共振波长对导模共振生物传感器灵敏度的影响

导模共振生物传感器由于具有微型化、免标签、高通量和实时检测等优势被广泛研究。利用严格耦合波理论分析了该生物传感器对样品折射率和厚度的灵敏度随共振波长的变化规律。当样品厚度和共振波长一定时,其折射率灵敏度恒定;随着共振波长的增大,折射率灵敏度显著提高。当样品折射率和共振波长一定时,厚度灵敏度随着厚度的增加而降低,最后趋近于0;当共振波长增加时,厚度灵敏度明显提高,厚度测量范围增大。结果表明:选取较长的共振波长有利于样品的检测和分析。     

阴极不同进气对PEMFC性能影响的实验研究

针对阴极通纯氧气或空气两种情况,实验研究了温度及化学计量比的变化对反应面积为9 cm2、具有平行流场的PEMFC性能的影响.结果表明:升高电池温度可提高PEMFC的性能及极限电流密度;在本实验条件下,为提高电池性能,阴极通纯氧时,阳极化学计量比/阴极化学计量比应高于1.5/3.0,通空气时,两者之值应高于3.0/6.0;相对于阴极通空气的情况,阴极通氧气时电池性能显著提高,故在条件允许的前提下应尽量以纯氧作为氧化气体.     

胡椒生物碱提取、几何结构以及红外光谱的研究

以海南胡椒果为原料,95%乙醇溶液为溶剂,采用回流法提取胡椒生物碱。通过调节pH值除去胡椒酸,乙醚除去脂溶物,用丙酮为溶剂重结晶纯化胡椒生物碱,并用高效液相色谱仪检测其纯度,以及对胡椒生物碱进行了红外光谱表征。同时运用密度泛函B3LYP/6-31G(d, p)方法,对胡椒生物碱的结构进行优化、频率和能量的计算,得到四种构型(构型Ⅰ胡椒碱、构型Ⅱ异胡椒碱、构型Ⅲ异胡椒脂碱和构型Ⅳ胡椒脂碱)的64种构象的稳定结构,并利用吉布斯自由能计算常温(298.15 K)下四种构型分子体系稳定构象的热力学平衡分布。并对实验红外光谱与理论红外光谱的特征峰进行了对比。结果表明,所提取的胡椒生物碱主要以构型Ⅰ中的构象1结构存在,即胡椒碱结构;经纯化后得到胡椒碱含量为7%,纯度达99%。经分析建立的胡椒生物碱提取、分离和纯化方法效果良好,建立的胡椒生物碱模型能与实验结果相吻合。该研究对指导胡椒生物碱的提取、结构模型的建立、表征和应用有重大意义。     

充分发展槽道湍流的小波数值分析

数值计算了高斯子波变换Navier Stokes(N-S)方程后得到的积分方程.在利用高斯子波得到的以弯曲度为基本量的无穷域中N-S方程的基础上,得到了有界区域内的以弯曲度为基本量的N-S方程.将此N-S方程看作一个特殊的扩散方程,将压力项与对流项看作是源项,得到一个积分方程.利用特征线法对该方程求解,得到通解.并将所得结果运用于对称槽道湍流和非对称槽道湍流的研究中.将计算与实验所得的平均量与实验结果进行了对比.     

氮作稀释剂DF化学激光器性能评价

对氮作稀释剂DF化学激光器的实用化途径进行探讨,对实验输出性能进行分析研究,并与一般的氦稀释剂DF激光器性能作一比较,结果表明,单从器件本身输出性能来说,氮稀释剂略次于氦稀释剂,但从综合性能考虑,氮稀释剂DF化学激光器仍是实用型器件理想的候选者之一。     

极性超晶格中电子—声子的相互作用

本文在Wendler、潘金声研究双层极性晶体时得出的声子振动极化场所满足的微分、积分方程及归一化条件的基础上,讨论周期性排列的层状极性晶体中声子振动极化场所满足的微分、积分方程,得到了SO声子的色散关系,SO声子和LO声子极化强度矢量.用声子产生、湮灭算符表出了声子振动能量及电子—声子的相互作用哈密顿量.     

Low-noise operation of fluoride-based erbium-doped fiber amplifiers with (4)I(11/2)-level pumping

The low-noise operation of fluoride-based erbium-doped fiber amplifiers (EDFA's) is demonstrated with (4)I(11/2)-level pumping for what we believe to be the first time. A noise figure as low as 3.5 +/- 0.5 dB at 1550 nm is achieved by means of 970-nm pumping. It is shown that it is possible to construct fluoride-based EDFA's with a noise figure as low as that of silica-based EDFA's.     

Exact solutions for the flow of Casson fluid over a stretching surface with transpiration and heat transfer effects

The effects of transpiration on forced convection boundary layer non-Newtonian fluid flow and heat transfer toward a linearly stretching surface are reported.The flow is caused solely by the stretching of the sheet in its own plane with a velocity varying linearly with the distance from a fixed point.The constitutive relationship for the Casson fluid is used.The governing partial differential equations corresponding to the momentum and energy equations are converted into non-linear ordinary differential equations by using similarity transformations.Exact solutions of the resulting ordinary differential equations are obtained.The effect of increasing Casson parameter,i.e.,with decreasing yield stress(the fluid behaves as a Newtonian fluid as the Casson parameter becomes large),is to suppress the velocity field.However,the temperature is enhanced as the Casson parameter increases.It is observed that the effect of transpiration is to decrease the fluid velocity as well as the temperature.The skin-friction coefficient is found to increase as the transpiration parameter increases.     

A study of transverse charge density of pions in relativistic quantum mechanics

The transverse charge density of pions is calculated based on relativistic quantum mechanics, where the pion is regarded as a quark-antiquark bound state. Corrections from the two spin-1/2 constituents and from the wave function of a quark and antiquark inside the bound system are discussed. The calculated results are compared to the results with a realistic effective Lagrangian approach as well as to that with a simple covariant model where the pion is regarded as a composite system with two scalar particles.     

L1 generalized inverse beam-forming algorithm resolving coherent/incoherent, distributed and multipole sources

To resolve coherent/incoherent, distributed/compact, and multipole aerodynamic-sound sources with phased-array pressure data, a new source-detection algorithm is developed based on L₁ generalized inverse techniques. To extract each coherent signal, a cross spectral matrix is decomposed into eigenmodes. Subsequently, the complex source-amplitude distribution that recovers each eigenmode is solved using generalized inverse techniques with reference solutions which include multipoles as well as a monopole. Namely, the source distribution consisting of pre-defined source types is solved as an L₁ norm problem using iteratively re-weighted least squares (IRLS). The capabilities of the proposed algorithm are demonstrated using various benchmark problems to compare the results with several existing beam-forming algorithms, and it is found that distributed sources as well as dipoles with arbitrary orientation can be identified regardless of coherency with another source. The resolution is comparable to existing deconvolution techniques, such as DAMAS or CLEAN, and the computational cost is only several times more than that of DAMAS2. The proposed algorithm is also examined using previous model-scale test data taken in an open-jet wind-tunnel for a study on jet-flap interaction, and some indication of dipole radiation is discerned near the flap edge.     

固态检测器－ICP－AES中的计算机差谱改进技术──Ⅰ．原理和实验

本文使用固态检测器－光电二极管阵列（ＰＤＡ）或电荷耦合器件（ＣＣＤ）在ＩＣＰ－ＡＥＳ上实现了无需知道基体浓度情况下对复杂组分中微量元素进行测定的计算机差谱改进法。用Ｃ语言编写了实施差谱技术以及实验室例行分析的软件，探讨了方法的原理，对Ｖ基体中Ａｌ，Ａｌ和Ｍｇ基体中Ｖ的测定结果表明，该差谱技术能准确消除复杂基体产生的光谱干扰。     

Analysis of arbitrary index profile planar optical waveguides and multilayer nonlinear structures: a simple finite difference algorithm

we present here a simple numerical method to obtain the mode effective indices as well as field distributions of modes of any arbitrary profile planar optical waveguide. The method is based on the solutions of scalar and semivectorial Helmoltz’s equation by finite difference algorithm and devised with a field convergence technique. This approach is quite general and can be applied straightforwardly to calculate the guided as well as quasi- or leaky modes of any arbitrary planar structure without the need to solve any eigenvalue equation or any complex matrix formalism. Besides providing the ease of application, the algorithm is particularly useful for waveguides with any graded index profile or with irregular multilayered structure and multilayered waveguides with a localised arbitrary nonlinear film. The performance of our method is verified against typical problems with analytical solutions or having results known otherwise, and is shown to yield results with good accuracy.     

A rigorous construction of the chiral anomaly on a spin manifold

The quantum field for Dirac fermion is rigorously formulated on a compact spin manifold by using the functional integral defined as the continuum limit of a lattice approximation with a new action. Within this framework, the chiral anomaly for a fermion interacting with gauge as well as gravitational fields is calculated with mathematical rigor.     

Highly efficient mode-locked Yb:Sc2O3 laser

Passive mode locking of the Yb:Sc2O3 laser is demonstrated. We investigate the laser performance with Ti:sapphire and diode-laser pumping. The laser is mode locked by use of a semiconductor saturable-absorber mirror and emits as much as 0.8 W of power in the picosecond range with a pump efficiency as high as 47%. With dispersion compensation, pulses as short as 230 fs for an average power of 0.54 W are obtained at 1044 nm. This is, to our knowledge, the first femtosecond oscillator based on an Yb-doped sesquioxide crystal.     

Space-time theories and symmetry groups

This paper addresses the significance of the general class of diffeomorphisms in the theory of general relativity as opposed to the Poincaré group in a special relativistic theory. Using Anderson's concept of an absolute object for a theory, with suitable revisions, it is shown that the general group of local diffeomorphisms is associated with the theory of general relativity as its local dynamical symmetry group, while the Poincaré group is associated with a special relativistic theory as both its global dynamical symmetry group and its geometrical symmetry group. It is argued that the two groups are of equal significance as symmetry groups of their associated theories.     

The effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer and its computation

For hypersonic vehicles,as the temperature in its boundary layer usually exceeds 600 K,for which the molecular vibrational degree of freedom is excited,the perfect gas model is no longer valid.In this paper,the effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer of flat plates is investigated by direct numerical simulations with the perfect gas model,i.e.with constant specific heat,as well as with a variable specific heat gas model.The comparison of the results from the two gas models has found that the effect of the variation of specific heat on the velocity of the turbulent boundary layers is relatively small,while its effect on temperature,such as the mean temperature,the temperature fluctuations,is appreciable.It is also found that the mean specific heat is quite close to the specific heat calculated by using the mean temperature,indicating that it is possible to do turbulence modeling.The modeling is done under the variable specific heat gas model with the mean temperature as the variable.The feasibility of such consideration is verified by applying the SST model for variable specific heat turbulence computation.     

Complex dynamics of a distributed parametric oscillator

The dynamics of a system with three parametrically coupled waves with delayed feedback is considered. Results of the detailed numerical simulation of the onset of self-modulation, as well as complex dynamic and chaotic regimes, are presented. The relation of self-modulation regimes with the formation and propagation of solitons is investigated. It is discovered that as the pump parameter increases, the synchronization of phases of the interacting waves, which is characteristic of stationary generation and periodic self-modulation regimes, is violated, and the system goes to a chaotic regime via intermittency.     

Invariance of the Doppler bandwidth with flow displacement in the illuminating field.

It is known that if single frequency continuously transmitted ultrasound or electromagnetic energy is reflected from "straight line flow," defined here as one or more scatters moving with constant velocity along an infinite straight line, the Doppler effect will shift the echo spectrum center frequency from the transmitted value, and broaden its bandwidth. It is proved that if such straight line flow is shifted laterally or in range anywhere in the field, i.e., without change of orientation, its Doppler bandwidth remains unchanged. (The "Doppler bandwidth" is here defined as the frequency difference between the extrema of the echo power spectrum.) The theorem holds true even though the time domain echo changes dramatically with motion of the flow path, and is believed to be valid for electromagnetic as well as ultrasound waves. Its implications with respect to flow measurement, as well as preliminary experimental and computational confirmation, will be discussed.