Rahul K. Gupta

Tracking moving targets in a smart sensor network

Networks of small, densely distributed wireless sensor nodes are capable of solving a variety of collaborative problems such as monitoring and surveillance. We develop a simple algorithm that detects and tracks a moving target, and alerts sensor nodes along the projected path of the target. The algorithm involves only simple computation and localizes communication only to the nodes in the vicinity of the target and its projected course. The algorithm is evaluated on a small-scale testbed of Berkeley motes using a light source as the moving target. The performance results are presented emphasizing the accuracy of the technique, along with a discussion about our experience in using such a platform for target tracking experiments.

The viscoelastic behaviour of raw and anaerobic digested sludge: Strong similarities with soft-glassy materials

Over the last few decades, municipal and industrial wastewater treatment activities have been confronted with a dramatically increasing flow of sewage sludge. To improve treatment efficiency, process and material parameters are needed but engineers are dealing with vast quantities of fundamentally poorly understood and unpredictable material Thus, accurate prediction of critically important, but analytically elusive process parameters is unattainable and is a matter of grave concern. Because engineers need reliable flow properties to simulate the process, this work is an attempt to approach sludge rheological behaviour with well-known materials which have similar characteristics. Sludge liquid-like behaviour is already well documented so, we have focused mainly on the solid-like behaviour of both raw and digested sludge by performing oscillatory measurements in the linear and non-linear regimes. We have shown that the viscoelastic behaviour of sludge presents strong similarities with soft-glassy materials but differences can be observed between raw and digested sludge. Finally, we confirm that colloidal glasses and emulsions may be used to model the rheological behaviour of raw and anaerobic digested sludge.

Preparation and rheological characteristics of ethylene-vinyl acetate copolymer/organoclay nanocomposites

Ethylene‐vinyl acetate copolymer (EVA) with 40 wt.% vinyl acetate content (EVA40)/organoclay nanocomposites were prepared using a melt intercalation method with several different clay concentrations (2.5, 5.0, 7.5, and 10.0 wt.%). X‐ray diffraction confirmed the formation of exfoliated nanocomposite in all cases with disappearance of the characteristic peak corresponding to the d‐spacing of the pristine organoclay. Transmission electron microscopy studies also showed an exfoliated morphology of the nanocomposites. Morphology and thermal properties of the nanocomposites were further examined by means of scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA), respectively. Rheological properties of the EVA40/organoclay nanocomposites were investigated using a rotational rheometer with parallel‐plate geometry in both steady shear and dynamic modes, demonstrating remarkable differences with the clay contents in comparison to that of pure EVA40 copolymer.

Analysis of gas permeability characteristics of poly(lactic acid)/poly(butylene succinate) nanocomposites

Gas permeability and morphological properties of nanocomposites prepared by the mixing of poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and clay was investigated. While the composition of PLA and PBS polymers was fixed as 80% and 20% by weight, respectively, for all the nanocomposites, clay contents varied from 1 to 10wt%. From the morphological studies using both wide angle X-ray diffraction and transmission electron microscopy, the nanocomposite having 1wt% of clay was considered to have a mixed morphology of intercalated and delaminated structure, while some clusters or agglomerated particles were detected for nanocomposites having 3 and more than 3wt% of clay content. However, the average particle size of the dispersed PBS phase was reduced significantly from 7 µm to 30-40nm with the addition of clay in the blend. The oxygen barrier property was improved significantly as compared to the water vapor. A model based on gas barrier property was used for the validation of the oxygen relative permeabilities of PLA/PBS/clay nanocomposites. PLA/PBS/clay nanocomposites validated the Bharadwaj model up to 3wt% of clay contents only, while for nanocomposites of higher clay contents the Bharadwaj model was invalid due to the clusters and agglomerates formed.

Poly (L-lactic acid)/layered silicate nanocomposite blown film for packaging application: thermal, mechanical and barrier properties

In an attempt to alleviate the global solid waste disposal problem and to reduce the dependence on petroleum-based plastics for packaging materials, biodegradable and compostable thermoplastic polymers are required. Polylactic acid (PLLA) is a highly versatile biodegradable polymer derived from 100% renewable resources. Three types of PLA nanocomposites containing 1, 3 and 5 phr of nanoclay were compounded in a co-rotating twin screw extruder, to study the effect of nanoclay content on film processibility of composites as well as properties of blown films. Differential scanning calorimetry CDSC) showed that the cold crystallization and melting temperatures were influenced by the presence of nanoclay. The thennogravimetric analysis (TGA) showed increase in the decomposition temperature for all of the nanocomposites. Mechanical properties of the nanocomposite film showed that the elongation (%) increased up to 3 phr of clay whereas tensile strength and modulus increased only up to 1 phr of the nanoclay. N anocomposite films showed an improvement in oxygen barrier and water vapor barrier in comparison to the neat PLA up to 3 phr of nanoclay.

The design and realization of uniplanar CPW fed PICA slot antennas

In modern wireless communication system design, antennas with wide impedance bandwidth are desirable for numerous reasons. An antenna with a wide impedance bandwidth may be used for transmission and reception of multiple narrowband services in a multi-purpose platform. Alternatively a single wideband service may be of interest for various radar and imaging applications, or for impulse based radio communications in the FCC ultra-wideband (UWB) regime from 3.1 GHz to 10.6 GHz.

Visualization of multi-factor changes in HTV silicone rubber in response to environmental exposures

In this paper, we present a tool for visualizing multi-factor changes in HTV silicone rubber using results from ATR-FTIR, color coordinates, contact angle, and voltage breakdown test. Experimental works were performed on samples collected from a 22 KV silicone rubber insulator. The specimens were subjected to accelerated degradation using an Accelerated Weathering Tester (QUV). The proposed 3D scatter plot based on the obtained data shows a clear trajectory on how a new specimen degrades over time and eventually leads to complete failure. In addition, the application of Multiple Linear Regression method provides linear plane equation which quantitatively describes the changes in silicone rubber in response to environmental exposures over time.

The effect of die geometries and extrusion rates on melt strength of high melt strength polypropylene

The effect of die geometry on the melt strength of conventional and high melt strength polypropylene (HMS PP) was studied. It was found that the melt strength of highly elastic PP is sensitive to changes in die geometry and that die diameter has greater effect on melt strength than on the length of the die. The effect of die entrance angle on melt strength was also studied. No significant difference in melt strength was observed when die with different entrance angles was used. This may be because dies with high L/D ratio used in this study helped to relax the polymer and dissipate stresses caused by different entrance angles. Higher extrusion rates enhance the melt strength of PP because higher molecular orientations are developed in the entrance region of the die.

Chemically imaging the interaction of acetylated nanocrystalline cellulose (NCC) with a polylactic acid (PLA) polymer matrix

The non-covalent interaction of acetylated nanocrystalline cellulose (AC-NCC) with polylactic acid (PLA) in a composite blend has been studied at the micron scale by synchrotron Fourier transform infrared (FTIR) microspectroscopy. Microtomed sections of AC-NCC in PLA showed strong, localized carbonyl stretching (νC=O) absorbance characteristic of the cellulose acetylation, and this was observed on the surface of larger aggregated AC-NCC particles. A shift in the νC=O IR absorption peak of AC-NCC in PLA, relative to unblended AC-NCC was observed, which is indicative of an intermolecular interaction between AC-NCC and PLA matrix. Acetylation can therefore potentially improve the performance of the composite by enabling linkages between carbonyl groups, helping to establish a good stress transfer between the fiber and the matrix. This could in turn lead to a material with high yield elastic modulus. This is the first reported chemical imaging of acetylated nanocrystalline cellulose-based composite materials using synchrotron FTIR microspectroscopy.

Dielectric breakdown characteristics of HTV silicone rubber under multiple stress conditions

This study investigates the aging of high-temperature-vulcanized (HTV) silicone rubber insulator under multiple stress conditions. Silicone rubber specimens were subjected to accelerate degradation using an accelerated weathering chamber. The specimen was subjected to accelerated aging cycle in accordance to ASTM G154 cycle 4 for a total of 3000 hours. The aging cycle goes through a cycle of 70°C and ultraviolet exposure at irradiation intensity of 1.55 W/m2 for eight hours followed by four hours condensation at 50°C. Morphology examination and chemical characterization using Scanning Electron Microscope (SEM) and Fourier Transforms Infrared Spectroscopy (ATR-FTIR) method are performed on the specimen. In this study, the aging performance of the silicone rubber insulator and the interdependence between the stressed material and dielectric breakdown strength are also under investigation. The results in this paper show that there are clear trend developed in the interval plots of the chemical elements such as carbon, oxygen, silicon and aluminum. These results agree with the decrease in the dielectric breakdown voltage as the period of aging cycle increases. The results obtained in this work indicate that the chemical characterization methods combining with electrical testing method can be used an effective tool to quantify and understand the aging process of silicone rubber insulator.