Characteristics of multistage column crystallizer for gas-liquid reactive crystallization of calcium carbonate

Crystallization of calcium carbonate using a gas (CO₂)-liquid (Ca(OH)₂) reaction was conducted using a three-stage column crystallizer. In this study, the staging effect of the multistage column crystallizer and the effect of the operating parameters on the particle size distribution were experimentally and theoretically investigated. From an economic viewpoint, the multistage column crystallizer has been developed to replace a cascade of MSMPR crystallizers, which requires a large installation area and high operating cost because some crystallizers are connected in a series. In the multistage column crystallizer, a narrower particle size distribution was obtained compared to that obtained in the standard column crystallizer. The theoretical approach to predict the particle size distribution is based on the population balance equation which takes account of the back flow into the crystallizer. The calculation results of particle size distribution fairly coincide with the experimental results, which indicates the particle size distribution in the multistage column crystallizer can be roughly predicted by this theoretical model.     

运用流体包体分析川西二叠系裂缝形成和油气运移时期

本文利用川西二叠系阳新统裂缝充填物中流体包裹体的均一温度资料,经压力校正后,求得了真实的成矿温度。进而用以重塑了阳新统不同类型裂缝的形成时期、张启时间及其与油气运移的关系。为寻找油气富集区块提供了重要的资料。     

RESIDENCE TIMES OF TWO- AND THREE-COMPONENT MIXTURES IN CASCADING ROTARY DRYERS

The residence times of the components of two- and three-component mixtures of fine (195 µm), coarse (1315 µm) and very coarse (5040 µm) sands were measured in a pilot-scale cascading rotary dryer. The effects of mixture composition and air velocity (0-5.4 m s^-1) were determined. With no air flowing through the drum, the residence times of the individual components were almost the same as that of the overall mixture. Increasing the gas velocity caused a large decrease in residence time. In contrast, particle size had very little effect. The spread of residence times increased with air velocity, peaking between 2 and 4 m s^-1; composition had very little effect on the spread. The residence time of the overall mixture could be calculated using the particle transport model of Matchett and Baker if both the modified drag coefficient Φ_d and the particle Reynolds number Re_p were based on the superficial air velocity and the mass-average particle diameter.     

Migration of Oxides in a Composite Coating and Its Effect on Inhibiting Coating Degradation

Based on the fact that the dispersed rare earth oxide particles in an electrolytic co-depositedNi-R_2O_3 layer migrated and accumulated at the substrate/coating interface immediately afteraluminizing,the mechanism of migration of the oxides and its effect on the behaviour of degradationof the coatings oxidized at 1100℃ were studied in this paper.The Ni-R_2O_3 layers were treated invacuum at 900℃ and aluminized at 1100℃ separately.The results indicated that the migration andaccumulation of R_2O_3 particles were favorable to the gathering of R_2O_3 at higher temperatures,andthe small size oxides were easier to migrate and gather.The drawing effect of grain boundary wasused to explain this behaviour.The microstructures of the coatings oxidized at 1100℃ were ob-served.It was found that the coating degradations were related to the amount and distribution of theaccumulated R_2O_3 at the alloy/coating interface.Three typical kinds of the accumulated layerswere identified.The continuous oxide layers acted as diffusion barrier which could inhibit the coat-ing degradation effectively.     

A knowledge-based framework for intelligent-data migration

Abstract: The Object-Inferencing Framework (OIF) is a knowledge-based system developed for intelligent-data migration. The framework provides a mechanism to integrate relational data which represents a source model; a project-specific rulebase which specifies plausible migration scenarios; and a deduction system to facilitate the migration of source data to a new, complex target model. Typically, the target model includes constituents that possess both graphic and tabular components. Although the framework is experimental, industrial applications built upon OIF have been successfully deployed in scenarios in which the source data contained implicit information in that semantic relationships and structure conveyed by the data had to be inferred by a domain expert. This framework provides a substrate for migration from any unstructured or semi-structured data representation to a complex, semantically rich target data model. Examples of the migration of CAD data, which represents an electrical-distribution system, to a client-server based Automated Mapping/Facilities Management (AM/FM) platform are presented to convey the salient features of the design and utility of the OIF. Even though the examples are taken from a specific domain, the approach has potential applications in a myriad of domains, including business enterprises in which the migration of data created and managed by legacy systems to object-oriented and clientserver environments is an area of intense research and development.     

Planar millimetre wave structures

Periodic structures in the millimetre wave range, with high precision requirements such as those needed for travelling wave tubes or for particle acceleration, must be planar structures for fabricational reasons. This paper treats single and double periodic devices semi-analytically with the mode matching technique. The method is explained for a side-coupled structure where Floquets theorem was generalized for point-symmetric arrangements. With only slight modifications, the results can be adjusted to the case of on-axis coupled double-periodic structures. A special case is the standard single-periodic structure. Results show dispersion diagrams, field plots and beam coupling impedances.An erratum to this article can be found at     

Planar millimetre wave structures

Periodic structures in the millimetre wave range, with high precision requirements such as those needed for travelling wave tubes or for particle acceleration, must be planar structures for fabricational reasons. This paper treats single and double periodic devices semi-analytically with the mode matching technique. The method is explained for a side-coupled structure where Floquets theorem was generalized for point-symmetric arrangements. With only slight modifications, the results can be adjusted to the case of on-axis coupled double-periodic structures. A special case is the standard single-periodic structure. Results show dispersion diagrams, field plots and beam coupling impedances.The online version of the original article can be found at Electr Eng (2004) 86:147–155 The equations throughout the printed contribution in the issue vol. 86, no. 3, pp. 147-155 were reproduced with many errors. The version published online 29 October 2003 is free of errors. For this reason, the complete contribution is being published as an Erratum.     

Nanoparticle engineering processes for enhancing the dissolution rates of poorly water soluble drugs

Poor water solubility is an industry wide issue, especially for pharmaceutical scientists in drug discovery and drug development. In recent years, nanoparticle engineering processes have become promising approaches for the enhancement of dissolution rates of poorly water soluble drugs. Nanoparticle engineering enables manufacturing of poorly water soluble drugs into nanoparticles alone, or incorporation with a combination of pharmaceutical excipients. The use of these processes has dramatically improved in vitro dissolution rates and in vivo bioavailabilities of many poorly water soluble drugs. This review highlights several commercially or potentially commercially available nanoparticle engineering processes recently reported in the literature for increasing the dissolution properties of poorly water soluble drugs.     

Process of extrusion in the unit of special design

Extrusion of paste materials is a means of processing powder materials to a granulated form. A powder material is mixed with a liquid and transformed to the form of paste. The paste has to have the appropriate flow properties to be able to be extruded. This is very important especially in the area of reduction between the barrel and die. There is the place where the paste has to deform itself and to flow into the holes of die that have a smaller cross section than is in the barrel. It is the zone where the rheology properties of paste and its speed have the biggest influence on the extrusion pressure. It can even happen that the paste can be dewatered under the pressure gradient in this place. If the rotor with blades is situated in this zone it has a positive influence on the process of extrusion. This element has an influence on the rate of shear strain and decreasing of the apparent viscosity with a following drop in the extrusion pressure. This paper describes research of the process of extrusion in equipment with separated drives of the screw and a rotor that is placed in the input zone in the hole of matrix. First influence of the operating speeds of screw and rotor on extrusion pressure is studied here, then it is compared with the torque that is needed for the drive of the rotor. According to the results it is evident that the extrusion pressure increases with the accrual of the speed of flowing paste and decreases with the increase of the rotors operating speed. The influence of flowing paste on the torque is complicated. There is an interval where the torque goes up and then an interval in which the torque decreases. The results of experiments confirmed that the rotor has a positive influence on the process of extrusion.We would like to thank the Grant Agency of the Slovak Republic for supporting our research work performed in the frame of Grant Project No.1/8092/01.     

On probability distributions of contact force magnitudes in loaded dense granular media

This paper discusses possible models for probability distributions of contact force magnitudes in loaded granular media. Many authors have studied such distributions, based on experiments with real particles as well as simulations in 2D and 3D. This has led to various and partly contradicting suggestions for the form of those distributions, which are described in the present paper. Its new theoretical investigations start from the empirically justified assumption that the components of contact forces follow exponential distributions with a certain dependence structure. This leads to distributions of force magnitudes similar to Gamma distributions with shape parameters depending on space dimension, which is in good agreement to results from experiments and numerical simulations. Also the analytical and statistical difficulties of the problem of determination of distributions of force magnitudes are discussed.In a discussion of Stefan Luding and D.S. the idea arose to consider dependent force components. Niels Kruyt supported our work by sending his papers and by patient discussions via e-mail and a careful reading of an earlier version of this paper.We had a very useful discussion with Farhang Radjai about the problem P(0)=0 and experiments with real disks. Finally, we are grateful to Tomaso Aste for leading our attention to infinitely divisible distributions.