The representation by an equivalent winding of the eddy currents in magnetic circuits

Summary The concept of replacing the eddy current paths in a magnetic circuit by an equivalent winding is given a general theoretical treatment. It is shown that the equivalent winding is strictly valid if the eddy current pattern remains constant in time. Expressions for the circuit parameters are presented, which will generally yield a good approximation on closing a D.C. excited magnetic circuit. Some results from a numerical study of the current and magnetic flux on closing a telephone relay are given.

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Übersicht Die Möglichkeit einer Darstellung der Wirbelstromvorgänge in einem magnetischen Kreis mit Hilfe einer Ersatzwindung wird theoretisch allgemein untersucht. Es wird gezeigt, daß eine streng gültige Ersatzwindung möglich ist falls das geometrische Bild der Wirbelstromverteilung zeitlich konstant bleibt. Für die Kreiskonstanten werden Ausdrücke angegeben, die für den Fall des Einschaltens eines magnetischen Gleichstromkreises im Allgemeinen eine gute Annäherung geben. Die Ergebnisse einer Untersuchung des magnetischen Elusses und des Primärstromes bei Einschaltung eines Telephonrelais werden angedeutet.

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Presented at the First International Conference on Electromagnetic Relays, held at Tohoku University, Sendai, Japan, Oct. 8–11, 1963.     

Evaluation of the Energy Efficiencies for a Gas Heated Industrial Infrared Paper Dryer

The radiation and total efficiencies, the amount of gas radiation from vapour and carbon dioxide and contribution from convective heat transfer for different operating conditions have been measured and modelled in an industrial gas heated IR dryer. Instrumentation to facilitate the measurement of the spectral distribution of the radiation heat fluxes in industrial infrared equipment has been developed. The radiation efficiency ranges between 35 to 39 % and the total energy efficiency has been calculated as 28-31 %. This is in good agreement with previous measurements. The emitter radiosity was measured as 101 kW/m2 which is in reasonable agreement with the calculated value of 115 kW/m2. The total efficiency can be much improved if the excess air factor is reduced or the preheating temperature of the combustion air is increased. More work could be directed towards improvements of the gas flow behaviour between emitter and web, contributing to increased convective heat transfer to the web.     

Cohesion energy densities and solubility parameters for the n-alkanes expressed as a new homomorph equation

A new correlation formula for the calculation of the cohesive energy density for n-alkanes and the corresponding homomorphs for polar solvents has been developed. Constants of the Antoine equation and literature values of heat of vaporisation at the boiling point and at 25°C were used. For the C₂-C₁₆ n-alkanes the new correlation equation describes the cohesion energy density as a function of molal volume and reduced temperature within the accuracy of experimental data. In the range of reduced temperatures 0.4 < T_r < 0.7 and molal volumes 50 < V <300 cm³ the maximum deviation for this fit is less than ± 0.05 J^1/2 cm^?3/2. In the region of T_r and V for polar homomorphs to the n-alkanes at 25°C the deviations are typically less than half this value.     

Starch Biosynthesis. I. The Size Distributions of Amylose and Amylopectin and Their Relationships to the Biosynthesis of Starch

Equations for the size distributions of both linear and branched polymers were applied to debranched amylopectin, linear amylose, and branched amylose polymers. The experimental size distribution of linear amylose corresponds to the broad size distribution of an A–B condensation polymer, whereas that of debranched amylopectin linear chains corresponds to the much narrower Poisson size distribution. These dramatic differences illustrate that different types of enzymes synthesize the linear chains of amylose as compared to those of amylopectin. These results support the previously proposed mechanism. The polymodal behavior of debranched amylopectin is due to the existance of individual Poisson-type polymers created by tier structures in a statistically formed precursor glycogen. Equations were developed which enable the calculation of the percentages of these individual Poisson polymers. When applied to the differences between shx and Bomi barley amylopectins, it is concluded that both studies agree that two different short, inner tier, A-chains exist, where the longer chain is located in the more external third tier in the amylopectins. In amylose, three different polymers exist: A linear amylose A–B type condensation polymer, a branched amylose which behaves as a statistical A–R–B₂ type polymer, and an intermediate, non-statistically branched amylose polymer.     

Starch Biosynthesis. 3: The Glycogen Precursor Mechanism Using Phosphorylase in the Production of the Precursor Glycogen

Based on the previously proposed glycogen precursor mechanism (S. R. Erlander, Enzymologia 19 (1958), 273–283), it is now proposed that phosphorylase is the primary enzyme for the production of linear chains in the precursor glycogen. The mechanism involves the translocation of ADPglucose (ADPGlu), and is suppressed by ATP because of a reverse of the ADPglucose pyrophosphorylase (ADPG pp) mechanism. Soluble starch synthase II (SSS II) is a back-up system, involves the translocation of glucose-6-phosphate (Glu-6-P), and is activated, not suppressed, by ATP, and is used if phosphorylase or the ADPGlu translocator is destroyed. Each system is independent and produces products which suppress the other. Hence, only one system works at a time. Both mechanisms produce a glycogen precursor and both are dependent upon ADPGlu pp. The initial higher radioactivity of amylose and the constant yield of amylose can be explained by a three or four day biosynthesis of this glycogen, followed by the removal of the glycogen's exterior branches by debranching enzymes to produce amylose and amylopectin. These removed branches are first degraded (using SSS I and II) to ADPGlu, which is the only source of ADPGlu for amylose synthesis. The retention of the polymodal behavior of debranched amylopectin in going from Bomi to shx barley amylopectins is most likely due to a change from phosphorylase to SSS II since both debranched amylopectins produce Poisson distributions.     

Industry evaluation of the Requirements Abstraction Model

Software requirements are often formulated on different levels and hence they are difficult to compare to each other. To address this issue, a model that allows for placing requirements on different levels has been developed. The model supports both abstraction and refinement of requirements, and hence requirements can both be compared with each other and to product strategies. Comparison between requirements will allow for prioritization of requirements, which in many cases is impossible if the requirements are described on different abstraction levels. Comparison to product strategies will enable early and systematic acceptance or dismissal of requirements, minimizing the risk for overloading. This paper presents an industrial evaluation of the model. It has been evaluated in two different companies, and the experiences and findings are presented. It is concluded that the requirements abstraction model provides helpful improvements to the industrial requirements engineering process.

Control volume based modelling in one space dimension of oscillating, compressible flow in reciprocating machines

We present an approach for modelling unsteady, primarily one-dimensional, compressible flow. The conservation laws for mass, energy, and momentum are applied to a staggered mesh of control volumes and loss mechanisms are included directly as extra terms. Heat transfer, flow friction, and multidimensional effects are calculated using empirical correlations. Transformations of the conservation equations into new variables, artificial dissipation for dissipating acoustic phenomena, and an asymmetric interpolation method for minimising numerical diffusion and non physical temperature oscillations are presented. The capabilities of the approach are illustrated with an example solution and an experimental validation of a Stirling engine model.     

Interfacial Tension; a Stabilizing Factor for Janus Emulsions of Silicone Bixa Orellana Oils

The destabilization process was investigated for a Janus emulsion of silicone and Bixa Orellana oils stabilized by polyoxyethylene sorbitan monooleate (Tw 80) and carboxymethyl cellulose. The emulsion stabilized with Tw 80 showed significant and fast creaming, a process that was prevented by the addition of the polymer. During the extensive coalescence of the emulsions stabilized by Tw 80, the Janus topology was retained for months of storage until, finally, separation of the oils occurred. This result strongly indicates an unexpected stabilizing action of the i nterfacial free energy. This conclusion was supported by a calculation for a realistic model system of the interfacial energy difference between two cases of coalescence. In the first case, the two coalescing Janus drops united into a larger Janus drop, while in the second case two drops formed, each with only one oil. The first case gave a spontaneous reaction (reduced interfacial energy), while the second one meant an increase of energy, i.e. it cannot happen without adding energy. The authors are aware that this stabilization is a new phenomenon in emulsion science with potential ramifications in future emulsion technology. However, it is essential to realize that the stabilization is of temporary occurrence in the destabilization process, and the free energy to give a final emulsion state with separated oils is overwhelmingly dominant. In short, Janus emulsions will, in the end, separate into layers of the liquids, like all emulsions.     

I. CONDITIONS OF MASHING AND CARBOHYDRATE COMPOSITION OF THE WORT

Experimental mashings of ungerminated barley and 5–10% of malt with addition of the debranching enzyme pullulanase have been carried out. Worts with high attenuation are obtained in good yield. Of the fermentable sugars, there is less glucose, and more maltose and maltotriose than normally observed. The dextrin pattern is different from, but not necessarily inferior to, that traditionally seen. The worts resulting from the action of pullulanase are deprived of the dextrins with 8–14 glucose units, whereas the amounts of dextrins with 4–6 glucose units are close to those normally observed. The pullulanase preparations used are accompanied by proteolytic activity. It is suggested that debranching enzymes such as pullulanase offer an alternative choice of carbohydrases to be used in brewing from unmalted cereals.