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本文基于UG(Unigraphics NX)设计平台,创建人字形齿轮参数化模型。通过对人字形齿轮参数化设计中所用到的渐开线、螺旋线和过渡曲线进行的分析,建立了人字形齿轮的数学模型。最终给出了人字形齿轮的参数化造型的方法和步骤。 相似文献
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本文介绍了参数化设计的特点,给出CATIA系统下实现模型参数化设计的手段,着重讨论了飞机外形参数化设计方法,以供飞机外形设计人员参考。 相似文献
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介绍了在CATIA环境下绘制渐开线的几种方式,并加以比较;列举了参考资料中斜齿轮轮齿创建的几种错误方法,分析原因,并给出正确的画法;通过渐开线斜齿轮的参数化设计,阐述了CATIA中参数化建模的基本方法和步骤。 相似文献
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针对工程设计中常用的可展曲面,给出其有理参数化算法.给定一个隐式曲面,首先根据几何性质判定它是否是可展曲面,并给出判定算法;然后应用近年来新兴发展的隐式化代数工具———μ基方法,得到可展曲面的μ基的次数界.在此基础上,设计计算隐式曲面μ基的算法,并通过计算其对偶曲面的重新参数化,得到原隐式曲面的参数表示.结合已有的参数曲面隐式化算法,给出了有理可展曲面的代数交换算法图. 相似文献
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介绍了基于uG的齿轮参数化建模思路,用数学方法建立渐开线单齿齿廓的曲线方程,将齿廓的曲线方程转化uG的表达式,利用uG的强大的参数化设计工具,完全实现了渐开线直齿轮圆柱齿轮的全参数化精确建模,建模结果能直接用于有限元分析和机构仿真、数控加工等都需要。 相似文献
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为了提高计算的精度和效率,将NURBS参数曲面应用到电大尺寸目标的RCS预估中.使用CAD软件建立模型,通过对模型IGES文件中数据结构的分析,并以IGES文件为接口,从CAD软件模型中提取出NURBS曲面信息,然后用Cox-DeBoor算法把NURBS曲面转换为Bezier曲面,结合物理光学法和渐进积分展开法精确、高效的求解出任意理想导体目标曲面的RcS. 相似文献
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Generating gene summaries from biomedical literature: A study of semi-structured summarization 总被引：3，自引：0，他引：3
Xu Ling Jing Jiang Xin He Qiaozhu Mei Chengxiang Zhai Bruce Schatz 《Information processing & management》2007,43(6):1777
Most knowledge accumulated through scientific discoveries in genomics and related biomedical disciplines is buried in the vast amount of biomedical literature. Since understanding gene regulations is fundamental to biomedical research, summarizing all the existing knowledge about a gene based on literature is highly desirable to help biologists digest the literature. In this paper, we present a study of methods for automatically generating gene summaries from biomedical literature. Unlike most existing work on automatic text summarization, in which the generated summary is often a list of extracted sentences, we propose to generate a semi-structured summary which consists of sentences covering specific semantic aspects of a gene. Such a semi-structured summary is more appropriate for describing genes and poses special challenges for automatic text summarization. We propose a two-stage approach to generate such a summary for a given gene – first retrieving articles about a gene and then extracting sentences for each specified semantic aspect. We address the issue of gene name variation in the first stage and propose several different methods for sentence extraction in the second stage. We evaluate the proposed methods using a test set with 20 genes. Experiment results show that the proposed methods can generate useful semi-structured gene summaries automatically from biomedical literature, and our proposed methods outperform general purpose summarization methods. Among all the proposed methods for sentence extraction, a probabilistic language modeling approach that models gene context performs the best. 相似文献
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《Journal of The Franklin Institute》2022,359(17):9690-9702
This paper proposes a novel data-driven control for stabilization of a class of uncertain discrete-time nonlinear systems. The proposed method is based on the compact form dynamic linearization technique, which relates the first variation of the output signal with the fractional-order variation of the input one. Then, a discrete-time controller is proposed, based on the obtained fractional-order data-driven equivalent model. In order to compute the proposed controller and estimator, only input-output data information is considered. The uniform ultimately boundedness of the tracking errors are demonstrated by a formal analysis. Finally, comparison results based on simulations are presented to highlight the effectiveness of the proposed methodology. 相似文献
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Liang Jia Junguo Zhang Shuyue Chen Zhenjie Hou 《Journal of The Franklin Institute》2018,355(15):7764-7798
Automated fabric inspection is a challenging task due to the unpredictable visual forms of the fabric defects and their scarcity compared with the tremendous amount of defect-free fabric products. This paper proposes a novel method based on lattice segmentation and lattice templates which automatically identifies the defects of fabric images. With the proposed method, a fabric image is segmented to lattices by inferring the placement rule of the texture primitives categorized to distinct texture classes. Each texture class is modeled by multiple templates inferred from the defect-free samples based on some metrics determined a priori according to their inspection efficiencies. For a lattice segmented from a given image, the most similar template is identified through a template matching process which compensates the local deformations around the lattice, and the distances between the lattice and the identified template are estimated based on the selected metrics. The lattices of distances exceeding the learnt distance range are identified as defective. The performance of the proposed method is evaluated based on two databases respectively providing pixel-level and image-level evaluations. For both databases, the receiver operating characteristic curves are plotted and the average areas under curves are 0.86 and 0.95, respectively, for pixel-level and image-level databases. The proposed method is further tested on the blurred and noisy version of images from pixel-level database and the resulting area is 0.81 on average. The proposed method outperforms the state-of-the-art methods by comparing corresponding areas. 相似文献
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《Information processing & management》2016,52(3):430-445
The explosion of online user-generated content (UGC) and the development of big data analysis provide a new opportunity and challenge to understand and respond to public opinions in the G2C e-government context. To better understand semantic searching of public comments on an online platform for citizens’ opinions about urban affairs issues, this paper proposed an approach based on the latent Dirichlet allocation (LDA), a probabilistic topic modeling method, and designed a practical system to provide users—municipal administrators of B-city—with satisfying searching results and the longitudinal changing curves of related topics. The system is developed to respond to actual demand from B-city's local government, and the user evaluation experiment results show that a system based on the LDA method could provide information that is more helpful to relevant staff members. Municipal administrators could better understand citizens’ online comments based on the proposed semantic search approach and could improve their decision-making process by considering public opinions. 相似文献
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Parry Moon 《Journal of The Franklin Institute》1940,230(5):583-617
A wealth of data on sunlight has been obtained by astrophysicists, meteorologists, and others; but this information has been scattered through the literature and has not been generally available to engineers.The present paper correlates some of the data and specifies a proposed standard spectral-distribution curve for sunlight outside the atmosphere. Methods are given also for the calculation of the spectral irradiation curve for any elevation above sea level and for any air mass, and these methods lead to proposed standard curves to be used in engineering calculations dealing with direct sunlight at sea level.These curves are checked against independent data on total irradiation, ultraviolet irradiation, illumination, and color temperature. In all cases, the agreement between calculated and experimental results gives confidence in the validity of the proposed curves for various engineering applications. 相似文献
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N. Zerroug M.N. Harmas S. Benaggoune Z. Bouchama K. Zehar 《Journal of The Franklin Institute》2018,355(5):2329-2343
Finite time convergence based on robust synergetic control (SC) theory and terminal attractor techniques is investigated. To this end a fast terminal synergetic control law (FTSC) is applied to drive a DC–DC Buck converter via simulation and through a dSpace based experimental setup to validate the approach. As robust as sliding mode control, the synergetic approach used is chattering free and provides rapid convergence. Efficacy of the proposed fast terminal synergetic controller is tested for step load change and output voltage variation and results compared to classical synergetic and PI control. Experimental validation using dSpace DS1104 confirms the results obtained in simulation showing the soundness of this approach compared to synergetic and PI controllers. 相似文献
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《Journal of The Franklin Institute》2022,359(15):8188-8200
This work investigates the improved stability conditions for linear systems with time-varying delays via various augmented approaches. Some augmented approaches are augmented Lyapunov-Krasovskii functionals, augmented zero equalities, and the augmented zero equality approach. At first, by constructing augmented Lyapunov-Krasovskii functionals including the state vectors which were not considered in the previous works and augmented zero equalities, a stability criterion is proposed in the forms of linear matrix inequalities. Through the proposed Lyapunov-Krasovskii functionals and an additional functional derived from the integral inequality, a slightly improved result is derived. The proposed results do not consider the increase in the computational complexity to achieve a larger delay bound. So, by applying the augmented zero equality approach, which is a method of grafting the proposed augmented zero equality proposed in Finsler Lemma, to the proposed result, an enhanced stability result was derived. Also, the computational complexity is reduced by appropriately adjusting any vector of the integral inequality utilized in the proposed criteria. By applying some numerical examples to the proposed conditions, the effectiveness and superiority of the results are confirmed. 相似文献
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This paper focuses on input-to-state stability of a class of switched stochastic delayed systems which are drived by Lévy noise. By multiple Lyapunov function and average dwell time approach, the sufficient conditions of the ψλ(t)-weighted input-to-state stability can be obtained if all the subsystems are input-to-state stable. Then utilizing comparison principle and the method of constant variation, the sufficient criteria of the eλt-weighted input-to-state stability of the switched stochastic delayed systems containing both input-to-state stable subsystems and non-input-to-state stable subsystems can also be derived. Finally, an example is given to illustrate the effectiveness of the proposed results. 相似文献