Sharif Digital Repository

Fast-swelling highly porous superabsorbent hydrogels were synthesized through a rapid radical polymerization under normal atmospheric conditions. To synthesize a biopolymer-based superabsorbent hydrogel, 2-hydroxyethyl acrylate (HEA) and sodium acrylate (AANa) were grafted on the starch backbone in an aqueous solution. The graft copolymerization reaction was carried out in the presence of ammonium persulfate (APS) as an initiator and N, N′-methylenebisacrylamide (MBA) as a cross-linker in a homogeneous medium. The chemical structure of the hydrogels was confirmed by FT-IR spectroscopy and thermogravimetric analysis (TGA). The morphology of the samples was examined by scanning electron... 

A novel approach was developed to prepare a highly porous hydrogel with superior salt- and pH-resisting properties. According to this method, synthetic comonomers, i.e. acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), were polymerized and crosslinked in the presence of hydrolyzed collagen as a natural backbone. The characterizations of hydrogels were investigated by swelling experiment, Fourier transform infrared (FT-IR) spectroscopy, acid-base titration and thermogravimetric analysis (TGA). Morphology of the samples was examined by scanning electron microscopy (SEM). Experimental results indicate that the hydrogel has an absorbency of 360 and 73-82 g/g for distilled... 

Temperature-sensitive hydrogels based on N-t-butylacrylamide (TBA), acrylamide (AAm), and sodium alginate were prepared by free radical polymerization method. Methylenebisacrylamide (MBA) and amonium persulfate (APS) were applied as water soluble crosslinker and initiator, respectively. The chemical structure of the hydrogels was confirmed by FT-IR spectroscopy and thermogravimetric analysis (TCA) methods. Morphology of the samples was examined by scanning electron microscopy (SEM). By changing the initial TBA/AAm mole ratios, hydrogels with different swelling properties were obtained. The rate parameters were found to be 2.0, 2.4, and 3.5 min for the superabsorbents with AAm/TBA weight... 

In some industries such as the consumable product industry because of small differences between products made by various companies, customer loyalty is directly related to the availability of products required at that time. In other words, in such industries demand cannot be backlogged but can be totally or partly lost. So companies of this group use make-to-stock (MTS) production policy. Therefore, in these supply chains, final product warehouses play a very important role, which will be highlighted by considering the demand uncertainty as it happens in real world, especially in the consumable product industries in which demand easily varies according to the customer's taste variation,... 

Security is a critical and vital task in WSNs. Recently, key management as the core of a secure communication has received lots of attention, but in most of the proposed methods security has been compromised in favor of reducing energy consumption. Consequently, perfect resiliency has not been achieved by most of the previous works. Hostile environment, ability of adversary to capture the nodes, and dead nodes with sensitive data scattered in the region, calls for a more secure and yet practical method. This paper proposes a novel authentication scheme based on broadcast messages from BS to improve security of key management system. Through simulation it is shown that energy consumption of... 

Event cameras are bio-inspired sensors. They have outstanding properties compared to frame-based cameras: high dynamic range (120 vs 60), low latency, and no motion blur. Event cameras are appropriate to use in challenging scenarios such as vision systems in self-driving cars and they have been used for high-level computer vision tasks such as semantic segmentation and depth estimation. In this work, we worked on semantic segmentation using an event camera for self-driving cars. i) This work introduces a new event-based semantic segmentation network and we evaluate our model on DDD17 dataset and Event-Scape dataset which was produced using Carla simulator. ii) Event-based networks are robust... 

Purpose: Different studies have analyzed the relationship between organizational learning (OL) and innovation performance (IP). However, the question of how innovation culture (IC) affects the relationship between OL and IP remains unexplored. This study aims to examine the impact of IC on the relationship between OL and various dimensions of IP, including product, process and objective innovation. Design/methodology/approach: A research model was developed and performed based on the relevant literature in the field of OL, IC and IP. The hypotheses are tested with the data collected from companies operating in an intensive knowledge-based industry. Findings: Based on the results of 625... 

Sleep study is very important in the health since sleep disorders affect the productivity of individuals. One of the important topics in sleep research is the classification of sleep stages using the electroencephalogram (EEG) signal. Electrical activities of brain are measured by EEG signal in the laboratory. In real-world environments, EEG signal is also used in portable monitoring devices to analyze sleep. In this study, we propose an efficient method for classification of sleep stages. EEG signals are examined by a new model from autoregressive (AR) family, namely logistic smooth transition autoregressive (LSTAR) to study sleep process. In contrast to the AR model, LSTAR is a non-linear... 

Attention deficit hyperactivity disorder (ADHD) is a common brain disorder among children. It presents various symptoms, hence, utilizing the information obtained from functional magnetic resonance imaging (fMRI) time-series data can be useful. Finding functional connections in typically developed control (TDC) and ADHD patients can be helpful in classification. The aim of this paper is to present a multifold method for the study of fMRI data to diagnose ADHD patients. In the proposed method, first, by applying the Stockwell transform (ST), we obtain detailed information about the time-series of the region of interests (ROIs) in the time and frequency domains. ST provides information about... 

Various challenging pollutants are produced in the environment by organic materials of diverse industries including leather, paint, and textile. Nowadays, it is vital to develop efficient manners regarding the fundamental issues and removing pollutants. Such pollutants can be effectively removed from the environment through heterogeneous catalysts. Recently, a huge deal of interest has been attracted by hydrogel-based metal catalysts as heterogeneous and efficient catalysts. In this regard, silver with its unique features is suitable for environmental remediation. Hence, the present review deals with summarizing the present advances in the synthesis of silver-based hydrogel catalysts, as... 

The influence of Zr 2 on the crystallization behavior, microstructure, and machinability of SiO 2-Al 2O 3-MgO-K 2O-B 2O 3-F glasses was investigated. The crystallization of the glass-ceramic was markedly affected by addition of ZrO 2. These glasses crystallize more rapidly. The number of mica crystals increases, whereas the size of the mica crystals decreases drastically. Machining of these glass-ceramics was found to be good, as confirmed by a drilling test using conventional steel tools. Such mechanical properties are attributable to the microstructure of these glass-ceramics. Very fine crystals are homogeneously distributed in glass matrix  

Formation of machinable glass-ceramic in the system MgO-SiO 2-Al2O3-K2O-B2O 3-F with and without addition of MgF2 has been investigated. Crystallization of glass sample was done by controlled thermal heat treatment at nucleation and crystallization temperatures. The results showed that MgF2 in high concentration had a synergistic effect and enhanced the formation of interlockedmica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of MgF2 were changed in the range of 548-752 kJ/mol  

Physical properties of low cement castable containing 22 wt.% Al 2O3-rich MgO-Al2O3 spinel and 1.7 wt.% CaO with addition of polyacrylates, castament FS20, TPP and citric acid were investigated. Results showed castables including castament FS20 have higher flow values and better final properties comparing with castables including Darvan 7S and TPP. Also in this study we investigated the effect of addition of microsilica up to 4 wt.% on the properties of alumina-spinel castables. Microsilica is the finest particles in the system and due to suitable distribution of microsilica among other particle the open porosity reduced and mechanical strength increased. Slag penetrations resistance... 

Different concentrations of CaF2 were incorporated in mica glass-ceramics to evaluate their effects on the crystallization and microstructure. The kinetics of phase transformations, and the microstructures of the final crystalline phase were found to be dependent on the concentration of nucleation agents. The results showed that CaF2 in high concentration had a synergistic effect and enhanced the formation of interlocked mica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of CaF2 were changed in the range of 419-747... 

Chalcopyrite CuAlS2 nanoparticles were synthesized with polyol method. The solvothermal with autoclave nanoparticles synthesized are investigated. The amount and temperature of reducer, the solvent of salts could be important parameters that were studied. The nanoparticles were synthesized with CuCl, AlCl3 and thiourea (SC(NH2)2) as precursors, diethylene glycol ((CH2CH2 OH)2O) and polyethylene glycol 600 (HO(C2H4O)nH) as solvent and capping agent respectively, and ammonia (NH4OH) as reducing agent. The parameters of synthesis were studied by X-Ray diffraction (XRD) for analysis of structure, scanning electron microscope (SEM) for morphology and by ultraviolet-visible (UV-VIS)... 

Formation of transparent glass-ceramic in the system MgO-SiO 2-Al 2O 3-K 2O-B 2O 3-F with and without addition of LiF and NaF has been investigated. Crystallization of glass-sample was conducted by controlled thermal heat-treatment, at determined nucleation and crystallization temperatures. In this regard, the effects of addition of LiF and NaF were investigated on the crystallization behavior and transparency of the samples. Low transmission (less than 80% at 600. nm) was observed in the basic composition (K).The addition of NaF and LiF caused more intense phase separation in the system. The results indicated that the glass-ceramic can remain transparent if fine grains with nano size are... 

A holding or a multi-business corporate seeks to coordinate its supply for minimum overall costs. A Corporate Supply Optimizer (CSO), as a central entity taking advantage, of the notion of flow networks, gathers necessary operational information from members of the corporate supply chain. The CSO then guides supply chain members on ordering decisions for a minimum overall cost for the entire supply chain. Its computational engine models the entire supply chain with multiple members in four stages to satisfy customer demand. The CSO seeks a solution with minimum total costs, unlike noncooperative supply chains where individual members compete, to optimize, their local costs. The existing...