Enhanced Strength in Cu-Ag-Zr Alloy by Combination of Cold Working and Aging

In this investigation, the effect of different degree of cold rolling and post-aging treatment on the microstructure and mechanical properties of a Cu-3wt.%Ag-0.5wt.%Zr alloy was studied by means of hardness measurement, tensile tests, optical and electron microscopy. The alloy was subjected to cold rolling up to 80% followed by aging in the temperature range of 400-500 °C. The yield strength, ultimate tensile strength and hardness were found to increase as degree of cold rolling increased, but at the expense of ductility. Aging of cold rolled samples in the studied temperature range has resulted in different combinations of strength and ductility. However, aging of cold rolled samples at 400 °C for 1 h has resulted in a combination of high strength and moderate ductility. A yield strength and ultimate tensile strength of 511 and 560 MPa, respectively with a ductility of 12% were achieved for 80% cold rolled and aged (400 °C for 1 h) sample. The high strength achieved after 80% cold rolling and aging is mainly attributed to precipitation of fine silver precipitates.     

SYNTHESIS OF HYDROCARBONS FROM DIMETHYL ETHER: SELECTIVTTIES TOWARDS LIGHT HYDROCARBONS

ABSTRACT

The depleting supplies of non-renewable petroleum reserves, as well as their escalating costs, have directed a great deal of research toward the synthesis of hydrocarbons from coal. Synthesis of methanol from coal-derived synthesis gas is a well established technology, and methanol has been used as a feedstock for the synthesis of gasoline range hydrocarbons and olefins commercially. However, an efficient hydrocarbon synthesis process has been developed at the University of Akron using dimethyl ether as the starting feedstock. This UA/ EPRI' s DTH ( Dimethyl Ether to Hydrocarbons) process has significant advantages over its counterpart methanol conversion process in the areas of heat duties, hydrocarbon selectivities, product yield, and reactor size

Lower olefins are the intermediate products in the conversion of dimethyl ether to aromatic hydrocarbons. C2-C4 olefins and paraffins can be selectively produced by varying the operating parameters of the process, viz., temperature, pressure, DME concentration in the feed, space time, catalyst-to-inert packing ratio, etc. The present work focuses on the effect of key process variables on the dimethyl ether conversion to low molecular weight hydrocarbons in a fixed bed microreactor system over ZSM-5 type zeolite catalyst. Experimental results with respect to gaseous hydrocarbon product yields and selectivities have been examined in this study     

Assessment of Hydrogeochemical Processes and Mine Water Suitability for Domestic,Irrigation, and Industrial Purposes in East Bokaro Coalfield,India

Mine water samples collected from the East Bokaro coalfield were analysed to assess suitability for domestic, irrigation, and industrial purposes. The pH of the samples ranged from 6.78 to 8.11 in the pre-monsoon season, 5.89–8.51 during the monsoon season, and 6.95–8.48 in the post-monsoon season. The anion chemistry was dominated by HCO₃^? and SO₄^2?, with minor amounts of Cl^?, NO₃^? and F^?. The Fe concentrations exceeded the maximum permissible limit of the BIS drinking water standard in about 44% of the collected samples. Turbidity, TDS, Fe, total hardness (TH), SO₄^2?, and Mg²⁺ also sometimes exceeded drinking water limits. The TDS, TH and SO₄^2? concentrations of the mine water makes it unsuitable for domestic purposes or for industrial use; high values of %Na, SAR, RSC, and Mg-hazard at certain sites restrict its suitability for agricultural use.     

A low cost optical hydrogen sensing device using nanocrystalline Pd grating

A Pd grating of periodicity of 1.5 μm comprising of 1 μm wide nanocrystalline Pd lines has been obtained by a direct micromolding method to serve as Hydrogen sensor element in an optical diffraction set up. The device uses a low power diode laser and a photodetector and works with sensitivity of ∼20%. The hydrogen sensing action is based on monitoring the changes in the diffraction efficiency (DE) which is defined as the ratio of the first and the zeroth order diffracted beam intensities. The diffraction efficiency undergoes large and sudden changes as the nanocrystalline grating becomes disordered due to PdH_x formation, as monitored using in-situ microscopy and optical profilometric measurements. This is truly a low cost, portable hydrogen sensor meant for large installations.     

Efficient Red Downshifting in Layered Structure: A Broad Spectral Converter for Enhancing Photo-response of Solar Cell

Spectral convertors are promising materials for solar cells as they engineered the band gap necessary for suppressing the losses. Existing spectral convertors have small stokes shift which exerts re-absorption losses due to the overlap of spectrum and limits light catching ability. Here we present large stoke shift chromium doped rhombohedral Al₂O₃: Cr³⁺ as a spectral convertor from UV–VIS to red region as single doped with maximum coverage of solar spectrum in UV region. The large stoke shifts in red region around 694 nm originate from ²E_g to ⁴A_2g and broad absorption originates from \(^{{\text{4}}}{{\text{A}}_{{\text{2g}}}}{ \to ^{\text{4}}}{{\text{T}}_{{\text{1g}}}},{{\text{ }}^{\text{4}}}{{\text{A}}_{{\text{2g}}}}{ \to ^{\text{4}}}{{\text{T}}_{{\text{2g}}}}\). This broad absorption (300–600 nm) and large stokes shift emission at 694 nm suggest that the Cr³⁺ dopant rhombohedral Al₂O₃ is well suited as spectral convertors for enhancing the efficiency of the solar cell through better matching of spectral response with spectral distribution of light striking on the solar cell.     

A subtree‐based transformation model for cryptosystem using chaotic maps under cloud computing environment for fuzzy user data sharing

Cloud computing technologies have been prospering in recent years and have opened an avenue for a wide variety of forms of adaptable data sharing. Taking advantage of these state‐of‐the‐art innovations, the cloud storage data owner must, however, use a suitable identity‐based cryptographic mechanism to ensure the safety prerequisites while sharing data to large numbers of cloud data users with fuzzy identities. As a successful way to guarantee secure fuzzy sharing of cloud data, the identity‐based cryptographic technology still faces an effectiveness problem under multireceiver configurations. The chaos theory is considered a reasonable strategy for reducing computational complexity while meeting the cryptographic protocol's security needs. In an identity‐based cryptographic protocol, public keys for individual clients are distributed, allowing the clients to separately select their own network identities or names as their public keys. In fact, in a public‐key cryptographic protocol, it is for the best that the confirmation of the public key is done in a safe, private manner, because this way the load of storage on the server's side can be considerably relieved. The objective of this paper is to outline and examine a conversion process that can transfer cryptosystems using Chebyshev's chaotic maps over the Galois field to a subtree‐based protocol in the cloud computing setting for fuzzy user data sharing, as opposed to reconcocting a different structure. Furthermore, in the design of our conversion process, no adjustment of the original cryptosystem based on chaotic maps is needed.     

Lead content in household paints in India

Lead and its compounds are used in paints not only to impart colour but also to make it durable, corrosion resistant and to improve drying. Adverse health impacts of lead especially on children have led countries to restrict or ban its use in paints. While U.S. and other developed countries instituted measures to limit the use of lead in paints, some developing countries including India have failed to regulate their lead content. The present study was undertaken to determine the levels of lead in new latex (water-based) and enamel paints (oil-based) intended for residential use in India. A total of 69 paint samples (38 latex and 31 enamel samples) from six of the most popular brands were analysed for lead concentrations. While all latex paint samples contained low levels of lead, (i.e., well below 600 ppm as regulated by United States' Consumer Products Safety Commission) the enamel paint samples of all but one brand contained significant concentrations of lead, ranging up to 140,000 ppm. In fact 84% of the enamel paints tested exceeded 600 ppm whereas only 38 % of all samples (including latex and enamel types) exceeded this regulatory level.     

Mechanically adjustable and electrically gated single-molecule transistors

We demonstrate a device geometry for single-molecule electronics experiments that combines both the ability to adjust the spacing between the electrodes mechanically and the ability to shift the energy levels in the molecule using a gate electrode. With the independent in-situ variations of molecular properties provided by these two experimental "knobs", we are able to achieve a much more detailed characterization of electron transport through the molecule than is possible with either technique separately. We illustrate the performance of the device using C(60) molecules.