WorldWideScience

Sample records for choppers

  1. New chopper control at ILL

    Energy Technology Data Exchange (ETDEWEB)

    Descamps, F. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Proper phasing is an essential characteristic of the chopper systems used at ILL. A wide variety of choppers and selectors differing in weight, speed and bearing types are controlled by a unique electronic card performing digital adaptative filtering. The chopper regulation system is described. (author).

  2. Infrared Sensor with Liquid Crystal Chopper

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An infrared sensor using the liquid crystal chopper is presented. The infrared sensor is designed to detect infrared rays with a pyroelectric element used as a liquid crystal chopper in such an infrared sensor or the like.

  3. ExB chopper system

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Christoph [Institut fuer Angewandte Physik, Goethe-Universitaet, Frankfurt/Main (Germany)

    2010-07-01

    A chopper system for high intensity proton beams of up to 200 mA and repetition rates up to 250 kHz is under development at IAP to be tested and applied at the Frankfurt Neutron Source FRANZ. The chopper system consists of a fast kicker for transversal separation of the beams and a static septum magnet to lower the dynamic deflection angle. Multi-particle simulations and preliminary experiments are presented. The simulations were made using a Particle in Cell (PIC)-Code developed at IAP. It permits the study of collective effects of compensation and secondary electrons on the proton beam in time-dependent kicker fields. A magnetic kicker with high repetition rate would entail high power consumption while electrostatic deflection in combination with intense beams can lead to voltage breakdown. Therefore a Wien filter-type E x B configuration consisting of a static magnetic dipole field and a pulsed electric field to compensate the magnetic deflection is discussed. The 25 kV high voltage pulser (250 kHz,100 ns) will apply fast MOSFET transistor technology in the primary circuit, while the high voltage is provided at the secondary circuit around a metglas transformer core.

  4. Capacitively-coupled chopper amplifiers

    CERN Document Server

    Fan, Qinwen; Huijsing, Johan H

    2017-01-01

    This book describes the concept and design of the capacitively-coupled chopper technique, which can be used in precision analog amplifiers. Readers will learn to design power-efficient amplifiers employing this technique, which can be powered by regular low supply voltage such as 2V and possibly having a +\\-100V input common-mode voltage input. The authors provide both basic design concepts and detailed design examples, which cover the area of both operational and instrumentation amplifiers for multiple applications, particularly in power management and biomedical circuit designs. Discusses basic working principles and details of implementation for proven designs; Includes a diverse set of applications, along with measurement results to demonstrate the effectiveness of the technique; Explains advantages and drawbacks of the technique, given particular circumstances.

  5. Chopper:Efficient Algorithm for Tree Mining

    Institute of Scientific and Technical Information of China (English)

    Chen Wang; Ming-Sheng Hong; Wei Wang; Bai-Le Shi

    2004-01-01

    With the development of Internet, frequent pattern mining has been extended to more complex patterns like tree mining and graph mining. Such applications arise in complex domains like bioinformatics, web mining, etc. In this paper, we present a novel algorithm, named Chopper, to discover frequent subtrees from ordered labeled trees. An extensive performance study shows that the newly developed algorithm outperforms TreeMinerV, one of the fastest methods proposed previously, in mining large databases. At the end of this paper,the potential improvement of Chopper is mentioned.

  6. Conceptual design of a Disk Chopper Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Copley, J.R.D. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    1997-09-01

    We describe methods that we have used for the conceptual design of the Disk Chopper Spectrometer at the Cold Neutron Research Facility, National Institute of Standards and Technology. Most of the discussion concerns the multiple chopper system. No single design method is best in every situation. We believe that an analytical approach is preferable, whenever possible. Graphical methods of expressing problems have been very instructive. We have also found it useful, and occasionally invaluable, to cross-check results obtained using different methods, such as analytical integration and ray-tracing.

  7. Negative coupled inductors for polyphase choppers

    Science.gov (United States)

    Jamieson, Robert S. (Inventor)

    1984-01-01

    A technique for negatively coupling the outputs of polyphase choppers is disclosed, wherein the output inductance of each phase is divided into two windings, and each winding is negatively coupled to a corresponding winding of a neighboring phase. In a preferred embodiment for a three-phase chopper circuit, the output inductance of phase A is divided into windings 100 and 102, the output inductance of phase B is divided into windings 110 and 112, and the output inductance of phase C is divided into windings 120 and 122. Pairs of windings 100 and 110, 112 and 120, and 102 and 122 are respectively disposed in transformers arranged for negatively coupling the windings of each pair.

  8. Choppers to optimise the repetition rate multiplication technique on a direct geometry neutron chopper spectrometer

    DEFF Research Database (Denmark)

    Vickery, Anette; Deen, P. P.

    2014-01-01

    In recent years the use of repetition rate multiplication (RRM) on direct geometry neutron spectrometers has been established and is the common mode of operation on a growing number of instruments. However, the chopper configurations are not ideally optimised for RRM with a resultant 100 fold flux...

  9. A CMOS low-noise instrumentation amplifier using chopper modulation

    DEFF Research Database (Denmark)

    Nielsen, Jannik Hammel; Bruun, Erik

    2005-01-01

    This paper describes a low-power, low-noise chopper stabilized CMOS instrumentation amplifier for biomedical applications. Low thermal noise is achieved by employing MOSTs biased in the weak/moderate inversion region, whereas chopper stabilization is utilized to shift 1/f-noise out of the signal...

  10. A fast chopper for medium energy beams

    Energy Technology Data Exchange (ETDEWEB)

    Madrak, R. [Fermilab; Wildman, D. [Fermilab

    2014-10-30

    The key elements have been constructed for a fast chopper system capable of removing single 2.5 MeV proton bunches spaced at 325 MHz. The average chopping rate is ~ 1 MHz. The components include a pulse delaying microstrip structure for deflecting the beam, high voltage (1.2 kV) fast (ns rise time) pulsers, and an associated wideband combiner. Various designs for the deflecting structures have been studied. Measurements of the microstrip structures' coverage factors and pulse shapes are presented.

  11. A design study on the CSNS LEBT pre-chopper

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The China Spallation Neutron Source (CSNS) front end incorporates a pre-chopper in the Low Energy Beam Transport line (LEBT) that will remove a 530 ns section of beam at approximately 1 MHz rate, which is the RF frequency of the ring at injection. It’s one of the most critical devices for properly controlling the injecting beam loss. Physical designing of the pre-chopper is carried out, and the RFQ itself is used as the beam dump of the chopper system. In order to examine the reliability of the pre-chopper design, the beam study of a similar chopper system is successfully performed. The results of physical design and experiments are presented.

  12. Linac4 chopper line commissioning strategy

    CERN Document Server

    Bellodi, G; Lombardi, A M; Posocco, P A; Sargsyan, E

    2010-01-01

    The report outlines the strategy for beam-based commissioning of the Linac4 3 MeV chopper line as currently scheduled to start in the second half of 2011 in the Test Stand Area. A dedicated temporary diagnostics test bench will complement the measurement devices foreseen for permanent installation in the chopper line. A commissioning procedure is set out as a series of consecutive phases, each one supposed to meet a well- defined milestone in the path to fully characterise the beam-line. Specific set-ups for each stage are defined in terms of beam characteristics, machine settings and diagnostics used. Operational guidelines are given and expected results at the relative points of measurements are shown for simulated scenarios (on the basis of multi-particle tracking studies carried out with the codes PATH and TRACEWin). These are then interpreted in the light of the resolution limits of the available diagnostics instruments to assess the precision reach on individual measurements and the feasibility of techn...

  13. Analysis of Input and Output Ripples of PWM AC Choppers

    Directory of Open Access Journals (Sweden)

    Pekik Argo Dahono

    2008-11-01

    Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

  14. Neural network based PWM AC chopper fed induction motor drive

    Directory of Open Access Journals (Sweden)

    Venkatesan Jamuna

    2009-01-01

    Full Text Available In this paper, a new Simulink model for a neural network controlled PWM AC chopper fed single phase induction motor is proposed. Closed loop speed control is achieved using a neural network controller. To maintain a constant fluid flow with a variation in pressure head, drives like fan and pump are operated with closed loop speed control. The need to improve the quality and reliability of the drive circuit has increased because of the growing demand for improving the performance of motor drives. With the increased availability of MOSFET's and IGBT's, PWM converters can be used efficiently in low and medium power applications. From the simulation studies, it is seen that the PWM AC chopper has a better harmonic spectrum and lesser copper loss than the Phase controlled AC chopper. It is observed that the drive system with the proposed model produces better dynamic performance, reduced overshoot and fast transient response. .

  15. Experimental performance of an E ×B chopper system

    Science.gov (United States)

    Wiesner, C.; Droba, M.; Meusel, O.; Noll, D.; Payir, O.; Ratzinger, U.; Schneider, P.

    2017-02-01

    Beam operation of a novel E ×B chopper system has started in the low-energy beam transport (LEBT) section of the accelerator-driven neutron source FRANZ. The chopper is designed for low-energy high-perveance beams and high repetition rates, and will finally operate with 120 keV protons. It combines a static magnetic deflection field with a pulsed electric compensation field in a Wien filter-type E ×B configuration. The chopper was designed, manufactured and successfully commissioned at the required repetition rate of 257 kHz using a 14 keV helium beam with up to 3.5 mA of beam current. Beam pulses with rise times of (120 ±10 ) ns , flat-top lengths of (85 ±10 ) ns to (120 ±10 ) ns and full width at half maximum (FWHM) between (295 ±10 ) ns and (370 ±10 ) ns were experimentally achieved.

  16. A MEMS-based high frequency x-ray chopper.

    Science.gov (United States)

    Siria, A; Dhez, O; Schwartz, W; Torricelli, G; Comin, F; Chevrier, J

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  17. A MEMS-based high frequency x-ray chopper

    Energy Technology Data Exchange (ETDEWEB)

    Siria, A; Schwartz, W; Chevrier, J [Institut Neel, CNRS-Universite Joseph Fourier Grenoble, BP 166, F-38042 Grenoble Cedex 9 (France); Dhez, O; Comin, F [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble Cedex 9 (France); Torricelli, G [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  18. Four Quadrant Chopper Drive with Specialized Integrated Circuits

    Directory of Open Access Journals (Sweden)

    Alexandru Morar

    2009-12-01

    Full Text Available The paper presents a high performance system for separately-excited D.C. motor control, which was designed and performed with a specialized integrated circuit (L292, made by SGS-THOMSON Microelectronics Company. With an interface and an adequate software, L292 circuit can be used as a chopper in 2 or 4 quadrant.

  19. Four Quadrant Chopper Drive with Specialized Integrated Circuits

    OpenAIRE

    Alexandru Morar

    2009-01-01

    The paper presents a high performance system for separately-excited D.C. motor control, which was designed and performed with a specialized integrated circuit (L292), made by SGS-THOMSON Microelectronics Company. With an interface and an adequate software, L292 circuit can be used as a chopper in 2 or 4 quadrant.

  20. Fast Chopper Structure for the CERN Superconducting Proton Linac

    CERN Document Server

    Caspers, Friedhelm; Kurennoy, S S

    2002-01-01

    The SPL chopper is a travelling wave device, which deflects a slow beam (b = v/c = 0.08) by its transverse electric field. We discuss the chopper deflecting structure based on a meander line printed on an alumina substrate. This concept profits from the radiation resistance of alumina, its excellent out-gassing properties and its good thermal conductivity. The use of well established MIC (microwave integrated circuit) thick film technology allows easy implementation of prototypes; the thickness of the printed layer should be increased by means of an electrochemical deposition method. The topology of the structure has been chosen from standard MIC layouts and was subsequently optimized using numerical simulations. Several prototypes have been manufactured and measurements have shown encouraging results.

  1. Observability and observer design for hybrid multicell choppers

    Science.gov (United States)

    Bejarano, F. J.; Ghanes, M.; Barbot, J.-P.

    2010-03-01

    Multicell choppers are part of a class of hybrid systems in which the continuous state vector is always unobservable, in the sense that the observability matrix never has full rank. Due to their hybrid behaviour, the recent concept of Z(T N )-observability can be applied and analysed in the context of multicell choppers, which allows to give conditions, in terms of the switching sequence, under which the voltage across each capacitor can be reconstructed, not instantly, but after some number of switchings. The case when a DC-motor is coupled to the multicell chopper is also considered. It is shown that, under certain admissible assumptions, the voltages across the capacitors and the motor speed can be acceptably estimated. Two observers, one based on the super-twisting algorithm and the other one based on an adaptive approach, are designed. Additionally, we design an observer for the partial state observation. Simulations are given where the proposed observers are compared and the effectiveness of both is shown.

  2. Beam chopper For the Low-Energy Undulator Test Line (LEUTL) in the APS

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Y.; Wang, J.; Milton, S.; Teng, L. [and others

    1997-08-01

    The low-energy undulator test line (LEUTL) is being built and will be tested with a short beam pulse from an rf gun in the Advanced Photon Source (APS) at the Argonne National Laboratory. In the LEUTL a beam chopper is used after the rf gun to deflect the unwanted beam to a beam dump. The beam chopper consists of a permanent magnet and an electric deflector that can compensate for the magnetic deflection. A 30-kV pulsed power supply is used for the electric deflector. The chopper subsystem was assembled and tested for beamline installation. The electrical and beam properties of the chopper assembly are presented.

  3. Development and characterization of a 2D precision cryogenic chopper for METIS

    NARCIS (Netherlands)

    Paalvast, Sander L.; Huisman, Robert; Brandl, Bernhard R.; Huub, Janssen; Jayawardhana, Bayu; Molster, Frank; Teuwen, Maurice; Venema, Lars

    2014-01-01

    This paper discusses the development, realization, and characterization of a demonstrator cryogenic chopper for METIS, the third instrument on the ELT. The chopper has to tip/tilt in 2D with a combined angle of up to 13.6mrad and achieve a 95% duty cycle at 5Hz. The mirror (Ø64mm) is guided by a mon

  4. Simulations of chopper jitter at the LET neutron spectrometer at the ISIS TS2

    DEFF Research Database (Denmark)

    Klenø, Kaspar Hewitt; Lefmann, Kim; Willendrup, Peter Kjær

    2014-01-01

    The effect of uncertainty in chopper phasing (jitter) has been investigated for the high-resolution time-of-flight spectrometer LET at the ISIS second target station. The investigation is carried out using virtual experiments, with the neutron simulation package McStas, where the chopper jitter i...

  5. Thermal chopper spectrometer for the European spallation source

    DEFF Research Database (Denmark)

    Klenø, Kaspar Hewitt; Lefmann, Kim

    2011-01-01

    One of the instruments being considered for the ESS is a thermal chopper spectrometer, intended for the study of lattice vibrations and magnetic excitations. However, as the ESS will be a long pulsed source, we propose a very long instrument (180–300 m). We here present a guide system that can ac...... achieve a flux of 3.47 ×108 n/(s·cm2) and a resolution of dE/E = 5.3% for 1 Å neutrons on the sample with a transport efficiency of 80%. Furthermore, we demonstrate the efficiency of the instrument using a virtual experiment measuring an elastic line width...

  6. Status of CERN Chopper Driver and the Solid State Alternative

    CERN Document Server

    Paoluzzi, M

    2005-01-01

    The Superconducting H- Linac under study at CERN requires a high performance 3 MeV chopper. It has to establish the required beam time-structure by dumping part of the beam exiting the RFQ in 0.6 ms bursts of 1 ns bunches spaced by 2.84 ns and repeated at 50 Hz. For maximum flexibility, the system must be able to remove any number of consecutive bunches with a minimum of 3 and up to a few thousand. The amplifier driving the chopper structure has thus to provide 500 V on 50 omega, with rise and fall times below 2 ns and repetition rate as high as 45 MHz. To achieve the very wide frequency response required for this application a first proposal based on the idea of generating the low and high frequency part of the required spectrum with distinct amplifiers has been followed. In-depth studies and prototyping have proven the principle but also shown its fragilities. Distortions, saturation effects in the ferrite or in the driving circuits, vacuum tube ageing, etc. are difficult to keep within the limits required ...

  7. Analysis of Variable Speed PFC Chopper Fed BLDC Motor Drive

    Directory of Open Access Journals (Sweden)

    A Jeya Selvan Renius

    2015-02-01

    Full Text Available This paper provides the detailed analysis of the DC-DC chopper fed Brushless DC motor drive used for low-power applications. The various methods used to improve the power quality at the ac mains with lesser number of components are discussed. The most effective method of power quality improvement is also simulated using MATLAB Simulink. Improved method of speed control by controlling the dc link voltage of Voltage Source Inverter is also discussed with reduced switching losses. The continuous and discontinuous modes of operation of the converters are also discussed based on the improvement in power quality. The performance of the most effective solution is simulated in MATLAB Simulink environment and the obtained results are presented.

  8. The Control Method for Pyroelectric Chopper%热释电斩波器控制

    Institute of Scientific and Technical Information of China (English)

    王敏; 李晶; 朱洪洋; 刘愚; 郭小军; 陈如造; 罗凤旺; 秦伟; 朱光明

    2014-01-01

    斩波器是热释电型热像仪的重要组成部份,其平稳、匀速且按要求相位精确地运转,关系到整机成像质量的好坏。提出了一种对热释电斩波器进行闭环控制的方法,该方法的使用,解决了斩波器的控制问题。%Chopper is the important part of the pyroelectric thermal imager. The stable and uniform operation of chopper is related to the imaging quality. This paper presents a method about the closed-loop control for pyroelectric chopper, which solves the problem of the chopper control.

  9. Fabrication of the MEBT chopper system for the spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Hardekopf, R. A.; Kurennoy, S. (Sergey); Power, J. F. (John F.); Roybal, R. J. (Raymond J.(Ray); Schrage, D. L. (Dale L.); Sherwood, R. (Ron); Collins, S. (Shaun)

    2003-01-01

    Los Alamos completed design, fabrication, procurement, and initial testing (without beam) of the SNS medium-energy beam-transport (MEBT) chopper, including the meander-line traveling-wave structure and the electrical-pulser system. This report reviews the design parameters and discusscs the fabrication process for the chopper structures, including measurements of the impedance and rise time. (The MEBT vacuum system and chopper-target beam stop were developed at and reported by LBNL.) We discuss the spccifications for the pulse generator and its fabrication and testing at Directed Energy, Inc. of Boulder, CO. Experimental tests of the chopper system are currently being performed at the SNS site at ORNL and will be reported separately.

  10. Risk Assessment of the Chopper Dipole Kicker Magnets for the MedAustron Facility

    CERN Document Server

    Kramer, T; Barnes, M J; Benedikt, M; Fowler, T

    2011-01-01

    The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research [1]. Different types of kicker magnets will be used in the accelerator complex, including fast beam chopper dipoles: these allow the beam to be switched on and off for routine operational reasons or in case of emergency. Main requirements for the beam chopper system are safety and reliability. A criticality analysis, to chart the probability of failure modes against the severity of their consequences of the fault, has been carried out for the chopper dipole system. This "Failure Mode, Effects, and Criticality Analysis" (FMECA), has been used to highlight failure modes with relatively high probability and severity of consequences: conservative ratings of critical components and appropriate redundancy, together with measurements and interlocks, have been used to reduce the probability and criticality of faults. This paper gives an overview of the Risk Assessment approach and pres...

  11. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Science.gov (United States)

    Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.

    2015-03-01

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  12. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Müller, O., E-mail: o.mueller@uni-wuppertal.de; Lützenkirchen-Hecht, D.; Frahm, R. [Bergische Universität Wuppertal, Gaußstraße 20, Wuppertal 42119 (Germany)

    2015-03-15

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  13. The Monte Carlo simulation of neutron transmitted and scattered by disk choppers of various compositions

    Energy Technology Data Exchange (ETDEWEB)

    Baek, I.; Carpenter, J.M. [Intense Pulsed Neutron Source, Argonne National Laboratory, Argonne, IL (United States); Iverson, E.B. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2001-03-01

    We consider the transmission of neutrons through disk-type neutron choppers, considering both the uncollided neutron fraction ({phi}{sub u}) and scattered neutron fraction ({phi}{sub s}). We computed {phi}{sub u}, {phi}{sub s}, and the ratio {phi}{sub u}/{phi}{sub s} through plates of five different absorber materials of various thicknesses to give information for selecting optimum materials and thicknesses. We also studied variance-reducing techniques for Monte Carlo calculation of chopper using MCNP4b, selecting those most effective for these calculations. (author)

  14. A design study of VOR: A versatile optimal resolution chopper spectrometer for the ESS

    Directory of Open Access Journals (Sweden)

    Deen P.P.

    2015-01-01

    Full Text Available VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS, 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1–120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from ΔE/E = 1% up to ΔE/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1–3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM and is therefore able to measure, in a single ESS period, 6–14 incident wavelengths, across a wavelength band of 9 Å with a novel chopper configuration that transmits all incident wavelengths with equivalent counting statistics. The characteristics of VOR make it a unique instrument with capabilities to access small, limited-lifetime samples and transient phenomena with inelastic neutron scattering.

  15. Development of a fast traveling-wave beam chopper for the National Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, S.S.; Jason, A.J.; Krawczyk, F.L.; Power, J.

    1997-10-01

    High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the National Spallation Neutron Source (NSNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns to accommodate a 402.5-MHz beam structure--beam chopping in its front end, at the beam energy 2.5 MeV. The R and D program includes both modification of the existing LANSCE coax-plate chopper to reduce parasitic coupling between adjacent plates, and development of new traveling-wave deflecting structures, in particular, based on a meander line. Using analytical methods and three-dimensional time-domain computer simulations the authors study transient effects in such structures to choose an optimal chopper design.

  16. Development of a Fast Traveling-Wave Beam Chopper for National Spallation Neutron Source.

    Science.gov (United States)

    Kurennoy, Sergey S.; Jason, Andrew J.; Krawczyk, Frank L.

    1997-05-01

    High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the NSNS require clean and fast (with the rise time from 2% to 98% less than 2.5 ns to accommodate a 402.5 MHz beam structure) beam chopping in its front end, at beam energy 2.5 MeV. The present R&D program includes both modification of the existing LANSCE coax-plate chopper to reduce parasitic coupling between adjacent plates, and development of new traveling-wave deflecting structures, in particular, based on a meander line. Using analytical methods and three-dimensional time-domain computer simulations we study transient effects in such structures to choose an optimal chopper design.

  17. Development of a fast traveling-wave beam chopper for the SNS project

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, S.S.; Power, J.F.

    1998-12-31

    High current and stringent restrictions on beam losses, below 1 nA/m, in the designed linac for the Spallation Neutron Source (SNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns--beam chopping in its front end, at the beam energy 2.5 MeV. The development of new traveling-wave deflecting current structures based on meander lines is discussed. Three-dimensional time-domain computer simulations with MAFIA are used to study transient effects in the chopper and to optimize current structure design. Two options for the fast pulsed voltage generator--based on FETs and vacuum tubes--are considered, and their advantages and shortcomings for the SNS chopper are discussed.

  18. MEANDER-LINE CURRENT STRUCTURE DEVELOPMENT FOR SPALLATION NEUTRON SOURCE FAST CHOPPER

    Energy Technology Data Exchange (ETDEWEB)

    S. KURRENOY; J. POWER

    2000-10-01

    A new current structure for the fast traveling-wave 2.5-MeV beam chopper in the front end of the Spallation Neutron Source (SNS) has been suggested in [1]. The structure is based on the meander-folded notched stripline with dielectric supports and separators. Its design has been optimized using electromagnetic 3-D modeling with the MAFIA code package to provide rise and fall times in the range of 1 to 2 ns. A full-length (50 cm) prototype has been manufactured, and its preliminary measurements showed a good agreement with the calculations. Detailed measurements results and their comparison with simulations are presented. The latest front-end design requires a shorter, 35-cm chopper with a higher pulse voltage. Its meander-line current structure, based on the same principles, has also been optimized with MAFIA.

  19. Application of a simple asynchronous mechanical light chopper to multielectron coincidence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Kenji; Suzuki, Isao H. [Photon Factory, IMSS, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan); Penent, Francis; Lablanquie, Pascal [Universite Pierre et Marie Curie (UPMC), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, LCPMR(UMR 7614), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Hikosaka, Yasumasa; Shigemasa, Eiji [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Eland, John H. D. [PTCL, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    2009-12-15

    A simple asynchronous mechanical light chopper, based on modification of a turbo-molecular pump, has been developed to extend the interval between light pulses in single bunch operation at the Photon Factory storage ring. A pulse repetition rate of 80 kHz was achieved using a cylinder rotating at 48000 rpm, with 100 slits of 80 {mu}m width. This allows absolute timing of particles up to 12.48 {mu}s instead of the single-bunch period of 624 ns. We have applied the chopper together with a light pulse monitor to measure multielectron coincidence spectra using a magnetic bottle time-of-flight electron spectrometer. With such a system, the electron energies are determined without any ambiguity, the folding of coincidence spectra disappears and the effect of false coincidences is drastically reduced.

  20. Vehicle test report: South Coast Technology electric Volkswagen Rabbit with developmental low-power armature chopper

    Science.gov (United States)

    Marte, J. E.; Bryant, J. A.; Livingston, R.

    1983-01-01

    Dynamometer performance of a South Coast Technology electric conversion of a Volkswagen (VW) Rabbit designated SCT-8 was tested. The SCT-8 vehicle was fitted with a transistorized chopper in the motor armature circuit to supplement the standard motor speed control via field weakening. The armature chopper allowed speed control below the motor base speed. This low speed control was intended to reduce energy loss at idle during stop-and-go traffic; to eliminate the need for using the clutch below base motor speed; and to improve the drivability. Test results indicate an improvement of about 3.5% in battery energy economy for the SAE J227a-D driving cycle and 6% for the C-cycle with only a minor reduction in acceleration performance. A further reduction of about 6% would be possible if provision were made for shutting down field power during the idle phases of the driving cycles. Drivability of the vehicle equipped with the armature chopper was significantly improved compared with the standard SCT Electric Rabbit.

  1. Broad-band chopper for a CW proton linac at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Gianfelice-Wendt, E.; Lebedev, V.A.; Solyak, N.; Nagaitsev, S.; Sun, D.; /Fermilab

    2011-03-01

    The future Fermilab program in the high energy physics is based on a new facility called the Project X [1] to be built in the following decade. It is based on a 3 MW CW linear accelerator delivering the 3 GeV 1 mA H{sup -} beam to a few experiments simultaneously. Small fraction of this beam will be redirected for further acceleration to 8 GeV to be injected to the Recycler/Main Injector for a usage in a neutrino program and other synchrotron based high energy experiments. Requirements and technical limitations to the bunch-by-bunch chopper for the Fermilab Project X are discussed.

  2. Electromagnetic Modeling of a Fast Traveling-Wave Beam Chopper for the SNS Project.

    Science.gov (United States)

    Kurennoy, Sergey

    1998-04-01

    High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the Spallation Neutron Source (SNS) require clean and fast --- with the rise time from 2% to 98% less than 2.5 ns --- beam chopping in its front end, at the beam energy 2.5 MeV. The development of new traveling-wave deflecting current structures, based on meander lines, is discussed. Three-dimensional time-domain computer simulations are used to study transient effects in the chopper and to optimize its design.

  3. Note: significant increase to the temporal resolution of 2D X-ray detectors using a novel beam chopper system.

    Science.gov (United States)

    Küchemann, Stefan; Mahn, Carsten; Samwer, Konrad

    2014-01-01

    The investigation of short time dynamics using X-ray scattering techniques is commonly limited either by the read out frequency of the detector or by a low intensity. In this paper, we present a chopper system, which can increase the temporal resolution of 2D X-ray detectors by a factor of 13. This technique only applies to amorphous or polycrystalline samples due to their circular diffraction patterns. Using the chopper, we successfully increased the temporal resolution up to 5.1 ms during synchrotron experiments. For the construction, we provide a mathematical formalism, which, in principle, allows an even higher increase of the temporal resolution.

  4. Considerations about Chopper Configuration at a time-of-flight SANS Instrument at a Spallation Source

    CERN Document Server

    Jaksch, Sebastian

    2016-01-01

    In any neutron scattering experiment the measurement of the position of the scattered neutrons and their respective velocities is necessary. In order to do so, a position sensitive detector as well as a way to determine the velocities is needed. Measuring the velocities can either be done by using only a single wavelength and therefore velocity or by creating pulses, where the start and end time of each pulse is known and registering the time of arrival at the detector, which is the case we want to consider here. This pulse shaping process in neutron scattering instruments is usually done by using a configuration of several choppers. This set of choppers is then used to define both the beginning and the end of the pulse. Additionally there is of course also a selection in phase space determining the final resolution that can be achieved by the instrument. Taking into account the special requirements of a specific instrument, here a small-angle neutron scattering instrument, creates an additional set of restri...

  5. Posterior segment nucleotomy for dislocated sclerotic cataractous lens using chandelier endoilluminator and sharp tipped chopper

    Institute of Scientific and Technical Information of China (English)

    Brijesh; Takkar; Rajvardhan; Azad; Shorya; Azad; Anubha; Rathi

    2015-01-01

    · AIM: To describe a new surgical technique for managing dislocated sclerotic cataractous lens.· METHODS: Six patients with advanced posteriorly dislocated cataracts were operated at a tertiary care centre and analyzed retrospectively. After standard 3 port23 G pars plana vitrectomy and perfluorocarbon liquid(PFCL) injection, the dislocated white cataract was held with occlusion using phaco fragmatome and then chopped into smaller pieces with a sharp tipped chopper using 25 G chandelier endoilluminator. Each piece was emulsified individually. Following aspiration of PFCL,Fluid Air Exchange was done in all the cases and surgery completed uneventfully.·RESULTS: Best corrected visual acuity(BCVA) in all the patients was better than 6/12 after one month of follow up. No serious complications were noted till minimum 6mo of follow up.·CONCLUSION: Four port posterior segment nucleotomy with a chandelier endoilluminator, fragmatome and a chopper appears to be a safe, easy and effective procedure for managing dislocated sclerotic cataractous nuclei. Ultrasonic energy used and adverse thermal effects of the fragmatome on the sclera may be lesser.

  6. ARCS A wide-Anglular Range Chopper Spectrometer at the SNS

    Energy Technology Data Exchange (ETDEWEB)

    Prof. Brent Fultz; Dr. Doug Abernathy

    2005-01-03

    The ARCS spectrometer project has been funded for 39 months. Procurements are now amain activity, although engineering effort remains, and installation has begun. Most of the subsystems are under control, and represent no risk to the project. These are: cryo-goniometer, detectors and electronics, Fermi chopper system, computing cluster, basic reduction software, T0 chopper and main neutron guide. The sample hutch and radiationshielding are still items of some risk. At the time of this writing, we are awaiting vendor proposals for the scattering chamber with integrated sample isolation system. This is thelargest uncertainty in the ARCS project today. The ARCS Chief Engineer, Kevin Shaw, joined the project in 2004. Project controlsservices are now performed by the SNS. A construction progress review was held in the August, 2004, before which the project was rebaselined, and after which the ProjectExecution Plan was updated. The ARCS project will be rebaselined in March 2005 after a vendor is selected for the scattering chamber with integrated isolation system. Projectcompletion by Sept. 2006 is possible but challenging.

  7. Research on a new active power filter topology based on chopper circuit

    CERN Document Server

    Xiaoling, Guo; Bo, Zhang; Jing, Zhang

    2015-01-01

    The active power filter (APF) is attracting more and more attention for its outstanding performance in current and voltage ripple compensation. As modern high-energy accelerators are demanding much more stringent current ripple guideline, the APF is introduced to the magnet power supply (MPS) in accelerator system. However, the conventional APF has a lot of shortages and drawbacks due to its traditional topology, such as complex structure, nonadjustable working voltage, requirement of power supply, and so on. This paper proposes a new topology of APF, which is working as two types of chopper circuits. This APF need not extra electricity, but to use the power of the MPS current ripple to realize ripple depressing. At the end of this paper, the experiment result proves its feasibility and effect.

  8. FPGA-based genetic algorithm implementation for AC chopper fed induction motor

    Science.gov (United States)

    Mahendran, S.; Gnanambal, I.; Maheswari, A.

    2016-12-01

    Genetic algorithm (GA)-based harmonic elimination technique is proposed for designing AC chopper. GA is used to calculate optimal firing angles to eliminate lower order harmonics in output voltage. Total harmonic distortion of output voltage is taken for the fitness function used in the GA. Thus, the ratings of the load are not mandatory to be known for calculating the switching angles using proposed technique. For the performance assessment of GA, Newton-Raphson (NR) method is applied in this present work. Simulation results show that the proposed technique is better in terms of less computational complexity and quick convergence. Simulation results were verified by field programmable gate array controller-based prototype. Simulation study and experimental investigations show that the proposed GA method is superior to the conventional methods.

  9. Non-periodic multi-slit masking for a single counter rotating 2-disc chopper and channeling guides for high resolution and high intensity neutron TOF spectroscopy

    Science.gov (United States)

    Bartkowiak, M.; Hofmann, T.; Stüßer, N.

    2017-02-01

    Energy resolution is an important design goal for time-of-flight instruments and neutron spectroscopy. For high-resolution applications, it is required that the burst times of choppers be short, going down to the μs-range. To produce short pulses while maintaining high neutron flux, we propose beam masks with more than two slits on a counter-rotating 2-disc chopper, behind specially adapted focusing multi-channel guides. A novel non-regular arrangement of the slits ensures that the beam opens only once per chopper cycle, when the masks are congruently aligned. Additionally, beam splitting and intensity focusing by guides before and after the chopper position provide high intensities even for small samples. Phase-space analysis and Monte Carlo simulations on examples of four-slit masks with adapted guide geometries show the potential of the proposed setup.

  10. 新型级联式交流斩波器%Cascade Mode Three-Level AC Chopper

    Institute of Scientific and Technical Information of China (English)

    李磊; 唐栋材

    2012-01-01

    Three-level(TL) AC switch unit is produced by two-level AC switch unit connected together in series manner.TL AC converter is produced by applying TL AC switch unit in basic converter.By combining Buck mode TL and Boost mode AC converters,a novel cascade mode AC chopper was proposed.The AC chopper can chopper unsteady high AC voltage with distortion into regulated sinusoidal voltage with low THD.The AC chopper,which is suit for high input voltage fields,has such following fetures as less power stages,bi-directional power flow,lower voltage stress in the front stage,low THD of output voltage,Buck and Boost mode conversion,unchanged voltage stress in the back stage.The operation principle was also investigated.For cascade mode TL AC chopper,control strategy of flying capacitor voltage was also presented.The AC chopper and the control strategy are fully proved by experimental results.%两电平交流开关单元串联后可得到三电平交流开关单元,将其应用到基本变换器中,可以获得三电平交流变换器。本文将Buck型三电平和Boost型两电平交流变换器进行组合,提出了一种新颖的级联式交流斩波器,并研究了其工作原理。该交流斩波器能够将不稳定、畸变的高压交流电变换成稳定或可调的优质正弦交流电,具有功率变换级数少,双向功率流,前级开关管的电压应力可降低,输出电压波形质量好,可实现升降压变换,后级电压应力未降低等特点,适用于高输入电压的交流变换场合。针对浮动电容电压控制问题,本文还提出了相应的控制策略。实验结果充分证实了本文所提出的级联式交流斩波器及其控制策略的可行性和正确性。

  11. 嵌套式斩波运放的分析与设计%Analysis and Design of Nested Chopper Operational Amplifier

    Institute of Scientific and Technical Information of China (English)

    张锗源; 杨发顺; 杨法明; 张荣芬; 邓朝勇

    2012-01-01

    A nested chopper operational amplifier was designed to solve the problem of large residual offset in traditional chopper amplifiers. Simulation with Spectre based on SMIC 0. 18 μm CMOS process showed that the circuit had an open loop gain of 78. 3 dB and a CMMR up to 112 dB. With chopper frequency /chophigh = 10 kHz and fchoplow=500 Hz, the single chopper and nested chopper opamp were simulated, respectively, using non-matched chopper switch. Results indicated that the nested chopper was helpful to reduce residual offset The nested chopper opamp is suitable for processing weak signal with low bandwidth, such as front-end readout circuit in sensors and audio signal amplifier circuit.%针对传统的斩波运放具有大残余失调的特点,设计了一个嵌套式斩波运放.基于SMIC0.18μm工艺,通过Spectre仿真工具进行验证与仿真,运放的开环增益达到78.3 dB,共模抑制比达到112 dB.在斩波频率fchophigh=10 kHz、fchoplow=500 Hz的条件下,通过使用非匹配斩波开关,分别对单斩波和嵌套式斩波运放进行仿真.结果表明,嵌套式斩波技术能有效减小残余失调的影响.适用于带宽较低的微弱信号检测与处理电路,如传感器前端读出电路和音频信号放大电路等.

  12. Design of a medium-energy beam-transport line with an anti-chopper for the JAERI/KEK project

    CERN Document Server

    Wang Sheng; Kato, T

    2002-01-01

    The medium-energy beam-transport line (MEBT) plays an important role in reducing beam loss in the JAERI/KEK project. A MEBT was designed two years ago, with good beam matching and lower beam loss. To further reduce beam loss during the transient time of the chopper to meet the new requirement from the DTL, a medium-energy beam-transport line with an anti-chopper has been designed. The 3.5 m long transport line consists of nine quadrupole magnets, three bunchers and four chopper/anti-chopper cavities. It accomplishes two tasks: matching the beam from the RFQ to the acceptance of the DTL and chopping the beam to produce gaps for injection into the rapid-cycling ring, which follows the linac. A RF Chopper and an anti-chopper have been adopted in the lattice, resulting in a clean chopping effect and no beam losses during the transient time. Details of the beam dynamics analysis are given

  13. Flexible fault ride through of DFIG wind turbines with DC-chopper solution

    Energy Technology Data Exchange (ETDEWEB)

    Wessels, Christian; Laubrock, Malte; Bellgardt, Uwe [Nordex Energy GmbH, Hamburg (Germany). System Dept Grid and Grid Integration; Genius, Andreas [Woodward Kempen GmbH, Kempen (Germany). Wind Power Systems

    2012-07-01

    Grid code requirements are becoming increasingly challenging due to the growing integration of decentralized power generators like renewable energy devices. One of the most challenging grid code requirements is the fault ride through (FRT) of wind turbines. Internationally varying and quickly revised grid code requirements are making it necessary for wind turbine manufacturers to apply competitive hardware and flexible software structures to respond quickly to renewed requirements or project specific changes. In this paper an industrially applied and field-tested hardware solution for the FRT of a DFIG wind turbine is presented. The method using a DC-chopper is making the utilization of the conventionally used rotor crowbar unnecessary. Thus, the consumption of reactive power during grid faults is avoided. Instead, a controlled current can be fed dynamically in order to support the grid voltage and to avoid mechanical stress on the drivetrain of the turbine. Using the presented technology, the application of a flexible FRT software structure is possible to fulfill the internationally varying FRT requirements, which is described here. Selected measurement results from long term FRT tests from a wind turbine manufacturer of a real 2.5 MW wind turbine during grid faults are presented and verify the results. (orig.)

  14. The multiple functions of T stellate/multipolar/chopper cells in the ventral cochlear nucleus.

    Science.gov (United States)

    Oertel, Donata; Wright, Samantha; Cao, Xiao-Jie; Ferragamo, Michael; Bal, Ramazan

    2011-06-01

    Acoustic information is brought to the brain by auditory nerve fibers, all of which terminate in the cochlear nuclei, and is passed up the auditory pathway through the principal cells of the cochlear nuclei. A population of neurons variously known as T stellate, type I multipolar, planar multipolar, or chopper cells forms one of the major ascending auditory pathways through the brainstem. T Stellate cells are sharply tuned; as a population they encode the spectrum of sounds. In these neurons, phasic excitation from the auditory nerve is made more tonic by feedforward excitation, coactivation of inhibitory with excitatory inputs, relatively large excitatory currents through NMDA receptors, and relatively little synaptic depression. The mechanisms that make firing tonic also obscure the fine structure of sounds that is represented in the excitatory inputs from the auditory nerve and account for the characteristic chopping response patterns with which T stellate cells respond to tones. In contrast with other principal cells of the ventral cochlear nucleus (VCN), T stellate cells lack a low-voltage-activated potassium conductance and are therefore sensitive to small, steady, neuromodulating currents. The presence of cholinergic, serotonergic and noradrenergic receptors allows the excitability of these cells to be modulated by medial olivocochlear efferent neurons and by neuronal circuits associated with arousal. T Stellate cells deliver acoustic information to the ipsilateral dorsal cochlear nucleus (DCN), ventral nucleus of the trapezoid body (VNTB), periolivary regions around the lateral superior olivary nucleus (LSO), and to the contralateral ventral lemniscal nuclei (VNLL) and inferior colliculus (IC). It is likely that T stellate cells participate in feedback loops through both medial and lateral olivocochlear efferent neurons and they may be a source of ipsilateral excitation of the LSO.

  15. Charging of capacitors with double switch. The principle of operation of auto-zero and chopper-stabilized DC amplifiers

    CERN Document Server

    Yordanov, Vasil G; Manolev, Stojan G; Mishonov, Todor M

    2015-01-01

    The principle of operation of auto-zero and chopper-stabilized DC amplifiers, which is realized in many contemporary operational amplifiers is illustrated by a simple experimental setup given at the Open Experimental Physics Olympiad 2014 - "The Day of the Capacitor", held in Sofia and Gevgelija. The Olympiad was organized by the Sofia Branch of the Union of Physicists in Bulgaria and the Regional Society of Physicists of Strumica, Macedonia. In addition to the solution of the secondary school task in the paper is given a detailed engineering description of the patent by Edwin Goldberg and Jules Lehmann, Stabilized direct current amplifier, U.S. Patent 2,684,999 (1949).

  16. Micro EEG/ECG signal’s chopper-stabilization amplifying chip for novel dry-contact electrode

    Science.gov (United States)

    Sun, Jianhui; Wang, Chunxing; Wang, Gongtang; Wang, Jinhui; Hua, Qing; Cheng, Chuanfu; Cai, Xinxia; Yin, Tao; Yu, Yang; Yang, Haigang; Li, Dengwang

    2017-02-01

    Facing the body’s EEG (electroencephalograph, 0.5–100 Hz, 5–100 μV) and ECG’s (electrocardiogram, ECG’s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal’s detection instrument and has a critical real application value. Project supported by the National Natural Science Foundation of China (Nos. 61527815, 31500800, 61501426, 61471342), the National Key Basic Research Plan (No. 2014CB744600), the Beijing Science and Technology Plan (No. Z141100000214002), and the Chinese Academy of Sciences’ Key Project (No. KJZD-EW-L11-2).

  17. Current Detection Method for Chopper Circuit%斩波电路电流检测方法

    Institute of Scientific and Technical Information of China (English)

    周新云; 樊少波; 胡燕娇; 黄赛帅; 王青青

    2012-01-01

    A current detection method for chopper circuit based on MOSFET was introduced, the relationship between MOSFET Turn-on current and voltage was analyzed, while the effection of temperature to MOSFET on-resistance was taken into account. According to the curve relationship between MOSFET on-resistance and temperature,a current detection method with temperature compensation function for chopper circuit was proposed, current sensor was replaced by this method. Experimental results show that it has the characteristics of high precision,lower cost and high practical value.%提出了1种基于MOSFET开关管的斩波电路电流检测方法,利用MOSFET导通电流与电压的关系,考虑了温度对MOSFET的导通阻抗的影响,根据MOSFET导通阻抗与温度关系曲线,设计1种具有温度补偿功能的斩波电路MOSFET导通电流检测方案,取代了传统的电流传感器检测方法.实验结果证明,该检测方法测量精度高,成本较低,具有很高的实用价值.

  18. The cold neutron chopper spectrometer at the Spallation Neutron Source—A review of the first 8 years of operation

    Science.gov (United States)

    Ehlers, G.; Podlesnyak, A. A.; Kolesnikov, A. I.

    2016-09-01

    The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8 T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.

  19. The Cold Neutron Chopper Spectrometer at the Spallation Neutron Source - A Review of the first 8 Years of Operation

    CERN Document Server

    Ehlers, Georg; Kolesnikov, Alexander I

    2016-01-01

    The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T~0.05K, p>=2GPa and B=8T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.

  20. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 μs

    Science.gov (United States)

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P.

    2015-05-01

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br2 and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  1. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 microseconds

    CERN Document Server

    Lam, Jessica; Softley, Tim

    2015-01-01

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 microseconds. Molecular beams seeded with NO or with Br2 and an initial pulse width of greater or equal to 200 microseconds were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3,000 rpm to 80,000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 microseconds to 13 microseconds, and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  2. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br{sub 2} down to 13 μs

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P. [Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA (United Kingdom)

    2015-05-15

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br{sub 2} and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br{sub 2}. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  3. A microfluidic chip for formation and collection of emulsion droplets utilizing active pneumatic micro-choppers and micro-switches.

    Science.gov (United States)

    Lai, Chia-Wei; Lin, Yen-Heng; Lee, Gwo-Bin

    2008-10-01

    The formation of emulsification droplets is crucial for many industrial applications. This paper reports a new microfluidic chip capable of formation and collection of micro-droplets in liquids for emulsion applications. This microfluidic chip comprising microchannels, a micro-chopper and a micro-switch was fabricated by using micro-electro-mechanical-systems (MEMS) technology. The microfluidic chip can generate uniform droplets with tunable sizes by using combination of flow-focusing and liquid-chopping techniques. The droplet size can be actively fine-tuned by controlling either the relative sheath/sample flow velocity ratios or the chopping frequency. The generated droplets can be then sorted to a specific collection area utilizing an active pneumatic micro-switch formed with three micro-valves. Experimental data showed that the olive oil and sodium-alginate (Na-alginate) droplets with diameters ranging from 3 mum to 70 mum with a variation less than 14% is successfully generated and collected. The development of this microfluidic system can be promising for emulsion, drug delivery and nano-medicine applications.

  4. 基于Matlab的Boost-Buck Chopper的建模与仿真%Modeling and simulation of Boost-Buck Chopper based on MATLAB

    Institute of Scientific and Technical Information of China (English)

    孟庆波; 崔刚

    2012-01-01

    对Matlab进行了简单介绍,建立了IGBT的仿真模型,运用Matlab/Simulink和Power System工具对Boost- Buck Chopper进行建模、参数选择和仿真分析.与常规电路分析方法相比,该方法具有很大的优越性.%The paper takes a brief introduction to MATLAB, and establishes a simulation model ofIGBT. It uses Matlab/Simulink and Power System tools to model, chooses parameters and simulatesBoost-Buck Chopper. Compared with conventional circuit analysis methods, this method has greatadvantages.

  5. A DSP-based modified slip energy recovery drive using a 12-pulse converter and shunt chopper for a speed control system of a wound rotor induction motor

    Energy Technology Data Exchange (ETDEWEB)

    Tunyasrirut, Satean; Ngamwiwit, Jongkol [Faculty of Engineering and Research Center for Communications and Information Technology, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand); Kinnares, Vijit [Department of Electrical Engineering, Faculty of Engineering, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand); Furuya, Tadayoshi [Department of Electronics and Control Engineering, Kitakyushu National College of Technology, Kitakyushu, Fukuoka (Japan); Yamamoto, Yoshiichi [Department of Electronic Control, Kumamoto National College of Technology, 2659-2 Suya Nishigoshi-machi Kikuchi-Gun, Kumamoto Prefecture 861-1102 (Japan)

    2008-05-15

    This paper introduces a modified slip energy recovery drive system for speed control of a wound rotor induction motor offering improvement of drive performance, particularly line power factor and overall system efficiency. A 12-pulse line commutated thyristor converter operating in an inverter mode in conjunction with an additional IGBT shunt chopper is employed to transfer slip energy back to ac mains supply via three phase transformers. This approach offers motor speed control by varying the duty cycle of the chopper instead of changing the inverter firing angle. As a consequence, supply power factor can be improved. The servo state feedback designed by linear quadratic regulator (LQR) with observer is also included in order to keep motor speed to be constant over a certain range of operating conditions by using the estimated dc link current derived from motor speed. The advantage of this technique is absence of current transducers for current feedback control loop. The overall control system is implemented on DSP, DS1104'TMS320F240 controller board. Experimental results are illustrated in order to validate performance of the proposed system. (author)

  6. A 55-dB SNDR, 2.2-mW double chopper-stabilized analog front-end for a thermopile sensor

    Science.gov (United States)

    Chengying, Chen; Xiaoyu, Hu; Jun, Fan; Yong, Hei

    2014-05-01

    A double chopper-stabilized analog front-end (DCS-AFE) circuit for a thermopile sensor is presented, which includes a closed-loop front-end amplifier and a 2nd-order 1 bit quantization sigma—delta modulator. The amplifier with a closed-loop structure ensures the gain stability against the temperature. Moreover, by adopting the chopper-stabilized technique both for the amplifier and 2nd-order 1-bit quantization sigma—delta modulator, the low-frequency 1/f noise and offset is reduced and high resolution is achieved. The AFE is implemented in the SMIC 0.18 μm 1P6M CMOS process. The measurement results show that in a 3.3 V power supply, 1 Hz input frequency and 3KHz clock frequency, the peak signal-to-noise and distortion ratio (SNDR) is 55.4 dB, the effective number of bits (ENOB) is 8.92 bit, and in the range of -20 to 85 degrees, the detection resolution is 0.2 degree.

  7. Investigating the Feasibility of a Travelling-wave Chopper for the Clean Separation of 10 MHz Bunches at HIE-ISOLDE

    CERN Document Server

    Mukhopadhyay, A; Calaga, R; Caspers, F; Paoluzzi, M

    2014-01-01

    The feasibility of cleanly separating the main 10.128MHz bunches from the 101.28MHz satellite bunches with a travelling-wave type chopper at HIE-ISOLDE was investigated using a simple model comprising a chain of synchronised capacitors pulsed at high-voltage. Even with a relatively large transverse aperture of 30mm it appears feasible to remove the satellite bunches spaced at 75mm without significantly perturbing the main bunch. We estimate that for a chopping voltage of 1.2 kV a string of 20 capacitors is required to impart the required deflection of 4 mrad to beams with A=q = 4:5 and the mechanical length of the system can be kept under 0.5 m. The deflection imparted on the main pulse is . 1% of that received by the discarded satellite bunches and the transverse emittance growth of the beam is small if the rise/fall times are kept below 5 ns. The HIE-ISOLDE specification is similar to the specification of the meander strip-line chopper developed at CERN for Linac4 and the application of this technology at ...

  8. Terahertz antenna electronic chopper

    Energy Technology Data Exchange (ETDEWEB)

    Sterczewski, L. A., E-mail: lukasz.sterczewski@pwr.edu.pl; Grzelczak, M. P.; Plinski, E. F. [Department of Electronics, Wroclaw University of Technology, 27 Wybrzeze Wyspianskiego St., 50-370 Wroclaw (Poland)

    2016-01-15

    In this paper, we present an electronic circuit used to bias a photoconductive antenna that generates terahertz radiation. The working principles and the design process for the device are discussed in detail. The noise and shape of the wave measurements for a built device are considered. Furthermore, their impact on a terahertz pulse and its spectra is also examined. The proposed implementation is simple to build, robust and offers a real improvement over THz instrumentation due to the frequency tuning. Additionally, it provides for galvanic isolation and ESD protection.

  9. Design of DC chopper power supply based on UC3842%基于UC3842直流斩波电源的设计

    Institute of Scientific and Technical Information of China (English)

    缪仲翠; 张海明

    2012-01-01

    为了给交流传动窄轨电机车的辅助设备提供直流电源,针对实际的需要利用电流型脉宽调制器UC3842设计了直流斩波电源,介绍了电流型脉宽调制器UC3842的基本原理,同时也介绍了基于UC3842直流斩波电源设计原理及应用.%To provide DC power to auxiliary equipment of AC narrow-gauge electric locomotive, a chopper power supply based on the current mode PWM controller UC 3842 was designed in order to satisfy the need of actual. The basic principle of UC3842 was introduced, and also the principles and applications of the design were given.

  10. Optimization of the proton chopper for {sup 7}Li(p,n) neutron spectrometry using a {sup 3}He ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Matysiak, W., E-mail: matysiw@mcmaster.c [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON, L8S 4K1 (Canada); Chettle, D.R.; Prestwich, W.V.; Byun, S.H. [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON, L8S 4K1 (Canada)

    2011-02-11

    Thick target {sup 7}Li(p,n) neutron spectra were measured with a {sup 3}He ion chamber in the proton energy region between 1.95 and 2.3 MeV using the McMaster pulsed accelerator neutron source. The pulsed neutron beam was produced by an electrostatic proton chopper to reject the slow neutron detection events, which seriously limit the fast neutron counting rate of the {sup 3}He ion chamber. To collect both arrival time and energy information of {sup 3}He detection events, a custom two-dimensional time-energy analyzer was built using a time scaler and a successive approximation peak-sensing ADC. At each proton energy, the optimum chopper operation was determined by taking into account the two competing requirements: high fast-to-slow neutron ratio and reasonable fast neutron counting rate. The proton pulse widths used were 10 {mu}s for 1.95 and 2.1 MeV proton energies, whereas a shorter, 5 {mu}s proton pulse was used for 2.3 MeV acquisition. The raw data were analyzed using three spectral unfolding methods: a simple division by detection efficiency, an iterative algorithm, and a regularized constrained inversion method. The three methods gave consistent neutron fluence spectra within 20% above 30 keV. Thanks to the enhanced fast-to-slow neutron ratio of the pulsed beam, the full detector response function could be employed in unfolding, which led to an extension of the dynamic energy range as well as a better stability of unfolding process in the low energy region.

  11. Chopper mode analysis of beam distribution based on time in HIRFL%兰州重离子加速器分时供束的Chopper模式解析

    Institute of Scientific and Technical Information of China (English)

    姜子运; 张玮; 安石; 陈云; 武俊奇; 杨锋; 顾可伟; 李朋

    2011-01-01

    Chopper is an important equipment in beam distribution system based on time of heavy ion research facility in Lanzhou(HIRFL). This paper introduces its mode analysis system's architecture and hardware composition, analyzes correspond ing software requirements, and designs the mode analysis program using multithreading technology. Firstly the program reads mode pulse data of chopper from data acquisition card by NI-DAQmx function, then uses the data for further analysis, and finally sends corresponding work mode control instruction to chopper controller through TCP/IP protocol. The designed program meets system requirements, realizing the function of chopper mode automatic conversion, and has passed the field test.%介绍了兰州重离子加速器分时供束系统中Chopper模式解析子系统的体系结构及硬件组成,分析了软件需求,并采用多线程技术设计了Chopper模式解析程序.首先使用NF-DAQmx函数实时读取PXI6133数据采集卡上采集的Chopper模式脉冲,然后对其作进一步分析,最后使用TCP/IP协议将相应的工作模式控制指令发送给控制器.设计的程序达到了系统要求,实现了Chopper模式自动转换的功能,并通过了现场测试.

  12. A Vector Switching Method of Multiphase Chopper in Superconducting Magnetic Energy Storage Systems%超导磁储能系统用多相斩波器矢量切换控制方法

    Institute of Scientific and Technical Information of China (English)

    施啸寒; 王少荣; 左文平

    2013-01-01

    在高功率超导磁储能装置(superconducting magnetic energy storage,SMES)中,电压源型功率调节系统首先利用多相斩波器将超导磁体电流转化成稳定的直流电压,再利用后级电压源型变流器(voltage source converter,VSC)与交流%In the high power superconducting magnetic energy storage (SMES) device, the voltage source converter (VSC) based power conditioning system (PCS) first converts the current of the superconducting magnetic to a stable DC voltage with the help of a multiphase chopper, and then utilizes a VSC to communicate power with the AC system. However, in the situation when the power communication between SMES and the grid changes too fast, a multiphase chopper with traditional current-self-shared PI controller has some problems such as the DC voltage deviation and transient current unbalance. The DC voltage deviation will further exert adverse effects on the control accuracy and speed of the succeeding VSC. To overcome these problems, this paper deduces the switching-function model of the multiphase chopper, and proposes a vector-switching-based control method using the deduced model. This method utilizes the hysteresis to switch the control vector to realize the DC voltage control, at the same time utilizes the redundant switch combinations of a control vector to realize the current sharing. Simulation shows that the proposed method can eliminate the DC voltage deviation when the power communication suddenly changing, and thus, provides a favorable condition for the fast and accurate control of the VSC. Besides, the proposed method can also realize current-sharing of the multiphase chopper in most of the situations, and therefore ensure the long-term operation of the system reliably.

  13. An Experimental Study of Choppers from the Yuzui Paleolithic Locality 2,Yunxian, Hubei Province%湖北郧县余嘴2号地点砍砸器的实验研究

    Institute of Scientific and Technical Information of China (English)

    陈慧; 陈胜前

    2012-01-01

    Experimental study is a fundamental method in lithic analysis to understand the strategy behind exploitation of raw materials, technological process,and past lithic functions.It is particularly useful to conductexperiments with raw materials from the cultural strata and neighboring areas of the archaeological site. In this paper, replication and use experiments of choppers were done at the Yuzui Paleolithic Locality 2 during the excavation season. In terms of replication we made 100 choppers from local gravels (from the cultural strata N=50; and from nearby site surfaces N=50). Then, we using the replicated choppers we cut fresh boughs according to raw material, chopper size and cutting edge angle. We then compared experimental results with artifacts. This work produced several interesting conclusions. First, sandstone was not a useable raw material for chopper manufacture, flint was much better. Interestingly, ancient peoples used more hornfel and quartzite, which were relatively abundant in the local area. Second, our replication experiments suggest that the anvil technique is fairly effective in chopper manufacture, but many site artifacts showed examples of free-hand percussion. The difference in technique probably related to the larger muscle strength of ancient people. Third, the use experiment indicated that there was an optimal axis of force and holding posture , as well as an optimal length of cutting edge. Examination of archaeological choppers confirmed our observation of this optimal holding posture and cutting edge with the used length of cutting edges usually no more than 6 centimeters.Based on this research, we further discuss the meaning of so-called chopper tradition and the functional interpretations of choppers. As a type of expedient tool, the chopper is characterized by a form of simple technology. As shown at the Yuzui Paleolithic Locality 2, free-hand percussion was used rather than anvil technique. The priority in ease in acquiring raw

  14. 基于Buck交-交斩波器的无功补偿器拓扑与控制方法设计%Topology and Control Strategy Design for Buck AC-AC Chopper Based Var Compensators

    Institute of Scientific and Technical Information of China (English)

    武伟; 谢少军; 汤雨; 许津铭

    2013-01-01

    首先介绍了一种新的交流斩波型无功补偿器,无需直流储能环节,系统可靠性得到加强.以Buck型交流斩波无功补偿器为对象,分析了交流斩波无功补偿的基本原理和补偿特性,推导出占空比与补偿电流之间的关系,建立了系统分析模型.在此基础上,提出了基于广义积分的直接电流控制策略,并给出了参数设计准则,最后进行了仿真和实验验证.仿真和实验结果表明,基于直接电流控制的Buck型交流斩波无功补偿器可以实现对网侧无功功率的实时补偿.%A new AC-AC chopper based var compensator is proposed. It does not require the DC-link energy storage and can effectively enhance the system reliability. The basic principles and compensation characteristics of the Buck AC/AC chopper based var compensator are described, the relationship between duty ratio and compensation current is derived, and the system analysis model is developed. A new direct current control method based on the second order generalized integral is proposed for the var compensator with detailed design criteria as well. The experimental and simulation results demonstrate that the realtime compensation of reactive power in grid side can be realized by this var compensator based on a direct current controlled Buck AC/AC chopper.

  15. 异步电机转子IGBT斩波调阻调速的准动态模型%Quasi-dynamic model of the rotor IGBT chopper controlled induction motor

    Institute of Scientific and Technical Information of China (English)

    沈天飞; 陈伯时; 龚幼民

    2001-01-01

    转子斩波调阻是异步电机一种简便有效的调速方法,本文提出了一种新型的采用IGBT作斩波管的具有吸收保护作用的斩波回路拓扑结构,并对该系统整流回路的准动态过程进行了详细研究,推导出斩波管占空比与等效电阻之间的非线性函数关系,给出了外接电阻阻值的选择方法。%Rotor chopper control is a simple and effective speed regulation method for induc tion motor. A novel IGBT chopper topology, which can both adjust rotor resistance and protect IGBT efficiently, is presented in this paper. A thorough investigation on the quasi transient state of the rotor rectifying circuit is made, and a nonlinear mapping between the equivalent resistance and the duty cycle is deduced. Furthermore, the method of determining the magnitude of the external resistor is introduced.

  16. Progress with PXIE MEBT Chopper

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, V.; Chen, A.; Pasquinelli, R; Peterson, D.; Saewert, G.; Shemyakin, A.; Sun, D.; Wendt, M.; /Fermilab; Tang, T.; /SLAC

    2012-05-01

    A capability to provide a large variety of bunch patterns is crucial for the concept of the Project X serving MW-range beam to several experiments simultaneously. This capability will be realized by the Medium Energy Beam Transport's (MEBT) chopping system that will divert 80% of all bunches of the initially 5 mA, 2.1 MeV CW 162.5 MHz beam to an absorber according to a pre-programmed bunch-by-bunch selection. Being considered one of the most challenging components, the chopping system will be tested at the Project X Injector Experiment (PXIE) facility that will be built at Fermilab as a prototype of the Pojrect X front end. The bunch deflection will be made by two identical sets of travelling-wave kickers working in sync. Presently, two versions of the kickers are being investigated: a helical 200 Ohm structure with a switching-type 500 V driver and a planar 50 Ohm structure with a linear {+-} 250 V amplifier. This paper describes the chopping system scheme and functional specifications for the kickers, present results of electromagnetic measurements of the models, discuss possible driver schemes, and show a conceptual mechanical design.

  17. Modeling and Simulation of Photovoltaic Energy Storage System Based on Current Reversible Chopper Circuit%基于电流可逆斩波电路的光伏储能系统建模与仿真

    Institute of Scientific and Technical Information of China (English)

    苏人奇; 任国臣; 程海军

    2016-01-01

    Aiming at the problem of the instability of the battery charging current in the energy storage systemcaused bythe randomness and volatility of the photovoltaic power generation system, the theoretical basis and circuit structure of the supercapacitor and battery hybrid energy storage based on the current reversible chopper circuitisstudied. Firstly, the shortcomings of the existing hybrid energy storage system and the advantages of the current reversible chopper circuitareanalyzed in theory. This circuit can adjust the input voltage and control current direction by controlling the working state of thethyristorsto achieve theenergytransferbetweensupercapacitor and battery. Secondly, a reasonable simulation experimentisdesigned to verify the hybrid energy storage structure of the current reversible chopper circuit in the MATLAB, which can make the charge current and voltage of the lead acid battery more stable.%针对由于光伏发电系统出力的随机性和波动性而导致的储能系统中蓄电池充电电流不稳定的问题,研究了基于电流可逆斩波电路的超级电容器和蓄电池混合储能的理论依据和电路结构。首先在理论上分析了现有混合储能系统并联方式的不足以及电流可逆斩波电路的优势,该电路通过控制开关管的工作状态来调节输入侧的电压及控制电流方向,实现超级电容器和蓄电池之间能量的转移。其次,通过在 MATLAB 上建立电路模型,设计合理的仿真实验,验证了经电流可逆斩波电路并联的混合储能结构,能使铅酸蓄电池的充电电流和电压更稳定。

  18. Determination of efficiencies, loss mechanisms, and performance degradation factors in chopper controlled dc vehical motors. Section 2: The time dependent finite element modeling of the electromagnetic field in electrical machines: Methods and applications. Ph.D. Thesis

    Science.gov (United States)

    Hamilton, H. B.; Strangas, E.

    1980-01-01

    The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.

  19. Single-phase dynamic voltage restorer based on a new chopper AC/DC/AC conversion%一种新型斩波 AC/DC/AC 变换的单相 DVR

    Institute of Scientific and Technical Information of China (English)

    巫付专; 侯婷婷; 韩梁; 冯占伟

    2015-01-01

    针对输入侧采用不可控整流AC/DC/AC结构的单相动态电压恢复器( DVR )输入侧功率因数低,谐波含量高等问题,提出了一种基于PWM斩波变换器的动态电压恢复器来补偿负载两端电压的跌落。该新型拓扑结构采用PWM斩波控制节省了直流侧电容,简化了滤波器设计,使输入侧线路中谐波含量降低,同时达到单位功率因数;电压检测采用单相信号构造成两相信号,利用瞬时无功理论对信号进行检测与处理,实时性高;搭建MATLAB/Simulink仿真和系统实验平台,验证其合理性和可行性。%In view of such problems as the low input side power factor of the single-phase dynamic voltage restorer ( DVR) with the structure of uncontrolled rectifier AC/DC/AC and high harmonic content , this paper proposed a DVR based on the PWM chopper to compensate for the voltage drop at the two load ends .The new topology , which a-dopted the PWM chopper control , saved the DC capacitor and simplified the filter design so that the harmonic content in the input-side circuit was reduced and the input side achieved the unit power factor .Single-phase signals were con-structed into two-phase signals to detect voltage and the instantaneous reactive power theory was used to detect and process the signals , which attained high real time .Finally, a MATLAB/Simulink simulation and experimental plat-form was constructed to verify the rationality and feasibility of the new structure .

  20. 永磁同步发电机与Boost斩波型变换器非线性速度控制%Nonlinear Speed Control for a Permanent Magnet Synchronous Generator and the Boost-Chopper Converter

    Institute of Scientific and Technical Information of China (English)

    耿强; 夏长亮; 王志强; 史婷娜

    2012-01-01

    直驱式永磁同步风电系统电机侧变换器的一种常见拓扑结构为二极管整流桥后接Boost斩波电路。此结构具有较强的非线性,采用普通PI控制器很难使系统在正常运行范围内保持较好的动态性能。针对其非线性特性,分区间建立了发电机与变换器整体非线性数学模型,在单区间内采用输入-输出反馈线性化方法将非线性系统转换为线性系统,在此基础上设计了转速最优控制器。该设计方法数学转换过程较为简单,参数整定方法较为成熟,且不同区间内线性控制器的参数相同。通过一套3kVA的实验系统,验证了该方法能明显改善系统动态性能,对此类风电系统电机侧变换器控制策略的设计具有一定的参考价值。%A diode bridge rectifier followed by a boost chopper circuit is a common topology of the generator side converter for a direct driven permanent magnet synchronous generator(PMSG)-based wind energy conversion system(WECS).Owing to its strong nonlinearity,it is difficult for the system to maintain good dynamic performance within a normal operating range under the ordinary proportional-integral(PI) controller.According to its nonlinear characteristics,the piecewise nonlinear mathematical model for the whole system including the surface permanent magnet synchronous generator(SPMSG) and the generator side converter is built.Then the nonlinear mathematical model is transformed into a linear one by the input-output feedback linearization(IOFL) method.In addition,a speed controller is designed based on the optimal control theory.The proposed strategy has the advantages of a simple conversion process,a relatively mature parameter tuning method and unchanged parameters for the linear optimal controller within different intervals.Experimental results are presented with a 3kVA prototype,verifying the effectiveness and practicability of the proposed strategy.

  1. Choppers Grounded: The Supply-Demand Problem

    Science.gov (United States)

    1988-01-01

    Mtulleni focuses in this essaxy on the availabl~Iitv of it si iigle. h ioh - tehnooy weapon system --the lii 1-ti)i i t’leI p ter. In an opening sc;enar io...priorities iind~ spend more for defense. Mobilization of US forces, in all lWelHOoM "dl ý!eMmerate a global miobilization of thme Free k\\orld which. in) turn... mobilized nation to one, with extreniely limited MO- hilIizat ion potential o(:curedl over it 30-year period. As t he overwhel muinxgly major holder of

  2. THE PECULIARITIES OF GRAIN DEFORMATION BY CHOPPERS WORKING PARTS

    Directory of Open Access Journals (Sweden)

    Semenikhin A. M.

    2014-03-01

    Full Text Available In this article we have given the description of grain deformation under grinding according to its visco-elastic peculiarities. The relations of time, deformation rate, dynamic coefficient and geometric parameters of the working disks having original design have been shown

  3. Polarization analysis for the thermal chopper spectrometer TOPAS

    Directory of Open Access Journals (Sweden)

    Voigt Jörg

    2015-01-01

    Full Text Available We report on the progress of the construction of the thermal time-of-flight spectrometer with polarization analysis TOPAS at the Mayer-Leibnitz Zentrum (MLZ. The instrument components approach the status to be ready for installation. The special feature of the instrument is its capability for wide-angle polarization analysis in the thermal spectral range. Here we describe a novel approach to rotate the neutron spin adiabatically into the X, Y or Z direction of the laboratory frame by combination of permanent magnets aligned as Halbach rings and electrically generated fields. Despite the severe spatial restrictions the design exhibits a very high adiabaticity and interacts only weakly with the coil layout for the analyzing 3He spin filter cell (SFC.

  4. A Novel Chopper Circuit Having Divided Multi-load

    Science.gov (United States)

    Yamamoto, Isamu; Matsui, Keiju; Mori, Hideki; Yao, Yugo

    A dc-dc converter is being widely used for various household appliances and for industry applications. The dc-dc converter is powered from single battery, and the voltage is varied according to the purpose. In the vehicle, various accessories whose electric power is different are being used. Thus, plural number of dc-dc converter should be provided, so these situations bring complicated circuits, and accordingly, higher cost. Moreover, this is not limited to the vehicle applications. For instance, for analog circuits and digital circuits, various power supplies with different voltages are used sometimes. Under such backgrounds, in this paper, we propose a novel dc-dc converter with simply circuit configuration which can supply to two or more different output loads. This converter can control output voltages by controlling duty ratio by using typically two switching devices, which is composed by single boost-switch and single buck-switch. The output voltage can be controlled widely. A few modified circuits developed from the fundamental circuit are represented including the general multi-load circuit. Theoretical equations are solved, where results are confirmed by simulations and experiments.

  5. Extracting source parameters from beam monitors on a chopper spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Abernathy, Douglas L [ORNL; Niedziela, Jennifer L [ORNL; Stone, Matthew B [ORNL

    2015-01-01

    The intensity distributions of beam monitors in direct-geometry time-of-flight neutron spectrometers provide important information about the instrument resolution. For short-pulse spallation neutron sources in particular, the asymmetry of the source pulse may be extracted and compared to Monte Carlo source simulations. An explicit formula using a Gaussian-convolved Ikeda-Carpenter distribution is given and compared to data from the ARCS instrument at the Spallation Neutron Source.

  6. Improving Low Voltage Ride Through Capability of Wind Farm Grid-Connected via Dynamic Chopper Controlled Breaking Resistor Based MMC-HVDC Transmission System%含动态直流泄能电阻的MMC-HVDC提高风电场低电压穿越能力研究

    Institute of Scientific and Technical Information of China (English)

    李文津; 汤广福; 康勇

    2014-01-01

    提出了基于动态直流泄能电阻的模块化多电平柔性输电直流方案,以提高基于感应双馈电机风电场的低电压穿越能力。基于矢量控制及无源电压跟随控制分别设计了系统侧、风场侧柔性直流换流器在风电场稳态运行时的控制策略。当交流系统故障导致电压跌落时,详细分析了动态直流泄能电阻的工作原理、动作判据及导通持续时间,以实现风电场低电压穿越;同时研究了其与系统侧模块化多电平换流器在故障清除后电压恢复期的协调控制,以快速恢复风电场有功输出能力。仿真结果表明:当交流系统故障时,含动态直流泄能电阻的柔性直流输电系统能够维持直流电压且不改变风电场输出电压电流;当故障清除后,风电场输出功率恢复速率远大于电力系统行业标准相关技术指标。%A modular multilevel voltage sourced converter-based HVDC (MMC-HVDC) power transmission scheme based on dynamic chopper controlled breaking resistor (DCCBR) is proposed to improve the low-voltage ride through (LVRT) capability of wind farm composed of doubly fed induction generators (DFIG). Based on vector control and network voltage tracing control the control strategies for grid side modular multilevel converter (GSMMC) and wind farm side modular multilevel converter (WFMMC) under steady state operation of wind farm are designed respectively. Under voltage sag caused by fault in AC power grid, the working principle, operating criterion and turn-on duration time of DCCBR are analyzed in depth to realize LVRT of wind farm;meanwhile, to recover the active power output capability of wind farm rapidly the coordinated control for DCCBR and GSMMC during the voltage recovery after clearing of the fault is researched. Simulation results show that during the fault in AC power grid the flexible HVDC transmission system containing DCCBR can maintain the DC voltage of HVDC system while

  7. A CMOS detection chip for amperometric sensors with chopper stabilized incremental ΔΣ ADC

    Science.gov (United States)

    Min, Chen; Yuntao, Liu; Jingbo, Xiao; Jie, Chen

    2016-06-01

    This paper presents a low noise complimentary metal-oxide-semiconductor (CMOS) detection chip for amperometric electrochemical sensors. In order to effectively remove the input offset of the cascaded integrators and the low frequency noise in the modulator, a novel offset cancellation chopping scheme was proposed in the Incremental ΔΣ analog to digital converter (IADC). A novel low power potentiostat was employed in this chip to provide the biasing voltage for the sensor while mirroring the sensor current out for detection. The chip communicates with FPGA through standard built in I2C interface and SPI bus. Fabricated in 0.18-μm CMOS process, this chip detects current signal with high accuracy and high linearity. A prototype microsystem was produced to verify the detection chip performance with current input as well as micro-sensors. Project supported by the State Key Development Program for Basic Research of China (No. 2015CB352100).

  8. Design Optimization of the Fast Switched Chopper Dipole Magnet for the MedAustron Project

    CERN Document Server

    AUTHOR|(CDS)2083482; Borburgh, Jan

    The MedAustron hadron therapy centre currently under construction in Wiener Neustadt, Austria, is a synchrotron based accelerator facility for cancer treatment with protons and carbon ions. The concept for such a machine first originated at the European Organization for Nuclear Research (CERN) in 1999 as the Proton-Ion Medical Machine Study (PIMMS). The first centre based on this concept was the National Centre for Oncological Treatment (CNAO) built in Italy, which treated its first patient in November 2012. The MedAustron accelerator complex consists of three particle sources, a linear accelerator, a synchrotron, an extraction line, and four irradiation rooms (1 experimental area with horizontal fixed beam, 2 fixed beam line rooms (one horizontal, and one horizontal and vertical) and a rotating gantry treatment room). It will be capable of accelerating 1H+ protons to energies of 60-250 MeV for clinical purposes, and up to 800 MeV for research purposes. It will also accelerate 12C6+ carbon ions to energies of...

  9. Parameterization of a synchronous generator to represent a doubly fed induction generator with chopper protection for fault studies

    DEFF Research Database (Denmark)

    Martinez, Jorge; Kjær, Philip C.; Rodriguez, Pedro

    2011-01-01

    knowledge of the wind turbine short circuit current contribution is needed for component sizing and protection relay settings during faults within the wind power plant collector system or in the external networks. When studying fault currents and protection settings for wind power installations...

  10. Momentum and Energy Dependent Resolution Function of the ARCS Neutron Chopper Spectrometer at High Momentum Transfer: Comparing Simulation and Experimen

    CERN Document Server

    Diallo, S O; Abernathy, D L; Azuah, R T

    2016-01-01

    Inelastic neutron scattering at high momentum transfers (i.e. $Q\\ge20$ {\\AA}) or DINS provides direct observation of the momentum distribution of light atoms, making it a powerful probe for studying single-particle motions in liquids and solids. The quantitative analysis of DINS data requires an accurate knowledge of the instrument resolution function $R_{i}({Q},E)$ at each $Q$ and energy transfer $E$, where the label $i$ indicates whether the resolution was experimentally observed $i={obs}$ or simulated $i=sim$. Here, we describe two independent methods for determining the total resolution function $R_{i}({Q},E)$ of the ARCS neutron instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. The first method uses experimental data from an archetypical system (liquid $^4$He) studied with DINS, which are then numerically deconvoluted using its previously determined intrinsic scattering function to yield $R_{obs}({Q},E)$. The second approach uses accurate Monte Carlo simulations of the ARCS spec...

  11. From scootes to choppers : Product protfolio change and organizational failure - Evidence from the UK motorcycle industry 1895 to 1993

    NARCIS (Netherlands)

    Wezel, FC; van Witteloostuijn, A

    2006-01-01

    This article explores the conditions under which organizational change increases the risk of organizational failure. To reach this goal, we examine the pros and cons of flexibility and inertia arguments. Empirically, we measure the survival consequences of product portfolio expansion in the British

  12. Momentum and energy dependent resolution function of the ARCS neutron chopper spectrometer at high momentum transfer: Comparing simulation and experiment

    Science.gov (United States)

    Diallo, S. O.; Lin, J. Y. Y.; Abernathy, D. L.; Azuah, R. T.

    2016-11-01

    Inelastic neutron scattering at high momentum transfers (i.e. Q ≥ 20 A ˚), commonly known as deep inelastic neutron scattering (DINS), provides direct observation of the momentum distribution of light atoms, making it a powerful probe for studying single-particle motions in liquids and solids. The quantitative analysis of DINS data requires an accurate knowledge of the instrument resolution function Ri(Q , E) at each momentum Q and energy transfer E, where the label i indicates whether the resolution was experimentally observed i = obs or simulated i=sim. Here, we describe two independent methods for determining the total resolution function Ri(Q , E) of the ARCS neutron instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. The first method uses experimental data from an archetypical system (liquid 4He) studied with DINS, which are then numerically deconvoluted using its previously determined intrinsic scattering function to yield Robs(Q , E). The second approach uses accurate Monte Carlo simulations of the ARCS spectrometer, which account for all instrument contributions, coupled to a representative scattering kernel to reproduce the experimentally observed response S(Q , E). Using a delta function as scattering kernel, the simulation yields a resolution function Rsim(Q , E) with comparable lineshape and features as Robs(Q , E), but somewhat narrower due to the ideal nature of the model. Using each of these two Ri(Q , E) separately, we extract characteristic parameters of liquid 4He such as the intrinsic linewidth α2 (which sets the atomic kinetic energy ∼α2) in the normal liquid and the Bose-Einstein condensate parameter n0 in the superfluid phase. The extracted α2 values agree well with previous measurements at saturated vapor pressure (SVP) as well as at elevated pressure (24 bars) within experimental precision, independent of which Ri(Q , y) is used to analyze the data. The actual observed n0 values at each Q vary little with the model Ri(Q , E), and the effective Q-averaged n0 values are consistent with each other, and with previously reported values.

  13. Design Considerations for an MEBT Chopper Absorber of 2.1 MeV H- at the Project X Injector Experiment at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Baffes, C.; Awida, M.; Chen, A.; Eidelman, Y.; Lebedev, V.; Prost, L.; Shemyakin, A.; Solyak, N.; Yakovlev, V.; /Fermilab

    2012-05-14

    The Project X Injector Experiment (PIXIE) will be a prototype of the Project X front end that will be used to validate the design concept and decrease technical risks. One of the most challenging components of PIXIE is the wide-band chopping system of the Medium Energy Beam Transport (MEBT) section, which will form an arbitrary bunch pattern from the initially CW 162.5 MHz 5mA beam. The present scenario assumes diverting 80% of the beam to an absorber to provide a beam with the average current of 1mA to SRF linac. This absorber must withstand a high level of energy deposition and high ion fluence, while being positioned in proximity of the superconductive cavities. This paper discusses design considerations for the absorber. Thermal and mechanical analyses of a conceptual design are presented, and future plans for the fabrication and testing of a prototype are described.

  14. D类音频系统中斩波运放电路的设计%Design of A chopper OPAMP in CLASS-D Audio System

    Institute of Scientific and Technical Information of China (English)

    徐光煜; 颜永红

    2009-01-01

    本文提出了一种应用于D类音频系统的低噪声斩波运放电路.该电路主运放采用全差分电路结构,具有很高的PSRR和电压摆幅,同时采用T/H解调技术,有效地降低了低频噪声和残余电压失调.仿真结果表明在5V电源电压下,斩波频率150KHz时,输入等效噪声为31.12nV/√Hz,满足D类功放的要求.该电路已在SMIC 0.3Sum N阱工艺上MPW流片成功,功能测试正常.

  15. Design and optimization of a double-disk chopper%双盘斩波器的设计与优化

    Institute of Scientific and Technical Information of China (English)

    李新喜; 黄朝强; 王燕; 陈波

    2008-01-01

    中子双盘位相斩波器目前广泛地应用于中子散射设备上,其作用是将连续中子束斩成脉冲中子束.本文结合拟建飞行时间模式中子反射谱仪,详细介绍了中子双盘位相斩波器的设计,并从原理上对斩波器主要物理参数进行了优化,采用McStas程序对其中子注量率情况进行了模拟计算,为斩波器设计制造提供参考.

  16. 盘间距可调斩波器设计及模拟%Design and simulation of a space-adjustable chopper

    Institute of Scientific and Technical Information of China (English)

    李新喜; 王燕; 黄朝强; 陈波

    2010-01-01

    不同实验样品精度需求对中子反射谱仪的分辨要求不同.为实现反射谱仪中的中子斩波器的斩波特性可调,斩波器设计采用四斩盘结构.设计原理主要是变换使用第三和第四斩盘,利用第三盘和第四盘与第二盘问距的不同,结合斩盘转速的调节,实现斩波特性可调.运用Mcstas程序软件模拟计算,获得客观物理条件下相关物理参数对脉冲注量率及脉冲水平发散度的影响曲线.计算结果可为水平散射几何中子反射谱仪中四盘斩波器的理论设计及相关物理参数的选择提供理论参考.

  17. CMOS磁场传感器芯片中斩波放大器的设计%CMOS Chopper Amplifier for Monolithic Magnetic Hall Sensor

    Institute of Scientific and Technical Information of China (English)

    宁伟超; 程东方; 张春燕; 王书凯

    2007-01-01

    介绍了一个应用在无刷电机上的开关式磁敏传感器中的高灵敏度斩波放大器的设计,它能够有效地放大Hall片产生的低频微弱信号.该电路应用斩波技术抑制放大器的低频噪声和失调,采用跟踪-保持解调器进一步减少由调制器开关引起的残余失调.在Candence环境下用1.5μ CMOS工艺模型进行仿真,该放大器能有效的消除5 mV的输入失调电压且能减少由调制器开关引起的残余失调,而不需要任何的滤波器.

  18. Weld Technology Improvement of Purple Copper Water-Cooled Radiator Used in High-Power Chopper%大功率斩波器紫铜水冷散热器焊接加工工艺改进

    Institute of Scientific and Technical Information of China (English)

    祝乐

    2003-01-01

    本文通过对大功率斩波器紫铜水冷散热器的焊接工艺、技术进行分析研究,得出了一种新型实用的直流反接焊接技术.解决了类似大型水冷散热器在防渗漏焊接技术方面的难题,并进行了可行性验证.

  19. Research on Mechanical Characteristics of AC Motor with Cascade DC Chopper Speed Control System%斩波串级调速系统电机机械特性曲线的研究

    Institute of Scientific and Technical Information of China (English)

    王归新; 裴合伟; 晓琼; 鲜万春

    2012-01-01

    In high power application, wound AC motor rotor loop cascade control system has very good speed performance and energy-saving effect. Based on the analysis that the equivalent internal impedance of three-phase rectifier bridge influence rectifier output,rectifier bridge and follow-up circuit equivalent to the mo-tor rotor loop resistance, inferred to the mechanical characteristics in the cascade control system.Came to con-clusion that two influence factors for mechanical characteristics. The rotor loop equivalent impedance is more serious than rotor leakage reactance effect commutation overlap angle to mechanical characteristics influence. The simulation and the experiment verify the theory.%绕线转子式交流电机转子回路串级调速系统具有很好的调速性能和节电效果,在中大功率领域应用较多.基于对三相整流电路电源等效内阻抗对桥路整流输出的影响分析,将整流桥及其后续电路等效为电机转子回路的电阻,推导出在有串级调速系统下电机的机械特性,得出了影响电机机械特性的两方面因素,其中转子回路的等效阻抗对机械特性的影响相对于转子漏抗影响换相重叠角对机械特性的影响尤为严重的结论.仿真结果证实了理论推导的结论,并进行了实验验证.

  20. Simulation of Chopper Cascade Adjustable Speed System Based on PWM Rectifier%基于PWM整流技术的斩波串级调速系统的仿真

    Institute of Scientific and Technical Information of China (English)

    祝龙记; 周森

    2012-01-01

    A rotor-side chop cascade adjustable speed system based on PWM rectifier was proposed.The PWM rectifier worked on inverter condition and returns slip power of the rotor;this could not only improve the power factor of the system,but also reduce harmonic content of net-side.In Matlab/Simulink,the simulation model of chop cascade adjustable speed system was established.The reasonability and validity were testified by the coincidence of the simulation and experimentation results and theory analysis.%提出将PWM整流技术引入转子侧斩波串级调速系统中,PWM整流器工作于逆变状态回馈转差功率,不仅可以提高串级调速系统的功率因数,还可以减少网侧的谐波含量。在Matlab/Simulink环境下给出了基于PWM整流技术的斩波串级调速系统的仿真模型,最后通过仿真实验验证了控制方案的正确性。

  1. 基于电压型PWM整流器的新型内馈斩波串级调速系统%New Feeding Chopper Cascade Adjustable Speed System Based on PWM Voltage Rectifier

    Institute of Scientific and Technical Information of China (English)

    杨磊; 张敏; 江博

    2011-01-01

    提出一种新型的内馈斩波串级调速系统,将PWM整流技术引入串级调速系统中,不仅有效提高串级调速系统的功率因数和减少网侧谐波含量,而且排除了逆变颠覆的故障.介绍了电压型PWM整流器的工作原理和控制策略,并通过MATLAB仿真进行了验证.

  2. Triple-disk chopper design of horizontal neutron scattering reflectometer%水平散射几何中子反射谱仪的三盘斩波器设计

    Institute of Scientific and Technical Information of China (English)

    李新喜; 黄朝强; 王燕; 陈波

    2009-01-01

    为提高水平散射几何中子反射谱仪分辨,希望谱仪前端的中子斩波器能斩出脉冲强度大水平发散度较小的中子脉冲束流,采用新设计的三斩盘斩波器模型,运用Mcstas程序软件考察了不同物理参数下三盘斩波器的中子斩波特性.获得了特定物理条件下相关物理参数对束流强度和发散度的影响关系曲线.计算结果可为水平散射几何中子反射谱仪中三盘斩波器的设计及物理参数的选择提供理论依据.

  3. Design of Hybrid Maglev System Based on 4 Quadrant Chopper%基于四象限斩波器的混合磁悬浮系统设计

    Institute of Scientific and Technical Information of China (English)

    廖长鑫; 张俊; 陈国辉; 王莉

    2006-01-01

    针对单一的电磁吸力型磁悬浮系统能耗大、悬浮气隙小的问题,提出采用能耗小、可实现大气隙悬浮的永久磁铁和常导线圈构成的混合式磁悬浮系统的方案.阐述了能满足混合磁悬浮系统负向电流需要的H型四象限斩波器的原理,介绍了基于DSP和CPLD的保护电路和控制器.试验表明,混合磁悬浮系统悬浮过程中和负重变化时都能很快达到稳定悬浮,悬浮气隙可达到20~30 mm,并且负载电流小.

  4. Simulation of AC Chopper Feeding Single-phase Motors with Semihex~(TM) Connection%AC斩波器-Semihex~(TM)接法单相电动机调速系统仿真研究

    Institute of Scientific and Technical Information of China (English)

    罗德荣; 邓建国; 罗隆福

    2010-01-01

    着重研究了AC斩波调压器在Semihex~(TM)接法单相电动机中的应用,建立了AC斩波器-semihex~(TM)接法单相电动机调速系统的瞬态数学模型,对单相buck型对称PWM交流斩波调压器供电的Semihex~(TM)接法单相电动机的瞬态特性进行了仿真计算,仿真结果与理论分析相符.对正弦波电源供电和AC斩波调压器供电的仿真结果进行了比较分析,所做的工作对AC斩波调压器一三绕组单相电容电动机调速系统设计有一定的工程实际意义和参考价值.

  5. Design and experiment on banana stalk chopper with feeding type spindle flail%喂入式立轴甩刀香蕉秸秆粉碎还田机设计与试验

    Institute of Scientific and Technical Information of China (English)

    甘声豹; 李粤; 张喜瑞; 张国健; 王能

    2014-01-01

    由于香蕉秸秆粗大、含水率高,现有的粉碎还田机大多操作繁琐、作业不稳定。针对上述问题,研制了一种喂入式立轴甩刀香蕉秸秆粉碎还田机,描述了该机的总体设计方案及主要部件的结构,分析了各部件之间的相互关系,确定了其关键参数的最优值。试验结果表明:该机在前进速度为2.16~3.60 km/h、压辊进料转速为127.39 r/min、立轴甩刀旋转速度为1080 r/min时,秸秆粉碎质量合格率达94.9%、田间覆盖率达88.61%、茎杆留茬高度为30~35 mm,一次作业可将秸秆粉碎成丝状残渣,且残渣抛洒还田均匀。试验结果对解决因秸秆难处理而制约农村合作社小规模种植的难题具有重要意义。%Bananas occupy an extremely important position in the world of fruit trade; it is the most important fruit in tropical and subtropical areas. China is one of the world’s largest producers of bananas, and bananas have become an agricultural pillar industry in China’s subtropical regions. However, the banana stalks are a major agricultural waste. According to the Food and Agriculture Organization (FAO), in 2010, 24 million tons of annual output of waste is banana straw in China. If such a large amount of waste straw is not handled in time, it would seriously pollute the environment and affect the renewal of the banana plantation. Because banana stalks are thick with a high level of moisture and other issues, there are less mature mechanical equipments for banana stalks treatment at the present. There are usually two main types of banana stalk treatment: one is to cut down and pile the stalk in the fields by laborers, and then let it rot; the other one is a centrally smash processing with machines. This kind of machine can achieve a certain crushing effect, but, due to the characteristics of its own design, can't achieve the field operations, and thus brings great inconvenience for the laborers. In view of above situations, according to craft about the banana stalks’ crushing and returning in the field, this study designed a feeding type vertical shaft flail extracting machine for banana stalks’ crushing and returning, and expounded the machine's overall configuration and the main components of the structure, and determined the key parameters of the optimal value through the analysis of the relationship between components and performance test. The machine could work directly in the field under the tractor traction, for the stalks to achieve down, tackle, grab, feed, crush and return. Field experiments showed that: with the speed for forwarding at 2.16 - 3.60 km/h, for the feed roller at 127.39 r/min, and for the vertical sling knife at 1080 r/min, this machine could achieve a qualification rate of straw smashing of 94.9%, field coverage of 88.61%, stem stubble height of 30 - 35 mm, energy consumption of 4.625 kg/h, and working efficiency of 0.39 hm2/h. This machine was easy to operate and its crushing effect was satisfactory. Its successful implementation could not only greatly improve the production efficiency, and solve the problem of large-scale banana cultivation facing massive stalks processing, but also prevent the pollution of the environment and had important economic and ecological benefits.

  6. Summary of electric vehicle dc motor-controller tests

    Science.gov (United States)

    Mcbrien, E. F.; Tryon, H. B.

    1982-01-01

    The differences in the performance of dc motors are evaluated when operating with chopper type controllers, and when operating on direct current. The interactions between the motor and the controller which cause these differences are investigated. Motor-controlled tests provided some of the data the quantified motor efficiency variations for both ripple free and chopper modes of operation.

  7. The performance and efficiency of four motor/controller/battery systems for the simpler electric vehicles

    Science.gov (United States)

    Shipps, P. R.

    1980-05-01

    A test and analysis program performed on four complete propulsion systems for an urban electric vehicle (EV) is described and results given. A dc series motor and a permanent magnet (PM) motor were tested, each powered by an EV battery pack and controlled by (1) a series/parallel voltage-switching (V-switch) system; and (2) a system using a pulse width modulation, 400 Hz transistorized chopper. Dynamometer tests were first performed, followed by eV performance predictions and data correlating road tests. During dynamometer tests using chopper control; current, voltage, and power were measured on both the battery and motor sides of the chopper, using three types of instrumentation. Conventional dc instruments provided adequate accuracy for eV power and energy measurements, when used on the battery side of the controller. When using the chopper controller, the addition of a small choke inductor improved system efficiency in the lower duty cycle range (some 8% increase at 50% duty cycle) with both types of motors. Overall system efficiency rankings during road tests were: (1) series motor with V-switch; (2) PM motor with V-switch; (3) series motor with chopper; and (4) PM motor with chopper. Chopper control of the eV was smoother and required less driver skill than V-switch control.

  8. 三相电压型PWM整流器在内馈斩波串级调速中的应用研究%The Application Research Of the Three-phase PWM Voltage Rectifier in the Inner-feed Chopper Cascade Speed Drive System

    Institute of Scientific and Technical Information of China (English)

    庞科旺; 袁文华; 刘丽丽

    2008-01-01

    把PWM整流技术引入到内馈斩波串级调速系统中,这样不仅可以提高串级调速系统的功率因数和减少交流侧的谐波含量,还可以有效地防止系统的逆变颠覆故障.建立了应用于串级调速系统的电压型PWM整流器的静态解耦模型,以此为基础进行了系统设计,并通过仿真验证了该方案的可行性.

  9. Operating Characteristic Analysis of Permanent Magnet Synchronous Generator with Chopper Circuit Responded to the Power System Short Circuit Fault%含chopper电路的直驱风机响应电网短路的运行特性分析

    Institute of Scientific and Technical Information of China (English)

    刘勇; 麻广林; 宁波; 魏鑫

    2016-01-01

    In order to analyze the operating characteristics of permanent magnet synchronous generator ( PMSG) impacted by the power system short circuit fault, this paper researches maximum wind energy tracking control strat⁃egy of the wind turbine the machine side decoupling control strategy of active and reactive power of the AC⁃DC⁃AC converter and voltage orientation strategy of the gird side by mathematical model. For meeting the wind turbine low voltage ride through ( LVRT) requirement, DC capacitor chooper protection circuit is used. When short⁃circuit fault occurs discharge resistance in chooper circuit can unload the energy, which could maintain the DC capacitor voltage stabilitily. At the same time the reference current limiter can also limit the impaction on the grid side con⁃verter by power system short circuit fault. The PMSG simulation model is constructed in emtp⁃rv platform, and its operating characteristics is simulated in the condition of power system three⁃phase short⁃circuit fault, causing the grid voltage drops below 0. 2. The simulation results verify the control strategy correctly and DC capacitor chooper protection circuit effectively. The results provide the basis for the operating characteristic of the PMSG grid⁃con⁃necting to the power system and the influence of power system short⁃circuit fault on the PMSG.%为了分析电网短路时的直驱风电机组运行特性,从数学模型入手,研究了风轮机最大风能追踪控制策略,以及交直交变频器机侧的有功无功解耦控制策略和网侧的电压定向控制策略。为了满足风电机组的低电压穿越要求,采用了直流电容chooper保护电路。电网短路故障时, chooper回路中的卸能电阻能很大程度地消耗短路冲击带来的能量,从而维持直流电容电压稳定。同时参考电流限值器也限制了短路冲击对网侧变频器的影响。在empt⁃rv中搭建了直驱风机模型,分析了电网三相短路导致并网电压跌落到0.2以下时风电机组的运行特性。仿真结果验证了所采取的控制策略正确性,以及直流电容chooper保护电路的有效性。研究结果对直驱风机并网运行以及电网短路对风机运行特性的影响提供了依据。

  10. A design study of VOR

    DEFF Research Database (Denmark)

    Deen, P. P.; Vickery, Anette; Andersen, K. H.

    2015-01-01

    on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1-3%. Further relaxing the energy resolution enables VOR to gain...... an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM) and is therefore able to measure, in a single ESS period, 6-14 incident wavelengths, across a wavelength band of 9 Å with a novel chopper configuration that transmits all incident wavelengths...

  11. Design of a wavelength frame multiplication system using acceptance diagrams

    CERN Document Server

    Nekrassov, D; Lieutenant, K

    2013-01-01

    The concept of Wavelength Frame Multiplication (WFM) was developed to extend the usable wavelength range on long pulse neutron sources for instruments using pulse shaping choppers. For some instruments, it is combined with a pulse shaping double chopper, which defines a constant wavelength resolution, and a set of frame overlap choppers that prevent spurious neutrons from reaching the detector thus avoiding systematic errors in the calculation of wavelength from time of flight. Due to its complexity, the design of such a system is challenging and there are several criteria that need to be accounted for. In this work, the design of the WFM chopper system for the potential future liquids reflectometer at the European Spallation Source (ESS) is presented, which makes use of acceptance diagrams. They prove to be a powerful tool for understanding the work principle of the system and recognizing potential problems. The authors assume that the presented study can be useful for design or upgrade of further instrument...

  12. High-Performance Operational and Instrumentation Amplifiers

    OpenAIRE

    Shahi, B.

    2015-01-01

    This thesis describes techniques to reduce the offset error in precision instrumentation and operational amplifiers. The offset error which is considered a major error source associated with gain blocks, together with other errors are reviewed. Conventional and newer approaches to remove offset and low frequency noise are discussed, with a focus on the work of this thesis “Chopper-Stabilized Auto-Zeroed Chopper Instrumentation Amplifiers”. The technique is demonstrated through the application...

  13. Unity power factor switching regulator

    Science.gov (United States)

    Rippel, Wally E. (Inventor)

    1983-01-01

    A single or multiphase boost chopper regulator operating with unity power factor, for use such as to charge a battery is comprised of a power section for converting single or multiphase line energy into recharge energy including a rectifier (10), one inductor (L.sub.1) and one chopper (Q.sub.1) for each chopper phase for presenting a load (battery) with a current output, and duty cycle control means (16) for each chopper to control the average inductor current over each period of the chopper, and a sensing and control section including means (20) for sensing at least one load parameter, means (22) for producing a current command signal as a function of said parameter, means (26) for producing a feedback signal as a function of said current command signal and the average rectifier voltage output over each period of the chopper, means (28) for sensing current through said inductor, means (18) for comparing said feedback signal with said sensed current to produce, in response to a difference, a control signal applied to the duty cycle control means, whereby the average inductor current is proportionate to the average rectifier voltage output over each period of the chopper, and instantaneous line current is thereby maintained proportionate to the instantaneous line voltage, thus achieving a unity power factor. The boost chopper is comprised of a plurality of converters connected in parallel and operated in staggered phase. For optimal harmonic suppression, the duty cycles of the switching converters are evenly spaced, and by negative coupling between pairs 180.degree. out-of-phase, peak currents through the switches can be reduced while reducing the inductor size and mass.

  14. RF Modeling of a Helical Kicker for Fast Chopping

    Energy Technology Data Exchange (ETDEWEB)

    Awida, Mohamed [Fermilab; Chen, Alex [Fermilab; Khabiboulline, Timergali [Fermilab; Saewert, Gregory [Fermilab; Yakovlev, Vyacheslav [Fermilab

    2015-06-01

    High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).

  15. Enhanced Performance Neutron Scattering Spectroscopy by Use of Correlation Techniques

    CERN Document Server

    Mezei, F; Migliardo, F; Magazù, S

    2016-01-01

    Neutron correlation spectroscopy can exceed direct spectroscopy in the incoming beam intensity by up to two orders of magnitude at the same energy resolution. However, the propagation of the counting noise in the correlation algorithm of data reduction is disadvantageous for the lowest intensity parts of the observed spectrum. To mitigate this effect at pulsed neutron sources we propose two dimensional time-of-flight recording of each neutron detection event: with respect to both the neutron source pulses and to the rotation phase of the pseudo-random beam modulation statistical chopper. We have identified a formulation of the data reduction algorithm by matching the data processing time channel width to the inherent time resolution of this chopper, which makes the reconstruction of the direct time-of-flight spectra exact and independent of all other contributions to instrumental resolution. Two ways are proposed for most flexible choice of intensity vs. resolution without changing the statistical chopper or ...

  16. The effect of input phase modulation to a phase-sensitive optical amplifier

    CERN Document Server

    Li, Tian; Horrom, Travis; Jones, Kevin M; Lett, Paul D

    2016-01-01

    Many optical applications depend on amplitude modulating optical beams using devices such as acousto-optical modulators (AOMs) or optical choppers. Methods to add amplitude modulation (AM) often inadvertently impart phase modulation (PM) onto the light as well. While this PM is of no consequence to many phase-insensitive applications, phase-sensitive processes can be affected. Here we study the effects of input phase and amplitude modulation on the output of a quantum-noise limited phase-sensitive optical amplifier (PSA) realized in hot $^{85}$Rb vapor. We investigate the dependence of PM on AOM alignment and demonstrate a novel approach to quantifying PM by using the PSA as a diagnostic tool. We then use this method to measure the alignment-dependent PM of an optical chopper which arises due to diffraction effects as the chopper blade passes through the optical beam.

  17. Genome sequence of Kocuria varians G6 ssolated from a slaughterhouse in Denmark

    DEFF Research Database (Denmark)

    Raghupathi, Prem Krishnan; Herschend, Jakob; Røder, Henriette Lyng;

    2016-01-01

    We report here the first draft genome sequence ofKocuria variansG6, which was isolated from a meat chopper at a small slaughterhouse in Denmark. The 2.90-Mb genome sequence consists of 95 contigs and contains 2,518 predicted protein-coding genes.......We report here the first draft genome sequence ofKocuria variansG6, which was isolated from a meat chopper at a small slaughterhouse in Denmark. The 2.90-Mb genome sequence consists of 95 contigs and contains 2,518 predicted protein-coding genes....

  18. Implementation of Brushed DC Motor Control in LabVIEW FPGA

    Directory of Open Access Journals (Sweden)

    K. Lamár

    2013-12-01

    Full Text Available The paper introduces the fundamentals of motor control. It explains the basic equations and introduces the control diagram of the brushed DC motor. It introduces the four quadrant DC chopper circuit and the basic methods to operate it. After that, it explains the fundamentals of the current control of DC motors and its two basic methods: the pulse width modulation and the hysteresis current control. Finally it gives a short example of the practical implementation of the hysteresis current controller for the four quadrant DC chopper in LabVIEW FPGA.

  19. A modified time-of-flight method for precise determination of high speed ratios in molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Salvador Palau, A.; Eder, S. D., E-mail: sabrina.eder@uib.no; Kaltenbacher, T.; Samelin, B.; Holst, B. [Department of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen (Norway); Bracco, G. [Department of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen (Norway); CNR-IMEM, Department of Physics, University of Genova, V. Dodecaneso 33, 16146 Genova (Italy)

    2016-02-15

    Time-of-flight (TOF) is a standard experimental technique for determining, among others, the speed ratio S (velocity spread) of a molecular beam. The speed ratio is a measure for the monochromaticity of the beam and an accurate determination of S is crucial for various applications, for example, for characterising chromatic aberrations in focussing experiments related to helium microscopy or for precise measurements of surface phonons and surface structures in molecular beam scattering experiments. For both of these applications, it is desirable to have as high a speed ratio as possible. Molecular beam TOF measurements are typically performed by chopping the beam using a rotating chopper with one or more slit openings. The TOF spectra are evaluated using a standard deconvolution method. However, for higher speed ratios, this method is very sensitive to errors related to the determination of the slit width and the beam diameter. The exact sensitivity depends on the beam diameter, the number of slits, the chopper radius, and the chopper rotation frequency. We present a modified method suitable for the evaluation of TOF measurements of high speed ratio beams. The modified method is based on a systematic variation of the chopper convolution parameters so that a set of independent measurements that can be fitted with an appropriate function are obtained. We show that with this modified method, it is possible to reduce the error by typically one order of magnitude compared to the standard method.

  20. Determination of the velocity of meteors based on sinodial modulation and frequency analysis

    NARCIS (Netherlands)

    Bettonvil, F.C.M.

    2008-01-01

    In meteor photography the velocity of meteors is generally obtained from a chopper which blocks periodically the incident light beam in front of the camera lens. In this paper I examine modulation of the meteor trail instead with a sinodial function and use frequency analysis to compute accurately t

  1. Q-Switching in a Neodymium Laser

    Science.gov (United States)

    Holgado, Warein; Sola, Inigo J.; Jarque, Enrique Conejero; Jarabo, Sebastian; Roso, Luis

    2012-01-01

    We present a laboratory experiment for advanced undergraduate or graduate laser-related classes to study the performance of a neodymium laser. In the experiment, the student has to build the neodymium laser using an open cavity. After that, the cavity losses are modulated with an optical chopper located inside, so the Q-switching regime is…

  2. A Multifunction Low-Power Preamplifier for MEMS Capacitive Microphones

    DEFF Research Database (Denmark)

    Jawed, Syed Arsalan; Nielsen, Jannik Hammel; Gottardi, Massimo;

    2009-01-01

    A multi-function two-stage chopper-stabilized preamplifier (PAMP) for MEMS capacitive microphones (MCM) is presented. The PAMP integrates digitally controllable gain, high-pass filtering and offset control, adding flexibility to the front-end readout of MCMs. The first stage of the PAMP consists...

  3. CSR Pulsed Switching Power Supplies

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In 2001, CSR power supply system made a great progress. Three prototypes were designed for CSR quadruple and correct magnet. Three different companies provided the three prototypes, but the same circuit-chopper were employed. The simplified diagram is showed in Fig.1. All pulsed switching power supply prototypes were tested successfully before the end of 2001.

  4. Air Power in Irregular Warfare

    Science.gov (United States)

    2012-12-01

    bombardment attacks with fighter offense for the control of the air.”57 Douhet commonly bucked the theory of fighter offense, relying solely on “a...morale booster as well. Now patrols could cut a landing zone with chain saws and explosives to receive a medevac chopper rather than face an extended

  5. Spin waves in antiferromagnetic FeF2

    DEFF Research Database (Denmark)

    Hutchings, M T; Rainford, B.D.; Guggenheim, H J

    1970-01-01

    Spin-wave dispersion in antiferromagnetic FeF2 has been investigated by inelastic neutron scattering using a chopper time-of-flight spectrometer. The single mode observed has a relatively flat dispersion curve rising from 53 cm-1 at the zone centre to 79 cm-1 at the zone boundary. A spin...

  6. Visit to FDI Technology, Saint Petersburg 4-6th December 2006 Travel Report

    CERN Document Server

    Paoluzzi, M

    2006-01-01

    The design and manufacture of the pulse amplifier required for the 3 MeV test stand chopper has been attributed to FID gmbh which is a branch of FID Technology of Saint Petersburg. This visit has been made to monitor the status of the supply.

  7. Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Xu, Honghua

    2014-01-01

    This paper presents a fast coordinated control scheme of the rotor side converter (RSC), the DC chopper and the grid side converter (GSC) of doubly fed induction generator (DFIG) wind turbine generators (WTGs) which is to improve the low voltage ride through (LVRT) and high voltage ride through (...... verified by time domain simulations using MATLAB-Simulink....

  8. Design and performance of the pulsed positron beam at Chalmers University of Technology

    Science.gov (United States)

    Mileshina, L.; Nordlund, A.

    2009-09-01

    A slow monoenergetic pulsed positron beam at Chalmers University of Technology has been built. The system consists mainly of chopper, buncher and accelerator. The achieved positron energy range is in range between 230 eV and 15 keV. The FWHM of the beam resolution function is around 700 ps. The beam intensity is around 103 cps.

  9. Micromanipulatie: Nederlands onderdeel reuzentelescoop doorstaat alle tests

    NARCIS (Netherlands)

    Pil, A.

    2014-01-01

    De eerste Nederlandse bijdrage aan de European Extremely Large Telescope (E-ELT) is succesvol getest. Het gaat om de chopper, een zeer wendbaar spiegeltje dat is ontwikkeld door een samenwerkingsverband van universiteiten, technologische instituten en het bedrìjfsleven. Het hightech spiegeltje is ee

  10. Green-cane harvest of sugarcane effects on biomass and energy yields and nutrient removal

    Science.gov (United States)

    Sugarcane yields in Louisiana can approach 40 dry Mg ha-1, making sugarcane an attractive biofuel feedstock as well as a profitable sugar crop. Existing technology used in green-cane harvesting can be used to allow chopper harvester extractor fans to remove variable amounts of extraneous leaf materi...

  11. 50 CFR 260.103 - Operations and operating procedures shall be in accordance with an effective sanitation program.

    Science.gov (United States)

    2010-10-01

    ... be in accordance with an effective sanitation program. 260.103 Section 260.103 Wildlife and Fisheries... Operations and operating procedures shall be in accordance with an effective sanitation program. (a) All..., choppers, and containers which fail to meet appropriate and adequate sanitation requirements will...

  12. FOCUS: neutron time-of-flight spectrometer at SINQ: recent progress

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S.; Mesot, J.; Holitzner, L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Hempelmann, R. [Saarbruecken Univ. (Germany)

    1997-09-01

    At the Swiss neutron spallation source SINQ a time-of-flight spectrometer for cold neutrons is under construction. The design foresees a Hybrid solution combining a Fermi chopper with a doubly focusing crystal monochromator. During 1996 important progress has been made concerning the main spectrometer components such as the spectrometer housing and the detector system. (author) 2 figs., 3 refs.

  13. First flux measurement in a SINQ supermirror neutron guide

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S.; Schlumpf, N.; Bauer, G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    On Dec. 3, 1996, the Swiss spallation neutron source SINQ was taken into operation and produced its first neutrons successfully. The neutron spectrum within one of the supermirror guides was estimated by a chopper Time-of-Flight method. The result shows a 30% higher neutron intensity at the flux maximum than expected from previous Monte-Carlo simulations. (author) 1 fig., 4 refs.

  14. Draft genome sequences of two Kocuria isolates, K. salsicia G1 and K. rhizophila G2, isolated from a slaughterhouse in Denmark

    DEFF Research Database (Denmark)

    Herschend, Jakob; Raghupathi, Prem Krishnan; Røder, Henriette Lyng;

    2016-01-01

    We report here the draft genome sequences ofKocuria salsiciaG1 andKocuria rhizophilaG2, which were isolated from a meat chopper at a small slaughterhouse in Denmark. The two annotated genomes are 2.99 Mb and 2.88 Mb in size, respectively....

  15. Draft genome assembly of two Pseudoclavibacter helvolus strains, G8 and W3, isolated from slaughterhouse environments

    DEFF Research Database (Denmark)

    Raghupathi, Prem Krishnan; Herschend, Jakob; Røder, Henriette Lyng;

    2016-01-01

    We report the draft genome sequences of twoPseudoclavibacter helvolusstrains. Strain G8 was isolated from a meat chopper and strain W3 isolated from the wall of a small slaughterhouse in Denmark. The two annotated genomes are 3.91 Mb and 4.00 Mb in size, respectively....

  16. Genome sequence of Kocuria varians G6 ssolated from a slaughterhouse in Denmark

    DEFF Research Database (Denmark)

    Raghupathi, Prem Krishnan; Herschend, Jakob; Røder, Henriette Lyng;

    2016-01-01

    We report here the first draft genome sequence ofKocuria variansG6, which was isolated from a meat chopper at a small slaughterhouse in Denmark. The 2.90-Mb genome sequence consists of 95 contigs and contains 2,518 predicted protein-coding genes....

  17. 76 FR 23854 - Reclassification of Motorcycles (Two and Three Wheeled Vehicles) in the Guide to Reporting...

    Science.gov (United States)

    2011-04-28

    ..., cruiser, chopper, touring, dual purpose, standard, sport touring, unclad sport, sport, and super sports... of charge. The FHWA appreciates this offer, and may pursue this cooperative research outside the... ignore the rules of the road than operators of on-road vehicles. These comments are outside the scope...

  18. Simulation of Low Voltage Ride-through of Permanent Magnet Synchronous Wind Turbines%永磁同步风力发电机低电压穿越仿真分析

    Institute of Scientific and Technical Information of China (English)

    孙树敏; 万文锋; 梁得亮

    2013-01-01

    One purpose of this study is to verify by means of simulation that chopper resistor is effective in improving low voltage ride-through capacity of permanent magnet synchronous generator (PMSG) wind turbines in all kinds of voltage dips.Another purpose is to give the method to choose the value of chopper.This study analyzed the fault characteristics of PMSG wind turbines from the point of view of energy and got that the capacitor voltage of converter would keep increasing during voltage dips.Accordingly,a chopper resistor,which was installed in parallel with the capacitor,was proposed to prevent the capacitor voltage from increasing to a very high value.This study also analyzed the symmetrical and unsymmetrical fault characteristics of PMSG wind turbines through simulation when the generator was equipped with a chopper.It shows that chopper resistor is able to fulfill the demand of low voltage ride-through capacity of PMSG wind turbines and therefore provide theoretical basis for the application of chopper resistor.%通过仿真分析验证了限制电阻低电压穿越策略在各种电网电压跌落情况下的有效性,并给出了限制电阻阻值选择的原则.首先从能量平衡角度分析了永磁同步发电机的故障特性,其故障危害是变流器的电容电压会不断上升,从而得出在电容两端并联限制电阻的保护措施.然后通过仿真分析了永磁同步发电机配置限制电阻后的对称故障特性和非对称故障特性,证明了限制电阻可以实现永磁同步发电机低电压穿越要求,为限制电阻的实际应用提供了理论基础.

  19. Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2014-06-01

    Full Text Available This paper presents a fast coordinated control scheme of the rotor side converter (RSC, the Direct Current (DC chopper and the grid side converter (GSC of doubly fed induction generator (DFIG wind turbine generators (WTGs to improve the low voltage ride through (LVRT and high voltage ride through (HVRT capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the DC chopper circuit were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were verified by time domain simulations using Matlab-Simulink.

  20. A New Reference Signal Generation and DC-link Control for Fault Mitigation and Power Quality Improvement of DFIG

    Directory of Open Access Journals (Sweden)

    P.T. Rajan

    2015-07-01

    Full Text Available This study delivers a new approach for reference signal generation to improve the power quality problem of Doubly Fed Induction Generator (DFIG. DFIG consists of RSC (Rotor Side Converter and GSC (Grid Side Converter and common DC-Link. RSC converter used to mitigate the sag and swell compensation by enhanced phase lock loop and variable speed Limit. The aim of GSC is to mitigate the current harmonics and load balancing control by non-linear adaptive filter approach. The 60% of DC-Link voltage control obtained by GSC and remaining 40% of sag is controlled by the external chopper through the DC-Link voltage balancing. Additional chopper is presented to reduce the size, stress of DC-Link capacitor and also it avoids additional control loop in GSC. The system power qualities are verified through simulation studies.

  1. Modeling and simulation of a solar power source at 3kW for a clean energy without pollution

    Directory of Open Access Journals (Sweden)

    Louzazni M.

    2014-04-01

    Full Text Available The air pollution was much worse, and it became necessary to replace the fossil energy sources by the renewable energies. The causes are related to reserves that can be exhausted, to pollution and their impacts on the environment. Production of toxic gases from the combustion of coal for the effect of increasing the temperature of the earth. Solar energy is a clean and inexhaustible excellent alternative. We propose a modeling and simulation of a solar system consists of a photovoltaic generator (PVG, a boost chopper, to supply a telecommunications relay station (BTS, According to the load characteristics (I = 60A, V = 48V DC (3 kW. A stage adaptation composed of this chopper controlled by a PWM controller (Pulse Width Modulation is used to control the optimal operating point (MPPT and optimize system performance using Matlab / Simulink.

  2. Data Reduction Algorithm for Optical Wide Field Patrol (OWL)

    Science.gov (United States)

    Park, S.; Park, Y.; Yim, H.; Jo, J.; Moon, H.; Bae, Y.; Lim, Y.; Choi, J.; Choi, Y.; Park, J.; Son, J.

    2014-09-01

    OWL (Optical Wide-field Patrol) has a detector system which has the chopper which consists of 4 blades in front of the CCD camera to acquire efficiently the position and time information of moving objects such as artificial satellites. Using this system, it is possible to get more position data by splitting the streaks of the moving object into many pieces with fast rotating blades during tracking. At the same time, the time data of the rotating chopper can be acquired by the time tagger connected to the photo diode. In order to derive the orbits of the targets, we need a sequential data reduction procedure including the calculation of WCS (World Coordinate System) solution to transform the positions into equatorial coordinate systems, and the combination of the time data from the time tagger and the position data. We present such a data reduction procedure and the preliminary results after applying this procedure to the observation images.

  3. The NC Power Supply Design of Large Current and Wide Frequency Pulse in SEAM

    Directory of Open Access Journals (Sweden)

    Jianping Zhou

    2013-07-01

    Full Text Available There are a lot of ways to achieve large current pulse power supply, and the more common way is to adopt the inverter switching circuit to achieve pulse power supply. The core of the NC power supply design of large current and wide frequency pulse in SEAM is using two-stage modulation. Combined with inverter technology, DC chopper technology and NC technology, it not only can achieve the adjustability of the output pulse amplitude, but also can realize continuous adjustment of the output pulses and the duty cycle. The front stage of power supply uses DC/DC transformation circuit with the UC3879 integrated control chip as the core. With the microcontroller as the control core, the backward stage uses DC chopper circuit to achieve the NC power supply of multi-parameter adjustable output large current pulse.

  4. Monte-Carlo simulations of a high-resolution neutron TOF instrument

    Science.gov (United States)

    Bernhardt, Ph; Demmel, F.; Magerl, A.

    2000-03-01

    It is proposed to build a flexible, high-resolution time-of-flight diffractometer and spectrometer at the new reactor FRM II of the Technische Universität München. To optimize the layout of individual components and to estimate the performance of the entire instrument, we have made analytical calculations and Monte-Carlo simulations mainly with “McStas”, programmed by RISØ, Denmark. MC simulation routines for neutron devices like curved guides, disc- and Fermi choppers have been added. The influence of curved guides in neutron phase space has been developed and will be presented. Line shapes of neutron pulses and transmission have been studied for a Fermi chopper with straight slits and will be compared with the results of simulation.

  5. Electrical Structure of Future Off-shore Wind Power Plant with a High Voltage Direct Current Power Transmission

    DEFF Research Database (Denmark)

    Sharma, Ranjan

    to control and as such a high current capacity of the WPP side VSC might be required. Detailed simulation results are included in the report. The other option is to use a DC chopper, the results of which are also presented in detail in the report. It is observed that a DC chopper can provide a simple...... are related to surplus reactive power and added losses. On the other hand, HVDC transmission system can be arbitrarily long and for long distance power transmission requirement it provides much better efficiency compared to a corresponding HVAC system. HVDC may provide a viable solution for high power...... to trip off during temporary grid side faults, commonly described as low voltage fault-ride-through requirement. There are four different fault-ride-through options discussed in the report. The first option includes controlling of collector network frequency. This provides a very good opportunity to use...

  6. Design of the low energy beam transport line for the China spallation neutron source

    Institute of Scientific and Technical Information of China (English)

    LI Jin-Hai; OUYANG Hua-Fu; FU Shi-Nian; ZHANG Sua-Shun; HE Wei

    2008-01-01

    The design of the China Spallation Neutron Source (CSNS) low-energy beam transport (LEBT) line, which locates between the ion source and the radio-frequency quadrupole (RFQ), has been completed with the TRACE3D code. The design aims at perfect matching, primary chopping, a small emittance growth and sufficient space for beam diagnostics. The line consists of three solenoids, three vacuum chambers, two steering magnets and a pre-chopper. The total length of LEBT is about 1.74 m. This LEBT is designed to transfer 20 mA of H-pulsed beam from the ion source to the RFQ. An induction cavity is adopted as the pre-chopper.The electrostatic octupole steerer is discussed as a candidate. A four-quadrant aperture for beam scraping and beam position monitoring is designed.

  7. Time-of-flight measurements in atomic beam devices using adiabatic high frequency transitions and sextupole magnets

    CERN Document Server

    Baumgarten, C; Brunn, I; Court, G; Ciullo, G; Ferretti, P; Golendukhin, A; Graw, G; Haeberli, W; Henoch, M; Hertenberger, R; Koch, N; Kolster, H; Lenisa, P; Nass, A; Podyachev, S P; Reggiani, D; Rith, K; Simani, M C; Steffens, E; Stewart, J; Wise, T

    2002-01-01

    Atomic beam devices are frequently equipped with sextupole magnets to focus the beam or to act as spin filters in combination with RF-transitions for manipulating the hyperfine population within the atomic beam. A useful tool for the analysis of sextupole systems, the application of time-of-flight (TOF) measurements is presented. TOF measurements are enabled without mechanical beam chopper by utilizing adiabatic radio frequency transitions to select atoms within a certain time interval. This method is especially interesting for the use in atomic beam devices that are already equipped with RF-transitions and sextupole magnets and where space limitations or the required quality of the vacuum do not allow the installation of a mechanical chopper. The measurements presented here were performed with the atomic beam polarimeter of the HERMES polarized deuterium target and the results have been used to optimize the sextupole system of the polarimeter.

  8. Identification of RBC and WBC Count in Human Blood Using ARM Based Instrumentation

    Directory of Open Access Journals (Sweden)

    B.Dodda Basavanagoud

    2015-06-01

    Full Text Available The rapid growth in microelectronics and crunching RISC in the field of bio-medical sciences incorporated of soft tools to diagnose various parameters of human fluids. Conventional method of blood sample analysis makes use of laboratory technique of titration, which is operator-dependent and results in lot of errors depending on the skill of the technician. In order to eliminate the human errors involved in the conventional method, in this paper an attempt has been made to present a capillary centrifuge technique driven by high speed DC motor fed by Morgan chopper and controlled by powerful ARM processor. It results in accurate analysis of the blood samples. The various techniques involved in accurate sensing of speed using timer and generation of firing pulses to thyristor in the Morgan chopper is judiciously achieved. This paper clearly brings out the advantages of the proposed blood measurement technique which effectively gives blood analysis faster and at a low cost.

  9. A Particle In Cell code development for high current ion beam transport and plasma simulations

    CERN Document Server

    Joshi, N

    2016-01-01

    A simulation package employing a Particle in Cell (PIC) method is developed to study the high current beam transport and the dynamics of plasmas. This package includes subroutines those are suited for various planned projects at University of Frankfurt. In the framework of the storage ring project (F8SR) the code was written to describe the beam optics in toroidal magnetic fields. It is used to design an injection system for a ring with closed magnetic field lines. The generalized numerical model, in Cartesian coordinates is used to describe the intense ion beam transport through the chopper system in the low energy beam section of the FRANZ project. Especially for the chopper system, the Poisson equation is implemented with irregular geometries. The Particle In Cell model is further upgraded with a Monte Carlo Collision subroutine for simulation of plasma in the volume type ion source.

  10. Coordinated system services from offshore wind power plants connected through HVDC networks

    DEFF Research Database (Denmark)

    Zeni, L.; Glasdam, Jakob Bærholm; Hesselbæk, B.

    2014-01-01

    This paper presents an overview of power system services in networks involving multiple onshore power systems, a voltage sourced converter (VSC) based high voltage direct current (HVDC) offshore network and an offshore wind power plant (OWPP). A comprehensive list of services regarding onshore...... control and communication delays of OWPPs, and their influence on the successful delivery of the targeted services. Furthermore, it is shown that as an HVDC network increases in size from the point-to-point, the handling of onshore short circuits calls for the proper combination of DC chopper(s) and fast...... as well as offshore network operation – both AC and DC – will be discussed from a state of the art perspective. Among them, the most interesting have been selected and will be treated in more detail and the main contribution of this paper will be to shed light on the most relevant aspects related...

  11. Securing Australia – for SIVs, from SIEVs, via Edinburgh Gardens NYE

    Directory of Open Access Journals (Sweden)

    Pete Chambers

    2016-03-01

    Full Text Available Edinburgh Gardens is the crown jewel of Fitzroy North, one of inner northern Melbourne’s most gentrified suburbs. In 2009, Christian Lander, author of Stuff White People Like, dubbed Fitzroy North Melbourne’s whitest suburb. In January 2015, the median house price hit $1,050,000, a far cry from Chopper Reid’s stomping ground and the setting of precarious 70s student lives in Monkey Grip.

  12. The ARCS radial collimator

    OpenAIRE

    Stone M.B.; Niedziela J.L.; Overbay M.A.; Abernathy D.L.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. W...

  13. Phacoemulsification in hard cataracts: the "chop, trip and free" technique Facoemulsificação em cataratas duras: "Faco rasteira"

    OpenAIRE

    José Marcos S. Gonçalves

    2004-01-01

    Very hard cataracts continue to be a challenge to phacoemulsification due to the difficulty in breaking the nucleus and also in separating the broken nucleus from the adjacent epinucleus. The present technique is the presentation of a surgical maneuver which uses the Nagahara chopper and the phaco tip to divide the nucleus (including the epinucleus) as a whole and then emulsify it using little time and not very much phaco power.Cataratas muito duras continuam sendo um desafio para a facoemuls...

  14. Phacoemulsification in hard cataracts: the "chop, trip and free" technique

    OpenAIRE

    José Marcos S. Gonçalves

    2004-01-01

    Very hard cataracts continue to be a challenge to phacoemulsification due to the difficulty in breaking the nucleus and also in separating the broken nucleus from the adjacent epinucleus. The present technique is the presentation of a surgical maneuver which uses the Nagahara chopper and the phaco tip to divide the nucleus (including the epinucleus) as a whole and then emulsify it using little time and not very much phaco power.

  15. Characterization of Infrared Properties of Layered Semiconductors.

    Science.gov (United States)

    1987-02-20

    to avoid thequantity due tn background oe If w relate subharmonics of the background chopper channel, due to sample and background together. If we...spectroscopy. Electro-modulation, piezo - tration of deep levels (and optical cross section in some modulation, thermo-modulation, and wavelength modula...or subharmonic pickup. It can also be at fixed wavelengths where the absorption coefficient can be used to conveniently and very precisely calibrate

  16. A 600 VOLT MULTI-STAGE, HIGH REPETITION RATE GAN FET SWITCH

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, D. [Fermilab; Pfeffer, H. [Fermilab; Saewert, G. [Fermilab

    2016-10-05

    Using recently available GaN FETs, a 600 Volt three- stage, multi-FET switch has been developed having 2 nanosecond rise time driving a 200 Ohm load with the potential of approaching 30 MHz average switching rates. Possible applications include driving particle beam choppers kicking bunch-by-bunch and beam deflectors where the rise time needs to be custom tailored. This paper reports on the engineering issues addressed, the design approach taken and some performance results of this switch.

  17. A multi-DSP system for the neutron high resolution Fourier diffractometer

    Energy Technology Data Exchange (ETDEWEB)

    Drozdov, V.A.; Butenko, V.A.; Prikhodko, V.I. [Joint Inst. of Nuclear Research, Moscow (Russian Federation). Frank Lab. of Neutron Physics

    1998-08-01

    The multi-DSP data acquisition system for neutron time-of-flight spectrum measurements requiring fast real-time data processing is designed and is operated at the neutron High Resolution Fourier Diffractometer (HRFD). The use of high performance DSPs and front-end electronics based on flexible PLDs allows increasing of the efficiency of neutron diffractometers with a Fourier chopper and a multi-element detector system by the method of electronic time-focusing.

  18. A Practical and Portable Solids-State Electronic Terahertz Imaging System

    OpenAIRE

    Ken Smart; Jia Du; Li Li; David Wang; Keith Leslie; Fan Ji; Xiang Dong Li; Da Zhang Zeng

    2016-01-01

    A practical compact solid-state terahertz imaging system is presented. Various beam guiding architectures were explored and hardware performance assessed to improve its compactness, robustness, multi-functionality and simplicity of operation. The system performance in terms of image resolution, signal-to-noise ratio, the electronic signal modulation versus optical chopper, is evaluated and discussed. The system can be conveniently switched between transmission and reflection mode according to...

  19. Determination and Analysis of Jet and Missile Fuel Deposits.

    Science.gov (United States)

    1981-08-14

    provides for a high signal/noise ratio with weak sources,I and (iv) the software we built into our dedicated minicomputer contains batteries of numerical... chloride window. The thjee regions. 630 cm - 1230 cm . 1275 - 1850 cm , and 2600 - 3600 cm , are shown in Figures 7. 8. and 9. The low frequency region of...which is shielded by air-cooled aluminium sheet except for a conical opening directed toward the chopper. The temperature of the reference is so

  20. Beyond Demonstration: The Role of Fuel Cells in DoD’s Energy Strategy

    Science.gov (United States)

    2011-10-19

    CARBON FOOTPRINT AND OUR USE OF THE LOCAL POWER GRID.” Ron Lewis, Vice President of Supply Chain, Coca - Cola . UTC POWER FUEL CELL SYSTEM, COCA - COLA ...Connecticut and Massa- chusetts, with another installation planned in San Jose, CA); Price Chopper; Albertson’s; and Star Market Coca - Cola Refreshments...system at its cam- pus in San Jose, CA Staples, with a 300 kW installation at its distribution center in Ontario, CA The Coca - Cola Company

  1. FEM Simulation of Small Wind Power Generating System Using PMSG

    Science.gov (United States)

    Kesamaru, Katsumi; Ohno, Yoshihiro; Sonoda, Daisuke

    The paper describes a new approach to simulate the small wind power generating systems using PMSG, in which the output is connected to constant resistive load, such as heaters, through the rectifier and the dc chopper. The dynamics of the wind power generating system is presented, and it is shown by simulation results that this approach is useful for system dynamics, such as starting phenomena.

  2. Chopping of near- and mid-infrared radiation using a curled electrostatic MEMS actuator

    Science.gov (United States)

    Dausch, David E.; Goodwin, Scott H.; Exarhos, Gregory J.

    2003-09-01

    An electrostatic MEMS actuator known as the "Artificial Eyelid" can be used as a micromechanical chopper for IR detectors. The actuator structure consists of a curled polymer/metal film stack which is microfabricated and released from an IR transparent substrate. The film stack is uncurled by applying an electric field between the curled film and the transparent fixed electrode on the substrate. These flexible film actuators can act as IR choppers, providing transmission of radiation to the sensor elements when open (curled) and reflection when closed (uncurled). Arrays of actuators were fabricated on ITO-coated glass substrates and ranged in size from 4 x 4 mm to 7.5 x 15 mm with individual elements ranging from 250 to 500 μm on a side. Actuation for devices with average radius of curvature of 120 μ was consistently achieved at 150-170 V operation with 98-100% of the elements functioning and long lifetimes. IR chopper characteristics were measured using a blackbody source and pyroelectric detector by applying sine and square wave voltage to the actuators at a frequency of 30 Hz. The capability of the artificial eyelid for chopping near- and mid-IR radiation, including future fabrication of devices using NiCo2O4 or NiRh2O4 films for IR transparent electrodes, will be discussed.

  3. A 97 dB dynamic range CSA-based readout circuit with analog temperature compensation for MEMS capacitive sensors

    Science.gov (United States)

    Tao, Yin; Chong, Zhang; Huanming, Wu; Qisong, Wu; Haigang, Yang

    2013-11-01

    This paper presents a charge-sensitive-amplifier (CSA) based readout circuit for capacitive microelectro-mechanical-system (MEMS) sensors. A continuous-time (CT) readout structure using the chopper technique is adopted to cancel the low frequency noise and improve the resolution of the readout circuits. An operational trans-conductance amplifier (OTA) structure with an auxiliary common-mode-feedback-OTA is proposed in the fully differential CSA to suppress the chopper modulation induced disturbance at the OTA input terminal. An analog temperature compensation method is proposed, which adjusts the chopper signal amplitude with temperature variation to compensate the temperature drift of the CSA readout sensitivity. The chip is designed and implemented in a 0.35 μm CMOS process and is 2.1 × 2.1 mm2 in area. The measurement shows that the readout circuit achieves 0.9 aF / √Hz capacitive resolution, 97 dB dynamic range in 100 Hz signal bandwidth, and 0.8 mV/fF sensitivity with a temperature drift of 35 ppm/°C after optimized compensation.

  4. Equine preantral follicles obtained via the Biopsy Pick-Up method: histological evaluation and validation of a mechanical isolation technique.

    Science.gov (United States)

    Haag, K T; Magalhães-Padilha, D M; Fonseca, G R; Wischral, A; Gastal, M O; King, S S; Jones, K L; Figueiredo, J R; Gastal, E L

    2013-03-15

    The aims of this study in mares were to: (1) compare preantral follicle parameters between in vitro Biopsy Pick-Up (BPU) and scalpel blade collection methods and between histological and mechanical isolation processing (experiment 1); (2) histologically evaluate preantral follicles (experiment 2); and (3) compare histological analysis with a previously established mechanical isolation technique using a tissue chopper (experiment 3) for ovarian cortical fragments obtained in vivo using a BPU instrument. In experiment 1, preantral follicles were analyzed (N = 220; 90% primordial and 10% primary). Proportions of primordial and primary follicles did not differ (P > 0.05) between tissue collection (BPU vs. scalpel blade dissection) or processing (mechanical isolation vs. histology) methods. Follicle viability and morphology rates were similar (P > 0.05) between tissue collection methods, but mechanical isolation produced more (P 0.05) by processing methods. In conclusion, most parameters evaluated for preantral follicles were similar between histological and tissue chopper processing techniques; hence, mechanical isolation efficiently dissociated equine preantral follicles from the ovarian cortex. Therefore, the tissue chopper could be used to isolate large numbers of morphologically normal equine preantral follicles for cryopreservation and/or in vitro culture.

  5. Initial Emittance Measurements of the Fermilab Linac Beam Using the MTA Beamline

    CERN Document Server

    Johnstone, C

    2012-01-01

    The MTA beam line has been specifically designed to facilitate measurements of the Fermilab Linac beam emittance and properties utilizing a long, 10m, element-free straight. Linac beam is extracted downstream of the 400-MeV electrostatic chopper located in the Booster injection line. This chopper cannot be utilized for MTA beam, and therefore the entire Linac beam pulse is directed into the MTA beamline. Pulse length manipulation is provided by the 750-keV electrostatic chopper at the upstream end of the Linac and, using this device, beam can be delivered from 8 {\\mu}sec up to the full 50 {\\mu}sec Linac pulse length. The 10 m emittance measurement straight exploits and begins at the 12' shield wall that separates the MTA Experimental Hall and beamline stub from the Linac enclosure. A quadrupole triplet has been installed upstream of the shield wall in order to focus a large, 1.5-2" (~95% width) beam through the shield wall and onto a profile monitor located at the exit of the shielding. Another profile monito...

  6. Fully Integrated Biopotential Acquisition Analog Front-End IC.

    Science.gov (United States)

    Song, Haryong; Park, Yunjong; Kim, Hyungseup; Ko, Hyoungho

    2015-09-30

    A biopotential acquisition analog front-end (AFE) integrated circuit (IC) is presented. The biopotential AFE includes a capacitively coupled chopper instrumentation amplifier (CCIA) to achieve low input referred noise (IRN) and to block unwanted DC potential signals. A DC servo loop (DSL) is designed to minimize the offset voltage in the chopper amplifier and low frequency respiration artifacts. An AC coupled ripple rejection loop (RRL) is employed to reduce ripple due to chopper stabilization. A capacitive impedance boosting loop (CIBL) is designed to enhance the input impedance and common mode rejection ratio (CMRR) without additional power consumption, even under an external electrode mismatch. The AFE IC consists of two-stage CCIA that include three compensation loops (DSL, RRL, and CIBL) at each CCIA stage. The biopotential AFE is fabricated using a 0.18 μm one polysilicon and six metal layers (1P6M) complementary metal oxide semiconductor (CMOS) process. The core chip size of the AFE without input/output (I/O) pads is 10.5 mm². A fourth-order band-pass filter (BPF) with a pass-band in the band-width from 1 Hz to 100 Hz was integrated to attenuate unwanted signal and noise. The overall gain and band-width are reconfigurable by using programmable capacitors. The IRN is measured to be 0.94 μVRMS in the pass band. The maximum amplifying gain of the pass-band was measured as 71.9 dB. The CIBL enhances the CMRR from 57.9 dB to 67 dB at 60 Hz under electrode mismatch conditions.

  7. Auditory nerve inputs to cochlear nucleus neurons studied with cross-correlation.

    Science.gov (United States)

    Young, E D; Sachs, M B

    2008-06-12

    The strength of synapses between auditory nerve (AN) fibers and ventral cochlear nucleus (VCN) neurons is an important factor in determining the nature of neural integration in VCN neurons of different response types. Synaptic strength was analyzed using cross-correlation of spike trains recorded simultaneously from an AN fiber and a VCN neuron in anesthetized cats. VCN neurons were classified as chopper, primarylike, and onset using previously defined criteria, although onset neurons usually were not analyzed because of their low discharge rates. The correlograms showed an excitatory peak (EP), consistent with monosynaptic excitation, in AN-VCN pairs with similar best frequencies (49% 24/49 of pairs with best frequencies within +/-5%). Chopper and primarylike neurons showed similar EPs, except that the primarylike neurons had shorter latencies and shorter-duration EPs. Large EPs consistent with end bulb terminals on spherical bushy cells were not observed, probably because of the low probability of recording from one. The small EPs observed in primarylike neurons, presumably spherical bushy cells, could be derived from small terminals that accompany end bulbs on these cells. EPs on chopper or primarylike-with-notch neurons were consistent with the smaller synaptic terminals on multipolar and globular bushy cells. Unexpectedly, EPs were observed only at sound levels within about 20 dB of threshold, showing that VCN responses to steady tones shift from a 1:1 relationship between AN and VCN spikes at low sound levels to a more autonomous mode of firing at high levels. In the high level mode, the pattern of output spikes seems to be determined by the properties of the postsynaptic spike generator rather than the input spike patterns. The EP amplitudes did not change significantly when the presynaptic spike was preceded by either a short or long interspike interval, suggesting that synaptic depression and facilitation have little effect under the conditions studied

  8. A Practical and Portable Solids-State Electronic Terahertz Imaging System

    Directory of Open Access Journals (Sweden)

    Ken Smart

    2016-04-01

    Full Text Available A practical compact solid-state terahertz imaging system is presented. Various beam guiding architectures were explored and hardware performance assessed to improve its compactness, robustness, multi-functionality and simplicity of operation. The system performance in terms of image resolution, signal-to-noise ratio, the electronic signal modulation versus optical chopper, is evaluated and discussed. The system can be conveniently switched between transmission and reflection mode according to the application. A range of imaging application scenarios was explored and images of high visual quality were obtained in both transmission and reflection mode.

  9. Base drive circuit for a four-terminal power Darlington

    Science.gov (United States)

    Lee, Fred C.; Carter, Roy A.

    1983-01-01

    A high power switching circuit which utilizes a four-terminal Darlington transistor block to improve switching speed, particularly in rapid turn-off. Two independent reverse drive currents are utilized during turn off in order to expel the minority carriers of the Darlington pair at their own charge sweep-out rate. The reverse drive current may be provided by a current transformer, the secondary of which is tapped to the base terminal of the power stage of the Darlington block. In one application, the switching circuit is used in each power switching element in a chopper-inverter drive of an electric vehicle propulsion system.

  10. FOCUS: time-of-flight spectrometer for cold neutrons at SINQ

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S.; Mesot, J. [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland); Hempelmann, R. [Saarbruecken Univ., Physical Chemistry, Saarbruecken (Germany)

    1996-11-01

    The physical layout of the Time-Of-Flight spectrometer at the new spallation source SINQ is presented. The concept shows up a hybrid-TOF combining a Fermi-chopper with a crystal monochromator. The demand of a versatile and flexible instrument for several applications is taken into account by the option of switching from time-focusing to monochromatic focusing mode such that the spectrometer can be optimised for both quasielastic and inelastic scattering applications. (author) 5 figs., 2 tabs., 16 refs.

  11. The front end test stand high performance H- ion source at Rutherford Appleton Laboratory.

    Science.gov (United States)

    Faircloth, D C; Lawrie, S; Letchford, A P; Gabor, C; Wise, P; Whitehead, M; Wood, T; Westall, M; Findlay, D; Perkins, M; Savage, P J; Lee, D A; Pozimski, J K

    2010-02-01

    The aim of the front end test stand (FETS) project is to demonstrate that chopped low energy beams of high quality can be produced. FETS consists of a 60 mA Penning Surface Plasma Ion Source, a three solenoid low energy beam transport, a 3 MeV radio frequency quadrupole, a chopper, and a comprehensive suite of diagnostics. This paper details the design and initial performance of the ion source and the laser profile measurement system. Beam current, profile, and emittance measurements are shown for different operating conditions.

  12. Determination of refraction nonlinear index, for effect thermal, of solutions with nanoparticles of gold

    Science.gov (United States)

    Olivares-Vargas, A.; Trejo-Durán, M.; Alvarado-Méndez, E.; Cornejo-Monroy, D.; Mata-Chávez, R. I.; Estudillo-Ayala, J. M.; Castaño-Meneses, V.

    2013-09-01

    Research of nonlinear optical properties of materials for manufacturing opto-electronic devices, had a great growth in the last years. The solutions with nanoparticle metals present nonlinear optical properties. In this work we present the results of characterizing, analyzing and determining the magnitude and sign of the nonlinear refractive index, using the z-scan technique in solutions with nanoparticles of gold, lipoic acid and sodium chloride. We used a continuous Argon laser at 514 nm with variable power, an 18 cms lens, and a chopper. We determined the nonlinear refractive index in the order of 10-9. These materials have potential applications mainly as optical limiters.

  13. Dynamic Behaviour of DFIG-Based Wind Turbines During Grid Faults

    Science.gov (United States)

    Erlich, Istvan; Wrede, Holger; Feltes, Christian

    According to grid codes issued by utilities, tripping of wind turbines following grid faults is not allowed. Besides, to provide voltage support to the grid mandatory reactive current supply is necessary. To enable wind turbines ride-through low voltage periods special protection measures have to be implemented. In this paper the behavior of DFIG based wind turbines during grid faults is discussed and elucidated using simulation results. It is shown that with properly designed crowbar and DC-link chopper even zero voltage ride-through is possible.

  14. Modulation spectrometry of neutrons with diffractometry applications

    CERN Document Server

    Hiismäki, Pekka

    1997-01-01

    Modulation spectrometry of neutrons refers to a measuring principle, characterized by classification of neutron histories in a probabilistic way, not the usual deterministic way. In order to accomplish this, neutron beams entering the sample are modulated by high-transmission, white-beam selectors of the multislit type, such as Fourier or statistical choppers or high-frequency-modulated spin-flippers. In this scheme it is impossible to decide in a unique way through which particular slit any single neutron passed, but the distribution of histories for a large population of neutrons can neverth

  15. The pyroelectric vidicon - Ten years on

    Science.gov (United States)

    Burgess, D.; Nixon, R.; Ritchie, J.

    1986-01-01

    A technology development status evaluation is presented for British high performance pyroelectric vidicon, IR-sensitive TV cameras, the first tubes and cameras of which were demonstrated over a decade ago. Attention is given to the improvements that had to be instituted in camera design in order to obtain optimum performance from the vidicon tubes. A rotating disk chopper and flicker processing were incorporated into the camera's design. Pyroelectric cameras have been extensively applied in industry and the police and military services for fire detection and in rescue operations.

  16. The ARCS radial collimator

    Directory of Open Access Journals (Sweden)

    Stone M.B.

    2015-01-01

    Full Text Available We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. We present here characterization of the collimator's performance and methodologies for its effective use.

  17. The ARCS radial collimator

    Science.gov (United States)

    Stone, M. B.; Niedziela, J. L.; Overbay, M. A.; Abernathy, D. L.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. We present here characterization of the collimator's performance and methodologies for its effective use.

  18. Nucleodissecção & facoemulsificação Nucleodissection and phacoemulsification

    OpenAIRE

    Marcelo Siqueira de Freitas

    2002-01-01

    O autor descreve uma técnica para dissecar o núcleo cataratoso em duas porções: uma externa, ou camada externa, e outra interna, ou núcleo interno. A camada externa é segmentada com a ponteira do facoemulsificador e o gancho de Sinskey ou um "chopper" e o núcleo interno luxado e emulsificado sempre em primeiro lugar. A emulsificação da camada externa originou dois modelos cirúrgicos, um para cataratas maduras e outro para cataratas moderadamente duras. Nas cataratas maduras, emulsificamos cad...

  19. Digital humanitarians how big data is changing the face of humanitarian response

    CERN Document Server

    Meier, Patrick

    2015-01-01

    The Rise of Digital HumanitariansMapping Haiti LiveSupporting Search And Rescue EffortsPreparing For The Long Haul Launching An SMS Life Line Sending In The Choppers Openstreetmap To The Rescue Post-Disaster Phase The Human Story Doing Battle With Big Data Rise Of Digital Humanitarians This Book And YouThe Rise of Big (Crisis) DataBig (Size) Data Finding Needles In Big (Size) Data Policy, Not Simply Technology Big (False) Data Unpacking Big (False) Data Calling 991 And 999 Big (

  20. MODELING AN IMPROVED METHOD FOR DOUBLE MODULATION PHOTO REFLECTANCE EXPERIMENTS

    Directory of Open Access Journals (Sweden)

    M. Hernández

    2004-04-01

    Full Text Available This paper describes an improved method to be used in double modulation photo reflectance experiments, inorder to reduce the influence of parasitic effects in the useful signal. The method uses the inner and outer sectionsof a single chopper disk to modulate the monochromator and the laser beam, eliminating the need of complexelectronic filters, and two additional PIN photodiodes for scattered light compensation. The method has beennumerically simulated using LabVIEW in order to investigate the influence of the modulator finite switching timeand the finite resolution of the digital acquisition system. Results show that a relative error less than 1% can beachieved.

  1. Advanced DC/DC converters

    CERN Document Server

    Luo, Fang Lin

    2003-01-01

    INTRODUCTIONHistorical ReviewMultiple Quadrant ChoppersPump CircuitsDevelopment of DC/DC Conversion TechniqueCategorize Prototypes and DC/DC Converters Family TreeVOLTAGE-LIFT CONVERTERSIntroductionSeven Self-Lift ConvertersPositive Output Luo-ConvertersNegative Output Luo-ConvertersModified Positive Output Luo-Converters Double Output Luo-ConvertersPOSITIVE OUTPUT SUPER-LIFT LUO-CONVERTERS IntroductionMain SeriesAdditional SeriesEnhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of Positive Output

  2. High-Quality Continuous-Wave Imaging with a 2.53 THz Optical Pumped Terahertz Laser and a Pyroelectric Detector

    Institute of Scientific and Technical Information of China (English)

    BING Pi-Bin; YAO Jian-Quan; XU De-Gang; XU Xiao-Yan; LI Zhong-Yang

    2010-01-01

    @@ A CW terahertz(THz)transmission imaging system is demonstrated and a high-quality THz image can be obtained using a pyroelectric detector.The factors that affect the imaging quality,such as the THz wavelength,spot size on the sample surface,step length of the motor,and frequency of the chopper,are theoretically and experimentally investigated.The experimental results show that the maximum resolution of the THz image can reach 0.4mm with the THz wavelength of 118.8μm.the spot size of 1.8 mm and the step length of 0.25mm.

  3. Fourier-Transform Infrared Spectrometer

    Science.gov (United States)

    Schindler, R. A.

    1986-01-01

    Fourier-transform spectrometer provides approximately hundredfold increase in luminosity at detector plane over that achievable with older instruments of this type. Used to analyze such weak sources as pollutants and other low-concentration substances in atmosphere. Interferometer creates fringe patterns on two distinct arrays of light detectors, which observe different wavelength bands. Objective lens focuses scene on image plane, which contains optical chopper. To make instrument less susceptible to variations in scene under observation, field and detector lenses focus entrance aperture, rather that image, onto detector array.

  4. VESPA: The vibrational spectrometer for the European Spallation Source

    Science.gov (United States)

    Fedrigo, Anna; Colognesi, Daniele; Bertelsen, Mads; Hartl, Monika; Lefmann, Kim; Deen, Pascale P.; Strobl, Markus; Grazzi, Francesco; Zoppi, Marco

    2016-06-01

    VESPA, Vibrational Excitation Spectrometer with Pyrolytic-graphite Analysers, aims to probe molecular excitations via inelastic neutron scattering. It is a thermal high resolution inverted geometry time-of-flight instrument designed to maximise the use of the long pulse of the European Spallation Source. The wavelength frame multiplication technique was applied to provide simultaneously a broad dynamic range (about 0-500 meV) while a system of optical blind choppers allows to trade flux for energy resolution. Thanks to its high flux, VESPA will allow the investigation of dynamical and in situ experiments in physical chemistry. Here we describe the design parameters and the corresponding McStas simulations.

  5. Neutron Instrumentation and Neutron Investigation of Archaeometallurgical Arms and Armours

    DEFF Research Database (Denmark)

    Fedrigo, Anna

    and a system of optical blind choppers, which make it possible to trade flux for energy resolution. The application of neutron diffraction and imaging techniques have long demonstrated their potential in the characterisation of dense materials in engineering and material science. In this project they have been...... used as a non-destructive analytical tool for the study of metallic artefacts of archaeometric interest. Three “pattern-welded” sword blades from the Viking age, provided by the National Museum of Denmark, have been fully characterised in terms of composition, manufacturing processes, and conservation...

  6. Local Optical Spectroscopies for Subnanometer Spatial Resolution Chemical Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Paul

    2014-01-20

    The evanescently coupled photon scanning tunneling microscopes (STMs) have special requirements in terms of stability and optical access. We have made substantial improvements to the stability, resolution, and noise floor of our custom-built visible-photon STM, and will translate these advances to our infrared instrument. Double vibration isolation of the STM base with a damping system achieved increased rigidity, giving high tunneling junction stability for long-duration and high-power illumination. Light frequency modulation with an optical chopper and phase-sensitive detection now enhance the signal-to-noise ratio of the tunneling junction during irradiation.

  7. Controller for computer control of brushless dc motors. [automobile engines

    Science.gov (United States)

    Hieda, L. S. (Inventor)

    1981-01-01

    A motor speed and torque controller for brushless d.c. motors provides an unusually smooth torque control arrangement. The controller provides a means for controlling a current waveform in each winding of a brushless dc motor by synchronization of an excitation pulse train from a programmable oscillator. Sensing of torque for synchronization is provided by a light beam chopper mounted on the motor rotor shaft. Speed and duty cycle are independently controlled by controlling the frequency and pulse width output of the programmable oscillator. A means is also provided so that current transitions from one motor winding to another is effected without abrupt changes in output torque.

  8. Development of pulsed positron beam line with compact pulsing system

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Masaki, E-mail: maekawa.masaki@jaea.go.jp [Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawasuso, Atsuo [Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2012-01-01

    We have developed a pulsed slow positron beam with a pulse width of less than 200 ps and a period of 25 ns. The beam apparatus is composed of a Munich-type pre-buncher, a chopper and a buncher. Instead of the conventional RF cavity, a simple double-cylinder electrode is used for the buncher. The beam will be used for positron lifetime measurements. The time resolution of the whole system including lifetime measurement circuits is 250 ps, which is adequate for studying semiconductors and metals.

  9. Bulanık Kazanç Ayarlamalı Nonlineer PI Kontrolörün Kalıcı Mıknatıslı Doğru Akım Motor-Dinamo Sistemine Uygulanması = Applying the Fuzzy Gain Scheduling Nonlinear PI Controller to Permanent Magnet Direct Current Motor - Dynamo System

    Directory of Open Access Journals (Sweden)

    Kamil Burak DALCI

    2004-01-01

    Full Text Available This paper describes the realization of a fuzzy gain scheduling scheme of a PI controller using a RISC microcontroller. Fuzzy rules and reasoning are utilised on-line to determine the PI controller parameters based on the error signal and its first difference. The Fuzzy control algorithm is implemented in the RISC microcontroller to regulate the speed of a permanent magnet DC motor (PMDC and works on-line. The microcontroller directly tunes the motor speed with a chopper converter which changes the motor terminal voltage. Application results demonstrate that better control performance can be achieved in comparison with traditional PI controllers.

  10. Conceptual design of a polarized 3He neutron spin filter for polarized neutron spectrometer POLANO at J-PARC

    Science.gov (United States)

    Ino, T.; Ohoyama, K.; Yokoo, T.; Itoh, S.; Ohkawara, M.; Kira, H.; Hayashida, H.; Sakai, K.; Hiroi, K.; Oku, T.; Kakurai, K.; Chang, L. J.

    2016-04-01

    A 3He neutron spin filter (NSF) has been designed for a new polarized neutron chopper spectrometer called the Polarization Analysis Neutron Spectrometer with Correlation Method (POLANO) at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. It is designed to fit in a limited space on the spectrometer as an initial neutron beam polarizer and is polarized in situ by spin exchange optical pumping. This will be the first generation 3He NSF on POLANO, and a polarized neutron beam up to 100 meV with a diameter of 50 mm will be available for research on magnetism, hydrogen materials, and strongly correlated electron systems.

  11. 基于超级电容电动汽车制动能回收的研究%Research on the Recovery of Electric Vehicle Braking Energy Based on Super Capacitor

    Institute of Scientific and Technical Information of China (English)

    肖佐无; 王海波

    2015-01-01

    针对电动汽车制动能回收的问题,采用超级电容为储能器件,无刷直流电机的制动能通过BUCK斩波器以恒流充电的方式给超级电容充电,既能回收制动能又使制动力矩可控。采用电流闭环负反馈,自动调节BUCK斩波器的占空比,达到恒流充电的目的。仿真实验表明:这种方法是可行的、有效的。%For the problem of electric vehicle braking energy recovery, using the super capacitor as energy storage device, the braking energy of Brushless DC motor charging the super capacitor with the constant current charge by BUCK chopper, not only recovers the braking energy but also makes the brake torque controllable. Negative feedback of current closed-loop was adopted, and the duty cycle of the BUCK chopper is adjusted automatically, which achieves the constant current charging. The simulation experiment shows that this method is feasible and effective.

  12. Influence of the external and internal parameters on the characteristics of generator PV

    Science.gov (United States)

    Zouli, Mounir; Ghoudelbourk, Sihem; Ouari, Ahmed; Dib, Djallel

    2017-02-01

    The growing demand for electric power and inevitable future depletion of conventional sources require major research on the alternative sources, like renewable energies. Among which, solar energy is the most largely used because of its many applications. And as Algeria comprises an exceptional solar layer thanks to its large surfaces, therefore it represents an important source of photovoltaic energy. The objective of this work is to be ensured that the energy produced by the photovoltaic plant supplies the electrical distribution network. The configuration of this system comprises a photovoltaic generator, connected to a chopper booster. For an optimal operation of the system, one must connect in cascades partial generators each one connected to a chopper booster adapted by an order MPPT by the method of Disturbance and Observation (P&O) to ensure the operation of their maximum powers whatever the climatic conditions, and also allows to raise the output voltage of these photovoltaic generators. The adaptation between the photovoltaic generator and the load was carried out with the help of converter DC/DC.

  13. Phacoemulsification in hard cataracts: the "chop, trip and free" technique Facoemulsificação em cataratas duras: "Faco rasteira"

    Directory of Open Access Journals (Sweden)

    José Marcos S. Gonçalves

    2004-08-01

    Full Text Available Very hard cataracts continue to be a challenge to phacoemulsification due to the difficulty in breaking the nucleus and also in separating the broken nucleus from the adjacent epinucleus. The present technique is the presentation of a surgical maneuver which uses the Nagahara chopper and the phaco tip to divide the nucleus (including the epinucleus as a whole and then emulsify it using little time and not very much phaco power.Cataratas muito duras continuam sendo um desafio para a facoemulsificação devido à dificuldade em quebrar o núcleo e também em separar este pedaço quebrado do epinúcleo adjacente. Esta técnica é a apresentação de uma manobra cirúrgica ("Faco rasteira", em que se utiliza o Nagahara "chopper" e a caneta de faco para dividir o núcleo (incluindo o epinúcleo em sua totalidade e assim emulsificá-lo, utilizando tempo e poder de ultra-som baixo.

  14. Visit to FDI Technology, Saint Petersburg, 7-9 November 2005 Travel Report

    CERN Document Server

    Paoluzzi, M

    2005-01-01

    The Superconducting H- Linac under study at CERN, and thus the LINAC 4 and, well before, the 3 MeV test stand, require a high performance beam chopper. It has to establish the required beam time-structure by deflecting towards a dump part of the beam entering the chopper line. The deflector basically consists of two 50  lines facing each other and driven with opposite polarity signals so as to establish an electric field in between. The pulse generators required for driving these lines are very sophisticated items because they must exhibit fast pulse fronts (2 ns), wide pulse length dynamic range (8 ns to 1 s), high repetition frequency (45 MHz) and high output voltage (>500 V). Although a CERN in-house solution to provide the required drivers has been identified , we continued prospecting the market for possible industrial alternatives. In this contest FID Technology has been contacted and the visit showed that their proprietary solid-state devices might indeed be the key element of a simpler pulse gen...

  15. SOLAR TO AC POWER SOURCE FOR REMOTE AREAS USING SEIG

    Directory of Open Access Journals (Sweden)

    MEHMET AKBABA

    2012-02-01

    Full Text Available Photovoltaic generators (PVG are increasingly used to provide electricity in remote areas. However, in many applications the DC generated electricity by a PVG need to be converted to AC. Traditionally DC to AC inverters have been widely used for this purpose. In this paper, a different system is proposed in which a self excited induction generator (SEIG driven by a permanent magnet DC motor (DCM and powered from a PVG through a maximum power point tracker (MPPT are used. A step-up chopper is utilized as an MPPT unit. The proposed system is modelled in time domain, and a detailed transient and steady-state analysis are presented. The main reason behind analyzing the system in the time domain is because of the fact that for unknown speeds, the methods developed for steady-state analysis of SEIGs can not be applied. The presented work shows that the full available power of the PVG can be harnessed by selecting suitable values for the duty cycle and the frequency of the step up chopper and the excitation capacitor of the SEIG. It is also shown that with such a combination power utilization efficiency of more than 83% can be achieved.

  16. Modelling and characterization of the PEM fuel cell to study interactions with power converters; Modelisation et caracterisation de la pile pem pour l'etude des interactions avec les convertisseurs statiques

    Energy Technology Data Exchange (ETDEWEB)

    Fontes, G.

    2005-09-15

    The climatic and energy challenges were now clearly stated. The use of hydrogen is one of the best ways which gives many hopes. Fuel cells are an essential link in the chain of the use of hydrogen. Thus, a lot of studies have been undertaken throughout the world on fuel cells in many fields of physics. Concerning the field of power electronics, a lot of work on distributed generation technologies using fuel cells has been realised too and a great number of power converters dedicated to fuel cells have been studied. However, very few studies have been undertaken on the interactions between fuel cells and power converters. The goals of this work are to study interactions between fuel cells and power converters. Some requirements for the power electronic engineer can follow from this work. This work proposes high signal dynamic models of a H{sub 2}/O{sub 2} PEM fuel cell. These models include the different physical and chemical phenomena. Specific methods based on a limited number of original experiments (low frequency current sweeps) allow to extract the model parameters. These models are used to study the interactions between fuel cells and power converters which are the most used: buck chopper, boost chopper, inverters. The important part of the double layer capacitors has thus been underlined: they can filter the current harmonics created by the power converters. Finally, some choices of filtering elements to be connected to the fuel cell are proposed. (author)

  17. Investigation Into the Utilization of 3D Printing in Laser Cooling Experiments

    Science.gov (United States)

    Hazlett, Eric; Nelson, Brandon; de Leon, Sam Diaz; Shaw, Jonah

    2016-05-01

    With the advancement of 3D printing new opportunities are abound in many different fields, but with the balance between the precisions of atomic physics experiments and the material properties of current 3D printers the benefit of 3D printing technology needs to be investigated. We report on the progress of two investigations of 3D printing of benefit to atomic physics experiments: laser feedback module and the other being an optical chopper. The first investigation looks into creation of a 3D printed laser diode feedback module. This 3D printed module would allow for the quick realization of an external cavity diode laser that would have an adjustable cavity distance. We will report on the first tests of this system, by looking at Rb spectroscopy and mode-hop free tuning range as well as possibilities of using these lasers for MOT generation. We will also discuss our investigation into a 3D-printed optical chopper that utilizes an Arduino and a computer hard drive motor. By implementing an additional Arduino we create a low cost way to quickly measure laser beam waists.

  18. BEER - The Beamline for European Materials Engineering Research at the ESS

    Science.gov (United States)

    Fenske, J.; Rouijaa, M.; Šaroun, J.; Kampmann, R.; Staron, P.; Nowak, G.; Pilch, J.; Beran, P.; Šittner, P.; Strunz, P.; Brokmeier, H.-G.; Ryukhtin, V.; Kadeřávek, L.; Strobl, M.; Müller, M.; Lukáš, P.; Schreyer, A.

    2016-09-01

    The Beamline for European Materials Engineering Research (BEER) will be built at the European Spallation Source (ESS). The diffractometer utilizes the high brilliance of the long-pulse neutron source and offers high instrument flexibility. It includes a novel chopper technique that extracts several short pulses out of the long pulse, leading to substantial intensity gain of up to an order of magnitude compared to pulse shaping methods for materials with high crystal symmetry. This intensity gain is achieved without compromising resolution. Materials of lower crystal symmetry or multi-phase materials will be investigated by additional pulse shaping methods. The different chopper set-ups and advanced beam extracting techniques offer an extremely broad intensity/resolution range. Furthermore, BEER offers an option of simultaneous SANS or imaging measurements without compromising diffraction investigations. This flexibility opens up new possibilities for in-situ experiments studying materials processing and performance under operation conditions. To fulfil this task, advanced sample environments, dedicated to thermo-mechanical processing, are foreseen.

  19. Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg peak onto an ultrasound image

    Science.gov (United States)

    Patch, S. K.; Kireeff Covo, M.; Jackson, A.; Qadadha, Y. M.; Campbell, K. S.; Albright, R. A.; Bloemhard, P.; Donoghue, A. P.; Siero, C. R.; Gimpel, T. L.; Small, S. M.; Ninemire, B. F.; Johnson, M. B.; Phair, L.

    2016-08-01

    The potential of particle therapy due to focused dose deposition in the Bragg peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg peak location with target structure, by overlaying the location of the Bragg peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in 2 μ \\text{s} . The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.

  20. Experimental Investigations on PV Powered SVM-DTC Induction Motor without AC Phase Current Sensors

    Directory of Open Access Journals (Sweden)

    T. Muthamizhan

    2014-05-01

    Full Text Available The paper presents a low-cost, phase-current reconstruction algorithm for space vector modulated direct torque controlled induction motor using the information obtained from only one shunt resistor which is in series with low side switches in a conventional three-phase inverter. The aim is to develop a low-cost high - performance induction motor drive. It uses the dc-link voltage and dc current to reconstruct the stator currents needed to estimate the motor flux and the electromagnetic torque. Photovoltaic arrays convert solar power to dc electric power; uses chopper and dc-ac inverter to fed three phase Induction Motor. The chopper used here is current fed full bridge boost dc-dc converter, which is preferred and extensively used in high voltage applications and advantageous over voltage fed converters. The inverter switches are controlled by PWM techniques obtained from SVM-DTC of IM. The experimental investigations are given to prove the ability of the proposed scheme of reproducing the performances of a SVM- DTC IM drive.

  1. Development of a Data Reduction Algorithm for Optical Wide Field Patrol (OWL) II: Improving Measurement of Lengths of Detected Streaks

    Science.gov (United States)

    Park, Sun-Youp; Choi, Jin; Roh, Dong-Goo; Park, Maru; Jo, Jung Hyun; Yim, Hong-Suh; Park, Young-Sik; Bae, Young-Ho; Park, Jang-Hyun; Moon, Hong-Kyu; Choi, Young-Jun; Cho, Sungki; Choi, Eun-Jung

    2016-09-01

    As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

  2. Self-calibrated active pyrometer for furnace temperature measurements

    Science.gov (United States)

    Woskov, Paul P.; Cohn, Daniel R.; Titus, Charles H.; Surma, Jeffrey E.

    1998-01-01

    Pyrometer with a probe beam superimposed on its field-of-view for furnace temperature measurements. The pyrometer includes a heterodyne millimeter/sub-millimeter-wave or microwave receiver including a millimeter/sub-millimeter-wave or microwave source for probing. The receiver is adapted to receive radiation from a surface whose temperature is to be measured. The radiation includes a surface emission portion and a surface reflection portion which includes the probe beam energy reflected from the surface. The surface emission portion is related to the surface temperature and the surface reflection portion is related to the emissivity of the surface. The simultaneous measurement of surface emissivity serves as a real time calibration of the temperature measurement. In an alternative embodiment, a translatable base plate and a visible laser beam allow slow mapping out of interference patterns and obtaining peak values therefor. The invention also includes a waveguide having a replaceable end portion, an insulating refractory sleeve and/or a source of inert gas flow. The pyrometer may be used in conjunction with a waveguide to form a system for temperature measurements in a furnace. The system may employ a chopper or alternatively, be constructed without a chopper. The system may also include an auxiliary reflector for surface emissivity measurements.

  3. HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE.

    Energy Technology Data Exchange (ETDEWEB)

    SHAPIRO,S.M.ZALIZNYAK,I.PASSELL,L.GHOSH,V.

    2003-05-12

    HYSPEC combines time-of-flight spectroscopy with focusing Bragg optics to enhance the flux on small single crystal samples. It will look at a coupled H{sub 2} moderator and will use a 20-25 meter supermirror guide to transport the neutron beam. A counter-rotating chopper pair will monochromate the beam and determine the neutron burst width. A short distance from the chopper pair a vertical focusing crystal is placed in a drum shield that will focus the beam to a 2 cm height, thus maximizing the flux at the sample position. Collimators and beam definers will be placed before and after the sample, which will allow standard sample environment equipment to be used covering a wide range of temperatures and magnetic fields. About 200 He{sup 3} position sensitive detectors will be housed in a moveable detector bank 4.5 m from the sample to cover a horizontal range of 60{sup o} and a vertical range of {+-}7.5{sup o}. HYSPEC can easily be converted to a polarized beam instrument by using a Heusler crystal for a monochromator, and supermirror benders for polarization analysis of the scattered beam. HYSPEC is a moderate resolution instrument optimized for an incident energy range of 5

  4. Performance analysis of reverse recovery minimization effects in DC/DC converter using PSpice

    Energy Technology Data Exchange (ETDEWEB)

    Yahaya, N.Z.; Heng, D.K.; Wen, L.H.; Ng, A. [Petronas Technological Univ., Tronoh, Perak Darul Ridzuan (Malaysia)

    2007-07-01

    Diodes play a significant role in many power electronic such as freewheeling and/or snubber components. In order to reduce the overall power loss of the circuit, many design features are required for the diode. Therefore, fast switching and fast recovery power diode have been developed for use the design. One of the circuit losses is due to reverse recovery current of the power diode, which affects performance of the power systems in terms of switching losses and noises. By reducing the reverse recovery current, the power loss of the power diode will also be reduced. In order to reduce the power loss in the circuit, this paper investigated the minimization of the reverse recovery effects in the power diode. An inductive chopper circuit using a CoolMOS power switch was set up to serve as the platform for investigation. The paper presented how the variations of the parameter's values in the inductive load chopper circuit affected the diode's reverse recovery characteristics. The parameters that were considered in the study included the gate drive, duty ratio, CoolMOS switching frequency, and operating temperature. In order to investigate the impact of each parameter on the reverse recovery effects, a PSpice device simulation model using a power diode was utilized. It was concluded that the switching frequency affected the total energy losses more significantly than factors of temperature, gate resistance and the duty ratio. 8 refs., 4 tabs., 10 figs.

  5. STATUS REPORT ON DEVELOPMENT OF A HIGH-SPEED HIGH-INTENSITY MOLECULAR BEAM

    Energy Technology Data Exchange (ETDEWEB)

    Knuth, Eldon L.

    1963-07-15

    Status of a high-speed high-intensity molecular beam under development is described. Bases for designs of the several components are presented. Using an arc-heated source and a hypersonic jet, molecular energies exceeding 1 ev and beam intensities of the order of 10/sup 16/ molecules/ cm/sup 2/ sec are anticipated. A two-disk beam chopper and speed selector provides a means for analyzing the speed distribution in the generated beam, for chopping the beam into bursts of nearly monoenergetic molecules suitable for scattering studies using the time-of-flight technique, and for modulating the beam in order to facilitate detection. A through-flow ionization detector possesses the versatility required for scattering studies using the time-of-flight technique. A sorption pump and a turbo pump serve as central components of alternative pumping systems for the collimating chamber. Using the arc-heated source, the converging nozzle, the conduction-radiation-cooled skimmer, the turbo pump (turning at 3400 rpm), the chopperselector (acting only as a chopper), and the detector, an arc-heated beam is generated and detected. (auth)

  6. Low noise and high CMRR front-end amplifier dedicated to portable EEG acquisition system.

    Science.gov (United States)

    Chebli, Robert; Sawan, Mohamad

    2013-01-01

    This paper concerns the design and implementation of a fully integrated low noise and high CMRR rail-to-rail preamplifier dedicated to EEG acquisition channel. The preamplification technique is based on two complementary CMOS True Logarithmic Amplifier (TLA) stages connected in parallel. The TLA largely amplifies small amplitude of EEG signals, and moderately the large amplitude ones created during epileptic. A chopper stabilization technique is used to filter the 1/ƒ noise and the DC offset voltage of the input CMOS transistors and to increase the common-mode rejection ratio (CMRR). Due to the TLA structure, a high CMRR and high power supply rejection ratio are achieved and the signal-to-noise ratio (of the channel is better enhanced). To snugly fit the ADC input window to the EEG signal magnitude a new programming gain approach is implemented. Also, a chopper spike filter is used to cancel the spike voltages generated by the charge injections of modulator/demodulator switches. The proposed preamplifier is implemented in 0.18 µm CMOS technology. Post-layout simulation results exhibit 253 dB @50/60 Hz as CMRR, 500 nVrms @100 Hz as input-referred noise while consuming 55 µA from a 1.8 V supply.

  7. The design and construction of a pulsed beam generation system based on high intensity cyclotron

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In order to perform the studies on a pulsed beam generation system based on a high intensity cyclotron, a test beam line with a pulsed beam generation for a 10 MeV compact cyclotron (CYCIAE-10) has been designed and constructed at China Institute of Atomic Energy (CIAE). A 70 MHz continuous H- beam can be pulsed to the pulse length of less than 10 ns with a repetition rate of 4.4 MHz. The sine waveform with a frequency of 2.2 MHz is adopted for the chopper and a mesh structure with single drift and dual gaps is used for the 70 MHz buncher. A helical resonator is designed and constructed based on simulations and experiments on the RF matching for the chopper. A helical inductance loop that is exceptionally large of its kind and equipped with water cooling for the resonator has been successfully wound and a 500 W solid RF amplifier has been manufactured. A special measuring device has been designed, which can be used to measure both the DC beam and the pulsed beam. The required pulsed beam was obtained after pulsed beam tuning.

  8. AMOR – the time-of-flight neutron reflectometer at SINQ/PSI

    Indian Academy of Sciences (India)

    Mukul Gupta; T Gutberlet; J Stahn; P Keller; D Clemens

    2004-07-01

    The apparatus for multioptional reflectometry (AMOR) at SINQ/PSI is a versatile reflectometer operational in the time-of-flight (TOF) mode (in a wavelength range of 0.15 nm > > 1.3 nm) as well as in the monochromatic ( - 2) mode with both polarized and unpolarized neutrons. AMOR is designed to perform reflectometry measurements in horizontal sample-plane geometry which allows studying both solid–liquid and liquid–liquid interfaces. A pulsed cold neutron beam from the end position of the neutron guide is produced by a dual-chopper system (side-by-side) having two windows at 180° and rotatable with a maximum frequency of 200 Hz. In the TOF mode, the chopper frequency, width of the gating window and the chopper–detector distance can be selected independently providing a wide range of -resolution ( / = 1–10%). Remanent FeCoV/Ti : N supermirrors are used as polarizer/analyzer with a polarization efficiency of ∼ 97%. For the monochromatic wavelength mode, a Ni/Ti multilayer is used as a monochromator, giving ∼ 50% reflectivity at a wavelength of 0.47 nm. In the present work, a detailed description of the instrument and setting-up of the polarization option is described. Results from some of the recent studies with polarized neutrons and measurements on liquid surfaces are presented.

  9. High-Contrast Visualization of Upconversion Luminescence in Mice Using Time-Gating Approach.

    Science.gov (United States)

    Zheng, Xianlin; Zhu, Xingjun; Lu, Yiqing; Zhao, Jiangbo; Feng, Wei; Jia, Guohua; Wang, Fan; Li, Fuyou; Jin, Dayong

    2016-04-01

    Optical imaging through the near-infrared (NIR) window provides deep penetration of light up to several centimeters into biological tissues. Capable of emitting 800 nm luminescence under 980 nm illumination, the recently developed upconversion nanoparticles (UCNPs) suggest a promising optical contrast agent for in vivo bioimaging. However, presently they require high-power lasers to excite when applied to small animals, leading to significant scattering background that limits the detection sensitivity as well as a detrimental thermal effect. In this work, we show that the time-gating approach implementing pulsed illumination from a NIR diode laser and time-delayed imaging synchronized via an optical chopper offers detection sensitivity more than 1 order of magnitude higher than the conventional approach using optical band-pass filters (S/N, 47321/6353 vs 5339/58), when imaging UCNPs injected into Kunming mice. The pulsed laser illumination (70 μs ON in 200 μs period) also reduces the overall thermal accumulation to 35% of that under the continuous-wave mode. Technical details are given on setting up the time-gating unit comprising an optical chopper, a pinhole, and a microscopy eyepiece. Being generally compatible with any camera, this provides a convenient and low cost solution to NIR animal imaging using UCNPs as well as other luminescent probes.

  10. Neutron optics concept for the materials engineering diffractometer at the ESS

    Science.gov (United States)

    Šaroun, J.; Fenske, J.; Rouijaa, M.; Beran, P.; Navrátil, J.; Lukáš, P.; Schreyer, A.; Strobl, M.

    2016-09-01

    The Beamline for European Materials Engineering Research (BEER) has been recently proposed to be built at the European Spallation Source (ESS). The presented concept of neutron delivery optics for this instrument addresses the problems of bi-spectral beam extraction from a small moderator, optimization of neutron guides profile for long-range neutron transport and focusing at the sample under various constraints. They include free space before and after the guides, a narrow guide section with gaps for choppers, closing of direct line of sight and cost reduction by optimization of the guides cross-section and coating. A system of slits and exchangeable focusing optics is proposed in order to match various wavelength resolution options provided by the pulse shaping and modulation choppers, which permits to efficiently trade resolution for intensity in a wide range. Simulated performance characteristics such as brilliance transfer ratio are complemented by the analysis of the histories of “useful” neutrons obtained by back tracing neutrons hitting the sample, which helps to optimize some of the neutron guide parameters such as supermirror coating.

  11. 胶体微粒间相互作用势测量系统%Measurement System of Interaction Potential between Colloidal Particles

    Institute of Scientific and Technical Information of China (English)

    任洪亮; 周金华; 丁攀峰; 李银妹

    2011-01-01

    A mechanical chopper is designed based on the programmable logic controller, servo motor amplifier, servo motor and encoder. The interaction potential measurement system is constructed by the mechanical chopper and dual optical tweezers. The characteristic of the system such as the design of the chopper, the switching time of the blinking optical tweezers, the tuning range, the origin position return feature, the compatibility and the usability of the system are discussed. The system is used to measure the interaction potential of a pair polystyrene spheres. The result is consistent with the Darjaguin-Landau-Verwey-Overbeek theory, which demonstrates the reliability of the apparatus. In addition, the apparatus provides an effective technique for measuring the interaction potential between two micro colloidal particles.%设计出以可编程控制器、伺服电机放大器、伺服电机和编码器为主要部件的可编程机械斩光器,并将其与多光镊系统相耦合,构建了胶体微粒间相互作用势测量系统.利用该系统测量聚苯乙烯球悬浮液中两个小球之间的静电相互作用势,其结果与胶体稳定理论符合,验证了系统的可靠性.该斩光器具有良好的易用性、兼容性和可移植性.并且该系统能在可控的物理化学条件下从粒子层次直接测量胶体粒子间不同类型的相互作用势,为深入研究胶体的微观机制提供了一种有效的测量手段和技术平台.

  12. The Structure and Experimental Study on Optimization Design of 2 ZLF-500 Wheel Type Silage Cutter%2 ZLF-500型轮刀式青贮饲料切碎机的结构组成及试验研究

    Institute of Scientific and Technical Information of China (English)

    赵娅

    2017-01-01

    当前我国畜牧业的青贮饲料切碎作业中,亟待优化设计切碎机结构,以提升切碎机应用效益。为此,优化设计了2 ZLF-500型轮刀式青贮饲料切碎机的结构,并结合试验验证其优化后在实际中的应用效益。经试验研究表明:优化设计2ZLF-500型轮刀式青贮饲料切碎机结构之后,提高青贮饲料质量20%,提高饲草切碎机使用可靠性12%。优化设计2 ZLF-500型轮刀式青贮饲料切碎机结构,改进切碎机工作部件结构与参数,可以有效推广应用青贮饲料技术,对促进畜牧业的持续稳定发展,发挥积极作用。%This article aims to analysis of the composition and structure of 2 ZLF-500 type wheel knife type silage chop-per , and related experimental research .For the livestock industry in our country at present silage cutting operation , ur-gent need to optimize the design cutter structure , enhance the shredder application benefit , this analysis optimization de-sign 2 ZLF-500 round knife type silage cutting machine structure of demand , combined with experimental verification op-timization 2 ZLF-500 round knife type silage chopper structure after in actual application efficiency .Results after the test and research show that the optimization design 2ZLF-500 wheel knife type silage chopper structure after , improve the si-lage quality , increased by 20%, improve forage cutterhead with reliability , increased by 12% play practical benefits . Results show that the optimization design 2 ZLF-500 round knife type silage cutter structure , improved shredding machine components of the structure and parameters , can effectively promote the application of silage technology , our country to promote the sustained and stable development of animal husbandry , play a positive meaning .

  13. A study on a micro-stepping drive system for space pointing platform

    Science.gov (United States)

    Yang, Shuang; Li, Bao-quan; Zhang, Xin

    2011-08-01

    Along with the continuous development of the research in the space exploration field, the precision rotation control system is widely utilized in a lot of payloads of the satellites. It is stepping motor cooperating with reduction gear wheel to accomplish the precision rotation in some pointing platforms of the camera used in the satellite. By contrast with that, the approach of this paper could precisely control the rotation angle of the stepping motor without using reduction gear wheel. Therefore, the size and the height of the instrument would be reduced base on simplifying the structural design. Moreover, it reduces the cost to some extent. In this paper, it is adopted that the digital signal processor (DSP) controller and bipolar constant current motor drive circuit UC3717 to make a high performance, high subdivision, miniature control system come true, which is used to drive two-phase hybrid stepping motor. The methods are applied by the driver system that sine cosine micro stepping and constant current chopper drive with a fixed chopper period. The driver system also supplies the functions that involve subdivision selection, clockwise rotation or counter clockwise rotation control, and over current or over voltage or under voltage or overload protection, and so on. The description in this paper also includes the total schematic design, the approach to get current table in different subdivision levels, the current control method in hybrid stepping motor, the way to reduce electro- magnetic interference (EMI) of the hybrid stepping motor. And the total schematic design contains the DSP controller, the communication interface of the driver system, the design of power driving circuit, the interface circuit between the electrical sources, the constant current chopper drive circuit for the two-phase hybrid stepping motor. At last, it is verified by some experimental investigations that the control system not only has miniature size, simplified system design

  14. Efeitos de sistemas de colheita e de aplicação de fungicidas no desempenho da soca do arroz irrigado Effect of harvesting systems and fungicide application on the performance of irrigated ratoon rice

    Directory of Open Access Journals (Sweden)

    Alberto B. dos Santos

    2003-12-01

    Full Text Available O cultivo da soca de arroz pode constituir-se em uma fonte de renda significativa; entretanto, para o seu êxito é necessário um sistema de colheita adequado da cultura principal. Com o objetivo de se avaliar a resposta da soca da cultivar Epagri 108 de arroz irrigado aos equipamentos da colhedora, alturas de corte, manejos da palhada após a colheita mecanizada e fungicidas, conduziram-se experimentos por dois anos consecutivos. No primeiro ano, foram avaliados três equipamentos de colhedoras: picador de palha, espalhador de palha e sem picador e espalhador de palha; duas alturas de corte e quatro tratamentos fungicidas e, no segundo ano, além dos equipamentos de colheita foram avaliados também três manejos da palhada: passada de rolo compactador; passada de roçadora e sem manejo, e cinco tratamentos fungicidas. O picador de palha propiciou melhor qualidade e maior produtividade de grãos, em comparação com o sistema de colheita em que não se o utiliza. A roçadora danificou os colmos das plantas, reduzindo o perfilhamento e a produtividade, enquanto os fungicidas proporcionaram maior produtividade e menor incidência de doenças nos grãos e, conseqüentemente, melhor qualidade do produto colhido. O rolo compactador não trouxe benefícios ao crescimento nem à produtividade da soca de arroz irrigado, ao passo que o espalhador de palha apenas em menor altura de corte.The cultivation of ratoon rice may constitute a source of additional income. However, to make it economically viable an adequate harvesting system of the main crop is necessary. With the objective of evaluating the response of irrigated ratoon rice to the harvest equipment, cutting height, management of stubble after harvest and fungicides, experiments were conducted during two consecutive years. In the first year, harvesters with three types of equipment (straw chopper, straw spreader, without chopper and spreader; two heights of cutting and four fungicide treatments

  15. Noise and mismatch optimization for capacitive MEMS readout

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Chong; Wu Qisong; Yin Tao; Yang Haigang, E-mail: yanghg@mail.ie.ac.c [Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

    2009-11-15

    This paper presents a high precision CMOS readout circuit for a capacitive MEMS gyroscope. A continuous time topology is employed as well as the chopper noise cancelling technique. A detailed analysis of the noise and mismatch of the capacitive readout circuit is given. The analysis and measurement results have shown that thermal noise dominates in the proposed circuit, and several approaches should be used for both noise and mismatch optimization. The circuit chip operates under a single 5 V supply, and has a measured capacitance resolution of 0.2 aF/sq rootHz. With such a readout circuit, the gyroscope can accurately measure the angular rate with a sensitivity of 15.3 mV/{sup 0}/s. (semiconductor integrated circuits)

  16. Noise and mismatch optimization for capacitive MEMS readout

    Institute of Scientific and Technical Information of China (English)

    Zhang Chong; Wu Qisong; Yin Tao; Yang Haigang

    2009-01-01

    This paper presents a high precision CMOS readout circuit for a capacitive MEMS gyroscope. A continuous time topology is employed as well as the chopper noise cancelling technique. A detailed analysis of the noise and mismatch of the capacitive readout circuit is given. The analysis and measurement results have shown that thermal noise dominates in the proposed circuit, and several approaches should be used for both noise and mismatch optimization. The circuit chip operates under a single 5 V supply, and has a measured capacitance resolution of 0.2 aF/√Hz. With such a readout circuit, the gyroscope can accurately measure the angular rate with a sensitivity of 15.3 mV/°/s.

  17. 3 MeV Test Stand commissioning report

    CERN Document Server

    Bellodi, Guilia; Andreassen, O; Comblin, J-F; Dimov, V; Lallement, J-B; Martin, C; Midttun, O; Ovalle, E; Raich, U; Roncarolo, F; Rossi, C; Scrivens, R; Vollaire, J; Yarmohammadi Satri, M; Zocca, Z

    2013-01-01

    Linac4 is a normal-conducting 160 MeV H- linear accelerator, presently under construction, that will replace the present 50 MeV Linac2 as injector of the CERN proton accelerator complex with the goal of increasing the LHC luminosity. The Linac4 front-end, composed of a 45 keV ion source, a Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) housing a beam chopper, was commissioned at the 3 MeV test stand area during the first half of 2013. This report gives details of the installation and operational systems used, describes the commissioning phases and measurements performed and summarizes the results that were finally achieved and the lessons learnt in the process.

  18. A new controller for battery-powered electric vehicles

    Science.gov (United States)

    Belsterling, C. A.; Stone, J.

    1980-01-01

    This paper describes the development, under a NASA/DOE contract, of a new concept for efficient and reliable control of battery-powered vehicles. It avoids the detrimental effects of pulsed-power controllers like the SCR 'chopper' by using rotating machines to meter continuous currents to the traction motor. The concept is validated in a proof-of-principle demonstration system and a complete vehicle is simulated on an analog computer. Test results show exceptional promise for a full-scale system. Optimum control strategies to minimize controller weight are developed by means of the simulated vehicle. The design for an Engineering Model is then prepared in the form of a practical, compact two-bearing package with forced air cooling. Predicted performance is outstanding, with controller efficiency of over 90% at high speed.

  19. Artificial Intelligence Tools for Scaling Up of High Shear Wet Granulation Process.

    Science.gov (United States)

    Landin, Mariana

    2017-01-01

    The results presented in this article demonstrate the potential of artificial intelligence tools for predicting the endpoint of the granulation process in high-speed mixer granulators of different scales from 25L to 600L. The combination of neurofuzzy logic and gene expression programing technologies allowed the modeling of the impeller power as a function of operation conditions and wet granule properties, establishing the critical variables that affect the response and obtaining a unique experimental polynomial equation (transparent model) of high predictability (R(2) > 86.78%) for all size equipment. Gene expression programing allowed the modeling of the granulation process for granulators of similar and dissimilar geometries and can be improved by implementing additional characteristics of the process, as composition variables or operation parameters (e.g., batch size, chopper speed). The principles and the methodology proposed here can be applied to understand and control manufacturing process, using any other granulation equipment, including continuous granulation processes.

  20. A single-ended CMOS sensing circuit for MEMS gyroscope with noise cancellation

    KAUST Repository

    Elsayed, Mohannad Yomn

    2010-06-01

    In this work, a complete single-ended readout circuit for capacitive MEMS gyroscope using chopper stabilization technique is presented. A novel noise cancellation technique is used to get rid of the bias noise. The circuit offers superior performance over state of the art readout circuits in terms of cost, gain, and noise for the given area and power consumption. The full circuit exhibits a gain of 58dB, a power dissipation of 1.3mW and an input referred noise of 12nV/√Hz. This would significantly improve the overall sensitivity of the gyroscope. The full circuit has been fabricated in 0.6um CMOS technology and it occupies an area of 0.4mm × 1mm. © 2010 IEEE.

  1. An upward looking airborne millimeter wave radiometer for atmospheric water vapor sounding and rain detection

    Science.gov (United States)

    Gagliano, J. A.; Platt, R. H.

    1985-01-01

    A 90/180 GHz multichannel radiometer is currently under development for NASA's 1985 Hurricane Mission onboard the Convair 990 research aircraft. The radiometer will be a fixed beam instrument with dual corrugated horns and a common lens antenna designed to operate simultaneously at 90 and 180 GHz. The all solid state front-end will contain three double side band data channels at 90 + or - 3 GHz, 180 + or - 3 GHz, and 180 + or - 7 GHz. The airborne radiometer will mount in a window port on the CV-990 and will maintain a fixed beam view approximately 14 degrees off zenith. The radiometer design is a Dicke chopper arrangement selected to achieve maximum absolute temperature accuracy and minimum brightness temperature sensitivity. Analog outputs of the three data channels will be calibrated dc voltages representing the observed radiometric brightness temperatures over the selected integration time.

  2. Some general reflections on {open_quotes}long pulse{close_quotes} neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, G.S. [Paul Scherrer Inst., Villigen (Switzerland)

    1995-12-31

    A long pulse spallation neutron source (LPSS) having about 20 times more time average thermal flux than its short pulse counterpart (SPSS) at the same proton beam power and featuring a pronounced time structure not available on CW sources (CWNS) of equal time average flux can in principle host instruments typical for both classes of facilities. While the need for additional choppers introduces some restrictions on inverted time of flight techniques typical for SPSS and high incident neutron energies are not easier to use on LPSS than on CWNS, taking advantage of the pulsed nature of the neutron flux can enhance significantly the performance of direct time of flight instruments and of crystal spectrometers or diffractometers. In the paper some of the options are reviewed in a general manner and criteria are discussed which can be used to optimize the performance enhancement.

  3. Principle component analysis and linear discriminant analysis of multi-spectral autofluorescence imaging data for differentiating basal cell carcinoma and healthy skin

    Science.gov (United States)

    Chernomyrdin, Nikita V.; Zaytsev, Kirill I.; Lesnichaya, Anastasiya D.; Kudrin, Konstantin G.; Cherkasova, Olga P.; Kurlov, Vladimir N.; Shikunova, Irina A.; Perchik, Alexei V.; Yurchenko, Stanislav O.; Reshetov, Igor V.

    2016-09-01

    In present paper, an ability to differentiate basal cell carcinoma (BCC) and healthy skin by combining multi-spectral autofluorescence imaging, principle component analysis (PCA), and linear discriminant analysis (LDA) has been demonstrated. For this purpose, the experimental setup, which includes excitation and detection branches, has been assembled. The excitation branch utilizes a mercury arc lamp equipped with a 365-nm narrow-linewidth excitation filter, a beam homogenizer, and a mechanical chopper. The detection branch employs a set of bandpass filters with the central wavelength of spectral transparency of λ = 400, 450, 500, and 550 nm, and a digital camera. The setup has been used to study three samples of freshly excised BCC. PCA and LDA have been implemented to analyze the data of multi-spectral fluorescence imaging. Observed results of this pilot study highlight the advantages of proposed imaging technique for skin cancer diagnosis.

  4. A Survey of Control Issues in PMSG-Based Small Wind-Turbine Systems

    DEFF Research Database (Denmark)

    Orlando, Natalia Angela; Liserre, Marco; Mastromauro, Rosa Anna

    2013-01-01

    In the field of wind energy generation particular interest has been focused in recent years on distributed generation through small wind-turbines (power unit 200 kW) because of their limited size and lower environmental impact. The field of small generation was dominated by the use of asynchronous...... generators directly connected to the grid, while recently permanent magnet synchronous generators (PMSG) with power converter, either partially or fully controlled, became popular. This paper reviews the control issues related to these small wind-turbine systems: generator torque control, speed....../position estimation, pitch control, braking chopper control, dc/dc converter control, and grid converter control. Specific issues for small wind-turbines arise in the wind energy extraction optimization and limitation and in the innovative concept of “universal” wind-turbine operation, that leads these system...

  5. A Wind Farm Electrical Systems Evaluation with EeFarm-II

    Directory of Open Access Journals (Sweden)

    Jan Pierik

    2010-03-01

    Full Text Available EeFarm-II is used to evaluate 13 different electrical systems for a 200 MW wind farm with a 100 km connection to shore. The evaluation is based on component manufacturer data of 2009. AC systems are compared to systems with DC connections inside the wind farm and DC connection to shore. Two options have the best performance for this wind farm size and distance: the AC system and the system with a DC connection to shore. EeFarm-II is a user friendly computer program for wind farm electrical and economic evaluation. It has been built as a Simulink Library in the graphical interface of Matlab-Simulink. EeFarm-II contains models of wind turbines, generators, transformers, AC cables, inductors, nodes, splitters, PWM converters, thyristor converters, DC cables, choppers and statcoms.

  6. Low Emittance Growth in a LEBT with Un-Neutralized Section

    Energy Technology Data Exchange (ETDEWEB)

    Prost, Lionel [Fermilab; Carneiro, Jean-Paul [Fermilab; Shemyakin, Alexander [Fermilab

    2016-06-01

    In a Low Energy Beam Transport line (LEBT), the emittance growth due to the beam's own space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report discusses the experimental realization of such a scheme at Fermilab's PXIE, where low beam emittance dilution was demonstrated

  7. Intelligent Microstepping System for Bipolar Stepper Motor Control with Step and Direction Interface

    Directory of Open Access Journals (Sweden)

    Alexandru Morar

    2010-06-01

    Full Text Available The paper presents a intelligent system for stepper motor control in a microstepping mode, which was designed and performed with a specialized integrated circuit (L292, made by SGS-THOMSON Microelectronics Company. With an interface and an adequate software, L292 circuit can be used as a chopper in 2 or 4 quadrant. The microstepping control system improves the positioning accuracy and eliminates low speed ripple and resonance effects in a stepper motor electric drive. The same microstepping system is ideal for robotics, printers, plotters, X-Y-Z tables and can facilitate the construction of very sophisticated positioning control systems while significantly reducing component cost, board space, design time and systems cost.

  8. A battery-powered high-current power supply for superconductors

    CERN Document Server

    Wake, M; Suda, K

    2002-01-01

    Since superconductors do not require voltages, a high-current power supply could run with low power if the voltage is sufficiently reduced. Even a battery-powered power supply could give as much as 2,000A for a superconductor. To demonstrate this hypothesis, a battery-powered 2,000A power supply was constructed. It uses an IGBT chopper and Schottky diode together with a specially arranged transformer to produce a high current with low voltage. Testing of 2,000A operation was performed for about 1.5 hr using 10 car batteries. Charging time for this operation was 8 hr. Ramping control was smooth and caused no trouble. Although the IGBT frequency ripple of 16.6 kHz was easily removed using a passive filter, spike noise remained in the output voltage. This ripple did not cause any trouble in operating a pancake-type inductive superconducting load. (author)

  9. Radiation damage/activity calculation for CSNS target station

    Science.gov (United States)

    Yin, W.; Liang, T. J.; Yu, Q. Z.; Jia, X. J.

    2010-03-01

    The radiation damages have been performed for Chinese spallation neutron source (CSNS) target center components that relies on Monte Carlo simulation code MCNPX. During the calculation, Bertini intranuclear cascade model, three level-density formulation GCCI, and multistage pre-equilibrium model MPM on which are provided within MCNPX are employed. We calculate the displacement per atom (DPA) and afterheat of the tungsten target, the stainless steel target vessel window and the aluminum alloy moderator vessel. As a hundred kW-level source, these spallation center components have the lifetime more than 5 year. We also give the activity for the T0 chopper of the beam line HIPD to get the primary data for making out a maintenance scenario.

  10. Molecular structure-property correlations from optical nonlinearity and thermal-relaxation dynamics.

    Science.gov (United States)

    Bhattacharyya, Indrajit; Priyadarshi, Shekhar; Goswami, Debabrata

    2009-02-01

    We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560 nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560 nm thermal lens pump and 780 nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

  11. Recent Progress with the KWISP Force Sensor

    CERN Document Server

    Cantatore, G; Hoffmann, D.H.H.; Karuza, M.; Semertzidis, Y.K.; Zioutas, K.

    2015-01-01

    The KWISP opto-mechanical force sensor has been built and calibrated in the INFN Trieste optics laboratory and is now under off-beam commissioning at CAST. It is designed to detect the pressure exerted by a flux of solar Chameleons on a thin (100 nm) Si$_3$N$_4$ micromembrane thanks to their direct coupling to matter. A thermally-limited force sensitivity of $1.5 \\cdot 10^{-14}~\\mbox{N}/\\sqrt{\\mbox{Hz}}$, corresponding to $7.5 \\cdot 10^{-16}~\\mbox{m}/\\sqrt{\\mbox{Hz}}$ in terms of displacement, has been obtained. An originally developed prototype chameleon chopper has been used in combination with the KWISP force sensor to conduct preliminary searches for solar chamaleons.

  12. Status and Operation of the Linac4 Ion Source Prototypes

    CERN Document Server

    Lettry, J; Andersson, P; Bertolo, S; Butterworth, A; Coutron, Y; Dallocchio, A; Chaudet, E; Gil-Flores, J; Guida, R; Hansen, J; Koszar, I; Mahner, E; Mastrostefano, C; Mathot, S; Mattei, S; Midttun, O; Moyret, P; Nisbet, D; O’Neil, M; Paoluzzi, M; Pasquino, C; Pereira, H; Rochez, J; Sanchez Alvarez, J; Sanchez Arias, J; Scrivens, R; Steyaert, D; Thaus, N; Hatayama, A; Nishida, K; Shibata, T; Yamamot, T; Otha, M

    2014-01-01

    CERN’s Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma and pulsed high voltages are described. The first experimental results of two prototypes relying on 2MHz RF- plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the LEBT, RFQ and chopper of Linac4.

  13. An integrated low 1/f noise and high-sensitivity CMOS instrumentation amplifier for TMR sensors

    Science.gov (United States)

    Gao, Zhiqiang; Luan, Bo; Zhao, Jincai; Liu, Xiaowei

    2017-03-01

    In this paper, a very low 1/f noise integrated Wheatstone bridge magnetoresistive sensor ASIC based on magnetic tunnel junction (MTJ) technology is presented for high sensitivity measurements. The present CMOS instrumentation amplifier employs the gain-boost folded-cascode structure based on the capacitive-feedback chopper-stabilized technique. By chopping both the input and the output of the amplifier, combined with MTJ magnetoresistive sensitive elements, a noise equivalent magnetoresistance 1 nT/Hz1/2 at 2 Hz, the equivalent input noise spectral density 17 nV/Hz1/2(@2Hz) is achieved. The chip-scale package of the TMR sensor and the instrumentation amplifier is only about 5 mm × 5 mm × 1 mm, while the whole DC current dissipates only 2 mA.

  14. Time-resolved X-ray scattering program at the Advanced Photon Source

    Energy Technology Data Exchange (ETDEWEB)

    Rodricks, B.

    1994-08-01

    The Time-Resolved Scattering Program`s goal is the development of instruments and techniques for time-resolved studies. This entails the development of wide bandpass and focusing optics, high-speed detectors, mechanical choppers, and components for the measurement and creation of changes in samples. Techniques being developed are pump-probe experiments, single-bunch scattering experiments, high-speed white and pink beam Laue scattering, and nanosecond to microsecond synchronization of instruments. This program will be carried out primarily from a white-beam, bend-magnet source, experimental station, 1-BM-B, that immediately follows the first optics enclosure (1-BM-A). This paper will describe the experimental station and instruments under development to carry out the program.

  15. Super-capacitor based energy storage system for improved load frequency control

    Energy Technology Data Exchange (ETDEWEB)

    Mufti, Mairaj ud din; Lone, Shameem Ahmad; Iqbal, Shiekh Javed; Ahmad, Muzzafar; Ismail, Mudasir [Electrical Engineering Department, National Institute of Technology, Hazratbal, Srinagar 190006, Jammu and Kashmir (India)

    2009-01-15

    A fuzzy-logic controlled super-capacitor bank (SCB) for improved load frequency control (LFC) of an interconnected power system is proposed, in this paper. The super-capacitor bank in each control area is interfaced with the area control bus through a power conversion system (PCS) comprising of a voltage source converter (VSC) and a buck-boost chopper. The fuzzy controller for SCB is designed in such a way that the effects of load disturbances are rejected on a continuous basis. Necessary models are developed and control and implementation aspects are presented in a detailed manner. Time domain simulations are carried out to demonstrate the effectiveness of the proposed scheme. The performance of the resulting power system under realistic situation is investigated by including the effects of generation rate constraint (GRC) and governor dead band (DB) in the simulation studies. (author)

  16. Soft x-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J.C.; Polewski, K.; Monteleone, D.C. [and others

    1998-01-23

    We have constructed an experimental station (beamline) at the National Synchrotron Light Source to measure circular dichroism (CD) using soft x-rays (250 {le} hv {le} 900 eV) from a time modulated elliptically polarizing wiggler. The polarization of the soft x-ray beam switches periodically between two opposite polarizations, hence permitting the use of phase-sensitive (lock-in) detection. While the wiggler can be modulated at frequencies up to 100 Hz, switching transients limit the actual practical frequency to {approx}25 Hz. With analog detection, switching transients are blocked by a chopper synchronized to the frequency and phase of the wiggler. The CD is obtained from the ratio of the signal recovered at the frequency of polarization modulation, f, to the average beam intensity, which is recovered by synchronous detection at frequency 2f.

  17. Single-mode oscillation of a diode-pumped Nd:YAG microchip laser at 1835 nm

    Science.gov (United States)

    Lan, Jinglong; Cui, Qin; Wang, Yi; Xu, Bin; Xu, Huiying; Cai, Zhiping

    2016-10-01

    Single-mode oscillation of a diode-pumped conventional Nd:YAG laser at 1835 nm is demonstrated, for the first time to our knowledge, in the form of microchip configuration. The achieved maximum output power reaches 189 mW with slope efficiency of about 5.5% with respect to absorbed pump power. The laser spectra are measured with linewidth less than 0.08 nm indicating a single longitudinal mode. The output laser beam is also measured to be near diffraction-limited with M2 factors of about 1.2 and 1.5 in x and y directions. Using a mechanical chopper with 50% duty cycle, the maximum output power is improved to 253 mW with slope efficiency of about 9.7%.

  18. Performance Analysis of a Grid connected Wind Energy system

    Directory of Open Access Journals (Sweden)

    Manju Khare

    2016-07-01

    Full Text Available This paper is concerned with the study of a small wind generation system used for battery charging. A topology that aims at the exploitation of maximum energy from the generator, generated at low speed is proposed. The characteristics of the wind turbine and the generator are discussed, providing the overview of the system modeling. Simulation tests of the system are obtained using MATLAB/SIMULINK. We adopt compact permanent magnet type synchronous generator, which doesn’t need exciting current, and step- up /down buck-boost chopper to wind power generating system of a few kW output with rotor speed sensor. In addition, we employ rectifier circuit using Diode Bridge instead of AC-DC converter with PWM method and a battery charging system. Using these methods we achieve a simple wind power generation system

  19. Optical dating of the Jingshuiwan Paleolithic site of Three Gorges, China

    Institute of Scientific and Technical Information of China (English)

    PEI Shuwen; ZHANG Jiafu; GAO Xing; ZHOU Liping; FENG Xingwu; CHEN Fuyou

    2006-01-01

    The Jingshuiwan Paleolithic site occupies the second terrace on the right bank of the Yangtze River. The lithic assemblage is characterized by choppers and scrapers made on pebbles and large flakes--the typical lithic industry of South China. Deposits of the site are mainly composed of fluvial sediments. Quartz grains extracted from these fluvial sediments from which the artifacts were uncovered were dated using the optically stimulated luminescence/single-aliquot regenerative-dose technique. The dating results show that ancient human activities at this site took place in the early Upper Pleistocene (ca. 70 ka). The successful age analysis of the Jingshuiwan site is considered as a major break- through in chronological analysis of Paleolithic open site in the Three Gorges region and even in South China. The dates obtained help to establish a more complete chronological framework of the Paleolithic cultural sequence in the region, and bear significant implications in studying modern human origins in China.

  20. Characterization of radiated electromagnetic fields using equivalent sources - Application to the EMC of power printed circuit boards

    Science.gov (United States)

    Beghou, Lotfi; Pichon, Lionel; Costa, François

    2009-01-01

    This article presents an original methodology to characterize electromagnetic disturbances radiated from power electronic devices. The method is based on the substitution of the power device by an equivalent set of elemental dipoles (electric and magnetic dipoles). The set of dipoles radiates the same near-field. The dipoles are determined from a near field cartography of the fields obtained with a measurement bench. The dipoles parameters are determined by solving an inverse problem using a genetic algorithm. The efficiency of the approach is demonstrated on an academic DC-DC converter. Finally some results about the chopper are presented. The methodology has two advantages: first it allows one to define some threshold limitations for electromagnetic fields on the surroundings and secondly it gives the location of the real source distribution. To cite this article: L. Beghou et al., C. R. Physique 10 (2009).

  1. A 0.18 micrometer CMOS Thermopile Readout ASIC Immune to 50 MRAD Total Ionizing Dose (SI) and Single Event Latchup to 174MeV-cm(exp 2)/mg

    Science.gov (United States)

    Quilligan, Gerard T.; Aslam, Shahid; Lakew, Brook; DuMonthier, Jeffery J.; Katz, Richard B.; Kleyner, Igor

    2014-01-01

    Radiation hardened by design (RHBD) techniques allow commercial CMOS circuits to operate in high total ionizing dose and particle fluence environments. Our radiation hard multi-channel digitizer (MCD) ASIC (Figure 1) is a versatile analog system on a chip (SoC) fabricated in 180nm CMOS. It provides 18 chopper stabilized amplifier channels, a 16- bit sigma-delta analog-digital converter (SDADC) and an on-chip controller. The MCD was evaluated at Goddard Space Flight Center and Texas A&M University's radiation effects facilities and found to be immune to single event latchup (SEL) and total ionizing dose (TID) at 174 MeV-cm(exp 2)/mg and 50 Mrad (Si) respectively.

  2. High efficiency and long life of a three-phase power conditioner via interleave control

    Directory of Open Access Journals (Sweden)

    Kenji Amei

    2016-01-01

    Full Text Available This study describes the high efficiency and long life of three-phase power conditioners of a photovoltaic (PV system. The current PV system, which is widely spread, has two problems. The first problem is the lifetime of a power conditioner, whereas the other problem is the drop in the efficiency of the conversion because of the characteristics of the solar cell. For those problems, the solar panel and boost chopper circuit were divided into a plurality to configure a power conditioner, and an electrolytic capacitor-less driver with interleave control was realized. The drop in the current generated by the solar cell was suppressed, and an improvement in power generation efficiency was expected. The configuration and principle of a proposed circuit were explained, and results of simulation and experiment were reported.

  3. Implementation of fuzzy-sliding mode based control of a grid connected photovoltaic system.

    Science.gov (United States)

    Menadi, Abdelkrim; Abdeddaim, Sabrina; Ghamri, Ahmed; Betka, Achour

    2015-09-01

    The present work describes an optimal operation of a small scale photovoltaic system connected to a micro-grid, based on both sliding mode and fuzzy logic control. Real time implementation is done through a dSPACE 1104 single board, controlling a boost chopper on the PV array side and a voltage source inverter (VSI) on the grid side. The sliding mode controller tracks permanently the maximum power of the PV array regardless of atmospheric condition variations, while The fuzzy logic controller (FLC) regulates the DC-link voltage, and ensures via current control of the VSI a quasi-total transit of the extracted PV power to the grid under a unity power factor operation. Simulation results, carried out via Matlab-Simulink package were approved through experiment, showing the effectiveness of the proposed control techniques.

  4. Orbit Determination with Angle-only Data from the First Korean Optical Satellite Tracking System, OWL-Net

    Science.gov (United States)

    Choi, J.; Jo, J.

    2016-09-01

    The optical satellite tracking data obtained by the first Korean optical satellite tracking system, Optical Wide-field patrol - Network (OWL-Net), had been examined for precision orbit determination. During the test observation at Israel site, we have successfully observed a satellite with Laser Retro Reflector (LRR) to calibrate the angle-only metric data. The OWL observation system is using a chopper equipment to get dense observation data in one-shot over 100 points for the low Earth orbit objects. After several corrections, orbit determination process was done with validated metric data. The TLE with the same epoch of the end of the first arc was used for the initial orbital parameter. Orbit Determination Tool Kit (ODTK) was used for an analysis of a performance of orbit estimation using the angle-only measurements. We have been developing batch style orbit estimator.

  5. The SOFIA Observatory at the Start of Routine Science Operations : Mission capabilities and performance

    CERN Document Server

    Temi, Pasquale; Young, Erick; Adams, Joseph D; Adams, Sybil; Andersson, B -G; Becklin, Eric E; Boogert, Adwin; Brewster, Rick; Burgh, Eric; Cobleigh, Brent R; Culp, Steven; De Buizer, Jim; Dunham, Edward W; Engfer, Christian; Ediss, Geoffrey; Fujieh, Maura; Grashuis, Randy; Gross, Michael; Harmon, Edward; Helton, Andrew; Hoffman, Douglas; Homan, Jeff; Hutwohl, Michael; Jakob, Holger; Jensen, Stephen C; Kaminski, Charles; Kozarsky, Daniel; Krabbe, Alfred; Klein, Randolf; Lammen, Yannick; Lampater, Ulrich; Latter, William B; Le, Jeanette; McKown, Nancy; Melchiorri, Riccardo; Meyer, Allan W; Miles, John; Miller, Walter E; Miller, Scott; Moore, Elizabeth; Nickison, Donald J; Opshaug, Kortney; Pfueller, Enrico; Radomski, James; Rasmussen, John; Reach, William; Reinacher, Andreas; Roellig, Thomas L; Sandell, Goran; Sankrit, Ravi; Savage, Maureen L; Shenoy, Sachindev; Schonfeld, Julie E; Shuping, Ralph Y; Smith, Erin C; Talebi, Ehsan; Teufel, Stefan; Tseng, Ting C; Vacca, William D; Vaillancourt, John; Van Cleve, Jeffrey E; Wiedemann, Manuel; Wolf, Jurgen; Zavala, Eddie; Zeile, Oliver; Zell, Peter T; Zinnecker, Hans

    2014-01-01

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities are viewed as a first comprehensive assessment of the Observatory's performance and are used to guide future development activities, as well as to identify additional Observatory upgrades. Pointing stability was evaluated, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an active mass damper system installed on the telescope. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have also been performed. Additional tests targeted basic Observatory capabilities and requirements, including pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights ...

  6. Comparative study of energy conversion system dedicated to a small wind turbine; Etude comparative de chaines de conversion d'energie dediees a une eolienne de petite puissance

    Energy Technology Data Exchange (ETDEWEB)

    Mirecki, A

    2005-07-01

    This study presents a comparison of architectures and strategies of energy management dedicated to VAWT turbines such as Savonius. A Maximum Power Point Tracking must be implemented in order to optimize the energetic behavior. A torque or a speed control, or an indirect control of the DC bus current is possible. In the fact that the wind turbine characteristic is unknown, an operational research based on fuzzy logic is proposed. Aiming to minimize the cost of the static conversion structure, simple structures (diode bridge inverter, associated with DC-DC chopper) are analyzed and compared with a system based on a PWM Voltage Source Inverter. A test bench has been realized in the meantime as a system simulation. Comparisons of the provided energy are made for different wind speeds allowing to evaluate the performance of each structure and of the control strategies. (author)

  7. Analog integrated circuits design for processing physiological signals.

    Science.gov (United States)

    Li, Yan; Poon, Carmen C Y; Zhang, Yuan-Ting

    2010-01-01

    Analog integrated circuits (ICs) designed for processing physiological signals are important building blocks of wearable and implantable medical devices used for health monitoring or restoring lost body functions. Due to the nature of physiological signals and the corresponding application scenarios, the ICs designed for these applications should have low power consumption, low cutoff frequency, and low input-referred noise. In this paper, techniques for designing the analog front-end circuits with these three characteristics will be reviewed, including subthreshold circuits, bulk-driven MOSFETs, floating gate MOSFETs, and log-domain circuits to reduce power consumption; methods for designing fully integrated low cutoff frequency circuits; as well as chopper stabilization (CHS) and other techniques that can be used to achieve a high signal-to-noise performance. Novel applications using these techniques will also be discussed.

  8. Statistical simulations of machine errors for LINAC4

    CERN Document Server

    Baylac, M; Froidefond, E; Sargsyan, E

    2006-01-01

    LINAC 4 is a normal conducting H- linac proposed at CERN to provide a higher proton flux to the CERN accelerator chain. It should replace the existing LINAC 2 as injector to the Proton Synchrotron Booster and can also operate in the future as the front end of the SPL, a 3.5 GeV Superconductingg Proton Linac. LINAC 4 consists of a Radio-Frequency Quadrupole, a chopper line, a Drift Tube Linac (DTL) and a Cell Coupled DTL all operating at 352 MHz and finally a Side Coupled Linac at 704 MHz. Beam dynamics was studied and optimized performing end-to-end simulations. This paper presents statistical simulations of machine errors which were performed in order to validate the proposed design.

  9. Study of the design of CSNS MEBT

    Institute of Scientific and Technical Information of China (English)

    OUYANG Hua-Fu; LIU Hua-Chang; FU Shi-Nian

    2009-01-01

    The design of CSNS MEBT has two objectives: (1) to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL; (2) to further chop the beam into the required time structure asked by RCS. It is very difficult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly, the optical design is done and optimized, and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly, based on the different beam envelopes obtained by TRACE-3D and PARMELA, the least deflecting angle of the chopper is determined by TRACE-3D. At last, the field of steering magnet is determined through simulations.

  10. ACCELERATORS: Study of the design of CSNS MEBT

    Science.gov (United States)

    Ouyang, Hua-Fu; Liu, Hua-Chang; Fu, Shi-Nian

    2009-07-01

    The design of CSNS MEBT has two objectives: (1) to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL; (2) to further chop the beam into the required time structure asked by RCS. It is very difficult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly, the optical design is done and optimized, and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly, based on the different beam envelopes obtained by TRACE-3D and PARMELA, the least deflecting angle of the chopper is determined by TRACE-3D. At last, the field of steering magnet is determined through simulations.

  11. Picosecond time-resolved laser pump/X-ray probe experiments using a gated single-photon-counting area detector

    DEFF Research Database (Denmark)

    Ejdrup, T.; Lemke, H.T.; Haldrup, Martin Kristoffer

    2009-01-01

    . The capability of the gated PILATUS detector to selectively detect the signal from a given X-ray pulse in 24 bunch mode at the APS storage ring is demonstrated. A test experiment performed on polycrystalline organic thin films of [alpha]-perylene illustrates the possibility of reaching an X-ray pulse duration......The recent developments in X-ray detectors have opened new possibilities in the area of time-resolved pump/probe X-ray experiments; this article presents the novel use of a PILATUS detector to achieve X-ray pulse duration limited time-resolution at the Advanced Photon Source (APS), USA...... limited time-resolution of 60 ps using the gated PILATUS detector. This is the first demonstration of X-ray pulse duration limited data recorded using an area detector without the use of a mechanical chopper array at the beamline....

  12. Measurement and Analysis of Magnetic Field Radiated from D.C. Tramway: A case study for Tunis’s metro

    Directory of Open Access Journals (Sweden)

    J. Ben Hadj Slama

    2008-06-01

    Full Text Available High-power electrical drives, subsystems, and equipment mounted on board of rolling stock make the internal environment potentially harsh from the point of view of electromagnetic (EM field emissions. In particular, at low frequencies, electronically controlled power drive systems behave as effective emission sources. This paper deals with characterization of electromagnetic field radiated from D.C. railway systems. The D.C. railway system of Tunis’s urban electric metro is described. The magnetic field is measured at different points inside and near the moving D.C. train. Measurement results are presented and analyzed. Analysis of measurement results shows that, within frequency range 100kHz-20MHz, the radiated magnetic field is coming from power electronic systems embedded on the train. In particular, choppers, D.C. motors and their connecting cables represent the most important emitting source of magnetic field in the D.C. tramway.

  13. Beam-transport optimization for cold-neutron spectrometer

    Directory of Open Access Journals (Sweden)

    Nakajima Kenji

    2015-01-01

    Full Text Available We report the design of the beam-transport system (especially the vertical geometry for a cold-neutron disk-chopper spectrometer AMATERAS at J-PARC. Based on the elliptical shape, which is one of the most effective geometries for a ballistic mirror, the design was optimized to obtain, at the sample position, a neutron beam with high flux without serious degrading in divergence and spacial homogeneity within the boundary conditions required from actual spectrometer construction. The optimum focal point was examined. An ideal elliptical shape was modified to reduce its height without serious loss of transmission. The final result was adapted to the construction requirements of AMATERAS. Although the ideas studied in this paper are considered for the AMATERAS case, they can be useful also to other spectrometers in similar situations.

  14. Basic Design Report of DC-TOF Inelastic Neutron Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    So, Ji Yong; Park, Je Geun; Moon, Myung Kook; Cho, Sang Jin; Choi, Yung Hyun; Lee, Chang Hee

    2006-04-15

    We made Basic designs of neutron guide, choppers, and detectors in order to optimize the design parameters of DC-TOF to be built in the HANARO Cold Neutron Guide Hall. In addition, we calculated the expected performance of DC-TOF using Monte Carlo simulations and evaluated the properties of neutron beam. Based on the results we obtained, we have compared the expected performance of the DC-TOF with those of existing instruments overseas. In conclusion, we believe that we will be able to construct the DC-TOF at HANARO as one of the best instruments of its kinds and it will become an invaluable instrument to researchers in the related field.

  15. Fast Monte Carlo simulation of a dispersive sample on the SEQUOIA spectrometer at the SNS

    Energy Technology Data Exchange (ETDEWEB)

    Granroth, Garrett E [ORNL; Chen, Meili [ORNL; Kohl, James Arthur [ORNL; Hagen, Mark E [ORNL; Cobb, John W [ORNL

    2007-01-01

    Simulation of an inelastic scattering experiment, with a sample and a large pixilated detector, usually requires days of time because of finite processor speeds. We report simulations on an SNS (Spallation Neutron Source) instrument, SEQUOIA, that reduce the time to less than 2 hours by using parallelization and the resources of the TeraGrid. SEQUOIA is a fine resolution (∆E/Ei ~ 1%) chopper spectrometer under construction at the SNS. It utilizes incident energies from Ei = 20 meV to 2 eV and will have ~ 144,000 detector pixels covering 1.6 Sr of solid angle. The full spectrometer, including a 1-D dispersive sample, has been simulated using the Monte Carlo package McStas. This paper summarizes the method of parallelization for and results from these simulations. In addition, limitations of and proposed improvements to current analysis software will be discussed.

  16. Research and Development of Digital RF Admittance Level Meter%数字式射频导纳物位仪的研究与开发

    Institute of Scientific and Technical Information of China (English)

    刘虎; 周蕾

    2014-01-01

    分析了电容式物位测量仪挂料产生的原因及其对测量的影响,提出采用斩波积分方法消除或减小挂料影响,提高信噪比,设计了基于MSP430F149的数字式射频导纳物位仪,并给出了硬件原理框图。%Through analyzing the reasons which causing probe attachment and the effects on the measure re-sult , a chopper integral method was proposed to eliminate or reduce the probe attachment influence so that sig -nal noise ratio can be improved;and a MSP430F149-based digital RF admittance level meter was developed , including hardware block diagram .

  17. A Circadian and Cardiac Intraocular Pressure Sensor for Smart Implantable Lens.

    Science.gov (United States)

    Donida, Achille; Di Dato, Giuseppe; Cunzolo, Paolo; Sala, Marco; Piffaretti, Filippo; Orsatti, Paolo; Barrettino, Diego

    2015-12-01

    This paper presents a new system to measure the Intraocular Pressure (IOP) with very high accuracy (0.036 mbar) used for monitoring glaucoma. The system not only monitors the daily variation of the IOP (circadian IOP), but also allows to perform an spectral analysis of the pressure signal generated by the heartbeat (cardiac IOP). The system comprises a piezoresistive pressure sensor, an application-specific integrated circuit (ASIC) to read out the sensor data and an external reader installed on customized glasses. The ASIC readout electronics combines chopping modulation with correlated double sampling (CDS) in order to eliminate both the amplifier offset and the chopper ripple at the sampling frequency. In addition, programmable current sources are used to compensate for the atmospheric pressure ( 800-1200 mbar ) and the circadian component (± 7 mbar) thus allowing to read out the very weak cardiac signals (± 1.6 mbar) with a maximum accuracy of 0.036 mbar.

  18. Practical Application of the AC Chopping PWM Control Timing%一种实用化的交流斩波PWM控制时序研究

    Institute of Scientific and Technical Information of China (English)

    雷鸣; 郭斌; 雷志勇

    2012-01-01

    针对交流斩波电路容易产生短路,电压过冲和过电流等问题,提出一种基于交流电压和交流电流过零检测的交流斩波控制方法.通过对不同性质负载的电压和电流的相位研究,使用对电压和电流过零信号进行滤波,调相和逻辑运算后使能交流斩波的方法,避开过零点附近振荡过零区域,避免主电路产生短路.通过对斩波电路拓扑和控制时序的研究,使用逐渐改 变PWM控制信号占空比的方法,实现电压软过度.通过实验检测,交流斩波调压电路实现了电压软过度的目的,并且不再出现短路,电压过冲和过电流现象.使用这种方法,从本质上解决了传统交流斩波电路中的短路,电压过冲和过电流现象,保证了交流斩波系统安全持久运行.%Short circuit,voltage overshoot and over current are liable to happen in an AC chopper. To solve these problems, an AC chopping PWM control method based on the AC voltage and AC current zero-crossing detection is proposed. Based on the analysis of the voltage and current phase of different loads,the method of voltage and current zero crossing signal filterring, phase modulation and logical operations which can realize AC chopping is used to keep away from the zero-crossing oscillations near the zero area,avoiding short circuit happening in the main circuit. Based on the study of the AC chopper topology and sequence control,the method for gradually changing the duty cycle of PWM control signal is used to achieve soft excessive, avoiding over shoot and over current happening in the main circuit. Through the experimental detection, the AC chopper realized voltage soft excessive with no short circuit, voltage overshoot and over current. By using this method,the traditional problems--AC chopper short circuit, voltage overshoot and over current can be solved essentially,ensuring AC chopping system's security and lasting operation.

  19. CHARACTERIZATION OF LITHIC COMPLEXES FROM BUIA (DANDIERO BASIN, DANAKIL DEPRESSION, ERITREA

    Directory of Open Access Journals (Sweden)

    FABIO MARTINI

    2004-12-01

    Full Text Available This paper discusses a very partial sampling of the archeological evidence found in more than 200 sites containing lithic artefacts and faunal remains which have been surveyed in the Dandiero (Buia Basin (Danakil Depression, Eritrea. All the lithic complexes are referred to the Acheulean. The authors present the results of  a preliminary study carried on some of the most important assemblages, especially the complex referred to the Homo-bearing levels. The lithic assemblages are characterized by different frequencies of hand-axes, cleavers, choppers and flakes. The techno-typological characters of the artefacts, all of which coform to an Acheulean standard, allow us to propose some preliminary hypotheses about their variability. The analyzed assemblages are then compared to the Early Paleolithic lithic complexes in east Africa. 

  20. A Simulation-Based Study of Dorsal Cochlear Nucleus Pyramidal Cell Firing Patterns

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Daliri

    2012-02-01

    Full Text Available A two-variable integrate and fire model is presented to study the role of transient outward potassium currents in producing temporal aspects of dorsal cochlear nucleus (DCN pyramidal cells with different profiles namely the chopper, the pauser and the buildup. This conductance based model is a reduced version of KM-LIF model (Meng & Rinzel, 2010 which captures qualitative firing features of a detailed physiological model (Kanold & Manis, 2000.For our development we benefit from transient potassium currents properties i.e.fast activation and slow inactivation to generate long latency before start of firing.We compare our minimal model outputs in response to a hyperpolarizing stimulus fallowed by a depolarizing one with the data of KM-LIF model.The results conform well to the KM-LIF model with lower complexity.

  1. Two-color mid-infrared thermometer with a hollow glass optical fiber.

    Science.gov (United States)

    Small, W; Celliers, P M; Da Silva, L B; Matthews, D L; Soltz, B A

    1998-10-01

    We have developed a low-temperature optical-fiber-based two-color infrared thermometer. A single 700-mum-bore hollow glass optical fiber collects and transmits radiation that is then modulated and split into two paths by a reflective optical chopper. Two different thermoelectrically cooled mid-infrared HgCdZnTe photoconductors monitor the chopped signals that are recovered with lock-in amplification. With the two previously obtained blackbody calibration equations, a computer algorithm calculates the true temperature and emissivity of a target in real time, taking into account reflection of the ambient radiation field from the target surface. The small numerical aperture of the hollow glass fiber and the fast response of the detectors, together with the two-color principle, permit high spatial and temporal resolution while allowing the user to dynamically alter the fiber-to-target distance.

  2. An Induction Motor Drive System Based on the Back-To-Back Connection of Two Five-Level Diode-Clamped PWM Converters

    Science.gov (United States)

    Kondo, Yosuke; Natchpong, Hatti; Akagi, Hirofumi

    This paper discusses a 6.6-kV transformerless motor drive system based on the back-to-back connection of two five-level diode-clamped PWM converters. In addition, this paper designs, constructs and experimentally tests a down-scaled model rated at 200V and 5.5kW. This system consist of the two five-level converters, a common dc-link, and voltage-balancing circuits using two bi-directional buck-boost choppers. Experimental results obtained from the down-scaled model verify the validity of the system design, giving promise of the viability of the 6.6-kV transformerless motor drive system.

  3. A 6.6-kV Transformerless STATCOM Based on a Five-Level Diode-Clamped Converter

    Science.gov (United States)

    Kondo, Yosuke; Fujita, Hideaki; Akagi, Hirofumi

    This paper discusses a 6.6-kV transformerless STATCOM intended for installation on industrial and utility distribution systems in the near future. In addition, this paper provides experimental results obtained from a laboratory model rated at 200V and 10kVA. The authors propose such a control method as to superimpose a 6th-harmonic zero-sequence component on each of three-phase voltage references. This helps to stabilize the voltage of the inner midpoint in the dc link. As a result, the laboratory model installs two bi-directional buck-boost choppers on the dc link for the porpose of stabilizing the voltages of two outer midpoints. Experimental results obtained from the laboratory model verify the validity of the system design, giving promise of the viability of the 6.6-kV transformerless STATCOM.

  4. Fault Tolerant Operation of ISOP Multicell Dc-Dc Converter Using Active Gate Controlled SiC Protection Switch

    Directory of Open Access Journals (Sweden)

    Yusuke Hayashi

    2016-01-01

    Full Text Available An active gate controlled semiconductor protection switch using SiC-MOSFET is proposed to achieve the fault tolerant operation of ISOP (Input Series and Output Parallel connected multicell dc-dc converter. The SiC-MOSFET with high temperature capability simplifies the configuration of the protection circuit, and its on-resistance control by the active gate controller realizes the smooth protection without the voltage and the current surges. The first laboratory prototype of the protection switch is fabricated by using a SiC-MOSFET with a high frequency buck chopper for the active gate controller. The effectiveness of the proposed protection switch is verified, taking the impact of the volume reduction into account.

  5. Beam diagnostics measurements at 3 MeV of the LINAC4 H- beam at CERN

    CERN Document Server

    Zocca, F; Duraffourg, M; Focker, G J; Gerard, D; Kolad, B; Lenardon, F; Ludwig, M; Raich, U; Roncarolo, F; Sordet, M; Tan, J; Tassan-Viol, J; Vuitton, C; Feshenko, A

    2014-01-01

    As part of the CERN LHC injector chain upgrade, LINAC4 [1, 2] will accelerate H- ions to 160 MeV, replacing the old 50 MeV proton linac. The ion source, the Low Energy Beam Transfer (LEBT) line, the 3 MeV Radio Frequency Quadrupole and the Medium Energy Beam Transfer (MEBT) line hosting a chopper, have been commissioned in the LINAC4 tunnel. Diagnostic devices are installed in the LEBT and MEBT line and in a movable diagnostics test bench which is temporarily added to the MEBT exit. The paper gives an overview of all the instruments used, including beam current transformers, beam position monitors, wire scanners and wire grids for transverse profile measurements, a longitudinal bunch shape monitor and a slit-and-grid emittance meter. The instrumentation performance is discussed and the measurement results that allowed characterizing the 3 MeV beam in the LINAC4 tunnel are summarized.

  6. Semiconductor device models for circuit simulation power electronics; Modeles de composants semiconducteurs pour la simulation des circuits en electronique de puissance

    Energy Technology Data Exchange (ETDEWEB)

    Berraies, M.O.

    1998-09-10

    In this thesis, an alternative strategy based on a regional approach to modeling and a new partition of the model library in the simulation is proposed. The main objective is to substitute for the usual concept of `one device, on model` that of an adaptable assembly of a limited number of submodels associated with well-identified regions of semiconductor structures. In other words, the library will only contain the primitive building-blocks of the power device models. This strategy guarantees the compatibility of the various semiconductor models in terms of physical concepts, validity domain, accuracy, homogeneity of parameter identification procedures, similarly of implementation in the simulator. This approach has been applied to PIN diodes and IGBTs for experimental validation. The next step consisted on the simulation of circuit involving several interacting devices. A simple IGBT/PIN diode chopper cell has been chosen. The results obtained compare well with experiment. This demonstrates the consistency of the proposed approach. (author) 43 refs.

  7. Performance Analysis of Savonius Rotor Based Hydropower Generation Scheme with Electronic Load Controller

    Directory of Open Access Journals (Sweden)

    Rajen Pudur

    2016-01-01

    Full Text Available This paper describes the performance of electronic load controller (ELC of asynchronous generator (AG coupled to an uncontrolled Savonius turbine and variable water velocity. An AC-DC-AC converter with a dc link capacitor is employed to maintain the required frequency. The ELC which is feeding a resistive dump load is connected in parallel with the generating system and the power consumption is varied through the duty cycle of the chopper. Gate triggering of ELC is accomplished through sinusoidal pulse width modulation (SPWM by sensing the load current. A MATLAB/Simulink model of Savonius rotor, asynchronous generator, ELC, and three-phase load is presented. The proposed scheme is tested under various load conditions under varying water velocities and the performances are observed to be satisfactory.

  8. Testing and evaluation of an alcohol production facility utilizing potatoes as a feedstock. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kuby, W.; Nackord, S.; Wyss, W.

    1984-05-01

    This study presents the sampling and analysis results for the characterization of liquid effluents and solid residuals from a culled potato feedstock process for the production of ethanol for use as fuel. The facility tested produces approximately 1 million gallons per year of ethanol and is located in eastern Idaho. Liquid and solid samples were taken throughout the process from the following locations: sluice/flume water, chopper product, makeup water, cooker product, fermenter product, beer tank, stillage, interim and final product, washwater, fuel oil, bath and 'Sparkle' bath. Analytical results for the ethanol plant effluents include: ethanol and sugar content, conventional parameters, metals, cyanide, phenols, nutrients, oil and grease, priority pollutant organics, and selected pesticides. The most significant characteristics of concern were the BOD and COD levels.

  9. Design and Development of DSP Controlled Filament Power Supply for 1 MW, 352.2 MHz Klystron

    Directory of Open Access Journals (Sweden)

    Akhilesh Tripathi# , M. K. Badapanda and P. R. Hannurkar

    2013-04-01

    Full Text Available A digitally controlled current regulated 20 V, 25 A dc power supply employing IGBT based chopper is developed as the filament power supply for 1 MW, 352.2 MHz, Thales make TH 2089 klystron amplifier. The filament of this klystron is floating at cathode voltage of -100 kV dc, hence this power supply is kept on a floated platform and isolated through a suitable HV isolation transformer. Control and protection of this power supply is implemented through Texas make TMS320F2812 digital signal processor (DSP and fibre optics based optical communication is adopted. Detailed simulation is carried out and a close match between simulated and experimental results was obtained, which are presented in this paper. The long term output current stability and peak to peak output current ripple of this power supply are found to be below 0.5 %

  10. Experimental research on spectrum and imaging of continuous-wave terahertz radiation based on interferometry

    Science.gov (United States)

    Lu, Tie-Lin; Yuan, Hui; Kong, Ling-Qin; Zhao, Yue-Jin; Zhang, Liang-Liang; Zhang, Cun-Lin

    2016-08-01

    A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values. Project supported by the National Natural Science Foundation of China (Grant Nos. 61377109 and 11374007).

  11. Tests of modulated intensity small angle scattering in time of flight mode

    Energy Technology Data Exchange (ETDEWEB)

    Brandl, G. [Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universitaet Muenchen, Lichtenbergstr. 1, 85747 Garching (Germany); Physik Department E21, Technische Universitaet Muenchen, James-Franck-Str., 85747 Garching (Germany); Lal, J. [Argonne National Laboratory, Materials Science Division, Argonne, IL 60439 (United States); Carpenter, J. [Argonne National Laboratory, Materials Science Division, Argonne, IL 60439 (United States); Oak Ridge National Laboratory, Oak Ridge, TN 37831-6477 (United States); Crow, L.; Robertson, L. [Oak Ridge National Laboratory, Oak Ridge, TN 37831-6477 (United States); Georgii, R., E-mail: Robert.Georgii@frm2.tum.de [Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universitaet Muenchen, Lichtenbergstr. 1, 85747 Garching (Germany); Physik Department E21, Technische Universitaet Muenchen, James-Franck-Str., 85747 Garching (Germany); Boeni, P. [Physik Department E21, Technische Universitaet Muenchen, James-Franck-Str., 85747 Garching (Germany); Bleuel, M. [Technical University of Delft, Mekelweg 15, 2629 JB Delft (Netherlands)

    2012-03-01

    We report results of tests of the MISANS technique at the CG-1D beamline at the High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). A chopper at 40 Hz simulated a pulsed neutron source at the beamline. A compact turn-key MISANS module operating with the pulsed beam was installed and a well characterized MnSi sample was tested. The feasibility of application of high magnetic fields at the sample position was also explored. These tests demonstrate the great potential of this technique, in particular for examining magnetic and depolarizing samples, under extreme sample environments at pulsed sources, such as the Spallation Neutron Source (SNS) or the planned European Spallation Source (ESS).

  12. A new regional group of the lower paleolithic in Brittany (France), recently dated by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Monnier, J.L.; Hinguant, S.; Gebhardt, A.; Marguerie, D.; Molines, N.; Morzadec, H. (Rennes-1 Univ., 35 (France)); Hallegouet, B. (Brest Univ., 29 (France)); Laurent, M.; Auguste, P.; Bahain, J.J.; Falgueres, C.; Yokoyama, Y. (Institut de Paleontologie, 75 - Paris (France))

    1994-07-07

    ESR dates obtained at Menez-Dregan 1 (Brittany, France) focus interest on this Lower Paleolithic site and demonstrate that the preserved anthropic combustion structures are among the oldest known in the world. It allows the dating not only of the little known 'Colombanian Group' (it is an 'archaic' original group characterized by many choppers and very few handaxes, different from the Acheulian), but also, for the first time, of the old beaches on the southern coast of Brittany. Preserved bone remains are also very infrequent in Palaeolithic sites of Western France. The dating of the paleolithic layer at the top of the third fossil beach can be connected with isotopic stage 11 or the beginning of isotopic stage 10; it shows that the age of the geological and archaeological layers of Menez-Dregan 1 is probably between 350.000 and 500.000 years.

  13. Low Voltage Ride-Through Capability Solutions for Permanent Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Victor F. Mendes

    2016-01-01

    Full Text Available Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC, i.e., the system capability to sustain operation during voltage sags. In this sense, the present paper intends to investigate the behavior of a full-converter wind generator with a permanent magnet synchronous machine during symmetrical and asymmetrical voltage sags. Two solutions to improve the low voltage ride-through capability (LVRT of this technology are analyzed: discharging resistors (brake chopper and resonant controllers (RCs. The design and limitations of these solutions and the others proposed in the literature are discussed. Experimental results in a 34 kW test bench, which represents a scaled prototype of a real 2 MW wind conversion system, are presented.

  14. Installation and first operation of the International Fusion Materials Irradiation Facility injector at the Rokkasho site

    Energy Technology Data Exchange (ETDEWEB)

    Gobin, Raphael, E-mail: rjgobin@cea.fr; Bogard, Daniel; Bolzon, Benoit; Bourdelle, Gilles; Chauvin, Nicolas; Chel, Stéphane; Girardot, Patrick; Gomes, Adelino; Guiho, Patrice; Harrault, Francis; Loiseau, Denis; Lussignol, Yves; Misiara, Nicolas; Roger, Arnaud; Senée, Franck; Valette, Matthieu [Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/Saclay, DSM/IRFU, 91191 Gif/Yvette (France); Cara, Philippe; Duglué, Daniel; Gex, Dominique [Fusion for Energy, BFD Department, Garching (Germany); Okumura, Yoshikazu [IFMIF/EVEDA Project Team, Obuchi-Omotedate, 2-166, Rokkasho, Aomori (Japan); and others

    2016-02-15

    The International Fusion Materials Irradiation Facility (IFMIF) linear IFMIF prototype accelerator injector dedicated to high intensity deuteron beam production has been designed, built, and tested at CEA/Saclay between 2008 and 2012. After the completion of the acceptance tests at Saclay, the injector has been fully sent to Japan. The re-assembly of the injector has been performed between March and May 2014. Then after the check-out phase, the production of the first proton beam occurred in November 2014. Hydrogen and deuteron beam commissioning is now in progress after having proceeded with the final tests on the entire injector equipment including high power diagnostics. This article reports the different phases of the injector installation pointing out the safety and security needs, as well as the first beam production results in Japan and chopper tests. Detailed operation and commissioning results (with H{sup +} and D{sup +} 100 keV beams) are reported in a second article.

  15. Inelastic neutron scattering and lattice dynamics of GaPO4

    Indian Academy of Sciences (India)

    R Mittal; S L Chaplot; A I Kolesnikov; C-K Loong; O D Jayakumar; S K Kulshreshtha

    2004-08-01

    We report here measurements of phonon spectrum and lattice dynamical calculations for GaPO4. The measurements in low-cristobalite phase of GaPO4 are carried out using high-resolution medium-energy chopper spectrometer at ANL, USA in the energy transfer range 0–160 meV. Semiempirical interatomic potential in GaPO4, previously determined using ab-initio calculations have been widely used in studying the phase transitions among various polymorphs. The calculated phonon spectrum using the available potential show fair agreement with the experimental data. However, the agreement between the two is improved by including the polarisability of the oxygen atoms in the framework of the shell model. The lattice dynamical models are also exploited for calculations of various thermodynamic properties of GaPO4.

  16. The design of the inelastic neutron scattering mode for the Extreme Environment Diffractometer with the 26 T High Field Magnet

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, Maciej, E-mail: maciej.bartkowiak@helmholtz-berlin.de; Stüßer, Norbert; Prokhnenko, Oleksandr

    2015-10-11

    The Extreme Environment Diffractometer is a neutron time-of-flight instrument, designed to work with a constant-field hybrid magnet capable of reaching fields over 26 T, unprecedented in neutron science; however, the presence of the magnet imposes both spatial and technical limitations on the surrounding instrument components. In addition to the existing diffraction and small-angle neutron scattering modes, the instrument will operate also in an inelastic scattering mode, as a direct time-of-flight spectrometer. In this paper we present the Monte Carlo ray-tracing simulations, the results of which illustrate the performance of the instrument in the inelastic-scattering mode. We describe the focussing neutron guide and the chopper system of the existing instrument and the planned design for the instrument upgrade. The neutron flux, neutron spatial distribution, divergence distribution and energy resolution are calculated for standard instrument configurations.

  17. First commissioning experience with the LINAC4 3 MeV front-end at CERN

    CERN Document Server

    Lallement, J B; Bellodi, G; Comblin, J F; Dimov, V A; Granemann Souza, E; Lettry, J; Lombardi, A M; Midttun, O; Ovalle, E; Raich, U; Roncarolo, F; Rossi, C; Sanchez Alvarez, R; Scrivens, C A; Valerio-Lizarraga, C A; Vretenar, M; Yarmohammadi Satri, M

    2013-01-01

    Linac4 is a normal-conducting 160 MeV H- linear accelerator presently under construction at CERN. It will replace the present 50 MeV Linac2 as injector of the proton accelerator complex as part of a project to increase the LHC luminosity. The Linac front-end, composed of a 45 keV ion source, a Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) housing a beam chopper, have been commissioned at the 3 MeV test stand during the first half of 2013. The status of the installation and the results of the first commissioning stage are presented in this paper.

  18. Transient behaviour of a ``beam loaded`` prebuncher cavity and linac structure

    Energy Technology Data Exchange (ETDEWEB)

    Messina, Giovanni; Picardi, Luigi; Ronsivalle, Concetta; Vignati, Angelo [ENEA, Centro Ricerche Frascati, Rome (Italy)

    1997-03-01

    They present the evaluation of the effect of the beam loading on the time response of a 3 GHz prebuncher cavity to the generator and to an input 120 deg chopped electron beam for two different cavity materials. The lumped-element representation of the cavity as a parallel RLC circuit is used which allows to compute also the sensitivity of the prebuncher voltage amplitude and phase with respect to beam current fluctuations. The analysis has been extended to the transient behaviour of a linac positioned after the prebuncher cavity. The consequences of the computation results on the application of a chopper-prebuncher system in a linac devoted to the MUH FEL experiment are discussed.

  19. Measurement of the total neutron cross-section of germanium at energies below 2 eV

    Energy Technology Data Exchange (ETDEWEB)

    Salama, M.

    1983-01-01

    The total neutron cross-section of germanium has been measured at room temperature as a function of neutron energy in the range between 2.2 eV and 7 meV for randomly distributed crystals of germanium by transmission method using a chopper time-of-flight spectrometer at ET-RR-1 research reactor. The measured cross-section showed an evidence of 1/..nu.. thermal slope in the energy range 1.20 eV to 0.20 eV. Crystal structure effects were also observed. Calculations were performed giving values for the coherent scattering amplitude as well as the coherent scattering cross-section. The results obtained showed also the absence of scattering nuclear spin dependence in case of germanium.

  20. A Novel MPPT Control Method of Thermoelectric Power Generation with Single Sensor

    Directory of Open Access Journals (Sweden)

    Tadashi Sakaguchi

    2013-04-01

    Full Text Available This paper proposes a novel Maximum Power Point Tracking (MPPT control method of thermoelectric power generation for the constant load. This paper reveals the characteristics and the internal resistance of thermoelectric power module (TM. Analyzing the thermoelectric power generation system with boost chopper by state space averaging method, the output voltage and current of TM are estimated by with only single current sensor. The proposed method can seek without calculating the output power of TM in this proposed method. The basic principle of the proposed MPPT control method is discussed, and then confirmed by digital computer simulation using PSIM. Simulation results demonstrate that the output voltage can track the maximum power point voltage by the proposed MPPT control method. The generated power of the TM is 0.36 W when the temperature difference is 35 °C. This is well accorded with the V-P characteristics.

  1. Interspecies interactions result in enhanced biofilm formation by co-cultures of bacteria isolated from a food processing environment

    DEFF Research Database (Denmark)

    Røder, Henriette Lyng; Raghupathi, Prem Krishnan; Herschend, Jakob

    2015-01-01

    examined for multispecies biofilm formation. Eight strains from each sampling site were chosen and all possible combinations of four member co-cultures were tested for enhanced biofilm formation at 15°C and 24°C. In approximately 20% of the multispecies consortia grown at 15°C, the biofilm formation......Bacterial attachment and biofilm formation can lead to poor hygienic conditions in food processing environments. Furthermore, interactions between different bacteria may induce or promote biofilm formation. In this study, we isolated and identified a total of 687 bacterial strains from seven...... different locations in a meat processing environment and evaluated their biofilm formation capability. A diverse group of bacteria was isolated and most were classified as poor biofilm producers in a Calgary biofilm device assay. Isolates from two sampling sites, the wall and the meat chopper, were further...

  2. Analytical Investigation and Control System Set-up of Medium Scale PV Plants for Power Flow Management

    Directory of Open Access Journals (Sweden)

    Rosario Miceli

    2012-11-01

    Full Text Available In the field of photovoltaic (PV plants and energy conversion from renewable sources, a large part of the technical literature is more devoted to practical aspects (new solar cells, electrically driven PV panels, safety, reduction of parasitic currents, etc. than to theoretical investigations. Despite this tendency, this paper presents a mathematical analysis of a medium scale photovoltaic power generation system connected to the distribution network and of its control system. In such a system, the conversion stage is unique due to the absence of a boost chopper. The conducted analysis leads to the interesting conclusion that the inverter used in the plant presents two degrees of freedom, easy to exploit in a control system in which the inverter simultaneously realizes the interconnection to the grid and the MPPT control. The structure of the control system is then presented, discussed and validated by means of numerical simulations.

  3. Tests of Modulated Intensity Small Angle Scattering in time of flight mode

    CERN Document Server

    Brandl, G; Carpenter, J; Crow, L; Robertson, L; Georgii, R; Böni, P; Bleuel, M

    2011-01-01

    We report results of tests of the MISANS technique at the CG-1D beamline at High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). A chopper at 40 Hz simulated a pulsed neutron source at the beamline. A compact turn-key MISANS module operating with the pulsed beam was installed and a well characterised MnSi sample was tested. The feasibility of application of high magnetic fields at the sample position was also explored. These tests demonstrate the great potential of this technique, in particular for examining magnetic and depolarizing samples, under extreme sample environments at pulsed sources, such as the Spallation Neutron Source (SNS) or the planned European Spallation Source (ESS).

  4. Grid-connected Technology for Two Stages Hybrid PV-wind Generation System with Double Input%采用双输入两级式风光互补发电的并网技术

    Institute of Scientific and Technical Information of China (English)

    於锋; 胡国文

    2011-01-01

    A new Buck/Buck-Boost DC chopper circuit for hybrid PV-wind generation system is proposed and variable step perturbation method is used to achieve the maximum power point tracking (MPPT) on the basis of the proposed circuit. Grid-connected side, a new design method of grid-connected combinating dynamic reactive power compensation and active power filter is presented which based onip-iq current detection method of instaneous reactive power theory.From the simulation results, it is demonstrated that the proposed DC chopper circuit is enable to achieve the MPPT of the input side on the power system isimultaneously or individually. The proposed grid-connected scheme can achieve hybrid PV-wind generation and can also improve power quality effectively.%提出了一种新颖的供风光互补发电系统发电侧输入的升降压直流斩波电路.在该电路基础上,通过变步长扰动法实现对系统的最大功率点跟踪(MPPT).在其并网侧,基于瞬时无功理论的i-i电流检测法,成功实现了具有动态无功补偿、有源滤波功能的并网发电技术.仿真结果表明,所设计的直流斩波电路能够同时或独立地对发电系统输入端进行MPPT,所提出的并网方案在实现风光互补并网发电的同时,有效改善了电能质量.

  5. A high-resolution tunneling magneto-resistance sensor interface circuit

    Science.gov (United States)

    Li, Xiangyu; Yin, Liang; Chen, Weiping; Gao, Zhiqiang; Liu, Xiaowei

    2017-02-01

    In this paper, a chopper instrumentation amplifier and a high-precision and low-noise CMOS band gap reference in a standard 0.5 μm CMOS technology for a tunneling magneto-resistance (TMR) sensor is presented. The noise characteristic of TMR sensor is an important factor in determining the performance of the sensor. In order to obtain a larger signal to noise ratio (SNR), the analog front-end chip ASIC weak signal readout circuit of the sensor includes the chopper instrumentation amplifier; the high-precision and low-noise CMOS band gap reference. In order to achieve the low noise, the chopping technique is applied in the first stage amplifier. The low-frequency flicker noise is modulated to high-frequency by chopping switch, so that the modulator has a better noise suppression performance at the low frequency. The test results of interface circuit are shown as below: At a single 5 V supply, the power dissipation is 40 mW; the equivalent offset voltage is less than 10 uV; the equivalent input noise spectral density 30 nV/Hz1/2(@10 Hz), the equivalent input noise density of magnetic is 0.03 nTHz1/2(@10 Hz); the scale factor temperature coefficient is less than 10 ppm/∘C, the equivalent input offset temperature coefficient is less than 70 nV/∘C; the gain error is less than 0.05%, the common mode rejection ratio is greater than 120 dB, the power supply rejection ratio is greater than 115 dB; the nonlinear is 0.1% FS.

  6. 一种新型软开关 BUCK变换器%A NoveI Soft-switching BUCK Converter

    Institute of Scientific and Technical Information of China (English)

    刘吉星; 沈锦飞

    2014-01-01

    磁耦合谐振式无线电能传输采用直流斩波调压控制传输功率,传统的直流斩波电路开关损耗大,因此提出了一种新型的软开关BUCK变换器的改进电路,在电路中添加耦合电感、辅助电感和二极管,可以实现零电流开通和零电压关断。变换器结构简单,便于控制。介绍了电路工作原理和过程,设计了电路参数,进行了仿真和实验研究,最后给出了仿真和实验波形。%The magnetically coupled resonant wireless power transmission adopts DC chopper control over transmission power,while traditional DC chopper circuit switching has a high loss.This paper presents an improved circuit for a novel soft-switching BUCK DC-DC converter,where a coupled inductor,auxiliary inductor and diode are added to realize zero current switching-on and zero voltage switching-off.The converter has a simple structure and is easy to control.Furthermore,the paper describes the working principle and process of the circuit,designs circuit parameters,completes simulation and experimental research,and finally gives simulation and test waveforms.

  7. Simulation of Some of the Power Electronics Case Studies in Matlab Simpowsystem Toolbox

    Science.gov (United States)

    Alasooly, Hedaya; Redha, Mohammed

    2010-06-01

    Matlab SimPowerSystems is a modern design tool that allows scientists and engineers to rapidly and easily build models that simulate power systems. Not only can you draw the circuit topology rapidly, but your analysis of the circuit can include its interactions with mechanical, thermal, control, and other disciplines. The paper covers some case studies that provide detailed, realistic examples of how to use SimPowerSystems in power system analysis. The following types of studies is coverted on the paper: 1. Thyristor-Based Static Var Compensator: Study the steady-state and dynamic performance of a static var compensator (SVC) on a transmission system. 2. Transient Stability of a Power System with SVC and PSS: Study of the application of static var compensator (SVC) and power system stabilizers (PSS) to improve transient stability and power oscillation damping of the system. 3. GTO-Based STATCOM: Study the steady-state and dynamic performance of a static synchronous compensator (STATCOM) on a transmission system. 4. Control of load flow using UPFC: Study the steady-state and dynamic performance of a unified power flow controller (UPFC). 5. Chopper-Fed DC Motor Drive: Study of a DC motor drive with armature voltage controlled by a GTO thyristor chopper. 6. VSC-Based HVDC Link: Modeling of a forced-commutated Voltage-Sourced Converter high-voltage direct current (VSC-HVDC) transmission link. 7. Three-Phase Network with Electrical Machines: Simulation of a three-phase power system containing electrical machines and other three-phase models. 8. Variable-Frequency Induction Motor Drive: Study of a PWM inverter-driven variable-frequency AC induction motor in variable-voltage, variable-speed operation.

  8. [Quality by design based high shear wet granulation process development for the microcrystalline cellulose].

    Science.gov (United States)

    Luo, Gan; Xu, Bing; Sun, Fei; Cui, Xiang-long; Shi, Xin-yuan; Qiao, Yan-jiang

    2015-03-01

    The design space of the high shear wet granulation process was established and validated within the framework of quality by design (QbD). The system of microcrystalline cellulose-de-ioned water was used in this study. The median granule size and bulk density of granules were identified as critical quality attributes. Plackeet-Burmann experimental design was used to screen these factors as follows: dry mixing time, the impeller and chopper speed of dry mixing, water amount, water addition time, wet massing time, the impeller and chopper speed of wet massing and drying time. And the optimization was implemented with the central composite experimental design based on screened critical process parameters. The design space of the high shear wet granulation process was established based on the quadratic polynomial regression model. Since the P-values of both models were less than 0.05 and values of lack of fit were more than 0.1, the relationship between critical quality attributes and critical process parameters could be well described by the two models. The reliability of design space, illustrated by overlay plot, was improved with the addition of 95% confidence interval. For those granules whose process parameters were in the design space, the granule size could be controlled within 250 to 355 μm, and the bulk density could be controlled within a range of 0.4 to 0.6 g x cm(-3). The robustness and flexibility of the high shear wet granulation process have been enhanced via the establishment of the design space based on the QbD concept.

  9. Catenary DC Ice-Melting Technology and Device Development of Electrified Railway%电气化铁路接触网直流融冰技术及装置研制

    Institute of Scientific and Technical Information of China (English)

    敬华兵; 年晓红

    2012-01-01

    The icing of traction network seriously affects the normal operation of trunk railway. The characteristics of catenary ice-melting are described. The regulated method of ice-melting current and voltage be changed with the thickness of ice and the distance of the ice-melting line is discussed. A new ice-melting circuit topology witch based on power unit chopper cascaded is proposed. Equivalent circuit of this device with parallel input and output series is promoted, and the control methods of multiple rectifier is analysised. The input harmonic and power factor of phase dislocation four-quadrant rectifier is studied. The control method of chopper tolerant-phase output of cascaded power units is put forword. The working state of the circuit is analysised.The relationship of cascaded power unit voltage balance control principle, chopper output duty cycle, and capacitor voltage are studied and simulated. The high power experimental prototype is designed and full power experimental is completed with short of voltage feedback method. The results show that this ice-melting circuit has steady output voltage with low input harmonic content.It will do little influence on electric network, and can be aoolied to engineering oractice effectively.%铁路牵引网覆冰会严重影响铁路干线的正常运行,本文阐述了接触网融冰的特点,论述了融冰电流、电压随距离和覆冰厚度的调节方法,提出了新型功率单元斩波级联全控整流融冰电路拓扑,推出了该融冰装置的并联输入串联输出(IPOC)等效电路。分析了输入侧多重整流控制的方式,对四象限错相整流的输入谐波及功率因数控制进行了探讨,提出了级联功率单元的斩波错相输出控制方法,分析了电路的工作状态。研究了级联功率单元的均压控制原则以及斩波输出占空比与电容电压的关系,并进行了仿真研究。在此基础上设计了大功率实验样机

  10. The Neutron Spectrum in a Uranium Tube

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, E.; Jonsson, E.; Lindberg, M.; Mednis, J.

    1963-10-15

    A series of experimental and theoretical investigations on neutron spectra in lattice cells has been started at the reactor R1. This report gives the results from the first one of these cells - one with a tube of natural -uranium surrounded by heavy water. In the measurements the cell was placed in the central, vertical channel of the reactor. The neutron spectrum from a lead scatterer in the uranium tube - outer diameter 49.2 mm, inner diameter 28.3 mm - was measured with a fast chopper in the energy region 0.01 to 100 eV. Subsidiary measurements indicated that the spectrum in the beam from the lead piece corresponds to the spectrum of the angular flux integrated over all angles. This correspondence is important for the interpretation of the experimental data. The thermal part of the spectrum was found to deviate significantly from a Maxwellian. However, the deviation is not very large, and one could use a Maxwellian, at least to give a rough idea of the hardness of the spectrum. For the present tube the temperature of this Maxwellian was estimated as 90 to 100 deg C above the moderator temperature (33 deg C). In the joining region the rise of the spectrum towards the thermal part is slower than for the cell boundary spectrum, measured earlier. In the epithermal region the limited resolution of the chopper has affected the measurements at the energies of the uranium resonances. However, the shape of the spectrum on the flanks of the first resonance in {sup 238}U (6.68 eV) has been obtained accurately. In the theoretical treatment the THERMOS code with a free gas scattering model has been used. The energy region was 3.06 - 0.00025 eV. The agreement with the measurements is good for the thermal part - possibly the theoretical spectrum is a little softer than the experimental one. In the joining region the results from THERMOS are comparatively high - probably due to the scattering model used.

  11. Nucleodissecção & facoemulsificação Nucleodissection and phacoemulsification

    Directory of Open Access Journals (Sweden)

    Marcelo Siqueira de Freitas

    2002-03-01

    Full Text Available O autor descreve uma técnica para dissecar o núcleo cataratoso em duas porções: uma externa, ou camada externa, e outra interna, ou núcleo interno. A camada externa é segmentada com a ponteira do facoemulsificador e o gancho de Sinskey ou um "chopper" e o núcleo interno luxado e emulsificado sempre em primeiro lugar. A emulsificação da camada externa originou dois modelos cirúrgicos, um para cataratas maduras e outro para cataratas moderadamente duras. Nas cataratas maduras, emulsificamos cada divisão da camada externa anterior e depois a porção posterior, deslocada para câmara anterior. Nas cataratas moderadamente duras, é possível separar um conjunto de lamelas formadas por fibras duras, tanto anteriores como posteriores das lamelas superficiais que permanecem protegendo a cápsula posterior. As lamelas duras são emulsificadas no espaço que surge depois da emulsificação do núcleo interno, que denominamos de espaço intranuclear. A nucleodissecção assim como os modelos cirúrgicos referidos mostraram-se de grande utilidade e são usados na nossa rotina cirúrgica.The author describes a technique for dissection of the nucleus of the cataract into two parts: an external one or external layer, and an internal one or internal nucleus. The anterior portion of the external layer is divided into segmentes like a "pizza" with the phaco tip and a Sinskey hook or a "chopper" and the internal nucleus is dislocated and emulsified. The emulsification of the external layer gives rise to two different surgical models, one for mature and the other for moderately hard cataracts. In the case of mature cataracts we emulsify each segment of the anterior external layer and then the posterior portion, which has already been moved to the anterior chamber. In the case of moderately hard cataracts it is possible to separate a set of layers made of hard anterior and posterior fibers, emulsify them, and leave the superficial layers which continue

  12. Complete affordable system for simultaneous VIS/NIR and MWIR/LWIR spectral atmospheric transmittance measurements (ATMS)

    Science.gov (United States)

    Cabib, Dario; Gil, Amir; Biran, Oren

    2010-04-01

    During the second half of the '70's Ben-Shalom et al.1 developed a system for research of the spectral transmittance of the atmosphere in the infrared range on nearly horizontal atmospheric paths between 2.5 and 14 microns. The system configuration is bi-static: a source (of known emission) and a measuring sensor station linked by line of sight. Comparison of the measured radiation with the known emission gives the fraction of transmitted radiation. The longest path published there was a respectable 44 Km. and provided significant data. However, the system required a very high temperature (2400K) short lived (~3 hours) emitter element, home-built projection optics, and a cumbersome closed cycle water cooling system for the 6 KWatt source. The sensor end of the system was a Circular Variable Filter (CVF) based spectroradiometer using liquid nitrogen (LN2) cooled detectors. The signal processing electronics was based on a synchronous detection method using a chopper at the source and a radio-transmitted reference signal in phase with the chopper. In this paper we describe the Atmospheric Transmittance Measurement System (ATMS) recently built by CI and presently undergoing reliability and accuracy tests. Its main advantages over the old system are: it is built of only commercial off-the-shelf items (COTS), it can measure in both the IR and visible ranges simultaneously, it is cost effective and easy to use and maintain. The calibration method and transmittance measurement algorithm are also described. A transmittance measurement of a nearly horizontal sea level path of 6.5 Km. is shown here as an example for the whole spectral range of 0.4 to 14 microns in less than very clear and dry weather conditions. The result shows agreement with the MODTRAN model on the spectral behavior but at the time of publication we are still investigating the accuracy of the actual transmittance values. We believe that the ATMS can be used for longer paths, based on the signal to noise

  13. A user configurable data acquisition and signal processing system for high-rate, high channel count applications

    Energy Technology Data Exchange (ETDEWEB)

    Salim, Arwa, E-mail: arwa.salim@eee.strath.ac.uk [University of Strathclyde, Scotland (United Kingdom); Crockett, Louise [University of Strathclyde, Scotland (United Kingdom); McLean, John; Milne, Peter [D-TACQ Solutions, Scotland (United Kingdom)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The development of a new digital signal processing platform is described. Black-Right-Pointing-Pointer The system will allow users to configure the real-time signal processing through software routines. Black-Right-Pointing-Pointer The architecture of the DRUID system and signal processing elements is described. Black-Right-Pointing-Pointer A prototype of the DRUID system has been developed for the digital chopper-integrator. Black-Right-Pointing-Pointer The results of acquisition on 96 channels at 500 kSamples/s per channel are presented. - Abstract: Real-time signal processing in plasma fusion experiments is required for control and for data reduction as plasma pulse times grow longer. The development time and cost for these high-rate, multichannel signal processing systems can be significant. This paper proposes a new digital signal processing (DSP) platform for the data acquisition system that will allow users to easily customize real-time signal processing systems to meet their individual requirements. The D-TACQ reconfigurable user in-line DSP (DRUID) system carries out the signal processing tasks in hardware co-processors (CPs) implemented in an FPGA, with an embedded microprocessor ({mu}P) for control. In the fully developed platform, users will be able to choose co-processors from a library and configure programmable parameters through the {mu}P to meet their requirements. The DRUID system is implemented on a Spartan 6 FPGA, on the new rear transition module (RTM-T), a field upgrade to existing D-TACQ digitizers. As proof of concept, a multiply-accumulate (MAC) co-processor has been developed, which can be configured as a digital chopper-integrator for long pulse magnetic fusion devices. The DRUID platform allows users to set options for the integrator, such as the number of masking samples. Results from the digital integrator are presented for a data acquisition system with 96 channels simultaneously acquiring data

  14. A Novel Infrared Gas Monitor

    Science.gov (United States)

    Wang, Yingding; Zhong, Hongjie

    2000-03-01

    In the paper a novel non-dispersive infrared(IR) gas monitor is described.It is based on the principle that certain gases absorb IR radiation at specific(and often unique) wavelengths.Conventional devices typically include several primary components:a broadband source, usually an incandescent filament,a rotating chopper shutter,a narrow-band filter,a sample tube and a detector. We have developed a number of IR light emitting diodes(LED) having narrow optical bandwidths and which can be intensity modulated by electrical means,for example InAsSbP(4.2 micron)LED.The IR LED can thus replace the thermal source,narrow-band filter and chopper assembly of the conventional IR gas monitor,yielding a solid state,low- powered,compact and almost maintenance-free instrument with high sensitivity and stability and which free of the effects of mechanical vibration too. The detector used in the IR gas monitor is the solid-state detector,such as PbS,PbSe, InSb,HgCdTe,TGS,LT and PZT detector etc. The different configuration of the IR gas monitor is designed.For example,two-path version for measuring methane concentration by monitoring the 3.31 micron absorption band,it can eliminate the interference effects,such as to compensate for LED intensity changes caused by power and temperature variations,and for signal fluctuations due to changes in detector bias. we also have designed portable single-beam version without the sample tube.Its most primary advantage is very cheap(about cost USD 30 ).It measures carbon dioxide concentration by monitoring the 4.25 micron absorption band.Thought its precisions is low,it is used to control carbon dioxide concentration in the air in the green houses and plastic houses(there are about twenty millon one in the China).Because more carbon dioxide will increase the quanity of vegetable and flower production to a greatextent. It also is used in medical,sanitary and antiepidemic applications,such as hospital, store,hotel,cabin and ballroom etc. Key words

  15. OPTIMIZATION OF THE HYSPEC DESIGN USING MONTE CARLO SIMULATIONS.

    Energy Technology Data Exchange (ETDEWEB)

    GHOSH, V.J.; HAGEN, M.E.; LEONHARDT, W.J.; ZALIZNYAK, I.; SHAPIRO, S.M.; PASSELL, L.

    2005-04-25

    HYSPEC is a direct geometry spectrometer to be installed at the SNS [1] on beamline 14B where it will view a cryogenic coupled hydrogen moderator, The ''hybrid'' design combines time-of-flight spectroscopy with focusing Bragg optics to provide a high monochromatic flux on small single crystal samples, with a very low background at an extended detector bank. The instrument is optimized for an incident energy range of 3-90meV. It will have a medium energy resolution (2-10%) and will provide a flux on sample of the order of 10{sup 6}-10{sup 7} neutrons/s-cm{sup 2}. The spectrometer will be located in a satellite building outside the SNS experimental hall at the end of a 35m curved supermirror guide. A straight-slotted Fermi chopper will be used to monochromate the neutron beam and to determine the burst width. The 15cm high, 4cm wide beam will be focused onto a 2cm by 2cm area at the sample position using Bragg reflection from one of two crystal arrays. For unpolarized neutron studies these will be Highly Oriented Pyrolitic graphite crystals while for polarized neutron studies these will be replaced with Heusler alloy crystals. These focusing crystal arrays will be placed in a drum shield similar to those used for triple axis spectrometers. Hyspec will have a movable detector bank housing 160 position sensitive detectors. This detector bank will pivot about the sample axis. It will have a radius of 4.5m, a horizontal range of 60{sup o}, and a vertical range of {+-} 7.5{sup o}. In order to reduce background at the detector bank both a curved guide and a T0 chopper will be used. A bank of 20 supermirror bender polarization analyzers [2] will be used to spatially separate the polarized neutrons in the scattered beam so that both scattered neutron spin states can be measured simultaneously. The results of Monte Carlo simulations performed to optimize the instrument design will be discussed.

  16. The System of the Calibration for Visibility Measurement Instrument Under the Atmospheric Aerosol Simulation Environment

    Directory of Open Access Journals (Sweden)

    Shu Zhifeng

    2016-01-01

    Full Text Available Visibility is one of the most important parameters for meteorological observation and numerical weather prediction (NWP.It is also an important factor in everyday life, mainly for surface and air traffic especially in the Aeronautical Meteorology. The visibility decides the taking off and landing of aircraft. If the airport visibility is lower than requirement for aircraft taking off stipulated by International Civil Aviation Administration, then the aircraft must be parked at the airport. So the accurate measurement of visibility is very important. Nowadays, many devices can be measured the visibility or meteorological optical range (MOR such as Scatterometers, Transmissometers and visibility lidar. But there is not effective way to verify the accuracy of these devices expect the artificial visual method. We have developed a visibility testing system that can be calibration and verification these devices. The system consists of laser transmitter, optical chopper, phase-locking amplifier, the moving optic receiving system, signal detection and data acquisition system, atmospheric aerosol simulation chamber. All of them were placed in the atmosphere aerosol simulation chamber with uniform aerosol concentration. The Continuous wave laser, wavelength 550nm, has been transmitted into the collimation system then the laser beam expanded into 40mm diameter for compressing the laser divergence angle before modulated by optical chopper. The expanding beam transmitting in the atmosphere aerosol cabin received by the optic receiving system moving in the 50m length precision guide with 100mm optical aperture. The data of laser signal has been acquired by phase-locking amplifier every 5 meter range. So the 10 data points can be detected in the 50 meters guide once. The slope of the fitting curve can be obtained by linear fitting these data using the least square method. The laser extinction coefficient was calculated from the slope using the Koschmieder

  17. Research on the Pulse Electrolysis Power Supply with Soft-switch and Energy-release Function%带软开关和能量释放功能的脉冲电解电源的研制

    Institute of Scientific and Technical Information of China (English)

    石必利; 张永俊; 罗红平

    2015-01-01

    针对现有电解电源稳定性不足及对工具、工件保护不够及时的问题,提出一种带特殊保护功能的脉冲电解电源的实现方法。为改善输出电流波形,提高加工质量,电源采用全桥逆变加斩波的拓扑结构。在传统的过压、过流保护的基础上,增加能量快速释放功能模块,实现快速短路保护,及时为残留在电感电容中的电能提供泄放通道,防止电源系统损坏和工具、工件损伤。在常规斩波方式的基础上,提出基于FPGA的斩波软开关功能,在一定程度上降低斩波IGBT的开关损耗,减小了温升,提高了稳定性。%Aim at the problem of insufficient stability and no rapid protection for tools and workpiece in existing electrolytic power supply ,a specific protection functions is introduced. To improve current waveform and processing quality ,a topology including full-bridge inverter and chopper is employed on this power supply. Based on the traditional over current and over voltage protection ,the energy-release module is added to the power supply to provide a quick short-circuit protection system and a discharge channel for residual electric energy in inductor and capacitor timely ,in order to prevent voltage spike damage to the device ,and prevent large current damage to tools and workpiece. Based on routine chopper,soft-switch function module based on FPGA is proposed to reduce switch loss on chopping IGBT to decrease the temperature rise and improve the stability.

  18. A tunable microflow focusing device utilizing controllable moving walls and its applications for formation of micro-droplets in liquids

    Science.gov (United States)

    Lee, Chun-Hong; Hsiung, Suz-Kai; Lee, Gwo-Bin

    2007-06-01

    This study reports a new microfluidic device capable of fine-tuned sample-flow focusing and generation of micro-droplets in liquids by controlling moving wall structures. Two microfluidic components including an 'active microchannel width controller' and a 'micro chopper' can be used to fine-tune the width of the hydrodynamically pre-focused stream and subsequently generate micro-droplets. In this study, a basic concept of a 'controllable moving wall' structure was addressed and applied as the active microchannel width controller and the micro chopper to generate the proposed function. Pneumatic side chambers were placed next to a main flow channel to construct the controllable moving wall structures. The deformation of the controllable moving wall structure can be generated by the pressurized air injected into the pneumatic side chambers. The proposed chip device was fabricated utilizing polymer material such as PDMS (polydimethylsiloxane) to provide the flexibility of the controllable moving wall deformation. The microfluidic chip device with dimensions of 2.5 cm in width and 3.0 cm in length can be fabricated using a simple fabrication process. Experimental data showed that the deformation of the controllable moving wall structure can be adjusted by applying different air pressures, so that the width of the main flow channel can be controlled accordingly. By utilizing the proposed mechanism, the pre-focused dispersed phase stream could be actively focused into a narrower stream, and well-controlled micro-droplets with smaller diameters could be generated. The stream width can be reduced from 30 µm to 9 µm and micro-droplets with a diameter of 76 µm could be generated by utilizing the proposed device. In addition, to generate micro-droplets within smaller diameters, uniform size distribution of the micro-droplets can be obtained. According to the experimental results, development of the microfluidic device could be promising for a variety of applications such

  19. Power supply system for KSTAR neutral beam injector

    Energy Technology Data Exchange (ETDEWEB)

    Cho, W., E-mail: franciscocho@nfri.re.kr; Bae, Y.S.; Han, W.S.; Jeong, J.H.; Kim, J.S.; Park, H.T.; Yang, H.L.; Oh, Y.K.; Kwak, J.G.

    2015-10-15

    Highlights: • The power supply system in KSTAR NBI consists of DC power supplies for ion source. • For operation NBI, DC High Voltage based on the low voltage transformer with chopper. • The surge absorber near the ion source limit the energy deposited to accelerator grid. - Abstract: The power supply system in KSTAR neutral beam injector consists of low voltage and high current DC power supplies for plasma generator of ion source and high voltage and high current DC power supply for accelerator grid system. The arc discharge is initiated by an arc power supply supplying the arc voltage between the chamber wall and 12 filaments which are heated by individual filament power supply. The negative output of arc power supply is common to each positive output of 12 filament power supplies. To interrupt the arc discharging for the fault condition of the arc current unbalance, DCCT current monitor is placed at the positive output cable of the filament power supply. The plasma grid (G1) power supply has the maximum capability of 120 kV/70 A which consists of low voltage regulator with IGBT-switched chopper array system for the voltage control in unit of 600 V and the high voltage rectified transformers to supply DC voltage of 20 kV, 30 kV, and 50 kV. The output voltage of the G1 power supply is also connected to the input of the voltage divider system which supplies the gradient voltage to the gradient grid (G2) in the range of 80–90% of G1 voltage by changing tap of winding resistors in unit of 1%. The charged G1 voltage is turned on and off by the high voltage switch (HVS) system consisting of MOSFET fast semiconductor switches which can immediately be opened less than 1 μs when the ion source grid breakdown occurs. The decelerating grid (G3) power supply is inverter system using capacitor-charge power supply to supply maximum −5 kV/5 A. The important component in power supply system is the surge absorber near the ion source to limit the arc energy deposited to

  20. A survey of silage management practices on California dairies.

    Science.gov (United States)

    Heguy, J M; Meyer, D; Silva-del-Río, N

    2016-02-01

    The aim of the present study was to gather baseline information on corn silage-management practices to develop an outreach curriculum for dairy producers and growers. In spring 2013, dairy producers in the San Joaquin Valley (California) were surveyed on their silage-management practices. Response rate was 14.5% (n=160) and herd size averaged 1,512 milking cows. Harvest date was set solely by the dairy producer (53.4%) or with the assistance of the crop manager, custom chopper, or nutritionist (23.3%). On some dairies (23.3%), the dairy producer delegated the harvest date decision. Most dairies (75.0%) estimated crop dry matter before harvest, and the preferred method was milk line evaluation. Dairy producers were mostly unfamiliar with harvest rate but the number [1 (35.9%), 2 (50.3%), or 3 to 5 (13.8%)] and size [6-row (17.7%), 8-row (67.3%), or 10-row (15.0%)] of choppers working simultaneously was reported. Most dairies used a single packing tractor (68.8%) and weighed every load of fresh chopped corn delivered to the silage pit (62%). During harvest, dry matter (66.9%), particle length (80.4%), and kernel processing (92.5%) were monitored. Most dairies completed filling their largest silage structure in less than 3 d (48.5%) or in 4 to 7 d (30.9%). Silage covering was completed no later than 7 2h after structure completion in all dairies, and was often completed within 24 h (68.8%). Packed forage was covered as filled in 19.6% of dairies. Temporary covers were used on some dairies (51.0%), with filling durations of 1 to 60 d. When temporary covers were not used, structures were filled in no more than 15 d. After structure closure, silage feedout started in 1 to 3 wk (44.4%), 4 to 5 wk (31.4%), or 8 or more wk (24.2%). Future considerations included increasing the silage storage area (55.9%), increasing the number of packing tractors (37.0%), planting brown mid-rib varieties (34.4%), buying a defacer to remove silage (33.1%), and creating drive-over piles (32

  1. Outbreak of gastroenteritis in Tibetan transit school, dharamshala, Himachal Pradesh, India, 2006

    Directory of Open Access Journals (Sweden)

    Gupta Surender

    2009-01-01

    Full Text Available Background: On 28 th June, 2006, 55 cases of the gastroenteritis were reported among the hostellers of the Tibetan Transit School, Dharamshala. We investigated the outbreak to identify the source, propose control and preventive measures. Materials and Methods: We defined a case of the gastroenteritis as the occurrence of more than three smelly loose motions between 28 th June to 2 nd July, 2006 among some sections of the resident hostellers. We determined age and sex specific attack rate. We hypothesized it as a food borne beef meat outbreak. We conducted the case control study and collected the information about the food items consumed inside and outside the hostel at dinner using the standardized questionnaire. We calculated floor wise incidences of four hostels, odds ratios and attributable fractions. We interviewed food handlers. We lifted the seven rectal stool, four water and three samples from floor, kitchen and meat chopper room for culture and sensitivity. Results: 116 cases patients of 802 hostellers met the case definition. The maximum attack rate (16% was in the youngest group (15-20yrs and nil in staff and 31-40 years age group with 5 overall attack rate as 14%. Sex specific attack rate was more (18% in females. The floor wise incidences of the case patients were the highest in 2nd and 3rd floors, occupied by the youngest group. The median age was 20 yrs (Range 17-40 yrs. The most common symptoms were watery diarrhea (71/116, 61% and bloody diarrhea-(45/116, 39%; abdominal pains- (87/116, 75%. Of the six food/water items examined, the food specific attack rate was highly statistically significant in the beef meat eaters (82% with PAF 71%, and Odds Ratio 19.19 (95% C.I. as 9.3-140. The food handlers & their cooking conditions in the kitchen were unhygienic. The food was not available for testing. Escherichia coli were detected in the samples from rectal stools, kitchen and meat chopper room. No fatality was reported. Conclusion

  2. Overview of the conceptual design of the future VENUS beamline at the Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Bilheux, Hassina Z [ORNL; Herwig, Kenneth W [ORNL; Keener, Wylie S [ORNL; Davis, Larry E [ORNL

    2015-01-01

    VENUS will be a world-class neutron-imaging instrument that will uniquely utilize the Spallation Neutron Source (SNS) time-of-flight (TOF) capabilities to measure and characterize objects across several length scales (mm to m). When completed, VENUS will provide academia, industry and government laboratories with the opportunity to advance scientific research in areas such as energy, materials, additive manufacturing, geosciences, transportation, engineering, plant physiology, biology, etc. It is anticipated that a good portion of the VENUS user community will have a strong engineering/industrial research focus. Installed at Beamline 10 (BL10), VENUS will be a 25-m neutron imaging facility with the capability to fully illuminate (i.e., umbra illumination) a 20 cm x 20 cm detector area. The design allows for a 28 cm x 28 cm field of view when using the penumbra to 80% of the full illumination flux. A sample position at 20 m will be implemented for magnification measurements. The optical components are comprised of a series of selected apertures, T0 and bandwidth choppers, beam scrapers, a fast shutter to limit sample activation, and flight tubes filled with Helium. Techniques such as energy selective, Bragg edge and epithermal imaging will be available at VENUS

  3. PXIE Optics and Layout

    CERN Document Server

    Lebedev, V A; Ostiguy, J -F; Shemyakin, A V; Shteynas, B G; Solyak, N; Solyak, N

    2013-01-01

    The Project X Injector Experiment (PXIE) will serve as a prototype for the Project X front end. The aim is to validate the Project-X design and to decrease technical risks, known to be mainly related to the front end. PXIE will accelerate a 1 mA CW beam to about 25 MeV. It will consist of an ion source, LEBT, CW RFQ, MEBT, two SC cryomodules, a diagnostic section and a beam dump. A bunch-by-bunch chopper located in the MEBT section will allow formation of an arbitrary bunch structure. PXIE deviates somewhat from the current Project-X front end concept in that it provides additional instrumentation and relies on a reduced number of kickers for bunch chopping; the diagnostic section also include an RF separator to allow studying extinction of removed bunches. The paper discusses the main requirements and constraints motivating the facility layout and optics. Final adjustments to the Project X front end design, if needed, will be based on operational experience gained with PXIE.

  4. Short term depression unmasks the ghost frequency.

    Directory of Open Access Journals (Sweden)

    Tjeerd V Olde Scheper

    Full Text Available Short Term Plasticity (STP has been shown to exist extensively in synapses throughout the brain. Its function is more or less clear in the sense that it alters the probability of synaptic transmission at short time scales. However, it is still unclear what effect STP has on the dynamics of neural networks. We show, using a novel dynamic STP model, that Short Term Depression (STD can affect the phase of frequency coded input such that small networks can perform temporal signal summation and determination with high accuracy. We show that this property of STD can readily solve the problem of the ghost frequency, the perceived pitch of a harmonic complex in absence of the base frequency. Additionally, we demonstrate that this property can explain dynamics in larger networks. By means of two models, one of chopper neurons in the Ventral Cochlear Nucleus and one of a cortical microcircuit with inhibitory Martinotti neurons, it is shown that the dynamics in these microcircuits can reliably be reproduced using STP. Our model of STP gives important insights into the potential roles of STP in self-regulation of cortical activity and long-range afferent input in neuronal microcircuits.

  5. Digitally compensated beam current transformer

    CERN Document Server

    Kesselman, Martin

    2005-01-01

    The Spallation Neutron Source (SNS) is being built by a collaboration of six laboratories. Beam current monitors (BCMs) will be used to record the current of H-minus and H-plus beams ranging from 15 mA (tune-up in the Front End and Linac) to over 60A fully accumulated in the Ring and dumped to the load as a single pulse in the Ring to Beam Target (RTBT). The time structure of these beams ranges from 645ns "mini" bunches at the 1.05 MHz ring revolution rate, to an overall 1 ms long macro-pulse. The requirements for the BCMs will depend upon their location within the system. The need to measure individual mini-pulses, examine the characteristics of the chopper edge, as well as the longer average current pulse of the macropulse, or long duration pulses during Linac tuning place wide requirements upon the response of current transformers. To obtain the desired accuracy and resolution, current transformers must have less than 1 ns rise time and droops of 0.1 %/ms. This places a significant design burden on the cur...

  6. All-optical logic gate based on transient grating from disperse red 1 doped organic-inorganic hybrid films with an improved figure of merit

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Tianxi; Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn; Shao, Jinyou [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, International Center for Dielectric Research, School of Electronic and Information Engineering, State Key Laboratory for Manufacturing Systems Engineering, Xi' an Jiaotong University, Xi' an 710049, Shaanxi (China); Wang, Yushu [School of Materials Science and Engineering, Georgia Institute of Technology, 500 Tenth Street NW, Atlanta, Georgia 30318 (United States)

    2015-10-21

    Azobenzene dyes have large refractive index near their main resonance, but the poor figure of merit (FOM) limits their potential for all-optical applications. To improve this situation, disperse red 1 (DR1) molecules were dispersed in a sol-gel germanium/Ormosil organic-inorganic hybrid matrix. Z-scan measurement results showed a good compatibility between the dopant and the matrix, and also, an improved FOM was obtained as compared to the DR1/polymer films reported previously. To demonstrate the all-optical signal processing effect, a cw Nd:YAG laser emitting at 532 nm and a He-Ne laser emitting at 632.8 nm were used as pump and probe beams, respectively. DR1 acts as an initiator of the photo-induced transient holographic grating, which is attributed to the trans-cis-trans photoisomerization. Thus, a three inputs AND all-optical logic gate was achieved by using choppers with different frequencies. The detailed mechanism of operation is discussed. These results indicate that the DR1 doped germanium/Ormosil organic-inorganic hybrid film with an improved FOM has a great potential in all-optical devices around its main resonance.

  7. A multi-spectral band stellar photo-polarimeter

    CERN Document Server

    Srinivasulu, G; Muneer, S; Mekkaden, M V; Jayavel, N; Somashekar, M R; Sagayanathan, K; Ramamoorthy, S; Rosario, M J; Jayakumar, K

    2015-01-01

    We designed and built a new astronomical photo-polarimeter that can measure linear polarization simultaneously in three spectral bands. It has a Calcite beamdisplacement prism as the analyzer. The ordinary and extra-ordinary emerging beams in each spectral bands are quasi-simultaneously detected by the same photomultiplier by using a high speed rotating chopper. A rotating superachromatic Pancharatnam halfwave plate is used to modulate the light incident on the analyzer. The spectral bands are isolated using appropriate dichroic and glass filters. We show that the reduction of 50% in the efficiency of the polarimeter because of the fact that the intensities of the two beams are measured alternately is partly compensated by the reduced time to be spent on the observation of the sky background. The use of a beam-displacement prism as the analyzer completely removes the polarization of background skylight, which is a major source of error during moonlit nights, especially, in the case of faint stars. The field t...

  8. A beam-displacement prism based, three band stellar photo-polarimeter

    CERN Document Server

    Raveendran, A V; Muneer, S; Mekkaden, M V; Jayavel, N; Somashekar, M R; Sagayanathan, K; Ramamoorthy, S; Rosario, M J; Jayakumar, K

    2015-01-01

    A new astronomical photo-polarimeter that can measure linear polarization of point sources simultaneously in three spectral bands was designed and built in Indian Institute of Astrophysics. The polarimeter has a Calcite beam-displacement prism as the analyzer. The ordinary and extra-ordinary emerging beams in each spectral band are quasi-simultaneously detected by the same photomultiplier by using a high speed rotating chopper. The effective chopping frequency can be set to as high as 200 Hz. A rotating superachromatic Pancharatnam halfwave plate is used to modulate the light incident on the analyzer. The spectral bands are isolated using appropriate dichroic and glass filters. A detailed analysis shows that the reduction of 50% in the efficiency of the polarimeter because of the fact that the intensities of the two beams are measured alternately is partly compensated by the reduced time to be spent on the observation of the sky background. The position angle of polarization produced by the Glan-Taylor prism ...

  9. High performance magnet power supply optimization

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, L.T.

    1988-01-01

    The power supply system for the joint LBL--SLAC proposed accelerator PEP provides the opportunity to take a fresh look at the current techniques employed for controlling large amounts of dc power and the possibility of using a new one. A basic requirement of +- 100 ppM regulation is placed on the guide field of the bending magnets and quadrupoles placed around the 2200 meter circumference of the accelerator. The optimization questions to be answered by this paper are threefold: Can a firing circuit be designed to reduce the combined effects of the harmonics and line voltage combined effects of the harmonics and line voltage unbalance to less than 100 ppM in the magnet field. Given the ambiguity of the previous statement, is the addition of a transistor bank to a nominal SCR controlled system the way to go or should one opt for an SCR chopper system running at 1 KHz where multiple supplies are fed from one large dc bus and the cost--performance evaluation of the three possible systems.

  10. A multi-sensor analysis of Nimbus 5 data on 22 January 1973. [meteorological parameters

    Science.gov (United States)

    Allison, L. J.; Rodgers, E. B.; Wilheit, T. T.; Wexler, R.

    1973-01-01

    The Nimbus 5 meteorological satellite carried aloft a full complement of radiation sensors, the data from which were analyzed and intercompared during orbits 569-570 on 22 January 1973. The electrically scanning microwave radiometer (ESMR) which sensed passive microwave radiation in the 19.35 GHz region, delineated rain areas over the ocean off the U.S. east coast, in good agreement with WSR-57 and FPS-77 radar imagery and permitted the estimation of rainfall rates in this region. Residual ground water in the lower Mississippi Valley, which resulted from abnormal rainfall in previous months, was indicated under clear sky conditions by soil brightness temperature values in the Nimbus 5 ESMR and U.S. Air Force Data Acquisition and Processing Program (DAPP) IR data. The temperature-humidity infrared radiometer showed the height and spatial configuration of frontal clouds along the east coast and outlined the confluence of a polar jet stream with a broad sub-tropical jet stream along the U.S. Gulf Coast. Temperature profiles from three vertical temperature sounders, the infrared temperature profile radiometer (ITPR), the Nimbus E microwave spectrometer (NEMS) and the selective chopper radiometer (SCR) were found to be in good agreement with related radiosonde ascents along orbit 569 from the sub-tropics to the Arctic Circle.

  11. DREAM — a versatile powder diffractometer at the ESS

    Science.gov (United States)

    Schweika, W.; Violini, N.; Lieutenant, K.; Zendler, C.; Nekrassov, D.; Houben, A.; Jacobs, P.; Henry, P. F.

    2016-09-01

    The instrument DREAM, in construction at the long pulse European Spallation Source (ESS), is a new type of neutron time-of-flight powder diffractometer, which utilizes additional choppers to meet the typical high resolution requests. Pulses will be of symmetric shape and their width can be varied from 10 μs to 1 ms, providing an unprecedented flexibility from highest to low resolution with optimized intensities at the superior brightness of the 5 MW source. The design is driven particularly by the needs and challenges for small and complex samples, large unit cell materials, thermoelectric cage structures or metal-organic framework structures, multiphase battery materials and complex magnetic structures. Therefore, the chosen wavelength bandwidth of 3.7 Å may cover well the peak intensities of the thermal and cold moderator used simultaneously and provides a sufficient Q (and d) range for obtaining diffraction patterns in a single setting. VITESS simulations show a performance that is about two orders of magnitude higher than current best instruments.

  12. The neutron reflectometer at `SINQ`

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, D. [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland)

    1996-11-01

    SINQ`s dedicated reflectometer will be a flexible instrument in many respect. A `white beam time of flight` as well as a `constant wavelength` setup are possible for reflectometric experiments in a vertical scattering geometry. The phase controlled double chopper at the beginning of the instrument together with properly chosen time channels at the detector allow for the variation of the temporal resolution. Collimation slits serve to determine the angular resolution. In combination, the resolution can be tailored to the experimental needs. Additionally, one can adjust the illumination of the sample by setting the sample table and the detector to an appropriate distance. A mounting for exchangeable mirrors can be used to supply polarized neutrons by a multilayer polarizer or monochromatic neutrons by a multilayer monochromator. When it is equipped with a supermirror as a deflecting unit one can maintain a horizontal sample position which makes reflectometry on liquid samples practicable. Remanent polarizers are assigned for the changing over of the neutron polarization. A 1 T electromagnet installed on the sample manipulation table and polarization analyzers complete the polarized reflectometry setup. Alternately, an x-y-detector and single detectors will be available. By 1997/1998 the neutron reflectometer will be operational as a users` instrument. (author) 9 figs., 2 tabs., 30 refs.

  13. Monte Carlo simulation of the spear reflectometer at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, G.S. [Los Alamos National Laboratory, NM (United States)

    1995-12-31

    The Monte Carlo instrument simulation code, MCLIB, contains elements to represent several components found in neutron spectrometers including slits, choppers, detectors, sources and various samples. Using these elements to represent the components of a neutron scattering instrument, one can simulate, for example, an inelastic spectrometer, a small angle scattering machine, or a reflectometer. In order to benchmark the code, we chose to compare simulated data from the MCLIB code with an actual experiment performed on the SPEAR reflectometer at LANSCE. This was done by first fitting an actual SPEAR data set to obtain the model scattering-length-density profile, {Beta}(z), for the sample and the substrate. Then these parameters were used as input values for the sample scattering function. A simplified model of SPEAR was chosen which contained all of the essential components of the instrument. A code containing the MCLIB subroutines was then written to simulate this simplified instrument. The resulting data was then fit and compared to the actual data set in terms of the statistics, resolution and accuracy.

  14. Pulsed irradiation improves target selectivity of infrared laser-evoked gene operator for single-cell gene induction in the nematode C. elegans.

    Directory of Open Access Journals (Sweden)

    Motoshi Suzuki

    Full Text Available Methods for turning on/off gene expression at the experimenter's discretion would be useful for various biological studies. Recently, we reported on a novel microscope system utilizing an infrared laser-evoked gene operator (IR-LEGO designed for inducing heat shock response efficiently in targeted single cells in living organisms without cell damage, thereby driving expression of a transgene under the control of a heat shock promoter. Although the original IR-LEGO can be successfully used for gene induction, several limitations hinder its wider application. Here, using the nematode Caenorhabditis elegans (C. elegans as a subject, we have made improvements in IR-LEGO. For better spatial control of heating, a pulsed irradiation method using an optical chopper was introduced. As a result, single cells of C. elegans embryos as early as the 2-cell stage and single neurons in ganglia can be induced to express genes selectively. In addition, the introduction of site-specific recombination systems to IR-LEGO enables the induction of gene expression controlled by constitutive and cell type-specific promoters. The strategies adopted here will be useful for future applications of IR-LEGO to other organisms.

  15. Quantitative contrast-enhanced MR imaging of the optic nerve

    Energy Technology Data Exchange (ETDEWEB)

    Simon, J.H. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Rubinstein, D. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Brown, M. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Yuh, W. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Birch-Iensen, M. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Szumowski, J. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States); Stears, J. [Depts. of Radiology, Univ. of Colorado Health Sciences Center, Denver, CO (United States)]|[Iowa Univ., Iowa City, IA (United States)

    1994-11-01

    During the acute stages of optic neuritis damage to the blood-optic nerve barrier can be detected using i.v. paramagnetic contrast-enhanced MR imaging. Quantification of the enhancement pattern of the optic nerve, intraorbital fat and muscle was determined in 15 normal subjects using 3 fat-suppression MR imaging methods: T1-weighted spin-echo and spoiled gradient-echo sequences preceded by a flat-frequency selective pulse (FATSAT+SE and FATSAT+SPGR, respectively) and a pulse sequence combining CHOPPER fat suppression with a fat-frequency selective preparation pulse (HYBRID). Pre- and postcontrast-enhanced studies were acquired for FATSAT+SE and FATSAT+SPGR. There was no significant enhancement of the optic nerve by either method (mean increase of 0.96% and 5.3%, respectively), while there was significant enhancement in muscle (mean 118.2% and 108.2%, respectively; p<0.005) and fat (mean increase of 13% and 37%, respectively; p<0.05). Postcontrast optic nerve/muscle signal intensity ratios (mean, SD) were 0.51 (0.07), 0.58 (0.05) and 0.75 (0.05) for FATSAT+SE, FATSAT+SPGR and HYBRID, respectively. These results suggest a practical methodology and range of values for normal signal intensity increases and ratios of tissue signal that can be used as objective measures of optic neuritis for natural history studies and treatment trials. (orig.).

  16. Status and operation of the Linac4 ion source prototypes

    Energy Technology Data Exchange (ETDEWEB)

    Lettry, J., E-mail: Jacques.lettry@cern.ch; Aguglia, D.; Andersson, P.; Bertolo, S.; Butterworth, A.; Coutron, Y.; Dallocchio, A.; Chaudet, E.; Gil-Flores, J.; Guida, R.; Hansen, J.; Koszar, I.; Mahner, E.; Mastrostefano, C.; Mathot, S.; Mattei, S.; Midttun, Ø.; Moyret, P.; Nisbet, D.; O’Neil, M. [CERN, 1211 Geneva 23 (Switzerland); and others

    2014-02-15

    CERN's Linac4 45 kV H{sup −} ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H{sup −} beam of 16–22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

  17. 5. New types of stone tools found in Soanian Regime of the NW sub-Himalayas of India

    Directory of Open Access Journals (Sweden)

    A.S. Soni,

    2014-01-01

    Full Text Available Though Northwestern sub-Himalayas are as yet known only for the Soanian tools but many new tool types have now been found by us from a large part of this region when it was vigilantly explored. It is for the first time that in addition to the conventionally known Soanians, many new tool types like pitted cobbles, edge-ground flakes, Hoabinhian tools, cutting tools on large flakes, finely made chisels, hand adzes and some other tools with typical functions were recovered from several sites occurring in an approximately 40x6 Kilometer area of Punjab and Himachal Pradesh region of the sub-Himalayas. All such tool types have also been found from the sites dated from mid to late mid-Holocene times. These tool were being used along with chopper/chopping tool and flakes etc., and they seem to represent some expedient technology that was employed by different societal communities who gathered in the sub-Himalayas during mid-Holocene dry phase/s.

  18. Analysis on simulation teaching for power electronics based on PLECS%基于PLECS软件的电力电子仿真教学分析

    Institute of Scientific and Technical Information of China (English)

    王武; 葛瑜

    2011-01-01

    针对电力电子技术课程传统教学过程中强调主电路而忽视控制电路分析的情况,提出在电力电子技术课程教学中引入系统级电力电子仿真软件PLECS进行辅助教学的新方法,通过在降压斩波电路的应用,说明该方法能灵活应用于仿真教学,加深学生对电力电子控制技术知识的理解.%Faced with traditional teaching process for power electronics, which was highlighted on main circuit but ignored control circuit analysis, the simulation software of PLECS was introduced into power electronics teaching and applied into Buck chopper circuit. The teaching practice shows the method is flexible and can strengthen the understanding of control technique in power electronics.

  19. An improved injector bunching geometry for ATLAS

    Indian Academy of Sciences (India)

    Richard C Pardo; J Bogaty; B E Clifft; S Sherementov; P Strickhorn

    2002-12-01

    The bunching system of the ATLAS positive ion injector (PII) has been improved by relocating the harmonic buncher to a point significantly closer to the second stage sine-wave buncher and the injector LINAC. The longitudinal optics design has also been modified and now employs a virtual waist from the harmonic buncher feeding the second stage sine-wave buncher. This geometry improves the handling of space charge for high-current beams, significantly increases the capture fraction into the primary rf bucket and reduces the capture fraction of the unwanted parasitic rf bucket. Total capture and transport through the PII has been demonstrated as high as 80% of the injected dc beam while the population of the parasitic, unwanted rf bucket is typically less than 3% of the total transported beam. To remove this small residual parasitic component a new traveling-wave transmission-line chopper has been developed reducing both transverse and longitudinal emittance growth from the chopping process. This work was supported by the U.S. Department of Energy under contract W-31-109-ENG-38.

  20. Fermentation and epiphytic microflora dynamics in sugar cane silage

    Directory of Open Access Journals (Sweden)

    Pedroso André de Faria

    2005-01-01

    Full Text Available Sugar cane silages are characterized by extensive yeast activity, alcohol production and great dry matter - DM - losses. Better knowledge of the fermentation process is fundamental to the development of efficient ensilage techniques for this forage. This study evaluates temporal changes in chemical composition, DM losses and epiphytic microflora in sugar cane silage. Mature sugar cane, variety RB835486 (12 months of vegetative growth, was hand harvested, processed in a stationary chopper and ensiled in 20-L plastic buckets provided with valves for gas release and a device for effluent collection. Laboratory silos were kept at ambient temperature and sampled after fraction one-half, 1, 2, 3, 7, 15, 45, 90, 120 and 180 days. Ethanol concentration reached 6.4% in DM after 15 days of ensilage, followed by 71% water soluble carbohydrates - WSCs - disappearance. Gas and total DM losses reached a plateau on day 45 (16% and 29% of DM, respectively. Yeast count was higher on the second day (5.05 log cfu g-1. Silage pH declined to below 4.0 on the third day. Effluent yield was negligible (20 kg t-1. DM content in the forage decreased (35% to 26% from day 0 to day 45. The increase in ethanol concentration showed an opposite trend to WSCs and true in vitro dry matter digestibility reductions in the silage. Developing methods to control yeasts, most probably through the use of additives, will enable more efficient production of sugar cane silage by farmers.

  1. H- Ion Sources For CERN’s Linac4

    CERN Document Server

    Lettry, J; Coutron, Y; Chaudeta, E; Dallocchio, A; Gil Flores, J; Hansen, J; Mahner, E; Mathot, S; Mattei, S; Midttun, O; Moyret, P; Nisbet, D; O’Neil, M; Paoluzzi, M; Pasquino, C; Pereira, H; Sanchez Arias, J; Schmitzer, C; Scrivens, R; Steyaert, D

    2013-01-01

    The specifications set to the Linac4 ion source are: H- ion pulses of 0.5 ms duration, 80 mA intensity and 45 keV energy within a normalized emittance of 0.25 mmmrad RMS at a repetition rate of 2 Hz. In 2010, during the commissioning of a prototype based on H- production from the plasma volume, it was observed that the powerful co-extracted electron beam inherent to this type of ion source could destroy its electron beam dump well before reaching nominal parameters. However, the same source was able to provide 80 mA of protons mixed with a small fraction of H2+ and H3+ molecular ions. The commissioning of the radio frequency quadrupole accelerator (RFQ), beam chopper and H- beam diagnostics of the Linac4 are scheduled for 2012 and its final installation in the underground building is to start in 2013. Therefore, a crash program was launched in 2010 and reviewed in 2011 aiming at keeping the original Linac4 schedule with the following deliverables: Design and production of a volume ion source prototype suitabl...

  2. The Effect of a Brief Salivary α-Amylase Exposure During Chewing on Subsequent in Vitro Starch Digestion Curve Profiles

    Directory of Open Access Journals (Sweden)

    Charles S. Brennan

    2010-07-01

    Full Text Available There is inconsistency between current in vitro digestion methods with regard to accommodation of a (salivary α-amylase exposure during the oral phase. The effect of a salivary α-amylase pre-exposure on subsequent in vitro starch digestion curve profiles for various foods was investigated. Foods were chewed, expectorated and the boluses left to rest for 0–15 min. During pancreatic digestion, aliquots were taken and hydrolysis curves constructed for comparison against those of the same foods comminuted with a manually-operated chopper, hence spared exposure to saliva. Hydrolysate aliquots taken at T0 (time zero of the digestion of chewed samples contained higher levels of glucose and dextrins compared with chopped samples. Pancreatin activity immediately overwhelmed differences in sugar released due to salivary amylase activity. Within 10 min no differences were detectable between hydrolysis curves for chewed and chopped foods. Salivary amylase pretreatment does not contribute to the robustness or relative accuracy of in vitro methods.

  3. Design of dual Beam multi-wavelength UV-visible absorbance detectors based on CCD

    Institute of Scientific and Technical Information of China (English)

    SHEN Shuang; TANG Zhen-an; LI Tong

    2006-01-01

    @@ Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source,a dual beam multi-wavelength UV-Visible detector based on CCD was designed.The ray of light source is divided into a signal ray and a reference ray by the beam splitter after it passes through the chopper.The signal ray shines into the sample cell.The signal ray passing through the sample cell falls onto a concave mirror which focuses it onto a slot that is imaged on one portion of CCD by a concave grating.The reference ray is imaged on the other portion of CCD by the concave grating after the slot.The signal spectrum,the reference spectrum and the dark current of CCD can be measured on the same CCD under the cooperation of the optical system and accessorial circuits.The real-time compensation for the signal spectrum by using the reference spectrum and the dark current of CCD can effectively depress the noise and drift of the detector.The short-term noise is 10-5AU and the drift is 10-4AU/h.

  4. Overview of the Conceptual Design of the Future VENUS Neutron Imaging Beam Line at the Spallation Neutron Source

    Science.gov (United States)

    Bilheux, Hassina; Herwig, Ken; Keener, Scott; Davis, Larry

    VENUS (Versatile Neutron Imaging Beam line at the Spallation Neutron Source) will be a world-class neutron-imaging instrument that will uniquely utilize the Spallation Neutron Source (SNS) time-of-flight (TOF) capabilities to measure and characterize objects across several length scales (mm to μm). When completed, VENUS will provide academia, industry and government laboratories with the opportunity to advance scientific research in areas such as energy, materials, additive manufacturing, geosciences, transportation, engineering, plant physiology, biology, etc. It is anticipated that a good portion of the VENUS user community will have a strong engineering/industrial research focus. Installed at Beam line 10 (BL10), VENUS will be a 25-m neutron imaging facility with the capability to fully illuminate (i.e., umbra illumination) a 20 cm x 20 cm detector area. The design allows for a 28 cm x 28 cm field of view when using the penumbra to 80% of the full illumination flux. A sample position at 20 m will be implemented for magnification measurements. The optical components are comprised of a series of selected apertures, T0 and bandwidth choppers, beam scrapers, a fast shutter to limit sample activation, and flight tubes filled with Helium. Techniques such as energy selective, Bragg edge and epithermal imaging will be available at VENUS.

  5. Evaluation of a handling system for ley crop used in biogas production. Capacities and costs for a centralised system

    Energy Technology Data Exchange (ETDEWEB)

    Vaagstroem, Lena

    2005-07-01

    Within the Vaextkraft project in Vaesteraas, Sweden, biogas is to be produced out of ley crop and organic waste. The aim of this study has been to estimate the capacities within the handling system used for the ley crop harvest, and the resources needed. For this purpose a model in the form of a calculation program in Excel was built. The model makes it possible to vary parameters such as transport system design, distance from fields to storage, dry matter content and yield. The results showed that it is essential to match the capacities between chopper and transport to minimise the time and cost connected to the harvest. To avoid creating costly bottlenecks in the Vaextkraft case the transport system has to consist of at least two trucks with trailers. The estimates made with the model suggests that the distance to storage is strongly linked to the dimensioning of the transport system, whereas the number of fields and their size has a lesser impact on harvest time and cost. Variation of the dry matter yield from a base scenario had an impact on the cost for harvesting, but not on the choice of transport system. The model couldn't detect any reliable differences in total costs due to the variation of dry matter content between 25-45%. The choice of chopping machinery in the Vaextkraft project leads to small timeliness costs. Together with a reasonable choice of transport system they will only constitute a few percent of the total costs for harvesting.

  6. MCTs and IGBTs - A comparison of performance in power electronic circuits

    Science.gov (United States)

    Sul, S. K.; Profumo, F.; Cho, G. H.; Lipo, T. A.

    1989-01-01

    There is a continuous demand for improvements in the quality of switching power devices, such as higher switching frequency, higher withstand voltage capability, larger current-handling capability, and lower conduction losses. However, for single-conduction-mechanism devices (SCRs, GTOs, BJTs, FETs), possessing all these features is probably unrealizable for physical reasons. An attractive solution appears to be double-mechanism devices, in which the features of both a minority carrier device (BJT or SCR) and a majority carrier device (MOSFET) are embedded. Both IGBTs (insulated-gate bipolar transistors) and MCTs (MOS-controlled thyristors) belong to this family of double-mechanism devices and promise to have a major impact on converter circuit signs. The authors deal with the major features of these two devices, pointing out those that are most critical to the design of converter topologies. In particular, the two devices have been tested both in a chopper and in two resonant link converter topologies, and the experimental results are reported.

  7. Experimental imaging research on continuous-wave terahertz in-line digital holography

    Science.gov (United States)

    Huang, Haochong; Wang, Dayong; Rong, Lu; Wang, Yunxin

    2014-09-01

    The terahertz (THz) imaging is an advanced technique on the basis of the unique characteristics of terahertz radiation. Due to its noncontact, non-invasive and high-resolution capabilities, it has already shown great application prospects in biomedical observation, sample measurement, and quality control. The continuous-wave terahertz in-line digital holography is a combination of terahertz technology and in-line digital holography of which the source is a continuous-wave terahertz laser. Over the past decade, many researchers used different terahertz sources and detectors to undertake experiments. In this paper, the pre-process of the hologram is accomplished after the holograms' recording process because of the negative pixels in the pyroelectric detector and the air vibration caused by the chopper inside the camera. To improve the quality of images, the phase retrieval algorithm is applied to eliminate the twin images. In the experiment, the pin which terahertz wave can't penetrate and the TPX slice carved letters "THz" are chosen for the samples. The amplitude and phase images of samples are obtained and the twin image and noise in the reconstructed images are suppressed. The results validate the feasibility of the terahertz in-line digital holographic imaging technique. This work also shows the terahertz in-line digital holography technique's prospects in materials science and biological samples' detection.

  8. Equivalent modeling of PMSG-based wind power plants considering LVRT capabilities: electromechanical transients in power systems.

    Science.gov (United States)

    Ding, Ming; Zhu, Qianlong

    2016-01-01

    Hardware protection and control action are two kinds of low voltage ride-through technical proposals widely used in a permanent magnet synchronous generator (PMSG). This paper proposes an innovative clustering concept for the equivalent modeling of a PMSG-based wind power plant (WPP), in which the impacts of both the chopper protection and the coordinated control of active and reactive powers are taken into account. First, the post-fault DC link voltage is selected as a concentrated expression of unit parameters, incoming wind and electrical distance to a fault point to reflect the transient characteristics of PMSGs. Next, we provide an effective method for calculating the post-fault DC link voltage based on the pre-fault wind energy and the terminal voltage dip. Third, PMSGs are divided into groups by analyzing the calculated DC link voltages without any clustering algorithm. Finally, PMSGs of the same group are equivalent as one rescaled PMSG to realize the transient equivalent modeling of the PMSG-based WPP. Using the DIgSILENT PowerFactory simulation platform, the efficiency and accuracy of the proposed equivalent model are tested against the traditional equivalent WPP and the detailed WPP. The simulation results show the proposed equivalent model can be used to analyze the offline electromechanical transients in power systems.

  9. Final safeguards analysis, high temperature lattice test reactor. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Hanthorn, H.E.; Brown, W.W.; Clark, R.G.; Heineman, R.E.; Humes, R.M.

    1966-01-01

    The PMACS `reactor-normal` signal signifies that important process variables do not exceed their set points, that various interlocks are properly set, that functional tests of the computer operation are satisfactory, and that the reactor flux level and period derived from two additional, independent, and dissimilar channels are within set limits. This safety circuit combines the features of redundancy, dissimilar components, and frequent testing which are required for best reliability. The experimental equipment auxiliary to the reactor includes two oscillator mechanisms, one to move the test cell or the adjoining cell into and out of position, the other to move small specimens in the test cell or adjoining cells. They have cooling chambers for the removal of specimens from the test cell without the necessity of cooling the reactor. A neutron chopper and time-of-flight spectrometer are provided; the neutron detectors, at the end of a 25-meter flight tube, are in an adjoining small building. Test cores may be assembled on a core dolly have a load capacity of 14,000 lb. Two wire traverse mechanisms are provided for measurements of flux distribution.

  10. A hardware/software simulation for the video tracking system of the Kuiper Airborne Observatory telescope

    Science.gov (United States)

    Boozer, G. A.; Mckibbin, D. D.; Haas, M. R.; Erickson, E. F.

    1984-01-01

    This simulator was created so that C-141 Kuiper Airborne Observatory investigators could test their Airborne Data Acquisition and Management System software on a system which is generally more accessible than the ADAMS on the plane. An investigator can currently test most of his data acquisition program using the data computer simulator in the Cave. (The Cave refers to the ground-based computer facilities for the KAO and the associated support personnel.) The main Cave computer is interfaced to the data computer simulator in order to simulate the data-Exec computer communications. However until now, there has been no way to test the data computer interface to the tracker. The simulator described here simulates both the KAO Exec and tracker computers with software which runs on the same Hewlett-Packard (HP) computer as the investigator's data acquisition program. A simulator control box is hardwired to the computer to provide monitoring of tracker functions, to provide an operator panel similar to the real tracker, and to simulate the 180 deg phase shifting of the chopper squre-wave reference with beam switching. If run in the Cave, one can use their Exec simulator and this tracker simulator.

  11. A 2.5 mW 370 mV/pF high linearity stray-immune symmetrical readout circuit for capacitive sensors

    Institute of Scientific and Technical Information of China (English)

    Zhou Kaimin; Wang Ziqiang; Zhang Chun; Wang Zhihua

    2012-01-01

    A stray-insensitive symmetrical capacitance-to-voltage converter for capacitive sensors is presented.By introducing a reference branch,a symmetrical readout circuit is realized.The linear input range is increased,and the systematic offsets of two input op-amps are cancelled.The common-mode noise and even-order distortion are also rejected.A chopper stabilization technique is adopted to further reduce the offset and flicker noise of the op-amps,and a Verilog-A-based varaetor is used to model the real variable sensing capacitor.Simulation results show that the output voltage of this proposed readout circuit responds correctly,while the under-test capacitance changes with a frequency of 1 kHz.A metal-insulator-metal capacitor array is designed on chip for measurement,and the measurement results show that this circuit achieves sensitivity of 370 mV/pF,linearity error below 1% and power consumption as low as 2.5 mW.This symmetrical readout circuit can respond to an FPGA controlled sensing capacitor array changed every 1 ms.

  12. Status and Operation of the Linac4 Ion Source Prototypes

    CERN Document Server

    Lettry, J; Andersson, P; Bertolo, S; Butterworth, A; Coutron, Y; Dallocchio, A; Chaudet, E; Gil-Flores, J; Guida, R; Hansen, J; Hatayama, A; Koszar, I; Mahner, E; Mastrostefano, C; Mathot, S; Mattei, S; Midttun, O; Moyret, P; Nisbet, D; Nishida, K; O’Neil, M; Ohta, M; Paoluzzi, M; Pasquino, C; Pereira, H; Rochez, J; Sanchez Alvarez, J; Sanchez Arias, J; Scrivens, R; Shibata, T; Steyaert, D; Thaus, N; Yamamoto, T

    2014-01-01

    CERN’s Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma and pulsed high voltages are described. The first experimental results of two prototypes relying on 2MHz RF- plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator and chopper of Linac4.

  13. BioRef II—Neutron reflectometry with relaxed resolution for fast, kinetic measurements at HZB

    Science.gov (United States)

    Trapp, M.; Steitz, R.; Kreuzer, M.; Strobl, M.; Rose, M.; Dahint, R.

    2016-10-01

    We present an upgrade to the time-of-flight neutron reflectometer BioRef at the research reactor BER II of the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB). Through the integration of an additional chopper into the existing setup, the available wavelength resolution is significantly extended. Now two distinct operation modes can be used: a high resolution mode with Δλ/λ ranging from 1% to 5%, which allows for the investigation of thick films up to 4000 Å, and a high flux mode with Δλ/λ = 7%-11%. In the high flux mode, reflectivity curves from 0.007 Å-1 to 0.2 Å-1 with three angular settings can be recorded in 7 min. For a single angular setting and its respective window in Q-space, a time resolution of even less than 4 min is reached. The different configurations are documented by respective measurements (a) on a Ni-Ti multilayer and (b) the swelling kinetics of a solid-supported phospholipid coating upon incubation in a polyelectrolyte solution.

  14. 矿用电机车矢量控制系统的研究设计%Research of Vector Control System of Mine Electrical Locomotive

    Institute of Scientific and Technical Information of China (English)

    邓永红; 潘玉民; 张全柱; 黄成玉

    2012-01-01

    为了实现矿用电机车交流传动的高性能控制运行,提高电机车运行的可靠性,以代替传统的矿用电机车直流调阻调速和直流斩波调速,实现节能降耗,提高牵引性能.基于16位单片机dsPIC30F6010A,研制设计了一种反馈解耦型电压矢量矿用电机车交流变频调速牵引控制系统,改善了电机车低速性能,实现了电流的快速凋节和无静差控制.试验结果证明了这种控制策略的有效性.%Mine electrical locomotive speed controlling modified from traditional changing DC Resistance and DC Chopper to VVVF, realizing mine electric locomotive to have high-performance control, saving energy and improving the reliability of operation of motor vehicles. The feedback decoupling voltage vector control system of mine locomotive traction based on the Microchip 16-bit single-chip microcomputer dsPIC30F6010A was designed, improved low-speed performance of mine electric locomotive, realized rapid adjustment of the current and no static error control. Experimental showed the feasibility of the control strategy.

  15. 一种连续/离散混合结构的电容数字自校准Sigma Delta模数转换器设计%A Mixed CT/DT ∑△ ADC with Capacitor Digital Self-Calibration for RC Spread Compensation

    Institute of Scientific and Technical Information of China (English)

    刘岩; 华斯亮; 王东辉; 侯朝焕

    2011-01-01

    This paper provides a mixed continuous-time/discrete-time sigma delta ADC. This ADC combines the benefits of Cr and DT circuits,and the self-calibration control circuits compensate for the variation of the RC product in the continuous-time integrator. Chopper stabilization can remove the flicker noise especially problematic in deep submicron MOS devices. Measurement results show that the peak SNR of this ADC reaches 102dB and the total power consumption is less than 30mW.%本文根据连续时间调制器和离散时间调制器的各自优缺点,提出了一种新型混合调制器结构的音频Siena Delta模数转换器,电容数字自校准电路用来补偿连续时间积分器的RC常数,斩波稳定技术用来降低深亚微米CMOS工艺下的闪烁噪声.测试结果表明连续/离散混合结构Sigma Delta模数转换器的峰值信噪比达到102dB,芯片总体功耗为30mW.

  16. Pink-beam focusing with a one-dimensional compound refractive lens.

    Science.gov (United States)

    Dufresne, Eric M; Dunford, Robert W; Kanter, Elliot P; Gao, Yuan; Moon, Seoksu; Walko, Donald A; Zhang, Xusheng

    2016-09-01

    The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm(-2) was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental. Only the fundamental of the undulator focuses at the experiment. A two-chopper system reduces the power density on the imaging system and lens by four orders of magnitude, enabling imaging of the focal plane without any X-ray filter. A method to measure such high power density as well as the performance of the lens in focusing the pink beam is reported.

  17. Development and application of the intense slow positron beam at IHEP

    Institute of Scientific and Technical Information of China (English)

    WANG Bao-Yi; MA Yan-Yun; WANG Ping; CAO Xing-Zhong; QIN Xiu-So; ZHANG Zhe; YU Run-Sheng; WEI Long

    2008-01-01

    This paper describes the development and application of an intense slow positron beam at IHEP with regard to its two main components.The Variable-Energy Positron Lifetime Spectroscopy (VEPLS) based on the pulsing system consisting of a chopper,a prebuncher and a buncher has been constructed in order to meet the needs of materials science development.At present,the time resolution of the VEPLS can easily reach about 386 ps with a peak-to-background ratio of about 600:1.A plugged-in 22Na positron source section for adjusting the newly built experimental station and for increasing the beam operation efficiency has been constructed.A slow positron beam with an intensity of 2.5x105 e+/s and the beam profile whose diameter is 10 mm has been obtained;the moderation efficiency of the tungsten mesh moderator reaches 5.1x 10-4 as calculated with an original positron source activity of 52 mCi.

  18. Interspecies interactions result in enhanced biofilm formation by co-cultures of bacteria isolated from a food processing environment.

    Science.gov (United States)

    Røder, Henriette L; Raghupathi, Prem K; Herschend, Jakob; Brejnrod, Asker; Knøchel, Susanne; Sørensen, Søren J; Burmølle, Mette

    2015-10-01

    Bacterial attachment and biofilm formation can lead to poor hygienic conditions in food processing environments. Furthermore, interactions between different bacteria may induce or promote biofilm formation. In this study, we isolated and identified a total of 687 bacterial strains from seven different locations in a meat processing environment and evaluated their biofilm formation capability. A diverse group of bacteria was isolated and most were classified as poor biofilm producers in a Calgary biofilm device assay. Isolates from two sampling sites, the wall and the meat chopper, were further examined for multispecies biofilm formation. Eight strains from each sampling site were chosen and all possible combinations of four member co-cultures were tested for enhanced biofilm formation at 15 °C and 24 °C. In approximately 20% of the multispecies consortia grown at 15 °C, the biofilm formation was enhanced when comparing to monospecies biofilms. Two specific isolates (one from each location) were found to be present in synergistic combinations with higher frequencies than the remaining isolates tested. This data provides insights into the ability of co-localized isolates to influence co-culture biofilm production with high relevance for food safety and food production facilities.

  19. Word-decoding as a function of temporal processing in the visual system.

    Directory of Open Access Journals (Sweden)

    Steven R Holloway

    Full Text Available This study explored the relation between visual processing and word-decoding ability in a normal reading population. Forty participants were recruited at Arizona State University. Flicker fusion thresholds were assessed with an optical chopper using the method of limits by a 1-deg diameter green (543 nm test field. Word decoding was measured using reading-word and nonsense-word decoding tests. A non-linguistic decoding measure was obtained using a computer program that consisted of Landolt C targets randomly presented in four cardinal orientations, at 3-radial distances from a focus point, for eight compass points, in a circular pattern. Participants responded by pressing the arrow key on the keyboard that matched the direction the target was facing. The results show a strong correlation between critical flicker fusion thresholds and scores on the reading-word, nonsense-word, and non-linguistic decoding measures. The data suggests that the functional elements of the visual system involved with temporal modulation and spatial processing may affect the ease with which people read.

  20. Two instruments for far-infrared astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Bonomo, J.L.

    1983-05-01

    Two instruments for far-infrared astrophysics are described. The first is a broad-band photometer used on White Mountain for astronomical observations from 10 to 30 cm/sup -1/ (300 GHz to 1 THz; lambda, 1 mm to 330 ..mu..). The optical system of the telescope includes a light-weight, high-speed, chopping secondary. The L /sup 4/He-cooled photometer uses low-pass filters and a L/sup 3/He-cooled, composite bolometer. The system performance is evaluated, and the site is compared to other possible platforms. The second project is a balloon-borne spectroradiometer to measure the cosmic background radiation from 3 to 10 cm/sup -1/ (100 GHz to 300 GHz; lambda, 3 mm to 1 mm). The apparatus has five band-pass filters with excellent rejection at higher frequencies, a low-noise chopper, and an internal calibrator. We describe the design and use of calibrators for such an experiment and develop a model of calibration procedures. The calibrations of several reported measurements are analyzed with this model, and flaws are found in one procedure. Finally, the system performance is used to estimate the accuracy this experiment can achieve.

  1. Trapped field measurements of Gd-Ba-Cu-O bulk superconductor in controlled pulse field magnetizing

    Energy Technology Data Exchange (ETDEWEB)

    Ida, T [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsakikamijima-cho, Toyota-gun, Hiroshima 725-0231 (Japan); Kimura, Y; Sano, T; Yamaguchi, K; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Miki, M [Kitano Seiki Co. Ltd., 7-13-7, Chuo, Ohta-ku, Tokyo 143-0024 (Japan)], E-mail: ida@hiroshima-cmt.ac.jp

    2008-02-01

    For large-scale electric power application of the melt-processed high temperature superconductor (HTS) bulks, especially at rotating machine, development of trapping much higher magnetic fields by using pulsed magnetization technique is essential. It is difficult to use static field cooling (FCM) technique that is most effective magnetizing method for the general industrial HTS applications, because the FCM requires large-scale superconducting magnets. Because the rise in temperature due to the magnetic flux motion decreases the pinning force, we controlled the magnetic flux penetrating to the bulk for the effective magnetization. A couple of vortex-type copper coils applied a magnetic field to a Gd-Ba-Cu-O bulk, which dimension was 45mm in diameter and 19 mm in thickness. HTS bulk was magnetized by the controlled pulse field without passive LCR pulse. We controlled waveform by using the discharge current that IGBT chopper in pulse magnetizer intermitted. We applied the pulse magnetic field with the various risetime to the HTS bulk in liquid nitrogen. The various conditions of the controlled waveform pulse to trap well-dressed profile magnetized the Gd-Ba-Cu-O bulk, strongly at 77K. In the present study, we show several properties which was measured in the PFM of the HTS bulk.

  2. Pixel-level continuous-time incremental sigma-delta A/D converter for THz sensors

    Science.gov (United States)

    Khatib, Moustafa; Perenzoni, Matteo

    2016-04-01

    A readout channel based on continuous-time incremental sigma-delta analog-to-digital converter for FET-based terahertz (THz) imaging applications was implemented in a 0.15 μm standard CMOS technology. The designed readout circuit is suitable for implementation in pixel arrays due to its compact size and power consumption. The system-level analysis used to define the modulator parameters and to specify its analog building blocks is presented. The loop filter has been realized by using a Gm-C integrator. Circuit linearization techniques have been implemented to improve the linearity of the transconductor cell and reduce the impact of parasitic capacitances. Moreover, chopper stabilization technique is adopted in the loop filter, significantly reducing the low-frequency flicker noise thereby preserving the Noise Equivalent Power (NEP) of the FET detector within the required specifications of minimum detectable signal. The resulting input referred noise voltage is 87.5 nV/√Hz . The incremental ADC achieves 68-dB peak signal-to-noise-and-distortion-ratio (SNDR), equivalent to 11 bits effective resolution over 1 kHz signal bandwidth at 1 MHz sampling frequency. In order to meet the requirements of large sensor arrays, a first order architecture is realized. This leads to lower area occupancy and power consumption. The readout circuit draws 80 μW of power from a supply voltage of 1.8 V. The channel occupies an area of 90 x 273μm2.

  3. Development of a Laser Induced Fluorescence (LIF) system on the Plasma Material Interaction System (PLAMIS-II) device

    Science.gov (United States)

    Kang, I. J.; Lee, K. Y.; Lee, K. I.; Choi, Y.-S.; Cho, S. G.; Bae, M. K.; Lee, D.-H.; Hong, S. H.; Lho, T.; Chung, K.-S.

    2015-12-01

    A laser induced fluorescence (LIF) system has been developed for the plasma material interaction system (PLAMIS-II) device, which is equipped with a unique plasma gun composed of a LaB6 cathode and two anodes with electromagnets to generate a focused dense plasma. PLAMIS-II simulates the interactions of plasma with different materials and is to be used for the test of plasma facing components of fusion devices. The LIF system is composed of a seed laser with Littmann/Metcalf cavity and a master oscillator power amplifier to pump 3d4F7/2 metastable argon ion to 4p4D5/2 level at the wavelength of 668.61 nm, which has the following input parameters: laser power = 20 mW, line width 70 GHz. For in-situ measurement of laser wavelength, the wavelength spectrum of an iodine cell was measured by a photo-transistor during LIF measurement. To measure argon ion temperature (Ti) and drift velocity (vd) in PLAMIS-II, the fluorescence light with the wavelength of 442.72 nm, emitted from 4p4D5/2 level to 4s4P3/2 level and passing through 1 nm band-width filter, was collected by the photomultiplier tube combined with a lock-in amplifier and a chopper with frequency of 3 kHz. Initial data of Ti and vd were analysed in terms of gas flow rate and applied power.

  4. A Prototype of Reflection Pulse Oximeter Designed for Mobile Healthcare.

    Science.gov (United States)

    Lu, Zhiyuan; Chen, Xiang; Dong, Zhongfei; Zhao, Zhangyan; Zhang, Xu

    2016-09-01

    This paper introduces a pulse oximeter prototype designed for mobile healthcare. In this prototype, a reflection pulse oximeter is embedded into the back cover of a smart handheld device to offer the convenient measurement of both heart rate (HR) and SpO2 (estimation of arterial oxygen saturation) for home or mobile applications. Novel and miniaturized circuit modules including a chopper network and a filtering amplifier were designed to overcome the influence of ambient light and interferences that are caused by embedding the sensor into a flat cover. A method based on adaptive trough detection for improved HR and SpO2 estimation is proposed with appropriate simplification for its implementation on mobile devices. A fast and effective photoplethysmogram validation scheme is also proposed. Clinical experiments have been carried out to calibrate and test our oximeter. Our prototype oximeter can achieve comparable performance to a clinical oximeter with no significant difference revealed by paired t -tests ( p = 0.182 for SpO2 measurement and p = 0.496 for HR measurement). The design of this pulse oximeter will facilitate fast and convenient measurement of SpO2 for mobile healthcare.

  5. VizieR Online Data Catalog: Bok globule BHR 160 radio lines spectra (Haikala+, 2017)

    Science.gov (United States)

    Haikala, L. K.; Reipurth, B.

    2016-11-01

    Radio spectral lines in maps covering approximately 2' by 2' with 20" spacing and a tilt of 60 degrees of the Bok globule BHR160 are presented. The spectra were obtained at Swedish ESO Submillimetre Telescope (SEST) in 1999. The observed molecular lines were 12CO(1-0), 12CO(2-1), 13CO(1-0), 13CO (2-1), C18O(1-0), C18O(2-1), CS(2-1) and CS(3-2). The SEST 2 and 3mm SESIS and 1 and 3mm IRAM dual SIS SSB receivers and the high resolution 2000 channel AOS spectrometer (channel spacing 41.711kHz) were used. The spectrometer was split into two to observe both channels simultaneously. The observations were made in the frequency switch mode. The switch was 5MHz (the 3mm channels) and 15MHz (the 1 and 2mm channels). The calibration was obtained using the chopper wheel method. The temperature scale of the spectra is in Ta* units, i.e. corrected to outside of the atmosphere but not for beam coupling. The 12CO spectra have been processed to correct for the artefact produced by the frequency switching method by the atmospheric CO and the -5km/s component (12CO (1-0)) and the -5km/s velocity component (12CO(2-1). The spectra are presented in 9 binary table FITS files. (10 data files).

  6. Status and operation of the Linac4 ion source prototypes.

    Science.gov (United States)

    Lettry, J; Aguglia, D; Andersson, P; Bertolo, S; Butterworth, A; Coutron, Y; Dallocchio, A; Chaudet, E; Gil-Flores, J; Guida, R; Hansen, J; Hatayama, A; Koszar, I; Mahner, E; Mastrostefano, C; Mathot, S; Mattei, S; Midttun, Ø; Moyret, P; Nisbet, D; Nishida, K; O'Neil, M; Ohta, M; Paoluzzi, M; Pasquino, C; Pereira, H; Rochez, J; Sanchez Alvarez, J; Sanchez Arias, J; Scrivens, R; Shibata, T; Steyaert, D; Thaus, N; Yamamoto, T

    2014-02-01

    CERN's Linac4 45 kV H(-) ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H(-) beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

  7. Commissioning of the Linac4 RFQ at the 3 MeV test stand

    CERN Document Server

    Rossi, C; Bellodi, G; Broere, J; Brunner, O; Lombardi, A M; Balula, J M; Yanez, P M; Noirjean, J; Pasquino, C; Raich, U; Roncarolo, F; Vretenar, M; Desmons, M; France, A; Piquet, O

    2013-01-01

    Linac4, the future 160 MeV Hˉ injector to the CERN Proton Synchrotron Booster, is presently under construction at CERN as a first step of the planned upgrade of the LHC injectors. The low energy section of LINAC4, consisting of an ion source, a 352.2 MHz Radio Frequency Quadrupole (RFQ) and a chopper line is being commissioned in a dedicated test stand before installation in its final position in the tunnel. The RFQ is designed to accelerate a 45 keV, 70 mA, Hˉ beam to 3 MeV, with an efficiency of 95% while preserving the transverse emittance. The RFQ, a four-vane structure 3 m in length, has been designed in collaboration with CEA/IRFU and is has been fabricated at the CERN workshop. The precise fabrication has allowed achieving a field flatness of 1%. The completion of the accelerating structure in September 2012 was followed by a complete series of bead-pull measurements and by high-power conditioning to the nominal power of 0.39 MW corresponding to a voltage of 78 kV across the 3 meters. Measurements wi...

  8. A Power-Efficient Capacitive Read-Out Circuit With Parasitic-Cancellation for MEMS Cochlea Sensors.

    Science.gov (United States)

    Wang, Shiwei; Koickal, Thomas Jacob; Hamilton, Alister; Mastropaolo, Enrico; Cheung, Rebecca; Abel, Andrew; Smith, Leslie S; Wang, Lei

    2016-02-01

    This paper proposes a solution for signal read-out in the MEMS cochlea sensors that have very small sensing capacitance and do not have differential sensing structures. The key challenge in such sensors is the significant signal degradation caused by the parasitic capacitance at the MEMS-CMOS interface. Therefore, a novel capacitive read-out circuit with parasitic-cancellation mechanism is developed; the equivalent input capacitance of the circuit is negative and can be adjusted to cancel the parasitic capacitance. Chip results prove that the use of parasitic-cancellation is able to increase the sensor sensitivity by 35 dB without consuming any extra power. In general, the circuit follows a low-degradation low-amplification approach which is more power-efficient than the traditional high-degradation high-amplification approach; it employs parasitic-cancellation to reduce the signal degradation and therefore a lower gain is required in the amplification stage. Besides, the chopper-stabilization technique is employed to effectively reduce the low-frequency circuit noise and DC offsets. As a result of these design considerations, the prototype chip demonstrates the capability of converting a 7.5 fF capacitance change of a 1-Volt-biased 0.5 pF capacitive sensor pair into a 0.745 V signal-conditioned output at the cost of only 165.2 μW power consumption.

  9. Development of a new in-air micro-PIXE set-up with in-vacuum charge measurements in Atomki

    Energy Technology Data Exchange (ETDEWEB)

    Török, Zs.; Huszánk, R.; Csedreki, L. [Institute for Nuclear Research, Hungarian Academy of Sciences (MTA Atomki), Laboratory of Ion Beam Applications, P.O. Box 51, H-4001 Debrecen (Hungary); Dani, J. [Déri Museum, Déri tér 1, H-4026 Debrecen (Hungary); Szoboszlai, Z.; Kertész, Zs. [Institute for Nuclear Research, Hungarian Academy of Sciences (MTA Atomki), Laboratory of Ion Beam Applications, P.O. Box 51, H-4001 Debrecen (Hungary)

    2015-11-01

    Highlights: • We installed an external microbeam set-up as the extension of our microprobe system. • We measured the integrated charge by a beam chopper installed in the vacuum chamber. • We determined the concentration of the ornament on the Hajdúsámson Bronze Age sword. - Abstract: A new external microbeam set-up has recently been installed as the extension of the existing microprobe system at the Laboratory of Ion Beam Applications of Atomki, Debrecen, Hungary. The external beam set-up, based on the system of Oxford Microbeams (OM), is equipped with two X-ray detectors for PIXE analysis, a digital microscope, two alignment lasers and a precision XYZ stage for easy and reproducible positioning of the sample. Exit windows with different thicknesses and of different materials can be used according to the actual demands, currently silicon-nitride (Si{sub 3}N{sub 4}) film with 200 nm thickness is employed in our laboratory. The first application was demonstrated in the field of archaeometry, on Bronze Age hoards from Hungary.

  10. Investigation of torque control using a variable slip induction generator

    Energy Technology Data Exchange (ETDEWEB)

    Bossanyi, E.A.; Gamble, C.R.

    1991-07-01

    An investigation of the possibilities of using a variable slip induction generator to control wind turbine transmission torque has been carried out. Such a generator consists of a wound rotor induction generator with its rotor winding connected to an external variable resistance circuit. By controlling the external resistance, the torque-slip characteristic of the generator can be modified, allowing efficient, low-slip operation below rated wind speed and compliant, high-slip operation above rated, where the additional losses are of no consequence but the resulting compliance allows a much reduced duty to be specified for the transmission and gearbox. A number of hardware options have been investigated for the variable resistance rotor circuit, the main options being either a rectifier and DC chopper or an AC regulator. Both of these options use semiconductor switching devices, for which the relative merits of thyristors, MOSFETs, GTOs and transistors have been investigated. A favoured scheme consisting of an AC regulator using GTOs has been provisionally selected. This choice uses some non-standard equipment but is expected to give negligible problems with harmonics. A comprehensive simulation model has been set up and used to investigate the behaviour of the whole system. (author).

  11. J-PARC Commissioning Results

    CERN Document Server

    Hasegawa, Kazuo

    2005-01-01

    The J-PARC (Japan Proton Accelerator Research Complex)comprises a 400-MeV linac, a 3-GeV rapid-cycling synchrotron (RCS), a 50-GeV main ring synchrotron (MR) and experimental facilities. A peak current of 30 mA was accelerated up to 20 MeV of the DTL beam commissioning at the KEK site. The buildings and conventional facilities will be completed in succession in the Japanese Fiscal Year 2005, when the installation of the accelerator components will be actually started at Tokai site. The beam commissioning of the 181 MeV linac will be started in September, 2006, followed by the RCS and MR beam commissioning. To achieve the high beam power with low beam loss, the J-PARC accelerators are based on many newly developed technologies; pi-mode stabilizing loops in the RFQ, RF choppers in the medium energy beam transport, magnetic alloy loaded RF cavities in the synchrotrons, etc. The recent results of the developments of these new technologies, the present construction status and the commissioning schedule will be pre...

  12. Two Axes Sun Tracking System for Heliostat: Case Study in Algeria

    Directory of Open Access Journals (Sweden)

    Mihoub Sofiane

    2016-03-01

    Full Text Available In this paper, using Proteus software, sun tracking system with 2 axes has developped to site of GHARDAIA, in the south of ALGERIA.O2 DC motors have used to move heliostat in N–S and E–W axis polar, in order to tracking the sun path.the distinction between day and night has provided by light dependent resistor (LDR.An algorithm of two axes sun tracking system hab developed and simulated under Proteus software, after DC motor’s parameters have verified and simulated under MATLAB software. The results show that: in the first, the development of the heliostat control requires the knowledge of the position of each heliostat relative to the tower to ensure the proper operation of the motors, and the uniformity of the reflected beam to the target.Then the choice of the drive motors is based on the useful power, including the weight of the heliostat, and all efforts affects on operation of motors in different seasons of the year, like the wind.And The position of the heliostat depends of chopper duty cycle.Finally,Conducting a power tower with mobile heliostats requires a techno-economic study on all components (heliostats, tower... of the plant, for example weather two motors for each heliostat field.

  13. The design of CMOS general-purpose analog front-end circuit with tunable gain and bandwidth for biopotential signal recording systems.

    Science.gov (United States)

    Chen, Wei-Ming; Yang, Wen-Chia; Tsai, Tzung-Yun; Chiueh, Herming; Wu, Chung-Yu

    2011-01-01

    In this paper an 8-channel CMOS general-purpose analog front-end (AFE) circuit with tunable gain and bandwidth for biopotential signal recording systems is presented. The proposed AFE consists of eight chopper stabilized pre-amplifiers, an 8-to-1 analog multiplexer, and a programmable gain amplifier. It can be used to sense and amplify different kinds of biopotential signals, such as electrocorticogram (ECoG), electrocardiogram (ECG) and electromyogram (EMG). The AFE chip is designed and fabricated in 0.18-μm CMOS technology. The measured maximum gain of AFE is 60.8 dB. The low cutoff frequency can achieve as low as 0.8 Hz and high cutoff frequency can be adjusted from 200 Hz to 10 kHz to suit for different kinds of biopotential signals. The measured input-referred noise is 0.9 μV(rms), with the power consumption of 18μW per channel at 1.8-V power supply. And the noise efficiency factor (NEF) is only 1.3 for pre-amplifier.

  14. Production design of the drift tube Linac for the CERN Linac4

    CERN Document Server

    Ramberger, S; Cuvet, Y; Dallocchio, A; De Michele, G; Gerigk, F; Giguet, J M; Lallement, J B; Lombardi, A M; Sargsyan, E; Vretenar, M

    2010-01-01

    The design of the Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN has been made ready for production: H--ion beams of up to 40 mA average pulse current are to be accelerated from 3 to 50 MeV by three RF cavities operating at 352.2MHz and at duty cycles of up to 10%. In order to provide a margin for longitudinal matching from the chopper line, the longitudinal acceptance has been increased. The synchronous phase starts at -35 deg in Tank1 and ramps linearly to -24 deg over the tank while it went from -30 to -20 deg in the previous design. The accelerating gradient has been reduced to 3.1MV/m in Tank1 and increased to 3.3 MV/m in Tank2 and Tank3 for a better distribution of RF power between tanks that is compatible with a mechanical design. To make the transverse acceptance less sensitive to alignment and gradient errors, the focusing scheme is now FFDD over all 3 tanks. Design features that were demonstrated in earlier reports have been improved for series production. Results of high power...

  15. Beams dynamics optimisation of LINAC4 structures for increased operational flexibility

    CERN Document Server

    Bellodi, G; Garcia Tudela, M; Hein, L M; Lallement, J B; Lombardi, A M; Posocco, P A; Sargsyan, E; Stovall, J

    2010-01-01

    Linac4 is a new 160 MeV, 40 mA pulsed beam current H- accelerator which will be the source of particles for all proton accelerators at CERN. Construction started in October 2008, and beam commissioning of the 3 MeV front-end is scheduled for early next year. A baseline design of the linac beam dynamics was completed 2 years ago and validated by a systematic campaign of transverse and longitudinal error studies to assess tolerance limits and machine activation levels. Recent studies have been mainly focused on optimising this design to achieve both a smoother performance for nominal beam conditions and to gain operational flexibility for non-nominal scenarios. These include a review of the chopper beam dynamics design, a re-definition of the DTL and CCDTL inter-tank regions and a study of operational schemes for reduced beam currents (either permanent or in pulse-to-pulse mode). These studies have been carried out in parallel to first specifications for a beam commissioning strategy of the linac and its low-en...

  16. An improved injector bunching geometry for ATLAS

    CERN Document Server

    Pardo, Richard C; Clifft, B E; Sherementov, S; Strickhorn, P

    2002-01-01

    The bunching system of the ATLAS positive ion injector (PII) has been improved by relocating the harmonic buncher to a point significantly closer to the second stage sine-wave buncher and the injector LINAC. The longitudinal optics design has also been modified and now employs a virtual waist from the harmonic buncher feeding the second stage sine-wave buncher. This geometry improves the handling of space charge for high-current beams, significantly increases the capture fraction into the primary rf bucket and reduces the capture fraction of the unwanted parasitic rf bucket. Total capture and transport through the PH has been demonstrated as high as 80% of the injected dc beam while the population of the parasitic, unwanted rf bucket is typically less than 3% of the total transported beam. To remove this small residual parasitic component a new traveling-wave transmission- line chopper has been developed reducing both transverse and longitudinal emittance growth from the chopping process. This work was suppor...

  17. Archaic Industries of Roussillon (South of France: Geochronological Correlation with the Terraces of the Têt, Tech and Agly Rivers

    Directory of Open Access Journals (Sweden)

    Joan GARCÍA GARRIGA

    2014-06-01

    Full Text Available This article studies the lithic industry of the Early Palaeolithic from the terraces of the Roussillon, in the S of France. The geomorphological revision of the flood levels allows these industries to be related to the geochronology of the terraces which were formed in between the late Early Pleistocene and the Middle Pleistocene, and thus allows a regional chrono-cultural framework to be established. By analyzing the technology of the lithic industry derived from the concept of chaîne opératoire and studying the patinas, the technical Modes and the technological aspects of the processes related to configuration and knapping sequences are differentiated. In the fluvial sequence, Mode 1 is documented in the terrace of Mas Ferréol and Mode 2 is identified in the Plane d’en Bourgat and Butte du Four-Llabanère, thus showing a technological continuity in the form of choppers and chopping-tools and poorly organized chains of exploitation (polyhedral. This technological substratum is common to the coeval sites from the NE of the Iberian Peninsula and the S of France, although with a margin of variability between the industries from the different regions.

  18. 基于 STM32的全桥逆变器的设计%The Design of Full Bridge Inverter Based on STM32

    Institute of Scientific and Technical Information of China (English)

    黎山峰; 黄超龙

    2016-01-01

    The paper introduces a design of the full bridge inverter based on the STM 32 microcontroller as the controlling core in order to design a low power digital sine-inverter, which uses a high resolution SPWM pulse produced by the MCU ’ s high speed timer , and operates the SPWM pulse into chopper inversion by the photoelectric coupler and IR 2111 to amplify power with the help of the full bridge converter made of IRF 840 , with the LC filtering circuit , finally changing high voltage SPWM pulse into AC power .%为设计一种低功耗的数字化正弦逆变器,设计了以STM32单片机为控制核心的全桥逆变器,该逆变器采由单片机的高速定时器产生高分辨率的SPWM脉冲,通过光耦隔离和IR2111驱动芯片把SPWM脉冲信号对由IRF840场效应管构成的全桥电路实现斩波逆变,经过LC滤波电路,最后实现高压SPWM脉冲转换成交流电源。

  19. Simulation of the backscattering spectrometer IN16: how much can be gained by using the phase space transformation technique?

    Science.gov (United States)

    González, M. A.; Frick, B.

    IN16 is a backscattering spectrometer combining high flux and an excellent resolution. We have studied a possibility to improve both the flux and the dynamic range of this instrument by using the phase space transformation technique to monochromatize a white neutron beam. By using a crystal mounted on a chopper that moves perpendicularly to the average scattering vector of the incident neutrons, it is possible to increase significantly the number of neutrons in a given wavelength band at the expense of worsening the Q resolution. In order to obtain reliable information about the improvement that could be achieved by applying this principle to the existing instrument, we have performed simulations with the McStas package to compare the flux of IN16 in its present configuration with that of an hypothetical IN16B located at the end position of a straight focusing neutron guide. The simulations reproduce well several test experiments performed on IN16 and allow us to predict that a gain in flux of about an order of magnitude can be expected.

  20. Une doble sépulture chalcolithique sous tumulus, et son paléoenvironnement (Pomps, P.A..

    Directory of Open Access Journals (Sweden)

    Claude Blanc

    1988-01-01

    Full Text Available Este túmulo funerario, hoy arrasado, estaba situado en el extremo noroeste de la meseta de «Pont-Long». Contenía en su centro unos cantos enrojecidos o cuarteados por el fuego, sobre el cual fueron depositados los restos de dos esqueletos humanos incinerados. Una corona de cantos de 40 cm. de espesor rodeaba la estructura central por todos los lados. La datación por el C14 dió: 3.850 ± 120 B.P., es decir el final del Calcolítico. El mobiliario recogido es interesante sobre todo por la serie de   «choppers» y de «chopping-tools» (42 piezas encontradas en su  mayor parte en la corona exterior. El análisis polínico de este túmulo revela un paisaje muy antropizado. Las frecuencias del haya, del avellano y del aliso permiten situarlo cronológicamente en la fase subboreal. Este túmulo aporta valiosas informaciones sobre ciertas funciones de los túmulos de la protohistoria antigua. Suministra además el primer elemento cronológico para los Pirineos Occidentales Franceses sobre el comienzo de la práctica de la incineración.

  1. Word-decoding as a function of temporal processing in the visual system.

    Science.gov (United States)

    Holloway, Steven R; Náñez, José E; Seitz, Aaron R

    2013-01-01

    This study explored the relation between visual processing and word-decoding ability in a normal reading population. Forty participants were recruited at Arizona State University. Flicker fusion thresholds were assessed with an optical chopper using the method of limits by a 1-deg diameter green (543 nm) test field. Word decoding was measured using reading-word and nonsense-word decoding tests. A non-linguistic decoding measure was obtained using a computer program that consisted of Landolt C targets randomly presented in four cardinal orientations, at 3-radial distances from a focus point, for eight compass points, in a circular pattern. Participants responded by pressing the arrow key on the keyboard that matched the direction the target was facing. The results show a strong correlation between critical flicker fusion thresholds and scores on the reading-word, nonsense-word, and non-linguistic decoding measures. The data suggests that the functional elements of the visual system involved with temporal modulation and spatial processing may affect the ease with which people read.

  2. Exploring control parameters of two photon processes in solutions

    Indian Academy of Sciences (India)

    Debabrata Goswami; Amit Nag

    2012-01-01

    Two-photon microscopy depends extensively on the two-photon absorption cross-sections of biologically relevant chromophores. High repetition rate (HRR) lasers are essential in multiphoton microscopy for generating satisfactory signal to noise at low average powers. However, HRR lasers generate thermal distortions in samples even with the slightest single photon absorption. We use an optical chopper with HRR lasers to intermittently `blank’ irradiation and effectively minimize thermal effects to result in a femtosecond z-scan setup that precisely measures the two-photon absorption (TPA) cross-sections of chromophores. Though several experimental factors impact such TPA measurements, a systematic effort to modulate and influence TPA characteristics is yet to evolve. Here, we present the effect of several control parameters on the TPA process that are independent of chromophore characteristics for femtosecond laser pulse based measurements; and demonstrate how the femtosecond laser pulse repetition rate, chromophore environment and incident laser polarization can become effective control parameters for such nonlinear optical properties.

  3. Modelling and control of an electric vehicle; Modelisation et controle d`un vehicule electrique

    Energy Technology Data Exchange (ETDEWEB)

    Kwartnik, J.

    1995-11-28

    The work described in this report provides to engineers or researchers a tool for electric vehicle simulation. The different components included in the system are described with in particular the choppers, the pedal accelerator and the vehicle dynamic represented by the different constraints applied to the vehicle (efforts of drag, of lift, of rolling and slope resistance). This study has been realized by considering nonlinear phenomenons such as the armature magnetic reaction or the resistance change due to temperature increasing. The complexity of the system leads to use several of control. The theory of linear systems made possible the synthesis of PID controllers after few hypothesis. An on line adaptation technique completed this synthesis by considering nonlinear effects. For the cruise control we have used a control based on fuzzy set theory. We showed through two examples, the cruise control and the motor control using a strategy which minimize the Joule effect looses, the interest and the possibilities of the model evolution. (author) 21 refs.

  4. Neutron diffractometers for structural biology at spallation neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Schoenborn, B.P.; Pitcher, E. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Spallation neutron sources are ideal for diffraction studies of proteins and oriented molecular complexes. With spoliation neutrons and their time dependent wavelength structure, it is easy to electronically select data with an optimal wavelength bandwidth and cover the whole Laue spectrum as time (wavelength) resolved snapshots. This optimized data quality with best peak-to-background ratios and provides adequate spatial and energy resolution to eliminate peak overlaps. The application of this concept will use choppers to select the desired Laue wavelength spectrum and employ focusing optics and large cylindrical {sup 3}He detectors to optimize data collection rates. Such a diffractometer will cover a Laue wavelength range from 1 to 5{Angstrom} with a flight path length of 10m and an energy resolution of 0.25{Angstrom}. Moderator concepts for maximal flux distribution within this energy range will be discussed using calculated flux profiles. Since the energy resolution required for such timed data collection in this super Laue techniques is not very high, the use of a linac only (LAMPF) spoliation target is an exciting possibility with an order of magnitude increase in flux.

  5. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Simeoni, G. G., E-mail: ggsimeoni@outlook.com [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Valicu, R. G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Borchert, G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Böni, P. [Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Rasmussen, N. G. [Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A. [Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln (Germany)

    2015-12-14

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  6. Magnetic excitations in ferromagnetic phase of MnP

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Shin-ichiro [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara 229-8558 (Japan); Itoh, Shinichi, E-mail: shinichi.itoh@kek.jp [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Yokoo, Tetsuya; Satoh, Setsuo [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Kawana, Daichi [Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Kousaka, Yusuke; Akimitsu, Jun [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara 229-8558 (Japan); Endoh, Yasuo [Neutron Science Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2013-12-15

    Inelastic neutron scattering experiments were performed on an intermetallic compound, MnP. We used a newly developed High Resolution Chopper Spectrometer, HRC, for energy transfers E≤75meV, besides various triple axis spectrometers; LTAS for energy transfers E≤2meV, TOPAN for E≤7.5meV and TAS-1 for E≤35meV. Spin wave excitations were observed in the ferromagnetic phase of MnP in the entire Brillouin zone along the a{sup ⁎}- and b{sup ⁎}-axes. The zone boundary energies of spin waves were determined to be around 60 meV along the a{sup ⁎}-axis and around 75 meV along the b{sup ⁎}-axis, and the dispersion relations showed two branches for both axes. The observed dispersion relations of spin waves were well described by an isotropic Heisenberg interaction adding a single ion anisotropy with two sub-lattices. - Highlights: • Inelastic neutron scattering experiments were performed mainly using pulsed neutrons. • Spin waves were observed in the ferromagnetic phase of an intermetallic compound MnP. • The dispersion relations were determined entirely along the a{sup ⁎}- and b{sup ⁎}-axes. • We could describe the observed dispersion relations by a two sub-lattice model.

  7. Analysis of energy performance in two systems of cogeneration used in plants of sugar cane; Analise de desempenho energetico em dois sistemas de cogeracao empregados em usinas de cana de acucar

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Felipe A.A.; Rosa, Rodrigo A. [Cogeracao Sistemas de Energia Ltda., Recife, PE (Brazil)

    2004-07-01

    One of the options to overcome the current volatility in Brazil's power consumption outlook relates to the employment of other sources for power generation, namely solar energy, wind power or the use of biomass, namely the power generation through the cane bagasse. One should realize, however, that the economic accomplishment for launching a generation system should depend on the level of effectiveness of all processes and/or equipment comprising the system thereof. As far as the sugar-alcohol industry is concerned, the larger the system effectiveness is, the bigger the surplus of bagasse becomes and, hence, the better the chance of achieving financial earnings. Two generation systems shall be evaluated, aiming to thermo-dynamically identify the differences between the use of small equipment-driven turbines (like choppers, shredders and mills) and multi-stage turbo-generators, in order to replace the electric-powered drive units. Therefore, one shall follow thermodynamic-based criteria, namely the steam specific consumption, the equipment availability and effectiveness, thus allowing a comparison for each engine. Such survey shows that the effectiveness reaches nearly 68% for the turbo-generators and 43% for the small turbines. Under the economic perspective, one can find a saving of 89.500 tonnes per crop of bagasse, standing for an additional turnover of US$ 895.000,00 annually. (author)

  8. A 2.5 mW 370 mV/pF high linearity stray-immune symmetrical readout circuit for capacitive sensors

    Science.gov (United States)

    Kaimin, Zhou; Ziqiang, Wang; Chun, Zhang; Zhihua, Wang

    2012-06-01

    A stray-insensitive symmetrical capacitance-to-voltage converter for capacitive sensors is presented. By introducing a reference branch, a symmetrical readout circuit is realized. The linear input range is increased, and the systematic offsets of two input op-amps are cancelled. The common-mode noise and even-order distortion are also rejected. A chopper stabilization technique is adopted to further reduce the offset and flicker noise of the op-amps, and a Verilog-A-based varactor is used to model the real variable sensing capacitor. Simulation results show that the output voltage of this proposed readout circuit responds correctly, while the under-test capacitance changes with a frequency of 1 kHz. A metal-insulator-metal capacitor array is designed on chip for measurement, and the measurement results show that this circuit achieves sensitivity of 370 mV/pF, linearity error below 1% and power consumption as low as 2.5 mW. This symmetrical readout circuit can respond to an FPGA controlled sensing capacitor array changed every 1 ms.

  9. Pertimbangan Sifat Mekanik Pelepah Sawit Terhadap Proses Pengomposan Sebagai Acuan Desain Mesin Pencacah

    Directory of Open Access Journals (Sweden)

    Ramayanty Bulan

    2016-10-01

    Full Text Available Physical and mechanical properties of palm frond are very important factor for the development of palm oil waste utilization technology. The objective of this research was to determine mechanical properties of palm frond Frond for Chopper Machine Designing. The research of composting conduct with two composting factor combination, namely: composting starter composition (i.e. Bokashi, vermi-compost and natural composting and piece of frond dimension (2 cm, 4 cm, and 6 cm. Sample was obtained from 5 years and 20 years palm oil trees. The average length of palm frond was 675.89 cm, average leaflet length at the palm frond base was 103.89 cm and average leaflet length at palm frond tip was 23.83 cm. Maximum compression strength at the 20 years-palm frond base was 8134.62 N and at the 5 years-palm midrib base was 4893.52 N. Maximum force requirement for cutting palm leaf was 67.67 N. The composting process indicates that Bokashi starter composition gives higher percentage of mass reduction on all variant of piece of frond dimension. Smaller piece of frond (2 cm enable the composting process quicker and had a better result. Statistical analysis reveals that combination of composting factors have significant effect on C/N ratio but insignificant on NPK content.

  10. Device-level vacuum packaged uncooled microbolometer on a polyimide substrate

    Science.gov (United States)

    Ahmed, Moinuddin; Butler, Donald P.; Celik-Butler, Zeynep

    2016-11-01

    Uncooled infrared detectors (IR) on a polyimide substrate have been demonstrated where amorphous silicon (a-Si) was used as the thermometer material. New concepts in uncooled microbolometers were implemented during the design and fabrication, such as the integration of a germanium long-pass optical filter with the device-level vacuum package and a double layer absorber structure. Polyimide was used for this preliminary work towards vacuum-packaged flexible microbolometers. The detectors were fabricated utilizing a carrier wafer and low adhesion strength release layer to hold the flexible polyimide substrate during fabrication in order to increase the release yield. The IR detectors showed a maximum detectivity of 4.54 × 106 cm Hz1/2/W at a 4 Hz chopper frequency and a minimum noise equivalent power (NEP) of 7.72 × 10-10 W/Hz1/2 at a biasing power of 5.71 pW measured over the infrared wavelength range of 8-14 μm for a 35 μm × 35 μm detector. These values are comparable to other flexible microbolometers with device-level vacuum packaging which are found in literature.

  11. Exploration of Whole Atmosphere Lidar: Mach-zehnder Receiver to Extend Fe Doppler Lidar Wind Measurements from the Thermosphere to the Ground

    Science.gov (United States)

    Smith, John A.; Chu, Xinzhao

    2016-06-01

    A receiver employing a field-widened Mach-Zehnder interferometer (MZI) is investigated for extending the wind measurement range of a narrowband Fe Doppler (372 nm) lidar from its existing measurement range in the mesosphere and lower thermosphere (MLT) down to the ground. This design uses the multiple transmitted frequencies available from the base Fe Doppler lidar in combination with an MZI receiver to make a measurement of the Doppler shift from Rayleigh-Mie scattering that is independent of aerosol backscatter ratio, temperature and pressure of the lidar volume and also independent of geometric overlap, the chopper function and any other factor affecting the signal in both MZI channels equally. A ratio is constructed from the three frequencies and two channels of the interferometer that exhibits a measurement performance of 1.75 times the Cramer-Rao lower bound, which is comparable to the dual MZI (DMZ) while preserving the insensitivity to backscatter spectrum of the quad MZI (QMZ). Using actual data obtained recently from the Fe Doppler lidar, we show the expected measurement performance of this whole atmosphere lidar instrument concept.

  12. Design of mini-multi-gas monitoring system based on IR absorption

    Science.gov (United States)

    Tan, Qiu-lin; Zhang, Wen-dong; Xue, Chen-yang; Xiong, Ji-jun; Ma, You-chun; Wen, Fen

    2008-07-01

    In this paper, a novel non-dispersive infrared ray (IR) gas detection system is described. Conventional devices typically include several primary components: a broadband source (usually an incandescent filament), a rotating chopper shutter, a narrow-band filter, a sample tube and a detector. But we mainly use the mini-multi-channel detector, electrical modulation means and mini-gas-cell structure. To solve the problems of gas accidents in coal mines, and for family safety that results from using gas, this new IR detection system with integration, miniaturization and non-moving parts has been developed. It is based on the principle that certain gases absorb infrared radiation at specific (and often unique) wavelengths. The infrared detection optics principle used in developing this system is mainly analyzed. The idea of multi-gas detection is introduced and guided through the analysis of the single-gas detection. Through researching the design of cell structure, a cell with integration and miniaturization has been devised. By taking a single-chip microcomputer (SCM) as intelligence handling, the functional block diagram of a gas detection system is designed with the analyzing and devising of its hardware and software system. The way of data transmission on a controller area network (CAN) bus and wireless data transmission mode is explained. This system has reached the technology requirement of lower power consumption, mini-volume, wide measure range, and is able to realize multi-gas detection.

  13. Beam-surface scattering studies of the individual and combined effects of VUV radiation and hyperthermal O, O2, or Ar on FEP Teflon surfaces.

    Science.gov (United States)

    Brunsvold, Amy L; Zhang, Jianming; Upadhyaya, Hari P; Minton, Timothy K

    2009-01-01

    Beam-surface scattering experiments were used to probe products that scattered from FEP Teflon surfaces during bombardment by various combinations of atomic and molecular oxygen, Ar atoms, and vacuum ultraviolet (VUV) light. A laser-breakdown source was used to create hyperthermal (translational energies in the range 4-13 eV) beams of argon and atomic/molecular oxygen. The average incidence energy of these beams was tunable and was controlled precisely with a synchronized chopper wheel. A filtered deuterium lamp provided a source of VUV light in a narrow-wavelength range centered at 161 nm. Volatile products that exited the surfaces were monitored with a rotatable mass spectrometer detector. Hyperthermal O atoms with average translational energies above approximately 4 eV may react directly with a pristine FEP Teflon surface, and the reactivity appears to increase with the translational energy of the incident O atoms. VUV light or highly energetic collisions of O2 or Ar may break chemical bonds and lead to the ejection of volatile products; the ejection of volatile products is enhanced when the surface is subjected to VUV light and energetic collisions simultaneously. Exposure to VUV light or to hyperthermal O2 or Ar may increase the reactivity of an FEP Teflon surface to O atoms.

  14. Studies on selected polymeric materials using the photoacoustic spectroscopic technique

    Institute of Scientific and Technical Information of China (English)

    Hukum Singh

    2011-01-01

    Polymethylmethacrylate-graft-polybisphenol-A-carbonate (PMMA-G-PC) with 50% grafting is synthesized. The acid (0.18 M, 100 ml) in air at (45±12) ℃ for 3.0 h. Condensation of (PMMA-G-PC) with N-[p-(carboxyl phenyl amino acetic acid)] hydrazide (PCPH) affords polybisphenol-A-carbonate-graft-polymethylmethacrylate hydrazide (PCGH).The photoacoustic (PA) spectra of (PCGH) are recorded in a wavelength range from 200 nm to 800 nm at a modulation frequency of 22 Hz, and compared with those of pure polybisphenol-A-carbonate (PC), (PMMA-G-PC) and (PCPH).In the present work, a non-destructive and non-contact analytical method, namely the photoacoustic technique, is successfully implemented for optical and thermal characterization of selected polymeric materials. The indigenous PA spectrometer used in the present study consists of a 300-W xenon arc lamp, a lock-in amplifier, a chopper, a (1/8)-m monochromator controlled by computer and a home-made PA cell.

  15. Performance Analysis of Phase Controlled Unidirectional and Bidirectional AC Voltage Controllers

    Directory of Open Access Journals (Sweden)

    Abdul Sattar Larik

    2011-01-01

    Full Text Available AC voltage controllers are used to vary the output ac voltage from a fixed ac input source. They are also commonly called ac voltage regulators or ac choppers. The output voltage is either controlled by PAC (Phase Angle Control method or on-off control method. Due to various advantages of ac voltage controllers, such as high efficiency, simplicity, low cost and ability to control large amount of power they efficiently control the speed of ac motors, light dimming and industrial heating, etc. These converters are variable structure systems and generate harmonics during the operation which will affect the power quality when connected to system network. During the last couple of years, a number of new semiconductor devices and various power electronic converters has been introduced. Accordingly the subject of harmonics and its problems are of great concern to power industry and customers. In this research work, initially the simulation models of single phase unidirectional and bidirectional ac voltage controllers were developed by using MATLAB software. The harmonics of these models are investigated by simulation. In the end, the harmonics were also analyzed experimentally. The simulated as well as experimental results are presented.

  16. Computational analysis on plug-in hybrid electric motorcycle chassis

    Science.gov (United States)

    Teoh, S. J.; Bakar, R. A.; Gan, L. M.

    2013-12-01

    Plug-in hybrid electric motorcycle (PHEM) is an alternative to promote sustainability lower emissions. However, the PHEM overall system packaging is constrained by limited space in a motorcycle chassis. In this paper, a chassis applying the concept of a Chopper is analysed to apply in PHEM. The chassis 3dimensional (3D) modelling is built with CAD software. The PHEM power-train components and drive-train mechanisms are intergraded into the 3D modelling to ensure the chassis provides sufficient space. Besides that, a human dummy model is built into the 3D modelling to ensure the rider?s ergonomics and comfort. The chassis 3D model then undergoes stress-strain simulation. The simulation predicts the stress distribution, displacement and factor of safety (FOS). The data are used to identify the critical point, thus suggesting the chassis design is applicable or need to redesign/ modify to meet the require strength. Critical points mean highest stress which might cause the chassis to fail. This point occurs at the joints at triple tree and bracket rear absorber for a motorcycle chassis. As a conclusion, computational analysis predicts the stress distribution and guideline to develop a safe prototype chassis.

  17. The System of Nanosecond 280-keV-He+ Pulsed Beam

    CERN Document Server

    Junphong, Pimporn; Lekprasert, Banyat; Suwannakachorn, Dusadee; Thongnopparat, N; Vilaithong, Thiraphat; Wiedemann, Helmut

    2005-01-01

    At Fast Neutron Research Facility,the 150 kV-pulseds neutron generator is being upgraded to produce a 280-keV-pulsed-He beam for time-of-flight Rutherford backscattering spectrometry. It involves replacing the existing beam line elements by a multicusp ion source, a 400-kV accelerating tube, 45o-double focusing dipole magnet and quadrupole lens. The Multicusp ion source is a compact filament-driven of 2.6 cm in diameter and 8 cm in length. The current extracted is 20.4 μA with 13 kV of extraction voltage and 8.8 kV of Einzel lens voltage. The beam emittance has been found to vary between 6-12 mm mrad. The beam transport system has to be redesigned based on the new elements. The important part of a good pulsed beam depends on the pulsing system. The two main parts are the chopper and buncher. An optimized geometry for the 280 keV pulsed helium ion beam will be presented and discussed. The PARMELA code has been used to optimize the space charge effect, resulting in pulse width of less than 2 ns at a t...

  18. Development of a DC propulsion system for an electric vehicle

    Science.gov (United States)

    Kelledes, W. L.

    1984-01-01

    The suitability of the Eaton automatically shifted mechanical transaxle concept for use in a near-term dc powered electric vehicle is evaluated. A prototype dc propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the contractor's site. The system consisted of a two-axis, three-speed, automatically-shifted mechanical transaxle, 15.2 Kw rated, separately excited traction motor, and a transistorized motor controller with a single chopper providing limited armature current below motor base speed and full range field control above base speed at up to twice rated motor current. The controller utilized a microprocessor to perform motor and vehicle speed monitoring and shift sequencing by means of solenoids applying hydraulic pressure to the transaxle clutches. Bench dynamometer and track testing was performed. Track testing showed best system efficiency for steady-state cruising speeds of 65-80 Km/Hz (40-50 mph). Test results include acceleration, steady speed and SAE J227A/D cycle energy consumption, braking tests and coast down to characterize the vehicle road load.

  19. Neutron scattering instruments for residual stress/strain measurements at KUR

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Masayoshi [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.

    1997-06-01

    A Kyoto University Reactor project research finished on March, 1997 is a first trial in Japan. In this research, some residual stress measurement in accompany with thermal and processing deformation history of various superconductive composite wires and so on were conducted to obtain a lot of research results. At TOF system, simultaneous measurement of the direction dependent collective texture using a multi point detector was useful, and at PSD system the strain measurement in a region under 10{sup -4} became possible to conduct. In addition, it is intending now to establish high performance instruments such as a two-stage type disc chopper at the TOF system and a high resolution vent type Si monocrystal monochromator at the PSD system. In particular, it is expected a the TOF system that a direction dependent collective texture and a stress distribution state in various kinds of functional materials can be measured simultaneously and without destruction. The mechanical property research of the metallic materials using low speed neutron scattering method is now a big interest in and out of Japan. This research contains a lot of contents coinciding to the industrial fields in an application research field of nuclear basic research and is expected in future to powerfully promote international cooperative research and to deeply recognize its usefulness and importance. (G.K.)

  20. Burner ignition system

    Science.gov (United States)

    Carignan, Forest J.

    1986-01-21

    An electronic ignition system for a gas burner is battery operated. The battery voltage is applied through a DC-DC chopper to a step-up transformer to charge a capacitor which provides the ignition spark. The step-up transformer has a significant leakage reactance in order to limit current flow from the battery during initial charging of the capacitor. A tank circuit at the input of the transformer returns magnetizing current resulting from the leakage reactance to the primary in succeeding cycles. An SCR in the output circuit is gated through a voltage divider which senses current flow through a flame. Once the flame is sensed, further sparks are precluded. The same flame sensor enables a thermopile driven main valve actuating circuit. A safety valve in series with the main gas valve responds to a control pressure thermostatically applied through a diaphragm. The valve closes after a predetermined delay determined by a time delay orifice if the pilot gas is not ignited.

  1. Weak absorption test and defect analysis of optical coatings

    Institute of Scientific and Technical Information of China (English)

    HE Hong-bo; LI Xia; FAN Shu-hai; ZHAO Yuan-an; SHAO Jian-da; FAN Zheng-xiu

    2005-01-01

    Surface thermal lensing technique was developed into a high-sensitive apparatus for weak absorption test and defect analysis of optical coatings. A continuous-wave 1 064 nm Nd:YAG laser and a He-Ne laser were employed as pump source and probe source, respectively. Low noise photoelectrical components and a lock-in amplifier were used for photo-thermal deformation signal detection. In order to improve sensitivity, the apparatus configuration was optimized by choosing appropriate parameters, including pump beam spot size, chopper frequency, detection distance, waist radius and position of probe beam. Coating samples were mounted on a x-y stage. Different procedures, such as single spot, linear scan and 2-dimension area scan, could be performed manually or automatically. Various optical coatings were prepared by both electron beam evaporation and ion beam sputtering deposition. High sensitivity was obtained and low to 1×10-7 weak absorption was tested in low-loss coating samples. For the sensitivity extreme of the system, 1×10-8 absorption was reason out to be measured by surface thermal lensing technique. Very small standard deviation was achieved for the reproducibility evaluation. Moreover, a spatial resolution of 25 micron was proved according to the area scan which traced out the profile of photo-thermal defects inside optical coatings. The system was employed in the analyses of optical absorption, absorption uniformity and defect characterization, and revealed the relationship between laser-induced damage and absorption of optical coatings.

  2. Comparison of harvesting and transport issues when biomass crops are handled as hay vs silage

    Energy Technology Data Exchange (ETDEWEB)

    Worley, J.W. [Georgia Univ., Athens, GA (United States). Dept. of Biological and Agricultural Engineering; Cundiff, J.S. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Biological Systems Engineering

    1996-04-01

    Because of frequent rainfall, hay making is problematic in central Florida. High biomass yields can be produced, but the crops must be handled as silage. Because of the long available harvest season, the cost of making silage should be less here than in other regions. Harvest of silage in central Florida with two different systems, standard (35-55 Mg/ha yield) and high-capacity (based on a hypothesized forage chopper expected to handle 55-75 Mg/ha yield), was simulated. Simulated harvest and transport cost for three versions of the standard system ranged from $108.10/dry Mg, when juice was expressed prior to ensiling in 320-Mg silage bags, to $114.15, when the chopped material was directly ensiled in an above-ground pile. Total cost was $101.70 for the high-capacity system. These costs compare to $57.25/dry Mg for hay. It appears that silage is not competitive with hay for cellulose feedstock, even in the advantageous climate of central Florida. (Author)

  3. Beam dynamics and commissioning of low and medium energy H- beam at Linac4

    CERN Document Server

    Satri, Masoomeh Yarmohammadi; Lamehi-Rachti , Mohammad

    The First step of the CERN Large Hadron Collider injectors upgrade (LIU) project is Linac4. It accelerates H- ions to 160 MeV in an 80 m long accelerator housed in a tunnel 12 m underground, presently under construction. It will replace the present 50 MeV proton Linac2 as injector of the proton accelerator complex to increase the LHC luminosity. It consists of a 45 keV RF volume source, a twosolenoid Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ) accelerating the beam to 3 MeV, a Medium Energy Beam Transport (MEBT) line. The MEBT houses a fast chopper to selectively remove unwanted micro-bunches in the 352 MHz sequence and avoid losses at capture in the CERN PSB (1 MHz). After chopping, the beam acceleration continues by a 50 MeV Drift Tube Linac (DTL), a 100 MeV Cell-Coupled Drift Tube Linac and a Pi-Mode Structure bringing the beam to the final energy of 160 MeV. Linac4 has been commissioned with a temporary source up to 12 MeV. The beam commissioning stages of Linac4 in LEBT...

  4. Versatile inelastic neutron spectrometer (VINS) project for J-PARC

    Energy Technology Data Exchange (ETDEWEB)

    Sato, T.J. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Shirakata, Tokai, Ibaraki 319-1106 (Japan)], E-mail: taku@issp.u-tokyo.ac.jp; Yamamuro, O.; Hirota, K.; Shibayama, M.; Yoshizawa, H. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Shirakata, Tokai, Ibaraki 319-1106 (Japan); Itoh, S. [High Energy Accerelator Research Organization (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan); Watanabe, S.; Asami, T. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Shirakata, Tokai, Ibaraki 319-1106 (Japan); Kindo, K.; Uwatoko, Y. [Institute for Solid State Physics, University of Tokyo, Kashiwanoha, Chiba 277-8581 (Japan); Kanaya, T. [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Higashi, N.; Ueno, K. [High Energy Accerelator Research Organization (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2009-02-21

    We have proposed a Versatile Inelastic Neutron Spectrometer (VINS) for the spallation neutron source at the Materials and Life Science Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC). VINS is a direct-geometry Fermi chopper spectrometer designed to provide considerably high neutron flux with moderate energy and Q resolutions. VINS is characterized by its wide energy and Q range (0.5<{delta}E<1000 meV and Q< 40 A{sup -1} at {delta}E=1000 meV), enabled by an array of detectors covering large solid angle [-30 deg.<2{theta}<130 deg. horizontally and -30 deg.<{phi}<30 deg. vertically (2.8 Sr)]. Monte Carlo ray-tracing simulation estimates the sample position neutron flux as high as roughly 1x10{sup 6} neutrons cm{sup -2} s{sup -1} for the {delta}E/E{sub i}{approx}5% mode at E{sub i}=10 meV. With these wide E-Q coverage and high neutron flux, VINS will be one of the most efficient and versatile inelastic spectrometers at J-PARC. Target science ranges from conventional solid-state physics, such as highly correlated electron systems, frustrated magnets and relaxors, to rather interdisciplinary areas, exemplified by glasses, quasicrystals, polymers and liquids. A particular focus is placed on extreme sample environments; high magnetic-field and high-pressure environments are planned.

  5. 永磁直驱风电系统运行特性的仿真分析%Simulation Analysis on Low Voltage Ride Through of PMSG Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    罗苏华; 陆显斌; 杨贵杰

    2011-01-01

    对采用永磁同步电机的直接驱动型变速恒频风电系统进行建模,详细分析了系统在最佳叶尖速比捕捉最大风能、Chopper电路及桨距角控制增强低电压穿越能力的机理.利用Matlab/Simulink构建了采用全功率变流器的永磁直驱风力发电系统的仿真模型,对系统的最大风能捕捉及低电压穿越的动态响应进行了仿真验证.仿真结果表明,系统具有较高的效率和良好的低电压穿越能力.%The model of direct-drive varible speed constant frequency wind generation system which uses permanentmagnet synchronous machine was established. The theory of working at optimal tip speed ratio to capture maximum wind energy and taking chopper circuit or pitch control to enhance the LVRT ability was analysed. The simulation model of direct drive PMSG wind turbine with full power converter was configured using Matlab/Simulink. The dynamic responses of MPPT and LVRT were simulated. The results indicate that the DDPMSG wind turbine has high efficiency and good LVRT ability.

  6. Diting: A polarized time-of-flight neutron reflectometer at CMRR reactor in China

    Science.gov (United States)

    Li, Xinxi; Huang, Chaoqiang; Wang, Yan; Chen, Bo; Sun, Guang'ai; Liu, Yaoguang; Gong, Jian; Kang, Wu; Liu, Hangang

    2016-11-01

    A new time-of-flight neutron reflectometer with a polarization option is developed and tested at the Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, China. Its scattering geometry is horizontal. The constructed neutron reflectometer is a multipurpose instrument that can be used for the characterization of a stratified microstructure and hidden interfaces of solid thin films. Diting is designed for both magnetic and nonmagnetic multi-layer thin films. Spin polarization and analysis are achieved by transmission magnetized supermirrors. The sample unit is equipped with an electromagnet, which can provide a vertical magnetic field range of 0-1.2 tesla. The available neutron beam is a white beam with wavelength range of 0.15-1.25 nm, which can be cut into different wavelength resolution neutron pulses by a four-disk chopper. A two-dimensional position-sensitive detector is employed to count the specular and off-specular reflected neutron beam. A minimum reflectivity of 10-6 is measured on this instrument.

  7. A new type of mine electrical locomotive traction power controller development%基于单片机矿用电机车牵引控制器的研制

    Institute of Scientific and Technical Information of China (English)

    张全柱; 黄成玉; 邓永红

    2009-01-01

    为了实现矿用电机车交流传动的高性能控制运行,提高电机车运行的可靠性,以代替传统的矿用电机车直流调阻调速和直流斩波调速,实现节能降耗.本文研制设计了基于16位单片微机SPMC75F2413A的矿用电机车交流变频调速牵引控制器,给出了牵引控制器三相SPWM波形发生器的硬件和软件的实现方案和电路结构.实验结果证明,该牵引控制器能够满足矿用电机车交流变频调速运行的要求.%Mine electrical locomotive speed controlling modified from traditional changing DC Resistance and DC Chopper to VVVF, realizing mine electric locomotive to have high-performance control, saving energy and improving the reliability of operation of motor vehicles.This article is designed based on the Sunplus 16-bit single-chip microcomputer SPMC75F2413A mine locomotive traction power controller, providing the controller three-phase SPWM waveform generator hardware and software implementation program.

  8. Two thermal methods to measure the energy fluence of a brief exposure of diagnostic x rays.

    Science.gov (United States)

    Carvalho, A A; Mascarenhas, S; dePaula, M H; Cameron, J R

    1992-01-01

    This paper describes two simple thermal methods for measuring the energy fluence in J/cm2 from a diagnostic x-ray exposure. Both detectors absorb essentially 100% of the radiation and give a signal that is directly proportional to the energy fluence of the x-ray beam. One detector measures the thermal effect when a pulse of x rays is totally absorbed in the pyroelectric detector of lead-zirconium-titanate (PZT). The other detector measures the expansion of a gas surrounding a lead disk detector in a photoacoustic chamber. The increased pressure of the gas is transmitted through a 1-mm duct to a sensitive microphone. Both detectors have previously been used to measure the energy fluence rate of continuous x-ray beams in the same energy region using a chopped beam and a lock-in amplifier. Measurement of the energy fluence of a pulse of radiation eliminates the need for the beam chopper and lock-in amplifier and results in a simple, rugged, and inexpensive dosimeter. Either method can be combined with the area of the beam to give an estimate of the imparted energy to the patient from a diagnostic x-ray exposure.

  9. The beam bunching and transport system of the Argonne positive ion injector

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, P.K.; Bogaty, J.M.; Bollinger, L.M.; Clifft, B.E.; Pardo, R.C.; Shepard, K.W.

    1989-01-01

    A new positive ion injector (PII) is currently under construction at Argonne that will replace the existing 9-MV tandem electrostatic accelerator as an injector into ATLAS. It consists of an electron-cyclotron resonance-ion source on a 350-kV platform injecting into a superconducting linac optimized for very slow (..beta.. less than or equal to .007 c) ions. This combination can potentially produce even higher quality heavy-ion beams than are currently available from the tandem since the emittance growth within the linac is largely determined by the quality of the bunching and beam transport. The system we have implemented uses a two-stage bunching system, composed of a 4-harmonic gridded buncher located on the ECR high-voltage platform and a room temperature spiral-loaded buncher of novel design. A sinusoidal beam chopper is used for removal of tails. The beam transport is designed to provide mass resolution of M/..delta..M > 250 and a doubly-isochronous beamline is used to minimize time spread due to path length differences. 4 refs., 2 figs.

  10. A Single-Phase Multilevel Current-Source Converter using H-Bridge and DC Current Modules

    Directory of Open Access Journals (Sweden)

    Suroso Suroso

    2014-03-01

    Full Text Available This paper presents a different topology of H-bridge based multilevel current-source inverter (CSI. In this new topology, an H-bridge CSI is connected with a single or more current modules to generate a multilevel output current waveform with lower di/dt, and less distortion. Using the proposed multilevel CSI, the number of the power switching devices, and isolated gate drive circuits can be reduced. Moreover, chopper based DC current sources are presented to reduce the inductor size effectively to be in micro-Henry order, and ensure the balance of the intermediate current levels. The proposed topology is inherently able to reduce the inductor conduction losses if compared with the conventional multilevel CSIs and the H-bridge CSI. Seven-level PWM inverter configurations with non-isolated DC current sources and with a single DC power source are verified through computer simulations. Furthermore, laboratory prototypes of seven-level CSI is setup and tested. The results show that the inverter circuit works properly to generate the multilevel output current waveform with low harmonics currents, small inductors and with less conduction losses which proves feasibility of the proposed multilevel CSI. Normal 0 false false false EN-US X-NONE X-NONE

  11. Diffusion in membranes: Toward a two-dimensional diffusion map

    Directory of Open Access Journals (Sweden)

    Toppozini Laura

    2015-01-01

    Full Text Available For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  12. Mechanical modulation method for ultrasensitive phase measurements in photonics biosensing.

    Science.gov (United States)

    Patskovsky, S; Maisonneuve, M; Meunier, M; Kabashin, A V

    2008-12-22

    A novel polarimetry methodology for phase-sensitive measurements in single reflection geometry is proposed for applications in optical transduction-based biological sensing. The methodology uses altering step-like chopper-based mechanical phase modulation for orthogonal s- and p- polarizations of light reflected from the sensing interface and the extraction of phase information at different harmonics of the modulation. We show that even under a relatively simple experimental arrangement, the methodology provides the resolution of phase measurements as low as 0.007 deg. We also examine the proposed approach using Total Internal Reflection (TIR) and Surface Plasmon Resonance (SPR) geometries. For TIR geometry, the response appears to be strongly dependent on the prism material with the best values for high refractive index Si. The detection limit for Si-based TIR is estimated as 10(-5) in terms Refractive Index Units (RIU) change. SPR geometry offers much stronger phase response due to a much sharper phase characteristics. With the detection limit of 3.2*10(-7) RIU, the proposed methodology provides one of best sensitivities for phase-sensitive SPR devices. Advantages of the proposed method include high sensitivity, simplicity of experimental setup and noise immunity as a result of a high stability modulation.

  13. Research on fault characteristics of grid-connected large scale wind farms with LVRT capability%具有低电压穿越能力的集群接入风电场故障特性仿真研究

    Institute of Scientific and Technical Information of China (English)

    齐尚敏; 李凤婷; 何世恩; 刘光途; 黄蓉

    2015-01-01

    Based on the structure of wind turbines and its grid-connection principle, an improvedlow voltage ride through control scheme with "DC chopper + reactive compensation" of PMSG is proposed. An improvedlow voltage ride through control scheme with DC chopper and series dynamic braking resistor of DFIG is adopted. The grid-connection simulation models of PMSG and DFIG which have thecapability of low voltage ride through are built in the PSCAD/EMTDC. Based on " Technical rule for connecting wind farm to power system", the low voltage ride through capability are verified with voltage sag generator (VSG) for PMSG and DFIG. Combined with the accessing scheme of Dabancheng wind farm group, a simulation example of wind farm groups which all the PMSG and DFIG have the capability of low voltage ride through is built, the characteristics of wind farm groups during fault ride-through in condition of different fault types of tie line and voltage drop at wind farm outgoing line as well as voltage drop at tie line between the groups are researched. Results indicate that the voltage drop of grid-connected large scale wind farms outgoing line have influence on voltage and frequency for the adjacent wind farm and power system, the whole wind power system can be restored to steady state operationafter the failure.Research results contribute to analyze the running characteristic of grid-connected large scale wind farms and improve the receptivity ability for wind power.%结合风电机组的结构和并网原理,对直驱风电机组提出了"卸荷电路+无功补偿"的低电压穿越改进控制方法,对双馈风电机组采用了DC-Chopper和SDBR(series dynamic braking resistor)代替Crowbar的低电压穿越改进控制方法.以 PSCAD 为平台分别构建了具备低电压穿越能力的直驱风电机组和双馈风电机组的并网仿真模型;结合风电并网技术规程,采用电压跌落器仿真验证了直驱、双馈风电机组在电网电压跌

  14. Advanced fault ride-through control of DFIG based wind turbines including grid connection via VSC-HVDC

    Energy Technology Data Exchange (ETDEWEB)

    Feltes, Christian

    2012-07-01

    With the growing renewable energy share in the power generation mix it becomes inevitable that also these new generation technologies participate on the provision of grid services to guarantee stable operation of the grid, especially when one considers the decreasing number of conventional power plants in operation as a result of the expansion of wind based generation plants. These so-called ancillary services include frequency / active power control, voltage / reactive power control and fault ride-through (FRT) with fast voltage control and are stipulated in modern grid codes. In the context of this thesis advanced control algorithms have been developed for wind turbines based on doubly-fed induction generator (DFIG) to allow safe FRT during symmetrical and unsymmetrical faults. This covers the control for conventional AC grid connection as well as for the connection through voltage source converter (VSC) based high voltage direct current transmission (HVDC). Currently, the DFIG is the most used generator technology in modem wind turbines, since it combines a relatively simple slip-ring induction machine with a frequency converter rated to only approx. 30% of the total power. This makes the DFIG a cost-effective concept, which offers a variable speed range and a high degree of flexibility in control. However, due to the direct coupling of the generator stator circuit to the grid, grid faults are a special challenge for the frequency converter, its protection circuits and control algorithms. As base for the detailed evaluation of the impact of grid faults to the DFIG, this thesis contains the analytical derivation of the DFIG short circuit currents under consideration of frequency converter control. The DFIG concept presented in this thesis makes use of a DC chopper in the frequency converter, which allows safe FRT with grid voltage support through both converter sides. The developed control contains a new algorithm for a clear separation and control of positive

  15. Control Strategy and Experiment of High Voltage Ride Through for DFIG-based Wind Turbines%双馈风电机组高电压穿越控制策略与试验

    Institute of Scientific and Technical Information of China (English)

    李少林; 王伟胜; 王瑞明; 孙勇; 陈晨

    2016-01-01

    In research of frequent tripping of wind turbines under high voltage conditions , the requirements for high voltage ride through ( HVRT) of the main grid integration guide to wind power are introduced . A comparative analysis of electromagnetic transient characteristics of doubly‐fed induction generator (DFIG) based wind turbines is carried out under dip and voltage swell conditions , and the full control of the DFIG‐based wind turbines HVRT process is demonstrated if the voltage is less than 1 .3 nominal voltage . Then , a collaborative HVRT control strategy for DFIG‐based wind turbines based on main controller and the convertor is proposed , which is implemented just by software improvement without hardware modification , and avoids the adverse effect of Crowbar or Chopper protection action on the characteristics of HVRT . A 2 MW DFIG‐based wind turbines model for HVRT research is built in MATLAB/Simulink , and the HVRT process of DFIG‐based wind turbines is simulated . The field test is carried out on a 2 MW DFIG‐based wind turbines by high voltage generator for the first time . The simulation and experimental results support the theoretical analysis and verifies the effectiveness of the proposed control strategy .%针对风电的高电压脱网问题,介绍了主要风电并网导则对高电压穿越的要求,对比分析了双馈风电机组低电压和高电压的电磁暂态特性,论证了双馈风电机组1.3倍额定电压的高电压穿越过程全程可控的可行性。提出了一种基于双馈变流器动态无功控制的高电压穿越控制策略和风电机组主控系统与变流器协同控制完成高电压穿越的实现方法,避免了 Crowbar 或 Chopper 保护动作对高电压穿越特性的不利影响。在 MATLAB/Simulink 中建立了2 MW 双馈风电机组高电压穿越仿真模型,实现了高电压穿越全过程仿真;利用高电压发生装置,在2 MW 双馈风电机组上进行了高电压穿越

  16. SOFIA's secondary mirror assembly: in-flight performance and control approach

    Science.gov (United States)

    Reinacher, Andreas; Lammen, Yannick; Roeser, Hans-Peter

    2016-08-01

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5m infrared telescope built into a Boeing 747 SP. In 2014 SOFIA reached its Full Operational Capability milestone and nowadays takes off about three times a week to observe the infrared sky from altitudes above most of the atmosphere's water vapor content. An actively controlled 352mm SiC secondary mirror is used for infrared chopping with peak-to-peak amplitudes of up to 10 arcmin and chop frequencies of up to 20Hz and also as actuator for fast pointing corrections. The Swiss-made Secondary Mirror Mechanism (SMM) is a complex, highly integrated and compact flexure based mechanism that has been performing with remarkable reliability during recent years. Above mentioned capabilities are provided by the Tilt Chopper Mechanism (TCM) which is one of the two stages of the SMM. In addition the SMM is also used to establish a collimated telescope and to adjust the telescope focus depending on the structure's temperature which ranges from about 40°C at takeoff in Palmdale, CA to about -40°C in the stratosphere. This is achieved with the Focus Center Mechanism (FCM) which is the base stage of the SMM on which the TCM is situated. Initially the TCM was affected by strong vibrations at about 300 Hz which led to unacceptable image smearing. After some adjustments to the PID-type controller it was finally decided to develop a completely new control algorithm in state space. This pole placement controller matches the closed loop system poles to those of a Bessel filter with a corner frequency of 120 Hz for optimal square wave behavior. To reduce noise present on the position and current sensors and to estimate the velocity a static gain Kalman Filter was designed and implemented. A system inherent delay is incorporated in the Kalman filter design and measures were applied to counteract the actuators' hysteresis. For better performance over the full operational temperature range and to represent an amplitude

  17. 太赫兹成像系统的分析与控制%Analysis and Control of Terahertz Imaging System

    Institute of Scientific and Technical Information of China (English)

    孟令坤; 袁杰

    2011-01-01

    太赫兹波能穿透许多物质,相对于可见光和X射线,其具有非常强的互补特征;它的光子能量极低,且没有X射线的电离性质,因此太赫兹成像技术的应用前景非常广阔.在太赫兹成像系统中,系统参数的合理选择,软件部分的合适控制,对系统的成像结果有着至关重要的作用.从调试过程中得到的图像来看,不合适的处理如斩波器、锁相放大器参数选择不当等,将会导致两行之间错位、信噪比不高,以至于图像失真,甚至无法辨认.对出现这种错位现象的原因进行了研究,在硬件参数选择和软件两个层次,对导致该现象的系统偏差进行控制、补偿和消除,最后给出成像结果.扫描成像结果表明,搭建了稳定合适的光路,选择了适当的仪器参数,在软件上控制了偏差,通过实验和测试,系统达到了较好的成像效果.%Terahertz wave can penetrate many materials and has a very strong complementary characteristic compared with visible light and X-ray, whose photon has very low energy, and does not have ionization characteristic of X-ray, so Terahertz imaging technology has a broad application prospecL The system referred in the paper consists of Terahertz radiation source FIRL100 laser, Terahertz detecting instrument golay cell detector, stepper motor controller and translation stage, lock-in amplifier SR830 and chopper and so on. In Terahertz imaging system, it plays a crucial role for the imaging results which we properly choose the parameters of system and appropriately control the software. Inappropriate handling, such as improperly choosing the parameters of chopper and lock-in amplifier, will lead to dislocation between two rows and get low signal-to-noise, so that the images produce distortion, even can not be recognized. In this paper, the reasons for dislocation phenomenon occumng is analyzed, then the control, compensation and elimination of systematic deviation which led to the

  18. 无刷直流电动机调压系统BUCK直流变换仿真%Simulation on BUCK DC Transformer of Brushless DC Motor Voltage Regulation System

    Institute of Scientific and Technical Information of China (English)

    张旭

    2016-01-01

    In order to improve the brushless DC motor voltage regulation system voltage conversion efficiency and reduce power consumption, based on BUCK transformer chopper voltage regulation technology was put forward. In this paper elaborat-ed the circuit structure and mathematical model of brushless DC motor with BUCK mode, analyzed technology of DC converter and BUCK dc transform. Take advantage of MATLAB software SIMULINK module modeling BUCK DC converter, simula-tion for BUCK DC transform under the 20kHz working frequency, got the switch tube gate trigger pulse, inductive voltage and inductance current, output voltage, switching tube and diode current simulation curve. The simulation results and theoretical analysis of waveform basically the same, the rationality was proved of BUCK DC converter model.%为了提高无刷直流电动机调压系统电压转换效率、降低功率消耗,提出基于BUCK变换的斩波调压技术。在阐述BUCK模式下无刷直流电动机电路结构、数学模型基础上,对直流变换器和BUCK直流变换技术进行分析。利用MATLAB软件SIMULINK模块对BUCK直流变换器进行建模,对20kHz工作频率下BUCK直流变换进行仿真,得到开关管门极触发脉冲、电感电压、电感电流、输出电压、开关管电流和二极管电流仿真曲线。仿真结果与理论分析波形基本一致,表明BUCK直流变换器模型的合理性。

  19. The measurement system of birefringence and Verdet constant of optical fiber

    Science.gov (United States)

    Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun

    2013-12-01

    The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.

  20. Reverberation impairs brainstem temporal representations of voiced vowel sounds: challenging periodicity-tagged segregation of competing speech in rooms

    Directory of Open Access Journals (Sweden)

    Mark eSayles

    2015-01-01

    Full Text Available The auditory system typically processes information from concurrently active sound sources (e.g., two voices speaking at once, in the presence of multiple delayed, attenuated and distorted sound-wave reflections (reverberation. Brainstem circuits help segregate these complex acoustic mixtures into auditory objects. Psychophysical studies demonstrate a strong interaction between reverberation and fundamental-frequency (F0 modulation, leading to impaired segregation of competing vowels when segregation is on the basis of F0 differences. Neurophysiological studies of complex-sound segregation have concentrated on sounds with steady F0s, in anechoic environments. However, F0 modulation and reverberation are quasi-ubiquitous.We examine the ability of 129 single units in the ventral cochlear nucleus of the anesthetized guinea pig to segregate the concurrent synthetic vowel sounds /a/ and /i/, based on temporal discharge patterns under closed-field conditions. We address the effects of added real-room reverberation, F0 modulation, and the interaction of these two factors, on brainstem neural segregation of voiced speech sounds. A firing-rate representation of single-vowels’ spectral envelopes is robust to the combination of F0 modulation and reverberation: local firing-rate maxima and minima across the tonotopic array code vowel-formant structure. However, single-vowel F0-related periodicity information in shuffled inter-spike interval distributions is significantly degraded in the combined presence of reverberation and F0 modulation. Hence, segregation of double-vowels’ spectral energy into two streams (corresponding to the two vowels, on the basis of temporal discharge patterns, is impaired by reverberation; specifically when F0 is modulated. All unit types (primary-like, chopper, onset are similarly affected. These results offer neurophysiological insights to perceptual organization of complex acoustic scenes under realistically challenging

  1. 改进的DFIG与VSC-HVDC协调控制改善风电场低电压穿越能力%Improvement of low voltage ride through capability of wind farm using coordinated control of the improved DFIG and VSC-HVDC

    Institute of Scientific and Technical Information of China (English)

    边晓燕; 王本利; 陈建平; 杨立宁

    2016-01-01

    经VSC-HVDC并网风电系统在风电场侧故障时,风电机组出口母线电压过低,极易引起风力机脱网.而双馈风力发电机(DFIG)传统的Crowbar技术在故障时将转子侧变流器(RSC)短接,使发电机定子侧失去了为电网提供无功的能力,风力机的低电压穿越能力较低.提出一种改进的DFIG模型,加入了主动式DC-Chopper,与传统的Crowbar相配合,降低Crowbar动作的概率,使得DFIG转子侧变流器可以控制定子侧在故障时期继续提供无功功率.并利用此改进的DFIG与VSC-HVDC协调控制,改善风电场侧母线电压水平.通过算例仿真表明,在严重故障时采用改进式DFIG的Crowbar仍未动作.从而大大降低Crowbar动作的概率,双馈风电机组RSC故障期间可以继续投入运行并为电网提供无功支持.完成故障期间DFIG两侧变流器与VSC-HVDC风电场侧变流器(WFVSC)之间的无功协调,使风电场具有更好的低电压穿越能力(Low Voltage Ride Though,LVRT).

  2. Steel Pulsed Eddy Current Testing Method%钢板脉冲涡流检测方法

    Institute of Scientific and Technical Information of China (English)

    杨理践; 裴磊; 杨继华

    2011-01-01

    In order to effectively increase the depth of penetration of pulsed eddy current signals to detect cracks in steel plate,this paper presented the method of increasing the excitation current. It used low voltage high current power supply and power MOSFET chopper means to produce a large current pulse. It designed the pulsed eddy current probe which composed of the rectangular coils and two Hall sensors. And the amplifying and filtering circuit was made. It adopted the data acquisition card to acquire signals. It used LabVIEW platform, with peak scanning method, realized pulsed eddy current signals differential detection, to effectively identify the sub-surface cracks in thick steel plate.%为了有效增加脉冲涡流信号的渗透深度以检测较厚钢板裂纹缺陷,提出了增大激励电流的方法.用低压大电流电源和功率MOSFET斩波的方式产生大电流脉冲;设计了由矩形激励线圈和2片霍尔传感器构成的脉冲涡流检测探头并制作放大滤波电路;采用数据采集卡采集信号,以LabVIEW为平台,采用峰值扫描方法,实现脉冲涡流信号的差分检测,达到有效识别较厚钢板亚表面裂纹缺陷.

  3. Preliminary Approach to Mechanization Planting Technology of Short Cotton after Wheat in Southern Shanxi%山西南部麦后短季棉机械化播种技术初探

    Institute of Scientific and Technical Information of China (English)

    姜艳丽; 石跃进; 宋建中; 皇甫张龙; 胡晓丽

    2012-01-01

    Different wheat stubble treatments and usage of machines were designed to study seedling emergence, growth and development of direct seeding short cotton. The cultivation technique to cut poles and break stubbles using field straw chopper, to prepare soil with rotary tiller, then to sow naked seed cotton with maize seeding machine or with non-standard fuzzy seed cotton seeding machine, sowing first and watering later was applied, the results showed the technology was rapid and labour-saving, good seedling emergence, one more week effective growth period for cotton, and guaranteed beneficial stable production, high yield and good quality of cotton sowing directly after wheat.%通过对小麦收获后麦茬的不同处理和不同的播种机械使用,探讨其对麦后直播夏棉的出苗及生长发育的影响.结果表明,用秸秆还田机切秆灭茬、旋耕机整地后,用玉米播种机播种光籽棉种或用非标准棉花毛籽播种机,采用先播后浇的栽培技术,简约、省时、省工,棉花出苗好,为棉花增加了1周的有效生长时间,为麦后直播棉稳产、高产、优质提供了一定的保证.

  4. XMOS XC-2 Development Board for Mechanical Control and Data Collection

    Science.gov (United States)

    Jarnot, Robert F.; Bowden, William J.

    2011-01-01

    The scanning microwave limb sounder (SMLS) will use technological improvements in low-noise mixers to provide precise data on the Earth s atmospheric composition with high spatial resolution. This project focuses on the design and implementation of a realtime control system needed for airborne engineering tests of the SMLS. The system must coordinate the actuation of optical components using four motors with encoder readback, while collecting synchronized telemetric data from a GPS receiver and 3-axis gyrometric system. A graphical user interface for testing the control system was also designed using Python. Although the system could have been implemented with an FPGA(fieldprogrammable gate array)-based setup, a processor development kit manufactured by XMOS was chosen. The XMOS architecture allows parallel execution of multiple tasks on separate threads, making it ideal for this application. It is easily programmed using XC (a subset of C). The necessary communication interfaces were implemented in software, including Ethernet, with significant cost and time reduction compared to an FPGA-based approach. A simple approach to control the chopper, calibration mirror, and gimbal for the airborne SMLS was needed. The XMOS board allows for multiple threads and real-time data acquisition. The XC-2 development kit is an attractive choice for synchronized, real-time, event-driven applications. The XMOS is based on the transputer microprocessor architecture developed for parallel computing, which is being revamped in this new platform. The XMOS device has multiple cores capable of running parallel applications on separate threads. The threads communicate with each other via user-defined channels capable of transmitting data within the device. XMOS provides a C-based development environment using XC, which eliminates the need for custom tool kits associated with FPGA programming. The XC-2 has four cores and necessary hardware for Ethernet I/O.

  5. The influence of the pre-hospital application of non-invasive measurements of carboxyhemoglobin in the practice of emergency medical services in multiple and mass casualty incidents (MCI – A case report

    Directory of Open Access Journals (Sweden)

    Robert Gałązkowski

    2014-04-01

    Full Text Available In 2013 a fire broke out in the Nursing Home (NH in the Henryszew village 5 km away from the district hospital in Żyrardów. At the time of the incident 52 residents and 16 staff members were present in the building. Due to a large number of casualties, the occurrence was classified as a potentially mass casualty incident (MCI. Troops of the State Fire Brigade, Paramedic Rescue Squads, choppers of the Helicopter Emergency Medical Service, the Police, and the NH staff took part in the rescue operation. The priority was given to the evacuation of the NH residents carried out by the NH staff and firefighters, extinguishing the fire, as well as to primary and secondary survey triage. Due to the pre-accident health state of the victims, the latter posed a considerable difficulty. A decisive role was played by the need to conduct non-invasive measurements of carboxyhemoglobin in all the casualties, which then made it possible to adequately diagnose the patients and implement proper procedures. The rescue operation was correctly followed although it proved to be a serious logistical and technical undertaking for the participating emergency services. The residents were not found to be suffering from carbon monoxide poisoning, therefore 46 of the residents safely returned to the building. The fact that all the Paramedic Rescue Squads were equipped with medical triage sets and were able to conduct non-invasive measurements of carboxyhemoglobin made it possible to introduce effective procedures in the cases of suspected carbon monoxide poisoning and abandon costly and complicated organisational procedures when they proved to be unnecessary. Med Pr 2014;65(2:289–295

  6. Intelligently controlled superconducting magnetic energy storage for improved load frequency control

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, S.J.; Mufti, M.D.; Lone, S.A. [National Inst. of Technology, Kazratbal, Kashmir (India). Dept. of Electrical Engineering; Mushtaq, I. [ALSTOM Projects India Ltd., Maharashtra (India)

    2009-07-01

    Small load perturbations disturb the normal operation of a power system. Whenever there is a change in customer load demand, control engineers are faced with the problem of continuous electromechanical oscillations to which the tie-lines are subjected. This paper proposed a method to solve the load frequency control (LFC) problem in multi-area power systems with steam reheat constraint and governor dead band nonlinearity. The approach consisted of a nonlinear neural adaptive predictive control for active modulation of a superconducting magnetic energy storage system (SMES) equipped with an insulated gate bipolar transistor (IGBT) converter. The SMES is a fast acting device that can absorb the oscillations and help reduce the frequency and tie-power deviations. A two-layer nonlinear network with tapped delay line (TDL) inputs was used for online nonlinear identification of each control area of the power system. A one-step ahead prediction of the new area control error (NACE) was then used to generate an optimal power command for SMES. The NACE was a newly introduced variable in this paper. It consisted of area control error (ACE), a term proportional to derivative of ACE and a term proportional to SMES coil current deviation. The resulting control signal had an anticipatory character and met the control objectives. The power conditioning system (PCS) for the SMES included an IGBT-based voltage source converter (VSC) and a two-quadrant DC chopper. This paper presented simulation results for various components of the hybrid system. The S-function code in MATLAB was used to build 2 special blocks, one for the SMES unit and its PCS and the other for adaptive neural identification, prediction and control. These blocks were used together with other standard blocks in SIMULINK to demonstrate the effectiveness of the proposed scheme. 23 refs., 21 figs.

  7. Ultra-miniature wireless temperature sensor for thermal medicine applications

    Science.gov (United States)

    Khairi, Ahmad; Hung, Shih-Chang; Paramesh, Jeyanandh; Fedder, Gary; Rabin, Yoed

    2011-03-01

    This study presents a prototype design of an ultra-miniature, wireless, battery-less, and implantable temperature-sensor, with applications to thermal medicine such as cryosurgery, hyperthermia, and thermal ablation. The design aims at a sensory device smaller than 1.5 mm in diameter and 3 mm in length, to enable minimally invasive deployment through a hypodermic needle. While the new device may be used for local temperature monitoring, simultaneous data collection from an array of such sensors can be used to reconstruct the 3D temperature field in the treated area, offering a unique capability in thermal medicine. The new sensory device consists of three major subsystems: a temperature-sensing core, a wireless data-communication unit, and a wireless power reception and management unit. Power is delivered wirelessly to the implant from an external source using an inductive link. To meet size requirements while enhancing reliability and minimizing cost, the implant is fully integrated in a regular foundry CMOS technology (0.15 μm in the current study), including the implant-side inductor of the power link. A temperature-sensing core that consists of a proportional-to-absolute-temperature (PTAT) circuit has been designed and characterized. It employs a microwatt chopper stabilized op-amp and dynamic element-matched current sources to achieve high absolute accuracy. A second order sigma-delta (Σ-Δ) analog-to-digital converter (ADC) is designed to convert the temperature reading to a digital code, which is transmitted by backscatter through the same antenna used for receiving power. A high-efficiency multi-stage differential CMOS rectifier has been designed to provide a DC supply to the sensing and communication subsystems. This paper focuses on the development of the all-CMOS temperature sensing core circuitry part of the device, and briefly reviews the wireless power delivery and communication subsystems.

  8. New power-conditioning systems for superconducting magnetic energy storage

    Science.gov (United States)

    Han, Byung Moon

    1992-06-01

    This dissertation presents the development of new power-conditioning systems for superconducting magnetic energy storage (SMES), which can regulate fast and independently the active and reactive powers demanded in the ac network. Three new power-conditioning systems were developed through a systematic approach to match the requirements of the superconducting coil and the ac power network. Each of these new systems is composed of ten 100-MW modules connected in parallel to handle the large current through the superconducting coil. The first system, which was published in the IEEE Transactions on Energy Conversion, consists of line-commutated 24-pulse converter, a thyristor-switched tap-changing transformer, and a thyristor-switched capacitor bank. The second system, which was accepted for publication in the IEEE Transactions on Energy Conversion, consists of a 12-pulse GTO (gate turn-off thyristor) converter and a thyristor-switched tap-changing transformer. The third system, which was submitted to the International Journal of Energy System, consists of a dc chopper and a voltage-source PWM (pulse width modulation) converter. The operational concept of each new system is verified through mathematical analyses and computer simulations. The dynamic interaction of each new system with the ac network and the superconducting coil is analyzed using a simulation model with EMTP (electro-magnetic transients program). The analysis results prove that each new system is feasible and realizable. Each system can regulate the active and reactive powers of the utility network rapidly and independently, and each offer a significant reduction of the system rating by reducing the reactive power demand in the converter. Feasible design for each new system was introduced using a modular design approach based on the 1000 MW/5000 MWH plant, incorporating commercially available components and proven technologies.

  9. Precision electronic speed controller for an alternating-current motor

    Science.gov (United States)

    Bolie, V.W.

    A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. The motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The speed error signal is generated by a novel vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error is also computed by digital logic, with adjustable sensitivity around a 0 mid-scale value. The drift error signal, generated by long-term counting of the phase error, is used to compensate for any slow changes in the average friction drag on the motor. An auxillary drift-byte status sensor prevents any disruptive overflow or underflow of the drift-error counter. An adjustable clocked-delay unit is inserted between the controller and the source of the reference pulse train to permit phase alignment of the rotor to any desired offset angle. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of read-only memories, and a pair of digital-to-analog converters.

  10. Broadband enhanced graphene photodetector with fractal metasurface (Conference Presentation)

    Science.gov (United States)

    Wang, Di; Fang, Jieran; DeVault, Clayton T.; Chung, Ting-Fung; Chen, Yong P.; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.

    2016-09-01

    Graphene has been demonstrated to be a promising photo-detection material because of its ultra-broadband absorption, compatibility with CMOS technology, and dynamic tunability. There are multiple known photo-detection mechanisms in graphene, among which the photovoltaic effect has the fastest response time thus is the prioritized candidate for ultrafast photodetector. There have been numerous efforts to enhance the intrinsically low sensitivity in graphene photovoltaic detectors using metallic plasmonic structures, but such plasmonic enhancements are mostly narrowband and polarization dependent. In this work, we propose a gold Cayley-tree fractal metasurface design that has a multi-band resonance, to realize broadband and polarization-insensitive plasmonic enhancement in graphene photovoltaic detectors. When illuminated with visible light, the fractal metasurface exhibits multiple hotspots at the metal-graphene interface, where the electric field of the incident electromagnetic wave is enhanced and contributes to generating excess electron-hole pairs in graphene. The large metal-graphene interface length in the fractal metasurface also helps to harvest at a higher efficiency the electron-hole pairs by built-in electric field due to metal-graphene potential gradient. To demonstrate the concept, we carried out experiment using Ar-Kr CW laser, an optical chopper, and lock-in amplifier. We obtained experimentally an almost constant ten-fold enhancement of photocurrent generated on the fractal metasurface compared to that generated on the plain gold-graphene edge, at all tested wavelengths (488 nm, 514 nm, 568 nm, and 647 nm). We also observed an unchanged photoresponse with respect to incident light polarization angles, which is a result of the highly symmetric geometry of the fractal metasurface.

  11. Research and development of digital photovoltaic simulator in DC micro-network experiments%直流微网实验中数字式光伏模拟器的研究与开发

    Institute of Scientific and Technical Information of China (English)

    卢志伟; 胡仁杰; 杨文燮

    2013-01-01

      直流微网实验中,光伏电池必不可少,然而,光伏电池的铺设面积及输出等不确定因素使得光伏模拟器的研究成为必然。根据光伏模块的等效电路模型,并结合Simulink中的模块,搭建立了光伏电池仿真模型,根据模型的输出特性,采用了基于DSP28335控制的Buck斩波电路实现光伏特性的输出,给出了主电路及检测保护电路的设计,分析并研究了光伏跟踪的几种算法,最后给出了几种算法下的输出波形并绘制了光伏模拟器的输出特性曲线。%In DC micro-network experiments, the photovoltaic cells are essential, however, it is necessary to develop digital photovoltaic simulator because of the laying area and uncertain output of the photovoltaic cells. A photovoltaic cell simulation model is established based on the equivalent circuit model by combining with the block of Simulink. According to the model′s output characteristics, a Buck chopper controlled by DSP 28335 is designed to achieve the output of photovoltaic properties. The design of main circuit and detection protection circuit are given, several algorithms of photovoltaic tracking are analyzed. Finally, the photovoltaic simulator output characteristic curve and output waveform of different algorithms are also put forward.

  12. Design and Construction of the First Prototype of Liquid Scintillator Detector for Fast Beam Loss Monitor(FBLM) System%快响应束流损失监控(FBLM)系统液闪探测器初样的研制

    Institute of Scientific and Technical Information of China (English)

    韩晨霞; 陈昌; 田建民; 赵中亮; 徐美杭; 李公平; 陈元柏; 徐韬光; 赵海泉

    2011-01-01

    给出快响应束流损失监控(Fast Beam Lost Monitor,FBLM)系统的液体闪烁体探测器初样的研制.在高频四极加速器(Radio Frequency Quadrupole,RFQ)实验装置上的测试表明,液闪探测器能给出宽度为500 μs 束流宏脉冲结构,能逐个显示出宏脉冲内490 ns的束流切束脉冲.液闪输出信号脉冲较490 ns束流切束脉冲延迟约70 ns.液闪型FBLM输出的信号幅度大于塑闪型.液闪探测器初样的成功研制,为其性能进一步改进提高,打下了良好的基础.%Design and constmction of the first prototype of liquid scintillator detector for fast beam loss monitor ( FBLM ) system are given. A beam chopping device can remove a 490 ns section of beam at approximately 1 MHz repetition rate within a 500 μs macro beam pulse - width. The liquid scintillator displays the measured beam - pulse structure after the beam chopper. Through RFQ special beam structure, the response time of FBLM is measured. The response time of FBLM is about nano second. The signal amplitude from liquid scintillator is larger than plastic scintillator. All of these give us good experiences for the futher improvement of liquid seintillator detector design and construction. According to the measurement data. liquid seintillator is suggested as the detector of FBLM system.

  13. Elemental distribution and sample integrity comparison of freeze-dried and frozen-hydrated biological tissue samples with nuclear microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Vavpetič, P., E-mail: primoz.vavpetic@ijs.si [Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Vogel-Mikuš, K. [Biotechnical Faculty, Department of Biology, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana (Slovenia); Jeromel, L. [Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Ogrinc Potočnik, N. [Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); FOM-Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands); Pongrac, P. [Biotechnical Faculty, Department of Biology, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana (Slovenia); Department of Plant Physiology, University of Bayreuth, Universitätstr. 30, 95447 Bayreuth (Germany); Drobne, D.; Pipan Tkalec, Ž.; Novak, S.; Kos, M.; Koren, Š.; Regvar, M. [Biotechnical Faculty, Department of Biology, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana (Slovenia); Pelicon, P. [Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2015-04-01

    The analysis of biological samples in frozen-hydrated state with micro-PIXE technique at Jožef Stefan Institute (JSI) nuclear microprobe has matured to a point that enables us to measure and examine frozen tissue samples routinely as a standard research method. Cryotome-cut slice of frozen-hydrated biological sample is mounted between two thin foils and positioned on the sample holder. The temperature of the cold stage in the measuring chamber is kept below 130 K throughout the insertion of the samples and the proton beam exposure. Matrix composition of frozen-hydrated tissue is consisted mostly of ice. Sample deterioration during proton beam exposure is monitored during the experiment, as both Elastic Backscattering Spectrometry (EBS) and Scanning Transmission Ion Microscopy (STIM) in on–off axis geometry are recorded together with the events in two PIXE detectors and backscattered ions from the chopper in a single list-mode file. The aim of this experiment was to determine differences and similarities between two kinds of biological sample preparation techniques for micro-PIXE analysis, namely freeze-drying and frozen-hydrated sample preparation in order to evaluate the improvements in the elemental localisation of the latter technique if any. In the presented work, a standard micro-PIXE configuration for tissue mapping at JSI was used with five detection systems operating in parallel, with proton beam cross section of 1.0 × 1.0 μm{sup 2} and a beam current of 100 pA. The comparison of the resulting elemental distributions measured at the biological tissue prepared in the frozen-hydrated and in the freeze-dried state revealed differences in elemental distribution of particular elements at the cellular level due to the morphology alteration in particular tissue compartments induced either by water removal in the lyophilisation process or by unsatisfactory preparation of samples for cutting and mounting during the shock-freezing phase of sample preparation.

  14. Acute toxicity of commonly used forestry herbicide mixtures to Ceriodaphnia dubia and Pimephales promelas.

    Science.gov (United States)

    Tatum, Vickie L; Borton, Dennis L; Streblow, William R; Louch, Jeffrey; Shepard, James P

    2012-12-01

    Because many herbicides selectively control specific species or types of vegetation, they are often applied as mixtures to achieve better control over undesirable vegetation. When herbicides are applied in forest ecosystems, streams, ponds, and other bodies of water are typically protected by buffer zones in which no herbicide is applied. However, in some landscapes, small wetlands and streams are difficult to see and avoid, thus the potential acute toxicity of herbicide mixtures to aquatic organisms is of interest, yet it has not been well-studied. We examined the acute toxicity of 23 different herbicide mixtures to Ceriodaphnia dubia and fathead minnows (Pimephales promelas) at environmentally relevant concentrations, and, where possible, characterized mixture interactions using Marking's Additive Index. Maximum exposure concentrations were equivalent to applying the maximum allowable rate for each component directly to the surface of a 6-in. deep pond with no dissipation following application. Under the conditions of this study, herbicide formulations containing Accord Concentrate (glyphosate), Arsenal AC (imazapyr), Chopper (imazapyr), Escort (metsulfuron methyl), Oust XP (sulfometuron methyl), and Velpar L (hexazinone) were not associated with appreciable acute toxicity to fathead minnows or C. dubia when used alone or in mixtures with each other and various surfactants and adjuvants. Herbicide mixtures for which Additive Indexes could be calculated exhibited primarily antagonistic or simple additive toxicity. In the few cases where synergistic toxicity was observed, the degree of synergism was slight, never exceeding approximately twice the effect estimated based on additive toxicity. Based on the results of this study, neither acute toxicity nor enhanced acute aquatic toxicity due to synergistic mixture effects appears to be a significant concern for applications of the herbicide mixtures most commonly used in forestry.

  15. A new experimental setup for the study of carbon particles as model of cosmic dust

    Science.gov (United States)

    Marino, E.; Beyssac, O.; Reynaud, C.; Guillois, O.; Herlin, N.; Porterat, D.; Rouzaud, J. N.

    2003-04-01

    Carbon nanoparticles are considered as good candidates to explain part of the Unidentified Infrared Bands (UIBs) recorded from cosmic dust (Reynaud et al. 2001). The size of these nanoparticles is supposed to determine part of their physical properties, but we have little knowledge about the relationships between this size and both structural and optical properties. A new experimental setup (SONATE), dedicated to the synthesis of nanoparticles and based on laser pyrolysis in the gas phase, is presented. Infrared laser pyrolysis is used to synthesize nanoparticles, the size and structure of which being controlled by adjusting the flow and the laser power to act mainly on residence time and flame temperature respectively. The aim of this experiment is (1) to analyze the size distribution within the flow, and (2) to extract nanoparticles to study their own physical properties as a function of their size. In this setup, the pyrolysis reactor is coupled to a molecular beam and allows to extract part of the gas flow rich in nanoparticles towards a differential pumping setup. The velocity of the nanoparticles in the so-formed supersonic expansion is size dependant (Ehbrecht and Huisken 1999) and is used as a parameter to analyze the particles size distribution using a time-of-flight spectrometer. Moreover, it is planned to place a chopper system within the beam to select and extract the nanoparticles for further characterization. Scientific background, theoretical and practical aspects of this new setup will be presented. Reynaud C. et al. (2001) Spectrochimica Acta, A, 57, 797-814. Ehbrecht M. and Huisken F. (1999) Physical Review B, 59, 2975-2985.

  16. Mirror Illumination and Spillover Measurements of the Atacama Cosmology Telescope

    Science.gov (United States)

    Gallardo, Patricio; Dunner, Rolando; Wollack, Ed; Jerez-Hanckes, Carlos

    2012-01-01

    The Atacama Cosmology Telescope (ACT) is a 6 m telescope designed to map the Cosmic Microwave Background (CMB) simultaneously at 145 GHz, 220GHz and 280GHz, The receiver in ACT, the Millimeter Bolometer Array Camera, features 1000 TES bolometers in each band, The detector performance depends critically on the total optical loading, requiring the spmover contributions from the optics to be minimal. This inspired the use of a cold Lyot stop to limit the illumination of the primary and the use of guard rings surrounding the primary and secondary reflectors. Here, we present a direct measurement of the illumination aperture for both reflectors and of the attenuation level outside the main optical path. We used a 145 GHz, 1 m W source and a chopper wheel to produce a time-varying signal with a broad heam proflle, We sampled the response of the camera for different locations of the source, placed in front and beside the primary and secondary mirrors. The aperture of the primary was measured to be 5,72 plus or minus 0,17m in diameter (95 plus or minus 3% of its geometrical size), while the aperture of the secondary yielded 2 plus or minus 0.12m in diameter. Both apertures are consistent with the optical design. Comparing to previous measurements of the beam solid angle from planet observations, we estimate an optical efficiency of 72.3 plus or minus 4,8%. We found that the attenuation outside the primary aperture was -16 plus or minus 2dB, which is below the theoretical expectations, and -22 plus or minus 1 dB outside the secondary aperture, which is consistent with simulations. These results motivated the extension of the baffles surrounding the secondary mirror, with the following reduction in detector optical loading from 2,24 pW to 188pW.

  17. Effects of Cutting Time, Ensiling Duration and Microbial Additives on Chemical Composition of Alfalfa Silage

    Directory of Open Access Journals (Sweden)

    M.H. Delavar

    2012-09-01

    Full Text Available This experiment was conducted to assess the effects of daytime cutting management (p.m. vs. a.m. cut, ensiling duration and adding microbial inoculants on chemical composition of alfalfa silage. For this, Second growth Alfalfa harvested at the early bud stage of development after a sunny day at sundown (about 1900 h; PM alfalfa, whereas the second half was cut next day at sunup (about 0800 h; AM alfalfa. After cutting, alfalfa Forage was chopped by using a chopper to a length of 8 to10 cm, and then ensiled without or with microbial additive as factorial experiment (2×2 with repeated measurement design. Silages were provided in laboratory silos (6 repeats in every treatment lined with two layers of plastic, after air exclusion. Silos were opened at 3, 10 and 30 day for determination of pH and other chemical analysis. The numerically lower pH of PM vs. AM silages indicates that the former forage was more extensively fermented possibly because of its increased total non structural carbohydrate (TNC concentration. Shifting alfalfa harvesting from sun up to sundown significantly decreased NDF% and ADF%, because of the dilution effect associated with increased concentrations of TNC in the former forage. The NPN content and N-NH3 concentration of the silages treated in the afternoon was lower compared with AM group. CP content decreased, but NDF, ADF, NPN and N-NH3 concentration increased during ensiling time. Silage pH decreased by using of microbial additive and ensiling time. Dry matter and nitrogen losses were lower in silages treated by microbial inoculants, and, increased with increasing fermentation time. It can be concluded that microbial additives and time of cutting can be used as proper way to improve fermentation situation and silage quality.

  18. Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer

    Directory of Open Access Journals (Sweden)

    Granroth G.E.

    2015-01-01

    Full Text Available Monte Carlo ray tracing simulations, of direct geometry spectrometers, have been particularly useful in instrument design and characterization. However, these tools can also be useful for experiment planning and analysis. To this end, the McStas Monte Carlo ray tracing model of SEQUOIA, the fine resolution fermi chopper spectrometer at the Spallation Neutron Source (SNS of Oak Ridge National Laboratory (ORNL, has been modified to include the time of flight resolution sample and detector components. With these components, the resolution ellipsoid can be calculated for any detector pixel and energy bin of the instrument. The simulation is split in two pieces. First, the incident beamline up to the sample is simulated for 1 × 1011 neutron packets (4 days on 30 cores. This provides a virtual source for the backend that includes the resolution sample and monitor components. Next, a series of detector and energy pixels are computed in parallel. It takes on the order of 30 s to calculate a single resolution ellipsoid on a single core. Python scripts have been written to transform the ellipsoid into the space of an oriented single crystal, and to characterize the ellipsoid in various ways. Though this tool is under development as a planning tool, we have successfully used it to provide the resolution function for convolution with theoretical models. Specifically, theoretical calculations of the spin waves in YFeO3 were compared to measurements taken on SEQUOIA. Though the overall features of the spectra can be explained while neglecting resolution effects, the variation in intensity of the modes is well described once the resolution is included. As this was a single sharp mode, the simulated half intensity value of the resolution ellipsoid was used to provide the resolution width. A description of the simulation, its use, and paths forward for this technique will be discussed.

  19. Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer

    Science.gov (United States)

    Granroth, G. E.; Hahn, S. E.

    2015-01-01

    Monte Carlo ray tracing simulations, of direct geometry spectrometers, have been particularly useful in instrument design and characterization. However, these tools can also be useful for experiment planning and analysis. To this end, the McStas Monte Carlo ray tracing model of SEQUOIA, the fine resolution fermi chopper spectrometer at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory (ORNL), has been modified to include the time of flight resolution sample and detector components. With these components, the resolution ellipsoid can be calculated for any detector pixel and energy bin of the instrument. The simulation is split in two pieces. First, the incident beamline up to the sample is simulated for 1 × 1011 neutron packets (4 days on 30 cores). This provides a virtual source for the backend that includes the resolution sample and monitor components. Next, a series of detector and energy pixels are computed in parallel. It takes on the order of 30 s to calculate a single resolution ellipsoid on a single core. Python scripts have been written to transform the ellipsoid into the space of an oriented single crystal, and to characterize the ellipsoid in various ways. Though this tool is under development as a planning tool, we have successfully used it to provide the resolution function for convolution with theoretical models. Specifically, theoretical calculations of the spin waves in YFeO3 were compared to measurements taken on SEQUOIA. Though the overall features of the spectra can be explained while neglecting resolution effects, the variation in intensity of the modes is well described once the resolution is included. As this was a single sharp mode, the simulated half intensity value of the resolution ellipsoid was used to provide the resolution width. A description of the simulation, its use, and paths forward for this technique will be discussed.

  20. Precision and Resolution on Tore-Supra Ece Electron Temperature Profile Measurements

    Science.gov (United States)

    Ségui, J. L.; Molina, D.; Goniche, M.

    2003-02-01

    A 16-channel heterodyne radiometer, 2 GHz spaced, is used on Tore-Supra to measure the electron cyclotron emission in the frequency range 78-110 GHz for the O mode and 94 -126 GHz for the Xmode. In the equatorial plane, a dual polarisation gaussian optics lens antenna, with a perpendicular line of sight (with respect to the magnetic field), gives ECE measurements with very low refraction and Doppler effects. A separate O/X mode RF front-end allows the use of an IF electronic mode selector. This improves time stability calibration and gives the potentiality of simultaneous O/X mode measurements in the 94 -110 Ghz RF band for polarisation studies. RF and IF filters reject the gyrotron frequency (118 Ghz) in order to perform temperature measurements during ECRH plasmas. A precise absolute spectral calibration is performed outside the vacuum vessel by using a 600°C black body, a digital signal averaging on the waveform generated by a mechanical chopper placed directly in front of it, and a simulation window without Fabry-Pérot effects. The calibration precision leads to ECE temperature profiles which are very consistent with Thomson scattering measurements and guarantees a good stability of the ECE profiles for small changes on the magnetic field (absolute precision +/-6%, relative precision between channels +/-3%). Post-pulse data processing takes routinely into account the total magnetic field (Bvacuum with ripple, Bpara, Bdia, Bpol, all with analytical formulations), the radial relativistic shift (analytical formulation is used), the refractionREFID="9789812705082_0032FN001"> (cut-offs detection with safety margin to avoid strong refraction), the nonthermal ECE spectraREFID="9789812705082_0032FN001"> during LHCD (using an electron density threshold criterion). These previous analytical formulations are compatible with real time processing. Relativistic radial broadening simulations show that it is useful to fulfil 32 channels (1GHz spaced).

  1. The pulsed beam facility at the 3 MV Van de Graaff accelerator in Florence: Overview and examples of applications

    Science.gov (United States)

    Taccetti, N.; Giuntini, L.; Casini, G.; Stefanini, A. A.; Chiari, M.; Fedi, M. E.; Mandò, P. A.

    2002-04-01

    An electrostatic chopper has been installed at the KN 3000 accelerator in Florence to obtain short beam pulses with a number of particles per pulse whose average value can be chosen by varying the current intensity at the deflector plates input. Beam pulses can be obtained containing an average number of particles per pulse from less than one to thousands. The transmitted beam pulses can be as short as 200 ps FWHM, at a repetition rate up to about 100 kHz. Among the many applications of the facility, the direct measurement of energy loss and straggling of protons in Kapton and aluminium is reported. In this measurement, the facility has been tuned for transmission of mainly single-proton pulses; the beam energy is directly measured downstream with a good energy-resolution detector, without and with absorbers in front. In general, measurements of this kind can be directed both to study the basic processes of charged particles interactions in materials, or more practically to obtain the effective values of energy parameters useful in many IBA applications, avoiding the need to rely on simulations or theoretical estimates. Also briefly described is an application to Si-detector testing. In this case, the facility has been tuned for transmission of pulses containing many hundreds of protons of energy Ep=2.5 MeV and the detector is directly exposed to the pulses. Spectra containing equally spaced peaks at energies multiple of Ep are obtained and the response linearity of the detector plus electronics system can thus be checked.

  2. The pulsed beam facility at the 3 MV Van de Graaff accelerator in Florence: Overview and examples of applications

    Energy Technology Data Exchange (ETDEWEB)

    Taccetti, N.; Giuntini, L. E-mail: giuntini@fi.infn.it; Casini, G.; Stefanini, A.A.; Chiari, M.; Fedi, M.E.; Mando, P.A

    2002-04-01

    An electrostatic chopper has been installed at the KN 3000 accelerator in Florence to obtain short beam pulses with a number of particles per pulse whose average value can be chosen by varying the current intensity at the deflector plates input. Beam pulses can be obtained containing an average number of particles per pulse from less than one to thousands. The transmitted beam pulses can be as short as 200 ps FWHM, at a repetition rate up to about 100 kHz. Among the many applications of the facility, the direct measurement of energy loss and straggling of protons in Kapton and aluminium is reported. In this measurement, the facility has been tuned for transmission of mainly single-proton pulses; the beam energy is directly measured downstream with a good energy-resolution detector, without and with absorbers in front. In general, measurements of this kind can be directed both to study the basic processes of charged particles interactions in materials, or more practically to obtain the effective values of energy parameters useful in many IBA applications, avoiding the need to rely on simulations or theoretical estimates. Also briefly described is an application to Si-detector testing. In this case, the facility has been tuned for transmission of pulses containing many hundreds of protons of energy E{sub p}=2.5 MeV and the detector is directly exposed to the pulses. Spectra containing equally spaced peaks at energies multiple of E{sub p} are obtained and the response linearity of the detector plus electronics system can thus be checked.

  3. The Technical Approach for Lifting the Stability and Reliability of HSPECM Power%提升HSPECM电源稳定性及可靠性的技术途径

    Institute of Scientific and Technical Information of China (English)

    袁炎成; 王建业; 余艳青; 怀华培; 戴立强

    2013-01-01

    High frequency short pulse electro-chemical machining (HSPECM) is a new process technology which can enhance ECM accuracy significantly, and the stability and reliability of HSPECM power supply are key factors affecting whether the equipment could be manufactured applied in batch production or not. The chopper unit is applied to such power supply, which is consisted of new generation of MOSFET modules in parallel. In process of development of HSPECM power supply , we have carried out a series of experiment studies, and have found out the critical factors which affect reliability and stability of the power supply, and the technical approach to solve such problems. This paper introduced technical measure and scheme from three aspects: topological and routing design, component selection and circuit configuration in order to improve reliability and stability of the power supply.%高频窄脉冲电解加工(HSPECM)新技术显著提高了ECM的加工精度,而其电源的稳定性和可靠性是直接影响批量生产的关键.电源采用新一代模块式MOSFET(功率场效应管)多路并联的斩波装置,在其研制过程中进行了一系列稳定性和可靠性的试验研究,找出了影响电源稳定性和可靠性的因素和解决此关键问题的技术途径.从布局走线、器件选型及电路构成三方面,分另别论述了提高HSPECM电源稳定性和可靠性的技术措施和方案.

  4. Solar Observations at THz Frequencies on Board of a Trans-Antartic Stratospheric Balloon Flight

    Science.gov (United States)

    Kaufmann, Pierre; Abrantes, André; Bortolucci, Emilio; Caspi, Amir; Fernandes, Luis Olavo T.; Kropotov, Grigory; Kudaka, Amauri; Laurent, Glenn Thomas; Machado, Nelson; Marcon, Rogério; Marun, Adolfo; Nicolaev, Valery; Hidalgo Ramirez, Ray Fernando; Raulin, Jean-Pierre; Saint-Hilaire, Pascal; Shih, Albert; Silva, Claudemir; Timofeevsky, Alexander

    2016-05-01

    Sub-THz and 30 THz solar burst observations revealed a new spectral component, with fluxes increasing towards THz frequencies, simultaneously with the well known component peaking at microwaves, bringing challenging constraints for interpretation. The THz flare spectra can be completed with measurements made from space. A new system of two photometers was built to observe the Sun at 3 and 7 THz named SOLAR-T. An innovative optical setup allows observations of the full solar disk and detect small burst with sub-second time resolution. The photometers use two Golay cell detectors at the foci of 7.6 cm Cassegrain telescopes. The incoming radiation undergoes low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. The system has been integrated to redundant data acquisition system and Iridium short-burst data services telemetry for monitoring during the flight. SOLAR-T has been flown coupled to U.C. Berkeley solar hard X-ray and gamma-ray imaging spectro-polarimeter GRIPS experiment launched on a NASA CSBF stratospheric balloon from U.S. McMurdo base on January 19, 2016, on a trans-Antarctic flight. The mission ended on January 30. The SOLAR-T on-board computers were recovered from the payload that landed in the Argentina Mountain Range, nearly 2100 km from McMurdo. The SOLAR-T performance was successfully attained, with full space qualification instrumentation. Preliminary results provide the solar disk THz brightness temperatures and indicate a 7 THz burst enhancement time coincident to a sub-THz burst observed by SST during the 28 January GOES C9.6 class soft X-ray burst, the largest occurred during the flight.

  5. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. II. Dynamics

    Science.gov (United States)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Taub, H.; Dimeo, R. M.; Neumann, D. A.; Copley, J. R. D.

    2007-03-01

    The dynamics of monolayer films of the n-alkane tetracosane (n-C24H52) and the branched alkane squalane (C30H62) adsorbed on graphite have been studied by quasielastic and inelastic neutron scattering and molecular dynamics (MD) simulations. Both molecules have 24 carbon atoms along their carbon backbone, and squalane has an additional six methyl side groups symmetrically placed along its length. The authors' principal objective has been to determine the influence of the side groups on the dynamics of the squalane monolayer and thereby assess its potential as a nanoscale lubricant. To investigate the dynamics of these monolayers they used both the disk chopper spectrometer (DCS) and the high flux backscattering spectrometer (HFBS) at the National Institute of Standards and Technology. These instruments made it possible to study dynamical processes such as molecular diffusive motions and vibrations on very different time scales: 1-40ps (DCS) and 0.1-4ns (HFBS). The MD simulations were done on corresponding time scales and were used to interpret the neutron spectra. The authors found that the dynamics of the two monolayers are qualitatively similar on the respective time scales and that there are only small quantitative differences that can be understood in terms of the different masses and moments of inertia of the two molecules. In the course of this study, the authors developed a procedure to separate out the low-frequency vibrational modes in the spectra, thereby facilitating an analysis of the quasielastic scattering. They conclude that there are no major differences in the monolayer dynamics caused by intramolecular branching. It remains to be seen whether this similarity in monolayer dynamics also holds for the lubricating properties of these molecules in confined geometries.

  6. Hybrid electric system based on fuel cell and battery and integrating a single dc/dc converter for a tramway

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Luis M., E-mail: luis.fernandez@uca.e [Department of Electrical Engineering, EPS Algeciras, University of Cadiz, Avda. Ramon Puyol, s/n. 11202 Algeciras (Cadiz) (Spain); Garcia, Pablo, E-mail: pablo.garcia@uca.e [Department of Electrical Engineering, EPS Algeciras, University of Cadiz, Avda. Ramon Puyol, s/n. 11202 Algeciras (Cadiz) (Spain); Garcia, Carlos Andres, E-mail: carlosandres.garcia@uca.e [Department of Electrical Engineering, EPS Algeciras, University of Cadiz, Avda. Ramon Puyol, s/n. 11202 Algeciras (Cadiz) (Spain); Jurado, Francisco, E-mail: fjurado@ujaen.e [Department of Electrical Engineering, EPS Linares, University of Jaen, C/Alfonso X, No. 28. 23700 Linares (Jaen) (Spain)

    2011-05-15

    Research highlights: {yields} Hybrid electric power system for a real surface tramway. {yields} Hybrid system based on PEM fuel cell with dc/dc converter and Ni-MH battery. {yields} New control strategy for the energy management of the tramway. {yields} Hybrid system demonstrated to meet appropriate driving cycle of the tramway. -- Abstract: This paper presents a hybrid electric power system for a real surface tramway. The hybrid system consists of two electrical energy sources integrating a single dc/dc converter to provide the power demanded by the tramway loads (four electric traction motors and auxiliary services): (1) a Polymer Electrolyte Membrane (PEM) fuel cell (FC) as the primary and (2) a rechargeable Ni-MH battery as electrical energy storage to supplement the FC over the driving cycle. According to the requirements of the real driving cycle of the tramway, it was considered a 200 kW PEM FC system with two FCs connected in parallel and a 34 Ah Ni-MH battery. The PEM FC and Ni-MH battery models were designed from commercially available components. The power conditioning system provides the appropriate power for the tramway. It is composed of: (1) a unique dc/dc boot converter which adapts the FC output voltage to the 750 V traction standard dc bus; (2) three phase inverters to drive properly each electric motors; and (3) a braking chopper to dissipate excess of regenerative braking energy. Suitable state machine control architecture is presented for the hybrid system, its objective being to provide demanded power by the driving cycle, optimizing the energy generated. Following this objective, a new state machine control strategy based on eight states decides the operating point of each component of the system and a cascade control structure allows achieving the operating points determined by the strategy. Simulation results of the real driving cycle of the tramway check the adequacy of the hybrid electric power system.

  7. Elemental distribution and sample integrity comparison of freeze-dried and frozen-hydrated biological tissue samples with nuclear microprobe

    Science.gov (United States)

    Vavpetič, P.; Vogel-Mikuš, K.; Jeromel, L.; Ogrinc Potočnik, N.; Pongrac, P.; Drobne, D.; Pipan Tkalec, Ž.; Novak, S.; Kos, M.; Koren, Š.; Regvar, M.; Pelicon, P.

    2015-04-01

    The analysis of biological samples in frozen-hydrated state with micro-PIXE technique at Jožef Stefan Institute (JSI) nuclear microprobe has matured to a point that enables us to measure and examine frozen tissue samples routinely as a standard research method. Cryotome-cut slice of frozen-hydrated biological sample is mounted between two thin foils and positioned on the sample holder. The temperature of the cold stage in the measuring chamber is kept below 130 K throughout the insertion of the samples and the proton beam exposure. Matrix composition of frozen-hydrated tissue is consisted mostly of ice. Sample deterioration during proton beam exposure is monitored during the experiment, as both Elastic Backscattering Spectrometry (EBS) and Scanning Transmission Ion Microscopy (STIM) in on-off axis geometry are recorded together with the events in two PIXE detectors and backscattered ions from the chopper in a single list-mode file. The aim of this experiment was to determine differences and similarities between two kinds of biological sample preparation techniques for micro-PIXE analysis, namely freeze-drying and frozen-hydrated sample preparation in order to evaluate the improvements in the elemental localisation of the latter technique if any. In the presented work, a standard micro-PIXE configuration for tissue mapping at JSI was used with five detection systems operating in parallel, with proton beam cross section of 1.0 × 1.0 μm2 and a beam current of 100 pA. The comparison of the resulting elemental distributions measured at the biological tissue prepared in the frozen-hydrated and in the freeze-dried state revealed differences in elemental distribution of particular elements at the cellular level due to the morphology alteration in particular tissue compartments induced either by water removal in the lyophilisation process or by unsatisfactory preparation of samples for cutting and mounting during the shock-freezing phase of sample preparation.

  8. Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2

    Science.gov (United States)

    Radulescu, Aurel; Szekely, Noemi Kinga; Appavou, Marie-Sousai; Pipich, Vitaliy; Kohnke, Thomas; Ossovyi, Vladimir; Staringer, Simon; Schneider, Gerald J.; Amann, Matthias; Zhang-Haagen, Bo; Brandl, Georg; Drochner, Matthias; Engels, Ralf; Hanslik, Romuald; Kemmerling, Günter

    2016-01-01

    The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to µm. The instrument is optimized for the exploration of the wide momentum transfer Q range between 1x10-4 and 0.5 Å-1 by combining classical pinhole, focusing (with lenses), and time-of-flight (with chopper) methods, while simultaneously providing high-neutron intensities with an adjustable resolution. Because of its ability to adjust the intensity and the resolution within wide limits during the experiment, combined with the possibility to equip specific sample environments and ancillary devices, the KWS-2 shows a high versatility in addressing the broad range of structural and morphological studies in the field. Equilibrium structures can be studied in static measurements, while dynamic and kinetic processes can be investigated over time scales between minutes to tens of milliseconds with time-resolved approaches. Typical systems that are investigated with the KWS-2 cover the range from complex, hierarchical systems that exhibit multiple structural levels (e.g., gels, networks, or macro-aggregates) to small and poorly-scattering systems (e.g., single polymers or proteins in solution). The recent upgrade of the detection system, which enables the detection of count rates in the MHz range, opens new opportunities to study even very small biological morphologies in buffer solution with weak scattering signals close to the buffer scattering level at high Q. In this paper, we provide a protocol to investigate samples with characteristic size levels spanning a wide length scale and exhibiting ordering in the mesoscale structure using KWS-2. We present in detail how to use the multiple working modes that are offered by the instrument and the level of performance that is achieved. PMID:28060296

  9. Quantification, morphology, and viability of equine preantral follicles obtained via the Biopsy Pick-Up method.

    Science.gov (United States)

    Haag, K T; Magalhães-Padilha, D M; Fonseca, G R; Wischral, A; Gastal, M O; King, S S; Jones, K L; Figueiredo, J R; Gastal, E L

    2013-03-01

    A Biopsy Pick-Up (BPU) method was tested to determine the feasibility of retrieving preantral follicles from mare ovaries in vivo. A total of 33 ovarian biopsy procedures were performed on 18 mares during the breeding season. Mares were 5 to 21 years old and biopsies were performed during the estrous and/or diestrous phase, as confirmed by transrectal ultrasonography. Follicles were mechanically isolated using a tissue chopper, counted, and classified as normal or abnormal and primordial or primary. Viability of isolated follicles was determined by Trypan Blue dye. A total of 256 biopsy attempts were made resulting in 185 successful tissue sample collections (72% success rate). The mean weight of ovarian tissue collected per procedure was 25.0 ± 1.6 mg. Overall, 620 preantral follicles were collected and isolated (95% primordial and 5% primary). The mean (±SEM) number of follicles isolated per biopsy procedure was 18.8 ± 1.9. Primordial and primary follicles had an average diameter of 31.3 ± 6.2 and 41.1 ± 6.6 μm, respectively. Viability rate was higher (P 0.05) according to phase of the estrous cycle. Younger mares (5 to 7 years old) had more (P 0.05) by any biopsy procedure, and there were no adverse effects on cyclicity or general reproductive health. In conclusion, the BPU method provided large numbers of normal and viable preantral follicles for the study of early follicular development in mares. The BPU method might be used in the future to obtain preantral follicles for in vitro culture to enable the use of numerous oocytes present within the equine ovary. This could allow for the preservation of genetic material or large-scale embryo production.

  10. 兆瓦级直驱永磁风电系统低电压穿越研究%LVRT of a MW-level wind turbine unit with a direct-driven permanent magnet synchronous generator

    Institute of Scientific and Technical Information of China (English)

    刘胜文; 包广清; 范少伟; 刘峻; 李正元

    2011-01-01

    通过对兆瓦级直驱式永磁同步风力发电机(PMSG)系统低电压穿越能力的研究,提出一种改进的直流母线电压控制策略.该策略通过调节直流电流和控制发电机的输出功率,抑制直流母线动态过电压.与传统控制策略相比,该策略中升压斩波变换器采用电流内环、直流母线电压外环的双闭环控制结构;网侧逆变器采用电流内环和转速外环的双闭环控制结构.仿真结果表明,该控制策略可有效提高PMSG系统的低电压穿越能力.%By studying the low voltage ride through (LVRT) capability of a MW-level variable speed wind turbine unit with a direct-driven permanent magnet synchronous generator (PMSG), an improved DC link voltage control strategy was proposed. This strategy can suppress dynamic over-voltage at DC buses by adjusting DC current and controlling the generator output. Compared with the traditional control strategy, the improved one uses the double closed-loop control structure with the current inner loop and the DC link voltage outer loop in the boost chopper converter. And its inverter has also the double closed-loop structure with the current inner loop and the rotating speed outer loop. The simulation results show that the improved control strategy can effectively improve the LVRT capability of a variable speed wind turbine unit with a PMSG.

  11. The Design and Implementation of a New Ultra - Narrow Pulse Power Supply%新型超窄脉宽脉冲电源的设计与实现

    Institute of Scientific and Technical Information of China (English)

    林伟; 张春林

    2011-01-01

    脉冲电源的脉宽及占空比对电化学加工的精度有着重要的影响.传统的脉冲电源一般采用开关斩波形式,对开关器件的开关速度要求很严格,且对开关器件的驱动也有很高的要求.对于电化学微细精加工,常用的开关器件很难达到超窄脉宽的要求.利用DDS信号电路产生基本信号,结合脉冲调理电路,设计一种新型超窄脉宽脉冲电源.实践表明:该超窄脉宽脉冲电源的脉宽最低可达10ns,占空比可调,输出信号稳定性强,被成功应用于光学码板的加工.%The Pulse width and pulse duty cycle of the pulse power have a significant impact for the precision of the electrochemical machining. The form of switching chopper is used by the traditional Pulse power generally, so the switching speed of the switching device is very important, and the drive for switching devices also have high demands for. The common switching devices are difficult to achieve ultra narrow pulse width. A new type of pulse power supply with the minimum pulse width of 10ns is designed based on DDS chip, pulse shaping circuit in this paper. The Output signal is stability,and successly used in the processing of optical codes board。

  12. Statistical distributions describing microbial quality of surfaces and foods in food service operations.

    Science.gov (United States)

    Montville, Rebecca; Schaffner, Donald W

    2004-01-01

    Data on the microbial quality of food service kitchen surfaces and ready-to-eat foods were collected over a period of 10 years in Rutgers University dining halls. Surface bacterial counts, total aerobic plate counts, and total and fecal coliform counts were determined using standard methods. Analysis was performed on foods tested more than 50 times (primarily lunch meats and deli salads) and on surfaces tested more than 500 times (36 different surfaces types, including pastry brushes, cutting boards, and countertops). Histograms and statistical distributions were determined using Microsoft Excel and Palisades Bestfit, respectively. All data could be described by lognormal distributions, once data above and below the lower and upper limits of detection were considered separately. Histograms for surfaces counts contained one peak near 1 CFU/4 cm2. Surfaces with higher levels of contamination tended to be nonmetal, with the exception of buffalo chopper bowls, which commonly had high counts. Mean counts for foods ranged from 2 to 4 log CFU/g, with shrimp salad, roast beef, and bologna having higher means. Coleslaw, macaroni salad, and potato salad (all commercially processed products, not prepared in the dining halls) had lowest overall means. Coliforms were most commonly found in sealeg salad (present in 61% of samples) and least commonly found in coleslaw (present in only 7% of samples). Coliform counts (when present) were highest on average in shrimp salad and lowest in coleslaw. Average coliform counts for most products were typically between 1 and 2 log most probable number per gram. Fecal coliforms were not typically found in any deli salads or lunch meats.

  13. A 1.83 μJ/Classification, 8-Channel, Patient-Specific Epileptic Seizure Classification SoC Using a Non-Linear Support Vector Machine.

    Science.gov (United States)

    Bin Altaf, Muhammad Awais; Yoo, Jerald

    2016-02-01

    A non-linear support vector machine (NLSVM) seizure classification SoC with 8-channel EEG data acquisition and storage for epileptic patients is presented. The proposed SoC is the first work in literature that integrates a feature extraction (FE) engine, patient specific hardware-efficient NLSVM classification engine, 96 KB SRAM for EEG data storage and low-noise, high dynamic range readout circuits. To achieve on-chip integration of the NLSVM classification engine with minimum area and energy consumption, the FE engine utilizes time division multiplexing (TDM)-BPF architecture. The implemented log-linear Gaussian basis function (LL-GBF) NLSVM classifier exploits the linearization to achieve energy consumption of 0.39 μ J/operation and reduces the area by 28.2% compared to conventional GBF implementation. The readout circuits incorporate a chopper-stabilized DC servo loop to minimize the noise level elevation and achieve noise RTI of 0.81 μ Vrms for 0.5-100 Hz bandwidth with an NEF of 4.0. The 5 × 5 mm (2) SoC is implemented in a 0.18 μm 1P6M CMOS process consuming 1.83 μ J/classification for 8-channel operation. SoC verification has been done with the Children's Hospital Boston-MIT EEG database, as well as with a specific rapid eye-blink pattern detection test, which results in an average detection rate, average false alarm rate and latency of 95.1%, 0.94% (0.27 false alarms/hour) and 2 s, respectively.

  14. Crushing pretreatment parameter optimization of soybean straw used as raw material of mulch%用于地膜原料的大豆秸秆粉碎预处理工艺参数优化

    Institute of Scientific and Technical Information of China (English)

    刘爽; 房欣; 张颖; 陈泓睿; 陈海涛

    2015-01-01

    length of 70-85 mm. By removing the chopper, the shearing effect was reduced, and the crushing was mainly realized by hammering effects of chopper holder, hammering on the soybean straw. After improvement the usual operation parameters are not applicable; thus, to optimize soybean straw crushing pretreatment parameters, the machine spindle speed, feed quantity and straw moisture content were selected as experiment factors, and a quadratic orthogonal rotatable central composite design experiment with three factors and five levels was conducted. The results showed that: 1) For the straw crushing length of improved rubbing and cutting machine, from high to low ranking of contribution rate, the factors are the spindle speed, moisture content and feed rate. The spindle speed and moisture content show significant interaction effect on soybean straw crushing length. There are two reasons for the interaction effect. Firstly, the increase of soybean straw moisture content causes the increase of straw plasticity, which weakens the shearing effect caused by increasing spindle speed. Secondly, with the increase of straw moisture content, lubrication film forms between straw and chopper holder, which also weakens the shearing effect caused by increasing spindle speed. 2) The optimized pretreatment parameters are as follows: the feeding quantity is 168 kg/h, moisture content of soybean straw is in range of 36%-58%, and the machine spindle speed is in range of 1 100- 1 300 r/min. Under the optimized parameters, the processed length of soybean straw is in range of 70-85 mm, which meets length requirement of the plant fiber preparing machine for raw materials. To verify the optimization results, 10 random groups of soybean straw were crushed under the optimal combination of parameters, the verification experiment results showed that there was no significant difference between predicted values and observed values.

  15. When epilepsy may have changed history: Antônio Moreira César as the commander of the third expedition in the war of Canudos Quando a epilepsia pode ter mudado a história: Antônio Moreira César no comando da terceira expedição na Guerra de Canudos

    Directory of Open Access Journals (Sweden)

    Elza Márcia Targas Yacubian

    2003-06-01

    Full Text Available Colonel Antônio Moreira César, the Commander of the third Expedition against Canudos (1896-1897, nicknamed "head-chopper", was considered an implacable military man, a synonym of ferocity and extreme brutality against his adversaries. Therefore, he was nominated the Commander of an expedition considered almost invincible. Since his 30's he presented epileptic seizures, which increased in frequency and severity on his way to Canudos. After several well-documented episodes and probably considering himself the winner in anticipation, he ordered a premature and almost ingenuous attack against Canudos. His misjudging is attributed to the effect of successive seizures. He was shot and killed on the very first day of that battle and his expedition had a horrible and unexpected end. Based on the descriptions of his biographer we discuss the nature of his disease probably characterized by focal seizures with elementary and complex visual hallucinations followed by language deficits and episodes of complex partial seizures and secondary generalization and its role in this episode of Brazilian history.O coronel Antônio Moreira César, comandante da terceira expedição contra Canudos (1896-1897, conhecido como "corta-cabeças", foi considerado um militar implacável e seu nome um sinônimo de ferocidade e brutalidade extrema contra seus adversários. Por estes motivos, foi nomeado comandante de uma expedição considerada quase invencível. Desde aproximadamente 30 anos apresentou crises epilépticas, as quais aumentaram em freqüência e gravidade a caminho de Canudos. Tendo apresentado vários episódios bem documentados e provavelmente considerando-se vencedor antecipadamente, ordenou o ataque precipitado e quase ingênuo contra Canudos. Sua falta de julgamento é atribuída ao efeito das crises epilépticas sucessivas. Ele morreu de um ferimento por tiro no primeiro dia da batalha e sua expedição teve um final horrível e inesperado. Com base na

  16. X-ray BodySearch eliminates strip search in Montana prison

    Science.gov (United States)

    de Moulpied, David S.; Rothschild, Peter J.; Smith, Gerald J.

    1998-12-01

    Work release details at prisons have been a continuing source of inspection problems for prison wardens. At the Montana State Prison in deer Lodge 400 prisoners leave the prison in the morning to work outside the walls. They return at lunch and again in the evening. Past practice has been to do a 100% pat search and selective strip searches. These procedures are an irritant to both prisoners and prison personnel involved. However, they were felt to be essential based on the quantity of contraband materials being brought into the prison by these work release inmates. BodySearch is an x-ray scanning system which uses backscatter x-ray to form an image of prisoners as they stand next to the system. Typically prisoners are scanned two at a time, with one scan being taken from the back and the second from the front. Although privacy was considered to be an issue, the prisoners have been relived not to have to go through full pat searches and periodic strip searches. The automatic equipment has also sped up the inspection process and eliminated some of the waiting lines. The problem was so bad that one warden was contemplating having all prisoners issued two sets of clothing (a several hundred thousand dollar investment), which they would change on the way in and out of the prison facility. The new system has all but eliminated any attempt by prisoners to smuggle contraband into the prison by concealing it on their person as they return from work detail. Operationally, a pencil beam is generated by a rotating chopper, which scans horizontally as it is moved vertically. Scintillator detectors mounted adjacent and parallel to the direction of the scanning beam collect the scattered radiation. The result is a photo-like image of the body surface facing the system. The use of a scanning pencil beam in a backscatter geometry with a 140 kV x-ray source eliminates any issue of radiation safety. In fact, the dose delivered by the system (under 10 micro rem for a two

  17. Moderator Demonstration Facility Design and Optimization

    Energy Technology Data Exchange (ETDEWEB)

    McClanahan, Tucker C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gallmeier, Franz X. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Iverson, Erik B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-02-01

    The Spallation Neutron Source (SNS) facility at Oak Ridge National Laboratory (ORNL) is implementing a Moderator Demonstration Facility (MDF) to demonstrate the performance characteristics of advanced moderators central to the Second Target Station (STS) for SNS. The MDF will use the "spare" front-end installation within the SNS accelerator support complex – an ion source, radio-frequency quadrupole (RFQ) accelerator, and medium-energy beam transport (MEBT) chopper - to provide a 2.5 MeV proton beam of peak current 50 mA and maximum pulse length of less than 10 s at a repetition rate of no more than 60 Hz to a suitable neutron-producing target to demonstrate those aspects of moderator performance necessary to meet the goals of the STS design e ort. The accelerator beam parameters are not open to variation beyond that described above - they are fixed by the nature of the spare front-end installation (the Integrated Test Stand Facility; ITSF). Accordingly, there are some neutronic challenges in developing prototypic moderator illumination from a very non-prototypic primary neutron source; the spallation source we are attempting to mimic has an extended neutron source volume approximately 40 cm long (in the direction of the proton beam), approximately 10 cm wide (horizontally transverse to the proton beam) and approximately 5 cm high (vertically transverse to the proton beam), and an isotropic evaporation energy spectrum with mean energy above 1 MeV. In contrast, the primary neutron source available from the 7Li(p,n) reaction (the most prolific at 2.5 MeV proton energy by more than an order of magnitude) is strongly anisotropic, with an energy spectrum that is both strongly dependent on emission angle and kinematically limited to less than 700 keV, and the interaction zone between the incident protons and any target material (neutron-producing or not) is intrinsically limited to a few tens of microns. The MDF will be unique and innovative amongst the world

  18. Development of a full-bridge three-level ZVS DC-DC converter experimental equipment based on DSP digital control%基于 DSP数字控制的零电压全桥三电平 DC-DC变换器实验装置研制

    Institute of Scientific and Technical Information of China (English)

    孙铁成; 王钰; 郭超; 鞠雪强

    2014-01-01

    A-setting-of-three-level-ZVS-DC-DC-converter-based-on-DSP-is-developed-.This-experimental-setting-provides-a-chance-for-study-and-practice-of-multi-level-and-soft-switching-technology-in-the-power-electronics-technology-.The-experimental-device-is-improved-based-on-full-bridge-DC-DC-converter-by-joining-the-three-level-and-ZVS-technology-.The-device-can-achieve-ZVS-of-MOSFET-by-using-phase-shift-and-chopper-and-DSP-controller-.The-experimental-device-is-technologically-advanced-,-safe-,-reliable-and-easy-to-operate-.-It-is-particularly-suitable-for-application-in-the-experimental-teaching-,so-that-students-can-operate-by-themselves-to-see-the-corresponding-experimental-waveforms-of-the-three-level-and-soft-switching-technology-.This-paper-focuses-on-analyzing-the-working-principle-and-the-design-of-system-of-the-converter-.%设计并开发了一种基于DSP控制的零电压全桥三电平DC-DC变换器。该实验装置是对电力电子技术中多电平和软开关技术的学习和实践,是在全桥结构DC-DC变换器的基础上进行改进,加入了三电平技术和ZVS技术。以DSP为控制器,通过采用移相斩波的控制方法,实现各只MOS管零电压开关。该实验装置具有技术先进、安全可靠、操作简便等优点,尤其适合在实验教学中应用,让学生动手实践,测量观察三电平和软开关技术的相应实验波形。重点分析了变换器的工作原理以及系统的设计方案。

  19. 风力发电机组最大功率追踪%Maximum Power Point Tracking for Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    马卫东

    2012-01-01

    根据最大功率追踪点的基本原理及常用风力发电控制系统的特点,提出了基于占空比扰动的改进三点比较法.风力发电系统实际上应用最大功率追踪技术搭配数字信号处理器(TMS320C6711)调整DC/DC斩波器转换器的占空比,使风力发电机系统运转在最大功率输出.以1.5 kW风力发电机组为验证对象,基于TMS320C6711硬件平台对电流型扰动观察法与笔者所提出的三点比较法进行试验验证.结果表明:采用改进三点比较法的风力发电系统能够有效追踪最大功率点.同时,在风速发生变化时,能快速找到最大功率点.%According to the basic principle of maximum power point tracking(MPPT) and the characteristics of common control system for wind power conversion, a three-point comparison method based on duty cycle perturbation is presented. In the practical system implementation, the MPPT methods are integrated in the digital signal processor (DSP) TMS320C6711 to adjust the duty ratios of DC/DC chopper converter to control the generator working with maximum power output. Taking a 1.5 kW wind turbine for example, the experiment results from the TMS320C6711 based platform show that the present three-point comparison method can track the maximum power point more effectively and rapidly, compared with the conventional current-type perturbation & observation (P&0)method.

  20. Differentiation of human bone marrow precursor cells into neuronal-like cells after transplantation into canine spinal cord organotypic slice cultures

    Institute of Scientific and Technical Information of China (English)

    FEI Zhi-qiang; XIONG Jian-yi; CHEN Lei; SHEN Hui-yong; Ngo Stephanie; Wang Jeffrey; WANG Da-ping

    2012-01-01

    Background Treatments to regenerate different tissue involving the transplantation of bone marrow derived mesenchymal precursor cells are anticipated.Using an alternative methods,in vitro organotypic slice culture method,would be useful to transplant cells and assessing the effects.This study was to determine the possibility of differentiating human bone marrow precursor cells into cells of the neuronal lineage by transplanting into canine spinal cord organotypic slice cultures.Methods Bone marrow aspirates were obtained from posterior superior iliac spine(PSIS)of patients that had undergone spinal fusion due to a degenerative spinal disorder.For cell imaging,mesenchymal precursor cells(MPCs)were pre-stained with PKH-26 just before transplantation to canine spinal cord slices.Canine spinal cord tissues were obtained from three adult beagle dogs.Spinal cords were cut into transverse slices of 1 mm using tissue chopper.Two slices were transferred into 6-well plate containing 3 ml DMEM with antibiotics.Prepared MPCs(1×104)were transplanted into spinal cord slices.On days 0,3,7,14,MPCs were observed for morphological changes and expression of neuronal markers through immunofluorescence and reverse transcription-polymerase chain reaction(RT-PCR).Results The morphological study showed:spherical cells in the control and experiment groups on day 0;and on day 3,cells in the control group had one or two thick,short processes and ones in the experiment group had three or four thin,long processes.On day 7,these variously-sized processes contacted each other in the experiment group,but showed typical spindle-shaped cells in the control group.Immunofluorescence showed that PKH-26(+)MPCs stained positive for NeuN(+)and GFAP(+)in experimental group only.Also RT-PCR showed weak expression of β-tubulinⅢ?and GFAP.Conclusions Human bone marrow mesenchymal precursor cells(hMPCs)have the potential to differentiate into the neuronal like cells in this canine spinal cord organotypic

  1. 电流型 PWM 变流器在串级调速中的应用%Application of the Current Mode PWM Converter to the Cascade Speed Regulation System

    Institute of Scientific and Technical Information of China (English)

    冯阳; 王奔; 王亚芳; 马明智

    2014-01-01

    Using the current mode PWM rectifier technology in the cascade speed regulation system for motor can e-liminate the need for the dc Boost chopper of the voltage - type converter cascade speed regulation system,thus,sim-plify the topology of the system,and improve the power factor of the regulation system and reduce the content of the transformer network side harmonic. But thecurrent mode PWM inverter under the dq coordinate system is a nonlinear coupling system,which is not conducive to the controller design,so This paper proposed precise linearization to line-arize and decouple the original system,constructed its pseudo linear system model,and designed a closed loop con-troller of the pseudo linear system by usingthe sliding mode variable structure control theory. At the same time,in the Matlab / Simulink software,a simulation model was established based on this control strategy. The simulation results showed that the control strategy could achieve rapidand effective regulation of the motor speed,and meanwhile could improve th epower factor of the system and reduce the harmonic content.%采用电流型 PWM 整流技术的串级调速系统,省去了电压型斩波串级调速系统中的直流 Boost 斩波环节,简化了系统的拓扑结构,同时也能够实现系统功率因数的提高和变压器网侧谐波含量的减少。考虑到电流型PWM 逆变器在 dq 坐标系下是一个非线性耦合系统,不利于控制器的设计,采用精确线性化方法对原系统进行线性化并解耦,构造其伪线性系统模型,运用滑模变结构控制理论设计该伪线性系统的闭环控制器。同时,在Matlab/ Simulink 软件下,建立了基于此控制策略的模型并进行仿真。结果表明,该控制策略可实现电动机转速的快速、有效调节,同时可提高系统的功率因数,减少谐波含量。

  2. Design of an AC Contactor Control Module Started by Closed Loop Chopping%闭环斩波起动交流接触器控制模块设计

    Institute of Scientific and Technical Information of China (English)

    汤龙飞; 许志红

    2013-01-01

    将斩波控制技术引入到交流接触器智能控制中,设计一种闭环斩波起动的交流接触器智能控制模块,使交流接触器具有闭环直流起动、闭环直流保持、抗电压跌落等功能,进一步增强其工作可靠性,满足了企业对大容量抗电压跌落交流接触器的需求:起动闭环采用线圈电流反馈,可以快速调节接触器线圈电流,便于优化控制;保持闭环可以根据接触器线圈电阻自动进行保持电压闭环与保持电流闭环的快速切换,拓展模块的适用范围;对模块工作原理进行瞬态及交流仿真,分析线圈尖峰电流的抑制方法,设计控制回路补偿网络,并结合相关实验验证设计的有效性.%In this paper,the chopper control technology was introduced into the intelligent control of the AC contactor and an AC contactor control module starting with closed loop chopping has been designed.With this control module,the AC contactor has the functions of closed-loop DC starting,closed-loop DC keeping and anti-voltage sag.The proposed control module not only satisfies enterprises for high-capacity AC contactors with the function of anti-voltage sag but also makes it more robust.Starting closed loop uses coil current as feedback and allows the module to adjust the contactor coil current quickly.The optimization of starting process can be realized easier.The keeping closed loop can use coil voltage or coil current as feedback,it depends on the coil resistance.According to the control principle,the transient analysis and the AC analysis have been made,this paper also analyzed the suppression measures of current spike and designed the compensation network.The experimental results verify the validity of the control module.

  3. PGNAA 方法学的发展与现状%Development and Status of Prompt Gamma Neutron Activation Analysis Technique Methodology

    Institute of Scientific and Technical Information of China (English)

    王兴华; 孙洪超; 姚永刚; 肖才锦; 张贵英; 金象春; 华龙; 周四春

    2014-01-01

    瞬发伽马中子活化分析(PGNAA)为非破坏性、在线测量的核分析方法。目前国际上有30多座研究堆建立了PGNAA实验室。本文介绍了三种定量瞬发伽马活化分析方法:相对法、校准曲线法、k0因子法,阐述了基本原理及其应用领域,以及针对短寿命核素高精度测量的束流斩波器技术,针对大样品测量带来的中子自吸收和伽马自屏蔽效应的内标法。此外还简介了基于CARR堆的热中子瞬发伽马活化分析装置进展情况,对国内的PGNAA问题进行了探讨。%Prompt Gamma Neutron Activation Analysis (PGNAA) is one of the nonde‐structive and On‐line measurement of nuclear analytical methods ,There are more than 30 PGNAA laboratories which are established based on the research reactor currently . The basic principle and the application field of three kinds of analytical method of PGNAA were introduced ,such as the relative comparison method、calibration method、k0‐factor method .T he short life nuclides is proposed using the beam chopper technique in order to improve the measurement accuracy . T he internal standard method w as proposed for that large sample neutron measurement that brings self absorption and gamma‐ray self shielding effect .The PGNAA system was introduced at CARR .It pro‐vides methodology reference to establish the prompt gamma activation analysis on the base of CARR for our country .

  4. Commande adaptive d'une machine asynchrone

    Science.gov (United States)

    Slama-Belkhodja, I.; de Fornel, B.

    1996-06-01

    The paper deals with an indirect self-tuning speed control for an induction motor supplied by a chopper-filter-inverter system. Input/Output models are identified with the recursive least squares algorithm and the controller adaptation is based on a pole assignement strategy. Emphasis is put on the evaluation of the parameter identification in order to avoid instabilities because of disturbances or insufficient excitations. This is especially of importance when the adaptive control is carried out in closed loop systems and without additional test signals. Simulation results show the improvement of the dynamic responses and the robustness against load variations or parameters variations (rotor resistance, inertia). Cat article décrit une stratégie de commande adaptive indirecte à Placement de Pôles (PP), appliquée à la commande en vitesse d'une machine asynchrone alimentée par un ensemble hacheur-filtre-onduleur de tension. L'algorithme des Moindres Carrés Récursifs (MCR) est utilisé pour l'identification des modèles de comportement type entrées/sorties. Un intérêt particulier est porté à la mise en oeuvre de cet algorithme et à la discussion de ses résultats, tenant compte des erreurs de modélisation et de la nature peu riche en excitations des entrées du processus. Différents régimes transitoires ont été simulés pour apprécier l'apport de cette association (MCR-PP) : démarrages et inversion des sens de rotation, à vide et en charges, applications d'échelons de couple résistant, variations paramétriques. Les résultats permettent d'illustrer, tant au niveau des performances que de la robustesse, l'apport d'une telle commande adaptive pour des entraînements électriques avec une machine asynchrone.

  5. An improved single crystal adsorption calorimeter for determining gas adsorption and reaction energies on complex model catalysts

    Science.gov (United States)

    Fischer-Wolfarth, Jan-Henrik; Hartmann, Jens; Farmer, Jason A.; Flores-Camacho, J. Manuel; Campbell, Charles T.; Schauermann, Swetlana; Freund, Hans-Joachim

    2011-02-01

    A new ultrahigh vacuum microcalorimeter for measuring heats of adsorption and adsorption-induced surface reactions on complex single crystal-based model surfaces is described. It has been specifically designed to study the interaction of gaseous molecules with well-defined model catalysts consisting of metal nanoparticles supported on single crystal surfaces or epitaxial thin oxide films grown on single crystals. The detection principle is based on the previously described measurement of the temperature rise upon adsorption of gaseous molecules by use of a pyroelectric polymer ribbon, which is brought into mechanical/thermal contact with the back side of the thin single crystal. The instrument includes (i) a preparation chamber providing the required equipment to prepare supported model catalysts involving well-defined nanoparticles on clean single crystal surfaces and to characterize them using surface analysis techniques and in situ reflectivity measurements and (ii) the adsorption/reaction chamber containing a molecular beam, a pyroelectric heat detector, and calibration tools for determining the absolute reactant fluxes and adsorption heats. The molecular beam is produced by a differentially pumped source based on a multichannel array capable of providing variable fluxes of both high and low vapor pressure gaseous molecules in the range of 0.005-1.5 × 1015 molecules cm-2 s-1 and is modulated by means of the computer-controlled chopper with the shortest pulse length of 150 ms. The calorimetric measurements of adsorption and reaction heats can be performed in a broad temperature range from 100 to 300 K. A novel vibrational isolation method for the pyroelectric detector is introduced for the reduction of acoustic noise. The detector shows a pulse-to-pulse standard deviation ≤15 nJ when heat pulses in the range of 190-3600 nJ are applied to the sample surface with a chopped laser. Particularly for CO adsorption on Pt(111), the energy input of 15 nJ (or 120 nJ cm

  6. An Ultra-Low Voltage Analog Front End for Strain Gauge Sensory System Application in 0.18µm CMOS

    Science.gov (United States)

    Edward, Alexander; Chan, Pak Kwong

    This paper presents analysis and design of a new ultra-low voltage analog front end (AFE) dedicated to strain sensor applications. The AFE, designed in 0.18µm CMOS process, features a chopper-stabilized instrumentation amplifier (IA), a balanced active MOSFET-C 2nd order low pass filter (LPF), a clock generator and a voltage booster which operate at supply voltage (Vdd) of 0.6V. The designed IA achieves 30dB of closed-loop gain, 101dB of common-mode rejection ratio (CMRR) at 50Hz, 80dB of power-supply rejection ratio (PSRR) at 50Hz, thermal noise floor of 53.4 nV/√Hz, current consumption of 14µA, and noise efficiency factor (NEF) of 9.7. The high CMRR and rail-to-rail output swing capability is attributed to a new low voltage realization of the active-bootstrapped technique using a pseudo-differential gain-boosting operational transconductance amplifier (OTA) and proposed current-driven bulk (CDB) biasing technique. An output capacitor-less low-dropout regulator (LDO), with a new fast start-up LPF technique, is used to regulate this 0.6V supply from a 0.8-1.0V energy harvesting power source. It achieves power supply rejection (PSR) of 42dB at frequency of 1MHz. A cascode compensated pseudo differential amplifier is used as the filter's building block for low power design. The filter's single-ended-to-balanced converter is implemented using a new low voltage amplifier with two-stage common-mode cancellation. The overall AFE was simulated to have 65.6dB of signal-to-noise ratio (SNR), total harmonic distortion (THD) of less than 0.9% for a 100Hz sinusoidal maximum input signal, bandwidth of 2kHz, and power consumption of 51.2µW. Spectre RF simulations were performed to validate the design using BSIM3V3 transistor models provided by GLOBALFOUNDRIES 0.18µm CMOS process.

  7. Space charge effect measurements for a multi-channel ionization chamber used for synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, Amgad

    2012-07-18

    operating the chamber in the saturation region. Time response measurement is carried out by filling the chamber with different gases pressure of argon methane mixture of (90%:10%) and pure nitrogen gas, using a lead slit chopper for pulsating the incoming synchrotron beam. The output current signal is measured with tuning the applied high voltage from recombination regime up to saturation regime. The numerical simulation is applied to understand the effect of the space charge, recombination effects and the charge dynamics behavior inside the ionization chamber.

  8. The CNAO dose delivery system for modulated scanning ion beam radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Giordanengo, S.; Marchetto, F. [Istituto Nazionale di Fisica Nucleare, Section of Torino, Torino 10125 (Italy); Garella, M. A.; Donetti, M. [Istituto Nazionale di Fisica Nucleare, Section of Torino, Torino 10125, Italy and Centro Nazionale Adroterapia Oncologica, Pavia 27100 (Italy); Bourhaleb, F.; Monaco, V.; Hosseini, M. A.; Peroni, C.; Sacchi, R.; Cirio, R. [Istituto Nazionale di Fisica Nucleare, Section of Torino, Torino 10125, Italy and Physics Department, University of Torino, Torino 10125 (Italy); Ciocca, M.; Mirandola, A. [Centro Nazionale Adroterapia Oncologica, Pavia 27100 (Italy)

    2015-01-15

    Purpose: This paper describes the system for the dose delivery currently used at the Centro Nazionale di Adroterapia Oncologica (CNAO) for ion beam modulated scanning radiotherapy. Methods: CNAO Foundation, Istituto Nazionale di Fisica Nucleare and University of Torino have designed, built, and commissioned a dose delivery system (DDS) to monitor and guide ion beams accelerated by a dedicated synchrotron and to distribute the dose with a full 3D scanning technique. Protons and carbon ions are provided for a wide range of energies in order to cover a sizable span of treatment depths. The target volume, segmented in several layers orthogonally to the beam direction, is irradiated by thousands of pencil beams which must be steered and held to the prescribed positions until the prescribed number of particles has been delivered. For the CNAO beam lines, these operations are performed by the DDS. The main components of this system are two independent beam monitoring detectors, called BOX1 and BOX2, interfaced with two control systems performing the tasks of real-time fast and slow control, and connected to the scanning magnets and the beam chopper. As a reaction to any condition leading to a potential hazard, a DDS interlock signal is sent to the patient interlock system which immediately stops the irradiation. The essential tasks and operations performed by the DDS are described following the data flow from the treatment planning system through the end of the treatment delivery. Results: The ability of the DDS to guarantee a safe and accurate treatment was validated during the commissioning phase by means of checks of the charge collection efficiency, gain uniformity of the chambers, and 2D dose distribution homogeneity and stability. A high level of reliability and robustness has been proven by three years of system activity needing rarely more than regular maintenance and working with 100% uptime. Four identical and independent DDS devices have been tested showing

  9. Stirling to Flight Initiative

    Science.gov (United States)

    Hibbard, Kenneth E.; Mason, Lee S.; Ndu, Obi; Smith, Clayton; Withrow, James P.

    2016-01-01

    NASA has a consistent need for radioisotope power systems (RPS) to enable robotic scientific missions for planetary exploration that has been present for over four decades and will continue into the foreseeable future, as documented in the most recent Planetary Science Decadal Study Report. As RPS have evolved throughout the years, there has also grown a desire for more efficient power systems, allowing NASA to serve as good stewards of the limited plutonium-238 (238Pu), while also supporting the ever-present need to minimize mass and potential impacts to the desired science measurements. In fact, the recent Nuclear Power Assessment Study (NPAS) released in April 2015 resulted in several key conclusion regarding RPS, including affirmation that RPS will be necessary well into the 2030s (at least) and that 238Pu is indeed a precious resource requiring efficient utilization and preservation. Stirling Radioisotope Generators (SRGs) combine a Stirling cycle engine powered by a radioisotope heater unit into a single generator system. Stirling engine technology has been under development at NASA Glenn Research Center (GRC) in partnership with the Department of Energy (DOE) since the 1970's. The most recent design, the 238Pu-fueled Advanced Stirling Radioisotope Generator (ASRG), was offered as part of the NASA Discovery 2010 Announcement of Opportunity (AO). The Step-2 selections for this AO included two ASRG-enabled concepts, the Titan Mare Explorer (TiME) and the Comet Hopper (CHopper), although the only non-nuclear concept, InSight, was ultimately chosen. The DOE's ASRG contract was terminated in 2013. Given that SRGs utilize significantly less 238Pu than traditional Radioisotope Thermoelectric Generators (RTGs) - approximately one quarter of the nuclear fuel, to produce similar electrical power output - they provide a technology worthy of consideration for meeting the aforementioned NASA objectives. NASA's RPS Program Office has recently investigated a new Stirling to

  10. 一种采用斩波调制的高精度带隙基准源的设计%Design of High Precision Bandgap Voltage Reference with Chopped Modulator

    Institute of Scientific and Technical Information of China (English)

    杨晓春; 于奇; 宋文青; 董铸祥; 郑志威

    2013-01-01

    为了抑制运算放大器的输入失调电压对带隙基准源的影响,提高输出电压的精度,基于斩波调制技术,设计了一种高精度带隙基准源电路.通过0.25 μm BiCMOS工艺模型仿真验证,结果表明,运算放大器的差分输入对管的失配为±2%时,该基准源的输出电压波动峰峰值为0.38 mV,与传统带隙基准源相比,相对精度提高了113倍.当电源电压在2.5~6.0V内,基准电压源的波动小于0.085 mV,温度为-40~125℃时,电路的温度系数为19ppm/℃.%A high precision bandgap voltage reference with chopped modulator is presented in this paper. The chopper modulator is used to compensate the Random error caused by the offset of the opamp and improve the accuracy of the bandgap refrence. In the 0. 25 μm BiCMOS models, Results from simulation showed that, Considering ±2% mismatch of input pairs respectively, the peak-to-peak value of the output ripple is 0. 38 mV. The relative accuracy is increased by 113 times compared with the traditional bandgap voltage reference. With supply voltage range from 2. 5 V to 6. 0 V, the variation of the output is approximately 0. 085 mV. In the temperature range from -40℃ to 125℃ ,the bandgap voltage reference had a temperature coefficient of 19 ppm/℃.

  11. Willow as fuel for district heating. Experiences from test combustion; Energipil som braendsel til fjernvarme - Erfaringsindsamling fra testfyringer

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, Joergen

    2012-10-15

    The project has been a study of the fuel characteristics of willow chips. The study was carried out on Trustrup-Lyngby Heating Plant and Assens District Heating Plant in the period 2011-12. Operating experiences were collected from the two plants. Furthermore, yield and crop data were collected from suppliers of willow chips to Assens District Heating Plant, and the analysis of particle size distribution of the willow chips is carried out. The collected data on yield and particle size distribution are compared with results from previous studies. The project has shown that willow chips generally are a suitable and attractive fuel in wood-fired heat and power plants. The plants are very aware of quality of willow chips and want chips with coarse structure. Furthermore, there is the wish that water content of willow chips are on par with the moisture content of wood chips, i.e. around 30-40%; woodchips are the vast majority of the chips used in the plants. Wood chips produced from fresh willow shoots with chopper will typically have a moisture content of 50-60 %. Such ''wet'' chips will of some plants be deselected during winter, where there is a requirement of safe and high boiler output. Other plants will simply mix the ''wet'' willow chips with other, drier types of chips and can use it almost all the year. If the willow shoots are harvested as branches, which subsequently are allowed to dry for a period before chipping, willow chips can be produced with a moisture content that is in line with what is typical in wood chips. Analysis of particle size distribution shows that willow chips harvested with a cutting machine usually can meet the requirements for quality classes ''fine'', ''medium'' and ''coarse''. An account of the harvested yields of willow among the growers who supplied willow chips to Assens Heating Plant, showed a relatively low yield of 5.1 tonnes dry

  12. 斩波调制的1.25V CMOS带隙基准电压源%1.25V Chopped CMOS Bandgap Voltage Reference Source

    Institute of Scientific and Technical Information of China (English)

    黄灿灿

    2014-01-01

    带隙基准电压源广泛应用在模拟集成电路中,为集成电路芯片系统提供稳定的直流参考电压,是电路设计中不可或缺的一个单元模块。设计了1.25V CMOS 带隙基准电压源电路,采用斩波调制技术改进了电路结构,以提高输出基准电压的精度。基于CSMC 0.5μm CMOS 工艺,使用Cadence工具对未采用斩波调制的电路和采用斩波调制的电路的输出电压分别在typical工艺角下进行仿真。仿真结果显示,采用斩波调制后,输出基准电压由1.05V变化到1.21V,误差由16%减小到了3.28%。%As one of the most important unit or module, bandgap voltage reference source is widely used in analog integrated circuits, in order to provide stable DC reference for the integrated circuits (IC) chip systems. A 1.25V CMOS bandgap voltage reference source is designed and the schematic diagram is restructured by adding chopper structure to improve the accuracy of output reference voltage. In this paper, based on CSMC’s 0.5μm CMOS process, the output voltages of the circuit without chopped structure and the chopped circuit is respectively simulated under typical process corner with Cadence tools. The simulation results show that output voltage of circuit changes from 1.06V to 1.21V by adding chopped structure;the error of output accuracy is decreased from16%to 3.28%.

  13. A compact time-of-flight SANS instrument optimised for measurements of small sample volumes at the European Spallation Source

    Science.gov (United States)

    Kynde, Søren; Hewitt Klenø, Kaspar; Nagy, Gergely; Mortensen, Kell; Lefmann, Kim; Kohlbrecher, Joachim; Arleth, Lise

    2014-11-01

    The high flux at European Spallation Source (ESS) will allow for performing experiments with relatively small beam-sizes while maintaining a high intensity of the incoming beam. The pulsed nature of the source makes the facility optimal for time-of-flight small-angle neutron scattering (ToF-SANS). We find that a relatively compact SANS instrument becomes the optimal choice in order to obtain the widest possible q-range in a single setting and the best possible exploitation of the neutrons in each pulse and hence obtaining the highest possible flux at the sample position. The instrument proposed in the present article is optimised for performing fast measurements of small scattering volumes, typically down to 2×2×2 mm3, while covering a broad q-range from about 0.005 1/Å to 0.5 1/Å in a single instrument setting. This q-range corresponds to that available at a typical good BioSAXS instrument and is relevant for a wide set of biomacromolecular samples. A central advantage of covering the whole q-range in a single setting is that each sample has to be loaded only once. This makes it convenient to use the fully automated high-throughput flow-through sample changers commonly applied at modern synchrotron BioSAXS-facilities. The central drawback of choosing a very compact instrument is that the resolution in terms of δλ / λ obtained with the short wavelength neutrons becomes worse than what is usually the standard at state-of-the-art SANS instruments. Our McStas based simulations of the instrument performance for a set of characteristic biomacromolecular samples show that the resulting smearing effects still have relatively minor effects on the obtained data and can be compensated for in the data analysis. However, in cases where a better resolution is required in combination with the large simultaneous q-range characteristic of the instrument, we show that this can be obtained by inserting a set of choppers.

  14. A compact time-of-flight SANS instrument optimised for measurements of small sample volumes at the European Spallation Source

    Energy Technology Data Exchange (ETDEWEB)

    Kynde, Søren, E-mail: kynde@nbi.ku.dk [Niels Bohr Institute, University of Copenhagen (Denmark); Hewitt Klenø, Kaspar [Niels Bohr Institute, University of Copenhagen (Denmark); Nagy, Gergely [SINQ, Paul Scherrer Institute (Switzerland); Mortensen, Kell; Lefmann, Kim [Niels Bohr Institute, University of Copenhagen (Denmark); Kohlbrecher, Joachim, E-mail: Joachim.kohlbrecher@psi.ch [SINQ, Paul Scherrer Institute (Switzerland); Arleth, Lise, E-mail: arleth@nbi.ku.dk [Niels Bohr Institute, University of Copenhagen (Denmark)

    2014-11-11

    The high flux at European Spallation Source (ESS) will allow for performing experiments with relatively small beam-sizes while maintaining a high intensity of the incoming beam. The pulsed nature of the source makes the facility optimal for time-of-flight small-angle neutron scattering (ToF-SANS). We find that a relatively compact SANS instrument becomes the optimal choice in order to obtain the widest possible q-range in a single setting and the best possible exploitation of the neutrons in each pulse and hence obtaining the highest possible flux at the sample position. The instrument proposed in the present article is optimised for performing fast measurements of small scattering volumes, typically down to 2×2×2 mm{sup 3}, while covering a broad q-range from about 0.005 1/Å to 0.5 1/Å in a single instrument setting. This q-range corresponds to that available at a typical good BioSAXS instrument and is relevant for a wide set of biomacromolecular samples. A central advantage of covering the whole q-range in a single setting is that each sample has to be loaded only once. This makes it convenient to use the fully automated high-throughput flow-through sample changers commonly applied at modern synchrotron BioSAXS-facilities. The central drawback of choosing a very compact instrument is that the resolution in terms of δλ/λ obtained with the short wavelength neutrons becomes worse than what is usually the standard at state-of-the-art SANS instruments. Our McStas based simulations of the instrument performance for a set of characteristic biomacromolecular samples show that the resulting smearing effects still have relatively minor effects on the obtained data and can be compensated for in the data analysis. However, in cases where a better resolution is required in combination with the large simultaneous q-range characteristic of the instrument, we show that this can be obtained by inserting a set of choppers.

  15. Dynamic voltage decoupling compensation control of distributed DC grid converter for permanent magnet wind generator%永磁风力发电机分布式直流并网动态电压解耦补偿控制

    Institute of Scientific and Technical Information of China (English)

    唐任远; 张洪阳; 张志锋; 朱建光

    2011-01-01

    In order to satisfy the demands of distributed DC grid with permanent magnet (synchronous)wind generator, the control strategy of distributed DC grid converter based on dynamic voltage compensation is proposed and studied with wide operation range. The control principle of excitation component was analyzed, and the basis was provided for high performances and so on. The disturbance variable was defined considering the cross coupling and voltage fluctuates based on the coordinate rotary system, and then the system was compensated. The DC chopper circuit was adopted with auxiliary support capacitance for the matching of diffirent DC voltage level. Fnially, the ariable speed constant voltage control of permanent magnet wind generator was implemented. Simulation and experimental vertify the teasibility and validity of the control stategies.%针对永磁(同步)风力发电机分布式直流并网的要求,提出并研究了一种基于机侧电压动态解耦补偿的且具有宽运行范围的分布式直流并网控制策略.分析了永磁风力发电机励磁分量控制原则,进而为电机的高性能运行提供依据.基于同步旋转坐标系把宽范围运行下系统所有的交叉耦合项和电压波动等原因造成的系统扰动统一定义为一个新的变量扰动,然后对控制系统进行补偿.采用辅助支撑电容的直流斩波电路进一步实现不同直流电压等级的匹配,最终实现永磁风力发电机的变速恒压控制.通过仿真和实验验证了控制策略的可行性和有效性.

  16. Photoproducts ejected from liquid surfaces: The importance of photochemical, diffusional, kinetic, and surface structural effects

    Energy Technology Data Exchange (ETDEWEB)

    Furlan, A. [Physikalisch-Chemisches Institut der Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Hall, G.E. [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

    1998-12-01

    Gas-phase products of liquid surface photochemistry in high vacuum were analyzed by time-of-flight/quadrupole mass spectroscopy. A thin liquid film of a long-chain alkyl iodide, C{sub 18}H{sub 37}I, dissolved in squalane (C{sub 30}H{sub 62}) was irradiated with nanosecond laser pulses at 275 nm. The photoproducts leaving the liquid after a low-fluence laser pulse (0.5 mJ/cm{sup 2}) were I, HI, and I{sub 2}. Since these species may desorb at times delayed by diffusion in the liquid phase, time-of-flight profiles were also recorded using a chopper wheel in front of the surface. This allowed a reconstruction of the time-dependent flux from the surface. The flight time distributions were compared to model calculations which take into account laser photolysis of C{sub 18}H{sub 37}I, diffusion and surface evaporation of I, HI, and I{sub 2}, and the condensed-phase kinetics of radical reactions, and allow for a component of direct photodissociation of surface layer molecules, leading to hyperthermal I atoms. Simulations based on a comprehensive kinetic scheme are in good agreement with our measurements, with no specific surface processes other than evaporation of thermalized species formed at, or diffusing to the surface. However, compared to results previously found for liquid C{sub 2}H{sub 5}I, the caging of the geminate pair is much stronger in our system, and the fraction of I atoms promptly reacting to HI is smaller. The absence of prompt hyperthermal I fragments is interpreted by a preferential orientation of the C{sub 18}H{sub 37}I molecules in the topmost liquid layer with the I atom pointing into the liquid. The sensitivity of the method is discussed with respect to surface-specific processes, as well as primary and secondary radical reactions occurring in the bulk liquid. {copyright} {ital 1998 American Institute of Physics.}

  17. 基于C8051F120单片机的混合式步进电机驱动系统设计%Design of Composite Stepping Motor Drive System Based on C8051F120 SCM

    Institute of Scientific and Technical Information of China (English)

    刘春桐; 何祯鑫; 黄先祥; 张洋; 孟献策

    2013-01-01

    高精度、低振动的步进电机控制是经纬仪精确自动调平的关键.针对一般混合式步进电机控制分立器件多、电路复杂,本文提出了使用单片机C8051F120为核心的步进电机控制方案.利用C8051F120单片机的高集成度和高运行速度,根据经纬仪自动调平系统要求,阐述基于C8051F120单片机的斩波恒流细分驱动技术,重点讨论了硬件电路实现方法,给出硬件功能框图及软件设计思想,设计的电机驱动电路能够简化硬件结构,提高调平精度和电机运行稳定性.%The stepping motor control with high precision and low vibration is the key of the precise and automatic theodolite leveling.For general hybrid steppng motor contol with many discrete circuit components and complicated,this paper puts forward the stepper motor control scheme using the chip microcomputer C8051F120 as the control core.The C8051F120 SCM with high integration and high operation speed was used,according to the automatic leveling system requirements of the theodolite,the chopper constant current subdivided driver technology was set forth based on the C8051F 120 SCM,and the implementation method of the hardware circuit was discussed,the hardware function diagramand and software design idea were given,the designed motor driver circuit can simplify the hardware structure and improve the leveling precision and motor operation stability.

  18. Direct Power Control of Direct-driven Wind Energy Conversion System Based on PLECS%基于PLECS的直驱永磁风电系统直接功率控制研究

    Institute of Scientific and Technical Information of China (English)

    包广清; 毛开富

    2012-01-01

    Based on the mechanism of wind turbine and characteristics of permanent magnet synchronous generator (PMSG), the mathematic models of direct-driven wind power generation system with PMSG were established. The relations between booster chopper modulation and load impedance variation were analyzed so as to estimate the optimal rotor speed of the wind turbine and implement the maximum power point tracking (MPPT). A virtual grid flux based direct power control (DPC) with space vector modulation for grid-connected converter was proposed. The active and reactive powers were used as the control variables instead of the currents applied in conventional voltage oriented control method. Moreover, grid voltage sensors were replaced by a virtual flux (VF) estimator. The complete model of the wind energy conversion system was established through the Matlab/Simulink PLECS Toolbox. The digital simulation results confirm that the low voltage ride through capability and control robustness, evaluating the feasibility of PLECS in modeling and simulation of wind energy conversion system.%在研究风力机特性和永磁同步发电机运行机理的基础上,建立了直驱式永磁风力发电系统数学模型,在实现最大风能捕获的同时,分析了负载变化对发电机侧电能转换单元控制参数的影响。对于网侧逆变器控制,采用基于直轴虚拟电网磁链定向的直接功率控制,避免了对电网电压的检测和电流闭环控制,有效简化了系统结构,提高了工作可靠性。通过在Matlab/Simulink环境下嵌入PLECS工具箱进行仿真研究,结果表明该系统具有较好的控制鲁棒性和低电压穿越能力,进一步验证了基于PLECS工具箱进行风电系统建模与仿真的可行性。

  19. Investigation of a field-widened Mach-Zehnder receiver to extend Fe Doppler lidar wind measurements from the thermosphere to the ground.

    Science.gov (United States)

    Smith, John A; Chu, Xinzhao

    2016-02-20

    A receiver employing a field-widened Mach-Zehnder interferometer (MZI) is investigated for extending the wind measurement range of a narrow-band Fe Doppler lidar operating at 372 nm from its existing measurement range in the mesosphere and lower thermosphere (MLT) down to near the ground. This design uses the multiple transmitted frequencies available from the base Fe Doppler lidar in combination with a novel MZI receiver to make a measurement of the Doppler shift that rejects the influence of atmospheric parameters such as the aerosol backscatter ratio, temperature, and pressure of the lidar volume and receiver parameters such as the geometric overlap, the chopper function, and any other factor affecting the proportion of the signal in both channels of the MZI equally. A ratio is constructed from the three frequencies and two channels of the interferometer that exhibits a measurement performance of 1.75 times the Cramer-Rao lower bound, which is comparable to the dual MZI (DMZ) while preserving the insensitivity to backscatter spectrum of the quad MZI (QMZ). In addition, we show how the use of multiple transmitted frequencies can yield a wind measurement wherein the accuracy is insensitive to the optical imperfection and misalignment of the MZI or any other factor that affects the contrast, though the precision is still impacted by the fringe contrast. Simply adding a second surface mirror of a particular thickness to the basic tilted MZI can allow the field of the MZI to be widened sufficiently for most resonance Doppler lidar receivers in operation today. Provided that the detection sensitivity in each channel is known, the original resonance fluorescence and Rayleigh scattering signals can be recovered by simply scaling and adding the contributions from both channels. Consequently, the wind and temperature from the MLT region and the temperature from the Rayleigh region can be derived alongside the Rayleigh Doppler wind measurement without compromising the

  20. Ultrastructure and immunocytochemical characteristics of cells in the octopus cell area of the rat cochlear nucleus: comparison with multipolar cells.

    Science.gov (United States)

    Alibardi, Lorenzo

    2003-01-01

    colliculus and cochlear nucleus. Based on this study, two types of large multipolar cells are present in the octopus cell area: 1) those that receive about 70% of axo-somatic R boutons and stain more intensely for glutamate may correspond to pure onset neurons (Oi); 2) those with less than 33% of R axosomatic boutons, with less immunoreactivity to glutamate and sometimes glycine positive may represent the onset chopper neurons (Oc). In the octopus cell area the first type appears more prevalent. The present study suggests that octopus cells are a special type of excitatory D-multipolar neuron confined to the octopus cell area and mainly innervated by glutamatergic cochlear nerve terminals.

  1. Spontaneous Raman Scattering Diagnostics: Applications in Practical Combustion Systems. Chapter 5

    Science.gov (United States)

    Kojima, Jun; Viet-Nguyen, Quang; Lackner, Maximilian (Editor); Winter, Franz (Editor); Agarwal, Avinash (Editor)

    2010-01-01

    In this chapter, the recent advancements and practical aspects of laser SRS diagnostics have been reviewed wi til regards to applications in practical combustion systems. Clearly, SRS represents a theoretically and experimentally mature diagnostic technology that has become an essential tool for multiscalar measurements in turbulent combustion at elevated pressures. Today, time-, space-, spectrally, and even polarization-resolved S RS diagnostics is at hand, with aid from recent innovations in theoretical and technological developments on electro-optical or electromechanical devices. Whilst a linear increase in SRS signals can be expected in high-pressure systems (this is perhaps one of the most important advantages for using SRS in high-pressure systems), there are practical (often severe) restrictions associated with pressurized vessels, due mainly to the limited degree of optical access. This narrows ti,e available choice of diagnostics that can be employed at any given time. Point-wise SRS diagnostics provides the highest accuracy on the chemical species and temperature measurements, and will continue to remain a vital approach for the study in such harsh environments. The practical design considerations and hands-on set-up guide for SRS diagnostics provided in this chapter are rarely presented elsewhere. Although the second-harmonic Nd:YAG pulsed laser (532 nm), combined with pulse-stretching optics or the recently introduced White Cell-based laser, seems to be the most favored excitation source of choice by the research community, UV excitation will undoubtedly continue to be used on many occasions, and especially in sooting flames. Detection methods may be divided into ICCD-based nanosecond-gate detection or a rotary-chopper electromechanical shutter-based CCD array detection, and the levels of background flame emission in individual cases would determine this critical design choice. Here, a process of Raman signal calibration based on ti,e crosstalk matrix

  2. LANDFORM,LOESS DEPOSIT AND PALEOENVIRONMENTAL CHANGES IN THE SOUTH LUOHE RIVER(CENTRAL CHINA) DURING THE HOMININ OCCUPATIONS%中国中部南洛河流域地貌、黄土堆积与更新世古人类生存环境

    Institute of Scientific and Technical Information of China (English)

    鹿化煜; 弋双文; 马萧林; Ming Wei; 张红艳; 孙雪峰; 王社江; Richard Cosgrove; Chen Shen; 张文超; 张小兵; 王先彦

    2012-01-01

    Over the past 20 years, more than 300 Paleolithic sites have been found in catchment of South Luohe River, Central China. This river is located at the environmental boundary between North and South China. To its south, climate is characterized by the subtropical monsoon; to the north,it is a warm temperate climate. Many lithic artifacts are scattered on the surface of various landforms and buried in aeolian loess deposits and cave sediments. The Paleolithic artifacts are made up of chopper-chopping ( Mode 1 ) assemblages such as cores, flakes, choppers, scrapers and points and Acheulian-like large-cutting tools (Mode 2) such as hand-axes, cleavers, trihedrals, knives. The region contains both small tools reminiscent of North China and biface technology produced on large pebbles characteristic of South China. It appears that early humans repeatedly occupied this region.In summer of 2004, our interdisciplinary team was set up and field exploration focussed on different landforms, particularly loess deposits that reflected past environmental changes, was undertaken. Eight archaeological sites were excavated, and sediment samples were taken from 14 loess-paleosol sections. Over 20000 lithic artefacts were collected and more than 10 thousand loess samples have been obtained and studied.In this paper, we discuss recent findings during 2009 -2011 on understanding landform evolution, the loess-paleosol record, paleoenvironmental reconstruction and relationship between hominines behavior and these landforms. The results show that the landforms of the South Luohe River can be divided into two parts; the upper part is characterized by mountains and intermountain basins,with gorges and narrow rivers,where the channel gradient ratio is greater and the river current is relatively swift. The lower part is characterised by a piedmont plain with a smaller stream channel gradient ratio, where the river is braided with relatively slow flowing water. There is an extensive loess cover

  3. Technical development to increase the use of reed canary grass - Full scale demonstration; Teknikutveckling foer oekad etablering och nyttjande av roerflen - Demonstrationsfoersoek i fullskala

    Energy Technology Data Exchange (ETDEWEB)

    Oerberg, Haakan; Skoglund, Nils; Grimm, Alejandro; Bostroem, Dan; Oehman, Marcus

    2010-06-15

    Introducing fuels from agricultural crops into the heat and power sector in Sweden is a desired and needed development, thus it is connected to some obstacles. For the crop producers it is important to use the most efficient handling for harvest, collection, loading and transport technology in order to reach low production costs. For the fuel consumers it is of high importance that these fuels work together with other utilized fuels in mixtures without complications. This includes fuel mixing, fuel feeding, combustion behavior and ash transformation mechanisms. Specifically for the combustion process, gaseous and particle emissions, ash behavior and deposit formation on cooled surfaces should not be negatively effected by mixing in agricultural crops. In this study these aspects of the energy crop reed canary grass (RCG) have been examined. The recommended harvest period for harvesting RCG in Sweden is during springtime when the crop from the year before is collected, called delayed harvest. During this period the grass is very dry and has been harvested in this project with an average water content of 11,3 %. Two major different harvest systems have been tested. One where the energy grass is chopped directly in the field by a chopper connected to a wagon. The other system was based on baling the crop with round balers or big square balers. The chopped or baled material is transported 6 km to a farm center or terminal for unloading. Further transport to CHP (Combined Heat and Power) plant, 12 km, was done with road truck (135 m3). In the case of field chopped RCG the mixing of the other fuels has been easily done since the material was well chopped (40-50 mm). The RCG was mixed into a mixture of peat and wood to a share of 10-12% of the total energy content of the mixture. Also the baled material was transported to a farm centre or terminal for unloading the farm wagon and loading on a road truck (135 m3). In this case an additional procedure is needed for chopping

  4. Reliability evaluation and analysis of sugarcane 7000 series harvesters in sugarcane harvesting

    Directory of Open Access Journals (Sweden)

    P Najafi

    2015-09-01

    Full Text Available Introduction: The performance of agricultural machines depends on the reliability of the equipment used, the maintenance efficiency, the operation process, the technical expertise of workers, etc. As the size and complexity of agricultural equipment continue to increase, the implications of equipment failure become even more critical. Machine failure probability is (1-R and R is machine reliability (Vafaei et al., 2010. Moreover, system reliability is the probability that an item will perform a required function without failure under stated conditions for a stated period of time (Billinton and Allan, 1992. Therefore, we must be able to create an appropriate compromise between maintenance methods and acceptable reliability levels. Precision failure data gathering in a farm is a worthwhile work, because these can represent a good estimate of machine reliability combining the effects of machine loading, surrounding effects and incorrect repair and maintenance. Each machine based on its work conditions, parts combinationand manufacturing process follows a failures distribution function depending on the environment where the machine work and the machine’s specifications (Meeker and Escobar, 1998. General failures distributions for contiguous data are normal, log-normal, exponential and Weibull (Shirmohamadi, 2002. Each machine can represent proportionate behavior with these functions in short or long time. Materials and methods: The study area was the Hakim Farabi agro-industry Company located 35 kilometers south of Ahvaz in Iran. Arable lands of this company are located in 31 to 31°10 N latitude and 45 to 48°36 E longitudes. The region has dry and warm climate. A total of 24 Austoft 7000 sugarcane chopper harvester are being used in the company. Cane harvesters were divided into 3 group consisting of old, middle aged and new. From each group, one machine was chosen. Data from maintenance reports of harvesters which have been recorded within 400

  5. Fast Pyrolysis Process Development Unit for Validating Bench Scale Data

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Robert C. [Iowa State Univ., Ames, IA (United States). Biorenewables Research Lab.. Center for Sustainable Environmental Technologies. Bioeconomy Inst.; Jones, Samuel T. [Iowa State Univ., Ames, IA (United States). Biorenewables Research Lab.. Center for Sustainable Environmental Technologies. Bioeconomy Inst.

    2010-03-31

    The purpose of this project was to prepare and operate a fast pyrolysis process development unit (PDU) that can validate experimental data generated at the bench scale. In order to do this, a biomass preparation system, a modular fast pyrolysis fluidized bed reactor, modular gas clean-up systems, and modular bio-oil recovery systems were designed and constructed. Instrumentation for centralized data collection and process control were integrated. The bio-oil analysis laboratory was upgraded with the addition of analytical equipment needed to measure C, H, O, N, S, P, K, and Cl. To provide a consistent material for processing through the fluidized bed fast pyrolysis reactor, the existing biomass preparation capabilities of the ISU facility needed to be upgraded. A stationary grinder was installed to reduce biomass from bale form to 5-10 cm lengths. A 25 kg/hr rotary kiln drier was installed. It has the ability to lower moisture content to the desired level of less than 20% wt. An existing forage chopper was upgraded with new screens. It is used to reduce biomass to the desired particle size of 2-25 mm fiber length. To complete the material handling between these pieces of equipment, a bucket elevator and two belt conveyors must be installed. The bucket elevator has been installed. The conveyors are being procured using other funding sources. Fast pyrolysis bio-oil, char and non-condensable gases were produced from an 8 kg/hr fluidized bed reactor. The bio-oil was collected in a fractionating bio-oil collection system that produced multiple fractions of bio-oil. This bio-oil was fractionated through two separate, but equally important, mechanisms within the collection system. The aerosols and vapors were selectively collected by utilizing laminar flow conditions to prevent aerosol collection and electrostatic precipitators to collect the aerosols. The vapors were successfully collected through a selective condensation process. The combination of these two mechanisms

  6. 基于PSM技术的70kV/90A高压脉冲电源的研制%Development of the 70kV/90A High-Voltage Pulse Power Supply Based on PSM Technology

    Institute of Scientific and Technical Information of China (English)

    徐伟东; 陈文光; 宣伟民; 姚列英; 王英翘

    2011-01-01

    The high microwave and neutral beam injection of the auxiliary heating systems are used to heat or drive the plasma in the controlled nuclear fusion devices. These equipment can be destroyed easily with low energy when arcing occurs. So the high-voltage power supply which supplies to the auxiliary heating systems should have many features, such as flexible control, high stability, fast response, high power factor, short protective time, very low energy discharged to these equipment when the loads are arcing. The power supply based on PSM technology is a method of controlling the total output voltage of many identical DC choppers connected in series by means of managing the work of them step by step and modulating their pulse widths in a certain sequence. This kind of power supply has some advantages which have been mentioned, especially the low energy stored in the whole system and short protective time. Such a high voltage power supply system has already been developed. Its circuit is simple and control mode is flexible. The results show that the output is about 72kV/90A and the parameters are superior to the high-voltage power supply based on thyristors.%在受控核聚变实验中,辅助加热系统采用高功率微波和高能粒子对等离子体进行加热或驱动。这些部件不仅要求为其供电的高压电源稳定度高,而且要求在它们发生打火现象时,保护时间短(〈10gs),高压电源对其释放的能量小,否则这些关键部件极易受到损坏。基于脉冲步进调制PSM技术的高压脉冲电源是许多相同的脉冲电源串联并经过特定的调制方式控制,从而实现高压大功率输出。该高压电源有控制方式灵活、输出功率高、功率因数高、稳定度高、响应速度快、保护时间短、故障时系统对负载的释能小等众多优点。尤其保护时该电源系统储能小,时间短,满足各种高功率微波管和加速器的要求。本文分析了基于

  7. Photonuclear Contributions to SNS Pulse Shapes

    Energy Technology Data Exchange (ETDEWEB)

    McClanahan, Tucker C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Iverson, Erik B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gallmeier, Franz X. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-03-01

    cross sections available and the CEM03 physics model within MCNPX 2.6.0 in the simulation, we are able to estimate the impact of photoneutron production on both overall neutron production and delayed neutron production. We find that a significant number of photon-induced neutrons are produced a few milliseconds after the proton pulse, following prompt gamma emission through the capture of neutrons in the slowing-down and thermalization processes. We name these "slowing-down delayed neutrons" to distinguish them from either "activation-delayed neutrons" or "beta-delayed neutrons." The beta-delayed and activation-delayed neutrons were not part of this study, and will be addressed elsewhere. While these other delayed neutron channels result in the time-independent (constant) production of fast neutrons outside of the prompt pulse, the slowing-down delayed neutrons also a ect the shape of the pulses. Although numerically insignificant in most cases, we describe a set of scenarios related to T0-chopper operation in which the slowing-down delayed neutrons may be important.

  8. Rational management of tobacco (Nicotiana tabacum L. crop residues to obtain organic compostManejo racional de resíduos da cultura do fumo (Nicotiana tabacum L. para obtenção de composto orgânico

    Directory of Open Access Journals (Sweden)

    Antonio Carlos Souza Borges Filho

    2011-10-01

    Full Text Available Crop residues may be used to produce organic composts for agricultural use. The aim of this study was to evaluate the effect of two inoculums on the decomposition speed of tobacco residues (stems. The experiment was carried out in a completely randomized design, with three treatments and six replications. The residue used in the study was passed through a forage chopper and mixed to the inoculums in a concrete truck mixer. The treatments evaluated were: TF + EB + RB - tobacco residue, bovine manure and bovine rumen; TF + EB + MP - tobacco residue, bovine manure and Microsept-Dust and TF + EB - tobacco residue and bovine manure. The temperature and humidity of the piles were monitored weekly. The piles were initially turned up side down every seven days, and then every fourteen days till closing 60 days. Samples for chemical analysis of the composted material were collected at 30, 60 and 90 days after the beginning of the composting process. The temperature of the piles stayed around 57 to 60 ºC in the period between the 20 to 40 days after the beginning of the composting process. The mix containing cattle rumen (RB presented the lowest temperature after forty days. At the end of the composting the mix containing Microsept-Dust (MP presented the lowest humidity. The C/N relation of the composts obtained was around 10/1 and 11/1. The three treatments presented pH values close to the neutrality in the mature stage. A period of sixty days seems to be sufficient to obtain a mature and stable biocompost of tobacco waste using manure independent of the addition of inoculums.Os resíduos vegetais podem ser utilizados na produção de adubo orgânico por meio da compostagem. O objetivo deste estudo foi avaliar o efeito de dois inoculantes sobre a velocidade de decomposição do resíduo da cultura do fumo. O experimento foi conduzido em delineamento inteiramente casualizado, com três tratamentos e seis repetições, sendo o resíduo picado em picadeira

  9. Analysis of a utility-interactive wind-photovoltaic hybrid system with battery storage using neural network

    Science.gov (United States)

    Giraud, Francois

    1999-10-01

    This dissertation investigates the application of neural network theory to the analysis of a 4-kW Utility-interactive Wind-Photovoltaic System (WPS) with battery storage. The hybrid system comprises a 2.5-kW photovoltaic generator and a 1.5-kW wind turbine. The wind power generator produces power at variable speed and variable frequency (VSVF). The wind energy is converted into dc power by a controlled, tree-phase, full-wave, bridge rectifier. The PV power is maximized by a Maximum Power Point Tracker (MPPT), a dc-to-dc chopper, switching at a frequency of 45 kHz. The whole dc power of both subsystems is stored in the battery bank or conditioned by a single-phase self-commutated inverter to be sold to the utility at a predetermined amount. First, the PV is modeled using Artificial Neural Network (ANN). To reduce model uncertainty, the open-circuit voltage VOC and the short-circuit current ISC of the PV are chosen as model input variables of the ANN. These input variables have the advantage of incorporating the effects of the quantifiable and non-quantifiable environmental variants affecting the PV power. Then, a simplified way to predict accurately the dynamic responses of the grid-linked WPS to gusty winds using a Recurrent Neural Network (RNN) is investigated. The RNN is a single-output feedforward backpropagation network with external feedback, which allows past responses to be fed back to the network input. In the third step, a Radial Basis Functions (RBF) Network is used to analyze the effects of clouds on the Utility-Interactive WPS. Using the irradiance as input signal, the network models the effects of random cloud movement on the output current, the output voltage, the output power of the PV system, as well as the electrical output variables of the grid-linked inverter. Fourthly, using RNN, the combined effects of a random cloud and a wind gusts on the system are analyzed. For short period intervals, the wind speed and the solar radiation are considered as

  10. Mortadella sausage formulations with mechanically separated layer hen meat preblended with antioxidants Mortadela elaborada com cms de galinhas poedeiras pré-misturada com antioxidantes

    Directory of Open Access Journals (Sweden)

    Marco Antonio Trindade

    2006-06-01

    Full Text Available At the end of the laying cycle, layer hens can be used for production of mechanically separated meat (MSML for sausage manufacture. However, mechanically separated meats are susceptible to lipid and pigment oxidation during storage, problems that could be prevented by the use of antioxidants present in curing additives traditionally used in meat processing. The objective of this work was to evaluate the quality and stability of Mortadella produced with MSML added of sodium erythorbate (1000 ppm and sodium nitrite (150 ppm through preblending or during chopper processing (control treatment, after long term frozen storage of raw meat ingredient. The products were stored for 40 days at 7ºC and evaluated in regard to the oxidative stability of lipids (TBARS values, objective color, and microbiological and sensory attributes. Preblending MSML lessened rancidity of the final product in comparison to the control (0.2 and 2.2 mg malonaldehyde per kg, respectively, and elicited better color (a* = 7.5 and 10.5, respectively. Total counts of psychrotrophic microorganisms were similar for both treatments (2 log CFU g-1. Previous blending of nitrite (150 ppm and erythorbate (1000 ppm in mechanically separated meat soon after the extraction is recommended when the raw material will eventually go through prolonged frozen storage before its use in Mortadella sausage processing.Uma das formas de utilização das galinhas poedeiras ao final do ciclo de postura é a obtenção de carne mecanicamente separada (MSML para a elaboração de embutidos. Entretanto, carnes mecanicamente separadas apresentam alta susceptibilidade à oxidação lipídica e dos pigmentos. O uso de antioxidantes tradicionalmente utilizados na cura de carne para incorporação prévia à matéria prima poderia evitar estes problemas. Assim, o objetivo deste trabalho foi avaliar a qualidade e a estabilidade de mortadelas elaboradas com MSML com adição de eritorbato (1000 ppm e nitrito (150

  11. Upgraded ECE radiometer on the Tore Supra Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Segui, J.L.; Molina, D.; Goniche, M.; Maget, P.; Udintsev, V.S. [Association Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Antar, G.Y. [Center for Energy Research, UCSD, La Jolla CA (United States); Kraemer-Flecken, A. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Plasmaphysik

    2004-07-01

    An upgraded 32-channel heterodyne radiometer, 1 GHz spaced, is used on the Tore-Supra tokamak to measure the electron cyclotron emission (ECE) in the frequency range 78-110 GHz for the ordinary mode (O1) and 94-126.5 GHz for the extraordinary mode (X2). From now radial resolution is essentially limited by ECE relativistic effects related to electron temperature and density, not by the channels frequency spacing. For example, this leads to precise electron temperature mapping during magneto hydrodynamic activities (MHD). In the equatorial plane, we use a dual polarisation Gaussian optics lens antenna. It has low spreading and a perpendicular line-of-sight that gives ECE measurements very low refraction and Doppler effects. Assuming that the plasma is a black body and there is no overlap between ECE harmonics, one can deduce the electron temperature profile by using the first harmonic ordinary mode (O1) or the second harmonic extraordinary mode (X2). The principle radio frequency emitter (RF) has its frequencies down shifted into intermediary frequencies (IF) that span from 2 to 18 GHz in the single side band mode (SSB). It is amplified by low noise IF amplifiers before forming channels. A separate O/X mode RF front-end allows the use of an IF electronic mode selector. This gives the potentiality of simultaneous O/X mode measurements in the 94-110 GHz. RF and IF filters reject the gyrotron frequency (118 GHz) in order to perform electron temperature measurements during electron cyclotron resonance heated plasmas. A precise absolute spectral calibration is performed outside the tokamak vacuum vessel by using a 600 deg C black body hot source, a double coherent digital signal averaging (trigger, turn and clock) on the waveform generated by a mechanical chopper, and a simulated tokamak window. The use of differential electronics and strong electromagnetic shielding improves also the calibration precision. The fast and slow data acquisition systems are free of aliasing

  12. Rostock bioenergy forum. Future technologies for bioenergy. Proceedings; 4. Rostocker Bioenergieforum. Zukunftstechnologien fuer Bioenergie. Tagungsband

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-07-01

    Within the 4th Rostock bioenergy forum 'future technologies for bioenergy' at 27th and 28th October, 2010, in Rostock (Federal Republic of Germany) the following lectures were held: (1) Sustainable supply of biomass from the agriculture (Christian Gienapp); (2) Biogas plants in conflict of different legal regulation systems (Michael Kern); (3) Logistics of biomass - Do you know the real costs? (Nadine Doden); (4) Potentials of wooden biomass from the landscape conservation using the Lower Saale valley (Sachsen-Anhalt) as an example (Karen Runge); (5) Value creation with energy wood in rural area - Results of a potential study (Marco Hahs); (6) Soil ecological evaluation of short rotational plantations on farmland (Christel Baum); (7) Development of moulds and dry weight losses in bulk wood chips (Christine Idler); (8) Logistics of pellets during the harvest of short-term rotation areas with a field chopper (Franz Handler); (9) Concepts of combustion of biomass within the scope of the BMU funding program 'Energetic utilization of biomass' (Diana Pfeiffer); (10) Thermoelectric transformer for biogenic heat (Karl-Ernst Schnorr); (11) Emissions of benzene in the combustion f gases from wood in cogeneration plants (Christian Hirschmeier); (12) Utilization of additives in the combustion of miscanthus pellets in a small-scale furnace < 100 kW{sub N}WL (Thomas Zeng); (13) Practical experiences with dust separators for small-scale furnaces (Peter Turowski); (14) Analysis for gaining the minimum goal of 10 % renewable energy in traffic sector (Karin Naumann); (15) New diesel components from glycerine (E. Paetzold); (16) Challenges and possibilities in the utilization of biofuels in customary auxiliary heatings (Hajo Hoffmann); (17) Demands on biofuels for the use in combustion engines (Volker Wichmann); (18) Alternative fuel dimethyl ether (Martin Werner); (19) Long-term investigation of the stability of rapeseed fuel and field study of modern Common Rail

  13. Pyroelectric IRFPA mosaic image acquisition system with multi channels%多通道热释电 IRFPA 图像拼接采集系统

    Institute of Scientific and Technical Information of China (English)

    程瑶

    2014-01-01

    为了实现分辨率高的大规模热释电IRFPA 探测器,设计了多路通道并行输出的读出电路。针对多路输出的热释电IRFPA探测器,依据热释电探测的时序要求,设计了图像拼接采集系统。利用外部驱动信号控制采集卡的触发及采样时钟,由斩波器同步信号判断热释电探测器的亮场及暗场信号。构造PC-DA Q虚拟仪器系统对多通道输出的热释电型IRFPA进行多路并行图像采集,并对每路图像信号进行亮、暗场判断后进行差分处理,通过软件拼接处理成一副完整的图像,最终在软件平台上显示。对实验室研制的160列×120行双通道读出及320列×120行四通道读出的热释电读出电路进行了图像采集实验,对于同样阵列大小的单通道读出探测器,双通道结构读出速度提高了1倍,四通道结构读出速度提高了3倍。通过采集成像实验验证了系统的可行性。%In order to achieve large-scale pyroelectric infrared focal plane array (IRFPA ) detec-tor with high resolution ,the readout circuit with multi-channel parallel output was designed . Based on the pyroelectric IRFPA detector of multiple-output and the pyroelectric detecting tim-ing requirements ,the system of mosaic imaging acquisition was designed .The external driving signals were used to control the trigger and sampling clock of acquisition card ,and a chopper synchronizing signal was used to judge the bright field and dark field signal of the pyroelectric detector .The system was constructed with PC-DAQ virtual instrument system to acquire multi-channel parallel image ,judge the bright and dark field for differential processing on each channel ,and display a whole image after mosaic processing on software platform .The experi-mental image acquisition of the pyroelectric readout circuit with 160 × 120 two-channels read-out and 320 × 120 four-channels readout were taken and the output signal waveform and image were

  14. Desempenho de uma semeadora-adubadora direta, em função da velocidade de eslocamento e do tipo de manejo da biomassa da cultura de cobertura do solo Performance of a seeding-fertilizer machine in function of the displacement speed and soil cover crop biomass management

    Directory of Open Access Journals (Sweden)

    Klinger B. Branquinho

    2004-08-01

    Full Text Available O objetivo do presente trabalho foi estudar o desempenho de uma semeadora-adubadora, operando em duas velocidades sobre a palhada da cultura do milheto (Pennisetum glaucum (L. R. Brown, após diferentes manejos, na semeadura direta da cultura da soja (Glycine Max L.. O experimento foi realizado com seis tratamentos, em esquema fatorial, delineados em blocos ao acaso, com quatro repetições. Os tratamentos combinaram três manejos (triturador de palhas tratorizado, rolo- faca e herbicida com duas velocidades de deslocamento da semeadora-adubadora (5,2 e 7,3 km h-1. Foram analisadas as seguintes variáveis: acúmulo e decomposição de massa seca do milheto, índice de emergência da cultura da soja, uniformidade de distribuição longitudinal de sementes, capacidade de campo efetiva da semeadora-adubadora e produtividade da soja. Os resultados mostraram que não houve diferença na decomposição da massa de milheto após os manejos e que esses, juntamente com a velocidade de deslocamento do conjunto trator-semeadora-adubadora, não influenciaram no número de dias para a emergência das plântulas de soja e na distribuição longitudinal das sementes. A capacidade de campo efetiva da semeadora-adubadora foi maior na velocidade mais alta. O rendimento de grãos não diferiu significativamente nos tratamentos estudados.The objective of the present work was to evaluate three different managements of the Pennisetum glaucum (L. R. Brown crop and two-speed displacement in a no-tillage system of soybean (Glycine max L. crop on a typical Eutrophic Red Latosol. The experiment was arranged in six treatments, in a factorial array, in a randomized complete block design, with four replications. The treatments were constituted from three combination of crop managements (straw chopper, residue coulter and herbicide and two speed displacement of the seeding-fertilizer machine (5.2 and 7.3 km h-1. The following variables have been analyzed: emergency index of

  15. Analysis and design of modular three-phase power factor correction schemes for utility interface

    Science.gov (United States)

    Hahn, Jae-Hong

    The extensive use of non-linear and electronically switched loads in power system has lead to higher incidences of harmonic distortion of the voltage and current waveforms. Harmonic currents degrade power quality and are considered the main source of many system malfunctions. Technical guidelines and standards regarding suppressions of system harmonic contents have been enacted. This dissertation proposes several new three-phase power factor correction (PFC) schemes using single-phase PFC modules. An integrated single-switch approach is first proposed. This is essentially an add-on solution to standard ASD's. This approach is based on circulating third harmonic current between neutral and DC mid-point by utilizing a lossless resistor. Single-phase PFC emulates this resistor to control the amplitude of the current, which is implemented by the dynamic breaking chopper available in standard adjustable speed drives (ASD's). This approach is also capable of reducing harmonic distortion in multiple drives. Analysis, design and simulations are conducted to determine the performance of the proposed scheme with different line impedances and with and without dc-link inductance in the ASD. Experimental results are presented using commercial ASD retrofitted with the proposed approach. Second scheme proposes a three-phase PFC using two standard single-phase PFC modules. In this approach, three-phase input is transformed into two-phase by means of 0.14 pu autotransformer. Two standard single-phase PFC modules are employed to process two-phase power to do output. Split inductors and diodes are employed to limit the interaction between the two phases. A method to eliminate the interaction between phases is also described. Due to cascade operation of two PFC stages, low frequency (120Hz) ripple in dc-link is cancelled. An active interphase transformer (IPT) scheme is proposed to draw sinusoidal input line currents, in the third study. This scheme utilizes a unique combination of a

  16. Balanço de nitrogênio, concentrações de ureia e síntese de proteína microbiana em caprinos alimentados com dietas contendo cana-de-açúcar tratada com óxido de cálcio Nitrogen balance, urea concentrations and microbial protein synthesis in goats fed diets containing sugar cane treated with calcium oxide

    Directory of Open Access Journals (Sweden)

    Gleidson Giordano Pinto de Carvalho

    2010-10-01

    were composed of 70% sugar cane (treated with 0; 0.75; 1.5 or 2.25% of calcium oxide in natural matter basis and corrected with 1% urea and 30% of concentrate given ad libitum to animals. Sugar cane with calcium oxide was chopped in a stationary chopper, weighted and stored in 50-L plastic buckets and treated with calcium oxide to be given to the animals after 24 hours of storage. Nitrogen balance, urine and plasma urea concentrations and urine urea excretion were not affected by sugar cane +calcium oxide treatment. Concetration of allantoin (% total purine was higher and the uric acid concentration was lower in diets with sugar cane hidrolised with calcium oxide in relation to in natura sugar cane. The microbial production and efficiency are not affected by addition of calcium oxide to sugar cane in diets for growing goats.

  17. 风速及风机地理位置分布特性对直驱风电场故障特征的影响分析%Analysis of Impact of Wind Speed and Wind Turbine Location Distribution Characteristics on PMSG Wind Farm Fault Characteristics

    Institute of Scientific and Technical Information of China (English)

    宋国兵; 李端祯; 常仲学; 王晨清; 郭润生

    2016-01-01

    为探讨直驱风电场分群建模的必要性,研究了风速和风机地理位置分布特性对直驱风电场故障特征的影响。故障特征分析是继电保护构造判据的基础,考虑到故障暂态时段极短且继电保护动作速度快,故障特征分析时可以假定故障切除前风速不变。在此基础上,由于故障阻滞了有功功率的传输,故障后直驱风机产生的有功不能全部传送到网侧。卸荷电路保持了逆变器直流电容电压的稳定,并将多余电能释放。在直流电容电压恒定的情况下,逆变器向故障点注入的多为无功电流,且仅与控制策略和电压跌落程度有关,而与负荷电流无关。理论上,风机对故障点注入的电流与风机所处的地理位置有关。但由于直驱风机的弱馈特性,各风机感受到的电压跌落差别不大,对故障点的注入电流基本相同;虽然各风机距离故障点远近存在差异,但就电气量传输延迟对应的相角差而言,几乎可以忽略不计。综上分析,直驱电场无需分群建模,无需考虑负荷和地理位置影响。最后,仿真结果验证了理论分析的正确性。%For study of PMSG wind farm equivalent with single PMSG, it needs to study influence of wind speed and wind turbine location on fault characteristics of PMSG wind farm. Capacitance at PMSG DC side can isolate turbine side from power grid. When fault happens, chopper circuit will consume excess energy, so wind speed will not affect fault characteristics of PMSG wind farm. Because the line within wind farm is not very long, influence of wind turbine location to fault characteristics can be ignored in normal conditions. However, when a part of PMSGs in collection line turns into LVRT but the others not, influence of wind turbine location to fault characteristics should be considered. With constructed models of PMSG wind farm and single PMSG, simulation result confirms above conclusion.

  18. Proceedings of the International Workshop on Current Challenges in Liquid and Glass Science, (The Cosener's House, Abingdon 10-12 January 2007).

    Science.gov (United States)

    Hannon, Alex C; Salmon, Philip S; Soper, Alan K

    2007-10-17

    to the success of the meeting. The present special issue stems from the interest of many of those present to collect their work into a single volume. [Formula: see text] The workshop participants. Spencer Howells is in the centre of the front row. DEDICATION William Spencer Howells It is a great pleasure to dedicate this Special Issue on Current Challenges in Liquid and Glass Science to the many contributions Spencer Howells has made to the structure and dynamics of liquids and glasses over some 40 years of work with the neutron scattering technique. After completing a first degree in Physics at Cambridge in 1966, Spencer started a postgraduate program with Gordon Squires at Cambridge, exploiting the early neutron scattering instrumentation that was available in those days at the Harwell reactors. This resulted in a Ph D thesis in 1970 on the twin topics of 'Neutron scattering of phonons in single-crystal molybdenum, using a time-of-flight chopper spectrometer (Part I)' and 'Neutron studies of the metal-insulator transition (Part II)'. The thesis was split into two parts because the hydrogen moderator blew-up on the chopper instrument used for the first part! From Cambridge, he moved to Leicester University as a post-doctoral Fellow with John Enderby, who was setting up a programme of study on the liquid state of matter. Here Spencer continued to use the Harwell Dido reactor, now to measure the structure of liquid metal alloys and molten salts - a topic that has kept his interest right through into retirement. He also initiated the first structural studies of aqueous solutions using neutron scattering, eventually pursuing this work as one of the first UK users of the Institut Laue-Langevin, Grenoble, France (ILL). In 1973 Spencer moved to the ILL, which was then and has remained the world's leading steady-state neutron source, as instrument scientist on IN10, the quasi-elastic neutron scattering beam line. Here he led the field in developing the quasi

  19. Comportamento ingestivo em caprinos alimentados com dietas contendo cana-de-açúcar tratada com óxido de cálcio Ingestive behavior in goats fed diets containing sugar cane treated with calcium oxide

    Directory of Open Access Journals (Sweden)

    Gleidson Giordano Pinto de Carvalho

    2011-08-01

    individual feeders and drinkers. The diets were formulated to be isoproteic, with 14% crude protein (CP and presented 70% sugar cane treated with 0; 0.75; 1.5 or 2.25% of calcium oxide (on natural matter basis corrected with 1% urea and 30% of concentrate fed ad libitum. Sugar cane added with doses of calcium oxide was crushed in stationary chopper, weighed and stored in 50-L plastic buckets and treated with calcium oxide, given to the animals after 24 hours of storage. Times spent in feeding, ruminating (min/day; min/kg DM and min/kg NDF and idle (min/day were not affected by addition of calcium oxide to sugar cane. Addition of calcium oxide to sugar cane did not influence effciency of feeding and rumination mad it reduced average time spent per feeding period. Ingestive behavior of growing goats is not affected by utilization of diets with sugar cane treated with up to 2.25% of calcium oxide.

  20. Lactic acid bacteria community andLactobacillus Plantarum improving silaging effect of switchgrass%乳酸菌复合系和植物乳杆菌提高柳枝稷青贮效果

    Institute of Scientific and Technical Information of China (English)

    刘晶晶; 高丽娟; 师建芳; 王小芬; 袁旭峰; 崔宗均

    2015-01-01

    Switchgrass (Panicum virgatumL.) is a warm-season perennial bunchgrass, and the crude protein content of its whole pant is higher than the whole plant of soybean. It is a kind of excellent grass as a livestock feed, which not only has high yield and outstanding quality, but also shows very strong tolerance or resistance to the adverse environment. Lactic acid bacteria (LAB) are often added to forage crops for improving the silage fermentation at the ensiling period, and LAB community has been widely used to prepare the fermented feed, such as alfalfa, crop stalks, bagasse and manioc waste. However, few studies have been done about the effect of LAB on the characteristics of switchgrass silage. Considering the selectivity of inoculants, a stable LAB community named SGL was detected from switchgrass silage by continuous restricted subcultivation. The results of the pyrosequencing showed that the major components in the SGL wereLactobacillus nantensis (78.78%),Lactobacillus plantarum (7.92%),Lactobacillus panthers(5.27%),Bacillus coagulans(4.41%) andLactococcus lactic(3.31%), of whichLactobacillus plantarum (LP) is one of the most frequently used LAB species. The present experiment was conducted to investigate the effects of the SGL community or a single componentLactobacillus plantarum on the fermentation, microbial diversity and rumen fermentation of the resulting silage. Switchgrass was harvested by hand in mid-June when it was just in the vegetative growth stage (26.43% dry matter), and chopped to about 1.5 cm with a laboratory type chopper. The chopped forages were ensiled in 2 L anaerobic jars in the following treatments: control that is untreated, SGL and LP. SGL and LP were both applied in the same quantity of distilled water (10 mL solution per kg forage) at the dose of 1 OD600/kg of fresh forage. The control also received 10 mL water per kg forage forage. Three jars per treatment were sampled on the 3rd, 10th, 20th and 30th day after ensiling, for chemical

  1. Protection of Cactus Polysaccharide against H2O2-induced damage in the rat cerebral cortex and hippocampus Differences In time of administration

    Institute of Scientific and Technical Information of China (English)

    Xianju Huang; Qin Li; Lianjun Guo; Zankai Yan

    2008-01-01

    BACKGROUND: Pharmacological research has shown that cactus polysaccharide (CP) has anti-oxidant, anti-inflammatory, antitumor, anti-aging, and immune-stimulating activities. It may also provide protective effects against oxidative stress injuries in the rat brain.OBJECTIVE: To validate the effects of CP on H2O2-induced oxidative stress injuries in the ratcerebral cortex and hippocampal slices 30 minutes prior to injury, as well as 30 minutes and 2.5 hours after injury.DESIGN: A randomized controlled experiment.SETTINGS: Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology; Department of Pharmacology, College of Medical Science, Yangtze University.MATERIALS: A total of 50 male Sprague Dawley (SD) rats, normal grade and weighing 200-300 g, were provided by the Laboratory Animal Center of Tongji Medical College, Huazhong University of Science and Technology. The protocol was performed in accordance with ethical guidelines for the use and care of ani-mals. Cactus polysaccharide, a dried needle crystal, was extracted from Opuntia milpa alta at the Chemistry and Environment Engineering School of Yangtze University. The following chemicals and instruments were used: 2,3,5-triphenyl tetrazolium chloride (Sigma, St Louis, Missouri, USA); lactate dehydrogenase (LDH), superoxide dismutase (SOD), glutathione (GSH), and total antioxidant competence (T-AOC) assays (Jiancheng-Bioeng Institute, Nanjing); McIllwain tissue chopper (Mickle Laboratory Engineering, USA); and ELISA reader and Magellan software (TECAN, Austria).METHODS: This experiment was performed at the Department of Pharmacology, Medical College of Yangtze University, between March and June 2006. All rats were sacrificed after anesthesia. The cerebral cortex and hippocampus were dissected. Several cerebral cortex and hippocampus slices were selected as controls, while other sections were co-incubated with H2O2 for 30 minutes to induce an oxidative stress injury. The

  2. Development and experiment of combined operation machine for cotton straw chopping and plastic film collecting%棉秆粉碎还田与残膜回收联合作业机研制与试验

    Institute of Scientific and Technical Information of China (English)

    胡凯; 王吉奎; 李斌; 蒋蓓; 丁双双; 李天文

    2013-01-01

    According to the problems of plastic film without distinction as straw, the plastic film recovery rate is low, the effect is poor in removing the collected film, and plastic films are easy to wind in cotton straw chopping and a plastic film collecting combined machine in Xinjiang province, the 4JM-1500 straw chopping and plastic film collecting machine has been designed. It consists of a traction device, straw chopping device, straw conveying device, floating gear-rake institution and chain rake device, film removing device, driven system, plastic film box, and rack and wheel, etc. It can realize straw chopper returning, the straw separation with plastic film, and the plastic film recycling with one operation. This machine combining the hammer device of cotton straw chopping and scraper conveyor device, the machine could separate cotton straws and plastic film, and collect the plastic film by the floating gear-rake institution and chain rake device. It also has a good effect for ground profile modeling and improving the plastic film recovery ratio. It can remove the collected film though the air force device in the operating process, which can prevent the plastic film winding with the film stripping device and affect the work. The structure and working principle of the machine, and the parameters of working parts, and main structures were determined through the main components designed. Knife shaft speed n 3=1800~2200 r/min, straw conveying speed n1=120~150 r/min, plastic film conveying chains speed n2=60~90 r/min, film removing wind speed v 1=6.2~10.5 m/s and the working width was 1500 mm. It effectively decreased the labor cost and enhanced the plastic film collecting efficiency. Field trials demonstrated that the separation ratio of cotton straws and plastic film was 97%, the plastic film collecting ratio was 88.6%, and the film removing ratio was 89.4%under the conditions of machine operating speed of 5-5.5 km/h and straw conveying speed of 1.8m/s, which could

  3. Obituary: Cornell H. Mayer, 1921-2005

    Science.gov (United States)

    Radhakrishnan, Venkataraman

    2006-12-01

    Cornell (Connie) H. Mayer, a pioneer of radio astronomy, died on 19 November 2005 of congestive heart failure at his home in Mt. Vernon, Virginia. He was eighty-three. Cornell Mayer was born in Ossian, Iowa on 10 December 1921. After graduating from the University of Iowa in 1943, he joined the Navy during World War II and was stationed at the Naval Research Laboratory (NRL) in Washington, DC. There he assisted Fred T. Haddock in the development of the first radar antenna inside a submarine periscope. This device has been credited with shortening the war in the Pacific because of the number of Japanese ships that were sunk with its aid. With Haddock, Connie also discovered centimeter-wave radio bursts from the sun coincident with solar flares. They made the first detection of thermal radio emission from the Orion nebula and other galactic HII regions. They also detected extragalactic objects and thus initiated the important field of centimeter-wave astronomy. Their observations were made with a 50-foot parabolic reflector on a gun mount located on the roof of one of the NRL buildings. This telescope had the world's highest radio resolving power for many years. With Haddock's departure to the University of Michigan in 1956 to create a new radio observatory there, Connie became head of a group in the Radio Astronomy Branch at NRL, where he remained until his retirement in 1980. Much of his work involved the measurement of planetary temperatures by analysis of radio emissions. By making technical innovations in instrumentation--such as replacing disc choppers with a ferrite switch to compare the sky and reference load, or using argon gas tubes for calibration--Connie greatly improved the performance of his equipment. This resulted in the discovery of an astonishing, 600oC surface temperature of Venus, which contradicted the widespread notion that Venus was similar to the Earth and potentially habitable. In spite of the extraordinarily careful and systematic way that