Effect of Duplex Ageing on the Properties of A356 Alloy Containing Rare Earth Elements

Reduced weight of automobiles for the purpose of fuel economy has encouraged the use of light metals especially aluminium alloys. A356 Al alloy containing 7% Si and 0.3% Mg is widely used in automobile and aircraft industries due to excellent castability, good corrosion resistance and good pressure tightness. A356 is age hardenable alloy and there is appreciable improvement in strength and hardness achievable due to precipitation of intermetallic compound Mg₂Si. In the present investigation, aluminium alloy A356 with and without rare earth (RE) addition (0.5 wt%) was subjected to single ageing as well as double aging treatment. The results were compared for mechanical properties like hardness and ultimate tensile strength with the material not containing RE additions.     

Determination of deuterium site occupancy in ZrCoD3 and its role in improved durability of Zr–Co–Ni deuterides against disproportionation

In the present study, we have for the first time reported the occupancy of deuterium in a new interstitial site of ZrCoD₃ which explain the hydrogen induced disproportionation behavior of ZrCo alloy. We have also reported the effect of Ni substitution on interstitial site occupancy of deuterium in ZrCo_1−xNi_xD₃, which in turn explains the improved durability of these Ni substituted deuterides against disproportionation. The crystal structure of the ZrCo_1−xNi_x (x = 0.0, 0.1, 0.2, 0.3) deuterides was investigated by X-ray powder diffraction and neutron diffraction methods. The XRD data reveals a single phase formation for all deuterides with varying Ni content (x). The neutron diffraction study shows that deuterium occupies a new site 8e in addition to 4c₂ and 8f₁. Additionally, the Zr–D distance in 8e site is shorter than that in ZrD₂. Therefore, increase in 8e site occupancy will in turn decreases the durability against disproportionation and vice-versa. Furthermore, the neutron diffraction reveals that occupancy of new 8e site decreases and its Zr–D distance increases with increase in Ni content, which explicate the higher durability against disproportionation for Ni rich compound.     

Simultaneous extraction of source and drain resistances in top contact organic thin film transistors from a single test structure

A method of extraction of source and drain resistances in linear mode of operation from a single transistor is described. The proposed method can also be used to measure source resistance over the entire operating range from linear to saturation mode of operation. The method uses two floating probes outside the channel, one adjacent to the source and the other to the drain to sense the voltage under these contacts. Using transmission line analysis, the source and drain resistances are directly extracted from these measurements. 2D numerical simulation results confirm the validity of the proposed technique and sensitivity analysis shows that the method is more accurate than the conventional gated four probe technique, especially, when the source resistance is much smaller than the channel resistance. Experimental results obtained with Pentacene top-contact transistors are used to illustrate the proposed technique. Analysis of two devices with very different source resistance is carried out to highlight the ability of the proposed technique to offer insight into the different contributing factors. Current crowding under the source contact and accurate estimation of mobility without the distorting effects of source resistance are also described.     

Oxime-Modified Aluminum(III) Isopropoxide: A Promising Sol–Gel Precursor for Corrosion Resistive Nano-Alumina Coating on an Aluminum Alloy

Protection of Metals and Physical Chemistry of Surfaces - Dense alumina coatings were fabricated over aluminum alloy via dip coating method using oxime-modified aluminum(III) isopropoxide as a...     

Uncertainty Assessment in Cognitive Load for Multiple Object Tracking Based on EEG

Cognitive load varies the attention level, which has serious consequences in complex dynamic situations. Assessment of uncertainty in cognitive load during multiple object tracking task is necessary, as it is used to improve the cognitive capabilities. The present research work investigates the uncertainty in cognitive load of multiple object tracking task using electroencephalograph (EEG) on 25 football players. A d2 test of neuropsychological measure of attention was employed before starting the experiment. Each player participated in four levels of the task with variation in the cognitive load, which varies in terms of the targets from 2 to 5. Percentage changes in the power spectral density were estimated for the cognitive levels. Results show that the percentage changes were much more in high cognitive load than in low cognitive load. Significant changes (p < 0.05) were observed in level 1 (− 11.07 to 1.91%), level 2 (− 3.13 to − 14.51%), level 3 (− 6.33 to − 19.46%) and level 4 (− 8.10 to − 20.88%). Variation in the EEG data in terms of the combined uncertainty corresponds very well with low to high cognitive loads. The fourth level of the task with high cognitive load has more uncertainty than the low cognitive load levels. The results are useful for assessing the cognitive state of the player, which is valuable for the design of the effective training model.     

Controlled morphology and optical properties of n-type porous silicon: effect of magnetic field and electrode-assisted LEF

Fabrication of photoluminescent n-type porous silicon (nPS), using electrode-assisted lateral electric field accompanied with a perpendicular magnetic field, is reported. The results have been compared with the porous structures fabricated by means of conventional anodization and electrode-assisted lateral electric field without magnetic field. The lateral electric field (LEF) applied across the silicon substrate leads to the formation of structural gradient in terms of density, dimension, and depth of the etched pores. Apart from the pore shape tunability, the simultaneous application of LEF and magnetic field (MF) contributes to a reduction of the dimension of the pores and promotes relatively more defined pore tips as well as a decreased side-branching in the pore walls of the macroporous structure. Additionally, when using magnetic field-assisted etching, within a certain range of LEF, an enhancement of the photoluminescence (PL) response was obtained.     

Carbon nanotube reinforced hydroxyapatite composite for orthopedic application: A review

Application of hydroxyapatite (HA) in orthopedic implants suffers from its low fracture toughness and poor wear resistance. Carbon nanotube (CNT), with its high stiffness and mechanical strength, is an attractive reinforcement for HA to surmount these issues. The last 7–8 years have seen a number of studies to explore the efficiency of CNT reinforcement in strengthening HA, in the form of composites and coatings. Impressive improvement in the fracture toughness and wear resistance of HA with CNT reinforcement and beneficial effects on biocompatibility has sparked further research interests, for possible clinical applications. This review article aims to cover a wide span of this exciting and expanding research arena – from detailed technical discussions on HA–CNT system, their processing techniques and the influence of CNT dispersion in the HA matrix. Role of CNT in the improvement of mechanical properties and tribological behavior of the composite has been discussed in light of different processing techniques. Other important issues related to HA–CNT system, e.g., phase transformation and crystallinity of HA and HA–CNT interfacial bonding has been stressed upon. Biocompatibility of HA–CNT composites, which is extremely important for its intended orthopedic application, has been summarized with an overview of the present status. An in-depth analysis of the information presented in this review facilitates a better understanding of the current state of HA–CNT research and allows framing guidelines toward future research direction for its successful clinical application.     

Power Spectral Density Analysis of Pressure Fluctuation in Pneumatic Conveying of Powders

In order to reveal the unsteady features of gas–solid flow, the pressure fluctuations were measured at different locations along the length of the pipeline while conveying powders through the pipeline. Power spectral density (PSD) functions were obtained for the analysis of the pressure fluctuation. Two types of powders (fly ash and alumina) were used in this analysis. The PSD analysis was conducted by taking into account different aspects such as flow conditions (dilute or dense), location of transmitter (top and bottom transmitters), location of transmitter along the length of the pipeline (three different locations), material property (fly ash or alumina), etc. Analysis of signals from top and bottom transmitters shows that it is not possible to identify the flow mode at upper and lower portions of pipeline. The magnitude of power is found to be higher for alumina as compared to fly ash. PSD parametric analysis reveals that frequency bandwidth and average power decreases exponentially with increase in solid loading ratio.     

An economical and efficient protocol for total RNA isolation from Jatropha curcas

Jatropha curcas is an important non feed crop, increasingly important as a biofuel crop. It is hardy and resistant to different stress conditions in the field. In the wastelands of Gujarat (India), it is being grown for land reclamation and for socio-economic benefits. The long coastline in this state also promotes the growth of a large number of halophytes. Exploiting the genetic resource of Jatropha and halophytes for drought and salt-induced gene is an important area of research. For the isolation of genes and to study the molecular mechanism a good qualitative and quantitative RNA is a prerequisite. Jatropha leaves have latex, and therefore isolating RNA using guanidine thiocyanate or cetyltrimethylammonium bromide did not yield desirable quality of RNA. This paper reports a very simple and economical protocol for the isolation of good quality RNA from Jatropha and a few halophytes. The sodium dodecyl sulphate was used as a detergent for lysis of plant cells in the extraction buffer along with bentonite, which inhibits the ribonuclease’s activity. The addition of water saturated phenol in mortar-pestle, during grinding, facilitated better homogenisation of the tissues. Absolute RNA precipitation was obtained with the help of 2-butoxyethanol. Further this RNA was used successfully in preparation of complementary DNA and subsequently used for gene isolation.