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THE use of liquid oxygen as an oxidizer for various fuels in liquid rocket propellent systems is not new. Professor Goddard used liquid oxygen in his rocket experiments and the well known German V‐2 rockets used this material as an oxidizer. However, its effect on non‐metallic materials ordinarily used in rocket systems was not investigated until recent years. This investigation was prompted by phenomena which had been experienced by rocket engine and rocket aircraft manufacturers and by suppliers of the material. It was observed that when some organic materials came in intimate contact with liquid oxygen they became prone to detonation when subjected to certain impact energies. This was undoubtedly due to the formation of unstable organo‐peroxide compounds which when impacted released high levels of energy resulting in an explosion. Specifically, when liquid oxygen was accidently spilled on asphalt and inadvertently stepped on, the asphalt would often explode. Also, leather gaskets immersed in liquid oxygen and subjected to surge impact detonated with disastrous effects.

In the paper the optimization procedure of a direct current motor with a hybrid excitation has been presented. The excitation system consists of a shunt field winding disposed around field pole and permanent magnet, both acting in parallel. The field distribution in motor for various magnet and field pole dimensions has been determined using finite element method. The flux linkage with the armature winding has been computed. Demagnetizing effect of armature current was taken into account. The optimal permanent magnet and the field pole dimensions, ensuring minimum total cost of purchase and work during assumed period of time were calculated. Motor characteristics e.g. rated torque, rated current, speed regulation limit were used as constraints. In worked up algorithm and computer program Carroll internal penalty function method was used. Some basic suggestions tor design of optimal hybrid excited dc motors with parallel permanent magnet and electromagnetic excitation are given.

I‐V characteristics of GaAs n‐i‐n structures are calculated by considering impact ionization of carriers. Impact ionization at reverse‐biased n‐i junction becomes a cause of steep current rise when an acceptor density in the i‐layer is high. It is shown that an optimum acceptor density exists to keep a good isolation. Photoconduction transients of GaAs n‐i‐n structures are also simulated, and are shown to be strongly affected by existence of n‐i junctions.

In the course of development of human communities towards industrially advanced societies of today, there have been changes not only in economic conditions in the majority of fields of human activity but also in the ways of providing for food, which went hand in hand with changes in living conditions. Large‐scale industrial production has brought about major changes in the way of life of the population. The development of industrial agglomerations results in a growing number of city dwellers, most of whom have no chance of producing foodstuffs of their own in kind. The distance between residential and industrial areas has been growing, the number of employed women has risen considerably. These are but a few factors affecting the way of boarding, particularly in households.

This paper aims to encourage PR practitioners to appreciate their role as the pivot of their organisation’s reputation management. It discusses the importance of codes of ethics, claiming that these should be reviewed by public relations associations every 4‐5 years. Good conduct is essential for every PR practitioner as a reputation manager, and PR associations must ensure that codes of ethics are enforced. PR associations should address the challenge posed by the boom in the labour markets for PR practitioners by ensuring that all practitioners are well trained.

Often, real estate factors are given much of the credit for a particular site’s success or failure when it comes to sales. The current paper asserts that some of the praise or blame heaped onto real estate decision‐makers may be undue. Sometimes success or failure is due to non‐real estate factors such as a marketing or advertising strategy, operations, or brand awareness. The paper discusses non‐real estate variables that contribute to a site’s overall success or failure, and offers diagnostics and suggestions to help address non‐real estate problems that could influence sales.

For the corporate real estate executive who is in the process of transforming the department to be a strategic business partner, this paper presents examples of initiatives used to ensure the workplace is aligned with the long‐term corporate strategy. This paper analyses the benefits of corporate real estate being viewed as a business partner in addition to a service provider.

On parle peu de la rénovation du patrimoine bâti en vue d'une utilisation pour le tourisme social. Pourtant après la dernière guerre, dans les démocraties populaires, nombre de propriétés ont été reconverties en sanatoriums ou en maisons de repos pour travailleurs.

The commercial practice of tourism avails itself of a whole range of classical methods of research into market, its dispersion and trends, starting with statistics and ending up with public opinion polls. The pattern and volume of tourism demand as well as its principal trends may be compared on the basis of international statistics that are more or less uniform. However, not even more detailed statistical observations are adequate for the formulation of long‐term marketing strategy of the given country.

Economic effects are only one aspect of the total impact of tourism. For example, the development of a tourist industry in a particular country has varying repurcussions on the long term socio‐cultural, environmental and ecological development of the local community as a whole. This article examines the main non‐economic aspects of tourism in Greece.