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Such systems play an important role in timefrequency analysis and digital signal processing.


There are many advantages in the use of Hadamard matrices in digital signal


An Inhomogeneous Uncertainty Principle for Digital LowPass Filters


This article introduces an inhomogeneous uncertainty principle for digital lowpass filters.


The measure for uncertainty is a product of two factors evaluating the frequency selectivity in comparison with the ideal filter and the effective length of the filter in the digital domain, respectively.

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 The problem of large deflection of a clamped circular plate under uniform pressure is studied by the method of successive approximation in terms of the parameter representing the ratio of the center deflection to the thickness. The tedious numerical computations, involved in Way's power series solution are thus avoided. The yielding condition at the edge checks very well with the experimental results given by McPherson, Ramberg and Levy. The method may be easily extended to any other boundary conditions and... The problem of large deflection of a clamped circular plate under uniform pressure is studied by the method of successive approximation in terms of the parameter representing the ratio of the center deflection to the thickness. The tedious numerical computations, involved in Way's power series solution are thus avoided. The yielding condition at the edge checks very well with the experimental results given by McPherson, Ramberg and Levy. The method may be easily extended to any other boundary conditions and loading details.  本文所研究者,为一周缘夹紧之圆板,在匀布之侧向重压下所生之巨大挠曲。本文用圆板中点之挠曲距离与板厚之比率为参数,逐步求得本题之近似解答,藉此避免前人Way氏之幂级数法中繁重之数字计算。圆板周缘呈现委屈现象之条件,亦可求得,其结果与McPherson,Ramberg及Levy诸氏之实验,完全吻合。本法亦可适用于一圆板在其它周缘条件及其它荷重情况下之诸问题。  The principal object of this paper is to present a direct method of finding the elevation of the exposuae station and conseqently the tilt and the swing, if desired, of an aerial photograph. Since the elevation of the exposure station is found, the plumbline coordinate system can, in the sense of numerical calculation, be established however. The determination of the plumbline coordinate system, relating to three ground control points and their cooresponding images on the photograph, means a determination... The principal object of this paper is to present a direct method of finding the elevation of the exposuae station and conseqently the tilt and the swing, if desired, of an aerial photograph. Since the elevation of the exposure station is found, the plumbline coordinate system can, in the sense of numerical calculation, be established however. The determination of the plumbline coordinate system, relating to three ground control points and their cooresponding images on the photograph, means a determination of the position of the photograph in space. As can be seen the plumbline coordinate system is definitely independent of the swing of an aerial photograph, the swing is not necessary in solving the space resection problem as the classical procedure done.The treetment in this problem involves only simple computations and produces exceptionally accurate results, as indecated in a numerical calculation during the preparation of this paper. Owing to the impossibility of publishing the numerical example in whole length, only the final results are referred here for comparing:  本文的目的,在於推導出一直接的算學方法,以求空中攝影的高度,進而求出其像片的倾角;如有必須時也求出像片的旋角來,但在本文的理論推導過程中,過去一般認為要先解决旋角的問題,而後才能解決空間定位問题的歷史看法,已經完全修正;旋角並不是解决空間定位問題所必須的。因為攝影高度既經决定,我們可以建立一垂綫坐標系,與像片在空間的轉動無關。每一像點在此垂綫坐標系上的關係完全可以藉攝影高度的得知而決定;此種關係的決定即相當於像片在攝影瞬間的空間位置的决定。這對於無論是像片的糾正、製圖、交會定點都是非常有幫助的。本文所論的方法,經數字計算的結果,表明精度是很高的,而計算手續也是簡便的。由於避免篇幅過長故未將全部計算例引出,只在此地列出一結果以相比較:  The object of the present work is to investigate the characteristics of piezoelectric resonantors which are cut from the natural coloured quartz, and compare the results with those obtained from those plates cut from the ordinary clear quartz in order to see if coloured quartz might be used as piezoelectric material in practice. In this work four points were stressed, they are: (1) the frequency constants of piezoelectric oscillation, (2) its stability, (3) its selectivity and activity and (4) its frequencytemperature... The object of the present work is to investigate the characteristics of piezoelectric resonantors which are cut from the natural coloured quartz, and compare the results with those obtained from those plates cut from the ordinary clear quartz in order to see if coloured quartz might be used as piezoelectric material in practice. In this work four points were stressed, they are: (1) the frequency constants of piezoelectric oscillation, (2) its stability, (3) its selectivity and activity and (4) its frequencytemperature coefficient curves. Further more a comparison of the characteristics of oscillations before and after the heattreatment of the material was made. By the results of these experiments it concludes that the natural coloured quartz plates can be excited into piezoelectric oscillation and serve as piezoelectric resonantors. The frequency constant of a Ycut plate from coloured quartz is about 2% lower than that of same type cut plate from clear quartz, while the frequency constants of the Xcut plate and the ATcut plate from the coloured and clear quartz are practically the same. The heattreatment to the three types cut plates of both kinds of quartz has a definite influence on their frequency. This effect is more pronounced to the coloured quartz plates. Likewise, heattreatment improves, from the pointview of statistics, the selectivity and activity of oscillation of both kinds of quartz. Finally, the values of some coefficients of stiffness of the coloured and clear quartz were discussed.  本文的目的在于研究天然有色水晶在当作压电共振器用时它的压电振荡性能,并与无色水晶在这方面的性能上作一比较,以推断有色水晶是否可以应用到实际的控制电路振荡的工作中去。我们的工作分四方面进行:(一)有色水晶压电振荡的频率常数,(二)有色水晶压电振荡的稳定性,(三)有色水晶压电振荡的选择性及活动性,(四)有色水晶压电振荡的频率——温度系数。并且把有色水晶在用热处理方法去色后的这四方面实验结果与去色前的作一比较。实验的结果证明有色水晶是可以被激发压电振荡的,和无色水晶一样可以作控制电路振荡之用。有色水晶的Y截法的频率常数比无色水晶的约低2％。至于两种水晶的其余两种X截法及AT截法的频率常数基本上无差别。热处理能使两种水晶的三种截法的压电振荡频率有增高的倾向,这效应在有色水晶中更为显著。同样,热处理对于两种水晶三种截法的压电振荡的选择性及活动性,在统计数字上看来是有益处的。最后,就以上测量的结果,推算了并讨论了有色水晶和无色水晶的若干劲度系数异同之点。   << 更多相关文摘 
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