Tuning the crystal structure and optical properties of selective area grown InGaAs nanowires

Catalyst-free InGaAs nanowires grown by selective area epitaxy are promising building blocks for future optoelectronic devices in the infrared spectral region.D...     

Reformulated gasoline: Cleaner air on the road to nowhere

U.S. legislation taking effect in 1995 and requiring the sale of cleaner reformulated gasoline in heavily polluted areas provides limited environmental benefits, but it fails to take into account the world's dwindling reserves of oil, the eroding economics of using oil, and the political and military costs of maintaining access to non-domestic supplies. In contrast, natural gas offers greater emissions reductions than reformulated gasoline, at lower fuel costs and with greater domestic supply and energy security. In the long term, the expansion of the infrastructure that would support natural gas vehicles could facilitate the transition to hydrogen which, when produced from renewable resources, could become the optimum fuel for a sustainable transportation energy economy.     

An Implicit Approach for Numerical Simulation of Water Hammer Induced Pressure in a Straight Pipe

Water Resources Management - An accurate prediction of propagation speed and the magnitude induced pressure in water hammer is very critical for the analysis, design, and operation of pipeline...     

Micromachining of amplitude and phase modulated reflective computer generated hologram patterns in silicon

Silicon has been machined on lateral resolutions of micrometers and on depth resolutions of nanometers using a recently-developed process based on ion irradiation and electrochemical anodisation. Here we investigate its use as a recording medium for computer generated hologram patterns. We describe the fabrication of both amplitude and phase binary modulated reflective computer generated hologram patterns on a silicon surface with pixel sizes of 5 μm. We further discuss the use of micromachined silicon to variably modulate both amplitude and phase in a continuous, rather than a binary fashion.     

Development of asphalt cements for road pavement using sustainable nanomaterials: A review

In today's world, transportation infrastructure plays a vital role in global competitiveness and quality of life in societies. The pavement industry deals with tremendous amounts of construction materials. Thus, even a small improvement in the technology can lead to significant environmental benefits and a reduction in the life-cycle cost of road networks. Asphalt cement is an integral part of road pavement construction, and despite favorable properties at the processing temperature, some challenges need to be addressed to reduce cost and improve performance. This review discusses the nanocellulose modification of asphalt cement for pavement application. Three primary cellulose-based nanoparticles were studied, including bacterial cellulose, cellulose nanofibers, and cellulose nanocrystals, and their applications in asphalt cement modification. Various research results show significant improvement in pavement's rheological and performance properties with the help of cellulose-based nanoparticles. However, this review provides the reader with an objective evaluation of the benefits and practical challenges ahead of the industrial-scale application of nanocellulose in the pavement industry.     

Optimal design of engineered gas adsorbents: Pore-scale level

This study presents an optimization methodology and results for the structure of gas adsorbents at a pore level by evaluating the effect of pore geometry, size and overall adsorbent porosity on ultimate working capacity of adsorbents used in pressure swing adsorption (PSA) processes. Three model pore network topologies are studied: parallel, grid-like and branched structures. These are “near” optimal structures for an adsorbent particle and their relative performance is compared in a two-step PSA cycle. The macropore network of such structured adsorbents is optimized through maximization of an objective function i.e. working capacity WC, defined as the number of moles adsorbed per unit volume of slab. Molecular and Knudsen diffusion are considered as the sole transport mechanisms in the macropore channels. An unexpected finding of this optimization technique is that the branched structure with a porosity of less than 50% represents an optimum structure with highest working capacity for the system considered. Furthermore, for faster cycles the advantage of branched structures is more obvious, reflecting the advantages of the pore network in facilitating diffusion more efficiently than other structures. A macropore channel density (defined as the density of macropores per metre of external surface) of below 10 is suggested for optimum performance for both “fast” and “slow” PSA cycles. The theoretical results of this study will be used as a priori results for the design of adsorbents at the macro-scale (bed) level.     

Thermal performance analysis of arbitrary-profile fins with non-fourier heat conduction behavior

The thermal performance of variable cross-section fins is considered using the Maxwell–Cattaneo–Vernotte (MCV) heat conduction model. Four different fins, namely rectangular, triangular, convex, and concave fins, with a periodic thermal condition are examined. The governing equations are hyperbolic and are solved numerically using an implicit finite difference method. In the MCV model, the thermal wave propagates with a finite speed, and hence sharp discontinuities appear in the temperature profiles. In this study, temperature profiles at various times, heat transfer rates, and thermal efficiencies of Fourier and non-Fourier fins are presented. In addition, the effect of relaxation time is considered. The results show that the effects of cross-sectional area and relaxation time are considerable on the thermal performance of various non-Fourier fins. To validate our findings, the results for non-Fourier fins with constant cross-sectional area obtained from this study are compared to those of other numerical solutions. This comparison confirms the correctness of the current results.     

Semi-automatic measurement of rigid gas-permeable contact lens movement in keratoconus patients using blinking images

Purpose

To introduce a method for estimation of the rigid gas-permeable contact lens (RGP) movement.

Synthesis of a novel Zn-MOF/PVA nanofibrous composite as bioorganic material: Design,systematic study and an efficient arsenic removal

Metal organic framework (Zn-MOF)/polyvinyl alcohol (PVA) nanofibrous composite new material has been fabricated using electrospinning and is characterized by a variety of physicochemical analyses, including Fourier transmitting infrared spectroscopy, X-ray powder diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy, nitrogen adsorption surface, and thermo gravimetric-derivative of thermogravimetry. In this study, the effects of a systematic study including a fractional factorial design were studied for arsenic removal. The results showed that although conventional methods have a high level of arsenic removal, the fractional factor method results in a relatively high level of absorption of arsenic. This high level of arsenic removal allows the potential use of nano adsorbents in various environmental fields. The systematic study developed in this study can be used as a novel protocol to eradicate pollution from different areas, including water, air, and soil.