Sharif Digital Repository

The paper deals with the investigation of nonlinear static and dynamic behaviors of electrostatically actuated carbon nanotubes with different geometries and boundary conditions. The deflection and pull-in properties are studied in detail in the presence of DC and combined DC+AC electrostatic voltages accompanying the interatomic interactions. The considered nano system can be applied in a wide range of nanoelectronics devices such as nano switches, nano resonators, nano transistors, nano capacitors and random access memories. Moreover, a useful mathematical model of the nano sensor application of the studied nano system to sense the stiffness of the nano particles is presented  

The effect of carbon and silicon on the occurence of dynamic recrystallization as well as on the flow stress of steel was investigated. For this purpose, three grades of steels including low carbon, medium carbon and high silicon low carbon steel were examined. Single hit experiments at temperatures of 900-1200 °C and strain rate of 0.01-2 s-1 were performed to determine the phase transformation kinetics. Different socking times were utilized to detect the effect of initial austenite grain size on the kinetics of dynamic recrystallization and flow behavior of the steels. It was found that increasing the carbon content leads to a higher rate of dynamic recrystallization at high temperatures... 

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacrylamide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator andN,N′-methylenebisacrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g-PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-polymethacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the... 

In this study, the effect of nanoclay on the rheological and morphological properties of polyamide 6 (PA6)/acrylonitrile-butadiene-styrene (ABS) blends was investigated. The scanning electron microscopy micrographs showed that with increment in the nanoclay content, the dispersed phase droplets size and their polydispersity index decreased, and the finer and more uniform dispersed phase was obtained. The transmission electron microscopy micrographs of nanocomposites indicated well-dispersed nanoclay tactoids in the polymer matrix produced by exfoliation of the nanoclay in the polymeric blends. Dynamic strain sweep experiments showed that the extent of the linear viscoelastic region is... 

Purpose: The purpose of this paper is to develop a behavioral mode (as opposed to a numerical one), which considers any parasitic behavior as an indication of a potentially contributing element in the overall system deficiency. Design/methodology/approach: Similar to that associated with general systems theory, this paper concentrates on the organization and functions of natural systems which exhibit a loss of efficiency due to some general parasitic behavior. Based on the philosophy of "Bionics", it clarifies the functional architecture and root-cause of this behavior in living systems in order to model subsystems characteristics which exhibit the same behavior in a complex system. In... 

FEM study is carried out for predicting the behavior of the short fiber composites in the steady state creep with application in optoelectronic and photonic devices. The study on the creep behavior is necessary in order for failure, fracture, fatigue, and creep resistance of the short fiber composites. In this article, the creep behavior of the short fiber composite is predicted under tensile axial loading by the numerical method. One of the significant applications of the work is in the short fiber composite designing and optimizing. Also, the available experimental results [10] are used for the FEM simulation  

In this research, cold compaction behavior and pressureless sinterability of WC, WC-10%wtCu and WC-30%wtCu powders were investigated. WC and WC/Cu powders were milled in a planetary ball mill for 20h. The milled powders were cold compacted at 100, 200, 300 and 400 MPa pressures. The compressibility behavior of the powders was evaluated using the Heckel, Panelli-Ambrosio and Ge models. The results showed that the PanelliAmbrosio was the preferred equation for description the cold compaction behavior of the milled WC and WC-30%wtCu powders. Also, the most accurate model for describing the compressibility of WC-10%wtCu powders was the Heckel equation. The cold compacts were sintered at 1400oC.... 

In this paper the principles of submarine dynamics modeling have been gathered as distinguished steps. Of course, in these few pages the details cannot be discussed and the formulae cannot be proved. The interested reader has to study more detailed references to attain a better perception of the subject. The paper, in addition to gathering and editing principles, has gone through offering simplifications in each part of modeling. Such simplifications will result in a good approximation of submarine dynamic behavior, which is exactly complicated in reality. In higher levels of modeling each part can be completed and details can be processed  

The Ni-base superalloy GTD-111 is employed in high-power stationary gas turbines because of its high temperature strength and oxidation resistance. The temperature dependence of the tensile behavior of GTD-111 has been studied by tensile tests in the temperature range of 25-900°C with a constant strain rate of 10-4s-1. The results showed an abnormal tensile property variation with increasing temperature. The yield strength decreased slightly with temperature up to about 650°C and then increased between 650 and 750°C. Above 750°C, a rapid decrease in the yield strength was found. The tensile strength showed a similar behavior except for its maximum that occurred at 650°C. The elongation... 

In this paper, a new approach for behavior based architecture in mobile robot navigation in unknown environments is presented. In this approach, the general actions of a mobile robot are classified into three thoroughly separated tasks. Then, an individual fuzzy controller is designed and implemented for each task (behavior). Finally, a behavior selector is designed to switch between the robot tasks (behavior patterns) and manage all separated fuzzy controllers to navigate a mobile robot in a fully unknown environment. Another case considered in this paper is to test and examine the proposed algorithm in an environment including the static and dynamic (moving) obstacles. The most difficult... 

The influence of manufacturing parameters such as compacting pressure, heat treatment and microstructure on the static and dynamic properties of Fe-1.75 Ni-1.5 Cu-0.5 Mo-0.6 C was investigated. Wear and fatigue tests were carried out on reciprocate wearing and tension compression mode, respectively. The results show that delamination wear mechanism of sintered steel is similar to that of conventional wrought or cast materials. But, in sintered material, open porosity acts as sites of generation and collection of wear debris or formation of subsurface cracks. Wear rate is decreased and fatigue strength is increased by heat treatment. © 2002 Elsevier Science Ltd. All rights reserved  

In the published article, there was an error regarding the affiliations for Saba Saneinia. As well as having affiliation 1, she should also have Key Laboratory of Immersive Media Technology (Anhui Xinhua Media Co, Ltd.), Ministry of Culture and Tourism, Hefei, China. In the published article, there was an error regarding the affiliations for Rongting Zhou. As well as having affiliations 2, he should also have Key Laboratory of Immersive Media Technology (Anhui Xinhua Media Co, Ltd.), Ministry of Culture and Tourism, Hefei, China. In the published article, there was an error regarding the affiliations for Fahad Asmi. As well as having affiliations 2, he should also have Key Laboratory of... 

Insider threat is a significant security risk for organizations and hard to detect. Most introduced detection methods need contextual data entries about users, or preprocessed user activity logs to detect insider threats which it is costly and time-consuming. In this paper, we introduce a behavior analysis method that learns its context and detects multiple types of insider threats from raw logs and network traffic in real-time. This method, named XABA, learns user roles and exclusive behaviors, through analyzing raw logs related to each network session of the user. Then it checks for some abnormal patterns, and if so, triggers the appropriate alert. XABA is implemented on the big-stream... 

The virtual reality (VR) applications in entertainment and tourism industry have become growingly intense among generation Z. Interestingly, some pilot research on tourism studied concluded the positive impact of its flow experience on adoption of VR tourism, which is also driving the risk of immersive addictive. In the context of tourism and information and communication technology (ICT)-based innovation, there is a lack of immersive addictive behavior (IAB)-related literature. In addition, during the currently ongoing pandemic crisis, VR technology has gained particular importance in the tourism industry among generation Z. The present venture underlines the mechanism of IAB, investigates... 

Despite numerous studies, there is a lack of fundamental understanding about the displacement behavior of surfactant-crude oil systems under the influence of different fractures' geometrical properties in five-spot systems. In this work, a series of flow visualization experiments were carried out on one-quarter five spot glass micromodels at various fractures' geometrical properties, such as fracture density and fracture continuity, under oil-wet condition. The influences of injection of Linear Alkyl Benzene Sulfonate and Sodium Dodecyl Sulfate surfactants as well as the effect of fracture geometrical parameters, on macroscopic and microscopic displacement behavior have been investigated.... 

Good knowledge of fracture parameters and cracking behavior of self-compacting concrete (SCC) from early ages until the SCC becomes mature plays an important role in design of SCC structure and also in evaluation of durability and consequently prevention of damage. In this paper, variation of fracture parameters and corresponding ductility behavior of SCC at different ages (e.g. 3days, 7days, 28days and 90days) for SCC mixes with w/c ratios of 0.45 and 0.65 have been experimentally studied. To do so, three-point bending tests were carried out on 120 notched beams. Then, size effect method (SEM) and work of fracture method (WFM) were applied to interpret the results. The results of analyses... 

Dimethyl ether (DME) as a clean fuel seems to be a superior candidate for high-quality diesel fuel in near future. In this study, a comprehensive three-dimensional dynamic heterogeneous model developed to simulate the flow behavior and catalytic coupling reactions for synthesis of the DME from hydrogenation of the CO and CO2, dehydration of methanol to dimethyl ether and water gas shift reaction in a fixed bed reactor. For this purpose, a CFD simulation was articulated where the standard k-ε model with 10% turbulence tolerations implemented. Then the concentration and temperature profiles along the reactor were determined. It was revealed that under conditions considered, a single phase...