Nachiketa Tiwari

Lumped parameter modelling and methodology for extraction of model parameters for an electrodynamic shaker

Shakers are widely used to simulate the vibrations for academic research, as well as for product testing. Thus, there is a significant necessity to study them in detail. Amongst the different types of shakers being used, the electrodynamic shaker is by far the most versatile. However, limited work has been done with regard to their integrated electro-mechanical modelling. In this work, we have developed a mobility-based lumped parameter model of an electrodynamic shaker and also a method to measure its various electrical and mechanical parameters using non-destructive and easy to use methods. Towards meeting the latter goal, we conducted experiments to determine the shaker table’s impedance and transfer functions, and used these data for subsequent parameter extraction. Such a model was later validated experimentally. Finally, we predicted the response of the shaker under loaded and unloaded conditions, and confirmed their validity through actual experimental data.

Alcohols for Fueling Internal Combustion Engines

The balance between production and consumption of energy is an important factor, which drives future direction of energy resource development. This largely depends on the decision made by producers, consumers, and governments. The deciding factors for aforesaid choices are their cost, quality, reliability, convenience, and social impact. Globally, the most commonly used automotive technology includes Otto- and diesel-cycle engines. Consequently, their fuels are gasoline and diesel. “Alternative fuels” are those existing fuels, which are neither gasoline nor diesel. Commonly available alternative fuels are alcohols, vegetable oils, and their derivatives such as biodiesel, gaseous fuels (natural gas, hydrogen, and liquefied petroleum gas), ethers, etc. Alcohols are oxygenates of primary hydrocarbons with hydroxyl groups. Presence of oxygen in them contributes to smoothness of combustion process in the IC engines. This results in cleaner burning characteristics compared to fossil fuels. Also, alcohols can help in lowering emission of hazardous gases and can reduce dependency on non-renewable energy sources.

Diesel Locomotive Noise Sources, Reduction Strategies, Methods and Standards

Diesel locomotives are the mainstay of modern railway systems. Despite the fact that they are noisy and polluting compared to electric locomotives, they continue to remain popular across the world. This is because they can run in areas where electric supply is either unavailable or unreliable, and also because in times of war their service does not get affected even if electric power lines get damaged. Since most railway networks cut across highly populated areas, efforts have to be made to ensure that diesel engine noise is reduced to a minimum. In this chapter this need has been addressed. Specifically, the chapter explains the working of a modern diesel engine locomotive in brief. Such an understanding is important, as all noise generating mechanisms in a diesel locomotive are tightly coupled with its working. Next, different types of noise emanating from a diesel locomotive have been described. Such a description will help the reader assess the nature of each noise component in terms of its magnitude and its frequency spectrum. Next a method to develop noise reduction strategy of diesel locomotive noise is proposed. Next, the chapter explains a diverse suite of noise reduction methods. These methods can be passive or active. The range of passive methods is fairly large. All these methods have been described in detail. This is followed up with a description of important regulations related to locomotive noise. Finally, an exhaustive list of relevant international standards has been provided. These references will be very useful to the reader if she is involved with reduction of train and locomotive noise.

Optimization of laser machining process for the preparation of photomasks, and its application to microsystems fabrication

Abstract. Conventional photolithography normally utilizes a photomask for patterning light onto a chemical resist film. Therefore, the accuracy of microfabrication is highly dependent on the accuracy of the photomasks. Fabrication of hard masks involves the use of expensive laser pattern generators and other sophisticated machines using very high-precision stages and the necessary control instrumentation; therefore, an inexpensive strategy is highly necessary for laboratory-level fabrication. As this technology is primarily based on raster scanning of a laser beam, the mask making as such becomes a low-throughput process. A strategy of high-throughput manufacturing of hard masks with laser micromachining using a one-step exposure process of a chromated glass slide through a micromachined aluminum shadow mask is proposed. The features that are finally embedded in the mask are highly demagnified and well focused. Optimization of the laser machining process is carried out by considering all processing parameters. The features are characterized using an optical microscope, a scanning electron microscope, and a self-developed image analysis code. Geometrical methods are used to estimate the average edge roughness and feature size. We have also validated the usage of these masks by performing microfabrication on films made of photoresist.