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This paper aims to develop a numerical model to investigate coupled conduction radiation heat transfer in a multilayer semi-transparent polymeric foam.

The model uses a multi-phase approach in which the radiative transfer is determined by solving the radiative transfer equation explicitly in the whole medium incorporating an interface condition valid in the geometric optics rgime. This is executed by using a combination of ray splitting and a discrete curved ray tracing technique. Both partial photon reflection and total internal reflection at the interface are considered in the present investigation.

The directional distribution of intensity within the whole medium can be determined, which is used to obtain the detailed temperature profile inside the domain. The performance of the proposed methodology has been tested by simulating the modelled foam at ambient conditions. The results obtained from the simulations are in good agreement with the published results and shows that there is a global non-linearity in the temperature profile in problems where conduction to radiation parameter is small.

Specular nature of radiative transfer at the interface is accounted for in the present analysis. Instead of working with direction integrated quantities (as in the case of P1 approximation), each bundle of rays is treated separately within the whole medium. This model serves as a starting point for a detailed spatially three dimensional study of heat transfer in foams and the mathematical nature of the formulation is such that it may result in an implementation to three-dimensions.

To illustrate the importance of nanometrology, the discipline of metrology at the nanoscale, and to describe the techniques involved.

This firstly highlights the importance of nanometrology and considers some future applications with particularly demanding metrological requirements. The main techniques used to characterise nanoscale devices are described. Research and the activities of certain national metrology institutes are discussed.

This illustrates that nanometrology is a critical discipline that will underpin the nanotechnology revolution. It shows that a range of techniques exist for characterising nanomaterials and devices, although most are costly and complex. It further shows that nanometrology developments are underway on a global scale.

This paper demonstrates the importance of nanometrology and describes in detail the techniques used.

Reports on developments at Optimet in the R&D Group, where a novel distance probe performs high accuracy distance measurement over broad length scales. Considers applications.

THIS very broad subject may be divided into two main sections:

From X‐ray studies of iron‐nickel‐aluminium alloys a new phase a′ was discovered. Although, in the surface layers of these alloys an unstable γ‐phase is observed in the early stage of annealing, this phase disappears entirely with prolonged annealing, the X‐ray pattern showing the co‐existence of the a‐ and a′‐phases. In the interiors of the specimens the unstable γ‐phase is never found, only diffused X‐ray interference lines being observed there. However, by very long annealing extending to 3,500 hours at 1,000 deg., the writer succeeded in observing a splitting phenomenon of the X‐ray pattern in the interiors of the specimens also.

The purpose of this paper is to consider the time-splitting Fourier spectral (TSFS) method to solve the fractional coupled Klein–Gordon–Schrödinger (K-G-S) equations. A time-splitting spectral approach is applied for discretizing the Schrödinger-like equation and along with that, a pseudospectral discretization has been accurately utilized for the temporal derivatives in the Klein–Gordon-like equation. Furthermore, the time-splitting scheme is proved to be unconditionally stable. Numerical experiments guarantee high accuracy of the TSFS scheme for the K-G-S equations. Here, the derivative of fractional order is taken in the Riesz sense.

The focus of this paper is to study the Riesz fractional coupled K-G-S equations using the TSFS method. This method is dependent on evaluating the solution to the given problem in small steps, and treating the nonlinear and linear steps separately. The nonlinear step is made in the time domain, while the linear step is made in the frequency domain, which necessitates the use of Fourier transform back and forth. It is a very effective, powerful and efficient method to solve the nonlinear differential equations, as in previous works (Bao et al., 2002; Bao and Yang, 2007; Muslu and Erbay, 2003; Borluk et al., 2007), the initial and boundary-value problem is decomposed into linear and nonlinear subproblems. Summarizing the technique of the TSFS method, it can be stated that first the Schrödinger-like equation is solved in two splitting steps. Then, the Klein–Gordon-like equation is solved by discretizing the spatial derivatives by means of the pseudospectral method.

The utilized method is found to be very efficient and accurate. Moreover, the time-splitting spectral scheme is found to be unconditionally stable. By means of thorough study, it is found that the spectral method is time-reversible, is gauge-invariant and also conserves the total charge. Moreover, the results have been graphically presented to exhibit the accuracy of the proposed methods. Apart from that, the numerical solutions have been also compared with the exact solutions. Numerical experiments establish that the proposed technique manifests high accuracy and efficiency.

To the authors’ best knowledge, the Riesz fractional coupled K-G-S equations have been for the first time solved by using the TSFS method.

Describes a generalized two‐cycle componentwise splitting method for solving three‐dimensional parabolic differential equations with variable coefficients which has been developed based on the idea of the regularized difference scheme. The method is simple, unconditionally stable and well suited for simulating fast transient phenomena and for computations on fine spatial meshes. A numerical procedure that employs the generalized two‐cycle componentwise splitting scheme was developed to solve three‐dimensional parabolic differential equations with variable coefficients on multilayers. In the procedure, the generalized “divide and conquer” method for solving tridiagonal linear systems is applied in order to overcome the problem with the unknown value at the interface between layers. Numerical results show that the procedure is accurate and efficient.

It has been reported in previous papers that X‐ray studies of the magnetic iron‐nickel‐aluminium ternary system resulted in the discovery of a new phase α', as well as a complete change both in the ternary equilibrium diagram and in the explanation of the cause of the high coercivity in this system.

The aim of this research is to study the role and formation of hydration products particularly crystalline portlandite Ca(OH)2 in MWCNT-reinforced concrete at 28 days. Concrete is the largest manufactured building material in world in which cement, sand aggregates and water cement ratio plays governing role. Water–Cement ratio decides it strength, usage, serviceability and durability. As strength of concrete depends on formation of crystalline hydrates; therefore, water–cement ratio can alter formation of hydrates also. Unfortunately, concrete is the most brittle material and to overcome brittleness of conventional concrete is tailored with some fibers. Till now, multiwalled carbon nano tubes are the most tensile and strongest materials discovered. Addition of multiwalled carbon nano tubes changes basic properties of conventional concrete. Therefore, it is important to evaluate formation of crystalline hydrates in multiwalled carbon nano tube–reinforced concrete by micro structure analysis.

Till now, multiwalled carbon nano tube–reinforced concrete has not been analyzed at micro structure level. To accomplish the objective, four concrete mixes with 0.45, 0.48, 0.50 and 0.55 water–cement ratio having 0.5 and 1% multiwalled carbon nano tubes incorporated by weight of cement, respectively. For hardening property analysis, compressive strength was obtained by crushing cubes; flexural strength was obtained by three-point loading; and split tensile strength was obtained by splitting cylindrical specimens. For analyzing role and formation of crystalline portlandite Ca(OH)2 hydrates, X-ray diffraction test was conducted on 75-µ dust of each mix. Scanning electron microscopy analysis was performed on fractured samples of crushed cubes of multiwalled carbon nano tube–reinforced concrete samples to check aggloremation.

It was observed multiwalled carbon nano tubes successfully enhanced compressive strength, flexural strength and split tensile strength by 8.89, 5.33 and 28.90%, respectively, in comparison to reference concrete at 0.45 water–cement ratio and 0.5% multiwalled carbon nano tubes by weight of cement. When its content was increased from 0.5 to 1% by weight of cement compressive strength, flexural strength and split tensile strength diminished by 2.04, 0.32 and 1.18%, respectively, at 0.45 water–cement ratio. With the increment of water–cement ratio, overall strength decreased in all mixes, but in multiwalled carbon nano tube–reinforced concrete mixes, strength was more than reference mixes. In reference, concrete at 0.45 water–cement ratio crystalline portlandite Ca(OH)2 crystals are of nano metre size, but in carbon nano tube–reinforced concrete mix having 0.45 water–cement ratio and 0.5% multiwalled carbon nano tubes by weight of cement, its size is much smaller than reference mix, thereby enhancing mechanical strength. In reference, concrete at 0.55 water–cement ratio size of crystalline portladite Ca(OH)2 crystals is large, but with incorporation of multiwalled carbon nano tubes, their size reduced, thereby enhancing mechanical strength of carbon nano tube–reinforced concrete having 0.55 water–cement ratio and 0.5 and 1% multiwalled carbon nano tubes by weight of cement, respectively. Also at 1% multiwalled carbon nano tubes by weight of cement, agglomeration and reduction in formation of crystalline portlandite Ca(OH)2 crystals were observed. Multiwalled carbon nano tubes effectively refine pores and restrict propagation of micro cracks and act as nucleation sites for Calcium-Silicate-Hydrate phase. Geometry of crystalline axis of fracture for portlandite Ca(OH)2 crystals is altered with incorporation of multiwalled carbon nano tubes. Crystalline portlandite Ca(OH)2 crystals and bridging effect of multiwalled carbon nano tubes is governing factor for enhancing strength of multiwalled carbon nano tube reinforced concrete.

Multiwalled carbon nano tube–reinforced concrete can be used to make strain sensing concrete.

Change in geometry and size of axis of fracture of crystalline portladite Ca(OH)2 crystals with incorporation of multiwalled carbon nano tubes.

Concrete, the second most used material in the world, surpassed only by water, relies on a vast amount of cement. The process of cement production emits substantial amounts of carbon dioxide (CO₂). Consequently, it is crucial to search for cement alternatives. Geopolymer concrete (GC) uses industrial by-product material instead of traditional cement, which not only reduces CO₂ emissions but also enhances concrete durability. On the other hand, the disposal of concrete waste in the landfills represents a significant environmental challenge, emphasising the urgent need for sustainable solutions. This study aimed to investigate waste concrete's best form and rate as the alternative aggregates in self-compacting and ambient-cured GC to preserve natural resources, reduce construction and demolition waste and decrease pertinent CO₂ emissions. The binding material employed in this research encompasses fly ash, slag, micro fly ash and anhydrous sodium metasilicate as an alkali activator. It also introduces the best treatment method to improve the recycled concrete aggregate (RCA) quality.

A total of25%, 50% and 100% of coarse aggregates are replaced with RCAs to cast self-compacting geopolymer concrete (SCGC) and assess the impact of RCA on the fresh, hardened and water absorption properties of the ambient-cured GC. Geopolymer slurry was used for coating RCAs and the authors examined the effect of one-day and seven-day cured coated RCA. The mechanical properties (compressive strength, splitting tensile strength and modulus of elasticity), rheological properties (slump flow, T500 and J-ring) and total water absorption of RCA-based SCGC were studied. The microstructural and chemical compositions of the concrete mixes were studied by the methods of energy dispersive X-Ray and scanning electron microscopy.

It is evident from the test observations that 100% replacement of natural aggregate with coated RCA using geopolymer slurry containing fly ash, slag, micro fly ash and anhydrous sodium metasilicate cured for one day before mixing enhances the concrete's quality and complies with the flowability requirements. Assessment is based on the fresh and hardened properties of the SCGC with various RCA contents and coating periods. The fresh properties of the mix with a seven-day curing time for coated RCA did not meet the requirements for self-compacting concrete, while this mix demonstrated better compressive strength (31.61 MPa) and modulus of elasticity (15.39 GPa) compared to 29.36 MPa and 9.8 GPa, respectively, for the mix with one-day cured coated RCA. However, incorporating one-day-cured coated RCA in SCGC demonstrated better splitting tensile strength (2.32 MPa) and water absorption (15.16%).

A potential limitation of this study on SCGC with coated RCAs is the focus on the short-term behaviour of this concrete. This limited time frame may not meet the long-term requirements for ensuring the sustained durability of the structures throughout their service life.

This paper highlights the treatment technique of coating RCA with geopolymer slurry for casting SCGC.