Recent Submissions

  • On some results concerning the polygonal polynomials.

    Andrica, Dorin; Bagdasar, Ovidiu; Babeș-Bolyai University; University of Derby (Technical University of Cluj-Napoca., 2019-02-13)
    In this paper we define the $n$th polygonal polynomial $P_n(z) = (z-1)(z^2-1)\cdots(z^n-1)$ and we investigate recurrence relations and exact integral formulae for the coefficients of $P_n(z)$ and for those of the Mahonian polynomials $Q_n(z)=(z+1)(z^2+z+1)\cdots(z^{n-1}+\cdots+z+1)$. We also explore numerical properties of these coefficients, unraveling new meanings for old sequences and generating novel entries to the Online Encyclopedia of Integer Sequences (OEIS). Some open questions are also formulated.
  • Innovative approach to sustainable material sourcing and its impact on building performance

    Rajpurohit J.S., Ceranic B., Latham D.; University of Derby (WIT Press, 2019-01-29)
    In this paper, a novel use of building materials and their impact on the building performance and its climatic adaptability is explored, based on a complex case study of a unique low energy sustainable building project. In particular, an innovative use of sycamore and its suitability as a structural and constructional timber has been investigated and reported, given that the current codes of practice deem that is not appropriate for structural applications due to its durability. A research method of in-situ longitudinal study has been adopted, concentrating on the monitoring and assessment of its structural performance and conditions in which it might deteriorate. On the component level, the research reports on the methods and standards of sycamore grading and classification, service classes, resistance to decay, impact of the moisture movement and results of its laboratory and in situ testing. On the system level, the climatic adaptability of the building as a whole has been analysed via dynamic performance simulation and compared to the in-situ measurements. This was important in order to develop a holistic building performance monitoring strategy, but in particular, to understand the impact of building microclimate on the sycamore frame and hempcrete components of the external load-bearing wall. So far research has concluded that sycamore can be used as structural and constructional material in building design, but due attention has to be paid to construction detailing and provision of a breathable, low humidity environment with an effective resistance to decay and insect attack. This includes measures that ensure a low equilibrium moisture content conditions, effective ventilation provision and appropriate service class uses. It is important to state however, given the single site locality of sycamore sourcing, that results can only be interpreted in the context of the given case study, i.e. they cannot be extrapolated to broader geographical extents.
  • Multi-objective evolutionary—fuzzy augmented flight control for an F16 aircraft

    Stewart, P; Gladwin, D; Parr, M; Stewart, J; University of Sheffield (2009-11-05)
    In this article, the multi-objective design of a fuzzy logic augmented flight controller for a high performance fighter jet (the Lockheed-Martin F16) is described. A fuzzy logic controller is designed and its membership functions tuned by genetic algorithms in order to design a roll, pitch, and yaw flight controller with enhanced manoeuverability which still retains safety critical operation when combined with a standard inner-loop stabilizing controller. The controller is assessed in terms of pilot effort and thus reduction of pilot fatigue. The controller is incorporated into a six degree of freedom motion base real-time flight simulator, and flight tested by a qualified pilot instructor.
  • Behavioural Digital Forensics Model: Embedding Behavioural Evidence Analysis into the Investigation of Digital Crimes

    Al Mutawa, Noora; Bryce, Joanne; Franqueira, Virginia N.L.; Marrington, Andrew; Read, Janet C.; University of Derby (Elsevier, 2019-03)
    The state-of-the-art and practice show an increased recognition, but limited adoption, of Behavioural Evidence Analysis (BEA) within the Digital Forensics (DF) investigation process. Yet, there is currently no BEA-driven process model and guidelines for DF investigators to follow in order to take advantage of such an approach. This paper proposes the Behavioural Digital Forensics Model to fill this gap. It takes a multidisciplinary approach which incorporates BEA into in-lab investigation of seized devices related to interpersonal cases (i.e., digital crimes involving human interactions between offender(s) and victim(s)). The model was designed based on the application of traditional BEA phases to 35 real cases, and evaluated using 5 real digital crime cases - all from Dubai Police archive. This paper, however, provides details of only one case from this evaluation pool. Compared to the outcome of these cases using a traditional DF investigation process, the new model showed a number of benefits. It allowed a more effective focusing of the investigation, and provided logical directions for identifying the location of further relevant evidence. It also enabled a better understanding and interpretation of victim/offender behaviours (e.g., probable offenders' motivations and modus operandi), which facilitated a more in depth understanding of the dynamics of the specific crime. Finally, in some cases, it enabled the identification of suspect's collaborators, something which was not identified via the traditional investigative process.
  • Comparison of two novel MRAS based strategies for identifying parameters in permanent magnet synchronous motors.

    Liu, Kan; Zhang, Qiao; Zhu, Zi-Qiang; Zhang, Jing; Shen, An-Wen; Stewart, Paul; University of Lincoln UK (Springer., 2010-11-11)
    Two Model Reference Adaptive System (MRAS) estimators are developed for identifying the parameters of permanent magnet synchronous motors (PMSM) based on Lyapunov stability theorem and Popov stability criterion, respectively. The proposed estimators only need online detection of currents, voltages and rotor rotation speed, and are effective in the estimation of stator resistance, inductance and rotor flux-linkage simultaneously. Their performances are compared and verified through simulations and experiments. It shows that the two estimators are simple and have good robustness against parameter variation and are accurate in parameter tracking. However, the estimator based on Popov stability criterion, which can overcome the parameter variation in a practical system, is superior in terms of response speed and convergence speed since there are both proportional and integral units in the estimator in contrast to only one integral unit in the estimator based on Lyapunov stability theorem. In addition, there is no need of the expert experience which is required in designing a Lyapunov function
  • Improved decision support for engine-in-the-loop experimental design optimization.

    Gladwin, D; Stewart, P; Stewart, J; Chen, R; Winward, E; University of Sheffield; University of Lincoln.; Loughborough university (Sage., 2009-09-25)
    Experimental optimization with hardware in the loop is a common procedure in engineering and has been the subject of intense development, particularly when it is applied to relatively complex combinatorial systems that are not completely understood, or where accurate modelling is not possible owing to the dimensions of the search space. A common source of difficulty arises because of the level of noise associated with experimental measurements, a combination of limited instrument precision, and extraneous factors. When a series of experiments is conducted to search for a combination of input parameters that results in a minimum or maximum response, under the imposition of noise, the underlying shape of the function being optimized can become very difficult to discern or even lost. A common methodology to support experimental search for optimal or suboptimal values is to use one of the many gradient descent methods. However, even sophisticated and proven methodologies, such as simulated annealing, can be significantly challenged in the presence of noise, since approximating the gradient at any point becomes highly unreliable. Often, experiments are accepted as a result of random noise which should be rejected, and vice versa. This is also true for other sampling techniques, including tabu and evolutionary algorithms. After the general introduction, this paper is divided into two main sections (sections 2 and 3), which are followed by the conclusion. Section 2 introduces a decision support methodology based upon response surfaces, which supplements experimental management based on a variable neighbourhood search and is shown to be highly effective in directing experiments in the presence of a significant signal-to-noise ratio and complex combinatorial functions. The methodology is developed on a three-dimensional surface with multiple local minima, a large basin of attraction, and a high signal-to-noise ratio. In section 2, the methodology is applied to an automotive combinatorial search in the laboratory, on a real-time engine-in-the-loop application. In this application, it is desired to find the maximum power output of an experimental single-cylinder spark ignition engine operating under a quasi-constant-volume operating regime. Under this regime, the piston is slowed at top dead centre to achieve combustion in close to constant volume conditions. As part of the further development of the engine to incorporate a linear generator to investigate free-piston operation, it is necessary to perform a series of experiments with combinatorial parameters. The objective is to identify the maximum power point in the least number of experiments in order to minimize costs. This test programme provides peak power data in order to achieve optimal electrical machine design. The decision support methodology is combined with standard optimization and search methods — namely gradient descent and simulated annealing— in order to study the reductions possible in experimental iterations. It is shown that the decision support methodology significantly reduces the number of experiments necessary to find the maximum power solution and thus offers a potentially significant cost saving to hardware-in-the-loop experimentation.
  • Mathematical model of a constructional coanda effect nozzle.

    Trancossi, Michele; Stewart, Jill; Subhash, M; Angeli, Diego; Sheffield Hallam University (Physics Society of Iran., 2016)
    This paper analyses the ACHEON Coanda effect nozzle for aircraft propulsion, based on the dynamic equilibrium of two jet streams. The ACHEON concept, and, in particular, the HOMER nozzle, which is its main component, are presented, together with the literature milestones from which the idea originally stems. A subsystem analysis inspired by the principles of Constructal Theory is presented for the current architecture. A mathematical model of a 2D case of the system is developed, focusing on the combined effect of the mixing of the two streams and the Coanda adhesion over a convex surface. A validation of the model is also reported, based on 2D CFD analyses, under the hypothesis of incompressible flow. Results highlight that, in spite of its relative simplicity, the model produces accurate results.
  • Constructal design of an entropic wall With circulating water inside.

    Trancossi, Michele; Stewart, Jill; Dumas, Antonio; Madonia, Mauro; Marques, Jose Pascoa; Sheffield Hallam University (ASME, 2016-04-26)
    An entropic wall with circulating water inside could be a solution for acclimatizing a new building with high-energy efficiency and high levels of internal comfort. If circulating water is thermally stabilized by exchanging in the ground such has it happens in geothermal plants, a thermal shield could be realized keeping walls in comfort conditions and minimizing energy needs for further temperature regulations. This paper presents optimization guidelines of such a wall with the objective of maximizing the performances of the wall for reaching optimal internal wellness conditions. Optimization has been realized by a constructal law based method, which has been personalized by a step-by-step process and has been named constructal design for efficiency (CDE). The optimization of the system has been produced at different levels. It starts from a preliminary analysis at system levels, which allow defining the best objectives that could be reached. After this preliminary process, the system has been divided into modules, and the critical ones which have higher influence on the performances of the system have been evaluated. This analysis has been coupled also with an industrial analysis with the goal of defining an effective layout, which could be also manufactured with acceptable costs. The result has produced a final solution with a very good compromise between energetic performances and minimization of costs at industrial level. The results open interesting perspectives for the constructal law to become the core of an effective methodology of an industrial design which can couple perfectly with the modular approach which is currently the major part of industrial companies.
  • Increasing the impact of mathematics support on aiding student transition in higher education.

    Gallimore, M.; Stewart, J.; University of Lincoln (Oxford University Press, 2014-04-10)
    The ever growing gap between secondary and university level mathematics is a major concern to higher education institutions. The increase in diversity of students’ background in mathematics, with entry qualifications ranging from the more traditional A-level programmes to BTEC or international qualifications is compounded where institutions attempt to widen participation. For example, work-based learners may have been out of education for prolonged periods and, consequently, are often unprepared for the marked shift in levels, and catering for all abilities is difficult in the normal lecture, tutorial format. Lack of sufficient mathematical knowledge not only affects students’ achievement on courses but also leads to disengagement and higher drop-out rates during the first 2 years of study. Many universities now offer a maths support service in an attempt to overcome these issues, but their success is varied. This article presents a novel approach to maths support designed and adopted by the University of Lincoln, School of Engineering, to bridge this transition gap for students, offer continued support through Assessment for Learning and Individual Learning Plans, and ultimately increase student achievement, engagement and retention. The article then extends this proven approach and discusses recently implemented enhancements through the use of online diagnostic testing and a ‘student expert’ system to harness mathematical knowledge held by those gifted and talented students (often overlooked by higher education institutions) and to promote peer-to-peer mentoring. The article shows that with the proven system in place, there is a marked increase in student retention compared with national benchmark data, and an increase in student engagement and achievement measured through student feedback and assessments. Although the online enhancements are in the early stages of implementation, it is expected, based on these results, that further improvements will be shown.
  • Integrated flight/thrust vectoring control for jet-powered unmanned aerial vehicles with ACHEON propulsion.

    Cen, Zhaohui; Smith, Tim; Stewart, Paul; Stewart, Jill; University of Lincoln; University of Hull; University of Chester (SAGE, 2014-07-29)
    As a new alternative to tilting rotors or turbojet vector mechanical oriented nozzles, ACHEON (Aerial CoandaHigh Efficiency Orienting-jet Nozzle) has enormous advantages because it is free of moving elements and highly effective for Vertical/Short-Take-Off and Landing (V/STOL) aircraft. In this paper, an integrated flight/ thrust vectoringcontrol scheme for a jet powered Unmanned Aerial Vehicle (UAV) with an ACHEON nozzle is proposed to assess its suitability in jet aircraft flight applications. Firstly, a simplified Thrust-Vectoring (TV) population model is built based on CFD simulation data and parameter identification. Secondly, this TV propulsion model is embedded as a jet actuatorfor a benchmark fixed-wing ‘Aerosonde’ UAV, and then a four “cascaded-loop” controller, based on nonlinear dynamic inversion (NDI), is designed to individually control the angular rates (in the body frame), attitude angles (in the wind frame), track angles (in the navigation frame), and position (in the earth-centered frame) . Unlike previous research on fixed-wing UAV flight controls or TV controls, our proposed four-cascaded NDI control law can not only coordinatesurface control and TV control as well as an optimization controller, but can also implement an absolute self-position control for the autopilot flight control. Finally, flight simulations in a high-fidelity aerodynamic environment are performed to demonstrate the effectiveness and superiority of our proposed control scheme.
  • Man-In-The-Middle attacks in Vehicular Ad-Hoc Networks: Evaluating the impact of attackers’ strategies.

    Ahmad, Farhan; Adnane, Asma; Franqueira, Virginia N. L.; Kurugollu, Fatih; Liu, Lu; University of Derby; Loughborough University (MDPI, 2018-11-20)
    Vehicular Ad-Hoc Network (VANET), a vital component of Intelligent Transportation Systems (ITS) technology, relies on communication between dynamically connected vehicles and static Road Side Units (RSU) to offer various applications (e.g., collision avoidance alerts, steep-curve warnings and infotainment). VANET has a massive potential to improve traffic efficiency, and road safety by exchanging critical information between nodes (vehicles and RSU), thus reducing the likelihood of traffic accidents. However, this communication between nodes is subject to a variety of attacks, such as Man-In-The-Middle (MITM) attacks which represent a major risk in VANET. It happens when a malicious node intercepts or tampers with messages exchanged between legitimate nodes. In this paper, we studied the impact on network performance of different strategies which attackers can adopt to launch MITM attacks in VANET, such as fleet or random strategies. In particular, we focus on three goals of MITM attacks—message delayed, message dropped and message tampered. The simulation results indicate that these attacks have a severe influence on the legitimate nodes in VANET as the network experience high number of compromised messages, high end-to-end delays and preeminent packet losses.
  • Experimental and numerical investigation of fuel–air mixing in a radial swirler slot of a dry low emission gas turbine combustor.

    Agbonzikilo, Festus Eghe; Owen, Ieuan; Stewart, Jill; Sadasivuni, Suresh Kumar; Riley, Mike; Sanderson, Victoria; University of Lincoln; Sheffield Hallam University (ASME, 2015-11-17)
    This paper presents the results of an investigation in which the fuel/air mixing process in a single slot within the radial swirler of a dry low emission (DLE) combustion system is explored using air/air mixing. Experimental studies have been carried out on an atmospheric test facility in which the test domain is a large-scale representation of a swirler slot from a Siemens proprietary DLE combustion system. Hot air with a temperature of 300 °C is supplied to the slot, while the injected fuel gas is simulated using air jets with temperatures of about 25 °C. Temperature has been used as a scalar to measure the mixing of the jets with the cross-flow. The mixture temperatures were measured using thermocouples while Pitot probes were used to obtain local velocity measurements. The experimental data have been used to validate a computational fluid dynamics (CFD) mixing model. Numerical simulations were carried out using CFD software ansys-cfx. Due to the complex three-dimensional flow structure inside the swirler slot, different Reynolds-averaged Navier–Stokes (RANS) turbulence models were tested. The shear stress transport (SST) turbulence model was observed to give best agreement with the experimental data. The momentum flux ratio between the main air flow and the injected fuel jet, and the aerodynamics inside the slot were both identified by this study as major factors in determining the mixing characteristics. It has been shown that mixing in the swirler can be significantly improved by exploiting the aerodynamic characteristics of the flow inside the slot. The validated CFD model provides a tool which will be used in future studies to explore fuel/air mixing at engine conditions.
  • Generator voltage stabilisation for series-hybrid electric vehicles.

    Stewart, P.; Gladwin, D.; Stewart, J.; Cowley, R.; University of Sheffield (Elsevier, 2008-02-11)
    This paper presents a controller for use in speed control of an internal combustion engine for series-hybrid electric vehicle applications. Particular reference is made to the stability of the rectified DC link voltage under load disturbance. In the system under consideration, the primary power source is a four-cylinder normally aspirated gasoline internal combustion engine, which is mechanically coupled to a three-phase permanent magnet AC generator. The generated AC voltage is subsequently rectified to supply a lead-acid battery, and permanent magnet traction motors via three-phase full bridge power electronic inverters. Two complementary performance objectives exist. Firstly to maintain the internal combustion engine at its optimal operating point, and secondly to supply a stable 42 V supply to the traction drive inverters. Achievement of these goals minimises the transient energy storage requirements at the DC link, with a consequent reduction in both weight and cost. These objectives imply constant velocity operation of the internal combustion engine under external load disturbances and changes in both operating conditions and vehicle speed set-points. An electronically operated throttle allows closed loop engine velocity control. System time delays and nonlinearities render closed loop control design extremely problematic. A model-based controller is designed and shown to be effective in controlling the DC link voltage, resulting in the well-conditioned operation of the hybrid vehicle.
  • Analytical tools for blockchain: review, taxonomy and open challenges.

    Balaskas, Anastasios; Franqueira, Virginia N. L.; University of Derby (IEEE Computer Society, 2018-12-06)
    Bitcoin has introduced a new concept that could feasibly revolutionise the entire Internet as it exists, and positively impact on many types of industries including, but not limited to, banking, public sector and supply chain. This innovation is grounded on pseudo-anonymity and strives on its innovative decentralised architecture based on the blockchain technology. Blockchain is pushing forward a race of transaction-based applications with trust establishment without the need for a centralised authority, promoting accountability and transparency within the business process. However, a blockchain ledger (e.g., Bitcoin) tend to become very complex and specialised tools, collectively called “Blockchain Analytics”, are required to allow individuals, law enforcement agencies and service providers to search, explore and visualise it. Over the last years, several analytical tools have been developed with capabilities that allow, e.g., to map relationships, examine flow of transactions and filter crime instances as a way to enhance forensic investigations. This paper discusses the current state of blockchain analytical tools and presents a thematic taxonomy model based on their applications. It also examines open challenges for future development and research.
  • Framework for a chemical substance reporting system.

    Takhar, Sukhraj Singh; Liyanage, Kapila; University of Derby (2018-10-25)
    In this paper a chemical substance reporting system is presented to enable industry to assess the impacts of increasing chemical regulations. Chemical regulations impose the need to monitor, control and restrict the use of hazardous substances. As chemical substances become more regulated, industry requires mechanisms to identify potential business continuity risks, posed by increased regulation. A chemical reporting system is one such mechanism that identifies chemical substances used on their (i) own, (ii) in mixtures, (iii) in materials, (iv) in internally defined articles (products) and (v) from articles (products) procured from the supply chain. The chemical reporting system will contrast product related information against chemical regulation substance lists, identifying the applicable reporting obligations and potential supply chain risks.
  • LQR controller design for quad-rotor helicopters.

    E. Okyere; A. bousbaine; G. T. Poyi; A.K. Joseph; J.M. Andrade; University of Derby (The Institute of Engineering and Technology., 2018-06-22)
    This paper presents an analysis and performance of a LQR control algorithm for quadrotor helicopters. For a successful analysis, first the dynamic model has been developed for the quadcopter and then the controller was designed, tuned and tested. In tuning the LQR, much attention was given to the feedback gain matrix (K). The controller’s performance wasverified in terms of delay time, rise time, overshoot, settling time and tolerance limits. The overall performance of theLQR controller was analysed.
  • Identification of the mechanical properties of tires for wheelchair simulation.

    Doria, Alberto; Taraborrelli,Luca; Jomaa, Tarek; Peijs, Tom; Potter, Mario; Advani, Sunjoo; Crichlow,Larry; University of Padova; International Development of Technology B.V.; Toronto Rehabilitation Institute (Bentham Open, 2016-12-30)
    The development of high performance wheelchairs and wheelchair simulators requires dynamic models taking into account the properties of tires. In this paper the properties of two wheelchair tires are measured by means of a rotating disc testing machine and are compared with the properties of bicycle tires, which have similar dimensions and structure. Tests are carried out considering variations in speed, inflation pressure and load. The possibility of fitting experimental results with the Magic Formula, the Dugoff formula and a linear model is discussed. A dynamic model of a wheelchair is developed, which includes a linear tire model derived from experimental results. Steady turning and slalom manoeuvres are simulated. Numerical results show the effect of tire properties on the handling characteristics of the wheelchair.
  • Blockchain-Based Distributed Marketplace.

    Kabi, Oliver R.; Franqueira, Virginia N. L.; University of Derby (Springer Nature, 2019-01-03)
    Developments in Blockchain technology have enabled the creation of smart contracts; i.e., self-executing code that is stored and executed on the Blockchain. This has led to the creation of distributed, decentralised applications, along with frameworks for developing and deploying them easily. This paper describes a proof-of-concept system that implements a distributed online marketplace using the Ethereum framework, where buyers and sellers can engage in e-commerce transactions without the need of a large central entity coordinating the process. The performance of the system was measured in terms of cost of use through the concept of ‘gas usage’. It was determined that such costs are significantly less than that of Amazon and eBay for high volume users. The findings generally support the ability to use Ethereum to create a distributed on-chain market, however, there are still areas that require further research and development.
  • A novel one variable first-order shear deformation theory for biaxial buckling of a size-dependent plate based on the Eringen's nonlocal differential law.

    Malikan, Mohammad; Nguyen, Van Bac; Islamic Azad University; University of Derby; Islamic Azad University Mashhad Branch Mashhad Iran (the Islamic Republic of); University of Derby Derbyshire United Kingdom of Great Britain and Northern Ireland (Emerald Group Publishing Limited, 2018-10-04)
    Purpose – This paper aims to present a new one-variable first-order shear deformation theory (OVFSDT) using nonlocal elasticity concepts for buckling of graphene sheets. Design/methodology/approach – The FSDT had errors in its assumptions owing to the assumption of constant shear stress distribution along the thickness of the plate, even though by using the shear correction factor (SCF), it has been slightly corrected, the errors have been remained owing to the fact that the exact value of SCF has not already been accurately identified. By using two-variable first-order shear deformation theories, these errors decreased further by removing the SCF. To consider nanoscale effects on the plate, Eringen’s nonlocal elasticity theory was adopted. The critical buckling loads were computed by Navier’s approach. The obtained numerical resultswere then compared with previous studies’ results using molecular dynamics simulations and other plate theories for validation which also showed the accuracy and simplicity of the proposed theory. Findings – In comparing the biaxial buckling results of the proposed theory with the two-variable shear deformation theories and exact results, it revealed that the two-variable plate theories were not appropriate for the investigation of a symmetrical analyses. Originality/value – A formulation for FSDT was innovated by reconsidering its errors to improve the FSDT for investigation of mechanical behavior of nanoplates.
  • Experimental studies of turbulent intensity around a tidal turbine support structure

    Walker, Stuart; Cappietti, Lorenzo; University of Sheffield; Università degli Studi di Firenze (MDPI, 2017-04-07)
    Tidal stream energy is a low-carbon energy source. Tidal stream turbines operate in a turbulent environment, and the effect of the structure between the turbine and seabed on this environment is not fully understood. An experimental study using 1:72 scale models based on a commercial turbine design was carried out to study the support structure influence on turbulent intensity around the turbine blades. The study was conducted using the wave-current tank at the Laboratory of Maritime Engineering (LABIMA), University of Florence. A realistic flow environment (ambient turbulent intensity = 11%) was established. Turbulent intensity was measured upstream and downstream of a turbine mounted on two different support structures (one resembling a commercial design, the other the same with an additional vertical element), in order to quantify any variation in turbulence and performance between the support structures. Turbine drive power was used to calculate power generation. Acoustic Doppler velocimetry (ADV) was used to record and calculate upstream and downstream turbulent intensity. In otherwise identical conditions, performance variation of only 4% was observed between two support structures. Turbulent intensity at 1, 3 and 5 blade diameters, both upstream and downstream, showed variation up to 21% between the two cases. The additional turbulent structures generated by the additional element of the second support structure appears to cause this effect, and the upstream propagation of turbulent intensity is believed to be permitted by surface waves. This result is significant for the prediction of turbine array performance.

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