Gas distribution in shallow large diameter packed beds

It is important to maintain a uniform distribution of gas and liquid in large diameter packed columns to maintain mass transfer efficiency on scaling up. This work presents measurements and methods of evaluating maldistributed gas flow in packed columns. Little or no previous work has been done in this field. A gas maldistribution number, F, was defined, based on point to point velocity variations in the gas emerging from the top of packed beds. f has a minimum value for a uniformly distributed flow and much larger values for maldistributed flows. A method of testing the quality of vapour distributors is proposed, based on "the variation of f with packed height. A good gas distributor requires a short packed depth to give a good gas distribution. Measurements of gas maldistribution have shown that the principle of dynamic similarity is satisfied if two geometrically similar beds are operated at the same Reynold's number. The validity of f as a good measure of gas maldistribution, and the principle of dynamic similarity are tested statistically by Multi-Factor Analysis of the variance, and visually by the response "surfaces technique. Pressure distribution has been measured in a model of a large diameter packed bed, and shown to be associated with the velocity of the gas in a tangential feed pipe. Two simplified theoretical models are proposed to describe the flow of gases through packed beds and to support the principle of dynamic similarity. These models explain why the packed bed itself causes the flow of gas to become more uniformly distributed. A 1.2m. diameter scaled-down model was constructed geometrically similar to a 7.3m. diameter vacuum crude distillation column. The previously known internal cylinder gas distributor was tested. Three new distributors suitable for use in a large diameter column were developed and tested, these are: Internal Cylinder with Slots and Cross Baffles, Internal Cylinder with Guides in the Annulus, Internal Cylinder with Internal Cross Baffles - It has been shown that this is an excellent distributor.

From cardinal spline wavelet bases to highly coherent dictionaries

Wavelet families arise by scaling and translations of a prototype function, called the mother wavelet. The construction of wavelet bases for cardinal spline spaces is generally carried out within the multi-resolution analysis scheme. Thus, the usual way of increasing the dimension of the multi-resolution subspaces is by augmenting the scaling factor. We show here that, when working on a compact interval, the identical effect can be achieved without changing the wavelet scale but reducing the translation parameter. By such a procedure we generate a redundant frame, called a dictionary, spanning the same spaces as a wavelet basis but with wavelets of broader support. We characterize the correlation of the dictionary elements by measuring their 'coherence' and produce examples illustrating the relevance of highly coherent dictionaries to problems of sparse signal representation.

Intra-cavity dynamics in high power mode-locked fiber lasers

A theoretical model allows for the characterization and optimization of the intra-cavity pulse evolutions in high-power fiber lasers. Multi-parameter analysis of laser performance can be made at a fraction of the computational cost.

An exploration of female leadership language:case studies of senior women in Bahrain

This is a multiple case study of the leadership language of three senior women working in a large corporation in Bahrain. The study’s main aim is to explore the linguistic practices the women leaders use with their colleagues and subordinates in corporate meetings. Adopting a Foucauldian (1972) notion of ‘discourses’ as social practices and a view of gender as socially constructed and discursively performed (Butler 1990), this research aims to unveil the competing discourses which may shape the leadership language of senior women in their communities of practice. The research is situated within the broader field of Sociolinguistics and the specific field of Language and Gender. To address the research aim, a case study approach incorporating multiple methods of qualitative data collection (observation, interviews, and shadowing) was utilised to gather information about the three women leaders and produce a rich description of their use of language in and out of meeting contexts. For analysis, principles of Qualitative Data Analysis (QDA) were used to organise and sort the large amount of data. Also, Feminist Post- Structuralist Discourse Analysis (FPDA) was adopted to produce a multi-faceted analysis of the subjects, their language leadership, power relations, and competing discourses in the context. It was found that the three senior women enact leadership differently making variable use of a repertoire of conventionally masculine and feminine linguistic practices. However, they all appear to have limited language resources and even more limiting subject positions; and they all have to exercise considerable linguistic expertise to police and modify their language in order to avoid the ‘double bind’. Yet, the extent of this limitation and constraints depends on the community of practice with its prevailing discourses, which appear to have their roots in Islamic and cultural practices as well as some Western influences acquired throughout the company’s history. It is concluded that it may be particularly challenging for Middle Eastern women to achieve any degree of equality with men in the workplace because discourses of Gender difference lie at the core of Islamic teaching and ideology.

Solar thermal collectors for use in hybrid solar-biomass power plants in India

This thesis examined solar thermal collectors for use in alternative hybrid solar-biomass power plant applications in Gujarat, India. Following a preliminary review, the cost-effective selection and design of the solar thermal field were identified as critical factors underlying the success of hybrid plants. Consequently, the existing solar thermal technologies were reviewed and ranked for use in India by means of a multi-criteria decision-making method, the Analytical Hierarchy Process (AHP). Informed by the outcome of the AHP, the thesis went on to pursue the Linear Fresnel Reflector (LFR), the design of which was optimised with the help of ray-tracing. To further enhance collector performance, LFR concepts incorporating novel mirror spacing and drive mechanisms were evaluated. Subsequently, a new variant, termed the Elevation Linear Fresnel Reflector (ELFR) was designed, constructed and tested at Aston University, UK, therefore allowing theoretical models for the performance of a solar thermal field to be verified. Based on the resulting characteristics of the LFR, and data gathered for the other hybrid system components, models of hybrid LFR- and ELFR-biomass power plants were developed and analysed in TRNSYS®. The techno-economic and environmental consequences of varying the size of the solar field in relation to the total plant capacity were modelled for a series of case studies to evaluate different applications: tri-generation (electricity, ice and heat), electricity-only generation, and process heat. The case studies also encompassed varying site locations, capacities, operational conditions and financial situations. In the case of a hybrid tri-generation plant in Gujarat, it was recommended to use an LFR solar thermal field of 14,000 m2 aperture with a 3 tonne biomass boiler, generating 815 MWh per annum of electricity for nearby villages and 12,450 tonnes of ice per annum for local fisheries and food industries. However, at the expense of a 0.3 ¢/kWh increase in levelised energy costs, the ELFR increased saving of biomass (100 t/a) and land (9 ha/a). For solar thermal applications in areas with high land cost, the ELFR reduced levelised energy costs. It was determined that off-grid hybrid plants for tri-generation were the most feasible application in India. Whereas biomass-only plants were found to be more economically viable, it was concluded that hybrid systems will soon become cost competitive and can considerably improve current energy security and biomass supply chain issues in India.

Strategic logistics outsourcing: an integrated QFD and AHP approach

Third-party logistics service providers (3PLs) play a vital role in contemporary supply chain management. Evaluation and selection of the right 3PLs depends on a wide range of quantitative and qualitative criteria rather than cost-based factors. Although various multi-criteria decision making approaches have been proposed, they have not considered the impact of business objectives and requirements of company stakeholders on the evaluating criteria. To enable the "voice" of company stakeholders is considered, this paper develops an integrated approach for selecting 3PL strategically. In the approach, multiple evaluating criteria are derived from the requirements of company stakeholders using a series of house of quality (HOQ). The importance of evaluating criteria is prioritized with respect to the degree of achieving the stakeholder requirements using analytic hierarchy process (AHP). Based on the ranked criteria, alternative 3PLs are evaluated and compared with each other using AHP again to make an optimal selection.

Strategic sourcing in the UK bioenergy industry

Successful supply chain management requires the management of a complex, multi-stakeholder, multi-criteria system. Stakeholder inclusion in the supply chain design and decision making processes is an area of growing interest for companies looking to design sustainable supply chains or produce sustainable products. This paper demonstrates the use of the integrated quality function deployment and analytic hierarchy process (QFD-AHP) method for the inclusion of a wide group of stakeholder requirements into the supplier selection process. The method provides a weighted ranked list of evaluating criteria which can be used to assess potential suppliers in the UK renewable bioenergy industry. The bioenergy industry is suitable as there are many stakeholders placing various requirements upon potential biomass suppliers. The paper uses a mixture of literature review and semi-structured industry interviews to answer three research questions: which stakeholder groups are important when selecting biomass suppliers for the UK? What requirements are made by these stakeholders on the supply of biomass fuels and feedstocks? Which evaluating criteria are most important? © 2013 Elsevier B.V.

Intra-cavity dynamics in high power mode-locked fiber lasers

A theoretical model allows for the characterization and optimization of the intra-cavity pulse evolutions in high-power fiber lasers. Multi-parameter analysis of laser performance can be made at a fraction of the computational cost. © 2010 Optical Society of America.

Religious compliance in Islamic financial institutions

The central goal of this research is to explore the approach of the Islamic banking industry in defining and implementing religious compliance at regulatory, institutional, and individual level within the Islamic Banking and Finance (IBF) industry. It also examines the discrepancies, ambiguities and paradoxes that are exhibited in the individual and institutional behaviour in relation to the infusion and enactment of religious exigencies into compliance processes in IBF. Through the combined lenses of institutional work and a sensemaking perspective, this research portrays the practice of infusion of Islamic law in Islamic banks as being ambiguous and drifting down to the institutional and actor levels. In instances of both well-codified and non-codified regulatory frameworks for Shariah compliance, institutional rules ambiguity, rules interpretation and enactment ambiguities were found to be prevalent. The individual IBF professionals performed retrospective and prospective actions to adjust the role and rules boundaries both in the case of a Muslim and a non-Muslim country. The sensitizing concept of religious compliance is the primary theoretical contribution of this research and provides a tool to understand the nature of what constitutes Shariah compliance and the dynamics of its implementation. It helps to explain the empirical consequences of the lack of a clear definition of Shariah compliance in the regulatory frameworks and standards available for the industry. It also addresses the calls to have a clear reference on what constitute Shariah compliance in IBF as proposed in previous studies (Hayat, Butter, & Kock, 2013; Maurer, 2003, 2012; Pitluck, 2012). The methodological and theoretical perspective of this research are unique in the use of multi-level analysis and approaches that blend micro and macro perspectives of the research field, to illuminate and provide a more complete picture of religious compliance infusion and enactment in IBF.