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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Intelligent PID controller based on fuzzy logic control and neural network technology for indoor environment quality improvement

Song, Yang January 2014 (has links)
The demand for better indoor environment has led to a wide use of heating, ventilating and air conditioning (HVAC) systems. Employing advanced HVAC control strategies is one of the strategies to maintain high quality indoor thermal comfort and indoor air quality (IAQ). This thesis aims to analyse and discuss the potential of using advanced control methods to improve the indoor occupants’ comfort. It focuses on the development of controllers of the major factors of indoor environment quality in buildings including indoor air temperature, indoor humidity and indoor air quality. Studies of the development of control technologies for HVAC systems are reviewed firstly. The problems in existing and future perspectives on HVAC control systems for occupants’ comfort are investigated. As both the current conventional and intelligent controllers have drawbacks that limit their applications, it is necessary to design novel control strategies for the urgent issue of indoor climate improvement. Hence, a concept of designing the controllers for indoor occupants’ comfort is proposed in this thesis. The proposed controllers in this research are designed by combining the conventional and intelligent control technologies. The purpose is to optimize the advantages of both conventional and intelligent control methods and to avoid poor control performance due to their drawbacks. The main control technologies involved in this research are fuzzy logic control (FLC), proportional-integral-derivative (PID) control and neural network (NN). Three controllers are designed by combining these technologies. Firstly, the fuzzy-PID controller is developed for improvement of indoor environment quality including temperature, humidity and indoor air quality. The control algorithm is introduced in detail in Section 3.2. The computer simulation is carried out to verify its control performance and potential of indoor comfort improvement in Section 4.1. Step signal is used as the input reference in simulation and the controller shows fast response speed since the time constant is 0.033s and settling time is 0.092s with sampling interval of 0.001s. The simulating result also proves that the fuzzy-PID controller has good control accuracy and stability since the overshot and steady state error is zero. In addition, the experimental investigation was also carried out to indicate the fuzzy-PID control performance of indoor temperature, humidity and CO2 control as introduced in Chapter 5. The experiments are taken place in an environmental chamber used to simulated the indoor space during a wide period from late fall to early spring. The results of temperature control show that the temperature is controlled to be varying around the set-point and control accuracy is 4.4%. The humidity control shows similar results that the control accuracy is 3.2%. For the IAQ control the maximum indoor concentration is kept lower than 1100ppm which is acceptable and health CO2 level although it is slightly higher than the set-point of 1000ppm. The experimental results show that the proposed fuzzy-PID controller is able to improve indoor environment quality. A radial basis function neural network (RBFNN) PID controller is designed for humidity control and a back propagation neural network (BPNN) PID controller is designed for indoor air quality control. Then, in order to further analyze the potential of using advanced control technologies to improve indoor environment quality, two more controllers are developed in this research. A radial basis function neural network (RBFNN) PID controller is designed for humidity control and a back propagation neural network (BPNN) PID controller is designed for indoor air quality control. Their control algorithms are developed and introduced in Section 3.3 and Section 3.4. Simulating tests were carried out in order to verify their control performances using Matlab in Section 4.2 and Section 4.3. The step signal is used as the input and the sampling interval is 0.001s. For RBFNN-PID controller, the time constant is 0.002s, and there is no overshot and steady state error. For BPNN-PID controller, the time constant is 0.003s, the overshot percentage is 4.2% and the steady state error is zero based on the simulating results. Simulating results show that the RBFNN-PID controller and BPNN-PID controller have fast control speed, good control accuracy and stability. The experimental investigations of the RBFNN-PID controller and BPNN-PID control are not included in this research and will carried out in future work. Based on the simulating and experimental results shown in this thesis, the indoor environment quality improvement can be guaranteed by the proposed controllers.
122

Technological innovation systems : the case of hydrogen from waste

Baxter, Jenifer January 2013 (has links)
Actor characterisation using Q methodology and three case study investigations of regional technological innovation systems using novel interaction matrices. This thesis addresses regional aspects of the technological field of hydrogen production from waste. It develops the characterisation of experts involved in the innovation of hydrogen from waste technologies through the use of Q methodology; and a new model (IM-TIS) for the analysis of technological innovation systems. The literature review revealed that the sustainable production of hydrogen from waste processes was not well represented. Truffer et al. (2012) identified a need to further investigate the relationships between functions of innovation and how a technological innovation system may change over time. This was reflected in other innovation and transitions literature. Q methodology revealed three different group identities associated with actors involved in the technological innovation system for hydrogen from waste. These identities are, Hydrogen from Waste Advocates, Cautionary Environmentalists and Hydrogen Technologists. The IM-TIS model developed for this research was applied to three case study regions in the field of hydrogen production from waste in the UK. The model is an adaptation of two existing conceptual models, Rock Engineering Systems (RES) and Functions of Innovation. The thesis identifies and reports on the characteristics of groups of experts involved in hydrogen production from waste and their potential importance. The application of IM-TIS to the three regional case studies of Tees Valley, London and South Wales is presented. A further application of the IM-TIS model using pathway analysis is applied to the case study region of London and results are presented in a worked example. This is the first time a model of this type has been applied to technological innovation system case studies in the UK. It is also the first time a variation of the RES model has been applied in the ways presented in this thesis. The new model provides the opportunity to examine the relationships between functions of innovation and identify what may change within the system over time. It is concluded that the IM-TIS model offers an analysis tool for technological innovation systems that can incorporate the relationships and interactions that occur within the system in a non-linear fashion. Evidence from the research suggests that these interactions have not been adequately addressed in previous studies. A further conclusion is that by addressing the production of hydrogen from waste using these methods, hydrogen technologies are shown to be still in an emergent state.
123

Effect of gypsum on the hydro-mechanical characteristics of partially saturated sandy soil

Ahmed, Khalid Ibrahim January 2013 (has links)
Gypsum rich soils are of wide occurrence in the Middle East. They cover large areas of Iraq. Gypsum is one of the moderately soluble salts that can have significant effect on the engineering properties of soils. The effect of gypsum content and the stress state on the main hydraulic functions, volume change, shear strength and deformation characteristics of unsaturated silty clayey sand were experimentally examined. Statically compacted specimens of synthetic sand-gypsum mixtures were used. A new stress controllable pressure plate device was developed. The modified device was used to establish simultaneously both the stress-dependent soil-water characteristic curves (SD-SWCCs) and the stress-dependent hydraulic conductivity functions (SD-HCFs) during drying and wetting paths. The test results revealed that the parameters of the drying SWCC such as the water holding capacity, the air-entry suction, the air-entry water content, and the residual suction are clearly increased with increasing gypsum content. Same effect of gypsum was noticed on the wetting SWCC parameters. A clear decrease in saturated water content, desorption rate, absorption rate, and water holding capacity with increasing the applied net normal stress was noticed. Transient outflow methods were used to measure the SD-HCFs. An increase in the SD-HCFs with increasing gypsum content was found. Clear hysteresis effects on k(ψ) and minor hysteresis on k(w) were noticed. It was found that the outflow methods can be applicable between the air-entry suction and residual suction only. Direct shear tests were carried out on saturated and unsaturated specimens. The unsaturated specimens were air-dried and tested under constant water content conditions. Matric suction values were evaluated by incorporating the SD-SWCC test results. The friction angle related to matric suction (b), the effective stress parameter (χ), and the suction stress (s′) were found clearly decrease with increasing gypsum content and with increasing the net normal stress level. However, test results of saturated specimens revealed that the effective shear strength parameters (′, c′) are noticeably increased with increasing gypsum content in the soil mixture.
124

The effects of powerboat emissions on the water quality of Loch Lomond

Bannan, Mark January 1999 (has links)
Recently, there has been increased concern about the potential impact of powerboating on freshwater ecosystems. In the case of Loch Lomond, such concern led to the commencement of a programme of boat counting surveys in 1989. In these surveys, it was found that maximum boat numbers are increasing in Loch Lomond. As a logical progression from these surveys, the present study examined the impact of powerboat chemical pollution on the water quality of Loch Lomond. In the first stage of this study, the scale of powerboat pollution was assessed. This was achieved by constructing a simple mathematical model to estimate the total annual discharge of hydrocarbons (HCs) from powerboat emissions into Loch Lomond. By using boat census data and published information about the emission rates of different types of powerboat engines, the total annual input for Loch Lomond was estimated at 25.50 tonnes in 1989 and this input has greatly increased since then. This indicates that there is real potential for hydrocarbon (HC) pollution of Loch Lomond from powerboat operation. Most of the HC material discharged emanated from speedboats powered by outboard motors. To identify and quantify HC pollutant compounds entering water from outboard engines, Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed on water subject to a controlled pollution discharge from an outboard motor. Altogether, 47 compounds were detected in this exhaust-polluted water (EPW), with most of these being volatile aromatic HCs, such as benzene and alkylated benzenes. Water samples were also taken from three sites in Loch Lomond on two occasions: once in winter, during negligible boat activity and once in summer, at a time of high powerboat activity. No HCs were detected in winter, but some volatile aromatic HC compounds were clearly detectable in summer. These compounds were the same as those most abundant in EPW and found in similar relative proportions. Further experiments in this study involved the analysis of a large number of water samples. To enable this, it was necessary to develop an appropriate new method for the analysis of powerboat exhaust pollutants, which are mostly aromatic HC. All aromatic HCs fluoresce and the new method involved fluorescence spectroscopy analysis, following sample purification by normal-phase column chromatography. This technique is non-destructive allowing subsequent confirmatory analysis by GC-MS. It was found that the new method was fast, precise, highly sensitive and specific to volatile aromatic HCs. The capability of measuring HCs in a large number of samples allowed previously unfeasible experiments investigating: 1) The geographical distribution of powerboat exhaust HCs in Loch Lomond. 2) The depth profile of powerboat exhaust pollutants in the top 1.5 m of the water column. 3) Recovery of water quality, following peak weekend boat activity in summer. It was found that: 1) Volatile aromatic HCs from powerboat exhaust are detectable over much of Loch Lomond on days of heavy powerboat activity, with concentrations of up to 37 ug.l" occurring. 2) Pollutant HCs are found at depths of at least 1.5 m, and are not confined to the surface microlayer (100 urn), The HC distribution with depth was mostly uniform in the field and this was confirmed in controlled experiments in a tank. 3) Recovery of water quality was difficult to demonstrate in the field, possibly as pollution incidents occur continually during summer. 4) HC concentration declined in controlled experiments, in which water was subjected by a controlled pollution discharge from an outboard motor. The time taken for the HC concentration to reach 50 % of the initial HC loading varied but was approximately 7 - 9 days. The toxicity of EPW was investigated by performing 24 hour LC50 (Lethal Concentration for 50 % of test organisms) tests, using the water flea, Daphnia magna (an international standard test organism). The mean LC50 recorded in this study, expressed as the total concentrations ofHC compounds, was 3.72 mg.l". Previous studies suggest that multiplying the Le50 for D. magna by an application factor of 0.001 gives an approximate safe level of a pollutant. Using data collected in this study, a safe level of exhaust He compounds of 3.72 Jlg.r1 would result. In summer, during times of high powerboat activity, such levels are exceeded at many locations in Loch Lomond. The current study has shown that He pollution from a relatively small number of inefficient powered recreational craft using Loch Lomond poses a potential threat to the maintenance of water quality.
125

Accelerated carbonation of municipal solid waste incineration residues

Li, Xiaomin January 2008 (has links)
Incineration can reduce the mass and volume of municipal waste significantly but produces solid waste in the form of bottom ash and air pollution control (APC) residues. Landfill is currently the most commonly used disposal option for these ash residues, however, the impact of hazardous compounds in these wastes on the environment during landfilling is becoming more widely appreciated and cheaper, alternative, management options need to be explored. In this research, the treatment of these municipal solid waste incinerator (MSWI) residues by accelerated carbonation is investigated and compared with naturally aged ashes. Both bottom ash and APC residues were carbonated in an atmosphere composed of gaseous CO2. It was found that the carbonation of calcium oxides/hydroxides resulted in the rapid formation of calcium carbonate and that silicate compounds were hydrated. The reduction of pH from 12-12.5 to 7-9 observed upon carbonation was associated with a reduction in availability of soluble salts and meals. Carbonated ash had a higher buffering capacity to acid attack when compared to the untreated, non-carbonated, ash. The bottom and APC ashes sequestrated between 6% and 13% CO2 (w/w dry weight), respectively upon carbonation; and this may be important where the reduction of greenhouse emissions to the atmosphere is concerned.
126

Industrial toxic waste and health : a practical case study

Eizagguirre-Garcia, Domingo January 1996 (has links)
The objective of this thesis is to develop a standard, simple methodology for the assessment of health in areas near sources of pollution. This methodology should make use of readily available data and computing facilities. A literature review on previous studies on the subject was carried out in order to draw from existing experience. A total of twenty-five studies on health near sources of pollution were reviewed. These studies were carried out between 1982 and 1991, most of them in Britain, two in France. The types of pollution sources studied ranged from waste dumps to incinerators, to nuclear power stations. Each study was described, stressing on their respective backgrounds, building on geographical (study) areas, data, analysis and results. Brief synopses of the studies were next grouped, according to those using conventional epidemiological methods and more innovative ones. Finally, it was concluded from the review that the methodology intended should be descriptive, making use of routinely collected data, with a study area based on small geographical divisions (small areas) and taking into account socio-economic differences over its study area. In the absence of accurate data on pollution levels, and from the previous experience of one of the studies reviewed, circular study areas centred on the source of pollution and subdivided into rings were used, with distance of each ring to the centre as a proxy indicator of levels of pollution. The new methodology was found valid and the objective of the study was met. It compared favourably with previously reviewed methodologies. The methodology is intended to be used as a descriptive, exploratory tool, whose findings may warrant further analytic studies, which the method is not designed to, and can not, replace. The use of routinely collected data greatly facilitated the study, although caveats for future studies exist on them. Distance as a surrogate for exposure is seen as a simplistic approach, but in the absence of reliable exposure data it is a useful one. Standardization by Deprivation category has also been found useful to account for factors for which little data exist.
127

Effects of pure and impure carbon dioxide (CO2) on soil chemistry

Wei, Yang January 2013 (has links)
A cleaner use of fossil fuels supported by Carbon Capture and Storage (CCS) techniques is considered to be one of the main short-term strategies for addressing the global climate change problem. However, potential CO2 or CO2/SO2 seepage during some of the phases of a CCS project not only reduces its performing efficiency, but also impacts the local environment, which could have further impacts on human health. It is therefore essential to assess the potential risks and provide evidence that the impacts are well understood. Moreover, studying the effects of CO2 leakage is useful for identifying monitoring parameters if the leakage does happen, leading to the development of new approaches in detecting CO2 leaks. Accordingly, this research is carried out to assess the relevant impacts on the local environment of CO2 leakage, focusing on the environmental impacts caused by CO2 seepage associated with various soil types, mostly on the soil geochemical changes, which is currently lacked. As a cost effective approach, this research was carried out with two types of well controlled laboratory experiments: Stage I- Closed reactor experiments and Stage II- A flow through column system (designed by the author). As a supplementary study to the research of the ASGARD site, Stage I experiments were carried out with soil samples collected from the ASGARD site and gave directions for Stage II column system design. Stage II experiments were carried out with two contrasting mono-mineral sediments considering sensitivity to CO2 gas, Trucal 5 and Trucal 6 (limestone sand of different particle size) and silica sand. Certain limitations of this research have to be considered. Firstly, highly idealised samples were used in the experiments instead of true soils and there was no heterogeneity in the samples used, which is not representative of the full complexity of a natural system. Secondly, the scale limitation of the laboratory work would lead to a higher gas/mineral ratio compared with field conditions. Therefore, results from the laboratory work cannot simply represent all the soils in the field, except the specific soil related problem and the results are better to be used to demonstrate the conditions where the soils/sediments are surrounded by high levels of CO2, such as the ones nearby a leaking injection well or along a fracture/fault. Nevertheless, this study is believed to provide a step towards understanding the potential impacts of CO2 seepage in soil, and potentially to be useful as a mean of identifying indicators of related problems when applying to the full-scale design, leading to the development of new approaches in detecting CO2 leaks. Throughout the experiments, the experimental apparatus (the continuous column system) newly designed by the author was run successfully, providing an alternative way in respect to the majority of soil-column studies for assessing issues of CO2 seepage. The main impact of CO2 emissions on soil properties is to drop the pH which triggers metals mobilisation from soils (all within safety limits to plant growth). The change of pH associated with both limestone and silica sand indicates that pH is an excellent parameter to indicate the CO2 intrusion into sediments once the background is set. The response of calcium (Ca) to CO2 flux highlights that carbonate minerals are sensitive to CO2 increase and could possibly be used as a parameter to monitor CO2 leakage once the baseline for the pre-injection concentration is set.
128

The integrated design of new build multi vector energy supply schemes

Rees, Marc January 2012 (has links)
Future energy supply infrastructure schemes for the built environment are set to consist of a diverse mix of distributed generation technologies, increasingly stringent local emissions reduction targets, and potentially complex ownership structures. This thesis presents a new modelling method that integrates technical design, green house gas emissions analysis and financial analysis models for new build multi energy vector systems. The model was used to compare and characterise several alternative heating technology options for the carbon constrained design of a generic UK market town residential development. Of the options examined, natural gas combined heat and power based district heating was shown to provide the least cost solution for projects built before 2020. Beyond 2025, electric heat pumps provided the cheapest option in response to the decarbonisation of the grid supplied electricity. The integrated model was used as the basis of an optimised infrastructure design tool. This was applied to determine the least cost energy supply technology mix for a new build community redevelopment scheme at Ebbw Vale, South Wales. It was shown that both the optimal design and corresponding optimal cost is dependent upon the year of build completion for the project and the
129

Improving urban water quality for livelihoods enhancement in the Odaw-Korle river catchment of Accra, Ghana

Abraham, Ernest Mensah January 2011 (has links)
Water and environmental resources which provide opportunities for households are threatened by human activities that leads to pollution. The research objectives were to understand the contribution water makes to the livelihoods of urban and peri-urban households; the factors influencing perceptions, attitudes and behaviour in relation to surface water and environmental quality, and measures for promoting community participation in water and environmental management. Ten communities were selected in Accra and its surrounding communities to reflect different levels of infrastructure provision for the study. Four focus group discussions were held in each community, with a mixed group, men, women, and young adults. Issues which emerged were investigated further in a structured household questionnaire survey involving 443 respondents. Key informant interviews were held with the most important government and non government regulatory, research and service provision departments and organizations in water, sanitation, and the environment sectors. Water samples from some of the selected communities were analyzed in the laboratory to compare with respondents’ perceptions. Among the households surveyed, 59.14% were engaged in a water dependent occupation which contributed over 80% of household income in some cases. The study also found that perceptions of water and environment are influenced by the existing social and cultural setting. There were common concepts which helped groups to interpret and make meaning from their environment. The prospects for successful water and environmental interventions can be enhanced through an understanding of this local knowledge and perceptions. There was no clear relationship between attitudes and environmental behaviour or between attitudes and socioeconomic status. Actual behaviour was influenced by ability to pay for services, their availability and the influence of shared community norms. Although citizen participation in water and environmental management decision making is very limited at present, community collective action holds good prospects for future interventions in water and environmental management.
130

Harnessing collective intelligence on social networks

Chamberlain, Jon January 2015 (has links)
Crowdsourcing is an approach to replace the work traditionally done by a single person with the collective action of a group of people via the Internet. It has established itself in the mainstream of research methodology in recent years using a variety of approaches to engage humans in solving problems that computers, as yet, cannot solve. Several common approaches to crowdsourcing have been successful, including peer production (in which the participants are inherently interested in contributing), microworking (in which participants are paid small amounts of money per task) and games or gamification (in which the participants are entertained as they complete the tasks). An alternative approach to crowdsourcing using social networks is proposed here. Social networks offer access to large user communities through integrated software applications and, as they mature, are utilised in different ways, with decentralised and unevenly-distributed organisation of content. This research investigates whether collective intelligence systems are facilitated better on social networks and how the contributed human effort can be optimised. These questions are investigated using two case studies of problem solving: anaphoric coreference in text documents and classifying images in the marine biology domain. Social networks themselves can be considered inherent, self-organised problem solving systems, an approach defined here as ‘groupsourcing’, sharing common features with other crowdsourcing approaches; however, the benefits are tempered with the many challenges this approach presents. In comparison to other methods of crowdsourcing, harnessing collective intelligence on social networks offers a high-accuracy, data-driven and low-cost approach.

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