Direct synthesis of pseudo-random ternary perturbation signals with harmonic multiples of two and three suppressed

This paper proposes an analytical method to directly synthesise pseudo-random ternary perturbation signals for the identification of frequency response functions, through the multiplication of two components signals which satisfy a prescribed set of properties. The ternary signals generated have harmonic multiples of two and three suppressed; this specification is useful for reducing the effects of nonlinear distortion on the linear estimate. The signals have uniform magnitude in all, except two, of the nonzero harmonics. The method is significant in overcoming the existing problem of sparsity in the available periods when analytical methods are used, as well as the relatively long computational time required in approaches based on exhaustive search or computer optimisation. The proposed technique presents a breakthrough as it eliminates the sequence-to-signal conversion stage required in the existing conventional methods. A direct consequence is the increased signal power within amplitude constraints, which now equals the theoretical limit for the specification considered. If it is necessary to further increase the number of available periods, the mathematical derivation can be extended to a class of suboptimal direct synthesis signals; however, these possess reduced signal power compared with direct synthesis signals.     

Effects of monitoring under high and low taskload on detection of flashing and coloured radar targets

Abstract

While midair collisions between aircraft are extremely rare occurrences, ‘near midair’, incidents are more common. The present study sought to evaluate the gains in conspicuity that might be realized if flashing or colour were added as redundant cues to indicate the presence of unexpected, non-tracked aircraft entering controlled airspace, and to examine the extent to which increased taskload and fatigue might influence the expected gains. Sixty-four subjects monitored a simulated air traffic control task over a 2 h period for possible conflict situations (their primary task) under either high or low primary taskload conditions. They also monitored for occasional intrusions by light aircraft identifiable on the basis of target shape alone or with colour and/or flashing added as redundant cues. Flashing as a redundant cue was found to be superior to colour in all aspects tested; unlike colour, detection of flashing targets was unaffected by screen location and by changes in primary taskload. Flashing was also least affected by monitoring fatigue. It was concluded that the superiority of flashing over colour in attracting attention to objects in a display must be weighed against its possible potential for distraction. A practical means of accomplishing this in operational situations is through the use of touch sensitive displays to both acknowledge/confirm target location and to deactivate flashing.     

COMPRESSED SPEECH SIGNAL SENSING BASED ON THE STRUCTURED BLOCK SPARSITY WITH PARTIAL KNOWLEDGE OF SUPPORT

Structural and statistical characteristics of signals can improve the performance of Compressed Sensing (CS).Two kinds of features of Discrete Cosine Transform (DCT) coefficients of voiced speech signa...     

关于大型铝电解槽新型节能技术优化的探讨

阐述了具有新型结构的铝电解槽节能技术,并以特定电解槽为模型进行了计算,分析了这些节能技术应用的可行性。     

基于TIN模型和直接暴露方法的长沙土壤中重金属来源识别及人类健康风险评价(英文)

通过采集153个样品分析长沙市土壤中As、Cd、Cr、Cu、Hg、Mn、Ni、Pb和Zn的含量,利用多元统计、地学统计、直接暴露以及不规则三角网模型(TIN模型)等方法分析土壤中重金属的来源、空间分布以及对儿童的健康风险。结果表明:长沙地区部分区域需经过污染治理后才适合人类生活;约9.0%的区域风险值超过了临界值1.0,1.9%的区域风险值大于2.0,其中高风险主要集中在南部和西部地区;元素As和口腔摄入途径是儿童的主要健康风险来源;土壤重金属的直接暴露对儿童所产生的健康风险应该受到研究者的重视。     

磁记忆切向分量信号的检测试验

针对金属磁记忆切向信号检测方向难以确定的问题,提出同时检测切向平面上相互垂直的两个切向分量,采用矢量合成法进行合成,进而得到金属磁记忆最大切向分量的方法,并用ANSYS仿真对该分量的有效性进行验证。通过铁磁性金属构件拉伸试验对磁记忆切向分量信号与应力集中部位和应力集中程度的关系进行研究,并对磁记忆切向分量信号的K曲线进行分析。结果表明,采用矢量合成法合成的金属磁记忆切向分量信号可以作为金属磁记忆最大切向分量,能直观和准确地反映应力集中部位和应力集中程度。     

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 主要介绍了使用单片机实现多路容栅位移传感器的数据信号的采集、处理与传输。CD4514BE以及STC89系列单片机实现对多路容栅位移传感器的信号采集与处理,中继仪通过无线通讯与上位机相连,实现数据在上位机的显示与实时存储。通过实践证明该系统符合要求,使用方便,精确度高,同时实现数据的实时储存与显示。     

基于位移的非规则梁桥抗震设计

为防止非规则梁桥在地震下的不确定破坏,需要对其进行基于位移的抗震设计。以一类常见的非规则梁桥横桥向作为研究对象,采用推倒分析探讨如何建立合理的能力谱,提出如何将此能力谱与非弹性需求谱组合来预计非规则梁桥的地震位移需求,最后,在此基础上提出一种非规则梁桥基于位移的简化抗震设计方法。结果表明:以反应谱分析的位移形状作为分布力模式推倒结构,以最先屈服墩墩顶节点作为位移参考点,得到的推倒曲线可作为能力谱,其弹性段、低屈服段和高屈服段对应的位移形状比例系数需要分别取值;此能力谱与非弹性需求谱的组合能够预计非规则梁桥的地震位移需求,相应的基于位移的简化抗震设计方法能够对非规则梁桥进行合理的抗震设计。     

对某小公寓因形体极不规则需经抗震超限专项审查的反思

通过对一规模不大的高层公寓楼的抗震超限专项审查文本的操作经历,尤其是其中必备的多项结构验算,说明建筑设计如果不严格区分高层建筑与低层建筑在抗震方面的本质区别,轻则徒增结构设计的难度,造成结构构造的复杂性从而无谓地增加结构造价,重则可能形成抗震结构严重不规则而造成返工重做,两者都不可取.     

L型平面不规则结构抗震设计分析

运用SATWE和GSSAP程序,对某L型平面不规则结构进行了详细的抗震设计分析,列出了多项结构指标的对比结果,并提出了相应的抗震加强措施,为同类超限高层结构设计提供参考.