Sharif Digital Repository

Multivariate monitoring techniques such as multivariate control charts are used to control the processes that contain more than one correlated characteristic. Although the majority of previous researches are focused on controlling only the mean vector of multivariate processes, little work has been performed to monitor the covariance matrix. In this research, a new method is presented to detect possible shifts in the covariance matrix of multivariate processes. The basis of the proposed method is to eliminate the correlation structure between the quality characteristics by transformation technique and then use an S chart for each variable. The performance of the proposed method is then... 

Estimating the process capability index (PCI) for non-normal processes has been discussed by many researches. There are two basic approaches to estimating the PCI for non-normal processes. The first commonly used approach is to transform the non-normal data into normal data using transformation techniques and then use a conventional normal method to estimate the PCI for transformed data. This is a straightforward approach and is easy to deploy. The alternate approach is to use non-normal percentiles to calculate the PCI. The latter approach is not easy to implement and a deviation in estimating the distribution of the process may affect the efficacy of the estimated PCI. The aim of this... 

Cu-based metal organic framework/rGO was used as an effective cocatalyst to synthesis novel Ag3VO4/Cu-MOF/rGO nanocomposite. The resulting photocatalysts were characterized by different microscopic and spectroscopic methods. The photocatalytic degradation studies on acid blue 92 showed that Ag3VO4/Cu-MOF/rGO nanocomposite indicated significant improved activity compared with pure Ag3VO4 and Cu-MOF/rGO. The improved photocatalytic activity of nanocomposite was attributed to the increased surface area and effective charge carrier separation and transport in the nanocomposite. © 2019 Elsevier Ltd  

In recent years, subsidy payment has been made a main challenge for governments due to growth of population and energy price in global markets. Targeted subsidy plan has been implemented in Iran since last year, and this article discusses its effects on costs and revenues of Tehran Electricity Company as one of the major subdivisions of Iran's electricity industry. In the new system, structural changes have been made in electricity tariffs, so it is not possible to predict the future trends in electricity consumption only based on the past consumptions. In order to model the decision making structure in the recent conditions, a system dynamics method is applied. In addition to modeling the... 

In the current study, the prospect improvements on desalination and anti-fouling performance of polyamide (PA)-based TFN membranes modified with MIL-53-NH-Asp have been investigated. MIL-53-NH2 nanoparticles (NPs) have been treated through a single-step post-synthesis modification reaction to enhance the hydrophilicity feature and compatibility with the PA layer. Various concentrations of synthesized NPs were dispersed in an aqueous phase consisting m-phenylenediamine and 2,6-diaminopyridine monomers for incorporation in the PA rejection layer. Analysis data of fabricated membranes provide evidence of changes in their physico-chemical properties after NPs incorporation. In comparison with... 

Multi-walled carbon nanotubes (MWCNTs) with diameter of about 50 nm were synthesized using thermal chemical vapor deposition. We have investigated the influence of Mg doping to the MWCNTs on its hydrogen storage property. TEM micrographs showed that Mg was attached to the MWCNTs and discontinuous arrangement of the carbon walls was recognized in the MWCNTs. According to XPS and BET analyses, the surface functional groups and pore size of the Mg-MWCNTs are increased by interactions between the Mg and the MWCNT's outer walls. The electrochemical discharging curves of the MWCNTs and Mg-doped MWCNTs revealed that the hydrogen storage capacity was 363 and 450 mAhg -1, respectively. Volumetric... 

The effects of HCl, HNO3, H2SO4 and HF acids on the purification and the electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) were studied. The MWCNTs were synthesized on Fe-Ni catalyst by thermal chemical vapor deposition method. The X-ray diffraction and thermal gravimetric analysis results indicated that the MWCNTs purified by HF acid had the highest impurities as compared with the other acids. The N2 adsorption results at 77 K indicated that all the samples were mainly mesoporous and the purified MWCNTs by HF acid had the highest surface area as compared with the other acids. The hydrogen storage capacities of the purified MWCNTs by the following acids were in... 

Over the past few decades, biological hazards and organic pollution have become major environmental concerns. Photocatalysis has been found to be effective in minimizing the negative impacts of these issues in air and water. Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method, including hydrothermal and coprecipitation. The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach. The prepared photocatalysts offered excellent nitrophenol mineralization (>90%) after 90 min of visible light irradiation. Based on the spin-trapping ESR technique, •O2̅–... 

We report a study on hydrogen storage in Ca, Co, Fe, Ni, and Pd decorated multiwalled carbon nanotubes (MWCNTs) by using two techniques: volumetric and electrochemical. The results showed that hydrogen molecules are adsorbed on the defect sites and transported to the spaces between adjacent carbon via diffusion through both defect sites and opened tips into the layers. Hydrogen storage capacity can be improved in the decorated MWCNT by Co, Fe, Ni, and Ca metals in two approaches: (i) H2 adsorption via Kubas interaction and (ii) dissociation of H2 molecules on the metal particles. The results reveal that Pd are more effective catalyst for hydrogen storage process. It was found that... 

The continuum theory of dislocations is applied to formulate the problem of a double ended dislocation pileup under quadratic applied stress. Accordingly, a second order stress gradient plasticity model is presented to address the contribution of the first and the second stress gradients in the effect interpretation. The model is employed to predict the initial strengthening and subsequent hardening in curved and straight thin foils under pure bending within the continuum framework. It is shown that the so-called stress gradient plasticity model that ignores the second stress gradient may not give sound interpretations of the size effects. The plastic response of thin foils is affected by... 

Significant energy subsidies are believed to be the main factor that has resulted in high energy intensities of Iranian industries. The Subsidy Reform Act of 2010 was directed at modifying energy consumption pattern and fostering energy efficiency enhancement. This study aims at analyzing the effect of energy subsidy reform on promoting energy efficiency in six energy intensive industries of Iran. In order to do so, the energy efficiency practices that have not been adopted after the implementation of the first phase of energy subsidy reform are investigated. Data analysis reveals that if financially interesting investments are determined as those with payback periods less than three years,... 

Numerous investigations have focused on creating effective membranes for desalination in order to alleviate the water scarcity crisis. In this study, first, LDH nanoplates were synthesized and utilized to alter the surface of thin-film composite (TFC) membranes in the course of this investigation. Following that, a simple technique was used to produce a novel nanocomposite incorporating LDH layers and Na14(P2W18Co4O70)·28H2O polyoxometalate nanoparticles, resulting in the creation of a fresh variety of thin-film nanocomposite (TFN). The performance of all of the membranes acquired was examined in the process of forward osmosis (FO). The impact of the compounds that were prepared was assessed... 

Mass transfer efficiency and catalytic reactivity are the two major hurdles for heterogeneous catalytic wet peroxide oxidation (CWPO) technologies. To address these issues, nanocomposite CuFeO2/Al2O3 was synthesized and assessed as a novel catalyst for enhanced adsorption and oxidation of anionic pollutants (catechol and reactive red 195 (RR195)) in waters. With a positive charge on the nanocomposite by introducing Al2O3, the adsorption of anionic pollutants was promoted. The surface complexation reaction on CuFeO2/Al2O3, which fits well to the Langmuir isotherm, has engined the mass transfer of pollutants to the nanocatalyst that demonstrated 96.46% and 99.75% removal of catechol and RR195... 

Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as... 

Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350°C. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range... 

The most challenging requirement for depositing NiTi-based shape memory thin films is the control of film composition because a small deviation can strongly shift the transformation temperatures. This article presents a technique to control film composition via adjustment of the power supplied to the targets during simultaneous sputter deposition from separate Ni, Ti, and X (e.g., Hf) targets. After optimization of sputter parameters such as working gas pressure, target-substrate distance, and target power ratio, binary Ni100-x Tix thin films were fabricated and characterized by energy dispersive x-ray spectroscopy in a scanning electron microscope (to measure the film composition and... 

The integration of Electronic Health Records (EHRs) with Machine Learning (ML) models has become imperative in examining patient outcomes due to the vast amounts of clinical data they provide. However, critical information regarding social and behavioral factors that affect health, such as social isolation, stress, and mental health complexities, is often recorded in unstructured clinical notes, hindering its accessibility. This has resulted in an over-reliance on clinical data in current EHR-based research, potentially leading to disparities in health outcomes. This study aims to evaluate the impact of incorporating patient-specific context from unstructured EHR data on the accuracy and... 

In this study, the authors present a new criterion which can be used to decompose the coding advantage (CA) of space-frequency block codes (SFBCs). The proposed decomposition separates the CA into two parts, called precoder-CA and channel-CA. The precoder-CA represents the effects of the precoder and the signal constellation, and can be used in the design of the precoder of SFBCs. The channel-CA, on the other hand, gives an indication of the effects of the channel characteristics, and can be utilised for optimising the permutation parameter. The authors have shown that the proposed decomposition method leads to a lower computational complexity for the optimisation procedure compared with the... 

A novel basic poly(ionic liquid) (PIL) was synthesized by miniemulsion polymerization of ionic liquid monomer 1-ethyl-3-vinylimidazolium bromide [EVim][Br] which was cross-linked by ionic liquid cross-linker 1,4-butanediyl-3,3'-bis-l-vinylimidazolium dibromide (BVD). Exchange of bromide anions in PIL nanogel with hydroxide, produced a supported basic ionic liquid catalyst. The catalytic performances of PIL nanogel with a size of about 200. nm was evaluated in the synthesis of 4. H-benzo[. b]pyrans by multi-component reaction in water. The present protocol represents a simple, ecologically safe and cost-effective route to synthesize 4. H-benzo[. b]pyrans with high products yield  

Cavitation behavior of fully submerged propellers is an important issue in the marine engineering field. Cavitation tunnel is usually used for studying hydrodynamic performances and cavitation behavior of a propeller. In the present study, the cavitation behavior of the DTMB P4119 propeller was studied both in a uniform flow and in the wake field of a specific vessel. Considering the dimensions of the test section of K23 cavitation tunnel of Sharif University of Technology and related blockage effects, the propeller was scaled so that the model was 0.195 (m) in diameter. A wake screen was used to generate the desired wake field, which itself was primarily determined by CFD simulations around...