The Pathology of Cryptology—A Current Survey

Abstract

“The Pathology of Cryptology” is the title of a chapter in David Kahn's book The Codebreakers. This chapter mainly deals with hidden messages, which amateur scientists claim to have discovered in the works of William Shakespeare and in other literary works. The present article picks up this subject and provides it with a theoretic framework under the name of “para-steganography.” Moreover, further case studies are added to those given by Kahn, including many examples that only became known after the publication of The Codebreakers. These considerations show that a hidden code can be found almost anywhere, provided that one looks for it in a suitable manner.     

Morphology and failure in nanocomposites. Part II: surface investigation

Polymer composites filled with calcium carbonate (CaCO₃) nanofillers (<100 nm), and kaolin filler of layered structure, both well suited to create nanocomposites, were analysed. The aim of this study was to investigate the influence of surface properties of the filler and matrix on the adhesion parameters at the interface in composites. The inverse gas chromatography, contact angle and capillary measurements were used for the surface characterization of filler and matrix. Although these methods are based on different assumptions, we found the same trends in the effects of filler surface treatment and/or matrix chemical structure on the changes in the dispersive and polar components of the surface energy. The energetics of the filler and matrix was varied in order to investigate the work of adhesion, interfacial energy and coefficient of spreading, and their influence on the composite properties. We found that the surface treatment of calcium carbonate filler lowered the filler surface energy and the work of adhesion in the composite with poly (vinyl acetate) matrix. The mechanical, thermal and morphological properties of the composite with treated CaCO₃, measured in the first part of this paper, indicated a weak and thin interphase. In the composite with kaolin filler the higher interaction with the polyacrylate copolymer matrix based on styrene as compared to the one based on methyl methacrylate, was confirmed by the higher work of adhesion in the interphase, resulting in a stronger reinforcing of the composite.     

永磁低速同步电动机应用技术概况

介绍了永磁低速同步电动机的基本工作原理、主要特点和典型的应用场合，并进一步论述了该类电机的国内外发展概况。     

Differences in the rheology and surface chemistry of kaolin clay slurries: The source of the variations

Kaolinite clays from two sources were found to display different rheological and electrokinetic behaviour despite having similar mineral composition. This difference is mainly due to the surface chemistry at the edges of the clay particles. Making the edge surface chemistry similar with an adsorbed small anionic additive such as citrate, produced a similar yield stress-pH behaviour for the different kaolin clay slurries. Heterogeneous attraction between positively charged edges and negatively charged faces of the clay particles is responsible for the yield stress behaviour of the clay slurry. However, the different points of zero charge of the edge caused the clay slurries to display different yield stress-pH behaviour. Adsorption of anionic citrate on negatively charged kaolin clay particles is reflected in a significant increase in the magnitude of the negative zeta potential. The adsorption is likely to be on the edge of the clay particles. Adsorbed citrate generally reduces or eliminates heterogeneous charge attraction leading to a much denser sediment being formed in the kaolin slurries with a coarser particle size distribution.     

SNIPPET ON DRYING

ABSTRACT

When regarding the atmospheric contact drying of granular beds wetted with a liquid mixture, both the drying rate and the selectivity of the process, i.e. the change of moisture composition, are of interest. The batch drying of a free flowing ceramic substance, wetted with a 2-propanol-water mixture, is investigated in a rotary dryer with heated wall and air flow.

The theoretical analysis is based on physical models for heat and mass transfer, moisture migration and particle transport, which are presented in examples.

The experimental and theoretical results show that higher selectivities can be achieved by reducing the particle size because of the lower liquid-phase mass-transfer resistance. An increase of the rotational speed leads to a higher drying rate with slightly decreased selectivity if the particles are sufficiently small, since contact heat transfer is enhanced.     

Feedback control with signal transmission after‐effects

In many practical systems, the physical plant, controller, sensor, and actuator are difficult to be located at the same place, and thus signals are required to be transmitted from one place to another. One immediate problem arising from such situations is that signals may exhibit after‐effect phenomena during their transmission. In this paper, we present a new model to characterize the state‐feedback control systems with signal transmission after‐effects, which deals with the transmission after‐effects from sensor to controller and from controller to actuator separately. Analysis and synthesis results based on this new model are established by using a Lyapunov–Krasovskii approach. Numerical simulations are provided to illustrate the usefulness of the theoretical results. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical modelling of radiative heat transfer in an internal indirect reforming-type SOFC

The present paper describes numerical modelling of the radiative heat transfer process in the module chamber of an internal indirect reforming-type SOFC. The ability to do internal reforming is one of the characteristics of high-temperature fuel cells, SOFC. As in any high-temperature system, radiative heat transfer is important. In this article, heat transfer between the fuel reformer surface and all other surfaces facing the reformer surfaces is modelled. Governing equations for radiative heat transfer are described using Hottel's zone method. The resulting radiation–conduction conjugate heat transfer problems are numerically solved with a combination of Gauss–Seidel and Newton–Raphson methods. The steam reforming reaction occurring inside the fuel reformer is described using Achenbach model. The obtained results indicate that, for the development of effective indirect internal reforming, the position of the reformer in the module chamber and emissivity of the surfaces of the reformer, cell and other elements in the SOFC module all play a key role.     

水平圆柱与平板下相变材料接触熔化的基本方程

讨论相变材料围绕水平圆柱与平板下各种形式的接触熔化过程，系统分析了压力与摩擦作用下熔化的基本特生和规律，推得不同驱动条件下接触熔化所应满足与遵循的基本方程，给出了求解这些方程的一般步骤，最后，指出有关文献中的错误。     

Microfluidic modeling and simulation of flow in membrane microreactors

We study the development of a mathematical model that describes isothermal microfluidic steady flow in a membrane microreactor, i.e., a silicon microreactor that houses a permeable membrane in one wall. The model employs the Navier-Stokes equation with appropriate boundary conditions for fluid permeation through the membrane and velocity slip at the walls to account for high Knudsen number. The model equations are solved analytically using finite Fourier transforms. The model solution is used to evaluate the effect of fluid permeation through the membrane and the Knudsen number on the velocity profile and pressure drop. For the simplified cases of no permeation and/or no slip, the derived solution is in excellent agreement with published experimental and theoretical results available in the literature. The utility of the model is illustrated by applying the results to a membrane microseparator used to separate hydrogen from the other effluents in a microreformer.