Reception pattern influence on magnetoacoustic tomography with magnetic induction

Based on the acoustic radiation theory of a dipole source,the influence of the transducer reception pattern is studied for magnetoacoustic tomography with magnetic induction(MAT-MI).Numerical studies are conducted to simulate acoustic pressures,waveforms,and reconstructed images with unidirectional,omnidirectional,and strong directional transducers.With the analyses of equivalent and projection sources,the influences of the model dimension and the layer effect are qualitatively analyzed to evaluate the performance of MAT-MI.Three-dimensional simulation studies show that the strong directional transducer with a large radius can reduce the influences of equivalent sources,projection sources,and the layer effect effectively,resulting in enhanced pressure and improved image contrast,which is beneficial for boundary pressure extraction in conductivity reconstruction.The reconstructed conductivity contrast images present the conductivity boundaries as stripes with different contrasts and polarities,representing the values and directions of the conductivity changes of the scanned layer.The favorable results provide solid evidence for transducer selection and suggest potential practical applications of MAT-MI in biomedical imaging.     

Alteration in Cross Diffusivities Governs the Nature and Dynamics of Spatiotemporal Pattern Formation

Realizing spatiotemporal patterns out of a chemical reaction diffusion system remains an experimental challenge owing to the difficulty in overcoming the stringent condition of diffusion driven instability. Herein, by considering the spatially extended Gray-Scott model system, we have investigated how the cross diffusivities of the reactants involved influence the nature and dynamics of spatiotemporal patterns. Our study unravels that in absence of diffusion driven instability, spatially inhomogeneous patterns can be obtained for the Gray-Scott model system, and unstable time dependent patterns can be stabilized just by adjusting cross diffusivities of the reactants. Interestingly, the effect of cross diffusion in presence of the diffusion driven instability can differentially alter the speed of pattern formation, and potentially modify the nature of the spatiotemporal patterns obtained under different parametric conditions. Experimental verification of our findings may allow us to observe spatiotemporal patterns beyond the regime of classical Turing instability.     

Comparison of the active components of Aster tataricus from different regions and related processed products by ultra‐high performance liquid chromatography with tandem mass spectrometry

We investigated crude Aster tataricus, vinegar‐processed Aster tataricus, honey‐processed Aster tataricus, and steamed Aster tataricus as a case study and developed a comprehensive strategy integrating quantitative analysis and chemical pattern recognition methods for the evaluation and differentiation of Aster tataricus from different regions, as well as related processed products. In the study, 15 batches of raw Aster tataricus collected from seven provinces were analyzed. A sensitive and rapid ultra‐high performance liquid chromatography with tandem mass spectrometry method for simultaneous determination of 15 compounds was established to evaluate the quality of raw and processed Aster tataricus. Furthermore, multivariate statistical techniques were applied to compare the differences among Aster tataricus samples. As a result, the herbs collected from seven provinces were divided into two categories, and chlorogenic acid was the most important component distinguishing between the regions. Moreover, all of the raw and processed samples were classified by partial least squares discriminant analysis based on the 15 analyzed compounds. Results showed that raw Aster tataricus, vinegar‐processed Aster tataricus, honey‐processed Aster tataricus, and steamed Aster tataricus were clustered in four different areas. Shionone, chlorogenic acid and kaempferol were the significant constituents differentiating the raw and differently processed Aster tataricus samples.     

Discrete element simulation of effects of multicontact loading on single particle crushing

Particle crushing commonly occurs in granular materials and affects their structures and mechanical properties. Unlike idealized particles in experimental single particle crushing tests with two loading points, natural particles are crushed under multicontact loading. To date, the criteria and patterns of particle crushing under multicontact conditions are not fully understood. By using the three-dimensional discrete element method, this report explores the effect of multicontact loading on the crushing criterion of a single particle, the crushing pattern, and the relationship between the particle crushing strength and loading distribution. The particles are modelled as aggregates of glued Voronoi polyhedra. The numerical results indicate that the logarithm of the mean principal stress has a good linear correlation with the coordination number. For a specific coordination number, the number of child particles presents a significant normal distribution. For a specific number of child particles, the volumes of child particles can be statistically described as normal or gamma distribution. Three typical models are proposed to qualitatively analyse the relationship between the loading distribution and crushing strength. The relevant conclusions can be helpful in engineering practice and in further studies on crushable granular materials via the discrete element method.     

微分中值问题中辅助函数的构造程式

给出解决微分中值问题时，所需辅助函数的构造程式，并通过实例加以详细解释．所给程式具有一定的可操作性，可帮助学生掌握同类问题解决方案中的规律性．     

First Experience in Using Microdensitometer “Scandig 3” — Joyce Loebl for Autoradiographs Evaluation

The Device is composed of the basic microdensitometer, the control computer, the magnetic tape unit, the teletype, the interface, and the software package.

This apparatus is designated for digitalization of image data point by point (system “flying spot”) and for their record on magnetic tape for further data processing. The software package makes possible to realize some basic evaluation only by using configuration mentioned above — for example recording of measured values, determination of numbers of occurrences particular optical density (histogram), tresholding and mapping of measured values.

This paper describes the instrument and its using for autoradiographs evaluating.     

Computing the partial word avoidability indices of ternary patterns

We study pattern avoidance in the context of partial words. The problem of classifying the avoidable binary patterns has been solved, so we move on to ternary and more general patterns. Our results, which are based on morphisms (iterated or not), determine all the ternary patternsʼ avoidability indices or at least give bounds for them.     

Evaluation of the piezoelectric behaviour produced by a thick-film transducer using digital speckle pattern interferometry

This paper presents an interferometric measurement of the out-of-plane deflections produced by a piezoelectric transducer, manufactured by thick-film deposition of a ceramic paste over an alumina substrate, when is subjected to a DC electric voltage. It is shown that a digital speckle pattern interferometer with an incorporated phase-shifting facility allows the measurement of nanometer displacements generated by the piezoelectric device. These measurements are used to evaluate the effective piezoelectric charge constant along the polarization direction (d₃₃)_eff that characterizes the thick-film transducer.     

Weak temperature gradient effect on the stability of the circular Couette flow

We have investigated the influence of a weak radial temperature gradient in a wide gap and large aspect ratio Couette-Taylor system. The inner cylinder is rotating and can be heated or cooled, the outer cylinder is at rest and immersed in a large thermal bath. We found that a radial temperature gradient destabilizes the Couette flow leading to a pattern of traveling helicoidal vortices occurring only near the bottom of the system. The size of the pattern increases as the rotation frequency of the cylinder is increased. We have characterized the spatiotemporal properties of the pattern and we have shown that it behaves as a wall mode found in the simulation of the complex Ginzburg-Landau equation with homogeneous boundary conditions.