Surface charge and function of cellulose battery separators

The results of zeta-potential determination using the electro-osmotic method in dilute (10^–3 mol dm^–3) solutions of NH₄Cl and ZnCl₂ and diffusion parameters measured in 20% NH₄Cl and 30% ZnCl₂ solutions are presented. In both cases cellulosic membrane separators from different manufacturers, already in practical usage in Leclanché cells, were examined. From the measured data, diffusion potentials were calculated and compared with experimental values. Transport numbers calculated from diffusion potentials are compared to values in free solution (i.e. without a membrane). The relevance of these parameters to the role of cellulosic separators in Leclanché-type cells is briefly discussed.     

Straining mechanisms of hard elastic fibers obtained by broad line nuclear magnetic resonance measurements

Summary Broad line NMR measurements give information on energy-elastic processes during straining of hard elastic fibers, as there are the shearing of the crystalline regions and transformation of parts of the crystalline into amorphous. The amount of these parts is proportional to straining and recrystallizes again, dependent on temperature and time. Sheared crystalline regions relax within few days, even at very low temperature (–175°C, –120°C). In the case of isotactic polypropylene the mobility of various groups depends not directly on the temperature but on the nearest neighbour distances. Thus methyl groups in the sheared crystalline regions even at –175°C undergo hindered rotation.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, July 20–23, 1981     

The optimal stochastic control of an epitaxial process unit

The problem of computerized batch control of the silicon epitaxial layer deposition technological process has been solved using optimal stochastic control methods. A control algorithm is presented the main emphasis being given to the forecasting and compensating of disturbing processes which act on a process unit under real operation conditions. The method of multidimensional time series, stochastic model form identification for the process noise is developed based on multidimensional time series, correlation analysis results. The “maximum likelihood” identification method is applied in order to obtain efficient estimates of the model parameters. The identification of the model form and model parameters is carried out on the basis of a rather extensive set of data obtained from operation records of a high capacity epitaxial unit. The adequacy of the identified models is checked by means of a correlation analysis of the model residuals. It is demonstrated that results comparable to those with an intuitive process control by an experienced operator, can be achieved when using the algorithm presented in the present work for process computer control. This algorithm thus represents a reliable and rational basis for process control computer software development.     

TREE STRUCTURES OF LINEAR THRESHOLD UNITS FOR THE CLASSIFICATION OF NUMERIC EXAMPLES

A decision tree-based system for learning from numeric data is described. Results from linear algebra (pseudoinverse matrices) help the system to generate decision trees where the nodes are represented by linear threshold units minimizing the mean square error. The system's capability to provide good classifications with small decision trees is demonstrated on artificial and benchmark data.     

A rough set approach to reasoning under uncertainty

Abstract

Reasoning with uncertain information is a problem of key importance when dealing with information about the real world. Obtaining the precise numbers required by many uncertainty handling formalisms can be a problem. The theory of rough sets makes it possible to handle uncertainty without the need for precise numbers, and so has some advantages in such situations. This paper presents an introduction to various forms of reasoning under uncertainty that are based on rough sets. In particular, a number of sets of numerical and symbolic truth values which may be used to augment propositional logic are developed, and a semantics for these values is provided based upon the notion of possible worlds. Methods of combining the truth values are developed so that they may be propagated when augmented logic formulae are combined, and their use is demonstrated in theorem proving.     

Advanced LMI based analysis and design for Acrobot walking

This article aims to further improve previously developed design for Acrobot walking based on partial exact feedback linearisation of order 3. Namely, such an exact system transformation leads to an almost linear system where error dynamics along trajectory to be tracked is a 4-dimensional linear time-varying system having three time-varying entries only, the remaining entries being either zero or one. In such a way, exponentially stable tracking can be obtained by quadratically stabilising a linear system with polytopic uncertainty. The current improvement is based on applying linear matrix inequalities (LMI) methods to solve this problem numerically. This careful analysis significantly improves previously known approaches. Numerical simulations of Acrobot walking based on the above-mentioned LMI design are demonstrated as well.     

EVALUATION OF MINIMUM FLUIDIZING VELOCITY IN GAS FLUIDIZED BED FROM PRESSURE FLUCTUATIONS*

A new experimental method for the evaluation of minimum fluidizing velocity in gas fluidized beds is proposed based on the pressure fluctuations measurements. The minimum fluidizing velocity is determined solely from the measurements in the fluidized bed regime, unlike the traditional method, where experiments in the fixed bed regime are also necessary. Using the proposed method the on-line evaluation and prediction of the minimum fluidizing velocity is possible which is important for the control of industrial fluidized bed reactors.     

Brachistochronic motion of a nonholonomic rheonomic mechanical system

The brachistochrone problem of the rheonomic mechanical system whose motion is subject to nonholonomic constraints is solved with nonlinear differential equations of motion. Apart from control forces, the system is influenced by the action of other known potential and nonpotential forces as well. The problem of optimal control is solved by applying Pontryagin’s Maximum Principle and the singular optimal control theory. This procedure results in the two-point boundary value problem for the system of ordinary nonlinear differential equations of the first order, with a corresponding number of initial and end conditions. This paper determines the control forces that are realized by imposing on the system a corresponding number of independent ideal holonomic constraints, without the action of active control forces. These constraints must be in accordance with the previously determined brachistochronic motion. The method is illustrated with a single complex example that represents the first known concrete demonstration of brachistochronic motion of the nonholonomic rheonomic mechanical system.     

High‐Pressure Generator of Singlet Oxygen

The generation of gaseous singlet oxygen by gas‐liquid reaction of chlorine with alkaline solution of hydrogen peroxide in spray form was studied experimentally on the originally designed device with a fast separation of reacted liquid from gas. The singlet oxygen yield, residual chlorine, and water vapor content in gas were measured under different experimental conditions of the centrifugal spray singlet oxygen generator (CSSOG) using nitrogen as a dilution gas. A characteristic feature of the CSSOG is a high utilization of the chemicals and production of singlet oxygen at a very high total pressure even near the atmospheric pressure. This generator developed originally for driving a chemical oxygen‐iodine laser (COIL) could be employed also as an efficient singlet oxygen source in material science, chemical synthesis, and others.     

Mechanochemical and Low‐Temperature Synthesis of Nanocrystalline Fluorohydroxyapatite/Fluorapatite

Low‐temperature synthesis of fluorapatite/fluorohydroxyapatite with precursor mixture previously mechanochemically treated is described in this article. Ethylene vinylacetate/versatate copolymer as a surface active substance was mechanically treated to obtain a core‐shell system with strongly controlled grain size. Despite usual behavior of mechanically activated systems, only an amorphous phase formed from precursor ions present in the mixture composed of β‐Ca₂P₂O₇, CaCO₃, CaF₂, and unreacted Ca(OH)₂ was obtained during milling for 5 min to 8 h. The mixture contained depots of labile F^? ions conserved in micelles cages, which are useful for teeth protection from carries. For transformation of these amorphous phases into fluorapatite, an additional low thermal treatment was necessary. The mechanism of the precursor mixture transformation into fluorapatite during milling and thermal treatment was investigated using FTIR spectroscopy and X‐ray diffraction. The morphology and size distribution of the obtained powders was studied using SEM and TEM.