bluuebunny/crossref_metadata_2025_split huggingface dataset:
Definition of power density as a general utilization factor of electrical machines
Authors: Gutt H.‐J. , Grüner A. 
Published: July 2010

AbstractDerived from the objective of developing high‐density electrical machines of new type and proceeding from the Poynting vector, the power density is defined to determine the machines' main dimensions by introducing the so‐called flux coverage as a new universally valid quantity of magnetic stress. Because very often there does not exist a well‐defined rotor volume which the formerly used utilization factor (in Germany called “Esison‐number”) could refer to, e. g. in linear motors, disk rotor motors or machines using high‐power permanent magnet or high‐temperature superconducting magnet excitation, the power density implementing the flux coverage becomes not only useful but even necessary. On the contrary to the above‐mentioned utilization factor C the power density is referred to a power‐transmitting surface, in general within a space defined by the air‐gap area. From a mathematical point of view the flux coverage can be treated like the current coverage but having the additional advantage to be independent of the winding cooling. Therefore it is a more general quantity for the design process also of new unconventional machines.
Correspondence and difference between the FBD and czarnecki current‐decomposition methods for linear loads
Authors: le Roux W. , van Wyk J. D. 
Published: July 2010

AbstractThe currents in a three‐phase, three‐wire system with linear load impedances, i. e. no distortion generation in the load, are decomposed by the FBD‐ and Czarnecki methods to investigate the correspondence between the two methods. The different systems used are systems with balanced loads and systems with unbalanced loads with combinations of additional inductive loads and distorted voltages. The different current components of the methods are compared to each other for balanced and unbalanced conditions. It is concluded that good correspondence can only be established in the case of a balanced three‐phase system.
Evaluation of residual network distortion during compensation according to the “instantaneous power theory”
Authors: le Roux W. , van Wyk J. D. 
Published: July 2010

AbstractA theoretical evaluation is done on a three‐phase three‐wire system to show the unwanted network influence when a dynamic filter is controlled according to the “instantaneous power theory”. The evaluation is also simulated on Mathcad for various network configurations and compared to known experiments. The quantities with unwanted frequencies introduced by the compensation increase with the complexity of the systems. It is concluded that the use of this power theory for control of dynamic filters is less desirable. Two examples of rectifier systems are also given to show that the results with compensation by the “instantaneous power theory” can in some systems be worse than in others, since its effectiveness is load‐type dependent.
On the energy approach to the theory of coupled inductors
Authors: Arturi C. M. 
Published: July 2010

AbstractThe paper presents a revisited energy approach to the theory of a set of n coupled inductors. The hybrid constitutive relations are analyzed. It is shown that the fundamental relation expressing the energy of the system requires a minimum number of coupling terms if a set of hybrid independent variables is adopted. The hybrid independent variables also allow to represent singular systems having zero magnetizing energy or zero leakage field energy, or both, and to give a rigorous definition of the ideal transformer. Exact equivalent networks of both two‐ and three‐winding transformers are presented.
Voltage profile optimization as influenced by power‐system configuration
Authors: Abdel‐Salam M. S. , El‐Sadek M. Z. , Ibrahim A. A. , Ahmed A. 
Published: July 2010

AbstractThis paper extends a linear‐programming optimization‐based method proposed before for reactive‐power scheduling using generator terminal voltages and reactive powers, transformer tap‐settings and switchable reactive power sources as control variables. The system configuration following contingencies is considered ‐for the first time ‐ as an additional control variable in the optimization‐method. It is proposed to use all of the possible modifications of system configuration by opening one or nvo lines simultaneously. For this to be accurately achieved, a technique was proposed for ranking the line outages, which is based on system losses obtained by AC and/or DC load‐flow studies. The ranking agreed satisfactorily with the voltage‐reactive power index used for contingency analysis in system security studies. Voltage stability is checked before and after optimum adjustment of the control variables and proved to be better after optimum adjustment.
Computation of power systems eigenvalues using the modified nodal approach
Authors: Oswald B. R. 
Published: July 2010

AbstractThis paper presents a new method of forming state‐space equations of large power systems which allows to calculate their eigenvalues. The method does not require any topological tools. It is based on the extended modified nodal approach, which was presented at the IPST '97 in Seattle. The extended modified nodal approach generates a set of algebraic and state‐space equations using Kirchhoff's nodal law exclusively. Eliminating the algebraic part of these equations results in the desired state‐space equations in an explicit form.
A new space‐vector transformation for four‐conductor systems
Authors: Ferrero A. , Giuliani L. , Willems J. L. 
Published: July 2010

AbstractLinear transformations are often employed in the study of three‐phase systems, since they allow for simplifying the equations describing the system behaviour. Among them, the Fortescue, Clarke and Park transformations are very widely employed. In particular, the last one leads to the formulation of the Space‐Vector theory, that is currently employed in the fields of AC machine theory, power definitions and active filtering. The greatest limitation in the use of these transformations is that they are restricted to systems with only three conductors. However, four‐conductor systems are often present in the common practice of the electric systems and the application of the Space‐ Vector theory to such systems is not as straightforward as in the case of the three‐conductor systems: a zero‐sequence quantity must be considered separately. This paper proposes a linear transformation that extends the properties of the Space‐ Vector theory to four‐conductor systems, and includes the Park transformation as a special case. The mathematical derivation of this new transformation is reported, and its application is discussed by means of some examples.
Damping circuit design for ferroresonance in floating power systems
Authors: van Craenenbroeck T. , Van Dommelen D. , Janssens N. 
Published: July 2010

AbstractPractical countermeasures to prevent the occurrence of ferroresonance in floating systems are compared. Most attention is paid to the design of practical damping circuits. Existing criteria to determine the necessary ohmic load are evaluated and a new mathematical tool based on harmonic balance is presented. As the damping resistor can cause thermal overload of the voltage transformers, the use of a non‐linear damping circuit is advocated in some cases. Therefore, the proposed calculation method is extended to include the effect of non‐linear damping.
Optimal capacitor placement incorporating voltage stability and system security
Authors: Arini M. El 
Published: July 2010

AbstractThe purpose of this paper is to derive a systematic procedure for reactive power control to decide the optimal location and size of compensation shunt capacitors so as to improve the system voltage profile. The proposed algorithm for locating the compensators is based on the sensitivities of the reactive power flow of system lines with respect to the reactive power injection at system buses where the reactive power of shunt compensation is considered as an important strategy in controlling voltage stability. After identifying the candidate buses, the problem is formulated as linear programming problem of the minimization of the possibility of voltage collapse and improving the system voltage profile by defining fewer equations and constraints, and saving computer storage and time. A test system is selected to verify the effectiveness and to confirm the accuracy of the proposed method. We therefore conclude that the practical application of this technique would enhance the security of a power system by reducing the risk of voltage collapse.
New converter‐fed power source to increase the dynamic performance of the three‐phase electric arc furnace
Authors: Wolf A. , Thamodharan M. 
Published: July 2010

AbstractThe conventional three‐phase electric arc furnaces frequently cause undesired distortions in the power system, which has a low short‐circuit capacity in the form of voltage fluctuations (flicker) at the point of common coupling. This is due to the fluctuating reactive power consumption of the furnace. This paper describes a electronic‐controlled furnace transformer which enables the reactive power consumed by the furnace to be kept constant. This is made possible if the conventional power system of the three‐phase electric arc furnace is supplemented with three‐phase power controllers and a booster transformer. By regulating the (reactive) power input, these disturbances can be reduced to a minimum. This new power source was experimentally tested on a single‐phase model and the results, which are presented, are very satisfactory.
Depression following open‐heart surgery: A path model involving interleukin‐6, spiritual struggle, and hope under preoperative distress
Authors: Ai Amy L. , Pargament Kenneth I. , Appel Hoa B. , Kronfol Ziad 
Published: July 2010

AbstractFaith factors (i.e., factors pertaining to religion/spirituality) have been linked with well‐being and adequate coping. Few studies have investigated negative aspects of religious coping, such as spiritual struggle. Based on the multidisciplinary literature and on previous findings, the study's analysis estimated parallel psychophysiological pathways from preoperative distress to postoperative depression in patients undergoing open heart surgery. Plasma samples for interleukin(IL)‐6 were obtained before surgery. The results showed that a link between spiritual struggle and IL‐6 mediated the indirect effects of preoperative anxiety on postoperative depression. Avoidant coping also mediated the influence of anxiety on postoperative maladjustment. Further, hope played a protective mediating role to moderate the undesirable influences of the spiritual struggle–IL‐6 link and maladaptive coping on postoperative mental health attributes. © 2010 Wiley Periodicals, Inc. J Clin Psychol 66:1–19, 2010.
The chemical denaturation of groundnut protein and fibre formation
Authors: Naismith W. E. F. 
Published: July 2010

AbstractTwo types of denaturing agents, (a) urea, guanidine salts and related compounds and (b) amines, have been investigated with groundnut protein for fibre formation. The considerable rise in the viscosity increment of the protein on denaturation with urea and the hydrochloride and thiocyanate of guanidine, and with bases of dissociation constant higher than 10−4, has been interpreted in terms of increased asymmetry of the protein molecules, and only where such a rise was observed could solutions of the protein with the denaturant be prepared suitable for extrusion into fibre.
The chemistry of some complex zinc and cadmium chrome pigments
Authors: Cole H. G. , le Brocq L. F. 
Published: July 2010

AbstractWith the help of pH curves, conditions have been found for the formation of basic double chromates of general formula R2CrO43MCrO4,M(OH)2,2H2O, where R is Na, K or NH4 and M is Zn or Cd. No NaCd compound was encountered, and the NH,Zn compound was of a different type. The decomposition of these compounds by alkali and by copious leaching with hot and cold water (KZn and KCd only) into basic zinc and cadmium compounds has been studied. Cadmium chromate and the monoxychromates of zinc and cadmium have been prepared. The identity of each compound has been characterized by equation of formation, composition, X‐ray diffraction pattern and solubility. Many of these compounds are of commercial importance as paint pigments. The NaZn, KZn, KCd and NH,Cd compounds have been prepared.
A systematic assessment of dissolved oxygen supply in a 20‐litre culture vessel
Authors: Elsworth R. , Williams V. , Harris‐Smith R. 
Published: July 2010

AbstractThe factors influencing aeration are discussed and, using the sulphite oxidation method of measurement, the influence of impeller diameter and speed, air rate, and air pressure on the aeration efficiency of a 20‐litre culture vessel has been determined and the power consumed by the impeller measured. Conditions are given for obtaining sulphite oxidation rates of 200–250 millimoles of O2 per litre of medium per hour which can be increased to 500–600 millimoles by raising the operating gauge pressure from zero to 1·36 atm.
Polymers from oxacyclobutanes. I. Synthesis and general properties
Authors: Farthing A. C. 
Published: July 2010

AbstractA wide range of substituted oxacyclobutanes have been polymerized to give novel products, of which the polymer from 3: 3‐bis(chloromethyl)oxacyclobutane was selected for further study. Monomer syntheses, polymerization kinetics and thermodynamics, and structure—property relationships are briefly reviewed.
On the anodic polarization behaviour of aluminium
Authors: Anderson P. J. , Hocking M. E. 
Published: July 2010

AbstractThe behaviour of aluminium during anodic polarization in electrolytes containing anodic inhibitors and chloride ion has been examined. The existence of a critical potential of film breakdown, above which pitting corrosion occurs, has been established. The dependence of this potential on electrolyte composition shows that the anodic reactions are largely determined by competitive adsorption of anions at the film‐solution interface. Possible mechanisms by which anion adsorption may determine the anodic reactions are discussed.
Oxygen transfer in laboratory fermentersxs
Authors: Solomons G. L. 
Published: July 2010

AbstractBased on the oxygen‐transfer rate as measured by the sulphite oxidation method, and using fermenters of fixed design, a series of equations was derived which enables the required power, Reynolds number and stirrer speed to be calculated for a chosen oxygen‐transfer rate. The over‐all controlling process of oxygen transfer was shown to be a function of degree of turbulence/power per unit volume.
Development of a large‐scale distillation process for purifying crude sulphur dichloride. I. Laboratory scale investigations
Authors: Rosser R. J. , Whitt F. R. 
Published: July 2010

AbstractThe basic principles underlying a satisfactory laboratory‐scale distillation procedure, operating at atmospheric pressure, to separate pure sulphur dichloride from a mixture with other sulphur and chlorine compounds, are recorded. The novel use of anti‐catalytic additives, such as phosphorus chlorides, to suppress decomposition during distillation at atmospheric pressures and on storage, is described.
The corrosion of aluminium
Authors: Lorking K. F. , Mayne J. E. O. 
Published: July 2010

AbstractThe corrosion of aluminium at room temperature has been investigated in nine decinormal solutions over the pH range 2.0–12.0. Corrosion was dependent more on the nature of the anion than on the pH of the solution.The solubilities of hydrated and anhydrous aluminium oxide were examined and it was concluded that, except in the presence of chloride ions, corrosion was associated with the initial rate of solution of the anhydrous oxide.Potential and anodic polarisation measurements indicated that whereas the normal anodic reaction is the formation of anhydrous oxide, in the presence of chloride, bromide and iodide ions soluble aluminium salts are formed.It is suggested that when aluminium, carrying its air‐formed film, is immersed in a solution in the presence of oxygen, the film breaks down and a small corrosion current commences to flow. In the absence of chlorides, and similar ions, film repair can take place and the behaviour of the aluminium is controlled by the relative rates of film repair and film breakdown. In the presence of chlorides film repair does not occur and once corrosion has been initiated by film breakdown it proceeds apace. If initiation is suppressed, by saturating the solution with aluminium oxide, corrosion is inhibited.
Factors determining the ‘water requirement’ of gypsum plaster
Authors: Ridge M. J. 
Published: July 2010

AbstractAn investigation has been made of the relationship between the ‘water requirement’ of gypsum plaster, the surface area of the plaster determined by gas adsorption and by permeability to air, and the bulk volume. The water requirement will undoubtedly depend upon the factors determining the surface area of the plaster, i.e. the particle size and shape, but the results show that other factors exert strong effects. The water requirement of hemihydrate prepared by still methods is shown to be considerably reduced by grinding in a mortar with a pestle, which increases the surface area. In contrast to its marked effects upon the rate of setting, recalcination does not affect the water requirement. There is a pronounced correlation between the water requirement and bulk volume. It appears that the factors that determine the bulk volume also play a large part in determining the water requirement. These factors involve the condition of the surface of the particles rather than their size and shape.
Raschig synthesis of hydrazine: The stability of chloramine in the reaction solution
Authors: Jeffreys G. V. , Wharton J. T. 
Published: July 2010

AbstractThe effect of temperature, ammonia, ethylenediaminetetra‐acetic acid (EDTA), hydrazine, ammonium chloride and caustic soda on the stability of chloramine has been studied in a small laboratory batch reactor. It has been found that all these substances accelerate the decomposition rate and would reduce the yield of hydrazine in the Raschig synthesis if they were present in excess during the initial stage of the reaction process.
The adsorption of benzene vapour from an air stream, by beds of charcoal: I. The most efficient physical arrangement of the bed
Authors: Jones W. M. 
Published: July 2010

AbstractAir is often cleaned by passing contaminated air through a granular bed of an adsorbent such as charcoal. In such a situation the rate of flow of air is fixed and there is an upper limit to the physical size of the bed and an upper limit to the resistance of the bed to air‐flow through it. The problem considered is the optimum size of granule to be used in the bed and the optimum shape of the granule, leading to the longest life‐time of the bed. An empirical answer to the problem is given for the uptake of benzene by a BCNU steam‐activated charcoal; apparatus, experiments and results used are described. The method of working and the conclusion are applicable to any vapour/solid system.
Reactivity of lime and related oxides. XVI. Sintering of lime
Authors: Glasson D. R. 
Published: July 2010

AbstractCalcium carbonate samples containing known amounts of additives and impurities have been calcined in air at a series of temperatures for different lengths of time. Changes in specific surface and average crystallite size show the effect of the additives and impurities (accessory minerals in limestones and chalks) on the lime sintering.Salt and calcium sulphate each accelerate lime sintering at between 800° and 1100°. The presence of the chloride during the carbonate decomposition affects mainly the subsequent surface activity and sintering behaviour of the lime. Added phosphates have comparatively little influence on lime sintering at 800°, 900° or 1000°. When lime separates from the decomposition of carbonato‐apatites, the phosphate recrystallises to fluor‐apatite and sinters.Ferric oxide progressively increases lime sintering at 800°, 900°, 1000° and 1100°. Like anhydrite, its low Tammann temperature (650°) readily permits ion diffusion into lime cracks and fissures, promoting sintering. Alumina, with a higher Tammann temperature (890°), appreciably enhances lime sintering only above 1100°. The comparatively low Tammann temperature of silica (730°) does not, however, lead to greatly increased lime sintering below 1100°, probably because of formation and separation of calcium silicates with higher Tammann temperatures similar to that of alumina.
Formation of acetylene in electron‐activated cracking of liquid hydrocarbons
Authors: Brooks J. D. , Hesp W. R. , Rigby D. 
Published: July 2010

AbstractBy cracking pure liquid hydrocarbons such as n‐heptane, cyclohexane and benzene by means of an anomalous glow discharge in a small bench‐scale apparatus at reduced pressure (15 torr) and at flow rates of 0.5–4.0 × 10−3gmole/min and power inputs of 100–450 watts, high degrees of total conversion (up to 85% on carbon basis) and acetylene formation (up to 50%) were secured. Optimum yields of acetylene were obtained at low flow rates and medium power inputs. The major competing reaction was found to be the secondary decomposition of acetylene into carbon and hydrogen, which became intensive at high specific power inputs.In spite of the complexity of the reactions involved, the results showed a uniform correlation between acetylene yield and current flow. The extent of the reactions was affected by the presence of diluent gases, which had the effect of varying the concentration and energy content of the electrons in the discharge. With the benzene‐hydrogen system there was also a strong chemical effect. Thermodynamic calculations indicate that the reactions proceed in part through electron‐activation, which is characterised by the specific rate of acetylene formation related to a given number of charge carriers.The possibility of practical applications of the results is examined.
Studies in transesterification V. Molecular sieve absorbents
Authors: Haken J. K. 
Published: July 2010

AbstractAn improved method for preparing methacrylate esters by transesterification makes use of molecular sieves to remove the alcohol of lower boiling point as it is formed. The procedure avoids the use of a large excess of reactant methacrylate or other entraining agent and the protracted collection of methanol or ethanol azeotropes. The reaction temperature and the reaction rate are thereby increased.
Reactivity of lime and related oxides. XIX. Production of strontium oxide
Authors: Glasson D. R. , Sheppard Margaret A. 
Published: July 2010

AbstractStrontium oxide has been prepared by calcining the hydroxide and the carbonate at several temperatures up to 1200°.Strontium hydroxide sinters considerably before decomposing above 500°. There is appreciable carbonation of the oxide products by atmospheric carbon dioxide at temperatures up to 800°.Strontium carbonate decomposes at a reasonable yield at temperatures above 1000°. The oxide products can be activated by milling, but they sinter when subsequently calcined, especially at temperatures between 800° and 1000°. Crystallite and aggregate sizes of the strontium oxide produced from the carbonate at 1000°–1200° are similar to those of lime prepared under corresponding conditions.
Observations on calcium sulphate dihydrate formed in media rich in phosphoric acid. I. Precipitation of calcium sulphate dihydrate
Authors: Adami A. , Ridge M. J. 
Published: July 2010

AbstractA study has been made of the properties of the products of digesting calcium sulphate hemihydrate in media containing finally 29·4% P2O5. Hydration to the dihydrate occurred at temperatures between 35° and 65°. The product was almost phosphate‐free when the reaction was carried out between 52·5° and 57·5°.