共查询到20条相似文献,搜索用时 140 毫秒
1.
伽利略系统GSTB-V1的时间尺度算法与实现 总被引:1,自引:0,他引:1
欧洲伽利略导航卫星系统已经进入基础设施建设阶段,实现一个独立、精准和稳定的伽利略系统时间尺度成为了关键.基于原子钟模型,首先介绍了ALGOS和Kalman时间尺度算法,利用伽利略实验平台V1的实测数据,计算出了基于上述两种算法的伽利略系统时间尺度.实验结果表明,两种时间尺度的短期和长期频率稳定度均优于钟组中任一原子钟. 相似文献
2.
伽利略卫星导航系统概述 总被引:1,自引:0,他引:1
0引言伽利略计划是欧洲提出的民用全球卫星导航系统研制计划。1999年至2000年,在欧洲委员会与欧洲空间局领导下,从战略、经济、资金筹集、法规、用户需求及技术性能要求等方面,对伽利略计划开展了一系列的研究。目前,伽利略计划主要包括中高度地球轨道卫星星座及其地面基础设施的研制,以及用户设备、系统应用与服务的开发研究。伽利略计划的最终目标是建 相似文献
3.
伽利略卫星导航系统概述 总被引:1,自引:0,他引:1
伽利略系统是欧盟提出的由民间管理的以意大利天文学家伽利略(Galieo)名字命名的卫星导航定位系统。本文介绍了伽利略系统的研究计划、系统组成、提供的服务,并对伽利略系统与GPS的性能进行了比较。 相似文献
4.
5.
伽利略系统及其在海事方面的应用 总被引:3,自引:0,他引:3
卫星导航在各领域的应用越来越普及,欧洲自主开发的民用全球卫星导航系统GNSs(Global Navigation Satellite System),即伽利略(Galileo)计划正受到广泛关注,我国也积极参与了该计划的研究与应用开发。在简要介绍伽利略计划的基础上,对伽利略系统提供的服务、伽利略系统的结构及其在海事方面的应用做了进一步探讨。 相似文献
6.
7.
本文针对中高频条件下的铁耗计算,用三种常用铁耗计算方法对某硅钢片在中高频条件下的损耗曲线进行了计算,对比分析了这三种铁耗计算方法的误差,给出了三种方法的一般适用范围,同时对Bertitto分离铁耗计算方法的损耗系数进行了修正. 相似文献
8.
首先采用极限平衡法对某金矿尾矿坝在不同工况条件下的稳定性进行了计算,得到了尾矿坝在正常和洪水条件下的稳定性系数,根据计算结果发现坝体稳定性满足相关规范要求。采用有限元法对坝体的变形和稳定性进行了计算,得到了坝体变形特征和稳定性系数,有限元法和极限平衡法计算结果基本一致。 相似文献
9.
10.
对传感器数据融合的模型-理论框架中模型算子的保持性和相容性等概念的定义进行了泛化研究推广,对相关特性在算子作用下的不变性或守恒性进行了分析探讨,得到了十九个定理结果. 相似文献
11.
12.
13.
Hiroshi Isshiki 《Journal of Marine Science and Technology》2001,6(2):93-109
To discuss water-wave problems in unlimited waters, it is important to know what type of wave radiation condition should
be placed on a virtual surface corresponding to infinity. For this kind of problem, the Sommerfeld radiation condition is
well known. In this article, the condition is extended to treat a case with an incident wave. Furthermore, a more general
wave radiation condition is introduced from a different point of view. The above-mentioned wave radiation conditions are introduced
into the variational principles of the Kelvin, Hellinnger–Reissner, and Dirichlet type. The Dirichlet-type variational principles
are then used in numerical calculations for bending waves in a bar, and the effectiveness of the wave radiation conditions
and the variational principles is shown. The numerical results for one-dimensional water-wave problems are then given. As
expected, the region required for the numerical solution is reduced drastically compared with that required by the Sommerfeld-type
formulation. Furthermore, the amplitude of the diverging wave is obtained in the process of reaching the variational solution.
Finally, two-dimensional water-wave problems are briefly discussed.
Received: August 9, 2001 / Accepted: September 17, 2001 相似文献
14.
基于Greenberg方法推导了含有阻抗边界条件的浅水Green函数,利用边界元法研究了含阻抗的三维海洋波导与散射体相互作用的问题.分析了海底阻抗对声波与结构体相互作用时的散射特性影响,数值分析表明:含有阻抗边界条件的浅海目标的散射特性与理想海底明显不同,海底阻抗对水平断面以及垂直断面的散射场都有一定的影响,目标距离海底越近,场点散射声压受海底边界条件的影响越大;阻抗越大,散射声压越大.指向性的分布对受海底阻抗的大小比较敏感.分析浅海声散射时,海底阻抗的影响不可忽视. 相似文献
15.
16.
参数横摇是船舶因复原特性改变而引起的典型非线性现象。文章采用三维时域方法预报规则迎浪中船舶的参数横摇运动。该方法引入匹配面将流域分为内域和外域,内域中采用Rankine源来满足物面条件和线性自由面条件,而外域中应用时域格林函数来满足线性自由面条件和远场辐射条件。数值方法中,Froude-Krylov力和恢复力是通过对船舶瞬时湿表面积积分获得,同时考虑了横摇、垂荡和纵摇三自由度之间的耦合作用,以及非线性横摇阻尼的影响。数值结果与试验结果吻合很好,说明该方法可以有效地预报参数横摇。 相似文献
17.
18.
This paper presents the joint optimization of signal setting parameters and dynamic user equilibrium (DUE) traffic assignment for the congested urban road network. The simulation-based approach is employed to obtain the DUE condition for the case of multiple-origin multiple-destination traffic flows. The dynamic traffic assignment simulation program (DTASP), developed in C language is used to assign the traffic dynamically on the road network, whereas method of successive averages (MSA) is modified and used to arrive at the DUE condition. The artificial intelligence technique of genetic algorithms (GAs) is applied to obtain the optimal signal setting parameters and path flow distribution factor for DUE condition. The methodology developed in such a way that joint optimization of signal setting parameters with DUE is obtained. The proposed method is applied to the real network data of Fort Area of Mumbai city comprising of 17 nodes and 56 unidirectional links with 72 Origin–Destination pairs, where all the 17 nodes are signalized intersections. The traffic flow condition for the optimized signal setting parameters is considerably improved compared to the existing signal settings. The results prove that the GA is an effective technique to solve the joint optimization problem for the real network data. 相似文献
19.
港口建港条件评价是一项系统工程,从自然条件、技术条件、经济条件、城市港口及区域条件、社会及环境条件等5个方面进行评价。河口港建港条件的评价,既要符合一般港口的规律,也要考虑河口港的具体特点,取舍或重点突出某些对建港条件影响大的因素,形成合理的评价指标体系和评判标准。由于港口评价需要决策的目标多,模糊性强,对拟建港址建港条件的优劣做出准确的评判十分困难。文中采用系统工程的方法,把多目标决策技术中的模糊数学理论与层次分析方法结合起来,提出了河口港建港条件的多层次模糊综合评判模型。并以广州南沙港为例进行实证分析,研究情况与工程实际吻合较好,该项分析方法对今后类似工程评价具有良好的适应性。 相似文献
20.
Hiroshi Kawabe 《Journal of Marine Science and Technology》2002,6(3):135-147
This report is concerned with the statistical analysis of the long-term distribution of a wave-induced load, and examines
which factors influence the long-term distribution of the load level, e.g., the significant wave height, the mean wave period
of the supposed wave condition, and the relative angle between the ship's course and the wave direction. The long-term distribution
is broken down into these factors, and a contribution rate analysis method for each factor in each load level in the long-term
distribution is introduced. Based on the method used, the contribution rate of a specific mean wave period and a wave angle
encountered is clarified, when the long-term distribution is larger than other wave periods and wave angles. The specific
mean wave period and wave angle encountered are defined as the wave condition which governs the long-term distribution. The
maximum wave-induced load in the vicinity of a probability of exceedance of around 10−8 in the long-term distribution is decided by the most severe short-term wave condition which has the largest significant wave
height with a specific mean wave period. Based on S–N curves and Miner's rule, the relation between the fatigue damage and the supposed wave condition is examined. The contribution
rate analysis method for fatigue damage is introduced. The governing wave condition and the most severe short-term wave condition
also have an important effect on the fatigue damage. A simple estimation method for the long-term distribution, described
by the Weibull distribution from the statistical properties of the most severe short-term wave condition, is introduced. Several
examples show the applicability of the estimation method.
Received: November 22, 2001 / Accepted: January 9, 2002 相似文献