Improving the efficiency of IMS-IMS by a combing technique

A simple method for increasing the efficiency of multidimensional ion mobility spectrometry (IMS-IMS) measurements (as defined by the number of two-dimensional data sets necessary to sample all of the ions in a complex mixture) is illustrated. In this approach, components from a packet containing a mixture of ions are introduced into the first IMS drift region where they are separated based on differences in mobility. At the exit of this region, narrow distributions of ions having identical mobilities are selected, subjected to gentle activation conditions that are intended to induce conformational changes, and transmitted into a second IMS drift region where the new conformations are separated. Here, we describe a simple timing sequence associated with selection and activation of multiple distributions at the entrance of the second drift region in a systematic fashion that improves the efficiency of two-dimensional IMS-IMS by a factor of approximately 8. The method is illustrated by examination of a mixture of tryptic peptides from human hemoglobin.     

A finite difference-Galerkin finite element solution of compressible laminar boundary-layer flows

A finite difference-Galerkinfinite element method is presented for the solution of the two-dimensional compressible laminar boundary-layer flow problem. The streamwise derivatives in the momentum and energy equations are approximated by finite differences. An iterative scheme, due to the non-linearity of the problem, in conjunction with the Galerkin finite element method is then proposed for the solution of the problem through the boundary-layer thickness. Numerical results are presented and these are compared with other numerical and analytical solutions in order to show the applicability and the effectiveness of the proposed formulation. In all the cases here examined, the results obtained attained the same accuracy of other numerical methods for a much smaller number of points in the boundary-layer.     

Use of woven CFRP for externally pressurized domes

Sensitivity of bifurcation buckling, first-ply failure (FPF) and last-ply failure (LPF) to the different modelling methods of woven cloth is examined numerically for a range of torispherical shells. Axisymmetric and two two-dimensional models are used for externally pressurized multi-ply domes. In the first two-dimensional model, angles between warp and weft directions on torispheres are obtained through an optical projection of an initially orthogonal woven net. In the second type of modelling, a planar/orthogonal mapping is preserved on the torispherical geometry. Bifurcation buckling seems to be insensitive to the method of modelling. Results for FPF show that differences between axisymmetric and planar models can be as high as 50%, whilst the differences for optical and planar models can reach 30%. The magnitude of LPF pressures is also sensitive to the two-dimensional modelling method adopted. Ultimate collapse loads, associated with LPFs and based on optical modelling, are up to 30% higher than those obtained for planar modelling for carbon cloth.     

Development of non-gel-based two-dimensional separation of intact proteins by an on-line hyphenation of capillary isoelectric focusing and hollow fiber flow field-flow fractionation

A rapid, non-gel-based, on-line, two-dimensional separation method is introduced for proteome analysis. Protein fractionation was carried out by first exploiting the differences in their respective isoelectric points (pI) in a Teflon capillary using isoelectric focusing (IEF), followed by a molecular weight (MW)-based separation in a hollow fiber by flow field-flow fractionation (FlFFF). The method developed here (CIEF-HFFlFFF) may be a powerful alternative to two-dimensional polyacrylamide gel electrophoresis, which is currently used for the separation and purification of proteins. In CIEF-HFFlFFF, proteins can be collected as a fraction of a certain pI and MW interval without being denatured. Additionally, the ampholyte solution is simultaneously removed during separation in the hollow fiber, and the overall process time is significantly reduced. This method was applied to a human urinary proteome sample, leading to the identification of 114 proteins with the subsequent off-line use of nanoflow liquid chromatography-tandem mass spectrometry after the tryptic digestion of each collected protein fraction.     

Automated computer simulation of two-dimensional elastostatic problems by the finite element method

A software system for the automated computer simulation of two-dimensional elastostatic problems by the finite element method is described. This system consists of two parts, automated mesh generation and automated stress analysis. The mesh generation is based on a method in which equilateral triangles are generated successively in the unmeshed region. Automated mesh refinement is carried out in the latter part of the simulation process. The stress analysis is based on the assumed stress hybrid method and the successive over relaxation method. The computer program developed for this paper can generate a succession of increasingly refined triangular meshes until a certain mesh convergence criterion is achieved. The mesh convergence criterion is based on a comparison of nodal stresses in successive analyses until all the stress differences are within a specified tolerance.     

A direct Numerical Simulation Approach to the Study of Intrusion Fronts

A direct numerical simulation approach for the study of gravity currents in a plane channel is described. The numerical method employed is based on a mixed spectral/spectral-element discretization in space together with finite differences in time. For the validation of the code, simulations of Rayleigh–Bénard convection are performed and the results are compared with theoretical predictions and reference data from the literature. The dynamics of gravity currents is then studied by simulations of two-dimensional lock-exchange flow. The results obtained in these simulations are in good agreement with recent experimental data. By a systematic variation of the Grashof number the influence of viscous diffusion on the characteristics of the propagating fronts is assessed.     

Method of including the anisotropy of the optical properties of the surface and the nonunidimensionality of the system in determining the effective radiation

Based on the method of successive substitutions, an integral equation is derived in which multiple reflections are explicitly identified. This equation is used provide simple methods of estimating the local effective radiation of two-dimensional and three-dimensional systems of surfaces, with due regard for the anisotropy of their optical properties. A cylindrical cavity confined by the surface of a right circular cylinder with a side pyrometric hole is treated as an example. The results obtained by the suggested method are compared with the data of direct solution of an integral equation for the two-dimensional problem.     

代换梁法在自锚式悬索桥上的推广应用

为了解决自锚式悬索桥活载内力计算问题,按照我国著名学者李国豪教授提出的代换梁法的基本原理,分析了自锚式悬索桥和传统地锚式悬索桥的构造和受力的不同点,对自锚式悬索桥提出了新的计算模型,由此导出了因活载对主缆产生水平拉力分量的计算公式,从而解决了确定自锚式悬索桥加劲梁内力的问题。通过一座桥例的分析,用该方法所得到的计算结果与空间及平面有限元法的分析值基本吻合。因此,该方法对设计具有实用意义。     

A simple method for prediction of chilling times for objects of two-dimensional irregular shape

A simple chilling time prediction method applicable to two-dimensional irregular shapes is proposed. The method uses the first term in the series analytical solution for convective cooling of a sphere in conjunction with two geometric parameters determined by empirical algebraic equations. The real geometric shape is related to an equivalent infinite ellipse using dimensional measurements of the shape, and the two parameters determined for the ellipse. Experimental measurements with seven irregular geometric shapes (38 runs) and finite element numerical method predictions were used to test the methodology for predicting chilling rates at the thermal centre position. Observed differences were largely explainable by data uncertainties. The method has theoretical capability to predict mass-average temperatures, but this capability has not been experimentally tested.     

Meetings Calendar

A general method is described for the reconstruction of an object from several incomplete images and affected by random noise. The method is based on filtering by means of a periodical two-dimensional sampling filter in reciprocal space. A theoretical analysis of this method is made and compared with experimental results. Finally, different parameters involved in the process are analysed and discussed with reference to the experiments.     

The reproducing kernel particle method for two-dimensional unsteady heat conduction problems

The numerical solution to two-dimensional unsteady heat conduction problem is obtained using the reproducing kernel particle method (RKPM). A variational method is employed to furnish the discrete equations, and the essential boundary conditions are enforced by the penalty method. Convergence analysis and error estimation are discussed. Compared with the numerical methods based on mesh, the RKPM needs only the scattered nodes instead of meshing the domain of the problem. The effectiveness of the RKPM for two-dimensional unsteady heat conduction problems is examined by two numerical examples.     

Three-dimensional dynamic stress intensity factors around two parallel square cracks in an infinite elastic medium subjected to a time-harmonic stress wave

Summary Dynamic stresses around two parallel square cracks in an infinite elastic medium are determined. A time-harmonic stress wave impinges on the two cracks normal to their surfaces. The two-dimensional Fourier transform technique is applied to reduce the mixed boundary value conditions to dual integral equations. To solve the equations, differences of the displacements in the upper square crack are expanded using a double series of functions which are equal to zero outside the crack. Those in the lower crack are also expanded using a similar series. Unknown coefficients in the series are determined by applying the Schmidt method. Dynamic stress intensity factors are calculated numerically assuming that the shape of the upper crack is identical to that of the lower crack.     

Geometrically non-linear method of incompatible modes in application to finite elasticity with independent rotations

We discuss a geometrically non-linear method of incompatible modes. The model problem chosen for the discussion is the finite elasticity with independent rotations. The conditions which ensure the convergence of the method and the methodology to construct incompatible modes are presented. A detailed derivation of variational equations and their linearized form is given for a two-dimensional plane problem. A couple of geometrically non-linear two-dimensional elements with independent rotational freedoms are proposed based on the presented methodology. The elements exhibit a very satisfying performance over a set of problems in finite elasticity.     

An experimental-numerical hybrid technique for two-dimensional stress analysis

A numerical procedure for obtaining the stress components in the interior of a two-dimensional body from the values of stresses measured along the boundary, is presented. In this method the two-dimensional elasticity equations are re-written in a convenient form and solved using the finite difference technique along with the boundary stress values. The application of the method is illustrated with examples.     

Analysis of Two-Dimensional Effect in the Measurement of Thermal Diffusivity of Thin Films with an AC Calorimetric Method1

An ac calorimetric method for measuring the thermal diffusivity of thin-film materials has been widely applied. In the application of this method, the systematic errors caused by the heat loss effect, the edge reflection effect, etc., have been analyzed and corresponding correction methods have been developed. But when measuring films with low thermal diffusivity or with thickness comparable to the thermal diffusion length, a two-dimensional effect which will also result in a systematic error of the measurement is present. In this paper, the mechanism of two-dimensional heat conduction within a thin sample which is supplied a periodic heat flux by a chopped light beam is analyzed. A numerical analysis method is developed to study the effect of the two-dimensional heat conduction on the measured thermal diffusivity values. The relations between the measured thermal diffusivity and independent parameters such as frequency, thickness of sample, width of light spot, etc., are demonstrated to indicate the two-dimensional effect. The experimental precondition for minimizing the systematic error caused by the two-dimensional effect is determined. In addition, the analysis method presented in this paper should be useful for more difficult problems such as error estimation of the thermal diffusivity measurement of coatings or composite films.     

Canonical-Element Method for Modeling Hydrodynamics and Heat and Mass Exchange in Arbitrarily Shaped Regions

A numerical method of solution of nonstationary problems of flow and heat and mass exchange of a viscous incompressible fluid in two-dimensional multiply connected regions of an arbitrary shape with curvilinear boundaries is presented; this numerical method is based on the canonical-element method, the three-layer scaling difference scheme, and the three-layer explicit difference scheme. A method of finding the vortex function at the curvilinear boundaries of the region is proposed. Results of solution of some two-dimensional problems of hydrodynamics and heat exchange for different regimes of flow are presented.     

Exact Power Function of Compendial Test Requirements for Content Uniformity

The exact distributions associated with the current compendial test requirements are generated by resorting to the well known Computer Intensive Algorithm method to establish the exact percentage point (limit) for RSD, corresponding to each selected cut-off probability level (confidence level) for each of the four possible experimental outcomes based on the USP-NF test requirements. A table is constructed to present the two-dimensional power function. The similarities between these tabular values and the current compendial RSD limits for 10 and 30 dosage units are extremely remarkable.

Minor differences exist, however. It is suggested that both the theoretical as well as the numerical approaches should be carried out to arrive at a comprehensive solution.     

Two-dimensional fluorescence correlation in capillary electrophoresis for peak resolution and species identification

A new spectroscopic dimension-fluorescence intensity correlation--is introduced to enhance peak resolution and species identification in capillary electrophoresis. In two-dimensional correlation CE, a conventional electropherogram is spread into two dimensions through cross-correlation analysis of fluorescence time response. A laser that is sinusoidally modulated in intensity is used as the excitation source. Three channels of information are collected during a CE run: the steady-state intensity, the ac amplitude, and the phase-resolved fluorescence intensity. The correlation between two chosen channels is then evaluated. A two-dimensional correlation electropherogram consists of a plot of the correlation intensity versus two axes of migration time. Through correlation analysis, species discrimination and peak resolution are significantly enhanced without having to physically separate the solutes. Two-dimensional correlation CE showed complete resolution between two overlapping sample peaks with a resolution of 0.28 in the conventional one-dimensional electropherogram. In separations of polycyclic aromatic hydrocarbons by micellar electrokinetic chromatography (MEKC), two-dimensional correlation analysis resolved all overlapping elution peaks unseparable by one-dimensional MEKC, demonstrating the utility of 2D correlation in separation method development. The capability of 2D correlation CE in species identification is demonstrated with a sequence of 39 consecutively injected peaks containing four fluorescent dyes. Species identification in sequencing is achieved without complex data treatment in two-dimensional correlation CE.     

二维直方图斜分Tsallis–Havrda–Charvát熵图像阈值分割

本文指出了现有二维直方图区域直分法中存在明显的错分,提出了二维直方图区域斜分方法,即通过与主对角线平行的四条斜线将直方图分成内点区、边界点区和噪声点区,并按灰度级与邻域平均灰度级之和的大小进行分割.该方法可以运用于所有的基于二维直方图的阈值分割.文中导出了基于二维直方图区域斜分的Tsallis–Havrda–Charvát 熵阈值选取公式及其快速递推算法,给出了分割结果和运行时间.与基于二维直方图直分的Tsallis–Havrda–Charvát 熵原始算法相比,本文提出的基于二维直方图斜分的Tsallis–Havrda–Charvát 熵阈值分割算法,使分割后的图像内部区域均匀,边界形状准确,更有稳健的抗噪性,其运行时间减少了五个数量级.     

Method of singular integrodifferential equations in plane dynamic problems of fracture mechanics

We develop a method for the solution of two-dimensional dynamic problems of the theory of elasticity for infinite bodies with smooth curvilinear cracks combining a modified method of finite differences in time with the method of singular integrodifferential equations in the space variables. Integral representations of the wave potentials are constructed and used to reduce the first boundary-value problem to the solution of systems of integrodifferential equations by the method of mechanical quadratures. The time dependences of the computed dynamic stress intensity factors at the tips of a rectilinear crack are analyzed for various impact and pulsed loads acting upon the crack lips.