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Dynamic Instability Analysis of Multifunctional Composite Structures
No full textA dynamic instability analysis of fiber reinforced composite cantilever beams has been carried out in this study. Both experimental and numerical studies are performed to estimate the flutter speeds. Three different types of composite beams namely, glass fiber reinforced plastics, aluminum fiber reinforced (glass reinforced aluminum), and multifunctional carbon fiber reinforced composites] have been considered in the analysis. A graphite fiber reinforced polymer matrix composite laminate with dimensions of 320 x 75 x 12 mm is used in the experiments. The fibers are oriented along 0 deg: that is, along the direction of major dimension of the laminate. The experiments are conducted on three such beams by clamping one end of the beam to a heavy steel frame and leaving the other end free. The natural frequencies, mode shapes, and structural damping characteristics of each beam are estimated using the modal analysis through the fast Fourier transform analyzer. Variation of the damping and the frequency with wind velocity for each beam is illustrated through the v - g and v - f plots. The modal assurance criterion is also verified. Experiments are further continued to perform a dynamic instability analysis by clamping the beam inside the test chamber of a low-speed suction-type wind tunnel. The beam response at various wind speeds is captured through an accelerometer mounted at the tip. Based on the experiments, the flutter speed of the tested beams is estimated to be around 32 m/s. A numerical analysis framework is developed using the ZAERO code to perform the modal and flutter analyses. Numerical results are compared to the experimental results and are found to be in excellent agreement. Therefore, the numerical framework has been further extended to carry out the flutter analysis of the multifunctional composite beams, such as glass reinforced aluminum and plastic lithium-ion battery embedded composite beams. The multifunctional laminated composite beams are observed to have better dynamic stability as compared to the glass fiber reinforced polymer composite beams
A Geometric Characterization of Polygonal Radon Planes
No full textWe study unit circles of polygonal Radon planes from a geometric point of view. In particular, we prove that a two-dimensional real polygonal Banach space X cannot be a Radon plane if the number of vertices of its unit circle is 4n, for some n is an element of N. Also we obtain a complete characterization of polygonal Radon planes in terms of a tractable geometric concept introduced in this article. It follows from our characterization that every regular polygon with 4n+2 vertices, where n is an element of N, is the unit circle of a Radon plane. Furthermore, we describe types of Radon planes for which the unit circles are hexagons, but not regular ones
Stochastic thermodynamics of a harmonically trapped colloid in linear mixed flow
No full textIn this paper, motivated by a general interest in the stochastic thermodynamics of small systems, we derive an exact expression-via path integrals-for the conditional probability density of a two-dimensional harmonically confined Brownian particle acted on by linear mixed flow. This expression is a generalization of the expression derived earlier by Foister and Van De Ven J. Fluid Mech. 96, 105 (1980)] for the case of the corresponding free Brownian particle, and reduces to it in the appropriate unconfined limit. By considering the long-time limit of our calculated probability density function, we show that the flow-driven Brownian oscillator attains a well-defined steady state. We also show that, during the course of a transition from an initial flow-free thermal equilibrium state to the flow-driven steady state, the integral fluctuation theorem, the Jarzynski equality, and the Bochkov-Kuzovlev relation are all rigorously satisfied. Additionally, for the special cases of pure rotational flow we derive an exact expression for the distribution of the heat dissipated by the particle into the medium, and for the special case of pure elongational flow we derive an exact expression for the distribution of the total entropy change. Finally, by examining the system's stochastic thermodynamics along a reverse trajectory, we also demonstrate that in elongational flow the total entropy change satisfies a detailed fluctuation theorem
Non-linearity in dipolar solvation dynamics in water-ethanol mixture: Composition dependence of free energy landscape
No full textLiquid mixtures of water and amphiphilic solutes exhibit a string of yet unexplained anomalies in the low cosolvent (or solute) concentration regime. Among such solutions, mixtures of water and ethanol stand out for their distinctive role in biology. We study, in this binary mixture, the composition dependent difference between the nonequilibrium and the equilibrium solvent responses to a dipolar probe indole in the low-to-intermediate concentration regime. The usually employed linear response formalism seems to break down at low ethanol concentration. The nonequilibrium solvent response is particularly different from that of the equilibrium solvent response in the concentration (x(EtOH)) between 0.07 and 0.12. We introduce an order parameter in terms of the changing local composition at the nearest neighbor separation. This order parameter captures the anomalies faithfully. The anomalies are seen to arise from a competition between hydrophilic and hydrophobic interactions and are most prominent at the small-to-intermediate length scale. We attempt to rationalize the results in terms of a composition dependent free energy length scale
Development of a nanoscale hot-wire probe for supersonic flow applications
No full textA new nanoscale thermal anemometry probe (NSTAP) was designed and fabricated to measure mass flux in supersonic flows. This sensor was evaluated in the Trisonic Wind Tunnel Munich (TWM) at both subsonic and supersonic speeds. Subsonic compressible flow tests were performed to confirm the new sensor's repeatability and to compare its behaviour to measurements from a conventional cylindrical hot-wire, while supersonic tests were performed to investigate the nature of the convective heat transfer from the nanoscale sensor at those conditions. For the range of mass fluxes tested in the supersonic regime, a linear relationship between the Nusselt number and the Reynolds number fit the data well. A linear relationship has previously been noticed at length scales close to the molecular mean free path of the flow and has been attributed to the free-molecule flow regime, where the Knudsen number is on the order of unity
Effect of spin-orbit interaction on the vortex dynamics in LaAlO3/SrTiO3 interfaces near the superconducting transition
No full textControlling spin-orbit interaction and its effect on superconductivity has been a long-standing problem in two-dimensional inversion-symmetry-broken superconductors. An open challenge is to understand the role of various energy scales in shaping the complex phase diagram in these systems. From a combined experimental and theoretical study of resistance fluctuations and its higher-order statistics, we propose a phase diagram for the superconducting phase in the magnetic-field-spin-orbit interaction energy plane for the quasi-two-dimensional electron gas at the interface of LaAlO3/SrTiO3 heterostructures. The relative variance of resistance fluctuations increases by few orders of magnitude below the spin-orbit field B-SO and a non-Gaussian component to the fluctuations arises for fields below the upper critical field B-c2. Theoretical calculations show that the non-Gaussian noise predominantly arises due to percolative nature of the superconducting transition. We quantify the strength and the relative importance of the spin-orbit interaction energy, Zeeman energy, and the pairing potential. Our work highlights the important role played by the interplay between these energy scales in framing the fascinating phases seen in two-dimensional inversion-symmetry-broken superconductors
Rapid annealing-transformed, intense-red-emitting Eu-doped ZnGa2O4 nanoparticles with high colour purity, for very-high-resolution display applications
No full textRapid annealing (RA), an eco-friendly, soft processing technique was employed to manipulate emission properties of nanocrystalline ZnGa1.99Eu0.01O4. With RA processing that lasts only minutes, nanocrystals with weak emission were transformed into intense red-emitting phosphor. Effect of RA process parameters: temperature, duration, and cycling, on emission properties has been thoroughly studied. Compared to furnace annealing that usually lasts hours, RA, which involves simple and inexpensive apparatus, is shown to be very efficient and beneficial, as the total process time is only 15 min. This swift processing leads to enhanced quantum yield and higher colour purity (84%), without grain growth. Even after RA at 900 degrees C, crystallites measure (similar to)7-8 nm, suggesting that they might serve as pixels for very-high-resolution applications. Two PL-lifetimes obtained, imply Eu3+ distribution (i) on the nanocrystal surface, (ii) within host-lattice (spinel gallate); the distribution changes gradually with RA. Judd-Ofelt analysis and spectroscopic analysis of the PL have been discussed in detail
Real-Time Water Quality Modeling with Ensemble Kalman Filter for State and Parameter Estimation in Water Distribution Networks
No full textThis study presents a novel approach to real-time water quality state (chlorine concentration) and reaction parameter estimation in water distribution systems (WDSs) using ensemble Kalman filter (EnKF)-based data assimilation techniques. Two different types of EnKF-based methods are used in this study: noniterative restart-EnKF (NIR-EnKF) and iterative restart-EnKF (IR-EnKF). The use of these data assimilation frameworks for addressing key uncertainties in water quality models, such as uncertainty in the source or initial concentration of chlorine and uncertainty in the wall reaction parameter, is studied. The effect of ensemble size, number and location of measurement nodes, measurement error, and noise are also studied extensively in this work. The performance of the proposed methodology is tested on two different water networks: a brushy plains network and a large, citywide WDS, the Bangalore inflow network. The results of the simulation study show that both the NIR-EnKF and IR-EnKF methods are appropriate for dealing with uncertainty in source chlorine concentration, but the IR-EnKF method performs better than the NIR-EnKF method in the case of reaction parameter uncertainty
Effect of Soil Conditions on the Electromagnetic Field From an Impulse Radiating Antenna and on the Induced Voltage in a Buried Cable
No full textImpulse Radiating Antenna (IRA) is a highly efficient antenna that has a number of applications in both civilian and military sectors. These antennae produce fast rising pulses in a narrow beam that can give rise to high intensity electromagnetic fields having a wide impact on electrical and electronic systems. One such area where the impact becomes prominent is the present day telecommunication network. This system consists of buried coaxial cables connected to sensitive equipments at their terminations. Henceforth, there could be situations where the incident IRA field can interfere with the cables laid in the area. As the cables pass over different regions with varied soil texture and characteristics, the proportion of the IRA field incident on it will vary, that is dependent upon the nature of the soil in which the cable is buried. This paper reports the response of different types of soils to incident IRA fields and the induced voltage in a cable buried in such soils. A case study of different types of soils is also included in the paper. It is found that the soils in industrial areas are more prone to electromagnetic interference from IRA rather than in a highly moist ground
