Kinematic Self-Similar Solutions of Locally Rotationally Symmetric Spacetimes

This paper contains locally rotationally symmetric kinematic self-similar perfect fluid and dust solutions. We consider three families of metrics which admit kinematic self-similar vectors of the first, second, zeroth and infinite kinds, not only for the tilted fluid case but also for the parallel and orthogonal cases. It is found that the orthogonal case gives contradiction both in perfect fluid and dust cases for all the three metrics while the tilted case reduces to the parallel case in both perfect fluid and dust cases for the second metric. The remaining cases give self-similar solutions of different kinds. We obtain a total of seventeen independent solutions out of which two are vacuum. The third metric yields contradiction in all the cases.Comment: 17 pages, accepted for publication Brazilian J. Physic

On the Capacity Region of Multi-Antenna Gaussian Broadcast Channels with Estimation Error

In this paper we consider the effect of channel estimation error on the capacity region of MIMO Gaussian broadcast channels. It is assumed that the receivers and the transmitter have (the same) estimates of the channel coefficients (i.e., the feedback channel is noiseless). We obtain an achievable rate region based on the dirty paper coding scheme. We show that this region is given by the capacity region of a dual multi-access channel with a noise covariance that depends on the transmit power. We explore this duality to give the asymptotic behavior of the sum-rate for a system with a large number of user, i.e., n rarr infin. It is shown that as long as the estimation error is of fixed (w.r.t n) variance, the sum-capacity is of order M log log n, where M is the number of antennas deployed at the transmitter. We further obtain the sum-rate loss due to the estimation error. Finally, we consider a training-based scheme for block fading MISO Gaussian broadcast channels. We find the optimum length of the training interval as well as the optimum power used for training in order to maximize the achievable sum-rate

Knowledge representation within information systems in manufacturing environments

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Representing knowledge as information content alone is insufficient in providing us with an understanding of the world around us. A combination of context as well as reasoning of the information content is fundamental to representing knowledge in an information system. Knowledge Representation is typically concerned with providing structures and theories that are used as a basis for intelligent reasoning. For this research however, the author defines an alternative meaning, which is related to how knowledge is used in a given context. Thus, this dissertation provides a contribution to the field of knowledge within information systems, in terms of the development of a frame-of-reference that will support the reader in navigating through the different forms of explicit and tacit knowledge use within the manufacturing industry. In doing so, the dissertation also presents the generation of a novel classification of three forms of knowledge (Structural, Interpretive and Evaluative forms); the development of a conceptual framework which highlights the drivers for knowledge transformation; and the development of a conceptual model which seeks to envelop both the content as well as the context of knowledge (Semiotic as well as Symbiotic factors). This is established through the use of an Empirical, Quantitative case study approach, that seeks to explore an interpretivist view of knowledge representation within two information systems contexts, within two UK manufacturing organisations. The first case study presents how a-priori knowledge assumptions are used in a computer aided engineering decision-making task within a high technology manufacturing company. The second case study shows how knowledge is used within the IT/IS investment evaluation decision making process, within a manufacturing SME. In doing so, both case studies attempt to elucidate the inherent, underlying relationship between explicit and tacit knowledge, via a frame-of-reference developed by the author which defines key drivers for knowledge transformation

Neural and Evolutionary Computing in Finite Element Analysis

This paper presents a discussion of current neural and evolutionary techniques, applied to the field of Finite Element Analysis and Finite Element Mesh Generation. This numerical method is widely used in many science, and engineering analyses to compute many forms of static and dynamic fields and potentials, such as heat, stress or velocity, on a mesh of interconnecting elements. The accuracy of the underlying finite element mesh determines the magnitude of the error of the solution to the differential equations. Meshes have to be adapted to limit this as far as possible, usually in an a-posteriori sense. These techniques have been widely automated and used with great success, but no means yet exist which allow the efficient a-priori evaluation of a prospective finite element mesh before the equations are to be solved. As such, the application of expert and heuristic knowledge is largely required to produce visible benefits from adaptive remeshing processes. This paper discusses how neural and evolutionary architectures have addressed this problem and presents a complementary evolutionary model, which may aid in the generation of finite element meshes, as a result of on-going research into the development of such \u27intelligent\u27 techniques

Information technology and performance management for build-to-order supply chains

En las siguientes líneas se plantea un artículo de reflexión que tiene en cuenta parte del marco teórico que sustenta la investigación titulada “Prácticas pedagógicas que promueven la competencia argumentativa escrita (CAE) en niños campesinos de los grados 4° y 5° del Centro Educativo Municipal La Caldera, Sede Principal de Pasto”, desarrollada en el año 2012. En él se contemplan los aportes de las ciencias del lenguaje y la comunicación, la teoría de la argumentación, la didáctica de la lengua escrita y los géneros discursivos, que dan cuenta de la necesidad de desarrollar la capacidad crítica en los estudiantes a través de la argumentación, lo cual implica transformar las prácticas pedagógicas para que se alejen de la transmisión de conocimientos y den paso a la comunicación, para que la palabra escrita sea apropiada de manera significativa

Sustainable food security futures: Perspectives on food waste and information across the food supply chain

YesThe purpose of this paper is to signpost the genesis of food security and associated factors such that organisations, enterprises, policy makers and interested stakeholders can seek to explore and understand this important societal issue. The challenges that food security poses are eclectic in nature and cut through country, society, organisation and individual boundaries. Only through identifying these factors – hence identifying underlying factors of food waste and usage of information within food supply chains to untangle them – can we adopt enterprise interventions in order to initiate and mitigate food security risk. As a viewpoint piece, there is no empirical work to report in this paper. An exploratory review of the literature has allowed for the extraction of food security concerns that need the attention of stakeholders across the enterprise to ensure robust food supply chains can be are created, maintained and sustained through a better understanding and usage of information, knowledge and data This paper articulates six constructs that underpin the challenges of establishing food security. It is suggested that information relating to factors may support decision-makers within communities, organisations and enterprises to better understand these factors that then contribute towards enhanced food security. Relevant strategies or policies can then emerge and be developed such that strategic as well as operational interventions can be prioritised across national, regional or industry level. Underpinning the above, the waste within and across the food supply chain contributes to the six factors, also highlighting where additional focus may need to be applied to sustain food supply chains. This paper is a position paper that does not offer factual insight but rather highlights a direction of thought that others can consider exploring as part of wider research agendas in the topical area where enterprise, organisational, and information-based contributions may support the development of strategy-led food security policy. This paper provides reassuring insights that will help decision and policy makers assemble their thoughts when it comes to prioritising their communications and interventions amongst organisational/enterprise-level stakeholder groups involved in food security and food supply chain contexts. This paper has highlighted the need for more research around the human and organisational factors that are identified as both underpinning the need for food security and, as drivers of waste throughout the food supply chain. Indeed, there is further work needed to highlight the inter-relationships that exist and, which then feed into resulting interventions. To raise the importance of food security amongst differing stakeholder community groups at the organisational and enterprise level

Is broadcast plus multiaccess optimal for Gaussian wireless networks?

In this paper we show that "separation"-based approaches in wireless networks do not necessarily give good performance in terms of the capacity of the network. Therefore in optimal design of a wireless network, its total structure should be considered. In other words, achieving capacity on the subnetworks of a wireless network does not guarantee globally achieving capacity. We will illustrate this fact by considering some examples of multistage Gaussian wireless relay networks. We will consider a wireless Gaussian relay network with one stage in both fading and nonfading environment. We show that as the number of relay nodes, n, grows large, the capacity of this network scales like log n. We then show that with the "separation"-based scheme, in which the network is viewed as the concatenation of a broadcast and a multiaccess network, the achievable rate scales as log log n and as a constant for fading and nonfading environment, respectively, which is clearly suboptimal

User Adoption of a CRM-based Information System Within a Financial Services Organization: An Empirical Analysis

Financial Services firms require processes and systems which can support and maintain customer-related information for the purposes of core business-focussed activity. Specifically within the investment banking sector, the importance and criticality of such customer information underpins the firm’s ability to transact sales, trading and other advisory-based services in an efficient and relevant manner. The design and development of Customer Relationship Management (CRM) systems to address the given external vs. internal customer information touchpoints, therefore provides a vital link between financial services professionals, client data and business processes. In doing so, the input of CRM user requirements is a key step in deriving benefit from such a technology solution. This paper henceforth identifies and details user requirements and experiences of such an information system within a case study company and highlights pertinent issues for the adoption of such systems within the given sector