研究对象,根据2009-2011年间TN、TP和CODMn月监测数据,提出了一种基于ARIMA和RBF-NN的组合模型,该模型能同时反映水质的渐变性和非线性变化的特点,最后用5个精度评价指标对组合模型的预测结果进行了评价,并和基于ARMMA和时间序列神经网络预测模型的预测结果进行了比较。结果表明,大部分指标显示ARIMA/RBF-NN组合模型对受内生变量影响较大的TN、TP的预测效果最好,ARIMA模型对受外生变量影响较大的CODMn的预测效果最优。  相似文献   

10.
本文提出了一种基于人工神经网络的巢湖流域水体总磷和总氮的预测模型,可以预测出水体中总磷和总氮的浓度,有利于巢湖流域水体富营养化的治理,节省了水质监测的成本;该模型使用易于测量且和总磷、总氮密切相关的水质指标作为输入,利用巢湖流域历史水质数据进行人工神经网络的训练、测试和验证。结果表明,人工神经网络可以有效的预测水体的总磷和总氮浓度。  相似文献   

11.
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.  相似文献   

12.
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.  相似文献   

13.
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.  相似文献   

14.
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.  相似文献   

15.
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.  相似文献   

16.
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China's science enterprise by making S&T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party's Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.  相似文献   

17.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.  相似文献   

18.
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."  相似文献   

19.
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.  相似文献   

20.
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.  相似文献   

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