DMRG studies on linear-exchange quantum spin models in one dimension

We study a class of spin-1/2 quantum antiferromagnetic chains using DMRG technique. The exchange interaction in these models decreases linearly as a function of the separation between the spins, $J_{ij} = R-|i-j|$ for $|i-j| \le R$. For the separations beyond $R$, the interaction is zero. The range parameter $R$ takes positive integer values. The models corresponding to all the odd values of $R$ are known to have the same exact doubly degenerate dimer ground state as for the Majumdar-Ghosh (MG) model. In fact, R=3 is the MG model. For even $R$, the exact ground state is not known in general, except for R=2 (the Bethe ansatz solvable Heisenberg chain) and in the asymptotic limit of $R$ where the two MG dimer states again emerge as the exact ground state. In the present work, we numerically investigate the even-$R$ models whose ground state is not known analytically. In particular, for R=4, 6 and 8, we have computed a number of ground state properties. We find that, unlike R=2, the higher even-$R$ models are spin-gapped, and show strong dimer-dimer correlations of the MG type. Moreover, the spin-spin correlations decay very rapidly, albeit showing weak periodic revivals.Comment: 8 pages, 12 figure

The Process of Generating Single Large Combined Cloud for Grid-Free Solvers

Dealing with moving body problems, where one component moves relatively with respect to other, is a difficult task in CFD due to the efforts needed in grid handling for every delta change in position of the moving component. The inherent nature of mesh-free solvers reduces the efforts needed for these kinds of problems by operating on a cloud of points rather than a grid. A new method to handle moving body problems is proposed, where individual clouds are generated around each component and are combined into a single large combined cloud. The proposed method is applied to store separation problem and results generated using NAL-MCIR mesh-less solver is compared with experimental results

Experimental Characterisation of GLass Aluminum REinforced (GLARE™) laminates

Fibre metal laminates such as GLARE™ have found promising application in the aerospace industry. These laminates were developed at the structures and materials laboratory of Delft University of Technology, Netherlands. GLARE™ is a material belonging to the family of Fibre Metal Laminates consisting of thin aluminum layers bonded with unidirectional S2-Glass fibres with an adhesive. Aluminum and S2-Glass when combined as a hybrid material can provide best features of the both metals and composites. These materials have excellent fatigue, impact and damage tolerance characteristics and a lower density compared to aluminum. GLARE™ has found major application in front and aft upper fuselage, leading edges of empennages of advanced civil aircrafts like A380. This document looks into the evaluation of two configuration of GLARE™ for its mechanical and impact characteristics. The mechanical characterisation was carried out for tensile, compression, Flexure, ILSS, Open Hole Tension, Open Hole Compression and Shear (Iosipescu). The impact behaviour were characterised based on a low velocity drop weight impact carried on these laminates. The study shows that the basic properties evaluated were more dictated by the property of the S2-Glass used. The studies show that GLARE™ laminates posses’ high impact damage resistance compared to other composite material. All the test datas generated for this study will be brought out in this document

Non-Destructive Evaluation—A Pivotal Technology for Qualification of Composite Aircraft Structures

Tremendous advances in composite materials and a deeper understanding of their behavior have been responsible for the increased use of composites in the development of advanced, new generation civil and military aircraft. Composites play an important role in any aircraft development programme and are strong contenders to their metal counterparts due to their significant contributions towards improving strength, stiffness, fatigue properties & weight reduction. As materials, structural design & processing have evolved, strong emphasis is placed on effective & reliable damage detection, durability and damage tolerance. As a consequence, Non-destructive Evaluation (NDE) has also undergone significant advances towards meeting the growing demands of quality assurance. Advanced Composites Division (ACD) of National Aerospace Laboratories (NAL), has been involved in the development of composite structures for both civil and military aircraft for over a decade and a half. Innovative composite processing methods like co-curing/co-bonding have been successfully employed to realize airworthy structures. The role of NDE in the development of these structures has been critical and not limited to damage detection alone. On several occasions, NDE has provided valuable inputs towards improving design and process parameters. In-spite of the complexity of the structures, stringent quality requirements and tight delivery schedules, NDE has been successful in certifying these composite structures for airworthiness. This paper discusses the implementation of key NDE techniques like ultrasonics, radiography, acoustic emission and thermography for reliable flaw detection, characterization and quality assurance of composite aircraft structures

Impact of optimally placed VAR support on electricity spot pricing

In view of deregulation and privatization processes, electricity pricing becomes one of the most important issues. The increases in power flows and environmental constraints are forcing electricity utilities to install new VAR equipment to enhance network operation. In this thesis a nonlinear multi-objective optimization problem has been formulated to maximize both social welfare and the maximum distance to collapse point in an open power market using reactive support like Static Var Compensator (SVC). The production and consumption costs of reactive power are intended to provide proper market signals to the electricity market agents. They are included in the multi-objective Optimal Power Flow (OPF) coupled with an (N-1) contingency criterion which is based on power flow sensitivity analysis.;Considering the cost associated with the investment of VAR support, placing them at the optimal location in the network is an important issue. An index to find the optimal site for VAR support considering various technical and economical parameters based on Cost Benefit Analysis (CBA) is proposed. The weights for these parameters are computed through an Analytic Hierarchy Process (AHP). A new approach of transmission pricing calculation taking VSC-OPF based multi-objective maximization as the objective and studied the impact of SVC on it. The integrated approach is illustrated on a 6-bus and a standard IEEE 14-bus test systems and shows promising results

Daily Peak Load Forecast Using Artificial Neural Network

The paper presents an Artificial Neural Network (ANN) model for short-term load forecasting of daily peak load. A multi-layered feed forward neural network with Levenberg-Marquardt learning algorithm is used because of its good generalizing property and robustness in prediction. The input to the network is in terms of historical daily peak load data and corresponding daily peak temperature data. The network is trained to predict the load requirement ahead. The effectiveness of the proposed ANN approach to the short-term load forecasting problems is demonstrated by practical data from the Bangalore Electricity Supply Company Limited (BESCOM). The comparison between the proposed and the conventional methods is made in terms of percentage error and it is found that the proposed ANN model gives more accurate predictions with optimal number of neurons in the hidden layer

Scanning electron microscope studies on the radula teeth of four species of marine gastropods from the Gulf of Mannar, India

In this study scanning electron microscopy (SEM) was used to elucidate the surface morphology of radula teeth of four species of marine gastropods belonging to muricids and tonnoideans from the Gulf of Mannar. The species studied were Tonna dolium (Linne, 1758), Phalium glaucum (Linne, 1758), Murex virgineus (Roding, 1798) and Rapana rapiformis (Born, 1778). The radulae of muricid gastropods were of stenoglossan type (1+R+1) while the radulae of tonnoidean gastropods were of taenioglossate type (2+1+R+1+2). Very large radula and solid teeth in all four species indicate that they are well adapted to capture of prey and showed characteristic representation of the sharp and pointed apex. The shafts of the teeth of R. rapiformis, T. dolium and M virgeneus are thickened and expanded at the base to form a butt and the basal spur as well as their marginal and central teeth are sickle shaped. Radulae of both groups are well suited for tearing and rasping. The examination of the central tooth, the lateral and marginal ones, by SEM provides further information for species differentiation

Analysis of Mechanical Properties of Hybrid Burmese Silk Orchid and Glass Fibers Composite Material

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