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An asymptotic approximation for TCP CUBIC
No full textIn this paper, we derive an expression for computing the average window size of a single TCP CUBIC connection under random losses. For this we consider a throughput expression for TCP CUBIC computed earlier under deterministic periodic packet losses. We validate this expression theoretically. We then use insights from the deterministic loss-based model to scale appropriately a sequence of Markov chains with random losses indexed by the probability of loss p. We show that this sequence converges to a limiting Markov chain as p tends to 0. The stationary distribution of the limiting Markov chain is then used to derive the average window size for small packet error rates. We then use a simple approximation to extend our current results with negligible queuing to a setup with multiple connections and non-negligible queuing. We validate our model and approximations via simulations
Model Predictive Static Programming for Optimal Command Tracking: A Fast Model Predictive Control Paradigm
No full textInspired by fast model predictive control (MPC), a new nonlinear optimal command tracking technique is presented in this paper, which is named as ``Tracking-oriented Model Predictive Static Programming (T-MPSP).'' Like MPC, a model-based prediction-correction approach is adopted. However, the entire problem is converted to a very low-dimensional ``static programming'' problem from which the control history update is computed in closed-form. Moreover, the necessary sensitivity matrices (which are the backbone of the algorithm) are computed recursively. These two salient features make the computational process highly efficient, thereby making it suitable for implementation in real time. A trajectory tracking problem of a two-wheel differential drive mobile robot is presented to validate and demonstrate the proposed philosophy. The simulation studies are very close to realistic scenario by incorporating disturbance input, parameter uncertainty, feedback sensor noise, time delays, state constraints, and control constraints. The algorithm has been implemented on a real hardware and the experimental validation corroborates the simulation results
Heat fluctuation of a harmonically trapped particle in an active bath
No full textWe study the heat fluctuation of an overdamped Brownian particle trapped in a harmonic potential and driven by active noise. Employing the phase-space path integral method we derive a general formula for the probability distribution of heat exchange in a generic model of an active bath. The work has been extended by considering two particular models of active noise and computing an exact analytical expression for distribution in Gaussian colored noise and a semianalytical result in the Poissonian bath. We corroborate the fluctuation theorem with our analytical findings by introducing the familiar concept of effective temperature and as a corollary the total entropy production is calculated
Finite-Element Limit Analysis of Strip and Circular Skirted Footings on Sand
No full textThe lower- and upper-bound theorems of the limit analysis have been used in conjunction with finite elements and second-order cone programming (SOCP) for determining the bearing capacity of strip and circular skirted footings on sand. The analysis follows the Mohr-Coulomb's yield criterion and the associated flow rule; sand is not usually considered to obey this rule, but the results of using it are discussed. The friction angle of sand was varied between 30 and 45 degrees, and the depth (D-s) of the skirt increased from 0.25 to 2B; here B implies: (1) the width of a skirted strip footing, and (2) the diameter of a circular skirted footing. The results are expressed in terms of the bearing capacity ratio (BCR): the ratio of the bearing capacities of a skirted footing to that of the surface footing, with the same value of B but without any skirt element. The results reveal that the magnitude of the BCR increases quite extensively with an increase in the value of D-s/B. The skirted footing was found to be especially quite advantageous for loose sand. With the same D-s/B, the BCR for a circular skirted footing was found to be substantially greater than that for the strip skirted footing
Measurement of differential cross sections for inclusive isolated-photon and photon plus jet production in proton-proton collisions at root s=13TeV
No full textMeasurements of inclusive isolated-photon and photon+jet production in proton-proton collisions at =13TeV are presented. The analysis uses data collected by the CMS experiment in 2015, corresponding to an integrated luminosity of 2.26fb-1. The cross section for inclusive isolated photon production is measured as a function of the photon transverse energy in a fiducial region. The cross section for photon+jet production is measured as a function of the photon transverse energy in the same fiducial region with identical photon requirements and with the highest transverse momentum jet. All measurements are in agreement with predictions from next-to-leading-order perturbative QCD
Effect of NaNbO3 addition on structure, dielectric and energy storage properties of lead free piezoelectric Bi0.5Na0.5TiO3-K0.5Na0.5NbO3 ceramics
No full textNaNbO3 modified Bi0.5Na0.5TiO3-K0.5Na0.5NbO3 ceramics are prepared as per the nominal formula (1-x) 0.93Bi(0.5)Na(0.5)TiO(3)-0.07K(0.5)Na(0.5)NbO(3)]-xNaNbO(3) (1-x)(0.93BNT-0.07KNN)-xNN; 0 <= x <= 0.16] using conventional solid state synthesis route. Detailed analysis of the compositions indicate decrease in the polarization, increase in the energy storage property and flattening in the temperature dependent dielectric permittivity with increasing NaNbO3 (NN) concentration. Structural study confirms the increasing tendency of cubic like phase formation with increasing NN concentration. Our results suggest that among other factors, cubic like phase formation at room temperature is the responsible factor for the observed trends in various properties. Flattening in the temperature dependent dielectric permittivity indicates that the prepared ceramics are suitable for capacitor applications
A Finite Input Alphabet Perspective on the Rate-Energy Tradeoff in SWIPT Over Parallel Gaussian Channels
No full textSimultaneous wireless information and power transfer (SWIPT) has gained significant popularity in the recent past owing to its applications in a wide range of use cases. Although SWIPT has been fairly well investigated in the literature, the existing work has mainly focused on attaining the optimal rate energy (RE) tradeoff assuming Gaussian input alphabet. However, practical systems operate with finite input alphabets such as quadratic-amplitude modulation (QAM)/phase-shift keying. We characterize the attainable RE tradeoff in SWIPT systems employing finite input alphabet for transmission over parallel Gaussian channels of say orthogonal frequency-division multiplexing subcarriers or multiple-input multiple-output streams. Some of the key results in the literature that assume Gaussian input alphabet are shown to be special cases of our results. Furthermore, we provide insights into our results with the aid of graphical illustrations, which throw light on the optimal power allocation policy for various energy-harvesting constraints. Furthermore, we consider practically relevant time-sharing and power-splitting schemes operating with finite input alphabet and characterize their RE tradeoff. Their optimal solutions in the asymptotic regime are obtained, which serve as low-complexity solutions suitable for practical implementation. Our simulation studies have demonstrated that the Gaussian input assumption significantly over-estimates the attainable RE tradeoff, especially when the signal set employed is small. Furthermore, it is observed through numerical simulations that the proposed optimal power allocation performs significantly better than the power allocation based on the Gaussian input assumption. Specifically, as much as 30% rate improvement is observed when employing the classic 4-QAM signal set
Enhanced corrosion resistance by SnCu-graphene oxide composite coatings
No full textSnCu-graphene oxide composite coatings with different amount of graphene oxide (GO) content were electro-deposited over a mild steel substrate. Morphological, microstructural evolution and electrochemical properties of coatings were investigated as a function of GO content. All the coatings exhibited compact and crack free morphology. Structural characterization revealed the presence of Sn and Cu6Sn5 phase in all the coatings. Addition of GO considerably reduced the grain size of Sn phase while the Cu6Sn5 phase remained unaltered. GO altered the coating texture facilitating growth along the low index planes. Corrosion behaviour of the coatings was examined through potentiodynamic polarization and electrochemical impedance spectroscopy methods. An aspect of ``optimum'' GO amount for best corrosion resistance for the SnCu-GO composite coatings was witnessed. With the addition of GO, the corrosion rate initially decreased to a minimum value and then, upon further addition of GO, it increased to values much higher than the pristine coating. In the case of lower GO amounts, the textured growth coupled with inertness of GO increased the corrosion resistance whereas, at higher GO concentrations, the galvanic coupling between cathodic GO and anodic SnCu dominated, leading to lowering of the corrosion resistance
Synthesis of novel luminescent copper nanoclusters with substituent driven self-assembly and aggregation induced emission (AIE)
No full textWe demonstrate a novel strategy to synthesize highly stable luminescent mercaptoimidazole-capped copper nanoclusters (CuNCs). Herein we depict that a simple modification of substituents on the mercaptoimidazole ligand dictates the self-assembly and photophysical properties of the clusters. These CuNCs showed aggregation induced emission (AIE) with a large Stokes shift ( > 200 nm), and the formation of clusters corresponding to Cu4L3 was confirmed by MALDI-TOF mass spectrometric analyses. Interestingly, these nanoclusters effectively internalize into mammalian cells while retaining their fluorescent properties and exhibit negligible toxicity
Spin density encodes intramolecular singlet exciton fission in pentacene dimers
No full textThe formation of two triplet excitons at the cost of one photon via singlet exciton fission in organic semiconductors can potentially enhance the photocurrent in photovoltaic devices. However, the role of spin density distribution in driving this photophysical process has been unclear until now. Here we present the significance of electronic spin density distribution in facilitating efficient intramolecular singlet exciton fission (iSEF) in pi-bridged pentacene dimers. We synthetically modulate the spin density distribution in a series of pentacene dimers using phenyl-, thienyl- and selenyl-flanked diketopyrrolopyrrole (DPP) derivatives as pi-bridges. Using femtosecond transient absorption spectroscopy, we find that efficient iSEF is only observed for the phenyl-derivative in similar to 2.4 ps while absent in the other two dimers. Electronic structure calculations reveal that phenyl-DPP bridge localizes alpha- and beta-spin densities on distinct terminal pentacenes. Upon photoexcitation, a spin exchange mechanism enables iSEF from a singlet state which has an innate triplet pair character