Electric discharge phenomenon in dielectric and electrolyte medium

Electric discharge is a common tool nowadays for machining of materials. It may be through a liquid medium or through air. Any metals, hard alloys, and nonmetals can be machined using the energy of electric discharge. In electric discharge machining (EDM), the discharge occurs between two electrodes through a liquid medium and it is applicable only for electrically conducting materials and alloys. In electrochemical discharge machining (ECDM), the medium is an aqueous electrolyte and it is of two types. In the first type, the discharge occurs between two electrodes. One of the electrodes is the workpiece, and the other is the tool. In the second type, the discharge occurs between one electrode and an electrolyte. It is used for electrically nonconducting materials and the discharge energy is utilized maintaining the nonconducting workpiece in proximity of the discharge. All these electrical discharges are transient phenomena and do not result in a stable discharge in the form of arc. The output parameters depend on the discharge energy that requires precise control to maintain the accuracy of the machining. For micromachining, the control of the discharge is paramount both in terms of energy and pattern. Using various shaped tools, machining media with additives, different types of applied potentials, and supporting mechanical motions are some of the attempts made to improve the machining output. Optimization of these parameters for machining particular materials (or alloys) is a popular field of research. The present work is directed toward the investigation of discharge initiation and development by analyzing the cell current and discharge voltage relationship for both EDM and ECDM. The rectangular direct current (DC) pulse with different frequencies and the duty factor (on-off time ratio) are used for investigation. Observations on the voltage-current relationship are made for the external potential prior to discharge at discharge and above the discharge potential. Though the external potential above the discharge voltage is useful for machining, these observations elucidate the mechanism regarding the initiation of the electric discharge under different conditions. The manner of discharge development in dielectrics and electrolytes is observed to be different. This understanding will aid in deciding the design of the discharge circuit including the external potential and its pattern for certain desired outputs in machining.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0221-1     

Combustion characteristics of high ash Indian thermal,heat affected coal and their blends

Onsite mine fire generates large volumes of heat-affected coal in Jharia coalfields,India.Direct utilization of such heat-affected coal in thermal utilities is ...     

Development of assessment criteria for clustering algorithms

In this paper, new measures—called clustering performance measures (CPMs)—for assessing the reliability of a clustering algorithm are proposed. These CPMs are defined using a validation measure, which determines how well the algorithm works with a given set of parameter values, and a repeatability measure, which is used for studying the stability of the clustering solutions and has the ability to estimate the correct number of clusters in a dataset. These proposed CPMs can be used to evaluate clustering algorithms that have a structure bias to certain types of data distribution as well as those that have no structure biases. Additionally, we propose a novel cluster validity index, V _I index, which is able to handle non-spherical clusters. Five clustering algorithms on different types of real-world data and synthetic data are evaluated. The first dataset type refers to a communications signal dataset representing one modulation scheme under a variety of noise conditions, the second represents two breast cancer datasets, while the third type represents different synthetic datasets with arbitrarily shaped clusters. Additionally, comparisons with other methods for estimating the number of clusters indicate the applicability and reliability of the proposed cluster validity V _I index and repeatability measure for correct estimation of the number of clusters.

A Comprehensive Investigation of Vertically Stacked Silicon Nanosheet Field Effect Transistors: an Analog/RF Perspective

Silicon - In this article, the analog/RF performance of n-channel vertically stacked gate all around (GAA) silicon nanosheet field effect transistors (Si-NSFETs) are investigated using 3-D TCAD...