We present a theoretical framework to study the thermal responses of one-dimensional multilayered systems, functionally graded solid media, and porous materials. The method for thermal analysis ...resorts to non-Fourier heat conduction theories including three-phase-lag, dual-phase-lag, and hyperbolic heat conduction. The graded media are modeled as multilayered systems displaying finite numbers of layers. For each homogenous layer, the differential equations of heat conduction describing the wave-like three-phase-lag are solved in closed-form in the Laplace domain. Solutions accounting for proper interfacial and boundary conditions are first presented to describe the thermal behavior of heterogeneous solids and porous media. Transient temperature and heat flux are obtained in time domain via fast Laplace inversion. We then apply the solutions obtained with each heat conduction theory to one-dimensional media and compare their thermal behavior. Finally, maps are presented to visualize the thermal responses of cellular materials, functionally graded cellular materials, and multilayered systems. For the latter, particular attention is devoted to investigate the impact of key attributes defining graded media, such as layer bond imperfections and material heterogeneity.
Hierarchical cellular materials are ubiquitous in nature and lead to many extraordinary mechanical properties, such as ultralight, ultrastiff, and high toughness properties. Inspired by the ...biological materials, the purpose of this paper is to analyze three families, including cubic, octahedron, and hybrid, of 3D hierarchical lattice ferroelectric metamaterials and determine the relationship between architecture and effective thermo-electro-mechanical properties by proposing a multiscale asymptotic homogenization technique. The effect of hierarchical order, lattice topology and relative density on piezoelectric and pyroelectric figures of merit, measure for assessing the performance of ferroelectric metamaterials as sensors and energy harvesters, is explored. The 1st-order ferroelectric metamaterials remarkably improve the figures of merit compared to the fully-solid ferroelectrics; increasing hierarchical order can magnify these improvements. Hybrid hierarchical ferroelectric metamaterials show further improvement in ferroelectric properties, not achievable by fractal-like metamaterials. For example, compared to the 1st-order body centered cube (BCC) with a piezoelectric energy harvesting figure of merit (FOM33) of more than 50 times higher than the bulk ferroelectric materials, FOM33 of 2nd-order hybrid hierarchical octet truss/BCC can be 50.7% higher, this improvement is 43.8% and 43.2% for 2nd-order hierarchical fractal-like BCC and octet truss, respectively. Finally, scaling relationships for predicting the multiphysical behavior of ferroelectric metamaterials, covering the whole range of relative densities, are proposed. This study introduces bioinspired hierarchical ferroelectric metamaterials as a new class of lightweight multifunctional advanced materials with integrated mechanical, piezoelectric and pyroelectric properties for developing the next generation of hydrophones, pressure and temperature sensors, and energy harvesters.
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Solar pond has been a reliable supply of heat source for industrial process that requires heat at the temperature <100 °C. In this paper, the prospect of solar pond in generating electricity has been ...explored with the aid of using TEGs (thermoelectric generators) for converting the heat available at LCZ (lower convective zone) into electricity. By using the transient heat transfer model developed and the testing result of a thermoelectric module, this study has covered the potential of generating electricity for the solar pond operates in the climate of Group A, B, and C under Köppen climate classification. The effect of heat extraction, climatic variation, temperature polarisation, and the conversion efficiency of TEG on the thermal performance and electrical performance of the system has been discussed. The solar pond operates in Riyadh (Group B of Köppen climate classification) possesses the highest potential in generating electricity, which is about 4.834 kWh/year-m2 at heat extraction of 15% of year average horizontal solar radiation (i.e. solar pond yearly efficiency of 15%) while having average LCZ temperature of 80 °C throughout the year. Overall, the thermal-electrical conversion efficiency, ηt of this system is in the range of 1%–1.5% from the heat extracted.
•The electric power generation from solar pond using TEGs is analysed.•The numerical result is compared with a commissioned commercial 500 m2 solar pond.•The method presented has a high scalability for further analysis in the future.
The mechanical properties of nanowires are significantly affected by surface effects. In this work, we investigate the potential mechanisms of surface residual stress and surface layer stiffness on ...the bending behavior of nanowires. The deflection equation of nanowires under pure bending is first derived from the Young–Laplace equation and the Euler–Bernoulli beam theory. Subsequently, a new finite element model based on Galerkin’s weighted residual method is developed to verify the accuracy of the theoretical solution. The theoretical and numerical solutions present the significant effects of surface residual stress and surface layer stiffness on the elastic properties of nanowires depending on the feature size, boundary conditions, and sectional geometry of the nanowires. Specifically, the surface residual stress makes the simply-supported and fixed–fixed nanobeams stiffer; however, it makes the cantilever nanobeam softer. Besides, the sectional geometry of the nanowires has a noticeable impact on their transverse deflection. If the size of circumscribed circle of the cross section remains constant, the nanowires become harder as the numbers of sectional sides increase for the specific feature size and boundary conditions. If the cross-sectional area remains unchanged, the deflection of the nanowires fluctuates as the number of cross-sectional side increases. We realize that the overall Young’s modulus of nanowires is closely related to the feature size. As the cross-sectional feature size is below a critical value, the surface residual stress dominates the bending behavior of the nanowire. As the sectional feature size exceeds the critical feature size that is correlated to the nanowire boundary conditions, the factor dominating the bending behavior gradually transforms from the surface residual stress to the surface layer stiffness. This study provides a theoretical framework for developing a design strategy that incorporates surface effects in the engineering of nano/microscale architected advanced materials.
Neat and arginine modified montmorillonite, Mt and Mt-Arg, were embedded into polysulfone (PSf) to prepare adsorptive mixed matrix membranes (AMMMs) for arsenate removal from contaminated water. ...Prepared membranes were characterized by FE-SEM, XRD, AFM, pure water flux and contact angle measurement. Equilibrium adsorption capacity and adsorption kinetic of AMMMs were determined using batch adsorption experiments. In addition, dynamic adsorption and regeneration studies were also investigated in dead-end filtration setup. Adsorption kinetic of arsenate was found to follow pseudo-second-order kinetic model and equilibrium data showed good correlation with the Langmuir model for AMMMs. The obtained results revealed that the arsenate adsorption was favorable for PSf/Mt-Arg. Regeneration capability of the Mt-Arg embedded PSf membranes was assessed by conducting ten cycles of adsorption-desorption experiments. Arg modified Mt provides interesting properties to adsorb As(V) from water in neutral pH and desorb in alkaline condition; pH=9, due to negative side group. The obtained results confirmed the applicability of the prepared PSf/Mt-Arg in As(V) removal for multiple cycles.
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•Arginine modified Mt was incorporated into PSf to prepare adsorptive membranes.•Adsorptive membranes were used for As(V) removal from water.•PSf/Mt-Arg membrane showed higher adsorption capacity than PSf/Mt membrane.•Mt-Arg provides interesting properties to adsorb and desorb As(V).•PSf/Mt-Arg membrane was re-generable and easy for multiple applications.
Complex solid‐state hydrides can store hydrogen at very high volumetric and gravimetric densities. We present a theoretical framework, which automatically determines phase diagrams and ...thermodynamically favored hydrogen storage reactions in complex multicomponent systems, such as Li‐Mg‐N‐H (see figure). This method can be used to efficiently scan the phase space and pinpoint those compositions, which have the greatest potential for thermodynamically reversible H2 storage.
In recent years, many research works focused on improving and reducing the cost of solar collectors. This paper focuses upon the development of an efficient modeling and optimization of solar ...collector. The approach adopted in modeling utilizes a parabolic trough collector absorber tube with non-uniform heat flux, fully developed mixed convection flow and Al2O3/synthetic oil as a base fluid. Optimization of thermal analysis in a solar trough collector using nanofluid is non-convex, non-linear and computationally intensive process. In order to overcome these difficulties, a hybrid optimization method involving GA (genetic algorithm) and SQP (sequential quadratic programming) is introduced in the optimization process. The optimization problem used in this study involves maximization of a non-dimensional correlation consisting of Nusselt number and pressure drop with Reynolds and Richardson number which are used as design constraints. The methodology implemented within an integrated environment involving Matlab, Gambit and Fluent. The results obtained show that heat transfer enhancement has a direct relationship with the nanoparticle concentration ratio whereas it has inverse relationship with the operational temperature. In addition, the results show that the proposed methodology provides an effective way of solving thermal analysis in a solar parabolic trough collectors based on simulation models.
•The thermal behavior of synthetic oil/Al2O3 in a trough collector is simulated.•The thermal performance of the system is improved using hybrid GA-SQP algorithm.•The optimum values of diameter and velocity are 0.065 m and 0.31 m/s, respectively.•The results show 10% improvement in the assigned objective function.
TiN nanoparticle reinforced AlSi10Mg composite powder was produced by a novel ultrasonic vibration dispersion technique. The TiN/AlSi10Mg composites were fabricated via selective laser melting (SLM). ...The effects of scanning speed on the microstructure, particle distribution state, and tribological properties of the as-built composites were studied. Experimental results showed a better SLM processibility for the composite powder due to the considerable improvement of laser absorption capacity. The microstructure of as-built composite parts was remarkably refined with a gradually decreased average grain size from 0.388 μm to 0.284 μm by increasing scanning speed compared to that of AlSi10Mg part (∼ 0.579 μm). Nano-sized TiN particles were evenly distributed and well-bonded in the composite matrix while minimized agglomerated TiN particles gathered and grew into large spherical clusters. Because of the in-situ reaction occurred between TiN cluster and AlSi10Mg matrix, novel graded interfacial layers were observed. The mean layer thickness increased from 0.11 μm to 0.38 μm by decreasing the scanning speed from 600 mm/s to 200 mm/s. Taking advantage of the dispersion strengthening, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (145 ± 4.9 HV), and enhanced wear performance were achieved.
A simple approach is introduced to assess the toxicity of nitroaromatic compounds in terms of an oral LD
50
dose (50% lethal dose) for rats. Most of the presented Quantitative Structure-Activity ...Relationship (QSAR) models for prediction of in vivo toxicity of nitroaromatics are calculated by quantum computing descriptors which are more difficult to interpret and apply, while the new model requires only the molecular structure of a desirable nitroaromatic compound. The novel model is based on the constitutional descriptors, such as the number of oxygen, sulphur, phosphorous and molecular fragments. Experimental data of 90 nitroaromatics are used to derive and test the new model as the logarithm of LD
50
values, i.e. -log (LD
50
). Although it is based on only simple structural parameters, the reliability of the new model is also higher than the complex QSAR model because the values of the root-mean-square deviation (RMSD) of -log (LD
50
) for the new and the outputs of the latest QSAR method are 0.342 and 0.377, respectively.
•An assessment of salinity gradient stability of an industrial solar pond was performed.•Two methodologies based on the stratification principle were adapted and used.•The boundaries of the salinity ...gradient appeared as the main source of instability.•The methodology based on coefficients of expansion is useful to control the solar pond.
In this study, an assessment of salinity gradient stability of an industrial solar pond during two operation seasons (2014 and 2105) is presented. An industrial solar pond was constructed to supply a low-temperature heat (up to 60 °C) to achieve the temperature requirements of the flotation stage in a mineral processing plant (Solvay Minerales in Granada (Spain)). Along the first season, the salinity gradient was considered technically destroyed in April 2015 as the height to the upper convective zone increases from 0.3 m in July 2014 to 0.8 m. Two different methodologies based on the stratification principle were adapted and used in order to evaluate the salinity gradient stability. The boundaries of the salinity gradient appeared as the main source of instability. In the upper zone it is associated with the environmental parameters (e.g., rain and wind) that affect the upper convective zone and the upper layers of the non-convective zone that subsequently transmit the instability to the lower layers. In the bottom zone it is caused by operation parameters, such as the heat extraction or the addition of salt. Both methodologies provided similar predictive capability of stability results. However, the results provided by the stability analysis using the thermal and salinity expansion coefficients are a more useful tool in the control of the salinity gradient for solar pond technology.
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