6,362 research outputs found

    Birefringence analysis of multilayer leaky cladding optical fibre

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    We analyse a multilayer leaky cladding (MLC) fibre using the finite element method and study the effect of the MLC on the bending loss and birefringence of two types of structures: (i) a circular core large-mode-area structure and (ii) an elliptical-small-core structure. In a large-mode-area structure, we verify that the multilayer leaky cladding strongly discriminates against higher order modes to achieve single-mode operation, the fibre shows negligible birefringence, and the bending loss of the fibre is low for bending radii larger than 10 cm. In the elliptical-small-core structure we show that the MLC reduces the birefringence of the fibre. This prevents the structure from becoming birefringent in case of any departures from circular geometry. The study should be useful in the designs of MLC fibres for various applications including high power amplifiers, gain flattening of fibre amplifiers and dispersion compensation.Comment: 18 page

    Modelling the dynamics of turbulent floods

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    Consider the dynamics of turbulent flow in rivers, estuaries and floods. Based on the widely used k-epsilon model for turbulence, we use the techniques of centre manifold theory to derive dynamical models for the evolution of the water depth and of vertically averaged flow velocity and turbulent parameters. This new model for the shallow water dynamics of turbulent flow: resolves the vertical structure of the flow and the turbulence; includes interaction between turbulence and long waves; and gives a rational alternative to classical models for turbulent environmental flows

    CONFLLVM: A Compiler for Enforcing Data Confidentiality in Low-Level Code

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    We present an instrumenting compiler for enforcing data confidentiality in low-level applications (e.g. those written in C) in the presence of an active adversary. In our approach, the programmer marks secret data by writing lightweight annotations on top-level definitions in the source code. The compiler then uses a static flow analysis coupled with efficient runtime instrumentation, a custom memory layout, and custom control-flow integrity checks to prevent data leaks even in the presence of low-level attacks. We have implemented our scheme as part of the LLVM compiler. We evaluate it on the SPEC micro-benchmarks for performance, and on larger, real-world applications (including OpenLDAP, which is around 300KLoC) for programmer overhead required to restructure the application when protecting the sensitive data such as passwords. We find that performance overheads introduced by our instrumentation are moderate (average 12% on SPEC), and the programmer effort to port OpenLDAP is only about 160 LoC.Comment: Technical report for CONFLLVM: A Compiler for Enforcing Data Confidentiality in Low-Level Code, appearing at EuroSys 201

    Determination of New Isomer of Palmitoleic Acid in Mucuna Pruriens Seed Oil

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    Palmitoliec acid is an unsaturated fatty acid and it is very important in different essential enoic acid. Most of which are not synthesized by the body and are to be supplied through edibles. By the formation of DMOX derivative of FAME, allows the determination of deposition of the double bond in fatty acid carbon chain.This work is also important to quick and reproducible methods used to screen the utility of non conventional sources of oil for edible and industrial purposes. For the present investigation, non conventional source mucuna puriens (pepilionaceae) seed is used. Seeds have been reported to cure diarrhea and Parkinson’s disease. It is a natural source of L-dopa. Keywords: FAME, DMOX derivative, palmitoleic aci

    Fine needle cytology-diagnostic tool for palpable orbital and eyelid lesions

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    Background: Fine needle aspiration cytology in orbital lesions gained importance in the last 3 decades. FNAC can be used for aiding the clinician to plan treatment of orbital and eyelid tumors study was undertaken to evaluate the role of FNAC as a diagnostic tool for diagnosis and management of various orbital and eyelid lesions, as it is of great value in the diagnosis of new primary, recurrent and metastatic orbital tumors.Methods: Patients of different age groups presenting with orbital and eyelid lesions were studied over a period of 4 years from March 2013 to Feb 2017. The 75 patients selected for this study were clinically evaluated and then investigated with computed tomograpghy (CT) scanning. Each patient was subjected to FNAC under direct vision/ultrasongraphy guidance with sterile 22 guage needle without anaesthesia. Biopsy was done to confirm the cytological diagnosis.Results: The age of patients varied from 3 years to 70 years. On cytology 61 cases were benign and 14 malignant. Histopathological examination of 53 cases was done which confirmed the cytological diagnosis.Conclusions: FNAC is a useful, rapid, safe and cost effective method for diagnosing orbital and eyelid pathology

    Critical behavior at de-pinning of a driven disordered vortex matter in 2H-NbS2

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    We report unusual jamming in driven ordered vortex flow in 2H-NbS2. Reinitiating movement in these jammed vortices with a higher driving force, and halting it thereafter once again with a reduction in drive, unfolds a critical behavior centered around the de-pinning threshold via divergences in the lifetimes of transient states, validating the predictions of a recent simulation study, which also pointed out a correspondence between plastic de-pinning in vortex matter and the notion of random organization proposed in the context of sheared colloids undergoing diffusive motion.Comment: Phys. Rev. B (in press, 2012). The paper has 14 pages of Text+ Refs. with 4 figures. (Note as some of the figure files are large in size, to enable faster download, the file size has been kept small and the figure resolution are low. The online version of the paper to appear in PRB will contain the higher resolution figures