Effect of post drawing on morphology of bubbfil-spun polyvinyl alcohol nanofibers was firstly investigated. Bamboo-like nanofibers were observed after drawing. The increase of surface area of the unsmooth fibers has many potential applications in various fields.
The semi-inverse method applied to the search for variational formulae directly from the field equations and boundary conditions is introduced, a family of variational principles for thermoelasticity with voids is deduced systematically without using the Lagrange multiplier method.
By the semi-inverse method, a variational principle is obtained for the Thomas–Fermi equation, then the Ritz method is applied to solve an analytical solution, which is a much simpler and more efficient method.
Water pollution has become a major global problem and requires an immediate action. It was generally considered that pollutants were diffused gradually from surface to underwater region, where plants and animals should have less affected. However, diffusion of contamination is very slow in comparison with penetration. Here we show saline water has a highly selective penetration, and the penetration rate is much higher than that of diffusion. An experiment was carried out using a drop of red ink as a point pollution source to check both diffusion and penetration processes in various salt solutions with different concentrations, the salt concentration greatly affects the penetration process and there is a threshold value beyond which no penetration occurs. An imaged capillary is adopted in this paper to explain the selective penetration on a molecular scale, revealing that the salt concentration and temperature will greatly affect the capillary pressure and the penetration depth. Our results demonstrate that the penetration is the main pollution dispersion, and we anticipate our theory would shed light upon the major pollution problem from theoretical analysis to pollution control.
No abstract is provided for this article.
Rocks have good chemical and thermal properties, which are widely distributed in mountainous areas and contain a great number of chemical elements. Weathered rock powders were used as an additive in an electrospun solution to fabricate rock powder-based nanofibers, and the morphology and thermal property of nanofibers were studied. The results revealed that the rock powder was the most economical approach to fabrication of nanofibers with excellent thermal property and high hydrophilicity. This paper sheds a light on rock powder-based nano-fibers with well-defined characteristics for advanced applications for high temperature filtration and absorption, fire prevention and others.
?Everything should be made as simple as possible?, as said by Albert Einstein, and thermal science is the best candidate to make a complex problem simple. This article introduces that the virus prevention is simple, only a cup of hot water is enough. Beyond its towering contribution to everyday life, thermal science is also an avid helper in each research frontier of science and technology, nothing is impossible. The new emerging two-scale thermal science is also elucidated.
Polar bears can live in an extremely cold environment due to their hairs which possess some remarkable properties. The hollow structure of the hair enables the bear to absorb energy from water, and the white and transparent hairs possess amazing optical properties. However, the surface morphology function of bear hairs has been little-studied. Herein, we demonstrate that the micro-structured scales distributed periodically along the hair can absorb maximal radiative flux from the Sun. This polar bear hair effect has the ability for the hair surface not to reflect radiation with a wavelength of about 500 nm. Mimicking the polar bears' solar performance in the fabrication of nanofibers will certainly stimulate intelligent nanomaterials for efficient solar energy absorption. Therefore, a new technology is discussed in this work for the fabrication of periodic unsmooth nanofibers toward solar energy harvesting.
The polar bear hairs have special hierarchical structure with fractal dimensions of golden ratio, which endows the creature with remarkable cool prevention. Fractal calculus is adopted in this paper to reveal its thermal properties, and a fractal derivative model of one-dimensional heat conduction along the hair is established and solved, the results reveal that there is an optimal hair length for the cool prevention. This paper sheds a new light on bio-inspired fabrics for fire-protection clothing and clothing for extreme environment.
A charged jet can be accelerated by an electrostatic field for fabrication of continuous micro/nanofibers. A higher voltage results in smaller nanofibers. However, when the voltage surpasses a threshold value, discontinuous nanomaterials can be fabricated.
Along with the advent of an ever-increasing demand for the nano-industrialization, nanofibers become a unique class with many fascinating properties due to their nanoscale diameters and high surface area to volume ratio [...].
The current work examines the application of the viscous potential flow to the Kelvin-Helmholtz instability (KHI) of a planar interface between two visco-elastic Walters’ B fluids. The fluids are fully saturated in porous media in the presence of heat and mass transfer across the interface. Additionally, the structure is pervaded via a uniform, normal electrical field in the absence of superficial charges. The nonlinear scheme basically depends on analyzing the linear principal equation of motion, and then applying the appropriate nonlinear boundary-conditions. The current organization creates a nonlinear characteristic equation describing the amplitude performance of the surface waves. The classical Routh–Hrutwitz theory is employed to judge the linear stability criteria. Once more, the implication of the multiple time scale with the aid of Taylor theory yields a Ginzburg–Landau equation, which controls the nonlinear stability criteria. Furthermore, the Poincaré–Lindstedt technique is implemented to achieve an analytic estimated bounded solution for the surface deflection. Many special cases draw upon appropriate data selections. Finally, all theoretical findings are numerically confirmed in such a way that ensures the effectiveness of various physical parameters.
A new direction in Sirospinning is nano-sirospinning, i.e., composition of a micro-composite yarn from thousands of nano fibers, just like that in spider-spinning, to improve the bulk of the parent nanofibers, the obtained yarn is predicted to be of excellent texturing with desirable properties. Bubble electrospinning is be used for this purpose.
