Statistical laws of the pressure fluctuations in a hypersonic turbulent boundary layer

The results of measuring the pressure fluctuations on the wall of the nozzle of a hypersonic wind tunnel beneath a developed turbulent boundary layer are presented for the Mach number M_∞ = 7.5. On the basis of a statistical analysis, it is shown that the action of the turbulent flow is dynamically similar to the propagation of a random sequence of wave packets with continuously distributed temporal and spatial scales. Low-frequency disturbances are associated with large-scale structures of long duration that propagate at a mean-statistical velocity similar in value to the outer flow velocity. The continuous generation of weakly-correlated small-scale disturbances ensuring the maintenance and development of turbulence occurs chiefly in the inner region of the boundary layer. Spectral estimates of the power generated by the turbulent flow in the wall region of the boundary layer are presented.     

遥感FTIR测定固体推进剂燃烧的红外光谱特性

应用高分辨率的Bruker EQUINOX55型遥感FTIR,对含有大量高氯酸铵和聚四氟乙烯的高红外活性的固体推进剂燃烧火焰的红外光谱特性进行了研究。设定遥感FTIR光谱仪的光谱分辨率为4 cm-1,连续实时地收集燃烧进行到0,9,18,27和36 s时火焰的红外发射光谱图。采用分子转振光谱测温法,实时测定了固体推进剂的燃烧温度,测得的温度分别为1 992.5,2 610.9,2 294.4,2 361.1和1 916.9 K,校正了仪器的响应函数,得到了固体推进剂燃烧火焰的绝对光谱能量分布图,以及在不同时刻燃烧产物HCl,HF,CO₂和CO的实时浓度。研究结果表明,遥感FTIR可以用于研究特种红外源的红外光谱特性,特别是用于军事上红外目标识辨和制导与反制导,以及研究和改进固体推进剂的配方,是一种很有潜力的技术。     

一种新型芴类衍生物的光谱性质研究

合成了具有大π共轭性的对称型芴类衍生物9,9-二(2-乙基已基)-2,7-二(2-(4-甲氧基)苯-2,1-乙烯基)芴(简写为MO-Flu-MO)。通过元素分析、质谱、紫外-可见光谱和红外光谱对其进行了表征。测试了该染料在乙腈、二氯甲烷、四氢呋喃和正己烷4种不同极性溶剂中的线性吸收光谱和单光子荧光谱。结果发现溶剂效应对吸收光谱和荧光光谱表现出不同程度的影响,对产生这些光谱行为的主要原因进行了讨论。     

Spectral Parameters of Nd^3＋ Ion in Nd^3＋：KLu（WO4）2 Crystal

1 INTRODUCTION There has been increasing interest in the re-search of diode laser-pumped solid-state lasers in re-cent years because of the rapid development of highpower diode lasers. Nd:YAG and Nd:YVO crystalsare commercially available, but limited to low Nd3 (= 1 at.%) doping concentration and to narrow ab-sorption bands near the diode emission wavelengthof 808 nm. Therefore, it is necessary to explore moreefficient crystal materials for diode-pumped solid-state lasers. The alkali …     

1,2,4-三唑并[3,4-b]-1,3,4-噻二唑的合成

近年来稠杂环化合物的合成及其生物活性的研究日益成为杂环化学研究的热门课题。3,6-二取代-1,2,4-三唑并噻二唑衍生物是具有广谱生物活性的稠杂环化合物,如抗菌、消炎、杀微生物、调节植物生长、除草等,因而引起各国化学家的广泛兴趣。此类化合物的生物活性,     

水热法白宝石晶体和籽晶界面研究

用分光光度计研究发现水热法白宝石晶体和籽晶界面使晶体透过率降低,用大视场偏光显微镜和原子力显微镜分析了该界面的包裹物分布以及界面的显微结构.结果表明平行于(1123)面的籽晶和生长层晶体界面包裹物含量少.界面的缺陷主要来自于晶格畸变及生长初期的温场不稳定所引起的结构缺陷,这也是引起晶体透过率下降的主要因素.     

Higher Toda Mechanics and Spectral Curves

For each of the Lie algebras gln and g~ln we construct a family of integrable generalizations of the Toda chains characterized by two integers m and m_. The Lax matrices and the equations of motion are given explicitly, and the integrals of motion can be calculated in terms of the trace of powers of the Lax matrix L. For the case of m =m_,we find a symmetric reduction for each generalized Toda chain we found, and the solution to the initial value problems of the reduced systems is outlined. We also studied the spectral curves of the periodic (m ,m_)-Toda chains, which turns out to be very different for different pairs of m and m_. Finally we also obtain the nonabelian generalizations of the (m ,m_)-Toda chains in an explicit form.     

Spectral Energy Density in a Kerr Nonlinear Blackbody

In a Kerr nonlinear blackbody, bare photons with opposite wave vectors and helicities are bound into pairsand unpaired photons are transformed into a new kind of quasiparticle, the nonpolariton. The nonpolariton system constitutes free thermal radiation in the blackbody. The present paper investigates the spectral energy density of the thermal radiation. It is found that the spectral energy density of a Kerr nonlinear blackbody is larger than that of a normal blackbody.     

Anomalous spectral behaviour of diffracted chirped Gaussian pulses in the near field

By using the Fourier transform method, analytical expressions for the axial power spectrum and near-field intensity in the spacetime domain of chirped Gaussian pulses diffracted at an aperture are derived, which permit us to study changes in spectral and temporal profiles of the chirped Gaussian pulses both analytically and numerically. Detailed numerical results and physical analysis show that spectral anomalies take place in the neighbourhood of certain critical distances, and the shifting of maximum and splitting of temporal intensity profiles appear. In particular, for ultrashort chirped pulses, there exists also spectral switch. Besides the truncation parameter, the chirp parameter and pulse duration affect the behaviour of spectral switches.     

Comment on “A Hierarchy of Integrable Nonlinear Lattice Equations and New Integrable Symplectic Map”

Comment on a recent paper on Commun. Theor. Phys. (Beijing, China) 38 (2002) pp. 523-528.