2,902 research outputs found

    Non-local gyrokinetic model of linear ion-temperature-gradient modes

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    A theory of non-local linear ion-temperature-gradient (ITG) drift modes while retaining non-adiabatic electrons is presented, extending the previous work [S. Moradi, et al {\em Phys. Plasmas} {\bf 18}, 062106 (2011)]. A dispersion relation is derived to quantify the effects of the fractional velocity operator in the Fokker-Planck equation modified by temperature gradients and non-adiabatic electrons on the real frequency and growth rate. Solving the dispersion relation, it is shown here that as the plasma becomes more turbulent, it deviates from a Maxwellian distribution and becomes L\'{e}vy distributed. The resulting L\'{e}vy distribution of the plasma may thus significantly alter the transport. The relative effect of the fractional derivative is larger on the real frequency than on the growth rate of the ITG mode.Comment: 14pages 1 Figure submitted to Phys. Rev.

    Attributes of Big Data Analytics for Data-Driven Decision Making in Cyber-Physical Power Systems

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    Big data analytics is a virtually new term in power system terminology. This concept delves into the way a massive volume of data is acquired, processed, analyzed to extract insight from available data. In particular, big data analytics alludes to applications of artificial intelligence, machine learning techniques, data mining techniques, time-series forecasting methods. Decision-makers in power systems have been long plagued by incapability and weakness of classical methods in dealing with large-scale real practical cases due to the existence of thousands or millions of variables, being time-consuming, the requirement of a high computation burden, divergence of results, unjustifiable errors, and poor accuracy of the model. Big data analytics is an ongoing topic, which pinpoints how to extract insights from these large data sets. The extant article has enumerated the applications of big data analytics in future power systems through several layers from grid-scale to local-scale. Big data analytics has many applications in the areas of smart grid implementation, electricity markets, execution of collaborative operation schemes, enhancement of microgrid operation autonomy, management of electric vehicle operations in smart grids, active distribution network control, district hub system management, multi-agent energy systems, electricity theft detection, stability and security assessment by PMUs, and better exploitation of renewable energy sources. The employment of big data analytics entails some prerequisites, such as the proliferation of IoT-enabled devices, easily-accessible cloud space, blockchain, etc. This paper has comprehensively conducted an extensive review of the applications of big data analytics along with the prevailing challenges and solutions

    Charged particle dynamics in the presence of non-Gaussian L\'evy electrostatic fluctuations

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    Full orbit dynamics of charged particles in a 33-dimensional helical magnetic field in the presence of α\alpha-stable L\'evy electrostatic fluctuations and linear friction modeling collisional Coulomb drag is studied via Monte Carlo numerical simulations. The L\'evy fluctuations are introduced to model the effect of non-local transport due to fractional diffusion in velocity space resulting from intermittent electrostatic turbulence. The probability distribution functions of energy, particle displacements, and Larmor radii are computed and showed to exhibit a transition from exponential decay, in the case of Gaussian fluctuations, to power law decay in the case of L\'evy fluctuations. The absolute value of the power law decay exponents are linearly proportional to the L\'evy index α\alpha. The observed anomalous non-Gaussian statistics of the particles' Larmor radii (resulting from outlier transport events) indicate that, when electrostatic turbulent fluctuations exhibit non-Gaussian L\'evy statistics, gyro-averaging and guiding centre approximations might face limitations and full particle orbit effects should be taken into account.Comment: 5 pages, 5 figures. Accepted as a letter in Physics of Plasma

    Correlation between hepatitis B G1896A precore mutations and HBeAg in chronic HBV patients

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    Background: Hepatitis B virus (HBV) infection is an important health concern worldwide, with critical outcomes. Hepatitis B e antigen (HBeAg) negative chronic hepatitis B is frequently caused by a mutation (G1896A) in the hepatitis B virus (HBV) precore (PC) reading frame, which creates a stop codon, causing premature termination of the HBe protein. Objectives: This study aimed to investigate the G1896A PC mutation and its effect on HBeAg detection in chronic HBV patients. Patients and Methods: In this study, 120 chronic HBV patients neither vaccinated or who had benefited from immunoglobulin therapy, were recruited. The HBV-DNA was extracted from plasma and polymerase chain reaction (PCR) was performed. Positive PCR products were subjected to automated sequencing. The HBV serological markers hepatitis B s antigen (HBsAg), HBeAg were tested. Results: One hundred out of 120 (83.3%) patients were HBeAg negative and 100% were HBsAg positive. The comparison of nucleotide sequences with the reference sequence (Accession number: AB033559) in HBeAg negative patients showed that there was a high rate of mutations in G1896A (93.18%). Conclusions: This study indicates that the rate of G1896A mutation at the PC region among HBeAg negative patients, in the Golestan province of Iran, was similar to the average rate encountered in other parts of Iran. The PC stop codon mutation was detected in 93.18% of HBeAg negative patients. Further studies with larger sample sizes are required to elucidate the exact role of these mutations in the clinical course of chronic HBV infection. © 2015, Ahvaz Jundishapur University of Medical Sciences

    A theory of non-local linear drift wave transport

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    Transport events in turbulent tokamak plasmas often exhibit non-local or non-diffusive action at a distance features that so far have eluded a conclusive theoretical description. In this paper a theory of non-local transport is investigated through a Fokker-Planck equation with fractional velocity derivatives. A dispersion relation for density gradient driven linear drift modes is derived including the effects of the fractional velocity derivative in the Fokker-Planck equation. It is found that a small deviation (a few percent) from the Maxwellian distribution function alters the dispersion relation such that the growth rates are substantially increased and thereby may cause enhanced levels of transport.Comment: 22 pages, 2 figures. Manuscript submitted to Physics of Plasma

    Entanglement of Dirac fields in an expanding spacetime

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    We study the entanglement generated between Dirac modes in a 2-dimensional conformally flat Robertson-Walker universe. We find radical qualitative differences between the bosonic and fermionic entanglement generated by the expansion. The particular way in which fermionic fields get entangled encodes more information about the underlying space-time than the bosonic case, thereby allowing us to reconstruct the parameters of the history of the expansion. This highlights the importance of bosonic/fermionic statistics to account for relativistic effects on the entanglement of quantum fields.Comment: revtex4, 7 figures, I.F. previously published as Fuentes-Guridi and Fuentes-Schuller. Journal reference update

    A Fractional Fokker-Planck Model for Anomalous Diffusion

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    In this paper we present a study of anomalous diffusion using a Fokker-Planck description with fractional velocity derivatives. The distribution functions are found using numerical means for varying degree of fractionality observing the transition from a Gaussian distribution to a L\'evy distribution. The statistical properties of the distribution functions are assessed by a generalized expectation measure and entropy in terms of Tsallis statistical mechanics. We find that the ratio of the generalized entropy and expectation is increasing with decreasing fractionality towards the well known so-called sub-diffusive domain, indicating a self-organising behavior.Comment: 22 pages, 14 figure

    Study of hydatid cyst in hospitalized patients with operation in Chaharmahal va Bakhtiary province (1988-2007)

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    زمینه و هدف: بیماری کیست هیداتید یکی از شایع ترین بیماری های مشترک انسان و دام است که ناشی از ابتلای انسان به مرحله لاروی انگل اکی نوکوکوس گرانولوزوس می باشد. شناخت جنبه های اپیدمیولوژیکی بیماری در کنترل و پیشگیری از بیماری ضروری است. این مطالعه با هدف بررسی ده ساله فراوانی بیماران مبتلا به کیست هیداتید جراحی شده در بیمارستان های استان چهارمحال و بختیاری انجام شد. روش بررسی: در این مطالعه توصیفی -تحلیلی، بیماران مبتلا به کیست هیداتید استان طی سالهای1386 -1377 که در بیمارستان های آیت اله کاشانی شهرکرد، سید الشهداء (ع)فارسان و ولی عصر بروجن (عج) بستری و جراحی شده بودند مورد بررسی قرار گرفتند. اطلاعات به کمک پرسشنامه جمع آوری و با استفاده از آمار توصیفی و تحلیلی (کای دو) تجزیه و تحلیل گردیدند. یافته ها: از مجموع 144 بیمار بررسی شده 98 نفر (68) زن، 93 نفر (65) ساکن روستاها و عشایر و 51 نفر (35) شهرنشین بودند. دامنه سنی بیماری بین 92-11 سال و بیشترین شیوع در گروه سنی 41-27 سال (44 مورد) و کمترین شیوع در گروه سنی بالای 72 سال بود (6 مورد) دیده شد. بیشترین فراوانی در بین زنان خانه دار (60) و کمترین میزان در افراد کارمند (3) دیده شد. از نظر چگونگی محل قرار گرفتن کیست، کیست ها به ترتیب در لوب راست کبد (67) و لوب چپ کبد (10)، قسمت های راست و چپ ریه (6) بودند. نتیجه گیری: با توجه به شیوع بالای این بیماری در بین روستاییان و عشایر و همچنین ارتباط نزدیک انسان، دام و سگ در این مناطق ضرورت آموزش جهت شناخت بهتر بیماری در آنان و شناسایی سگ های آلوده عشایر و درمان آنها جهت کنترل بیماری اجتناب ناپذیر است
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