Search results

A comparison between a classical classification card system—like UDC—and a modern selection system which makes use of the co‐ordinate indexing principle—like the Uniterm system of Dr Taube—is a rather tricky affair, because of two reasons:

The search for an easily installed, practicable and inexpensive information retrieval system continues unabated. This is reflected in the Aslib Library almost daily by requests for advice on the feasibility of installing this or that system, or for information on what systems are available in Great Britain. Study of the following bibliography, which covers only a narrow selection of information retrieval systems, will reveal that much original thought has been producing concrete results in this country. In fact, one of the earliest references is to a paper given at the twenty‐second Aslib Conference in 1947 by W. E. Batten, in which he describes his development of an ‘aspect’ card system—more often referred to today as ‘Peek‐a‐boo’ or ‘feature’ cards. Mr C. W. Cleverdon's Cranfield project is also adding considerable knowledge on the use of various indexing methods, including Uniterm.

TDCK uses a combination of uniterms and descriptors for its information retrieval system. In order to index two series of about twenty thousand documents each per year, a punched card with twenty thousand positions has been designed. In each series about eight thousand uniterms are used to describe the documents.

Within the framework of a research project into alternative ways of representing documentation languages and into their flexibility, an attempt is made to draw up a list of performance criteria that an ‘ideal’ thesaurus graphic display should respect. However, a study of the main bibliographies listing thesauri, shows that less than 6 per cent of them contain graphic displays, even though a concurrent literature survey reveals that such displays offer many potential advantages. Up to now, use of displays was probably limited by technology and by the rarity of studies into the cognitive processes of the users of automated systems. Current research in several disciplines (computer graphics, ergonomic psychology and spatial representation) should contribute to the emergence of new types of documentation retrieval tools, well adapted to a broader and more diversified clientele.

Interest in the objective testing and evaluation of document searching systems and procedures has grown steadily during the past decade. The reason for such interest is perhaps obvious: a great deal of attention has been, and is being, given to the development of new methods, including mechanized methods, for storing and searching characterizations of scientific and technical documents. To determine the effectiveness and utility of these new methods, particularly in comparison with the more conventional methods still in use, we need objective means of assessing their performance. Although some progress has been made, much remains to be done on the development of evaluation methods and criteria, a high priority area of study in the view of many individuals and organizations.

Since the second world war, considerable research funds and effort have been spent on developing means for controlling the ever‐increasing flood of recorded knowledge. As far as librarians and information officers are concerned, the problem can be divided up into five distinct stages, as shown in Figure 1.

Thirty years or more ago, a favoured question in examination papers for librarians was some variation on the theme ‘Compare the merits of a classified catalogue and an alphabetical subject catalogue’. This was a subject which it was possible to write on or to discuss at great length, advancing a number of theoretical arguments or opinions expressed by pundits, without ever stating a single demonstrable fact. When, in the early 1950's, various people, such as Taube and Mooers, proposed new techniques for indexing, the reaction from the traditionally‐minded was such that it appeared there was to be a repetition of all the old arguments. In an editorial in American Documentation in 1955, Perry expressed a viewpoint, shared by many others, when he wrote:

The aim of this project was to devise and put into practice a system that would permit publication of an index (the Index Medicus) of greater coverage, currency, and ease of use than the previous Current List of Medical Literature, published by the National Library of Medicine. The latter was the largest indexing service of a specialized subject anywhere in the world, 1,600 journals being indexed regularly every month. Further expansion of the Current List was impossible without considerably speeding up the collating and numbering of the entries for each issue and the hand‐mounting of all entry slips on page‐boards to be sent to the printers. These operations could not begin until all the material for a month's issue had been collected and a twenty‐four‐hour timetable for these processes had already been introduced to reduce the delay to the minimum. Mechanization was clearly necessary.

Selective laser melting (SLM) is an advanced rapid prototyping or additive manufacturing technology that uses high power density laser to fabricate metal/alloy components with minimal geometric constraints. The SLM process is multi-physics in nature and its study requires development of complex simulation tools. The purpose of this paper is to study – for the first time, to the best of the authors’ knowledge – the electromagnetic wave interactions and thermal processes in SLM based dense powder beds under the full-wave formalism and identify prospective metal powder bed particle distributions that can substantially improve the absorption rate, SLM volumetric deposition rate and thereby the overall build time.

We present a self-consistent thermo-optical model of the laser-matter interactions pertaining to SLM. The complex electromagnetic interactions and thermal effects in the dense metal powder beds are investigated by means of full-wave finite difference simulations. The model allows for accurate simulations of the excitation of gap, bulk and surface electromagnetic resonance modes, the energy transport across the particles, time dependent local permittivity variations under the incident laser intensity, and the thermal effects (joule heating) due to electromagnetic energy dissipation.

Localized gap and surface plasmon polariton resonance effects are identified as possible mechanisms toward improved absorption in small and medium size titanium powder beds. Furthermore, the observed near homogeneous temperature distributions across the metal powders indicates fast thermalization processes and allows for development of simple analytical models to describe the dynamics of the SLM process.

To the best of the authors’ knowledge, for the first time the electromagnetic interactions and thermal processes with dense powder beds pertaining to SLM processes are investigated under full-wave formalism. Explicit description is provided for important SLM process parameters such as critical laser power density, saturation temperature and time to melt. Specific guidelines are presented for improved energy efficiency and optimization of the SLM process deposition rates.

This study aims to integrate entrepreneurship theories and acculturation perspectives into a unified lens to understand opportunity development by transnational entrepreneurs (TNEs).

This study uses a conceptual method, considering how acculturation strategies of TNEs influence cross-cultural arbitrage.

We develop six propositions that define how acculturation strategies relate to different levels of cultural embeddedness of transnational entrepreneurs and ultimately influence the process by which the entrepreneur engages in cross-cultural arbitrage.

We are one of the first to integrate the sociology of immigrants with entrepreneurship to better understand how TNEs engage in cross-cultural arbitrage.