A New Seco-Abietanoid from the Bark of Cryptomeria japonica

Chemistry of Natural Compounds - A new seco-abietanoid, 12-hydroxy-6,7-seco-abieta-8,11,13-triene-6,7-dioic acid (1), was isolated from the methanol extract of the bark of Cryptomeria japonica. The...     

Seco-Abietanoids from Cryptomeria japonica and Their Inhibitory Activity Toward Xanthine Oxidase

Chemistry of Natural Compounds - A new seco-abietanoid, 12-methoxy-7-oxo-6,7-secoabieta-8,11,13-trien-6-oic acid (1), and a known seco-abietanoid,12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial...     

On 3-dimensional non-axisymmetrical deformation analyses for finite hollow circular cylinders

In this paper, 3-dimensional non-axisymmetrical deformation analyses for finite hollow circular cylinders have been carried out by Pickett's double series expansion method^[1]. Through expanding the displacement potentials as the sum of fourier series and Fourier-Bessel series, we could express the coefficients of one series by those of another under certain boundary conditions. Thus, a set of linear algebraic equations were derived. Solving these equations, we could obtain the solutions of the problems. Numerical examples have been given to show that the method presented here is workable for practical applications.     

Determining transverse impact force on a composite laminate by signal deconvolution

Dynamic impact forces on a composite structure were recovered by using experimentally generated Green's functions and signal deconvolutions. The signal processing is straightforward. Extra windowing and filtering the recorded signals are unnecessary. The Green's functions account for boundary conditions, material properties and structure geometry. This approach can be applied to linearly elastic structures with different boundary conditions. It is realistic and convenient to use for the recovery of impact force on anisotropic or isotropic solid structures.     

Crack trajectories influenced by mechanical and thermal disturbance in anisotropic material

This work is concerned with the application of the volume energy density criterion for predicting the crack trajectories as influenced by mechanical and thermal disturbance in an anisotropic material. Two-dimensional linear thermoelasticity is employed in conjunction with the well-known complex potentials such that a linear relationship is obtained for the boundary conditions across the crack or line of discontinuity. Boundary collocation is then used to determine the unknown coefficients from which the contours of the volume energy density in the cracked plate can be obtained. The crack path is assumed to coincide with the loci where dilatation would dominate. This corresponds to the locations of relative minimum energy density which can be found by visual inspection. An equal and opposite mechanical stress and thermal gradient are applied on the cracked plate. The former and latter enhance symmetric and asymmetric crack growth, respectively. They would complete depending on the magnitude of the mechanical and thermal load. Numerical results are presented for three (3) different cases of a plate whose principal axes of material symmetry are tilted to the crack plane. The influence of anisotropy on crack path is found to be secondary.     

Laser-generated rayleigh waves in graphite/epoxy composites

This study explores the potential for application of laser-induced surface or Rayleigh waves on graphite/epoxy composites. Rayleigh waves were generated by a Q-switched ruby laser in the ablation regime and detected by a pinducer which permitted accurate phase-velocity measurements. The Rayleigh wave velocity was measured in various directions relative to the fiber direction. Experimental results agreed closely with numerical predictions in the thick plate, but showed some increase of phase velocity in the thin plate. Laser-generated Rayleigh waves, particularly along the fiber direction, showed good potential for applications in NDT.     

Nonlinear stability analysis of miscible displacements

A simulator for three-dimensional horizontal miscible displacements in porous media is developed. Using this simulator, we examine the initiation and development of instabilities, viscous fingers and gravity tongues.With the only perturbations to the system being truncation and round-off errors, a density ratio (the ratio of the density of the displacing fluid to that of the displaced fluid) different from one is responsible for the initiation of the instabilities, and an unfavorable mobility ratio (the ratio of the viscosity of the displaced fluid to that of the displacing fluid) is responsible for the growth of the instabilities.     

Thermal stresses in a viscoelastic three-phase composite cylinder

A thermoviscoelastic analysis of a three-phase composite cylinder is presented in this work. The solutions of the heat conduction and thermoelastic problem for three dissimilar media are derived based on the method of analytic continuation associated with the alternation technique. A rapidly convergent series solution for both the temperature and stress field, which is expressed in terms of an explicit general term of the corresponding homogeneous potential, is obtained in an elegant form. The hereditary integral in conjunction with the Kelvin–Maxwell model is applied to simulate the thermoviscoelastic properties while a thermorheologically simple material is considered. According to the correspondence principle, the Laplace transformed thermoviscoelastic solution is directly determined from the corresponding thermoelastic one. The real time solution can then be solved numerically by taking inverse Laplace transform. Finally, some typical examples of interfacial stresses are discussed.     

Flow-induced structure in a system of nuclear waste simulant slurries

Thixotropy and antithixotropy were characterized in nuclear waste simulant slurries. For the neutralized current acid nuclear waste (NCAW) simulant slurries, NCAW with glycolic acid (NCAW+GA), and NCAW with nitric acid (NCAW+NA) (pH 4), a pre-shear flow at constant shear rate destroys the aggregates in the suspension and reduces viscosity. For the NCAW+NA (pH7–9), a pre-shear enhances the aggregates in the suspension and increases viscosity. With the addition of silica to the NCAW+GA and NCAW+NA slurries, the pre-shear effect tends to promote aggregation due to the formation of a network in the suspension, and hence, the viscosity increases. The macroscopic rheological property variation due to the microstructural aspects of the suspensions associated with the shear-induced effect are addressed.     

On the unsymmetrical deformation and reverse snapping of a spinning non-flat disk

In this paper we study the steady state deflection and reverse snapping phenomenon of a spinning non-flat disk. Both the initial and the deformed shapes of the disk are allowed to have axisymmetrical and unsymmetrical components. For the analysis of a rotating axisymmetrical disk, we conclude that there is no need to include the unsymmetrical assumed modes in the solution because all the unsymmetrical steady state deformations are unstable. In addition, the stability of the axisymmetrical positions will not be affected by the inclusion of the unsymmetrical assumed modes. In the case when the initial shape of the disk contains a dominant axisymmetrical component and a smaller unsymmetrical component, attention is focused on the effect of this unsymmetrical component on the overall deformation and stability of the spinning disk. It is found that the unsymmetrical component with one nodal diameter tends to slightly defer the occurrence of the reverse snapping phenomenon. On the other hand, all other unsymmetrical components with more than one nodal diameter tend to reduce dramatically the reverse snapping speed. Experiment is conducted on a non-flat brass disk containing an axisymmetrical component and an unsymmetrical component with two nodal diameters. The experimental measurement confirms the theoretical prediction.