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Trajectory Tracking and Control of Car-Like Robots
No full textThis paper deals with trajectory tracking control of a car-like robot. By exploiting the differential flatness property of the system based on the dynamics, a trajectory tracking controller using flatness-based control techniques is designed. A singularity in the system for the chosen control inputs, which does not allow direct application of feedback linearization control, is identified and this singularity is overcome by applying the dynamics-extension algorithm to obtain a dynamic feedback linearized controller. This controller results in asymptotic tracking convergence of the system's trajectory to the reference trajectory. Through numerical simulations, the control system is shown to track prescribed trajectories satisfactorily even in the presence of parametric uncertainties
Multi-satellite retrieval of single scattering albedo using the OMI-MODIS algorithm
No full textSingle scattering albedo (SSA) represents a unique identification of aerosol type and can be a determinant factor in the estimation of aerosol radiative forcing. However, SSA retrievals are highly uncertain due to cloud contamination and aerosol composition. The recent improvement in the SSA retrieval algorithm has combined the superior cloud-masking technique of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the higher sensitivity of the Ozone Monitoring Instrument (OMI) to aerosol absorption. The combined OMI-MODIS algorithm has only been validated over a small spatial and temporal scale. The present study validates the algorithm over global oceans for the period from 2008 to 2012. The geographical heterogeneity in the aerosol type and concentration over the Atlantic Ocean, the Arabian Sea and the Bay of Bengal was useful to delineate the effect of aerosol type on the retrieval algorithm. We also noted that OMI overestimated SSA when absorbing aerosols were present closer to the surface. We attribute this overestimation to data discontinuity in the aerosol height climatology derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. OMI uses predefined aerosol heights over regions where CALIPSO climatology is not present, leading to the overestimation of SSA. The importance of aerosol height was also studied using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The results from the joint retrievals were validated using cruise-based measurements. It as seen that OMI-MODIS SSA retrievals performed better than the OMI only retrieval over the Bay of Bengal during winter, when the aerosols are present closer to the surface. Discrepancy between satellite retrievals and cruise measurements was seen when elevated aerosols were present which might not have been detected by the cruise instruments
An Error Analysis of Discontinuous Finite Element Methods for the Optimal Control Problems Governed by Stokes Equation
No full textIn this article, an abstract framework for the error analysis of discontinuous finite element method is developed for the distributed and Neumann boundary control problems governed by the stationary Stokes equation with control constraints. A priori error estimates of optimal order are derived for velocity and pressure in the energy norm and the L-2-norm, respectively. Moreover, a reliable and efficient a posteriori error estimator is derived. The results are applicable to a variety of problems just under the minimal regularity possessed by the well-posedness of the problem. In particular, we consider the abstract results with suitable stable pairs of velocity and pressure spaces like as the lowest-order Crouzeix-Raviart finite element and piecewise constant spaces, piecewise linear and constant finite element spaces. The theoretical results are illustrated by the numerical experiments
Phospholipid Headgroups Govern Emergent Bending Energy of Membranes with Implications for Lipid-Protein Interactions
No full textSearch for t t ¯ H production in the H → b b ¯ decay channel with leptonic t t ¯ decays in proton-proton collisions at √s=13 TeV
No full textA search is presented for the associated production of a standard model Higgs boson with a top quark-antiquark pair (t t ¯ H), in which the Higgs boson decays into a b quark-antiquark pair, in proton-proton collisions at a centre-of-mass energy s=13 TeV. The data correspond to an integrated luminosity of 35.9 fb −1 recorded with the CMS detector at the CERN LHC. Candidate t t ¯ H events are selected that contain either one or two electrons or muons from the t t ¯ decays and are categorised according to the number of jets. Multivariate techniques are employed to further classify the events and eventually discriminate between signal and background. The results are characterised by an observed t t ¯ H signal strength relative to the standard model cross section, μ = σ/σ SM , under the assumption of a Higgs boson mass of 125 GeV. A combined fit of multivariate discriminant distributions in all categories results in an observed (expected) upper limit on μ of 1.5 (0.9) at 95% confidence level, and a best fit value of 0.72 ± 0.24(stat) ± 0.38(syst), corresponding to an observed (expected) signal significance of 1.6 (2.2) standard deviations above the background-only hypothesis.[Figure not available: see fulltext.]. © 2019, The Author(s)
Spleen Tyrosine Kinase-Mediated Autophagy Is Required for Epithelial-Mesenchymal Plasticity and Metastasis in Breast Cancer
No full textThe ability of breast cancer cells to transiently transition between epithelial and mesenchymal states contributes to their metastatic potential. Therefore, driving tumor cells into a stable mesenchymal state, as opposed to complete tumor cell eradication, presents an opportunity to pharmacologically limit disease progression by promoting an asymptomatic state of dormancy. Here, we compare a reversible model of epithelial-mesenchymal transition (EMT) induced by TGF beta to a stable mesenchymal phenotype induced by chronic exposure to the ErbB kinase inhibitor lapatinib. Only cells capable of returning to an epithelial phenotype resulted in skeletal metastasis. Gene expression analyses of the two mesenchymal states indicated similar transition expression profiles. A potently downregulated gene in both datasets was spleen tyrosine kinase (SYK). In contrast to this similar diminution in mRNA, kinome analyses using a peptide array and DNA-conjugated peptide substrates showed a robust increase in SYK activity upon TGF beta-induced EMT only. SYK was present in cytoplasmic RNA processing depots known as P-bodies formed during the onset of EMT, and SYK activity was required for autophagy-mediated clearance of P-bodies during mesenchymal-epithelial transition (MET). Genetic knockout of autophagy-related 7 (ATG7) or pharmacologic inhibition of SYK activity with fostamatinib, a clinically approved inhibitor of SYK, prevented P-body clearance and MET, inhibiting metastatic tumor outgrowth. Overall, this study suggests assessment of SYK activity as a biomarker for metastatic disease and the use of fostamatinib as a means to stabilize the latency of disseminated tumor cells
Evidence of adaptive modulation and magnetic field induced reorientation i of variants in epitaxially grown Ni-Mn-Ga thin film on Al2O3 (11(2)over-bar0) substrate
No full textEpitaxial Ni-Mn-Ga thin films with a room temperature martensite phase were fabricated on single crystal Al2O3 (11 (2) over bar0) substrate using direct current (DC) magnetron sputtering. The X-ray pole figure measurements confirm the epitaxial relationship of Ni-Mn-Ga (101)(7M) parallel to Al2O3 (11 (2) over bar0) and Ni-Mn-Ga-7M parallel to Al2O3 (1 (1) over bar 01) between the film and substrate. Transmission electron microscopy reveals the presence of (220) micro-twins at an angle of 62.5 degrees and 56.3 degrees with respect to (202) growth plane. Coexistence of non-modulated martensite phase (a(NM) = 5.45 angstrom and c(NM) = 6.56 angstrom) and seven modulated martensite phases (a(14M) = 6.26 angstrom, b(14M )= 5.89 angstrom and c(14M) = 5.56 angstrom) has been observed in the film. The in-situ high-temperature X-ray diffraction indicates reversible thermal phase transformation in the film with a very low thermal hysteresis. The magnetic field induced reorientation (MIR) effect is displayed by the film
Partitioning a reaction-diffusion ecological network for dynamic stability
No full textThe loss of dispersal connections between habitat patches may destabilize populations in a patched ecological network. This work studies the stability of populations when one or more communication links is removed. An example is finding the alignment of a highway through a patched forest containing a network of metapopulations in the patches. This problem is modelled as that of finding a stable cut of the graph induced by the metapopulations network, where nodes represent the habitat patches and the weighted edges model the dispersal between habitat patches. A reaction-diffusion system on the graph models the dynamics of the predator-prey system over the patched ecological network. The graph Laplacian's Fiedler value, which indicates the well-connectedness of the graph, is shown to affect the stability of the metapopulations. We show that, when the Fiedler value is sufficiently large, the removal of edges without destabilizing the dynamics of the network is possible. We give an exhaustive graph partitioning procedure, which is suitable for smaller networks and uses the criterion for both the local and global stability of populations in partitioned networks. A heuristic graph bisection algorithm that preserves the preassigned lower bound for the Fiedler value is proposed for larger networks and is illustrated with examples
A Mechanochemical Route to Cutting Highly Strain-Hardening Metals
No full textHighly strain-hardening metals such as Al, Ni, and stainless steels, although relatively soft, are well known as being difficult to cut, because of an unsteady and highly redundant mode of plastic deformationsinuous flowprevailing during chip formation. This difficulty in cutting is greatly ameliorated, if the workpiece surface ahead of the chip formation region is coated with certain chemical media such as glues, inks, and alcohols that are quite benign. High-speed imaging shows that the media effect a change in the local plastic deformation mode, from sinuous flow to one characterized by periodic fracturesegmented flow. This flow transition, due to a mechanochemical effect, results in significant reduction of deformation forces and energy, often >50%, thus facilitating the cutting. The effect is mostly pronounced at smaller undeformed chip thickness, typical of finish and semi-finish machining regimes. The quality of the cut surface, as measured by defect density and surface roughness, improves by an order of magnitude, when the media are applied. Furthermore, this surface is relatively strain free in contrast to conventionally machined surfaces. The mechanochemical effect, with a strong coupling to the flow mode, is controllable, with the media showing similar efficacy across different metal systems. The results suggest opportunities for improving performance of machining processes for many difficult-to-cut gummy metals
On the lifetime of evaporating confined sessile droplets
No full textConfinement effects may trigger certain non-trivial characteristics of droplet evaporation, which may incur far-reaching implications in practical scenarios. In effect, the vapor mediated interactions in a confined droplet may alter its intrinsic evaporation characteristics altogether, primarily as a consequence of significant increase in droplet lifetime due to enriched accumulation of the vapor field in the vicinity. Here, we derive a universal scaling law for the evaporation lifetime of a geometrically confined sessile droplet, appropriate to a wide gamut of droplet-substrate combinations. With asymptotic convergence to the classical picture in case of an unconfined droplet, the validity of our scaling law for droplet lifetime is comprehensively tested and benchmarked against a wide range of experimental data sets. These findings may turn out to be of profound importance in several emerging applications including micro-scale combustion and droplet based microfluidic technology