Effect of Cryogenic Cooling on the Heat Transfer during Turning of AZ31C Magnesium Alloy

ABSTRACT

A combined analytical and experimental study was carried out to analyze the effects of cryogenic cooling on temperature during turning of AZ31C magnesium alloy. Finite element method was employed to model and simulating the cryogenic and dry turning. Results obtained from the model were found to be in good agreement with the experimental observations. For the maximum temperature at the turned surface, the difference in the experimental and predicted value observed during dry and cryogenic turning was only 4 and 8% respectively. A significant reduction in the maximum temperature on the chip surface (around 35%) and tool surface (around 29%) was observed during the cryogenic turning compared to dry turning. This reduction in temperature was an attribute of liquid nitrogen, which produces intense cooling effect around the vicinity cutting zone where heat generation takes place hence enhancing the heat transfer. The isothermal region belonging to the highest temperature on the tool surface was also reduced by about 42%. The reduction in temperature during cryogenic conditions were found to be beneficial for the machining of magnesium alloys under safe conditions, reducing the risk of ignition and explosions, and also increases the sustainability of the process.     

Bi2MoO6 hierarchical microflowers for electrochemical oxygen evolution reaction

Solvothermal Bi₂MoO₆ hierarchical microflowers synthesis has been successfully attempted. Methanol, ethanol and isopropanol have been mediated to synthesize three kinds of Bi₂MoO₆ hierarchical microflowers. Highly oriented (311) plane growth of orthorhombic Bi₂MoO₆ hierarchical microflowers have been confirmed. Interstitial vacancies and its role on electrochemical activity have been extensively discussed. Electrode fabrication was constructively done by using Ni foam substrate. Half cell arrangement of each electrode in alkaline medium has been designed to measure the electrochemical activity towards water oxidation. High current density of 356 mA/cm² was afforded by Bi₂MoO₆ hierarchical microflowers mediated by ethanol solvent during synthesis. Low Tafel slope value of 43 mV/dec has been reported to obtain 10 mA/cm² current density. Higher conductivity long with very good electron transportation has been achieved and is also adapted for 12 h long time stability test and achieved 86% of retention in its performance. Hence, optimally prepared Bi₂MoO₆ hierarchical microflowers could be an efficient electrode for clean energy fabrication.     

Cloud vendor selection for the healthcare industry using a big data-driven decision model with probabilistic linguistic information

Applied Intelligence - The role of cloud services in the data-intensive industry is indispensable. Cision recently reported that the cloud market would grow to 55 billion USD, with an active...     

Design and analysis of a sleep and wake-up CMOS low noise amplifier for 5G applications

Telecommunication Systems - This brief proposes a two-stage cascoded CMOS LNA with common drain envelope detection based power reduction method for the 5G applications of 28 GHz frequency....     

NMR inspired energy efficient protocol for heterogeneous wireless sensor network

Wireless Networks - This paper presents a naked mole rat (NMR) inspired energy efficient protocol for heterogeneous wireless sensor network. NMR uses strategic deployment among three types of nodes...     

An Adaptive Prediction Strategy with Clustering in Wireless Sensor Network

In Wireless Sensor Network, sensed data reflects two types of correlations of physical attributes: spatial and temporal. In this paper, a scheme named, Adaptive Prediction Strategy with ClusTering (APSCT) is proposed. In APSCT, a data-driven clustering and grey prediction model is used to exploit both the correlations. APSCT minimizes the transmission of messages in the network. However, the use of prediction includes additional computation overhead. There is a trade-off between prediction accuracy and energy consumption in computation and communication in wireless networks. This paper also gives an approach to calculate the upper and lower bound of the prediction interval which is used to evaluate different confidence levels and provides an energy-efficient sensor environment. Simulation is carried out on real-world data collected by Intel Berkeley Lab and results are compared with existing approaches.

     

Identification of Drought Occurrences Using Ensemble Predictions up to 20-Days in Advance

In the present study, skill of an extended range forecast system has been evaluated for identifying droughts over central India 20-days in advance. Rainfall forecasts from 44 ensemble members of the forecast system developed Indian Institute of Tropical Meteorology (IITM), Pune have been used to prepare probabilistic rainfall forecasts. It is seen that the uncertainties in the forecasts (in terms of ensemble spread) increases from day-5 to day 20. As the focus of the study is for drought predictions, forecasts in the bins 0-5 mm/5 day and 5-25 mm/5 day (no rain or less rain) were studied in detail. It is found that the modeling system has a tendency to over-forecast rainfall probabilities. With bias correction, the forecasts become more reliable. Various drought indices were computed using the mean of the forecast distribution up to 20-days in advance. Standardized precipitation index (SPI) computed using Gamma and Pearson type-III distributions are similar in the study region. It was found that these are in reasonable agreement with those from observations. Probabilistic forecasts of standardized precipitation index (SPI) were made and the relative operating characteristics (ROC) scores indicate that the forecasted SPI values are suitable for application.     

Structural investigation and giant dielectric response of CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> ceramic by Nd/Zr co-doping for energy storage applications

High performance dielectric materials are highly required for practical application for energy storage technologies. In this work, high-k pristine and modified calcium copper titanate having nominal formula Ca_0.95Nd_0.05Cu₃Ti_4?xZr_xO₁₂ (x?=?0.01, 0.03 & 0.10) were synthesized and characterized for structural and dielectric properties. Single phase formation of the synthesized compositions was confirmed by X-ray diffraction patterns and further analysed using Rietveld refinement technique. Phase purity of the synthesized ceramics was further confirmed by Energy-dispersive X-ray Spectroscopy (EDX) analysis. SEM images demonstrated that grain size of the modified CCTO ceramics was controlled by Zr⁴⁺ ions due to solute drag effect. Impedance spectroscopy was employed to understand the grain, grain boundaries and electrode contribution to the dielectric response. Nyquist plots were fitted with a 2R-CPE model which confirms the non-ideality of the system. Substitution of specific concentration of Nd and Zr improved the dielectric properties of high dielectric permittivity (ε′ ~?16,902) and minimal tanδ (≤?0.10) over a wide frequency range. The giant ε′ of the investigated system was attributed to internal barrier layer capacitance (IBLC) effect and reduced tanδ accredited to enhanced grain boundaries resistance due to substitution of Zr⁴⁺ ions at Ti⁴⁺ site.     

Cage like ordered carboxylic acid functionalized mesoporous silica with enlarged pores for enzyme adsorption

Cubic FDU-12 type mesoporous silicas with enlarged pores and carboxylic acid (–COOH) functionality in the pore channels (denoted as LP-FTC-x) are synthesized using tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CES) as silica sources, Pluronic F127 triblock copolymer as template, and trimethylbenzene (TMB) as pore expander, and utilized them as supports for enzyme immobilization. When the –COOH content is increased from 0 to 30%, the pore size of LP-FTC-x decreases from 23.6 to 11.1 nm, and its particle size decreases from around 2 μm to 600–800 nm. The material exhibits a high papain adsorption capacity (895 mg g^?1) with a low leaching rate at pH 8.2 due to the well-defined surface chemistry in the pore channel. The adsorption kinetics and isotherms follow the pseudo-second-order model and the Langmuir isotherm model, respectively. The excellent structural properties of LP-FTC-x are also advantageous for enhancement in stability of enzyme toward the temperature, solution pH, and incubation time variations.     

Ion implantation effects of negative oxygen on copper nanowires

Copper nanowires of diameter 80 nm were synthesized in polycarbonate membrane using template technique. Samples were then implanted with 160 keV O^?1 ion beam with varying particle fluence of 1?×?10¹², 5?×?10¹² and 1?×?10¹³ ions/cm². The SRIM (Stopping and range of ions in matter) software was used to study the processes involved. Compositional analysis confirms implantation of oxygen ions and the stoichiometry of Cu:O was found to be 6:1 by weight % when implanted at 1?×?10¹³ ions/cm². Scanning electron microscopy reveals no changes in morphology of nanowires on implantation. X-ray diffraction analysis showed no shifting in the ‘2θ’ position of diffraction peaks however some new diffraction peaks of oxygen were seen. Implantation with oxygen ion led to the increased crystallite size and reduced strain. The conductivity of the nanowires was found to increase linearly with the ion fluence presenting constructive effect of negative ion implantation on copper nanowires.