Design,Modeling and Control of a Simulator of an Aircraft Maneuver in the Wind Tunnel Using Cable Robot

International Journal of Control, Automation and Systems - In this paper, a new controllable simulator is proposed and modeled by which, experimental tests of the aircraft’s models can be...     

Investigation of thermal comfort in nanofibrous three‐layer fabric for cold weather protective clothing

The development of functional nanofiber materials with high specific surface area and porosity has been a highly interesting field of research in recent years due to its versatile properties for diverse applications. The combination of nanofibers into material clothes can open up new opportunities to improve comfort performance and thermal management properties. In this work, we demonstrated that the porous lightweight nanofibrous membrane could be coated on the fabric and laminated to improve its thermal comfort. The polyacrylonitrile was electrospun onto the surface of the polyester fabric with three different fineness and laminated with a warp knitted interlining in a controlled condition by sewing/fusing. The effect of the nanofibers diameter, sewing and fusing process on thermal insulation, air permeability, breathability, and water resistance of the obtained three‐layer samples were studied. The results showed that the presence of the nanofibers thin layer could improve the thermal comfort by controlling the studied parameters compared to the external face fabric as control. It was obtained that the fusing technique is more efficient than sewing for this purpose. The fused samples are waterproof and windproof, while instantly venting moisture and had good thermal insulation to protect the body from cold. POLYM. ENG. SCI., 59:2032–2040, 2019. © 2019 Society of Plastics Engineers     

High performance anti-smog window screens via electrospun nanofibers

Scientific studies clearly link air pollution with adverse effects on human health, which includes reduction of cognitive abilities. Hence quality indoor air is essential in rapidly urbanizing societies. The aim of this research work is to develop anti-smog, air permeable, water-proof, and transparent window screens suitable for natural ventilation. For this purpose, we bonded polyethylene terephthalate (PET) nanofibers on PET grids by electrospinning method with relative near spinning distance. During the process, the incomplete solvent evaporation of the collected jet could enhance the bonding of the PET nanofibers to the PET grids. The experimental results showed that the PET nanofibers had a thick deposition at the yarn edge of the PET grids, which also increased the bonding area between the PET nanofibers and the grids. At the same time, PET nanofibers had a thin deposition between the gaps of the PET grids, which not only increased the number of micron-nano-sized holes but also increased the light transmittance of the window screen. After filtration test for 5 h, the PM2.5 filtration efficiency of this anti-smog window screen was high as to 87% and the PET nanofiber window screen still maintained high light transmittance and superhydrophobicity. This research work is a promising way to prepare anti-smog window screens. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48657.     

Sensorless optimization of dead times in DC-DC converters with synchronous rectifiers

This paper introduces an approach to achieve optimum dead times in dc-dc converters with synchronous rectifiers without sensing any of the power-stage signals other than the output voltage. The dead times are adjusted adaptively to minimize the duty-cycle command, which results in maximization of the converter efficiency. The method is particularly well suited for digital controller implementation, requiring no additional analog components or modifications of standard gate-drive circuitry. Experimental results for a digitally controlled 5V-to-1V, 5-A synchronous buck converter demonstrate practical implementation of the sensorless dead-time optimization algorithm.     

High-efficiency preparation of polypropylene nanofiber by melt differential centrifugal electrospinning

Melt differential centrifugal electrospinning (MDCE) method is proposed by integrating the advantages of centrifugal spinning and melt differential electrospinning, including high efficiency, solvent-free, multiple jets formation from nozzle-less spinning system, and small diameter. A mathematical model of jet diameter in MDCE is established. An orthogonal experiment is carried out to explore the effects of main processing parameters on the average diameter and the diameter standard deviation of the prepared fibers. Ultimately, polypropylene (PP) nanofibers with an average diameter of 790 nm are successfully prepared in a higher flow rate of 124.26 g h⁻¹ than that of other methods. The X-ray diffraction and differential scanning calorimeter indicate that the introduction of high-voltage electrostatic field in centrifugal spinning contribute to the crystal orientation of the PP molecular chain. Therefore, tensile mechanical strength is enhanced as the increase of the loading voltage. MDCE may provide an efficient and eco-friendly method for nanofiber manufacturing in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48299.     

Fabrication of althea officinalis loaded electrospun nanofibrous scaffold for potential application of skin tissue engineering

The Althea Officinalis (AO) extract is well known as a traditional herbal drug for its wound healing ability owing to the anti-inflammatory and antimicrobial properties. Furthermore, its mucilaginous properties provide moisturizing and nutritional effects on skin cell proliferation. Therefore, AO extract can be applied in the temporary skin substitute for the ability to expedite the therapy duration. In this study, different concentrations of AO extract (0, 5, 10, 15, and 20 wt %) were incorporated into the nanofibrous scaffolds to study their potential for the skin tissue repairing. The desired scaffolds were prepared by electrospinning the blend of poly(ε -caprolactone) and gelatin as a synthesized and natural polymer. The electrospun nanofibers were characterized by SEM, FTIR, DSC, TGA, tensile, AO extract release, and cellular culture tests. This study proposed incorporating the AO extract into the nanofibrous scaffolds for accelerating the skin tissue repairing and the optimized amount of AO extract as about 15% was introduced for offering the most desirable electrospun scaffolds for this application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48587.     

Effect of Geometrical Parameters on Piezoresponse of Nanofibrous Wearable Piezoelectric Nanofabrics Under Low Impact Pressure

Piezoelectric polymers are potential energizers for wearable electronics due to the possibility of developing their yarns for various textile products. The present study is aimed at understanding the effect of geometrical parameters, viz., yarn linear density (measured as Tex), twist per meter (TPM), plying, as well as weft and warp density on the piezoelectric voltage of electrospun yarns of polyvinylidene fluoride (PVDF) polymer and poly[(vinylidene fluoride)-co-trifluoroethylene] [P(VDF-TrFE)] copolymer. Yarns are developed by twisting and plying electrospun nanofibers and their mechanical and piezoelectric properties are systematically investigated. Relative advantages of the yarns of the copolymer with respect to PVDF in both aligned and random fiber geometries are evaluated. The studies show that piezoresponse of the woven nanogenerators can be enhanced by decreasing Tex and increasing the TPM, the plying number, and the fabric density. A record piezovoltage of ≈2.5 V is achieved through this work. The results of the present work can be used for the fabrication of flexible and breathable nanogenerators or sensors.     

Preparation and characterization of nanocomposite hydrogels based on polyacrylamide for enhanced oil recovery applications

In the present work, attempts have been made to prepare nanocomposite type of hydrogels (NC gels) by crosslinking the polyacrylamide/montmorillonite (Na‐MMT) clay aqueous solutions with chromium (III). The X‐ray diffraction patterns of the NC gels exhibited a significant increase in d₀₀₁ spacing between the clay layers, indicating the formation of intercalated as well as exfoliated type of morphology. Exfoliation of the clay layers through out the gel network was found to be predominated, which evidences the high interaction between the polyacrylamide segments and montmorillonite layers. Gelation time as well as variation of viscoelastic parameters such as storage modulus (G′) of the gel network during gelation process at 75°C was studied and followed by rheomechanical spectroscopy (RMS). The NC gels prepared with lower crosslinker concentration showed higher strength and elastic modulus compared with the similar but unfilled polyacrylamide gel. This distinct characteristic of the NC gels yields a gel network structure with high resistance towards syneresis at high temperature in the presence of the oil reservoir formation water. The effects of the composition, such as clay content, crosslinker concentration, and also water salinity upon the gelation rate, gel strength as well as rate of syneresis have been investigated. To optimize the injectivity of the intercalated polyacrylamide solution before the onset of gelation with the gel strength of the final developed gel, sodium lactate was employed as retarder. This was found to be effective to balance these two characteristics of the NC gels, which are aimed to be used for water shut‐off and as profile modifier in enhanced oil recovery (EOR) process during water flooding process. The nanocomposite gels showed much more elasticity and extensibility at low crosslinker concentration compared with the similar but unfilled gel, which makes the NC gels suitable as an in‐depth profile modifier, and also as an oil displacing agent in the heterogeneous oil reservoir in chemical EOR. Effects of the clay content on the thermal stability of the gel network have also been investigated by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) has been performed upon the NC‐gel samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2096–2103, 2006     

Investigation of Hydrocarbon Recovery Failure in a Gas Refinery

Theoretical Foundations of Chemical Engineering - $${\text{C}}_{2}^{ + }$$ recovery is considered as a case study in a conventional turbo-expander process. Some practical problems occurred in the...     

Polymer melt differential electrospinning from a linear slot spinneret

Preparation of melt electrospun fibers with high efficiency and high productivity remains a big challenge. A polymer melt differential electrospinning system with linear slot spinneret (LSSP) was proposed in this work. Under a high electric field, multiple jets distributed at the tip of LSSP were self-organized from the polymer melt film with controlled thickness. The spinning parameters were investigated, and the electric filed between spinneret and collector was analyzed. The results showed that the interjet distance decreased significantly with the decrease of the thickness of polymer melt film and the Tayler cone size. The smallest average interjet distance of 1.9 mm with deviation of 0.5 mm was obtained under the condition of applied voltage of 45 kV, collecting distance of 9 cm, temperature of 250 °C, and slot thickness of 0.2 mm. The high output of 75.6 g/h was achieved and could be increased just by increasing the slot width. It was demonstrated that the proposed technology was a promising way to fabricate melt electrospun fibers with high efficiency. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48922.