Towards Scalable Network Traffic Measurement With Sketches

Driven by the ever-increasing data volume through the Internet, the per-port speed of network devices reached 400 Gbps, and high-end switches are capable of processing 25.6 Tbps of network traffic. To improve the efficiency and security of the network, network traffic measurement becomes more important than ever. For fast and accurate traffic measurement, managing an accurate working set of active flows (WSAF) at line rates is a key challenge. WSAF is usually located in high-speed but expensive memories, such as TCAM or SRAM, and thus their capacity is quite limited. To scale up the per-flow measurement, we pursue three thrusts. In the first thrust, we propose to use In-DRAM WSAF and put a compact data structure (i.e., sketch) called FlowRegulator before WSAF to compensate for DRAM\u27s slow access time. Per our results, FlowRegulator can substantially reduce massive influxes to WSAF without compromising measurement accuracy. In the second thrust, we integrate our sketch into a network system and propose an SDN-based WLAN monitoring and management framework called RFlow+, which can overcome the limitations of existing traffic measurement solutions (e.g., OpenFlow and sFlow), such as a limited view, incomplete flow statistics, and poor trade-off between measurement accuracy and CPU/network overheads. In the third thrust, we introduce a novel sampling scheme to deal with the poor trade-off that is provided by the standard simple random sampling (SRS). Even though SRS has been widely used in practice because of its simplicity, it provides non-uniform sampling rates for different flows, because it samples packets over an aggregated data flow. Starting with a simple idea that independent per-flow packet sampling provides the most accurate estimation of each flow, we introduce a new concept of per-flow systematic sampling, aiming to provide the same sampling rate across all flows. In addition, we provide a concrete sampling method called SketchFlow, which approximates the idea of the per-flow systematic sampling using a sketch saturation event

Immobilization of allantoinase for the development of an optical biosensor of oxidative stress states

Allantoin, the natural end product of purine catabolism in mammals, is non-enzymatically produced from the scavenging of reactive oxygen species through the degradation of uric acid. Levels of allantoin in biological fluids are sensitively influenced by the presence of free radicals, making this molecule a candidate marker of acute oxidative stress in clinical analyses. With this aim, we exploited allantoinase—the enzyme responsible for allantoin hydrolization in plants and lower organisms—for the development of a biosensor exploiting a fast enzymatic-chemical assay for allantoin quantification. Recombinant allantoinase was entrapped in a wet nanoporous silica gel matrix and its structural properties, function, and stability were characterized through fluorescence spectroscopy and circular dichroism measurements, and compared to the soluble enzyme. Physical immobilization in silica gel minimally influences the structure and the catalytic efficiency of entrapped allantoinase, which can be reused several times and stored for several months with good activity retention. These results, together with the relative ease of the sol-gel preparation and handling, make the encapsulated allantoinase a good candidate for the development of an allantoin biosensor

A Portable Colorimetric Sensing Platform for the Evaluation of Carbon Dioxide in Breath

abstract: This work describes the development of a device for measuring CO2 in breath, which has applications in monitoring a variety of health issues, such as Chronic Obstructive Pulmonary Disease (COPD), asthma, and cardiovascular disease. The device takes advantage of colorimetric sensing technology in order to maintain a low cost and high user-friendliness. The sensor consists of a pH dye, reactive element, and base coated on a highly porous Teflon membrane. The transmittance of the sensor is measured in the device via a simple LED/photodiode system, along with the flow rate, ambient relative humidity, and barometric pressure. The flow is measured by a newly developed flow meter described in this work, the Confined Pitot Tube (CPT) flow meter, which provides a high accuracy with reduced flow-resistance with a standard differential pressure transducer. I demonstrate in this work that the system has a high sensitivity, high specificity, fast time-response, high reproducibility, and good stability. The sensor has a simple calibration method which requires no action by the user, and utilizes a sophisticated, yet lightweight, model in order to predict temperature changes on the sensor during breathing and track changes in water content. It is shown to be effective for measuring CO2 waveform parameters on a breath-by-breath basis, such as End-Tidal CO2, Alveolar Plateau Slope, and Beginning Exhalation Slope.Dissertation/ThesisDoctoral Dissertation Chemical Engineering 201

Rheology and Processing of Polymers

This book covers the latest developments in the field of rheology and polymer processing, highlighting cutting-edge research focusing on the processing of advanced polymers and their composites. It demonstrates that the field of rheology and polymer processing is still gaining increased attention. Presented within are cutting-edge research results and the latest developments in the field of polymer science and engineering, innovations in the processing and characterization of biopolymers and polymer-based products, polymer physics, composites, modeling and simulations, and rheology

Silver Nanoparticles: Synthesis, Characterization and Applications

Day by day augmenting importance of metal nanoparticles in the versatile fields like, catalyst, electronic, magnetic, mechanic, optical optoelectronic, materials for solar cell and fuel cell, medical, bioimaging, cosmetic, ultrafast data communication and optical data storage, etc, is increasing their value. Nanoparticles of alkali metals and noble metals (copper, silver, platinum, palladium, and gold, etc.) have a broad absorption band in the visible region of the electromagnetic spectrum of light, because the solutions of these metal nanoparticles show the intense color, which is absent in their bulk counterparts as well as their atomic level. The main cause behind this phenomenon is attributed to the collective oscillations of the free conductive electrons that are induced by an interaction with electromagnetic field. The whole incidence is known as localized surface plasmonic resonance. Out of these, we have selected the silver nanoparticles for the studies. In this article, we will discuss the synthesis, characterization, and application of the silver nanoparticles. Future prospective and challenges in the field commercialization of the nanosilver is also discussed

EFFECTS OF CONFINEMENT ON IONIC LIQUIDS AND DEEP EUTECTIC SOLVENTS FOR THE DESIGN OF CATALYTIC SYSTEMS, ELECTROCHEMICAL DEVICES, AND SEPARATIONS

Confinement of ionic liquids (ILs) and deep eutectic solvents (DESs) within mesoporous materials such as silica helps to control the local environment within the pores for applications such as catalysis, electrochemistry, and absorption. Silica thin films with 2.5 and 8 nm pores and micron-sized silica particles with pore diameters of 5.4 and 9 nm were synthesized to study the effect of nanoconfinement on ILs 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), and DESs reline and ethaline (choline chloride and urea or ethylene glycol). Silica thin films with vertically aligned, well ordered, and accessible pores were synthesized via the evaporation-induced self-assembly (EISA) method with cetyltrimethylammonium bromide (CTAB) templated EISA and titania doping giving 2.5 nm pores and Pluronic P123 (P123) templated films with a neutrally charged substrate giving 8 nm pores. Grazing incidence small angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM) characterization gave evidence that the pores were aligned perpendicular to the substrate. Micron-sized mesoporous silica nanoparticles were synthesized through a sol-gel hydrothermal aging method where CTAB and P123 are used for templating and the pore diameter may be controlled through temperature, with higher temperatures giving larger pore sizes (2-12 nm). Diffusion properties of confined ILs is relevant to understanding how solute molecules will behave when entering and moving through the confined IL. The diffusivity of a probe molecule to serve as an example solute are two fluorescent dyes rhodamine 6G (R6G), a cationic dye, and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), a neutral dye. The dyes were mixed with [BMIM][PF6] and confined within mesoporous silica microparticles with 5.4 and 9 nm pores. The 9 nm diameter particles were functionalized (tethered) with an IL-like molecule, 3-methyl-1-[3-(trimethoxysilyl)propyl]-1-imidazolium chloride [TMS-MIM][Cl]. The fluorescence recovery after photobleaching (FRAP) technique in confocal microscopy was used to estimate the diffusivity of the probes within the confined IL. Water saturated particles and pore diameter differences did not significantly impact the diffusion. The cationic dye had a lower diffusivity than the neutral dye from interactions between the dye and pore wall and anion of IL, while tethering increased the diffusivity of the dye by making the interior of the pore more hydrophobic. These results are important for diffusion considerations of species to catalytic sites in nanoconfined IL. To further understand the interactions between ILs and the silica substrate, mesoporous silica thin films were synthesized with 3.5 and 8.5 nm pores and loaded with [BMIM][Cl]. The 8.5 nm pores were also functionalized with [TMS-MIM][Cl]. The films were characterized with x-ray photoelectron spectroscopy to measure the electronic environment of the elements within the sample. Bulk IL only has one peak in the nitrogen spectra due to the shared positive charge on the imidazolium ring. After confinement, a second peak at lower binding energy (BE) appeared from interfacial interactions between the imidazolium group in the IL with the pore wall of the silica. The reduction in positive charge on the imidazolium from this interaction causes a reduction in BE. This work gives insight into the ordering and location of the IL within the pores and is an important consideration since catalysis occurs on the surface of a material. DESs are an emerging area of alternative solvents; often considered analogous to ILs, they are made of natural components that are customizable (choline chloride and urea being the classical example) but are still usually highly viscous so confinement is still advantageous. They can be used as a solvent for catalysis with metal additives, so the diffusion of FeCl3 was studied using cyclic voltammetry. Mesoporous silica thin films with 3 and 8 nm pores were synthesized as above on Fluorine-doped Tin Oxide glass slides and used as a working electrode. The diffusion was calculated using the Randles-Sevcik equation where the diffusion can be calculated by varying the voltage scan rate and measuring the peak current output for either the oxidation or reduction event of the probe molecule. The diffusion of FeCl4- in reline was hindered significantly in both pore diameters compared to the bulk value, while ethaline had pore size dependent accessibility. This result is beneficial to catalysis and electrochemical research with redox active species

Two-Dimensional Materials for Organic Reaction Vessels and Proton Exchange Membranes

Department of Energy Engineering (Energy Engineering)Two-dimensional (2D) materials are promising candidates for use in membrane applications owing to their high chemical stability, thermal stability, and outstanding mechanical strength. Especially, the graphene sandwich structure has been studied extensively as a container for well-defined 2D confined spaces. Many researchers have attempted to understand chemical reactions in confined spaces because unexpected reactions can occur owing to the nanoconfinement effect and high van der Waals (vdW) pressure. To understand chemical reactions in confined spaces, creating a well-defined 2D confined space is very important. Also, it was demonstrated that hexagonal boron nitride (h-BN) showed the highest proton conductivity than other 2D materials, and so interesting of h-BN for proton exchange membrane (PEM) has been increased. Since h-BN showed high chemical and thermal stability than conventional polymer PEM, it is important to explore application of h-BN for PEM. This paper discussed our approaches to understand organic chemical reaction in confined space of graphene sandwich and apply h-BN for proton exchange membrane. The first part of my thesis pertains to the use of graphene sandwich nanoreactors for carrying out organic chemical reactions. Studies have observed phase transitions or hydrolysis of inorganic materials in the graphene sandwich structure, but organic chemical reactions in this structure have not been reported to date. To understand reactions in confined spaces, it is important to study organic chemical reactions in the graphene sandwich structure. I synthesized three monomers, namely dopamine, o-phenylendiamine (oPD), and 3,4-ethylene-dioxythiophene (EDOT) in a graphene sandwich. These monomers were 2D polymerized in a 2D confined space with polycrystallinity. In addition, 2D polycrystalline polydopamine exhibited reduced sheet resistance and increased bending stability and Young???s modulus. The second part pertains to the use of hexagonal boron nitride (h-BN) for fabricating proton exchange membranes. A fuel cell with a large-area single-oriented AA???-stacked trilayer h-BN were fabricated. The fuel cell with the AA???-stacked trilayer h-BN exhibited high power density of 0.66 W cm-1 and an open circuit voltage (OCV) of 0.958 V. The OCV degradation rate of h-BN (10% for single-layer BN and 5% for AA-stacked trilayer h-BN) was low compared to that of Nafion (56%) in stability tests conducted under harsh condition because the h-BN blocked gas crossover and reduced generation of reactive radicals. Furthermore, I tried to fabricate new fuel cell structure for trilayer h-BN with AA???-stacking by Pt deposition in third part. To reduce costs of Pt and oxygen resistance in cathode reaction, deposition of Pt nanoparticles on trilayer h-BN with AA???-stacking were studied. By atomic layer deposition, uniform high density of Pt nanoparticles was prepared, successfully. Uniform Pt nanoparticles were used cathodes of new fuel cell based on trilayer h-BN with AA???-stacking.clos