Origin of porosity in cast metals

A literature survey on the whole field of pore formation is assembled into the form of a general theory of the causes of porosity in castings. The conventionally accepted modes of feeding are assessed: liquid-, mass-, and interdendritic- feeding; and two further mechanisms are proposed: burst- and solid-feeding. The latter is investigated theoretically using various flow models: elastic-plastic, viscous, creep and Bingham flow. A new theory is proposed for the origin of layer porosity in castings. Experimental work on a wide variety of alloys: Al-Cu, Fe-C, Complex Ni- and Co-base alloys, cast both in air and in vacuum are investigated for the effect of section thickness, taper, and mould and metal temperatures. The formation of porosity appears to change from a non-nucleation to a nucleation mechanism as section thickness increases. A new method of interpreting radiographs based upon a longitudinal line count reveals that solid feeding becomes important in reducing porosity at high mould temperatures. Experiments on the effect of composition of an alloy on porosity cast doubt on the widely accepted theory that the presence of non-equilibrium eutectic liquid reduces porosity, but indicate that the non-equilibrium freezing range of the alloy may be the critical parameter. The effect of pressure on porosity is investigated utilising pressures below atmospheric; the results are inadequately explained by current theories and are discussed in terms of the nucleation and growth of pores; the effect would also appear to have considerable industrial potential for reducing porosity in vacuum cast components

System modelling and control

Not Availabl

Planning for post-industrial society : a theoretical framework

Bibliography: leaf 395-409.This research stems from the proposition that important qualitative changes are occurring within Western Society, and that these changes call for new forms of individual and organisational adaptation. Planning is a pre-eminently suitable way of adapting in an appropriate fashion to the complexities of change, rather than through ad hoc responses. Four tendencies appear to be prevalent and to persist within what may be termed these technologically advanced societies; these are: high and accelerating rates of technological and social change; an unevenness in these rates of change, especially among different parts of the environment in which organisations operate; an increasing interconnectedness and interdependence among these environmental parts; and an increasing overall size and complexity of the environment and its consistuent organisations. System's theory, it is felt, will provide a particularly apt conceptual framework for the consideration of these problems, which will be made explicit and amplified primarily through an exploration of these concepts which are central to a theory of behavioural systems. It is argued that the conditions in which social activity occurs are, in many parts of the world, becoming subject to important qualitative changes which demand new responses and modes of adaptation of behaviour, which look to what may be termed a new 'appreciative' outlook, in which a central element will be a recognition that units within ecological consideration must become the basis for achieving equitable outcomes. Chapters 7 and 8 discuss planning, the method which all social units at all levels use when attempting to regulate relations with others in order to continue functioning effectively. Here, the conceptual framework will be used to examine this problem of planning. Further, to refine the notion of planning, technical, natural, institutional, economic, conflict and social systems will be examined. In particular, urban planning will be looked at as of increasingly critical concern as the result of the world urbanisation process. A new paradigm for planning will be suggested which draws together the main elements of the thesis, in which the aims and techniques of enquiry will be from the making of explanations which derive from single purpose approaches to the furtherance of understanding desired from a more inclusive and comprehensive standpoint

Light scattering spectroscopy: studies of electronic excitations and atomic vibrations in matter

This thesis comprises a compendium of forty-two publications on various research topics unified by a common theme s light scattering spectroscopy. The research work presented ranges from experimental studies of the dynamics of atoms in various phases of matter through to theoretical investigations of the light scattering process. The topics discussed are the dynamics of structural phase transitions in proper and improper ferroelectrics, and in antiferroelectrics, for both ordered and disordered systems; the magnetic phase transitions in ordered and disordered compounds; the electronic properties of divalent transition metal ions in pure and dilute systems; the lattice vibrations of ionic, covalent and molecular crystals; the selection rules governing higher-order light scattering processes; the weak interactions occurring between chemical species in both aqueous and non-aqueous solvents; and the use of automation techniques in light scattering spectroscopy

Aeronautical engineering: A cumulative index to a continuing bibliography (supplement 235)

This publication is a cummulative index to the abstracts contained in Supplements 223 through 234 of Aeronautical Engineering: A Continuing Bibliography. The bibliographic series is compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). Seven indexes are included -- subject, personal author, corporate source, foreign technology, contract number, report number and accession number

Studies in the linguistic sciences. 08 (1978)

MLA international bibliography of books and articles on the modern languages and literatures (Complete edition) 0024-821

Northeastern Illinois University, Board of Governors Universities, Academic Catalog 1993-1994

https://neiudc.neiu.edu/catalogs/1034/thumbnail.jp

The Austronesian languages

This is a revised edition of the 2009 The Austronesian languages, which was published as a paperback in the then Pacific Linguistics series (ISBN 9780858836020). This revision includes typographical corrections, an improved index, and various minor content changes. The release of the open access edition serves to meet the strong ongoing demand for this important handbook, of which only 200 copies of the first edition were printed. This is the first single-authored book that attempts to describe the Austronesian language family in its entirety. Topics covered include: the physical and cultural background, official and national languages, largest and smallest languages in all major geographical regions, language contact, sound systems, linguistic palaeontology, morphology, syntax, the history of scholarship on Austronesian languages, and a critical assessment of the reconstruction of Proto Austronesian phonology.Australian National University, College of Asia and the Pacifi