Er~(3+)-Yb~(3+)-Na~+:ZnWO_4 phosphors for enhanced visible upconversion and temperature sensing applications

The crystal structure and surface morphology of the Er³⁺/Yb³⁺/Na+:ZnWO₄ phosphors synthesized by solid state reaction method were analyzed by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) analysis.The frequency upconversion(UC) emission study in the developed phosphors was investigated by using 980 nm laser diode excitation.The effect of codoping in the Er³⁺:ZnWO₄ phosphors on the UC emission intensity was studied.The UC emission bands that are exhibited in the blue(490 nm),green(530,552 nm),red(668 nm) and NIR(800 nm) region correspond to the ⁴F_7/2→⁴I_15/2.²H_11/2,⁴S_3/2→⁴I_15/2,⁴F_9/2→⁴I_15/2 and ⁴I9/2→⁴I_15/2 transitions,respectively.The temperature sensing performance of the Er³⁺-Yb³⁺-Na+:ZnWO₄ phosphors was investigated based on the 2 H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 thermally coupled transitions of the Er³⁺ions.The photometric study was also carried out for the developed phosphors.     

Ligand‐Free Copper‐Manganese Spinel Oxide‐Catalyzed Tandem One‐Pot C–H Amidation and N‐Arylation of Benzylamines: A Facile Access to 2‐Arylquinazolin‐4(3H)‐ones

An efficient ligand‐free copper‐manganese (Cu‐Mn) spinel oxide‐catalyzed direct tandem C−H oxygenation and N‐arylation of benzylamines has been developed. The method has been utilized for the synthesis of medicinally important 2‐arylquinazolin‐4(3H)‐ones. Salient features of this method include recyclable catalyst, no ligand, excellent product yields, shorter reaction times and a broad substrate scope.

     

Phytic acid in Indian soybean: genotypic variability and influence of growing location

Phytic acid, the heat‐stable anti‐nutritional factor, was determined in 80 cultivars/strains of Indian soybean to identify genotypes that possess low concentrations of phytic acid. Variation of values of 28.6–46.4 g kg⁻¹ soy flour was observed. Information on the influence of growing locations with widely differing soil types on phytic acid content being scarce, phytic acid in the mature dry seeds of eight Indian soybean cultivars grown over four locations was evaluated. Variation in different varieties at different locations was 27.8–45.0 g kg⁻¹ soy flour. Averaged over eight genotypes, the maximum mean value for phytic acid was observed at Pantnagar and the minimum at Palampur. These differences in locational mean values for phytic acid can be explained on the basis of characteristics of the soils and environment. The higher mean value at Pantnagar may be attributed to higher soil organic phosphorus, nearly neutral pH and favorable temperature from flowering to maturity. However, the lower value observed at Palampur can be explained by the acidic nature of its soil, with lower maximum and minimum temperatures prevailing from flowering to maturity. Locational and genotypic × locational effects were found to be significant (p < 0.01). The results indicated that soil characteristics and soil environment play a significant role in the accumulation of phytic acid in soybean seeds. Copyright © 2005 Society of Chemical Industry     

Heat transfer during microwave combination heating: Computational modeling and MRI experiments

Combination of heating modes such as microwaves, convection, and radiant heating can be used to realistically achieve the quality and safety needed for cooking processes and, at the same time, make the processes faster. Physics‐based computational modeling used in conjunction with MRI experimentation can be used to obtain critical understanding of combination heating. The objectives were to: (1) formulate a fully coupled electromagnetics ‐ heat transfer model, (2) use magnetic resonance imaging (MRI) experiments to determine the 3D spatial and temporal variation of temperatures and validate the numerical model, (3) use the insight gained from the model and experiments to understand the combination heating process and to optimize it. The different factors that affect heating patterns during combination heating such as the type of heating modes used, placement of sample, and microwave cycling were considered. Objective functions were defined and minimized for design and optimization. The use of such techniques can lead to greater control and automation of combination heating process benefitting the food process and product developers immensely. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Microstructure and Properties of Spark Plasma Sintered Carbon Nanotube Reinforced Aluminum Matrix Composites

In this paper, spark plasma sintering (SPS) of multi‐walled carbon nanotube (CNT) reinforced aluminum matrix composites is reported. Ball milling of the Al‐CNT mixture with polyacrylic acid (PAA) dispersion agent followed by SPS resulted in uniform dispersion of CNTs in dense composite compacts. Significant improvement in microhardness, nanohardness, and compressive yield strength was observed with 2 wt% CNT reinforcement in aluminum matrix composites. The Al‐CNT composites further exhibited improved wear resistance and lower friction coefficient due to strengthening and self‐lubricating effects of CNTs.     

Nucleation and Location of Kirkendall Voids at the Tin-Based Solder/Copper Joint: A Review

Void nucleation is a critical issue in wetting because it negatively impacts the solder joint and diminishes its electrical and mechanical properties. Generally, the Kirkendall effect (unbalanced diffusion) and Kirkendall voids (KVs) are developed due to dissimilar diffusivities of species (Cu and Sn) in a diffusion process. However, voids are also nucleated in the supersaturating condition, creating an additional position at or inside the “Kirkendall voids” interface. Various factors (surface modification, reinforcement of fourth elements, substrate type, and impurities) and the environment also support the nucleation of voids. Many researchers have discussed that KVs are nucleated into to intermetallic compounds layers. Reviewing the significant parameters for developing the KV in solid–liquid and solid–solid conditions is essential. Hence, in this review, the potential process of development of the KVs, concepts of thermodynamics, chemical reactions, and growth kinetics are developed. The position and reduction of KVs nucleation are also explained in this paper.     

Hydrogen embrittlement in different materials: A review

Hydrogen embrittlement (HE) is a widely known phenomenon in high strength materials. HE is responsible for subcritical crack growth in material, fracture initiation and catastrophic failure with subsequent loss in mechanical properties such as ductility, toughness and strength. This hydrogen is induced in the material during electrochemical reaction and high-pressure gaseous hydrogen environment. LIST, SSRT and TDS techniques are performed to know the effect in mechanical properties and amount of hydrogen available in the material. For microstructure examination SEM, FESEM and TEM are performed to know the effect of hydrogen in the internal crystal structure. Also, various mechanisms which are responsible for crack growth and final fracture are discussed. This paper deals with HE definition, mechanisms which causes HE, subcritical crack growth, the concentration of hydrogen measurement and prevention activities are discussed which act as a barrier for hydrogen diffusion.     

Characterization of Fe–C–Cr Based Hardfacing Alloys

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.     

Evaluation of position tracking technologies for user localization in indoor construction environments

Evolving technologies such as location-aware computing offer significant potential of improving important decision-making tasks on construction sites by providing support for tedious and time-consuming tasks associated with timely and accurate access to project information. For example, rapid and convenient access to contextual project information, through continuous position tracking of engineers, managers, and inspectors, can lead to significant cost and time savings due to the accuracy and immediacy with which relevant project information can be made available to field personnel. Considering the spatial expanse and dynamic nature of typical construction projects, mobile users need to be constantly tracked both outdoors as well as indoors. The Global Positioning System (GPS) is an attractive option for outdoor environments, but is not suitable for indoor applications because it needs a clear line-of-sight to orbital satellites in order to track position. As a result, alternate means of tracking users' location in indoor environments without relying on GPS is needed. This paper presents research that investigated the effectiveness of three wireless technologies for dynamic indoor user position tracking. In particular, Wireless Local Area Networks (WLAN), Ultra-Wide Band (UWB), and Indoor GPS positioning systems are evaluated and compared. Experimental results demonstrate the ability of Indoor GPS, in particular, to estimate a mobile user's location with relatively low uncertainty (1 to 2 cm).     

Effect of tool rotation in near-dry EDM process on machining characteristics of HSS

Rotary tool near-dry electrical discharge machining (RT-ND-EDM) is a process variant of EDM, which utilizes two phase dielectric medium instead of a conventional liquid or gaseous dielectric medium. The present work, RT-ND-EDM was investigated while machining of high speed steel (AISI M2 grade) using glycerin-air dielectric medium. The effect of various input process parameters was investigated on material removal rate (MRR), surface roughness (SR), and hole overcut (HOC). The input parameters considered were tool rotation speed, current, pulse on time, liquid flow rate, and gas pressure. Experiments were designed and conducted using response surface methodology. Regression models were also developed. The results revealed that the tool rotation speed has a significant effect on MRR, SR, and HOC. FE-SEM micrographs showed that the machined surfaces obtained by RT-ND-EDM have relatively lower micro-cracks, debris accumulation and craters. Also, deep through holes were successfully drilled in 24 mm plate using RT-ND-EDM process.