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基于Python语言,在ABAQUS有限元通用平台上开发了用于内凹六边形负泊松比蜂窝结构自动建模的程序。内凹六边形负泊松比蜂窝力学性能的研究中,通常需要进行变参数的系列计算。为提高计算效率,首先对蜂窝进行离散和参数化表达,用Python语言开发蜂窝单胞结构自动建模的程序;在此基础上,进行双向阵列操作获得内凹六边形蜂窝结构;最后,通过与内凹蜂窝局部压缩试验结果的对比,验证了有限元自动建模方法的正确性。基于Python 的ABAQUS自动建模二次开发的思路,可以大大减轻变参数系列分析过程中的工作量,提高有限元分析效率。 相似文献
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Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the
medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme
can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These
two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those
applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper
we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth
allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated
by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth
allocation priority, the SD performances will be better.
Foundation item: the National Basic Research Program (973) of China (No. 2005C13321804) 相似文献
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In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited
bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem
very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method
based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the
challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET
are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down
to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their
z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel
propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed
scheme is much more efficient than the 2D-ALS. 相似文献
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矿山法已在城市轨道交通建设中得到广泛应用,本文以武汉市轨道交通3号线王家湾站-宗关站区间矿山法左隧道塌方事故为研究对象,经过现场诊断分析,认为拱顶塌方主要原因为:拱顶上方的10-2黏土层受裂隙水的浸泡,发生软化变为流塑状,进而引发涌泥突水造成塌方。本文重点介绍了塌方前后采取的处理措施:稳定左线塌方土体,加固右线已开挖段及左右线之间的土体。经过多方案比选,最终得到较为合理可行的复工方案。最后,本文针对地铁王-宗区间塌方原因及处理措施进行了总结,得到相关结论,可为后续工程提供参考借鉴。 相似文献
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新造货车整车落成后车钩高数据存在大范围波动,对产品质量产生较大影响.通过建立模型对影响车钩高的有关因素进行全面分析,找出了整车落成后车钩高波动的原因,并以C70E型通用敞车为例进行计算,得出牵引梁上翘下垂的取值范围.最后总结了控制车钩高的方法. 相似文献
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An improved scalar Costa scheme (SCS) was proposed by using improved Watson perceptual model to adaptively decide quantization step size and scaling factor. The improved scheme equals to embed hiding data based on an actual image. In order to withstand amplitude scaling attack, the Watson perceptual model was redefined, and the improved scheme using the new definition can insure quantization step size in decoder that is proportional to amplitude scaling attack factor. The performance of the improved scheme outperforms that of SCS with fixed quantization step size. The improved scheme combines information theory and visual model. 相似文献
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