607 research outputs found
sj-docx-1-pie-10.1177_09544089231190225 - Supplemental material for Investigation of mechanical and viscoelastic properties of <i>Agave cantala</i> fiber-reinforced green composites for structural applications
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089231190225 for Investigation of mechanical and viscoelastic properties of Agave cantala fiber-reinforced green composites for structural applications by M Ramesh, M Tamil Selvan, A Felix Sahayaraj, I Jenish, P Balakrishnan and Arivumani Ravanan in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
First-Principles Simulations of Functional Materials for Energy Conversion
No full textComputational modeling has become a very effective approach in predicting properties of materials, and in designing functional materials with targeted structural, thermal, or optical properties. Many electronic structure methods have been developed, including density functional theory. Among them, DFT has been widely used in physics and materials science because it is computationally cheaper than other methods but still gives desired accuracy. It also provides a good starting point for higher levels of theory, such as many-body perturbation theory and quantum Monte Carlo. In parallel to these electronic structure method developments, a dramatic increase in computing capabilities over the last decade has enabled large-scale electronic structure calculations to address leading-edge materials science problems. In particular, with Theta at the Argonne Leadership Computing Facility (ALCF), our early science project investigated large-scale nanostructured ma- terials for energy conversion and storage using two open-source electronic structure codes Qbox (http://qboxcode.org) and WEST (http://west-code.org). Qbox is an ab-initio molecular dynamics code based on plane wave DFT, and WEST is a post-DFT code for excited state calculations within many-body perturbation theory
Large and detached eddy simulation of separated flow over 3D hill geometries with surface roughness to mimic flows over complex terrains
No full textWith the push to making wind power a significant contributor to the energy portfolio in the U.S. and Europe, there is considerable effort to deploy the currently available peta-scale computational resources to assess and improve well known simulation techniques, such as the large eddy simulation (LES) and detached eddy simulation (DES) techniques, to model the complex flows in wind farms, taken as a whole, as opposed to individual wind turbines. Simulating turbulent flows in wind farms, consisting of arrays of wind turbines, begins with the modeling and simulation of the atmospheric boundary layer (ABL) over complex terrain that is characterized by regions of separated flow with a high degree of turbulence anisotropy. Over the years there has been considerable work on applying LES and Reynolds Averaged Navier--Stokes (RANS) simulations over terrain geometries, such as the Askervein Hill, to understand turbulence closure models for flow over complex terrain. Such studies, however, have had limited success due to difficulties associated with the closure models in the near wall region of the flow. At the same time, turbulence simulations over \emph{canonical} geometries, such as the periodic and axisymmetric hills, have been shown to compare well with data obtained from laboratory scale experiments, where the inflow turbulence and boundary conditions are better characterized and defined respectively. In an effort to extend these canonical flows to be more representative of flows over complex terrain, this paper aims to present results of large and detached eddy simulations of separated flow over three dimensional hill geometries with roughness parametrization, with the objective of developing better closure models for flow over complex terrain
Agricultural Crisis in India: The Root Cause and Consequences
No full textAgricultue in India is undergoing a structural change leading to a crisis situation. The rate of growth of agricultural output is gradually declining in the recent years. The relative contribution of agriculture to the GDP has been declining over time steadily. The performance of agriculture by crop categories also clearly indicates the slowing down process of agriculture in India. The onset of deceleration in agriculture began from early nineties and it became sharp from the late nineties. The trends in the area, input use, capital stock and technology also reflect the agricultural downfall and the farmer’s response accordingly. It is alarming that India is moving towards a point of no return, from being a self-reliant nation of food surplus to a net importer of food. All these trends indicate that the agricultural sector in India is facing a crisis today. It is argued that the root cause of the crisis was that agriculture is no more a profitable economic activity when compared to other enterprises. It means that the income derived from these activities is not sufficient enough to meet the expenditure of the cultivators. And therefore, unless agriculture is made a profitable enterprise, the present crisis cannot be solved. The related factors responsible for the crisis include: dependence on rainfall and climate, liberal import of agricultural products, reduction in agricultural subsidies, lack of easy credit to agriculture and dependence on money lenders, decline in government investment in the agricultural sector and conversion of agricultural land for alternative uses. It is argued that the consequence of agricultural crisis in India is very vast and likely to hit all the other sectors and the national economy in several ways. In specific, it has adverse effects on food supply, prices of foodgrains, cost of living, health and nutrition, poverty, employment, labour market, land loss from agriculture and foreign exchange earnings. In sum, it revealed that the agricultural crisis would be affecting a majority of the people in India and the economy as a whole in the long run. And therefore, it can be argued that the crisis in agriculture is a crisis of the country as a whole. Ihe only remedy to the crisis is to do all that is possible to make agriculture a profitable enterprise and attract the farmers to continue the crop production activities. As an effort towards this direction, the government should augment its investment and expenditure in the farm sector. Investment in agriculture and its allied sectors, including irrigation, transport, communication, rural market, rural infrastructure and farm research, should be drastically increased, and the government should aim at integrated development of the rural areas. The solution of the problem is not in a few “packages” but in drastic changes in the present economic policies related to agriculture. No other sector’s growth and development must be at the cost of agriculture. All farmers, agricultural labourers, societies, Government and People’s Organisations should work collectively to revive agriculture and “Save India from Agriculture Crisis”.Agriculture; Agriculture Crisis; Crisis; Agricultural Crisis; agriculture deceleration; slowdown; Farming Crisis; India; Causes; Consequences; impact; Foodgrains; Public Investment; Agriculural Credit; Agriculture performance; Contribution from Agriculture; Agricultural Situation;
On defect CFT and path integral methods for entanglement in quantum field theories
No full textIn the first few chapters of the thesis, we will study defect CFT methods based on the replica trick for characterizing quantum information in quantum field theories. We calculate a coefficient that characterizes the strength of the two point function of the displacement operator in the replica twist defect placed in a holographic CFT, which controls the second order shape dependence of Renyi entropy. We introduce defect CFT methods for calculating correlation functions involving the modular Hamiltonian together with probe operators inserted at lightcone separation. We use these methods to further calculate correlation functions involving modular flows of these probe operators. Tomita-Takesaki theory constrains these correlation functions, which when combined with our defect CFT calculations, provides a proof of the Quantum Null Energy Condition.
In the last few chapters of this thesis, we will calculate entanglement measures for states that are defined by a Euclidean path integral together with a source for an operator inserted in the path integral. We provide a purely Lorentzian formula for the modular Hamiltonians for these states for flat entangling cuts which systematizes the task of writing time-ordered expressions for relative entropy of these states with respect to the vacuum to all orders in the source. We further apply this method to calculate a formula for shape deformed modular Hamiltonian for the vacuum state to all orders in the shape deformation. In the case of null shape deformation, we recover the formula for the vacuum modular Hamiltonian for null cuts. We then calculate the shape deformation of relative entropy and provide evidence for the presence of a shock in the stress tensor expectation value when one performs the Connes cocycle flow of the state.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-12-01The student, Srivatsan Balakrishnan, accepted the attached license on 2021-07-16 at 15:10.The student, Srivatsan Balakrishnan, submitted this Dissertation for approval on 2021-07-16 at 15:25.This Dissertation was approved for publication on 2021-07-19 at 10:22.DSpace SAF Submission Ingestion Package generated from Vireo submission #16990 on 2022-04-06 at 17:16:09Made available in DSpace on 2022-04-29T21:41:38Z (GMT). No. of bitstreams: 3
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Previous issue date: 2021-07-19Embargo set by: Seth Robbins for item 123298
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LU-SGS Implicit Scheme For A Mesh-Less Euler Solver
No full textLeast Square Kinetic Upwind Method (LSKUM) belongs to the class of mesh-less method that solves compressible Euler equations of gas dynamics. LSKUM is kinetic theory based upwind scheme that operates on any cloud of points. Euler equations are derived from Boltzmann equation (of kinetic theory of gases) after taking suitable moments. The basic update scheme is formulated at Boltzmann level and mapped to Euler level by suitable moments. Mesh-less solvers need only cloud of points to solve the governing equations. For a complex configuration, with such a solver, one can generate a separate cloud of points around each component, which adequately resolves the geometric features, and then combine all the individual clouds to get one set of points on which the solver directly operates. An obvious advantage of this approach is that any incremental changes in geometry will require only regeneration of the small cloud of points where changes have occurred. Additionally blanking and de-blanking strategy along with overlay point cloud can be adapted in some applications like store separation to avoid regeneration of points. Naturally, the mesh-less solvers have advantage in tackling complex geometries and moving components over solvers that need grids. Conventionally, higher order accuracy for space derivative term is achieved by two step defect correction formula which is computationally expensive. The present solver uses low dissipation single step modified CIR (MCIR) scheme which is similar to first order LSKUM formulation and provides spatial accuracy closer to second order. The maximum time step taken to march solution in time is limited by stability criteria in case of explicit time integration procedure. Because of this, explicit scheme takes a large number of iterations to achieve convergence. The popular explicit time integration schemes like four stages Runge-Kutta (RK4) are slow in convergence due to this reason. The above problem can be overcome by using the implicit time integration procedure. The implicit schemes are unconditionally stable i.e. very large time steps can be used to accelerate the convergence. Also it offers superior robustness. The implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) scheme is very attractive due to its low numerical complexity, moderate memory requirement and unconditional stability for linear wave equation. Also this scheme is more efficient than explicit counterparts and can be implemented easily on parallel computers. It is based on the factorization of the implicit operator into three parts namely lower triangular matrix, upper triangular matrix and diagonal terms. The use of LU-SGS results in a matrix free implicit framework which is very economical as against other expensive procedures which necessarily involve matrix inversion. With implementation of the implicit LU-SGS scheme larger time steps can be used which in turn will reduce the computational time substantially. LU-SGS has been used widely for many Finite Volume Method based solvers. The split flux Jacobian formulation as proposed by Jameson is most widely used to make implicit procedure diagonally dominant. But this procedure when applied to mesh-less solvers leads to block diagonal matrix which again requires expensive inversion. In the present work LU-SGS procedure is adopted for mesh-less approach to retain diagonal dominancy and implemented in 2-D and 3-D solvers in matrix free framework.
In order to assess the efficacy of the implicit procedure, both explicit and implicit 2-D solvers are tested on NACA 0012 airfoil for various flow conditions in subsonic and transonic regime. To study the performance of the solvers on different point distributions two types of the cloud of points, one unstructured distribution (4074 points) and another structured distribution (9600 points) have been used. The computed 2-D results are validated against NASA experimental data and AGARD test case. The density residual and lift coefficient convergence history is presented in detail. The maximum speed up obtained by use of implicit procedure as compared to explicit one is close to 6 and 14 for unstructured and structured point distributions respectively. The transonic flow over ONERA M6 wing is a classic test case for CFD validation because of simple geometry and complex flow. It has sweep angle of 30° and 15.6° at leading edge and trailing edge respectively. The taper ratio and aspect ratio of the wing are 0.562 and 3.8 respectively. At M∞=0.84 and α=3.06° lambda shock appear on the upper surface of the wing. 3¬D explicit and implicit solvers are tested on ONERA M6 wing. The computed pressure coefficients are compared with experiments at section of 20%, 44%, 65%, 80%, 90% and 95% of span length. The computed results are found to match very well with experiments. The speed up obtained from implicit procedure is over 7 for ONERA M6 wing. The determination of the aerodynamic characteristics of a wing with the control surface deflection is one of the most important and challenging task in aircraft design and development. Many military aircraft use some form of the delta wing. To demonstrate the effectiveness of 3-D solver in handling control surfaces and small gaps, implicit 3-D code is used to compute flow past clipped delta wing with aileron deflection of 6° at M∞ = 0.9 and α = 1° and 3°. The leading edge backward sweep is 50.4°. The aileron is hinged from 56.5% semi-span to 82.9% of semi-span and at 80% of the local chord from leading edge. The computed results are validated with NASA experiment
Buy-Side Agency Algorithms: Institutional Investor Trades and Market Quality around SEC Filings
No full textIn modern markets, institutional investors employ agency algorithms that strategically subdivide large orders to minimize the price-impact and signaling of their trades. As a consequence, the daily level of institutional market activity has become increasingly difficult to identify. In this paper, I exploit an intraday artifact caused by the repeated order submission of agency algorithms – Clock-Time Periodicity – to quantify their use and illuminate the trading behavior of the institutional investors that employ them. I show that agency algorithms are utilized on a daily basis and account for an average of 3.1% of trade volume. I show that the arrival of historically informative SEC filings increases the volume of institutional trading. Earnings Announcements and Regulation Fair Disclosure filings have the largest impact, with an increase in institutional trade volume of 13.9% and 2.56% respectively. I present evidence supporting two plausible motivations for the increased activity: a) Urgency and b) Liquidity. First, the increase in institutional volume is contrasted by a stark decrease in the number of limit-orders used to achieve it. An indication that agency algorithms not only trade more but do so more aggressively. Second, on filing dates an increase in institutional volume worsens trade conditions with magnitudes that rival the effect of the news itself. Lastly, the increase in the size of institutional trades is overshadowed by an even larger increase in the size of non-institutional trades. This suggests that the trading behavior of non-institutional traders provides a ‘smokescreen’ for agency algorithms to trade more aggressively while remaining stealthy
LBR: Load balancing routing algorithm for wireless sensor networks
No full textHomogeneous wireless sensor networks (WSNs) are organized using identical sensor nodes, but the nature of WSNs operations results in an imbalanced workload on gateway sensor nodes which may lead to a hot-spot or routing hole problem. The routing hole problem can be considered as a natural result of the tree-based routing schemes that are widely used in WSNs, where all nodes construct a multi-hop routing tree to a centralized root, e.g., a gateway or base station. For example, sensor nodes on the routing path and closer to the base station deplete their own energy faster than other nodes, or sensor nodes with the best link state to the base station are overloaded with traffic from the rest of the network and experience a faster energy depletion rate than their peers. Routing protocols for WSNs are reliability-oriented and their use of reliability metric to avoid unreliable links makes the routing scheme worse. However, none of these reliability oriented routing protocols explicitly uses load balancing in their routing schemes. Since improving network lifetime is a fundamental challenge of WSNs, we present, in this chapter, a novel, energy-wise, load balancing routing (LBR) algorithm that addresses load balancing in an energy efficient manner by maintaining a reliable set of parent nodes. This allows sensor nodes to quickly find a new parent upon parent loss due to the existing of node failure or energy hole. The proposed routing algorithm is tested using simulations and the results demonstrate that it outperforms the MultiHopLQI reliability based routing algorithm
Maximizing Water--Food--Energy Nexus Synergies at Basin Scale
No full textIn this short paper, we show how solutions for mitigating resource security in one sector can be found in another. We demonstrate—by means of a case study in Burkina Faso and Ghana—how investing in the electricity grid in the south leads to increase food security in the north. A new nexus framework was developed (‘MAXUS’) which was built to understand, simulate and optimize intersectoral (and international) development strategies in the water, food and energy sectors. We believe this new type of geospatial integral resource management, supported by the exponential increase of data availability of the twenty-first century, could finally turn nexus models into decision support tools.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Water Resource
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