Sharif Digital Repository

A novel algorithm is introduced to reduce the number of detailed kinetic mechanisms. The algorithm uniquely employs a classification of species and a defined parameter that quantitatively identifies the contribution of each species under a combustion condition of interest with specific species targeting. It also incorporates sensitivity analysis, the directed relation graph (DRG) method, and dynamic refinement. The proposed procedure is applied to the GRI-3.0 mechanism with atmospheric pollutants (CO, CO2, NO, and NO2) targeted in a lean methane-air flame at high pressures. The performance of the reduced mechanism is assessed, and good accuracy with considerable computational cost reduction... 

The main objective here is to introduce and analyze a novel design to provide heat at higher temperatures, via a thermoacoustic super-heater, supplied by industrial wasted heat. The system includes two standing wave thermoacoustic engines with a symmetric configuration inside a resonator tube, with a constant linear temperature distribution (500–300 K) on stack plates. A high-temperature heat exchanger (HTHX) is placed in the middle of the resonator tube to extract heat at very high temperatures. This system is numerically simulated in which all non-linear terms are preserved. Two configurations were studied, the first includes an insulated HTHX which reached a high temperature of 800 K,... 

Revealing the complex relationship between corporation-chosen strategies and financial performance is crucial in navigating today's dynamic business landscape. This research delves into the profound impact of business strategies on both corporation performance and investors' behavior, seeking to identify the strategy that yields the highest returns and efficiency for the corporation and its beneficiaries (investors, loan-holders, and stock-holders). This study proposes a multi-criteria decision-making (MCDM) model that integrates the distance correlation-based criteria importance through inter-criteria correlation (D-CRITIC) weighting method with multi-objective optimization on the basis of... 

This paper suggests methods for improving efficiency of a high step up high efficiency converter based on three state commutation cells. A loss analysis has been performed to identify the source of power loss. Based on this analysis, methods are presented to reduce losses in the most power dissipating elements. These methods include replacing some power diodes with large conduction losses with MOSFETs having small on-state resistance. Efficiency improvement up to %1.25 percent is verified in simulation and experimental results  

The rheological behaviour of dilute soil-water mixtures, such as hyperconcentrated mixtures and interstitial fluids in debris flows, can significantly affect the flow dynamics of flow-type landslides. These mixtures often contain clay, silt, and sandy particles. Despite great efforts, the effects of soil type and texture on the rheological behaviour of these mixtures are still not well understood. To tackle this issue, an experimental investigation is carried out using a narrow-gap rotational viscometer to evaluate the interactions from colloidal (clay) and non-colloidal (silt and sand) particles and possibility of flow regime change. The flow curves of dilute mixtures are determined with... 

In this paper we present a semiclassical model for explanation of the nonlinear optical effect and phase matching. We calculate momentary quantities of the delay time of photon-electron interaction in each layer. We show that for phase matching, the average delay time for the fundamental photons must be equal to the average delay time for the harmonic photons. Additionally, we calculate the number of layers that the harmonic photon needs to be absorbed or converted to fundamental photons. This calculation applies to different wavelengths with different phase matching angles. Our simulation results are in good agreement with experimental data. © 2008 IOP Publishing Ltd  

In this article, we present a semiclassical approach for modeling of electro-optic (EO) effect. We calculate phase retardation between x and y polarizations of optical electric field when a transverse external electric field is applied. Our results are well agreed with experimental measurements. Moreover, we show when wavelength of optical signal decreases, the phase retardation increases. © 2008 Elsevier B.V. All rights reserved  

The flow dynamics of dry granular flows is significantly affected by a prominent feature of a granular mass known as dilatancy. Although their rheological behaviour has been characterised via friction and dynamic dilatancy laws, the role of dilatancy in a granular flow has not been much appreciated. In this study, using a vane rheometer, an experimental investigation was conducted on uniform glass beads of (d = 3 mm) at different initial relative densities (15 ≤ Dr ≤ 66%) and shear rates that span over four orders of magnitude. The flow characteristics in terms of effective friction, volume change, and velocity field were obtained and evaluated. The effective friction shows a... 

Optical tweezers provide an accurate measurement technique for evaluating mechanical properties of the living cells and many experimental studies have been done to understand the behavior of cells due to external forces. Numerical studies such as finite element methods have been used in order to simulate mechanical behavior of the Red Blood Cells (RBCs). Recent studies have shown that the particle methods are useful tools to simulate the mechanical behavior of living cells. Since in microscopic scales, using discrete models are preferred than continuum methods, a particle-based method is used to simulate the deformation of RBC which is stretched by optical tweezers. The cytoplasm of RBC is... 

Governments in developing countries have invested in institutions of higher learning in order to develop homegrown, high technology products. Among these, the National University of Malaysia (Universiti Kebangsaan Malaysia), recognized as a Research University, is actively involved in projects related to medical technology through its various faculties. The net result of these activities is impressing from the point of view of patents and publications, but unfortunately not yet in terms of commercialization. This paper starts by presenting the main obstacles towards the objective of bringing a laboratory prototype to the market in the context of Malaysia. Then, a framework is presented... 

In order to optimize the aging treatment of Mg-1.8Zn-0.7Si-0.4Ca alloy, different times and temperatures of solid solution and age hardening were applied to the alloy specimens. Microstructures and mechanical properties of the specimens were investigated using the optical microscopy, field emission scanning electron microscopy equipped with an energy dispersive x-ray spectrometer, x-ray diffraction, hardness, and shear punch tests. The lowest hardness and strength were achieved by solution treating of the alloy at 500 °C for 8 h, presenting the optimal condition for solution treatment of the alloy. The microstructural examinations revealed three different precipitates consisting of CaMgSi,... 

Recognizing the flow behaviours across a Riga plate can reveal information about the aerodynamic efficiency of aircraft, heat propagation, vehicles, and other structures. These data are critical for optimizing design and lowering drag. Therefore, the purpose of the current analysis is to examine the energy and mass transfer across the mixed convective nanofluid flows over an extending Riga plate. The fluid flow is deliberated under the influences of viscous dissipation, exponential heat source/sink, activation energy, and thermal radiation. The Buongiorno's concept is utilized for the thermophoretic effect and Brownian motion along with the convective conditions. The modelled are simplified... 

It is very significant and practical to explore a triple hybrid nanofluid flow across the stuck zone of a stretching/ shrinking curved surface with impacts from stuck and Lorentz force factors. The combination (Ag-TiO2-Al2O3/blood) hybrid nanofluid is studied herein as it moves across a stagnation zone of a stretching/shrinking surface that curves under the impact of pressure and Lorentz force. Exact unsolvable nonlinear partial differential equations can be transformed into ordinary differential equations that can be solved numerically by similarity transformation. It was discovered that predominant heat transfers andmovement characteristics of quaternary hybrid nanofluids are dramatically... 

Hybrid or binary nanofluids have superior mechanical and thermal characteristics but the tri-hybrid nanofluids comprise of more embellished thermal properties, better physical strength, and enhanced stability. The present work characterizes the thermal and physical aspects of the hybrid and tri-hybrid nanofluids. The nano-composition of graphene oxide (Go) and cobalt (Co) is used in the amalgamation of hybrid nanofluid Go-Co/H2O, whereas the addition of zirconium oxide (ZrO2) in this mixture gives rise to the ternary Go-Co-ZrO2/H2O hybrid nanofluid. The activation energy and viscous dissipation terms are also amended in the governing equations. The mathematical framework consists of a...