Design of sliding mode controller for chaotic Josephson-junction

It is known that a shunted nonlinear resistive-capacitive-inductance Josephson-junction (RCLSJ) model has a chaotic attractor. This attractor is created as a result of Hopf bifurcation that occurs when a certain direct current (DC) applied to one of the junction terminals. This chaotic attractor prevents the system from reaching the phase-locked state and hence degrade the performance of the junction. This paper aims at controlling and taming this chaotic attractor induced in this model and pulling the system to the phase-locked state. To achieve this task, a sliding mode controller is proposed. The design procedures involve two steps. In the first one, we construct a suitable sliding surface so that the dynamic of the system follows the sliding manifolds in order to meet design specifications. Secondly, a control law is created to force the chaotic attractor to slide on the sliding surface and hence stabilizes system trajectory. The RCLSJ model under consideration is simulated with and without the designed controller. Results demonstrate the validity of the designed controller in taming the induced chaos and stabilizing the system under investigation

XMM-Newton, Chandra, and CGPS observations of the Supernova Remnants G85.4+0.7 and G85.9-0.6

We present an XMM-Newton detection of two low radio surface brightness SNRs, G85.4+0.7 and G85.9-0.6, discovered with the Canadian Galactic Plane Survey (CGPS). High-resolution XMM-Newton images revealing the morphology of the diffuse emission, as well as discrete point sources, are presented and correlated with radio and Chandra images. The new data also permit a spectroscopic analysis of the diffuse emission regions, and a spectroscopic and timing analysis of the point sources. Distances have been determined from HI and CO data to be 3.5 +/- 1.0 kpc for SNR G85.4+0.7 and 4.8 +/- 1.6 kpc for SNR G85.9-0.6. The SNR G85.4+0.7 is found to have a temperature of ~12-13 MK and a 0.5-2.5 keV luminosity of ~1-4 x 10^33 D(3.5)^2 erg/s (where D(3.5) is the distance in units of 3.5 kpc), with an electron density n_e of ~0.07-0.16(fD(3.5))^-1/2 cm^-3 (where f is the volume filling factor), and a shock age of ~9-49(fD(3.5))^1/2 kyr. The SNR G85.9-0.6 is found to have a temperature of ~15-19 MK and a 0.5-2.5 keV luminosity of ~1-4 x 10^34 D(4.8)^2 erg/s (where D(4.8) is the distance in units of 4.8 kpc), with an electron density n_e of ~0.04-0.10(fD(4.8))^-1/2 cm^-3 and a shock age of ~12-42(fD(4.8))^1/2 kyr. Based on the data presented here, none of the point sources appears to be the neutron star associated with either SNR.Comment: 30 pages using emulateapj, 16 figures with quality reduced for astro-ph only. The original version with high-resolution figures can be downloaded from: http://www.physics.umanitoba.ca/~samar/astro-ph/G85s-ms09102007.pdf To appear in ApJ (Jan 20 2008 issue, v673, n1

First-Year Male Students\u27 Adherence to Traditional Male Gender Roles and Their Attitudes toward Bystander Approach Behaviors to Stop Sexual Assault

Sexual assault on university campuses may affect any person at any time. However, university-aged women are disproportionally affected by it, with 25% of women reporting being assaulted on campus, and 84% to 97.8% of them perpetrated by young, heterosexual men known to the victim. To curb sexual assault on the university campus, research studies have advocated for the bystander approach. It encourages bystanders (observers) to intervene and ultimately stop a potentially dangerous situation in which a friend or stranger may experience a sexual assault. Despite its popularity, research studies evaluating the bystander approach have reported, at best, modest success with college men. Therefore, the purpose of this study was to investigate the relationship between first-year male students\u27 adherence to traditional gender roles (masculinity) as measured by their reported level of stress and their attitudes toward bystander approach behaviors. The need for this specific research was evident given the lack of research studies on first-year male\u27s socialization as a variable for the poor success of the bystander approach with college men. Accordingly, the significance of this study\u27s result was the addition of new empirical data gathered to reduce the number of sexual assaults to the existing research knowledge base on male college students. The survey research study was conducted at a university with a sample of 403 frosh. Ten percent of the study sample responded to the voluntary online survey that was composed of two instruments, the male gender role stress scale (the revised MGRS-R) and the bystander attitude scale (the revised BAS-R). The study findings indicated that first-year male students adhered to traditional male gender roles and reported positive attitudes toward bystander approach behaviors. However, a statistically significant indirect correlation was only found between study samples who had low MGRS-R scores and high BAS-R scores. Thus, first-year male students who did not adhere to traditional male gender roles were more likely to hold positive attitudes toward bystander intervention. In addition, there was an indirect, statistically significant correlation between two stress factors: subornation to women and intellectual superiority. Hence, first-year students who did not consider themselves superior to women were more likely to have positive attitudes toward bystander approach behaviors. In conclusion, the study findings called for a review of the bystander approach to consider traditional male socialization, and to create male specific awareness and prevention programs to stop sexual assault on college campuses

Controlling Chaos and Bifurcation of Subsynchronous Resonance in Power System

Linear and nonlinear state feedback controllers are proposed to control the bifurcation of a new phenomenon in power system, this phenomenon of electro-mechanical interaction between the series resonant circuits and torsional mechanical frequencies of the turbine generator sections, which known as Subsynchronous Resonance (SSR). The first system of the IEEE second benchmark model is considered. The dynamics of the two axes damper windings, Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS) are included. The linear controller gives better initial disturbance response than that of the nonlinear, but in a small narrow region of compensation factors. The nonlinear controller not only can be easily implemented, but also it stabilizes the operating point for all values of the bifurcation parameter

Chaos and Bifurcation Control Using Nonlinear Recursive Controller

Chaos and bifurcation control is achieved by nonlinear controller that is able to mitigate the characteristics of a class of nonlinear systems that are experiencing such phenomenon. In this paper, a backstepping nonlinear recursive controller is presented. Comparison has been made between it and a Pole Placement controller. The study shows the effectiveness of the proposed control under various operating conditions

Discovery of an Energetic Pulsar Associated with SNR G76.9+1.0

We report the discovery of PSR J2022+3842, a 24 ms radio and X-ray pulsar in the supernova remnant G76.9+1.0, in observations with the Chandra X-ray telescope, the Robert C. Byrd Green Bank Radio Telescope, and the Rossi X-ray Timing Explorer (RXTE). The pulsar's spin-down rate implies a rotation-powered luminosity Edot = 1.2 x 10^{38} erg/s, a surface dipole magnetic field strength B_s = 1.0 x 10^{12} G, and a characteristic age of 8.9 kyr. PSR J2022+3842 is thus the second-most energetic Galactic pulsar known, after the Crab, as well as the most rapidly-rotating young, radio-bright pulsar known. The radio pulsations are highly dispersed and broadened by interstellar scattering, and we find that a large (delta-f / f ~= 1.9 x 10^{-6}) spin glitch must have occurred between our discovery and confirmation observations. The X-ray pulses are narrow (0.06 cycles FWHM) and visible up to 20 keV, consistent with magnetospheric emission from a rotation-powered pulsar. The Chandra X-ray image identifies the pulsar with a hard, unresolved source at the midpoint of the double-lobed radio morphology of SNR G76.9+1.0 and embedded within faint, compact X-ray nebulosity. The spatial relationship of the X-ray and radio emissions is remarkably similar to extended structure seen around the Vela pulsar. The combined Chandra and RXTE pulsar spectrum is well-fitted by an absorbed power-law model with column density N_H = (1.7\pm0.3) x 10^{22} cm^{-2} and photon index Gamma = 1.0\pm0.2; it implies that the Chandra point-source flux is virtually 100% pulsed. For a distance of 10 kpc, the X-ray luminosity of PSR J2022+3842 is L_X(2-10 keV) = 7.0 x 10^{33} erg s^{-1}. Despite being extraordinarily energetic, PSR J2022+3842 lacks a bright X-ray wind nebula and has an unusually low conversion efficiency of spin-down power to X-ray luminosity, L_X/Edot = 5.9 x 10^{-5}.Comment: 8 pages in emulateapj format. Minor changes (including a shortened abstract) to reflect the version accepted for publicatio

Multiplexed communication over a high-speed quantum channel

In quantum information systems it is of particular interest to consider the best way in which to use the non-classical resources consumed by that system. Quantum communication protocols are integral to quantum information systems and are amongst the most promising near-term applications of quantum information science. Here we show that a multiplexed, digital quantum communications system supported by comb of vacuum squeezing has a greater channel capacity per photon than a source of broadband squeezing with the same analogue bandwidth. We report on the time-resolved, simultaneous observation of the first dozen teeth in a 2.4 GHz comb of vacuum squeezing produced by a sub-threshold OPO, as required for such a quantum communications channel. We also demonstrate multiplexed communication on that channel