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Predicting delamination in multilayer composite circuit boards with bonded microelectronic components
, Article Engineering Fracture Mechanics ; Volume 187 , 2018 , Pages 225-240 ; 00137944 (ISSN) ; Nourani, A ; Spelt, J. K ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of...
Multi-objective optimisation of steam methane reforming considering stoichiometric ratio indicator for methanol production
, Article Journal of Cleaner Production ; Volume 180 , 2018 , Pages 655-665 ; 09596526 (ISSN) ; Iranshahi, D ; Saeidi, S ; Pourazadi, E ; Klemeš, J. J ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This work proposes a novel configuration for steam methane reformers (SMR) in order to improve their syngas stoichiometric ratio (SR). This is a decisive element for methanol producers to increase their production tonnage. While the optimum theoretical SR value is around 2, many conventional SMRs operate far beyond this value due to thermodynamic equilibrium limitations. In the new SMR design CO2, which could be an industrial off gas, is injected into the reactor in multiple stages. The corresponding CO2 injection flow rate is determined by a multi-objective optimization method. The optimum flow rate at each stage is chosen to minimise abs (SR-2) while maintaining the CH4 conversion at its...
A numerical study of reactive pollutant dispersion in street canyons with green roofs
, Article Building Simulation ; Volume 11, Issue 1 , February , 2018 , Pages 125-138 ; 19963599 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Tsinghua University Press
2018
Abstract
Roof greening is a new technique for improvement of outdoor thermal environment which influences air quality through its impacts on thermal and flow field. In order to examine effects of green roofs on reactive pollutant dispersion within urban street canyons, a computational fluid dynamics (CFD) model was employed which contained NO-NO2-O3 photochemistry and energy balance models. Simulations were performed for street canyons with different aspect ratios (H/W) of 0.5, 1.0, and 2.0 such that leaf area density (LAD) of green roofs changed. It was found that roof greening led distribution of pollutants to alter for H/W = 0.5 and 1.0 cases in such a manner that their averaged concentrations had...
Shear band propagation in honeycombs: numerical and experimental
, Article Rapid Prototyping Journal ; Volume 24, Issue 2 , 2018 , Pages 477-484 ; 13552546 (ISSN) ; Bagheri, R ; Altstadt, V ; Sharif University of Technology
Emerald Group Publishing Ltd
2018
Abstract
Purpose: Hexagonal honeycombs with meso-metric cell size show excellent load bearing and energy absorption potential, which make them attractive in many applications. However, owing to their bend-dominated structure, honeycombs are susceptible to deformation localization. The purpose of this study is to provide insight about shear band propagation in struts of 3D-printed honeycombs and its relation to the achieved macroscopic mechanical behavior. Design/methodology/approach: Hexagonal honeycombs and unit cell models are 3D-printed by fused deposition modeling (FDM). The samples are exposed to compression loading and digital image correlation technique and finite element analyses are...
Meta-model based multi-objective optimisation method for computer-aided tolerance design of compliant assemblies
, Article International Journal of Computer Integrated Manufacturing ; 2018 ; 0951192X (ISSN) ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
Optimal tolerance design is a time-consuming and multi-disciplinary procedure and involves several aspects of design, manufacturing, quality and cost problems. In addition, the quality of assemblies can be significantly affected by the flexibility of components which has not been considered in most of the previous research. In this paper, a new method is proposed for multi-objective optimal tolerance design of compliant assemblies based on an integrated Kriging meta-modelling–NSGA-II–Shannon’s Entropy TOPSIS algorithm. The tolerance propagation of flexible components in the assembly process is modelled through the enhanced Method of Influence Coefficients (MIC). Geometrical variations of key...
Calibration of parallel kinematic machine tools using mobility constraint on the tool center point
, Article International Journal of Advanced Manufacturing Technology ; Volume 45, Issue 5-6 , 2009 , Pages 531-539 ; 02683768 (ISSN) ; Pendar, H ; Alasty, A ; Vossoughi, G. R ; Sharif University of Technology
2009
Abstract
In the application of parallel kinematic machine tools (PKM), because of errors in the geometric parameters, it is necessary to calibrate the PKM to improve the positioning accuracy. In existing self-calibration methods, either some redundant sensors on passive joints or some mobility constraints on the kinematic chains are used. However, the mobility constraints imposed on kinematic chains might apply large forces during the test on legs and passive joints. Also, these kinds of calibrating are applicable only on PKMs in which their actuated joints can be used as passive joints. To overcome weaknesses of existing methods, a novel approach to calibration based on imposing position constraints...
Dynamic analysis of electrically actuated rectangular microplates with nonlinear plate theory under squeeze-film damping effect
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 13, Issue PART A , 2009 , Pages 401-408 ; 9780791848746 (ISBN) ; Moghimi Zand, M ; Ahmadian, M. T ; Sharif University of Technology
2009
Abstract
In this paper, dynamic behavior and pull-in phenomenon of electrically actuated rectangular micro plates under the effect of squeeze-film damping and nonlinear electrostatic force is studied. Finite element method is implemented in order to drive weak formulations of linear and nonlinear micro plate equations of motion based on classical plate theory (CPT) (for thin microplates with moderate nonlinearity) and squeeze-film damping based on Reynolds nonlinear equation. Finally, an efficient reduced-order model contingent on singular value decomposition method (SVD) is used to study dynamic pull-in phenomenon. This model is constructed by the global basis functions achieved from a few runs of...
Pore structure evolution during sintering of HDPE particles
, Article Polymer ; Volume 183 , 2019 ; 00323861 (ISSN) ; Pircheraghi, G ; Foudazi, R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Sintering is a processing technique in which loose particles consolidate at elevated temperatures to form porous monoliths. Sintering is also a critical stage in recent additive manufacturing method like selective laser sintering. In this study, using an affordable alternative to X-ray tomography technique, we analyze the pore structure evolution in sintered parts made of nascent high-density polyethylene (HDPE) particles in terms of pore surface genus and pore surface curvature. Also, we investigate the underlying microstructural development and macroscopic properties of sintered parts. It is observed that pore structure and macroscopic permeability are strongly influenced by the...
Geopolymers vs. alkali-activated materials (AAMs): A comparative study on durability, microstructure, and resistance to elevated temperatures of lightweight mortars
, Article Construction and Building Materials ; Volume 222 , 2019 , Pages 49-63 ; 09500618 (ISSN) ; Shoaei, P ; Zareei, S. A ; Behforouz, B ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper studied the durability, microstructure, and fire behavior of lightweight mortars based on cement, metakaolin (MK), ultrafine ground granulated blast furnace slag (UGGBFS), ceramic waste powder (CWP), and clay brick waste powder (CBWP). Two sets of mixes were prepared with two types of lightweight aggregate including lightweight expanded clay aggregate (LECA) and pumice aggregate. Regarding the durability assessment, the electrical resistivity and water absorption of the mortars were measured. The UGGBFS-based alkali-activated mortar with pumice aggregate exhibited the highest electrical resistivity and lowest water absorption, while CBWP-based geopolymer mortar with LECA showed...
An efficient uniform-segmented neuron model for large-scale neuromorphic circuit design: Simulation and FPGA synthesis results
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 66, Issue 6 , 2019 , Pages 2336-2349 ; 15498328 (ISSN) ; Abolfathi, H ; Ahmadi, A ; Ahmadi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Large-scale simulation of spiking neural networks on hardware with a remarkable resemblance to their mathematical models is a key objective of the neuromorphic discipline. This issue is, however, considerably resource-intensive due to the presence of nonlinear terms in neuron models. This paper proposes a novel uniform piecewise linear segmentation approach for nonlinear function evaluations. Employing the proposed approach, we present a uniform-segmented adaptive exponential neuron model capable of accurately producing various responses exhibited by the original model and suitable for efficient large-scale implementation. In contrast to previous nonuniform-segmented neuron models, the...
High-Photoresponsive backward diode by two-dimensional SnS2/Silicon heterostructure
, Article ACS Photonics ; Volume 6, Issue 3 , 2019 , Pages 728-734 ; 23304022 (ISSN) ; Esfandiar, A ; Iraji Zad, A ; Hosseini Shokouh, S. H ; Mahdavi, S. M ; Sharif University of Technology
American Chemical Society
2019
Abstract
Two-dimensional semiconductor materials can be combined with conventional silicon-based technology and sort out part of the future challenges in semiconductor technologies due to their novel electrical and optical properties. Here, we exploit the optoelectronics property of the silicon/SnS2 heterojunction and present a new class of backward diodes using a straightforward fabrication method. The results indicate an efficient device with fast photoresponse time (5-10 μs), high photoresponsivity (3740 AW-1), and high quantum efficiency (490%). We discuss device behavior by considering the band-to-band tunneling model and band bending characteristics of the heterostructure. This device structure...
Improved winding proposal for wound rotor resolver using genetic algorithm and winding function approach
, Article IEEE Transactions on Industrial Electronics ; Volume 66, Issue 2 , 2019 , Pages 1325-1334 ; 02780046 (ISSN) ; Nasiri Gheidari, Z ; Tootoonchian, F ; Oraee, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Among position sensors, resolvers are superior from reliability point of view. However, obtaining lower output voltage harmonics and simple manufacturing process is a challenge in the design and optimization of resolvers. In this paper, a metaheuristic optimization algorithm is used to minimize total harmonic distortion of the output signals, and consequently the estimated position error in concentrated coil wound field resolvers. Meanwhile, to minimize total coil numbers, manufacturing costs, and complexity of the winding process, modified objective function and constraints are proposed. In this way, a modified winding function method is employed for performance analysis of the axial flux...
Meta-model based multi-objective optimisation method for computer-aided tolerance design of compliant assemblies
, Article International Journal of Computer Integrated Manufacturing ; Volume 32, Issue 1 , 2019 , Pages 27-42 ; 0951192X (ISSN) ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Optimal tolerance design is a time-consuming and multi-disciplinary procedure and involves several aspects of design, manufacturing, quality and cost problems. In addition, the quality of assemblies can be significantly affected by the flexibility of components which has not been considered in most of the previous research. In this paper, a new method is proposed for multi-objective optimal tolerance design of compliant assemblies based on an integrated Kriging meta-modelling–NSGA-II–Shannon’s Entropy TOPSIS algorithm. The tolerance propagation of flexible components in the assembly process is modelled through the enhanced Method of Influence Coefficients (MIC). Geometrical variations of key...
Vibration control and manufacturing of intelligibly designed axially functionally graded cantilevered macro/micro-tubes
, Article 13th IFAC Workshop on Intelligent Manufacturing Systems, IMS 2019, 12 August 2019 through 14 August 2019 ; Volume 52, Issue 10 , 2019 , Pages 382-387 ; 24058963 (ISSN) ; Ebrahimi Mamaghani, A ; Ahmadian, M. T ; Barari A ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In the last decade, extensive attention is devoted to intelligibly designed materials of macro/micro-structures containing the fluid flow. In this study, intelligent control and vibrational stability of cantilevered fluid conveying macro/micro-tubes utilizing axially functionally graded (AFG) materials are considered. The governing equation of motion of the system is derived based on modified couple stress theory and then is discretized using Galerkin method. A detailed investigation is carried out to elaborate the influence of various parameters such as material properties, axial compressive load, and Pasternak foundation on the dynamical behavior of the system, all of which are influential...
A hydrogen-bonded extracellular matrix-mimicking bactericidal hydrogel with radical scavenging and hemostatic function for ph-responsive wound healing acceleration
, Article Advanced Healthcare Materials ; 2020 ; Correia, A ; Hasany, M ; Figueiredo, P ; Dobakhti, F ; Eskandari, M. R ; Hosseini, H ; Abiri, R ; Khorshid, S ; Hirvonen, J ; Santos, H. A ; Shahbazi, M. A ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Generation of reactive oxygen species, delayed blood clotting, prolonged inflammation, bacterial infection, and slow cell proliferation are the main challenges of effective wound repair. Herein, a multifunctional extracellular matrix-mimicking hydrogel is fabricated through abundant hydrogen bonding among the functional groups of gelatin and tannic acid (TA) as a green chemistry approach. The hydrogel shows adjustable physicochemical properties by altering the concentration of TA and it represents high safety features both in vitro and in vivo on fibroblasts, red blood cells, and mice organs. In addition to the merit of facile encapsulation of cell proliferation-inducing hydrophilic drugs,...
Propane steam reforming on mesoporous NiO–MgO–SiO2 catalysts for syngas production: Effect of the MgO/SiO2 molar ratio
, Article International Journal of Hydrogen Energy ; Volume 45, Issue 46 , 2020 , Pages 24840-24858 ; Kazemeini, M ; Rezaei, M ; Farhadi, F ; Keshavarz, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this research, a series of NiO-xMgO-SiO2 catalysts with various MgO/SiO2 molar ratios were prepared via precipitation method followed by a hydrothermal treatment in the presence of PVP as surfactant. The synergic effect between MgO and SiO2 leading to the various characteristic and catalytic performance during propane steam reforming was investigated in detail. The results showed that 15 wt% NiO-0.5MgO–SiO2 catalyst possessed the highest catalytic activity (68.9% conversion for C3H8 at 550 °C) with a negligible amount of carbon formation after 20 h of reaction duration. This superior catalytic performance can be attributed to the enhanced basicity strength along with strong metal-support...
Preparation of mesoporous nanostructure NiO–MgO–SiO2 catalysts for syngas production via propane steam reforming
, Article International Journal of Hydrogen Energy ; Volume 45, Issue 11 , 2020 , Pages 6604-6620 ; Kazemeini, M ; Farhadi, F ; Rezaei, M ; Keshavarz, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this research, the propane steam reforming (PSR) as a promising alternative route over a mesoporous NiO–MgO–SiO2 catalyst to produce syngas (SG) was undertaken. This catalyst was prepared using a co-precipitation method followed by hydrothermal treatment. The influence of such catalyst preparation factors as the hydrothermal time and temperature, pH and calcination temperature on the physicochemical characteristics of the prepared samples were examined. Next, these materials were characterized through the BET-BJH, XRD, TPR, and FTIR analyses. The thermal stability of this catalyst was tested through the TGA and DTA techniques. Furthermore, the deactivation of the calcined catalysts at...
Evaluation of a polymer-steel laminated sheet composite structure produced by friction stir additive manufacturing (FSAM) technology
, Article Polymer Testing ; Volume 90 , 2020 ; Khodabakhshi, F ; Simchi, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Laminated polymer-steel composites are promising layered materials for practical applications in the automotive industry considering their superior crush resistance capacity in terms of enhanced damping potential. In this research, the sheet lamination (SL) route of friction stir additive manufacturing (FTAM) technology was implemented for the production of a poly-methyl-methacrylate (PMMA) polymer matrix composite structure as reinforced by textile stainless steel layers, and feeding of PMMA granulates inside the stirred region. Layers bonding and the soundness of composite formation during fabrication of the laminated structure were studied. Possible chemical interactions between the steel...
Developing a new superhydrophilic and superoleophobic poly(4-(1-vinyl-1H-imidazol-3-ium-3-yl) butane-1-sulfonate): vinyl imidazole@Perfluorooctanoic acid@SiO2 coated stainless steel mesh for highly efficient, stable, and durable oil/water separation
, Article Journal of Coatings Technology and Research ; 2020 ; Siavash Moakhar, R ; Amirpoor, S ; Azad, M ; Dolati, A ; Sharif University of Technology
Springer
2020
Abstract
The design and development of efficient approaches for water–oil separation have had widespread interest. Most previously introduced techniques and materials used for development of the successful separation of oily wastewater could not answer all the desired demands, such as being efficient and environmentally and economically friendly. Therefore, in seeking a novel method capable of answering these expectations, surfaces with special wettability were introduced. A novel, reusable, and recyclable superhydrophilic and superoleophobic poly(Vsim-Vim)@PFOA@SiO2 nanocomposite-coated stainless steel mesh was synthesized through a facile preparation process. Since the most important factors of...
An optimal analytical solution for maximizing expected battery lifetime using the calculus of variations
, Article Integration ; Volume 71 , March , 2020 , Pages 86-94 ; Ejlali, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
The exponential growth in the semiconductor industry and hence the increase in chip complexity, has led to more power usage and power density in modern processors. On the other hand, most of today's embedded systems are battery-powered, so the power consumption is one of the most critical criteria in these systems. Dynamic Voltage and Frequency Scaling (DVFS) is known as one of the most effective energy-saving methods. In this paper, we propose the optimal DVFS profile to minimize the energy consumption of a battery-based system with uncertain task execution time under deadline constraints using the Calculus of Variations (CoV). The contribution of this work is to analytically calculate the...