Influence of transverse load on the high cycle fatigue behaviour of low pressure cast AZ91 magnesium alloy

A new testing procedure, employing transverse load was adopted to investigate the high cycle fatigue behaviour of low pressure cast AZ91 magnesium alloy. The tests were conducted with an electro dynamic shaker system by employing specimens fabricated as per ASTM standard. S–N plot was generated from the test results and compared with that of gravity cast AZ91 alloy tested in identical ambience. The influence of transverse load on the fatigue behaviour of these alloys is discussed. As fatigue cracks were found to have initiated in pores in most of the tested samples, pores were assumed as initial cracks as per linear fracture mechanics and the critical stress intensity amplitude (K_cr) was estimated. Structure–fatigue property correlations are discussed using fractographs. Mean stress effect on the fatigue properties and effects of alloying constituents are also discussed.     

Frequency tunable circularly polarized antenna with branch line coupler feed network for wireless applications

In this article, frequency tuning and circularly polarized concentric circular microstrip antenna is investigated. The proposed antenna consist of varactor diode for frequency tuning and branch line coupler (BLC) feed network to achieve the circular polarization (RHCP/LHCP). By changing the varactor diode capacitance between 12.33 pF (0 V) to 1.30 pF (15 V) attain the frequency tuning (2.34‐2.68 GHz). The right hand circular polarization (RHCP) and left hand circular polarizations (LHCP) are realized in the antenna through BLC feed network output ports. The impedance bandwidth (2.05‐3.13 GHz) of BLC feed network is well‐matched with the circular microstrip antenna frequency tunable bandwidth. The proposed antenna is fabricated, and simulated results are verified using the mathematical modeling and experimental verification.     

Numerical and experimental investigation on the thermochemical gasification potential of Cocoa pod husk (Theobroma Cacoa) in an open-core gasifier

Clean Technologies and Environmental Policy - Thermochemical conversion is a promising technology to generate producer gas (PG) from different types of agroforestry biomass residues. To use an...     

Synthesis,characterization and magnetic properties of Mg2+ doped green pigment Cobalt aluminate nanoparticles

Journal of Materials Science: Materials in Electronics - The green pigment cobalt aluminate nanoparticles have been prepared by the simple and cost-effective co-precipitation method. And also, the...     

3D printing-assisted combinatorial approach for designing mechanically-tunable and vascular supportive nanofibrous membranes to repair perforated eardrum

Perforation of eardrum or tympanic membrane (TM) is a common clinical condition, which occurs due to infection or injury of the eardrum, and could results in varying degrees of conductive hearing loss among all ages. In this study, the authors report the combinatorial approach of designing mechanically-tunable and vascular supportive nanofibrous membranes by 3D printing-assisted electrospinning (e-spin) using polycaprolactone (PCL) and gelatin with different mass ratios suitable to repair a perforated eardrum. The physicochemical, mechanical, and biological properties of the membranes were characterized. The results show that the membrane has nanofibrous morphology with fibers are of varying size (400–600 nm in diameter) depending on processing conditions. The wettability and mechanical properties of the membrane can be tuned by regulating the gelatin content. Moreover, a biomimetic repair strategy inspired by chicken eggshell membrane, often used in wound dressings, was also presented for study and results show that the suture retention strength of the fabricated membrane can meet clinical translational requirements to promote TM healing. The vascular cell responsiveness of PCL/gelatin nanofibrous membrane was evaluated using human umbilical vein endothelial cells (HUVECs) and the results showed satisfactory biocompatibility, vascular cell responsiveness, and cell proliferation. The findings of this study demonstrate that the combinatorically engineered PCL/gelatin nanofibrous membrane has great potential for repairing perforated eardrum.     

Printed Planar Monopole Antenna Design for Ultra-Wideband Communications

This paper presents an ultra wideband (UWB) planar printed monopole antenna fed by microstrip line. The antenna configuration contains a beveled ground plane. The beveled partial ground plane improves the impedance bandwidth. The measured frequency response demonstrates that the fabricated antenna exhibits an impedance bandwidth of 7.9 GHz over 3.1 to 11 GHz for VSWR < 2. The proposed antenna has ultra-wideband characteristics with omnidirectional radiation pattern and stable gain. Ultra-wideband performance of the proposed antenna is examined through the simulated surface current distributions. Measured results confirm that the antenna is suitable for UWB applications due to its compact size and high performance characteristics.     

Optimization of weld bead geometry for stainless steel claddings deposited by FCAW

The quality of cladded components depends on the weld bead geometry, coefficients of shape of welds and dilution, which have to be controlled. Optimum range of bead parameters and dilution are required for better economy and to ensure the desired mechanical and corrosion resistant properties of the overlay. The above objectives can easily be achieved by developing mathematical equations to predict the weld bead geometry. This paper presents the development of such equations using the data obtained by conducting three factor five level factorial experiments. The experiments were conducted by depositing Type AISI 317L flux cored stainless steel wire onto IS: 2062 structural steel base plate. The results of the confirmation experiments showed that the models developed are able to predict the bead geometries and dilution with reasonable accuracy. The studies have indicated that both main and interaction effects of the process variables play a major role in determining the bead dimensions and dilution, and the effect of interaction between the process variables cannot be neglected. The process parameters were also optimized using response surface methodology (RSM) which will help the plant engineers to select and control the process variables effectively, to achieve the desired clad qualities.     

Visibility improvement of underwater turbid image using hybrid restoration network with weighted filter

Due to the attenuation of light passes through water, the captured underwater images suffer from low-contrast, halo artifacts, etc. To address this issue, the hybrid network with a weighted filter is proposed to improve the visibility of the obscured (turbid) images. In the captured image, the brighter pixels (near-to-source) are called foreground regions and the darker pixels (far-from-source) are called background regions. In order to ensure the adaptability of the proposed algorithm, the considered datasets are collected on different atmospheric light such as pond, lake, and fisheries tank. The foreground area of an image can be enhanced using the thresholding and masking technique. The background hazy region can be recovered by a hybrid Dehazenet called Generative Adversarial Network and Convolutional Neural Network. With this, the transmission map with high accuracy and color deviation can be addressed. Then both the regions are blended and the Amended Unsharp Mask filter is used to toughen the distorted edges. Finally, the blended restored image is weighted with a contrast factor to obtain the visibility improved image. The subjective and objective evaluation is done on considering the standard non-reference metric called Underwater Image Quality Measure comprises measures of color, sharpness, and contrast for a variety of water types with different atmospheric light. It is observed that the proposed technique showed a metric improvement of 57% compared to other existing techniques in an average manner. Overall, it is inferred that the proposed technique produces better results in both subjective and objective evaluation, thus it outperforms other state-of-the-art techniques.

     

Decision Tree-Based Entries Reduction scheme using multi-match attributes to prevent flow table overflow in SDN environment

The software-defined networking is used extensively in data centers that provide centralized control for the widely deployed networking resources. The traffic is shaped by rules created by the controller dynamically without modifying the individual switch. The key component that stores rules which are used to process the flows is the flow table which resides in the ternary content addressable memory. The current commercial OpenFlow appliances accommodate limited entries up to 8000 due to its high cost and high power consumption. There are two issues to be considered, where (1) flow table's inability to provide rules during flow table overflow leads to dropping of incoming packets and (2) the significant amount of rule replacement occurs when the traffic in data centers increases which creates massive route requests to controller creating overhead. The proposed scheme prevents flow table overflow using the robust machine learning algorithm called decision tree (Iterative Dichotomiser 3) that allows the flow table to learn its high prioritized fine-grained entries by means of multiple matching attributes. The entries are classified, and the usual eviction process is replaced by pushing the low important entries into counting bloom filter which acts as a cache to prevent flow entry miss. The simulations were carried out using real-time network traffic datasets, and the comparisons with the various existing schemes prove that the proposed approach reduces 99.99% of the controller's overhead and the entries are minimized to 99% providing extra space for new flows.     

Modeling and simulation of wire feed rate for steady current and pulsed current gas metal arc welding using 317L flux cored wire

Wire feed rate plays a vital role in determining the weld characteristics in gas metal arc welding (GMAW). The wire feed rate is affected by any change in welding current in the case of steady current GMA welding and by any change in frequency, peak current, base current and duration of peak and base currents in the case of pulsed GMA welding. To predict the wire feed rate for any set of these parameters, a mathematical model was developed from the results obtained by conducting experiments. Electrode resistance heating constant and arc resistance heating constant were also determined by fitting a regression model. The above parametric constants have been used to simulate the wire feed rates for pulsed GMA welding for different pulse parameters using MATLAB. The effects of pulse parameters on the burnoff factor and burnoff rates were also analysed. The investigation was carried out using AWS 5.22–95 filler wire of size 1.2 mm diameter and the base metal used was IS:2062 structural steel plate of 20 mm thickness. An argon and 5% CO₂ gas mixture at a flow rate of 16 l/min was used for shielding throughout the welding.