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Sub-TeV quintuplet minimal dark matter with left-right symmetry
No full textA detailed study of a fermionic quintuplet dark matter in a left-right symmetric scenario is performed in this article. The minimal quintuplet dark matter model is highly constrained from the WMAP dark matter relic density (RD) data. To elevate this constraint, an extra singlet scalar is introduced. It introduces a host of new annihilation and co-annihilation channels for the dark matter, allowing even sub-TeV masses. The phenomenology of this singlet scalar is studied in detail in the context of the Large Hadron Collider (LHC) experiment. The production and decay of this singlet scalar at the LHC give rise to interesting resonant di-Higgs or diphoton final states. We also constrain the RD allowed parameter space of this model in light of the ATLAS bounds on the resonant di-Higgs and diphoton cross-sections
Total Synthesis of Sch 725674
No full textA concise total synthesis of the macrolactone natural product Sch 725674 is accomplished starting from commercially available 2-deoxy-o-ribose. Pivotal reactions employed in the synthesis include the addition of 4-pentenylmagnesium bromide to the lactol derived from 2-deoxy-o-ribose, olefin cross metathesis and Yamaguchi macrolactonization. (C) 2018 Elsevier Ltd. All rights reserved
Determination of Workspace Volume of Parallel Manipulators Using Monte Carlo Method
No full textIn this paper, we present a Monte Carlo simulation based method to determine the workspace of spatial parallel and hybrid manipulators. The method does not need the solution of the forward kinematics problem which is often difficult for spatial multi-degree-of-freedom parallel and hybrid manipulators. The method uses the solution of the inverse kinematics problem, which is often much simpler. The method can also readily incorporate joint limits and obtain the well-conditioned workspace. The approach is illustrated with a six-degree-of-freedom hybrid parallel manipulator which is a model for a human hand with three fingers. A typical human hand geometry and the range of motion at the joints are incorporated and the inverse kinematics equations for each finger is derived and used to obtain the volume of the hybrid parallel manipulator
Soft Switched Multilevel Unidirectional High Frequency Link DC/AC converter for Medium Voltage Grid Integration
No full textThis paper describes a cascaded multilevel converter topology for direct medium voltage grid integration of photovoltaic sources. The topology uses high frequency magnetic isolation and hence, reducing volume and cost of overall system. The topology is single stage and does not have any inter-stage bulky filter capacitor, thus improving reliability. The low voltage DC side converter active switches are high frequency switched. These active switches are zero voltage switched (ZVS) for most part of the line cycle. The soft-switching is achieved without additional snubber elements. The active switches interfacing the medium voltage grid are switched at line frequency incurring negligible switching loss. The converter has modular structure which also has added advantages of easy repair-replacement. Modulation strategy and soft-switching technique are analyzed in detail. Key simulation results are presented to verify the circuit operation
Towards a data-driven IoT software architecture for smart city utilities
No full textThe Internet of things (IoT) is emerging as the next big wave of digital presence for billions of devices on the Internet. Smart cities are a practical manifestation of IoT, with the goal of efficient, reliable, and safe delivery of city utilities like water, power, and transport to residents, through their intelligent management. A data-driven IoT software platform is essential for realizing manageable and sustainable smart utilities and for novel applications to be developed upon them. Here, we propose such service-oriented software architecture to address 2 key operational activities in a smart utility: the IoT fabric for resource management and the data and application platform for decision-making. Our design uses Open Web standards and evolving network protocols, cloud and edge resources, and streaming big data platforms. We motivate our design requirements using the smart water management domain; some of these requirements are unique to developing nations. We also validate the architecture within a campus-scale IoT testbed at the Indian Institute of Science, Bangalore and present our experiences. Our architecture is scalable to a township or city while also generalizable to other smart utility domains. Our experiences serve as a template for other similar efforts, particularly in emerging markets and highlight the gaps and opportunities for a data-driven IoT software architecture for smart cities
Statistics of spatial averages and optimal averaging in the presence of missing data
No full textWe estimate statistics of spatial averages defined by linearly weighting available observations over a spatial domain, and derive an account of bias and variance in the presence of missing observations. With missing observations, the spatial average is a ratio of random variables, and estimators are derived by truncating Taylor series of functions of the ratio followed by taking suitable expectations ('delta method'). The resulting estimators are approximate, and perform well when compared with simulations. Previous authors have examined ``optimal averaging'' strategies for minimizing mean squared error (MSE) of a spatial average, and we extend the analysis to the case of missing observations. It is shown that to minimize variance primarily requires higher weights where local variance and covariance are small, whereas minimizing bias requires higher weights where observations lie nearer to true spatial average. Missing data increases variance and contributes to bias, and reducing both effects involves emphasizing locations with observations nearer to the spatial average. The framework is applied to spatially averaged rainfall over India. We estimate standard error of all-India rainfall as the combined effect of measurement uncertainty and bias, in the case where weights are chosen to minimize MSE. We also discuss different special cases of the estimators, and applications thereof. (C) 2018 Elsevier B.V. All rights reserved
Observation of ex-situ microstructure relaxation of non-conventional misorientations post femtosecond laser shock exposure in cp-Ti
No full textThe effect of shock passage in commercially pure titanium (cp-Ti) with minimal macroscopic plastic strain was investigated in the present study. For the first time, ex-situ residual strain relaxation in a shocked material was recorded post-shock exposure. Femtosecond laser was used to produce a shock in cp-Ti. Post-shock investigation was carried using EBSD, TEM imaging, and TEM OIM. Uniform but low misorientations were observed inside the grains. Lamella like structures and nano grain pockets were present in the material. Observed misorientations of the remnant nanograins correspond to the multiple twinned region of twins with low twinning shear. However, a large fraction of misorientation pertains to the double twinned structure. Lattice misorientation build-up was absent in the microstructure, in spite of a large number of defects observed. This is confirmed by the GND component analysis, indicating that the macroscopic plastic strain is minimal. The lattice displays alternating curvature which cancels out over long distances, which indicates the presence of SSDs. Ex-situ strain relaxation was observed in the TEM sample resulting in bending of the TEM lamella about the triple point junction of grain. This resulted in the reverting back of defects to the parent grain, which is similar to defect annihilation on shock unloading as reported in previous MD simulations. A schematic spanning the microstructural changes before and after shock passage, and showing the effect of further strain relaxation on the microstructure is shown. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Enhanced spin wave propagation in magnonic rings by bias field modulation
No full textWe simulate the spin wave (SW) dynamics in ring structures and obtain the omega - k dispersion relations corresponding to the output waveguide. Different bias field configurations affect the transfer of SW power from one arm of the structure to the other arm. To this end, we show that circular or radial bias fields are more suitable for energy transfer across the ring than the conventional horizontal bias field H-x. The SW dispersion shows that modes excited, when the bias field is along the ring radius, are almost 10 dB higher in power when compared to the modal power in the case of H-x. This is also corroborated by the SW energy density in the receiving stub. (C) 2017 Author(s)
The roots of the drought: Hydrology and water uptake strategies mediate forest-wide demographic response to precipitation
No full text1. Drought-induced tree mortality is expected to increase globally due to climate change, with profound implications for forest composition, function and global climate feedbacks. How drought is experienced by different species is thought to depend fundamentally on where they access water vertically below-ground, but this remains untracked so far due to the difficulty of measuring water availability at depths at which plants access water (few to several tens of metres), the broad temporal scales at which droughts at those depths unfold (seasonal to decadal), and the difficulty in linking these patterns to forest-wide species-specific demographic responses. 2. We address this problem through a new eco-hydrological framework: we used a hydrological model to estimate below-ground water availability by depth over a period of two decades that included a multi-year drought. Given this water availability scenario and 20year long-records of species-specific growth patterns, we inversely estimated the relative depths at which 12 common species in the forest accessed water via a model of water stress. Finally, we tested whether our estimates of species relative uptake depths predicted mortality in the multi-year drought. 3. The hydrological model revealed clear below-ground niches as precipitation was decoupled from water availability by depth at multi-annual scale. Species partitioned the hydrological niche by diverging in their uptake depths and so in the same forest stand, different species experienced very different drought patterns, resulting in clear differences in species-specific growth. Finally, species relative water uptake depths predicted species mortality patterns after the multi-year drought. Species that our method ranked as relying on deeper water were the ones that had suffered from greater mortality, as the zone from which they access water took longer to recharge after depletion. 4. Synthesis. This research changes our understanding of how hydrological niches operate for trees, with a trade-off between realized growth potential and survival under drought with decadal scale return time. The eco-hydrological framework highlights the importance of species-specific below-ground strategies in predicting forest response to drought. Applying this framework more broadly may help us better understand species coexistence in diverse forest communities and improve mechanistic predictions of forests productivity and compositional change under future climate
Smart Textile Fabrics for Screening Millimeter Wavelength Radiations: Challenges and Future Perspectives
No full textThe conductive fabrics are widely used in smart protective textile, specifically to shield millimeter wavelength radiations. In this context, intrinsically conducting polymers (ICPs) have gained enormous interest in the recent past due to their myriad applications in the field of textile specifically because of their tunable conductivity, lightweight, ease of coating etc. Numerous research studies have been focused to develop electromagnetic (EM) shielding fabric using ICPs and various functional conducting, magnetic and dielectric nanoparticles. The objective of this review article is to highlight the state-of-the-art literature and recent developments in this field involving surface modification of textile fabrics using physical/chemical methods targeted towards EM shielding application. Furthermore, this review also provides useful insight in the shielding mechanism and diverse processes to design and develop smart EM shielded flexible fabrics as protective textiles