Mechanics of longitudinal rolling of tube through three-grooved rolls

This investigation examined the process of the longitudinal rolling of tubes through a set of three driven grooved rolls. Tubes were rolled with or without internal support i.e. under mandrel rolling or sinking conditions. Knowledge was required of the way in which the roll separating force and rolling torque vary for different conditions of rolling. The objective of this work being to obtain a better understanding and optimization of the mechanics of the process. The design and instrumentation of a complete experimental three-roll mill for the rolling of lead tube as an analogue material for hot steel, with the measurement of the individual roll force and torque is described. A novel type of roll load cell was incorporated and its design and testing discussed. Employing three roll sizes of 170 mm, 255 mm and 340 mm shroud diameter, precise tube specimens of various tube diameter to thickness ratios were rolled under sinking and mandrel rolling conditions. To obtain an indication of the tube-roll contact areas some of the specimens were partially rolled. For comparative purposes the remaining tubes were completely rolled as a single pass. The roll forces, torques and tube parameters e.g. reduction of area, D/t ratio, were collated and compared for each of the three roll diameters considered. The influence of friction, particularly in the mandrel rolling process, was commented upon. Theoretical studies utilising the equilibrium and energy methods were applied to both the sinking and mandrel rolling processes. In general, the energy approach gave better comparison with experiment, especially for mandrel rolling. The influence of the tube deformation zones on the two processes was observed and on the subsequent modification of the tube-roll arc contact length. A rudimentary attempt was made in the theoretical sinking analysis to allow for the deformation zone prior to roll contact; some success was noted. A general survey of the available tube rolling literature, for both the sinking and mandrel processes has been carried out.

The influence of cutting tool geometry upon aspects of chip flow and tool wear:a theoretical, three dimensional examination of the cutting geometry and the shape of the twist drill

This work is undertaken in the attempt to understand the processes at work at the cutting edge of the twist drill. Extensive drill life testing performed by the University has reinforced a survey of previously published information. This work demonstrated that there are two specific aspects of drilling which have not previously been explained comprehensively. The first concerns the interrelating of process data between differing drilling situations, There is no method currently available which allows the cutting geometry of drilling to be defined numerically so that such comparisons, where made, are purely subjective. Section one examines this problem by taking as an example a 4.5mm drill suitable for use with aluminium. This drill is examined using a prototype solid modelling program to explore how the required numerical information may be generated. The second aspect is the analysis of drill stiffness. What aspects of drill stiffness provide the very great difference in performance between short flute length, medium flute length and long flute length drills? These differences exist between drills of identical point geometry and the practical superiority of short drills has been known to shop floor drilling operatives since drilling was first introduced. This problem has been dismissed repeatedly as over complicated but section two provides a first approximation and shows that at least for smaller drills of 4. 5mm the effects are highly significant. Once the cutting action of the twist drill is defined geometrically there is a huge body of machinability data that becomes applicable to the drilling process. Work remains to interpret the very high inclination angles of the drill cutting process in terms of cutting forces and tool wear but aspects of drill design may already be looked at in new ways with the prospect of a more analytical approach rather than the present mix of experience and trial and error. Other problems are specific to the twist drill, such as the behaviour of the chips in the flute. It is now possible to predict the initial direction of chip flow leaving the drill cutting edge. For the future the parameters of further chip behaviour may also be explored within this geometric model.

Self-attentional processes in anxiety:an experimental study

Self-attention research has demonstrated a relationship between dispositional self-focus, anxiety proneness and fear arousal. In addition, the effect of self-focus manipulations on approach-avoidance tasks involving a feared stimulus are strikingly similar to the effects obtained from manipulation of other cognitive factors such as perceived self-efficacy. A number of experiments were designed to explore the relationship between self-focused attention and ffilxiety. Data from the experiments demonstrate that self-attention influences a variety of cognitive variables which have been considered as central factors in anxiety. Concomitants of self-focus are increased awareness of physiological arousal and overestimation of such arousal, the identification of self-discrepancies, cognitive failures and performance deficits and the activation of physical threat concepts in memory. These factors are conceptualised as central in the negative evaluation of physiological arousal and coping resources in anxiety. Clinically anxious individuals typically have high scores in dispositional self-consciousness and body-consciousness. In patients suffering from generalised anxiety or panic disorders maladaptive self-focusing tendencies can be related to specific life stressors which render aspects of the self salient. An analysis of the ideational component of anxiety revealed three subcomponents; negative social ideation (worry about other people's reaction to the self), negative somatic ideation (worry about physical symptoms and health) and obsessional ideation (the experience of uncontrollable and repetitive thoughts) which were differentially associated with measures of dispositional self-focus. The frequency and content of an.xious w-orry is associated with specific self-focusing tendencies. It is proposed that the 'attentional style' of the individual is an important determinant of the nature and intensity of their affective response in a threatening situation. A self-attentional model of anxiety is proposed and the complex interaction between self-focus and other cognitive factors in anxiety such as appraisal of arousal and coping resources and perceived levels of self-efficacy is discussed. The model presents new directions for research and therapeutic intervention in anxiety.

Micromechanics of agglomerate damage processes

This thesis reports a detailed investigation of the micromechanics of agglomerate behaviour under free-fall impact, double (punch) impact and diametrical compression tests using the simulation software TRUBAL. The software is based on the discrete element method (DEM) which incorporates the Newtonian equations of motion and contact mechanics theory to model the interparticle interactions. Four agglomerates have been used: three dense (differing in interface energy and contact density) and one loose. Although the simulated agglomerates are relatively coarse-grained, the results obtained are in good agreement with laboratory test results reported in the literature. The computer simulation results show that, in all three types of test, the loose agglomerate cannot fracture as it is unable to store sufficient elastic energy. Instead, it becomes flattened for low loading-rates and shattered or crushed at higher loading-rates. In impact tests, the dense agglomerates experience only local damage at low impact velocities. Semi-brittle fracture and fragmentation are produced over a range of higher impact velocities and at very high impact velocities shattering occurs. The dense agglomerates fracture in two or three large fragments in the diametrical compression tests. Local damage at the agglomerate-platen interface always occurs prior to fracture and consists of local bond breakage (microcrack formation) and local dislocations (compaction). The fracture process is dynamic and much more complex than that suggested by continuum fracture mechanics theory. Cracks are always initiated from the contact zones and propagate towards the agglomerate centre. Fracture occurs a short time after the start of unloading when a fracture crack "selection" process takes place. The detailed investigation of the agglomerate damage processes includes an examination of the evolution of the fracture surface. Detailed comparisons of the behaviour of the same agglomerate in all three types of test are presented. The particle size distribution curves of the debris are also examined, for both free-fall and double impact tests.

The impact of visual-verbal relationships on native-nonnative english speakers' reading processes and comprehension

The aim of this study was to comparatively investigate the impact of visual-verbal relationships that exist in expository texts on the reading process and comprehension of readers from different language background: native speakers of English (LI) and speakers of English as a foreign language (EFL). The study focussed, in this respect, on the visual elements (VEs) mainly graphs and tables that accompanied the selected texts. Two major experiments were undertaken. The first, was for the reading process using the post-reading questionnaire technique. Participants were 163 adult readers representing three groups: 77 (LI), 56 (EFL postgraduates); and 30 (EFL undergraduates). The second experiment was for the reading comprehension using cloze procedure. Participants were 123 representing the same above gorups: 50, 33 and 40 respectively. It was hypothesised that the LI readers would make use of VEs in the reading process in ways different from both EFL groups and that use would enhance each group's comprehension in different aspects and to different levels. In the analysis of the data of both experiments two statistical measurements were used. The chi-square was used to measure the differences between frequencies and the t-test was used to measure the differences between means. The results indicated a significant relationship between readers' language background and the impact of visual-verbal relationships on their reading processes and comprehension of such type of texts. The results also revealed considerable similarities between the two EFL groups in the reading process of texts accompanied by VEs. In the reading comprehension, however, the EFL undergraduates seemed to benefit from the visual-verbal relationships in their comprehension more than the postgraduates, suggesting a weak relationship of this impact for older EFL readers. Furthermore, the results showed considerable similarities between the reading process of texts accompanied by VEs and of whole prose texts. Finally an evaluation of this study was undertaken as well as practical implications for EFL readers and suggestions for future research.

Flow processes in a radiant tube burner: isothermal flow

This paper presents the first part of a study of the combustion processes in an industrial radiant tube burner (RTB). The RTB is used typically in heat-treating furnaces. The work was initiated because of the need for improvements in burner lifetime and performance. The present paper is concerned with the flow of combustion air; a future paper will address the combusting flow. A detailed three-dimensional computational fluid dynamics model of the burner was developed, validated with experimental air flow velocity measurements using a split-film probe. Satisfactory agreement was achieved using the k-e turbulence model. Various features along the air inlet passage were subsequently analysed. The effectiveness of the air recuperator swirler was found to be significantly compromised by the need for a generous assembly tolerance. Also, a substantial circumferential flow maldistribution introduced by the swirler is effectively removed by the positioning of a constriction in the downstream passage.

Flow processes in a radiant tube burner:combusting flow

This paper describes a study of the combustion process in an industrial radiant tube burner (RTB), used in heat treating furnaces, as part of an attempt to improve burner performance. A detailed three-dimensional Computational Fluid Dynamics model has been used, validated with experimental test furnace temperature and flue gas composition measurements. Simulations using the Eddy Dissipation combustion model with peak temperature limitation and the Discrete Transfer radiation model showed good agreement with temperature measurements in the inner and outer walls of the burner, as well as with flue gas composition measured at the exhaust (including NO). Other combustion and radiation models were also tested but gave inferior results in various aspects. The effects of certain RTB design features are analysed, and an analysis of the heat transfer processes within the burner is presented.

In situ imaging and height reconstruction of phase separation processes in polymer blends during spin coating

Spin coating polymer blend thin films provides a method to produce multiphase functional layers of high uniformity covering large surface areas. Applications for such layers include photovoltaics and light-emitting diodes where performance relies upon the nanoscale phase separation morphology of the spun film. Furthermore, at micrometer scales, phase separation provides a route to produce self-organized structures for templating applications. Understanding the factors that determine the final phase-separated morphology in these systems is consequently an important goal. However, it has to date proved problematic to fully test theoretical models for phase separation during spin coating, due to the high spin speeds, which has limited the spatial resolution of experimental data obtained during the coating process. Without this fundamental understanding, production of optimized micro- and nanoscale structures is hampered. Here, we have employed synchronized stroboscopic illumination together with the high light gathering sensitivity of an electron-multiplying charge-coupled device camera to optically observe structure evolution in such blends during spin coating. Furthermore the use of monochromatic illumination has allowed interference reconstruction of three-dimensional topographies of the spin-coated film as it dries and phase separates with nanometer precision. We have used this new method to directly observe the phase separation process during spinning for a polymer blend (PS-PI) for the first time, providing new insights into the spin-coating process and opening up a route to understand and control phase separation structures. © 2011 American Chemical Society.

Measurement of implicit leadership theories and their effect on leadership processes and outcomes

The leadership categorisation theory suggests that followers rely on a hierarchical cognitive structure in perceiving leaders and the leadership process, which consists of three levels; superordinate, basic and subordinate. The predominant view is that followers rely on Implicit Leadership Theories (ILTs) at the basic level in making judgments about managers. The thesis examines whether this presumption is true by proposing and testing two competing conceptualisations; namely the congruence between the basic level ILTs (general leader) and actual manager perceptions, and subordinate level ILTs (job-specific leader) and actual manager. The conceptualisation at the job-specific level builds on context-related assertions of the ILT explanatory models: leadership categorisation, information processing and connectionist network theories. Further, the thesis addresses the effects of ILT congruence at the group level. The hypothesised model suggests that Leader-Member Exchange (LMX) will act as a mediator between ILT congruence and outcomes. Three studies examined the proposed model. The first was cross-sectional with 175 students reporting on work experience during a 1-year industrial placement. The second was longitudinal and had a sample of 343 students engaging in a business simulation in groups with formal leadership. The final study was a cross-sectional survey in several organisations with a sample of 178. A novel approach was taken to congruence analysis; the hypothesised models were tested using Latent Congruence Modelling (LCM), which accounts for measurement error and overcomes the majority of limitations of traditional approaches. The first two studies confirm the traditional theorised view that employees rely on basic-level ILTs in making judgments about their managers with important implications, and show that LMX mediates the relationship between ILT congruence and work-related outcomes (performance, job satisfaction, well-being, task satisfaction, intragroup conflict, group satisfaction, team realness, team-member exchange, group performance). The third study confirms this with conflict, well-being, self-rated performance and commitment as outcomes.

Techno-economic assessment and uncertainty analysis of thermochemical processes for second generation biofuels

Biomass-To-Liquid (BTL) is one of the most promising low carbon processes available to support the expanding transportation sector. This multi-step process produces hydrocarbon fuels from biomass, the so-called “second generation biofuels” that, unlike first generation biofuels, have the ability to make use of a wider range of biomass feedstock than just plant oils and sugar/starch components. A BTL process based on gasification has yet to be commercialized. This work focuses on the techno-economic feasibility of nine BTL plants. The scope was limited to hydrocarbon products as these can be readily incorporated and integrated into conventional markets and supply chains. The evaluated BTL systems were based on pressurised oxygen gasification of wood biomass or bio-oil and they were characterised by different fuel synthesis processes including: Fischer-Tropsch synthesis, the Methanol to Gasoline (MTG) process and the Topsoe Integrated Gasoline (TIGAS) synthesis. This was the first time that these three fuel synthesis technologies were compared in a single, consistent evaluation. The selected process concepts were modelled using the process simulation software IPSEpro to determine mass balances, energy balances and product distributions. For each BTL concept, a cost model was developed in MS Excel to estimate capital, operating and production costs. An uncertainty analysis based on the Monte Carlo statistical method, was also carried out to examine how the uncertainty in the input parameters of the cost model could affect the output (i.e. production cost) of the model. This was the first time that an uncertainty analysis was included in a published techno-economic assessment study of BTL systems. It was found that bio-oil gasification cannot currently compete with solid biomass gasification due to the lower efficiencies and higher costs associated with the additional thermal conversion step of fast pyrolysis. Fischer-Tropsch synthesis was the most promising fuel synthesis technology for commercial production of liquid hydrocarbon fuels since it achieved higher efficiencies and lower costs than TIGAS and MTG. None of the BTL systems were competitive with conventional fossil fuel plants. However, if government tax take was reduced by approximately 33% or a subsidy of £55/t dry biomass was available, transport biofuels could be competitive with conventional fuels. Large scale biofuel production may be possible in the long term through subsidies, fuels price rises and legislation.

Enhancing enterprise knowledge processes via cross-media extraction

In large organizations the resources needed to solve challenging problems are typically dispersed over systems within and beyond the organization, and also in different media. However, there is still the need, in knowledge environments, for extraction methods able to combine evidence for a fact from across different media. In many cases the whole is more than the sum of its parts: only when considering the different media simultaneously can enough evidence be obtained to derive facts otherwise inaccessible to the knowledge worker via traditional methods that work on each single medium separately. In this paper, we present a cross-media knowledge extraction framework specifically designed to handle large volumes of documents composed of three types of media text, images and raw data and to exploit the evidence across the media. Our goal is to improve the quality and depth of automatically extracted knowledge.

Antecedents, mechanisms and processes of deinstitutionalization and institutional change:a case study approach to understanding enterprise under duress

Adopting a grounded theory methodology, the study describes how an event and pressure impact upon a process of deinstitutionalization and institutional change. Three case studies were theoretically sampled in relation to each other. They yielded mainly qualitative data from methods that included interviews, observations, participant observations, and document reviews. Each case consisted of a boundaried cluster of small enterprises that were not industry specific and were geographically dispersed. Overall findings describe how an event, i.e. a stimulus, causes disruption, which in turn may cause pressure. Pressure is then translated as a tension within the institutional environment, which is characterized by opposing forces that encourage institutional breakdown and institutional maintenance. Several contributions are made: Deinstitutionalization as a process is inextricable from the formation of institutions – both are needed to make sense of institutional change on a conceptual level but are also inseparable experientially in the field; stimuli are conceptually different to pressures; the historical basis of a stimulus may impact on whether pressure and institutional change occurs; pressure exists in a more dynamic capacity rather than only as a catalyst; institutional breakdown is a non-linear irregular process; ethical and survival pressures as new types were identified; institutional current, as an underpinning mechanism, influences how the tension between institutional breakdown and maintenance plays out.

Exploring the impact of e-business adoption on logistics processes:empirical evidence from the food industry

The objectives of the research were to identify factors that influence e-business adoption and its impact on logistics processes in the Greek food industry. Drawing on existing research, a conceptual framework and propositions were developed and six in depth case studies were carried out. In the framework, three major categories of influencing factors were distinguished: intra-enterprise, sector and supply chain factors. Findings suggest that e-business adoption is more affected by supply chain and sector factors, rather than intra-enterprise factors. Regarding the impact of e-business on logistics process, it seems that it is affected by the frequency of its use and it is greater in processes occurring at the company-customer interface. Finally, e-business impact is more related to the dimensions of time and quality, rather than cost improvements.

Wind power forecasts using Gaussian processes and numerical weather prediction

Since wind at the earth's surface has an intrinsically complex and stochastic nature, accurate wind power forecasts are necessary for the safe and economic use of wind energy. In this paper, we investigated a combination of numeric and probabilistic models: a Gaussian process (GP) combined with a numerical weather prediction (NWP) model was applied to wind-power forecasting up to one day ahead. First, the wind-speed data from NWP was corrected by a GP, then, as there is always a defined limit on power generated in a wind turbine due to the turbine controlling strategy, wind power forecasts were realized by modeling the relationship between the corrected wind speed and power output using a censored GP. To validate the proposed approach, three real-world datasets were used for model training and testing. The empirical results were compared with several classical wind forecast models, and based on the mean absolute error (MAE), the proposed model provides around 9% to 14% improvement in forecasting accuracy compared to an artificial neural network (ANN) model, and nearly 17% improvement on a third dataset which is from a newly-built wind farm for which there is a limited amount of training data. © 2013 IEEE.

Real-time error compensation of a three-axis machine tool using a laser tracker

The concept of measurement-enabled production is based on integrating metrology systems into production processes and generated significant interest in industry, due to its potential to increase process capability and accuracy, which in turn reduces production times and eliminates defective parts. One of the most promising methods of integrating metrology into production is the usage of external metrology systems to compensate machine tool errors in real time. The development and experimental performance evaluation of a low-cost, prototype three-axis machine tool that is laser tracker assisted are described in this paper. Real-time corrections of the machine tool's absolute volumetric error have been achieved. As a result, significant increases in static repeatability and accuracy have been demonstrated, allowing the low-cost three-axis machine tool to reliably reach static positioning accuracies below 35 μm throughout its working volume without any prior calibration or error mapping. This is a significant technical development that demonstrated the feasibility of the proposed methods and can have wide-scale industrial applications by enabling low-cost and structural integrity machine tools that could be deployed flexibly as end-effectors of robotic automation, to achieve positional accuracies that were the preserve of large, high-precision machine tools.