Signal generation and spatial resolution in scanning electron acoustic microscopy

The thermal conduction and Navier-Stokes equations are usedto obtain the stress field generated by a chopped electron beam incident ona disk sample.The piezoelectric equation is then used to obtain the out-put signal of the transducer coupled to the sample.The results lead to aconsideration of the signal generation mechanism and spatial resolution inscanning electron acoustic microscopy(SEAM).It is shown that atime-variant heat source generated both a thermal wave and an acousticwave simultaneously,and thermal-to-acoustic wave mode conversion oc-cured on the boundary surfaces depends on the amplitudes and the gra-dients at boundary surfaces of both heat source and thermal waves.It isargued that the spatial resolution of a imaging system operated in thenear field,such as SEAM and thermal wave microscope,is dependent onthe distance between the heat source and scatterer and,at best,the lateralresolution in SEAM is of the order of the diameter of the focal spot ofthe electron beam.     

高效液相色谱死体积的热力学定义

本文讨论了高效液相色谱死体积的定义和如何以吉布斯热力学理论为基础对其测定。推荐的热力学理论方法能应用于任何一种液相色谱方法,如正相、反相、离子交换、甚至体积排斥色谱。提出了一种能在整个浓度范围内准确计算流动相组分干扰峰死体积的方法。对某些化合物容量因子出现负值也作了解释。     

用边界元法分析试样宽度对非织造土工织物拉伸性能的影响

用边界元法从理论上分析非织造土工织物的拉伸性能。理论分析和试验表明：非织造土工织物的断裂强度随试样宽度的增加而增大。由于试样的不均匀性等原因，理论值一般高于试验值。通过回归分析得出非织遣土工织物试样宽度与断裂强度呈幂函数关系。     

A FAMILY OF BERNSTEIN QUASI-INTERPOLANTS ON[0,1]

Suppose that we want to approximate fC[0,1]by polynomials in P_n,using only itsvalues on X_n={i/n,0≤i≤n}.This can be done by the Lagrange interpolant L_n f or theclassical Bernstein polynomial B_n f.But,when n tends to infinity,L_n f does not converge to fin general and the convergence of B_n f to fis very slow.We define a family of operators B~(k)_n,n≥k,which are intermediate ones between B(0)_n=B~(1)_n=B_n and B~(n)_n=L_n,and we studysome of their properties.In particular,we prove a Voronovskaja-type theorem which assertsthat B~(k)_n f-f=0(n~(-[(k+2)/2))for f sufficiently regular.Moreover,B(k)_n f uses only values of B_n f and its derivaties and can be computed by DeCasteljau or subdivision algorithms.     

Studies on the properties of flow-induced oscillation and sound radiation in streamlined protuberant special cavities

I.IntroductionAsanuidpassingthroughthecavityatcertainflowrate,themediuminthemouthandthccavityisoscillatingandsoundisradiated.Noton1ystochasticturbu1encenoiscispossi-blyproducedbutsinglefrequencysoundofspecia1lydesignatedpitchisalsoproduced.Andthusthespcctrumofthcradiatedsoundisshownascontinuousspectrumandcharacteristiclinespcctrum.Inthiscascwcmaycallitflow-inducedosci1lation.Flow-inducedoscillationandsoundradiationcanbeproducedasafluid(waterorgas)passingthroughthecavitybysinkingcavityunderint…     

乙烷—丙烷混合裂解模型及产率预计

本文研究了乙烷和丙烷的混合裂解,并与乙烷、丙烷单独裂解进行了比较。解决了微分方程组的刚性问题,提出了混合裂解反应动力学模型。明确了三种选择性的概念,即;真实选择性、迭加选择性和总选择性,从而澄清了国际上对于选择性有正偏差和负偏差的不同观点。为乙烯生产提供了有效利用乙烷和丙烷的分析评价方法。     

APPROXIMATION OF CONTINUOUS FUNCTIONS BY GENERALIZED KARAMATA MEANS

A sufficient condition for the order of approximation of a continuous 2π periodic function with a givenmajorant for the modulus of continuity by the [F, d_n] means of its Fourier serier to be of Jackson order isobtained. This sufficient condition is shown to be not enough for the order of approximation by partial sums oftheir Fourier series to be of Jackson order. The error estimate is shown to be the best possible.