Stevens Institute of Technology

About: Stevens Institute of Technology is a education organization based out in Hoboken, New Jersey, United States. It is known for research contribution in the topics: Computer science & Cognitive radio. The organization has 5440 authors who have published 12684 publications receiving 296875 citations. The organization is also known as: Stevens & Stevens Tech.

Thermodynamics of surface degradation, self-organization and self-healing for biomimetic surfaces

Abstract: Friction is a dissipative irreversible process; therefore, entropy is produced during frictional contact. The rate of entropy production can serve as a measure of degradation (e.g. wear). However, in many cases friction leads to self-organization at the surface. This is because the excess entropy is either driven away from the surface, or it is released at the nanoscale, while the mesoscale entropy decreases. As a result, the orderliness at the surface grows. Self-organization leads to surface secondary structures either due to the mutual adjustment of the contacting surfaces (e.g. by wear) or due to the formation of regular deformation patterns, such as friction-induced slip waves caused by dynamic instabilities. The effect has practical applications, since self-organization is usually beneficial because it leads to friction and wear reduction (minimum entropy production rate at the self-organized state). Self-organization is common in biological systems, including self-healing and self-cleaning surfaces. Therefore, designing a successful biomimetic surface requires an understanding of the thermodynamics of frictional self-organization. We suggest a multiscale decomposition of entropy and formulate a thermodynamic framework for irreversible degradation and for self-organization during friction. The criteria for self-organization due to dynamic instabilities are discussed, as well as the principles of biomimetic self-cleaning, self-lubricating and self-repairing surfaces by encapsulation and micro/nanopatterning.

Strain Engineering and Raman Spectroscopy of Monolayer Transition Metal Dichalcogenides

Abstract: We describe a facile technique based on polymer encapsulation to apply several percent (>5%) controllable strains to monolayer and few-layer transition metal dichalcogenides (TMDs) We use this technique to study the lattice response to strain via polarized Raman spectroscopy in monolayer WSe2 and WS2 The application of strain causes mode-dependent red shifts, with larger shift rates observed for in-plane modes We observe a splitting of the degeneracy of the in-plane E′ modes in both materials and measure the Gruneisen parameters At large strain, we observe that the reduction of crystal symmetry can lead to a change in the polarization response of the A′ mode in WS2 While both WSe2 and WS2 exhibit similar qualitative changes in the phonon structure with strain, we observe much larger changes in mode positions and intensities with strain in WS2 These differences can be explained simply by the degree of iconicity of the metal–chalcogen bond

In situ sterilization and decontamination system using a non-thermal plasma discharge

Abstract: A sterilization and decontamination system in which a non-thermal plasma discharge device is disposed upstream of a suspension media (e.g., a filter, electrostatic precipitator, carbon bed). The plasma discharge device generates a plasma that is emitted through apertures (e.g., capillaries or slits) in the primary dielectric. Plasma generated active sterilizing species when exposed to contaminants or undesirable particulate matter is able to deactivate or reduce such matter in contaminated fluid stream and/or on objects. Thus, the undesirable contaminants in the fluid to be treated are first reduced during their exposure to the plasma generated active sterilizing species in the plasma region of the discharge device. Furthermore, the plasma generated active sterilizing species are carried downstream to suspension media and upon contact therewith deactivate the contaminants collected on the suspension media itself. Advantageously, the suspension media may be cleansed in situ. To increase the sterilization efficiency an additive, free or carrier gas (e.g., alcohol, water, dry air) may be injected into the apertures defined in the primary dielectric. These additives increase the concentration of plasma generated active sterilizing agents while reducing the byproduct of generated undesirable ozone pollutants. Downstream of the filter the fluid stream may be further treated by being exposed to a catalyst media or additional suspension media to further reduce the amount of undesirable particulate matter.

Smartphone based user verification leveraging gait recognition for mobile healthcare systems

Abstract: The rapid deployment of sensing technology in smartphones and the explosion of their usage in people's daily lives provide users with the ability to collectively sense the world. This leads to a growing trend of mobile healthcare systems utilizing sensing data collected from smartphones with/without additional external sensors to analyze and understand people's physical and mental states. However, such healthcare systems are vulnerable to user spoofing attacks, in which an adversary distributes his registered device to other users such that data collected from these users can be claimed as his own to obtain more healthcare benefits and undermine the successful operation of mobile healthcare systems. Existing mitigation approaches either only rely on a secret PIN number (which can not deal with colluded attacks) or require an explicit user action for verification. In this paper, we propose a user verification scheme leveraging unique gait patterns derived from acceleration readings in mobile healthcare systems to detect possible user spoofing attacks. Our framework exploits the readily available accelerometers embedded within smartphones for user verification. Specifically, our user spoofing attack mitigation scheme (which consists of three components, namely Step Cycle Identification, Step Cycle Interpolation, and Similarity Score Computation) is used to extract gait patterns from run-time accelerometer measurements to perform robust user verification under various walking speeds. Our experiments using 322 smartphone-based traces over a period of 6 months confirm that our scheme is highly effective for detecting user spoofing attacks. This strongly indicates the feasibility of using smartphone based low grade accelerometer to conduct gait recognition and facilitate effective user verification without active user cooperation.

Structure of Mo2Cx and Mo4Cx Molybdenum Carbide Nanoparticles and Their Anchoring Sites on ZSM-5 Zeolites

Abstract: Mo carbide nanoparticles supported on ZSM-5 zeolites are promising catalysts for methane dehydroaromatization. For this and other applications, it is important to identify the structure and anchoring sites of Mo carbide nanoparticles. In this work, structures of Mo2Cx (x = 1, 2, 3, 4, and 6) and Mo4Cx (x = 2, 4, 6, and 8) nanoparticles are identified using a genetic algorithm with density functional theory (DFT) calculations. The ZSM-5 anchoring sites are determined by evaluating infrared vibrational spectra for surface OH groups before and after Mo deposition. The spectroscopic results demonstrate that initial Mo oxide species preferentially anchors on framework Al sites and partially on Si sites on the external surface of the zeolite. In addition, Mo oxide deposition causes some dealumination, and a small fraction of Mo oxide species anchor on extraframework Al sites. Anchoring modes of Mo carbide nanoparticles are evaluated with DFT cluster calculations and with hybrid quantum mechanical and molecular ...