• Vulnerability and adaptive capacity of rural coastal fishing communities in Ghana to climatic and socio-economic stressors

      Davies-Vollum, Kathrine; Raha, Debadayita; Koomson, Daniel (University of Derby, 2021-08-13)
      The global fishing industry is a source of livelihood for about 820 million people. About 90% of this number are small-scale fisherfolk and traders, living in rural fishing-dependent communities in tropical, developing, and least developed countries. Although the industry generates about $362 billion annually, fishing-dependent communities are generally characterised by chronic poverty and deprivation. Decrease in fish productivity and availability in tropical regions, as well as, increase in the frequency and intensity of extreme weather events due to climate change processes have exacerbated the plight of fishing-dependent communities. In 1970, an agenda for research and development of small-scale fishing was set out. However, rural fishing communities are still considered the poorest of the poor today. They are also considered the most vulnerable as future climate change predictions indicate more extreme events and further reductions in maximum fish catch and revenue potentials. Therefore, there are continued calls for research efforts to understand the impacts of multiple climatic and socioeconomic stressors on small-scale fishing livelihoods, in order to identify viable, context-specific management and policy interventions that can reduce their vulnerability. Using two rural coastal fishing communities in Ghana as a case study, the purpose of this study was to explicate how rural coastal fishing-dependent communities in a tropical context are impacted by the interaction of climatic and socio-economic factors and identify viable policy and management options to enhance their adaptive capacity. Three key research questions guided the study: (i) what are the various factors that impact small-scale fishing livelihoods/households, and how do they interact to shape vulnerability? (ii) how are the fishing communities adapting to current livelihood stressors? and, (iii) What context-specific policy and management interventions are needed to enhance their adaptive capacity and safeguard their wellbeing. The Intergovernmental Panel on Climate Change’s (IPCC) vulnerability framework and the Sustainable Livelihoods Approach (SLA) were integrated as the theoretical underpinnings of the study. A mixed-methods approach was adopted. A total of 120 fishing households were selected and surveyed through a stratified-snowball sampling technique. Several gender and age-group disaggregated focus groups with participatory activities, semi-structured interviews, and key informant discussions were also conducted to collect primary data. These were combined with climatic data to assess each household’s vulnerability, and through triangulated analyses, explicate how it is mediated by socio-cultural, institutional, and policy structures.
    • Crashworthiness Characterisation of the Car Front Bumper System Based on FEA Analysis

      Lu, Yiling; Harmanto, Dani; Zhang, Xiyuan (University of Derby, 2020-11-19)
      This thesis investigated different designs and material selections of vehicle front bumper system to improve the vehicle crashworthiness during the low impact speed (impact velocity=15km/h, 9.32mph) via FEA simulations. The primary purpose is to identify the most important parameters directly related to the improvement of crashworthiness using numerical parametric study. It is found the cross-section profile, curvature shape, material of the bumper beam, together with the connection to the crash box have been all identified that directly influence the crashworthiness performance of the front bumper system. The bumper system, including the sub-components such as bumper beam, crash box, and the connection methods were carried all the parameters, including a number of folds, curvature shapes and spot welds were in-built while creating them into the CAD models using Solidworks. The final assembled complete bumper system is then imported into the ANSYS for further geometry checks and adjustment. Solver Autodyn is used to perform the FEA simulation, and numbers of results files were generated. Results files such as force reaction, plastic work, and equivalent stress, normal stress was all exported it into the Excel for parametric analysis and discussions. Cross-section Profile-Out of proposed Single fold (fold 1) and Triple fold(fold 3) bumper beam profiles, Double fold (fold 2) bumper beam profile presented the best results of force reaction on both smoothness and force value, while the plastic work remained almost identical to profile fold 1 and 3 gained. Fold 2 profile is considered as a good performer since this profile regulated the deformation behaviour of the beam resulted in a smooth increasing force reaction curve. Where the force reaction curve on both fold 1 and fold 3 were fluctuated dramatically due to catastrophic structural failure. Material-In between structural steel and aluminium alloy used in the bumper beam, while the structural steel made bumper beam achieved good force reaction and plastic work. Switched to aluminium can achieve similar force reaction trend and rate with Cross-section neglectable amount of plastic work reduced. Particularly the weight of the bumper beam is dropped down to 5.357 kg while maintaining similar crashworthiness performance to the structural steel. Crash box Crash box connection- The bonded connection is considered as an ideal scenario and was xvii Sensitivity: Internal favoured in much other literature due to it simplifies the connection setting in the FEA environment since it automatically considers it as perfect contact. Three alternative connection methods were therefore proposed to simulate the more realistic scenario. It defined as welding connection that is constituted by a number of spot welds at left, right, top and bottom of the crash box. Since the bonded method contains no spot welds, a method of weld L+R was indicated by totally 4 spot welds appeared at both left and right side of the crash box. On top of this, 4 additional spot welds were added to the top and bottom of the crash box. Totally 4 spot welds were added only to both the top and bottom of the crash box to extend the comparison. While both bonded and weld L+R methods suffered from buckling effect to the crash box, particularly concentrated at the left and right side with high equivalent and normal stresses. It is discovered weld full method provided promising results by reducing the buckling effect to both left and right faces of the crash box, and also managed to lower the equivalent stress down to 336.48MPa and normal stress on the connection surface down to 66MPa. Weld T+B also observed similar performance when compared with both bonded and weld L+R methods. While registered with very small amount of equivalent and normal stresses, the buckling effect is significantly reduced. This thesis contributed the knowledge to the improvement of vehicle front bumper system. Particularly to the failure mode of both bumper beam and crash box, and offered the related optimisation.
    • Thermo-mechanical reliability studies of lead-free solder interconnects

      Mallik, Sabuj; Lu, Yiling; Depiver, Joshua Adeniyi (University of DerbyN/A, 2021-06-03)
      Solder interconnections, also known as solder joints, are the weakest link in electronics packaging. Reliability of these miniature joints is of utmost interest - especially in safety-critical applications in the automotive, medical, aerospace, power grid and oil and drilling sectors. Studies have shown that these joints' critical thermal and mechanical loading culminate in accelerated creep, fatigue, and a combination of these joints' induced failures. The ball grid array (BGA) components being an integral part of many electronic modules functioning in mission-critical systems. This study investigates the response of solder joints in BGA to crucial reliability influencing parameters derived from creep, visco-plastic and fatigue damage of the joints. These are the plastic strain, shear strain, plastic shear strain, creep energy density, strain energy density, deformation, equivalent (Von-Mises) stress etc. The parameters' obtained magnitudes are inputted into established life prediction models – Coffin-Manson, Engelmaier, Solomon (Low cycle fatigue) and Syed (Accumulated creep energy density) – to determine several BGA assemblies' fatigue lives. The joints are subjected to thermal, mechanical and random vibration loadings. The finite element analysis (FEA) is employed in a commercial software package to model and simulate the responses of the solder joints of the representative assemblies' finite element models. As the magnitude and rate of degradation of solder joints in the BGA significantly depend on the composition of the solder alloys used to assembly the BGA on the printed circuit board, this research studies the response of various mainstream lead-free Sn-Ag-Cu (SAC) solders (SAC305, SAC387, SAC396 and SAC405) and benchmarked those with lead-based eutectic solder (Sn63Pb37). In the creep response study, the effects of thermal ageing and temperature cycling on these solder alloys' behaviours are explored. The results show superior creep properties for SAC405 and SAC396 lead-free solder alloys. The lead-free SAC405 solder joint is the most effective solder under thermal cycling condition, and the SAC396 solder joint is the most effective solder under isothermal ageing operation. The finding shows that SAC405 and SAC396 solders accumulated the minimum magnitudes of stress, strain rate, deformation rate and strain energy density than any other solder considered in this study. The hysteresis loops show that lead-free SAC405 has the lowest dissipated energy per cycle. Thus the highest fatigue life, followed by eutectic lead-based Sn63Pb37 solder. The solder with the highest dissipated energy per cycle was lead-free SAC305, SAC387 and SAC396 solder alloys. In the thermal fatigue life prediction research, four different lead-free (SAC305, SAC387, SAC396 and SAC405) and one eutectic lead-based (Sn63Pb37) solder alloys are defined against their thermal fatigue lives (TFLs) to predict their mean-time-to-failure for preventive maintenance advice. Five finite elements (FE) models of the assemblies of the BGAs with the different solder alloy compositions and properties are created with SolidWorks. The models are subjected to standard IEC 60749-25 temperature cycling in ANSYS 19.0 mechanical package environment. SAC405 joints have the highest predicted TFL of circa 13.2 years, while SAC387 joints have the least life of circa 1.4 years. The predicted lives are inversely proportional to the magnitude of the areas of stress-strain hysteresis loops of the solder joints. The prediction models are significantly consistent in predicted magnitudes across the solder joints irrespective of the damage parameters used. Several failure modes drive solder joints and damage mechanics from the research and understand an essential variation in the models' predicted values. This investigation presents a method of managing preventive maintenance time of BGA electronic components in mission-critical systems. It recommends developing a novel life prediction model based on a combination of the damage parameters for enhanced prediction. The FEA random vibration simulation test results showed that different solder alloys have a comparable performance during random vibration testing. The fatigue life result shows that SAC405 and SAC396 have the highest fatigue lives before being prone to failure. As a result of the FEA simulation outcomes with the application of Coffin-Manson's empirical formula, the author can predict the fatigue life of solder joint alloys to a higher degree of accuracy of average ~93% in an actual service environment such as the one experienced under-the-hood of an automobile and aerospace. Therefore, it is concluded that the combination of FEA simulation and empirical formulas employed in this study could be used in the computation and prediction of the fatigue life of solder joint alloys when subjected to random vibration. Based on the thermal and mechanical responses of lead-free SAC405 and SAC396 solder alloys, they are recommended as a suitable replacement of lead-based eutectic Sn63Pb37 solder alloy for improved device thermo-mechanical operations when subjected to random vibration (non-deterministic vibration). The FEA simulation studies' outcomes are validated using experimental and analytical-based reviews in published and peer-reviewed literature.
    • Adversarial Thresholding Semi-Bandits

      Anjum, Ashiq; Bagdasar, Ovidiu; Xue, Yong; Bower, Craig (University of Derby, 2020-12)
      The classical multi-armed bandit is one of the most common examples of sequential decision-making, either by trading-off between exploiting and exploring arms to maximise some payoff or purely exploring arms until the optimal arm is identified. In particular, a bandit player wanting to only pull arms with stochastic feedback exceeding a given threshold, has been studied extensively in a pure exploration context. However, numerous applications fail to be expressed, where a player wishes to balance the need to observe regions of an uncertain environment that are currently interesting (exploit) and checking if neglected regions have become interesting since last observed (explore). We introduce the adversarial thresholding semi-bandit problem: a non-stochastic bandit model, where a player wants to only pull (potentially several) arms with feedback meeting some threshold condition. Our main objective is to design algorithms that meet the requirements of the adversarial thresholding semi-bandit problem theoretically, empirically and algorithmically, for a given application. In other words, we want to develop a machine that learns to select options according to some threshold condition and adapts quickly if the feedback from selecting an option unexpectedly changes. This work has many real-world applications and is motivated by online detector control monitoring in high-energy physics experiments, on the Large Hadron Collider. We begin by describing the adversarial thresholding semi-bandit problem (ATSBP) in terms of a multi-armed bandit with multiple plays and extending the stochastic thresholding bandit problem to the adversarial setting. The adversarial thresholding exponentially-weighted exploration and exploitation with multiple plays algorithm (T-Exp3.M) and an algorithm combining label efficient prediction (LET-Exp3.M), are introduced that satisfy theoretical and computational Research specifications, but either perform poorly or fail completely under certain threshold conditions. To meet empirical performance requirements, we propose the dynamic label efficient adversarial thresholding exponentially-weighted exploration and exploitation with multiple plays algorithm (dLET-Exp3.M). Whilst computational requirements match those for T-Exp3.M, theoretical upper bounds on performance are proven to be worse. We also introduce an ATSBP algorithm (AliceBandit) that decomposes the action of pulling an arm into selection and observation decisions. Computational complexity and empirical performance under two different threshold conditions are significantly improved, compared with exponentially weighted adversarial thresholding semi-bandits. Theoretical upper bounds on performance are also significantly improved, for certain environments. In the latter part of this thesis, we address the challenge of efficiently monitoring multiple condition parameters in high-energy experimental physics. Due to the extreme conditions experienced in heavy-ion particle colliders, the power supply to any device exceeding safe operating parameters is automatically shut down or tripped, to preserve integrity and functionality of the device. Prior to recent upgrades, a device or channel trip would halt data-taking for the entire experiment. Post-trip recovery requires a costly procedure both in terms of expertise and data-taking time. After the completion of the current upgrading phase (scheduled for 2021), the detector will collect data continuously. In this new regime, a channel trip will result in only the affected components of the experiment being shut down. However, since the new upgraded experiment will enable data-taking to increase by a factor of 100, each trip will have a significant impact on the experiments ability to provide physicists with reliable data to analyse. We demonstrate that adversarial thresholding semi-bandits efficiently identify device channels either exceeding a fixed threshold or deviating by more than a prescribed range prior to a trip, extending the state-of-the-art in high-energy physics detector control.
    • Contractors’ selection criteria for sustainable infrastructure delivery in Nigeria

      Ceranic, Boris; Dean, Angela; Arowosafe, Oluwumi I. (University of Derby, 2020)
      The research reported in this study developed and validated a framework for the pre-evaluation of contractors for sustainable infrastructure projects through Public-Private Partnership (PPP) in Nigeria. The proposed framework uses the Analytic Network Process (ANP) to select contractors for build-operate-transfer (BOT) contractors. Theoretically grounded on a system theory, a sustainable infrastructure delivery (SID) model is developed in this research. One of its important features is the ability to solve complex decision problems, typical of a decision-making process that involves selection of contractors for PPP projects. At the deductive phase of the proposed model is the integration of the ANP (multi-criteria decision-making technique) for data synthesis. An extensive literature review was conducted with regard to selection criteria for contractors. Furthermore, a web-based questionnaire survey was undertaken, aimed at capturing the perception of the Nigerian construction professionals regarding the importance of these criteria for pre-evaluation of contractors for public infrastructure procurement. A total of 143 questionnaires was received and their feedbacks were analysed with the IBM SPSS statistical package. The findings revealed a broad range of 55 relevant criteria that were linked to sustainable contractor selection. Through the application of factor analysis, the number of the criteria was reduced to 16, after multicollinearity issues in the data set had been resolved. The 16 factors were modelled to pairwise comparison matrices, transforming decision making process from linear to a systemic approach. A purposeful sampling methodology was then applied for the selection of decision-making panel (DM), who completed the pairwise comparison survey. The survey results were synthesised by ANP. The final solution derived order of significance of the two categories of contractors- multinational construction corporations (MCC) and local construction contractors (LCC) in respect to the delivery of a sustainable infrastructure. Sensitivity analysis of the research findings reveals that the 16 criteria have differential comparative advantages, which requires critical judgement during contractors’ pre-evaluation process. Although the overall priorities rank multinational construction corporations (MCC) higher than local construction companies (LCC), it is not absolute that MCC will deliver a better value for money on all tangible and intangible elements of sustainable infrastructure attributes. LCC outperform on some of the key criteria such as local employment creation and local material sourcing, which are essential pre-evaluation criteria. This research proposes a novel framework to harmonise sustainability indicators in contractor selection and offers a new theoretical insight into the approach to contractors’ selection criteria during pre-evaluation process, which contributes to the enhancement of PPP delivery in Nigeria. Overall, the proposed SID model has demonstrated the need for a shift in the modus operandi of the government’s ministries, department and agencies (MDAs) in Nigeria from unidirectional to systemic selection techniques. It clearly demonstrates the appropriateness of the ANP to predict the contractor that will deliver more sustainable infrastructure.
    • A Novel Mathematical Layout Optimisation Method and Design Framework for Modularisation in Industrial Process Plants and SMRs

      Wood, Paul; Hall, Richard; Robertson, Daniel; Wrigley, Paul (University of DerbyInstitute for Innovation in Sustainable EngineeringUniversity of Derby, 2021-01-19)
      Nuclear power has been proposed as a low carbon solution to electricity generation when intermittent wind and solar renewable energy are not generating. Nuclear can provide co-generation through district heating, desalination, hydrogen production or aid in the process of producing synfuels. However, current new large nuclear power plants are expensive, time consuming to build and plagued by delays and cost increases. An emerging trend in the construction industry is to manufacture parts off the critical path, off site in factories, through modular design to reduce schedules and direct costs. A study from shipbuilding estimates work done in a factory may be 8 times more efficient than performing the same work on site. This productivity increase could be a solution to the problems in nuclear power plant construction. It is an emerging area and the International Atomic Energy Agency records over 50 Small Modular Reactor designs in commercial development worldwide. Most Small Modular Reactor designs focus on integrating the Nuclear Steam Supply System into one module. The aim of this Applied Research Programme was to develop an efficient and effective analysis tool for modularisation in industrial plant systems. The objectives were to understand the state of the art in modular construction and automating design through a literature review. The literature review in this thesis highlighted that automating earlier parts of the plant design process (equipment databases, selection tools and modular Process and Instrumentation Diagrams) have been developed in modular industrial process plant research but 3D layout has not been studied. It was also found that layout optimisation for industrial process plants has not considered modularisation. It was therefore proposed to develop a novel mathematical layout optimisation method for modularisation of industrial plants. Furthermore, the integration within the plant design process would be improved by developing a method to integrate the output of the optimisation with the plant design software. A case study was developed to analyse how this new method would compare against the current design process at Rolls-Royce. A systems engineering approach was taken to develop the capabilities of the optimisation by decomposing the three required constituents of modularisation: development of a model to optimise layout of modules utilising the module designs from previous research (Lapp, 1989), development of a model to optimise the layout equipment within modules and development of a combined and integrated model to optimise assignment and layout of equipment to modules. The objective function was to reduce pipe length as it can constitute up to 20% of process plant costs (Peters, Timmerhaus, & West, 2003) and to reduce the number of modules utilised. The results from the mathematical model were compared against previous layout designs (Lapp, 1989), highlighting a 46-88.7% reduction in pipework and considering pipework costs can be up to 20% of a process plant cost, this could be a significant saving. This does not consider the significant schedule and productivity savings by moving this work offsite. The second model (Bi) analysed the layout of the Chemical Volume and Control System and Boron Thermal Regeneration System into one and two modules, reducing pipe cost and installation by 67.6% and 85% respectively compared to the previously designed systems from (Lapp, 1989). The third model (Bii) considered the allocation of equipment to multiple modules, reducing pipe cost and installation by 80.5% compared to the previously designed systems from (Lapp, 1989), creating new data and knowledge. Mixed Integer Linear Programming formulations and soft constraints within the genetic algorithm function were utilised within MATLAB and Gurobi. Furthermore, by integrating the optimisation output with the plant design software to update the new locations of equipment and concept pipe routing, efficiency is vastly improved when the plant design engineer interprets the optimisation results. Not only can the mathematical layout optimisation analyse millions more possible layouts than an engineering designer, it can perform the function in a fraction of the time, saving time and costs. It at least gives the design engineer a suitable starting point which can be analysed and the optimisation model updated in an iterative process. This novel method was compared against the current design process at Rolls-Royce, it was found that an update to a module would take minutes with the novel optimisation and integration with the plant design software method, rather than days or weeks for the manual process. However, the disadvantage is that more upfront work is required to convert engineering knowledge into mathematical terms and relationships. The research is limited by the publicly available nuclear power plant data. Future work could include applying this novel method to wider industrial plant design to understand the broader impact. The mathematical optimisation model can be developed in the future to include constraints in other research such as assembly, operation and maintenance costs.
    • Numerical Study of Track-Trailer Gap Aerodynamics

      Yang, Zhiyin; Lu, Yiling; Charles, Terrance Priestley (University of Derby, 2020-12-08)
      Aerodynamics have become an essential design process for ground vehicles in order to improve the fuel consumption by lowering the emissions along with increasing the range of vehicles using different source of power. A significant portion of the world CO2 emissions is a result of ground vehicles with a more significant portion of these contributed by trucks. The boxy nature of trucks is the desired shape to carry maximum payload. However, a box shaped geometry is not aerodynamically efficient. Several manufacturers have developed aerodynamic add on devices that are optimized to the shape of the truck, in order to achieve gains in lowering emission and improving range by deeper understanding of the flow physics around the vehicle. The thesis reports an in-depth understanding of the flow field within the gap region of a tractor trailer combination truck and how several aerodynamic add on devices reduce the overall drag of a truck. The gap region of a truck typically contributes to about 20-25% of the overall vehicle drag and hence presents an opportunity for considerable level of drag reduction. A basic two box bluff body (2D & 3D) model was used to investigate how the flow field changes by changing the gap width between the two bluff bodies. A section of the thesis investigates the sudden increase in drag coefficient of the downstream cube around 2D tandem bluff bodies. Distinct flow patterns were observed in the gap and around the 2D tandem at different gap ratios. The sudden change in drag coefficient for the 2D downstream bluff body is well captured numerically, which is due to the wake of the upstream cube impinging onto the front face of the downstream cube. A steady increase in drag coefficient is witnessed for the 3D cubes which are consistent with previous experimental findings. The steady increase in drag coefficient is due to the vortical structures formed around the 3D cubes which are different, which consist of a smooth transition. Hence, they result in steady increase in drag coefficient. A second study was conducted on a realistic truck like test case with the simplified truck model where the leading edges of the tractor were rounded off to manipulate the flow separation. As a result of leading edge rounding off the flow separation reduced significantly resulting in a major portion of the flow remain attached to the lateral walls of the tractor. This was seen to increase the flow entering the gap region between the tractor and trailer. Finally, several add on devices which were subdivided based on tractor and trailer mounted devices were numerically assessed with several other devices within the gap region. Significant level of drag reduction was achieved for the entire truck with these add on devices. The highest drag reduction was achieved with the base bleeding technique. Overall, the research has shown that it is important to control the flow condition within the gap region and maintain an even pressure on the front face of the trailer. The base bleeding method proved to be a vital technique to further reduce drag.
    • Multiprocessor System-on-Chips based Wireless Sensor Network Energy Optimization

      Panneerselvam, John; Xue, Yong; Ali, Haider (University of DerbyDepartment of Electronics, Computing and Mathematics, 2020-10-08)
      Wireless Sensor Network (WSN) is an integrated part of the Internet-of-Things (IoT) used to monitor the physical or environmental conditions without human intervention. In WSN one of the major challenges is energy consumption reduction both at the sensor nodes and network levels. High energy consumption not only causes an increased carbon footprint but also limits the lifetime (LT) of the network. Network-on-Chip (NoC) based Multiprocessor System-on-Chips (MPSoCs) are becoming the de-facto computing platform for computationally extensive real-time applications in IoT due to their high performance and exceptional quality-of-service. In this thesis a task scheduling problem is investigated using MPSoCs architecture for tasks with precedence and deadline constraints in order to minimize the processing energy consumption while guaranteeing the timing constraints. Moreover, energy-aware nodes clustering is also performed to reduce the transmission energy consumption of the sensor nodes. Three distinct problems for energy optimization are investigated given as follows: First, a contention-aware energy-efficient static scheduling using NoC based heterogeneous MPSoC is performed for real-time tasks with an individual deadline and precedence constraints. An offline meta-heuristic based contention-aware energy-efficient task scheduling is developed that performs task ordering, mapping, and voltage assignment in an integrated manner. Compared to state-of-the-art scheduling our proposed algorithm significantly improves the energy-efficiency. Second, an energy-aware scheduling is investigated for a set of tasks with precedence constraints deploying Voltage Frequency Island (VFI) based heterogeneous NoC-MPSoCs. A novel population based algorithm called ARSH-FATI is developed that can dynamically switch between explorative and exploitative search modes at run-time. ARSH-FATI performance is superior to the existing task schedulers developed for homogeneous VFI-NoC-MPSoCs. Third, the transmission energy consumption of the sensor nodes in WSN is reduced by developing ARSH-FATI based Cluster Head Selection (ARSH-FATI-CHS) algorithm integrated with a heuristic called Novel Ranked Based Clustering (NRC). In cluster formation parameters such as residual energy, distance parameters, and workload on CHs are considered to improve LT of the network. The results prove that ARSH-FATI-CHS outperforms other state-of-the-art clustering algorithms in terms of LT.
    • Effects of the graphene on the mechanical properties of fibre reinforced polymer - a numerical and experimental study

      Lu, Yiling; Dean, Angela; Pawlik, Marzena (University of Derby, 2019-11)
      Mechanical properties of carbon fibre reinforced polymer (CFRP) are greatly affected by interphase between fibre and matrix. Coating fibre with nanofillers, i.e. graphene nanoplatelets (GNPs) or carbon nanotubes (CNTs) has suggested improving the interphase properties. Although the interphase is of small thickness, it plays an important role. Quantitative characterisation of the interphase region using an experimental technique such as nanoindentation, dynamic mechanical mapping remains challenging. More recently, computational modelling has become an alternative way to study the effects of interphase on CFRP properties. Simulation work of CFRP reinforced with nanofillers mainly focuses on CNTs grown on the fibre surface called fuzzy fibre reinforced polymers. Modelling work on the effects of GNPs on CFRP properties is rather limited. This project aims to study numerically and experimentally the effects of the nano-reinforced interphase on mechanical properties of CFRP. A multiscale model was developed to study the effects of the GNPs reinforced interphase on the elastic properties of CFRP laminate. The effective material properties of the reinforced interphase were determined by considering transversely isotropic features of GNPs and various orientation. The presence of GNPs in the interphase enhances the elastic properties of CFRP lamina, and the enhancement depends on its volume fraction. The incorporation of randomly orientated GNPs in the interphase increased longitudinal and transverse lamina moduli by 5 and 12 % respectively. While aligned GNPs in the interphase yielded less improvement. The present multiscale modelling was able to reproduce experimental measurements for GNPs reinforced CFRP laminates well. The multiscale model was also proven successful in predicting fuzzy fibre reinforced polymer. Moreover, the interphase properties were inversely quantified by combining with the multiscale model with some standard material testing. A two-step optimisation process was proposed, which involved the microscale and macroscale modelling. Based on the experimental data on flexural modulus, the lamina properties were derived at macroscale modelling, which were later used to determine the interphase properties from the optimisation at the microscale. The GNPs reinforced interphase modulus was 129.1 GPa which is significantly higher than epoxy coated carbon fibre of 60.51 GPa. In the experiment, a simple spraying technique was proposed to introduce GNPs and CNTs into the CFRP. Carbon fibre prepreg was sprayed with a nanofillers-ethanol solution using an airbrush. The extremely low volume fraction of nanofillers introduced between prepreg plies caused a noticeable improvement in mechanical properties, i.e. 7% increase in strain energy release. For the first time, the GNPs-ethanol-epoxy solution was sprayed directly on the carbon fibre fabric. Resultant nano-reinforced interphase created on fibre surface showed moderate improvement in samples flexural properties. In conclusion, a multiscale modelling framework was developed and tested. The GNPs reinforced interphase improved the mechanical properties of CFRP. This enhancement depended on the orientation and volume fraction of GNPs in the interphase. Spraying was a cost-effective method to introduce nanofillers in CFRP and showed huge potential for the scale-up manufacturing process. In a combination of multiscale framework and optimisation process, the nanofillers reinforced interphase was for the first time determined. This framework could be used to optimise the development process of new fibre-reinforced composites.
    • Shape grammar based adaptive building envelopes: Towards a novel climate responsive facade systems for sustainable architectural design in Vietnam.

      Ceranic, Boris; Tracada, Eleni; Nguyen, Ngoc Son Tung (University of Derby, 2020-01-14)
      The concept of a dynamic building enclosure is a relatively novel and unexplored area in sustainable architectural design and engineering and as such, could be considered a new paradigm. These façade systems, kinetic and adaptive in their nature, can provide opportunities for significant reductions in building energy use and CO2 emissions, whilst at the same time having a positive impact on the quality of the indoor environment. Current research in this area reports on a growing increase in the application of new generative design approaches and computational techniques to assist the design of adaptable kinetic systems and to help quantify their relationships between the building envelope and the environment. In this research, a novel application of shape grammar for the design of kinetic façade shading systems has been developed, based upon a generative design approach that controls the creation of complex shape composites, starting from a set of initial shapes and pre-defined rules of their composition. Shape grammars provide an interesting generative design archetype in which a set of shape rules can be recursively applied to create a language of designs, with the rules themselves becoming descriptors of such generated designs. The research is inspired by traditional patterns and ornaments in Vietnam, seen as an important symbol of its cultural heritage, especially in the era of globalisation where many developing countries, including Vietnam, are experiencing substantial modernist transformations in their cities. Those are often perceived as a cause of the loss of both visual and historical connections with indigenous architectural origins and traditions. This research hence investigates how these aspects of spatial culture could be interpreted and used in designing of novel façade shading systems that draw their inspiration from Vietnamese vernacular styles and cultural identity. At the same time, they also have to satisfy modern building performance demands, such as a reduction in energy consumption and enhanced indoor comfort. This led to the exploration of a creative form-finding for different building façade shading configurations, the performance of which was tested via simulation and evaluation of indoor daylight levels and corresponding heating and cooling loads. The developed façade structures are intended to adapt real-time, via responding to both results of an undertaken simulation and data-regulation protocols responsible for sensing and processing building performance data. To this extent, a strategy for BIM integrated sustainable design analysis (SDA) has also been deliberated, as a framework for exploring the integration of building management systems (BMS) into smart building environments (SBEs). Finally, the research reports on the findings of a prototype system development and its testing, allowing continuous evaluation of multiple solutions and presenting an opportunity for further improvement via multi-objective optimisation, which would be very difficult to do, if not impossible, with conventional design methods.
    • Parallaxical identities: Architectural semantics of contemporary arts institutions and the curation of cultural identity

      Tracada, Eleni; D'Arcy-Reed, Louis (University of Derby, 2019-09-19)
      The research project interrogates the identity forming principles beneath contemporary arts museum architecture across physical and psychoanalytical dimensions. In identifying a metaphysical distance, or barrier, between the unconscious of the cultural architectural intervention and the identity within the cities’ fabric, the state of a parallaxical identity manifests itself. The parallaxical identity, developed from Slavoj Žižek’s parallax gap in psychoanalysis, elicits the presentation of ego-ideal, ideal-ego, and superego of architectural interventions seen as regenerative for culture, the city and its communities. Developing the parallax within architecture allows the thesis to include a rigorous interrogation of theory across disciplines of psychoanalysis, architecture, contemporary art and museology, whilst also remediating the position of architectural practice beyond its conventional boundaries and rhetoric. Adopting a mixed methodology across theoretical and practical disciplines, the thesis reveals unconscious interpretations and embodied analyses through a weaving of para-architectural methods including, photography, questionnaires, exploratory installations, written prose, and imagined cultural visualisations. Three major arts institutions act as case study analysands for psychoanalytical observation and diagnosis to take place, informing the resulting framework for observing parallaxical identities, whilst also producing recommendations for the future of the cultural institution of the museum/gallery. Alongside the thesis’ position as a critical commentary, a supplementary PhD exhibition proposal centered on Parallaxical Identities questions the role of architecture as a discipline that necessitates para-architectural and psychoanalytic methodologies, whilst also presenting new artistic works in response to the thesis to reveal to audiences’ the haptic and hidden structures within architecture and the ‘expected or unexpected’ parallaxical interventions of place.
    • Dynamic collaboration and secure access of services in multi-cloud environments

      Liu, Lu; Zhu, Shao Ying; Kazim, Muhammad (University of DerbyCollege of Engineering and Technology, 2019-08-19)
      The cloud computing services have gained popularity in both public and enterprise domains and they process a large amount of user data with varying privacy levels. The increasing demand for cloud services including storage and computation requires new functional elements and provisioning schemes to meet user requirements. Multi-clouds can optimise the user requirements by allowing them to choose best services from a large number of services offered by various cloud providers as they are massively scalable, can be dynamically configured, and delivered on demand with large-scale infrastructure resources. A major concern related to multi-cloud adoption is the lack of models for them and their associated security issues which become more unpredictable in a multi-cloud environment. Moreover, in order to trust the services in a foreign cloud users depend on their assurances given by the cloud provider but cloud providers give very limited evidence or accountability to users which offers them the ability to hide some behaviour of the service. In this thesis, we propose a model for multi-cloud collaboration that can securely establish dynamic collaboration between heterogeneous clouds using the cloud on-demand model in a secure way. Initially, threat modelling for cloud services has been done that leads to the identification of various threats to service interfaces along with the possible attackers and the mechanisms to exploit those threats. Based on these threats the cloud provider can apply suitable mechanisms to protect services and user data from these threats. In the next phase, we present a lightweight and novel authentication mechanism which provides a single sign-on (SSO) to users for authentication at runtime between multi-clouds before granting them service access and it is formally verified. Next, we provide a service scheduling mechanism to select the best services from multiple cloud providers that closely match user quality of service requirements (QoS). The scheduling mechanism achieves high accuracy by providing distance correlation weighting mechanism among a large number of services QoS parameters. In the next stage, novel service level agreement (SLA) management mechanisms are proposed to ensure secure service execution in the foreign cloud. The usage of SLA mechanisms ensures that user QoS parameters including the functional (CPU, RAM, memory etc.) and non-functional requirements (bandwidth, latency, availability, reliability etc.) of users for a particular service are negotiated before secure collaboration between multi-clouds is setup. The multi-cloud handling user requests will be responsible to enforce mechanisms that fulfil the QoS requirements agreed in the SLA. While the monitoring phase in SLA involves monitoring the service execution in the foreign cloud to check its compliance with the SLA and report it back to the user. Finally, we present the use cases of applying the proposed model in scenarios such as Internet of Things (IoT) and E-Healthcare in multi-clouds. Moreover, the designed protocols are empirically implemented on two different clouds including OpenStack and Amazon AWS. Experiments indicate that the proposed model is scalable, authentication protocols result only in a limited overhead compared to standard authentication protocols, service scheduling achieves high efficiency and any SLA violations by a cloud provider can be recorded and reported back to the user.
    • Proposing a framework for organisational sustainable development: integrating quality management, supply chain management and sustainability

      Liyanage, Kapila; Bastas, Ali (University of DerbyCollege of Engineering and Technology, 2019-07-04)
      Increasing worldwide demand for products and services is applying a significant pressure on firms and supply chains operationally and financially, along with negative implications on our planet and the public. New approaches are highly required to be adopted by all members of the society, including the businesses for sustainable development. On the other hand, enabling such integration from an organisational management perspective is not straightforward, due to complexities and conflicts associated with balanced integration of economic, environmental and social agendas. Aimed towards addressing this important research requirement, a tailored conceptual framework is presented, constructed upon the synergistic principles of quality management (QM) and supply chain management (SCM) to facilitate integration of triple bottom line sustainability into business management. As the first step of the research, a systematic literature review was conducted, evidencing research gaps, and opportunities. A conceptual framework was established, and an implementation procedure to facilitate operationalisation of the framework was developed including a business diagnostic tool contribution, aiding current state maturity assessment as one of the key implementation steps. These developments were verified, validated and improved through the Delphi method, and applied at an organisation in Cyprus as the final validation step, using the action research method. Positive relationships were established and verified conceptually between the ISO 9001 principles of QM, supply chain integration principle of SCM, and organisational triple bottom line sustainability integration. The relative importance of these principles adopted in the framework were determined based on expert Delphi panel feedback. The action research demonstrated the application of the framework, outlined its contextual implementation factors, and concluded positive effects on the sustainable development of the participating organisation. Several contributions to knowledge were made, including the refinement of existing QM and SCM concepts for organisational sustainability improvement, and formulation of a practical framework including a novel diagnostic tool to facilitate integration of triple bottom line sustainability through QM and SCM. Particularly, a new management perspective was introduced with implications to many organisational managers that adopt ISO 9001 and supply chain integration principles, setting the way for extending these principles beyond their original QM and SCM agendas towards organisational sustainable development.
    • Smart City: A Traffic Signal Control System for Reducing the Effects of Traffic Congestion in Urban Environments

      Hardy, James (University of Derby, 2019-06-10)
      This thesis addresses the detrimental effects of road traffic congestion in the Smart City environment. Urban congestion is a recognisable problem that affects much of the world’s population through delays and pollution although the delays are not an entirely modern phenomena. The progressive increase in urbanisation and the numbers of powered road vehicles have led to an increasing need to control traffic in order to maintain flows and avoid gridlock situations. Signalised methods typically control flows through reduction, frequently increasing delays, holding traffic within the urban area and increasing local pollution. The current levels of vehicular congestion may relate to an increase in traffic volumes of 300% over 50 years while traffic control methods based on delaying moving traffic have changed very little. Mobility and Socio-economics indicate that the number of active road vehicles will increase or at least remain at the same levels in the foreseeable future and as a result congestion will continue to be a problem. The Smart City concept is intended to improve the urban environment through the application of advanced technology. Within the context of road transportation, the urban area consists of a wide variety of low to moderate speed transportation systems ranging from pedestrians to heavy goods vehicles. Urban roadways have a large number of junctions where the transport systems and flows interact presenting additional and more complex challenges as compared to high speed dual carriageways and motorways. Congestion is a function of population density while car ownership is an indicator of affluence; road congestion can therefore be seen as an indicator of local economic and social prosperity. Congestion cannot be resolved while there is a social benefit to urbanisation, high density living and a materialistic population. Recognising that congestion cannot be resolved, this research proposes a method to reduce the undesirable consequences and side effects of traffic congestion such as transit delays, inefficient fuel use and chemical pollution without adversely affecting the social and economic benefits. Existing traffic signal systems manage traffic flows based on traffic arrivals, prediction and traffic census models. Flow modification is accomplished by introducing delays through signal transition in order to prioritise a conflicting direction. It is incorrectly assumed that traffic will always be able to move and therefore signal changes will always have an effect. Signal transitions result in lost time at the junction. Existing Urban Traffic Control systems have limited capability as they are unable to adapt immediately to unexpected conditions, have a finite response, cannot modify stationary flow and may introduce needless losses through inefficient transition. This research proposes and develops Available Forward Road Capacity (AFRC), an algorithm with the ability to detect the onset of congestion, actively promote clearance, prevent unnecessary losses due to ineffective transitions and can influence other AFRC equipped junctions to ensure the most efficient use of unoccupied road capacity. AFRC is an additional function that can be applied to existing traffic controllers, becoming active only during congestion conditions; as a result it cannot increase congestion above current levels. By reducing the duration of congestion periods, AFRC reduces delays, improves the efficiency of fuel use and reduces pollution. AFRC is a scalable, multi-junction generalised solution which is able to manage traffic from multiple directions without prior tuning; it can detect and actively resolve problems with stationary traffic. AFRC is evaluated using a commercial traffic simulation system and is shown to resolve inbound and outbound congestion in less time than Vehicle Actuated and Fully Timed systems when simulating both morning and evening rush-hours.
    • High Performance Video Stream Analytics System for Object Detection and Classification

      Anjum, Ashiq; Yaseen, Muhammad Usman (University of DerbyCollege of Engineering and Technology, 2019-02-05)
      Due to the recent advances in cameras, cell phones and camcorders, particularly the resolution at which they can record an image/video, large amounts of data are generated daily. This video data is often so large that manually inspecting it for object detection and classification can be time consuming and error prone, thereby it requires automated analysis to extract useful information and meta-data. The automated analysis from video streams also comes with numerous challenges such as blur content and variation in illumination conditions and poses. We investigate an automated video analytics system in this thesis which takes into account the characteristics from both shallow and deep learning domains. We propose fusion of features from spatial frequency domain to perform highly accurate blur and illumination invariant object classification using deep learning networks. We also propose the tuning of hyper-parameters associated with the deep learning network through a mathematical model. The mathematical model used to support hyper-parameter tuning improved the performance of the proposed system during training. The outcomes of various hyper-parameters on system's performance are compared. The parameters that contribute towards the most optimal performance are selected for the video object classification. The proposed video analytics system has been demonstrated to process a large number of video streams and the underlying infrastructure is able to scale based on the number and size of the video stream(s) being processed. The extensive experimentation on publicly available image and video datasets reveal that the proposed system is significantly more accurate and scalable and can be used as a general purpose video analytics system.
    • A Trust Evaluation Framework in Vehicular Ad-Hoc Networks

      Adnane, Asma; Franqueira, Virginia N. L.; Anjum, Ashiq; Ahmad, Farhan (University of DerbyCollege of Engineering and Technology, 2019-03-11)
      Vehicular Ad-Hoc Networks (VANET) is a novel cutting-edge technology which provides connectivity to millions of vehicles around the world. It is the future of Intelligent Transportation System (ITS) and plays a significant role in the success of emerging smart cities and Internet of Things (IoT). VANET provides a unique platform for vehicles to intelligently exchange critical information, such as collision avoidance or steep-curve warnings. It is, therefore, paramount that this information remains reliable and authentic, i.e., originated from a legitimate and trusted vehicle. Due to sensitive nature of the messages in VANET, a secure, attack-free and trusted network is imperative for the propagation of reliable, accurate and authentic information. In case of VANET, ensuring such network is extremely difficult due to its large-scale and open nature, making it susceptible to diverse range of attacks including man-in-the-middle (MITM), replay, jamming and eavesdropping. Trust establishment among vehicles can increase network security by identifying dishonest vehicles and revoking messages with malicious content. For this purpose, several trust models (TMs) have been proposed but, currently, there is no effective way to compare how they would behave in practice under adversary conditions. Further, the proposed TMs are mostly context-dependent. Due to randomly distributed and highly mobile vehicles, context changes very frequently in VANET. Ideally the TMs should perform in every context of VANET. Therefore, it is important to have a common framework for the validation and evaluation of TMs. In this thesis, we proposed a novel Trust Evaluation And Management (TEAM) framework, which serves as a unique paradigm for the design, management and evaluation of TMs in various contexts and in presence of malicious vehicles. Our framework incorporates an asset-based threat model and ISO-based risk assessment for the identification of attacks against critical risks. TEAM has been built using VEINS, an open source simulation environment which incorporates SUMO traffic simulator and OMNET++ discrete event simulator. The framework created has been tested with the implementation of three types of TM (data-oriented, entity-oriented and hybrid) under four different contexts of VANET based on the mobility of both honest and malicious vehicles. Results indicate that TEAM is effective to simulate a wide range of TMs, where the efficiency is evaluated against different Quality of Service (QoS) and security-related criteria. Such framework may be instrumental for planning smart cities and for car manufacturers.
    • Simulation-based impact analysis for sustainable manufacturing design and management

      University of Derby (2018)
      This research focuses on effective decision-making for sustainable manufacturing design and management. The research contributes to the decision-making tools that can enable sustainability analysts to capture the aspects of the economic, environmental and social dimensions into a common framework. The framework will enable the practitioners to conduct a sustainability impact analysis of a real or proposed manufacturing system and use the outcome to support sustainability decision. In the past, the industries had focused more on the economic aspects in gaining and sustaining their competitive positions; this has changed in the recent years following the Brundtland report which centred on incorporating the sustainability of the future generations into our decision for meeting today’s needs (Brundtland, 1987). The government regulations and legislation, coupled with the changes in consumers’ preference for ethical and environmentally friendly products are other factors that are challenging and changing the way companies, and organisations perceive and drive their competitive goals (Gu et al., 2015). Another challenge is the lack of adequate tools to address the dynamism of the manufacturing environment and the need to balance the business’ competitive goal with sustainability requirements. The launch of the Life Cycle Sustainability Analysis (LCSA) framework further emphasised the needs for the integration and analysis of the interdependencies of the three dimensions for effective decision-making and the control of unintended consequences (UNEP, 2011). Various studies have also demonstrated the importance of interdependence impact analysis and integration of the three sustainability dimensions of the product, process and system levels of sustainability (Jayal et al., 2010; Valdivia et al., 2013; Eastwood and Haapala, 2015). Although there are tools capable of assessing the performance of either one or two of the three sustainability dimensions, the tools have not adequately integrated the three dimensions or address the holistic sustainability issues. Hence, this research proposes an approach to provide a solution for successful interdependence impact analysis and trade-off amongst the three sustainability dimensions and enable support for effective decision-making in a manufacturing environment. This novel approach explores and integrates the concepts and principles of the existing sustainability methodologies and frameworks and the simulation modelling construction process into a common descriptive framework for process level assessment. The thesis deploys Delphi study to verify and validate the descriptive framework and demonstrates its applicability in a case study of a real manufacturing system. The results of the research demonstrate the completeness, conciseness, correctness, clarity and applicability of the descriptive framework. Thus, the outcome of this research is a simulation-based impact analysis framework which provides a new way for sustainability practitioners to build an integrated and holistic computer simulation model of a real system, capable of assessing both production and sustainability performance of a dynamic manufacturing system.
    • Computer aided design of 3D of renewable energy platform for Togo's smart grid power system infrastructure

      Komlanvi, Moglo; University of Derby (2018-09-04)
      The global requirement for sustainable energy provision will become increasingly important over the next fifty years as the environmental effects of fossil fuel use become apparent. Therefore, the issues surrounding integration of renewable energy supplies need to be considered carefully. The focus of this work was the development of an innovative computer aided design of a 3 Dimensional renewable energy platform for Togo’s smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications. The Wind, Hydro, and PV system forming our 3 Dimensional renewable energy power generation systems introduces a new path for hybrid systems which extends the system capacities to include, a stable and constant clean energy supply, a reduced harmonic distortion, and an improved power system efficiency. Issues requiring consideration in high percentage renewable energy systems therefore includes the reliability of the supply when intermittent sources of electricity are being used, and the subsequent necessity for storage and back-up generation The adoption of Genetic algorithms in this case was much suited in minimizing the THD as the adoption of the CHB-MLI was ideal for connecting renewable energy sources with an AC grid. Cascaded inverters have also been proposed for use as the main traction drive in electric vehicles, where several batteries or ultra-capacitors are well suited to serve as separate DC sources. The simulation done in various non-linear load conditions showed the proportionality of an integral control based compensating cascaded passive filter thereby balancing the system even in non-linear load conditions. The measured total harmonic distortion of the source currents was found to be 2.36% thereby in compliance with IEEE 519-1992 and IEC 61000-3 standards for harmonics This work has succeeded in developing a more complete tool for analysing the feasibility of integrated renewable energy systems. This will allow informed decisions to be made about the technical feasibility of supply mix and control strategies, plant type, sizing and storage sizing, for any given area and range of supply options. The developed 3D renewable energy platform was examined and evaluated using CAD software analysis and a laboratory base mini test. The initial results showed improvements compared to other hybrid systems and their existing control systems. There was a notable improvement in the dynamic load demand and response, stability of the system with a reduced harmonic distortion. The derivatives of this research therefore proposes an innovative solution and a path for Togo and its intention of switching to renewable energy especially for its smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications
    • Evaluation and improvement on service quality of Chinese university libraries under new information environments.

      Fan,Yue Qian; University of Derby (2018-06)
      The rapid development of information technology in the recent years has added a range of new featuresto the traditional information environment, which has a profound impact on university library services and users. The Quality of Service parameter in library services has reached a broader consensus,which directly reflects customer satisfactions and loyalty. Exploring the evaluation frameworks for service quality in university libraries cannot be undermined in this context. Besides, existing evaluation frameworks of service quality of university library services are also facing numerous challenges due to their imperfections. Thus,there is an urgency and necessity to explore and enhance the efficiencies of the evaluation frameworks of service quality. To this end, this thesis conducts a systematic analysisof evaluation frameworks with a motivation of identifying the core components that needs enhancements for achieving effective service quality in Chinese university libraries through empirical methods. Furthermore, the inferences extracted from the analysis has been exploited to provide suitable recommendations for improving the service quality of university libraries.
    • Towards an efficient indexing and searching model for service discovery in a decentralised environment.

      Miao, Dejun; University of Derby (2018-05)
      Given the growth and outreach of new information, communication, computing and electronic technologies in various dimensions, the amount of data has explosively increased in the recent years. Centralised systems suffer some limitations to dealing with this issue due to all data is stored in central data centres. Thus, decentralised systems are getting more attention and increasing in popularity. Moreover, efficient service discovery mechanisms have naturally become an essential component in both large-scale and small-scale decentralised systems and. This research study is aimed at modelling a novel efficient indexing and searching model for service discovery in decentralised environments comprising numerous repositories with massive stored services. The main contributions of this research study can be summarised in three components: a novel distributed multilevel indexing model, an optimised searching algorithm and a new simulation environment. Indexing model has been widely used for efficient service discovery. For instance; the inverted index is one of the popular indexing models used for service retrieval in consistent repositories. However, redundancies are inevitable in the inverted index which is significantly time-consuming in the service discovery and retrieval process. This theeis proposes a novel distributed multilevel indexing model (DM-index), which offers an efficient solution for service discovery and retrieval in distributed service repositories comprising massive stored services. The architecture of the proposed indexing model encompasses four hierarchical levels to eliminate redundancy information in service repositories, to narrow the searching space and to reduce the number of traversed services whilst discovering services. Distributed Hash Tables have been widely used to provide data lookup services with logarithmic message costs which only require maintenance of limited amounts of routing states. This thesis develops an optimised searching algorithm, named Double-layer No-redundancy Enhanced Bi-direction Chord (DNEB-Chord), to handle retrieval requests in distributed destination repositories efficiently. This DNEB-Chord algorithm achieves faster routing performances with the double-layer routing mechanism and optimal routing index. The efficiency of the developed indexing and searching model is evaluated through theoretical analysis and experimental evaluation in a newly developed simulation environment, named Distributed Multilevel Bi-direction Simulator (DMBSim), which can be used as cost efficient tool for exploring various service configurations, user retrieval requirements and other parameter settings. Both the theoretical validation and experimental evaluations demonstrate that the service discovery efficiency of the DM-index outperforms the sequential index and inverted index configurations. Furthermore, the experimental evaluation results demostrate that the DNEB-Chord algorithm performs better than the Chord in terms of reducing the incurred hop counts. Finally, simulation results demonstrate that the proposed indexing and searching model can achieve better service discovery performances in large-scale decentralised environments comprising numerous repositories with massive stored services.