Improved Formulae for the Inductance of Straight Wires

The best analytical formulae for the self-inductance of rectangular coils of circular cross section available in the literature were derived from formulae for the partial inductance of straight wires, which, in turn, are based on the well-known formula for the mutual inductance of parallel current filaments, and on the exact value of the geometric mean distance (GMD) for integrating the mutual inductance formula over the cross section of the wire. But in this way, only one term of the mutual inductance formula is integrated, whereas it contains also other terms. In the formulae found in the literature, these other terms are either completely neglected, or their integral is only coarsely approximated. We prove that these other terms can be accurately integrated by using the arithmetic mean distance (AMD) and the arithmetic mean square distance (AMSD) of the wire cross section. We present general formulae for the partial and mutual inductance of straight wires of any cross section and for any frequency based on the use of the GMD, AMD, and AMSD. Since partial inductance of single wires cannot be measured, the errors of the analytical approximations are computed with the help of exact computations of the six-dimensional integral defining induction. These are obtained by means of a coordinate transformation that reduces the six-dimensional integral to a three-dimensional one, which is then solved numerically. We give examples of an application of our analytical formulae to the calculation of the inductance of short-circuited two-wire lines. The new formulae show a substantial improvement in accuracy for short wires

National identification, endorsement of acculturation ideologies and prejudice: The impact of perceived threat of immigration

This paper examines how the perceived threat of immigration affects the links between national identification, endorsement of assimilation or multiculturalism, and prejudice against immigrants in France. One hundred thirty-five French undergraduates completed a questionnaire measuring these factors. Path analysis showed that higher national identification increased perception of immigrants as a threat, which in turn predicted increased endorsement of assimilation for immigrants. The link between endorsement of assimilation and prejudice was not significant. In contrast, lower national identification decreased perception of immigrants as a threat and, in turn, increased endorsement of multiculturalism and reduced levels of prejudice. An alternative model specifying perception of threat as an outcome of preferences for multiculturalism or assimilation did not fit the data well. Results suggest that perceived threat from immigration is the key factor that guides the preferences of the majority group for acculturation ideologies and, through these preferences, shapes intergroup attitudes

The grey partridge in the UK: population status, research, policy and prospects

La perdiz pardilla en el Reino Unido: estado de la población, investigación, gestión y perspectivas Durante los últimos cincuenta años, los efectivos de la perdiz pardilla (Perdix perdix) han descendido catastróficamente en el Reino Unido. Por el contrario, el Programa de Recuento de la Perdiz de la GWCT (Fundación para la Conservación de la Caza y la Fauna Salvaje) presenta un 81% de aumento desde el año 2000 en los lugares del Reino Unido en que interviene. En este estudio exploramos los antecedentes y las razones de estos resultados tan contradictorios. Las investigaciones de la GWCT han tenido como consecuencias recomendaciones científicamente demostradas para la mejora del medio ambiente de la perdiz en el Reino Unido, desde los requerimientos del hábitat hasta la densidad de depredadores. Dichas investigaciones han influido en la política gubernamental del Reino Unido, que ahora incluye uno de los proyectos de Europa más orientadas hacia la conservación y más flexible en cuanto a hábitat y agricultura, lo que permite a los gestores del territorio recuperar gran parte del hábitat costero de la perdiz pardilla. Actualmente, los proyectos sobre agricultura y medio ambiente no abarcan la selección de los depredadores más comunes, de manera que son principalmente los cotos de caza con guardabosques privados los que han aplicado todas las medidas de gestión. El futuro de la perdiz pardilla en el Reino Unido reside en el equilibrio entre la economía de la producción agrícola, las medidas agro–medioambientales, y la caza.La perdiz pardilla en el Reino Unido: estado de la población, investigación, gestión y perspectivas Durante los últimos cincuenta años, los efectivos de la perdiz pardilla (Perdix perdix) han descendido catastróficamente en el Reino Unido. Por el contrario, el Programa de Recuento de la Perdiz de la GWCT (Fundación para la Conservación de la Caza y la Fauna Salvaje) presenta un 81% de aumento desde el año 2000 en los lugares del Reino Unido en que interviene. En este estudio exploramos los antecedentes y las razones de estos resultados tan contradictorios. Las investigaciones de la GWCT han tenido como consecuencias recomendaciones científicamente demostradas para la mejora del medio ambiente de la perdiz en el Reino Unido, desde los requerimientos del hábitat hasta la densidad de depredadores. Dichas investigaciones han influido en la política gubernamental del Reino Unido, que ahora incluye uno de los proyectos de Europa más orientadas hacia la conservación y más flexible en cuanto a hábitat y agricultura, lo que permite a los gestores del territorio recuperar gran parte del hábitat costero de la perdiz pardilla. Actualmente, los proyectos sobre agricultura y medio ambiente no abarcan la selección de los depredadores más comunes, de manera que son principalmente los cotos de caza con guardabosques privados los que han aplicado todas las medidas de gestión. El futuro de la perdiz pardilla en el Reino Unido reside en el equilibrio entre la economía de la producción agrícola, las medidas agro–medioambientales, y la caza.Numbers of grey partridges (Perdix perdix) have declined catastrophically over the last 50 years in the UK. By contrast, the Partridge Count Scheme of the Game & Wildlife Conservation Trust (GWCT) shows an 81% increase on participating UK sites since 2000. We explore the background and reasons for this conflicting picture. GWCT research has led to scientifically proven recommendations for improving the UK partridge environment, ranging from habitat requirements to predator density. The research has influenced UK government policy, which now includes one of the most conservation–oriented and flexible agri–environment schemes in Europe, allowing land managers to recover much of the cost of grey partridge habitat creation. Culling common predators is not covered by agri–environment schemes, so it is primarily shooting estates with private gamekeepers that have implemented the full package of management measures. The future fate of the grey partridge in the UK rests on the balance between the economics of agricultural production, agri–environment measures and shooting

Improved Formulae for the Inductance of Straight Wires

The best analytical formulae for the self-inductance of rectangular coils of circular cross section available in the literature were derived from formulae for the partial inductance of straight wires, which, in turn, are based on the well-known formula for the mutual inductance of parallel current filaments, and on the exact value of the geometric mean distance (GMD) for integrating the mutual inductance formula over the cross section of the wire. But in this way, only one term of the mutual inductance formula is integrated, whereas it contains also other terms. In the formulae found in the literature, these other terms are either completely neglected, or their integral is only coarsely approximated. We prove that these other terms can be accurately integrated by using the arithmetic mean distance (AMD) and the arithmetic mean square distance (AMSD) of the wire cross section. We present general formulae for the partial and mutual inductance of straight wires of any cross section and for any frequency based on the use of the GMD, AMD, and AMSD. Since partial inductance of single wires cannot be measured, the errors of the analytical approximations are computed with the help of exact computations of the six-dimensional integral defining induction. These are obtained by means of a coordinate transformation that reduces the six-dimensional integral to a three-dimensional one, which is then solved numerically. We give examples of an application of our analytical formulae to the calculation of the inductance of short-circuited two-wire lines. The new formulae show a substantial improvement in accuracy for short wires

The GMD Method for Inductance Calculation Applied to Conductors with Skin Effect

The GMD method (geometric mean distance) to calculate inductance offers undoubted advantages over other methods. But so far it seemed to be limited to the case where the current is uniformly distributed over the cross section of the conductor, i.e. to DC (direct current). In this paper, the definition of the GMD is extended to include cases of nonuniform distribution observed at higher frequencies as the result of skin effect. An exact relation between the GMD and the internal inductance per unit length for infinitely long conductors of circularly symmetric cross section is derived. It enables much simpler derivations of Maxwell’s analytical expressions for the GMD of circular and annular disks than were known before. Its salient application, however, is the derivation of exact expressions for the GMD of infinitely long round wires and tubular conductors with skin effect. These expressions are then used to verify the consistency of the extended definition of the GMD. Further, approximate formulae for the GMD of round wires with skin effect based on elementary functions are discussed. Total inductances calculated with the help of the derived formulae for the GMD with and without skin effect are compared to measurement results from the literature. For conductors of square cross section, an analytical approximation for the GMD with skin effect based on elementary functions is presented. It is shown that it allows to calculate the total inductance of such conductors for frequencies from DC up to 25 GHz to a precision of better than 1 %

Drift waves and magnetic field oscillations in cylindrical plasmas

A general investigation of linear drift-wave phenomena in cylindrically bounded plasmas, immersed in a magnetic field without shear and curvature, is performed within the two-fluid hydrodynamical approximation, taking into account electron-temperature oscillations and inhomogeneous radial distributions of the undisturbed electron density and temperature. For plasmas in which the electron temperature strongly exceeds the ion temperature the problem is reduced to an ordinary complex second-order differential equation describing the radial distribution of the oscillating electric potential. It is shown that the presence of electron-temperature oscillations (which must always exist in order to satisfy electron-energy conservation) and of radial gradients in the undisturbed electron temperature (which must always exist owing to cooling of the plasma at the boundary) leads to an important modification of the theory of drift waves in cylindrical plasmas (with regard to their stability and the radial distribution of the oscillating quantities) compared with previous papers in which these phenomena were disregarded. A numerical program for solving the corresponding complex-eigenvalue problem has been derived that allows a realistic calculation of all the quantities pertaining to drift-wave phenomena. It has been applied, in particular, to the calculation of the radial distribution of the oscillating coherent magnetic fields accompanying the coherent drift waves. The numerical results prove to be in good agreement with experiments performed with a helium plasm

The GMD Method for Inductance Calculation Applied to Conductors with Skin Effect

The GMD method (geometric mean distance) to calculate inductance offers undoubted advantages over other methods. But so far it seemed to be limited to the case where the current is uniformly distributed over the cross section of the conductor, i.e. to DC (direct current). In this paper, the definition of the GMD is extended to include cases of nonuniform distribution observed at higher frequencies as the result of skin effect. An exact relation between the GMD and the internal inductance per unit length for infinitely long conductors of circularly symmetric cross section is derived. It enables much simpler derivations of Maxwell’s analytical expressions for the GMD of circular and annular disks than were known before. Its salient application, however, is the derivation of exact expressions for the GMD of infinitely long round wires and tubular conductors with skin effect. These expressions are then used to verify the consistency of the extended definition of the GMD. Further, approximate formulae for the GMD of round wires with skin effect based on elementary functions are discussed. Total inductances calculated with the help of the derived formulae for the GMD with and without skin effect are compared to measurement results from the literature. For conductors of square cross section, an analytical approximation for the GMD with skin effect based on elementary functions is presented. It is shown that it allows to calculate the total inductance of such conductors for frequencies from DC up to 25 GHz to a precision of better than 1 %

Hexa-peri-hexabenzocoronenes – Controlling their Self-Assembly by Engineering the Lateral Substituents

Polycondensed aromatic hydrocarbons (PAH), which can be regarded as two-dimensional subsections of graphite, have begun to attract increasing interest in supramolecular chemistry. Substituted hexa-peri-hexabenzocoronenes (HBC), an outstanding class of PAH, are well-known to self-organize in solution into highly ordered columnar molecular stacks. The formed structures are very sensitive to any variation of the medium as well as the lateral substituents of the HBC derivatives. Various perfluoroalkylated HBC compounds have been prepared and investigated by powder XRD, DSC, fluorescence and cryo-SEM in order to gain certain control over the self-assembling behavior of this class of compounds

Synthesis of perfluoroalkylated bulky triarylamines

The synthesis of two new triarylamine compounds bearing perfluoroalkylated side chains is described. Good thermal stabilities combined with a blue emission make these compounds promising candidates for materials applications

Restoration of a wild grey partridge shoot: a major development in the Sussex study, UK

Restauración de la caza de la perdiz pardilla: un importante progreso en el estudio de Sussex, Reino Unido Desde hace una generación se conoce la base científica de la gestión de la perdiz pardilla. Ésta incluye el control de los depredadores de nidos, la provisión de material para la nidificación, tener suficientes insectos para alimentar a las crías, y un control adecuado de la caza. Más recientemente también se ha considerado importante proveer alimento para las aves adultas y y hábitats para protegerlas de las aves rapaces. El abastecimiento del hábitat puede ser caro, pero en el Reino Unido los costos pueden recuperarse parcialmente mediante proyectos agro-medioambientales. El propietario de la tierra aún tiene que pagar por los servicios de los guardabosques. Desde 2003/2004, una parte del área de estudio de Sussex de la GWCT ha puesto en práctica estos principios de gestión ambiental, con la intención de restaurar la caza de la perdiz pardilla en esta zona del sur de Inglaterra. Los resultados han sido impresionantes, con un aumento de la densidad de parejas en primavera de 0,3/100 ha en 2003 hasta casi 20 parejas/100 ha en el 2010, en un área total de más de 10 km2. Durante los últimos dos años se ha practicado la caza de la perdiz pardilla y los propietarios de las tierras y sus equipos se han ganado el reconocimiento nacional por su labor conservacionista.Restauración de la caza de la perdiz pardilla: un importante progreso en el estudio de Sussex, Reino Unido Desde hace una generación se conoce la base científica de la gestión de la perdiz pardilla. Ésta incluye el control de los depredadores de nidos, la provisión de material para la nidificación, tener suficientes insectos para alimentar a las crías, y un control adecuado de la caza. Más recientemente también se ha considerado importante proveer alimento para las aves adultas y y hábitats para protegerlas de las aves rapaces. El abastecimiento del hábitat puede ser caro, pero en el Reino Unido los costos pueden recuperarse parcialmente mediante proyectos agro-medioambientales. El propietario de la tierra aún tiene que pagar por los servicios de los guardabosques. Desde 2003/2004, una parte del área de estudio de Sussex de la GWCT ha puesto en práctica estos principios de gestión ambiental, con la intención de restaurar la caza de la perdiz pardilla en esta zona del sur de Inglaterra. Los resultados han sido impresionantes, con un aumento de la densidad de parejas en primavera de 0,3/100 ha en 2003 hasta casi 20 parejas/100 ha en el 2010, en un área total de más de 10 km2. Durante los últimos dos años se ha practicado la caza de la perdiz pardilla y los propietarios de las tierras y sus equipos se han ganado el reconocimiento nacional por su labor conservacionista.The scientific basis of wild grey partridge management has been known for a generation. This includes controlling nest predators, providing nesting cover, having sufficient insect food for chicks and appropriate rates of shooting. More recently, measures such as providing food for adult birds and habitats for protection from birds of prey have also been considered important. Habitat provision can be expensive, but in the UK costs can be partially recovered through governmental agri–environment schemes. The landowner still needs to pay for the essential gamekeeper. Since 2003/04, one part of the Game & Wildlife Conservation Trust’s (GWCT) Sussex Study area has put these principles of environmental management into practice with the aim of restoring a wild grey partridge shoot to this part of Southern England. Results have been impressive, with the spring pair density increasing from 0.3 pairs/100 ha in 2003 to nearly 20 pairs/100 ha in 2010 on an area of just over 10 km2. Over the past two years a wild grey partridge shoot has taken place, and the landowner and his team have gained national recognition for their conservation work