共查询到19条相似文献,搜索用时 140 毫秒
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三维信息模型协同编辑技术及系统 总被引:3,自引:0,他引:3
对现有协同设计系统在协同编辑方面的工作进行研究,在分析它们研究对象和方法的基础上,结合MCAM对大型三维信息模型设计的需要,提出并开发了网络MCAM系统。利用基于“消息”的通信机制,将设计中对三维信息模型的编辑过程包装为网络传输的“消息”,大大减少了网络传输中的数据量,并较好的实现了三维信息模型的协同编辑技术。 相似文献
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本文试图按照社会技术系统的概念来描述企业,这一概念包括将企业作为一个自相似系统进行建模,这类系统能够不断变化和发展以便达到完成其任务的所有要求,为此目的,有必要对结构和过程的自相似性加以并行考虑,拥有各部门和工作小组的企业结构的自相似性与过程变革的自相似性。 相似文献
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按照苏通长江大桥实际的施工过程及其施工荷载分布,考虑施工过程的影响,建立全桥空间组合结构计算模型,用有限元法研究了主桥斜拉桥自索塔施工开始直到全桥合龙的各施工阶段的结构稳定安全系数及其失稳模态,对主桥钢箱梁架设施工过程中的结构稳定行为给出了综合评价. 相似文献
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在扩展自相似过程的基础上提出了一种新的业务模型。该业务模型可以实现任意的边缘概率分布,并且可以实现众多形状的相关函数,较之现有的ATM业务模型具有更广的适用范围。 相似文献
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燃机在贫燃工况下易出现燃烧不稳定,分析和预测不稳定燃烧特性对保证燃烧室正常工作具有重要意义。通过数值仿真得到燃烧室的火焰描述函数(flame describing function,FDF),并结合低阶热声网络模型预测了燃烧室的热声不稳定特性。首先,通过模型旋流燃烧室自激振荡实验,得到振荡燃烧发生时的工况和主频;其次,利用大涡模拟(large eddy simulation,LES),得到火焰燃烧热释放率对不同入口扰动的响应特征,通过拟合得到FDF;最后,建立了燃烧室低阶热声网络模型,并分析了燃烧室不稳定特性。结果表明:模型预测的振荡特性与实验数据相符,说明该模型能够从机理上预测燃烧不稳定特性。 相似文献
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针对当前虚拟维修过程中模型庞大,维修流程不可反复,部件间关系描述混乱等问题,论文提出一种Petri网和语义网络结合的过程建模方法——TJ(Training Join)网。TJ网上层利用语义网络对部件进行层次结构分解和资源规范聚类,实现子部件间逻辑互联;下层运用Petri网的变迁和触发规则提炼出Petri网元素模型,提高模型的通用性和建模效率。同时模型中的状态收集模块可实现部件属性状态间信息共享。最后,以虚拟维修平台中飞机电子设备架的维护为例,验证了TJ网的有效性。 相似文献
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对现实露天矿运输系统进行描述,在此基础上构建露天矿运输系统的网络模型,包括运输系统网络的组成和描述、节点的选取、权值的确定和运输网络的生成,并将网络模型实现。其中包括数据库的设计和网络数据的操作。 相似文献
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网络传输层可以产生自相似性的发现,引发了对网络长相关性流量模型更进一步的研究,文章结合网络流量的研究进展,介绍现有网络传输层产生自相似业务的一个原因。 相似文献
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下一代网络Next Generation Networking(NGN),是基于已有的计算机结构和技术包含广泛的技术术语,总体上描述了数据和话音(PSTN)甚至多媒体例如视频和网络传输.ITU(世界电信联盟)对下一代网络(NGN)的定义是全业务的网络,包括电话和Internet接入业务、数据业务、视频流媒体业务、 相似文献
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在分析MPEG-1标准下的可变比特率(VBR)视频业务特性的基础上,对这类业务提出了一种新模型。仿真结果表明,该模型能够很好地逼近这类业务的统计特性。 相似文献
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Mo Chen Xiaojuan Wang Mingshu He Lei Jin Khalid Javeed Xiaojun Wang 《计算机、材料和连续体(英文)》2020,64(2):941-959
Attacks on websites and network servers are among the most critical threats in
network security. Network behavior identification is one of the most effective ways to
identify malicious network intrusions. Analyzing abnormal network traffic patterns and
traffic classification based on labeled network traffic data are among the most effective
approaches for network behavior identification. Traditional methods for network traffic
classification utilize algorithms such as Naive Bayes, Decision Tree and XGBoost.
However, network traffic classification, which is required for network behavior
identification, generally suffers from the problem of low accuracy even with the recently
proposed deep learning models. To improve network traffic classification accuracy thus
improving network intrusion detection rate, this paper proposes a new network traffic
classification model, called ArcMargin, which incorporates metric learning into a
convolutional neural network (CNN) to make the CNN model more discriminative.
ArcMargin maps network traffic samples from the same category more closely while
samples from different categories are mapped as far apart as possible. The metric learning
regularization feature is called additive angular margin loss, and it is embedded in the
object function of traditional CNN models. The proposed ArcMargin model is validated
with three datasets and is compared with several other related algorithms. According to a
set of classification indicators, the ArcMargin model is proofed to have better
performances in both network traffic classification tasks and open-set tasks. Moreover, in
open-set tasks, the ArcMargin model can cluster unknown data classes that do not exist in
the previous training dataset. 相似文献
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Due to the success of the Internet and the diversity of communication applications, it is becoming increasingly difficult to forecast traffic patterns. To capture the traffic variations, we introduce a flexible model where traffic belongs to a polytope. We assume that the traffic demands between nodes can be carried on many paths, with respect to network resources. Moreover, to guarantee the network stability and to make the routing easy to implement, the proportions of traffic flowing through each path have to be independent of the current traffic demands. We show that a minimum-cost routing satisfying the previous properties can be efficiently computed by column and constraint generations. We then present several strategies related to certain algorithmic details. Finally, theoretical and computational studies show that this new flexible model can be much more economical than a classical deterministic model based on a given traffic matrix. This paper can be considered as a mathematical framework for a new flexible virtual private network service offer. It also introduces a new concept: the routing of a polytope.This work was done in part while the authors were working at France Telecom Research and Development, Issy-les-Moulineaux, France. 相似文献
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Sampling has become an essential component of scalable Internet traffic monitoring and anomaly detection. A new flow-based sampling technique that focuses on the selection of small flows, which are usually the source of malicious traffic, is introduced and analysed. The proposed approach provides a flexible framework for preferential flow sampling that can effectively balance the tradeoff between the volume of the processed information and the anomaly detection accuracy. The performance evaluation of the impact of selective flow-based sampling on the anomaly detection process is achieved through the adoption and application of a sequential non-parametric change-point anomaly detection method on realistic data that have been collected from a real operational university campus network. The corresponding numerical results demonstrate that the proposed approach achieves to improve anomaly detection effectiveness and at the same time reduces the number of selected flows. 相似文献