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Sliding mode guidance for impact time and angle constraints
No full textThis paper proposes a guidance strategy, which caters to both impact angle and impact time terminal constraints. This guidance scheme is based on switching between impact time and impact angle guidance laws. Unlike the existing impact time guidance laws, the proposed guidance strategy takes into account the curvature of the trajectory due to requirement of impact angle. The guidance law is derived using sliding mode control theory with the switching surface based on impact time error. The interceptor first corrects its course to nullify the impact time error and then aims to achieve interception with desired impact angle. In order to reduce transitions between the two guidance laws, a novel hysteresis loop is introduced in the switching conditions. The guidance law is initially designed for stationary targets, and later it is extended to constant velocity targets using the notion of predicted interception point. In order to validate the efficacy of the proposed guidance strategy, simulation results are presented with constant as well as realistic time-varying speed interceptor models for different engagement scenarios against stationary and constant velocity targets. The performance of the guidance law is evaluated under noisy measurements and the presence of system lag and its performance is compared with other existing guidance laws
A Generic Axiomatic Characterization for Measuring Influence in Social Networks
No full textMeasuring influence, through centrality measures, has been a center-piece of research in the analysis of complex social networks, such as finding coherent communities (clusters) and locating trend setters (prototypes) in viral marketing. Even though there exists a few axiomatic frameworks associated with some specific forms of influence measures in the literature, these formal frameworks are not generic in nature in terms of characterizing the space of influence measures for complex social networks. To address this research gap, we propose a generic axiomatic framework, in this paper, to capture most of the key intrinsic properties of any influence measure in networks. We further analyze certain popular centrality measures using this framework. Interestingly, our analysis reveals that none of the centrality measures considered satisfies all the desirable axioms. We finally conclude this paper by stating an appealing conjecture on a potential impossibility theorem associated with the proposed axiomatic framework
Biases in the Facebook News Feed: a Case Study on the Italian Elections
No full textFacebook News Feed personalization algorithm has a significant impact, on a daily basis, on the lifestyle, mood and opinion of millions of Internet users. Nonetheless, the behavior of such algorithms usually lacks transparency, motivating measurements, modeling and analysis in order to understand and improve its properties. In this paper, we propose a reproducible methodology encompassing measurements and an analytical model to capture the visibility of publishers over a News Feed. First, measurements are used to parameterize and to validate the expressive power of the proposed model. Then, we conduct a what-if analysis to assess the visibility bias incurred by the users against a baseline derived from the model. Our results indicate that a significant bias exists and it is more prominent at the top position of the News Feed. In addition, we found that the bias is non-negligible even for users that are deliberately set as neutral with respect to their political views
Filling of closed surfaces
No full textLet F-g denote a closed oriented surface of genus g. A set of simple closed curves is called a filling of F-g if its complement is a disjoint union of discs. The mapping class group Mod(F-g) of genus g acts on the set of fillings of F-g. The union of the curves in a filling forms a graph on the surface which is a so-called decorated fat graph. It is a fact that two fillings of F-g are in the same Mod(F-g)-orbit if and only if the corresponding fat graphs are isomorphic. We prove that any filling of F-2 whose complement is a single disc (i.e. a so-called minimal filling) has either three or four closed curves and in each of these two cases, there is a unique such filling up to the action of Mod(F-2). We provide a constructive proof to show that the minimum number of discs in the complement of a filling pair of F-2 is two. Finally, given positive integers g and k with (g, k) not equal (2, 1), we construct a filling pair of F-g such that the complement is a union of k topological discs
Search for supersymmetry in events with a tau lepton pair and missing transverse momentum in proton-proton collisions at root s=13TeV
No full textA search for the electroweak production of supersymmetric particles in protonproton collisions at a center-of-mass energy of 13TeV is presented in final states with a tau lepton pair. Both hadronic and leptonic decay modes are considered for the tau leptons. Scenarios involving the direct pair production of tau sleptons, or their indirect production via the decays of charginos and neutralinos, are investigated. The data correspond to an integrated luminosity of 35: 9 fb collected with the CMS detector in 2016. The observed number of events is consistent with the standard model background expectation. The results are interpreted as upper limits on the cross section for tau slepton pair production in di ff erent scenarios. The strongest limits are observed in the scenario of a purely left-handed low mass tau slepton decaying to a nearly massless neutralino. Exclusion limits are also set in the context of simpli fi ed models of chargino-neutralino and chargino pair production with decays to tau leptons, and range up to 710 and 630 GeV, respectively
EpsN from Bacillus subtilis 168 has UDP-2,6-dideoxy 2-acetamido 4-keto glucose aminotransferase activity in vitro
No full textThe gene epsN of Bacillus subtilis 168 was cloned and overexpressed in Escherichia coli. Purified recombinant EpsN is shown to be a pyridoxal 5'-phosphate (PLP)-dependent aminotransferase by absorption spectroscopy, L-cycloserine inhibition and reverse phase HPLC studies. EpsN catalyzes the conversion of UDP-2,6-dideoxy 2-acetamido 4-keto glucose to UDP-2,6-dideoxy 2-acetamido 4-amino glucose. Lys190 was found by sequence comparison and site-directed mutagenesis to form Schiff base with PLP. Mutagenesis studies showed that, in addition to Lys190, Ser185, Glu164, Gly58 and Thr59 are essential for aminotransferase activity
A COMPARISON OF EVAPORATING SPRAY STRUCTURE OF JATROPHAMETHYL ESTER AND DIESEL, AND SURROGATE FUELS
No full textIn the present study, the spray characteristics of Jatropha methyl ester (JME), diesel, and two surrogate fuels, n-dodecane and n-hexadecane, are investigated under evaporating ambient conditions. A high-pressure chamber with optical access is used for the study. Nitrogen gas filled in the chamber is heated to reach a final pressure of 50 bar and a final temperature of 900 K. A single-hole nozzle with a hole size of 190 mu m has been used for fuel injection. The results showed that the liquid length of JME is longer by 19%, 17%, and 11% compared to that of diesel at injection pressures of 500 bar, 1000 bar, and 1500 bar, respectively. At a given operating condition, the vapor penetration of JME and diesel are observed to be similar. Two surrogate fuels, n-dodecane and n-hexadecane, with similar property differences as those between diesel and a typical biodiesel, have been studied. The results show that the liquid length of n-hexadecane is about 20% longer than that of n-dodecane whereas both fuels have similar vapor penetration. Thus, the surrogate fuels exhibit differences between spray characteristics similar to those of diesel and biodiesel. A separate comparison of spray characteristics of diesel and n-hexadecane showed that it is an acceptable spray surrogate for diesel. An analytical model for vapor penetration has been verified against the experimental data and found to match well with the data. A parametric variation of fuel density showed that the effect of fuel density variation is compensated by the corresponding variation in injection velocity at a given injection pressure, which explains the experimentally observed trend of similar vapor penetration of all the fuel
A variant selection mechanism in the deformed and recrystallized matrix of a metastable -titanium alloy
No full textThe variant selection criteria during to phase transformations in a metastable -titanium alloy (Ti-5553) in the presence of deformation are examined. Two distinct metallurgical states in the matrix, heavily deformed and fully recrystallized, were obtained from a 90% cold-rolled alloy. The deformed and recrystallized samples were subjected to aging heat treatment for a short time to allow the precipitation of an intragranular phase. Electron backscattered diffraction was used to assess the crystallographic variant occurrence in the deformed as well as in the recrystallized grains. A discrete pole figure analysis revealed that a limited number of variants were evolved in the deformed grains while there was no variant selection in the recrystallized matrix. The results suggest that activation of {112}<111> slip systems determines a strong variant selection in the plastically deformed matrix
Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 Cathode and Fe3O4 Anode
No full textA facile route to anchor pseudocapacitive materials on multiwalled carbon nanotubes (CNTs) to realize high-performance electrode materials for asymmetric super capacitors (ASCs) is reported. The anchoring process is developed after direct decomposition of metal-hexacyanoferrate complex on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over the CNT surface without forming a uniform layer, thus making most of the entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn3O4 nanocomposite cathode shows significantly improved capacitive performance as compared to pristine CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe3O4 nanocomposite as the paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8 V in the aqueous electrolyte and retains almost 100% of its initial capacitance after 15,000 cycles. The serially connected ASCs can power commercial light-emitting diodes (LEDs) and mobile phones, reflecting their potential in next-generation storage applications
Subsurface imaging of brown coal bearing Tertiary sedimentaries Deccan Trap interface using microtremor method
No full textWe propose an application of the microtremor (ambient noise) H/V spectral ratio technique to identify significant rheological boundaries at shallow depths, estimate thickness of both lignite bearing Tertiary sedimentary sequence and late Cretaceous Deccan basalt flows and comprehend basinal geometry of Umarsar Basin (Babia syncline). Forty-six stations were gauged in a grid format at similar to 250 m resolution during the microtremor survey. The microtremor H/V spectral ratio technique takes into account the frequency of the ratio between the horizontal (NS + EW) and vertical components of persistent Rayleigh waves in the area. Depth estimates are made using Mean_VS (433.69 m/s) from three borehole records (MMA_Vs (431.6 m/s), MMB_Vs (406.86 m/s) and MMC_Vs (462.6 m/s) using standard relationship between depth and velocity. In the present study, we recognize three rheological interfaces viz., L-1 interface (0.2328 Hz to 0.3862 Hz), L-2 interface (0.7843 Hz to 2.5123 Hz) and L-3 interface (6.2477 Hz to 27.1119 Hz). The geology and stratigraphic records supplement correlation for L1,L2 and L-3 interfaces with Mesozoic-Deccan Trap (M-DT) boundary, Deccan Trap-Tertiary (DT-T) boundary, and boundaries between shale-carbonate hardpans within sediment sequence belonging to Naredi Formation respectively. The estimated depth range for M-DT boundary (L-1) is 281-466 m and for DT-T boundary (L-2)is 43-138 m. The subsurface image acquired from the frequency records advocates for a palaeo high in SE portion that retains its entity over the present landscape. The frequency records advocate for 369 m to 206 m thick Deccan basalt and 85 m to 18 m thick lignite bearing Naredi Formation. The ambient noise seismic study further suggests NW-SE trending basin geometry of Babia syncline comprising three distinct depressions having six local depocenters. Finally, we propose the microtremor H/V spectral ratio technique as a tool to develop economical borehole plan with realistic reserve estimate and a step forward towards rapid economical assessment covering large mining lease areas complementary to local geological studies. (C) 2018 Elsevier B.V. All rights reserved