Early visual detection of oriented line targets: spatial characteristics,and reference frames of early visual orientation-processing

The orientations of lines and edges are important in defining the structure of the visual environment, and observers can detect differences in line orientation within the first few hundred milliseconds of scene viewing. The present work is a psychophysical investigation of the mechanisms of early visual orientation-processing. In experiments with briefly presented displays of line elements, observers indicated whether all the elements were uniformly oriented or whether a uniquely oriented target was present among uniformly oriented nontargets. The minimum difference between nontarget and target orientations that was required for effective target-detection (the orientation increment threshold) varied little with the number of elements and their spatial density, but the percentage of correct responses in detection of a large orientation-difference increased with increasing element density. The differing variations with element density of thresholds and percent-correct scores may indicate the operation of more than one mechanism in early visual orientation-processIng. Reducing element length caused threshold to increase with increasing number of elements, showing that the effectiveness of rapid, spatially parallel orientation-processing depends on element length. Orientational anisotropy in line-target detection has been reported previously: a coarse periodic variation and some finer variations in orientation increment threshold with nontarget orientation have been found. In the present work, the prominence of the coarse variation in relation to finer variations decreased with increasing effective viewing duration, as if the operation of coarse orientation-processing mechanisms precedes the operation of finer ones. Orientational anisotropy was prominent even when observers lay horizontally and viewed displays by looking upwards through a black cylinder that excluded all possible visual references for orientation. So, gravitational and visual cues are not essential to the definition of an orientational reference frame for early vision, and such a reference can be well defined by retinocentric neural coding, awareness of body-axis orientation, or both.

Spiral mechanisms are required to account for summation of complex motion components

Stimuli from one family of complex motions are defined by their spiral pitch, where cardinal axes represent signed expansion and rotation. Intermediate spirals are represented by intermediate pitches. It is well established that vision contains mechanisms that sum over space and direction to detect these stimuli (Morrone et al., Nature 376 (1995) 507) and one possibility is that four cardinal mechanisms encode the entire family. We extended earlier work (Meese & Harris, Vision Research 41 (2001) 1901) using subthreshold summation of random dot kinematograms and a two-interval forced choice technique to investigate this possibility. In our main experiments, the spiral pitch of one component was fixed and that of another was varied in steps of 15° relative to the first. Regardless of whether the fixed component was aligned with cardinal axes or an intermediate spiral, summation to-coherence-threshold between the two components declined as a function of their difference in spiral pitch. Similar experiments showed that none of the following were critical design features or stimulus parameters for our results: superposition of signal dots, limited life-time dots, the presence of speed gradients, stimulus size or the number of dots. A simplex algorithm was used to fit models containing mechanisms spaced at a pitch of either 90° (cardinal model) or 45° (cardinal+model) and combined using a fourth-root summation rule. For both models, direction half-bandwidth was equated for all mechanisms and was the only free parameter. Only the cardinal+model could account for the full set of results. We conclude that the detection of complex motion in human vision requires both cardinal and spiral mechanisms with a half-bandwidth of approximately 46°. © 2002 Elsevier Science Ltd. All rights reserved.

IL-8 released constitutively by primary bronchial epithelial cells in culture forms an inactive complex with secretory component

The bronchial epithelium is a source of both α and β chemokines and, uniquely, of secretory component (SC), the extracellular ligand-binding domain of the polymeric IgA receptor. Ig superfamily relatives of SC, such as IgG and α2-macroglobulin, bind IL-8. Therefore, we tested the hypothesis that SC binds IL-8, modifying its activity as a neutrophil chemoattractant. Primary bronchial epithelial cells were cultured under conditions to optimize SC synthesis. The chemokines IL-8, epithelial neutrophil-activating peptide-78, growth-related oncogene α, and RANTES were released constitutively by epithelial cells from both normal and asthmatic donors and detected in high m.w. complexes with SC. There were no qualitative differences in the production of SC-chemokine complexes by epithelial cells from normal or asthmatic donors, and in all cases this was the only form of chemokine detected. SC contains 15% N-linked carbohydrate, and complete deglycosylation with peptide N-glycosidase F abolished IL-8 binding. In micro-Boyden chamber assays, no IL-8-dependent neutrophil chemotactic responses to epithelial culture supernatants could be demonstrated. SC dose-dependently (IC50 ∼0.3 nM) inhibited the neutrophil chemotactic response to rIL-8 (10 nM) in micro-Boyden chamber assays and also inhibited IL-8-mediated neutrophil transendothelial migration. SC inhibited the binding of IL-8 to nonspecific binding sites on polycarbonate filters and endothelial cell monolayers, and therefore the formation of haptotactic gradients, without effects on IL-8 binding to specific receptors on neutrophils. The data indicate that in the airways IL-8 may be solubilized and inactivated by binding to SC

Early spatial vision:a view through two eyes

Simple features such as edges are the building blocks of spatial vision, and so I ask: how arevisual features and their properties (location, blur and contrast) derived from the responses ofspatial filters in early vision; how are these elementary visual signals combined across the twoeyes; and when are they not combined? Our psychophysical evidence from blur-matchingexperiments strongly supports a model in which edges are found at the spatial peaks ofresponse of odd-symmetric receptive fields (gradient operators), and their blur B is givenby the spatial scale of the most active operator. This model can explain some surprisingaspects of blur perception: edges look sharper when they are low contrast, and when theirlength is made shorter. Our experiments on binocular fusion of blurred edges show that singlevision is maintained for disparities up to about 2.5*B, followed by diplopia or suppression ofone edge at larger disparities. Edges of opposite polarity never fuse. Fusion may be served bybinocular combination of monocular gradient operators, but that combination - involvingbinocular summation and interocular suppression - is not completely understood.In particular, linear summation (supported by psychophysical and physiological evidence)predicts that fused edges should look more blurred with increasing disparity (up to 2.5*B),but results surprisingly show that edge blur appears constant across all disparities, whetherfused or diplopic. Finally, when edges of very different blur are shown to the left and righteyes fusion may not occur, but perceived blur is not simply given by the sharper edge, nor bythe higher contrast. Instead, it is the ratio of contrast to blur that matters: the edge with theAbstracts 1237steeper gradient dominates perception. The early stages of binocular spatial vision speak thelanguage of luminance gradients.

Finding closest targets in non-oriented DEA models:the case of convex and non-convex technologies

This paper draws attention for the fact that traditional Data Envelopment Analysis (DEA) models do not provide the closest possible targets (or peers) to inefficient units, and presents a procedure to obtain such targets. It focuses on non-oriented efficiency measures (which assume that production units are able to control, and thus change, inputs and outputs simultaneously) both measured in relation to a Free Disposal Hull (FDH) technology and in relation to a convex technology. The approaches developed for finding close targets are applied to a sample of Portuguese bank branches.

A semi-oriented radial measure for measuring the efficiency of decision making units with negative data, using DEA

Data Envelopment Analysis (DEA) is a nonparametric method for measuring the efficiency of a set of decision making units such as firms or public sector agencies, first introduced into the operational research and management science literature by Charnes, Cooper, and Rhodes (CCR) [Charnes, A., Cooper, W.W., Rhodes, E., 1978. Measuring the efficiency of decision making units. European Journal of Operational Research 2, 429–444]. The original DEA models were applicable only to technologies characterized by positive inputs/outputs. In subsequent literature there have been various approaches to enable DEA to deal with negative data. In this paper, we propose a semi-oriented radial measure, which permits the presence of variables which can take both negative and positive values. The model is applied to data on a notional effluent processing system to compare the results with those yielded by two alternative methods for dealing with negative data in DEA: The modified slacks-based model suggested by Sharp et al. [Sharp, J.A., Liu, W.B., Meng, W., 2006. A modified slacks-based measure model for data envelopment analysis with ‘natural’ negative outputs and inputs. Journal of Operational Research Society 57 (11) 1–6] and the range directional model developed by Portela et al. [Portela, M.C.A.S., Thanassoulis, E., Simpson, G., 2004. A directional distance approach to deal with negative data in DEA: An application to bank branches. Journal of Operational Research Society 55 (10) 1111–1121]. A further example explores the advantages of using the new model.

The nature of an object-oriented program:how do practitioners understand the nature of what they are creating?

Object-oriented programming is seen as a difficult skill to master. There is considerable debate about the most appropriate way to introduce novice programmers to object-oriented concepts. Is it possible to uncover what the critical aspects or features are that enhance the learning of object-oriented programming? Practitioners have differing understandings of the nature of an object-oriented program. Uncovering these different ways of understanding leads to agreater understanding of the critical aspects and their relationship tothe structure of the program produced. A phenomenographic studywas conducted to uncover practitioner understandings of the nature of an object-oriented program. The study identified five levels of understanding and three dimensions of variation within these levels. These levels and dimensions of variation provide a framework for fostering conceptual change with respect to the nature of an object-oriented program.

The effective use of implicit parallelism through the use of an object-oriented programming language

This thesis explores translating well-written sequential programs in a subset of the Eiffel programming language - without syntactic or semantic extensions - into parallelised programs for execution on a distributed architecture. The main focus is on constructing two object-oriented models: a theoretical self-contained model of concurrency which enables a simplified second model for implementing the compiling process. There is a further presentation of principles that, if followed, maximise the potential levels of parallelism. Model of Concurrency. The concurrency model is designed to be a straightforward target for mapping sequential programs onto, thus making them parallel. It aids the compilation process by providing a high level of abstraction, including a useful model of parallel behaviour which enables easy incorporation of message interchange, locking, and synchronization of objects. Further, the model is sufficient such that a compiler can and has been practically built. Model of Compilation. The compilation-model's structure is based upon an object-oriented view of grammar descriptions and capitalises on both a recursive-descent style of processing and abstract syntax trees to perform the parsing. A composite-object view with an attribute grammar style of processing is used to extract sufficient semantic information for the parallelisation (i.e. code-generation) phase. Programming Principles. The set of principles presented are based upon information hiding, sharing and containment of objects and the dividing up of methods on the basis of a command/query division. When followed, the level of potential parallelism within the presented concurrency model is maximised. Further, these principles naturally arise from good programming practice. Summary. In summary this thesis shows that it is possible to compile well-written programs, written in a subset of Eiffel, into parallel programs without any syntactic additions or semantic alterations to Eiffel: i.e. no parallel primitives are added, and the parallel program is modelled to execute with equivalent semantics to the sequential version. If the programming principles are followed, a parallelised program achieves the maximum level of potential parallelisation within the concurrency model.

The realisation of JSD specifications in object oriented languages

Jackson System Development (JSD) is an operational software development method which addresses most of the software lifecycle either directly or by providing a framework into which more specialised techniques can fit. The method has two major phases: first an abstract specification is derived that is in principle executable; second the specification is implemented using a variety of transformations. The object oriented paradigm is based on data abstraction and encapsulation coupled to an inheritance architecture that is able to support software reuse. Its claims of improved programmer productivity and easier program maintenance make it an important technology to be considered for building complex software systems. The mapping of JSD specifications into procedural languages typified by Cobol, Ada, etc., involves techniques such as inversion and state vector separation to produce executable systems of acceptable performance. However, at present, no strategy exists to map JSD specifications into object oriented languages. The aim of this research is to investigate the relationship between JSD and the object oriented paradigm, and to identify and implement transformations capable of mapping JSD specifications into an object oriented language typified by Smalltalk-80. The direction which the transformational strategy follows is one whereby the concurrency of a specification is removed. Two approaches implementing inversion - an architectural transformation resulting in a simulated coroutine mechanism being generated - are described in detail. The first approach directly realises inversions by manipulating Smalltalk-80 system contexts. This is possible in Smalltalk-80 because contexts are first class objects and are accessible to the user like any other system object. However, problems associated with this approach are expounded. The second approach realises coroutine-like behaviour in a structure called a `followmap'. A followmap is the results of a transformation on a JSD process in which a collection of followsets is generated. Each followset represents all possible state transitions a process can undergo from the current state of the process. Followsets, together with exploitation of the class/instance mechanism for implementing state vector separation, form the basis for mapping JSD specifications into Smalltalk-80. A tool, which is also built in Smalltalk-80, supports these derived transformations and enables a user to generate Smalltalk-80 prototypes of JSD specifications.

Person-oriented and process-oriented teachers : an investigation of the links between ESOL teachers' personal belief systems and approaches to teaching

This thesis looks to two traditions in research into language teaching, teacher beliefs and classroom interaction, in order to investigate the question: Do teachers of ESOL have an identifiable and coherent system of beliefs about teaching and learning that may account for different approaches to teaching? A qualitative approach to research is taken, following a case study tradition, in order to carry out an in-depth study into the beliefs of six ESOL teachers. Five teachers participated in an initial pilot study and two subsequently became the main case studies for the research. The beliefs of a sixth teacher were then investigated to verify the findings. Semi-structured interviews and classroom observations were carried out with all the teachers. The teachers in the study were found to have personal belief systems that cohere around two orientations to teaching and learning - a person orientation and a process orientation. Moreover, the findings suggest that underlying the orientations is the perception that teachers have of their teacher identity, in terms of whether this is seen as a separate identity or as part of their personality. It is suggested that the two orientations may offer a powerful tool for teacher education as it is increasingly recognised that, in order to be effective, teacher educators must take into account the beliefs that teachers bring with them to training and development programmes. An initial investigations into the teachers’ classroom behaviour suggests that while their methodologies approach may be very similar there are fundamental differences in their interactions patterns and these differences may be a result of their own orientation. However, while teachers’ personal belief systems undoubtedly underlie their approach to teaching, further research is needed to establish the extent and the nature of the relationship between orientation and classroom interaction.

Differences in market-oriented behaviour levels across firms' domestic and export marketing operations:a study of antecedents and consequences

Researchers are beginning to recognise that organisations often have different levels of market orientation across different aspects of their operations. Focusing on firms involved in export marketing, this study examines how market-oriented behaviour differs across firms' domestic and export marketing operations. In this respect, the study is the first of its kind since it investigates three main issues: (1) to what extent do differences exist in firms' levels of market-oriented behaviour in their domestic markets (i.e., their domestic market-oriented behaviour) and in their export markets (i.e., their export market-oriented behaviour), (2) what are the key drivers of such differences, and (3) what are the performance implications for firms of having different levels of domestic and export market-oriented behaviour. To shed light on these research questions, data were collected from 225 British exporting firms using a mail questionnaire. Structural equation modelling techniques were used to develop and purify measures of all construct of interest, and to test the theoretical models developed. The results indicate that many of businesses sampled have very different levels of market orientation in their domestic and exporting operations: typically, firms tend to be more market-oriented in their domestic markets relative to their export markets. Several key factors were identified as drivers of differences in market orientation levels across firms' domestic and export markets. In particular, it was found that differences were more pronounced when: (i) interfunctional interactions between domestic marketing and export marketing are rare, (ii) when domestic and export marketing follow asymmetric business strategies, (iii) when mutual dependence between the functions is low, (iv) when one or other of the functions dominates the firm's sales, and (v) when there are pronounced differences in the degree to which the domestic and the export markets are experiencing environmental turbulence. The consequences of differences in market-oriented behaviour across firms' domestic and export markets were also studied. The results indicate that overall sales performance of firms (as determined by the composite of firms' domestic sales and export sales performance) is positively related to levels of domestic market-oriented behaviour under high levels of environmental turbulence in firms' domestic markets. However, as domestic market turbulence decreases, so to does the strength of this positive relationship. On the other hand, export market-oriented behaviour provides a positive contribution to firms' overall sales success under conditions of relatively low export market turbulence. As the turbulence in export markets increases, this positive relationship becomes weaker. These findings indicate that there are numerous situations in which it is sub-optimal for firms to have identical levels of market-oriented behaviour in their domestic and exporting operations. The theoretical and practical implications of these findings are discussed.

Investigation of two-wave mixing in arbitrary oriented sillenite crystals

A generalized systematic description of the Two-Wave Mixing (TWM) process in sillenite crystals allowing for arbitrary orientation of the grating vector is presented. An analytical expression for the TWM gain is obtained for the special case of plane waves in a thin crystal (|g|d«1) with large optical activity (|g|/?«1, g is the coupling constant, ? the rotatory power, d the crystal thickness). Using a two-dimensional formulation the scope of the nonlinear equations describing TWM can be extended to finite beams in arbitrary geometries and to any crystal parameters. Two promising applications of this formulation are proposed. The polarization dependence of the TWM gain is used for the flattening of Gaussian beam profiles without expanding them. The dependence of the TWM gain on the interaction length is used for the determination of the crystal orientation. Experiments carried out on Bi12GeO20 crystals of a non-standard cut are in good agreement with the results of modelling.

Design of an expandable manufacturing simulator through the application of object-oriented principles

In analysing manufacturing systems, for either design or operational reasons, failure to account for the potentially significant dynamics could produce invalid results. There are many analysis techniques that can be used, however, simulation is unique in its ability to assess detailed, dynamic behaviour. The use of simulation to analyse manufacturing systems would therefore seem appropriate if not essential. Many simulation software products are available but their ease of use and scope of application vary greatly. This is illustrated at one extreme by simulators which offer rapid but limited application whilst at the other simulation languages which are extremely flexible but tedious to code. Given that a typical manufacturing engineer does not posses in depth programming and simulation skills then the use of simulators over simulation languages would seem a more appropriate choice. Whilst simulators offer ease of use their limited functionality may preclude their use in many applications. The construction of current simulators makes it difficult to amend or extend the functionality of the system to meet new challenges. Some simulators could even become obsolete as users, demand modelling functionality that reflects the latest manufacturing system design and operation concepts. This thesis examines the deficiencies in current simulation tools and considers whether they can be overcome by the application of object-oriented principles. Object-oriented techniques have gained in popularity in recent years and are seen as having the potential to overcome any of the problems traditionally associated with software construction. There are a number of key concepts that are exploited in the work described in this thesis: the use of object-oriented techniques to act as a framework for abstracting engineering concepts into a simulation tool and the ability to reuse and extend object-oriented software. It is argued that current object-oriented simulation tools are deficient and that in designing such tools, object -oriented techniques should be used not just for the creation of individual simulation objects but for the creation of the complete software. This results in the ability to construct an easy to use simulator that is not limited by its initial functionality. The thesis presents the design of an object-oriented data driven simulator which can be freely extended. Discussion and work is focused on discrete parts manufacture. The system developed retains the ease of use typical of data driven simulators. Whilst removing any limitation on its potential range of applications. Reference is given to additions made to the simulator by other developers not involved in the original software development. Particular emphasis is put on the requirements of the manufacturing engineer and the need for Ihe engineer to carrv out dynamic evaluations.

Modelling manufacturing planning and control systems:the application of object-oriented principles and discrete-event simulation

Manufacturing planning and control systems are fundamental to the successful operations of a manufacturing organisation. 10 order to improve their business performance, significant investment is made by companies into planning and control systems; however, not all companies realise the benefits sought Many companies continue to suffer from high levels of inventory, shortages, obsolete parts, poor resource utilisation and poor delivery performance. This thesis argues that the fit between the planning and control system and the manufacturing organisation is a crucial element of success. The design of appropriate control systems is, therefore, important. The different approaches to the design of manufacturing planning and control systems are investigated. It is concluded that there is no provision within these design methodologies to properly assess the impact of a proposed design on the manufacturing facility. Consequently, an understanding of how a new (or modified) planning and control system will perform in the context of the complete manufacturing system is unlikely to be gained until after the system has been implemented and is running. There are many modelling techniques available, however discrete-event simulation is unique in its ability to model the complex dynamics inherent in manufacturing systems, of which the planning and control system is an integral component. The existing application of simulation to manufacturing control system issues is limited: although operational issues are addressed, application to the more fundamental design of control systems is rarely, if at all, considered. The lack of a suitable simulation-based modelling tool does not help matters. The requirements of a simulation tool capable of modelling a host of different planning and control systems is presented. It is argued that only through the application of object-oriented principles can these extensive requirements be achieved. This thesis reports on the development of an extensible class library called WBS/Control, which is based on object-oriented principles and discrete-event simulation. The functionality, both current and future, offered by WBS/Control means that different planning and control systems can be modelled: not only the more standard implementations but also hybrid systems and new designs. The flexibility implicit in the development of WBS/Control supports its application to design and operational issues. WBS/Control wholly integrates with an existing manufacturing simulator to provide a more complete modelling environment.