Scale-space theory: a basic tool for analyzing structures at different scales

An inherent property of objects in the world is that they only exist as meaningful entities over certain ranges of scale. If one aims to describe the structure of unknown real-world signals, then a multi-scale representation of data is of crucial importance. This paper gives a tutorial review of a special type of multi-scale representation—linear scale-space representation—which has been developed by the computer vision community to handle image structures at different scales in a consistent manner. The basic idea is to embed the original signal into a one-parameter family of gradually smoothed signals in which the fine-scale details are successively suppressed. Under rather general conditions on the type of computations that are to be performed at the first stages of visual processing, in what can be termed 'the visual front-end', it can be shown that the Gaussian kernel and its derivatives are singled out as the only possible smoothing kernels. The conditions that specify the Gaussian kernel are, basically, linearity and shift invariance, combined with different ways of formalizing the notion that structures at coarse scales should correspond to simplifications of corresponding structures at fine scales-they should not be accidental phenomena created by the smoothing method. Notably, several different ways of choosing scale-space axioms give rise to the same conclusion. The output from the scale-space representation can be used for a variety of early visual tasks; operations such as feature detection, feature classification and shape computation can be expressed directly in terms of (possibly non-linear) combinations of Gaussian derivatives at multiple scales. In this sense the scale-space representation canserve as a basis for early vision. During the last few decades, a number of other approaches to multiscale representations have been developed, which are more or less related to scale-space theory, notably the theories of pyramids, wavelets and multi grid methods.Despite their qualitative differences, the increasing propularity of each of these approaches indicates that the crucial notion of scale is increasingly appreciated by the computer.vision community and by researchers in other related fields. An interesting similarity to biological vision is that the scale-space operators closely resemble receptive field profiles registered in neurophysiological studies of the mam- malian retina and visual cortex.     

A NOTE ON MODELING PROJECT INTERDEPENDENCE IN RESEARCH AND DEVELOPMENT*

This note is concerned with the problem of resource allocation under uncertainty in a research and development laboratory. A distinction is defined between project interrelationships that are specific (or internal) to certain projects and interrelationships resulting from external environmental factors. Formulations are introduced that allow both types of interrelationships to be formally included in a resource allocation optimization model. In the case of external environmental factors, an example is presented and analyzed.     

Social positioning theory and quantum mechanics

Social positioning theory, or an account of the human individual that it grounds, qualifies as a quantum social theory. This is an assessment that I explain and defend in the paper. It is of interest in that, in a world where increasing numbers are seeking to construct quantum social theories, it serves to help demonstrate that this goal can be achieved without giving up on meeting criteria like explanatory intelligibility or power or discarding real-world notions like human (and other) entities. As it turns out, a central feature of the account defended and a core element of the ‘standard’ interpretation of quantum mechanics are found to stand in an interesting, unanticipated and suggestive relation to each other.     

Changes in Racial Apathy Among White Young Adults: A Five-Year National Panel Study

This study investigates changes in racial apathy among white young adults using nationally representative panel survey data from the NSYR. Our regression models include social background, social values, and academic orientation variables specified as important correlates of racial apathy in prior cross-sectional studies. We also include interracial contact variables, which existing studies neglect. According to intergroup contact theory, interracial contact should predict decreases in racial apathy. We find variables specified as important correlates in prior cross-sectional studies do not explain changes in racial apathy across time. Surprisingly, interracial friendship associates negatively with increases and decreases in racial apathy. Further, interracial dating predicts increases in racial apathy across time. These findings suggest racial apathy may be dissimilar to other forms of white racial prejudice and interracial contact may be an ineffective method to reduce contemporary forms of white racial prejudice.     

Employment of Older People in the European Union

Abstract. This article identifies the alternative employment modes of older workers in the European Union. Against a background of changing levels of labour force participation and declining employment opportunities the paper describes and discusses the relative significance for older workers of alternative employment modes. Two atypical modes, part‐time and self‐employment, are discussed in detail. The paper concludes that atypical employment modes offer ageing employees the opportunity to gradually retire by providing a bridge between full‐time employment and final retirement.