Flexure analysis of unsymmetric orthotropic beams with an interlayer

This paper presents a layer-wise stress and deformation analysis of a three-layer beam configuration consisting of two dissimilar orthotropic adherends of different thicknesses that are joined together by a deformable interlayer of finite thickness. Analytical solutions for the case of three-point flexure loading are presented for both compressible and incompressible interlayers. Parametric analysis reveals the influences of asymmetry of moduli and adherend thicknesses, interlayer thickness, and overhang of the beams on the beam compliance. Analytical predictions of beam compliance show very good agreement with finite element results. Experimental measurements of compliance of various unsymmetric beams consisting of aluminum adherends separated by a rubber interlayer were performed in order to validate the analysis. Excellent agreement between measured and predicted compliance values was observed.     

Profit maximization from the sales of products which have limited lifetimes in a fixed price market

The optimization of profit resulting from the sales of products which have limited lifetimes is discussed. The factors considered in the analysis are selling price, cost price, disposal price and loss of goodwill. Demand which is considered to be stochastic is represented by an exponential distribution function. It is found that the factors most influential in the determination of expected profit are the cost price to produce the product and the administrative cost involved in the disposal of the product after its useful lifetime has been exceeded.     

Effect of excluded volume on 2D discrete stochastic chemical kinetics

The stochastic simulation algorithm (SSA) is widely used in the discrete stochastic simulation of chemical kinetics. The propensity functions which play a central role in this algorithm have been derived under the point-molecule assumption, i.e., that the total volume of the molecules is negligible compared to the volume of the container. It has been shown analytically that for a one-dimensional system and the A + A reaction, when the point-molecule assumption is relaxed, the propensity function need only be adjusted by replacing the total volume of the system with the free volume of the system. In this paper we investigate via numerical simulations the impact of relaxing the point-molecule assumption in two dimensions. We find that the distribution of times to the first collision is close to exponential in most cases, so that the formalism of the propensity function is still applicable. In addition, we find that the area excluded by the molecules in two dimensions is usually higher than their close-packed area, requiring a larger correction to the propensity function than just the replacement of the total volume by the free volume.     

Ein Durchflusscalorimeter

Ohne Zusammenfassung     

Phenomenological modeling of the response of a dense colloidal suspension under dynamic squeezing flow

The split Hopkinson pressure bar experimental technique is used to evaluate the squeezing flow response of a concentrated, discontinuously thickening colloidal suspension of spherical silica particles loaded at high stresses/strain rates. These results provide insight into the transitional behavior of these materials, as well as the post-transitional response under compressive loading. A method of analyzing the strain and strain rate dependent behavior is presented to identify modes of material response (viscous, elastic, etc.). Experimental results are presented as stress–strain–strain rate plots and a surface fitting approach is used to develop a phenomenological model describing the overall response. From this model, it is possible to identify regions of elastic and viscous behavior using a gradient analysis approach. It was found that, after an initial period of viscous deformation, the suspension behaves like a viscoelastic material – this regime corresponds well with transition in which large clusters of particles percolate. This is followed by a third, viscous regime in which the material undergoes viscous deformation. At the highest stresses, a plateau region of plastic deformation has been identified. This approach and the conditions under which it may be applied are described in detail in the paper.     

Thermodynamic quantities for the protonation of amino acid amino groups from 323.15 to 398.15 K

Flow claorimetry has been used to study the interaction of protons with glycine, DL--alanine, -alanine, DL-2-aminobutyric acid, 4-aminobutyric acid, and 6-aminocaproic acid in aqueous solutions at temperatures from 323.15 to 398.15 K. By combining the measured heats for amino acid solutions titrated with NaOH solutions with the heat of ionization for water, the log K, H^o, S^o, and C_p ^o values for the protonation of the amino groups of these amino acids have been obtained at each temperature studied. Equations are given expressing these values as functions of temperature. The H^o and S^o values increase while log K values decrease as temperacture increases. The trends for log K, H^o, S^o, and C_p ^o are discussed in terms of changes in long-range and short-range solvent effects. The trend in H^o, S^o, and C_p ^o values with temperature and with charge separation in the zwitterions is interpreted in terms of solvent-solute interactions and the electrostatic interaction between the two oppositely charged groups within the molecule.     

Simulating prescribed particle densities in the grand canonical ensemble using iterative algorithms

We present two efficient iterative Monte Carlo algorithms in the grand canonical ensemble with which the chemical potentials corresponding to prescribed (targeted) partial densities can be determined. The first algorithm works by always using the targeted densities in the kT log(rho(i)) (ideal gas) terms and updating the excess chemical potentials from the previous iteration. The second algorithm extrapolates the chemical potentials in the next iteration from the results of the previous iteration using a first order series expansion of the densities. The coefficients of the series, the derivatives of the densities with respect to the chemical potentials, are obtained from the simulations by fluctuation formulas. The convergence of this procedure is shown for the examples of a homogeneous Lennard-Jones mixture and a NaCl-CaCl(2) electrolyte mixture in the primitive model. The methods are quite robust under the conditions investigated. The first algorithm is less sensitive to initial conditions.