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Following the publication of the above article, the authors contacted the Editorial Office to explain that they had identified a pair of duplicate images in the control (Vehicle) group of mouse images in Fig. 1A on p. 1792. Specifically, the same image (corresponding correctly to the 'Day 5' experiment) was inadvertently chosen to represent the cutaneous manifestations of mice in the Vehicle group on 'Day 3' and 'Day 5' in Fig. 1A. This error arose as a consequence of repetitive application and duplication procedures within the image set, resulting in the inadvertent reuse of the same photo. Additionally, due to minimal alterations observed in the skin condition of mice from the control group following treatment, each mouse exhibited a similar appearance; this similarity further contributed to the delayed identification of this error during the paper revision stage. Consequently, this duplication of the same image was made as a result of insufficient scrutiny. The revised version of Fig. 1, showing the correct image for the 'Day 3' experiment in Fig. 1A, is shown on the next page. The authors can confirm that the error associated with the assembly of this figure did not have any significant impact on either the results or the conclusions reported in this study, and all the authors agree with the publication of this Corrigendum. The authors are grateful to the Editor of International Journal of Molecular Medicine for allowing them the opportunity to publish this; furthermore, they apologize to the readership of the Journal for any inconvenience caused. [International Journal of Molecular Medicine 43: 1789‑1805, 2019; DOI: 10.3892/ijmm.2019.4098].

Wire arc additive manufacturing (WAAM), also known as directed energy deposition (DED) process, is an efficient additive manufacturing technology, offers high potential to rapidly fabricate large-scale parts with complex geometries layer-by-layer. However, the fundamental understanding of the fatigue behaviour of such parts and the material requirements need to be significantly improved at all levels before this unique technology can be implemented for critical applications. This work aims to investigate the fatigue behaviour of WAAM built ER70S-6 steel under uniaxial, torsion and multiaxial loading conditions. Specimens were extracted in two different orientations: vertical and horizontal, to explore if the orientation direction has any effect on the fatigue results. Scanning Electron Microscopy (SEM) was conducted to examine the fracture surface of broken specimens and identify crack initiation regions and fracture mechanisms. The obtained results were compared with the fatigue data available in the literature on common structural steels fabricated using conventional welding and WAAM technique, showing similar fatigue behaviour with wrought S355 specimens. Moreover, the uniaxial data set on ER70S-6 WAAM specimens was evaluated according to the DNV RP-C203 standard for continuous welds, demonstrating advantageous fatigue resistance in the examined material.

A pneumatic drying model, developed in a previous work, was tested and validated based on a series of 56 experiments of cassava starch drying conducted on a pilot-scale pneumatic dryer. After fitting two parameters, the average diameter of starch particles and a heat loss factor, the model predicted the effects of main operating conditions with a level of accuracy comparable to that of the experimental measurements. Transient phases with sudden variations of product feed rate were also successfully simulated. The model is therefore suitable for equipment design purposes. The experimental results showed that the size of starch particles considerably decreases with increasing air velocity. As a result, at high air velocity, despite the shorter residence time in the drying pipe, the overall drying performance is improved due to the smaller particle size. It is therefore possible to increase air velocity, and hence product feed rate and production capacity, without detrimental effect on the drying efficiency.

A novel extended cohesive damage element method is used to develop a numerical snowpack model to study the fundamental damage mechanisms of snowpack under external drivers and to investigate multiple mixed mode damage propagation within snowpack. A new mixed mode damage criterion is introduced to account for tensile and shear fractures as well as compressive crushing together with shear crack for approximating the mixed mode damage initiation and propagation in the weak layer in snowpack. A propagation saw test (PST) is considered to understand basic damage involution in snowpack under self-weight related bending. The nonlinear fracture modelling prediction agrees with the PST sample well. This paper provides an alternative approach as a predictive method using the extended cohesive damage element for potentially forecasting slab avalanches in snow terrain according to weather forecast and planned human activities in the future.

The ability to measure the very high heat fluxes that typically occur during the hypersonic re-entry phase of space vehicles is generally considered a subject of great importance in the aerospace field. Most of the sensors used for these measurements need to be checked periodically and re-calibrated accordingly. Another bottleneck relates to the need to procure thermal sources that are able to generate reliable reference heat fluxes in the range between 100 and 1000 kW/m2 (as order of magnitude). In the present study, a method is presented by which, starting from a calibration system with a capacity of approximately 500 kW/m2 only, heat fluxes in the range of interest for hypersonic applications are generated. The related procedure takes advantage of established standards for the characterization of a radiative heat flux. It also builds on the hybrid radiative-convective nature of typical hypersonic heat fluxes and the yet poorly explored possibility to use convective sources of heat to produce high-intensity fluxes. The reliability of such a strategy has been tested using a high enthalpy supersonic flow facility relying on an electric arc-heater and pure Nitrogen as work gas. Stagnation-point heat fluxes have been successfully measured (with reasonable accuracy) in the range between 600 and 1500 kW/m2 for values of the centerline enthalpy spanning the interval from to 6 to 24 MJ/kg.

The frequency-dependent mass and stiffness matrices of a Timoshenko–Ehrenfest beam are developed through extensive application of symbolic computation. Explicit algebraic expressions for the frequency dependent shape functions and each of the independent elements of the frequency-dependent mass and stiffness matrices are presented concisely. The ensuing frequency-dependent mass and stiffness matrices of the Timoshenko–Ehrenfest beam are applied with particular reference to the Wittrick–Williams algorithm to investigate the free vibration characteristics of an individual Timoshenko–Ehrenfest beam and a framework. The results are discussed with significant conclusions drawn. The proposed method retains the exactness of results like the dynamic stiffness method, but importantly, it opens the possibility of including damping in the analysis.

Wake interactions between wind turbines have a great impact on the overall performance of a wind farm. In this work, a novel deep learning method, called Bilateral Convolutional Neural Network (BiCNN), is proposed and then employed to accurately model dynamic wind farm wakes based on flow field data generated by high-fidelity simulations. Different from the existing machine-learning-based dynamic wake models where dimensionality reduction is essential, the proposed BiCNN is designed to directly process the different types of inputs through a background path and a foreground path, thus avoiding the errors due to dimensionality reduction. Substantial results show that the developed machine learning based wake model can achieve accurate wake predictions in real time, i.e. it captures the spatial variations of the dynamic wakes similarly as high-fidelity wake models and runs as fast as low-fidelity static wake models. The overall prediction error of the developed model is 3.7% with respect to the freestream wind speed. Furthermore, the results for a test farm consisting of 25 turbines show that the developed model can predict the dynamic wind farm wakes within several seconds using

Existing researches about unsupervised cross-domain bearing fault diagnosis mostly consider global alignment of feature distributions in various domains, and focus on relatively ideal diagnosis scenario under the steady speeds. Therefore, unsupervised feature adaptation between all the corresponding subdomains under speed fluctuation remains great challenges. This paper proposes a modified deep subdomain adaptation network (MDSAN) for more practical and challenging cross-domain diagnostic scenarios from the fluctuating speeds to steady speeds. Firstly, to extract the representative features and effectively suppress negative transfer, a novel shared feature extraction module guided by multi-headed self-attention mechanism is constructed. Then, a new trade-off factor is designed to improve the convergence performance and optimization process of MDSAN. The proposed method is used for analyzing experimental bearing vibration data, and the results show that it has higher diagnostic accuracy, faster convergence, better distribution alignment, and is more suitable for unsupervised cross-domain fault diagnosis under speed fluctuation scenario compared with the existing methods.

A study has been conducted to evaluate the mechanical and fatigue crack propagation properties of wire + arc additively manufactured ER70S-6 components. A parallel-built deposition strategy was employed to fabricate the additively manufactured wall. The hardness values were slightly higher at the bottom and top of the wall due to the presence of Widmanstätten ferrite and carbides. The characterization of mechanical properties in both orientations; parallel and perpendicular to the deposition direction showed a marginal difference in yield strength and ultimate tensile strength. The crack growth rates were correlated with linear elastic fracture mechanics parameter ΔK and compared with an oscillation-built deposition strategy from the literature. The crack growth rates of both deposition strategies were found to be very similar to each other. Furthermore, it has been demonstrated that the variability in the crack growth histories can be reasonably well captured by using the NASGRO crack growth equation.

Interface creep cracking is very common to be seen in various kinds of welded components which are used widely in engineering practice. In the present paper, the interface creep crack tip field by considering material mismatch effect is studied. The interface creep crack is found to be close to the HRR field which can produce the faster creep crack growth rate. A material mismatch constraint parameter is proposed based on the validation of the local mismatch effect on the interface creep crack tip field which also maintains the self-similarity. An averaged material mismatch constraint M avg ∗ is presented to represent the material mismatch constraint effect. It reveals that the material mismatch constraint effect for interface creep crack decreases with the increase of the local mismatch factor. The physical meaning of the material mismatch constraint effect for the interface creep crack and its future application to engineering failure analysis is also discussed and presented.

The matrix component of composite structures is generally brittle. In any damage occurrence, fracture propagates rapidly through the structure. This study proposes a novel toughening enhancement model for unidirectional (UD) composites to overcome these damage-propagation issues. The toughening mechanism is established by introducing the so-called micro defects/cracks for increasing the toughness of the matrix constituent of the composite structure. Mechanical simulations are performed utilizing a non-local continuum formulation known as Peridynamics (PD). The PD formulation facilitates modeling material discontinuities such as complex crack/defect formations with arbitrary size, orientation, and location features in composite structures. Here, the toughening enhancement models are established by allocating various micro-crack formations in three different fiber orientations (0°, 45°, 90°) of UD composite plates. The toughening effects of micro-crack clusters are thoroughly analyzed by making comprehensive comparisons of the propagation speed of an initially introduced macro-crack and its tip strain energy density. As a result, various micro-crack distributions are established to provide an augmented toughness to the brittle composite materials, and their key features are assessed in detail.

The design of an adsorption solar air conditioning system is investigated by using a model with an activated carbon–methanol working pair. This system is analysed with the solar insolation levels and ambient temperatures of Singapore. The proposed design mainly consists of two tubular reactor heat exchangers (TRHEXs) operating out of phase and driven by heat from an evacuated tube solar collector (ETSC). The pair of TRHEXs act as a thermal compressor and contain about 2.275 kg of activated carbon per reactor. The evacuated tube solar collector (ETSC) has better performance and is more cost effective than the flat plate solar collector (FPSC), even though it has a higher cost per unit. On the hottest day of the year, the proposed adsorption system has a maximum cooling power of 2.6 kW and a COP of 0.43 at a maximum driving temperature of 139 °C with a 9.8 m2 ETSC area. The system has a total estimated cost of EUR 10,550 corresponding to about SGD 14,800 with a 7-year payback time. At similar cooling capacities, the adsorption air conditioning system is expected to be more cost effective than the conventional system beyond an expected period of 7 years, with an expected lifetime of 15 to 20 years. Published version

The results of a study of environmental ageing on the apparent interfacial shear strength of glass fibre – vinyl ester microbond samples are presented. The scale related issues of estimating water absorption levels in microbond samples are reviewed and discussed and a solution based on Fickian diffusion is given. Interphase strength of microdroplets aged in water at 23 °C was relatively stable up to 6 days exposure after which strength degradation was fairly rapid. Immersion in water at 50 °C resulted in an immediate 20-30% irreversible loss of strength. Further exposure beyond 2 days led to total loss of integrity of the microbond samples. Electron microscope images of aged microdroplets appeared to show the development of a bi-phasic microstructure. The presence of two phases in small scale vinyl ester polymer samples was confirmed by DMA on thin films.

In this paper, an Advanced Dynamic Model Predictive Control (AMPC) based on a Nonlinear Model Predictive Control (NMPC) framework with a multi-objective cost function driven by dynamic weights is proposed to improve the energy performance of fuel cell hybrid electric vehicles whilst prolonging their component lifetime. By the use of dynamic weights, the cost function is effectively formulated as the combination of fuel consumption, rate of change of fuel cell power, battery power, the fuel cell efficiency, state of charge of the battery, and their temperatures. In order to enhance the adaptability of the AMPC, a Fuzzy Cognitive Map (FCM) is then newly designed to regulate online the dynamic weights to adjust the importance of each cost component according to the conditions prevailing during driving. A comparative study between the proposed AMPC, a constant weight based NMPC and a conventional NMPC having cost function with fewer objectives has been carried out by means of simulation using a FCHEV model from the simulation tool ADVISOR to illustrate the efficacy of the proposed AMPC.

An accurate battery model is essential for battery management system (BMS) applications. However, existing models either don't describe battery physics or are too computationally intensive for practical applications. This paper presents a non-linear equivalent circuit model with diffusion dynamics (NLECM-diff) which phenomenologically describes the main electrochemical behaviours, such as ohmic, charge-transfer kinetics, and solid-phase diffusion. A multisine approach is applied to identify the elements for high frequency dynamics, as well as a distributed SoC dependent diffusion model block is optimised to account for long time dynamics. The model identification procedure is conducted on a three-electrode experimental cell, such that NLECM-diff models are developed for each electrode to then obtain the full cell voltage. Results imply that the NLECM-diff reduces the voltage root mean square error (RMSE) by 49.6% compared to a conventional ECM in the long duration discharge and has comparable accuracy to a parameterised SPMe in the NEDC driving cycle. Additionally, the variation of diffusion-related characteristics of the negative electrode under different currents is determined as the primary reason of the battery models' large low-SoC-range error. Furthermore, the diffusion process is determined as the dominant voltage loss contributor in the long duration discharge and the ohmic voltage loss is identified as the dominant dynamic under NEDC driving profile.

The Covid-19 pandemic disrupted the normal mode of teaching and a remote learning model was substituted in the academic year of 2020-21. As part of the move, a series of additional summative assessments were introduced in many modules of the host department of this study to ensure students' engagement and provide them with feedback while they were learning remotely. Coursework, online quizzes and online exams were used to assess students' learning in this academic year. A student workload model was used to predict the effect of assessments and ensure students have enough time to study all their modules. Surveys were used to determine how different forms of assessment contributed to students learning as well as their impact on students’ workload. Questionnaires were designed to collect information on the number of hours students spent on different forms of assessments, how they perceived the effect of those assessments on their learning and how well they have learned different subjects. Irrespective of the weighting of the assessments and their types, students have treated all summative assessments very seriously and spent considerable time on even small pieces of assessments such as weekly online quizzes with a very low weighting. They perceived completing harder and longer assessments contributed relatively less to their learning. Amongst all three types of assessment, students reported reviewing for online exams helped them the most to enhance their learning.

This study investigates the mechanical behaviour of elastomeric bearings with a low shape factor (LSF). Such bearings can offer an effective solution for three-dimensional seismic isolation of structures, that is, isolation in vertical as well as horizontal directions. They could also be employed for developing low-cost isolation systems for developing countries due to their reduced weight and manufacturing cost. The first part of the study describes tests carried out at Tun Abdul Razak Research Centre (TARRC) on low-damping rubber double-shear test pieces and LSF bearings. The material tests are used to inform the development of a finite element (FE) model of the bearings, which is validated against the bearing test results. It is shown that the proposed FE model can be used to describe accurately the global non-linear horizontal force-displacement behaviour of the compressed bearings, while providing an insight into the local distribution of stresses and strains. It can also be used to investigate the bearing response under boundary conditions that differ from the one considered in the tests. The second part of the study illustrates the numerical simulations of shaking table tests carried out at the University of Naples Federico II on a structural prototype mounted on the low-damping LSF bearings. Useful insights are provided into the effect of the vertical bearing flexibility on the response and the attainment of critical conditions of zero tangent horizontal stiffness under horizontal displacements.

How actors react to change is a crucial question for social scientists interested in global energy system transformation (EST). The global oil industry's response to the challenges associated with climate change and EST is a particular topic of discussion. Here, we argue for an interdisciplinary approach, bringing together insights from multiple disciplines within the social sciences that study oil companies, to further our understanding of what they are doing and why they are doing it. Although research on the political economy and socio-technical nature of EST has led to important insights, it tends to treat the global oil industry as a monolith with common interests and strategic objectives. We argue that the analytical and conceptual tools provided by the management and business literature can help unpack this ‘black box’. We explain how this is the case by exploring some of these tools and applying them to a novel heuristic, the ‘Transition Strategy Continuum’ that helps categorise and analyse the emerging strategies of the publicly-traded ‘International Oil Companies’ (IOCs). As such, we respond to the call for interdisciplinarity raised in the inaugural issue of this Journal. Ultimately, we want social scientists working on energy to take serious insights from other fields of inquiry that help illuminate the complexities of the task of transformation ahead for the IOCs and other related stakeholders.

A new inter-module connection was developed, adopting structural topology optimisation (STO) and the inter-locking method of joining. The structural performance of the connection was assessed through a series of monotonic and cyclic FE analyses. Results revealed that the structural behaviour of the new connection was comparable to that of other inter-module joints in the literature, while managing to tackle their limitations by introducing both an easy-to-install and easy-to-disassemble configuration with promising opportunities for reuse, demonstrating that inter-locking joints can be worthy competitors for traditional means of attachment in the future of modular construction.

Defect-free welds between A-516 ferritic and 316L austenitic stainless steel were achieved using inertia friction welding (IFW) under varying friction and forge pressures. The microstructural evolution and the associated mechanical properties were characterised across different weld regimes. The welds were free from microcracks and demonstrated higher strength and hardness than the parent metal (PM), indicating enhanced properties. Carbide precipitates were not observed at the weld interface, implying no occurrence of sensitisation in the stainless steel. The presence of refined grains coupled with low grain orientation spread (GOS) values was the indication of continuous dynamic recrystallisation (CDRX) occurring during IFW.

Seaports are global players in the maritime industry with the responsibility of promoting the well-being of employees and customers in the workplace. However, over the past years safety performance of seaports operating within the West African sub-region has become a major concern due to the lack of enforcement of national occupational health and safety regulations. This has compelled some seaports to adopt the occupational health and safety management system (OHSMS) ISO 45001:2018 standard. The aim of this study is therefore to assess the progress seaports have made in the implementation of ISO 45001:2018 standard and discuss the challenges that need to be overcome when implementing ISO 45001:2018 standard in seaports. Through the use of questionnaire, observations and review of institutional document, data was gathered from workers and senior managers of export, container depot and the stevedoring sections of seaports operating in Ghana. The findings of this study revealed that seaports within Ghana have made some progress with regards to workers’ awareness of occupational health and safety issues, usage of personal protective equipment (PPEs) and safe working procedures. However, it was also established that a lot more needs to be done to improve the current levels of communication, safety training and resources in relation to health and safety management. The findings of this research are useful to maritime institutions wishing to migrate from OHSAS 18001:2007 certification to ISO 45001:2018 certification or seeking to improve on already existing system.

The present investigation focuses on developing cost-effective Carbon/Glass/Kevlar fiber-reinforced polymer hybrid composite laminates for achieving its synergistic effect on flexural and impact performance. It investigates the effect of stacking sequence induced by the use of different fiber types (Kevlar = K, glass = G, and carbon = C) on the flexural and impact performance of the composites. Five hybrid composites (labelled as A = [G2K3G2], B = [KG2CG2K], C = [CKGCGKC], D = [CGKCKGC], E = [CK2CK2C]) and three plain (i.e., non-hybrid) composites (F = [K]7, G = [G]7, H = [C]7) have been fabricated through manual pre-preg lay-up manufacturing techniques. The flexural strength and modulus, hardness, and Izod impact strength have been evaluated for the fabricated composites and compared. The results showed that the D-type hybrid composite achieves the maximum positive hybrid effect as compared to other hybrid composites, possesses a hardness of 59 BHN, a flexural strength of 380 MPa, and modulus of 36 GPa, and impact strength of 80 KJ/m2. The fracture surfaces of the hybrid composite specimen have been analysed using scanning electron microscopy, and compared against the properties achieved for enabling correlations. Furthermore, the cost-efficiency of the hybridization in terms of flexural strength/cost, modulus/cost, and impact strength/cost ratio were evaluated for potential engineering and design applications.

This paper aims to maximize the total power generation for wind farms subject to strong wake effects and stochastic inflow wind speeds. A data-driven control method that only requires the accessible measurements of every turbine in the farm is proposed via deep reinforcement learning (DRL). We employ a grouping strategy to mitigate the high computational complexity induced by DRL and enhance our method’s applicability to large-scale wind farms. Based on the levels of aerodynamic interactions among turbines, this grouping strategy divides the whole farm into small sub-groups. Therefore, one can execute DRL on these sub-groups instead of carrying on a complicated learning process for the entire farm. Simulations verify the advantages of the proposed DRL-based wind farm control method over the commonly employed greedy strategy. Results also show that the proposed method can significantly reduce the overall computing cost compared with the direct execution of DRL on the whole wind farm.

According to the Food and Agriculture Organization, fishing at sea is a risky activity with the highest mortality rate due to accidents. Many ship accidents are experienced by small ships, especially on boats with a length of smaller than 24 metres. With a large number of small fishing boats in Indonesia, the risk of potential ship accidents is high. Therefore, an operability analysis must be carried out for various loading conditions to address any safety issues due to severe vessel motion in advance. The operation of fishing vessels is different from that of merchant ships. The net cargo of merchant ships tends to remain unchanged during a voyage. By contrast, the net cargo of a fishing boat, which is fish caught, will change during its operation at sea. This change will also affect the ship’s seakeeping characteristics. This study aims to determine the effect of changes in load and their effect on a traditional fishing boat’s operability in Indonesia, taking into account the ship’s intact stability. In addition, this study also highlights the response of the ship roll motion to prevent stability failure. The stability curve is used to relate ship stability analysis to seakeeping analysis. Percentage operability and Operability Robustness Index are used to assess the root mean square (RMS) roll response and the ship's expected maximum roll motion. In this study, it is shown that the percentage operability of the fishing boat satisfying all pre-determined seakeeping criteria varies between 61% to 74%. Among all criteria, the limiting boundary for RMS roll motions and RMS pitch motion are relatively low, affecting the overall operability.

Loss models are used to evaluate the aerodynamic performance of axial turbines at the preliminary design stage. The commonly used loss models were derived for air and steam turbines and have not been sufficiently investigated for turbines working with non-conventional working fluids, relevant to new power systems, such as organic fluids and supercritical CO (sCO). Thus, the aim of this study is to explore the deviation between the performance predictions of different loss models, namely Dunham and Came, Kacker and Okapuu, Craig and Cox and Aungier, for non-conventional working fluids where turbines may differ in design and operation than conventional air or steam turbines. Additionally, this paper aims to investigate the effect of the turbine scale on the trends in the performance predictions of these models. Three different case-studies are defined for air, organic Rankine cycle (ORC) and sCO turbines and each one is evaluated at two different scales. It is found that the selected loss models resulted in varying loss predictions; particularly for predicting the losses due to the clearance gap for all small scale designs. Furthermore, large variations were found in predicting the effect of the flow regime on the turbine performance for all models.

This work proposes a distribution-free stochastic model updating framework to calibrate the joint probabilistic distribution of the multivariate correlated parameters. In this framework, the marginal distributions are defined as the staircase density functions and the correlation structure is described by the Gaussian copula function. The first four moments of the staircase density functions and the correlation coefficients are updated by an approximate Bayesian computation, in which the Bhattacharyya distance-based metric is proposed to define an approximate likelihood that is capable of capturing the stochastic discrepancy between model outputs and observations. The feasibility of the framework is demonstrated on two illustrative examples and a followed engineering application to the updating of a nonlinear dynamic system using observed time signals. The results demonstrate the capability of the proposed updating procedure in the very challenging condition where the prior knowledge about the distribution of the parameters is extremely limited (i.e., no information on the marginal distribution families and correlation structure is available).

The microbond test has been widely adopted by researchers seeking to characterise the fibre-matrix interface in polymer composites. This test requires the preparation of polymer droplets with a mass as little as 20 ng. This brings with it the possibility of scaling issues causing unanticipated significant differences to the properties and performance of these droplets in comparison to macroscale samples. This paper reviews a number of these potential scaling issues in a range of polymer systems which users of the microbond test should be aware of. Some of these phenomena can affect the magnitude of the test results obtained much more than the fibre-matrix interface effects which the test is used to detect. It is concluded that in many cases the structure and properties of the polymer in such microdroplets is not representative of the same polymer, with the same thermal and environmental exposure history, prepared on the macroscale.

In this study, combustion synthesis involving mechanical milling and subsequent sintering process was utilised to fabricate Cu/AlxCuy/Al2O3 in-situ composite through the aluminothermic reduction of CuO powders. First, CuO and Al powders were mixed, and ball milled for 30–150 min to facilitate self-propagating high-temperature synthesis (SHS). Then, mechanically activated Al-CuO powders were mixed with elemental Cu powders and experienced subsequent cold compaction and sintering processes. The reactions during synthesis were studied utilising differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Densification and hardness of green and sintered bodies were also obtained. The results indicated that despite the negative free energy of the aluminothermic reaction, an initial activation energy supply is required, and mixed Al-CuO powders did not show significant progress in the combustion synthesis method. The aluminothermic reaction became probable whenever the activation energy was entirely provided by high-energy ball milling or by the sintering of ball-milled Al-CuO mixed powders. DTA results showed that the aluminothermic reaction temperature of Al-CuO decreased with milling times, whereas after 150 min of ball milling, the reaction was completed. XRD patterns revealed that the formation of Al2Cu and Al2O3 reinforcing phases resulted from CuO reduction with Al. Al4Cu9, Cu solid solution, and Al oxide phases were observed in sintered samples. The relative density of the samples was reduced compared to the green compacted parts due to the nature of the Cu-Al alloy and the occurrence of the swelling phenomenon. The hardness results indicated that in-situ formation of reinforcing phases in samples that experienced thermally assisted thermite reaction yielded superior hardness.

Commercial Li-ion cell electrodes comprise a random mix of the constituent materials largely unchanged for more than three decades. During fast charge/discharge, electrode-scale Li-ion concentration gradients develop, along with a spatially heterogeneous distribution of overpotential, utilization and degradation of active material, which ultimately restricts the range of realizable energy-power combinations. We expand energy-power characteristics and reduce cell degradation rate using electrodes that are compositionally graded at the microscale to homogenize active material utilization. Trapezoidal-graded composition LiFePO4 cathodes, enabled by a layer-by-layer deposition technique, are compared with conventional electrodes: at an energy density of 500 Wh L−1 the best graded electrode design increased power density from approximately 100 W L−1 to 630 W L−1, while at a power density of 300 W L−1, the energy density increased from approximately 420 Wh L−1 to 600 Wh L−1. The results highlight the potential for new manufacturing approaches and electrode designs to provide performance enhancements for existing and future Li ion battery chemistries.

The aim of this paper is to investigate the potential of using shallow geothermal energy in Lebanon for cooling a power cycle. The study includes ground temperature measurement, operating system management, and pressure drop assessment. Temperatures were monitored at six positions underground reaching to a depth of 2 m in Bekaa-Lebanon during the whole of 2020. The temperature sensors were placed at depths of 0.3, 0.6, 1, 1.3, 1.6, and 2 m underground. At 2 m depth, the ground temperature showed high stability with an annual temperature difference of 7 °C, while that of high and low ambient temperatures were 40 °C and 33 °C, respectively. Based on the comparison between ambient and ground temperatures, the ground cooling system can operate 207 days/year partially with full operations of 51 days. This shows that shallow geothermal energy has a great potential to activate a ground-based cooling system in this region. However, to avoid heat accumulation, use of another heat exchanger is recommended to support the ground cooling system. This heat exchanger can also provide coolth compensation when the power cycle is turned off. The pressure drop inside the heat exchangers was found to be highly significant, hence, it was essential to add an intermediate water loop between the power cycle and the ground loop.

This paper proposes two significant developments of the Wittrick–Williams (W–W) algorithm for an exact wave propagation analysis of lattice structures based on analytical dynamic stiffness (DS) model for each unit cell of the structures. Based on Bloch's theorem, the combination of both the DS and the W–W algorithm makes the wave propagation analysis exact and efficient in contrast to existing methods such as the finite element method (FEM). Any number or order of natural frequencies can be computed within any desired accuracy from a very small-size DS matrix; and the W–W algorithm ensures that no natural frequency of the structure is missed in the computation. The proposed method is then applied to analyze the band gap characteristics and mode shapes of hexagonal honeycomb lattice structures and the results are validated and contrasted against the FE results. The effects of different primitive unit cell configurations on band diagrams and iso-frequency contours are thoroughly investigated. It is demonstrated that the proposed method gives exact eigenvalues and eigenmodes with the advantage of at least two orders of magnitude in computational efficiency over other methods. This research provides a powerful, reliable analysis and design tool for the wave propagations of lattice structures.

A novel approach for predicting the intermetallic compound (IMC) formation during friction stir welding (FSW) of AA6061 to commercially pure copper has been developed, in addition to their effect on mechanical properties. The temperature distribution of the aluminium to copper weld nugget determined by a finite element model, the use of an Al–Cu phase diagram and the elemental concentration of copper and aluminium in the weld nugget have been combined to predict and validate several IMCs present in the different zones of the weldment. The results of performing butt-welding of these dissimilar metals using the FSW process demonstrated that the highest ultimate tensile strength of 194.5 MPa was achieved at 1500 rev min −1 tool rotational speed, 100 mm min −1 traverse speed and a zero-tool offset.

Microchannel resonators containing a miniaturized volume of a solution can have various applications in different fields. In this study, a microchannel cantilever was loaded with a solution containing a very small number of Pseudomonas fluorescens bacteria suspended in M9 growth medium. The liquid-filled microchannel cantilever was irradiated with a 532-nm laser. The shift in the frequency of the cantilever due to varying bacterial loads is less reliable; therefore, it could not be used for monitoring the bacterial concentration. The energy loss of the cantilever extracted from the quality factor exhibited reliable results and a very strong correlation with the bacterial concentration. The results showed a linear relation between the damping factor of the cantilever and the bacterial concentration. Accordingly, these findings were expected because the bacteria inside the solution can be considered as particles acting against the cantilever motion due to the solution’s viscosity. Thus, more bacteria caused more damping, in agreement with the experimental observations. A semiquantitative experiment was conducted with a heat source (i.e., laser beam) that focused at the cantilever tip to demonstrate the redistribution of the bacterial load within the solution due to the thermal gradient.

The flexural ultrasonic transducer has traditionally been limited to proximity measurement applications, such as car-parking systems and industrial metrology. Principally, their classical form is unsuitable for environments above atmospheric 1 bar pressure, due to an internal air cavity which creates a pressure imbalance across the transducer’s vibrating membrane. This imbalance leads to physical deformation and degradation of the transducer’s structure, restricting the membrane’s capacity to vibrate at resonance to transmit and receive ultrasound. There is a requirement for ultrasonic sensors which can withstand environments of elevated pressure, for example in ultrasonic gas metering. Recent research demonstrated the dynamic performance of flexural ultrasonic transducers with vented structures, allowing the pressure to balance across the transducer membrane. However, a hermetically sealed transducer is a more practical and robust solution, where the internal components of the transducer, such as the piezoelectric ceramic disc, will be protected from harmful environmental fluids. In this research, the design and fabrication of a new form of flexural ultrasonic transducer for environments of elevated pressure is demonstrated, where the internal air cavity is filled with an incompressible fluid in the form of a non-volatile oil. Dynamic performance is measured through acoustic microphone measurements, electrical impedance analysis, and pulse-echo ultrasound measurement. Together with finite element analysis, stable ultrasound measurement is achieved above 200 bar in air, opening the possibility for reliable ultrasound measurement in hostile environments of elevated pressure.\ud

We study the dynamic behaviour of a hybrid system where manufacturing and remanufacturing operations occur simultaneously to produce the same serviceable inventory for order fulfilment. Such a hybrid system, commonly found in the photocopier and personal computer industries, has received considerable attention in the literature. However, its dynamic performance and resulting bullwhip effect, under push and pull remanufacturing policies, remain unexplored. Relevant analysis would allow considering the adoption of appropriate control strategies, as some of the governing rules in a push-based environment may break down in pull-driven systems, and vice versa. Using nonlinear control theory and discrete-time simulation, we develop and linearise a nonlinear stylised model, and analytically assess bullwhip performance of push- and pull-controlled hybrid systems. We find the product return rate to be the key influencing factor of the order variance performance of pull-controlled hybrid systems, and thus, to play an important role towards push or pull policy selection. Product demand frequency is another important factor, since order variance has a U-shaped relation to it. Moreover, the product return delay shows a supplementary impact on the system's dynamics. In particular, the traditional push-controlled hybrid system may be significantly influenced by this factor if the return rate is high. The results highlight the importance of jointly considering ordering structure and product demand characteristics for bullwhip avoidance.

The effects of surface topography, processing, and environment conditions during tribological contact between Ti6Al4V titanium alloy and UHMWPE friction pairs were systematically evaluated. Hence, in this research the polyethylene samples (blocks) having a constant surface roughness were rubbed against counter-bodies (rollers) made of titanium alloy with different roughness of surfaces. The counter-samples were manufactured using either dry machining and/or minimum quantity lubrication (MQL) conditions. Such cutting conditions are harmless to humans and the environment. Simulated body fluid (SBF) and distilled water was used to simulate the tribological trials. We have noted that the lubricant applied to protect the integrity of machined parts, the rollers, have only minor impact on the tribological features of the friction pairs tested. Further, the samples produced with dry machining demonstrated a slightly lower momentary friction coefficient and temperature. In contrast, the MQL method enable reduced friction surface and significant wear accumulation. Further, it was found that the minimum and maximum values of the Sa texture parameter associated to tribological parameters do not exceed 21% and 4%, when is used dry and MQL methods, respectively. Nevertheless, the distilled water revealed a much better wear resistance when comparing to SBF, and the later one trigger as well as an accentuated wear progress with different patterns. The results of the study are important in the design of new biomedical components produced by finish turning.

Monocular Visual Simultaneous Localisation and Mapping (VSLAM) systems are widely utilised for intelligent mobile robots to work in unknown environments. However, complex and varying illuminations challenge the accuracy and robustness of VSLAM systems significantly. Existing feature-based VSLAM methods often fail due to the insufficient feature points that can be extracted in those challenging illumination environments. Therefore, this paper proposes an improved ORB-SLAM algorithm based on adaptive FAST threshold and image enhancement (AFE-ORB-SLAM), which works in the environments with complex lighting conditions. An improved truncated Adaptive Gamma Correction (AGC) is combined with unsharp masking to reduce the effect caused by different illuminations. What is more, an improved ORB feature extraction method with the adaptive FAST threshold is proposed and adopted to obtain more reliable feature points. To verify the performance of the AFE-ORB-SLAM, three public datasets (the extended Imperial College London and National University of Ireland Maynooth (ICL-NUIM) dataset with different lighting conditions, Onboard Illumination Visual-Inertial Odometry (OIVIO) dataset and the European Robotics Challenge (EuRoC) dataset) are utilised. The results are compared with other state-of-the-art monocular VSLAM methods. The experimental results demonstrate that the AFE-ORB-SLAM could achieve the highest average localisation accuracy with robust performance in the environments with complex lighting conditions while keeping similar performance in the normal lighting scenarios.

The curing performance of two epoxy resin systems has been investigated using the microbond test and FTIR spectroscopy. A novel sample preparation technique involving curing epoxy droplets on thin steel filaments allowed for high-throughput determination of microbond droplet cure state using a conventional benchtop spectrometer. Parity between steel filament and glass fibre microbond samples was confirmed by infrared microspectroscopy. It is shown that cure schedules used in the manufacture of composite parts produced microbond droplets with degrees of cure lower than that of bulk matrix specimens subjected to an identical thermal history. For a commercial resin system, testable microbond droplets could only be produced when a room temperature pre-curing time of at least 2 hours was introduced. It is concluded that microbond testing be supported by some method of droplet cure state characterisation to ensure that interfacial effects are not artefacts of droplet sample preparation.

Epoxy is an important class of thermosetting material which have been used in many fields such as aerospace, automobile and energy sectors. cured epoxy, however, exhibits poor resistance to crack initiation and growth, thus low toughness and brittleness at failure. To improve the mechanical properties, in numerous studies the epoxy matrix in polymer composites has been modified by various techniques such as the inclusion of a second phase (e.g. core-shell rubber, thermoplastics or nanofillers). Inclusion of these materials in epoxy improves toughness and the impact resistance properties, but very few studies have focused on offering an ‘active toughening’ mechanism, meaning an increase in toughness activated by a stimulation (mechanical, electrical, thermal etc.) in high-performance rigid structures. In this study, aerospace grade epoxy resin modified with tetragonal barium titanate (BaTiO3) nanoparticles has been prepared, and its instantaneous toughening behaviour has been analysed under contact-less electromagnetic fields. For this reason, different wt.% of BaTiO3 nanoparticles (1, 5, 10 wt%) have been functionalised with silane coupling agents and dispersed uniformly into epoxy Araldite LY1564, a diglycidyl ether of bisphenol A (DGEBA) associated with its curing agent Aradur 3487. Real-time strain measurement (Tensile measurements) of the modified epoxy along with in-situ Raman shift study have been carried out in situ under an electric field stimulation. The results demonstrate that the activation of dipole displacements in BaTiO3 via an electromagnetic field introduces an interfacial compressive stress onto its surrounding rigid (fully cured) epoxy that enhances the toughness of the nanocomposite via suppressing the coalesce of inherent or process induced microcracks in the epoxy. The mechanism provides an effective route for mechanical property tailoring, specifically toughening of thermoset composites, under an electric field. The in-situ Tensile and Raman (during the stimulation) along with the materials characterisation (post stimulation) provides a unique quantitative framework for design of a toughening mechanism.

Matrix toughening is one of the most popular approaches to improve the overall fracture toughness of polymer composite materials. The most widely known approach for matrix toughening is the addition of a second phase such as rigid or/and rubber particles to dissipate the fracture energy, and vessels that containing healing agents that prevent further crack propagation when ruptured. Only a few studies have shown an alternative ‘active toughening’ by introducing an internal compressive stress field in the matrix via the mismatch in filler/matrix thermal expansion under heating. In this study, epoxy composite materials with embedded ferroelectric barium titanate nanoparticles are fabricated with the aid of silane surface functionalisation. Surface-bonded fibre grating sensors are employed to investigate the strain and temperature change of the epoxy nanocomposite materials under microwave exposure, as an attempt to introduce such field aided strain tailoring of the epoxy matrix as an active toughening mechanism.

A feasibility study has been performed systematically to develop a real-time contactless measurement of the dielectric properties (DP) of composite surface by means of a high-frequency, free-space vector network analyser (VNA) associated with one steel conical horn antenna (mono- static method). Examinations of the dielectric spectra of thermoset epoxy systems over a frequency range of 1kHz to 10GHz have shown

This article presents a case study on the thermal assessment of a reinforced concrete (RC) foundation exposed to low temperatures. The foundation supports a 19,500 m3-capacity tank with low-temperature (−89 °C) ethane. Icing and bubbling were observed on the tank’s surface soon after it started operations. Condensation was also observed at the bottom of the 0.8-m-depth RC slab, which raised concerns about the structural condition of the concrete. This study provides details of the field and analytical investigations conducted to assess the structural condition of the foundation. Heat transfer finite element (FE) analyses were performed to examine the concrete sections subjected to low temperatures. It was found that the ethane leakage produced a low temperature on the top side of the concrete foundation of +9.7 °C. Overall, the temperatures calculated by the FE analyses were in good agreement with actual field measurements, within a ±5% accuracy. The simplified heat transfer equation for porous media used in this study was sufficiently accurate to model the effects of the ethane leakage in the concrete foundation, provided that the ambient temperature at the site is taken into account in the analysis. The results also confirm that reinforcing bars can be neglected in the thermal analysis of massive concrete slabs. The results from the field measurements and FE analyses confirmed that the structural integrity of the RC foundation was never compromised. The approaches, methods and techniques discussed in this article are deemed suitable to solve the practical and scientific challenges involved in the thermal assessment and repairs of large special structures. Accordingly, they can serve as useful reference and guidance for engineers and practitioners working in the field of forensic engineering., Walailak University research grant (contract no. WU 64252).

In this paper, the shear behavior of glass fiber reinforced polymer (GFRP) bars reinforced Ultra-High-Performance Concrete (UHPC) beams was investigated through experimental tests. Eight GFRP bars reinforced UHPC I-beams were tested until shear failure with various stirrup ratio, reinforcement ratio and shear span to depth ratio. The shear capacity, load-deflection relationship, cracking pattern and failure mode were investigated in detail. The results show that the shear span to depth ratio has the greatest influence on the shear capacity of the beam among the three parameters, followed by the stirrup ratio and reinforcement rate. The stirrup configuration can significantly improve the shear capacity and deformation resistance of the beam and can effectively reduce the stress concentration caused by the uneven distribution of steel fibers, which affects the failure mode of the beam. Increasing the stirrup ratio and reinforcement rate can improve the stiffness of the beam after cracking, and the larger the shear span to depth ratio is, the more significant the improvement effect is. Moreover, stirrup enable the full development of the tensile capacity of GFRP bars. The existing equations of shear strength from five design codes and 7 literatures are compared to the experimental results of 54 UHPC beams. It showed that the formula from the codes AFGC-2013 and JSCE-2006 codes are more accurate. The equations by Kwak, Jin and Thiemicke's provide best predictions.

We report on the reversible, electrochemical (de)fluorination of CsMnFeF6 at room temperature using a liquid electrolyte. CsMnFeF6 was synthesized via three methods (hydrothermal, ceramic, and mechanochemical), each of which yields products in a defect pyrochlore structure with varying particle sizes and phase purities. After three galvanostatic cycles, approximately one fluoride ion can be reversibly (de)inserted into mechanochemical CsMnFeF6 for multiple cycles. Ex situ X-ray absorption spectroscopy confirmed that both Mn2+ and Fe3+ are redox active. The cell impedance decreases after one cycle, suggesting that the formation of fluoride vacancies in early cycles generates mixed-valent Fe and enhances the material’s conductivity. Ex situ synchrotron diffraction revealed subtle expansion and contraction of the CsMnFeF6 cubic lattice on insertion and removal, respectively, during the first two cycles. New reflections intensify in the ex situ diffraction patterns from cycle 3, corresponding to a topotactic transformation of CsMnFeF6 from the pyrochlore structure into an orthorhombic polytype that continues cycling fluoride ions reversibly.\ud \ud