Comparison of deformation induced precipitation behaviour in Alloy 718 under two microstructural conditions

Alloy 718 samples under two initial microstructural conditions, viz., solution annealed to form only γ phase (ST) and aged to precipitate only δ particles (DELTA), were deformed in tension till fracture in the temperatures range from 200°C–700°C. From the comparison of the evolved microstructure of deformed and undeformed specimens that have been subjected to similar thermal history, deformation induced precipitation could be identified. Deformation in the range of 550°C to 650°C promoted the precipitation of γ′ and γ″ phases in both structures. In case of DELTA alloy, the γ′ precipitation was found to precede the γ′ phase precipitation while no such preference for precipitation could be identified in ST specimens. This difference in the precipitation behaviour and the sequence of precipitation has been explained on the basis of the relative concentration of solutes in the matrix of the starting microstructures of ST and DELTA specimens.     

Response of Materials During Sliding on Various Surface Textures

In the present investigation, soft materials, such as Al-4Mg alloy, high-purity Al and pure Mg pins were slid against hard steel plates of various surface textures to study the response of materials during sliding. The experiments were conducted using an inclined pin-on-plate sliding apparatus under both dry and lubricated conditions in an ambient environment. Two kinds of frictional response, namely steady-state and stick-slip, were observed during sliding. In general, the response was dependent on material pair, normal load, lubrication, and surface texture of the harder material. More specifically, for the case of Al-4Mg alloy, the stick-slip response was absent under both dry and lubricated conditions. For Al, stick-slip was observed only under lubricated conditions. For the case of Mg, the stick-slip response was seen under both dry and lubricated conditions. Further, it was observed that the amplitude of stick-slip motion primarily depends on the plowing component of friction. The plowing component of friction was the highest for the surfaces that promoted plane strain conditions and was the lowest for the surfaces that promoted plane stress conditions near the surface.     

X-ray diffraction and H-storage in ultra-small palladium particles

In situ X-ray diffraction (XRD) and gravimetric hydrogen uptake measurements of d ∼ 2–3 nm spherical PdH_x particles have been studied in the temperature and pressure range of 323 < T < 428 K and 0 < P < 10 bar. The Pd particles were protected from sintering with a hydrogen-permeable carbon coating. While only containing ∼300–1000 atoms, the Pd particles were found to exhibit the same fcc structure and lattice constant as the bulk. Our isothermal studies show that, with increasing x, these highly crystalline PdH_x nanoparticles also exhibit a complete transformation from the dilute α solid solution phase to the more concentrated β hydride phase. However, we observed that the character of the α–β phase transition in these nanoparticles is very different from that in the bulk. Indeed, the hydrogen uptake isotherm exhibits a noticeable positive slope in the α + β co-existence region. Furthermore, we also observed a noticeable narrowing of the α + β co-existence region (δx) in the nanoparticles. Also, a significant suppression of the critical temperature T_c for the phase boundary was observed: T_c(nano) ≈ 430 K while T_c(bulk) ≈ 570 K. These results signal a significant change in the thermodynamic behavior of very small hydride nanoparticles that may be common to many other nano-scale metal hydride systems as well.     

Variability of mesopause temperature derived from two independent methods using meteor radar and its comparison with SABER and EOS MLS and a collocated multi-wavelength dayglow photometer over an equatorial station,Thumba (8.5° N, 76.5° E)

Two independent methods for deriving mesopause temperature using meteor radar installed at an equatorial station, Thumba (8.5° N, 76.5° E), are discussed in this article. This meteor radar-derived mesopause temperature is then compared with two different types of spaceborne measurement, namely (i) Sounding the Atmosphere using Broadband Emission Radiometry (SABER) and (ii) the Earth Observing System Microwave Limb Sounder (EOS MLS), and a collocated multi-wavelength dayglow photometer (DGPM). The meteor radar-derived temperature is in fairly good agreement with all the three measurement techniques, with an uncertainty of ±10°. This study focuses on a detailed evaluation and inter-comparison of mesopause temperature derived from different measurement techniques. An attempt is also made to compare the suitability of these observations to study planetary waves and other oscillation activities in the mesospheric region.     

Features of ultrasonic wave propagation to identify defects in composite materials modelled by finite element method

A two-dimensional plane strain finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave propagation in isotropic and orthotropic media. It is capable of simulating the experimental pulse echo technique to obtain A-scan data, when a short duration pulse is transmitted into a domain with or without a flaw. The flaw can either be a crack or an inclusion of different material such as a Teflon insert or a resin rich zone. After performing FFT on the A-scan data, frequency domain feature analysis is done. The study provides a guideline regarding the suitability of certain harmonics sensitive to certain types of flaw. The simulation shows other important artifacts of wave propagation such as mode conversion and scattering due to the presence of flaws.     

Computational study on metal hydride based three-stage hydrogen compressor

A mathematical model for predicting the performances of a three-stage metal hydride based hydrogen compressor (MHHC) is presented. The performance of the MHHC is predicted by solving the unsteady heat and mass transfer characteristics of the coupled metal hydride beds of cylindrical configuration. The governing equations for energy, momentum and mass conservations, and reaction kinetic equations are solved simultaneously using the finite volume method. Metal hydrides chosen for a three-stage MHHC are LaNi₅, MmNi_4.6Al_0.4 and Ti_0.99Zr_0.01V_0.43Fe_0.99Cr_0.05Mn_1.5. Numerical results obtained for a single-stage MHHC using MmNi_4.6Al_0.4 are in good agreement with the experimental data reported in the literature. Using three-stage compression, a maximum pressure ratio of 28 is achieved for the supply conditions of 20 °C absorption temperature and 2.5 bar supply pressure. A maximum delivery pressure of 100 bar is obtained for the operating conditions of 20 °C absorption temperature and 120 °C desorption temperature.     

Exploitation of microbial antagonists for the control of postharvest diseases of fruits: a review

Fungal diseases result in significant losses of fruits and vegetables during handling, transportation and storage. At present, post-production fungal spoilage is predominantly controlled by using synthetic fungicides. Under the global climate change scenario and with the need for sustainable agriculture, biological control methods of fungal diseases, using antagonistic microorganisms, are emerging as ecofriendly alternatives to the use of fungicides. The potential of microbial antagonists, isolated from a diversity of natural habitats, for postharvest disease suppression has been investigated. Postharvest biocontrol systems involve tripartite interaction between microbial antagonists, the pathogen and the host, affected by environmental conditions. Several modes for fungistatic activities of microbial antagonists have been suggested, including competition for nutrients and space, mycoparasitism, secretion of antifungal antibiotics and volatile metabolites and induction of host resistance. Postharvest application of microbial antagonists is more successful for efficient disease control in comparison to pre-harvest application. Attempts have also been made to improve the overall efficacy of antagonists by combining them with different physical and chemical substances and methods. Globally, many microbe-based biocontrol products have been developed and registered for commercial use. The present review provides a brief overview on the use of microbial antagonists as postharvest biocontrol agents and summarises information on their isolation, mechanisms of action, application methods, efficacy enhancement, product formulation and commercialisation.     

An Innovative Tree Gradient Boosting Method Based Image Object detection from a Uniform Background Scene

Object detection is a wide area problem domain in the field of computer and machine vision. Complex background adds challenge and error margin as well to the problem significantly lot algorithms for object detection are hard to comply with occlusion and pixel bending moment affect. In this paper a highly robust algorithm ORBTRIAN for a less resolution image has been proposed and implemented using ORB detection with gradient boosting machine learning algorithm. The work has been compared with Adaboost and Surf based technology. The analysis shows 3.8% increase in performance of earlier model. The feature points extracted from ORB method are further processed to reduce the processing further. Only those points are selected which are triangularly farthest from centroid of it and only 1 point of feature selected. Thus the result is around 28%, much faster than earlier computation. The tree based GB has been implemented in this algorithm. With more number of feature points more classes need to be recognized and hence the computations performed is required an unreasonable amount of effort and time. So some nearby classes are assigned at same level using our algorithm to reduce the number of tree nodes. Overall performance of the proposed algorithm shows a significant increase in efficiency in computation time.     

Effect of Blockage on Heat Transfer Phenomena of Spheroid Particles at Moderate Reynolds and Prandtl Numbers

Effects of the confining wall or blockage on the heat transfer phenomena of spheroid particles were numerically investigated. The heated spheroid particles were maintained at constant temperature and allowed to sediment in cylindrical tubes filled with Newtonian liquids. In this flow configuration, the heat transfer took place from the heated spheroid particles to the surrounding Newtonian liquid. The governing conservation equations of the mass, momentum, and energy together with appropriate boundary conditions were numerically solved using commercial software based on computational fluid dynamics. A simple correlation for the average Nusselt number of the confined spheroid particles was developed which can be applied in new applications.     

Synthesis and Biological Evaluation of Imidazo[2,1‐b][1,3,4]thiadiazole‐Linked Oxindoles as Potent Tubulin Polymerization Inhibitors

A series of imidazo[2,1‐b][1,3,4]thiadiazole‐linked oxindoles composed of an A, B, C and D ring system were synthesized and investigated for anti‐proliferative activity in various human cancer cell lines; test compounds were variously substituted at rings C and D. Among them, compounds 7 ((E)‐5‐fluoro‐3‐((6‐p‐tolyl‐2‐(3,4,5‐trimethoxyphenyl)‐imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one), 11 ((E)‐3‐((6‐p‐tolyl‐2‐(3,4,5‐trimethoxyphenyl)imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one), and 15 ((E)‐6‐chloro‐3‐((6‐phenyl‐2‐(3,4,5‐trimethoxyphenyl)imidazo[2,1‐b][1,3,4]thiadiazol‐5‐yl)methylene)indolin‐2‐one) exhibited potent anti‐proliferative activity. Treatment with these three compounds resulted in accumulation of cells in G₂/M phase, inhibition of tubulin assembly, and increased cyclin‐B1 protein levels. Compound 7 displayed potent cytotoxicity, with an IC₅₀ range of 1.1–1.6 μM , and inhibited tubulin polymerization with an IC₅₀ value (0.15 μM ) lower than that of combretastatin A‐4 (1.16 μM ). Docking studies reveal that compounds 7 and 11 bind with αAsn101, βThr179, and βCys241 in the colchicine binding site of tubulin.