Sharif Digital Repository

In the current investigation, four novel donoracceptor type organic dyes including (DPA-Ba, DPA-Hy, DPA-Rh, DPA-Cy), are proposed and their photophysical and electrochemical properties as well as dye-sensitized solar cell performance are systematically investigated. Among these dyes diphenylamine is utilized as an-electron donor while barbituric acid, hydantoin, rhodanine-n-acetic acid and cyano acetic acid, are proposed as anchoring groups as dye-sensitized solar cells (DSSCs). The synthesized dyes are characterized using FT-IR, NMR, mass spectrometry, absorbance and electrochemical measurements. The photophysical, electrochemical and photovoltaic properties of the solar cells based on... 

Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of... 

With the development of science and technology through social networks, the process of diffusion has become a controversial subject. In social networks, the process of diffusion is transmitted from one individual to another. The influence maximization problem, in which at least k nodes are chosen as the initial nodes of the spreader in the smallest amount of time, is one of the most critical aspects of the diffusion process. Furthermore, the initial nodes in the social network should generate the most influence on the other nodes in the network. However, in the algorithms proposed to solve the problem of influence maximization, the real-world factors which affect the influence probability in... 

Carbazole is an alternant polycyclic aromatic hydrocarbon consisting of three fused rings with a large, aromatic system, containing nitrogen atom showing extensive electron delocalization. In this work, carbazole applied as π-conjugated bridge to construct electron donor–π–electron acceptor (D–π–A) organic dyes, where barbutiric acid and thiazolidine-2,4-dione as electron acceptor. The effects of these three acceptors and length of alkyl on the performance of the DSSCs were investigated systematically along with their photophysical and photo electrochemical properties. These series of organic dyes include (B-CH, B-C B, DT-CB, DB-CB). Our investigation indicate among dyes containing butyl as... 

During last decade, the electricity demand in Iran grows up more than 8% per year due to an increasing economic growth. The main part of this load growth is related to industrial and agricultural demand. At this period, electric utilities tried to provide the peak load demand using all different types of available generating units especially with hydro generation plants. However, moving the time of peak demand occurring from night hours to day time and also increasing of load demand at mid day hours, created a new challenge to hydro-generation planning. As the number of daily peak hours increases from the nightly to daily peak hours and considering that Iran is a sub-tropical country, use of... 

This study aims at analyzing the performance of three units known as low salt rejection reverse osmosis (LSRRO), split-feed counterflow reverse osmosis (SF-CFRO), and split-brine counterflow reverse osmosis (SB-CFRO) and implementing them in a modified multi-stage multi-feed counter-current membrane with cascade recycle for dewatering hypersaline streams to the salinity appropriate for crystallizers' feed. Exergy and primitive pinch analysis showed that dewatering is limited in SF-CFRO as the permeate inlet dictates the maximum salinity difference at the pinch point as well as high frictional pressure loss in the permeate channel. SB-CFRO and LSRRO units can reach high salinities by... 

Polymer supported reagents have found many applications in recent years. Scientists in research laboratories of agrochemical and pharmaceutical industries now routinely utilize these compounds to prepare ensembles of small organic molecules for screening. This review is aimed to highlight some of the most important applications of these promising materials in organic synthesis. Furthermore, an extensive listing of polymeric reagents that were recently used in organic synthesis is included. © Springer-Verlag 2007  

Abstract New bi-anchoring donor-π-acceptor metal-free organic dyes based on diphenylamine as donor, and barbituric acid and thiobarbituric acid as the acceptor/anchor were synthesized, characterized and used in dye-sensitized solar cells applications. Among the fabricated dye sensitized solar cells, device based on the diphenylamine as donor, and barbituric acid as the acceptor exhibits a high power conversion efficiency of 1.53% with a short circuit current density of 3.71 mA cm-2, an open-circuit photo voltage of 0.55 V and a fill factor of 0.75% under AM 1.5 illumination (85 mW cm-2) compared to the other fabricated devices. The structure of synthesized dyes was optimized and their... 

In this study, cobalt-ruthenium nanocatalysts supported on nitrogen-doped graphene aerogel (NGA) and carbon nanotubes (CNT) were synthesized using the wet impregnation method for Fischer-Tropsch process with a cobalt to ruthenium ratio of 1:50. The synthesized catalysts underwent various characterizations such as FTIR, ICP, BET, XRD, EDX, TPR and TEM. The performance of the synthesized catalysts was compared to that of a cobalt-ruthenium nanostructured catalyst supported on NGA and CNTs. The catalysts were evaluated in a fixed-bed reactor at 25 bar, with a gas ratio H2/CO: 2 and Gas Hourly Space Velocity (GHSV) 10,000 mlg-1h-1, at temperatures of 260 °C and 280 °C. The use of NGA as a cobalt... 

Cognitive functions such as working memory require integrated activity among different brain regions. Notably, entorhinal cortex (EC) activity is associated with the successful working memory task. Olfactory bulb (OB) oscillations are known as rhythms that modulate rhythmic activity in widespread brain regions during cognitive tasks. Since the OB is structurally connected to the EC, we hypothesized that OB could modulate EC activity during working memory performance. Herein, we explored OB–EC functional connectivity during spatial working memory performance by simultaneous recording local field potentials when rats performed a Y-maze task. Our results showed that the coherence of delta,... 

In this paper, modified Adomian decomposition (MAD) is introduced to investigate the effect of the Casimir attraction on pull-in instability of beam-type NEMS theoretically. Two engineering cases including cantilever and double cantilever nano-beam are considered. The proposed MAD method is employed to solve the nonlinear constitutive equation of nano-beams. The basic engineering parameters such as critical deflection and pull-in voltage of nano-beams are computed. It is found that the Casimir forces decrease the pull-in deflection and voltage of nano-beams. On the other hand, the fringing field increases the pull-in deflection while decreases the pull-in voltage of the actuators. As a... 

Fatigue behavior of quasi-isotropic carbon/epoxy laminates were studied, using six stacking sequences. Experimental results show that there is a significant stacking sequence effect on monotonic and cyclic performance of laminates. Though by changing the stacking sequence the difference between failure strength of the strongest and weakest lay-ups reaches only to ∼ 12 %, the difference between fatigue lives (cycles to failure) increased ∼ 1000% in some loading regions. In addition, both linear and sigmoidal functions were examined to model the fatigue life behavior  

qPCR is still the gold standard for gene expression quantification. However, its accuracy is highly dependent on the normalization procedure. The conventional method involves using the geometric mean of multiple study-specific reference genes (RGs) expression for cross-sample normalization. While research on selecting stably expressed RGs is extensive, scant literature exists regarding the optimal approach for aggregating multiple RGs into a unified RG. In this paper, we introduce a family of scale-invariant functions as an alternative to the geometric mean aggregation. Our candidate method (weighted geometric mean minimizing standard deviation) demonstrated significantly better results... 

The novel N2O2 unsymmetrical tetradentate Schiff bases complexes are used as catalysts for the selective aerobic oxidation of cyclohexene. In general, conversion percentages decrease with increasing ΔEp and decreasing Eredox 0′. Catalytic activity increases with decrease of the number of electron-donating groups and the catalytic selectivity varies according to the types of substituents in the ligands. The catalytic system described here is an inexpensive method for selective oxidation of olefins, with advantages of high activity, selectivity, re-usability and short reaction times. Analysing GC and redox potential results shows a moderate correlation between selectivity and activity. © 2004... 

An easy and ecofriendly method for designing double-network (DN) hydrogels based on chitosan and poly(vinyl alcohol) (PVA) with high mechanical performance is described. When covalent bonds in the networks are used as crosslinking agents in the achievement of a higher mechanical strength, the irreversible deformation of these hydrogels after a large force is applied is still one of the most important obstacles. To overcome this problem, we used physical crosslinking for both networks. The mechanical strength, surface morphology, and cytotoxicity of the films were studied by tensile testing, scanning electron microscopy analysis, and an MTT assay. The synthesized chitosan–PVA DN hydrogels... 

In this paper, we study a supply chain problem where a whole seller/producer distributes goods among different retailers. Such problems are always faces with uncertainty with input data and we have to use various techniques to handle the uncertainty. The proposed model of this paper considers different input parameters such as demand, capacity and cost in trapezoid fuzzy forms and using two ranking methods, we handle the uncertainty. The results of the proposed model of this paper have been compared with the crisp and other existing fuzzy techniques using some randomly generated data. The preliminary results indicate that the proposed models of this paper provides better values for the... 

Arbitrary Lagrangian Eulerian (ALE) method is widely used for simulation of large deformation problems, such as metal forming. However, in many such applications, modeling of the heat generation and transfer in conjunction with the stress analysis is necessary. In this work, a fully coupled dynamic ALE formulation is developed. The ALE form of energy balance equation is derived, and is coupled with the dynamic, rate dependent ALE stress analysis. The proposed formulation is used for simulation of a few thermo-mechanical problems. The effectiveness and efficiency of the ALE method is verified by comparing the results of this simulation with available experimental and numerical results  

A series of superabsorbent composites were synthesized through graft copolymerization of acrylic acid (AA) onto carboxymethyl cellulose (CMC) in the presence of celite powder using N,N'-methylenebisacrylamide (MBA) as a cross-linking agent and ammonium persulphate (APS) as an initiator. The chemical structure and thermal properties of the composite hydrogels were characterized by FTIR spectroscopy and TGA methods, respectively. Morphology of the samples was examined by scanning electron microscopy (SEM). In free-state, the swelling conditions and hence the related data are not real, because in all their applications the swelling particles of superabsorbent must absorb aqueous solutions while... 

Biological oxidation of ferrous sulfate by Acidithiobacillus ferrooxidans has proved to be a significant step in the bioleaching of sulfide minerals and the treatment of acid mine drainage. The same bioreaction also has beneficial applications in the desulphurization of coal and removal of hydrogen sulfide from gaseous effluents. In this research, the effects of some process variables such as pH, temperature, elemental sulfur, amount of initial ferrous and magnesium ions on oxidation of ferrous sulfate by a native A. ferrooxidans, which was isolated from a chalcopyrite concentrate, were investigated. All experiments carried out in shake flasks at 33 °C that was obtained as optimum...