Samira Gharehkhani

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

Abstract Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.

Basic effects of pulp refining on fiber properties—A review

The requirement for high quality pulps which are widely used in paper industries has increased the demand for pulp refining (beating) process. Pulp refining is a promising approach to improve the pulp quality by changing the fiber characteristics. The diversity of research on the effect of refining on fiber properties which is due to the different pulp sources, pulp consistency and refining equipment has interested us to provide a review on the studies over the last decade. In this article, the influence of pulp refining on structural properties i.e., fibrillations, fine formation, fiber length, fiber curl, crystallinity and distribution of surface chemical compositions is reviewed. The effect of pulp refining on electrokinetic properties of fiber e.g., surface and total charges of pulps is discussed. In addition, an overview of different refining theories, refiners as well as some tests for assessing the pulp refining is presented.

Entropy Generation during Turbulent Flow of Zirconia-water and Other Nanofluids in a Square Cross Section Tube with a Constant Heat Flux

The entropy generation based on the second law of thermodynamics is investigated for turbulent forced convection flow of ZrO2-water nanofluid through a square pipe with constant wall heat flux. Effects of different particle concentrations, inlet conditions and particle sizes on entropy generation of ZrO2-water nanofluid are studied. Contributions from frictional and thermal entropy generations are investigated, and the optimal working condition is analyzed. The results show that the optimal volume concentration of nanoparticles to minimize the entropy generation increases when the Reynolds number decreases. It was also found that the thermal entropy generation increases with the increase of nanoparticle

Spongy nitrogen-doped activated carbonaceous hybrid derived from biomass material/graphene oxide for supercapacitor electrodes

Carbon derived from low cost agricultural waste material was used as a precursor for the preparation of a spongy-like nitrogen doped activated composite from carbon/graphene oxide via a one-step thermal treatment. N-doping and activation of the carbon/graphene oxide mixture were achieved simultaneously by the treatment of urea and potassium hydroxide at 800 °C. The nitrogen content and ratio between the nitrogen species was controlled by the mass ratio of KOH : carbon. The composite was prepared with a KOH : carbon ratio of 1 which resulted in a moderate surface area (1712.4 m2 g−1) and a high nitrogen content (14.51%). The hybrid material gave high specific capacitance (267 F g−1 at 5 mV s−1) and good cycling stability (92.3% capacitance retention after 5000 cycles) in 6 M KOH electrolyte. Hence, the new composite presented in this work can be used as an advanced material for supercapacitor applications.

Numerical investigation of heat transfer enhancement in a rectangular heated pipe for turbulent nanofluid.

Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM). The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2 at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations.

Mathematical Modeling for Nanofluids Simulation: A Review of the Latest Works

Exploiting nanofluids in thermal systems is growing day by day. Nanofluids having ultrafine solid particles promise new working fluids for application in energy devices. Many studies have been conducted on thermophysical properties as well as heat and fluid flow characteristics of nanofluids in various systems to discover their advantag‐ es compared to conventional working fluids. The main aim of this study is to present the latest developments and progress in the mathematical modeling of nanofluids flow. For this purpose, a comprehensive review of different nanofluid computational fluid dynamics (CFD) approaches is carried out. This study provides detailed information about the commonly used formulations as well as techniques for mathematical modeling of nanofluids. In addition, advantages and disadvantages of each method are rendered to find the most appropriate approach, which can give valid results.

Sustainability and environmental impact of ethanol as a biofuel

Abstract Biofuels are acting as a renewable replacement for petroleum fuels due to some environmental and economic benefits. They are prepared by blending a major portion of diesel fuel and a certain minor percentage of bio-oils, which provides less greenhouse gas (GHG) compared to pure diesel. Recently, bioethanol has been the most widely used biofuel for transportation. Bioethanol can be produced from different kinds of agricultural raw materials classified into three categories: simple sugars, starch, and lignocellulose. Use of bioethanol-blended gasoline fuel for automobiles can significantly reduce petroleum use and exhaust GHG emission. Bioethanol from sugar cane, produced under the proper conditions, is essentially a clean fuel and has several clear advantages over petroleum-derived gasoline in reducing GHG emissions and improving air quality in metropolitan areas. However, there remains a compromise between GHG emission and saving of fossil fuel energy by introducing bioethanol either totally or as a blending component of engine fuel. Thus, considering biofuel as a replenishable energy source, the future pathway of energy management could be planned.

Ion size, loading, and charge determine the mechanical properties, surface apatite, and cell growth of silver and tantalum doped calcium silicate

This study describes how various loadings of two ions with different size and charge, such as silver and tantalum, can affect the mechanical and biological properties of calcium silicate (CS). The incorporation of 5 wt% tantalum (Ta, charge: 5+, ion radius: 0.68 A) in the CS lattice raised the hardness and fracture toughness values significantly. Increasing the Ta concentration to 10 wt% and 15 wt%, did not lead to further improvements. Additions of silver (Ag, charge: 1+, ion radius: 1.13 A) to 5, 10 and 15 wt%, resulted in an increase in hardness and fracture toughness values in comparison to undoped CS; however, these values did not change significantly with different concentrations of Ag. Both Ta and Ag doped CS formed surface layers of apatite in simulated body fluid (SBF). CS was found to stimulate hFOB proliferation. The incorporation of Ta into CS did not change this and hFOB proliferation was stimulated even at higher concentrations. With increasing Ag content in the CS structure, the cell proliferation was slightly inhibited.

Extension of Weighted Sum of Gray Gas Data to Mathematical Simulation of Radiative Heat Transfer in a Boiler with Gas-Soot Media

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Fosters data as well as Trueloves data for CO2-H2O mixture and the total emissivities are calculated and compared with the Trueloves parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

The effect of nanocrystalline cellulose on flow properties of fiber crop aqueous suspension

Nanocrystalline cellulose (NCC) a nature-based material, has gained significant attentions for its unique properties. The present study aims to investigate the flow behavior of cellulosic suspension containing non-wood pulp fibers and NCC, by means of rheological and pressure drop measurements. The NCC sample was prepared by sulfuric acid hydrolysis from Acacia mangium fibers. The rheological properties of kenaf/NCC suspensions were studied using viscosity and yield stress measurements. The pressure drop properties of the suspension flow were studied with respect to variation in flow velocity (0.4 m/s-3.6 m/s) and the NCC concentration (70 mg/l and 150 mg/l). The pressure drop results showed that the pulp suspension containing 150 mg/l NCC had higher drag reduction than kenaf suspension alone. The present insights into the flow of pulp/NCC suspension provide a new data and promote the application of NCC in industries.