Cotton fabric was treated by corona plasma discharge at different powers and numbers of passages. The carboxyl group content was determined by Methylene Blue staining and titration. Then, the ...untreated and treated cotton fabrics were treated with silver nitrate, and laundering test was carried out. The inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for silver and antibacterial tests were done. The surface bonding and morphology were studied by FTIR/ATR spectroscopy and scanning electron microscopy (SEM), respectively. The plasma corona discharge treatment of cotton fabric increases the content of carboxyl groups. An increase in the power of plasma treatment increases the content of carboxyl groups and adsorption of silver ions. As a result, the antibacterial effect is enhanced and becomes more stable after repeated laundering.
The effect of pump impeller modification by a new approach, pump impeller shroud trimming (PIST), on the flow field and pump performance is examined both numerically and experimentally. The primary ...purpose of this study is to investigate the hydraulic performance of single-phase centrifugal pumps, which are refined by the PIST method, with low and medium specific speeds. In this type of shroud trimming, different trimming sizes are applied only to the shroud plate of the closed impeller, while the geometries (diameters) of the hub and blades remain unchanged. This modification, which increases the clearance between the impeller and casing from the shroud side, causes desirable conditions for pumping fluid containing undissolved gas. Computational fluid dynamics software (ANSYS-CFX) is used to predict the hydraulic performance of centrifugal pumps. Two well-known turbulence models, the renormalization group (RNG) k-ϵ developed model and shear stress transport (SST) k-ω, are used to predict the flow patterns. The computational results are verified through the comparison of experimental and unsteady numerical simulations with steady numerical data. After ensuring the accuracy of the flow-field simulation approach, further numerical analysis is performed for both pumps by changing the impeller shroud diameter. The effects of the geometric changes on the performance curves, efficiency, flow field, pressure distribution inside the pump components and the radial force acting on both pump types are investigated comprehensively. The results show that the shroud trimming reduces the produced head and efficiency at the design points. Examination of the radial force, which is applied on the rotating parts, shows that shroud-trimmed impellers experience higher radial forces than closed impellers in both pump types owing to the lack of a uniform pressure distribution around the impeller outlet. Accordingly, the relevant information obtained is used to modify the existing coefficients to predict the radial forces.
Previous research has demonstrated the potential of pico-hydro turbines to provide reliable electricity in applications such as rural electrification. However, the literature has primarily focused on ...the development of turbine systems for design environments where spatial and flow rate constraints tend to be non-restrictive. The work detailed in this paper presents the development of a novel, compact, high efficiency turbine capable of powering a compact electrochemical cell for off-grid water disinfection. The turbine with the generator is capable of generating nearly 100 W of power with a footprint of only 8″ in length and 4″ in diameter. A basic mathematical model of a DC generator is coupled to a computational fluid dynamics (CFD) turbine model to evaluate different system configurations. Following a Taguchi Method study to computationally explore the turbine design space, experimental testing of improved turbine configurations is shown to provide electrical power output improvements of 20%. Selection of a more compatible DC generator also provides electrical power output and efficiency improvements of a factor of 2 and 2.5 respectively.
•Design study of a novel pico-hydro turbine for a low flow application was conducted.•Suitable generator pairing resulted in a factor of 2 improvement in power output.•Taguchi method discretization of the turbine design space was performed.•CFD analysis of turbine configurations used to assess effects of multiple parameters.•Refined turbine design provided an improvement in power output of 20%.
Regenerative pump is a low specific speed and rotor-dynamic turbomachine capable of developing high heads at low flow rates. In this paper, a numerical study has been carried out in order to ...investigate the effect of blade angle on the performance of a regenerative pump. Two groups of impellers were employed. The first type has symmetric angle blades with identical inlet/outlet angles of ±10°, ±30°, and ±50° and the second group has nonsymmetric angle blades in which the inlet angle was set to 0° and six different angles of ±10°, ±30°, and ±50° were designed for the outlet of the blades. A total of 12 impellers, as well as primary radial blades impeller, were investigated in this study. The results showed that all forward blades have higher head coefficients than radial blades impeller at design flow coefficient. It was found that regenerative pumps with symmetric angle forward blades have better performance than other types. Also, it is worth mentioning that the highest head coefficient and efficiency occur at angle + 10 < β < + 30 of symmetric angle blades. It was found that the maximum efficiency occurs at angle of +15.5° by curve fitting to the data obtained from numerical simulations for symmetric angle forward blades.
Determination of the parameters of modified Drucker–Prager Cap (DPC) constitutive model for Al7075 powder is investigated in this work. The parameters are normally identified by experiment which is ...time consuming, tedious and expensive. In this study, the constants of DPC model are identified by conducting only a simple uniaxial powder compaction test, using finite element (FE) simulations in ABAQUS/standard, and utilizing artificial neural networks (ANN). The relation between the Young’s modulus (
E
) and relative density of the powder was incorporated in ABAQUS code using a USDFLD user-defined subroutine. In the proposed approach, the neural networks are trained to predict the DPC parameters in a way to minimize the differences between experimental and FE curves of uniaxial powder compaction. The input parameters of the ANN were features of uniaxial powder compaction load–displacement curve. A reasonable agreement was observed between the experimental and numerical load–displacement curves of the powder compaction for the DPC parameters predicted by ANN. Moreover, the accuracy of this DPC model was verified again in compaction of a bush-type sample.
Polycaprolactone is a biodegradable and biocompatible polyester which has a wide range of applications in tissue engineering. Electrospinning, the versatile technique, used for the fabrication of ...fibrous scaffolds, which is widely used in tissue engineering, due to the ability of fabrication of nano/micro-scale fiber scaffolds. Polycaprolactone nanofiber scaffolds are widely used in tissue engineering and drug delivery. Polycaprolactone can be used in a wide variety of scaffolds construction. In this review, we will discuss the recent advances in the electrospinning of polycaprolactone nanofiber scaffolds in bone, cardiovascular, nerve, and skin tissue engineering.
In this paper, an anisotropic ductile fracture is studied using a phase-field model. This model is on the basis of the energy principle in which a scalar field is added as a phase-field variable to ...determine the probability paths of cracks. Therefore, the system of equations, included for the displacement and phase field, is obtained and solved in a nonlinear finite element procedure through a user element subroutine in ABAQUS commercial software. The effect of anisotropy on cracks’ paths for an anisotropic fracture is assessed according to the Hill criterion for ductile materials. Moreover, an implicit integration algorithm for an anisotropy model combined with a phase field is shown for the plane strain state. The proposed model can also be used for the combination of various constitutive models along with an anisotropy such as the anisotropic rate-dependent (visco-Hill) and the anisotropic rate-independent (elasto-Hill). Furthermore, the threshold parameter is introduced to examine the plastic deformation influence on cracks initiation and propagation in this study. Finally, the influence of the anisotropy on the responses of different specimens in various fracture processes is interrogated. The accuracy of the suggested model is demonstrated by juxtaposing the achieved and given experimental and numerical results in the way that it can be able to simulate the anisotropy effects on the gradual evolution of cracks from ductile to brittle.
Recently, cobalt ferrite nanoparticles have attracted much attention due to their physical, chemical and magnetic properties. Numerous studies have focused on facile production of these ...nanoparticles. In this study, CoFe
2
O
4
, Zn
0.4
Co
0.6
Fe
2
O
4
, Cd
0.4
Co
0.6
Fe
2
O
4
, and Cd
0.2
Zn
0.2
Co
0.6
Fe
2
O
4
were successfully synthesized by using economical and simple microwave-modified Pechini sol–gel method, calcined by microwave radiation. The nanoparticles were characterized by some techniques such as X-ray diffraction, energy dispersive spectroscopy, field emission scanning electron microscopy, Fourier transform infrared, and vibrating sample magnetometer analyses. The X-ray diffraction, energy dispersive spectroscopy and Fourier transform infrared results confirmed the formation of CoFe
2
O
4
nanoparticles. Fourier transform infrared indicated two fundamental absorption bands of spinel structure. The diameters of the spherical and rod form structures of nanoparticles ranged from 18 to 39 nm. The results indicated that the substitution of Co with Zn and Cd in cobalt ferrite influenced the physical properties, magnetic properties and cytotoxicity of these nanoparticles as medical devices. Zn doping had the significant effect on decreasing the size of cobalt ferrite nanoparticles and improving the magnetic properties. Zn-doped nanoparticles exhibited super paramagnetic behavior (coercivity was nearly 0oe and saturation magnetization was 52.78 emu/g). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (in vitro cytotoxicity MTT assay) assay confirmed that all samples were non-toxic and potentially can be used in biomedical application.
Graphical abstract
Using aluminum metal matrix nanocomposites has recently gained increased attention in the industry due to their high strength and ductility. In this paper, TiO2 nanoparticles in three volume ...percentages of 0.5, 1 and 1.5 were added to Al2024 alloy using stir casting method. TiO2 nanoparticles were added to the matrix using a novel Powder injection system. The influence of TiO2 content on the mechanical properties, porosity, microstructure and wear resistance of the samples was investigated. SEM images showed that TiO2 nanoparticles uniformly distributed into the metal matrix. This was due to increased wettability of nanoparticles as a result of their controlled injection using the new system. By increasing the percentage of nanoparticles, dendrite size decreased while the hardness of samples increased. At 1.5 volume percentage of nanoparticles the Rockwell B hardness was increased by 31.57%. The elongation of samples was reduced with increasing the nanoparticles content. The sample with 1.5 volume percentage of TiO2 showing 13.8% reduction in elongation compared to the unreinforced sample. Mechanical strength increased with increasing the nanoparticles content until 1% (14.6% higher than the unreinforced sample), while at 1.5% TiO2 was 6.6% higher than the unreinforced sample. The results of the wear test showed that wear resistance significantly increasing with increasing the nanoparticle content and wear mechanism changes from adhesive into abrasive.
In this study, ceramic coatings were deposited on AZ31 magnesium alloy by micro arc oxidation (MAO) technique in sodium phosphate electrolytes (Na3PO4.12H2O) containing different concentrations of ...sodium hydroxide (NaOH) and borax (Na2B4O7) under voltage of 420 V for 5 min. Hank's solution was used to investigate the corrosion behavior of the samples. Potentiodynamic polarization and electrochemical impedance spectroscopy were also employed. X-ray diffraction and scanning electron microscopy were applied for phase and microstructure characterization. The prepared MAO layers consisted mainly of ZnO and Mg3PO4. Results indicated that use of micro arc oxidation technique for coating may result in significant increase of corrosion resistance of magnesium alloy in Hank's solution. One of the important parameters which affects this coatings properties is the electrolyte composition which used in the process. The coating deposited by application of 10 g/l Na3PO4 + 1.5 g/l NaOH, exhibited the highest corrosion resistance in Hank's solution among the samples.
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