Smarandachely t-path step signed graphs

Characterizing signed graphs which are switching equivalent to their Smarandachely 3-path step signed graphs

Application of Laser Micromachining on Polymeric and Metallic Substrates

LASER (Light Amplification by Stimulated Emission of Radiation) has many applications in engineering, biology, biomedical etc. Recent years, laser micromachining has become a promising technology for mass production of surface texturing on various polymeric substrates and metals. However, excessive roughness of channel surface, lack of control of process parameters and no uniformity of channel geometry are the ongoing challenges. The goal of the study is to determine the effect of laser system parameters on the surface of different kinds of polymers (PMMA, PDMS and Glass) as well as metals (Titanium). There are two specific objectives in this study. The first objective was to determine the effect of laser parameters on different kinds of polymers. A commercial MUSE laser system was used for machining three widely used microfluidic substrates to create microfluidic channels, which consists of a 45W laser tube with three degree of freedom (lateral, longitudinal and vertical). Four laser system parameters - speed, power, focal distance and number of passes are varied to fabricate straight microchannel on glass, PDMS and PMMA. The results show that higher speed produces lower depth while higher laser power produces deeper channel regardless of the substrate materials. The out-of-focus laser cut produces wider but shallower channel. However, for same speed and power, PDMS channel had the roughest surface and PMMA had smoother surface. In PMMA, a uniform and wider channel was produced with the number of passes, which when increased can control the bulging phenomenon. This comprehensive experimental investigation can provide guidance for the substrate material-based mass production of microchannels. The second objective was to investigate the effect of nitriding on a laser textured titanium surface to improve its optical properties for application in solar thermo photovoltaic. Nitriding of titanium alloy samples were carried out in plasma nitriding furnace after laser engraving. Full spectrum high power laser machine was used to make grooves on titanium alloy. The study found that laser textured nitride titanium has better surface properties and increased optical properties when compared to those of non-nitride titanium. For better understanding of the TiN on Ti , X-ray photoelectron spectroscopy (XPS) was carried out before and after plasma treatment. XPS analysis found nitriding has positive influence on the surface characteristics. Nitriding makes the laser grooved Ti surface more reflective compared to those of non-nitriding Ti surface

Efficient Time of Arrival Calculation for Acoustic Source Localization Using Wireless Sensor Networks

Acoustic source localization is a very useful tool in surveillance and tracking applications. Potential exists for ubiquitous presence of acoustic source localization systems. However, due to several significant challenges they are currently limited in their applications. Wireless Sensor Networks (WSN) offer a feasible solution that can allow for large, ever present acoustic localization systems. Some fundamental challenges remain. This thesis presents some ideas for helping solve the challenging problems faced by networked acoustic localization systems. We make use of a low-power WSN designed specifically for distributed acoustic source localization. Our ideas are based on three important observations. First, sounds emanating from a source will be free of reflections at the beginning of the sound. We make use of this observation by selectively processing only the initial parts of a sound to be localized. Second, the significant features of a sound are more robust to various interference sources. We perform key feature recognition such as the locations of significant zero crossings and local peaks. Third, these features which are compressed descriptors, can also be used for distributed pattern matching. For this we perform basic pattern analysis by comparing sampled signals from various nodes in order to determine better Time Of Arrivals (TOA). Our implementation tests these ideas in a predictable test environment. A complete system for general sounds is left for future wor

Efficient Time of Arrival Calculation for Acoustic Source Localization Using Wireless Sensor Networks

Acoustic source localization is a very useful tool in surveillance and tracking applications. Potential exists for ubiquitous presence of acoustic source localization systems. However, due to several significant challenges they are currently limited in their applications. Wireless Sensor Networks (WSN) offer a feasible solution that can allow for large, ever present acoustic localization systems. Some fundamental challenges remain. This thesis presents some ideas for helping solve the challenging problems faced by networked acoustic localization systems. We make use of a low-power WSN designed specifically for distributed acoustic source localization. Our ideas are based on three important observations. First, sounds emanating from a source will be free of reflections at the beginning of the sound. We make use of this observation by selectively processing only the initial parts of a sound to be localized. Second, the significant features of a sound are more robust to various interference sources. We perform key feature recognition such as the locations of significant zero crossings and local peaks. Third, these features which are compressed descriptors, can also be used for distributed pattern matching. For this we perform basic pattern analysis by comparing sampled signals from various nodes in order to determine better Time Of Arrivals (TOA). Our implementation tests these ideas in a predictable test environment. A complete system for general sounds is left for future wor

Efficient Time of Arrival Calculation for Acoustic Source Localization Using Wireless Sensor Networks

Acoustic source localization is a very useful tool in surveillance and tracking applications. Potential exists for ubiquitous presence of acoustic source localization systems. However, due to several significant challenges they are currently limited in their applications. Wireless Sensor Networks (WSN) offer a feasible solution that can allow for large, ever present acoustic localization systems. Some fundamental challenges remain. This thesis presents some ideas for helping solve the challenging problems faced by networked acoustic localization systems. We make use of a low-power WSN designed specifically for distributed acoustic source localization. Our ideas are based on three important observations. First, sounds emanating from a source will be free of reflections at the beginning of the sound. We make use of this observation by selectively processing only the initial parts of a sound to be localized. Second, the significant features of a sound are more robust to various interference sources. We perform key feature recognition such as the locations of significant zero crossings and local peaks. Third, these features which are compressed descriptors, can also be used for distributed pattern matching. For this we perform basic pattern analysis by comparing sampled signals from various nodes in order to determine better Time Of Arrivals (TOA). Our implementation tests these ideas in a predictable test environment. A complete system for general sounds is left for future wor

A Note On Line Graphs

In this note we define two generalizations of the line graph and obtain some results. Also, we mark some open problems

Characterization of ice adhesion strength over different surfaces pertinent to aircraft anti-/de-icing

Aircraft icing is widely recognized as a significant hazard to aircraft operations in cold weather. A number of anti-/de-icing systems have been developed recently for aircraft icing mitigation and protection, which can generally be classified into two categories: active and passive methods. While active methods rely on energy input from an external system for the anti-/de-icing operation, passive methods take advantage of the physical properties of the surfaces to prevent ice formation and accretion. While there is no known passive system that can completely eliminate ice formation over the protected surfaces, passive anti-/de-icing methods, especially icephobic surface coatings, have been proved to be very helpful to mitigate the problematic effects of icing for various icing related applications. In the present study, a comprehensive study was conducted to characterize ice adhesion strength over various surfaces by using a custom-built shear strength tester. The studied surfaces include recently developed functionalized surfaces like Slippery Liquid-Infused Porous Surfaces (SLIPS) and commercially-available surface coatings like Hydrobeadî, NeverWetî; polymer-based surfaces such as PMMA and PTFE, and conventional metals like aluminum and stainless steel. In addition, the static and dynamic contact angles for all the control surfaces were also measured in order to correlate the measured ice adhesion strength with the surface wettability. Furthermore, surface topography analysis was performed to acquire the 3-D surface profiles along with the averaged surface roughness in order to examine the effects of surface roughness on ice adhesion strength. Similarly, the ice adhesion strength was also analyzed at different temperatures (i.e., -50C, -100C, -150C and -200C ) to reveal the temperature effects on the ice adhesion strength over hydrophilic and hydrophobic surfaces. The influence of the durability of surface coatings on the ice adhesion performance of hydro-/ice-phobic coatings was also investigated experimentally in the present study. In coordinating with the experimental study, a numerical analysis was also performed to explore/optimize experimental design paradigms to minimize the measurement uncertainties