WorldWideScience

Sample records for backward wave tubes

  1. Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields

    International Nuclear Information System (INIS)

    Recent development of plasma-assisted slow-wave oscillators [Goebel IEEE Trans. Plasma Sci. >22, 547 (1994)], microwave sources that operate without guiding magnetic fields, has stimulated interest in the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields, due to the space charge forces and the radial electric field of the wave, the electrons may propagate radially outward which increases electron coupling to the slow wave whose field is localized near the slow-wave structure (SWS). This increases the wave growth rate and efficiency, and hence allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it does not lead to interception of electrons by the SWS. To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on the operation of traveling-wave tubes and backward-wave oscillators with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting the SWS from electron bombardment at different power levels. Theoretical predictions of the efficiency enhancement due to the weak magnetic field are confirmed in experiments

  2. Exact numerical solution of the dispersion relation in relativistic backward-wave oscillator and relativistic travelling-wave tube filled with plasma

    International Nuclear Information System (INIS)

    In this paper, the dispersion relation of the relativistic travelling-wave tube (RTWT) and relativistic backward-wave oscillator (RBWO) filled with plasma is obtained in the presence of an annular electron beam and solved by an exact numerical solution. The interaction of the beam with the waveguide modes is clearly identified and beam line splitting into the slow and fast waves is observed. In addition, the growth rates of each structure are investigated. The results show that the effect of plasma on the temporal growth rate of the TM01 mode in the RBWO is negligible and the higher modes are not affected. Conversely, the spatial growth rate in the RTWT increases significantly with the plasma density. (paper)

  3. Terahertz backward wave oscillator circuits

    Science.gov (United States)

    Oviedo Vela, Guillermo Antonio

    This work focuses on increasing the electric field mode-electron beam interaction in terahertz backward-wave oscillators through increasing the interaction impedance of the slow wave circuit. In a backward wave oscillator (BWO) or a traveling wave tube (TWT), the electric field traveling in the waveguide interacts with an electron beam grazing or piercing the electric field of a slow wave circuit and transfers energy from the beam to the circuit mode. The mechanism of this interaction is analyzed and the traditional model is adapted to provide one that is scalable to terahertz frequencies. The efficiency of the BWO can be enhanced by improving the interaction between the beam and the circuit modes, utilizing beam sources with greater current densities and using larger magnetic fields. This work presents the results on the modeling, fabrication and performance of the mode-piercing and mode-grazing slow wave circuits studied. Meandering folded waveguides and interdigital lines were modeled to evaluate their interaction impedance and electron beam requirements at terahertz frequencies. The models were verified against published results. Because of their low interaction impedance, terahertz meandering waveguides would need to be excited with large current density electron beams which in turn would require large magnets for their control. Interdigital lines were found to be the slow-wave circuit of choice in this work because their high interaction impedance and their ability to operate with low voltage, and low current density electron beams. Finite element numerical calculations were used to design, optimize and scale a terahertz free interdigital line (FIDL) circuit. The designed free interdigital line was fabricated using microfabrication technologies. Characterization of a free interdigital line (FIDL) circuit was performed in a tube body with a dispenser cathode and a three-anode Pierce gun. The FIDL measured output was compared with the calculated result and its

  4. Power microwave pulse generation of resonant relativistic backward wave tube with power supply based on explosive magnetocumulative generators

    International Nuclear Information System (INIS)

    High-power microwave radiation has been generated using a resonant relativistic backward wave oscillator (BWO) powered by a high voltage source comprising an inductive energy storage and an electric-explosion current switch, the results of the experiment are provided. The high voltage source and the BWO magnetic system are energy pumped by explosive magnetocumulative generators. In the experiments the setup generated 30-ns single-mode radiation pulses with a carrier frequency of 3.6 GHz at a peak power of 0.75 GW

  5. Development of a 2 MW relativistic backward wave oscillator

    Indian Academy of Sciences (India)

    Yaduvendra Choyal; Lalit Gupta; Prasad Deshpande; Krishna Prasad Maheshwari; Kailash Chander Mittal; Suresh Chand Bapna

    2008-12-01

    In this paper, a high power relativistic backward wave oscillator (BWO) experiment is reported. A 230 keV, 2 kA, 150 ns relativistic electron beam is generated using a Marx generator. The beam is then injected into a hollow rippled wall metallic cylindrical tube that forms a slow wave structure. The beam is guided using an axial pulsed magnetic field having a peak value 1 T and duration 1 ms. The field is generated by the discharge of a capacitor bank into a solenoidal coil. A synchronization circuit ensures the generation of the electron beam at the instant when the axial magnetic field attains its peak value. The beam interacts with the SWS modes and generates microwaves due to Cherenkov interaction. Estimated power of 2 MW in TM 01 mode is observed.

  6. Traveling-Wave Tubes

    Science.gov (United States)

    Kory, Carol L.

    1998-01-01

    The traveling-wave tube (TWT) is a vacuum device invented in the early 1940's used for amplification at microwave frequencies. Amplification is attained by surrendering kinetic energy from an electron beam to a radio frequency (RF) electromagnetic wave. The demand for vacuum devices has been decreased largely by the advent of solid-state devices. However, although solid state devices have replaced vacuum devices in many areas, there are still many applications such as radar, electronic countermeasures and satellite communications, that require operating characteristics such as high power (Watts to Megawatts), high frequency (below 1 GHz to over 100 GHz) and large bandwidth that only vacuum devices can provide. Vacuum devices are also deemed irreplaceable in the music industry where musicians treasure their tube-based amplifiers claiming that the solid-state and digital counterparts could never provide the same "warmth" (3). The term traveling-wave tube includes both fast-wave and slow-wave devices. This article will concentrate on slow-wave devices as the vast majority of TWTs in operation fall into this category.

  7. Linear theory of plasma filled backward wave oscillator

    Indian Academy of Sciences (India)

    Preeti Vyas; Arti Gokhale; Y Choyal; K P Maheshwari

    2001-05-01

    An analytical and numerical study of backward wave oscillator (BWO) in linear regime is presented to get an insight into the excitation of electromagnetic waves as a result of the interaction of the relativistic electron beam with a slow wave structure. The effect of background plasma on the BWO instability is also presented.

  8. Terahertz Imaging System Based on a Backward-Wave Oscillator

    Science.gov (United States)

    Dobroiu, Adrian; Yamashita, Masatsugu; Ohshima, Yuichi N.; Morita, Yasuyuki; Otani, Chiko; Kawase, Kodo

    2004-10-01

    We present an imaging system designed for use in the terahertz range. As the radiation source a backward-wave oscillator was chosen for its special features such as high output power, good wave-front quality, good stability, and wavelength tunability from 520 to 710 GHz. Detection is achieved with a pyroelectric sensor operated at room temperature. The alignment procedure for the optical elements is described, and several methods to reduce the etalon effect that are inherent in monochromatic sources are discussed. The terahertz spot size in the sample plane is 550 µm (nearly the diffraction limit), and the signal-to-noise ratio is 10,000:1; other characteristics were also measured and are presented in detail. A number of preliminary applications are also shown that cover various areas: nondestructive real-time testing for plastic tubes and packaging seals; biological terahertz imaging of fresh, frozen, or freeze-dried samples; paraffin-embedded specimens of cancer tissue; and measurement of the absorption coefficient of water by use of a wedge-shaped cell.

  9. Reverse Doppler effect in backward spin waves scattered on acoustic waves

    OpenAIRE

    A. V. Chumak; Dhagat, P.; Jander, A.; Serga, A. A.; Hillebrands, B

    2009-01-01

    We report on the observation of reverse Doppler effect in backward spin waves reflected off of surface acoustic waves. The spin waves are excited in a yttrium iron garnet (YIG) film. Simultaneously, acoustic waves are also generated. The strain induced by the acoustic waves in the magnetostrictive YIG film results in the periodic modulation of the magnetic anisotropy in the film. Thus, in effect, a travelling Bragg grating for the spin waves is produced. The backward spin waves reflecting off...

  10. Detecting electromagnetic cloaks using backward-propagating waves

    KAUST Repository

    Salem, Mohamed

    2011-08-01

    A novel approach for detecting transformation-optics invisibility cloaks is proposed. The detection method takes advantage of the unusual backward-propagation characteristics of recently reported beams and pulses to induce electromagnetic scattering from the cloak. Even though waves with backward-propagating energy flux cannot penetrate the cloaking shell and interact with the cloaked objects (i.e., they do not make the cloaked object visible), they provide a mechanism for detecting the presence of cloaks. © 2011 IEEE.

  11. Relativistic backward-wave oscillator with coaxial extractor

    International Nuclear Information System (INIS)

    The author brings forth a new relativistic backward-wave oscillator with coaxial extractor. Numerical simulation is conducted using KARAT code. This simulation produces a microwave pulse power of 2.0 GW at 9.28 GHz for 730 kV, 6 kV injecting beam. Power transform efficiency of 45% is obtained. The interaction between beam and slow wave structure is tracked and analyzed. SUPERFISH code is used to calculate axial electric field distribution, and the results show that the relativistic backward-wave oscillator with coaxial extractor has the advantage of increasing efficiency

  12. Observation of the backward electrostatic ion cyclotron wave

    International Nuclear Information System (INIS)

    The backward branch of the electrostatic ion cyclotron wave has been observed, we believe, for the first time. The wave, which was driven by a phased antenna structure inserted in a neon plasma, exists in the parameter ranges 2T/sub i//m/sub i/ 2 Ω/sub i/. Double-tip probe interferomety data agree with the theoretical dispersion relation

  13. Negative refraction and backward waves in layered acoustic metamaterials

    OpenAIRE

    Christensen, Johan; García de Abajo, F. Javier

    2012-01-01

    We investigate layered acoustic metamaterials capable of exhibiting a wide variety of wave propagation phenomena, including backward and forward waves with and without negative refraction. The metamaterials are formed by periodically perforated hard plates, which we describe analytically in the limit of small holes compared to both the period and the separation between plates. In particular, we derive expressions for the index of refraction and the transmission and reflection coefficients of ...

  14. Tree-wave mixing of ordinary and backward electromagnetic waves: extraordinary transients

    OpenAIRE

    Slabko, Vitaly V.; Popov, Alexander K.; Tkachenko, Viktor A.; Myslivets, Sergey A.

    2016-01-01

    Three-wave mixing of ordinary and backward electromagnetic waves in pulsed regime is investigated in the metamaterials, which enable co-existence and phase matching of such waves. It is shown that opposite direction of phase velocity and energy flux in backward waves gives rise to extraordinary transient processes in greatly enhanced optical parametric amplification and in frequency up or down shifting nonlinear reflectivity. The discovered transients resemble slowed response of an oscillator...

  15. Tree-wave mixing of ordinary and backward electromagnetic waves: extraordinary transients

    CERN Document Server

    Slabko, Vitaly V; Tkachenko, Viktor A; Myslivets, Sergey A

    2016-01-01

    Three-wave mixing of ordinary and backward electromagnetic waves in pulsed regime is investigated in the metamaterials, which enable co-existence and phase matching of such waves. It is shown that opposite direction of phase velocity and energy flux in backward waves gives rise to extraordinary transient processes in greatly enhanced optical parametric amplification and in frequency up or down shifting nonlinear reflectivity. The discovered transients resemble slowed response of an oscillator on pulsed excitation in the vicinity of its resonance

  16. Competition of Azimuthally Asymmetric Modes in a Relativistic Backward-Wave Oscillator

    Science.gov (United States)

    Abubakirov, E. B.; Sergeev, A. S.

    2016-01-01

    We analyze the operation of a relativistic backward-wave oscillator, in which two waves with opposite directions of rotation of the azimuthal structure of the high-frequency field interact with the electron beam simultaneously. Based on the nonstationary model of such a tube, several characteristic features of dynamics of this system are identified, both in the autonomous regime of its operation, and under the action of an external-signal source. The list of such features includes the instability of azimuthally standing waves, the existence of stable regimes of stationary generation of two waves with different frequencies and opposite rotation directions, and the possibility of spatial self-modulation of the output radiation of a high-frequency oscillator.

  17. AN INNER-FEEDBACK-STYLE TRAVELING-WAVE TUBE OSCILLATOR

    Institute of Scientific and Technical Information of China (English)

    Wang Zicheng; Li Haiqiang; Xu Anyu; Liu Qinglun; Liu Wei

    2012-01-01

    A new concept of inner-feedback-style traveling wave tube oscillator,which is based on a traveling-wave tube having a partial reflector located at near the junction between the slow-wave structure and the output coupler and a mechanical tuner connected to the input coupler,is proposed.Simulations by CHIPIC code show that the inner-feedback-style traveling wave tube oscillator having 100W of power,about 10% of electron efficiency and a tunable band of 73.35-73.91 GHz may be achieved.Compared with Backward Wave Oscillators (BWOs),the new devices have similar ability for tuning,and have much higher electron efficiency,suggesting much more potential as a Terahertz source.

  18. Analytic theory of the backward wave oscillator: dispersion characteristics

    International Nuclear Information System (INIS)

    Recent experiments with high power microwave generation in backward wave oscillators have employed annular relativistic electron beams and slow wave structures consisting of cylindrical waveguides with a sinusoidally perturbed wall radius. A linearized theory of the dispersion characteristics for these systems is presented here. The theory is valid for beams that are thin in radial extent, axial magnetic fields that are large, and structures that are many ripple periods in length. The dispersion relation at the heart of this analysis is three dimensional. Solutions for the frequency passbands in cold structures with no beam are given, and the full dispersion relation including beam effects is analyzed to determine the effect of varying system parameters on the frequencies and growth rates of the instabilities that lead to microwave production

  19. Improved Traveling-Wave Tube

    Science.gov (United States)

    Rousseau, Art; Tammaru, Ivo; Vaszari, John

    1988-01-01

    New space traveling-wave tube (TWT) provides coherent source of 75 watts of continuous-wave power output over bandwidth of 5 GHz at frequency of 65 GHz. Coupled-cavity TWT provides 50 dB of saturated gain. Includes thermionic emitter, M-type dispenser cathode providing high-power electron beam. Beam focused by permanent magnets through center of radio-frequency cavity structure. Designed for reliable operation for 10 years, and overall efficiency of 35 percent minimizes prime power input and dissipation of heat.

  20. Experimental study on backward wave oscillation based on cylindrical surface wave of Smith-Purcell free electron laser

    International Nuclear Information System (INIS)

    Backward wave oscillation based on a cylindrical surface wave of Smith-Purcell free electron laser (SP-FEL) is demonstrated. The SP-FEL is composed of a metal cylinder having a periodically corrugated wall and a surrounding hollow straight waveguide. Corrugation parameters are those used in K-band backward wave oscillators (BWOs). The metal cylinder has a surface wave due to the corrugation. The cylindrical surface wave is excited by an axially injected coaxial annular beam. Radiations due to the backward wave oscillation based on the cylindrical surface wave are examined in a weakly relativistic region less than 100 kV. An oscillation starting voltage exists for the backward wave oscillation as in the case of hollow oversized BWO. The frequencies are in K-band and are determined by the cylindrical corrugation. Radiations up to tens of kW are obtained. (author)

  1. Interpretation of Cluster data on chorus emissions using the backward wave oscillator model

    International Nuclear Information System (INIS)

    The measurements of chorus emissions by four closely separated Cluster spacecraft provide important information concerning the chorus generation mechanism. They confirm such properties of the wave source as their strong localization near the equatorial cross section of a magnetic flux tube, an almost parallel average wave-vector direction with respect to the geomagnetic field, and an energy flux direction pointing outward from the generation region. Inside this region, Cluster discovered strong temporal and spatial variations in the amplitude with correlation scale lengths of the order of 100 km across the magnetic flux. The wave electric field reached 30 mV/m, and the maximum growth and damping rates are of the order of a few hundreds of s-1. These and other properties of the detected chorus emissions are discussed here in relation with the backward wave oscillator mechanism. According to this mechanism, a succession of whistler wave packets is generated in a small near-equatorial region with temporal and spatial characteristics close to the Cluster data. Amplitudes and frequency spectra, as well as dynamical features of the Poynting flux of chorus are estimated and compared with the Cluster measurements

  2. Investigation of a 140 GHz gryo-backward wave oscillator and a 95 GHz gyro-traveling wave

    International Nuclear Information System (INIS)

    There is current interest in developing a high-power source of continuously tunable millimeter wave radiation as a RF driver for high-power gyrotron, CARM, or FEL amplifiers. The gyrotron backward wave oscillator is a voltage-tunable fast-wave device that can satisfy these requirements. This thesis reports on the design and experimental investigation of a 130--145 GHz gyrotron backward wave oscillator Novel operating features of this design include the use of a 80-kV, 6.2-A Pierce-wiggler electron beam source, a broadband motheye window and an overmoded TE1,2 cylindrical interaction waveguide. Although this device has demonstrated voltage-tunable operation over the design range in the TE1,2 mode, the frequency tuning is not continuous, output powers were low and full-beam transmission through the interaction region was not possible. Simulations indicate that the beam has very high velocity spread induced by space charge forces in the compression region. After increasing the diameter of the beam tunnel to achieve full transmission, the TE1,2 was not found. It is felt that the scraping off of the beam edge in the initial experiments allowed a better quality beam to enter the interaction region and inhibited coupling into competing forward wave modes. The need for radar systems with greater resolution has led to renewed interest in the development of efficient high-power amplifiers at 95 GHz. Current sources are limited to 6--8 kW of output power due to ohmic loading on the slow-wave circuit. A gyrotron traveling wave tube amplifier is capable of efficient operation over a wide bandwidth with the added attraction of low ohmic loading on the smooth fast-wave circuit. This thesis reports of the design a 95-GHz gyrotron traveling wave tube amplifier that is capable of high power (125 kW), high gain (38 dB), large bandwidth > 5 GHz and high efficiencies (> 30%)

  3. Beam interactions with surface waves and higher-order modes in oversized backward wave oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Kazuo; Kojima, Akihiko; Kawabe, Fumiaki; Yambe, Kiyoyuki [Niigata University, Niigata (Japan); Amin, Ruhul [Islamic University of Technology, Gazipur (Bangladesh)

    2014-10-15

    Beam interactions with surface waves and higher-order modes in an oversized backward wave oscillator (BWO) are studied. In addition to the well-known Cherenkov interaction, the slow cyclotron interaction occurs due to transverse perturbations of the electron beam. The Cherenkov interaction dominates the slow cyclotron interaction. Growth rates of both the interactions for the higher order modes are small compared with those for the surface-wave modes in an oversized BWO. The coaxial slow-wave structure exhibits a reduced number of higher-order modes, which consequently reduces the mode competition problem and improves beam interactions with higher order modes. For higher values of beam currents, the slow cyclotron wave grows at a faster rate than the Cherenkov waves.

  4. Experimental study of beam auto-oscillations in LU section on a backward wave

    International Nuclear Information System (INIS)

    The investigation of beam self-oscillations has been carried out by means of the proton linear accelerator with a backward wave. The relation connecting the conditions of the self-oscillations initiation with accelerator parameters was obtained

  5. Effects of Rubber Loading on the Ultrasonic Backward Radiation Profile of Leaky Lamb Wave

    International Nuclear Information System (INIS)

    The characterization of adhesive property in multi-layer materials has been hot issue for a long time. In order to evaluate adhesive properties, we constructed fully automated system for the backward radiation of leaky Lamb wave. The backward radiation profiles were obtained for the bare steel plate and plates with rubber-loading. The rf waveforms and frequency spectra of backward radiation show the characteristics of involved leaky Lamb wave modes. As the thickness of rubber-loading increased, the amplitude of profile at the incident angle of 13.4' exponentially decreased. Scanning the incident position over the partially rubber-loaded specimen shows good agreement with the actual rubber-loading. The backward radiation of leaky Lamb wave has great potential to evaluate the adhesive condition as well as material properties of plates

  6. Phase matched backward-wave second harmonic generation in a hyperbolic carbon nanoforest

    OpenAIRE

    Popov, A. K.; Nefedov, I.S.; Myslivets, S A

    2016-01-01

    We show that deliberately engineered spatially dispersive metamaterial slab can enable co-existence and phase matching of contra-propagating ordinary fundamental and backward second harmonic electromagnetic modes. Energy flux and phase velocity are contra-directed in backward waves which determines extraordinary nonlinear-optical propagation processes. Frequencies, phase and group velocities, as well as nanowavequide losses inherent to the electromagnetic modes supported by the metamaterial c...

  7. Three-wave mixing of ordinary and backward electromagnetic waves: extraordinary transients in the nonlinear reflectivity and parametric amplification.

    Science.gov (United States)

    Slabko, Vitaly V; Popov, Alexander K; Tkachenko, Viktor A; Myslivets, Sergey A

    2016-09-01

    Three-wave mixing of ordinary and backward electromagnetic waves in a pulsed regime is investigated in the metamaterials that enable the coexistence and phase-matching of such waves. It is shown that the opposite direction of phase velocity and energy flux in backward waves gives rise to extraordinary transient processes due to greatly enhanced optical parametric amplification and frequency up- and down-shifting nonlinear reflectivity. The differences are illustrated through comparison with the counterparts in ordinary, co-propagating settings. PMID:27607951

  8. Quarter-wave pulse tube

    Science.gov (United States)

    Swift, G. W.; Gardner, D. L.; Backhaus, S. N.

    2011-10-01

    In high-power pulse-tube refrigerators, the pulse tube itself can be very long without too much dissipation of acoustic power on its walls. The pressure amplitude, the volume-flow-rate amplitude, and the time phase between them evolve significantly along a pulse tube that is about a quarter-wavelength long. Proper choice of length and area makes the oscillations at the ambient end of the long pulse tube optimal for driving a second, smaller pulse-tube refrigerator, thereby utilizing the acoustic power that would typically have been dissipated in the first pulse-tube refrigerator's orifice. Experiments show that little heat is carried from the ambient heat exchanger to the cold heat exchanger in such a long pulse tube, even though the oscillations are turbulent and even when the tube is compactly coiled.

  9. Phase matched backward-wave second harmonic generation in a hyperbolic carbon nanoforest

    CERN Document Server

    Popov, A K; Myslivets, S A

    2016-01-01

    We show that deliberately engineered spatially dispersive metamaterial slab can enable co-existence and phase matching of contra-propagating ordinary fundamental and backward second harmonic electromagnetic modes. Energy flux and phase velocity are contra-directed in backward waves which determines extraordinary nonlinear-optical propagation processes. Frequencies, phase and group velocities, as well as nanowavequide losses inherent to the electromagnetic modes supported by the metamaterial can be tailored to optimize nonlinear-optical conversion of frequencies and propagation directions of the coupled waves. Such a possibility, which is of paramount importance for nonlinear photonics, is proved with numerical model of the hyperbolic metamaterial made of carbon nanotubes standing on metal surface. Extraordinary properties of backward-wave second harmonic in the THz and IR propagating in the reflection direction are investigated with focus on pulsed regime.

  10. Wave propagation in spatially modulated tubes

    CERN Document Server

    Ziepke, A; Engel, H

    2016-01-01

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we can observe finite intervals of propagation failure of waves induced by the tube's modulation. In addition, using the Fick-Jacobs approach for the highly diffusive limit we show that wave velocities within tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pul...

  11. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    Science.gov (United States)

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics. PMID:26873972

  12. Characterization of rubber loading on the steel plate using ultrasonic backward radiation of leaky lamb wave

    International Nuclear Information System (INIS)

    The characterization of adhesive property in multi-layer materials has been hot issue for a long time. In order to evaluate adhesive properties, we constructed fully automated system for the backward radiation of leaky Lamb wave. The backward radiation profiles were obtained for the bare steel plate an(1 plates with rubber-lending. The RF waveforms and frequency spectra of backward radiation show the characteristics of involved leaky Lamb wave modes. As thickness of rubber-loading increased, the amplitude of profile at the incident angle of 13.4 degrees exponentially decreased. Scanning the incident position over the partially rubber-loaded specimen shows good agreement with the actual rubber-loading.

  13. Backward spoof surface wave in plasmonic metamaterial of ultrathin metallic structure

    Science.gov (United States)

    Liu, Xiaoyong; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

    2016-02-01

    Backward wave with anti-parallel phase and group velocities is one of the basic properties associated with negative refraction and sub-diffraction image that have attracted considerable interest in the context of photonic metamaterials. It has been predicted theoretically that some plasmonic structures can also support backward wave propagation of surface plasmon polaritons (SPPs), however direct experimental demonstration has not been reported, to the best of our knowledge. In this paper, a specially designed plasmonic metamaterial of corrugated metallic strip has been proposed that can support backward spoof SPP wave propagation. The dispersion analysis, the full electromagnetic field simulation and the transmission measurement of the plasmonic metamaterial waveguide have clearly validated the backward wave propagation with dispersion relation possessing negative slope and opposite directions of group and phase velocities. As a further verification and application, a contra-directional coupler is designed and tested that can route the microwave signal to opposite terminals at different operating frequencies, indicating new application opportunities of plasmonic metamaterial in integrated functional devices and circuits for microwave and terahertz radiation.

  14. Terahertz wave two-dimensional transmission imaging with a backward wave oscillator

    Science.gov (United States)

    Yuan, Hongyang; Ge, Xinhao; Zhang, Cunlin

    2008-12-01

    We present a terahertz (THz) imaging system with a Backward Wave Oscillator (BWO). BWO Continuous-Wave THz imaging is a new approach to non-destructive testing. Many materials that are opaque to visible and infrared light are transparent to THz radiation. THz wave image provides a higher spatial resolution than microwave image by having much shorter wavelength. It also poses no known harm to living organisms, making it a safe and powerful imaging technology. Unlike pulsed THz imaging, BWO THz imaging only yields intensity data without providing any depth, frequency-domain or time-domain information about the subject. However, in most cases the energy plots are sufficient for identification of targets. In exchange for the loss of depth, time-domain and frequency-domain information, BWO imaging offers a simple, fast and relatively low-cost system. In this work we show a simple Terahertz (THz) 2-dimentional scanning imaging system utilizing a BWO source tunable from 0.52 to 0.71 THz and a pyroelectric sensor detector operated in THz range. The sample is placed on an X-Z two-dimensional stage controlled by a computer. The intensity information of the terahertz wave after passing sample is collected. Two-dimensional image of the sample is obtained by raster scanning the sample in X and Z directions. A number of potential imaging applications are demonstrated using the 0.71 THz radiation, including nondestructive real-time testing for campus debit card and various articles contained in an envelop. And we present the digital image processing based on the result of the imaging system. This work reveals that a BWO THz imaging system is very practical, effective and promising in nondestructive identification and security inspections applications in future.

  15. Improvement of economy of wave power generation by Backward Bent Duct Buoy (BBDB)

    International Nuclear Information System (INIS)

    Floating type wave power generator KAIMEI test by JAMSTEC certified mooring safety, long life of turbine and generator and cable line, but conversion efficiency from wave power to air-output was poor. This paper describes Backward Bent Duct Buoy (BBDB) which has high conversion efficiency, and it has frontward movement in wave by function of bent duct. In addition, improvement of turbine and generator solved technical problems, double rotor Wells turbine and Heller's Generator are introduced. High wave power locals on high latitude area, and east coast of ocean, for example, North-West of USA has very high wave power. BBDB is designed and power cost is calculated by water tank data, and sea test data and cost estimations by several sources and sea wave data. Power cost by BBDB on high wave area is estimated to be cheap enough for commercial use

  16. Wave propagation in spatially modulated tubes.

    Science.gov (United States)

    Ziepke, A; Martens, S; Engel, H

    2016-09-01

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi-two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we observe finite intervals of propagation failure of waves induced by the tube's modulation and derive an analytically tractable condition for their occurrence. For the highly diffusive limit, using the Fick-Jacobs approach, we show that wave velocities within modulated tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pulse trains. We observe period changes by integer fractions dependent on the bottleneck width and the period of the entering pulse train. PMID:27608990

  17. Properties of the magnetospheric backward wave oscillator inferred from CLUSTER measurements of VLF chorus elements

    OpenAIRE

    Titova, E; Demekhov, A; Kozelov, B; Santolík, O; E. Macúšová; Rauch, J. L.; J. G. Trotignon; Gurnett, D.; J. Pickett

    2012-01-01

    [1] According to the backward wave oscillator (BWO) model, a sharp gradient (or step-like deformation) on the electron distribution function is the most important factor in chorus generation, but such a feature is very difficult to observe directly. The properties of the step in the BWO model determine the dimensionless parameter q quantifying the excess of the energetic electron flux above the absolute-instability threshold. This parameter, in turn, is related to the frequency sweep rate of ...

  18. A Numerical Study of Evanescent Fields in Backward-Wave Slabs

    OpenAIRE

    Karkkainen, M. K.; Tretyakov, S. A.; Maslovski, S. I.; P. A. Belov

    2003-01-01

    Numerical study of evanescent fields in an isotropic backward-wave (BW) (double negative or "left-handed") slab is performed with the FDTD method. This system is expected to be able to restore all spatial Fourier components of the spectrum of a planar source, including evanescent fields, realizing a "superlens". The excitation of surface modes on the interfaces of the slab, which is the key process responsible for the sub-wavelength focusing, is numerically confirmed and the time-domain field...

  19. THz Backward-wave oscillators for plasma diagnostic in nuclear fusion

    OpenAIRE

    Paoloni, Claudio; Yue, Lingna; Tang, Xiaopin; Zhang, Fuzhi; Popovic, Branko; Himes, Logan; Barchfeld, Robert; Gamzina, Diana; Mineo, Mauro; Letizia, Rosa; Luhmann Jr., Neville C

    2015-01-01

    Summary form only given. The understanding of plasma turbulence in nuclear fusion is related to the availability of powerful THz sources and the possibility to map wider plasma regions. A novel approach to realize compact THz sources to be implemented in the plasma diagnostic at NSTX experiment (Princeton Plasma Physics Laboratory, USA) is reported.Two novel 0.346 THz Backward-Wave Oscillators (BWOs) have been designed and are presently in the fabrication phase. One BWO is based on the Double...

  20. Mode selection in an S-band relativistic backward wave oscillator based on a coaxial waveguide

    Science.gov (United States)

    Totmeninov, E. M.; Klimov, A. I.; Konev, V. Yu.; Pegel, I. V.; Rostov, V. V.; Tsygankov, R. V.; Tarakanov, V. P.

    2014-02-01

    The competition of oscillations in a relativistic backward wave oscillator (RBWO) based on a coaxial waveguide has been studied by theoretical and experimental methods. It is established that the starting current for asymmetric magnetic TE m1 type waves is lower than that for the TEM wave. Predominant excitation of the former waves is confirmed by numerical simulations using the PIC-code KARAT. In an experimental RBWO prototype, the excitation of asymmetric oscillations was suppressed by longitudinal cuts in the central conductor of the coaxial waveguide. As a result, stable generation of the TEM wave has been achieved at a frequency of 1.23 GHz, a peak power of 260 MW, and a 28% efficiency of electron-beam-power conversion into radiation power for a microwave-pulse duration of 33 ns.

  1. Generation of broadband terahertz radiation using a backward wave oscillator and pseudospark-sourced electron beam

    Energy Technology Data Exchange (ETDEWEB)

    He, W.; Zhang, L.; Bowes, D.; Yin, H.; Ronald, K.; Phelps, A. D. R.; Cross, A. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG Scotland (United Kingdom)

    2015-09-28

    This paper presents for the generation of a small size high current density pseudospark (PS) electron beam for a high frequency (0.2 THz) Backward Wave Oscillator (BWO) through a Doppler up-shift of the plasma frequency. An electron beam ∼1 mm diameter carrying a current of up to 10 A and current density of 10{sup 8} A m{sup −2}, with a sweeping voltage of 42 to 25 kV and pulse duration of 25 ns, was generated from the PS discharge. This beam propagated through the rippled-wall slow wave structure of a BWO beam-wave interaction region in a plasma environment without the need for a guiding magnetic field. Plasma wave assisted beam-wave interaction resulted in broadband output over a frequency range of 186–202 GHz with a maximum power of 20 W.

  2. Standing wave tube electro active polymer wave energy converter

    Science.gov (United States)

    Jean, Philippe; Wattez, Ambroise; Ardoise, Guillaume; Melis, C.; Van Kessel, R.; Fourmon, A.; Barrabino, E.; Heemskerk, J.; Queau, J. P.

    2012-04-01

    Over the past 4 years SBM has developed a revolutionary Wave Energy Converter (WEC): the S3. Floating under the ocean surface, the S3 amplifies pressure waves similarly to a Ruben's tube. Only made of elastomers, the system is entirely flexible, environmentally friendly and silent. Thanks to a multimodal resonant behavior, the S3 is capable of efficiently harvesting wave energy from a wide range of wave periods, naturally smoothing the irregularities of ocean wave amplitudes and periods. In the S3 system, Electro Active Polymer (EAP) generators are distributed along an elastomeric tube over several wave lengths, they convert wave induced deformations directly into electricity. The output is high voltage multiphase Direct Current with low ripple. Unlike other conventional WECs, the S3 requires no maintenance of moving parts. The conception and operating principle will eventually lead to a reduction of both CAPEX and OPEX. By integrating EAP generators into a small scale S3, SBM achieved a world first: direct conversion of wave energy in electricity with a moored flexible submerged EAP WEC in a wave tank test. Through an extensive testing program on large scale EAP generators, SBM identified challenges in scaling up to a utility grid device. French Government supports the consortium consisting of SBM, IFREMER and ECN in their efforts to deploy a full scale prototype at the SEMREV test center in France at the horizon 2014-2015. SBM will be seeking strategic as well as financial partners to unleash the true potentials of the S3 Standing Wave Tube Electro Active Polymer WEC.

  3. Fracture diagnostics with tube wave reflection logs

    International Nuclear Information System (INIS)

    This paper reports on the Tube Wave Reflection Log (TWRL) which is acoustic logging method which provides information about the height, location and conductivity of hydraulically induced fractures behind perforated casing. The TWRL tool consists of a transmitter and closely spaced receiver. The transmitter is driven with a short, low frequency tone burst to generate long wavelength tube waves which are little attenuated in unperforated casing. They are partially reflected when they pass perforated intervals communicating with a hydraulically induced fracture. The tool listens for such reflections for 0.1 seconds following each excitation burst. As the tool is moved uphole at logging speed, the transmitter is excited at each foot of depth. VDL displays of the TWRL records provide reflection traces whose projections define the uppermost and lower-most perforations communicating with the fracture. The strength of the reflections depends on the ease of fluid flow into the fracture and thus, is an indicator of fracture conductivity

  4. Experimental study on G-band oversized backward wave oscillator driven by weakly relativistic electron beam

    International Nuclear Information System (INIS)

    We studied a G-band oversized backward wave oscillator (BWO) driven by a weakly relativistic electron beam of less than 100 kV. Rectangular corrugations are used as slow-wave structures having surface waves with upper cutoff frequencies above 150 GHz (G-band). We examine how dispersion characteristics of surface waves are affected by accuracy in machining the corrugation amplitude, width, and period length. Of these, accuracy in the amplitude has the largest effect. Uniformly distributed annular electron beams are generated by a disk-type cold cathode and injected into the G-band BWO. G-band BWO operations in 137 - 173 GHz and above 173 GHz are achieved by changing the corrugation amplitude. The radiation patterns are fairly broad, and the estimated radiation power is at kW level. (author)

  5. An optimization method of relativistic backward wave oscillator using particle simulation and genetic algorithms

    International Nuclear Information System (INIS)

    Optimal design method of high-power microwave source using particle simulation and parallel genetic algorithms is presented in this paper. The output power, simulated by the fully electromagnetic particle simulation code UNIPIC, of the high-power microwave device is given as the fitness function, and the float-encoding genetic algorithms are used to optimize the high-power microwave devices. Using this method, we encode the heights of non-uniform slow wave structure in the relativistic backward wave oscillators (RBWO), and optimize the parameters on massively parallel processors. Simulation results demonstrate that we can obtain the optimal parameters of non-uniform slow wave structure in the RBWO, and the output microwave power enhances 52.6% after the device is optimized

  6. Suppressing RF breakdown of powerful backward wave oscillator by field redistribution

    Directory of Open Access Journals (Sweden)

    W. Song

    2012-03-01

    Full Text Available An over mode method for suppressing the RF breakdown on metal surface of resonant reflector cavity in powerful backward wave oscillator is investigated. It is found that the electric field is redistributed and electron emission is restrained with an over longitudinal mode cavity. Compared with the general device, a frequency band of about 5 times wider and a power capacity of at least 1.7 times greater are obtained. The results were verified in an X-band high power microwave generation experiment with the output power near 4 gigawatt.

  7. Investigation of a 1 GHz permanent magnet packaging coaxial relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    A permanent magnet system with 0.4 T axial plane magnetic field is designed by a structure composed of radial magnetized permanent magnet rings and axial magnetized permanent magnet rings. Guided by this permanent magnet system, the 1 GHz compact coaxial relativistic backward wave oscillator is simulated using the 2.5D fully electromagnetic particle-in-cell code, KARAT. Typical simulation results show that, with the 320 kV, 2.52 kA electron beam, the microwave is generated with power of 245 MW and the interaction efficiency is about 30%. The result is valuable for designing a compact low-band HPM sources. (authors)

  8. Space-Qualified Traveling-Wave Tube

    Science.gov (United States)

    Wilson, Jeffrey D.; Krawczyk, Richard; Simons, Rainee N.; Williams, Wallace D.; Robbins, Neal R.; Dibb, Daniel R.; Menninger, William L.; Zhai, Xiaoling; Benton, Robert T.

    2010-01-01

    The L-3 Communications Electron Technologies, Inc. Model 999HA traveling-wave tube (TWT), was developed for use as a high-power microwave amplifier for high-rate transmission of data and video signals from deep space to Earth (see figure). The 999HA is a successor to the 999H a non-space qualified TWT described in High-Power, High-Efficiency Ka-Band Traveling-Wave Tube (LEW-17900-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 32. Operating in the 31.8-to-32.3 GHz frequency band, the 999HA has been shown to generate 252 W of continuous- wave output power at 62 percent overall power efficiency a 75-percent increase in output power over the 999H. The mass of the 999HA is 35 percent less than that of the 999H. Moreover, taking account of the elimination of a Faraday cage that is necessary for operation of the 999H but is obviated by a redesign of high-voltage feed-throughs for the 999HA, the overall reduction in mass becomes 57 percent with an 82 percent reduction in volume. Through a series of rigorous tests, the 999HA has been qualified for operation aboard spacecraft with a lifetime exceeding seven years. Offspring of the 999HA will fly on the Kepler and Lunar Reconnaissance Orbiter missions.

  9. A tunable relativistic backward wave oscillator based on changing concentration of the filling dielectric

    Science.gov (United States)

    Zhou, Hongyu; Liu, Lie; Zhao, Xuelong; Cai, Dan

    2015-04-01

    The tunable capability expands the application fields of backward wave oscillator (BWO), especially for large range modulation. This paper presents analysis, PIC simulation, and preliminary design of a novel relativistic BWO which achieves the purpose of modulation among three or more frequencies within two bands. A new dielectric slow-wave structure (SWS) with hollow section was designed in the novel BWO instead of the conventional SWS with fixed solid conductors. The wide range of adjustment of propagation constant and output frequency could be easily achieved by modulating the concentration (permittivity) of the dielectric filled in the hollow section. The results of PIC simulation show the output has three stable situations at two bands with a magnetic field of 3T: 6.9 GHz, 0.9 GW; 7.3 GHz, 1.1 GW; and 10.0 GHz, 1 GW. The specific permittivities of the corresponding SWSs are 15.7, 34.3, and 42.0, respectively.

  10. Investigation of a K-band large coaxial relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    A K-band large coaxial relativistic backward wave oscillator has been investigated by the 2.5-D particle-in-cell code. This device can generate high-power microwave at a constant frequency with a constant efficiency by increasing the radius of the electron beam and the average radius of the slow-wave structure. The simulation results show that the power conversion efficiency can reach 38.8% at the frequency of 25.48 GHz with the output power of 1.65 GW, while the electron beam has the energy of 196 kV and carries the current of 21.6 kA guided by the magnetic field of 2.5 T

  11. Design and Realization Aspects of 1-THz Cascade Backward Wave Amplifier Based on Double Corrugated Waveguide

    DEFF Research Database (Denmark)

    Paoloni, Claudio; Di Carlo, Aldo; Bouamrane, Fayçal;

    2013-01-01

    The design and fabrication challenges in the first ever attempt to realize a 1-THz vacuum tube amplifier are described. Implementation of innovative solutions including a slow-wave structure in the form of a double corrugated waveguide, lateral tapered input and output couplers, deep X-ray LIGA f...

  12. Experimental observation of sub-terahertz backward-wave amplification in a multi-level microfabricated slow-wave circuit

    Energy Technology Data Exchange (ETDEWEB)

    Baik, Chan-Wook, E-mail: cw.baik@samsung.com; Ahn, Ho Young; Kim, Yongsung; Lee, Jooho; Hong, Seogwoo; Lee, Sang Hun; Choi, Jun Hee; Kim, Sunil; Kim, Jong Min; Hwang, Sungwoo [Samsung Advanced Institute of Technology, Suwon 443-803 (Korea, Republic of); Jeon, So-Yeon; Yu, SeGi [Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Collins, George; Read, Michael E.; Lawrence Ives, R. [Calabazas Creek Research, Inc., San Mateo, California 94404-1010 (United States)

    2015-11-09

    In our earlier paper dealing with dispersion retrieval from ultra-deep, reactive-ion-etched, slow-wave circuits on silicon substrates, it was proposed that splitting high-aspect-ratio circuits into multilevels enabled precise characterization in sub-terahertz frequency regime. This achievement prompted us to investigate beam-wave interaction through a vacuum-sealed integration with a 15-kV, 85-mA, thermionic, electron gun. Our experimental study demonstrates sub-terahertz, backward-wave amplification driven by an external oscillator. The measured output shows a frequency downshift, as well as power amplification, from beam loading even with low beam perveance. This offers a promising opportunity for the development of terahertz radiation sources, based on silicon technologies.

  13. Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Yan; Chen, Changhua; Sun, Jun; Shi, Yanchao; Ye, Hu; Wu, Ping; Li, Shuang; Xiong, Xiaolong [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2015-11-07

    This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.

  14. Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

    Science.gov (United States)

    Teng, Yan; Chen, Changhua; Sun, Jun; Shi, Yanchao; Ye, Hu; Wu, Ping; Li, Shuang; Xiong, Xiaolong

    2015-11-01

    This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.

  15. Influence of voltage rise time on microwave generation in relativistic backward wave oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ping; Deng, Yuqun [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China); Sun, Jun; Teng, Yan; Shi, Yanchao; Chen, Changhua [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2015-10-15

    In relativistic backward wave oscillators (RBWOs), although the slow wave structure (SWS) and electron beam determine the main characteristics of beam-wave interaction, many other factors can also significantly affect the microwave generation process. This paper investigates the influence of voltage rise time on beam-wave interaction in RBWOs. Preliminary analysis and PIC simulations demonstrate if the voltage rise time is moderately long, the microwave frequency will gradually increase during the startup process until the voltage reaches its amplitude, which can be explained by the dispersion relation. However, if the voltage rise time is long enough, the longitudinal resonance of the finitely-long SWS will force the RBWO to work with unwanted longitudinal modes for a while and then gradually hop to the wanted longitudinal mode, and this will lead to an impure microwave frequency spectrum. Besides, a longer voltage rise time will delay the startup process and thus lead to a longer microwave saturation time. And if unwanted longitudinal modes are excited due to long voltage rise time, the microwave saturation time will be further lengthened. Therefore, the voltage rise time of accelerators adopted in high power microwave technology should not be too long in case unwanted longitudinal modes are excited.

  16. Influence of voltage rise time on microwave generation in relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    In relativistic backward wave oscillators (RBWOs), although the slow wave structure (SWS) and electron beam determine the main characteristics of beam-wave interaction, many other factors can also significantly affect the microwave generation process. This paper investigates the influence of voltage rise time on beam-wave interaction in RBWOs. Preliminary analysis and PIC simulations demonstrate if the voltage rise time is moderately long, the microwave frequency will gradually increase during the startup process until the voltage reaches its amplitude, which can be explained by the dispersion relation. However, if the voltage rise time is long enough, the longitudinal resonance of the finitely-long SWS will force the RBWO to work with unwanted longitudinal modes for a while and then gradually hop to the wanted longitudinal mode, and this will lead to an impure microwave frequency spectrum. Besides, a longer voltage rise time will delay the startup process and thus lead to a longer microwave saturation time. And if unwanted longitudinal modes are excited due to long voltage rise time, the microwave saturation time will be further lengthened. Therefore, the voltage rise time of accelerators adopted in high power microwave technology should not be too long in case unwanted longitudinal modes are excited

  17. Influence of voltage rise time on microwave generation in relativistic backward wave oscillator

    Science.gov (United States)

    Wu, Ping; Sun, Jun; Teng, Yan; Deng, Yuqun; Shi, Yanchao; Chen, Changhua

    2015-10-01

    In relativistic backward wave oscillators (RBWOs), although the slow wave structure (SWS) and electron beam determine the main characteristics of beam-wave interaction, many other factors can also significantly affect the microwave generation process. This paper investigates the influence of voltage rise time on beam-wave interaction in RBWOs. Preliminary analysis and PIC simulations demonstrate if the voltage rise time is moderately long, the microwave frequency will gradually increase during the startup process until the voltage reaches its amplitude, which can be explained by the dispersion relation. However, if the voltage rise time is long enough, the longitudinal resonance of the finitely-long SWS will force the RBWO to work with unwanted longitudinal modes for a while and then gradually hop to the wanted longitudinal mode, and this will lead to an impure microwave frequency spectrum. Besides, a longer voltage rise time will delay the startup process and thus lead to a longer microwave saturation time. And if unwanted longitudinal modes are excited due to long voltage rise time, the microwave saturation time will be further lengthened. Therefore, the voltage rise time of accelerators adopted in high power microwave technology should not be too long in case unwanted longitudinal modes are excited.

  18. Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz

  19. Experimental study of an X-band phase-locked relativistic backward wave oscillator

    Science.gov (United States)

    Wu, Y.; Li, Z. H.; Xu, Z.

    2015-11-01

    To achieve high power microwave combined with high frequency band, an X-band phase-locked relativistic backward wave oscillator (RBWO) is proposed and investigated theoretically and experimentally using a modulated electron beam. In the device, an overmoded input cavity and a buncher cavity are employed to premodulate the electron beam. Particle-in-cell simulation shows that an input power of 90 kW is sufficient to lock the frequency and phase of 1.5 GW output microwave with the locking bandwidth of 60 MHz. Moreover, phase and frequency locking of an RBWO has been accomplished experimentally with an output power of 1.5 GW. The fluctuation of the relative phase difference between output microwave and input RF signal is less than ±20° with the locking duration of about 50 ns. The input RF power required to lock the oscillator is only 90 kW.

  20. Experimental study of an X-band phase-locked relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    To achieve high power microwave combined with high frequency band, an X-band phase-locked relativistic backward wave oscillator (RBWO) is proposed and investigated theoretically and experimentally using a modulated electron beam. In the device, an overmoded input cavity and a buncher cavity are employed to premodulate the electron beam. Particle-in-cell simulation shows that an input power of 90 kW is sufficient to lock the frequency and phase of 1.5 GW output microwave with the locking bandwidth of 60 MHz. Moreover, phase and frequency locking of an RBWO has been accomplished experimentally with an output power of 1.5 GW. The fluctuation of the relative phase difference between output microwave and input RF signal is less than ±20° with the locking duration of about 50 ns. The input RF power required to lock the oscillator is only 90 kW

  1. Emittance measurement of a DC gun for Smith-Purcell Backward Wave Oscillator FEL

    International Nuclear Information System (INIS)

    A Terahertz light source using Smith-Purcell Backward Wave Oscillator FEL(S-P BWO-FEL) has been studied at Laboratory of Nuclear Science, Tohoku University. The DC gun employs a high voltage of 50 kV to extract electrons, which is suitable to drive S-P BWO-FEL. A numerical simulation using a 3-D finite deference time domain (FDTD) method implies the S-P BWO-FEL oscillation at the terahertz wavelength region. Emittance measurement has been performed by means of the double slit method. The deduced normalized rms emittance is about 2πmm mrad. We will present the result of emittance measurement and analysis results. (author)

  2. An X-band phase-locked relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    For the purpose of coherent high power microwave combining at high frequency band, an X-band phase-locked relativistic backward wave oscillator is presented and investigated. The phase-locking of the oscillator is accomplished by modulation of the electron beam before it reaches the oscillator. To produce a bunched beam with an acceptable injected RF power requirement, an overmoded input cavity is employed to provide initial density modulation. And a buncher cavity is introduced to further increase the modulation depth. When the beam enters the oscillator, the modulation depth is enough to lock the frequency and phase of the output microwave generated by the oscillator. Particle-in-cell simulation shows that an input power of 90 kW is sufficient to lock the frequency and phase of 1.5 GW output microwave with locking bandwidth of 60 MHz

  3. Optimization of relativistic backward wave oscillator with non-uniform slow wave structure and a resonant reflector

    International Nuclear Information System (INIS)

    This letter optimizes synchronously 18 parameters of a relativistic backward wave oscillator with non-uniform slow wave structure (SWS) and a resonant reflector by using the parallel genetic algorithms and particle-in-cell simulation. The optimization results show that the generation efficiency of microwave from the electron beam has increased 32% compared to that of the original device. After optimization, the electromagnetic mode propagating in the resonant changes from the original TM020 mode of reflector to higher-order TM021 mode, which has a high reflection coefficient in a broader frequency range than that of the former. The modulation of current inside the optimized device is much deeper than that in the original one. The product of the electric field and current is defined. Observing this product, it is found that the interaction of the electron beam with the electromagnetic wave in the optimized device is much stronger than that in the original device, and at the rear part of SWS of the optimized device, the electron beam dominantly gives out the energy to the electromagnetic wave, leading to the higher generation efficiency of microwave than that of the original device

  4. Shock wave effects on shut-off-rod guide tubes

    International Nuclear Information System (INIS)

    Experimental and analytical investigations were made of the sudden loading of calandria and shut-off-rod guide tubes by an incident shock wave in water. The objective was to assess the possibility of tube collapse due to passage of a shock wave generated by a hypothesized pressure tube rupture in a pressure tube reactor. At the highest experimental shock strength (approximately 8 MPa) the measured deformation of zircaloy guide and calandria tubes was elastic even when the latter were air-filled. However, air-filled aluminium calandria tubes buckled at about 1 MPa shock strength. Numerical analysis, using an explicit finite difference code suitable for fluid-structure interaction was applied to unperforated fluid-filled tubes, for a shock strength of 10 MPa. This simulation showed that the shock accelerates the tube quickly to the velocity of the water so that no elastic deformation occurs. It appears that shut-off-rod guide tubes are unlikely to be collapsed by passage of a shock wave arising from a single pressure tube rupture. An adjacent calandria tube, being gas filled, would be more vulnerable to collapse though this was not demonstrated with zircaloy tubes

  5. Low frequency wave modes of liquid-filled flexible tubes

    Science.gov (United States)

    Chou, Yuan-Fang; Peng, Tzu-Huan

    2015-09-01

    Many canals in the human body are liquid-filled thin wall flexible tubes. In general the P-wave and S-wave velocities of tube material are much slower than the sound velocity of the liquid. It is interested to study the dynamic deformation of the wall caused by pressure fluctuation of liquid. In the low frequency range, the liquid pressure is essentially axial symmetric. Therefore, axial symmetric wave propagation modes are investigated. The calculated spectrum shows there are two modes with zero frequency limit. Phase velocities of these two modes are much smaller than the sound velocity of the liquid. They are also slower than the P-wave velocity of the tube material. At very low wave number, radial displacements of both liquid particles and tube are very small compared to their axial counter parts. As the frequency goes higher, boundary waves are observed.

  6. A broadband gyrotron backward-wave oscillator with tapered interaction structure and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, G. D.; Chang, P. C.; Chiang, W. Y.; Lin, P. N.; Kao, S. H.; Lin, Y. N.; Huang, Y. J.; Barnett, L. R.; Chu, K. R., E-mail: krchu@yahoo.com.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Chen, H. Y.; Fan, C. T. [Wave Power Technology, 232 Youyi Road, Zhunan, Miaoli, Taiwan (China)

    2015-11-15

    The gyro-monotron and gyrotron backward-wave oscillator (gyro-BWO) are the two oscillator versions of gyrotrons. While serving different functions, they are also radically different in the RF field formation mechanisms. The gyro-monotron RF field profile is essentially fixed by the resonant interaction structure, while the gyro-BWO possesses an extra degree of freedom in that the axial RF field profile is self-determined by the beam-wave interaction in a waveguide structure. The present study examines ways to utilize the latter feature for bandwidth broadening with a tapered magnetic field, while also employing a tapered waveguide to enhance the interaction efficiency. We begin with a mode competition analysis, which suggests the theoretical feasibility of broadband frequency tuning in single-mode operation. It is then shown in theory that, by controlling the RF field profile with an up- or down-tapered magnetic field, the gyro-BWO is capable of efficient operation with a much improved tunable bandwidth.

  7. A tunable relativistic backward wave oscillator based on changing concentration of the filling dielectric

    International Nuclear Information System (INIS)

    The tunable capability expands the application fields of backward wave oscillator (BWO), especially for large range modulation. This paper presents analysis, PIC simulation, and preliminary design of a novel relativistic BWO which achieves the purpose of modulation among three or more frequencies within two bands. A new dielectric slow-wave structure (SWS) with hollow section was designed in the novel BWO instead of the conventional SWS with fixed solid conductors. The wide range of adjustment of propagation constant and output frequency could be easily achieved by modulating the concentration (permittivity) of the dielectric filled in the hollow section. The results of PIC simulation show the output has three stable situations at two bands with a magnetic field of 3T: 6.9 GHz, 0.9 GW; 7.3 GHz, 1.1 GW; and 10.0 GHz, 1 GW. The specific permittivities of the corresponding SWSs are 15.7, 34.3, and 42.0, respectively

  8. Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator

    International Nuclear Information System (INIS)

    The RF breakdown of the slow wave structure (SWS), which will lead to the generation of the wall plasma, is an important cause for pulse shortening in relativistic backward wave oscillators. Although many researchers have performed profitable studies about this issue, the influence mechanism of this factor on the microwave generation still remains not-so-clear. This paper simplifies the wall plasma with an “effective” permittivity and researches its influence on the microwave frequency and power. The dispersion relation of the SWS demonstrates that the introduction of the wall plasma will move the dispersion curves upward to some extent, which is confirmed by particle-in-cell (PIC) simulations and experiments. The plasma density and volume mainly affect the dispersion relation at the upper and lower frequency limits of each mode, respectively. Meanwhile, PIC simulations show that even though no direct power absorption exists since the wall plasma is assumed to be static, the introduction of the wall plasma may also lead to the decrease in microwave power by changing the electrodynamic property of the SWS

  9. Plasma-filled rippled wall rectangular backward wave oscillator driven by sheet electron beam

    Indian Academy of Sciences (India)

    A Hadap; J Mondal; K C Mittal; K P Maheshwari

    2011-03-01

    Performance of the backward wave oscillator (BWO) is greatly enhanced with the introduction of plasma. Linear theory of the dispersion relation and the growth rate have been derived and analysed numerically for plasma-filled rippled wall rectangular waveguide driven by sheet electron beam. To see the effect of plasma on the TM01 cold wave structure mode and on the generated frequency, the parameters used are: relativistic factor = 1.5 (i.e. / = 0.741), average waveguide height 0 = 1.445 cm, axial corrugation period 0 = 1.67 cm, and corrugation amplitude = 0.225 cm. The plasma density is varied from zero to 2 × 1012 cm-3. The presence of plasma tends to raise the TM01 mode cut-off frequency (14 GH at 2 × 1012 cm-3 plasma density) relative to the vacuum cut-off frequency (5 GH) which also causes a decrease in the group velocity everywhere, resulting in a flattening of the dispersion relation. With the introduction of plasma, an enhancement in absolute instability was observed.

  10. Inspection of tubing defects with ultrasonic guided waves

    International Nuclear Information System (INIS)

    The purpose of this study is to show the utility of ultrasonic guided waves in 439 stainless steel heat exchanger and Inconel steam generator tubing inspection. Phase velocity and group velocity dispersion curves for the longitudinal and flexural modes of a sample Inconel steam generator tube were presented. In experimental studies, ultrasonic guided wave applications were demonstrated for man made flaws. For the detection of EDM wears under a tube support plate in the heater exchanger tubing, a bore probe generated axisymmetric longitudinal guided wave modes in the tubing. For the detection and sizing of circumferential Laser notches in Inconel steam generator tubes, a variable angle beam transducer set up was used. Excellent detection results were demonstrated for EDM wears and Laser Notches with various modes and L(0,1) modes, respectively. Circumferential sizing of Laser notches was achieved with L(0,1) mode at 3.5 MHz.

  11. A Low Cost Traveling Wave Tube for Wireless Communications

    Science.gov (United States)

    Vancil, Bernard Kenneth; Wintucky, Edwin G.; Williams, W. D. (Technical Monitor)

    2002-01-01

    Demand for high data rate wireless communications is pushing up amplifier power, bandwidth and frequency requirements. Some systems are using vacuum electron devices again because solid-state power amplifiers are not able to efficiently meet the new requirements. The traveling wave tube is the VED of choice because of its excellent broadband capability as well as high power efficiency and frequency. But TWTs are very expensive on a per watt basis below about 200 watts of output power. We propose a new traveling wave tube that utilizes cathode ray tube construction technology and electrostatic focusing. We believe the tube can be built in quantity for under $1,000 each. We discuss several traveling wave tube slow wave circuits that lend themselves to the new construction. We will present modeling results and data on prototype devices.

  12. Dynamics Calculation of Travel Wave Tube

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    During the dynamics calculating of the travel tube, we must obtain the field map in the tube. The field map can be affected by not only the beam loading, but also the attenuation coefficient. The calculation of the attenuation coefficient

  13. A millimeter wave relativistic backward wave oscillator operating in TM{sub 03} mode with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Hu; Wu, Ping [Department of Engineering Physics, Tsinghua University, Beijing100084 (China); Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an Shaanxi 710024 (China); Teng, Yan; Chen, Changhua; Ning, Hui; Song, Zhimin; Cao, Yibing [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an Shaanxi 710024 (China)

    2015-06-15

    A V-band overmoded relativistic backward wave oscillator (RBWO) guided by low magnetic field and operating on a TM{sub 03} mode is presented to increase both the power handling capacity and the wave-beam interaction conversion efficiency. Trapezoidal slow wave structures (SWSs) with shallow corrugations and long periods are adopted to make the group velocity of TM{sub 03} mode at the intersection point close to zero. The coupling impedance and diffraction Q-factor of the RBWO increase, while the starting current decreases owing to the reduction of the group velocity of TM{sub 03} mode. In addition, the TM{sub 03} mode dominates over the other modes in the startup of the oscillation. Via numerical simulation, the generation of the microwave pulse with an output power of 425 MW and a conversion efficiency of 32% are achieved at 60.5 GHz with an external magnetic field of 1.25 T. This RBWO can provide greater power handling capacity when operating on the TM{sub 03} mode than on the TM{sub 01} mode.

  14. A millimeter wave relativistic backward wave oscillator operating in TM03 mode with low guiding magnetic field

    International Nuclear Information System (INIS)

    A V-band overmoded relativistic backward wave oscillator (RBWO) guided by low magnetic field and operating on a TM03 mode is presented to increase both the power handling capacity and the wave-beam interaction conversion efficiency. Trapezoidal slow wave structures (SWSs) with shallow corrugations and long periods are adopted to make the group velocity of TM03 mode at the intersection point close to zero. The coupling impedance and diffraction Q-factor of the RBWO increase, while the starting current decreases owing to the reduction of the group velocity of TM03 mode. In addition, the TM03 mode dominates over the other modes in the startup of the oscillation. Via numerical simulation, the generation of the microwave pulse with an output power of 425 MW and a conversion efficiency of 32% are achieved at 60.5 GHz with an external magnetic field of 1.25 T. This RBWO can provide greater power handling capacity when operating on the TM03 mode than on the TM01 mode

  15. Traveling-Wave Tube Efficiency Enhancement

    Science.gov (United States)

    Dayton, James A., Jr.

    2011-01-01

    Traveling-wave tubes (TWT's) are used to amplify microwave communication signals on virtually all NASA and commercial spacecraft. Because TWT's are a primary power user, increasing their power efficiency is important for reducing spacecraft weight and cost. NASA Glenn Research Center has played a major role in increasing TWT efficiency over the last thirty years. In particular, two types of efficiency optimization algorithms have been developed for coupled-cavity TWT's. The first is the phase-adjusted taper which was used to increase the RF power from 420 to 1000 watts and the RF efficiency from 9.6% to 22.6% for a Ka-band (29.5 GHz) TWT. This was a record efficiency at this frequency level. The second is an optimization algorithm based on simulated annealing. This improved algorithm is more general and can be used to optimize efficiency over a frequency bandwidth and to provide a robust design for very high frequency TWT's in which dimensional tolerance variations are significant.

  16. Dual-band relativistic backward wave oscillators based on a single beam and dual beams

    Science.gov (United States)

    Ting, Wang; Jian-de, Zhang; Bao-liang, Qian; Xiao-ping, Zhang

    2010-04-01

    Two types of relativistic backward wave oscillators (RBWOs) used to produce dual-band microwaves are proposed and investigated by use of the particle-in-cell (PIC) simulation code KARAT [V. P. Tarakanov, User's Manual for Code Karat (Berkeley Research Associates, Springfield, VA, 1992)]. The first type of RBWO, for generation of C-band and X-band microwaves, is designed based on a single beam and a sectioned structure. With an electron beam of 650 keV and 5.0 kA guided by a magnetic field of 2.0 T, an average power of 380 MW with a total power conversion efficiency of 11.7% is obtained and the frequencies are 5.48 and 9.60 GHz, respectively. By changing the distance between the two sections, single-band oscillations are realized with higher power conversion efficiency than that of the dual-band oscillation. The second type, based on a coaxial structure and dual parallel annular beams, is a dual-band RBWO designed with separated beam-wave interaction regions for generation of C-band and X-band microwaves. With a dual beam of 650 keV and 11.8 kA (the outer beam current is 6.4 kA and inner beam current is 5.4 kA) guided by a magnetic field of 2.0 T, an output power of 1400 MW with a total power conversion efficiency of 18.3% is generated and the frequencies are 4.60 and 8.40 GHz, respectively. PIC simulations demonstrate that the two beam-wave interaction regions operate independently. The two types of dual-band RBWO are also compared and analyzed.

  17. Axial motion of collector plasma in a relativistic backward wave oscillator

    Science.gov (United States)

    Xiao, Renzhen; Chen, Changhua; Deng, Yuqun; Cao, Yibing; Sun, Jun; Li, Jiawei

    2016-06-01

    In this paper, it is proposed that plasma formed at the collector may drift back to the cathode and cause pulse shortening of the relativistic backward wave oscillator. Theoretical analysis shows that the axial drift velocity of plasma ions can be up to 5 mm/ns due to the presence of space charge potential provided by an intense relativistic electron beam. Particle-in-cell simulations indicate that the plasma electrons are initially trapped around the collector surface. With the accumulation of the plasma ions, a large electrostatic field forms and drives the plasma electrons to overcome the space charge potential and enter the beam-wave interaction region along the magnetic field lines. As a result, the beam current modulation is disturbed and the output microwave power falls rapidly. The plasma ions move in the beam-wave interaction region with an average axial velocity of 5-8 mm/ns. After the plasma ions reach the diode region, the emitted current at the cathode rises due to the charge neutralizations by the ions. The impedance collapse leads to further decrease of the microwave power. In experiments, when the diode voltage and beam current were 850 kV and 9.2 kA, and the collector radius was 2.15 cm, the output microwave power was 2.4 GW with a pulse width of less than 20 ns. The ion drift velocity was estimated to be about 5 mm/ns. After an improved collector with 3.35 cm radius was adopted, the pulse width was prolonged to more than 30 ns.

  18. Intense microwave radiation from a repetitive backward-wave oscillator driven by a relativistic electron beam

    International Nuclear Information System (INIS)

    High-power microwaves (20--50 MW, 8.8 GHz) have been produced in repetitive pulses at a rate of 10 Hz in a joint experiment by Harry Diamond Laboratories and Sandia National Laboratories. These microwaves were produced with Harry Diamond Laboratories' backward-wave oscillator (BWO), driven by a 600 to 800-kV, 2-kA electron beam, which was guided by a magnetic field of variable strength from 0.75 to 1.05 T. The beam was produced with Sandia National Laboratories' repetitive high-voltage pulser, RAVEN. Microwave diagnostic instrumentation included a directional coupler, heterodyne receiver, dispersive waveguide delay line, and calorimeter. In a train of 10 pulses, the shape, duration, and amplitude of the injection voltage and beam current remained unchanged for each individual pulse. The intensity of the final microwave pulse was 40% of the first pulse, and the final pulse was 80% as long as the first. The basic pulse shape remained unchanged. More intense microwave radiation should be obtained with a higher magnetic field. Computer simulations using the code magic predicted the characteristic dip in the magnetic field strength versus microwave power output curve. Code predictions of microwave power output with a warm beam agree very well with experimental results. Finally, cyclotron resonance is presented in a descriptive fashion to account for the power output dip. This is the first experiment with a repetitively pulsed high-power BWO driven by a relativistic electron beam performed outside the USSR

  19. Preliminary experimental investigation of a dual-band relativistic backward wave oscillator with dual beams

    International Nuclear Information System (INIS)

    A dual-band relativistic backward wave oscillator with dual electron beams generating C-band and X-band microwaves is investigated experimentally. The frequencies, powers, and radiation patterns of the dual-band microwaves are measured. With the diode voltage of 657 kV and the total beam current of 14 kA guided by a magnetic field of about 1.7 T, the dual-band microwaves are generated with dominant frequencies of 4.58 and 8.30 GHz close to the results from the particle-in-cell simulation. The powers of the C-band and X-band microwaves are 520 and 113 MW, respectively. The effects of variations in the guiding magnetic field and diode voltage on the powers of the dual-band microwaves are presented and discussed. The radiation patterns of the dual-band microwaves from the radiating antenna are tested both corresponding to a TM01 mode and the independency of the operation processes of them is discussed.

  20. Lifetime experimental study of graphite cathode for relativistic backward wave oscillator

    Science.gov (United States)

    Wu, Ping; Sun, Jun; Chen, Changhua

    2016-07-01

    Graphite cathodes are widely used due to their good emission properties, especially their long lifetime. Some previous papers have researched their lifetime under certain conditions and uncovered some important phenomena. This paper is dedicated to research the lifetime of the graphite cathode under higher power. In the lifetime test, the voltage and current amplitudes are about 970 kV and 9.7 kA, respectively. The repetition rate is 20 Hz. An X-band relativistic backward wave oscillator is used to generate high power microwave by utilizing the electron beam energy. The experimental results demonstrate that the emission property of the graphite cathode remains quite stable during 105 pulses, despite some slight deteriorations regarding the beam and microwave parameters. The macroscopic morphology change of the cathode blade due to material evaporation is observed by a laser microscope. The mass loss of the graphite cathode is about 60 μg/C. Meanwhile, the observation by a scanning electron microscope uncovers that the original numerous flaky micro-structures are totally replaced by a relatively smooth surface at the mid region of the cathode blade and a large number of new micro-protrusions at the blade edges during the lifetime test.

  1. Microfabricated, 94 GHz, 25 W, Helical Traveling Wave Tube Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Teraphysics Corporation proposes to design and develop a microfabricated, 94 GHz, 25 W traveling wave tube (TWT) with 53% efficiency for NASA applications. In Phase...

  2. Detonation Initiation in a Tube via Imploding Toroidal Shock Waves

    OpenAIRE

    Jackson, S. I.; Shepherd, J. E.

    2008-01-01

    The effectiveness of imploding waves at detonation initiation of stoichiometric ethylene- and propane–oxygen– nitrogen mixtures in a tube was investigated. Implosions were driven by twice-shocked gas located at the end of a shock tube, and wave strength was varied to determine the critical conditions necessary for initiation as a function of diluent concentration for each fuel. Hydrocarbon–air mixtures were not detonated due to facility limitations, however, detonations were achie...

  3. Pulsed current wave shaping with a transmission line by utilizing superposition of a forward and a backward voltage wave for fast capillary Z-pinch discharge

    International Nuclear Information System (INIS)

    By using a water transmission line, current wave shaping was demonstrated for a fast capillary Z-pinch discharge recombination soft x-ray laser study. The pulsed power system consists of a water capacitor, a gap switch, a transmission line, and a capillary plasma load. A voltage wave initiated at the water capacitor propagates toward the capillary load through the transmission line. Control of the pulse delay that occurred in the transmission line provides the superposition of the forward and the backward voltage waves effectively in order to perform current wave shaping with higher current amplitude and rapid current decay.

  4. Dual-cavity mode converter for a fundamental mode output in an over-moded relativistic backward-wave oscillator

    International Nuclear Information System (INIS)

    A dual-cavity TM02–TM01 mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM01 mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM01 mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM01 mode feedback

  5. Design and numerical simulation of a high power capacity relativistic backward wave oscillator with an electron collection cavity

    Science.gov (United States)

    Li, Xiaoze; Ye, Hu; Zhang, Yuchuan; Song, Wei; Su, Jiancang; Zhang, Ligang; Tan, Weibing; Hu, Xianggang; Zhu, Xiaoxin; Shen, Zhiyuan; Zhang, Min

    2016-05-01

    A high power capacity relativistic backward wave oscillator with an electron collection cavity (ECC) placed at the downstream of the slow wave structure (SWS) is presented. The breakdown threshold is increased, and the density of seed electron is suppressed by preventing the secondary electron, plasma, and powder generated from the bombardment of spent electron beam on the surface of the collector drifting to the extractor and beam-wave interaction region. The maximum longitudinal electric field in the device is reduced through extension of the span between electron beam and slow wave structure and weakening the Cerenkov radiation. The conversion efficiency reaches up to 52% owing to enhanced transit time radiation taking place at the entrance of the ECC. The maximum longitudinal electric field is 1.1 MV/cm on the surface of SWSs when the output power is 7.3 GW and the power capacity improves significantly.

  6. Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures

    International Nuclear Information System (INIS)

    We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections is adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the size of the period cell.

  7. Modulated pressure waves in large elastic tubes.

    Science.gov (United States)

    Mefire Yone, G R; Tabi, C B; Mohamadou, A; Ekobena Fouda, H P; Kofané, T C

    2013-09-01

    Modulational instability is the direct way for the emergence of wave patterns and localized structures in nonlinear systems. We show in this work that it can be explored in the framework of blood flow models. The whole modified Navier-Stokes equations are reduced to a difference-differential amplitude equation. The modulational instability criterion is therefore derived from the latter, and unstable patterns occurrence is discussed on the basis of the nonlinear parameter model of the vessel. It is found that the critical amplitude is an increasing function of α, whereas the region of instability expands. The subsequent modulated pressure waves are obtained through numerical simulations, in agreement with our analytical expectations. Different classes of modulated pressure waves are obtained, and their close relationship with Mayer waves is discussed. PMID:24089964

  8. Direct observation of isolated Damon-Eshbach and backward volume spin-wave packets in ferromagnetic microstripes.

    Science.gov (United States)

    Wessels, Philipp; Vogel, Andreas; Tödt, Jan-Niklas; Wieland, Marek; Meier, Guido; Drescher, Markus

    2016-01-01

    The analysis of isolated spin-wave packets is crucial for the understanding of magnetic transport phenomena and is particularly interesting for applications in spintronic and magnonic devices, where isolated spin-wave packets implement an information processing scheme with negligible residual heat loss. We have captured microscale magnetization dynamics of single spin-wave packets in metallic ferromagnets in space and time. Using an optically driven high-current picosecond pulse source in combination with time-resolved scanning Kerr microscopy probed by femtosecond laser pulses, we demonstrate phase-sensitive real-space observation of spin-wave packets in confined permalloy (Ni80Fe20) microstripes. Impulsive excitation permits extraction of the dynamical parameters, i.e. phase- and group velocities, frequencies and wave vectors. In addition to well-established Damon-Eshbach modes our study reveals waves with counterpropagating group- and phase-velocities. Such unusual spin-wave motion is expected for backward volume modes where the phase fronts approach the excitation volume rather than emerging out of it due to the negative slope of the dispersion relation. These modes are difficult to excite and observe directly but feature analogies to negative refractive index materials, thus enabling model studies of wave propagation inside metamaterials. PMID:26906113

  9. Direct observation of isolated Damon-Eshbach and backward volume spin-wave packets in ferromagnetic microstripes

    Science.gov (United States)

    Wessels, Philipp; Vogel, Andreas; Tödt, Jan-Niklas; Wieland, Marek; Meier, Guido; Drescher, Markus

    2016-02-01

    The analysis of isolated spin-wave packets is crucial for the understanding of magnetic transport phenomena and is particularly interesting for applications in spintronic and magnonic devices, where isolated spin-wave packets implement an information processing scheme with negligible residual heat loss. We have captured microscale magnetization dynamics of single spin-wave packets in metallic ferromagnets in space and time. Using an optically driven high-current picosecond pulse source in combination with time-resolved scanning Kerr microscopy probed by femtosecond laser pulses, we demonstrate phase-sensitive real-space observation of spin-wave packets in confined permalloy (Ni80Fe20) microstripes. Impulsive excitation permits extraction of the dynamical parameters, i.e. phase- and group velocities, frequencies and wave vectors. In addition to well-established Damon-Eshbach modes our study reveals waves with counterpropagating group- and phase-velocities. Such unusual spin-wave motion is expected for backward volume modes where the phase fronts approach the excitation volume rather than emerging out of it due to the negative slope of the dispersion relation. These modes are difficult to excite and observe directly but feature analogies to negative refractive index materials, thus enabling model studies of wave propagation inside metamaterials.

  10. Shock Wave Observation in Narrow Tubes for a Parametric Study on Micro Wave Rotor Design

    Institute of Scientific and Technical Information of China (English)

    Koji Okamoto; Mikiya Araki

    2008-01-01

    Wave rotor is expected to improve the performance of micro gas turbines drastically. In the wave rotor design, the rotor speed is determined principally by the tube length. Therefore, a longer tube is preferable for miniaturized wave rotors to avoid the difficulty in bearings and lubrication system, while it may yield thicker wall boundary layer, shock wave dissipation and so on. In the present study, an experimental apparatus was built to visualize the wave rotor internal flow dynamics in a narrow tube by schlieren method and Laser Doppler Anemometry. In addition, different lengths of the tube were adopted and compared to investigate the effect of wall friction. Finally, 2D numerical simulation was performed and the results were compared with those of experiments.

  11. Design and development of high linearity millimeter wave traveling-wave tube for satellite communications

    Institute of Scientific and Technical Information of China (English)

    何俊; 黄明光; 李现霞; 李海强; 赵磊; 赵建东; 李跃; 赵石雷

    2015-01-01

    The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6◦/dB and 2.5◦/dB, respectively, which are 20.1◦/dB and 1.6◦/dB lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 dBc lower than that of the original tube.

  12. Design and development of high linearity millimeter wave traveling-wave tube for satellite communications

    Science.gov (United States)

    He, Jun; Huang, Ming-Guang; Li, Xian-Xia; Li, Hai-Qiang; Zhao, Lei; Zhao, Jian-Dong; Li, Yue; Zhao, Shi-Lei

    2015-10-01

    The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6°/dB and 2.5°/dB, respectively, which are 20.1°/dB and 1.6°/dB lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 dBc lower than that of the original tube. Project supported by the National Natural Science Foundation of China (Grant No. 61401430).

  13. K-Band Traveling-Wave Tube Amplifier

    Science.gov (United States)

    Force, Dale A.; Simons, Rainee N.; Peterson, Todd T.; Spitsen, Paul C.

    2010-01-01

    A new space-qualified, high-power, high-efficiency, K-band traveling-wave tube amplifier (TWTA) will provide high-rate, high-capacity, direct-to-Earth communications for science data and video gathered by the Lunar Reconnaissance Orbiter (LRO) during its mission. Several technological advances were responsible for the successful demonstration of the K-band TWTA.

  14. On frequency and time domain models of traveling wave tubes

    CERN Document Server

    Théveny, Stéphane; Elskens, Yves

    2016-01-01

    We discuss the envelope modulation assumption of frequency-domain models of traveling wave tubes (TWTs) and test its consistency with the Maxwell equations. We compare the predictions of usual frequency-domain models with those of a new time domain model of the TWT.

  15. Attosecond Interference Induced by Coulomb-Field-Driven Transverse Backward-Scattering Electron Wave-Packets

    CERN Document Server

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Yu, Xianhuan; Yang, Weifeng; Hu, Shilin; Chen, Jing; Xu, SongPo; Chen, YongJu; Quan, Wei; Liu, XiaoJun

    2016-01-01

    A novel and universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a new form of Coulomb-field-driven backward-scattering of photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 attosecond around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or the second return times, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference ...

  16. How Accurate Is Pierce's Theory of Traveling Wave Tube?

    Science.gov (United States)

    Simon, D. H.; Chernin, D.; Wong, P.; Zhang, P.; Lau, Y. Y.; Dong, C. F.; Hoff, B.; Gilgenbach, R. M.

    2015-11-01

    This paper provides a rigorous test of the accuracy of Pierce's classical theory of traveling wave tubes (TWTs). The EXACT dispersion relation for a dielectric TWT is derived, from which the spatial amplification rate, ki, is calculated. This ki is compared with that obtained from Pierce's widely used 3-wave theory and his more general 4-wave theory (which includes the reverse propagating circuit mode). We have used various procedures to extract Pierce's gain parameter C and space charge parameter Q from the exact dispersion relation. We find that, in general, the 3-wave theory is a poor representation to the exact dispersion relation if C >0.05. However, the 4-wave theory gives excellent agreement even for C as high as 0.12 and over more than 20 percent bandwidth, if the quantity (k2 × C3) is evaluated accurately as a function of frequency, and if Q is expanded to first order in the wavenumber k, where Q is the difference between the exact dispersion relation and its 4-wave representation in which Q is set to zero. Similar tests will be performed on the disk-on-rod slow wave TWT, for which the hot tube dispersion relation including all space harmonics has been obtained. Supported by AFOSR FA9550-14-1-0309, FA9550-15-1-0097, AFRL FA9451-14-1-0374, and L-3 Communications.

  17. Numerical Simulations of Backward-to-Forward Leaky-Wave Antenna with Composite Right/Left-Handed Coplanar Waveguide

    International Nuclear Information System (INIS)

    A composite right / left-handed (CRLH) coplanar waveguide (CPW) structure and its leaky-wave antenna (LWA) with continuous backward-to-forward scanning applications are proposed. The structure of the CRLH transmission line (TL) is composed of split-ring resonators (SRRs) for left-handed (LH) series capacitance and short-circuited stubs connected between the CPW central signal line and the ground for LH shunt inductance, while the unavoidable right-handed (RH) parasitic effects series inductance and shunt capacitance are generated by wave propagation through the host transmission line. The dispersion relations are calculated and compared with the equivalent circuit model method and 3D full-wave simulations, which can be used to determine the physical dimensions of the CRLH-CPW, such as in the balanced CRLH-TL case. As a main example, a CRLH-CPW-LWA operating from 1.67 GHz to 1.80 GHz with the dispersion characteristics of the balanced CRLH-TL case shows continuous leakage frequency band (fast wave region) from LH (phase constant β 0, 1.74 0). (fundamental areas of phenomenology (including applications))

  18. Nonlinear fast sausage waves in homogeneous magnetic flux tubes

    Science.gov (United States)

    Mikhalyaev, Badma B.; Ruderman, Michael S.

    2015-12-01

    > We consider fast sausage waves in straight homogeneous magnetic tubes. The plasma motion is described by the ideal magnetohydrodynamic equations in the cold plasma approximation. We derive the nonlinear Schrödinger equation describing the nonlinear evolution of an envelope of a carrier wave. The coefficients of this equation are expressed in terms Bessel and modified Bessel functions. They are calculated numerically for various values of parameters. In particular, we show that the criterion for the onset of the modulational or Benjamin-Fair instability is satisfied. The implication of the obtained results for solar physics is discussed.

  19. Air-coupled detection of the S1-ZGV lamb mode in a concrete plate based on backward wave propagation

    Science.gov (United States)

    Bjurström, H.; Ryden, N.

    2013-01-01

    Impact Echo is commonly used to determine thickness of concrete plate like structures. The method is based on the generation and detection of the plate thickness resonance frequency, where the group velocity of the first higher symmetric Lamb mode goes to zero (S1-ZGV). When using air-coupled microphones as receivers it is hard to determine the correct resonance frequency due to low signal to noise ratio. In this study multichannel signal processing is used to identify the S1-ZGV frequency, based on backward wave propagation instead of the conventional amplitude spectrum approach. The original PDF file of this article, as supplied to AIP Publishing, contained some minor font problems within Figures 1, 4, 7, 8, and 9. An updated PDF file using the correct font within those figures was issued on June 3, 2013. There are no other changes to the scientific content.

  20. An investigation on density wave oscillations in helical coiled tubes

    International Nuclear Information System (INIS)

    Density wave instability in helical coiled tubes has been systematically observed using high pressure ranging from 3.0 to 10.0 Mpa, mass velocity from 400 to 1200 kg/sm2, inlet subcooling from 10 to 120 degrees C and heat flux up to 450 kw/m2. In the experimental research the effects of system pressure, mass velocity, heat flux, inlet subcooling, inlet resistence and exit resistence have been studied. The experimental results show that the density wave oscillation occurred at positive slope part to mass velocity versus total pressure drop curve, the phase difference of the density wave oscillation between the inlet and exit flow rate is approximately 180 degrees. Increasing heat flux, the periods of density wave oscillation decreased. The periods are about 1-2 times the residence time of fluid in the heater, about 3-14s. System presure, inlet subcooling, mass velocity, inlet resistance and exit resistence affected the threshold of density wave oscillation. Increasing the system pressure, mass velocity and inlet resistence, the limit heat flux of density wave oscillation increased. Increasing exit resistence, the limit heat flux decreased. The stability boundary diagrams of the system have been found. In this paper the empirical correlations for predicting the threshold of density wave oscillations are presented

  1. Nonlinear time-dependent simulation of helix traveling wave tubes

    International Nuclear Information System (INIS)

    A one-dimensional nonlinear time-dependent theory for helix traveling wave tubes is studied. A generalized electromagnetic field is applied to the expression of the radio frequency field. To simulate the variations of the high frequency structure, such as the pitch taper and the effect of harmonics, the spatial average over a wavelength is substituted by a time average over a wave period in the equation of the radio frequency field. Under this assumption, the space charge field of the electron beam can be treated by a space charge wave model along with the space charge coefficient. The effects of the radio frequency and the space charge fields on the electrons are presented by the equations of the electron energy and the electron phase. The time-dependent simulation is compared with the frequency-domain simulation for a helix TWT, which validates the availability of this theory. (interdisciplinary physics and related areas of science and technology)

  2. Variations in the chorus source location deduced from fluctuations of the ambient magnetic field: Comparison of Cluster data and the backward wave oscillator model

    Czech Academy of Sciences Publication Activity Database

    Kozelov, B. V.; Demekhov, A. G.; Titova, E. E.; Trakhtengerts, V. Y.; Santolík, Ondřej; Macúšová, Eva; Gurnett, D. A.; Pickett, J. S.

    2008-01-01

    Roč. 113, A6 (2008), A06216/1-A06216/10. ISSN 0148-0227 R&D Projects: GA AV ČR IAA301120601 Grant ostatní: NSF(US) 0307319 Institutional research plan: CEZ:AV0Z30420517 Keywords : chorus emissions * backward-wave oscillator model * VLF chorus * BWO model * wave-particle interaction Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.147, year: 2008

  3. Hydrogen attack evaluation of boiler tube using ultrasonic wave

    International Nuclear Information System (INIS)

    The presence of hydrogen in industrial plants is a source of damage. Hydrogen attack is one such form of degradation and often causing large tube ruptures that necessitate an immediate shutdown. Hydrogen attack may reduce the fracture toughness as well as the strength of steels. This reduction is caused partially by the presence of cavities and microcracks at the grain boundaries. In the past several techniques have been used with limited results. This paper describes the application of an ultrasonic velocity, attenuation and backscatter techniques for detecting the presence of hydrogen damage in utility boiler tubes. Ultrasonic tests showed a decrease in wave velocity and an increase in attenuation. Such results demonstrate the potential for ultrasonic nondestructive testing to quantify damage. Based on this study, recommendations are that both velocity and attenuation be used to detect hydrogen attack in steels.

  4. Comparing the Robustness of High-Frequency Traveling-Wave Tube Slow-Wave Circuits

    Science.gov (United States)

    Chevalier, Christine T.; Wilson, Jeffrey D.; Kory, Carol L.

    2007-01-01

    A three-dimensional electromagnetic field simulation software package was used to compute the cold-test parameters, phase velocity, on-axis interaction impedance, and attenuation, for several high-frequency traveling-wave tube slow-wave circuit geometries. This research effort determined the effects of variations in circuit dimensions on cold-test performance. The parameter variations were based on the tolerances of conventional micromachining techniques.

  5. A Numerical Investigation of Peristaltic Waves in Circular Tubes

    Science.gov (United States)

    Xiao, Q.; Damodaran, M.

    Peristaltic pumping is a process of fluid transport arising from the progressive waves, which travel along the walls of a flexible channel. It is a primary physiological transport mechanism that is inherent in many tubular organs of the human body such as the ureter, the gastro-intestinal tract, the urethra, and so on. Many studies exist in literature with the aim of understanding the characteristics of peristaltic flow under the assumption of low Reynolds number and infinitely long wavelength in a two-dimensional channel. However, peristaltic pumping is also the mechanism used in other industrial applications such as the blood pump for which the Reynolds number has a moderately high value. As studies concerning moderate to high Reynolds number flow in the circular tube are rare in literature, in the present study, the peristaltic flow of an incompressible fluid is numerically simulated using the finite volume method for solving the incompressible Navier-Stokes equations in primitive variable formulation by means of an infinite train of sinusoidal waves traveling along the wall of an axi-symmetric tube. The computational model presented in this work covers a wider range of Reynolds number (0.01-100), wave amplitude (0-0.8), and wavelength (0.01-0.4) than the those attempted in previous studies reported in literature and some new results pertaining to the distribution of velocity, pressure, wall shear stress for different peristaltic flow conditions characterizing flow at moderately higher Reynolds number have been obtained. The effect of the wave amplitude, wavelength, and Reynolds number on the "flow trapping" mechanism induced by peristalsis has also been investigated here for higher ranges of values of the parameters characterizing peristalsis.

  6. Properties of the magnetospheric backward wave oscillator inferred from CLUSTER measurements of VLF chorus elements

    Czech Academy of Sciences Publication Activity Database

    Titova, E.; Demekhov, A.; Kozelov, B.; Santolík, Ondřej; Macúšová, Eva; Rauch, J. L.; Trotignon, J. G.; Gurnett, D.; Pickett, J.

    2012-01-01

    Roč. 117, A8 (2012), A08210/1-A08210/10. ISSN 0148-0227 R&D Projects: GA ČR GAP205/10/2279; GA MŠk(CZ) ME10001 Institutional support: RVO:68378289 Keywords : chorus emission * cyclotron maser * magnetosphere * very low frequency * waves Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.174, year: 2012 http://onlinelibrary.wiley.com/doi/10.1029/2012JA017713/abstract

  7. A $55 Shock Tube for Simulated Blast Waves

    CERN Document Server

    Courtney, Elijah; Courtney, Michael

    2015-01-01

    Shock tubes are commonly employed to test candidate armor materials, validate numerical models, and conduct simulated blast experiments in animal models. As DoD interests desire to field wearable sensors as blast dosimeters, shock tubes may also serve for calibration and testing of these devices. The high blast pressures needed for experimental testing of candidate armors are unnecessary to test these sensors. An inexpensive, efficient, and easily available way of testing these pressure sensors is desirable. It is known that releasing compressed gas suddenly can create a repeatable shock front, and the pressures can be finely tuned by changing the pressure to which the gas is compressed. A Crosman 0.177 caliber air pistol was used (without loading any pellets) to compress and release air in one end of a 24 inch long 3/4 inch diameter standard pipe nipple to simulate a blast wave at the other end of the tube. A variable number of pumps were used to vary the peak blast pressure. As expected, the trials where 10...

  8. Sausage Waves in Transversely Nonuniform Monolithic Coronal Tubes

    Science.gov (United States)

    Lopin, I.; Nagorny, I.

    2015-09-01

    We investigate fast sausage waves in a monolithic coronal magnetic tube, modeled as a local density inhomogeneity with a continuous radial profile. This work is a natural extension of our previous results, obtained for a slab loop model for the case of cylindrical geometry. Using Kneser’s oscillating theorem, we provided the criteria for the existence of trapped and leaky wave regimes as a function of the profile features. For a number of density profiles there are only trapped modes for the entire range of longitudinal wave numbers. The phase speed of these modes tends toward the external Alfvén speed in the long wavelength limit. The generalized results were supported by the analytic solution of the wave equation for the specific density profiles. The approximate Wentzel-Kramers-Brillouin solutions allowed us to obtain the desired dispersion relations and to study their properties as a function of the profile parameters. The multicomponent quasi-periodic pulsations in flaring loops, observed on 2001 May 2 and 2002 July 3, are interpreted in terms of the transversely fundamental trapped fast sausage mode with several longitudinal harmonics in a smooth coronal waveguide.

  9. Diagnosis of Carburized Degradation in Cracking Tube by Ultrasonic Wave

    International Nuclear Information System (INIS)

    The ultrasonic method, which is well known as non-destructive test method, is widely used to evaluate the material damage caused by degradation practically. However, this method is just used for measuring the crack size and the thickness loss of tube. The purpose of this study is to investigate the applicability of the ultrasonic technique for the evaluation of carburized material and to suggest the correlations between the ultrasonic characteristics and carburized degradation. The miniaturized specimens(40x20x6.3mm) are adopted from the HK-40 (25Cr-20Ni-0.4C) centrifugal cast tube after carburization treatment. Carburization was carried at 1200 .deg. C by the pack method. The results of ultrasonic test present that the longitudinal wave velocity increased with the increase of carburized depth. The correlation between the longitudinal wave velocity and carburization was changed with the density and Young's modulus. Therefore, the average velocity in the materials carburized for 336 hours and the unused one were 5,840 m/s and 5,755 m/s at 5 MHz, respectively. With the obtained results from this study, it can be recognized that the technique using the ultrasonic velocity property is very useful method to evaluate the degree of carburized material non-destructively

  10. Design and analytical modeling of folded waveguide traveling wave tube

    International Nuclear Information System (INIS)

    We are developing a simple analytical model for the design of the folded waveguide traveling wave tube (FWTWT). Numerical software does exist for the design of FWTWT but requires large computer run time, is costly and does not provide the physical view for rapid design optimization of the FWTWT. In this paper, the design and analysis of the FWTWT using the spatial harmonics method of the TE10 mode of the EM wave are presented. An X-band FWTWT is used to verify this method. The normalized dispersion and beam line equations are used to simplify the design process so that the FWTWT can be designed to operate at any desired frequency. Both the S parameter-ABCD-S parameter conversion method and the equivalent circuit model method using Marcuvitz theorem are used for deriving the S parameters and for the analysis of dispersion curve of the 90 deg. sharp-cornered bend of the FWTWT. The analysis is developed by considering the straight and curved portions of the structure supporting the TE10 mode of the EM wave.

  11. Backward Propagation of Otoacoustic Emissions

    Institute of Scientific and Technical Information of China (English)

    HE Wenxuan; REN Tianying

    2006-01-01

    Normal mammalian ears not only detect but also generate sounds. The ear-generated sounds, I.e., otoacoustic emissions (OAEs), can be measured in the external ear canal using a tiny sensitive microphone. In spite of wide applications of OAEs in diagnosis of hearing disorders and in studies of cochlear functions, the question of how the cochlea emits sounds remains unclear. The current dominating theory is that the OAE reaches the cochlear base through a backward traveling wave. However, recently published works, including experimental data on the spatial pattern ofbasilar membrane vibrations at the emission frequency, demonstrated only forward traveling waves and no signs of backward traveling waves. These new findings indicate that the cochlea emits sounds through cochlear fluids as compression waves rather than through the basilar membrane as backward traveling waves. This article reviews different mechanisms of the backward propagation of OAEs and summarizes recent experimental results.

  12. Three-Dimensional Electron Optics Model Developed for Traveling-Wave Tubes

    Science.gov (United States)

    Kory, Carol L.

    2000-01-01

    A three-dimensional traveling-wave tube (TWT) electron beam optics model including periodic permanent magnet (PPM) focusing has been developed at the NASA Glenn Research Center at Lewis Field. This accurate model allows a TWT designer to develop a focusing structure while reducing the expensive and time-consuming task of building the TWT and hot-testing it (with the electron beam). In addition, the model allows, for the first time, an investigation of the effect on TWT operation of the important azimuthally asymmetric features of the focusing stack. The TWT is a vacuum device that amplifies signals by transferring energy from an electron beam to a radiofrequency (RF) signal. A critically important component is the focusing structure, which keeps the electron beam from diverging and intercepting the RF slow wave circuit. Such an interception can result in excessive circuit heating and decreased efficiency, whereas excessive growth in the beam diameter can lead to backward wave oscillations and premature saturation, indicating a serious reduction in tube performance. The most commonly used focusing structure is the PPM stack, which consists of a sequence of cylindrical iron pole pieces and opposite-polarity magnets. Typically, two-dimensional electron optics codes are used in the design of magnetic focusing devices. In general, these codes track the beam from the gun downstream by solving equations of motion for the electron beam in static-electric and magnetic fields in an azimuthally symmetric structure. Because these two-dimensional codes cannot adequately simulate a number of important effects, the simulation code MAFIA (solution of Maxwell's equations by the Finite-Integration-Algorithm) was used at Glenn to develop a three-dimensional electron optics model. First, a PPM stack was modeled in three dimensions. Then, the fields obtained using the magnetostatic solver were loaded into a particle-in-cell solver where the fully three-dimensional behavior of the beam

  13. Rheological fluid motion in tube by metachronal wave of cilia

    CERN Document Server

    Maiti, S

    2013-01-01

    The purpose of this paper is a theoretical study of a non-linear problem of rheological fluid transport in an axisymmetric tube by cilium. However, an attempt has been made to explain the role of cilia motion on the transport of fluid through the ductus efferentes of the male reproductive tract. Ostwald-de Waele power law viscous fluid has been considered to represent the rheological fluid to analyze pumping by means of a sequence of beat of cilia from row to row of cilia in a given row of cells and from one row of cells to the next (metachronal wave movement) under conditions for which the corresponding Reynolds number is small enough for inertial effects to be negligible and the wavelength to diameter ratio is large enough for the pressure to be considered uniform over the cross-section. Analyses and computations of the detailed fluid motions reveal that the time-averaged flow rates are directly dependent on epsilon, a non-dimensional measure involving the mean radius R of the tube and the cilia length. Thu...

  14. Dissipation of Alfven wave pulses propagating along dipole magnetic tubes with reflections at the ionosphere

    NARCIS (Netherlands)

    Erkaev, NV; Shaidurov, VA; Semenov, VS; Biernat, HK; Heidorn, D; Lakhina, GS

    2006-01-01

    A ratio of the maximal and minimal cross sections of the magnetic tube (contraction ratio) is a crucial parameter which affects very strongly on reflections of MHD wave pulses propagating along a narrowing magnetic flux tube. In cases of large contraction ratios of magnetospheric magnetic tubes, the

  15. Dispersive characteristics and longitudinal resonance properties in a relativistic backward wave oscillator with the coaxial arbitrary-profile slow-wave structure

    International Nuclear Information System (INIS)

    The method for calculating the dispersion relations of the slow-wave structures (SWSs) with arbitrary geometrical structures is studied in detail by using the Fourier series expansion. In addition, dispersive characteristics and longitudinal resonance properties of the SWSs with the cosinusoidal, trapezoidal, and rectangular corrugations are analyzed by numerical calculation. Based on the above discussion, a comparison on an L-band coaxial relativistic backward wave oscillator (BWO) and an L-band coaxial BWO with a coaxial extractor is investigated in detail with particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). Furthermore, experiments are carried out at the TORCH-01 accelerator under the low guiding magnetic field. At diode voltage of 647 kV, beam current of 9.3 kA, and guiding magnetic field strength of 0.75 T, the microwave is generated with power of 1.07 GW, mode of TM01, and frequency of 1.61 GHz. That is the first experimental report of the L-band BWO.

  16. Dispersive characteristics and longitudinal resonance properties in a relativistic backward wave oscillator with the coaxial arbitrary-profile slow-wave structure

    Science.gov (United States)

    Ge, Xingjun; Zhong, Huihuang; Qian, Baoliang; Zhang, Jun; Fan, Yuwei; Shu, Ting; Liu, Jinliang

    2009-11-01

    The method for calculating the dispersion relations of the slow-wave structures (SWSs) with arbitrary geometrical structures is studied in detail by using the Fourier series expansion. In addition, dispersive characteristics and longitudinal resonance properties of the SWSs with the cosinusoidal, trapezoidal, and rectangular corrugations are analyzed by numerical calculation. Based on the above discussion, a comparison on an L-band coaxial relativistic backward wave oscillator (BWO) and an L-band coaxial BWO with a coaxial extractor is investigated in detail with particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). Furthermore, experiments are carried out at the TORCH-01 accelerator under the low guiding magnetic field. At diode voltage of 647 kV, beam current of 9.3 kA, and guiding magnetic field strength of 0.75 T, the microwave is generated with power of 1.07 GW, mode of TM01, and frequency of 1.61 GHz. That is the first experimental report of the L-band BWO.

  17. A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes

    Institute of Scientific and Technical Information of China (English)

    Yong-Hun Kweon; Heuy-Dong Kim; Toshiaki Setoguchi; Toshiyuki Aoki

    2003-01-01

    The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee's total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The Mach number Ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d,is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tubes, the peak pressure produced by the twin impulse waves and its location strongly depend upon the distance between two-parallel tubes, L/d and the incident shock Mach number,Ms. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

  18. 0.22 THz wideband sheet electron beam traveling wave tube amplifier: Cold test measurements and beam wave interaction analysis

    International Nuclear Information System (INIS)

    In this paper, we describe micro-fabrication, RF measurements, and particle-in-cell (PIC) simulation modeling analysis of the 0.22 THz double-vane half period staggered traveling wave tube amplifier (TWTA) circuit. The TWTA slow wave structure comprised of two sections separated by two sever ports loaded by loss material, with integrated broadband input/output couplers. The micro-metallic structures were fabricated using nano-CNC milling and diffusion bonded in a three layer process. The 3D optical microscopy and SEM analysis showed that the fabrication error was within 2–3 μm and surface roughness was measured within 30–50 nm. The RF measurements were conducted with an Agilent PNA-X network analyzer employing WR5.1 T/R modules with a frequency range of 178-228 GHz. The in-band insertion loss (S21) for both the short section and long section (separated by a sever) was measured as ∼−5 dB while the return loss was generally around ∼−15 dB or better. The measurements matched well with the S-matrix simulation analysis that predicted a 3 dB bandwidth of ∼45 GHz with an operating frequency at 220 GHz. However, the measured S21 was ∼3 dB less than the design values, and is attributed to surface roughness and alignment issues. The confirmation measurements were conducted over the full frequency band up to 270 GHz employing a backward wave oscillator (BWO) scalar network analyzer setup employing a BWO in the frequency range 190 GHz–270 GHz. PIC simulations were conducted for the realistic TWT output power performance analysis with incorporation of corner radius of 127 μm, which is inevitably induced by nano-machining. Furthermore, the S21 value in both sections of the TWT structure was reduced to correspond to the measurements by using a degraded conductivity of 10% International Annealed Copper Standard. At 220 GHz, for an elliptic sheet electron beam of 20 kV and 0.25 A, the average output power of the tube was predicted to be reduced from 90 W (for

  19. 0.22 THz wideband sheet electron beam traveling wave tube amplifier: Cold test measurements and beam wave interaction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Baig, Anisullah; Gamzina, Diana; Barchfeld, Robert; Domier, Calvin; Barnett, Larry R.; Luhmann, Neville C. Jr. [Department of Electrical and Computer Engineering, University of California, Davis, California 95616 (United States)

    2012-09-15

    In this paper, we describe micro-fabrication, RF measurements, and particle-in-cell (PIC) simulation modeling analysis of the 0.22 THz double-vane half period staggered traveling wave tube amplifier (TWTA) circuit. The TWTA slow wave structure comprised of two sections separated by two sever ports loaded by loss material, with integrated broadband input/output couplers. The micro-metallic structures were fabricated using nano-CNC milling and diffusion bonded in a three layer process. The 3D optical microscopy and SEM analysis showed that the fabrication error was within 2-3 {mu}m and surface roughness was measured within 30-50 nm. The RF measurements were conducted with an Agilent PNA-X network analyzer employing WR5.1 T/R modules with a frequency range of 178-228 GHz. The in-band insertion loss (S{sub 21}) for both the short section and long section (separated by a sever) was measured as {approx}-5 dB while the return loss was generally around {approx}-15 dB or better. The measurements matched well with the S-matrix simulation analysis that predicted a 3 dB bandwidth of {approx}45 GHz with an operating frequency at 220 GHz. However, the measured S{sub 21} was {approx}3 dB less than the design values, and is attributed to surface roughness and alignment issues. The confirmation measurements were conducted over the full frequency band up to 270 GHz employing a backward wave oscillator (BWO) scalar network analyzer setup employing a BWO in the frequency range 190 GHz-270 GHz. PIC simulations were conducted for the realistic TWT output power performance analysis with incorporation of corner radius of 127 {mu}m, which is inevitably induced by nano-machining. Furthermore, the S{sub 21} value in both sections of the TWT structure was reduced to correspond to the measurements by using a degraded conductivity of 10% International Annealed Copper Standard. At 220 GHz, for an elliptic sheet electron beam of 20 kV and 0.25 A, the average output power of the tube was predicted

  20. Oblique detonation waves stabilized in rectangular-cross-section bent tubes

    OpenAIRE

    Kudo, Yusuke; Nagura, Yuuto; Kasahara, Jiro; Sasamoto, Yuya; Matsuo, Akiko

    2011-01-01

    Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through rectangular-cross-section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The obliq...

  1. Propagation and dispersion of sausage wave trains in magnetic flux tubes

    CERN Document Server

    Oliver, R; Terradas, J

    2015-01-01

    A localized perturbation of a magnetic flux tube produces a pair of wave trains that propagate in opposite directions along the tube. These wave packets disperse as they propagate, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. (2014) we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. Previous studies on wave propagation in magnetic wave guides have emphasized that the wave train dispersion is influenced by the particular dependence of the group velocity on the longitudinal wavenumber. Here we also find that long initial perturbations result in low amplitude wave packets and that large values of the magnetic tube to environment density ratio yield longer wave trains. To test the detectability ...

  2. Mechanisms for phase distortion in a traveling wave tube

    International Nuclear Information System (INIS)

    We present a view of the physics of phase distortion in a traveling wave tube (TWT) based on unique insights afforded by the MUSE models of a TWT [ J. Woehlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002) ]. The conclusion, supported by analytic theory and simulations, is that prior to gain compression phase distortion is due to harmonic frequencies in the electron beam and the resulting 'intermodulation' frequency at the fundamental, and not the often cited 'slowing down of electrons in the electron beam'. We draw these conclusions based on MUSE simulations that allow explicit control of electron beam frequency content, an analytic solution to the S-MUSE model [ J. Woehlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002) ] that reveals that phase distortion is due to the fact that the fundamental frequency is an intermodulation product of itself, and large signal LATTE [ J. Woehlbier, J. Booske, and I. Dobson, IEEE Trans. Plasma Sci. 30, 1063 (2002) ] simulations that are modified to remove the effect of the slowing down of electrons in the electron beam. As applications of the theory we compare S-MUSE simulations to an amplitude phase model using the analytic phase transfer curve, we study dependence of phase distortion on circuit dispersion and electron beam parameters at the second harmonic with large signal LATTE simulations for narrow and wide band TWT designs, and we consider the phase distortion theory in the context of TWT linearization

  3. Suppression of parasitic noise by strong Langmuir wave damping in quasitransient regimes of backward Raman amplification of intense laser pulses in plasmas.

    Science.gov (United States)

    Malkin, Vladimir; Fisch, Nathaniel

    2009-11-01

    Currently built powerful soft x-ray sources may be able to access intensities needed for backward Raman amplification (BRA) of x-ray pulses in plasmas. However, high plasma densities, needed to provide enough coupling between the pump and seed x-ray pulsed, cause strong damping of the Langmuir wave that mediates energy transfer from the pump to the seed pulse. Such damping could reduce the coupling, thus making efficient BRA impossible. This work shows that efficient BRA can survive despite the Langmuir wave damping significantly exceeding the linear BRA growth rate. Moreover, the strong Langmuir wave damping can suppress deleterious instabilities of BRA seeded by the thermal noise. This shows that it may be feasible to observe x-ray BRA for the first time soon.

  4. Evaluation of Some Slow-wave Vane Structures for Aminiature Traveling-wave Tube at 30 Ghz

    Science.gov (United States)

    Kavanagh, Frank; Ebihara, Ben; Wallett, Thomas M.; Dayton, James A., Jr.

    1994-01-01

    The dispersion characteristics of six vane type slow wave structures were experimentally measured near 1 GHz to determine applicability in an electrostatically focused 30 GHz miniature traveling wave tube (TWT). From the measured results, the trapezoidal vane structure appeared to be the most promising exhibiting an interaction impedance equal to 337.9 ohms at beta(L)/pi equal to 0.3. A 30 GHz trapezoidal vane structure with coupling irises was fabricated using electrical discharge machining (EDM). This structure, however, was too lossy for a short electrostatically focused tube, but several of the structures are amenable to a tube with permanent magnetic focusing.

  5. Characterization of mechanical and geometrical properties of a tube with axial and circumferential guided waves.

    Science.gov (United States)

    Yeh, Cheng-Hung; Yang, Che-Hua

    2011-05-01

    Guided waves propagating in cylindrical tubes are frequently applied for the characterization of material or geometrical properties of tubes. In a tube, guided waves can propagate in the axial direction and called axial guided waves, or in the circumferential direction called circumferential guided waves. Dispersion spectra for the axial and circumferential guided waves share some common behaviors and however exhibit some particular behaviors of their own. This study provides an investigation with theoretical modeling, experimental measurements, and a simplex-based inversion procedure to explore the similarity and difference between the axial guided waves and circumferential guided waves, aiming at providing useful information while axial and circumferential guided waves are applied in the area of material characterization. The sensitivity to the radius curvature for the circumferential guided waves dispersion spectra is a major point that makes circumferential guided waves different from axial guided waves. For the purpose of material characterization, both axial and circumferential guided waves are able to extract an elastic moduli and wall-thickness information from the dispersion spectra, however, radius information can only be extracted from the circumferential guided waves spectra. PMID:21211810

  6. Propagation of Long-Wavelength Nonlinear Slow Sausage Waves in Stratified Magnetic Flux Tubes

    Science.gov (United States)

    Barbulescu, M.; Erdélyi, R.

    2016-05-01

    The propagation of nonlinear, long-wavelength, slow sausage waves in an expanding magnetic flux tube, embedded in a non-magnetic stratified environment, is discussed. The governing equation for surface waves, which is akin to the Leibovich-Roberts equation, is derived using the method of multiple scales. The solitary wave solution of the equation is obtained numerically. The results obtained are illustrative of a solitary wave whose properties are highly dependent on the degree of stratification.

  7. Laser Interferometer Gravitational-Wave Observatory beam tube component and module leak testing

    OpenAIRE

    Carpenter, W. A.; Shaw, P. B.; Jones, L; Weiss, R.

    2000-01-01

    Laser Interferometer Gravitational-Wave Observatory (LIGO) is a joint project of the California Institute of Technology and the Massachusetts Institute of Technology funded by the National Science Foundation. The project is designed to detect gravitational waves from astrophysical sources such as supernova and black holes. The LIGO project constructed observatories at two sites in the U.S. Each site includes two beam tubes (each 4 km long) joined to form an "L" shape. The beam tube is a 1.25 ...

  8. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

    OpenAIRE

    Courtney, Amy; Andrusiv, Lubov; Courtney, Michael

    2011-01-01

    This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27 - 79 mm. A range of peak press...

  9. Geophysical borehole logging in Lavia borehole - results and interpretation of sonic and tube wave measurements

    International Nuclear Information System (INIS)

    Swedish Nuclear Fuel and Waste Management Co, SKB has been contracted by Industrial Power Company LTD, TVO to perform geophysical logging in a borehole at Lavia in Western Finland. The logging has been conducted by Swedish Geological Co, SGAB in accordance with an agreement for cooperation with SKB. The depth of the borehole is 1001 m, diameter 56 mm and inclination 10-20 degrees to the vertical. The aim of the logging was to determine the various geophysical parameters in the borehole in order to interpret and understand the rock mass properties in the vicinity of the borehole. According to the contract the report covers the following main objectives: a technical description of the field work and the equipment used; a review of the theoretical base for the sonic and tube wave methods; an interpretation and presentation of the results obtained by sonic and tube wave mesurements. The evaluation of the sonic and tube wave measurements shows good correlation. On a qualitative basis there seems to be a correlation between tube wave generating points, the relative tube wave amplitudes and the hydraulic conductivity measurements performed as hydraulical tests between packers in the borehole. The low velocity anamalies in the sonic log are mainly caused by tectonic features like fractures and fracture zones but to some extent also by contacts between granite and diorite. The estimation of elastic properties of the rock mass from observation of tube wave velocity are in accordance with laboratory determinations made on core samples. (author)

  10. Backward Traceability

    OpenAIRE

    Triguis Gonzalez, Matilde Mabel

    2013-01-01

    This thesis proposes a new concept, the User Use Case (UUC), to explain at the requirements level, how, under the command of the user, an application is really used, as opposed to how the application is actually implemented at the code level. The aim is to compare the UUC diagrams to what an application must do using law-based ontology. The thesis implements a process, Relational to User Use Case (RUC), to build a backward traceability, using the end product, the accomplished application, and...

  11. Research and development on high-power millimeter-wave and submillimeter-wave electron tubes

    Science.gov (United States)

    Mourier, G.

    Several high-power generators operating in the frequency range above 20 GHz are examined. These are hot-cathode vacuum tubes of the gyrotron type, which operate at voltages under 200 kV and in a magnetic field under 40 kG. A gyrotron research and development program is described, with particular emphasis on its computer-aided design and the use of superconducting magnets. Devices operating in frequency ranges above 200-300 GHz are described, and the concept of using transverse interaction rather than longitudinal interaction is discussed. Although transverse interaction has less energetic efficiency, its uniform magnetic field, high value of deceleration, and the possibility of using a wave with low group velocity make it a viable option. Devices incorporating a small electron accelerator in the same vacuum envelope and operating at relatively low voltage at higher frequencies are presently being investigated.

  12. Torsional Guided Wave Inspection for the Small Bore Tubes using Magnetostrictive Transducer

    International Nuclear Information System (INIS)

    A magnetostrictive transducer was applied to investigate the guided wave propagation and the effect of outer supports of a small bore tube. The width of Ni strip for the static magnetic bias was optimized for the small bore tube. Because of the geometrical limitation of Ni strip, a F(1,1) mode vibration was accompanied with the main T(0,1) mode vibration. In the viewpoint of long range attenuation the L(0,1) mode vibration is better than the T(0,1) mode vibration for the case of the small bore tube and unwanted signals from the tube holders or pads were not able to eliminate or suppressed in this experiment. After the review of various wave structures and dispersion characteristics of the tube, the frequency and vibration mode could be optimized to reduce the reflections from those outer support structures.

  13. A $55 Shock Tube for Simulated Blast Waves

    OpenAIRE

    Courtney, Elijah; Courtney, Amy; Courtney, Michael

    2015-01-01

    Shock tubes are commonly employed to test candidate armor materials, validate numerical models, and conduct simulated blast experiments in animal models. As DoD interests desire to field wearable sensors as blast dosimeters, shock tubes may also serve for calibration and testing of these devices. The high blast pressures needed for experimental testing of candidate armors are unnecessary to test these sensors. An inexpensive, efficient, and easily available way of testing these pressure senso...

  14. Fully nonlinear time-domain simulation of a backward bent duct buoy floating wave energy converter using an acceleration potential method

    Science.gov (United States)

    Lee, Kyoung-Rok; Koo, Weoncheol; Kim, Moo-Hyun

    2013-12-01

    A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

  15. Discharge of a shock Wave from an Open End of a Tube

    Institute of Scientific and Technical Information of China (English)

    HideoKashimura; HiroyasuNakayama; 等

    2000-01-01

    When a pressure wave propagates along a constant area straight tube and reaches at the open end,an impulsive wave is emitted outwared from the tube exit toward the surrounding area and causes an impulsive noise like a sonic oom.In order to clarify the magnitude of an impulsive wave obtainde by the discharge of a weak shock wave from an open end of a tube in relation to the noise problem and the industrial devices,the experimental and numerical investigations have been carried out for various strength of a shock wave.A simple open end shock tuby with the flange at the tube exit was used and the numerical calculation using the TVD scheme was performed.The effective equations which concerns with the magnitude of an impulsive wave generated by the emission of a shock wave have been obtained from the procedure of the open end correction based on the aeroacoustic theory and the numerical results.The influence of open end correction length and the diameter of a flange on the magnitude of an impulsive wave has been discussed.

  16. On the propagation mechanism of a detonation wave in a round tube with orifice plates

    Science.gov (United States)

    Ciccarelli, G.; Cross, M.

    2016-06-01

    This study deals with the investigation of the detonation propagation mechanism in a circular tube with orifice plates. Experiments were performed with hydrogen air in a 10-cm-inner-diameter tube with the second half of the tube filled with equally spaced orifice plates. A self-sustained Chapman-Jouguet (CJ) detonation wave was initiated in the smooth first half of the tube and transmitted into the orifice-plate-laden second half of the tube. The details of the propagation were obtained using the soot-foil technique. Two types of foils were used between obstacles, a wall-foil placed on the tube wall, and a flat-foil (sooted on both sides) placed horizontally across the diameter of the tube. When placed after the first orifice plate, the flat foil shows symmetric detonation wave diffraction and failure, while the wall foil shows re-initiation via multiple local hot spots created when the decoupled shock wave interacts with the tube wall. At the end of the tube, where the detonation propagated at an average velocity much lower than the theoretical CJ value, the detonation propagation is much more asymmetric with only a few hot spots on the tube wall leading to local detonation initiation. Consecutive foils also show that the detonation structure changes after each obstacle interaction. For a mixture near the detonation propagation limit, detonation re-initiation occurs at a single wall hot spot producing a patch of small detonation cells. The local overdriven detonation wave is short lived, but is sufficient to keep the global explosion front propagating. Results associated with the effect of orifice plate blockage and spacing on the detonation propagation mechanism are also presented.

  17. Experiments on the acoustic solitary wave generated thermoacoustically in a looped tube

    Science.gov (United States)

    Shimizu, Dai; Sugimoto, Nobumasa

    2015-10-01

    Emergence of an acoustic solitary wave is demonstrated in a gas-filled, looped tube with an array of Helmholtz resonators connected. The solitary wave is generated thermoacoustically and spontaneously by a pair of stacks positioned diametrically on exactly the opposite side of the loop. The temperature gradient is imposed on both stacks in the same sense along the tube. The stacks made of ceramics and of many square pores are sandwiched by hot and cold heat exchangers. The pressure profile measured and the propagation speed show good agreements with the theoretical ones of the acoustic solitary wave obtained by Sugimoto (J. Acoust. Soc. Am., 99, 1971-1976 (1996)).

  18. Shock wave formation in flame propagation in a gas-air mixture within a tube

    Energy Technology Data Exchange (ETDEWEB)

    Abinov, A.G.; Plotnikov, V.M.; Shebeko, Yu.N.; Eremenko, O.Ya.; Fialkov, B.S.; Muravlev, V.K.; Abramovich, A.L.; Chekhovskikh, A.M.

    1987-07-01

    Attention is given to determination of the inter-relationship of shock and pressure wave parameters (pressure and wave impulse) with the energy contained in the explosive cloud. The experiments were performed in shock tubes. Oscillograms are shown for the cases of strong (blasting cord) and weak (copper wire fuse) initiation. The dependence of shock-wave impulse for strong initiation on the reserve of chemical energy contained in the explosive mixture and on the cross-sectional area of the tube is give. The analogous relationships for weak initiation are shown and interpreted.

  19. Development and Test of a Travelling Wave Tube mm-wave Source

    Science.gov (United States)

    Field, Mark; Kimura, Takuji; Atkinson, John; Gamzina, Diana; Barnett, Larry; Zhao, Jinfeng; Luhmann, Neville; Griffith, Zachary; Reed, Thomas; Rodwell, Mark

    2013-03-01

    We report on the fabrication and test of a Traveling Wave Tube (TWT) amplifier designed for operation over a 40 GHz bandwidth centered on 220 GHz, and producing 50 W output power. The TWT amplifier uses a slow wave structure with staggered interdigitated vanes within a waveguide. Each vane is 110 micron wide situated inside a 770 micron wide waveguide, and was directly machined into copper using a 100 micron wide end mill. This structure slows radiation down to group velocity of 8.16 x 107 ms-1 where the velocity matches the speed of electrons from a 20 keV source. The TWT uses a sheet electron beam of 7:1 aspect ratio and 400 A/cm2 charge density stabilized by a Brillouin flow magnetic field provided by an external permanent magnet. RF vacuum windows were designed and built using brazed diamond windows, providing less than 1 dB insertion loss across the full 40 GHz bandwidth. Solid state preamplifiers have been developed which provide 20 dB gain and 50 mW output power over the full bandwidth to the input of the TWT. DARPA HiFIVE Program, Contract # W911NF-08-C-0050.

  20. Experimental study on the standing-wave tube with tapered section and its extremely nonlinear standing-wave field

    Institute of Scientific and Technical Information of China (English)

    MIN Qi; YIN Yao; LI Xiaodong; LIU Ke

    2011-01-01

    A standing-wave tube with tapered section (STTS) was evolved from a standingwave tube with abrupt section (STAS) whose abrupt section was replaced with tapered section. The research was intended to compare the acoustic properties and the extremely nonlinear pure standing waves of STTS with those of STAS. The acoustic properties of the STTS were studied with transfer matrix. It was proved, like the STAS, that the STTS was dissonant standingwave tube. With its dissonant property, the 181 dB extremely nonlinear pure standing wave was obtained in the STTS excited at its first resonance frequency. Then the comparative experimental studies on the saturation properties of the extremely nonlinear standing waves were carried out in the STTS and the STAS with the same length. It was found that the STTS could suppress the harmonics and meanwhile reduce energy loss of the standing wave more effectively. Compared with the STAS, under the same voltage of loudspeaker, the STTS obtained a higher extremely nonlinear pure standing wave. Moreover, it was found for the STTS that the third harmonic of the third resonance frequency was close to the seventh resonance frequency of sound source impedance, to which the valley value of the sound pressure level transfer function corresponded. Because of this, the third harmonic increased rapidly with the increase of fundamental wave and tended to saturate.

  1. Low-frequency pressure wave propagation in liquid-filled, flexible tubes. (A)

    DEFF Research Database (Denmark)

    Bjørnø, Leif; Bjelland, C.

    1992-01-01

    A model has been developed for propagation of low-frequency pressure waves in viscoelastic tubes with distensibility of greater importance than compressibility of the liquid. The dispersion and attenuation are shown to be strongly dependent on the viscoelastic properties of the tube wall. The com......A model has been developed for propagation of low-frequency pressure waves in viscoelastic tubes with distensibility of greater importance than compressibility of the liquid. The dispersion and attenuation are shown to be strongly dependent on the viscoelastic properties of the tube wall......) moduli determined by stress wave transfer function measurements in simple extension experiments. The moduli are used in the model to produce realistic dispersion relations and frequency dependent attenuation. Signal transfer functions between positions in the liquid-filled tube can be synthesized from...... the model and are compared with results of experimental pressure wave propagation in the liquid-filled, flexible tube. A good agreement between experimental data and theoretical predictions is found....

  2. Traveling-Wave Tube Amplifier for THz Frequencies

    DEFF Research Database (Denmark)

    Kotiranta, Mikko; Krozer, Viktor; Zhurbenko, Vitaliy

    tubes and gas lasers, but the ones available are too expensive or large for many applications. This work is related to the European project OPTHER (Optically driven terahertz amplifiers) which aims to realise a compact, powerful and efficient vacuum tube amplifier for the frequency range of 0.3 – 2......The lack of a compact and powerful terahertz source has been hindering the application of terahertz radiation in many fields. Frequency multipliers can be used in conjunction with an electronic solid-state source to obtain power levels up to around 1 mW. A higher power may be generated with vacuum...

  3. A three-dimensional time-dependent theory for helix traveling wave tubes in beam-wave interaction

    Institute of Scientific and Technical Information of China (English)

    Peng Wei-Feng; Hu Yu-Lu; Yang Zhong-Hai; Li Jian-Qing; Lu Qi-Ru; Li Bin

    2011-01-01

    This paper presents a three-dimensional time-dependent nonlinear theory of helix traveling wave tubes for beam-wave interaction. The radio frequency electromagnetic fields are represented as the superposition of azimuthally symmetric Waves in a vacuum sheath helix. Coupling impedance is introduced to the electromagnetic field equations' stimulating sources, which makes the theory easier and more flexible to realize. The space charge fields are calculated by electron beam space-charge waves expressed as the superposition solutions of Helmholtz equations. The focusing forces due to either a solenoidal field or a periodic permanent magnetic field is also included. The dynamical equations of electrons are Lorentz equations associating with electromagnetic fields, focusing fields and space-charge fields. The numerically simulated results of a tube are presented.

  4. A three-dimensional time-dependent theory for helix traveling wave tubes in beam-wave interaction

    International Nuclear Information System (INIS)

    This paper presents a three-dimensional time-dependent nonlinear theory of helix traveling wave tubes for beam-wave interaction. The radio frequency electromagnetic fields are represented as the superposition of azimuthally symmetric waves in a vacuum sheath helix. Coupling impedance is introduced to the electromagnetic field equations' stimulating sources, which makes the theory easier and more flexible to realize. The space charge fields are calculated by electron beam space-charge waves expressed as the superposition solutions of Helmholtz equations. The focusing forces due to either a solenoidal field or a periodic permanent magnetic field is also included. The dynamical equations of electrons are Lorentz equations associating with electromagnetic fields, focusing fields and space-charge fields. The numerically simulated results of a tube are presented. (cross-disciplinary physics and related areas of science and technology)

  5. Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

    Science.gov (United States)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.

  6. Numerical Investigation Of Nonlinear Waves Connected To Blood Flow In An Elastic Tube With Variable Radius

    Science.gov (United States)

    Dimitrova, Zlatinka I.

    2015-12-01

    We investigate flow of incompressible fluid in a cylindrical tube with elastic walls. The radius of the tube may change along its length. The discussed problem is connected to the fluid-structure interaction in large human arteries and especially to nonlinear effects. The long-wave approximation is applied to solve model equations. The obtained model Korteweg-deVries equation possessing a variable coefficient is reduced to a nonlinear dynamical system of three first order differential equations. The low probability of a solitary wave arising is shown. Periodic wave solutions of the model system of equations are studied and it is shown that the waves, that are consequence of the irregular heart pulsations may be modelled by a sequence of parts of such periodic wave solutions.

  7. Discrete-State Simulated Annealing For Traveling-Wave Tube Slow-Wave Circuit Optimization

    Science.gov (United States)

    Wilson, Jeffrey D.; Bulson, Brian A.; Kory, Carol L.; Williams, W. Dan (Technical Monitor)

    2001-01-01

    Algorithms based on the global optimization technique of simulated annealing (SA) have proven useful in designing traveling-wave tube (TWT) slow-wave circuits for high RF power efficiency. The characteristic of SA that enables it to determine a globally optimized solution is its ability to accept non-improving moves in a controlled manner. In the initial stages of the optimization, the algorithm moves freely through configuration space, accepting most of the proposed designs. This freedom of movement allows non-intuitive designs to be explored rather than restricting the optimization to local improvement upon the initial configuration. As the optimization proceeds, the rate of acceptance of non-improving moves is gradually reduced until the algorithm converges to the optimized solution. The rate at which the freedom of movement is decreased is known as the annealing or cooling schedule of the SA algorithm. The main disadvantage of SA is that there is not a rigorous theoretical foundation for determining the parameters of the cooling schedule. The choice of these parameters is highly problem dependent and the designer needs to experiment in order to determine values that will provide a good optimization in a reasonable amount of computational time. This experimentation can absorb a large amount of time especially when the algorithm is being applied to a new type of design. In order to eliminate this disadvantage, a variation of SA known as discrete-state simulated annealing (DSSA), was recently developed. DSSA provides the theoretical foundation for a generic cooling schedule which is problem independent, Results of similar quality to SA can be obtained, but without the extra computational time required to tune the cooling parameters. Two algorithm variations based on DSSA were developed and programmed into a Microsoft Excel spreadsheet graphical user interface (GUI) to the two-dimensional nonlinear multisignal helix traveling-wave amplifier analysis program TWA3

  8. Wave propagation and induced steady streaming in viscous fluid contained in a prestressed viscoelastic tube

    Science.gov (United States)

    Ma, Ye; Ng, Chiu-On

    2009-05-01

    The oscillatory and time-mean motions induced by a propagating wave of small amplitude through a viscous incompressible fluid contained in a prestressed and viscoelastic (modeled as a Voigt material) tube are studied by a perturbation analysis based on equations of motion in the Lagrangian system. The classical problem of oscillatory viscous flow in a flexible tube is re-examined in the contexts of blood flow in arteries or pulmonary gas flow in airways. The wave kinematics and dynamics, including wavenumber, wave attenuation, velocity, and stress fields, are found as analytical functions of the wall and fluid properties, prestress, and the Womersley number for the cases of a free or tethered tube. On extending the analysis to the second order in terms of the small wave steepness, it is shown that the time-mean motion of the viscoelastic tube with sufficient strength is short lived and dies out quickly as a limit of finite deformation is approached. Once the tube has attained its steady deformation, the steady streaming in the fluid can be solved analytically. Results are generated to illustrate the combined effects on the first-order oscillatory flow and the second-order steady streaming due to elasticity, viscosity, and initial stresses of the wall. The present model as applied to blood flow in arteries and gas flow in pulmonary airways during high-frequency ventilation is examined in detail through comparison with models in the literature.

  9. Fuel tube spacer-pad spot-weld quality estimation using guided ultrasonic waves

    Science.gov (United States)

    Suresh, P.; Balasubramaniam, Krishnan

    2012-05-01

    A guided wave technique for quality analysis of the spot weld spacer pad on the Pressurized Heavy Water Reactor (PHWR) fuel tubes using the strength of signal energy that is reflected from the welds is discussed here. The development of a real-time ultrasonic system for spot weld quality monitoring for the fuel tube, potentially allows for the elimination of expensive destructive testing, reduce the amount of time-consuming off-line ultrasonic inspections and ensures quality and reliability during operation. Due to the rather small spot size of these welds (less than 2 mm in diameter), the current methods such as ultrasonic scanning were found to be difficult to implement, particularly under production conditions Hence, a guided wave method was explored in this work that has the potential to be implemented in the welding. A fixture was developed in order to generate L (0, 1) mode in the wall of the tube and travelling along the length of the tube. Couplant was not used and instead uniform pressure was applied to ensure the coupling of the wave into the tube. The experimentally obtained guided wave reflected signals were correlated destructive assays. The main goal of such testing systems is to reduce operational time and provide reliable means of quality inspection.

  10. Modeling and experiments with low-frequency pressure wave propagation in liquid-filled, flexible tubes

    DEFF Research Database (Denmark)

    Bjelland, C; Bjarnø, Leif

    1992-01-01

    A model for wave propagation in a liquid-filled viscoelastic tube with arrays of receivers inside, is being used to analyze the influence of noise generated by in-line vibrational noise sources. In this model, distensibility is of greater importance than compressibility of the liquid...... relations and frequency-dependent attenuation. A 12-m-long, liquid-filled tube with interior stress members and connectors in each end is hanging vertically from an upper fixture. The lower end connector is excited by a power vibrator to generate the relevant wave modes. Measurements with reference...

  11. Empirical Study Of Tube Wave Suppression For Single Well Seismic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    West, P.B.; Weinberg, D.M.; Fincke, J.R.

    2002-05-31

    This report addresses the Idaho National Engineering and Environmental Laboratory's portion of a collaborative effort with Lawrence Berkeley National Laboratory and Sandia National Laboratories on a borehole seismic project called Single Well Seismic Imaging. The INEEL's role was to design, fabricate, deploy, and test a number of passive devices to suppress the energy within the borehole. This energy is generally known as tube waves. Heretofore, tube waves precluded acquisition of meaningful single-well seismic data. This report addresses the INEEL tests, theories, observations, and test results.

  12. Empirical Study Of Tube Wave Suppression For Single Well Seismic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    West, Phillip Bradley; Weinberg, David Michael; Fincke, James Russell

    2002-05-01

    This report addresses the Idaho National Engineering and Environmental Laboratory's portion of a collaborative effort with Lawrence Berkeley National Laboratory and Sandia National Laboratories on a borehole seismic project called Single Well Seismic Imaging. The INEEL's role was to design, fabricate, deploy, and test a number of passive devices to suppress the energy within the borehole. This energy is generally known as tube waves. Heretofore, tube waves precluded acquisition of meaningful single-well seismic data. This report addresses the INEEL tests, theories, observations, and test results.

  13. THE EFFECTS OF AREA CONTRACTION ON SHOCK WAVE STRENGTH AND PEAK PRESSURE IN SHOCK TUBE

    Directory of Open Access Journals (Sweden)

    A. M. Mohsen

    2012-06-01

    Full Text Available This paper presents an experimental investigation into the effects of area contraction on shock wave strength and peak pressure in a shock tube. The shock tube is an important component of the short duration, high speed fluid flow test facility, available at the Universiti Tenaga Nasional (UNITEN, Malaysia. The area contraction was facilitated by positioning a bush adjacent to the primary diaphragm section, which separates the driver and driven sections. Experimental measurements were performed with and without the presence of the bush, at various diaphragm pressure ratios, which is the ratio of air pressure between the driver (high pressure and driven (low pressure sections. The instantaneous static pressure variations were measured at two locations close to the driven tube end wall, using high sensitivity pressure sensors, which allow the shock wave strength, shock wave speed and peak pressure to be analysed. The results reveal that the area contraction significantly reduces the shock wave strength, shock wave speed and peak pressure. At a diaphragm pressure ratio of 10, the shock wave strength decreases by 18%, the peak pressure decreases by 30% and the shock wave speed decreases by 8%.

  14. Linear MHD Wave Propagation in Time-Dependent Flux Tube. III. Leaky Waves in Zero-Beta Plasma

    Science.gov (United States)

    Williamson, A.; Erdélyi, R.

    2016-01-01

    In this article, we evaluate the time-dependent wave properties and the damping rate of propagating fast magneto-hydrodynamic (MHD) waves when energy leakage into a magnetised atmosphere is considered. By considering a cold plasma, initial investigations into the evolution of MHD wave damping through this energy leakage will take place. The time-dependent governing equations have been derived previously in Williamson and Erdélyi (2014a, Solar Phys. 289, 899 - 909) and are now solved when the assumption of evanescent wave propagation in the outside of the waveguide is relaxed. The dispersion relation for leaky waves applicable to a straight magnetic field is determined in both an arbitrary tube and a thin-tube approximation. By analytically solving the dispersion relation in the thin-tube approximation, the explicit expressions for the temporal evolution of the dynamic frequency and wavenumber are determined. The damping rate is, then, obtained from the dispersion relation and is shown to decrease as the density ratio increases. By comparing the decrease in damping rate to the increase in damping for a stationary system, as shown, we aim to point out that energy leakage may not be as efficient a damping mechanism as previously thought.

  15. Evaluation of single crystal LaB6 cathodes for use in a high frequency backward wave oscillator tube

    Science.gov (United States)

    Swanson, L. W.; Davis, P. R.; Schwind, G. A.

    1984-01-01

    The results of thermionic emission and evaporation studies of single crystal LaB6 cathodes are given. A comparison between the (100), (210) and (310) crystal planes shows the (310) and (210) planes to possess a work function approx 0.2 eV lower than (100). This translates into a significant increase in current density, J, at a specified temperature. Comparison with a state-of-the-art impregnated dispenser cathode shows that LaB6 (310) is a superior cathode in nearly all respects except operating temperature at j 10 A/sq cm. The 1600 K thermionic and room temperature retarding potential work functions for LaB6 (310) are 2.42 and 2.50 respectively.

  16. Three-dimensional simulation of helix traveling-wave tube cold-test characteristics using MAFIA

    Energy Technology Data Exchange (ETDEWEB)

    Kory, C.L. [ANALEX Corp, Cleveland, OH (United States)

    1996-08-01

    The cold-test parameters including dispersion, impedance, and attenuation have been calculated for a helix traveling-wave tube (TWT) slow-wave circuit using MAFIA, the three-dimensional (3-D) electromagnetic finite-integration computer code. The helix model includes tape thickness, rectangular dielectric supports, and material properties consistent with the actual circuit. Measured cold-test data and computer-derived results for the helix circuit are presented with excellent agreement.

  17. A Novel Multimode Waveguide Coupler for Accurate Power Measurement of Traveling Wave Tube Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2014-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.

  18. The flexible asymmetric shock tube (FAST): a Ludwieg tube facility for wave propagation measurements in high-temperature vapours of organic fluids

    NARCIS (Netherlands)

    Mathijssen, T.; Gallo, M.; Casati, E.; Nannan, N.R.; Zamfirescu, C.; Guardone, A.; Colonna, P.

    2015-01-01

    This paper describes the commissioning of the flexible asymmetric shock tube (FAST), a novel Ludwieg tube-type facility designed and built at Delft University of Technology, together with the results of preliminary experiments. The FAST is conceived to measure the velocity of waves propagating in de

  19. Traveling wave tube measurements for low-frequency properties of underwater acoustic materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A traveling wave tube measurement technique for measuring acoustic properties of underwater acoustic materials was developed. Water temperature and pressure environments of the ocean can be simulated in a water-filled tube, and the acoustic parameters of samples of underwater acoustic materials are measured in the range of low-frequency. A tested sample is located at central position of the tube. A pair of projectors is separately located at both ends of the tube. Using an active anechoic technique, the sound wave transmitting the tested sample is hardly reflected by the surface of secondary transducer. So the traveling sound field is built up in the tube. By separately calculating the transfer functions of every pair of double hydrophones in the sound fields from the both sides of the sample, its reflection coefficients and transmission coefficients are obtained. In the measurement system, the inside diameter of the tube is Φ208 mm, the working frequency range is from 100 to 4000 Hz, the maximum pressure is 5 MPa. The reflection coefficients and transmission coefficients of a water layer and a stainless steel layer samples are measured actually and calculated theoretically. The results show that the measured values are in good agreement with the values calculated, and the measurement uncertainty is not greater than 1.5 dB.

  20. The computation of pressure waves in shock tubes by a finite difference procedure

    International Nuclear Information System (INIS)

    A finite difference solution of one-dimensional unsteady isentropic compressible flow equations is presented. The computer program has been tested by solving some cases of the Riemann shock tube problem. Predictions are in good agreement with those presented by other authors. Some inaccuracies may be attributed to the wave smearing consequent of the finite-difference treatment. (author)

  1. An interleaved structure for a high-voltage planar transformer for a Travelling-wave Tube

    DEFF Research Database (Denmark)

    Zhao, Bin; Wang, Gang; Hurley, William G.;

    2016-01-01

    proposed to reduce leakage inductance and the insulation’s thickness is adjusted to optimize the electric isolation. In addition, the resistance and parasitic capacitance are investigated. With this method, a planar transformer used for a Travelling-Wave Tube Amplifier (TWTA) is designed. Calculations of...... leakage inductances and experimental results validate the effectiveness of the proposed method....

  2. Design and performance verification of advanced multistage depressed collectors. [traveling wave tubes for ECM

    Science.gov (United States)

    Kosmahl, H.; Ramins, P.

    1975-01-01

    Design and performance of a small size, 4-stage depressed collector are discussed. The collector and a spent beam refocusing section preceding it are intended for efficiency enhancement of octave bandwidth, high CW power traveling wave tubes for use in ECM.

  3. Mode conversion of guided waves in Inconel tubes with Ni coating

    International Nuclear Information System (INIS)

    Electrosleeving is one of the promising methods to repair a defective steam generator tubing in the nuclear power plant. It requires a nondestructive inspection in order to verify the structural Integrity in the coated region. In this study, a feasibility of ultrasonic guided wave for Inconel tube with Ni coating was investigated. Phase and group velocity dispersion curves for Inconel tube with Ni coating were calculated to get an optimum condition of guided wave propagation. An eight-segments ultrasonic transducer was designed and fabricated to generate L(0,2) mode, and receive signals around circumference. The received signal from the beginning of Ni coating showed almost similar amplitude along the angular circumference and matched to longitudinal L(0,2) mode. However, the received signals from the end of Ni coating were different along the angular circumferences. It seems that the longitudinal mode be converted to flexural mode at the end of Ni coating.

  4. Pressure and wall heat transfer behind a hydrogen/azide detonation wave in narrow tubes

    International Nuclear Information System (INIS)

    The reported study is concerned with the pressure evolution behind the detonation wave in tubes with an interior diameter in the range from 1 to 10 mm. Hydrogen azide in tubes with length-to-diameter ratios greater than 375 was detonated. The initial pressures were in the range from 1 to 20 Torr. The pressure behind the leading shock was measured with piezoelectrical transducers made of lead titanate and lead zirconate. It was found that the detonation velocity depends on wall heat losses. The wall heat flux observed behind the wave front was not in agreement with that calculated for constant flow parameters. In the diameter and pressure range considered, the wall heat flux varies strongly with tube diameter. This observation can be related to flow deviations regarding the Chapman-Jouguet parameters

  5. Studies on an improved indigenous pressure wave generator and its testing with a pulse tube cooler

    Science.gov (United States)

    Jacob, S.; Karunanithi, R.; Narsimham, G. S. V. L.; Kranthi, J. Kumar; Damu, C.; Praveen, T.; Samir, M.; Mallappa, A.

    2014-01-01

    Earlier version of an indigenously developed Pressure Wave Generator (PWG) could not develop the necessary pressure ratio to satisfactorily operate a pulse tube cooler, largely due to high blow by losses in the piston cylinder seal gap and due to a few design deficiencies. Effect of different parameters like seal gap, piston diameter, piston stroke, moving mass and the piston back volume on the performance is studied analytically. Modifications were done to the PWG based on analysis and the performance is experimentally measured. A significant improvement in PWG performance is seen as a result of the modifications. The improved PWG is tested with the same pulse tube cooler but with different inertance tube configurations. A no load temperature of 130 K is achieved with an inertance tube configuration designed using Sage software. The delivered PV power is estimated to be 28.4 W which can produce a refrigeration of about 1 W at 80 K.

  6. Helical waves and non-linear dynamics of fluid/structure interactions in a tube row

    Energy Technology Data Exchange (ETDEWEB)

    Moon, F.C.; Thothadri, M. [Cornell Univ., Ithaca, NY (United States)

    1997-12-31

    The goal of this study has been to investigate low-dimensional models for fluid-structure dynamics of flow across a row of cylindrical tubes. Four principle results of this experimental-theoretical study are discussed. (i) Experimental evidence has shown that the dynamic instability of the tube row is a subcritical Hopf bifurcation. (ii) The critical flow velocity decreases as the number of flexible cylinders increases. (iii) The linear model exhibits coupled helical wave solutions in the tube dynamics. (iv) A nonlinear model of the tube motions shows a complex subcritical Hopf bifurcation with a secondary bifurcation to a torus or quasi-periodic oscillation. In this analysis the tools of center manifolds, normal forms and numerical simulation are used.

  7. Characteristics of Spherical Shock Wave and Circular Pulse Jet Generated by Discharge of Propagating Shock Wave at Open End of Tube

    Institute of Scientific and Technical Information of China (English)

    Tsukasa Irie; Tsuyoshi Yasunobu; Hideo Kashimura; Toshiaki Setoguchi; Kazuyasu Matsuo

    2003-01-01

    When the shock wave propagating in the straight circular tube reaches at the open end, the impulsive wave is generated by the emission of a shock wave from an open end, and unsteady pulse jet is formed near the open end behind the impulsive wave under the specific condition. The pulse jet transits to spherical shock wave with the increase in the strength of shock wave. The strength is dependent on the Mach number of shock wave, which attenuates by propagation distance from the open end. In this study, the mechanism of generating the unsteady pulse jet, the characteristics of the pressure distribution in the flow field and the emission of shock wave from straight circular tube which has the infinite flange at open end are analyzed numerically by the TVD method. Strength of spherical shock wave, relation of shock wave Mach number, distance decay of spherical shock wave and directional characteristics are clarified.

  8. Imaging hydraulic fractures at Median Tectonic Line, Japan using multiply generated and scattered tube waves in a shallow VSP experiment

    Science.gov (United States)

    Minato, Shohei; Ghose, Ranajit; Tsuji, Takeshi; Ikeda, Michiharu; Onishi, Kozo

    2016-04-01

    Tube waves are low frequency guided waves that propagate along a fluid-filled borehole. The analysis of tube waves is a promising approach to image and characterize hydraulic fractures intersecting a borehole. It exploits tube waves generated by an external seismic wavefield which compresses fractures and injects fluid into the borehole. It also utilizes the attenuation of tube waves due to fluid exchange between the fracture and the borehole, which creates scattered waves (reflection and transmission). Conventional approaches consider tube waves due to a single fracture. However, when the spacing between multiple fractures is short relative to the wavelength of the tube waves, the generated and scattered tube waves interfere with each other, making it difficult to isolate the effect of a single fracture. The analysis of closely spaced fractures is important in highly fractured areas, such as a fault zone. In this study, we explore the possibility of prediction and utilization of generated and scattered tube waves due to multiple fractures. We derive a new integral equation of the full tube wavefield using 1D wavefield representation theory incorporating nonwelded interfaces. We adapt the recent developments in modeling tube wave generation/scattering at a fracture. In these models, a fracture is represented as a parallel wall or a thin poloelastic layer. This allowed us to consider the effects of a dynamic fracture aperture with fracture compliances and the permeability. The representation also leads to a new imaging method for the hydraulic fractures, using multiply-generated and scattered tube waves. This is achieved by applying an inverse operator to the observed tube waves, which focuses the tube waves to the depth where they are generated and/or scattered. The inverse operator is constructed by a tube wave Green's function with a known propagation velocity. The Median Tectonic Line (MTL) is the most significant fault in Japan, extending NE-SW for over 1000 km

  9. Three-dimensional simulation of helix traveling-wave tube cold-test characteristics using MAFIA

    Energy Technology Data Exchange (ETDEWEB)

    Kory, C.L. [Analex Corp., Cleveland, OH (United States)

    1996-12-31

    A critically important step in the traveling-wave tube (TWT) design process is the cold-testing of the slow-wave circuit for dispersion, beam interaction impedance and RF losses. Experimental cold-tests can be very time-consuming and expensive, thus limiting the freedom to examine numerous variations to the test circuit. This makes the need for computational methods crucial as they can lower cost, reduce tube development time and allow the freedom to introduce novel and improved designs. The cold-test parameters have been calculated for a C-Band Northrop-Grumman helix TWT slow-wave circuit using MAFIA, the three-dimensional electromagnetic finite-integration computer code. Measured and simulated cold-test data for the Northrop-Grumman helix TWT including dispersion, impedance and attenuation will be presented. Close agreement between simulated and measured values of the dispersion, impedance and attenuation has been obtained.

  10. Experimental studies on guided waves for the on-line inspection of steam generator tubes

    International Nuclear Information System (INIS)

    Deployment of an advanced on-line monitoring of the component integrity offers the prospect of improved performance, enhanced safety, and reduced overall cost for nuclear power plants. Guided ultrasonic waves have been known as one of promising techniques that could be utilized for on-line monitoring. The present work is aimed at developing a new method for on-line monitoring of the pipes during the operation period of nuclear power plants. For this purpose, steam generator (S/G) tube was selected as the object of the experiment. Dispersion curves and the incident angles corresponding to the specific modes were calculated for the S/G tube. The modes of guided wave were identified by time-frequency diagrams obtained by short time Fourier transform. Group velocities were also determined from the time-frequency diagrams obtained at the different separations of transducers. It was experimentally confirmed that there was no mode conversion when the guided ultrasound passed curved region of the S/G tube. The optimum mode of guided wave for the S/G tube was suggested and verified by experiments (orig.)

  11. Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope

    International Nuclear Information System (INIS)

    Hydraulic machines operating in a wider range are subjected to cavitation developments inducing undesirable pressure pulsations which could lead to potential instability of the power plant. The occurrence of pulsating cavitation volumes in the runner and the draft tube is considered as a mass source of the system and is depending on the cavitation compliance. This dynamic parameter represents the cavitation volume variation with the respect to a variation of pressure and defines implicitly the local wave speed in the draft tube. This parameter is also decisive for an accurate prediction of system eigen frequencies. Therefore, the local wave speed in the draft tube is intrinsically linked to the eigen frequencies of the hydraulic system. Thus, if the natural frequency of a hydraulic system can be determined experimentally, it also becomes possible to estimate a local wave speed in the draft tube with a numerical model. In the present study, the reduced scale model of a Francis turbine (v=0.29) was investigated at off-design conditions. In order to measure the first eigenmode of the hydraulic test rig, an additional discharge was injected at the inlet of the hydraulic turbine at a variable frequency and amplitude to excite the system. Thus, with different pressure sensors installed on the test rig, the first eigenmode was determined. Then, a hydro-acoustic test rig model was developed with the In-house EPFL SIMSEN software and the local wave speed in the draft tube was adjusted to obtain the same first eigen frequency as that measured experimentally. Finally, this method was applied for different Thoma and Froude numbers at part load conditions

  12. Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope

    Science.gov (United States)

    Landry, C.; Favrel, A.; Müller, A.; Nicolet, C.; Yamamoto, K.; Avellan, F.

    2014-03-01

    Hydraulic machines operating in a wider range are subjected to cavitation developments inducing undesirable pressure pulsations which could lead to potential instability of the power plant. The occurrence of pulsating cavitation volumes in the runner and the draft tube is considered as a mass source of the system and is depending on the cavitation compliance. This dynamic parameter represents the cavitation volume variation with the respect to a variation of pressure and defines implicitly the local wave speed in the draft tube. This parameter is also decisive for an accurate prediction of system eigen frequencies. Therefore, the local wave speed in the draft tube is intrinsically linked to the eigen frequencies of the hydraulic system. Thus, if the natural frequency of a hydraulic system can be determined experimentally, it also becomes possible to estimate a local wave speed in the draft tube with a numerical model. In the present study, the reduced scale model of a Francis turbine (v=0.29) was investigated at off-design conditions. In order to measure the first eigenmode of the hydraulic test rig, an additional discharge was injected at the inlet of the hydraulic turbine at a variable frequency and amplitude to excite the system. Thus, with different pressure sensors installed on the test rig, the first eigenmode was determined. Then, a hydro-acoustic test rig model was developed with the In-house EPFL SIMSEN software and the local wave speed in the draft tube was adjusted to obtain the same first eigen frequency as that measured experimentally. Finally, this method was applied for different Thoma and Froude numbers at part load conditions.

  13. Torsional Alfven Waves in Solar Magnetic Flux Tubes of Axial Symmetry

    CERN Document Server

    Murawski, K; Musielak, Z E; Srivastava, A K; Kraskiewicz, J

    2015-01-01

    Aims: Propagation and energy transfer of torsional Alfv\\'en waves in solar magnetic flux tubes of axial symmetry is studied. Methods: An analytical model of a solar magnetic flux tube of axial symmetry is developed by specifying a magnetic flux and deriving general analytical formulae for the equilibrium mass density and a gas pressure. The main advantage of this model is that it can be easily adopted to any axisymmetric magnetic structure. The model is used to simulate numerically the propagation of nonlinear Alfv\\'en waves in such 2D flux tubes of axial symmetry embedded in the solar atmosphere. The waves are excited by a localized pulse in the azimuthal component of velocity and launched at the top of the solar photosphere, and they propagate through the solar chromosphere, transition region, and into the solar corona. Results: The results of our numerical simulations reveal a complex scenario of twisted magnetic field lines and flows associated with torsional Alfv\\'en waves as well as energy transfer to t...

  14. Three-dimensional simulation of traveling-wave tube cold-test characteristics using MAFIA

    Science.gov (United States)

    Kory, Carol L.; Wilson, Jeffrey D.

    1995-05-01

    The three-dimensional simulation code MAFIA was used to compute the cold-test parameters - frequency-phase dispersion, beam on-axis interaction impedance, and attenuation - for two types of traveling-wave tube (TWT) slow-wave circuits. The potential for this electromagnetic computer modeling code to reduce the time and cost of TWT development is demonstrated by the high degree of accuracy achieved in calculating these parameters. Generalized input files were developed for ferruled coupled-cavity and TunneLadder slow-wave circuits. These files make it easy to model circuits of arbitrary dimensions. The utility of these files was tested by applying each to a specific TWT slow-wave circuit and comparing the results with experimental data. Excellent agreement was obtained.

  15. Effects of an elastic membrane on tube waves in permeable formations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.; Johnson, D.

    1996-10-01

    In this paper, the modified properties were calculated for tube wave propagation in a fluid-filled borehole penetrating a permeable rock due to the presence of a mudcake which forms on the borehole wall. The mudcake was characterized by an impermeable elastic layer. The mudcake partial sealing mechanism was simulated using a finite membrane stiffness. Consequently, it was shown that the mudcake can reduce, but not eliminate, the permeability effects on the tube wave slowness and attenuation. Moreover, this paper discusses a variety of values for the relevant parameters especially the mudcake thickness and membrane stiffness. The important combinations of mudcake parameters were clarified by using an analytic expression for the low-frequency limit.

  16. Investigating Dielectric and Metamaterial Effects in a Terahertz Traveling-Wave Tube Amplifier

    Science.gov (United States)

    Starinshak, David P.; Wilson, Jeffrey D.

    2008-01-01

    Adding material enhancements to a terahertz traveling-wave tube amplifier is investigated. Isotropic dielectrics, negative-index metamaterials, and anisotropic crystals are simulated, and plans to increase the efficiency of the device are discussed. Early results indicate that adding dielectric to the curved sections of the serpentine-shaped slow-wave circuit produce optimal changes in the cold-test characteristics of the device and a minimal drop in operating frequency. Additional results suggest that materials with simultaneously small relative permittivities and electrical conductivities are best suited for increasing the efficiency of the device. More research is required on the subject, and recommendations are given to determine the direction.

  17. Propagation of a Light-Emitting Wave-Front in a Fine Tube Positive Column Discharge

    Science.gov (United States)

    Jeong, Jong-Mun; Kim, Jung-Hyun; Hwang, Hachung; Jin, Dong-Jun; Koo, Je-Huan; Choi, Eun-Ha; Verboncoeur, John P.; Uhm, Han Sup; Cho, Guangsup

    2010-02-01

    The propagation velocity of a light-emitting wave-front is observed to be up˜2×10+5 m/s before Townsend breakdown and up˜5×10+6 m/s after Townsend breakdown along a discharge tube of inner diameter ro˜1.2 mm and length of 900 mm relevant to liquid crystal display television backlighting. Before Townsend breakdown, the origin of this wave is the ambipolar diffusion of plasma flux with the propagation speed up∝Da/ro for the plasma bounded by the radius ro with the diffusion coefficient Da along the positive column. After Townsend breakdown, the light-emitting wave-front propagates with the electron plasma wave generated by the pulses of driving voltage. The electron plasma wave propagates such a long distance along the tube without damping due to the effect of localized plasma generation by electron impact ionization collisions. The propagation velocity is described by up˜2ue2/ud, which is larger than the electron thermal velocity ue as well as the electron drift velocity ud.

  18. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

    CERN Document Server

    Courtney, Michael

    2011-01-01

    Instrumentation is needed to produce realistic blast waves in a laboratory setting. This paper describes the development and characterization of oxy-acetylene driven, laboratory scale shock tubes for use in studying blast injury, candidate armor materials, and material properties at blast loading rates. The pressure-time profiles show a true shock front and exponential decay characteristic of blast waves and have relevant durations. The modular design includes shock tube diameters of 27 mm and 41 mm, and a selection of peak pressures from 204 kPa to 920 kPa can be produced by selection of the driver section diameter and placement of the test sample. Characterization studies of several driver/driven section combinations showed consistent results, with peak pressures having 0.8 - 6.9 percent uncertainty in the mean. This shock tube design provides a more realistic blast profile than current air-driven shock tubes. In addition, operation does not require specialized personnel or facilities like most blast-driven...

  19. MEASUREMENTS OF SHOCK WAVE FORCE IN SHOCK TUBE WITH INDIRECT METHODS

    OpenAIRE

    2005-01-01

    Tests have been conducted at the “Laboratory for testing of civil explosives, detonators, electrical detonators and pyrotechnical materials”, Department for mining and geotechnics of the Faculty of mining, geology and petroleum engineering, University of Zagreb with the purpose of designing a detonator that would unite advantages of a non-electric system and the precision in regulation of time delay in electronic initiation system. Sum of energy released by the wave force in shock tube is a p...

  20. Investigation of a traveling wave thermoacoustic engine in a looped-tube

    OpenAIRE

    Novotný Petr; Hsu Shu-Shen; Wang An-Bang; Vít Tomáš

    2014-01-01

    In the present paper, four configurations of a traveling wave thermoacoustic engine in a looped tube were investigated by means of theoretical calculations and experiments. The effect of natural heat convection on their functionality was observed. Acoustic intensity was measured using a dual two microphone method. The stack was designed with few times higher dimension of channels than thermal penetration depth, due to the stack should not be called regenerator. Pressure distribution in the re...

  1. Thermal effect on the thermomechanical behavior of contacts in a Traveling Wave Tube (TWT)

    OpenAIRE

    Chbiki, M; Da Silva Botelho, T; Bauzin, J. G.; Laraqi, N.; Jarno, J.-F

    2015-01-01

    International audience A new thermo-elasto-plastic study of the contact between the helix and the rods of the delay line of Traveling Waves Tubes (TWT) was realized. Our study is focused on the analysis of the hot lines shrinking phenomenon. In the studied case, unlike brazed configuration, the contact areas are not perfect, resulting in a diminution of the heat transfer process. In order to maximize the contact area and to homogenize the contact pressure, a soft thermal conductive materia...

  2. A staggered double vane circuit for a W-band traveling-wave tube amplifier

    International Nuclear Information System (INIS)

    Based on the combination of a staggered double vane slow wave structure (SWS) and round electron beam, a 200-W W-band traveling-wave tube (TWT) amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell (PIC) simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules (MPM) and for other portable applications. (interdisciplinary physics and related areas of science and technology)

  3. Continuous-wave radar to detect defects within heat exchangers and steam generator tubes.

    Energy Technology Data Exchange (ETDEWEB)

    Nassersharif, Bahram (New Mexico State University, Las Cruces, NM); Caffey, Thurlow Washburn Howell; Jedlicka, Russell P. (New Mexico State University, Las Cruces, NM); Garcia, Gabe V. (New Mexico State University, Las Cruces, NM); Rochau, Gary Eugene

    2003-01-01

    A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique was researched for detection of defects using a continuous-wave radar method within metal tubing. The experimental program resulted in a completed product development schedule and the design of an experimental apparatus for studying handling of the probe and data acquisition. These tests were completed as far as the prototypical probe performance allowed. The prototype probe design did not have sufficient sensitivity to detect a defect signal using the defined radar technique and did not allow successful completion of all of the project milestones. The best results from the prototype probe could not detect a tube defect using the radar principle. Though a more precision probe may be possible, the cost of design and construction was beyond the scope of the project. This report describes the probe development and the status of the design at the termination of the project.

  4. Effect of regenerator positioning on thermoacoustic effect in a looped tube traveling wave thermoacoustic engine

    International Nuclear Information System (INIS)

    Highlights: • Effect of regenerator positioning on thermoacoustic effect is studied. • Five regenerator positions are tested for temperature behavior. • Ambient side behavior showed peak in thermoacoustic behavior intensity. • Hot side behavior showed peak in position matching ambient side. • An optimum regenerator position relative to the straight portion of the tube is suggested. - Abstract: This paper discusses the effect of regenerator positioning on the intensity of the thermoacoustic effect in a looped-tube traveling wave thermoacoustic engine (TAE). Traveling wave thermoacoustic engines work on the principle of the acoustic wave moving through the loop of the engine, across the regenerator, with the pressure and velocity curves in phase, amplifying the acoustic effect. Increasing the intensity of the effect, while keeping the energy input the same increases the efficiency of the TAE, and can be further applied in a thermoacoustic refrigeration system to increase the COP. The intensity of the effect in relation to the positioning of the regenerator, also called a stack in standing wave devices, is proven here to have an optimum positioning inside of the straight part of the loop. The increase in intensity under constant heat input proves an increase in efficiency

  5. Acoustic wave detection of chemical species electrokinetically transported within a capillary tube.

    Science.gov (United States)

    Li, Paul C H; Prasad, Ronald

    2003-06-01

    For the first time, we report the acoustic wave detection of chemical species being transported in a capillary tube to a region where acoustic coupling occurs. The measured parameter was a change in phase, which was originally only attributed to a change in solution density as the analyte passed by the detection region. Accordingly, we report the detection of change in phase as various chemical species (e.g. Cy5 dye, Cy5-derivatized glycine and underivatized glycine) were introduced into and migrated along a capillary tube through electrokinetic processes. To improve detection sensitivity, we modified various experimental parameters, such as run buffer concentration, capillary wall thickness and transducer frequency. Although acoustic wave detection was feasible, the peak width and detection limit were inadequate as compared to conventional detection methods for HPLC or CE. Nevertheless, the effects of various physical and chemical relaxation processes on acoustic wave absorption were discussed, and this has shed some light on explaining some observations, which cannot be explained by density differences alone. Accordingly, the acoustic wave method is suggested to investigate these processes, as studied in ultrasonic relaxation spectroscopy, in a flow system. PMID:12866892

  6. Traveling-wave tube amplifier characteristics study for stochastic beam-cooling experiments

    International Nuclear Information System (INIS)

    The characteristics of continuous-wave wideband traveling-wave tube amplifiers have been experimentally investigated over a frequency range of 1.5 to 4.5 GHz. We present measurements of characteristics important for stochastic beam cooling systems that are generally not available from manufacturers' data sheets. The amplifers measured include models 1177 H01 and 1277 H01 having output power capabilities of 10 to 20 W, respectively, at frequencies of 2 to 4 GHz. The power transfer characteristics, the phase-shift characteristics as functions of frequency and the input power level, the voltage standing-wave ratio, noise drive transfer characteristics, harmonics and intermodulation products content were accurately measured and are discussed. Measurement procedures and description of measuring systems, which include measuring system error corrections, are given in detail. Also several approaches are discussed for the reduction of harmonics and intermodulation products

  7. THE INTERACTION BETWEEN SHOCK WAVES AND FOAM IN A SHOCK TUBE

    Institute of Scientific and Technical Information of China (English)

    施红辉; Kazuhiko Kawai; Motoyuki Itoh; 俞鸿儒; 姜宗林

    2002-01-01

    An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80 mm in inner diameter, 10 mm in wall thickness and 5 360 mm in length). The velocities of the incident and reflected compression waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients α and β are quantitatively determined.

  8. Traveling-wave-tube simulation: The IBC [Interactive Beam-Circuit] code

    International Nuclear Information System (INIS)

    Interactive Beam-Circuit (IBC) is a one-dimensional many particle simulation code which has been developed to run interactively on a PC or Workstation, and displaying most of the important physics of a traveling-wave-tube. The code is a substantial departure from previous efforts, since it follows all of the particles in the tube, rather than just those in one wavelength, as commonly done. This step allows for nonperiodic inputs in time, a nonuniform line and a large set of spatial diagnostics. The primary aim is to complement a microwave tube lecture course, although past experience has shown that such codes readily become research tools. Simple finite difference methods are used to model the fields of the coupled slow-wave transmission line. The coupling between the beam and the transmission line is based upon the finite difference equations of Brillouin. The space-charge effects are included, in a manner similar to that used by Hess; the original part is use of particle-in-cell techniques to model the space-charge fields. 11 refs., 11 figs

  9. Several results from numerical investigation of nonlinear waves connected to blood flow in an elastic tube of variable radius

    CERN Document Server

    Dimitrova, Zlatinka I

    2015-01-01

    We investigate flow of incompressible fluid in a cylindrical tube with elastic walls. The radius of the tube may change along its length. The discussed problem is connected to the blood flow in large human arteries and especially to nonlinear wave propagation due to the pulsations of the heart. The long-wave approximation for modeling of waves in blood is applied. The obtained model Korteweg-deVries equation possessing a variable coefficient is reduced to a nonlinear dynamical system of 3 first order differential equations. The low probability of arising of a solitary wave is shown. Periodic wave solutions of the model system of equations are studied and it is shown that the waves that are consequence of the irregular heart pulsations may be modeled by a sequence of parts of such periodic wave solutions.

  10. A novel slotted helix slow-wave structure for high power Ka-band traveling-wave tubes

    International Nuclear Information System (INIS)

    A novel slotted helix slow-wave structure (SWS) is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube (TWT). This novel structure, which has higher heat capacity than a conventional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz. (interdisciplinary physics and related areas of science and technology)

  11. An open-styled dielectric-lined azimuthally periodic circular waveguide for a millimeter wave traveling-wave tube

    Institute of Scientific and Technical Information of China (English)

    Liu Yang; Wei Yan-Yu; Xu Jin; Yin Hai-Rong; Yue Ling-Na; Gong Yu-Bin; Wang Wen-Xiang

    2012-01-01

    An open-styled dielectric-lined azimuthally periodic circular waveguide (ODLAP-CW) for a millimeter-wave traveling-wave tube (TWT) is proposed,which is a modified form of a dielectric-lined azimuthally periodic circular waveguide (DLAP-CW).The slow-wave characteristics of the open-styled DLAP-CW are studied by using the spatial harmonics method,which includes normalized phase velocity and interaction impedance.The complicated dispersion equations are numerically solved with MATLAB and the results are in good agreement with the simulation results obtained from HFSS.The influence of structural parameters on the RF properties is investigated based on our theory.The numerical results show that the optimal thickness of the metal rod can increase the interaction impedance,with the dielectric constant held fixed.Finally,the slow-wave characteristics and transmission properties of an open-styled structure are compared with those of the DLAP-CW.The results validate that the mode competition is eliminated in the improved structure with only a slight influence on the dispersion characteristics,which may significantly improve the stability of an open-styled DLAP-CW-based TWT,and the interaction efficiency is also improved.

  12. Shock Tube Design for High Intensity Blast Waves for Laboratory Testing of Armor and Combat Materiel

    CERN Document Server

    Courtney, Elijah; Courtney, Michael

    2015-01-01

    Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 1...

  13. Particle propagation, wave growth and energy dissipation in a flaring flux tube

    Science.gov (United States)

    White, S. M.; Melrose, D. B.; Dulk, G. A.

    1986-01-01

    Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

  14. Detection of coatings within liquid-filled tubes and containers by mode conversion of leaky Lamb waves

    Directory of Open Access Journals (Sweden)

    M. Schmitt

    2013-05-01

    Full Text Available In this paper, a new acoustic sensor principle for coating detection within liquid-filled tubes and containers based on mode conversion of leaky Lamb waves is introduced. Leaky Lamb waves are excited and detected by single-phase transducers, which are attached on the outer side of a tube or container. By transmission time and amplitude measurements, coating formation within the liquid-filled tube and container is detected non-invasively. This new sensor principle is subdivided into the separate considerations of Lamb wave excitation, mode conversion and inverse mode conversion. The Lamb wave excitation by a single-phase transducer is visualized by scanning laser Doppler vibrometer imaging. The mode conversion process of leaky Lamb waves is measured by membrane hydrophone measurements and Schlieren visualization; afterwards, the measured emission angles are compared with the theoretical one. The inverse mode conversion process of pressure waves back to leaky Lamb waves is visualized by Schlieren images. By merging the results of Lamb wave excitation, mode conversion and inverse mode conversion, the new sensor concept is explained. Theoretical considerations and measurement results of adhesive tape coating inside a liquid-filled plastic tube and a liquid-filled stainless steel container verify the new acoustic sensor principle. Finally the measuring sensitivity and the technical realization are discussed.

  15. Dynamics of nonlinear resonant slow MHD waves in twisted flux tubes

    Directory of Open Access Journals (Sweden)

    R. Erdélyi

    2002-01-01

    Full Text Available Nonlinear resonant magnetohydrodynamic (MHD waves are studied in weakly dissipative isotropic plasmas in cylindrical geometry. This geometry is suitable and is needed when one intends to study resonant MHD waves in magnetic flux tubes (e.g. for sunspots, coronal loops, solar plumes, solar wind, the magnetosphere, etc. The resonant behaviour of slow MHD waves is confined in a narrow dissipative layer. Using the method of simplified matched asymptotic expansions inside and outside of the narrow dissipative layer, we generalise the so-called connection formulae obtained in linear MHD for the Eulerian perturbation of the total pressure and for the normal component of the velocity. These connection formulae for resonant MHD waves across the dissipative layer play a similar role as the well-known Rankine-Hugoniot relations connecting solutions at both sides of MHD shock waves. The key results are the nonlinear connection formulae found in dissipative cylindrical MHD which are an important extension of their counterparts obtained in linear ideal MHD (Sakurai et al., 1991, linear dissipative MHD (Goossens et al., 1995; Erdélyi, 1997 and in nonlinear dissipative MHD derived in slab geometry (Ruderman et al., 1997. These generalised connection formulae enable us to connect solutions obtained at both sides of the dissipative layer without solving the MHD equations in the dissipative layer possibly saving a considerable amount of CPU-time when solving the full nonlinear resonant MHD problem.

  16. Magnetohydrodynamic kink waves in nonuniform solar flux tubes: phase mixing and energy cascade to small scales

    CERN Document Server

    Soler, Roberto

    2015-01-01

    Magnetohydrodynamic (MHD) kink waves are ubiquitously observed in the solar atmosphere. The propagation and damping of these waves may play relevant roles for the transport and dissipation of energy in the solar atmospheric medium. However, in the atmospheric plasma dissipation of transverse MHD wave energy by viscosity or resistivity needs very small spatial scales to be efficient. Here, we theoretically investigate the generation of small scales in nonuniform solar magnetic flux tubes due to phase mixing of MHD kink waves. We go beyond the usual approach based on the existence of a global quasi-mode that is damped in time due to resonant absorption. Instead, we use a modal expansion to express the MHD kink wave as a superposition of Alfv\\'en continuum modes that are phase mixed as time evolves. The comparison of the two techniques evidences that the modal analysis is more physically transparent and describes both the damping of global kink motions and the building up of small scales due to phase mixing. In ...

  17. Simulation of TunneLadder Traveling-Wave Tube Input/Output Coupler Characteristics Using MAFIA

    Science.gov (United States)

    Kory, Carol L.; Qureshi, A. Haq

    1996-01-01

    RF input/output coupler characteristics for the TunneLadder traveling-wave tube have been calculated using the three-dimensional computer code, MAFIA and compared to experimental data with good agreement. Theory behind coupling of the TunneLadder interaction circuit to input and output waveguides is presented and VSWR data is calculated for variations on principal coupler dimensions to provide insight into manufacturing tolerances necessary for acceptable performance. Accuracy of results using MAFIA demonstrates how experimental hardware testing of three-dimensional coupler designs can be reduced.

  18. Investigating Holey Metamaterial Effects in Terahertz Traveling-Wave Tube Amplifier

    Science.gov (United States)

    Starinshak, David P.; Wilson, Jeffrey D.; Chevalier, Christine T.

    2007-01-01

    Applying subwavelength holes to a novel traveling-wave tube amplifier is investigated. Plans to increase the on-axis impedance are discussed as well as optimization schemes to achieve this goal. Results suggest that an array of holes alone cannot significantly change the on-axis electric field in the vicinity of the electron beam. However, models of a beam tunnel with corrugated walls show promise in maximizing the amplifier s on-axis impedance. Additional work is required on the subject, and suggestions are made to determine research directions.

  19. Investigation of a traveling wave thermoacoustic engine in a looped-tube

    Directory of Open Access Journals (Sweden)

    Novotný Petr

    2014-03-01

    Full Text Available In the present paper, four configurations of a traveling wave thermoacoustic engine in a looped tube were investigated by means of theoretical calculations and experiments. The effect of natural heat convection on their functionality was observed. Acoustic intensity was measured using a dual two microphone method. The stack was designed with few times higher dimension of channels than thermal penetration depth, due to the stack should not be called regenerator. Pressure distribution in the resonator was measured, and a good agreement with theoretical calculations from DELTAEC has been demonstrated.

  20. Optimization Design of Helix Pitch for Efficiency Enhancement in the Helix Travelling Wave Tubes

    Institute of Scientific and Technical Information of China (English)

    DUAN Zhao-Yun; GONG Yu-Bin; L(U) Ming-Yi; WEI Yan-Yu; WANG Wen-Xiang

    2008-01-01

    @@ The output section of a helix travelling wave tube usually contains a helix pitch taper for high rf electron efficiency.By keeping the rf field as synchronous as possible with the decelerating electron beam bunches,the rf field can extract much more energy from the beam,and thus the maximum electron efficiency can be realized.Recently,a global simulated annealing algorithm has been employed to design the helix pitch profile so as to improve the electron efficiency as much as possible.From the numerical results,it is concluded that the electron efficiency can be enhanced by about 4%-8%.

  1. Bandwidth broadening effect in a traveling-wave-tube amplifier by using impulse electron beam

    International Nuclear Information System (INIS)

    This paper reports on a wideband amplification mechanism involving an impulse electron beam. To prove broadband amplification with the impulse beam, we perform 3-dimensional particle-in-cell (3D PIC) code simulation. An impulse electron beam with a pulse width of 1 ns with electric potential 17.2 kV is injected into an interaction circuit of a coupled-cavity traveling-wave-tube (CCTWT) driven by a continuous-wave (CW) signal of 29.1 GHz. The resulting output bandwidth was 2.96%, and the peak output power of 713 W was the same as that obtained with CW operation at a single frequency. The simulation yielded very similar results with ultra short impulse signal from the simulation.

  2. 3D Simulations of Magnetohydrodynamic Waves in Lower Solar Atmospheric Flux Tubes Driven by Photospheric Motion

    CERN Document Server

    Mumford, S J; Erdélyi, R

    2013-01-01

    Aims. Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions small-scale magnetic flux tubes are generated due to the interaction of granulation motion and background magnetic field. This paper aims to study the effects of these motions, in regions of enhanced magnetic field, on magnetohydrodynamic wave excitation, propagation and energy flux from the solar photosphere up towards the solar corona. Methods. Numerical experiments of magnetohydrodynamic wave propagation in a realistic gravitationally stratified solar atmosphere from five different modelled photospheric drivers are performed. Horizontal and vertical drivers to mimic granular buffeting and solar global oscillations, a uniform torsional driver, an Archimedean spiral and a logarithmic spiral to mimic observed torsional motions in the solar photosphere are investigated. The numerical results are analysed using a novel method for extracting the parallel...

  3. Multiple Scattering of Seismic Waves from Ensembles of Upwardly Lossy Thin Flux Tubes

    CERN Document Server

    Hanson, Chris S

    2015-01-01

    Our previous semi-analytic treatment of f- and p-mode multiple scattering from ensembles of thin flux tubes (Hanson and Cally, Astrophys. J. 781, 125; 791, 129, 2014) is extended by allowing both sausage and kink waves to freely escape at the top of the model using a radiative boundary condition there. As expected, this additional avenue of escape, supplementing downward loss into the deep solar interior, results in substantially greater absorption of incident f- and p-modes. However, less intuitively, it also yields mildly to substantially smaller phase shifts in waves emerging from the ensemble. This may have implications for the interpretation of seismic data for solar plage regions, and in particular their small measured phase shifts.

  4. Study on Ka-Band Sheet Beam Traveling Wave Tube Focused by Closed PCM

    Science.gov (United States)

    Wang, Zhan-Liang; Shi, Xianbao; Gong, Yu-Bin; Wei, Yan-Yu; Duan, Zhao-Yun; Su, Xiaogang; Gong, Huarong; Feng, Jinjun; Huang, Hua

    2016-01-01

    This paper reports a Ka-band sheet beam traveling wave tube (TWT) focused by a 0.2 T closed periodic cusped magnet (PCM) system. The TWT with one section of staggered double-vane slow-wave structure (SWS) is driven by a 0.8-A sheet beam with rectangular cross-sectional area of 3.2 mm × 0.6 mm. This sheet beam TWT can produce 100 W output power, and the 3 dB band is 33-38.5 GHz. In order to improve the output power, an optimized sheet beam TWT with two sections of SWSs focused by a novel closed PCM system is proposed. The new closed PCM system is with annular magnetic blocks and can be fabricated and adjusted easily. The simulation shows that the optimized sheet beam TWT can produce 2000 W output power and the 3 dB band ranging from 33 to 40 GHz.

  5. MEASUREMENTS OF SHOCK WAVE FORCE IN SHOCK TUBE WITH INDIRECT METHODS

    Directory of Open Access Journals (Sweden)

    Mario Dobrilović

    2005-12-01

    Full Text Available Tests have been conducted at the “Laboratory for testing of civil explosives, detonators, electrical detonators and pyrotechnical materials”, Department for mining and geotechnics of the Faculty of mining, geology and petroleum engineering, University of Zagreb with the purpose of designing a detonator that would unite advantages of a non-electric system and the precision in regulation of time delay in electronic initiation system. Sum of energy released by the wave force in shock tube is a pre-condition for operation of the new detonator, and measurement of wave force is the first step in determining the sum of energy. The sum of energy is measured indirectly, based on two principles: movement sensors and strain.

  6. THE BEHAVIOR OF TRANSVERSE WAVES IN NONUNIFORM SOLAR FLUX TUBES. I. COMPARISON OF IDEAL AND RESISTIVE RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Goossens, Marcel, E-mail: roberto.soler@uib.es [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven (Belgium)

    2013-11-10

    Magnetohydrodynamic (MHD) waves are ubiquitously observed in the solar atmosphere. Kink waves are a type of transverse MHD waves in magnetic flux tubes that are damped due to resonant absorption. The theoretical study of kink MHD waves in solar flux tubes is usually based on the simplification that the transverse variation of density is confined to a nonuniform layer much thinner than the radius of the tube, i.e., the so-called thin boundary approximation. Here, we develop a general analytic method to compute the dispersion relation and the eigenfunctions of ideal MHD waves in pressureless flux tubes with transversely nonuniform layers of arbitrary thickness. Results for kink waves are produced and compared with fully numerical resistive MHD eigenvalue computations in the limit of small resistivity. We find that the frequency and resonant damping rate are the same in both ideal and resistive cases. The actual results for thick nonuniform layers deviate from the behavior predicted in the thin boundary approximation and strongly depend on the shape of the nonuniform layer. The eigenfunctions in ideal MHD are very different from those in resistive MHD. The ideal eigenfunctions display a global character regardless of the thickness of the nonuniform layer, while the resistive eigenfunctions are localized around the resonance and are indistinguishable from those of ordinary resistive Alfvén modes. Consequently, the spatial distribution of wave energy in the ideal and resistive cases is dramatically different. This poses a fundamental theoretical problem with clear observational consequences.

  7. Continuous-Wave Radar to Detect Defects Within Heat Exchangers and Steam Generator Tubes ; Revised September 3, 2003

    Energy Technology Data Exchange (ETDEWEB)

    Gary E. Rochau and Thurlow W.H. Caffey, Sandia National Laboratories, Albuquerque, NM 87185-0740; Bahram Nassersharif and Gabe V. Garcia, Department of Mechanical Engineering, New Mexico State University, Las Cruces, NM 88003-8001; Russell P. Jedlicka, Klipsch School of Electrical and Computer Engineering, New Mexico State University, Las Cruces, NM 88003-8001

    2003-05-01

    OAK B204 Continuous-Wave Radar to Detect Defects Within Heat Exchangers and Steam Generator Tubes ; Revised September 3, 2003. A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique was researched for detection of defects using a continuous-wave radar method within metal tubing. The technique is 100% volumetric, and may find smaller defects, more rapidly, and less expensively than present methods. The project described in this report was a joint development effort between Sandia National Laboratories (SNL) and New Mexico State University (NMSU) funded by the US Department of Energy. The goal of the project was to research, design, and develop a new concept utilizing a continuous wave radar to detect defects inside metallic tubes and in particular nuclear plant steam generator tubing. The project was divided into four parallel tracks: computational modeling, experimental prototyping, thermo-mechanical design, and signal detection and analysis.

  8. Continuous-Wave Radar to Detect Defects Within Heat Exchangers and Steam Generator Tubes; Revised September 3, 2003

    International Nuclear Information System (INIS)

    OAK B204 Continuous-Wave Radar to Detect Defects Within Heat Exchangers and Steam Generator Tubes ; Revised September 3, 2003. A major cause of failures in heat exchangers and steam generators in nuclear power plants is degradation of the tubes within them. The tube failure is often caused by the development of cracks that begin on the outer surface of the tube and propagate both inwards and laterally. A new technique was researched for detection of defects using a continuous-wave radar method within metal tubing. The technique is 100% volumetric, and may find smaller defects, more rapidly, and less expensively than present methods. The project described in this report was a joint development effort between Sandia National Laboratories (SNL) and New Mexico State University (NMSU) funded by the US Department of Energy. The goal of the project was to research, design, and develop a new concept utilizing a continuous wave radar to detect defects inside metallic tubes and in particular nuclear plant steam generator tubing. The project was divided into four parallel tracks: computational modeling, experimental prototyping, thermo-mechanical design, and signal detection and analysis

  9. AN INVESTIGATION OF ELECTROMAGNETIC WAVE PROPAGATION IN PLASMA BY SHOCK TUBE

    Institute of Scientific and Technical Information of China (English)

    ZHU Naiyi; LI Xuefen; HUANG Lishun; YU Xilong; YANG Qiansuo

    2004-01-01

    This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters ne, v, ω, L, ωb. The φ800 mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2 ~ 35) GHz (ω = 2π f, wave length λ = 15 cm ~ 8 mm). The electron density in the plasma is ne = (3 × 1010 ~ 1× 1014) cm-3. The collision frequency v = (1× 10s ~ 6 × 1010)Hz. The thickness of the plasma layer L = (2 ~ 80) cm. The electron circular frequency ωb = eBo/me, magnetic flux density B0 = (0 ~ 0.84)T. The experimental results show that when the plasma layer is thick (such as L/λ≥ 10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters ne, v, ω, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and λ are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range,but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters ne, v, ω, L. In fact, if ω<ωp, v2 <<ω2, the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if ω>ωp, v2 <<ω2 (just v ≈ f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power

  10. Thermal analysis and structural Optimization of electron gun for traveling wave tube

    International Nuclear Information System (INIS)

    Steady-state and transient thermal analysis of electron gun for a Ka-band traveling wave tube are theoretically performed with a newly-developed 2 mm cathode model by ANSYS software. The heat flux vector chart and temperature distribution chart as well as warm-up time are also derived. The discrepancy of 2% between simulation results and test results, proves that the finite element method is feasible. The ultimate temperature reached by cathode, at given heater power, remarkably depends on the thermal conduction mechanism through cathode module. Based on the heat flux vector chart, the structure of cathode support sleeve with the highest flux is optimized. After optimization, the temperature of cathode increases 28 ℃ the highest temperature of electron gun increases 27 ℃ and the warm-up time of cathode reduces 40 s under the same given heater power. The optimized structure can effectively shorten the warm-up time of cathode by 33% and thus improve fast warm-up the performance of cathode, enhancing the rapid response capability of traveling wave tube. (authors)

  11. Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

    Institute of Scientific and Technical Information of China (English)

    Elijah COURTNEY; Amy COURTNEY; Michael COURTNEY

    2014-01-01

    Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from w1 MPa to w5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral prim-ing section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.

  12. Numerical and experimental study of shock waves emanating from an open-ended rectangular tube

    Science.gov (United States)

    Koroteeva, E. Yu.; Znamenskaya, I. A.; Glazyrin, F. N.; Sysoev, N. N.

    2016-04-01

    We examine the dynamics of a high-speed shock-induced flow near the open end of a shock tube using the particle image velocimetry (PIV) and the background oriented schlieren (BOS) methods along with two- and three-dimensional numerical simulations. In experiments, planar shock waves (M=1.3 -1.6) are discharged from a rectangular (24 mm × 48 mm ) low-pressure section of a shock tube open to the atmosphere. Due to the rectangular exit geometry, the resulting flow is highly three-dimensional and, thus, more complicated, compared to well-studied circular/axisymmetric geometries. The study focuses on the spatio-temporal flow structure up to 1 ms after the shock wave diffraction. PIV and BOS visualization techniques share the same post-processing principle, and the iterative multi-step cross-correlation algorithm applied in the PIV software is adapted here for the calculation of background pattern displacement on the BOS images. Particular attention is given to the resolution of flow regions where sharp gradients are present, such as a diffracted shock front or embedded shocks. Computational fluid dynamic simulations of the problem are also conducted to validate the experimental results and methods and to gain more insight into the three-dimensional flow dynamics. PIV and BOS images are found to be consistent with the corresponding numerical flow visualizations.

  13. Numerical and experimental study of shock waves emanating from an open-ended rectangular tube

    Science.gov (United States)

    Koroteeva, E. Yu.; Znamenskaya, I. A.; Glazyrin, F. N.; Sysoev, N. N.

    2016-05-01

    We examine the dynamics of a high-speed shock-induced flow near the open end of a shock tube using the particle image velocimetry (PIV) and the background oriented schlieren (BOS) methods along with two- and three-dimensional numerical simulations. In experiments, planar shock waves (M=1.3-1.6) are discharged from a rectangular (24 mm × 48 mm) low-pressure section of a shock tube open to the atmosphere. Due to the rectangular exit geometry, the resulting flow is highly three-dimensional and, thus, more complicated, compared to well-studied circular/axisymmetric geometries. The study focuses on the spatio-temporal flow structure up to 1 ms after the shock wave diffraction. PIV and BOS visualization techniques share the same post-processing principle, and the iterative multi-step cross-correlation algorithm applied in the PIV software is adapted here for the calculation of background pattern displacement on the BOS images. Particular attention is given to the resolution of flow regions where sharp gradients are present, such as a diffracted shock front or embedded shocks. Computational fluid dynamic simulations of the problem are also conducted to validate the experimental results and methods and to gain more insight into the three-dimensional flow dynamics. PIV and BOS images are found to be consistent with the corresponding numerical flow visualizations.

  14. Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

    Directory of Open Access Journals (Sweden)

    Elijah Courtney

    2014-06-01

    Full Text Available Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ∼1 MPa to ∼5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform. The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.

  15. 振荡管复合阻尼陷波%ELIMINATION OF REFLECT SHOCK WAVE IN OSCILLATORY TUBE

    Institute of Scientific and Technical Information of China (English)

    李学来; 朱彻

    2001-01-01

    A new concept,compound damp drip for absorbing shock wave in oscillatory tube,is developed in the present paper.The main idea of the concept is that the shock wave absorber must has the two functions,that is,it can not only exhaust the energy of the incident shock wave fully but also transfer the energy out promptly.In the experiment,the compound damp drip is structured with a multi-orifice for intensifying the energy dissipation of the shock wave and an internal cooling system for strengthening the heat transfer.The experimental results show that a strong reflect shock wave,whose strength is 66%of the incident shock wave ,is measured at the position of the relative tube length x/L=0.3 when the oscillatory tube without the compound damp drip.But,after the compound damp drip is amounted at the closed end of the tube,the reflect shock wave is eliminated effectively and the refrigerating efficiency η is increased by 4?%~10?% in case of the L/d ratio is 140 and the expansion ratio ε is changed from 2.0 to 6.0.What is more ,the refrigerating efficiency in case of L/d=140 and the tube is mounted with the compound damp drip is still higher by 2?%~6?% than that the tube without damp drip but L/d=300.The above result means that while the damp drip is used,the refrigerating efficiency can be increased and the size of the refrigerator can be decreased significantly.

  16. The flexible asymmetric shock tube (FAST): a Ludwieg tube facility for wave propagation measurements in high-temperature vapours of organic fluids

    Science.gov (United States)

    Mathijssen, T.; Gallo, M.; Casati, E.; Nannan, N. R.; Zamfirescu, C.; Guardone, A.; Colonna, P.

    2015-10-01

    This paper describes the commissioning of the flexible asymmetric shock tube (FAST), a novel Ludwieg tube-type facility designed and built at Delft University of Technology, together with the results of preliminary experiments. The FAST is conceived to measure the velocity of waves propagating in dense vapours of organic fluids, in the so-called non-ideal compressible fluid dynamics (NICFD) regime, and can operate at pressures and temperatures as high as 21 bar and 400°C, respectively. The set-up is equipped with a special fast-opening valve, separating the high-pressure charge tube from the low-pressure plenum. When the valve is opened, a wave propagates into the charge tube. The wave speed is measured using a time-of-flight technique employing four pressure transducers placed at known distances from each other. The first tests led to the following results: (1) the leakage rate of 5 × {10}^{-4} {mbar l s^{-1}} for subatmospheric and 5 × {10}^{-2} {mbar l s^{-1}} for a superatmospheric pressure is compatible with the purpose of the conceived experiments, (2) the process start-up time of the valve has been found to be between 2.1 and 9.0 ms, (3) preliminary rarefaction wave experiments in the dense vapour of siloxane {D}_6 (dodecamethylcyclohexasiloxane, an organic fluid) were successfully accomplished up to temperatures of 300°C, and (4) a method for the estimation of the speed of sound from wave propagation experiments is proposed. Results are found to be within 2.1 % of accurate model predictions for various gases. The method is then applied to estimate the speed of sound of {D}_6 in the NICFD regime.

  17. High-Efficiency, High-Power Ka-Band Elliptic-Beam Traveling-Wave-Tube Amplifier for Long-Range Space RF Telecommunications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Space telecommunications require amplifiers that are efficient, high-power, wideband, small, lightweight, and highly reliable. Currently, helix traveling wave tube...

  18. Experimental approach to shape field relevant blast wave profiles in compressed gas-driven shock tube

    Directory of Open Access Journals (Sweden)

    Aravind eSundaramurthy

    2014-12-01

    Full Text Available Detonation of a high explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects even at farther distances, which is termed as primary blast injury, which is the theme of this work. The shock-blast profile is characterized with blast overpressure, positive time duration, and impulse as shock-blast wave parameters (SWPs. These parameters in turn are a function of field factors, such as the strength of high explosive and the distance of the human subjects from the epicenter. The shape and magnitude of the profile determine the severity of injury to the subjects. As shown in some of our recent works (Chandra et al., 2011;Sundaramurthy et al., 2012;Skotak et al., 2013, the profile not only determines the survival of the animal but also the acute and chronic biomechanical injuries along with the following bio-chemical sequelae. It is extremely important to carefully design and operate the shock tube to produce field relevant SWPs. Furthermore, it is vital to identify and eliminate the artifacts that are inadvertently introduced in the shock-blast profile that may affect the results. In this work, we examine the relationship between shock tube adjustable parameters (SAPs and SWPs that can be used to control the blast profile; the results can be easily applied to many of the laboratory shock tubes. Further, exact replication of shock profile (magnitude and shape can be related to field explosions and can be a standard in comparing results across different laboratories. 40 experiments are carried out by judiciously varying SAPs such as membrane thickness, breech length (66.68 to 1209.68 mm, measurement location, and type of driver gas (nitrogen, helium. The relationships between SAPs and the resulting shock-blast profiles are characterized. Finally, shock-blast profiles of a TNT explosion from ConWep software is compared with the profiles obtained

  19. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    International Nuclear Information System (INIS)

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by “fresh” electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam

  20. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    Science.gov (United States)

    Ginzburg, N. S.; Zotova, I. V.; Sergeev, A. S.; Zaslavsky, V. Yu.; Zheleznov, I. V.; Samsonov, S. V.; Mishakin, S. V.

    2015-11-01

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by "fresh" electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.

  1. Bak-Sneppen Backwards

    OpenAIRE

    Alberts, Tom; Lee, Ga Yeong; Simper, Mackenzie

    2015-01-01

    We study the backwards Markov chain for the Bak-Sneppen model of biological evolution and derive its corresponding reversibility equations. We show that, in contrast to the forwards Markov chain, the dynamics of the backwards chain explicitly involve the stationary distribution of the model, and from this we derive a functional equation that the stationary distribution must satisfy. We use this functional equation to derive differential equations for the stationary distribution of Bak-Sneppen...

  2. High-Power, High-Efficiency Ka-Band Space Traveling-Wave Tube

    Science.gov (United States)

    Krawczyk, Richard; Wilson, Jeffrey; Simons, Rainee; Williams, Wallace; Bhasin, Kul; Robbins, Neal; Dibb, Daniel; Menninger, William; Zhai, Xiaoling; Benton, Robert; Burdette, James

    2007-01-01

    The L-3 Communications Model 999H traveling-wave tube (TWT) has been demonstrated to generate an output power of 144 W at 60-percent overall efficiency in continuous-wave operation over the frequency band from 31.8 to 32.3 GHz. The best TWT heretofore commercially available for operation in the affected frequency band is characterized by an output power of only 35 W and an efficiency of 50 percent. Moreover, whereas prior TWTs are limited to single output power levels, it has been shown that the output power of the Model 999H can be varied from 54 to 144 W. A TWT is a vacuum electronic device used to amplify microwave signals. TWTs are typically used in free-space communication systems because they are capable of operating at power and efficiency levels significantly higher than those of solid-state devices. In a TWT, an electron beam is generated by an electron gun consisting of a cathode, focusing electrodes, and an anode. The electrons pass through a hole in the anode and are focused into a cylindrical beam by a stack of periodic permanent magnets and travel along the axis of an electrically conductive helix, along which propagates an electromagnetic wave that has been launched by an input signal that is to be amplified. The beam travels within the helix at a velocity close to the phase velocity of the electromagnetic wave. The electromagnetic field decelerates some of the electrons and accelerates others, causing the beam to become formed into electron bunches, which further interact with the electromagnetic wave in such a manner as to surrender kinetic energy to the wave, thereby amplifying the wave. The net result is to amplify the input signal by a factor of about 100,000. After the electrons have passed along the helix, they impinge on electrodes in a collector. The collector decelerates the electrons in such a manner as to recover most of the remaining kinetic energy and thereby significantly increase the power efficiency of the TWT.

  3. Measurement of the polarizability of Ar+, Kr+, and Xe+ ions at a shock wave tube

    International Nuclear Information System (INIS)

    The polarizability of Argon ions, Krypton ions, and Xenon ions has been measured by two-wavelength-interferometry with plasmas produced in a shock-wave tube with a membrane. For Mach numbers from 11 to 25, electron densities in the range of 1016 up to some 1017 cm-3, neutral densities up to some 1018 cm-3 and plasma temperature between 9000 K and 13500 K were found. The ratio of the ion polarizability and the well known atom polarizability turned out to be 0.629 for argon, 0.577 for krypton, and 0.528 for xenon, with statistical error of approximately 5% and total error smaller than 10%. (orig./AH)

  4. Modular Low-Heater-Power Cathode/Electron Gun Assembly for Microwave and Millimeter Wave Traveling Wave Tubes

    Science.gov (United States)

    Wintucky, Edwin G.

    2000-01-01

    A low-cost, low-mass, electrically efficient, modular cathode/electron gun assembly has been developed by FDE Inc. of Beaverton, Oregon, under a Small Business Innovation Research (SBIR) contract with the NASA Glenn Research Center at Lewis Field. This new assembly offers significant improvements in the design and manufacture of microwave and millimeter wave traveling-wave tubes (TWT's) used for radar and communications. It incorporates a novel, low-heater-power, reduced size and mass, high-performance barium dispenser type thermionic cathode and provides for easy integration of the cathode into a large variety of conventional TWT circuits. Among the applications are TWT's for Earth-orbiting communication satellites and for deep space communications, where future missions will require smaller spacecraft, higher data transfer rates (higher frequencies and radiofrequency output power), and greater electrical efficiency. A particularly important TWT application is in the microwave power module (a hybrid microwave/millimeter wave amplifier consisting of a low-noise solid-state driver, a small TWT, and an electronic power conditioner integrated into a single compact package), where electrical efficiency and thermal loading are critical factors and lower cost is needed for successful commercialization. The design and fabrication are based on practices used in producing cathode ray tubes (CRT's), which is one of the most competitive and efficient manufacturing operations in the world today. The approach used in the design and manufacture of thermionic cathodes and electron guns for CRT's has been optimized for fully automated production, standardization of parts, and minimization of costs. It is applicable to the production of similar components for microwave tubes, with the additional benefits of low mass and significantly lower cathode heater power (less than half that of dispenser cathodes presently used in TWT s). Modular cathode/electron gun assembly. The modular

  5. Long range guided wave inspection of a small-bone tube with the magnetostrictive transducer technique

    International Nuclear Information System (INIS)

    There are several incidents from the leakage of the pipes which are in the category of a safety class as well as a non-safety class in nuclear power plants. However, in many cases, because of their geometrical complexity and inaccessibility, it is difficult to inspect them by the conventional ultrasonic method. A long-range guided ultrasonic inspection, thus, is an option to inspect them during an outage period. The magnetostrictive transducer technique has several advantages for practical applications, for such as a 100-percent volumetric coverage of a long segment of a structure, the inspection time and its cost effective, with a relatively simple and easy transducer structure. This study investigated the applicability of a long-rang guided ultrasonic method for the detection of artificial notches even in the presence of various foreign objects. Both the torsional (T(0,1) mode) and the longitudinal (L(0,1) mode) guided ultrasonic waves were effective for the long-range inspection of the tubes. It showed that it had a good detectability for the notch in the tubes, even though several obstacles are attached in front of the notch.

  6. Blast Wave Formation by Laser-Sustained Nonequilibrium Plasma in the Laser-Driven In-Tube Accelerator Operation

    International Nuclear Information System (INIS)

    Understanding the dynamics of laser-produced plasma is essentially important for increasing available thrust force in a gas-driven laser propulsion system such as laser-driven in-tube accelerator. A computer code is developed to explore the formation of expanding nonequilibrium plasma produced by laser irradiation. Various properties of the blast wave driven by the nonequilibrium plasma are examined. It is found that the blast wave propagation is substantially affected by radiative cooling effect for lower density case

  7. Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

    International Nuclear Information System (INIS)

    A novel slow-wave structure (SWS), the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1–1.27 dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS (FWSWS) shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency. (fundamental areas of phenomenology (including applications))

  8. Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

    Institute of Scientific and Technical Information of China (English)

    HE Jun; WEI Yan-Yu; GONG Yu-Bin; WANG Wen-Xiang

    2009-01-01

    A novel slow-wave structure (SWS), the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1-1.27dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS (FWSWS) shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency.

  9. Development of Magneto-static Solver Module for the design of compact and light-weight Traveling Wave Tubes

    International Nuclear Information System (INIS)

    Traveling Wave Tubes are the unique class of microwave amplifiers with broad bandwidth, which makes it preferred for space applications. The constraints for a space application are very stringent demanding compactness and less weight. Entire size of the tube is mainly decided by the size of the collector, as it is the bulkiest component in a tube. Hence, if the size of the collector is reduced then the entire tube size will reduce. Researches reveal that in order to reduce the size of the collector, application of the magnetic field is necessary. Therefore, to study the effect of magnetic field on the collector performance, a magneto-static solver module has been developed. This paper describes the development of the magneto-static solver.

  10. Backward adaptive biorthogonalization

    OpenAIRE

    L. Rebollo-Neira

    2004-01-01

    A backward biorthogonalization approach is proposed, which modifies biorthogonal functions so as to generate orthogonal projections onto a reduced subspace. The technique is relevant to problems amenable to be represented by a general linear model. In particular, problems of data compression, noise reduction, and sparse representations may be tackled by the proposed approach.

  11. Tailoring the Blast Exposure Conditions in the Shock Tube for Generating Pure, Primary Shock Waves: The End Plate Facilitates Elimination of Secondary Loading of the Specimen.

    Science.gov (United States)

    Kuriakose, Matthew; Skotak, Maciej; Misistia, Anthony; Kahali, Sudeepto; Sundaramurthy, Aravind; Chandra, Namas

    2016-01-01

    The end plate mounted at the mouth of the shock tube is a versatile and effective implement to control and mitigate the end effects. We have performed a series of measurements of incident shock wave velocities and overpressures followed by quantification of impulse values (integral of pressure in time domain) for four different end plate configurations (0.625, 2, 4 inches, and an open end). Shock wave characteristics were monitored by high response rate pressure sensors allocated in six positions along the length of 6 meters long 229 mm square cross section shock tube. Tests were performed at three shock wave intensities, which was controlled by varying the Mylar membrane thickness (0.02, 0.04 and 0.06 inch). The end reflector plate installed at the exit of the shock tube allows precise control over the intensity of reflected waves penetrating into the shock tube. At the optimized distance of the tube to end plate gap the secondary waves were entirely eliminated from the test section, which was confirmed by pressure sensor at T4 location. This is pronounced finding for implementation of pure primary blast wave animal model. These data also suggest only deep in the shock tube experimental conditions allow exposure to a single shock wave free of artifacts. Our results provide detailed insight into spatiotemporal dynamics of shock waves with Friedlander waveform generated using helium as a driver gas and propagating in the air inside medium sized tube. Diffusion of driver gas (helium) inside the shock tube was responsible for velocity increase of reflected shock waves. Numerical simulations combined with experimental data suggest the shock wave attenuation mechanism is simply the expansion of the internal pressure. In the absence of any other postulated shock wave decay mechanisms, which were not implemented in the model the agreement between theory and experimental data is excellent. PMID:27603017

  12. STANDARD BASED RELIABILITY PREDICTION OF TRAVELING WAVE TUBE IN COMMUNICATION SATELLITE

    Directory of Open Access Journals (Sweden)

    M. SIVANANDAM

    2011-10-01

    Full Text Available A Traveling Wave Tube (TWT is a vital component of satellite communication transponder. Before launch, it is essential to ensure that TWT meets the life of the satellite in the orbit.. Standard based reliability prediction is fairly accurate, widely used in USA and Europe and specified to the contractors. Part stress and parts count analysis are considered in all the standards. In this paper, part stress analysis based on US Military standard,MIL – HDBK – 217F is considered. Since the standard does not provide the failure rate of individual components used in TWT, Preferred Reliability Practices specified by NASA USA in their documents No PD – ED – 1216 is considered for parts count analysis. The reliability estimated by the above standards does not meet the life of 10 years .In the past five years, tremendous improvements have occurred in the materials,design, fabrication, testing and simulation of TWT. Based on these improvements, reliability is recalculated. The revised reliability estimate meets the life of 10 years and coincides with the reliability claimed by the global suppliers of space TWT.

  13. Resolving Structural Isomers of Monosaccharide Methyl Glycosides Using Drift Tube and Traveling Wave Ion Mobility Mass Spectrometry

    OpenAIRE

    Li, Hongli; Giles, Kevin; Bendiak, Brad; Kaplan, Kimberly; Siems, William F.; Hill, Herbert H.

    2012-01-01

    Monosaccharide structural isomers including sixteen methyl-D-glycopyranosides and four methyl-N-acetylhexosamines were subjected to ion mobility measurements by electrospray ion mobility mass spectrometry. Two ion mobility-MS systems were employed: atmospheric pressure drift tube ion mobility time-of-flight mass spectrometry and a Synapt G2 HDMS system which incorporates a low pressure traveling wave ion mobility separator. All the compounds were investigated as [M+Na]+ ions in the positive m...

  14. Novel Low-Cost, Low-Power Miniature Thermionic Cathode Developed for Microwave/Millimeter Wave Tube and Cathode Ray Tube Applications

    Science.gov (United States)

    Wintucky, Edwin G.

    1999-01-01

    A low cost, small size and mass, low heater power, durable high-performance barium dispenser thermionic cathode has been developed that offers significant advancements in the design, manufacture, and performance of the electron sources used in vacuum electronic devices--such as microwave (and millimeter wave) traveling-wave tubes (TWT's)--and in display devices such as high-brightness, high-resolution cathode ray tubes (CRT's). The lower cathode heater power and the reduced size and mass of the new cathode are expected to be especially beneficial in TWT's for deep space communications, where future missions are requiring smaller spacecraft, higher data transfer rates (higher frequencies and radiofrequency output power), and greater electrical efficiency. Also expected to benefit are TWT's for commercial and government communication satellites, for both low and geosynchronous Earth orbit, with additional benefits offered by lower cost and potentially higher cathode current loading. A particularly important TWT application is in the microwave power module (MPM), which is a hybrid microwave (or millimeter wave) amplifier consisting of a low-noise solid state driver, a vacuum power booster (small TWT), and an electronic power conditioner integrated into a single compact package. The attributes of compactness and potentially high electrical efficiency make the MPM very attractive for many commercial and government (civilian and defense) applications in communication and radar systems. The MPM is already finding application in defense electronic systems and is under development by NASA for deep space communications. However, for the MPM to become competitive and commercially successful, a major reduction in cost must be achieved.

  15. Accelerated Backward Warping

    Institute of Scientific and Technical Information of China (English)

    ZHANG YanCi(张严辞); LIU XueHui(刘学慧); WU EnHua(吴恩华)

    2003-01-01

    In this paper a plane-based backward warping algorithm is proposed to generate novel views from multiple reference images. First, depth information is employed to reconstruct space planes from individual reference images and calculate the potential occluding relationship between these planes. Then the planes which represent each identical space plane from different reference images are compared with each other to decide the one with the best sample rate to be preserved and used in the later warping period while the other samples are abandoned. While the image of a novel view is produced, traditional methods in computer graphics, such as visibility test and clipping, are used to process the planes reconstructed. Then the planes processed are projected onto the desired image from the knowledge on which plane the desired image pixels are warped from can be acquired. Finally, pixels' depth of the desired image is calculated and then a backward warping is performed from these pixels to the reference images to obtain their colors. The storage requirement in the algorithm is small and increases slowly with the number of reference images increases. By combining the strategy of only preserving the best sample parts and the backward warping algorithm, the sample problem could be well tackled.

  16. Injector for a high frequency wave generating tube of the central injection Gyrotron type

    International Nuclear Information System (INIS)

    This theoretical and at the same time experimental study was carried out at the 'Service Ionique Generale' in Grenoble. High frequency wave generators are already in use there, making it possible to approach the fusion conditions of light elements such as deuterium. The plasma confined by the toroidal magnetic field uses to heat itself the electromagnetic energy provided by sources from which a good performance is required. Klystron and Magnetron are devices in which the interaction between the electric and magnetic fields of a resonating cavity and the continuous energy of a beam produces a positive result. In the Klystron, the velocity modulation is axial whereas in the Magnetron it is azimuthal. Therefore packets of electrons are formed. If this modulation of the velocities occurs radially, the beam will swell and compress periodically. The name of 'Central Injection Gyrotron' has been associated recently in the literature to this type of interaction exhibiting a good performance. Placing on trajectory the electrons forming the beam is one of the difficulties of the good working of this ultra high frenquency tube. Since no device gives safisfaction at the present time, the devising of a new type of injector specially adapted to the forming of the beam is therefore justified. The originality is that it uses on the electrostatic gun side a cathode immersed in a magnetic field of which the axial component is in the opposite direction to that which maintains the formed beam injected in the cavity. The magnetic correction of the trajectories is the most practical with respect to the experiment, providing that the electrostatic gun does not disperse them individually. This leads to seeking an improvement in the geometry of the gun. However, it will be necessary to consider the problems of power limitation due to the space charge

  17. Predictive value of low tube voltage and dual-energy CT for successful shock wave lithotripsy: an in vitro study.

    Science.gov (United States)

    Largo, Remo; Stolzmann, Paul; Fankhauser, Christian D; Poyet, Cédric; Wolfsgruber, Pirmin; Sulser, Tullio; Alkadhi, Hatem; Winklhofer, Sebastian

    2016-06-01

    This study investigates the capabilities of low tube voltage computed tomography (CT) and dual-energy CT (DECT) for predicting successful shock wave lithotripsy (SWL) of urinary stones in vitro. A total of 33 urinary calculi (six different chemical compositions; mean size 6 ± 3 mm) were scanned using a dual-source CT machine with single- (120 kVp) and dual-energy settings (80/150, 100/150 Sn kVp) resulting in six different datasets. The attenuation (Hounsfield Units) of calculi was measured on single-energy CT images and the dual-energy indices (DEIs) were calculated from DECT acquisitions. Calculi underwent SWL and the number of shock waves for successful disintegration was recorded. The prediction of required shock waves regarding stone attenuation/DEI was calculated using regression analysis (adjusted for stone size and composition) and the correlation between CT attenuation/DEI and the number of shock waves was assessed for all datasets. The median number of shock waves for successful stone disintegration was 72 (interquartile range 30-361). CT attenuation/DEI of stones was a significant, independent predictor (P waves with the best prediction at 80 kVp (β estimate 0.576) (P waves ranged between ρ = 0.31 and 0.68 showing the best correlation at 80 kVp (P < 0.001). The attenuation of urinary stones at low tube voltage CT is the best predictor for successful stone disintegration, being independent of stone composition and size. DECT shows no added value for predicting the success of SWL. PMID:26391614

  18. A Simple Experiment to Explore Standing Waves in a Flexible Corrugated Sound Tube

    Science.gov (United States)

    Amorim, Maria Eva; Sousa, Teresa Delmira; Carvalho, P. Simeao; Sousa, Adriano Sampaioe

    2011-01-01

    Sound tubes, pipes, and singing rods are used as musical instruments and as toys to perform amusing experiments. In particular, corrugated tubes present unique characteristics with respect to the sounds they can produce; that is why they have been studied so intensively, both at theoretical and experimental levels. Experimental studies usually…

  19. Methods of generation and amplification of micro- and millimeter waves in vacuum tubes

    Science.gov (United States)

    Steyskal, H.

    1981-01-01

    The principles underlying electron tubes, such as gyrotrons, peniotrons, free electron lasers, orotrons, and gyrocons are described. These generators for very high frequency and very high power generators are considerably different from conventional microwave tubes. They are at present in the research and development stage but may soon become important for fusion and radar technology.

  20. A parametric approach to shape field-relevant blast wave profiles in compressed-gas-driven shock tube.

    Science.gov (United States)

    Sundaramurthy, Aravind; Chandra, Namas

    2014-01-01

    Detonation of a high-explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects, even at farther distances. When a pure shock-blast wave encounters the subject, in the absence of shrapnels, fall, or gaseous products the loading is termed as primary blast loading and is the subject of this paper. The wave profile is characterized by blast overpressure, positive time duration, and impulse and called herein as shock-blast wave parameters (SWPs). These parameters in turn are uniquely determined by the strength of high explosive and the distance of the human subjects from the epicenter. The shape and magnitude of the profile determine the severity of injury to the subjects. As shown in some of our recent works (1-3), the profile not only determines the survival of the subjects (e.g., animals) but also the acute and chronic biomechanical injuries along with the following bio-chemical sequelae. It is extremely important to carefully design and operate the shock tube to produce field-relevant SWPs. Furthermore, it is vital to identify and eliminate the artifacts that are inadvertently introduced in the shock-blast profile that may affect the results. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs that can be used to control the blast profile; the results can be easily applied to many of the laboratory shock tubes. Further, replication of shock profile (magnitude and shape) can be related to field explosions and can be a standard in comparing results across different laboratories. Forty experiments are carried out by judiciously varying SAPs such as membrane thickness, breech length (66.68-1209.68 mm), measurement location, and type of driver gas (nitrogen, helium). The effects SAPs have on the resulting shock-blast profiles are shown. Also, the shock-blast profiles of a TNT explosion from ConWep software is compared

  1. Backward-Propagating MeV Electrons in Ultra-Intense Laser Interactions: Standing Wave Acceleration and Coupling to the Reflected Laser Pulse

    CERN Document Server

    Orban, Chris; Chowdhury, Enam D; Nees, John A; Frische, Kyle; Roquemore, W Melvyn

    2014-01-01

    Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense ($\\sim10^{18}$ W/cm$^2$), 30 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-In-Cell (PIC) simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave "injects" electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standing wave acceleration: a highly relativistic case ($a_0~\\geq~1$), and a moderately relativistic case ($a_0~\\sim~0.5$) which operates over a larger fraction of the laser period. Previous work by other groups investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this ...

  2. Backward-propagating MeV electrons in ultra-intense laser interactions: Standing wave acceleration and coupling to the reflected laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Orban, Chris, E-mail: orban@physics.osu.edu; Feister, Scott [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Morrison, John T. [National Research Council, Washington, DC 20001 (United States); Intense Energy Solutions, LLC, Plain City, Ohio 43064 (United States); Chowdhury, Enam A. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Center for Ultra-Fast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Nees, John A. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Intense Energy Solutions, LLC, Plain City, Ohio 43064 (United States); Frische, Kyle [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Roquemore, W. M. [Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

    2015-02-15

    Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense (∼10{sup 18 }W/cm{sup 2}), ∼40 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-in-Cell simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave can “inject” electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standing wave acceleration: a highly relativistic case (a{sub 0} ≥ 1), and a moderately relativistic case (a{sub 0} ∼ 0.5) which operates over a larger fraction of the laser period. In previous studies, other groups have investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this by investigating electron acceleration in the specular (back reflection) direction and over a wide range of intensities (10{sup 17}–10{sup 19 }W cm{sup −2})

  3. Traveling-wave tube reliability estimates, life tests, and space flight experience

    Science.gov (United States)

    Lalli, V. R.; Speck, C. E.

    1977-01-01

    Infant mortality, useful life, and wearout phase of twt life are considered. The performance of existing developmental tubes, flight experience, and sequential hardware testing are evaluated. The reliability history of twt's in space applications is documented by considering: (1) the generic parts of the tube in light of the manner in which their design and operation affect the ultimate reliability of the device, (2) the flight experience of medium power tubes, and (3) the available life test data for existing space-qualified twt's in addition to those of high power devices.

  4. Klystrons, traveling wave tubes, magnetrons, crossed-field amplifiers, and gyrotrons

    CERN Document Server

    Gilmour, A S

    2011-01-01

    Microwave tubes are vacuum electron devices used for the generation and amplification of radio frequencies in the microwave range. An established technology area, the use of tubes remains essential in the field today for high-power applications. The culmination of the author's 50 years of industry experience, this authoritative resource offers you a thorough understanding of the operations and major classes of microwave tubes.Minimizing the use of advanced mathematics, the book places emphasis on clear qualitative explanations of phenomena. This practical reference serves as an excellent intro

  5. Toward a Comprehensive Understanding of Transition Zone Seismic Discontinuities: Part I. New Constraints from Receiver Function Forward and Backward Scattering Waves

    Science.gov (United States)

    Shen, X.; Song, T. R. A.; Yuan, X.

    2014-12-01

    Transition zone discontinuities, among all, hold the key to resolve the mystery of mass and heat transport in the Earth's mantle and the composition of the Earth's interior. In previous efforts, the data are limited to either upper mantle triplications, converted waves or mantle reflections (e.g. SS precursors, ScS reverberations). When multiple datasets are jointly analyzed, they are often restrained at relatively long period (~ 0.1 Hz). To complement previous efforts, we advocate a simple and effective strategy to tackle a number of seismic observables altogether. Specifically, we involve broadband direct converted waves (e.g., P410s, P660s) and the topside reflections (the multiples, e.g., PpP410s, PpP660s) in the context of P wave receiver function technique. Such a tactic not only minimizes tradeoffs between velocity and density jumps, but also allows a superior resolution on the sharpness of the boundary and a detailed description of transition zone discontinuities. Here we summarize our first attempt in the region of stagnant slab beneath Chinese continent. We processed waveforms from 1000 stations of the Chinese seismic array using an automatic scheme to remove noisy waveforms and retained close to ~300,000 high quality receiver functions in the L-Q-T coordinate system. While avoiding interferences from other mantle waves, we perform slowness stacking of direct converted waves and the multiples, respectively, at several discrete frequency bands between 0.05 Hz and 1Hz and obtain amplitude estimates and uncertainties through the bootstrap method. To properly calibrate the amplitudes of receiver functions, we take into account the effect of incoherent stacking due to discontinuity topography and frequency-dependent attenuation. Our findings indicate that the 410 is a sharp boundary with a small density jump ( 3x10-3 km/s/km, > 3x10-3 g/cm3/km). We will discuss the implications of these new findings in the context of thermochemical state of the transition zone

  6. Backward semantic inhibition in toddlers

    OpenAIRE

    Chow, J.; Aimola Davies, AM; Fuentes, LJ; Plunkett, KR

    2016-01-01

    Attention-switching is a crucial ability required in our everyday life, from toddlerhood to adulthood. In adults, shifting attention from one word (e.g., dog) to another (e.g., sea) results in backward semantic inhibition, i.e., the inhibition of the initial word (dog). This study examines whether attention-switching is accompanied by backward semantic inhibition in toddlers using the preferential looking paradigm. The findings demonstrate that a backward inhibitory mechanism operates during ...

  7. Design and microwave test of an ultrawideband input/output structure for sheet beam travelling wave tubes

    International Nuclear Information System (INIS)

    Broadband operation is of great importance for the applications of travelling wave tubes such as high-data communication and wideband radar. An input/output (I/O) structure operating with broadband property plays a significant role to achieve these applications. In this paper, a Y-type branch waveguide (YTBW) coupler and its improvements are proposed and utilized to construct an extremely wideband I/O structure to ensure the broadband operation for sheet beam travelling wave tubes (SB-TWTs). Cascaded reflection resonators are utilized to improve the isolation characteristic and transmission efficiency. Furthermore, to minimize the reflectivity of the port connected with the RF circuit, wave-absorbing material (WAM) is loaded in the resonator. Simulation results for the YTBW loaded with WAM predict an excellent performance with a 50.2% relative bandwidth for port reflectivity under −15 dB, transmission up to −1.5 dB, and meanwhile isolation under −20 dB. In addition, the coupler has a relatively compact configuration and the beam tunnel can be widened, which is beneficial for the propagation of the electrons. A Q-band YTBW loaded with two reflection resonators is fabricated and microwave tested. Vector network analyzer (VNA) measured results have an excellent agreement with our simulation, which verify our theoretical analysis and simulation calculation

  8. High Power and Efficiency Space Traveling-Wave Tube Amplifiers With Reduced Size and Mass for NASA Missions

    Science.gov (United States)

    Simons, Rainee N.; Wilson, Jeffrey D.; Force, Dale A.

    2008-01-01

    Recent advances in high power and efficiency space traveling-wave tube amplifiers (TWTAs) for NASA s space-to-Earth communications are presented in this paper. The RF power and efficiency of a new K-Band amplifier are 40 W and 50 percent and that of a new Ka-Band amplifier are 200 W and 60 percent. An important figure-of-merit, which is defined as the ratio of the RF power output to the mass (W/kg) of a TWT has improved by a factor of ten over the previous generation Ka-Band devices.

  9. Backward pion photoproduction

    Energy Technology Data Exchange (ETDEWEB)

    Sibirtsev, A; Haidenbauer, J; Huang, F; Krewald, S; Meissner, U -G

    2009-04-01

    We present a systematic analysis of backward pion photoproduction for the reactions $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p and $ \\gamma$ p $ \\rightarrow$ $ \\pi^{+}_{}$ n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on $ \\pi^{0}_{}$ - and $ \\pi^{+}_{}$ -photoproduction at $ \\vartheta$ = 180° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around $ \\sqrt{{s}}$ ≃ 3 GeV. In the energy region of $ \\sqrt{{s}}$ $ \\le$2.5 GeV, covered by the new measurements of $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons.

  10. Optimal design of a standing-wave accelerating tube with a high shunt impedance based on a genetic algorithm

    Science.gov (United States)

    Tang, Zhenxing; Pei, Yuanji; Pang, Jian

    2015-08-01

    In this paper, we present an optimal design based on a genetic algorithm for a compact standing-wave (SW) accelerating tube with an operating frequency of 2998 MHz for industrial and medical applications. It consists of bi-periodic structures with a nose cone whose inter-cavity coupling is achieved through electric coupling rather than magnetic coupling. A mathematical model is established to optimize the arc at the cavity wall to reduce the microwave power loss and to optimize the nose cone to increase the electric field along the axis to achieve a high shunt impedance. The simulation results indicate that with the proper nose cone and arc, the shunt impedance of the cavity can be as high as 114 MΩ / m. Afterward, we present the tuning of the tube using SUPERFISH and the calculation of the beam dynamics using ASTRA and Parmela. The total length of the optimal tube is only 30.175 cm. Finally, a coupler is designed with a small-aperture coupling using CST MICROWAVE STUDIO.

  11. Analytic model of the stress waves propagation in thin wall tubes, seeking the location of a harmonic point source in its surface

    International Nuclear Information System (INIS)

    Leaks in pressurized tubes generate acoustic waves that propagate through the walls of these tubes, which can be captured by accelerometers or by acoustic emission sensors. The knowledge of how these walls can vibrate, or in another way, how these acoustic waves propagate in this material is fundamental in the detection and localization process of the leak source. In this work an analytic model was implemented, through the motion equations of a cylindrical shell, with the objective to understand the behavior of the tube surface excited by a point source. Since the cylindrical surface has a closed pattern in the circumferential direction, waves that are beginning their trajectory will meet with another that has already completed the turn over the cylindrical shell, in the clockwise direction as well as in the counter clockwise direction, generating constructive and destructive interferences. After enough time of propagation, peaks and valleys in the shell surface are formed, which can be visualized through a graphic representation of the analytic solution created. The theoretical results were proven through measures accomplished in an experimental setup composed of a steel tube finished in sand box, simulating the condition of infinite tube. To determine the location of the point source on the surface, the process of inverse solution was adopted, that is to say, known the signals of the sensor disposed in the tube surface , it is determined through the theoretical model where the source that generated these signals can be. (author)

  12. Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope

    OpenAIRE

    Landry, C; Favrel, A; Müller, A.; Nicolet, C.; Yamamoto, K.; Avellan, F.

    2014-01-01

    Hydraulic machines operating in a wider range are subjected to cavitation developments inducing undesirable pressure pulsations which could lead to potential instability of the power plant. The occurrence of pulsating cavitation volumes in the runner and the draft tube is considered as a mass source of the system and is depending on the cavitation compliance. This dynamic parameter represents the cavitation volume variation with the respect to a variation of pressure and defines implicitly th...

  13. Energy loss of solar p modes due to the excitation of magnetic sausage tube waves: Importance of coupling the upper atmosphere

    International Nuclear Information System (INIS)

    We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation of Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = –z0).

  14. Energy loss of solar p modes due to the excitation of magnetic sausage tube waves: Importance of coupling the upper atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Gascoyne, A.; Jain, R. [Applied Mathematics Department, University of Sheffield, Sheffield S3 7RH (United Kingdom); Hindman, B. W., E-mail: a.d.gascoyne@sheffield.ac.uk, E-mail: r.jain@sheffield.ac.uk [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CO 80309-0440 (United States)

    2014-07-10

    We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation of Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = –z{sub 0}).

  15. Analysis of the axial electric field in a plasma-loaded-helix travelling wave tube

    Institute of Scientific and Technical Information of China (English)

    Xie Hong-Quan; Liu Pu-Kun

    2006-01-01

    A helix type slow wave structure filled with plasma is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated radially into three regions. By means of the sheath model and Maxwell equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analysed respectively in different plasma densities, plasma column radius and dielectric constant by numerical computation. Some useful results are obtained on the basis of the discussion.

  16. Multivelocity electron beam as a source of microwave oscillations in the collector region of a traveling-wave tube

    Science.gov (United States)

    Starodubov, A. V.; Kalinin, Yu. A.

    2013-10-01

    The generation of noise-like broadband oscillations in the collector system region of a traveling-wave tube (TWT) is investigated experimentally. Analysis of experimental results shows that noise-like broad-band oscillations are generated in the collector region of the TWT due to the injection of a multivelocity electron beam into it. It is found that the maximal integrated power output from the collector region of the TWT is 12 W, and the maximal frequency and generation band are f max = 7 GHz and Δ f/ f ≈ 0.8, respectively. It is shown that a TWT with a collector-generator can simultaneously operate as an amplifier of an external signal and as a generator.

  17. Backward Tamm states in left-handed metamaterials

    OpenAIRE

    Namdar, Abdolrahman; Ilya V. Shadrivov; Yuri S. Kivshar

    2006-01-01

    We study the electromagnetic surface waves localized at an interface separating a one-dimensional photonic crystal and left-handed metamaterial, the so-called surface Tamm states. We demonstrate that the metamaterial allows for a flexible control of the dispersion properties of surface states, and can support the Tamm states with a backward energy flow and a vortex-like structure.

  18. 3D problem of pressure wave propagation in the tube with inconstant

    Czech Academy of Sciences Publication Activity Database

    Pochylý, F.; Habán, V.; Foldyna, Josef; Sitek, Libor

    Vienna: Viena University of Technology , 2007, s. 1-4. ISBN N. [International Congress on Ultrasonics. Vienna (AT), 09.04.2007-12.04.2007] R&D Projects: GA ČR GA101/07/1451 Institutional research plan: CEZ:AV0Z30860518 Keywords : pressure pulsations * wave equation * second viscosity Subject RIV: JQ - Machines ; Tools

  19. Contributions to the theory of longitudinal vibrations and wave propagation in rods and tubes: I. A mathematical model for linear elastic and hereditary elastic materials

    International Nuclear Information System (INIS)

    After a brief historical survey of some work done on the linear theory of longitudinal vibrations and wave propagation in rods and tubes of uniform cross-section, a simple mathematical model for rods and tubes of linear elastic materials is proposed. Three suitably selected propagation modes (one extensional and two shear modes) with dispersion relations corresponding to mixed boundary conditions are coupled in order to approximately comply with zero-stress boundary conditions. The coupling gives a set of partial differential equations in the mode amplitudes, with time and a single space coordinate (along the axis of symmetry of the rod or tube) as independent variables. Then, the model is generalized to a set of partial integral-differential equations in order to be able to describe vibrations and wave propagation in rods and tubes made of linear hereditary-elastic solids. In this first part of the work, the focus is in either very low frequency or very high frequency phenomena using a simple model with only two coupled modes. The model allows a fairly elegant and comparatively powerful analytical approach to longitudinal vibrations and to longitudinal pulse propagation in solid waveguides. Analytical formulae for group velocities are derived, as well as asymptotic expressions for the propagation of mode amplitudes. The limitations and pitfalls of the model are assessed, and new experiments and digital simulations are suggested to test some of its predictions, wave propagation; elastic and hereditary-elastic materials; propagation modes in rods and tubes

  20. Energy Loss of Solar $p$ Modes due to the excitation of Magnetic Sausage Tube Waves: Importance of Coupling the Upper Atmosphere

    CERN Document Server

    Gascoyne, Andrew; Hindman, Bradley

    2014-01-01

    We consider damping and absorption of solar $p$ modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of $p$ modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by $p$ modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux-tube. The deficit of $p$-mode energy is quantified through the damping rate, $\\Gamma$ and absorption coefficient, $\\alpha$. The variation of $\\Gamma$ and $\\alpha$ as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modelled as a polytrope that has been truncated at the photosphere (Bogdan et al. (1996), Hindman & Jain 2008, Gascoyne et al. (2011)). Such studies have found that the resulting energy loss by the $p$ modes is very sensitiv...

  1. Design, fabrication, and performance of brazed, graphite electrode, multistage depressed collectors with 500-W, continuous wave, 4.8- to 9.6-GHz traveling-wave tubes

    Science.gov (United States)

    Ramins, Peter; Ebihara, Ben

    1989-01-01

    A small, isotropic graphite electrode, multistage depressed collector (MDC) was designed, fabricated, and evaluated in conjunction with a 500-W, continuous wave (CW), 4.8- to 9.6-GHz traveling-wave tube (TWT). The carbon electrode surfaces were used to improve the TWT overall efficiency by minimizing the secondary electron emission losses in the MDC. The design and fabrication of the brazed graphite MDC assembly are described. The brazing technique, which used copper braze filler metal, is compatible with both vacuum and the more commonly available hydrogen atmosphere brazing furnaces. The TWT and graphite electrode MCC bakeout, processing, and outgassing characteristics were evaluated and found to be comparable to TWT's equipped with copper electrode MDC's. The TWT and MDC performance was optimized for broadband CW operation at saturation. The average radiofrequency (RF), overall, and MDC efficiencies were 14.9, 46.4, and 83.6 percent, respectively, across the octave operating band. A 1500-hr CW test, conducted without the use of an appendage ion pump, showed no gas buildup and excellent stability of the electrode surfaces.

  2. Performance of textured carbon on copper electrode multistage depressed collectors with medium-power traveling wave tubes

    Science.gov (United States)

    Ramins, Peter; Curren, Arthur N.

    1986-01-01

    Performance of multistage depressed collectors (MDCs) using textured carbon on copper substrate electrode surfaces was evaluated in conjunction with medium-power traveling wave tubes (TWTs). The MDC and TWT overall efficiencies for these electrodes were measured and compared with those obtained with the same TWT and a copper electrode MDC of identical design. Long-term stability of the carbon-coated copper electrode surfaces was investigated by periodic evaluation of TWT-MDC performance over an extended period of continuous wave (CW) operation. Application of textured carbon coating on copper MDC electrode surfaces produced a 13% improvement in both MDC and TWT overall efficiencies for the TWT-MDC tests. During 1600 hr of CW operation with a medium power TWT, no significant changes in MDC performance were noted. This indicated good stability of the textured carbon electrode surfaces. This stability was confirmed by scanning electron microscope examinations of the electrode surfaces before assembly of the MDC and after completion of the test program.

  3. 3D Hot Test Simulations of a 220 GHz Folded Waveguide Traveling Wave Tube Using a CFDTD PIC Method

    Science.gov (United States)

    Lin, Ming-Chieh; Song, Heather

    2015-11-01

    Millimeter or sub-THz wave sources centered at 220 GHz is of interest due to the potential for its commercial and military applications including high resolution radar, remote sensing, and high-data-rate communications. It has been demonstrated via 3D cold test finite element method (FEM) simulations that a folded waveguide traveling wave tube (FWTWT) can be designed and optimized at this frequency range with a small signal gain of 18 dB over a comparatively broad (-3 dB) bandwidth of ~ 10%. On the other hand, 3D hot test simulations of a V-band ladder TWT have been successfully demonstrated using a conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method for center frequency of 50 GHz. In the present work, the 220 GHz FWTWT designs have been reviewed and studied. 3D Cold test simulations using both the CFDTD and FEM methods have been carried out and compared with each other as basis for 3D hot test CFDTD PIC simulations. The preliminary simulation result shows that the gain-bandwidth features at 220 GHz are achievable while carefully avoiding beam interceptions. Our study shows that the interaction characteristics are very sensitive to the operating beam parameters. Detail simulation results and discussions will be presented.

  4. A More Accurate and Efficient Technique Developed for Using Computational Methods to Obtain Helical Traveling-Wave Tube Interaction Impedance

    Science.gov (United States)

    Kory, Carol L.

    1999-01-01

    The phenomenal growth of commercial communications has created a great demand for traveling-wave tube (TWT) amplifiers. Although the helix slow-wave circuit remains the mainstay of the TWT industry because of its exceptionally wide bandwidth, until recently it has been impossible to accurately analyze a helical TWT using its exact dimensions because of the complexity of its geometrical structure. For the first time, an accurate three-dimensional helical model was developed that allows accurate prediction of TWT cold-test characteristics including operating frequency, interaction impedance, and attenuation. This computational model, which was developed at the NASA Lewis Research Center, allows TWT designers to obtain a more accurate value of interaction impedance than is possible using experimental methods. Obtaining helical slow-wave circuit interaction impedance is an important part of the design process for a TWT because it is related to the gain and efficiency of the tube. This impedance cannot be measured directly; thus, conventional methods involve perturbing a helical circuit with a cylindrical dielectric rod placed on the central axis of the circuit and obtaining the difference in resonant frequency between the perturbed and unperturbed circuits. A mathematical relationship has been derived between this frequency difference and the interaction impedance (ref. 1). However, because of the complex configuration of the helical circuit, deriving this relationship involves several approximations. In addition, this experimental procedure is time-consuming and expensive, but until recently it was widely accepted as the most accurate means of determining interaction impedance. The advent of an accurate three-dimensional helical circuit model (ref. 2) made it possible for Lewis researchers to fully investigate standard approximations made in deriving the relationship between measured perturbation data and interaction impedance. The most prominent approximations made

  5. Generalized Forward-Backward Splitting

    CERN Document Server

    Raguet, Hugo; Peyré, Gabriel

    2011-01-01

    This paper introduces the generalized forward-backward splitting algorithm for minimizing convex functions of the form $F + \\sum_{i=1}^n G_i$, where $F$ has a Lipschitz-continuous gradient and the $G_i$'s are simple in the sense that their Moreau proximity operators are easy to compute. While the forward-backward algorithm cannot deal with more than $n = 1$ non-smooth function, our method generalizes it to the case of arbitrary $n$. Our method makes an explicit use of the regularity of $F$ in the forward step, and the proximity operators of the $G_i$'s are applied in parallel in the backward step. This allows the generalized forward backward to efficiently address an important class of convex problems. We prove its convergence in infinite dimension, and its robustness to errors on the computation of the proximity operators and of the gradient of $F$. Examples on inverse problems in imaging demonstrate the advantage of the proposed methods in comparison to other splitting algorithms.

  6. Anticipated backward stochastic differential equations

    OpenAIRE

    Peng, Shige; Yang, Zhe

    2009-01-01

    In this paper we discuss new types of differential equations which we call anticipated backward stochastic differential equations (anticipated BSDEs). In these equations the generator includes not only the values of solutions of the present but also the future. We show that these anticipated BSDEs have unique solutions, a comparison theorem for their solutions, and a duality between them and stochastic differential delay equations.

  7. High-Efficiency K-Band Space Traveling-Wave Tube Amplifier for Near-Earth High Data Rate Communications

    Science.gov (United States)

    Simons, Rainee N.; Force, Dale A.; Spitsen, Paul C.; Menninger, William L.; Robbins, Neal R.; Dibb, Daniel R.; Todd, Phillip C.

    2010-01-01

    The RF performance of a new K-Band helix conduction cooled traveling-wave tube amplifier (TWTA), is presented in this paper. A total of three such units were manufactured, tested and delivered. The first unit is currently flying onboard NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft and has flawlessly completed over 2000 orbits around the Moon. The second unit is a proto-flight model. The third unit will fly onboard NASA's International Space Station (ISS) as a very compact and lightweight transmitter package for the Communications, Navigation and Networking Reconfigurable Testbed (CoNNeCT), which is scheduled for launch in 2011. These TWTAs were characterized over the frequencies 25.5 to 25.8 GHz. The saturated RF output power is greater than 40 W and the saturated RF gain is greater than 46 dB. The saturated AM-to-PM conversion is 3.5 /dB and the small signal gain ripple is 0.46 dB peak-to-peak. The overall efficiency of the TWTA, including that of the electronic power conditioner (EPC) is as high as 45%.

  8. Analytical study of nuclear-coupled density-wave instability in a natural circulation pressure tube type boiling water reactor

    International Nuclear Information System (INIS)

    An analytical model has been developed to study the nuclear-coupled density-wave instability in the Indian advanced heavy water reactor (AHWR) which is a natural circulation pressure tube type boiling water reactor. The model considers a point kinetics model for the neutron dynamics and a lumped parameter model for the fuel thermal dynamics along with the conservation equations of mass, momentum and energy and equation of state for the coolant. In addition, to study the effect of neutron interactions between different parts of the core, the model considers a coupled multipoint kinetics equation in place of simple point kinetics equation. Linear stability theory was applied to reveal the instability of in-phase and out-of-phase modes in the boiling channels of the AHWR. The results indicate that the stability behavior of the reactor is greatly influenced by the void reactivity coefficient, fuel time constant, radial power distribution and channel inlet orificing. The delayed neutrons were found to have a strong influence on the Type I and Type II instabilities observed at low and high channel powers, respectively. Also, it was found that the coupled multipoint kinetics model and the modal point kinetics model predict the same threshold power for out-of-phase instability if the coupling coefficient in the former model is half the eigen value separation between the fundamental and the first harmonic mode in the latter model. Decay ratio maps were predicted considering various operating parameters of the reactor, which are useful for its design. (orig.)

  9. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

    Science.gov (United States)

    He, Jun; Wei, Yan-Yu; Gong, Yu-Bin; Wang, Wen-Xiang

    2009-11-01

    A novel slow-wave structure (SWS), the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1-1.27 dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS (FWSWS) shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency.

  10. Design of a re-entrant double-staggered ladder circuit for V-band coupled-cavity traveling-wave tubes

    Institute of Scientific and Technical Information of China (English)

    Liu Yang; Xu Jin; Lai Jian-Qiang; Xu Xiong; Shen Fei; Wei Yan-Yu; Huang Min-Zhi; Tang Tao; Gong Yu-Bin

    2012-01-01

    The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube.This structure has a wide bandwidth,a moderate interaction impedance,and excellent thermal dissipation properties,as well as easy fabrication.A well-matched waveguide coupler is proposed for the structure.Combining the design of attenuators,a full-scale three-dimensional circuit model for the V-band coupled-cavity travelingwave tube is constructed.The electromagnetic characteristics and the beam-wave interaction of this structure are investigated.The beam current is set to be 100 mA,and the cathode voltage is tuned from 16.8 kV to 15.8 kV.The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz.The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%,respectively.

  11. LEPS backward gamma detector reassembled

    International Nuclear Information System (INIS)

    A new electro-magnetic (EM) calorimeter complex FOREST covering a solid angle of about 4π sr is under construction. It consists of three calorimeters: the EPS forward one made up of pure CsI crystals, the middle one of lead scintillating fiber (Lead/SciFi) modules, and the backward one of lead glass Cerenkov counters. We have reassembled the middle calorimeter, comprised of 252 Lead/SciFi modules, which used to be the LEPS Backward Gamma detector system utilized in a LEPS experiment at SPring-8. A performance test for the gamma detector system has been made with a photon beam in the GeV γ experimental hall. The π0 peak is clearly observed in the γγ invariant mass distribution. (author)

  12. Looking Backward and Looking Forward

    OpenAIRE

    Gao, Zhengyuan; Hafner, Christian M.

    2016-01-01

    Filtering has had a profound impact as a device of perceiving information and deriving agent expectations in dynamic economic models. For an abstract economic system, this paper shows that the foundation of applying the filtering method corresponds to the existence of a conditional expectation as an equilibrium process. Agent-based rational behavior of looking backward and looking forward is generalized to a conditional expectation process where the economic system is approximated by a class ...

  13. Physical Processes of the Interaction Between Laser-Generated Plasma and Blast Wave Appearing in Laser-Driven In-Tube Accelerator Configuration

    International Nuclear Information System (INIS)

    Flow visualizations of the interaction between a laser-pulse-generated plasma and a shock wave driven by it have been experimentally conducted. The configuration of the experimental set-up corresponds to the laser-driven, in-tube accelerator. Primary-mode deformation of the plasma is governed by Richtmyer-Meshkov instability which is produced by the vector product between the pressure and density gradients, which in turn correspond to a reflected shock wave and to the plasma, respectively. Higher-mode contact surface deformations are supposedly originated in Rayleigh-Taylor instability in the shrinkage phase of the plasma, and is enhanced due to the passage of the reflected shock wave

  14. Development of a 2.0W at 60K single-stage coaxial pulse tube cryocooler for long-wave infrared focal plane array applications

    Science.gov (United States)

    Dang, H. Z.; Wang, L. B.; Wu, Y. N.; Yang, K. X.; Li, S. S.; Shen, W. B.

    2010-04-01

    A 2.0W@60K single-stage coaxial pulse tube cryocooler has been developed to provide reliable low-vibration cooling for the space-borne long wave infrared focal plane array. The coaxial configuration result in a compact system and the inertance tube together with a gas reservoir serves as the only phase-shifting to realize a highly reliable system. The inertance tube consists of two parts with different inner diameter and length to obtain the desirable phase relationship. Both cold tip and warm flange integrated with fine slit heat exchanges fabricated with electro discharge machining technology to enhance heat exchange performance. A split Oxford-type linear compressor with dual-opposed piston configuration is connected to the cold finger with a 30 cm flexible metallic tube. The overall weight without control electronics is below 8 kg. The preliminary experiments show that a no-load temperature of 46 K and a cooling power of 2 W at 60 K with 104 W of input power at 300K reject temperature have been achieved.

  15. The friction in rod forward and backward micro extrusion

    Directory of Open Access Journals (Sweden)

    J. Piwnik

    2010-01-01

    Full Text Available Micro parts are increasingly applied in industry because of the trend to miniaturization every day devices. Microforming is a method of manufacturing metal micro elements using a plastic treatment. This kind of production ensures high productivity, shapes and dimensions repeatability and good surface quality. Size effect connected with small dimensions affects changes in treatment processes of micro parts. While forming in micro scale, surface roughness is size independent and does not decrease with decreasing detail dimensions. The article presents schemas for forward and backward extrusion of metal rods. Using FEM, tool’s roughness as a triangle wave has been assumed, taking into account thereby size effect. Influence of roughness on extrusion forces by comparison with traditional flat tools and constant friction shear factor m has been specified. Impact of roughness caused growth of extrusion forces while forward extruding. On the contrary, backward extrusion ensured stable required forces, regardless of a surface structure.

  16. Microfabrication of diamond-based slow-wave circuits for mm-wave and THz vacuum electronic sources

    International Nuclear Information System (INIS)

    Planar and helical slow-wave circuits for THz radiation sources have been made using novel microfabrication and assembly methods. A biplanar slow-wave circuit for a 650 GHz backward wave oscillator (BWO) was fabricated through the growth of diamond into high aspect ratio silicon molds and the selective metallization of the tops and sidewalls of 90 µm tall diamond features using lithographically created shadow masks. Helical slow-wave circuits for a 650 GHz BWO and a 95 GHz traveling wave tube were created through the patterning of trenches in thin film diamond, electroplating of gold half-helices, and high accuracy bonding of helix halves. The development of new techniques for the microfabrication of vacuum electronic components will help to facilitate compact and high-power sources for terahertz range radiation

  17. Microfabrication of diamond-based slow-wave circuits for mm-wave and THz vacuum electronic sources

    Science.gov (United States)

    Lueck, M. R.; Malta, D. M.; Gilchrist, K. H.; Kory, C. L.; Mearini, G. T.; Dayton, J. A.

    2011-06-01

    Planar and helical slow-wave circuits for THz radiation sources have been made using novel microfabrication and assembly methods. A biplanar slow-wave circuit for a 650 GHz backward wave oscillator (BWO) was fabricated through the growth of diamond into high aspect ratio silicon molds and the selective metallization of the tops and sidewalls of 90 µm tall diamond features using lithographically created shadow masks. Helical slow-wave circuits for a 650 GHz BWO and a 95 GHz traveling wave tube were created through the patterning of trenches in thin film diamond, electroplating of gold half-helices, and high accuracy bonding of helix halves. The development of new techniques for the microfabrication of vacuum electronic components will help to facilitate compact and high-power sources for terahertz range radiation.

  18. Analytical prediction and experimental verification of performance at various operating conditions of a dual-mode traveling wave tube with multistage depressed collectors

    Science.gov (United States)

    Dayton, J. A., Jr.; Kosmahl, H. G.; Ramins, P.; Stankiewicz, N.

    1981-01-01

    A comparison of analytical and experimental results is presented for a high performance dual-mode traveling wave tube (TWT) operated over a wide range conditions. The computations are carried out with advanced multidimensional computer programs. These programs model the electron beam as a series of disks or rings of charge and follow their trajectories from the rf input of the TWT through the slow-wave structure refocusing system to their points of impacts in the depressed collector. TWT performance, collector efficiency, and collector current distribution are computed and compared with measurements. Very good agreement was obtained between computed and measured TWT performance and collector efficiencies, and the computer design of a highly efficient collector was demonstrated.

  19. Signal processing for plane wave actuators

    OpenAIRE

    T. Corbach; Holters, M.; U. Zölzer

    2010-01-01

    Plane wave actuators without an enclosure per se have a forward and backward radiation. The backward radiation is unwanted in many applications when a single direction radiation is desired. To avoid the disadvantages of an enclosure a system is proposed, which provides a high suppression of the unwanted backward radiation using a pair of plane wave actuators. This is achieved by adapted input signal filters. The influences of the second plane wave actuator to the forward rad...

  20. Proof of Concept of Crack Localization Using Negative Pressure Waves in Closed Tubes for Later Application in Effective SHM System for Additive Manufactured Components

    Directory of Open Access Journals (Sweden)

    Michaël F. Hinderdael

    2016-01-01

    Full Text Available Additive manufactured components have a different metallurgic structure and are more prone to fatigue cracks than conventionally produced metals. In earlier papers, an effective Structural Health Monitoring solution was presented to detect fatigue cracks in additive manufactured components. Small subsurface capillaries are embedded in the structure and pressurized (vacuum or overpressure. A crack that initiated at the component’s surface will propagate towards the capillary and finally breach it. One capillary suffices to inspect a large area of the component, which makes it interesting to locate the crack on the basis of the pressure measurements. Negative pressure waves (NPW arise from the abrupt encounter of high pressure fluid with low pressure fluid and can serve as a basis to locate the crack. A test set-up with a controllable leak valve was built to investigate the feasibility of using NPW to localize a leak in closed tubes with small lengths. Reflections are expected to occur at the ends of the tube, possibly limiting the localization accuracy. In this paper, the results of the tests on the test set-up are reported. It will be shown that the crack could be localized with high accuracy (millimeter accuracy which proves the concept of crack localization on basis of NPW in a closed tube of small length.

  1. A friction regulation hybrid driving method for backward motion restraint of the smooth impact drive mechanism

    Science.gov (United States)

    Wang, Liang; Chen, Dong; Cheng, Tinghai; He, Pu; Lu, Xiaohui; Zhao, Hongwei

    2016-08-01

    The smooth impact drive mechanism (SIDM) is a type of piezoelectric actuator that has been developed for several decades. As a kind of driving method for the SIDM, the traditional sawtooth (TS) wave is always employed. The kinetic friction force during the rapid contraction stage usually results in the generation of a backward motion. A friction regulation hybrid (FRH) driving method realized by a composite waveform for the backward motion restraint of the SIDM is proposed in this paper. The composite waveform is composed of a sawtooth driving (SD) wave and a sinusoidal friction regulation (SFR) wave which is applied to the rapid deformation stage of the SD wave. A prototype of the SIDM was fabricated and its output performance under the excitation of the FRH driving method and the TS wave driving method was tested. The results indicate that the backward motion can be restrained obviously using the FRH driving method. Compared with the driving effect of the TS wave, the backward rates of the prototype in forward and reverse motions are decreased by 83% and 85%, respectively.

  2. Transferability of decompression wave speed measured by a small-diameter shock tube to full size pipelines and implications for determining required fracture propagation resistance

    International Nuclear Information System (INIS)

    The control of propagating ductile (or tearing) fracture is a fundamental requirement in the fracture control design of pipelines. The Battelle two-curve method developed in the early 1970s still forms the basis of the analytical framework used throughout the industry. GASDECOM is typically used for calculating decompression speed, and idealizes the decompression process as isentropic and one-dimensional, taking no account of frictional effects. While this approximation appears not to have been a major issue for large-diameter pipes and for moderate pressures (up to 12 MPa), there have been several recent full-scale burst tests at higher pressures and smaller diameters for which the measured decompression velocity has deviated progressively from the predicted values, in general towards lower velocities. The present research was focused on determining whether pipe diameter was a major factor that could limit the applicability of frictionless models such as GASDECOM. Since potential diameter effects are primarily related to wall friction, which in turn is related to the ratio of surface roughness-to-diameter, an experimental approach was developed based on keeping the diameter constant, at a sufficiently small value to allow for an economical experimental arrangement, and varying the internal roughness. A series of tests covering a range of nominal initial pressures from 10 to 21 MPa, and involving a very lean gas and three progressively richer compositions, were conducted using two specialized high-pressure shock tubes (42 m long, I.D. = 38.1 mm). The first is honed to an extremely smooth surface finish, in order to minimize frictional effects and better simulate the behaviour of larger-diameter pipelines, while the second has a higher internal surface roughness. The results show that decompression wave speeds in the rough tube are consistently slower than those in the smooth tube under the same conditions of mixture composition and initial pressure and temperature

  3. Using COMSOL Multiphysics Software to Model Anisotropic Dielectric and Metamaterial Effects in Folded-Waveguide Traveling-Wave Tube Slow-Wave Circuits

    Science.gov (United States)

    Starinshak, David P.; Smith, Nathan D.; Wilson, Jeffrey D.

    2008-01-01

    The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.

  4. A Parametric Approach to Shape Field-Relevant Blast Wave Profiles in Compressed-Gas-Driven Shock Tube

    OpenAIRE

    Sundaramurthy, Aravind; Chandra, Namas

    2014-01-01

    Detonation of a high-explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects, even at farther distances. When a pure shock-blast wave encounters the subject, in the absence of shrapnels, fall, or gaseous products the loading is termed as primary blast loading and is the subject of this paper. The wave profile is characterized by blast overpressure, positive time duration, and impulse a...

  5. The effect of interfacial roughness under painting layed on the ultrasonic backward radiation

    International Nuclear Information System (INIS)

    Generalized Lamb surface waves are generated in a surface region when ultrasonic waves are incident upon the layered substrates such as painted specimen in liquid. Then, backward radiated waves are returned to the direction of incidence by scattering and energy radiation of the surface waves. Hence, the backward radiation could be used in assessing the interfacial state between layer and substrate because the surface wave is sensitive to the change of physical properties in a surface region. Painting surface treatment of commercial products and articles occasionally hide the surface region trouble such as roughness and crack. The evaluation of interfacial state under painting layer is very important in the prevention of great accidence, hence the evaluation technique should be nondestructive, fast and easy applicable to the fields. The backward radiations were measured for the painted glass with periodic interfacial roughness immersed in water tank. The effect of interfacial roughness on the angular pattern and frequency spectrum of the ultrasonic backward radiation was investigated to develop the nondestructive technique for interfacial roughness evaluation.

  6. On Backward-Style Anonymity Verification

    Science.gov (United States)

    Kawabe, Yoshinobu; Mano, Ken; Sakurada, Hideki; Tsukada, Yasuyuki

    Many Internet services and protocols should guarantee anonymity; for example, an electronic voting system should guarantee to prevent the disclosure of who voted for which candidate. To prove trace anonymity, which is an extension of the formulation of anonymity by Schneider and Sidiropoulos, this paper presents an inductive method based on backward anonymous simulations. We show that the existence of an image-finite backward anonymous simulation implies trace anonymity. We also demonstrate the anonymity verification of an e-voting protocol (the FOO protocol) with our backward anonymous simulation technique. When proving the trace anonymity, this paper employs a computer-assisted verification tool based on a theorem prover.

  7. Mathematical Evaluation of Steady, Laminar Flow by the Use of Continuous-Wave (cw) Doppler and Pitot Tube System.

    Science.gov (United States)

    Sharif, Malek Mansoor

    Investigation, as to the usefulness of spectral analysis of the acoustical signal from the Doppler ultrasonic flowmeter, is being conducted. The hypothesis was that both hematocrit ((')H) and pressure head (H) influence the amplitude of the spectrum (A). Experiments were designed to: (a) evaluate their roles on amplitude; (b) derive the associated functional relationship. Preliminary experiments revealed that: (a) the accuracy of our Doppler flowmeter was satisfactory; (b) the relative weight of (')H on flow velocity was twice that of H. A pitot tube system whose bent tube component was capable of radial movement was developed to measure the instantaneous blood velocity. The bent tube was moved across the lumen of the vessel in steps of 0.1 mm, and particle velocity was measured at each sampling point. The distribution of velocity was parabolic and the agreement between experimental data and the second degree polynomial fit was good ((xi) = .94). An array of small bent tubes, each placed successively deeper within the lumen of the rubber tubing and connected to a small syringe, was constructed to measure the particle profile. The profile was parabolic and (')H, as a function of radius, was expressible in terms of a second degree polynomial. To determine the dependency of ultrasonic energy backscattering on hematocrit, Doppler signals were recorded, digitized, and frequency resolved via the fast Fourier transform for hematocrits ranging from 4.5% to 46.5%. The amplitude corresponding to each given hematocrit was calculated by evaluating the area under the curve fitted to the transformed data. A((')H) was found to be a linear function of hematocrit. A generalized Doppler amplitude function A(H,(')H) was also derived. It was hypothesized that blood viscosity ((mu)) is an exponential function of hematocrit, that is, (mu) = A exp (B(.)(')H). Experimental results using a Falling ball type viscosimeter supported the theory with a high correlation between the data and the

  8. A Comparison of Three-Dimensional Simulations of Traveling-Wave Tube Cold-Test Characteristics Using CST MICROWAVE STUDIO and MAFIA

    Science.gov (United States)

    Chevalier, C. T.; Herrmann, K. A.; Kory, C. L.; Wilson, J. D.; Cross, A. W.; Williams, W. D. (Technical Monitor)

    2001-01-01

    Previously, it was shown that MAFIA (solutions of Maxwell's equations by the Finite Integration Algorithm), a three-dimensional simulation code, can be used to produce accurate cold-test characteristics including frequency-phase dispersion, interaction impedance, and attenuation for traveling-wave tube (TWT) slow-wave structures. In an effort to improve user-friendliness and simulation time, a model was developed to compute the cold-test parameters using the electromagnetic field simulation software package CST MICROWAVE STUDIO (MWS). Cold-test parameters were calculated for several slow-wave circuits including a ferruled coupled-cavity, a folded waveguide, and a novel finned-ladder circuit using both MWS and MAFIA. Comparisons indicate that MWS provides more accurate cold-test data with significantly reduced simulation times. Both MAFIA and MWS are based on the finite integration (FI) method; however, MWS has several advantages over MAFIA. First, it has a Windows based interface for PC operation, making it very user-friendly, whereas MAFIA is UNIX based. MWS uses a new Perfect Boundary Approximation (PBA), which increases the accuracy of the simulations by avoiding stair step approximations associated with MAFIA's representation of structures. Finally, MWS includes a Visual Basic for Applications (VBA) compatible macro language that enables the simulation process to be automated and allows for the optimization of user-defined goal functions, such as interaction impedance.

  9. Backward Induction versus Forward Induction Reasoning

    OpenAIRE

    Andres Perea

    2010-01-01

    In this paper we want to shed some light on what we mean by backward induction and forward induction reasoning in dynamic games. To that purpose, we take the concepts of common belief in future rationality (Perea [1]) and extensive form rationalizability (Pearce [2], Battigalli [3], Battigalli and Siniscalchi [4]) as possible representatives for backward induction and forward induction reasoning. We compare both concepts on a conceptual, epistemic and an algorithm level, thereby highlighting ...

  10. Electron Emission And Beam Generation Using Ferroelectric Cathodes (electron Beam Generation, Lead Lanthanum Zicronate Titanate, High Power Traveling Wave Tube Amplfier)

    CERN Document Server

    Flechtner, D D

    1999-01-01

    In 1989, researchers at CERN published the discovery of significant electron emission (1– 100 A/cm2) from Lead- Lanthanum-Zirconate-Titanate (PLZT). The publication of these results led to international interest in ferroelectric cathodes studies for use in pulsed power devices. At Cornell University in 1991, experiments with Lead-Zirconate-Titanate (PZT) compositions were begun to study the feasibility of using this ferroelectric material as a cathode in the electron gun section of High Power Traveling Wave Tube Amplifier Experiments. Current-voltage characteristics were documented for diode voltages ranging from 50– 500,000 V with anode cathode gaps of.5– 6 cm. A linear current-voltage relation was found for voltages less than 50 kV. For diode voltages ≥ 200 kV, a typical Child-Langmuir V3/2 dependence was observed...

  11. Thermal decomposition of 1-chloropropane behind the reflected shock waves in the temperature range of 1015-1220 K: Single pulse shock tube and computational studies

    Indian Academy of Sciences (India)

    G Sudhakar; B Rajakumar

    2014-07-01

    The thermal decomposition of 1-chloropropane in argon was studied behind reflected shock waves in a single pulse shock tube over the temperature range of 1015-1220 K. The reaction mainly goes through unimolecular elimination of HCl. The major products observed in the decomposition are propylene and ethylene, while the minor products identified are methane and propane. The rate constant for HCl elimination in the studied temperature range is estimated to be k(1015-1220 K) = 1.63 × 1013exp(-(60.1 ± 1.0) kcal mol-1/RT) s-1. The DFT calculations were carried out to identify the transition state(s) for the major reaction channel; and rate coefficient for this reaction is obtained to be k(800-1500 K) = 5.01 × 1014exp(-(58.8) kcal mol-1/RT) s-1. The results are compared with the experimental findings.

  12. Ultrasonic nondestructive tubing inspection system

    International Nuclear Information System (INIS)

    A system for measuring the extent of tube wall erosion in an inspection region of a heat exchanger tube of a nuclear steam generator, uses an ultrasonic means driven helically inside the eroded tube which may be filled with a fluid (e.g., water) to minimize ultrasonic wave attenuation. A control means cooperates with the ultrasonic means to produce a map of the tube wall thickness in an inspection region

  13. Analytical prediction with multidimensional computer programs and experimental verification of the performance, at a variety of operating conditions, of two traveling wave tubes with depressed collectors

    Science.gov (United States)

    Dayton, J. A., Jr.; Kosmahl, H. G.; Ramins, P.; Stankiewicz, N.

    1979-01-01

    Experimental and analytical results are compared for two high performance, octave bandwidth TWT's that use depressed collectors (MDC's) to improve the efficiency. The computations were carried out with advanced, multidimensional computer programs that are described here in detail. These programs model the electron beam as a series of either disks or rings of charge and follow their multidimensional trajectories from the RF input of the ideal TWT, through the slow wave structure, through the magnetic refocusing system, to their points of impact in the depressed collector. Traveling wave tube performance, collector efficiency, and collector current distribution were computed and the results compared with measurements for a number of TWT-MDC systems. Power conservation and correct accounting of TWT and collector losses were observed. For the TWT's operating at saturation, very good agreement was obtained between the computed and measured collector efficiencies. For a TWT operating 3 and 6 dB below saturation, excellent agreement between computed and measured collector efficiencies was obtained in some cases but only fair agreement in others. However, deviations can largely be explained by small differences in the computed and actual spent beam energy distributions. The analytical tools used here appear to be sufficiently refined to design efficient collectors for this class of TWT. However, for maximum efficiency, some experimental optimization (e.g., collector voltages and aperture sizes) will most likely be required.

  14. Forward-backward Stochastic Differential Equations and Backward Linear Quadratic Stochastic Optimal Control Problem

    Institute of Scientific and Technical Information of China (English)

    ZHANG DE-TAO

    2009-01-01

    In this paper, we use the solutions of forward-backward stochastic differential equations to get the optimal control for backward stochastic linear quadratic optimal control problem. And we also give the linear feedback regulator for the optimal control problem by using the solutions of a group of Riccati equations.

  15. Resonant behaviour of MHD waves on magnetic flux tubes. I - Connection formulae at the resonant surfaces. II - Absorption of sound waves by sunspots

    Science.gov (United States)

    Sakurai, Takashi; Goossens, Marcel; Hollweg, Joseph V.

    1991-01-01

    The present method of addressing the resonance problems that emerge in such MHD phenomena as the resonant absorption of waves at the Alfven resonance point avoids solving the fourth-order differential equation of dissipative MHD by recourse to connection formulae across the dissipation layer. In the second part of this investigation, the absorption of solar 5-min oscillations by sunspots is interpreted as the resonant absorption of sounds by a magnetic cylinder. The absorption coefficient is interpreted (1) analytically, under certain simplifying assumptions, and numerically, under more general conditions. The observed absorption coefficient magnitude is explained over suitable parameter ranges.

  16. Large power electron tubes for high frequency heating

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Tadashi; Sato, Hisaaki.

    1988-07-01

    On the large power electron tubes used for electron cyclotron heating, lower hybrid resonance frequency heating, and ion cyclotron range of frequency heating, namely gyrotron, klystron and quadrupole tube, the features, the present status of development, the construction, the principle and so on are explained. The research and development of gyrotrons are most advanced in USSR, the inventor. The course of the development of gyrotrons in foreign countries and in Japan is described. There are many variants of gyrotrons, for example whispering gallery mode, klystron type, backward wave oscillator type, gyro-peniotron and others. The principle of gyrotrons is explained, and about the examples of the developed gyrotrons, the design parameters are shown. For the purpose of using for the LHRF heating in JT-60, a superlarge power klystron of 1 MW output at 2 GHz frequency, which is the largest class in the world, has been developed. Its total length is 2.7 m, and weight is 1.5 t. It features, construction, function and performance are reported. The trend of large power quadrupole tubes is toward stable action with large power in VHF zone, and the typical products in USA and Europe are shown. (Kako, I.).

  17. Evaluation of beryllium stiffening on zirconium plate using backward radiation profiles

    International Nuclear Information System (INIS)

    The ultrasonic backward radiation profiles of Be(13μm)/Zr(1.32 mm) alloy plate and pure Zr(1.32 mm) plate were measured at various incidence positions to evaluate the embedded Be layer. Four principal subprofiles of backward ultrasound radiated from leaky Lamb waves were discovered. The peak angles and the peak intensities of the subprofiles decreased by stiffening effect of Be layer. The generation and change of the subprofile was explained by acoustical property, group velocity and leaky factor. New evaluation factor of angular dispersion was suggested to evaluate very thin stiffening layer on plate.

  18. Backward Bifurcation in Simple SIS Model

    Institute of Scientific and Technical Information of China (English)

    Zhan-wei Wang

    2009-01-01

    We describe and analyze a simple SIS model with treatment.In particular,we give a completely qualitative analysis by means of the theory of asymptotically autonomous system.It is found that a backward bifurcation occurs if the adequate contact rate or the capacity is small.It is also found that there exists bistable endemic equilibria.In the case of disease-induced death,it is shown that the backward bifurcation also occurs.Moreover,there is no limit cycle under some conditions,and the subcritical Hopf bifurcation occurs under another conditions.

  19. Flipping photons backward: reversed Cherenkov radiation

    Directory of Open Access Journals (Sweden)

    Hongsheng Chen

    2011-01-01

    Full Text Available Charged particles moving faster than light in a medium produce Cherenkov radiation. In traditional, positive index-of-refraction materials this radiation travels forward. Metamaterials, with negative indices of refraction, flip the radiation backward. This readily separates it from the particles, providing higher flexibility in photon manipulation and is useful for particle identification and counting. Here we review recent advances in reversed Cherenkov radiation research, including the first demonstration of backward emission. We also discuss the potential for developing new types of devices, such as ones that pierce invisibility cloaks.

  20. Top quark forward-backward asymmetry

    International Nuclear Information System (INIS)

    The recent forward-backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than 2σ deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a W' boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward-backward asymmetry without producing too many top and anti-top quark pairs. Other models presented previously in the literature that can produce such effects are also briefly discussed.

  1. Top quark forward-backward asymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Cheung Kingman [Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of); Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan (China); Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan (China); Keung, W.-Y. [Department of Physics, University of Illinois, Chicago, IL 60607-7059 (United States); Yuan, T.-C., E-mail: tcyuan@phys.sinica.edu.t [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China)

    2009-12-07

    The recent forward-backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than 2sigma deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a W{sup '} boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward-backward asymmetry without producing too many top and anti-top quark pairs. Other models presented previously in the literature that can produce such effects are also briefly discussed.

  2. Top Quark Forward-Backward Asymmetry

    CERN Document Server

    Cheung, Kingman; Yuan, Tzu-Chiang

    2009-01-01

    The recent forward-backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than $2\\sigma$ deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a $W'$ boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward-backward asymmetry without producing too many top and anti-top quark pairs. Other models presented erstwhile in the literature that can produce such effects are also discussed.

  3. Limits of Lubrication in Backward Can Extrusion

    DEFF Research Database (Denmark)

    Bennani, B; Bay, Niels

    1996-01-01

    The increasing demand in industry to produce cans at low reduction by the backward extrusion process involves better understanding of this process. To analyse the process, numerical simulations by the finite-element method and experimental simulations by physical modelling using wax as a model...

  4. On Backward Stochstic Partial Differential Equations.

    OpenAIRE

    2001-01-01

    We prove an existence and uniqueness result for a general class of backward stochastic partial differential equations. This is a type of equations which appear as adjoint equations in the maximum principle approach to optimal control of systems described by stochastic partial differential equations.

  5. Backward iteration in strongly convex domains

    CERN Document Server

    Abate, Marco

    2011-01-01

    We prove that a backward orbit with bounded Kobayashi step for a hyperbolic, parabolic or strongly elliptic holomorphic self-map of a bounded strongly convex domain in d-dimensional complex Euclidean space necessarily converges to a repelling or parabolic boundary fixed point, generalizing previous results obtained by Poggi-Corradini in the unit disk and by Ostapyuk in the unit ball.

  6. Using backward design in NASA educational resources

    Science.gov (United States)

    Peticolas, L. M.; Mendez, B.; Schultz, G.; Luhmann, J. G.; Craig, N.

    2003-12-01

    It is important to create NASA educational resources that are effective in imparting deep understanding of space physics concepts, which link to main ideas outlined in the National Science Education Standards (NSES). One way of ensuring success in such a task is to use the backward design philosophy described in the book, "Understanding by Design" by Wiggins and McTighe. Using this design philosophy together with inquiry-based activities, we have developed a teacher's magnetism guide with three main lessons. The goal of this teacher's guide is to help middle school kids learn about motions and forces, magnetism, including electromagnetism, science as inquiry, and science as a human endeavor. We reach these goals in part by using the story of the NASA STEREO Mission together with the design process of the STEREO-IMPACT magnetic boom. We found that using a backward design guarantees that our activities teach the ideas we want the students to learn and also that the lessons include a variety of assessment and evaluation tools along the way. However, we also found that it is difficult to implement the backward design without a long lesson using several assessment tools. This could be a problem for teachers who may not be able to use such time-consuming NASA activities and tools in their classroom. In this presentation, we will further discuss the ideas of backward design in the context of the three activities we created, and the benefits and difficulties we encountered using this philosophy.

  7. Ultra High Power and Efficiency Space Traveling-Wave Tube Amplifier Power Combiner with Reduced Size and Mass for NASA Missions

    Science.gov (United States)

    Simons, Rainee N.; Wintucky, Edwin G.; Wilson, Jeffrey D.; Force, Dale A.

    2009-01-01

    In the 2008 International Microwave Symposium (IMS) Digest version of our paper, recent advances in high power and efficiency space traveling-wave tube amplifiers (TWTAs) for NASA s space-to-Earth communications are presented. The RF power and efficiency of a new K-Band amplifier are 40 W and 50 percent and that of a new Ka-Band amplifier are 200 W and 60 percent. An important figure-of-merit, which is defined as the ratio of the RF power output to the mass (W/kg) of a TWT, has improved by a factor of ten over the previous generation Ka-Band devices. In this extended paper, a high power, high efficiency Ka-band combiner for multiple TWTs, based on a novel hybrid magic-T waveguide circuit design, is presented. The measured combiner efficiency is as high as 90 percent. In addition, at the design frequency of 32.05 GHz, error-free uncoded BPSK/QPSK data transmission at 8 megabits per second (Mbps), which is typical for deep space communications is demonstrated. Furthermore, QPSK data transmission at 622 Mbps is demonstrated with a low bit error rate of 2.4x10(exp -8), which exceeds the deep space state-of-the-art data rate transmission capability by more than two orders of magnitude. A potential application of the TWT combiner is in deep space communication systems for planetary exploration requiring transmitter power on the order of a kilowatt or higher.

  8. High Efficiency Traveling-Wave Tube Power Amplifier for Ka-Band Software Defined Radio on International Space Station-A Platform for Communications Technology Development

    Science.gov (United States)

    Simons, Rainee N.; Force, Dale A.; Kacpura, Thomas J.

    2013-01-01

    The design, fabrication and RF performance of the output traveling-wave tube amplifier (TWTA) for a space based Ka-band software defined radio (SDR) is presented. The TWTA, the SDR and the supporting avionics are integrated to forms a testbed, which is currently located on an exterior truss of the International Space Station (ISS). The SDR in the testbed communicates at Ka-band frequencies through a high-gain antenna directed to NASA s Tracking and Data Relay Satellite System (TDRSS), which communicates to the ground station located at White Sands Complex. The application of the testbed is for demonstrating new waveforms and software designed to enhance data delivery from scientific spacecraft and, the waveforms and software can be upgraded and reconfigured from the ground. The construction and the salient features of the Ka-band SDR are discussed. The testbed is currently undergoing on-orbit checkout and commissioning and is expected to operate for 3 to 5 years in space.

  9. Kinetics of the Thermal Decomposition of Tetramethylsilane behind the Reflected Shock Waves in a Single Pulse Shock Tube (SPST) and Modeling Study

    Science.gov (United States)

    Parandaman, A.; Sudhakar, G.; Rajakumar, B.

    Thermal reactions of Tetramethylsilane (TMS) diluted in argon were studied behind the reflected shock waves in a single-pulse shock tube (SPST) over the temperature range of 1085-1221 K and pressures varied between 10.6 and 22.8 atm. The stable products resulting from the decomposition of TMS were identified and quantified using gas chromatography and also verified with Fourier Transform Infrared (FTIR) spectrometer. The major reaction products are methane (CH4) and ethylene (C2H4). The minor reaction products are ethane (C2H6) and propylene (C3H6). The initiation of mechanism in the decomposition of TMS takes plays via the Si-C bond scission by ejecting the methyl radicals (CH3) and trimethylsilyl radicals ((CH3)3Si). The measured temperature dependent rate coefficient for the total decomposition of TMS was to be ktotal = 1.66 ×1015 exp (-64.46/RT) s-1 and for the formation of CH4 reaction channel was to be k = 2.20 × 1014 exp (-60.15/RT) s-1, where the activation energies are given in kcal mol-1. A kinetic scheme containing 17 species and 28 elementary reactions was used for the simulation using chemical kinetic simulator over the temperature range of 1085-1221 K. The agreement between the experimental and simulated results was satisfactory.

  10. Levelized Cost of Energy for a Backward Bent Duct Buoy

    Energy Technology Data Exchange (ETDEWEB)

    Bull, Diana; Jenne, D. Scott; Smith, Christopher S.; Copping, Andrea E.; Copeland, Guild

    2016-12-01

    The Reference Model Project, supported by the U.S. Department of Energy, was developed to provide publically available technical and economic benchmarks for a variety of marine energy converters. The methodology to achieve these benchmarks is to develop public domain designs that incorporate power performance estimates, structural models, anchor and mooring designs, power conversion chain designs, and estimates of the operations and maintenance, installation, and environmental permitting required. The reference model designs are intended to be conservative, robust, and experimentally verified. The Backward Bent Duct Buoy (BBDB) presented in this paper is one of three wave energy conversion devices studied within the Reference Model Project. Comprehensive modeling of the BBDB in a Northern California climate has enabled a full levelized cost of energy (LCOE) analysis to be completed on this device.

  11. Every Choice Function is Backwards-Induction Rationalizable

    OpenAIRE

    BOSSERT, Walter; Sprumont, Yves

    2013-01-01

    A choice function is backwards-induction rationalizable if there exists a finite perfect-information extensive-form game such that, for each subset of alternatives, the backwards-induction outcome of the restriction of the game to that subset of alternatives coincides with the choice from that subset. We prove that every choice function is backwards-induction rationalizable.

  12. Wave

    OpenAIRE

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for t...

  13. Wave

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many...... times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for the UK is estimated at 25% of current demand; a lot less, but a very substantial amount nonetheless....

  14. Transform coding with backwards adaptive updates

    OpenAIRE

    Goyal, Vivek K; Zhuang, Jun; Vetterli, Martin

    2000-01-01

    The Karhunen–Loève transform (KLT) is optimal for trans- form coding of a Gaussian source. This is established for all scale-invariant quantizers, generalizing previous results. A backward adaptive technique for combating the data dependence of the KLT is proposed and analyzed. When the adapted transform converges to a KLT, the scheme is universal among transform coders. A variety of convergence results are proven.

  15. Understanding backward design to strengthen curricular models.

    Science.gov (United States)

    Emory, Jan

    2014-01-01

    Nurse educators have responded to the call for transformation in education. Challenges remain in planning curricular implementation to facilitate understanding of essential content for student success on licensure examinations and in professional practice. The conceptual framework Backward Design (BD) can support and guide curriculum decisions. Using BD principles in conjunction with educational models can strengthen and improve curricula. This article defines and describes the BD process, and identifies reported benefits for nursing education. PMID:24743175

  16. Influence of a backward reflection on low-threshold mode instability in Yb3+-doped few-mode fiber amplifiers.

    Science.gov (United States)

    Antipov, Oleg; Kuznetsov, Maxim; Alekseev, Dmitriy; Tyrtyshnyy, Valentin

    2016-06-27

    An influence of backward reflection on spatio-temporal instability of the fundamental mode in Yb3+-doped few-mode polarization maintaining fiber amplifiers with a core diameter of 10 μm was studied experimentally and theoretically. The mode instability threshold was registered to decrease dramatically in the presence of a backward reflection of the signal from the output fiber end; an increase of the signal bandwidth or input power resulted in the increase of the threshold. Numerical simulation revealed a self-consistent growth of the higher-order mode LP11 and a traveling index grating accompanying the population grating induced by the mode interference field (due to different polarizability of the excited and unexcited Yb3+ ions). The presence of the backward-propagating wave resulted in four-wave mixing on the common index grating induced by the interference field of pairs of the fundamental LP01 and LP11 modes. PMID:27410639

  17. Kinematics and Aerodynamics of Backward Flying Dragonflies

    Science.gov (United States)

    Bode-Oke, Ayodeji; Zeyghami, Samane; Dong, Haibo

    2015-11-01

    Highly maneuverable insects such as dragonflies have a wide range of flight capabilities; precise hovering, fast body reorientations, sideways flight and backward takeoff are only a few to mention. In this research, we closely examined the kinematics as well as aerodynamics of backward takeoff in dragonflies and compared them to those of forward takeoff. High speed videography and accurate 3D surface reconstruction techniques were employed to extract details of the wing and body motions as well as deformations during both flight modes. While the velocities of both forward and backward flights were similar, the body orientation as well as the wing kinematics showed large differences. Our results indicate that by tilting the stroke plane angle of the wings as well as changing the orientation of the body relative to the flight path, dragonflies control the direction of the flight like a helicopter. In addition, our detailed analysis of the flow in these flights shows important differences in the wake capture phenomena among these flight modes. This work is supported by NSF CBET-1313217.

  18. Design and Fabrication of a 1 THz Backward Wave Amplifier

    DEFF Research Database (Denmark)

    Paoloni, Claudio; Di Carlo, Aldo; Brunetti, Francesca;

    2011-01-01

    require a level of power not achievable by optoelectronic devices at room temperature or by solid-state technology. The recent availability of three-dimensional simulators and high aspect ratio micro-fabrication techniques has stimulated a class of vacuum electron devices operating in the THz regime, to...

  19. Design and Fabrication of a 1 THz Backward Wave Amplifier

    OpenAIRE

    Paoloni, Claudio; Di Carlo, Aldo; Brunetti, Francesca; Mineo, Mauro; Ulisse, Giacomo; DURAND, Alain; Krozer, Viktor; Kotiranta, Mikko; Fiorello, Anna Maria; Dispenza, Massimiliano; Secchi, Alberto; Zhurbenko, Vitaliy; Bouamrane, Faycal; Bouvet, Thomas; Megtert, Stephan

    2011-01-01

    The THz frequency range represents a true challenge for designers, fabrication technologies and characterization systems. So far, huge technological obstacles have prohibited any system realization different from laboratory one. Furthermore, most of the applications in the THz frequency range require a level of power not achievable by optoelectronic devices at room temperature or by solid-state technology. The recent availability of three-dimensional simulators and high aspect ratio micro-fab...

  20. Effects of drift gas on collision cross sections of a protein standard in linear drift tube and traveling wave ion mobility mass spectrometry.

    Science.gov (United States)

    Jurneczko, Ewa; Kalapothakis, Jason; Campuzano, Iain D G; Morris, Michael; Barran, Perdita E

    2012-10-16

    There has been a significant increase in the use of ion mobility mass spectrometry (IM-MS) to investigate conformations of proteins and protein complexes following electrospray ionization. Investigations which employ traveling wave ion mobility mass spectrometry (TW IM-MS) instrumentation rely on the use of calibrants to convert the arrival times of ions to collision cross sections (CCS) providing "hard numbers" of use to structural biology. It is common to use nitrogen as the buffer gas in TW IM-MS instruments and to calibrate by extrapolating from CCS measured in helium via drift tube (DT) IM-MS. In this work, both DT and TW IM-MS instruments are used to investigate the effects of different drift gases (helium, neon, nitrogen, and argon) on the transport of multiply charged ions of the protein myoglobin, frequently used as a standard in TW IM-MS studies. Irrespective of the drift gas used, recorded mass spectra are found to be highly similar. In contrast, the recorded arrival time distributions and the derived CCS differ greatly. At low charge states (7 ≤ z ≤ 11) where the protein is compact, the CCS scale with the polarizability of the gas; this is also the case for higher charge states (12 ≤ z ≤ 22) where the protein is more unfolded for the heavy gases (neon, argon, and nitrogen) but not the case for helium. This is here interpreted as a different conformational landscape being sampled by the lighter gas and potentially attributable to increased field heating by helium. Under nanoelectrospray ionization (nESI) conditions, where myoglobin is sprayed from an aqueous solution buffered to pH 6.8 with 20 mM ammonium acetate, in the DT IM-MS instrument, each buffer gas can yield a different arrival time distribution (ATD) for any given charge state. PMID:22974196

  1. Possibly to Test the Mechanism of Elastic Backward Proton-Deuteron Scattering ?

    CERN Document Server

    Illarionov, A Yu

    2000-01-01

    The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the invariant expansion of the reaction amplitude. The relativistic invariant equations for all the polarization observables are presented. Within the impulse approximation the relation of the tensor analyzing power $T_{20}$ and the polarization transfer $\\kappa_0$ to $P$-wave components of the deuteron wave function is found. The comparison of the theoretical calculations with experimental data is presented. An experimental verification of the reaction mechanism is suggested by constructing some combinations of different observables.

  2. Beyond nonlinear saturation of backward Raman amplifiers

    Science.gov (United States)

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A.; Fisch, Nathaniel J.

    2016-06-01

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

  3. Focusing on Plates: Controlling Guided Waves using Negative Refraction

    OpenAIRE

    Franck D. Philippe; Murray, Todd W.; Claire Prada

    2015-01-01

    Elastic waves are guided along finite structures such as cylinders, plates, or rods through reflection, refraction, and mode conversion at the interfaces. Such wave propagation is ubiquitous in the world around us, and studies of elastic waveguides first emerged in the later part of the 19th century. Early work on elastic waveguides revealed the presence of backward propagating waves, in which the phase velocity and group velocity are anti-parallel. While backward wave propagation exists natu...

  4. Dynamic Simulation of Backward Diffusion Based on Random Walk Theory

    Science.gov (United States)

    Dung, Vu Ba; Nguyen, Bui Huu

    2016-06-01

    Results of diffusion study in silicon showed that diffusion of the selfinterstitial and vacancy could be backward diffusion and their diffusivity could be negative [1]. The backward diffusion process and negative diffusivity is contrary to the fundamental laws of diffusion such as the law of Fick law, namely the diffusive flux of backward diffusion goes from regions of low concentration to regions of high concentration. The backward diffusion process have been explained [2]. In this paper, the backward diffusion process is simulated. Results is corresponding to theory and show that when thermal velocity of the low concentration area is greater than thermal velocity of the high concentration area, the backward diffusion can be occurred.

  5. Ultrasonic inspection of tube to tube plate welds

    International Nuclear Information System (INIS)

    To monitor the deterioration of a weld between a tube and tube plate which has been repaired by a repair sleeve inside the tube and brazed at one end to the tube, ultrasound from a crystal at the end of a rod is launched, in the form of Lamb-type waves, into the tube through the braze and allowed to travel along the tube to the weld and be reflected back along the tube. The technique may also be used for the type of heat exchanger in which, during construction, the tubes are welded to the tube plate via external sleeves in which case the ultrasound is used in a similar manner to inspect the sleeve/tube plate weld. an electromagnetic transducer may be used to generate the ultrasound. The ultrasonic head comprising the crystal and an acoustic baffle is mounted on a Perspex (RTM) rod which may be rotated by a stepping motor. Echo signals from the region of deterioration may be isolated by use of a time gate in the receiver. The device primarily detects circumferentially orientated cracks, and may be used in heat exchangers in nuclear power plants. (author)

  6. Breaking of forward-backward symmetry in driven systems

    DEFF Research Database (Denmark)

    Szolnoki, Attila; Szabó, György

    1993-01-01

    The dynamical pair approximation was modified to study the stationary states in a two-dimensional repulsive-lattice-gas model driven far from equilibrium by the application of an external field. This approximation distinguishes between the forward, backward, and transverse directions with respect...... to the electric field. In the present driven system, the forward-backward symmetry is broken at the level of the pair approximation. The difference between the forward and backward directions is confirmed by Monte Carlo simulations....

  7. Forward and backward inference in spatial cognition.

    Directory of Open Access Journals (Sweden)

    Will D Penny

    Full Text Available This paper shows that the various computations underlying spatial cognition can be implemented using statistical inference in a single probabilistic model. Inference is implemented using a common set of 'lower-level' computations involving forward and backward inference over time. For example, to estimate where you are in a known environment, forward inference is used to optimally combine location estimates from path integration with those from sensory input. To decide which way to turn to reach a goal, forward inference is used to compute the likelihood of reaching that goal under each option. To work out which environment you are in, forward inference is used to compute the likelihood of sensory observations under the different hypotheses. For reaching sensory goals that require a chaining together of decisions, forward inference can be used to compute a state trajectory that will lead to that goal, and backward inference to refine the route and estimate control signals that produce the required trajectory. We propose that these computations are reflected in recent findings of pattern replay in the mammalian brain. Specifically, that theta sequences reflect decision making, theta flickering reflects model selection, and remote replay reflects route and motor planning. We also propose a mapping of the above computational processes onto lateral and medial entorhinal cortex and hippocampus.

  8. Backwards compatible high dynamic range video compression

    Science.gov (United States)

    Dolzhenko, Vladimir; Chesnokov, Vyacheslav; Edirisinghe, Eran A.

    2014-02-01

    This paper presents a two layer CODEC architecture for high dynamic range video compression. The base layer contains the tone mapped video stream encoded with 8 bits per component which can be decoded using conventional equipment. The base layer content is optimized for rendering on low dynamic range displays. The enhancement layer contains the image difference, in perceptually uniform color space, between the result of inverse tone mapped base layer content and the original video stream. Prediction of the high dynamic range content reduces the redundancy in the transmitted data while still preserves highlights and out-of-gamut colors. Perceptually uniform colorspace enables using standard ratedistortion optimization algorithms. We present techniques for efficient implementation and encoding of non-uniform tone mapping operators with low overhead in terms of bitstream size and number of operations. The transform representation is based on human vision system model and suitable for global and local tone mapping operators. The compression techniques include predicting the transform parameters from previously decoded frames and from already decoded data for current frame. Different video compression techniques are compared: backwards compatible and non-backwards compatible using AVC and HEVC codecs.

  9. PANDA EMC backward end-cap mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Capozza, Luigi; Ceballos, Jorge; Lin, Dexu; Maas, Frank; Rodriguez, David; Valente, Roserio; Welzel, Felix [Helmholtz-Institut Mainz (Germany); Collaboration: PANDA-Collaboration

    2013-07-01

    The PANDA experiment at the FAIR facility will be a multipurpose hermetic spectrometer covering the full solid angle range. A key role for several physics cases will be played by the electromagnetic calorimeter. This includes ca. 15000 PbWO{sub 4} scintillating crystals arranged in a central barrel, a forward and a backward end-cap. The backward end-cap of the PANDA electromagnetic calorimeter is composed by 540 straight crystals covering the scattering angles between 147 {sup circle} and 161 {sup circle}. They are housed in the so-called alveoli which are carbon fibre boxes, providing both strength and low material budget. The crystals are to work at -25 C in order to improve the light yield. To achieve this temperature a cooling system and thermal insulation are needed. The cooling system removes the heat coming from the electronics and through walls, cables and mechanical supports. Vacuum insulated panels are installed as a thermal shielding. Avalanche Photodiodes (APD) have been chosen as photon detectors, since they are still functional under strong magnetic fields. ASIC chips will be used to amplify the APD signal, this preamplifier features low noise and low heat generation. Due to the weight of this detector, it will be supported from the outside of the PANDA target spectrometer in a counter lever arm position.

  10. Kolakoski sequence as an element to radiate giant forward and backward second harmonic signals

    Energy Technology Data Exchange (ETDEWEB)

    Parvini, T. S. [Physics Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Tehranchi, M. M., E-mail: m-hamidi@sbu.ac.ir, E-mail: teranchi@sbu.ac.ir [Physics Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Hamidi, S. M., E-mail: m-hamidi@sbu.ac.ir, E-mail: teranchi@sbu.ac.ir; Sarkarati, S. [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

    2015-11-14

    We propose a novel type of aperiodic one-dimensional photonic crystal structures which can be used for generating giant forward and backward second harmonic signals. The studied structure is formed by stacking together the air and nonlinear layers according to the Kolakoski self-generation scheme in which each nonlinear layer contains a pair of antiparallel 180° poled LiNbO{sub 3} crystal layers. For different generation stages of the structure, conversion efficiencies of forward and backward second harmonic waves have been calculated by nonlinear transfer matrix method. Numerical simulations show that conversion efficiencies in the Kolakoski-based multilayer are larger than the perfect ones for at least one order of magnitude. Especially for 33rd and 39th generation stages, forward second harmonic wave are 42 and 19 times larger, respectively. In this paper, we validate the strong fundamental field enhancement and localization within Kolakoski-based multilayer due to periodicity breaking which consequently leads to very strong radiation of backward and forward second harmonic signals. Following the applications of analogous aperiodic structures, we expect that Kolakosi-based multilayer can play a role in optical parametric devices such as multicolor second harmonic generators with high efficiency.

  11. Kolakoski sequence as an element to radiate giant forward and backward second harmonic signals

    International Nuclear Information System (INIS)

    We propose a novel type of aperiodic one-dimensional photonic crystal structures which can be used for generating giant forward and backward second harmonic signals. The studied structure is formed by stacking together the air and nonlinear layers according to the Kolakoski self-generation scheme in which each nonlinear layer contains a pair of antiparallel 180° poled LiNbO3 crystal layers. For different generation stages of the structure, conversion efficiencies of forward and backward second harmonic waves have been calculated by nonlinear transfer matrix method. Numerical simulations show that conversion efficiencies in the Kolakoski-based multilayer are larger than the perfect ones for at least one order of magnitude. Especially for 33rd and 39th generation stages, forward second harmonic wave are 42 and 19 times larger, respectively. In this paper, we validate the strong fundamental field enhancement and localization within Kolakoski-based multilayer due to periodicity breaking which consequently leads to very strong radiation of backward and forward second harmonic signals. Following the applications of analogous aperiodic structures, we expect that Kolakosi-based multilayer can play a role in optical parametric devices such as multicolor second harmonic generators with high efficiency

  12. Monte Carlo simulation on backward steps of single kinesin molecule

    Institute of Scientific and Technical Information of China (English)

    Wang Hong; Zhang Yong; Dou Shuo-Xing; Wang Peng-Ye

    2008-01-01

    Kinesin is a stepping molecular motor travelling along the microtubule. It moves primarily in the plus end direction of the microtubule and occasionally in the minus-end, backward, direction. Recently, the backward steps of kinesin under different loads and temperatures start to attract interests, and the relations among them are revealed. This paper aims to theoretically understand these relations observed in experiments. After introducing a backward pathway into the previous model of the ATPase cycle of kinesin movement, the dependence of the backward movement on the load and the temperature is explored through Monte Carlo simulation. Our results agree well with previous experiments.

  13. Effect of initial pressure on propagation of detonation wave in round tube%初始压力对爆轰波在管道内传播的影响

    Institute of Scientific and Technical Information of China (English)

    喻健良; 高远; 闫兴清; 高伟

    2014-01-01

    建立爆轰管道研究不同初始压力下爆轰波在管道内传播规律。选用 CH4+2O2气体,采用光纤探针测量爆轰波在管道内的传播速度,采用烟迹法记录爆轰波胞格结构。结果表明:爆轰波在管道内传播时出现5种不同传播模式,分别为稳态式、快速波动式、结巴式、驰振式与失效模式。在稳态传播模式下,爆轰波局部速度波动很小且平均速度接近理论爆轰 CJ 速度,并呈现多头胞格结构。随着初始压力的降低,爆轰波局部速度波动增加且其平均速度产生衰减。在驰振式爆轰解耦处,爆轰波胞格结构消失,过载爆轰时,重新形成胞格结构。进一步降低初始压力至爆轰失效时,则无胞格结构。%Detonation tube was built to investigate the effect of initial pressure on the propagation of detonation wave in round tube.The premixed gas of CH4+2O2 was selected as experimental gas. Optical fiber probe was used to measure the local velocity of detonation wave.Smoked foils were used to register the cellular structure of detonation wave in tubes.The experimental results show that there are five distinct modes during the propagation of detonation wave in tubes,which are stable mode,rapid fluctuation mode,stuttering mode,galloping mode and failure mode.Under the mode of stable detonation,the fluctuations of the local velocity of detonation wave are generally small and the averaged velocity of detonation wave is close to the theoretical CJ value.The detonation wave has multi-headed cellular structure.With decreasing of the initial pressure,the fluctuations of the local velocity of detonation wave increase,and the averaged velocity of detonation wave decreases.For the galloping detonation,at the decoupled position,cellular structure disappears.Cellular structure forms again when overdriven detonation occurs.If the initial pressure is further decreased till the detonation failure,no cellular structure is

  14. DYNAMICS OF FREE STRAIGHT SWIMMING OF ANGULLA ANGULLA INCLUDING FORWARD, BRAKING AND BACKWARD LOCOMOTION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Eels can swim backward by reversing the direction of the traveling wave along the body. The propulsive mechanism of an eel, angulla angulla, during its self-propelled straight swimming, including forward swimming, braking and switching direction to backward swimming was numerically studied. The problem was reasonably simplified to a loose-coupling problem of fish swimming dynamics and hydrodynamics only in the swimming direction. The approach involved the simulation of the flow by solving the two-dimensional unsteady incompressible N-S equations and the fish motion dynamic problem with Newton's second law. Visualizations of flow fields and vortex structures were performed. The propulsive mechanism and dynamics during each process were investigated and the effects of controllable factors on forward free swimming were discussed.

  15. Classic and novel electromagnetic source. The High Power Electron Tube

    International Nuclear Information System (INIS)

    Electron tubes which generate and amplify radio waves relying on the motion of electrons in vacuum are developing in fields where large electric-power and microwave are necessary. Fundamental structures and major purposes of use of practically available electron tubes including transmitting tube, magnetron, travelling-wave tube, and gyrotron are presented. As for microwave tubes, the process where electrons are bunched by the effect of the microwave and fall into the decelerating phase of the microwave are shown for each tube. Also introduced are used materials, outline of fabrication process, the cathode technology which strongly affects the reliability and the lifetime of electron tubes. (author)

  16. Simultaneous stimulated Raman forward and backward scattering in hot, well-underdense plasmas

    International Nuclear Information System (INIS)

    The competition of stimulated Raman forward scattering and backscattering in a high-temperature, underdense, nearly homogeneous plasma slab is investigated. In such plasmas Landau damping limits the growth of the Raman backscattering, and the weaker forward process may reach comparable levels. A modest seeding of one of the scattered electromagnetic waves influences the competition to a large extent. The conversion of the pump wave to scattered waves is calculated. The simultaneous operation of the two processes can lead to considerable modifications in the electron distribution; e.g., two hot tail components are formed because the plasma waves involved have different phase velocities. The generation regions of the scattering processes are spatially separated. Consequently, a large number of thermal electrons can be accelerated to very high energies in two stages. The backward plasmons preaccelerate the electrons and the faster plasmons, excited in the forward scattering, operate as a booster. (Author)

  17. Dynamic Backward Slicing of Rewriting Logic Computations

    CERN Document Server

    Alpuente, María; Espert, Javier; Romero, Daniel

    2011-01-01

    Trace slicing is a widely used technique for execution trace analysis that is effectively used in program debugging, analysis and comprehension. In this paper, we present a backward trace slicing technique that can be used for the analysis of Rewriting Logic theories. Our trace slicing technique allows us to systematically trace back rewrite sequences modulo equational axioms (such as associativity and commutativity) by means of an algorithm that dynamically simplifies the traces by detecting control and data dependencies, and dropping useless data that do not influence the final result. Our methodology is particularly suitable for analyzing complex, textually-large system computations such as those delivered as counter-example traces by Maude model-checkers.

  18. Backwardation in energy futures markets: Metalgesellschaft revisited

    International Nuclear Information System (INIS)

    Energy supply contracts negotiated by the US Subsidiary of Metalgesellschaft Refining and Marketing (MGRM), which were the subject of much subsequent debate, are re-examined. The contracts were hedged by the US Subsidiary barrel-for-barrel using short-dated energy derivatives. When the hedge program experienced difficulties, the derivatives positions were promptly liquidated by the parent company. Revisiting the MGRM contracts also provides the opportunity to explore the latest evidence on backwardation in energy markets. Accordingly, the paper discusses first the theoretical reasons for backwardation, followed by an empirical examination using the MGRM data available at the time of the hedge program in 1992 and a second set of data that became available in 2000. By using a more up-to-date data set covering a longer time period and by controlling the time series properties of the data, the authors expect to provide more reliable empirical evidence on the behaviour of energy futures prices. Results based on the 1992 data suggest that the strategy employed by MGRM could be expected to be profitable while the risks are relatively low. However, analysis based on the 2000 data shows lower, although still significant profits, but higher risks. The final conclusion was that the likelihood of problems similar to those faced by MGRM in 1992 are twice as high with the updated 2000 data, suggesting that the risk-return pattern of the stack-and-roll hedging strategy using short-dated energy future contracts to hedge long-tem contracts is less appealing now than when MGRM implemented its hedging program in 1992. 24 refs., 3 tabs., 6 figs

  19. The Effect of Gender on the Construction of Backward Inferences

    Science.gov (United States)

    Cakir, Ozler

    2008-01-01

    The main objective in the present study is to examine the effect of gender on primary school students' construction of elaborative backward inferences during text processing. A total of 333 children, aged 10-11 years (n = 158 girls and 175 boys) participated in the study. Each participant completed a backward inference test. The results indicate…

  20. The Equivalence Forms of Random Kolmogorov Forward (Backward) Equations

    Institute of Scientific and Technical Information of China (English)

    HU Di-he; HU Xiao-yu

    2005-01-01

    The concepts of Markov process in random environment, q-matrix in random environment and q-process in random environment are introduced. Three forms of random Kolmoogrov farward (or backward) equations are introduced and the equivalence of these three forms are also proved. Moreover any conservative q-process in random environment satisfies random Kolmogrov backward equation.

  1. COMPARISON THEOREM OF BACKWARD DOUBLY STOCHASTIC DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper is devoted to deriving a comparison theorem of solutions to backward doubly stochastic differential equations driven by Brownian motion and backward It-Kunita integral. By the application of this theorem, we give an existence result of the solutions to these equations with continuous coefficients.

  2. Resonant reflector of an X-band relativistic backward oscillator

    International Nuclear Information System (INIS)

    A high power microwave experiment is carried out based on TPG2000 pulse power generator and X-band relativistic backward wave oscillator(RBWO) with a resonant reflector. A microwave with a power of about 2.5 GW and a pulse width of about 20 ns is obtained and the pulse shortening phenomenon is observed, which is caused by resonant reflector breakdown and secondary electron emitting. Chamfering is used to decrease the electric field and restrain the electron emitting on the edge of the resonant reflector. The electric field and reflective parameter varying with chamfered radius is analyzed and corresponding experiments have been conducted. The results indicate that the pulse width increases and the efficiency decreases, with chamfered radius increasing. With a 900 kV, 9 kA electron beam and a 5 mm chamfered-radius resonant reflector, a microwave with a power of about 2.5 GW and a pulse width of about 25 ns is obtained. (authors)

  3. Negative group velocity and three-wave mixing in dielectric crystals

    OpenAIRE

    Slabko, Vitaly V.; Myslivets, Sergey A.; Shalaev, Mikhail I.; Popov, Alexander K.

    2011-01-01

    Extraordinary features of optical parametric amplification of Stokes electromagnetic waves are investigated, which originate from three-wave mixing of two ordinary electromagnetic and one backward phonon wave with negative group velocity. A similarity with the counterpart in the negative-index plasmonic metamaterials and differences with those utilizing contra-propagating ordinary electromagnetic waves as well as electromagnetic and acoustic phonon waves are shown. They stem from backwardness...

  4. Magnetosonic Waveguide Model of Solar Wind Flow Tubes

    Indian Academy of Sciences (India)

    A. K. Srivastava; B. N. Dwivedi

    2006-06-01

    We consider solar wind flow tubes as a magnetosonic wave-guide. Assuming a symmetric expansion in edges of slab-modelled wave-guide, we study the propagation characteristics of magnetosonic wave in the solar wind flow tubes. We present the preliminary results and discuss their implications.

  5. Gastrostomy Tube (G-Tube)

    Science.gov (United States)

    ... endoscope (a thin, flexible tube with a tiny camera and light at the tip) inserted through the ... Nemours Foundation, iStock, Getty Images, Corbis, Veer, Science Photo Library, Science Source Images, Shutterstock, and Clipart.com

  6. Ear tube insertion

    Science.gov (United States)

    Myringotomy; Tympanostomy; Ear tube surgery; Pressure equalization tubes; Ventilating tubes; Ear infection - tubes; Otitis - tubes ... trapped fluid can flow out of the middle ear. This prevents hearing loss and reduces the risk ...

  7. Quasitransient regimes of backward Raman amplification of intense x-ray pulses

    Science.gov (United States)

    Malkin, V. M.; Fisch, N. J.

    2009-10-01

    New powerful soft x-ray sources may be able to access intensities needed for backward Raman amplification (BRA) of x-ray pulses in plasmas. However, high plasma densities, needed to provide enough coupling between the pump and seed x-ray pulses, cause strong damping of the Langmuir wave that mediates energy transfer from the pump to the seed pulse. Such damping could reduce the coupling, thus making efficient BRA impossible. This work shows that efficient BRA can survive despite the Langmuir wave damping significantly exceeding the linear BRA growth rate. Moreover, the strong Langmuir wave damping can automatically suppress deleterious instabilities of BRA to the thermal noise. The class of “quasitransient” BRA regimes identified here shows that it may be feasible to observe x-ray BRA within available x-ray facilities.

  8. Quasitransient regimes of backward Raman amplification of intense x-ray pulses

    International Nuclear Information System (INIS)

    New powerful soft x-ray sources may be able to access intensities needed for backward Raman amplification (BRA) of x-ray pulses in plasmas. However, high plasma densities, needed to provide enough coupling between the pump and seed x-ray pulses, cause strong damping of the Langmuir wave that mediates energy transfer from the pump to the seed pulse. Such damping could reduce the coupling, thus making efficient BRA impossible. This work shows that efficient BRA can survive despite the Langmuir wave damping significantly exceeding the linear BRA growth rate. Moreover, the strong Langmuir wave damping can automatically suppress deleterious instabilities of BRA to the thermal noise. The class of 'quasitransient' BRA regimes identified here shows that it may be feasible to observe x-ray BRA within available x-ray facilities.

  9. Lubrication in Hot Tube Extrusion of Superalloys and Ti Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Tubular products made of superalloys and titanium alloys usually work in high temperature environment and applied heavy loading. Hot extrusion is the best technology to form tubular billets with fine microstructures and good mechanical properties. Lubrication is one of the key techniques in hot extrusion, glass lubricants are most suitable for hot extrusion. Lubrication technique in hot extrusion is dealt with in this paper, the lubrication principle of hot tube extrusion is presented. Experiments of glass lubricated backward tube extrusion of titanium alloys and forward tube extrusion of superalloys are also discussed.

  10. Coiled tubing

    International Nuclear Information System (INIS)

    Oil and gas wells that flow on initial completion eventually reach a condition of liquid loading that kills the wells. This results form declining reservoir pressure, decreased gas volume (velocity), increased water production and other factors that cause liquids to accumulate at the bottom of the well and exert back pressure on the formation. This restricts or in some cases prevents fluid entry into the wellbore form the formation. Flowing production can be restored or increased by reducing surface backpressure, well bore stimulation, pressure maintenance or by installing a string of smaller diameter tubing. This paper reports on installation (hanging off) of a concentric string of coiled tubing inside existing production tubing which is an economically viable, safe, convenient and effective alterative for returning some of these liquid loaded )logged-up) wells to flowing status

  11. Ionization tube simmer current circuit

    Science.gov (United States)

    Steinkraus, Jr., Robert F.

    1994-01-01

    A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

  12. Complete experiment for dp and 3He,d backward elastic scattering

    International Nuclear Information System (INIS)

    The problem of the complete experiment in backward elastic scattering of particles with spins of 1 and 1/2 is considered. For the first time all possible effects caused by polarization of one or two initial and one final particles are touched upon. The minimal set of measurements allowing to reconstruct each of four amplitudes describing this process is suggested. Some observables are expected to be sensitive to such deuteron peculiarities as possible P-wave components. The developed technique is a good tool to calculate easily the expectations in the Impulse Approximation for any observables. The geography of the complete experiment is briefly discussed

  13. Quasitransient backward Raman amplification of powerful laser pulses in dense plasmas with multicharged ions

    Science.gov (United States)

    Malkin, V. M.; Fisch, N. J.

    2010-07-01

    The range of plasma parameters, where the efficient quasitransient backward Raman amplification (QBRA) of powerful laser pulses is possible, is determined for dense plasmas with multicharged ions. Approximate scalings that portray in a simple way the efficient QBRA range in multidimensional parameter space are found. The calculation, applicable to infrared, ultraviolet, soft x-ray, and x-ray laser pulses, takes into account plasma heating by the lasers. It is shown that efficient QBRA can survive even the nonsaturated linear Landau damping of the Langmuir wave mediating the energy transfer from the pump to the seed laser pulse; moreover, this survival does not require very intense seed laser pulses.

  14. Quasitransient backward Raman amplification of powerful laser pulses in dense plasmas with multicharged ions

    International Nuclear Information System (INIS)

    The range of plasma parameters, where the efficient quasitransient backward Raman amplification (QBRA) of powerful laser pulses is possible, is determined for dense plasmas with multicharged ions. Approximate scalings that portray in a simple way the efficient QBRA range in multidimensional parameter space are found. The calculation, applicable to infrared, ultraviolet, soft x-ray, and x-ray laser pulses, takes into account plasma heating by the lasers. It is shown that efficient QBRA can survive even the nonsaturated linear Landau damping of the Langmuir wave mediating the energy transfer from the pump to the seed laser pulse; moreover, this survival does not require very intense seed laser pulses.

  15. Inverse bremsstrahlung stabilization of noise in the generation of ultrashort intense pulses by backward Raman amplification

    International Nuclear Information System (INIS)

    Inverse bremsstrahlung absorption of the pump laser beam in a backward Raman amplifier over the round-trip light transit time through the subcritical density plasma can more than double the electron temperature of the plasma and produce time-varying axial temperature gradients. The resulting increased Landau damping of the plasma wave and detuning of the resonance can act to stabilize the pump against unwanted amplification of Langmuir noise without disrupting nonlinear amplification of the femtosecond seed pulse. Because the heating rate increases with the charge state Z, only low-Z plasmas (hydrogen, helium, or helium-hydrogen mixtures) will maintain a low enough temperature for efficient operation

  16. Ant Colony Optimisation for Backward Production Scheduling

    Directory of Open Access Journals (Sweden)

    Leandro Pereira dos Santos

    2012-01-01

    Full Text Available The main objective of a production scheduling system is to assign tasks (orders or jobs to resources and sequence them as efficiently and economically (optimised as possible. Achieving this goal is a difficult task in complex environment where capacity is usually limited. In these scenarios, finding an optimal solution—if possible—demands a large amount of computer time. For this reason, in many cases, a good solution that is quickly found is preferred. In such situations, the use of metaheuristics is an appropriate strategy. In these last two decades, some out-of-the-shelf systems have been developed using such techniques. This paper presents and analyses the development of a shop-floor scheduling system that uses ant colony optimisation (ACO in a backward scheduling problem in a manufacturing scenario with single-stage processing, parallel resources, and flexible routings. This scenario was found in a large food industry where the corresponding author worked as consultant for more than a year. This work demonstrates the applicability of this artificial intelligence technique. In fact, ACO proved to be as efficient as branch-and-bound, however, executing much faster.

  17. Doing hydrology backwards in tropical humid catchments

    Science.gov (United States)

    Real Rangel, R.; Brena-Naranjo, J. A.; Pedrozo-Acuña, A.

    2015-12-01

    Top-down approaches in hydrology offer the possibility to predict water fluxes at the catchment scale based on the interpretation of the observed hydrological response at the catchment itself. Doing hydrology backwards (inferring precipitation and evapotranspiration rates at the catchment scale from streamflow measurements, see Kirchner (2009)) can be a useful methodology for estimating water fluxes at the catchment and regional scales. Previous studies using this inverse modeling approach have been performed in regions (UK, Switzerland, France, Eastern US) where energy-limited (in winter and early spring) and water-limited conditions (in summer) prevail during a large period of the year. However, such approach has not been tested in regions characterized by a quasi-constant supply of water and energy (e.g. humid tropics). The objective of this work is to infer annual rates of precipitation and evapotranspiration over the last decade in 10 catchments located in Mexico's tropical humid regions. Hourly discharge measurements during recession periods were analyzed and parameters for the nonlinear storage-discharge relationship of each catchment were derived. Results showed large variability in both catchment-scale precipitation and evapotranspiration rates among the selected study sites. Finally, a comparison was done between such estimates and those obtained from remotely-sensed data (TRMM for precipitation and MOD16 for evapotranspiration).

  18. Pulse tube cooler having 1/4 wavelength resonator tube instead of reservoir

    Science.gov (United States)

    Gedeon, David R. (Inventor)

    2008-01-01

    An improved pulse tube cooler having a resonator tube connected in place of a compliance volume or reservoir. The resonator tube has a length substantially equal to an integer multiple of 1/4 wavelength of an acoustic wave in the working gas within the resonator tube at its operating frequency, temperature and pressure. Preferably, the resonator tube is formed integrally with the inertance tube as a single, integral tube with a length approximately 1/2 of that wavelength. Also preferably, the integral tube is spaced outwardly from and coiled around the connection of the regenerator to the pulse tube at a cold region of the cooler and the turns of the coil are thermally bonded together to improve heat conduction through the coil.

  19. Fields in multilayer beam tubes

    International Nuclear Information System (INIS)

    Equations are presented for calculating the fields from a bunched beam that penetrate into the layers of a beam tube of circular cross section. Starting from the radial wave impedance of an outer surface, the wave functions in inner layers are calculated numerically to obtain field strengths or the longitudinal beam impedance. Examples of a vertex-detector region and of an injection kicker are given

  20. Reverse Quantum Waves

    Science.gov (United States)

    Boyd, Jeffrey

    2010-02-01

    As preposterous as it might sound, if quantum waves travel in the reverse direction from subatomic particles, then most of quantum physics can be explained without quantum weirdness or Schr"odinger's cat. Quantum mathematics is unchanged. The diffraction pattern on the screen of the double slit experiment is the same. This proposal is not refuted by the Innsbruck experiments; this is NOT a hidden local variable theory. Research evidence will be presented that is consistent with the idea waves travel in the opposite direction as neutrons. If one's thinking shifts from forwards to backwards quantum waves, the world changes so drastically it is almost unimaginable. Quantum waves move from the mathematical to the real world, multiply in number, and reverse in direction. Wave-particle duality is undone. In the double slit experiment every part of the target screen is emitting such quantum waves in all directions. Some pass through the two slits. Interference occurs on the opposite side of the barrier than is usually imagined. They impinge on ``S'' and an electron is released at random. Because of the interference it is more likely to follow some waves than others. It follows one and only one wave backward; hitting the screen where it's wave originated. )

  1. Nondiffracting Accelerating Waves: Weber waves and parabolic momentum

    CERN Document Server

    Bandres, Miguel A

    2012-01-01

    Diffraction is one of the universal phenomena of physics, and a way to overcome it has always represented a challenge for physicists. In order to control diffraction, the study of structured waves has become decisive. Here, we present nondiffracting spatially accelerating solutions of the Maxwell equations: the Weber waves. These nonparaxial waves propagate along a parabolic trajectory while preserving its shape to a good approximation. They are expressed in analytic closed form and naturally separate in forward and backward propagation. We show that the Weber waves are self-healing, can form periodic breather waves, and have a well-defined conserved quantity: the parabolic momentum. We find that our Weber waves for moderate to large values of the parabolic momenta can be described by a modulated Airy function. Because the Weber waves are exact time-harmonic solution of the wave equation, they have implications to many linear wave systems in nature, ranging from acoustic and elastic waves to surface waves in ...

  2. Ear Tubes

    Science.gov (United States)

    ... of the ear drum or eustachian tube, Down Syndrome, cleft palate, and barotrauma (injury to the middle ear caused by a reduction of air pressure, ... specialist) may be warranted if you or your child has experienced repeated ... fluid in the middle ear, barotrauma, or have an anatomic abnormality that ...

  3. Wavefunction Properties of a Single and a System of Magnetic Flux Tube(s) Oscillations

    CERN Document Server

    Esmaeili, Shahriar; Dadashi, Neda; Safari, Hossein

    2015-01-01

    In this study, the properties of wavefunctions of the MHD oscillations for a single and a system of straight flux tubes are investigated. Magnetic flux tubes with a straight magnetic field and longitudinally density stratification under coronal conditions were considered. With repect to the density inhomogeneity in the radial direction of the flux tube, a smoothed step function at the lateral surface is employed. A single three-dimensional wave equation for longitudinal component of the perturbed magnetic field is solved using the finite element method (FEM). Wavefunctions of the MHD oscillations are categorized into kink, sausage, and torsional modes. Concerning the amplitude location of the waves which are arisen from the flux tube, those waves identified as body, surface, and leaky waves and appeared in both a single and a system of flux tubes cases. Exact recognition of the wavefunctions can be used in coronal seismology and also helps to future the high resolution instruments that would be designed for s...

  4. Backward volume contraction for endomorphisms with eventual volume expansion

    OpenAIRE

    Pinheiro, Vilton; Castro, Armando; Alves, J. F.

    2009-01-01

    We consider smooth maps on compact Riemannian manifolds. We prove that under some mild condition of eventual volume expansion Lebesgue almost everywhere we have uniform backward volume contraction on every pre-orbit for Lebesgue almost every point.

  5. Backward flow in a surface tension driven micropump

    International Nuclear Information System (INIS)

    A surface tension driven micropump harnessing the pressure difference generated by drops of different curvature radii proves to be a simple and attractive passive method to drive fluid flow in microdevices. Here we observed the appearance of backward flow when the initial sizes of the droplets at the inlet and outlet ports are similar. To explain this phenomenon several hypotheses have been investigated. Consideration of the inertia of the fluid in the channel revealed that it alone is insufficient to explain the observed backward flow. We discovered that rotational flow inside the outlet droplet could be a source of inertia, explaining the generation of the backward flow. In addition, we have experimentally determined that the ratio of the volumes of the initial outlet drop and inlet drop correlates with the occurrence of the backward flow. (note)

  6. Kundt's Tube Experiment Using Smartphones

    Science.gov (United States)

    Parolin, Sara Orsola; Pezzi, Giovanni

    2015-01-01

    This article deals with a modern version of Kundt's tube experiment. Using economic instruments and a couple of smartphones, it is possible to "see" nodes and antinodes of standing acoustic waves in a column of vibrating air and to measure the speed of sound.

  7. Experience and Abstract Reasoning in Learning Backward Induction

    OpenAIRE

    DanielR.Hawes; AldoRustichini; AlexanderVostroknutov

    2012-01-01

    Backward induction is a benchmark of game theoretic rationality, yet surprisingly little is known as to how humans discover and initially learn to apply this abstract solution concept in experimental settings. We use behavioral and functional magnetic resonance imaging (fMRI) data to study the way in which subjects playing in a sequential game of perfect information learn the optimal backward induction strategy for the game. Experimental data from our two studies support two main findings: Fi...

  8. Uncertainty and the convenience yield in crude oil price backwardations

    International Nuclear Information System (INIS)

    This study examines why firms hold stocks of crude oil, particularly during price backwardations when spot prices exceed prices for forward delivery. Using a stochastic control model, this paper shows that the equilibrium value of inventories contains: the conventional Hotelling principle; the convenience yield from the classical theory of storage; and an option value related to price uncertainty. Our empirical results suggest that a convenience yield and risk premium are important elements of crude oil price backwardations

  9. On-line simulations of models for backward masking.

    Science.gov (United States)

    Francis, Gregory

    2003-11-01

    Five simulations of quantitative models of visual backward masking are available on the Internet at http://www.psych.purdue.edu/-gfrancis/Publications/BackwardMasking/. The simulations can be run in a Web browser that supports the Java programming language. This article describes the motivation for making the simulations available and gives a brief introduction as to how the simulations are used. The source code is available on the Web page, and this article describes how the code is organized. PMID:14748495

  10. 波面管式结晶器处理含盐废水的实验研究%Experimental Study of Using Wave Surface Tube Crystallizer to Treat the Salinity Wastewater

    Institute of Scientific and Technical Information of China (English)

    刘洋

    2014-01-01

    研究设计一种新型波面管式结晶器,建立晶体生长的动力学模型,测试晶体成核和晶体生长的动力学参数,并拟合出盐水中晶体在结晶器内的成核速率方程和生长速率方程。实验结果表明,改变进料温度和进料流量,会改变晶体产率。%Develop a new wave surface tube crystallizer . Establish the dynamic model of crystal grow th ,measure the dynamic parameters of crystal nucleation and crystal grow th ,and find both the fitting equations of crystal nucleation rate and growth rate . The experiment results show that changing the feed temperature and feed flow will change the crystal yield .

  11. Design and fabrication of pill-box window for 0.14 THz folded waveguide traveling wave tubes%0.14 THz折叠波导行波管盒型窗设计与制作

    Institute of Scientific and Technical Information of China (English)

    王亚军; 陈樟; 刘俊

    2013-01-01

    This paper mainly discusses the pill-box window with sapphire piece for 0.14 THz folded waveguide traveling wave tubes. The dimension of the window is computed and optimized by HFSS. The VSWR is below 1.2 when the main structure parameters range at ±0.01 mm. Cold-test result shows the attenuation of the window test structure is about 0.7 dB during 0.135 THz-0.145 THz,which meets the practical requirements in 0.14 THz folded waveguide traveling wave tubes.%  研究用于0.14 THz 折叠波导行波管的盒形窗结构,采用三维模拟软件 HFSS 进行计算与优化,设计出基于蓝宝石窗片的盒型窗结构。分析了结构参数对盒形窗电压驻波比的影响,主要结构参数在±0.01 mm范围变化时,盒形窗电压驻波比仍然低于1.2,保证零件加工的可行性。装配完成盒形窗测试结构,冷测结果显示,在0.135 THz~0.145 THz范围内衰减系数为0.7 dB左右,满足整管要求。

  12. Electron tube

    Energy Technology Data Exchange (ETDEWEB)

    Suyama, Motohiro (Hamamatsu, JP); Fukasawa, Atsuhito (Hamamatsu, JP); Arisaka, Katsushi (Los Angeles, CA); Wang, Hanguo (North Hills, CA)

    2011-12-20

    An electron tube of the present invention includes: a vacuum vessel including a face plate portion made of synthetic silica and having a surface on which a photoelectric surface is provided, a stem portion arranged facing the photoelectric surface and made of synthetic silica, and a side tube portion having one end connected to the face plate portion and the other end connected to the stem portion and made of synthetic silica; a projection portion arranged in the vacuum vessel, extending from the stem portion toward the photoelectric surface, and made of synthetic silica; and an electron detector arranged on the projection portion, for detecting electrons from the photoelectric surface, and made of silicon.

  13. Neutron tubes

    Science.gov (United States)

    Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani

    2008-03-11

    A neutron tube or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift tube. The target may have a tapered or conical surface to increase target surface area.

  14. Straightening tubes

    International Nuclear Information System (INIS)

    Hexagonal wrapper tubes, especially for nuclear reactor core sub-assemblies, may suffer from unacceptable bow as a result of welding wear pads to the wrapper and heat treatment. Straightening of the bow is effected by a method wherein at each of a series of axially spaced locations the faces or vertices of the tube are measured relative to a reference to determine the direction of bow at the locations. From these measurements, the appropriate axial locations for the application of corrective loading can be determined, whereby by application of the loading at a selected face or vertex for such measurements the bow is reduced. Such loading, by an actuator, can be repeated at the locations until the bow is reduced to within tolerances. (author)

  15. Electron tube with transverse cyclotron interaction

    Energy Technology Data Exchange (ETDEWEB)

    Chodorow, M.

    1985-04-23

    An electron-beam tube for generating high microwave power at high frequencies comprises a fast-wave circuit such as a hollow waveguide. The circuit wave has a component of electric field perpendicular to its propagation axis. This field interacts with motions of the electrons transverse to the axis, in particular cyclotron rotation in an axial magnetic field. The above features are common to the well-known ''gyrotrons''. In the inventive tube the fast-wave circuit has means for locking a linearly polarized transverse-electric mode to the orientation of a circuit member such as the ridge in a ridged waveguide. The member (ridge) rotates spirally with distance along the guide. The added periodicity permits interaction with a space harmonic of the circuit wave. The -1 harmonic has a dispersion characteristic which provides beam-wave interaction over a wider frequency range than is possible in prior-art tubes of the gyrotron type.

  16. Electron tube with transverse cyclotron interaction

    International Nuclear Information System (INIS)

    An electron-beam tube for generating high microwave power at high frequencies comprises a fast-wave circuit such as a hollow waveguide. The circuit wave has a component of electric field perpendicular to its propagation axis. This field interacts with motions of the electrons transverse to the axis, in particular cyclotron rotation in an axial magnetic field. The above features are common to the well-known ''gyrotrons''. In the inventive tube the fast-wave circuit has means for locking a linearly polarized transverse-electric mode to the orientation of a circuit member such as the ridge in a ridged waveguide. The member (ridge) rotates spirally with distance along the guide. The added periodicity permits interaction with a space harmonic of the circuit wave. The -1 harmonic has a dispersion characteristic which provides beam-wave interaction over a wider frequency range than is possible in prior-art tubes of the gyrotron type

  17. The Numerical Simulation Research for the Bend Tube Defects Detection Based on Ultrasonic Guided Wave%基于超声导波检测的弯管缺陷数值模拟研究

    Institute of Scientific and Technical Information of China (English)

    赵冬梅; 罗月迎; 贾传伟; 巫帅珍

    2015-01-01

    For the problem of bend tube defects detection , did some numerical simulation research for the bend tube defects detection based on ultrasonic guided wave testing by using finite element method .First of all, this paper built a 90 degrees bend model , and set double defects like different sizes and different distances in the bend model .Secondly , set the parameters of finite element calculation based on the ultra-sonic guided wave theory .Then, according to the calculation results , made a fitting curve of the influence of corrosion pit defect dimensional change in straight pipe to crack curve reflection coefficient in elbow , and the variation tendency curve of the reflection coefficient with the change of the distances between de -fects is made as well .The results show that when the size of the elbow defects remains constant , the re-flection coefficient decreases with the straight pipe flaw size increasing , and the changing relationship be-tween the reflection coefficient and the distance of the two defects can be ignored .These results have an application value for the bend tube degree of defects detection .%针对弯管缺陷检测的问题,利用有限元方法,对弯管缺陷超声导波检测进行数值模拟. 通过建立90°弯管模型,在弯管中设置不同尺寸以及不同距离的双缺陷,根据超声导波理论设置有限元计算的参数,由计算结果拟合出双缺陷中直管段腐蚀坑缺陷尺寸变化对弯头处裂纹缺陷反射系数的影响曲线以及缺陷间距离不同时反射系数的变化趋势曲线. 结果表明,当弯头处缺陷的尺寸不变时,其反射系数随直管段缺陷尺寸的变大而减小,两个缺陷间的反射系数与两缺陷间的距离变化关系可忽略不计. 研究结果对弯管缺陷程度检测有一定应用价值.

  18. Quasi-phase-matched backward second-harmonic generation by complementary media in nonlinear metamaterials.

    Science.gov (United States)

    Quan, Li; Liu, Xiaozhou; Gong, Xiufen

    2012-10-01

    High efficiency of the second-harmonic and sum-frequency generation can be obtained in optical superlattice by using the conventional quasi-phase-matched (QPM) method. Although this trick can be played on the acoustic wave, the media with negative nonlinear parameters are not common in acoustics. Furthermore, the QPM method used in acoustic metamaterials has been less studied. In this work, a protocol is provided to realize the QPM method by using nonlinear complementary media in acoustic metamaterials in order to obtain large backward second-harmonic generation. Compared with the conventional method, the method gains a broader bandwidth and can be used in both acoustic and electromagnetic waves. PMID:23039551

  19. Numerical modeling of quasitransient backward Raman amplification of laser pulses in moderately undercritical plasmas with multicharged ions

    International Nuclear Information System (INIS)

    It was proposed recently that powerful optical laser pulses could be efficiently compressed through backward Raman amplification in ionized low density solids, in spite of strong damping of the resonant Langmuir wave. It was argued that, even for nonsaturated Landau damping of the Langmuir wave, the energy transfer from the pump laser pulse to the amplified seed laser pulse can nevertheless be highly efficient. This work numerically examines such regimes of strong damping, called quasitransient regimes, within the simplest model that takes into account the major effects. The simulations indicate that compression of powerful optical laser pulses in ionized low density solids indeed can be highly efficient.

  20. Numerical modeling of quasitransient backward Raman amplification of laser pulses in moderately undercritical plasmas with multicharged ions

    Science.gov (United States)

    Balakin, A. A.; Fisch, N. J.; Fraiman, G. M.; Malkin, V. M.; Toroker, Z.

    2011-10-01

    It was proposed recently that powerful optical laser pulses could be efficiently compressed through backward Raman amplification in ionized low density solids, in spite of strong damping of the resonant Langmuir wave. It was argued that, even for nonsaturated Landau damping of the Langmuir wave, the energy transfer from the pump laser pulse to the amplified seed laser pulse can nevertheless be highly efficient. This work numerically examines such regimes of strong damping, called quasitransient regimes, within the simplest model that takes into account the major effects. The simulations indicate that compression of powerful optical laser pulses in ionized low density solids indeed can be highly efficient.

  1. Fuel cladding tubes and fuel elements

    International Nuclear Information System (INIS)

    Purpose: To enable non-destructive measurement for the thickness of zirconium barriers. Constitution: Regions capable of non-destructive inspection are provided at the boundary between a fuel cladding tube made of zirconium alloy and the zirconium barrier lined to the inner circumference surface of the tube. As the regions being capable of distinguishing by ultrasonic wave reflection, solid materials, for example, non-metal materials different from that for the tube and the barrier are placed or gaps are provided at the boundary between the zirconium alloy cladding tube and the zirconium barrier. Since ultrasonic waves are reflected at each of the boundaries by the presence of these regions, thickness of the zirconium barrier can be measured in a non-destructive manner from either the inner or the outer surface of the tube. (Yoshino, Y.)

  2. photomultiplier tubes

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  3. photomultiplier tube

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  4. Double detonation drivers for a shock tube/tunnel

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong; FENG Heng; YU Hongru

    2004-01-01

    Recent progress on detonation drivers is reviewed. Performances of the forward detonation driver and backward detonation driver have been observed. To eliminate occurrence of a Taylor wave following the detonation wave in the primary driver and to improve the performance of the detonation driver, an additional backward detonation driver was proposed to attach to the end of the forward detonation driver.When the ratio of the initial pressures between the additional and the primary drivers becomes larger than or equal to a critical value, the Taylor wave will disappear, and thus a homogeneous driving gas with high pressure and high temperature can be generated.Furthermore, an over-driving detonation wave will be also obtained, which can increase the driving capability.

  5. Linear elastic response of tubes to internal detonation loading

    NARCIS (Netherlands)

    Beltman, W.M.; Shepherd, J.E.

    2002-01-01

    This paper deals with the structural response of a tube to an internal gaseous detonation. An internal detonation produces a pressure load that propagates down the tube. Because the speed of the gaseous detonation can be comparable to the flexural wave group speed, excitation of flexural waves in th

  6. Detuning, wavebreaking, and Landau damping as limiting effects on laser compression by resonant backward Raman scattering

    Science.gov (United States)

    Yampolsky, Nikolai

    2010-11-01

    Plasma waves mediate high-power pulse compression, where the persistence of the plasma wave is critical. In this scheme, the plasma wave mediates the energy transfer between long pump and short seed laser pulses through backward Raman scattering. High efficiency of the plasma wave excitation defines both the overall efficiency of the energy transfer and the duration of the amplified pulse. Based on recent extensive experiments, it is possible to deduce that the experimentally realized efficiency of the amplifier is likely constrained by two factors, namely the pump chirp and the plasma wavebreaking [1]. The limits arise because for compression the frequency of the plasma wave should match the bandwidth of the instability and the plasma wave amplitude should be small enough to be sustained by plasma. Both the detuning and the wavebreaking effects can be suppressed by using low pump intensity in plasma having the appropriate density gradient [1]. When these constraints are avoided, Landau damping will be the main limiting factor. However, the Landau damping rate can be significantly reduced in the presence of a strong plasma wave. Currently, nonlinear Landau damping can be described within two recently developed models [2,3]. We show that these two different descriptions result in the same dynamics for the plasma wave amplitude. We use the quasilinear description of nonlinear Landau damping [3] to identify a regime where initially high linear Landau damping can be significantly saturated. Because of the saturation effect, higher temperatures can be tolerated in achieving efficient amplification. Significantly, the plasma temperature can be as much as 50% larger compared to the case of unsaturated Landau damping.[4pt] [1] N.A. Yampolsky et al., Phys. Plasmas 15, 113104 (2008).[0pt] [2] D. Benisti et al., Phys. Rev. Lett. 103, 155002 (2009).[0pt] [3] N.A. Yampolsky and N.J. Fisch, Phys. Plasmas 16, 072104 (2009).

  7. Backward Causation, Isolation and the Pursuit of Justice

    CERN Document Server

    Cirkovic, M M; Cirkovic, Milan M.; Cveticanin, Suzana

    2001-01-01

    The recent operationalization of the famous Newcomb's game by Schmidt (1998) offers an interesting and thought-provoking look at the plausibility of backward causation in a Newtonian universe. Hereby we investigate two details of the Schmidt's scenario which may, at least in principle, invalidate his conclusion in two different domains: one dealing with the issue of Newtonian predictability in specific instance of human actions, and the other stemming from a possible strategy aimed at obviating the anthropically oriented view of backward causation as applied to a judicial and ethical problem posed by a version of the scenario. We conclude that the scenario is at least to be more complex than originally presented in order to remain viable. However, it points to a very deep and delicate question of compatibility of backward causation with the conventional ethical standards.

  8. Simultaneous observation of forward-backward attosecond photoelectron holography

    CERN Document Server

    Du, Hongchuan; Wang, Huiqiao; Yue, Shengjun; Hu, Bitao

    2015-01-01

    Photoelectron angular momentum distribution of He+ driven by a few-cycle laser is investigated numerically. We simultaneously observe two dominant interference patterns with one shot of lasers by solving the 3D time-dependent Schrodinger equation (TDSE). The analysis of a semiclassical model identi?es these two interference patterns as two kinds of photoelectron holography. The interference pattern with Pz > 0 is a kind of forward rescattering holography, which comes from the interference between direct (reference) and rescattered (signal) forward electrons ionized in the same quarter-cycle. The interference pattern with Pz < 0 is a kind of backward rescattering holography, which comes from the interference between direct electron ionized in the third quarter- cycle and rescattered backward electron ionized in the ?rst quarter-cycle. Moreover, we propose a method to distinguish this backward rescattering holography and intracycle interference patterns of direct electrons. This is an important step for dyna...

  9. Production of extremely deep sleeves by backward cold extrusion

    Directory of Open Access Journals (Sweden)

    Labanova Nadja

    2015-01-01

    Full Text Available The production of extremely deep sleeves by backward cold extrusion has drawn significant attention and interest in recent years in metal forming area, due to their unique and superior properties and their economic and technological advantages. This work describes the limitation related to buckling of extrusion punch during backward extrusion process and also represents the design of a new tool concept to avoid such risks of effects. Application of this tool concept for many cases in industry provides new opportunities to produce deep sleeves with ratio of the overall height of a sleeve (H to its inner diameter (d higher than three within one process stage by backward cold extrusion. Developed concept of tool has been supported by previous fundamental and applied research studies.

  10. Sausage Mode Propagation in a Thick Magnetic Flux Tube

    CERN Document Server

    Pardi, Anabele-Linda; Marcu, Alexandru; Orza, Beniamin

    2013-01-01

    The aim of this paper is to model the propagation of slow magnetohydrodynamic (MHD) sausage waves in a thick expanding magnetic flux tube in the context of the quiescent (VAL C) solar atmosphere. The propagation of these waves is found to be described by the Klein-Gordon equation. Using the governing MHD equations and the VAL C atmosphere model we study the variation of the cut-off frequency along and across the magnetic tube guiding the waves. Due to the radial variation of the cut-off frequency the flux tubes act as low frequency filters for waves.

  11. Sausage Mode Propagation in a Thick Magnetic Flux Tube

    Science.gov (United States)

    Pardi, A.; Ballai, I.; Marcu, A.; Orza, B.

    2014-04-01

    The aim of this paper is to model the propagation of slow magnetohydrodynamic (MHD) sausage waves in a thick expanding magnetic flux tube in the context of the quiescent (VAL-C) solar atmosphere. The propagation of these waves is found to be described by the Klein-Gordon equation. Using the governing MHD equations and the VAL-C atmosphere model we study the variation of the cut-off frequency along and across the magnetic tube guiding the waves. Due to the radial variation of the cut-off frequency the flux tubes act as low frequency filters for the waves.

  12. Effect of the inertance tube on the performance of the Stirling type pulse tube refrigerator

    International Nuclear Information System (INIS)

    The Pulse Tube Refrigerator(PTR), which has no moving parts at its cold section, is attractive for obtaining higher reliability, simpler construction and lower vibration than in any other small cryocoolers. Commonly used mean to achieve optimum performance of the PTR are orifice or inertance tube. The Stirling type Pulse Tube Refrigerator in the experiments consists of a compressor driven by linear motors, which make pressure waves, a regenerator, a pulse tube with inertance tube, and a buffer. The pressures and temperature are measured to explore the dependency of inertance tube on the performance of the PTR. The results show the dependency of cool-down characteristics, no-load temperature on frequency of operation and inertance tube

  13. Mechanics and kinematics of backward burrowing by the polychaete Cirriformia moorei.

    Science.gov (United States)

    Che, James; Dorgan, Kelly M

    2010-12-15

    The polychaete Cirriformia moorei burrows in muddy sediments by fracture, using its hydrostatic skeleton to expand its anterior region and exert force against its burrow wall to extend a crack. Burrowing occurs in four phases: stretching forward into the burrow, extending the crack anteriorly, thickening the burrowing end to amplify stress at the tip of the crack, and bringing the rest of the body forward as a peristaltic wave travels posteriorly. Here, we show that C. moorei is also able to burrow with its posterior end using a similar mechanism of crack propagation and exhibiting the same four phases of burrowing. Worms burrowed backwards with similar speeds and stress intensity factors as forward burrowing, but were thinner and less blunt and did not slip as far away from the crack tip between cycles of burrowing. The anterior end is more muscular and rigid, and differences in body shapes are consistent with having reduce musculature to dilate the posterior segments while burrowing. Backward burrowing provides a unique opportunity to study the effects of morphology on burrowing mechanics within the same species under identical conditions. PMID:21113009

  14. Broadband diffuse terahertz wave scattering by flexible metasurface with randomized phase distribution

    OpenAIRE

    Yin Zhang; Lanju Liang; Jing Yang; Yijun Feng; Bo Zhu; Junming Zhao; Tian Jiang; Biaobing Jin; Weiwei Liu

    2016-01-01

    Suppressing specular electromagnetic wave reflection or backward radar cross section is important and of broad interests in practical electromagnetic engineering. Here, we present a scheme to achieve broadband backward scattering reduction through diffuse terahertz wave reflection by a flexible metasurface. The diffuse scattering of terahertz wave is caused by the randomized reflection phase distribution on the metasurface, which consists of meta-particles of differently sized metallic patche...

  15. Verification of computer-aided designs of traveling-wave tubes utilizing novel dynamic refocusers and graphite electrodes for the multistage depressed collector

    Science.gov (United States)

    Ramins, P.; Kosmahl, H. G.; Force, D. A.; Palmer, R. W.; Dayton, J. A., Jr.

    1985-01-01

    A computational procedure for the design of TWT-refocuser-MDC systems was used to design a short dynamic refocusing system and highly efficient four-stage depressed collector for a 200-W, 8- to 18-GHz, TWT. The computations were carried out with advanced, multidimensional computer programs which model the electron beam as a series of disks of charge and follow their trajectories from the RF input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semi-quantitatively by injecting a representative beam of secondary electrons into the MDC analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particular form of isotropic graphite that was selected for its low secondary electron yield, ease of machinability, and vacuum properties. This MDC was tested (at CW) for more than 1000 hr with negligible degradation in TWT and MDC performances.

  16. Experience and abstract reasoning in learning backward induction

    Directory of Open Access Journals (Sweden)

    Daniel R. Hawes

    2012-02-01

    Full Text Available Backward induction is a benchmark of game theoretic rationality, yet surprisingly little is known as to how humans discover and initially learn to apply this abstract solution concept in experimental settings. We use behavioral and functional magnetic resonance imaging (fMRI data to study the way in which subjects playing in a sequential game of perfect information learn the optimal backward induction strategy for the game. Experimental data from our two studies support two main findings:First, subjects converge to a common process of recursive inference similar to the backward induction procedure for solving the game. The process is recursive because earlier insights and conclusions are used as inputs in later steps of the inference. This process is matched by a similar pattern in brain activation, which also proceeds backward, following the prediction error: brain activity initially codes the responses to losses in final positions; in later trials this activity shifts to the starting position.Second, the learning process is not exclusively cognitive, but instead combines experience based learning and abstract reasoning. Critical experiences leading to the adoption of an improved solution strategy appear to be stimulated by brain activity in the reward system. This indicates that the negative affect induced by initial failures facilitates the switch to a different method of solving the problem. Abstract reasoning is combined with this response, and is expressed by activation in the ventrolateral prefrontal cortex. Differences in brain activation match differences in performance between subjects who show different learning speeds.

  17. Effect of forward/backward standing posture on foot shape

    NARCIS (Netherlands)

    Daanen, H.A.M.; Tan, T.K.; Punte, P.A.J.

    2000-01-01

    Foot length and breadth are generally used to determine the correct shoe size. An important question is whether foot length and foot breadth are dependent upon body posture. Therefore, the effect of leaning forward/backward on foot length and breadth is investigated in this study. Seven subjects par

  18. Backward Orbit Conjecture for Latt\\'es Maps

    OpenAIRE

    Sookdeo, Vijay A.

    2014-01-01

    For a Latt\\`es map $\\phi:\\mathbb P^1 \\to \\mathbb P^1$ defined over a number field $K$, we prove a conjecture on the integrality of points in the backward orbit of $P\\in \\mathbb P^1(\\overline K)$ under $\\phi$.

  19. On the discretization of backward doubly stochastic differential equations

    OpenAIRE

    Aboura, Omar

    2009-01-01

    In this paper, we are dealing with the approximation of the process (Y,Z) solution to the backward doubly stochastic differential equation with the forward process X . After proving the L2-regularity of Z, we use the Euler scheme to discretize X and the Zhang approach in order to give a discretization scheme of the process (Y,Z).

  20. Mean Field Forward-Backward Stochastic Differential Equations

    OpenAIRE

    Carmona, René; Delarue, François

    2013-01-01

    The purpose of this note is to provide an existence result for the solution of fully coupled Forward Backward Stochastic Differential Equations (FBSDEs) of the mean field type. These equations occur in the study of mean field games and the optimal control of dynamics of the McKean Vlasov type.

  1. Looking Backward at Feasible Socialism: Using Bellamy to Teach Schumpeter.

    Science.gov (United States)

    Bogart, William T.

    1995-01-01

    Compares and contrasts Joseph Schumpeter's 1942 classic of economic thought, "Capitalism, Socialism, and Democracy," with Edward Bellamy's 1888 utopian novel, "Looking Backward." Both works criticize capitalism and arrive at socialist solutions. Bellamy's entertaining novel provides a useful benchmark for students analyzing Schumpeter. (MJP)

  2. Experimental and Numerical Study of Backward-Facing Step Flow

    Czech Academy of Sciences Publication Activity Database

    Mouza, A.A.; Pantzali, M.N.; Paras, S.V.; Tihon, Jaroslav

    -: -, 2005, s. 1-4. [Hellenic Chemical Engineering Conference /5./. Thessaloniki (GR), 26.05.2005-28.05.2005] R&D Projects: GA ČR(CZ) GA101/04/0745 Institutional research plan: CEZ:AV0Z40720504 Keywords : electrodiffusion diagnstics * backward-facing step flow Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  3. The Application and Extension of Backward Software Analysis

    CERN Document Server

    Perisic, Aleksandar

    2010-01-01

    The backward software analysis is a method that emanates from executing a program backwards - instead of taking input data and following the execution path, we start from output data and by executing the program backwards command by command, analyze data that could lead to the current output. The changed perspective forces a developer to think in a new way about the program. It can be applied as a thorough procedure or casual method. With this method, we have many advantages in testing, algorithm and system analysis. For example, in testing the advantage is obvious if the set of output data is smaller than possible inputs. For some programs or algorithms, we know more precisely the output data, so this backward analysis can help in reducing the number of test cases or even in strict verification of an algorithm. The difficulty lies in the fact that we need types of data that no programming language currently supports, so we need additional effort to understand how this method works, or what effort we need to ...

  4. Subversive English in "Raining Backwards": A Different Kind of Spanglish

    Science.gov (United States)

    Alvarez, Stephanie

    2013-01-01

    This essay explores the relationship(s) between English and Spanish in the novel "Raining Backwards" (1988) by Cuban American Roberto G. Fernandez. While the many linked plots and characters suggest many protagonists, this study demonstrates how language itself takes on the role of protagonist. Through the author's use of calques…

  5. Tracheostomy tube - eating

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000464.htm Tracheostomy tube - eating To use the sharing features on ... when you swallow foods or liquids. Eating and Tracheostomy Tubes When you get your tracheostomy tube, or ...

  6. Self-reflection of intense electromagnetic waves in plasmas

    International Nuclear Information System (INIS)

    A uniform electromagnetic wave of high power density, propagating in a collisional plasma gives rise to a modification in temperature-dependent collision frequency and in turn induces a gradient in the complex refractive index of the medium. A WKB solution of the problem predicts a backward propagating wave on account of the self-induced inhomogeneity. The amplitude of the backward (i.e. reflected) wave increases with increasing power density of the wave. This is a volume nonlinear effect and is appreciable for usually employed power densities. (orig.)

  7. Titanium condenser tubes

    International Nuclear Information System (INIS)

    The corrosion resistance of titanium in sea water is extremely excellent, but titanium tubes are expensive, and the copper alloy tubes resistant in polluted sea water were developed, therefore they were not used practically. In 1970, ammonia attack was found on the copper alloy tubes in the air-cooled portion of condensers, and titanium tubes have been used as the countermeasure. As the result of the use, the galvanic attack an copper alloy tube plates with titanium tubes as cathode and the hydrogen absorption at titanium tube ends owing to excess electrolytic protection were observed, but the corrosion resistance of titanium tubes was perfect. These problems can be controlled by the application of proper electrolytic protection. The condensers with all titanium tubes adopted recently in USA are intended to realize perfectly no-leak condensers as the countermeasure to the corrosion in steam generators of PWR plants. Regarding large condensers of nowadays, three problems are pointed out, namely the vibration of condenser tubes, the method of joining tubes and tube plates, and the tubes of no coolant leak. These three problems in case of titanium tubes were studied, and the problem of the fouling of tubes was also examined. The intervals of supporting plates for titanium tubes should be narrowed. The joining of titanium tubes and titanium tube plates by welding is feasible and promising. The cleaning with sponge balls is effective to control fouling. (Kako, I.)

  8. A Table-top Blast Driven Shock Tube

    CERN Document Server

    Courtney, Michael; 10.1063/1.3518970

    2011-01-01

    The prevalence of blast-induced traumatic brain injury in conflicts in Iraq and Afghanistan has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. This paper describes the design and performance of a table-top shock tube that is more convenient and widely accessible than traditional compression driven and blast driven shock tubes. The design is simple: it is an explosive driven shock tube employing a rifle primer which explodes when impacted by the firing pin. The firearm barrel acts as the shock tube, and the shock wave emerges from the muzzle. The small size of this shock tube can facilitate localized application of a blast wave to a subject, tissue, or material under test.

  9. The physics of vacuum tubes - principles, technology and current developments; Physique des tubes hyperfrequences, point de situation sur les principes, la technologie et leur evolution

    Energy Technology Data Exchange (ETDEWEB)

    Durand, A.J. [Thales Electron Devices, 78 - Velizy (France)

    2001-04-01

    Microwave vacuum tubes make use of the interaction between an electron beam and an electromagnetic wave in order to generate power at microwave frequencies. The vacuum tubes may be classified in terms of electron beam type (O and M), and whether the standing wave or propagating wave is employed. The performance of this type of vacuum tube is limited both by design considerations and the materials employed in its construction. (authors)

  10. Ultrasonic measurement of gap between calandria tube and liquid injection shutdown system tube in PHWR

    International Nuclear Information System (INIS)

    Sag of CT or liquid injection shutdown system tubes in pressurized heavy water reactor is known to occur due to irradiation creep and growth during plant operation. When the sag of CT is big enough, the CT tube possibly comes in contact with liquid injection shutdown system tube (LIN) crossing beneath the CT, which subsequently may prevent the safe operation. It is therefore necessary to check the gap between the two tubes in order to confirm no contacts when using a proper measure periodically during the plant life. An ultrasonic gap measuring probe assembly which can be fed through viewing port installed on the calandria was developed and utilized to measure the sags of both tubes in a pressurized heavy water reactor in Korea. It was found that the centerlines of CT and LIN can be precisely detected by ultrasonic wave. The gaps between two tubes were easily obtained from the relative distance of the measured centerline elevations of the tubes. But the measured gap data observed at the viewing port were actually not the data at the crossing point of CT and LIN. To get the actual gap between two tubes, mathematical modeling for the deflection curves of two tubes was used. The sags of CT and LIN tubes were also obtained by comparison of the present centerlines with the initial elevations at the beginning of plant operation. The gaps between two tubes in the unmeasurable regions were calculated based on the measurement data and the channel power distribution

  11. 小径管对接焊缝超声波探伤规程、导则的应用及缺陷波的识别%Discussion on Application of Small Diameter Tube Related Ultrasonic Testing Guides or Rules and Defects Wave Identification

    Institute of Scientific and Technical Information of China (English)

    李树军; 王志永; 牛晓光; 董国振; 梁红方

    2012-01-01

    Combining with the practical experience, this article gave the comparative analysis of the small diameter tube related ultrasonic testing guides and the rules, and discussed the wave identification features of ultrasonic testing of the small diameter tubes. Through the analysis and comparison, this article gave the suggestion on application of different thicknesses of small diameter tubes ultrasonic testing guides and rules.%结合多年实践,对小径管对接焊缝超声波探伤相关规程、导则主要异同及其对缺陷判伤影响进行了分析,并对缺陷波的识别进行了论述,对不同壁厚的小径管超声波探伤如何执行规程和导则给出了建议。

  12. Alfvén wave mixing and non-JWKB waves in stellar winds

    International Nuclear Information System (INIS)

    Alfvén wave mixing equations used in locally incompressible turbulence transport equations in the solar wind contain as a special case, non-Jeffreys–Wentzel–Kramers–Brouillon (non-JWKB) wave equations used in models of Alfvén wave driven winds. We discuss the canonical wave energy equation; the physical wave energy equation, and the JWKB limit of the wave interaction equations. Lagrangian and Hamiltonian variational principles for the waves are developed. Noether’s theorem is used to derive the canonical wave energy equation which is associated with the linearity symmetry of the equations. A further conservation law associated with time translation invariance of the action, applicable for steady background wind flows is also derived. In the latter case, the conserved density is the Hamiltonian density for the waves, which is distinct from the canonical wave energy density. The canonical wave energy conservation law is a special case of a wider class of conservation laws associated with Green’s theorem for the wave mixing system and the adjoint wave mixing system, which are related to Noether’s second theorem. In the sub-Alfvénic flow, inside the Alfvén point of the wind, the backward and forward waves have positive canonical energy densities, but in the super-Alfvénic flow outside the Alfvén critical point, the backward Alfvén waves are negative canonical energy waves, and the forward Alfvén waves are positive canonical energy waves. Reflection and transmission coefficients for the backward and forward waves in both the sub-Alfvénic and super-Alfvénic regions of the flow are discussed. (paper)

  13. Inverse Bremsstrahlung Stabilization of Noise in the Generation of Ultra-short Intense Pulses by Backward Raman Amplification

    International Nuclear Information System (INIS)

    Inverse bremsstrahlung absorption of the pump laser beam in a backward Raman amplifier over the round-trip light transit time through the sub-critical density plasma can more than double the electron temperature of the plasma and produce time-varying axial temperature gradients. The resulting increased Landau damping of the plasma wave and detuning of the resonance can act to stabilize the pump against unwanted amplification of Langmuir noise without disrupting nonlinear amplification of the femtosecond seed pulse. Because the heating rate increases with the charge state Z, only low-Z plasmas (hydrogen, helium, or helium-hydrogen mixtures) will maintain a low enough temperature for efficient operation

  14. Reaction mechanism and characteristics of T_{20} in d + ^3He backward elastic scattering at intermediate energies

    OpenAIRE

    Tanifuji, M.; Ishikawa, S.; Iseri, Y.; Uesaka, T.; Sakamoto, N; Satou, Y.; Itoh, K.; Sakai, H.; Tamii, A.; Ohnishi, T.; Sekiguchi, K.; Yako, K.; Sakoda, S.; Okamura, H.; Suda, K.

    1999-01-01

    For backward elastic scattering of deuterons by ^3He, cross sections \\sigma and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are analyzed by the PWIA and by the general formula which includes virtual excitations of other channels, with the assumption of the proton transfer from ^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev equation, the PWIA describes global features of the experimental data, while the virtual excitation effects are impor...

  15. Tamm-Langmuir surface waves

    CERN Document Server

    Golenitskii, K U; Bogdanov, A A

    2016-01-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states - we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  16. Detection of blister formation and evaluation of pressure tube/calandria tube contact location by ultrasonic velocity ratio measurement technique

    International Nuclear Information System (INIS)

    Presence of hydrogen in zircaloy pressure tube affects the velocity of ultrasound propagation. Both longitudinal wave velocity (VL) and shear wave velocity (VS) are affected depending on the concentration of hydrogen. Velocity ratio (VL/VS) changes as per the concentrations of hydrogen in different locations along the length of pressure tube. A hydride blister which forms at the pressure tube and calandria tube contact point is a distinct zone containing hydrogen 2-3 order of magnitude more than the parent matrix and hence, can be detected by sharp change in velocity ratio. (author)

  17. How superluminal motion can lead to backward time travel

    CERN Document Server

    Nemiroff, Robert J

    2015-01-01

    It is commonly asserted that superluminal particle motion can enable backward time travel, but little has been written providing details. It is shown here that the simplest example of a "closed loop" event -- a twin paradox scenario where a single spaceship both traveling out and returning back superluminally -- does {\\it not} result in that ship straightforwardly returning to its starting point before it left. However, a more complicated scenario -- one where the superluminal ship first arrives at an intermediate destination moving subluminally -- can result in backwards time travel. This intermediate step might seem physically inconsequential but is shown to break Lorentz-invariance and be oddly tied to the sudden creation of a pair of spacecraft, one of which remains and one of which annihilates with the original spacecraft.

  18. Transverse top quark polarization and the forward-backward asymmetry

    Science.gov (United States)

    Baumgart, Matthew; Tweedie, Brock

    2013-08-01

    The forward-backward asymmetry in top pair production at the Tevatron has long been in tension with the Standard Model prediction. One of the only viable new physics scenarios capable of explaining this anomaly is an s-channel axigluon-like resonance, with the quantum numbers of the gluon but with significant axial couplings to quarks. While such a resonance can lead to a clear bump or excess in the or dijet mass spectra, it may also simply be too broad to cleanly observe. Here, we point out that broad resonances generally lead to net top and antitop polarizations transverse to the production plane. This polarization is consistent with all discrete spacetime symmetries, and, analogous to the forward-backward asymmetry itself, is absent in QCD at leading order. Within the parameter space consistent with the asymmetry measurements, the induced polarization can be sizable, and might be observable at the Tevatron or the LHC.

  19. A nonlinear analysis of the terahertz serpentine waveguide traveling-wave amplifier

    International Nuclear Information System (INIS)

    A nonlinear model for the numerical simulation of terahertz serpentine waveguide traveling-wave tube (SW-TWT) is described. In this model, the electromagnetic wave transmission in the SW is represented as an infinite set of space harmonics to interact with an electron beam. Analytical expressions for axial electric fields in axisymmetric interaction gaps of SW-TWTs are derived and compared with the results from CST simulation. The continuous beam is treated as discrete macro-particles with different initial phases. The beam-tunnel field equations, space-charge field equations, and motion equations are combined to solve the beam-wave interaction. The influence of backward wave and relativistic effect is also considered in the series of equations. The nonlinear model is used to design a 340 GHz SW-TWT. Several favorable comparisons of model predictions with results from a 3-D Particle-in-cell simulation code CHIPIC are presented, in which the output power versus beam voltage and interaction periods are illustrated. The relative error of the predicted output power is less than 15% in the 3 dB bandwidth and the relative error of the saturated length is less than 8%.The results show that the 1-D nonlinear analysis model is appropriate to solve the terahertz SW-TWT operation characteristics

  20. Land markets and agrarian backwardness (Spain, 1900-1936)

    OpenAIRE

    Carmona, Juan; Rosés, Joan R.

    2009-01-01

    To what extent were land markets the cause of Spanish agrarian backwardness? This paper uses new provincial data on average real land prices, together with provincial level variation in land productivity, to analyse land markets efficiency. To address this unresolved issue, we test whether land markets were spatially integrated and whether their prices can be explained with the present value model. Our results suggest that land prices converged across provinces and that variations were driven...

  1. Effect of Backward Walking on Attention: Possible Application on ADHD

    OpenAIRE

    2015-01-01

    The human requires attentive effort as assessed in dual-task experiments. Consistently, an attentive task can modify the walking pattern and a attention deficit and hyperactivity disorder (ADHD) is accompanied by gait modifications. Here we investigated the relationships between backward walking and attentive performances in ADHD children (n=13) and healthy age-, height and weight matched controls (n=17). We evaluated the attentive/impulsive profile by means of a Go/No-Go task and the backwar...

  2. Trigger electronics for the forward and backward hodoscopes of ANKE

    International Nuclear Information System (INIS)

    Trigger electronics of the forward and backward scintillation hodoscopes of ANKE, the magnetic spectrometer placed at the internal beam line of the COSY-Juelich accelerator, is described. The two developed sets of trigger electronic modules are implemented in the whole ANKE trigger system and are used for the running experiments. For selection of double particle events in the hodoscope both the combinatory logic and the charge discrimination are used

  3. Olfactory interference during inhibitory backward pairing in honey bees.

    Directory of Open Access Journals (Sweden)

    Matthieu Dacher

    Full Text Available BACKGROUND: Restrained worker honey bees are a valuable model for studying the behavioral and neural bases of olfactory plasticity. The proboscis extension response (PER; the proboscis is the mouthpart of honey bees is released in response to sucrose stimulation. If sucrose stimulation is preceded one or a few times by an odor (forward pairing, the bee will form a memory for this association, and subsequent presentations of the odor alone are sufficient to elicit the PER. However, backward pairing between the two stimuli (sucrose, then odor has not been studied to any great extent in bees, although the vertebrate literature indicates that it elicits a form of inhibitory plasticity. METHODOLOGY/PRINCIPAL FINDINGS: If hungry bees are fed with sucrose, they will release a long lasting PER; however, this PER can be interrupted if an odor is presented 15 seconds (but not 7 or 30 seconds after the sucrose (backward pairing. We refer to this previously unreported process as olfactory interference. Bees receiving this 15 second backward pairing show reduced performance after a subsequent single forward pairing (excitatory conditioning trial. Analysis of the results supported a relationship between olfactory interference and a form of backward pairing-induced inhibitory learning/memory. Injecting the drug cimetidine into the deutocerebrum impaired olfactory interference. CONCLUSIONS/SIGNIFICANCE: Olfactory interference depends on the associative link between odor and PER, rather than between odor and sucrose. Furthermore, pairing an odor with sucrose can lead either to association of this odor to PER or to the inhibition of PER by this odor. Olfactory interference may provide insight into processes that gate how excitatory and inhibitory memories for odor-PER associations are formed.

  4. Forward and Backward Intergenerational Goods: A Theory of Intergenerational Exchange

    OpenAIRE

    Antonio Rangel

    2000-01-01

    December 1999 This papers develops a theory of intergenerational exchange for generations that are either selfish or have non-dynastic altruism. The main building blocks of the theory are forward and backward intergenerational goods (FIGs and BIGs) and the relationship between them. A FIG is a transfer from present to future generations, like parental investments in education and the preservation of the environment. A BIG is a transfer from future to present generations, like pay-as-you-go so...

  5. Solutions to general forward-backward doubly stochastic differential equations

    Institute of Scientific and Technical Information of China (English)

    Qing-feng ZHU; Yu-feng SHI; Xian-jun GONG

    2009-01-01

    A gcneral type of forward-backward doubly stochastic differential equations (FBDSDEs) is studied. It extends many important equations that have been well stud-led, including stochastic Hamiltonian systems. Under some much weaker monotonicity assumptions, the existence and uniqueness of measurable solutions are established with a method of continuation. Furthermore, the continuity and differentiability of the solutions to FBDSDEs depending on parameters is discussed.

  6. Measurement of Forward-Backward Charged Particle Correlations with ALICE

    DEFF Research Database (Denmark)

    Søgaard, Carsten

    (NBI). In order for this calibration system to work, a special trigger interface was implemented. The developed and tested firmware for the FPGA (Field-Programmable Gate Array) will be presented. Part II is the presentation of the analysis - a study of, so-called, forward-backward correlations....... The correlations between charged particles, produced in proton-proton collisions at vs=900 GeV and vs=7 TeV over a wide range in pseudoradidity (-3.5

  7. Numerical approximation of Backward Stochastic Differential Equations with Jumps

    OpenAIRE

    Lejay, Antoine; Mordecki, Ernesto; Torres, Soledad

    2014-01-01

    In this paper we propose a numerical method to approximate the solution of a Backward Stochastic Differential Equations with Jumps (BSDEJ). This method is based on the construction of a discrete BSDEJ driven by a complete system of three orthogonal discrete time-space martingales, the first a random walk converging to a Brownian motion; the second, another random walk, independent of the first one, converging to a Poisson process. The solution of this discrete BSDEJ is shown to weakly converg...

  8. Initiation of backward erosion piping in uniform sands

    OpenAIRE

    Van Beek, VM; Bezuijen, Adam; Sellmeijer, JB; Barends, FBJ

    2014-01-01

    The process of backward erosion piping poses a threat to dams and dikes on foundations of nonplastic sands and silts. The available models for design and predictions focus predominantly on the progression of the pipe. However, sand boils in the field will occur as a result of the initiation of sand transport. Although criteria are available for predicting sand boiling and heaving in columns, there is no model describing the initiation of piping in situations where the exit flow is not uniform...

  9. Extrapyramidal involvement in amyotrophic lateral sclerosis: backward falls and retropulsion

    OpenAIRE

    Desai, J.; M. Swash

    1999-01-01

    Three patients with sporadic amyotrophic lateral sclerosis (ALS) presented with a history of backward falls. Impaired postural reflexes and retropulsion accompanied clinical features of ALS. Hypokinesia, decreased arm swing, and a positive glabellar tap were noted in two of these three patients. Cognitive impairment, tremor, axial rigidity, sphincter dysfunction, nuchal dystonia, dysautonomia, and oculomotor dysfunction were absent. Brain MRI disclosed bilateral T2 weighted hyperinte...

  10. Plasma waves in parametric interactions

    Science.gov (United States)

    Yampolsky, Nikolai Andreevich

    The nonlinear laser-plasma interaction is widely discussed in the modern plasma literature with applications to inertial confinement fusion, generation of fast electrons, and amplification of high power radiation. Among nonlinear wave phenomena in plasma, the parametric wave coupling often plays the dominant role in laser-plasma interaction at moderate laser intensities since it is the lowest order nonlinear effect. The plasma wave can mediate the parametric laser coupling with high efficiency. We study the interplay of the parametric laser-plasma interaction and other physical effects which may affect this interaction. We study this interplay with an emphasis on the plasma-based backward Raman amplifier (BRA) based on the three-wave coupling. Three major types of physical effects in the parametric wave coupling are studied. In the first part of the thesis, we find the longitudinal profiles of the interacting waves in cases of interest for pulse compression. We find the solution for the output pulse in backward Raman amplification seeded by a laser pulse of finite duration. We also propose a new scheme for high-power amplification for pulses in the terahertz frequency range. For this scheme, based on the four-wave mixing in a capillary filled with plasma, we find the profile of the output pulse. The second part of this thesis is devoted to transverse effects, which may reduce the focusability of the output pulse in backward Raman amplification. We find that the transverse modulations of the pump can be averaged and do not reduce the amplified pulse focusability if the longitudinal length of these modulations is much smaller than the amplification length. In the third part, we study the kinetic effects. We propose a simplified fluid model for the nonlinear Landau damping of a parametrically driven plasma wave and study the effect of nonlinear Landau damping in backward Raman amplification. This simplified model can be useful not only for understanding complex

  11. Switching Game of Backward Stochastic Differential Equations and Associated System of Obliquely Reflected Backward Stochastic Differential Equations

    OpenAIRE

    Hu, Ying; Tang, Shanjian

    2015-01-01

    This paper is concerned with the switching game of a one-dimensional backward stochastic differential equation (BSDE). The associated Bellman-Isaacs equation is a system of matrix-valued BSDEs living in a special unbounded convex domain with reflection on the boundary along an oblique direction. In this paper, we show the existence of an adapted solution to this system of BSDEs with oblique reflection by the penalization method, the monotone convergence, and the a priori estimates.

  12. Diffraction of surface and bulk magnetostatic waves in a ferromagnetic film

    OpenAIRE

    A. S. Beregov; I. V. Stashuk

    1986-01-01

    The analysis of the diffraction magnetostatic waves (MSW) in a ferromagnetic film. Calculated diffraction profiles and estimated degree of diffraction spreading of the beam for surface and backward volume MSW.

  13. Diffraction of surface and bulk magnetostatic waves in a ferromagnetic film

    Directory of Open Access Journals (Sweden)

    A. S. Beregov

    1986-04-01

    Full Text Available The analysis of the diffraction magnetostatic waves (MSW in a ferromagnetic film. Calculated diffraction profiles and estimated degree of diffraction spreading of the beam for surface and backward volume MSW.

  14. Computation and measurement of calandria tube sag in PHWR

    International Nuclear Information System (INIS)

    Calandria tubes and liquid injection shutdown system (LISS) tubes in a pressurized heavy water reactor (PHWR) is known to sag due to irradiation creep and growth during plant operation. When the sag of calandria tube becomes bigger, the calandria tube possibly comes in contact with LISS tube crossing beneath and calandria tube. The contact subsequently may cause the damage on the calandria tube resulting in unpredicted outage of the plant. It is therefore necessary to check the gap between the two tubes in order to periodically confirm no contact by using a proper measure during the plant life. An ultrasonic gap measuring probe assembly which can be inserted into two viewing ports of the calandria was developed in Korea and utilized to measure the sags of both tubes in the PHWR. It was found that the centerlines of calandria tubes and liquid injection shutdown system tubes can be precisely detected by ultrasonic wave. The gaps between two tubes were easily obtained from the relative distance of the measured centerline elevations of the tubes. Based on the irradiation creep equation and the measurement data, a computer program to calculate the sags was also developed. With the computer program, the sag at the end of plant life was predicted. (author)

  15. Negative group velocity and three-wave mixing in dielectric crystals

    CERN Document Server

    Slabko, Vitaly V; Shalaev, Mikhail I; Popov, Alexander K

    2011-01-01

    Extraordinary features of optical parametric amplification of Stokes electromagnetic waves are investigated, which originate from three-wave mixing of two ordinary electromagnetic and one backward phonon wave with negative group velocity. A similarity with the counterpart in the negative-index plasmonic metamaterials and differences with those utilizing contra-propagating ordinary electromagnetic waves as well as electromagnetic and acoustic phonon waves are shown. They stem from backwardness of optical phonons with negative dispersion. Nonlinear-optical photonic devices with the properties similar to those predicted for the negative-index metamaterials are proposed.

  16. Acoustic emission from magnetic flux tubes in the solar network

    CERN Document Server

    Vigeesh, G

    2013-01-01

    We present the results of three-dimensional numerical simulations to investigate the excitation of waves in the magnetic network of the Sun due to footpoint motions of a magnetic flux tube. We consider motions that typically mimic granular buffeting and vortex flows and implement them as driving motions at the base of the flux tube. The driving motions generates various MHD modes within the flux tube and acoustic waves in the ambient medium. The response of the upper atmosphere to the underlying photospheric motion and the role of the flux tube in channeling the waves is investigated. We compute the acoustic energy flux in the various wave modes across different boundary layers defined by the plasma and magnetic field parameters and examine the observational implications for chromospheric and coronal heating.

  17. Shock propagation through a bubbly liquid in a deformable tube

    OpenAIRE

    Ando, Keita; Sanada, T; Inaba, K; Damazo, J. S.; Shepherd, J. E.; Colonius, T.; Brennen, C. E.

    2011-01-01

    Shock propagation through a bubbly liquid contained in a deformable tube is considered. Quasi-one-dimensional mixture-averaged flow equations that include fluid–structure interaction are formulated. The steady shock relations are derived and the nonlinear effect due to the gas-phase compressibility is examined. Experiments are conducted in which a free-falling steel projectile impacts the top of an air/water mixture in a polycarbonate tube, and stress waves in the tube material and pressur...

  18. np Pair transfer mechanism for backward elastic p 3He scattering at intermediate energies

    International Nuclear Information System (INIS)

    The two-body transfer mechanism for elastic rearrangement scattering from the three-body bound state i+{jkl}→j+{ikl} has been investigated on the basis of 4-dimensional formalism of covariant nonrelativistic graphs. The relation between this approach and the 3-dimensional graph formalism has been analyzed in detail. This approach is applied to describing backward elastic p 3He scattering in the energy range 0.5-1.7 GeV. The Faddeev 5-channel wave function is used for the bound state of the 3He nucleus. Numerical calculations show that the mechanism of sequential transfer of a noninteracting np-pair dominates while transfer of an interacting pair as well as nonsequential transfer of a noninteracting np-pair give a negligible contribution. The dominating mechanism is insensitive to the D-components of the 3He wave function and relativistic effects in spite of high momentum transfer. Taking into consideration Glauber rescatterings in the entrance and exit channels one obtains agreement with the experimental data in energy and angular dependence of the differential cross section at energies 0.9-1.7 GeV. (orig.)

  19. Kundt’s tube experiment using smartphones

    Science.gov (United States)

    Orsola Parolin, Sara; Pezzi, Giovanni

    2015-07-01

    This article deals with a modern version of Kundt’s tube experiment. Using economic instruments and a couple of smartphones, it is possible to ‘see’ nodes and antinodes of standing acoustic waves in a column of vibrating air and to measure the speed of sound.

  20. A Table-top Blast Driven Shock Tube

    OpenAIRE

    Courtney, Michael; Courtney, Amy

    2011-01-01

    The prevalence of blast-induced traumatic brain injury in conflicts in Iraq and Afghanistan has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. This paper describes the design and performance of a table-top shock tube that is more convenient and widely accessible than traditional compression driven and blast driven shock tubes. The d...

  1. Neural Tube Defects

    Science.gov (United States)

    Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the first month ... that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In spina bifida, ...

  2. Tracheostomy tube - speaking

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000465.htm Tracheostomy tube - speaking To use the sharing features on ... are even speaking devices that can help you. Tracheostomy Tubes and Speaking Air passing through vocal cords ( ...

  3. Backwards planning approach for rapid attitude maneuvers steering

    Science.gov (United States)

    Verbin, D.

    Remote sensing satellites are often built with payloads that do not include line of sight steering mechanisms. In cases, when frequent line of sight retargeting is required, there is a need for efficient actuators and control schemes that would support rapid attitude manoeuvring together with adequate pointing accuracy and stability between the manoeuvres. Within this frame, this research develops the Backwards Planning approach as one of the possible control methods for rapid manoeuvring. The method is based on state feedback and combines time efficient together with straight forward computation flow. Novel efficient methods to execute the Backwards Planning Control in the 3D attitude space are proposed here. The methods refer both for the first saturated control phase of the manoeuvre and for the last braking phase. The actuators used for the spacecraft control in this research are either Reaction Wheels (RWs) or Single Gimbal Control Moments Gyros (SGCMGs) or both of them together. The advantage of the SGCMG is in rapid rotational manoeuvring, but their application for high quality pointing requires very accurate gimbal mechanisms. On the other hand, RWs are usually more suitable for accurate pointing, but their torque to power performance is inferior in manoeuvring. It is shown that the coordination of SGCMGs and RWs together enables to draw more performance from the SGCMGs in terms of agility and meet the pointing requirements between manoeuvres where only the RWs are used. Novel SGCMG steering laws are suggested as well. While the steering laws determine the required angular rate for each gimbal, most steering laws are defined in the angular momentum domain and output the gimbals angular rates to produce a given required torque or angular momentum increment. This research however, practices a novel steering law in the gimbal angles domain. While both steering laws turn to be dynamically equivalent for small control signals, as in the steady state, it is shown

  4. Traveling wave solutions in a nonlinear oppositely-directional coupler

    International Nuclear Information System (INIS)

    The propagation of coupled forward and backward waves in the system of two tunnel-coupled waveguides, one with negative, and the other with positive refractive index, is considered. General solution of the evolution equations describing the wave propagation is found taking the traveling wave into account. Dependence of wave amplitude and frequency on arbitrary constants is analyzed. We have observed three types of waves in the nonlinear oppositely-directional coupler. Two of them are periodic and solitary waves that are well known in nonlinear optics. We also have found a new type of nonlinear waves for optics of artificial materials that is compacton.

  5. Magnetostatic wave device characterization by Brillouin light scattering

    Science.gov (United States)

    Patton, Carl E.; Srinivasan, Gopalan

    1989-02-01

    This final report summarizes the important results of the Brillouin light scattering investigations of magnetic excitations in magnetostatic wave (MSW) devices which were carried out under the RADC contract. The key accomplishments were the observation and characterization of surface waves, forward volume waves, backward volume waves, parametric spin waves, and a new type of evanescent surface wave in yttrium iron garnet film MSW devices. The propagation characteristics for surface wave in Fe, Co-Cr, and Ni-Fe films were also examined, in order to investigate the possible use of such films in MSW devices. Details on technical publications and participating personnel during this contract period are also provided.

  6. Backward bifurcation and optimal control of Plasmodium Knowlesi malaria

    Science.gov (United States)

    Abdullahi, Mohammed Baba; Hasan, Yahya Abu; Abdullah, Farah Aini

    2014-07-01

    A deterministic model for the transmission dynamics of Plasmodium Knowlesi malaria with direct transmission is developed. The model is analyzed using dynamical system techniques and it shows that the backward bifurcation occurs for some range of parameters. The model is extended to assess the impact of time dependent preventive (biological and chemical control) against the mosquitoes and vaccination for susceptible humans, while treatment for infected humans. The existence of optimal control is established analytically by the use of optimal control theory. Numerical simulations of the problem, suggest that applying the four control measure can effectively reduce if not eliminate the spread of Plasmodium Knowlesi in a community.

  7. High order backward discretization of the neutron diffusion equation

    International Nuclear Information System (INIS)

    Fast codes capable of dealing with three-dimensional geometries, are needed to be able to simulate spatially complicated transients in a nuclear reactor. We propose a new discretization technique for the time integration of the neutron diffusion equation, based on the backward difference formulas for systems of stiff ordinary differential equations. This method needs to solve a system of linear equations for each integration step, and for this purpose, we have developed an iterative block algorithm combined with a variational acceleration technique. We tested the algorithm with two benchmark problems, and compared the results with those provided by other codes, concluding that the performance and overall agreement are very good. (author)

  8. Laser-induced backward transfer of nanoimprinted polymer elements

    Science.gov (United States)

    Feinaeugle, Matthias; Heath, Daniel J.; Mills, Benjamin; Grant-Jacob, James A.; Mashanovich, Goran Z.; Eason, Robert W.

    2016-04-01

    Femtosecond laser-induced backward transfer of transparent photopolymers is demonstrated in the solid state, assisted by a digital micromirror spatial light modulator for producing shaped deposits. Through use of an absorbing silicon carrier substrate, we have been able to successfully transfer solid-phase material, with lateral dimensions as small as ~6 µm. In addition, a carrier of silicon incorporating a photonic waveguide relief structure enables the transfer of imprinted deposits that have been accomplished with surface features exactly complementing those present on the substrate, with an observed minimum feature size of 140 nm.

  9. Backward- and Forward-Looking Potential of Anaphors

    Science.gov (United States)

    Schumacher, Petra B.; Backhaus, Jana; Dangl, Manuel

    2015-01-01

    Personal pronouns and demonstratives contribute differently to the encoding of information in the mental model and they serve distinct backward- and forward-looking functions. While (unstressed) personal pronouns are the default means to indicate coreference with the most prominent discourse entity (backward-looking function) and typically mark the maintenance of the current topic, demonstratives are used to refer to a less prominent entity and serve the additional forward-looking function of signaling a possible topic shift. In Experiment 1, we present an ERP study that examines the time course of processing personal and d-pronouns in German (er vs. der) and assesses the impact of two prominence features of the antecedent, thematic role and sentential position, as well as neurophysiological correlates of backward- and forward-looking functions of referential expressions. We tested the comprehension of personal and d-pronouns following context sentences containing two potential antecedents. In addition to the factor pronoun type (er vs. der), we varied the verb type (active accusative verbs vs. dative experiencer verbs) and the thematic role order (canonical vs. non-canonical) in the context sentences to vary the antecedent's prominence. Time-locked to pronoun-onset, the ERPs revealed a general biphasic N400-Late Positivity for d-pronouns over personal pronouns with further subtle interactions of the prominence-lending cues in the early time window. The findings indicate that the calculation of the referential candidates' prominence (backward-looking function) is guided by thematic role and positional information. Thematic role information, in combination with initial position, thus represents a central predictor during referential processing. Coreference with a less prominent entity (assumed for d-pronouns) results in processing costs (N400). The additional topic shift signaled by d-pronouns (forward-looking function) results in attentional reorienting (Late

  10. Numerical simulations of separation behind backward facing steps

    Czech Academy of Sciences Publication Activity Database

    Louda, P.; Sváček, P.; Kozel, K.; Příhoda, Jaromír

    Vol. II. Athens : LFME Athens, 2011 - (Tsahalis, D.), s. 437-444 ISBN 978-960-98941-8-0. [International Conference on Experiments/Process/System Modeling/Simulation/ Optimization Proceedings /4./. Athens (GR), 06.06.2011-09.06.2011] R&D Projects: GA ČR GA103/09/0977; GA ČR GAP101/10/1230 Institutional research plan: CEZ:AV0Z20760514 Keywords : backward facing step * SST and EARSM turbulence models * turbulent heat flux model Subject RIV: BK - Fluid Dynamics

  11. Backward causation, hidden variables and the meaning of completeness

    Indian Academy of Sciences (India)

    Huw Price

    2001-02-01

    Bell’s theorem requires the assumption that hidden variables are independent of future measurement settings. This independence assumption rests on surprisingly shaky ground. In particular, it is puzzlingly time-asymmetric. The paper begins with a summary of the case for considering hidden variable models which, in abandoning this independence assumption, allow a degree of ‘backward causation’. The remainder of the paper clarifies the physical significance of such models, in relation to the issue as to whether quantum mechanics provides a complete description of physical reality.

  12. A nonhomogeneous backward heat problem: Regularization and error estimates

    Directory of Open Access Journals (Sweden)

    Trong Dang Duc

    2008-03-01

    Full Text Available We consider the problem of finding the initial temperature, from the final temperature, in the nonhomogeneous heat equation $$displaylines{ u_t-u_{xx}= f(x,t,quad (x,tin (0,piimes (0,T,\\ u(0,t= u(pi,t= 0, quad (x,t in (0,piimes(0,T. }$$ This problem is known as the backward heat problem and is severely ill-posed. Our goal is to present a simple and convenient regularization method, and sharp error estimates for its approximate solutions. We illustrate our results with a numerical example.

  13. Gastrostomy feeding tube - bolus

    Science.gov (United States)

    ... a gastrostomy tube. Delmar’s Fundamental and Advanced Nursing Skills . 2nd Ed. Albany, NY: Delmar Thomson Learning; 2003: 742-749. Simmons, Remmington R.The percutaneous endoscopic gastrostomy tube: a nurse's guide to PEG tubes. Medsurg Nurs . 2013 Mar- ...

  14. KER-2 tube history

    Energy Technology Data Exchange (ETDEWEB)

    Banister, W.C.

    1963-08-16

    Zirconium process tube No. 1986 was installed in KE Reactor tube channel No. 2864 on April 16, 1959. This report describes the history and the conditions to which it was exposed during its residence in the reactor. The tube was removed on May 31, 1963.

  15. Electron cyclotron maser based on the combination two-wave resonance

    International Nuclear Information System (INIS)

    A mechanism of a combination two-wave cyclotron interaction between an electron beam and the forward/backward components of a far-from-cutoff standing wave is analyzed. This regime can be promising for the realization of high-power continuous-wave electron cyclotron masers operating in the THz frequency range.

  16. 21 CFR 868.5800 - Tracheostomy tube and tube cuff.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheostomy tube and tube cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy tube and tube cuff. (a) Identification. A tracheostomy tube and tube cuff is a device intended to be placed into...

  17. Are forwards and backwards digit recall the same? A dual task study of digit recall

    OpenAIRE

    St. Clair-Thompson, HL; Allen, RJ

    2013-01-01

    There is some debate surrounding the cognitive resources underlying backwards digit recall. Some researchers consider it to differ from forwards digit recall due to the involvement of executive control, while others suggest that backwards recall involves visuo-spatial resources. Five experiments therefore investigated the role of executive-attentional and visuo-spatial resources in both forwards and backwards digit recall. In the first, participants completed visuo-spatial 0-back and 2-back t...

  18. Generating Property-Directed Potential Invariants By Backward Analysis

    Directory of Open Access Journals (Sweden)

    Adrien Champion

    2012-12-01

    Full Text Available This paper addresses the issue of lemma generation in a k-induction-based formal analysis of transition systems, in the linear real/integer arithmetic fragment. A backward analysis, powered by quantifier elimination, is used to output preimages of the negation of the proof objective, viewed as unauthorized states, or gray states. Two heuristics are proposed to take advantage of this source of information. First, a thorough exploration of the possible partitionings of the gray state space discovers new relations between state variables, representing potential invariants. Second, an inexact exploration regroups and over-approximates disjoint areas of the gray state space, also to discover new relations between state variables. k-induction is used to isolate the invariants and check if they strengthen the proof objective. These heuristics can be used on the first preimage of the backward exploration, and each time a new one is output, refining the information on the gray states. In our context of critical avionics embedded systems, we show that our approach is able to outperform other academic or commercial tools on examples of interest in our application field. The method is introduced and motivated through two main examples, one of which was provided by Rockwell Collins, in a collaborative formal verification framework.

  19. Backward bifurcation and control in transmission dynamics of arboviral diseases.

    Science.gov (United States)

    Abboubakar, Hamadjam; Claude Kamgang, Jean; Tieudjo, Daniel

    2016-08-01

    In this paper, we derive and analyze a compartmental model for the control of arboviral diseases which takes into account an imperfect vaccine combined with individual protection and some vector control strategies already studied in the literature. After the formulation of the model, a qualitative study based on stability analysis and bifurcation theory reveals that the phenomenon of backward bifurcation may occur. The stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the reproduction number, R0, is less than unity. Using Lyapunov function theory, we prove that the trivial equilibrium is globally asymptotically stable. When the disease-induced death is not considered, or/and, when the standard incidence is replaced by the mass action incidence, the backward bifurcation does not occur. Under a certain condition, we establish the global asymptotic stability of the disease-free equilibrium of the principal model. Through sensitivity analysis, we determine the relative importance of model parameters for disease transmission. Numerical simulations show that the combination of several control mechanisms would significantly reduce the spread of the disease, if we maintain the level of each control high, and this, over a long period. PMID:27321192

  20. Heat exchanger tube tool

    International Nuclear Information System (INIS)

    Certain types of heat-exchangers have tubes opening through a tube sheet to a manifold having an access opening offset from alignment with the tube ends. A tool for inserting a device, such as for inspection or repair, is provided for use in such instances. The tool is formed by a flexible guide tube insertable through the access opening and having an inner end provided with a connector for connection with the opening of the tube in which the device is to be inserted, and an outer end which remains outside of the chamber, the guide tube having adequate length for this arrangement. A flexible transport hose for internally transporting the device slides inside of the guide tube. This hose is long enough to slide through the guide tube, into the heat-exchanger tube, and through the latter to the extent required for the use of the device. The guide tube must be bent to reach the end of the heat-exchanger tube and the latter may be constructed with a bend, the hose carrying anit-friction elements at interspaced locations along its length to make it possible for the hose to negotiate such bends while sliding to the location where the use of the device is required

  1. An analysis of the advantages and limitations of vacuum tubes in terms of performance and reliability; Analyse des avantages specifiques des tubes: performances, limitations, fiabilite

    Energy Technology Data Exchange (ETDEWEB)

    Payen, F. [Thales Electron Devices, 78 - Velizy (France)

    2001-04-01

    Vacuum tubes have many advantages over semiconductor devices in applications between 300 MHz and 300 GHz. Each family of vacuum tubes (triodes, tetrodes, and their derivatives including magnetrons, klystrons, crossed field amplifiers, travelling wave tubes and gyrotrons) have their own characteristics in terms of operating frequency, instantaneous bandwidth, peak power, mean power, gain (amplifiers), electrical efficiency, linearity, reliability and lifetime. This makes it easier to select the most suitable vacuum tube for a given application. (authors)

  2. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... NEI YouTube Videos > NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration ... Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia NEI on Twitter NEI on YouTube ...

  3. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... YouTube Videos > NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia ... of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia NEI on Twitter NEI on YouTube NEI ...

  4. Ultrasonic inspection of inpile tubes

    International Nuclear Information System (INIS)

    The in-service inspection (ISI) of inpile tubes can be performed accurately and safely with a semiautomatic ultrasonic inspection system. The ultrasonic technique uses a set of multiple transducers to detect and size cracks, voids, and laminations radially and circumferentially. Welds are also inspected for defects. The system is designed to inspect stainless steel and Inconel tubes ranging from 53.8 mm (2.12 in.) to 101.6 mm (4 in.) inner diameter with wall thickness on the order of 5 mm. The inspection head contains seven transducers mounted in a surface-following device. Six angle-beam transducers generate shear waves in the tubes. Two of the six are oriented to detect circumferential cracks, and two detect axial cracks. Although each of these four transducers is used in the pulse-echo mode, they are oriented in aligned sets so pitch-catch operation is possible if desired. The remaining angle-beam transducers are angulated to detect flaws that are off axial or circumferential orientation. The seventh transducer is used for longitudinal inspection and detects and sizes laminar-type defects

  5. Three-dimensional computer simulation of shell and tube heat exchangers

    International Nuclear Information System (INIS)

    A three dimensional, conservative, fully implicit, colocated control volume based calculation procedure is described for the simulation of shell side flow in shell and tube heat exchangers. The colocated method uses momentum interpolation to avoid an oscillatory pressure field, and incorporates a flexible boundary condition interface that permits the specification of a wide range of problems. The simulation of shell and tube heat exchangers is based on a distributed resistance method and employs a two-equation κ-ε turbulence model. Volume porosities and non homogeneous surface permeabilities account for the obstructions due to the tubes and arbitrary arrangement of baffles. Geometry generators for tubes, baffles and inlets have been created. Non-equilibrium wall functions (Launder and Spalding, 1974) are used to compute momentum and heat transfer coefficients close to plane surface walls. Various test problems presented include the driven cavity, a laminar backward facing step with heat transfer, a turbulent backward facing step with heat transfer, and turbulent sudden pipe expansion. Good agreement is obtained between the computations and experiments and the computations of other researchers. A No Tubes In Window (NTIW) heat exchanger simulation is compared with experimental data. This work forms a basis for studying the significance of geometry on the mixing and heat transfer process in shell and tube heat exchangers

  6. Pediatric cuffed endotracheal tubes

    Directory of Open Access Journals (Sweden)

    Neerja Bhardwaj

    2013-01-01

    Full Text Available Endotracheal intubation in children is usually performed utilizing uncuffed endotracheal tubes for conduct of anesthesia as well as for prolonged ventilation in critical care units. However, uncuffed tubes may require multiple changes to avoid excessive air leak, with subsequent environmental pollution making the technique uneconomical. In addition, monitoring of ventilatory parameters, exhaled volumes, and end-expiratory gases may be unreliable. All these problems can be avoided by use of cuffed endotracheal tubes. Besides, cuffed endotracheal tubes may be of advantage in special situations like laparoscopic surgery and in surgical conditions at risk of aspiration. Magnetic resonance imaging (MRI scans in children have found the narrowest portion of larynx at rima glottides. Cuffed endotracheal tubes, therefore, will form a complete seal with low cuff pressure of <15 cm H 2 O without any increase in airway complications. Till recently, the use of cuffed endotracheal tubes was limited by variations in the tube design marketed by different manufacturers. The introduction of a new cuffed endotracheal tube in the market with improved tracheal sealing characteristics may encourage increased safe use of these tubes in clinical practice. A literature search using search words "cuffed endotracheal tube" and "children" from 1980 to January 2012 in PUBMED was conducted. Based on the search, the advantages and potential benefits of cuffed ETT are reviewed in this article.

  7. Flaw Detection in Thin-Walled Tubes

    International Nuclear Information System (INIS)

    The author considers the special features and advantages of ultrasonic methods of detecting flaws in thin-walled tubes by means of Lamb's waves and describes the apparatus used. In addition to standard methods of inspecting and testing tubes, ultrasonics and eddy currents are now widely used in detecting concealed defects (fissures, non-metallic inclusions, foliation, blisters), deep notches, cracks and scratches on inner surfaces, determining grain size, and measuring wall thickness and corrosion depth. For the ultrasonic detection of flaws in thin-walled tubes using Lamb's waves one must work on the relatively flat parts of the dispersion curves. For example, greatest sensitivity to foliation during inspection by the reflection method is possessed by anti-symmetrical waves of the first and second modes. The author shows the effect of non-uniform thickness and ovalness of tubes on signal fluctuations in inspection by the shadow method. Metal structure is tested by the ''ratio'' method based on a comparison between signals of different frequency which are reflected by or which pass through the materials. In smooth and finned thin-walled tubes with diameters of 3 to 60 mm and wall thickness of 0.2 mm or more, made of stainless steel, high-nickel, zirconium, aluminium and other alloys, defects are detected with IDTs-3M, IDTs-5, UDT-4M, UKT-2 and other ultrasonic apparatus. Inspection is carried out by the immersion technique, the shadow method and the reflection method with working frequencies up to 10 MHz. Positive detection is achieved of defects over 0.5 mm in length and with a depth of 5% of the wall thickness. Grain size is controlled by USAD-61 structure analysers. Eddy-current apparatus is used for measuring the wall thickness of tubes made of non-magnetic materials. (author)

  8. Resonance wave pumping with surface waves

    Science.gov (United States)

    Carmigniani, Remi; Gharib, Morteza; Violeau, Damien; Caltech-ENPC Collaboration

    2015-11-01

    The valveless impedance pump enables the production or amplification of a flow without the use of integrated mobile parts, thus delaying possible failures. It is usually composed of fluid-filled flexible tubing, closed by solid tubes. The flexible tube is pinched at an off-centered position relative to the tube ends. This generates a complex wave dynamic that results in a pumping phenomenon. It has been previously reported that pinching at intrinsic resonance frequencies of the system results in a strong pulsating flow. A case of a free surface wave pump is investigated. The resonance wave pump is composed of a rectangular tank with a submerged plate separating the water into a free surface and a recirculation rectangular section connected through two openings at each end of the tank. A paddle placed at an off-center position above the submerged plate is controlled in a heaving motion with different frequencies and amplitudes. Similar to the case of valveless impedance pump, we observed that near resonance frequencies strong pulsating flow is generated with almost no oscillations. A linear theory is developed to pseudo-analytically evaluate these frequencies. In addition, larger scale applications were simulated using Smoothed Particle Hydrodynamic codes.

  9. Internal switching and backward inhibition in depression and rumination.

    Science.gov (United States)

    Chen, Xiao; Feng, Zhengzhi; Wang, Tao; Su, Hong; Zhang, Lihong

    2016-09-30

    Prior research has suggested that impairments of switching abilities are associated with depression as well as rumination. Backward inhibition (BI) refers to the ability to inhibit the processing of previously relevant information and is demonstrated to be one of the key mechanisms underlying switching abilities. However, the association between BI in internal switching and depression/rumination remains uninvestigated. To examine this association, a modified Internal Shifting Task (IST) was administered to a sample of dysphoric and healthy control undergraduates. Results showed that depressive symptoms were not associated with difficulties in switching among subjects held in working memory, while trait ruminators performed poorly in switching internally. Surprisingly, no association between BI in internal switching and rumination/depressive symptoms was found. These findings indicate that rumination is characterized by poor performance in internal switching, but this deficit is not associated with BI. PMID:27449002

  10. Stochastic differential equations, backward SDEs, partial differential equations

    CERN Document Server

    Pardoux, Etienne

    2014-01-01

    This research monograph presents results to researchers in stochastic calculus, forward and backward stochastic differential equations, connections between diffusion processes and second order partial differential equations (PDEs), and financial mathematics. It pays special attention to the relations between SDEs/BSDEs and second order PDEs under minimal regularity assumptions, and also extends those results to equations with multivalued coefficients. The authors present in particular the theory of reflected SDEs in the above mentioned framework and include exercises at the end of each chapter. Stochastic calculus and stochastic differential equations (SDEs) were first introduced by K. Itô in the 1940s, in order to construct the path of diffusion processes (which are continuous time Markov processes with continuous trajectories taking their values in a finite dimensional vector space or manifold), which had been studied from a more analytic point of view by Kolmogorov in the 1930s. Since then, this topic has...

  11. Backward stochastic differential equations and its application to stochastic control

    Czech Academy of Sciences Publication Activity Database

    Veverka, Petr

    Praha : Nakladatelství ČVUT - výroba, 2010 - (Hobza, T.), s. 181-189 ISBN 978-80-01-04641-8. [Stochastic and Physical Monitoring Systems 2010. Děčín (CZ), 27.06.2010-03.07.2010] R&D Projects: GA ČR GD402/09/H045; GA ČR GAP402/10/1610 Institutional research plan: CEZ:AV0Z10750506 Keywords : BSDE * Stochastic control Subject RIV: BA - General Mathematics http://library.utia.cas.cz/separaty/2010/E/veverka-backward%20stochastic%20differential%20equations%20and%20its%20application%20to%20stochastic%20control.pdf

  12. On Forward and Backward Scattering from Fog and Rain Drops

    Czech Academy of Sciences Publication Activity Database

    Fišer, O.; Rejfek, Luboš; Brázda, Vladimír

    New York : IEEE, 2013, s. 152-155. ISBN 978-1-4673-5513-1. - (CFP1312E-PRT). [Conference on Microwave Techniques - COMITE 2013 /13./. Pardubice (CZ), 17.04.2013-18.04.2013] R&D Projects: GA ČR(CZ) GAP102/11/1376; GA MŠk(CZ) LD13036 Grant ostatní: COST(CZ) IC1101 Institutional support: RVO:68378289 Keywords : Forward scattering * backward scattering * efficiency factor * Rayleigh region * Mie region * Optical region Subject RIV: DG - Athmosphere Sciences, Meteorology http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6545060&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6545060

  13. Conduction cooled tube supports

    Science.gov (United States)

    Worley, Arthur C.; Becht, IV, Charles

    1984-01-01

    In boilers, process tubes are suspended by means of support studs that are in thermal contact with and attached to the metal roof casing of the boiler and the upper bend portions of the process tubes. The support studs are sufficiently short that when the boiler is in use, the support studs are cooled by conduction of heat to the process tubes and the roof casing thereby maintaining the temperature of the stud so that it does not exceed 1400.degree. F.

  14. Tubing weld cracking test

    International Nuclear Information System (INIS)

    A tubing weld cracking (TWC) test was developed for applications involving advanced austenitic alloys (such as modified 800H and 310HCbN). Compared to the Finger hot cracking test, the TWC test shows an enhanced ability to evaluate the crack sensitivity of tubing materials. The TWC test can evaluate the cracking tendency of base as well as filter materials. Thus, it is a useful tool for tubing suppliers, filler metal producers and fabricators

  15. A simple theory of Rijke tube oscillation

    Institute of Scientific and Technical Information of China (English)

    Maa Dah-You

    2002-01-01

    A simple theory of Rijke tube oscillation is presented based on mathematical realization of Rayleigh's qualitative explanation of the mechanism of Rijke tube. This is done by assuming a single point of high temperature in an otherwise uniform tube and the sound source produced when cold air flows passing this point. The wave equation thus obtained is then rigorously solved. It is found that the Rijke tube oscillation is a feedback system. There is no feedback nor oscillation when the hot spot is at a node or antinode in the tube. The mean flow is necessary for the oscillation, the particle velocity of which is proportional to the mean velocity, and the ratio is proportional to the gauze temperature when the later is low and the feedback does not affect much the magnitude of the particle velocity. When the temperature is high, the feedback increases rapidly and the particle velocity might grow to several or even tens of times of the mean velocity, and almost indefinitely when the heater temperature is high enough. Otherwise the growth is rather slow, when the mean flow or high temperature is first applied. The oscillations stop immediately when the mean flow is stopped. If the mean flow is controlled by a valve or a paddle at one end of the tube, an interesting sound is produced.

  16. Coupled backward- and forward-propagating solitons in a composite right- and left-handed transmission line

    Science.gov (United States)

    Veldes, G. P.; Cuevas, J.; Kevrekidis, P. G.; Frantzeskakis, D. J.

    2013-07-01

    We study the coupling between backward- and forward-propagating wave modes, with the same group velocity, in a composite right- and left-handed nonlinear transmission line. Using an asymptotic multiscale expansion technique, we derive a system of two coupled nonlinear Schrödinger equations governing the evolution of the envelopes of these modes. We show that this system supports a variety of backward- and forward-propagating vector solitons of the bright-bright, bright-dark, and dark-bright type. Performing systematic numerical simulations in the framework of the original lattice that models the transmission line, we study the propagation properties of the derived vector soliton solutions. We show that all types of the predicted solitons exist, but differ on their robustness: Only bright-bright solitons propagate undistorted for long times, while the other types are less robust, featuring shorter lifetimes. In all cases, our analytical predictions are in very good agreement with the results of the simulations, at least up to times of the order of the solitons’ lifetimes.

  17. Practical aspects of backward bifurcation in a mathematical model for tuberculosis.

    Science.gov (United States)

    Gerberry, David J

    2016-01-01

    In this work, we examine practical aspects of backward bifurcation for a data-based model of tuberculosis that incorporates multiple features which have previously been shown to produce backward bifurcation (e.g. exogenous reinfection and imperfect vaccination) and new considerations such as the treatment of latent TB infection (LTBI) and the BCG vaccine's interference with detecting LTBI. Understanding the interplay between these multiple factors and backward bifurcation is particularly timely given that new diagnostic tests for LTBI detection could dramatically increase rates of both LTBI detection and vaccination in the coming decades. By establishing analytic thresholds for the existence of backward bifurcation, we identify those aspects of TB's complicated pathology that make backward bifurcation more or less likely to occur. We also examine the magnitude of the backward bifurcation produced by the model and its sensitivity to various model parameters. We find that backward bifurcation is unlikely to occur. While increased vaccine coverage and/or increased detection and treatment of LTBI can push the threshold for backward bifurcation into the region of biological plausibility, the resulting bifurcations may still be too small to have any noticeable epidemiological impact. PMID:26493359

  18. A regression Monte-Carlo method for Backward Doubly Stochastic Differential Equations

    OpenAIRE

    Aboura, Omar

    2011-01-01

    This paper extends the idea of E.Gobet, J.P.Lemor and X.Warin from the setting of Backward Stochastic Differential Equations to that of Backward Doubly Stochastic Differential equations. We propose some numerical approximation scheme of these equations introduced by E.Pardoux and S.Peng.

  19. Classical Solutions of Path-Dependent PDEs and Functional Forward-Backward Stochastic Systems

    Directory of Open Access Journals (Sweden)

    Shaolin Ji

    2013-01-01

    Full Text Available In this paper we study the relationship between functional forward-backward stochastic systems and path-dependent PDEs. In the framework of functional Itô calculus, we introduce a path-dependent PDE and prove that its solution is uniquely determined by a functional forward-backward stochastic system.

  20. Investigation of enhanced forward and backward anti-stokes Raman signals in lithium niobate waveguides

    International Nuclear Information System (INIS)

    We have observed enhancements of the anti-Stokes Raman signals generated in lithium niobate waveguides in the forward and backward configurations by at least one order of magnitude under the pump power of the microwatt level. These output signals were measured using a single photon detector. The forward and backward propagating anti-Stokes signals exhibited different spectral features

  1. Categorising YouTube

    OpenAIRE

    Thomas Mosebo Simonsen

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a...

  2. Calibrations of photomultiplier tubes

    International Nuclear Information System (INIS)

    The experimental methods for calibration photomultiplier tubes used in the multichannel fast-pulse-detection system of Thomson scattering measurements for nuclear fusion devices is reported. The most important parameters of the photomultiplier tubes to be calibrated include: linearity of output electric signals to input light signals, response time of pulsed light, spectral response, absolute responsibility, and sensitivity as a function of the chain voltage. The calibrations of all these parameters are carried out by using EMI 9558 B and RCA 7265 photomultiplier tubes respectively. The experimental methods presented in the paper are common to those quantitative measurements that require phomultiplier tubes as detectors

  3. Composite Pulse Tube

    Science.gov (United States)

    Martin, Jerry L.; Cloyd, Jason H.

    2007-01-01

    A modification of the design of the pulse tube in a pulse-tube cryocooler reduces axial thermal conductance while preserving radial thermal conductance. It is desirable to minimize axial thermal conductance in the pulse-tube wall to minimize leakage of heat between the warm and cold ends of the pulse tube. At the same time, it is desirable to maximize radial thermal conductance at the cold end of the pulse tube to ensure adequate thermal contact between (1) a heat exchanger in the form of a stack of copper screens inside the pulse tube at the cold end and (2) the remainder of the cold tip, which is the object to which the heat load is applied and from which heat must be removed. The modified design yields a low-heat-leak pulse tube that can be easily integrated with a cold tip. A typical pulse tube of prior design is either a thin-walled metal tube or a metal tube with a nonmetallic lining. It is desirable that the outer surface of a pulse tube be cylindrical (in contradistinction to tapered) to simplify the design of a regenerator that is also part of the cryocooler. Under some conditions, it is desirable to taper the inner surface of the pulse tube to reduce acoustic streaming. The combination of a cylindrical outer surface and a tapered inner surface can lead to unacceptably large axial conduction if the pulse tube is made entirely of metal. Making the pulse-tube wall of a nonmetallic, lowthermal- conductivity material would not solve the problem because the wall would not afford the needed thermal contact for the stack of screens in the cold end. The modified design calls for fabricating the pulse tube in two parts: a longer, nonmetallic part that is tapered on the inside and cylindrical on the outside and a shorter, metallic part that is cylindrical on both the inside and the outside. The nonmetallic part can be made from G-10 fiberglass-reinforced epoxy or other low-thermal-conductivity, cryogenically compatible material. The metallic part must have high

  4. Manual tube welding torch

    International Nuclear Information System (INIS)

    In a welding torch which fits over a tube intermediate the ends thereof for welding the juncture between the tube and a boss on the back side of a tube plate, a split housing encloses a tungsten electrode, a filler wire duct and a fiber optic bundle arranged to observe the welding process. A shielding gas duct is provided in the housing. A screw is provided for setting electrode/work distance. Difficult remote tube welding operations can be performed with the apparatus. (author)

  5. Steam generator tube performance

    International Nuclear Information System (INIS)

    A survey of steam generator operating experience for 1986 has been carried out for 184 pressurized water and pressurized heavy-water reactors, and 1 water-cooled, graphite-moderated reactor. Tubes were plugged at 75 of the reactors (40.5%). In 1986, 3737 tubes were plugged (0.14% of those in service) and 3148 tubes were repaired by sleeving. A small number of reactors accounted for the bulk of the plugged tubes, a phenomenon consistent with previous years. For 1986, the available tubesheet sludge data for 38 reactors has been compiled into tabular form, and sludge/deposit data will be incorporated into all future surveys

  6. K-p backward elastic scattering between 476 and 1084 MeV/c

    International Nuclear Information System (INIS)

    The differential cross-section for K-p backward elastic scattering was measured in steps of 10-20 MeV/c between 476 and 1084 MeV/c at the Brookhaven AGS. A negative kaon beam was focused onto a 21 cm long liquid hydrogen target and the forward scattered protons were identified kinematically by means of a single arm magnetic spectrometer. A Monte Carlo computer program aided in the subtraction of background events and in the calculation of correction factors. The new data have an average statistical precision of 2.5% which is an order of magnitude improvement over previous results. Together with a new partial wave analysis, the new data give additional evidence for a resonance between 1700 and 1725 MeV. The best fit to the data finds this to be a D13 resonance with a mass of 1708 MeV and a width of 27 MeV. Comparable improvement in precision was also obtained in a measurement of the differential cross section for K-p → Σ-π+ in which the π+ emerges at 00. 47 references

  7. Spin correlation parameter Cyy of p+3He elastic backward scattering

    International Nuclear Information System (INIS)

    We measured the differential cross section and the spin correlation parameter Cyy of the p-vector+3He-vector elastic backward scattering at 200, 300, and 400 MeV at θ=180 deg. in the center-of-mass frame to study the mechanism of the reaction and to examine the validity of the 3He wave functions based on two different realistic two-body forces. This is the first measurement of the spin correlation parameter Cyy of the p-vector+3He-vector EBS at intermediate energies. The experimental results were compared with few-body calculations, including three reaction mechanisms: two-nucleon-pair exchange, pion exchange, and direct pp scattering. It was found that few-body calculations describe the differential cross-section data reasonably well. The spin correlation parameter Cyy shows clear evidence for the two-nucleon-pair exchange processes in the reaction, demonstrating that the spin observables are helpful for deeper understanding of the reaction mechanism

  8. Steam generator tube failures

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, P.E.; Shah, V.N.; Ward, L.W.; Ellison, P.G.

    1996-04-01

    A review and summary of the available information on steam generator tubing failures and the impact of these failures on plant safety is presented. The following topics are covered: pressurized water reactor (PWR), Canadian deuterium uranium (CANDU) reactor, and Russian water moderated, water cooled energy reactor (VVER) steam generator degradation, PWR steam generator tube ruptures, the thermal-hydraulic response of a PWR plant with a faulted steam generator, the risk significance of steam generator tube rupture accidents, tubing inspection requirements and fitness-for-service criteria in various countries, and defect detection reliability and sizing accuracy. A significant number of steam generator tubes are defective and are removed from service or repaired each year. This wide spread damage has been caused by many diverse degradation mechanisms, some of which are difficult to detect and predict. In addition, spontaneous tube ruptures have occurred at the rate of about one every 2 years over the last 20 years, and incipient tube ruptures (tube failures usually identified with leak detection monitors just before rupture) have been occurring at the rate of about one per year. These ruptures have caused complex plant transients which have not always been easy for the reactor operators to control. Our analysis shows that if more than 15 tubes rupture during a main steam line break, the system response could lead to core melting. Although spontaneous and induced steam generator tube ruptures are small contributors to the total core damage frequency calculated in probabilistic risk assessments, they are risk significant because the radionuclides are likely to bypass the reactor containment building. The frequency of steam generator tube ruptures can be significantly reduced through appropriate and timely inspections and repairs or removal from service.

  9. Steam generator tube failures

    International Nuclear Information System (INIS)

    A review and summary of the available information on steam generator tubing failures and the impact of these failures on plant safety is presented. The following topics are covered: pressurized water reactor (PWR), Canadian deuterium uranium (CANDU) reactor, and Russian water moderated, water cooled energy reactor (VVER) steam generator degradation, PWR steam generator tube ruptures, the thermal-hydraulic response of a PWR plant with a faulted steam generator, the risk significance of steam generator tube rupture accidents, tubing inspection requirements and fitness-for-service criteria in various countries, and defect detection reliability and sizing accuracy. A significant number of steam generator tubes are defective and are removed from service or repaired each year. This wide spread damage has been caused by many diverse degradation mechanisms, some of which are difficult to detect and predict. In addition, spontaneous tube ruptures have occurred at the rate of about one every 2 years over the last 20 years, and incipient tube ruptures (tube failures usually identified with leak detection monitors just before rupture) have been occurring at the rate of about one per year. These ruptures have caused complex plant transients which have not always been easy for the reactor operators to control. Our analysis shows that if more than 15 tubes rupture during a main steam line break, the system response could lead to core melting. Although spontaneous and induced steam generator tube ruptures are small contributors to the total core damage frequency calculated in probabilistic risk assessments, they are risk significant because the radionuclides are likely to bypass the reactor containment building. The frequency of steam generator tube ruptures can be significantly reduced through appropriate and timely inspections and repairs or removal from service

  10. Transverse modulational instability of collinear waves

    International Nuclear Information System (INIS)

    The transverse modulational instability, or filamentation, of two collinear waves is investigated using a coupled nonlinear Schro at sign;udinger-equation model. For infinite media it is shown that the presence of the second laser field increases the growth rate of the instability and decreases the scale length of the most unstable filaments. Systems of two copropagating waves are shown to be convectively unstable and systems of two counterpropagating waves are shown to be absolutely unstable, even when the ratio of backward- to forward-wave intensity is small. For two counterpropagating waves in finite media, the threshold intensities for the absolute instability depend only weakly on the ratio of wave intensities. The general theory is applied to the pondermotive filamentation of two light waves in homogeneous plasma

  11. Pyrotechnic Tubing Connector

    Science.gov (United States)

    Graves, Thomas J.; Yang, Robert A.

    1988-01-01

    Tool forms mechanical seal at joint without levers or hydraulic apparatus. Proposed tool intended for use in outer space used on Earth by heavily garbed workers to join tubing in difficult environments. Called Pyrotool, used with Lokring (or equivalent) fittings. Piston slides in cylinder when pushed by gas from detonating pyrotechnic charge. Impulse of piston compresses fittings, sealing around butting ends of tubes.

  12. Welding Tubes In Place

    Science.gov (United States)

    Meredith, R.

    1984-01-01

    Special welding equipment joins metal tubes that carry pressurized cyrogenic fluids. Equipment small enough to be used in confined spaces in which such tubes often mounted. Welded joints lighter in weight and more leak-proof than joints made with mechanical fittings.

  13. Reaction mechanism and characteristics of $T_{20}$ in $d + ^3He$ backward elastic scattering at intermediate energies

    CERN Document Server

    Tanifuji, M; Iseri, Y; Uesaka, T; Sakamoto, N; Satou, Y; Itoh, K; Sakai, H; Tamii, A; Ohnishi, T; Sekiguchi, K; Yako, K; Sakoda, S; Okamura, H; Suda, K; Wakasa, T

    2000-01-01

    For backward elastic scattering of deuterons by ^3He, cross sections \\sigma and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are analyzed by the PWIA and by the general formula which includes virtual excitations of other channels, with the assumption of the proton transfer from ^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev equation, the PWIA describes global features of the experimental data, while the virtual excitation effects are important for quantitative fits to the T_{20} data. Theoretical predictions on T_{20}, K_y^y (polarization transfer coefficient) and C_{yy} (spin correlation coefficient) are provided up to GeV energies.

  14. Categorising YouTube

    DEFF Research Database (Denmark)

    Simonsen, Thomas Mosebo

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube’s...... technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a user-driven bottom-up folksonomy and a hierarchical browsing system that emphasises a culture of competition...... and which favours the already popular content of YouTube. With this taxonomic approach, the UGC videos are registered and analysed in terms of empirically based observations. The article identifies various UGC categories and their principal characteristics. Furthermore, general tendencies of the UGC...

  15. Underwater implosions of large format photo-multiplier tubes

    International Nuclear Information System (INIS)

    Large, deep, well shielded liquid detectors have become an important technology for the detection of neutrinos over a wide dynamic range from few MeV to TeV. The critical component of this technology is the large format semi-hemispherical photo-multiplier tube with diameters in the range of 25–50 cm. The survival of an assembled array of these photo-multiplier tubes under high hydrostatic pressure is the subject of this study. These are the results from an R and D program which is intended to understand the modes of failure when a photo-multiplier tube implodes under hydrostatic pressure. Our tests include detailed measurements of the shock wave which results from the implosion of a photo-multiplier tube and a comparison of the test data to modern hydrodynamic simulation codes. Using these results we can extrapolate to other tube geometries and make recommendation on deployment of the photo-multiplier tubes in deep water detectors with a focus on risk mitigation from a tube implosion shock wave causing a chain reaction loss of multiple tubes.

  16. Towards a THz Backward Wave Amplifier in European FP7 OPTHER Project

    DEFF Research Database (Denmark)

    Dispenza, Massimiliano; Cojocaru, C.-S.; De Rossi, Alfredo;

    2010-01-01

    Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable technological effort is being undertaken, in terms of technological development, THz device design and integration. The ultimate goal is to develop a miniaturised THz amplifier based on vacuum...

  17. "Backward" Curriculum Design and Assessment: What Goes Around Comes Around, or Haven't We Seen This Before?

    Science.gov (United States)

    Cho, Jeasik; Trent, Allen

    2005-01-01

    In this paper, the authors explore the latest manifestation of backward curriculum discourse, namely, a theory of "backward" unit design. The authors view this "backward" curriculum discourse as foundationally positivist and/or structural, yet they adopt a poststructural point of view. This theoretical undergirding makes it possible to rethink…

  18. Pressure tube type reactor

    International Nuclear Information System (INIS)

    Heretofore, a pressure tube type reactor has a problem in that the evaluation for the reactor core performance is complicate and no sufficient consideration is made for the economical property, to increase the size of a calandria tank and make the cost expensive. Then, in the present invention, the inner diameter of a pressure tube is set to greater than 50% of the lattice gap in a square lattice like arrangement, and the difference between the inner and the outer diameters of the calandria tube is set smaller than 20% of the lattice gap. Further, the inner diameter of the pressure tube is set to greater than 40% and the difference between the inner and the outer diameters of the calandria tube is set smaller than 30% of the lattice gap in a triangle lattice arrangement. Then, heavy water-to-fuel volume ratio can be determined appropriately and the value for the coolant void coefficient is made more negative side, to improve the self controllability inherent to the reactor. In particular, when 72 to 90 fuel rods are arranged per one pressure tube, the power density per one fuel rod is can be increased by about twice. Accordingly, the number of the pressure tubes can be reduced about to one-half, thereby enabling to remarkably decrease the diameter of the reactor core and to reduce the size of the calandria, which is economical. (N.H.)

  19. Electroproduction of π+ mesons at forward and backward direction in the region of the D13(1520) and F15(1688) resonances

    International Nuclear Information System (INIS)

    We report on measurements of the reaction ep → enπ+ in the region of the D13(1520) and F15(1688) resonances. At an invariant four-momentum transfer q2 = 0.3 (GeV/c)2 the outgoing pion was detected in the forward and backward directions. The values of the helicity-1/2-partial wave amplitudes A2-(D13(1520)) and A3-(F15(1688)) are determined from these measurements. A comparison of the results with single quark transition models is made.

  20. Unified View of Backward Backtracking in Short Read Mapping

    Science.gov (United States)

    Mäkinen, Veli; Välimäki, Niko; Laaksonen, Antti; Katainen, Riku

    Mapping short DNA reads to the reference genome is the core task in the recent high-throughput technologies to study e.g. protein-DNA interactions (ChIP-seq) and alternative splicing (RNA-seq). Several tools for the task (bowtie, bwa, SOAP2, TopHat) have been developed that exploit Burrows-Wheeler transform and the backward backtracking technique on it, to map the reads to their best approximate occurrences in the genome. These tools use different tailored mechanisms for small error-levels to prune the search phase significantly. We propose a new pruning mechanism that can be seen a generalization of the tailored mechanisms used so far. It uses a novel idea of storing all cyclic rotations of fixed length substrings of the reference sequence with a compressed index that is able to exploit the repetitions created to level out the growth of the input set. For RNA-seq we propose a new method that combines dynamic programming with backtracking to map efficiently and correctly all reads that span two exons. Same mechanism can also be used for mapping mate-pair reads.