School of Engineering and Sustainable Development
Permanent URI for this collection
Browse
Recent Submissions
Item Embargo Mini-Grid Sustainability Framework and its Application to Selected Mini-Grids in Kenya(Trans Tech Publications, 2025-02-03) Kausya, Mourice; Nyumba, Rosebella; Onsongo, Elsie; Kerr, Daniel; Bhattacharyya, SubhesThis paper presents an indicator-based framework for the sustainability analysis of mini grids and applies this to a selection of mini-grids in Kenya. Although various frameworks exist, they have been criticised for lack of attention to long-term perspectives, high data needs, prescriptive nature of the attributes and limited user-friendliness. Considering that data availability is a major concern and that data available is qualitative in nature, this paper proposes a set of indicators and a scoring system that can be used with a broad qualitative understanding of the sustainability attributes of the mini-grids. The paper first presents the framework and the scoring system and applies this to the data gathered from the fieldwork in Kenya. The results indicate that the significant variation in sustainability performance of the mini-grids covered and the performance is relatively good in technical and economic dimensions and relatively poor in social, institutional and environmental dimensions.Item Metadata only Efficacy evaluation of an air handling system (ENHANCE) in mitigating aerosol exposure in enclosed spaces at a transport hub(2024-02-15) Tiwary, Abhishek; Krishnan, Athul; Swallow, Bethany; Shivkumar, MaitreyiThis study presents a set of proof-of-concept evaluations towards developing a methodological capacity to assess the efficacy of an innovative air treatment unit (henceforth the ENHANCE system) in enclosed spaces. Based on an inlet-outlet monitoring scheme, the overall PM2.5 removal efficacy ranged between 97-100%, irrespective of the time of the day and season. The 10-min averaged total volatile organic carbon (TVOC, including benzene, toluene) concentrations however showed varied levels of removal efficacies, ranging between 25-95%; typically, higher TVOC removal efficacies were noted when the inlet concentrations were high. However, the outlet concentrations were lower than inlet on all occasions (and ranged between 50150 μg m-3, which has been considered acceptable limits in indoor UK settings). Controlled upwind-downwind chamber experiments in virology lab, using both human coronavirus (HCoV)-OC43, enveloped virus, diameter ~80-120 nm) and mouse norovirus 1 (MNV-1, non-enveloped virus, diameter ~25-40 nm), showed ≥4 log10 reduction in infectivity. A CFD-based analytical case study, exploring the optimal placement strategy of the system in a real train station lounge environment, offered some operational best practice in order to maximize the scope of offering fresh, clean (air pollutant and pathogen free) air in the deeper parts of the room when the lounge is fully occupied. Our evaluations demonstrate the system is deemed suitable for its deployment in a transport environment to reduce exposure in a constrained space, such as waiting lounge and lifts. We reckon full-scale deployment of the ENHANCE system in such locations would serve two-fold purpose – first, provide a control measure towards any future pandemic preparation; second, offer an active health intervention at public transport facilities, specifically alleviating the health risk posed from air pollution and pathogen exposure to vulnerable population, who tend to use these facilities more frequently.Item Open Access Effect of Counterbody Material on the Boundary Lubrication Behavior of Commercially Pure Titanium in a Motor Oil(MDPI, 2024-12-10) Liu, Yizhao; Al-Shan, Mohammed; Bailey, Richard; Sun, YongTitanium possesses many useful properties and is a technologically important material in engi-neering. However, lubrication of titanium has long been a problem that has prevented titanium from being more widely used. This is due to its poor tribological properties deriving from its high tendency towards adhesive wear, material transfer and abrasive wear. Lubrication is a system engineering which involves material combinations, material surfaces, lubricants and operating conditions as a system. In this work, the boundary lubrication behavior of commercially pure tita-nium (CP-Ti) sliding against various counterbody materials in a motor oil (0W-30) was investigated under ball-on-plate reciprocating sliding conditions. The counterbody materials (balls) include CP-Ti, ceramic (Al2O3), steel (AISI 52100) and polymer (nylon). The results show that depending on material combination, the lubricating behavior can be divided into three categories, i.e. (1) lubri-cation failure (Ti-Ti), (2) improved lubrication but with friction instability (Ti-Al2O3), and (3) effec-tive lubrication (Ti-steel and Ti-nylon). Lubrication failure of the Ti-Ti pair leads to high and un-stable friction and severe wear from both the plate and ball, while friction instability of the Ti-Al2O3 pair leads to friction spikes and high wear rates. Effective lubrication of the Ti-steel pair results in low and smooth friction and much reduced wear rates of the Ti plate by nearly 10000 times. However, there is a load-dependence of the lubrication effectiveness of the Ti-steel pair. Although the Ti-nylon pair is effectively lubricated in terms of much reduced friction, the nylon ball suffers from severe wear. The friction and wear mechanisms of the various sliding pairs are discussed in this paper.Item Open Access Insights into the flow characteristics during hydraulic fracturing(Springer Nature, 2024-12-22) Abdi, Rezvan; Krzaczek, Marek; Abdi, MeisamThis paper presents a numerical model to study fracture propagation during water-based hydraulic fracturing. To address the computational challenges associated with the numerical model, the proposed approach employs a set of overlapping spheres arranged in a monolayer to construct a porous specimen containing pre-existing cracks. The fluid-filled cracks represent various stages of initiation and propagation of fluid-driven fracture. The high-pressure fluid flow within the fractures is considered under isothermal conditions. Unlike the conventional focus on rock fracture analysis, the presented approach focuses on flow characteristics during fracture growth. The main objective of the presented study is to provide a detailed description of the computational fluid dynamics (CFD) aspects of fracture propagation during hydraulic fracturing to aid in calibration and validation of simplified discrete element method (DEM) models coupled with CFD representing this phenomenon. Experimental validations performed in previous studies support the model’s reliability, making it useful in particular for calibration and validation of coupled 2D DEM-CFD models constructed from one layer of spheres. Obtaining experimental data for such cases is practically challenging, and the proposed model addresses the lack of reliable experimental data for hydraulic fracturing. To achieve this, representative specimens are designed, accurate simulations are conducted and precise assessments of the results are performed. Key variables such as density, pressure, velocity, porosity, and permeability were measured to facilitate the validation and calibration of future DEM-CFD studies.Item Open Access Advancing Agricultural Practices: Analyzing the Role of Robotics in Corn Farming(Materials and Energy Research Center, 2025-01-25) Moshayedi, Ata Jahangir; Khan, Amin Soheil; Geng, K.; Hu, J.; Kolahdooz, AminThe need for robots in corn farming arises from the complexity and labor-intensive nature of tasks such as planting, weeding, harvesting, and monitoring. Robots offer precision, efficiency, and data-driven decision-making, addressing challenges in resource management, crop health, and productivity to meet the demands of modern agriculture. In this paper, the current landscape of robotics in corn farming, exploring various robotic systems, their functionalities, and their potential impacts on agricultural practices were studied. Additionally, analyzing the benefits and challenges associated with the adoption of robotic technology in corn farming, considering factors such as cost, compatibility with existing infrastructure, and regulatory considerations. Furthermore, the future directions and opportunities for research and development in the field of agricultural robotics, emphasizing the need for interdisciplinary collaboration and innovation to maximize the benefits of robotic technology in corn farming and contribute to sustainable food production are being discussed. The primary focus of this article is to analyze the components and design features of robots employed in our corn fields. This analysis not only serves as a comparison tool for designers but also encourages the development of more diverse designs. The structure of robots in corn farming plays a crucial role in advancing agricultural practices by boosting efficiency, precision, adaptability, data collection capabilities, environmental sustainability, and safety standards.Item Embargo Progressive Knowledge Transfer Network Based on Human Visual Perception Mechanism for No-Reference Point Cloud Quality Assessment(IEEE, 2025) Su, Honglei; Liu, Yiyun; Liu, Qi; Yuan, Hui; Hamzaoui, RaoufPoint cloud perceptual quality assessment plays a critical role in many applications, including compression and communication. We propose PKT-PCQA, a point-based no-reference point cloud quality assessment deep learning network that emulates the human visual system by using progressive knowledge transfer to convert coarse-grained quality classification knowledge into a fine-grained quality prediction task. PKTPCQA exploits local and global features, as well as an attention mechanism based on spatial and channel attention modules. Experiments on three large and independent point cloud assessment datasets show that PKT-PCQA outperforms existing no-reference and reduced-reference point cloud quality assessment methods and achieves better or similar performance compared to several state-of-the-art full-reference methods. The code will be available for download at https://github.com/sdqi/PKT-PCQA.Item Open Access Improving Corrosion and Wear Resistance of 316L Stainless Steel via In Situ Pure Ti and Ti6Al4V Coatings: Tribocorro-sion and Electrochemical Analysis(MDPI, 2025-01-25) Alontseva, Darya; İsmail Yavuz, Hasan; Azamatov, Bagdat; Khoshnaw, Fuad; Safarova , Yuliya; Dogadkin, Dmitriy; Avcu, Egemen; Yamanoğlu, RidvanThis study aims to achieve in situ-formed pure Ti and Ti6Al4V coatings on 316L stain-less steel through hot pressing and examine their wear and corrosion properties thor-oughly in two simulated body fluids: physiological serum (0.9% NaCl) and Hanks’ so-lution. The sintering and diffusion bonding process was conducted at 1050 °C under a uniaxial pressure of 40 MPa for 30 min in a vacuum environment of 10−4 mbar. Fol-lowing sintering, in situ-formed pure Ti and Ti6Al4V coatings, approximately 1000 µm thick, were produced on 316L substrates approximately 3000 µm in thickness. The mean hardness of 316L substrates, pure Ti, and Ti6Al4V coatings are around 165 HV, 170 HV, and 420 HV, respectively. The interface of the stainless steel substrate and the pure Ti and Ti6Al4V coatings exhibited no microstructural defects, while the interface exhibited significantly higher hardness values (ranging from 600 to 700 HV) due to the intermetallic compounds formed through diffusion. The coatings improved corrosion resistance in both electrolytes compared to the 316L substrate. Wet wear tests revealed reduced friction coefficients in 0.9% NaCl relative to Hanks’ solution, highlighting the chemical interactions between the material surface and the electrolyte type and the significance of tribocorrosion in biocoatings.Item Open Access Enhancing the Goman–Khrabrov dynamic stall model through flow delay analysis(AIP publishing, 2025-01-08) Zheng, Boda; Yao, Weigang; Xu, MinThe complete dynamic stall process encompasses a series of complex developmental stages, such as flow separation, leading edge vortex shedding, and reattachment. Unlike static stall, dynamic stall exhibits hysteresis, rendering phenomenological models as complex nonlinear state-space systems, often accompanied by numerous empirical parameters, which complicates practical applications. To address this issue, the Goman-Khrabrov (G-K) dynamic stall model simplifies the state space and retains only two empirical parameters related to time delays. Our study finds that different developmental stages of dynamic stall exhibit various time delay scales. The G-K dynamic stall model, which utilizes a first-order time-invariant inertia system, forcibly unifies the time scales across different stages. Consequently, this leads to intractable non-physical modeling errors. This paper introduces the latest revised G-K model that employs a time-varying state space system. This model not only maintains a concise form but also eliminates the non-physical modeling errors previously mentioned. In response to the challenge of identifying empirical parameters, this paper presents a parameter identification method for both the original and revised G-K models utilizing a Physics-Informed Neural Network (PINN). The revised model was validated through dynamic stall load prediction cases for mild, moderate and deep dynamic stall on various airfoils, achieving a maximum accuracy improvement of up to 74.5%. The revised G-K model is capable of addressing a broader range and more complex practical applications.Item Open Access Race to Zero Carbon Accelerator: Evaluation Report(2022-10) Lee, Sandra; Reeves, Andrew; Mistry, Asha; Ahmed, Mahfuja; Jackson, AliceLeicester and Leicestershire’s three universities (University of Leicester, De Montfort University and Loughborough University) partnered to provide Leicester City small and medium-sized enterprises (SMEs) with a fully-funded direct sustainability support package to help businesses work towards net zero. This programme offered a comprehensive sustainability support package including: • Sustainability Audits • Funding to Employ Students • Carbon Reduction Plan • Climate education and support This proved to be highly appropriate and, as well as the existing informal professional relationships, the three universities have now signed a formal Civic Universities Agreement (the Universities Partnership) and this project formed one of its first, and so far biggest, formal undertakings, which will hopefully also provide a platform to continue delivering from. One of the aims of the UK Shared Prosperity Fund is to contribute to a better evidence base for supporting local business support interventions. The launch of the Universities Partnership between all three Leicestershire universities has formalised an already strong collaborative approach and provides an ideal opportunity for us to respond to SPF guidance to deliver interventions at the regional scale in order to obtain higher value for money and better outcomes for local people and businesses. Findings from this project are informing the future direction of the Universities Partnership Environmental Sustainability theme.Item Open Access The Influence of Architecture on the Tensile and Flexural Properties of Single-Polymer Composites(MDPI, 2025-01-15) Yogeshvaran R. Nagarajan; Farukh, Farukh; Karthikeyan, KandanThis study investigates the tensile and flexural properties of self-reinforced polylactic acid (SrPLA) and poly(ethylene terephthalate) (SrPET) for prosthetic socket applications. These self-reinforced polymer (srP) composites utilize both a matrix and reinforcement made from the same material, resulting in an optimal matrix–interface bond that significantly enhances mechanical properties compared to traditional bulk polymers and composites. Prosthetic sockets serve as a critical interface between an amputee’s residuum and the prosthetic components, such as pylons and feet. Conventional socket materials, including monolithic high-density polyethylene and polypropylene, as well as advanced fillers reinforced with thermoset resins, often fall short in strength or affordability, particularly for amputees in low- to middle-income countries. In this study, we employed srP composites with various architectural stitch densities, aiming to achieve superior material properties. The results demonstrate that these materials exhibit higher strength and strain capabilities than many existing prosthetic materials. Notably, the low-density srPET composites achieved a tensile strength of 85.11 MPa and a strain of 19.7%, while high-density srPLA exhibited a failure strength of 36.65 MPa and a strain of 1.4%. Additionally, our findings reveal that the stiffness of both srPLA and srPET increases as the density of the reinforcement decreases. Overall, this study suggests that srP composites represent a viable and sustainable alternative for the manufacturing of prosthetic sockets, offering both enhanced performance and cost-effectiveness.Item Embargo Global Spatial-Temporal Information-based Residual ConvLSTM for Video Space-Time Super-Resolution(IEEE, 2024) Fu, Congrui; Yuan, Hui; Jiang, Shiqi; Zhang, Guanghui; Shen, Liquan; Hamzaoui, RaoufBy converting low-frame-rate, low-resolution videos into high-frame-rate, high-resolution ones, space-time video super-resolution techniques can enhance visual experiences and facilitate more efficient information dissemination. We propose a convolutional neural network (CNN) for space-time video super-resolution, namely GIRNet. Our method combines long-term global information and short-term local information from the video to better extract complete and accurate spatial-temporal information To generate highly accurate features and thus improve performance, the proposed network integrates a feature-level temporal interpolation module with deformable convolutions and a global spatial-temporal information-based residual convolutional long short-term memory (convLSTM) module. In the feature-level temporal interpolation module, we leverage deformable convolution, which adapts to deformations and scale variations of objects across different scene locations. This provides a more efficient solution than conventional convolution for extracting features from moving objects. Our network effectively uses forward and backward feature information to determine inter-frame offsets, leading to the direct generation of interpolated frame features. In the global spatial-temporal information-based residual convLSTM module, the first convLSTM is used to derive global spatial-temporal information from the input features, and the second convLSTM uses the previously computed global spatial-temporal information feature as its initial cell state. This second convLSTM adopts residual connections to preserve spatial information, thereby enhancing the output features. Experiments on the Vimeo90K dataset show that the proposed method outperforms open source state-of-the-art techniques in peak signal-to-noise-ratio (by 1.45 dB, 1.14 dB, and 0.2 dB over STARnet, TMNet, and 3DAttGAN, respectively), structural similarity index(by 0.027, 0.023, and 0.006 over STARnet, TMNet, and 3DAttGAN, respectively), and visual quality.Item Metadata only Optimization of air suspension system for improved ride and handling performance in road vehicles dynamic(Universitas Muhammadiyah Magelang, 2024-12-15) Armansyah; Keshavarzi, Ahmad; Kolahdooz, Amin; Rizal, Reda; Destri Mardhani, MuhammadThis study focused on the optimization of air suspension systems (ASs) for road vehicles concerning on-ride and handling criteria. A quarter DOF vehicle model is used in this study to develop an optimized system based on nonlinear equations. The extracted equations are then linearized and transformed into dimensionless form to gain insights into the system's behavior. By employing the Root-Mean-Square (RMS) method, the dimensionless equations are utilized to optimize the system parameters focused on stability and ride comfort. The five main components are attached in the model which consisted of the sprung mass (SM), unsprung mass (USM), gas spring (GS), auxiliary reservoir (AR), and orifice (O). The optimization procedure involved adjustment to the orifice resistance coefficient, air spring volume, air spring area, and auxiliary volume using the RMS-based method. Simulation analysis revealed the superior performance of the RMS-optimized system in both ride quality and handling. The study concludes by emphasizing the advantages of utilizing the RMS method for optimizing air suspension, resulting in decreased sprung mass acceleration and enhanced handling qualities. Selecting the appropriate design point for the suspension system based on the method outlined in this article can ensure both stability and comfort in the vehicle simultaneously.Item Open Access Robots in Agriculture: Revolutionizing Farming Practices(European Alliance for Innovation (EAI), 2024-06-20) Moshayedi, Ata Jahangir; Khan, Amir Soheil; Yang, Yingo; Hu, Jiandong; Kolahdooz, AminRobotics for farming is a game changer for economy and sustainability. Agricultural robots automateactivities and help solve industrial difficulties. These robots are designed for precise planting, weeding,and harvesting, automating labor-intensive procedures. Implementing these practices improves productivity,reduces operating costs, and minimises environmental impact by optimising resource use. This researchexamines the various processes and designs used in agricultural robotic structures to understand theirfunctionality. This study delves into the intricate structure of agricultural robots, highlighting the technicalwonders that enable precision farming. From articulated arms to autonomous unmanned aircraft, the studyexplores a variety of robot designs and their roles in automating jobs crucial to contemporary agriculture.Item Open Access Optimization and comparative analysis of an AISD suspension system with inerter element for enhanced ride and handling(Sage, 2024-05-23) Ridal, Reda; Keshavarzi, Ahmad; Armansyah; Harmanto, Dani; Kolahdooz, AminThis paper presents a comprehensive study on the modeling and optimization of an advanced suspension system, known as the Air Springs Inerter-Spring-Damper (AISD) system, incorporating an inerter element. A linear quarter car model is utilized to analyze the vibrational behavior of the AISD system when subjected to harmonic road disturbances. The steady-state response of the system is investigated by deriving the root mean square (RMS) values of the absolute relative displacement and acceleration of the sprung mass. To optimize the quarter car model, a criterion based on minimizing the absolute acceleration RMS while considering the relative displacement RMS is employed to calculate the inerter coefficient. The performance of the AISD suspension system is compared to that of both conventional quarter car systems and traditional air quarter car systems, with a focus on ride comfort and handling. The results demonstrate that the proposed AISD system outperforms the other two suspension systems, exhibiting a significant improvement in ride quality. Specifically, the AISD system achieves a 45% enhancement over the air suspension and an 82% improvement over the classic suspension system.Item Metadata only Case study investigation of overheating in low-energy homes: insights from a post-occupancy evaluation in England(Taylor and Francis, 2024-12-16) Toledo, Linda; Wright, A. J.; Cropper, PaulThis paper presents evidence of overheating in present-day low-energy homes and explores the causes of this phenomenon. The study involved in-depth research on four low-energy homes in England. Three of these were newly built, while the other was retrofitted. Over a period of 11 months, the homes underwent environmental monitoring, and user perspectives were gathered. Additionally, a retrospective analysis was conducted based on the Building Regulations 2010 Overheating: Approved Document O. Overheating was primarily attributed to design factors related to ventilation (linked to both mechanical ventilation and natural ventilation), solar control (inadequate G-values), and the unique architectural elements (roof pod and sunspace). While most occupants employed adaptive behaviours whenever possible to cope with the high indoor temperatures, these strategies proved insufficient in preventing overheating in three out of four cases. The study also compared different methods for assessing overheating in low-energy homes. CIBSE-TM59 was found to be effective in identifying overheating issues and aligning with occupant perceptions. England Building Regulations Part O simplified method failed to account for potential overheating from deep energy retrofits, as well as possible exacerbations from roof pods and from transition spaces. Moreover, all assessments failed to encompass the elevated risk for (permanent or transitory) vulnerable occupants.Item Open Access From Darcy to turbulent flow: Investigating flow characteristics and regime transitions in porous media(AIP Publishing, 2024) Abdi, Rezvan; Krzaczek, Marek; Abdi, MeisamThis research addresses the flow characteristics within a porous medium composed of a monolayer of closely packed spheres, spanning from viscous-dominated to turbulent flow regimes. In the first part of this paper, the turbulent flow characteristics at a 30 MPa pressure drop within the domain are presented. The results are averaged across different cross-sections between the inlet and outlet. In the second part of the study, simulations are conducted with pressure drops, ranging from nearly 0 to 100 MPa. The analysis finds distinct flow patterns within the domain and provides estimations for the permeability and the inertial term coefficient. Moreover, the transition from Darcy to non-Darcy and turbulent flow is achieved through the use of different criteria. The specified geometry is suitable for validating and calibrating simplified Discrete Element Method (DEM) models coupled with Computational Fluid Dynamics (CFD). The main goal of this research is to produce a reliable benchmark to figure out the challenge of limited experimental data concerning fluid flow characteristics in densely packed granules specially subjected to high pressure conditions. To do this, representative specimens are designed, accurate simulations are conducted, and precise assessments of the results are carried out.Item Open Access Experimental and Mathematical Modelling Investigation of Plasma Electrolytic Oxidation (PEO) for Surface Hardening of 20Ch Steel(MDPI, 2024-12-10) Kombayev, Kuat; Khoshnaw, Fuad; Uazyrkhanova, Gulzhaz; Moldabayeva, GulzhazThis study aimed to develop an alternative surface hardening technique for low-carbon steel alloy type 20Ch using plasma electrolytic oxidation (PEO). The surface hardening of 20Ch alloy steel samples was achieved through PEO in a Na2CO3 electrolyte solution. Optimal processing parameters were determined experimentally by measuring voltage and applied current. Quenching was performed in the electrolyte stream, and plasma was ionised through excitation. A mathematical model based on thermal conductivity equations and regression analysis was developed to relate the key parameters of the hardening process. The results from both the experimental and mathematical models demonstrated that PEO significantly reduces hardening time compared to traditional methods. The microstructural images revealed the transformation of the coarse-grained pearlite–ferrite structure into quenched martensite. Vickers microhardness tests indicated a substantial increase in surface hardness after PEO treatment, compared to the untreated samples. The major advantages of PEO include lower energy consumption, high quenching rates, and the ability to perform localised surface treatments. These benefits contribute to overall cost reduction, making PEO a promising surface-hardening method for various industrial applications.Item Open Access Optimizing Composting Process Through Mixture Design for a Sustainable Valorization of Residual Biomass from Medicinal and Aromatic Plants(IOP, 2024-12-06) Mehdaoui, Imane; Majbar, Zineb; Hassani, El Mokhtar Saoudi; Mahmoud, Rachid; Ben Abbou, Mohamed; Bougarne, Loubna; Sakar, Al Hassan; Taleb, Mustapha; Rais, Zakia; Khoshnaw, FuadRecently, medicinal and aromatic plants (MAP) gained a particular interest for their application in various fields such as food science, pharmacy, etc). MAP processing results in huge amounts of residual biomasses (RB). Such RB are valuable as they contain nutrients that can be recycled into high-value products rather than being considered waste. Composting emerges as a promising solution, effectively converting this biomass into a nutrient-rich product essential for plant growth. This research aimed to valorize RB from MAP through co-composting with green waste (GW) and poultry manure (PM) by optimising the initial mixture composition and evaluating the compost's quality. A statistical mixture design approach was utilized to optimize the initial mixture composition. Sixteen experiments were performed, focusing on pH and C/N ratio as response parameters. After monitoring the composting process, physicochemical parameters and the quality of the compost produced were evaluated. The results led to the successful development and validation of two response models using analysis of variance. The ideal mixture composition was found to be 45% RB-MAP, 25%PM, and 30% GW. The final compost exhibited a low C/N ratio, was rich in fertilizing and nutritive elements, and importantly, showed no phytotoxic effects. This research underscores the potential of composting as a sustainable method to convert RB into valuable agricultural resources.Item Metadata only Optimized Quantization Parameter Selection for Video-based Point Cloud Compression(Frontiers, 2024-07-02) Yuan, Hui; Hamzaoui, Raouf; Neri, Ferrante; Yang, Shengxiang; Lu, Xin; Zhu, Linwei; Zhang, YunPoint clouds are sets of points used to visualize three-dimensional (3D) objects. Point clouds can be static or dynamic. Each point is characterized by its 3D geometry coordinates and attributes such as color. High-quality visualizations often require millions of points, resulting in large storage and transmission costs, especially for dynamic point clouds. To address this problem, the moving picture experts group has recently developed a compression standard for dynamic point clouds called video-based point cloud compression (V-PCC). The standard generates two-dimensional videos from the geometry and color information of the point cloud sequence. Each video is then compressed with a video coder, which converts each frame into frequency coefficients and quantizes them using a quantization parameter (QP). Traditionally, the QPs are severely constrained. For example, in the low-delay configuration of the V-PCC reference software, the quantization parameter values of all the frames in a group of pictures are set to be equal. We show that the rate-distortion performance can be improved by relaxing this constraint and treating the QP selection problem as a multi-variable constrained combinatorial optimization problem, where the variables are the QPs. To solve the optimization problem, we propose a variant of the differential evolution (DE) algorithm. Differential evolution is an evolutionary algorithm that has been successfully applied to various optimization problems. In DE, an initial population of randomly generated candidate solutions is iteratively improved. At each iteration, mutants are generated from the population. Crossover between a mutant and a parent produces offspring. If the performance of the offspring is better than that of the parent, the offspring replaces the parent. While DE was initially introduced for continuous unconstrained optimization problems, we adapt it for our constrained combinatorial optimization problem. Also, unlike standard DE, we apply individual mutation to each variable. Furthermore, we use a variable crossover rate to balance exploration and exploitation. Experimental results for the low-delay configuration of the V-PCC reference software show that our method can reduce the average bitrate by up to 43% compared to a method that uses the same QP values for all frames and selects them according to an interior point method.Item Open Access Self-Reinforced Composite Materials: Frictional Analysis and Its Implications for Prosthetic Socket Design(MDPI, 2024-11-18) Nagarajan, Yogeshvaran R.; Hewavidana, Yasasween; Demirci, Emrah; Sun, Yong; Farukh, Farukh; Kandan, KarthikeyanFriction and wear characteristics play a critical role in the functionality and durability of prosthetic sockets, which are essential components in lower-limb prostheses. Traditionally, these sockets are manufactured from bulk polymers or composite materials reinforced with advanced carbon, glass, and Kevlar fibres. However, issues of accessibility, affordability, and sustainability remain, particularly in less-resourced regions. This study investigates the potential of self-reinforced polymer composites (SRPCs), including poly-lactic acid (PLA), polyethylene terephthalate (PET), glass fibre (GF), and carbon fibre (CF), as sustainable alternatives for socket manufacturing. The tribological behaviour of these self-reinforced polymers (SrPs) was evaluated through experimental friction tests, comparing their performance to commonly used materials like high-density polyethylene (HDPE) and polypropylene (PP). Under varying loads and rotational speeds, HDPE and PP exhibited lower coefficients of friction (COF) compared to SrPLA, SrPET, SrGF, and SrCF. SrPLA recorded the highest average COF of 0.45 at 5 N and 240 rpm, while SrPET demonstrated the lowest COF of 0.15 under the same conditions. Microscopic analysis revealed significant variations in wear depth, with SrPLA showing the most profound wear, followed by SrCF, SrGF, and SrPET. In all cases, debris from the reinforcement adhered to the steel ball surface, influencing the COF. While these findings are based on friction tests against steel, they provide valuable insights into the durability and wear resistance of SRPCs, a crucial consideration for socket applications. This study highlights the importance of tribological analysis for optimising prosthetic socket design, contributing to enhanced functionality and comfort for amputees. Further research, including friction testing with skin-contact scenarios, is necessary to fully understand the implications of these materials in real-world prosthetic applications.