High efficiency switching using graphene based electron 'optics'

The absence of a band-gap in graphene limits the gate modulation of its electron conductivity, both in regular graphene as well as in PN junctions, where electrostatic barriers prove transparent to Klein tunneling. We demonstrate a novel way to directly open a gate-tunable transmission gap across graphene PN junctions (GPNJ) by introducing an additional barrier in the middle that replaces Klein tunneling with regular tunneling, allowing us to electrostatically modulate the current by several orders of magnitude. The gap arises by angularly sorting electrons by their longitudinal energy and filtering out the hottest, normally incident electrons with the tunnel barrier, and the rest through total internal reflection. Using analytical and atomistic numerical studies of quantum transport, we show that the complete filtering of all incident electrons causes the GPNJ to act as a novel metamaterial with a unique gate-tunable transmission-gap that generates a sharp non-thermal switching of electrons. In fact, the transmission gap gradually diminishes to zero as we electrostatically reduce the voltage gradient across the junction towards the homogeneous doping limit. The resulting gate tunable metal-insulator transition enables the electrons to overcome the classic room temperature switching limit of kTln10/q = 60mV/decade for subthreshold conduction

Variations on the Misogynistic Nature of 'The Seven Sages' in Different Arabic Manuscript Copies (17th - 18th Centuries)

Variants of ‘The Malice of Women and the Malice of Men’, known under the title of ‘The Seven Sages’, have circulated since the 9th century throughout the world and have been susceptible to various kinds of influence, be they religious, linguistic, or thematic. Moreover, the text functioned as a ‘mirror for princes’ and was entertaining for many readers, who were predominantly men. Comparing the existing Arabic manuscripts – Sprenger 1368 (Staatsbibliothek zu Berlin), Glaser 166 (Staatsbibliothek zu Berlin), and Paris arabe 3639 (Bibliothèque nationale de France) – this article aims to show variance among the Arabic versions of ‘The Seven Viziers’ and their implications for the theme of misogyny that runs through the book. The variance, this article argues, is one of degree and not kind. Special attention is given to certain structural (story corpus), linguistic, and thematic elements (associations to the story of Potiphar and his wife in the Qurʾān), all of which have implications for the theme of misogyny. Finally, the article looks into the reception of the text, especially by general readers, who used it to confirm their negative perception of women

Early SQL Injection Detection

Computer security is a moving target that moves or increases with the growth of technology. Organizations during the 21st century have to create and/or adopt new technologies in order to stay in business and be competitive. These new technologies involve thousands of lines of code using programming languages, crossing servers, and database engines. Along with the growth of technology, organizations’ IT professionals are trying to prevent any data breach to valuable data from hackers by locking all vulnerable doors that hackers might use to access a system. While IT professionals are trying to lock all vulnerable doors, hackers need only one door to hack a given system using one of the hacking methods available. One of the most used hacking methods and most security concerning is SQL Injection that hackers use to bypass a system by gaining unauthorized access to retrieve or modify valuable data such as Social Security Numbers, bank information, health records, etc. SQL Injection can be achieved through injecting SQL commands into a SQL statement via a web page. There is a number of SQL Injection methods used to gain unauthorized access into a given system; however, SQL Injection through Sign-in/Log-in process is the most used technique with 63% of all SQL injection types used [1]. Therefore, this research focuses on SQL Injection through Sign-in/Log-in process and presents a new way of alerting the system admin of any SQL Injection attempts and blocks, as well as any further access attempts by the same user (abuser)

How Imbalanced Excitation and Inhibition May Cause Low Entropy Brain Dynamics

To study the effect of the imbalance of excitation and inhibition neurons on brain entropy using a computer model of a brain. The brain model will be composed of a neural network and entropy of the neural network will be measured quantitatively. Entropy in this context quantifies how many different patterns of activated neurons the brain can create. Imbalance between excitation and inhibition neurons causes the brain to malfunction, which can be an underlying cause of autism

Mid Infrared Supercontinuum Generation in Photonic Crystal Fiber

Hlavním cílem této práce je navrhnout jednoduchý Bragg Fiber pro supercontinuum generaci ve střední infračervené oblasti. Navrhuji a dále optimalizovat nové Bragg Fiber má mezikruží strukturu pomocí chalkogenid skla. V dalším kroku šití nulové disperze vlnové délky až do 2,0 mikrometru a 2,5 mikrometru, generace supercontinuum získané v navrhovaném fotonického krystalu vlákna ve anomální disperze režimu. Celý design byl zaměřen na vlákna na bázi materiálů, jako je arsen-selenid skla a arzenu sulfidu skla, s použitím arsen selenid sklo získané supercontinuum rozšiřující se od 1,2 mikrometru do 9,0 mikrometru. Navrhovaný kruhová mřížka fotonického krystalu vlákna s ultra-širokopásmovou supercontinuum je vysoce žádoucí pro účely spektroskopie, kontroly kvality potravin, komprese impulsů, snímání plynu a různé nelineární aplikace. Vedle tohoto supercontinuum generace na suspendované jádra vlákna a šestiúhelníkové Bragg Fiber založené na PBG-08 skla je také analyzovány. Z číselné výsledky supercontinuum spekter se získá až 2,5 mikrometru na základě PBG-08 skla. Účinky na Supercontinuum spekter změnou špičkový výkon, pulsu, délka PCF jsou studovány.The main aim of this thesis is to design a simple photonic crystal fiber for supercontinuum generation in the mid-infrared region. I propose and further optimize a new photonic crystal fiber having circular ring structure by using chalcogenide glass. In next step by tailoring zero-dispersion wavelength up to 2.0 ?m and 2.5 ?m, supercontinuum generation obtained in the proposed photonic crystal fiber in the anomalous dispersion regime. Whole design was focused on fibers based on materials as arsenic-selenide glass and arsenic-sulfide glass, using arsenic selenide glass obtained supercontinuum broadening from 1.2 ?m up to 9.0 ?m. The proposed circular lattice photonic crystal fiber with ultra-wideband supercontinuum is highly desirable for purposes of spectroscopy, food quality control, pulse compression, gas sensing and various nonlinear applications. Beside this supercontinuum generation on suspended core fiber and hexagonal photonic crystal fiber based on PBG-08 glass is also analyzed. From numerical results supercontinuum spectra up to 2.5 ?m based on PBG-08 glass is obtained. The effects on Supercontinuum spectra by varying peak power, pulse duration, length of PCF are studied