Sharif Digital Repository

Stoichiometric hydroxyapatite (HA) powder was synthesized by wet method using orthophosphoric acid and calcium hydroxide, as raw materials. In this regard, the time-depending changes of the precipitated particles and effects of heating on them were investigated. The as-precipitated and heated powder samples were examined using field emission electron microscopy (FESEM), XRD and Raman spectroscopy methods. The results revealed that the morphology and size of the precipitated particles change in each stage of the process. After drying, these nanoparticles tend to form small agglomerates. © 2003 Elsevier Science B.V. All rights reserved  

The precipitation process considered here, involved the addition of orthophosphoric acid solution to a calcium hydroxide solution. Several parameters such as the effects of atmosphere controlling, pH, adding extra acid solution, the amount of stirring speed, and post-chemical treatment were studied. In order to study the thermal stability of synthesised powders, they were sintered for 2 h at 1200 °C and the as-precipitated and sintered powder samples were examined using SEM, XRD, FTIR and ICP methods. The results clearly revealed that the final precipitated powder is hydroxyapatite (HA) with good purity, stoichiometry and successful thermal stability. SEM high magnification micrographs... 

A model for prediction the stress-strain behavior of particulate composite over wide ranges of filler concentration and composite deformation has been developed through combination of Anderson's and Yilmizer's model. The constitutive equations are extracted from first law of thermodynamic and nonlinear dilatational effects which are produced by filler-matrix debonding process. In addition to nonlinear behavior that has been resulted by filler-matrix debonding and was presented by Yilmizer, the formation and growing of void or cavitations has been also introduced in this model, whereas Anderson's model, most important reason for deviation of linear behavior is filler-matrix debonding and has... 

We study active galactic nucleus (AGN) activity in the fossil galaxy cluster RX J1416.4+2315. Radio observations were carried out using the Giant Metrewave Radio Telescope at two frequencies, 1420 and 610 MHz. A weak radio lobe that extends from the central nucleus is detected in the 610 MHz map. Assuming the radio lobe originated from the central AGN, we show that the energy injection into the intergalactic medium is only sufficient to heat up the central 50 kpc within the cluster core, while the cooling radius is larger (∼130 kpc). In the hardness ratio map, three low energy cavities have been identified. No radio emission is detected for these regions. We evaluated the power required to... 

Support vector machines (SVMs) were used as a novel learning machine in the authentication of the origin of salmon. SVMs have the advantage of relying on a well-developed theory and have already proved to be successful in a number of practical applications. This paper provides a new and effective method for the discrimination between wild and farm salmon and eliminates the possibility of fraud through misrepresentation of the country of origin of salmon. The method requires a very simple sample preparation of the fish oils extracted from the white muscle of salmon samples. 1H NMR spectroscopic analysis provides data that is very informative for analysing the fatty acid constituents of the... 

In CHES 2008 a generic side-channel distinguisher, Mutual Information, has been introduced to be independent of the relation between measurements and leakages as well as between leakages and data processed. Assuming a Gaussian model for the side-channel leakages, correlation power analysis (CPA) is capable of revealing the secrets efficiently. The goal of this paper is to compare mutual information analysis (MIA) and CPA when leakage of the target device fits into a Gaussian assumption. We first theoretically examine why MIA can reveal the correct key guess amongst other hypotheses, and then compare it with CPA proofs. As our theoretical comparison confirms and shown recently in ACNS 2009... 

Sensor network deployment is very challenging due to hostile and unpredictable nature of usage environments. In this letter, we propose two methods for the self-deployment of mobile sensors. The first one is a randomized solution that provides both simplicity and applicability to different environments. Inspired by simulated annealing, it improves both speed and energy conservation of the deployment process. The other method is suggested for environments where sensors form a connected graph, initially. At the cost of this extra limitation, we gain considerable improvements. © 2006 IEEE  

On July 24th, 2010, several explosions and fires devastated a hydrocarbon processing plant in Kharg Island, Iran. Four workers were killed and many others were severely injured. The plant became out of service for 80 days. The way the accident happened and its sequence was representing as a domino accident. In this paper, events leading up to the disaster have been analyzed in details. Graphic presentation techniques such as Fish Bone Analysis and Event Sequence Diagram (ESD) have been utilized to enhance the understanding of the accident mechanism. Finally major lessons learnt from this domino accident have been addressed  

Anchoring of copper sulfate in layered poly(imidazole-imidazolium) coated magnetic nanoparticles provided a highly stable, active, reusable, high loading, and green catalyst for the click synthesis of 1,2,3-triazoles via a one-pot cycloaddition of alkyl halide, azide, and alkyne (Cu-A3C). The catalyst was characterized by FTIR, TGA, TEM, SEM, XRD, EDAX, VSM and AAS. High selectivity, broad diversity of alkyl/benzyl bromide/chloride and alkyl/aryl terminal alkynes, and good to excellent yields of products were obtained using 0.7 mol% catalyst. The catalyst was readily recovered and reused up to 6 times without significant loss of activity  

A heterogeneous polymeric catalyst was synthesized by immobilization of copper ions in a graphene oxide/poly(vinyl imidazole) nanocomposite. This catalyst has proven to be highly active in a practical protocol for click synthesis of 1,2,3-triazole via one-pot three-component cycloaddition of halides, terminal alkynes and sodium azide. The reaction was carried out in water medium and good to excellent yields of products were obtained using only 1.0 mol% of catalyst. The catalyst can be readily recovered and reused eight times under the described reaction conditions without significant loss of activity. The reaction also proceeded well with only 0.002 mol% of catalyst, which shows the high... 

A multi-layered catalyst based on poly(imidazole/imidazolium) and graphene oxide, with high loading capacity for immobilization of palladium nanoparticles was prepared. The catalyst was proven to be highly efficient for reduction of nitroarenes and also for Heck reaction with the use of only 0.1 mol% of the catalyst. The reduction of nitroarenes and Heck reaction were performed in water medium and excellent yields of products were achieved. The synthesized catalyst was readily recovered and reused for up to 10 subsequent runs without significant loss of activity  

A heterogeneous recoverable catalyst was prepared via the complexation of palladium onto the surface of magnetic nanoparticles coated by a poly(1-vinyl imidazole) brush. The stable, active and reusable catalyst was proven to be highly active in aerobic oxidation of primary and secondary alcohols with excellent yields. Only 0.1 mol% of the catalyst was used to oxidize 1 mmol of primary and secondary alcohols. The catalyst was readily recovered and reused up to 10 times under the described reaction conditions without significant loss of activity  

In this paper, copper oxide nanoparticle was synthesized, and its surface was modified using N-(2-aminoethyl)-3-(trimethoxysilyl)propylamine. The bi-amino surface functionalized nanoparticle (BASFN) was used to remove anionic dyes from single and binary systems. The scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDAX) and X-ray diffraction were used to characterize the nanoparticle. Direct Red 80 (DR80) and Direct Green 6 (DG6) were used as anionic dyes. The effect of adsorbent dosage, dye concentration and pH on dye removal was evaluated. Kinetic of dye adsorption on BASFN followed pseudo-second order. The results... 

Despite the great promise of hybrid solar-wind-biomass energy systems to power future sustainable cities, complexities associated with their optimal planning and design limit their wide-scale implementation. This study provides a novel systematic framework to identify optimal hybrid renewable solutions for urban areas at neighborhood scales. In particular, we examine the role of economies of scale in the techno-economic feasibility and environmental performance of hybrid renewable systems. For demonstration, we assess the impact of the economics of scale (at the neighborhood scales of 1/500, 1/250, and 1/100 of the city's electrical load) on the life-cycle costs of optimal hybrid renewable... 

This article presents the design and implementation of a microcontroller-based system for the automatic movement of control rods in nuclear reactors of either power or research types. This system is controlled automatically, is linked to a personal computer system, and has manual controlling ability as well. The important features of this system are: automatic scram of the control rods, activation of alarm in emergency situations, and the ability to tune the control rod movement course both upwards and downwards. In this system, a small tank has been improvised as a coolant reservoir for pool type reactors such as Tehran Research Reactor and its water level is continuously adjusted by... 

A thorough understanding of determining factors in angiogenesis is a necessary step to control the development of new blood vessels. Extracellular matrix density is known to have a significant influence on cellular behaviors and consequently can regulate vessel formation. The utilization of experimental platforms in combination with numerical models can be a powerful method to explore the mechanisms of new capillary sprout formation. In this study, using an integrative method, the interplay between the matrix density and angiogenesis was investigated. Owing the fact that the extracellular matrix density is a global parameter that can affect other parameters such as pore size, stiffness,... 

We consider a group of m trusted and authenticated nodes that aim to create a shared secret key K over a wireless channel in the presence of an eavesdropper Eve. We assume that there exists a state dependent wireless broadcast channel from one of the honest nodes to the rest of them including Eve. All of the trusted nodes can also discuss over a cost-free, noiseless and unlimited rate public channel which is also overheard by Eve. For this setup, we develop an information-theoretically secure secret key agreement protocol. We show the optimality of this protocol for "linear deterministic" wireless broadcast channels. This model generalizes the packet erasure model studied in literature for... 

In this paper, we propose a novel method for extracting fiducial points (FPs) of the beats in electrocardiogram (ECG) signals using switching Kalman filter (SKF). In this method, according to McSharry's model, ECG waveforms (P-wave, QRS complex and T-wave) are modeled with Gaussian functions and ECG baselines are modeled with first order auto regressive models. In the proposed method, a discrete state variable called “switch” is considered that affects only the observation equations. We denote a mode as a specific observation equation and switch changes between 7 modes and corresponds to different segments of an ECG beat. At each time instant, the probability of each mode is calculated and... 

Land use regression (LUR) has not been applied thus far to ambient alkylbenzenes in highly polluted megacities. We advanced LUR models for benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene (BTEX), and total BTEX using measurement based estimates of annual means at 179 sites in Tehran megacity, Iran. Overall, 520 predictors were evaluated, such as The Weather Research and Forecasting Model meteorology predictions, emission inventory, and several new others. The final models with R2 values ranging from 0.64 for p-xylene to 0.70 for benzene were mainly driven by traffic-related variables but the proximity to sewage treatment plants was present in all models indicating a major local... 

We consider a group of m trusted and authenticated nodes that aim to create a shared secret key K over a wireless channel in the presence of an eavesdropper Eve. We assume that there exists a state-dependent wireless broadcast channel from one of the honest nodes to the rest of them including Eve. All of the trusted nodes can also discuss over a cost-free, noiseless and unlimited rate public channel which is also overheard by Eve. For this setup, we develop an information-theoretically secure secret key agreement protocol. We show the optimality of this protocol for 'linear deterministic' wireless broadcast channels. This model generalizes the packet erasure model studied in the literature...