published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The research question was offered by the sponsor of this Ph.D., The National Examining Board of Supervision and Management (NEBS Management). This research is a study of the First Line Management (FLM) role in Small and Medium Sized Enterprises (SMEs) in the UK and China. Different culture background, management styles, and communication systems, can be expected to affect the roles of managers. The Chinese style of managing the organisation has long been a subject of interest to researchers and practitioners. Research studies on managerial work and managerial roles have been well established in Western countries. Until recently, the cultural and political climate in China was less conducive to research into areas that might have caused too much debate. As a result, those researching management in China tended, until relevantly recently, to be isolated from main stream academic debate. It is believed that this study is unique in focusing on the FLM in China as well as in the UK. In both countries research on the FLM in SMEs is limited. This research attempts to bridge this gap by trying to define, for the first time, the roles, functions and skills required of FLMs in SMEs in the UK and China. The study argues that it is crucial to understand the FLM's role and place it within the organisation. The FLM is a critical link in any organisation because it is at this level that managerial and non managerial employees meet face to face and work in a close relationship with each other. The evidence from the research suggests that the FLM's role in the SME is broader than that of equivalent FLM role in the large organisation. It was found that FLMs in SMEs were seen as 'non-specialist', expected to cope with whatever aspect of work came their way. The implication of this broad 'nonspecialist' role was that they were expected to be a 'master of many trades'. The skills required to perform the FLM role were not perceived, despite their breadth as specialist skills such as finance, quality, purchasing and so on. Rather they were perceived as underpinning generic key skills which could, and should, be further supported by improved training and development. The research revealed that FLMs in SMEs perform a unique and a valuable role.There has been some concern about the extent to which models and practices of supervisory management are capable of being transferred from one country to another. The UK and China have evolved supervisory management styles and systems which are rooted in their respective social, economic and political circumstances but which are now being shaped increasingly by external, international and global patterns, trends and models. The study revealed there was a surprising degree of consistency in certain aspect of the FLM role in both countries. In particular, responsibility for 'organising and managing' was perceived as the core element ·of the FLM role. Differences were reviewed in how this core role was delivered in the two countries. For example, FLMs in the UK favoured a team working approach which was not adopted to the same degree by their Chinese counterparts. Other examples of differences included greater involvement and responsibility for financial matters in China than in the UK. These and other examples arise from different social, cultural and political circumstances and help illuminate the detail differences in both countries. In conclusion, the influence of international and global trends is likely to reduce the level of difference in the future. Summarising the FLM role in the SME, the research suggests that the FLMs are both co-ordinators and human relations engineers.

Realistic four-dimensional model building from string theory has been a focus of the string theory community ever since its inception. Toroidal orientifold constructions have emerged as a technically simple class of candidate models. Novel ingredients, such as background fluxes, have been discovered and intensely studied over the past few years. They allow for a (partial) solution of several long standing problems associated with model building in this framework. In this thesis, I summarize progress that has been made in toroidal orientifold constructions in type IIA string theory.This includes a detailed discussion of moduli stabilization and (non-) supersymmetric AdS and Minkowski vacua. Furthermore I commence a systematic study of generalized NSNS, i.e., metric and non-geometric, fluxes. The emergence of novel D-terms is presented in detail. While most of the discussion applies to generic orientifolds of T⁶, most features are exemplified by and studied in terms of a certain orientifold of T⁶/ℤ₄ owing to its somewhat richer structure compared to simpler models studied before. It is also briefly reported on efforts of finding de Sitter vacua and inflation in this class of models. / text

By formulating the six dimensional (0,2) superconformal field theory X[j] on a Riemann surface decorated with certain codimension two defects, a multitude of four dimensional N=2 supersymmetric field theories can be constructed. In this dissertation, various aspects of this construction are investigated in detail for j=A,D,E. This includes, in particular, an exposition of the various partial descriptions of the codimension two defects that become available under dimensional reductions and the relationships between them. Also investigated is a particular observable of this class of four dimensional theories, namely the partition function on the four sphere and its relationship to correlation functions in a class of two dimensional non-rational conformal field theories called Toda theories. It is pointed out that the scale factor that captures the Euler anomaly of the four dimensional theory has an interpretation in the two dimensional language, thereby adding one of the basic observables of the 4d theory to the 4d/2d dictionary. / text

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A theory is presented which describes the global reflection and transmission characteristics of a self-focused channel propagating at an oblique angle of incidence to an interface separating two or more self-focusing nonlinear dielectric media. A complete characterization of the different behavior of the channel is given in the proper parameter space. In the dominant region, the nonlinear wavepacket representing the self-focused channel is represented as an equivalent particle moving in an equivalent potential. The dynamics of the particle is described by Newton's equations of motion, with the asymptotic propagation paths of the channel being read off from the associated phase planes of the equivalent potential. This theory provides therefore, the nonlinear Snell's Laws of refleciton or transmission since the particle dynamics gives the critical angle of total reflection and in the case of transmission, the corresponding angle of transmission. This theory also gives the stability characteristics of nonlinear surface waves, which had only been partially established in the past through numerical simulations. Finally, some applications of the theory are presented such as the design of an all-optical power adjustable spatial scanning element and an all optical switch. Extensions of the theory to waveguides with multiple interfaces are also given and possible new directions are also suggested.

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