High electron emission from branched tree-like carbon nanotubes suitable for field emission applications

Fabrication of branched tree-like carbon nanostructures has been carried out by means of a sequential hydrogenation and growth process in a direct-current plasma enhanced chemical vapor deposition unit. The field emission characteristic of the tree-like structures has been investigated showing a dramatic improvement with respect to vertical nanotubes. The fabrication process consists of the growth of vertical nanotubes, hydrogenation treatment, encapsulation and a secondary treatment and growth. The secondary growth takes advantage of the tip growth mechanism and is seeded on top of the initial nanotubes. The emission characteristic of the evolved nanostructures is expected to promote considerably due to a field enhancement as observed from the emission characteristics of the nanostructures. A preliminary field emission display has been realized at pixel level.     

Controlled Laser Transformation Hardening of Martensitic Stainless Steel by Pulsed Nd：YAG Laser

Laser transformation hardening(LTH) was applied to the surface of the AISI 420 martensitic stainless steel by a pulsed Nd:YAG laser to obtain optimum hardness.The influences of process para-meters(laser pulse energy,duration time,and travel speed) on the depth and hardness of laser treated area were investigated.Image analysis of SEM micros-tructure of AISI 420 showed that plate-like carbide have almost fully and(30~40)% of globular carbide particles dissolved into the matrix after laser transformation hard...     

Patterns of authors’ information scattering: towards a causal explanation of information scattering from a scholarly information-seeking behavior perspective

This study primarily aims to reveal the worldwide patterns of authors’ information scattering through illustrating the possible differences among authors based on subject, country, geographic region, institution, economic and scientific level factors. Second, changes in patterns of information scattering during the past 21 years are checked. Finally, a hypothesis aimed at demonstrating a probable relationship among the three research domains including information scattering, scholarly information-seeking behavior and scholarly journal usage is presented. 176,943 authors, who have more than ten papers in WoS from 1990 to 2010 were examined. The findings revealed that patterns of information scattering have changed during the past 21 years, and the number of journals in the core and middle zones has almost doubled. It was also found that authors tend to use a small number of journals to retrieve the majority of their required information, while a small amount of their information needs come from a wide variety of journals. However, with regard to patterns of information scattering, some differences exist among authors based on factors including institutions, countries and subject fields. In addition, this study shows that information-scattering patterns might be affected by scholars’ information-seeking behaviors. A causal explanation of information scattering through scholarly information-seeking behavior has, without a doubt, the potential to provide practical solutions to better meet scholars’ information needs and requirements.     

Electromechanical properties of wearable strain gauge transducers

Electro-conductive yarns can be used to create electrically active areas in textile structures to develop wearable strain gauges. The electromechanical properties of the strain gauge have been studied. Three lab experiments have been conducted: the first analyses the electrometrical properties of the yarns which were used to produce knitted sensors; the second investigates the properties of a single stitch to understand the effect of contact points between yarns on the electrical properties of knitted fabric. Finally, the electrical properties of the knitted fabrics which contain electrically active conductive areas, i.e. knitted sensors, were tested.     

Estimation of thermodiffusion coefficients in ternary associating mixtures

Following the non‐equilibrium thermodynamics formulation and taking into account the complexities in the structure of aqueous associating mixtures, expressions are proposed to estimate the thermodiffusion coefficients in ternary associating mixtures, such as water and alcohol mixtures. The model expressions are used to estimate the thermodiffusion coefficients in methanol–ethanol–water, dimethyl sulfoxide (DMSO)–ethanol–water and DMSO–t‐butanol–water mixtures at various concentrations. The perturbed‐chain statistical associating fluid theory (PC‐SAFT) equation of state is used to obtain the mixture properties, such as the derivatives of the chemical potentials needed to evaluate the thermodiffusion coefficient expressions. The results show that at certain concentrations of one component, variation of the concentration of the other two components can cause a sign change in the thermodiffusion coefficients. While the model cannot be evaluated due to the lack of any pertinent experimental data, the model predictions may be used to choose suitable mixture compositions in space experiments to be performed onboard the International Space Station (ISS) in near future. © 2011 Canadian Society for Chemical Engineering     

Estimation of mid‐distillates production rate in a low temperature Fischer–Tropsch process

BACKGROUND: The Fischer–Tropsch process is the most important path for converting natural gas to high quality liquid hydrocarbons. Low temperature Fischer–Tropsch synthesis in slurry bubble column reactors with cobalt‐based catalysts is used for mid‐distillates production. RESULTS: In this work the slurry bubble column reactor was simulated by applying the two‐bubble class mathematical model. In addition, the effect of operating parameters on synthesis gas conversion was studied. The distribution of products was also predicted from the simulation framework. CONCLUSIONS: The effect of synthesis gas inlet velocity on mid‐distillates production rate was studied in the present work. A maximum production rate for mid‐distillates of about 23 kg s^?1 was predicted from the simulation program. Copyright © 2011 Society of Chemical Industry     

Preparation of alginate and chitosan nanoparticles using a new reverse micellar system

Alginate and chitosan nanoparticles were prepared using a new reverse micelle system, composed of cetyltrimethylammonium bromide (CTAB) as a surfactant, isooctane as a solvent, and 1-hexananol as a co-solvent. The obtained nanoparticles were characterized by FTIR, DLS and TEM techniques. The main objective of this study was to investigate the effects of polymer concentration, water content, and volumetric ratio of co-solvent to solvent on the physical and morphological properties of the prepared nanoparticles. To evaluate the results, the design of experimental was initially carried out and then the obtained data were statistically analyzed using the Qualitek-4^? software. Results revealed that the size of the prepared alginate and chitosan nanoparticles varied in the range 220?C490 and 210?C1,050?nm, respectively. Furthermore, increasing either alginate or chitosan concentration increased the size of their nanoparticles. The results also showed that the size of nanoparticles was decreased with increasing the volumetric ratio of co-solvent/solvent. Finally, the size of alginate nanoparticles was increased by increasing the water content while it decreased the size of chitosan nanoparticles. Considering the statistical analysis of experiments, the polymer concentration is the major parameter affecting nanoparticles?? size. In contrast, water content has the smallest effect on the size of nanoparticles. However, the difference between the particle sizes of chitosan and alginate nanoparticles cab be attributed to the electrostatic repulsion between chitosan and CTAB.     

Correlation of nanostructural parameters and macromechanical behaviour of hyperbranched‐modified polypropylene using time‐resolved small‐angle X‐ray scattering measurements

Polypropylene (PP) is modified utilizing a poly(ester amide)‐based hyperbranched polymer (PS). A maleic‐modified PP is used to enhance the compatibility. Usual tensile experiments are carried out. The nanocrystalline structure is studied using small‐angle X‐ray scattering (SAXS) while a uniaxial mechanical load is simultaneously applied. SAXS patterns are analysed using procedures written in PV‐WAVE. The chord distribution function (CDF) is calculated and nanostructural parameters such as long period (l_p) and nanodeformation (?_Nano) are extracted. The correlations between macromechanical parameters and nanostructures are studied. Mechanical results show that PS has a plasticizing effect. Reactively blended samples demonstrate enhanced mechanical properties. SAXS patterns reveal a well‐known structure of PP as a peculiar architecture of the nanostructure. Crystalline branching occurs in a geometry that is known as a mother–daughter crystal lamellar structure, also called a crosshatching structure. It is concluded that adding PS distorts the stacking of crystalline domains. The structural information from SAXS patterns in reciprocal space is visualized in real space in the calculated CDFs. The CDFs indicate that in simple blends, l_p of the crystalline stacks increases compared to blank PP. Nevertheless, reactively blended samples show an increase of l_p compared to blank PP; however, they possess smaller l_p compared to simple blends. © 2012 Society of Chemical Industry     

Mineral recovery from inland reverse osmosis concentrate using isothermal evaporation

Mineral recovery from reverse osmosis (RO) concentrate after concentration by a secondary sea water-type RO system with lime–soda pretreatment was the focus of this study. Lime–soda pretreatment removed Ca, Mg and Si allowing for the application of sea water-type RO resulting in a concentrate composed of sodium, potassium, sulfate and chloride. The overall objective was reduction in concentrate volume that will require disposal by evaporation while producing by-products with potential resale value. Thermodynamic phase equilibrium calculations using Pitzer’s correlations for 25 °C, accurately predicted the solubility and evaporation path of the sodium sulfate minerals as potential by-products. Bench-scale evaporation experiments verified the model predictions and indicated that 81–88% of the sodium sulfate by-products were Na₂SO₄.