Recent Submissions

  • Buckling and strength analysis of panels with discrete stiffness tailoring

    Culliford, Lucie; Choudhry, Rizwan Saeed; Butler, Richard; Rhead, Andrew T.; University of Bath; University of Derby (Elsevier, 2019-11-05)
    Continuous variation of stiffness across flat plates has been shown, theoretically, to improve buckling performance by up to 60%. However, steered fibre manufacturing methods cannot achieve the minimum radius of curvature required for improvement whilst maintaining a high deposition rate. An alternative concept, Discrete Stiffness Tailoring (DST), which varies stiffness within a ply through discrete changes of angle, is compatible with high rate deposition methods such as Advanced Tape Laying. Through the simple example of redistribution of the material in a quasi-isotropic [±45/90/0]2S laminate whilst maintaining ply percentages, DST is shown both experimentally and theoretically to improve buckling stress by at least 15% with no indication of failure in regions of discrete angle change (seams). However, the reduced tensile strength of seams obtained by virtual and experimental testing means that increased buckling performance in the principle load direction needs to be balanced against loss of transverse strength
  • Creep damage of BGA solder interconnects subjected to thermal cycling and isothermal ageing

    Depiver, Joshua Adeniyi; Mallik, Sabuj; Amalu, Emeka H; Harmanto, Dani; University of Derby (IEEE Xplore, 2019-12)
    Solder joints of electronic components are the most critical part of any electronic device. Their untimely failure during the system’s operation often culminates in catastrophic failure of the device. The determination of creep damage in electronic component solder joint is vital to the prediction of crack initiation and prevention of premature failure. This paper presents the creep damage in solder joints in a ball grid array (BGA) soldered on a printed circuit board (PCB) and subjected to thermal cycling as well as isothermal ageing. ANSYS 19.0 package is employed to model the isothermal gaining at -40, 25, 75 and 150℃ temperatures for 45 days. Standard temperature cycle profile is used to simulate the effect of the coefficient of thermal expansion mismatch on the bonded materials in the BGA component. The solders studied are lead-based eutectic solder alloy and lead-free SAC396, SAC387, and SAC305. Based on the results obtained for the stress, strain and strain energy of the solders, the research investigation advises on the most effective solder for achieving improvement in the thermo-mechanical reliability of solder joints in BGA soldered on PCB.
  • Numerical analysis of flow in the gap of a simplified tractor-trailer model with cross vortex trap device

    charles, terrance; Yang, Zhiyin; lu, yiling; University of Derby (World Academy of Science, Engineering and Technology, 2019-12)
    Heavy trucks are aerodynamically inefficient due to their un-streamlined body shapes, leading to more than of 60% engine power being required to overcome the aerodynamics drag at 60 m/hr. There are many aerodynamics drag reduction devices developed and this paper presents a study on a drag reduction device called Cross Vortex Trap Device (CVTD) deployed in the gap between the tractor and the trailer of a simplified tractor-trailer model. Numerical simulations have been carried out at Reynolds number 0.51×106 based on inlet flow velocity and height of the trailer using the Reynolds-Averaged Navier-Stokes (RANS) approach. Three different configurations of CVTD have been studied, ranging from single to three slabs, equally spaced on the front face of the trailer. Flow field around three different configurations of trap device have been analysed and presented. The results show that a maximum of 12.25% drag reduction can be achieved when a triple vortex trap device is used. Detailed flow field analysis along with pressure contours are presented to elucidate the drag reduction mechanisms of CVTD and why the triple vortex trap configuration produces the maximum drag reduction among the three configurations tested.
  • A new approach for strength and stiffness prediction of discontinuous fibre reinforced composites (DFC)

    Shah, S.Z.H; Choudhry, Rizwan, Saeed; Mahadzir, Shuhaimi; University of Derby; Universiti Teknologi, Malaysia (Elsevier, 2020-12-03)
    A new modelling methodology for strength and stiffness prediction of discontinuous fibre-reinforced composites (DFC) is proposed. This has been validated for both thermoplastic and thermoset, prepreg based, carbon fibre reinforced, random DFC laminates having high volume fraction, by implementing it in a commercial FE solver. The methodology involves explicit generation of internal architecture of DFC through an algorithm which is efficient (faster model generation and solution), easily customizable and scalable. It captures many of the realistic features of the DFC such as variation in volume fraction, interlacing of strands, random orientation and thickness variation of strands. Thus, the model accounts for the natural mechanical property variation, which is characteristic of random DFCs and was found to be conservative in terms of prediction of tensile strength and stiffness for all the validation cases considered. It is generic in the sense that it can be easily extended to generate preferentially aligned and hybrid DFC laminates.
  • Exploring educational advantage in the UK via graduate employment of joint honours degrees by examining pre-university tariff and degree classification

    Pigden, Louise; Moore, Garford; University of Derby (Emerald, 2019-12-17)
    In the UK, the majority of university students specialise and study just one subject at bachelor degree level, commonly known in the UK as a single honours degree. However, nearly all British universities will permit students if they wish to study two or even three subjects, so-called joint or combined honours degrees, internationally known as a double major. The purpose of this paper is to explore the relationship between graduate employment, pre-university educational attainment and degree classification achieved. The study also explored student choice with respect to university prestige. The authors analysed the complete data set provided from the Higher Education Statistics Agency Destination of Leavers from the Higher Education survey, and combined this with data from the POLAR4 quintiles, Universities and Colleges Admissions Service (UCAS) tariff points and degree classification. The data were analysed to establish whether there was a difference in the choices and highly skilled graduate employment of the joint honours students, focussing particularly on Russell Group and Post-92 Universities, in order to build on previous published work. For any UCAS tariff band, the higher the POLAR4 quintile the higher the rate of highly skilled destination. Russell Group outperform the Post-92 graduates in their rates of highly skilled destinations, for any tariff band and for both joint and single honours degrees. Higher POLAR4 quintile graduates are more likely to study at the Russell Group, with this effect increasing the higher the UCAS tariff. With the exception of first class honours graduates from Post-92 universities, joint and single honours from the Russell Group have a higher rate of highly skilled destination than Post-92 in the next higher degree classification. Low POLAR4 quintile students with high UCAS tariffs are “under-matching” and there is an impact on their graduate employment as a result. This study adds new insights into joint honours degrees and also reinforces the literature around educational advantage and achievement prior to university, and the impact on graduate employment. Educational disadvantage persists over the course of a university degree education, from the perspective of gaining graduate employment. Higher quintile graduates are proportionately more likely to achieve the highest degree classifications, and proportionately less likely to achieve the lowest classifications, than graduates from the lower quintiles. Joint honours graduates are less likely to achieve a first class honours degree than single honours, and this will affect their rate of highly skilled destination.
  • Graph data modelling for genomic variants

    Anjum, Ashiq; Aizad, Sanna; University of Derby (IEEE, 2019)
    Genome variant analysis is performed on Variant Call Format (VCF) files. It can take days to process these files for genome analytics due to challenges such as loading the files for each user query and processing them to answer questions of interest. As data sizes grow, timely processing of this data is putting enormous pressure on the computational resources, leading to significant processing delays and may jeopardise the ultimate goal of bringing the genomic discoveries to masses. We believe this problem will not be solved until the underlying data structure to organise and process these files undergoes a transformation. To overcome this problem, we have proposed a graph based system to represent the data in VCF files. This allows the data to be loaded once in a graph model which is then subsequently queried and processed numerous times without any additional computational and data access penalties. This helps reduce data access time by giving a constant time access to any node and addresses performance and scalability challenges that have been a limiting factor for the mass scale adoption of genome analytics. It takes only 2ms to access any data node in our graph model and remains constant for any number of nodes.
  • A review on recent developments of thermoelectric materials for room-temperature applications

    Solemaini, Zohreh; Zoras, Stamatis; Ceranic, Boris; Shahzad, Sally; Cui, YUANLONG; University of Derby; University of Sheffield (Elsevier, 2019-12-13)
    Wearable thermoelectric generators (TEGs) emerge as a viable renewable energy source, which directly convert the heat dissipated from human skin into electricity. Extensive reviews have been conducted on the efficiency of thermoelectric materials (TE) as the dominant element of TEGs. TE materials are categorised as inorganic, organic, and hybrid. Each of these reviews focused on either a specific type of TE materials, or on a certain specification (i.e. flexibility) of them. However, less attention has been paid to comprehensively review all these types without taking into account a certain specification. Therefore, the purpose of this paper is to summarize the progress and current state-of-the-art research on the three types of TE materials respecting their TE properties and efficiency at 300K, which is the operating temperature of wearable TEGs. Concerning the inorganic TE materials, the results show that Bi0.4-xSb1.6+xTe3 and Bi2Te2.7Se0.3 are the most optimal TE materials, which exhibit the greatest efficiencies at room temperature. In addition, it is remarkably more efficient to replace polymer based TE composites with carbon based TE composites in the organic and the hybrid types. In total, this comprehensive review paves the way for researchers to find out the most suitable TE materials at room temperatures.
  • The evolution of turbulence characteristics in the wake of a horizontal axis tidal stream turbine

    Ahmadi, Mohammad H.B.; Yang, Zhiyin; University of Derby (Elsevier BV, 2019-11-21)
    The evolution of turbulence characteristics downstream of a laboratory-scale three-bladed horizontal axis turbine is investigated in this study. Large eddy simulation (LES) coupled with the Actuator Line Modelling (ALM) is used to simulate the flow. The numerical results compare well against experimental data, which shows that the LES/ALM technique is a powerful tool for simulating tidal stream turbines. The present study aims to obtain a better understanding of the turbulence characteristics of flow in the turbine wake by removing deterministic velocity fluctuations stemmed from the turbine rotation. Large eddy simulation is able to provide high-resolution spatial and temporal information needed for this work. The filtering process helps to have a clearer view of the flow structures downstream by tracking the streamwise variations of turbulence intensity and turbulent kinetic energy and, reveals a transition zone started shortly behind the turbine with a peak in the turbulence intensity. This study introduces turbulence intensity and turbulent kinetic energy as quantitative criteria to split the turbine wake into distinct regions. This research shows that to investigate and explain the influence of different upstream and operation conditions on the flow characteristics in the turbine wake, a well understanding of flow characteristic changes in the transition zone is necessary.
  • Multiple geophysical techniques for investigation and monitoring of sobradinho landslide, Brazil

    Hussain, Yawar; Cardenas-Soto, Martin; Martino, Salvatore; Moreira, Cesar; Borges, Welitom; Hamza, Omar; Prado, Renato; Uagoda, Rogerio; Rodríguez-Rebolledo, Juan; Silva, Rafeal; et al. (MDPI AG, 2019-11-26)
    Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differentiation between landslide debris and other Quaternary deposits, and (ii) the delineation of the landslide sliding surface. However, the innovative seismic based techniques, particularly ambient noise based (HVSR and ANI) and emitted seismic based (NM), were not very effective for the dynamic monitoring of landslide, which might be attributed to the short-time duration of the data acquisition campaigns. The HVSR was also unsuccessful in landslide site characterization i.e., identification of geometry and sliding surface. In particular, there was no clear evidence of the light seasonal variations, which could have been potentially detected from the physical parameters during the (short-time) ambient noise and microseismic acquisition campaigns. Nevertheless, the experienced integration of these geophysical techniques may provide a promising tool for future applications
  • Invoking humanism in modernity: architecture and spectacle in fascist Italy

    Tracada, Eleni; Temple, Nicholas; University of Derby; University of Huddersfield (Routledge, 2019-11-01)
    The influence of Fascism on intellectual, artistic and architectural developments in interwar Italy has been the subject of intense debate. This has given rise to contested views about the combined impact of modernism and historical precedents on Fascist ideology, the arguments often clouded by disputes concerning the patrimony of art in Italy and whether Fascism should cultivate its own distinctive aesthetic. 2 However, many of the leading voices of Italian cultural life during the Fascist regime refused to discriminate between different aesthetic choices, believing that “Italian cultural traditions precluded aesthetic regulation.” 3 The debate becomes most revealing when considered in the context of the origins of Fascism. The eminent Italian philosopher and historian Benedetto Croce believed, for example, that Fascism could be traced back almost exclusively to the futurist movement, both in its artistic aspirations and in political activism … in the resolution to go down to the piazza, to impose one’s own feelings, to shut the mouths of those who are dissenting, to be unafraid of commotions and riots; in the eagerness of the new, in the desire to break every tradition, in the exaltation of youth, which was proper to futurism.” 4
  • Calibration approaches for higher order ambisonic microphones

    Middlicott, Charlie; Wiggins, Bruce; University of Derby; Sky Labs (Audio Engineering Society, 2019-10-08)
    Recent years have seen an increase in the capture and production of ambisonic material due to companies such as YouTube and Facebook utilizing ambisonics for spatial audio playback. Consequently, there is now a greater need for affordable high order microphone arrays due to this uptake in technology. This work details the development of a five-channel circular horizontal ambisonic microphone intended as a tool to explore various optimization techniques, focusing on capsule calibration & pre-processing approaches for unmatched capsules.
  • A case study on sound level monitoring and management at large-scale music festivals

    Hill, Adam J.; Kok, Marcel; Mulder, Johannes; Burton, Jon; Kociper, Alex; Berrios, Anthony; University of Derby; Murdoch University; dBcontrol; Gand Concert Sound (Institute of Acoustics, 2019-11)
    Sound level management at live events has been made immeasurably easier over the past decade or so through use of commercially-available sound level monitoring software. This paper details a study conducted at a large-scale multi-day music festival in Chicago, USA. The focus was twofold: first to explore how the use of noise monitoring software affects the mix level from sound engineers and second on how crowd size, density and distribution affect the mix level. Additionally, sound levels at various points in the audience were monitored to indicate audience sound exposure over the duration of the festival. Results are presented in relation to those from previous studies with key findings pointing towards recommendations for best practice.
  • The transparency of binaural auralisation using very high order circular harmonics

    Dring, Mark; Wiggins, Bruce; University of Derby (Institute of Acoustics, 2019-11)
    Ambisonics to binaural rendering has become the de facto format for processing and reproducing spatial sound scenes, but direct capture and software generated output is limited to low orders; limiting the accuracy of psycho-acoustic cues and therefore the illusion of a ‘real-world’ experience. Applying a practical method through the use of acoustic modelling software, this study examines the potential of using very high horizontal only Ambisonic orders (up to 31st) to binaural rendering. A novel approach to the scene capturing process is implemented to realise these very high orders for a reverberant space with head-tracking capabilities. A headphone based subjective test is conducted, evaluating specific attributes of a presented auditory scene to determine when a limit to the perceived auditory differences of varying orders has been reached.
  • Analysis and optimal design of a vibration isolation system combined with electromagnetic energy harvester

    Diala, Uchenna; Mofidian, SM Mahdi; Lang, Zi-Qiang; Bardaweel, Hamzeh; University of Sheffield (SAGE Publications, 2019-07-17)
    This work investigates a vibration isolation energy harvesting system and studies its design to achieve an optimal performance. The system uses a combination of elastic and magnetic components to facilitate its dual functionality. A prototype of the vibration isolation energy harvesting device is fabricated and examined experimentally. A mathematical model is developed using first principle and analyzed using the output frequency response function method. Results from model analysis show an excellent agreement with experiment. Since any vibration isolation energy harvesting system is required to perform two functions simultaneously, optimization of the system is carried out to maximize energy conversion efficiency without jeopardizing the system’s vibration isolation performance. To the knowledge of the authors, this work is the first effort to tackle the issue of simultaneous vibration isolation energy harvesting using an analytical approach. Explicit analytical relationships describing the vibration isolation energy harvesting system transmissibility and energy conversion efficiency are developed. Results exhibit a maximum attainable energy conversion efficiency in the order of 1%. Results suggest that for low acceleration levels, lower damping values are favorable and yield higher conversion efficiencies and improved vibration isolation characteristics. At higher acceleration, there is a trade-off where lower damping values worsen vibration isolation but yield higher conversion efficiencies.
  • Remarks on a family of complex polynomials

    Andrica, Dorin; Bagdasar, Ovidiu; University of Derby (University of Belgrade, 2019-10-30)
    Integral formulae for the coefficients of cyclotomic and polygonal polynomials were recently obtained in [2] and [3]. In this paper, we define and study a family of polynomials depending on an integer sequence m1, . . . , mn, . . . , and on a sequence of complex numbers z1, . . . , zn, . . . of modulus one. We investigate some particular instances such as: extended cyclotomic, extended polygonal-type, and multinomial polynomials, for which we obtain formulae for the coefficients. Some novel related integer sequences are also derived.
  • Value chain impacts of EU waste framework directive 2018/851 as a result of reporting substances of very high concern from 2021

    Takhar, Sukhraj; Liyanage, Kapila; College of Engineering and Technology, University of Derby; Assent Compliance, Canada (University of Cambridge, 2019-09-27)
    The EU Waste Framework Directive 2018/851 sets out requirements for producers and importers of products within the EEA, to report data on Substances of Very High Concern (SVHC) content within products into a new central European database to from 5th January 2021. The reporting requirements: (1) support chemical regulations that impose the need on industry to record the use of hazardous chemicals; (2) identification of products entering waste streams containing hazardous chemicals; (3) support circular economy initiatives within the EU. To meet these new reporting requirements industry will need to collect additional information from all supply chain actors, who as duty holders will also be required to report into the new EU SVHC database system. Failure to provide the required information may result in enforcement actions from the authorities, which could see products being restricted from the EEA. The new EU database system will be accessible to industry, regulators, NGOs and the general public. This paper explores the new requirements, together with feedback received from various stakeholders for collection of data and reporting into the new EU database system from 2021.
  • Creep response of various solders used in soldering ball grid array (BGA) on printed circuit board (PCB)

    Depiver, Joshua Adeniyi; Mallik, Sabuj; Amalu, Emeka H; University of Derby (Newsroom Limited, 2019-10)
    In electronics packaging, solder joints play a critical role by providing electrical, thermal and mechanical connections between the package and the printed circuit board (PCB). As the joint is both miniature and brittle, it is the weakest part of the assembly and thus susceptible to untimely damage. This paper presents the creep response of solder joints in a ball grid array (BGA) soldered on a PCB subjected to isothermal ageing in one experiment and temperature cycling in another test. The ageing is simulated in an ANSYS package environment at -40, 25, 75 and 150℃ temperatures applied for 45 days. The thermal cycling profile started from 22℃ and cycled between -40℃ and 150℃ with 15 minutes dwell time at the lowest and highest temperatures. The solders used in the investigation are lead-based eutectic solder alloy and lead-free SAC305, SAC387, and SAC396 solders. The research seeks to qualify these solders against strain and strain energy response for improved reliability in operation. The results show that the lead-free SAC387 accumulated the maximum strain and thus strain energy while the lead-based eutectic solder is found to accrue the least amount of the quantities. Further results show the distribution of damage in the BGA solder bump. Based on the results, it is proposed that lead-free SAC396 is the best replacement of the lead-based eutectic solder in the drive for the achievement of comparable thermo-mechanical reliability of assembled BGA on PCB.
  • Charged-particle pseudorapidity density at mid-rapidity in p–Pb collisions at √sNN = 8.16 TeV

    Acharya, S.; Acosta, F.-T.; Adamová, D.; Adhya, S. P.; Adler, A.; Adolfsson, J.; Aggarwal, M. M.; Rinella, G. Aglieri; Agnello, M.; Ahammed, Z.; et al. (Springer Science, 2019-04-04)
    The pseudorapidity density of charged particles, dNch/dη, in p–Pb collisions has been measured at a centreof-mass energy per nucleon–nucleon pair of √sNN = 8.16 TeV at mid-seudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, |η| < 1.8. The dNch/dη value is 19.1 ± 0.7 at |η| < 0.5. This quantity divided by Npart /2 is 4.73±0.20, where Npart is the average number of participating nucleons, is 9.5% higher than the corresponding value for p–Pb collisions at √sNN = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the dNch/dη distribution. Saturation-based models reproduce the distributions well for η > −1.3. The dNch/dη is also measured for different centrality estimators, based both on the chargedparticle multiplicity and on the energy deposited in the ZeroDegree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p–Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.
  • A software platform for noise reduction in sound sensor equipped drones

    Kang, Byungseok; University of Derby (IEEE, 2019-07-08)
    A flying drone provides multiple video capturing options for filming videos. Since a noise is generated by the propellers and rotors of a drone, the quality of sound in the recorded video is quite low. Large drones are used singly in missions while small ones are used in formations or swarms. The small drones are proving to be useful in civilian applications. These are effective with multiple drones. Consideration of small drones for the applications, such as group flight, entertainment, and signal emission lead to deployment of networked drones. To solve the noise problem and develop group display applications, a software platform for these issues in networked drones is proposed. Noise reduction combines the active noise control and spectral subtraction. In addition, drones form group displays for an entertainment and displaying application. We develop a small-scale testbed to measure the service quality of proposed platform. The experimental results show that the proposed noise reduction produces a speech signal with up to 67.5% similarity to the original signal. It outperforms active noise control and spectral subtraction with the similarities of 53.1% and 39.6%, respectively. We see that drone formation can form a group display to show messages effectively.
  • A location aware fast PMIPv6 for low latency wireless sensor networks

    Kang, Byungseok; University of Derby (IEEE, 2019-06-28)
    Recently, mobile sensor networks (MSN) have been actively studied due to the emergence of mobile sensors such as Robomote and robotic sensor agents (RSAs). The research on existing mobile sensor networks mainly focuses on solving the coverage hole, which is a problem that occurs in the existing stationary sensor network (SSN). These studies have disadvantages in that they cannot make the most use of the mobile ability given to the moving sensors. In order to solve this problem, there is a proposal for sensing a wider area than a fixed sensor network by giving the moving sensor continuous mobility. However, the research is still in the early stage, and communication path to the sink node and data transmission problems. In this paper, we propose a location-aware fast PMIPv6 (LA-FPMIPv6) protocol that enables efficient routing and data transmission in a mobile sensor network environment composed of mobile sensors with continuous mobility. In the proposed protocol, the fixed sensor is arranged with the moving sensor so that the fixed sensor transmits the sensing data to the sink node instead of the moving sensor. For performance evaluation, the LA-FPMIPv6 is compared with existing methods through mathematical analysis and computer simulation. The results of the performance evaluation show that the LA-FPMIPv6 effectively reduces the handover latency, signaling cost, and buffering cost compared with the conventional methods.

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