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Sample records for wave transmission technique

  1. Performance evaluation of compounding and directional beamforming techniques for carotid strain imaging using plane wave transmissions

    DEFF Research Database (Denmark)

    Hansen, Hendrik H.G.; Stuart, Matthias Bo; Villagómez Hoyos, Carlos Armando

    2014-01-01

    techniques have been developed to cope with the low off - axis image quality when performing 2D (and in future 3D) motion estimation: cross correlation with directional beamforming (with or without RF (coherent) compounding) and displacement compounding. This study compares the precision of these techniques...

  2. Radio Wave Propagation: A Handbook of Practical Techniques for Computing Basic Transmission Loss and Field Strength

    Science.gov (United States)

    1982-09-01

    Rosman , NC 15.3 42 1/70-1/71 NASA Yes Clarksburg, MD 15.3 38 7/70-7/71 COMSAT No TABLE 7-6 MEASUREMENTS 19-29 GHZ Freq. Measured Location (GHz) (Deg...Planning Meeting, NASA , Greenbelt, MD, 3 December 1980. -. . .. . . . ./.-.-...-...-... . .• .\\ . . . . . . RADIO WAVE PROPAGATION: A HANDBOOK OF...1/77-1/78 NASA Yes Greenbelt, MD 11.7 29 1/78-1/79 NASA Yes Blacksburg, VA 11.7 33 1/78-1/79 VPI Yes Waltham, MA 11.7 24 6/77-1/78 GTE Yes , Waltham

  3. Sound wave transmission (image)

    Science.gov (United States)

    When sounds waves reach the ear, they are translated into nerve impulses. These impulses then travel to the brain where they are interpreted by the brain as sound. The hearing mechanisms within the inner ear, can ...

  4. Development of Measurement and Extraction Technique of Complex Permittivity Using Transmission Parameter S 21 for Millimeter Wave Frequencies

    Science.gov (United States)

    Ozturk, Turgut; Hudlička, Martin; Uluer, İhsan

    2017-12-01

    This study provides an overview of measured S-parameters and its processing to extract the dielectric properties of materials such as Teflon, PMMA, and PVC which are preferred for materials characterization process. In addition, a correction model is presented for transmission parameter ( S 21) to obtain the dielectric constant with high accuracy. A non-destructive and non-contact free space measurement method has been used to measure S-parameters of thin samples in the low THz frequency range. S-parameters are measured in free space by vector network analyzer supported with two frequency extenders. Additionally, the parabolic mirrors are used to collimate the generated beam in wide frequency range. Furthermore, a standard filter process is performed to remove the undesired ripples in signal using singular spectrum analyzer before the implementation of extraction process. Newton-Raphson extraction technique is used to extract the material complex permittivity as a function of the frequency in Y-band (325-500 GHz).

  5. MHD wave transmission in the Sun's atmosphere

    Science.gov (United States)

    Stangalini, M.; Del Moro, D.; Berrilli, F.; Jefferies, S. M.

    2011-10-01

    Magnetohydrodynamics (MHD) wave propagation inside the Sun's atmosphere is closely related to the magnetic field topology. For example, magnetic fields are able to lower the cutoff frequency for acoustic waves, thus allowing the propagation of waves that would otherwise be trapped below the photosphere into the upper atmosphere. In addition, MHD waves can be either transmitted or converted into other forms of waves at altitudes where the sound speed equals the Alfvén speed. We take advantage of the large field-of-view provided by the IBIS experiment to study the wave propagation at two heights in the solar atmosphere, which is probed using the photospheric Fe 617.3 nm spectral line and the chromospheric Ca 854.2 nm spectral line, and its relationship to the local magnetic field. Among other things, we find substantial leakage of waves with five-minute periods in the chromosphere at the edges of a pore and in the diffuse magnetic field surrounding it. By using spectropolarimetric inversions of Hinode SOT/SP data, we also find a relationship between the photospheric power spectrum and the magnetic field inclination angle. In particular, we identify well-defined transmission peaks around 25° for five-minute waves and around 15° for three-minute waves. We propose a very simple model based on wave transmission theory to explain this behavior. Finally, our analysis of both the power spectra and chromospheric amplification spectra suggests the presence of longitudinal acoustic waves along the magnetic field lines.

  6. Wave transmission in mangrove forests

    NARCIS (Netherlands)

    Schiereck, G.J.; Booij, N.

    1995-01-01

    There is an increasing awareness of the role of mangrove forests in coastal ecosystems and coastal protection. At the transition between ocean and land, they have to absorb the energy that comes from the motion of the water. Little quantitative in formation is available, however, on wave

  7. Investigation of Wave Transmission from a Floating Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke

    2012-01-01

    This paper focuses on the calibration of the MIKE21BW model against the measured wave height reduction behind a 24 kW/m Wave Dragon (WD) wave energy converter. A numerical model is used to determine the wave transmission through the floating WD in varying wave conditions. The transmission obtained...... from the MIKE21BW model is compared to results from a simpler model, based on the integration of wave energy flux. The conclusion is that the simplified approach provides results similar to the transmission obtained from the numerical model, both for a single WD and a farm of multiple WDs....

  8. Novel transmission lines for the submillimeter-wave region

    Science.gov (United States)

    Katehi, Linda P. B.

    1992-01-01

    Accounts are given of the two approaches to the design of low-loss sub-mm-wave transmission lines for intelligent computer control guidance, command systems for space applications, and sensors operating in an optically opaque environment. These are: (1) the extension of the mm-wave monolithic technology to higher frequencies, although this approach is restricted to the lower end of the sub-mm spectrum, up to 500 GHz, due to ohmic losses; and (2) the extension of optical techniques to lower frequencies. This second approach is also limited, to the higher end of the sub-mm spectrum. Available characterizations of these technologies' electrical properties are presented.

  9. Wave energy transmission apparatus for high-temperature environments

    Science.gov (United States)

    Buckley, John D. (Inventor); Edwards, William C. (Inventor); Kelliher, Warren C. (Inventor); Carlberg, Ingrid A. (Inventor)

    2010-01-01

    A wave energy transmission apparatus has a conduit made from a refractory oxide. A transparent, refractory ceramic window is coupled to the conduit. Wave energy passing through the window enters the conduit.

  10. 10 Gbps WDM transmission performance limits using in-line SOAs and an optical phase conjugator based on four-wave mixing in SOAs as a mid-span spectral inversion technique.

    Science.gov (United States)

    Hur, Sub; Kim, Yonggyou; Jang, Hodeok; Jeong, Jichai

    2006-05-29

    We have theoretically investigated the transmission performance limits of all semiconductor optical amplifiers (SOA)-based 10 Gb/s wavelength division multiplexing (WDM) systems using in-line SOAs and an optical phase conjugator (OPC) based on four-wave mixing in SOAs as a mid-span spectral inversion technique. With a verified numerical model of SOAs, we have found that the crosstalk from SOAs in OPC is a dominant factor to limit the number of channels in WDM systems. In order to increase the available number of channels, we optimize the input optical power and the injection current to SOAs in OPC with using a reservoir channel in in-line SOAs. All SOA-based 10 Gb/s WDM systems using the OPC can transmit 16 channel signals up to 240 km distance with a 3 dB power penalty.

  11. Wave transmission at low-crested structures using neural networks

    NARCIS (Netherlands)

    Van Oosten, R.P.; Peixó Marco, J.; Van der Meer, J.W.; Van Gent, M.; Verhagen, H.J.

    2006-01-01

    The European Union funded project DELOS was focused on wave transmission and an extensive database on low-crested rubble mound structures was generated. During DELOS, new empirical wave transmission formulae were derived. These formulae still showed a considerable scatter due to a limited number of

  12. Reflection and transmission of plane harmonic waves at an interface ...

    Indian Academy of Sciences (India)

    Reflection and transmission of plane harmonic waves at an interface between liquid and micropolar viscoelastic solid with stretch. Baljeet Singh. Volume 25 Issue 6 December 2000 pp 589-600 ... Keywords. Micropolar viscoelastic solid; axial stretch; reflection coefficient; longitudinal wave; micropolar viscoelastic waves.

  13. Stopping power determinations by the transmission technique

    Science.gov (United States)

    Räisänen, J.; Wätjen, U.; Plompen, A. J. M.; Munnik, F.

    1996-09-01

    Details of the experimental procedures related to the transmission technique are described. Parameters affecting the stopping power measurements by this technique are pointed out and discussed. For example, the importance of an accurate foil areal density determination is emphasized, and methods for the determination are introduced. The accuracy and possible error sources of the stopping power values are reviewed. Advantages as well as limitations of the method are discussed. As an example the stopping powers of 600-3200 keV 4He ions in polyimide (Kapton) have been determined. The experimental results are compared with the predictions of widely used semiempirical models.

  14. Transmission techniques for 4G systems

    CERN Document Server

    Da Silva, Mario Marques

    2012-01-01

    Fourth Generation (4G) wireless communication systems support current and emergent multimedia services such as mobile TV, social networks and gaming, high-definition TV, video teleconferencing, and messaging services. These systems feature the All-over-IP concept and boast improved quality of service. Several important R&D activities are currently under way in the field of wireless communications for 4G systems, but the coverage is widespread in the literature. Transmission Techniques for 4G Systems presents a compilation of the latest developments in the field of wireless communications for 4

  15. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bing; Tan, K. T., E-mail: ktan@uakron.edu [Department of Mechanical Engineering, The University of Akron, Akron, Ohio 44325-3903 (United States)

    2016-08-21

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  16. Enhanced transmission of electromagnetic waves through 1D plasmonic crystals.

    Science.gov (United States)

    So, Jin-Kyu; Jung, Hoe-Cheon; Min, Sun-Hong; Jang, Kyu-Ha; Bak, Seung-Ho; Park, Gun-Sik

    2010-09-13

    Transmission of electromagnetic waves through thick perfect conducting slabs perforated by one-dimensional arrays of rectangular holes was studied experimentally in the microwave frequency range. The observed thickness-dependent transmission clearly exhibits the evanescent and propagating nature of the involved electromagnetic excitations on the considered structures, which are effective surface plasmons and localized waveguide resonances, respectively. The 1D crystals showing transmission based on localized resonances further manifests the frequency-dependent effective refractive index depending on the filling ratio of the holes and accompanies resonant guided wave propagation.

  17. Reflection and Transmission of Acoustic Waves at Semiconductor - Liquid Interface

    Directory of Open Access Journals (Sweden)

    J. N. Sharma

    2011-09-01

    Full Text Available The study of reflection and transmission characteristics of acoustic waves at the interface of a semiconductor halfspace underlying an inviscid liquid has been carried out. The reflection and transmission coefficients of reflected and transmitted waves have been obtained for quasi-longitudinal (qP wave incident at the interface from fluid to semiconductor. The numerical computations of reflection and transmission coefficients have been carried out with the help of Gauss elimination method by using MATLAB programming for silicon (Si, germanium (Ge and silicon nitride (Si3N4 semiconductors. In order to interpret and compare, the computer simulated results are plotted graphically. The study may be useful in semiconductors, seismology and surface acoustic wave (SAW devices in addition to engines of the space shuttles.

  18. A comparison of wave mode identification techniques

    Directory of Open Access Journals (Sweden)

    S. N. Walker

    2004-09-01

    Full Text Available The four point measurements available from the Cluster mission enable spatiotemporal effects in data sets to be resolved. One application of these multipoint measurements is the determination of the wave vectors and hence the identification of wave modes that exist within the plasma. Prior to multi-satellite missions, wave identification techniques were based upon the interpretation of observational data using theoretically defined relations. However, such techniques are limited by the quality of the data and the type of plasma model employed. With multipoint measurements, wave modes can be identified and their wave directions determined purely from the available observations. This paper takes two such methods, a phase differencing technique and k-filtering and compares their results. It is shown that both methods can resolve the k vector for the dominant mirror mode present in the data. The phase differencing method shows that the nature of the wave environment is constantly changing and as such both methods result in an average picture of the wave environment in the period analysed. The k-filtering method is able to identify other modes that are present.

  19. Wave transmission by suspended pipe breakwater

    Digital Repository Service at National Institute of Oceanography (India)

    Mani, J.S.; Jayakumar, S.

    ratio of 0.46), a 5% reduction in incident-wave height can be achieved. The cost and performance of conventionally adopted pile breakwater (involving a row of closely spaced piles driven on the seabed) were compared with the present system...

  20. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    Science.gov (United States)

    Host, Nick; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix

    2013-01-01

    Phased array antennas showcase many advantages over mechanically steered systems. However, they are also more complex, heavy and most importantly costly. This presentation paper presents a concept which overcomes these detrimental attributes by eliminating all of the phase array backend (including phase shifters). Instead, a wave velocity reconfigurable transmission line is used in a series fed array arrangement to allow phase shifting with one small (100mil) mechanical motion. Different configurations of the reconfigurable wave velocity transmission line are discussed and simulated and experimental results are presented.

  1. Analysis of data transmission technique based on pulsed laser

    Science.gov (United States)

    Drozd, T.; Zygmunt, M.; Knysak, P.; Wojtanowski, J.

    2012-03-01

    Pulsed lasers are used mainly in lidar systems as sources of short and highly energetic light pulses. In data transmission systems continuous wave lasers are typically applied, however it is also possible to use pulsed lasers in such systems. Such approach seems to be especially reasonable for devices where a pulsed laser is applied anyway and executes another function (rangefinding). The article discusses a data transmission concept based on a pulsed laser technology. Advantages and limits of such a transmission method are described. Influence of individual transmission elements on the effective data transmission speed is analysed.

  2. Extremely flat transmission band of forward volume spin wave using gold and yttrium iron garnet

    Science.gov (United States)

    Shimada, Kei; Goto, Taichi; Kanazawa, Naoki; Takagi, Hiroyuki; Nakamura, Yuichi; Uchida, Hironaga; Inoue, Mitsuteru

    2017-07-01

    An extremely flat transmission band for a forward volume spin wave (SW) propagating in an SW waveguide composed of yttrium iron garnet film and SW absorbers was obtained, using the finite integration technique. Three-dimensional analysis of the calculated results showed that the transmission ripples of the SWs propagating in the waveguide were caused by SW interference, especially that due to two standing waves originating from the waveguide edge-edge and the waveguide-antenna edge. To suppress these waves, SW absorbers composed of gold film were introduced and the resultant positions and shapes were investigated precisely. Hence, an extremely flat transmission band was obtained. The results of this study have potential application in the development of one- and two-dimensional magnonic crystals for integrated SW devices.

  3. Resonant Wave-Particle Manipulation Techniques

    Science.gov (United States)

    Zhmoginov, Andrey I.

    Charged particle dynamics can be altered considerably even by weak electromagnetic waves if some of the particles are in resonance. Depending on the wave parameters, the resonances in the phase space can either be well separated, in which case the particle dynamics is regular almost everywhere, or they can overlap leading to stochastic particle motion in a large volume of the phase space. Although different, both of these regimes allow one to manipulate particle ensembles by arranging resonant interactions with appropriate waves. This thesis is devoted to studying two wave-particle manipulation techniques having potential applications in fusion and laser-plasma interaction research. Specifically, we study the alpha-channeling effect (which relies on stochastic diffusion of resonant particles) and the so-called negative-mass effect (NME) (which involves the conservation of the adiabatic invariant). The alpha-channeling effect entails the use of radio-frequency waves to expel and cool high-energetic alpha particles born in a fusion reactor; the device reactivity can then be increased even further by redirecting the extracted energy to fuel ions. Recently, the alpha-channeling technique, originally proposed for tokamaks, was shown to be suitable for application in mirror machines as well. In the first part of this thesis, we deepen the understanding of issues and possibilities of the alpha-channeling implementation in open-ended reactors. We verify the feasibility of this technique and identify specific waves and supplementary techniques, which can potentially be used for implementing the alpha-channeling in realistic mirror devices. We also propose a new technique for using the alpha-channeling wave energy to catalyze fusion reaction by employing minority ions as a mediator species. In the second part of this thesis, the NME manifesting itself as an unusual response of a resonant particle to external adiabatic perturbations mimicking the behavior of a particle with a

  4. Transmission of wave energy through an offshore wind turbine farm

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Johnson, Martin; Sørensen, Ole Rene

    2013-01-01

    The transmission of wave energy passing an offshore wind farm is studied. Three effects that can change the wave field are analysed, which is the A) energy dissipation due to drag resistance, B) wave reflection/diffraction from structures, and C) the effect of a modified wind field inside...... and on the lee side of the wind farm. The drag dissipation, A), is quantified by a quadratic resistance law. The effect of B) is parameterised based on 1st order potential theory. A method to find the amount of reflected and transmitted wave energy is developed based on the panel method WAMIT™ and a radiation...... condition at infinity. From airborne and Satellite SAR (Synthetic Aperture Radar) a model has been derived for the change of the water surface friction C) inside and on the lee side of the offshore wind farm. The effects have been implemented in a spectral wind wave model,MIKE21 SW, and a parametric study...

  5. Wave Forecasting Using Neuro Wavelet Technique

    Directory of Open Access Journals (Sweden)

    Pradnya Dixit

    2014-12-01

    Full Text Available In the present work a hybrid Neuro-Wavelet Technique is used for forecasting waves up to 6 hr, 12 hr, 18 hr and 24 hr in advance using hourly measured significant wave heights at an NDBC station 41004 near the east coast of USA. The NW Technique is employed by combining two methods, Discrete Wavelet Transform and Artificial Neural Networks. The hourly data of previously measured significant wave heights spanning over 2 years from 2010 and 2011 is used to calibrate and test the models. The discrete wavelet transform of NWT analyzes frequency of signal with respect to time at different scales. It decomposes time series into low (approximate and high (detail frequency components. The decomposition of approximate can be carried out up to desired multiple levels in order to provide more detail and approximate components which provides relatively smooth varying amplitude series. The neural network is trained with decorrelated approximate and detail wavelet coefficients. The outputs of networks during testing are reconstructed back using inverse DWT. The results were judged by drawing the wave plots, scatter plots and other error measures. The developed models show reasonable accuracy in prediction of significant wave heights from 6 to 24 hours. To compare the results traditional ANN models were also developed at the same location using the same data and for same time interval.

  6. Transmission of longitudinal wave through micro-porous elastic ...

    African Journals Online (AJOL)

    An investigation of reflection and transmission phenomena of plane longitudinal wave from a plane interface between two distinct micropolar porous elastic solid half-spaces in welded contact has been made. Using the method of potentials, the appropriate boundary conditions at the interface are solved to obtain the ...

  7. Transmission techniques for emergent multicast and broadcast systems

    CERN Document Server

    da Silva, Mario Marques; Dinis, Rui; Souto, Nuno; Silva, Joao Carlos

    2010-01-01

    Describing efficient transmission schemes for broadband wireless systems, Transmission Techniques for Emergent Multicast and Broadcast Systems examines advances in transmission techniques and receiver designs capable of supporting the emergent wireless needs for multimedia broadcast and multicast service (MBMS) requirements. It summarizes the research and development taking place in wireless communications for multimedia MBMS and addresses the means to improved spectral efficiency to allow for increased user bit rate, as well as increased capacity of the digital cellular radio network.The text

  8. Possibilities for Advanced Encoding Techniques at Signal Transmission in the Optical Transmission Medium

    Directory of Open Access Journals (Sweden)

    Filip Čertík

    2016-01-01

    Full Text Available This paper presents a possible simulation of negative effects in the optical transmission medium and an analysis for the utilization of different signal processing techniques at the optical signal transmission. An attention is focused on the high data rate signal transmission in the optical fiber influenced by linear and nonlinear environmental effects presented by the prepared simulation model. The analysis includes possible utilization of OOK, BPSK, DBPSK, BFSK, QPSK, DQPSK, 8PSK, and 16QAM modulation techniques together with RS, BCH, and LDPC encoding techniques for the signal transmission in the optical fiber. Moreover, the prepared simulation model is compared with real optical transmission systems. In the final part, a comparison of the selected modulation techniques with different encoding techniques and their implementation in real transmission systems is shown.

  9. Diodelike asymmetric transmission of linearly polarized waves using magnetoelectric coupling and electromagnetic wave tunneling.

    Science.gov (United States)

    Mutlu, Mehmet; Akosman, Ahmet E; Serebryannikov, Andriy E; Ozbay, Ekmel

    2012-05-25

    An asymmetric, reciprocal, diffraction-free transmission of linearly polarized waves in a new diodelike, three-layer, ultrathin, chiral structure is studied theoretically and experimentally. The exploited physical mechanism is based on the maximization of the cross-polarized transmission in one direction due to the polarization selectivity dictated by the peculiar eigenstate combination, which is efficiently controlled by the electromagnetic tunneling through the metallic subwavelength mesh sandwiched between these layers. Simulation and microwave experiment results demonstrate a nearly total intensity transmission at normal incidence in one direction and a small intensity transmission in the opposite direction.

  10. Asymmetric transmission of terahertz waves using polar dielectrics.

    Science.gov (United States)

    Serebryannikov, Andriy E; Ozbay, Ekmel; Nojima, Shunji

    2014-02-10

    Asymmetric wave transmission is a Lorentz reciprocal phenomenon, which can appear in the structures with broken symmetry. It may enable high forward-to-backward transmittance contrast, while transmission for one of the two opposite incidence directions is blocked. In this paper, it is demonstrated that ultrawideband, high-contrast asymmetric wave transmission can be obtained at terahertz frequencies in the topologically simple, i.e., one- or two-layer nonsymmetric gratings, which are entirely or partially made of a polar dielectric working in the ultralow-ε regime inspired by phonon-photon coupling. A variety of polar dielectrics with different characteristics can be used that gives one a big freedom concerning design. Simple criteria for estimating possible usefulness of a certain polar dielectric are suggested. Contrasts exceeding 80dB can be easily achieved without a special parameter adjustment. Stacking a high-ε corrugated layer with a noncorrugated layer made of a polar dielectric, one can enhance transmission in the unidirectional regime. At large and intermediate angles of incidence, a better performance can be obtained owing to the common effect of nonsymmetric diffractions and directional selectivity, which is connected with the dispersion of the ultralow-ε material. At normal incidence, strong asymmetry in transmission may occur in the studied structures as a purely diffraction effect.

  11. Fast cooling techniques for gravitational wave antennas

    CERN Document Server

    Furtado, S R

    2002-01-01

    The resonant-mass technique for the detection of gravitational waves may involve, in the near future, the cooling of very large masses (about 100 tons) from room temperature (300 K) to extreme cryogenic temperatures (20 mK). To cool these detectors to cryogenic temperatures an exchange gas (helium) is used, and the heat is removed from the antenna to the cold reservoir by thermal conduction and natural convection. With the current technique, cooling times of about 1 month can be obtained for cylindrical bar antennas of 2.5 tons. Should this same technique be used to cool a 100 ton spherical antenna the cooling time would be about 10 months, making the operation of these antennas impracticable. In this paper, we study the above-mentioned cooling technique and others, such as thermal switching and forced convection from room temperature to liquid nitrogen temperature (77 K) using an aluminium truncated icosahedron of 19 kg weight and 25 cm diameter.

  12. Reflection and transmission of electromagnetic waves at a temporal boundary.

    Science.gov (United States)

    Xiao, Yuzhe; Maywar, Drew N; Agrawal, Govind P

    2014-02-01

    We consider propagation of an electromagnetic (EM) wave through a dynamic optical medium whose refractive index varies with time. Specifically, we focus on the reflection and transmission of EM waves from a temporal boundary and clarify the two different physical processes that contribute to them. One process is related to impedance mismatch, while the other results from temporal scaling related to a sudden change in the speed of light at the temporal boundary. Our results show that temporal scaling of the electric field must be considered for light propagation in dynamic media. Numerical solutions of Maxwell's equations are in full agreement with our theory.

  13. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    Science.gov (United States)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  14. Wave transmission prediction of multilayer floating breakwater using neural network

    Digital Repository Service at National Institute of Oceanography (India)

    Mandal, S.; Patil, S.G.; Hegde, A.V.

    in unison to solve a specific problem. The network learns through examples, so it requires good examples to train properly and further a trained network model can be used for prediction purpose. Proceedings of ICOE 2009 Wave transmission... prediction of multilayer floating breakwater using neural network 577 In order to allow the network to learn both non-linear and linear relationships between input nodes and output nodes, multiple-layer neural networks are often used...

  15. Continuous wave terahertz transmission imaging of nonmelanoma skin cancers.

    Science.gov (United States)

    Joseph, Cecil S; Yaroslavsky, Anna N; Neel, Victor A; Goyette, Thomas M; Giles, Robert H

    2011-08-01

    Continuous wave terahertz imaging has the potential to offer a safe, noninvasive medical imaging modality for delineating human skin cancers. Terahertz pulse imaging (TPI) has already shown that there is contrast between basal cell carcinoma and normal skin. Continuous-wave imaging offers a simpler, lower cost alternative to TPI. The goal of this study was to investigate the feasibility of continuous wave terahertz imaging for delineating skin cancers by demonstrating contrast between cancerous and normal tissue in transmission mode. Two CO(2) optically pumped far-infrared molecular gas lasers were used for illuminating the tissue at two frequencies, 1.39 and 1.63 THz. The transmitted signals were detected using a liquid Helium cooled Silicon bolometer. Fresh skin cancer specimens were obtained from Mohs surgeries. The samples were processed and imaged within 24 hours after surgery. During the imaging experiment the samples were kept in pH-balanced saline to prevent tissue dehydration. At both THz frequencies two-dimensional THz transmission images of nonmelanoma skin cancers were acquired with spatial resolution of 0.39 mm at 1.4 THz and 0.49 mm at 1.6 THz. For evaluation purposes, hematoxylin and eosin (H&E) histology was processed from the imaged tissue. A total of 10 specimens were imaged and it was determined that for both frequencies, the areas of decreased transmission in the THz image correlated well with cancerous areas in the histopathology. Two negative controls were also imaged. The difference in transmission between normal and cancerous tissue was found to be approximately 60% at both frequencies, which suggests that contrast between normal and cancerous tissue at these frequencies is dominated by differences in water content. Our results suggest that intraoperative delineation of nonmelanoma skin cancers using continuous-wave terahertz imaging is feasible. Copyright © 2011 Wiley-Liss, Inc.

  16. Reflection and transmission of normally incident full-vector X waves on planar interfaces

    KAUST Repository

    Salem, Mohamed

    2011-12-23

    The reflection and transmission of full-vector X waves normally incident on planar half-spaces and slabs are studied. For this purpose, X waves are expanded in terms of weighted vector Bessel beams; this new decomposition and reconstruction method offers a more lucid and intuitive interpretation of the physical phenomena observed upon the reflection or transmission of X waves when compared to the conventional plane-wave decomposition technique. Using the Bessel beam expansion approach, we have characterized changes in the field shape and the intensity distribution of the transmitted and reflected full-vector X waves. We have also identified a novel longitudinal shift, which is observed when a full-vector X wave is transmitted through a dielectric slab under frustrated total reflection condition. The results of our studies presented here are valuable in understanding the behavior of full-vector X waves when they are utilized in practical applications in electromagnetics, optics, and photonics, such as trap and tweezer setups, optical lithography, and immaterial probing. © 2011 Optical Society of America.

  17. Micro-blast waves using detonation transmission tubing

    Science.gov (United States)

    Samuelraj, I. Obed; Jagadeesh, G.; Kontis, K.

    2013-07-01

    Micro-blast waves emerging from the open end of a detonation transmission tube were experimentally visualized in this study. A commercially available detonation transmission tube was used (Nonel tube, M/s Dyno Nobel, Sweden), which is a small diameter tube coated with a thin layer of explosive mixture (HMX + traces of Al) on its inner side. The typical explosive loading for this tube is of the order of 18 mg/m of tube length. The blast wave was visualized using a high speed digital camera (frame rate 1 MHz) to acquire time-resolved schlieren images of the resulting flow field. The visualization studies were complemented by computational fluid dynamic simulations. An analysis of the schlieren images showed that although the blast wave appears to be spherical, it propagates faster along the tube axis than along a direction perpendicular to the tube axis. Additionally, CFD analysis revealed the presence of a barrel shock and Mach disc, showing structures that are typical of an underexpanded jet. A theory in use for centered large-scale explosions of intermediate strength (10 blast trajectory along the tube axis. The energy of these micro-blast waves was found to be 1.25 ± 0.94 J and the average TNT equivalent was found to be 0.3. The repeatability in generating these micro-blast waves using the Nonel tube was very good (± 2 %) and this opens up the possibility of using this device for studying some of the phenomena associated with muzzle blasts in the near future.

  18. A Comparative Analysis of Transmission Control Protocol Improvement Techniques over Space-Based Transmission Media

    National Research Council Canada - National Science Library

    Lawson, Joseph M

    2006-01-01

    ... justification for the implementation of a given enhancement technique. The research questions were answered through model and simulation of a satellite transmission system via a Linux-based network topology...

  19. Recent techniques used in transmission line protection: A review ...

    African Journals Online (AJOL)

    include almost all the techniques and philosophies of transmission line protection reported in the literature up to October 2010. The focus of this article is on the most recent techniques, like artificial neural network, fuzzy logic, fuzzy-neuro, fuzzy logicwavelet based and phasor measurement unit-based concepts as well as ...

  20. Ultrafast vascular strain compounding using plane wave transmission.

    Science.gov (United States)

    Hansen, H H G; Saris, A E C M; Vaka, N R; Nillesen, M M; de Korte, C L

    2014-03-03

    Deformations of the atherosclerotic vascular wall induced by the pulsating blood can be estimated using ultrasound strain imaging. Because these deformations indirectly provide information on mechanical plaque composition, strain imaging is a promising technique for differentiating between stable and vulnerable atherosclerotic plaques. This paper first explains 1-D radial strain estimation as applied intravascularly in coronary arteries. Next, recent methods for noninvasive vascular strain estimation in a transverse imaging plane are discussed. Finally, a compounding technique that our group recently developed is explained. This technique combines motion estimates of subsequently acquired focused ultrasound images obtained at various insonification angles. However, because the artery moves and deforms during the multi-angle acquisition, errors are introduced when compounding. Recent advances in computational power have enabled plane wave ultrasound acquisition, which allows 100 times faster image acquisition and thus might resolve the motion artifacts. In this paper the performance of strain imaging using plane wave compounding is investigated using simulations of an artery with a vulnerable plaque and experimental data of a two-layered vessel phantom. The results show that plane wave compounding outperforms 0° focused strain imaging. For the simulations, the root mean squared error reduced by 66% and 50% for radial and circumferential strain, respectively. For the experiments, the elastographic signal-to-noise and contrast-to-noise ratio (SNR(e) and CNR(e)) increased with 2.1 dB and 3.7 dB radially, and 5.6 dB and 16.2dB circumferentially. Because of the high frame rate, the plane wave compounding technique can even be further optimized and extended to 3D in future. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Measurement of weld penetration depths in thin structures using transmission coefficients of laser-generated Lamb waves and neural network.

    Science.gov (United States)

    Yang, Lei; Ume, I Charles

    2017-07-01

    The Laser/EMAT ultrasonic (LEU) technique has shown the capability to measure weld penetration depths in thick structures based on ray-tracing of laser-generated bulk and surface waves. The ray-tracing method is not applicable to laser-generated Lamb waves when the LEU technique is used to measure weld penetration depths in thin structures. In this work, transmission coefficients of Lamb waves present in the LEU signals are investigated against varying weld penetration depths. An artificial neural network is developed to use transmission coefficients of sensitive Lamb waves and LEU signal energy to predict weld penetration depths accurately. The developed method is very attractive because it allows a quick inspection of weld penetration depths in thin structures. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Advanced Control Techniques for WEC Wave Dragon

    DEFF Research Database (Denmark)

    Tedd, James; Kofoed, Jens Peter; Jasinski, M.

    2007-01-01

    This paper presents the ongoing work on control of the Wave Dragon wave energy converter. Research is being conducted in and between several centers across Europe. This is building upon the knowledge gained in the prototype project, and will enable much better performance of the future deployment...

  3. Data analysis techniques for gravitational wave observations

    Indian Academy of Sciences (India)

    Abstract. Astrophysical sources of gravitational waves fall broadly into three categories: (i) transient and bursts, (ii) periodic or continuous wave and (iii) stochastic. Each type of source requires a different type of data analysis strategy. In this talk various data analysis strategies will be reviewed. Optimal filtering is used for ...

  4. Data analysis techniques for gravitational wave observations

    Indian Academy of Sciences (India)

    Astrophysical sources of gravitational waves fall broadly into three categories: (i) transient and bursts, (ii) periodic or continuous wave and (iii) stochastic. Each type of source requires a different type of data analysis strategy. In this talk various data analysis strategies will be reviewed. Optimal filtering is used for extracting ...

  5. Exact analytical representations for broadband transmission properties of quarter-wave multilayers.

    Science.gov (United States)

    Grigoriev, Victor; Biancalana, Fabio

    2011-10-01

    The formalism of the scattering matrix is applied to describe the transmission properties of multilayered structures with deep variations of the refractive index and arbitrary arrangements of the layers. We show that there is an exact analytical formula for the transmission spectrum, which is valid for the full spectral range and which contains only a limited number of parameters for structures satisfying the quarter-wave condition. These parameters are related to the poles of the scattering matrix, and we present an efficient algorithm to find them, which is based on considering the ray propagation inside the structure and subsequent application of the harmonic inversion technique. These results are significant for analyzing the reshaping of ultrashort pulses in multilayered structures. © 2011 Optical Society of America

  6. Phase study of the generated surface plasmon waves in light transmission through a subwavelength aperture

    DEFF Research Database (Denmark)

    Hashemi, Mahdieh; Xiao, Sanshui; Farzad, Mahmood Hosseini

    2014-01-01

    Interference of surface plasmon (SP) waves plays a key role in light transmission through a subwavelength aperture surrounded by groove structures. In order to characterize interference of the hole and groove-generated SP waves, their phase information was carefully investigated using finite...... difference time domain simulations. In a structure with only one groove, constructive interference of the generated SP waves will enhance transmitted light by a factor of 5.4 compared with that of a single hole. Increasing the groove number to 3 in the design, which supports constructive interference of SP...... waves, will enhance the transmission coefficient to 10.5 times that for the single-hole transmission coefficient....

  7. Microfabrication Techniques for Millimeter Wave Vacuum Electronics

    Science.gov (United States)

    2015-01-01

    Figure 4. (a) 220 GHz TWT circuit fabricated by UV-LIGA, (b) completed compact tube, (c) small signal gain, (d) power drive curve achieving 63 W...output. Demonstration A 220 GHz traveling wave tube ( TWT ) circuit was created using the UV-LIGA method with a photomask in two layers with the...gain TWTs . Acknowledgements This work was funded by the U.S. Office of Naval Research. The authors wish to thank R. E. Myers, B. S. Albright, and

  8. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial.

    Science.gov (United States)

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-02-16

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities.

  9. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial

    Science.gov (United States)

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-01-01

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities. PMID:28202903

  10. Optical communication equalized technique suitable for high-speed transmission

    Science.gov (United States)

    Zhu, Yaolin; Guan, Hao

    2017-07-01

    To solve the phase distortion and high error rate in optical signal transmission, an equalized technique is proposed, which aims to improve the constant modulus algorithm (CMA). In order to correct phase rotating and reduce the error rate with 64 quadrature amplitude modulation (QAM), the method takes the mean square error as the judgment and utilizes the time-varying step size. Simulation results demonstrate that the proposed algorithm can improve the convergence speed of constellation points, make the eye opening larger, and the signal noise ratio (SNR) can be increased by 4 dB under the same bit error rate (BER), which is efficient for the recovery of information in high-speed transmission.

  11. Reflection and transmission of full-vector X-waves normally incident on dielectric half spaces

    KAUST Repository

    Salem, Mohamed

    2011-08-01

    The reflection and transmission of full-vector X-Waves incident normally on a planar interface between two lossless dielectric half-spaces are investigated. Full-vector X-Waves are obtained by superimposing transverse electric and magnetic polarization components, which are derived from the scalar X-Wave solution. The analysis of transmission and reflection is carried out via a straightforward but yet effective method: First, the X-Wave is decomposed into vector Bessel beams via the Bessel-Fourier transform. Then, the reflection and transmission coefficients of the beams are obtained in the spectral domain. Finally, the transmitted and reflected X-Waves are obtained via the inverse Bessel-Fourier transform carried out on the X-wave spectrum weighted with the corresponding coefficient. © 2011 IEEE.

  12. A new shock wave assisted sandalwood oil extraction technique

    Science.gov (United States)

    Arunkumar, A. N.; Srinivasa, Y. B.; Ravikumar, G.; Shankaranarayana, K. H.; Rao, K. S.; Jagadeesh, G.

    A new shock wave assisted oil extraction technique from sandalwood has been developed in the Shock Waves Lab, IISc, Bangalore. The fragrant oil extracted from sandalwood finds variety of applications in medicine and perfumery industries. In the present method sandal wood specimens (2.5mm diameter and 25mm in length)are subjected to shock wave loading (over pressure 15 bar)in a constant area shock tube, before extracting the sandal oil using non-destructive oil extraction technique. The results from the study indicates that both the rate of extraction as well as the quantity of oil obtained from sandal wood samples exposed to shock waves are higher (15-40 percent) compared to non-destructive oil extraction technique. The compressive squeezing of the interior oil pockets in the sandalwood specimen due to shock wave loading appears to be the main reason for enhancement in the oil extraction rate. This is confirmed by the presence of warty structures in the cross-section and micro-fissures in the radial direction of the wood samples exposed to shock waves in the scanning electron microscopic investigation. In addition the gas chromatographic studies do not show any change in the q uality of sandal oil extracted from samples exposed to shock waves.

  13. The wave phase velocity in superconducting transmission lines near T{sub c}

    Energy Technology Data Exchange (ETDEWEB)

    Kuzhakhmetov, A.R.; Lobov, G.D.; Shtykov, V.V.; Zhgoon, S.A. [Moscow Power Engineering Inst. (Russian Federation). Radio Engineering Dept.

    1998-06-01

    A peculiarity in behavior of electromagnetic waves phase velocity ({nu}{sub ph}), propagating in superconducting planar transmission lines, in the vicinity of the transition temperature (T{sub c}) was observed in experiment and deduced theoretically. (orig.) 5 refs.

  14. Nonlinear Waves in Transmission Lines Periodically Loaded with Tunneling Diodes

    OpenAIRE

    Narahara, Koichi

    2010-01-01

    This chapter reviews the pulse propagation characteristics of TD lines.We found that a pulse wave propagates on the line either by theunstable exponential-sinusoidal hybrid mode or stable exponential-exponential mode. Through thesepeculiar wave propagation properties, an input impulse experiences width shortening and an edge of the step pulse oscillates. These provide efficient methods for generating short pulses and continuous waves. Moreover, TD lines can be used to manage pulse amplitude a...

  15. The wave surveyor technique for fast plasma wave detection in multi-spacecraft data

    Directory of Open Access Journals (Sweden)

    J. Vogt

    2008-06-01

    Full Text Available Multi-satellite missions like Cluster allow to study the full spatio-temporal variability of plasma processes in near-Earth space, and both the frequency and the wave vector dependence of dispersion relations can be reconstructed. Existing wave analysis methods include high-resolution beamformers like the wave telescope or k-filtering technique, and the phase differencing approach that combines the correlations measured at pairs of sensors of the spacecraft array. In this paper, we make use of the eigendecomposition of the cross spectral density matrix to construct a direct wave identification method that we choose to call the wave surveyor technique. The analysis scheme extracts only the dominant wave mode but is much faster to apply than existing techniques, hence it is expected to ease survey-type detection of waves in large data sets. The wave surveyor technique is demonstrated by means of synthetic data, and is also applied to Cluster magnetometer measurements.

  16. Experimental assessment of the influence of welding process parameters on Lamb wave transmission across ultrasonically welded thermoplastic composite joints

    Science.gov (United States)

    Ochôa, Pedro; Fernandez Villegas, Irene; Groves, Roger M.; Benedictus, Rinze

    2018-01-01

    One of the advantages of thermoplastic composites relative to their thermoset counterparts is the possibility of assembling components through welding. Ultrasonic welding in particular is very promising for industrialization. However, uncertainty in the fatigue and fracture behaviour of composites is still an obstacle to the full utilisation of these materials. Health monitoring is then of vital importance, and Lamb wave techniques have been widely recognised as some of the most promising approaches for that end. This paper presents the first experimental study about the influence of welding travel on the transmission of Lamb waves across ultrasonically welded thermoplastic composite joints in single-lap configuration. The main aim of this research is to start to understand how guided waves interact with the internal structure of ultrasonic welds, so that benign, manufacturing-related structural features can be distinguished from damaging ones in signal interpretation. The power transmission coefficient and the correlation coefficient proved to be suitable for analysing the wave propagation phenomena, allowing quantitative identification of small variations of weld-line thickness and intermolecular diffusion at the weld interface. The conclusions are used to develop a tentative damage detection criterion which can later on assist the design of a Lamb wave based structural health monitoring system for thermoplastic composite structures. The Lamb wave test results are backed up by phased-array inspections, which also provide some extra insight on the internal structure of ultrasonic welds.

  17. Exploiting the leaky-wave properties of transmission-line metamaterials for single-microphone direction finding.

    Science.gov (United States)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Hervé; Mosig, Juan R

    2016-06-01

    A transmission-line acoustic metamaterial is an engineered, periodic arrangement of relatively small unit-cells, the acoustic properties of which can be manipulated to achieve anomalous physical behaviours. These exotic properties open the door to practical applications, such as an acoustic leaky-wave antenna, through the implementation of radiating channels along the metamaterial. In the transmitting mode, such a leaky-wave antenna is capable of steering sound waves in frequency-dependent directions. Used in reverse, the antenna presents a well defined direction-frequency behaviour. In this paper, an acoustic leaky-wave structure is presented in the receiving mode. It is shown that it behaves as a sound source direction-finding device using only one sensor. After a general introduction of the acoustic leaky-wave antenna concept, its radiation pattern and radiation efficiency are expressed in closed form. Then, numerical simulations and experimental assessments of the proposed transmission-line based structure, implementing only one sensor at one termination, are presented. It is shown that such a structure is capable of finding the direction of an incoming sound wave, from backward to forward, based on received sound power spectra. This introduces the concept of sound source localization without resorting to beam-steering techniques based on multiple sensors.

  18. Studies on the transmission of sub-THz waves in magnetized inhomogeneous plasma sheath

    Science.gov (United States)

    Yuan, Kai; Shen, Linfang; Yao, Ming; Deng, Xiaohua; Chen, Zhou; Hong, Lujun

    2018-01-01

    There have been many studies on the sub-terahertz (sub-THz) wave transmission in reentry plasma sheaths. However, only some of them have paid attention to the transmission of sub-THz waves in magnetized plasma sheaths. In this paper, the transmission of sub-THz waves in both unmagnetized and magnetized reentry plasma sheaths was investigated. The impacts of temporal evolution of the plasma sheath on the wave transmission were studied. The transmission of "atmospheric window" frequencies in a magnetized plasma sheath was discussed in detail. According to the study, the power transmission rates (Tp) for the left hand circular (LHC) and the right hand circular modes in the magnetized plasma sheath are obviously higher and lower than those in the unmagnetized plasma sheath, respectively. The Tp of LHC mode increases with both wave frequency and external magnetic field strength. Also, the Tp of LHC mode in both magnetized and unmagnetized plasma sheaths varies with time due to the temporal evolution of the plasma sheath. Moreover, the performance of sub-THz waves in magnetized plasma sheath hints at a new approach to the "blackout" problem. The new approach, which is in the capability of modern technology, is to utilize the communication system operating at 140 GHz with an onboard magnet installed near the antenna.

  19. Optical sound wave recording by digital holography with heterodyne technique

    Science.gov (United States)

    Quan, Xiangyu; Rajput, Sudheesh; Nitta, Kouichi; Matoba, Osamu; Awatsuji, Yasuhiro

    2017-06-01

    A visualization technique of sound wave propagation using digital holography with heterodyne technique is presented. In the proposed method, the frequency of the interference pattern in an off-axis digital holography is down converted into the detectable frequency in an image sensor operated at the video frame rate by using the heterodyne interferometer. We present the principle of the recording technique and experimental results are described.

  20. Enhanced transmission of transverse electric waves through periodic arrays of structured subwavelength apertures

    DEFF Research Database (Denmark)

    Xiao, Sanshui; Peng, Liang; Mortensen, Asger

    2010-01-01

    Transmission through sub-wavelength apertures in perfect metals is expected to be strongly suppressed. However, by structural engineering of the apertures, we numerically demonstrate that the transmission of transverse electric waves through periodic arrays of subwavelength apertures in a thin...

  1. Propagation of nonlinear waves in bi-inductance nonlinear transmission lines

    Science.gov (United States)

    Kengne, Emmanuel; Lakhssassi, Ahmed

    2014-10-01

    We consider a one-dimensional modified complex Ginzburg-Landau equation, which governs the dynamics of matter waves propagating in a discrete bi-inductance nonlinear transmission line containing a finite number of cells. Employing an extended Jacobi elliptic functions expansion method, we present new exact analytical solutions which describe the propagation of periodic and solitary waves in the considered network.

  2. Transmission of electromagnetic waves through sub-wavelength channels

    DEFF Research Database (Denmark)

    Zhang, Jingjing; Luo, Yu; Mortensen, Asger

    2010-01-01

    We propose a method of tunneling electromagnetic (EM) waves through a channel with sub-wavelength cross section. By filling the channel with high-ε isotropic material and implementing two matching layers with uniaxial metamterial substrates, the guided waves can go through the narrow channel...... without being cut off, as if it has just passed through the original empty waveguide. Both the magnitude and phase information of the EM fields can be effectively restored after passing this channel, regardless of the polarization of the incoming wave. The performance of this subwavelength channel, which...

  3. Transmission of electromagnetic waves through sub-wavelength channels.

    Science.gov (United States)

    Zhang, Jingjing; Luo, Yu; Mortensen, Niels Asger

    2010-02-15

    We propose a method of tunneling electromagnetic (EM) waves through a channel with sub-wavelength cross section. By filling the channel with high-epsilon isotropic material and implementing two matching layers with uniaxial metamterial substrates, the guided waves can go through the narrow channel without being cut off, as if it has just passed through the original empty waveguide. Both the magnitude and phase information of the EM fields can be effectively restored after passing this channel, regardless of the polarization of the incoming wave. The performance of this sub-wavelength channel, which is designed with coordinate transformation methodology, is studied theoretically and numerically.

  4. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    Directory of Open Access Journals (Sweden)

    Jung-San Chen

    2016-09-01

    Full Text Available This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  5. Cylindrical millimeter-wave imaging technique for concealed weapon detection

    Science.gov (United States)

    Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.

    1998-03-01

    A novel cylindrical millimeter-wave imaging technique has been developed at the Pacific Northwest National Laboratory for the detection of metallic and non-metallic concealed weapons. This technique uses a vertical array of millimeter- wave antennas which is mechanically swept around a person in a cylindrical fashion. The wideband millimeter-wave data is mathematically reconstructed into a series of high- resolution images of the person being screened. Clothing is relatively transparent to millimeter-wave illumination,whereas the human body and concealed items are reflective at millimeter wavelengths. Differences in shape and reflectivity are revealed in the images and allow a human operator to detect and identify concealed weapons. A full 360 degree scan is necessary to fully inspect a person for concealed items. The millimeter-wave images can be formed into a video animation sequence in which the person appears to rotate in front of a fixed illumination source.This is s convenient method for presenting the 3D image data for analysis. This work has been fully sponsored by the FAA. An engineering prototype based on the cylindrical imaging technique is presently under development. The FAA is currently opposed to presenting the image data directly to the operator due to personal privacy concerns. A computer automated system is desired to address this problem by eliminating operator viewing of the imagery.

  6. Theory of reflection reflection and transmission of electromagnetic, particle and acoustic waves

    CERN Document Server

    Lekner, John

    2016-01-01

    This book deals with the reflection of electromagnetic and particle waves by interfaces. The interfaces can be sharp or diffuse. The topics of the book contain absorption, inverse problems, anisotropy, pulses and finite beams, rough surfaces, matrix methods, numerical methods,  reflection of particle waves and neutron reflection. Exact general results are presented, followed by long wave reflection, variational theory, reflection amplitude equations of the Riccati type, and reflection of short waves. The Second Edition of the Theory of Reflection is an updated and much enlarged revision of the 1987 monograph. There are new chapters on periodically stratified media, ellipsometry, chiral media, neutron reflection and reflection of acoustic waves. The chapter on anisotropy is much extended, with a complete treatment of the reflection and transmission properties of arbitrarily oriented uniaxial crystals. The book gives a systematic and unified treatment reflection and transmission of electromagnetic and particle...

  7. Survey of Temperature Measurement Techniques For Studying Underwater Shock Waves

    Science.gov (United States)

    Danehy, Paul M.; Alderfer, David W.

    2004-01-01

    Several optical methods for measuring temperature near underwater shock waves are reviewed and compared. The relative merits of the different techniques are compared, considering accuracy, precision, ease of use, applicable temperature range, maturity, spatial resolution, and whether or not special additives are required.

  8. Millimeter-wave Imaging Systems with Aperture Synthesis Techniques

    DEFF Research Database (Denmark)

    Löffler, Torsten; Krozer, Viktor; Zhurbenko, Vitaliy

    2010-01-01

    The paper describes development of a millimetre-wave imaging system using multi-element aperture filling techniques [1]. Such imaging systems are increasingly demonstrated for security applications and in particular standoff imaging of persons and bonding flaw and defect detection [2]. The major...

  9. Detection of Contrast Agents: Plane Wave Versus Focused Transmission

    NARCIS (Netherlands)

    J. Viti (Jacopo); H.J. Vos (Rik); N. de Jong (Nico); F. Guidi (Francesco); P. Tortoli (Piero)

    2016-01-01

    textabstractUltrasound contrast agent (UCA) imaging provides a cost-effective diagnostic tool to assess tissue perfusion and vascular pathologies. However, excessive transmission (TX) levels may negatively impact both uniform diffusion and survival rates of contrast agents, limiting their density

  10. Transmission line resonance technique for eccentric core optical fibers

    Science.gov (United States)

    Georgantzos, E.; Boucouvalas, A. C.

    2016-12-01

    In several cases optical fibers in telecommunications have cores of non circular geometry. Fibre optic deformations appear in optical fibres for many reasons. Optical fibre core ellipticity for example where the fibre optic core is not perfectly circular due to fibre optic manufacturing tolerances, is measured and often is a problem. Optical fibre core eccentricity, where the fibre core is not on the axis of the fibre, but it is offset by a small length. This is another issue and very important for ensuring performance low loss splices and connector losses. Both of ellipticity and eccentricity are specified in accordance to international standards for fibre optic manufacturing telecommunications grade fibres. The present paper studies ellipticity and core eccentricity specifically and presents a new method for analysing their effect. We present an extension of the transmission line technique as a means of studying such fibers and deriving necessary parameters. Conformal mapping on the other hand is a simple mathematical tool by which we can generate sets of orthogonal two-dimensional coordinate systems. Shortly a conformal map of Cartesian two-dimensional space is defined by any analytical function W(z) where z, w, are: z = x + jy, W = θ + j φ The function deriving by the conformal mapping transformation h(θ ,φ )=| ∂w/∂z | = 1/|∂z/∂w|, can be used in order to define ∇A → and ∇×A → where A → is the magnetic or electric field in the derived orthogonal coordinate system. Useful conformal maps for fiber optics applications should have the property that the equation θ(x, y) = constant, is forming closed curves in a Cartesian two-dimensional space (x,y). If θ(x, y) = constant represents a set of co-eccentric circles, we obtain the normal case of conventional fibers with circular cores. If θ(x, y) = constant represents a set of eclipses, we are have the formation of elliptic core optical fibers. If θ(x, y) = constant represents a set of

  11. Reflection and transmission of light waves from the air-magnetoplasma interface: Spatial and angular Imbert-Fedorov shifts

    Science.gov (United States)

    Borhanian, Jafar

    2015-03-01

    We have investigated the reflection and transmission of an electromagnetic wave from the air-magnetoplasma interface. The reflection and transmission coefficients are obtained for an arbitrary polarized incident wave. The spatial and angular Imbert-Fedorov (IF) shifts are discussed. The numerical results are presented to study the dependence of the reflection and transmission coefficients and IF shifts on relevant parameters of the system. The plasma and wave parameters can be used to control the reflection coefficients and IF shifts.

  12. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    Science.gov (United States)

    Host, Nicholas Keith; Chen, Chi-Chih; Volakis, John L.

    2012-01-01

    This presentation discussed a novel phased array with an emphasis to simplify the array feed. Specifically, we will demonstrate a simple, low cost feeding approach by mechanically controlling the substrate thickness. The array feed lines are constructed from parallel plate transmission lines whose thickness are adjusted to control their effective dielectric constant (Epsilon_eff). As a result the phase delay/excitation at each array element will be adjusted per desired beam direction. The proposed antenna elements will be overlapping dipoles operating over a 2:1 bandwidth in the Ku-Band spectrum. Preliminary simulation and experimental demonstration of such an array will be presented.

  13. Ultrafast vascular strain compounding using plane wave transmission

    NARCIS (Netherlands)

    Hansen, H.H.G.; Saris, A.E.C.M.; Vaka, N.R.; Nillesen, M.M.; Korte, C.L. de

    2014-01-01

    Deformations of the atherosclerotic vascular wall induced by the pulsating blood can be estimated using ultrasound strain imaging. Because these deformations indirectly provide information on mechanical plaque composition, strain imaging is a promising technique for differentiating between stable

  14. Wave propagation in and sound transmission through sandwich plates

    Science.gov (United States)

    Nilsson, A. C.

    1990-04-01

    Some dynamical and acoustical properties of sandwich plates are investigated. The types of sandwich elements discussed are three-layered plates with a thick lightweight core, with thin and comparatively stiff laminates bonded to each side of the core. In the model derived it is assumed that the laminates and core are isotropic. The laminates are treated as thin plates, whereas the deflection in the core is described by means of the general field equations. This means that bending shear and rotation, as well as longitudinal deflection, are considered in the core. Wavenumbers, loss factors and apparent bending stiffness for symmetric and asymmetric plates are derived. In addition, the sound transmission loss for sandwich plates is discussed. Measured and predicted results are compared. It is found that bending stiffness and loss factor not only depend on material parameters and plate geometries but also on frequency. The core thickness is very critical for the sound transmission loss of a sandwich plate. Sandwich plates are frequently used in the shipbuilding industry for light and fast passenger vessels. The effects of a fluid load on a sandwich plate is therefore also included.

  15. Structural damage diagnostics via wave propagation-based filtering techniques

    Science.gov (United States)

    Ayers, James T., III

    Structural health monitoring (SHM) of aerospace components is a rapidly emerging field due in part to commercial and military transport vehicles remaining in operation beyond their designed life cycles. Damage detection strategies are sought that provide real-time information of the structure's integrity. One approach that has shown promise to accurately identify and quantify structural defects is based on guided ultrasonic wave (GUW) inspections, where low amplitude attenuation properties allow for long range and large specimen evaluation. One drawback to GUWs is that they exhibit a complex multi-modal response, such that each frequency corresponds to at least two excited modes, and thus intelligent signal processing is required for even the simplest of structures. In addition, GUWs are dispersive, whereby the wave velocity is a function of frequency, and the shape of the wave packet changes over the spatial domain, requiring sophisticated detection algorithms. Moreover, existing damage quantification measures are typically formulated as a comparison of the damaged to undamaged response, which has proven to be highly sensitive to changes in environment, and therefore often unreliable. As a response to these challenges inherent to GUW inspections, this research develops techniques to locate and estimate the severity of the damage. Specifically, a phase gradient based localization algorithm is introduced to identify the defect position independent of excitation frequency and damage size. Mode separation through the filtering technique is central in isolating and extracting single mode components, such as reflected, converted, and transmitted modes that may arise from the incident wave impacting a damage. Spatially-integrated single and multiple component mode coefficients are also formulated with the intent to better characterize wave reflections and conversions and to increase the signal to noise ratios. The techniques are applied to damaged isotropic finite

  16. Wave propagation in fluids models and numerical techniques

    CERN Document Server

    Guinot, Vincent

    2012-01-01

    This second edition with four additional chapters presents the physical principles and solution techniques for transient propagation in fluid mechanics and hydraulics. The application domains vary including contaminant transport with or without sorption, the motion of immiscible hydrocarbons in aquifers, pipe transients, open channel and shallow water flow, and compressible gas dynamics. The mathematical formulation is covered from the angle of conservation laws, with an emphasis on multidimensional problems and discontinuous flows, such as steep fronts and shock waves. Finite

  17. Multiband Circular Polarizer Based on Fission Transmission of Linearly Polarized Wave for X-Band Applications

    Directory of Open Access Journals (Sweden)

    Farman Ali Mangi

    2016-01-01

    Full Text Available A multiband circular polarizer based on fission transmission of linearly polarized wave for x-band application is proposed, which is constructed of 2 × 2 metallic strips array. The linear-to-circular polarization conversion is obtained by decomposing the linearly incident x-polarized wave into two orthogonal vector components of equal amplitude and 90° phase difference between them. The innovative approach of “fission transmission of linear-to-circular polarized wave” is firstly introduced to obtain giant circular dichroism based on decomposition of orthogonal vector components through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer and two transmitted waves impinge on the upper printed strips layer to convert into four orthogonal vector components at the end of structure. This projection and transmission sequence of orthogonal components sustain the chain transmission of electromagnetic wave and can achieve giant circular dichroism. Theoretical analysis and microwave experiments are presented to validate the performance of the structure. The measured results are in good agreement with simulation results. In addition, the proposed circular polarizer exhibits the optimal performance with respect to the normal incidence. The right handed circularly polarized wave is emitted ranging from 10.08 GHz to 10.53 GHz and 10.78 GHz to 11.12 GHz, while the left handed circular polarized wave is excited at 10.54 GHz–10.70 GHz and 11.13 GHz–11.14 GHz, respectively.

  18. Preliminary design of high-power wave-guide/transmission system ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 59; Issue 5. Preliminary design of high-power wave-guide/transmission system for multimegawatt CW requirements of 100 MeV proton LINAC. Purushottam Shrivastava Y D Wanmode P R Hannurkar. Volume 59 Issue 5 November 2002 pp 829-834 ...

  19. Ultrafast vascular strain compounding using plane wave transmission

    OpenAIRE

    Hansen, H.H.G.; Saris, A.E.C.M.; Vaka, N.R.; Nillesen, M.M.; de Korte, C.L.

    2014-01-01

    Deformations of the atherosclerotic vascular wall induced by the pulsating blood can be estimated using ultrasound strain imaging. Because these deformations indirectly provide information on mechanical plaque composition, strain imaging is a promising technique for differentiating between stable and vulnerable atherosclerotic plaques. This paper first explains 1-D radial strain estimation as applied intravascularly in coronary arteries. Next, recent methods for noninvasive vascular strain es...

  20. An ultrasonic guided wave approach for the inspection of overhead transmission line cables

    DEFF Research Database (Denmark)

    Yücel, Mehmet K.; Legg, Mathew; Kappatos, Vasileios

    2017-01-01

    technique for untensioned aluminium conductor steel reinforced cable specimens. The identification and analysis of wave propagation for a broad range of frequencies is performed using a laser scanning vibrometer, and the effect of defect size on wave propagation is studied. Signal processing algorithms...

  1. Transmission properties of terahertz waves through asymmetric rectangular aperture arrays on carbon nanotube films

    Directory of Open Access Journals (Sweden)

    Yue Wang

    2016-04-01

    Full Text Available Transmission spectra of terahertz waves through a two-dimensional array of asymmetric rectangular apertures on super-aligned multi-walled carbon nanotube films were obtained experimentally. In this way, the anisotropic transmission phenomena of carbon nanotube films were observed. For a terahertz wave polarization parallel to the orientation of the carbon nanotubes and along the aperture short axis, sharp resonances were observed and the resonance frequencies coincided well with the surface plasmon polariton theory. In addition, the minima of the transmission spectra were in agreement with the location predicted by the theory of Wood’s anomalies. Furthermore, it was found that the resonance profiles through the carbon nanotube films could be well described by the Fano model.

  2. Analysis of the effect of a rectangular cavity resonator on acoustic wave transmission in a waveguide

    Science.gov (United States)

    Porter, R.; Evans, D. V.

    2017-11-01

    The transmission of acoustic waves along a two-dimensional waveguide which is coupled through an opening in its wall to a rectangular cavity resonator is considered. The resonator acts as a classical band-stop filter, significantly reducing acoustic transmission across a range of frequencies. Assuming wave frequencies below the first waveguide cut-off, the solution for the reflected and transmitted wave amplitudes is formulated exactly within the framework of inviscid linear acoustics. The main aim of the paper is to develop an approximation in closed form for reflected and transmitted amplitudes when the gap in the thin wall separating the waveguide and the cavity resonator is assumed to be small. This approximation is shown to accurately capture the effect of all cavities resonances, not just the fundamental Helmholtz resonance. It is envisaged this formula (and more generally the mathematical approach adopted) could be used in the development of acoustic metamaterial devices containing resonator arrays.

  3. Transmission of electromagnetic waves through a two-layer plasma structure with spatially nonuniform electron density.

    Science.gov (United States)

    Denysenko, I B; Ivko, S; Smolyakov, A; Azarenkov, N A

    2012-11-01

    Transmission of a p-polarized electromagnetic wave through a two-layer plasma structure with spatially nonuniform distributions of electron density in the layers is studied. The case, when the electromagnetic wave is obliquely incident on the structure and is evanescent in both plasma layers, is considered. The conditions for total transparency of the two-layer structure are found for the thin slab case and when the plasma inhomogeneity is weak. It is shown that the transmission coefficient of the p-polarized wave can be about unity, even if the plasma inhomogeneity is large. The effects of plasma inhomogeneity on transparency of the structure are more important if the slabs are thick, comparing with the case of thin layers.

  4. Special Course on Interaction of Propagation and Digital Transmission Techniques

    Science.gov (United States)

    1986-10-01

    fibre transmission systems may well operate with bandwidths approaching a GHz. Clearly, it is important to use bandwidth-efficient modulation schemes...reflection". Rep.250-5, Intern. Telecomm. Union, Geneva, 1982. C15] K.Rawer, " Optique geometrique de 1’ionosphere", Revue scientifique, 86, 1948

  5. Ionospheric wave and irregularity measurements using passive radio astronomy techniques

    Science.gov (United States)

    Erickson, W. C.; Mahoney, M. J.; Jacobson, A. R.; Knowles, S. H.

    1988-01-01

    The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities.

  6. The Transmission of Lamb Waves Across Adhesively Bonded lap Joints to Evaluate Interfacial Adhesive Properties

    Science.gov (United States)

    Siryabe, Emmanuel; Renier, Mathieu; Meziane, Anissa; Castaings, Michel

    The present work attempts to infer mechanical interfacial properties for lap joint like structures, using Lamb wave modes. A pair of air-coupled, ultrasonic transducers is used to generate and detect a desired Lamb mode. The Lamb waves are launched from one plate and propagate towards the other plate, via the joint. Signals are picked up by the receiving transducer, before and past the joint, and post-processed to obtain the experimental transmission coefficient versus frequency. In addition, a two-dimensional Finite Element-based model is developed and used to compare predicted transmission coefficients with experimental results. The FE model simulates the excitation produced by the transmittertakes into account the viscoelastic properties of the adhesive layer and distributions of longitudinal (kL) and shear (kT) springs at both interfaces between the adhesive and the substrates. Temporal responses of the receiving transducer are predicted before and past the joints, as well as the transmission coefficient versus frequency. This paper discusses preliminary results for aluminium substrates. Values for both kLand kTare optimized so that best fit is obtained between numerical and experimental transmission coefficients. These results demonstrate the potential of Lamb waves to infer mechanical properties at interfaces in adhesively bonded joints.

  7. Application of MIMO Techniques in sky-surface wave hybrid networking sea-state radar system

    Science.gov (United States)

    Zhang, L.; Wu, X.; Yue, X.; Liu, J.; Li, C.

    2016-12-01

    The sky-surface wave hybrid networking sea-state radar system contains of the sky wave transmission stations at different sites and several surface wave radar stations. The subject comes from the national 863 High-tech Project of China. The hybrid sky-surface wave system and the HF surface wave system work simultaneously and the HF surface wave radar (HFSWR) can work in multi-static and surface-wave networking mode. Compared with the single mode radar system, this system has advantages of better detection performance at the far ranges in ocean dynamics parameters inversion. We have applied multiple-input multiple-output(MIMO) techniques in this sea-state radar system. Based on the multiple channel and non-causal transmit beam-forming techniques, the MIMO radar architecture can reduce the size of the receiving antennas and simplify antenna installation. Besides, by efficiently utilizing the system's available degrees of freedom, it can provide a feasible approach for mitigating multipath effect and Doppler-spread clutter in Over-the-horizon Radar. In this radar, slow-time phase-coded MIMO method is used. The transmitting waveforms are phase-coded in slow-time so as to be orthogonal after Doppler processing at the receiver. So the MIMO method can be easily implemented without the need to modify the receiver hardware. After the radar system design, the MIMO experiments of this system have been completed by Wuhan University during 2015 and 2016. The experiment used Wuhan multi-channel ionospheric sounding system(WMISS) as sky-wave transmitting source and three dual-frequency HFSWR developed by the Oceanography Laboratory of Wuhan University. The transmitter system located at Chongyang with five element linear equi-spaced antenna array and Wuhan with one log-periodic antenna. The RF signals are generated by synchronized, but independent digital waveform generators - providing complete flexibility in element phase and amplitude control, and waveform type and parameters

  8. Reflection and transmission of thermo-elastic waves without energy dissipation at the interface of two dipolar gradient elastic solids.

    Science.gov (United States)

    Li, Yueqiu; Wei, Peijun

    2018-01-01

    The reflection and transmission of thermal elastic waves at the interface between two different dipolar gradient elastic solids are studied based on the generalized thermo-elastic theory of Green and Naghdi [(1993). J. Elasticity 31, 189-208] (type II of no energy dissipation). First, some thermodynamic formulas are generalized to a dipolar gradient elastic solid and the function of free energy density is postulated. Second, equations of thermal motion and constitutive relations in a dipolar gradient elasticity are derived. Then the nontraditional interfacial conditions are used to determine the amplitude ratio of the reflection and transmission waves with respect to the incident wave. Some numerical results of the reflection and transmission coefficients in the form of an energy flux ratio are given for different microstructure parameters while thermal parameters are fixed. The numerical results are validated by the consideration of energy conservation. It is found that there are a total of five modes of dispersive waves, namely, coupled MT1 wave, coupled MT2 wave, coupled MT3 wave, SV wave, and one evanescent wave which reduces to the surface waves at an interface, namely, SS wave. The thermal parameters mainly affect the coupled MT2 wave while the microstructure parameters affect not only the coupled waves but also the SS surface waves.

  9. In Vivo Characterization of Cortical Bone Using Guided Waves Measured by Axial Transmission.

    Science.gov (United States)

    Vallet, Quentin; Bochud, Nicolas; Chappard, Christine; Laugier, Pascal; Minonzio, Jean-Gabriel

    2016-09-01

    Cortical bone loss is not fully assessed by the current X-ray methods, and there is an unmet need in identifying women at risk of osteoporotic fracture, who should receive a treatment. The last decade has seen the emergence of the ultrasound (US) axial transmission (AT) techniques to assess a cortical bone. Recent AT techniques exploit the multimode waveguide response of the long bones such as the radius. A recent ex vivo study by our group evidenced that a multimode AT approach can yield simultaneous estimates of cortical thickness (Ct.Th) and stiffness. The aim of this paper is to move one step forward to evaluate the feasibility of measuring multimode guided waves (GW) in vivo and to infer from it cortical thickness. Measurements were taken on the forearm of 14 healthy subjects with the goal to test the accuracy of the estimated thickness using the bidirectional AT method implemented on a dedicated 1-MHz linear US array. This setup allows determining in vivo the dispersion curves of GW transmitted in the cortical layer of the radius. An inverse procedure based on the comparison between the measured and modeled dispersion curves predicted by a 2-D transverse isotropic free plate waveguide model allowed an estimation of cortical thickness, despite the presence of soft tissue. The Ct.Th values were validated by comparison with the site-matched estimates derived from X-ray high-resolution peripheral quantitative computed tomography. Results showed a significant correlation between both measurements ( r2 = 0.7 , , and [Formula: see text] mm). This pilot study demonstrates the potential of bidirectional AT for the in vivo assessment of cortical thickness, a bone strength-related factor.

  10. Increased range of ultrasonic guided wave testing of overhead transmission line cables using dispersion compensation.

    Science.gov (United States)

    Legg, Mathew; Yücel, Mehmet K; Kappatos, Vassilios; Selcuk, Cem; Gan, Tat-Hean

    2015-09-01

    Overhead Transmission Line (OVTL) cables can experience structural defects and are, therefore, inspected using Non-Destructive Testing (NDT) techniques. Ultrasonic Guided Waves (UGW) is one NDT technique that has been investigated for inspection of these cables. For practical use, it is desirable to be able to inspect as long a section of cable as possible from a single location. This paper investigates increasing the UGW inspection range on Aluminium Conductor Steel Reinforced (ACSR) cables by compensating for dispersion using dispersion curve data. For ACSR cables, it was considered to be difficult to obtain accurate dispersion curves using modelling due to the complex geometry and unknown coupling between wire strands. Group velocity dispersion curves were, therefore, measured experimentally on an untensioned, 26.5m long cable and a method of calculating theoretical dispersion curves was obtained. Attenuation and dispersion compensation were then performed for a broadband Maximum Length Sequence (MLS) excitation signal. An increase in the Signal to Noise Ratio (SNR) of about 4-8dB compared to that of the dispersed signal was obtained. However, the main benefit was the increased ability to resolve the individual echoes from the end of the cable and an introduced defect in the form of a cut, which was 7 to at least 13dB greater than that of the dispersed signal. Five echoes were able to be clearly detected using MLS excitation signal, indicating the potential for an inspection range of up to 130m in each direction. To the best of the authors knowledge, this is the longest inspection range for ACSR cables reported in the literature, where typically cables, which were only one or two meter long, have been investigated previously. Narrow band tone burst and Hann windowed tone burst excitation signal also showed increased SNR and ability to resolve closely spaced echoes. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Downlink Multihop Transmission Technique for Asymmetric Traffic Accommodation in DS-CDMA/FDD Cellular Communications

    Science.gov (United States)

    Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo

    This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission to downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, vacant uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The relay route selection method and power control method for the multihop transmissions are also investigated in the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

  12. Analysis of the transmission characteristics of radio waves in inhomogeneous weakly ionized dusty plasma sheath based on high order SO-DGTD

    Directory of Open Access Journals (Sweden)

    Bing Wei

    Full Text Available Based on high order hierarchical basis function and the ideal of shift operator, shift operator discontinuous Galerkin time domain (SO-DGTD technique for dealing with weakly ionized dusty plasma electromagnetic problems is proposed. Lagrange interpolation is used to transform the metallic blunt cone aircraft with weakly ionized dusty plasma sheath from geometric model built by COMSOL to electromagnetic computational model. In the case of two-dimensional transverse magnetic (TM wave, the electromagnetic wave propagation in weakly ionized dusty plasma sheath is calculated by SO-DGTD technique. And then, the influence of dust particle concentration and dust radius on the radio wave transmission is analyzed, and the radio wave propagation characteristics pass through the sheath is compared with the flight speed and height change. Keywords: SO-DGTD, Weakly ionized dusty plasma sheath, High order hierarchical basis function

  13. Analysis of the transmission characteristics of radio waves in inhomogeneous weakly ionized dusty plasma sheath based on high order SO-DGTD

    Science.gov (United States)

    Wei, Bing; Li, Linqian; Yang, Qian; Ge, Debiao

    Based on high order hierarchical basis function and the ideal of shift operator, shift operator discontinuous Galerkin time domain (SO-DGTD) technique for dealing with weakly ionized dusty plasma electromagnetic problems is proposed. Lagrange interpolation is used to transform the metallic blunt cone aircraft with weakly ionized dusty plasma sheath from geometric model built by COMSOL to electromagnetic computational model. In the case of two-dimensional transverse magnetic (TM) wave, the electromagnetic wave propagation in weakly ionized dusty plasma sheath is calculated by SO-DGTD technique. And then, the influence of dust particle concentration and dust radius on the radio wave transmission is analyzed, and the radio wave propagation characteristics pass through the sheath is compared with the flight speed and height change.

  14. Transmission characteristics of the S0 and A0 Lamb waves at contacting edges of plates.

    Science.gov (United States)

    Mori, Naoki; Biwa, Shiro

    2017-11-01

    In order to gain basic insight into the interaction between ultrasonic guided waves and structural discontinuities with contacting surfaces, the transmission characteristics of Lamb waves at contacting edges of two plates are studied experimentally. The edges of two 2.5-mm thick aluminum alloy plates are mated together to constitute a contacting interface of plates and subjected to different levels of compressive loading. The transmission measurements of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb modes across the contacting interface are performed in a frequency range below the cut-off frequencies of the higher-order modes. As a result, it is found that the transmission coefficient of the S0 mode increases monotonically with the applied contact pressure, but the transmission coefficient of the A0 mode exhibits non-monotonic dependence on the contact pressure and the frequency showing a local minimum. For the incidence of the S0 mode, the resonance at the contacting interface is observed as a long-time oscillation tail in the transmission waveform. The resonance frequency is found to increase with the contact pressure. The experimental results are discussed in the light of the theoretical results based on the spring-type interface model. The normal and tangential stiffnesses of the contacting interface are identified from the transmission coefficients as well as from the resonance frequency. The estimated interfacial stiffnesses increase monotonically with the contact pressure, and indicate their dependence on the frequency. Implications of the present results to the Lamb-wave based characterization of the plate contact condition are discussed briefly. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Study of transmission line attenuation in broad band millimeter wave frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Hitesh Kumar B. [ITER-India, IPR, Gandhinagar, Gujarat (India); Austin, M. E. [Institute for Fusion Studies, the University of Texas at Austin, Austin, Texas (United States); Ellis, R. F. [Laboratory for Plasma and Fusion Energy Studies, University of Maryland, College Park, Maryland 20742 (United States)

    2013-10-15

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  16. Study of transmission line attenuation in broad band millimeter wave frequency range.

    Science.gov (United States)

    Pandya, Hitesh Kumar B; Austin, M E; Ellis, R F

    2013-10-01

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  17. mm-Wave Hybrid Photonic Wireless Links for Ultra-High Speed Wireless Transmissions

    DEFF Research Database (Denmark)

    Rommel, Simon; Vegas Olmos, Juan José; Tafur Monroy, Idelfonso

    Hybrid photonic-wireless transmission schemes in the mm-wave frequency range are promising candidates to enable the multi-gigabit per second data communications required from wireless and mobile networks of the 5th and future generations. Large FCC spectrum allocations for wireless transmission...... at 71–76GHz and 81–86GHz allow high-bandwidth, long and medium distance point-to-point links. Photonic integration may pave the way to practical applicability of such hybrid links by reduction in complexity, size and – most important – cost....

  18. Power transmission through a hollow cylinder by acoustic waves and piezoelectric transducers with radial polarization

    Science.gov (United States)

    Lü, C. F.; Yang, J. S.; Wang, J.; Chen, W. Q.

    2009-09-01

    Transmission of electric energy through an elastic hollow cylinder by acoustic waves is investigated using the linear theories of piezoelectricity and elasticity. The elastic cylinder is between two perfectly bonded piezoelectric layers of piezoelectric ceramics with radial polarization. Power transmission is achieved through the electrical excitation of axisymmetric thickness-stretch vibrations. An exact solution is obtained which is validated by comparison with a solution from the state space method (SSM). Numerical results are presented for the transmitted voltage, power, efficiency, input admittance, and the radial distributions of displacement and stress. The effects of the load impedance and driving frequency are examined.

  19. 146-GHz millimeter-wave radio-over-fiber photonic wireless transmission system.

    Science.gov (United States)

    Fice, M J; Rouvalis, E; van Dijk, F; Accard, A; Lelarge, F; Renaud, C C; Carpintero, G; Seeds, A J

    2012-01-16

    We report the experimental implementation of a wireless transmission system with a 146-GHz carrier frequency which is generated by optical heterodyning the two modes from a monolithically integrated quantum dash dual-DFB source. The monolithic structure of the device and the inherent low noise characteristics of quantum dash gain material allow us to demonstrate the transmission of a 1 Gbps ON-OFF keyed data signal with the two wavelengths in a free-running state at 146-GHz carrier wave frequency. The tuning range of the device fully covers the W-band (75 - 110 GHz) and the F-band (90 - 140 GHz).

  20. All-dielectric metasurface realizing giant asymmetric transmission for linearly polarized wave

    Science.gov (United States)

    Pan, Weikang; Kang, Yuanyuan; Wang, Chuan; Tang, Dengfei; Dong, Jianfeng

    2018-01-01

    In this paper, a kind of chiral all-dielectric metasurface is demonstrated numerically to achieve giant asymmetric transmission (AT) in fiber communication region. The incoming polarized electromagnetic wave excites magnetic and electric resonances and the resonances in AT spectrum coincide with eigen frequencies of this structure. The all dielectric metasurface shows more excellent properties compared with its metal counterpart. AT is influenced significantly by material permittivity as well as unit cell period. The concept of all-dielectric metasurface offers a new way to manipulate electromagnetic waves and the phenomenon remains effective in other frequencies.

  1. Asymmetric transmission and polarization conversion of linearly polarized waves with bilayer L-shaped metasurfaces

    Science.gov (United States)

    Shang, Xiong-Jun; Zhai, Xiang; Wang, Ling-Ling; He, Meng-Dong; Li, Quan; Luo, Xin; Duan, Hui-Gao

    2017-05-01

    We numerically and theoretically investigate the optical anisotropy of ultra-thin bilayer L-shaped metal metasurfaces separated by a 200-nm-thick silicon dioxide (SiO2) substrate spacer. A broadband asymmetric transmission (AT) to forward and backward propagate electromagnetic waves can be acquired from linearly polarized waves. Additionally, narrowband cross-polarization conversion (CPC) can be realized by x linearly polarized electromagnetic illumination. The calculated results demonstrate that the full width at half maximum (FWHM) of AT is 965 nm, and the maximum value of the asymmetric parameter can reach up to 0.48. The polarization conversion rate (PCR) for CPC is more than 80%.

  2. Role of spatial dispersion of electromagnetic wave at its transmission through quantum well

    CERN Document Server

    Korovin, L I; Contreras-Solorio, D A; Pavlov, S T

    2001-01-01

    The theory on the light transmission through the quantum well, placed in the strong magnetic field, perpendicular to the well plane, wherein the interzone transitions take place, is developed. The light wave length is assumed to be comparable with the well width. The formulae for reflection, absorption and transmission wherein the spatial dispersion of the monochromatic light wave and the difference in the reflection indices of the quantum well and the barrier are accounted for, are obtained. It is shown that accounting for these factors effects the reflection most of all, because along with the reflection, caused by the interzonal transitions in the quantum well there appears the additional reflection from the well boundaries. The most radical changes in the reflection take place in the case, when the reverse radiation lifetime of the excited state in the quantum well is shorter as compared to the reverse non-radiation lifetime

  3. Gigabit radio-over-fiber link for converged baseband and millimeter-wave band signal transmission using cascaded injection-locked Fabry-Pérot laser diodes.

    Science.gov (United States)

    Hong, Moon-Ki; Won, Yong-Yuk; Han, Sang-Kook

    2009-05-11

    A novel scheme, for both baseband and millimeter-wave band gigabit data transmission in radio-over-fiber system, is proposed and experimentally demonstrated by using cascaded injection-locked Fabry- Pérot laser diodes. It was able to improve suppression ratio of carrier suppressed signal using the cascaded injection-locking. The suppression ratio improvement of the optical carrier suppressed signal of 20 dB was verified. Applying this mechanism, 60-GHz millimeter-wave carrier of enhanced signal quality could be accomplished. Its peak power and phase noise were obtained as -40 dBm and -103.5 dBm/Hz respectively, which was suitable for 60-GHz data transmission. In addition, a successful bidirectional transmission of 1.25-Gbps wired and wireless data was achieved by adopting remodulation technique using a gain-saturated reflective semiconductor optical amplifier for uplink.

  4. Ignition of a Thermonuclear Detonation Wave in the Focus of Two Magnetically Insulated Transmission Lines

    Science.gov (United States)

    Winterberg, F.

    2003-04-01

    For the ignition of a thermonuclear detonation wave assisted by a strong magnetic field, it is proposed to use two concentrically nested magnetically insulated transmission lines, the inner one transmitting a high- voltage lower-current-, and the outer one a high-current lower-voltage- electromagnetic pulse drawn from two Marx generators. The concept has the potential of large thermonuclear gains with an input energy conceivably as small as 105 J.

  5. Resent developments in high-frequency surface-wave techniques

    Science.gov (United States)

    Xia, J.; Pan, Y.; Zeng, C.

    2012-12-01

    High-frequency Rayleigh-wave methods, such as Multi-channel Analysis of Surface Waves (MASW), are getting increasingly attention in the near-surface geophysics and geotechnique community in the last 20 years because of their non-invasive, non-destructive, efficient, and low-cost advantages and their success in environmental and engineering applications. They are viewed by near-surface geophysics community as the one of most promise techniques in the future. However, they face unique problems related to extremely irregular velocity variations in near-surface geology or man-made constructions, for example, highway, foundation, dam, levee, jetty, etc., which are not solvable by techniques or algorithms widely used in earthquake seismology or oil/gas seismic exploration. We present solutions to the problems associated with near-surface materials that possess velocity inverse and high Poisson's ratio. Calculation of dispersion curves by existing algorithms may fail for some special velocity models due to velocity inverse (a high-velocity layer on the top of a low-velocity layer). Two velocity models are most common in near-surface applications. One is a low-velocity half space model and the other a high-velocity topmost layer. The former model results in a complex matrix that no roots can be found in the real number domain, which implies that no phase velocities can be calculated in certain frequency ranges based on current exist algorithms. A solution is to use the real part of the root of the complex number. It is well-known that phase velocities approach about 91% of the shear (S)-wave velocity of the topmost layer when wavelengths are much shorter than the thickness of the topmost layer. The later model, however, results in that phase velocities in a high-frequency range calculated using the current algorithms approach a velocity associated with the S-wave velocity of the second layer NOT the topmost layer. A solution to this problem is to use a two-layer model to

  6. Thermal wave interferometry of gas-liquid using optical fibre thermal wave resonator cavity technique

    Energy Technology Data Exchange (ETDEWEB)

    Azmi, B Z; Noroozi, M; Sulaiman, Z A; Wahab, Z A; Moksin, M M, E-mail: azmizak@gmail.co [Physics Department, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2010-03-01

    The optical fibre thermal wave resonator cavity (OF-TWRC) technique was used to measure thermal diffusivity of a two-layer sample; air-liquid. The thermal waves were generated by transmitting the modulated laser beam through one end of optical fibre and illuminating the other fibre end surface that metalised with silver paint. The cavity length scan was done by moving the fibre end surface towards the pyroelectric detector continuously through air and then into the liquid. A good linear relationship of pyroelectric amplitude with respect to cavity length was obtained in thermally thick region in both media; air and liquid. The thermal diffusivity of air, glycerol and water obtained were closed to the literature values.

  7. Optimization of hydrostatic transmissions by means of virtual instrumentation technique

    Science.gov (United States)

    Ion Guta, Dragos Daniel; Popescu, Teodor Costinel; Dumitrescu, Catalin

    2010-11-01

    Obtaining mathematical models, as close as possible to physical phenomena which are intended to be replicated or improved, help us in deciding how to optimize them. The introduction of computers in monitoring and controlling processes caused changes in technological systems. With support from the methods for identification of processes and from the power of numerical computing equipment, researchers and designers can shorten the period for development of applications in various fields by generating a solution as close as possible to reality, since the design stage [1]. The paper presents a hybrid solution of modeling / simulation of a hydrostatic transmission with mixed adjustment. For simulation and control of the examined process we have used two distinct environments, AMESim and LabVIEW. The proposed solution allows coupling of the system's model to the software control modules developed using virtual instrumentation. Simulation network of the analyzed system was "tuned" and validated by an actual model of the process. This paper highlights some aspects regarding energy and functional advantages of hydraulic transmissions based on adjustable volumetric machines existing in their primary and secondary sectors [2].

  8. Controlling the transmission of ultrahigh frequency bulk acoustic waves in silicon by 45° mirrors.

    Science.gov (United States)

    Wang, Shengxiang; Gao, Jiaming; Carlier, Julien; Campistron, Pierre; NDieguene, Assane; Guo, Shishang; Matar, Olivier Bou; Dorothee, Debavelaere-Callens; Nongaillard, Bertrand

    2011-07-01

    In this paper, we present a feasible microsystem in which the direction of localized ultrahigh frequency (∼1GHz) bulk acoustic wave can be controlled in a silicon wafer. Deep etching technology on the silicon wafer makes it possible to achieve high aspect ratio etching patterns which can be used to control bulk acoustic wave to transmit in the directions parallel to the surface of the silicon wafer. Passive 45° mirror planes obtained by wet chemical etching were employed to reflect the bulk acoustic wave. Zinc oxide (ZnO) thin film transducers were deposited by radio frequency sputtering with a thickness of about 1μm on the other side of the wafer, which act as emitter/receptor after aligned with the mirrors. Two opponent vertical mirrors were inserted between the 45° mirrors to guide the transmission of the acoustic waves. The propagation of the bulk acoustic wave was studied with simulations and the characterization of S(21) scattering parameters, indicating that the mirrors were efficient to guide bulk acoustic waves in the silicon wafer. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Dual-frequency continuous-wave terahertz transmission imaging of nonmelanoma skin cancers

    Science.gov (United States)

    Joseph, Cecil S.; Yaroslavsky, Anna N.; Lagraves, Julie L.; Goyette, Thomas M.; Giles, Robert H.

    2010-02-01

    Continuous wave terahertz imaging has the potential for diagnosing and delineating skin cancers. While contrast has been observed between cancerous and normal tissue at terahertz frequencies, the source mechanism behind this contrast is not clearly understood.1Transmission measurements of 240μm thick sections of nonmelanoma skin cancer were taken at two frequencies of 1.39 THz and 1.63 THz that lie within and outside the tryptophan absorption band, respectively. Two CO2 pumped Far-Infrared molecular gas lasers were used for illuminating the tissue while the transmitted signals were detected using a liquid Helium cooled Silicon bolometer. At both THz frequencies 2-dimensional THz transmission images of nonmelanoma skin cancers were acquired with better than 0.5mm spatial resolution. The resulting images were compared to the sample histology and showed a correlation between cancerous tissue and decreased transmission. The results of the imaging experiments will be presented and discussed.

  10. First Eigenmode Transmission by High Efficient CSI Estimation for Multiuser Massive MIMO Using Millimeter Wave Bands

    Directory of Open Access Journals (Sweden)

    Kazuki Maruta

    2016-07-01

    Full Text Available Drastic improvements in transmission rate and system capacity are required towards 5th generation mobile communications (5G. One promising approach, utilizing the millimeter wave band for its rich spectrum resources, suffers area coverage shortfalls due to its large propagation loss. Fortunately, massive multiple-input multiple-output (MIMO can offset this shortfall as well as offer high order spatial multiplexing gain. Multiuser MIMO is also effective in further enhancing system capacity by multiplexing spatially de-correlated users. However, the transmission performance of multiuser MIMO is strongly degraded by channel time variation, which causes inter-user interference since null steering must be performed at the transmitter. This paper first addresses the effectiveness of multiuser massive MIMO transmission that exploits the first eigenmode for each user. In Line-of-Sight (LoS dominant channel environments, the first eigenmode is chiefly formed by the LoS component, which is highly correlated with user movement. Therefore, the first eigenmode provided by a large antenna array can improve the robustness against the channel time variation. In addition, we propose a simplified beamforming scheme based on high efficient channel state information (CSI estimation that extracts the LoS component. We also show that this approximate beamforming can achieve throughput performance comparable to that of the rigorous first eigenmode transmission. Our proposed multiuser massive MIMO scheme can open the door for practical millimeter wave communication with enhanced system capacity.

  11. Broadband asymmetric transmission of linearly polarized electromagnetic waves based on chiral metamaterial

    Science.gov (United States)

    Stephen, Lincy; Yogesh, N.; Subramanian, V.

    2018-01-01

    The giant optical activity of chiral metamaterials (CMMs) holds great potential for tailoring the polarization state of an electromagnetic (EM) wave. In controlling the polarization state, the aspect of asymmetric transmission (AT), where a medium allows the EM radiation to pass through in one direction while restricting it in the opposite direction, adds additional degrees of freedom such as one-way channelling functionality. In this work, a CMM formed by a pair of mutually twisted slanted complementary metal strips is realized for broadband AT accompanied with cross-polarization (CP) conversion for linearly polarized EM waves. Numerically, the proposed ultra-thin (˜λ/42) CMM shows broadband AT from 8.58 GHz to 9.73 GHz (bandwidth of 1.15 GHz) accompanied with CP transmission magnitude greater than 0.9. The transmission and reflection spectra reveal the origin of the asymmetric transmission as the direction sensitive cross polarization conversion and anisotropic electric coupling occurring in the structure which is then elaborated with the surface current analysis and electric field distribution within the structure. An experiment is carried out to verify the broadband AT based CP conversion of the proposed CMM at microwave frequencies, and a reliable agreement between numerical and experimental results is obtained. Being ultra-thin, the reported broadband AT based CP conversion of the proposed CMM is useful for controlling radiation patterns in non-reciprocal EM devices and communication networks.

  12. Transmission, attenuation and reflection of shear waves in the human brain.

    Science.gov (United States)

    Clayton, Erik H; Genin, Guy M; Bayly, Philip V

    2012-11-07

    Traumatic brain injuries (TBIs) are caused by acceleration of the skull or exposure to explosive blast, but the processes by which mechanical loads lead to neurological injury remain poorly understood. We adapted motion-sensitive magnetic resonance imaging methods to measure the motion of the human brain in vivo as the skull was exposed to harmonic pressure excitation (45, 60 and 80 Hz). We analysed displacement fields to quantify the transmission, attenuation and reflection of distortional (shear) waves as well as viscoelastic material properties. Results suggest that internal membranes, such as the falx cerebri and the tentorium cerebelli, play a key role in reflecting and focusing shear waves within the brain. The skull acts as a low-pass filter over the range of frequencies studied. Transmissibility of pressure waves through the skull decreases and shear wave attenuation increases with increasing frequency. The skull and brain function mechanically as an integral structure that insulates internal anatomic features; these results are valuable for building and validating mathematical models of this complex and important structural system.

  13. The short-wave broadband communication device for transmission the analog narrowband signals

    Directory of Open Access Journals (Sweden)

    Andreyev O.V.

    2016-12-01

    Full Text Available The transmission of information via the radio channel always involves the selection of radio waves modulation and the frequency band occupied by the radio signal. For the narrowband analog signals, the transmission via the radio channels in areas with difficult terrain the short-wave range is widely used. The majority of radio stations use frequency modulation of the transmitter without any message encryption. This gives the opportunity to detect and intercept messages that are transmitted. The use of the voice scramblers allows to hide information that is transmitted via the communication channel, but it is impossible to hide the radiation of the transmitter. The article suggests the use of a broadband signal with a modulation which is not associated with the change of the frequency of the transmitter in accordance with information, which is transmitted. The calculations showed that the proposed communication system can operate in a common frequency band with existing narrowband means of the short-wave range not creating them the substantial interference. The calculated signal/noise ratio on the input of the radio signals monitoring receiver is almost two orders less than for existing narrowband means of the short-wave range.

  14. Large-scale transmission-type multifunctional anisotropic coding metasurfaces in millimeter-wave frequencies

    Science.gov (United States)

    Cui, Tie Jun; Wu, Rui Yuan; Wu, Wei; Shi, Chuan Bo; Li, Yun Bo

    2017-10-01

    We propose fast and accurate designs to large-scale and low-profile transmission-type anisotropic coding metasurfaces with multiple functions in the millimeter-wave frequencies based on the antenna-array method. The numerical simulation of an anisotropic coding metasurface with the size of 30λ × 30λ by the proposed method takes only 20 min, which however cannot be realized by commercial software due to huge memory usage in personal computers. To inspect the performance of coding metasurfaces in the millimeter-wave band, the working frequency is chosen as 60 GHz. Based on the convolution operations and holographic theory, the proposed multifunctional anisotropic coding metasurface exhibits different effects excited by y-polarized and x-polarized incidences. This study extends the frequency range of coding metasurfaces, filling the gap between microwave and terahertz bands, and implying promising applications in millimeter-wave communication and imaging.

  15. A flexible millimeter-wave radio-over-fiber system for various transmission bit rate

    Science.gov (United States)

    Yang, Tao; Gao, Mingyi; Qian, Jiaqin; Zhang, Junfeng; Chen, Wei

    2017-11-01

    In this paper, we propose a flexible scheme to generate millimeter-waves (MMWs) for millimeter-wave radio-over-fiber (MMW-RoF) system. The proposed scheme has two configurations to adapt to various transmission bit rate by slightly rearranging the allocation of the system. The main structure of the system is cascaded LiNbO3 Mach-Zehnder modulators (LiNbO3-MZMs). The first configuration is cost effective method, where we utilize a wavelength division multiplexing de-multiplexer (WDM Demux) and an optical splitter (OS) to generate two unmodulated optical signals and a modulated optical signal. Each unmodulated optical signal and the modulated signal will form an optical single sideband (OSSB) modulation and therefore we simultaneously achieve a Q-band (45 GHz) and a V-band (60 GHz) MMWs in the receiver. The bit-error-ratio (BER) curves show that the power penalties of 45 GHz and 60 GHz are 0.6 dB and 1.1 dB at a BER of 1 × 10-9 with 2.5 Gb/s transmission data rate and 50 km fiber transmission distances. The second configuration can accommodate high bit rate, where few optical devices is rearranged to only generate a 60 GHz MMW with 40 Gb/s 4 quadrature amplitude modulation orthogonal frequency division multiplexing (4-QAM OFDM) signals. The power penalty is 1.1 dB at a BER of 1 × 10-9 with 50 km fiber transmission distances. Therefore, the proposed scheme can flexibly generate either two Q&V-band MMWs (45 GHz and 60 GHz) for the applications of the low data-rate transmission systems or one V-band MMW (60 GHz) for the applications of the high data-rate transmission systems.

  16. A Code Division Technique for Multiple Element Synthetic Aperture Transmission

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt; Jakobsson, Andreas

    2004-01-01

    . The method was verified using Field II. A 7 MHz transducer was simulated with 128 receiving elements and 64 transmitting elements divided into subapertures so that 4 virtual transmission centers were formed. The point spread function was measured and the axial resolution was 0.2312 mm (-3dB) and 0.3083 mm...... (-6dB), lateral resolution 0.5301 mm (-3dB) and 0.7068 mm (-6dB) and maximum lateral sidelobe level less than 44 dB. Conventional STA is given as a reference with the same setup excited with a single cycle sinusoid at 7 MHz with axial resolution 0.2312 mm (-3dB) and 0.3083 mm (-6dB), lateral...... resolution 0.5301 mm (-3dB) and 0.7068 mm (-6dB) and maximum lateral sidelobe level less than 44 dB....

  17. Real-time holographic deconvolution techniques for one-way image transmission through an aberrating medium: characterization, modeling, and measurements

    Science.gov (United States)

    Haji-Saeed, B.; Sengupta, S. K.; Testorf, M.; Goodhue, W.; Khoury, J.; Woods, C. L.; Kierstead, J.

    2006-05-01

    We propose and demonstrate a new photorefractive real-time holographic deconvolution technique for adaptive one-way image transmission through aberrating media by means of four-wave mixing. In contrast with earlier methods, which typically required various codings of the exact phase or two-way image transmission for correcting phase distortion, our technique relies on one-way image transmission through the use of exact phase information. Our technique can simultaneously correct both amplitude and phase distortions. We include several forms of image degradation, various test cases, and experimental results. We characterize the performance as a function of the input beam ratios for four metrics: signal-to-noise ratio, normalized root-mean-square error, edge restoration, and peak-to-total energy ratio. In our characterization we use false-color graphic images to display the best beam-intensity ratio two-dimensional region(s) for each of these metrics. Test cases are simulated at the optimal values of the beam-intensity ratios. We demonstrate our results through both experiment and computer simulation.

  18. Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

    Directory of Open Access Journals (Sweden)

    Markel Penalba

    2017-07-01

    Full Text Available Considering the full dynamics of the different conversion stages from ocean waves to the electricity grid is essential to evaluate the realistic power flow in the drive train and design accurate model-based control formulations. The power take-off system for wave energy converters (WECs is one of the essential parts of wave-to-wire (W2W models, for which hydraulic transmissions are a robust solution and offer the flexibility to design specific drive-trains for specific energy absorption requirements of different WECs. The potential hydraulic drive train topologies can be classified into two main configuration groups (constant-pressure and variable-pressure configurations, each of which uses specific components and has a particular impact on the preceding and following stages of the drive train. The present paper describes the models for both configurations, including the main nonlinear dynamics, losses and constraints. Results from the mathematical model simulations are compared against experimental results obtained from two independent test rigs, which represent the two main configurations, and high-fidelity software. Special attention is paid to the impact of friction in the hydraulic cylinder and flow and torque losses in the hydraulic motor. Results demonstrate the effectiveness of the models in reproducing experimental results, capturing friction effects and showing similar losses.

  19. Wave transmission over permeable submerged breakwaters; Transmision del oleaje en rompeolas sumergidos permeables

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-y-Zurvia-Flores, Jaime Roberto; Fragoso-Sandoval, Lucio [Instituto Politecnico Nacional(Mexico)

    2008-10-15

    The permeable submerged breakwaters represent a coastal protection alternative, where some degree of wave energy transmission is acceptable. Such would be the case of tourist beach protection in Mexico. In previous researches, like those performed by D'Angremond et al. (1996), Seabrook and Hall (1998), and Briganti et al. (2003), the empirical formulas developed, give only some limited information over the spatial distribution of wave energy over the structure. Therefore, a decision was made to conduct a study on a reduced physical model of a permeable submerged breakwater based on the results presented by those researchers and with possible applications. Therefore this paper presents the development of a study of wave transmission over permeable submerged breakwaters performed in a reduced physical model of different sections of a submerged rockfill breakwater of the trapezoidal type. This was done in a narrow wave flume with a hydraulic irregular wave generator controlled by a computer that was used to generate and to reproduce different types of irregular waves to be used in the tests. It also has a wave meter with four sensors, and they are connected to a computer in order to process the wave data. The main objective of the study was to determine in an experimental way the influence of the several parameters of submerged breakwater over the wave transmission coefficient. Our experimental results were comparable to those obtained by D'Angremond et al. (1996) and Seabrook and Hall (1998). The results show that the sumerged breakwater parameters of most influence over the wave transmission coefficient were relative submergence and the relative width crest of the sumerged breakwater, and that the formula by Seabrook and Hall correlates best with our results. [Spanish] Los rompeolas sumergidos permeables representan actualmente una alternativa de proteccion de costas, donde un cierto grado de transmision de energia del oleaje es aceptable, como seria el

  20. Eigenvalues analysis for EM waves in anisotropic materials and its applications for unidirectional transmission and unidirectional invisibility

    Science.gov (United States)

    Wu, Xiaohu; Jin, Can; Fu, Ceji

    2017-11-01

    We conduct a comprehensive analysis of the eigenvalues for propagation of electromagnetic (EM) waves in anisotropic materials. The analysis can be employed to judge the characteristics of the eigenvalues for EM waves in anisotropic materials. Taking the advantage of the non-opposite eigenvalues, we show that unidirectional transmission and unidirectional invisibility can be realized with a slab of natural anisotropic material. Our results in this work may provide important guidelines for design of novel devices of unidirectional transmission or unidirectional invisibility.

  1. Charge mitigation techniques using glow and corona discharges for advanced gravitational wave detectors

    Science.gov (United States)

    Campsie, P.; Cunningham, L.; Hendry, M.; Hough, J.; Reid, S.; Rowan, S.; Hammond, G. D.

    2011-11-01

    Charging of silica test masses in gravitational wave detectors could potentially become a significant low-frequency noise source for advanced detectors. Charging noise has already been observed and confirmed in the GEO600 detector and is thought to have been observed in one of the LIGO detectors. In this paper, two charge mitigation techniques using glow and corona discharges were investigated to create repeatable and robust procedures. The glow discharge procedure was used to mitigate charge under vacuum and would be intended to be used in the instance where an optic has become charged while the detector is in operation. The corona discharge procedure was used to discharge samples at atmospheric pressure and would be intended to be used to discharge the detector optics during the cleaning of the optics. Both techniques were shown to reduce both polarities of surface charge on fused silica to a level that would not limit advanced LIGO. Measurements of the transmission of samples that had undergone the charge mitigation procedures showed no significant variation in transmission, at a sensitivity of ~ 200 ppm, in TiO2-doped Ta2O5/SiO2 multi-layer coated fused silica.

  2. Reflection and transmission of elastic waves through a couple-stress elastic slab sandwiched between two half-spaces

    Science.gov (United States)

    Wang, Changda; Chen, Xuejun; Wei, Peijun; Li, Yueqiu

    2017-12-01

    The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, there are three types of elastic waves in the couple-stress elastic solid, two of which are dispersive. The interface conditions between two couple-stress solids involve the surface couple and rotation apart from the surface traction and displacement. The nontraditional interface conditions between the slab and two solid half-spaces are used to obtain the linear algebraic equation sets from which the amplitude ratios of reflection and transmission waves to the incident wave can be determined. Then, the energy fluxes carried by the various reflection and transmission waves are calculated numerically and the normal energy flux conservation is used to validate the numerical results. The special case, couple-stress elastic slab sandwiched by the classical elastic half-spaces, is also studied and compared with the situation that the classical elastic slab sandwiched by the classical elastic half-spaces. Incident longitudinal wave (P wave) and incident transverse wave (SV wave) are both considered. The influences of the couple-stress are mainly discussed based on the numerical results. It is found that the couple-stress mainly influences the transverse modes of elastic waves.

  3. Development of a hybrid wave based-transfer matrix model for sound transmission analysis.

    Science.gov (United States)

    Dijckmans, A; Vermeir, G

    2013-04-01

    In this paper, a hybrid wave based-transfer matrix model is presented that allows for the investigation of the sound transmission through finite multilayered structures placed between two reverberant rooms. The multilayered structure may consist of an arbitrary configuration of fluid, elastic, or poro-elastic layers. The field variables (structural displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The boundary and continuity conditions in the rooms determine the participation factors in the pressure expansions. The displacement of the multilayered structure is determined by the mechanical impedance matrix, which gives a relation between the pressures and transverse displacements at both sides of the structure. The elements of this matrix are calculated with the transfer matrix method. First, the hybrid model is numerically validated. Next a comparison is made with sound transmission loss measurements of a hollow brick wall and a sandwich panel. Finally, numerical simulations show the influence of structural damping, room dimensions and plate dimensions on the sound transmission loss of multilayered structures.

  4. Electromagnetic wave localization using a left-handed transmission-line superlens

    Science.gov (United States)

    Cui, Tie Jun; Cheng, Qiang; Huang, Zhi Zhong; Feng, Yijun

    2005-07-01

    We realize the localization of electromagnetic (EM) waves and energies using a left-handed transmission-line (LHTL) superlens. A detailed procedure is given to design right-handed and left-handed transmission-line media, which correspond to a vacuum and a slightly mismatched anti-vacuum, respectively. After properly designed and properly matched with terminal loads, we have generated a LHTL superlens. With the aid of microwave circuit simulations using the Agilent’s advanced design system (ADS), we show that nearly all EM fields and energies are confined in a region between two voltage sources with the same amplitude and anti-phases when they are placed at the image points of the superlens. In the simulation results, strong surface waves are clearly observed, which are consistent with the theoretical analysis of a homogeneous and slightly lossy left-handed medium superlens. Here, the slight loss is caused by the spatial dispersion of the transmission-line networks. We also show that different mismatches of the left-handed anti-vacuum will result in a different performance of the LHTL superlens, which are governed by the circuit parameters. Finally, the tolerance of circuit parameters to the energy localization is discussed.

  5. High-Resolution Transmission Electron Microscopy - and Associated Techniques

    Science.gov (United States)

    Buseck, Peter; Cowley, John; Eyring, Leroy

    1989-02-01

    This book provides an introduction to the fundamental concepts, techniques, and methods used for electron microscopy at high resolution in space, energy, and even in time. It delineates the theory of elastic scattering, which is most useful for spectroscopic and chemical analyses. There are also discussions of the theory and practice of image calculations, and applications of HRTEM to the study of solid surfaces, highly disordered materials, solid state chemistry, mineralogy, semiconductors and metals. Contributors include J. Cowley, J. Spence, P. Buseck, P. Self, and M.A. O'Keefe. Compiled by experts in the fields of geology, physics and chemistry, this comprehensive text will be the standard reference for years to come.

  6. A Data Transmission Technique for Personal Health Systems

    Directory of Open Access Journals (Sweden)

    Jih-Fu Tu

    2013-01-01

    Full Text Available We used the modular technique to design a personal health data transmitter (PHDT that is composed of the following components: (1 the core is an embedded signal chip, (2 three kinds of transmutation modules such as USB, RF, and UART, (3 an I2C interface is used to acquire the users data, and (4 through Internet it links to the cloud server to store the personal-health data. By the experiment, we find that the modular manner is feasible, stable of functional, integral, and accurate, while it is exploited to design the PHDT. For the experiment, we present each module algorithm to find that our system is very helpful to people.

  7. Evaluation of Shipboard Wave Estimation Techniques through Model-scale Experiments

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam; Galeazzi, Roberto; H. Brodtkorb, Astrid

    2016-01-01

    The paper continues a study on the wave buoy analogy that uses shipboard measurements to estimate sea states. In the present study, the wave buoy analogy is formulated directly in the time domain and relies only partly on wave-vessel response amplitude operators (RAOs), which is in contrast to all...... previous works that either are formulated in the frequency domain and/or depend entirely on RAOs. Specifically, the paper evaluates a novel concept for wave estimation based on combined techniques using a wave frequency estimator, not dependent on RAOs, to detect wave frequency and, respectively, nonlinear...... least squares fitting to estimate wave amplitude and phase. The concept has been previously tested with only numerical simulations but in this study the techniques are applied to model-scale experiments. It is shown that the techniques successfully can be used to estimate the wave parameters...

  8. Observation of nonreciprocal transmission in binary phase-shift keying modulation using traveling-wave Mach-Zehnder modulators.

    Science.gov (United States)

    Dong, Po; Gui, Chengcheng

    2016-06-15

    In coherent optical transmission, traveling-wave Mach-Zehnder modulators are commonly used to generate various advanced formats where the modulators are biased at the minimum transmission point. Here, we report that an optical isolation effect with lower backward transmission occurs under this condition. This concept is successfully demonstrated to achieve ∼7  dB isolation over a 90-nm wavelength span under binary phase-shift keying modulation using a commercial lithium niobate modulator.

  9. Measured and calculated transmission losses of sound waves through a helium layer

    Science.gov (United States)

    Norum, T. D.

    1973-01-01

    An experiment was performed to measure the transmission losses of sound waves traversing an impedance layer. The sound emanated from a point source and the impedance layer was created by a low-speed helium jet. The transmission losses measured were of the order of 12 db for frequencies of the source between 4 and 12 kHz. These losses are greater than those predicted from analysis when the observer angle is less than about 35 deg, but less than those predicted for larger observer angles. The experimental results indicate that appreciable noise reductions can be realized for an observer shielded by an impedance layer, irrespective of his position relative to the source of sound.

  10. Optical and millimeter-wave radio seamless MIMO transmission based on a radio over fiber technology.

    Science.gov (United States)

    Kanno, Atsushi; Kuri, Toshiaki; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Yasumura, Yoshihiro; Kitayama, Ken-ichi

    2012-12-31

    Multi-input multi-output (MIMO) transmission of two millimeter-wave radio signals seamlessly converted from polarization-division-multiplexed quadrature-phase-shift-keying optical signals is successfully demonstrated, where a radio access unit basically consisting of only optical-to-electrical converters and a radio receiver performs total signal equalization of both the optical and the radio paths and demodulation with digital signal processing (DSP). Orthogonally polarized optical components that are directly converted to two-channel radio components can be demultiplexed and demodulated with high-speed DSP as in optical digital coherent detection. 20-Gbaud optical and radio seamless MIMO transmission provides a total capacity of 74.4 Gb/s with a forward error correction overhead of 7%.

  11. Enhancing Secrecy With Multiantenna Transmission in Millimeter Wave Vehicular Communication Systems

    KAUST Repository

    Eltayeb, Mohammed E.

    2017-03-14

    Millimeter wave (mmWave) vehicular communication systems will provide an abundance of bandwidth for the exchange of raw sensor data and support driver-assisted and safety-related functionalities. Lack of secure communication links, however, may lead to abuses and attacks that jeopardize the efficiency of transportation systems and the physical safety of drivers. In this paper, we propose two physical layer (PHY) security techniques for vehicular mmWave communication systems. The first technique uses multiple antennas with a single radio-frequency (RF) chain to transmit information symbols to a target receiver and noise-like signals in nonreceiver directions. The second technique uses multiple antennas with a few RF chains to transmit information symbols to a target receiver and opportunistically inject artificial noise in controlled directions, thereby reducing interference in vehicular environments. Theoretical and numerical results show that the proposed techniques provide higher secrecy rate when compared to traditional PHY security techniques that require digital or more complex antenna architectures.

  12. An Interference-Aware Distributed Transmission Technique for Dense Small Cell Networks

    DEFF Research Database (Denmark)

    Mahmood, Nurul Huda; Berardinelli, Gilberto; Pedersen, Klaus I.

    2015-01-01

    transmission technique that can efficiently manage the interference in an uncoordinated dense small cell network is investigated in this work. The proposed interference aware scheme only requires instantaneous channel state information at the transmitter end towards the desired receiver. Motivated by penalty...... methods in optimization studies, an interference dependent weighting factor is introduced to control the number of parallel transmission streams. The proposed scheme can outperform a more complex benchmark transmission scheme in terms of the sum network throughput in certain scenarios and with realistic...

  13. Infrared and millimeter waves v.14 millimeter components and techniques, pt.V

    CERN Document Server

    Button, Kenneth J

    1985-01-01

    Infrared and Millimeter Waves, Volume 14: Millimeter Components and Techniques, Part V is concerned with millimeter-wave guided propagation and integrated circuits. In addition to millimeter-wave planar integrated circuits and subsystems, this book covers transducer configurations and integrated-circuit techniques, antenna arrays, optoelectronic devices, and tunable gyrotrons. Millimeter-wave gallium arsenide (GaAs) IMPATT diodes are also discussed. This monograph is comprised of six chapters and begins with a description of millimeter-wave integrated-circuit transducers, focusing on vario

  14. A Paging Indicator Transmission Technique for Mobile WiMAX Systems

    Science.gov (United States)

    Kim, Yeong-Jun; Yoo, Hyun-Il; Woo, Kyung-Soo; Lee, Jung-Ryun; Lee, Heesoo; Cho, Yong-Soo

    In a cellular system, efficient power saving techniques for a mobile station (MS) are necessary because of its inherently limited battery capacity. The paging indicator (PI) transmission scheme in CDMA cellular systems is known to be an effective power saving strategy. However, in OFDM-based cellular systems, the MS has to operate FFT for PI symbol detection, resulting in a significant power consumption. In this letter, a PI transmission technique with reduced power consumption using the preamble in OFDM-based cellular systems, especially for mobile WiMAX systems, is proposed for the MS under power saving mode. Simulations indicate a 30-50% power saving from our proposed PI transmission technique, at the expense of a slight increase in paging response delay.

  15. Physical optics and full-wave simulations of transmission of electromagnetic fields through electrically large planar meta-sheets

    Science.gov (United States)

    Öziş, Ezgi; Osipov, Andrey V.; Eibert, Thomas F.

    2017-09-01

    Ultra-thin metamaterials, called meta-surfaces or meta-sheets, open up new opportunities in designing microwave radomes, including an improved transmission over a broader range of antenna scan angles, tailorable and reconfigurable frequency bands, polarization transformations, one-way transmission and switching ability. The smallness of the unit cells combined with the large electrical size of microwave radomes significantly complicates full-wave numerical simulations as a very fine sampling over an electrically large area is required. Physical optics (PO) can be used to approximately describe transmission through the radome in terms of the homogenized transmission coefficient of the radome wall. This paper presents the results of numerical simulations of electromagnetic transmission through planar meta-sheets (infinite and circularly shaped) obtained by using a full-wave electromagnetic field simulator and a PO-based solution.

  16. Fluorescence enhancement and nonreciprocal transmission of light waves by nanomaterial interfaces

    Science.gov (United States)

    Nyman, M.; Shevchenko, A.; Kaivola, M.

    2017-11-01

    In an optically absorbing or amplifying linear medium, the energy flow density of interfering optical waves is in general periodically modulated in space. This makes the wave transmission through a material boundary, as described by the Fresnel transmission coefficients, nonreciprocal and apparently violating the energy conservation law. The modulation has been previously described in connection to ordinary homogeneous nonmagnetic materials. In this work, we extend the description to nanomaterials with designed structural units that can be magnetic at optical frequencies. We find that in such a "metamaterial" the modulation in energy flow can be used to enhance optical far-field emission in spite of the fact that the material is highly absorbing. We also demonstrate a nanomaterial design that absorbs light, but simultaneously eliminates the power flow modulation and returns the reciprocity, which is impossible to achieve with a nonmagnetic material. We anticipate that these unusual optical effects can be used to increase the efficiency of nanostructured light emitters and absorbers, such as light-emitting diodes and solar cells.

  17. Development of Wireless Techniques in Data and Power Transmission - Application for Particle Physics Detectors

    CERN Document Server

    Locci, E.; Dehos, C.; De Lurgio, P.; Djurcic, Z.; Drake, G.; Gimenez, J. L. Gonzalez; Gustafsson, L.; Kim, D.W.; Roehrich, D.; Schoening, A.; Siligaris, A.; Soltveit, H.K.; Ullaland, K.; Vincent, P.; Wiednert, D.; Yang, S.; Brenner, R.

    2015-01-01

    Wireless techniques have developed extremely fast over the last decade and using them for data and power transmission in particle physics detectors is not science- fiction any more. During the last years several research groups have independently thought of making it a reality. Wireless techniques became a mature field for research and new developments might have impact on future particle physics experiments. The Instrumentation Frontier was set up as a part of the SnowMass 2013 Community Summer Study [1] to examine the instrumentation R&D for the particle physics research over the coming decades: {\\guillemotleft} To succeed we need to make technical and scientific innovation a priority in the field {\\guillemotright}. Wireless data transmission was identified as one of the innovations that could revolutionize the transmission of data out of the detector. Power delivery was another challenge mentioned in the same report. We propose a collaboration to identify the specific needs of different projects that m...

  18. Axial Wave Reflection and Transmission in Stepped Nanorods Using Doublet Mechanics Theory

    Directory of Open Access Journals (Sweden)

    Aydogdu Metin

    2018-01-01

    Full Text Available A numerical investigation of the reflection and transmission of axial waves at stepped nanorods is presented. The scale dependent doublet mechanics theory is used in the analysis. The main difference of the doublet mechanics from other scale dependent models (stress gradient, strain gradient and couple stress theories is its direct dependence to the micro/nano structure of the solid. Scale parameter is directly related to atomic structure of the material in doublet mechanics theory and it is assumed as carbon-carbon bond length in the present study. However, identification of scale parameters in other scale dependent theories is difficult compared to doublet mechanics theory. Governing equations of stepped nanorods are derived in the framework of doublet mechanics using the Hamilton Principle. The numerical results predicted by doublet mechanics are shown and compared with the classical elasticity.

  19. Review of radio wave for power transmission in medical applications with safety

    Science.gov (United States)

    Day, John; Geddis, Demetris; Kim, Jaehwan; Choi, Sang H.; Yoon, Hargsoon; Song, Kyo D.

    2015-04-01

    The integration of biosensors with radio frequency (RF) wireless power transmission devices is becoming popular, but there are challenges for implantable devices in medical applications. Integration and at the same time miniaturization of medical devices in a single embodiment are not trivial. The research reported herein, seeks to review possible effects of RF signals ranging from 900 MHz to 100 GHz on the human tissues and environment. Preliminary evaluation shows that radio waves selected for test have substantial influence on human tissues based on their dielectric properties. In the advancement of RF based biosensors, it is imperative to set up necessary guidelines that specify how to use RF power safely. In this paper, the dielectric properties of various human tissues will be used for estimation of influence within the selected RF frequency ranges.

  20. Critical diameter for the transmission of a detonation wave into a porous medium

    Energy Technology Data Exchange (ETDEWEB)

    Makris, A.; Oh, T.J.; Lee, J.H.S.; Knystautas, R. [McGill Univ., Montreal, Quebec (Canada)

    1994-12-31

    An experimental investigation has been undertaken to elucidate the existence of a critical diameter for the transmission of gaseous detonation into a porous medium. A Chapman-Jouguet (CJ) detonation is first established in a tube and allowed to transmit through an orifice plate into a porous medium comprised of inert spheres of equal diameter. It is found that detonation can successfully transmit past the orifice for diameters much smaller than the normal critical diameter (d{sub c}) of the mixture. An immediate transition from detonation to quasi-detonation normally takes place upon wave entry in the porous medium. Failure of detonation is observed to take place downstream of the orifice in the near-limit regime and is followed by deflagration to detonation transition (DDT) within the porous medium. Wave velocities in the porous medium are found to be identical to the corresponding values measured for direct transmission (without an orifice). For subcritical conditions, there is complete quenching of combustion in the pores. The critical composition (lean and rich) for mixtures with high activation energy is found to be practically the same as the propagation limits in the porous medium without an orifice. This indicates that the phenomenon is governed by the smallest physical dimension of the pore size, and thus a local failure mechanism exists. In mixtures highly diluted with argon, i.e., (C{sub 2}H{sub 2}-O{sub 2}) + 75% Ar, which have, a lower activation energy and for which the ``d{sub c} = 13{lambda}`` correlation (where {lambda} is the cell size) is known to break down, the critical composition appears to depend on the orifice diameter. The orifice now introduces a larger controlling length scale at the limits compared to the pore size, indicating that a global failure mechanism may prevail for such mixtures. Present findings are consistent with a local and global failure mechanism for normal detonation failure recently proposed by Lee.

  1. Comment on "Dynamics and properties of waves in a modified Noguchi electrical transmission line".

    Science.gov (United States)

    Kenmogne, Fabien; Yemélé, David; Marquié, Patrick

    2016-09-01

    A recent paper [Phys. Rev. E 91, 022925 (2015)PRESCM1539-375510.1103/PhysRevE.91.022925] presents the derivation of the nonlinear equation modeling envelope waves in a specific case of band passed filter discrete nonlinear electrical transmission line (NLTL), called "A modified Noguchi electrical transmission line" according to the authors. Using the reductive perturbation approach in the semidiscrete approximation, they showed that the modulated waves propagating in this NLTL are described by the ordinary nonlinear Schrödinger (NLS) equation. On the basis of their results, the authors claimed that all previous works on the band passed filter NLTL, which considered the vanishing of the dc component of the signal voltage, are incorrect, and this dc term is nonzero. As a consequence, the dispersion and nonlinearity coefficients of the NLS equation are strongly different from those usually obtained, and they found, according to the sign of the product PQ, the existence of one more region (compared to the work of Marquié et al. [Phys. Rev. E 49, 828 (1994)]PLEEE81063-651X10.1103/PhysRevE.49.828) in the dispersion curve that allows the motion of envelope solitons of higher frequency in the system. In this Comment we provide sufficient theoretical and numerical evidence showing that the evidence obtained by the authors otherwise is due to certain terms missed in their mathematical developments when they derived the NLS equation. Our results also suggest that the previous work of Marquié and co-workers correctly predict the fact that the dc term of the signal voltage does not exist and there exist only two regions in the dispersion curve according to the sign of the product PQ.

  2. Wave Characteristics in Breaststroke Technique with and Without Snorkel Use

    Science.gov (United States)

    Conceição, Ana; Silva, António J.; Boaventura, José; Marinho, Daniel A.; Louro, Hugo

    2013-01-01

    The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables. PMID:24511354

  3. Anatomy-based transmission factors for technique optimization in portable chest x-ray

    Science.gov (United States)

    Liptak, Christopher L.; Tovey, Deborah; Segars, William P.; Dong, Frank D.; Li, Xiang

    2015-03-01

    Portable x-ray examinations often account for a large percentage of all radiographic examinations. Currently, portable examinations do not employ automatic exposure control (AEC). To aid in the design of a size-specific technique chart, acrylic slabs of various thicknesses are often used to estimate x-ray transmission for patients of various body thicknesses. This approach, while simple, does not account for patient anatomy, tissue heterogeneity, and the attenuation properties of the human body. To better account for these factors, in this work, we determined x-ray transmission factors using computational patient models that are anatomically realistic. A Monte Carlo program was developed to model a portable x-ray system. Detailed modeling was done of the x-ray spectrum, detector positioning, collimation, and source-to-detector distance. Simulations were performed using 18 computational patient models from the extended cardiac-torso (XCAT) family (9 males, 9 females; age range: 2-58 years; weight range: 12-117 kg). The ratio of air kerma at the detector with and without a patient model was calculated as the transmission factor. Our study showed that the transmission factor decreased exponentially with increasing patient thickness. For the range of patient thicknesses examined (12-28 cm), the transmission factor ranged from approximately 21% to 1.9% when the air kerma used in the calculation represented an average over the entire imaging field of view. The transmission factor ranged from approximately 21% to 3.6% when the air kerma used in the calculation represented the average signals from two discrete AEC cells behind the lung fields. These exponential relationships may be used to optimize imaging techniques for patients of various body thicknesses to aid in the design of clinical technique charts.

  4. Novel inductive decoupling technique for flexible transceiver arrays of monolithic transmission line resonators.

    Science.gov (United States)

    Kriegl, Roberta; Ginefri, Jean-Christophe; Poirier-Quinot, Marie; Darrasse, Luc; Goluch, Sigrun; Kuehne, Andre; Moser, Ewald; Laistler, Elmar

    2015-04-01

    This article presents a novel inductive decoupling technique for form-fitting coil arrays of monolithic transmission line resonators, which target biomedical applications requiring high signal-to-noise ratio over a large field of view to image anatomical structures varying in size and shape from patient to patient. Individual transmission line resonator elements are mutually decoupled using magnetic flux sharing by overlapping annexes. This decoupling technique was evaluated by electromagnetic simulations and bench measurements for two- and four-element arrays, comparing single- and double-gap transmission line resonator designs, combined either with a basic capacitive matching scheme or inductive pickup loop matching. The best performing array was used in 7T MRI experiments demonstrating its form-fitting ability and parallel imaging potential. The inductively matched double-gap transmission line resonator array provided the best decoupling efficiency in simulations and bench measurements (<-15 dB). The decoupling and parallel imaging performance proved robust against mechanical deformation of the array. The presented decoupling technique combines the robustness of conventional overlap decoupling regarding coil loading and operating frequency with the extended field of view of nonoverlapped coils. While demonstrated on four-element arrays, it can be easily expanded to fabricate readily decoupled form-fitting 2D arrays with an arbitrary number of elements in a single etching process. © 2014 Wiley Periodicals, Inc.

  5. In vivo transmission of impact shock waves in the distal forelimb of the horse.

    Science.gov (United States)

    Gustås, P; Johnston, C; Roepstorff, L; Drevemo, S

    2001-04-01

    There is a high prevalence of lameness among Standardbred trotters, most commonly caused by noninfectious joint diseases, mainly related to training and competition. In this context, impact-related shock waves transmitted through the skeleton and joints have been proposed to be one important factor in the development of osteoarthritis. The aim of the present study was to investigate the characteristic pattern of the events immediately following first contact, with a focus on the in vivo transmission of impact shock waves in the distal forelimb. Two horses were trotted by hand over a force plate. Recordings of 3-D kinematics of the distal forelimb were carried out by use of a 240 Hz video system. Tri-axial accelerometer data were collected from a bone-mounted accelerometer on the midlateral side of the third metacarpal bone (McIII) and from another accelerometer attached to the lateral side of the hoof. Force plate and accelerometer data were sampled at 4.8 kHz using a 16-bit A/D-converter, synchronised with the kinematic data. The results indicate that the time lapse of the horizontal retardation of the hoof is an important factor in the attenuation of the impact. A shorter period of hoof braking showed higher amplitudes in the longitudinal retardation of McIII and a more rapid oscillation. This makes all parameters that affect the horizontal hoof braking potentially important to the orthopaedic health of the horse.

  6. Applicability of coda wave interferometry technique for measurement of acoustoelastic effect of concrete

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sung Woo [Dept. of Safety Engineering, Pukyong National University, Busan (Korea, Republic of)

    2016-12-15

    In this study, we examined the applicability of coda wave interferometry (CWI) technique, which was developed to characterize seismic waves, to detect and evaluate change in the velocity of ultrasonic waves in concrete due to acoustoelastic effect. Ultrasonic wave measurements and compressive loading tests were conducted on a concrete specimen. The measured wave signals were processed with CWI to detect and evaluate the relative velocity change with respect to the stress state of the specimen. A phase change due to the acoustoelastic effect of concrete was clearly detected in the late-arriving coda wave. This shows that the relative velocity change of ultrasonic waves in concrete due to the acoustoelastic effect can be evaluated successfully and precisely using CWI.

  7. Ultra-High-Speed Travelling Wave Protection of Transmission Line Using Polarity Comparison Principle Based on Empirical Mode Decomposition

    Directory of Open Access Journals (Sweden)

    Dong Wang

    2015-01-01

    Full Text Available The traditional polarity comparison based travelling wave protection, using the initial wave information, is affected by initial fault angle, bus structure, and external fault. And the relationship between the magnitude and polarity of travelling wave is ignored. Because of the protection tripping and malfunction, the further application of this protection principle is affected. Therefore, this paper presents an ultra-high-speed travelling wave protection using integral based polarity comparison principle. After empirical mode decomposition of the original travelling wave, the first-order intrinsic mode function is used as protection object. Based on the relationship between the magnitude and polarity of travelling wave, this paper demonstrates the feasibility of using travelling wave magnitude which contains polar information as direction criterion. And the paper integrates the direction criterion in a period after fault to avoid wave head detection failure. Through PSCAD simulation with the typical 500 kV transmission system, the reliability and sensitivity of travelling wave protection were verified under different factors’ affection.

  8. The study on surface characteristics of high transmission components by 3D printing technique

    Science.gov (United States)

    Kuo, Hui-Jean; Huang, Chien-Yao; Wang, Wan-Hsuan; Lin, Ping-Hung; Tsay, Ho-Lin; Hsu, Wei-Yao

    2017-06-01

    3D printing is a high freedom fabrication technique. Any components, which designed by 3D design software or scanned from real parts, can be printed. The printing materials include metals, plastics and biocompatible materials etc. Especially for those high transmission components used in optical system or biomedical field can be printed, too. High transmission lens increases the performances of optical system. And high transmission cover or shell using in biomedical field helps observers to see the structures inside, such as brain, bone, and vessels. But the surface of printed components is not transparent, even the inside layer is transparent. If we increase the transmittance of surface, the components which fabricated by 3D printing process could have high transmission. In this paper, we using illuminating and polishing methods to improve the transmittance of printing surface. The illuminating time is the experiment parameters in illuminating method. The roughness and transmission of printing components are the evaluating targets. A 3D printing machine, Stratasys Connex 500, has been used to print high transmittance components in this paper. The surface transmittance of printing components is increasing above 80 % by polishing method.

  9. Development of a Millimeter-Wave Beam Position and Profile Monitor for Transmission Efficiency Improvement in an ECRH System

    Directory of Open Access Journals (Sweden)

    Shimozuma T.

    2015-01-01

    Full Text Available In a high power Electron Cyclotron Resonance Heating (ECRH system, a long-distance and low-loss transmission system is required to realize effective heating of nuclear fusion-relevant plasmas. A millimeter-wave beam position and profile monitor, which can be used in a high-power, evacuated, and cooled transmission line, is proposed, designed, manufactured, and tested. The beam monitor consists of a reflector, Peltier-device array and a heat-sink. It was tested using simulated electric heater power or gyrotron output power. The data obtained from the monitor were well agreed with the heat source position and profile. The methods of data analysis and mode-content analysis of a propagating millimeter-wave in the corrugated wave-guide are proposed.

  10. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    Science.gov (United States)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  11. Convergence des techniques de transmission fibre optique et radio MIMO haut débit

    OpenAIRE

    Dobremez, Vincent

    2013-01-01

    New technological uses such as cloud computing, smartphones, take part to the huge current increase of data consumption. This growth goes along with the development of optical networks, which will replace the copper networks with an higher and higher transmission capacity, thanks to new standards of fibers. This situation raises the question of the obsolete optical fibers reuse. It's shown in this thesis that MIMO techniques can be applied to multimode optical fibers in order to benefit from ...

  12. Reflection and Transmission of Plane Electromagnetic Waves by a Geologic Layer.

    Energy Technology Data Exchange (ETDEWEB)

    Aldridge, David F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-04-01

    Electric field and magnetic field reflection and transmission responses generated by a plane wave normally incident onto a finite - thickness geologic layer are mathematically derived and numerically evaluated. A thin layer with enhanced electric current conductivity and/or magnetic permeability is a reasonable geophysical representation of a hydraulic fracture inject ed with a high - contrast proppant pack. Both theory and numerics indicate that backward - and forward - scattered electromagnetic wavefields are potentially observable in a field experiment, despite the extreme thinness of a fracture compared to a typical low - frequency electromagnetic wavelength. The First Born Approximation (FBA) representation of layer scattering, significant for inversion studies, is shown to be accurate for a thin layer with mild medium parameter (i.e., conductivity, permeability, and per mittivity) contrasts with the surrounding homogeneous wholespace. However, FBA scattering theory breaks down for thick layers and strong parameter contrasts. ACKNOWLEDGEMENTS Sandia National Laboratories is a multi - mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000. This research is conducted under the auspices of CRADA (Cooperative Research and Development Agreement) SC11/01780.00 between Carbo Ceramics Inc. and Sandia National Laboratories. The author acknowledges former Carbo R&D Vic e - President Mr. Chad Cannan and former SNL Geophysics Department manage r Ms. Amy Halloran for their interest i n and support of this work. Technical discussions with Project Manager and Principal Investigator Dr. Chester J. Weiss of the SNL Geophysics Department greatly benefited this work. Dr. Lewis C. Bartel, formerly with S NL and presently a consultant to Carbo Ceramics, provided many useful and intuitive insights, and

  13. A Second Look at Neutron Resonance Transmission Analysis as a Spent Fuel NDA Technique

    Energy Technology Data Exchange (ETDEWEB)

    James W .Sterbentz; David L. Chichester

    2011-07-01

    Many different nondestructive analysis techniques are currently being investigated as a part of the United States Department of Energy's Next Generation Safeguards Initiative (NGSI) seeking methods to quantify plutonium in spent fuel. Neutron Resonance Transmission Analysis (NRTA) is one of these techniques. Having first been explored in the mid-1970s for the analysis of individual spent-fuel pins a second look, using advanced simulation and modeling methods, is now underway to investigate the suitability of the NRTA technique for assaying complete spent nuclear fuel assemblies. The technique is similar to neutron time-of-flight methods used for cross-section determinations but operates over only the narrow 0.1-20 eV range where strong, distinguishable resonances exist for both the plutonium (239, 240, 241,242Pu) and uranium (235,236,238U) isotopes of interest in spent fuel. Additionally, in this energy range resonances exists for six important fission products (99Tc, 103Rh, 131Xe, 133Cs, 145Nd, and 152Sm) which provide additional information to support spent fuel plutonium assay determinations. Initial modeling shows excellent agreement with previously published experimental data for measurements of individual spent-fuel pins where plutonium assays were demonstrated to have a precision of 2-4%. Within the simulation and modeling analyses of this project scoping studies have explored fourteen different aspects of the technique including the neutron source, drift tube configurations, and gross neutron transmission as well as the impacts of fuel burn up, cooling time, and fission-product interferences. These results show that NRTA may be a very capable experimental technique for spent-fuel assay measurements. The results suggest sufficient transmission strength and signal differentiability is possible for assays through up to 8 pins. For an 8-pin assay (looking at an assembly diagonally), 64% of the pins in a typical 17 ? 17 array of a pressurized water reactor

  14. Guided-wave tomographic imaging of plate defects by laser-based ultrasonic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junpil; Lim, Ju Young; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-12-15

    Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

  15. Evaluation of cross-connected waveguides as transfer standards of transmission at high millimetre-wave frequencies

    Science.gov (United States)

    Ridler, Nick; Clarke, Roland; Huang, Hui; Zinal, Sherko

    2016-08-01

    At the present time, transfer and verification standards of transmission coefficient (or, equivalently, transmission loss) are not readily available at high millimetre-wave frequencies (i.e. at frequencies ranging typically from 100 GHz to 300 GHz). In recent years, cross-connected waveguide devices have been proposed to provide calculable standards of transmission loss at these frequencies. This paper investigates the viability of these cross-connected waveguides as transfer standards of transmission for inter-laboratory measurement comparison exercises. This relates to their potential use in activities such as international key comparison exercises and measurement audit programmes. A trial inter-laboratory comparison involving four laboratories using two cross-connected waveguides in the WR-05 waveguide size (covering frequencies from 140 GHz to 220 GHz) is described and includes an analysis of the measurement results obtained during the comparison exercise.

  16. Analytical study of dynamics of matter-wave solitons in lossless nonlinear discrete bi-inductance transmission lines.

    Science.gov (United States)

    Kengne, E; Lakhssassi, A

    2015-03-01

    We consider a lossless one-dimensional nonlinear discrete bi-inductance electrical transmission line made of N identical unit cells. When lattice effects are considered, we use the reductive perturbation method in the semidiscrete limit to show that the dynamics of modulated waves can be modeled by the classical nonlinear Schrödinger (CNLS) equation, which describes the modulational instability and the propagation of bright and dark solitons on a continuous-wave background. Our theoretical analysis based on the CNLS equation predicts either two or four frequency regions with different behavior concerning the modulational instability of a plane wave. With the help of the analytical solutions of the CNLS equation, we investigate analytically the effects of the linear capacitance CS on the dynamics of matter-wave solitons in the network. Our results reveal that the linear parameter CS can be used to manipulate the motion of bright, dark, and kink soliton in the network.

  17. Neutron Imaging Device Using Wave Length Shifting Fibre Technique

    CERN Document Server

    Gorin, A; Kiyanagi, Y

    2002-01-01

    A high resolution imaging device for cold neutrons detection has been constructed for the neutron optics (nop) Group in RIKEN, and tested with thermal neutrons at the Laue-Langevin Institute in Grenoble. It consists of a thin plate of ZnS(Ag)+6LiF scintillator optically coupled with Y11(400) wave-length shifting (WLS) fibres. The space resolution was found to be ~ 0.45 mm in FWHM as expected from the pitch of WLS fibres with a crossection of 0.4 ´ 0.4 mm2. The detection efficiency for thermal neutrons (l = 2.5 ) was estimated with respect to 3He monitor, and found to be ~ 10 %, which ensured a reasonable efficiency for cold neutrons (l = 10 ).

  18. Nonreciprocal wave transmission through an extended discrete nonlinear Schrödinger dimer

    Science.gov (United States)

    Wasay, Muhammad Abdul

    2017-11-01

    We analyze a one-dimensional extended discrete nonlinear Schrödinger (DNLS) dimer model for nonreciprocal wave transmission. The extension corresponds to the addition of a nonlocal or intersite nonlinear response in addition to a purely cubic local (on-site) nonlinear response, which refines the purely cubic model and aligns to more realistic situations. We observe that a diodelike action persists in the extended case; however, the inclusion of nonlocal response tends to reduce the diode action. We show that this extension results in achieving the diode effect at lower incoming intensities as compared to the purely cubic case. We also report that a nearly perfect diode action is possible in the extended case for a higher level of asymmetry between on-site potentials than its cubic counterpart. Moreover, we vary different site-dependent parameters to probe for regimes of a better diode effect within this extended model. We also present the corresponding stability analysis for the exact stationary solutions to the extended DNLS equation, we discuss the bifurcation behavior in detail, and we explicitly give the regions of stability.

  19. A Ku-band magnetically insulated transmission line oscillator with overmoded slow-wave-structure

    Science.gov (United States)

    Jiang, Tao; He, Jun-Tao; Zhang, Jian-De; Li, Zhi-Qiang; Ling, Jun-Pu

    2016-12-01

    In order to enhance the power capacity, an improved Ku-band magnetically insulated transmission line oscillator (MILO) with overmoded slow-wave-structure (SWS) is proposed and investigated numerically and experimentally. The analysis of the dispersion relationship and the resonant curve of the cold test indicate that the device can operate at the near π mode of the TM01 mode, which is useful for mode selection and control. In the particle simulation, the improved Ku-band MILO generates a microwave with a power of 1.5 GW and a frequency of 12.3 GHz under an input voltage of 480 kV and input current of 42 kA. Finally, experimental investigation of the improved Ku-band MILO is carried out. A high-power microwave (HPM) with an average power of 800 MW, a frequency of 12.35 GHz, and pulse width of 35 ns is generated under a diode voltage of 500 kV and beam current of 43 kA. The consistency between the experimental and simulated far-field radiation pattern confirms that the operating mode of the improved Ku-band MILO is well controlled in π mode of the TM01 mode. Project supported partly by the National Natural Science Foundation of China (Grant No. 61171021).

  20. On the Importance of Wave Simulation Techniques for Forecasting Shoreline Change

    Science.gov (United States)

    Anderson, D. L.; Alvarez Antolinez, J. A.; Mendez, F. J.; Ruggiero, P.

    2016-02-01

    Global climate change is projected to alter large-scale atmospheric circulation, storm tracks, and consequently the regional wave climates produced by these patterns. Since shorelines naturally evolve towards dynamic equilibrium with the local wave climate, any redistribution of wave energy has the potential to result in morphological changes equal to or greater than those induced by sea-level rise over the next several decades. Because nearly all state of the art coastal modeling frameworks require a representation of the wave climate as input, the development of methodologies that create realistic wave climate scenarios is necessary to forecast possible shoreline change. Here we use a simple, one-line shoreline change model to assess the importance of wave simulation techniques on shoreline modeling. Our study site, the U.S. Pacific Northwest, exhibits significant seasonal to multi-decadal shoreline variability along relatively straight embayed beaches. One-line models, which calculate spatial gradients of alongshore sediment transport as a function of wave energy flux and angle, can represent this temporal variability if the wave input time series accurately represents the chronology and joint-probabilities of heights, periods, and directions. Because dynamically downscaling waves from general circulation models is computationally expensive, we explore several statistical input-reduction techniques for constructing time series that capture realistic seasonal to multi-decadal variability and the chronology of storm events. Methods include continuous-time Markov Chains, data mining techniques, fitting of non-stationary distribution functions, auto-regressive logistic models, and trivariate copula dependence structures formed from correlating observed wave records with coincident sea level pressures. The wave climates produced by each method places an emphasis on either the chronological progression or the joint probabilities of the wave parameters or both. We

  1. Transmission of high frequency sound waves through a slug flow jet

    Science.gov (United States)

    Parthasarathy, S. P.; Vijayaraghavan, A.

    1980-01-01

    An analysis has been performed of sound waves which propagate in a pipe with gas flow. At the pipe exit these waves are partially reflected and the remainder are diffracted. The analysis is carried out by resolving the sound at the exit into its Fourier components and then continuing the solution, which is a combination of elementary plane waves, beyond the exit. These waves are of two types: homogeneous waves which propagate to infinity, and inhomogeneous waves with complex wave numbers which decay. The reflected waves are evaluated from the inhomogeneous waves. At the boundary of the jet, refraction of the elementary plane waves is accounted for and the far field sound is evaluated by the method of stationary phase. Comparisons of the theoretical calculations are made with experimental results and with calculations of other theories.

  2. Faithful replication of foraging techniques along cultural transmission chains by chimpanzees and children

    Science.gov (United States)

    Horner, Victoria; Whiten, Andrew; Flynn, Emma; de Waal, Frans B. M.

    2006-01-01

    Observational studies of wild chimpanzees (Pan troglodytes) have revealed population-specific differences in behavior, thought to represent cultural variation. Field studies have also reported behaviors indicative of cultural learning, such as close observation of adult skills by infants, and the use of similar foraging techniques within a population over many generations. Although experimental studies have shown that chimpanzees are able to learn complex behaviors by observation, it is unclear how closely these studies simulate the learning environment found in the wild. In the present study we have used a diffusion chain paradigm, whereby a behavior is passed from one individual to the next in a linear sequence in an attempt to simulate intergenerational transmission of a foraging skill. Using a powerful three-group, two-action methodology, we found that alternative methods used to obtain food from a foraging device (“lift door” versus “slide door”) were accurately transmitted along two chains of six and five chimpanzees, respectively, such that the last chimpanzee in the chain used the same method as the original trained model. The fidelity of transmission within each chain is remarkable given that several individuals in the no-model control group were able to discover either method by individual exploration. A comparative study with human children revealed similar results. This study is the first to experimentally demonstrate the linear transmission of alternative foraging techniques by non-human primates. Our results show that chimpanzees have a capacity to sustain local traditions across multiple simulated generations. PMID:16938863

  3. Rayleigh-Wave Dispersion Technique for Rapid Subsurface Exploration

    Science.gov (United States)

    1973-04-01

    density of the soil is known or can be esatimated. Heukelom and Foster (1960), in the’r ayniunic testing of pave- mnsusing the vibratory technique...Heiland, C. A., 1940, Geophy.icai explorationt New York, Prentice-Hall. Heukelom , W., and Foster, C. R., 1960, Dynamic testing of pavements; Journal

  4. DEVELOPMENT OF WIRELESS TECHNIQUES IN DATA AND POWER TRANSMISSION APPLICATION FOR PARTICLE-PHYSICS DETECTORS

    CERN Document Server

    Brenner, R; Dehos, C; De Lurgio, P; Djurcic, Z; Drake, G; Gonzales Gimenez, JL; Gustafsson, L; Kim, DW; Locci, E; Pfeiffer, U; Röhrich, D; Rydberg, D; Schöning, A; Siligaris, A; Soltveit, HK; Ullaland, K; Vincent, P; Vasquez, PR; Wiedner, D; Yang, S

    2017-01-01

    In the WADAPT project described in this Letter of Intent, we propose to develop wireless techniques for data and power transmission in particle-physics detectors. Wireless techniques have developed extremely fast over the last decade and are now mature for being considered as a promising alternative to cables and optical links that would revolutionize the detector design. The WADAPT consortium has been formed to identify the specific needs of different projects that might benefit from wireless techniques with the objective of providing a common platform for research and development in order to optimize effectiveness and cost. The proposed R&D will aim at designing and testing wireless demonstrators for large instrumentation systems.

  5. Thermal wave imaging techniques for inspection of plywood materials

    Science.gov (United States)

    Mulaveesala, Ravibabu; Venkata Nagarjuna, P.; Ravi, Dadda; Amarnath, Muniyappa

    2012-06-01

    Infrared non-destructive testing and evaluation (IRNDT&E) is an emerging approach for materials characterization due to its capability to test wide variety of solid materials such as metals, composites and semiconductors of industrial interest. Further it supports thorough inspection and evaluation by its unique remote and fast and whole field testing capabilities. Wood is one of the most commonly used house hold building material it has both structural and decorative applications. It is used both in natural and processed form like ply wood, veneer, ply-board etc. Defects like knots, worm track, delaminations, glue smear etc. influences its in-service capabilities. Even though various non-destructive methods such as optical, ultrasonic and radiography are commonly used to inspect wooden materials, infrared imaging has its own advantage due to its safe, whole field inspection capabilities. This paper describes the applicability of the transient thermal wave imaging (TWI) method for inspection of ply wood. This paper highlights applicability of transient pulsed thermal imaging approach for finding out the hidden defects. Capability of the proposed method and its defect detection capabilities have been highlighted through experimental results.

  6. A Temporal Millimeter Wave Propagation Model for Tunnels Using Ray Frustum Techniques and FFT

    Directory of Open Access Journals (Sweden)

    Choonghyen Kwon

    2014-01-01

    Full Text Available A temporal millimeter wave propagation model for tunnels is presented using ray frustum techniques and fast Fourier transform (FFT. To directly estimate or simulate effects of millimeter wave channel properties on the performance of communication services, time domain impulse responses of demodulated signals should be obtained, which needs rather large computation time. To mitigate the computational burden, ray frustum techniques are used to obtain frequency domain transfer function of millimeter wave propagation environment and FFT of equivalent low pass signals are used to retrieve demodulated waveforms. This approach is numerically efficient and helps to directly estimate impact of tunnel structures and surfaces roughness on the performance of millimeter wave communication services.

  7. Guided Wave Propagation Study on Laminated Composites by Frequency-Wavenumber Technique

    Science.gov (United States)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara A. C.

    2014-01-01

    Toward the goal of delamination detection and quantification in laminated composites, this paper examines guided wave propagation and wave interaction with delamination damage in laminated carbon fiber reinforced polymer (CFRP) composites using frequency-wavenumber (f-kappa) analysis. Three-dimensional elastodynamic finite integration technique (EFIT) is used to acquire simulated time-space wavefields for a CFRP composite. The time-space wavefields show trapped waves in the delamination region. To unveil the wave propagation physics, the time-space wavefields are further analyzed by using two-dimensional (2D) Fourier transforms (FT). In the analysis results, new f-k components are observed when the incident guided waves interact with the delamination damage. These new f-kappa components in the simulations are experimentally verified through data obtained from scanning laser Doppler vibrometer (SLDV) tests. By filtering the new f-kappa components, delamination damage is detected and quantified.

  8. Efficient techniques for wave-based sound propagation in interactive applications

    Science.gov (United States)

    Mehra, Ravish

    Sound propagation techniques model the effect of the environment on sound waves and predict their behavior from point of emission at the source to the final point of arrival at the listener. Sound is a pressure wave produced by mechanical vibration of a surface that propagates through a medium such as air or water, and the problem of sound propagation can be formulated mathematically as a second-order partial differential equation called the wave equation. Accurate techniques based on solving the wave equation, also called the wave-based techniques, are too expensive computationally and memory-wise. Therefore, these techniques face many challenges in terms of their applicability in interactive applications including sound propagation in large environments, time-varying source and listener directivity, and high simulation cost for mid-frequencies. In this dissertation, we propose a set of efficient wave-based sound propagation techniques that solve these three challenges and enable the use of wave-based sound propagation in interactive applications. Firstly, we propose a novel equivalent source technique for interactive wave-based sound propagation in large scenes spanning hundreds of meters. It is based on the equivalent source theory used for solving radiation and scattering problems in acoustics and electromagnetics. Instead of using a volumetric or surface-based approach, this technique takes an object-centric approach to sound propagation. The proposed equivalent source technique generates realistic acoustic effects and takes orders of magnitude less runtime memory compared to prior wave-based techniques. Secondly, we present an efficient framework for handling time-varying source and listener directivity for interactive wave-based sound propagation. The source directivity is represented as a linear combination of elementary spherical harmonic sources. This spherical harmonic-based representation of source directivity can support analytical, data

  9. Optimization technique for improved microwave transmission from multi-solar power satellites

    Energy Technology Data Exchange (ETDEWEB)

    Arndt, G.D.; Kerwin, E.M.

    1982-08-01

    An optimization technique for generating antenna illumination tapers allows improved microwave transmission efficiencies from proposed solar power satellite (SPS) systems and minimizes sidelobe levels to meet preset environmental standards. The cumulative microwave power density levels from 50 optimized SPS systems are calculated at the centroids of each of the 3073 counties in the continental United States. These cumulative levels are compared with Environmental Protection Agency (EPA) measured levels of electromagnetic radiation in seven eastern cities. Effects of rectenna relocations upon the power levels/population exposure rates are also studied.

  10. Using high speed smartphone cameras and video analysis techniques to teach mechanical wave physics

    Science.gov (United States)

    Bonato, Jacopo; Gratton, Luigi M.; Onorato, Pasquale; Oss, Stefano

    2017-07-01

    We propose the use of smartphone-based slow-motion video analysis techniques as a valuable tool for investigating physics concepts ruling mechanical wave propagation. The simple experimental activities presented here, suitable for both high school and undergraduate students, allows one to measure, in a simple yet rigorous way, the speed of pulses along a spring and the period of transverse standing waves generated in the same spring. These experiments can be helpful in addressing several relevant concepts about the physics of mechanical waves and in overcoming some of the typical student misconceptions in this same field.

  11. Multispectral illumination and image processing techniques for active millimeter-wave concealed object detection.

    Science.gov (United States)

    Zhang, Lixiao; Stiens, Johan; Elhawil, Amna; Vounckx, Roger

    2008-12-01

    Active millimeter-wave imaging systems for concealed object detection offer the possibility of much higher image contrast than passive systems, especially in indoor applications. By studying active millimeter-wave images of different test objects derived in the W band, we show that multispectral illumination is critical to the detectability of targets. We also propose to use image change detection techniques, including image differencing, normalized difference vegetation index, and principle component analysis to process the multispectral millimeter-wave images. The results demonstrate that multispectral illumination can significantly reveal the object features hidden by image artifacts and improve the appearance of the objects.

  12. Infrared and millimeter waves v.15 millimeter components and techniques, pt.VI

    CERN Document Server

    Button, Kenneth J

    1986-01-01

    Infrared and Millimeter Waves, Volume 15: Millimeter Components and Techniques, Part VI is concerned with millimeter-wave guided propagation and integrated circuits. This book covers low-noise receiver technology for near-millimeter wavelengths; dielectric image-line antennas; EHF satellite communications (SATCOM) terminal antennas; and semiconductor antennas for millimeter-wave integrated circuits. A scanning airborne radiometer for 30 and 90 GHz and a self-oscillating mixer are also described. This monograph is comprised of six chapters and begins with a discussion on the design of low-n

  13. Fast characterization of two ultrasound longitudinal waves in cancellous bone using an adaptive beamforming technique.

    Science.gov (United States)

    Taki, Hirofumi; Nagatani, Yoshiki; Matsukawa, Mami; Mizuno, Katsunori; Sato, Toru

    2015-04-01

    The received signal in through-transmission ultrasound measurements of cancellous bone consists of two longitudinal waves, called the fast and slow waves. Analysis of these fast and slow waves may reveal characteristics of the cancellous bone that would be good indicators of osteoporosis. Because the two waves often overlap, decomposition of the received signal is an important problem in the characterization of bone quality. This study proposes a fast and accurate decomposition method based on the frequency domain interferometry imaging method with a modified wave transfer function that uses a phase rotation parameter. The proposed method accurately characterized the fast and slow waves in the experimental study, and the residual intensity, which was normalized with respect to the received signal intensity, was less than -20 dB over the bone specimen thickness range from 6 to 15 mm. In the simulation study, the residual intensity was less than -20 dB over the specimen thickness range from 3 to 8 mm. Decomposition of a single received signal takes only 5 s using a laptop personal computer with a single central processing unit. The proposed method has great potential to provide accurate and rapid measurements of indicators of osteoporosis in cancellous bone.

  14. An improved dual-frequency technique for the remote sensing of ocean currents and wave spectra

    Science.gov (United States)

    Schuler, D. L.; Eng, W. P.

    1984-01-01

    A two frequency microwave radar technique for the remote sensing of directional ocean wave spectra and surface currents is investigated. This technique is conceptually attractive because its operational physical principle involves a spatial electromagnetic scattering resonance with a single, but selectable, long gravity wave. Multiplexing of signals having different spacing of the two transmitted frequencies allows measurements of the entire long wave ocean spectrum to be carried out. A new scatterometer is developed and experimentally tested which is capable of making measurements having much larger signal/background values than previously possible. This instrument couples the resonance technique with coherent, frequency agility radar capabilities. This scatterometer is presently configured for supporting a program of surface current measurements.

  15. In vivo effects of focused shock waves on tumor tissue visualized by fluorescence staining techniques.

    Science.gov (United States)

    Lukes, Petr; Zeman, Jan; Horak, Vratislav; Hoffer, Petr; Pouckova, Pavla; Holubova, Monika; Hosseini, S Hamid R; Akiyama, Hidenori; Sunka, Pavel; Benes, Jiri

    2015-06-01

    Shock waves can cause significant cytotoxic effects in tumor cells and tissues both in vitro and in vivo. However, understanding the mechanisms of shock wave interaction with tissues is limited. We have studied in vivo effects of focused shock waves induced in the syngeneic sarcoma tumor model using the TUNEL assay, immunohistochemical detection of caspase-3 and hematoxylin-eosin staining. Shock waves were produced by a multichannel pulsed-electrohydraulic discharge generator with a cylindrical ceramic-coated electrode. In tumors treated with shock waves, a large area of damaged tissue was detected which was clearly differentiated from intact tissue. Localization and a cone-shaped region of tissue damage visualized by TUNEL reaction apparently correlated with the conical shape and direction of shock wave propagation determined by high-speed shadowgraphy. A strong TUNEL reaction of nuclei and nucleus fragments in tissue exposed to shock waves suggested apoptosis in this destroyed tumor area. However, specificity of the TUNEL technique to apoptotic cells is ambiguous and other apoptotic markers (caspase-3) that we used in our study did not confirmed this observation. Thus, the generated fragments of nuclei gave rise to a false TUNEL reaction not associated with apoptosis. Mechanical stress from high overpressure shock wave was likely the dominant pathway of tumor damage. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Comparative study of shear wave-based elastography techniques in optical coherence tomography

    Science.gov (United States)

    Zvietcovich, Fernando; Rolland, Jannick P.; Yao, Jianing; Meemon, Panomsak; Parker, Kevin J.

    2017-03-01

    We compare five optical coherence elastography techniques able to estimate the shear speed of waves generated by one and two sources of excitation. The first two techniques make use of one piezoelectric actuator in order to produce a continuous shear wave propagation or a tone-burst propagation (TBP) of 400 Hz over a gelatin tissue-mimicking phantom. The remaining techniques utilize a second actuator located on the opposite side of the region of interest in order to create three types of interference patterns: crawling waves, swept crawling waves, and standing waves, depending on the selection of the frequency difference between the two actuators. We evaluated accuracy, contrast to noise ratio, resolution, and acquisition time for each technique during experiments. Numerical simulations were also performed in order to support the experimental findings. Results suggest that in the presence of strong internal reflections, single source methods are more accurate and less variable when compared to the two-actuator methods. In particular, TBP reports the best performance with an accuracy error TBP was tested in a fresh chicken tibialis anterior muscle with a localized thermally ablated lesion in order to evaluate its performance in biological tissue.

  17. Joint analysis of shear wave velocity from SH-wave refraction and MASW techniques for SPT-N estimation

    Directory of Open Access Journals (Sweden)

    Sawasdee Yordkayhun

    2014-06-01

    Full Text Available Horizontally polarized shear wave (SH refraction and multichannel analysis of surface wave (MASW methods have been carried out in Hatyai City, southern Thailand, a pilot study for site classification, part of the National Earthquake Hazards Reduction Program (NEHRP. The objectives of this study are the comparison of the efficiencies of different shear wave velocity (Vs determination techniques and the use of Vs measurements of the prediction of standard penetration resistance (SPT-N. Good correlation between all Vs profiles and SPT-N values and local lithology are observed. However, there are systematic differences between SH-refraction based-Vs and MASW based-Vs, which might be explained by possible converted waves, limitations of the assumptions used, poor quality of the acquired data, and limitations of the inversion procedures of the methods applied. From the integrated use of Vs from both methods an empirical formula to describe the correlation between Vs and SPT-N values has been proposed and can be used to estimate geotechnical parameters in areas where no borehole or geophysical investigation exist.

  18. Data processing techniques for a wireless data transmission application via mud

    Directory of Open Access Journals (Sweden)

    Zhao Qingjie

    2011-01-01

    Full Text Available Abstract The data measured by well bottom sensors can be transmitted to the surface through the drilling mud during oil drilling operations. This article introduces a data processing scheme for a wireless data transmission application via mud. The detailed signal processing procedure is given, and several data processing techniques used are discussed, mainly including data encoding and signal integrating method, signal filtering, data storage and manage method, peak detection, signal recognition, and data decoding method. The article uses M pulses in N slots to encode the values of actual parameters. A two step filtering method and a dynamic data storing and managing method are proposed. A mix peak detection method is utilized to find the position of a pulse by combining threshold method and neighbor comparison method. These techniques have been successfully used in an oil well drilling operation.

  19. Quantify fluid saturation in fractures by light transmission technique and its application

    Science.gov (United States)

    Ye, S.; Zhang, Y.; Wu, J.

    2016-12-01

    The Dense Non-Aqueous Phase Liquids (DNAPLs) migration in transparent and rough fractures with variable aperture was studied experimentally using a light transmission technique. The migration of trichloroethylene (TCE) in variable-aperture fractures (20 cm wide x 32.5 cm high) showed that a TCE blob moved downward with snap-off events in four packs with apertures from 100 μm to 1000 μm, and that the pattern presented a single and tortuous cluster with many fingers in a pack with two apertures of 100 μm and 500 μm. The variable apertures in the fractures were measured by light transmission. A light intensity-saturation (LIS) model based on light transmission was used to quantify DNAPL saturation in the fracture system. Known volumes of TCE, were added to the chamber and these amounts were compared to the results obtained by LIS model. Strong correlation existed between results obtained based on LIS model and the known volumes of T CE. Sensitivity analysis showed that the aperture was more sensitive than parameter C2 of LIS model. LIS model was also used to measure dyed TCE saturation in air sparging experiment. The results showed that the distribution and amount of TCE significantly influenced the efficient of air sparging. The method developed here give a way to quantify fluid saturation in two-phase system in fractured medium, and provide a non-destructive, non-intrusive tool to investigate changes in DNAPL architecture and flow characteristics in laboratory experiments. Keywords: light transmission, fluid saturation, fracture, variable aperture AcknowledgementsFunding for this research from NSFC Project No. 41472212.

  20. Fault Classification and Location in Transmission Lines Using Traveling Waves Modal Components and Continuous Wavelet Transform (CWT

    Directory of Open Access Journals (Sweden)

    Farhad Namdari

    2016-06-01

    Full Text Available Accurate fault classification and localization are the bases of protection for transmission systems. This paper presents a new method for classifying and showing location of faults by travelling waves and modal analysis. In the proposed method, characteristics of different faults are investigated using Clarke transformation and initial current traveling wave; then, appropriate indices are introduced to identify different types of faults. Continuous wavelet transform (CWT is employed to extract information of current and voltage travelling waves. Fault location and classification algorithm is being designed according to wavelet transform coefficients relating to current and voltage modal components. The performance of the proposed method is tested for different fault conditions (different fault distance, different fault resistances, and different fault inception angles by using PSCAD and MATLAB with satisfactory results

  1. Phase Conjugated Twin Waves in 8×21×224Gbit/s DP-16QAM Multi-core Fiber Transmission

    DEFF Research Database (Denmark)

    Asif, Rameez; Ye, Feihong; Morioka, Toshio

    2014-01-01

    Efficient suppression of non-linear interactions has been n umerically analyzed via phase conjugated twin waves in 8 × 21 × 224 Gbit/s multi-core fiber transmission. Results show a Q-factor improvement of 2.8 dB, consequently doubling the transmission distance.......Efficient suppression of non-linear interactions has been n umerically analyzed via phase conjugated twin waves in 8 × 21 × 224 Gbit/s multi-core fiber transmission. Results show a Q-factor improvement of 2.8 dB, consequently doubling the transmission distance....

  2. Electron tomography of whole cultured cells using novel transmission electron imaging technique.

    Science.gov (United States)

    Okumura, Taiga; Shoji, Minami; Hisada, Akiko; Ominami, Yusuke; Ito, Sukehiro; Ushiki, Tatsuo; Nakajima, Masato; Ohshima, Takashi

    2018-01-01

    Since a three-dimensional (3D) cellular ultrastructure is significant for biological functions, it has been investigated using various electron microscopic techniques. Although transmission electron microscopy (TEM)-based techniques are traditionally used, cells must be embedded in resin and sliced into ultrathin sections in sample preparation processes. Block-face observation using a scanning electron microscope (SEM) has also been recently applied to 3D observation of cellular components, but this is a destructive inspection and does not allow re-examination. Therefore, we developed electron tomography using a transmission electron imaging technique called Plate-TEM. With Plate-TEM, the cells cultured directly on a scintillator plate are inserted into a conventional SEM equipped with a Plate-TEM observation system, and their internal structures are observed by detecting scintillation light produced by electrons passing through the cells. This technology has the following four advantages. First, the cells cultured on the plate can be observed at electron-microscopic resolution since they remain on the plate. Second, both surface and internal information can be obtained simultaneously by using electron- and photo-detectors, respectively, because a Plate-TEM detector is installed in an SEM. Third, the cells on the scintillator plate can also be inspected using light microscopy because the plate has transparent features. Finally, correlative observation with other techniques, such as conventional TEM, is possible after Plate-TEM observation because Plate-TEM is a non-destructive analysis technique. We also designed a sample stage to tilt the samples for tomography with Plate-TEM, by which 3D organization of cellular structures can be visualized as a whole cell. In the present study, Mm2T cells were investigated using our tomography system, resulting in 3D visualization of cell organelles such as mitochondria, lipid droplets, and microvilli. Correlative observations

  3. Real-time optical monitoring of radio-frequency tissue fusion by continuous wave transmission spectroscopy.

    Science.gov (United States)

    Floume, Timmy; Syms, Richard R A; Darzi, Ara W; Hanna, George B

    2008-01-01

    Radio-frequency (RF) tissue fusion is a novel method of tissue approximation that can seal tissue without the need for sutures or staples, based on the combined effects of heat and pressure on the apposed tissue surfaces. RF delivery must be controlled and optimized to obtain a reproducible, reliable seal. We use real-time optical measurements to improve understanding of the tissue modifications induced by RF fusion. The main macroscopic transformations are thermal denaturation and dehydration. Light propagation in tissue is a function of both and therefore should provide interesting insight into the dynamic of occurring phenomena. Quantification by continuous wave technique has proven challenging. We proposed an algorithm based on the measurement of the absolute transmittance of the tissue, making use of the modified Beer-Lambert law. The experimental method and the data algorithm are demonstrated by RF fusion of porcine small bowel. The proposed optical measurement modality is well adapted to modern surgical instrumentation used for minimally invasive procedures.

  4. Investigation on experimental techniques to detect, locate and quantify gear noise in helicopter transmissions

    Science.gov (United States)

    Flanagan, P. M.; Atherton, W. J.

    1985-01-01

    A robotic system to automate the detection, location, and quantification of gear noise using acoustic intensity measurement techniques has been successfully developed. Major system components fabricated under this grant include an instrumentation robot arm, a robot digital control unit and system software. A commercial, desktop computer, spectrum analyzer and two microphone probe complete the equipment required for the Robotic Acoustic Intensity Measurement System (RAIMS). Large-scale acoustic studies of gear noise in helicopter transmissions cannot be performed accurately and reliably using presently available instrumentation and techniques. Operator safety is a major concern in certain gear noise studies due to the operating environment. The man-hours needed to document a noise field in situ is another shortcoming of present techniques. RAIMS was designed to reduce the labor and hazard in collecting data and to improve the accuracy and repeatability of characterizing the acoustic field by automating the measurement process. Using RAIMS a system operator can remotely control the instrumentation robot to scan surface areas and volumes generating acoustic intensity information using the two microphone technique. Acoustic intensity studies requiring hours of scan time can be performed automatically without operator assistance. During a scan sequence, the acoustic intensity probe is positioned by the robot and acoustic intensity data is collected, processed, and stored.

  5. Memory, transmission and persistence of alternative foraging techniques in wild common marmosets

    Science.gov (United States)

    Gunhold, Tina; Massen, Jorg J.M.; Schiel, Nicola; Souto, Antonio; Bugnyar, Thomas

    2014-01-01

    Experimental studies on traditions in animals have focused almost entirely on the initial transmission phase in captive populations. We conducted an open diffusion field experiment with 13 groups of wild common marmosets, Callithrix jacchus. Seven groups contained individuals that were already familiar with the task (‘push or pull’ box) and thus served as potential models for naïve individuals. Additionally, in four groups one individual was trained for one of the two possible techniques and in two control groups no skilled individuals were present. First, we investigated whether experienced individuals would remember how to solve the task even after 2 years without exposure and whether they would still prefer their learned technique. Second, we tested whether naïve individuals would learn socially from their skilled family members and, more importantly, whether they would use the same technique. Third, we conducted several test blocks to see whether the individual and/or group behaviour would persist over time. Our results show that wild common marmosets were able to memorize, learn socially and maintain preferences of foraging techniques. This field experiment thus reveals a promising approach to studying social learning in the wild and provides the basis for long-term studies on tradition formation. PMID:24910466

  6. BEYOND-LINE-OF-SIGHT DATA TRANSMISSION USING ADAPTIVE ARRAY TECHNIQUES,

    Science.gov (United States)

    DATA TRANSMISSION SYSTEMS , MICROWAVE COMMUNICATIONS), (*MICROWAVE COMMUNICATIONS, DATA TRANSMISSION SYSTEMS ), ANTENNAS, DIPOLE ANTENNAS, ANTENNA RADIATION PATTERNS, POLARIZATION, MODULATION, FREQUENCY MODULATION, AMPLITUDE MODULATION.

  7. An evaluation of directional analysis techniques for multidirectional, partially reflected waves .1. numerical investigations

    DEFF Research Database (Denmark)

    Ilic, C; Chadwick, A; Helm-Petersen, Jacob

    2000-01-01

    , non-phased locked methods are more appropriate. In this paper, the accuracy of two non-phased locked methods of directional analysis, the maximum likelihood method (MLM) and the Bayesian directional method (BDM) have been quantitatively evaluated using numerical simulations for the case......Recent studies of advanced directional analysis techniques have mainly centred on incident wave fields. In the study of coastal structures, however, partially reflective wave fields are commonly present. In the near structure field, phase locked methods can be successfully applied. In the far field...... of multidirectional waves with partial reflections. It is shown that the results are influenced by the ratio of distance from the reflector (L) to the length of the time series (S) used in the spectral analysis. Both methods are found to be capable of determining the incident and reflective wave fields when US > 0...

  8. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    Science.gov (United States)

    Jackson, F. C.

    1980-01-01

    Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

  9. Lamb-Wave-Based Tomographic Imaging Techniques for Hole-Edge Corrosion Monitoring in Plate Structures

    Directory of Open Access Journals (Sweden)

    Dengjiang Wang

    2016-11-01

    Full Text Available This study presents a novel monitoring method for hole-edge corrosion damage in plate structures based on Lamb wave tomographic imaging techniques. An experimental procedure with a cross-hole layout using 16 piezoelectric transducers (PZTs was designed. The A0 mode of the Lamb wave was selected, which is sensitive to thickness-loss damage. The iterative algebraic reconstruction technique (ART method was used to locate and quantify the corrosion damage at the edge of the hole. Hydrofluoric acid with a concentration of 20% was used to corrode the specimen artificially. To estimate the effectiveness of the proposed method, the real corrosion damage was compared with the predicted corrosion damage based on the tomographic method. The results show that the Lamb-wave-based tomographic method can be used to monitor the hole-edge corrosion damage accurately.

  10. Random-Access Technique for Self-Organization of 5G Millimeter-Wave Cellular Communications

    Directory of Open Access Journals (Sweden)

    Jasper Meynard Arana

    2016-01-01

    Full Text Available The random-access (RA technique is a key procedure in cellular networks and self-organizing networks (SONs, but the overall processing time of this technique in millimeter-wave (mm-wave cellular systems with directional beams is very long because RA preambles (RAPs should be transmitted in all directions of Tx and Rx beams. In this paper, two different types of preambles (RAP-1 and RAP-2 are proposed to reduce the processing time in the RA stage. After analyzing the correlation property, false-alarm probability, and detection probability of the proposed RAPs, we perform simulations to show that the RAP-2 is suitable for RA in mm-wave cellular systems with directional beams because of the smaller processing time and high detection probability in multiuser environments.

  11. Beam Diffraction Effects in the Backward Wave Regions of Viscoelastic Leaky Lamb Modes for Plate Transmission at Normal Incidence.

    Science.gov (United States)

    Aanes, Magne; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne

    2017-10-01

    Plane-wave theory for fluid-embedded isotropic plates is often used in ultrasonic guided-wave applications, and to estimate wall thickness, corrosion, or sound velocities in plates and pipes. In such structures, measured ultrasonic transmission through the solid material is affected by acoustic beam diffraction effects, and the results may deviate from plane-wave descriptions, which are insufficient to describe the complex effects that occur. When exciting a fluid-embedded steel plate with a pulsed ultrasonic beam at normal incidence, resonance frequency downshift, axial sound pressure level increase, and beam narrowing have been observed, for measured resonance peaks in the frequency regions of certain leaky Lamb mode branches of the plate. In the ranges of other leaky Lamb mode branches, the observed effects are different. Measurements, finite element, and angular spectrum modeling are used to indicate a close connection between these beam diffraction phenomena and the backward wave characteristics of certain leaky Lamb mode pairs, in the frequency and Poisson's ratio regions around coincidence of two Lamb mode cutoff frequencies of similar symmetry. In particular, such observations made for the steel plate's fundamental thickness-extensional (TE) mode appear to be caused by acoustic beam excitation of the backward wave regions of the S -2 vl and S 2 vl leaky Lamb modes.

  12. Using High Speed Smartphone Cameras and Video Analysis Techniques to Teach Mechanical Wave Physics

    Science.gov (United States)

    Bonato, Jacopo; Gratton, Luigi M.; Onorato, Pasquale; Oss, Stefano

    2017-01-01

    We propose the use of smartphone-based slow-motion video analysis techniques as a valuable tool for investigating physics concepts ruling mechanical wave propagation. The simple experimental activities presented here, suitable for both high school and undergraduate students, allows one to measure, in a simple yet rigorous way, the speed of pulses…

  13. An EMAT-based shear horizontal (SH) wave technique for adhesive bond inspection

    Science.gov (United States)

    Arun, K.; Dhayalan, R.; Balasubramaniam, Krishnan; Maxfield, Bruce; Peres, Patrick; Barnoncel, David

    2012-05-01

    The evaluation of adhesively bonded structures has been a challenge over the several decades that these structures have been used. Applications within the aerospace industry often call for particularly high performance adhesive bonds. Several techniques have been proposed for the detection of disbonds and cohesive weakness but a reliable NDE method for detecting interfacial weakness (also sometimes called a kissing bond) has been elusive. Different techniques, including ultrasonic, thermal imaging and shearographic methods, have been proposed; all have had some degree of success. In particular, ultrasonic methods, including those based upon shear and guided waves, have been explored for the assessment of interfacial bond quality. Since 3-D guided shear horizontal (SH) waves in plates have predominantly shear displacement at the plate surfaces, we conjectured that SH guided waves should be influenced by interfacial conditions when they propagate between adhesively bonded plates of comparable thickness. This paper describes a new technique based on SH guided waves that propagate within and through a lap joint. Through mechanisms we have yet to fully understand, the propagation of an SH wave through a lap joint gives rise to a reverberation signal that is due to one or more reflections of an SH guided wave mode within that lap joint. Based upon a combination of numerical simulations and measurements, this method shows promise for detecting and classifying interfacial bonds. It is also apparent from our measurements that the SH wave modes can discriminate between adhesive and cohesive bond weakness in both Aluminum-Epoxy-Aluminum and Composite-Epoxy-Composite lap joints. All measurements reported here used periodic permanent magnet (PPM) Electro-Magnetic Acoustic Transducers (EMATs) to generate either or both of the two lowest order SH modes in the plates that comprise the lap joint. This exact configuration has been simulated using finite element (FE) models to

  14. Absorptance measurements of transmissive optical components by the surface thermal lensing technique

    Energy Technology Data Exchange (ETDEWEB)

    Chow, R.; Taylor, J.R.; Wu, Z.L.; Han, Y.; Tian, L.Y.

    1997-09-24

    The surface thermal lensing technique (STL) successfully resolved and measured the absorptance of transmissive optical components: near- normal angle-of-incidence anti-reflectors and beam splatters. The STL system uses an Ar ion laser to pump the components at 514.5 mn. The absorptance-induced surface deformation diffracts the HeNe probe beam into a photo-detector. The signal intensity was calibrated with a sample of known absorptance. The optical components were designed to function in a copper vapor laser (CVL) transport system, and were previously tested for absorptance with a high power CVL system at 511 rtm. To assure proper absorptance data from the STL system, the pump laser power densities were set at the operational level of the coatings, absorptance time trends were monitored, and absorptance area scans were made. Both types of transmissive optics are more stable than the CVL high reflectors that were measured in another study. Parameter studies based on Fresnel diffraction theory were also performed to optimize experimental condition. The STL system was assessed to have 10 ppb sensitivity for absorption measurement given 2 W of pump power.

  15. Low-Loss Flexible Dielectric Waveguide for Millimeter-Wave Transmission and Its Application to Devices.

    Science.gov (United States)

    1984-08-01

    New York, 1958. 11-3. S. Ratio, J.R. Whinnery, and T. Van Duzer , FIELDS AND WAVES IN II COHMUNICATION ELECTRONICS, Wiley, New York, 1966, pp. 432...October, 1974. 111-2. S. Ramo, J.R. Whinnery, and T. Van Duzer , FIELDS AND WAVES 11. COMMUNICATION ELECTRONICS, Wiley, New York, 1966, Chapter 7. 111-3. H.G

  16. Optimization FSO Performance Under Strong Turbulence Effect By Enhanced New Carrier Data Transmission Technique

    Directory of Open Access Journals (Sweden)

    Ummul K.R.

    2017-01-01

    Full Text Available This paper focus on mitigating the atmospheric turbulence effect in free space optical communication using a dual diffuser modulation (DDM technique. The most deteriorate the FSOC is scintillation where it affected the wave front cause to fluctuating signal and ultimately receiver can turn into saturate or loss signal. DD approach enhances the detecting bit ‘1’ and bit ‘0’ and improves the power received to combat with turbulence effect. The performance focus on Signal-to-Noise (SNR and Bit Error Rate (BER by using the Kolmogorov’s scintillation theory. The numerical result shows that the DD approach improves the range where estimated approximately 40% improvement under weak turbulence and 80% under strong turbulence.

  17. Nanostructure characterisation of flow-formed Cr–Mo–V steel using transmission Kikuchi diffraction technique

    Energy Technology Data Exchange (ETDEWEB)

    Birosca, S., E-mail: s.birosca@swansea.ac.uk [Materials Research Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Ding, R. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Ooi, S. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Buckingham, R.; Coleman, C. [Materials Research Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Dicks, K. [Oxford Instruments NanoAnalysis, Halifax Road, High Wycombe, Buckinghamshire HP12 3SE (United Kingdom)

    2015-06-15

    Nowadays flow-forming has become a desired near net shape manufacturing method as it provides excellent mechanical properties with improved surface finish and significant manufacturing cost reduction. However, the material is subjected to excessive plastic deformation during flow-forming process, generating a very fine and complex microstructure. In addition, the intense dislocation density and residual stress that is generated in the component during processing makes the microstructure characterisation using conventional micro-analytical tools challenging. Thus, the microstructure/property relationship study in such a material is rather difficult. In the present study a flow-formed Cr–Mo–V steel nanostructure and crystallographic texture were characterised by means of Transmission Kikuchi Diffraction (TKD). Here, TKD is shown to be a powerful technique in revealing very fine martensite laths within an austenite matrix. Moreover, fine precipitates in the order of 20–70 nm on the martensite lath boundaries were clearly imaged and characterised. This greatly assisted in understanding the preferable site formation of the carbides in such a complex microstructure. The results showed that the actual TKD spatial resolution was in the range of 5–10 nm using 25 kV for flow-formed Cr–Mo–V steel. - Highlights: • Optimum Transmission Kikuchi Diffraction (TKD) technique's configuration is reported. • TKD could reveal detailed nanostructural features and the microtexture of martensite laths. • Actual TKD spatial resolution was in the range of 5–10 nm using 25 kV for flow-formed Cr-Mo-V steel. • At nano scale the sub-structure morphology of martensite lath were determined using TKD.

  18. A three-microphone acoustic reflection technique using transmitted acoustic waves in the airway.

    Science.gov (United States)

    Fujimoto, Yuki; Huang, Jyongsu; Fukunaga, Toshiharu; Kato, Ryo; Higashino, Mari; Shinomiya, Shohei; Kitadate, Shoko; Takahara, Yutaka; Yamaya, Atsuyo; Saito, Masatoshi; Kobayashi, Makoto; Kojima, Koji; Oikawa, Taku; Nakagawa, Ken; Tsuchihara, Katsuma; Iguchi, Masaharu; Takahashi, Masakatsu; Mizuno, Shiro; Osanai, Kazuhiro; Toga, Hirohisa

    2013-10-15

    The acoustic reflection technique noninvasively measures airway cross-sectional area vs. distance functions and uses a wave tube with a constant cross-sectional area to separate incidental and reflected waves introduced into the mouth or nostril. The accuracy of estimated cross-sectional areas gets worse in the deeper distances due to the nature of marching algorithms, i.e., errors of the estimated areas in the closer distances accumulate to those in the further distances. Here we present a new technique of acoustic reflection from measuring transmitted acoustic waves in the airway with three microphones and without employing a wave tube. Using miniaturized microphones mounted on a catheter, we estimated reflection coefficients among the microphones and separated incidental and reflected waves. A model study showed that the estimated cross-sectional area vs. distance function was coincident with the conventional two-microphone method, and it did not change with altered cross-sectional areas at the microphone position, although the estimated cross-sectional areas are relative values to that at the microphone position. The pharyngeal cross-sectional areas including retropalatal and retroglossal regions and the closing site during sleep was visualized in patients with obstructive sleep apnea. The method can be applicable to larger or smaller bronchi to evaluate the airspace and function in these localized airways.

  19. Review of Synthetically Focused Guided Wave Imaging Techniques With Application to Defect Sizing

    Science.gov (United States)

    Davies, J.; Simonetti, F.; Lowe, M.; Cawley, P.

    2006-03-01

    Synthetically focused imaging has been used for some time in the NDE community. The techniques have primarily been directed towards imaging using bulk waves. There has recently been use of SAFT (Synthetic Aperture Focusing Technique) using guided waves in plates. Here, we review three different synthetically focused imaging algorithms for a linear array aperture: CSM (Common Source Method), SAFT and TFM (Total Focusing Method). The resolution of the different techniques is obtained from scalar diffraction theory and then validated by means of a low frequency (50kHz) steel plate experiment using PZT excitation and laser reception of the A0 mode. Imaging of through thickness slits parallel to the array is then discussed.

  20. Square rooter using saw tooth wave-based time division technique

    Directory of Open Access Journals (Sweden)

    Krishnagiri Chinnathambi Selvam

    2014-02-01

    Full Text Available A simple square rooter using two op-amps and a switch is described. It uses a saw tooth wave as reference clock and the square rooting principle is obtained by a time division technique. The circuit accepts an input dc voltages V(I and produce an output voltage V(O = √V(I V(T. V(T is a constant voltage which is the peak value of the reference saw tooth wave. Verification of the feasibility of the circuit configuration is established by way of test results.

  1. Further Evaluation of the Neutron Resonance Transmission Analysis (NRTA) Technique for Assaying Plutonium in Spent Fuel

    Energy Technology Data Exchange (ETDEWEB)

    J. W. Sterbentz; D. L. Chichester

    2011-09-01

    This is an end-of-year report (Fiscal Year (FY) 2011) for the second year of effort on a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The second-year goals for this project included: (1) assessing the neutron source strength needed for the NRTA technique, (2) estimating count times, (3) assessing the effect of temperature on the transmitted signal, (4) estimating plutonium content in a spent fuel assembly, (5) providing a preliminary assessment of the neutron detectors, and (6) documenting this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes work performed over a nine month period from January-September 2011 and is to be considered a follow-on or add-on report to our previous published summary report from December 2010 (INL/EXT-10-20620).

  2. Analysis of power-dependent phase-matched four-wave mixing in dispersion-managed transmission systems.

    Science.gov (United States)

    Gao, Shiming; Yang, Changxi; Jin, Guofan

    2003-12-20

    We investigate power-dependent phase-matched four-wave mixing (FWM) in wavelength division multiplexing transmission lines, in which positive and negative dispersion fibers are alternately arranged to manage the dispersion and the dispersion slope. The FWM effect shows power-independent phase matching when the channel power is low. However, it is power dependent at high power. The maximum FWM conversion efficiency is shifted away from the zero channel space in the case of power-dependent phase matching. Optimization of the dispersion system for suppression of the FWM effect is determined.

  3. Observation of genuine wave vector (k or β) gap in a dynamic transmission line and temporal photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Reyes-Ayona, J. R.; Halevi, P., E-mail: halevi@inaoep.mx [Electronics Department, Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla 72840 (Mexico)

    2015-08-17

    By definition, a temporal photonic crystal (TPC) has a permittivity ε(t) that varies periodically with time. We prove that, in the long wavelength limit, a TPC is accurately mimicked by a dynamic transmission line (DTL) having a capacitance (inductance) per unit length equal to ε(t) (μ). Employing a DTL in the microwave region, we measured the photonic band structure, which results to display a genuine wave vector (k or β) gap, in very good agreement with our theoretical model and the equivalent TPC.

  4. Prediction of transmission, reflection and absorption coefficients of periodic structures using a hybrid Wave Based - Finite Element unit cell method

    Science.gov (United States)

    Deckers, Elke; Jonckheere, Stijn; Van Belle, Lucas; Claeys, Claus; Desmet, Wim

    2018-03-01

    This paper presents a hybrid Wave Based Method - Finite Element unit cell method to predict the absorption, reflection and transmission properties of arbitrary, two-dimensional periodic structures. The planar periodic structure, represented by its unit cell combined with Bloch-Floquet periodicity boundary conditions, is modelled within the Finite Element Method, allowing to represent complex geometries and to include any type of physics. The planar periodic structure is coupled to semi-infinite acoustic domains above and/or below, in which the dynamic pressure field is modelled with the Wave Based Method, applying a wave function set that fulfills the Helmholtz equation and satisfies the Sommerfeld radiation condition and the Bloch-Floquet periodicity conditions inherently. The dynamic fields described within both frameworks are coupled using a direct coupling strategy, accounting for the mutual dynamic interactions via a weighted residual formulation. The method explicitly accounts for the interaction between the unit cell and the surrounding acoustic domain, also accounting for higher order periodic waves. The convergence of the method is analysed and its applicability is shown for a variety of problems, proving it to be a useful tool combining the strengths of two methods.

  5. Seamless Optical Fiber-Wireless Millimeter- Wave Transmission Link for Access Networks

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Lebedev, Alexander; Vegas Olmos, Juan José

    2013-01-01

    This paper presents an experimental demonstration of a millimeter-wave wireless bridge in the W-band for transparent broadband fiber access in the sub-urban areas, where full fiber connections are impracticable....

  6. Fabrication of high-transmission microporous membranes by proton beam writing-based molding technique

    Science.gov (United States)

    Wang, Liping; Meyer, Clemens; Guibert, Edouard; Homsy, Alexandra; Whitlow, Harry J.

    2017-08-01

    Porous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth substrates, and plasma filtration. Conventional silicon fabrication approaches are not suitable for microporous membranes due to the low mechanical stability of thin film substrates. Other techniques like ion track etching are limited to the production of randomly distributed and randomly orientated pores with non-uniform pore sizes. In this project, we developed a procedure for fabricating high-transmission microporous membranes by proton beam writing (PBW) with a combination of spin-casting and soft lithography. In this approach, focused 2 MeV protons were used to lithographically write patterns consisting of hexagonal arrays of high-density pillars of few μm size in a SU-8 layer coated on a silicon wafer. After development, the pillars were conformably coated with a thin film of poly-para-xylylene (Parylene)-C release agent and spin-coated with polydimethylsiloxane (PDMS). To facilitate demolding, a special technique based on the use of a laser-cut sealing tape ring was developed. This method facilitated the successful delamination of 20-μm thick PDMS membrane with high-density micropores from the mold without rupture or damage.

  7. Localization of human immunodeficiency virus antigens in infected cells by scanning/transmission-immunogold techniques

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, M.I.; Santa Maria, I.; de Andres, R.; Najera, R.

    1988-01-01

    An application of high resolution scanning/transmission electron microscopy (STEM) and gold-labelling techniques for the rapid detection of human immunodeficiency virus (HIV) in infected cells has been developed. Experimental in vitro studies for detecting two HIV structural proteins, gp41 and p17, were performed following an indirect labeling procedure that uses monoclonal anti-p17 and anti-gp41 antibodies as primary antibodies and 40 nm gold-linked goat antimouse IgG as secondary antibodies. The cells were then studied by STEM in the scanning mode. Unambiguous localization of the viral antigens was possible by combining the three-dimensional image provided by the secondary electron image and the atomic number-dependent backscattered electron image for the identification of the gold marker. This technique combines both the morphological information and the rapid procedures of scanning electron microscopy with the precise and sensitive antigen detection provided by the use of STEM and immunological methods. The preliminary results of its application to the study of peripheral blood mononuclear cells from four anti-HIV-seropositive patients showing the presence of specific labeling in all of them suggest that it might prove useful for early detection of HIV infection before seroconversion, as well as for quantitative studies.

  8. Wavefront Correction of Ionospherically Propagated HF Radio Waves Using Covariance Matching Techniques

    Directory of Open Access Journals (Sweden)

    Y. Zhu

    2017-04-01

    Full Text Available High Frequency (HF radio waves propagating in the ionospheric random inhomogeneous media exhibit a spatial nonlinearity wavefront which may limit the performance of conventional high-resolution methods for HF sky wave radar systems. In this paper, the spatial correlation function of wavefront is theoretically derived on condition that the radio waves propagate through the ionospheric structure containing irregularities. With this function, the influence of wavefront distortions on the array covariance matrix can be quantitatively described with the spatial coherence matrix, which is characterized with the coherence loss parameter. Therefore, the problem of wavefront correction is recast as the determination of coherence loss parameter and this is solved by the covariance matching (CM technique. The effectiveness of the proposed method is evaluated both by the simulated and real radar data. It is shown numerically that an improved direction of arrival (DOA estimation performance can be achieved with the corrected array covariance matrix.

  9. Laser photoacoustic technique for ultrasonic surface acoustic wave velocity evaluation on porcelain

    Science.gov (United States)

    Qian, K.; Tu, S. J.; Gao, L.; Xu, J.; Li, S. D.; Yu, W. C.; Liao, H. H.

    2016-10-01

    A laser photoacoustic technique has been developed to evaluate the surface acoustic wave (SAW) velocity of porcelain. A Q-switched Nd:YAG laser at 1064 nm was focused by a cylindrical lens to initiate broadband SAW impulses, which were detected by an optical fiber interferometer with high spatial resolution. Multiple near-field surface acoustic waves were observed on the sample surface at various locations along the axis perpendicular to the laser line source as the detector moved away from the source in the same increments. The frequency spectrum and dispersion curves were obtained by operating on the recorded waveforms with cross-correlation and FFT. The SAW phase velocities of the porcelain of the same source are similar while they are different from those of different sources. The marked differences of Rayleigh phase velocities in our experiment suggest that this technique has the potential for porcelain identification.

  10. Symmetry breaking and restoring wave transmission in diode-antidiode double chains.

    Science.gov (United States)

    Lepri, Stefano; Malomed, Boris A

    2013-04-01

    We introduce a system of two parallel-coupled discrete nonlinear Schrödinger inhomogeneous chains. Each one favors the unidirectional transmission of incident packets, in the opposite directions with respect to each other. Two different configurations of the diode-antidiode pair are considered, i.e., a ladder and a plaquette. They feature, respectively, the uniform transverse linear coupling or the coupling limited to the central nonlinear segment of the system. In the case of weak linear coupling, the symmetry breaking is observed (i.e., the pair still features the diode behavior), while the moderately strong coupling restores the symmetry, making the transmission effectively bidirectional. In the case of the ladder, an oscillatory dependence of the transmission on the strength of the coupling is observed and qualitatively explained.

  11. Remarkable transmission characteristics of optical waves through modulated double-layered metallic slit arrays

    Directory of Open Access Journals (Sweden)

    Yasunori Tokuda

    2012-12-01

    Full Text Available We reveal the distinct wavelength dependence of not only the transmission power but also the phase change in double-layered metallic slit array systems with gradually modulated slit intervals, which are promising structures for achieving novel optical phased-array functions, through finite-difference time-domain simulations. In spite of the structural modifications, the transmittance of the non-periodic system displays waveguide mode resonance for a conventional constant-period array system. By the resonance effect, maximum phase change is achieved with sufficiently high output powers around the transmission peak wavelength, and further enhanced to values much larger than those estimated simply from the optical path.

  12. A Novel High-Frequency Voltage Standing-Wave Ratio-Based Grounding Electrode Line Fault Supervision in Ultra-High Voltage DC Transmission Systems

    Directory of Open Access Journals (Sweden)

    Yufei Teng

    2017-03-01

    Full Text Available In order to improve the fault monitoring performance of grounding electrode lines in ultra-high voltage DC (UHVDC transmission systems, a novel fault monitoring approach based on the high-frequency voltage standing-wave ratio (VSWR is proposed in this paper. The VSWR is defined considering a lossless transmission line, and the characteristics of the VSWR under different conditions are analyzed. It is shown that the VSWR equals 1 when the terminal resistance completely matches the characteristic impedance of the line, and when a short circuit fault occurs on the grounding electrode line, the VSWR will be greater than 1. The VSWR will approach positive infinity under metallic earth fault conditions, whereas the VSWR in non-metallic earth faults will be smaller. Based on these analytical results, a fault supervision criterion is formulated. The effectiveness of the proposed VSWR-based fault supervision technique is verified with a typical UHVDC project established in Power Systems Computer Aided Design/Electromagnetic Transients including DC(PSCAD/EMTDC. Simulation results indicate that the proposed strategy can reliably identify the grounding electrode line fault and has strong anti-fault resistance capability.

  13. Ground-Wave Propagation Effects on Transmission Lines through Error Images

    Directory of Open Access Journals (Sweden)

    Uribe-Campos Felipe Alejandro

    2014-07-01

    Full Text Available Electromagnetic transient calculation of overhead transmission lines is strongly influenced by the natural resistivity of the ground. This varies from 1-10K (Ω·m depending on several media factors and on the physical composition of the ground. The accuracy on the calculation of a system transient response depends in part in the ground return model, which should consider the line geometry, the electrical resistivity and the frequency dependence of the power source. Up to date, there are only a few reports on the specialized literature about analyzing the effects produced by the presence of an imperfectly conducting ground of transmission lines in a transient state. A broad range analysis of three of the most often used ground-return models for calculating electromagnetic transients of overhead transmission lines is performed in this paper. The behavior of modal propagation in ground is analyzed here into effects of first and second order. Finally, a numerical tool based on relative error images is proposed in this paper as an aid for the analyst engineer to estimate the incurred error by using approximate ground-return models when calculating transients of overhead transmission lines.

  14. Leaky wave antenna with amplitude controlled beam steering based on composite right/left-handed transmission lines

    Science.gov (United States)

    Eberspächer, M. A.; Eibert, T. F.

    2010-09-01

    An antenna comprising two different composite right/left-handed transmission line structures is proposed which enables easy beam steering at an operation frequency of 10 GHz. The composite right/left-handed transmission lines are based on planar, periodically arranged via free unit cells, implemented in microstrip technology. Both transmission lines exhibit the infinite wavelength phenomenon which occurs at 9.72 GHz and 9.89 GHz, respectively. Thus, operating the different leaky wave structures at 10 GHz, radiation with azimuth angles of ±8° and ±17° can be achieved depending on the selected input port. In order to obtain a tunable main beam direction, the radiation patterns of both structures are superimposed by feeding them simultaneously. The influence of each guiding structure, and hence the direction of the main beam, can be controlled via the feeding amplitude. As a result of this, the beam can be steered between ±17° with a gain of up to 10 dBi. The guiding structures are arranged in parallel with a clearance of a=12.2 mm which is less than half of the wavelength in free space. This allows in a further step the attachment of additional guiding structures in order to increase the tunable angle range or creating an antenna array with a small beamwidth in the elevation plane without the occurrence of grating lobes. An antenna prototype was fabricated and validated by measurements.

  15. Transmission loss of multilayer panels containing a fluid using progressive wave model: Comparison with impedance progressive model and experiments

    Science.gov (United States)

    Mohammadi, N.; Mahjoob, M. J.

    2009-04-01

    The progressive wave model is applied to calculate transmission loss (TL) of triple layer panels. Theoretical values are then compared with impedance progressive model and experimental results. The triple layer panel comprises two solid layers with a middle layer of air or liquid. An impedance tube is employed to measure the TL values experimentally. The comparison of the two analytical models shows that the results of both models are relatively close. However, the progressive wave model leads to slightly larger values for a wide range of frequencies. Also, for the case of an air middle layer, a shift of the resonances to higher frequencies is observed in the results of the progressive wave model. Computational results also demonstrate that applying a liquid middle layer (replacing air) significantly improves the performance of the acoustic panel particularly at frequencies below 4000 rad/s (640 Hz). Shifting resonance frequencies to higher frequencies is another advantage of incorporating the liquid layer. Good agreement was also found between theoretical and experimental results. To cite this article: N. Mohammadi, M.J. Mahjoob, C. R. Mecanique 337 (2009).

  16. A Novel Noise Free Transmission Technique for Designing 100Gb/s Future Generation Optical Communication System

    DEFF Research Database (Denmark)

    Das, Bhagwan; Abdullah, M.F.L.; Pandey, Bishwajeet

    2017-01-01

    that BER of 10-12+, Q-factor 98 at power penalty of 14 dB is attained using the designed technique for transmitting 100Gb/s at 300 Km. Whereas, existing NRZ technique achieved a BER of 10-6, Q-factor 32 at power penalty of 11 dB for same similar transmission data rate and distance. The designed offers...

  17. The forced sound transmission of finite single leaf walls using a variational technique

    DEFF Research Database (Denmark)

    Brunskog, Jonas

    2012-01-01

    , and the fact that the wave field in the wall is consisting of two types of waves, namely forced waves due to the exciting acoustic field, and free bending waves due to reflections in the boundary. The aim of the present paper is to derive simple analytical formulas for the forced part of the airborne sound......The single wall is the simplest element of concern in building acoustics, but there still remain some open questions regarding the sound insulation of this simple case. The two main reasons for this are the effects on the excitation and sound radiation of the wall when it has a finite size...

  18. Monitoring in the post-closure phase. Development of wireless techniques for data transmission from the repository to the surface

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Thomas J.; Rosca-Bocancea, Ecaterina; Hart, Jaap [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands)

    2015-07-01

    When the in-situ monitoring in a geological disposal facility is continued during the post-closure phase, monitoring data need to be transmitted wirelessly from the repository to the surface. Wireless data transmission is used today in many applications, but the large attenuation by the geologic medium between the disposal facility and the surface makes the application of high-frequency based techniques impractical. As part of the EURATOM FP-7 project MoDeRn (Monitoring Developments for safe Repository operation and staged closure), NRG has investigated the feasibility of wireless data transmission through an argillaceous host rock (Boom Clay), making use of low frequency magnetic fields. The main focus of the contribution was to analyze and optimize the energy efficiency of this technique. Therefore, a mathematical model description has been developed that allows to estimate the expected signal strength on the earth's surface on basis of the most relevant characteristics of transmitter, receiver and transmission path. The model is used to analyze the complex interactions of different system parameters, and is applied to design an optimized set-up for through-the-earth data transmission and to estimate minimum energy demands for signal transmission. To demonstrate the potentials of this technique, experiments were performed in the 225 m deep underground research facility HADES in Mol, Belgium. Signal propagation and attenuation by the geologic medium between the HADES and the surface has been measured, and the site-specific magnetic background noise at the surface in Mol has been characterized. Based on the results, optimum conditions for signal transmission have been derived and data transmission experiments have been performed. Results show that despite large local interferences on the surface in Mol, wireless data transmission through 225 m of a geological medium is possible. Data transmission rates up to 100 bit/s has been successfully tested. The

  19. Data transmission at millimeter waves exploiting the 60 GHz band on silicon

    CERN Document Server

    Khalaf, Khaled; Wambacq, Piet; Long, John R

    2015-01-01

    This book describes the design of a receiver front-end circuit for operation in the 60GHz range in 90nm CMOS. Physical layout of the test circuit and post-layout simulations for the implementation of a test chip including the QVCO and the first stage divider are also presented. The content of this book is particularly of interest to those working on mm-wave frequency generation and signal reception.

  20. Interpretation of VLF phase data. [analysis of effects of various parameters on electromagnetic wave transmission

    Science.gov (United States)

    Reder, F.; Hargrave, J.; Crouchley, J.

    1972-01-01

    The specific applications of very low frequency phase tracking are described. The requirements for correct interpretation of very low frequency phase data are defined. The effects of the lower ionosphere and the ground along the path of signal propagation are analyzed. The following subjects are discussed: (1) interpretation equipment, (2) representation of very low frequency waves, (3) diurnal effects and mode interference phenomena, (4) antipodal interference, and (5) overall effects resulting from solar flares, galactic X-rays, and geomagnetic parameters.

  1. Application of background-oriented schlieren (BOS) technique to a laser-induced underwater shock wave

    CERN Document Server

    Yamamoto, Shota; Kameda, Masaharu

    2015-01-01

    We build an ultra-high-speed imaging system based on the background-oriented schlieren (BOS) technique in order to capture a laser-induced underwater shock wave. This BOS technique is able to provide two-dimensional density-gradient field of fluid and requires a simple setup. The imaging system consists of an ultra-high speed video camera, a laser stroboscope, and a patterned background. This system takes images every 0.2 $\\mu$s. Furthermore, since the density change of water disturbed by the shock is exceedingly small, the system has high spatial resolution $\\sim$ 10 $\\mu$m/pixel. Using this BOS system, we examine temporal position of a shock wave. The position agrees well with that measured by conventional shadowgraph, which indicates that the high-speed imaging system can successfully capture the instantaneous position of the underwater shock wave that propagates with the speed of about 1500 m/s. The local density gradient can be determined up to $O$(10$^3$ kg/m$^4$), which is confirmed by the gradient est...

  2. Experimental demonstration of 24-Gb/s CAP-64QAM radio-over-fiber system over 40-GHz mm-wave fiber-wireless transmission.

    Science.gov (United States)

    Zhang, Junwen; Yu, Jianjun; Chi, Nan; Li, Fan; Li, Xinying

    2013-11-04

    We propose and demonstrate a novel CAP-ROF system based on multi-level carrier-less amplitude and phase modulation (CAP) 64QAM with high spectrum efficiency for mm-wave fiber-wireless transmission. The performance of novel CAP modulation with high order QAM, for the first time, is investigated in the mm-wave fiber-wireless transmission system. One I/Q modulator is used for mm-wave generation and base-band signal modulation based on optical carrier suppression (OCS) and intensity modulation. Finally, we demonstrated a 24-Gb/s CAP-64QAM radio-over-fiber (ROF) system over 40-km stand single-mode-fiber (SMMF) and 1.5-m 38-GHz wireless transmission. The system operation factors are also experimentally investigated.

  3. A calibration technique for measuring the complex permittivity of materials with planar transmission lines

    Science.gov (United States)

    A simple two-standard calibration procedure for determining the permittivity of a material from the propagation constant measured with planar transmission lines is presented. The suitability of this procedure is demonstrated by using a coplanar waveguide transmission-line sensor to measure the permi...

  4. Measuring the complex permittivity of thin grain samples by the free-space transmission technique

    Science.gov (United States)

    In this paper, a numerical method for solving a higherorder model that relates the measured transmission coefficient to the permittivity of a material is used to determine the permittivity of thin grain samples. A method for resolving the phase ambiguity of the transmission coefficient is presented....

  5. Transmission of rectal electric waves: is it through circular or longitudinal smooth muscle layers or both?

    Science.gov (United States)

    Shafik, A; El-Sibai, O

    2001-04-01

    The rectum possesses electric activity in the form of pacesetter (PPs) and action potentials (APs). In recent studies we suggested that the waves are not initiated by the extrarectal autonomic innervation but might be triggered by a 'rectosigmoid pacemaker' and are transmitted in the rectal wall through the rectal musculature and not the enteric nerve plexus. To investigate whether the rectal waves are transmitted through the circular or longitudinal muscle layer, the rectum of 18 mongrel dogs was exposed under anesthesia through an abdominal incision. Three electrodes were applied to the rectal wall (longitudinal muscle layer) and another 3 electrodes to the circular muscle; the latter was exposed by splitting apart the fibers of the longitudinal muscle. Rectal electric activity and pressure were recorded from the 6 electrodes before and after performing individual myotomy of the rectal longitudinal (9 dogs), circular (9 dogs), and then the whole muscle layers (18 dogs). The myotomy was performed proximal to and between the electrodes. Pacesetter (PPs) and action potentials (APs) were recorded from the 3 electrodes on the longitudinal muscle but no waves were registered from those on the circular muscle. After longitudinal muscle myotomy was performed between electrodes 1 and 2, PPs and APs were recorded from electrode 1 but not 2 and 3 and when performed proximally to electrode 1, no waves were registered. The rectal pressure increased concomitantly with occurrence of APs. Circular muscle myotomy effected no change in the rectal electric activity recorded from the 3 electrodes applied to the longitudinal muscle. In total muscle myotomy, the electric waves were recorded from the electrodes proximal but not distal to the myotomy. We propose that the motile activity of the rectal longitudinal muscle is initiated by the electric activity which appears to be triggered by the rectosigmoid pacemaker, while that of the circular muscle fibers is believed to be initiated

  6. Full-Wave Techniques for the Analysis of Electrodynamics and Coherent Quantum Transport in Graphene Nanodevices.

    Directory of Open Access Journals (Sweden)

    Luca Pierantoni

    2012-11-01

    Full Text Available We report on full-wave techniques in the frequency (energy-domain and the time-domain, aimed at the investigation of the combined electromagnetic-coherent transport problem in carbon based nanostructured materials and devices viz. graphene nanoribbons. The frequency-domain approach is introduced in order to describe a Poisson-Schrödinger / Dirac system in a quasi static framework. Thetime-domain approach deals with the full-wave solution of the combined Maxwell-Schrödinger / Dirac system of equations. From the above theoretical platforms, home-made solvers are provided, aimed atdealing with challenging problems in realistic devices / systems environments, typical of the area of radio-frequency nanoelectronics.

  7. 45  Gb/s PAM4 transmission based on VCSEL with light injection and optoelectronic feedback techniques.

    Science.gov (United States)

    Lu, Hai-Han; Li, Chung-Yi; Chen, Hwan-Wei; Yang, Zih-Yi; Lin, Xin-Yao; Cheng, Ming-Te; Lu, Chang-Kai; Shih, Tien-Tsorng

    2016-11-01

    A 45 Gb/s four-level pulse amplitude modulation (PAM4) transmission based on an 850 nm/7.4 GHz vertical cavity surface emitting laser (VCSEL) with light injection and optoelectronic feedback techniques is proposed. Experimental results show that such an 850 nm/7.4 GHz VCSEL with light injection and optoelectronic feedback techniques is powerful enough for a 45 Gb/s PAM4 signal transmission. To the best of our knowledge, this Letter is the first to adopt a VCSEL transmitter with light injection and optoelectronic feedback techniques in a 45 Gb/s PAM4 transmission system. Good bit error rate performance and three independent clear eye diagrams are achieved over a 200-m OM4 multimode fiber transport. This proposed 45 Gb/s PAM4 VCSEL-based transmission system has great potential for providing effective bandwidth in short-reach optical data communications.

  8. Reflection and transmission of electromagnetic waves at a temporal boundary: comment.

    Science.gov (United States)

    Bakunov, M I; Maslov, A V

    2014-10-15

    Recently, Xiao et al. [Opt. Lett. 39, 574 (2014)] compared two sets of boundary conditions and the resulting transformation coefficients for an electromagnetic wave at a temporal boundary. They claimed to identify a correct set and to resolve the existing discrepancy in the literature. We point out that the boundary conditions discarded by Xiao et al. as incorrect have been used in the literature for rapidly growing plasma, for which the material model of Xiao et al. is not appropriate. We show that Xiao et al. misinterpreted the results from the literature by opposing two sets of boundary conditions that are related to different material models of the temporal boundary.

  9. Propagation of Torsional Alfvén Waves from the Photosphere to the Corona: Reflection, Transmission, and Heating in Expanding Flux Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Ballester, José Luis, E-mail: roberto.soler@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2017-05-01

    It has been proposed that Alfvén waves play an important role in the energy propagation through the solar atmospheric plasma and its heating. Here we theoretically investigate the propagation of torsional Alfvén waves in magnetic flux tubes expanding from the photosphere up to the low corona and explore the reflection, transmission, and dissipation of wave energy. We use a realistic variation of the plasma properties and the magnetic field strength with height. Dissipation by ion–neutral collisions in the chromosphere is included using a multifluid partially ionized plasma model. Considering the stationary state, we assume that the waves are driven below the photosphere and propagate to the corona, while they are partially reflected and damped in the chromosphere and transition region. The results reveal the existence of three different propagation regimes depending on the wave frequency: low frequencies are reflected back to the photosphere, intermediate frequencies are transmitted to the corona, and high frequencies are completely damped in the chromosphere. The frequency of maximum transmissivity depends on the magnetic field expansion rate and the atmospheric model, but is typically in the range of 0.04–0.3 Hz. Magnetic field expansion favors the transmission of waves to the corona and lowers the reflectivity of the chromosphere and transition region compared to the case with a straight field. As a consequence, the chromospheric heating due to ion–neutral dissipation systematically decreases when the expansion rate of the magnetic flux tube increases.

  10. Determining Engineering Properties of the Shallow Lunar Subsurface using Seismic Surface Wave Techniques

    Science.gov (United States)

    Yeluru, P. M.; Baker, G. S.

    2008-12-01

    The geology of Earth's moon has previously been examined via telescopic observations, orbiting spacecraft readings, lunar sample analysis, and also from some geophysical data. Previous researchers have examined layering of the moon and models exist explaining the velocity variations in the mantle and core. However, no studies (or datasets) currently exist regarding the engineering properties of the shallow (channel Analysis of Surface Wave (MASW), has greatly increased our ability to map subsurface variations in physical properties. The MASW method involves deployment of multiple seismometers to acquire 1-D or 2-D shear wave velocity profiles that can be directly related to various engineering properties. The advantage of this technique over drilling boreholes or any other geophysical technique is that it is less intensive, non-invasive, more cost- effective, and more robust because strong surface-wave records are almost guaranteed. In addition, data processing and analysis is fairly straightforward, and the MASW method allows for analysis of a large area of interest as compared to drilling boreholes. A new scheme using randomly distributed geophones (likely deployed from a mortar-type device) instead of a conventional linear array will be presented. A random array is necessary for lunar exploration because of the logistical constraints involved in deploying a linear or circular array robotically or by astronaut. Initial results indicate that robust dispersion curves (and thus subsurface models of engineering properties) can be obtained from the random array geometry. This random geometry will also be evaluated (a) for potential improvements in the resolution of the dispersion image and (b) as more accurate method for assessing azimuthal variations in the subsurface geology. Based on the extreme logistics imposed by lunar exploration and the anticipated engineering needs of lunar exploration, information obtained on the moon using this technique should prove to be

  11. Ultrasound Transmission Times in Biologically Deteriorated Wood

    Science.gov (United States)

    Christopher Adam Senalik; Robert J. Ross; Rodney DeGroot

    2015-01-01

    The use of a variety of stress wave transmission techniques for the in-service condition assessment of deteriorated wood is well documented. This paper summarizes results from an extensive study designed to examine the relationship between ultrasound transmission times and the deterioration of exposed wood. Two hundred seventy (270) southern pine lumber specimens were...

  12. A singularity extraction technique for computation of antenna aperture fields from singular plane wave spectra

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel

    2008-01-01

    An effective technique for extracting the singularity of plane wave spectra in the computation of antenna aperture fields is proposed. The singular spectrum is first factorized into a product of a finite function and a singular function. The finite function is inverse Fourier transformed...... numerically using the Inverse Fast Fourier Transform, while the singular function is inverse Fourier transformed analytically, using the Weyl-identity, and the two resulting spatial functions are then convolved to produce the antenna aperture field. This article formulates the theory of the singularity...

  13. Broadband multiple-cascaded integration of electroabsorption modulators and high impedance transmission lines by lowering standing-wave effect.

    Science.gov (United States)

    Wu, Jui-Pin; Chen, Rui-Ren; Chiu, Yi-Jen

    2012-04-09

    Standing wave effect of applied electrical field on optical modulation in multiple-cascaded integration (CI) electroabsorption modulator (EAM) and high-impedance transmission line (HITL) has been investigated in this paper. As modulation frequency is increased to the scale that electrical wavelength is in the order of optical modulator length, multiple electrical reflection and self-interference on impedance-mismatch boundaries becomes significant, leading to strong position-dependent field distribution and degrading modulation bandwidth. Sharp bandwidth roll of electrical-optical (EO) conversion by standing wave has been found experimentally in CI structure, consistent with simulation results. By comparing different segment number and length of CI- structure, larger section number of design can overcome such problem to get more flatten bandwidth response. Such simple CI for 300μm long EAM has been demonstrated with flat EO response of -3dB drop 45GHz and -10dB microwave reflection (up to 65GHz) in 6-segement device, suggesting this scheme design is quite useful for efficient broad band modulation.

  14. Power transmission planning using heuristic optimisation techniques: Deterministic crowding genetic algorithms and Ant colony search methods

    OpenAIRE

    Chebbo, Hind Munzer

    2000-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. The goal of transmission planning in electric power systems is a robust network which is economical, reliable, and in harmony with its environment taking into account the inherent uncertainties. For reasons of practicality, transmission planners have normally taken an incremental approach and tended to evaluate a relatively small number of expansion alternatives over a relatively short time h...

  15. Super-ensemble techniques applied to wave forecast: performance and limitations

    Directory of Open Access Journals (Sweden)

    F. Lenartz

    2010-06-01

    Full Text Available Nowadays, several operational ocean wave forecasts are available for a same region. These predictions may considerably differ, and to choose the best one is generally a difficult task. The super-ensemble approach, which consists in merging different forecasts and past observations into a single multi-model prediction system, is evaluated in this study. During the DART06 campaigns organized by the NATO Undersea Research Centre, four wave forecasting systems were simultaneously run in the Adriatic Sea, and significant wave height was measured at six stations as well as along the tracks of two remote sensors. This effort provided the necessary data set to compare the skills of various multi-model combination techniques. Our results indicate that a super-ensemble based on the Kalman Filter improves the forecast skills: The bias during both the hindcast and forecast periods is reduced, and the correlation coefficient is similar to that of the best individual model. The spatial extrapolation of local results is not straightforward and requires further investigation to be properly implemented.

  16. HTS-SQUID NDE Technique for Pipes based on Ultrasonic Guided Wave

    Science.gov (United States)

    Hatsukade, Y.; Masutani, N.; Teranishi, S.; Masamoto, K.; Kanenaga, S.; Adachi, S.; Tanabe, K.

    2017-07-01

    This article describes research on the novel high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) non-destructive evaluation (NDE) technique for metallic pipes based on ultrasonic guided waves. We constructed HTS-SQUID NDE system for pipes based on ultrasonic guided waves, which were generated and received by means of the magnetostrictive effects. Using the system, we measured magnetic signals due to T (0, 1) mode ultrasonic guided waves that transmitted on aluminium pipe, and investigated influences of measurement parameters to the magnetic signals, such as direction of a HTS-SQUID gradiometer, lift-off distance, and intensity and frequency of input current fed to a magnetostrictive transmitter. With the gradiometer oriented parallel to the pipe axis, more than 10 times larger signals were measured compared with that oriented perpendicular to the pipe axis. Magnetic signals measured by the gradiometer were inverse proportional to the power of the list- off distance, and proportional to the intensity of the input current up to 1 App. Relation between the frequency of the input current and the measured signal was shown and discussed.

  17. Numerical study on air turbines with enhanced techniques for OWC wave energy conversion

    Science.gov (United States)

    Cui, Ying; Hyun, Beom-Soo; Kim, Kilwon

    2017-10-01

    In recent years, the oscillating water column (OWC) wave energy converter, which can capture wave energy from the ocean, has been widely applied all over the world. As the essential part of the OWC system, the impulse and Wells turbines are capable of converting the low pressure pneumatic energy into the mechanical shaft power. As an enhanced technique, the design of endplate or ring attached to the blade tip is investigated numerically in this paper. 3D numerical models based on a CFD-software FLUENT 12.0 are established and validated by the corresponding experimental results from the reports of Setoguchi et al. (2004) and Takao et al. (2001). Then the flow fields and non-dimensional evaluating coefficients are calculated and analyzed under steady conditions. Results show that the efficiency of impulse turbine with ring can reach up to 0.49 when ϕ=1, which is 4% higher than that in the cases for the endplate-type and the original one. And the ring-type Wells turbine with fixed guide vanes shows the best performance with the maximal efficiency of 0.55, which is 22% higher than that of the original one. In addition, the quasi-steady analysis is used to calculate the mean efficiency and output-work of a wave cycle under sinusoidal flow condition. Taking all together, this study provides support for structural optimization of impulse turbine and Wells turbine in the future.

  18. Electromagnetic Wave Absorbing Technique Using Periodic Patterns for Low RCS Patch Array Antenna

    Science.gov (United States)

    Jang, Hong-Kyu; Lee, Yeon-Gwan; Shin, Jae-Hwan; Kim, Chun-Gon

    2013-07-01

    This paper presents an electromagnetic wave absorbing technique to reduce a radar cross-section (RCS) of a patch array antenna without compromising their antenna performance. The technique is based on periodic patterns, which is made of resistive materials. The 2×2 patch array antenna with a resonance frequency of 3.0 GHz was designed and fabricated. To reduce the RCS of the patch array antenna, the periodic patterns using a square patch element were proposed and applied to the surface between the four antenna patches. The printed lossy periodic patterns have radar absorbing performance at 12.0 GHz frequency. The measured results show that the lossy periodic patterns have no significant effect on the antenna radiation performance. On the other hand, the RCS is reduced by more than 98% compared to the conventional antenna at the target frequency.

  19. Condition assessment of concrete pavements using both ground penetrating radar and stress-wave based techniques

    Science.gov (United States)

    Li, Mengxing; Anderson, Neil; Sneed, Lesley; Torgashov, Evgeniy

    2016-12-01

    Two stress-wave based techniques, ultrasonic surface wave (USW) and impact echo (IE), as well as ground penetrating radar (GPR) were used to assess the condition of a segment of concrete pavement that includes a layer of concrete, a granular base and their interface. Core specimens retrieved at multiple locations were used to confirm the accuracy and reliability of each non-destructive testing (NDT) result. Results from this study demonstrate that the GPR method is accurate for estimating the pavement thickness and locating separations (air voids) between the concrete and granular base layers. The USW method is a rapid way to estimate the in-situ elastic modulus (dynamic elastic modulus) of the concrete, however, the existence of air voids at the interface could potentially affect the accuracy and reliability of the USW test results. The estimation of the dynamic modulus and the P-wave velocity of concrete was improved when a shorter wavelength range (3 in. to 8.5 in.) corresponding to the concrete layer thickness was applied instead of the full wavelength rage (3 in. to 11 in.) based on the standard spacing of the receiver transducers. The IE method is proved to be fairly accurate in estimating the thickness of concrete pavements. However, the flexural mode vibration could affect the accuracy and reliability of the test results. Furthermore, the existence of air voids between the concrete and granular base layers could affect the estimation of the compression wave velocity of concrete when the full wavelength range was applied (3 in. to 11 in.). Future work is needed in order to improve the accuracy and reliability of both USW and IE test results.

  20. On a two-dimensional mode-matching technique for sound generation and transmission in axial-flow outlet guide vanes

    Science.gov (United States)

    Bouley, Simon; François, Benjamin; Roger, Michel; Posson, Hélène; Moreau, Stéphane

    2017-09-01

    The present work deals with the analytical modeling of two aspects of outlet guide vane aeroacoustics in axial-flow fan and compressor rotor-stator stages. The first addressed mechanism is the downstream transmission of rotor noise through the outlet guide vanes, the second one is the sound generation by the impingement of the rotor wakes on the vanes. The elementary prescribed excitation of the stator is an acoustic wave in the first case and a hydrodynamic gust in the second case. The solution for the response of the stator is derived using the same unified approach in both cases, within the scope of a linearized and compressible inviscid theory. It is provided by a mode-matching technique: modal expressions are written in the various sub-domains upstream and downstream of the stator as well as inside the inter-vane channels, and matched according to the conservation laws of fluid dynamics. This quite simple approach is uniformly valid in the whole range of subsonic Mach numbers and frequencies. It is presented for a two-dimensional rectilinear-cascade of zero-staggered flat-plate vanes and completed by the implementation of a Kutta condition. It is then validated in sound generation and transmission test cases by comparing with a previously reported model based on the Wiener-Hopf technique and with reference numerical simulations. Finally it is used to analyze the tonal rotor-stator interaction noise in a typical low-speed fan architecture. The interest of the mode-matching technique is that it could be easily transposed to a three-dimensional annular cascade in cylindrical coordinates in a future work. This makes it an attractive alternative to the classical strip-theory approach.

  1. A comparative study of surface waves inversion techniques at strong motion recording sites in Greece

    Science.gov (United States)

    Panagiotis C. Pelekis,; Savvaidis, Alexandros; Kayen, Robert E.; Vlachakis, Vasileios S.; Athanasopoulos, George A.

    2015-01-01

    Surface wave method was used for the estimation of Vs vs depth profile at 10 strong motion stations in Greece. The dispersion data were obtained by SASW method, utilizing a pair of electromechanical harmonic-wave source (shakers) or a random source (drop weight). In this study, three inversion techniques were used a) a recently proposed Simplified Inversion Method (SIM), b) an inversion technique based on a neighborhood algorithm (NA) which allows the incorporation of a priori information regarding the subsurface structure parameters, and c) Occam's inversion algorithm. For each site constant value of Poisson's ratio was assumed (ν=0.4) since the objective of the current study is the comparison of the three inversion schemes regardless the uncertainties resulting due to the lack of geotechnical data. A penalty function was introduced to quantify the deviations of the derived Vs profiles. The Vs models are compared as of Vs(z), Vs30 and EC8 soil category, in order to show the insignificance of the existing variations. The comparison results showed that the average variation of SIM profiles is 9% and 4.9% comparing with NA and Occam's profiles respectively whilst the average difference of Vs30 values obtained from SIM is 7.4% and 5.0% compared with NA and Occam's.

  2. A numerical dispersion compensation technique for time recompression of Lamb wave signals.

    Science.gov (United States)

    Sicard, René; Goyette, Jacques; Zellouf, Djamel

    2002-05-01

    A Fourier domain numerical reconstruction technique has been created in order to eliminate the time spread of Lamb wave signals caused by their dispersive nature. This method allows a good time compaction of the echoes obtained from a Lamb wave inspection. In a pulse-echo setup, reflection peaks coming from targets located close one from each other that could not be separated or seen within raw signals are identified using this procedure. The utility of this new technique goes from simple signal analysis to imaging purposes such as the improvement of B-scan images or SAFT processing. It has been tested in three different situations with the S0 mode generated in a frequency bandwidth where it is highly dispersive. The reconstruction of a pure reflection coming from the edge of a plate, the separation of the echoes resulting from reflections on two targets near one each other and the effects of the presence of an obstacle between the emitter and the receiver are treated. Good results are obtained for every case studied.

  3. Coordination between Generation and Transmission Maintenance Scheduling by Means of Multi-agent Technique

    Science.gov (United States)

    Nagata, Takeshi; Tao, Yasuhiro; Utatani, Masahiro; Sasaki, Hiroshi; Fujita, Hideki

    This paper proposes a multi-agent approach to maintenance scheduling in restructured power systems. The restructuring of electric power industry has resulted in market-based approaches for unbundling a multitude of service provided by self-interested entities such as power generating companies (GENCOs), transmission providers (TRANSCOs) and distribution companies (DISCOs). The Independent System Operator (ISO) is responsible for the security of the system operation. The schedule submitted to ISO by GENCOs and TRANSCOs should satisfy security and reliability constraints. The proposed method consists of several GENCO Agents (GAGs), TARNSCO Agents (TAGs) and a ISO Agent(IAG). The IAG’s role in maintenance scheduling is limited to ensuring that the submitted schedules do not cause transmission congestion or endanger the system reliability. From the simulation results, it can be seen the proposed multi-agent approach could coordinate between generation and transmission maintenance schedules.

  4. Interpreting the behavior of a quarter-wave transmission line resonator in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Gogna, G. S., E-mail: gurusharansingh.gogna@gmail.com; Turner, M. M. [NCPST, School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Karkari, S. K., E-mail: skarkari@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India)

    2014-12-15

    The quarter wave resonator immersed in a strongly magnetized plasma displays two possible resonances occurring either below or above its resonance frequency in vacuum, f{sub o}. This fact was demonstrated in our recent articles [G. S. Gogna and S. K. Karkari, Appl. Phys. Lett. 96, 151503 (2010); S. K. Karkari, G. S. Gogna, D. Boilson, M. M. Turner, and A. Simonin, Contrib. Plasma Phys. 50(9), 903 (2010)], where the experiments were carried out over a limited range of magnetic fields at a constant electron density, n{sub e}. In this paper, we present the observation of dual resonances occurring over the frequency scan and find that n{sub e} calculated by considering the lower resonance frequency is 25%–30% smaller than that calculated using the upper resonance frequency with respect to f{sub o}. At a given magnetic field strength, the resonances tend to shift away from f{sub o} as the background density is increased. The lower resonance tends to saturate when its value approaches electron cyclotron frequency, f{sub ce}. Interpretation of these resonance conditions are revisited by examining the behavior of the resonance frequency response as a function of n{sub e}. A qualitative discussion is presented which highlights the practical application of the hairpin resonator for interpreting n{sub e} in a strongly magnetized plasma.

  5. Computation of corona effects in transmission lines using state-space techniques

    Energy Technology Data Exchange (ETDEWEB)

    Herdem, Saadetdin [Nigde Univ., Dept. of Electrical and Electronics Engineering, Malatya (Turkey); Mamis, M. Salih [Inonu Univ., Dept. of Electrical and Electronics Engineering, Malatya (Turkey)

    2003-07-01

    In this paper, state-space method is applied to compute transients in power transmission lines by considering corona effects. Transmission line is modeled by lumped parameter identical sections to simulate the distribution nature of the line and nonlinear corona branches are combined with these sections. The whole system is composed of RLC elements, sources and switches. The response of the system is calculated using state-space method which has been developed for the analysis of nonlinear power electronic circuits with periodically operated switches. (Author)

  6. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

    Science.gov (United States)

    Campbell, J. F.; Lin, B.; Obland, M. D.; Liu, Z.; Kooi, S. A.; Fan, T. F.; Nehrir, A. R.; Meadows, B.; Browell, E. V.

    2016-12-01

    Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 MeasurementsJoel F. Campbell1, Bing Lin1, Michael D. Obland1, Zhaoyan Liu1, Susan Kooi2, Tai-Fang Fan2, Amin R. Nehrir1, Byron Meadows1, Edward V. Browell31NASA Langley Research Center, Hampton, VA 23681 2SSAI, NASA Langley Research Center, Hampton, VA 23681 3STARSS-II Affiliate, NASA Langley Research Center, Hampton, VA 23681 AbstractGlobal and regional atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission and the Atmospheric Carbon and Transport (ACT) - America project are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space and airborne platforms to meet the ASCENDS and ACT-America science measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud returns. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby minimizing bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new sub-meter hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. These techniques are used in a new data processing

  7. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for ASCENDS O2 Column Measurements

    Science.gov (United States)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. Wallace; Obland, Michael D.; Meadows, Byron

    2015-01-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

  8. The effect of autoclaving and polishing techniques on energy transmission of light-curing tips.

    Science.gov (United States)

    Kofford, K R; Wakefield, C W; Nunn, M E

    1998-08-01

    The purpose of this study was to investigate if autoclaving light-curing tips in sterilization packages using a properly maintained autoclave filled with distilled water reduced the buildup of boiler scale and allowed the tips to maintain their ability to transmit energy. Thirty light-curing tips were divided into groups: control, never autoclaved; group 1, no light-curing tip treatment, autoclaved only; group 2, autoclaved and treated with the Demetron/Kerr Optics Maintenance Kit; group 3, autoclaved and treated with the EFOS Fiberoptic Cleaning Kit; group 4, autoclaved and treated with Shofu Brownie and Greenie polishing points; and group 5, autoclaved and treated with a standard rubber prophylaxis cup. The curing tips were packaged and subjected to 30 autoclave cycles in a clinical autoclave with standard loads of clinical instruments. The light transmission was measured with a curing radiometer. Results showed a 7% decrease in energy transmission for the untreated tips compared to the control. Both polishing system groups demonstrated a 4% decrease. There was no significant difference between the control and the first three groups. The polishing point and prophylaxis cup groups showed significantly decreased energy transmission (decreases of 11% and 25%, respectively). Light-curing tips can be autoclaved with routine packaged loads of clinical instruments and retain their ability to transmit light energy, provided that the tips are packaged and the autoclave is properly maintained and filled with distilled water. Commercially available optics maintenance kits are effective in removing deposits and restoring light energy transmission.

  9. Transient and time-resolved four-wave mixing with collinear pump and probe pulses using the heterodyne technique

    DEFF Research Database (Denmark)

    Mecozzi, A.; Mørk, Jesper

    1998-01-01

    We review the recently proposed heterodyne technique for four-wave mixing experiments with collinear and co-polarized pulses. We discuss issues related to the parameters of the nonlinear dynamics of the sample that can be extracted by this technique....

  10. Closer to the native state. Critical evaluation of cryo-techniques for Transmission Electron Microscopy: preparation of biological samples.

    Science.gov (United States)

    Mielanczyk, Lukasz; Matysiak, Natalia; Michalski, Marek; Buldak, Rafal; Wojnicz, Romuald

    2014-01-01

    Over the years Transmission Electron Microscopy (TEM) has evolved into a powerful technique for the structural analysis of cells and tissues at various levels of resolution. However, optimal sample preservation is required to achieve results consistent with reality. During the last few decades, conventional preparation methods have provided most of the knowledge about the ultrastructure of organelles, cells and tissues. Nevertheless, some artefacts can be introduced at all stagesofstandard electron microscopy preparation technique. Instead, rapid freezing techniques preserve biological specimens as close as possible to the native state. Our review focuses on different cryo-preparation approaches, starting from vitrification methods dependent on sample size. Afterwards, we discuss Cryo-Electron Microscopy Of VItreous Sections (CEMOVIS) and the main difficulties associated with this technique. Cryo-Focused Ion Beam (cryo-FIB) is described as a potential alternative for CEMOVIS. Another post-processing route for vitrified samples is freeze substitution and embedding in resin for structural analysis or immunolocalization analysis. Cryo-sectioning according to Tokuyasu is a technique dedicated to high efficiency immunogold labelling. Finally, we introduce hybrid techniques, which combine advantages of primary techniques originally dedicated to different approaches. Hybrid approaches permit to perform the study of difficult-to-fix samples and antigens or help optimize the sample preparation protocol for the integrated Laser and Electron Microscopy (iLEM) technique.

  11. New technique for generating light source array in tilted wave interferometer

    Science.gov (United States)

    Li, Jia; Shen, Hua; Zhu, Rihong; Lu, Qing

    2017-06-01

    Smaller and lighter optical systems with better performance can be built by the use of freeform optics. However, most optical systems were constrained to traditional surfaces for the accurate metrology of freeform surface is a challenge so far unsolved. One high-precision approach to measure freeform surface with less time and expense is using tilted wave interferometer. A lens array is placed in the test path of the interferometer, which can generate light source array that locally compensate the gradient of test surface. But each source generated by lens array is not ideal spherical wave which contains aberrations. In addition, the sources cannot be activated individually during the measurement, so that it is impossible to perform an irregular source array according to the gradient variation of each test surface. Thus, a novel technique based on fiber array is proposed for generating irregular source array. Whereas, the position deviation of each fiber and phase difference produced by the length of each fiber affect the measurement result. In this paper, the consequences of above errors are analyzed. A calibration method can obtain the exact spatial coordinates of each fiber is suggested to calculate the position deviation of each fiber. Meanwhile, a method based on Mach-Zehnder interference system is presented, which can get phase difference produced by the length of each fiber accurately. Afterwards, the data obtained by the two calibration methods are introduced into the mathematical model of system error for eliminating the measurement error introduced by the use of fiber array. An elliptical mirror is measured by our tilted wave interferometer based on fiber array showing the feasibility of the proposed methods.

  12. Deconvolution of teleseismicp-waves using the SVA and autoregressive techniques

    Science.gov (United States)

    Dasgupta, Saptarshi

    In this study, the deconvolution of three-component teleseismic P-waves is investigated using the autocorrelation of the P to SV scattered waves. By assuming that the P to SV scattering coefficients are random and white, the autocorrelation of the SV component (SVA) provides an estimate of the autocorrelation of the source and distant earth signature. This is similar to using the autocorrelation of a reflection seismogram for deconvolution in exploration seismology where the P to P scattering coefficients are assumed to be random and white. For earthquake data the source signature is generally not minimum phase. However a minimum phase wavelet obtained from the SV autocorrelation can be used to deconvolve the original data that have been processed to be minimum phase. The SVA approach has been tested using synthetic data and then applied to observed teleseismic data from the 1993 Cascadia experiment. Since deconvolution results are often restricted in frequency range, an extrapolation of the deconvolved frequency spectra is next investigated using an autoregressive (AR) approach and an extended time-domain deconvolution approach to obtain better temporal resolution. A prediction error filter is used to perform the autoregressive extrapolation to estimate the unknown spectral values of the deconvolution results. An extended time-domain deconvolution approach is also developed where the deconvolved spectra are enhanced using increased high-cut filters for the time-domain deconvolution. The AR and extended time-domain deconvolution approaches are compared using synthetic data and observed data from the GBA seismic array in India. The deconvolution of vertical component seismic data using the SVA technique is finally applied to selected INDEPTH II and CDSN seismic stations to investigate the P-wave velocity structure in southern Tibet. The deconvolved vertical component seismic data are inverted for P-velocity crustal structure and the resulting Moho depths at each

  13. Microwave and Millimeter Wave Imaging Using Synthetic Aperture Focusing and Holographical Techniques

    Science.gov (United States)

    Case, Joseph Tobias

    2005-01-01

    Microwave and millimeter wave nondestructive testing and evaluation (NDT&E) methods have shown great potential for determining material composition in composite structures, determining material thickness or debond thickness between two layers, and determining the location and size of flaws, defects, and anomalies. The same testing methods have also shown great potential to produce relatively high-resolution images of voids inside Spray On Foam Insulation (SOFI) test panels using real focused methods employing lens antennas. An alternative to real focusing methods are synthetic focusing methods. The essence of synthetic focusing is to match the phase of the scattered signal to measured points spaced regularly on a plane. Many variations of synthetic focusing methods have already been developed for radars, ultrasonic testing applications, and microwave concealed weapon detection. Two synthetic focusing methods were investigated; namely, a) frequency-domain synthetic aperture focusing technique (FDSAFT), and b) wide-band microwave holography. These methods were applied towards materials whose defects were of low dielectric contrast like air void in SOFI. It is important to note that this investigation used relatively low frequencies from 8.2 GHz to 26.5 GHz that are not conducive for direct imaging of the SOFI. The ultimate goal of this work has been to demonstrate the capability of these methods before they are applied to much higher frequencies such as the millimeter wave frequency spectrum (e.g., 30-300 GHz).

  14. Theory and application of calibration techniques for an NDBC directional wave measurements buoy

    Science.gov (United States)

    Steele, K. E.; Lau, J. C.-K.; Hsu, Y.-H. L.

    1985-01-01

    The National Data Buoy Center (NDBC) of the National Oceanic and Atmospheric Administration (NOAA) deployed a 10-m-diameter discus-type hull in the Pacific Ocean some 185 km southwest of Los Angeles, CA, in April 1984. Aboard this hull was an electronic system capable of acquiring, processing, and transmitting to shore directional wave measurements. For this system to produce accurate data, a number of factors had to be taken into account. These factors included noise, amplitude and phase alterations due to mechanical and electrical components, and magnetic fields arising from the hull. Comprehensive calibration and verification techniques were developed and applied to ensure data quality. The system configuration is described with emphasis on the methods used in the data processing to correct for the various factors. Examples of the resulting corrected data are given.

  15. Second harmonic reflection and transmission from primary S0 mode Lamb wave interacting with a localized microscale damage in a plate: A numerical perspective.

    Science.gov (United States)

    Wan, Xiang; Tse, Peter W; Chen, Jingming; Xu, Guanghua; Zhang, Qing

    2018-01-01

    Second harmonic generation has been widely used in characterizing microstructural changes which are evenly distributed in a whole structure. However, few attention has been paid to evaluating localized micro-scale damages. In this paper, second harmonic reflection and transmission from the primary S0 mode Lamb wave interacting with a localized microstructural damage is numerically discussed. Schematic diagram for deriving fundamental temporal waveform and reconstructing the second harmonic temporal waveform based on Morlet wavelet transform is presented. Second harmonic reflection and transmission from an interface between the zones of linear elastic and nonlinear materials is firstly studied to verify the existence of interfacial nonlinearity. Compositions contributing to second harmonic components in the reflected and transmitted waves are analyzed. Amplitudes of the reflected and transmitted second harmonic components generated at an interface due to the interfacial nonlinearity are quantitatively evaluated. Then, second harmonic reflection and transmission from a localized microscale damage is investigated. The effects of the length and width of a microscale damage on WCPA (wavelet coefficient profile area) of the reflected and transmitted second harmonic components are studied respectively. It is found that the second harmonic component in the reflected waves mainly reflects the interfacial nonlinearity while second harmonic in the transmitted waves reflects the material nonlinearity. These findings provide some basis on using second harmonic generation for characterization and detection of localized microstructural changes. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Fiber Transmission Stabilization by Optical Heterodyning Techniques and Synchronization of Mode-Locked Lasers Using Two Spectral Lines

    CERN Document Server

    Staples, J W

    2005-01-01

    Stabilization of the transit time through a glass fiber using an optical heterodyne technique promises to provide jitter reduction down to the few femtosecond level using inexpensive commodity hardware. An acousto-optical frequency shifter provides the optical frequency offset that is used to downconvert phase shifts at optical frequency to equivalent phase shifts at radio frequency which are used to close a phase-lock loop driving a piezoelectric phase shifter. Using the stabilized fiber transmission medium, two spectral lines of a mode locked laser lock two low-power CW lasers which are transmitted to a receiver which phase locks the same spectral lines of a second mode-locked laser to the first. The optical transmission system operates at low power and is linear, providing excellent signal-to-noise ratio and allows many signals to be transmitted without mutual interference. Experimental results will be presented.

  17. Comprehensive techniques to determine broadband physically-consistent material characteristics using transmission lines

    Science.gov (United States)

    Zhou, Zhen

    Dispersion, attenuation, and crosstalk are several major challenges that both a high-speed digital and a microwave serial link must overcome to achieve their desirable performance. These phenomena are directly related to the frequency dependency of the dielectric property of the material used in package and interconnect. The dielectric property of a material is commonly measured by its manufacturer in a particular direction at a few discrete frequencies using resonator and waveguide methodology. Since the dielectric property may vary during manufacturing processing, the measurements taken by the manufacturer might be not adequate. Moreover, the dielectric property of a material in a bandwidth that covers at least the second harmonics of the fundamental operational frequency is required to accurately predict the link performance. One of the efforts in this research is to investigate the methodology of realizing broadband characteristics of the dielectric property of a material in its "as packaged" configuration using various transmission line topologies, such as microstrip line and Co-Planar Waveguide (CPW). Transitions from CPW to other transmission line topologies are mandatory if CPW probes are used to achieve broadband and repeatable measurements. Since microstrip line is one of the transmission line topologies involved in this research, a research effort is dedicated to develop a broadband CPW-to-microstrip line transition. An effort is also expended to creating casual material models that can be used in electromagnetic simulators to appropriately model the link based on the polarization mechanism of the materials. In addition to focusing on the measurement method in frequency domain, Short Pulse Propagation (SPP), a time domain method, is investigated as well. A virtual test bench is created to investigate the correlation between impedance variations in stripline structures due to fabricated tolerance and the attenuation predicted by SPP.

  18. Optimal imaging techniques in the scanning transmission electron microscope: applications to biological macromolecules.

    Science.gov (United States)

    Ohtsuki, M; Crewe, A V

    1980-01-01

    We show applications of the optimal imaging method to stained biological macromolecules. This optimal imaging method involves the following basic procedures: (i) for any given resolution, which is represented by the electron probe size in the scanning transmission electron microscope, a preferred magnification is used; (ii) the micrographs taken at the condition described above are then spatially filtered by using a low-pass filter (nu < 1/2d, in which d is the space between scan lines) to optically reconstruct the final optimal image. It is found that the micrographs obtained by using the optimal imaging method clearly show an improvement in contrast. Images PMID:6933454

  19. Economics and a novel voltage conversion technique associated with exporting Wyoming's energy by HVDC transmission

    Science.gov (United States)

    Xu, Kaili

    Wyoming is by far the largest coal producing state in the US, but local utilization is extremely low. As much as 92% of Wyoming's coal is shipped to the other states and is mainly consumed by their electricity producers. Coal accounts for more than 50% of the US electricity generation and is one of the least expensive energy sources. Wyoming could utilize its coal better by exporting electricity instead of exporting the coal only in its raw form. Natural gas is another important energy resource in Wyoming but local utilization is even lower. As a result of the development in coalbed methane fields, natural gas production in Wyoming is almost in pace with its coal production. In addition to constructing more new pipelines, new transmission lines should be considered as an alternative way of exporting this energy. Because of their enormous electricity market sizes and high electricity prices, California, Texas and Illinois are chosen to be the target markets for Wyoming's electricity. The proposed transmission schemes use High Voltage DC (HVDC) lines, which are suitable for long distance and cross-system power transmission. Technical and economic feasibilities are studied in details. The Wyoming-California scheme has a better return of investment than both the Wyoming-Texas and the Wyoming-Illinois schemes. A major drawback of HVDC transmission is the high level of harmonics generated by the converters. Elaborate filtering is required at both the AC and the DC sides. A novel pulse-multiplication method is proposed in the thesis to reduce the harmonics from the converter source. By introducing an averaging inductor, the proposed method uses less thyristors to achieve the same high-pulse operation as the existing series scheme. The reduction of thyristors makes the switching circuit more reliable and easier to control and maintain. Harmonic analysis shows that the harmonic level can be reduced to about one third of the original system. The proposed method is also

  20. Electron cyclotron waves transmission: new approach for the characterization of electron distribution functions in Tokamak hot plasmas; La transmission d`ondes cyclotroniques electroniques: une approche nouvelle pour caracteriser les fonctions de distribution electronique des plasmas chauds de Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Michelot, Y.

    1995-10-01

    Fast electrons are one of the basic ingredients of plasma operations in many existing thermonuclear fusion research devices. However, the understanding of fast electrons dynamics during creation and sustainment of the superthermal electrons tail is far for being satisfactory. For this reason, the Electron Cyclotron Transmission (ECT) diagnostic was implemented on Tore Supra tokamak. It consists on a microwave transmission system installed on a vertical chord crossing the plasma center and working in the frequency range 77-109 GHz. Variations of the wave amplitude during the propagation across the plasma may be due to refraction and resonant absorption. For the ECT, the most common manifestation of refraction is a reduction of the received power density with respect to the signal detected in vacuum, due to the spreading and deflection of the wave beam. Wave absorption is observed in the vicinity of the electron cyclotron harmonics and may be due both to thermal plasma and to superthermal electron tails. It has a characteristic frequency dependence due to the relativistic mass variation in the wave-electron resonance condition. This thesis presents the first measurements of: the extraordinary mode optical depth at the third harmonics, the electron temperature from the width of a cyclotron absorption line and the relaxation times of the electron distribution during lower hybrid current drive from the ordinary mode spectral superthermal absorption line at the first harmonic. (J.S.). 175 refs., 110 figs., 9 tabs., 3 annexes.

  1. Real-time visualization of electromagnetic waves propagating in air using live electro-optic imaging technique.

    Science.gov (United States)

    Kanno, Atsushi; Sasagawa, Kiyotaka; Shiozawa, Takahiro; Tsuchiya, Masahiro

    2010-05-10

    Electromagnetic waves propagating in air are visually observed with phase evolution in real time by live electro-optic imaging technique. We show how geometrical and crystallographic arrangements of an electro-optic sensor plate enable the realization of the real-time visual observation of traveling 100-GHz electromagnetic waves. For this purpose, a generation technique for a 100-GHz optical local oscillator signal at 780 nm was newly developed, whose optical wavelength is suitable for the ultra-parallel RF electric field data acquisition by a Si-CMOS image sensor. (c) 2010 Optical Society of America.

  2. Miniaturized Human Insertable Cardiac Monitoring System with Wireless Power Transmission Technique

    Directory of Open Access Journals (Sweden)

    Jong-Ha Lee

    2016-01-01

    Full Text Available Prolonged monitoring is more likely to diagnose atrial fibrillation accurately than intermittent or short-term monitoring. In this study, an implantable electrocardiograph (ECG sensor to monitor atrial fibrillation patients in real time was developed. The implantable sensor is composed of a micro controller unit, an analog-to-digital converter, a signal transmitter, an antenna, and two electrodes. The sensor detects ECG signals from the two electrodes and transmits these to an external receiver carried by the patient. Because the sensor continuously transmits signals, its battery consumption rate is extremely high; therefore, the sensor includes a wireless power transmission module that allows it to charge wirelessly from an external power source. The integrated sensor has the approximate dimensions 3 mm × 4 mm × 14 mm, which is small enough to be inserted into a patient without the need for major surgery. The signal and power transmission data sampling rate and frequency of the unit are 300 samples/s and 430 Hz, respectively. To validate the developed sensor, experiments were conducted on small animals.

  3. A Novel Technique for Transmission of M-Ary Signal through Wireless Fading Channel Using Wavelet Denoising

    Directory of Open Access Journals (Sweden)

    Md. Zahangir Alam

    2011-01-01

    Full Text Available The paper proposes a novel technique for reducing noise in M-ary signal transmission through wireless fading channel using wavelet denoising that play the key role. The paper also explains that the conventional threshold-based technique is not capable of denoising M-ary quadrature amplitude modulated (M-QAM signals having multilevel wavelet coefficients through wireless fading channels. A detailed step by step wavelet decomposition and reconstruction processes are discussed here to transform a signal function into wavelet coefficients using simulation software like MATLAB. A 16-QAM modulated symbol through a Rician fading channel is weighted by a control variable of complex form to force the mean of each detail coefficient except low frequency component to zero to enhance noiseless property. The bit error rate (BER performance of the simulation results are furnished to show the effectiveness of the proposed technique. The root mean square of the deviation of the reconstruct signal from the original signal is used to express the effectiveness of the proposed technique. The traditional denoising provides very high value (above 90% of the percentage root mean square difference (PDR and the proposed technique provides only 10% PDR value for the symbol through a noisy channel. The result of the simulation study reveals that the BER performance can be increased using an appropriate control variable to force the mean of each detail coefficient to zero.

  4. Neutron Resonance Transmission Analysis (NRTA): A Nondestructive Assay Technique for the Next Generation Safeguards Initiative’s Plutonium Assay Challenge

    Energy Technology Data Exchange (ETDEWEB)

    J. W. Sterbentz; D. L. Chichester

    2010-12-01

    This is an end-of-year report for a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The first-year goals for this project were modest and included: 1) developing a zero-order MCNP model for the NRTA technique, simulating data results presented in the literature, 2) completing a preliminary set of studies investigating important design and performance characteristics for the NRTA measurement technique, and 3) documentation of this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes a nine month period of work.

  5. Probing the atomic structure of amorphous Ta2O5 mirror coatings for advanced gravitational wave detectors using transmission electron microscopy

    Science.gov (United States)

    Bassiri, R.; Borisenko, K. B.; Cockayne, D. J. H.; Hough, J.; MacLaren, I.; Rowan, S.

    2010-07-01

    Advanced generations of ground-based gravitational wave detectors will use ultra-low-loss amorphous dielectric multilayer mirror coatings in order to minimise thermal noise, a limiting factor in detector sensitivity. Transmission electron microscopy is a promising way to probe the atomic structure of these coatings in an effort to better understand the causes of the observed mechanical loss (internal friction) and hence thermal noise.

  6. All-optical delay technique for supporting multiple antennas in a hybrid optical - wireless transmission system

    DEFF Research Database (Denmark)

    Prince, Kamau; Chiuchiarelli, A; Presi, M

    2008-01-01

    We introduce a novel continuously-variable optical delay technique to support beam-forming wireless communications systems using antenna arrays. We demonstrate delay with 64-QAM modulated signals at a rate of 15 Msymbol/sec with 2.5 GHz carrier frequency.......We introduce a novel continuously-variable optical delay technique to support beam-forming wireless communications systems using antenna arrays. We demonstrate delay with 64-QAM modulated signals at a rate of 15 Msymbol/sec with 2.5 GHz carrier frequency....

  7. A non-intrusive and continuous-in-space technique to investigate the wave transformation and breaking over a breakwater

    Directory of Open Access Journals (Sweden)

    Ferrari Simone

    2016-01-01

    Full Text Available To design longshore breakwaters, the evaluation of the wave motion transformations over the structures and of the energy they are able to absorb, dissipate and reflect is necessary. To characterize features and transformations of monochromatic wave trains above a breakwater, both submerged and emerged, we have designed and developed a non-intrusive and continuous-in-space technique, based on Image Analysis, and carried out an experimental campaign, in a laboratory flume equipped with a wave-maker, in order to test it. The investigation area was lighted with a light sheet and images were recorded by a video-camera. The working fluid was seeded with non buoyant particles to make it bright and clearly distinct from dark background and breakwater. The technique, that is based on a robust algorithm to identify the free surface, has showed to properly work also in prohibitive situations for traditional resistive probes (e.g., very shallow waters and/or breaking waves and to be able to measure the free surface all over the investigation field in a non-intrusive way. Two kind of analysis were mainly performed, a statistical and a spectral one. The peculiarities of the measurement technique allowed to describe the whole wave transformation and to supply useful information for design purposes.

  8. Comment on ``Enhanced transmission of light through a gold film due to excitation of standing surface-plasmon Bloch waves"

    OpenAIRE

    Weiner, J.

    2007-01-01

    The purpose of this comment is first to correct a misapprehension of the role played by composite wave diffraction on surface-wave generation at subwavelength structures and second to point out that periodic Bloch structures are unnecessary for the efficient production of the surface plasmon polariton (SPP) guided mode either as traveling or standing waves. Guided surface waves originate from simple slit or groove edges illuminated under normal incidence, and one-dimensional (1-D) surface cav...

  9. Microbubble Void Imaging: A Non-invasive Technique for Flow Visualisation and Quantification of Mixing in Large Vessels Using Plane Wave Ultrasound and Controlled Microbubble Contrast Agent Destruction.

    Science.gov (United States)

    Leow, Chee Hau; Iori, Francesco; Corbett, Richard; Duncan, Neill; Caro, Colin; Vincent, Peter; Tang, Meng-Xing

    2015-11-01

    There is increasing recognition of the influence of the flow field on the physiology of blood vessels and their development of pathology. Preliminary work is reported on a novel non-invasive technique, microbubble void imaging, which is based on ultrasound and controlled destruction of microbubble contrast agents, permitting flow visualisation and quantification of flow-induced mixing in large vessels. The generation of microbubble voids can be controlled both spatially and temporally using ultrasound parameters within the safety limits. Three different model vessel geometries-straight, planar-curved and helical-with known effects on the flow field and mixing were chosen to evaluate the technique. A high-frame-rate ultrasound system with plane wave transmission was used to acquire the contrast-enhanced ultrasound images, and an entropy measure was calculated to quantify mixing. The experimental results were cross-compared between the different geometries and with computational fluid dynamics. The results indicated that the technique is able to quantify the degree of mixing within the different configurations, with a helical geometry generating the greatest mixing, and a straight geometry, the lowest. There is a high level of concordance between the computational fluid dynamics and experimental results. The technique could also serve as a flow visualisation tool. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  10. Turbo Equalization Techniques Toward Robust PDM 16-QAM Optical Fiber Transmission

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Caballero Jambrina, Antonio; Borkowski, Robert

    2014-01-01

    In this paper, we show numerically and experimentally that turbo equalization (TE) is an efficient technique to mitigate performance degradations stemming from optical fiber propagation effects in both optical fiber dispersion managed and unmanaged coherent detection links. The effectiveness of t...

  11. Validity and reproducibility of arterial pulse wave velocity measurement using new device with oscillometric technique: A pilot study

    Directory of Open Access Journals (Sweden)

    Patnaik Amar

    2005-08-01

    Full Text Available Abstract Background Availability of a range of techniques and devices allow measurement of many variables related to the stiffness of large or medium sized arteries. There is good evidence that, pulse wave velocity is a relatively simple measurement and is a good indicator of changes in arterial properties. The pulse wave velocity calculated from pulse wave recording by other methods like doppler or tonometry is tedious, time-consuming and above all their reproducibility depends on the operator skills. It requires intensive resource involvement. For epidemiological studies these methods are not suitable. The aim of our study was to clinically evaluate the validity and reproducibility of a new automatic device for measurement of pulse wave velocity that can be used in such studies. Methods In 44 subjects including normal healthy control and patients with coronary artery disease, heart brachial, heart ankle, brachial ankle and carotid femoral pulse wave velocities were recorded by using a new oscillometric device. Lead I and II electrocardiogram and pressure curves were simultaneously recorded. Two observers recorded the pulse wave velocity for validation and one observer recorded the velocity on two occasions for reproducibility. Results and Discussion Pulse wave velocity and arterial stiffness index were recorded in 24 control and 20 coronary artery disease patients. All the velocities were significantly high in coronary artery disease patients. There was highly significant correlation between the values noted by the two observers with low standard deviation. The Pearson's correlation coefficient for various velocities ranged from (r = 0.88–0.90 with (p Conclusion The new device "PeriScope" based on oscillometric technique has been found to be a simple, non-invasive and reproducible device for the assessment of pulse wave velocity and can be used to determine arterial stiffness in large population based studies.

  12. 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....

  13. Nondestructive testing by using long-wave infrared interferometric techniques with CO2 lasers and microbolometer arrays.

    Science.gov (United States)

    Alexeenko, Igor; Vandenrijt, Jean-François; Pedrini, Giancarlo; Thizy, Cédric; Vollheim, Birgit; Osten, Wolfgang; Georges, Marc P

    2013-01-01

    We describe three different interferometric techniques (electronic speckle pattern interferometry, digital holographic interferometry, and digital shearography), using a long-wave infrared radiation produced by a CO(2) laser and recorded on a microbolometer array. Experimental results showing how these methods can be used for nondestructive testing are presented. Advantages and disadvantages of these approaches are discussed.

  14. Superluminal advanced transmission of X waves undergoing frustrated total internal reflection: the evanescent fields and the Goos-Hänchen effect.

    Science.gov (United States)

    Shaarawi, Amr M; Tawfik, Bassem H; Besieris, Ioannis M

    2002-10-01

    A study of X waves undergoing frustrated total internal reflection at a planar slab is provided. This is achieved by choosing the spectral plane wave components of the incident X wave to fall on the upper interface at angles greater than the critical angle. Thus, evanescent fields are generated in the slab and the peak of the field tunneling through the slab appears to be transmitted at a superluminal speed. Furthermore, it is shown that for deep barrier penetration, the peak of the transmitted field emerges from the rear interface of the slab before the incident peak reaches the front interface. To understand this advanced transmission of the peak of the pulse, a detailed study of the behavior of the evanescent fields in the barrier region is undertaken. The difference in tunneling behavior between deep and shallow barrier penetrations is shown to be influenced by the sense of the Goos-Hänchen shift.

  15. High range free space optic transmission using new dual diffuser modulation technique

    Science.gov (United States)

    Rahman, A. K.; Julai, N.; Jusoh, M.; Rashidi, C. B. M.; Aljunid, S. A.; Anuar, M. S.; Talib, M. F.; Zamhari, Nurdiani; Sahari, S. k.; Tamrin, K. F.; Jong, Rudiyanto P.; Zaidel, D. N. A.; Mohtadzar, N. A. A.; Sharip, M. R. M.; Samat, Y. S.

    2017-11-01

    Free space optical communication fsoc is vulnerable with fluctuating atmospheric. This paper focus analyzes the finding of new technique dual diffuser modulation (ddm) to mitigate the atmospheric turbulence effect. The performance of fsoc under the presence of atmospheric turbulence will cause the laser beam keens to (a) beam wander, (b) beam spreading and (c) scintillation. The most deteriorate the fsoc is scintillation where it affected the wavefront cause to fluctuating signal and ultimately receiver can turn into saturate or loss signal. Ddm approach enhances the detecting bit `1' and bit `0' and improves the power received to combat with turbulence effect. The performance focus on signal-to-noise (snr) and bit error rate (ber) where the numerical result shows that the ddm technique able to improves the range where estimated approximately 40% improvement under weak turbulence and 80% under strong turbulence.

  16. High range free space optic transmission using new dual diffuser modulation technique

    Directory of Open Access Journals (Sweden)

    Rahman A.K

    2017-01-01

    Full Text Available Free space optical communication fsoc is vulnerable with fluctuating atmospheric. This paper focus analyzes the finding of new technique dual diffuser modulation (ddm to mitigate the atmospheric turbulence effect. The performance of fsoc under the presence of atmospheric turbulence will cause the laser beam keens to (a beam wander, (b beam spreading and (c scintillation. The most deteriorate the fsoc is scintillation where it affected the wavefront cause to fluctuating signal and ultimately receiver can turn into saturate or loss signal. Ddm approach enhances the detecting bit ‘1’ and bit ‘0’ and improves the power received to combat with turbulence effect. The performance focus on signal-to-noise (snr and bit error rate (ber where the numerical result shows that the ddm technique able to improves the range where estimated approximately 40% improvement under weak turbulence and 80% under strong turbulence.

  17. Novel low-dose imaging technique for characterizing atomic structures through scanning transmission electron microscope

    Science.gov (United States)

    Su, Chia-Ping; Syu, Wei-Jhe; Hsiao, Chien-Nan; Lai, Ping-Shan; Chen, Chien-Chun

    2017-08-01

    To investigate dislocations or heterostructures across interfaces is now of great interest to condensed matter and materials scientists. With the advances in aberration-corrected electron optics, the scanning transmission electron microscope has demonstrated its excellent capability of characterizing atomic structures within nanomaterials, and well-resolved atomic-resolution images can be obtained through long-exposure data acquisition. However, the sample drifting, carbon contamination, and radiation damage hinder further analysis, such as deriving three-dimensional (3D) structures from a series of images. In this study, a method for obtaining atomic-resolution images with significantly reduced exposure time was developed, using which an original high-resolution image with approximately one tenth the electron dose can be obtained by combining a fast-scan high-magnification image and a slow-scan low-magnification image. The feasibility of obtaining 3D atomic structures using the proposed approach was demonstrated through multislice simulation. Finally, the feasibility and accuracy of image restoration were experimentally verified. This general method cannot only apply to electron microscopy but also benefit to image radiation-sensitive materials using various light sources.

  18. Development of laser decontamination technique (3). Experiments of laser beam transmission

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, Yasutaka; Ogawa, Ryuichirou; Ishijima, Noboru; Tanimoto, Kenichi [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1999-04-01

    Laser decontamination system is able to decontaminate thoroughly, and it is able to mitigate the secondary waste quantity, and the system is able to operate by remote control. It is advantageous compared with other decontamination methods. YAG laser is competent for decontamination of stainless steel surface. In this paper, using normal and Q switch pulse YAG laser, experiments to confirm transmission efficiency using mirror and optical fiber, shape dependency at decontamination, and secondary waste size distribution were performed. The results are as follows. (1) The beam energy of normal pulse YAG laser is able to transmit using optical fiber. The beam energy of Q switch pulse YAG laser is difficult to transmit using a single optical fiber. (2) Normal pulse YAG laser has 10{sup 2} Decontamination Factor (DF) on L-shaped, bolt-shaped, and cylindrical-shaped waste. Q switch pulse YAG laser has over 10{sup 2} DF on L-shaped and cylindrical-shaped waste, but on the other hand, under 10 DF on bolt-shaped waste. (3) In the case of argon as auxiliary gas, most secondary products are dropped as dross. In this case, scattered area is within 1 m. In the case of the atmosphere as auxiliary gas, most particles of secondary products are floated in the air, their diameter being less 3 {mu}m. (J.P.N.)

  19. X-ray transmission/scattering technique for thickness-independent density measurement

    Energy Technology Data Exchange (ETDEWEB)

    Giacomelli, E.J.

    1978-12-20

    A nondestructive technique, using penetrating x radiation, has been developed to measure the density uniformity of low-Z, compressible materials that is independent of material thickness. Thickness independence is achieved by simultaneously monitoring the transmitted and scattered x rays. Results on samples of pressed carbon materials have demonstrated that there is the expected linear relationship between measured quantities and material density, independent of material thickness, and that this is a viable means of measuring density uniformity.

  20. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    Directory of Open Access Journals (Sweden)

    R. Q. Shaddad

    2014-01-01

    Full Text Available The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO signals feeding multiple antennas in the fiber wireless (FiWi system. A novel optical frequency upconversion (OFU technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF. The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM. The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  1. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    Science.gov (United States)

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  2. Remote sensing of atmospheric NO2 by employing the continuous-wave differential absorption lidar technique.

    Science.gov (United States)

    Mei, Liang; Guan, Peng; Kong, Zheng

    2017-10-02

    Differential absorption lidar (DIAL) technique employed for remote sensing has been so far based on the sophisticated narrow-band pulsed laser sources, which require intensive maintenance during operation. In this work, a continuous-wave (CW) NO2 DIAL system based on the Scheimpflug principle has been developed by employing a compact high-power CW multimode 450 nm laser diode as the light source. Laser emissions at the on-line and off-line wavelengths of the NO2 absorption spectrum are implemented by tuning the injection current of the laser diode. Lidar signals are detected by a 45° tilted area CCD image sensor satisfying the Scheimpflug principle. Range-resolved NO2 concentrations on a near-horizontal path are obtained by the NO2 DIAL system in the range of 0.3-3 km and show good agreement with those measured by a conventional air pollution monitoring station. A detection sensitivity of ± 0.9 ppbv at 95% confidence level in the region of 0.3-1 km is achieved with 15-minute averaging and 700 m range resolution during hours of darkness, which allows accurate concentration measurement of ambient NO2. The low-cost and robust DIAL system demonstrated in this work opens up many possibilities for field NO2 remote sensing applications.

  3. Apical microleakage of epoxy resin and methacrylate resin-based sealer with continuous wave obturation technique

    Directory of Open Access Journals (Sweden)

    Haslinda Haslinda

    2016-04-01

    Full Text Available The aim of this research was to determine the microleakage apical sealer based on epoxy resin and methacrylate resin with continuous wave obturation technique.Thirty  permanent  lateral incisors were selected at random and  divided into 3 groups (N=10, namely AH Plus obturator group (epoxy resin, EndoREZ group (methacrylate resin, and negative control. The samples were decoronated, root canal preparation, then kept in incubator of 37°C for 72 hours. Sample were coated with nail varnish then immersed in methylene blue for 48 hours. The samples were washed with distilled water, dried and nail varnish removed. The samples were clearing. Penetration was measured using microscope and given score 0-4. Measurements were analyzed statistically. By using Kruskal Wallis test and Mann Whitney test, there is no significant difference between the apical microleakage of the the epoxy resin root canal sealer with methacrylate root canal sealer based (p>0,05. It means that the apical microleakage of the epoxy resin root canal sealer based comparable with merhacrylate root canal sealer based. It was concluded that the apical microleakage of epoxy resin based sealer does not different to the methacrylate resin based sealer

  4. Gravitational waves from rotating neutron stars and evaluation of fast chirp transform techniques

    CERN Document Server

    Strohmayer, T E

    2002-01-01

    X-ray observations suggest that neutron stars in low mass x-ray binaries (LMXB) are rotating with frequencies in the range 300-600 Hz. These spin rates are significantly less than the break-up rates for essentially all realistic neutron star equations of state, suggesting that some process may limit the spin frequencies of accreting neutron stars to this range. If the accretion-induced spin up torque is in equilibrium with gravitational radiation losses, these objects could be interesting sources of gravitational waves. I present a brief summary of current measurements of neutron star spins in LMXBs based on the observations of high-Q oscillations during thermonuclear bursts (so-called 'burst oscillations'). Further measurements of neutron star spins will be important in exploring the gravitational radiation hypothesis in more detail. To this end, I also present a study of fast chirp transform (FCT) techniques as described by Jenet and Prince (Prince T A and Jenet F A 2000 Phys. Rev. D 62 122001) in the conte...

  5. Comparative study of electromechanical impedance and Lamb wave techniques for fatigue crack detection and monitoring in metallic structures

    Science.gov (United States)

    Lim, Say Ian; Liu, Yu; Soh, Chee Kiong

    2012-04-01

    Fatigue cracks often initiate at the weld toes of welded steel connections. Usually, these cracks cannot be identified by the naked eyes. Existing identification methods like dye-penetration test and alternating current potential drop (ACPD) may be useful for detecting fatigue cracks at the weld toes. To apply these non-destructive evaluation (NDE) techniques, the potential sites have to be accessible during inspection. Therefore, there is a need to explore other detection and monitoring techniques for fatigue cracks especially when their locations are inaccessible or cost of access is uneconomical. Electro-mechanical Impedance (EMI) and Lamb wave techniques are two fast growing techniques in the Structural Health Monitoring (SHM) community. These techniques use piezoelectric ceramics (PZT) for actuation and sensing. Since the monitoring site is only needed to be accessed once for the instrumentation of the transducers, remote monitoring is made possible. The permanent locations of these transducers also translate to having consistent measurement for monitoring. The main focus of this study is to conduct a comparative investigation on the effectiveness and efficiency of the EMI technique and the Lamb wave technique for successful fatigue crack identification and monitoring of welded steel connections using piezoelectric transducers. A laboratory-sized non-load carrying fillet weld specimen is used in this study. The specimen is subjected to cyclic tensile load and data for both techniques are acquired at stipulated intervals. It can be concluded that the EMI technique is sensitive to the crack initiation phase while the Lamb wave technique correlates well with the crack propagation phase.

  6. Advantages of active love wave techniques in geophysical characterizations of seismographic station - Case studies in California and the central and eastern United States

    Science.gov (United States)

    Martin, Antony; Yong, Alan K.; Salomone, Larry A.

    2014-01-01

    Active-source Love waves, recorded by the multi-channel analysis of surface wave (MASLW) technique, were recently analyzed in two site characterization projects. Between 2010 and 2012, the 2009 American Recovery and Reinvestment Act (ARRA) funded GEOVision to conduct geophysical investigations at 191 seismographic stations in California and the Central Eastern U.S. (CEUS). The original project plan was to utilize active and passive Rayleigh wave-based techniques to obtain shear-wave velocity (VS) profiles to a minimum depth of 30 m and the time-averaged VS of the upper 30 meters (VS30). Early in this investigation it became clear that Rayleigh wave techniques, such as multi-channel analysis of surface waves (MASRW), were not suited for characterizing all sites. Shear-wave seismic refraction and MASLW techniques were therefore applied. In 2012, the Electric Power Research Institute funded characterization of 33 CEUS station sites. Based on experience from the ARRA investigation, both MASRW and MASLW data were acquired by GEOVision at 24 CEUS sites. At shallow rock sites, sites with steep velocity gradients, and, sites with a thin, low velocity, surficial soil layer overlying stiffer sediments, Love wave techniques generally were found to be easier to interpret, i.e., Love wave data typically yielded unambiguous fundamental mode dispersion curves and thus, reduce uncertainty in the resultant VS model. These types of velocity structure often excite dominant higher modes in Rayleigh wave data, but not in the Love wave data. It is possible to model Rayleigh wave data using multi- or effective-mode techniques; however, extraction of Rayleigh wave dispersion data was found to be difficult in many cases. These results imply that field procedures should include careful scrutiny of Rayleigh wave-based dispersion data in order to also collect Love wave data when warranted.

  7. Performance study of an adaptive reservation multiple access technique for data transmissions

    Science.gov (United States)

    Tsai, D.; Chang, J.-F.

    1986-07-01

    The performance of a differential PCM type adaptive reservation multiaccess technique is studied. The frame structure of the time-axis remains identical to that reported by Guha et al. (1982). However, channel reservation is handled differently. Analyses, both transient and steady-state, have been successfully completed. Results obtained include average frame length, queue length, average delay, etc. The validity of analysis is also verified by computer simulations. Through examples, it is shown that this new protocol generally has better performance than the Guha procedure.

  8. Transmission electron microscopy for nanomedicine: novel applications for long-established techniques.

    Science.gov (United States)

    Malatesta, Manuela

    2016-12-09

    During the last twenty years, the research in nanoscience and nanotechnology has dramatically increased and, in the last decade, the interest has progressively been oriented towards biomedical applications, giving rise to a new field termed nanomedicine. Transmis - sion electron microscopy is a valuable technique not only for the thorough physico-chemical characterization of newly synthesized nanoparticulates, but especially to explore the effects of nanocomposites on biological systems, providing essential information for the development of efficient therapeutic and diagnostic strategies. Thus, for the progress of nanotechnology in the biomedical field, experts in cell biology, histochemistry and ultramicroscopy should always support the chemists, physicists and pharmacologists engaged in the synthesis and characterization of innovative nanoconstructs.

  9. Study of latent and etched tracks by a charged particle transmission technique

    CERN Document Server

    Vacik, J; Hnatowicz, V; Fink, D; Kobayashi, Y; Hirata, K; Apel, P Y; Strauss, P

    1999-01-01

    A recently suggested technique for non-destructive investigation of inhomogeneities in thin objects, which is based on the measurement of the energy spectra of charged particles transmitted through the object, is used for the study of thermal annealing of 10-20 mu m thick polyethylene terephtalate, polypropylene and polycarbonate foils irradiated with 1-10 MeV/amu heavy ions. At elevated temperature a foil linear contraction is observed on pristine and irradiated material. Also the foil roughness increases with increasing temperature. On the same foils with etched pores 0.5-1.0 mu m in diameter, the thermal annealing results in gradual closing of the pores up to about 30% of their initial diameter at the temperatures of 150-175 deg. C. At higher temperatures the pore diameter increases and achieves its initial value.

  10. Data transmission techniques for short-range optical fiber and wireless communication links

    DEFF Research Database (Denmark)

    Pham, Tien Thang

    The research work described in this thesis is devoted to experimental investigation of techniques for cost-effective high-speed optical communications supporting both wired and wireless services. The main contributions of this thesis have expanded the state-of-the-art in two main areas: high......-speed optical/wireless integration and advanced modulation formats for intensity modulation with direct detection (IM/DD) optical systems. Regarding optical/wireless integration, this thesis focuses on integration of broadband ultra-wide band (UWB) and 60-GHz band wireless systems into optical fiber access......)-compliant gigabit UWB signals and integrate them into baseband wavelength division multiplexingpassive optical networks (WDM-PONs). Performance of UWB signals and other wired/wireless signals in different scenarios including heterogeneous wired and wireless access networks, converged communication and sensing...

  11. Multi-wave and hybrid imaging techniques: a new direction for nondestructive testing and structural health monitoring.

    Science.gov (United States)

    Cheng, Yuhua; Deng, Yiming; Cao, Jing; Xiong, Xin; Bai, Libing; Li, Zhaojun

    2013-11-27

    In this article, the state-of-the-art multi-wave and hybrid imaging techniques in the field of nondestructive evaluation and structural health monitoring were comprehensively reviewed. A new direction for assessment and health monitoring of various structures by capitalizing the advantages of those imaging methods was discussed. Although sharing similar system configurations, the imaging physics and principles of multi-wave phenomena and hybrid imaging methods are inherently different. After a brief introduction of nondestructive evaluation (NDE) , structure health monitoring (SHM) and their related challenges, several recent advances that have significantly extended imaging methods from laboratory development into practical applications were summarized, followed by conclusions and discussion on future directions.

  12. A study of the noncollinear ultrasonic-wave-mixing technique under imperfect resonance conditions

    NARCIS (Netherlands)

    Demcenko, A.; Mainini, L.; Korneev, V.A.

    2015-01-01

    Geometrical and material property changes cause deviations in the resonant conditions used for noncollinear wave mixing. These deviations are predicted and observed using the SV(ω1) + L(ω2) → L(ω1 + ω2) interaction, where SV and L are the shear vertical and longitudinal waves, respectively, and ω1,

  13. Acoustic waves in transversely excited atmospheric CO2 laser discharges: effect on performance and reduction techniques

    CSIR Research Space (South Africa)

    von Bergmann, HM

    2008-08-01

    Full Text Available Results are presented on the influence of acoustic waves on the performance of high-repetition-rate TEA CO2 lasers. It is shown that acoustic waves generated inside the laser cavity lead to nonuniform discharges, resulting in a deterioration...

  14. Nano-Scale Structure Investigation of Vapour Deposited AlCrSiN Coating Using Transmission Electron Microscope Techniques

    Directory of Open Access Journals (Sweden)

    Lukaszkowicz K.

    2016-06-01

    Full Text Available The investigations concerned the structural analysis of the AlCrSiN coating deposited by arc Physical Vapour Deposition method on the X40CrMoV5-1 hot work tool steel substrate. The deposition process was carried out on a device equipped with a technique of lateral, rotating cathodes. The nano/microstructure, phase identification and chemical state of the coating were analysed by high-resolution transmission electron microscopy. It was found that the investigated coatings have nanostructured nature consisting of fine crystallites. The fractographic tests were made using the scanning electron microscope and allow to state, that the coating was deposited uniformly and tightly adhere to the substrate material. In the work is presented the nature of a transition zone between the produced AlCrSiN coating and substrate material.

  15. Riding the Hype Wave: Evaluating new AI Techniques for their Applicability in Earth Science

    Science.gov (United States)

    Ramachandran, R.; Zhang, J.; Maskey, M.; Lee, T. J.

    2016-12-01

    Every few years a new technology rides the hype wave generated by the computer science community. Converts to this new technology who surface from both the science community and the informatics community promulgate that it can radically improve or even change the existing scientific process. Recent examples of new technology following in the footsteps of "big data" now include deep learning algorithms and knowledge graphs. Deep learning algorithms mimic the human brain and process information through multiple stages of transformation and representation. These algorithms are able to learn complex functions that map pixels directly to outputs without relying on human-crafted features and solve some of the complex classification problems that exist in science. Similarly, knowledge graphs aggregate information around defined topics that enable users to resolve their query without having to navigate and assemble information manually. Knowledge graphs could potentially be used in scientific research to assist in hypothesis formulation, testing, and review. The challenge for the Earth science research community is to evaluate these new technologies by asking the right questions and considering what-if scenarios. What is this new technology enabling/providing that is innovative and different? Can one justify the adoption costs with respect to the research returns? Since nothing comes for free, utilizing a new technology entails adoption costs that may outweigh the benefits. Furthermore, these technologies may require significant computing infrastructure in order to be utilized effectively. Results from two different projects will be presented along with lessons learned from testing these technologies. The first project primarily evaluates deep learning techniques for different applications of image retrieval within Earth science while the second project builds a prototype knowledge graph constructed for Hurricane science.

  16. Using dual-band asymmetric transmission effect of 2D metamaterial to manipulate linear polarization state of electromagnetic waves

    National Research Council Canada - National Science Library

    Pan, Xun-Yong; Han, Song; Wang, Gaofeng

    2014-01-01

    ... (AT) effect for linear polarization. The measured cross-polarization transmissions are 0.88 at 5.68 GHz and 0.92 at 10.7 GHz in one direction, while the corresponding cross-polarization transmissions are suppressed down...

  17. Design of polarizers for a mega-watt long-pulse millimeter-wave transmission line on the large helical device.

    Science.gov (United States)

    Ii, T; Kubo, S; Shimozuma, T; Kobayashi, S; Okada, K; Yoshimura, Y; Igami, H; Takahashi, H; Ito, S; Mizuno, Y; Okada, K; Makino, R; Kobayashi, K; Goto, Y; Mutoh, T

    2015-02-01

    The polarizer is one of the critical components in a high-power millimeter-wave transmission line. It requires full and highly efficient coverage of any polarization states, high-power tolerance, and low-loss feature. Polarizers with rounded shape at the edge of the periodic groove surface are designed and fabricated by the machining process for a mega-watt long-pulse millimeter-wave transmission line of the electron cyclotron resonance heating system in the large helical device. The groove shape of λ/8- and λ/4-type polarizers for an 82.7 GHz transmission line is optimally designed in an integral method developed in the vector theories of diffraction gratings so that the efficiency to realize any polarization state can be maximized. The dependence of the polarization states on the combination of the two polarizer rotation angles (Φλ/8, Φλ/4) is examined experimentally in a low-power test with the newly developed polarization monitor. The results show that the measured polarization characteristics are in good agreement with the calculated ones.

  18. Electromagnetic waves reflection, transmission and absorption by graphene - magnetic semiconductor - graphene sandwich-structure in magnetic field: Faraday geometry

    OpenAIRE

    Kuzmin, Dmitry A.; Bychkov, Igor V.; Shavrov, Vladimir G.

    2014-01-01

    Electrodynamic properties of the graphene - magnetic semiconductor - graphene sandwich-structure have been investigated theoretically with taking into account the dissipation processes. Influence of graphene layers on electromagnetic waves propagation in graphene - semi-infinte magnetic semiconductor and graphene - magnetic semiconductor - graphene sandwich-structure has been analyzed. Frequency and field dependences of the reflectance, transmittance and absorbtance of electromagnetic waves b...

  19. Transient Topology Optimization of Two-Dimensional Elastic Wave Propagation

    DEFF Research Database (Denmark)

    Matzen, René; Jensen, Jakob Søndergaard; Sigmund, Ole

    2008-01-01

    A tapering device coupling two monomodal waveguides is designed with the topology optimization method based on transient wave propagation. The gradient-based optimization technique is applied to predict the material distribution in the tapering area such that the squared output displacement (a...... measure for transmission) in the taper is maximized. High transmission in a large frequency range is gained by use of incident wave packets. To avoid nondiscrete properties in the design domain a density filtering technique is employed....

  20. A method for detecting crack wave arrival time and crack localization in a tunnel by using moving window technique

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Young Chul; Park, Tae Jin [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    Source localization in a dispersive medium has been carried out based on the time-of-arrival-differences (TOADs) method: a triangulation method and a circle intersection technique. Recent signal processing advances have led to calculation TOAD using a joint time-frequency analysis of the signal, where a short-time Fourier transform(STFT) and wavelet transform can be included as popular algorithms. The time-frequency analysis method is able to provide various information and more reliable results such as seismic-attenuation estimation, dispersive characteristics, a wave mode analysis, and temporal energy distribution of signals compared with previous methods. These algorithms, however, have their own limitations for signal processing. In this paper, the effective use of proposed algorithm in detecting crack wave arrival time and source localization in rock masses suggest that the evaluation and real-time monitoring on the intensity of damages related to the tunnels or other underground facilities is possible. Calculation of variances resulted from moving windows as a function of their size differentiates the signature from noise and from crack signal, which lead us to determine the crack wave arrival time. Then, the source localization is determined to be where the variance of crack wave velocities from real and virtual crack localization becomes a minimum. To validate our algorithm, we have performed experiments at the tunnel, which resulted in successful determination of the wave arrival time and crack localization.

  1. Interference-Assisted Techniques for Transmission and Multiple Access in Optical Communications

    Science.gov (United States)

    Guan, Xun

    communication (VLC) by adopting PNC, with a newly proposed phase-aligning method. PNC could improve the throughput at the bottlenecking relay node in a VLC system, and the proposed phase aligning method can improve the BER performance. The second part of this thesis discusses another interference-assisted technology in communication, that is, non-orthogonal multiple access (NOMA). NOMA multiplexes signals from multiple users in another dimension: power domain, with a non-orthogonal multiplexing in other dimensions such as time, frequency and code. Three schemes are proposed in this part. The first and the second schemes both realize NOMA in VLC, with different multiuser detection (MUD) techniques and a proposed phase pre-distortion method. Although both can decrease the system BER compared to conventional NOMA, the scheme using joint detection (JD) outperforms the one using successive interference cancellation (SIC). The third scheme investigated in this part is a combination of NOMA and a multicarrier precoding (MP) technology based on an orthogonal circulant transform matrix (OCT). This combination can avoid the complicated adaptive bit loading or electronic equalization, making NOMA more attractive in a practical system.

  2. Inversion of Love wave phase velocity using smoothness-constrained least-squares technique; Heikatsuka seiyakutsuki saisho jijoho ni yoru love ha iso sokudo no inversion

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, S. [Nippon Geophysical Prospecting Co. Ltd., Tokyo (Japan)

    1996-10-01

    Smoothness-constrained least-squares technique with ABIC minimization was applied to the inversion of phase velocity of surface waves during geophysical exploration, to confirm its usefulness. Since this study aimed mainly at the applicability of the technique, Love wave was used which is easier to treat theoretically than Rayleigh wave. Stable successive approximation solutions could be obtained by the repeated improvement of velocity model of S-wave, and an objective model with high reliability could be determined. While, for the inversion with simple minimization of the residuals squares sum, stable solutions could be obtained by the repeated improvement, but the judgment of convergence was very hard due to the smoothness-constraint, which might make the obtained model in a state of over-fitting. In this study, Love wave was used to examine the applicability of the smoothness-constrained least-squares technique with ABIC minimization. Applicability of this to Rayleigh wave will be investigated. 8 refs.

  3. Full-duplex transmission of FTTX/ethernet services in a RSOA based WDM-PON architecture using polarization multiplexing technique

    Science.gov (United States)

    Das, Anindya Sundar; Patra, Ardhendu Sekhar

    2015-06-01

    In this paper a simple architecture has been developed for full-duplex transmission of different services like Ethernet, FTTX etc through single optical carrier wavelength employing polarization multiplexing technique in the transmitter end and the user end simultaneously. 10 Gbps and 2.5 Gbps datarates are bidirectionally transported over 50 km single mode fiber (SMF) to provide Ethernet and FTTX services concurrently to the user. Reflective semiconductor optical amplifier (RSOA) is used to reuse and remodulate the downlink signal to uplink transmission. The upstream and the downstream transmission performances are observed by the bit error rate (BER) values and the eye diagrams obtained by the BER analyzer at both ends.

  4. Non-destructive testing (NDT) and inspection of the blast furnace refractory lining by stress wave propagation technique

    OpenAIRE

    Sadri, A; Gebski, P.; Gordon, Y.

    2014-01-01

    Generally speaking, a blast furnace is the main equipment in Ironmaking and the campaign life of a blast furnace depends on its remaining hearth refractory lining [1]. The Acousto Ultrasonic- Echo (AU-E) is a stress wave propagation technique that uses time and frequency data analysis to determine coarse-grained material thicknesses, such as refractory and stave materials in operating blast furnaces. A mechanical impact on the surface of the structure (via a hammer or a mechanical impactor) g...

  5. Wave Generation Theory

    DEFF Research Database (Denmark)

    Frigaard, Peter; Høgedal, Michael; Christensen, Morten

    The intention of this manual is to provide some formulas and techniques which can be used for generating waves in hydraulic laboratories. Both long crested waves (2-D waves) and short crested waves (3-D waves) are considered....

  6. Optical coherence tomography of scattering media using frequency-modulated continuous-wave techniques with tunable near-infrared laser

    Science.gov (United States)

    Haberland, Udo; Jansen, Peter; Blazek, Vladimir; Schmitt, Hans J.

    1997-05-01

    A new near-infrared coherent imaging technique that can reveal scattering bodies embedded in highly scattering media is presented. Its underlying principle is extended from frequency modulated continuous wave radar systems. This technique has advantages over low coherence tomography as it does not require the reference mirror to be scanned. The tunable laser is characterized and the system's performance is demonstrated on images recorded from solid scattering phantoms. Furthermore a combination of our chirp-tomography (C-OCT) and laser Doppler perfusion imaging (LDPI) is demonstrated. The influence of moving scatterers on the tomographic images are discussed.

  7. Variability of Liver Shear Wave Measurements Using a New Ultrasound Elastographic Technique.

    Science.gov (United States)

    Nadebaum, David P; Nicoll, Amanda J; Sood, Siddharth; Gorelik, Alexandra; Gibson, Robert N

    2017-09-29

    A new 2-dimensional (2D) shear wave elastographic (SWE) device has been developed for the noninvasive assessment of liver fibrosis. Guidelines on measurement acquisition parameters are not yet well established for this technique. Our study aimed to assess 2D SWE measurement variability and to determine the number of measurements required per patient to reliably assess liver stiffness. Two-dimensional SWE was assessed in 55 patients with mixed-etiology chronic liver disease on an Aplio 500 ultrasound system (Toshiba Medical Systems Corporation, Tochigi, Japan). Ten measurements were obtained per patient by an operator blinded to all preceding readings. Results were analyzed with clinical information obtained from medical records. The median interquartile range/median ratio for 2D SWE was 0.131 (quartiles 1-3, 0.089-0.174). Five readings provided an approximation within 0.11 m/s, or 4.2% of the median velocity of 10 measurements. Factors associated with increased measurement variability included body mass index (ρ = 0.388; P = .01), increased skin-to-liver capsule distance (ρ = 0.426; P = .002), and measurements taken within 1.5 cm of the liver capsule (P  0.15) showed greater deviation from the set's median velocity than those with an ROI SD/speed ratio of 0.15 or lower (0.42 versus 0.22 m/s; P = .001). Two-dimensional SWE showed low overall measurement variability, with a minimum of 5 readings providing equivalent precision to the existing method using 10 samples. Obesity, increasing abdominal wall thickness, subcapsular measurements and an ROI SD/speed ratio of greater than 0.15 were all associated with increased measurement variability. The ROI SD/speed ratio warrants further evaluation as a quality assessment metric, to allow objective operator assessment of individual 2D SWE measurement reliability in real time. © 2017 by the American Institute of Ultrasound in Medicine.

  8. Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique.

    Directory of Open Access Journals (Sweden)

    Osamu Togao

    Full Text Available In this study, we evaluated the dependence of saturation pulse length on APT imaging of diffuse gliomas using a parallel transmission-based technique. Twenty-two patients with diffuse gliomas (9 low-grade gliomas, LGGs, and 13 high-grade gliomas, HGGs were included in the study. APT imaging was conducted at 3T with a 2-channel parallel transmission scheme using three different saturation pulse lengths (0.5 s, 1.0 s, 2.0 s. The 2D fast spin-echo sequence was used for imaging. Z-spectrum was obtained at 25 frequency offsets from -6 to +6 ppm (step 0.5 ppm. A point-by-point B0 correction was performed with a B0 map. Magnetization transfer ratio (MTRasym and ΔMTRasym (contrast between tumor and normal white matter at 3.5 ppm were compared among different saturation lengths. A significant increase in MTRasym (3.5 ppm of HGG was found when the length of saturation pulse became longer (3.09 ± 0.54% at 0.5 s, 3.83 ± 0.67% at 1 s, 4.12 ± 0.97% at 2 s, but MTRasym (3.5 ppm was not different among the saturation lengths in LGG. ΔMTRasym (3.5 ppm increased with the length of saturation pulse in both LGG (0.48 ± 0.56% at 0.5 s, 1.28 ± 0.56% at 1 s, 1.88 ± 0.56% at 2 s and HGG (1.72 ± 0.54% at 0.5 s, 2.90 ± 0.49% at 1 s, 3.83 ± 0.88% at 2 s. In both LGG and HGG, APT-weighted contrast was enhanced with the use of longer saturation pulses.

  9. Monitoring transmission routes of Listeria spp. in smoked salmon production with repetitive element sequence-based PCR techniques.

    Science.gov (United States)

    Zunabovic, M; Domig, K J; Pichler, I; Kneifel, W

    2012-03-01

    Various techniques have been used for tracing the transmission routes of Listeria species and for the assessment of hygiene standards in food processing plants. The potential of repetitive element sequence-based PCR (Rep-PCR) methods (GTG₅ and REPI + II) for the typing of Listeria isolates (n = 116), including Listeria monocytogenes (n = 46), was evaluated in a particular situation arising from the relocation of a company producing cold-smoked salmon. Pulsed-field gel electrophoresis (PFGE) using three restriction enzymes (ApaI, AscI, and SmaI) was used for comparison. Identical transmission scenarios among two companies could be identified by cluster analysis of L. monocytogenes isolates that were indistinguishable by both Rep-PCR and PFGE. The calculated diversity index (DI) indicates that Rep-PCR subtyping of Listeria species with primer sets GTG₅ and REPI + II has a lower discrimination power than does PFGE. When concatenated Rep-PCR cluster analysis was used, the DI increased from 0.934 (REPI + II) and 0.923 (GTG₅) to 0.956. The discrimination power of this method was similar to that of PFGE typing based on restriction enzyme Apa I (DI = 0.955). Listeria welshimeri may be useful as an indicator for monitoring smoked salmon processing environments. Rep-PCR meets the expectations of a reasonable, fast, and low-cost molecular subtyping method for the routine monitoring of Listeria species. The discriminatory power as characterized by the DI sufficiently quantifies the probability of unrelated isolates being characterized as different subtypes. Therefore, Rep-PCR typing based on two primer systems (GTG₅ and REPI + II) may be a useful tool for monitoring industrial hygiene.

  10. A Sparse Stochastic Collocation Technique for High-Frequency Wave Propagation with Uncertainty

    KAUST Repository

    Malenova, G.

    2016-09-08

    We consider the wave equation with highly oscillatory initial data, where there is uncertainty in the wave speed, initial phase, and/or initial amplitude. To estimate quantities of interest related to the solution and their statistics, we combine a high-frequency method based on Gaussian beams with sparse stochastic collocation. Although the wave solution, uϵ, is highly oscillatory in both physical and stochastic spaces, we provide theoretical arguments for simplified problems and numerical evidence that quantities of interest based on local averages of |uϵ|2 are smooth, with derivatives in the stochastic space uniformly bounded in ϵ, where ϵ denotes the short wavelength. This observable related regularity makes the sparse stochastic collocation approach more efficient than Monte Carlo methods. We present numerical tests that demonstrate this advantage.

  11. Intelligent feature selection techniques for pattern classification of Lamb wave signals

    Science.gov (United States)

    Hinders, Mark K.; Miller, Corey A.

    2014-02-01

    Lamb wave interaction with flaws is a complex, three-dimensional phenomenon, which often frustrates signal interpretation schemes based on mode arrival time shifts predicted by dispersion curves. As the flaw severity increases, scattering and mode conversion effects will often dominate the time-domain signals, obscuring available information about flaws because multiple modes may arrive on top of each other. Even for idealized flaw geometries the scattering and mode conversion behavior of Lamb waves is very complex. Here, multi-mode Lamb waves in a metal plate are propagated across a rectangular flat-bottom hole in a sequence of pitch-catch measurements corresponding to the double crosshole tomography geometry. The flaw is sequentially deepened, with the Lamb wave measurements repeated at each flaw depth. Lamb wave tomography reconstructions are used to identify which waveforms have interacted with the flaw and thereby carry information about its depth. Multiple features are extracted from each of the Lamb wave signals using wavelets, which are then fed to statistical pattern classification algorithms that identify flaw severity. In order to achieve the highest classification accuracy, an optimal feature space is required but it's never known a priori which features are going to be best. For structural health monitoring we make use of the fact that physical flaws, such as corrosion, will only increase over time. This allows us to identify feature vectors which are topologically well-behaved by requiring that sequential classes "line up" in feature vector space. An intelligent feature selection routine is illustrated that identifies favorable class distributions in multi-dimensional feature spaces using computational homology theory. Betti numbers and formal classification accuracies are calculated for each feature space subset to establish a correlation between the topology of the class distribution and the corresponding classification accuracy.

  12. Techniques for Targeted Fermi-GBM Follow-Up of Gravitational-Wave Events

    Science.gov (United States)

    Blackburn, L.; Camp, J.; Briggs, M. S.; Connaughton, V.; Jenke, P.; Christensen, N.; Veitch, J.

    2012-01-01

    The Advanced LIGO and Advanced Virgo ground-based gravitational-wave (GW) detectors are projected to come online 2015 2016, reaching a final sensitivity sufficient to observe dozens of binary neutron star mergers per year by 2018. We present a fully-automated, targeted search strategy for prompt gamma-ray counterparts in offline Fermi-GBM data. The multi-detector method makes use of a detailed model response of the instrument, and benefits from time and sky location information derived from the gravitational-wave signal.

  13. Development of a non-destructive testing technique using ultrasonic wave for evaluation of irradiation embrittlement in nuclear materials

    Science.gov (United States)

    Ishii, T.; Ooka, N.; Hoshiya, T.; Kobayashi, H.; Saito, J.; Niimi, M.; Tsuji, H.

    2002-12-01

    To develop a non-destructive testing technique for evaluating embrittlement of irradiated materials, the correlation between ultrasonic characteristics and embrittlement was investigated from the results of the ultrasonic wave measurement and the Charpy impact test of irradiated specimens of commercial A533B-1 steel and welded material at the hot laboratory of the Japan Materials Testing Reactor (JMTR) in the Japan Atomic Energy Research Institute (JAERI). After irradiation at 523 or 563 K up to a fast neutron fluence of 1×10 24 N/m 2 ( E>1 MeV), velocities of both shear and longitudinal waves in the irradiated specimen were lower than those in the unirradiated one. The decrease in the velocities may be caused by the reductions of the shear and Young's moduli in the irradiated specimen. The attenuation coefficient of the longitudinal wave in the irradiated specimens increased compared with unirradiated ones. With increasing the shift amount of the Charpy transition temperature at 41 J absorbed energy, the velocity and attenuation coefficient of the ultrasonic waves decreased and increased, respectively.

  14. Using dual-band asymmetric transmission effect of 2D metamaterial to manipulate linear polarization state of electromagnetic waves

    Directory of Open Access Journals (Sweden)

    Xun-Yong Pan

    2014-09-01

    Full Text Available This work demonstrates a two-dimensional (2D bilayered metamaterial that exhibits dual-band asymmetric transmission (AT effect for linear polarization. The measured cross-polarization transmissions are 0.88 at 5.68 GHz and 0.92 at 10.7 GHz in one direction, while the corresponding cross-polarization transmissions are suppressed down to 0.17 and 0.18 in the opposite direction, and the AT parameters Δx/Δy reach 0.73/−0.73 and 0.80/−0.80 respectively. The simulated surface current distributions reveal that the underlying physics originates from the induced magnetic coupling. The simulated resonant electric/magnetic field distributions show that the proposed structure follows the principle of metamaterials’ subwavelength.

  15. 3D printed electromagnetic transmission and electronic structures fabricated on a single platform using advanced process integration techniques

    Science.gov (United States)

    Deffenbaugh, Paul Issac

    3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is known about the RF and microwave properties and applications of the standard materials which have been developed for 3D printing. Measurement of a wide variety of materials over a broad spectrum of frequencies up to 10 GHz using a variety of well-established measurement methods is performed throughout chapter 2. Several types of high frequency RF transmission lines are fabricated and valuable model-matched data is gathered and provided in chapter 3 for future designers' use. Of particular note is a fully 3D printed stripline which was automatically fabricated in one process on one machine. Some core advantages of 3D printing RF/microwave components include rapid manufacturing of complex, dimensionally sensitive circuits (such as antennas and filters which are often iteratively tuned) and the ability to create new devices that cannot be made using standard fabrication techniques. Chapter 4 describes an exemplary fully 3D printed curved inverted-F antenna.

  16. Design of InP DHBT power amplifiers at millimeter-wave frequencies using interstage matched cascode technique

    DEFF Research Database (Denmark)

    Yan, Lei; Johansen, Tom Keinicke

    2013-01-01

    In this paper, the design of InP DHBT based millimeter-wave(mm-wave) power amplifiers(PAs) using an interstage matched cascode technique is presented. The output power of a traditional cascode is limited by the early saturation of the common-base(CB) device. The interstage matched cascode can...... be employed to improve the power handling ability through optimizing the input impedance of the CB device. The minimized power mismatch between the CB and the common-emitter(CE) devices results in an improved saturated output power. To demonstrate the technique for power amplifier designs at mm......-wave frequencies, a single-branch cascode based PA using single-finger devices and a two-way combined based PA using three-finger devices are fabricated. The single-branch design shows a measured power gain of 9.2dB and a saturated output power of 12.3dBm at 67.2GHz and the two-way combined design shows a power...

  17. Noncontact, nondestructive elasticity evaluation of sound and demineralized human dental enamel using a laser ultrasonic surface wave dispersion technique

    Science.gov (United States)

    Wang, Hsiao-Chuan; Fleming, Simon; Lee, Yung-Chun; Law, Susan; Swain, Michael; Xue, Jing

    2009-09-01

    Laser ultrasonic nondestructive evaluation (NDE) methods have been proposed to replace conventional in vivo dental clinical diagnosis tools that are either destructive or incapable of quantifying the elasticity of human dental enamel. In this work, a laser NDE system that can perform remote measurements on samples of small dimensions is presented. A focused laser line source is used to generate broadband surface acoustic wave impulses that are detected with a simplified optical fiber interferometer. The measured surface wave velocity dispersion spectrum is in turn used to characterize the elasticity of the specimen. The NDE system and the analysis technique are validated with measurements of different metal structures and then applied to evaluate human dental enamel. Artificial lesions are prepared on the samples to simulate different states of enamel elasticity. Measurement results for both sound and lesioned regions, as well as lesions of different severity, are clearly distinguishable from each other and fit well with physical expectations and theoretical value. This is the first time, to the best of our knowledge, that a laser-based surface wave velocity dispersion technique is successfully applied on human dental enamel, demonstrating the potential for noncontact, nondestructive in vivo detection of the development of carious lesions.

  18. A time domain finite-difference technique for oblique incidence of antiplane waves in heterogeneous dissipative media

    Directory of Open Access Journals (Sweden)

    A. Caserta

    1998-06-01

    Full Text Available This paper deals with the antiplane wave propagation in a 2D heterogeneous dissipative medium with complex layer interfaces and irregular topography. The initial boundary value problem which represents the viscoelastic dynamics driving 2D antiplane wave propagation is formulated. The discretization scheme is based on the finite-difference technique. Our approach presents some innovative features. First, the introduction of the forcing term into the equation of motion offers the advantage of an easier handling of different inputs such as general functions of spatial coordinates and time. Second, in the case of a straight-line source, the symmetry of the incident plane wave allows us to solve the problem of oblique incidence simply by rotating the 2D model. This artifice reduces the oblique incidence to the vertical one. Third, the conventional rheological model of the generalized Maxwell body has been extended to include the stress-free boundary condition. For this reason we solve explicitly the stress-free boundary condition, not following the most popular technique called vacuum formalism. Finally, our numerical code has been constructed to model the seismic response of complex geological structures: real geological interfaces are automatically digitized and easily introduced in the input model. Three numerical applications are discussed. To validate our numerical model, the first test compares the results of our code with others shown in the literature. The second application rotates the input model to simulate the oblique incidence. The third one deals with a real high-complexity 2D geological structure.

  19. Comparative analysis on resistance profiling along tapered semiconductor nanowires: multi-tip technique versus transmission line method

    Science.gov (United States)

    Nägelein, Andreas; Liborius, Lisa; Steidl, Matthias; Blumberg, Christian; Kleinschmidt, Peter; Poloczek, Artur; Hannappel, Thomas

    2017-10-01

    The detection of doping dependent values like contact- and path resistances along nanowires (NWs) still proves to be rather challenging compared to planar structures. Unfortunately, the usually used and well established TLM (transmission line measurement) setup exhibits some drawbacks. Complex preliminary preparation steps and the necessity of ohmic contacts limit the investigation to certain semiconductor materials. The simultaneous determination of contact- and path resistances with an unknown distribution makes an analysis on complex structures like tapered nanowires very challenging. Our approach is the utilization of a multi-tip scanning tunneling microscope (MT-STM) as a four point prober, which allows the investigation of freestanding nanowires with an increased spatial resolution. Here, the used measurement setup allows a local separation of current injection and potential measurement and thus a highly precise determination of path resistances. Tapered p-doped GaAs-NWs were used to compare both techniques. Whereas the evaluation of the axial doping profile by MT-STM was rather simple, correction factors had to be introduced for the TLM measurement to calculate the specific resistances and transfer length. By comparing the results of both methods for the very same NW-sample, the precision and accuracy of MT-STM measurements was demonstrated. We found an agreement, which allows the conclusion that both methods exhibit advantages; however the MT-STM was determined as the more precise setup, which enables additional characterization capabilities, such as surface, temperature or light dependent measurements.

  20. Comparative analysis on resistance profiling along tapered semiconductor nanowires: multi-tip technique versus transmission line method.

    Science.gov (United States)

    Nägelein, Andreas; Liborius, Lisa; Steidl, Matthias; Blumberg, Christian; Kleinschmidt, Peter; Poloczek, Artur; Hannappel, Thomas

    2017-10-04

    The detection of doping dependent values like contact- and path resistances along nanowires (NWs) still proves to be rather challenging compared to planar structures. Unfortunately, the usually used and well established TLM (transmission line measurement) setup exhibits some drawbacks. Complex preliminary preparation steps and the necessity of ohmic contacts limit the investigation to certain semiconductor materials. The simultaneous determination of contact- and path resistances with an unknown distribution makes an analysis on complex structures like tapered nanowires very challenging. Our approach is the utilization of a multi-tip scanning tunneling microscope (MT-STM) as a four point prober, which allows the investigation of freestanding nanowires with an increased spatial resolution. Here, the used measurement setup allows a local separation of current injection and potential measurement and thus a highly precise determination of path resistances. Tapered p-doped GaAs-NWs were used to compare both techniques. Whereas the evaluation of the axial doping profile by MT-STM was rather simple, correction factors had to be introduced for the TLM measurement to calculate the specific resistances and transfer length. By comparing the results of both methods for the very same NW-sample, the precision and accuracy of MT-STM measurements was demonstrated. We found an agreement, which allows the conclusion that both methods exhibit advantages; however the MT-STM was determined as the more precise setup, which enables additional characterization capabilities, such as surface, temperature or light dependent measurements.

  1. Measurement Verification of Plane Wave Synthesis Technique Based on Multi-probe MIMO-OTA Setup

    DEFF Research Database (Denmark)

    Fan, Wei; Carreño, Xavier; Nielsen, Jesper Ødum

    2012-01-01

    Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring. This paper investigates...

  2. Application of a Magnetostrictive Guided wave Technique to Monitor the Evolution of Defect Signals

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Yong-Moo; Oh, Se-Beom; Lee, Duck-Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that wave patterns are clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaw. Of course, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Therefore, the different frequency components of the guided waves will travel at different speeds and the shape of the received signal will changed as it propagates along the pipe. Once the magnetostrictive sensors are attached in the pipe permanently and the signal shape and phase can be compared to the signals before and after, we can monitor the evolution of the flow for the given period. We developed a program to subtract the guided wave signal. The program has a capability of adjusting the time scale and can minimize the noise level after subtraction. By applying the newly developed program, a notch with 2% of CSA can be detected with increased accuracy with noise reduction.

  3. Wave propagation method as an accurate technique for effective refractive index retrieving

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei

    2009-01-01

    An effective parameters retrieval method based on the wave propagation simulation is proposed and compared with the standard S-parameter procedure. The method is free from possible mistakes originated by the multiple branching of solutions in the S-parameter procedure and shows high accuracy. The...

  4. Coefficients of Reflection and Transmission of Transverse and Longitudinal Acoustic Wave in the Blatz-Ko Material

    Directory of Open Access Journals (Sweden)

    Major Maciej

    2014-12-01

    Full Text Available The purpose of this paper is to analyze the propagation of transverse and longitudinal acoustic wave in a composite made of hyperelastic Blatz-Ko material. Composite consists of a homogeneous layer of predetermined thickness d separating two infinite homogeneous material areas. In the paper it is assumed that the middle layer is filled with a homogeneous rubber (ƒ=1, whereas the external areas with foam rubber (ƒ=0. The final effect of paper are graphs of coefficients reflection of transverse and longitudinal acoustic wave, propagating in this composite.

  5. Novel Observational Technique of Gravitational Wave (GW) Events: Detecting and Locating Electromagnetic Counterparts to GW Sources using Dust Scattering Halos

    Science.gov (United States)

    Nederlander, Richard; Paerels, Frits

    2018-01-01

    We discuss a novel observational technique for detecting and locating the electromagnetic counterpart to its GW source, providing astronomers with a several-hour reprieve after a GW event’s occurrence. The technique relies on identifying a dust scattering halo caused by GW-produced X-rays scattering off Galactic dust clouds. The travel time delay of these scattered photons makes them detectable for up to several hours after the prompt event, and the location of the gravitational wave source will be at the geometric center of the halo. The center can be determined with precision sufficient enough to allow the host galaxy to be discerned. This novel technique will be especially relevant for binary black-hole mergers because their counterparts have, as of now, been difficult to detect.

  6. Traveling-wave-tube efficiency improvement by a low-cost technique for deposition of carbon on multistage depressed collector

    Science.gov (United States)

    Ebihara, Ben T.; Ramins, Peter; Peet, Shelly

    1987-01-01

    A simple method of improving the traveling-wave-tube (TWT) and multistage depressed collector (MDC) efficiency has been demonstrated. The efficiency improvement was produced by the application of a thin layer of carbon to the copper electrodes of the MDC by means of a rapid, low-cost technique involving the pyrolysis of hydrocarbon oil in electric arc discharges. Experimental results with a representative TWT and MDC showed an 11 percent improvement in both the TWT and MDC efficiencies as compared to those of the same TWT and MDC efficiencies with bare copper electrode surfaces. An extended test with a 500-W, continuous wave (CW) TWT and small-sized MDC indicated good stability of the carbon coated electrode surfaces after a relatively small initial degradation in TWT overall and apparent MDC efficiencies.

  7. Multi-Wave and Hybrid Imaging Techniques: A New Direction for Nondestructive Testing and Structural Health Monitoring

    Directory of Open Access Journals (Sweden)

    Yuhua Cheng

    2013-11-01

    Full Text Available In this article, the state-of-the-art multi-wave and hybrid imaging techniques in the field of nondestructive evaluation and structural health monitoring were comprehensively reviewed. A new direction for assessment and health monitoring of various structures by capitalizing the advantages of those imaging methods was discussed. Although sharing similar system configurations, the imaging physics and principles of multi-wave phenomena and hybrid imaging methods are inherently different. After a brief introduction of nondestructive evaluation (NDE , structure health monitoring (SHM and their related challenges, several recent advances that have significantly extended imaging methods from laboratory development into practical applications were summarized, followed by conclusions and discussion on future directions.

  8. Optical-flow-based background-oriented schlieren technique for measuring a laser-induced underwater shock wave

    CERN Document Server

    Hayasaka, Keisuke; Liu, Tianshu; Kameda, Masaharu

    2016-01-01

    The background-oriented schlieren (BOS) technique with the physics-based optical flow method (OF-BOS) is developed for measuring the pressure field of a laser-induced underwater shock wave. Compared to BOS with the conventional cross-correlation method in PIV (called PIV-BOS), by using the OF-BOS, the displacement field generated by the small density gradient in water can be obtained at the spatial resolution of one vector per pixel. The corresponding density and pressure fields can be further extracted. It is particularly demonstrated that the sufficiently high spatial resolution of the extracted displacement vector field is required in the tomographic reconstruction to correctly infer the pressure field of the spherical underwater shock wave. The capability of the OF-BOS is critically evaluated based on synchronized hydrophone measurements. Special emphasis is placed on direct comparison between the OF-BOS with the PIV-BOS.

  9. Study of interaction of ELF-ULF range (0.1-200 Hz) electromagnetic waves with the earth's crust and the ionosphere in the field of industrial power transmission lines (FENICS experiment)

    Science.gov (United States)

    Zhamaletdinov, A. A.; Shevtsov, A. N.; Velikhov, E. P.; Skorokhodov, A. A.; Kolesnikov, V. E.; Korotkova, T. G.; Ryazantsev, P. A.; Efimov, B. V.; Kolobov, V. V.; Barannik, M. B.; Prokopchuk, P. I.; Selivanov, V. N.; Kopytenko, Yu. A.; Kopytenko, E. A.; Ismagilov, V. S.; Petrishchev, M. S.; Sergushin, P. A.; Tereshchenko, P. E.; Samsonov, B. V.; Birulya, M. A.; Smirnov, M. Yu.; Korja, T.; Yampolski, Yu. M.; Koloskov, A. V.; Baru, N. A.; Poljakov, S. V.; Shchennikov, A. V.; Druzhin, G. I.; Jozwiak, W.; Reda, J.; Shchors, Yu. G.

    2015-12-01

    This article is devoted to describing the theory, technique, and first experimental results of a control source electromagnetic (CSEM) study of the Earth's crust and ionosphere with the use of two mutually orthogonal industrial transmission lines 109 and 120 km in length in the frame of FENICS (Fennoscandian Electrical Conductivity from Natural and Induction Control Source Soundings) experiment. The main part of the measurements is executed on the territory of the Fennoscandian shield at distances from the first hundreds kilometers up to 856 km from the source with the purpose of the deep electromagnetic sounding of the Earth's crust and upper mantle. According to the results of these studies clarifying the parameters of "normal" (standard) geoelectric section of the lithosphere to a depth of 60-70 km, the anisotropy parameters are evaluated and a geothermal and rheological interpretation in conjunction with the analysis of the seismic data is executed. Furthermore, to study the propagation of ELF-LLF waves (0.1-200 Hz) in an "Earth-Ionosphere" waveguide, the measurements are carried out apart from Fennoscandian shield at distances up to 5600 km from the source (in Ukraine, Spitsbergen, Poland, Kamchatka, and other areas). According to the results of these studies, the experimental estimates of the influence of the ionosphere and of the displacement currents on the propagation of ELF-ULF waves in the upper half-space at the different azimuths generation of the primary field are obtained.

  10. Transmission Enhancement of High-$k$ Waves through Metal-InGaAsP Multilayers Calculated via Scattering Matrix Method with Semi-Classical Optical Gain

    CERN Document Server

    Smalley, Joseph S T; Shahin, Shiva; Kanté, Boubacar; Fainman, Yeshaiahu

    2015-01-01

    We analyze the steady-state transmission of high-momentum (high-$k$) electromagnetic waves through metal-semiconductor multilayer systems with loss and gain in the near-infrared (NIR). Using a semi-classical optical gain model in conjunction with the scattering matrix method (SMM), we study indium gallium arsenide phosphide (InGaAsP) quantum wells as the active semiconductor, in combination with the metals, aluminum-doped zinc oxide (AZO) and silver (Ag). Under moderate external pumping levels, we find that NIR transmission through Ag/InGaAsP systems may be enhanced by several orders of magnitude relative to the unpumped case, over a large angular and frequency bandwidth. Conversely, transmission enhancement through AZO/InGaAsP systems is orders of magnitude smaller, and has a strong frequency dependence. We discuss the relative importance of Purcell enhancement on our results and validate analytical calculations based on the SMM with numerical finite-difference time domain simulations.

  11. On the source-frequency dependence of fracture-orientation estimates from shear-wave transmission experiments

    Science.gov (United States)

    Santos, Leo K.; de Figueiredo, J. J. S.; Omoboya, Bode; Schleicher, Jörg; Stewart, Robert R.; Dyaur, Nikolay

    2015-03-01

    Shear-wave propagation through anisotropic fractured or cracked media can provide valuable information about these fracture swarms and their orientations. The main goal of this work is to recover information about fracture orientation based on the shear waveforms (S-waveforms). For this study, we carried out ultrasonic S-wave measurements in a synthetic physical model made of epoxy resin (isotropic matrix proxy), with small cylindrical rubber strips as inclusions (artificial cracks) inserted in it to simulate a homogeneous anisotropic medium. In these experiments, we used low, intermediate, and high frequency shear-wave sources, with frequencies 90, 431, and 840 kHz. We integrated and interpreted the resulting S-wave seismograms, cross-correlation panels and anisotropic parameter-analysis curves. We were able to estimate the crack orientation in single-orientation fracture zones. The high frequency peaks associated with scattered S-waves provided interpretable information about the fracture orientations when the propagation direction was parallel to the fracture plane. The analysis was possible utilizing results from frequency-versus-polarization-angle curves. Moreover, we applied a bandpass filtering process to the intermediate and high frequency seismograms in order to obtain low frequency seismograms. A spectral analysis using frequency-wavenumber (F-K) spectra supports this filtering process. The results obtained using an analysis of cross-correlograms and the Thomsen parameter γ extracted from filtered high-frequency data were quite similar to those obtained using a low-frequency source. This highlighted the possibility of using less expensive high-frequency sources to recover information about the fracture set.

  12. Adaptable Design Improvements for Electromagnetic Shock Wave Lithotripters and Techniques for Controlling Cavitation

    Science.gov (United States)

    Smith, Nathan Birchard

    In this dissertation work, the aim was to garner better mechanistic understanding of how shock wave lithotripsy (SWL) breaks stones in order to guide design improvements to modern electromagnetic (EM) shock wave lithotripters. To accomplish this goal, experimental studies were carefully designed to isolate mechanisms of fragmentation, and models for wave propagation, fragmentation, and stone motion were developed. In the initial study, a representative EM lithotripter was characterized and tested for in vitro stone comminution efficiency at a variety of field positions and doses using phantom kidney stones of variable physical properties, and in different fluid mediums to isolate the contribution of cavitation. Through parametric analysis of the acoustic field measurements alongside comminution results, a logarithmic correlation was determined between average peak pressure incident on the stone surface and comminution efficiency. It was also noted that for a given stone type, the correlations converged to an average peak pressure threshold for fragmentation, independent of fluid medium in use. The correlation of average peak pressure to efficacy supports the rationale for the acoustic lens modifications, which were pursued to simultaneously enhance beam width and optimize the pulse profile of the lithotripter shock wave (LSW) via in situ pulse superposition for improved stone fragmentation by stress waves and cavitation, respectively. In parallel, a numerical model for wave propagation was used to investigate the variations of critical parameters with changes in lens geometry. A consensus was reached on a new lens design based on high-speed imaging and stone comminution experiments against the original lens at a fixed acoustic energy setting. The results have demonstrated that the new lens has improved efficacy away from the focus, where stones may move due to respiration, fragmentation, acoustic radiation forces, or voluntary patient movements. Using the

  13. Basic examination of a technique to visualize space filled with dense smoke using millimeter-wave radar

    Science.gov (United States)

    Omine, Yukio; Sakai, Masaki; Aoki, Yoshimitsu; Takagi, Mikio

    2004-10-01

    In recent years, crisis management in response to terrorist attacks and natural disasters, as well as accelerating rescue operations has become an important issue. Rescue operations greatly influence human lives, and require the ability to accurately and swiftly communicate information as well as assess the status of the site. Currently, considerable amount of research is being conducted for assisting rescue operations, with the application of various engineering techniques such as information technology and radar technology. In the present research, we believe that assessing the status of the site is most crucial in rescue and firefighting operations at a fire disaster site, and aim to visualize the space that is smothered with dense smoke. In a space filled with dense smoke, where visual or infrared sensing techniques are not feasible, three-dimensional measurements can be realized using a compact millimeter wave radar device combined with directional information from a gyro sensor. Using these techniques, we construct a system that can build and visualize a three-dimensional geometric model of the space. The final objective is to implement such a system on a wearable computer, which will improve the firefighters' spatial perception, assisting them in the baseline assessment and the decision-making process. In the present paper, we report the results of the basic experiments on three-dimensional measurement and visualization of a space that is smoke free, using a millimeter wave radar.

  14. W-Band Technology and Techniques for Analog Millimeter-Wave Photonics

    Science.gov (United States)

    2015-08-19

    this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data...applied field with a rich history [1] that finds utility in numerous areas. An inherent advantage of photonics over electronics is the available...millimeter-wave application is associated with wireless links [5-7], radio astronomy [8], or military systems, the main components that determine the

  15. A Source-Model Technique for analysis of wave guiding along chains of metallic nanowires in layered media.

    Science.gov (United States)

    Szafranek, Dana; Leviatan, Yehuda

    2011-12-05

    A method for determining the modes that can be guided along infinite chains of metallic nanowires when they are embedded, as in most realistic set-ups, in layered media is presented. The method is based on a rigorous full-wave frequency-domain Source-Model Technique (SMT). The method allows efficient determination of the complex propagation constants and the surface-plasmon type modal fields. Sample results are presented for silver nanowires with circular and triangle-like cross-sections lying in an air-Si-glass layered structure.

  16. Geophysical techniques in the historical center of Venice (Italy): preliminary results from HVSR and multichannel analysis of surface waves

    Science.gov (United States)

    Trevisani, Sebastiano; Rocca, Michele; Boaga, Jacopo

    2014-05-01

    This presentation aims to outline the preliminary findings related to an extensive seismic survey conducted in the historical center of Venice, Italy. The survey was conducted via noninvasive and low-cost seismic techniques based on surface waves analysis and microtremor methods, mainly using single station horizontal to vertical spectral ratio techninques (HVSR) and multichannel analysis of surface waves in passive (ReMI) and active (MASW) configurations. The importance and the fragility of the cultural heritage of Venice, coupled with its peculiar geological and geotechnical characteristics, stress the importance of a good knowledge of its geological architecture and seismic characteristics as an opportunity to improve restoration and conservation planning. Even if Venice is located in a relatively low seismic hazard zone, a local characterization of soil resonance frequencies and surficial shear waves velocities could improve the planning of engineering interventions, furnishing important information on possible local effects related to seismic amplification and possible coupling within buildings and soil resonance frequencies. In the specific we collected more than 50 HVSR single station noise measurements and several passive and active multichannel analysis of surface waves located in the historical center. In this work we report the characteristics of the conducted seismic surveys (instrumentation, sampling geometry, etc.) and the preliminary findings of our analysis. Moreover, we discuss briefly the practical issues, mainly of logistic nature, of conducting this kind of surveys in a peculiar and crowed historical center as represented by Venice urban contest. Acknowledgments Instrumentation acquired in relation to the project co-financed by Regione Veneto, POR-CRO, FESR, 2007-2013, action 1.1.1. "Supporto ad attività di ricerca, processi e reti di innovazione e alla creazione di imprese in settori a elevato contenuto tecnologico"

  17. A Stream Function Theory Based Calculation of Wave Kinematics for Very Steep Waves Using a Novel Non-linear Stretching Technique

    DEFF Research Database (Denmark)

    Stroescu, Ionut Emanuel; Sørensen, Lasse; Frigaard, Peter Bak

    2016-01-01

    A non-linear stretching method was implemented for stream function theory to solve wave kinematics for physical conditions close to breaking waves in shallow waters, with wave heights limited by the water depth. The non-linear stretching method proves itself robust, efficient and fast, showing good...

  18. Characterization of electron clouds in the Cornell Electron Storage Ring Test Accelerator using TE-wave transmission

    Energy Technology Data Exchange (ETDEWEB)

    De Santis, S.; Byrd, J. M.; Billing, M.; Palmer, M.; Sikora, J.; Carlson, B.

    2010-01-02

    A relatively new technique for measuring the electron cloud density in storage rings has been developed and successfully demonstrated [S. De Santis, J.M. Byrd, F. Caspers, A. Krasnykh, T. Kroyer, M.T.F. Pivi, and K.G. Sonnad, Phys. Rev. Lett. 100, 094801 (2008).]. We present the experimental results of a systematic application of this technique at the Cornell Electron Storage Ring Test Accelerator. The technique is based on the phase modulation of the TE mode transmitted in a synchrotron beam pipe caused by the periodic variation of the density of electron plasma. Because of the relatively simple hardware requirements, this method has become increasingly popular and has been since successfully implemented in several machines. While the principles of this technique are straightforward, quantitative derivation of the electron cloud density from the measurement requires consideration of several effects, which we address in detail.

  19. A Methodological Review of Piezoelectric Based Acoustic Wave Generation and Detection Techniques for Structural Health Monitoring

    Directory of Open Access Journals (Sweden)

    Zhigang Sun

    2013-01-01

    Full Text Available Piezoelectric transducers have a long history of applications in nondestructive evaluation of material and structure integrity owing to their ability of transforming mechanical energy to electrical energy and vice versa. As condition based maintenance has emerged as a valuable approach to enhancing continued aircraft airworthiness while reducing the life cycle cost, its enabling structural health monitoring (SHM technologies capable of providing on-demand diagnosis of the structure without interrupting the aircraft operation are attracting increasing R&D efforts. Piezoelectric transducers play an essential role in these endeavors. This paper is set forth to review a variety of ingenious ways in which piezoelectric transducers are used in today’s SHM technologies as a means of generation and/or detection of diagnostic acoustic waves.

  20. Transmission of infrasonic pressure waves from cerebrospinal to intralabyrinthine fluids through the human cochlear aqueduct: Non-invasive measurements with otoacoustic emissions.

    Science.gov (United States)

    Traboulsi, Raghida; Avan, Paul

    2007-11-01

    The cochlear aqueduct connecting intralabyrinthine and cerebrospinal fluids (CSF) acts as a low-pass filter that should be able to transmit infrasonic pressure waves from CSF to cochlea. Recent experiments have shown that otoacoustic emissions generated at 1kHz respond to pressure-related stapes impedance changes with a change in phase relative to the generator tones, and provide a non-invasive means of assessing intracochlear pressure changes. In order to characterize the transmission to the cochlea of CSF pressure waves due to respiration, the distortion-product otoacoustic emissions (DPOAE) of 12 subjects were continuously monitored around 1kHz at a rate of 6.25epochs/s, and their phase relative to the stimulus tones was extracted. The subjects breathed normally, in different postures, while thoracic movements were recorded so as to monitor respiration. A correlate of respiration was found in the time variation of DPOAE phase, with an estimated mean amplitude of 10 degrees , i.e. 60mm water, suggesting little attenuation across the aqueduct. Its phase lag relative to thoracic movements varied between 0 degrees and -270 degrees . When fed into a two-compartment model of CSF and labyrinthine spaces, these results suggest that respiration rate at rest is just above the resonance frequency of the CSF compartment, and just below the corner frequency of the cochlear-aqueduct low-pass filter, in line with previous estimates from temporal bone and intracranial measurements. The fact that infrasonic CSF waves can be monitored through the cochlea opens diagnostic possibilities in neurology.

  1. Wave transmission through silicone foam pads in a compression Kolsky bar apparatus. Comparisons between simulations and measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Corona, Edmundo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-01-01

    This memo concerns the transmission of mechanical signals through silicone foam pads in a compression Kolsky bar set-up. The results of numerical simulations for four levels of pad pre-compression and two striker velocities were compared directly to test measurements to assess the delity of the simulations. The nite element model simulated the Kolsky tests in their entirety and used the hyperelastic `hyperfoam' model for the silicone foam pads. Calibration of the hyperfoam model was deduced from quasi-static compression data. It was necessary, however, to augment the material model by adding sti ness proportional damping in order to generate results that resembled the experimental measurements. Based on the results presented here, it is important to account for the dynamic behavior of polymeric foams in numerical simulations that involve high loading rates.

  2. Simultaneous generation of 40, 80 and 120 GHz optical millimeter-wave from one Mach-Zehnder modulator and demonstration of millimeter-wave transmission and down-conversion

    Science.gov (United States)

    Zhou, Wen; Qin, Chaoyi

    2017-09-01

    We demonstrate multi-frequency QPSK millimeter-wave (mm-wave) vector signal generation enabled by MZM-based optical carrier suppression (OCS) modulation and in-phase/quadrature (I/Q) modulation. We numerically simulate the generation of 40-, 80- and 120-GHz vector signal. Here, the three different signals carry the same QPSK modulation information. We also experimentally realize 11Gbaud/s QPSK vector signal transmission over 20 km fiber, and the generation of the vector signals at 40-GHz, 80-GHz and 120-GHz. The experimental results show that the bit-error-rate (BER) for all the three different signals can reach the forward-error-correction (FEC) threshold of 3.8×10-3. The advantage of the proposed system is that provide high-speed, high-bandwidth and high-capacity seamless access of TDM and wireless network. These features indicate the important application prospect in wireless access networks for WiMax, Wi-Fi and 5G/LTE.

  3. Characterization of electron clouds in the Cornell Electron Storage Ring Test Accelerator using TE-wave transmission

    Directory of Open Access Journals (Sweden)

    S. De Santis

    2010-07-01

    Full Text Available A relatively new technique for measuring the electron cloud density in storage rings has been developed and successfully demonstrated [S. De Santis, J. M. Byrd, F. Caspers, A. Krasnykh, T. Kroyer, M. T. F. Pivi, and K. G. Sonnad, Phys. Rev. Lett. 100, 094801 (2008.PRLTAO0031-900710.1103/PhysRevLett.100.094801]. We present the experimental results of a systematic application of this technique at the Cornell Electron Storage Ring Test Accelerator. The technique is based on the phase modulation of the TE mode transmitted in a synchrotron beam pipe caused by the periodic variation of the density of electron plasma. Because of the relatively simple hardware requirements, this method has become increasingly popular and has been since successfully implemented in several machines. While the principles of this technique are straightforward, quantitative derivation of the electron cloud density from the measurement requires consideration of several effects, which we address in detail.

  4. Simulation of Acoustic Wave Propagation in Anisotropic Media Using Dynamic Programming Technique

    OpenAIRE

    Botkin, Nikolai; Turova, Varvara

    2013-01-01

    International audience; It is known that the Hamiltonian of the eikonal equation for an anisotropic medium may be nonconvex, which excludes the application of Fermat’s minimum-time principle related to minimum-time control problems. The idea proposed in this paper consists in finding a conflict control problem (differential game) whose Hamiltonian coincides with the Hamiltonian of the eikonal equation. It turns out that this is always possible due to Krasovskii’s unification technique. Having...

  5. Applanation tonometry: a reliable technique to assess aortic pulse wave velocity in spinal cord injury.

    Science.gov (United States)

    Currie, K D; Hubli, M; Krassioukov, A V

    2014-04-01

    Within-subject repeated measures. To determine the intra- and inter-tester reliability of aortic pulse wave velocity (aPWV) measurements collected using applanation tonometry in individuals with spinal cord injury (SCI). Inpatient Rehabilitation Centre and outpatient Clinic in Vancouver, BC, Canada. Fifteen men and three women with traumatic SCI (age: 46±16 years; C3-L1; American Spinal Injury Association Impairment Scale A-D; 2-284 months post injury) participated in two testing sessions separated by an average of 2 days. During each testing session, aPWV measurements were collected in the supine position following 10 min of rest. Arterial blood pressure waveforms were collected simultaneously by two trained raters at the carotid and femoral arterial sites using applanation tonometry. Heart rate was continuously measured using a single-lead electrocardiogram, whereas brachial blood pressures were measured at 5-min intervals using an automated device. Intra- and inter-tester aPWV measurements demonstrated almost perfect reliability with intraclass correlation coefficients of 0.91 and 0.98 (Pblood pressure between intra- and inter-testing sessions. Applanation tonometry measurements of aPWV are reliable in individuals with SCI. In addition, the SDDs were smaller than a clinically relevant value, suggesting that this measurement is suitable for repeated measures study designs in SCI.

  6. Hybrid multicore/vectorisation technique applied to the elastic wave equation on a staggered grid

    Science.gov (United States)

    Titarenko, Sofya; Hildyard, Mark

    2017-07-01

    In modern physics it has become common to find the solution of a problem by solving numerically a set of PDEs. Whether solving them on a finite difference grid or by a finite element approach, the main calculations are often applied to a stencil structure. In the last decade it has become usual to work with so called big data problems where calculations are very heavy and accelerators and modern architectures are widely used. Although CPU and GPU clusters are often used to solve such problems, parallelisation of any calculation ideally starts from a single processor optimisation. Unfortunately, it is impossible to vectorise a stencil structured loop with high level instructions. In this paper we suggest a new approach to rearranging the data structure which makes it possible to apply high level vectorisation instructions to a stencil loop and which results in significant acceleration. The suggested method allows further acceleration if shared memory APIs are used. We show the effectiveness of the method by applying it to an elastic wave propagation problem on a finite difference grid. We have chosen Intel architecture for the test problem and OpenMP (Open Multi-Processing) since they are extensively used in many applications.

  7. Retrieving reflection responses by crosscorrelating transmission responses from deterministic transient sources : Application to ultrasonic data

    NARCIS (Netherlands)

    Draganov, D.; Wapenaar, K.; Thorbecke, J.; Nishizawa, O.

    2007-01-01

    By crosscorrelating transmission recordings of acoustic or elastic wave fields at two points, one can retrieve the reflection response between these two points. This technique has previously been applied to measured elastic data using diffuse wave-field recordings. These recordings should be

  8. Modeling seismic wave propagation across the European plate: structural models and numerical techniques, state-of-the-art and prospects

    Science.gov (United States)

    Morelli, Andrea; Danecek, Peter; Molinari, Irene; Postpischl, Luca; Schivardi, Renata; Serretti, Paola; Tondi, Maria Rosaria

    2010-05-01

    beneath the Alpine mobile belt, and fast lithospheric signatures under the two main Mediterranean subduction systems (Aegean and Tyrrhenian). We validate this new model through comparison of recorded seismograms with simulations based on numerical codes (SPECFEM3D). To ease and increase model usage, we also propose the adoption of a common exchange format for tomographic earth models based on JSON, a lightweight data-interchange format supported by most high-level programming languages, and provide tools for manipulating and visualising models, described in this standard format, in Google Earth and GEON IDV. In the next decade seismologists will be able to reap new possibilities offered by exciting progress in general computing power and algorithmic development in computational seismology. Structural models, still based on classical approaches and modeling just few parameters in each seismogram, will benefit from emerging techniques - such as full waveform fitting and fully nonlinear inversion - that are now just showing their potential. This will require extensive availability of supercomputing resources to earth scientists in Europe, as a tool to match the planned new massive data flow. We need to make sure that the whole apparatus, needed to fully exploit new data, will be widely accessible. To maximize the development, so as for instance to enable us to promptly model ground shaking after a major earthquake, we will also need a better coordination framework, that will enable us to share and amalgamate the abundant local information on earth structure - most often available but difficult to retrieve, merge and use. Comprehensive knowledge of earth structure and of best practices to model wave propagation can by all means be considered an enabling technology for further geophysical progress.

  9. Generation of 1.024-Tb/s Nyquist-WDM phase-conjugated twin vector waves through polarization-insensitive optical parametric amplification enabling transmission over 4000-km dispersion-managed TWRS fiber

    DEFF Research Database (Denmark)

    Liu, Xiang; Hu, Hao; Chandrasekhar, S.

    2013-01-01

    We experimentally demonstrate the first Tb/s Nyquist-WDM phase-conjugated twin waves, consisting of eight 128-Gb/s PDM-QPSK signals and their idlers, by a broadband polarization-insensitive fiber optical parametric amplifier, enabling more than doubled reach in dispersion-managed transmission...

  10. Compact Liquid Crystal Based Tunable Band-Stop Filter with an Ultra-Wide Stopband by Using Wave Interference Technique

    Directory of Open Access Journals (Sweden)

    Longzhu Cai

    2017-01-01

    Full Text Available A wave interference filtering section that consists of three stubs of different lengths, each with an individual stopband of its own central frequency, is reported here for the design of band-stop filters (BSFs with ultra-wide and sharp stopbands as well as large attenuation characteristics. The superposition of the individual stopbands provides the coverage over an ultra-wide frequency range. Equations and guidelines are presented for the application of a new wave interference technique to adjust the rejection level and width of its stopband. Based on that, an electrically tunable ultra-wide stopband BSF using a liquid crystal (LC material for ultra-wideband (UWB applications is designed. Careful treatment of the bent stubs, including impedance matching of the main microstrip line and bent stubs together with that of the SMA connectors and impedance adaptors, was carried out for the compactness and minimum insertion and reflection losses. The experimental results of the fabricated device agree very well with that of the simulation. The centre rejection frequency as measured can be tuned between 4.434 and 4.814 GHz when a biased voltage of 0–20 Vrms is used. The 3 dB and 25 dB stopband bandwidths were 4.86 GHz and 2.51 GHz, respectively, which are larger than that of other recently reported LC based tunable BSFs.

  11. Interferenceless coded aperture correlation holography-a new technique for recording incoherent digital holograms without two-wave interference.

    Science.gov (United States)

    Vijayakumar, A; Rosen, Joseph

    2017-06-12

    Recording digital holograms without wave interference simplifies the optical systems, increases their power efficiency and avoids complicated aligning procedures. We propose and demonstrate a new technique of digital hologram acquisition without two-wave interference. Incoherent light emitted from an object propagates through a random-like coded phase mask and recorded directly without interference by a digital camera. In the training stage of the system, a point spread hologram (PSH) is first recorded by modulating the light diffracted from a point object by the coded phase masks. At least two different masks should be used to record two different intensity distributions at all possible axial locations. The various recorded patterns at every axial location are superposed in the computer to obtain a complex valued PSH library cataloged to its axial location. Following the training stage, an object is placed within the axial boundaries of the PSH library and the light diffracted from the object is once again modulated by the same phase masks. The intensity patterns are recorded and superposed exactly as the PSH to yield a complex hologram of the object. The object information at any particular plane is reconstructed by a cross-correlation between the complex valued hologram and the appropriate element of the PSH library. The characteristics and the performance of the proposed system were compared with an equivalent regular imaging system.

  12. Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals.

    Science.gov (United States)

    Scaife, B K P; Vij, J K

    2005-05-01

    The theory of absorbance is developed for the entire electromagnetic spectrum of radiation in a semi-infinite anisotropic medium with a second rank dielectric tensor, the elements of which are complex and frequency dependent. The theory of the absorbance A(omega,theta) of an optically anisotropic liquid in an infrared (IR) test cell is then outlined and applied to IR transmission experiments. A formula for the dependence of A(omega,theta), on theta (theta being the angle between the electric vector and the principal optical axis) is derived from first principles. The formula, for radiation of angular frequency omega, viz, A(omega,theta)=-log(10)[10(-A(omega,0))cos(2)theta+10(-A(omega,pi2))sin(2)theta] is in agreement with that proposed by Jang, Park, Maclennan, Kim, and Clark [Ferroelectrics 180, 213 (1996) ] and confirms some of the work of Kocot, Wrzalik, and Vij [Liq. Cryst. 21, 147 (1996)]. The comments on this formula by Jang, Park, Kim, Glaser, and Clark [Phys. Rev. E 62, 5027 (2000)], and by Kocot et al. are discussed. The absorbance A(omega,0) and A(omega,pi2) have been expressed in terms of the optical properties of the material and the dimensions of the cell.

  13. Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission of liquid crystals: comparison with experiments.

    Science.gov (United States)

    Scaife, B K P; Sigarev, A A; Vij, J K; Goodby, J W

    2009-08-01

    The theory of the absorbance of a semi-infinite medium characterized by a second-rank dielectric tensor for the entire electromagnetic spectrum, as given by Scaife and Vij [J. Chem. Phys. 122, 174901 (2005)], is extended to include molecules of prolate spheriodal shape with longitudinal and transverse polarizabilities and to cover the case of elliptically polarized incident radiation. The theory is applied to the infrared transmission experiments of biaxial liquid crystals. It is found that the formula for the dependence on frequency and on angle of polarization of the absorbance A(omega,theta)= -log(10)[10(A(omega,0)) cos(2) theta + (10(-A(omega,pi/2)) sin(2) theta)] is unaffected by the anisotropy of the molecules and by the elliptical polarization of the incident radiation. A small (+/-5%) discrepancy between theory and experiment has been found for bands with high absorbances. It is found that this discrepancy does not depend on birefringence of the sample but may depend on the precise method of absorbance measurement and on effects at the surface of the cell containing the liquid crystal under test.

  14. Axial transmission method for long bone fracture evaluation by ultrasonic guided waves: simulation, phantom and in vitro experiments.

    Science.gov (United States)

    Xu, Kailiang; Ta, Dean; He, Runxin; Qin, Yi-Xian; Wang, Weiqi

    2014-04-01

    Mode conversion occurs when the ultrasonic guided waves encounter fractures. The aim of this study was to investigate the feasibility of fracture assessment in long cortical bone using guided-mode conversion. Mode conversion behavior between the fundamental modes S0 and A0 was analyzed. The expressions proposed for modal velocity were used to identify the original and converted modes. Simulations and phantom experiments were performed using 1.0-mm-thick steel plates with a notch width of 0.5 mm and notch depths of 0.2, 0.4, 0.6 and 0.8 mm. Furthermore, in vitro experiments were carried out on nine ovine tibias with 1.0-mm-wide partial transverse gap break and cortical thickness varying from 2.10 to 3.88 mm. The study confirmed that mode conversion gradually becomes observable as fracture depth increases. Energy percentages of the converted modes correlated strongly with fracture depth, as illustrated by the frequency-sweeping experiments on steel phantoms (100-1100 kHz, r(2) = 0.97, p < 0.0069) and the fixed-frequency experiments on nine ovine tibias (250 kHz, r(2) = 0.97, p < 0.0056). The approaches described, including mode excitation, velocity expressions and energy percentage criteria, may also contribute to ultrasonic monitoring of long bone fracture healing. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. Transmission eigenvalues

    Science.gov (United States)

    Cakoni, Fioralba; Haddar, Houssem

    2013-10-01

    In inverse scattering theory, transmission eigenvalues can be seen as the extension of the notion of resonant frequencies for impenetrable objects to the case of penetrable dielectrics. The transmission eigenvalue problem is a relatively late arrival to the spectral theory of partial differential equations. Its first appearance was in 1986 in a paper by Kirsch who was investigating the denseness of far-field patterns for scattering solutions of the Helmholtz equation or, in more modern terminology, the injectivity of the far-field operator [1]. The paper of Kirsch was soon followed by a more systematic study by Colton and Monk in the context of developing the dual space method for solving the inverse scattering problem for acoustic waves in an inhomogeneous medium [2]. In this paper they showed that for a spherically stratified media transmission eigenvalues existed and formed a discrete set. Numerical examples were also given showing that in principle transmission eigenvalues could be determined from the far-field data. This first period of interest in transmission eigenvalues was concluded with papers by Colton et al in 1989 [3] and Rynne and Sleeman in 1991 [4] showing that for an inhomogeneous medium (not necessarily spherically stratified) transmission eigenvalues, if they existed, formed a discrete set. For the next seventeen years transmission eigenvalues were ignored. This was mainly due to the fact that, with the introduction of various sampling methods to determine the shape of an inhomogeneous medium from far-field data, transmission eigenvalues were something to be avoided and hence the fact that transmission eigenvalues formed at most a discrete set was deemed to be sufficient. In addition, questions related to the existence of transmission eigenvalues or the structure of associated eigenvectors were recognized as being particularly difficult due to the nonlinearity of the eigenvalue problem and the special structure of the associated transmission

  16. On the Security of Millimeter Wave Vehicular Communication Systems Using Random Antenna Subsets

    KAUST Repository

    Eltayeb, Mohammed E.

    2017-03-20

    Millimeter wave (mmWave) vehicular communication systems have the potential to improve traffic efficiency and safety. Lack of secure communication links, however, may lead to a formidable set of abuses and attacks. To secure communication links, a physical layer precoding technique for mmWave vehicular communication systems is proposed in this paper. The proposed technique exploits the large dimensional antenna arrays available at mmWave systems to produce direction dependent transmission. This results in coherent transmission to the legitimate receiver and artificial noise that jams eavesdroppers with sensitive receivers. Theoretical and numerical results demonstrate the validity and effectiveness of the proposed technique and show that the proposed technique provides high secrecy throughput when compared to conventional array and switched array transmission techniques.

  17. High-resolution wave number spectrum using multi-point measurements in space – the Multi-point Signal Resonator (MSR technique

    Directory of Open Access Journals (Sweden)

    Y. Narita

    2011-02-01

    Full Text Available A new analysis method is presented that provides a high-resolution power spectrum in a broad wave number domain based on multi-point measurements. The analysis technique is referred to as the Multi-point Signal Resonator (MSR and it benefits from Capon's minimum variance method for obtaining the proper power spectral density of the signal as well as the MUSIC algorithm (Multiple Signal Classification for considerably reducing the noise part in the spectrum. The mathematical foundation of the analysis method is presented and it is applied to synthetic data as well as Cluster observations of the interplanetary magnetic field. Using the MSR technique for Cluster data we find a wave in the solar wind propagating parallel to the mean magnetic field with relatively small amplitude, which is not identified by the Capon spectrum. The Cluster data analysis shows the potential of the MSR technique for studying waves and turbulence using multi-point measurements.

  18. New Method For Modeling and Design Optical SDM Transmission System Using Long Haul FMF with PDM/DWDM Techniques Enabling QPSK Modulation Format

    Directory of Open Access Journals (Sweden)

    Ibrahim Abdullah

    2017-07-01

    Full Text Available This paper presents the modeling and design of ultra high capacity Space Division Multiplexing (SDM transmission system. Polarization Division Multiplexing (PDM and Dense Wavelength Division Multiplexing (DWDM techniques are also proposed in this system to increase total system data rate. For the ultra-high capacity need of SDM, Few Mode Fiber (FMF was proposed as SDM best technology for obtaining ultra-high bit rates with long haul transmission. The description and design of 8-DWDM channels over 7 modes SDM/PDM system was explored as future of ultra-high capacity optical network. A long-haul transmission of 1080 Km recorded for 8-WDM channels-7modes-SDM/PDM system by using QPSK modulation format. The total bit rate achieved by our designed system is 4.48 Tb/s at 40Gb/s. Channel estimation techniques were proposed to enable the transmitter pre-shaping design for the linear effects mitigation by using different DSP algorithms. The presence of linear and nonlinear losses limits the acceptable range of input power that produce the required BER for our proposed system from -4dBm to 4dBm.

  19. Standardizing operational vector sampling techniques for measuring malaria transmission intensity: evaluation of six mosquito collection methods in western Kenya

    OpenAIRE

    Wong, Jacklyn; Bayoh, Nabie; Olang, George; Killeen, Gerry; Hamel, Mary J; Vulule, John M.; Gimnig, John E.

    2013-01-01

    Background\\ud Operational vector sampling methods lack standardization, making quantitative comparisons of malaria transmission across different settings difficult. Human landing catch (HLC) is considered the research gold standard for measuring human-mosquito contact, but is unsuitable for large-scale sampling. This study assessed mosquito catch rates of CDC light trap (CDC-LT), Ifakara tent trap (ITT), window exit trap (WET), pot resting trap (PRT), and box resting trap (BRT) relative to HL...

  20. Fibrin glue: an alternative technique for nerve coaptation--Part I. Wave amplitude, conduction velocity, and plantar-length factors.

    Science.gov (United States)

    Ornelas, Lorraine; Padilla, Luis; Di Silvio, Mauricio; Schalch, Paul; Esperante, Sandro; Infante, Paul López; Bustamante, Juan Carlos; Avalos, Pablo; Varela, Deborah; López, Manuel

    2006-02-01

    The search for better surgical repair of nerve injuries should be aimed at uncovering alternatives that not only are efficient, but also enhance nerve growth. The purpose of this study was to compare functional nerve responses following repair with either a traditional microsuture technique or Quixil human fibrin sealant. Thirty female Lewis rats received transection of the right sciatic nerve. Nerve repair was achieved with either epineurial microsuture (n = 15) or Quixil fibrin glue (n = 15). Functional results were assessed at 2, 6, and 12 weeks postoperatively with walking-track analysis. Electrophysiologic nerve recordings were also performed 12 weeks postoperatively. Rats receiving Quixil nerve repair returned to baseline performance on the walking-track analysis significantly faster than those with microsuture repairs (6 and 12 weeks postoperatively; p < 0.0001). Recovery of nerve conduction velocities and wave amplitudes was also significantly better in the nerves repaired with Quixil than in those repaired with microsuture (p's < 0.0001). Quixil human fibrin sealant is a good alternative to traditional microsuture nerve repair techniques.

  1. Characterization of an array of Love-wave gas sensors developed using electrospinning technique to deposit nanofibers as sensitive layers.

    Science.gov (United States)

    Matatagui, D; Fernández, M J; Fontecha, J; Sayago, I; Gràcia, I; Cané, C; Horrillo, M C; Santos, J P

    2014-03-01

    The electrospinning technique has allowed that very different materials are deposited as sensitive layers on Love-wave devices forming a low cost and successful sensor array. Their excellent sensitivity, good linearity and short response time are reported in this paper. Several materials have been used to produce the nanofibers: polymers as Polyvinyl alcohol (PVA), Polyvinylpyrrolidone (PVP) and Polystirene (PS); composites with polymers as PVA+SnCl4; combined polymers as PS+Poly(styrene-alt-maleic anhydride) (PS+PSMA) and metal oxides (SnO2). In order to test the array, well-known chemical warfare agent simulants (CWAs) have been chosen among the volatile organic compounds due to their importance in the security field. Very low concentrations of these compounds have been detected by the array, such as 0.2 ppm of DMMP, a simulant of sarin nerve gas, and 1 ppm of DPGME, a simulant of nitrogen mustard. Additionally, the CWA simulants used in the experiment have been discriminated and classified using pattern recognition techniques, such as principal component analysis and artificial neural networks. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. On increasing the spectral efficiency and transmissivity in the data transmission channel on the spacecraft-ground tracking station line

    Science.gov (United States)

    Andrianov, M. N.; Kostenko, V. I.; Likhachev, S. F.

    2018-01-01

    The algorithms for achieving a practical increase in the rate of data transmission on the space-craft-ground tracking station line has been considered. This increase is achieved by applying spectral-effective modulation techniques, the technology of orthogonal frequency compression of signals using millimeterrange radio waves. The advantages and disadvantages of each of three algorithms have been revealed. A significant advantage of data transmission in the millimeter range has been indicated.

  3. Evaluation of lightning performance of transmission lines protected by metal oxide surge arresters using artificial intelligence techniques

    Energy Technology Data Exchange (ETDEWEB)

    Christodoulou, C.A.; Perantzakis, G. [Technological Educational Institute (TEI) of Lamia, Department of Electrical Engineering, Lamia (Greece); Spanakis, G.E. [School of Electrical and Computer Engineering, National Technical University of Athens, Athens (Greece); Karampelas, P. [Hellenic American University, Manchester, NH (United States)

    2012-12-15

    Lightning and switching overvoltages are the main causes for faults in electrical networks. In the last decades, several different conventional methodologies have been used for the adjustment of the lightning performance of high voltage transmission lines, which are protected against lightning using overhead ground wires and surge arresters. The current paper proposes a new developed Artificial Neural Network (ANN), based on the Q-learning algorithm, in order to estimate the lightning failure rate of lines of the Hellenic system. The results obtained by the ANN model exhibit a satisfactory correlation in comparison with the real recorded data or the simulations results taken from a conventional method. (orig.)

  4. Metal nano-grid reflective wave plate.

    Science.gov (United States)

    Pang, Y; Gordon, R

    2009-02-16

    We propose an optical wave plate using a metal nano-grid. The wave plate operates in reflection mode. A single-mode truncated modematching theory is presented as a general method to design such nano-grid wave plates with the desired phase difference between the reflected TM and TE polarizations. This analytical theory allows angled incidence calculations as well, and numerical results agree-well with comprehensive finite-difference time-domain electromagnetic simulations. Due to the subwavelength path-length, the reflective wave plate is expected to have improved broad-band functionality over existing zero-order transmissive wave plates, for which an example is provided. The proposed wave plate is simple and compact, and it is amenable to existing nanofabrication techniques. The reflective geometry is especially promising for applications including liquid-crystal displays and laser feedback experiments.

  5. Survey of WBSNs for Pre-Hospital Assistance: Trends to Maximize the Network Lifetime and Video Transmission Techniques.

    Science.gov (United States)

    Gonzalez, Enrique; Peña, Raul; Vargas-Rosales, Cesar; Avila, Alfonso; de Cerio, David Perez-Diaz

    2015-05-22

    This survey aims to encourage the multidisciplinary communities to join forces for innovation in the mobile health monitoring area. Specifically, multidisciplinary innovations in medical emergency scenarios can have a significant impact on the effectiveness and quality of the procedures and practices in the delivery of medical care. Wireless body sensor networks (WBSNs) are a promising technology capable of improving the existing practices in condition assessment and care delivery for a patient in a medical emergency. This technology can also facilitate the early interventions of a specialist physician during the pre-hospital period. WBSNs make possible these early interventions by establishing remote communication links with video/audio support and by providing medical information such as vital signs, electrocardiograms, etc. in real time. This survey focuses on relevant issues needed to understand how to setup a WBSN for medical emergencies. These issues are: monitoring vital signs and video transmission, energy efficient protocols, scheduling, optimization and energy consumption on a WBSN.

  6. Detection of coffee flavour ageing by solid-phase microextraction/surface acoustic wave sensor array technique (SPME/SAW).

    Science.gov (United States)

    Barié, Nicole; Bücking, Mark; Stahl, Ullrich; Rapp, Michael

    2015-06-01

    The use of polymer coated surface acoustic wave (SAW) sensor arrays is a very promising technique for highly sensitive and selective detection of volatile organic compounds (VOCs). We present new developments to achieve a low cost sensor setup with a sampling method enabling the highly reproducible detection of volatiles even in the ppb range. Since the VOCs of coffee are well known by gas chromatography (GC) research studies, the new sensor array was tested for an easy assessable objective: coffee ageing during storage. As reference method these changes were traced with a standard GC/FID set-up, accompanied by sensory panellists. The evaluation of GC data showed a non-linear characteristic for single compound concentrations as well as for total peak area values, disabling prediction of the coffee age. In contrast, the new SAW sensor array demonstrates a linear dependency, i.e. being capable to show a dependency between volatile concentration and storage time. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Modelling the optical response of human retinal photoreceptors to plane wave illumination with the finite integration technique

    Science.gov (United States)

    Akhlagh Moayed, Alireza; Dang, Shannon; Ramahi, Omar M.; Bizheva, Kostadinka K.

    2009-02-01

    The early stages of ocular diseases such as Diabetic Retinopathy are manifested by morphological changes in retinal tissue occurring on cellular level. Therefore, a number of ophthalmic diseases can be diagnosed at an early stage by detecting spatial and temporal variations in the scattering profile of retinal tissue. It was recently demonstrated that, OCT can be used to probe the functional response of retinal photoreceptors to external light stimulation [1]-[3]. fUHROCT measures localized differential changes in the retina reflectivity over time resulting from external light stimulation of the retina. Currently the origins of the observed reflectivity changes are not well understood. However, due to the complex nature of retinal physiology using purely experimental approaches in this case is problematic. For example fUHROCT is sensitive to small changes in the refractive index of biological tissue which as demonstrated previously, can result from a number of processes such as membrane hyperpolarization, osmotic swelling, metabolic changes, etc. In this paper, we present a computational model of interaction between photoreceptor cells and optical plane wave based on the Finite Integration Technique (FIT).

  8. Parallel transmission techniques in magnetic resonance imaging: experimental realization, applications and perspectives; Parallele Sendetechniken in der Magnetresonanztomographie: experimentelle Realisierung, Anwendungen und Perspektiven

    Energy Technology Data Exchange (ETDEWEB)

    Ullmann, P.

    2007-06-15

    The primary objective of this work was the first experimental realization of parallel RF transmission for accelerating spatially selective excitation in magnetic resonance imaging. Furthermore, basic aspects regarding the performance of this technique were investigated, potential risks regarding the specific absorption rate (SAR) were considered and feasibility studies under application-oriented conditions as first steps towards a practical utilisation of this technique were undertaken. At first, based on the RF electronics platform of the Bruker Avance MRI systems, the technical foundations were laid to perform simultaneous transmission of individual RF waveforms on different RF channels. Another essential requirement for the realization of Parallel Excitation (PEX) was the design and construction of suitable RF transmit arrays with elements driven by separate transmit channels. In order to image the PEX results two imaging methods were implemented based on a spin-echo and a gradient-echo sequence, in which a parallel spatially selective pulse was included as an excitation pulse. In the course of this work PEX experiments were successfully performed on three different MRI systems, a 4.7 T and a 9.4 T animal system and a 3 T human scanner, using 5 different RF coil setups in total. In the last part of this work investigations regarding possible applications of Parallel Excitation were performed. A first study comprised experiments of slice-selective B1 inhomogeneity correction by using 3D-selective Parallel Excitation. The investigations were performed in a phantom as well as in a rat fixed in paraformaldehyde solution. In conjunction with these experiments a novel method of calculating RF pulses for spatially selective excitation based on a so-called Direct Calibration approach was developed, which is particularly suitable for this type of experiments. In the context of these experiments it was demonstrated how to combine the advantages of parallel transmission

  9. Left Ventricular Function Evaluation on a 3T MR Scanner with Parallel RF Transmission Technique: Prospective Comparison of Cine Sequences Acquired before and after Gadolinium Injection.

    Science.gov (United States)

    Caspar, Thibault; Schultz, Anthony; Schaeffer, Mickaël; Labani, Aïssam; Jeung, Mi-Young; Jurgens, Paul Thomas; El Ghannudi, Soraya; Roy, Catherine; Ohana, Mickaël

    To compare cine MR b-TFE sequences acquired before and after gadolinium injection, on a 3T scanner with a parallel RF transmission technique in order to potentially improve scanning time efficiency when evaluating LV function. 25 consecutive patients scheduled for a cardiac MRI were prospectively included and had their b-TFE cine sequences acquired before and right after gadobutrol injection. Images were assessed qualitatively (overall image quality, LV edge sharpness, artifacts and LV wall motion) and quantitatively with measurement of LVEF, LV mass, and telediastolic volume and contrast-to-noise ratio (CNR) between the myocardium and the cardiac chamber. Statistical analysis was conducted using a Bayesian paradigm. No difference was found before or after injection for the LVEF, LV mass and telediastolic volume evaluations. Overall image quality and CNR were significantly lower after injection (estimated coefficient cine after > cine before gadolinium: -1.75 CI = [-3.78;-0.0305], prob(coef>0) = 0% and -0.23 CI = [-0.49;0.04], prob(coef>0) = 4%) respectively), but this decrease did not affect the visual assessment of LV wall motion (cine after > cine before gadolinium: -1.46 CI = [-4.72;1.13], prob(coef>0) = 15%). In 3T cardiac MRI acquired with parallel RF transmission technique, qualitative and quantitative assessment of LV function can reliably be performed with cine sequences acquired after gadolinium injection, despite a significant decrease in the CNR and the overall image quality.

  10. Application of Refraction Microtremor (ReMi) technique for determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2010-06-01

    The application of the Refraction Microtremor (ReMi) method on slopes affected by or prone to landsliding is complicated by the presence of lateral lithological heterogeneities and irregular topography, which may hinder the extension of the geophone array to the minimum lengths (100-200 m) usually adopted in standard applications of this technique. We focus on deriving one-dimensional shear-wave velocity (Vs) vertical profiles from the analysis of microtremor recordings carried out in the municipality of Caramanico Terme (central Italy) where the seismic response has been monitored with a local accelerometer network since 2002. The stability of the ReMi data acquisitions and the reliability of the results in irregular landslide terrain were tested by using ReMi campaigns in three different periods and different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also investigated the possible presence of directional variations in soil properties by carrying out noise recordings along L-shaped arrays. The influence of changing environmental conditions and of different acquisition parameters was tested by comparing the data obtained from different campaigns, using the same acquisition parameters, with the data from simultaneous acquisitions using different parameters. The tests showed that stable results can be obtained under different acquisition conditions provided that i) the ratio between the coherent and incoherent part of ambient noise is sufficiently high and ii) spatial aliasing does not contaminate the signal in the p (slowness)- f (frequency) matrix near the picking area: the latter condition can be satisfied by selecting geophone frequency and spacing appropriate for the site characteristics and for the investigation purpose. The differences in Vs measured in two orthogonal directions did not exceed 10-20 % and their analysis suggests that these directional variations are most likely due to anisotropy in noise source

  11. Unified Application of Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

    Science.gov (United States)

    Erickson, Gary E.

    2010-01-01

    Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack. The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

  12. Unified Application Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

    Science.gov (United States)

    Erickson, Gary E.

    2008-01-01

    Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack (alpha). The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

  13. Transmission optical coherence tomography sensing

    Science.gov (United States)

    Trull, A. K.; van der Horst, J.; Bijster, J. G.; Kalkman, J.

    2016-04-01

    We demonstrate that Fourier-domain transmission OCT is a versatile tool to measure optical material properties of turbid media. We develop an analytical expression for the transmission OCT signal. Based on this analysis we determine the group refractive index, group velocity dispersion, absorption coefficient, and scattering coefficient. The optical dispersion is accurately measured for glasses, liquids, and water/glucose mixtures. The optical attenuation is measured in the spatial domain and compared to Mie calculations combined with concentration dependent scattering effects. In the wave vector domain the spectral dependence of the optical attenuation is measured and compared to literature values. The developed technique can be used for optical sensing of attenuation and dispersion.

  14. Generation of 1.024-Tb/s Nyquist-WDM phase-conjugated twin vector waves by a polarization-insensitive optical parametric amplifier for fiber-nonlinearity-tolerant transmission

    DEFF Research Database (Denmark)

    Liu, Xiang; Hu, Hao; Chandrasekhar, S.

    2014-01-01

    We experimentally demonstrate the generation of 1.024-Tb/s Nyquist-WDM phase-conjugated vector twin waves (PCTWs), consisting of eight 128-Gb/s polarization-division-multiplexed QPSK signals and their idlers, by a broadband polarization-insensitive fiber optic parametric amplifier. This novel all...... reach in a dispersion-managed transmission link. We further study the impact of polarization-mode dispersion on the performance gain brought by the phase-conjugated twin waves, showing a gain of ∼3.8 dB in signal quality factors.......-optical signal processing approach to generate WDM-PCTWs enables a 2-fold reduction in the needed optical transmitters as compared to the conventional approach where each idler is generated by a dedicated transmitter. Digital coherent superposition of the twin waves at the receiver enables more than doubled...

  15. Comparison of preoperative and postoperative pressure transmission ratio and urethral pressure profilometry in patients with successful outcome following the vaginal wall patch sling technique.

    Science.gov (United States)

    Mikhail, Magdy S; Rosa, Hector; Palan, Prabhudas; Anderson, Patrick

    2005-01-01

    We studied preoperative and postoperative pressure transmission ratio (PTR) and urethral pressure profilometry in patients undergoing the vaginal wall patch sling technique as a first surgical approach for genuine stress incontinence (GSI) with urethral hypermobility. The specific aims were to determine the exact urodynamic parameters, if any, that may be improved postoperatively and to report the urodynamic outcome of the vaginal wall patch sling technique in successful cases. Preoperatively, all patients had a positive standing stress test, urethral hypermobility on Q-tip testing, and normal postvoid residual volume. On urodynamics, all patients had equalization of maximum urethral closure pressure (MUCP) on cough profilometry, and absence of detrusor contractions on subtracted cystometry. The PTR for each cough was calculated. Cough spikes were assigned locations in the first, second, third, or fourth quartile of the functional urethral length (FUL). Urethral pressure profilometry was performed at bladder capacity in the sitting position. All urodynamic tests were repeated 3-6 months postoperatively. A two-tailed t-test was used for statistical analysis. Forty-eight patients demonstrated successful outcome at initial follow up and constituted the study population. There was a statistically significant increase in MUCP at stress as well as a statistical increase in PTR in the first, second, and third quartiles of the FUL postoperatively. The vaginal patch sling technique appears to restore continence both by buttressing the urethra at times of stress as well as repositioning the proximal urethra into the intra-abdominal pressure zone, thus, enhancing pressure transmission to the proximal urethra.

  16. Application of advanced signal processing techniques to the rectification and registration of spaceborne imagery. [technology transfer, data transmission

    Science.gov (United States)

    Caron, R. H.; Rifman, S. S.; Simon, K. W.

    1974-01-01

    The development of an ERTS/MSS image processing system responsive to the needs of the user community is discussed. An overview of the TRW ERTS/MSS processor is presented, followed by a more detailed discussion of image processing functions satisfied by the system. The particular functions chosen for discussion are evolved from advanced signal processing techniques rooted in the areas of communication and control. These examples show how classical aerospace technology can be transferred to solve the more contemporary problems confronting the users of spaceborne imagery.

  17. Comparison between balanced and unbalanced precoding technique in high-order QAM vector mm-wave signal generation based on intensity modulator with photonic frequency doubling.

    Science.gov (United States)

    Qin, Chaoyi; Li, Xinying; Chi, Nan; Yu, Jianjun

    2016-03-07

    We experimentally investigate high-order quadrature-amplitude-modulation (QAM) vector millimeter-wave (mm-wave) signal generation based on intensity modulator (IM) with photonic frequcney doubling and precoding in this paper. In order to obtain an ordinary QAM modulated radio-frequency (RF) signal after the square-law detection of the photodiode, amplitude and phase precoding technique should be employed. In this paper, we experimentally investigate the generation of 1~4 Gbaud vector mm-wave signal with the modulation formats of 8QAM and 16QAM at the carrier frequency of 40 GHz, and study the bit-error-rate (BER) performance of both balanced precoding scheme and unbalanced precoding scheme adopting high-order QAM modulation.

  18. Gravitation Waves

    CERN Multimedia

    CERN. Geneva

    2005-01-01

    We will present a brief introduction to the physics of gravitational waves and their properties. We will review potential astrophysical sources of gravitational waves, and the physics and astrophysics that can be learned from their study. We will survey the techniques and technologies for detecting gravitational waves for the first time, including bar detectors and broadband interferometers, and give a brief status report on the international search effort, with special emphasis on the LIGO detectors and search results.

  19. Standardizing operational vector sampling techniques for measuring malaria transmission intensity: evaluation of six mosquito collection methods in western Kenya.

    Science.gov (United States)

    Wong, Jacklyn; Bayoh, Nabie; Olang, George; Killeen, Gerry F; Hamel, Mary J; Vulule, John M; Gimnig, John E

    2013-04-30

    Operational vector sampling methods lack standardization, making quantitative comparisons of malaria transmission across different settings difficult. Human landing catch (HLC) is considered the research gold standard for measuring human-mosquito contact, but is unsuitable for large-scale sampling. This study assessed mosquito catch rates of CDC light trap (CDC-LT), Ifakara tent trap (ITT), window exit trap (WET), pot resting trap (PRT), and box resting trap (BRT) relative to HLC in western Kenya to 1) identify appropriate methods for operational sampling in this region, and 2) contribute to a larger, overarching project comparing standardized evaluations of vector trapping methods across multiple countries. Mosquitoes were collected from June to July 2009 in four districts: Rarieda, Kisumu West, Nyando, and Rachuonyo. In each district, all trapping methods were rotated 10 times through three houses in a 3 × 3 Latin Square design. Anophelines were identified by morphology and females classified as fed or non-fed. Anopheles gambiae s.l. were further identified as Anopheles gambiae s.s. or Anopheles arabiensis by PCR. Relative catch rates were estimated by negative binomial regression. When data were pooled across all four districts, catch rates (relative to HLC indoor) for An. gambiae s.l (95.6% An. arabiensis, 4.4% An. gambiae s.s) were high for HLC outdoor (RR = 1.01), CDC-LT (RR = 1.18), and ITT (RR = 1.39); moderate for WET (RR = 0.52) and PRT outdoor (RR = 0.32); and low for all remaining types of resting traps (PRT indoor, BRT indoor, and BRT outdoor; RR type varied from district to district. ITT, CDC-LT, and WET appear to be effective methods for large-scale vector sampling in western Kenya. Ultimately, choice of collection method for operational surveillance should be driven by trap efficacy and scalability, rather than fine-scale precision with respect to HLC. When compared with recent, similar trap evaluations in Tanzania and Zambia, these data suggest

  20. An Encryption Technique for Provably Secure Transmission from a High Performance Computing Entity to a Tiny One

    Directory of Open Access Journals (Sweden)

    Miodrag J. Mihaljević

    2016-01-01

    Full Text Available An encryption/decryption approach is proposed dedicated to one-way communication between a transmitter which is a computationally powerful party and a receiver with limited computational capabilities. The proposed encryption technique combines traditional stream ciphering and simulation of a binary channel which degrades channel input by inserting random bits. A statistical model of the proposed encryption is analyzed from the information-theoretic point of view. In the addressed model an attacker faces the problem implied by observing the messages through a channel with random bits insertion. The paper points out a number of security related implications of the considered channel. These implications have been addressed by estimation of the mutual information between the channel input and output and estimation of the number of candidate channel inputs for a given channel output. It is shown that deliberate and secret key controlled insertion of random bits into the basic ciphertext provides security enhancement of the resulting encryption scheme.

  1. Correcting transmission losses in short-wave infrared spatially offset Raman spectroscopy measurements to enable reduced fluorescence through-barrier detection.

    Science.gov (United States)

    Hopkins, R J; Lee, L; Shand, N C

    2017-09-25

    Spatially offset Raman spectroscopy (SORS) is a proven technique for sub-surface detection. SORS is able to separate Raman signals from a container and its contents, thereby demonstrating application to through-barrier detection for defence and security. Whilst SORS has been demonstrated to reduce fluorescence from the barrier (or surface), fluorescence from the sample (or sub-surface) can still be problematic for some materials when using Raman excitation wavelengths typical in commercially available instrumentation (e.g. 785 nm). Previous work has demonstrated that short-wave infrared (SWIR) excited SORS (e.g. 1064 nm) can reduce fluorescence from the sample and barrier, thereby providing the potential to detect a wider range of materials through a wider range of barriers. In this paper we highlight an additional challenge for detection through some plastic container materials (e.g. high density polyethylene (HDPE) and other opaque plastics) that absorb and scatter both incident and Raman scattered photons in the SWIR band, leading to distortion of the resultant SORS spectrum. The existence of this effect and its impact is explored, along with a potential solution to overcome this challenge that uses multi-wavelength Raman excitation to avoid the detrimental HDPE absorption region.

  2. The Efficacy of the WaveOne Reciprocating File System versus the ProTaper Retreatment System in Endodontic Retreatment of Two Different Obturating Techniques.

    Science.gov (United States)

    Jorgensen, Ben; Williamson, Anne; Chu, Rene; Qian, Fang

    2017-06-01

    This ex vivo study aimed to evaluate the efficacy of retreating GuttaCore (Dentsply Tulsa Dental Specialties, Tulsa, OK) and warm vertically condensed gutta-percha in moderately curved canals with 2 different systems: ProTaper Universal Retreatment (Dentsply Tulsa Dental) and WaveOne (Dentsply Tulsa Dental). Eighty mesial roots of mandibular molars were used in this study. The mesiobuccal canals in each sample were prepared to length with the WaveOne Primary file (Dentsply Tulsa Dental). The canals were obturated with either a warm vertical approach or with GuttaCore and divided into 4 retreatment groups with the same mean root curvature: warm vertical retreated with ProTaper, warm vertical retreated with WaveOne, GuttaCore retreated with ProTaper, and GuttaCore retreated with WaveOne. The warm vertical groups were obturated using a continuous-wave technique of gutta-percha compaction, and the GuttaCore groups were obturated according to the manufacturer's instructions. After allowing sealer to set, each specimen was retreated with either the ProTaper Universal Retreatment files D1, D2, or D3 or with the WaveOne Primary file to the predetermined working length. The time taken to reach the working length was recorded. Instrument fatigue and failure were also evaluated. The post hoc 2-sample t tests showed that the overall mean total time taken to reach the working length for the warm vertical groups was significantly greater than that observed for the GuttaCore groups (mean = 87.11 vs 60.16 seconds, respectively), and the overall mean total time taken to reach the working length for WaveOne was significantly greater than that observed for ProTaper (99.09 vs 48.18 seconds, respectively). Two-way analysis of variance showed a significant main effect for both the type of experiment groups (F1,76 = 15.32, P = .0002) and the type of retreatments (F1,76 = 54.67, P < .0001). Also, the WaveOne Primary file underwent more separations than the ProTaper files. The

  3. Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II; Methodes d'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol et automatisation de ces methodes sur ordinateur IBM 7094 II

    Energy Technology Data Exchange (ETDEWEB)

    Corge, Ch. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-01-01

    Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [French] L'automatisation, sur ordinateur IBM 7094/II, de l'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol a ete accomplie en la decomposant selon un schema articule en quatre phases: 1 - le traitement des donnees experimentales brutes pour obtenir les transmissions interfero-resonnantes, 2 - la determination des grandeurs d'analyse a partir des transmissions precedentes, 3 - l'analyse proprement dite des resonances dont les parametres sont obtenus par la resolution d'un systeme surabondant. Quatre methodes d'analyse sont groupees en un meme programme, 4 - la procedure de verification graphique. (auteur)

  4. Late gadolinium enhancement cardiac imaging on a 3T scanner with parallel RF transmission technique: prospective comparison of 3D-PSIR and 3D-IR

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Anthony [Nouvel Hopital Civil, Strasbourg University Hospital, Radiology Department, Strasbourg Cedex (France); Nouvel Hopital Civil, Service de Radiologie, Strasbourg Cedex (France); Caspar, Thibault [Nouvel Hopital Civil, Strasbourg University Hospital, Cardiology Department, Strasbourg Cedex (France); Schaeffer, Mickael [Nouvel Hopital Civil, Strasbourg University Hospital, Public Health and Biostatistics Department, Strasbourg Cedex (France); Labani, Aissam; Jeung, Mi-Young; El Ghannudi, Soraya; Roy, Catherine [Nouvel Hopital Civil, Strasbourg University Hospital, Radiology Department, Strasbourg Cedex (France); Ohana, Mickael [Nouvel Hopital Civil, Strasbourg University Hospital, Radiology Department, Strasbourg Cedex (France); Universite de Strasbourg / CNRS, UMR 7357, iCube Laboratory, Illkirch (France)

    2016-06-15

    To qualitatively and quantitatively compare different late gadolinium enhancement (LGE) sequences acquired at 3T with a parallel RF transmission technique. One hundred and sixty participants prospectively enrolled underwent a 3T cardiac MRI with 3 different LGE sequences: 3D Phase-Sensitive Inversion-Recovery (3D-PSIR) acquired 5 minutes after injection, 3D Inversion-Recovery (3D-IR) at 9 minutes and 3D-PSIR at 13 minutes. All LGE-positive patients were qualitatively evaluated both independently and blindly by two radiologists using a 4-level scale, and quantitatively assessed with measurement of contrast-to-noise ratio and LGE maximal surface. Statistical analyses were calculated under a Bayesian paradigm using MCMC methods. Fifty patients (70 % men, 56yo ± 19) exhibited LGE (62 % were post-ischemic, 30 % related to cardiomyopathy and 8 % post-myocarditis). Early and late 3D-PSIR were superior to 3D-IR sequences (global quality, estimated coefficient IR > early-PSIR: -2.37 CI = [-3.46; -1.38], prob(coef > 0) = 0 % and late-PSIR > IR: 3.12 CI = [0.62; 4.41], prob(coef > 0) = 100 %), LGE surface estimated coefficient IR > early-PSIR: -0.09 CI = [-1.11; -0.74], prob(coef > 0) = 0 % and late-PSIR > IR: 0.96 CI = [0.77; 1.15], prob(coef > 0) = 100 %. Probabilities for late PSIR being superior to early PSIR concerning global quality and CNR were over 90 %, regardless of the aetiological subgroup. In 3T cardiac MRI acquired with parallel RF transmission technique, 3D-PSIR is qualitatively and quantitatively superior to 3D-IR. (orig.)

  5. Study of molecule-metal interfaces by means of the normal incidence X-ray standing wave technique

    Energy Technology Data Exchange (ETDEWEB)

    Mercurio, Giuseppe

    2012-07-01

    Functional surfaces based on monolayers of organic molecules are currently subject of an intense research effort due to their applications in molecular electronics, sensing and catalysis. Because of the strong dependence of organic based devices on the local properties of the molecule-metal interface, a direct investigation of the interface chemistry is of paramount importance. In this context, the bonding distance, measured by means of the normal incidence X-ray standing wave technique (NIXSW), provides a direct access to the molecule-metal interactions. At the same time, NIXSW adsorption heights are used to benchmark different density functional theory (DFT) schemes and determine the ones with predictive power for similar systems. This work investigates the geometric and chemical properties of different molecule/metal interfaces, relevant to molecular electronics and functional surfaces applications, primarily by means of the NIXSW technique. All NIXSW data are analyzed with the newly developed open source program Torricelli, which is thoroughly documented in the thesis. In order to elucidate the role played by the substrate within molecule/metal interfaces, the prototype organic molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) is explored on the Ag(110) surface. The molecule results more distorted and at smaller bonding distances on the more reactive Ag(110) surface, in comparison with the Ag(100), the Ag(111) and Au(111) substrates. This conclusion follows from the detailed molecular adsorption geometry obtained from the differential analysis of nonequivalent carbon and oxygen species (including a careful error analysis). Subsequently, the chemisorptive PTCDA/Ag(110) interaction is tuned by the co-deposition of an external alkali metal, namely K. As a consequence, the functional groups of PTCDA unbind from the surface, which, in turn, undergoes major reconstruction. In fact, the resulting nanopatterned surface consists of alternated up and down

  6. Comparison Study between RMS and Edge Detection Image Processing Algorithms for a Pulsed Laser UWPI (Ultrasonic Wave Propagation Imaging)-Based NDT Technique.

    Science.gov (United States)

    Lee, Changgil; Zhang, Aoqi; Yu, Byoungjoon; Park, Seunghee

    2017-05-26

    In this study, a non-contact laser ultrasonic propagation imaging technique was applied to detect the damage of plate-like structures. Lamb waves were generated by an Nd:YAG pulse laser system, while a galvanometer-based laser scanner was used to scan the preliminarily designated area. The signals of the structural responses were measured using a piezoelectric sensor attached on the front or back side of the plates. The obtained responses were analyzed by calculating the root mean square (RMS) values to achieve the visualization of structural defects such as crack, corrosion, and so on. If the propagating waves encounter the damage, the waves are scattered at the damage and the energy of the scattered waves can be expressed by the RMS values. In this study, notch and corrosion were artificially formed on aluminum plates and were considered as structural defects. The notches were created with different depths and angles on the aluminum plates, and the corrosion damage was formed with different depths and areas. To visualize the damage more clearly, edge detection methodologies were applied to the RMS images and the feasibility of the methods was investigated. The results showed that most of the edge detection methods were good at detecting the shape and/or the size of the damage while they had poor performance of detecting the depth of the damage.

  7. Ultrasound wave propagation through rough interfaces: Iterative methods

    NARCIS (Netherlands)

    Berkhoff, Arthur P.; Thijssen, J.M.; van den Berg, P.M.

    Two iterative methods for the calculation of acoustic transmission through a rough interface between two media are compared. The methods employ a continuous version of the conjugate gradient technique. One method is based on plane-wave expansions and the other on boundary integral equations and

  8. Simulation of wave propagation through aberrating layers of biological media

    NARCIS (Netherlands)

    Berkhoff, Arthur P.; van den Berg, P.M.; Thijssen, J.M.

    2004-01-01

    Two iterative methods for the calculation of acoustic reflection and transmission at a rough interface between two media are compared. The methods are based on a continuous version of the conjugate gradient technique. One method is based on plane-wave expansions while the other method is based on

  9. Validation of the k-filtering technique for a signal composed of random-phase plane waves and non-random coherent structures

    Directory of Open Access Journals (Sweden)

    O. W. Roberts

    2014-12-01

    Full Text Available Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame and those described as being structure-like (advected by the plasma bulk velocity. Typically with single-spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed for temporal and spatial changes to be resolved, using techniques such as k filtering. While this technique does not assume Taylor's hypothesis it requires both weak stationarity of the time series and that the fluctuations can be described by a superposition of plane waves with random phases. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random-phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.

  10. Dual-channel polarization holography: a technique for recording two complex amplitude components of a vector wave.

    Science.gov (United States)

    Barada, Daisuke; Ochiai, Takanori; Fukuda, Takashi; Kawata, Shigeo; Kuroda, Kazuo; Yatagai, Toyohiko

    2012-11-01

    In this Letter, the principle of polarization holography for recording an arbitrary vector wave on a thin polarization-sensitive recording medium is proposed. It is analytically shown that the complex amplitudes of p- and s-polarization components are simultaneously recorded and independently reconstructed by using an s-polarized reference beam. The characteristics are experimentally verified.

  11. ELF wave generation in the ionosphere using pulse modulated HF heating: initial tests of a technique for increasing ELF wave generation efficiency

    Directory of Open Access Journals (Sweden)

    R. Barr

    1999-06-01

    Full Text Available This paper describes the results of a preliminary study to determine the effective heating and cooling time constants of ionospheric currents in a simulated modulated HF heating, `beam painting' configuration. It has been found that even and odd harmonics of the fundamental ELF wave used to amplitude modulate the HF heater are sourced from different regions of the ionosphere which support significantly different heating and cooling time constants. The fundamental frequency and its odd harmonics are sourced in a region of the ionosphere where the heating and cooling time constants are about equal. The even harmonics on the other hand are sourced from regions of the ionosphere characterised by ratios of cooling to heating time constant greater than ten. It is thought that the even harmonics are sourced in the lower ionosphere (around 65 km where the currents are much smaller than at the higher altitudes around 78 km where the currents at the fundamental frequency and odd harmonics maximise.Key words. Electromagnetics (antennae · Ionosphere (active experiments · Radio science (non linear phenomena

  12. Simultaneous recording of pulsed wave Doppler signals in the innominate vein and transverse aortic arch: a new technique to evaluate AV conduction and fetal heart rhythm.

    Science.gov (United States)

    Howley, Lisa W; Schuchardt, Eleanor; Park, Dawn; Gilbert, Lisa; Gruenwald, Jeanine; Cuneo, Bettina F

    2018-02-02

    Fetal heart rhythm abnormalities are common. Simultaneous pulsed Doppler interrogation of the superior vena cava (SVC) and ascending aorta (AAo) is widely used to analyze fetal arrhythmias. However, the SVC/AAo Doppler technique can be limited by a suboptimal angle of interrogation and poor visualization of atrial systole in the SVC. We present our experience with a novel Doppler technique using simultaneously recorded pulsed wave Doppler signals in the innominate vein (InnV) and transverse aortic arch (Ao) from an axial view of the fetal thorax. Advantages of the InnV/Ao Doppler technique include improved acquisition feasibility and a near 0-degree angle of insonation of the InnV, improving visualization of atrial systolic events. This article is protected by copyright. All rights reserved.

  13. KEEN Wave Simulations: Comparing various PIC to various fixed grid Vlasov to Phase-Space Adaptive Sparse Tiling & Effective Lagrangian (PASTEL) Techniques

    Science.gov (United States)

    Afeyan, Bedros; Larson, David; Shadwick, Bradley; Sydora, Richard

    2017-10-01

    We compare various ways of solving the Vlasov-Poisson and Vlasov-Maxwell equations on rather demanding nonlinear kinetic phenomena associated with KEEN and KEEPN waves. KEEN stands for Kinetic, Electrostatic, Electron Nonlinear, and KEEPN, for electron-positron or pair plasmas analogs. Because these self-organized phase space structures are not steady-state, or single mode, or fluid or low order moment equation limited, typical techniques with low resolution or too much noise will distort the answer too much, too soon, and fail. This will be shown via Penrose criteria triggers for instability at the formation stage as well as particle orbit statistics in fully formed KEEN waves and KEEN-KEEN and KEEN-EPW interacting states. We will argue that PASTEL is a viable alternative to traditional methods with reasonable chances of success in higher dimensions. Work supported by a Grant from AFOSR PEEP.

  14. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) using Synthetic Aperture Focusing Techniques (SAFT}

    Science.gov (United States)

    Case, J. T.; Robbins, J.; Kharkivskiy, S.; Hepburn, F.; Zoughi, R.

    2005-01-01

    The Space Shuttle Columbia s catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

  15. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) Using Synthetic Aperture Focusing Techniques (SAFT)

    Science.gov (United States)

    Case, J. T.; Robbins, J.; Kharkovsky, S.; Hepburn, F.; Zoughi, R.

    2006-03-01

    The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbon/carbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

  16. Analysis of gravity waves in the tropical middle atmosphere over La Reunion Island (21°S, 55°E with lidar using wavelet techniques

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    2000-04-01

    Full Text Available The capabilities of the continuous wavelet transform (CWT and the multiresolution analysis (MRA are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1-2 km from the stratopause, 3-4 km and 6-10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of -0.3 m/s and observed periods peaking at 3-4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes.Key words: Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides

  17. Analysis of gravity waves in the tropical middle atmosphere over La Reunion Island (21°S, 55°E with lidar using wavelet techniques

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    Full Text Available The capabilities of the continuous wavelet transform (CWT and the multiresolution analysis (MRA are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1-2 km from the stratopause, 3-4 km and 6-10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of -0.3 m/s and observed periods peaking at 3-4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes.

    Key words: Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides

  18. Analysis of Bending Waves in Phononic Crystal Beams with Defects

    Directory of Open Access Journals (Sweden)

    Yongqiang Guo

    2018-01-01

    Full Text Available Existing investigations on imperfect phononic crystal beams mainly concern periodic multi-span beams carrying either one or two channel waves with random or deterministic disorder in span-length. This paper studies the two channel bending waves in phononic crystal beams consisting of many phases of materials with defects introduced as one structural segment having different cross-sectional dimensions or material parameters. The method of reverberation-ray matrix (MRRM based on the Timoshenko beam theory, which can conduct high-frequency analysis, is extended for the theoretical analysis of dispersion and transmission of bending waves. The supercell technique and the Floquet–Bloch theorem are adopted for modeling the dispersion characteristics, and the whole finite structural model is used to calculate the transmission spectra. Experimental measurements and numerical calculations are provided to validate the displacement transmission obtained by the proposed MRRM, with the effect of damping on transmission spectra being concerned. The high-frequency calculation applicability of the proposed MRRM is also confirmed by comparing the present results with the corresponding ones either using the transfer matrix method (TMM or MRRM based on Euler—Bernoulli beam theory. The influences of defect size, defect form, and unit-cell number on the transmission spectra and the band structures are discussed. The drawn conclusions may be useful for designing or evaluating the defected phononic crystal beams in bending wave control. In addition, our conclusions are especially potential for identifying the defect location through bending wave signals.

  19. Spectral Analysis of Surface Wave for Empirical Elastic Design of Anchored Foundations

    Directory of Open Access Journals (Sweden)

    S. E. Chen

    2012-01-01

    Full Text Available Helical anchors are vital support components for power transmission lines. Failure of a single anchor can lead to the loss of an entire transmission line structure which results in the loss of power for downstream community. Despite being important, it is not practical to use conventional borehole method of subsurface exploration, which is labor intensive and costly, for estimating soil properties and anchor holding capacity. This paper describes the use of an empirical and elasticity-based design technique coupled with the spectral analysis of surface wave (SASW technique to provide subsurface information for anchor foundation designs. Based on small-strain wave propagation, SASW determines shear wave velocity profile which is then correlated to anchor holding capacity. A pilot project involving over 400 anchor installations has been performed and demonstrated that such technique is reliable and can be implemented into transmission line structure designs.

  20. Ability of pulse wave transit time to detect changes in stroke volume and to estimate cardiac output compared to thermodilution technique in isoflurane-anaesthetised dogs.

    Science.gov (United States)

    Sano, H; Chambers, J P

    2017-04-26

    To evaluate the ability of pulse wave transit time (PWTT) to detect changes in stroke volume (SV) and to estimate cardiac output (CO) compared with the thermodilution technique in isoflurane-anaesthetized dogs. Prospective, experimental study. Eight adult laboratory dogs. The dogs were anaesthetized with isoflurane and mechanically ventilated. Reference CO (TDCO) was measured via a pulmonary artery catheter using the thermodilution technique and reference SV (TDSV) was calculated. PWTT was calculated as the time from the electrocardiogram R-wave peak to the rise point of the pulse oximeter wave. Estimated CO (esCO) was derived from PWTT after calibration with arterial pulse pressure (both non-invasive and invasive methods) and TDCO. Haemodynamic changes were induced by administration of phenylephrine (vasoconstriction), high isoflurane (vasodilatation and negative inotropy) and dobutamine (vasodilatation and positive inotropy). Trending between percentage change in PWTT and TDSV was assessed using concordance analysis and receiver operator characteristic (ROC) curve. The agreement between esCO and TDCO was evaluated using the Bland-Altman method. The direction of percentage change between consecutive PWTT and the corresponding TDSV showed a concordance rate of 95%, with correlation coefficients of -0.86 (pblood pressure showed a bias (precision of agreement) of 0.58 (1.54) and 0.57 (1.59) L minute(-1) with a percentage error of ±61% and ±63%, respectively. In isoflurane-anaesthetized dogs, PWTT showed a good trending ability to detect 15% changes in SV. This technique is easy to use, inexpensive, non-invasive and could become routine anaesthetic monitoring. However, the agreement between absolute esCO and TDCO was unacceptable. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

  1. Dynamic acousto-elastic testing of concrete with a coda-wave probe: comparison with standard linear and nonlinear ultrasonic techniques.

    Science.gov (United States)

    Shokouhi, Parisa; Rivière, Jacques; Lake, Colton R; Le Bas, Pierre-Yves; Ulrich, T J

    2017-11-01

    The use of nonlinear acoustic techniques in solids consists in measuring wave distortion arising from compliant features such as cracks, soft intergrain bonds and dislocations. As such, they provide very powerful nondestructive tools to monitor the onset of damage within materials. In particular, a recent technique called dynamic acousto-elasticity testing (DAET) gives unprecedented details on the nonlinear elastic response of materials (classical and non-classical nonlinear features including hysteresis, transient elastic softening and slow relaxation). Here, we provide a comprehensive set of linear and nonlinear acoustic responses on two prismatic concrete specimens; one intact and one pre-compressed to about 70% of its ultimate strength. The two linear techniques used are Ultrasonic Pulse Velocity (UPV) and Resonance Ultrasound Spectroscopy (RUS), while the nonlinear ones include DAET (fast and slow dynamics) as well as Nonlinear Resonance Ultrasound Spectroscopy (NRUS). In addition, the DAET results correspond to a configuration where the (incoherent) coda portion of the ultrasonic record is used to probe the samples, as opposed to a (coherent) first arrival wave in standard DAET tests. We find that the two visually identical specimens are indistinguishable based on parameters measured by linear techniques (UPV and RUS). On the contrary, the extracted nonlinear parameters from NRUS and DAET are consistent and orders of magnitude greater for the damaged specimen than those for the intact one. This compiled set of linear and nonlinear ultrasonic testing data including the most advanced technique (DAET) provides a benchmark comparison for their use in the field of material characterization. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. (Investigations of ultrasonic wave interactions with grain boundaries and grain imperfections)

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The main objective of our research is to obtain a better understanding of ultrasonic wave interaction with interfaces in polycrystalline materials. This report discusses two recently developed experimental techniques: scanning acoustic microscope and optical point sensors. As for general wave propagation problems in anisotropic media, four major topics are discussed in separate sections. First, single boundaries between large bicrystals are considered. The reflection and transmission coefficients of such interfaces are calculated for imperfect boundary conditions by using the finite interface stiffness approach. Ultrasonic transmission through multiple-grain structures are investigated by computer simulation based on the statistical evaluation of repeated acoustical wave interactions with individual grain boundaries. The number of grains interacting with the propagating acoustical wave is considered to be high enough to approximate the wave-material interaction as scattering on elastic inhomogeneities. The grain scattering induced attenuation of Rayleigh waves is investigated in polycrystalline materials. 41 refs., 43 figs.

  3. Wave Solutions

    CERN Document Server

    Christov, Ivan C

    2012-01-01

    In classical continuum physics, a wave is a mechanical disturbance. Whether the disturbance is stationary or traveling and whether it is caused by the motion of atoms and molecules or the vibration of a lattice structure, a wave can be understood as a specific type of solution of an appropriate mathematical equation modeling the underlying physics. Typical models consist of partial differential equations that exhibit certain general properties, e.g., hyperbolicity. This, in turn, leads to the possibility of wave solutions. Various analytical techniques (integral transforms, complex variables, reduction to ordinary differential equations, etc.) are available to find wave solutions of linear partial differential equations. Furthermore, linear hyperbolic equations with higher-order derivatives provide the mathematical underpinning of the phenomenon of dispersion, i.e., the dependence of a wave's phase speed on its wavenumber. For systems of nonlinear first-order hyperbolic equations, there also exists a general ...

  4. Use of Refraction Microtremor (ReMi) technique for the determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2009-04-01

    In the context of an ongoing study on seismic response of landslide-prone hill-slopes in Central Italy (area of Caramanico Terme), we tested the applicability of the Refraction Microtremor (ReMi) analysis technique (Louie, 2001) to obtain geometrical and physical parameters needed for numerical modelling. In particular, we used this technique to determine one-dimensional shear-wave velocity profiles (Vs) at sites located on and close to a recent landslide that mobilized 30-40 m thick Quaternary colluvium overlying Pliocene mudstones. The use of this technique in unstable slope areas presents difficulties related to rough topography and lateral lithological heterogeneities, which prevent the extension of geophone array up to the minimum lengths (100 - 200 m) commonly adopted in standard applications. Moreover, sites distant from anthropic sources of microtremors can have unfavourable noise conditions in comparison with other well established cases of application. To check the stability of the ReMi data in these operative conditions and the confidence level of the results, three ReMi campaigns were conducted at different times using different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also tested simultaneous noise recording along orthogonal arrays to investigate a possible presence of directional variations of soil properties. The Rayleigh wave velocity dispersion data derived from picking carried out on p (slowness)-f (frequency) matrix showed the presence in noise recordings of different Rayleigh wave vibration modes (fundamental and first two higher modes), which prevail at different frequency intervals. This indicates that it is essential to correctly identify the different vibration modes to avoid erroneous data interpretation (e.g. fictitious identification of velocity decrease with depth). An analysis of the influence of changing environmental conditions and of different acquisition parameters was conducted through

  5. Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

    Science.gov (United States)

    Wright, Corwin J.; Hindley, Neil P.; Hoffmann, Lars; Alexander, M. Joan; Mitchell, Nicholas J.

    2017-07-01

    Gravity waves (GWs) transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20-60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs), and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60° S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (˜ 80-100 mPa or more at 30 km altitude). These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity vectors show clear observational

  6. Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

    Directory of Open Access Journals (Sweden)

    C. J. Wright

    2017-07-01

    Full Text Available Gravity waves (GWs transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20–60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs, and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60° S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (∼ 80–100 mPa or more at 30 km altitude. These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity

  7. Self-Concept Clarity in Adolescents and Parents : A Six-Wave Longitudinal and Multi-Informant Study on Development and Intergenerational Transmission

    NARCIS (Netherlands)

    Crocetti, Elisabetta; Rubini, Monica; Branje, Susan; Koot, Hans M.; Meeus, Wim

    2016-01-01

    The purpose of this study was twofold: (a) to disentangle patterns of change and stability in self-concept clarity (SCC) in adolescents and in their parents and (b) to examine processes of intergenerational transmission of SCC in families with adolescents. Participants were 497 Dutch families

  8. Traveling-wave photodetector

    Science.gov (United States)

    Hietala, Vincent M.; Vawter, Gregory A.

    1993-01-01

    The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.

  9. A Quantitative Transmission Line Experiment

    Science.gov (United States)

    Johnston, D. C.; Silbernagel, B. G.

    1969-01-01

    Describes modifications of a commercially available strip-type transmission line, which makes possible reproducible measurements of standing waves on the line. Experimental data yield values for the characteristic impedance, phase velocity and line wavelength of radiation in the transmission line, and the dielectric constant of material in the…

  10. Imaging of spatial distributions of the millimeter wave intensity by using the Visible Continuum Radiation from a discharge in a Cs-Xe mixture. Part II: Demonstration of application capabilities of the technique

    Science.gov (United States)

    Gitlin, M. S.; Glyavin, M. Yu.; Fedotov, A. E.; Tsvetkov, A. I.

    2017-07-01

    The paper presents the second part of the review on a high-sensitive technique for time-resolved imaging and measurements of the 2D intensity profiles of millimeter-wave radiation by means of Visible Continuum Radiation emitted by the positive column of a medium-pressure Cs-Xe DC Discharge (VCRD method). The first part of the review was focused on the operating principles and fundamentals of this new technique [Plasma Phys. Rep. 43, 253 (2017)]. The second part of the review focuses on experiments demonstrating application of this imaging technique to measure the parameters of radiation at the output of moderate-power millimeter-wave sources. In particular, the output waveguide mode of a moderate-power W-band gyrotron with a pulsed magnetic field was identified and the relative powers of some spurious modes at the outputs of this gyrotron and a pulsed D-band orotron were evaluated. The paper also reviews applications of the VCRD technique for real-time imaging and nondestructive testing with a frame rate of higher than 10 fps by using millimeter waves. Shadow projection images of objects opaque and transparent for millimeter waves have been obtained using pulsed watt-scale millimeter waves for object illumination. Near video frame rate millimeter-wave shadowgraphy has been demonstrated. It is shown that this technique can be used for single-shot screening (including detection of concealed objects) and time-resolved imaging of time-dependent processes.

  11. The identification of solar wind waves at discrete frequencies and the role of the spectral analysis techniques

    Science.gov (United States)

    Di Matteo, S.; Villante, U.

    2017-05-01

    The occurrence of waves at discrete frequencies in the solar wind (SW) parameters has been reported in the scientific literature with some controversial results, mostly concerning the existence (and stability) of favored sets of frequencies. On the other hand, the experimental results might be influenced by the analytical methods adopted for the spectral analysis. We focused attention on the fluctuations of the SW dynamic pressure (PSW) occurring in the leading edges of streams following interplanetary shocks and compared the results of the Welch method (WM) with those of the multitaper method (MTM). The results of a simulation analysis demonstrate that the identification of the wave occurrence and the frequency estimate might be strongly influenced by the signal characteristics and analytical methods, especially in the presence of multicomponent signals. In SW streams, PSW oscillations are routinely detected in the entire range f ≈ 1.2-5.0 mHz; nevertheless, the WM/MTM agreement in the identification and frequency estimate occurs in ≈50% of events and different sets of favored frequencies would be proposed for the same set of events by the WM and MTM analysis. The histogram of the frequency distribution of the events identified by both methods suggests more relevant percentages between f ≈ 1.7-1.9, f ≈ 2.7-3.4, and f ≈ 3.9-4.4 (with a most relevant peak at f ≈ 4.2 mHz). Extremely severe thresholds select a small number (14) of remarkable events, with a one-to-one correspondence between WM and MTM: interestingly, these events reveal a tendency for a favored occurrence in bins centered at f ≈ 2.9 and at f ≈ 4.2 mHz.

  12. Pandemic (H1N1) 2009 influenza in hospitalized children in Manitoba: nosocomial transmission and lessons learned from the first wave.

    Science.gov (United States)

    Fanella, Sergio T; Pinto, Michelle A; Bridger, Natalie A; Bullard, Jared M P; Coombs, Jennifer M L; Crockett, Maryanne E; Olekson, Karen L; Poliquin, Philippe G; Van Caeseele, Paul G; Embree, Joanne E

    2011-05-01

    To review the experiences at Winnipeg Children's Hospital (WCH) during the 2009 influenza season, with an emphasis on nosocomial transmission and infection prevention and control responses. A case series of patients admitted to WCH who had laboratory-confirmed cases of influenza between January 1 and July 31, 2009, with a comparison of patients with seasonal influenza and those with pandemic (H1N1) 2009 influenza; a review of the impact of infection prevention and control modifications on nosocomial transmission. A total of 104 inpatients with influenza, 81 of whom had pandemic (H1N1) 2009 influenza, were reviewed at a large Canadian pediatric tertiary care center. There were no differences in risk factors, presentation, or outcome between patients with seasonal influenza and those with pandemic (H1N1) 2009 influenza. There were 8 nosocomial cases of pandemic (H1N1) 2009 influenza. Excluding patients with nosocomial cases, mean length of hospital stay was significantly shortened to 3.7 days for individuals who had pandemic (H1N1) 2009 influenza and who received empiric oseltamivir on admission to the hospital, compared with 12.0 days for patients for whom treatment was delayed (P = .02). Treatment with oseltamivir of all patients with suspected cases of influenza and prompt modifications to infection control practices, including playroom closures and enhanced education of visitors and staff, terminated nosocomial transmission. Infection with pandemic (H1N1) 2009 influenza virus resulted in a substantial number of hospitalizations of pediatric patients in Manitoba, including those with nosocomial cases, thereby stressing the capacity of WCH. Immediate therapy with oseltamivir on admission to the hospital resulted in a significantly reduced length of hospitalization. This, coupled with intensified infection prevention and control practices, halted nosocomial transmission. These strategies should be considered in future pandemic influenza or other respiratory viral

  13. Studies of impedance in cardiac tissue using sucrose gap and computer techniques. II. Circuit simulation of passive electrical properties and cell-to-cell transmission.

    Science.gov (United States)

    Stibitz, G R; McCann, F V

    1974-02-01

    The impedance measured in a strip of heart tissue from the moth Hyalophora cecropia is fitted by circuit models of several configurations. The circuits include: (a) a single R-C circuit (b) a double R-C circuit (c) terminated transmission lines, and (d) a pattern of cells with cell-to-cell transmission paths. The last of these is found to give the best fit. Calculation of the model impedances and optimization of element values are performed by a computer. The possibility that the mechanism of cell-to-cell transmission may be capacitative rather than conductive is explored using values of capacitance derived from the circuit models to calculate the effect of capacitative coupling alone on signal transmission. The calculations show that sufficient voltage can be transmitted from the excited cell to an adjacent cell to effect excitation.

  14. Study of a new technique for measuring the travel time of ultrasonic waves using the frequency spectrum; Estudo de uma nova tecnica de medida do tempo de percurso da onda ultra-sonica usando o espectro de frequencia

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Allan Xavier dos

    2010-07-01

    During the operation of a nuclear plant and other industrial plants, the operational time and the exposition to severe working conditions may cause the wear of its components, consequently, compromising the safety and the performance of the installation. The implementation of periodical inspections helps to ensure the safe operation and the best performance of the plant. In this way, the use of ultrasonic techniques for inspection and materials characterization becomes more and more attractive, since they offer quick, precise results and are technically ease to implement. The usual ultrasonic techniques, need to the measure the travelling time of the ultrasonic wave in the material examined in order to extract information useful to characterize it. Thus, the measurement of the travelling time of the ultrasonic wave is the overriding factor in most of the applications made with ultrasound. In this work a new technique was developed for measuring the travelling time of the ultrasonic wave using a Fourier's Fast Transformer (FFT). It will be shown mathematically and experimentally that it is possible to use the ultrasonic signal in the frequency domain to determine the travelling time of the ultrasonic wave. Five experiments were carried out for the experimental validation of this new technique. The materials used were 20 ceramic pastilles with different porosities and 3 aluminum plates of different thicknesses. The obtained results have shown that the new technique proposed in this work was able to determine the travelling time of the ultrasonic wave with the same precision as the conventional technique. It was shown, furthermore, that this new technique is able to measure the travelling time of the ultrasonic wave in situations where the conventional technique cannot be applied greatly expanding the range of application of ultrasonic testing and inspections. (author)

  15. Negative refraction of elastic waves in 2D phononic crystals: Contribution of resonant transmissions to the construction of the image of a point source

    Directory of Open Access Journals (Sweden)

    Anne-Christine Hladky-Hennion

    2011-12-01

    Full Text Available Negative refraction properties of a two-dimensional phononic crystal (PC, made of a triangular lattice of steel rods embedded in epoxy are investigated both experimentally and numerically. First, experiments have been carried out on a prism shaped PC immersed in water. Then, for focusing purposes, a flat lens is considered and the construction of the image of a point source is analyzed in details, when indices are matched between the PC and the surrounding fluid medium, whereas acoustic impedances are mismatched. Optimal conditions for focusing longitudinal elastic waves by such PC flat lens are then discussed.

  16. Combined laser ultrasonics, and Raman scattering in diamond anvil cell system operating in the transmission configuration

    Science.gov (United States)

    Zinin, P. V.; Burgess, K.; Prakapenka, V.; Sharma, S. K.; Kutuza, I. B.; Chigarev, N.; Gusev, V.

    2017-10-01

    Recently it has been demonstrated that it is possible to detect both longitudinal and shear waves as well as measure their velocities for a non-transparent iron layer compressed in a diamond anvil cell (DAC) to pressures approaching 23 GPa by using laser ultrasonics (LU) technique. These experiments were conducted in the reflection configuration when point source and point receiver were located at the same side of the specimen. The purpose of the present study is to examine the generation and detection of the acoustical waves in the LU-DAC system operating in the transmission configuration. The experimental results obtained at 16.4 GPa presented in this article demonstrate that the LU-DAC technique can be applied for longitudinal wave velocity measurements in small specimens under high pressure in the transmission configuration.

  17. Architectures for radio over fiber transmission of high-quality video and data signals

    DEFF Research Database (Denmark)

    Lebedev, Alexander

    In this Ph.D. project, design and performance evaluation of mm-wave radio over fiber links for diverse applications including video transmission are conducted. Major objective of this Thesis is to study performance of video and data signals transmitted in radio over fiber (RoF) setups...... frequency (RF) power fading in a simple intensity modulation-direct detection mm-wave RoF link through introduction of a degree of frequency tunability at the RoF transmitter. We study advanced RoF infrastructures to better suit video transmission. To enable efficient dynamic multicast/broadcast of video...... to designated BSs is evaluated for diverse lightwave generation and data modulation techniques. Mm-wave RoF links employing various lightwave generation techniques are experimentally demonstrated for diversified fiber infractructure including standard single mode fiber, multimode fiber and dispersion shifted...

  18. Estimation of Effective Transmission Loss Due to Subtropical Hydrometeor Scatters using a 3D Rain Cell Model for Centimeter and Millimeter Wave Applications

    Science.gov (United States)

    Ojo, J. S.; Owolawi, P. A.

    2014-12-01

    The problem of hydrometeor scattering on microwave radio communication down links continues to be of interest as the number of the ground and earth space terminals continually grows The interference resulting from the hydrometeor scattering usually leads to the reduction in the signal-to-noise ratio ( SNR) at the affected terminal and at worst can even end up in total link outage. In this paper, an attempt has been made to compute the effective transmission loss due to subtropical hydrometeors on vertically polarized signals in Earth-satellite propagation paths in the Ku, Ka and V band frequencies based on the modified Capsoni 3D rain cell model. The 3D rain cell model has been adopted and modified using the subtropical log-normal distributions of raindrop sizes and introducing the equivalent path length through rain in the estimation of the attenuation instead of the usual specific attenuation in order to account for the attenuation of both wanted and unwanted paths to the receiver. The co-channels, interference at the same frequency is very prone to the higher amount of unwanted signal at the elevation considered. The importance of joint transmission is also considered.

  19. Manipulating electromagnetic wave propagating non-reciprocally by a chain of ferrite rods.

    Science.gov (United States)

    Ju, Cheng; Wu, Rui-Xin; Li, Zhen; Poo, Yin; Liu, Shi-Yang; Lin, Zhi-Fang

    2017-09-04

    We demonstrated that non-reciprocal wave propagation could be manipulated by a magnetic rod chain under bias DC magnetic fields. Made of ferrite material YIG and designed working in the microwave X-band, the rod chain exhibited almost a total reflection when the incident wave obliquely impinged on the rod chain, but exhibited nearly a total transmission when the wave reversed its propagation direction. The non-reciprocal wave propagation was due to the non-reciprocal diffraction of the rod chain for the orders 0 and ± 1. Further, the non-reciprocal wave propagation was directly observed by using the field mapping technique. The unique non-reciprocal wave property of the magnetic rod chain provides a new way to control the flow of EM waves.

  20. A Comparison Between Compounding Techniques Using Large Beam-Steered Plane Wave Imaging for Blood Vector Velocity Imaging in a Carotid Artery Model.

    Science.gov (United States)

    Saris, Anne E C M; Hansen, Hendrik H G; Fekkes, Stein; Nillesen, Maartje M; Rutten, Marcel C M; de Korte, Chris L

    2016-11-01

    Conventional color Doppler imaging is limited, since it only provides velocity estimates along the ultrasound beam direction for a restricted field of view at a limited frame rate. High-frame-rate speckle tracking, using plane wave transmits, has shown potential for 2-D blood velocity estimation. However, due to the lack of focusing in transmit, image quality gets reduced, which hampers speckle tracking. Although ultrafast imaging facilitates improved clutter filtering, it still remains a major challenge in blood velocity estimation. Signal dropouts and poor velocity estimates are still present for high beam-to-flow angles and low blood flow velocities. In this paper, ultrafast plane wave imaging was combined with multiscale speckle tracking to assess the 2-D blood velocity vector in a common carotid artery (CCA) flow field. A multiangled plane wave imaging sequence was used to compare the performance of displacement compounding, coherent compounding, and compound speckle tracking. Zero-degree plane wave imaging was also evaluated. The performance of the methods was evaluated before and after clutter filtering for the large range of velocities (0-1.5 m/s) that are normally present in a healthy CCA during the cardiac cycle. An extensive simulation study was performed, based on a sophisticated model of the CCA, to investigate and evaluate the performance of the methods at different pulse repetition frequencies and signal-to-noise levels. In vivo data were acquired of a healthy carotid artery bifurcation to support the simulation results. In general, methods utilizing compounding after speckle tracking, i.e., displacement compounding and compound speckle tracking, were least affected by clutter filtering and provided the most robust and accurate estimates for the entire velocity range. Displacement compounding, which uses solely axial information to estimate the velocity vector, provided most accurate velocity estimates, although it required sufficiently high pulse

  1. Wave scattering from statistically rough surfaces

    CERN Document Server

    Bass, F G; ter Haar, D

    2013-01-01

    Wave Scattering from Statistically Rough Surfaces discusses the complications in radio physics and hydro-acoustics in relation to wave transmission under settings seen in nature. Some of the topics that are covered include radar and sonar, the effect of variations in topographic relief or ocean waves on the transmission of radio and sound waves, the reproduction of radio waves from the lower layers of the ionosphere, and the oscillations of signals within the earth-ionosphere waveguide. The book begins with some fundamental idea of wave transmission theory and the theory of random processes a

  2. Stratospheric gravity wave activities inferred through the GPS radio occultation technique; Ondas de gravidade na estratosfera terrestre inferida atraves da tecnica de radio ocultacao de GPS

    Energy Technology Data Exchange (ETDEWEB)

    Wrasse, Cristiano Max [Universidade do Vale do Paraiba (UNIVAP), Instituto de Pesquisa e Desenvolvimento (IPeD), Sao Jose dos Campos, SP (Brazil); Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Wickert, Jens, E-mail: cmw@univap.br, E-mail: hisaotak@laser.inpe.br, E-mail: joaquim@laser.inpe.br, E-mail: denardin@dae.inpe.br, E-mail: jens.wickert@gfz-potsdam.de [GeoForschungsZentrum, Potsdam (GFZ), Department of Geodesy and Remote Sensing (Germany)

    2007-07-01

    Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

  3. Characterization of wedge waves propagating along wedge tips with defects.

    Science.gov (United States)

    Chen, Ming-I; Tesng, Seng-Po; Lo, Pei-Yuan; Yang, Che-Hua

    2018-01-01

    Wedge waves are guided acoustic waves propagating along the tip of a wedge with the energy tightly confined near the wedge. Anti-symmetric flexural (ASF) modes are wedge waves with their particle motion anti-symmetric with the apex mid-plane. This study investigates the behaviors of ASF modes propagation along wedge tips with perfect and imperfect rectangular defects. Numerical finite element simulations and experimental measurements using a laser ultrasound technique are employed to explore the behaviors of ASF modes interacting with defects. Complex reflections and transmissions involved with direct reflections and transmissions as well as the newly discovered mode conversions will be explored and quantified in numerical as well as experimental ways. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Prospective validation of intra- and interobserver reproducibility of a new point shear wave elasto graphic technique for assessing liver stiffness in patients with chronic liver disease

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Su Joa; Lee, Jeong Min; Chang, Won; Lee, Sang Min; Kang, Hyo Jin; Yang, Hyun Kyung; Yoon, Jeong Hee; Park, Sae Jin; Han, Joon Koo [Dept. of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2017-11-15

    To assess intra- and inter-observer reproducibility of a new point shear wave elastography technique (pSWE, S-Shearwave, Samsung Medison) and compare its accuracy in assessing liver stiffness (LS) with an established pSWE technique (Virtual Touch Quantification, VTQ). Thirty-three patients were enrolled in this Institutional Review Board-approved prospective study. LS values were measured by VTQ on an Acuson S2000 system (Siemens Healthineer) and S-Shearwave on an RS-80A (Samsung Medison) in the same session, followed by two further S-Shearwave sessions for inter- and intra-observer variation at 8-hour intervals. The technical success rate (SR) and reliability of the measurements of both pSWE techniques were compared. The intra- and inter-observer reproducibility of S-Shearwave was determined by intraclass correlation coefficients (ICCs). LS values were measured by both methods of pSWE. The diagnostic performance in severe fibrosis (F ≥ 3) and cirrhosis (F = 4) was evaluated using the receiver operating characteristics curve analysis and the Obuchowski measure with the LS values of transient elastography as the referenced standard. The VTQ (100%, 33/33) and S-Shearwave (96.9%, 32/33) techniques did not display a significant difference in technical SR (p = 0.63) or reliability of LS measurements (96.9%, 32/33; 93.9%, 30/32, respectively, p = 0.61). The inter- and intra-observer agreement for LS measurements using the S-Shearwave technique was excellent (ICC = 0.98 and 0.99, respectively). The mean LS values of both pSWE techniques were not significantly different and exhibited a good correlation (r = 0.78). To detect F ≥ 3 and F = 4, VTQ and S-Shearwave showed comparable diagnostic accuracy as indicated by the following outcomes: areas under receiver operating characteristics curve (AUROC) = 0.87 (95% confidence intervals [CI] 0.70–0.96), 0.89 for VTQ (95% CI 0.74–0.97), respectively; and AUROC = 0.84 (95% CI 0.67–0.94), 0.94 (95% CI 0.80–0.99) for S

  5. Prospective Validation of Intra- and Interobserver Reproducibility of a New Point Shear Wave Elastographic Technique for Assessing Liver Stiffness in Patients with Chronic Liver Disease.

    Science.gov (United States)

    Ahn, Su Joa; Lee, Jeong Min; Chang, Won; Lee, Sang Min; Kang, Hyo-Jin; Yang, Hyunkyung; Yoon, Jeong Hee; Park, Sae Jin; Han, Joon Koo

    2017-01-01

    To assess intra- and inter-observer reproducibility of a new point shear wave elastography technique (pSWE, S-Shearwave, Samsung Medison) and compare its accuracy in assessing liver stiffness (LS) with an established pSWE technique (Virtual Touch Quantification, VTQ). Thirty-three patients were enrolled in this Institutional Review Board-approved prospective study. LS values were measured by VTQ on an Acuson S2000 system (Siemens Healthineer) and S-Shearwave on an RS-80A (Samsung Medison) in the same session, followed by two further S-Shearwave sessions for inter- and intra-observer variation at 8-hour intervals. The technical success rate (SR) and reliability of the measurements of both pSWE techniques were compared. The intra- and inter-observer reproducibility of S-Shearwave was determined by intraclass correlation coefficients (ICCs). LS values were measured by both methods of pSWE. The diagnostic performance in severe fibrosis (F ≥ 3) and cirrhosis (F = 4) was evaluated using the receiver operating characteristics curve analysis and the Obuchowski measure with the LS values of transient elastography as the referenced standard. The VTQ (100%, 33/33) and S-Shearwave (96.9%, 32/33) techniques did not display a significant difference in technical SR (p = 0.63) or reliability of LS measurements (96.9%, 32/33; 93.9%, 30/32, respectively, p = 0.61). The inter- and intra-observer agreement for LS measurements using the S-Shearwave technique was excellent (ICC = 0.98 and 0.99, respectively). The mean LS values of both pSWE techniques were not significantly different and exhibited a good correlation (r = 0.78). To detect F ≥ 3 and F = 4, VTQ and S-Shearwave showed comparable diagnostic accuracy as indicated by the following outcomes: areas under receiver operating characteristics curve (AUROC) = 0.87 (95% confidence intervals [CI] 0.70-0.96), 0.89 for VTQ (95% CI 0.74-0.97), respectively; and AUROC = 0.84 (95% CI 0.67-0.94), 0.94 (95% CI 0.80-0.99) for S

  6. Ultrasonic wave propagation through aberrating layers: experimental verification of the conjugate gradient Rayleigh method

    NARCIS (Netherlands)

    Ledoux, L.A.F.; Berkhoff, Arthur P.; Thijssen, J.M.

    The Conjugate Gradient Rayleigh method for the calculation of acoustic reflection and transmission at a rough interface between two media was experimentally verified. The method is based on a continuous version of the conjugate gradient technique and plane-wave expansions. We measured the beam

  7. Residual Stress Measurement and Calibration for A7N01 Aluminum Alloy Welded Joints by Using Longitudinal Critically Refracted ( LCR) Wave Transmission Method

    Science.gov (United States)

    Zhu, Qimeng; Chen, Jia; Gou, Guoqing; Chen, Hui; Li, Peng; Gao, W.

    2016-10-01

    Residual stress measurement and control are highly important for the safety of structures of high-speed trains, which is critical for the structure design. The longitudinal critically refracted wave technology is the most widely used method in measuring residual stress with ultrasonic method, but its accuracy is strongly related to the test parameters, namely the flight time at the free-stress condition ( t 0), stress coefficient ( K), and initial stress (σ0) of the measured materials. The difference of microstructure in the weld zone, heat affected zone, and base metal (BM) results in the divergence of experimental parameters. However, the majority of researchers use the BM parameters to determine the residual stress in other zones and ignore the initial stress (σ0) in calibration samples. Therefore, the measured residual stress in different zones is often high in errors and may result in the miscalculation of the safe design of important structures. A serious problem in the ultrasonic estimation of residual stresses requires separation between the microstructure and the acoustoelastic effects. In this paper, the effects of initial stress and microstructure on stress coefficient K and flight time t 0 at free-stress conditions have been studied. The residual stress with or without different corrections was investigated. The results indicated that the residual stresses obtained with correction are more accurate for structure design.

  8. Traveling-wave solutions of a modified Hodgkin-Huxley type neural model via Novel analytical results for nonlinear transmission lines with arbitrary I(V characteristics

    Directory of Open Access Journals (Sweden)

    Valentino Anthony Simpao

    2000-01-01

    Full Text Available Herein an enhanced Hodgkin-Huxley (H-H type model of neuron dynamics is solved analytically via formal methods. Our model is a variant of an earlier one by M.A. Mahrous and H.Y. Alkahby [1]. Their modified model is realized by a hyperbolic quasi-linear diffusion operator with time-delay parameters; this compared to the original H-H model with standard parabolic quasi-linear diffusion operator and no time-delay parameters. Besides these features, the present model also incorporates terms describing signal dissipation into the background substrate (e.g., conductance to ground, making it more experimentally amenable. The solutions which results via the present scheme are of traveling-wave profile, which agree qualitatively with those observed in actual electro-physiological measurements made on the neural systems originally studied by H-H These results confirm the physiological soundness of the enhanced model and of the preliminary assumptions which motivated the present solution strategy; the comparison of the present results with actual electro-physiological data displays shall appear in later publications.

  9. Analyses of the most influential factors for vibration monitoring of planetary power transmissions in pellet mills by adaptive neuro-fuzzy technique

    Science.gov (United States)

    Milovančević, Miloš; Nikolić, Vlastimir; Anđelković, Boban

    2017-01-01

    Vibration-based structural health monitoring is widely recognized as an attractive strategy for early damage detection in civil structures. Vibration monitoring and prediction is important for any system since it can save many unpredictable behaviors of the system. If the vibration monitoring is properly managed, that can ensure economic and safe operations. Potentials for further improvement of vibration monitoring lie in the improvement of current control strategies. One of the options is the introduction of model predictive control. Multistep ahead predictive models of vibration are a starting point for creating a successful model predictive strategy. For the purpose of this article, predictive models of are created for vibration monitoring of planetary power transmissions in pellet mills. The models were developed using the novel method based on ANFIS (adaptive neuro fuzzy inference system). The aim of this study is to investigate the potential of ANFIS for selecting the most relevant variables for predictive models of vibration monitoring of pellet mills power transmission. The vibration data are collected by PIC (Programmable Interface Controller) microcontrollers. The goal of the predictive vibration monitoring of planetary power transmissions in pellet mills is to indicate deterioration in the vibration of the power transmissions before the actual failure occurs. The ANFIS process for variable selection was implemented in order to detect the predominant variables affecting the prediction of vibration monitoring. It was also used to select the minimal input subset of variables from the initial set of input variables - current and lagged variables (up to 11 steps) of vibration. The obtained results could be used for simplification of predictive methods so as to avoid multiple input variables. It was preferable to used models with less inputs because of overfitting between training and testing data. While the obtained results are promising, further work is

  10. Breaking Rossby Waves in a Model Stratosphere Diagnosed by a Vortex-Following Coordinate System and a Technique for Advecting Material Contours.

    Science.gov (United States)

    Norton, Warwick A.

    1994-02-01

    This paper presents results from a single-layer, shallow-water, 100-day model integration that reproduces many features of the wintertime stratosphere, particularly in the tropics, more realistically than earlier single-layer integrations. The advective transport of passive tracers by breaking Rossby waves is examined using a new polar-vortex-following coordinate system and a technique for advecting material contours, in which they are followed very accurately using the contour-dynamics algorithm of Dritschel. Unlike any Eulerian tracer advection scheme, the technique for advecting material contours has no numerical diffusion and can handle the ultrafinescale, exponentially shrinking tracer features characteristic of chaotic advective transport or `stirring,' which is conspicuous here in the stratospheric `surfzone.' The technique may become important as a benchmark for quantitative comparison with Eulerian tracer advection schemes, such as those used in general circulation models.Averages with respect to the vortex-following coordinate system give a clearer picture of the gross features of the tracer transport than conventional Eulerian zonal averages, because the reversible displacements associated with undulating Rossby waves are largely eliminated. Results indicate that the edge of the polar vortex acts as a flexible, `Rossby elastic' barrier to eddy transport of air from the surf zone into the vortex, with air well inside the vortex completely isolated for the entire 100 days. This last point is precisely demonstrated by results from the technique for advecting material contours. Erosion of material from the vortex during days 30 to 100 of the model integration was not more than about 16% of the area of the model's surf zone, counted as the area between 30°N and 60°N. The model integration also shows, more realistically than earlier single-layer integrations, a partial barrier to exchange of air between the tropics and middle latitudes.Results using the

  11. Conversion from surface wave to surface wave on reflection

    DEFF Research Database (Denmark)

    Novitsky, Andrey

    2010-01-01

    We discuss the reflection and transmission of an incident surface wave to a pure surface wave state at another interface. This is allowed only for special media parameters: at least one of the media must be magnetic. We found such material characteristics that the obliquely incident surface wave...... can be transmitted without changing its direction (nevertheless the amplitude varies). For other media parameters, only normally incident surface waves can be converted to surface waves. We propose applications of the predicted conversion as a beam splitter and polarization filter for surface waves....

  12. Porous Si as a substrate for the monolithic integration of RF and millimeter-wave passive devices (transmission lines, inductors, filters, and antennas): Current state-of-art and perspectives

    Science.gov (United States)

    Sarafis, Panagiotis; Nassiopoulou, Androula G.

    2017-09-01

    The increasing need for miniaturization, reliability, and cost efficiency in modern telecommunications has boosted the idea of system-on-chip integration, incorporating the RF front-end circuitry and the passive elements such as RF transmission lines, inductors, antennas, and filters. However, the performance of the passive elements of these circuits is highly degraded when integrated on standard CMOS Si, due to its low resistivity. Porous silicon (PSi) has emerged as a promising local substrate material for the on-chip monolithic integration of high performance passive RF and mm-wave devices, because it combines high resistivity and low permittivity along with CMOS compatibility. This review paper aims at summarizing the obtained results so far in the above area, including transmission lines, inductors, filters, and miniaturized antennas, monolithically integrated on porous Si in a CMOS-compatible environment. In this respect, we first present the requirements for a low-loss, CMOS-compatible RF substrates and we then argue on how PSi fulfills the set requirements. Then, we present the methods used so far to extract the dielectric properties of PSi, which are necessary inputs for designing RF devices. The performance of different passive RF devices such as coplanar waveguides, inductors, filters, and antennas on the local porous Si substrate is then reviewed and compared with the performance of other state-of-the-art RF passive devices based on different technologies. Finally, we discuss the progress made so far towards the industrialization of PSi local RF substrate technology and the challenges that are currently faced towards this objective.

  13. Radio and line transmission 2

    CERN Document Server

    Roddy, Dermot

    2013-01-01

    Radio and Line Transmission, Volume 2 gives a detailed treatment of the subject as well as an introduction to additional advanced subject matter. Organized into 14 chapters, this book begins by explaining the radio wave propagation, signal frequencies, and bandwidth. Subsequent chapters describe the transmission lines and cables; the aerials; tuned and coupled circuits; bipolar transistor amplifiers; field-effect transistors and circuits; thermionic valve amplifiers; LC oscillators; the diode detectors and modulators; and the superheterodyne receiver. Other chapters explore noise and interfere

  14. Food Prices Transmission In Rwanda: Econometric Analysis ...

    African Journals Online (AJOL)

    This paper analyses the food prices transmission using econometric techniques where vector autoregressive models were formulated. Price transmission means the change of one price caused by the change of another price. Spatial price transmission is used in this study and price transmission is affected by different ...

  15. Millimetre-Wave Backhaul for 5G Networks: Challenges and Solutions.

    Science.gov (United States)

    Feng, Wei; Li, Yong; Jin, Depeng; Su, Li; Chen, Sheng

    2016-06-16

    The trend for dense deployment in future 5G mobile communication networks makes current wired backhaul infeasible owing to the high cost. Millimetre-wave (mm-wave) communication, a promising technique with the capability of providing a multi-gigabit transmission rate, offers a flexible and cost-effective candidate for 5G backhauling. By exploiting highly directional antennas, it becomes practical to cope with explosive traffic demands and to deal with interference problems. Several advancements in physical layer technology, such as hybrid beamforming and full duplexing, bring new challenges and opportunities for mm-wave backhaul. This article introduces a design framework for 5G mm-wave backhaul, including routing, spatial reuse scheduling and physical layer techniques. The associated optimization model, open problems and potential solutions are discussed to fully exploit the throughput gain of the backhaul network. Extensive simulations are conducted to verify the potential benefits of the proposed method for the 5G mm-wave backhaul design.

  16. Estimation of beat-to-beat changes in stroke volume from arterial pressure: a comparison of two pressure wave analysis techniques during head-up tilt testing in young, healthy men

    NARCIS (Netherlands)

    Jellema, W. T.; Imholz, B. P.; Oosting, H.; Wesseling, K. H.; van Lieshout, J. J.

    1999-01-01

    OBJECTIVE: The aim of this study was to compare beat-to-beat changes in stroke volume (SV) estimated by two different pressure wave analysis techniques during orthostatic stress testing: pulse contour analysis and Modelflow, i.e., simulation of a three-element model of aortic input impedance.

  17. Estimation of beat-to-beat changes in stroke volume from arterial pressure: A comparison of two pressure wave analysis techniques during head- up tilt testing in young, healthy men

    NARCIS (Netherlands)

    Jellema, W.T.; Imholz, B.P.M.; Oosting, H.; Wesseling, K.H.; Lieshout, J.J. van

    1999-01-01

    Objective: The aim of this study was to compare beat-to-beat changes in stroke volume (SV) estimated by two different pressure wave analysis techniques during orthostatic stress testing: pulse contour analysis and Modelflow, ie, simulation of a three-element model of aortic input impedance. Methods:

  18. Experimental Study of the Interfacial Waves in Horizontal Stratified Gas-liquid Two-phase Flows by Using the Developed Image Processing Technique

    CERN Document Server

    Kuntoro, Hadiyan Yusuf; Dinaryanto, Okto; Deendarlianto,; Indarto,

    2015-01-01

    Experimental series of stratified gas-liquid two-phase flows had been carried out in a 26 mm i.d. transparent acrylic horizontal pipe. The study was aimed to determine the interfacial wave characteristics of the flow and to develop a high quality database of it. The longitudinal section of the pipe was used as the reference section of image recording. Air and water were used as the test fluids, flowing co-currently inside the pipe. The flow behavior was recorded by using a high-speed video camera around 5 m in axial distance from the inlet pipe to ensure the fully-developed stratified gas-liquid two-phase flow. To correct the refraction due to the acrylic pipe, a correction box was employed in the visualization test section. The group of stratified smooth and wavy two-phase flows were successfully recorded and classified on the basis of the visualization study from 24 couples of test condition of superficial water and air velocities. Digital image processing technique was then used to perform quantitative ana...

  19. High-Power Microwave Transmission and Mode Conversion Program

    Energy Technology Data Exchange (ETDEWEB)

    Vernon, Ronald J. [Univ. of Wisconsin, Madison, WI (United States)

    2015-08-14

    This is a final technical report for a long term project to develop improved designs and design tools for the microwave hardware and components associated with the DOE Plasma Fusion Program. We have developed basic theory, software, fabrication techniques, and low-power measurement techniques for the design of microwave hardware associated gyrotrons, microwave mode converters and high-power microwave transmission lines. Specifically, in this report we discuss our work on designing quasi-optical mode converters for single and multiple frequencies, a new method for the analysis of perturbed-wall waveguide mode converters, perturbed-wall launcher design for TE0n mode gyrotrons, quasi-optical traveling-wave resonator design for high-power testing of microwave components, and possible improvements to the HSX microwave transmission line.

  20. Millimeter Wave Electromagnetic Measurement Techniques.

    Science.gov (United States)

    1982-05-01

    in the Nonlinear Portion of the p• 4 Mixer’scu Chaaceritis) 2 C- 2 o4h p 0,1,2,3,..., and q = 1,2,3.... In Equation C-1 p represents the harmonic of...07703 US Army Topographic Labs ATTN: ETL- TD -EA 519 CDR, US Army Avionics Lab 001 Fort Belvoir, VA 22060 AVRADCOM ATTN: DAVAA-D 572 Commander 001 Fort...Powder Mill Road ATTN: Mr. Leedy 001 Adelphi, MD 20783 001 Washington, DC 20231 622 HQ, Harry Diamond Lab 707 TACTECATTN: DELHD- TD (Dr. W.W. Carter

  1. Analysis of frequency quadrupling using a single Mach-Zehnder modulator for millimeter-wave generation and distribution over fiber systems.

    Science.gov (United States)

    Mohamed, Mohmoud; Zhang, Xiupu; Hraimel, Bouchaib; Wu, Ke

    2008-07-07

    We comprehensively investigate three modulation techniques for the generation of millimeter-wave (mm-wave) using optical frequency quadrupling with a dual???electrode Mach-Zehnder modulator (MZM), i.e. Technique-A, Technique-B and Technique-C. For Technique-A, an RF signal drives the two electrodes of the MZM with maximum transmission bias, and this MZM is used for both the mm-wave generation and signal modulation. Technique-B is the same as Technique-A, but 180(0) phase shift between the two electrodes is applied. Technique-C is the same as Technique-B, but the MZM is only used for the mm-wave generation without signal modulation. It is found that Technique-B and Technique-C are better for frequency quadrupling than frequency doubling, tripling and sextupling. Both theoretical analysis and simulation show that the generated mm-wave suffers from constructive/destructive interaction due to fiber chromatic dispersion in Technique-A. However, the generated mm-wave is almost robust to fiber chromatic dispersion in Technique-B and Technique- C. It is found that Technique-C is the best in the quality of the generated mm-wave, especially when poor optical filtering is used. In addition, we develop a theory for calculation of Q-factor for mm-wave generation using the three modulation techniques. We consider an RF at 7.5 GHz and obtain an mm-wave at 30 GHz as an example, i.e. a frequency quadrupler. We evaluate the generation and distribution in terms of system Q-factor. The impact of RF modulation index, chromatic dispersion, MZM extinction ratio and optical filtering on Q-factor are investigated.

  2. Wave Dragon Wave Energy Converters Used as Coastal Protection

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke; Kofoed, Jens Peter

    2011-01-01

    This paper deals with wave energy converters used to reduce the wave height along shorelines. For this study the Wave Dragon wave energy converter is chosen. The wave height reduction from a single device has been evaluated from physical model tests in scale 1:51.8 of the 260 x 150 m, 24 kW/m model....... Different stiffness of the mooring system and reflector joints has been tested for different wave steepness and relative floating ratios. The influence of each of these parameters on the wave transmission is presented. Additionally, a numerical case study is performed for the Santander Bay in the northern...... Spain, to evaluate the potential for reducing wave heights close the shore by means of Wave Dragons....

  3. Modulation of propagation-invariant Localized Waves for FSO communication systems

    KAUST Repository

    Salem, Mohamed

    2012-01-01

    The novel concept of spatio-Temporal modulation of Nyquist pulses is introduced, and the resulting wave-packets are termed Nyquist Localized Waves (LWs). Ideal Nyquist LWs belong to the generic family of LW solutions and can propagate indefinitely in unbounded media without attenuation or chromatic dispersion. The possibility of modulating Nyquist LWs for free-space optical (FSO) communication systems is demonstrated using two different modulation techniques. The first technique is on-off keying (OOK) with alternate mark inversion (AMI) coding for 1-bit per symbol transmission, and the second one is 16-Ary quadrature amplitude modulation (16-QAM) for 4-bits per symbol transmission. Aspects related to the performance, detection and generation of the spatio-Temporally coupled wave-packets are discussed and future research directions are outlined. © 2012 Optical Society of America.

  4. Data transmission

    National Research Council Canada - National Science Library

    Tugal, Dogan A; Tugal, Osman

    1989-01-01

    This updated second edition provides working answers to today's critical questions about designing and managing all types of data transmission systems and features a new chapter on local area networks (LANs...

  5. Stopping power measurements for {sup 16}O, {sup 19}F and {sup 28}Si ions in Mylar by a transmission technique

    Energy Technology Data Exchange (ETDEWEB)

    Chekirine, M., E-mail: chekirine_mamoun@yahoo.fr [Departement de physique, Faculte des sciences, Universite Saad Dahleb, B.P. 270, route de Soumaa, Blida (Algeria); Ammi, H., E-mail: hakim_ammi@yahoo.fr [Centre de Recherche Nucleaire d' Alger, 2, Bd. Frantz Fanon, B.P. 399, Alger-Gare (Algeria); Choudhury, R.K.; Biswas, D.C. [Bhabha Atomic Research Centre, Nuclear Physics Division, Mumbai (India); Tobbeche, S., E-mail: said_tobbeche@yahoo.com [Faculte des sciences, Universite El-Hadj Lakhdar, Batna 05000 (Algeria)

    2011-12-15

    Electronic energy loss of charged particles in materials is a fundamental process responsible for the unique response of materials in applications of advanced nuclear power, radiation detectors and advanced processing of electronic devices. In this study, stopping powers of {sup 16}O, {sup 19}F and {sup 28}Si heavy ions crossing thin Mylar foils have been determined in transmission geometry. The energy loss was measured over a continuous range of energies from 1.6 to 5.5 MeV/n (MeV per nucleon) using the data that was tagged by a surface barrier detector (SBD) with and without stopping foils. We have compared the obtained stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables and MSTAR calculations. The effective charge values of these heavy ions have been also deduced from the experimental set of data.

  6. Pulsars and Gravitational Waves

    Science.gov (United States)

    Lee, K. J.; Xu, R. X.; Qiao, G. J.

    2010-04-01

    The relationship between pulsar-like compact stars and gravitational waves is briefly reviewed. Due to regular spins, pulsars could be useful tools for us to detect ~nano-Hz low-frequency gravitational waves by pulsar-timing array technique; besides, they would also be ~kilo-Hz high-frequency gravitational wave radiators because of their compactness. The wave strain of an isolated pulsar depends on the equation state of cold matter at supra-nuclear densities. Therefore, a real detection of gravitational wave should be very meaningful in gravity physics, micro-theory of elementary strong interaction, and astronomy.

  7. Nanosecond Pulse Technique

    Science.gov (United States)

    1989-03-17

    wave impedance can and exerts stanta infuence on wave impedance obtained on the basis (1.29), if capacity/capacitance of line is calculated from...in media and transmission lines with nonlinear parameters [70-77]. Phenomenon of impact of will in nonlinear media is known in hydrodynamics and gas...dynamics. Thus, for instance, velocity of propagation of the sonic of will in the nonlinear media depends on sound intensity and shock acoustic waves

  8. Microstructural characterization of porous materials by X-ray microtomography and gamma ray transmission techniques; Caracterizacao da microestrutura de materiais porosos por microtomografia de raios X e transmissao de raios gama

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, Anderson Camargo

    2006-07-01

    This work presents the application of the X-ray microtomography and gamma ray transmission techniques for the microstructure characterization of different kinds of materials. Total porosity, pore size distribution and the two point correlation functions were measured. The two point correlation function, which allows the reconstruction of 3D models, was carried out for two samples. Seven ceramic tablets of Alumina (Al{sub 2}O{sub 3}), seven tablets of Boron Carbide (B{sub 4}C), three samples of sedimentary rocks and one sample of Titanium foam were analyzed. The experimental set up for the Gamma Ray Transmission technique consisted of: a 2'' x 2'' crystal NaI(Tl) detector, an {sup 241} Am radioactive source (59,53 keV, 100 mCi), an automatic micrometric table for the sample XZ movement and standard gamma spectrometry electronics. Two microtomography systems were used: a Fein Focus system, constituted by an X-ray tube, operated at 160 kV and 0.3 to 1.1 mA, a CCD camera and the movement sample system, and a Skyscan system, model 1072, with a X-ray tube operated at 100 kV and 100{mu}A, and a CCD camera. The ceramic tablets, analyzed by the gamma ray transmission technique presented results for most of the porosities data with smaller confidence intervals and inside the intervals supplied by the tablets manufacturer. The Titanium porous sample was analyzed by the two techniques, its microtomography images achieved a resolution of 17{mu}m, obtained employing the Fein Focus system. For both techniques, this sample showed high porosity, which allows its application for this purpose. The sandstones samples were analyzed by the Skyscan system, achieving resolutions of 19{mu}m, 11{mu}m and 3.8{mu}m for each sample, respectively. The resolutions of 11{mu}m and 3.8{mu}m were the ones that generated better 2D sections for the respective samples and, consequently, more reliable porosities. The 3.8{mu}m resolution was the one that best quantified the pore size

  9. Local principles of wave propagation in inhomogeneous media

    Science.gov (United States)

    Gingold, Harry; She, Jianming; Zorumski, William E.

    1993-01-01

    Four local principles are proven for waves propagating in a layered medium with a variable wave speed. These principles are (1) that inhomogeneities increase the amplitude of waves generated by a source of fixed strength, (2) that inhomogeneities reduce spatial oscillation, or increase the wavelength, (3) that inhomogeneities decrease transmission, or increase reflection, and (4) that transmission increases monotonically with frequency. Definitions of inhomogeneity, local wave function, and local reflection and transmission coefficients are made as a basis for stating these principles.

  10. A study of methods to predict and measure the transmission of sound through the walls of light aircraft. A survey of techniques for visualization of noise fields

    Science.gov (United States)

    Marshall, S. E.; Bernhard, R.

    1984-01-01

    A survey of the most widely used methods for visualizing acoustic phenomena is presented. Emphasis is placed on acoustic processes in the audible frequencies. Many visual problems are analyzed on computer graphic systems. A brief description of the current technology in computer graphics is included. The visualization technique survey will serve as basis for recommending an optimum scheme for displaying acoustic fields on computer graphic systems.

  11. Gravitational wave astronomy

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    In the past year, the LIGO-Virgo Collaboration announced the first secure detection of gravitational waves. This discovery heralds the beginning of gravitational wave astronomy: the use of gravitational waves as a tool for studying the dense and dynamical universe. In this talk, I will describe the full spectrum of gravitational waves, from Hubble-scale modes, through waves with periods of years, hours and milliseconds. I will describe the different techniques one uses to measure the waves in these bands, current and planned facilities for implementing these techniques, and the broad range of sources which produce the radiation. I will discuss what we might expect to learn as more events and sources are measured, and as this field matures into a standard part of the astronomical milieu.

  12. Wave scattering theory a series approach based on the Fourier transformation

    CERN Document Server

    Eom, Hyo J

    2001-01-01

    The book provides a unified technique of Fourier transform to solve the wave scattering, diffraction, penetration, and radiation problems where the technique of separation of variables is applicable. The book discusses wave scattering from waveguide discontinuities, various apertures, and coupling structures, often encountered in electromagnetic, electrostatic, magnetostatic, and acoustic problems. A system of simultaneous equations for the modal coefficients is formulated and the rapidly-convergent series solutions amenable to numerical computation are presented. The series solutions find practical applications in the design of microwave/acoustic transmission lines, waveguide filters, antennas, and electromagnetic interference/compatibilty-related problems.

  13. Self-supporting polymer pipes for low loss single-mode THz transmission.

    Science.gov (United States)

    Xiao, Mingfei; Liu, Jing; Zhang, Wei; Shen, Jingling; Huang, Yidong

    2013-08-26

    In this paper, a self-supporting polymer pipe is proposed and investigated for THz wave transmission. Utilizing fiber drawing technique for polymer fiber, self-supporting pipes with wall thickness of several tens micrometers can be fabricated using polymethylmethacrylate (PMMA). The guiding mechanism and transmission characteristics of the self-supporting pipes are investigated theoretically, showing that it can support single-mode transmission at THz band. The self-supporting pipe samples with different structure parameters are fabricated and measured experimentally, showing that it can support single HE(11) mode transmission. Theoretical analysis and experimental results show that this self-supporting polymer pipe is a promising candidate for low loss THz fibers.

  14. Determination of Transmission Line Impedance Matching Parameters

    African Journals Online (AJOL)

    In this work, transmission line impedance matching parameters were determined in Ugbowo ED0024GI Global System for Mobile Communication (GSM) base station in Benin City, Edo State, Nigeria. The transmission line impedance matching parameter viz voltage standing wave ratio was measured with the aid of the ...

  15. Transmission Electron Microscopy and Diffractometry of Materials

    CERN Document Server

    Fultz, Brent

    2013-01-01

    This book explains concepts of transmission electron microscopy (TEM) and x-ray diffractometry (XRD) that are important for the characterization of materials. The fourth edition adds important new techniques of TEM such as electron tomography, nanobeam diffraction, and geometric phase analysis. A new chapter on neutron scattering completes the trio of x-ray, electron and neutron diffraction. All chapters were updated and revised for clarity. The book explains the fundamentals of how waves and wavefunctions interact with atoms in solids, and the similarities and differences of using x-rays, electrons, or neutrons for diffraction measurements. Diffraction effects of crystalline order, defects, and disorder in materials are explained in detail. Both practical and theoretical issues are covered. The book can be used in an introductory-level or advanced-level course, since sections are identified by difficulty. Each chapter includes a set of problems to illustrate principles, and the extensive Appendix includes la...

  16. Spin wave generation by surface acoustic waves

    Science.gov (United States)

    Li, Xu; Labanowski, Dominic; Salahuddin, Sayeef; Lynch, Christopher S.

    2017-07-01

    Surface acoustic waves (SAW) on piezoelectric substrates can excite spin wave resonance (SWR) in magnetostrictive films through magnetoelastic coupling. This acoustically driven SWR enables the excitation of a single spin wave mode with an in-plane wave vector k matched to the magnetoelastic wave vector. A 2D frequency domain finite element model is presented that fully couples elastodynamics, micromagnetics, and piezoelectricity with interface spin pumping effects taken into account. It is used to simulate SAW driven SWR on a ferromagnetic and piezoelectric heterostructure device with an interdigital transducer configuration. These results, for the first time, present the spatial distribution of magnetization components that, together with elastic wave, exponentially decays along the propagation direction due to magnetic damping. The results also show that the system transmission rate S21(dB) can be tuned by both an external bias field and the SAW wavevector. Acoustic spin pumping at magnetic film/normal metal interface leads to damping enhancement in magnetic films that decreases the energy absorption rate from elastic energy. This weakened interaction between the magnetic energy and elastic energy leads to a lower evanescence rate of the SAW that results in a longer distance propagation. With strong magnetoelastic coupling, the SAW driven spin wave is able to propagate up to 1200 μm. The results give a quantitative indication of the acoustic spin pumping contribution to linewidth broadening.

  17. Gravitation Waves seminar

    CERN Multimedia

    CERN. Geneva HR-RFA

    2006-01-01

    We will present a brief introduction to the physics of gravitational waves and their properties. We will review potential astrophysical sources of gravitational waves, and the physics and astrophysics that can be learned from their study. We will survey the techniques and technologies for detecting gravitational waves for the first time, including bar detectors and broadband interferometers, and give a brief status report on the international search effort.

  18. Multivariate optimization of differential pulse polarographic–catalytic hydrogen wave technique for the determination of nickel(II) in real samples

    OpenAIRE

    Kanchi, S.; Sabela, M.I.; Singh, P.; Bisetty, K.

    2013-01-01

    Multivariate optimized experimental conditions were established for the determination of nickel(II) in 92 grape samples after complexation with ammonium piperidine dithiocarbamate (APDC) and ammonium morpholine dithiocarbamate (AMDC). Differential pulse polarographic (DPP) studies of the wave characteristics indicated that it is of the catalytic hydrogen wave (CHW) type sensitive to pH, concentration and scan rates. A single, sharp peak obtained at −1.22 V allowed for the trace determination ...

  19. Acoustic tomography. Laboratory technique Implementation.

    Science.gov (United States)

    Galvis, Jorge; Carvajal, Jenny

    2010-05-01

    From geomechanical tests carried out on rocks it is possible to determine its physico-mechanical properties, which relate the strain and applied stress; even so, conventional tests do not allow to identify how stress is distributed and how it has affected porous media. Today, techniques like acoustic tomography widely used in medicine, geophysics and others sciences, generates images by sections of the interior of a body. Acoustic tomography allows inferring the stress state within porous media; since wave velocities are closely related to media density, if a stress is applied to a rock, it will generate grains compaction and this will be showed by an increase of wave velocity. Implementation was conducted on rock plugs under diverse stress fields, simultaneously recording P-wave velocities (Compressional) on perpendicular planes to sample vertical axis. Transmission and reception of acoustic waves through porous media were done by piezoelectric crystals (PZT) used as sensors. A transmitting crystal excited by a voltage pulse causes a mechanical vibration, which travels across media; this is known as inverse piezoelectric effect. This vibration is recorded by a receiving crystal in which the direct piezoelectric effect appears; which dictates that if a piezoelectric is disturbed mechanically, an electrical signal between its terminals will appear. This electrical signal is used to obtain the wave velocity. Nevertheless, acoustic tomography corresponds to one of those called inverse Problems that arise when from observed data the model parameters must be obtained; in this way, tomography involves iterative reconstruction techniques (ART or SIRT) which are projections of observed data and its later inversion. Obtained results are cross-sectional images of velocity within the rock. In these images it is possible to identify where stress has a greater concentration observing the color map generated; thus, a greater velocity density area corresponding to a greater

  20. Calculating scattering matrices by wave function matching

    Energy Technology Data Exchange (ETDEWEB)

    Zwierzycki, M. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan (Poland); Khomyakov, P.A.; Starikov, A.A.; Talanana, M.; Xu, P.X.; Karpan, V.M.; Marushchenko, I.; Brocks, G.; Kelly, P.J. [Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Xia, K. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Turek, I. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, 616 62 Brno (Czech Republic); Bauer, G.E.W. [Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands)

    2008-04-15

    The conductance of nanoscale structures can be conveniently related to their scattering properties expressed in terms of transmission and reflection coefficients. Wave function matching (WFM) is a transparent technique for calculating transmission and reflection matrices for any Hamiltonian that can be represented in tight-binding form. A first-principles Kohn-Sham Hamiltonian represented on a localized orbital basis or on a real space grid has such a form. WFM is based upon direct matching of the scattering-region wave function to the Bloch modes of ideal leads used to probe the scattering region. The purpose of this paper is to give a pedagogical introduction to WFM and present some illustrative examples of its use in practice. We briefly discuss WFM for calculating the conductance of atomic wires, using a real space grid implementation. A tight-binding muffin-tin orbital implementation very suitable for studying spin-dependent transport in layered magnetic materials is illustrated by looking at spin-dependent transmission through ideal and disordered interfaces. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. HIV Transmission

    Science.gov (United States)

    ... Abroad Treatment Basic Statistics Get Tested Find an HIV testing site near you. Enter ZIP code or city Follow HIV/AIDS CDC HIV CDC HIV/AIDS See RSS | ... on HIV Syndicated Content Website Feedback HIV/AIDS HIV Transmission Language: English (US) Español (Spanish) Recommend on ...

  2. The techniques of metallic foil electrically exploding driving hypervelocity flyer to more than 10 km/s for shock wave physics experiments.

    Science.gov (United States)

    Wang, Guiji; He, Jia; Zhao, Jianheng; Tan, Fuli; Sun, Chengwei; Mo, Jianjun; Xong, Xin; Wu, Gang

    2011-09-01

    Electrical explosion of metallic foil or wire is widely used to the fields of material science (preparation of nao-meter materials), dynamics of materials, and high energy density physics. In this paper, the techniques of gaining hypervelocity flyer driven by electrical explosion of metallic foil were researched, which are used to study dynamics of materials and hypervelocity impact modeling of space debris. Based on low inductance technologies of pulsed storage energy capacitor, detonator switch and parallel plate transmission lines with solid films insulation, two sets of experimental apparatuses with storage energy of 14.4 kJ and 40 kJ were developed for launching hypervelocity flyer. By means of the diagnostic technologies of velocity interferometer system for any reflectors and fibre-optic pins, the hypervelocity polyester (Mylar) flyers were gained. For the apparatus of 14.4 kJ, flyer of diameter φ6 ~ φ10 mm and thickness of 0.1 ~ 0.2 mm was accelerated to the hypervelocity of 10 ~ 14 km/s. And for the apparatus of 40 kJ, flyer of diameter φ20 ~ 30 mm and thickness of 0.2 mm was launched to the velocity of 5 ~ 8 km/s. The flatness of the flyer is not more than 34 ns for the flyer with diameter of 20 mm, and less than 22 ns for the flyer with diameter of 10 mm. Based on the Lagrange hydrodynamic code, one dimensional simulation was done by introducing database of equation of states, discharging circuit equation and Joule heat equation, and modifying energy equation. The simulation results are well agreed with the experimental results in accelerating processing. The simulation results can provide good advices in designing new experiments and developing new experimental devices. Finally, some experiments of materials dynamics and hypervelocity impact of space debris were done by using the apparatus above. The results show that the apparatus of metallic foil electrically exploding driving hypervelocity flyer is a good and versatile tool for shock dynamics.

  3. Capacitive micromachined ultrasonic Lamb wave transducers using rectangular membranes.

    Science.gov (United States)

    Badi, Mohammed H; Yaralioglu, Goksen G; Ergun, A Sanli; Hansen, Sean T; Wong, Eehern J; Khuri-Yakub, Butrus T

    2003-09-01

    This paper details the theory, fabrication, and characterization of a new Lamb wave device. Built using capacitive micromachined ultrasonic transducers (CMUTs), the structure described uses rectangular membranes to excite and receive Lamb waves on a silicon substrate. An equivalent circuit model for the transducer is proposed that produces results, which match well with those observed by experiment. During the derivation of this model, emphasis is placed on the resistance presented to the transducer membranes by the Lamb wave modes. Finite element analysis performed in this effort shows that the dominant propagating mode in the device is the lowest order antisymmetric flexural wave (A0). Furthermore, most of the power that couples into the Lamb wave is due to energy in the vibrating membrane that is transferred to the substrate through the supporting posts of the device. The manufacturing process of the structure, which relies solely on fundamental IC-fabrication techniques, is also discussed. The resulting device has an 18-microm-thick substrate that is almost entirely made up of crystalline silicon and operates at a frequency of 2.1 MHz. The characterization of this device includes S-parameter and laser vibrometer measurements as well as delay-line transmission data. The insertion loss, as determined by both S-parameter and delay-line transmission measurements, is 20 dB at 2.1 MHz. When configured as a delay-line oscillator, the device functions well as a sensor with sensitivity to changes in the mass loading of its substrate.

  4. Investigation of Wave Height Reduction behind the Wave Dragon Wave Energy Converters and Application in Santander, Spain

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Quvang Harck; Andersen, Thomas Lykke

    This paper deals with a case study on the wave height reduction behind floating Wave Dragon wave energy converters in Santander Bay, Spain. The study is performed using the MIKE21 Boussinesq model from DHI. The Wave Dragon transmission characteristics in the numerical wave propagation model...... are based on previously performed physical model tests in scale 1:51. Typical winter storm conditions are considered in the case study together with different stiffness in the mooring system of the floating device. From the study it is found that if multiple Wave Dragons are positioned in a farm the wave...

  5. Identification of Potential High-Risk Habitats within the Transmission Reach of Oncomelania hupensis after Floods Based on SAR Techniques in a Plane Region in China.

    Science.gov (United States)

    Shi, Yuanyuan; Qiu, Juan; Li, Rendong; Shen, Qiang; Huang, Duan

    2017-08-30

    Schistosomiasis japonica is an infectious disease caused by Schistosoma japonicum , and it remains endemic in China. Flooding is the main hazard factor, as it causes the spread of Oncomelania hupensis , the only intermediate host of Schistosoma japonicum , thereby triggering schistosomiasis outbreaks. Based on multi-source real-time remote sensing data, we used remote sensing (RS) technology, especially synthetic aperture radar (SAR), and geographic information system (GIS) techniques to carry out warning research on potential snail habitats within the snail dispersal range following flooding. Our research result demonstrated: (1) SAR data from Sentinel-1A before and during a flood were used to identify submerged areas rapidly and effectively; (2) the likelihood of snail survival was positively correlated with the clay proportion, core area standard deviation, and ditch length but negatively correlated with the wetness index, NDVI (normalized difference vegetation index), elevation, woodland area, and construction land area; (3) the snail habitats were most abundant near rivers and ditches in paddy fields; (4) the rivers and paddy irrigation ditches in the submerged areas must be the focused of mitigation efforts following future floods.

  6. Identification of Potential High-Risk Habitats within the Transmission Reach of Oncomelania hupensis after Floods Based on SAR Techniques in a Plane Region in China

    Directory of Open Access Journals (Sweden)

    Yuanyuan Shi

    2017-08-01

    Full Text Available Schistosomiasis japonica is an infectious disease caused by Schistosoma japonicum, and it remains endemic in China. Flooding is the main hazard factor, as it causes the spread of Oncomelania hupensis, the only intermediate host of Schistosoma japonicum, thereby triggering schistosomiasis outbreaks. Based on multi-source real-time remote sensing data, we used remote sensing (RS technology, especially synthetic aperture radar (SAR, and geographic information system (GIS techniques to carry out warning research on potential snail habitats within the snail dispersal range following flooding. Our research result demonstrated: (1 SAR data from Sentinel-1A before and during a flood were used to identify submerged areas rapidly and effectively; (2 the likelihood of snail survival was positively correlated with the clay proportion, core area standard deviation, and ditch length but negatively correlated with the wetness index, NDVI (normalized difference vegetation index, elevation, woodland area, and construction land area; (3 the snail habitats were most abundant near rivers and ditches in paddy fields; (4 the rivers and paddy irrigation ditches in the submerged areas must be the focused of mitigation efforts following future floods.

  7. AN ANTHOLOGY OF THE DISTINGUISHED ACHIEVEMENTS IN SCIENCE AND TECHNIQUE. PART 34: DISCOVERY AND STUDY OF QUANTUM-WAVE NATURE OF MICROSCOPIC WORLD OF MATTER

    Directory of Open Access Journals (Sweden)

    M. I. Baranov

    2016-11-01

    Full Text Available Purpose. Implementation of brief analytical review of the basic distinguished scientific achievements of the world scientists-physicists in area of discovery and study of quantum-wave nature of physical processes and phenomena flowing in the microscopic world of circumferential people matter. Methodology. Scientific methods of collection, analysis and analytical treatment of scientific and technical information in area of theoretical and experimental physics, devoted the results of researches| of quantum and physical processes flowing in nature on atomic and subatomic levels. Results. The brief scientific and technical review of the basic scientific discovery and achievements of scientists-physicists is resulted in area of structure of atom of matter, generation, radiation, distribution and absorption of physical bodies of short-wave hertzian waves, indicative on a dominating role in the microscopic financial world of positions and conformities to the law of wave (by quantum mechanics, carrying especially probabilistic character a microstructure. Originality. Systematization is executed with exposition in the short concentrated form| of the known materials| on the quantum theory (electromagnetic of caloradiance, quantum theory of atom, electronic waves, quantum theory of actinoelectricity, quantum statistics of microparticless, quantum theory of the phenomenon superfluidity of liquid helium, quantum electronics and quantum-wave nature of drift of lone electrons in the metal of explorers with an electric current. Practical value. Popularization and deepening of fundamental physical and technical knowledges for students and engineer and technical specialists in area of classic and quantum physics, extending their scientific range of interests, and also support a further scientific study by them surrounding nature and to development of scientific and technical progress in society.

  8. Magnetically applied pressure-shear : a new technique for direct strength measurement at high pressure (final report for LDRD project 117856).

    Energy Technology Data Exchange (ETDEWEB)

    Lamppa, Derek C.; Haill, Thomas A.; Alexander, C. Scott; Asay, James Russell

    2010-09-01

    A new experimental technique to measure material shear strength at high pressures has been developed for use on magneto-hydrodynamic (MHD) drive pulsed power platforms. By applying an external static magnetic field to the sample region, the MHD drive directly induces a shear stress wave in addition to the usual longitudinal stress wave. Strength is probed by passing this shear wave through a sample material where the transmissible shear stress is limited to the sample strength. The magnitude of the transmitted shear wave is measured via a transverse VISAR system from which the sample strength is determined.

  9. Spin-wave logic devices based on isotropic forward volume magneto-static waves

    OpenAIRE

    Klingler, Stefan; Pirro, Philipp; Brächer, Thomas; Leven, Britta; Hillebrands, Burkard; Chumak, Andrii V.

    2015-01-01

    We propose the utilization of isotropic forward volume magneto-static spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Mor...

  10. Analysis of Waves

    DEFF Research Database (Denmark)

    Frigaard, Peter; Andersen, Thomas Lykke

    The present book describes the most important aspects of wave analysis techniques applied to physical model tests. Moreover, the book serves as technical documentation for the wave analysis software WaveLab 3, cf. Aalborg University (2012). In that respect it should be mentioned that supplementary...... to the present technical documentation exists also the online help document describing the WaveLab software in detail including all the inputs and output fields. In addition to the two main authors also Tue Hald, Jacob Helm-Petersen and Morten Møller Jakobsen have contributed to the note. Their input is highly...... acknowledged. The outline of the book is as follows: • Chapter 2 and 3 describes analysis of waves in time and frequency domain. • Chapter 4 and 5 describes the separation of incident and reflected waves for the two-dimensional case. • Chapter 6 describes the estimation of the directional spectra which also...

  11. Research Techniques in Wave Propagation and Scattering. Program and Abstracts of Workshop/Symposium held at the Ohio State University on 18-21 October 1982.

    Science.gov (United States)

    1982-01-01

    Colorado Boulder, CO 80309 F.J. Sabina Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas 04510 Mexico, D.F. Diffraction of elastic...EXPANSIONS APPLIED TO -. DIFFRACTION OF ELASTIC WAVES S.K. Vatta, Univeu,,a o6 Colouado F.J. Sabina, In6titto de Inve.tigacione. en Matematica ., Mexico 10:20

  12. Electromagnetic Waves

    DEFF Research Database (Denmark)

    This book is dedicated to various aspects of electromagnetic wave theory and its applications in science and technology. The covered topics include the fundamental physics of electromagnetic waves, theory of electromagnetic wave propagation and scattering, methods of computational analysis...

  13. 64-GHz millimeter-wave photonic generation with a feasible radio over fiber system

    Science.gov (United States)

    Al-Dabbagh, Rasha K.; Al-Raweshidy, Hamed S.

    2017-02-01

    A full-duplex radio over fiber (RoF) link with the generation of a 64-GHz millimeter wave (mm-wave) is investigated. This system is proposed as a solution to cope with the demands of a multi-Gb/s data transmission in the fifth generation (5G) and beyond for small cell networks. Cost reduction and performance improvement are achieved by simplifying the mm-wave generation method with an RoF technique. High-frequency radio signals are considered challenging in the electrical generation domain; therefore, our photonic generation method is introduced and examined. RoF design is proposed for mm-wave generation using both phase modulation and the effect of stimulated Brillouin scattering in the optical fiber for the first time. RoF system with transmission rates of 5 Gb/s is successfully achieved. In our scheme, one laser source is utilized and a fiber Bragg grating is used for wavelength reuse for the uplink connection. Stable mm-wave RoF link is successfully achieved in up to a 100-km fiber link length with high quality carrier. Simulation results show a reduction in fiber nonlinearity effects and the mm-wave signal has low noise equal to -75 dBm. This study ensures a practical mm-wave RoF link, and it could be appropriate for small cell 5G networks by reducing the installation cost.

  14. Caustics of atmospheric waves

    Science.gov (United States)

    Godin, Oleg A.

    2015-04-01

    Much like light and sound, acoustic-gravity waves in inhomogeneous atmosphere often have a caustic or caustics, where the ray theory predicts unphysical, divergent values of the wave amplitude and needs to be modified. Increase of the wave magnitude in the vicinity of a caustic makes such vicinities of primary interest in a number of problems, where a signal needs to be separated from a background noise. The value of wave focusing near caustics should be carefully quantified in order to evaluate possible nonlinearities promoted by the focusing. Physical understanding of the wave field in the vicinity of a caustic is also important for understanding of the wave reflection from and transmission (tunneling) through the caustic. To our knowledge, in contrast to caustics of acoustic, electromagnetic, and seismic waves as well as gravity waves in incompressible fluids, asymptotics of acoustic-gravity waves in the vicinity of a caustic have never been studied systematically. In this paper, we fill this gap. Atmospheric waves are considered as linear acoustic-gravity waves in a neutral, horizontally stratified, moving ideal gas of variable composition. Air temperature and wind velocity are assumed to be gradually varying functions of height, and slowness of these variations determines the large parameter of the problem. The scale height of the atmosphere can be large or small compared to the vertical wavelength. It is found that the uniform asymptotics of the wave field in the presence of a simple caustic can be expressed in terms of the Airy function and its derivative. As for the acoustic waves, the argument of the Airy function is expressed in terms of the eikonal calculated in the ray, or WKB, approximation. The geometrical, or Berry, phase, which arises in the consistent WKB approximation for acoustic-gravity waves, plays an important role in the caustic asymptotics. In the uniform asymptotics, the terms with the Airy function and its derivative are weighted by cosine

  15. Application of State of the Art Modeling Techniques to Predict Flooding and Waves for a Coastal Area within a Protected Bay

    Directory of Open Access Journals (Sweden)

    Malcolm L. Spaulding

    2017-03-01

    Full Text Available Flood Insurance Rate Maps (FIRMs are developed by the Federal Emergency Management Agency (FEMA to provide guidance in establishing the risk to structures and infrastructure from storm surge sand associated waves in the coastal zone. The maps are used by state agencies and municipalities to help guide coastal planning and establish the minimum elevation and construction standards for new or substantially improved structures. A summary of the methods used and a comparison with the results of 2013 FIRM mapping are presented for Warwick, Rhode Island (RI, a coastal community located within Narragansett Bay. Because of its location, Warwick is protected from significant coastal erosion and wave attacks, but is subject to surge amplification. Concerns surrounding the FEMA methods used in the 2013 FIRM analysis are put in context with the National Research Council’s (NRC 2009 review of the FEMA coastal mapping program. New mapping is then performed using state of the art, fully coupled surge and wave modeling, and data analysis methods, to address the NRC concerns. The new maps and methodologies are in compliance with FEMA regulations and guidelines. This new approach makes extensive use of the numerical modeling results from the recent US Army Corp of Engineers, North Atlantic Coast Comprehensive Study (NACCS, 2015. Revised flooding maps are presented and compared to the 2013 FIRM maps, to provide insight into the differences. The new maps highlight the importance of developing better estimates of surge dynamics and the advancement in nearshore mapping of waves in flood inundated areas by the use of state of the art, two-dimensional, wave transformation models.

  16. Dual Waves

    OpenAIRE

    Kallosh, Renata

    1994-01-01

    We study the gravitational waves in the 10-dimensional target space of the superstring theory. Some of these waves have unbroken supersymmetries. They consist of Brinkmann metric and of a 2-form field. Sigma-model duality is applied to such waves. The corresponding solutions we call dual partners of gravitational waves, or dual waves. Some of these dual waves upon Kaluza-Klein dimensional reduction to 4 dimensions become equivalent to the conformo-stationary solutions of axion-dilaton gravity...

  17. Nonlinear waves and weak turbulence

    CERN Document Server

    Zakharov, V E

    1997-01-01

    This book is a collection of papers on dynamical and statistical theory of nonlinear wave propagation in dispersive conservative media. Emphasis is on waves on the surface of an ideal fluid and on Rossby waves in the atmosphere. Although the book deals mainly with weakly nonlinear waves, it is more than simply a description of standard perturbation techniques. The goal is to show that the theory of weakly interacting waves is naturally related to such areas of mathematics as Diophantine equations, differential geometry of waves, Poincaré normal forms, and the inverse scattering method.

  18. Measurement of guided mode wave vectors by analysis of the transfer matrix obtained with multi-emitters and multi-receivers in contact

    Science.gov (United States)

    Minonzio, Jean-Gabriel; Talmant, Maryline; Laugier, Pascal

    2011-01-01

    Different quantitative ultrasound techniques are currently developed for clinical assessment of human bone status. This paper is dedicated to axial transmission: emitters and receivers are linearly arranged on the same side of the skeletal site, preferentially the forearm. In several clinical studies, the signal velocity of the earliest temporal event has been shown to discriminate osteoporotic patients from healthy subjects. However, a multi parameter approach might be relevant to improve bone diagnosis and this be could be achieved by accurate measurement of guided waves wave vectors. For clinical purposes and easy access to the measurement site, the length probe is limited to about 10 mm. The limited number of acquisition scan points on such a short distance reduces the efficiency of conventional signal processing techniques, such as spatio-temporal Fourier transform. The performance of time-frequency techniques was shown to be moderate in other studies. Thus, optimised signal processing is a critical point for a reliable estimate of guided mode wave vectors. Toward this end, a technique, taking benefit of using both multiple emitters and multiple receivers, is proposed. The guided mode wave vectors are obtained using a projection in the singular vectors basis. Those are determined by the singular values decomposition of the transmission matrix between the two arrays at different frequencies. This technique enables us to recover accurately guided waves wave vectors for moderately large array.

  19. Dual-mode acoustic wave biosensors microarrays

    Science.gov (United States)

    Auner, Gregory W.; Shreve, Gina; Ying, Hao; Newaz, Golam; Hughes, Chantelle; Xu, Jianzeng

    2003-04-01

    We have develop highly sensitive and selective acoustic wave biosensor arrays with signal analysis systems to provide a fingerprint for the real-time identification and quantification of a wide array of bacterial pathogens and environmental health hazards. We have developed an unique highly sensitive dual mode acoustic wave platform prototype that, when combined with phage based selective detection elements, form a durable bacteria sensor. Arrays of these new real-time biosensors are integrated to form a biosensor array on a chip. This research and development program optimizes advanced piezoelectric aluminum nitride wide bandgap semiconductors, novel micromachining processes, advanced device structures, selective phage displays development and immobilization techniques, and system integration and signal analysis technology to develop the biosensor arrays. The dual sensor platform can be programmed to sense in a gas, vapor or liquid environment by switching between acoustic wave resonate modes. Such a dual mode sensor has tremendous implications for applications involving monitoring of pathogenic microorganisms in the clinical setting due to their ability to detect airborne pathogens. This provides a number of applications including hospital settings such as intensive care or other in-patient wards for the reduction of nosocomial infections and maintenance of sterile environments in surgical suites. Monitoring for airborn pathogen transmission in public transportation areas such as airplanes may be useful for implementation of strategies for redution of airborn transmission routes. The ability to use the same sensor in the liquid sensing mode is important for tracing the source of airborn pathogens to local liquid sources. Sensing of pathogens in saliva will be useful for sensing oral pathogens and support of decision-making strategies regarding prevention of transmission and support of treatment strategies.

  20. Comparison between multi-channel LDV and PWI for measurement of pulse wave velocity in distensible tubes: Towards a new diagnostic technique for detection of arteriosclerosis

    Science.gov (United States)

    Campo, Adriaan; Dudzik, Grzegorz; Apostolakis, Jason; Waz, Adam; Nauleau, Pierre; Abramski, Krzysztof; Dirckx, Joris; Konofagou, Elisa

    2017-10-01

    The aim of this work, was to compare pulse wave velocity (PWV) measurements using Laser Doppler vibrometry (LDV) and the more established ultrasound-based pulse wave imaging (PWI) in smooth vessels. Additionally, it was tested whether changes in phantom structure can be detected using LDV in vessels containing a local hardening of the vessel wall. Results from both methods showed good agreement illustrated by the non-parametric Spearman correlation analysis (Spearman-ρ = 1 and pmarkers and larger distances between beams. In further studies, more LDV beams will be used to allow detection of local changes in arterial wall dynamics due to e.g. small inclusions or local hardenings of the vessel wall.

  1. High frequency techniques an introduction to RF and microwave engineering

    CERN Document Server

    White, Joseph F

    2004-01-01

    A practical guide for today's wireless engineerHigh Frequency Techniques: An Introduction to RF and Microwave Engineering is a clearly written classical circuit and field theory text illustrated with modern computer simulation software. The book's ten chapters cover: *The origins and current uses of wireless transmission *A review of AC analysis, Kirchhoff's laws, RLC elements, skin effect, and introduction to the use of computer simulation software*Resonators, Q definitions, and Q-based impedance matching *Transmission lines, waves, VSWR, reflection phenomena, Fano's reflection bandwidth limits, telegrapher, and impedance transformation equations*Development and in-depth use of the Smith Chart *Matrix algebra with Z, Y, ABCD, S, and T matrix applications*An unusually thorough introduction to electromagnetic field theory, step-by-step development of vector calculus, Maxwell's equations, waveguides, propagation, and antennas*Backward wave, branch line, rat race and Wilkinson couplers, impedance measurements, a...

  2. Transcending Transmission

    DEFF Research Database (Denmark)

    Schoeneborn, Dennis; Trittin, Hannah

    2013-01-01

    Purpose – Extant research on corporate social responsibility (CSR) communication primarily relies on a transmission model of communication that treats organizations and communication as distinct phenomena. This approach has been criticized for neglecting the formative role of communication...... in the emergence of organizations. This paper seeks to propose to reconceptualize CSR communication by drawing on the “communication constitutes organizations” (CCO) perspective. Design/methodology/approach – This is a conceptual paper that explores the implications of switching from an instrumental...... to a constitutive notion of communication. Findings – The study brings forth four main findings: from the CCO view, organizations are constituted by several, partly dissonant, and potentially contradictory communicative practices. From that viewpoint, the potential impact of CSR communication becomes a matter...

  3. Data transmission networks

    Science.gov (United States)

    Alexovich, Robert

    1990-01-01

    A task order was written by the High Resolution, High Frame Rate Video Technology (HHVT) project engineers to investigate data compression techniques that could be applied to the HHVT system, and both existing and planned downlink/uplink capabilities of the Space Shuttle and Space Station Freedom. The following tasks were included: (1) Investigate signal channel availability and determine both the maximum possible data rate and the average data rate; (2) Identify time blocks for HHVT video transmission assuming time sharing and interruptions in the communication links; (3) Determine the bit error rates to be expected; and (4) Define the transmit and receive interfaces. A summary chart of the data transmission capabilities for Tracking and Data Relay Satellite System (TDRSS), the Space Shuttle, Space Station Freedom, Spacelab, and USLab are also presented.

  4. Regional transmission subsystem planning

    Energy Technology Data Exchange (ETDEWEB)

    Costa Bortoni, Edson da [Quadrante Softwares Especializados Ltda., Itajuba, MG (Brazil); Bajay, Sergio Valdir; Barros Correia, Paulo de [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica; Santos, Afonso Henriques Moreira; Haddad, Jamil [Escola Federal de Engenharia de Itajuba, MG (Brazil)

    1994-12-31

    This work presents an approach for the planning of transmission systems by employing mixed--integer linear programming to obtain a cost and operating characteristics optimized system. The voltage loop equations are written in a modified form, so that, at the end of the analysis, the model behaves as a DC power flow, with the help of the two Kirchhoff`s laws, exempting the need of interaction with an external power flow program for analysis of the line loading. The model considers the occurrence of contingencies, so that the final result is a network robust to the most severe contingencies. This whole technique is adapted to the regional electric power transmission subsystems. (author) 9 refs., 4 figs.

  5. Transmission ultrasonography. [time delay spectrometry for soft tissue transmission imaging

    Science.gov (United States)

    Heyser, R. C.; Le Croissette, D. H.

    1973-01-01

    Review of the results of the application of an advanced signal-processing technique, called time delay spectrometry, in obtaining soft tissue transmission images by transmission ultrasonography, both in vivo and in vitro. The presented results include amplitude ultrasound pictures and phase ultrasound pictures obtained by this technique. While amplitude ultrasonographs of tissue are closely analogous to X-ray pictures in that differential absorption is imaged, phase ultrasonographs represent an entirely new source of information based on differential time of propagation. Thus, a new source of information is made available for detailed analysis.

  6. WAVES VHDL interface

    Science.gov (United States)

    Hanna, James P.

    1994-06-01

    The Waveform and Vector Exchange Specification (WAVES) is the Industry standard representation for digital stimulus and response for both the design and test communities. The VHSIC Hardware Description Language (VHDL) is the Industry standard language for the design, modeling, and simulation of digital electronics. Together VHDL and WAVES provide powerful support for top-down design and test methodologies and concurrent engineering practices. Although the syntax of WAVES is a subset of VHDL, no special support for using WAVES in a VHDL environment is defined within the language. This report will introduce and describe a VHDL package that was developed at Rome Laboratory to provide a software interface to support the use of WAVES in a VHDL environment. This VHDL package is referred to as the WAVES VHDL interface and has been proposed as a standard practice for a top-down design and test methodology using WAVES and VHDL. This report is not intended to provide a tutorial on VHDL or WAVES. It is assumed that the reader has an adequate understanding of the VHDL language and some modeling techniques. Further, it is assumed that the reader has an understanding of the WAVES language and can follow a simple Level 1 dataset description.

  7. Guaranteed estimation of solutions to Helmholtz transmission problems with uncertain data from their indirect noisy observations

    Science.gov (United States)

    Podlipenko, Yu. K.; Shestopalov, Yu. V.

    2017-09-01

    We investigate the guaranteed estimation problem of linear functionals from solutions to transmission problems for the Helmholtz equation with inexact data. The right-hand sides of equations entering the statements of transmission problems and the statistical characteristics of observation errors are supposed to be unknown and belonging to certain sets. It is shown that the optimal linear mean square estimates of the above mentioned functionals and estimation errors are expressed via solutions to the systems of transmission problems of the special type. The results and techniques can be applied in the analysis and estimation of solution to forward and inverse electromagnetic and acoustic problems with uncertain data that arise in mathematical models of the wave diffraction on transparent bodies.

  8. Nearly zero transmission through periodically modulated ultrathin metal films

    DEFF Research Database (Denmark)

    Xiao, Sanshui; Zhang, Jingjing; Peng, Liang

    2010-01-01

    Transmission of light through an optically ultrathin metal film with a thickness comparable to its skin depth is significant. We demonstrate experimentally nearly-zero transmission of light through a film periodically modulated by a one-dimensional array of subwavelength slits. The suppressed opt...... optical transmission is due to the excitation of surface plasmon polaritons and the zero-transmission phenomenon is strongly dependent on the polarization of the incident wave....

  9. Quantum Opportunities in Gravitational Wave Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Mavalvala, Negris (MIT)

    2012-03-14

    Direct observation of gravitational waves should open a new window into the Universe. Gravitational wave detectors are the most sensitive position meters ever constructed. The quantum limit in gravitational wave detectors opens up a whole new field of study. Quantum opportunities in gravitational wave detectors include applications of quantum optics techniques and new tools for quantum measurement on truly macroscopic (human) scales.

  10. One-way propagation of acoustic waves through a periodic structure

    Science.gov (United States)

    Xu, Zheng; Xu, Wei; Yan, Xu; Qian, Menglu; Cheng, Qian

    2018-02-01

    One-way acoustic transmission is achieved through a brass plate with a periodic grating on the surface. Using the Schlieren imaging technique, the positive and negative propagation processes of acoustic waves through the periodic structure were experimentally observed. Simulations were performed using the finite-element method. Both the experimental and simulation results revealed a very large transmission ratio between positive and negative incidence, thus demonstrating the feasibility of using this structure as an acoustic rectifier. The results indicate that the structure has a broadband working frequency. The structure has potential applications in ultrasonic medical devices and sonochemical reactors.

  11. Development of hydroacoustical techniques for the monitoring and classification of benthic habitats in Puck Bay: Modeling of acoustic waves scattering by seagrass

    Science.gov (United States)

    Raczkowska, A.; Gorska, N.

    2012-12-01

    Puck Bay is an area of high species biodiversity belonging to the Coastal Landscape Park of Baltic Sea Protected Areas (BSPA) and is also included in the list of the World Wide Fund for Nature (WWF) and covered by the protection program "Natura 2000". The underwater meadows of the Puck Bay are important for Europe's natural habitats due to their role in enhancing the productivity of marine ecosystems and providing shelter and optimal feeding conditions for many marine organisms. One of the dominant species comprising the underwater meadows of the Southern Baltic Sea is the seagrass Zostera marina. The spatial extent of underwater seagrass meadows is altered by pollution and eutrophication; therefore, to properly manage the area one must monitor its ecological state. Remote acoustic methods are useful tools for the monitoring of benthic habitats in many marine areas because they are non-invasive and allow researchers to obtain data from a large area in a short period of time. Currently there is a need to apply these methods in the Baltic Sea. Here we present an analysis of the mechanism of scattering of acoustic waves on seagrass in the Southern Baltic Sea based on the numerical modeling of acoustic wave scattering by the biological tissues of plants. The study was conducted by adapting a model developed on the basis of DWBA (Distorted Wave Born Approximation) developed by Stanton and Chu (2005) for fluid-like objects, including the characteristics of the Southern Baltic seagrass. Input data for the model, including the morphometry of seagrass leaves, their angle of inclination and the density plant cover, was obtained through the analysis of biological materials collected in the Puck Bay in the framework of a research project financed by the Polish Government (Development of hydroacoustic methods for studies of underwater meadows of Puck Bay, 6P04E 051 20). On the basis of the developed model, we have analyzed the dependence of the target strength of a single

  12. Efficient transformer for electromagnetic waves

    Science.gov (United States)

    Miller, R.B.

    A transformer structure for efficient transfer of electromagnetic energy from a transmission line to an unmatched load provides voltage multiplication and current division by a predetermined constant. Impedance levels are transformed by the square of that constant. The structure includes a wave splitter, connected to an input transmission device and to a plurality of output transmission devices. The output transmission devices are effectively connected in parallel to the input transmission device. The output transmission devices are effectively series connected to provide energy to a load. The transformer structure is particularly effective in increasing efficiency of energy transfer through an inverting convolute structure by capturing and transferring energy losses from the inverter to the load.

  13. Near-Shore Floating Wave Energy Converters

    DEFF Research Database (Denmark)

    Ruol, Piero; Zanuttigh, Barbara; Martinelli, Luca

    2011-01-01

    Aim of this note is to analyse the possible application of a Wave Energy Converter (WEC) as a combined tool to protect the coast and harvest energy. Physical model tests are used to evaluate wave transmission past a near-shore floating WEC of the wave activated body type, named DEXA. Efficiency...... and transmission characteristics are approximated to functions of wave height, period and obliquity. Their order of magnitude are 20% and 80%, respectively. It is imagined that an array of DEXA is deployed in front of Marina di Ravenna beach (IT), a highly touristic site of the Adriatic Coast. Based on the CERC...

  14. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  15. Plasma waves

    CERN Document Server

    Swanson, DG

    1989-01-01

    Plasma Waves discusses the basic development and equations for the many aspects of plasma waves. The book is organized into two major parts, examining both linear and nonlinear plasma waves in the eight chapters it encompasses. After briefly discussing the properties and applications of plasma wave, the book goes on examining the wave types in a cold, magnetized plasma and the general forms of the dispersion relation that characterize the waves and label the various types of solutions. Chapters 3 and 4 analyze the acoustic phenomena through the fluid model of plasma and the kinetic effects. Th

  16. Modern acoustic emission technique and its application in aviation industry.

    Science.gov (United States)

    Geng, Rongsheng

    2006-12-22

    This paper proposes the concept of modern acoustic emission (MAE) technique and describes its application in aviation industry. Modern AE is characterized by the combination of AE parameter and waveform analysis based on the understanding of AE source mechanism, the property of sound wave propagation and the interaction between sound wave and the medium in which the sound wave is propagating. Another feature of MAE is characterized by the application of so-called fully digital AE apparatus with low noise, high speed of data transmission and accurate AE source locating capability. MAE is merely an imagination without the realization of the advanced fully digital AE instrument. The application of MAE in monitoring the conditions of aircraft structures during a fatigue test was taken as an example for showing the important role played by AE. Roles of AE in the evaluation of (environment-related) corrosion damage of aircraft were also presented.

  17. Recognition of sine wave modeled consonants by normal hearing and hearing-impaired individuals

    Science.gov (United States)

    Balachandran, Rupa

    Sine wave modeling is a parametric tool for representing the speech signal with a limited number of sine waves. It involves replacing the peaks of the speech spectrum with sine waves and discarding the rest of the lower amplitude components during synthesis. It has the potential to be used as a speech enhancement technique for hearing-impaired adults. The present study answers the following basic questions: (1) Are sine wave synthesized speech tokens more intelligible than natural speech tokens? (2) What is the effect of varying the number of sine waves on consonant recognition in quiet? (3) What is the effect of varying the number of sine waves on consonant recognition in noise? (4) How does sine wave modeling affect the transmission of speech feature in quiet and in noise? (5) Are there differences in recognition performance between normal hearing and hearing-impaired listeners? VCV syllables representing 20 consonants (/p/, /t/, /k/, /b/, /d/, /g/, /f/, /theta/, /s/, /∫/, /v/, /z/, /t∫/, /dy/, /j/, /w/, /r/, /l/, /m/, /n/) in three vowel contexts (/a/, /i/, /u/) were modeled with 4, 8, 12, and 16 sine waves. A consonant recognition task was performed in quiet, and in background noise (+10 dB and 0 dB SNR). Twenty hearing-impaired listeners and six normal hearing listeners were tested under headphones at their most comfortable listening level. The main findings were: (1) Recognition of unprocessed speech was better that of sine wave modeled speech. (2) Asymptotic performance was reached with 8 sine waves in quiet for both normal hearing and hearing-impaired listeners. (3) Consonant recognition performance in noise improved with increasing number of sine waves. (4) As the number of sine waves was decreased, place information was lost first, followed by manner, and finally voicing. (5) Hearing-impaired listeners made more errors then normal hearing listeners, but there were no differences in the error patterns made by both groups.

  18. Propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Il [Kangwon National University, Chuncheon (Korea, Republic of); Choi, Bok Kyoung [Maritime Security Research Center, KIOST, Ansan (Korea, Republic of)

    2014-12-15

    The present study aims to investigate the propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom. The velocities of the guided waves in a 5-mm-thick acrylic plate were measured by using the axial transmission technique. A pure A0 Lamb mode could be successfully launched in the 5-mm-thick acrylic plate through a time reversal process of Lamb waves, consistent with the fact that the time reversal process can automatically compensate for the dispersive nature of Lamb waves. The experimental velocities of the slow guided wave (SGW) and the time-reversed Lamb wave were found to be in reasonable agreement with the theoretical group velocity of the A0 Lamb mode, suggesting that both the SGW and the time-reversed Lamb wave excited in the 5-mm-thick acrylic plate correspond to the A0 Lamb mode. These results suggest that the time reversal process of Lamb waves can be usefully applied to noninvasive characterization of long cortical bones.

  19. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star.......Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star....

  20. Heat Waves

    Science.gov (United States)

    Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and ... having trouble with the heat. If a heat wave is predicted or happening… - Slow down. Avoid strenuous ...