• Laboratory measurement of time-dependent deformation properties of muddy siltstone.

      Hamza, Omar; Stace, Rod; University of Derby; University of Nottingham (Chamber of Mining Engineers of Turkey, 2017-04-14)
      This paper investigates the time-dependent deformation of argillaceous rocks, drawing principally on laboratory experiments carried out on muddy siltstone recovered from an open pit mine located in the midlands, UK. A series of creep tests were conducted on both intact and fractured rock samples to cover the two ultimate structural conditions of rock mass. Based on the creep test results, the relationship between axial strain and time under different axial and deviatoric stresses was investigated. The creep data of both intact and fractured rock samples was successfully fitted to Burgers model to represent creep behaviours of pre and post failure. The study provides improved representation of the time-dependent deformation properties of rock mass, which is essential to enhance geomechanical modelling of long-term stability of abandoned mines and for the application of underground disposal of radioactive waste.
    • Large-eddy simulation of transition process in separated-reattached flows

      Yang, Zhiyin; University of Derby (WIT Press, 2011)
      It is important that scientists who perform experiments, researchers who develop computer codes, and those who carry out measurements on prototypes all communicate effectively. While computer models are now more reliable and better able to represent more realistic problems, experimental measurements need to be conditioned to the requirements of the computational models. Progress of engineering science depends on the orderly and progressive concurrent development of all three fields. This book contains the results of the latest in a biennial series of meetings to facilitate that communication and development that began in 1984. The papers presented at the conference included topics such as: Computational and Experimental Methods; Fluid Flow; Heat Transfer and Thermal Processes; Stress Analysis; Composite Materials; Detection and Signal Processing; Advances in Measurements and Data Acquisition; Multiscale Modelling; Ballistics; Railway Transport.
    • Large-eddy simulation of transitional flows using a co-located grid

      Langari, Mostafa; Yang, Zhiyin; Page, Gary J.; University of Sussex, Brighton, UK; University of Derby, UK (Taylor and Francis, 2013-07-12)
      A large-eddy simulation (LES) of a transitional separated flow over a plate with a semi-circular leading at low (<0.2%) and high (5.6%) free-stream turbulence (FST) has been performed, using a co-located grid with the Rhie–Chow pressure smoothing. A numerical trip is used to produce a high FST level and a dynamic subgrid-scale model is also employed in the current study. The entire transition process leading to breakdown to turbulence has been shown clearly by the flow visualisations using instantaneous spanwise vorticities, and the differences between the low- and high-FST cases are clearly visible. Coherent structures are also visualised using isosurfaces of the Q-criterion, and for the high-FST case, the spanwise-oriented quasi-two-dimensional rolls, which are clearly present in the low-FST case, are not visible anymore. Detailed quantitative comparisons between the present LES results and experimental data and the previous LES results at low FST using a staggered grid have been done and a good agreement has been obtained, indicating that the current LES using a co-located grid with pressure smoothing can also predict transitional flows accurately.
    • Large-eddy simulation: a glance at the past, a gaze at the present, a glimpse at the future

      Yang, Zhiyin; University of Derby, UK (2014-09-15)
      Large-Eddy Simulation (LES) was originally proposed for simulating atmospheric flows in the 1960s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computational power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, finish with the concluding remarks.
    • Large-eddy simulation: Past, present and the future

      Yang, Zhiyin; University of Derby, Derby, UK (Elsevier, 2015-02)
      Large-eddy simulation (LES) was originally proposed for simulating atmospheric flows in the 1960s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks.
    • Left atrial wall stress distribution and its relationship to electrophysiologic remodeling in persistent atrial fibrillation

      Hunter, R. J.; Liu, Yankai; Lu, Yiling; Wang, Wen; Schilling, R. J.; University of Derby (2012-01)
      Background—Atrial stretch causes remodeling that predisposes to atrial fibrillation. We tested the hypothesis that peaks in left atrial (LA) wall stress are associated with focal remodeling. Methods and Results—Nineteen patients underwent LA mapping before catheter ablation for persistent atrial fibrillation. Finite Element Analysis was used to predict wall stress distribution based on LA geometry from CT. The relationship was assessed between wall stress and (1) electrogram voltage and (2) complex fractionated atrial electrograms (CFAE), using CFAE mean (the mean interval between deflections). Wall stress varied widely within atria and between subjects (median, 36 kPa; interquartile range, 26–51 kP). Peaks in wall stress (≥90th percentile) were common at the pulmonary vein (PV) ostia (93%), the appendage ridge (100%), the high posterior wall (84%), and the anterior wall and septal regions (42–84%). Electrogram voltage showed an inverse relationship across quartiles for wall stress (19% difference across quartiles, P=0.016). There was no effect on CFAE mean across quartiles of wall stress. Receiver operating characteristic analysis showed high wall stress was associated with low voltage (ie, <0.5 mV) and electrical scar (ie, <0.05 mV; both P<0.0001) and with absence of CFAE (ie, CFAE mean <120 ms; P<0.0001). However, peaks in wall stress and CFAE were found at 88% of PV ostia. Conclusions—Peaks in wall stress were associated with areas of low voltage, suggestive of focal remodeling. Although peaks in wall stress were not associated with LA CFAE, the PV ostia may respond differently.
    • Light

      Shahzad, Sally; Azad University (Azad University, 2005)
    • Living with dementia condition in modern cities. Does urban renewal help vulnerable ageing population today?

      Tracada, Eleni; University of Derby (Network for Comfort and Energy Use in Buildings (NCEUB), 2017-07)
      Current debate on ageing in urban environments focuses on how designers and planners develop age-friendly cities or communities. Since 2007, World Health Organisation has been supporting “active ageing by optimizing opportunities for health, participation and security in order to enhance quality of life as people age”; a global network of age-friendly cities has been launched and city councils are now engaging with local communities to transform urban areas into healthier and fully inclusive places. In 2014, the National Health Service (NHS), UK published their Five Year Forward View for three health, care and financial gaps to be closed. The NHS is currently running a new pilot long-term partnership with five cities’ areas to develop healthier neighbourhoods by modernising services and integrating health and social care with welfare, education and affordable housing. The author of this paper and her colleagues formed a special cluster at their University to review recent national and international initiatives, such as the ones mentioned above. Their intention is to evaluate case studies and proposals related to ageing population with special needs and conditions, such as dementia, and apply innovative ideas of integration of arts not only in health places, but also in deprived neighbourhoods.
    • Mechanical properties and tribological behaviour of electroless Ni–P–Cu coatings on corrosion-resistant alloys under ultrahigh contact stress with sprayed nanoparticles.

      Leech, Andrew; Le, Huirong; Meng, Maozhou; University of Derby; Plymouth University (Elsevier, 2019-06-20)
      Threaded components manufactured from corrosion resistant alloys (CRA's) are vulnerable to galling. This paper develops a test matrix to systematically investigate the mechanical properties and tribological performance of electroless nickel phosphorous coatings on CRA's when subjected to high contact stress. Samples manufactured from 28Cr stainless steel were shot-peened for various periods prior to being electo/electroless coated. The coefficient of friction (CoF) of different coating systems was evaluated via sliding cross-pin method. Various wet and dry lubricants were utilised to examine tribological performance, furthermore the adhesion strength of the coatings was investigated by a bond and pull-off method. The study has shown a significant reduction in CoF for electroless nickel phosphorous coatings with prior shot-peening treatment and sprayed nanoparticles.
    • Mechanics and materials in the design of a buckling diaphragm wave energy converter

      Le, Huirong; Collins, Keri M.; Greaves, Deborah M.; Bellamy, Neil; University of Plymouth (2015-04-25)
    • Meshing strategy for PEM fuel cells CFD modelling – a systematic approach

      Choopanya, Pattarapong; Yang, Zhiyin; University of Sussex, Brighton, UK; University of Derby, Derby, UK (DEStech Publications, Inc., 2016-01)
      Typical PEM fuel cell models usually involve more than one million mesh elements making the computation very intense. This necessitates an effective way to mesh the computational domain with a minimum number of mesh points while, at the same time, maintaining good accuracy. The meshing strategy in each flow direction is investigated systematically in the current study and it has been found that mesh resolution in different directions has a different degree of influence on the accuracy of solutions. The proposed meshing strategy is capable of greatly reducing the number of mesh elements, hence computation time, while preserving the characteristics of important flow-field variables
    • A method for detecting abnormal program behavior on embedded devices

      Zhai, Xiaojun; Ehsan, Shoaib; Howells, Gareth; Dongbing, Gu; McDonald-Maier, Klaus; Appiah, Kofi; Hu, Huosheng; University of Leicester; University of Essex; University of Kent; et al. (IEEE, 2015-04-13)
      A potential threat to embedded systems is the execution of unknown or malicious software capable of triggering harmful system behavior, aimed at theft of sensitive data or causing damage to the system. Commercial off-the-shelf embedded devices, such as embedded medical equipment, are more vulnerable as these type of products cannot be amended conventionally or have limited resources to implement protection mechanisms. In this paper, we present a self-organizing map (SOM)-based approach to enhance embedded system security by detecting abnormal program behavior. The proposed method extracts features derived from processor's program counter and cycles per instruction, and then utilises the features to identify abnormal behavior using the SOM. Results achieved in our experiment show that the proposed method can identify unknown program behaviors not included in the training set with over 98.4% accuracy.
    • Methodologies for data collection and model documentation in computer simulation

      Liyanage, Kapila; The Open University of Sri Lanka (Siam Technology College, Bangkok, Thailand, 2005-10)
      In recent years, computer simulation has become a mainstream decision support tool in an industry. In order to maximise the benefits of using simulation within businesses, simulation models should be designed, developed and deployed in a shorter time span. A number of factors, such as excessive model details, inefficient data collection, lengthy model documentation and poorly planned experiments, increase the overall lead-time of simulation projects. Among these factors, input data modeling and model documentation are seen as major obstacles. Input data identification, collection, validation and analysis typically take more than one-third of project time. This paper presents an IDEF (Integrated computer-aided manufacturing DEFinition) based approach to accelerate identification and collection of input data. A functional module library and a reference data model, both developed using the IDEF family of constructs, are the core elements of the methodology. In addition, this paper also intends to give a methodological approach that helps and motivates the project team to document simulation projects.
    • Methodology for rapid identification and collection of input data in the simulation of manufacturing systems

      Perera, Terrence; Liyanage, Kapila; Sheffield Hallam University (Elsevier, 2000-02)
      Computer simulation is a well-established decision support tool in the manufacturing industry. The rapid development and deployment of simulation models however, are inhibited by factors such as inefficient data collection, lengthy model documentation, and poorly planned experimentation. Typically, more than one third of project time is spent on identification, collection, validation, and analysis of input data. Whilst most research work has been focused on statistical techniques for data analysis, less attention has been paid to the development of systematic approaches to input data gathering. This paper presents a methodology for rapid identification and collection of input data in batch manufacturing environments. A functional module library and a reference data model, both developed using the IDEF (Integrated computer aided manufacturing DEFinition) family of constructs, are the core elements of the methodology. The paper also identifies the major causes behind the inefficient collection of data.
    • Micro- climate adaptation of whole building energy simulation in large complexes.

      Zoras, Stamatis; Veranoudis, Sotiris; Dimoudi, Argyro; University of Derby; Democritus University of Thrace (Elsevier, 2017-05-26)
      The purpose of this study was to evaluate the cooling demand during a summer day over a large city area before and after bioclimatic interventions in outdoor spaces by using whole building thermal simulation. This kind of interventions ultimately leads to a microclimatic change in a city. Prediction of microclimate data for a whole day in a large area due to changes in outdoor spaces is time and cost demanding. A model for prediction of hourly microclimatic data in a region for a whole day by employing Fourier analysis of past (measured) and future (simulated from a CFD analysis) microclimate data of a limited period (sunlight hours) was also developed. The whole building energy simulation software TAS-EDSL was applied for a quite large built space (∼500 m × 500 m), for simultaneous simulations in all buildings in the area, and took into account detailed building construction data, mutual shading between buildings and local climatic conditions. In this context, strategies and practices that a building complex should follow in the future in relation to climate change could be investigated. Simulation estimations of cooling loads of building spaces were related to buildings’ age, orientation and height. Main outcome of the study was the ability to assess building energy performance due to exterior micro- climate improvement, simultaneously, for about 200 buildings.
    • Micro/Nanostructure and tribological characteristics of pressureless sintered carbon nanotubes reinforced aluminium matrix composites

      Manikandan, Paramasivan; Sieh, Raymond; Elayaperumal, A.; Le, Huirong; Basu, Sourajyoti; Anna University, India; Plymouth University, United Kingdom; University of Derby (2016-03-30)
      This study reports the manufacture, microstructure, and tribological behaviour of carbon nanotube reinforced aluminium composites against pure aluminium. The specimens were fabricated using powder metallurgy method. The nanotubes in weight percentages of 0.5, 1.0, 1.5, and 2.0 were homogeneously dispersed and mechanically alloyed using a high energy ball milling. The milled powders were cold compacted and then isothermally sintered in air. The density of all samples was measured using Archimedes method and all had a relative density between 92.22% and 97.74%. Vickers hardness increased with increasing CNT fraction up to 1.5 wt% and then reduced. The microstructures and surfaces were investigated using high resolution scanning electron microscope (SEM). The tribological tests showed that the CNT reinforced composites displayed lower wear rate and friction coefficient compared to the pure aluminium under mild wear conditions. However, for severe wear conditions, the CNT reinforced composites exhibited higher friction coefficient and wear rate compared to the pure aluminium. It was also found that the friction and wear behaviour of CNT reinforced composites is significantly dependent on the applied load and there is a critical load beyond which CNTs could have adverse impact on the wear resistance of aluminium.
    • Micromechanical modeling of 8-harness satin weave glass fiber-reinforced composites.

      Choudhry, Rizwan Saeed; Khan, Kamran A.; Khan, Sohaib Z.; Khan, Muhammad A.; Hassan, Abid; Capital University of Sciences and Technology; University of Manchester; National University of Science and Technology; Khalifa University of Science and Technology (Sage, 2016-05-26)
      This study introduces a unit cell (UC) based finite element (FE) micromechanical model that accounts for correct post cure fabric geometry, in-situ material properties and void content within the composite to accurately predict the effective elastic orthotropic properties of 8-harness satin weave glass fiber reinforced phenolic (GFRP) composites. The micromechanical model utilizes a correct post cure internal architecture of weave, which was obtained through X-ray microtomography (XMT) tests. Moreover, it utilizes an analytical expression to up-date the input material properties to account for in-situ effects of resin distribution within yarn (the yarn volume fraction) and void content on yarn and matrix properties. This is generally not considered in modeling approaches available in literature and in particular, it has not been demonstrated before for FE micromechanics models of 8-harness satin weave composites. The UC method is used to obtain the effective responses by applying periodic boundary conditions. The outcome of the analysis based on the proposed model is validated through experiments. After validation, the micromechanical model was further utilized to predict the unknown effective properties of the same composite.
    • Microstructural analysis of TRISO particles using multi-scale X-ray computed tomography

      Lowe, Tristan; Yue, Sheng; Bari, Klaudio; Gelb, Jeff; Rohbeck, Nadia; Turner, Joel; Withers, Philip; University of Derby (Elsevier, 2015-06)
      TRISO particles, a composite nuclear fuel built up by ceramic and graphitic layers, have outstanding high temperature resistance. TRISO fuel is the key technology for High Temperature Reactors (HTRs) and the Generation IV Very High Temperature Reactor (VHTR) variant. TRISO offers unparalleled containment of fission products and is extremely robust during accident conditions. An understanding of the thermal performance and mechanical properties of TRISO fuel requires a detailed knowledge of pore sizes, their distribution and interconnectivity. Here 50 nm, nano-, and 1 μm resolution, micro-computed tomography (CT), have been used to quantify non-destructively porosity of a surrogate TRISO particle at the 0.3–10 μm and 3–100 μm scales respectively. This indicates that pore distributions can reliably be measured down to a size approximately 3 times the pixel size which is consistent with the segmentation process. Direct comparison with Scanning Electron Microscopy (SEM) sections indicates that destructive sectioning can introduce significant levels of coarse damage, especially in the pyrolytic carbon layers. Further comparative work is required to identify means of minimizing such damage for SEM studies. Finally since it is non-destructive, multi-scale time-lapse X-ray CT opens the possibility of intermittently tracking the degradation of TRISO structure under thermal cycles or radiation conditions in order to validate models of degradation such as kernel movement. X-ray CT in-situ experimentation of TRISO particles under load and temperature could also be used to understand the internal changes that occur in the particles under accident conditions.
    • Modelling in ranking procedures: A case study of infrastructure failures in Nigeria

      Omoregie, Alohan; Ebohon, Obas John; Radford, Dennis; De Montfort University (International Council for Research and Innovation in Building and Construction, 2005-11-17)
      The lack of a scientific approach as to which factors are considered or chosen in a decision-making process can seriously influence the effectiveness of that process. Using the example of infrastructure failures in Nigeria, this paper presents a severity index in matrix order (SIMO) model that unambiguously ranks factors and also defines a threshold that demarcates between major variable factors that should not be compromised in policy and less important ones. Infrastructures failures in Nigeria have hindered economic processes which were meant to alleviate poverty. Constraints responsible for this situation are identified from a carefully conducted survey in Nigeria. Severity of these constraints is empirically ranked using a developed severity index in matrix order (SIMO) model. However, the investigation reveals that corruption, misallocation of investments, inadequate maintenance, lack of transparency and accountability, insufficient funding for infrastructure, lack of supportive institutions, inconsistent political, social and economic policies and the lack of suitable technical and managerial skill are the major variable factors responsible for infrastructure failures in Nigeria.
    • Modelling of the buckling of a diaphragm–spine structure for a wave energy converter

      Collins, Keri M.; Meng, Maozhou; Le, Huirong; Greaves, Deborah M.; Bellamy, Neil; Plymouth University; University of Derby; Sea Energy Associates Ltd. (Elsevier, 2017-01-15)
      A wide range of wave energy converter (WEC) designs exists, and the SeaWave WEC uses an unstable buckled spine mode of operation. The SeaWave consists of a hose and buckled spine-diaphragm, which pumps air along the device under wave action. A physical model and finite element analysis (FEA) is compared to a previous theoretical model in this paper. The FE model was developed in ABAQUS 6.14 using shell, solid and contact elements and the analysis was done with a quasi-static approach to reduce the computational costs. The physical model was a scale version of the novel arrangement of the spine and diaphragm made from steel, polycarbonate and latex rubber. Geometry of the deformed device was investigated results showed an increase in transverse and longitudinal curvature as the compression rate increased. The FEA tended to overestimate the bending stiffness of the model, and hence the transverse curvature, because certain behaviours of the physical model were not captured. The force required to switch from one buckled state to another was measured both in the physical and FEA models and the potential energy storage was estimated to be 0.5 J/m of device at a compression rate of 0.1%.