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In this study, polyurethane thermoplastic elastomers (TPU) were synthesized using isophorone diisocyanate (IPDI), 1,4-butanediol (BDO), and 1,6-hexanediol (HDO) as the chain extenders, and polycaprolactone diol (PCL-diol) with three different molecular weights (2000, 4000, and 10,000 g/mol) as polyols. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) patterns, and differential scanning calorimetry (DSC) were conducted to analyze the chemical microstructure and phase morphology of the prepared samples. The results showed that the change in the chain extender's type (BDO and HDO) leads to a decrease in the hydrogen bonding index (HBI). Increasing the molecular weight of PCL-diol in BDO-based TPUs has led to an increase in their crystallinity, Young's modulus, melting temperature, tensile strength, and a decrease in glass transition temperature and elongation at break. Moreover, the increase in the molecular weight of PCL-diol in HDO-based TPUs demonstrated an increase in the crystallinity and elongation at break and tensile strength up to the molecular weight 4000 in PCL-diol, after that, there was a decrease in those properties due to the increase of the soft segments content and change in the chain extender type. Permeability on TPU membranes was performed for N2 and CO2 at three different pressures 3, 6, and 9 atm at room temperature. An increase in pressure led to an increase in membrane permeability due to the increase in gas solubility in TPU based on Henry's law. The permeability of CO2 is higher than N2 due to the proper interactions of CO2 gas with the polar carbonyl groups of polyurethane. It is observed that the permeability increases in BDO-based samples with an increase in the molecular weight of PCL-diol, while the increase in permeability of HDO-based TPU is up to PCL-diol molecular weight 4000 and after that is decreased. The selectivity of CO2 has decreased with increasing pressure due to the higher rate of dissolution of N2 at higher pressures. [ABSTRACT FROM AUTHOR]

This research investigated the synthesis of thermoplastic polyurethane (TPU) with a hard segment content (HSC) of 30% weight. The chain extender, the polyols, and the diisocyanate utilized 1,4-butanediol (BDO), and the polycaprolactone diol (PCL-diol) with molecular weights of 2000, 4000, and 10,000 and isophorone diisocyanate (IPDI), respectively. Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H-NMR), and X-ray diffraction (XRD) were used to examine the chemical microstructure and physical properties of PCL diol and thermoplastic polyurethanes (TPUs). The molecular weight of the PCL diol as soft segments affected the crystallinity and glass transition temperature (Tg) of TPUs. An increase in PCL diol molecular weight resulted in a reduction in elongation at failure and an increase in ultimate tensile strength. This study was conducted to investigate the permeability and the permselectivity of CO2 and N2 gases over pressure ranges (3 to 9 atm). It was determined that the gas permeability of each sample increased in response to an increase in the pressure of the supplying gas. An elevation in the molecular weight of PCL-diols in TPU samples resulted in a reduction in selectivity and an increase in CO2 and N2 gas permeability. Although IPDI is a non-aromatic cyclic diisocyanate with a significant impact on thermoplastic polyurethane phase morphology, the goal of this paper is to create a change in the molecular weight of PCL-diol and investigate the effect of molecular weight on the resulting morphology as well. [ABSTRACT FROM AUTHOR]

We present a spacetime DG method for 1D spatial domains and three linear hyperbolic, damped hyperbolic, and parabolic PDEs. The latter two correspond to Maxwell-Cattaneo-Vernotte (MCV) and Fourier heat conduction problems. The method is called the tent-pitcher spacetime DG method (tpSDG) due to its resemblance to the causal spacetime DG method (cSDG) wherein the solution advances in time by pitching spacetime patches. The tpSDG method extends the applicability of such methods from hyperbolic to parabolic and hyperbolic PDEs. For problems with a spatially uniform mesh, a transfer matrix approach is derived wherein the inflow, boundary, and source term values are mapped to the solution coefficient and output values. This resembles a finite difference scheme, but with grid points at the Gauss points of the spatial elements and arbitrarily tunable order of accuracy in spacetime. The spectral stability analysis of the method provides stability correction factors for the parabolic case. Numerical examples demonstrate the applicability of the method to problems with heterogeneous material properties. • Extended spacetime tent-pitcher methods from hyperbolic to hyperbolic-parabolic PDEs. • Transfer matrices relate inflow and outflow solutions of a patch at the Gauss points. • Polynomial order-independent stability limit of tent-pitcher method is shown for wave equation. • The stability limit for parabolic heat conduction is obtained using the transfer matrices. • The transfer matrix method advances the solution of 1D uniform grids with tunable order. [ABSTRACT FROM AUTHOR]

The radiative transfer equation (RTE) is an integro-differential equation that describes the radiation energy absorbing, emitting, and scattering in both space and angle, which can be up to five-dimensional problems. It is difficult for a RTE solver to satisfy both accuracy and efficiency (less computational resources) for such high dimensional problems. In this paper, an iterative solver for one-dimensional cylindrical radiative transfer problems using the space-angle discontinuous Galerkin (DG) method is developed to achieve both accuracy and efficiency. The iterative solver is based on the angular decomposition (AD) scheme, which slices the spatial-angular domain into slabs and decouples the angular integration between slabs. Both Jacobi and successive over-relaxation (SOR) iterative schemes are investigated by numerical analysis and examples. The comparison of the two iterative schemes suggests that an appropriate relaxation factor for the SOR method may accelerate the convergence. Finally, the iterative scheme is more efficient than the direct solution of the system both in terms of memory usage and computational time, especially for finer meshes. [ABSTRACT FROM AUTHOR]

This article presents the application of cubic Statistical Volume Elements (SVEs) to homogenize the elasticity tensor of epoxy matrix chopped glass fiber composites using displacement boundary conditions. A virtual microstructure reconstruction algorithm is used to reconstruct three large domains of the composites with different fiber orientation distributions. A non-iterative parallel meshing algorithm, named CISAMR, is then implemented to generate high-fidelity finite element models and simulate the linear elastic response of 1536 SVEs extracted from these domains. While the fiber orientations imply transversely isotropic elasticity stiffness matrices, for the SVE sizes considered, the composite is not quite transversely isotropic. We propose two indices of transverse isotropy to (1) determine the orientation at which a given property most closely matches the transversely isotropic assumption for an SVE, (2) quantify the corresponding transversely isotropic discrepancy, and (3) state the extent of transverse isotropy by measuring the difference between transverse and average normal quantities. The former can be applied to any orientation-dependent quantity such as strength, whereas the latter only applies to the elasticity tensor. We demonstrate the superiority of the latter for elastic properties and use the former to show that a proposed initiation fracture strength is farther away from its transversely isotropic limit compared to the directional elasticity normal stiffness. • A virtual reconstruction algorithm is used to synthesize realistic composite microstructures. • Thousands of statistical volume elements (SVEs) are extracted from each composite model. • An automated meshing algorithm is employed to generate finite element models of SVEs. • Two indices are introduced to quantify the transverse isotropy of the elastic tensor. • A statistical analysis shows the superiority of these indices in quantifying the SVE properties. [ABSTRACT FROM AUTHOR]

• The parameter retrieval method is used to derive constitutive parameters of periodic structures. • The continuity of wave vector versus frequency in lossless systems is not guaranteed. • Loss is introduced to unambiguously determine stable solution branches of lossless structures. • The two loss models of nonzero damping and complex stiffness modulus are proposed. • The effectiveness of the loss models in time and frequency domain methods are compared. The parameter retrieval method based on scattering data is used to derive dynamic constitutive parameters of solids with periodic structure. There are inherent ambiguities in the real part of the retrieved wavenumber and the sign of impedance, though the latter has a one-to-one correspondence with the direction of energy flux. Moreover, for lossless structures there can be multiple solution branches that satisfy passivity and continuity of the wavenumber as a function of frequency, leading to potentially double positive or double negative (in terms of density and modulus) overall descriptions of the micro-structured medium. The continuity of wavenumber for lossy unit cells is used to unambiguously determine their constitutive parameters and by taking the limit when loss approaches zero, one can determine the stable solution branches of lossless micro-structures. The two loss models of nonzero damping and complex modulus are compared in terms of their energy loss characteristics and retrieved parameters. These models are employed in both time and frequency domain calculations. The lossy solutions demonstrate that from double-negative and double-positive solutions, only the latter is the stable solution branch in a pass-band of a lossless 1D unit cell. A 2D photonic crystal example is used to demonstrate that the wavenumber appears to jump, discontinuously, at the transition point between two consecutive stop-bands, hence rendering the existing methods based on continuity of wavenumber ineffective. In contrast, the proposed approach based on taking limit of lossy solutions can successfully be used to determine stable overall properties of such media. Finally, certain features of half- and full-cycle stop-bands are discussed. [ABSTRACT FROM AUTHOR]

Emissions from biodiesel combustion depend on types of feedstocks. This study investigated physicochemical properties of biodiesels in three various feedstocks generations and the effect of them on emissions and performance of the unmodified engine. Methyl esters from Eruca sativa (ES) which has crops with short production cycle and drought-tolerant capacity, waste cooking oil (WCO) as an economic feedstock, and microalgae Chlorella vulgaris (MCV) which have high growth rate and productivity without farmland requirement, were produced by transesterification process with methanol and KOH catalyst. Physicochemical properties of these biodiesels were determined by GC-MS and FTIR analysis and evaluated with ASTM D6751 standard. FAME components profile illustrated the high value of oleic acid (C18:1) in ES and WCO and long-chain fatty acids (C18:2 and higher) in MCV. The engine tests results indicated that MCV biodiesel produced slightly lower power and higher BSFC compared with others. There was a slight increase in NOx for MCV biodiesel compared with pure diesel. Conversely, ES and WCO biodiesels had a reduction in NOx. On the other hand, MCV biodiesel resulted in the greatest reduction in CO and HC emissions. Based on the results, MCV blends had the lowest emissions and the best function among all feedstocks. • Comprehensive comparative analysis for considering three biodiesel generations. • Microalgae methyl ester contains the longest chain fatty acids among other feedstocks. • ES biodiesel had maximum calorific value and engine performance output. • MCV biodiesel resulted in the greatest reduction in HC, CO, and CO 2 emissions. • Contrary to ES and WCO, NOx emissions in MCV biodiesel were higher than pure diesel. [ABSTRACT FROM AUTHOR]

A bulk damage formulation is presented for failure analysis of brittle materials under dynamic loading. A time-delay ordinary differential equation (ODE) is used to model damage evolution. The evolution is driven by the difference between a target static damage value and the instantaneous damage value. A damage length scale is introduced from the model's intrinsic relaxation time and elastic wave speeds. This length scale addresses the mesh sensitivity problem of some existing damage formulations for dynamic fracture, with less computational effort than some other existing remedies. The authors use the asynchronous spacetime discontinuous Galerkin (aSDG) method for the solution of the resulting hyperbolic system of equations. Local and asynchronous solution process, linear complexity of the solution versus the number of elements, local recovery of balance properties, and high spatial and temporal orders of accuracy are some of the main advantages of the aSDG method. Several numerical examples are presented to demonstrate mesh insensitivity of the method and the effect of boundary conditions on dynamic fracture patterns. [ABSTRACT FROM AUTHOR]

Abstract We propose an interfacial contact and fracture model based on Riemann solutions. Instead of penalty method and Lagrange multiplier approach we propose a regularization scheme—based on the interface displacement and separation velocity jumps—that smoothens contact-separation mode transitions. An aperture-based regularization approach smoothens the transfer of hydraulic load to in-situ cracks. A discontinuous Galerkin implementation is used to solve dynamic fracture problems for uniaxial compression and explosive examples. Moreover, we investigate contact–separation mode transitions and hydraulic load transfer in several hydraulic refracture problems and study the effect of loading rate and in-situ cracks in the number and orientation of activated perforations. [ABSTRACT FROM AUTHOR]

• Space-Angle Discontinuous Galerkin Method. • Specular Diffusive Boundary Conditions. • Two-Dimensional Radiative Transfer Equation. • Iterative Solver and Convergence Rate. A space-angle discontinuous Galerkin (saDG) method for solving radiative transfer problems in arbitrary 2D domains is proposed. The space-angle domain is fully discretized by the DG formulation. The angular decomposition scheme is adopted to help accelerate the process by solving the radiative transfer equation iteratively. The performance of the method is analyzed in the square geometry with different types of boundary conditions. We found that the number of iteration or convergence rate of the iteration for the specular reflection problems is not only effected by the number of the reflective surfaces in the domain, but also by the scattering and extinction properties of the media. the uniformly and directionally diffuse reflective boundary conditions are compared in the same medium. In addition, the approach is applied to the simulation of radiative transfer in a parabolic reflector to obtain the localization at the focal point. [ABSTRACT FROM AUTHOR]

Summary: The interaction of an advancing hydraulically loaded crack and in situ fracture network can yield highly complex patterns. We model the connectivity of cells in a finite element domain and in a fracture network by a simplicial complex data structure. The complete adjacency information between cells is determined by one level down facet and one level up cofacet neighborhood information. Combined with a disjoint set data structure, explicit algorithms are derived to efficiently track network connectivity and load transfer between independent fracture sets. We also propose an approach to regularize the application of hydraulic load to newly intersected in situ cracks to smoothen the transition of pressure on intersected cracks from ambient to hydraulic pressure and to avoid the sudden loading of the entire length of these cracks. Numerical results demonstrate the performance of crack connectivity and load transfer models and the effect of regularization model. The results show that as the angle between an incoming hydraulically loaded crack and an in situ crack increases, the effect of in situ crack shifts from slight realignment to diversion/offsetting of the loaded crack. As the angle difference approaches the normal angle, the loaded crack tends to penetrate through the in situ crack. The proposed schemes are also used for transient simulation of 2D reservoirs with multiple perforations surrounded by in situ cracks with and without a bias in the distribution of their orientation. It was shown that from 2 perforations with angles closer to in situ cracks at low loading rates to all perforations at higher loading rates can result in active hydraulic crack propagation. The h‐adaptive method of asynchronous space‐time discontinuous Galerkin method is used to exactly track complex fracture patterns in these dynamic fracture simulations. [ABSTRACT FROM AUTHOR]

We present an asynchronous spacetime discontinuous Galerkin (aSDG) method for time domain electromagnetics in which space and time are directly discretized. By using differential forms we express Maxwell's equations and consequently their discontinuous Galerkin discretization for arbitrary domains in spacetime. The elements are discretized with electric and magnetic basis functions that are discontinuous across all inter-element boundaries and can have arbitrary high and per element spacetime orders. When restricted to unstructured grids that satisfy a specific causality constraint, the method has a local and asynchronous solution procedure with linear solution complexity in terms of the number of elements. We numerically investigate the convergence properties of the method for 1D to 3D uniform grids for energy dissipation, an error relative to the exact solution, and von Neumann dissipation and dispersion errors. Two dimensional simulations demonstrate the effectiveness of the method in resolving sharp wave fronts. [ABSTRACT FROM AUTHOR]

We propose an asynchronous spacetime discontinuous Galerkin (aSDG) method combined with a novel rate-dependent interfacial damage model as a means to simulate crack nucleation and propagation in quasi-brittle materials. Damage acts in the new model to smoothly transition the aSDG jump conditions on fracture surfaces between Riemann solutions for bonded and debonded conditions. We use the aSDG method's powerful adaptive meshing capabilities to ensure solution accuracy without resorting to crack-tip enrichment functions and extend those capabilities to support fracture nucleation, extension and intersection. Precise alignment of inter-element boundaries with flaw orientations and crack-propagation directions ensures mesh-independent crack-path predictions. We demonstrate these capabilities in a study of crack-path convergence as adaptive error tolerances tend to zero. The fracture response of quasi-brittle materials is highly sensitive to the presence and properties of microstructural defects. We propose two approaches to model these inhomogeneities. In the first, we represent defects explicitly as crack-like features in the analysis domain's geometry with random distributions of size, location, and orientation. In the second, we model microscopic flaws implicitly, with probabilistic distributions of strength and orientation, to drive nucleation of macroscopic fractures. Crack-path oscillation, microcracking, and crack branching make numerical simulation of dynamic fracture particularly challenging. We present numerical examples that explore the influence of model parameters and inhomogeneities on fracture patterns and the aSDG model's ability to capture complex fracture patterns and interactions. [ABSTRACT FROM AUTHOR]

Phononic crystals can be designed to show band gaps—ranges of frequencies whose propagation is strongly attenuated in the material. In essence, their working principle is based on destructive interference of waves reflecting from the periodic arrangement of material interfaces (i.e. , Bragg scattering). Consequently, capturing accurately the behavior at material interfaces requires appropriate numerical modeling and computational design techniques. However, the commonly used density-based representation in popular topology optimization methods results in a diffuse staircased boundary. The heavily refined finite element meshes required to compensate for this boundary description results in exceedingly large and expensive optimization problems. In this paper, we demonstrate the adverse effect of the density-based boundary description. Furthermore, we propose a level set-based topology optimization procedure with an enriched finite element method that shows improved performance when compared to the density-based approach. • Topology optimization of phononic crystal with crisp boundaries is attained. • Efficient computation of design sensitivities allows for gradient-based optimization. • Using less degrees of freedom, band gaps are computed accurately during optimization. [ABSTRACT FROM AUTHOR]

• Use mesoscale elements to statistically characterize elastic and fracture behavior. • Establish convergence metrics appropriate to define isotropic and heterogeneous limits. • Compare representative volume sizes with respect to heterogeneity and anisotropy. • Develop methods to decrease inaccuracy introduced by mesoscale partitioning scheme. • Relate volume element homogenization to stochastic partial differential equations. In this paper, a method is presented to describe the statistical behavior of mesoscale material property fields, which are useful in macroscopic fracture simulation. The use of representative volume element-based properties can result in unsatisfactory fracture patterns because this approach eliminates random variations. In contrast, statistical volume elements can approximate random and inhomogeneous material properties. We compare two material property convergence metrics based on 1) vanishing variations of a property and 2) the convergence of property mean value versus volume element size. We examine the trends with which the properties of a two-phase composite tend toward homogeneous and isotropic limits. Compared to fracture properties, elastic properties reach their homogeneous and isotropic limit at smaller sizes. Accordingly, a volume element size can be chosen such that only the apparent fracture strength remains random and inhomogeneous. This reduces the computational cost and has proven useful in capturing realistic fracture results. In addition, the geometry of the mesoscale partitioning scheme has an important effect on homogenized properties. The intersection of straight edges with inclusions results in nonphysical size effects, increases anisotropy of properties, and results in 30 to 60 times larger representative volume elements compared to a partitioning scheme based on Voronoi homogenization. [ABSTRACT FROM AUTHOR]

We use square Statistical Volume Elements (SVEs) to homogenize elastic and fracture properties of a carbon-nanofiber reinforced polymer. The effect of SVE size and boundary condition (BC) on homogenized properties is investigated. Three different criteria are proposed for the convergence of properties and reaching the Representative Volume Element (RVE) limit: (1) Variation-based criterion examines the trend at which the variation of a property decreases versus SVE size; (2) Mean-based criterion examines the rate at which the SVE-mean of property converges to its terminal value; (3) BC-based criterion examines whether the homogenized properties can be independent of the choice of BC. These criteria show that the geometric property of fiber volume fraction/mass density converges to its homogeneous limit first followed by the elasticity tensor. Fracture strengths have the most complex response as they remain highly inhomogeneous, random, anisotropic, and size-dependent for the SVE sizes considered. This is further discussed in the context of stochastic multiscale material modeling and well-known size effect models for fracture strength. Furthermore, the square shape of the SVE is shown to induce nonphysical bias angles wherein elastic and fracture properties often take their maximum or minimum values at integer multiples of 45 degrees. The traction BC is shown to be superior to displacement BC by having a weaker form of this anisotropy and higher strength values. Moreover, for the anisotropic domain anisotropy indices converge from below and above for traction and displacement BCs, respectively; thus resembling Reuss and Voigt hierarchy of bounds for elastic properties. • Derive elastic and fracture properties using Statistical Volume Elements (SVEs). • Compare the angular bias in homogenized properties for displacement and traction BCs. • Determine the Representative Volume Element (RVE) size from three perspectives. • Discuss inhomogeneity/randomness, anisotropy, and size-dependency of properties. • Relate the use of SVE-homogenized properties for stochastic differential equations. [ABSTRACT FROM AUTHOR]

Mentha longifolia L., commonly known as wild mint, belongs to family Lamiaceae. The aim of this study was to identify the chemical composition of essential oil extracted from four ecotypes of Mentha longifolia L. grown wild (Shahreza, Chadegan, Isfahan, and Falavarjan) in Isfahan province (Central Iran). The essential oil was extracted by a Clevenger approach and analyzed using GC/MS. In the aerial parts of the plant were identified 26, 30, 22 and 25 compounds for Shahreza, Chadegan, Isfahan and Falavarjan ecotypes, respectively. The major constituents of the essential oil from the aerial parts of M. longifolia in Shahreza province were piperitenone oxide (26.71%), 1,8-cineole (20.72%), α-pinene (14.28%), pulegone (7.81%), sabinene (7.06%) and transcaryophyllene (4.23%). The main compositions in Chadegan province were piperitenone oxide (29.13%), 1,8-cineole (28.84%), sabinene (9.05%), pulegone (8.97%) and α-pinene (6.31%). The main compositions in Isfahan province were pulegone (44.75%), 1,8-cineole (13.82%), 2-cyclohexen-1-ol, 1-methyl (8.49%), isopulegone (8.07%) and menthone (4.37%). In Falavarjan province the constituents were pulegone (33.39%), 1,8-cineole (29.79%), sabinene (11.23%) and isopulegone (7.28%). [ABSTRACT FROM AUTHOR]

Abstract: We derive Riemann solutions for stick, slip and separation contact modes in a linear elastic material with an isotropic Coulomb friction relation and explore their numerical implementation. The Riemann solutions preserve the characteristic structure of the underlying elastodynamic system and imply dynamic contact conditions that are distinct from the quasi-static conditions used in some numerical models. Nonphysical discontinuities in the standard Coulomb model at stick–slip transitions can cause contact-mode chatter in numerical simulations. We restate the Coulomb relation to remove these artificial discontinuities and eliminate the need for algorithmic remedies. Discontinuous response at abrupt separation-to-contact transitions is physically reasonable, and we propose a regularization scheme to address this case. We implement the Riemann contact solutions within an adaptive spacetime discontinuous Galerkin (SDG) code and report numerical results that demonstrate the model’s efficacy. [Copyright &y& Elsevier]

A space-angle discontinuous Galerkin (saDG) method is used to solve the steady-state radiative transfer equation (RTE) for 2D problems involving absorption, emission, and scattering for a semitransparent medium. This approach discretizes both spatial and angular domains. Parallel computing is based on angular decomposition (AD), and domain decomposition (DD) techniques. The DD technique directly solves the entire domain using the MUMPS library, whereas the AD technique results in an iterative approach for scattering media. This study proposes a novel hybrid AD-DD method, combining the best aspects of both techniques. Numerical results investigate the scalability, performance, and efficiency of AD and DD techniques. It is shown that a hybrid AD-DD technique is superior to these individual techniques by taking advantage of their strengths. Numerical methods demonstrate the applicability of the method of the best combination of hybrid AD-DD to 2D scattering gray media with complex geometries or enclosures with circular and square obstacles. • RTE fully discretizes both spatial and angular domains. • Proposed a parallel implementations of a saDG formulation for AD and DD. • Developed an innovative hybrid AD-DD technique. • Investigated the strong scaling performance for AD, DD and hybrid AD-DD. • The hybrid technique is more efficient than the individual technique. [ABSTRACT FROM AUTHOR]

Aims: Anticonvulsants are increasingly being advocated for the treatment of acute alcohol withdrawal syndrome (AWS) to avoid the addictive properties of established medications. Because earlier works showed that moderate gabapentin doses were too low to clearly ameliorate severe AWS, we tested a higher gabapentin entry dose. Methods: Inpatients (n = 37) with severe alcohol withdrawal symptoms (Clinical Institute Withdrawal Assessment for Alcohol revised (CIWA-AR) score ≥15 points) were given gabapentin 800 mg, and if their symptom score reduced within 2 h, they were termed ‘early responders’ and were then treated for 2 days with 600 mg gabapentin q.i.d. (i.e. a total of 3200 mg in the first 24 h) before beginning a taper. Results: Twenty-seven (73%) were early responders (baseline CIWA-AR improved from 17.3 ± 2.6 to 8.0 ± 3.6 points). In the remaining 10 patients, baseline CIWA-AR deteriorated within 2 h (from 20.1 ± 4.6 to 21.5 ± 4.65 points). These patients were switched to clomethiazole (n = 4) or clonazepam (n = 6), which is the usual treatment. Three of the ‘early responders’ worsened in the next 36 h and were then reclassified and treated as ‘non-responders’. Among them, two developed an epileptic seizure. Conclusion: Oral 800 mg gabapentin (loaded up to 3200 mg in the first 24 h) is helpful only in reducing less severe and less complicated acute AWS. [ABSTRACT FROM PUBLISHER]

• Discontinuous Galerkin Method (DGM) for solving radiative transfer equation (RTE). • DGM employed in both space and angles is superior to hybrid methods. • Convergence in polynomial order and mesh refinement is established. • Comparison with benchmark results shows good agreement. • Numerical examples show how DGM captures discontinuous solutions. The integro-differential radiative transfer equation (RTE) for concentric cylinders problem involving scattering, absorption and emission is solved using the discontinuous Galerkin (DG) finite element method (FEM). The space-angle DG method directly solves the cylindrically-symmetric RTE as a three-dimensional problem, where a 1D spatially domain in radial distance r is twice extruded in the cosine of polar angle (μ) and the difference in azimuthal angle (φ ˜) directions. Thus, the method has a higher accuracy than hybrid FEM-Discrete Ordinate (S N) and FEM-Spherical Harmonic (P N) methods. This is reflected by numerically verified convergence rate of p + 1 for smooth problems and space-angle polynomial interpolation order of p. The axisymmetric RTE formulation is more complicated than the plane-parallel formulation, for having two independent angle directions (μ and φ ˜) and an extra derivative term with respect to φ ˜ in the differential equation. This results in a complex characteristic structure in r − φ ˜ plane with strong discontinuity lines in radiation intensity I. A method of characteristics is formulated and implemented to verify the DG formulation and demonstrate its accuracy when such strong discontinuities persist in the solution, specifically when there are no scattering and absorption terms. The relaxation of inter-element continuity constraint of continuous FEMs by this DG method implies its superiority in numerically capturing such discontinuities. Finally, a benchmark problem pertained to heat radiation in a gray gas and another one with nonzero phase function demonstrate the effectiveness of the method in modeling black-body and scattering angular integration terms. [ABSTRACT FROM AUTHOR]

• Homogenized a mesoscopic fracture strength field using Statistical Volume Elements (SVEs). • Used Yuen-Long marble sample micocrack statistics for homogenization. • Studied the effect of the distribution shape of microcracks by using various Weibull models. • Studies the effect of the size of SVE and crack density on the homogenized strength field. • Microcrack distributions with narrower variation result in a stronger, tougher, and more brittle rock. To capture the randomness and inhomogeneity of rock at microscale, a statistical volume element (SVE) averaging approach is proposed. The microcrack statistics of a real-world Yuen-Long marble sample is used to realize 2D microcracked domains. The size effect, i. e. the decrease of the mean and variation of homogenized strength field by increasing SVE size, is analyzed. Increasing the crack density is shown to have a similar effect. While smaller SVEs maintain a greater level of inhomogeneity and are preferred for fracture analysis, it is shown that low density of microcracks pose a lower limit on the SVE size. Beside the actual power-law distribution of microcrack length, by varying the Weibull model shape parameter m other domains are created with different microcrack distribution shapes. Macroscopic fracture simulations, by the asynchronous Spacetime Discontinuous Galerkin (aSDG) method, study the effect of m for a uniaxial tensile problem. By increasing m from 0.5 to 4, the length distribution of microcracks become more uniform; this corresponds to a more uniform and stronger mesoscopic strength field, which results to about 3 and 6 times increase to macroscopic tensile strength and toughness, respectively. However, the more uniform length distribution of microcracks is shown to reduce rock brittleness. [ABSTRACT FROM AUTHOR]

Ayran is a traditional fermented dairy drink that is manufactured by mixing yoghurt with water. In this research, the development of phytosterol‐enriched probiotic Ayran, the efficacy of various concentrations of phytosterol (0, 0.5 and 1 mg/L) and inoculation type (free or encapsulated) were investigated. The viability of Lactobacillus casei L26 and physicochemical indices of samples during storage time was studied. Samples with encapsulated probiotics showed lower serum separation due to the hydration of encapsulated agents. Sensory scores revealed that phytosterols are suitable for the enrichment of the probiotic Ayran. Moreover, phytosterol showed no significant changes in pH, acidity and viscosity during storage. [ABSTRACT FROM AUTHOR]

• MCV biodiesel is promising alternative fuel for diesel engine without any modification. • MCV biodiesel had lower calorific value than diesel and decreased engine performance. • Hydrogen addition improved engine torque, power output and BSFC. • Hydrogen enrichment to MCV biodiesel decreased carbon based emissions. • NOx emissions for hydrogen addition to MCV biodiesel were increased. Microalgae have been mentioned as a favorable feedstock for biodiesel production. In this experimental study, the feasibility of using microalgae Chlorella vulgaris (MCV) biodiesel as an alternative fuel and the effects of various flow rates of hydrogen addition on engine performance and exhaust emissions were investigated. After biodiesel production via transesterification reaction, physical properties of MCV methyl ester were evaluated with regular diesel and ASTM standard. The blends of biodiesel-diesel fuel and hydrogen in the intake air (between 0 and 10 LPM) were injected in a diesel engine under full load operating condition and various speeds. The results revealed that using MCV biodiesel had led to lower emissions of CO, HC, and CO 2 and has reduced the engine power and torque, whereas there was a minor increase in NOx emissions. By hydrogen enrichment, CO, CO 2 , and HC emissions decreased more, compared with the emissions of pure diesel, while NOx emissions kept an increasing trend. When the B20 blend of MCV methyl ester was enriched by 10 LPM hydrogen gas, power and torque of the engine, as well as brake specific fuel consumption (BSFC), were improved by 7.6%, 10.6%, and 6.6%, respectively. The experimental results showed considerable capabilities of applied MVC methyl ester under hydrogen enrichment in diesel engines in diminishing the pollution with comparable performance. [ABSTRACT FROM AUTHOR]

Statistical Volume Elements (SVEs) are employed to evaluate homogenized mesoscopic ductile failure response of a carbon nanofiber reinforced composite under uniaxial tensile and compressive loadings. In the mesoscale analysis, after virtual reconstruction of the material microstructure, 2D finite element models are generated for each SVE using a non-iterative meshing algorithm named CISAMR, which fully automates the modeling process. The ductile damage response of each SVE is then simulated to derive its homogenized stress-strain curve. Corresponding initiation, maximum, and failure turning points, together with local fiber volume fraction and homogenized bulk modulus, are defined as mesoscopic Quantities of Interest (QoIs). While compressive loadings have slightly higher strength and nearly twice higher strains at failure compared to similar tensile cases, both loadings yield similar coefficients of variance for most QoIs. Further, a stochastic bulk damage model is calibrated from mesoscopic responses, which takes bilinear and linear forms versus strain for tensile and compressive loadings, respectively. Finally, cross-correlations are made between different QoIs, showing lower strain-based QoIs and higher strengths correspond to either higher local fiber volume fractions or more fibers being aligned with the loading direction. [ABSTRACT FROM AUTHOR]

In predicting failure of a material, small scale material properties are critical, and yet small scale random heterogeneities are difficult to characterize accurately and efficiently. In building fracture models, work has focused on statistical characterization of local random microstructure at small to intermediate scales (termed micro- or mesoscale). Many materials can be characterized as effectively isotropic and homogeneous at a large scale. In contrast, at a micro- or mesoscale, Statistical Volume Elements (SVE) often show significant anisotropy and heterogeneity. Characterizing the properties of SVE presents challenges because modeling choices, such as the length scale, boundary conditions applied, and boundary shape chosen, may introduce modeling bias. Modeling bias must be separated from the actual prediction of anisotropic and heterogeneous characteristics at the SVE level, in order to provide an accurate basis for fracture simulation. Much literature has been devoted to characterizing the size of an RVE in order to effectively homogenize a material, however, there is less study of the effective isotropic limit. The representative size may be different when approaching the homogeneous limit or the isotropic limit. In this work, elastic and strength properties will be evaluated at multiple scales using SVE with square and circular (so-called "regular") geometry. A Voronoi tessellation based geometry, where aggregation of Voronoi cells is achieved using square or circular grids, is studied and compared with regular partitioning methods. Models will be tested on two types of microstructures, one that is isotropic at the macroscale, and one which contains a slight directional bias. Results for different SVE geometries will be compared to demonstrate how SVE modeling choices affect the characterization of anisotropy and heterogeneity at the micro- and mesoscale. • Statistical Volume Elements (SVE) are generated using different edge geometries • SVE elastic and material strength properties are evaluated at multiple scales • SVE edge geometry affects characterization of anisotropy and heterogeneity • Circular SVE edge geometry is preferable to square geometry for capturing anisotropy • SVE boundaries that avoid phase intersections improve modeling accuracy. [ABSTRACT FROM AUTHOR]

• Space-angle Discontinuous Galerkin method is employed to solve radiative transfer equation. • DGM validated against exact solution. • Carried out convergence rate study. • Demonstrated the superior convergence of DGM simultaneously applied to space and angle. The radiative transfer equation (RTE) for a plane-parallel problem involving scattering, absorption and radiation is solved using the discontinuous Galerkin (DG) finite element method (FEM). Both space and angle directions are discretized by the DG method. Thus, while the method has a higher accuracy in angle direction than hybrid FEM-Discrete Ordinate (S N) and FEM-Spherical Harmonic (P N) methods, it removes the continuity constraint implied by the form of basis function for continuous FEMs in space and angle. The discrete formulation of the problem is presented for nonzero phase function and a variety of boundary conditions. The numerical results demonstrate a p + 1 convergence rate when the intensity is interpolated by an order p polynomial in both space and angle. The method is validated against exact solutions, and compared with other space-angle and hybrid FEMs for a few benchmark problems. The appropriateness of the DG formulation for problems with discontinuous solution is demonstrated by solving a problem with delta source term, where an in-element averaging of the source term eliminates negative intensity values for high order elements. Finally, a problem with an angular-line source term and a convergence study where the solution order is zero in angle are used to further demonstrate the advantages of the high order space-angle DG formulation; for the convergence study problem, the error was reduced by about 13 binary orders of magnitude, by increasing the order in both space and angle, rather than in space only. [ABSTRACT FROM AUTHOR]

Abstract To model the sample-to-sample variations and the effect of microscale inhomogeneities on fracture response, statistical volume elements (SVEs) are employed to homogenize the elastic and fracture properties of ZrB 2 -SiC, a two-phase particulate composite often used as a thermal coating. In the mesoscale analysis, 2D finite element models are generated using a non-iterative, automated mesh generation algorithm named Conforming to Interface Structured Adaptive Mesh Refinement (CISAMR). The analysis of SVEs under mixed, traction, and minimal kinematic boundary conditions yields their angle-dependent tensile and shear fracture strengths and elastic stiffnesses. This study shows that homogenized fracture strengths are highly dependent on the SVE size and the particular geometric distribution of inclusions (even for similar volume ratios), whereas elastic properties are mainly a function of the volume fraction. Moreover, mean values of strength and bulk modulus, respectively, decrease and remain almost constant as the SVE size increases. For the macroscale analysis, an isotropic, inhomogeneous field of fracture strength is generated from the homogenization of SVEs. The asynchronous Spacetime Discontinuous Galerkin (aSDG) method is subsequently employed for fracture analysis under uniaxial tensile and thermal strain loadings. [ABSTRACT FROM AUTHOR]

Accurate characterization of random heterogeneity in a material microstructure is essential to the accurate characterization of complex fracture patterns that result from random crack nucleation and propagation. It is also important to characterize microstructural behavior at intermediate scales, between the length scale of material heterogeneity and the scale of a Representative Volume Element (RVE). The availability of material property data at multiple scales will ultimately allow adjustment of computational cost and level of accuracy with respect to resolution of complex fracture patterns. Statistical Volume Elements (SVE) may be generated at the mesoscale by partitioning an RVE. SVE provide a probabilistic characterization of material heterogeneity, while also presenting a continuum representation of apparent properties. Appropriate definition of an SVE requires modeling choices, such as partitioning methods and size. An essential modeling assumption is the choice of loading condition used to approximate SVE apparent behavior, since the constitutive properties of an SVE are not necessarily invariant with respect to the boundary condition applied. This work develops a Voronoi tessellation based partitioning scheme applied at various length scales, for heterogeneous materials with various contrast ratios. Results show the variability of failure strength for a given SVE as a function of loading direction. Results of the mesoscale material property analysis are implemented in an asynchronous spacetime discontinuous Galerkin (aSDG) finite element based fracture model. [ABSTRACT FROM AUTHOR]