Effect of carbon nanoparticle addition on epoxy cure

The thesis reports studies of cure kinetics and the glass transition temperature advancements of three commercial epoxy resin systems: MY 750 / HY 5922 (Vantico), MTM 44 -1 (ACG) and 8552 (Hexcel Composites). This investigation was conducted with the utilisation of Differential Scanning Calorimetry (DSC) and Temperature Modulated DSC (TMDSC). Appropriate phenomenological cure kinetics models were built to predict the degree of cure as a function of temperature/time profile. The validity of superposition of dynamic and isothermal experimental data was established. Rheological measurements were performed in order to determine the gelation region under given cure conditions. The cure modelling methodology was validated against an international Round-Robin exercise led by the University of British Columbia (Canada). The effects of carbon nanoparticle incorporation on the cure kinetics and the glass transition temperature advancement of two of the epoxy systems were also studied. Cure kinetics models were developed for the nanocomposites containing commercial multiwalled carbon nanotubes and a direct comparison was made with the models of the neat resin systems. The glass transition temperature advancement is shown to be affected in the early stages of the cure. The state of the dispersion of the nanoparticles was studied in order to correlate it with the observed effects upon the cure and on the morphology of the cured samples. The presence of carbon nanotube clusters is shown to have an influence on the phase separation in the MTM 44-1 resin system. As a potential industrial application of this study, optical fibre refractometers were utilised as an on-line cure monitoring technique. A good correlation was established between the measured refractive index changes during the cure and the degree of cure predicted by the above mentioned models, for the neat resin systems and their nanocomposites

Probabilistic risk assessment of electrical substations

This thesis is concerned with the development of probabilistic risk assessment for substation earthing systems. A number of key parameters have been studied in detail which led to the development of a new approach that incorporates the recommendations of applicable standards and uses historical system fault data to take account of the probabilistic nature of load, protection systems and grid characteristics. In this work, an in-depth appraisal of existing standards has led to the development of safety-limit surfaces that can be used to quantify the benefits/disadvantages of particular earthing standards. The investigation has revealed that there are substantial differences between the recommended values of tolerable voltages attributed to a combination of factors: (i) difference in assumed tolerable body current (ii) differences in the parameters of the electrocution circuit (iii) differences in the predicted touch voltage and (iv) differences in the assumed worst-case shock location. The electricity industry, like other industries, is looking to reduce risk to minimum feasible while maintaining costs of mitigation within acceptable limits. Therefore, a more rigorous and comprehensive procedure of probabilistic risk assessment of the earthing systems is required. In order to achieve this, a detailed analysis of all parameters was undertaken in this work using more representative accidental circuits and parameters extracted from historical system fault data, provided by the collaborating transmission companies. These parameters were modelled and integrated into the proposed probabilistic risk assessment process. Work within this investigation on improving accuracy of calculation of heart fibrillation has led to the development of a probability surface of ventricular fibrillation and a computerised process that determines an accurate probability for a given body current and shock duration. This procedure takes into consideration the body current path and eliminates reading errors or assumptions that could result into conservative or optimistic conclusions. The above fundamental investigations on parameters affecting the overall risk were implemented in a new computerised risk assessment procedure CRAFTS suitable for transmission systems. CRAFTS allows a probabilistic risk assessment of the system under investigation. The application integrates the recent developments in the latest standard IEC 60479-1 and the developed probability surface of ventricular fibrillation. A case study performed on a typical grid has shown that the developed program is very useful when applying sensitivity analysis of the various parameters of the system and accidental circuit. The proposed full probabilistic risk assessment method incorporates the earthing system simulation results performed by specialised software, namely CDEGS, making it possible to simulate different electrocution scenarios throughout the substation instead of assuming a 'worst case scenario' and exposure to maximum possible voltages. Overall, the research in this thesis, offers an integrated solution of probabilistic risk assessment of earthing systems in aid of sound cost/benefit analysis and decision making.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Excision Repair Cross-Complementation Group 1 Enzyme as a Molecular Determinant of Responsiveness to Platinum-Based Chemotherapy for non Small-Cell Lung Cancer

Although platinum-based chemotherapy remains the “standard” in advanced non small-cell lung cancer, not all patients derive clinical benefit from such a treatment. Hence, the development of predictive biomarkers able to identify lung cancer patients who are most likely to benefit from cisplatin-based chemotherapy has become a scientific priority. Among the molecular pathways involved in DNA damage control after chemotherapy, the nucleotide excision repair (NER) is a critical process for the repair of DNA damage caused by cisplatin-induced DNA adducts. Many reports have explored the role of the excision repair cross-complementation group 1 enzyme (ERCC1) expression in the repair mechanism of cisplatin-induced DNA adducts in cancer cells

Probabilistic risk assessment of electrical substations

This thesis is concerned with the development of probabilistic risk assessment for substation earthing systems. A number of key parameters have been studied in detail which led to the development of a new approach that incorporates the recommendations of applicable standards and uses historical system fault data to take account of the probabilistic nature of load, protection systems and grid characteristics. In this work, an in-depth appraisal of existing standards has led to the development of safety-limit surfaces that can be used to quantify the benefits/disadvantages of particular earthing standards. The investigation has revealed that there are substantial differences between the recommended values of tolerable voltages attributed to a combination of factors: (i) difference in assumed tolerable body current (ii) differences in the parameters of the electrocution circuit (iii) differences in the predicted touch voltage and (iv) differences in the assumed worst-case shock location. The electricity industry, like other industries, is looking to reduce risk to minimum feasible while maintaining costs of mitigation within acceptable limits. Therefore, a more rigorous and comprehensive procedure of probabilistic risk assessment of the earthing systems is required. In order to achieve this, a detailed analysis of all parameters was undertaken in this work using more representative accidental circuits and parameters extracted from historical system fault data, provided by the collaborating transmission companies. These parameters were modelled and integrated into the proposed probabilistic risk assessment process. Work within this investigation on improving accuracy of calculation of heart fibrillation has led to the development of a probability surface of ventricular fibrillation and a computerised process that determines an accurate probability for a given body current and shock duration. This procedure takes into consideration the body current path and eliminates reading errors or assumptions that could result into conservative or optimistic conclusions. The above fundamental investigations on parameters affecting the overall risk were implemented in a new computerised risk assessment procedure CRAFTS suitable for transmission systems. CRAFTS allows a probabilistic risk assessment of the system under investigation. The application integrates the recent developments in the latest standard IEC 60479-1 and the developed probability surface of ventricular fibrillation. A case study performed on a typical grid has shown that the developed program is very useful when applying sensitivity analysis of the various parameters of the system and accidental circuit. The proposed full probabilistic risk assessment method incorporates the earthing system simulation results performed by specialised software, namely CDEGS, making it possible to simulate different electrocution scenarios throughout the substation instead of assuming a 'worst case scenario' and exposure to maximum possible voltages. Overall, the research in this thesis, offers an integrated solution of probabilistic risk assessment of earthing systems in aid of sound cost/benefit analysis and decision making

Seismic design and assessment of resilient post-tensioned steel frames with viscous dampers.

Conventional seismic-resistant structural systems are currently designed to develop a global sway plastic mechanism under strong earthquakes, which is achieved by allowing the development of controlled inelastic deformations in specific locations of main structural members such as beams, bases of columns and braces. Inelastic deformations in structural members result in damage and residual drifts, and therefore, in economic losses such as repair costs and downtime. Moreover, earthquake reconnaissance reports reveal large economic losses related to non-structural damage, e.g. failure of walls due to large storey drifts or failure of acceleration-sensitive equipment due to large peak floor accelerations. These losses highlight the need for resilient structures with the potential to remain intact after frequently occurred earthquakes and return to service within an acceptable short, if not immediate, time after strong rare earthquakes. Moreover, resilient structures should provide a very low probability of collapse (i.e. increased life safety) under very rare maximum considered earthquake. Steel self-centering moment-resisting frames using post-tensioned beam-column connections are a promising class of resilient structures. They exhibit softening force-drift behaviour and eliminate inelastic deformations and residual drifts as the result of gap openings developed in beam-column interfaces and elastic post tensioned bars which clamp beams to columns and provide self-centering capability. Also, post tensioned connections use energy dissipation devices, which are activated when gaps open and can be easily replaced if damaged. Steel frames equipped with passive dampers are another class of resilient structures. Dampers provide supplemental damping to control drifts, and thus, provide an effective means to achieve economical designs with high performance. The main goal of this PhD is to develop a seismic design and assessment procedure for steel self-centering moment-resisting frames (SC-MRFs) with viscous dampers within the framework of Eurocodes 3 and 8. To achieve this goal, nonlinear models of post-tensioned connections, able to capture the strength and stiffness deterioration due to local buckling, are developed. These models enable the assessment of the seismic behaviour of SC-MRFs with viscous dampers up to collapse with the aid of nonlinear dynamic analysis. A seismic design method, which incorporates a robust way to estimate rotation demands in post-tensioned connections, is then formulated. Different SC-MRFs with viscous dampers are designed using the proposed design procedure to study different design scenarios. The accuracy of the design procedure is evaluated through nonlinear dynamic analysis. In addition, the superior collapse resistance of SC-MRFs with viscous dampers is validated through incremental dynamic analysis. The thesis concludes with the implementation of an advanced probabilistic framework for direct economic seismic loss estimation and its application to confirm the potential of SC-MRFs with viscous dampers to significantly reduce economic seismic losses

EC8-based seismic design and assessment of self-centering post-tensioned steel frames with viscous dampers

This paper focuses on seismic design and assessment of steel self-centering moment-resisting frames (SC-MRFs) with viscous dampers within the framework of Eurocode 8 (EC8). Performance levels are defined with respect to drifts, residual drifts and limit states in the post-tensioned (PT) connections. A preliminary pushover analysis is conducted at the early phase of the design process to estimate rotations and axial forces in post-tensioned (PT) connections instead of using approximate formulae. Different designs of an SC-MRF with viscous dampers are considered to investigate all possible scenarios, i.e. use of dampers to achieve drifts significantly lower than the EC8 drift limit; to significantly reduce steel weight without exceeding the EC8 drift limit; or to reduce steel weight and achieve drifts lower than the EC8 drift limit. Nonlinear dynamic analyses using models capable of simulating all structural limit states up to collapse confirm the minimal-damage performance of the SC-MRFs. It is shown that the use of the preliminary pushover analysis makes the design procedure very accurate in predicting structural and non-structural limit states. Supplemental damping along with strict design criteria for the post-tensioned connections are found to significantly improve the seismic performance of the SC-MRFs. Moreover, the paper shows that SC-MRFs with viscous dampers have superior collapse resistance compared to conventional steel MRFs even when the SC-MRF is significantly lighter than the conventional MRF

Effect of carbon nanoparticle addition on epoxy cure

The thesis reports studies of cure kinetics and the glass transition temperature advancements of three commercial epoxy resin systems: MY 750 / HY 5922 (Vantico), MTM 44 -1 (ACG) and 8552 (Hexcel Composites). This investigation was conducted with the utilisation of Differential Scanning Calorimetry (DSC) and Temperature Modulated DSC (TMDSC). Appropriate phenomenological cure kinetics models were built to predict the degree of cure as a function of temperature/time profile. The validity of superposition of dynamic and isothermal experimental data was established. Rheological measurements were performed in order to determine the gelation region under given cure conditions. The cure modelling methodology was validated against an international Round-Robin exercise led by the University of British Columbia (Canada). The effects of carbon nanoparticle incorporation on the cure kinetics and the glass transition temperature advancement of two of the epoxy systems were also studied. Cure kinetics models were developed for the nanocomposites containing commercial multiwalled carbon nanotubes and a direct comparison was made with the models of the neat resin systems. The glass transition temperature advancement is shown to be affected in the early stages of the cure. The state of the dispersion of the nanoparticles was studied in order to correlate it with the observed effects upon the cure and on the morphology of the cured samples. The presence of carbon nanotube clusters is shown to have an influence on the phase separation in the MTM 44-1 resin system. As a potential industrial application of this study, optical fibre refractometers were utilised as an on-line cure monitoring technique. A good correlation was established between the measured refractive index changes during the cure and the degree of cure predicted by the above mentioned models, for the neat resin systems and their nanocomposites.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Angiogenic cytokines profile in smoldering multiple myeloma: No difference compared to MGUS but altered compared to symptomatic myeloma

Background: Symptomatic multiple myeloma (MM) evolves from an asymptomatic precursor state termed monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM). Angiogenesis plays a key role in the pathogenesis of MM but there are very limited data for angiogenesis in SMM. Material/Methods We measured the circulating levels of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), vascular endothelial growth factor (VEGF), and angiogenin in 54 patients with SMM. The results were compared with those of 27 MGUS patients, 55 MM patients, and 22 healthy controls. The expression of VEGF-A gene was also evaluated in 10 patients with SMM, 10 with symptomatic MM, and 10 with MGUS. Results: The ratio of circulating Ang-1/Ang-2 was reduced in MM patients with symptomatic disease due to a dramatic increase of Ang-2 (p<0.001), but not in patients with SMM or MGUS, in whom it did not differ compared to controls. VEGF and angiogenin were increased in all patients compared to controls. However, circulating VEGF was higher in symptomatic MM compared to SMM and MGUS, while angiogenin was reduced. There were no differences in the expression of VEGF-A among the 3 patients categories. Conclusions: SMM has a circulating angiogenic cytokine profile similar to that of MGUS, but has altered profile compared to symptomatic MM. Thus, in the progression of MGUS to SMM, circulating angiogenic cytokines seem to be the same. On the contrary, in symptomatic myeloma, the alterations of angiopoietins along with VEGF contribute to myeloma cell growth, supporting the target of these molecules for the development of novel anti-myeloma agents