20413 research outputs found
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Impact of Lost Synchronous Generation on the Rate of Change of Frequency in Electrical Power Systems
No full textRenewable energy targets have resulted in high penetration of non-synchronous generation and consequently reducing power system inertia, and this could lead to power system frequency instability following a disturbance, such as the loss of generation. A concern to power system operators is the rate of change of frequency (ROCOF) following the loss of generation. Fast ROCOF presents many challenges for power systems but the primary concern is that fast ROCOF reduces the time-frame that primary frequency control has to arrest a frequency decline following the loss of generation. Therefore, power system operators need to develop strategies to operate power systems with high instantaneous penetrations of non-synchronous generation, reduced inertia and that are resilient to fast ROCOF. The focus of this research is on power system ROCOF following the loss of a synchronous generator in multi-bus networks.
Conventional methods used to estimate potential power system ROCOF and minimum inertia requirements often assume a single-bus network and constant power loads. Hence, the impact of lost reactive power, changes to individual bus voltages and load response are neglected. These assumptions often result in an over-estimated potential ROCOF and therefore surplus inertia requirements.
This research presents a detailed multi-bus ROCOF analysis of a power system following the loss of a synchronous generator. It investigates the most influential factors on ROCOF, such as the impact of lost active and reactive power, inertia distribution and load response on system ROCOF. Furthermore, this research has developed a novel method of estimating the potential ROCOF for the loss of a particular generator that, unlike conventional methods, also takes account of lost reactive power and the subsequent load response. It is shown that these two factors can have a significant impact on the speed of ROCOF and by taking both factors into account, a more accurate estimate of the potential ROCOF is possible. This will allow power system operators to more accurately estimate the potential ROCOF for the loss of a particular generator and confidently reduce system inertia and increase the instantaneous renewable generation
Assessment of Bifidobacterium longum ITT 13 as a Probiotic Candidate
No full textProbiotics are live microorganisms that when administered in adequate amounts confer a health benefit on the host. Beneficial microbes are found in several sites throughout the body such as the oral cavity, skin, respiratory tract, vagina, urinary tract, breast tissue and the gut. In this research, the culture Bifidobacterium longum ITT 13, which was previously isolated from a neonatal faecal sample, was examined for its potential as a probiotic candidate. Probiotics can have numerous desirable characteristics. The pertinent ones to this research are being of human or animal origin, not prone to antibiotic resistance, demonstration of antagonistic activity towards pathogens, absence of virulence factors and have its identification confirmed based on its genetic profile to eliminate any ambiguity.
When grown as a pure culture under anaerobic conditions at 37o C, without agitation, B. longum ITT 13 had a specific growth rate of 0.422 hr-1 . The addition to the culture medium of selected prebiotics namely starch, inulin, raffinose and fructooligosaccharide (FOS) at various concentrations, significantly altered the specific growth rate, with the addition of 0.1 % (w/v) starch resulting in the highest specific growth rate at 0.762 hr-1 . In separate experiments, B. longum ITT 13 was co-cultured with selected lactic acid bacteria (LAB), including L. acidophilus, L. lactis, L. casei and S. thermophilus. Of these organisms tested, co-culturing with L. acidophilus was found to produce the highest specific growth rate of 0.948 hr-1 as compared to 0.939 hr-1 for L. lactis, 0.576 hr-1 for S. thermophilus and 0.281 hr-1 for L. casei. This information may be helpful in scaling up and maximising the industrial biomass yield of the organism.
In a further set of experiments, the antimicrobial activity from the cell-free spent medium (CFSM) of B. longum ITT 13 against the pathogens Clostridium difficile and Salmonella Typhimurium was investigated. In the absence of prebiotics, B. longum ITT 13 CFSM did not show antimicrobial activity against these organisms. However, when grown with
the addition of the prebiotics inulin, raffinose and FOS to the culture medium, the CFSM showed promising antimicrobial activity against these two organisms. The antimicrobial activity against pathogenic Streptococcus pneumonia when B. longum ITT 13 was co-cultured with Lactobacillus acidophilus yielded a zone of clearance 17.9 mm in diameter. Antimicrobial activity against S. pneumoniae was not found in this research with the addition of any of the four prebiotics or co-culture of L. lactis, L. casei or S. thermophilus with B. longum ITT 13.
Biofilm production by bacteria is considered to be a virulence factor and has implications in pathogenicity. However, biofilm production can also allow so-called ‘good’ organisms to colonise the gut. Throughout these studies examining the ability of B. longum ITT 13 to produce a biofilm, the organism consistently failed to give positive results in tests employing Congo Red agar (CRA) plates and 96-well plates using crystal violet staining, indicating its inability to produce a biofilm. Furthermore, during a time-course study over a period of six days, the ability of B. longum ITT 13 to prevent the production of biofilms by indicator organisms was examined. When B. longum ITT 13 was co-cultured with indicator pathogens Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis and Escherichia coli, it was found that all required an adjustment period after which the level of biofilm production stabilised and large fluctuations in percentage biofilm were not observed. For example, E. faecalis yielded a biofilm of 16.8 % after 1 day incubation with this increasing to 63.2 % after 2 days but thereafter stabilising around 80 % biofilm for 3 to 6 days. Further studies in which the ability of B. longum ITT 13 to disrupt pre-existing biofilms indicate a decrease in the percentage of biofilm formed after 24 hours for each indicator organism tested. This could have implications with respect to using B. longum ITT 13 in treating but not preventing infections caused by biofilm producing pathogens.
An antibiotic resistance profile was drafted using the Kirby Bauer Disk Diffusion Susceptibility Test. Of the eighteen antibiotics tested, B. longum ITT 13 was susceptible to eleven, created intermediate zones (14 mm -15 mm) against two and was resistant to five.
The minimum inhibitory concentration (MIC) test was used to ascertain if addition of B. longum ITT 13 to a mix containing ampicillin or polymyxin B, enhanced the antibiotic’s action against two selected indicator pathogens (E. coli and S. aureus). The results were encouraging in the test with ampicillin, E. coli and B. longum ITT 13, where there was an overall reduction of E. coli bioburden relative to the effect of ampicillin on its own against E. coli. However, with increasing ampicillin concentration in combination with S. aureus and B. longum ITT 13, there appeared to be an enhancement in the growth of S. aureus, indicative of ‘Eagle Effect’, where bacteria have an increased ability to grow in the presence of antibiotic concentrations deemed to be higher than bactericidal concentrations. Co-culture of E. coli with B. longum ITT 13 in the presence of polymyxin B also did not demonstrate a positive synergistic effect.
Lastly, to confirm the identity of the test isolate, B. longum ITT 13, and satisfy the speciation requirement for a culture to qualify as a probiotic, next-generation sequencing (NGS) was performed using the Illumina MiSeq FGx which confirmed B. longum subsp. infantis speciation. The culture was aligned with a National Centre for Biotechnology Information (NCBI) reference strain using the bioinformatics software, Galaxy. This software annotated twenty genes in the B. longum ITT 13 genome and several hypothetical proteins which warrant further investigation. No antimicrobial or virulence genes were identified.
The culmination of all results in this research lead to a potentially promising future for B. longum ITT 13 to be classified as a probioti
Suitability of Mobile Phase Recycling for Methylxanthine Quantification in Coffee Samples using HPLC
No full textCaffeine, theobromine and theophylline fall under a drug class known as methylxanthines. These three compounds are of major interest in the food industry due to their presence in popular foods and beverages such as tea, coffee, and chocolate. As these compounds can cause physical and mental stress at high dosages, their quantification is essential to ensure product safety and quality. Here, we describe an eco-friendly HPLC method developed to quantify the amount of these analytes in coffee samples sourced across the SETU Waterford, Cork Road campus. Using an isocratic mixture of water and methanol, a mobile phase recycling approach was developed and investigated. The method was validated by determining linearity, standard error, LOD, LOQ, and repeatability. The caffeine content of 23 beverages ranged from 376.3 mg/L to 4127.5 mg/L of coffee, displaying high variation among sample type and source outlet. Theobromine was observed in a small number of samples; theophylline was not detected in any of the studied coffee samples. Solvent waste, and hence disposal, was significantly reduced by recycling the mobile phase, without adverse analytical impact over the lifetime of the study
Advancing Skin Cancer Diagnostics: A Comparative Analysis of Convolutional Neural Network Models for Skin Lesion Classification
No full textFor many years, skin cancer diagnosis and cancer research have been major focal points in the healthcare sector. Accurate classification of different types of skin lesions, including cancerous ones, is essential for proper diagnostics. Many machine learning (ML) techniques and models are used to solve various problems across various domains. One of such techniques is called neural networks. Convolutional Neural Networks (CNNs) are primarily used in computer vision-based problems, allowing computer systems to process and understand images. CNNs offer a potential tool for diagnosing skin lesions from images, occasionally demonstrating superior accuracy compared to trained dermatologists. This project explores various neural network models, including CNN-SVM, DenseNet201, and a sequential model, to diagnose skin lesions. It proposes developing multiple machine learning models using advanced techniques like transfer learning and hybrid models. The performance of these models is compared to determine which architecture yields the best results. Furthermore, this paper compares the results of these models with findings from other research studies to assess the validity of using computer vision for skin cancer detection and to explore whether such models can support or potentially replace dermatologists in clinical practice. The three models focused on this project also differed in accuracy values. Our experimental results show that the CNN-SVM solution is the best-performing of the three models, followed by the DenseNet201 model.
Furthermore, the project has led to the creation of an interactive website where users can upload images of skin lesions and observe how the three different models classify the images. To support early detection and ensure access to professional medical advice, the website includes a built-in hospital locator system, guiding users to nearby healthcare facilities if they have concerns about the classifications provided by the models
The role of Psychological Capital on Organisational Citizenship Behaviours within the Ghanaian public sector: A Conservation of Resources perspective.
No full textThe public sector of Ghana has been plagued with low productivity issues for over a decade. Psychological capital is a resource that can increase citizenship behaviours, which help to boost productivity. Conservation of resources theory provides a mechanism for explaining the role that psychological capital plays in encouraging organisational citizenship behaviours. This mechanism is reflected in the value of psychological capital among employees and context-specific factors within the omnibus and discrete contexts of the Ghanaian public sector. The thesis explored this through a two-phase research method. Firstly, employing semi-structured interviews to explore the value of psychological capital, and identify perception of abusive supervision, political skill, social capital, and in-group/out-group employee status as context-specific influencing factors in the Ghanaian public sector. A two-wave time-lagged survey was then adopted to examine the influence of these context-specific factors on the resource potential of psychological capital on organisational citizenship behaviours. Apart from the non-significant moderating influence of perception of abusive supervision, the results showed that psychological capital has a full mediating effect on the relationship between social capital and organisational citizenship behaviours. Furthermore, political skill acts as a moderator in the relationship between social capital and psychological capital, and this moderating effect is further moderated by the in-group/out-group status of the individual respondent when considering their ethnicity. These findings, which make several contributions to the literature along with implications for policy and managers, are presented in this thesi
A Review of 3D GIS for Use in Creating Virtual Historic Dublin
No full textThis paper illustrates how BIM integration with GIS is approached as part of the workflow in creating Virtual Historic Dublin. A design for a WEB based interactive 3D model of historic buildings and centres in Dublin City (Virtual Historic Dublin City) paralleling smart city initiates is now under construction and led by the National Monuments at the Office of Public Works in Ireland. The aim is to facilitate the conservation and maintenance of historic infrastructure and fabric and the dissemination of knowledge for education and cultural tourism using an extensive Historic Building Information Model. Remote sensing data is now processed with greater ease to create 3D intelligent models in Historic BIM. While the use of remote sensing, HBIM and game engine platforms are the main applications used at present, 3D GIS has potential to form part of the workflow for developing the Virtual Historic City. 2D GIS is now being replaced by 3D spatial data allowing more complex analysis to be carried out, 3D GIS can define and depict buildings, urban rural centres in relation to their geometry topological, semantic and visualisation properties. The addition of semantic attributes allows complex analysis and 3D spatial queries for modelling city and urban elements. This analysis includes fabric and structural elements of buildings, relief, vegetation, transportation, water bodies, city furniture and land use
Historic Building Information Modelling - Adding Intelligence to Laser and Image Based Surveys
No full textHistoric Building Information Modelling (HBIM) is a novel prototype library of parametric objects based on historic data and a system of cross platform programmes for mapping parametric objects onto a point cloud and image survey data. The HBIM process be-gins with remote collection of survey data using a terrestrial laser scanner combined with digital photo modelling. The next stage in-volves the design and construction of a parametric library of objects, which are based on the manuscripts ranging from Vitruvius to 18th century architectural pattern books. In building parametric objects, the problem of file format and exchange of data has been overcome within the BIM ArchiCAD software platform by using geometric descriptive language (GDL). The plotting of parametric objects onto the laser scan surveys as building components to create or form the entire building is the final stage in the reverse engineering process. The final HBIM product is the creation of full 3D models including detail behind the object’s surface concerning its methods of construction and material make-up. The resultant HBIM can automatically create cut sections, details and schedules in addition to the orthographic projections and 3D models (wire frame or textured)
Lessons in Low-Tech: A Handbook for Sustainable Education
Get PDFLT4SUSTAIN, an Erasmus+ funded transnational project, is at the forefront of responding to the increasing awareness of environmental and climate challenges. This awareness, particularly among youth, has led to a demand for social justice. With the coordinated work among six institutions, ranging from higher education institutions to private companies and associations, LT4SUSTAIN aims to raise awareness of Lowtech across society.
LT4SUSTAIN is pioneering a unique approach to technology design. By developing “hackathons” and other “hands-on” events, we are engaging students and industry in a way that improves inclusiveness. Our objective is to equip individuals with the skills to embark on entrepreneurial ventures that focus on sustainable and valuable solutions using a Low-tech paradigm.
Low-tech, based on the principles of usefulness, sustainability and accessibility, empowers practitioners to implement simple (as needed) technologies that are accessible and easily repairable, using common and locally available means. These solutions lean toward inexpensive technological solutions for fundamental and unsatisfied needs while positively contributing to generating a sustainable environment. This concept favours human know-how and practicality, making it an empowering solution for today’s and tomorrow’s social, cultural, ecological and economic challenges.
This guide presents a series of lessons and frameworks designed to teach Low-tech principles, offering step-by-step instructions for fostering practical and creative skills. From hands-on workshop activities to insights into sustainable design thinking, it equips educators and practitioners with tools to empower individuals and communities. Whether you’re crafting new materials, prototyping resilient solutions, or rethinking design for an era of degrowth, this book provides the knowledge and inspiration to drive meaningful change
