Parallel simulation of particle dynamics with application to micropolar peridynamic lattice modeling of reinforced concrete Structures

As the first goal of this thesis, we will explain a general purpose parallel particle dynamics code (pdQ2). We describe the re-architecting of pdQ (the MD/PD code that was developed in [Sakhavand 2011]) as pdQ2. pdQ2 is completely non-domain-specific in that user files are clearly separated from non-user files and no #ifdefs exist in the code. Thus, it operates as a particle simulation engine that is capable of executing any parallel particle dynamics model. As in the original pdQ, users can customize their own physical models without having to deal with complexities such as parallelization, but the ease of extensibility has been significantly improved. It is shown that pdQ2 is about four times as fast as pdQ using parallel supercomputers. In the second part of the thesis, we will model reinforced concrete structures based on peridynamic theory [Silling 1998]. We discard the continuum mechanics paradigm completely, and model reinforced concrete by introducing the micropolar peridynamic lattice model (MPLM)\u27. The MPLM models a structure as a close-packed particle lattice. In the MPLM, rather than viewing the structure as collection of truss or beam elements (as with traditional lattice models), the model is viewed as collection of particle masses (as with peridynamic models). The MPLM uses a finite number of equally-spaced interacting particles of finite mass. Thus, it does not need any ad hoc discretization and it is more straightforward to implement computationally. Also, the MPLM is conceptually simpler than both the lattice and peridynamic models [Gerstle et al. 2012]. After defining the MPLM, its application to reinforced concrete structures is investigated through several examples using pdQ2.\u2

Phonon Transport in Nanophononic Metamaterials Using Large-scale Atomistic Models

Understanding nanoscale thermal transport in materials is essential for developing efficient energy materials/devices for thermoelectric energy conversion. The performance of current thermoelectric materials (TEM) is relatively low and thus they are not cost- efficient compared to conventional technologies. One path towards improving the performance of TEM is the reduction of thermal conductivity in semiconducting materials, for which phonons are the dominant heat carriers. In the past two decades, the phonon thermal conductivity reduction by engineering the material at the atomistic level has shown remarkable promise due to the rapid progress in nano science and technology. In this thesis, using large-scale atomistic models, phonon transport in a recently discovered nanostructured material called nanophononic metamaterial (NPM) is extensively investigated at low-dimensional and bulk levels. A low-dimensional NPM can be created by attaching nanopillars to, for example, a thin silicon membrane. In this system, the leading mechanism is local resonance, whereby standing waves created by the nanopillars couple with the propagating phonons in the base membrane. These couplings affect the traveling phonons across the full frequency spectrum of the membrane, and are able to slow down the heat. These effects result in significantly low in-plane thermal conductivity. The low-dimensional NPM concept is unique because the nanoresonators are located outside the main medium of transport and are expected to have minimal impact on electron transport. Here, the resonance phenomenon, physical size effects, and design rules to achieve high TEM performance for realistic configurations and sizes of NPM are investigated, while ensuring that the emerging systems are amenable to fabrication and characterization by modern technologies. At the bulk level, phonon transport in crystalline silicon with resonant inclusions is also investigated. In this context, the resonance effects and the thermal conductivity reduction caused by two types of inclusions are studied. The first is an amorphous inclusion and the second is based on Van der Waals resonators. The resonant behavior of each of these systems is characterized directly from simulations. These unique configurations may provide a practical platform for thermal conductivity reduction using nanoresonators embedded in a bulk medium.</p

Experimental Investigation of Interfacial Tension Measurement and Oil Recovery by Carbonated Water Injection : A Case Study Using Core Samples from an Iranian Carbonate Oil Reservoir

The authors would like to gratefully acknowledge and appreciate the Department of Petroleum Engineering, Faculty of Engineering, Marvdasht Islamic Azad University, Marvdasht, 73711-13119, Iran, for the provision of the laboratory facilities necessary for completing this work.Peer reviewedPostprin

CO2 sequestration through direct aqueous mineral carbonation of red gypsum

The authors would like to appreciate the Department of Petroleum Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran for the provision of the laboratory facilities necessary for completing this work.Peer reviewedPublisher PD

CO2 sequestration using red gypsum via pH-swing process : Effect of carbonation temperature and NH4HCO3 on the process efficiency

The authors would like to appreciate the Department of Petroleum Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran for the provision of the laboratory facilities necessary for completing this work. We would also like to thank Dr. Peter Dunning from University of Aberdeen for English proofreading of this manuscript.Peer reviewedPostprin

Formulation and Optimization of Oral Mucoadhesive Patches of Myrtus Communis by Box Behnken Design

Purpose: Recurrent aphthous stomatitis (RAS) is the most common painful ulcerative disease of oral mucosa happening in ~20% of people. Aimed to develop Myrtus communis L. (Myrtle) containing oral patches, we applied box-behnken design to evaluate the effect of polymers such as Polyvinyl pyrrolidone (PVP), Gelatin, Methylcellulose (MC) and Pectin. Methods: The patches properties such as tensile strength, folding endurance, swelling index, thickness, mucoadhesive strength and the pattern of myrtle release were evaluated as dependent variables. Then, the model was adjusted according to the best fitted equation with box behnken design. Results: The results indicated that preparation of myrtle patch with hydrophilic polymers showed the disintegration time up to 24h and more. Using of polyvinyl pyrrolidone as a water soluble polymer and a pore-former polymer led to faster release of soluble materials from the patch to 29 (min-1). Also it decreases swelling index by increasing the patch disintegration. Gelatin and Pectin, with rigid matrix and water interaction properties, decreased the swelling ratio. Pectin increased the tensile strength, but gelatin produced an opposite effect. Thinner Myrtle patch (about 28μm) was obtained by formulation of methyl cellulose with equal ratio with polyvinyl pyrrolidone or gelatin. Conclusion: Altogether, the analysis showed that the optimal formulation was achieved with of 35.04 mg of Gelatin, 7.22 mg of Pectin, 7.20 mg of polyvinyl pyrrolidone, 50.52 mg of methyl cellulose and 20 mg of Myrtle extract

Semiconductor thermal and electrical properties decoupled by localized phonon resonances

Thermoelectric materials convert heat into electricity through thermally driven charge transport in solids, or vice versa for cooling. To be competitive with conventional energy-generation technologies, a thermoelectric material must possess the properties of both an electrical conductor and a thermal insulator. However, these properties are normally mutually exclusive because of the interconnection of the scattering mechanisms for charge carriers and phonons. Recent theoretical investigations on sub-device scales have revealed that silicon membranes covered by nanopillars exhibit a multitude of local phonon resonances, spanning the full spectrum, that couple with the heat-carrying phonons in the membrane and collectively cause a reduction in the in-plane thermal conductivity$-$while, in principle, not affecting the electrical properties because the nanopillars are external to the pathway of voltage generation and charge transport. Here this effect is demonstrated experimentally for the first time by investigating device-scale suspended silicon membranes with GaN nanopillars grown on the surface. The nanopillars cause up to 21 % reduction in the thermal conductivity while the electrical conductivity and the Seebeck coefficient remain unaffected, thus demonstrating an unprecedented decoupling in the semiconductor's thermoelectric properties. The measured thermal conductivity behavior for coalesced nanopillars and corresponding lattice-dynamics calculations provide further evidence that the reductions are mechanistically tied to the phonon resonances. This finding breaks a longstanding trade-off between competing properties in thermoelectricity and paves the way for engineered high-efficiency solid-state energy recovery and cooling