Sharif Digital Repository

The high computational costs of atomistic simulations for the investigation of nanostructures, despite their accuracy, necessitate efforts to develop efficient continuum models. Since the classical continuum mechanics assume the matter as continuous and ignore the size dependency of material properties, these theories fail to capture the behavior of materials at the nanoscale. Size-dependencies of nanostructures could result in the emergence of surface effects. This paper, for the first time, aims to develop and tune surface-enhanced continuum models to predict the vibrational properties of nanoplates which are inherently discrete at the nanoscale. Regarding this aim, we use a composite... 

Understanding the chemistry of sandstone acidizing is important in designing an effective treatment for subsurface rock formations. The complex chemistry of sandstone systems leads to the precipitation of minerals that contribute to formation damage. Thus, monitoring the concentration and location of precipitates is necessary. In this work, a continuum-scale sequential implicit LEA/PLEA reactive transport model is developed and programmed through coupling OpenFOAM and Reaktoro to improve the model prediction. The proposed LEA/PLEA models are compared for core acidizing simulations at relatively high and low Damköhler numbers. We found that the common assumption of kinetically-controlled flow... 

A Ground Source Heat Pump (GSHP) is a renewable energy-based HVAC system that extracts or supplies heat from/to the ground via a Ground Heat Exchanger (GHE). One of the most commonly used types of GHE in GSHP systems is the energy pile. In this realm, the GSHP system with a triple helix energy pile has become the focus of attention. To this aim, a comprehensive three-dimensional transient Computational Fluid Dynamics model of the energy pile with triple helix GHE and the surrounding soil is developed. The effect of several parameters, including helix pitch, helix diameter and pipe diameter, on the thermal performance of the system, is investigated. Simulated cases are chosen using the design... 

The present study is set out to systematically investigate the combined impact of operational, geometrical, and model uncertainties on the hemodynamics and performance characteristics in the U.S. Food and Drug Administration (FDA) benchmark centrifugal blood pump. Non-intrusive Polynomial Chaos Expansion (NIPCE) has been utilized to propagate the uncertainty of 12 random input variables in the flow field and the performance characteristics of the blood pump at three working conditions. The global sensitivity of the Quantities of Interest (QoI) to the uncertain input parameters was measured through the Sobol’ indices. The Multiple Reference Frames (MRF) approach and the SST k−ω turbulence... 

Objective: Spine kinematics, kinetics, and trunk muscle activities were evaluated during different stages of a fatigue-induced symmetric lifting task over time. Background: Due to neuromuscular adaptations, postural behaviors of workers during lifting tasks are affected by fatigue. Comprehensive aspects of these adaptations remain to be investigated. Method: Eighteen volunteers repeatedly lifted a box until perceived exhaustion. Body center of mass (CoM), trunk and box kinematics, and feet center of pressure (CoP) were estimated by a motion capture system and force-plate. Electromyographic (EMG) signals of trunk/abdominal muscles were assessed using linear and nonlinear approaches. The L5-S1... 

The renewed attention paid to rammed earth materials in recent decades is related to their sustainability, high thermo-buffering capacity and relatively low cost. The energy performance of rammed earth materials can be enhanced with stabilization. However, some of thermal enhancement methods have destructive side-effects. In the current study, the effect of three different methods was investigated on thirteen different alternatives of rammed earth materials to improve energy efficiency of buildings. These methods include using phase change materials, cementitious admixtures and external insulators. Thermo-dynamic parameters such as time lag, thermal conductivity and heat flux were measured... 

In the energy system, various sources are used to fulfill the energy demand of large buildings. The energy management of large-scale buildings is very important. The proposed system comprises solar PVs, energy storage systems, and electric vehicles. Demand response (DR) schemes are considered in various studies, but the analysis of the impact of dynamic DR on operational cost has been ignored. So, in this paper, renewable energy resources and storages are integrated considering the demand response strategies such as real-time pricing (RTP), critical peak pricing (CPP), and time of use (ToU). The proposed system is mapped in a linear model and simulated in MATLAB using linear programming... 

In Industry 4.0, the emergence of new information technology and advanced manufacturing technology (e.g., digital twin, and robot) promotes the flexibility and smartness of manufacturing systems to deal with production task fluctuation. Digital twin-driven manufacturing system with human-robot collaboration is a typical paradigm of intelligent manufacturing. When production task changes, manufacturing system reconfiguration with dynamic opeartion task allocation between operator (human) and robot is a key manner to maintain the production efficiency of intelligent manufacturing system with human-robot collaboration. However, the differences between operator and robot are neglected during... 

It has always been a human challenge to inspire natural configurations and phenomena and benefit from their merits in improving the performances of man-made proposed aero/hydro vehicles. For example, the manta rays are known for their great swimming performances. To design and fabricate an underwater robot based on the manta ray geometry and its kinematic characteristics, it is important to initially study its hydrodynamic behavior and possibly arrive at some key design parameters, which can remarkably help to figure out an optimum geometry with high swimming performances. The main objective of this study is to focus on the merits of gliding motion inspired by the manta ray fish considering... 

The elastodynamic behavior of layered media consisting of an arbitrary combination of isotropic and transversely isotropic layers is of great importance for many engineering applications. In this work, some appropriate elastodynamic Green’s functions pertinent to both the displacement and the stress fields are devised so that the problems associated with the n-layer semi-infinite and infinite media with any combinations of transversely isotropic and isotropic layers subjected to surface and buried oblique time-harmonic annular loading can all be treated in a unified manner. The material degeneracy arising due to the scenarios where one or more regions are isotropic is also discussed and... 

A highly controllable, green, and rapid strategy is demonstrated for fabricating of highly sensitive non-enzymatic glucose sensing platforms. Carbon nanohorns (CNHs) were decorated onto the screen-printed electrodes. Binary nickel-cobalt sulfide (NiCo-S) nanosheets (NSs) were then deposited on CNH-casted electrodes by a facile and scalable method. Following detailed structural characterization and the electrocatalytic activity of the fabricated NiCo-S/CNH electrodes towards electro-oxidation of glucose was examined in detail. The proposed electrodes operated within two distinct linear dynamic ranges of 0.001- 0.330 mM and 0.330 - 4.53 mM with sensitivities of 1842 µA.mM−1.cm−2 and 854... 

Over the past few years, due to increasing population, limited water resources, and other pressures on the urban water systems (UWS), urban water management has become a major concern for urban policymakers to develop efficient management solutions. In this study, a new hybrid model called sustainable dynamic urban water metabolism management (SDUWMM) is presented, based on urban water metabolism and system dynamics. Isfahan's UWS has been modeled by SDUWMM and its conditions have been simulated until 2041. SDUWMM considers effective internal relationships of the UWS components such as population, climate change, water supply and demand, infrastructures condition, water price, costs and... 

Water can be pumped in nanochannels by limiting it between the surfaces with different hydrophobicities and exerting a spinning electric field. The asymmetrical hydrophobicity combined with the spinning electric field and the fact that the water molecules have a dipole moment create a situation in which the angular momentum of water molecules is transformed into a linear momentum and the water is pumped into the nanochannel. The hydrophobicity of the surfaces can be manipulated by using nanostructures to reduce friction. In this study, two types of nanostructures have been used which are hierarchical nanostructures and polymer nanostructures made of Poly(N-isopropylacrylamide). The walls of... 

Multiphase flow is a challenging area of computational fluid dynamics (CFD) due to their potential large topological change and close coupling between the interface and fluid flow solvers. As such, Lagrangian meshless methods are very well suited for solving such problems. In this paper, we present a new fully explicit incompressible Smoothed Particle Hydrodynamics approach (EISPH) for solving multiphase flow problems. Assuming that the change in pressure between consecutive time-steps is small, due to small time steps in explicit solvers, an approximation of the pressure for following time-steps is derived. To verify the proposed method, several test cases including both single-phase and... 

This study aims to develop the Consistent Fish-Bone (CFB) simplified model for efficient estimation of Engineering Demand Parameters (EDPs) in irregular steel Moment Resisting Frames (steel-MRFs). To achieve this goal, some modifications based on the energy consistent approach have been applied to the Improved Fish-Bone (IFB) simplified model previously presented for reinforced concrete MRFs. These modifications include: 1) adding truss elements to the IFB model to consider the effect of flexural deformations and determining their areas by balancing the overturning moment and the strain energy due to the axial deformation of columns in the original steel-MRF with the overturning moment and... 

Performance and reliability are two prominent factors in the design of data storage systems. To achieve higher performance, recently storage system designers use DynamicDynamic RAMRAM (DRAM)-based buffers. The volatility of DRAM brings up the possibility of data loss and data inconsistency. Thus, a part of the main storage is conventionally used as the journal area to be able of recovering unflushed data pages in the case of power failure. Moreover, periodically flushing buffered data pages to the main storage is a common mechanism to preserve a high level of reliability. This scheme, however, leads to a considerable increase in storage write traffic, which adversely affects the performance.... 

Phosphatidylcholine (PC) possesses amphiphilic characteristics to form vesicles or liposome nanoparticles and can be utilized to deliver essential nutrients such as proteins, peptide antigens, and essential fatty acids. In this study, an attempt has been made to obtain purified PC and evaluate its potential in nanoliposome synthesis and its corresponding drug release profile. In this regard, four physical separation techniques comprising extraction, precipitation, static, and dynamic adsorption were assessed and applied to purify PC from soybean lecithin. Different solvents and the ratio of lecithin to solvent were used to achieve the highest PC percentage. The results of an HPLC test showed... 

Most modern multi-core edge devices work in outdoor situations with limited power supplies like energy harvester and batteries. Therefore, energy consumption is a fundamental issue in which the memory subsystem has a significant role. Scratchpad memories (SPM) can provide a broad potential for energy saving. Still, due to the insufficient SPM capacity in such edge devices, a rigorous SPM data allocation scheme is necessary to reduce the energy consumption of the memory subsystem. Emerging non-volatile memories (NVMs) are very useful to reduce the energy consumption of the memory subsystem. Compared with SRAM, NVMs have lower leakage power and higher density, but the read and write latencies... 

The slow kinetics of wettability alteration toward a more water-wetting state by low-salinity waterflooding (LSWF) in oil-brine-rock (OBR) systems is conjectured to be pertinent to the electrokinetic phenomena in the thin brine film. We hypothesize that the nanoscale physicochemical heterogeneities such as surface roughness and surface charge heterogeneity at the rock/brine interface control further the dynamics of electrodiffusion and electrostatic disjoining pressure (Πel), thus the time-scale and the magnitude of the low salinity effect (LSE). In this regard, film-scale computational fluid dynamics (CFD) simulations were performed. The coupled Poisson-Nernst-Planck (PNP) equations were... 

Understanding the adsorption dynamics of nanoparticles at solid-liquid interfaces is of paramount importance to engineer nanoparticles for a variety of applications. The nanoparticle surface chemistry is significant for controlling the adsorption dynamics. This study aimed to experimentally examine the adsorption of surface-modified round-shaped silica nanoparticles (with an average diameter of 12 nm), grafted with hydrophobic (propyl chains) and/or hydrophilic (polyethylene glycol chains) agents, at an aqueous solution-silica interface with spherical soda-lime glass beads (diameter of 3 mm) being used as adsorbents. While no measurable adsorption was observed for solely hydrophobic or...