The deformation physics of nanocrystalline metals: Experiments, analysis, and computations

This article presents a review of the principal mechanisms responsible for the plastic deformation of nanocrystalline metals. As the concentration of grain boundaries increases, with a decrease in grain size there is a gradual shift in the relative importance of the deformation mechanisms away from the ones operating in the conventional polycrystalline domain. This is predicted by molecular dynamics simulations that indicate a preponderance of dislocation emission/annihilation at grain boundaries and grain-boundary sliding when grain sizes are in the range 20–50 nm. Experiments show, in general, a saturation in work hardening at low strains, which is indicative of a steady-state dislocation density. This saturation is accompanied by an increased tendency toward shear localization, which is supportive of dislocation generation and annihilation at grain boundaries. Dislocation analyses recently proposed corroborate the computational predictions and provide a rational foundation for understanding the mechanical response.     

One-Step Atmospheric Pressure Synthesis of the Ground State of Fe Based LaFeAsO<Subscript>1−<Emphasis Type="Italic">δ</Emphasis></Subscript>

We report an easy and versatile one-step synthesis route for a newly discovered Fe based LaFeAsO_1−δ compound with 0.0≤δ≤0.15. Instead of widely used high-pressure-high-temperature (HPHT) synthesis, we applied the normal atmosphere solid-state reaction route. The stoichiometric mixtures of Fe, La₂O_3, La, and As in ratio LaFeAsO_1−δ with 0.0≤δ≤0.15 are sealed in an evacuated quartz tube and further heated at 500, 850, and 1,100 °C in Ar for 12, 12, and 33 hours, respectively, in a single step. The resulting compounds are single phase LaFeAsO crystallized in tetragonal P4/nmm structure. These samples showed the ground state spin density wave (SDW) like metallic behavior below around 150 K. In conclusion, the ground state (non-superconducting) of newly discovered Fe based superconductor is synthesized via an easy one-step solid-state reaction route.     

Influence of skew rays on the sensitivity and signal-to-noise ratio of a fiber-optic surface-plasmon-resonance sensor: a theoretical study

We have theoretically analyzed the influence of skew rays on the performance of a fiber-optic sensor based on surface plasmon resonance. The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for skewness dependence includes the material dispersion in fiber cores and metal layers, simultaneous excitation of skew rays, and meridional rays in the fiber core along with all guided rays launching from a collimated light source. The effect of skew rays on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the different values of design parameters such as numerical aperture, fiber core diameter, and the length of the surface-plasmon-resonance (SPR) active sensing region. This detailed analysis for the effect of skewness on the SNR and the sensitivity of the sensor leads us to achieve the best possible performance from a fiber-optic SPR sensor against the skewness in the optical fiber.     

Laminar Flow and Heat Transfer Phenomena Across a Confined Semicircular Bluff Body at Low Reynolds Numbers

The present study is concerned with the simulation of incompressible Newtonian fluid flow and heat transfer over a long semicircular bluff body in a channel at low Reynolds numbers. In particular, wall effects on the forced convection from a (heated) semicircular cylinder confined in a horizontal channel are investigated for Reynolds number = 1–40 and blockage ratio = 16.67–50% for air as the working fluid. Flow and thermal fields are found steady for the preceding range of settings. The onset of flow separation increases as the wall confinement increases. The size of the recirculation zone downstream of a semicircular cylinder is seen to increase almost linearly with Reynolds number for a fixed blockage ratio, but it decreases with increasing blockage ratio for a fixed Reynolds number. As expected, total drag coefficient and its components decrease with increasing value of Reynolds number. However, with increasing blockage ratio, the values of these drag coefficients increase. On the basis of equal projected area, the total drag coefficient for the present flow system is found to be greater than the corresponding drag in the case of the unconfined semicircular cylinder. Similarly, the overall drag in the case of a confined semicircular cylinder is found to be greater than that of a confined circular cylinder for the appropriate range of dimensionless control parameters. The maximum augmentation in heat transfer for blockage ratios of 25% and 50% is found to be approximately 16% and 51% with respect to the corresponding value at the blockage ratio of 16.67% at Reynolds number = 1. Finally, the correlations of wake length, drag coefficient, and average Nusselt number are obtained.     

A deep‐learning‐based computer vision solution for construction vehicle detection

This paper aims at providing researchers and engineering professionals from the first step of solution development to the last step of solution deployment with a practical and comprehensive deep‐learning‐based solution for detecting construction vehicles. This paper places particular focus on the often‐ignored last step of deployment. Our first phase of solution development involved data preparation, model selection, model training, and model validation. Given the necessarily small‐scale nature of construction vehicle image datasets, we propose as detection model an improved version of the single shot detector MobileNet, which is suitable for embedded devices. Our study's second phase comprised model optimization, application‐specific embedded system selection, economic analysis, and field implementation. Several embedded devices were proposed and compared. Results including a consistent above 90% mean average precision confirm the superior real‐time performance of our proposed solutions. Finally, the practical field implementation of our proposed solutions was investigated. This study validates the practicality of deep‐learning‐based object detection solutions for construction scenarios. Moreover, the detailed information provided by the current study can be employed for several purposes such as safety monitoring, productivity assessments, and managerial decision making.     

Use of aluminum oxide nanoparticles in wood composites to enhance the heat transfer during hot-pressing

In this study, the effect of Al₂O₃ nanoparticles on the heat-transfer properties of medium density fiberboard (MDF) was investigated. Al₂O₃ nanoparticles were added at two levels (0.5 and 1.0 %) by percentage weight fraction of dry wood fibers to urea formaldehyde (UF) resin. The core temperature profile and thermal conductivity tests showed higher rate of heat transfer after addition of nanoparticles, subsequently it has improved the bonding strength of MDF. Differential scanning calorimetry was used to estimate the heat evolved during the exothermic reaction of UF resin curing. Scanning electron microscopy shows good dispersion of nanoparticles. Thermal conductivity of UF resin improved after nanoparticles addition proved by KD2 pro results. Modulus of rupture, modulus of elasticity and thickness swelling also improved.     

Nickel silicide formation by electroless technique for ULSI technology

In this paper we report on the formation of nickel silicide by electroless process. The nickel plating solution was composed of a mixture of NiSO₄·6H₂O, NaH₂PO₂·H₂O, Na₃C₆H₅O₇, and NH₄Cl, where NiSO₄·6H₂O is the main nickel source and NaH₂PO₂·H₂O is the reducing agent. The nickel silicide formation was carried out by heating the deposited samples in vacuum at temperatures from 100 °C to 800 °C. The evolution of NiSi phase from the nickel film was verified using the X-ray diffraction technique and Raman spectroscopy. The surface morphology was studied using AFM technique. The electroless plating technique can provide a cheap and easy process for forming nickel silicide, and has potentiality of application for the electronic device industries.     

S-,N-and C-doped ZnO as semiconductor photocatalysts:A review

In the past few decades,many novel non-metal doped ZnO materials have developed hasty interest due to their adaptable properties such as low recombination rate and high activity under the solar light exposure.In this article,we compiled recent research advances in non-metal(S,N,C)doped ZnO,emphasizing on the related mechanism of catalysis and the effect of non-metals on structural,morphological,optical and photocatalytic characteristics of ZnO.This review will enhance the knowledge about the advancement in ZnO and will help in synthesizing new ZnO-based materials with modified structural and photocatalytic properties.     

Sugarcane bagasse and leaves: foreseeable biomass of biofuel and bio‐products

Sugarcane is among the principal agricultural crops cultivated in tropical countries. The annual world production of sugarcane is ～1.6 billion tons, and it generates ～279 million metric tons (MMT) of biomass residues (bagasse and leaves). Sugarcane residues, particularly sugarcane bagasse (SB) and leaves (SL) have been explored for both biotechnological and non‐biotechnological applications. For the last three decades, SB and SL have been explored for use in lignocellulosic bioconversion, which offers opportunities for the economic utilization of residual substrates in the production of bioethanol and value‐added commercial products such as xylitol, specialty enzymes, organic acids, single‐cell protein, etc. However, there are still major technological and economic challenges to be addressed in the development of bio‐based commercial processes utilizing SB and SL as raw substrates. This article aims to explore SB and SL as cheaper sources of carbohydrates in the developing world for their industrial implications, their use in commercial products including commercial evaluation, and their potential to advance sustainable bio‐based fuel systems. Copyright © 2011 Society of Chemical Industry     

Supermacroprous chitosan–agarose–gelatin cryogels: in vitro characterization and in vivo assessment for cartilage tissue engineering

The study focuses on the synthesis of a novel polymeric scaffold having good porosity and mechanical characteristics synthesized by using natural polymers and their optimization for application in cartilage tissue engineering. The scaffolds were synthesized via cryogelation technology using an optimized ratio of the polymer solutions (chitosan, agarose and gelatin) and cross-linker followed by the incubation at sub-zero temperature (−12°C). Microstructure examination of the chitosan–agarose–gelatine (CAG) cryogels was done using scanning electron microscopy (SEM) and fluorescent microscopy. Mechanical analysis, such as the unconfined compression test, demonstrated that cryogels with varying chitosan concentrations, i.e. 0.5–1% have a high compression modulus. In addition, fatigue tests revealed that scaffolds are suitable for bioreactor studies where gels are subjected to continuous cyclic strain. In order to confirm the stability, cryogels were subjected to high frequency (5 Hz) with 30 per cent compression of their original length up to 1 × 10⁵ cycles, gels did not show any significant changes in their mass and dimensions during the experiment. These cryogels have exhibited degradation capacity under aseptic conditions. CAG cryogels showed good cell adhesion of primary goat chondrocytes examined by SEM. Cytotoxicity of the material was checked by MTT assay and results confirmed the biocompatibility of the material. In vivo biocompatibility of the scaffolds was checked by the implantation of the scaffolds in laboratory animals. These results suggest the potential of CAG cryogels as a good three-dimensional scaffold for cartilage tissue engineering.