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Sample records for broadly tunable autocorrelator

  1. A broadly tunable autocorrelator for ultra-short, ultra-high power infrared optical pulses

    Energy Technology Data Exchange (ETDEWEB)

    Szarmes, E.B.; Madey, J.M.J. [Duke Univ., Durham, NC (United States)

    1995-12-31

    We describe the design of a crossed-beam, optical autocorrelator that uses an uncoated, birefringent beamsplitter to split a linearly polarized incident pulse into two orthogonally polarized pulses, and a Type II, SHG crystal to generate the intensity autocorrelation function. The uncoated beamsplitter accommodates extremely broad tunability while precluding any temporal distortion of ultrashort optical pulses at the dielectric interface, and the specific design provides efficient operation between 1 {mu}m and 4 {mu}m. Furthermore, the use of Type II SHG completely eliminates any single-beam doubling, so the autocorrelator can be operated at very shallow crossed-beam angles without generating a background pedestal. The autocorrelator has been constructed and installed in the Mark III laboratory at Duke University as a broadband diagnostic for ongoing compression experiments on the chirped-pulse FEL.

  2. Chip scale broadly tunable laser for laser spectrometer

    Science.gov (United States)

    Chao, Tien-Hsin; Lu, Thomas; Davis, Scott R.; Anderson, Michael H.

    2016-04-01

    We are developing an innovative Tunable Laser Spectrometer (TLS) that is compact, broad tuning range (> 200 nm) enabled by an innovative chip-scale (a waveguide based architecture), non-mechanical (voltage- controlled tuning), Waveguide External-cavity Semiconductor Laser (WECSL). This WECSL based TLS, with broad tuning range, will enable the simultaneous measurement of multiple gases abundances in Martian and other planetary atmospheres, adsorbed to soil; and bound to rocks. This monolithic, robust, integrated-optic Tunable Laser Absorption Spectrometer (TLS) will operate in the near infrared and infrared spectral bands. The system architecture, principles of operation and applications of the TLS will be reported in this paper.

  3. GaN-based metamaterial terahertz bandpass filter design: tunability and ultra-broad passband attainment.

    Science.gov (United States)

    Khodaee, M; Banakermani, M; Baghban, H

    2015-10-10

    Engineering metamaterial-based devices such as terahertz bandpass filters (BPFs) play a definitive role in advancement of terahertz technology. In this article, we propose a design procedure to obtain a considerably broadband terahertz BPF at a normal incidence; it shows promising filtering characteristics, including a wide passband of ∼1.34  THz at a central frequency of 1.17 THz, a flat top in a broad band, and high transmission, compared to previous reports. Then, exploiting the voltage-dependent carrier density control in an AlGaN/GaN heterostructure with a Schottky gate configuration, we investigate the tuning of the transmission properties in a narrow-band terahertz filter. A combination of the ultra-wide, flat-top BPF in series with the tunable, narrow band filter designed in the current study offers the ability to tune the desired resonance frequency along with high out-of-band rejection and the suppression of unwanted resonances in a large spectral range. The proposed structure exhibits a frequency tunability of 103 GHz for a voltage change between -8 and 2 V, and a transmission amplitude change of ∼0.51. This scheme may open up a route for the improved design of terahertz filters and modulators.

  4. Broadly tunable mid-infrared VECSEL for multiple components hydrocarbon gas sensing

    Science.gov (United States)

    Rey, J. M.; Fill, M.; Felder, F.; Sigrist, M. W.

    2014-12-01

    A new sensing platform to simultaneously identify and quantify volatile C1 to C4 alkanes in multi-component gas mixtures is presented. This setup is based on an optically pumped, broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) developed for gas detection. The lead-chalcogenide VECSEL is the key component of the presented optical sensor. The potential of the proposed sensing setup is illustrated by experimental absorption spectra obtained from various mixtures of volatile hydrocarbons and water vapor. The sensor has a sub-ppm limit of detection for each targeted alkane in a hydrocarbon gas mixture even in the presence of a high water vapor content.

  5. A tunable, linac based, intense, broad-band THz source forpump-probe experiments

    Energy Technology Data Exchange (ETDEWEB)

    Schmerge, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Corbett, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dolgashev, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Durr, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fazio, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fisher, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Frisch, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gaffney, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Guehr, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hastings, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hettel, B. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hoffmann, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hogan, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Holtkamp, N. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Kirchmann, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Limborg, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lindenberg, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Maxwell, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nilsson, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Raubenheimer, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Reis, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ross, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Z. -X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stupakov, G. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tantawi, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tian, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Wu, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Xiang, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Yakimenko, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-02

    We propose an intense THz source with tunable frequency and bandwidth that can directly interact with the degrees of freedom that determine the properties of materials and thus provides a new tool for controlling and directing these ultrafast processes as well as aiding synthesis of new materials with new functional properties. This THz source will broadly impact our understanding of dynamical processes in matter at the atomic-scale and in real time. Established optical pumping schemes using femtosecond visible frequency laser pulses for excitation are extended into the THz frequency regime thereby enabling resonant excitation of bonds in correlated solid state materials (phonon pumping), to drive low energy electronic excitations, to trigger surface chemistry reactions, and to all-optically bias a material with ultrashort electric fields or magnetic fields. A linac-based THz source can supply stand-alone experiments with peak intensities two orders of magnitude stronger than existing laser-based sources, but when coupled with atomic-scale sensitive femtosecond x-ray probes it opens a new frontier in ultrafast science with broad applications to correlated materials, interfacial and liquid phase chemistry, and materials in extreme conditions.

  6. Thermosensitive Triterpenoid-Appended Polymers with Broad Temperature Tunability Regulated by Host-Guest Chemistry.

    Science.gov (United States)

    Hao, Jie; Gao, Yuxia; Li, Ying; Yan, Qiang; Hu, Jun; Ju, Yong

    2017-09-05

    Thermoresponsive water-soluble polymers are of great importance since they typically show a lower critical solution temperature (LCST) in aqueous media. In this research, the LCST change in broad temperature ranges of copolymers composed of natural glycyrrhetinic acid (GA)-based methacrylate and N,N'-dimethylacrylamides (DMAs) was investigated as a function of the concentration and the content of GA pendants. By complexation of GA pendants with β-cyclodextrin (β-CD), a side-chain polypseudorotaxane was obtained, which exhibited a significant increase in the LCST of copolymers. Moreover, the precisely reversible control of the LCST behavior was realized through adding a competing guest molecule, sodium 1-admantylcarboxylate. This work illustrates a simple and effective approach to endow water-soluble polymers with broad temperature tunability and helps us further understand the effect of a biocompatible host-guest complementary β-CD/GA pair on the thermoresponsive process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Refractory oxide hosts for a high power, broadly tunable laser with high quantum efficiency and method of making same

    Science.gov (United States)

    Chen, Yok; Gonzalez, R.

    1985-07-03

    Refractory oxide crystals having high-quantum efficiency and high thermal stability for use as broadly tunable laser host materials. The crystals are formed by removing hydrogen from a single crystal of the oxide material to a level below about 10/sup 12/ protons per cm/sup 3/ and subsequently thermochemically reducing the oxygen content of the crystal to form sufficient oxygen anion vacancies so that short-lived F/sup +/ luminescence is produced when the crystal is optically excited.

  8. Highly Selective Volatile Organic Compounds Breath Analysis Using a Broadly-Tunable Vertical-External-Cavity Surface-Emitting Laser.

    Science.gov (United States)

    Tuzson, Béla; Jágerská, Jana; Looser, Herbert; Graf, Manuel; Felder, Ferdinand; Fill, Matthias; Tappy, Luc; Emmenegger, Lukas

    2017-06-20

    A broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) is employed in a direct absorption laser spectroscopic setup to measure breath acetone. The large wavelength coverage of more than 30 cm -1 at 3.38 μm allows, in addition to acetone, the simultaneous measurement of isoprene, ethanol, methanol, methane, and water. Despite the severe spectral interferences from water and alcohols, an unambiguous determination of acetone is demonstrated with a precision of 13 ppbv that is achieved after 5 min averaging at typical breath mean acetone levels in synthetic gas samples mimicking human breath.

  9. Broadly, independent-tunable, dual-wavelength mid-infrared ultrafast optical parametric oscillator.

    Science.gov (United States)

    Jin, Yuwei; Cristescu, S M; Harren, Frans J M; Mandon, Julien

    2015-08-10

    We demonstrate a two-crystal mid-infrared dual-wavelength optical parametric oscillator, synchronously pumped by a high power femtosecond Yb:fiber laser. The singly-resonant ring cavity, containing two periodically poled lithium niobate crystals, is capable of generating two synchronized idler wavelengths, independently tunable over 30 THz in the 2.9 - 4.2 μm wavelength region, due to the cascaded quadratic nonlinear effect. The independent tunability of the two idlers makes the optical parametric oscillator a promising source for ultrafast pulse generation towards the THz wavelength region, based on different frequency generation. In addition, the observed frequency doubled idler within the crystal indicates the possibility to realize a broadband optical self-phase locking between pump, signal, idler and higher order generated parametric lights.

  10. Maximum Autocorrelation Factorial Kriging

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.

    2000-01-01

    This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from...

  11. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

    Science.gov (United States)

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2015-06-30

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.

  12. Free space broad-bandwidth tunable laser diode based on Littman configuration for 3D profile measurement

    Science.gov (United States)

    Shirazi, Muhammad Faizan; Kim, Pilun; Jeon, Mansik; Kim, Chang-Seok; Kim, Jeehyun

    2018-05-01

    We developed a tunable laser diode for an optical coherence tomography system that can perform three-dimensional profile measurement using an area scanning technique. The tunable laser diode is designed using an Eagleyard tunable laser diode with a galvano filter. The Littman free space configuration is used to demonstrate laser operation. The line- and bandwidths of this source are 0.27 nm (∼110 GHz) and 43 nm, respectively, at the center wavelength of 860 nm. The output power is 20 mW at an operating current of 150 mA. A step height target is imaged using a wide-area scanning system to show the measurement accuracy of the proposed tunable laser diode. A TEM grid is also imaged to measure the topography and thickness of the sample by proposed tunable laser diode.

  13. Divided pulse soliton self-frequency shift: a multi-color, dual-polarization, power-scalable, broadly tunable optical source.

    Science.gov (United States)

    Zhang, Chenji; Bucklew, Victor; Edwards, Perry; Janisch, Corey; Liu, Zhiwen

    2017-02-01

    A versatile, broadly tunable, power scalable, multi-line, ultrafast source is presented, the operation of which is based on combining principles of pulse division with the phenomenon of the soliton self-frequency shift (SSFS). Interferometric pulse recombination is demonstrated showing that the source can decouple the generally limiting relationship between the output power and the center wavelength in SSFS-based optical sources. Broadly tunable two- and four-color soliton self-frequency shifted pulses are experimentally demonstrated. Simultaneous dual-polarization second-harmonic generation was performed with the source, demonstrating one novel imaging methodology that the source can enable. It is expected that this source architecture will be useful for advancing current nonlinear optical imaging methodologies.

  14. Functional Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus; Nielsen, Allan Aasbjerg

    2005-01-01

    \\verb+~+\\$\\backslash\\$cite{ramsay97} to functional maximum autocorrelation factors (MAF)\\verb+~+\\$\\backslash\\$cite{switzer85,larsen2001d}. We apply the method to biological shapes as well as reflectance spectra. {\\$\\backslash\\$bf Methods}. MAF seeks linear combination of the original variables that maximize autocorrelation between...

  15. Broad tunable photonic microwave generation based on period-one dynamics of optical injection vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Ji, Songkun; Hong, Yanhua; Spencer, Paul S; Benedikt, Johannes; Davies, Iwan

    2017-08-21

    Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers. The variation of the microwave power at the fundamental frequency and the second-harmonic distortion have also been characterized.

  16. Broadly tunable, beta-barium-borate-based, pulsed optical parametric oscillators and their potential applications in medicine

    Science.gov (United States)

    Sobey, Mark S.; Clark, Jim; Johnson, Bertram C.

    1995-05-01

    With the recent availability of Beta Barium Borate (BBO) crystals in useful sizes at acceptable market prices, the promise of Optical Parametric Oscillators (OPOs) becoming practical tunable systems is finally being realized. Wavelength coverage from such systems extends from 420 nm to over 2400 nm when pumped in the UV. For medical applications their usage will be limited in the near term to low repetition rates (suitable for selective absorption applications in medicine such as colored tattoo removal or treating vascular lesions. For such high energy devices peak powers necessitate the use of articulating arms for beam delivery. For high repetition rate systems, energy outputs will be in the range of 100 to 500 (mu) J at kHz frequencies (up to 1 W average power). Peak powers are low enough that fiber optic delivery is possible. These systems may find selective absorption applications in ophthalmology.

  17. Broadly tunable, high-power terahertz radiation up to 73 K from a stand-alone Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} mesa

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Nakade, K.; Shibano, Y.; Saiwai, Y. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Kashiwagi, T.; Minami, H.; Kadowaki, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Yamamoto, T. [Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, M. [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Klemm, R. A. [Department of Physics, University of Central Florida, Orlando, Florida 32816-2385 (United States)

    2014-11-17

    High-power, continuous, broadly tunable THz radiation from 0.29 to 1.06 THz, was obtained from the outer current-voltage characteristic (IVC) branch of a single stand-alone mesa of the high-transition temperature T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ}. The particular metallic film structures placed both beneath and atop the mesas resulted in more efficient heat dissipation, higher allowed applied dc voltages, larger IVC loops, wider emission temperature ranges, and much broader emission frequency tunability than obtained previously.

  18. Tunable and Memory Metamaterials

    Science.gov (United States)

    2015-12-02

    AFRL-AFOSR-VA-TR-2015-0402 TUNABLE AND MEMORY METAMATERIALS Dimitri Basov UNIVERSITY OF CALIFORNIA SAN DIEGO Final Report 12/02/2015 DISTRIBUTION A...DATES COVERED (From - To) 15-08-2010 to 14-08-2015 4. TITLE AND SUBTITLE TUNABLE AND MEMORY METAMATERIALS 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550...common limitations of infrared metamaterials in order to achieve low electromagnetic losses and broad tunability of the electromagnetic response. One

  19. Broadly tunable femtosecond near- and mid-IR source by direct pumping of an OPA with a 41.7 MHz Yb:KGW oscillator.

    Science.gov (United States)

    Krauth, Joachim; Steinmann, Andy; Hegenbarth, Robin; Conforti, Matteo; Giessen, Harald

    2013-05-06

    We generate over half a watt of tunable near-IR (1380-1830 nm) and several hundred milliwatts in the mid-IR (2.4-4.2 µm) as well as milliwatt level mid-IR (4.85-9.33 µm) femtosecond radiation by pumping an optical parametric amplifier directly with a 7.4 W Yb:KGW oscillator at 41.7 MHz repetition rate. We use 5 mm PPLN and 2 mm GaSe as downconversion crystals and seed this process by a supercontinuum from a tapered fiber. The system is extremely simple and very stable and could replace more complex OPOs as tunable light sources.

  20. Tunable laser applications

    CERN Document Server

    Duarte, FJ

    2008-01-01

    Introduction F. J. Duarte Spectroscopic Applications of Tunable Optical Parametric Oscillators B. J. Orr, R. T. White, and Y. He Solid-State Dye Lasers Costela, I. García-Moreno, and R. Sastre Tunable Lasers Based on Dye-Doped Polymer Gain Media Incorporating Homogeneous Distributions of Functional Nanoparticles F. J. Duarte and R. O. James Broadly Tunable External-Cavity Semiconductor Lasers F. J. Duarte Tunable Fiber Lasers T. M. Shay and F. J. Duarte Fiber Laser Overview and Medical Applications

  1. Decomposition using Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    2002-01-01

    , normally we have an ordering of landmarks (variables) along the contour of the objects. For the case with observation ordering the maximum autocorrelation factor (MAF) transform was proposed for multivariate imagery in\\verb+~+\\$\\backslash\\$cite{switzer85}. This corresponds to a R-mode analyse of the data...

  2. Application of mid-infrared cavity-ringdown spectroscopy to trace explosives vapor detection using a broadly tunable (6-8 μm) optical parametric oscillator

    Science.gov (United States)

    Todd, M. W.; Provencal, R. A.; Owano, T. G.; Paldus, B. A.; Kachanov, A.; Vodopyanov, K. L.; Hunter, M.; Coy, S. L.; Steinfeld, J. I.; Arnold, J. T.

    A novel instrument, based on cavity-ringdown spectroscopy (CRDS), has been developed for trace gas detection. The new instrument utilizes a widely tunable optical parametric oscillator (OPO), which incorporates a zinc-germanium-phosphide (ZGP) crystal that is pumped at 2.8 μm by a 25-Hz Er,Cr:YSGG laser. The resultant mid-IR beam profile is nearly Gaussian, with energies exceeding 200 μJ/pulse between 6 and 8 μm, corresponding to a quantum conversion efficiency of approximately 35%. Vapor-phase mid-infrared spectra of common explosives (TNT, TATP, RDX, PETN and Tetryl) were acquired using the CRDS technique. Parts-per-billion concentration levels were readily detected with no sample preconcentration. A collection/flash-heating sequence was implemented in order to enhance detection limits for ambient air sampling. Detection limits as low as 75 ppt for TNT are expected, with similar concentration levels for the other explosives.

  3. Tunable on chip optofluidic laser

    DEFF Research Database (Denmark)

    Bakal, Avraham; Vannahme, Christoph; Kristensen, Anders

    2016-01-01

    On chip tunable laser is demonstrated by realizing a microfluidic droplet array. The periodicity is controlled by the pressure applied to two separate inlets, allowing to tune the lasing frequency over a broad spectral range.......On chip tunable laser is demonstrated by realizing a microfluidic droplet array. The periodicity is controlled by the pressure applied to two separate inlets, allowing to tune the lasing frequency over a broad spectral range....

  4. A simple method to estimate interwell autocorrelation

    Energy Technology Data Exchange (ETDEWEB)

    Pizarro, J.O.S.; Lake, L.W. [Univ. of Texas, Austin, TX (United States)

    1997-08-01

    The estimation of autocorrelation in the lateral or interwell direction is important when performing reservoir characterization studies using stochastic modeling. This paper presents a new method to estimate the interwell autocorrelation based on parameters, such as the vertical range and the variance, that can be estimated with commonly available data. We used synthetic fields that were generated from stochastic simulations to provide data to construct the estimation charts. These charts relate the ratio of areal to vertical variance and the autocorrelation range (expressed variously) in two directions. Three different semivariogram models were considered: spherical, exponential and truncated fractal. The overall procedure is demonstrated using field data. We find that the approach gives the most self-consistent results when it is applied to previously identified facies. Moreover, the autocorrelation trends follow the depositional pattern of the reservoir, which gives confidence in the validity of the approach.

  5. Up to 30 mW of broadly tunable CW green-to-orange light, based on sum-frequency mixing of Cr4+:forsterite and Nd:YVO4 lasers

    DEFF Research Database (Denmark)

    Mortensen, Jesper Liltorp; McWilliam, Allan; G. Leburn, Christopher

    2006-01-01

    Efficient generation of continuous-wave (CW) tunable light in the yellow region is reported. The method is based on sum-frequency mixing of a tunable Cr4+:forsterite laser with a Nd:YVO4 laser. A periodically poled lithium niobate crystal was placed intra-cavity in a Nd:YVO4 laser, and the Cr4+:f...

  6. Broad band exciplex dye lasers

    International Nuclear Information System (INIS)

    Dienes, A.; Shank, C.V.; Trozzolo, A.M.

    1975-01-01

    The disclosure is concerned with exciplex dye lasers, i.e., lasers in which the emitting species is a complex formed only from a constituent in an electronically excited state. Noting that an exciplex laser, favorable from the standpoint of broad tunability, results from a broad shift in the peak emission wavelength for the exciplex relative to the unreacted species, a desirable class resulting in such broad shift is described. Preferred classes of laser media utilizing specified resonant molecules are set forth. (auth)

  7. General simulation algorithm for autocorrelated binary processes

    Science.gov (United States)

    Serinaldi, Francesco; Lombardo, Federico

    2017-02-01

    The apparent ubiquity of binary random processes in physics and many other fields has attracted considerable attention from the modeling community. However, generation of binary sequences with prescribed autocorrelation is a challenging task owing to the discrete nature of the marginal distributions, which makes the application of classical spectral techniques problematic. We show that such methods can effectively be used if we focus on the parent continuous process of beta distributed transition probabilities rather than on the target binary process. This change of paradigm results in a simulation procedure effectively embedding a spectrum-based iterative amplitude-adjusted Fourier transform method devised for continuous processes. The proposed algorithm is fully general, requires minimal assumptions, and can easily simulate binary signals with power-law and exponentially decaying autocorrelation functions corresponding, for instance, to Hurst-Kolmogorov and Markov processes. An application to rainfall intermittency shows that the proposed algorithm can also simulate surrogate data preserving the empirical autocorrelation.

  8. An Autocorrelation Term Method for Curve Fitting

    OpenAIRE

    Houston, Louis M.

    2013-01-01

    The least-squares method is the most popular method for fitting a polynomial curve to data. It is based on minimizing the total squared error between a polynomial model and the data. In this paper we develop a different approach that exploits the autocorrelation function. In particular, we use the nonzero lag autocorrelation terms to produce a system of quadratic equations that can be solved together with a linear equation derived from summing the data. There is a maximum of solutions when th...

  9. Mid-infrared tunable metamaterials

    Science.gov (United States)

    Brener, Igal; Miao, Xiaoyu; Shaner, Eric A; Passmore, Brandon Scott; Jun, Young Chul

    2015-04-28

    A mid-infrared tunable metamaterial comprises an array of resonators on a semiconductor substrate having a large dependence of dielectric function on carrier concentration and a semiconductor plasma resonance that lies below the operating range, such as indium antimonide. Voltage biasing of the substrate generates a resonance shift in the metamaterial response that is tunable over a broad operating range. The mid-infrared tunable metamaterials have the potential to become the building blocks of chip based active optical devices in mid-infrared ranges, which can be used for many applications, such as thermal imaging, remote sensing, and environmental monitoring.

  10. Mid-infrared tunable metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Brener, Igal; Miao, Xiaoyu; Shaner, Eric A.; Passmore, Brandon Scott

    2017-07-11

    A mid-infrared tunable metamaterial comprises an array of resonators on a semiconductor substrate having a large dependence of dielectric function on carrier concentration and a semiconductor plasma resonance that lies below the operating range, such as indium antimonide. Voltage biasing of the substrate generates a resonance shift in the metamaterial response that is tunable over a broad operating range. The mid-infrared tunable metamaterials have the potential to become the building blocks of chip based active optical devices in mid-infrared ranges, which can be used for many applications, such as thermal imaging, remote sensing, and environmental monitoring.

  11. Linear Prediction Using Refined Autocorrelation Function

    Directory of Open Access Journals (Sweden)

    M. Shahidur Rahman

    2007-07-01

    Full Text Available This paper proposes a new technique for improving the performance of linear prediction analysis by utilizing a refined version of the autocorrelation function. Problems in analyzing voiced speech using linear prediction occur often due to the harmonic structure of the excitation source, which causes the autocorrelation function to be an aliased version of that of the vocal tract impulse response. To estimate the vocal tract characteristics accurately, however, the effect of aliasing must be eliminated. In this paper, we employ homomorphic deconvolution technique in the autocorrelation domain to eliminate the aliasing effect occurred due to periodicity. The resulted autocorrelation function of the vocal tract impulse response is found to produce significant improvement in estimating formant frequencies. The accuracy of formant estimation is verified on synthetic vowels for a wide range of pitch frequencies typical for male and female speakers. The validity of the proposed method is also illustrated by inspecting the spectral envelopes of natural speech spoken by high-pitched female speaker. The synthesis filter obtained by the current method is guaranteed to be stable, which makes the method superior to many of its alternatives.

  12. Response predictions using the observed autocorrelation function

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam; H. Brodtkorb, Astrid; Jensen, Jørgen Juncher

    2018-01-01

    -induced response in study. Thus, predicted (future) values ahead of time for a given time history recording are computed through a mathematical combination of the sample autocorrelation function and previous measurements recorded just prior to the moment of action. Importantly, the procedure does not need input...

  13. Crustal thickness across the Trans-European Suture Zone from ambient noise autocorrelations

    Science.gov (United States)

    Becker, G.; Knapmeyer-Endrun, B.

    2018-02-01

    We derive autocorrelations from ambient seismic noise to image the reflectivity of the subsurface and to extract the Moho depth beneath the stations for two different data sets in Central Europe. The autocorrelations are calculated by smoothing the spectrum of the data in order to suppress high amplitude, narrow-band signals of industrial origin, applying a phase autocorrelation algorithm and time-frequency domain phase-weighted stacking. The stacked autocorrelation results are filtered and analysed predominantly in the frequency range of 1-2 Hz. Moho depth is automatically picked inside uncertainty windows obtained from prior information. The processing scheme we developed is applied to data from permanent seismic stations located in different geological provinces across Europe, with varying Moho depths between 25 and 50 km, and to the mainly short period temporary PASSEQ stations along seismic profile POLONAISE P4. The autocorrelation results are spatially and temporarily stable, but show a clear correlation with the existence of cultural noise. On average, a minimum of six months of data is needed to obtain stable results. The obtained Moho depth results are in good agreement with the subsurface model provided by seismic profiling, receiver function estimates and the European Moho depth map. In addition to extracting the Moho depth, it is possible to identify an intracrustal layer along the profile, again closely matching the seismic model. For more than half of the broad-band stations, another change in reflectivity within the mantle is observed and can be correlated with the lithosphere-asthenosphere boundary to the west and a mid-lithospheric discontinuity beneath the East European Craton. With the application of the developed autocorrelation processing scheme to different stations with varying crustal thicknesses, it is shown that Moho depth can be extracted independent of subsurface structure, when station coverage is low, when no strong seismic sources are

  14. Shape Modelling Using Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    2001-01-01

    of Active Shape Models by Timothy Cootes and Christopher Taylor by building new information into the model. This new information consists of two types of prior knowledge. First, in many situation we will be given an ordering of the shapes of the training set. This situation occurs when the shapes....... Both these types of knowledge may be used to defined Shape Maximum Autocorrelation Factors. The resulting point distribution models are compared to ordinary principal components analysis using leave-one-out validation.......This paper addresses the problems of generating a low dimensional representation of the shape variation present in a training set after alignment using Procrustes analysis and projection into shape tangent space. We will extend the use of principal components analysis in the original formulation...

  15. Modeling social influence through network autocorrelation : constructing the weight matrix

    NARCIS (Netherlands)

    Leenders, Roger Th. A. J.

    Many physical and social phenomena are embedded within networks of interdependencies, the so-called 'context' of these phenomena. In network analysis, this type of process is typically modeled as a network autocorrelation model. Parameter estimates and inferences based on autocorrelation models,

  16. Performances of estimators of linear model with auto-correlated ...

    African Journals Online (AJOL)

    Performances of estimators of linear model with auto-correlated error terms when the independent variable is normal. ... On the other hand, the same slope coefficients β , under Generalized Least Squares (GLS) decreased with increased autocorrelation when the sample size T is small. Journal of the Nigerian Association ...

  17. Auto-correlation analysis of ocean surface wind vectors

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    In this work, an auto-correlation analysis of a time series data of surface winds measured in situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time series data available for 240 hours in the month of May, 1999 were subjected to an auto-correlation analysis. The analysis indicates an exponential fall ...

  18. Balance Maintenance in the Upright Body Position: Analysis of Autocorrelation

    Directory of Open Access Journals (Sweden)

    Stodolka¹ Jacek

    2016-04-01

    Full Text Available The present research aimed to analyze values of the autocorrelation function measured for different time values of ground reaction forces during stable upright standing. It was hypothesized that if recording of force in time depended on the quality and way of regulating force by the central nervous system (as a regulator, then the application of autocorrelation for time series in the analysis of force changes in time function would allow to determine regulator properties and its functioning. The study was performed on 82 subjects (students, athletes, senior and junior soccer players and subjects who suffered from lower limb injuries. The research was conducted with the use of two Kistler force plates and was based on measurements of ground reaction forces taken during a 15 s period of standing upright while relaxed. The results of the autocorrelation function were statistically analyzed. The research revealed a significant correlation between a derivative extreme and velocity of reaching the extreme by the autocorrelation function, described as gradient strength. Low correlation values (all statistically significant were observed between time of the autocorrelation curve passing through 0 axis and time of reaching the first peak by the said function. Parameters computed on the basis of the autocorrelation function are a reliable means to evaluate the process of flow of stimuli in the nervous system. Significant correlations observed between the parameters of the autocorrelation function indicate that individual parameters provide similar properties of the central nervous system.

  19. MEASUREMENTS OF STELLAR MAGNETIC FIELDS USING AUTOCORRELATION OF SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Borra, E. F.; Deschatelets, D. [Département de physique, de génie physique et d’optique. Université Laval (Canada)

    2015-11-15

    We present a novel technique that uses the autocorrelation of the spectrum of a star to measure the line broadening caused by the modulus of its average surface magnetic field. The advantage of the autocorrelation comes from the fact that it can detect very small spectral line broadening effects because it averages over many spectral lines and therefore gives an average with a very high signal-to-noise ratio. We validate the technique with the spectra of known magnetic stars and obtain autocorrelation curves that are in full agreement with published magnetic curves obtained with Zeeman splitting. The autocorrelation also gives less noisy curves so that it can be used to obtain very accurate curves. We degrade the resolution of the spectra of these magnetic stars to lower spectral resolutions where the Zeeman splitting is undetectable. At these resolutions, the autocorrelation still gives good quality curves, thereby showing that it can be used to measure magnetic fields in spectra where the Zeeman splitting is significantly smaller than the width of the spectral line. This would therefore allow observing magnetic fields in very faint Ap stars with low-resolution spectrographs, thereby greatly increasing the number of known magnetic stars. It also demonstrates that the autocorrelation can measure magnetic fields in rapidly rotating stars as well as weak magnetic fields that give a Zeeman splitting smaller than the intrinsic width of the spectral lines. Finally, it shows that the autocorrelation can be used to find unknown magnetic stars in low-resolution spectroscopic surveys.

  20. Estimating the variation, autocorrelation, and environmental sensitivity of phenotypic selection

    NARCIS (Netherlands)

    Chevin, Luis-Miguel; Visser, Marcel E.; Tufto, Jarle

    Despite considerable interest in temporal and spatial variation of phenotypic selection, very few methods allow quantifying this variation while correctly accounting for the error variance of each individual estimate. Furthermore, the available methods do not estimate the autocorrelation of

  1. The basis function approach for modeling autocorrelation in ecological data.

    Science.gov (United States)

    Hefley, Trevor J; Broms, Kristin M; Brost, Brian M; Buderman, Frances E; Kay, Shannon L; Scharf, Henry R; Tipton, John R; Williams, Perry J; Hooten, Mevin B

    2017-03-01

    Analyzing ecological data often requires modeling the autocorrelation created by spatial and temporal processes. Many seemingly disparate statistical methods used to account for autocorrelation can be expressed as regression models that include basis functions. Basis functions also enable ecologists to modify a wide range of existing ecological models in order to account for autocorrelation, which can improve inference and predictive accuracy. Furthermore, understanding the properties of basis functions is essential for evaluating the fit of spatial or time-series models, detecting a hidden form of collinearity, and analyzing large data sets. We present important concepts and properties related to basis functions and illustrate several tools and techniques ecologists can use when modeling autocorrelation in ecological data. © 2016 by the Ecological Society of America.

  2. Autocorrelated logistic ridge regression for prediction based on proteomics spectra.

    Science.gov (United States)

    Goeman, Jelle J

    2008-01-01

    This paper presents autocorrelated logistic ridge regression, an extension of logistic ridge regression for ordered covariates that is based on the assumption that adjacent covariates have similar regression coefficients. The method is applied to the analysis of proteomics mass spectra.

  3. Estimation of Conditional Expected Value for Exponentially Autocorrelated Data

    Directory of Open Access Journals (Sweden)

    Kowalczyk Adam

    2017-03-01

    Full Text Available Autocorrelation of signals and measurement data makes it difficult to estimate their statistical characteristics. However, the scope of usefulness of autocorrelation functions for statistical description of signal relation is narrowed down to linear processing models. The use of the conditional expected value opens new possibilities in the description of interdependence of stochastic signals for linear and non-linear models. It is described with relatively simple mathematical models with corresponding simple algorithms of their practical implementation.

  4. Spatial Autocorrelation and Uncertainty Associated with Remotely-Sensed Data

    Directory of Open Access Journals (Sweden)

    Daniel A. Griffith

    2016-06-01

    Full Text Available Virtually all remotely sensed data contain spatial autocorrelation, which impacts upon their statistical features of uncertainty through variance inflation, and the compounding of duplicate information. Estimating the nature and degree of this spatial autocorrelation, which is usually positive and very strong, has been hindered by computational intensity associated with the massive number of pixels in realistically-sized remotely-sensed images, a situation that more recently has changed. Recent advances in spatial statistical estimation theory support the extraction of information and the distilling of knowledge from remotely-sensed images in a way that accounts for latent spatial autocorrelation. This paper summarizes an effective methodological approach to achieve this end, illustrating results with a 2002 remotely sensed-image of the Florida Everglades, and simulation experiments. Specifically, uncertainty of spatial autocorrelation parameter in a spatial autoregressive model is modeled with a beta-beta mixture approach and is further investigated with three different sampling strategies: coterminous sampling, random sub-region sampling, and increasing domain sub-regions. The results suggest that uncertainty associated with remotely-sensed data should be cast in consideration of spatial autocorrelation. It emphasizes that one remaining challenge is to better quantify the spatial variability of spatial autocorrelation estimates across geographic landscapes.

  5. Monitoring autocorrelated process: A geometric Brownian motion process approach

    Science.gov (United States)

    Li, Lee Siaw; Djauhari, Maman A.

    2013-09-01

    Autocorrelated process control is common in today's modern industrial process control practice. The current practice of autocorrelated process control is to eliminate the autocorrelation by using an appropriate model such as Box-Jenkins models or other models and then to conduct process control operation based on the residuals. In this paper we show that many time series are governed by a geometric Brownian motion (GBM) process. Therefore, in this case, by using the properties of a GBM process, we only need an appropriate transformation and model the transformed data to come up with the condition needs in traditional process control. An industrial example of cocoa powder production process in a Malaysian company will be presented and discussed to illustrate the advantages of the GBM approach.

  6. Investigation of Aperiodic Time Processes with Autocorrelation and Fourier Analysis

    Science.gov (United States)

    Exner, Marie Luise

    1958-01-01

    Autocorrelation and frequency analyses of a series of aperiodic time events, in particular, filtered noises and sibilant sounds, were made. The position and band width of the frequency ranges are best obtained from the frequency analysis, but the energies contained in the several bands are most easily obtained from the autocorrelation function. The mean number of zero crossings of the time function was determined from the curvature of the latter function in the vicinity of the zero crossing, and also with the aid of a decimal counter. The second method was found to be more exact.

  7. Binary codes with impulse autocorrelation functions for dynamic experiments

    International Nuclear Information System (INIS)

    Corran, E.R.; Cummins, J.D.

    1962-09-01

    A series of binary codes exist which have autocorrelation functions approximating to an impulse function. Signals whose behaviour in time can be expressed by such codes have spectra which are 'whiter' over a limited bandwidth and for a finite time than signals from a white noise generator. These codes are used to determine system dynamic responses using the correlation technique. Programmes have been written to compute codes of arbitrary length and to compute 'cyclic' autocorrelation and cross-correlation functions. Complete listings of these programmes are given, and a code of 1019 bits is presented. (author)

  8. Auto-correlation analysis of ocean surface wind vectors

    Indian Academy of Sciences (India)

    The nature of the inherent temporal variability of surface winds is analyzed by comparison of winds obtained through different measurement methods. In this work, an auto-correlation analysis of a time series data of surface winds measured in situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time ...

  9. Performances of estimators of linear auto-correlated error model ...

    African Journals Online (AJOL)

    The performances of five estimators of linear models with autocorrelated disturbance terms are compared when the independent variable is exponential. The results reveal that for both small and large samples, the Ordinary Least Squares (OLS) compares favourably with the Generalized least Squares (GLS) estimators in ...

  10. Autocorrelation in queuing network type production systems - revisited

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn

    -production systems (Takahashi and Nakamura, 1998) establishes that autocorrelation plays definitely a non-negligible role in relation to the dimensioning as well as functioning of Kanban-controlled production flow lines . This must logically either imply that production managers are missing an important aspect...

  11. Thirty-two phase sequences design with good autocorrelation ...

    Indian Academy of Sciences (India)

    Sequences with low aperiodic autocorrelation sidelobe levels are useful for channel estima- tion, radar, and .... The SA technique, introduced by Kirkpatrick et al 1983 proved efficient and powerful tool to find optimal or ... the global optimum of a nonlinear multivariable function by carefully controlling the rate of decrease of ...

  12. Performances Of Estimators Of Linear Models With Autocorrelated ...

    African Journals Online (AJOL)

    The performances of five estimators of linear models with Autocorrelated error terms are compared when the independent variable is autoregressive. The results reveal that the properties of the estimators when the sample size is finite is quite similar to the properties of the estimators when the sample size is infinite although ...

  13. Performances of estimators of linear model with auto-correlated ...

    African Journals Online (AJOL)

    A Monte Carlo Study of the small sampling properties of five estimators of a linear model with Autocorrelated error terms is discussed. The independent variable was specified as standard normal data. The estimators of the slop coefficients β with the help of Ordinary Least Squares (OLS), increased with increased ...

  14. Thirty-two phase sequences design with good autocorrelation ...

    Indian Academy of Sciences (India)

    Polyphase Barker Sequences are finite length, uniform complex sequences; the magnitude of their aperiodic autocorrelation sidelobes are bounded by 1. Such sequences have been used in numerous real-world applications such as channel estimation, radar and spread spectrum communication. In this paper, thirty-two ...

  15. Cross- and auto-correlation in early vision.

    Science.gov (United States)

    Barlow, Horace; Berry, David L

    2011-07-07

    Neurons that respond selectively to the orientation of visual stimuli were discovered in V1 more than 50 years ago, but it is still not fully understood how or why this is brought about. We report experiments planned to show whether human observers use cross-correlation or auto-correlation to detect oriented streaks in arrays of randomly positioned dots, expecting that this would help us to understand what David Marr called the 'computational goal' of V1. The streaks were generated by two different methods: either by sinusoidal spatial modulation of the local mean dot density, or by introducing coherent pairs of dots to create moiré patterns, as Leon Glass did. A wide range of dot numbers was used in the randomly positioned arrays, because dot density affects cross- and auto-correlation differently, enabling us to infer which method was used. This difference stems from the fact that the cross-correlation task is limited by random fluctuations in the local mean density of individual dots in the noisy array, whereas the auto-correlation task is limited by fluctuations in the numbers of randomly occurring spurious pairs having the same separation and orientation as the deliberately introduced coherent pairs. After developing a new method using graded dot luminances, we were able to extend the range of dot densities that could be used by a large factor, and convincing results were obtained indicating that the streaks generated by amplitude modulation were discriminated by cross-correlation, while those generated as moiré patterns were discriminated by auto-correlation. Though our current results only apply to orientation selectivity, it is important to know that early vision can do more than simple filtering, for evaluating auto-correlations opens the way to more interesting possibilities, such as the detection of symmetries and suspicious coincidences.

  16. MEMS Tunable Antennas

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Morris, Art; Pedersen, Gert Frølund

    2014-01-01

    Addressing low frequency bands is challenging on small platforms. Tunability is a promising solution to cover the bandwidth required for 4G mobile communication. The work presents two designs and shows that for comparable efficiency and bandwidth, the tunable antenna occupies half the volume requ...

  17. Autocorrelation Properties of OFDM Timing Synchronization Waveforms Employing Pilot Subcarriers

    Directory of Open Access Journals (Sweden)

    Oktay Üreten

    2009-01-01

    Full Text Available We investigate the autocorrelation properties of timing synchronization waveforms that are generated by embedded frequency domain pilot tones in orthogonal frequency division multiplex (OFDM systems. The waveforms are composed by summing a selected number of OFDM subcarriers such that the autocorrelation function (ACF of the resulting time waveform has desirable sidelobe behavior. Analytical expressions for the periodic and aperiodic ACF sidelobe energy are derived. Sufficient conditions for minimum and maximum aperiodic ACF sidelobe energy for a given number of pilot tones are presented. Several useful properties of the pilot design problem, such as invariance under transformations and equivalence of complementary sets are demonstrated analytically. Pilot tone design discussion is expanded to the ACF sidelobe peak minimization problem by including various examples and simulation results obtained from a genetic search algorithm.

  18. Autocorrelation Properties of OFDM Timing Synchronization Waveforms Employing Pilot Subcarriers

    Directory of Open Access Journals (Sweden)

    Taşcıoğlu Selçuk

    2009-01-01

    Full Text Available Abstract We investigate the autocorrelation properties of timing synchronization waveforms that are generated by embedded frequency domain pilot tones in orthogonal frequency division multiplex (OFDM systems. The waveforms are composed by summing a selected number of OFDM subcarriers such that the autocorrelation function (ACF of the resulting time waveform has desirable sidelobe behavior. Analytical expressions for the periodic and aperiodic ACF sidelobe energy are derived. Sufficient conditions for minimum and maximum aperiodic ACF sidelobe energy for a given number of pilot tones are presented. Several useful properties of the pilot design problem, such as invariance under transformations and equivalence of complementary sets are demonstrated analytically. Pilot tone design discussion is expanded to the ACF sidelobe peak minimization problem by including various examples and simulation results obtained from a genetic search algorithm.

  19. Biometric feature extraction using local fractal auto-correlation

    International Nuclear Information System (INIS)

    Chen Xi; Zhang Jia-Shu

    2014-01-01

    Image texture feature extraction is a classical means for biometric recognition. To extract effective texture feature for matching, we utilize local fractal auto-correlation to construct an effective image texture descriptor. Three main steps are involved in the proposed scheme: (i) using two-dimensional Gabor filter to extract the texture features of biometric images; (ii) calculating the local fractal dimension of Gabor feature under different orientations and scales using fractal auto-correlation algorithm; and (iii) linking the local fractal dimension of Gabor feature under different orientations and scales into a big vector for matching. Experiments and analyses show our proposed scheme is an efficient biometric feature extraction approach. (condensed matter: structural, mechanical, and thermal properties)

  20. Momentum autocorrelation function of a classic diatomic chain

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ming B., E-mail: mingbyu@gmail.com

    2016-10-23

    A classical harmonic diatomic chain is studied using the recurrence relations method. The momentum autocorrelation function results from contributions of acoustic and optical branches. By use of convolution theorem, analytical expressions for the acoustic and optical contributions are derived as even-order Bessel function expansions with coefficients given in terms of integrals of elliptic functions in real axis and a contour parallel to the imaginary axis, respectively. - Highlights: • Momentum autocorrelation function of a classic diatomic chain is studied. • It is derived as even-order Bessel function expansion using the convolution theorem. • The expansion coefficients are integrals of elliptic functions. • Addition theorem is used to reduce complex elliptic function to complex sum of real ones.

  1. Convergence of Sample Autocorrelation of Long-Range Dependent Traffic

    Directory of Open Access Journals (Sweden)

    Ming Li

    2013-01-01

    Full Text Available We depict our work on a fundamental issue in the theory of long-range dependent traffic in the aspect of the convergence of sample autocorrelation function (ACF of real traffic. The present results suggest that the sample ACF of traffic is convergent. In addition, we show that the sample size has considerable effects in estimating the sample ACF of traffic. More precisely, a sample ACF of traffic tends to be smoother when the sample size increases.

  2. Smoothing the Sample Autocorrelation of Long-Range-Dependent Traffic

    Directory of Open Access Journals (Sweden)

    Ming Li

    2013-01-01

    Full Text Available This paper depicts our work in smoothing the sample autocorrelation function (ACF of traffic. The experimental results exhibit that the sample ACF of traffic may be smoothed by the way of average. In addition, the results imply that the sum of sample ACFs of traffic convergences. Considering that the traffic data used in this research is long-range dependent (LRD, the latter may be meaningful for the theoretical research of LRD traffic.

  3. Construction of tunable peptide nucleic acid junctions.

    Science.gov (United States)

    Duan, Tanghui; He, Liu; Tokura, Yu; Liu, Xin; Wu, Yuzhou; Shi, Zhengshuang

    2018-03-15

    We report here the construction of 3-way and 4-way peptide nucleic acid (PNA) junctions as basic structural units for PNA nanostructuring. The incorporation of amino acid residues into PNA chains makes PNA nanostructures with more structural complexity and architectural flexibility possible, as exemplified by building 3-way PNA junctions with tunable nanopores. Given that PNA nanostructures have good thermal and enzymatic stabilities, they are expected to have broad potential applications in biosensing, drug delivery and bioengineering.

  4. Tunable Handset Antenna

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Foroozanfard, Ehsan; Morris, Art

    2017-01-01

    With the future LTE auction for TV white spaces at 600 MHz, there is a strong need for efficient handset antennas operating at very low frequencies. This paper shows a tunable antenna covering the LTE bands from 600 MHz to 2.6 GHz. The antenna uses state-of-the-art MEMS tunable capacitors in order...... to reconfigure its operating frequency. In this work, the design mitigates the tuning loss with a tunable extended ground plane. The resulting dual-resonant antenna exhibits a peak total efficiency of -3.9 dB at 600 MHz....

  5. Tunable Optical Polymer Systems

    National Research Council Canada - National Science Library

    Jenekhe, S. A; Bard, Allen J; Chen, S. H; Hammond, P. T; Rothberg, L. J

    2004-01-01

    This multidisciplinary university research initiative (MURI) program investigated tunable optical polymer systems suitable for large-area color-switchable coatings and devices, displays, sensors, and other electronic applications...

  6. Tunable micro-optics

    CERN Document Server

    Duppé, Claudia

    2015-01-01

    Presenting state-of-the-art research into the dynamic field of tunable micro-optics, this is the first book to provide a comprehensive survey covering a varied range of topics including novel materials, actuation concepts and new imaging systems in optics. Internationally renowned researchers present a diverse range of chapters on cutting-edge materials, devices and subsystems, including soft matter, artificial muscles, tunable lenses and apertures, photonic crystals, and complete tunable imagers. Special contributions also provide in-depth treatment of micro-optical characterisation, scanners, and the use of natural eye models as inspiration for new concepts in advanced optics. With applications extending from medical diagnosis to fibre telecommunications, Tunable Micro-optics equips readers with a solid understanding of the broader technical context through its interdisciplinary approach to the realisation of new types of optical systems. This is an essential resource for engineers in industry and academia,...

  7. Aspects of High-Q Tunable Antennas and Their Deployment for 4G Mobile Communications

    DEFF Research Database (Denmark)

    Bahramzy, Pevand; Jagielski, Ole; Svendsen, Simon

    2016-01-01

    Tunable antennas are very promising for future generations of mobile communications, where broad frequency coverage will be required increasingly. This work describes the design of small high-Quality factor (Q) tunable antennas based on Micro-Electro-Mechanical Systems (MEMS), which are capable o...

  8. Distributions of Autocorrelated First-Order Kinetic Outcomes: Illness Severity.

    Directory of Open Access Journals (Sweden)

    James D Englehardt

    Full Text Available Many complex systems produce outcomes having recurring, power law-like distributions over wide ranges. However, the form necessarily breaks down at extremes, whereas the Weibull distribution has been demonstrated over the full observed range. Here the Weibull distribution is derived as the asymptotic distribution of generalized first-order kinetic processes, with convergence driven by autocorrelation, and entropy maximization subject to finite positive mean, of the incremental compounding rates. Process increments represent multiplicative causes. In particular, illness severities are modeled as such, occurring in proportion to products of, e.g., chronic toxicant fractions passed by organs along a pathway, or rates of interacting oncogenic mutations. The Weibull form is also argued theoretically and by simulation to be robust to the onset of saturation kinetics. The Weibull exponential parameter is shown to indicate the number and widths of the first-order compounding increments, the extent of rate autocorrelation, and the degree to which process increments are distributed exponential. In contrast with the Gaussian result in linear independent systems, the form is driven not by independence and multiplicity of process increments, but by increment autocorrelation and entropy. In some physical systems the form may be attracting, due to multiplicative evolution of outcome magnitudes towards extreme values potentially much larger and smaller than control mechanisms can contain. The Weibull distribution is demonstrated in preference to the lognormal and Pareto I for illness severities versus (a toxicokinetic models, (b biologically-based network models, (c scholastic and psychological test score data for children with prenatal mercury exposure, and (d time-to-tumor data of the ED01 study.

  9. Stable Blind Deconvolution over the Reals from Additional Autocorrelations

    KAUST Repository

    Walk, Philipp

    2017-10-22

    Recently the one-dimensional time-discrete blind deconvolution problem was shown to be solvable uniquely, up to a global phase, by a semi-definite program for almost any signal, provided its autocorrelation is known. We will show in this work that under a sufficient zero separation of the corresponding signal in the $z-$domain, a stable reconstruction against additive noise is possible. Moreover, the stability constant depends on the signal dimension and on the signals magnitude of the first and last coefficients. We give an analytical expression for this constant by using spectral bounds of Vandermonde matrices.

  10. Size determinations of plutonium colloids using autocorrelation photon spectroscopy

    International Nuclear Information System (INIS)

    Triay, I.R.; Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Hobart, D.E.; Palmer, P.D.; Newton, T.W.; Thompson, J.L.

    1989-01-01

    Autocorrelation Photon Spectroscopy (APS) is a light-scattering technique utilized to determine the size distribution of colloidal suspensions. The capabilities of the APS methodology have been assessed by analyzing colloids of known sizes. Plutonium(IV) colloid samples were prepared by a variety of methods including: dilution; peptization; and alpha-induced auto-oxidation of Pu(III). The size of theses Pu colloids was analyzed using APS. The sizes determined for the Pu colloids studied varied from 1 to 370 nanometers. 7 refs., 5 figs., 3 tabs

  11. Spectral velocity estimation using autocorrelation functions for sparse data sets

    DEFF Research Database (Denmark)

    2006-01-01

    -mode image for orientation, and data for this has to acquired interleaved with the flow data. The power spectrum can be calculated from the Fourier transform of the autocorrelation function Ry (k), where its span of lags k is given by the number of emission N in the data segment for velocity estimation......The distribution of velocities of blood or tissue is displayed using ultrasound scanners by finding the power spectrum of the received signal. This is currently done by making a Fourier transform of the received signal and then showing spectra in an M-mode display. It is desired to show a B....... The lag corresponds to the difference in pulse number, so that for lag k data from emission i is correlated with i + k. The autocorrelation for lag k can be averaged over N-k pairs of emissions. It is possible to calculate Ry (k) for a sparse set of emissions, as long as all combinations of emissions...

  12. Extraction of scattering echo time by surf noise background subtracted autocorrelation.

    Science.gov (United States)

    Li, Xiaolei; Chi, Jing; Gao, Dazhi; Li, Jie; Wang, Ning

    2017-07-01

    Extracting echo time is an important step in scatterer detection by ambient noise, while in general the scattered signal is weak and submerged in the background. An experiment of a Polyvinyl chloride pipe in a coastline surf noise environment is designed to extract the pipe's echo time by noise autocorrelation. As expected, the scattered wave of the pipe is submerged in an autocorrelation signal. A method called background subtracted autocorrelation is proposed in this paper, which can retrieve scattered echo time from autocorrelation signal effectively. And the biggest relative error of extracted echo time is less than 2% in the experiment.

  13. Exploring autocorrelations in two-flavor Wilson Lattice QCD using DD-HMC algorithm

    Science.gov (United States)

    Chowdhury, Abhishek; De, Asit K.; De Sarkar, Sangita; Harindranath, A.; Maiti, Jyotirmoy; Mondal, Santanu; Sarkar, Anwesa

    2013-05-01

    We perform an extensive study of the autocorrelation of several observables in lattice QCD with two degenerate flavors of unimproved Wilson fermions and Wilson gauge action using the DD-HMC algorithm. We show that (1) at a given lattice spacing, autocorrelation of topological susceptibility and unsmeared plaquette show indication of a decrease with decreasing quark mass, (2) autocorrelation of topological susceptibility and topological charge density correlator increase with decreasing lattice spacing but the effect is milder in the latter case and (3) increasing the size and the smear level increase the autocorrelation of smeared Wilson loop.

  14. Tunable Microfluidic Dye Laser

    DEFF Research Database (Denmark)

    Olsen, Brian Bilenberg; Helbo, Bjarne; Kutter, Jörg Peter

    2003-01-01

    We present a tunable microfluidic dye laser fabricated in SU-8. The tunability is enabled by integrating a microfluidic diffusion mixer with an existing microfluidic dye laser design by Helbo et al. By controlling the relative flows in the mixer between a dye solution and a solvent......, the concentration of dye in the laser cavity can be adjusted, allowing the wavelength to be tuned. Wavelength tuning controlled by the dye concentration was demonstrated with macroscopic dye lasers already in 1971, but this principle only becomes practically applicable by the use of microfluidic mixing...

  15. Forecast model applied to quality control with autocorrelational data

    Directory of Open Access Journals (Sweden)

    Adriano Mendonça Souza

    2013-11-01

    Full Text Available This research approaches the prediction models applied to industrial processes, in order to check the stability of the process by means of control charts, applied to residues from linear modeling. The data used for analysis refers to the moisture content, permeability and compression resistance to the green (RCV, belonging to the casting process of green sand molding in A Company, which operates in the casting and machining, for which dynamic multivariate regression model was set. As the observations were auto-correlated, it was necessary to seek a mathematical model that produces independent and identically distribuibed residues. The models found make possible to understand the variables behavior, assisting in the achievement of the forecasts and in the monitoring of the referred process. Thus, it can be stated that the moisture content is very unstable comparing to the others variables.

  16. Tunability enhanced electromagnetic wiggler

    Science.gov (United States)

    Schlueter, R.D.; Deis, G.A.

    1992-03-24

    The invention discloses a wiggler used in synchrotron radiation sources and free electron lasers, where each pole is surrounded by at least two electromagnetic coils. The electromagnetic coils are energized with different amounts of current to provide a wide tunable range of the on-axis magnetic flux density, while preventing magnetic saturation of the poles. 14 figs.

  17. The specification of weight structures in network autocorrelation models of social influence

    NARCIS (Netherlands)

    Leenders, Roger Th.A.J.

    2002-01-01

    Many physical and social phenomena are embedded within networks of interdependencies, the so-called 'context' of these phenomena. In network analysis, this type of process is typically modeled as a network autocorrelation model. Parameter estimates and inferences based on autocorrelation models,

  18. A GaAs/AlAs superlattice autocorrelator for picosecond THz radiation pulses

    NARCIS (Netherlands)

    Winnerl, S.; Pesahl, S.; Schomburg, E.; Grenzer, J.; Renk, K. F.; Pellemans, H. P. M.; van der Meer, A. F. G.; Pavel' ev, D. G.; Koschurinov, Y.; Ignatov, A. A.; Melzer, B.; Ustinov, V.; Ivanov, S.; Kop' ev, P. S.

    1999-01-01

    We report on a GaAs/AlAs, wide-miniband, superlattice autocorrelator for picosecond THz radiation pulses (operated at room temperature); the autocorrelator is based on the THz radiation-induced reduction of current through the superlattice. THz radiation (frequency 7.2 THz) from the FELIX

  19. Generalised partial autocorrelations and the mutual information between past and future

    DEFF Research Database (Denmark)

    Proietti, Tommaso; Luati, Alessandra

    the generalized partial autocorrelations as the partial autocorrelation coefficients of an auxiliary process, we derive their properties and relate them to essential features of the original process. Based on a parameterisation suggested by Barndorff-Nielsen and Schou (1973) and on Whittle likelihood, we develop...

  20. MATLAB-Based Program for Teaching Autocorrelation Function and Noise Concepts

    Science.gov (United States)

    Jovanovic Dolecek, G.

    2012-01-01

    An attractive MATLAB-based tool for teaching the basics of autocorrelation function and noise concepts is presented in this paper. This tool enhances traditional in-classroom lecturing. The demonstrations of the tool described here highlight the description of the autocorrelation function (ACF) in a general case for wide-sense stationary (WSS)…

  1. The Effect of Autocorrelation on the Hotelling T-2 Control Chart

    DEFF Research Database (Denmark)

    Vanhatalo, Erik; Kulahci, Murat

    2015-01-01

    . It is well known that the autocorrelation affects the false alarm rate and the shift-detection ability of the traditional univariate control charts. However, how the false alarm rate and the shiftdetection ability of the Hotelling T-2 control chart are affected by various autocorrelation and cross......- correlation structures for different magnitudes of shifts in the process mean is not fully explored in the literature. In this article, the performance of the Hotelling T-2 control chart for different shift sizes and various autocorrelation and cross- correlation structures are compared based on the average...... run length using simulated data. Three different approaches in constructing the Hotelling T-2 chart are studied for two different estimates of the covariance matrix: (i) ignoring the autocorrelation and using the raw data with theoretical upper control limits; (ii) ignoring the autocorrelation...

  2. The 2010 Broad Prize

    Science.gov (United States)

    Education Digest: Essential Readings Condensed for Quick Review, 2011

    2011-01-01

    A new data analysis, based on data collected as part of The Broad Prize process, provides insights into which large urban school districts in the United States are doing the best job of educating traditionally disadvantaged groups: African-American, Hispanics, and low-income students. Since 2002, The Eli and Edythe Broad Foundation has awarded The…

  3. Tunable plasmonic filter based on graphene-layered waveguide

    Science.gov (United States)

    Feng, Yuncai; Liu, Youwen; Shi, Yaoyao; Teng, Jinghua

    2018-03-01

    We propose a tunable band-stop plasmonic filter based on monolayer graphene with different thickness of structure, and the corresponding transmission characteristic is numerically investigated by using finite-difference time-domain (FDTD) method. The results show that the proposed filter can achieve a broad stopband that can be tuned by various physical parameters such as the chemical potential of graphene, the thickness of packing layers and so on. Our studies may be important for designing tunable optical filter, the fabrication of nano-integrated plasmonic circuits and the refractive index sensitive sensors.

  4. MEMS for Tunable Photonic Metamaterial Applications

    Science.gov (United States)

    Stark, Thomas

    Photonic metamaterials are materials whose optical properties are derived from artificially-structured sub-wavelength unit cells, rather than from the bulk properties of the constituent materials. Examples of metamaterials include plasmonic materials, negative index materials, and electromagnetic cloaks. While advances in simulation tools and nanofabrication methods have allowed this field to grow over the past several decades, many challenges still exist. This thesis addresses two of these challenges: fabrication of photonic metamaterials with tunable responses and high-throughput nanofabrication methods for these materials. The design, fabrication, and optical characterization of a microelectromechanical systems (MEMS) tunable plasmonic spectrometer are presented. An array of holes in a gold film, with plasmon resonance in the mid-infrared, is suspended above a gold reflector, forming a Fabry-Perot interferometer of tunable length. The spectra exhibit the convolution of extraordinary optical transmission through the holes and Fabry-Perot resonances. Using MEMS, the interferometer length is modulated from 1.7 mum to 21.67 mum , thereby tuning the free spectral range from about 2900 wavenumbers to 230.7 wavenumbers and shifting the reflection minima and maxima across the infrared. Due to its broad spectral tunability in the fingerprint region of the mid-infrared, this device shows promise as a tunable biological sensing device. To address the issue of high-throughput, high-resolution fabrication of optical metamaterials, atomic calligraphy, a MEMS-based dynamic stencil lithography technique for resist-free fabrication of photonic metamaterials on unconventional substrates, has been developed. The MEMS consists of a moveable stencil, which can be actuated with nanometer precision using electrostatic comb drive actuators. A fabrication method and flip chip method have been developed, enabling evaporation of metals through the device handle for fabrication on an

  5. On the 2nd order autocorrelation of an XUV attosecond pulse train

    International Nuclear Information System (INIS)

    Tzallas, P.; Benis, E.; Nikolopoulos, L.A.A.; Tsakiris, G.D.; Witte, K.; Charalambidis, P

    2005-01-01

    Full text: We present the first direct measurement of sub-fs light bunching that has been achieved, extending well established fs optical metrology to XUV as pulses. A mean train pulse duration of 780 as has been extracted through a 2 nd order autocorrelation approach, utilizing a nonlinear effect that is induced solely by the XUV radiation to be characterized. The approach is based on (i) a bisected spherical mirror XUV wavefront divider used as an autocorrelator and (ii) the two photon ionization of atomic He by a superposition of the 7 th to the 15 th harmonic of a Ti:sapph laser. The measured temporal mean width is more than twice its Fourier transform limited (FTL) value, in contrast to the as train pulse durations measured through other approaches, which where found much closer to the FTL values. We have investigated, and discuss here the origin of this discrepancy. An assessment of the validity of the 2 nd order AC approach for the broad band XUV radiation of as pulses is implemented through ab initio calculations (solution of the 3D TDSE of He in the presence of the superposition of the harmonic superposition) modeling the spectral and temporal response of the two-XUV-photon He ionization detector employed. It is found that both the spectral and temporal response are not affecting the measured duration. The mean width of the as train bursts is estimated from the spectral phases of the individual harmonics as they result from the rescattering model, taking into account the spatially modulated temporal width of the radiation due to the spatiotemporal intensity distribution of the driving field during the harmonic generation process. The measured value is found in reasonable agreement with the estimated duration. The method used for the 2 nd order AC in itself initiates further XUV-pump-XUV-probe studies of sub-fs-scale dynamics and at the same time becomes highly pertinent in connection with nonlinear experiments using XUV free - electron laser sources. Refs

  6. Tunable surface plasmon devices

    Science.gov (United States)

    Shaner, Eric A [Rio Rancho, NM; Wasserman, Daniel [Lowell, MA

    2011-08-30

    A tunable extraordinary optical transmission (EOT) device wherein the tunability derives from controlled variation of the dielectric constant of a semiconducting material (semiconductor) in evanescent-field contact with a metallic array of sub-wavelength apertures. The surface plasmon resonance wavelength can be changed by changing the dielectric constant of the dielectric material. In embodiments of this invention, the dielectric material is a semiconducting material. The dielectric constant of the semiconducting material in the metal/semiconductor interfacial region is controllably adjusted by adjusting one or more of the semiconductor plasma frequency, the concentration and effective mass of free carriers, and the background high-frequency dielectric constant in the interfacial region. Thermal heating and/or voltage-gated carrier-concentration changes may be used to variably adjust the value of the semiconductor dielectric constant.

  7. Adaptive compressed sensing recovery utilizing the property of signal's autocorrelations.

    Science.gov (United States)

    Fu, Changjun; Ji, Xiangyang; Dai, Qionghai

    2012-05-01

    Perfect compressed sensing (CS) recovery can be achieved when a certain basis space is found to sparsely represent the original signal. However, due to the diversity of the signals, there does not exist a universal predetermined basis space that can sparsely represent all kinds of signals, which results in an unsatisfying performance. To improve the accuracy of recovered signal, this paper proposes an adaptive basis CS reconstruction algorithm by minimizing the rank of an accumulated matrix (MRAM), whose eigenvectors approximate the optimal basis sparsely representing the original signal. The accumulated matrix is constructed to efficiently exploit the second-order statistical property of the signal's autocorrelations. Based on the theory of matrix completion, MRAM reconstructs the original signal from its random projections under the observation that the constructed accumulated matrix is of low rank for most natural signals such as periodic signals and those coming from an autoregressive stationary process. Experimental results show that the proposed MRAM efficiently improves the reconstruction quality compared with the existing algorithms.

  8. Tunable laser optics

    CERN Document Server

    Duarte, FJ

    2015-01-01

    This Second Edition of a bestselling book describes the optics and optical principles needed to build lasers. It also highlights the optics instrumentation necessary to characterize laser emissions and focuses on laser-based optical instrumentation. The book emphasizes practical and utilitarian aspects of relevant optics including the essential theory. This revised, expanded, and improved edition contains new material on tunable lasers and discusses relevant topics in quantum optics.

  9. Tunable high pressure lasers

    Science.gov (United States)

    Hess, R. V.

    1976-01-01

    Atmospheric transmission of high energy CO2 lasers is considerably improved by high pressure operation which, due to pressure broadening, permits tuning the laser lines off atmospheric absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers and for vertical transmission through the entire atmosphere. Applications of tunable high pressure CO2 lasers to energy transmission and to remote sensing are discussed along with initial efforts in tuning high pressure CO2 lasers.

  10. Adaptive endpoint detection of seismic signal based on auto-correlated function

    International Nuclear Information System (INIS)

    Fan Wanchun; Shi Ren

    2001-01-01

    Based on the analysis of auto-correlation function, the notion of the distance between auto-correlation function was quoted, and the characterization of the noise and the signal with noise were discussed by using the distance. Then, the method of auto- adaptable endpoint detection of seismic signal based on auto-correlated similarity was summed up. The steps of implementation and determining of the thresholds were presented in detail. The experimental results that were compared with the methods based on artificial detecting show that this method has higher sensitivity even in a low signal with noise ratio circumstance

  11. Color-tunable photoluminescence from In-doped CdS nanowires

    Science.gov (United States)

    Xu, Jinyou; Quan, Songli; Zou, Zhijun; Guo, Pengfei; Lu, Yang; Yan, Hailong; Luo, Yongsong

    2016-05-01

    Color-tunable emission from semiconductor nanostructures holds promising applications in developing multi-color/color-tunable nano-devices. Herein, we reported the growth of In-doped CdS nanowires with various dopant concentrations via a thermal evaporation method. Optical measurement revealed the photoluminescence of these doped nanowires consists of a narrow bandedge emission and a broad trap-state emission, and the intensity ratio between them is tunable depending on excitation laser intensities and trap-state concentrations. On the basis of this variable intensity ratio, a tunable photoluminescent color from red to green was demonstrated. Our work indicates that trap-state emission from doped nanostructures might be useful for color-tunable emissions.

  12. Tunable X-ray source

    Science.gov (United States)

    Boyce, James R [Williamsburg, VA

    2011-02-08

    A method for the production of X-ray bunches tunable in both time and energy level by generating multiple photon, X-ray, beams through the use of Thomson scattering. The method of the present invention simultaneously produces two X-ray pulses that are tunable in energy and/or time.

  13. Tunable femtosecond Cherenkov fiber laser

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Svane, Ask Sebastian; Lægsgaard, Jesper

    2014-01-01

    We demonstrate electrically-tunable femtosecond Cherenkov fiber laser output at the visible range. Using an all-fiber, self-starting femtosecond Yb-doped fiber laser as the pump source and nonlinear photonic crystal fiber link as the wave-conversion medium, ultrafast, milliwatt-level, tunable...

  14. MLS/Aura L1 Radiances from Digital Autocorrelators V004

    Data.gov (United States)

    National Aeronautics and Space Administration — ML1RADD is the EOS Aura Microwave Limb Sounder (MLS) product containing the level 1 radiances from the digital autocorrelators. The current version is 4.2. Data...

  15. Performing T-tests to Compare Autocorrelated Time Series Data Collected from Direct-Reading Instruments.

    Science.gov (United States)

    O'Shaughnessy, Patrick; Cavanaugh, Joseph E

    2015-01-01

    Industrial hygienists now commonly use direct-reading instruments to evaluate hazards in the workplace. The stored values over time from these instruments constitute a time series of measurements that are often autocorrelated. Given the need to statistically compare two occupational scenarios using values from a direct-reading instrument, a t-test must consider measurement autocorrelation or the resulting test will have a largely inflated type-1 error probability (false rejection of the null hypothesis). A method is described for both the one-sample and two-sample cases which properly adjusts for autocorrelation. This method involves the computation of an "equivalent sample size" that effectively decreases the actual sample size when determining the standard error of the mean for the time series. An example is provided for the one-sample case, and an example is given where a two-sample t-test is conducted for two autocorrelated time series comprised of lognormally distributed measurements.

  16. MLS/Aura L1 Radiances from Digital Autocorrelators V002

    Data.gov (United States)

    National Aeronautics and Space Administration — ML1RADD is the EOS Aura Microwave Limb Sounder (MLS) product containing the level 1 radiances from the digital autocorrelators. The current version is 2.3. Data...

  17. Tunable resistance coatings

    Science.gov (United States)

    Elam, Jeffrey W.; Mane, Anil U.

    2015-08-11

    A method and article of manufacture of intermixed tunable resistance composite materials containing at least one of W:Al.sub.2O.sub.3, Mo:Al.sub.2O.sub.3 or M:Al.sub.2O.sub.3 where M is a conducting compound containing either W or Mo. A conducting material and an insulating material are deposited by such methods as ALD or CVD to construct composites with intermixed materials which do not have structure or properties like their bulk counterparts.

  18. MEMS Tunable nanostructured photodetector

    DEFF Research Database (Denmark)

    Learkthanakhachon, Supannee

    This thesis was prepared at the department of Photonics Engineering, the Technical University of Denmark in fulfilment of the requirements for acquiring a Philosophiae doctor (Ph.D.) in Photonics Engineering. The thesis deals with the design and fabrication of tunable resonant......-cavity-enhanced photodetector using dielectric subwavelength gratings as reflectors operating at 1550 nm optical communication wavelength. The main work in this thesis divided equally into device design and process development. The properties of dielectric subwavelength grating are described. The main result of the thesis...

  19. Tunable multiwalled nanotube resonator

    Science.gov (United States)

    Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

    2013-11-05

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  20. Tunable Nitride Josephson Junctions.

    Energy Technology Data Exchange (ETDEWEB)

    Missert, Nancy A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Henry, Michael David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lewis, Rupert M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howell, Stephen W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolfley, Steven L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brunke, Lyle Brent [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolak, Matthaeus [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-12-01

    We have developed an ambient temperature, SiO2/Si wafer - scale process for Josephson junctions based on Nb electrodes and Ta x N barriers with tunable electronic properties. The films are fabricated by magnetron sputtering. The electronic properties of the TaxN barriers are controlled by adjusting the nitrogen flow during sputtering. This technology offers a scalable alternative to the more traditional junctions based on AlOx barriers for low - power, high - performance computing.

  1. Integrated tunable CMOS laser.

    Science.gov (United States)

    Creazzo, Timothy; Marchena, Elton; Krasulick, Stephen B; Yu, Paul K L; Van Orden, Derek; Spann, John Y; Blivin, Christopher C; He, Lina; Cai, Hong; Dallesasse, John M; Stone, Robert J; Mizrahi, Amit

    2013-11-18

    An integrated tunable CMOS laser for silicon photonics, operating at the C-band, and fabricated in a commercial CMOS foundry is presented. The III-V gain medium section is embedded in the silicon chip, and is hermetically sealed. The gain section is metal bonded to the silicon substrate creating low thermal resistance into the substrate and avoiding lattice mismatch problems. Optical characterization shows high performance in terms of side mode suppression ratio, relative intensity noise, and linewidth that is narrow enough for coherent communications.

  2. Improving Seismic Velocity Models with Constraints from Autocorrelation of Ambient Seismic Noise and Signal

    Science.gov (United States)

    2016-03-24

    AFRL-RV-PS- AFRL-RV-PS- TR-2016-0098 TR-2016-0098 IMPROVING SEISMIC VELOCITY MODELS WITH CONSTRAINTS FROM AUTOCORRELATION OF AMBIENT SEISMIC ...TYPE Final Report 3. DATES COVERED (From - To) 24 Apr 2014 – 24 Mar 2016 4. TITLE AND SUBTITLE Improving Seismic Velocity Models with Constraints from...Autocorrelation of Ambient Seismic Noise and Signal 5a. CONTRACT NUMBER FA9453-14-C-0214 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F 6

  3. Rotation Periods of 34,030 Kepler Main-sequence Stars: The Full Autocorrelation Sample

    Science.gov (United States)

    McQuillan, A.; Mazeh, T.; Aigrain, S.

    2014-04-01

    We analyzed three years of data from the Kepler space mission to derive rotation periods of main-sequence stars below 6500 K. Our automated autocorrelation-based method detected rotation periods between 0.2 and 70 days for 34,030 (25.6%) of the 133,030 main-sequence Kepler targets (excluding known eclipsing binaries and Kepler Objects of Interest), making this the largest sample of stellar rotation periods to date. In this paper we consider the detailed features of the now well-populated period-temperature distribution and demonstrate that the period bimodality, first seen by McQuillan et al. in the M-dwarf sample, persists to higher masses, becoming less visible above 0.6 M ⊙. We show that these results are globally consistent with the existing ground-based rotation-period data and find that the upper envelope of the period distribution is broadly consistent with a gyrochronological age of 4.5 Gyr, based on the isochrones of Barnes, Mamajek, & Hillenbrand and Meibom et al. We also performed a detailed comparison of our results to those of Reinhold et al. and Nielsen et al., who measured rotation periods of field stars observed by Kepler. We examined the amplitude of periodic variability for the stars with detection rotation periods, and found a typical range between ~950 ppm (5th percentile) and ~22,700 ppm (95th percentile), with a median of ~5600 ppm. We found typically higher amplitudes for shorter periods and lower effective temperatures, with an excess of low-amplitude stars above ~5400 K.

  4. Tunable Topological Phononic Crystals

    KAUST Repository

    Chen, Zeguo

    2016-05-27

    Topological insulators first observed in electronic systems have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial band gaps. Such band gaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that we verify by the Chern number calculation and edge-mode analysis. We develop a complete model based on the tight binding to uncover the physical mechanisms of the topological transition. Both the model and numerical simulations show that the topology of the band gap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.

  5. Electrothermally Tunable Arch Resonator

    KAUST Repository

    Hajjaj, Amal Z.

    2017-03-18

    This paper demonstrates experimentally, theoretically, and numerically a wide-range tunability of electrothermally actuated microelectromechanical arch beams. The beams are made of silicon and are intentionally fabricated with some curvature as in-plane shallow arches. An electrothermal voltage is applied between the anchors of the beam generating a current that controls the axial stress caused by thermal expansion. When the electrothermal voltage increases, the compressive stress increases inside the arch beam. This leads to an increase in its curvature, thereby increasing its resonance frequencies. We show here that the first resonance frequency can increase monotonically up to twice its initial value. We show also that after some electrothermal voltage load, the third resonance frequency starts to become more sensitive to the axial thermal stress, while the first resonance frequency becomes less sensitive. These results can be used as guidelines to utilize arches as wide-range tunable resonators. Analytical results based on the nonlinear Euler Bernoulli beam theory are generated and compared with the experimental data and the results of a multi-physics finite-element model. A good agreement is found among all the results. [2016-0291

  6. Tunable grating with active feedback

    Science.gov (United States)

    Rosset, Samuel; O'Brien, Benjamin M.; Gisby, Todd; Xu, Daniel; Shea, Herbert R.; Anderson, Iain A.

    2013-04-01

    We report on the use of capacitive self-sensing to operate a DEA-based tunable grating in closed-loop mode. Due to their large strain capabilities, DEAs are key candidates for tunable optics applications. However, the viscoelasticity of elastomers is detrimental for applications that require long-term stability, such as tunable gratings and lenses. We show that capacitive sensing of the electrode strain can be used to suppress the strain drift and increase the response speed of silicone-based actuators. On the other hand, VHB actuators exhibit a time-dependent permittivity, which causes a drift between the device capacitance and its strain.

  7. Spatial Autocorrelation Can Generate Stronger Correlations between Range Size and Climatic Niches Than the Biological Signal - A Demonstration Using Bird and Mammal Range Maps.

    Science.gov (United States)

    Boucher-Lalonde, Véronique; Currie, David J

    2016-01-01

    Species' geographic ranges could primarily be physiological tolerances drawn in space. Alternatively, geographic ranges could be only broadly constrained by physiological climatic tolerances: there could generally be much more proximate constraints on species' ranges (dispersal limitation, biotic interactions, etc.) such that species often occupy a small and unpredictable subset of tolerable climates. In the literature, species' climatic tolerances are typically estimated from the set of conditions observed within their geographic range. Using this method, studies have concluded that broader climatic niches permit larger ranges. Similarly, other studies have investigated the biological causes of incomplete range filling. But, when climatic constraints are measured directly from species' ranges, are correlations between species' range size and climate necessarily consistent with a causal link? We evaluated the extent to which variation in range size among 3277 bird and 1659 mammal species occurring in the Americas is statistically related to characteristics of species' realized climatic niches. We then compared how these relationships differed from the ones expected in the absence of a causal link. We used a null model that randomizes the predictor variables (climate), while retaining their broad spatial autocorrelation structure, thereby removing any causal relationship between range size and climate. We found that, although range size is strongly positively related to climatic niche breadth, range filling and, to a lesser extent, niche position in nature, the observed relationships are not always stronger than expected from spatial autocorrelation alone. Thus, we conclude that equally strong relationships between range size and climate would result from any processes causing ranges to be highly spatially autocorrelated.

  8. Spatial Autocorrelation Can Generate Stronger Correlations between Range Size and Climatic Niches Than the Biological Signal — A Demonstration Using Bird and Mammal Range Maps

    Science.gov (United States)

    Boucher-Lalonde, Véronique; Currie, David J.

    2016-01-01

    Species’ geographic ranges could primarily be physiological tolerances drawn in space. Alternatively, geographic ranges could be only broadly constrained by physiological climatic tolerances: there could generally be much more proximate constraints on species’ ranges (dispersal limitation, biotic interactions, etc.) such that species often occupy a small and unpredictable subset of tolerable climates. In the literature, species’ climatic tolerances are typically estimated from the set of conditions observed within their geographic range. Using this method, studies have concluded that broader climatic niches permit larger ranges. Similarly, other studies have investigated the biological causes of incomplete range filling. But, when climatic constraints are measured directly from species’ ranges, are correlations between species’ range size and climate necessarily consistent with a causal link? We evaluated the extent to which variation in range size among 3277 bird and 1659 mammal species occurring in the Americas is statistically related to characteristics of species’ realized climatic niches. We then compared how these relationships differed from the ones expected in the absence of a causal link. We used a null model that randomizes the predictor variables (climate), while retaining their broad spatial autocorrelation structure, thereby removing any causal relationship between range size and climate. We found that, although range size is strongly positively related to climatic niche breadth, range filling and, to a lesser extent, niche position in nature, the observed relationships are not always stronger than expected from spatial autocorrelation alone. Thus, we conclude that equally strong relationships between range size and climate would result from any processes causing ranges to be highly spatially autocorrelated. PMID:27855201

  9. Electrothermally Tunable Bridge Resonator

    KAUST Repository

    Hajjaj, Amal Z.

    2016-12-05

    This paper demonstrates experimentally, theoretically, and numerically a wide-range tunability of an in-plane clamped-clamped microbeam, bridge, and resonator compressed by a force due to electrothermal actuation. We demonstrate that a single resonator can be operated at a wide range of frequencies. The microbeam is actuated electrothermally, by passing a DC current through it. We show that when increasing the electrothermal voltage, the compressive stress inside the microbeam increases, which leads eventually to its buckling. Before buckling, the fundamental frequency decreases until it drops to very low values, almost to zero. After buckling, the fundamental frequency increases, which is shown to be as high as twice the original resonance frequency. Analytical results based on the Galerkin discretization of the Euler Bernoulli beam theory are generated and compared to the experimental data and to simulation results of a multi-physics finite-element model. A good agreement is found among all the results.

  10. Electrostatically Tunable Nanomechanical Shallow Arches

    KAUST Repository

    Kazmi, Syed N. R.

    2017-11-03

    We report an analytical and experimental study on the tunability of in-plane doubly-clamped nanomechanical arches under varied DC bias conditions at room temperature. For this purpose, silicon based shallow arches are fabricated using standard e-beam lithography and surface nanomachining of a highly conductive device layer on a silicon-on-insulator (SOI) wafer. The experimental results show good agreement with the analytical results with a maximum tunability of 108.14% for 180 nm thick arch with a transduction gap of 1 μm between the beam and the driving/sensing electrodes. The high tunability of shallow arches paves the ways for highly tunable band pass filtering applications in high frequency range.

  11. Rigorous home range estimation with movement data: a new autocorrelated kernel density estimator.

    Science.gov (United States)

    Fleming, C H; Fagan, W F; Mueller, T; Olson, K A; Leimgruber, P; Calabrese, J M

    2015-05-01

    Quantifying animals' home ranges is a key problem in ecology and has important conservation and wildlife management applications. Kernel density estimation (KDE) is a workhorse technique for range delineation problems that is both statistically efficient and nonparametric. KDE assumes that the data are independent and identically distributed (IID). However, animal tracking data, which are routinely used as inputs to KDEs, are inherently autocorrelated and violate this key assumption. As we demonstrate, using realistically autocorrelated data in conventional KDEs results in grossly underestimated home ranges. We further show that the performance of conventional KDEs actually degrades as data quality improves, because autocorrelation strength increases as movement paths become more finely resolved. To remedy these flaws with the traditional KDE method, we derive an autocorrelated KDE (AKDE) from first principles to use autocorrelated data, making it perfectly suited for movement data sets. We illustrate the vastly improved performance of AKDE using analytical arguments, relocation data from Mongolian gazelles, and simulations based upon the gazelle's observed movement process. By yielding better minimum area estimates for threatened wildlife populations, we believe that future widespread use of AKDE will have significant impact on ecology and conservation biology.

  12. Pneumatically tunable optofluidic dye laser

    OpenAIRE

    Song, W.; Psaltis, D.

    2010-01-01

    We presented a tunable optofluidic dye laser with integrated elastomeric air-gap etalon controlled by air pressure. The chip was fabricated with polydimethylsiloxane (PDMS) via replica molding. It comprises a liquid waveguide and microscale air-gap mirrors providing the feedback. The lasing wavelength is chosen by the interference between two parallel PDMS-air interfaces inside the internal tunable air-gap etalon, of which pneumatic tuning can be realized by inflating the air-gap etalon with ...

  13. Spectral and Radiometric Calibration Using Tunable Lasers

    Science.gov (United States)

    McCorkel, Joel (Inventor)

    2017-01-01

    A tunable laser system includes a tunable laser, an adjustable laser cavity for producing one or more modes of laser light emitted from the tunable laser, a first optical parametric oscillator positioned in a light path of the adjustable laser cavity, and a controller operable to simultaneously control parameters of at least the tunable laser, the first optical parametric oscillator, and the adjustable laser cavity to produce a range of wavelengths emitted from the tunable laser system. A method of operating a tunable laser system includes using a controller to simultaneously control parameters of a tunable laser, an adjustable laser cavity for producing one or more modes of laser light emitted from the tunable laser, and a first optical parametric oscillator positioned in a light path of the adjustable laser cavity, to produce a range of wavelengths emitted from the tunable laser system.

  14. A high-speed superconducting digital autocorrelator operating at 20.48 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Steven B [HYPRES, Incorporated, 175 Clearbrook Road, Elmsford, NY 10523 (United States); Engseth, Henrik [Department of Microelectronics and Nanoscience, Chalmers University, Goeteborg SE-412 96 (Sweden)

    2007-11-15

    Digital autocorrelators have a number of applications, such as in astronomical observation in the terahertz range, and for spectrum monitoring over wide radio-frequency bands. We have simulated, designed and tested 16-lag superconducting digital autocorrelator circuits with parallel and also with serial data outputs. By using a novel clock line and a target critical current density of 4.5 kA cm{sup -2}, we have successfully tested this digital circuit up to a clock rate of 20.48 GHz with negligible bit error rates on each lag. Moreover, this autocorrelator design can be expanded with a larger number of lags by tiling chips in a multi-chip module. We also include details of our first multi-chip design.

  15. Spectrum sensing algorithm based on autocorrelation energy in cognitive radio networks

    Science.gov (United States)

    Ren, Shengwei; Zhang, Li; Zhang, Shibing

    2016-10-01

    Cognitive radio networks have wide applications in the smart home, personal communications and other wireless communication. Spectrum sensing is the main challenge in cognitive radios. This paper proposes a new spectrum sensing algorithm which is based on the autocorrelation energy of signal received. By taking the autocorrelation energy of the received signal as the statistics of spectrum sensing, the effect of the channel noise on the detection performance is reduced. Simulation results show that the algorithm is effective and performs well in low signal-to-noise ratio. Compared with the maximum generalized eigenvalue detection (MGED) algorithm, function of covariance matrix based detection (FMD) algorithm and autocorrelation-based detection (AD) algorithm, the proposed algorithm has 2 11 dB advantage.

  16. Spatial Autocorrelation Analysis of Chinese Inter-Provincial Industrial Chemical Oxygen Demand Discharge

    Directory of Open Access Journals (Sweden)

    Yibo Liu

    2012-05-01

    Full Text Available A spatial autocorrelation analysis method is adopted to process the spatial dynamic change of industrial Chemical Oxygen Demand (COD discharge in China over the past 15 years. Studies show that amount and intensity of industrial COD discharges are on a decrease, and the tendency is more remarkable for discharge intensity. There are large differences between inter-provincial discharge amount and intensity, and with different spatial differentiation features. Global spatial autocorrelation analysis reveals that Global Moran’s I of discharge amount and intensity is on the decrease. In space, there is an evolution from an agglomeration pattern to a discretization pattern. Local spatial autocorrelation analysis shows that the agglomeration area of industrial COD discharge amount and intensity varies greatly in space with time. Stringent environmental regulations and increased funding for environmental protections are the crucial factors to cut down industrial COD discharge amount and intensity.

  17. Spatial autocorrelation analysis of Chinese inter-provincial industrial chemical oxygen demand discharge.

    Science.gov (United States)

    Zhao, Xiaofeng; Huang, Xianjin; Liu, Yibo

    2012-06-01

    A spatial autocorrelation analysis method is adopted to process the spatial dynamic change of industrial Chemical Oxygen Demand (COD) discharge in China over the past 15 years. Studies show that amount and intensity of industrial COD discharges are on a decrease, and the tendency is more remarkable for discharge intensity. There are large differences between inter-provincial discharge amount and intensity, and with different spatial differentiation features. Global spatial autocorrelation analysis reveals that Global Moran's I of discharge amount and intensity is on the decrease. In space, there is an evolution from an agglomeration pattern to a discretization pattern. Local spatial autocorrelation analysis shows that the agglomeration area of industrial COD discharge amount and intensity varies greatly in space with time. Stringent environmental regulations and increased funding for environmental protections are the crucial factors to cut down industrial COD discharge amount and intensity.

  18. Recursive Estimation for Dynamical Systems with Different Delay Rates Sensor Network and Autocorrelated Process Noises

    Directory of Open Access Journals (Sweden)

    Jianxin Feng

    2014-01-01

    Full Text Available The recursive estimation problem is studied for a class of uncertain dynamical systems with different delay rates sensor network and autocorrelated process noises. The process noises are assumed to be autocorrelated across time and the autocorrelation property is described by the covariances between different time instants. The system model under consideration is subject to multiplicative noises or stochastic uncertainties. The sensor delay phenomenon occurs in a random way and each sensor in the sensor network has an individual delay rate which is characterized by a binary switching sequence obeying a conditional probability distribution. By using the orthogonal projection theorem and an innovation analysis approach, the desired recursive robust estimators including recursive robust filter, predictor, and smoother are obtained. Simulation results are provided to demonstrate the effectiveness of the proposed approaches.

  19. Adaptive endpoint detection of seismic signal based on auto-correlated function

    International Nuclear Information System (INIS)

    Fan Wanchun; Shi Ren

    2000-01-01

    There are certain shortcomings for the endpoint detection by time-waveform envelope and/or by checking the travel table (both labelled as the artificial detection method). Based on the analysis of the auto-correlation function, the notion of the distance between auto-correlation functions was quoted, and the characterizations of the noise and the signal with noise were discussed by using the distance. Then, the method of auto-adaptable endpoint detection of seismic signal based on auto-correlated similarity was summed up. The steps of implementation and determining of the thresholds were presented in detail. The experimental results that were compared with the methods based on artificial detecting show that this method has higher sensitivity even in a low SNR circumstance

  20. A Comparison of Decision Methods for C pk When Data are Autocorrelated

    DEFF Research Database (Denmark)

    Lundkvist, Peder; Vannman, Kerstin; Kulahci, Murat

    2012-01-01

    of this article is to compare decision methods using the process capability index C-pk when data are autocorrelated. This is done through a case study followed by a simulation study. In the simulation study the actual significance level and power of the decision methods are investigated. The outcome......In many industrial applications, autocorrelated data are becoming increasingly common due to, for example, on-line data collection systems with high-frequency sampling. Therefore, the basic assumption of independent observations for process capability analysis is not valid. The purpose...

  1. An autocorrelation technique for measuring sub-picosecond bunch length using coherent transition radiation

    International Nuclear Information System (INIS)

    Barry, W.

    1991-01-01

    A new technique for determining sub-picosecond bunch length using infrared transition radiation and interferometry is proposed. The technique makes use of an infrared Michelson interferometer for measuring the autocorrelation of transition radiation emitted from a thin conducting foil placed in the beam path. The theory of coherent radiation from a charged particle beam passing through a thin conducting foil is presented. Subsequently, the analysis of this radiation through Michelson interferometry is shown to provide the autocorrelation of the longitudinal bunch profile. An example relevant to the CEBAF front end test is discussed. (author)

  2. Green high-power tunable external-cavity GaN diode laser at 515 nm

    DEFF Research Database (Denmark)

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2016-01-01

    A 480 mW green tunable diode laser system is demonstrated for the first time to our knowledge. The laser system is based on a GaN broad-area diode laser and Littrow external-cavity feedback. The green laser system is operated in two modes by switching the polarization direction of the laser beam...... incident on the grating. When the laser beam is p-polarized, an output power of 50 mW with a tunable range of 9.2 nm is achieved. When the laser beam is s-polarized, an output power of 480 mW with a tunable range of 2.1 nm is obtained. This constitutes the highest output power from a tunable green diode...... laser system....

  3. Magnetostatic wave tunable resonators

    Science.gov (United States)

    Castera, J.-P.; Hartemann, P.

    1983-06-01

    Theoretical principles and techniques for the implementation of magnetostatic surface wave and volume wave resonators in high frequency oscillators are discussed. Magnetostatic waves are magnetic waves that propagate in materials exposed to a polarized magnetic field. The propagation speed ranges from 3-300 km/sec for wavelengths between 1 micron and 10 mm, in the presence of lags from 10-1000 nsec/ cm. Tunable resonators in the 1-20 GHz frequency range have been manufactured with YIG using liquid phase epitaxy for deposition on gadolinium and gallium substrates. Distributed-mirror Fabry-Perot cavity resonators are described and performance tests results are reported, including losses of 8 dB, a quality coefficient under voltage of 450, and frequency rejection outside of resonance better than 10 dB. However, saturation occurs at low power levels at frequencies lower than 4.2 GHz, a feature overcome with forward volume magnetostatic wave generators, which have a quality factor of 500, an insertion loss of 22 dB, and rejection around 15 dB.

  4. Tunable Multiband Microwave Photonic Filters

    Directory of Open Access Journals (Sweden)

    Mable P. Fok

    2017-11-01

    Full Text Available The increasing demand for multifunctional devices, the use of cognitive wireless technology to solve the frequency resource shortage problem, as well as the capabilities and operational flexibility necessary to meet ever-changing environment result in an urgent need of multiband wireless communications. Spectral filter is an essential part of any communication systems, and in the case of multiband wireless communications, tunable multiband RF filters are required for channel selection, noise/interference removal, and RF signal processing. Unfortunately, it is difficult for RF electronics to achieve both tunable and multiband spectral filtering. Recent advancements of microwave photonics have proven itself to be a promising candidate to solve various challenges in RF electronics including spectral filtering, however, the development of multiband microwave photonic filtering still faces lots of difficulties, due to the limited scalability and tunability of existing microwave photonic schemes. In this review paper, we first discuss the challenges that were facing by multiband microwave photonic filter, then we review recent techniques that have been developed to tackle the challenge and lead to promising developments of tunable microwave photonic multiband filters. The successful design and implementation of tunable microwave photonic multiband filter facilitate the vision of dynamic multiband wireless communications and radio frequency signal processing for commercial, defense, and civilian applications.

  5. Crude oil market efficiency and modeling. Insights from the multiscaling autocorrelation pattern

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Ramirez, Jose [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico D.F., 09340 (Mexico); Departamento de Economia, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico D.F., 09340 (Mexico); Alvarez, Jesus [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico D.F., 09340 (Mexico); Solis, Ricardo [Departamento de Economia, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico D.F., 09340 (Mexico)

    2010-09-15

    Empirical research on market inefficiencies focuses on the detection of autocorrelations in price time series. In the case of crude oil markets, statistical support is claimed for weak efficiency over a wide range of time-scales. However, the results are still controversial since theoretical arguments point to deviations from efficiency as prices tend to revert towards an equilibrium path. This paper studies the efficiency of crude oil markets by using lagged detrended fluctuation analysis (DFA) to detect delay effects in price autocorrelations quantified in terms of a multiscaling Hurst exponent (i.e., autocorrelations are dependent of the time scale). Results based on spot price data for the period 1986-2009 indicate important deviations from efficiency associated to lagged autocorrelations, so imposing the random walk for crude oil prices has pronounced costs for forecasting. Evidences in favor of price reversion to a continuously evolving mean underscores the importance of adequately incorporating delay effects and multiscaling behavior in the modeling of crude oil price dynamics. (author)

  6. Auto-correlation analysis of wave heights in the Bay of Bengal

    Indian Academy of Sciences (India)

    tion in numerical models and validation exercises of physical parameters obtained by different means. An auto-correlation analysis of ocean surface winds based on available time series over the Bay of Bengal was reported in our earlier work (Sarkar et al 2002). The present note attempts to carry out a similar exercise for ...

  7. Studies of the micromorphology of sputtered TiN thin films by autocorrelation techniques

    Science.gov (United States)

    Smagoń, Kamil; Stach, Sebastian; Ţălu, Ştefan; Arman, Ali; Achour, Amine; Luna, Carlos; Ghobadi, Nader; Mardani, Mohsen; Hafezi, Fatemeh; Ahmadpourian, Azin; Ganji, Mohsen; Grayeli Korpi, Alireza

    2017-12-01

    Autocorrelation techniques are crucial tools for the study of the micromorphology of surfaces: They provide the description of anisotropic properties and the identification of repeated patterns on the surface, facilitating the comparison of samples. In the present investigation, some fundamental concepts of these techniques including the autocorrelation function and autocorrelation length have been reviewed and applied in the study of titanium nitride thin films by atomic force microscopy (AFM). The studied samples were grown on glass substrates by reactive magnetron sputtering at different substrate temperatures (from 25 {}°C to 400 {}°C , and their micromorphology was studied by AFM. The obtained AFM data were analyzed using MountainsMap Premium software obtaining the correlation function, the structure of isotropy and the spatial parameters according to ISO 25178 and EUR 15178N. These studies indicated that the substrate temperature during the deposition process is an important parameter to modify the micromorphology of sputtered TiN thin films and to find optimized surface properties. For instance, the autocorrelation length exhibited a maximum value for the sample prepared at a substrate temperature of 300 {}°C , and the sample obtained at 400 {}°C presented a maximum angle of the direction of the surface structure.

  8. A second-order autocorrelator for single-shot measurement of ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    background intensity contrast ratio of 25 ps laser pulses from an active-passive mode-locked. Nd:YLF laser carried out in this mode are also presented. 2. Principle. The second order autocorrelation technique basically involves splitting a laser beam into two beams of equal intensity and overlapping them in a nonlinear ...

  9. Autocorrelation Function for Monitoring the Gap between The Steel Plates During Laser Welding

    Czech Academy of Sciences Publication Activity Database

    Mrňa, Libor; Horník, Petr

    2016-01-01

    Roč. 83, č. 3 (2016), s. 1223-1232 ISSN 1875-3892 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : laser weld ing * process monitoring * autocorrelation function Subject RIV: BH - Optics, Masers, Lasers

  10. Spatial Autocorrelation Patterns of Understory Plant Species in a Subtropical Rainforest at Lanjenchi, Southern Taiwan

    Directory of Open Access Journals (Sweden)

    Su-Wei Fan

    2010-06-01

    Full Text Available Many studies described relationships between plant species and intrinsic or exogenous factors, but few quantified spatial scales of species patterns. In this study, quantitative methods were used to explore the spatial scale of understory species (including resident and transient species, in order to identify the influential factors of species distribution. Resident species (including herbaceous species, climbers and tree ferns < 1 m high were investigated on seven transects, each 5-meter wide and 300-meter long, at Lanjenchi plot in Nanjenshan Reserve, southern Taiwan. Transient species (seedling of canopy, subcanopy and shrub species < 1 cm diameter at breast height were censused in three of the seven transects. The herb coverage and seedling abundance were calculated for each 5 × 5 m quadrat along the transects, and Moran’s I and Galiano’s new local variance (NLV indices were then used to identify the spatial scale of autocorrelation for each species. Patterns of species abundance of understory layer varied among species at fine scale within 50 meters. Resident species showed a higher proportion of significant autocorrelation than the transient species. Species with large size or prolonged fronds or stems tended to show larger scales in autocorrelation. However, dispersal syndromes and fruit types did not relate to any species’ spatial patterns. Several species showed a significant autocorrelation at a 180-meter class which happened to correspond to the local replicates of topographical features in hilltops. The spatial patterns of understory species at Lanjenchi plot are mainly influenced by species’ intrinsic traits and topographical characteristics.

  11. Logistic regression for southern pine beetle outbreaks with spatial and temporal autocorrelation

    Science.gov (United States)

    M. L. Gumpertz; C.-T. Wu; John M. Pye

    2000-01-01

    Regional outbreaks of southern pine beetle (Dendroctonus frontalis Zimm.) show marked spatial and temporal patterns. While these patterns are of interest in themselves, we focus on statistical methods for estimating the effects of underlying environmental factors in the presence of spatial and temporal autocorrelation. The most comprehensive available information on...

  12. Power properties of invariant tests for spatial autocorrelation in linear regression

    NARCIS (Netherlands)

    Martellosio, F.

    2006-01-01

    Many popular tests for residual spatial autocorrelation in the context of the linear regression model belong to the class of invariant tests. This paper derives a number of exact properties of the power function of such tests. In particular, we extend the work of Krämer (2005, Journal of Statistical

  13. Operator theory of angular momentum nad orientational auto-correlation functions

    International Nuclear Information System (INIS)

    Evans, M.W.

    1982-01-01

    The rigorous relation between the orientational auto-correlation function and the angular momentum autocorrelation function is described in two cases of interest. First when description of the complete zero THz- spectrum is required from the Mori continued fraction expansion for the angular momentum autocorrelation function and second when rotation/translation effects are important. The Mori-Evans theory of 1976, relying on the simple Shimizu relation is found to be essentially unaffected by the higher order corrections recently worked out by Ford and co-workers in the Markov limit. The mutual interaction of rotation and translation is important in determining the details of both the orientational and angular momentum auto-correlation function's (a.c.f.'s) in the presence of sample anisotropy or a symmetry breaking field. In this case it is essential to regard the angular momentum a.c.f. as non-Markovian and methods are developed to relate this to the orientational a.c.f. in the presence of rotation/translation coupling. (author)

  14. Limit theory for the sample autocorrelations and extremes of a GARCH (1,1) process

    NARCIS (Netherlands)

    Mikosch, T; Starica, C

    2000-01-01

    The asymptotic theory for the sample autocorrelations and extremes of a GARCH(I, 1) process is provided. Special attention is given to the case when the sum of the ARCH and GARCH parameters is close to 1, that is, when one is close to an infinite Variance marginal distribution. This situation has

  15. Transforming the autocorrelation function of a time series to detect land cover change

    CSIR Research Space (South Africa)

    Salmon, BP

    2015-07-01

    Full Text Available methods. A robust change detection metric can be derived by analyzing the area under the autocorrelation function for a time series. The time dependence on the first and second moment causes a non-stationary event within the time series which results...

  16. Evidence for faster-than-t-1 decay of the velocity autocorrelation function in a 2D fluid

    NARCIS (Netherlands)

    Hoef, M.A. van der; Frenkel, D.

    1991-01-01

    We report very accurate simulations of the velocity autocorrelation function of a tagged particle in a two-dimensional lattice-gas cellular automaton. We observe, for the first time, that the hydrodynamic long-time tail of the velocity autocorrelation function decays significantly faster than t-1.

  17. Tunable features of magnetoelectric transformers.

    Science.gov (United States)

    Dong, Shuxiang; Zhai, Junyi; Priya, Shashank; Li, Jie-Fang; Viehland, Dwight

    2009-06-01

    We have found that magnetostrictive FeBSiC alloy ribbons laminated with piezoelectric Pb(Zr,Ti)O(3) fiber can act as a tunable transformer when driven under resonant conditions. These composites were also found to exhibit the strongest resonant magnetoelectric voltage coefficient of 750 V/cm-Oe. The tunable features were achieved by applying small dc magnetic biases of -5 transformer features can be attributed to large changes in the piezomagnetic coefficient and permeability of the magnetostrictive phase under H(dc).

  18. Cobble cam: Grain-size measurements of sand to boulder from digital photographs and autocorrelation analyses

    Science.gov (United States)

    Warrick, J.A.; Rubin, D.M.; Ruggiero, P.; Harney, J.N.; Draut, A.E.; Buscombe, D.

    2009-01-01

    A new application of the autocorrelation grain size analysis technique for mixed to coarse sediment settings has been investigated. Photographs of sand- to boulder-sized sediment along the Elwha River delta beach were taken from approximately 1??2 m above the ground surface, and detailed grain size measurements were made from 32 of these sites for calibration and validation. Digital photographs were found to provide accurate estimates of the long and intermediate axes of the surface sediment (r2 > 0??98), but poor estimates of the short axes (r2 = 0??68), suggesting that these short axes were naturally oriented in the vertical dimension. The autocorrelation method was successfully applied resulting in total irreducible error of 14% over a range of mean grain sizes of 1 to 200 mm. Compared with reported edge and object-detection results, it is noted that the autocorrelation method presented here has lower error and can be applied to a much broader range of mean grain sizes without altering the physical set-up of the camera (~200-fold versus ~6-fold). The approach is considerably less sensitive to lighting conditions than object-detection methods, although autocorrelation estimates do improve when measures are taken to shade sediments from direct sunlight. The effects of wet and dry conditions are also evaluated and discussed. The technique provides an estimate of grain size sorting from the easily calculated autocorrelation standard error, which is correlated with the graphical standard deviation at an r2 of 0??69. The technique is transferable to other sites when calibrated with linear corrections based on photo-based measurements, as shown by excellent grain-size analysis results (r2 = 0??97, irreducible error = 16%) from samples from the mixed grain size beaches of Kachemak Bay, Alaska. Thus, a method has been developed to measure mean grain size and sorting properties of coarse sediments. ?? 2009 John Wiley & Sons, Ltd.

  19. Tunable electro-optic filter stack

    Energy Technology Data Exchange (ETDEWEB)

    Fontecchio, Adam K.; Shriyan, Sameet K.; Bellingham, Alyssa

    2017-09-05

    A holographic polymer dispersed liquid crystal (HPDLC) tunable filter exhibits switching times of no more than 20 microseconds. The HPDLC tunable filter can be utilized in a variety of applications. An HPDLC tunable filter stack can be utilized in a hyperspectral imaging system capable of spectrally multiplexing hyperspectral imaging data acquired while the hyperspectral imaging system is airborne. HPDLC tunable filter stacks can be utilized in high speed switchable optical shielding systems, for example as a coating for a visor or an aircraft canopy. These HPDLC tunable filter stacks can be fabricated using a spin coating apparatus and associated fabrication methods.

  20. Tunable on chip optofluidic laser

    DEFF Research Database (Denmark)

    Bakal, Avraham; Vannahme, Christoph; Kristensen, Anders

    2015-01-01

    A chip scale tunable laser in the visible spectral band is realized by generating a periodic droplet array inside a microfluidic channel. Combined with a gain medium within the droplets, the periodic structure provides the optical feedback of the laser. By controlling the pressure applied to two...

  1. Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

    Science.gov (United States)

    Yao, B. C.; Rao, Y. J.; Wang, Z. N.; Wu, Y.; Zhou, J. H.; Wu, H.; Fan, M. Q.; Cao, X. L.; Zhang, W. L.; Chen, Y. F.; Li, Y. R.; Churkin, D.; Turitsyn, S.; Wong, C. W.

    2015-12-01

    Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

  2. Tunable random packings

    International Nuclear Information System (INIS)

    Lumay, G; Vandewalle, N

    2007-01-01

    We present an experimental protocol that allows one to tune the packing fraction η of a random pile of ferromagnetic spheres from a value close to the lower limit of random loose packing η RLP ≅0.56 to the upper limit of random close packing η RCP ≅0.64. This broad range of packing fraction values is obtained under normal gravity in air, by adjusting a magnetic cohesion between the grains during the formation of the pile. Attractive and repulsive magnetic interactions are found to affect stongly the internal structure and the stability of sphere packing. After the formation of the pile, the induced cohesion is decreased continuously along a linear decreasing ramp. The controlled collapse of the pile is found to generate various and reproducible values of the random packing fraction η

  3. OFDM Signal Detector Based on Cyclic Autocorrelation Function and its Properties

    Directory of Open Access Journals (Sweden)

    Z. Fedra

    2011-12-01

    Full Text Available This paper is devoted to research of the general and particular properties of the OFDM signal detector based on the cyclic autocorrelation function. The cyclic autocorrelation function is estimated using DFT. The parameters of the testing signal have been chosen according to 802.11g WLAN. Some properties are described analytically; all events are examined via computer simulations. It is shown that the detector is able to detect an OFDM signal in the case of multipath propagation, inexact frequency synchronization and without time synchronization. The sensitivity of the detector could be decreased in the above cases. An important condition for proper value of the detector sampling interval was derived. Three types of the channels were studied and compared. Detection threshold SNR=-9 dB was found for the signal under consideration and for two-way propagation.

  4. IMPLEMENTATION OF REAL TIME AUTOCORRELATION METHOD EMPLOYING THE DS87C550 MICROCONTROLLER

    Directory of Open Access Journals (Sweden)

    A. Jiménez-Cañas

    2005-04-01

    Full Text Available In this work, the implementation of Real Time Autocorrelation method proposed by Takeuchi and Hogaki, isexposed. The purpose is to obtain the frequency of the fetal cardiac beats, originated from a Fetal Detector, using awide-benefits DS87C550 microcontroller. The value of frequency is showed in a LCD. The autocorrelation algorithmwas simulated in a PC to know its dynamic behavior from selected signals. A criterion to carry out the recognitionand the selection of the first conformed crest, was obtained. By means of this criterion, the period of the processedsignal is determined. Consequently, an optimized and original algorithm was created and implemented in themicrocontroller, where the value of the fetal cardiac frequency (given in pulses per minute, ppm. is obtained each1.2 sec. In that time, two calculated values of frequency are averaged.

  5. Autocorrelation and cross-correlation in time series of homicide and attempted homicide

    Science.gov (United States)

    Machado Filho, A.; da Silva, M. F.; Zebende, G. F.

    2014-04-01

    We propose in this paper to establish the relationship between homicides and attempted homicides by a non-stationary time-series analysis. This analysis will be carried out by Detrended Fluctuation Analysis (DFA), Detrended Cross-Correlation Analysis (DCCA), and DCCA cross-correlation coefficient, ρ(n). Through this analysis we can identify a positive cross-correlation between homicides and attempted homicides. At the same time, looked at from the point of view of autocorrelation (DFA), this analysis can be more informative depending on time scale. For short scale (days), we cannot identify auto-correlations, on the scale of weeks DFA presents anti-persistent behavior, and for long time scales (n>90 days) DFA presents a persistent behavior. Finally, the application of this new type of statistical analysis proved to be efficient and, in this sense, this paper can contribute to a more accurate descriptive statistics of crime.

  6. Effect of nonlinear crystal thickness on the parameters of the autocorrelator of femtosecond light pulses

    International Nuclear Information System (INIS)

    Masalov, Anatolii V; Chudnovsky, Aleksandr V

    2004-01-01

    It is shown that the finite thickness of the second-harmonic crystal distorts the results of measurements in nonlinear autocorrelators intended for measuring the durations and fields of femtosecond light pulses mainly due to dispersive broadening (or compression) of the pulses being measured, as well as due to the group velocity mismatch between the fundamental and sum-frequency pulses. The refractive index dispersion of the crystal, scaled by half its thickness, distorts the pulse duration to a certain extent depending on its initial chirp and thus determines the width of the energy distribution recorded in the autocorrelator. As the crystal thickness increases, the group velocity mismatch leads to a transformation of the recorded distribution from the correlation function of intensity to the squared modulus of the field correlation function. In the case of Gaussian pulses, such a transformation does not affect significantly the recorded distribution. Errors of pulse duration measurements are estimated. (nonlinear optical phenomena)

  7. First measurements of subpicosecond electron beam structure by autocorrelation of coherent diffraction radiation

    CERN Document Server

    Lumpkin, Alex H; Rule, D W

    2001-01-01

    We report the initial measurements of subpicosecond electron beam structure using a nonintercepting technique based on the autocorrelation of coherent diffraction radiation (CDR). A far infrared (FIR) Michelson interferometer with a Golay detector was used to obtain the autocorrelation. The radiation was generated by a thermionic rf gun beam at 40 MeV as it passed through a 5-mm-tall slit/aperture in a metal screen whose surface was at 45 deg. to the beam direction. For the observed bunch lengths of about 450 fs (FWHM) with a shorter time spike on the leading edge, peak currents of about 100 A are indicated. Also a model was developed and used to calculate the CDR from the back of two metal strips separated by a 5-mm vertical gap. The demonstrated nonintercepting aspect of this method could allow on-line bunch length characterizations to be done during free-electron laser experiments.

  8. Autocorrelation analysis of plasma plume light emissions in deep penetration laser welding of steel

    Czech Academy of Sciences Publication Activity Database

    Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

    2017-01-01

    Roč. 29, č. 1 (2017), s. 1-10, č. článku 012009. ISSN 1042-346X R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : laser welding * plasma plume * light emissions * autocorrelation analysis * weld depth Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.492, year: 2016

  9. Assessing the reliability of the modified three-component spatial autocorrelation technique

    OpenAIRE

    Kohler, A.; Ohrnberger, M.; Scherbaum, F.; Wathelet, M.; Cornou, Cécile

    2007-01-01

    Analysis of seismic ambient vibrations is becoming a widespread approach to estimate subsurface shear wave velocity profiles. However, the common restriction to vertical component wavefield data does not allow investigations of Love wave dispersion and the partitioning between Rayleigh and Love waves. In this study we extend the modified spatial autocorrelation technique (MSPAC) to three-component analysis (3c-MSPAC). By determination of Love wave dispersion curves, this technique provides ad...

  10. Modified Exponential Weighted Moving Average (EWMA) Control Chart on Autocorrelation Data

    Science.gov (United States)

    Herdiani, Erna Tri; Fandrilla, Geysa; Sunusi, Nurtiti

    2018-03-01

    In general, observations of the statistical process control are assumed to be mutually independence. However, this assumption is often violated in practice. Consequently, statistical process controls were developed for interrelated processes, including Shewhart, Cumulative Sum (CUSUM), and exponentially weighted moving average (EWMA) control charts in the data that were autocorrelation. One researcher stated that this chart is not suitable if the same control limits are used in the case of independent variables. For this reason, it is necessary to apply the time series model in building the control chart. A classical control chart for independent variables is usually applied to residual processes. This procedure is permitted provided that residuals are independent. In 1978, Shewhart modification for the autoregressive process was introduced by using the distance between the sample mean and the target value compared to the standard deviation of the autocorrelation process. In this paper we will examine the mean of EWMA for autocorrelation process derived from Montgomery and Patel. Performance to be investigated was investigated by examining Average Run Length (ARL) based on the Markov Chain Method.

  11. Sparse dictionary learning for fMRI analysis using autocorrelation maximization.

    Science.gov (United States)

    Khalid, Muhammad Usman; Shah, Adnan; Seghouane, Abd-Krim

    2015-08-01

    In this paper, the effect of temporal autocorrelations in functional magnetic resonance imaging (fMRI) data on sparse dictionary learning (SDL) is addressed. For sparse general linear model (sGLM), the fMRI time-series is modeled as a linear mixture of several signals such as neural dynamics, structured noise, random noise and unexplained signal variations on the basis of spatial sparseness. These signals are considered as underlying sources and SDL is used to estimate them. However, the sparse GLM model does not take into account the autocorrelations in fMRI data. To address this shortcoming, a new model is proposed to incorporate the prior knowledge about lag-1 autocorrelation into dictionary update stage. This helps improve the sensitivity and specificity of the fMRI data during statistical analysis. Using a simulation study, the effect of the proposed dictionary update on sGLM is compared to conventional sGLM by utilizing various detrending techniques. Furthermore, the proposed update is validated in an sGLM framework for real fMRI datasets, which shows its better capability to estimate neural dynamics in presence of spatiotemporal dependencies.

  12. Spatial autocorrelation method using AR model; Kukan jiko sokanho eno AR model no tekiyo

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Obuchi, T.; Saito, T. [Iwate University, Iwate (Japan). Faculty of Engineering

    1996-05-01

    Examination was made about the applicability of the AR model to the spatial autocorrelation (SAC) method, which analyzes the surface wave phase velocity in a microtremor, for the estimation of the underground structure. In this examination, microtremor data recorded in Morioka City, Iwate Prefecture, was used. In the SAC method, a spatial autocorrelation function with the frequency as a variable is determined from microtremor data observed by circular arrays. Then, the Bessel function is adapted to the spatial autocorrelation coefficient with the distance between seismographs as a variable for the determination of the phase velocity. The result of the AR model application in this study and the results of the conventional BPF and FFT method were compared. It was then found that the phase velocities obtained by the BPF and FFT methods were more dispersed than the same obtained by the AR model. The dispersion in the BPF method is attributed to the bandwidth used in the band-pass filter and, in the FFT method, to the impact of the bandwidth on the smoothing of the cross spectrum. 2 refs., 7 figs.

  13. Spatial autocorrelation in farmland grasshopper assemblages (Orthoptera: Acrididae) in western France.

    Science.gov (United States)

    Badenhausser, I; Gouat, M; Goarant, A; Cornulier, T; Bretagnolle, V

    2012-10-01

    Agricultural intensification in western Europe has caused a dramatic loss of grassland surfaces in farmlands, which have resulted in strong declines in grassland invertebrates, leading to cascade effects at higher trophic levels among consumers of invertebrates. Grasshoppers are important components of grassland invertebrate assemblages in European agricultural ecosystems, particularly as prey for bird species. Understanding how grasshopper populations are distributed in fragmented landscapes with low grassland availability is critical for both studies in biodiversity conservation and insect management. We assessed the range and strength of spatial autocorrelation for two grasshopper taxa (Gomphocerinae subfamily and Calliptamus italicus L.) across an intensive farmland in western France. Data from surveys carried out over 8 yr in 1,715 grassland fields were analyzed using geostatistics. Weak spatial patterns were observed at small spatial scales, suggesting important local effects of management practices on grasshopper densities. Spatial autocorrelation patterns for both grasshopper taxa were only detected at intermediate scales. For Gomphocerinae, the range of spatial autocorrelation varied from 802 to 2,613 m according to the year, depending both on grasshopper density and on grassland surfaces in the study site, whereas spatial patterns for the Italian locust were more variable and not related to grasshopper density or grassland surfaces. Spatial patterns in the distribution of Gomphocerinae supported our hypothesis that habitat availability was a major driver of grasshopper distribution in the landscape, and suggested it was related to density-dependent processes such as dispersal.

  14. What autocorrelation tells us about motor variability: insights from dart throwing.

    Directory of Open Access Journals (Sweden)

    Robert J van Beers

    Full Text Available In sports such as golf and darts it is important that one can produce ballistic movements of an object towards a goal location with as little variability as possible. A factor that influences this variability is the extent to which motor planning is updated from movement to movement based on observed errors. Previous work has shown that for reaching movements, our motor system uses the learning rate (the proportion of an error that is corrected for in the planning of the next movement that is optimal for minimizing the endpoint variability. Here we examined whether the learning rate is hard-wired and therefore automatically optimal, or whether it is optimized through experience. We compared the performance of experienced dart players and beginners in a dart task. A hallmark of the optimal learning rate is that the lag-1 autocorrelation of movement endpoints is zero. We found that the lag-1 autocorrelation of experienced dart players was near zero, implying a near-optimal learning rate, whereas it was negative for beginners, suggesting a larger than optimal learning rate. We conclude that learning rates for trial-by-trial motor learning are optimized through experience. This study also highlights the usefulness of the lag-1 autocorrelation as an index of performance in studying motor-skill learning.

  15. Graphene-assisted high-efficiency liquid crystal tunable terahertz metamaterial absorber.

    Science.gov (United States)

    Wang, Lei; Ge, Shijun; Hu, Wei; Nakajima, Makoto; Lu, Yanqing

    2017-10-02

    In this paper, few-layer porous graphene is integrated onto the surface of a metasurface layer to provide a uniform static electric field to efficiently control liquid crystal, thereby enabling flexible metamaterial designs. We demonstrate a tunable cross-shaped metamaterial absorber with different arm lengths driven by this combined metasurface and graphene electrode. The resulting absorber supports a resonant frequency tunable from 0.75 to 1 THz with a high-quality factor, and amplitude modulation of ~80% at these frequencies with an applied voltage of 10 V. Furthermore, the near-field intensity and hot spot distribution can be manipulated over a broad range.

  16. Integrating Hot and Cool Intelligences: Thinking Broadly about Broad Abilities

    Directory of Open Access Journals (Sweden)

    W. Joel Schneider

    2016-01-01

    Full Text Available Although results from factor-analytic studies of the broad, second-stratum abilities of human intelligence have been fairly consistent for decades, the list of broad abilities is far from complete, much less understood. We propose criteria by which the list of broad abilities could be amended and envision alternatives for how our understanding of the hot intelligences (abilities involving emotionally-salient information and cool intelligences (abilities involving perceptual processing and logical reasoning might be integrated into a coherent theoretical framework.

  17. Tunable excitons in bilayer graphene

    Science.gov (United States)

    Ju, Long; Wang, Lei; Cao, Ting; Taniguchi, Takashi; Watanabe, Kenji; Louie, Steven G.; Rana, Farhan; Park, Jiwoong; Hone, James; Wang, Feng; McEuen, Paul L.

    2017-11-01

    Excitons, the bound states of an electron and a hole in a solid material, play a key role in the optical properties of insulators and semiconductors. Here, we report the observation of excitons in bilayer graphene (BLG) using photocurrent spectroscopy of high-quality BLG encapsulated in hexagonal boron nitride. We observed two prominent excitonic resonances with narrow line widths that are tunable from the mid-infrared to the terahertz range. These excitons obey optical selection rules distinct from those in conventional semiconductors and feature an electron pseudospin winding number of 2. An external magnetic field induces a large splitting of the valley excitons, corresponding to a g-factor of about 20. These findings open up opportunities to explore exciton physics with pseudospin texture in electrically tunable graphene systems​.

  18. Tunable Meta-Liquid Crystals.

    Science.gov (United States)

    Liu, Mingkai; Fan, Kebin; Padilla, Willie; Powell, David A; Zhang, Xin; Shadrivov, Ilya V

    2016-02-24

    Meta-liquid crystals, a novel form of tunable 3D metamaterials, are proposed and experimentally demonstrated in the terahertz frequency regime. A morphology change under a bias electric field and a strong modulation of the transmission are observed. In comparison to conventional liquid crystals, there is considerable freedom to prescribe the electromagnetic properties through the judicious design of the meta-atom geometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Additive manufacturing of tunable lenses

    Science.gov (United States)

    Schlichting, Katja; Novak, Tobias; Heinrich, Andreas

    2017-02-01

    Individual additive manufacturing of optical systems based on 3D Printing offers varied possibilities in design and usage. In addition to the additive manufacturing procedure, the usage of tunable lenses allows further advantages for intelligent optical systems. Our goal is to bring the advantages of additive manufacturing together with the huge potential of tunable lenses. We produced tunable lenses as a bundle without any further processing steps, like polishing. The lenses were designed and directly printed with a 3D Printer as a package. The design contains the membrane as an optical part as well as the mechanical parts of the lens, like the attachments for the sleeves which contain the oil. The dynamic optical lenses were filled with an oil. The focal length of the lenses changes due to a change of the radius of curvature. This change is caused by changing the pressure in the inside of the lens. In addition to that, we designed lenses with special structures to obtain different areas with an individual optical power. We want to discuss the huge potential of this technology for several applications. Further, an appropriate controlling system is needed. Wéll show the possibilities to control and regulate the optical power of the lenses. The lenses could be used for illumination tasks, and in the future, for individual measurement tasks. The main advantage is the individuality and the possibility to create an individual design which completely fulfills the requirements for any specific application.

  20. Highly Tunable Electrostatic Nanomechanical Resonators

    KAUST Repository

    Kazmi, Syed Naveed Riaz

    2017-11-24

    There has been significant interest towards highly tunable resonators for on-demand frequency selection in modern communication systems. Here, we report highly tunable electrostatically actuated silicon-based nanomechanical resonators. In-plane doubly-clamped bridges, slightly curved as shallow arches due to residual stresses, are fabricated using standard electron beam lithography and surface nanomachining. The resonators are designed such that the effect of mid-plane stretching dominates the softening effect of the electrostatic force. This is achieved by controlling the gap-to-thickness ratio and by exploiting the initial curvature of the structure from fabrication. We demonstrate considerable increase in the resonance frequency of nanoresonators with the dc bias voltages up to 108% for 180 nm thick structures with a transduction gap of 1 $mu$m separating them from the driving/sensing electrodes. The experimental results are found in good agreement with those of a nonlinear analytical model based on the Euler-Bernoulli beam theory. As a potential application, we demonstrate a tunable narrow band-pass filter using two electrically coupled nanomechanical arch resonators with varied dc bias voltages.

  1. Highly tunable NEMS shallow arches

    KAUST Repository

    Kazmi, Syed N. R.

    2017-11-30

    We report highly tunable nanoelectromechanical systems NEMS shallow arches under dc excitation voltages. Silicon based in-plane doubly clamped bridges, slightly curved as shallow arches, are fabricated using standard electron beam lithography and surface nanomachining of a highly conductive device layer on a silicon-on-insulator wafer. By designing the structures to have gap to thickness ratio of more than four, the mid-plane stretching of the nano arches is maximized such that an increase in the dc bias voltage will result into continuous increase in the resonance frequency of the resonators to wide ranges. This is confirmed analytically based on a nonlinear beam model. The experimental results are found to be in good agreement with that of the results from developed analytical model. A maximum tunability of 108.14% for a 180 nm thick arch with an initially designed gap of 1 μm between the beam and the driving/sensing electrodes is achieved. Furthermore, a tunable narrow bandpass filter is demonstrated, which opens up opportunities for designing such structures as filtering elements in high frequency ranges.

  2. Autocorrelation and Cross-Correlation Analyses of Alpha Waves in Reflection to Subjective Preference of a Flickering Light

    National Research Council Canada - National Science Library

    Soeta, Y

    2001-01-01

    To clarify the relationship between the human brain activity and subjective preference of a flickering light under changing temporal frequency and mean luminance, alpha waves were analyzed by autocorrelation function (ACF...

  3. MLS/Aura L1 Radiances from Digital Autocorrelators V003 (ML1RADD) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — ML1RADD is the EOS Aura Microwave Limb Sounder (MLS) product containing the level 1 radiances from the digital autocorrelators. The data version is 3.3/3.4. Data...

  4. Spatial autocorrelation in predictors reduces the impact of positional uncertainty in occurrence data on species distribution modelling

    NARCIS (Netherlands)

    Naimi, B.; Skidmore, A.K.; Groen, T.A.; Hamm, N.A.S.

    2011-01-01

    Aim To investigate the impact of positional uncertainty in species occurrences on the predictions of seven commonly used species distribution models (SDMs), and explore its interaction with spatial autocorrelation in predictors. Methods A series of artificial datasets covering 155 scenarios

  5. Graphene plasmonics for tunable terahertz metamaterials.

    Science.gov (United States)

    Ju, Long; Geng, Baisong; Horng, Jason; Girit, Caglar; Martin, Michael; Hao, Zhao; Bechtel, Hans A; Liang, Xiaogan; Zettl, Alex; Shen, Y Ron; Wang, Feng

    2011-09-04

    Plasmons describe collective oscillations of electrons. They have a fundamental role in the dynamic responses of electron systems and form the basis of research into optical metamaterials. Plasmons of two-dimensional massless electrons, as present in graphene, show unusual behaviour that enables new tunable plasmonic metamaterials and, potentially, optoelectronic applications in the terahertz frequency range. Here we explore plasmon excitations in engineered graphene micro-ribbon arrays. We demonstrate that graphene plasmon resonances can be tuned over a broad terahertz frequency range by changing micro-ribbon width and in situ electrostatic doping. The ribbon width and carrier doping dependences of graphene plasmon frequency demonstrate power-law behaviour characteristic of two-dimensional massless Dirac electrons. The plasmon resonances have remarkably large oscillator strengths, resulting in prominent room-temperature optical absorption peaks. In comparison, plasmon absorption in a conventional two-dimensional electron gas was observed only at 4.2 K (refs 13, 14). The results represent a first look at light-plasmon coupling in graphene and point to potential graphene-based terahertz metamaterials.

  6. Lightweight Tunable Infrared Filter, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Michigan Aerospace Corporation has developed spaceflight qualified compact tunable Fabry-Perot interferometers for a number of applications, from ranging direct...

  7. Liquid Tunable Microlenses based on MEMS techniques

    Science.gov (United States)

    Zeng, Xuefeng; Jiang, Hongrui

    2013-01-01

    The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven, and those integrated within microfluidic systems. PMID:24163480

  8. Tunable Oleo-Furan Surfactants by Acylation of Renewable Furans

    Energy Technology Data Exchange (ETDEWEB)

    Park, Dae Sung; Joseph, Kristeen E.; Koehle, Maura; Krumm, Christoph; Ren, Limin; Damen, Jonathan N.; Shete, Meera H.; Lee, Han Seung; Zuo, Xiaobing; Lee, Byeongdu; Fan, Wei; Vlachos, Dionisios G.; Lobo, Raul F.; Tsapatsis, Michael; Dauenhauer, Paul J.

    2016-11-23

    An important advance in fluid surface control was the amphiphilic surfactant comprised of coupled molecular structures (i.e. hydrophilic and hydrophobic) to reduce surface tension between two distinct fluid phases. However, implementation of simple surfactants has been hindered by the broad range of applications in water containing alkaline earth metals (i.e. hard water), which disrupt surfactant function and require extensive use of undesirable and expensive chelating additives. Here we show that sugar-derived furans can be linked with triglyceride-derived fatty acid chains via Friedel-Crafts acylation within single layer (SPP) zeolite catalysts. These alkylfuran surfactants independently suppress the effects of hard water while simultaneously permitting broad tunability of size, structure, and function, which can be optimized for superior capability for forming micelles and solubilizing in water.

  9. The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

    Science.gov (United States)

    Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

    1995-01-01

    We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

  10. Auto-correlation of velocity-fluctuations and frequency-dependent diffusion constant for hot electrons

    International Nuclear Information System (INIS)

    Roy, M.D.; Nag, B.R.

    1981-01-01

    A method has been developed for determining the auto-correlation functions of the fluctuations in the transverse and the parallel components of hot carrier-velocity in a semiconductor by Monte Carlo simulation. The functions for electrons in InSb are determined by this method for applied electric fields of 50 V/cm, 75 V/cm, and 100 V/cm. With increasing value of the time interval the transverse auto-correlation function fall nearly exponentially to zero, but the parallel function falls sharply to a negative peak, then rises to positive values and finally becomes zero. The interval beyond which the auto-correlation function is zero and the correlation time are also evaluated. The correlation time is found to be approximately 1.6 times the relaxation time calculated from the chord mobility. The effect of the flight sampling time on the value of variance of the displacement, is investigated in terms of the low frequency diffusion constants, determined from the variation of the correlation functions. It is found that the diffusion constants become independent of the sampling time if it is of the order of one hundred times the relaxation time. The frequency-dependent diffusion constants are calculated from the correlation functions. The transverse diffusion constant falls monotonically with frequency for all the field strengths studied. The parallel diffusion constant has similar variation for the lower fields (50 V/cm and 75 V/cm) but it has a peak at about 44 GHz for the field of 100 V/cm. (orig.)

  11. A Poisson regression approach for modelling spatial autocorrelation between geographically referenced observations.

    Science.gov (United States)

    Mohebbi, Mohammadreza; Wolfe, Rory; Jolley, Damien

    2011-10-03

    Analytic methods commonly used in epidemiology do not account for spatial correlation between observations. In regression analyses, omission of that autocorrelation can bias parameter estimates and yield incorrect standard error estimates. We used age standardised incidence ratios (SIRs) of esophageal cancer (EC) from the Babol cancer registry from 2001 to 2005, and extracted socioeconomic indices from the Statistical Centre of Iran. The following models for SIR were used: (1) Poisson regression with agglomeration-specific nonspatial random effects; (2) Poisson regression with agglomeration-specific spatial random effects. Distance-based and neighbourhood-based autocorrelation structures were used for defining the spatial random effects and a pseudolikelihood approach was applied to estimate model parameters. The Bayesian information criterion (BIC), Akaike's information criterion (AIC) and adjusted pseudo R2, were used for model comparison. A Gaussian semivariogram with an effective range of 225 km best fit spatial autocorrelation in agglomeration-level EC incidence. The Moran's I index was greater than its expected value indicating systematic geographical clustering of EC. The distance-based and neighbourhood-based Poisson regression estimates were generally similar. When residual spatial dependence was modelled, point and interval estimates of covariate effects were different to those obtained from the nonspatial Poisson model. The spatial pattern evident in the EC SIR and the observation that point estimates and standard errors differed depending on the modelling approach indicate the importance of accounting for residual spatial correlation in analyses of EC incidence in the Caspian region of Iran. Our results also illustrate that spatial smoothing must be applied with care.

  12. A poisson regression approach for modelling spatial autocorrelation between geographically referenced observations

    Directory of Open Access Journals (Sweden)

    Jolley Damien

    2011-10-01

    Full Text Available Abstract Background Analytic methods commonly used in epidemiology do not account for spatial correlation between observations. In regression analyses, omission of that autocorrelation can bias parameter estimates and yield incorrect standard error estimates. Methods We used age standardised incidence ratios (SIRs of esophageal cancer (EC from the Babol cancer registry from 2001 to 2005, and extracted socioeconomic indices from the Statistical Centre of Iran. The following models for SIR were used: (1 Poisson regression with agglomeration-specific nonspatial random effects; (2 Poisson regression with agglomeration-specific spatial random effects. Distance-based and neighbourhood-based autocorrelation structures were used for defining the spatial random effects and a pseudolikelihood approach was applied to estimate model parameters. The Bayesian information criterion (BIC, Akaike's information criterion (AIC and adjusted pseudo R2, were used for model comparison. Results A Gaussian semivariogram with an effective range of 225 km best fit spatial autocorrelation in agglomeration-level EC incidence. The Moran's I index was greater than its expected value indicating systematic geographical clustering of EC. The distance-based and neighbourhood-based Poisson regression estimates were generally similar. When residual spatial dependence was modelled, point and interval estimates of covariate effects were different to those obtained from the nonspatial Poisson model. Conclusions The spatial pattern evident in the EC SIR and the observation that point estimates and standard errors differed depending on the modelling approach indicate the importance of accounting for residual spatial correlation in analyses of EC incidence in the Caspian region of Iran. Our results also illustrate that spatial smoothing must be applied with care.

  13. Bayesian modeling of the covariance structure for irregular longitudinal data using the partial autocorrelation function.

    Science.gov (United States)

    Su, Li; Daniels, Michael J

    2015-05-30

    In long-term follow-up studies, irregular longitudinal data are observed when individuals are assessed repeatedly over time but at uncommon and irregularly spaced time points. Modeling the covariance structure for this type of data is challenging, as it requires specification of a covariance function that is positive definite. Moreover, in certain settings, careful modeling of the covariance structure for irregular longitudinal data can be crucial in order to ensure no bias arises in the mean structure. Two common settings where this occurs are studies with 'outcome-dependent follow-up' and studies with 'ignorable missing data'. 'Outcome-dependent follow-up' occurs when individuals with a history of poor health outcomes had more follow-up measurements, and the intervals between the repeated measurements were shorter. When the follow-up time process only depends on previous outcomes, likelihood-based methods can still provide consistent estimates of the regression parameters, given that both the mean and covariance structures of the irregular longitudinal data are correctly specified and no model for the follow-up time process is required. For 'ignorable missing data', the missing data mechanism does not need to be specified, but valid likelihood-based inference requires correct specification of the covariance structure. In both cases, flexible modeling approaches for the covariance structure are essential. In this paper, we develop a flexible approach to modeling the covariance structure for irregular continuous longitudinal data using the partial autocorrelation function and the variance function. In particular, we propose semiparametric non-stationary partial autocorrelation function models, which do not suffer from complex positive definiteness restrictions like the autocorrelation function. We describe a Bayesian approach, discuss computational issues, and apply the proposed methods to CD4 count data from a pediatric AIDS clinical trial. © 2015 The Authors

  14. A Novel Acoustic Liquid Level Determination Method for Coal Seam Gas Wells Based on Autocorrelation Analysis

    Directory of Open Access Journals (Sweden)

    Ximing Zhang

    2017-11-01

    Full Text Available In coal seam gas (CSG wells, water is periodically removed from the wellbore in order to keep the bottom-hole flowing pressure at low levels, facilitating the desorption of methane gas from the coal bed. In order to calculate gas flow rate and further optimize well performance, it is necessary to accurately monitor the liquid level in real-time. This paper presents a novel method based on autocorrelation function (ACF analysis for determining the liquid level in CSG wells under intense noise conditions. The method involves the calculation of the acoustic travel time in the annulus and processing the autocorrelation signal in order to extract the weak echo under high background noise. In contrast to previous works, the non-linear dependence of the acoustic velocity on temperature and pressure is taken into account. To locate the liquid level of a coal seam gas well the travel time is computed iteratively with the non-linear velocity model. Afterwards, the proposed method is validated using experimental laboratory investigations that have been developed for liquid level detection under two scenarios, representing the combination of low pressure, weak signal, and intense noise generated by gas flowing and leakage. By adopting an evaluation indicator called Crest Factor, the results have shown the superiority of the ACF-based method compared to Fourier filtering (FFT. In the two scenarios, the maximal measurement error from the proposed method was 0.34% and 0.50%, respectively. The latent periodic characteristic of the reflected signal can be extracted by the ACF-based method even when the noise is larger than 1.42 Pa, which is impossible for FFT-based de-noising. A case study focused on a specific CSG well is presented to illustrate the feasibility of the proposed approach, and also to demonstrate that signal processing with autocorrelation analysis can improve the sensitivity of the detection system.

  15. Broadly tunable metal halide perovskites for solid-state light-emission applications

    NARCIS (Netherlands)

    Adjokatse, Sampson; Fang, Hong-Hua; Loi, Maria Antonietta

    2017-01-01

    The past two years have witnessed heightened interest in metal-halide perovskites as promising optoelectronic materials for solid-state light emitting applications beyond photovoltaics. Metal-halide perovskites are low-cost solution-processable materials with excellent intrinsic properties such as

  16. Bit corruption correlation and autocorrelation in a stochastic binary nano-bit system

    Science.gov (United States)

    Sa-nguansin, Suchittra

    2014-10-01

    The corruption process of a binary nano-bit model resulting from an interaction with N stochastically-independent Brownian agents (BAs) is studied with the help of Monte-Carlo simulations and analytic continuum theory to investigate the data corruption process through the measurement of the spatial two-point correlation and the autocorrelation of bit corruption at the origin. By taking into account a more realistic correlation between bits, this work will contribute to the understanding of the soft error or the corruption of data stored in nano-scale devices.

  17. A comparison of two least-squared random coefficient autoregressive models: with and without autocorrelated errors

    OpenAIRE

    Autcha Araveeporn

    2013-01-01

    This paper compares a Least-Squared Random Coefficient Autoregressive (RCA) model with a Least-Squared RCA model based on Autocorrelated Errors (RCA-AR). We looked at only the first order models, denoted RCA(1) and RCA(1)-AR(1). The efficiency of the Least-Squared method was checked by applying the models to Brownian motion and Wiener process, and the efficiency followed closely the asymptotic properties of a normal distribution. In a simulation study, we compared the performance of RCA(1) an...

  18. Impact of Autocorrelation on Principal Components and Their Use in Statistical Process Control

    DEFF Research Database (Denmark)

    Vanhatalo, Erik; Kulahci, Murat

    2015-01-01

    A basic assumption when using principal component analysis (PCA) for inferential purposes, such as in statistical process control (SPC), is that the data are independent in time. In many industrial processes, frequent sampling and process dynamics make this assumption unrealistic rendering sampled...... are generated using a stationary first-order vector autoregressive model. The results show that the descriptive ability of PCA may be seriously affected by autocorrelation causing a need to incorporate additional principal components to maintain the model's explanatory ability. When all variables have equal...

  19. Autocorrelation noise removal for optical coherence tomography by sparse filter design

    Science.gov (United States)

    Seck, Hon Luen; Zhang, Ying; Soh, Yeng Chai

    2012-07-01

    We present a reconstruction method to eliminate the autocorrelation noise (ACN) in optical coherence tomography (OCT). In this method, the optical fields scattered from the sample features are regarded as the response of a sparse finite impulse response (FIR) filter. Then the OCT reconstruction is formulated as one of identifying the parameters of a sparse FIR filter, which are obtained via an ℓ1 optimization with soft thresholding. The experimental results show that the proposed method can obtain OCT reconstruction results with effective attenuation of ACN.

  20. Microfluidic volumetric flow determination using optical coherence tomography speckle: An autocorrelation approach

    Energy Technology Data Exchange (ETDEWEB)

    De Pretto, Lucas R., E-mail: lucas.de.pretto@usp.br; Nogueira, Gesse E. C.; Freitas, Anderson Z. [Instituto de Pesquisas Energéticas e Nucleares, IPEN–CNEN/SP, Avenida Lineu Prestes, 2242, 05508-000 São Paulo (Brazil)

    2016-04-28

    Functional modalities of Optical Coherence Tomography (OCT) based on speckle analysis are emerging in the literature. We propose a simple approach to the autocorrelation of OCT signal to enable volumetric flow rate differentiation, based on decorrelation time. Our results show that this technique could distinguish flows separated by 3 μl/min, limited by the acquisition speed of the system. We further perform a B-scan of gradient flow inside a microchannel, enabling the visualization of the drag effect on the walls.

  1. Velocity-Autocorrelation Function in Liquids, Deduced from Neutron Incoherent Scattering Results

    DEFF Research Database (Denmark)

    Carneiro, Kim

    1976-01-01

    The Fourier transform p(ω) of the velocity-autocorrelation function is derived from neutron incoherent scattering results, obtained from the two liquids Ar and H2. The quality and significance of the results are discussed with special emphasis on the long-time t-3/2 tail, found in computer...... simulations and recent theories. The available experimental data from Na, Ar, and H2 close to their normal melting points are consistent with calculations which take into account the contribution to p(ω) from the tail at low frequencies....

  2. Revisiting Comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) with ALMA Autocorrelations

    Science.gov (United States)

    Yukiko Palmer, Maureen; Cordiner, Martin; de Val-Borro, Miguel; Charnley, Steven B.; Mumma, Michael J.

    2017-10-01

    The Atacama Large Millimeter/submillimeter array (ALMA) is a powerful tool for high-resolution mapping, but as an interferometer it is insensitive to large-scale structures due to the lack of zero-spacing (autocorrelation/single-dish) measurements. This is especially limiting in studies of cometary comae, which can extend up to hundreds of arcseconds. In this work, we make use of ALMA autocorrelations, treating the entire ALMA array as a collection of single-dish telescopes, to study the large comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON). This has significantly improved our spectral line sensitivity, allowing for the detection of new molecules in ISON's coma, including HCO+ and H(13C)N. We also present results from the combined use of ALMA autocorrelation (single dish) and cross-correlation (interferometric) data to create a more complete picture of the coma gas distribution in Lemmon. Since its initial detection in Hyakutake (Irvine et al. 1996), the origins of cometary HNC have been under investigation (Irvine et al. 1998; Rodgers & Charnley 2001, 2005; Lis et al. 2008). It might be produced from the degradation of a solid organic material. More measurements of the HNC parent scale length are needed to help understand the source of HNC. Using ALMA autocorrelation data, we follow up on the detection of HNC in comet Lemmon by Cordiner et al. (2014) and, assisted by newly-developed radiative transfer/excitation models, provide an analysis of its distribution in this comet.References: Irvine, W. M., Bockelee-Morvan, D., Lis, D. C., et al. 1996, Nature, 383, 418Irvine, W. M., Bergin, E. A., Dickens, J. E., et al. 1998, Nature, 393, 547; Rodgers, S. D., & Charnley, S. B. 2001, MNRAS, 323, 84; ---. 2005, MNRAS, 356, 1542; Lis, D. C., Bockelee-Morvan, D., Boissier, J., et al. 2008, ApJ, 675, 931; Cordiner, M. A., Remijan, A. J., Boissier, J., et al. 2014, ApJL, 792, L2Acknowledgments: NASA’s Astrobiology Program supported this work through the Goddard Center

  3. New autocorrelation technique for the IR FEL optical pulse width measurements

    Energy Technology Data Exchange (ETDEWEB)

    Amirmadhi, F.; Brau, K.A.; Becker, C. [Vanderbilt Univ., Nashville, TN (United States)] [and others

    1995-12-31

    We have developed a new technique for the autocorrelation measurement of optical pulse width at the Vanderbilt University FEL center. This method is based on nonlinear absorption and transmission characteristics of semiconductors such as Ge, Te and InAs suitable for the wavelength range from 2 to over 6 microns. This approach, aside being simple and low cost, removes the phase matching condition that is generally required for the standard frequency doubling technique and covers a greater wavelength range per nonlinear material. In this paper we will describe the apparatus, explain the principal mechanism involved and compare data which have been acquired with both frequency doubling and two-photon absorption.

  4. Influence of the nuclear autocorrelation function on the positron production in heavy-ion collisions

    International Nuclear Information System (INIS)

    Tomoda, T.; Weidenmueller, H.A.

    1983-01-01

    The influence of a nuclear reaction on atomic positron production in heavy-ion collisions is investigated. Using statistical concepts, we describe the nuclear S matrix for a heavy-ion induced reaction as a statistically fluctuating function of energy. The positron production rate is then dependent on the autocorrelation function of this S matrix, and on the ratio of the ''direct'' versus the ''fluctuating'' part of the nuclear cross section. Numerical calculations show that in this way, current experimental results on positron production in heavy-ion collisions can be reproduced in a semiquantitative fashion

  5. Artificial Oxide Heterostructures with Tunable Band Gap

    Science.gov (United States)

    2016-12-20

    tunable band gap and band structures in epitaxial grown CaMnO3. The efforts have been devoted to (1) the thin film growth; (2) the tunable optical...plan to pursue a claim for personal or organizational intellectual property? Changes in research objectives (if any): Change in AFOSR Program Officer

  6. Tunable synthesis of copper nanotubes

    International Nuclear Information System (INIS)

    Kaniukov, E; Yakimchuk, D; Kozlovsky, A; Shlimas, D; Zdorovets, M; Kadyrzhanov, K

    2016-01-01

    Simple method of tunable synthesis of copper nanotubes based on template synthesis was developed. A comprehensive study of the structural, morphological and electrical characteristics of the obtained nanostructures was carried out. Characterization of structural features was made by methods of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry analysis. Evaluation of wall thickness is made by methods of gas permeability. Electrical conductivity of nanotubes was define in the study of their current-voltage characteristics. The possibility to control of copper nanotubes physical properties by variation of the deposition parameters was shown. (paper)

  7. Automatically tunable continuous-wave optical parametric oscillator for high-resolution spectroscopy and sensitive trace-gas detection

    NARCIS (Netherlands)

    Ngai, A.K.Y.; Persijn, S.T.; Basum, G. von; Harren, F.J.M.

    2006-01-01

    We present a high-power (2.75 W), broadly tunable (2.75-3.83 mu m) continuous-wave optical parametric oscillator based on MgO-doped periodically poled lithium niobate. Automated tuning of the pump laser, etalon and crystal temperature results in a continuous wavelength coverage up to 450 cm(-1) per

  8. Spatial Pattern Analysis of Heavy Metals in Beijing Agricultural Soils Based on Spatial Autocorrelation Statistics

    Science.gov (United States)

    Huo, Xiao-Ni; Zhang, Wei-Wei; Sun, Dan-Feng; Li, Hong; Zhou, Lian-Di; Li, Bao-Guo

    2011-01-01

    This study explored the spatial pattern of heavy metals in Beijing agricultural soils using Moran’s I statistic of spatial autocorrelation. The global Moran’s I result showed that the spatial dependence of Cr, Ni, Zn, and Hg changed with different spatial weight matrixes, and they had significant and positive global spatial correlations based on distance weight. The spatial dependence of the four metals was scale-dependent on distance, but these scale effects existed within a threshold distance of 13 km, 32 km, 50 km, and 29 km, respectively for Cr, Ni, Zn, and Hg. The maximal spatial positive correlation range was 57 km, 70 km, 57 km, and 55 km for Cr, Ni, Zn, and Hg, respectively and these were not affected by sampling density. Local spatial autocorrelation analysis detected the locations of spatial clusters and spatial outliers and revealed that the pollution of these four metals occurred in significant High-high spatial clusters, Low-high, or even High-low spatial outliers. Thus, three major areas were identified and should be receiving more attention: the first was the northeast region of Beijing, where Cr, Zn, Ni, and Hg had significant increases. The second was the southeast region of Beijing where wastewater irrigation had strongly changed the content of metals, particularly of Cr and Zn, in soils. The third area was the urban fringe around city, where Hg showed a significant increase. PMID:21776217

  9. BetaBit: A fast generator of autocorrelated binary processes for geophysical research

    Science.gov (United States)

    Serinaldi, Francesco; Lombardo, Federico

    2017-05-01

    We introduce a fast and efficient non-iterative algorithm, called BetaBit, to simulate autocorrelated binary processes describing the occurrence of natural hazards, system failures, and other physical and geophysical phenomena characterized by persistence, temporal clustering, and low rate of occurrence. BetaBit overcomes the simulation constraints posed by the discrete nature of the marginal distributions of binary processes by using the link existing between the correlation coefficients of this process and those of the standard Gaussian processes. The performance of BetaBit is tested on binary signals with power-law and exponentially decaying autocorrelation functions (ACFs) corresponding to Hurst-Kolmogorov and Markov processes, respectively. An application to real-world sequences describing rainfall intermittency and the occurrence of strong positive phases of the North Atlantic Oscillation (NAO) index shows that BetaBit can also simulate surrogate data preserving the empirical ACF as well as signals with autoregressive moving average (ARMA) dependence structures. Extensions to cyclo-stationary processes accounting for seasonal fluctuations are also discussed.

  10. Broadband short pulse measurement by autocorrelation with a sum-frequency generation set-up

    Energy Technology Data Exchange (ETDEWEB)

    Glotin, F.; Jaroszynski, D.; Marcouille, O. [LURE, Orsay (France)] [and others

    1995-12-31

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength {lambda}=8.5 {mu}m suggested that very short light pulses could be generated, about 500 fs wide (FWHM). For these measurements a Michelson interferometer with a Te crystal, as a non-linear detector, was used as a second order autocorrelation device. More recent measurements in similar conditions have confirmed that the laser pulses observed are indeed single: they are not followed by other pulses distant by the slippage length N{lambda}. As the single micropulse length is likely to depend on the slippage, more measurements at different wavelengths would be useful. This is not directly possible with our actual interferometer set-up, based on a phase-matched non-linear crystal. However, we can use the broadband non-linear medium provided by one of our users` experiments: Sum-Frequency Generation over surfaces. With such autocorrelation set-up, interference fringes are no more visible, but this is largely compensated by the frequency range provided. First tests at 8 {mu}m have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up.

  11. A Comparison of Weights Matrices on Computation of Dengue Spatial Autocorrelation

    Science.gov (United States)

    Suryowati, K.; Bekti, R. D.; Faradila, A.

    2018-04-01

    Spatial autocorrelation is one of spatial analysis to identify patterns of relationship or correlation between locations. This method is very important to get information on the dispersal patterns characteristic of a region and linkages between locations. In this study, it applied on the incidence of Dengue Hemorrhagic Fever (DHF) in 17 sub districts in Sleman, Daerah Istimewa Yogyakarta Province. The link among location indicated by a spatial weight matrix. It describe the structure of neighbouring and reflects the spatial influence. According to the spatial data, type of weighting matrix can be divided into two types: point type (distance) and the neighbourhood area (contiguity). Selection weighting function is one determinant of the results of the spatial analysis. This study use queen contiguity based on first order neighbour weights, queen contiguity based on second order neighbour weights, and inverse distance weights. Queen contiguity first order and inverse distance weights shows that there is the significance spatial autocorrelation in DHF, but not by queen contiguity second order. Queen contiguity first and second order compute 68 and 86 neighbour list

  12. On the Decay Ratio Determination in BWR Stability Analysis by Auto-Correlation Function Techniques

    International Nuclear Information System (INIS)

    Behringer, K.; Hennig, D.

    2002-11-01

    A novel auto-correlation function (ACF) method has been investigated for determining the oscillation frequency and the decay ratio in BWR stability analyses. The neutron signals are band-pass filtered to separate the oscillation peak in the power spectral density (PSD) from background. Two linear second-order oscillation models are considered. These models, corrected for signal filtering and including a background term under the peak in the PSD, are then least-squares fitted to the ACF of the previously filtered neutron signal, in order to determine the oscillation frequency and the decay ratio. Our method uses fast Fourier transform techniques with signal segmentation for filtering and ACF estimation. Gliding 'short-term' ACF estimates on a record allow the evaluation of uncertainties. Numerical results are given which have been obtained from neutron data of the recent Forsmark I and Forsmark II NEA benchmark project. Our results are compared with those obtained by other participants in the benchmark project. The present PSI report is an extended version of the publication K. Behringer, D. Hennig 'A novel auto-correlation function method for the determination of the decay ratio in BWR stability studies' (Behringer, Hennig, 2002)

  13. Broadband short pulse measurement by autocorrelation with a sum-frequency generation set-up

    International Nuclear Information System (INIS)

    Glotin, F.; Jaroszynski, D.; Marcouille, O.

    1995-01-01

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength λ=8.5 μm suggested that very short light pulses could be generated, about 500 fs wide (FWHM). For these measurements a Michelson interferometer with a Te crystal, as a non-linear detector, was used as a second order autocorrelation device. More recent measurements in similar conditions have confirmed that the laser pulses observed are indeed single: they are not followed by other pulses distant by the slippage length Nλ. As the single micropulse length is likely to depend on the slippage, more measurements at different wavelengths would be useful. This is not directly possible with our actual interferometer set-up, based on a phase-matched non-linear crystal. However, we can use the broadband non-linear medium provided by one of our users' experiments: Sum-Frequency Generation over surfaces. With such autocorrelation set-up, interference fringes are no more visible, but this is largely compensated by the frequency range provided. First tests at 8 μm have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up

  14. Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics.

    Science.gov (United States)

    Xiang, Jie; Li, Yannian; Li, Quan; Paterson, Daniel A; Storey, John M D; Imrie, Corrie T; Lavrentovich, Oleg D

    2015-05-20

    Electrical tuning of selective reflection of light is achieved in a very broad spectral range from ultraviolet to visible and infrared by an oblique helicoidal state of a cholesteric liquid crystal in a wide temperature range (including room temperature). The phenomenon offers potential applications in tunable smart windows, lasers, optical filters and limiters, as well as in displays. © 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Low-loss tunable all-in-fiber filter for Raman spectroscopy

    DEFF Research Database (Denmark)

    Brunetti, Anna Chiara; Scolari, Lara; Lund-Hansen, Toke

    2011-01-01

    We show a novel in-line Rayleigh-rejection filter for Raman spectroscopy, based on a solid-core Photonic Crystal Fiber (PCF) filled with a high-index material. The device is low-loss and thermally tunable, and allows for a strong attenuation of the Rayleigh line at 532nm and the transmission...... of the Raman lines in a broad wavenumber range....

  16. Performance of signal-to-noise ratio estimation for scanning electron microscope using autocorrelation Levinson-Durbin recursion model.

    Science.gov (United States)

    Sim, K S; Lim, M S; Yeap, Z X

    2016-07-01

    A new technique to quantify signal-to-noise ratio (SNR) value of the scanning electron microscope (SEM) images is proposed. This technique is known as autocorrelation Levinson-Durbin recursion (ACLDR) model. To test the performance of this technique, the SEM image is corrupted with noise. The autocorrelation function of the original image and the noisy image are formed. The signal spectrum based on the autocorrelation function of image is formed. ACLDR is then used as an SNR estimator to quantify the signal spectrum of noisy image. The SNR values of the original image and the quantified image are calculated. The ACLDR is then compared with the three existing techniques, which are nearest neighbourhood, first-order linear interpolation and nearest neighbourhood combined with first-order linear interpolation. It is shown that ACLDR model is able to achieve higher accuracy in SNR estimation. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  17. Nonlinear, tunable and active metamaterials

    CERN Document Server

    Lapine, Mikhail; Kivshar, Yuri

    2015-01-01

    Metamaterials, artificial electromagnetic media achieved by structuring on the subwave-length-scale were initially suggested for the negative index and superlensing. They became a paradigm for engineering electromagnetic space and controlling propagation of waves. The research agenda is now shifting on achieving tuneable, switchable, nonlinear and sensing functionalities. The time has come to talk about the emerging research field of metadevices employing active and tunable metamaterials with unique functionalities achieved by structuring of functional matter on the subwave-length scale. This book presents the first systematic and comprehensive summary of the reviews written by the pioneers and top-class experts in the field of metamaterials. It addresses many grand challenges of the cutting edge research for creating smaller and more efficient photonic structures and devices.

  18. Tunable conductivity in mesoporous germanium

    Science.gov (United States)

    Beattie, Meghan N.; Bioud, Youcef A.; Hobson, David G.; Boucherif, Abderraouf; Valdivia, Christopher E.; Drouin, Dominique; Arès, Richard; Hinzer, Karin

    2018-05-01

    Germanium-based nanostructures have attracted increasing attention due to favourable electrical and optical properties, which are tunable on the nanoscale. High densities of germanium nanocrystals are synthesized via electrochemical etching, making porous germanium an appealing nanostructured material for a variety of applications. In this work, we have demonstrated highly tunable electrical conductivity in mesoporous germanium layers by conducting a systematic study varying crystallite size using thermal annealing, with experimental conductivities ranging from 0.6 to 33 (×10‑3) Ω‑1 cm‑1. The conductivity of as-prepared mesoporous germanium with 70% porosity and crystallite size between 4 and 10 nm is shown to be ∼0.9 × 10‑3 Ω‑1 cm‑1, 5 orders of magnitude smaller than that of bulk p-type germanium. Thermal annealing for 10 min at 400 °C further reduced the conductivity; however, annealing at 450 °C caused a morphological transformation from columnar crystallites to interconnecting granular crystallites and an increase in conductivity by two orders of magnitude relative to as-prepared mesoporous germanium caused by reduced influence of surface states. We developed an electrostatic model relating the carrier concentration and mobility of p-type mesoporous germanium to the nanoscale morphology. Correlation within an order of magnitude was found between modelled and experimental conductivities, limited by variation in sample uniformity and uncertainty in void size and fraction after annealing. Furthermore, theoretical results suggest that mesoporous germanium conductivity could be tuned over four orders of magnitude, leading to optimized hybrid devices.

  19. Estimating the Persistence and the Autocorrelation Function of a Time Series that is Measured with Error

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger

    2014-01-01

    An economic time series can often be viewed as a noisy proxy for an underlying economic variable. Measurement errors will influence the dynamic properties of the observed process and may conceal the persistence of the underlying time series. In this paper we develop instrumental variable (IV......) methods for extracting information about the latent process. Our framework can be used to estimate the autocorrelation function of the latent volatility process and a key persistence parameter. Our analysis is motivated by the recent literature on realized volatility measures that are imperfect estimates...... of actual volatility. In an empirical analysis using realized measures for the Dow Jones industrial average stocks, we find the underlying volatility to be near unit root in all cases. Although standard unit root tests are asymptotically justified, we find them to be misleading in our application despite...

  20. Estimating the Persistence and the Autocorrelation Function of a Time Series that is Measured with Error

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Lunde, Asger

    An economic time series can often be viewed as a noisy proxy for an underlying economic variable. Measurement errors will influence the dynamic properties of the observed process and may conceal the persistence of the underlying time series. In this paper we develop instrumental variable (IV......) methods for extracting information about the latent process. Our framework can be used to estimate the autocorrelation function of the latent volatility process and a key persistence parameter. Our analysis is motivated by the recent literature on realized (volatility) measures, such as the realized...... variance, that are imperfect estimates of actual volatility. In an empirical analysis using realized measures for the DJIA stocks we find the underlying volatility to be near unit root in all cases. Although standard unit root tests are asymptotically justified, we find them to be misleading in our...

  1. Artificial fingerprint recognition by using optical coherence tomography with autocorrelation analysis

    Science.gov (United States)

    Cheng, Yezeng; Larin, Kirill V.

    2006-12-01

    Fingerprint recognition is one of the most widely used methods of biometrics. This method relies on the surface topography of a finger and, thus, is potentially vulnerable for spoofing by artificial dummies with embedded fingerprints. In this study, we applied the optical coherence tomography (OCT) technique to distinguish artificial materials commonly used for spoofing fingerprint scanning systems from the real skin. Several artificial fingerprint dummies made from household cement and liquid silicone rubber were prepared and tested using a commercial fingerprint reader and an OCT system. While the artificial fingerprints easily spoofed the commercial fingerprint reader, OCT images revealed the presence of them at all times. We also demonstrated that an autocorrelation analysis of the OCT images could be potentially used in automatic recognition systems.

  2. [A unified autocorrelated method of electroencephalogram analysis and some results of its use].

    Science.gov (United States)

    Khizhun, A F; Saĭko, Iu V

    1993-01-01

    Unified autocorrelation method of EEG analysis (UNIFAC-EEG) represents some optimized algorithms of EEG-signals processing according to the sign of maximum stability to the broadband noise. These algorithms are united by the common aim to identify generation models of these signals narrowband components on the basis of concrete empirical data and estimation of their source dynamic parameters according to the identification results. On the basis of this method it was proved that alpha-rhythm sources belonged to the type of structural stable dynamic systems, and its decrement value could serve as one of the parameters of the functional state of the central nervous system. The effect was found of the interaction between the heart electric fields and human brain in EEG frequent alpha-range.

  3. Positron-electron autocorrelation function study of E-center in phosphorus-doped silicon

    International Nuclear Information System (INIS)

    Ho, K.F.; Beling, C.D.; Fung, S.; Biasini, M.; Ferro, G.; Gong, M.

    2004-01-01

    Two dimensional fourier transformed angular correlation of annihilation radiation (2D-FT-ACAR) spectra have been taken for 10 19 cm -3 phosphorus-doped Si in the as grown state and after being subjected to 1.8 MeV e - fluences of 2 x 10 18 cm -2 . In the spectra of the irradiated samples, the zero-crossing points are observed to displace outwards from the bravais lattice positions. It is suggested that this results from positrons annihilating with electrons in localized orbitals at the defect site. An attempt is made to extract just the component of the defect's positron-electron autocorrelation function that relates to the localized defect orbitals. It is argued that such an extracted real-space function may provide a suitable means for obtaining a mapping of localized defect orbitals. (orig.)

  4. Autocorrelation spectra of an air-fluidized granular system measured by NMR

    Science.gov (United States)

    Lasic, S.; Stepisnik, J.; Mohoric, A.; Sersa, I.; Planinsic, G.

    2006-09-01

    A novel insight into the dynamics of a fluidized granular system is given by a nuclear magnetic resonance method that yields the spin-echo attenuation proportional to the spectrum of the grain positional fluctuation. Measurements of the air-fluidized oil-filled spheres and mustard seeds at different degrees of fluidization and grain volume fractions provide the velocity autocorrelation that differs from the commonly anticipated exponential Enskog decay. An empiric formula, which corresponds to the model of grain caging at collisions with adjacent beads, fits well to the experimental data. Its parameters are the characteristic collision time, the free path between collisions and the cage-breaking rate or the diffusion-like constant, which decreases with increasing grain volume fraction. Mean-squared displacements calculated from the correlation spectrum clearly show transitions from ballistic, through sub-diffusion and into diffusion regimes of grain motion.

  5. Momentum autocorrelation function of an impurity in a classical oscillator chain with alternating masses II. Illustrations

    Science.gov (United States)

    Yu, Ming B.

    2015-11-01

    A classic diatomic chain with a mass impurity is studied using the recurrence relations method. The dependence of frequency and amplitude upon two mass ratios is illustrated in detail. By examining the figures we can learn a lot about the model, such as the widths of the acoustic and optical branches as well as the gap between them, the frequency and amplitude of the resonant modes, etc. The momentum autocorrelation functions of the impurity in different regions of the configuration space are numerically calculated and illustrated. A theorem is obtained governing the upper and lower frequencies of the acoustic and optical branches. The envelope of the integrand of the cut contribution is determined. The convergence of numerical calculations of time integration for parameter W to its theoretical value is confirmed.

  6. Nodule detection methods using autocorrelation features on 3D chest CT scans

    International Nuclear Information System (INIS)

    Hara, T.; Zhou, X.; Okura, S.; Fujita, H.; Kiryu, T.; Hoshi, H.

    2007-01-01

    Lung cancer screening using low dose X-ray CT scan has been an acceptable examination to detect cancers at early stage. We have been developing an automated detection scheme for lung nodules on CT scan by using second-order autocorrelation features and the initial performance for small nodules (< 10 mm) shows a high true-positive rate with less than four false-positive marks per case. In this study, an open database of lung images, LIDC (Lung Image Database Consortium), was employed to evaluate our detection scheme as an consistency test. The detection performance for solid and solitary nodules in LIDC, included in the first data set opened by the consortium, was 83% (10/12) true-positive rate with 3.3 false-positive marks per case. (orig.)

  7. The use of autocorrelation analysis in the longitudinal study of mood patterns in depressed patients.

    Science.gov (United States)

    Huba, G J; Lawlor, W G; Stallone, F; Fieve, R R

    1976-02-01

    The statistical method of autocorrelation, commonly used in econometrics and engineering, was applied to the daily mood scores of ten depressive hospital in-patients. The analyses made possible the quantification of two aspects of the longitudinal course of individual patients' psychopathology, the degree of day-to-day stability and the degree of periodicity in mood. Quantification of the degree of day-to-day mood stability yielded wide variations between patients and suggested that patients might be usefully categorized in terms of this characteristic. Mood stability during periods of severe depression was found to be less pronounced than during periods of relatively moderate depression. Furthermore, the existence of 'mini-cycles', cyclical fluctuations in mood of one to two weeks' duration occurring during the course of depressive episodes, was demonstrated in three cases.

  8. Spectral Velocity Estimation using the Autocorrelation Function and Sparse data Sequences

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2005-01-01

    the sparse sequence and averaged over a pulse length. The 1:2 sequence using 2 flow emission for one b-Mode emissions showed a nearly indistinguishable spectrum compared to a Fourier spectrum calculated on the full data. The sparser sequences give a higher noise in the spectrum proportional to the sparseness......Ultrasound scanners can be used for displaying the distribution of velocities in blood vessels by finding the power spectrum of the received signal. It is desired to show a B-mode image for orientation and data for this has to be acquired interleaved with the flow data. Techniques for maintaining...... both the B-mode frame rate, and at the same time have the highest possible $f_{prf}$ only limited by the depth of investigation, are, thus, of great interest. The power spectrum can be calculated from the Fourier transform of the autocorrelation function $R_r(k)$. The lag $k$ corresponds...

  9. Cut contribution to momentum autocorrelation function of an impurity in a classical diatomic chain

    Science.gov (United States)

    Yu, Ming B.

    2018-02-01

    A classic diatomic chain with a mass impurity is studied using the recurrence relations method. The momentum autocorrelation function of the impurity is a sum of contributions from two pairs of resonant poles and three branch cuts. The former results in cosine function and the latter in acoustic and optical branches. By use of convolution theorem, analytical expressions for the acoustic and optical branches are derived as even-order Bessel function expansions. The expansion coefficients are integrals of elliptic functions in the real axis for the acoustic branch and along a contour parallel to the imaginary axis for the optical branch, respectively. An integral is carried out for the calculation of optical branch: ∫0 ϕ dθ/√((1 - r 1 2 sin2 θ)(1 - r 2 2 sin2 θ)) = igsn -1 (sin ϕ) ( r 2 2 > r 1 2 > 1, g is a constant).

  10. Processing of pulse oximeter signals using adaptive filtering and autocorrelation to isolate perfusion and oxygenation components

    Science.gov (United States)

    Ibey, Bennett; Subramanian, Hariharan; Ericson, Nance; Xu, Weijian; Wilson, Mark; Cote, Gerard L.

    2005-03-01

    A blood perfusion and oxygenation sensor has been developed for in situ monitoring of transplanted organs. In processing in situ data, motion artifacts due to increased perfusion can create invalid oxygenation saturation values. In order to remove the unwanted artifacts from the pulsatile signal, adaptive filtering was employed using a third wavelength source centered at 810nm as a reference signal. The 810 nm source resides approximately at the isosbestic point in the hemoglobin absorption curve where the absorbance of light is nearly equal for oxygenated and deoxygenated hemoglobin. Using an autocorrelation based algorithm oxygenation saturation values can be obtained without the need for large sampling data sets allowing for near real-time processing. This technique has been shown to be more reliable than traditional techniques and proven to adequately improve the measurement of oxygenation values in varying perfusion states.

  11. Electro-Optic Tunable Laser Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will develop a compact, rugged, rapidly and widely tunable laser based on a quantum cascade diode laser at...

  12. Tunable Beam Diffraction in Infiltrated Microstructured Fibers

    DEFF Research Database (Denmark)

    Rosberg, Christian Romer; Bennet, Francis H.; Neshev, Dragomir N.

    We experimentally study beam propagation in two dimensional photonic lattices in microstructured optical fibers infiltrated with high index liquids. We demonstrate strongly tunable beam diffraction by dynamically varying the coupling between individual lattice sites.......We experimentally study beam propagation in two dimensional photonic lattices in microstructured optical fibers infiltrated with high index liquids. We demonstrate strongly tunable beam diffraction by dynamically varying the coupling between individual lattice sites....

  13. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.......We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  14. Three-dimensional broadband tunable terahertz metamaterials

    DEFF Research Database (Denmark)

    Fan, Kebin; Strikwerda, Andrew; Zhang, Xin

    2013-01-01

    We present optically tunable magnetic three-dimensional (3D) metamaterials at terahertz (THz) frequencies which exhibit a tuning range of ~30% of the resonance frequency. This is accomplished by fabricating 3D array structures consisting of double-split-ring resonators (DSRRs) on silicon on sapph...... as verified through electromagnetic simulations and parameter retrieval. Our approach extends dynamic metamaterial tuning to magnetic control, and may find applications in switching and modulation, polarization control, or tunable perfect absorbers....

  15. Electrically Tunable Plasmonic Resonances with Graphene

    DEFF Research Database (Denmark)

    Emani, Naresh K.; Chung, Ting-Fung; Ni, Xingjie

    2012-01-01

    Real time switching of a plasmonic resonance may find numerous applications in subwavelength optoelectronics, spectroscopy and sensing. We take advantage of electrically tunable interband transitions in graphene to control the strength of the plasmonic resonance.......Real time switching of a plasmonic resonance may find numerous applications in subwavelength optoelectronics, spectroscopy and sensing. We take advantage of electrically tunable interband transitions in graphene to control the strength of the plasmonic resonance....

  16. Tunable Multifunction Filter Using Current Conveyor

    OpenAIRE

    Kumar, Manish; Srivastava, M. C.; Kumar, Umesh

    2010-01-01

    The paper presents a current tunable multifunction filter using current conveyor. The proposed circuit can be realized as on chip tunable low pass, high pass, band pass and elliptical notch filter. The circuit employs two current conveyors, one OTA, four resistors and two grounded capacitors, ideal for integration. It has only one output terminal and the number of input terminals may be used. Further, there is no requirement for component matching in the circuit. The resonance frequency ({\\om...

  17. Custom 3D Printable Silicones with Tunable Stiffness.

    Science.gov (United States)

    Durban, Matthew M; Lenhardt, Jeremy M; Wu, Amanda S; Small, Ward; Bryson, Taylor M; Perez-Perez, Lemuel; Nguyen, Du T; Gammon, Stuart; Smay, James E; Duoss, Eric B; Lewicki, James P; Wilson, Thomas S

    2018-02-01

    Silicone elastomers have broad versatility within a variety of potential advanced materials applications, such as soft robotics, biomedical devices, and metamaterials. A series of custom 3D printable silicone inks with tunable stiffness is developed, formulated, and characterized. The silicone inks exhibit excellent rheological behavior for 3D printing, as observed from the printing of porous structures with controlled architectures. Herein, the capability to tune the stiffness of printable silicone materials via careful control over the chemistry, network formation, and crosslink density of the ink formulations in order to overcome the challenging interplay between ink development, post-processing, material properties, and performance is demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Broadband tunable terahertz polarization converter based on graphene metamaterial

    Science.gov (United States)

    Luo, Shiwen; Li, Bin; Yu, Anlan; Gao, Jun; Wang, Xinbing; Zuo, Duluo

    2018-04-01

    We design and numerically investigate a broadband tunable terahertz polarization converter based on graphene metamaterial. The converter presents a broad conversion band with high polarization conversion ratio (>0.95) in terahertz frequency over a bandwidth which is 25.8% of the central frequency. The converter can be dynamically tuned by varying the Fermi Energy of the graphene without changing the geometric structure. The converter shows high conversion ratio for a wide range of incident angles from 0 to 40°. By the scaling of the proposed structure, the broadband properties of the converter can be easily spread to other frequency. The proposed metamaterial offers an approach in the manipulation of the light polarization and has potential applications in imaging, sensing and communications.

  19. Surface defect assisted broad spectra emission from CdSe quantum dots for white LED application

    Science.gov (United States)

    Samuel, Boni; Mathew, S.; Anand, V. R.; Correya, Adrine Antony; Nampoori, V. P. N.; Mujeeb, A.

    2018-02-01

    This paper reports, broadband photoluminescence from CdSe quantum dots (QDs) under the excitation of 403 nm using fluorimeter and 403 nm CW laser excitation. The broad spectrum obtained from the colloidal quantum dots was ranges from 450 nm to 800 nm. The broadness of the spectra was attributed to the merging of band edge and defect driven emissions from the QDs. Six different sizes of particles were prepared via kinetic growth method by using CdO and elemental Se as sources of Cd and Se respectively. The particle sizes were measured from TEM images. The size dependent effect on broad emission was also studied and the defect state emission was found to be predominant in very small QDs. The defect driven emission was also observed to be redshifted, similar to the band edge emission, due to quantum confinement effect. The emission corresponding to different laser power was also studied and a linear relation was obtained. In order to study the colour characteristics of the emission, CIE chromaticity coordinate, CRI and CCT of the prepared samples were measured. It is observed that, these values were tunable by the addition of suitable intensity of blue light from the excitation source to yield white light of various colour temperatures. The broad photoluminescence spectrum of the QDs, were compared with that of a commercially available white LED. It was found that the prepared QDs are good alternatives for the phosphor in phosphor converted white LEDs, to provide good spectral tunability.

  20. The impact of temporal auto-correlation mismatch on the assimilation of satellite-derived surface soil moisture retrievals

    Science.gov (United States)

    Satellite-based surface soil moisture retrievals are commonly assimilated into eco-hydrological models in order to obtain improved profile soil moisture estimates. However, differences in temporal auto-correlation structure between these retrievals and comparable model-based predictions can potentia...

  1. Ultrafast detection and autocorrelation of picosecond THz radiation pulses with a GaAs/AlAs superlattice

    NARCIS (Netherlands)

    Winnerl, S.; Seiwerth, W.; Schomburg, E.; Grenzer, J.; Renk, K. F.; Langerak, Cjgm; van der Meer, A. F. G.; Pavel' ev, D. G.; Koschurinov, Y.; Ignatov, A. A.

    1998-01-01

    We used a wide miniband GaAs/AlAs superlattice (at room temperature) for detection and autocorrelation of picosecond THz radiation pulses (frequency 4.3 THz) from a free- electron laser. The detection was based on a THz-field induced change in conductivity of the superlattice, and the correlation on

  2. Cross- and Auto-Correlation Effects arising from Averaging: The Case of US Interest Rates and Equity Duration

    NARCIS (Netherlands)

    W.G.P.M. Hallerbach (Winfried)

    2000-01-01

    textabstractMost of the available monthly interest data series consist of monthly averages of daily observations. It is well- known that this averaging introduces spurious autocorrelation effects in the first differences of the series. It is exactly this differenced series we are interested in when

  3. Autocorrelation structure of convective rainfall in semiarid-arid climate derived from high-resolution X-Band radar estimates

    Science.gov (United States)

    Marra, Francesco; Morin, Efrat

    2018-02-01

    Small scale rainfall variability is a key factor driving runoff response in fast responding systems, such as mountainous, urban and arid catchments. In this paper, the spatial-temporal autocorrelation structure of convective rainfall is derived with extremely high resolutions (60 m, 1 min) using estimates from an X-Band weather radar recently installed in a semiarid-arid area. The 2-dimensional spatial autocorrelation of convective rainfall fields and the temporal autocorrelation of point-wise and distributed rainfall fields are examined. The autocorrelation structures are characterized by spatial anisotropy, correlation distances 1.5-2.8 km and rarely exceeding 5 km, and time-correlation distances 1.8-6.4 min and rarely exceeding 10 min. The observed spatial variability is expected to negatively affect estimates from rain gauges and microwave links rather than satellite and C-/S-Band radars; conversely, the temporal variability is expected to negatively affect remote sensing estimates rather than rain gauges. The presented results provide quantitative information for stochastic weather generators, cloud-resolving models, dryland hydrologic and agricultural models, and multi-sensor merging techniques.

  4. On the intermediate time behavior of the stress tensor and velocity autocorrelation functions for dense hard sphere systems

    NARCIS (Netherlands)

    Beijeren, H. van

    1984-01-01

    It is conjectured that the large values at intermediate times of the stress tensor autocorrelation function, found in computer simulations, may be caused by a coupling of the stress tensor to pairs of slowly decaying extended heat modes of large wave number. Approximate expressions, amenable to

  5. An autocorrelation analysis approach to detecting land cover change using hyper-temporal time-series data

    CSIR Research Space (South Africa)

    Kleynhans, W

    2011-07-01

    Full Text Available time-series satellite data is proposed. The method is a per pixel change alarm that uses the temporal autocorrelation to infer a change metric which yields a change or no-change decision after thresholding. Simulated change data was generated and used...

  6. Improved tunable microstrip SQUID amplifier for the Axion Dark Matter eXperiment (ADMX)

    Science.gov (United States)

    O'Kelley, Sean; Hansen, Jorn; Mol, Jan-Michael; Hilton, Gene; Clarke, John

    2015-03-01

    We present a series of tunable microstrip SQUID amplifiers (MSAs) for use in ADMX. The axion dark matter candidate is detected via Primakoff conversion to a microwave photon in a high-Q (~ 105) tunable microwave cavity, cooled to 1.6 K or lower, in the presence of a 7-tesla magnetic field. The microwave photon frequency is a function of the unknown axion mass, so that the cavity and amplifier must be scanned over a broad frequency range. An MSA is constructed by flux-coupling a resonant microstrip to a resistively-shunted SQUID biased into the voltage state. We demonstrate gains exceeding 20 dB, at frequencies above 900 MHz. Tunability is achieved by terminating the microstrip with a low inductance GaAs varactor diode that operates at cryogenic temperatures. By varying the voltage bias of the varactor we vary its capacitance, allowing a reflected phase varying from nearly 0 to π at the end of the microstrip, and thus a standing wave tunable from nearly λ/2 to λ/4. With proper design of the microwave environment, a noise temperature of 1/2 to 1/4 of the physical temperature is demonstrated.

  7. Field test comparison of an autocorrelation technique for determining grain size using a digital 'beachball' camera versus traditional methods

    Science.gov (United States)

    Barnard, P.L.; Rubin, D.M.; Harney, J.; Mustain, N.

    2007-01-01

    This extensive field test of an autocorrelation technique for determining grain size from digital images was conducted using a digital bed-sediment camera, or 'beachball' camera. Using 205 sediment samples and >1200 images from a variety of beaches on the west coast of the US, grain size ranging from sand to granules was measured from field samples using both the autocorrelation technique developed by Rubin [Rubin, D.M., 2004. A simple autocorrelation algorithm for determining grain size from digital images of sediment. Journal of Sedimentary Research, 74(1): 160-165.] and traditional methods (i.e. settling tube analysis, sieving, and point counts). To test the accuracy of the digital-image grain size algorithm, we compared results with manual point counts of an extensive image data set in the Santa Barbara littoral cell. Grain sizes calculated using the autocorrelation algorithm were highly correlated with the point counts of the same images (r2 = 0.93; n = 79) and had an error of only 1%. Comparisons of calculated grain sizes and grain sizes measured from grab samples demonstrated that the autocorrelation technique works well on high-energy dissipative beaches with well-sorted sediment such as in the Pacific Northwest (r2 ??? 0.92; n = 115). On less dissipative, more poorly sorted beaches such as Ocean Beach in San Francisco, results were not as good (r2 ??? 0.70; n = 67; within 3% accuracy). Because the algorithm works well compared with point counts of the same image, the poorer correlation with grab samples must be a result of actual spatial and vertical variability of sediment in the field; closer agreement between grain size in the images and grain size of grab samples can be achieved by increasing the sampling volume of the images (taking more images, distributed over a volume comparable to that of a grab sample). In all field tests the autocorrelation method was able to predict the mean and median grain size with ???96% accuracy, which is more than

  8. Broad-Application Test Reactor

    International Nuclear Information System (INIS)

    Motloch, C.G.

    1992-05-01

    This report is about a new, safe, and operationally efficient DOE reactor of nuclear research and testing proposed for the early to mid- 21st Century. Dubbed the Broad-Application Test Reactor (BATR), the proposed facility incorporates a multiple-application, multiple-mission design to support DOE programs such as naval reactors and space power and propulsion, as well as research in medical, science, isotope, and electronics arenas. DOE research reactors are aging, and implementing major replacement projects requires long lead times. Primary design drivers include safety, low risk, minimum operation cost, mission flexibility, waste minimization, and long life. Scientists and engineers at the Idaho National Engineering Laboratory are evaluating possible fuel forms, structural materials, reactor geometries, coolants, and moderators

  9. Broad-band beam buncher

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Flood, W.S.; Arthur, A.A.; Voelker, F.

    1986-01-01

    This patent describes a broad-band beam buncher. This beam buncher consists of: a housing adapted to be eacuated, an electron gun in the housing for producing a beam of electrons, buncher means in the housing forming a buncher cavity which has an entrance opening for receiving the electron beam and an exit opening through which the electron beam passes out of the buncher cavity, a drift tube electrode in the buncher cavity and disposed between the entrance opening and the exit opening with first and second gaps between the drift tube electrode and the entrance and exit openings, the drift tube electrode which has a first drift space through which the electron beam passes in traveling between the entrance and exit openings, modulating means for supplying an ultrahigh frequeny modulating signal to the drift tube electrode for producing velocity modulation of the electrons in the electron beam as the electrons pass through the buncher cavity and the drift tube electrode between the entrance opening and the exit opening, drift space means in the housing forming a second drift space for receiving the velocity modulated electron beam from the exit opening, the velocity modulated electron beam being bunched as it passes along the second drift space, the drift space means has a discharge opening through which the electron beam is discharged from the second drift space after being bunched therein, the modulating means containing a signal source for producing an ultrahigh frequency signal, a transmission line connected between the signal source and the drift tube electrode, and terminating means connected to the drift tube electrode for terminating the transmission line in approximately its characteristic impedance to afford a broad response band with minimum 6 variations therein

  10. Emission tunability and local environment in europium-doped OH{sup −}-free calcium aluminosilicate glasses for artificial lighting applications

    Energy Technology Data Exchange (ETDEWEB)

    Farias, Aline M.; Sandrini, Marcelo; Viana, José Renato M.; Baesso, Mauro L.; Bento, Antônio C.; Rohling, Jurandir H. [Departamento de Física, Universidade Estadual de Maringá, Av Colombo, 5790, 87020-900, Maringá, PR (Brazil); Guyot, Yannick [Laboratoire de Physico–Chimie des Matériaux Luminescents, Université de Lyon, Université Claude Bernard Lyon 1, Villeurbanne, UMR 5620 CNRS 69622 (France); De Ligny, Dominique [Department of Materials Science and Engineering, University of Erlangen Nürnberg, Martens str. 5, 91058, Erlangen (Germany); Nunes, Luiz Antônio O. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense400, 13566-590, São Carlos, SP (Brazil); Gandra, Flávio G. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil); Sampaio, Juraci A. [Lab Ciências Físicas, Universidade Estadual Norte Fluminense, 28013-602, Campos Dos Goytacazes, RJ (Brazil); Lima, Sandro M.; Andrade, Luis Humberto C. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul-UEMS, Dourados, MS, C. P. 351, CEP 79804-970 (Brazil); and others

    2015-04-15

    The relationship between emission tunability and the local environment of europium ions in OH{sup −}-free calcium aluminosilicate glasses was investigated, focusing on the development of devices for artificial lighting. Significant conversion of Eu{sup 3+} to Eu{sup 2+} was obtained by means of melting the glasses under a vacuum atmosphere and controlling the silica content, resulting in broad, intense, and tunable luminescence ranging from blue to red. Electron spin resonance and X-ray absorption near edge structure measurements enabled correlation of the luminescence behavior of the material with the Eu{sup 2+}/Eu{sup 3+} concentration ratio and changes in the surrounding ions' crystal field. The coordinates of the CIE 1931 chromaticity diagram were calculated from the spectra, and the contour maps showed that the light emitted from Eu{sup 2+} presented broad bands and enhanced color tuning, ranging from reddish-orange to blue. The results showed that these Eu doped glasses can be used for tunable white lighting by combining matrix composition and the adjustment of the pumping wavelength. - Highlights: • Eu{sup 2+}-doped OH{sup −} free calcium aluminosilicate glass as a new source for white lighting. • Correlation between emission tunability and local environment of europium ions. • Significant reduction of Eu{sup 3+} to Eu{sup 2+} by melting the glasses under vacuum atmosphere. • Broad, intense and tunable luminescence ranging from blue to red.

  11. Tunable High Harmonic Generation driven by a Visible Optical Parametric Amplifier

    Directory of Open Access Journals (Sweden)

    Keathley P.

    2013-03-01

    Full Text Available We studied high-harmonic generation (HHG in Ar, Ne and He gas jets using a broadly tunable, high-energy optical parametric amplifier (OPA in the visible wavelength range. We optimized the noncollinear OPA to deliver tunable, femtosecond pulses with 200-500 μJ energy at 1-kHz repetition rate with excellent spatiotemporal properties, suitable for HHG experiments. By tuning the central wavelength of the OPA while keeping energy, duration and beam size constant, we experimentally studied the scaling law of conversion efficiency and cut-off energy with the driver wavelength in argon and helium respectively. Our measurements show a λ−5.9±0.9 wavelength dependence of the conversion efficiency and a λ1.7±0.2 dependence of the HHG cut-off photon energy over the full visible range in agreement with previous experiments of near- and mid-IR wavelengths. By tuning the central wavelength of the driver source and changing the gas, the high order harmonic spectra in the extreme ultraviolet cover the full range of photon energy between ~25 eV and ~100 eV. Due to the high coherence intrinsic in HHG, as well as the broad and continuous tunability in the extreme UV range, a high energy, high repetition rate version of this source might be an ideal seed for free electron lasers.

  12. Characterization of Forested Landscapes From Remotely Sensed Data Using Fractals and Spatial Autocorrelation

    Science.gov (United States)

    Al-Hamdan, Mohammad Z.; Cruise, James F.; Rickman, Douglas L.; Quattrochi, Dale A.

    2007-01-01

    The characterization of forested areas is frequently required in resource management practice. Passive remotely sensed data, which are much more accessible and cost effective than are active data, have rarely, if ever, been used to characterize forest structure directly, but rather they usually focus on the estimation of indirect measurement of biomass or canopy coverage. In this study, some spatial analysis techniques are presented that might be employed with Landsat TM data to analyze forest structure characteristics. A case study is presented wherein fractal dimensions, along with a simple spatial autocorrelation technique (Moran s I), were related to stand density parameters of the Oakmulgee National Forest located in the southeastern United States (Alabama). The results of the case study presented herein have shown that as the percentage of smaller diameter trees becomes greater, and particularly if it exceeds 50%, then the canopy image obtained from Landsat TM data becomes sufficiently homogeneous so that the spatial indices reach their lower limits and thus are no longer determinative. It also appears, at least for the Oakmulgee forest, that the relationships between the spatial indices and forest class percentages within the boundaries can reasonably be considered linear. The linear relationship is much more pronounced in the sawtimber and saplings cases than in samples dominated by medium sized trees (poletimber). In addition, it also appears that, at least for the Oakmulgee forest, the relationships between the spatial indices and forest species groups (Hardwood and Softwood) percentages can reasonably be considered linear. The linear relationship is more pronounced in the forest species groups cases than in the forest classes cases. These results appear to indicate that both fractal dimensions and spatial autocorrelation indices hold promise as means of estimating forest stand characteristics from remotely sensed images. However, additional work is

  13. Narrowband tunable laser for uranium-233 cleanup process

    International Nuclear Information System (INIS)

    Singh, Sunita; Sridhar, G.; Rawat, V.S.; Kawde, Nitin; Sinha, A.K.; Bhatt, S.; Gantayet, L.M.

    2009-01-01

    Design, development and technology demonstration of proto type Single Longitudinal Mode pulsed tunable laser is reported in this work. The tunable laser has a narrow bandwidth less than 400 MHz required for isotopic clean up of 233 U. (author)

  14. High-Responsivity Graphene–Boron Nitride Photodetector and Autocorrelator in a Silicon Photonic Integrated Circuit

    Energy Technology Data Exchange (ETDEWEB)

    Shiue, Ren-Jye; Gao, Yuanda; Wang, Yifei; Peng, Cheng; Robertson, Alexander D.; Efetov, Dmitri K.; Assefa, Solomon; Koppens, Frank H. L.; Hone, James; Englund, Dirk

    2015-11-11

    Graphene and other two-dimensional (2D) materials have emerged as promising materials for broadband and ultrafast photodetection and optical modulation. These optoelectronic capabilities can augment complementary metal–oxide–semiconductor (CMOS) devices for high-speed and low-power optical interconnects. Here, we demonstrate an on-chip ultrafast photodetector based on a two-dimensional heterostructure consisting of high-quality graphene encapsulated in hexagonal boron nitride. Coupled to the optical mode of a silicon waveguide, this 2D heterostructure-based photodetector exhibits a maximum responsivity of 0.36 A/W and high-speed operation with a 3 dB cutoff at 42 GHz. From photocurrent measurements as a function of the top-gate and source-drain voltages, we conclude that the photoresponse is consistent with hot electron mediated effects. At moderate peak powers above 50 mW, we observe a saturating photocurrent consistent with the mechanisms of electron–phonon supercollision cooling. This nonlinear photoresponse enables optical on-chip autocorrelation measurements with picosecond-scale timing resolution and exceptionally low peak powers.

  15. Analytical and Numerical Characterization of Autocorrelation and Perturbation-Correlation Moving-Window Methods.

    Science.gov (United States)

    Lee, Young Jong

    2017-06-01

    Moving-window (MW) approaches to two-dimensional correlation spectroscopy (2D-COS) make it possible to characterize spectral changes occurring in a narrow range of perturbation variable (e.g., time, temperature, and concentration). Despite the wide range of application, the physical meanings of MW correlation intensities have been only qualitatively associated with the direction and curvature of spectral intensity change with regard to a perturbation variable. Here are full and simplified analytical expressions of autocorrelation moving-window (ACMW) and synchronous and asynchronous perturbation-correlation moving-window ( s-PCMW and as-PCMW) intensities. When the window is set sufficiently narrower than the bandwidth of spectral change, the square root of ACMW intensity and s-PCMW intensity becomes proportional to the first order derivative, and as-PCMW intensity becomes proportional to the negative of the second order derivative. This paper demonstrates that both ACMW and PCMW profiles can be significantly altered by non-uniform perturbation spacing. It is also found that intensity noise can cause ACMW to display a false offset drift. This analytical and numerical characterization of the two MW correlation intensities elucidates their physical meanings and ascertains the analysis conditions for reliable interpretation.

  16. Tunable inkjet-printed slotted waveguide antenna on a ferrite substrate

    KAUST Repository

    Nafe, Ahmed

    2015-04-13

    In this work an inkjet-printed frequency-tunable slotted waveguide antenna on a ferrite substrate is reported. Unlike the typical substrate integrated waveguide approach with via holes, a true 3D rectangular waveguide is realized by inkjet-printing of nano-particle based conductive ink on the broad faces as well as on sides of the substrate. The operating frequency of the antenna can be tuned by applying a variable static bias magnetic field that controls the permeability of the host ferrite substrate. The antenna operates about a center frequency of approximately 14 GHz with an instantaneous impedance bandwidth of 75 MHz. A fabricated prototype has demonstrated a tuning range of 10% (1.5 GHz) using an applied bias magnetic field of 3 kOe yielding it especially attractive for tunable and reconfigurable yet low cost microwave systems.

  17. Design of narrow band photonic filter with compact MEMS for tunable resonant wavelength ranging 100 nm

    Directory of Open Access Journals (Sweden)

    Guanquan Liang

    2011-12-01

    Full Text Available A prototype of planar silicon photonic structure is designed and simulated to provide narrow resonant line-width (∼2 nm in a wide photonic band gap (∼210 nm with broad tunable resonant wavelength range (∼100 nm around the optical communication wavelength 1550 nm. This prototype is based on the combination of two modified basic photonic structures, i.e. a split tapered photonic crystal micro-cavity embedded in a photonic wire waveguide, and a slot waveguide with narrowed slabs. This prototype is then further integrated with a MEMS (microelectromechanical systems based electrostatic comb actuator to achieve “coarse tune” and “fine tune” at the same time for wide range and narrow-band filtering and modulating. It also provides a wide range tunability to achieve the designed resonance even fabrication imperfection occurs.

  18. Tunable all-optical devices based on liquid-filled photonic crystal fibers

    DEFF Research Database (Denmark)

    Rosberg, Christian Romer; Bennet, Francis; Neshev, Dragomir N.

    , it is desirable to identify accessible experimental platforms that combine the advantages of high-quality fabricated structures with the attractiveness of tunable and strongly nonlinear materials for light control. In this work we suggest to use liquid-filled photonic crystal fibers (PCFs) for the study...... high-precision fabrication procedures, and provides high tunability and nonlinearity at moderate laser powers while taking advantage of a compact experimental setup. The increasingly broad range of PCF structures available could stimulate further efforts in applying them in discrete nonlinear optics...... and all-optical devices. The long propagation lengths accessible in fiber-based discrete systems could even allow for experimental studies of combined spatial and temporal nonlinear effects and thus pave the road for future demonstrations of spatiotemporal control of light....

  19. Highly Tunable Narrow Bandpass MEMS Filter

    KAUST Repository

    Hafiz, Md Abdullah Al

    2017-07-07

    We demonstrate a proof-of-concept highly tunable narrow bandpass filter based on electrothermally and electrostatically actuated microelectromechanical-system (MEMS) resonators. The device consists of two mechanically uncoupled clamped-clamped arch resonators, designed such that their resonance frequencies are independently tuned to obtain the desired narrow passband. Through the electrothermal and electrostatic actuation, the stiffness of the structures is highly tunable. We experimentally demonstrate significant percentage tuning (~125%) of the filter center frequency by varying the applied electrothermal voltages to the resonating structures, while maintaining a narrow passband of 550 ± 50 Hz, a stopband rejection of >17 dB, and a passband ripple ≤ 2.5 dB. An analytical model based on the Euler-Bernoulli beam theory is used to confirm the behavior of the filter, and the origin of the high tunability using electrothermal actuation is discussed.

  20. Adaptive Tunable Laser Spectrometer for Space Applications

    Science.gov (United States)

    Flesch, Gregory; Keymeulen, Didier

    2010-01-01

    An architecture and process for the rapid prototyping and subsequent development of an adaptive tunable laser absorption spectrometer (TLS) are described. Our digital hardware/firmware/software platform is both reconfigurable at design time as well as autonomously adaptive in real-time for both post-integration and post-launch situations. The design expands the range of viable target environments and enhances tunable laser spectrometer performance in extreme and even unpredictable environments. Through rapid prototyping with a commercial RTOS/FPGA platform, we have implemented a fully operational tunable laser spectrometer (using a highly sensitive second harmonic technique). With this prototype, we have demonstrated autonomous real-time adaptivity in the lab with simulated extreme environments.

  1. Perovskite Superlattices as Tunable Microwave Devices

    Science.gov (United States)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  2. Tunable high-gradient permanent magnet quadrupoles

    CERN Document Server

    Shepherd, B J A; Marks, N; Collomb, N A; Stokes, D G; Modena, M; Struik, M; Bartalesi, A

    2014-01-01

    A novel type of highly tunable permanent magnet (PM) based quadrupole has been designed by the ZEPTO collaboration. A prototype of the design (ZEPTO-Q1), intended to match the specification for the CLIC Drive Beam Decelerator, was built and magnetically measured at Daresbury Laboratory and CERN. The prototype utilises two pairs of PMs which move in opposite directions along a single vertical axis to produce a quadrupole gradient variable between 15 and 60 T/m. The prototype meets CLIC's challenging specification in terms of the strength and tunability of the magnet.

  3. Tunable Optofluidic Third Order DFB Dye Laser

    DEFF Research Database (Denmark)

    Gersborg-Hansen, Morten; Kristensen, Anders

    2007-01-01

    We present a low-threshold polymer-based nanofluidic dye laser. By employing a third order DFB laser resonator, we demonstrate a threshold fluence of ~7 muJ/mm2 and a tunability of 45 nm using a single laser dye......We present a low-threshold polymer-based nanofluidic dye laser. By employing a third order DFB laser resonator, we demonstrate a threshold fluence of ~7 muJ/mm2 and a tunability of 45 nm using a single laser dye...

  4. The influence of autocorrelation in signature extraction: An example from a geobotanical investigation of Cotter Basin, Montana

    Science.gov (United States)

    Labovitz, M. L.; Masuoka, E. J. (Principal Investigator)

    1981-01-01

    The presence of positive serial correlation (autocorrelation) in remotely sensed data results in an underestimate of the variance-covariance matrix when calculated using contiguous pixels. This underestimate produces an inflation in F statistics. For a set of Thematic Mapper Simulator data (TMS), used to test the ability to discriminate a known geobotanical anomaly from its background, the inflation in F statistics related to serial correlation is between 7 and 70 times. This means that significance tests of means of the spectral bands initially appear to suggest that the anomalous site is very different in spectral reflectance and emittance from its background sites. However, this difference often disappears and is always dramatically reduced when compared to frequency distributions of test statistics produced by the comparison of simulated training sets possessing equal means, but which are composed of autocorrelated observations.

  5. Efficient quasi-three-level Nd:YAG laser at 946 nm pumped by a tunable external cavity tapered diode laser

    DEFF Research Database (Denmark)

    Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter

    2010-01-01

    Using a tunable external cavity tapered diode laser (ECDL) pumped quasi-three-level Nd:YAG laser, a fivefold reduction in threshold and twofold increase in slope efficiency is demonstrated when compared to a traditional broad area diode laser pump source. A TEM00 power of 800 mW with 65% slope...

  6. A tunable electromechanical Helmholtz resonator

    Science.gov (United States)

    Liu, Fei

    Acoustic liners are used in turbofan engine nacelles for the suppression of engine noise. For a given engine, there are different optimum impedance distributions associated with take-off, cut-back, and approach flight conditions. The impedance of conventional acoustic liners is fixed for a given geometry, and conventional active liner approaches are impractical. This project addresses the need for a tunable impedance through the development of an electromechanical Helmholtz resonator (EMHR). The device consists of a Helmholtz resonator with the standard rigid backplate replaced by a compliant piezoelectric composite. Analytical models (i.e., a lumped element model (LEM) and a transfer matrix (TM) representation of the EMHR) are developed to predict the acoustic behavior of the EMHR. The EMHR is experimentally investigated using the standard two-microphone method (TMM). The measurement results validate both the LEM and the TM of the EMHR. Good agreement between predicted and measured impedance is obtained. Short- and open-circuit loads define the limits of the tuning range using resistive and capacitive loads. There is approximately a 9% tuning limit under these conditions for the non-optimized resonator configuration studied. Inductive shunt loads result in a 3 degree-of-freedom (DOF) system and an enhanced tuning range of over 47% that is not restricted by the short- and open-circuit limits. Damping coefficient measurements for a piezoelectric backplate in a vacuum chamber are performed and indicate that the damping is dominated by structural damping losses. A Pareto optimization design based on models of the EMHR is performed with non-inductive loads. The EMHR with non-inductive loads has 2DOF and two resonant frequencies. The tuning ranges of the two resonant frequencies of the EMHR with non-inductive loads cannot be optimized simultaneously, so a trade-off (Pareto solution) must be reached. The Pareto solution shows how design trade-offs can be used to satisfy

  7. Assessment of drug-induced arrhythmic risk using limit cycle and autocorrelation analysis of human iPSC-cardiomyocyte contractility

    International Nuclear Information System (INIS)

    Kirby, R. Jason; Qi, Feng; Phatak, Sharangdhar; Smith, Layton H.; Malany, Siobhan

    2016-01-01

    Cardiac safety assays incorporating label-free detection of human stem-cell derived cardiomyocyte contractility provide human relevance and medium throughput screening to assess compound-induced cardiotoxicity. In an effort to provide quantitative analysis of the large kinetic datasets resulting from these real-time studies, we applied bioinformatic approaches based on nonlinear dynamical system analysis, including limit cycle analysis and autocorrelation function, to systematically assess beat irregularity. The algorithms were integrated into a software program to seamlessly generate results for 96-well impedance-based data. Our approach was validated by analyzing dose- and time-dependent changes in beat patterns induced by known proarrhythmic compounds and screening a cardiotoxicity library to rank order compounds based on their proarrhythmic potential. We demonstrate a strong correlation for dose-dependent beat irregularity monitored by electrical impedance and quantified by autocorrelation analysis to traditional manual patch clamp potency values for hERG blockers. In addition, our platform identifies non-hERG blockers known to cause clinical arrhythmia. Our method provides a novel suite of medium-throughput quantitative tools for assessing compound effects on cardiac contractility and predicting compounds with potential proarrhythmia and may be applied to in vitro paradigms for pre-clinical cardiac safety evaluation. - Highlights: • Impedance-based monitoring of human iPSC-derived cardiomyocyte contractility • Limit cycle analysis of impedance data identifies aberrant oscillation patterns. • Nonlinear autocorrelation function quantifies beat irregularity. • Identification of hERG and non-hERG inhibitors with known risk of arrhythmia • Automated software processes limit cycle and autocorrelation analyses of 96w data

  8. Disease Mapping and Regression with Count Data in the Presence of Overdispersion and Spatial Autocorrelation: A Bayesian Model Averaging Approach

    Science.gov (United States)

    Mohebbi, Mohammadreza; Wolfe, Rory; Forbes, Andrew

    2014-01-01

    This paper applies the generalised linear model for modelling geographical variation to esophageal cancer incidence data in the Caspian region of Iran. The data have a complex and hierarchical structure that makes them suitable for hierarchical analysis using Bayesian techniques, but with care required to deal with problems arising from counts of events observed in small geographical areas when overdispersion and residual spatial autocorrelation are present. These considerations lead to nine regression models derived from using three probability distributions for count data: Poisson, generalised Poisson and negative binomial, and three different autocorrelation structures. We employ the framework of Bayesian variable selection and a Gibbs sampling based technique to identify significant cancer risk factors. The framework deals with situations where the number of possible models based on different combinations of candidate explanatory variables is large enough such that calculation of posterior probabilities for all models is difficult or infeasible. The evidence from applying the modelling methodology suggests that modelling strategies based on the use of generalised Poisson and negative binomial with spatial autocorrelation work well and provide a robust basis for inference. PMID:24413702

  9. Optimal filtering for systems with finite-step autocorrelated process noises, random one-step sensor delay and missing measurements

    Science.gov (United States)

    Chen, Dongyan; Xu, Long; Du, Junhua

    2016-03-01

    The optimal filtering problem is investigated for a class of discrete stochastic systems with finite-step autocorrelated process noises, random one-step sensor delay and missing measurements. The random disturbances existing in the system are characterized by the multiplicative noises and the phenomena of sensor delay and missing measurements occur in a random way. The random sensor delay and missing measurements are described by two Bernoulli distributed random variables with known conditional probabilities. By using the state augmentation approach, the original system is converted into a new discrete system where the random one-step sensor delay and missing measurements exist in the sensor output. The new process noises and observation noises consist of the original stochastic terms, and the process noises are still autocorrelated. Then, based on the minimum mean square error (MMSE) principle, a new linear optimal filter is designed such that, for the finite-step autocorrelated process noises, random one-step sensor delay and missing measurements, the estimation error is minimized. By solving the recursive matrix equation, the filter gain is designed. Finally, a simulation example is given to illustrate the feasibility and effectiveness of the proposed filtering scheme.

  10. An asymptotic theory for cross-correlation between auto-correlated sequences and its application on neuroimaging data.

    Science.gov (United States)

    Zhou, Yunyi; Tao, Chenyang; Lu, Wenlian; Feng, Jianfeng

    2018-04-20

    Functional connectivity is among the most important tools to study brain. The correlation coefficient, between time series of different brain areas, is the most popular method to quantify functional connectivity. Correlation coefficient in practical use assumes the data to be temporally independent. However, the time series data of brain can manifest significant temporal auto-correlation. A widely applicable method is proposed for correcting temporal auto-correlation. We considered two types of time series models: (1) auto-regressive-moving-average model, (2) nonlinear dynamical system model with noisy fluctuations, and derived their respective asymptotic distributions of correlation coefficient. These two types of models are most commonly used in neuroscience studies. We show the respective asymptotic distributions share a unified expression. We have verified the validity of our method, and shown our method exhibited sufficient statistical power for detecting true correlation on numerical experiments. Employing our method on real dataset yields more robust functional network and higher classification accuracy than conventional methods. Our method robustly controls the type I error while maintaining sufficient statistical power for detecting true correlation in numerical experiments, where existing methods measuring association (linear and nonlinear) fail. In this work, we proposed a widely applicable approach for correcting the effect of temporal auto-correlation on functional connectivity. Empirical results favors the use of our method in functional network analysis. Copyright © 2018. Published by Elsevier B.V.

  11. Exploring the effects of spatial autocorrelation when identifying key drivers of wildlife crop-raiding.

    Science.gov (United States)

    Songhurst, Anna; Coulson, Tim

    2014-03-01

    Few universal trends in spatial patterns of wildlife crop-raiding have been found. Variations in wildlife ecology and movements, and human spatial use have been identified as causes of this apparent unpredictability. However, varying spatial patterns of spatial autocorrelation (SA) in human-wildlife conflict (HWC) data could also contribute. We explicitly explore the effects of SA on wildlife crop-raiding data in order to facilitate the design of future HWC studies. We conducted a comparative survey of raided and nonraided fields to determine key drivers of crop-raiding. Data were subsampled at different spatial scales to select independent raiding data points. The model derived from all data was fitted to subsample data sets. Model parameters from these models were compared to determine the effect of SA. Most methods used to account for SA in data attempt to correct for the change in P-values; yet, by subsampling data at broader spatial scales, we identified changes in regression estimates. We consequently advocate reporting both model parameters across a range of spatial scales to help biological interpretation. Patterns of SA vary spatially in our crop-raiding data. Spatial distribution of fields should therefore be considered when choosing the spatial scale for analyses of HWC studies. Robust key drivers of elephant crop-raiding included raiding history of a field and distance of field to a main elephant pathway. Understanding spatial patterns and determining reliable socio-ecological drivers of wildlife crop-raiding is paramount for designing mitigation and land-use planning strategies to reduce HWC. Spatial patterns of HWC are complex, determined by multiple factors acting at more than one scale; therefore, studies need to be designed with an understanding of the effects of SA. Our methods are accessible to a variety of practitioners to assess the effects of SA, thereby improving the reliability of conservation management actions.

  12. Autocorrelation descriptor improvements for QSAR: 2DA_Sign and 3DA_Sign

    Science.gov (United States)

    Sliwoski, Gregory; Mendenhall, Jeffrey; Meiler, Jens

    2016-03-01

    Quantitative structure-activity relationship (QSAR) is a branch of computer aided drug discovery that relates chemical structures to biological activity. Two well established and related QSAR descriptors are two- and three-dimensional autocorrelation (2DA and 3DA). These descriptors encode the relative position of atoms or atom properties by calculating the separation between atom pairs in terms of number of bonds (2DA) or Euclidean distance (3DA). The sums of all values computed for a given small molecule are collected in a histogram. Atom properties can be added with a coefficient that is the product of atom properties for each pair. This procedure can lead to information loss when signed atom properties are considered such as partial charge. For example, the product of two positive charges is indistinguishable from the product of two equivalent negative charges. In this paper, we present variations of 2DA and 3DA called 2DA_Sign and 3DA_Sign that avoid information loss by splitting unique sign pairs into individual histograms. We evaluate these variations with models trained on nine datasets spanning a range of drug target classes. Both 2DA_Sign and 3DA_Sign significantly increase model performance across all datasets when compared with traditional 2DA and 3DA. Lastly, we find that limiting 3DA_Sign to maximum atom pair distances of 6 Å instead of 12 Å further increases model performance, suggesting that conformational flexibility may hinder performance with longer 3DA descriptors. Consistent with this finding, limiting the number of bonds in 2DA_Sign from 11 to 5 fails to improve performance.

  13. Frequency tunable surface magneto elastic waves

    NARCIS (Netherlands)

    Janusonis, J.; Chang, C. L.; van Loosdrecht, P. H. M.; Tobey, R. I.

    2015-01-01

    We use the transient grating technique to generate narrow-band, widely tunable, in-plane surface magnetoelastic waves in a nickel film. We monitor both the structural deformation of the acoustic wave and the accompanying magnetic precession and witness their intimate coupling in the time domain.

  14. Tunable structures and modulators for THz light

    Czech Academy of Sciences Publication Activity Database

    Kužel, Petr; Kadlec, Filip

    2008-01-01

    Roč. 9, - (2008), 197-214 ISSN 1631-0705 R&D Projects: GA AV ČR KJB100100512; GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : terahertz radiation * tunable devices * photonic crystals * strontium titanate * gallium arsenide Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.164, year: 2008

  15. Tunable metamaterials fabricated by fiber drawing

    DEFF Research Database (Denmark)

    Fleming, Simon; Stefani, Alessio; Tang, Xiaoli

    2017-01-01

    We demonstrate a practical scalable approach to the fabrication of tunable metamaterials. Designed for terahertz (THz) wavelengths, the metamaterial is comprised of polyurethane filled with an array of indium wires using the well-established fiber drawing technique. Modification of the dimensions...

  16. Absolute Distance Measurements with Tunable Semiconductor Laser

    Czech Academy of Sciences Publication Activity Database

    Mikel, Břetislav; Číp, Ondřej; Lazar, Josef

    T118, - (2005), s. 41-44 ISSN 0031-8949 R&D Projects: GA AV ČR(CZ) IAB2065001 Keywords : tunable laser * absolute interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.661, year: 2004

  17. 130-nm tunable grating-mirror VCSEL

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2014-01-01

    We have reported that a combination of the high-index-contrast grating (HCG) mirror as movable mirror and the extended cavity configuration with an antireflection layer can provide a tuning wavelength range of 100 nm for tunable VCSELs. Here, we report that using the air-coupled cavity...

  18. Tunability of optofluidic distributed feedback dye lasers

    DEFF Research Database (Denmark)

    Gersborg-Hansen, Morten; Kristensen, Anders

    2007-01-01

    We investigate the tunability of optofluidic distributed feedback (DFB) dye lasers. The lasers rely on light-confinement in a nano-structured polymer film where an array of nanofluidic channels constitutes a third order Bragg grating DFB laser resonator with a central phase-shift. The lasers...

  19. Tunable Water-based Microwave Metasurface

    DEFF Research Database (Denmark)

    Kapitanova, Polina; Odit, Mikhail; Dobrykh, Dmitry

    2017-01-01

    A water-based dynamically tunable microwave metasurface is developed and experimentally investigated. A simple approach to tune the metasurface properties by changing the shape of water-based unit cells by gravitation force is proposed. The transmission spectra of the metasurface for linear...... angle. The proposed approach can be used to design cheap metasurfaces for electromagnetic wave control in the microwave frequency range....

  20. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    Science.gov (United States)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  1. Tunable single and dual mode operation of an external cavity quantum-dot injection laser

    Energy Technology Data Exchange (ETDEWEB)

    Biebersdorf, A [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Lingk, C [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); De Giorgi, M [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Feldmann, J [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Sacher, J [Sacher Lasertechnik GmbH, Hannah Arendt Strasse 3-7, D-35037 Marburg (Germany); Arzberger, M [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Ulbrich, C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Boehm, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Amann, M-C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Abstreiter, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany)

    2003-08-21

    We investigate quantum-dot (QD) lasers in an external cavity using Littrow and Littman configurations. Here, we report on a continuously tunable QD laser with a broad tuning range from 1047 to 1130 nm with high stability and efficient side mode suppression. The full-width at half-maximum of the laser line is 0.85 nm determined mainly by the quality of the external grating. This laser can be operated in a dual-mode modus, where the mode-spacing can be tuned continuously between 1.1 and 34 nm. Simultaneous emission of the two laser modes is shown by sum frequency generation experiments.

  2. Observation of Broad d-Wave Feshbach Resonances with a Triplet Structure.

    Science.gov (United States)

    Cui, Yue; Shen, Chuyang; Deng, Min; Dong, Shen; Chen, Cheng; Lü, Rong; Gao, Bo; Tey, Meng Khoon; You, Li

    2017-11-17

    High partial-wave (l≥2) Feshbach resonance (FR) in an ultracold mixture of ^{85}Rb-^{87}Rb atoms is investigated experimentally aided by a partial-wave insensitive analytic multichannel quantum-defect theory. Two "broad" resonances from coupling between d waves in both the open and closed channels are observed and characterized. One of them shows a fully resolved triplet structure with a splitting ratio well explained by the perturbation to the closed channel due to interatomic spin-spin interaction. These tunable "broad" d-wave resonances, especially the one in the lowest-energy open channel, could find important applications in simulating d-wave coupling dominated many-body systems. In addition, we find that there is generally a time and temperature requirement, associated with tunneling through the angular momentum barrier, to establish and observe resonant coupling in nonzero partial waves.

  3. Accounting for and predicting the influence of spatial autocorrelation in water quality modeling

    Science.gov (United States)

    Miralha, L.; Kim, D.

    2017-12-01

    Although many studies have attempted to investigate the spatial trends of water quality, more attention is yet to be paid to the consequences of considering and ignoring the spatial autocorrelation (SAC) that exists in water quality parameters. Several studies have mentioned the importance of accounting for SAC in water quality modeling, as well as the differences in outcomes between models that account for and ignore SAC. However, the capacity to predict the magnitude of such differences is still ambiguous. In this study, we hypothesized that SAC inherently possessed by a response variable (i.e., water quality parameter) influences the outcomes of spatial modeling. We evaluated whether the level of inherent SAC is associated with changes in R-Squared, Akaike Information Criterion (AIC), and residual SAC (rSAC), after accounting for SAC during modeling procedure. The main objective was to analyze if water quality parameters with higher Moran's I values (inherent SAC measure) undergo a greater increase in R² and a greater reduction in both AIC and rSAC. We compared a non-spatial model (OLS) to two spatial regression approaches (spatial lag and error models). Predictor variables were the principal components of topographic (elevation and slope), land cover, and hydrological soil group variables. We acquired these data from federal online sources (e.g. USGS). Ten watersheds were selected, each in a different state of the USA. Results revealed that water quality parameters with higher inherent SAC showed substantial increase in R² and decrease in rSAC after performing spatial regressions. However, AIC values did not show significant changes. Overall, the higher the level of inherent SAC in water quality variables, the greater improvement of model performance. This indicates a linear and direct relationship between the spatial model outcomes (R² and rSAC) and the degree of SAC in each water quality variable. Therefore, our study suggests that the inherent level of

  4. Auto-correlation of journal impact factor for consensus research reporting statements: a cohort study.

    Science.gov (United States)

    Shanahan, Daniel R

    2016-01-01

    journal in which a reporting statement was published was shown to influence the number of citations that statement will gather over time. Similarly, the number of article accesses also influenced the number of citations, although to a lesser extent than the impact factor. This demonstrates that citation counts are not purely a reflection of scientific merit and the impact factor is, in fact, auto-correlated.

  5. Auto-correlation of journal impact factor for consensus research reporting statements: a cohort study

    Directory of Open Access Journals (Sweden)

    Daniel R. Shanahan

    2016-03-01

    . The impact factor of the journal in which a reporting statement was published was shown to influence the number of citations that statement will gather over time. Similarly, the number of article accesses also influenced the number of citations, although to a lesser extent than the impact factor. This demonstrates that citation counts are not purely a reflection of scientific merit and the impact factor is, in fact, auto-correlated.

  6. Characterizing tissue microstructure using an ultrasound system-independent spatial autocorrelation function

    Science.gov (United States)

    Dong, Fang

    1999-09-01

    The research described in this dissertation is related to characterization of tissue microstructure using a system- independent spatial autocorrelation function (SAF). The function was determined using a reference phantom method, which employed a well-defined ``point- scatterer'' reference phantom to account for instrumental factors. The SAF's were estimated for several tissue-mimicking (TM) phantoms and fresh dog livers. Both phantom tests and in vitro dog liver measurements showed that the reference phantom method is relatively simple and fairly accurate, providing the bandwidth of the measurement system is sufficient for the size of the scatterer being involved in the scattering process. Implementation of this method in clinical scanner requires that distortions from patient's body wall be properly accounted for. The SAF's were estimated for two phantoms with body-wall-like distortions. The experimental results demonstrated that body wall distortions have little effect if echo data are acquired from a large scattering volume. One interesting application of the SAF is to form a ``scatterer size image''. The scatterer size image may help providing diagnostic tools for those diseases in which the tissue microstructure is different from the normal. Another method, the BSC method, utilizes information contained in the frequency dependence of the backscatter coefficient to estimate the scatterer size. The SAF technique produced accurate scatterer size images of homogeneous TM phantoms and the BSC method was capable of generating accurate size images for heterogeneous phantoms. In the scatterer size image of dog kidneys, the contrast-to-noise-ratio (CNR) between renal cortex and medulla was improved dramatically compared to the gray- scale image. The effect of nonlinear propagation was investigated by using a custom-designed phantom with overlaying TM fat layer. The results showed that the correlation length decreased when the transmitting power increased. The

  7. Laser absorption spectroscopy using lead salt and quantum cascade tunable lasers

    Science.gov (United States)

    Namjou-Khales, Khosrow

    A new class of analytic instruments based on the detection of chemical species through their spectroscopic absorption 'fingerprint' is emerging based on the use of tunable semiconductor lasers as the excitation source. Advantages of this approach include compact device size, in-line measurement capability, and large signal-bandwidth product. To realize these advantages will require the marriage of laser devices with broad tunability in the infrared spectral range with sophisticated signal processing techniques. Currently, commercial devices based on short wavelength telecommunications type lasers exist but there is potential for much more versatile instruments based on longer wavelength operation. This thesis is divided into two parts. In the first part I present a theoretical analysis and experimental characterization of frequency and wavelength modulation spectroscopy using long wavelength infrared tunable lasers. The experimental measurements were carried out using commercially available lead salt lasers and excellent agreement is found between theoretically predicted performance and experimental verification. The lead salt laser has several important drawbacks as a source in practical instrumentation. In the second part of the thesis I report on the use of the quantum cascade (QC) laser for use in sensitive absorption spectroscopy. The QC laser is a new type of tunable device developed at Bell Laboratories. It features broad infrared tunability, single mode distributed feedback operation, and near room temperature lasing. Using the modulation techniques developed originally for the lead salt lasers, the QC laser was used to detect Nsb2O and other small molecules with absorption features near 8 mum wavelength. The noise equivalent absorption for our measurements was 5× 10sp{-5}/sqrt{Hz} which corresponds to a detection limit of ˜0.25 ppm-m/sqrt{Hz} for Nsb2O. The QC laser sensitivity was found to be limited by excess amplitude modulation in the detection

  8. Tunable Sparse Network Coding for Multicast Networks

    DEFF Research Database (Denmark)

    Feizi, Soheil; Roetter, Daniel Enrique Lucani; Sørensen, Chres Wiant

    2014-01-01

    This paper shows the potential and key enabling mechanisms for tunable sparse network coding, a scheme in which the density of network coded packets varies during a transmission session. At the beginning of a transmission session, sparsely coded packets are transmitted, which benefits decoding...... complexity. At the end of a transmission, when receivers have accumulated degrees of freedom, coding density is increased. We propose a family of tunable sparse network codes (TSNCs) for multicast erasure networks with a controllable trade-off between completion time performance to decoding complexity....... Coding density tuning can be performed by designing time-dependent coding matrices. In multicast networks, this tuning can be performed within the network by designing time-dependent pre- coding and network coding matrices with mild conditions on the network structure for specific densities. We present...

  9. Cutting and Folding for Tunable Materials Properties

    Science.gov (United States)

    Damasceno, Pablo; Dodd, Paul; Shyu, Terry; Shlian, Matthew; Shtein, Max; Kotov, Nicholas; Glotzer, Sharon

    2014-03-01

    Despite the small set of building blocks used for their assembly, naturally occurring materials such as proteins show remarkable diversity in their mechanical properties ranging from something resembling rubber-low stiffness, high resilience and extensibility-to silk-high stiffness and strength. Moreover, their self-folding properties inspire the design of structures capable of tunable reconfiguration. Motivated by such versatility, we report on simulations and experiments for the design of nanocomposites sheets whose mechanical properties can be made tunable via ``secondary structures'' patterning. Our simulations reveal the main cutting features needed to obtain desired material extensibility. Additionally, we study how similar sheets could self-fold into their desired ``native'' structure via stochastic forces. Our results open the possibilities for manufacture of flexible and reconfigurable materials with targeted strength and extensibility. Research supported by the National Science Foundation, Emerging Frontiers in Research and Innovation Award # EFRI-1240264.

  10. Optically tunable chirped fiber Bragg grating.

    Science.gov (United States)

    Li, Zhen; Chen, Zhe; Hsiao, V K S; Tang, Jie-Yuan; Zhao, Fuli; Jiang, Shao-Ji

    2012-05-07

    This work presents an optically tunable chirped fiber Bragg grating (CFBG). The CFBG is obtained by a side-polished fiber Bragg grating (SPFBG) whose thickness of the residual cladding layer in the polished area (D(RC)) varies with position along the length of the grating, which is coated with a photoresponsive liquid crystal (LC) overlay. The reflection spectrum of the CFBG is tuned by refractive index (RI) modulation, which comes from the phase transition of the overlaid photoresponsive LC under ultraviolet (UV) light irradiation. The broadening in the reflection spectrum and corresponding shift in the central wavelength are observed with UV light irradiation density of 0.64mW/mm. During the phase transition of the photoresponsive LC, the RI increase of the overlaid LC leads to the change of the CFBG reflection spectrum and the change is reversible and repeatable. The optically tunable CFBGs have potential use in optical DWDM system and an all-fiber telecommunication system.

  11. Computer control of pulsed tunable dye lasers

    International Nuclear Information System (INIS)

    Thattey, S.S.; Dongare, A.S.; Suri, B.M.; Nair, L.G.

    1992-01-01

    Pulsed tunable dye lasers are being used extensively for spectroscopic and photo-chemical experiments, and a system for acquisition and spectral analysis of a volume of data generated will be quite useful. The development of a system for wavelength tuning and control of tunable dye lasers and an acquisition system for spectral data generated in experiments with these lasers are described. With this system, it is possible to control the tuning of three lasers, and acquire data in four channels, simultaneously. It is possible to arrive at the desired dye laser wavelength with a reproducibility of ± 0.012 cm -1 , which is within the absorption width (atomic interaction) caused by pulsed dye lasers of linewidth 0.08 cm -1 . The spectroscopic data generated can be analyzed for spectral identification within absolute accuracy ± 0.012 cm -1 . (author). 6 refs., 11 figs

  12. A single-shot nonlinear autocorrelation approach for time-resolved physics in the vacuum ultraviolet spectral range

    International Nuclear Information System (INIS)

    Rompotis, Dimitrios

    2016-02-01

    In this work, a single-shot temporal metrology scheme operating in the vacuum-extreme ultraviolet spectral range has been designed and experimentally implemented. Utilizing an anti-collinear geometry, a second-order intensity autocorrelation measurement of a vacuum ultraviolet pulse can be performed by encoding temporal delay information on the beam propagation coordinate. An ion-imaging time-of-flight spectrometer, offering micrometer resolution has been set-up for this purpose. This instrument enables the detection of a magnified image of the spatial distribution of ions exclusively generated by direct two-photon absorption in the combined counter-propagating pulse focus and thus obtain the second-order intensity autocorrelation measurement on a single-shot basis. Additionally, an intense VUV light source based on high-harmonic generation has been experimentally realized. It delivers intense sub-20 fs Ti:Sa fifth-harmonic pulses utilizing a loose-focusing geometry in a long Ar gas cell. The VUV pulses centered at 161.8 nm reach pulse energies of 1.1 μJ per pulse, while the corresponding pulse duration is measured with a second-order, fringe-resolved autocorrelation scheme to be 18 ± 1 fs on average. Non-resonant, two-photon ionization of Kr and Xe and three-photon ionization of Ne verify the fifth-harmonic pulse intensity and indicate the feasibility of multi-photon VUV pump/VUV probe studies of ultrafast atomic and molecular dynamics. Finally, the extended functionally of the counter-propagating pulse metrology approach is demonstrated by a single-shot VUV pump/VUV probe experiment aiming at the investigation of ultrafast dissociation dynamics of O 2 excited in the Schumann-Runge continuum at 162 nm.

  13. Multilevel models for multiple-baseline data: modeling across-participant variation in autocorrelation and residual variance.

    Science.gov (United States)

    Baek, Eun Kyeng; Ferron, John M

    2013-03-01

    Multilevel models (MLM) have been used as a method for analyzing multiple-baseline single-case data. However, some concerns can be raised because the models that have been used assume that the Level-1 error covariance matrix is the same for all participants. The purpose of this study was to extend the application of MLM of single-case data in order to accommodate across-participant variation in the Level-1 residual variance and autocorrelation. This more general model was then used in the analysis of single-case data sets to illustrate the method, to estimate the degree to which the autocorrelation and residual variances differed across participants, and to examine whether inferences about treatment effects were sensitive to whether or not the Level-1 error covariance matrix was allowed to vary across participants. The results from the analyses of five published studies showed that when the Level-1 error covariance matrix was allowed to vary across participants, some relatively large differences in autocorrelation estimates and error variance estimates emerged. The changes in modeling the variance structure did not change the conclusions about which fixed effects were statistically significant in most of the studies, but there was one exception. The fit indices did not consistently support selecting either the more complex covariance structure, which allowed the covariance parameters to vary across participants, or the simpler covariance structure. Given the uncertainty in model specification that may arise when modeling single-case data, researchers should consider conducting sensitivity analyses to examine the degree to which their conclusions are sensitive to modeling choices.

  14. Disentangling the effects of forage, social rank, and risk on movement autocorrelation of elephants using Fourier and wavelet analyses.

    Science.gov (United States)

    Wittemyer, George; Polansky, Leo; Douglas-Hamilton, Iain; Getz, Wayne M

    2008-12-09

    The internal state of an individual-as it relates to thirst, hunger, fear, or reproductive drive-can be inferred by referencing points on its movement path to external environmental and sociological variables. Using time-series approaches to characterize autocorrelative properties of step-length movements collated every 3 h for seven free-ranging African elephants, we examined the influence of social rank, predation risk, and seasonal variation in resource abundance on periodic properties of movement. The frequency domain methods of Fourier and wavelet analyses provide compact summaries of temporal autocorrelation and show both strong diurnal and seasonal based periodicities in the step-length time series. This autocorrelation is weaker during the wet season, indicating random movements are more common when ecological conditions are good. Periodograms of socially dominant individuals are consistent across seasons, whereas subordinate individuals show distinct differences diverging from that of dominants during the dry season. We link temporally localized statistical properties of movement to landscape features and find that diurnal movement correlation is more common within protected wildlife areas, and multiday movement correlations found among lower ranked individuals are typically outside of protected areas where predation risks are greatest. A frequency-related spatial analysis of movement-step lengths reveal that rest cycles related to the spatial distribution of critical resources (i.e., forage and water) are responsible for creating the observed patterns. Our approach generates unique information regarding the spatial-temporal interplay between environmental and individual characteristics, providing an original approach for understanding the movement ecology of individual animals and the spatial organization of animal populations.

  15. Improved tunable microstrip SQUID amplifiers for the Axion Dark Matter eXperiment

    Science.gov (United States)

    O'Kelley, Sean; Hansen, Jørn; Hilton, Gene; Mol, Jan-Michael; Clarke, John; ADMX Collaboration

    2015-04-01

    We describe a series of tunable microstrip SQUID (Superconducting QUantum Interference Device) amplifiers (MSAs) used as the photon detector in the Axion Dark Matter eXperiment (ADMX). Cooled to 100mK or lower, an optimized MSA approaches the quantum limit of detection. The axion dark matter candidate would be detected via Primakoff conversion to a microwave photon in a high-Q (~ 105) tunable microwave cavity, cooled to 1.6 K or lower, in the presence of a 7-tesla magnetic field. The MSA consists of a square loop of thin Nb film, incorporating two resistively shunted Josephson tunnel junctions biased to the voltage state, flux-coupled to a resonant microstrip. The photon frequency is determined by the unknown axion mass, so the cavity and amplifier must be tunable over a broad frequency range. MSA tunability is achieved by terminating the microstrip with a GaAs varactor diode that operates at cryogenic temperatures. This voltage-controlled capacitance enables us to vary the resonant microstrip mode from nearly λ/2 to λ/4. We demonstrate gains exceeding 20 dB, at frequencies above 900 MHz. With proper design of the microwave environment, a noise temperature of 1/2 to 1/4 of the physical temperature is demonstrated. Supported by DOE Grants DE-FG02-97ER41029, DE-FG02-96ER40956, DE- AC52-07NA27344, DE-AC03-76SF00098, NSF Grant 1067242, and the Livermore LDRD program.

  16. Broad Prize: Do the Successes Spread?

    Science.gov (United States)

    Samuels, Christina A.

    2011-01-01

    When the Broad Prize for Urban Education was created in 2002, billionaire philanthropist Eli Broad said he hoped the awards, in addition to rewarding high-performing school districts, would foster healthy competition; boost the prestige of urban education, long viewed as dysfunctional; and showcase best practices. Over the 10 years the prize has…

  17. Broad Academy's Growing Reach Draws Scrutiny

    Science.gov (United States)

    Samuels, Christina A.

    2011-01-01

    Billionaire businessman Eli Broad, one of the country's most active philanthropists, founded the Broad Superintendents Academy in 2002 with an extraordinarily optimistic goal: Find leaders from both inside and outside education, train them, and have them occupying the superintendencies in a third of the 75 largest school districts--in just two…

  18. The anomalous tides near Broad Sound

    Science.gov (United States)

    Middleton, Jason H.; Buchwald, V. T.; Huthnance, John M.

    Observations of tidal current and height, in conjunction with theoretical mathematical models are used to investigate the propagation of the tide near Broad Sound, a narrowing estuary situated on a wide section of continental shelf toward the southern end of the Great Barrier Reef. The observations indicate that the dense offshore reefs severely inhibit tidal flow, with the result that tides flood toward Broad Sound from the north and from the south, along the main lagoon. There is a local magnification of the semi-diurnal tides within Broad Sound itself. Models of flow across reefs confirm the effectiveness of dense, shallow, and broad reefs in acting as a barrier to the tide. The diffraction of tides through large gaps in the reef is modelled using conformal mapping techniques and with the inclusion of energy leakage, the diffraction model predicts magnification of the semi-diurnal tidal heights by a factor of about 4 and a phase lag of 3 h on the shelf near Broad Sound, these values being consistent with observation. The observed convergence of the tide close to, and within Broad Sound itself is consistent with the proximity of the semi-diurnal tidal period to the natural period for flow in Broad Sound, considered as a narrowing estuary. This results in further amplification, by an additional factor of about 1.5, so that the tides in Broad Sound are increased by a factor of between 5 and 6, altogether, compared with those elsewhere on the east Australian coast.

  19. Tunable terahertz metamaterials with negative permeability

    Czech Academy of Sciences Publication Activity Database

    Němec, Hynek; Kužel, Petr; Kadlec, Filip; Kadlec, Christelle; Yahiaoui, R.; Mounaix, P.

    2009-01-01

    Roč. 79, č. 24 (2009), 241108/1-241108/4 ISSN 1098-0121 R&D Projects: GA AV ČR(CZ) IAA100100907; GA MŠk LC512; GA MŠk MEB020742 Institutional research plan: CEZ:AV0Z10100520 Keywords : tunable metamaterial * effective magnetic permeability * incipient ferroelectrics * strontium titanate * terahertz spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  20. Flow of Tunable Elastic Microcapsules through Constrictions

    OpenAIRE

    do Nascimento, D?bora F.; Avenda?o, Jorge A.; Mehl, Ana; Moura, Maria J. B.; Carvalho, Marcio S.; Duncanson, Wynter J.

    2017-01-01

    We design and fabricate elastically tunable monodisperse microcapsules using microfluidics and cross-linkable polydimethylsiloxane (PDMS). The overall stiffness of the microcapsules is governed by both the thickness and cross-link ratio of the polymer shell. Flowing suspensions of microcapsules through constricted spaces leads to transient blockage of fluid flow, thus altering the flow behavior. The ability to tune microcapsule mechanical properties enables the design of elastic microcapsules...

  1. Electronically Tunable Resistorless Mixed Mode Biquad Filters

    OpenAIRE

    Yesil, A.; Kacar, F.

    2013-01-01

    This paper presents a new realization of elec¬tronically tunable mixed mode (including transadmittance- and voltage-modes) biquad filter with single input, three outputs or three inputs, single output using voltage differ-encing transconductance amplifier (VDTA), a recently introduced active element. It can simultaneously realize standard filtering signals: low-pass, band-pass and high-pass or by selecting input terminals, it can realize all five different filtering signals: low-pass, band-pa...

  2. LTCC Phase Shifters Based on Tunable Ferroelectric Composite Thick Films

    Science.gov (United States)

    Nikfalazar, M.; Kohler, C.; Heunisch, A.; Wiens, A.; Zheng, Y.; Schulz, B.; Mikolajek, M.; Sohrabi, M.; Rabe, T.; Binder, J. R.; Jakoby, R.

    2015-11-01

    This paper presents, the investigation of tunable components based on LTCC technology, implementing ferroelectric tunable thick-film dielectric. The tunable loaded line phase shifters are fabricated with metal-insulator-metal (MIM) varactors to demonstrate the capabilities of this method for packaging of the tunable components. The MIM varactors consist of one tunable dielectric paste layer that is printed between two silver layers. The tunable ferroelectric paste is optimized for LTCC sintering temperature around 850°C. The phase shifters are fabricated in two different process. They were achieved a figure of merit of 24°/dB (phase shift 192°) at 3 GHz and 18°/dB (phase shift 98°) at 4.4 GHz by using seven unit cells that each unit cell consisting of two MIM varactors.

  3. Quantitative nanometer-scale mapping of dielectric tunability

    Energy Technology Data Exchange (ETDEWEB)

    Tselev, Alexander [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Klein, Andreas [Technische Univ. Darmstadt (Germany); Gassmann, Juergen [Technische Univ. Darmstadt (Germany); Jesse, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Li, Qian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kalinin, Sergei V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wisinger, Nina Balke [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-08-21

    Two scanning probe microscopy techniques—near-field scanning microwave microscopy (SMM) and piezoresponse force microscopy (PFM)—are used to characterize and image tunability in a thin (Ba,Sr)TiO3 film with nanometer scale spatial resolution. While sMIM allows direct probing of tunability by measurement of the change in the dielectric constant, in PFM, tunability can be extracted via electrostrictive response. The near-field microwave imaging and PFM provide similar information about dielectric tunability with PFM capable to deliver quantitative information on tunability with a higher spatial resolution close to 15 nm. This is the first time that information about the dielectric tunability is available on such length scales.

  4. Measurement of nonlinear optical refraction of composite material based on sapphire with silver by Kerr-lens autocorrelation method.

    Science.gov (United States)

    Yu, Xiang-xiang; Wang, Yu-hua

    2014-01-13

    Silver nanoparticles synthesized in a synthetic sapphire matrix were fabricated by ion implantation using the metal vapor vacuum arc ion source. The optical absorption spectrum of the Ag: Al2O3 composite material has been measured. The analysis of the supercontinuum spectrum displayed the nonlinear refractive property of this kind of sample. Nonlinear optical refraction index was identified at 800 nm excitation using the Kerr-lens autocorrelation (KLAC) technique. The spectrum showed that the material possessed self-defocusing property (n(2) = -1.1 × 10(-15) cm(2)W). The mechanism of nonlinear refraction has been discussed.

  5. AFM topographies of densely packed nanoparticles: a quick way to determine the lateral size distribution by autocorrelation function analysis

    Czech Academy of Sciences Publication Activity Database

    Fekete, Ladislav; Kůsová, Kateřina; Petrák, Václav; Kratochvílová, Irena

    2012-01-01

    Roč. 14, č. 8 (2012), s. 1-10 ISSN 1388-0764 R&D Projects: GA AV ČR KAN200100801; GA TA ČR TA01011165; GA ČR(CZ) GAP304/10/1951; GA ČR GPP204/12/P235 Institutional research plan: CEZ:AV0Z10100520 Keywords : lateral grain size distribution * AFM * autocorrelation function * nanodiamond Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.175, year: 2012

  6. Tunable nanoparticle arrays at charged interfaces.

    Science.gov (United States)

    Srivastava, Sunita; Nykypanchuk, Dmytro; Fukuto, Masafumi; Gang, Oleg

    2014-10-28

    Structurally tunable two-dimensional (2D) arrays of nanoscale objects are important for modulating functional responses of thin films. We demonstrate that such tunable and ordered nanoparticles (NP) arrays can be assembled at charged air-water interfaces from nanoparticles coated with polyelectrolyte chains, DNA. The electrostatic attraction between the negatively charged nonhybridizing DNA-coated gold NPs and a positively charged lipid layer at the interface facilitates the formation of a 2D hexagonally closed packed (HCP) nanoparticle lattice. We observed about 4-fold change of the monolayer nanoparticle density by varying the ionic strength of the subphase. The tunable NP arrays retain their structure reasonably well when transferred to a solid support. The influence of particle's DNA corona and lipid layer composition on the salt-induced in-plane and normal structural evolution of NP arrays was studied in detail using a combination of synchrotron-based in situ surface scattering methods, grazing incidence X-ray scattering (GISAXS), and X-ray reflectivity (XRR). Comparative analysis of the interparticle distances as a function of ionic strength reveals the difference between the studied 2D nanoparticle arrays and analogous bulk polyelectrolyte star polymers systems, typically described by Daoud-Cotton model and power law scaling. The observed behavior of the 2D nanoparticle array manifests a nonuniform deformation of the nanoparticle DNA corona due to its electrostatically induced confinement at the lipid interface. The present study provides insight on the interfacial properties of the NPs coated with charged soft shells.

  7. A Continuously Tunable Erbium-Doped Fibre Laser Using Tunable Fibre Bragg Gratings and Optical Circulator

    International Nuclear Information System (INIS)

    Peng, Liu; Feng-Ping, Yan; Jian, Li; Lin, Wang; Ti-Gang, Ning; Tao-Rong, Gong; Shui-Sheng, Jian

    2008-01-01

    A continuously tunable erbium-doped fibre laser (TEDFL) based on tunable fibre Bragger grating (TFBG) and a three-port optical circulator (OC) is proposed and demonstrated. The OC acts as a 100%-reflective mirror. A strain-induced uniform fibre Bragger grating (FBG) which functions as a partial-reflecting mirror is implemented in the linear cavity. By applying axial strain onto the TFBG, a continuously tunable lasing output can be realized. The wavelength tuning range covers approximately 7.00nm in C band (from 1543.6161 to 1550.3307nm). The side mode suppression ratio (SMSR) is better than 50 dB, and the 3 dB bandwidth of the laser is less than 0.01 nm. Moreover, an array waveguide grating (AWG) is inserted into the cavity for wavelength preselecting, and a 50 km transmission experiment was performed using our TEDFL at a 10Gb/s modulation rate

  8. Plasmonic Gold Nanorod Dispersions with Electrical and Optical Tunability

    Science.gov (United States)

    Grabowski, Christopher; Mahoney, Clare; Park, Kyoungweon; Jawaid, Ali; White, Timothy; Vaia, Richard

    The transmissive, absorptive, electrical, and thermal properties of plasmonic gold nanorods (NRs) have led to their employment in a broad range of applications. These electro-optical properties - governed by their size, shape, and composition - are widely and precisely tunable during synthesis. Gold NRs show promise for large scale optical elements as they have been demonstrated to align faster than liquid crystal films (μs) at low fields (1 V/ μm). Successfully dispersing a high volume fraction of gold NRs requires a strategy to control particle-particle separation and thus avoid aggregation. Herein, we discuss the role of theta temperature and the ability to swell or collapse the chains of polymer-grafted gold NRs to alter the interaction potential between particles. UV-Vis spectroscopy, scattering, and electrical susceptibility characterization methods were employed to determine nanoparticle dispersion along with the degree of gold NR alignment. The development of new agile photonic materials, controllable with both light and electric fields, will help address emerging needs in laser hardening (agile filters) and variable transmission visors.

  9. Combinatorial Screening for Transgenic Yeasts with High Cellulase Activities in Combination with a Tunable Expression System.

    Directory of Open Access Journals (Sweden)

    Yoichiro Ito

    Full Text Available Combinatorial screening used together with a broad library of gene expression cassettes is expected to produce a powerful tool for the optimization of the simultaneous expression of multiple enzymes. Recently, we proposed a highly tunable protein expression system that utilized multiple genome-integrated target genes to fine-tune enzyme expression in yeast cells. This tunable system included a library of expression cassettes each composed of three gene-expression control elements that in different combinations produced a wide range of protein expression levels. In this study, four gene expression cassettes with graded protein expression levels were applied to the expression of three cellulases: cellobiohydrolase 1, cellobiohydrolase 2, and endoglucanase 2. After combinatorial screening for transgenic yeasts simultaneously secreting these three cellulases, we obtained strains with higher cellulase expressions than a strain harboring three cellulase-expression constructs within one high-performance gene expression cassette. These results show that our method will be of broad use throughout the field of metabolic engineering.

  10. Tunable optical coherence tomography in the infrared range using visible photons

    Science.gov (United States)

    Paterova, Anna V.; Yang, Hongzhi; An, Chengwu; Kalashnikov, Dmitry A.; Krivitsky, Leonid A.

    2018-04-01

    Optical coherence tomography (OCT) is an appealing technique for bio-imaging, medicine, and material analysis. For many applications, OCT in mid- and far-infrared (IR) leads to significantly more accurate results. Reported mid-IR OCT systems require light sources and photodetectors which operate in mid-IR range. These devices are expensive and need cryogenic cooling. Here, we report a proof-of-concept demonstration of a wavelength tunable IR OCT technique with detection of only visible range photons. Our method is based on the nonlinear interference of frequency correlated photon pairs. The nonlinear crystal, introduced in the Michelson-type interferometer, generates photon pairs with one photon in the visible and another in the IR range. The intensity of detected visible photons depends on the phase and loss of IR photons, which interact with the sample under study. This enables us to characterize sample properties and perform imaging in the IR range by detecting visible photons. The technique possesses broad wavelength tunability and yields a fair axial and lateral resolution, which can be tailored to the specific application. The work contributes to the development of versatile 3D imaging and material characterization systems working in a broad range of IR wavelengths, which do not require the use of IR-range light sources and photodetectors.

  11. Real-time autocorrelator for fluorescence correlation spectroscopy based on graphical-processor-unit architecture: method, implementation, and comparative studies

    Science.gov (United States)

    Laracuente, Nicholas; Grossman, Carl

    2013-03-01

    We developed an algorithm and software to calculate autocorrelation functions from real-time photon-counting data using the fast, parallel capabilities of graphical processor units (GPUs). Recent developments in hardware and software have allowed for general purpose computing with inexpensive GPU hardware. These devices are more suited for emulating hardware autocorrelators than traditional CPU-based software applications by emphasizing parallel throughput over sequential speed. Incoming data are binned in a standard multi-tau scheme with configurable points-per-bin size and are mapped into a GPU memory pattern to reduce time-expensive memory access. Applications include dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) experiments. We ran the software on a 64-core graphics pci card in a 3.2 GHz Intel i5 CPU based computer running Linux. FCS measurements were made on Alexa-546 and Texas Red dyes in a standard buffer (PBS). Software correlations were compared to hardware correlator measurements on the same signals. Supported by HHMI and Swarthmore College

  12. Quantifying melanin spatial distribution using pump-probe microscopy and a 2-D morphological autocorrelation transformation for melanoma diagnosis

    Science.gov (United States)

    Robles, Francisco E.; Wilson, Jesse W.; Warren, Warren S.

    2013-12-01

    Pump-probe microscopy is an emerging molecular imaging technique that probes the excited state dynamics properties of pigmented samples. This method has been particularly intriguing for melanoma because, unlike other methods available, it can provide nondestructive, quantitative chemical information regarding different types of melanins, with high spatial resolution. In this Letter, we present a method based on mathematical morphology to quantify melanin structure (eumelanin, pheomelanin, and total melanin content, uniquely available with pump-probe microscopy) to aid in melanoma diagnosis. The approach applies a two-dimensional autocorrelation function and utilizes statistical parameters of the corresponding autocorrelation images, specifically, the second moments and entropy, to parameterize image structure. Along with bulk melanin chemical information, we show that this method can differentiate invasive melanomas from noninvasive and benign lesions with high sensitivity and specificity (92.3% and 97.5%, respectively, with N=53). The mathematical method and the statistical analysis are described in detail and results from cutaneous and ocular conjunctival melanocytic lesions are presented.

  13. Automatic Frequency Identification under Sample Loss in Sinusoidal Pulse Width Modulation Signals Using an Iterative Autocorrelation Algorithm

    Directory of Open Access Journals (Sweden)

    Alejandro Said

    2016-08-01

    Full Text Available In this work, we present a simple algorithm to calculate automatically the Fourier spectrum of a Sinusoidal Pulse Width Modulation Signal (SPWM. Modulated voltage signals of this kind are used in industry by speed drives to vary the speed of alternating current motors while maintaining a smooth torque. Nevertheless, the SPWM technique produces undesired harmonics, which yield stator heating and power losses. By monitoring these signals without human interaction, it is possible to identify the harmonic content of SPWM signals in a fast and continuous manner. The algorithm is based in the autocorrelation function, commonly used in radar and voice signal processing. Taking advantage of the symmetry properties of the autocorrelation, the algorithm is capable of estimating half of the period of the fundamental frequency; thus, allowing one to estimate the necessary number of samples to produce an accurate Fourier spectrum. To deal with the loss of samples, i.e., the scan backlog, the algorithm iteratively acquires and trims the discrete sequence of samples until the required number of samples reaches a stable value. The simulation shows that the algorithm is not affected by either the magnitude of the switching pulses or the acquisition noise.

  14. Tunable Soft X-Ray Oscillators

    International Nuclear Information System (INIS)

    Wurtele, Jonathan; Gandhi, Punut; Gu, X.-W.; Fawley, William M.; Reinsch, Matthia; Penn, Gregory; Kim, K.-J.; Lindberg, Ryan; Zholents, Alexander

    2010-01-01

    A concept for a tunable soft x-ray free electron laser (FEL) photon source is presented and studied numerically. The concept is based on echo-enabled harmonic generation (EEHG), wherein two modulator-chicane sections impose high harmonic structure with much greater efficacy as compared to conventional high harmonic FELs that use only one modulator-chicane section. The idea proposed here is to replace the external laser power sources in the EEHG modulators with FEL oscillators, and to combine the bunching of the beam with the production of radiation. Tunability is accomplished by adjusting the magnetic chicanes while the two oscillators remain at a fixed frequency. This scheme eliminates the need to develop coherent sources with the requisite power, pulse length, and stability requirements by exploiting the MHz bunch repetition rates of FEL continuous wave (CW) sources driven by superconducting (SC) linacs. We present time-dependent GINGER simulation results for an EEHG scheme with an oscillator modulator at 43 nm employing 50percent reflective dielectric mirrors and a second modulator employing an external, 215-nm drive laser. Peak output of order 300 MW is obtained at 2.7 nm, corresponding to the 80th harmonic of 215 nm. An alternative single-cavity echo-oscillator scheme based on a 13.4 nm oscillator is investigated with time-independent simulations that a 180-MW peak power at final wavelength of 1.12 nm. Three alternate configurations that use separate bunches to produce the radiation for EEHG microbunching are also presented. Our results show that oscillator-based soft x-ray FELs driven by CWSC linacs are extremely attractive because of their potential to produce tunable radiation at high average power together with excellent longitudinal coherence and narrow spectral bandwidth.

  15. Tunable Soft X-Ray Oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Wurtele, Jonathan; Gandhi, Punut; Gu, X-W; Fawley, William M; Reinsch, Matthia; Penn, Gregory; Kim, K-J; Lindberg, Ryan; Zholents, Alexander

    2010-09-17

    A concept for a tunable soft x-ray free electron laser (FEL) photon source is presented and studied numerically. The concept is based on echo-enabled harmonic generation (EEHG), wherein two modulator-chicane sections impose high harmonic structure with much greater efficacy as compared to conventional high harmonic FELs that use only one modulator-chicane section. The idea proposed here is to replace the external laser power sources in the EEHG modulators with FEL oscillators, and to combine the bunching of the beam with the production of radiation. Tunability is accomplished by adjusting the magnetic chicanes while the two oscillators remain at a fixed frequency. This scheme eliminates the need to develop coherent sources with the requisite power, pulse length, and stability requirements by exploiting the MHz bunch repetition rates of FEL continuous wave (CW) sources driven by superconducting (SC) linacs. We present time-dependent GINGER simulation results for an EEHG scheme with an oscillator modulator at 43 nm employing 50percent reflective dielectric mirrors and a second modulator employing an external, 215-nm drive laser. Peak output of order 300 MW is obtained at 2.7 nm, corresponding to the 80th harmonic of 215 nm. An alternative single-cavity echo-oscillator scheme based on a 13.4 nm oscillator is investigated with time-independent simulations that a 180-MW peak power at final wavelength of 1.12 nm. Three alternate configurations that use separate bunches to produce the radiation for EEHG microbunching are also presented. Our results show that oscillator-based soft x-ray FELs driven by CWSC linacs are extremely attractive because of their potential to produce tunable radiation at high average power together with excellent longitudinal coherence and narrow spectral bandwidth.

  16. Electrically tunable strong light-matter coupling in a transition metal dichalcogenide monolayer embedded in a plasmonic crystal cavity

    Science.gov (United States)

    Scuri, Giovanni; Zhou, You; High, Alexander; Dibos, Alan; de Greve, Kristiaan; Polking, Mark; Juaregui, Luis; Wild, Dominik; Joe, Andrew; Pistunova, Kateryna; Lukin, Mikhail; Kim, Philip; Park, Hongkun

    Two-dimensional transition-metal dichalcogenide (TMDC) monolayers exhibit direct bandgap excitons with large binding energy. The optical response of TMDCs is electrically tunable over a broad wavelength range, making these 2D materials promising candidates for optoelectronic devices. In this work, we enhance exciton-plasmon coupling by embedding a single layer of tungsten diselenide (WSe2) into a plasmonic crystal cavity, which confines surface plasmon polaritons in an analogous manner to photonic crystal cavities. We observe strong light-matter interactions and the formation of microcavity polaritons when the cavity mode is on resonance with the exciton absorption in WSe2. Using the electrostatically controllable response of such excitons, we also demonstrate tunable vacuum Rabi splitting in such a system.

  17. Development of frequency tunable gyrotrons for plasma diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Idehara, T.; Mitsudo, S.; Sabchevski, S.; Glyavin, M. [Research Center for Development of Far-Infrared Region, Fukui Univ., Fukui (Japan); Ogawa, I. [Faculty of Engineering, Fukui Univ., Fukui (Japan); Sato, M.; Kawahata, K. [National Inst. for Fusion Science, Toki, Gifu (Japan); Brand, G.F. [School of Physics, Univ. of Sydney, NSW (Australia)

    2000-03-01

    Development of two types of frequency tunable gyrotrons are described. One is frequency step-tunable gyrotrons (Gyrotron FU Series) which cover wide range from millimeter to submillimeter wavelength region. The other is a quasi-optical gyrotron operating in 90 and 180 GHz bands. Both are applicable for plasma diagnostics as power sources. (author)

  18. Development of frequency tunable gyrotrons for plasma diagnostics

    International Nuclear Information System (INIS)

    Idehara, T.; Mitsudo, S.; Sabchevski, S.; Glyavin, M.; Ogawa, I.; Sato, M.; Kawahata, K.; Brand, G.F.

    2000-01-01

    Development of two types of frequency tunable gyrotrons are described. One is frequency step-tunable gyrotrons (Gyrotron FU Series) which cover wide range from millimeter to submillimeter wavelength region. The other is a quasi-optical gyrotron operating in 90 and 180 GHz bands. Both are applicable for plasma diagnostics as power sources. (author)

  19. A low-loss, continuously tunable microwave notch filter

    DEFF Research Database (Denmark)

    Acar, Öncel; Johansen, Tom Keinicke; Zhurbenko, Vitaliy

    2016-01-01

    The development in high-end microwave transceiver systems toward the software defined radio has brought about the need for tunable frontend filters. Although the problem is being tackled by the microwave community, there still appears to be an unmet demand for practical tunable filter technologies...

  20. Water: Promising Opportunities For Tunable All-dielectric Electromagnetic Metamaterials

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Kuznetsova, Svetlana M.; Zhukovsky, Sergei

    2015-01-01

    We reveal an outstanding potential of water as an inexpensive, abundant and bio-friendly high-refractive-index material for creating tunable all-dielectric photonic structures and metamaterials. Specifically, we demonstrate thermal, mechanical and gravitational tunability of magnetic and electric...

  1. Tunable optical absorption in silicene molecules

    KAUST Repository

    Mokkath, Junais Habeeb

    2016-07-13

    Two-dimensional materials with a tunable band gap that covers a wide range of the solar spectrum hold great promise for sunlight harvesting. For this reason, we investigate the structural, electronic, and optical properties of silicene molecules using time dependent density functional theory. We address the influence of the molecular size, buckling, and charge state as well as that of a dielectric environment. Unlike planar graphene molecules, silicene molecules prefer to form low-buckled structures with strong visible to ultraviolet optical response. We also identify molecular plasmons.

  2. Tunable superconducting qudit mediated by microwave photons

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Sung Un [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Bae, Myung-Ho; Kim, Nam [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Kang, Kicheon [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of)

    2015-08-15

    We have investigated the time-domain characteristics of the Autler-Townes doublet in a superconducting circuit. The transition probabilities between the ground state and the Autler-Townes doublet states are shown to be controlled in a phase-coherent manner using a well-known microwave pulse pattern technique. The experimental results are well explained by a numerical simulation based on the Markovian master equation. Our result indicates that the Autler-Townes doublet states might be useful as a tunable qudit for implementation of quantum information processing, in particular as a multivalued quantum logic element.

  3. Tunable superconducting qudit mediated by microwave photons

    Directory of Open Access Journals (Sweden)

    Sung Un Cho

    2015-08-01

    Full Text Available We have investigated the time-domain characteristics of the Autler-Townes doublet in a superconducting circuit. The transition probabilities between the ground state and the Autler-Townes doublet states are shown to be controlled in a phase-coherent manner using a well-known microwave pulse pattern technique. The experimental results are well explained by a numerical simulation based on the Markovian master equation. Our result indicates that the Autler-Townes doublet states might be useful as a tunable qudit for implementation of quantum information processing, in particular as a multivalued quantum logic element.

  4. Active microring based tunable optical power splitters

    Science.gov (United States)

    Peter, Eldhose; Thomas, Arun; Dhawan, Anuj; Sarangi, Smruti R.

    2016-01-01

    In this paper we propose a set of novel tunable optical power splitters based on active microring resonators. They work by operating ring resonators in the transient zone between full resonance and off-resonance states for a specific wavelength. We can achieve different split ratios by either varying the bias voltage, or by selectively enabling a given resonator with a specific split ratio among an array of ring resonators. We take 500 ps to tune the resonator, which is at least 10× better that competing designs. Its split ratio varies from 0.4 to 1.8 for an applied voltage range of 0-5 V.

  5. Nano electro-mechanical optoelectronic tunable VCSEL.

    Science.gov (United States)

    Huang, Michael C Y; Zhou, Ye; Chang-Hasnain, Connie J

    2007-02-05

    We report a novel electrostatic actuated nano-electromechanical optoelectronic (NEMO) tunable vertical-cavity surface-emitting laser (VCSEL) centered at 850 nm. By integrating a movable, single-layer (230 nm), high-index-contrast subwavelength grating (HCG) as the VCSEL top mirror, single mode emission (SMSR >40 dB) and continuous wavelength tuning (~2.5 nm) was obtained at room temperature under CW operation. The small footprint of HCG enables the scaling down of each of the cantilever dimensions by a factor of 10, leading to 1000 times reduction in mass, which potentially increases the mechanical resonant frequency and tuning speed.

  6. Magnetic nanoparticles for tunable microwave metamaterials

    KAUST Repository

    Noginova, Natalia

    2012-09-24

    Commonly, metamaterials are electrically engineered systems with optimized spatial arrangement of subwavelength sized metal and dielectric components. We explore alternative methods based on use of magnetic inclusions, such as magnetic nanoparticles, which can allow permeability of a composite to be tuned from negative to positive at the range of magnetic resonance. To better understand effects of particle size and magnetization dynamics, we performed electron magnetic resonance study on several varieties of magnetic nanoparticles and determined potential of nanoparticle use as building blocks for tunable microwave metamaterials. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  7. Magnetocapacitance of an electrically tunable silicene device

    KAUST Repository

    Tahir, M.

    2012-09-26

    Despite their structural similarity, the electronic properties of silicene are fundamentally different from those of well-known graphene due to the strong intrinsic spin orbit interaction and buckled structure of silicene. We address the magnetocapacitance of spin and valley polarized silicene in an external perpendicular magnetic field to clarify the interplay of the spin orbit interaction and the perpendicular electric field. We find that the band gap is electrically tunable and show that the magnetocapacitance exhibits beating at low and splitting of the Shubnikov de Haas oscillations at high magnetic field.

  8. Reconciling monitoring and modeling: An appraisal of river monitoring networks based on a spatial autocorrelation approach - emerging pollutants in the Danube River as a case study.

    Science.gov (United States)

    Ginebreda, A; Sabater-Liesa, L; Rico, A; Focks, A; Barceló, D

    2018-03-15

    Rivers extend in space and time under the influence of their catchment area. Our perception largely relies on discrete spatial and temporal observations carried out at certain sites located throughout the catchment (monitoring networks, MN). However, MNs are constrained by (a) the distribution of sampling sites, (b) the dynamics of the variable considered and (c) the river hydrological conditions. In this study, all three aspects were captured and quantified by applying a spatial autocorrelation modeling approach. We exemplarily studied its application to 235 emerging contaminants (pesticides, pharmaceuticals, and personal care products [PPCP], industrial and miscellaneous) measured at 55 sampling sites in the Danube River. 22 out of the 235 compounds monitored were present at all sites and 125 were found in at least 50%.We first calculated the Moran Index (MI) to characterize the spatial autocorrelation of the compound set. 59 compounds showed MI≤0, which can be interpreted as 'no spatial correlation'. Next, spatial autocorrelation models were set for each compound. From the autocorrelation parameter ρ, catchment average correlation lengths were derived for each compound. MN optimality was examined and compounds were classified into three groups: (a) those with ρ≤0 [25%]; (b) those with ρ>0 and correl. length0 and correl. length>average distance between consecutive sites [73%]. The MN was considered optimal only for the latter class. Networks with the larger average distance between consecutive sites resulted in a decreasing number of optimally monitored compounds. Furthermore, neighbors vs. local relative contributions were quantified based on the spatial autocorrelation model for all the measured compounds. The results of this study show how autocorrelation models can aid water managers to improve the design of river MNs, which are a key aspect of the Water Framework Directive. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Determination of modulation transfer function of a printer by measuring the autocorrelation of the transmission function of a printed Ronchi grating

    International Nuclear Information System (INIS)

    Madanipour, Khosro; Tavassoly, Mohammad T.

    2009-01-01

    We show theoretically and verify experimentally that the modulation transfer function (MTF) of a printing system can be determined by measuring the autocorrelation of a printed Ronchi grating. In practice, two similar Ronchi gratings are printed on two transparencies and the transparencies are superimposed with parallel grating lines. Then, the gratings are uniformly illuminated and the transmitted light from a large section is measured versus the displacement of one grating with respect to the other in a grating pitch interval. This measurement provides the required autocorrelation function for determination of the MTF

  10. Streams of events and performance of queuing systems: The basic anatomy of arrival/departure processes, when the focus is set on autocorrelation

    DEFF Research Database (Denmark)

    Nielsen, Erland Hejn

    2004-01-01

    some arrival processes for some simulation study a thorough preliminary analysis has to be undertaken in order to uncover the basic time series nature of the interacting processes. Flexible methods for generating streams of autocorrelated variates of any desired distributional type, such as the ARTA...... method or some autocorrelation extended descriptive sampling method, can then easily be applied. The results from the Livny, Melamed and Tsiolis (1993) study as well as the results from this work both indicates that system performance measures as for instance average waiting time or average time...

  11. Elastic metamaterial beam with remotely tunable stiffness

    Science.gov (United States)

    Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.

    2016-02-01

    We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ˜30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.

  12. 130-nm tunable grating-mirror VCSEL

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2014-01-01

    We have reported that a combination of the high-index-contrast grating (HCG) mirror as movable mirror and the extended cavity configuration with an antireflection layer can provide a tuning wavelength range of 100 nm for tunable VCSELs. Here, we report that using the air-coupled cavity configurat......We have reported that a combination of the high-index-contrast grating (HCG) mirror as movable mirror and the extended cavity configuration with an antireflection layer can provide a tuning wavelength range of 100 nm for tunable VCSELs. Here, we report that using the air-coupled cavity...... configuration instead of the extended cavity configuration can bring 130-nm tuning range around 1330-nm wavelength. The air-coupled cavity is known to reduce the quantum confinement factor in VCSELs, increasing threshold. In our air-coupled cavity HCG VCSEL case, the very short power penetration length...... in the HCG minimizes this reduction of the quantum confinement factor, not as significant as in the air-coupled cavity DBR VCSEL....

  13. Directed growth of diameter-tunable nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ozturk, Birol; Talukdar, Ishan; Flanders, Bret N [Department of Physics, Oklahoma State University, 145 Physical Sciences II, Stillwater, OK 74078 (United States)

    2007-09-12

    This study characterizes a method for controlling the nanowire diameter in the directed electrochemical nanowire assembly technique, where alternating voltages applied to electrodes in simple salt solutions induce the crystallization of metallic wires. Dendritic solidification is identified as an important component of this technique. A characteristic of dendritic solidification is that the growth velocity and tip radius are anti-correlated. This relationship is exploited here to realize diameter-tunable nanowire growth. The experimental parameter that provides this control is {omega}, the frequency of the alternating voltage. Increasing {omega} effectively steepens the metal cation concentration gradient at the wire-solution interface, thereby increasing the growth velocity of the wire. For indium wires, increasing {omega} from 0.5 to 3.5 MHz increases their growth velocity from 11 to 78 {mu}m s{sup -1} and reduces their diameter from 770 to 114 nm. Gold wires exhibit diameter-tunability that ranges from 150 nm to 45 nm. Thus, it is possible to tune the wire diameter from the microscale down to the nanoscale. Moreover, this control is a consequence of non-stationary dendritic growth, which distinguishes this process from most previously studied examples of dendritic solidification.

  14. Elastic metamaterial beam with remotely tunable stiffness

    International Nuclear Information System (INIS)

    Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.

    2016-01-01

    We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ∼30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves

  15. Highly Tunable Electrothermally and Electrostatically Actuated Resonators

    KAUST Repository

    Hajjaj, Amal Z.

    2016-03-30

    This paper demonstrates experimentally, theoretically, and numerically for the first time, a wide-range tunability of an in-plane clamped-clamped microbeam, bridge, and resonator actuated electrothermally and electrostatically. Using both actuation methods, we demonstrate that a single resonator can be operated at a wide range of frequencies. The microbeam is actuated electrothermally by passing a dc current through it, and electrostatically by applying a dc polarization voltage between the microbeam and the stationary electrode. We show that when increasing the electrothermal voltage, the compressive stress inside the microbeam increases, which leads eventually to its buckling. Before buckling, the fundamental frequency decreases until it drops to very low values, almost to zero. After buckling, the fundamental frequency increases, which is shown to be as high as twice the original resonance frequency. Adding a dc bias changes the qualitative nature of the tunability both before and after buckling, which adds another independent way of tuning. This reduces the dip before buckling, and can eliminate it if desired, and further increases the fundamental frequency after buckling. Analytical results based on the Galerkin discretization of the Euler Bernoulli beam theory are generated and compared with the experimental data and simulation results of a multi-physics finite-element model. A good agreement is found among all the results. [2015-0341

  16. Tunable Mechanical Filter for Longitudinal Vibrations

    Directory of Open Access Journals (Sweden)

    S. Asiri

    2007-01-01

    Full Text Available This paper presents both theoretically and experimentally a new kind of vibration isolator called tunable mechanical filter which consists of four parallel hybrid periodic rods connected between two plates. The rods consist of an assembly of periodic cells, each cell being composed of a short rod and piezoelectric inserts. By actively controlling the piezoelectric elements, it is shown that the periodic rods can efficiently attenuate the propagation of vibration from the upper plate to the lower one within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation. In such a filter, longitudinal waves can propagate from the vibration source in the upper plate to the lower one along the rods only within specific frequency bands called the “Pass Bands” and wave propagation is efficiently attenuated within other frequency bands called the “Stop Bands”. The spectral width of these bands can be tuned according to the nature of the external excitation. The theory governing the operation of this class of vibration isolator is presented and their tunable filtering characteristics are demonstrated experimentally as functions of their design parameters. The concept of this mechanical filter as presented can be employed in many applications to control the wave propagation and the force transmission of longitudinal vibrations both in the spectral and spatial domains in an attempt to stop/attenuate the propagation of undesirable disturbances.

  17. Highly Tunable Electrothermally Actuated Arch Resonator

    KAUST Repository

    Hajjaj, Amal Z.

    2016-12-05

    This paper demonstrates experimentally, theoretically, and numerically a wide-range tunability of electrothermally actuated MEMS arch beams. The beams are made of silicon and are intentionally fabricated with some curvature as in-plane shallow arches. Analytical results based on the Galerkin discretization of the Euler Bernoulli beam theory are generated and compared to the experimental data and results of a multi-physics finite-element model. A good agreement is found among all the results. The electrothermal voltage is applied between the anchors of the clamped-clamped MEMS arch beam, generating a current that passes through the MEMS arch beam and controls its axial stress caused by thermal expansion. When the electrothermal voltage increases, the compressive stress increases inside the arch beam. This leads to increase in its curvature, thereby increases the resonance frequencies of the structure. We show here that the first resonance frequency can increase up to twice its initial value. We show also that after some electro-thermal voltage load, the third resonance frequency starts to become more sensitive to the axial thermal stress, while the first resonance frequency becomes less sensitive. These results can be used as guidelines to utilize arches as wide-range tunable resonators.

  18. Studies in astronomical time series analysis. III - Fourier transforms, autocorrelation functions, and cross-correlation functions of unevenly spaced data

    Science.gov (United States)

    Scargle, Jeffrey D.

    1989-01-01

    This paper develops techniques to evaluate the discrete Fourier transform (DFT), the autocorrelation function (ACF), and the cross-correlation function (CCF) of time series which are not evenly sampled. The series may consist of quantized point data (e.g., yes/no processes such as photon arrival). The DFT, which can be inverted to recover the original data and the sampling, is used to compute correlation functions by means of a procedure which is effectively, but not explicitly, an interpolation. The CCF can be computed for two time series not even sampled at the same set of times. Techniques for removing the distortion of the correlation functions caused by the sampling, determining the value of a constant component to the data, and treating unequally weighted data are also discussed. FORTRAN code for the Fourier transform algorithm and numerical examples of the techniques are given.

  19. AFM topographies of densely packed nanoparticles: a quick way to determine the lateral size distribution by autocorrelation function analysis

    International Nuclear Information System (INIS)

    Fekete, L.; Kůsová, K.; Petrák, V.; Kratochvílová, I.

    2012-01-01

    The distribution of sizes is one of the basic characteristics of nanoparticles. Here, we propose a novel way to determine the lateral distribution of sizes from AFM topographies. Our algorithm is based on the autocorrelation function and can be applied both on topographies containing spatially separated and densely packed nanoparticles as well as on topographies of polycrystalline films. As no manual treatment is required, this algorithm can be easily automatable for batch processing. The algorithm works in principle with any kind of spatially mapped information (AFM current maps, optical microscope images, etc.), and as such has no size limitations. However, in the case of AFM topographies, the tip/sample convolution effects will be the factor limiting the smallest size to which the algorithm is applicable. Here, we demonstrate the usefulness of this algorithm on objects with sizes ranging between 20 nm and 1.5 μm.

  20. FREQUENCY ANALYSIS OF RLE-BLOCKS REPETITIONS IN THE SERIES OF BINARY CODES WITH OPTIMAL MINIMAX CRITERION OF AUTOCORRELATION FUNCTION

    Directory of Open Access Journals (Sweden)

    A. A. Kovylin

    2013-01-01

    Full Text Available The article describes the problem of searching for binary pseudo-random sequences with quasi-ideal autocorrelation function, which are to be used in contemporary communication systems, including mobile and wireless data transfer interfaces. In the synthesis of binary sequences sets, the target set is manning them based on the minimax criterion by which a sequence is considered to be optimal according to the intended application. In the course of the research the optimal sequences with order of up to 52 were obtained; the analysis of Run Length Encoding was carried out. The analysis showed regularities in the distribution of series number of different lengths in the codes that are optimal on the chosen criteria, which would make it possible to optimize the searching process for such codes in the future.

  1. Autocorrelation studies of the arrival directions of UHECRs measured by the surface detector of the Pierre Auger Observatory

    International Nuclear Information System (INIS)

    Schulte, Stephan

    2011-01-01

    The history of cosmic rays started in the beginning of the 20th century. Since then one of the main questions is their origin. Due to the very low flux at the highest energies huge areas have to be instrumented to answer this question. For this purpose the distribution of the arrival directions of cosmic rays is studied. The largest experiment so far is the Pierre Auger Observatory, located in the Pampa in western Argentina with an area of about 3000 km 2 . In recent years it provided many major contributions to the field of cosmic ray physics and its data is the basis of this work. Among other things a correlation analysis of Ultra High Energy Cosmic Rays (UHECRs) with Active Galactic Nuclei (AGN) was performed leading to the first evidence that UHECRs are not isotropically distributed. Here the distribution of arrival directions of cosmic rays at the highest energies (>50 EeV) is examined by using autocorrelation methods to check whether it is compatible with the isotropic expectation or not.This thesis is organised as follows: in the first two chapters a short introduction to the topic is given, followed by a more general discussion on cosmic rays including models of acceleration, possible sources and the propagation of UHECRs in the third chapter. The fourth chapter focuses on the detector design of the Pierre Auger Observatory and event reconstruction at highest energies. Special attention is paid to the monitoring of the High Elevation Auger Telescopes (HEAT). It is a low energy enhancement of the observatory consisting of three tiltable fluorescence telescopes. The calibration of the new sensor setups is described as well as the installation in each HEAT shelter. The next chapter starts with a detailed description of the underlying ideas and motivations of autocorrelation methods: a representation of the 2pt-Correlation Function and its extension, a Minimum Spanning Tree and a Cluster Algorithm with different weighting procedures. The principle of each

  2. Autocorrelation studies of the arrival directions of UHECRs measured by the surface detector of the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, Stephan

    2011-07-11

    The history of cosmic rays started in the beginning of the 20th century. Since then one of the main questions is their origin. Due to the very low flux at the highest energies huge areas have to be instrumented to answer this question. For this purpose the distribution of the arrival directions of cosmic rays is studied. The largest experiment so far is the Pierre Auger Observatory, located in the Pampa in western Argentina with an area of about 3000 km{sup 2}. In recent years it provided many major contributions to the field of cosmic ray physics and its data is the basis of this work. Among other things a correlation analysis of Ultra High Energy Cosmic Rays (UHECRs) with Active Galactic Nuclei (AGN) was performed leading to the first evidence that UHECRs are not isotropically distributed. Here the distribution of arrival directions of cosmic rays at the highest energies (>50 EeV) is examined by using autocorrelation methods to check whether it is compatible with the isotropic expectation or not.This thesis is organised as follows: in the first two chapters a short introduction to the topic is given, followed by a more general discussion on cosmic rays including models of acceleration, possible sources and the propagation of UHECRs in the third chapter. The fourth chapter focuses on the detector design of the Pierre Auger Observatory and event reconstruction at highest energies. Special attention is paid to the monitoring of the High Elevation Auger Telescopes (HEAT). It is a low energy enhancement of the observatory consisting of three tiltable fluorescence telescopes. The calibration of the new sensor setups is described as well as the installation in each HEAT shelter. The next chapter starts with a detailed description of the underlying ideas and motivations of autocorrelation methods: a representation of the 2pt-Correlation Function and its extension, a Minimum Spanning Tree and a Cluster Algorithm with different weighting procedures. The principle of each

  3. Characterizing groundwater quality ranks for drinking purposes in Sylhet district, Bangladesh, using entropy method, spatial autocorrelation index, and geostatistics.

    Science.gov (United States)

    Islam, Abu Reza Md Towfiqul; Ahmed, Nasir; Bodrud-Doza, Md; Chu, Ronghao

    2017-12-01

    Drinking water is susceptible to the poor quality of contaminated water affecting the health of humans. Thus, it is an essential study to investigate factors affecting groundwater quality and its suitability for drinking uses. In this paper, the entropy theory, multivariate statistics, spatial autocorrelation index, and geostatistics are applied to characterize groundwater quality and its spatial variability in the Sylhet district of Bangladesh. A total of 91samples have been collected from wells (e.g., shallow, intermediate, and deep tube wells at 15-300-m depth) from the study area. The results show that NO 3 - , then SO 4 2- , and As are the most contributed parameters influencing the groundwater quality according to the entropy theory. The principal component analysis (PCA) and correlation coefficient also confirm the results of the entropy theory. However, Na + has the highest spatial autocorrelation and the most entropy, thus affecting the groundwater quality. Based on the entropy-weighted water quality index (EWQI) and groundwater quality index (GWQI) classifications, it is observed that 60.45 and 53.86% of water samples are classified as having an excellent to good qualities, while the remaining samples vary from medium to extremely poor quality domains for drinking purposes. Furthermore, the EWQI classification provides the more reasonable results than GWQIs due to its simplicity, accuracy, and ignoring of artificial weight. A Gaussian semivariogram model has been chosen to the best fit model, and groundwater quality indices have a weak spatial dependence, suggesting that both geogenic and anthropogenic factors play a pivotal role in spatial heterogeneity of groundwater quality oscillations.

  4. Giant Broad Line Regions in Dwarf Seyferts

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... High angular resolution spectroscopy obtained with the Hubble Space Telescope (HST) has revealed a remarkable population of galaxies hosting dwarf Seyfert nuclei with an unusually large broad-line region (BLR). These objects are remarkable for two reasons. Firstly, the size of the BLR can, in some ...

  5. Education and Broad Concepts of Agency

    Science.gov (United States)

    Winch, Christopher

    2014-01-01

    Drawing on recent debates about the relationship between propositional and practical knowledge, this article is concerned with broad concepts of agency. Specifically, it is concerned with agency that involves the forming and putting into effect of intentions over relatively extended periods, particularly in work contexts (called, for want of a…

  6. Giant Broad Line Regions in Dwarf Seyferts

    Indian Academy of Sciences (India)

    one can determine the inner and outer radii of the BLRs by modeling the ... The physics behind the production of broad emission lines in active galactic nuclei ... shapes. The inner radius of the volume defines the full velocity width at zero intensity of the model emission line, and the outer radius of the volume defines the ...

  7. Permanent magnetic ferrite based power-tunable metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guanqiao; Lan, Chuwen [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Gao, Rui [High Temperature Thermochemistry Laboratory, Department of Mining and Materials Engineering, McGill University, Montreal, Quebec H3A 0C5 (Canada); Zhou, Ji, E-mail: zhouji@tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-08-15

    Highlights: • Power-tunable metamaterials based on barium permanent magnetic ferrite have been proposed and fabricated. • It is observed that resonant frequency of the array shifts upon altering the output power. • This kind of power-tunable behavior is due to the temperature rise as a result of FMR-induced heat buildup. • This work offers a practical idea to tune ferrite metamaterials besides magneto-tunability and thermal-tunability. - Abstract: Power-tunable metamaterials based on barium permanent magnetic ferrite have been proposed and fabricated in this research. Scattering parameter measurements confirm a shift in resonant frequency in correlation to changes in incident electromagnetic power within microwave frequency band. The tunable phenomenon represented by a blue-shift in transmission spectra in the metamaterials array can be attributed to a decrease in saturation magnetization resulting from FMR-induced temperature elevation upon resonant conditions. This power-dependent behavior offers a simple and practical route towards dynamically fine-tunable ferrite metamaterials.

  8. Widely tunable Sampled Grating Distributed Bragg Reflector Quantum Cascade laser for gas spectroscopy applications

    Science.gov (United States)

    Diba, Abdou Salam

    Since the advent of semiconductor lasers, the development of tunable laser sources has been subject of many efforts in industry and academia arenas. This interest towards broadly tunable lasers is mainly due to the great promise they have in many applications ranging from telecommunication, to environmental science and homeland security, just to name a few. After the first demonstration of quantum cascade laser (QCL) in the early nineties, QCL has experienced a rapid development, so much so that QCLs are now the most reliable and efficient laser source in the Mid-IR range covering between 3 microm to 30 microm region of the electromagnetic spectrum. QCLs have almost all the desirable characteristics of a laser for spectroscopy applications such as narrow spectral linewidth ideal for high selectivity measurement, high power enabling high sensitivity sensing and more importantly they emit in the finger-print region of most of the trace gases and large molecules. The need for widely tunable QCLs is now more pressing than ever before. A single mode quantum cascade laser (QCL) such as a distributed feedback (DFB) QCL, is an ideal light source for gas sensing in the MIR wavelength range. Despite their performance and reliability, DFB QCLs are limited by their relatively narrow wavelength tuning range determined by the thermal rollover of the laser. An external cavity (EC) QCL, on the other hand, is a widely tunable laser source, and so far is the choice mid-infrared single frequency light sources for detecting multiple species/large molecules. However, EC QCLs can be complex, bulky and expensive. In the quest for finding alternative broadly wavelength tunable sources in the mid-infrared, many monolithic tunable QCLs are recently proposed and fabricated, including SG-DBR, DFB-Arrays, Slot-hole etc. and they are all of potentially of interest as a candidate for multi-gas sensing and monitoring applications, due to their large tuning range (>50 cm-1), and potentially low

  9. Design of Hilbert transformers with tunable THz bandwidths using a reconfigurable integrated optical FIR filter

    Science.gov (United States)

    Ngo, Nam Quoc; Song, Yufeng; Lin, Bo

    2011-02-01

    We present the design and analysis of a wideband and tunable optical Hilbert transformer (OHT) using a tunable waveguide-based finite-impulse response (FIR) filter structure by using the digital filter design method and the Remez algorithm. The tunable Nth-order waveguide-based FIR filter, which simply consists of N delay lines, N tunable couplers, N tunable phase shifters and a combiner, can be tuned, by thermally adjusting the tunable couplers and tunable phase shifters, to tune the bandwidth of an OHT using silica-based planar lightwave circuit (PLC) technology. To demonstrate the effectiveness of the method, the simulation results have an excellent agreement with the theoretical predictions. The tunable OHT can function as a wideband and tunable 90° phase shifter and thus has many potential applications. The two unique features of wideband characteristic (up to ~ 2 THz) and tunable bandwidth (THz tuning range) of the proposed OHT cannot be obtained from the existing OHTs.

  10. An attempt at solving the problem of autocorrelation associated with use of mean approach for pooling cross-section and time series in regression modelling

    International Nuclear Information System (INIS)

    Nuamah, N.N.N.N.

    1990-12-01

    The paradoxical nature of results of the mean approach in pooling cross-section and time series data has been identified to be caused by the presence in the normal equations of phenomena such as autocovariances, multicollinear covariances, drift covariances and drift multicollinear covariances. This paper considers the problem of autocorrelation and suggests ways of solving it. (author). 4 refs

  11. Tunability of laser based on Yb-doped hot-pressed CaF2 ceramics

    Science.gov (United States)

    Sulc, Jan; Doroshenko, Maxim E.; Jelínková, Helena; Basiev, Tasoltan T.; Konyushkin, Vasilii A.; Osiko, Vyacheslav V.

    2012-06-01

    The aim of presented study was an investigation of tunability of diode pumped laser based on hot-pressed Yb:CaF2 ceramics. The tested Yb:CaF2 sample was in the form of 3.5mm thick plane-parallel face-polished plate (without AR coatings). The Yb3+ concentration was 5.5 %. A fiber (core diameter 200 μm, NA= 0.22) coupled laser diode (LIMO, HLU25F200-980) with emission at wavelength 976 nm, was used for longitudinal Yb:CaF2 pumping. The laser diode was operating in the pulsed regime (4 ms pulse length, 20 Hz repetition rate). The duty-cycle 8% ensured a low thermal load even under the maximum diode pumping power amplitude 10W (crystal sample was only air-cooled). This radiation was focused into the crystal (pumping beam waist diameter ~ 170 μm). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ~ 98% @ 1.01 - 1.09 μm. Tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The extremely broad and smooth tuning was obtained. The laser was continuously tunable over ~ 66nm (from 1015nm to 1081 nm) and the tuning band was mostly limited by free spectral range of used birefringent filter. The tunability FWHM was 40 nm corresponding bandwidth 10 THz results in Fourier limited gaussian pulse width ~ 40 fs (FWHM). The maximum output power amplitude 0.68W was obtained at wavelength 1054nm for absorbed pump power amplitude 6W. The laser slope efficiency was 15%.

  12. Tunable Microwave Component Technologies for SatCom-Platforms

    Science.gov (United States)

    Maune, Holger; Jost, Matthias; Wiens, Alex; Weickhmann, Christian; Reese, Roland; Nikfalazar, Mohammad; Schuster, Christian; Franke, Tobias; Hu, Wenjuan; Nickel, Matthias; Kienemund, Daniel; Prasetiadi, Ananto Eka; Jakoby, Rolf

    2017-03-01

    Modern communication platforms require a huge amount of switched RF component banks especially made of different filters and antennas to cover all operating frequencies and bandwidth for the targeted services and application scenarios. In contrast, reconfigurable devices made of tunable components lead to a considerable reduction in complexity, size, weight, power consumption, and cost. This paper gives an overview of suitable technologies for tunable microwave components especially for SatCom applications. Special attention is given to tunable components based on functional materials such as barium strontium titanate (BST) and liquid crystal (LC).

  13. Co-extruded mechanically tunable multilayer elastomer laser

    Science.gov (United States)

    Crescimanno, Michael; Mao, Guilin; Andrews, James; Singer, Kenneth; Baer, Eric; Hiltner, Anne; Song, Hyunmin; Shakya, Bijayandra

    2011-04-01

    We have fabricated and studied mechanically tunable elastomer dye lasers constructed in large area sheets by a single-step layer-multiplying co-extrusion process. The laser films consist of a central dye-doped (Rhodamine-6G) elastomer layer between two 128-layer distributed Bragg reflector (DBR) films comprised of alternating elastomer layers with different refractive indices. The central gain layer is formed by folding the coextruded DBR film to enclose a dye-doped skin layer. By mechanically stretching the elastomer laser film from 0% to 19%, a tunable miniature laser source was obtained with ˜50 nm continuous tunability from red to green.

  14. Microwave photonic comb filter with ultra-fast tunability.

    Science.gov (United States)

    Jiang, H Y; Yan, L S; Pan, Y; Pan, W; Luo, B; Zou, X H; Eggleton, B J

    2015-11-01

    A microwave comb filter with ultra-fast tunability is proposed based on the fundamental delay-line microwave photonic filter. The central frequency of the passband or stopband in such a filter can be rapidly adjusted, along with the independent tunability of the free spectral range (FSR). Experimental results show that the central frequency of the transfer function is electronically tuned with a frequency difference of half of the FSR at a speed of <100  ps. Such high-speed tunability is vital for high-speed microwave switching, frequency hopping, cognitive radio, and next-generation radar systems.

  15. Tunable plasmonic lattices of silver nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Andrea; Sinsermsuksakul, Prasert; Yang, Peidong

    2008-02-18

    Silver nanocrystals are ideal building blocks for plasmonicmaterials that exhibit a wide range of unique and potentially usefuloptical phenomena. Individual nanocrystals display distinct opticalscattering spectra and can be assembled into hierarchical structures thatcouple strongly to external electromagnetic fields. This coupling, whichis mediated by surface plasmons, depends on their shape and arrangement.Here we demonstrate the bottom-up assembly of polyhedral silvernanocrystals into macroscopic two-dimensional superlattices using theLangmuir-Blodgett technique. Our ability to control interparticlespacing, density, and packing symmetry allows for tunability of theoptical response over the entire visible range. This assembly strategyoffers a new, practical approach to making novel plasmonic materials forapplication in spectroscopic sensors, sub-wavelength optics, andintegrated devices that utilize field enhancement effects.

  16. Tunable Magnetic Resonance in Microwave Spintronics Devices

    Science.gov (United States)

    Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

    2015-01-01

    Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe based tunable microwave spintronics devices, which is 10X higher than conventional methods.

  17. MEMS tunable grating micro-spectrometer

    Science.gov (United States)

    Tormen, Maurizio; Lockhart, R.; Niedermann, P.; Overstolz, T.; Hoogerwerf, A.; Mayor, J.-M.; Pierer, J.; Bosshard, C.; Ischer, R.; Voirin, G.; Stanley, R. P.

    2017-11-01

    The interest in MEMS based Micro-Spectrometers is increasing due to their potential in terms of flexibility as well as cost, low mass, small volume and power savings. This interest, especially in the Near-Infrared and Mid- Infrared, ranges from planetary exploration missions to astronomy, e.g. the search for extra solar planets, as well as to many other terrestrial fields of application such as, industrial quality and surface control, chemical analysis of soil and water, detection of chemical pollutants, exhausted gas analysis, food quality control, process control in pharmaceuticals, to name a few. A compact MEMS-based Spectrometer for Near- Infrared and Mid-InfraRed operation have been conceived, designed and demonstrated. The design based on tunable MEMS blazed grating, developed in the past at CSEM [1], achieves state of the art results in terms of spectral resolution, operational wavelength range, light throughput, overall dimensions, and power consumption.

  18. Switchable and Tunable Aerodynamic Drag on Cylinders

    Science.gov (United States)

    Guttag, Mark; Lopéz Jiménez, Francisco; Upadhyaya, Priyank; Kumar, Shanmugam; Reis, Pedro

    We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.

  19. Tunable Q-Factor RF Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Balcazar, Mario D. [Fermilab; Yonehara, Katsuya [Fermilab; Moretti, Alfred [Fermilab; Kazakevitch, Gregory [Fermilab

    2018-01-01

    Intense neutrino beam is a unique probe for researching beyond the standard model. Fermilab is the main institution to produce the most powerful and widespectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gasfilled RF cavity is proposed. The goal of this measurement is to study a tunable Qfactor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.

  20. Compact microstrip bandpass filter with tunable notch

    DEFF Research Database (Denmark)

    Christensen, Silas; Zhurbenko, Vitaliy; Johansen, Tom Keinicke

    2014-01-01

    notch filter ensures an attenuation level of 19.3 dB to 27.3 dB in the frequency range from 360–480 MHz. The measured passband ripple of the combined filter is less than 0.5 dB, while the insertion loss for the simplest design is less than 1.7 dB only 10 MHz from the notch frequency. Even though......Two different designs combining a bandpass and a notch filter are developed to operate in the receiving band from 350–470 MHz. The bandpass filter is designed from a simple structure, by use of only four short circuited stubs and a half wavelength transmission line connecting the stubs. The tunable...... the wavelength on the selected substrate (εr = 3.55) is approximately 45 cm, the outer dimensions of the final filter only measure 10×10 cm2....

  1. Stakeholder acceptance analysis: Tunable hybrid plasma

    International Nuclear Information System (INIS)

    Peterson, T.

    1995-12-01

    This report resents evaluations, recommendations, and requirements concerning Tunable Hybrid Plasma (THP) derived from a three-year program of stake holder involvement. THP destroys volatile organic compounds by directing a moderate energy electron beam into a flow of air containing organic contaminants. This report is for technology developers and for those responsible for making decisions about the use of technology to remediate contamination by volatile organic compounds. Stakeholders' perspectives help those responsible for technology deployment make good decisions concerning the acceptability and applicability of THP to the remediation problems the face. In addition, this report presents data requirements for the technology's field demonstration defined by stakeholders associated with the Hanford site in Washington State, as well as detailed comments on THP from stakeholders from four other sites throughout the western United States

  2. Camphor soot: a tunable light emitter

    Science.gov (United States)

    Swapna, M. S.; Saritha Devi, H. V.; Sankararaman, S.

    2018-01-01

    The work in this paper is the first report on the green synthesis of the blue light emitter from waxy, flammable solid collected from Cinnamomum camphora by controlled combustion for photonic applications. Analysis with field emission scanning electron microscope and high-resolution transmission electron microscope provides the morphology, whereas the thermogravimetric analysis gives the thermal stability of the soot. The optical and structural characterizations are done by recording UV-Visible, Photoluminescent, and Raman Spectrum. The CIE plot and the power spectrum of the sample show a blue emission at an excitation of 350 nm at room temperature with a quantum yield of 46.15%. The dependence of luminescent behavior on temperature and excitation wavelength reveals that the material is a tunable blue emitter. This green synthesis of the blue light emitter is highly significant, when the world is in search of a simple, phosphor-free, non-toxic, cost-effective material with good quantum efficiency.

  3. Tunable Gas Sensing Gels by Cooperative Assembly.

    Science.gov (United States)

    Hussain, Abid; Semeano, Ana T S; Palma, Susana I C J; Pina, Ana S; Almeida, José; Medrado, Bárbara F; Pádua, Ana C C S; Carvalho, Ana L; Dionísio, Madalena; Li, Rosamaria W C; Gamboa, Hugo; Ulijn, Rein V; Gruber, Jonas; Roque, Ana C A

    2017-07-19

    The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.

  4. Strain-tunable quantum dot devices

    International Nuclear Information System (INIS)

    Rastelli, A.; Trotta, R.; Zallo, E.; Atkinson, P.; Magerl, E.; Ding, F.; Plumhof, J.D.; Kumar, S.; Doerr, K.; Schmidt, O.G.

    2011-01-01

    We introduce a new class of quantum dot-based devices, in which the semiconductor structures are integrated on top of piezoelectric actuators. This combination allows on one hand to study in detail the effects produced by variable strains (up to about 0.2%) on the excitonic emission of single quantum dots and on the other to manipulate their electronic- and optical properties to achieve specific requirements. In fact, by combining strain with electric fields we are able to obtain (i) independent control of emission energy and charge-state of a QD, (II) wavelength-tunable single-QD light-emitting diodes and (III) frequency-stabilized sources of single photons at predefined wavelengths. Possible future extensions and applications of this technology will be discussed.

  5. Electronic thermometry in tunable tunnel junction

    Energy Technology Data Exchange (ETDEWEB)

    Maksymovych, Petro

    2016-03-15

    A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may be measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.

  6. Negative stiffness honeycombs as tunable elastic metamaterials

    Science.gov (United States)

    Goldsberry, Benjamin M.; Haberman, Michael R.

    2018-03-01

    Acoustic and elastic metamaterials are media with a subwavelength structure that behave as effective materials displaying atypical effective dynamic properties. These material systems are of interest because the design of their sub-wavelength structure allows for direct control of macroscopic wave dispersion. One major design limitation of most metamaterial structures is that the dynamic response cannot be altered once the microstructure is manufactured. However, the ability to modify wave propagation in the metamaterial with an external stimulus is highly desirable for numerous applications and therefore remains a significant challenge in elastic metamaterials research. In this work, a honeycomb structure composed of a doubly periodic array of curved beams, known as a negative stiffness honeycomb (NSH), is analyzed as a tunable elastic metamaterial. The nonlinear static elastic response that results from large deformations of the NSH unit cell leads to a large variation in linear elastic wave dispersion associated with infinitesimal motion superposed on the externally imposed pre-strain. A finite element model is utilized to model the static deformation and subsequent linear wave motion at the pre-strained state. Analysis of the slowness surface and group velocity demonstrates that the NSH exhibits significant tunability and a high degree of anisotropy which can be used to guide wave energy depending on static pre-strain levels. In addition, it is shown that partial band gaps exist where only longitudinal waves propagate. The NSH therefore behaves as a meta-fluid, or pentamode metamaterial, which may be of use for applications of transformation elastodynamics such as cloaking and gradient index lens devices.

  7. A novel optogenetically tunable frequency modulating oscillator.

    Directory of Open Access Journals (Sweden)

    Tarun Mahajan

    Full Text Available Synthetic biology has enabled the creation of biological reconfigurable circuits, which perform multiple functions monopolizing a single biological machine; Such a system can switch between different behaviours in response to environmental cues. Previous work has demonstrated switchable dynamical behaviour employing reconfigurable logic gate genetic networks. Here we describe a computational framework for reconfigurable circuits in E.coli using combinations of logic gates, and also propose the biological implementation. The proposed system is an oscillator that can exhibit tunability of frequency and amplitude of oscillations. Further, the frequency of operation can be changed optogenetically. Insilico analysis revealed that two-component light systems, in response to light within a frequency range, can be used for modulating the frequency of the oscillator or stopping the oscillations altogether. Computational modelling reveals that mixing two colonies of E.coli oscillating at different frequencies generates spatial beat patterns. Further, we show that these oscillations more robustly respond to input perturbations compared to the base oscillator, to which the proposed oscillator is a modification. Compared to the base oscillator, the proposed system shows faster synchronization in a colony of cells for a larger region of the parameter space. Additionally, the proposed oscillator also exhibits lesser synchronization error in the transient period after input perturbations. This provides a strong basis for the construction of synthetic reconfigurable circuits in bacteria and other organisms, which can be scaled up to perform functions in the field of time dependent drug delivery with tunable dosages, and sets the stage for further development of circuits with synchronized population level behaviour.

  8. Tunable lasers for waste management photochemistry applications

    International Nuclear Information System (INIS)

    Finch, F.T.

    1978-09-01

    A review of lasers with potential photochemical applications in waste management indicates that dye lasers, as a class, can provide tunable laser output through the visible and near-uv regions of the spectrum of most interest to photochemistry. Many variables can affect the performance of a specific dye laser, and the interactions of these variables, at the current state of the art, are complex. The recent literature on dye-laser characteristics has been reviewed and summarized, with emphasis on those parameters that most likely will affect the scaling of dye lasers in photochemical applications. Current costs are reviewed and correlated with output power. A new class of efficient uv lasers that appear to be scalable in both energy output and pulse rate, based on rare-gas halide excimers and similar molecules, is certain to find major applications in photochemistry. Because the most important developments are too recent to be adequately described in the literature or are the likely outcome of current experiments, the basic physics underlying the class of excimer lasers is described. Specific cost data are unavailable, but these new gas lasers should reflect costs similar to those of existing gas lasers, in particular, the pulsed CO 2 lasers. To complete the survey of tunable-laser characteristics, the technical characteristics of the various classes of lasers in the ir are summarized. Important developments in ir laser technology are being accelerated by isotope-separation research, but, initially at least, this portion of the spectrum is least likely to receive emphasis in waste-management-oriented photochemistry

  9. Industrial integration of high coherence tunable single frequency semiconductor lasers based on VECSEL technology for scientific instrumentation in NIR and MIR

    Science.gov (United States)

    Lecocq, Vincent; Chomet, Baptiste; Ferrières, Laurence; Myara, Mikhaël.; Beaudoin, Grégoire; Sagnes, Isabelle; Cerutti, Laurent; Denet, Stéphane; Garnache, Arnaud

    2017-02-01

    Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8-1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency laser micro-chip, intracavity element free, based on a patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high temporal coherence together with a low divergence diffraction limited TEM00 beam. They exhibit a class-A dynamics with a Relative Intensity Noise as low as -140dB/Hz and at shot noise level reached above 200MHz RF frequency (up to 160GHz), a free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), a linear polarization (>50dB suppression ratio), and broadband continuous tunability greater than 400GHz (state of the art commercial technologies thanks to a combination of power-coherence-wavelength tunability performances and integration.

  10. Broad line regions in Seyfert-1 galaxies

    International Nuclear Information System (INIS)

    Groningen, E. van.

    1984-01-01

    To reproduce observed emission profiles of Seyfert galaxies, rotation in an accretion disk has been proposed. In this thesis, the profiles emitted by such an accretion disk are investigated. Detailed comparison with the observed profiles yields that a considerable fraction can be fitted with a power-law function, as predicted by the model. The author analyzes a series of high quality spectra of Seyfert galaxies, obtained with the 2.5m telescope at Las Campanas. He presents detailed analyses of two objects: Mkn335 and Akn120. In both cases, strong evidence is presented for the presence of two separate broad line zones. These zones are identified with an accretion disk and an outflowing wind. The disk contains gas with very high densities and emits predominantly the lower ionization lines. He reports on the discovery of very broad wings beneath the strong forbidden line 5007. (Auth.)

  11. Hybrid three-dimensional dual- and broadband optically tunable terahertz metamaterials.

    Science.gov (United States)

    Meng, Qinglong; Zhong, Zheqiang; Zhang, Bin

    2017-03-30

    The optically tunable properties of the hybrid three-dimensional (3D) metamaterials with dual- and broadband response frequencies are theoretically investigated in the terahertz spectrum. The planar double-split-ring resonators (DSRRs) and the standup double-split-ring resonators are fabricated on a sapphire substrate, forming a 3D array structures. The bi-anisotropy of the hybrid 3D metamaterials is considered because the stand-up DSRRs are not symmetrical with respect to the electric field vector. Due to the electric and magnetic response realized by the planar and the standup double-split-ring resonators respectively, the dual-band resonance response and the negative refractive index can be achieved. The potential of the phase modulation under photoexcitation is also demonstrated. Further analysis indicates that, photoexcitation of free carriers in the silicon within the capacitive region of the standup DSRRs results in a broad resonance response bandwidth (about 0.47 THz), and also functions as a broadband negative refractive index that roughly lies between 0.80 and 2.01 THz. This tunable metamaterials is proposed for the potential application of electromagnetic wave propagation in terahertz area.

  12. IV-VI mid-IR tunable lasers and detectors with external resonant cavities

    Science.gov (United States)

    Zogg, H.; Rahim, M.; Khiar, A.; Fill, M.; Felder, F.; Quack, N.; Blunier, S.; Dual, J.

    2009-08-01

    Wavelength tunable emitters and detectors in the mid-IR wavelength region allow applications including thermal imaging and spectroscopy. Such devices may be realized using a resonant cavity. By mechanically changing the cavity length with MEMS mirror techniques, the wavelengths may be tuned over a considerable range. Vertical external cavity surface emitting lasers (VECSEL) may be applied for gas spectroscopy. Resonant cavity enhanced detectors (RCED) are sensitive at the cavity resonance only. They may be applied for low resolution spectroscopy, and, when arrays of such detectors are realized, as multicolor IR-FPA or IR-AFPA (IR-adaptive focal plane arrays). We review mid-infrared RCEDs and VECSELs using narrow gap IV-VI (lead chalcogenide) materials like PbTe and PbSe as the active medium. IV-VIs are fault tolerant and allow easy wavelength tuning. The VECSELs operate up to above room temperature and emit in the 4 - 5 μm range with a PbSe active layer. RCEDs with PbTe absorbing layers above 200 K operating temperature have higher sensitivities than the theoretical limit for a similar broad-band detector coupled with a passive tunable band-filter.

  13. Fourier evaluation of broad Moessbauer spectra

    International Nuclear Information System (INIS)

    Vincze, I.

    1981-01-01

    It is shown by the Fourier analysis of broad Moessbauer spectra that the even part of the distribution of the dominant hyperfine interaction (hyperfine field or quadrupole splitting) can be obtained directly without using least-square fitting procedures. Also the odd part of this distribution correlated with other hyperfine parameters (e.g. isomer shift) can be directly determined. Examples for amorphous magnetic and paramagnetic iron-based alloys are presented. (author)

  14. High-Q Tunable Microwave Superconducting Strip-Line Filters

    National Research Council Canada - National Science Library

    Anderson, Dean; Rehrig, Paul; Lanagan, Mike; Furman, Eugene; Xi, Xiaoxing

    2005-01-01

    The objective of the Phase II SBIR project was to develop high Q, tunable microwave filters by using a cryogenic piezoelectric actuator to mechanically tune a high temperature superconducting (HTS) resonator...

  15. Compact Tunable High-Efficiency Entangled Photon Source, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — MagiQ proposes to develop a compact tunable high-efficiency low-power-consumption entangled photon source. The source, based on inter-Fabry-Perot-cavity Spontaneous...

  16. Eye and sensor protection from tunable laser beams

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.H.; Garrett, W.R.; DiCillo, J.J.; Phillips, R.C. (Oak Ridge National Lab., TN (United States)); Payne, M.G. (Georgia Southern Univ., Statesboro, GA (United States)); Templeton, D. (Army Tank-Automotive Command, Warren, MI (United States))

    1993-01-01

    We describe successes achieved in two different approaches to the problem of providing eye protection to personnel and sensor protection to devices in combat vehicles from perceived threats from tunable, visible laser beams.

  17. Eye and sensor protection from tunable laser beams

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.H.; Garrett, W.R.; DiCillo, J.J.; Phillips, R.C. [Oak Ridge National Lab., TN (United States); Payne, M.G. [Georgia Southern Univ., Statesboro, GA (United States); Templeton, D. [Army Tank-Automotive Command, Warren, MI (United States)

    1993-06-01

    We describe successes achieved in two different approaches to the problem of providing eye protection to personnel and sensor protection to devices in combat vehicles from perceived threats from tunable, visible laser beams.

  18. Novel Tunable Dye Laser for Lidar Detection, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A tunable dye laser for Lidar detection will be fabricated based on the innovative dye-doped Holographic Polymer Dispersed Liquid Crystals (HPDLC) technology. The...

  19. Scaling issues in ferroelectric barium strontium titanate tunable planar capacitors.

    Science.gov (United States)

    Lam, Peter G; Haridasan, Vrinda; Feng, Zhiping; Steer, Michael B; Kingon, Angus I; Maria, Jon-Paul

    2012-02-01

    We report on the geometric limits associated with tunability of interdigitated capacitors, specifically regarding the impact of a parasitic non-tunable component that necessarily accompanies a ferroelectric surface capacitor, and can dominate the voltage-dependent response as capacitor dimensions are reduced to achieve the small capacitance values required for impedance matching in the X band. We present a case study of simple gap capacitors prepared and characterized as a function of gap width (i.e., the distance between electrodes) and gap length (i.e., the edge-to-edge gap distance). Our series of measurements reveals that for gap widths in the micrometer range, as gap lengths are reduced to meet sub-picofarad capacitance values, the non-tunable parasitic elements limit the effective tunability. These experimental measurements are supported by a companion set of microwave models that clarify the existence of parallel parasitic elements.

  20. New Temperature-Insensitive Electronically-Tunable Grounded Capacitor Simulator

    OpenAIRE

    Muhammad Taher Abuelma'atti; Muhammad Haroon Khan

    1996-01-01

    A new circuit for simulating a grounded capacitor is presented. The circuit uses one operationalamplifier (OA), three operational-transconductance amplifiers (OTAs), and one capacitor. The realized capacitor is temperature-insensitive and electronically tunable. Experimental results are included.

  1. Stirling-Cycle Cooling For Tunable Diode Laser

    Science.gov (United States)

    Durso, Santo S.; May, Randy D.; Tuchscherer, Matthew A.; Webster, Christopher R.

    1991-01-01

    Miniature Stirling-cycle cooler effective in continously cooling PbSnTe tunable diode laser to stable operating temperature near 80 K. Simplifies laboratory diode-laser spectroscopy and instruments for use aboard aircraft and balloons.

  2. Spectral and Radiometric Calibration using Tunable Lasers Project

    Data.gov (United States)

    National Aeronautics and Space Administration —  SIRCUS-based calibration relies on a set of monitoring radiometers and tunable laser sources to provide an absolute radiometric calibration that can approach...

  3. Designed synthesis of tunable amorphous carbon nanotubes (a ...

    Indian Academy of Sciences (India)

    Administrator

    Page 1. Electronic Supplementary Material. Graphical abstract. Designed synthesis of tunable amorphous carbon nanotubes (a-CNTs) by a novel route and their oxidation resistance properties by Longlong. Xu et al (pp 1397–1402).

  4. Extended Tunability in a Two-Chip VECSEL (Postprint)

    National Research Council Canada - National Science Library

    Fan, Li; Fallahi, Mahmoud; Zakharian, Aramais R; Hader, Joerg; Moloney, Jerome V; Bedford, Robert; Murray, James T; Stolz, Wolfgang; Koch, Stephan W

    2007-01-01

    We demonstrate a widely tunable vertical-external cavity surface-emitting laser (VECSEL) with a W-shaped cavity, in which two VECSEL chips serve as fold mirrors and a birefringent filter is inserted at Brewster's angle...

  5. Exploring the spatial heterogeneity of terraced landscapes using LiDAR: the Slope Local Length of Auto-Correlation (SLLAC).

    Science.gov (United States)

    Sofia, Giulia; Marinello, Francesco; Tarolli, Paolo

    2014-05-01

    Terraces represent an outstanding example that displays centuries of a ubiquitous human-Earth interaction, in a very specific and productive way, and they are a significant part of numerous local economies. They, in fact, optimise the local resources for agricultural purposes, but also exploit marginal landscapes, expanding local populations. The ubiquity, variety, and importance of terraces have motivated studies designed to understand them better both as cultural and ecological features, but also as elements that can deeply influence runoff generation and propagation, contributing to local instabilities, and triggering or aggravating land degradation processes. Their vulnerability in the face of fast-growing urban settlements and the changes in agricultural practices is also well known, prompting protection measures strongly supported by local communities, but also by national and international projects. This work explores the spatial heterogeneity of terraced landscapes, identifying a proper indicator able to discriminate a terraced landscape respect to a more natural one. Recognizing and characterizing terraced areas can offer important multi-temporal insights into issues such as agricultural sustainability, indigenous knowledge systems, human-induced impact on soil degradation or erosive and landslide processes, geomorphological and pedologic processes that influence soil development, and climatic and biodiversity changes. More in detail, the present work introduces a new morphological indicator from LiDAR, effectively implementable for the automatic characterization of terraced landscapes. For the study, we tested the algorithm for environments that differ in term of natural morphology and terracing system. Starting from a LiDAR Digital Terrain Models (DTM), we considered the local auto-correlation (~local self-similarity) of the slope, calculating the correlation between a slope patch and its surrounding areas. We define the resulting map as the "Slope Local

  6. Optimal design of tunable phononic bandgap plates under equibiaxial stretch

    International Nuclear Information System (INIS)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, M S; Guest, James K

    2016-01-01

    Design and application of phononic crystal (PhCr) acoustic metamaterials has been a topic with tremendous growth of interest in the last decade due to their promising capabilities to manipulate acoustic and elastodynamic waves. Phononic controllability of waves through a particular PhCr is limited only to the spectrums located within its fixed bandgap frequency. Hence the ability to tune a PhCr is desired to add functionality over its variable bandgap frequency or for switchability. Deformation induced bandgap tunability of elastomeric PhCr solids and plates with prescribed topology have been studied by other researchers. Principally the internal stress state and distorted geometry of a deformed phononic crystal plate (PhP) changes its effective stiffness and leads to deformation induced tunability of resultant modal band structure. Thus the microstructural topology of a PhP can be altered so that specific tunability features are met through prescribed deformation. In the present study novel tunable PhPs of this kind with optimized bandgap efficiency-tunability of guided waves are computationally explored and evaluated. Low loss transmission of guided waves throughout thin walled structures makes them ideal for fabrication of low loss ultrasound devices and structural health monitoring purposes. Various tunability targets are defined to enhance or degrade complete bandgaps of plate waves through macroscopic tensile deformation. Elastomeric hyperelastic material is considered which enables recoverable micromechanical deformation under tuning finite stretch. Phononic tunability through stable deformation of phononic lattice is specifically required and so any topology showing buckling instability under assumed deformation is disregarded. Nondominated sorting genetic algorithm (GA) NSGA-II is adopted for evolutionary multiobjective topology optimization of hypothesized tunable PhP with square symmetric unit-cell and relevant topologies are analyzed through finite

  7. Tunable pulse-shaping with gated graphene nanoribbons

    DEFF Research Database (Denmark)

    Prokopeva, Ludmila; Emani, Naresh K.; Boltasseva, Alexandra

    2014-01-01

    We propose a pulse-shaper made of gated graphene nanoribbons. Simulations demonstrate tunable control over the shapes of transmitted and reflected pulses using the gating bias. Initial fabrication and characterization of graphene elements is also discussed.......We propose a pulse-shaper made of gated graphene nanoribbons. Simulations demonstrate tunable control over the shapes of transmitted and reflected pulses using the gating bias. Initial fabrication and characterization of graphene elements is also discussed....

  8. Tunability response in exponentially graded ferroelectrics: A TIM model approach

    Energy Technology Data Exchange (ETDEWEB)

    Vivas C, H., E-mail: hvivasc@unal.edu.co [Grupo de Propiedades Opticas de los Materiales, Departamento de Fisica, Bloque Y, Universidad Nacional de Colombia, Manizales A.A. 127 (Colombia); Jurado, J.F.; Vargas-Hernandez, C. [Grupo de Propiedades Opticas de los Materiales, Departamento de Fisica, Bloque Y, Universidad Nacional de Colombia, Manizales A.A. 127 (Colombia)

    2012-02-01

    Relative dielectric function response associate to a non-homogeneous layered ferroelectric system is calculated in the framework of the Mean Field Approximation (MFA) for the Transverse Ising Model (TIM). Analytical self-consistent expressions for the average polarization, dielectric susceptibility, and tunability percentage are outlined and solved for different configurations and sizes. It is found that exponentially graded ferroelectrics magnify the tunability response for stronger interlayer coupling and it reaches its saturation value for smaller intensities of the applied electric field.

  9. Adaptive IR Sensing Based on Advanced Nanostructures with Tunable Kinetics

    Science.gov (United States)

    2015-11-05

    AFRL-AFOSR-VA-TR-2015-0360 ADAPTIVE IR SENSING BASED ON ADVANCED NANOSTRUCTURES WITH TUNABLE KINETICS Vladimir Mitin RESEARCH FOUNDATION OF STATE...1 August 2010 - 31 July 2015 4. TITLE AND SUBTITLE Adaptive IR Sensing Based on Advanced Nanostructures with Tunable Kinetics 5a. CONTRACT NUMBER...engineering, and technological basis for further development of IR nanomaterials with nanoscale potential profile that can be effectively controlled by

  10. Optically controlled tunable dispersion compensators based on pumped fiber gratings.

    Science.gov (United States)

    Shu, Xuewen; Sugden, Kate; Bennion, Ian

    2011-08-01

    We demonstrate optically tunable dispersion compensators based on pumping fiber Bragg gratings made in Er/Yb codoped fiber. The tunable dispersion for a chirped grating and also a uniform-period grating was successfully demonstrated in the experiment. The dispersion of the chirped grating was tuned from 900 to 1990 ps/nm and also from -600 to -950 ps/nm in the experiment. © 2011 Optical Society of America

  11. Freely tunable broadband polarization rotator for terahertz waves.

    Science.gov (United States)

    Fan, Ren-Hao; Zhou, Yu; Ren, Xiao-Ping; Peng, Ru-Wen; Jiang, Shang-Chi; Xu, Di-Hu; Xiong, Xiang; Huang, Xian-Rong; Wang, Mu

    2015-02-18

    A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Magnetically tunable superconductor filters using yttrium iron garnet films

    International Nuclear Information System (INIS)

    Tsutsumi, Makoto; Fukusako, Takeshi; Shimasaki, Hitoshi

    1995-01-01

    Magnetically tunable superconducting single-resonator filters using YIG films have been demonstrated experimentally. Tunability of 400 MHz at a center frequency of 6 GHz was achieved for a half wavelength microstrip comprising a YIG-YBCO-MgO composite structure. The reason why the quality factor of the filter is relatively low is possibly due to an increase of the magnetic linewidth ΔH at liquid nitrogen temperature. The theory on dispersion relation of the filter is also presented

  13. Tunable white light of a Ce3+,Tb3+,Mn2+triply doped Na2Ca3Si2O8phosphor for high colour-rendering white LED applications: tunable luminescence and energy transfer.

    Science.gov (United States)

    Lü, Wei; Xu, Huawei; Huo, Jiansheng; Shao, Baiqi; Feng, Yang; Zhao, Shuang; You, Hongpeng

    2017-07-18

    A tunable white light emitting Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na 2 Ca 3 Si 2 O 8 :Ce 3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb 3+ /Mn 2+ ions into Na 2 Ca 3 Si 2 O 8 , energy transfer from Ce 3+ to Tb 3+ and Ce 3+ to Mn 2+ ions is observed from the spectral overlap between Ce 3+ emission and Tb 3+ /Mn 2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce 3+ to Tb 3+ is demonstrated to be a dipole-quadrupole mechanism by the Inokuti-Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce 3+ , Tb 3+ and Mn 2+ , respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce 3+ , Tb 3+ and Mn 2+ . Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor. All the results suggest that Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.

  14. Oxygen Passivation Mediated Tunability of Trion and Excitons in MoS2

    KAUST Repository

    Gogoi, Pranjal Kumar

    2017-08-17

    Using wide spectral range in situ spectroscopic ellipsometry with systematic ultrahigh vacuum annealing and in situ exposure to oxygen, we report the complex dielectric function of MoS2 isolating the environmental effects and revealing the crucial role of unpassivated and passivated sulphur vacancies. The spectral weights of the A (1.92 eV) and B (2.02 eV) exciton peaks in the dielectric function reduce significantly upon annealing, accompanied by spectral weight transfer in a broad energy range. Interestingly, the original spectral weights are recovered upon controlled oxygen exposure. This tunability of the excitonic effects is likely due to passivation and reemergence of the gap states in the band structure during oxygen adsorption and desorption, respectively, as indicated by ab initio density functional theory calculation results. This Letter unravels and emphasizes the important role of adsorbed oxygen in the optical spectra and many-body interactions of MoS2.

  15. Tunable, omnidirectional structural color on reflection based on metal-SiOx-metal structure

    Science.gov (United States)

    Yang, Chenying; Mao, Kening; Shen, Weidong; Fang, Bo; Fang, Xu; Zhang, Xing; Zhang, Yueguang; Liu, Xu

    2016-12-01

    An omnidirectional structural color based on the metal-SiOx-metal stack structure is proposed, which can present the same perceived color for a broad range of incidence angles. The tunable structural color can be obtained with adjustable intermediate dielectric layer by simply adjusting the deposition condition, especially the oxygen flow rate during the deposition processes. The resonance condition can be satisfied across the whole visible light region with this special dielectric. The strong absorption caused by the resonance within the metal-SiOx-metal structure accounts for the efficient spectral filtering feature, and the constant phase shift within the dielectric layer leads to angle insensitivity of this color filter. This simple color tuning method for omnidirectional structural colors can have a great potential in various applications such as displaying, imaging, colorful decoration, anti-counterfeiting and so forth.

  16. Tunable defect mode realized by graphene-based photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Jiahui; Chen, Wan, E-mail: dhtyyobdc@126.com; Lv, Bo

    2016-04-29

    In this literature, we propose an active terahertz 1D photonic crystal, which consists of silicon layers and air layers. A graphene sheet is embedded at the interface between dielectric and air. Tunable photonic band gap is realized by changing the Fermi level of graphene. Transmission Matrix Method is utilized to explain the influence of the graphene layer. We also demonstrate that a dielectric slab attached with a thin sheet made of single-negative metamaterial acts like a pure dielectric slab with a thinner thickness. A tunable blue shift of the band gap can be realized by simply applying different chemical potentials on the graphene sheet. This feature can be utilized for the design of tunable high-gain antenna array and force generator in terahertz band. - Highlights: • A novel PhC embedded with grapheme sheets is presented, tunable defect is realized. • The mechanism of the tunable defect is explained using the change of equivalent thickness. • The electromagnetic force of a slab is calculated, which indicates the structure can serve as a tunable force generator.

  17. Novel technology in the treatment of acne scars: The matrix-tunable radiofrequency technology

    Directory of Open Access Journals (Sweden)

    M Ramesh

    2010-01-01

    Full Text Available Background : Despite the many advances, scarring, particularly acne or pimple scarring, does not have a satisfactory treatment. A new armamentarium in this field is this recently devised matrix-tunable radiofrequency technology, which utilizes radiofrequency emission in the treatment of acne scars. Aims : To evaluate the efficiency of the new matrix-tunable radiofrequency technology in patients with acne scars of varying sizes. Settings and Design : A prospective study of 30 randomly selected patients with acne scars was carried out. Materials and Methods : Thirty healthy patients with different types of acne scars - ice pick, box and rolling type - were randomly selected. The scars were either shallow or deep, varied in size from 2 to 20 mm and ranged in number from 10 to 50. These patients were first treated with broad-spectrum antibiotics and local exfoliating agents (topical tretinoin 0.025% and then subjected to matrix-tunable radiofrequency technology. Each scar was treated at intervals of 1 month. A maximum of four such sittings were carried out. Patients were followed-up every 15 days. Results were noted at the end of 2 months and 6 months. Improvement was assessed by using the visual analog scale (VAS at 2 months and 6 months, and results were noted in terms of percentage improvement of the whole face by calculating an average of percentage improvement on the basis of interviews of the patient and his/her accompanying relatives. The visual analog scaling was performed by means of high-resolution digital photographs taken at the baseline and at each subsequent visit. Results : The VAS improvement in scars ranged from 10 to 50% at the end of 2 months to 20 to 70% at the end of 6 months. Of the 30 patients of acne scars, the cosmetic result was excellent (>60% improvement in four, good (35-60% improvement in 18 and moderate to poor (<35% improvement in eight. A few patients reported burning sensation and a mild sunburn-like sensation for

  18. Fabrication of porous silicon based tunable distributed Bragg reflectors by anodic etching of irradiated silicon

    International Nuclear Information System (INIS)

    Vendamani, V.S.; Dang, Z.Y.; Ramana, P.; Pathak, A.P.; Ravi Kanth Kumar, V.V.; Breese, M.B.H.; Nageswara Rao, S.V.S.

    2015-01-01

    Highlights: • Fabrication of tunable distributed Bragg reflectors (DBRs) by gamma/ion irradiation of Si and subsequent formation of porous silicon multilayers has been described. • The central wavelength and the width of the stop band are found to decrease with increase in irradiation fluence. • The Si samples irradiated with highest fluence of 2 × 10 13 ions/cm 2 (100 MeV Ag ions) and 60 kGy (gamma) showed a central reflection at λ = 476 nm and 544 nm respectively, in contrast to un-irradiated sample, where λ = 635 nm. • The observed changes in the central wavelengths are attributed to the density of defects generated by gamma and ion irradiation in c-Si. • This study is expected to provide useful information for fabricating tunable wave reflectors for optical communication and other device applications. - Abstract: We report a study on the fabrication of tunable distributed Bragg reflectors (DBRs) by gamma/ion irradiation of Si and subsequent formation of porous silicon multilayers. Porous Si multilayers with 50 bilayers were designed to achieve high intensity of reflection. The reflection spectra appear to have a broad continuous band between 400 and 800 nm with a distinct central wavelength corresponding to different wave reflectors. The central wavelength and the width of the stop band are found to decrease with increase in irradiation fluence. The Si samples irradiated with highest fluence of 2 × 10 13 ions/cm 2 (100 MeV Ag ions) and 60 kGy (gamma) showed a central reflection at λ = 476 nm and 544 nm respectively, in contrast to un-irradiated sample, where λ = 635 nm. The observed changes are attributed to the density of defects generated by gamma and ion irradiation in c-Si. These results suggest that the gamma irradiation is a convenient and alternative method to tune the central wavelength of reflection without creating high density of defects by high energy ion implantation. This study is expected to provide useful information for

  19. Enhanced photoluminescence property and broad color emission of ZnGa2O4 phosphor due to the synergistic role of Eu3+ and carbon dots

    Science.gov (United States)

    Huo, Qiuyue; Tu, Weixia; Guo, Lin

    2017-10-01

    ZnGa2O4 phosphors co-composited with nanoscale carbon dots (CDs) and Eu3+ were presented for the tunable color emission. Novel single phase CDs or/and Eu3+ composited ZnGa2O4 phosphors were synthesized by microwave hydrothermal method and their optical properties were investigated. The ZnGa2O4 phosphors composited with CDs exhibited an intense broad blue light emission at 421 nm and a more enhanced photoluminescence intensity than those without CDs. The Eu3+ composited ZnGa2O4 phosphors gave an ideal red color emission. The CDs/Eu3+ co-composited ZnGa2O4 phosphors exhibited a wide emission band peak at 450 nm and narrow emission peak at 618 nm. Furthermore, the tunable color emissions of CDs/Eu3+ co-composited ZnGa2O4 phosphors from blue to the white light region, and then to red were obtained with the increasing Eu3+ concentration, which can be a promising single phased phosphor candidate in light emitting diodes. Broadly tunable emission single phased phosphor is tuned firstly through the synergistic role of the non-metal element and the rare earth metal ions.

  20. Surveillance of broad-spectrum antibiotic prescription in Singaporean hospitals: a 5-year longitudinal study.

    Directory of Open Access Journals (Sweden)

    Yi-Xin Liew

    Full Text Available BACKGROUND: Inappropriate prescription of antibiotics may contribute towards higher levels antimicrobial resistance. A key intervention for improving appropriate antibiotic prescription is surveillance of prescription. This paper presents the results of a longitudinal surveillance of broad-spectrum antibiotic prescription in 5 public-sector hospitals in Singapore from 2006 to 2010. METHODOLOGY/PRINCIPAL FINDINGS: Quarterly antibiotic prescription data were obtained and converted to defined daily doses (DDDs per 1,000 inpatient-days. The presence of significant trends in antibiotic prescription over time for both individual and combined hospitals was tested by regression analysis and corrected for autocorrelation between time-points. Excluding fluoroquinolones, there was a significant increase in prescription of all monitored antibiotics from an average of 233.12 defined daily doses (DDD/1,000 inpatient-days in 2006 to 254.38 DDD/1,000 inpatient-days in 2010 (Coefficient = 1.13, 95%CI: 0.16-2.09, p = 0.025. Increasing utilization of carbapenems, piperacillin/tazobactam, and Gram-positive agents were seen in the majority of the hospitals, while cephalosporins were less prescribed over time. The combined expenditure for 5 hospitals increased from USD9.9 million in 2006 to USD16.7 million in 2010. CONCLUSIONS/SIGNIFICANCE: The rate of prescription of broad-spectrum antibiotics in Singaporean hospitals is much higher compared to those of European hospitals. This may be due to high rates of antimicrobial resistance. The increase in expenditure on monitored antibiotics over the past 5 years outstripped the actual increase in DDD/1,000 inpatient-days of antibiotics prescribed. Longitudinal surveillance of antibiotic prescription on a hospital and countrywide level is important for detecting trends for formulating interventions or policies. Further research is needed to understand the causes for the various prescription trends and to act on these where

  1. Blending vocal music with a given sound field due to the characteristics of the running autocorrelation function of singing voices

    Science.gov (United States)

    Kato, Kosuke; Fujii, Kenji; Kawai, Keiji; Ando, Yoichi; Yano, Takashi

    2004-05-01

    This is a study to meet music and the opera house acoustics. It is said that singers adjust their interpretation style according to the acoustical condition of the sound field in a room. However, this mechanism of blending of musical performance with the sound field is unknown. In order to obtain a method of performance blending of opera house acoustics, we attempted to develop evaluation criteria for a singing voice in terms of the minimum value of the effective duration of the running autocorrelation function (r-ACF), (te)min, of sound source signals. This temporal factor has shown to have close correlation with the subjective response of both listeners and performers to sound fields [Y. Ando, Architectural Acoustics (AIP Press/Springer-Verlag, New York, 1998)]. As example for the control of (te)min due to performing style, effects of singing style, kind of vowel, relative pitch, vibrato extent, and intonation on the values of (te)min are demonstrated. In addition, the fine structure of the r-ACF is discussed with regard to the identification of vowels of singing voice. a)Now at 1-10-27 Yamanokami, Kumamoto, Japan.

  2. A method of noise reduction in heterodyne interferometric vibration metrology by combining auto-correlation analysis and spectral filtering

    Science.gov (United States)

    Hao, Hongliang; Xiao, Wen; Chen, Zonghui; Ma, Lan; Pan, Feng

    2018-01-01

    Heterodyne interferometric vibration metrology is a useful technique for dynamic displacement and velocity measurement as it can provide a synchronous full-field output signal. With the advent of cost effective, high-speed real-time signal processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. However, due to the coherent nature of the laser sources, the sequence of heterodyne interferogram are corrupted by a mixture of coherent speckle and incoherent additive noise, which can severely degrade the accuracy of the demodulated signal and the optical display. In this paper, a new heterodyne interferometric demodulation method by combining auto-correlation analysis and spectral filtering is described leading to an expression for the dynamic displacement and velocity of the object under test that is significantly more accurate in both the amplitude and frequency of the vibrating waveform. We present a mathematical model of the signals obtained from interferograms that contain both vibration information of the measured objects and the noise. A simulation of the signal demodulation process is presented and used to investigate the noise from the system and external factors. The experimental results show excellent agreement with measurements from a commercial Laser Doppler Velocimetry (LDV).

  3. A GLOBAL AUTOCORRELATION STUDY AFTER THE FIRST AUGER DATA: IMPACT ON THE NUMBER DENSITY OF UHECR SOURCES

    International Nuclear Information System (INIS)

    Cuoco, A.; Hannestad, S.; Haugboelle, T.; Kachelriess, M.; Serpico, P. D.

    2009-01-01

    We perform an autocorrelation study of the Auger data with the aim to constrain the number density n s of ultrahigh energy cosmic ray (UHECR) sources, estimating at the same time the effect on n s of the systematic energy scale uncertainty and of the distribution of UHECR. The use of global analysis has the advantage that no biases are introduced, either in n s or in the related error bar, by the a priori choice of a single angular scale. The case of continuous, uniformly distributed sources is nominally disfavored at 99% CL and the fit improves if the sources follow the large-scale structure of matter in the universe. The best-fit values obtained for the number density of proton sources are within a factor ∼2 around n s ≅ 1 x 10 -4 Mpc -3 and depend mainly on the Auger energy calibration scale, with lower densities being preferred if the current scale is correct. The data show no significant small-scale clustering on scales smaller than a few degrees. This might be interpreted as a signature of magnetic smearing of comparable size, comparable with the indication of a ∼3 deg. magnetic deflection coming from cross-correlation results. The effects of some approximations done on the above results are also discussed.

  4. Spatial autocorrelation of microbial communities atop a debris-covered glacier is evidence of a supraglacial chronosequence.

    Science.gov (United States)

    Darcy, John L; King, Andrew J; Gendron, Eli M S; Schmidt, Steven K

    2017-08-01

    Although microbial communities from many glacial environments have been analyzed, microbes living in the debris atop debris-covered glaciers represent an understudied frontier in the cryosphere. The few previous molecular studies of microbes in supraglacial debris have either had limited phylogenetic resolution, limited spatial resolution (e.g. only one sample site on the glacier) or both. Here, we present the microbiome of a debris-covered glacier across all three domains of life, using a spatially-explicit sampling scheme to characterize the Middle Fork Toklat Glacier's microbiome from its terminus to sites high on the glacier. Our results show that microbial communities differ across the supraglacial transect, but surprisingly these communities are strongly spatially autocorrelated, suggesting the presence of a supraglacial chronosequence. This pattern is dominated by phototrophic microbes (both bacteria and eukaryotes) which are less abundant near the terminus and more abundant higher on the glacier. We use these data to refute the hypothesis that the inhabitants of the glacier are randomly deposited atmospheric microbes, and to provide evidence that succession from a predominantly photosynthetic to a more heterotrophic community is occurring on the glacier. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. Development of an automated detection system for microcalcifications on mammograms by using the higher-order autocorrelation features

    Science.gov (United States)

    Ohe, Yoshitaka; Shinohara, Norimitsu; Hara, Takeshi; Fujita, Hiroshi; Endo, Tokiko; Iwase, Takuji

    2004-05-01

    The purpose of this work is to develop a new pattern recognition method using the higher-order autocorrelation features (HOAFs), and to apply this to our microcalcification detection system on mammographic images. Microcalcification is a typical sign of breast cancer and tends to show up as very subtle shadows. We developed a triple-ring filter for detecting microcalcifications, and the prototype detection system is nearly complete. However, our prototype system does not allow for the detection of three types of microcalcifications, two of which are amorphous and linear microcalcifications and the third is obscured microcalcifications which is often confused with the background or circumference that have almost the same density. We targeted the amorphous type of microcalcification, which has a low contrast and easily goes undetected. The various features of microcalcifications and false-positive (FP) shadows were extracted and trained using the multi-regression analysis, and unknown images were recognized as a result of this training. As a result, amorphous microcalcifications were successfully detected with no increase in the number of FPs compared with our existing detection method.

  6. Environmental Efficiency of Chinese Open-Field Grape Production: An Evaluation Using Data Envelopment Analysis and Spatial Autocorrelation

    Directory of Open Access Journals (Sweden)

    Dong Tian

    2016-11-01

    Full Text Available Grape production is associated with some negative environmental externalities. However, they are not considered in the traditional data envelopment analysis (DEA efficiency assessment models and the research literature. Hence, the assessment results cannot correctly reflect the technical efficiency level of open-field grape production. We measured the environmental efficiency of China’s open-field grape production under the constraint of carbon emissions using the slacks-based measure (SBM model, including the undesirable outputs. In addition, spatial relations of environmental efficiency in different open-field grape production areas in China were evaluated by adopting spatial econometric methods. The results indicate that the average environmental efficiency score of grape production in China is at a low level of 0.651. Overall, the average environmental efficiencies in southern, southwest, and northeast regions are lower than the average levels, which implies the imbalance in economic outputs, resource consumption, and environmental efficiency in open-field grape cultivation. Moreover, the spatial autocorrelation results show that the environmental efficiency of grape production has obvious continuity in neighboring regions and spatial correlation.

  7. Auto-correlation in the motor/imaginary human EEG signals: A vision about the FDFA fluctuations.

    Science.gov (United States)

    Zebende, Gilney Figueira; Oliveira Filho, Florêncio Mendes; Leyva Cruz, Juan Alberto

    2017-01-01

    In this paper we analyzed, by the FDFA root mean square fluctuation (rms) function, the motor/imaginary human activity produced by a 64-channel electroencephalography (EEG). We utilized the Physionet on-line databank, a publicly available database of human EEG signals, as a standardized reference database for this study. Herein, we report the use of detrended fluctuation analysis (DFA) method for EEG analysis. We show that the complex time series of the EEG exhibits characteristic fluctuations depending on the analyzed channel in the scalp-recorded EEG. In order to demonstrate the effectiveness of the proposed technique, we analyzed four distinct channels represented here by F332, F637 (frontal region of the head) and P349, P654 (parietal region of the head). We verified that the amplitude of the FDFA rms function is greater for the frontal channels than for the parietal. To tabulate this information in a better way, we define and calculate the difference between FDFA (in log scale) for the channels, thus defining a new path for analysis of EEG signals. Finally, related to the studied EEG signals, we obtain the auto-correlation exponent, αDFA by DFA method, that reveals self-affinity at specific time scale. Our results shows that this strategy can be applied to study the human brain activity in EEG processing.

  8. Auto-correlation in the motor/imaginary human EEG signals: A vision about the FDFA fluctuations.

    Directory of Open Access Journals (Sweden)

    Gilney Figueira Zebende

    Full Text Available In this paper we analyzed, by the FDFA root mean square fluctuation (rms function, the motor/imaginary human activity produced by a 64-channel electroencephalography (EEG. We utilized the Physionet on-line databank, a publicly available database of human EEG signals, as a standardized reference database for this study. Herein, we report the use of detrended fluctuation analysis (DFA method for EEG analysis. We show that the complex time series of the EEG exhibits characteristic fluctuations depending on the analyzed channel in the scalp-recorded EEG. In order to demonstrate the effectiveness of the proposed technique, we analyzed four distinct channels represented here by F332, F637 (frontal region of the head and P349, P654 (parietal region of the head. We verified that the amplitude of the FDFA rms function is greater for the frontal channels than for the parietal. To tabulate this information in a better way, we define and calculate the difference between FDFA (in log scale for the channels, thus defining a new path for analysis of EEG signals. Finally, related to the studied EEG signals, we obtain the auto-correlation exponent, αDFA by DFA method, that reveals self-affinity at specific time scale. Our results shows that this strategy can be applied to study the human brain activity in EEG processing.

  9. A perfect storm: the combined effects on population fluctuations of autocorrelated environmental noise, age structure, and density dependence.

    Science.gov (United States)

    Wilmers, Christopher C; Post, Eric; Hastings, Alan

    2007-05-01

    While it is widely appreciated that climate can affect the population dynamics of various species, a mechanistic understanding of how climate interacts with life-history traits to influence population fluctuations requires development. Here we build a general density-dependent age-structured model that accounts for differential responses in life-history traits to increasing population density. We show that as the temporal frequency of favorable environmental conditions increases, population fluctuations also increase provided that unfavorable environmental conditions still occur. As good years accumulate and the number of individuals in a population increases, successive life-history traits become vulnerable to density dependence once a return to unfavorable conditions prevails. The stronger this ratcheting of density dependence in life-history traits by autocorrelated climatic conditions, the larger the population fluctuations become. Highly fecund species, and those in which density dependence occurs in juvenile and adult vital rates at similar densities, are most sensitive to increases in the frequency of favorable conditions. Understanding the influence of global warming on temporal correlation in regional environmental conditions will be important in identifying those species liable to exhibit increased population fluctuations that could lead to their extinction.

  10. Depolarized light scattering from prolate anisotropic particles: The influence of the particle shape on the field autocorrelation function.

    Science.gov (United States)

    Passow, Christopher; ten Hagen, Borge; Löwen, Hartmut; Wagner, Joachim

    2015-07-28

    We provide a theoretical analysis for the intermediate scattering function typically measured in depolarized dynamic light scattering experiments. We calculate the field autocorrelation function g1(VH)(Q,t) in dependence on the wave vector Q and the time t explicitly in a vertical-horizontal scattering geometry for differently shaped solids of revolution. The shape of prolate cylinders, spherocylinders, spindles, and double cones with variable aspect ratio is expanded in rotational invariants flm(r). By Fourier transform of these expansion coefficients, a formal multipole expansion of the scattering function is obtained, which is used to calculate the weighting coefficients appearing in the depolarized scattering function. In addition to translational and rotational diffusion, especially the translational-rotational coupling of shape-anisotropic objects is considered. From the short-time behavior of the intermediate scattering function, the first cumulants Γ(Q) are calculated. In a depolarized scattering experiment, they deviate from the simple proportionality to Q(2). The coefficients flm(Q) strongly depend on the geometry and aspect ratio of the particles. The time dependence, in addition, is governed by the translational and rotational diffusion tensors, which are calculated by means of bead models for differently shaped particles in dependence on their aspect ratio. Therefore, our analysis shows how details of the particle shape--beyond their aspect ratio--can be determined by a precise scattering experiment. This is of high relevance in understanding smart materials which involve suspensions of anisotropic colloidal particles.

  11. Scattering images from autocorrelation functions of P-wave seismic velocity images: the case of Tenerife Island (Canary Islands, Spain)

    Science.gov (United States)

    García-Yeguas, A.; Sánchez-Alzola, A.; De Siena, L.; Prudencio, J.; Díaz-Moreno, A.; Ibáñez, J. M.

    2018-03-01

    We present a P-wave scattering image of the volcanic structures under Tenerife Island using the autocorrelation functions of P-wave vertical velocity fluctuations. We have applied a cluster analysis to total quality factor attenuation ( {Q}_t^{-1} ) and scattering quality factor attenuation ( {Q}_{PSc}^{-1} ) images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2D plane, corresponding to a depth of 2000 m, and check the robustness of the scattering imaging. The results show that scattering patterns are similar to total attenuation patterns in the south of the island. There are two main areas where patterns differ: at Cañadas-Teide-Pico Viejo Complex, high total attenuation and average-to-low scattering values are observed. We interpret the difference as induced by intrinsic attenuation. In the Santiago Ridge Zone (SRZ) region, high scattering values correspond to average total attenuation. In our interpretation, the anomaly is induced by an extended scatterer, geometrically related to the surficial traces of Garachico and El Chinyero historical eruptions and the area of highest seismic activity during the 2004-2008 seismic crises.

  12. Analysis of Onstage Acoustics Preference of Musicians of Traditional Performance of Javanese Gamelan Based on Normalized Autocorrelation Function

    Directory of Open Access Journals (Sweden)

    Suyatno

    2016-11-01

    Full Text Available On-stage sound field analysis of a traditional performance of the Javanese gamelan at Pendopo ISI Surakarta, Indonesia was conducted by analyzing the effective decay time of a normalized autocorrelation function called tau-e, , during a performance of the Gambyong Pare Anom dance. The parameter tau-e is used to describe the richness of the frequency content, tempo, and types of gamelan instruments being played at a certain time and position on stage. The tau-e parameter is important for musicians in order to maintain communication between each other such that they can keep the performance in harmony. In order to determine the acoustic parameters heard by gamelan musicians on stage, sound measurements were conducted at 4 points on stage during a performance. Each position represents a specific group of gamelan instruments, which have different characteristics of loudness and frequency, different functions and different ways the instruments are played. The analysis showed that each of the four positions had a different value of , which fluctuated throughout the performance. Overall, the dominant at position 1 was 20 ms; at position 2 it was 50 ms; at position 3 it was 20 ms; and at position 4 it was 40 ms. The distribution of on the stage shows that positions 1 and 3 had more frequency richness compared to positions 2 and 4.

  13. Broad-Spectrum Drugs Against Viral Agents

    Directory of Open Access Journals (Sweden)

    Jonathan P. Wong

    2008-09-01

    Full Text Available Development of antivirals has focused primarily on vaccines and on treatments for specific viral agents. Although effective, these approaches may be limited in situations where the etiologic agent is unknown or when the target virus has undergone mutation, recombination or reassortment. Augmentation of the innate immune response may be an effective alternative for disease amelioration. Nonspecific, broad-spectrum immune responses can be induced by double-stranded (dsRNAs such as poly (ICLC, or oligonucleotides (ODNs containing unmethylated deocycytidyl-deoxyguanosinyl (CpG motifs. These may offer protection against various bacterial and viral pathogens regardless of their genetic makeup, zoonotic origin or drug resistance.

  14. The broad utility of Trizac diamond tile

    Science.gov (United States)

    Gagliardi, John I.; Romero, Vincent D.; Sventek, Bruce; Zu, Lijun

    2017-10-01

    Sample finishing data from a broad range of materials — glasses, sapphire, silicon carbide, silicon, zirconium oxide, lithium tantalate, and flooring materials — are shown effectively processed with Trizact™ Diamond Tile (TDT). This data should provide the reader with an understanding of what to expect when using TDT on hard to grind or brittle materials. Keys to maintaining effective TDT pad wear rates, and therefore cost effect and stable processes, are described as managing 1) the proper lubricant flow rate for glasses and silicon-type materials and 2) the conditioning particle concentration for harder-to-grind materials

  15. Broad resonances and beta-decay

    DEFF Research Database (Denmark)

    Riisager, K.; Fynbo, H. O. U.; Hyldegaard, S.

    2015-01-01

    Beta-decay into broad resonances gives a distorted lineshape in the observed energy spectrum. Part of the distortion arises from the phase space factor, but we show that the beta-decay matrix element may also contribute. Based on a schematic model for p-wave continuum neutron states it is argued...... that beta-decay directly to the continuum should be considered as a possible contributing mechanism in many decays close to the driplines. The signatures in R-matrix fits for such decays directly to continuum states are discussed and illustrated through an analysis of the beta-decay of $^8$B into $2...

  16. Continuously tunable nucleic acid hybridization probes.

    Science.gov (United States)

    Wu, Lucia R; Wang, Juexiao Sherry; Fang, John Z; Evans, Emily R; Pinto, Alessandro; Pekker, Irena; Boykin, Richard; Ngouenet, Celine; Webster, Philippa J; Beechem, Joseph; Zhang, David Yu

    2015-12-01

    In silico-designed nucleic acid probes and primers often do not achieve favorable specificity and sensitivity tradeoffs on the first try, and iterative empirical sequence-based optimization is needed, particularly in multiplexed assays. We present a novel, on-the-fly method of tuning probe affinity and selectivity by adjusting the stoichiometry of auxiliary species, which allows for independent and decoupled adjustment of the hybridization yield for different probes in multiplexed assays. Using this method, we achieved near-continuous tuning of probe effective free energy. To demonstrate our approach, we enforced uniform capture efficiency of 31 DNA molecules (GC content, 0-100%), maximized the signal difference for 11 pairs of single-nucleotide variants and performed tunable hybrid capture of mRNA from total RNA. Using the Nanostring nCounter platform, we applied stoichiometric tuning to simultaneously adjust yields for a 24-plex assay, and we show multiplexed quantitation of RNA sequences and variants from formalin-fixed, paraffin-embedded samples.

  17. Patchy polymer colloids with tunable anisotropy dimensions.

    Science.gov (United States)

    Kraft, Daniela J; Hilhorst, Jan; Heinen, Maria A P; Hoogenraad, Mathijs J; Luigjes, Bob; Kegel, Willem K

    2011-06-09

    We present the synthesis of polymer colloids with continuously tunable anisotropy dimensions: patchiness, roughness, and branching. Our method makes use of controlled fusion of multiple protrusions on highly cross-linked polymer particles produced by seeded emulsion polymerization. Carefully changing the synthesis conditions, we can tune the number of protrusions, or branching, of the obtained particles from spheres with one to three patches to raspberry-like particles with multiple protrusions. In addition to that, roughness is generated on the seed particles by adsorption of secondary nucleated particles during synthesis. The size of the roughness relative to the smooth patches can be continuously tuned by the initiator, surfactant, and styrene concentrations. Seed colloids chemically different from the protrusions induce patches of different chemical nature. The underlying generality of the synthesis procedure allows for application to a variety of seed particle sizes and materials. We demonstrate the use of differently sized polyNIPAM (poly-N-isopropylacrylamide), as well as polystyrene and magnetite filled polyNIPAM seed particles, the latter giving rise to magnetically anisotropic colloids. The high yield together with the uniform, anisotropic shape make them interesting candidates for use as smart building blocks in self-assembling systems.

  18. Controlling superconductivity by tunable quantum critical points.

    Science.gov (United States)

    Seo, S; Park, E; Bauer, E D; Ronning, F; Kim, J N; Shim, J-H; Thompson, J D; Park, Tuson

    2015-03-04

    The heavy fermion compound CeRhIn5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn5. Slight tin-substitution for indium in CeRhIn5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn5, which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn5.

  19. Plasmonic spectral tunability of conductive ternary nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Kassavetis, S.; Patsalas, P., E-mail: ppats@physics.auth.gr [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Bellas, D. V.; Lidorikis, E. [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Abadias, G. [Institut Pprime, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, 86962 Chasseneuil-Futuroscope (France)

    2016-06-27

    Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as Ti{sub x}Ta{sub 1−x}N, Ti{sub x}Zr{sub 1−x}N, Ti{sub x}Al{sub 1−x}N, and Zr{sub x}Ta{sub 1−x}N share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

  20. Hybrid nanostructured materials with tunable magnetic characteristics

    Science.gov (United States)

    Torres-Martínez, Nubia E.; Garza-Navarro, M. A.; García-Gutiérrez, Domingo; González-González, Virgilio A.; Torres-Castro, Alejandro; Ortiz-Méndez, U.

    2014-12-01

    We report on the development of hybrid nanostructured materials (HNM) based on spinel-metal-oxide nanoparticles (SMON) stabilized in carboxymethyl-cellulose (CMC)/cetyltrimethyl-ammonium-bromide (CTAB) templates, with tunable magnetic characteristics. These HNM were synthesized using a one-pot chemical approach to obtain CMC/CTAB templates with controllable size and morphology, where the SMON could be densely arranged. The synthesized HNM were characterized by transmission electron microscopy and its related techniques, such as bright field (BF) and Z-contrast (HAADF-STEM) imaging, and selected area electron diffraction, as well as static magnetic measuring. Experimental evidence suggests that the morphology and size of the CMC/CTAB templates are highly dependent on the weight ratio of CTAB:SMON, as well as the hydration days of the CMC that is used for the synthesis of the HNM. Controlling these parameters allows modifying the density of the SMON arrangement in the CMC/CTAB templates. Moreover, magnetic features such as remanence, coercivity, and blocking/de-blocking processes of the particles' magnetic moments are highly dependent on the interactions among the SMON assembled in the templates. Hence, the magnetic characteristics of HNM can be modulated or tuned by controlling the manner the SMON are arranged within the CMC/CTAB templates.

  1. Hybrid nanostructured materials with tunable magnetic characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Martínez, Nubia E.; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; García-Gutiérrez, Domingo; González-González, Virgilio A.; Torres-Castro, Alejandro; Ortiz-Méndez, U. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2014-12-15

    We report on the development of hybrid nanostructured materials (HNM) based on spinel-metal-oxide nanoparticles (SMON) stabilized in carboxymethyl-cellulose (CMC)/cetyltrimethyl-ammonium-bromide (CTAB) templates, with tunable magnetic characteristics. These HNM were synthesized using a one-pot chemical approach to obtain CMC/CTAB templates with controllable size and morphology, where the SMON could be densely arranged. The synthesized HNM were characterized by transmission electron microscopy and its related techniques, such as bright field (BF) and Z-contrast (HAADF-STEM) imaging, and selected area electron diffraction, as well as static magnetic measuring. Experimental evidence suggests that the morphology and size of the CMC/CTAB templates are highly dependent on the weight ratio of CTAB:SMON, as well as the hydration days of the CMC that is used for the synthesis of the HNM. Controlling these parameters allows modifying the density of the SMON arrangement in the CMC/CTAB templates. Moreover, magnetic features such as remanence, coercivity, and blocking/de-blocking processes of the particles’ magnetic moments are highly dependent on the interactions among the SMON assembled in the templates. Hence, the magnetic characteristics of HNM can be modulated or tuned by controlling the manner the SMON are arranged within the CMC/CTAB templates.

  2. Electronically Tunable Resistorless Mixed Mode Biquad Filters

    Directory of Open Access Journals (Sweden)

    A. Yesil

    2013-12-01

    Full Text Available This paper presents a new realization of elec¬tronically tunable mixed mode (including transadmittance- and voltage-modes biquad filter with single input, three outputs or three inputs, single output using voltage differ-encing transconductance amplifier (VDTA, a recently introduced active element. It can simultaneously realize standard filtering signals: low-pass, band-pass and high-pass or by selecting input terminals, it can realize all five different filtering signals: low-pass, band-pass, high-pass, band-stop and all-pass. The proposed filter circuit offers the following attractive feature: no requirement of invert-ing type input signal which is require no addition circuit, critical component matching conditions are not required in the design, the circuit parameters ω0 and Q can be set orthogonally or independently through adjusting the bias currents of the VDTAs, the proposed circuit employs two active and minimum numbers of passive components. Fur-thermore, this filter was investigated from the point of view of limited frequency range, stability conditions, effects of parasitic elements and effects of non-ideal and sensitivity. Thus, taking these effects and conditions into considera¬tion, working conditions and boundaries of this filter are determined. We also performed Monte Carlo, THD and noise analyses. Simulation results are given to confirm theoretical analyses.

  3. Temporal downscaling: a comparison between artificial neural network and autocorrelation techniques over the Amazon Basin in present and future climate change scenarios

    Science.gov (United States)

    Mendes, David; Marengo, José A.

    2010-05-01

    Several studies have been devoted to dynamic and statistical downscaling for both climate variability and climate change. This paper introduces an application of temporal neural networks for downscaling global climate model output and autocorrelation functions. This method is proposed for downscaling daily precipitation time series for a region in the Amazon Basin. The downscaling models were developed and validated using IPCC AR4 model output and observed daily precipitation. In this paper, five AOGCMs for the twentieth century (20C3M; 1970-1999) and three SRES scenarios (A2, A1B, and B1) were used. The performance in downscaling of the temporal neural network was compared to that of an autocorrelation statistical downscaling model with emphasis on its ability to reproduce the observed climate variability and tendency for the period 1970-1999. The model test results indicate that the neural network model significantly outperforms the statistical models for the downscaling of daily precipitation variability.

  4. Perceptual interaction between carrier periodicity and amplitude modulation in broadband stimuli: A comparison of the autocorrelation and modulation-filterbank model

    DEFF Research Database (Denmark)

    Stein, A.; Ewert, Stephan; Wiegrebe, L.

    2005-01-01

    , autocorrelation is applied. Considering the large overlap in pitch and modulation perception, this is not parsimonious. Two experiments are presented to investigate the interaction between carrier periodicity, which produces strong pitch sensations, and envelope periodicity using broadband stimuli. Results show......Recent temporal models of pitch and amplitude modulation perception converge on a relatively realistic implementation of cochlear processing followed by a temporal analysis of periodicity. However, for modulation perception, a modulation filterbank is applied whereas for pitch perception...

  5. Spectrophotometry of six broad absorption line QSOs

    Science.gov (United States)

    Junkkarinen, Vesa T.; Burbidge, E. Margaret; Smith, Harding E.

    1987-01-01

    Spectrophotometric observations of six broad absorption-line QSOs (BALQSOs) are presented. The continua and emission lines are compared with those in the spectra of QSOs without BALs. A statistically significant difference is found in the emission-line intensity ratio for (N V 1240-A)/(C IV 1549-A). The median value of (N V)/(C IV) for the BALQSOs is two to three times the median for QSOs without BALs. The absorption features of the BALQSOs are described, and the column densities and limits on the ionization structure of the BAL region are discussed. If the dominant ionization mechanism is photoionization, then it is likely that either the ionizing spectrum is steep or the abundances are considerably different from solar. Collisional ionization may be a significant factor, but it cannot totally dominate the ionization rate.

  6. Study on broad beam heavy ion CT

    International Nuclear Information System (INIS)

    Ohno, Yumiko; Kohno, Toshiyuki; Sasaki, Hitomi; Nanbu, S.; Kanai, Tatsuaki

    2003-01-01

    To achieve the heavy ion radiotherapy more precisely, it is important to know the distribution of the electron density in a human body, which is highly related to the range of charged particles. From a heavy ion CT image, we can directly obtain the 2-D distribution of the electron density in a sample. For this purpose, we have developed a broad beam heavy ion CT system. The electron density was obtained using some kinds of solutions targets. Also the dependence of the spatial resolution on the target size and the kinds of beams was estimated in this work using cylinders targets of 40, 60 and 80 mm in diameter, each of them has a hole of 10 mm in diameter at the center of it. (author)

  7. Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene

    KAUST Repository

    Mansour, Ahmed E.

    2016-11-25

    , the conductivity increases compared modestly to intercalation as the electron transfer is limited to the uppermost graphene layers. Finally, a novel and universal multi-modal doping strategy is developed, thanks to the unique platform offered by FLG, where surface and intercalation doping are combined to mutually achieve high conductivity with an extended tunability of the work function. This work presents doped-FLG as a prospective and versatile candidate among emerging TCEs, given the need for efficient and stable doping routes capable of controllably tuning its properties to meet the criteria of a broad range of applications.

  8. Ceftaroline: a new broad-spectrum cephalosporin.

    Science.gov (United States)

    Lim, Lauren; Sutton, Elizabeth; Brown, Jack

    2011-03-15

    The pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of ceftaroline are reviewed. Ceftaroline, a new broad- spectrum antibiotic, is approved for the treatment of complicated skin and skin structure infections (cSSSIs) and community- acquired pneumonia (CAP). This β-lactam antibiotic has extended activity against gram-positive organisms and has activity against common gram-negative organisms. The drug's spectrum of activity includes both methicillin-resistant Staphylococcus aureus and multidrug-resistant Streptococcus pneumoniae. However, its activity against extended-spectrum β-lactamase-producing bacteria is limited. These bacteria, particularly those that express AmpC β-lactamase, greatly reduce the activity of ceftaroline. The prodrug of ceftaroline (ceftaroline fosamil) is rapidly converted to its active form (ceftaroline) in plasma. This dose-linear drug has been found to be pharmacodynamically best correlated with the percentage of time that free drug concentrations remain above the minimum inhibitory concentration. Ceftaroline's safety profile is similar to that of the other cephalosporins, with minimal adverse drug reactions, most of which are considered mild. Currently available pharmacokinetic, animal, and clinical studies have found that ceftaroline has reasonable efficacy and tolerability but have also revealed that dosing regimen modifications may be needed in patients with moderate-to-severe renal impairment. The recommended dosage of ceftaroline for the treatment of cSSSIs and CAP is 600 mg infused intravenously over 60 minutes every 12 hours. The recommended duration of therapy is 5-14 and 5-7 days for cSSSIs and CAP, respectively. Additional Phase III studies are currently underway. Ceftaroline is a new broad-spectrum cephalosporin indicated for the treatment of cSSSIs and CAP caused by susceptible gram-positive and gram-negative organisms.

  9. Can spatial autocorrelation method be applied to arbitrary array shape; Kukan jiko sokanho no nin`i array eno tekiyo kanosei

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Iwamoto, K.; Saito, T.; Tachibana, M. [Iwate University, Iwate (Japan). Faculty of Engineering

    1997-05-27

    Methods to learn underground structures by utilizing the dispersion phenomenon of surface waves contained in microtremors include the frequency-wave number analysis method (the F-K method) and the spatial autocorrelation method (the SAC method). Despite the fact that the SAC method is capable of exploring structures at greater depths, the method is not utilized because of its stringent restriction in arrangement of seismometers during observation that they must be arranged evenly on the same circumference. In order to eliminate this restriction in the SAC method, a research group in the Hokuriku University has proposed an expanded spatial autocorrelation (ESAC) method. Using the concept of the ESAC method as its base, a method was realized to improve phase velocity estimation by making a simulation on an array shifted to the radius direction. As a result of the discussion, it was found that the proposed improvement method can be applied to places where waves come from a number of directions, such as urban areas. If the improvement method can be applied, the spatial autocorrelation function needs not be even in the circumferential direction. In other words, the SAC method can be applied to arbitrary arrays. 1 ref., 7 figs.

  10. Wave packet autocorrelation functions for quantum hard-disk and hard-sphere billiards in the high-energy, diffraction regime.

    Science.gov (United States)

    Goussev, Arseni; Dorfman, J R

    2006-07-01

    We consider the time evolution of a wave packet representing a quantum particle moving in a geometrically open billiard that consists of a number of fixed hard-disk or hard-sphere scatterers. Using the technique of multiple collision expansions we provide a first-principle analytical calculation of the time-dependent autocorrelation function for the wave packet in the high-energy diffraction regime, in which the particle's de Broglie wavelength, while being small compared to the size of the scatterers, is large enough to prevent the formation of geometric shadow over distances of the order of the particle's free flight path. The hard-disk or hard-sphere scattering system must be sufficiently dilute in order for this high-energy diffraction regime to be achievable. Apart from the overall exponential decay, the autocorrelation function exhibits a generally complicated sequence of relatively strong peaks corresponding to partial revivals of the wave packet. Both the exponential decay (or escape) rate and the revival peak structure are predominantly determined by the underlying classical dynamics. A relation between the escape rate, and the Lyapunov exponents and Kolmogorov-Sinai entropy of the counterpart classical system, previously known for hard-disk billiards, is strengthened by generalization to three spatial dimensions. The results of the quantum mechanical calculation of the time-dependent autocorrelation function agree with predictions of the semiclassical periodic orbit theory.

  11. Tunable bandpass filter based on photonic crystal fiber filled with multiple liquid crystals

    DEFF Research Database (Denmark)

    Scolari, Lara; Tartarini, G.; Borelli, E.

    2007-01-01

    A tunable bandpass filter based on a photonic crystal fiber filled with two different liquid crystals is demonstrated. 130 nm bandwidth tunability is achieved by tuning the temperature from 30degC to 90degC.......A tunable bandpass filter based on a photonic crystal fiber filled with two different liquid crystals is demonstrated. 130 nm bandwidth tunability is achieved by tuning the temperature from 30degC to 90degC....

  12. Microwave photonic phase shifter based on tunable silicon-on-insulator microring resonator

    DEFF Research Database (Denmark)

    Pu, Minhao; Liu, Liu; Xue, Weiqi

    2010-01-01

    We demonstrate a microwave photonic phase shifter based on an electrically tunable silicon-on-insulator microring resonator. A continuously tunable phase shift of up to 315° at a microwave frequency of 15GHz is obtained.......We demonstrate a microwave photonic phase shifter based on an electrically tunable silicon-on-insulator microring resonator. A continuously tunable phase shift of up to 315° at a microwave frequency of 15GHz is obtained....

  13. Ultra-thin and broadband tunable metamaterial graphene absorber.

    Science.gov (United States)

    Xiong, Han; Wu, Ying-Bo; Dong, Ji; Tang, Ming-Chun; Jiang, Yan-Nan; Zeng, Xiao-Ping

    2018-01-22

    A broadband tunable metamaterial graphene absorber is investigated in this paper. The unit cell of the proposed metamaterial graphene absorber is composed of four patch resonators. By tuning the chemical potential of graphene and the geometric size of each patch, the simulated total reflectivity is less than -10 dB from 22.02 to 36.61 THz and with the total thickness of 0.76 um (only 0.09λ at the lowest frequency). The analysis of the surface current, magnetic field and power flow distributions has been performed to better understand the absorption mechanism. Moreover, this proposed absorber achieves its bandwidth tunable characteristics through a voltage biasing of the graphene's Fremi level. This proposed metamaterial graphene absorber (MGA) could be used as smart absorbers, photovoltaic devices and tunable sensors.

  14. Tunable defect mode realized by graphene-based photonic crystal

    Science.gov (United States)

    Fu, Jiahui; Chen, Wan; Lv, Bo

    2016-04-01

    In this literature, we propose an active terahertz 1D photonic crystal, which consists of silicon layers and air layers. A graphene sheet is embedded at the interface between dielectric and air. Tunable photonic band gap is realized by changing the Fermi level of graphene. Transmission Matrix Method is utilized to explain the influence of the graphene layer. We also demonstrate that a dielectric slab attached with a thin sheet made of single-negative metamaterial acts like a pure dielectric slab with a thinner thickness. A tunable blue shift of the band gap can be realized by simply applying different chemical potentials on the graphene sheet. This feature can be utilized for the design of tunable high-gain antenna array and force generator in terahertz band.

  15. Reconfigurable and tunable flat graphene photonic crystal circuits.

    Science.gov (United States)

    Chen, Zan Hui; Tan, Qi Long; Lao, Jieer; Liang, Yao; Huang, Xu Guang

    2015-07-07

    Photonic crystal waveguides and circuits are one of the basic modules for integrated photonic devices. They mainly rely on photonic bandgaps to achieve light confinement and manipulation. Herein, we propose a novel general principle or method to achieve reconfigurable and tunable flat graphene photonic crystals (FG-PCs) by selectively electrostatic gating a layer of graphene with periodic gold electrodes. The tunable flat photonic bandgap structure of the FG-PCs as a function of the Fermi level is investigated. Reconfigurable FG-PC defect waveguides and cavities created by external patterned-gate-voltage control are also proposed and discussed. The features of reconfigurable/tunable FG-PCs will add more flexibility and capabilities for the single chip integration of graphene-based integrated photonic devices.

  16. Narrow bandpass tunable terahertz filter based on photonic crystal cavity.

    Science.gov (United States)

    He, Jinglong; Liu, Pingan; He, Yalan; Hong, Zhi

    2012-02-20

    We have fabricated a very narrow bandpass tunable terahertz (THz) filter based on a one-dimensional photonic crystal cavity. Since the filter consists of silicon wafers and air spacers, it has a very high quality factor of about 1500. The full width at half maximum (FWHM) of the passband is only about 200 MHz, and the peak transmission is higher than -4 dB. Besides, the central frequency can be tuned rapidly over the entire bandgap with the length of cavity adjusted by a motorized linear stage. Further analytical calculations indicate that a high-Q tunable filter with both high peak transmission and wide tunable range is possible if thinner silicon layers are used. © 2012 Optical Society of America

  17. Critical electric field for maximum tunability in nonlinear dielectrics

    Science.gov (United States)

    Akdogan, E. K.; Safari, A.

    2006-09-01

    The authors develop a self-consistent thermodynamic theory to compute the critical electric field at which maximum tunability is attained in a nonlinear dielectric. They then demonstrate that the stored electrostatic free energy functional has to be expanded at least up to the sixth order in electric field so as to define the critical field, and show that it depends solely on the fourth and sixth order permittivities. They discuss the deficiency of the engineering tunability metric in describing nonlinear dielectric phenomena, introduce a critical field renormalized tunability parameter, and substantiate the proposed formalism by computing the critical electric field for prototypical 0.9Pb(Mg1/3,Nb2/3)-0.1PbTiO3 and Ba(Ti0.85,Sn0.15)O3 paraelectrics.

  18. CALiPER Report 23: Photometric Testing of White Tunable LED Luminaires

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-01-01

    This report documents an initial investigation of photometric testing procedures for white-tunable LED luminaires and summarizes the key features of those products. Goals of the study include understanding the amount of testing required to characterize a white-tunable product, and documenting the performance of available color-tunable luminaires that are intended for architectural lighting.

  19. Tunable mode-locked semiconductor laser with Bragg mirror external cavity

    DEFF Research Database (Denmark)

    Yvind, Kresten; Jørgensen, T.; Birkedal, Dan

    2002-01-01

    We present a simplified design for a wavelength tunable external cavity mode-locked laser by employing a wedged GaAs/AlGaAs Bragg mirror. The device emits 4-6 ps pulses at 10 GHz and is tunable over 15 nm. Although, in the present configuration, tunability is limited to 15 nm, however, we have...

  20. Broad-Band Activatable White-Opsin.

    Directory of Open Access Journals (Sweden)

    Subrata Batabyal

    Full Text Available Currently, the use of optogenetic sensitization of retinal cells combined with activation/inhibition has the potential to be an alternative to retinal implants that would require electrodes inside every single neuron for high visual resolution. However, clinical translation of optogenetic activation for restoration of vision suffers from the drawback that the narrow spectral sensitivity of an opsin requires active stimulation by a blue laser or a light emitting diode with much higher intensities than ambient light. In order to allow an ambient light-based stimulation paradigm, we report the development of a 'white-opsin' that has broad spectral excitability in the visible spectrum. The cells sensitized with white-opsin showed excitability at an order of magnitude higher with white light compared to using only narrow-band light components. Further, cells sensitized with white-opsin produced a photocurrent that was five times higher than Channelrhodopsin-2 under similar photo-excitation conditions. The use of fast white-opsin may allow opsin-sensitized neurons in a degenerated retina to exhibit a higher sensitivity to ambient white light. This property, therefore, significantly lowers the activation threshold in contrast to conventional approaches that use intense narrow-band opsins and light to activate cellular stimulation.

  1. Computer Processing Of Tunable-Diode-Laser Spectra

    Science.gov (United States)

    May, Randy D.

    1991-01-01

    Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

  2. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials

    International Nuclear Information System (INIS)

    Lani, Shane W.; Sabra, Karim G.; Wasequr Rashid, M.; Hasler, Jennifer; Levent Degertekin, F.

    2014-01-01

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range

  3. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Lani, Shane W., E-mail: shane.w.lani@gmail.com, E-mail: karim.sabra@me.gatech.edu, E-mail: levent.degertekin@me.gatech.edu; Sabra, Karim G. [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801Ferst Drive, Georgia 30332-0405 (United States); Wasequr Rashid, M.; Hasler, Jennifer [School of Electrical and Computer Engineering, Georgia Institute of Technology, Van Leer Electrical Engineering Building, 777 Atlantic Drive NW, Atlanta, Georgia 30332-0250 (United States); Levent Degertekin, F. [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801Ferst Drive, Georgia 30332-0405 (United States); School of Electrical and Computer Engineering, Georgia Institute of Technology, Van Leer Electrical Engineering Building, 777 Atlantic Drive NW, Atlanta, Georgia 30332-0250 (United States)

    2014-02-03

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.

  4. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials

    Science.gov (United States)

    Lani, Shane W.; Wasequr Rashid, M.; Hasler, Jennifer; Sabra, Karim G.; Levent Degertekin, F.

    2014-02-01

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.

  5. Electrically tunable electromagnetic switches based on zero-index metamaterials

    Science.gov (United States)

    Cao, Yanyang; Meng, Qingquan; Xu, Yadong

    2018-02-01

    In this work, we design a heterojunction in a two dimensional parallel-plate metallic waveguide by using zero-index metamaterials and anisotropic dielectrics which are electrically tunable. We show analytically and numerically that by only controlling the direct current voltage applied to the anisotropic dielectrics, the phenomena of perfect transmission and near perfect reflection can be tuned electrically. Such designed junctions can service as electrically tunable switches in waveguide systems, with good performances and high sensitivities. Our work provides another way to electrically control the propagation of electromagnetic waves in waveguide systems.

  6. Tunable graphene antennas for selective enhancement of THz-emission

    KAUST Repository

    Filter, Robert

    2013-01-01

    In this paper, we will introduce THz graphene antennas that strongly enhance the emission rate of quantum systems at specific frequencies. The tunability of these antennas can be used to selectively enhance individual spectral features. We will show as an example that any weak transition in the spectrum of coronene can become the dominant contribution. This selective and tunable enhancement establishes a new class of graphene-based THz devices, which will find applications in sensors, novel light sources, spectroscopy, and quantum communication devices. © 2013 Optical Society of America.

  7. High Q-factor tunable superconducting HF circuit

    CERN Document Server

    Vopilkin, E A; Pavlov, S A; Ponomarev, L I; Ganitsev, A Y; Zhukov, A S; Vladimirov, V V; Letyago, A G; Parshikov, V V

    2001-01-01

    Feasibility of constructing a high Q-factor (Q approx 10 sup 5) mechanically tunable in a wide range of frequencies (12-63 MHz) vibration circuit of HF range was considered. The tunable circuit integrates two single circuits made using YBaCuO films. The circuit frequency is tuned by changing distance X (capacity) between substrates. Potentiality of using substrates of lanthanum aluminate, neodymium gallate and strontium titanate for manufacture of single circuits was considered. Q-factor of the circuit amounted to 68000 at resonance frequency of 6.88 MHz

  8. Tunable reflecting terahertz filter based on chirped metamaterial structure

    Science.gov (United States)

    Yang, Jing; Gong, Cheng; Sun, Lu; Chen, Ping; Lin, Lie; Liu, Weiwei

    2016-01-01

    Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping. PMID:27941833

  9. Widely tunable femtosecond solitonic radiation in photonic crystal fiber cladding

    DEFF Research Database (Denmark)

    Peng, J. H.; Sokolov, A. V.; Benabid, F.

    2010-01-01

    We report on a means to generate tunable ultrashort optical pulses. We demonstrate that dispersive waves generated by solitons within the small-core features of a photonic crystal fiber cladding can be used to obtain femtosecond pulses tunable over an octave-wide spectral range. The generation...... process is highly efficient and occurs at the relatively low laser powers available from a simple Ti:sapphire laser oscillator. The described phenomenon is general and will play an important role in other systems where solitons are known to exist....

  10. Tunable Hybrid Qubit in a Triple Quantum Dot

    Science.gov (United States)

    Wang, Bao-Chuan; Cao, Gang; Li, Hai-Ou; Xiao, Ming; Guo, Guang-Can; Hu, Xuedong; Jiang, Hong-Wen; Guo, Guo-Ping

    2017-12-01

    We experimentally demonstrate quantum-coherent dynamics of a triple-dot-based multielectron hybrid qubit. Pulsed experiments show that this system can be conveniently initialized, controlled, measured electrically, and has a good ratio Q ˜29 between the coherence time and gate time. Furthermore, the current multielectron hybrid qubit has an operation frequency that is tunable in a wide range, from 2 to about 15 GHz. We also provide a qualitative understanding of the experimental observations by mapping them onto a three-electron system. The demonstration of the high tunability in a triple dot system could be potentially useful for future quantum control.

  11. Superconducting tunable flux qubit with direct readout scheme

    International Nuclear Information System (INIS)

    Chiarello, Fabio; Castellano, Maria Gabriella; Leoni, Roberto; Torrioli, Guido; Carelli, Pasquale; Cosmelli, Carlo; Gangemi, Lorenzo; Poletto, Stefano; Simeone, Daniela

    2005-01-01

    We describe a simple and efficient scheme for the readout of a tunable flux qubit, and present preliminary experimental tests for the preparation, manipulation and final readout of the qubit state, performed in the incoherent regime at liquid helium temperature. The tunable flux qubit is realized by a double SQUID with an extra Josephson junction inserted in the large superconducting loop, and the readout is performed by applying a current ramp to the junction and recording the value for which there is a voltage response, depending on the qubit state. This preliminary work indicates the feasibility and efficiency of the scheme

  12. Core-shell colloidal particles with dynamically tunable scattering properties.

    Science.gov (United States)

    Meng, Guangnan; Manoharan, Vinothan N; Perro, Adeline

    2017-09-27

    We design polystyrene-poly(N'-isopropylacrylamide-co-acrylic acid) core-shell particles that exhibit dynamically tunable scattering. We show that under normal solvent conditions the shell is nearly index-matched to pure water, and the particle scattering is dominated by Rayleigh scattering from the core. As the temperature or salt concentration increases, both the scattering cross-section and the forward scattering increase, characteristic of Mie scatterers. The magnitude of the change in the scattering cross-section and scattering anisotropy can be controlled through the solvent conditions and the size of the core. Such particles may find use as optical switches or optical filters with tunable opacity.

  13. Tunable cavity resonator including a plurality of MEMS beams

    Science.gov (United States)

    Peroulis, Dimitrios; Fruehling, Adam; Small, Joshua Azariah; Liu, Xiaoguang; Irshad, Wasim; Arif, Muhammad Shoaib

    2015-10-20

    A tunable cavity resonator includes a substrate, a cap structure, and a tuning assembly. The cap structure extends from the substrate, and at least one of the substrate and the cap structure defines a resonator cavity. The tuning assembly is positioned at least partially within the resonator cavity. The tuning assembly includes a plurality of fixed-fixed MEMS beams configured for controllable movement relative to the substrate between an activated position and a deactivated position in order to tune a resonant frequency of the tunable cavity resonator.

  14. Tunable waveguide bends with graphene-based anisotropic metamaterials

    KAUST Repository

    Chen, Zhao-xian

    2016-01-15

    We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.

  15. Tunable microbubble generator using electrolysis and ultrasound

    Science.gov (United States)

    Achaoui, Younes; Metwally, Khaled; Fouan, Damien; Hammadi, Zoubida; Morin, Roger; Debieu, Eric; Payan, Cédric; Mensah, Serge

    2017-01-01

    This letter reports on a method for producing on demand calibrated bubbles in a non-chemically controlled solution using localized micro-electrolysis and ultrasound. Implementing a feedback loop in the process leads to a point source of stable mono-dispersed microbubbles. This approach overcomes the inertial constraints encountered in microfluidics with the possibility to produce from a single to an array of calibrated bubbles. Moreover, this method avoids the use of additional surfactant that may modify the composition of the host fluid. It impacts across a broad range of scientific domains from bioengineering, sensing to environment.

  16. Tunable microbubble generator using electrolysis and ultrasound

    Directory of Open Access Journals (Sweden)

    Younes Achaoui

    2017-01-01

    Full Text Available This letter reports on a method for producing on demand calibrated bubbles in a non-chemically controlled solution using localized micro-electrolysis and ultrasound. Implementing a feedback loop in the process leads to a point source of stable mono-dispersed microbubbles. This approach overcomes the inertial constraints encountered in microfluidics with the possibility to produce from a single to an array of calibrated bubbles. Moreover, this method avoids the use of additional surfactant that may modify the composition of the host fluid. It impacts across a broad range of scientific domains from bioengineering, sensing to environment.

  17. Arctic Change Information for a Broad Audience

    Science.gov (United States)

    Soreide, N. N.; Overland, J. E.; Calder, J.

    2002-12-01

    Demonstrable environmental changes have occurred in the Arctic over the past three decades. NOAA's Arctic Theme Page is a rich resource web site focused on high latitude studies and the Arctic, with links to widely distributed data and information focused on the Arctic. Included is a collection of essays on relevant topics by experts in Arctic research. The website has proven useful to a wide audience, including scientists, students, teachers, decision makers and the general public, as indicated through recognition by USA Today, Science magazine, etc. (http://www.arctic.noaa.gov) Working jointly with NSF and the University of Washington's Polar Science Center as part of the Study of Environmental Arctic Change (SEARCH) program, NOAA has developed a website for access to pan-Arctic time series spanning diverse data types including climate indices, atmospheric, oceanic, sea ice, terrestrial, biological and fisheries. Modest analysis functions and more detailed analysis results are provided. (http://www.unaami.noaa.gov/). This paper will describe development of an Artic Change Detection status website to provide a direct and comprehensive view of previous and ongoing change in the Arctic for a broad climate community. For example, composite metrics are developed using principal component analysis based on 86 multivariate pan-Arctic time series for seven data types. Two of these metrics can be interpreted as a regime change/trend component and an interdecadal component. Changes can also be visually observed through tracking of 28 separate biophysical indicators. Results will be presented in the form of a web site with relevant, easily understood, value-added knowledge backed by peer review from Arctic scientists and scientific journals.

  18. Broadly sampled multigene trees of eukaryotes

    Directory of Open Access Journals (Sweden)

    Logsdon John M

    2008-01-01

    Full Text Available Abstract Background Our understanding of the eukaryotic tree of life and the tremendous diversity of microbial eukaryotes is in flux as additional genes and diverse taxa are sampled for molecular analyses. Despite instability in many analyses, there is an increasing trend to classify eukaryotic diversity into six major supergroups: the 'Amoebozoa', 'Chromalveolata', 'Excavata', 'Opisthokonta', 'Plantae', and 'Rhizaria'. Previous molecular analyses have often suffered from either a broad taxon sampling using only single-gene data or have used multigene data with a limited sample of taxa. This study has two major aims: (1 to place taxa represented by 72 sequences, 61 of which have not been characterized previously, onto a well-sampled multigene genealogy, and (2 to evaluate the support for the six putative supergroups using two taxon-rich data sets and a variety of phylogenetic approaches. Results The inferred trees reveal strong support for many clades that also have defining ultrastructural or molecular characters. In contrast, we find limited to no support for most of the putative supergroups as only the 'Opisthokonta' receive strong support in our analyses. The supergroup 'Amoebozoa' has only moderate support, whereas the 'Chromalveolata', 'Excavata', 'Plantae', and 'Rhizaria' receive very limited or no support. Conclusion Our analytical approach substantiates the power of increased taxon sampling in placing diverse eukaryotic lineages within well-supported clades. At the same time, this study indicates that the six supergroup hypothesis of higher-level eukaryotic classification is likely premature. The use of a taxon-rich data set with 105 lineages, which still includes only a small fraction of the diversity of microbial eukaryotes, fails to resolve deeper phylogenetic relationships and reveals no support for four of the six proposed supergroups. Our analyses provide a point of departure for future taxon- and gene-rich analyses of the

  19. Broad ion beam serial section tomography.

    Science.gov (United States)

    Winiarski, B; Gholinia, A; Mingard, K; Gee, M; Thompson, G E; Withers, P J

    2017-01-01

    Here we examine the potential of serial Broad Ion Beam (BIB) Ar + ion polishing as an advanced serial section tomography (SST) technique for destructive 3D material characterisation for collecting data from volumes with lateral dimensions significantly greater than 100µm and potentially over millimetre sized areas. Further, the associated low level of damage introduced makes BIB milling very well suited to 3D EBSD acquisition with very high indexing rates. Block face serial sectioning data registration schemes usually assume that the data comprises a series of parallel, planar slices. We quantify the variations in slice thickness and parallelity which can arise when using BIB systems comparing Gatan PECS and Ilion BIB systems for large volume serial sectioning and 3D-EBSD data acquisition. As a test case we obtain 3D morphologies and grain orientations for both phases of a WC-11%wt. Co hardmetal. In our case we have carried out the data acquisition through the manual transfer of the sample between SEM and BIB which is a very slow process (1-2 slice per day), however forthcoming automated procedures will markedly speed up the process. We show that irrespective of the sectioning method raw large area 2D-EBSD maps are affected by distortions and artefacts which affect 3D-EBSD such that quantitative analyses and visualisation can give misleading and erroneous results. Addressing and correcting these issues will offer real benefits when large area (millimetre sized) automated serial section BIBS is developed. Copyright © 2016. Published by Elsevier B.V.

  20. Broadly protective influenza vaccines: Redirecting the antibody response through adjuvation

    NARCIS (Netherlands)

    Cox, F.

    2016-01-01

    Influenza virus infections are responsible for significant morbidity worldwide and current vaccines have limited coverage, therefore it remains a high priority to develop broadly protective vaccines. With the discovery of broadly neutralizing antibodies (bnAbs) against influenza these vaccines

  1. MICROLENSING OF QUASAR BROAD EMISSION LINES: CONSTRAINTS ON BROAD LINE REGION SIZE

    Energy Technology Data Exchange (ETDEWEB)

    Guerras, E.; Mediavilla, E. [Instituto de Astrofisica de Canarias, Via Lactea S/N, La Laguna E-38200, Tenerife (Spain); Jimenez-Vicente, J. [Departamento de Fisica Teorica y del Cosmos, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada (Spain); Kochanek, C. S. [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, The Ohio State University, 4055 McPherson Lab, 140 West 18th Avenue, Columbus, OH 43221 (United States); Munoz, J. A. [Departamento de Astronomia y Astrofisica, Universidad de Valencia, E-46100 Burjassot, Valencia (Spain); Falco, E. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Motta, V. [Departamento de Fisica y Astronomia, Universidad de Valparaiso, Avda. Gran Bretana 1111, Valparaiso (Chile)

    2013-02-20

    We measure the differential microlensing of the broad emission lines between 18 quasar image pairs in 16 gravitational lenses. We find that the broad emission lines are in general weakly microlensed. The results show, at a modest level of confidence (1.8{sigma}), that high ionization lines such as C IV are more strongly microlensed than low ionization lines such as H{beta}, indicating that the high ionization line emission regions are more compact. If we statistically model the distribution of microlensing magnifications, we obtain estimates for the broad line region size of r{sub s} = 24{sup +22} {sub -15} and r{sub s} = 55{sup +150} {sub -35} lt-day (90% confidence) for the high and low ionization lines, respectively. When the samples are divided into higher and lower luminosity quasars, we find that the line emission regions of more luminous quasars are larger, with a slope consistent with the expected scaling from photoionization models. Our estimates also agree well with the results from local reveberation mapping studies.

  2. Validation, automatic generation and use of broad phonetic transcriptions

    NARCIS (Netherlands)

    Bael, Cristophe Patrick Jan Van

    2007-01-01

    Broad phonetic transcriptions represent the pronunciation of words as strings of characters from specifically designed symbol sets. In everyday life, broad phonetic transcriptions are often used as aids to pronounce (foreign) words. In addition, broad phonetic transcriptions are often used for

  3. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye lasers in two different configurations, namely Littrow and grazing incidence grating (GIG), were carried out in our lab at BARC, India. The single longitudinal mode (SLM) dye laser generates single-mode laser beams ...

  4. A Practical View on Tunable Sparse Network Coding

    DEFF Research Database (Denmark)

    Sørensen, Chres Wiant; Shahbaz Badr, Arash; Cabrera Guerrero, Juan Alberto

    2015-01-01

    Tunable sparse network coding (TSNC) constitutes a promising concept for trading off computational complexity and delay performance. This paper advocates for the use of judicious feedback as a key not only to make TSNC practical, but also to deliver a highly consistent and controlled delay......) can result in a radical improvement of the complexity-delay trade-off....

  5. Encapsulation of proteins into tunable and giant mesocage alumina.

    Science.gov (United States)

    El-Safty, Sherif A; Shenashen, Mohamed A; Ismael, Moahmed; Khairy, Mohamed

    2012-07-07

    Protein bioadsorption has rapidly attracted attention partially because of the promising advances in diagnostic assays, sensors, separations, and gene technology. Tunable and giant mesocage alumina cavities (5 nm to 20 nm) show capability in size-selective encapsulation and diffusivity of large proteins into interior pores.

  6. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    Laser & Plasma Technology Division, Bhabha Atomic Research Centre,. Mumbai 400 085, India ... Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye .... wavelength tuning was done through 50,000 steps per revolution microstepper mo- tor attached to the centre of ...

  7. Comparison between liquid and solid tunable focus lenses

    Energy Technology Data Exchange (ETDEWEB)

    Santiago-Alvarado, A; Cruz-Martinez, V M [Universidad Tecnologica de la Mixteca, Carre. Acatlima Km 2.5 Huajuapan de Leon Oaxaca (Mexico); Vazquez-Montiel, S; Munoz-Lopez, J; Diaz-Gonzalez, G [Instituto Nacional de Astrofisica, Optica y Electronica Luis Enrique Erro 1, Tonantzintla Puebla (Mexico); Campos-Garcia, M, E-mail: santiago@mixteco.utm.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-186, 04510, D.F. Mexico (Mexico)

    2011-01-01

    Nowadays more reports in the use of tunable lenses are reported, it is due to the benefits they offer in optical systems design. A tunable lens is an optical system that can focus on a range of positions by changing dynamically one of its geometric parameters. There are several types of tunable lenses, the most known types are the liquid, the solid elastic, with variable refractive index, and lenses that use a dielectric medium. This paper presents the analysis and opto-mechanical design of two tunable lenses, a liquid lens and another Solid Elastic Lens (SEL). Both lenses are made in mounting aluminium and polydimethylsiloxane (PDMS) as refractor medium, the liquid lens use two elastic membranes containing a liquid medium between them while the SEL only use PDMS material as body of the lens (medium refractor). We describe the opto-mechanical performance of both types of lens highlighting the main features of each. Finally, results of a opto-functional comparison between these prototypes are showed.

  8. Dielectric and metallic nanosuspensions with tunable optical nonlinearities

    Science.gov (United States)

    Fardad, Shima; Man, Weining; Zhang, Ze; Salandrino, Alessandro; Heinrich, Matthias; Chen, Zhigang; Christodoulides, Demetrios N.

    2014-09-01

    We provide a brief report on our recent work on dielectric and metallic colloidal nanosuspensions with negative polarizability where we observed robust propagation of self-trapped light over a long distance. Our results open up new opportunities in developing soft-matter systems with tunable optical nonlinearities.

  9. Liquid crystal parameter analysis for tunable photonic bandgap fiber devices

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Wei, Lei

    2010-01-01

    We investigate the tunability of splay-aligned liquid crystals for the use in solid core photonic crystal fibers. Finite element simulations are used to obtain the alignment of the liquid crystals subject to an external electric field. By means of the liquid crystal director field the optical...

  10. Tunable coupling and ultrastrong interaction in circuit quantum electrodynamics

    International Nuclear Information System (INIS)

    Baust, Alexander Theodor

    2015-01-01

    For future quantum information and quantum simulation architectures with superconducting circuits, a profound understanding of the coupling mechanisms between the individual building blocks is essential. In our work, we investigate galvanically coupled qubit-resonator systems, demonstrate the phenomenon of ultrastrong coupling and realize qubit mediated tunable and switchable coupling between two frequency-degenerate coplanar microwave resonators.

  11. Alternation and tunable composition in hydrogen bonded supramolecular copolymers.

    Science.gov (United States)

    Felder, Thorsten; de Greef, Tom F A; Nieuwenhuizen, Marko M L; Sijbesma, Rint P

    2014-03-07

    Sequence control in supramolecular copolymers is limited by the selectivity of the associating monomer end groups. Here we introduce the use of monomers with aminopyrimidinone and aminohydroxynaphthyridine quadruple hydrogen bonding end groups, which both homodimerize, but form even stronger heterodimers. These features allow the formation of supramolecular copolymers with a tunable composition and a preference for alternating sequences.

  12. Designed synthesis of tunable amorphous carbon nanotubes (a ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 6. Designed synthesis of tunable amorphous carbon nanotubes (a-CNTs) by a novel route and their oxidation resistance properties. Longlong Xu Yifu Zhang Xiongzhi Zhang Yu Huang Xiaoyu Tan Chi Huang Xiao Mei Fei Niu Changgong Meng Gongzhen ...

  13. Tunable two-phase coexistence in half-doped manganites

    Indian Academy of Sciences (India)

    Our recent work on half-doped manganites builds on those ideas to explain our data showing continuously tunable phase coexistence of FM and AFM states. Macroscopic hysteresis across transitions is often used to assert their first-order nature, and this has also been done in the case of half-doped manganites [6]. Kuwa-.

  14. Investigating tunable KRb gases and Bose-Einstein condensates

    DEFF Research Database (Denmark)

    Jørgensen, Nils Byg

    2015-01-01

    We present the production of dual-species Bose-Einstein condensates of 39K and 87Rb with tunable interactions. A dark spontaneous force optical trap was used for 87Rb to reduce the losses in 39K originating from light-assisted collisions in the magneto optical trapping phase. Using sympathetic...

  15. Electrically tunable liquid crystal photonic bandgap fiber laser

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei

    2010-01-01

    We demonstrate electrical tunability of a fiber laser by using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an al...

  16. Generation of high-energy sub-20 fs pulses tunable in the 250-310 nm region by frequency doubling of a high-power noncollinear optical parametric amplifier.

    Science.gov (United States)

    Beutler, Marcus; Ghotbi, Masood; Noack, Frank; Brida, Daniele; Manzoni, Cristian; Cerullo, Giulio

    2009-03-15

    We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

  17. Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis

    Directory of Open Access Journals (Sweden)

    Tura Andrea

    2012-02-01

    Full Text Available Abstract Background Symmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals. Methods Ten transfemoral amputees (AMP and ten control subjects (CTRL were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice. Reference values of step and stride regularity indices (Ad1 and Ad2 were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals. At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient. Results All Ad1 and Ad2 indices were lower in AMP than in CTRL (P Conclusions Without the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees.

  18. Heterogeneously grown tunable group-IV laser on silicon

    Science.gov (United States)

    Hudait, Mantu; Clavel, M.; Lester, L.; Saladukha, D.; Ochalski, T.; Murphy-Armando, F.

    2016-02-01

    Tunable tensile-strained germanium (epsilon-Ge) thin films on GaAs and heterogeneously integrated on silicon (Si) have been demonstrated using graded III-V buffer architectures grown by molecular beam epitaxy (MBE). epsilon-Ge epilayers with tunable strain from 0% to 1.95% on GaAs and 0% to 1.11% on Si were realized utilizing MBE. The detailed structural, morphological, band alignment and optical properties of these highly tensile-strained Ge materials were characterized to establish a pathway for wavelength-tunable laser emission from 1.55 μm to 2.1 μm. High-resolution X-ray analysis confirmed pseudomorphic epsilon-Ge epitaxy in which the amount of strain varied linearly as a function of indium alloy composition in the InxGa1-xAs buffer. Cross-sectional transmission electron microscopic analysis demonstrated a sharp heterointerface between the epsilon-Ge and the InxGa1-xAs layer and confirmed the strain state of the epsilon-Ge epilayer. Lowtemperature micro-photoluminescence measurements confirmed both direct and indirect bandgap radiative recombination between the Γ and L valleys of Ge to the light-hole valence band, with L-lh bandgaps of 0.68 eV and 0.65 eV demonstrated for the 0.82% and 1.11% epsilon-Ge on Si, respectively. The highly epsilon-Ge exhibited a direct bandgap, and wavelength-tunable emission was observed for all samples on both GaAs and Si. Successful heterogeneous integration of tunable epsilon-Ge quantum wells on Si paves the way for the implementation of monolithic heterogeneous devices on Si.

  19. Nonlinear optical refraction of Al2O3 single crystal doping with nickel nanoparticles measured by the Kerr-lens autocorrelation technique

    International Nuclear Information System (INIS)

    Yu, Xiangxiang; Wang, Yuhua; Wang, Yumei

    2014-01-01

    The nonlinear refraction of a nickel doped α-Al 2 O 3 single crystal was measured with a 800 nm pulse using the Kerr-lens autocorrelation technique. The sample was fabricated by ion implantation using a metal vapor vacuum arc ion source. The value of the nonlinear refractive index, n 2 , of the sample was determined to be 7.9 × 10 −16 cm 2 W −1 . The mechanisms of nonlinear refraction of the bulk material and the nanoparticles have been discussed through the UV–vis spectrum and supercontinuum spectra. (paper)

  20. Autocorrelation and cross-correlation between hCGβ and PAPP-A in repeated sampling during first trimester of pregnancy

    DEFF Research Database (Denmark)

    Nørgaard, Pernille; Wright, Dave; Ball, Susan

    2013-01-01

    Theoretically, repeated sampling of free β-human chorionic gonadotropin (hCGβ) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester of pregnancy might improve performance of risk assessment of trisomy 21 (T21). To assess the performance of a screening test involving repeated...... measures of biochemical markers, correlations between markers must be estimated. The aims of this study were to calculate the autocorrelation and cross-correlation between hCGβ and PAPP-A in the first trimester of pregnancy and to investigate the possible impact of gestational age at the first sample...

  1. Self-similar Hierarchical Wrinkles as a Potential Multifunctional Smart Window with Simultaneously Tunable Transparency, Structural Color, and Droplet Transport.

    Science.gov (United States)

    Lin, Gaojian; Chandrasekaran, Prashant; Lv, Cunjing; Zhang, Qiuting; Tang, Yichao; Han, Lin; Yin, Jie

    2017-08-09

    Smart window has immense potential for energy savings in architectural and vehicular applications, while most studies focus on the tunability of a single property of optical transmittance. Here we explore harnessing dynamically tunable hierarchical wrinkles for design of a potential multifunctional smart window with combined structural color and water droplet transport control. The self-similar hierarchical wrinkles with both nanoscale and microscale features are generated on a prestrained poly(dimethylsiloxane) elastomer through sequential strain release and multistep oxygen plasma treatment. We show that the hierarchically wrinkled elastomer displays both opaqueness and iridescent structural color. We find that restretching/releasing the elastomer leads to the reversible and repeatable switch from opaqueness to transparency, arising from the flattening of large wrinkles (micrometer scale), while a nonvanishing structural color occurs due to the nondisappearing small wrinkles (nanoscale). The unique features of combined reversible large wrinkles and irreversible small wrinkles during hierarchical wrinkling are well reproduced by corresponding finite element simulation. The criteria for generating self-similar hierarchical wrinkles is revealed through a simplified theoretical model and validated by experiments. In addition to its tunable optical property, we further show its ability in control of water droplet transport on demand through mechanical stretching and release. We find that an initially pinned water droplet on the tilted hierarchically wrinkled surface starts to slide when the surface is stretched, and becomes pinned again upon strain release. Such a process is reversible and repeatable. The hierarchically wrinkled surface could find broad potential applications not only in multifunctional smart windows with additional features of aesthetics and water collection, but in microfluidics, design of slippery surfaces, and directional water transportation.

  2. Time dependent auto-correlation, autospectrum and decay ratio estimation of transient signals in JET soft X-ray records

    International Nuclear Information System (INIS)

    Por, G.

    1999-08-01

    A program package was developed to estimate the time dependent auto-correlation function (ACF) from the time signals of soft X-ray records taken along the various lines-of-sights in JET-SHOTS, and also to estimate the time dependent Decay Ratio (DR) from that. On the basis of ACF the time dependent auto-power spectral density (APSD) was also calculated. The steps and objectives of this work were: eliminating the white detection noise, trends and slow variation from the time signals, since ordinary methods can give good estimate of the time dependent ACF and DR only for 'nearly' stationary signals, developing an automatic algorithm for finding the maxima and minima of ACF, since they are the basis for DR estimation, evaluating and testing different DR estimators for JET-SHOT, with the aim of finding parts of the signals, where the oscillating character is strong, estimating time dependent ACF and APSD that can follow the relatively fast variation in the time signal. The methods that we have developed for data processing of transient signals are: White detection noise removal and preparation for trend removal - weak components, white detection noise and high frequency components are filtered from the signal using the so-called soft-threshold wavelet filter. Removal of trends and slow variation - Three-point differentiation of the pre-filtered signal is used to remove trends and slow variation. Here we made use of the DERIV function of IDL program language. This leads to a filtered signal that has zero mean value in each time step. Calculation of the time dependent ACF - The signal treated by the two previous steps is used as the input. Calculated ACF value is added in each new time step, but the previously accumulated ACF value is multiplied by a weighting factor. Thus the new sample has 100% contribution, while the contributions from the previous samples are forgotten quickly. DR calculation - DR is a measure of the decay of oscillating ACF. This parameter was shown

  3. A low-temperature external cavity diode laser for broad wavelength tuning

    Science.gov (United States)

    Tobias, William G.; Rosenberg, Jason S.; Hutzler, Nicholas R.; Ni, Kang-Kuen

    2016-11-01

    We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to the spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64 °C, more than 85 °C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation is achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes.

  4. Controllable Assembly of Enzymes for Multiplexed Lab-on-a-Chip Bioassays with a Tunable Detection Range.

    Science.gov (United States)

    Xianyu, Yunlei; Wu, Jing; Chen, Yiping; Zheng, Wenshu; Xie, Mengxia; Jiang, Xingyu

    2018-02-26

    Multiplexed analysis of molecules with different concentrations requires assays with a tunable detection range. A strategy is outlined that uses click chemistry to assemble horseradish peroxidase in a controlled fashion to generate enzyme assemblies as probes for multiplexed bioassays. This controllable assembly of enzymes on detection antibodies allows for lab-on-a-chip immunoassays with a tunable detection range from pg mL -1 to μg mL -1 . Simultaneous, multiplexed bioassays of clinically relevant inflammatory biomarkers in serum are demonstrated in one lab-on-a-chip format, with a limit of detection of 0.47 pg mL -1 for interleukin-6, 2.6 pg mL -1 for procalcitonin, and 40 ng mL -1 for C-reactive protein. This controlled assembly technique provides a multiplexed platform for simultaneous and quantitative analyses of both low-abundance and high-abundance biomarkers with a broad detection range, which holds great promise as a point-of-care platform for biomedical diagnostics. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Applications of Random Nonlinear Photonic Crystals Based on Strontium Tetraborate

    Directory of Open Access Journals (Sweden)

    Alexandre I. Zaitsev

    2012-10-01

    Full Text Available Properties of strontium tetraborate (SBO and features of as-grown anti-parallel domains are summarized. From the point of view of nonlinear optics, these domains form nonlinear photonic crystals (NPC. Applications of NPC to the deep ultraviolet generation and fs pulse diagnostics are described. NPC and SBO are prospective media for the creation of a widely tunable source of fs pulses in the vacuum ultraviolet and for autocorrelation diagnostics of broadly tunable sources.

  6. Tunable Photoluminescent Core/Shell Cu(+)-Doped ZnSe/ZnS Quantum Dots Codoped with Al(3+), Ga(3+), or In(3+).

    Science.gov (United States)

    Cooper, Jason K; Gul, Sheraz; Lindley, Sarah A; Yano, Junko; Zhang, Jin Z

    2015-05-13

    Semiconductor quantum dots (QDs) with stable, oxidation resistant, and tunable photoluminescence (PL) are highly desired for various applications including solid-state lighting and biological labeling. However, many current systems for visible light emission involve the use of toxic Cd. Here, we report the synthesis and characterization of a series of codoped core/shell ZnSe/ZnS QDs with tunable PL maxima spanning 430-570 nm (average full width at half-maximum of 80 nm) and broad emission extending to 700 nm, through the use of Cu(+) as the primary dopant and trivalent cations (Al(3+), Ga(3+), and In(3+)) as codopants. Furthermore, we developed a unique thiol-based bidentate ligand that significantly improved PL intensity, long-term stability, and resilience to postsynthetic processing. Through comprehensive experimental and computational studies based on steady-state and time-resolved spectroscopy, electron microscopy, and density functional theory (DFT), we show that the tunable PL of this system is the result of energy level modification to donor and/or acceptor recombination pathways. By incorporating these findings with local structure information obtained from extended X-ray absorption fine structure (EXAFS) studies, we generate a complete energetic model accounting for the photophysical processes in these unique QDs. With the understanding of optical, structural, and electronic properties we gain in this study, this successful codoping strategy may be applied to other QD or related systems to tune the optical properties of semiconductors while maintaining low toxicity.

  7. New Markov-autocorrelation indices for re-evaluation of links in chemical and biological complex networks used in metabolomics, parasitology, neurosciences, and epidemiology.

    Science.gov (United States)

    González-Díaz, Humberto; Riera-Fernández, Pablo

    2012-12-21

    The development of new methods for the computational re-evaluation of links in chemical and biological complex networks is very important to save time and resources. The Moreau-Broto autocorrelation indices (MBis) are well-known topological indices (TIs) used in QSAR/QSPR studies to encode the structural information contained in molecular graphs. In addition, MBis and similar autocorrelation measures have been used to study other systems like, for example, proteins. In the present work, MBis are combined with Markov chains to develop a general class of stochastic MBis of order k (MB(k)) that is used to encode the structural information contained in different types of large complex networks. The MB(k) values obtained for the nodes (centralities) of these networks are used as input variables to seek QSPR-like equations (by means of linear discriminant analysis) in which the outputs are numerical scores S(L(ij)) that allow us to discriminate between connected and nonconnected nodes and therefore re-evaluate the connectivity of the whole network. The models developed in this work produced the following results in terms of overall accuracy for network reconstruction: metabolic networks (72.10%), parasite-host networks (88.70%), CoCoMac brain cortex coactivation network (81.89%), and fasciolosis spreading network (86.39%).

  8. Collagen Fibrils: Nature's Highly Tunable Nonlinear Springs.

    Science.gov (United States)

    Andriotis, Orestis G; Desissaire, Sylvia; Thurner, Philipp J

    2018-03-21

    Tissue hydration is well known to influence tissue mechanics and can be tuned via osmotic pressure. Collagen fibrils are nature's nanoscale building blocks to achieve biomechanical function in a broad range of biological tissues and across many species. Intrafibrillar covalent cross-links have long been thought to play a pivotal role in collagen fibril elasticity, but predominantly at large, far from physiological, strains. Performing nanotensile experiments of collagen fibrils at varying hydration levels by adjusting osmotic pressure in situ during atomic force microscopy experiments, we show the power the intrafibrillar noncovalent interactions have for defining collagen fibril tensile elasticity at low fibril strains. Nanomechanical tensile tests reveal that osmotic pressure increases collagen fibril stiffness up to 24-fold in transverse (nanoindentation) and up to 6-fold in the longitudinal direction (tension), compared to physiological saline in a reversible fashion. We attribute the stiffening to the density and strength of weak intermolecular forces tuned by hydration and hence collagen packing density. This reversible mechanism may be employed by cells to alter their mechanical microenvironment in a reversible manner. The mechanism could also be translated to tissue engineering approaches for customizing scaffold mechanics in spatially resolved fashion, and it may help explain local mechanical changes during development of diseases and inflammation.

  9. Using binary surfactant mixtures to simultaneously improve the dimensional tunability and monodispersity in the seeded growth of gold nanorods.

    Science.gov (United States)

    Ye, Xingchen; Zheng, Chen; Chen, Jun; Gao, Yuzhi; Murray, Christopher B

    2013-02-13

    We report a dramatically improved synthesis of colloidal gold nanorods (NRs) using a binary surfactant mixture composed of hexadecyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL). Both thin (diameter 30 nm) gold NRs with exceptional monodispersity and broadly tunable longitudinal surface plasmon resonance can be synthesized using seeded growth at reduced CTAB concentrations (as low as 0.037 M). The CTAB-NaOL binary surfactant mixture overcomes the difficulty of growing uniform thick gold NRs often associated with the single-component CTAB system and greatly expands the dimensions of gold NRs that are accessible through a one-pot seeded growth process. Gold NRs with large overall dimensions and thus high scattering/absorption ratios are ideal for scattering-based applications such as biolabeling as well as the enhancement of optical processes.

  10. Moiré volume Bragg grating filter with tunable bandwidth.

    Science.gov (United States)

    Mokhov, Sergiy; Ott, Daniel; Divliansky, Ivan; Zeldovich, Boris; Glebov, Leonid

    2014-08-25

    We propose a monolithic large-aperture narrowband optical filter based on a moiré volume Bragg grating formed by two sequentially recorded gratings with slightly different resonant wavelengths. Such recording creates a spatial modulation of refractive index with a slowly varying sinusoidal envelope. By cutting a specimen at a small angle, to a thickness of one-period of this envelope, the longitudinal envelope profile will shift from a sine profile to a cosine profile across the face of the device. The transmission peak of the filter has a tunable bandwidth while remaining at a fixed resonant wavelength by a transversal shift of incidence position. Analytical expressions for the tunable bandwidth of such a filter are calculated and experimental data from a filter operating at 1064 nm with bandwidth range 30-90 pm is demonstrated.

  11. Tunable signal processing through modular control of transcription factor translocation.

    Science.gov (United States)

    Hao, Nan; Budnik, Bogdan A; Gunawardena, Jeremy; O'Shea, Erin K

    2013-01-25

    Signaling pathways can induce different dynamics of transcription factor (TF) activation. We explored how TFs process signaling inputs to generate diverse dynamic responses. The budding yeast general stress-responsive TF Msn2 acted as a tunable signal processor that could track, filter, or integrate signals in an input-dependent manner. This tunable signal processing appears to originate from dual regulation of both nuclear import and export by phosphorylation, as mutants with one form of regulation sustained only one signal-processing function. Versatile signal processing by Msn2 is crucial for generating distinct dynamic responses to different natural stresses. Our findings reveal how complex signal-processing functions are integrated into a single molecule and provide a guide for the design of TFs with "programmable" signal-processing functions.

  12. Using MEMS Capacitive Switches in Tunable RF Amplifiers

    Directory of Open Access Journals (Sweden)

    Danson John

    2006-01-01

    Full Text Available A MEMS capacitive switch suitable for use in tunable RF amplifiers is described. A MEMS switch is designed, fabricated, and characterized with physical and RF measurements for inclusion in simulations. Using the MEMS switch models, a dual-band low-noise amplifier (LNA operating at GHz and GHz, and a tunable power amplifier (PA at GHz are simulated in m CMOS. MEMS switches allow the LNA to operate with 11 dB of isolation between the two bands while maintaining dB of gain and sub- dB noise figure. MEMS switches are used to implement a variable matching network that allows the PA to realize up to 37% PAE improvement at low input powers.

  13. MEMS Tunable Diffraction Grating for Spaceborne Imaging Spectroscopic Applications

    Directory of Open Access Journals (Sweden)

    Sanathanan S. Muttikulangara

    2017-10-01

    Full Text Available Diffraction gratings are among the most commonly used optical elements in applications ranging from spectroscopy and metrology to lasers. Numerous methods have been adopted for the fabrication of gratings, including microelectromechanical system (MEMS fabrication which is by now mature and presents opportunities for tunable gratings through inclusion of an actuation mechanism. We have designed, modeled, fabricated and tested a silicon based pitch tunable diffraction grating (PTG with relatively large resolving power that could be deployed in a spaceborne imaging spectrometer, for example in a picosatellite. We have carried out a detailed analytical modeling of PTG, based on a mass spring system. The device has an effective fill factor of 52% and resolving power of 84. Tuning provided by electrostatic actuation results in a displacement of 2.7 μ m at 40 V . Further, we have carried out vibration testing of the fabricated structure to evaluate its feasibility for spaceborne instruments.

  14. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

    This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modeling of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.

  15. Tunable polaritonic molecules in an open microcavity system

    Energy Technology Data Exchange (ETDEWEB)

    Dufferwiel, S.; Li, Feng, E-mail: f.li@sheffield.ac.uk; Giriunas, L.; Walker, P. M.; Skolnick, M. S.; Krizhanovskii, D. N., E-mail: d.krizhanovskii@sheffield.ac.uk [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Trichet, A. A. P.; Smith, J. M. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)

    2015-11-16

    We experimentally demonstrate tunable coupled cavities based upon open access zero-dimensional hemispherical microcavities. The modes of the photonic molecules are strongly coupled with quantum well excitons forming a system of tunable polaritonic molecules. The cavity-cavity coupling strength, which is determined by the degree of modal overlap, is controlled through the fabricated centre-to-centre distance and tuned in-situ through manipulation of both the exciton-photon and cavity-cavity detunings by using nanopositioners to vary the mirror separation and angle between them. We demonstrate micron sized confinement combined with high photonic Q-factors of 31 000 and lower polariton linewidths of 150 μeV at resonance along with cavity-cavity coupling strengths between 2.5 meV and 60 μeV for the ground cavity state.

  16. Tunable single-longitudinal-mode fiber optical parametric oscillator.

    Science.gov (United States)

    Yang, Sigang; Cheung, Kim K Y; Zhou, Yue; Wong, Kenneth K Y

    2010-02-15

    A tunable single-longitudinal-mode (SLM) fiber optical parametric oscillator (FOPO) is proposed and demonstrated experimentally. A sub-ring cavity with a short cavity length is used to suppress the longitudinal modes and broaden the longitudinal mode spacing. A fiber loop mirror, consisted of an unpumped erbium-doped fiber, acts as an autotracking filter for providing fine mode restriction and ensuring the single-frequency operation. The measurement based on a homodyne method shows that the FOPO provides the SLM output. Furthermore the SLM FOPO can be tunable over 14 nm for each of the signal and the idler, which is limited only by the gain bandwidth of the fiber optical parametric amplifier.

  17. Tunable gauge potential for spinless particles in driven lattices

    Science.gov (United States)

    Simonet, J.; Struck, J.; Weinberg, M.; Ölschläger, C.; Hauke, P.; Eckardt, A.; Lewenstein, M.; Sengstock, K.; Windpassinger, P.

    2013-08-01

    We present a universal method to create a tunable, artificial vector gauge potential for neutral particles trapped in an optical lattice. A suitable periodic shaking of the lattice allows to engineer a Peierls phase for the hopping parameters. This scheme thus allows one to address the atomic internal degrees of freedom independently. We experimentally demonstrate the realisation of such artificial potentials in a 1D lattice, which generate ground state superfluids at arbitrary non-zero quasimomentum [4]. This scheme offers fascinating possibilities to emulate synthetic magnetic fields in 2D lattices. In a triangular lattice, continuously tunable staggered fluxes are realised. Spontaneous symmetry breaking has recently been observed for a π-flux [23]. With the presented scheme, we are now able to study the influence of a small symmetry breaking perturbation.

  18. Tunable photonic bandgap fiber based devices for optical networks

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Scolari, Lara; Rottwitt, Karsten

    2005-01-01

    In future all optical networks one of the enabling technologies is tunable elements including reconfigurable routers, switches etc. Thus, the development of a technology platform that allows construction of tuning components is critical. Lately, microstructured optical fibers, filled with liquid...... crystals, have proven to be a candidate for such a platform. Microstructured optical fibers offer unique wave-guiding properties that are strongly related to the design of the air holes in the cladding of the fiber. These wave-guiding properties may be altered by filling the air holes with a material......, for example a liquid crystal that changes optical properties when subjected to, for example, an optical or an electrical field. The utilization of these two basic properties allows design of tunable optical devices for optical networks. In this work, we focus on applications of such devices and discuss recent...

  19. Membrane-based aberration-corrected tunable micro-lenses

    Science.gov (United States)

    Waibel, Philipp; Ermantraut, Eugen; Mader, Daniel; Zappe, Hans; Seifert, Andreas

    2010-05-01

    We present measurements and simulations of membrane-based micro-lens stacks, tunable in focal length in the range of 10mm to 50mm without chromatic aberration. The pressure-actuated, liquid-filled, membrane-based micro-lenses are fabricated by an all-silicone molding approach and consist of three chambers separated by two highly flexible silicone-membranes. Based on the idea of the classical achromatic Fraunhofer doublet, two different liquids with suitable optical properties are used. Pressure-dependent surface topologies are measured by profilometry for determining the correlation between refraction and applied pressure. The profiles are fit to polynomials; the coefficients of the polynomials are pressure-dependent and fit to empirically determined functions which are then used as an input for optical ray-tracing. Using this approach, the focal length is tunable while compensating for chromatic aberration by suitably applied pressures.

  20. Graphene induced tunable and polarization-insensitive broadband metamaterial absorber

    Science.gov (United States)

    Zhang, Yuping; Li, Yue; Cao, Yanyan; Liu, Yuanzhong; Zhang, Huiyun

    2017-01-01

    We design a tunable and broadband metamaterial absorber in the mid-infrared region based on graphene. The unit cell of the proposed metamaterial absorber consists of circular gold patches, which coupled with a graphene layer, and are separated by a dielectric spacer from the gold film on the bottom. The absorption bandwidth is effectively extended by patterning multi-circular gold patches of different dimension elements with appropriate geometrical parameters in a co-plane. The metamaterial absorber achieves its frequency tunable characteristics via changing the applied voltage or chemical doping to manipulate graphene's Fermi energy. We analyzed the surface current distributions and the distributions of the z-component electric field for understanding the absorption mechanism. Moreover, the design principle here could be regarded as a template to extend bandwidth by introducing more circular patches into each unit cell. Our design has potential applications in various fields of stealth technology, photovoltaic devices, sensors, and broadband communication.

  1. A dynamically-tunable graphene-based fano metasurface

    KAUST Repository

    Amin, Muhammad

    2013-09-01

    A planar graphene metasurface with rectangular holes, which is capable of supporting a dynamically tunable Fano resonance at Terahertz (THz) frequencies, is proposed. The rectangular hole is patterned asymmetrically within the metasurface\\'s unit cell to \\'brighten\\' an originally-dark quadrupolar surface plasmon mode. Fano resonance is achieved via the destructive interference of this mode with a dipolar surface plasmon. The spectral location and line shape of the Fano resonance can be dynamically tuned via a gate voltage applied to the metasurface to change graphene\\'s optical properties. The dynamic tunability of the Fano resonance suggests the applicability of the proposed metasurface in designing THz wave modulators and band-pass filters. © 2013 IEEE.

  2. Investigation of graphene-integrated tunable metamaterials in THz regime

    Science.gov (United States)

    Demir, S. Mahircan; Yüksek, Yahya; Sabah, Cumali

    2018-05-01

    A metallic fishnet metamaterial structure in sub-THz region is presented. The proposed structure is based on hexagonal resonators. Simulations have been performed by a 3D full-wave electromagnetic simulator and a negative refractive index has been observed at the frequency range between 0.55 and 0.70 THz with the help of the graphene layer. In order to observe the effect of the graphene layer, the metamaterial structure has been simulated and examined before and after graphene integration. Significant modification in the propagation properties has been observed after the graphene integration. Change in S-parameters with the size variation of hexagonal resonators and alteration in graphene thickness are also presented as a parametric study to show the tunability of the structure. Suitability of the metamaterial for sensor applications has been investigated. The proposed metamaterial structure is promising to be effectively used for tunability and sensor applications.

  3. Optically pumped 1550nm wavelength tunable MEMS VCSEL

    DEFF Research Database (Denmark)

    Sahoo, Hitesh Kumar; Ansbæk, Thor; Ottaviano, Luisa

    2016-01-01

    The paper presents the design and fabrication of an optically pumped 1550nm tunable MEMS VCSEL with anenclosed MEMS. The MEMS is defined in SOI and the active material, an InP wafer with quantum wells arebonded to the SOI and the last mirror is made from the deposition of dielectric materials. Th....... The design bringsin flexibility to fabricate MEMS VCSELs over a wider range of wavelengths. The paper discusses results fromthe simulations and bonding results from fabrication. The device will push the boundaries for wavelength sweepspeed and bandwidth.......The paper presents the design and fabrication of an optically pumped 1550nm tunable MEMS VCSEL with anenclosed MEMS. The MEMS is defined in SOI and the active material, an InP wafer with quantum wells arebonded to the SOI and the last mirror is made from the deposition of dielectric materials...

  4. Tunable protein harmonic diffractive micro-optical elements.

    Science.gov (United States)

    Sun, Yun-Lu; Liu, Dong-Xu; Dong, Wen-Fei; Chen, Qi-Dai; Sun, Hong-Bo

    2012-07-15

    Herein, tunable protein harmonic diffractive microlenses (PHDMs) have been constructed by femtosecond laser direct writing from bovine serum albumin. With excellent three-dimensional topography, PHDMs show distinct harmonic diffractive features, such as similarly good imaging performance with smaller thickness than refractive lenses and well controlled minus chromatic dispersion compared with simple diffractive lenses (∼5% focal length shift against ∼21% of the protein Fresnel zone plate with the same radius under light with wavelength 450-659 nm). Owing to the nature of protein molecules as "building blocks," the focal length of the PHDM can be facilely tuned within seconds by changing the pH value (focal length tunability of up to ∼20%).

  5. Tunability of the Berry phase in gapped graphene

    OpenAIRE

    Urru, Andrea; Cocco, Giulio; Fiorentini, Vincenzo

    2015-01-01

    When a gap of tunable size opens at the conic band intersections of graphene, the Berry phase does not vanish abruptly, but progressively decreases as the gap increases. The phase depends on the reciprocal-space path radius, i.e., for a doped system, the Fermi wave vector. The phase and its observable consequences can thus be tuned continuously via gap opening --by a modulating potential induced by strain, epitaxy, or nanostructuration-- and doping adjustment.

  6. Flexible and stretchable micromagnet arrays for tunable biointerfacing.

    Science.gov (United States)

    Tseng, Peter; Lin, Jonathan; Owsley, Keegan; Kong, Janay; Kunze, Anja; Murray, Coleman; Di Carlo, Dino

    2015-02-11

    A process to surface pattern polydimethylsiloxane (PDMS) with ferromagnetic structures of varying sizes (micrometer to millimeter) and thicknesses (>70 μm) is developed. Their flexibility and magnetic reach are utilized to confer dynamic, additive properties to a variety of substrates, such as coverslips and Eppendorf tubes. It is found that these substrates can generate additional modes of magnetic droplet manipulation, and can tunably steer magnetic-cell organization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Photodynamics and physics behind tunable solid-state lasers

    Science.gov (United States)

    Alfano, R. R.; Petricevic, V.; Demos, S. G.

    1991-02-01

    Research was focused in two areas. The use of excite-and-probe anti-Stokes Raman scattering apparatus, the nonequilibrium phonons which participate in the overall complex nonradiative decay in tunable solid state laser crystals, were directly identified. Rise and decay behavior of different Raman-active phonon modes were measured. A new laser ion, Chromium 4(+) in chromium-doped forsterite was discovered, and its spectroscopic and laser characteristics were investigated.

  8. Widely tunable picosecond optical parametric oscillator using highly nonlinear fiber.

    Science.gov (United States)

    Zhou, Yue; Cheung, Kim K Y; Yang, Sigang; Chui, P C; Wong, Kenneth K Y

    2009-04-01

    We demonstrated a fully fiber-integrated widely tunable picosecond optical parametric oscillator based on highly nonlinear fiber. The ring cavity with a 50 m highly nonlinear fiber was synchronously pumped with a picosecond mode-locked fiber laser. The tuning range was from 1413 to 1543 nm and from 1573 to 1695 nm, which was as wide as 250 nm. A high-quality pulse was generated with a pulse width narrower than that of the pump.

  9. Asymmetric tunable tunneling magnetoresistance in single-electron transistors

    CERN Document Server

    Pirmann, M; Schön, G

    2000-01-01

    We show that the tunneling magnetoresistance (TMR) of a ferromagnetic single-electron transistor in the sequential tunneling regime shows asymmetric Coulomb blockade oscillations as a function of gate voltage if the individual junction-TMRs differ. The relative amplitude of these oscillations grows significantly if the bias voltage is increased, becoming as large as 30% when the bias voltage is comparable to the charging energy of the single-electron transistor. This might be useful for potential applications requiring a tunable TMR.

  10. Dynamically tunable interface states in 1D graphene-embedded photonic crystal heterostructure.

    Science.gov (United States)

    Huang, Zhao; Li, Shuaifeng; Liu, Xin; Zhao, Degang; Ye, Lei; Zhu, Xuefeng; Zang, Jianfeng

    2018-03-07

    Optical interface states exhibit promising applications in nonlinear photonics, low-threshold lasing, and surface-wave assisted sensing. However, the further application of interface states in configurable optics is hindered by their limited tunability. Here, we demonstrate a new approach to generate dynamically tunable and angle-resolved interface states using graphene-embedded photonic crystal (GPC) heterostructure device. By combining the GPC structure design with in situ electric doping of graphene, a continuously tunable interface state can be obtained and its tuning range is as wide as the full bandgap. Moreover, the exhibited tunable interface states offer a possibility to study the correspondence between space and time characteristics of light, which is beyond normal incident conditions. Our strategy provides a new way to design configurable devices with tunable optical states for various advanced optical applications such as beam splitter and dynamically tunable laser.

  11. Dynamically tunable interface states in 1D graphene-embedded photonic crystal heterostructure

    Science.gov (United States)

    Huang, Zhao; Li, Shuaifeng; Liu, Xin; Zhao, Degang; Ye, Lei; Zhu, Xuefeng; Zang, Jianfeng

    2018-03-01

    Optical interface states exhibit promising applications in nonlinear photonics, low-threshold lasing, and surface-wave assisted sensing. However, the further application of interface states in configurable optics is hindered by their limited tunability. Here, we demonstrate a new approach to generate dynamically tunable and angle-resolved interface states using graphene-embedded photonic crystal (GPC) heterostructure device. By combining the GPC structure design with in situ electric doping of graphene, a continuously tunable interface state can be obtained and its tuning range is as wide as the full bandgap. Moreover, the exhibited tunable interface states offer a possibility to study the correspondence between space and time characteristics of light, which is beyond normal incident conditions. Our strategy provides a new way to design configurable devices with tunable optical states for various advanced optical applications such as beam splitter and dynamically tunable laser.

  12. A Novel Tunable Triple-Band Left-Handed Metamaterial

    Directory of Open Access Journals (Sweden)

    Si Li

    2017-01-01

    Full Text Available A novel tunable triple-band left-handed metamaterial (LHM composed of a single-loop resonator (SLR and a variable capacitor-loaded short wire pair (CL-SWP printed on both sides of a substrate is presented in this paper. The CL-SWP-based metamaterial (MTM is a novel single-sided LHM. It is theoretically analyzed capable of extracting tunable negative permeability and a wide-band negative permittivity. We ran simulations for the CL-SWP-based MTM, the SLR-based MTM, and the proposed LHM. Together with the measured results, it is identified that this novel LHM exhibits a tunable triple-band left-handed (LH property. With the increase of the loaded capacitance, one LH band is relatively stable, while the other two are moving towards lower frequencies with their bandwidth getting wider and narrower, respectively. The surface current density distributions indicate that the first LH band is mainly decided by the SLR, one of the rest 2 LH bands is mainly decided by the CL-SWP, and the other one is decided by the SLR and CL-SWP together.

  13. Fast tunable blazed MEMS grating for external cavity lasers

    Science.gov (United States)

    Tormen, Maurizio; Niedermann, Philippe; Hoogerwerf, Arno; Shea, Herbert; Stanley, Ross

    2017-11-01

    Diffractive MEMS are interesting for a wide range of applications, including displays, scanners or switching elements. Their advantages are compactness, potentially high actuation speed and in the ability to deflect light at large angles. We have designed and fabricated deformable diffractive MEMS grating to be used as tuning elements for external cavity lasers. The resulting device is compact, has wide tunability and a high operating speed. The initial design is a planar grating where the beams are free-standing and attached to each other using leaf springs. Actuation is achieved through two electrostatic comb drives at either end of the grating. To prevent deformation of the free-standing grating, the device is 10 μm thick made from a Silicon on Insulator (SOI) wafer in a single mask process. At 100V a periodicity tuning of 3% has been measured. The first resonant mode of the grating is measured at 13.8 kHz, allowing high speed actuation. This combination of wide tunability and high operating speed represents state of the art in the domain of tunable MEMS filters. In order to improve diffraction efficiency and to expand the usable wavelength range, a blazed version of the deformable MEMS grating has been designed. A key issue is maintaining the mechanical properties of the original device while providing optically smooth blazed beams. Using a process based on anisotropic KOH etching, blazed gratings have been obtained and preliminary characterization is promising.

  14. Atmospheric pressure photoionization using tunable VUV synchrotron radiation

    International Nuclear Information System (INIS)

    Giuliani, A.; Giorgetta, J.-L.; Ricaud, J.-P.; Jamme, F.; Rouam, V.; Wien, F.; Laprévote, O.; Réfrégiers, M.

    2012-01-01

    Highlights: ► Coupling of an atmospheric pressure photoionization source with a vacuum ultra-violet (VUV) beamline. ► The set up allows photoionization up to 20 eV. ► Compared to classical atmospheric pressure photoionization (APPI), our set up offers spectral purity and tunability. ► Allows photoionization mass spectrometry on fragile and hard to vaporize molecules. - Abstract: We report here the first coupling of an atmospheric pressure photoionization (APPI) source with a synchrotron radiation beamline in the vacuum ultra-violet (VUV). A commercial APPI source of a QStar Pulsar i from AB Sciex was modified to receive photons from the DISCO beamline at the SOLEIL synchrotron radiation facility. Photons are delivered at atmospheric pressure in the 4–20 eV range. The advantages of this new set up, termed SR-APPI, over classical APPI are spectral purity and continuous tunability. The technique may also be used to perform tunable photoionization mass spectrometry on fragile compounds difficult to vaporize by classical methods.

  15. Infrared metasurface with tunable composite right/left-handed dispersion

    Science.gov (United States)

    Ma, Jie; Luo, Yi; Wu, Xuefei; Xu, Hongyan; Jing, Hongwei; Wu, Zhiming; Jiang, Yadong; Liu, Zhijun

    2017-11-01

    The distinctive dispersion of composite right/left-handed transmission-line metamaterial offers a unique way of manipulating electromagnetic waves across a wide spectral range from microwave to the infrared. In this paper, we present a tunable mid-infrared composite right/left-handed metasurface based on the phase-change material of vanadium dioxide. The metasurface consists of an array of ‘H’-shaped gold pads separated from a metallic ground plane by a film of vanadium dioxide. As the insulator-to-metal phase transition is thermally triggered, both right-handed and left-handed metasurface modes redshift with reduced absorbance before they are eventually switched off. The tunabilities of right-handed mode frequency and left-handed mode frequency are measured to be approximately 3.6% and 2.7%, respectively. Our demonstrated metasurface with tunable composite right/left-handed dispersion could be useful for beam scanning for a fixed frequency in mid-infrared applications.

  16. Development of tunable flashlamp excited dye laser system

    International Nuclear Information System (INIS)

    Bhanthumnavin, V.; Apikitmata, S.; Kochareon, P.

    1991-01-01

    A tunable flashlamp excited dye laser (FEDL) was successfully developed for the first time in Thailand by Thai scientists at KMIT Thonburi (Bangmod). The Rhodamine 6G dissolved in ethyl alcohol was utilized as a laser medium and circulated by a pump through a laser head. The dye cuvette had an inner diameter of 4.0 mm and was 90 mm long. The cavity mirrors M 1 , and M 2 were concave mirrors with reflectivities of 100% and 73% respectively. A power supply of 0-20 kV and current of 0-50 mA charged a capacitor of 0.3 μ f at 10-15 kV which was then discharged via a spark gap through the flashlamp. The output laser wavelengths was tunable from λ = 550-640 nm. It is the first FEDL system, locally developed, which has a tunable wavelength for the laser output. The laser pulse width is about 1.0 μs with energy of 20 mJ and peak power pf 20 KW. The repetition rate of the laser is 1/15 Hz. (author). 14 refs, 7 figs

  17. Tunable dispersion compensator based on uniform fiber Bragg grating and its application to tunable pulse repetition-rate multiplication.

    Science.gov (United States)

    Han, Young-Geun; Lee, Sang

    2005-11-14

    A new technique to control the chromatic dispersion of a uniform fiber Bragg grating based on the symmetrical bending is proposed and experimentally demonstrated. The specially designed two translation stages with gears and a sawtooth wheel can simultaneously induce the tension and compression strain corresponding to the bending direction. The tension and compression strain can effectively control the chirp ratio along the fiber grating attached on a flexible cantilever beam and consequently the dispersion value without the center wavelength shift. We successfully achieve the wide tuning range of chromatic dispersion without the center wavelength shift, which is less than 0.02 nm. We also reduce the group delay ripple as low as ~+/-5 ps. And we also demonstrate the application of the proposed tunable dispersion compensation technique to the tunable pulse repetition-rate multiplication and obtain high-quality pulses at repetition rates of 20 ~ 40 GHz.

  18. Tunable polarization sensitive absorber made of graphene-based hyperbolic metamaterials

    Science.gov (United States)

    Madani, Amir; Babaei, Maryam

    2017-02-01

    Theoretically, the absorption properties of a hyperbolic metamaterial (HMM) slab constructed from graphene-dielectric multilayers are investigated using the transfer matrix method. The effective medium approximation reveals that the graphene-based HMM slab is an anisotropic and homogeneous medium. It is shown that the absorption of the slab depend on the polarization and incidence angle due to the strong anisotropy of the HMMs. The results revealed that the complete absorption is only possible for the TM-polarized waves in a broad region of wavelength. It is found that the region of total absorption can be controlled and tuned using some controlling parameters such as incidence angle, the orientation of the optical axis of the HMM medium and the chemical potential of the graphene monolayers. Finally, the intensity distribution of a TM-polarized Gaussian beam is simulated which verifies the strong absorption of the waves inside the HMM slab. This absorber may have potential applications in the design of tunable filters, polarizers, detectors, photovoltaic devices and so on.

  19. Rapidly tunable optical parametric oscillator based on aperiodic quasi-phase matching.

    Science.gov (United States)

    Descloux, Delphine; Dherbecourt, Jean-Baptiste; Melkonian, Jean-Michel; Raybaut, Myriam; Lai, Jui-Yu; Drag, Cyril; Godard, Antoine

    2016-05-16

    A new optical parametric oscillator (OPO) architecture with high tuning speed capability is demonstrated. This device exploits the versatility offered by aperiodic quasi-phase matching (QPM) to provide a broad parametric gain spectrum without changing the temperature, angle, or position of the nonlinear crystal. Rapid tuning is then straightforwardly achieved using a fast intracavity spectral filter. This concept is demonstrated here for a picosecond synchronously pumped OPO containing an aperiodically poled MgO-doped LiNbO3 crystal and a rapidly tunable spectral filter based on a diffraction grating. Tuning over 160 nm around 3.86 μm is achieved at fixed temperature and a fast tuning over 30 nm in 40 μs is demonstrated. Different configurations are tested and compared. The cavity length detuning is analyzed and discussed. This device is successfully used to detect N2O by absorption. This approach could be generalized to other spectral ranges (e.g., visible) and temporal regimes (e.g., continuous-wave or nanosecond).

  20. Electrothermally Tunable Graphene Resonators Operating at Very High Temperature up to 1200 K.

    Science.gov (United States)

    Ye, Fan; Lee, Jaesung; Feng, Philip X-L

    2018-02-23

    The unique negative thermal expansion coefficient and remarkable thermal stability of graphene make it an ideal candidate for nanoelectromechanical systems (NEMS) with electrothermal tuning. We report on the first experimental demonstration of electrothermally tuned single- and few-layer graphene NEMS resonators operating in the high frequency (HF) and very high frequency (VHF) bands. In single-, bi-, and trilayer (1L, 2L, and 3L) graphene resonators with carefully controlled Joule heating, we have demonstrated remarkably broad frequency tuning up to Δf/f 0 ≈ 310%. Simultaneously, device temperature variations imposed by Joule heating are monitored using Raman spectroscopy; we find that the device temperature increases from 300 K up to 1200 K, which is the highest operating temperature known to date for electromechanical resonators. Using the measured frequency and temperature variations, we further extract both thermal expansion coefficients and thermal conductivities of these devices. Comparison with graphene electrostatic gate tuning indicates that electrothermal tuning is more efficient. The results clearly suggest that the unique negative thermal expansion coefficient of graphene and its excellent tolerance to very high temperature can be exploited for engineering highly tunable and robust graphene transducers for harsh and extreme environments.