Role of the Power Supply and Inter-electrode Gap in Electrochemical Honing Process

AbstractThe process performance of electrochemical honing (ECH) is often increased by the use of the appropriate and optimal input process parameters. This study focuses on the types of power supply and inter-electrode gap in ECH of spur gears, with the aim to determine which parameters are most significant for the required output. Based on the experimental findings, pulse assisted ECH gives marginal improvement in surface finish at the cost of three times higher processing time as compared with direct current ECH and higher value of IEG up to 1mm helps to give controlled anodic dissolution in ECH of spur gears

Vacuum Electronic Devices and Applications

This issue of Defence Science Journal (DSJ) contains a collection of nine manuscripts from National Symposium on Vacuum Electronic Devices and Applications (VEDA-2019). Vacuum Electronic Devices and Applications Society organises VEDA symposium/conference/workshop every year at different locations of India. VEDA has established itself as a leading platform for active and innovative research of microwave tubes. It provides a forum for knowledge sharing and exhibition of theoretical and technological development in the general areas of vacuum electronics devices and its system applications. It organises special session to enhance Research Institutes – Industries and Academia Interaction

Automated design and STEP-NC machining of impellers

This paper presents the four stage approach followed for automated design and STEP-NC based machining of impellers. In the first stage, the design calculations are performed to construct the 'Meridional representation' of the radial impeller. Then 3D curves are projected from the 'Meridional representation' and 3D model is generated using UG-NX software. In the second stage, the process planning activities including tooling & setup plan are completed. Here, ball end mill cutters with suitable diameter and length are selected and appropriate process parameters as suited to 5 axis milling are considered. In the third stage, the tool path data based on contour area milling is generated and verified in the UG NX software. Finally, in the fourth stage, the model with the complete data is imported to STEP-NC software and the AP-238 format is generated. In this article the design procedure adopted for construction of 'Meridional Section' of a radial turbine is discussed with the general methdology to automate the process planning and tool path generation. A test case of radial impeller is presented with the results obtained by adopting STEP-NC format

Fabrication and Excellent Dielectric Performance of Exfoliated Graphite Sheets

In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical treatment of natural graphite flakes. In this process, the graphite expands almost 300-350 times of its original volume and takes the shape of worms. These worms can be pressed or rolled into any desired shape without any binder. The exfoliated graphite sheets show excellent electrical properties i.e. high dielectric constant (ε = 6.374 ×107) and comparatively low dielectric loss (tanδ = 138) across the frequency in the range 50 Hz to 30 MHz and temperature in the range 40-300 °C. The products developed from exfoliated graphite can have very good sealing applications in industrial areas, especially for gaskets in the automobile industries

Fabrication and Excellent Dielectric Performance of Exfoliated Graphite Sheets

In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical treatment of natural graphite flakes. In this process, the graphite expands almost 300-350 times of its original volume and takes the shape of worms. These worms can be pressed or rolled into any desired shape without any binder. The exfoliated graphite sheets show excellent electrical properties i.e. high dielectric constant (ε = 6.374 ×107) and comparatively low dielectric loss (tanδ = 138) across the frequency in the range 50 Hz to 30 MHz and temperature in the range 40-300 °C. The products developed from exfoliated graphite can have very good sealing applications in industrial areas, especially for gaskets in the automobile industries

ENHANCING CIRCULAR MICROSTRIP PATCH ANTENNA PERFORMANCE USING MACHINE LEARNING MODELS

Machine learning (ML) will be heavily used in the future generation of wireless communication networks. The development of diverse communication-based applications is expected to boost coverage and spectrum efficiency in relation to conventional systems. ML may be employed to develop solutions in a wide range of domains, such as antennas. This article describes the design and optimization of a circular patch antenna. The optimization is done through ML algorithms. Six ML models, Decision Tree, Random Forest, XG-Boost Regression, K-Nearest Neighbour (KNN), Gradient Boosting Regression (GBR), and Light Gradient Boosting Regression (LGBR), were employed in this work to predict the antenna's return loss (S11). The findings show that all of these models work well, with KNN having the highest accuracy in predicting return loss of 98.5%. The antenna design & optimization process can be accelerated with the support of ML. These developments allow designers to push beyond the limits of antenna technology, optimize performance, and offer novel solutions for emerging applications such as 5G, 6G, IoT, and flexible wireless communication systems)

Benthic diversity of River Gomti in relation to the prevailing environmental conditions in Lucknow

To evaluate the benthic diversity of River Gomti in relation to the prevailing environmental conditions, four stations, viz., Maa Chandrika Devi, Daliganj, Ambedkar Park and Aquaduct, were identified from upstream to downstream along the course of the river in Lucknow. Dissolved oxygen was low on many occasions at all the stations except Maa Chandrika Devi and chemical oxygen demand values were high. There was a gradual increase in mean nitrite and phosphate values from up to downstream. Benthic fauna was dominated by oligochaetes and chironomus larvae. Other groups reported were leeches, nematodes, sponges, crustaceans, pelycypodes, gastropods and fish fry. Population density was exceptionally high at Daliganj (20,135 m sub(-1) ) followed by Ambedkar Park (5,199 m sub(-1)) and Aquaduct (3,287 m sub(-1)), and low at Maa Chandrika Devi (264 m sub(-1)). Oligochaete genera common at all the four stations were Lumbricillus, Limnodrillus, Branchiura, Chaetogaster, Nais and Tubifex. Odonates were reported only from Maa Chandrika Devi while sponges were encountered at Daliganj and Aquaduct. On some occasions, fish fry were also found at Ambedkar Park and Aquaduct. Seasonally, maxima for population density were observed during pre-monsoon and minima during monsoon. The organic pollution indicator benthic species reported were tubificids, chironomids, culicoid larvae, Lamellidens sp., Corbicula sp., Lymnaea sp. and leech. Branchiurans, Tubifex sp. and Chironomus larvae were reported at all the stations. Filthy condition with foul smell throughout the length of the river coupled with poor water quality and appearance of indicator organisms at all the stations indicate that the river is under severe pollution stress due to anthropogenic discharges and it has reached an alarming stage

Fast and accurate exercise policies for Bermudan swaptions in the LIBOR market model

This paper describes an American Monte Carlo approach for obtaining fast and accurate exercise policies for pricing of callable LIBOR Exotics (e.g., Bermudan swaptions) in the LIBOR market model using the Stochastic Grid Bundling Method (SGBM). SGBM is a bundling and regression based Monte Carlo method where the continuation value is projected onto a space where the distribution is known. We also demonstrate an algorithm to obtain accurate and tight lower–upper bound values without the need for nested Monte Carlo simulations

Counterparty credit exposures for interest rate derivatives using the Stochastic Grid Bundling Method

The regulatory credit value adjustment (CVA) for an outstanding over-the-counter (OTC) derivative portfolio is computed based on the portfolio exposure over its lifetime. Usually, the future portfolio exposure is approximated using the Monte Carlo simulation, as the portfolio value can be driven by several market risk-factors. For derivatives, such as Bermudan swaptions, that do not have an analytical approximation for their Mark-to-Market (MtM) value, the standard market practice is to use the regression functions from the least squares Monte Carlo method to approximate their MtM along simulated scenarios. However, such approximations have significant bias and noise, resulting in inaccurate CVA charge. In this paper, we extend the Stochastic Grid Bundling Method (SGBM) for the one-factor Gaussian short rate model, to efficiently and accurately compute Expected Exposure, Potential Future exposure and CVA for Bermudan swaptions. A novel contribution of the paper is that it demonstrates how different measures, for instance spot and terminal measure, can simultaneously be employed in the SGBM framework, to significantly reduce the variance and bias of the solution