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101.
It is not possible to determine from the Hilbert series whether a commutative -graded Noetherian algebra is a complete intersection. Nevertheless, the Hilbert series of a complete intersection satisfies very stringent conditions and we define a concept CI-type for formal power series, that embodies some of these necessary properties. This definition becomes interesting mainly for algebras that are not standard i.e. not generated in degree 1. For the class of formal power series that occur as the Hilbert series of -graded Noetherian Cohen–Macaulay algebras, the main result is a criterion for a series to be of CI-type, that is formulated in terms of properties of truncated power series. Hence it can be used as the basis for an algorithm that provides in a finite number of steps either a rational function expression of the formal power series, or the information that the truncated power series is not of CI-type. Also sample computations using this algorithm on some non-standard graded invariant algebras are described. 相似文献
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103.
牛顿环干涉装置的若干变异结构 总被引:1,自引:0,他引:1
周国全 《武汉大学学报(工学版)》2000,33(5)
综合牛顿环干涉装置的几种变异结构 ,分析了各干涉结构的干涉条件 ,并给出了它们的干涉条纹分布律的统一的数学表达 相似文献
104.
The rapid introduction of wavelength division multiplexing (WDM) technology to cope with the increased bandwidth requirements of transmission networks has intensified the need for recovery mechanisms at the optical layer. A first step towards survivable optical networking will be seen through the introduction of optical rings. This paper presents different types of optical rings (dedicated and shared protection WDM rings) and the planning issues associated with these WDM rings. In particular, we give mathematical models as well as solution methods for the ring loading and wavelength assignment problem. We compare the wavelength requirement of dedicated and shared protection rings under scenarios with different demand patterns. We also discuss the influence of the WDM equipment cost, and present a mathematical model for the optimization of hybrid networks with both dedicated and shared protection rings. 相似文献
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106.
钢环组是金属带的关键组件之一,它的载荷分布关系到金属带的承载能力和使用寿命。本文分析了钢环组配合方式与其张应力分布的关系,提出了采用过盈配合组配钢环能使各层钢环均匀承载的方法,并得到了过盈量的求解算式。 相似文献
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在开展结冰试验时,结冰风洞风扇叶片前缘有结冰风险,影响风洞安全运行。针对大型旋转叶片结冰问题,提出了旋转叶片电加热防冰系统设计方法,研制了大型结冰风洞旋转叶片电加热防冰系统。首先,研制了内置电加热单元和温度反馈的防冰叶片。针对叶片复杂的工作环境,提出一种新的旋转叶片电加热防冰功率计算方法,通过精确测量和方案优化,设计了基于特殊环境的分半式、大尺寸、高线速度、碳刷自动移开/压紧的导电滑环。最后,采用变结构分级温度闭环和试验参数连锁防冰控制策略解决了旋转叶片结冰问题。该系统已应用于大型结冰风洞,运行中加热电流和叶片温度反馈信号传输连续,所有旋转叶片前缘快速加热且温度分布均匀,防冰效果好。 相似文献
110.
Resilient Packet Ring (RPR), or the Standard IEEE 802.17, is a new IP-based network technology proposed to replace SONET/SDH in metropolitan area networks. RPR is well-adapted to handle multimedia traffc and is effcient. However, when RPR networks are bridged, inter-ring packets, or packets with the destination on a remote RPR network other than on the source network, are flooded on the source and the destination networks, and also on the path of the intermediate networks between the source and the destination networks. This decreases the available bandwidth for other traffc in those networks and is ineffcient. As a result, we propose two solutions based on topology discovery, global topology discovery (GTD) and enhanced topology discovery (ETD), that prevent the flooding of inter-ring packets. GTD enables the bridges to determine the next-hop bridge for each destination. ETD enables the source node to determine a default ringlet, so that packets reach the next-hop bridge without flooding the source network. The proposed solutions were analyzed and the overhead bandwidth and stabilization time were shown to be bounded. Simulations performed showed that the proposed solutions successfully avoid flooding and achieve optimal effciency in the intermediate and destination networks, and in the source networks with one bridge. 相似文献