Sharif Digital Repository

A nontrivial portion of heavy-duty vehicle emissions of NOx and particulate matter (PM) occurs during idling. Regulators and the environmental community are interested in curtailing truck idling emissions, but current emissions models do not characterize them accurately, and little quantitative data exist to evaluate the relative effectiveness of various policies. The objectives of this study were to quantify the effect of accessory loading and engine speed on idling emissions from a properly functioning, modern, heavy-duty diesel truck and to compare these results with data from earlier model year vehicles. It was found that emissions during idling varied greatly as a function of engine... 

Purpose - The purpose of this paper is to study and review some major impacts of the disasters during the past 105 years and develop a new theoretical classification of disasters. Design/methodology/approach - A detailed study of disasters in the world during the period (1900-2005) has been obtained from the recent published sources. In that period more than 40 lessons have been reported based on statistical data analysis of disasters. Furthermore, a two-dimensional probability density function is developed to categorize the different types of disasters. This paper studies and reviews some major impacts of disasters during the past 105 years and summarizes some major lessons for the future.... 

The inception of transformation optics has opened avenues for designing of a plethora of applications related to the propagation of electromagnetic waves in anisotropic media. In this paper, an algorithm is proposed using a coordinate transformation for the purpose of designing a cloak for a body having an arbitrary convex geometry. For the purpose of verification of the algorithm, a ray tracing process is carried out for an ellipsoid as well as an irregularly shaped body, both having axial symmetry. The ray tracing is carried out in a two dimensional plane since the transmitted ray vector would lie in the plane of incidence containing the incident ray vector and the normal vector to the... 

The accomplishment of design for devices and applications such as cloaking has been feasible using transformation optics. This feasibility has been extended to the design of cloaks for concave bodies. Even though the process of cloaking in concave shaped bodies has been addressed in literature, the problem of poor accuracy and poor quality of cloaking remains. In accordance with the aim to outmanoeuvre the problem, the surface of interest which could be of convex or concave nature is modelled using a piecewise higher order parametric function. This function is expressed using Lagrange's interpolation. The calculation of piecewise model involves the inversion of the Lagrangian polynomial. But... 

Potassium fluoride supported on alumina efficiently catalyzes Michael addition of aromatic and aliphatic thiols to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, amides, nitriles and chalcones. The Michael adducts are produced in good to excellent yields and relatively in short times. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. Copyright © Taylor & Francis, Inc  

The precipitation process considered here, involved the addition of orthophosphoric acid solution to a calcium hydroxide solution. Several parameters such as the effects of atmosphere controlling, pH, adding extra acid solution, the amount of stirring speed, and post-chemical treatment were studied. In order to study the thermal stability of synthesised powders, they were sintered for 2 h at 1200 °C and the as-precipitated and sintered powder samples were examined using SEM, XRD, FTIR and ICP methods. The results clearly revealed that the final precipitated powder is hydroxyapatite (HA) with good purity, stoichiometry and successful thermal stability. SEM high magnification micrographs... 

The alkaline treatment condition plays a crucial role in governing the ultimate properties of flax fibers. In this study, flax fibers were modified with mild alkalization and severe mercerization conditions to give fundamental insight into how the molecular-scale changes in cell wall fine structure and cellulose supramolecular structure can affect the macroscopic properties of fibers. SEM, FTIR, XRD, TGA, and DSC techniques were employed to characterize the variations in morphology, composition, crystalline structure, and thermal properties of fibers. Also, tensile tests evaluated their reinforcing performance in polypropylene-based composites. The results indicated that alkalization in 5%... 

The alkaline treatment condition plays a crucial role in governing the ultimate properties of flax fibers. In this study, flax fibers were modified with mild alkalization and severe mercerization conditions to give fundamental insight into how the molecular-scale changes in cell wall fine structure and cellulose supramolecular structure can affect the macroscopic properties of fibers. SEM, FTIR, XRD, TGA, and DSC techniques were employed to characterize the variations in morphology, composition, crystalline structure, and thermal properties of fibers. Also, tensile tests evaluated their reinforcing performance in polypropylene-based composites. The results indicated that alkalization in 5%... 

In this paper, a semi-supervised graph-based method for estimating 3D body pose from a sequence of silhouettes, is presented. The performance of graph-based methods is highly dependent on the quality of the constructed graph. In the case of the human pose estimation problem, the missing depth information from silhouettes intensifies the occurrence of shortcut edges within the graph. To identify and remove these shortcut edges, we measure the similarity of each pair of connected vertices through the use of sliding temporal windows. Furthermore, by exploiting the relationships between labeled and unlabeled data, the proposed method can estimate the 3D body poses, with a small set of labeled... 

The authors regret that there was an error in the SEM images presented in Fig. 4 of the article. The corrected SEM images as presented here. It is noteworthy that this change does not affect any of the conclusions. The authors would like to apologize for any inconvenience caused. © 2022 Elsevier Ltd  

The aim of the present work is to evaluate the effect of fractures geometrical properties such as orientation, density, location, and networking on the conventional fire flooding (CFF) process performance through simulation analysis. Combustion parameters of a fractured low-permeable carbonate heavy oil reservoir in Iran called Kuh-E-Mond (KEM); applied for simulation study and simulator has been validated with KEM combustion tube experimental data. The validated model was modified to study CFF in 3D semi-scaled combustion cells. Simulation results confirmed that CFF is more feasible in the case of densely fractured reservoirs such as those in the Middle East  

Toe to heel air injection has been studied on non-fractured sandstone models and is found to be a promising enhanced oil recovery method for certain heavy oil reservoirs, such as those in Canada, but its applicability on fractured reservoirs, such as those in the Middle East, is not investigated yet. The objective of this article is to evaluate the effect of fractures geometrical parameters, such as fracture density, orientation, and location, on the performance of the process in laboratory scale. Simulation results showed that toe-to-heel air injection is more applicable on highly networked fractured reservoirs, such as those that occur in Persian Gulf coast compared to lower density... 

We study the simplest optomechanical system with a focus on the bistable regime. The covariance matrix formalism allows us to study both cooling and entanglement in a unified framework. We identify two key factors governing entanglement; namely, the bistability parameter (i.e., the distance from the end of a stable branch in the bistable regime) and the effective detuning, and we describe the optimum regime where entanglement is greatest. We also show that, in general, entanglement is a nonmonotonic function of optomechanical coupling. This is especially important in understanding the optomechanical entanglement of the second stable branch  

Experimental Investigation of the Asphaltene Deposition Process during Different Production Schemes - This paper presents the results of asphaltene precipitation and deposition during lean gas injection, CO2 injection and natural depletion in reservoir conditions. In addition, the effect of variations in operating pressure, injection gas concentration and production rate on asphaltene precipitation and deposition were investigated. The severity of asphaltene deposition was found to be more pronounced in lean gas injection in comparison with CO2 injection and natural depletion. Increasing the flow rate in natural depletion xperiments showed a considerable increase in asphaltene deposition,... 

We study the simplest optomechanical system in the presence of laser phase noise (LPN) using the covariance matrix formalism. We show that for any LPN model with a finite correlation time, the destructive effect of the phase noise is especially strong in the bistable regime. This explains why ground-state cooling is still possible in the presence of phase noise, as it happens far away from the bistable regime. We also show that the optomechanical entanglement is strongly affected by phase noise  

Field evidence indicates that the thermal and chemical regimes in wellbore considerably affect the wellbore stability. This study presents a general coupled model for transport of solute, solvent and heat including their combined effects on the wellbore stability. Optimization of drilling fluid parameters is crucial for wellbore stability analysis particularly in high pressure-high temperature environments. The coupled effects of chemical potential and temperature gradients on fluid flow significantly change the pore pressure and stress around a borehole. The effects of various parameters such as mud weight, solute concentration gradient, shale properties, and temperature gradient on... 

The Conventional Fire Flooding (CFF) process application feasibility on fractured carbonated reservoirs remained questionable. In this paper first combustion parameters and reaction kinetics of a naturally fractured low permeability carbonated heavy oil reservoir in Iran called Kuh-E-Mond applied to simulation study. After that, simulator has been validated with Kuh-E-Mond combustion tube experiment. Recovery mechanism in single block matrix is different from one in conventional model since oxygen first flows into the fractures and then diffuses from all sides into the matrix. Combustion of the oil in the fractures produces some water ahead of fracture combustion front which prohibits oxygen... 

This paper studies the relationship between the position of individual scientists within co-authorship networks and their scientific performance. Using co-authorship data from African scientists in the Health and Medical Sciences within a timespan of 15 years (2000–2015), we characterize the collaboration networks and calculate centrality measures for each scientist to explore how scientific production and impact can be associated with their position within the network. Our findings reveal that authors who occupy a better position within their network and are deemed to actively collaborate with others also have a higher research impact. In this regard, South African scientists do not differ... 

A t-(v, k, λ) design D = (X, B) with B = Pk(X) is called a full design. For t = 2, k; = 3 and any v, we give minimal defining sets for these designs. For v = 6 and v = 7, smallest defining sets are found  

Photocatalytic decolorization of methylene blue (MB) in aqueous solution was investigated using ZnO nanoparticles immobilized on glass plate. The ZnO nanoparticles were prepared by solution combustion method (SCM) using zinc nitrate as oxidant and glycine as fuel. In the slurry ZnO system the separation and recycling of the photocatalyst is practically difficult. Thus, the ZnO nanoparticles were immobilized on glass supports to solve this problem. The effects of process parameters like, catalyst loading, initial dye concentration, and UV-radiation intensity have been investigated. The best results of MB removal were reported in the 1800 μW cm-2 UVC using two layers immobilized ZnO...