Sharif Digital Repository

Hybrid-reinforced metals are novel composite materials in which nano-phases including nanoparticles and nanotubes/nanosheets are used simultaneously to reinforce metals or alloys to enhance physical, mechanical, wear and other properties. In this research, Cu/(CNT-SiC) hybrid nanocomposite was synthesized using flake powder metallurgy and spark plasma sintering method and the effects of hybrid reinforcements on microstructural, wear and corrosion properties of the developed material were investigated and compared with those of copper. Microstructural characterization showed reduction of average grain size from 419 to 307 nm and increase of low angle grain boundaries with the introduction and... 

LiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered as a promising cathode for Li-ion batteries (LIBs) due to its high electrochemical capacity and low cost; however, poor cycling stability is one of the main restricting factors in industrial applications of the NCM811 cathode material. Notably, the capacity fading and low structural stability of NCM811 are intensified at elevated temperatures. ZrO2- and composite rGO-ZrO2-coated NCM811 were fabricated by a facile wet chemical method and evaluated at 25 and 55 °C to overcome these impediments. The ZrO2 coating provides superior cycling and thermal stability and perfectly protects the cathode active material from deleterious side reactions, and... 

Wireless networks with the shared media require Medium Access Control (MAC) protocol that provides contention resolution mechanism. The design of MAC protocol in underwater sensor networks is a challenging issue because of limited energy source and high propagation delay. The most important goal of the MAC design for underwater sensor networks is to resolve data packet collision efficiently with respect to energy consumption. So, selection of MAC protocol is an important task because it has significant impact on the system efficiency. A suitable MAC protocol must consider some factors such as fairness, energy consumption, latency and throughput based on various applications. The bandwidth in... 

Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of... 

Solid waste is often buried in landfills isolated with a bentonite-based clay barrier to guarantee the high quality of groundwater. As the efficiency of clay barriers is highly dependent on solute concentration, this study aims to modify membrane efficiency, effective diffusion, and hydraulic conductivity of bentonite-based clayey barriers exposed to saline environments for numerical investigation of solute transport in such barriers. Therefore, the theoretical equations were modified as a function of solute concentration instead of constant values. First, a model was extended for membrane efficiency as a function of void ratio and solute concentration. Second, an apparent tortuosity model... 

In this work, the effects of rolling parameters, cooling media, and deformation path on mechanical properties and aging behavior of hot-rolled AA2017 were studied. First, hot-rolling experiments were conducted under different working conditions, and the rolled strips were then aged at room temperature for up to 57 days during which hardness and tensile tests were carried out to record the changes in the mechanical properties of the alloy. Furthermore, due to the importance of static recrystallization on subsequent aging behavior, the rate of recrystallization was also computed. To this end, a mathematical model was developed to predict thermomechanical responses during hot rolling using the... 

In the context of the care crisis in modern medicine, the existential needs of patients are not sufficiently satisfied. One idea to address the crisis is that physicians should be educated to be virtuous. This suggestion is inadequate because it does not take into account the role of (non-)human factors, including technologies. The paper focuses on online caring forums, arguing that they are technological factors that can play the role of “focal things”, in which the members gather together to do a care-related focal practice. We study empirically the online forums of Ninisite, a popular Persian website on pregnancy, childbirth, and parenting, and suggest that these forums shape focal... 

Background and objective: L-Sorbose, as a precursor of ascorbic acid, can be biologically produced using Gluconobacter oxydans. The aim of this study was to optimize production of L-Sorbose by controlling concentration of the substrates and starter cultures. Material and methods: In this study, effects of three various fermentation parameters on the concentration of L-sorbose were assessed using fermenter (28°C, 1.4 vvm) and response surface methodology. These parameters included quantities of D-sorbitol (120-180 g lDw-1) (Deionized water) and yeast extract (6-18 g lDw-1) and inoculum/substrate ratios (5-10%). Results and conclusion: Results showed that the fitted model with high values of... 

This paper proposes an innovative robust-fuzzy method for multi-objective, multi-period supplier selection problem under multiple uncertainties. This approach integrates robust optimization and fuzzy programming. Uncertain parameters are modeled as random variables that take value within a symmetrical interval. However, due to the complexity or ambiguity of some real world problems and especially the nature of some of the available input data, the length of interval is also highly uncertain. This ambiguity motivated us to present a new approach, which could be applicable to multiple uncertainties conditions. Thus, in our approach, the half-length of these intervals is also represented by... 

Thermal performance of a novel sintered wick heat pipe was investigated in this study. Two types of sintered wick heat pipes were fabricated and tested at different filling ratios of water, and their thermal resistances in different modes were compared. In the first type, wick was sintered annularly (conventional type), and in the other one (novel type of sintered wick) it was sintered only in one third of cross-section. Results showed that dry-out occurs at higher heat input by an increase in the filling ratio. Moreover, the best filling ratio is 20% for both heat pipes. Thermal resistances of the partly sintered wick heat pipe are approximately 28%, 17% and 47% lower than those of the... 

Heat pipes are important cooling devices that are widely used to transfer high heat loads with low temperature differences. In this paper, thermal performance of a novel type of sintered-wick heat pipe, namely, partly sintered-wick heat pipe, was investigated. The heat pipe was filled with degassed water and acetone, as working uids, and effects of filling ratio, orientation, and heat inputs were tested. Moreover, conditions at which dryout occurred were presented. The results showed that the best filling ratio for both working uids is about 20%. The heat pipe filled with water has better thermal performance than that filled with acetone; thus, the thermal resistances of the 20% water-filled... 

In this paper, a novel moving object modeling suitable for multicamera correspondence is introduced. Taking into consideration the color and motion features of foreground objects in each independent video stream, our method segments the existing moving objects and constructs a graph-based structure to maintain the relational information of each segment. Using such graph structures reduces our correspondence problem to a subgraph optimal isomorphism problem. The proposed method is robust against various resolutions and orientations of objects at each view. Our system uses the fuzzy logic to employ a human-like color perception in its decision making stage in order to handle color inconstancy... 

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions, and then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results of the model indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are...