Sample records for 35cl nqr frequency

  1. Anomalous H/D isotope effect on 35Cl NQR frequencies in piperidinium p-chlorobenzoate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Honda, Hisashi; Kimura, Taiki; Nakata, Eiichi; Takamizawa, Satoshi; Noro, Sumiko; Ishimaru, Shin'ichi

    2008-01-01

    Anomalous isotope effects were detected in the 35Cl nuclear quadrupole resonance (NQR) frequency of piperidinium p-chlrobenzoate (C5H10NH· ClC6H4COOH) by deuteration of hydrogen atoms. The atoms were determined to form two kinds of N H···O type H-bonds in the crystal structure. Large frequency shifts of the 35Cl resonance lines reaching 288 kHz at 77 K and 278 kHz at room temperature were caused upon deuteration, in spite of the fact that the Cl atoms in the molecule do not form hydrogen bonds in the crystal. Results of single crystal X-ray diffraction measurements and density-functional-theorem calculations suggest that a dihedral-angle change of 1.8° between benzene and the piperidine ring contributes to 35Cl NQR anomalous frequency shifts.

  2. Anomalous HID isotope effect on 35Cl NQR frequencies in piperidinium p-chlorobenzoate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Honda, Hisashi; Kimura, Taiki; Nakata, Eiichi; Takamizawa, Satoshi; Noro, Sumiko; Ishimaru, Shin'ichi

    Anomalous isotope effects were detected in the 35CI nuclear quadrupole resonance (NQR) frequency of piperidinium p-chlrobenzoate (C5H10NH· CIC6H4COOH) by deuteration of hydrogen atoms. The atoms were determined to form two kinds of N-H...O type H-bonds in the crystal structure. Large frequency shifts of the 35CI resonance lines reaching 288 kHz at 77 K and 278 kHz at room temperature were caused upon deuteration, in spite of the fact that the CI atoms in the molecule do not form hydrogen bonds in the crystal. Results of single crystal X-ray diffraction measurements and density-functional-theorem calculations suggest that a dihedral-angle change of 1.8° between benzene and the piperidine ring contributes to 35CINQR anomalous frequency shifts.

  3. 35Cl NQR of 1,5,2-Diazaphosphorine Derivatives

    NASA Astrophysics Data System (ADS)

    Dolgushin, G. V.; Nikitin, P. A.; Sapozhnikov, Yu. E.; Dmitrichenko, M. Yu.; Rozinov, V. G.; Voronkov, M. G.

    1994-02-01

    NQR frequencies and asymmetry parameters (?) of 35Cl chlorine-containing 1,5,2-diazaphosphorine derivatives are reported and discussed. NMDO calculations with total optimization of geometry have been carried out. The ?cal and ?cal values, calculated by means of the Townes and Dailey theory, correlate well with the experimenal data.

  4. The incommensurate phase of 4,4'-dichlorobiphenyl sulphone reinvestigated by 35Cl NQR

    Microsoft Academic Search

    J. Schneider; A. Wolfenson; A. Brunetti

    1994-01-01

    In order to acquire new information about the normal-incommensurate (IC) phase transition and to check the existence of a lock-in transition in 4,4'-dichlorobiphenyl sulphone (4,4'-DCBS), a comprehensive 35Cl nuclear quadrupole resonance (NQR) study is reported. Detailed NQR measurements of frequency, line width and spin relaxation time (Tl) were obtained in the temperature range 80-270 K. The results show that the

  5. Sodium and potassium salts of dichloroisocyanuric acid and their hydrates as antimicrobials agents studied by 35Cl-NQR spectroscopy and DFT calculations

    Microsoft Academic Search

    A. Walczak; B. Brycki; M. Kaczmarek; O. Kh. Poleshchuk; M. Ostafin; B. Nogaj

    2006-01-01

    The electronic structure of dichloroisocyanuric acid derivatives was analysed by 35Cl-NQR spectroscopy and DFT calculations. Here we concentrate our attention on three different factors: type of metallic substituent (sodium and potassium), temperature of the sample (liquid nitrogen and room) and degree of hydration (an amount of water molecules attached to analysed compounds). In particular, all the variations in 35Cl-NQR frequencies

  6. Electronic structure and biological activity of chosen DDT-type insecticides studied by 35Cl-NQR.

    PubMed

    Jadzyn, Maciej; Nogaj, Boles?aw

    2009-02-01

    A correlation between the electronic structure and biological activity of chosen dichlorodiphenyltrichloroethane (DDT)-type insecticides: 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene, 2,2-bis(4-chlorophenyl)ethanoic acid and 4,4'-dichlorobenzophenone (used in agriculture) has been analysed on the basis of the (35)Cl-nuclear quadrupole resonance (NQR) spectroscopy. The (35)Cl-NQR resonance frequencies measured at 77 K have been correlated with the lethal dose (LD(50)) parameter that characterises the biological activity of these insecticides. PMID:18942076

  7. Studies of the electronic structure and biological activity of chosen 1,4-benzodiazepines by 35Cl NQR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Bronisz, K.; Ostafin, M.; Poleshchuk, O. Kh.; Mielcarek, J.; Nogaj, B.

    2006-11-01

    Selected derivatives of 1,4-benzodiazepine: lorazepam, lormetazepam, oxazepam and temazepam, used as active substances in anxiolytic drugs, have been studied by 35Cl NQR method in order to find the correlation between electronic structure and biological activity. The 35Cl NQR resonance frequencies ( ?Q) measured at 77 K have been correlated with the following parameters characterising their biological activity: biological half-life period ( t0.5), affinity to benzodiazepine receptor (IC 50) and mean dose equivalent. The results of experimental study of some benzodiazepine derivatives by nuclear quadrupole resonance of 35Cl nuclei are compared with theoretical results based on DFT calculations which were carried out by means of Gaussian'98 W software.

  8. 35Cl NQR Spectra of several 2,2-bis- p-chlorophenyl chloroethane derivatives

    NASA Astrophysics Data System (ADS)

    Nogaj, B.; Pietrzak, J.; Wielopolska, E.; Schroeder, G.; Jarczewski, A.

    Measurement of NQR line frequency at 77 K have been performed for the following compounds: 1-chloro-2,2-bis-(p-chlorophenyl) ethylene (DDMU), 1,1-dichloro-2,2-bis-(p-chlorophenyl) ethylene (DDE), 1,1-dichloro-2,2-bis-(p-chlorophenyl) ethane (ODD), 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT). An attempt to assign spectrum lines to particular Cl nuclei in a molecule has been made. Molecular and crystallographic inequivalences occurring in these compounds have been considered. Comparison of the NQR and crystallographic data revealed the influence of phenyl rings conformation on electric charge distribution in the studied molecules.

  9. Detection of {sup 14}N and {sup 35}Cl in cocaine base and hydrochloride using NQR, NMR, and SQUID techniques

    SciTech Connect

    Yesinowski, J.P.; Buess, M.L.; Garroway, A.N. [Naval Research Lab., Washington, DC (United States); Ziegeweid, M.; Pines, A. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

    1995-07-01

    Results from {sup 14}N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e{sup 2}Qq/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter {eta} of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) {sup 14}N transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 ({+-}0.0014) MHz and the asymmetry parameter is 0.2632 ({+-}0.0034). Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum. The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies. 31 refs., 8 figs., 1 tab.

  10. Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes

    NASA Astrophysics Data System (ADS)

    Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

    2006-05-01

    Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

  11. Low Frequency NQR using Double Contact Cross-relaxation

    NASA Astrophysics Data System (ADS)

    Stephenson, David; Smith, John A. S.

    2000-02-01

    A cross-relaxation technique is described which involves two spin contacts per double reso-nance cycle. The result is an improvement in signal to noise ratio particularly at low frequencies. Experimental spectra and analyses are presented: 14N in ammonium sulphate showing that the tech-nique gives essentially the same information as previous studies; 14N in ammonium dichromate determining e2Qq/h as (76±3) kHz and ? = 0.84±.04; 7Li in lithium acetylacetonate for which the spectrum (corrected for Zeeman distortion) yields e2Qq/h = (152 ±5) kHz and ?=.5 ±.2. Calculated spectra are presented to demonstrate the ? dependence of the line shapes for 7Li.

  12. 35-Cl nuclear quadrupole resonance spectra in diazepam and its 1:1 complex with chloral hydrate

    NASA Astrophysics Data System (ADS)

    Brisson, Colette; Durand, Marcel; Jugie, Gérard; Pasdeloup, Maurice

    1980-11-01

    The 35-Cl NQR spectra of diazepam and some of its related compounds are reported; they yield information about the hydrogen bonded complex that diazepam forms with chloral hydrate. The results reflect large changes in electron distribution at the CCl 3 group while the diazepam chlorine at the 7 position remains almost unaffected.

  13. Electron density distribution in cladribine (2-chloro-2?-deoxyadenosine) - A drug against leukemia and multiple sclerosis - Studied by multinuclear NQR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Latosi?ska, J. N.; Latosi?ska, M.; Seliger, J.; Žagar, V.; Kazimierczuk, Z.

    2009-07-01

    2-Chloro-2'-deoxyadenosine (Cladribine) chemotherapeutic drug has been studied experimentally in solid state by 35Cl NQR and NMR-NQR double resonance and theoretically by the Density Functional Theory. Fifteen resonance frequencies on 14N have been detected and assigned to particular nitrogen sites in the 2-CdA molecule. The effects of tautomerism, regioisomerism, conformations and molecular aggregations, related to intermolecular hydrogen bond formation, on the NQR parameters have been analysed within the DFT and AIM ( Atoms in Molecules) formalism. The properties of the whole molecule, the so-called global reactivity descriptors, have been calculated for a comparison of both syn and anti conformations of 2-CdA molecule to check the effect of crystal packing on molecular conformation.

  14. Measurement of temperature and temperature gradient in millimeter samples by chlorine NQR

    NASA Astrophysics Data System (ADS)

    Lužnik, Janko; Pirnat, Janez; Trontelj, Zvonko

    2009-09-01

    A mini-thermometer based on the 35Cl nuclear quadrupole resonance (NQR) frequency temperature dependence in the chlorates KClO3 and NaClO3 was built and successfully tested by measuring temperature and temperature gradient at 77 K and higher in about 100 mm3 active volume of a mini Joule-Thomson refrigerator. In the design of the tank-circuit coil, an array of small coils connected in series enabled us (a) to achieve a suitable ratio of inductance to capacity in the NQR spectrometer input tank circuit, (b) to use a single crystal of KClO3 or NaClO3 (of 1-2 mm3 size) in one coil as a mini-thermometer with a resolution of 0.03 K and (c) to construct a system for measuring temperature gradients when the spatial coordinates of each chlorate single crystal within an individual coil are known.

  15. Explosives detection by nuclear quadrupole resonance (NQR)

    NASA Astrophysics Data System (ADS)

    Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.; Krauss, Ronald A.

    1994-10-01

    Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a laboratory prototype NQR explosives detector which interrogates a volume of 300 liters (10 ft3). This paper presents abbreviated results from a demonstration of the laboratory prototype NQR explosives detector conducted at the Federal Aviation Administration Technical Center in May 1994 on RDX-based explosives.

  16. H/D isotope effect of 1H MAS NMR spectra and 79Br NQR frequencies of piperidinium p-bromobenzoate and pyrrolidinium p-bromobenzoate

    NASA Astrophysics Data System (ADS)

    Honda, Hisashi; Kyo, Shinshin; Akaho, Yousuke; Takamizawa, Satoshi; Terao, Hiromitsu

    2010-04-01

    H/D isotope effects onto 79Br NQR frequencies of piperidinium p-bromobenzoate were studied by deuterium substitution of hydrogen atoms which form two kinds of N-H?O type hydrogen bonds, and the isotope shift of ca. 100 kHz were detected for a whole observed temperature range. In addition, 1H MAS NMR spectra measurements of piperidinium and pyrrolidinium p-bromobenzoate were carried out and little isotope changes of NMR line shape were detected. In order to reveal effects of molecular arrangements into the obtained isotope shift of NQR frequencies, single-crystal X-ray measurement of piperidinium p-bromobenzoate- d2 and density-functional-theory calculation were carried out. Our estimation showed the dihedral-angle change between piperidine and benzene ring contributes to isotope shift rather than those of N-H lengths by deuterium substitution.

  17. Chlorine NQR on Derivatives of Chloral

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masao; Weiden, Norbert; Weiss, Alarich

    1980-10-01

    The 35Cl-NQR spectrum of several derivatives of chloral, Cl3CCHO, was studied in the ranee 77 K ? T ? Tm. By use of the spin echo double resonance technique a relative assignment of the resonances to different Cl3C-groups within one crystallized compound was possible. The solid compounds studied are: High temperature phase of chloral hydrate, Cl3CCH(OH)2; parachloral, (Cl3CCHO)3, (?-and ß-isomer); the two phases of chloral hemihydrate Cl3CCHO · 1/2 H2O; chloralide (II); chloralhemithiohydrate, Cl3CCHO · 1/2 H2S. The structure of the molecules in the solid state and the fade out of the NQR resonances are discussed.

  18. 14N NQR in the tetrazole family

    NASA Astrophysics Data System (ADS)

    Pirnat, Janez; Lužnik, Janko; Jazbinšek, Vojko; Žagar, Veselko; Seliger, Janez; Klapötke, Thomas M.; Trontelj, Zvonko

    2009-10-01

    14N NQR frequencies and spin-lattice relaxation times were measured in technologically important 5-aminotetrazole and 5-aminotetrazole monohydrate at different temperatures between 77 K and 300 K. Five NQR triplets ?+, ?- and ?0 were found for the five inequivalent nitrogen atoms in each compound between 0.7 MHz and 4 MHz. Carr-Purcell based multipulse sequences were used to accumulate quadrupole echo signals before the FFT analysis. Assignment of the frequencies to atomic positions was made and the results are analysed in relation to the molecular chemical bonds and possible H-bonds in the crystal structures. The new NQR frequencies are reasonably related to the previously published NQR spectrum of the third family member, 1H-tetrazole.

  19. A miniaturized NQR spectrometer for a multi-channel NQR-based detection device

    NASA Astrophysics Data System (ADS)

    Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

    2014-10-01

    A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting 14N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring 14N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel 14N NQR based detection device.

  20. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, M.A.

    1995-11-29

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C{sub 5}H{sub 5}) and Sn({eta}{sup 1}-C{sub 5}H{sub 5}){sub 4}. This work was undertaken in the hope of gaining insight into the intramolecuhrr dynamics, specifically which fluxional processes exist in the solid state, by what mechanism rearrangements are occurring, and the activation energies by which these processes are governed.

  1. Successive Phase Transitions and High Ionic Conductivity of Trichlorogermanate (II) Salts as Studied by 35C1 NQR and Powder X-Ray Diffraction

    NASA Astrophysics Data System (ADS)

    Yamada, K.; Isobe, K.; Okuda, T.; Furukawa, Y.

    1994-02-01

    A series of trichlorogermanate(II) salts (AGeCl3, A = Rb, Cs, CH3N H3, and (CH3)4N) have been synthesized and characterized by 35Cl NQR , 35Cl NMR , AC conductivity, DTA, and X-ray diffraction techniques. In the temperature range studied two, two, five, and four phases were confirmed for the Rb, Cs, CH3NH3, and (CH3)4N salts, respectively. From the 35Cl NQR and structural data, isolated pyramidal GeCl3 anions were recognized in the low temperature phases. With increasing temperature the relaxation times of the 35Cl NQR decreased exponentially and the signals disappeared far below the melting point. This suggests that the reorientation of the anion about the pseudo three-fold axis is excited. With further increase in temperature, the ionic conductivity of CH3NH3GeCl3 and (CH3)4NGeCl3 increased drastically at the phase transitions to their cubic perovskite phases (CH3NH3GeCl3:?= 10-1 Sm-1 at 400 K, (CH3)4NGeCl3: ? = 5 x 10-2 Sm-1 at 420 K). The mobile ion was confirmed to be the chloride ion by means of 35Cl NMR and X-ray diffraction.

  2. NQR 127I Spectroscopy of Layered Inorganic Compounds Intercalated with Aromatic Amines

    NASA Astrophysics Data System (ADS)

    Babushkina, T. A.; Seryukova, I. V.

    1998-07-01

    NQR spectroscopy was used to study the intercalating influence on the iodine electric field gradient of lead(ll) and cadmium(ll) iodides. We used pyridine, piperidine, aniline and quinoline, as guest substances. In the intercalates the NQR frequencies and their dependence on temperature in different crystalline phases were studied. The peculiarities of chemical bonds and crystal structures were discussed.

  3. Quadrupole Coupling Parameters and Structural Aspects of Crystalline and Amorphous Solids by NMR and Nqr.

    NASA Astrophysics Data System (ADS)

    Mao, Degen

    Nuclear quadrupole interaction is very sensitive to the local electron distribution and chemical bondings. NMR and NQR techniques have been combined to obtain the quadrupole coupling constant ({Qcc}) and asymmetry parameter (eta) and extract structural information for several borate, gallate, and metavanadate compounds and glasses. ^{71}Ga and ^{69}Ga NMR has been used to study crystalline beta-Ga _2O_3 and several gallate glasses. Quadrupole parameters were acquired for GaO_6 and GaO_4 units in beta-Ga_2 O_3 by the computer simulation of the NMR powder patterns. A sensitive CW NQR spectrometer was built to detect NQR resonances below 2 MHz. The spectrometer includes a modified Robinson oscillator-detector, a new bi-symmetric square wave Zeeman modulator and a computerized data acquisition system. ^{51}V (I = 7/2) NQR resonances below 850 kHz have been detected for several metavanadates at both room temperature and liquid nitrogen temperature. Quadrupole parameters thus obtained are an order of magnitude more accurate than values obtained by previous NMR studies. For a spin 3/2 nucleus, the pure NQR frequency {Q_{cc}over 2}sqrt{1+{eta^2over 3}}is insufficient to determine either Q_{cc} or eta. However, two methods, Zeeman perturbed NQR powder pattern and ^{10}B NQR, can be employed to obtain both Q_{cc } and eta. An example is given for ^{11}B in CaO-B_2O_3. With a double coil tank circuit design, pure ^ {11}B NQR was used to determine the fraction of borons in BO_3 and BO _4 configurations in hydrated zinc borates. ^{11}B NMR and NQR were also used to study lead borate glasses. Small changes in Q_{cc} (less than 2%) and eta (less than 0.1) suggest that BO_3 units with non-bridging oxygens are not present in the lead borate glasses.

  4. Nqrs Data for C26H35Cl2CuNP (Subst. No. 1604)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for C26H35Cl2CuNP (Subst. No. 1604)

  5. Competition between the fusion-fission and deep-inelastic orbiting mechanisms in the 35 Cl + 12 C reaction

    Microsoft Academic Search

    C. Beck; B. Djerroud; F. Haas; R. M. Freeman; A. Hachem; B. Heusch; A. Morsad; M. Youlal; Y. Abe; A. Dayras; J. P. Wieleczko; B. T. Matsuse; S. M. Lee

    1992-01-01

    The binary decay properties of the47V nucleus, produced in the35Cl +12C reaction, have been investigated at the35Cl bombarding energiesElab = 180 and 200 MeV by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and a characteristic 1\\/sin(?cm) angular distribution. The elemental distribution of the fully-damped products is asymmetric, similar to what has previously been observed

  6. Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer

    SciTech Connect

    Black, B.E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

    1993-07-01

    Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe {sup 11}B and {sup 27}Al NQR resonances. The scope of this study was increased to include {sup 23}Na, {sup 51}V, and {sup 55}Mn NQR transitions. Also, a technique was presented to observe {sup 14}N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two {sup 14}N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

  7. 14 N NQR spectrum of sildenafil citrate

    NASA Astrophysics Data System (ADS)

    Stephenson, David; Singh, Nadia

    2015-04-01

    The 14N nuclear quadrupole resonance (NQR) spectrum of sildenafil citrate tablets has been recorded allowing the quadrupole coupling constants and asymmetry parameters of all six unique nitrogen atoms in its structure to be determined. A density function calculation gives results that are largely in agreement with the experimental values.

  8. A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La

    E-print Network

    G. S. Mitchell; C. S. Blessinger; J. D. Bowman; T. E. Chupp; K. P. Coulter; M. T. W. Gericke; G. L. Jones; M. B. Leuschner; H. Nann; S. A. Page; S. I. Penttila; T. B. Smith; W. M. Snow; W. S. Wilburn

    2004-01-08

    An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry $s_n \\cdot (k_{\\gamma} \\times k_n)$ were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries $s_n \\cdot k_{\\gamma}$ were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.

  9. A General Numerical Analysis of Time-Domain NQR Experiments

    SciTech Connect

    Harel, Elad; Cho, Herman M.

    2006-12-01

    We introduce a general numerical approach for solving the Liouville equation of a quadrupolar nuclide that we show can be used to analyze time-domain NQR experiments. A computer-based treatment is necessitated by the dimensionality of the Liouville space, which precludes analytical, closed form solutions for I > 3/2. Accurate simulations of experimental nutation curves, forbidden transition intensities, powder and single crystal spectra, and off-resonance irradiation dynamics can be computed with this method. We also examine the validity of perturbative approximations where the signal intensity of a transition is proportional to the transition moment between the eigenstates of the system, thus providing a simple basis for determining selection rules. Our method allows us to calculate spectra for all values of the asymmetry parameter, ?, and sample orientations relative to the coil axis. We conclude by demonstrating the methodology for calculating the response of the quadrupole system to amplitude- and frequency-modulated pulses.

  10. Formation of a necklike structure in 35Cl+12C and 197Au reactions at 43 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Larochelle, Y.; Gingras, L.; Beaulieu, L.; Qian, X.; Saddiki, Z.; Djerroud, B.; Doré, D.; Laforest, R.; Roy, R.; Samri, M.; St-Pierre, C.; Ball, G. C.; Bowman, D. R.; Galindo-Uribarri, A.; Hagberg, E.; Horn, D.; López, J. A.; Robinson, T.

    1997-04-01

    The experimental signature of the formation of a necklike structure, with a velocity between that of the projectilelike emitter and that of the targetlike emitter, is investigated with the same beam and experimental setup for targets lighter and heavier than the projectile. The reactions are 35Cl on 12C and on 197Au at 43 MeV/nucleon. Particle velocity distributions are compared with two-source statistical simulations and the presence of a necklike structure is inferred from the data. In the second part of the paper, dynamical model simulations with the formation of a necklike structure are presented for the 35Cl+12C system at 43 MeV/nucleon.

  11. Barrier distributions derived from quasielastic excitation functions for the 35Cl+105,106,110Pd systems

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.; Testoni, J. E.; Abriola, D.; Digregorio, D. E.; Fernández Niello, J. O.; Martí, G. V.; Pacheco, A. J.; Spinella, M. R.; Ramírez, M.; Balpardo, C.; Ortega, M.

    2002-06-01

    Quasielastic excitation functions for the 35Cl+105,106,110Pd systems were measured at a backward angle and at near barrier energies. Experimental fusion barrier distributions were derived from these measured cross sections and compared with simplified coupled-channel calculations. Coupling of inelastic excitations up to second order were insufficient to explain the data. The inclusion of specific transfer reaction channels improved the fits to these fusion barrier distributions.

  12. Rotationally Resolved LIF Spectra of the A 2? +– X 2? r Transition of Jet-Cooled 74Ge 35Cl

    Microsoft Academic Search

    David A Hostutler; Dennis J Clouthier; Ghassan Wannous

    2002-01-01

    The A2?+–X2?r band system of 74Ge35Cl has been rotationally resolved for the first time using isotopically enriched 74GeCl4 as the precursor in a pulsed discharge jet experiment. The previous vibrational analysis of W. J. Balfour and K. S. Chandrasekhar (1986, J. Phys. B19, L187–L191) has been verified from the observed isotopic splittings of both the chlorine and germanium isotopomers. The

  13. Crystallization and preliminary analysis of the NqrA and NqrC subunits of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae.

    PubMed

    Vohl, Georg; Nedielkov, Ruslan; Claussen, Björn; Casutt, Marco S; Vorburger, Thomas; Diederichs, Kay; Möller, Heiko M; Steuber, Julia; Fritz, Günter

    2014-07-01

    The Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) from Vibrio cholerae is a membrane protein complex consisting of six different subunits NqrA-NqrF. The major domains of the NqrA and NqrC subunits were heterologously expressed in Escherichia coli and crystallized. The structure of NqrA1-377 was solved in space groups C222? and P2? by SAD phasing and molecular replacement at 1.9 and 2.1?Å resolution, respectively. NqrC devoid of the transmembrane helix was co-expressed with ApbE to insert the flavin mononucleotide group covalently attached to Thr225. The structure was determined by molecular replacement using apo-NqrC of Parabacteroides distasonis as search model at 1.8?Å resolution. PMID:25005105

  14. Fourier transform zero field NMR and NQR

    SciTech Connect

    Zax, D.B.

    1984-09-01

    The characterization of the structural and chemical properties of matter, particularly in disordered condensed phases, is a difficult process. Few analytical methods work effectively on polycrystalline or amorphous solids. In many systems the chemical shifts measured by traditional high resolution solid state NMR methods are insufficiently sensitive or the information contained in the dipole-dipole couplings is more important. In these cases Fourier transform zero field magnetic resonance may make an important contribution. Zero field NMR and NQR is the subjecti of this thesis.

  15. 93Nb- and 27Al-NMR/NQR studies of the praseodymium based PrNb2Al20

    NASA Astrophysics Data System (ADS)

    Kubo, Tetsuro; Kotegawa, Hisashi; Tou, Hideki; Higashinaka, Ryuji; Nakama, Akihiro; Aoki, Yuji; Sato, Hideyuki

    2015-03-01

    We report a study of 93Nb- and 27Al-nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) in a praseodymium based compound PrNb2Al20. The observed NMR line at around 3 T and 30 K shows a superposition of typical powder patterns of one Nb signal and at least two Al signals. 93Nb-NMR line could be reproduced by using the previously reported NQR frequency ?Q ? 1.8MHz and asymmetry parameter ? ? 0 [Kubo T et al 2014 JPS Conf. Proc. 3 012031]. From 27Al-NMR/NQR, NQR parameters are obtained to be ?Q,A ? 1.53 MHz, and ?A ? 0.20 for the site A, and ?Q,B ? 2.28 MHz, and ?B ? 0.17 for the site B. By comparing this result with the previous 27Al-NMR study of PrT2Al20 (T = Ti, V) [Tokunaga Y et al 2013 Phys. Rev. B 88 085124], these two Al site are assigned to the two of three crystallographycally inequivalent Al sites.

  16. Fourier transform zero field NMR and NQR

    SciTech Connect

    Zax, D.B.

    1985-01-01

    In many systems the chemical shifts measured by traditional high resolution solid state NMR methods are insufficiently sensitive, or the information contained in the dipole-dipole couplings is more important. In these cases, Fourier transform zero field magnetic resonance may make an important contribution. Zero field NMR and NQR is the subject of this thesis. Chapter I presents the quantum mechanical background and notational formalism for what follows. Chapter II gives a brief review of high resolution magnetic resonance methods, with particular emphasis on techniques applicable to dipole-dipole and quadrupolar couplings. Level crossings between spin-1/2 and quadrupolar spins during demagnetization transfer polarization from high to low lambda nuclei. This is the basis of very high sensitivity zero field NQR measurements by field cycling. Chapter III provides a formal presentation of the high resolution Fourier transform zero field NMR method. Theoretical signal functions are calculated for common spin systems, and examples of typical spectra are presented. Chapters IV and V review the experimental progress in zero field NMR of dipole-dipole coupled spin-1/2 nuclei and for quadrupolar spin systems. Variations of the simple experiment describe in earlier chapters that use pulsed dc fields are presented in Chapter VI.

  17. Electric dipole moment functions of the hydrogen chloride ((1)H(35)Cl) and the carbon monoxide ((12)C(16)O) molecules using an anharmonic potential

    NASA Astrophysics Data System (ADS)

    Kiriyama, Fumika

    In the last two decades precise understanding of the structure of hydrogen chloride (1H35Cl) and carbon monoxide ( 12C16O) molecules has become important in many fields such as astrophysics, meteorology, physical chemistry, and environmental science. In this dissertation the electric dipole moment functions of HCl and CO in the ground electronic state are calculated. The transition frequencies of the vibration-rotation lines in the lowest four bands of CO and the lowest seven bands of HCl were measured by various investigators. From these frequencies potential constants of these two diatomic molecules were determined by solving the time- independent Schrödinger wave equation using an anharmonic potential function given by U(r)= nan(r-re re), n+2 where n=0,1,2,.... In addition, data on spectral line intensities were available. From potential constants and line intensities the coefficients of the electric dipole moment function, M(r), were evaluated using the equation M(r)= iMi( r-re), i where i=0,1,2,.... The dipole moment coefficients are then compared with the ones reported by other investigators.

  18. Zero field NMR and NQR

    SciTech Connect

    Zax, D.B.; Bielecki, A.; Zilm, K.W.; Pines, A.; Weitekamp, D.P.

    1985-11-15

    Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for /sup 1/H, /sup 2/D, /sup 7/Li, /sup 13/C, and /sup 27/Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra.

  19. Zero-field NMR and NQR spectrometer

    SciTech Connect

    Bielecki, A.; Zax, D.B.; Zilm, K.W.; Pines, A.

    1986-03-01

    In comparison to high-field NMR, zero-field techniques offer advantages in terms of spectral interpretability in studies of polycrystalline or amorphous solids. This article describes a technique and apparatus for time-domain measurements of nuclear magnetism in the absence of applied fields (Fourier transform zero-field NMR and NQR). Magnetic field cycling and high field detection are employed to enhance sensitivity. The field cycling is accomplished with an air-driven shuttle system which moves the sample between regions of high and low magnetic field, in combination with switchable electromagnets in the low-field region. Sudden field steps or pulses are used to initiate coherent nuclear spin evolution in zero field and to monitor such evolution as a function of time. Experimental results are shown and analyzed. Possible variations on the basic method are described and their relative advantages are discussed.

  20. Perturbation analysis in the C 4?-X 4? rovibronic transitions of 48Ti 35Cl at 3 ?m

    NASA Astrophysics Data System (ADS)

    Herbin, Hervé; Farrenq, Robert; Guelachvili, Guy; Pinchemel, Bernard; Picqué, Nathalie

    2004-07-01

    The emission spectrum of the C 4?-X 4? ? v=0 transitions of 48Ti 35Cl, with v=0,1,2,3, around 3 ?m has been recorded with a high resolution Fourier transform spectrometer. Eight new subbands between ??=-1 spin components of the 1-1, 2-2, and 3-3 transitions are observed. Effective parameters have been derived from the rovibrational analysis, as well as molecular constants from the diagonalization of the Hamiltonian matrix, leading to the equilibrium structure of the 4? state. Perturbations affecting the C 4?1/2v=0, 1, 2 levels have been accounted for. They arise both from ?-doubling and avoided crossing phenomena induced by the never observed B 4? and A 4?- states.

  1. sup 35 Cl NMR study of spin dynamics in Sr sub 2 CuO sub 2 Cl sub 2

    SciTech Connect

    Borsa, F. (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States) Dipartimento di Fisica A. Volta,'' Universita di Pavia, I-27100 Pavia (Italy)); Corti, M.; Goto, T.; Rigamonti, A. (Dipartimento di Fisica A. Volta,'' Universita di Pavia, I-27100 Pavia (Italy)); Johnston, D.C.; Chou, F.C. (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States))

    1992-03-01

    Measurements of the {sup 35}Cl nuclear-spin--lattice relaxation rate (NSLR) are reported for Sr{sub 2}CuO{sub 2}Cl{sub 2} around the antiferromagnetic transition temperature {ital T}{sub {ital N}}=260{plus minus}0.5 K. The temperature dependence of the Cu{sup 2+} spin correlation length {xi}({ital T}) is obtained indirectly by using the conventional description of NSLR and scaling arguments and compared with the {xi}({ital T}) obtained in La{sub 2}CuO{sub 4} by neutron scattering. In both systems {xi}({ital T}) follows the two-dimensional Heisenberg behavior renormalized by quantum fluctuations except close to {ital T}{sub {ital N}} where a crossover to a power-law {ital T} dependence is observed in Sr{sub 2}CuO{sub 2}Cl{sub 2}.

  2. NQR: From imaging to explosives and drugs detection

    NASA Astrophysics Data System (ADS)

    Osán, Tristán M.; Cerioni, Lucas M. C.; Forguez, José; Ollé, Juan M.; Pusiol, Daniel J.

    2007-02-01

    The main aim of this work is to present an overview of the nuclear quadrupole resonance (NQR) spectroscopy capabilities for solid state imaging and detection of illegal substances, such as explosives and drugs. We briefly discuss the evolution of different NQR imaging techniques, in particular those involving spatial encoding which permit conservation of spectroscopic information. It has been shown that plastic explosives and other forbidden substances cannot be easily detected by means of conventional inspection techniques, such as those based on conventional X-ray technology. For this kind of applications, the experimental results show that the information inferred from NQR spectroscopy provides excellent means to perform volumetric and surface detection of dangerous explosive and drug compounds.

  3. The ? 4 and ? 2 + ? 5 high resolution infrared bands of F 35Cl 18O 3 and F 37Cl 18O 3

    Microsoft Academic Search

    E. Cané; L. Fusina; K. Burczyk

    2008-01-01

    The high resolution infrared spectra of monoisotopic F35Cl18O3 and F37Cl18O3 have been studied in the region of the ?4 fundamentals, centered at 1278.3 and 1263.3cm?1, respectively. Large perturbations are observed in both bands due to a Fermi type anharmonic resonance with the ?2+?5 combination bands, centered at 1270.7cm?1 in F35Cl18O3 and 1257.3cm?1 in F37Cl18O3. In particular, they affect the kl>0

  4. NQR study of local structures and cooling rate dependent superconductivity in La sub 2 CuO sub 4+. delta

    SciTech Connect

    Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H.; Thompson, J.D.; Canfield, P.C.; Fisk, Z. (Los Alamos National Lab., NM (United States)); Schirber, J.E. (Sandia National Labs., Albuquerque, NM (United States))

    1992-01-01

    Structural properties of oxygen-annealed polycrystals of La{sub 2}CuO{sub 4 + {delta}} ({delta}{approximately}0.03) have been studied using {sup 139}La NQR spectroscopy. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range at about 195K. Preliminary analysis of the {sup 139}La NQR spectra suggest that the oxygen-rich phase-separated region is composed of two structurally distinct phases, both of which are metallic and super-conducting. One phase has a structure closely related to the stoichiometric oxygen-poor compound. The second shows a considerable amount of apical oxygen disorder, a large shift in NQR frequency {nu}{sub Q}, and a volume fraction which increases with cooling rate. The formation of the second phase below {minus}200K is indicative of the freezing Of CuO{sub 6} octahedral tilting. Abrupt shifts in {nu}{sub Q} above {Tc} were also observed for both phases, suggestive of a local structural anomaly or charge transfer to the Cu-O plane.

  5. Isospin symmetry breaking at high spin in the mirror nuclei {sup 35}Ar and {sup 35}Cl

    SciTech Connect

    Della Vedova, F. [Dipartimento di Fisica dell Universita and INFN, Padova (Italy); INFN, Laboratori Nazionali di Legnaro, Legnaro (Italy); Lenzi, S. M.; Bazzacco, D.; Brandolini, F.; Farnea, E.; Lunardi, S.; Menegazzo, R.; Nespolo, M.; Pavan, P.; Alvarez, C. Rossi; Venturelli, R. [Dipartimento di Fisica dell Universita and INFN, Padova (Italy); Ionescu-Bujor, M.; Bucurescu, D.; Iordachescu, A. [Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Marginean, N. [INFN, Laboratori Nazionali di Legnaro, Legnaro (Italy); Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Axiotis, M.; Martinez, T.; Napoli, D. R. [INFN, Laboratori Nazionali di Legnaro, Legnaro (Italy); Bizzeti-Sona, A. M.; Bizzeti, P. G. [Dipartimento di Fisica dell Universita and INFN, Florence (Italy)] (and others)

    2007-03-15

    High-spin states in {sup 35}Ar and {sup 35}Cl have been populated in the {sup 24}Mg({sup 16}O, {alpha}n) and {sup 24}Mg({sup 16}O, {alpha}p) reactions, respectively, at a beam energy of 70 MeV. The comparison between the level schemes of these mirror nuclei shows a striking asymmetry in the population yield of high-spin analog states of positive parity, which indicates different intensities of E1 transitions connecting positive- and negative-parity structures in both nuclei. Large energy differences are observed between analog states of negative parity with configurations of dominant pure single-particle character. This results from the comparison with large-scale shell-model calculations in the s{sub 1/2}d{sub 3/2}f{sub 7/2}p{sub 3/2} valence space. It is shown that important contributions to the energy differences arise from the multipole Coulomb and the relativistic electromagnetic spin-orbit interactions.

  6. NQR experiments on Sc-Y alloys at very low temperatures. [Absolute thermometry below 500[mu]K

    SciTech Connect

    Pollack, L.; Smith, E.N.; Richardson, R.C. (Cornell Univ., Ithaca, NY (United States))

    1992-10-01

    The authors performed Nuclear Quadrupole Resonance (NQR) experiments on an alloy of scandium and yttrium. They find that the characteristic resonance frequencies in zero external field are 50% larger than in pure scandium. This increase in frequency makes the Sc-Y alloy a better candidate for absolute thermometry below 500 [mu]K. However, the spin-lattice relaxation time of this alloy is more than an order of magnitude longer than in the pure scandium. In addition, an abrupt increase in the Korringa constant was observed for temperatures below 5mK.

  7. Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance

    E-print Network

    Romalis, Mike

    Hz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection-to-noise ratio SNR below a few megahertz. The NQR signal from 22 g of powdered ammonium nitrate located 2 cm away from the sensor is detected with a SNR of 9 in a 4.4-s-long multiple echo sequence, which represents

  8. The two-frequency nuclear quadrupole resonance for explosives detection

    Microsoft Academic Search

    G. V. Mozjoukhine

    2000-01-01

    The two-frequency nuclear quadrupole resonance (NQR) of14N nuclei is described for purposes of explosives detection. Two applications are known: two-frequency NQR for increasing the\\u000a signal intensity, two-frequency NQR for improved reliability of explosives detection. The two-frequency experiments were carried\\u000a out in hexahydro-1,3,5-trinitro-s-triazine C3H6N6O6 and sodium nitrite NaNO2 as a substitute for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocycine C4H8N8O8. The two-frequency sequences for NQR are proposed

  9. Direct studies of low-energy resonances in 31P(p, ) 28Si and 35Cl(p, )32S

    SciTech Connect

    Moazen, Brian [University of Tennessee, Knoxville (UTK); Matei, Catalin [Oak Ridge Associated Universities (ORAU); Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Chae, K. Y. [University of Tennessee, Knoxville (UTK); Chipps, K. [Colorado School of Mines, Golden; Hatarik, Robert [Rutgers University; Jones, K. L. [University of Tennessee, Knoxville (UTK); Kozub, R. L. [Tennessee Technological University; Matos, M. [Louisiana State University; Nesaraja, Caroline D [ORNL; O'Malley, Patrick [Rutgers University; Pain, S. D. [Rutgers University; Pelham, T. [University of Surrey, UK; Pittman, S. T. [University of Tennessee, Knoxville (UTK); Smith, Michael Scott [ORNL

    2011-01-01

    Low-energy resonances in 31P(p,a)28Si and 35Cl(p,a)32S were studied directly in order to gain a better understanding of reaction cycling in the Si-Ar region in novae, supernovae, and X-ray bursts. Resonance strengths at Ec:m = 600 and 622 keV in 31P(p,a)28Si were measured as well as the Ec:m: = 611 keV resonance in 35Cl(p,a)32S, the lowest energy that any resonance in this reaction has been observed. The strengths of these resonances were found to be lower than previously determined through indirect methods, resulting in weak cycling in the Si-Ar region.

  10. NQR and ? SR in Diluted Two-Dimensional S=1/2 Heisenberg Antiferromagnets

    NASA Astrophysics Data System (ADS)

    Carretta, P.; Rigamonti, A.; Todeschini, E.; Malavasi, L.

    2003-02-01

    139La NQR spectra and relaxation and ? SR precessional frequencies in La2Cu1-xMxO4 (for M = Zn and Mg) are reported in order to study the effect of spin dilution in the planar quantum Heisenberg antiferromagnet (2DQHAF) La2CuO4. The behavior of the spin stiffness ? s(x) and of the in-plane correlation length ? 2D(x,T), of the sublattice magnetization and of the Néel temperature, for a dilution approaching the percolation threshold depart sizeably from the ones expected in dilution-like models. In spite of the marked reduction of ? s the transition to the ordered state occurs at a temperature, where ? 2D(x,TN) reaches a value close to the one in undoped 2DQHAF.

  11. The far infrared pure rotational spectrum and the Coriolis coupling between v3 and v8 in CH35ClF2

    Microsoft Academic Search

    David Luckhaus; Martin Quack

    1989-01-01

    The FIR rotational spectrum of gaseous CH35ClF2 (chlorodifluoromethane, CFC22) is analysed improving vibrational ground state parameters for J up to 80. A new set of rotational and centrifugal distortion constants is given for the C-Cl stretching fundamental v4. The Coriolis coupling between the two C-F stretching fundamentals v3 and v8 is investigated. An effective coupling constant xia = 0·38 ±

  12. Rotationally Resolved LIF Spectra of the A2Sigma+-X2Pir Transition of Jet-Cooled 74Ge35Cl

    Microsoft Academic Search

    David A. Hostutler; Dennis J. Clouthier; Ghassan Wannous

    2002-01-01

    The A2Sigma+-X2Pir band system of 74Ge35Cl has been rotationally resolved for the first time using isotopically enriched 74GeCl4 as the precursor in a pulsed discharge jet experiment. The previous vibrational analysis of W. J. Balfour and K. S. Chandrasekhar (1986, J. Phys. B19, L187-L191) has been verified from the observed isotopic splittings of both the chlorine and germanium isotopomers. The

  13. A general numerical analysis of time-domain NQR experiments

    Microsoft Academic Search

    Elad Harel; Herman M. Cho

    2006-01-01

    We introduce a general numerical approach for solving the Liouville equation of an isolated quadrupolar nuclide that can be used to analyze the unitary dynamics of time-domain NQR experiments. A numerical treatment is necessitated by the dimensionality of the Liouville space, which precludes analytical, closed form solutions for I>3\\/2. Accurate simulations of experimental nutation curves, forbidden transition intensities, powder and

  14. Hydrogen Chloride Detection in Orion A and Monoceros R2 and Derivation of the H35Cl/H37Cl Isotopic Ratio

    NASA Astrophysics Data System (ADS)

    Salez, M.; Frerking, M. A.; Langer, W. D.

    1996-08-01

    We have detected the J = 1-0 transition of H35Cl in the Orion A and Monoceros R2 giant molecular clouds, using the Caltech Submillimeter Observatory and a new heterodyne receiver built at the Jet Propulsion Laboratory. We find a llCl fractional abundance of a few times 10-10 and a depletion of gas- phase chlorine by a factor of 550-640 for Orion and 65-125 for Mon R2. For both sources, we derived the line optical depth and excitation temperature using the relative intensities of the hyperfine components and determined the abundance and excitation conditions with a large velocity gradient (LVG) model. The LVG model indicates that radiative pumping of the molecules by moderately warm dust is required to explain the observed line intensities and optical depths. In addition, we report the first detection of the isotope H37Cl from its J = 1-0 emission in Orion. Because the chemical reactions involving hydrogen chloride in molecular clouds are relatively simple, [H35Cl]/[H37Cl] is believed to provide a good estimate of [35Cl]/[37Cl]. We find an isotopic ratio about 1.3-2 times that of the solar neighborhood, suggesting that this ratio is not constant throughout the galactic interstellar medium.

  15. NMR and NQR study of the thermodynamically stable quasicrystals

    SciTech Connect

    Shastri, A.

    1995-02-10

    {sup 27}Al and {sup 61,65}Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, {sup 27}Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of {sup 63}Cu NMR with {sup 27}Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

  16. [sup 35]Cl nuclear-magnetic-resonance study of magnetic ordering in Sr[sub 2]CuO[sub 2]Cl[sub 2] single crystal

    SciTech Connect

    Corti, M.; Borsa, F. (Dipartimento di Fisica A. Volta,'' Universita di Pavia, 27100 Pavia (Italy)); Miller, L.L. (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa (United States)); Rigamonti, A. (Dipartimento di Fisica A. Volta,'' Universita di Pavia, 27100 Pavia (Italy))

    1994-05-15

    [sup 35]Cl nuclear-magnetic-resonance (NMR) and relaxation measurements have been performed in a Sr[sub 2]CuO[sub 2]Cl[sub 2] single crystal as a function of orientation between the external magnetic field [bold H][sub 0] and the tetragonal [bold c] axis. The onset is found of an anisotropic inhomogeneous broadening of the NMR line without paramagnetic shift starting below about 320 K. The broadening is strongly temperature dependent and it increases with increasing [bold H][sub 0]. The relaxation rate [ital T][sup [minus]1][sub 1], on the other hand, diverges at [ital T][sub [ital N

  17. The Vibration-Rotation Bands of the Hydrogen Halides HF, H35Cl, H37Cl, H79Br, H81Br and H127I

    Microsoft Academic Search

    S. M. Naudé; H. Verleger

    1950-01-01

    The 2-0, 3-0 and 4-0 bands of 1H19F, the 4-0 and 5-0 bands of 1H35Cl and 1H37Cl, the 4-0 band of 1H79Br and 1H81Br, and the 4-0 band of 1H127I were photographed under great dispersion in the infra-red. The molecular constants have been calculated and are summarized in a table.

  18. Absence of Magnetic Dipolar Phase Transition and Evolution of Low-Energy Excitations in PrNb2Al20 with Crystal Electric Field ?3 Ground State: Evidence from 93Nb-NQR Studies

    NASA Astrophysics Data System (ADS)

    Kubo, Tetsuro; Kotegawa, Hisashi; Tou, Hideki; Higashinaka, Ryuji; Nakama, Akihiro; Aoki, Yuji; Sato, Hideyuki

    2015-07-01

    We report measurements of bulk magnetic susceptibility and 93Nb nuclear quadrupole resonance (NQR) in the Pr-based caged compound PrNb2Al20. By analyzing the magnetic susceptibility and magnetization, the crystal electric field (CEF) level scheme of PrNb2Al20 is determined to be ?3(0 K)-?4(21.32 K)-?5(43.98 K)-?1(51.16 K) within the framework of the localized 4f electron picture. The 93Nb-NQR spectra exhibit neither spectral broadening nor spectral shift upon cooling down to 75 mK. The 93Nb-NQR spin-lattice relaxation rate 1/T1 at 5 K depends on the frequency and remains almost constant below 5 K. The frequency dependence of 1/T1 is attributed to the magnetic fluctuation due to the hyperfine-enhanced 141Pr nuclear moment inherent in the nonmagnetic ?3 CEF ground state. The present NQR results provide evidence that no symmetry-breaking magnetic dipole order occurs down to 75 mK. Also, considering an invariant form of the quadrupole and octupole couplings between a 93Nb nucleus and Pr 4f electrons, Pr 4f quadrupoles and an octupole can couple with a 93Nb nuclear quadrupole moment and nuclear spin, respectively. Together with the results of bulk measurements, the present NQR results suggest that the possibility of a static quadrupole or octupole ordering can be excluded down to 100 mK. At low temperatures below 500 mK, however, the nuclear spin-echo decay rate gradually increases and the decay curve changes from Gaussian decay to Lorentzian decay, suggesting the evolution of a low-energy excitation.

  19. NMR and NQR investigations of local symmetry in the hidden order phase of URu2Si2

    NASA Astrophysics Data System (ADS)

    Mito, T.; Hattori, M.; Motoyama, G.; Sakai, Y.; Koyama, T.; Ueda, K.; Kohara, T.; Yokoyama, M.; Amitsuka, H.

    2012-12-01

    In order to study local symmetries at the 4e(Si)- and 4d(Ru)-sites above and below hidden order transition temperature TO = 17.5 K in URu2Si2, we have investigated the nuclear quadrupole interaction by 73Ge-nuclear magnetic resonance (NMR) measurement on a 10% 73Ge-substituted sample URu2(Si0.9Ge0.1)2, and by 101Ru-nuclear quadrupole resonance (NQR) measurement on a pure single crystal sample. The present 73Ge-NMR measurements do not give any evidence for change in the local symmetry at 4e-site within experimental accuracy. On the other hand, the precise measurement of 101Ru-NQR frequency has detected an anomaly just below TO as sensitively as the thermal expansion measurement dose. Its temperature dependence shows a linear relation with that of the in-plane lattice parameter, which may be a clue to clarify a modification in microscopic charge distribution at TO.

  20. New mesophases in ionic crystals: piperidinium perchlorate and nitrate studied by 1H, 2H, 14N and 35Cl NMR

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Ishimaru, Shin'ichi; Ikeda, Ryuichi; Ishida, Hiroyuki

    1997-09-01

    Measurements of 1H, 2H, 14N and 35Cl NMR, differential thermal analysis, differential scanning calorimetry and powder X-ray diffraction were carried out in solid piperidinium perchlorate and nitrate above room temperature. Two and one solid-solid phase transitions were observed for the perchlorate and nitrate, respectively. The crystal structure in the highest-temperature phase of the perchlorate is CsCl-type cubic ( a = 6.02(6) Å and Z = 1 ) while that of the nitrate is NaCl-type cubic ( a = 9.35(5) Å and Z = 4 ). In this phase of the perchlorate self-diffusion of the cation and isotropic rotation of both cation and anion were revealed. In the highest-temperature phase of the nitrate, the isotropic rotation of both ions was detected. These phases are highly disordered and especially the phase of the perchlorate can be assigned to an anionic plastic phase.

  1. Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z = 0.89 toward PKS 1830-211

    NASA Astrophysics Data System (ADS)

    Muller, S.; Black, J. H.; Guélin, M.; Henkel, C.; Combes, F.; Gérin, M.; Aalto, S.; Beelen, A.; Darling, J.; Horellou, C.; Martín, S.; Menten, K. M.; V-Trung, Dinh; Zwaan, M. A.

    2014-06-01

    We report the first extragalactic detection of chloronium (H2Cl+) in the z = 0.89 absorber in front of the lensed blazar PKS 1830-211. The ion is detected through its 111-000 line along two independent lines of sight toward the North-East and South-West images of the blazar. The relative abundance of H2Cl+ is significantly higher (by a factor ~7) in the NE line of sight, which has a lower H2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas component. From the ratio of the H235Cl+ and H237Cl+ absorptions toward the SW image, we measure a 35Cl/37Cl isotopic ratio of 3.1-0.2+0.3 at z = 0.89, similar to that observed in the Galaxy and the solar system.

  2. Localization and Function of the Membrane-bound Riboflavin in the Na+-translocating NADH:Quinone Oxidoreductase (Na+-NQR) from Vibrio cholerae*

    PubMed Central

    Casutt, Marco S.; Huber, Tamara; Brunisholz, René; Tao, Minli; Fritz, Günter; Steuber, Julia

    2010-01-01

    The sodium ion-translocating NADH:quinone oxidoreductase (Na+-NQR) from the human pathogen Vibrio cholerae is a respiratory membrane protein complex that couples the oxidation of NADH to the transport of Na+ across the bacterial membrane. The Na+-NQR comprises the six subunits NqrABCDEF, but the stoichiometry and arrangement of these subunits are unknown. Redox-active cofactors are FAD and a 2Fe-2S cluster on NqrF, covalently attached FMNs on NqrB and NqrC, and riboflavin and ubiquinone-8 with unknown localization in the complex. By analyzing the cofactor content and NADH oxidation activity of subcomplexes of the Na+-NQR lacking individual subunits, the riboflavin cofactor was unequivocally assigned to the membrane-bound NqrB subunit. Quantitative analysis of the N-terminal amino acids of the holo-complex revealed that NqrB is present in a single copy in the holo-complex. It is concluded that the hydrophobic NqrB harbors one riboflavin in addition to its covalently attached FMN. The catalytic role of two flavins in subunit NqrB during the reduction of ubiquinone to ubiquinol by the Na+-NQR is discussed. PMID:20558724

  3. Copper Nqr and NMR Study of Metal-Substituted Yttrium BARIUM(2) COPPER(3) OXYGEN(7) and Yttrium BARIUM(2) COPPER(4) OXYGEN(8)

    NASA Astrophysics Data System (ADS)

    Cheng, Show-Jye

    Pulsed nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) have been used to investigate the effect of metal-substitution for copper in YBa_2Cu_3O_7 (YBCO123) and YBa_2Cu_4O_8 (YBCO124). Among many metal substitutions, Zn has an especially dramatic effect in suppressing the superconducting temperature T_{c}, and hence superconductivity. More interesting is that Zn and Fe have the same T_{c} suppression effect in YBCO124. This study focuses on the Zn substitutions in YBCO123 and Zn, Fe, and Co substitutions in YBCO124. In Zn doped YBCO123, Cu(2), plane site, NQR spectra and the frequency dependence of the spin-lattice relaxation rates have been measured over a temperature range from 77 K to 300 K to study the correlation of the suppression of the relaxation rate with the distance between the probe Cu nuclei and the impurity. It is found that the relaxation rate is insensitive to the variation of the NQR resonance frequency. However, by comparing the results of the Zn doped YBCO124 with those of YBCO123, it can be concluded that the suppression of the relaxation rate for both YBCO compounds in the normal state is caused by destruction of short-range antiferromagnetic correlation with substitution of nonmagnetic ion Zn on the Cu(2) sites. NQR and NMR measurements were carried out on both Cu(2), plane, and Cu(1), chain sites, for various concentrations of Zn, Fe, and Co dopants in YBCO124 over a temperature range from 77 K to 300 K. A strong correlation of the enhancement of Cu(2) spin lattice relaxation rate and suppression of superconductivity by impurities was found. The temperature dependence of the Cu(2) NMR linewidth exhibits a strong RKKY type exchange interaction below 225 K for Zn and Fe doped samples, which indicates the formation of the local magnetic moment. The enhancement of the relaxation rate is caused by the local magnetic moment Fe^ {+3} ion and the moments on Cu(2) neighbors when Zn^{+2} is substituted on Cu(2). This study gives us a clear picture of the spin pseudogap behavior in the high temperature superconductor cuprates. It also suggests that the magnetic moment on the CuO_2 plane may relate to the suppression of T_{c} in metal-substituted YBCO124.

  4. Zero field NMR and NQR with selective pulses and indirect detection

    SciTech Connect

    Millar, J.M.; Thayer, A.M.; Bielecki, A.; Zax, D.B.; Pines, A.

    1985-08-01

    Zero field NMR and NQR spectra are obtained by the application of dc magnetic field pulses to a demagnetized sample. Pulsed dc fields allow for selective excitation of isotopic species and provide a means for coherent manipulation of the spin system in zero field. Using these selective pulses and level crossing techniques, indirect detection of a quadrupolar nucleus may be accomplished via protons without obtaining the proton background signal in the NQR spectrum. Experimental results from a variety of /sup 1/H, /sup 2/H, and /sup 14/N homo- and heteronuclear systems are presented as an illustration of these techniques.

  5. NQR DETECTION OF SODIUM NITRITE RECRYSTALLIZED IN WOOD Jrmy Jover(1), (3)

    E-print Network

    Paris-Sud XI, Université de

    often used as a model in Nitrogen- 14 Quadrupole Resonance, namely sodium nitrite NaNO2. It hasNQR DETECTION OF SODIUM NITRITE RECRYSTALLIZED IN WOOD Jérémy Jover(1), (3) , Sarra Aissani(1 sample tubes have been impregnated by an aqueous solution of sodium nitrite (NaNO2). They were

  6. NQR Line Broadening Due to Crystal Lattice Imperfections and Its Relationship to Shock Sensitivity

    NASA Astrophysics Data System (ADS)

    Caulder, S. M.; Buess, M. L.; Garroway, A. N.; Miller, P. J.

    2004-07-01

    The hydrodynamic hot spot model is used to explain the difference between shock sensitive and shock insensitive explosives. Among the major factors that influence the shock sensitivity of energetic compounds are the quality and particle size of the energetic crystals used to formulate the cast plastic bonded explosive. As do all energetic compounds, RDX and HMX exhibit internal crystal defects the magnitude and type of which depend on the manufacturing process used to synthesize and re-crystallize the energetic compound. Nuclear Quadrupole Resonance (NQR) spectroscopy was used to determine the crystal quality of RDX, HMX and CL-20 obtained from various manufacturers. The NQR experimental results are discussed. Cast plastic bonded explosives were made using the RDX and HMX obtained from the various manufacturers and subsequently subjected to the NOL large-scale gap test (LSGT). The results of the LSGT are discussed and correlated with the NQR results. A relationship between the crystal defect density and shock initiation pressure of the plastic bonded explosive is developed and discussed.

  7. Roles of the Sodium-Translocating NADH:Quinone Oxidoreductase (Na+-NQR) on Vibrio cholerae Metabolism, Motility and Osmotic Stress Resistance

    PubMed Central

    Minato, Yusuke; Halang, Petra; Quinn, Matthew J.; Faulkner, Wyatt J.; Aagesen, Alisha M.; Steuber, Julia; Stevens, Jan F.; Häse, Claudia C.

    2014-01-01

    The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

  8. Roles of the sodium-translocating NADH:quinone oxidoreductase (Na+-NQR) on vibrio cholerae metabolism, motility and osmotic stress resistance.

    PubMed

    Minato, Yusuke; Fassio, Sara R; Kirkwood, Jay S; Halang, Petra; Quinn, Matthew J; Faulkner, Wyatt J; Aagesen, Alisha M; Steuber, Julia; Stevens, Jan F; Häse, Claudia C

    2014-01-01

    The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

  9. Co-NQR Study on Successive Magnetic Phase under Pressure in Non-centrosymmetric CeCoGe3

    NASA Astrophysics Data System (ADS)

    Inagaki, T.; Matsumura, M.; Mizoo, M.; Kawamura, Y.; Kato, H.; Nishioka, T.

    2012-12-01

    We have performed Co-NQR study to clarify the complex magnetic phases in approaching to the quantum critical point (QCP). The successive transitions at TN2=12 K and TN3=8 K after the ferrimagnetic-like order at TN1=21 K in ambient pressure are confirmed by the spectral changes of Co-NQR However no critical slowing down of the nuclear spin-lattice relaxation rate 1/T1 or the nuclear spin-spin relaxation rate 1/T2 at TN2 and TN3 was observed, suggesting 1st order transitions. In applying pressure, a large spectral change of Co-NQR occurs in relatively low pressure of 0.3 Gpa. The Co-NQR spectrum becomes simple above about 0.7 GPa, consisting of the two Co sites with spectral weight ratio of 2. No successive transitions were observed in 1.5 GPa, indicating that the successive transitions are confined to relatively low pressure region. The extremely slower decrease of the sublattice magnetization than that expected in the mean field approximation is seen in 1.5 GPa.

  10. Measurement of in-situ stress in salt and rock using NQR techniques

    SciTech Connect

    Schempp, E.; Hirschfeld, T.; Klainer, S.

    1980-12-01

    A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising system involves pulsed nuclear double resonance detection; and alterative is to observe the quadrupolar splitting of the NMR signal. Choices to be made in the measurement and mapping techniques are discussed. The well-known perturbation of the homogenous stress field in the neighborhood of a borehole is shown to be advantageous from the point of view of obtaining directional information on the stress. Construction and operation of a borehole stress sensor are considered. The NQR technique seems feasible for measuring the magnitude and direction of underground stress with a resolution of about 25 psi, or 2.5% at 1000 psi. Downhole instrumentation suitable for in-situ determinations of stress appears within the state of the art. Additional tasks required on the project are identified.

  11. A mutation in Na(+)-NQR uncouples electron flow from Na(+) translocation in the presence of K(+).

    PubMed

    Shea, Michael E; Mezic, Katherine G; Juárez, Oscar; Barquera, Blanca

    2015-01-20

    The sodium-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is a bacterial respiratory enzyme that obtains energy from the redox reaction between NADH and ubiquinone and uses this energy to create an electrochemical Na(+) gradient across the cell membrane. A number of acidic residues in transmembrane helices have been shown to be important for Na(+) translocation. One of these, Asp-397 in the NqrB subunit, is a key residue for Na(+) uptake and binding. In this study, we show that when this residue is replaced with asparagine, the enzyme acquires a new sensitivity to K(+); in the mutant, K(+) both activates the redox reaction and uncouples it from the ion translocation reaction. In the wild-type enzyme, Na(+) (or Li(+)) accelerates turnover while K(+) alone does not activate. In the NqrB-D397N mutant, K(+) accelerates the same internal electron transfer step (2Fe-2S ? FMNC) that is accelerated by Na(+). This is the same step that is inhibited in mutants in which Na(+) uptake is blocked. NqrB-D397N is able to translocate Na(+) and Li(+), but when K(+) is introduced, no ion translocation is observed, regardless of whether Na(+) or Li(+) is present. Thus, this mutant, when it turns over in the presence of K(+), is the first, and currently the only, example of an uncoupled Na(+)-NQR. The fact the redox reaction and ion pumping become decoupled from each other only in the presence of K(+) provides a switch that promises to be a useful experimental tool. PMID:25486106

  12. Herschel* Observations of Interstellar Chloronium. II. Detections toward G29.96-0.02, W49N, W51, and W3(OH), and Determinations of the Ortho-to-Para and 35Cl/37Cl Isotopic Ratios

    NASA Astrophysics Data System (ADS)

    Neufeld, David A.; Black, John H.; Gerin, Maryvonne; Goicoechea, Javier R.; Goldsmith, Paul F.; Gry, Cecile; Gupta, Harshal; Herbst, Eric; Indriolo, Nick; Lis, Dariusz; Menten, Karl M.; Monje, Raquel; Mookerjea, Bhaswati; Persson, Carina; Schilke, Peter; Sonnentrucker, Paule; Wolfire, Mark G.

    2015-07-01

    We report additional detections of the chloronium molecular ion, H2Cl+, toward four bright submillimeter continuum sources: G29.96-0.02, W49N, W51, and W3(OH). With the use of the HIFI instrument on board the Herschel Space Observatory, we observed the {2}12-{1}01 transition of ortho-H{}235Cl+ at 781.627 GHz in absorption toward all four sources. Much of the detected absorption arises in diffuse foreground clouds that are unassociated with the background continuum sources and in which our best estimates of the N({{{H}}}2{{Cl}}+)/N({{H}}) ratio lie in the range (0.9–4.8) × {10}-9. These chloronium abundances relative to atomic hydrogen can exceed the predictions of current astrochemical models by up to a factor of 5. Toward W49N, we have also detected the {2}12-{1}01 transition of ortho-H{}237Cl+ at 780.053 GHz and the {1}11-{0}00 transition of para-H{}235Cl+ at 485.418 GHz. These observations imply {{{H}}}235Cl+/H{}237Cl+ column density ratios that are consistent with the solar system 35Cl/37Cl isotopic ratio of 3.1, and chloronium ortho-to-para ratios consistent with 3, the ratio of spin statistical weights. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  13. Chemical phase separation in carbon doped YBa 2Cu 3O 6+ x: a 63,65Cu NQR study

    NASA Astrophysics Data System (ADS)

    Grévin, B.; Berthier, Y.; Monot, I.; Wang, J.; Weiss, F.

    1997-02-01

    We report on 63,65Cu NQR spectra and nuclear spin-lattice relaxation rate (1/ T1) measurements at 4.2 K in YBa 2Cu 3O 6+ x powder samples with carbon concentrations ranging from 500 to 3000 ppm. A new NQR line appears at 30.90 MHz ( 63Cu line), the intensity of which is strongly correlated with the amount of carbon in the sample. The measurement of the spin-lattice relaxation rate for Cu corresponding to the different lines measured shows different relaxation behaviors. Furthermore a drastic change is observed for T1 between the two samples. We discuss the implications of these findings in the framework of chemical phase separation and compare to previous carbon retention studies in YBa 2Cu 3O 6+ x by other techniques.

  14. Structural and magnetic phase transitions in (Chloroanilinium) 2 CuX 4 (X = Cl, Br)

    Microsoft Academic Search

    T. Asaji

    2004-01-01

    Successive structural phase transitions of (4-ClC6H4NH3)2CuCl4, which occur in a very narrow temperature range were reinvestigated by Fourier transform nuclear quadrupole resonance (FT\\u000a NQR) measurements. The phase transitions at 275.5 and 277.0 K were confirmed. The effect of the deuteration of the ammonium\\u000a end on these transitions was studied. The35Cl NQR frequencies of organic cation were observed to decrease by

  15. Successive magnetic transition in non-centrosymmetric CeCoGe3 probed by Co-NQR

    NASA Astrophysics Data System (ADS)

    Matsumura, M.; Sato, Y.; Mizoo, M.; Kawamura, Y.; Kato, H.; Nishioka, T.

    2011-01-01

    Co-NQR measurements for non-centrosymmetric superconductor CeCoGe3 have been performed in ambient and under pressure up to 1.5 GPa to investigate the magnetic structures for the successive magnetic transition at TN1=21 K, TN2=12 K and TN3=8 K. In ambient pressure, the crystallographically equivalent one Co site becomes three sites at TN1 > T > TN2, and further becomes four sites at TN2 > T. Applying pressure at 4.2 K, the four Co sites becomes two sites above 0.3 Gpa. These Co sites acquire slightly different internal field parallel to the c-axis, consistent with the anisotropic magnetization with easy c-axis. The T-dependences of the internal fields and the spectral weights for respective sites are estimated. The magnetic structure in each phase is discussed referring to the recent results of neutron scattering.

  16. Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat

    NASA Technical Reports Server (NTRS)

    Borsa, F.; Rigamonti, A.

    1991-01-01

    La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for x ranging from 0 up to 0.3, with particular emphasis on the effect of doping on the Cu(2+) magnetic correlations and dynamics, are reviewed. In the low doping limit, x less than or equal to 0.05, the results can be interpreted consistently in terms of a simple phenomenological 'two-fluids' model whereby the effect of thermally-activated mobile O(2p) holes is the one of disrupting locally the Cu(2+) spin correlations. For x greater than or equal to 0.1, the results indicate the onset, as T approaches T(sub c)(+), of a strong coupling between Cu(2+) spins and the Fermi liquid of O(2p) holes leading to the apparent disappearance of localized Cu(2+) moment in connection with the opening of a superconducting gap.

  17. Vibrational pseudo-diffusive motion of the oxygen octahedra in La{sub 2}CuO{sub 4} and Sr doped La{sub 2}CuO{sub 4} from anelastic and {sup 139}La NQR relaxation

    SciTech Connect

    Cordero, F. [CNR, Roma (Italy)] [CNR, Roma (Italy); Campana, A.; Corti, M.; Rigamonti, A. [Unita INFM, Pavia (Italy)] [Unita INFM, Pavia (Italy); Cantelli, R. [Univ. di Roma La Sapienza (Italy). Dipt. di Fisica] [Univ. di Roma La Sapienza (Italy). Dipt. di Fisica; Ferretti, M. [Univ. di Genova (Italy). Dipt. di Chimica e Chimica Industriale] [Univ. di Genova (Italy). Dipt. di Chimica e Chimica Industriale

    1999-04-20

    The vibrational dynamics in nearly stoichiometric La{sub 2}CuO{sub 4+{delta}} has been studied by means of anelastic relaxation and by {sup 139}La NQR relaxation. Evidence of dynamical tilting of the octahedra in a double well local potential is obtained with both the experimental techniques. Anelastic relaxation at the quadrupole frequency {nu}{sub Q} {approximately} 19 MHz occurs at T {approximately} 330 K. The data are analyzed in terms of a model of pseudo-diffusive cooperative motion. The measured effective barrier is 2800 K, higher than the one of the local potential because of the cooperative character of the motion. Upon Sr doping the {sup 139}La relaxation is still dominated by the octahedra tilting waves for T > 100 K, while at low temperatures the magnetic relaxation mechanism related to Cu{sup 2+} spin fluctuation dominates. It is argued how the freezing of the tilts (occurring below 100 K in the undoped La{sub 2}CuO{sub 4}) might correspond to the formation of static stripes.

  18. Oxygen Content Dependence of 63Cu(1) NQR and Proton NMR in Hydrogen-Doped Antiferromagnetic YBa2Cu3O6+xHy

    NASA Astrophysics Data System (ADS)

    Niki, Haruo; Kano, Kikuhiro; Takase, Mitsuhiro; Majikina, Kensei; Yagasaki, Katsuma; Shinohara, Takeshi; Omori, Mamoru; Tomiyoshi, Shoichi; Akiba, Etsuo

    1998-07-01

    The oxygen content dependence of 63Cu NQR at the Cu(1) site and proton NMR have been measured in the antiferromagnetic phase of powdered samples of hydrogen-doped YBa2Cu3O6+xHy (0.07 NQR occur around 35 and 15 K, respectively. These enhancements increase with increasing oxygen concentration. The maximum values of T1-1 and T2-1 for the sample with x = 0.17 reach 200 sec-1 and more than 7 msec-1, respectively. The predominant source for the relaxation mechanism of 63Cu(l) NQR and the line broadening of 1H NMR are found to be the fluctuating magnetic field due to the staggered Cu2+ moments.

  19. Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat

    NASA Technical Reports Server (NTRS)

    Borsa, F.; Rigamonti, A.

    1990-01-01

    La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for O = to or less than 0.3 and in the temperature range 1.6 + 450 K are analyzed in terms of Cu(++) magnetic correlations and dynamics. It is described how the magnetic correlations that would result from Cu-Cu exchange are reduced by mobile charge defects related to x-doping. A comprehensive picture is given which explains satisfactorily the x and T dependence of the correlation time, of the correlation length and of the Neel temperature T(sub n)(x) as well as being consistent with known electrical resistivity and magnetic susceptibility measurements. It is discussed how, in the superconducting samples, the mobile defects also cause the decrease, for T yields T(sub c)(+) of the hyperfine Cu electron-nucleus effective interaction, leading to the coexistence of quasi-localized, reduced magnetic moments from 3d Cu electrons and mobile oxygen p-hole carriers. The temperature dependence of the effective hyperfine field around the superconducting transition yields an activation energy which could be related to the pairing energy. New specific heat measurements are also presented and discussed in terms of the above picture.

  20. NQR: a non-destructive method for studying oxygen content and defects in YBa 2Cu 3O 6+x superconducting thin films

    NASA Astrophysics Data System (ADS)

    Grévin, B.; Berthier, Y.; Pourtier, F.; Villégier, J. C.; Schmatz, U.

    1997-02-01

    NQR spectra of 63,65Cu isotopes were measured in YBa 2Cu 3O 6+x thin films at 1.4 K, which were prepared by cathodic sputtering and chemical vapor deposition. By comparison with powder spectra, we show that the films obtained by cathodic sputtering are overdoped. We discuss the possible reasons of the lower Tc commonly obtained in YBa 2Cu 3O 6+x thin films by comparison with powders and single crystals. Furthermore, we show that thin films synthesized by chemical vapor deposition could be affected by carbon retention.

  1. NMR and NQR study of the electronic and structural properties of Al-Cu-Fe and Al-Cu-Ru quasicrystals

    SciTech Connect

    Shastri, A.; Borsa, F.; Torgeson, D.R.; Shield, J.E.; Goldman, A.I. (Ames Laboratory, U.S. Department of Energy and Department of Physics Astronomy, Iowa State University, Ames, Iowa 50011 (United States))

    1994-12-01

    [sup 27]Al and [sup 63,65]Cu NMR is reported for powdered stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and crystalline approximants, and for an Al-Pd-Mn single-grain quasicrystal. [sup 27]Al NQR spectra at 4.2 K were observed in Al-Cu-Fe and Al-Cu-Ru samples. From quadrupole-perturbed NMR spectra at different magnetic fields, and from zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant successfully explained the observed NQR spectra. The average local gradient is largely determined by the [ital p]-electron wave function at the Al site, while the width of the distribution is due to EFG lattice contribution. Comparison of [sup 63]Cu and [sup 27]Al NMR shows the EFG distribution at the two sites is similar, but the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more [ital s]-type wave function of the conduction electrons. Overall spread of EFG values is well reproduced by calculation based on the approximant. However, the experimental spectra indicate a much larger number of nonequivalent sites when compared with the simulated NQR spectra based on the 1/1 approximant. The short-range, local chemical order is well represented by the approximant, but differences in coordination must be included at intermediate range in the quasicrystal. Measured [sup 27]Al Knight shift, magnetic susceptibility, and nuclear spin-lattice relaxation time as a function of temperature indicate reduced density of states at the Fermi level by a factor of 7 or 8 from the value in Al metal, consistent with the notion of a pseudogap for these quasicrystals. No differences in measured parameters were detected as a function of composition of the quasicrystalline alloys.

  2. Emission spectroscopy, harmonic vibrational frequencies, and improved ground state structures of jet-cooled monochloro- and monobromosilylene (HSiCl and HSiBr)

    Microsoft Academic Search

    David A. Hostutler; Nicholas Ndiege; Dennis J. Clouthier; Steven W. Pauls

    2001-01-01

    The ground state harmonic frequencies of gas phase H\\/DSi35Cl and H\\/DSi79Br have been determined by exciting single vibronic bands of the A~ 1A''-X~ 1A' electronic transition and recording the dispersed fluorescence. The jet-cooled radicals were produced in a pulsed discharge jet using H\\/DSiX3 (X=Cl or Br) precursors. The emission data were fitted to an anharmonic model and a normal coordinate

  3. Emission spectroscopy, harmonic vibrational frequencies, and improved ground state structures of jet-cooled monochloro- and monobromosilylene (HSiCl and HSiBr)

    Microsoft Academic Search

    David A. Hostutler; Nicholas Ndiege; Dennis J. Clouthier; Steven W. Pauls

    2001-01-01

    The ground state harmonic frequencies of gas phase H\\/DSi35Cl and H\\/DSi79Br have been determined by exciting single vibronic bands of the à 1A?–X˜ 1A? electronic transition and recording the dispersed fluorescence. The jet-cooled radicals were produced in a pulsed discharge jet using H\\/DSiX3(X=Cl or Br) precursors. The emission data were fitted to an anharmonic model and a normal coordinate analysis

  4. Correlated Spin Dynamics and Phase Transitions in Pure and in Disordered 2D S = 1/2 Antiferromagnets: Insights from NMR-NQR

    NASA Astrophysics Data System (ADS)

    Rigamonti, A.; Carretta, P.; Papinutto, N.

    A recall of the phase diagram for two-dimensional quantum Heisenberg antiferromagnets (2DQHAF) and of the main issues involving phase transitions and spin dynamics in these systems is first given. After a pedagogical description of the basic aspects for the NMR-NQR relaxation rates in terms of amplitudes and decay rates of spin fluctuations, the problem of the temperature dependence of the correlation length in prototype, pure 2DQHAF (CFTD and La2CuO4) is addressed. Then spin- and charge-doped systems (Zn/Mg for Cu and Sr for La substitutions in La2CuO4) are considered and the effects on the spin stiffness, on the correlation length and on the staggered Cu2+ magnetic moment are reported, in particular near the percolation threshold. A critical outline of the properties of the cluster spin glass phase in Sr- doped La2CuO4 is given. Finally the results of a 63Cu NQR-NMR relaxation study around the quantum critical point (in CeCu6-xAux) are presented. It is pointed out how the 2D response function with anomalous exponent and energy/ temperature scaling indicated by neutron scattering is basically confirmed, while the 63Cu relaxation measurements reveal novel effects involving low-energy spin excitations and the role of an external magnetic field.

  5. NQR study of ternary chalcogenides A3BX3, ABX2, and ABX where A = Cu, Ag, or TI, B = As or Sb, and X = S or Se

    Microsoft Academic Search

    T. J. Bastow; H. J. Whitfield

    1981-01-01

    121Sb, 123Sb, 75As, 63Cu, and 65Cu NQR resonances are reported for CuSbSe2, Tl3SbSe3, Tl3SbS3, Tl3AsS3, Tl3AsSe3, Ag3AsSe3, TlSbS2, CuAsS, AgAsS, and Cu5SbS3I2. Tl3SbSe3 is an incongruently melting compound not observed in an earlier phase-diagram study of the pseudobinary system Tl2Se-Sb2Se3. For isostructural arsenic and antimony chalcogenides the ratio of 75As to 121Sb quadrupole coupling constants is 0.42, and for the

  6. NMR-NQR study of the crossover from the spin-glass to the superconducting phase in La{sub 2{minus}x}Sr{sub x}CuO{sub 4}

    SciTech Connect

    Julien, M.H.; Carretta, P.; Borsa, F.; Rigamonti, A. [Unita INFM di Pavia (Italy). Dipt. di Fisica] [Unita INFM di Pavia (Italy). Dipt. di Fisica

    1999-04-20

    {sup 139}La and {sup 63}Cu NQR relaxation rates are used to obtain insights on the effects of itinerant holes on the magnetic in-plane correlation length, for x {le} 0.04 in La{sub 2{minus}x}Sr{sub x}CuO{sub 4}. For these concentrations, corresponding to spin-glass behavior at low temperature, evidence for the microsegregation of holes along stripes is presented. Preliminary relaxation results for an amount of Sr doping leading to superconductivity are also presented and discussed in terms of the crossover from the spin-glass to the underdoped superconducting regime: for x = 0.06 a slowing down of spin fluctuations is evidenced and superconductivity is found to coexist with spin-freezing.

  7. Spin dynamics in a two-dimensional disordered S=(1)/(2) Heisenberg paramagnet from {sup 63}Cu NQR relaxation in Zn-doped La{sub 2}CuO{sub 4}

    SciTech Connect

    Carretta, P.; Rigamonti, A.; Sala, R. [Department of Physics A. Volta, Unita INFM and Sezione INFN di Pavia, Via Bassi, 6, 27100-I Pavia (Italy)] [Department of Physics A. Volta, Unita INFM and Sezione INFN di Pavia, Via Bassi, 6, 27100-I Pavia (Italy)

    1997-02-01

    {sup 63}Cu NQR T{sub 1} and T{sub 2} relaxation measurements in La{sub 2}Cu{sub 1{minus}x}Zn{sub x}O{sub 4}, for 0{le}x{le}0.11 and in the temperature range T{sub N}{le}T{le}900 K, are presented. The results are used to derive insights into the Cu{sup 2+} correlated spin dynamics in the paramagnetic phase of the S=(1)/(2) two-dimensional (2D) Heisenberg (H) antiferromagnets (AF), and into the disorder effects associated with the spin vacancy due to Zn{sup 2+} (S=0) for Cu{sup 2+} substitution. In particular, by using scaling arguments for the static generalized susceptibility, {chi}({rvec q},0), and for the decay rate, {Gamma}{sub {rvec q}}, of the normal excitations, T{sub 2} and T{sub 1} are related to the in-plane correlation length {xi}{sub 2D}(x,T) and its dependence on temperature and Zn doping, x, is extracted. The experimental findings are analyzed in light of the quantum critical and renormalized classical behaviors for {xi}{sub 2D} predicted by recent theories for S=1/2 HAF on square lattices. It is shown that up to T{approx_equal}900 K, {xi}{sub 2D} is consistent with the assumption of a renormalized classical regime, in agreement with recent neutron scattering results and at variance with previous interpretations of the NQR data. It is discussed how Zn affects {xi}{sub 2D} through the modification in the spin stiffness and comparison with the disorder induced by itinerant extra holes is made.

  8. Frequency Modulation

    Microsoft Academic Search

    B. Van Der Pol

    1930-01-01

    The differential equation of a frequency modulated transmitter is considered and the expression of the current as a function of time is derived. Frequency analysis of this function is made for two specific cases, (A) sinusoidal frequency modulation (telephony) and (B), right-angle frequency modulation (telegraphy with \\

  9. Frequency curves

    USGS Publications Warehouse

    Riggs, H.C.

    1968-01-01

    This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

  10. Superconducting fluctuations and {sup 63}Cu NQR-NMR relaxation in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}: Effect of magnetic field and a test for the pairing-state symmetry

    SciTech Connect

    Carretta, P. [Department of Physics ``A. Volta,`` Sezione di Pavia, Istituto Nazionale di Fisica Nucleare and Unita Instituto Nazionale di Fisica della Materia, University of Pavia, Via Bassi 6, I-27100, Pavia (Italy)] [Department of Physics ``A. Volta,`` Sezione di Pavia, Istituto Nazionale di Fisica Nucleare and Unita Instituto Nazionale di Fisica della Materia, University of Pavia, Via Bassi 6, I-27100, Pavia (Italy); Livanov, D.V. [Department of Theoretical Physics, Moscow Institute of Steel and Alloys, 117936 Moscow (Russia)] [Department of Theoretical Physics, Moscow Institute of Steel and Alloys, 117936 Moscow (Russia); Rigamonti, A. [Department of Physics ``A. Volta,`` Sezione di Pavia, Istituto Nazionale di Fisica Nucleare and Unita Instituto Nazionale di Fisica della Materia, University of Pavia, Via Bassi 6, I-27100, Pavia (Italy)] [Department of Physics ``A. Volta,`` Sezione di Pavia, Istituto Nazionale di Fisica Nucleare and Unita Instituto Nazionale di Fisica della Materia, University of Pavia, Via Bassi 6, I-27100, Pavia (Italy); Varlamov, A.A. [Department of Theoretical Physics, Moscow Institute of Steel and Alloys, 117936 Moscow (Russia)] [Department of Theoretical Physics, Moscow Institute of Steel and Alloys, 117936 Moscow (Russia); [Laboratorium ``Forum,`` Instituto Nazionale di Fisica della Materia, Department of Physics, University of Florence, Florence (Italy)

    1996-10-01

    Evidence is presented of superconducting fluctuations in the {sup 63}Cu NQR-NMR relaxation rate in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, as obtained from a careful comparison of measurements carried out in the absence and in the presence of a field parallel to the {ital c} axis. It is shown that the field causes a reduction of the relaxation rate {ital W} in a range of about 10 K above {ital T}{sub {ital c}}. This effect is related to the suppression by the magnetic field of the phase-sensitive positive Maki-Thompson contribution while the negative contribution from the DOS fluctuations is almost field independent. Furthermore, it is argued how the fluctuation effects on {ital W} can be used to discuss the pairing state symmetry, at variance with the insensitivity of the transport measurements. It is pointed out that the existence of the Maki-Thompson contribution to {ital W} evidences an {ital s}-wave symmetry component for the pairing in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. {copyright} {ital 1996 The American Physical Society.}

  11. Landmine detection with nuclear quadrupole resonance

    Microsoft Academic Search

    Yingyi Tan; Stacy L. Tantum; Leslie M. Collins

    2002-01-01

    Nuclear quadrupole resonance (NQR) technology for the detection of explosives is of crucial importance in an increasing number of applications. For landmine detection, NQR has proven to be highly effective if the NQR sensor is not exposed to radio frequency interference (RFI). Since strong nonstationary RFI in the field is unavoidable, a robust detection method is required. With the aid

  12. Nuclear magnetic resonance with dc SQUID (Super-conducting QUantum Interference Device) preamplifiers

    SciTech Connect

    Fan, N.Q.; Heaney, M.B.; Clark, J.; Newitt, D.; Wald, L.; Hahn, E.L.; Bierlecki, A.; Pines, A.

    1988-08-01

    Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclear spin noise'', the emission of photons by /sup 35/Cl nuclei in a state of zero polarization. In the more conventional experiments in which one applies a large rf pulse to the spins, a Q-spoiler, consisting of a series array of Josephson junctions, is used to reduce the Q of the input circuit to a very low value during the pulse. The Q-spoiler enables the circuit to recover quickly after the pulse, and has been used in an NQR experiment to achieve a sensitivity of about 2 /times/ 10/sup 16/ nuclear Bohr magnetons in a single free precession signal with a bandwidth of 10 kHz. In a third experiment, a sample containing /sup 35/Cl nuclei was placed in a capacitor and the signal detected electrically using a tuned SQUID amplifier and Q-spoiler. In this way, the electrical polarization induced by the precessing Cl nuclear quadrupole moments was detected: this is the inverse of the Stark effect in NQR. Two experiments involving NMR have been carried out. In the first, the 30 MHz resonance in /sup 119/Sn nuclei is detected with a tuned amplifier and Q-spoiler, and a single pulse resolution of 10/sup 18/ nuclear Bohr magnetons in a bandwidth of 25 kHz has been achieved. For the second, a low frequency NMR system has been developed that uses an untuned input circuit coupled to the SQUID. The resonance in /sup 195/Pt nuclei has been observed at 55 kHz in a field of 60 gauss. 23 refs., 11 figs.

  13. ¹?N nuclear quadrupole resonance study of polymorphism in famotidine.

    PubMed

    Lu?nik, Janko; Pirnat, Janez; Jazbinšek, Vojko; Lavri?, Zoran; Žagar, Veselko; Sr?i?, Stane; Seliger, Janez; Trontelj, Zvonko

    2014-09-01

    (14)N nuclear quadrupole resonance (NQR) in two known polymorphs of famotidine was measured. At room temperature, seven quadrupolar sets of transition frequencies (?(+), ?(-), and ?(0)) corresponding to seven different nitrogen sites in the crystal structure of each of the two polymorphs were found. This confirms the expected ability of NQR to distinguish polymorph B from its analog A. NQR can also measure their ratio in a solid mixture and in the final dosage form, that is, a tablet. The NQR frequencies, line shapes, and tentative assignation to all seven molecular (14)N atoms were obtained. Unravelment of these two entangled NQR spectra presents a valuable contribution to the NQR database and enables studies of some possible correlations therein. Moreover, nondestructive (14)N NQR studies of commercial famotidine tablets can reveal some details of the drug fabrication process connected with compression. PMID:24668530

  14. NMR and NQR parameters of ethanol crystal

    E-print Network

    Milinkovic, M

    2012-01-01

    Electric field gradients and chemical shielding tensors of the stable monoclinic crystal phase of ethanol are computed. The projector-augmented wave (PAW) and gauge-including projector-augmented wave (GIPAW) models in the periodic plane-wave density functional theory are used. The crystal data from X-ray measurements, as well as the structures where either all atomic, or only hydrogen atom positions are optimized in the density functional theory are analyzed. These structural models are also studied by including the semi-empirical Van der Waals correction to the density functional theory. Infrared spectra of these five crystal models are calculated.

  15. Experimental implementation of quantum information processing by Zeeman-perturbed nuclear quadrupole resonance

    NASA Astrophysics Data System (ADS)

    Teles, João; Rivera-Ascona, Christian; Polli, Roberson S.; Oliveira-Silva, Rodrigo; Vidoto, Edson L. G.; Andreeta, José P.; Bonagamba, Tito J.

    2015-03-01

    Nuclear magnetic resonance (NMR) has been widely used in the context of quantum information processing (QIP). However, despite the great similarities between NMR and nuclear quadrupole resonance (NQR), no experimental implementation for QIP using NQR has been reported. We describe the implementation of basic quantum gates and their applications on the creation and manipulation of pseudopure states using linearly polarized radiofrequency pulses under static magnetic field perturbation. The NQR quantum operations were implemented using a single-crystal sample of {KClO}3 and observing ^{35}{Cl} nuclei, which possess spin 3/2 and give rise to a two-qubit system. The results are very promising and indicate that NQR can be successfully used for performing fundamental experiments in QIP. One advantage of NQR in comparison with NMR is that the main interaction is internal to the sample, which makes the system more compact, lowering its cost and making it easier to be miniaturized to solid-state devices. Furthermore, as an example, the study of squeezed spin states could receive relevant contributions from NQR.

  16. Frequency Measurement & Analysis Service

    E-print Network

    Magee, Joseph W.

    NIST Frequency Measurement & Analysis Service #12;A Complete Solution To All Frequency Measurement & Calibration Problems The NIST Frequency Measurement and Analysis Service makes it easy to measure and calibrate any quartz, rubidium, or cesium frequency standard. All measurements are made automatically

  17. 38 High Frequency Electronics High Frequency Design

    E-print Network

    Popovic, Zoya

    38 High Frequency Electronics High Frequency Design RF POWER AMPLIFIERS RF and Microwave Power, and predistortion. 8a. FEEDBACK Feedback linearization can be applied either directly around the RF amplifier (RF the amplifier is fed back to, and subtracted from, the RF-input signal without detection or down- conversion

  18. Frequency stability review

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    1987-01-01

    Certain aspects of the description and measurement of oscillator stability are treated. Topics covered are time and frequency deviations, Allan variance, the zero-crossing counter measurement technique, frequency drift removal, and the three-cornered hat.

  19. Variable Frequency Pump Drives 

    E-print Network

    Karassik, I. J.; Petraccaro, L. L.; McGuire, J. T.

    1986-01-01

    VARIABLE FREQUENCY PUMP DRIVES Igor J. Karassik, L. L. Petraccaro &J. T. McGuire Worthington Pump Division, Dresser Industries Inc. Mountainside, N. J. Variable frequency drive represents a major milestone in the evolution of centrifugal...

  20. Generalized frequency modulation

    E-print Network

    Torres, Wade Patrick

    2001-01-01

    In frequency modulation (FM) systems, a continuous-time information signal is modulated onto a sinusoidal carrier wave by using the information signal to modulate the frequency of the carrier wave. In this thesis, a more ...

  1. Frequency comb swept lasers

    E-print Network

    Tsai, Tsung-Han

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep ...

  2. Radio frequency spectrum management

    Microsoft Academic Search

    E. J. Sujdak Jr.

    1980-01-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC),

  3. Eastern Frequency Response Study

    SciTech Connect

    Miller, N.W.; Shao, M.; Pajic, S.; D'Aquila, R.

    2013-05-01

    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  4. Powerline frequency measurement

    Microsoft Academic Search

    R. B. Rochelle; R. W. Rochelle; R. K. Adams

    1986-01-01

    A microcomputer has been used to measure powerline frequency with a precision of six decimal digits (0.0001 Hz) using an averaging time of 3 to 4 min. The algorithm for frequency measurement requires no multiplication or division operations, so a very simple microprocessor can be used. The frequency measurement is sensitive enough to permit detection of small, controlled changes in

  5. INCREASING MILKING FREQUENCY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Milk Yield increases by a fixed amount due to increased milking frequency and not by some percentage of previous milk yields. Six times-a-day milking frequency from calving through six weeks post-partum results in not only increased production during the period of high frequency milking by also in ...

  6. Frequency detector for fast frequency lock of digital PLLs

    E-print Network

    Moon, Un-Ku

    Frequency detector for fast frequency lock of digital PLLs V. Kratyuk, P.K. Hanumolu, U.-K. Moon and K. Mayaram A new frequency detector, which allows for a fast frequency lock of phase-locked loops the frequency difference. The proposed frequency detector provides frequency difference informa- tion at each

  7. Frequency selective infrared sensors

    SciTech Connect

    Davids, Paul; Peters, David W

    2014-11-25

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  8. Regional flood frequency analysis

    SciTech Connect

    Singh, V.P.

    1987-01-01

    This book, the fourth of a four volume set, contains five sections encompassing major aspects of regional flood frequency analysis. Each section starts usually with an invited state-of-the-art paper followed by contributed papers. The first section provides an assessment of regional flood frequency analysis. Methods for performing regional frequency analysis for ungaged watersheds are presented in Section 2. More discussion on regional frequency analysis is provided in Section 3. Selection and comparison of regional frequency methods are dealt with in Section 4; these are of great interest to the user. Increasing attention is being focused these days on paleohydrologic flood analysis. This topic is covered in Section 5.

  9. Femtosecond Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Udem, Thomas; Holzwarth, Ronald; Hänsch, Theodor

    A laser frequency comb allows the conversion of the very rapid oscillations of visible light down to frequencies that can be handled with conventional electronics. This has enabled the most precise laser spectroscopy experiments yet, to determine fundamental constants and to limit their possible slow drift. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks. Frequency combs are also used to calibrate astronomical spectrographs and might reach an accuracy that is sufficient to observe the change of the expansion rate of the universe in real time.

  10. Frequency Bin Entangled Photons

    E-print Network

    L. Olislager; J. Cussey; A. T. Nguyen; Ph. Emplit; S. Massar; J. -M. Merolla; K. Phan Huy

    2010-02-10

    A monochromatic laser pumping a parametric down conversion crystal generates frequency entangled photon pairs. We study this experimentally by addressing such frequency entangled photons at telecommunication wavelengths (around 1550 nm) with fiber optics components such as electro-optic phase modulators and narrow band frequency filters. The theory underlying our approach is developed by introducing the notion of frequency bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate a Bell inequality adapted to our setup by more than five standard deviations.

  11. Radio frequency detection assembly and method for detecting radio frequencies

    DOEpatents

    Cown, Steven H. (Rigby, ID); Derr, Kurt Warren (Idaho Falls, ID)

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  12. Image restoration using fast Fourier and wavelet transforms

    NASA Astrophysics Data System (ADS)

    Harrod, William J.; Nagy, James G.; Plemmons, Robert J.

    1994-02-01

    Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.

  13. Narcotics and explosives detection by 14N pure nuclear quadrupole resonance

    NASA Astrophysics Data System (ADS)

    Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.

    1994-03-01

    Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.

  14. Frequency dependent squeezed light at audio frequencies

    NASA Astrophysics Data System (ADS)

    Miller, John

    2015-04-01

    Following successful implementation in the previous generation of instruments, squeezed states of light represent a proven technology for the reduction of quantum noise in ground-based interferometric gravitational-wave detectors. As a result of lower noise and increased circulating power, the current generation of detectors places one further demand on this technique - that the orientation of the squeezed ellipse be rotated as function of frequency. This extension allows previously negligible quantum radiation pressure noise to be mitigated in addition to quantum shot noise. I will present the results of an experiment which performs the appropriate rotation by reflecting the squeezed state from a detuned high-finesse optical cavity, demonstrating frequency dependent squeezing at audio frequencies for the first time and paving the way for broadband quantum noise reduction in Advanced LIGO. Further, I will indicate how a realistic implementation of this approach will impact Advanced LIGO both alone and in combination with other potential upgrades.

  15. Femtosecond optical frequency combs

    NASA Astrophysics Data System (ADS)

    Udem, Th.; Holzwarth, R.; Hänsch, Th.

    2009-06-01

    A laser frequency comb allows the conversion of the very rapid oscillations of visible light of some 100’s of THz down to frequencies that can be handled with conventional electronics. This capability has enabled the most precise laser spectroscopy experiments yet that allowed to test quantum electrodynamics, to determine fundamental constants and to search for possible slow changes of these constants. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks, that are now outperforming even the best cesium atomic clocks. In future direct frequency comb spectroscopy might enable high resolution laser spectroscopy in the extreme ultraviolet for the first time. Frequency combs are also used to calibrate astronomical spectrographs and might reach an accuracy that is sufficient to observe the expansion of the universe in real time.

  16. Transients in Frequency Modulation

    Microsoft Academic Search

    H. Salinger

    1942-01-01

    In a frequency-modulation system, a sudden jump in carrier frequency corresponding to a Heaviside unit signal will result in a transient depending on the receiving-filter bandwidth. If this bandwith exceeds twice the maximum frequency swing, the shape and duration of the transient is shown to be about the same as in an amplitude-modulation system with the same bandwidth; for narrower

  17. Variable Frequency Pump Drives

    E-print Network

    Karassik, I. J.; Petraccaro, L. L.; McGuire, J. T.

    VARIABLE FREQUENCY PUMP DRIVES Igor J. Karassik, L. L. Petraccaro &J. T. McGuire Worthington Pump Division, Dresser Industries Inc. Mountainside, N. J. Variable frequency drive represents a major milestone in the evolution of centrifugal... pumps and their application. The fundamentals of variable speed centrifugal pump operation are reviewed, then the advantages and evaluation approaches peculiar to variable frequency drive outlined. In addition to the immediate advantages available...

  18. Frequency selective terahertz retroreflectors

    NASA Astrophysics Data System (ADS)

    Williams, Richard James

    The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.

  19. Nonlinear Frequency Compression

    PubMed Central

    Scollie, Susan; Glista, Danielle; Seelisch, Andreas

    2013-01-01

    Frequency lowering technologies offer an alternative amplification solution for severe to profound high frequency hearing losses. While frequency lowering technologies may improve audibility of high frequency sounds, the very nature of this processing can affect the perceived sound quality. This article reports the results from two studies that investigated the impact of a nonlinear frequency compression (NFC) algorithm on perceived sound quality. In the first study, the cutoff frequency and compression ratio parameters of the NFC algorithm were varied, and their effect on the speech quality was measured subjectively with 12 normal hearing adults, 12 normal hearing children, 13 hearing impaired adults, and 9 hearing impaired children. In the second study, 12 normal hearing and 8 hearing impaired adult listeners rated the quality of speech in quiet, speech in noise, and music after processing with a different set of NFC parameters. Results showed that the cutoff frequency parameter had more impact on sound quality ratings than the compression ratio, and that the hearing impaired adults were more tolerant to increased frequency compression than normal hearing adults. No statistically significant differences were found in the sound quality ratings of speech-in-noise and music stimuli processed through various NFC settings by hearing impaired listeners. These findings suggest that there may be an acceptable range of NFC settings for hearing impaired individuals where sound quality is not adversely affected. These results may assist an Audiologist in clinical NFC hearing aid fittings for achieving a balance between high frequency audibility and sound quality. PMID:23539261

  20. Frequency Response Analysis Tool

    SciTech Connect

    Etingov, Pavel V.; Kosterev, Dmitry; Dai, T.

    2014-12-31

    Frequency response has received a lot of attention in recent years at the national level, which culminated in the development and approval of North American Electricity Reliability Corporation (NERC) BAL-003-1 Frequency Response and Frequency Bias Setting Reliability Standard. This report is prepared to describe the details of the work conducted by Pacific Northwest National Laboratory (PNNL) in collaboration with the Bonneville Power Administration and Western Electricity Coordinating Council (WECC) Joint Synchronized Information Subcommittee (JSIS) to develop a frequency response analysis tool (FRAT). The document provides the details on the methodology and main features of the FRAT. The tool manages the database of under-frequency events and calculates the frequency response baseline. Frequency response calculations are consistent with frequency response measure (FRM) in NERC BAL-003-1 for an interconnection and balancing authority. The FRAT can use both phasor measurement unit (PMU) data, where available, and supervisory control and data acquisition (SCADA) data. The tool is also capable of automatically generating NERC Frequency Response Survey (FRS) forms required by BAL-003-1 Standard.

  1. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D. (Orinda, CA); Fugitt, Jock A. (Berkeley, CA); Howard, Donald R. (Danville, CA)

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  2. Ultrastable automatic frequency control

    NASA Technical Reports Server (NTRS)

    Sabourin, D. J.; Furiga, A.

    1981-01-01

    Center frequency of wideband AFC circuit drifts only hundredths of percent per day. Since circuit responds only to slow frequency drifts and modulation signal has high-pass characteristics, AFC does not interfere with normal FM operation. Stable oscillator, reset circuit, and pulse generator constitute time-averaging discriminator; digital counter in pulse generator replaces usual monostable multivibrator.

  3. Radar frequency radiation

    Microsoft Academic Search

    E. Malowicki

    1981-01-01

    A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar.

  4. Wavelet frequency decomposition method

    NASA Astrophysics Data System (ADS)

    Rieder, Andreas; Wells, Raymond O., Jr.; Zhou, Xiaodong

    1994-03-01

    A wavelet variation of the frequency decomposition multigrid method of Hackbusch is presented. The perfect reconstruction property of the wavelet system enable us to perform the convergence analysis of the frequency decomposition method. Some applications of this method are also presented.

  5. Dialysis dose and frequency

    Microsoft Academic Search

    Francesco Locatelli; Umberto Buoncristiani; Bernard Canaud; Hans Kohler; Thierry Petitclerc; Pietro Zucchelli; Ospedale A. Manzoni; CHU Montpellier; Schwerpunkt Nephrologie

    2004-01-01

    Background. From the beginning of the dialysis era, the issue of optimal dialysis dose and frequency has been a central topic in the delivery of dialysis treatment. Methods. We undertook a discussion to achieve a consensus on key points relating to dialysis dose and frequency, focusing on the relationships with clinical and patient outcomes. Results. Traditionally, dialysis adequacy has been

  6. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  7. Optical frequency metrology

    Microsoft Academic Search

    Th. Udem; R. Holzwarth; T. W. Hänsch

    2002-01-01

    Extremely narrow optical resonances in cold atoms or single trapped ions can be measured with high resolution. A laser locked to such a narrow optical resonance could serve as a highly stable oscillator for an all-optical atomic clock. However, until recently there was no reliable clockwork mechanism that could count optical frequencies of hundreds of terahertz. Techniques using femtosecond-laser frequency

  8. The characteristic Rossby frequency

    NASA Technical Reports Server (NTRS)

    Straus, David M.; Lindzen, Richard S.; Dasilva, Arlindo Moraes

    1987-01-01

    The characteristic Rossby frequency is defined for a fixed zonal wavenumber perturbation as the variational integral of the Rayleigh-Ritz method. It is a measure of the time scale of the disturbance. For a disturbance which locally has the shape of an eigenfunction but is not global in extent, the characteristic Rossby frequency is very close to the true eigenvalue, and additionally remains unchanged under linear inviscid dynamics. Results are presented for the shallow water equations, both with and without a mean zonal wind. The characteristic Rossby frequency of a wavenumber 1 perturbation having the shape of the second symmetric Rossby mode but confined to the Northern Hemisphere is close to the corresponding Rossby frequency. This finding is helpful in understanding the behavior of the observed wavenumber 1 pattern of January 1979, which propagated westward with nearly the pure Rossby frequency but was discernible only in the Northern Hemisphere (as discussed by Daley and Williamson).

  9. Frequency comb swept lasers

    PubMed Central

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

    2010-01-01

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~?1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have ?10dB and ?5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

  10. Roll Out the Frequency

    NSDL National Science Digital Library

    2012-08-03

    In this activity, students use marks on a 1.4 m strip of paper to simulate light wave frequencies and measure the time it takes for different frequencies to pass through the "viewer" made from a manila folder. Students learn that different colors of light have different wave frequencies. The resource is part of the teacher's guide accompanying the video, NASA Why Files: The Case of the Mysterious Red Light. Lesson objectives supported by the video, additional resources, teaching tips and an answer sheet are included in the teacher's guide.

  11. Name That Frequency

    NSDL National Science Digital Library

    2012-06-26

    This activity was designed for blind learners, but all types of learners can model how vibrating particles, such as in a sound wave, bump into other particles causing them to vibrate, and that the vibrations travel. The chain reaction of sound waves will be demonstrated using old video cassettes (in a way similar to a dominoes game). Learners with visual impairments as well as sighted learners will have the chance to create tactile diagrams of varying wave frequencies. The activity includes setting up the row of tapes at various “frequencies,” closer together for higher frequency, farther apart for lower.

  12. Squeezing frequency combs

    E-print Network

    German J. De Valcarcel; Giuseppe Patera; Nicolas Treps; Claude Fabre

    2006-05-15

    We have developed the full theory of a synchronously pumped type I optical parametric oscillator (SPOPO). We derive expressions for the oscillation threshold and the characteristics of the generated mode-locked signal beam. We calculate the output quantum fluctuations of the device, and find that, in the degenerate case (coincident signal and idler set of frequencies), perfect squeezing is obtained when one approaches threshold from below for a well defined "super-mode', or frequency comb, consisting of a coherent linear superposition of signal modes of different frequencies which are resonant in the cavity.

  13. Quantum frequency downconversion experiment

    E-print Network

    Hiroki Takesue

    2010-06-02

    We report the first quantum frequency downconversion experiment. Using the difference frequency generation process in a periodically poled lithium niobate waveguide, we successfully observed the phase-preserved frequency downconversion of a coherent pulse train with an average photon number per pulse of $<$1, from the 0.7-$\\mu$m visible wavelength band to the 1.3-$\\mu$m telecom band. We expect this technology to become an important tool for flexible photonic quantum networking, including the realization of quantum repeater systems over optical fiber using atom-photon entanglement sources for the visible wavelength bands.

  14. Frequency Domain Controller Design 9.2 Frequency Response Characteristics

    E-print Network

    Gajic, Zoran

    Frequency Domain Controller Design 9.2 Frequency Response Characteristics The frequency transfer functions are defined for sinusoidal inputs having all possible frequencies . They are obtained from (9.1) by simply setting , that is (9.1) Typical diagrams for the magnitude and phase of the open-loop frequency

  15. DAVLL with Frequency Markers

    NASA Astrophysics Data System (ADS)

    Narducci, Frank A.; Elliott, Ethan R.; Lehman, Christopher J.

    2007-06-01

    The Dichroic Atomic Vapor Laser Lock (DAVLL) technique for locking lasers to atomic transitions has the advantage of a large capture range but the disadvantage that there are no convenient frequency markers to know very well where a laser is tuned relative to atomic transitions. On the other hand, saturated absorption spectroscopy has the frequency markers, but not the large capture range. We present a simple, compact scheme that combines the advantages of both techniques. Spectral measurements in all four Doppler absorption lines of Rubidium will be presented, showing a very rich structure with multiple features that can be used either as frequency references or additional frequency locking. The underlying physics of these features are sorted out and identified. Of particular use to the laser-cooling community is a large cross-over resonance that occurs right at the location of the cooling resonance independent of the strength of the magnetic field used to generate the DAVLL signal.

  16. Graphene Frequency Multipliers

    E-print Network

    Wang, Han

    In this letter, the ambipolar transport properties of graphene flakes have been used to fabricate full-wave signal rectifiers and frequency-doubling devices. By correctly biasing an ambipolar graphene field-effect transistor ...

  17. Radio Link Frequency Assignment

    Microsoft Academic Search

    Bertrand Cabon; Simon De Givry; Lionel Lobjois; Thomas Schiex; Joost P. Warners

    1999-01-01

    Abstract: The problem of radio frequency assignment is to provide communication channelsfrom limited spectral resources whilst keeping to a minimum the interference suered by thosewhishing to communicate in a given radio communication network. This problem is a combinatorial(NP-hard) optimization problem. In 1993, the CELAR (the French \\\\Centre d'Electronique del'Armement") built a suite of simplied versions of Radio Link Frequency Assignment

  18. High-Frequency Chromizing

    Microsoft Academic Search

    I. A. Menzies; D. Mortimer

    1962-01-01

    IN recent years new processes involving the use of a medium containing 75 per cent chromium with 25 per cent cryolite and high-frequency heating have been developed for the chromizing of ferrous and non-ferrous metals1-4. Generators operating with frequencies of 3-3.5 Mc\\/sec have been used, and it has been claimed that coatings which would require the treatment of mild steel

  19. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (inventor); Graham, Lloyd J. (inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  20. Characterization of Frequency Stability

    Microsoft Academic Search

    James A. Barnes; Andrew R. Chi; Leonard S. Cutler; Daniel J. Healey; David B. Leeson; Thomas E. McGunigal; James A. Mullen; Warren L. Smith; Richard L. Sydnor; Robert F. C. Vessot; Gernot M. R. Winkler

    1971-01-01

    Consider a signal generator whose instantaneous output voltage V(t) may be written as V(t) = [V0 + ??(t)] sin [2??v0t + s(t)] where V0 and v0 are the nominal amplitude and frequency, respectively, of the output. Provided that ??(t) and ??(t) = (d??\\/(dt) are sufficiently small for all time t, one may define the fractional instantaneous frequency deviation from nominal

  1. Twirling Rope Frequency

    NSDL National Science Digital Library

    Twin Cities Public Television, Inc.

    2006-01-01

    In this activity (page 1 of the PDF), learners will stand twelve feet apart swinging a rope at the slowest tempo possible while someone uses a stopwatch to record the number of twirls per minute. Based on this frequency, learners will predict whether the tempo will speed up or slow down when the twirlers move closer to each other. Use this activity to introduce the terms frequency and period. Relates to the linked video, DragonflyTV: Double Dutch.

  2. Photonic Frequency Upconversion by SBS-Based Frequency Tripling

    Microsoft Academic Search

    Chul Soo Park; Chung Ghiu Lee; Chang-Soo Park

    2007-01-01

    We describe a photonic frequency upconversion by the stimulated Brillouin scattering (SBS)-based frequency tripling method. The frequency tripling and the photonic frequency upconversion are simultaneously obtained by incorporating a dual-electrode electrooptic modulator (EOM) and a single optical source. Each electrode of the dual-electrode EOM is driven by both an intermediate frequency (IF) and a microwave radio frequency (RF) signal, respectively,

  3. Single frequency multitransmitter telemetry

    NASA Astrophysics Data System (ADS)

    Carreno, Victor A.

    1986-12-01

    The invention relates to a single frequency multitransmitter telemetry system that will deliver a substantial amount of data at low cost. The invention consists essentially of a plurality of sensor transmitter units at different locations, with individual signal conditioning and logic, which send sampled data signals to a single receiver. The transmitters operate independently on the same frequency in a frequency shift keying modulation system and are not synchronized to the receiver. The problem of reception of data from more than one transmitter simultaneously is solved by discarding the data - when there is overlap of data from two or more transmitters, the data is discarded and when there is no overlap the data is retained. The invention utilizes a unique overlap detection technique to determine if data should be retained or discarded. When data is received from a transmitter, it goes into a shift register.

  4. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  5. Hg(+) Frequency Standards

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2000-01-01

    In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

  6. Using Suffix Arrays to Compute Term Frequency and Document Frequency

    E-print Network

    Church, Kenneth W.

    Using Suffix Arrays to Compute Term Frequency and Document Frequency for All Substrings in a Corpus with much longer ngrams. Suffix arrays were first introduced to compute the frequency and location of a substring (ngram) in a sequence (corpus) of length N. To compute frequencies over all N(N +1)/2 substrings

  7. Low frequency phase signal measurement with high frequency squeezing

    E-print Network

    Zehui Zhai; Jiangrui Gao

    2011-08-24

    We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optics technology.

  8. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  9. Radio frequency identification (RFID)

    Microsoft Academic Search

    C. M. Roberts

    2006-01-01

    First conceived in 1948, Radio Frequency Identification (RFID) has taken many years for the technology to mature to the point where it is sufficiently affordable and reliable for widespread use. From Electronic Article Surveillance (EAS) for article (mainly clothing) security to more sophisticated uses, RFID is seen by some as the inevitable replacement for bar codes. With increasing use comes

  10. Radio Frequency Pulsewidth Modulation

    Microsoft Academic Search

    F. Raab

    1973-01-01

    The width of a train of square pulses can be varied to produce a modulated carrier at the pulse repetition frequency. When the pulse train is generated by switching (class D) transistors, highefficiency operation is possible. The efficiency of this type of amplifier can be significantly higher than that of conventional pulsewidth modulation amplifiers, since the switching rate is reduced.

  11. Frequency modulation (FM) spectroscopy

    Microsoft Academic Search

    G. C. Bjorklund; M. D. Levenson; W. Lenth; C. Ortiz

    1983-01-01

    Frequency modulation (FM) spectroscopy is a new method of optical heterodyne spectroscopy capable of sensitive and rapid measurement of the absorption or dispersion associated with narrow spectral features. The absorption or dispersion is measured by detecting the heterodyne beat signal that occurs when the FM optical spectrum of the probe wave is distorted by the spectral feature of interest. A

  12. Flood Frequency Analysis

    NSDL National Science Digital Library

    Sheila Roberts

    This assignment asks students to do a flood frequency analysis to determine the size and stage of various floods and determine if the town of Crawford, OH is likely to be flooded or not. Outcomes: learn to work with quantitative data, learn to use Excel, be able to use USGS data.

  13. Rotating Phasors- Negative Frequencies

    NSDL National Science Digital Library

    This interactive phasor page allows you to control the values of a rotating phasor and see a visualization of each change that is done. You can control: one, pos/neg, two, beats, delta, sawtooth, square, triangle, time, zoom, plus you can put into five different values: Frequency (rel, HZ, mHZ), Amplitude (raw, rel), and Phases (Deg, Rad, unitrad).

  14. Judged frequency of lethal events

    Microsoft Academic Search

    Sarah Lichtenstein; Baruch Fischhoff; Mark Layman; Barbara Combs

    1978-01-01

    A series of 5 experiments with 660 adult Ss studied how people judge the frequency of death from various causes. The judgments exhibited a highly consistent but systematically biased subjective scale of frequency. Two kinds of bias were identified: (a) a tendency to overestimate small frequencies and underestimate larger ones; and (b) a tendency to exaggerate the frequency of some

  15. Quantitative Analysis of Hydration Using Nitrogen-14 Nuclear Quadrupole Resonance.

    PubMed

    Gregorovi?, Alan

    2015-07-01

    Hydration is a quite common process in pharmaceutical solids. Sometimes it is desirable, as it stabilizes the crystal structure; in other cases it is unwanted, as it changes the physical and chemical properties of drugs. We here use (14)N NQR spectroscopy to quantitatively analyze hydration of a model compound, 5-aminotetrazole. (14)N NQR has some great advantages compared to other routinely used techniques to study hydration, like a very simple spectrum, single point calibration, and no need for special sample preparation, but the method's great disadvantage is a rather small sensitivity. Nevertheless, here we demonstrate that (14)N NQR, although being significantly less sensitive than XRD, NIR, and also (35)Cl NQR, is still capable of providing excellent quantitative accuracies. We can achieve errors <1% of the total amount, provided good temperature stabilization is implemented, which then allows long experimental times. We also present results obtained with a SLSE pulse sequence, which is a less robust approach but allows the use of much shorter measuring times (?200×) and could be used for quantitative real time monitoring of hydration or dehydration. PMID:26008906

  16. Fiber optic frequency transfer link

    NASA Technical Reports Server (NTRS)

    Primas, Lori E. (inventor); Sydnor, Richard L. (inventor); Lutes, George F. (inventor)

    1991-01-01

    A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.

  17. Flood Frequency Analysis

    NSDL National Science Digital Library

    2014-09-14

    The Flood Frequency Analysis module offers an introduction to the use of flood frequency analysis for flood prediction and planning. Through use of rich illustrations, animations, and interactions, this module explains the basic concepts, underlying issues, and methods for analyzing flood data. Common concepts such as the 100-year flood and return periods as well as issues affecting the statistical representation of floods are discussed. Common flood data analysis methods as well as an overview of design events are also covered. As a foundation topic for the Basic Hydrologic Science course, this module may be taken on its own, but it will also be available as a supporting topic providing factual scientific information to support students in completion of the case-based forecasting modules.

  18. Extended frequency turbofan model

    NASA Technical Reports Server (NTRS)

    Mason, J. R.; Park, J. W.; Jaekel, R. F.

    1980-01-01

    The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine.

  19. High frequency reference electrode

    DOEpatents

    Kronberg, James W. (Aiken, SC)

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  20. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  1. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique. PMID:25636803

  2. High Frequency Correlation Modelling

    Microsoft Academic Search

    Nicolas Huth; Frédéric Abergel

    2011-01-01

    \\u000a Many statistical arbitrage strategies, such as pair trading or basket trading, are based on several assets. Optimal execution\\u000a routines should also take into account correlation between stocks when proceeding clients orders. However, not so much effort\\u000a has been devoted to correlation modelling and only few empirical results are known about high frequency correlation. Depending\\u000a on the time scale under consideration,

  3. Multiwire thermocouples: Frequency response

    NASA Technical Reports Server (NTRS)

    Forney, L. J.; Fralick, G. C.

    1994-01-01

    Experimental measurements are made with a novel two wire thermocouple. Signals from two wires of unequal diameters are recorded from the thermocouple suspended in constant flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the two wire thermocouple requires no compensation for omega less than or equal to 2 omega(sub 1) where omega is the natural frequency of the smaller wire. A compensation factor is recommended for larger frequencies omega greater than 2 omega(sub 1). Theory and experimental measurements are compared with a novel three wire thermocouple. Signals from three wires of unequal diameters are recorded from the thermocouple suspended in constant flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the three wire thermocouple requires no compensation for omega less than or equal to 5 omega(sub 1) where omega (sub 1) is the natural frequency of the smaller wire. The latter result represents a significant improvement compared to previous work with two wire thermocouples. A correction factor has also been derived to account for wires of arbitrary diameter. Measurements are recorded for multiwire thermocouples consisting of either two or three wires of unequal diameters. Signals from the multiwire probe are recorded for a reversing gas flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the multiwire thermocouple requires no compensation provided omega/omega(sub 1) is less than 2.3 for two wires or omega/omega(sub 1) is less than 3.6 for three wires where omega(sub 1) is the natural frequency of the smaller wire based on the maximum gas velocity. The latter results were possible provided Fourier transformed data were used and knowledge of the gas velocity is available.

  4. Low frequency cavitation erosion

    NASA Astrophysics Data System (ADS)

    Pardue, Sally J.; Chandekar, Gautam

    2002-11-01

    Damage of diesel engine piston sleeve liners due to cavitation of the coolant fluid can be severe. Coolant fluid additives are used to inhibit cavitation damage, and are evaluated by industry suppliers using ASTM G32-98 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus. The ASTM G32-98 test procedure uses an ultrasonic horn at 20 kHz to vibrate a test button in the coolant. The test button mass loss and surface appearance are studied to sort the performance of new coolant additives. Mismatch between good lab performers and actual engine test runs has raised concerns over the current lab test. The frequency range of the current test has been targeted for investigation. A low frequency, less than 2000 Hz, test rig was built to explore the cavitation damage. The test system did produce cavitation on the surface of the test button for a period of 36 h, with minimal mass loss. The test rig experienced cyclic fatigue when test times were extended. The work is now focusing on designing a better test rig for long duration tests and on developing numerical models in order to explore the effects of cavitation excitation frequency on surface erosion.

  5. High frequency optoacoustic microscopy.

    PubMed

    Bost, Wolfgang; Stracke, Frank; Weiss, Eike C; Narasimhan, Sankar; Kolios, Michael C; Lemor, Robert

    2009-01-01

    Photoacoustic imaging--also called optoacoustic imaging--is a new hybrid modality of high tissue contrast which is based on the varying optical properties of tissue. The acoustic signal generated by pulsed laser absorption reports tissue-specific information with high spatial resolution. To increase the intrinsic contrast in tissue, absorbing particles are of great interest for optical imaging because of their considerable capacity to absorb and scatter light at visible and near-infrared wavelengths. The aim of the work presented here is to establish a scalable photoacoustic technology for volume imaging of biological samples down to diffraction limited microscopy. For this purpose a versatile photoacoustic microscopy platform has been developed with unmatched spatial resolution consisting of a microchip laser and a measurement cell with different transducers attached allowing generation and detection of laser-induced ultrasound signals in a frequency range up to 400 MHz. The performance of a versatile photoacoustic microscopy platform was evaluated via 2D optoacoustic images of light absorbing microparticles (5 microm Fe(3)0(4) and 1 micromblack toner particles) embedded in a polystyrene matrix. High frequency signals in the frequency range of 400 MHz generated by a single 1 microm particle could be recorded with a high signal to noise ratio (SNR) of 34 dB. PMID:19964880

  6. Frequency shifts of high frequency p-modes

    NASA Technical Reports Server (NTRS)

    Jain, Rekha

    1995-01-01

    Frequency shifts of high frequency p-modes during the solar cycle are calculated for a non-magnetic polytrope convection zone model. An isothermal chromospheric atmosphere threaded by a uniform horizontal magnetic field is correlated to this model. The relevant observations of such frequency changes are discussed. The calculated simultaneous changes in the field strength and chromospheric temperature result in the frequency shifts that are similar to those of the observations.

  7. Effects of increasing switching frequency in frequency modulated power converters

    Microsoft Academic Search

    Janis Jankovskis; Deniss Stepins; Dmitrijs Pikulins

    2010-01-01

    The paper considers the effect of increasing switching frequency on a frequency modulated (FM) buck converter parameters: efficiency, output voltage ripples and electromagnetic interference (EMI) attenuations. The converter operating in continuous and discontinuous conduction modes (CCM and DCM respectively) is analyzed analytically, by simulations in Simulink and experimentally. The results obtained show that increasing switching frequency can significantly reduce the

  8. Trapped Ion Frequency Standards

    NASA Astrophysics Data System (ADS)

    Tjoelker, R. L.

    1996-03-01

    Trapped ions form the basis for a high performance frequency standard since long interrogation times are possible in a nearly perturbation free environment. At JPL, approximately 2x10^6 ^199Hg+ ions are confined in a Linear Ion Trap (LIT)(J.D. Prestage, G.J. Dick, L. Maleki, J.Appl. Phys. 66, 1013 (1989).) and cooled to near room temperature by collisions with a helium buffer gas. Atomic state selection is accomplished by optical pumping using 194 nm light from a ^202Hg lamp and the 40.5 GHz ground state hyperfine transition is interrogated using Ramsey successive oscillatory fields. With an interrogation time of 8 seconds, the measured fractional frequency stability is ?_y(?)=6.5x10-14/ ?^1/2, where ? is the averaging interval in seconds. The frequency stability measured between two Hg^+ ion standards currently exceeds other standards between 10,000 seconds and 1 month. (R.L. Tjoelker, J.D. Prestage, L. Maleki, in Symp. on Freq. Standards & Metrology, Woods Hole MA,(1995).) The long term differential drift between an ion standard and a cavity tuned hydrogen maser over a 5 month interval was measured to be (2.1± 0.8)x10-16/day. A new two segment linear ion trap currently under development separates the ion loading and atomic state selection region from the microwave interrogation region. Initial measurements indicate a stability of ?_y(?)=5.6x10-14/ ?^1/2. Operating at reduced linear ion densities, this configuration should allow for improved accuracy and long term stability.

  9. Radar frequency radiation

    NASA Astrophysics Data System (ADS)

    Malowicki, E.

    1981-11-01

    A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar. The method is based on the following main assumptions that: (a) the total field can be computed as the vector summation of the individual fields due to each antenna element; (b) the individual field can be calculated using distances for which the field point is in the far field of the antenna element. An RFR computer program was coded for the RADC HE 6180 digital computer and exercised to calculate the radiation levels in the air and ground space for the present baseline and the possible Six DB and 10 DB growth systems of the PAVE PAWS radar system at OTIS AFB MA. The average radiation levels due to the surveillance fence were computed for three regions: in the air space in front of the radar, at the radar hazard fence at OTIS AFB MA and at representative ground points in the OTIS AFB vicinity. It was concluded that the radar frequency radiation of PAVE PAWS does not present a hazard to personnel provided there is no entry to the air hazard zone or to the area within the hazard fence. The method developed offers a cost effective way to determine radiation levels from a phased array radar especially in the near field and transition regions.

  10. Frequency Domain Identification Toolbox

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Juang, Jer-Nan; Chen, Chung-Wen

    1996-01-01

    This report documents software written in MATLAB programming language for performing identification of systems from frequency response functions. MATLAB is a commercial software environment which allows easy manipulation of data matrices and provides other intrinsic matrix functions capabilities. Algorithms programmed in this collection of subroutines have been documented elsewhere but all references are provided in this document. A main feature of this software is the use of matrix fraction descriptions and system realization theory to identify state space models directly from test data. All subroutines have templates for the user to use as guidelines.

  11. Microwave Frequency Polarizers

    NASA Technical Reports Server (NTRS)

    Ha, Vien The; Mirel, Paul; Kogut, Alan J.

    2013-01-01

    This article describes the fabrication and analysis of microwave frequency polarizing grids. The grids are designed to measure polarization from the cosmic microwave background. It is effective in the range of 500 to 1500 micron wavelength. It is cryogenic compatible and highly robust to high load impacts. Each grid is fabricated using an array of different assembly processes which vary in the types of tension mechanisms to the shape and size of the grids. We provide a comprehensive study on the analysis of the grids' wire heights, diameters, and spacing.

  12. Frequency doubling crystals

    SciTech Connect

    Wang, F.; Velsko, S.P.

    1989-10-24

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a harmonic generating unit which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L- arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  13. Time, Frequency and Physical Measurement.

    ERIC Educational Resources Information Center

    Hellwig, Helmut; And Others

    1978-01-01

    Describes several developments in atomic clocks and frequency standards pointing out the feasibility and practicality in adopting a unified standard of time and frequency to replace other base standards of length, mass, and temperature. (GA)

  14. Optical frequency standards and clocks

    Microsoft Academic Search

    H. S. Margolis

    2010-01-01

    Optical frequency standards based on single trapped ions or ensembles of neutral atoms have recently demonstrated stability and accuracy superior to that of the current generation of microwave primary frequency standards, with significant potential for further improvements. When combined with femtosecond optical frequency combs, these standards can be operated as optical clocks generating a direct microwave output signal, raising the

  15. Pitch Extraction and Fundamental Frequency

    E-print Network

    Regina, University of

    Pitch Extraction and Fundamental Frequency: History and Current Techniques David Gerhard Technical and Fundamental Frequency: History and Current Techniques David Gerhard Abstract: Pitch extraction (also called fundamental frequency estimation) has been a popular topic in many fields of research since the age

  16. Off-resonance effects and selectivity profiles in pulsed nitrogen-14 nuclear quadrupole resonance.

    PubMed

    Guendouz, L; Robert, A; Retournard, A; Leclerc, S; Aissani, S; Canet, D

    2012-01-01

    In order to alleviate base-line distortions in nitrogen-14 NQR spectra originating from pulse breakthrough, low power radio-frequency (rf) pulses were applied. It is recalled that the required power is four times lower than that for an equivalent NMR experiment. This is easily explained by the fact that, in NMR, half the amplitude of the rf field is active. Moreover, the selectivity profile (i.e. the peak amplitude as a function of the difference between the carrier frequency and the resonance frequency) exhibits a shape which is, in most cases, more favorable in NQR than in NMR. An appropriate theory has been developed for explaining these experimental observations. It is concluded that low power NQR is perfectly feasible and should even be recommended for most applications, provided that the line-width of the NQR signal is not too large. PMID:23063174

  17. Mid-infrared frequency combs

    E-print Network

    Schliesser, Albert; Hänsch, Theodor W

    2012-01-01

    Laser frequency combs are coherent light sources that emit a broad spectrum consisting of discrete, evenly spaced narrow lines, each having an absolute frequency measurable within the accuracy of an atomic clock. Their development, a decade ago, in the near-infrared and visible domains has revolutionized frequency metrology with numerous windfalls into other fields such as astronomy or attosecond science. Extension of frequency comb techniques to the mid-infrared spectral region is now under exploration. Versatile mid-infrared frequency comb generators, based on novel laser gain media, nonlinear frequency conversion or microresonators, promise to significantly expand the tree of applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the fingerprint region, with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may spark off new discoveries in the various fields relevant to molecular sciences.

  18. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing (Houston, TX); Zettl, Alexander K. (Kensington, TX)

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  19. Frequency mixing crystal

    DOEpatents

    Ebbers, Christopher A. (Livermore, CA); Davis, Laura E. (Manteca, CA); Webb, Mark (Salida, CA)

    1992-01-01

    In a laser system for converting infrared laser light waves to visible light comprising a source of infrared laser light waves and means of harmoic generation associated therewith for production of light waves at integral multiples of the frequency of the original wave, the improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2 Y(NO.sub.3).sub.5 .multidot.2 nZ.sub.2 o wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4.

  20. Flying radio frequency undulator

    SciTech Connect

    Kuzikov, S. V.; Vikharev, A. A. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Savilov, A. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod (Russian Federation)

    2014-07-21

    A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the ?1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse.

  1. Radio frequency coaxial feedthrough

    DOEpatents

    Owens, Thomas L. (Kingston, TN)

    1989-01-17

    An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

  2. Quadrature frequency conversion

    NASA Astrophysics Data System (ADS)

    Eimerl, David

    1987-08-01

    A technique for frequency conversion of high-power lasers is described which uses two crystals for each conversion step rather than one. The two crystals are oriented so that the waves generated in them are orthogonally polarized. The conversion efficiency of these quadrature arrangements is much less sensitive to laser pulse nonuniformities than that in single-crystal methods. Consequently, very high conversion efficiency is possible for typically nonuniform laser pulses. Realization of the quadrature concept for all types of nonlinear optical processes is described. Data taken on second harmonic generation of Gaussian pulses shows that very high (internal) conversion efficiency is possible (greater than 95 percent) over a substantial range of input energy.

  3. Matsubara Frequency Sums

    E-print Network

    Alok Kumar

    2010-02-25

    We cannot use directly the results of zero-temperature at finite temperature, for at finite temperature the average is to be carried over all highly degenerate excited states unlike zero-temperature average is only on unique ground state. One of the formal way to take into account the finite temperature into quantum field theory is due to Matsubara, to replace temporal component of eigenvalues $k_{4}$ by $\\omega_{n}=\\frac{2\\pi n}{\\beta}$ $(\\frac{2\\pi (n+{1/2})}{\\beta})$ with summation over all integer values of $n$. The summation is done with the infinite series expansion of $\\coth (\\pi y)$. With the chemical potential $\\mu$, $\\omega_{n}$ will be replaced by $\\omega_{n} - \\mu$ in the eigenvalues and the summation over $n$ cannot be done easily. Various methods exist to evaluate it. We use the infinite series expansion of $\\coth (\\pi y)$ to work operationally for such Matsubara frequency sums.

  4. Frequency doubling crystals

    SciTech Connect

    Wang, F.; Velsko, S.P.

    1988-08-15

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a harmonic generating unit'' which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyle hydroxyyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  5. Frequency doubling crystals

    DOEpatents

    Wang, Francis (Danville, CA); Velsko, Stephan P. (Livermore, CA)

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  6. A new technique of frequency synthesis

    Microsoft Academic Search

    W. Zhou

    1993-01-01

    A novel method for the design of a frequency synthesizer is described. It is based on precision frequency measurement techniques. The frequency synthesis can be accomplished by measuring the synthesized frequency signal, comparing it with the desired frequency, and time (pulse width) - voltage transformation. In this synthesizer there are no frequency multipliers, mixers, or any other frequency transformation circuits

  7. A technique for orthogonal frequency division multiplexing frequency offset correction

    Microsoft Academic Search

    P. H. Moose

    1994-01-01

    This paper discusses the effects of frequency offset on the performance of orthogonal frequency division multiplexing (OFDM) digital communications. The main problem with frequency offset is that it introduces interference among the multiplicity of carriers in the OFDM signal. It is shown, and confirmed by simulation, that to maintain signal-to-interference ratios of 20 dB or greater for the OFDM carriers,

  8. 47 CFR 87.305 - Frequency coordination.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Stations § 87.305 Frequency coordination. ...responsible Government Area Frequency Coordinators listed in...Procedures for Federal Radio Frequency Management.”...

  9. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...false Radiodetermination frequencies. 80.375 Section... SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination...375 Radiodetermination frequencies. This section...

  10. 47 CFR 87.305 - Frequency coordination.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Stations § 87.305 Frequency coordination. ...responsible Government Area Frequency Coordinators listed in...Procedures for Federal Radio Frequency Management.”...

  11. 47 CFR 87.305 - Frequency coordination.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Stations § 87.305 Frequency coordination. ...responsible Government Area Frequency Coordinators listed in...Procedures for Federal Radio Frequency Management.”...

  12. 47 CFR 87.305 - Frequency coordination.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Stations § 87.305 Frequency coordination. ...responsible Government Area Frequency Coordinators listed in...Procedures for Federal Radio Frequency Management.”...

  13. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...false Radiodetermination frequencies. 80.375 Section... SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination...375 Radiodetermination frequencies. This section...

  14. 47 CFR 87.305 - Frequency coordination.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Stations § 87.305 Frequency coordination. ...responsible Government Area Frequency Coordinators listed in...Procedures for Federal Radio Frequency Management.”...

  15. 47 CFR 80.375 - Radiodetermination frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...false Radiodetermination frequencies. 80.375 Section... SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiodetermination...375 Radiodetermination frequencies. This section...

  16. Radio Frequency Identification

    NSDL National Science Digital Library

    Leske, Cavin.

    A wealth of information about RFID is available at this site (1), ranging from background material to case studies. A discussion highlighting the myriad of uses for RFID is included. Transponder News (2) offers several articles that explore the technology in greater detail. Two in particular look at current and future trends, while others are editorial essays and technical notes. Pacific Northwest National Laboratory (3) is involved in the development of advanced tags for RFID systems. The project's homepage outlines current research efforts for three different types of radio frequency tags, which are being designed for varying degrees of sophistication and functionality. While RFID technology can be very useful, the fact that information about items is collected remotely raises concerns about privacy and security. This issue is addressed in a research paper from the Massachusetts Institute of Technology (4). The authors review current RFID systems and their operation, and then propose a number of security mechanisms that could reduce the risk associated with their use. A paper presented at the 2002 European Wireless Conference (5) compares the performance of RFID systems that use ultra-high frequency (UHF) communications to those that use microwave communications. It is argued that although microwave-based devices, such as Bluetooth, are suitable for worldwide operation, systems that communicate in the UHF range have greater range and less interference. The introduction of RFID smart tags in goods is discussed in this article (6). Now that these tags are cheap enough to be attached to thousands of items, stores will be able to track goods as they are transferred from storehouses to retail shelves, thereby minimizing the possibility of loss or theft. RFID technology has found another use in the war with Iraq. An article from May 20, 2003 (7) describes wristbands embedded with an RFID chip. The status and position of a wounded soldier who is wearing such a wristband can be monitored while he or she is recovering at a medical facility. For additional updates on the development of RFID technology, RFID News (8) maintains current news about emerging standards, innovative applications, and general issues.

  17. Light beam frequency comb generator

    DOEpatents

    Priatko, G.J.; Kaskey, J.A.

    1992-11-24

    A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics. 2 figs.

  18. High-frequency furnace

    NASA Astrophysics Data System (ADS)

    Zumbrunnen, A. D.

    1985-04-01

    An experimental furnace has been built for the purpose of evaluating a new technique for the high purity melting of certain metals and semiconductors. The melt is contained in a solidified skull of the same material being melted, thus avoiding crucible reactions that are a problem in conventional processing. A number of commercial applications of the invention are discussed, assuming that feasibility can be established. These include the melting and crystal growth of silicon, where the avoidance of crucible contamination would improve the energy conversion efficiency of solar cells; and the consolidation of titanium sponge and scrap, where energy savings and other process advantages would be realized. The production of ferrous and non-ferrous, specialty alloys is also discussed. Heating power is derived from the electrical, proximity effect which is used to concentrate a high-frequency (9.6 kHz) current in the melt zone. The power source is a conventional, 50 kW, solid-state inverter of the type used in induction heating practice. All heats were conducted on a cast iron workpiece in argon at atmospheric pressure. The melt temperature of the casting (2100 F) was not achieved in any test run; however, the ability of proximity effect to generate localized heating was clearly demonstrated.

  19. High frequency ultrasound torturer.

    PubMed

    Husain, Munawwar; Rizvi, Shameem Jahan; Usmani, Javed Ahmad

    2009-12-01

    The discernible aim of torture as everyone believes--and rightly so--is to destroy the personality of an individual in a way that would render his compliance in future. But to destroy a personality is easier said than done. It requires long sessions of detention and torture. The torturers risk themselves getting exposed. The Human Rights groups are active all around the world. Ultimately the personality may not be destroyed much to the chagrin of the torturers, and an unexpected resilient rebounding may take place. Therefore, with the repertoire of modern knowledge, the strategy may well change in the 21st century. Discreet methods may be employed to selectively destroy areas in brain by high dosage and high frequency ultrasound. It is completely a non-invasive technique that does not leave its fingerprint for painful, later denials of subornation. Nevertheless the personality will change--from rightful aggression to slavish submission. The aim of this article is to put forward the theoretical perspective and cofounded projection of the darker and menacing side of ultrasound technology so that future generation could be saved from sin of omission. PMID:20509473

  20. Flood frequency in Alaska

    USGS Publications Warehouse

    Childers, J.M.

    1970-01-01

    Records of peak discharge at 183 sites were used to study flood frequency in Alaska. The vast size of Alaska, its great ranges of physiography, and the lack of data for much of the State precluded a comprehensive analysis of all flood determinants. Peak stream discharges, where gaging-station records were available, were analyzed for 2-year, 5-year, 10-year, 25-year, and 50-year average-recurrence intervals. A regional analysis of the flood characteristics by multiple-regression methods gave a set of equations that can be used to estimate floods of selected recurrence intervals up to 50 years for any site on any stream in Alaska. The equations relate floods to drainage-basin characteristics. The study indicates that in Alaska the 50-year flood can be estimated from 10-year gaging- station records with a standard error of 22 percent whereas the 50-year flood can be estimated from the regression equation with a standard error of 53 percent. Also, maximum known floods at more than 500 gaging stations and miscellaneous sites in Alaska were related to drainage-area size. An envelope curve of 500 cubic feet per second per square mile covered all but 2 floods in the State.

  1. Frequency conversion in IMPATT diodes

    Microsoft Academic Search

    W. J. Evans; G. I. Haddad

    1969-01-01

    A large-signal model of the Read-type IMPATT diode has been used to analyze the frequency-mixing properties of the oscillating diode. The self-oscillating, two-port frequency converter is described in terms of its short-circuit admittance parameters. It is shown that in the proper circuit, parametric frequency conversion may result in a negative conductance at the input and output ports of the converter.

  2. Effective switching frequency multiplier inverter

    DOEpatents

    Su, Gui-Jia (Oak Ridge, TN); Peng, Fang Z. (Okemos, MI)

    2007-08-07

    A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

  3. Frequency-Shift Hearing Aid

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard M.

    1994-01-01

    Proposed hearing aid maps spectrum of speech into band of lower frequencies at which ear remains sensitive. By redirecting normal speech frequencies into frequency band from 100 to 1,500 Hz, hearing aid allows people to understand normal conversation, including telephone calls. Principle operation of hearing aid adapted to other uses such as, clearing up noisy telephone or radio communication. In addition, loud-speakers more easily understood in presence of high background noise.

  4. Flood Frequency Analysis: International Edition

    NSDL National Science Digital Library

    COMET

    2010-08-31

    Flood frequency analysis uses historical flow records to both estimate the frequency with which floods of a certain magnitude may occur and predict the possible flood magnitude over a certain time period. This module offers a thorough introduction to appropriately constructing the necessary historical data series, calculating the flooding probabilities, and gauging the reliability of the resulting probability values. Methods for assessing flood frequency in basins with limited data are also discussed.

  5. Broadband optical serrodyne frequency shifting.

    PubMed

    Johnson, D M S; Hogan, J M; Chiow, S-w; Kasevich, M A

    2010-03-01

    We demonstrate serrodyne frequency shifting of light from 200 MHz to 1.2 GHz with an efficiency of better than 60%. The frequency shift is imparted by an electro-optic phase modulator driven by a high-frequency high-fidelity sawtooth waveform that is passively generated by a commercially available nonlinear transmission line. We also implement a push-pull configuration using two serrodyne-driven phase modulators, allowing for continuous tuning between -1.6 GHz and +1.6 GHz. Compared with competing technologies, this technique is simple and robust, and it offers the largest available tuning range in this frequency band. PMID:20195339

  6. Dual frequency water vapor radiometer

    NASA Astrophysics Data System (ADS)

    Xu, Peiyuan; Jin, Peiyu; Yao, Zhunliang; Fang, Zhenhe; Li, Mingxiang

    A steerable dual frequency water vapor radiometer (DFWVR) is developed. A pair of optimum frequencies, 20.60 and 31.65 GHz, is adopted. Each frequency channel has its own offset parabola antenna and Dicke switched receiver, but both channels are mounted on one rotatable pedestal and controlled by one microcomputer system. This DFWVR is capable of continuous, unattended operation. The sensitivity at 1 second time constant and the accuracy of the brightness temperature are 0.2 and 0.5 K, respectively, at both frequencies. It is expected to promote the excess path length corrections to be better than 1 cm for geodetic VLBI and GPS measurements.

  7. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Frequencies. 87.173 ...SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Frequencies § 87.173 Frequencies...Emergency and distress frequency for use of survival...4200-4400 MHz F MA Radio altimeters....

  8. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Frequencies. 87.173 ...SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Frequencies § 87.173 Frequencies...Emergency and distress frequency for use of survival...4200-4400 MHz F MA Radio altimeters....

  9. 47 CFR 87.173 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Frequencies. 87.173 ...SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Frequencies § 87.173 Frequencies...Emergency and distress frequency for use of survival...4200-4400 MHz F MA Radio altimeters....

  10. Optimal filtering in multipulse sequences for nuclear quadrupole resonance detection

    NASA Astrophysics Data System (ADS)

    Osokin, D. Ya.; Khusnutdinov, R. R.; Mozzhukhin, G. V.; Rameev, B. Z.

    2014-05-01

    The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of explosive and narcotic substances has been studied. Various approaches to increase the signal to noise ratio (SNR) of signal detection are considered. We discussed two modifications of the phase-alternated multiple-pulse sequence (PAMS): the 180° pulse sequence with a preparatory pulse and the 90° pulse sequence. The advantages of optimal filtering to detect NQR in the case of the coherent steady-state precession have been analyzed. It has been shown that this technique is effective in filtering high-frequency and low-frequency noise and increasing the reliability of NQR detection. Our analysis also shows the PAMS with 180° pulses is more effective than PSL sequence from point of view of the application of optimal filtering procedure to the steady-state NQR signal.

  11. Acoustic resonance frequency locked photoacoustic spectrometer

    DOEpatents

    Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

    2003-09-09

    A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.

  12. ENEA Structures of the low frequency Alfven continuous spectrum 1 Structures of the low frequency Alfven

    E-print Network

    Zonca, Fulvio

    : · finite frequency fishbone oscillations at the GAM frequency and "low-frequency feature" of Alfv frequency fishbone oscillations at the GAM frequency (F. Nabais, et al. 2005, PoP 12 102509) and "low

  13. Low-Frequency Electromagnetic Scattering

    Microsoft Academic Search

    H. Ammari; J. c Nédélec

    1997-01-01

    The main result of this paper is to reduce the calculation of higherorderterms in the asymptotic expansions of the electric and magneticfields at low frequencies to the solutions of certain canonical problems.We also provide a new and simple variational proof of the convergenceof the electric and magnetic fields solutions of the scattering problemfor the Maxwell equations as the frequency goes

  14. Signal Frequency Spectra with Audacity®

    ERIC Educational Resources Information Center

    Gailey, Alycia

    2015-01-01

    The primary objective of the activity presented here is to allow students to explore the frequency components of various simple signals, with the ultimate goal of teaching them how to remove unwanted noise from a voice signal. Analysis of the frequency components of a signal allows students to design filters that remove unwanted components of a…

  15. Gaming Frequency and Academic Performance

    ERIC Educational Resources Information Center

    Ip, Barry; Jacobs, Gabriel; Watkins, Alan

    2008-01-01

    There are numerous claims that playing computer and video games may be educationally beneficial, but there has been little formal investigation into whether or not the frequency of exposure to such games actually affects academic performance. This paper explores the issue by analysing the relationships between gaming frequency--measured as the…

  16. Variable stars: Which Nyquist frequency?

    Microsoft Academic Search

    L. Eyer; P. Bartholdi

    1999-01-01

    In the analysis of variable stars, the problem of sampling is central. This article focusses on the determination of the Nyquist frequency. It is well defined in the case of regular sampling. However, the time series of variable stars observations are generally unevenly sampled. Fourier analysis using the spectral window furnishes some clues about the equivalent Nyquist frequency in the

  17. Frequency diversity in multistatic radars

    Microsoft Academic Search

    Byung Wook Jung; R aviraj S. Adve; Joohwan Chun

    2008-01-01

    This paper presents the model and analysis of a frequency-diverse radar system. Multistatic radar systems provide an inherent spatial diversity by processing signals from different platforms which view a potential target from different aspect angles. By using different frequencies at each platform, an additional diversity gain can be obtained on top of the advantages of spatial diversity. Here, since platforms

  18. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  19. Frequency Conversion of Entangled State

    E-print Network

    Aihong Tan; Xiaojun Jia; Changde Xie

    2006-03-01

    The quantum characteristics of sum-frequency process in an optical cavity with an input signal optical beam, which is a half of entangled optical beams, are analyzed. The calculated results show that the quantum properties of the signal beam can be maintained after its frequency is conversed during the intracavity nonlinear optical interaction. The frequency-conversed output signal beam is still in an entangled state with the retained other half of initial entangled beams. The resultant quantum correlation spectra and the parametric dependences of the correlations on the initial squeezing factor, the optical losses and the pump power of the sum-frequency cavity are calculated. The proposed system for the frequency conversion of entangled state can be used in quantum communication network and the calculated results can provide direct references for the design of experimental systems.

  20. Exploiting Spin Echo Decay in the Detection of Nuclear Quadrupole Resonance Signals

    Microsoft Academic Search

    Samuel D. Somasundaram; Andreas Jakobsson; John A. S. Smith; Kaspar Althoefer

    2007-01-01

    Nuclear quadrupole resonance (NQR) is a radio-frequency technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. In a typical application, one observes trains of decaying NQR echoes, in which the decay is governed by the spin echo decay time(s) of the resonant line(s). In most detection

  1. Single-frequency tunable laser for pumping cesium frequency standards

    SciTech Connect

    Zhuravleva, O V; Ivanov, Andrei V; Leonovich, A I; Kurnosov, V D; Kurnosov, K V; Chernov, Roman V; Shishkov, V V [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Pleshanov, S A [Federal State Unitary Enterprise 'Istok Research and Production Association', Fryazino, Moscow region (Russian Federation)

    2006-08-31

    A single-frequency tunable laser for pumping the cesium frequency standard is studied. It is shown experimentally that the laser emits at a single frequency despite the fact that a few longitudinal modes of the external cavity fall within the reflection band of a fibre Bragg grating (FBG) written in the optical fibre. The laser wavelength can be tuned by varying the pump current of the laser, its temperature, and the FBG temperature. The laser linewidth does not exceed 2 MHz for 10 mW of output power. (lasers)

  2. High power very low frequency\\/low frequency transmitting antennas

    Microsoft Academic Search

    PEDER HANSEN

    1990-01-01

    Very-low-frequency (VLF) and low-frequency (LF) transmitting antennas are small with respect to the wavelength and are required to radiate substantial power levels. Design parameters for these antennas are discussed, including the impact of technical advances in high-voltage design and bandwidth enhancement. Most of these antennas are various realizations of electrically small monopoles that can be modeled by a simple series

  3. Microcontroller interrupts in frequency controlling

    NASA Astrophysics Data System (ADS)

    Panoiu, C.; Rob, R.; Panoiu, M.

    2015-06-01

    Present paper represents an educational software application that permits to measure the signals frequency. The application is accomplished in MicroC compiler that also permit to user to program a microcontroller PIC18F45K22 using a developing board EasyPICv7. An important issue of present application is to measure the frequency of an external signal that is acquired by an input pin of the microcontroller. The frequency value is displayed on the seven segment display provided by the developing board.

  4. Parametric Effects of Word Frequency in Memory for Mixed Frequency Lists

    ERIC Educational Resources Information Center

    Lohnas, Lynn J.; Kahana, Michael J.

    2013-01-01

    The "word frequency paradox" refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and…

  5. Frequency-Modulation Correlation Spectrometer

    NASA Technical Reports Server (NTRS)

    Margolis, J. S.; Martonchik, J. V.

    1985-01-01

    New type of correlation spectrometer eliminates need to shift between two cells, one empty and one containing reference gas. Electrooptical phase modulator sinusoidally shift frequencies of sample transmission spectrum.

  6. Microwave Spectrum and Molecular Structure of ( Z)Chloroacetaldehyde Oxime

    Microsoft Academic Search

    Takeshi Sakaizumi; Soutarou Takeda; Osamu Ohashi; Kinya Iijima

    1996-01-01

    The microwave spectra of (Z)-35ClCH2CH=NOH, (Z)-37ClCH2CH=NOH, (Z)-35ClCH2CH=NOD, and (Z)-37ClCH2CH=NOD have been observed in the frequency range from 16.5 to 40.0 GHz. The rotational and centrifugal distortion constants of four isotopic species and the nuclear quadrupole coupling constants of the35Cl species were determined. The values of planar moment (Pcc= (Ia+ Ib? Ic)\\/2) obtained for four isotopic species were found to be

  7. Precision photodetector with frequency output

    SciTech Connect

    Martynyuk, A.S.; Sachkov, A.V.

    1986-04-01

    This paper describes a photodetector whose sensitivity threshold is close to the theoretical limit governed by the thermal noise of the photodiode. successive conversion of photocurrent to voltage and voltage to frequency provides a sensitivity threshold of up to 2.10/sup -13/ W with a nonlinearity of conversion of light intensity to frequency of less than or equal to 0.02% over a dynamic range of 10/sup 7/.

  8. Frequency dependencies of power noise

    Microsoft Academic Search

    Bernd Garben; Roland Frech; Jochen Supper; Michael F. McAllister

    2002-01-01

    In this paper, frequency dependencies of delta-I noise caused by variations of the on-chip switching activity have been analyzed by simulations for a complex computer system board with multi-chip module, especially the impact of coincidences with resonances of the power distribution system. The switching frequency and the noise source waveform have been varied in case of a single delta-I step.

  9. The Planck Low Frequency Instrument

    E-print Network

    N. Mandolesi; M. Bersanelli; C. Burigana; F. Villa; on behalf of LFI Consortium

    1999-04-12

    The Low Frequency Instrument (LFI) of the "Planck Surveyor" ESA mission will perform high-resolution imaging of the Cosmic Microwave Background anisotropies at four frequencies in the 30-100 GHz range. We review the LFI main scientific objectives, the current status of the instrument design and the on-going effort to develop software simulations of the LFI observations. In particular we discuss the design status of the PLANCK telescope, which is critical for reaching adequate effective angular resolution.

  10. Tables of molecular vibrational frequencies

    Microsoft Academic Search

    Takehiko Shimanouchi; Hiroatsu Matsuura; Yoshiki Ogawa; Issei Harada

    1978-01-01

    Fundamental vibrational frequencies of 109 molecular forms of 38 polyatomic chain molecules consisting of the CH3, CD3, CH2 CD2, CHD, O, and S groups are given as an extension of tables of molecular vibrational frequencies published in the NSRDS-NBS publication series and in this journal. On preparing the tables in this part, an approach, different from that in the previous

  11. Frequency regulator for synchronous generators

    DOEpatents

    Karlicek, R.F.

    1982-08-10

    The present invention is directed to a novel frequency regulator which controls a generator output frequency for variations in both the input power to the generator and the power supplied to an uncontrolled external load. The present invention further includes over current and current balance protection devices which are relatively inexpensive to manufacture, which may be encapsulated to provide protection from the operating environment and which respond more quickly than previously known electromechanical devices. 11 figs.

  12. Frequency regulator for synchronous generators

    DOEpatents

    Karlicek, Robert F. (1920 Camino Centroloma, Fullerton, CA 92633)

    1982-01-01

    The present invention is directed to a novel frequency regulator which controls a generator output frequency for variations in both the input power to the generator and the power supplied to an uncontrolled external load. The present invention further includes over current and current balance protection devices which are relatively inexpensive to manufacture, which may be encapsulated to provide protection from the operating environment and which respond more quickly than previously known electromechanical devices.

  13. Study on military shortwave frequency planning

    Microsoft Academic Search

    Lin Sun; Hao Liu; Fangsheng Li

    2011-01-01

    Starting from analyzing the necessity of military shortwave frequency planning, this paper illustrates its usable frequency set planning, working frequency subset planning and frequency pattern planning. It also studies the relative planning ways that have theoretical significance for realizing dynamic frequency management of military shortwave.

  14. Temperature and baric dependence of nuclear quadruple resonance spectra in indium and gallium monoselenides

    NASA Astrophysics Data System (ADS)

    Khandozhko, Victor; Raranskii, Nikolai; Balazjuk, Vitaly; Samila, Andriy; Kovalyuk, Zahar

    2013-12-01

    Pulsed radiospectroscopy method has been used to study nuclear quadruple resonance (NQR) spectra of 69Ga and 115In isotopes in the layered semiconductors GaSe and InSe. It has been found that in GaSe and InSe there is a considerable temperature dependence of NQR frequency which in the temperature range of 250 to 390 K is practically linear with conversion slope 1.54 kHz/degree for 69Ga and 2.35 kHz/degree for 115In. In the same crystals the effect of uniaxial pressure on NQR spectra applied along the optical axis ? up to the values of 500 kg/?m2 has been studied. A strong attenuation of NQR spectra intensity with increase in pressure on layered crystal package has been established. The unvaried multiplicity of resonance spectra indicates the absence of structural transformations in these layered crystals over the investigated range of temperatures and pressures.

  15. 47 CFR 87.133 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Frequency stability. 87... SAFETY AND SPECIAL RADIO SERVICES AVIATION...Requirements § 87.133 Frequency stability. ...non-pulse signal radio altimeters, the frequency at which maximum...

  16. 47 CFR 2.1507 - Test frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Test frequencies. 2.1507 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Procedures § 2.1507 Test frequencies. Testing of an EPIRB...

  17. 47 CFR 2.1507 - Test frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Test frequencies. 2.1507 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Procedures § 2.1507 Test frequencies. Testing of an EPIRB...

  18. 47 CFR 95.655 - Frequency capability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...service for which the frequency is authorized and for...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System...certificated.) (b) All frequency determining...

  19. 47 CFR 95.655 - Frequency capability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...service for which the frequency is authorized and for...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System...certificated.) (b) All frequency determining...

  20. 47 CFR 95.655 - Frequency capability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...service for which the frequency is authorized and for...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System...certificated.) (b) All frequency determining...

  1. 47 CFR 95.655 - Frequency capability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...service for which the frequency is authorized and for...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System...certificated.) (b) All frequency determining...

  2. 47 CFR 95.655 - Frequency capability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...service for which the frequency is authorized and for...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System...certificated.) (b) All frequency determining...

  3. 47 CFR 80.513 - Frequency coordination.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

  4. 47 CFR 80.513 - Frequency coordination.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

  5. 47 CFR 87.263 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequencies. 87.263 Section 87.263 Telecommunication...Aeronautical Enroute Stations § 87.263 Frequencies. (a) Domestic VHF service. (1) Frequencies in the 128.8125-132.125 MHz...

  6. 47 CFR 80.513 - Frequency coordination.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

  7. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 2011-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

  8. 47 CFR 87.41 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

  9. 47 CFR 80.513 - Frequency coordination.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

  10. 47 CFR 87.41 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

  11. 47 CFR 80.513 - Frequency coordination.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

  12. 47 CFR 87.41 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

  13. 47 CFR 87.41 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

  14. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 2010-10-01 2010-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

  15. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 2014-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

  16. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 2013-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

  17. 47 CFR 87.303 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 2012-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

  18. 47 CFR 87.41 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

  19. Frequency tracked gated pulse technique for ultrasonic frequency

    NASA Technical Reports Server (NTRS)

    Cantrell, Jr., John H. (Inventor); Heyman, Joseph S. (Inventor)

    1983-01-01

    A tracking generator 21 is slaved to a spectrum analyzer 23 to produce an input signal having a frequency that follows the frequency of the spectrum analyzer sweeping local oscillator 22. The input signal is gated to a transducer 26 by a transmitter gate 25 to produce ultrasonic waves in the sample 28. The resulting ultrasonic echoes are converted into electrical signals by the transducer and then gated into the spectrum analyzer by receiver gate 29. This arrangement produces spectra that are equivalent to shock-exciting the transducer with a true delta function shock-excitation.

  20. Frequency Stability of Atomic Frequency Standards beyond Quantum Projection Noise

    E-print Network

    G. M. Saxena

    2011-04-07

    In this paper we describe that the optically pumped frequency standards can have frequency stability beyond the quantum noise limit by detecting the Ramsey resonance through the squeezed light. In this paper we report that instead of considering the interaction of entangled atoms in the microwave region, it will be more practical to create the entanglement of the atoms in the detection region using the squeezed light, which is also used for the detection of the Ramsey resonance. The advantage of squeezing can be derived when the technical noises have been removed.

  1. Frequency translation method for low frequency variable gain amplification and filtering

    E-print Network

    Feng, Mabel Y

    2007-01-01

    This thesis discusses an innovative solution to an industry challenge. A frequency translation method is designed to shift low frequency signals to intermediate frequencies in order to utilize higher-frequency components. ...

  2. Intermediate-Frequency-to-Video-Band Converter

    NASA Technical Reports Server (NTRS)

    Ham, N. C.; Chavez, V. M.; Chen, V. S.; Sato, T.

    1986-01-01

    Analog and digital circuits combined to frequency-convert from intermediate frequencies directly to video-band frequencies to meet stringent requirements. IF-to-video-band converter operates on principle of signal-band cancellation in phase-quadrature circuits. Downconverts intermediate frequencies directly to video-band frequencies to near-zero frequency with good image-band rejection and low phase variation within passband.

  3. Active Faraday optical frequency standard.

    PubMed

    Zhuang, Wei; Chen, Jingbiao

    2014-11-01

    We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 ?W. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks. PMID:25361349

  4. Variable frequency drive applications guide

    SciTech Connect

    Laloudakis, D.J.

    1991-10-01

    Traditionally, fans and pumps have been designed to be capable of handling the maximum demand of the system in which they are installed. However, quite often the actual demand can vary and it can be much lower than the original design capacity. These situations have been corrected in the past through additions of outlet dampers to fans or throttling valves to pumps. While these can be effective and simple controls they severely affect the efficiency of the system. Variable frequency (speed) is the most efficient means of capacity control. The most cost effective method of achieving variable speed capacity control is using AC adjustable frequency drives. AC adjustable frequency controls convert any fixed speed AC motor into an adjustable speed device. Adjusting the speed of a motor, by controlling the frequency of the AC power to that motor, reduces its horsepower requirements. According to pump and fan laws, capacity is proportional to speed while horsepower is proportional to the cube of the speed. Therefore, by reducing the speed of an AC motor by 20 percent the horsepower requirement is reduced by nearly 50 percent. Reduced speed through variable frequency control allows for flexibility of meeting changing weather and comfort requirements without operating costly equipment at full capacity.

  5. Frequency-chirped subwavelength nanoantennas.

    PubMed

    Yaacobi, Ami; Watts, Michael R

    2012-12-01

    Herein we propose, theoretically investigate, and numerically demonstrate the first use to our knowledge of frequency chirping to achieve broadband, efficient subwavelength vertical emission from a dielectric waveguide. We demonstrate this unique and effective approach in the telecom C band in a nanophotonic frequency-chirped dipole antenna. The structure utilizes a plasmonic antenna placed above an Si3N4 waveguide and a ground plane to enhance emission efficiency. Three-dimensional finite-difference time-domain simulations reveal up to 55% vertical emission efficiency, and a bandwidth of 500 nm is possible in a structure less than half a wavelength long. The design methodology and theoretical underpinnings of frequency-chirped nanophotonic antennas coupled to dielectric waveguides are presented. PMID:23202110

  6. The Planck Low Frequency Instrument

    E-print Network

    N. Mandolesi; C. Burigana; R. C. Butler; F. Cuttaia; A. De Rosa; F. Finelli; E. Franceschi; A. Gruppuso; M. Malaspina; G. Morgante; G. Morigi; L. Popa; M. Sandri; L. Stringhetti; L. Terenzi; L. Valenziano; F. Villa

    2004-11-15

    Planck is the third generation of mm-wave instruments designed for space observations of the cosmic microwave background (CMB) anisotropies within the new Cosmic Vision 2020 ESA Science Program. Planck will map the whole sky with unprecedented sensitivity, angular resolution, and frequency coverage, and it likely leads us to the final comprehension of the CMB anisotropies. The Low Frequency Instrument (LFI), operating in the 30-70 GHz range, is one of the two instruments onboard Planck satellite, sharing the focal region of a 1.5 meter off-axis dual reflector telescope together with the High Frequency Instrument (HFI) operating at 100-857 GHz. We present LFI and discuss the major instrumental systematic effects that could degrade the measurements and the solutions adopted in the design and data analysis phase in order to adequately reduce and control them.

  7. High frequency audiometry. Clinical aspects.

    PubMed

    Osterhammel, D

    1980-01-01

    For 2 years past a previously described quasi-free-field high frequency audiometer delivering pure tones from 4 to 20 kHz has been incorporated in the audiological test battery. By this technique it is possible to obtain reliable and reproducible thresholds above the age of 8--9 years. In several case histories it is illustrated how high frequency audiometry (HFA) contributes to a better audiological diagnostic and it is predicted that HFA is of value in research studies on presbycusis, ototoxicity, noise vulnerability, and in hereditary studies on deafness. The physiological presbycusis demands normative reference values for each age decade. Many other factors, however, can cause an impaired high frequency hearing which is a severe limitation to the diagnostic value of abnormal findings. PMID:7466287

  8. Variable frequency microwave heating apparatus

    SciTech Connect

    Bible, D.W.; Lauf, R.J.; Johnson, A.C.; Thigpen, L.T.

    1999-10-05

    A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  9. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.67 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.14 5 12 57.14 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

  10. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.48 Missing 2 1.90 Missing 2 1.90 Response Frequency Percent Response Frequency Percent Course Materials were.62 5 65 61.90 Missing 2 1.90 Missing 2 1.90 Response Frequency Percent Response Frequency Percent

  11. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.19 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.56 5 43 79.63 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

  12. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.63 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.81 5 32 59.26 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

  13. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.94 Missing 1 1.89 Missing 1 1.89 Response Frequency Percent Response Frequency Percent Course Materials were.15 5 32 60.38 Missing 1 1.89 Missing 1 1.89 Response Frequency Percent Response Frequency Percent

  14. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.00 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were 40.00 5 15 37.50 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

  15. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.90 Missing 4 3.45 Missing 4 3.45 Response Frequency Percent Response Frequency Percent Course Materials were.28 5 63 54.31 Missing 2 1.72 Missing 2 1.72 Response Frequency Percent Response Frequency Percent

  16. Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in

    E-print Network

    Walters, Bradley B.

    Response Frequency Percent Response Frequency Percent I have learned and understood the subject.10 Missing 1 0.95 Missing 1 0.95 Response Frequency Percent Response Frequency Percent Course Materials were 44.76 5 45 42.86 Missing 1 0.95 Missing 1 0.95 Response Frequency Percent Response Frequency Percent

  17. The frequency selectivity of the 500 HZ frequency following response.

    PubMed

    Huis in't Veld, F; Osterhammel, P; Terkildsen, K

    1977-01-01

    In order to evaluate the frequency selectivity of the 500 Hz FFR we applied narrow-band masking at closely spaced center frequencies in the range 0.25 to 4 kHZ. The results show clearly that it is the apical part of the cochlea that generates the 500 Hz FFR, but the area of the basilar membrane that contributes is rather broad. It was evident that some of the masking effect that was observed in the Vertex-derived response stemmed from as yet obsure brain stem mechanisms. Examination of 3 patients with selected types of hearing impairment confirmed the masking results. When there is a low frequency loss there will still be a 500 Hz FFR and the same is true when the loss is in the medium to high frequencies. It is possible that precise determination of the latency to single waves in the response may allow a more exact prediction with regard to which location on the basilar membrane generates the response in the individual patient. PMID:594636

  18. Bichromatically pumped microresonator frequency combs

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Wabnitz, S.

    2014-07-01

    A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrödinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.

  19. Frequency Effects, Noticing, and Creativity

    ERIC Educational Resources Information Center

    Tarone, Elaine

    2002-01-01

    Ellis's target article suggests that language processing is based on frequency and probabilistic knowledge and that language learning is implicit. These findings are consistent with those of SLA researchers working within a variationist framework (e.g., Tarone, 1985; Bayley & Preston, 1996). This paper provides a brief overview of this research…

  20. Multi-frequency resonant antenna

    NASA Technical Reports Server (NTRS)

    Temps, A. J., Jr.; Visscher, J.

    1970-01-01

    Antenna is simultaneously resonant at 8.75 MHz, 11.825 MHz, and 20.562 MHz. It provides a near-field radiator which has a constant current distribution across its radiating elements for each of the resonant frequencies.

  1. Chladni Plates at High Frequencies

    Microsoft Academic Search

    R. C. Colwell

    1934-01-01

    IN order to make a high-frequency oscillator for brass plates, I wound a suitable inductance around a nickel rod twelve inches long and one eighth of an inch in diameter. The inductance was excited at 15,000 vibrations per second from an audio vacuum tube circuit connected through a power amplifier. The nickel rod was in a vertical position and the

  2. Frequency hopping evanescent mode filter

    Microsoft Academic Search

    Jim Sherman

    1998-01-01

    This paper describes a novel high speed varactor tuned evanescent (EV) mode hopping filter operating at C-Band. The 6 ?sec tuning speed is compatible with military frequency-hopping applications. Loss compensation is provided by variable gain MMIC amplifiers between 3-pole filter sections

  3. Coded Phase\\/Frequency Modulation

    Microsoft Academic Search

    R. Padovani; J. K. Wolf

    1986-01-01

    Channel coding combined with expanded signal sets has been shown [1] to improve error performance over uncoded modulation without expanding the bandwidth of the transmitted signals. In this paper, new coded modulation formats defined over an expanded set of signals varying both in phase and frequency are presented. The new schemes combine FSK and PSK modulation and make use of

  4. Micromachining techniques at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Arscott, S.; Duvillaret, Lionel; Mounaix, Patrick; Garet, Frederic; Coutaz, Jean-Louis; Lippens, D.

    1999-09-01

    In this paper we have characterized the refractive indexed and absorption coefficient of negative photoresist NANO XP SU-8 from 0.1-1.6 THz using THz time-domain spectroscopy. Over the measured frequency range it was found that the refractive index is a relatively flat function of frequency, decreasing from 1.8 to 1.7. The value of absorption coefficient is seen to increase in a line fashion over the given frequency range, being 25 cm-1 at 1 THz. From this data we have extracted functions of dielectric constant and dielectric loss tangent versus frequency, quantities which will be of use for future THz circuit design. In addition to these measurements, we have demonstrated two novel applications of SU-8. First, we have fabricated membrane-like features by using a multi-exposure photolithographic technique on a single layer of SU-8, and second we have utilized a thin layer of SU-8 as a patternable adhesion layer as part of a semiconductor epitaxial lift-off process designed to transfer III-V semiconductor epitaxial layers onto lower loss host substrates.

  5. Frequency analysis of digital holography

    Microsoft Academic Search

    Thomas M. Kreis

    2002-01-01

    A coherent optical imaging system consisting of recording a digital hologram by a CCD array and numerical reconstruction of the complex wave field in a computer is subjected to a frequency analysis. This analysis recognizes Fresnel and lensless Fourier transform holography; collimated and divergent reference waves; as well as the real image, the virtual image, and the dc term. The

  6. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  7. Frequency diversity and its applications

    Microsoft Academic Search

    F. Carassa; G. Tartara; E. Matricciani

    1988-01-01

    Adaptive shared resource methods may be the only available effective countermeasures to rain-induced attenuation in satellite communication systems above 20 GHz. Two of these methods, frequency diversity (FDV) and burst length control (BLC) are examined and compared by using a unified approach. The fundamental statistical relationships between unassisted and assisted conditions are derived, and optimum values are identified. It is

  8. Increasing the Frequency of Daydreaming.

    ERIC Educational Resources Information Center

    Gold, Steven R.; Cundiff, Gary

    1980-01-01

    Studied increased self-reported daydreaming as measured by the daydreaming frequency scale of the Imaginal Processes Inventory, after treatments of being presented with either a positive or neutral talk about the value of daydreaming and training v no training in the use of imagery. (Author)

  9. Increasing the Frequency of Stuttering.

    ERIC Educational Resources Information Center

    Young, Martin A.

    1985-01-01

    A literature review of conditions that might be expected to increase stuttering reveals that most investigators have not been able to raise stuttering frequency above control or base levels. Although some variables may increase stuttering, the research is too meager to speculate about underlying factors. (Author/CL)

  10. High frequency analysis of the

    E-print Network

    d'Orléans, Université

    ¡Equ S. This equation models accurately the propagation of the electromagnetic field of a laser, S : source term, h : wave length, 0 h 3 1. #12;High frequency analysis of the dissipative Helmholtz models accurately the propagation of the electromagnetic field of a laser in material medium. V1pxq

  11. Tracking frequency laser distance gauge

    Microsoft Academic Search

    J. D. Phillips; R. D. Reasenberg

    2005-01-01

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require laser distance gauges of substantially improved performance. We describe a laser gauge, based on Pound-Drever-Hall locking, in which the optical frequency is adjusted to maintain an interferometer's null condition. This technique has been demonstrated with pm performance. Automatic fringe hopping allows it to track arbitrary

  12. Emerging applications requiring precision time and frequency

    Microsoft Academic Search

    M. Bloch; D. Leonard; O. Mancini; T. McClelland

    2009-01-01

    Numerous commercial and military applications utilize precision quartz oscillators and\\/or atomic frequency standards to generate super-accurate frequencies and time signals crucial to system performance. Examples where precise time and frequency is essential are telecommunications, drilling for natural resources, synchronizing railroads, satellite ground stations, laboratory standards and various others. In military applications precise time and frequency is essential for synchronizing communications,

  13. Frequency stabilized 633 nm diode laser

    Microsoft Academic Search

    Janusz Pienkowski; Andrzej Grobelny

    2007-01-01

    Construction of a simple single-frequency diode laser 632.8 nm, used as a frequency standard in the laser interferometers is demonstrated. Two different systems applied for frequency stabilization of diode laser were used . For diode laser used as the secondary standard, the system stabilizes diode temperature, the frequency stability of the laser reaches value 1 part in 106. For diode

  14. Eggshell crack detection by dynamic frequency analysis

    Microsoft Academic Search

    Jun Wang; Ruishe Jiang

    2005-01-01

    Eggshell cracks were detected by the analysis of the dynamically measured frequency response wave of an egg excited with a light mechanical impact on different locations of the eggshell. As a result of the analysis, the dominant resonance frequency could be observed and the frequency value is lower in the intact eggs. For the cracked eggs, the same peak frequencies

  15. Very high frequency EMAT for resonant measurement

    Microsoft Academic Search

    K. Kawashima

    1994-01-01

    Very high frequency resonant EMAT technique is described at frequencies over 200 MHz which is a very high frequency room-temperature measurement of this type. This high frequency EMAT is very small, 25 mm×25 mm×40 mm, and is made from a permanent magnet with 20 mm diameter and a flat circular coil with 3 mm diameter. Longitudinal waves, slow and fast

  16. Time-Frequency localization of Multiband signals

    E-print Network

    Lakey, Joseph D.

    Time-Frequency localization of Multiband signals FFT, Norbert Wiener Center, February 20, 2009 Joe Lakey (w Scott Izu)1 February 20, 2009 Joe Lakey (w Scott Izu) Time-frequency multiband #12;Time and frequency localization Fourier transform: f () = R f (t) e-2it dt Joe Lakey (w Scott Izu) Time-frequency

  17. Time-Frequency localization of Multiband signals

    E-print Network

    Lakey, Joseph D.

    Time-Frequency localization of Multiband signals University of Arkansas, November 7, 2008 Joe Lakey (w Scott Izu)1 November 3, 2008 Joe Lakey (w Scott Izu) Time-frequency multiband #12;Time and frequency localization Fourier transform: f () = R f (t) e-2it dt Joe Lakey (w Scott Izu) Time-frequency

  18. Optical Frequency Synthesizer for Precision Spectroscopy

    Microsoft Academic Search

    R. Holzwarth; Th. Udem; T. W. Hänsch; J. C. Knight; W. J. Wadsworth; P. St. J. Russell

    2000-01-01

    We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the

  19. Low frequency and high-frequency cochlear nonlinearity in humans

    PubMed Central

    Gorga, Michael P.; Neely, Stephen T.; Dierking, Darcia M.; Kopun, Judy; Jolkowski, Kristin; Groenenboom, Kristin; Tan, Hongyang; Stiegemann, Bettina

    2008-01-01

    Low- and high-frequency cochlear nonlinearity was studied by measuring DPOAE I/O functions at 0.5 and 4 kHz in 103 normal-hearing subjects. Behavioral thresholds at both f2's were used to set L2 in dB SL for each subject. Primary levels were optimized by determining the L1 resulting in the largest Ldp for each L2 for each subject and both f2's. DPOAE I/O functions were measured using L2 inputs from ?10 dB SL (0.5 kHz) or ?20 dB SL (4 kHz) to 65 dB SL (both frequencies). Mean DPOAE I/O functions, averaged across subjects, differed between the two frequencies, even when threshold was taken into account. The slopes of the I/O functions were similar at 0.5 and 4 kHz for high-level inputs, with maximum compression ratios of about 4:1. At both frequencies, the maximum slope near DPOAE threshold was approximately 1, which occurred at lower levels at 4 kHz, compared to 0.5 kHz. These results suggest that there is a wider dynamic range and perhaps greater cochlear-amplifier gain at 4 kHz, compared to 0.5 kHz. Caution is indicated, however, because of uncertainties in the interpretation of slope and because the confounding influence of differences in noise level could not be completely controlled. PMID:17927427

  20. Automatic frequency control for FM transmitter

    NASA Technical Reports Server (NTRS)

    Honnell, M. A. (inventor)

    1974-01-01

    An automatic frequency control circuit for an FM television transmitter is described. The frequency of the transmitter is sampled during what is termed the back porch portion of the horizontal synchronizing pulse which occurs during the retrace interval, the frequency sample compared with the frequency of a reference oscillator, and a correction applied to the frequency of the transmitter during this portion of the retrace interval.

  1. Cross-frequency Doppler sensitive signal processing

    NASA Astrophysics Data System (ADS)

    Wagstaff, Ronald A.

    2005-04-01

    When there is relative motion between an acoustic source and a receiver, a signal can be Doppler shifted in frequency and enter or leave the processing bins of the conventional signal processor. The amount of the shift is determined by the frequency and the rate of change in the distance between the source and the receiver. This frequency Doppler shifting can cause severe reductions in the processors performance. Special cross-frequency signal processing algorithms have recently been developed to mitigate the effects of Doppler. They do this by using calculation paths that cut across frequency bins in order to follow signals during frequency shifting. Cross-frequency spectral grams of a fast-flying sound source were compared to conventional grams, to evaluate the performance of this new signal processing method. The Doppler shifts in the data ranged up to 70 contiguous frequency bins. The resulting cross-frequency grams showed that three paths provided small to no improvement. Four paths showed improvements for either up-frequency or down-frequency shifting, but not for both. Two paths showed substantial improvement for both up-frequency and down-frequency shifting. The cross-frequency paths will be defined, and comparisons between conventional and cross-frequency grams will be presented. [Work supported by Miltec Corporation.

  2. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, S.

    1984-02-09

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  3. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, Salvatore (Port Jefferson, NY)

    1985-01-01

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  4. High-Frequency Inductor Materials

    NASA Astrophysics Data System (ADS)

    Varga, L. K.

    2014-01-01

    The Finemet-type nanocrystalline alloy represents an advanced soft-magnetic metal-metal-type nanocomposite with an eddy-current-determined high- frequency limit. A survey of different heat treatments under tensile stress is presented to tailor the hysteresis loop by induced transversal anisotropy. The flattened loop having reduced effective permeability enhances the eddy- current limit in the MHz region; For example, continuous stress annealing in a tubular furnace of 1 m length at 650°C, pulling the ribbon with a velocity of 4 m/min under a tensile stress of 200 MPa, results in a wound core having a permeability of 120 and a frequency limit of 10 MHz. Careful annealing preserves the static coercivity below 10 A/m. The power loss at 0.1 T and 100 kHz is only 82 mW/cm3, which is an order of magnitude lower then the values obtained for Sendust™ cores in similar conditions.

  5. Frequency response of electrochemical cells

    NASA Technical Reports Server (NTRS)

    Thomas, Daniel L.

    1989-01-01

    Impedance concepts can be applied to the analysis of battery electrodes, yielding information about the structure of the electrode and the processes occurring in the electrode. Structural parameters such as the specific area (surface area per gram of electrode) can be estimated. Electrode variables such as surface overpotential, ohmic losses, and diffusion limitations may be studied. Nickel and cadmium electrodes were studied by measuring the ac impedance as a function of frequency, and the specific areas that were determined were well within the range of specific areas determined from BET measurements. Impedance spectra were measured for the nickel and cadmium electrodes, and for a 20 A-hr NiCd battery as functions of the state of charge. More work is needed to determine the feasibility of using frequency response as a nondestructive testing technique for batteries.

  6. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  7. Linear radio frequency power detector

    Microsoft Academic Search

    Ming-Liang Shieh; Wei-Ju Lai; Jin-Shun Li; Yen-Lung Chiang; Han-Hsin Wu; Chin-Chung Xsieh; Chih-Ho Tu; Sheng-Wen Chen; Janne-Wha Wu

    2009-01-01

    In this paper, a design for high dynamic range applicable of power detector by using successive detection logarithmic amplifier (SDLA) configuration consists of PMOS load limiting amplifier and unbalanced source-coupled pairs. This device was been fabricated by TSMC 0.18-¿m 1P6M CMOS process. The experimental results show that the dynamic range of the power detector the frequency 900-MHz is almost kept

  8. Frequency Conversion with Semiconductor Heterostructures

    Microsoft Academic Search

    V. Berger

    \\u000a In this lecture different aspects of frequency conversion in semiconductor heterostructures are reviewed. Thanks to the very\\u000a high degree of control of growth and technology of thin layers of semiconductors, both electronic wavefunction and optical\\u000a mode properties can be tailored, through band gap engineering and refractive index engineering. These two aspects lead to\\u000a the possibility of optimization of nonlinear susceptibilities

  9. Radio frequency coaxial feedthrough device

    DOEpatents

    Owens, Thomas L. (Kingston, TN); Baity, Frederick W. (Oak Ridge, TN); Hoffman, Daniel J. (Oak Ridge, TN); Whealton, John H. (Oak Ridge, TN)

    1987-01-01

    A radio frequency coaxial vacuum feedthrough is provided which utilizes a cylindrical ceramic vacuum break formed of an alumina ceramic. The cylinder is coaxially disposed and brazed between tapered coaxial conductors to form a vacuum sealed connection between a pressurized upstream coaxial transmission line and a utilization device located within a vacuum container. The feedthrough provides 50 ohm matched impedance RF feedthrough up to about 500 MHz at power levels in the multimegawatt range.

  10. Intelligent Radio Frequency (RF) Monitoring 

    E-print Network

    Kimbrough, B.

    2010-01-01

    ? Intelligent Radio Frequency (RF) Monitoring ? 2009 Armstrong International, Inc. www.armstronginternational.com 2 ?Expect many enjoyable experiences!? David M. Armstrong Present Process Challenges ? Identifying a failure ? Procedure... $1340 $5430 Steam Loss Per Blow-Thru Trap (lb/hr) Cost Avoidance Per Blow-Thru Trap ($$$/time period) 5 ?Expect many enjoyable experiences!? David M. Armstrong Location 6 ?Expect many enjoyable experiences!? David M. Armstrong Continuous RF...

  11. Superconducting Radio-Frequency Cavities

    NASA Astrophysics Data System (ADS)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  12. [The frequency of repeat radiograpy].

    PubMed

    van der Merwe, E J

    1980-01-12

    A study of the rates of repeat radiography in two hospitals in the Cape Peninsula was undertaken. The relationship between these rates and the type of examination as well as the contributing factors was established. The total frequencies for the two hospitals varied from 10,1% to 14%. The predominant reasons for 78% of repeat radiographs were over-exposure, under-exposure and positioning. PMID:7404029

  13. Lucid dreaming frequency and personality

    Microsoft Academic Search

    Michael Schredl; Daniel Erlacher

    2004-01-01

    The term lucid dream designates a dream in which the dreamer is––while dreaming––aware that she\\/he is dreaming. Within an unselected student sample, 82% of the participants reported the occurrence of at least one lucid dream. In this sample, lucid dreaming frequency was not associated with the Big Five personality factors and, thus, theories linking lucid dreaming with introversion or well-being,

  14. HELIOS dual swept frequency radiometer

    NASA Technical Reports Server (NTRS)

    White, J. R.

    1975-01-01

    The HELIOS dual swept frequency radiometer, used in conjunction with a dipole antenna, was designed to measure electromagnetic radiation in space. An engineering prototype was fabricated and tested on the HELIOS spacecraft. Two prototypes and two flight units were fabricated and three of the four units were integrated into the HELIOS spacecraft. Two sets of ground support equipment were provided for checkout of the radiometer.

  15. Tracking frequency laser distance gauge

    Microsoft Academic Search

    J. D. Phillips; R. D. Reasenberg

    2005-01-01

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require laser distance gauges of substantially improved performance. We describe a laser gauge, based on Pound–Drever–Hall locking, in which the optical frequency is adjusted to maintain an interferometer’s null condition. This technique has been demonstrated with pm performance. Automatic fringe hopping allows it to track arbitrary

  16. Phase and Frequency Noise Metrology

    NASA Astrophysics Data System (ADS)

    Rubiola, E.; Giordano, V.; Volyanskiy, K.; Larger, L.

    2009-04-01

    As a consequence of a general trend in the physics of oscillators and clocks towards optics, phase and frequency metrology is rapidly moving to optics too. Yet, optics is not replacing the traditional radio-frequency (RF) and microwave domains. Instead, it adds tough challenges. Precision frequency-stability measurements are chiefly based on the measurement of phase noise, which is the main focus of this article. Major progress has been achieved in two main areas. The first is the extreme low-noise measurements, based on the bridge (interferometric) method1,2 in real time or with sophisticated correlation and averaging techniques.3,4 The second is the emerging field of microwave photonics, which combines optics and RF/microwaves. This includes the femtosecond laser, the two-way fiber links,5 the noise measurement systems based on the fiber6 and the photonic oscillator.7,8 Besides, the phenomenology of flicker (1/f) noise is better understood, though the ultimate reasons are still elusive.

  17. Tracking frequency laser distance gauge

    NASA Astrophysics Data System (ADS)

    Phillips, J. D.; Reasenberg, R. D.

    2005-06-01

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require laser distance gauges of substantially improved performance. We describe a laser gauge, based on Pound-Drever-Hall locking, in which the optical frequency is adjusted to maintain an interferometer's null condition. This technique has been demonstrated with pm performance. Automatic fringe hopping allows it to track arbitrary distance changes. The instrument is intrinsically free of the nm-scale cyclic bias present in traditional (heterodyne) high-precision laser gauges. The output is a radio frequency, readily measured to sufficient accuracy. The laser gauge has operated in a resonant cavity, which improves precision, can suppress the effects of misalignments, and makes possible precise automatic alignment. The measurement of absolute distance requires little or no additional hardware, and has also been demonstrated. The proof-of-concept version, based on a stabilized HeNe laser and operating on a 0.5 m path, has achieved 10 pm precision with 0.1 s integration time, and 0.1 mm absolute distance accuracy. This version has also followed substantial distance changes as fast as 16 mm/s. We show that, if the precision in optical frequency is a fixed fraction of the linewidth, both incremental and absolute distance precision are independent of the distance measured. We discuss systematic error sources, and present plans for a new version of the gauge based on semiconductor lasers and fiber-coupled components.

  18. Tracking frequency laser distance gauge

    SciTech Connect

    Phillips, J.D.; Reasenberg, R.D. [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, MS63, 60 Garden St., Cambridge, Massachusetts 02138 (United States)

    2005-06-15

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require laser distance gauges of substantially improved performance. We describe a laser gauge, based on Pound-Drever-Hall locking, in which the optical frequency is adjusted to maintain an interferometer's null condition. This technique has been demonstrated with pm performance. Automatic fringe hopping allows it to track arbitrary distance changes. The instrument is intrinsically free of the nm-scale cyclic bias present in traditional (heterodyne) high-precision laser gauges. The output is a radio frequency, readily measured to sufficient accuracy. The laser gauge has operated in a resonant cavity, which improves precision, can suppress the effects of misalignments, and makes possible precise automatic alignment. The measurement of absolute distance requires little or no additional hardware, and has also been demonstrated. The proof-of-concept version, based on a stabilized HeNe laser and operating on a 0.5 m path, has achieved 10 pm precision with 0.1 s integration time, and 0.1 mm absolute distance accuracy. This version has also followed substantial distance changes as fast as 16 mm/s. We show that, if the precision in optical frequency is a fixed fraction of the linewidth, both incremental and absolute distance precision are independent of the distance measured. We discuss systematic error sources, and present plans for a new version of the gauge based on semiconductor lasers and fiber-coupled components.

  19. On Centralized and Distributed Frequency Assignment in Cognitive Radio Based Frequency Hopping Cellular Networks

    E-print Network

    Wichmann, Felix

    On Centralized and Distributed Frequency Assignment in Cognitive Radio Based Frequency Hopping Centre, RWTH Aachen University, Germany, gross@umic.rwth-aachen.de Abstract--Frequency Assignment frequency hopping as one possible frequency assignment approach. In particular we focus our attention

  20. E4.18 Radio Frequency Electronics Copyright 2006 Dr Stepan Lucyszyn Frequency Spectrum

    E-print Network

    Papavassiliou, Christos

    E4.18 Radio Frequency Electronics Copyright © 2006 Dr Stepan Lucyszyn Frequency Spectrum and Applications #12;E4.18 Radio Frequency Electronics Copyright © 2006 Dr Stepan Lucyszyn #12;E4.18 Radio Frequency Electronics Copyright © 2006 Dr Stepan Lucyszyn #12;E4.18 Radio Frequency Electronics Copyright

  1. The Low-Frequency Encoding Disadvantage: Word Frequency Affects Processing Demands

    E-print Network

    Reder, Lynne

    The Low-Frequency Encoding Disadvantage: Word Frequency Affects Processing Demands Rachel A. Diana-frequency disadvantage during encoding. That is, low-frequency words require more processing resources to be encoded episodically than high-frequency words. Under encoding conditions in which processing resources are limited

  2. Frequency distribution of combinational channels of a superheterodyne receiver with single frequency conversion

    Microsoft Academic Search

    S. M. Saraev; K. L. Afanasev

    1975-01-01

    The paper analyzes combinational noise which is generated in a superheterodyne receiver during frequency conversion. There is a set of signal frequencies whose harmonics, interacting with the harmonics of the heterodyne, form a frequency which is equal to the intermediate frequency. Frequencies which belong to this set are called combinational reception channels. When there is radiation of sufficient power whose

  3. Frequency-frequency correlation functions and apodization in two-dimensional infrared vibrational echo spectroscopy

    E-print Network

    Fayer, Michael D.

    Frequency-frequency correlation functions and apodization in two-dimensional infrared vibrational is to monitor the dynamical evolution of a molecular system by reporting the time dependent frequency fluctuations of an ensemble of vibrational probes. The vibrational frequency-frequency correlation function

  4. A tunable dual frequency dye laser - dual frequency oscillator design

    NASA Technical Reports Server (NTRS)

    Abury, Y.

    1983-01-01

    The pulsed dye laser offers a tunable oscillator, followed by three amplifiers. It is pumped by a dual frequency Nd:YAG laser. Tuning and spectral width are controlled by a holographic network connected to a high power telescope. The modified two wavelength dye laser allows for absorption lidar techniques for remote sensing of the atmosphere. Line switching is achieved by electrooptical commutation. A feasibility experiment was performed with the original oscillator. A model was then built, and tested with different dyes. After a few modifications were made to improve the conversion efficiency, this oscillator was inserted in the laser to check whether the amplifier stages were correctly adjusted.

  5. Design of multipass frequency selective surface

    NASA Astrophysics Data System (ADS)

    Zang, Jiefeng; Lin, Chuan; Qing, Anyong

    2015-03-01

    Equivalent circuit model of the frequency select surface is given, and a feasible method of design of multi-pass frequency selective surface is discussed. Based on the method, a novel frequency selective surface with two pass bands is presented. The simulation results indicate that, the center frequencies of the bands are at 2.95GHz and 8.6GHz, and the 3dB bandwidth is 3.5% and 5%. Also the center frequencies and the transmittance of the pass bands are affected less by the polarization direction and incident angel of the wave, or the structure exhibits a great filter feature as a frequency selective surface.

  6. Optical frequency synthesizer for precision spectroscopy

    PubMed

    Holzwarth; Udem; Hansch; Knight; Wadsworth; Russell

    2000-09-11

    We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the uncertainty of this new approach to 5. 1x10(-16). This opens the door for measurement and synthesis of virtually any optical frequency and is ready to revolutionize frequency metrology. PMID:10977987

  7. A low power prescaler, phase frequency detector, and charge pump for a 12 ghz frequency synthesizer

    E-print Network

    Eschenko, Evan Lee

    2009-05-15

    A low power implementation of a CMOS frequency synthesizer at 12 GHz is an important step to improve the efficiency of a wireless transceiver in this frequency band. Since synthesizers are often employed as reference frequency sources such as local...

  8. Frequency dependence and frequency control of microbubble streaming flows

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Rallabandi, Bhargav; Hilgenfeldt, Sascha

    2013-02-01

    Steady streaming from oscillating microbubbles is a powerful actuating mechanism in microfluidics, enjoying increased use due to its simplicity of manufacture, ease of integration, low heat generation, and unprecedented control over the flow field and particle transport. As the streaming flow patterns are caused by oscillations of microbubbles in contact with walls of the set-up, an understanding of the bubble dynamics is crucial. Here we experimentally characterize the oscillation modes and the frequency response spectrum of such cylindrical bubbles, driven by a pressure variation resulting from ultrasound in the range of 1 kHz raisebox {-.9ex{stackrel{textstyle <}{˜ }} }f raisebox {-.9ex{stackrel{textstyle <}{˜ }} } 100 kHz. We find that (i) the appearance of 2D streaming flow patterns is governed by the relative amplitudes of bubble azimuthal surface modes (normalized by the volume response), (ii) distinct, robust resonance patterns occur independent of details of the set-up, and (iii) the position and width of the resonance peaks can be understood using an asymptotic theory approach. This theory describes, for the first time, the shape oscillations of a pinned cylindrical bubble at a wall and gives insight into necessary mode couplings that shape the response spectrum. Having thus correlated relative mode strengths and observed flow patterns, we demonstrate that the performance of a bubble micromixer can be optimized by making use of such flow variations when modulating the driving frequency.

  9. Investigation of Wavelet-Based Enhancements to Nuclear Quadrupole Resonance Explosives Detectors

    SciTech Connect

    Kercel, Stephen W.; Dress, William B.; Hibbs, Andrew D.; Barrall, Geoffrey A.

    1998-06-01

    Nuclear Quadrupole Resonance (NQR) is effective for the detection and identification of certain types of explosives such as RDX, PETN and TNT. In explosive detection, the NQR response of certain 14N nuclei present in the crystalline material is probed. The 14N nuclei possess a nuclear quadrupole moment which in the presence of an electric field gradient produces an energy level splitting which may be excited by radio-frequency magnetic fields. Pulsing on the sample with a radio signal of the appropriate frequency produces a transient NQR response which may then be detected. Since the resonant frequency is dependent upon both the quadrupole moment of the 14N nucleus and the nature of the local electric field gradients, it is very compound specific. Under DARPA sponsorship, the authors are using multiresolution methods to investigate the enhancement of operation of NQR explosives detectors used for land mine detection. For this application, NQR processing time must be reduced to less than one second. False alarm responses due to acoustic and piezoelectric ringing must be suppressed. Also, as TNT is the most prevalent explosive found in land mines, NQR detection of TNT must be made practical despite unfavorable relaxation tunes. All three issues require improvement in signal-to-noise ratio, and all would benefit from improved feature extraction. This paper reports some of the insights provided by multiresolution methods that can be used to obtain these improvements. It includes results of multiresolution analysis of experimentally observed NQR signatures for RDX responses and various false alarm signatures in the absence of explosive compounds.

  10. Frequency Content in Glider Data

    NASA Astrophysics Data System (ADS)

    Mancero-Mosquera, Isaac; Gerin, Riccardo; Mauri, Elena; Poulain, Pierre Marie

    2013-04-01

    In the present work, a methodology to analyse the spectral content of Glider data is put forward, by showing the application to temperature series taken during the glider mission TENUSE-LIDEX in the Tyrrhenian Sea between 3 and 21 July 2010. An initial processing is made to ensure that every datum has a spatio-temporal reference, to correct the sensor lag errors, as well as to provide a basic quality control and eliminate unrealistic data (e.g., outliers, spikes). The main problem to overcome is the identification and separation of spectral content due exclusively to the experimental settings. Trajectory and bathymetry have an effect on the time span between a consecutive pair of a downcast-upcast profiles. The proposed procedure is based on the reconstruction of data series for fixed depths as a function of time. The main effect of the downcast-upcast sampling scheme is avoided by taking only the downcast profiles. Thus, the Fourier transform is applied to the reconstructed temperature series for every level and their power computed. Several groups of frequency with relatively high energy appear at selected depths. Oscillations of about 2.5 hours periodicity appear between 6 and 13 meters depth. Some periodicities of 11h, 17h, 21h and 24h also show strong energy peaks in the power spectra, appearing mainly at 9 m depth; while the 24h oscillation shows also reinforcement at 25 m depth. Additional investigation was carried out by estimating the coherence and phase of several groups of frequencies between different depths. For a specific depth, cross-spectra were computed with the series of all the successive levels. Coherent clusters of oscillations were identified at preferential depths between 9 and 30 meters, depending on the frequency, showing in-phase regime. Finally, techniques based on the Wavelet transform were applied in order to assess the stationarity and spatial homogeneity of the oscillations found in the analysis.

  11. 47 CFR 76.1804 - Aeronautical frequencies: leakage monitoring (CLI).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Aeronautical frequencies: leakage monitoring...Reports and Filings § 76.1804 Aeronautical frequencies: leakage monitoring...new frequency or frequencies in the aeronautical radio frequency bands...

  12. 47 CFR 76.1804 - Aeronautical frequencies: leakage monitoring (CLI).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Aeronautical frequencies: leakage monitoring...Reports and Filings § 76.1804 Aeronautical frequencies: leakage monitoring...new frequency or frequencies in the aeronautical radio frequency bands...

  13. Planet frequency from microlensing observations

    NASA Astrophysics Data System (ADS)

    Cassan, A.; Ranc, C.

    2014-12-01

    Galactic gravitational microlensing is a very efficient technique to detect brown dwarfs and extrasolar planets at large orbital distances from their stars, and down to Earth-mass planets. More than 50 planets have been discovered so far, with 31 already published. Recent statistical results on the frequency of exoplanets based on several years of microlensing observations find that planets should be the rule rather than the exception, and confirm that super-Earth are much more frequent that giant planets in the Galaxy.

  14. Oscillator Architectures and Enhanced Frequency Synthesizer 

    E-print Network

    Park, Sang Wook

    2009-11-16

    to implement. To address this problem, a frequency harmonic shaping technique is proposed. It utilizes a finite impulse response filter improving the linearity by rejecting certain harmonics. A prototype SC BPF oscillator with an oscillating frequency of 10 MHz...

  15. 47 CFR 90.613 - Frequencies available.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01false Frequencies available.90.613 Section...CONTINUED)SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICESRegulations Governing Licensing and Use of Frequencies in the 806-824,...

  16. 47 CFR 90.613 - Frequencies available.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01false Frequencies available.90.613 Section...CONTINUED)SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICESRegulations Governing Licensing and Use of Frequencies in the 806-824,...

  17. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE Technical Standards...Requirements § 5.101 Frequency stability. Experimental Radio Service licensees shall ensure...remain within the authorized frequency band under normal...

  18. 47 CFR 90.613 - Frequencies available.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01false Frequencies available.90.613 Section...CONTINUED)SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICESRegulations Governing Licensing and Use of Frequencies in the 806-824,...

  19. 47 CFR 90.613 - Frequencies available.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01false Frequencies available.90.613 Section...CONTINUED)SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICESRegulations Governing Licensing and Use of Frequencies in the 806-824,...

  20. 47 CFR 5.303 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequencies. 5.303 Section 5.303 Telecommunication...COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE Program Experimental Radio Licenses § 5.303 Frequencies. Licensees may operate in any...

  1. 47 CFR 5.303 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequencies. 5.303 Section 5.303 Telecommunication...COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE Program Experimental Radio Licenses § 5.303 Frequencies. Licensees may operate in...

  2. 47 CFR 90.613 - Frequencies available.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01false Frequencies available.90.613 Section...CONTINUED)SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICESRegulations Governing Licensing and Use of Frequencies in the 806-824,...

  3. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE Technical Standards...Requirements § 5.101 Frequency stability. Experimental Radio Service licensees shall ensure...remain within the authorized frequency band under normal...

  4. Multiple frequency printed slot and dipole antennas 

    E-print Network

    Kolsrud, Arild

    1997-01-01

    Multiple frequency antennas are becoming more and more important as the technology advances. Printed circuit antennas can be designed to achieve multiple frequency operation. The advantages like low cost, conformal and planar, and a possible...

  5. Frequency Synthesis in Wireless and Wireline Systems 

    E-print Network

    Turker, Didem 1981-

    2010-12-06

    First, a frequency synthesizer for IEEE 802.15.4 / ZigBee transceiver applications that employs dynamic True Single Phase Clocking (TSPC) circuits in its frequency dividers is presented and through the analysis and measurement ...

  6. Laser frequency modulation with electron plasma

    NASA Technical Reports Server (NTRS)

    Burgess, T. J.; Latorre, V. R.

    1972-01-01

    When laser beam passes through electron plasma its frequency shifts by amount proportional to plasma density. This density varies with modulating signal resulting in corresponding modulation of laser beam frequency. Necessary apparatus is relatively inexpensive since crystals are not required.

  7. Substructure coupling in the frequency domain

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

  8. Frequency Responses Of Hot-Wire Anemometers

    NASA Technical Reports Server (NTRS)

    Watmuff, Jonathan H.

    1992-01-01

    Report describes theoretical study of frequency response of constant-temperature hot-wire anemometer, with view toward increasing frequency response while maintaining stable operation in supersonic flow. Effects of various circuit parameters discussed.

  9. Calibration for Frequencies of Stellar Spectral Lines 

    E-print Network

    Gomez, Juana

    2010-07-14

    development is the use of laser frequency combs to provide the calibration frequencies. However, this approach is very time consuming and expensive. We are proposing a simple calibration approach using weak molecular absorption lines. Our new approach is based...

  10. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.349... (a) The frequency assigned to an aeronautical utility station at an airport...to the ground control frequency, an aeronautical utility station at an airport...

  11. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at...

  12. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is required to be changed because of an action by the FAA...

  13. 47 CFR 87.351 - Frequency changes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is required to be changed because of an action by the FAA...

  14. 47 CFR 87.349 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.349... (a) The frequency assigned to an aeronautical utility station at an airport...to the ground control frequency, an aeronautical utility station at an airport...

  15. 47 CFR 87.217 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at...

  16. ELM frequency feedback control on JET

    NASA Astrophysics Data System (ADS)

    Lennholm, M.; Beaumont, P. S.; Carvalho, I. S.; Chapman, I. T.; Felton, R.; Frigione, D.; Garzotti, L.; Goodyear, A.; Graves, J.; Grist, D.; Jachmich, S.; Lang, P.; Lerche, E.; de la Luna, E.; Mooney, R.; Morris, J.; Nave, M. F. F.; Rimini, F.; Sips, G.; Solano, E.; Tsalas, M.; EFDA Contributors, JET

    2015-06-01

    This paper describes the first development and implementation of a closed loop edge localized mode (ELM) frequency controller using gas injection as the actuator. The controller has been extensively used in recent experiments on JET and it has proved to work well at ELM frequencies in the 15–40 Hz range. The controller responds effectively to a variety of disturbances, generally recovering the requested ELM frequency within approximately 500 ms. Controlling the ELM frequency has become of prime importance in the new JET configuration with all metal walls, where insufficient ELM frequency is associated with excessive tungsten influx. The controller has allowed successful operation near the minimum acceptable ELM frequency where the best plasma confinement can be achieved. Use of the ELM frequency controller in conjunction with pellet injection has enabled investigations of ELM triggering by pellets while maintaining the desired ELM frequency even when pellets fail to trigger ELMs.

  17. Radio frequency power load and associated method

    NASA Technical Reports Server (NTRS)

    Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

    2010-01-01

    A radio frequency power load and associated method. A radio frequency power load apparatus includes a container and a fluid having an ion source therein, the fluid being contained in the container. Two conductors are immersed in the fluid. A radio frequency transmission system includes a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus includes a fluid having an ion source therein, and two conductors immersed in the fluid. A method of dissipating power generated by a radio frequency transmission system includes the steps of: immersing two conductors of a radio frequency power load apparatus in a fluid having an ion source therein; and connecting the apparatus to an amplifier of the transmission system.

  18. Frequency selective surfaces for Terahertz applications 

    E-print Network

    Sanz Fernandez, Juan Jose; Fernandez, Juan Jose Sanz

    2012-11-29

    This thesis presents both theoretical and experimental investigations of the performance and capabilities of frequency selective surfaces (FSS) applied at THz frequencies. The aim is to explore and extend the use of FSS, ...

  19. Reduction of frequency noise and frequency shift by phase shifting elements in frequency modulation atomic force microscopy.

    PubMed

    Kobayashi, Kei; Yamada, Hirofumi; Matsushige, Kazumi

    2011-03-01

    We recently reported the analysis of the frequency noise in the frequency modulation atomic force microscopy (FM-AFM) both in high-Q and low-Q environments [Rev. Sci. Instrum. 80, 043708 (2009)]. We showed in the paper that the oscillator noise, the frequency fluctuation of the oscillator, becomes prominent in the modulation frequency lower than f(0)?2Q, where f(0) and Q are the resonance frequency and Q-factor. The magnitude of the oscillator noise is determined by the slope of the phase versus frequency curve of the cantilever at f(0). However, in actual FM-AFM in liquids, the phase versus frequency curve may not be always ideal because of the existence of various phase shifting elements (PSEs). For example, the spurious resonance peaks caused by the acoustic excitation and a band-pass filter in the self-oscillation loop increase the slope of the phase versus frequency curve. Due to those PSEs, the effective Q-factor is often increased from the intrinsic Q-factor of the cantilever. In this article, the frequency noise in the FM-AFM system with the PSEs in the self-oscillation loop is analyzed to show that the oscillator noise is reduced by the increase of the effective Q-factor. It is also shown that the oscillation frequency deviates from the resonance frequency due to the increase of the effective Q-factor, thereby causing the reduction in the frequency shift signal with the same factor. Therefore the increase of the effective Q-factor does not affect the signal-to-noise ratio in the frequency shift measurement, but it does affect the quantitativeness of the measured force in the FM-AFM. Furthermore, the reduction of the frequency noise and frequency shift by the increase of the effective Q-factor were confirmed by the experiments. PMID:21456746

  20. Science with the Frequency Agile Solar Radiotelescope

    E-print Network

    m0.2-3 GHz~60LFA Low Frequency Array 2 m2-24 GHz~100HFA High Frequency Array Antenna Size Frequency CorrelatorCorrelator ~1 GHzInstantaneous Bandwidth Stokes IV (QU)Polarization 10 ms (LFA) 100 ms (HFA) Time Resolution 0.1% (LFA) 1% (HFA) Frequency Resolution SpecQuantity #12;EGU Meeting 2004 April 29 NJIT Center

  1. UWB Spatial-Frequency Channel Characterization

    Microsoft Academic Search

    Wen Zhang; Thushara D. Abhayapala; Jian Zhang

    This paper investigates the spatial-frequency chan- nel characterization of Ultra-wideband (UWB) wireless commu- nication systems. Firstly, a novel frequency dependent UWB channel model is constructed based on the theory of electro- magnetic diffraction mechanism, which causes the field strength to vary with the frequency in each multipath. Secondly, we build a space-frequency model, which includes spatial characteristics such as angular

  2. Atomic quantum memory for multimode frequency combs

    E-print Network

    Z. Zheng; O. Mishina; N. Treps; C. Fabre

    2015-04-06

    We propose a Raman quantum memory scheme that uses several atomic ensembles to store and retrieve the multimode highly entangled state of an optical quantum frequency comb, such as the one produced by parametric down-conversion of a pump frequency comb. We analyse the efficiency and the fidelity of such a quantum memory. Results show that our proposal may be helpful to multimode information processing using the different frequency bands of an optical frequency comb.

  3. METHODS OF RADIO-FREQUENCY CURRENT DRIVE

    E-print Network

    METHODS OF RADIO-FREQUENCY CURRENT DRIVE N. J. FISCH* Princeton Plasma Physics Laboratory-670 Radio-frequency waves can penetrate thermonuclear plasmas, depositing momentum and energy with great. INTRODUCTION Using radio-frequency (rf) waves to drive the toroidal current in tokamak reactors is attractive

  4. Temporal relationships between independent EEG frequency modulations

    E-print Network

    Makeig, Scott

    Temporal relationships between independent EEG frequency modulations Julie Onton1 and Scott Makeig1 was found across subjects between all lower frequency modulations (delta, theta, alpha, and beta) and the broadband gamma modulations, suggesting that within single cortical source domains, when low-frequency power

  5. DIODE LASER FREQUENCY STANDARD FOR LASER INTERFEROMETRY

    Microsoft Academic Search

    Janusz Pienkowski

    Diode lasers are becoming increasingly important in length metrology. We demonstrate construction of a simple single-frequency diode laser 632,8 nm, used as a frequency standard in the laser interferometers. We present two different systems applied for frequency stabil ization of diode laser . For diode laser used as the secondar y standard, the system stabilizes diode temperature, the frequ ency

  6. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W. (Livermore, CA); Johnson, Michael A. (Pleasanton, CA); Globig, Michael A. (Livermore, CA)

    1989-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of th frequency during the pulse.

  7. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W. (Livermore, CA); Johnson, Michael A. (Pleasanton, CA); Globig, Michael A. (Livermore, CA)

    1990-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of the frequency during the pulse.

  8. On zero frequency magnetic fluctuations in plasmas

    Microsoft Academic Search

    T. Tajima; S. Cable; R. M. Kulsrud

    1992-01-01

    A plasma sustains fluctuations of electromagnetic fields and particle density even in a thermal equilibrium and such fluctuations have a large zero frequency peak. The level of fluctuations in the plasma for a given wavelength and frequency of electromagnetic fields is calculated through the fluctuation-dissipation theorem. The frequency spectrum shows that the energy contained in this peak is complementary to

  9. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

    A description is given of a method to heat air coming from a turbojet compressor to a temperature necessary to produce required expansion without requiring fuel. This is done by high frequency heating, which heats the walls corresponding to the combustion chamber in existing jets, by mounting high frequency coils in them. The current transformer and high frequency generator to be used are discussed.

  10. ROBUST FREQUENCY DOMAIN ARMA Jonas Gillberg

    E-print Network

    Gustafsson, Fredrik

    ROBUST FREQUENCY DOMAIN ARMA MODELLING Jonas Gillberg Fredrik Gustafsson Rik Pintelon introduced by Hampel. The estimation takes place in the context of frequency domain continuous-time ARMA: robust estimation, outlier rejection, continuous-time, ARMA, CARMA, frequency Domain, influence function

  11. NBS time and frequency dissemination services

    Microsoft Academic Search

    S. Howe

    1979-01-01

    Detailed descriptions are given of the time and frequency dissemination services of the National Bureau of Standards. These services include the broadcasts from radio stations WWV, WWVH, WWVB, and WWVL, and new times and frequency calibration services using television. The services available on 1 April 1979 are indicated. A list of other publications available about the Time and Frequency Division

  12. Concerning Optimum Frequencies for Space Vehicle Communication

    Microsoft Academic Search

    S. Perlman; L. Kelley; W. Russell; W. Stuart

    1959-01-01

    Optimum frequencies for the varied needs of space vehicle communication can best be determined from the estimated system performance. Each of the contributing equipment and propagation factors over the range of the radio frequency spectrum affects the minimum tolerable signal-to-noise power ratio at the receiver. Over the range of the radio frequency spectrum, the behavior of the individual building blocks,

  13. Heterodyne laser instantaneous frequency measurement system

    SciTech Connect

    Wyeth, R.W.; Johnson, M.A.; Globig, M.A.

    1989-12-17

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of the frequency during the pulse.

  14. Recording small frequency drifts of microwave oscillators

    Microsoft Academic Search

    V. P. Denisov; S. A. Lebedinskiy; V. I. Nazarov

    1984-01-01

    A method of recording small frequency drifts of ultrahigh-stability microwave oscillators by heterodyning without causing instability is proposed, a method which involves two frequency stepdowns with subsequent measurement of period fluctuation in the low-frequency signal by means of an electronic period counter. The latter contains an internal quartz oscillator and its relative error of period measurement, which determines the sensitivity

  15. 47 CFR 74.402 - Frequency assignment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequency assignment. 74.402 Section...Broadcast Stations § 74.402 Frequency assignment. Operation on all...listed in this section (except: frequencies 26.07 MHz, 26.11 MHz,...

  16. 47 CFR 74.402 - Frequency assignment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequency assignment. 74.402 Section...Broadcast Stations § 74.402 Frequency assignment. Operation on all...listed in this section (except: frequencies 26.07 MHz, 26.11 MHz,...

  17. 47 CFR 74.502 - Frequency assignment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequency assignment. 74.502 Section 74...Broadcast Auxiliary Stations § 74.502 Frequency assignment. (a) Except as provided...the band in accordance with the Table of Frequency Allocations. These stations will...

  18. Frequency-Bin Entanglement with Tunable Phase

    E-print Network

    Xianxin Guo; Peng Chen; Chi Shu; M. M. T. Loy; Shengwang Du

    2015-04-15

    We describe a technique to produce narrow-band photon pairs with frequency-bin entanglement, whose relative phase can be tuned using linear polarization optics. We show that, making use of the polarization-frequency coupling effect, the phase of a complex polarizer can be transferred into the frequency entanglement.

  19. 47 CFR 74.502 - Frequency assignment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequency assignment. 74.502 Section 74...Broadcast Auxiliary Stations § 74.502 Frequency assignment. (a) Except as provided...the band in accordance with the Table of Frequency Allocations. These stations will...

  20. 47 CFR 74.502 - Frequency assignment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Frequency assignment. 74.502 Section 74...Broadcast Auxiliary Stations § 74.502 Frequency assignment. (a) Except as provided...the band in accordance with the Table of Frequency Allocations. These stations will...

  1. 47 CFR 74.402 - Frequency assignment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Frequency assignment. 74.402 Section...Broadcast Stations § 74.402 Frequency assignment. Operation on all...listed in this section (except: frequencies 26.07 MHz, 26.11 MHz,...

  2. 47 CFR 74.502 - Frequency assignment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Frequency assignment. 74.502 Section 74...Broadcast Auxiliary Stations § 74.502 Frequency assignment. (a) Except as provided...the band in accordance with the Table of Frequency Allocations. These stations will...

  3. Coverage Improvement for Dual Frequency SBAS

    E-print Network

    Stanford University

    ;13 Reference Networks with GAGAN and SDCM WAAS EGNOS MSAS GAGAN SDCM #12;14 Current Coverage WAAS EGNOS MSAS Frequency Coverage (with GAGAN + Russia) WAAS EGNOS MSAS GAGAN SDCM #12;19 Expanded Networks WAAS EGNOS MSAS GAGAN SDCM #12;20 Dual Frequency, Expanded Networks WAAS EGNOS MSAS GAGAN SDCM #12;21 Dual Frequency

  4. Low frequency ac waveform generator

    DOEpatents

    Bilharz, O.W.

    1983-11-22

    Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

  5. Low frequency AC waveform generator

    DOEpatents

    Bilharz, Oscar W. (Scotia, NY)

    1986-01-01

    Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

  6. ENEA-UCI Structures of the low frequency Alfven continuous spectrum 1 Structures of the low frequency Alfven

    E-print Network

    Zonca, Fulvio

    ´en continuum at low frequencies: · finite frequency fishbone oscillations at the GAM frequency and "low Observation of finite frequency fishbone oscillations at the GAM frequency (F. Nabais, et al. 2005, PoP 12

  7. Preferred frequencies for three unconsolidated earth materials

    SciTech Connect

    Gilcrist, Laura E.; Baker, Gregory S.; Sen, Surajit [Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260 (United States); Department of Earth and Planetary Science, University of Tennessee, Knoxville, Tennessee 37996 (United States); Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260 (United States)

    2007-12-17

    Exploring near-surface mechanical wave propagation through cohesive and noncohesive soils is important for detecting buried objects (i.e., landmines and unexploded ordnance). Here, we determine that certain preferred frequencies travel through specific soils more efficiently. A controlled-frequency acoustic seismic source was developed to modulate the applied frequency and amplitude. Surface response due to continuous waves traveling through soils was recorded both instantaneously and after a finite load time. Preferred frequencies for sand, clay loam, and silt loam were measured to be 300-330, 100-140, and 140-260 Hz, respectively. Observed frequency shifts were dependent upon applied amplitude and load time.

  8. Pressurized high frequency thermoacoustic engines

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas D.

    Acoustic heat engines show much promise for converting waste heat to electricity. Since most applications require high power levels, high frequency thermoacoustic engines can reach such performance by operating with a pressurized working gas. Results on a 3 kHz prime mover, consisting of a quarter-wave resonator and a random stack material between two heat exchangers, show that the acoustic power from such a device is raised substantially as the working gas is pressurized. At pressures up to approximately 10 bar, the increase in acoustic power is approximately linear to the increase in pressure, and thus is an effective way to increase the power output of thermoacoustic engines. Since the heat input was not changed during the experiments, the increases in acoustic power translate directly to increases in engine efficiency which is calculated as the output acoustic power divided by the input heat power. In most experiments run in this study, the engine efficiency increased by a factor of at least 4 as the pressure was increased from 2 bar up to about 10 bar. Further increases in pressure lead to acoustic power saturation and eventual attenuation. This is most likely due to a combination of several factors including the shrinking thermal penetration depth, and the fact that the losses increase faster with pressure in a random stack material than in traditional parallel plates. Pressurization also leads to a lower DeltaT for onset of oscillations in the range of 10 bar of mean pressure, potentially opening up even more heat sources that can power a thermoacoustic engine. Results from another 3 kHz engine, one that was pressurized itself as opposed to being placed in a pressurized chamber, are also presented. The configuration of this engine solves the problem of how to simultaneously pressurize the engine and inject heat into the hot heat exchanger. It was also noted that the geometry of the resonator cavity in the quarter wavelength pressurized engine plays an important role in the determination of the resonance frequency of the engine, and special care needs to be taken to ensure that the stack is positioned correctly with regards to the resonance frequency. Pressurization promises to greatly increase the number of applications of acoustic engines to a variety of real world settings, providing a key source of renewable energy for the future.

  9. Pulsation frequency distribution in Delta Scuti stars

    E-print Network

    Balona, L A; Pamyatnykh, A A

    2015-01-01

    We study the frequency distributions of Delta Scuti stars observed by the Kepler satellite in short-cadence mode. To minimize errors in the estimated stellar parameters, we divided the instability strip into ten regions and determined the mean frequency distribution in each region. We confirm that the presence of low frequencies is a property of all Delta Scuti stars, rendering meaningless the concept of Delta Sct/Gamma Dor hybrids. We obtained the true distribution of equatorial rotational velocities in each region and calculated the frequency distributions predicted by pulsation models, taking into account rotational splitting of the frequencies. We confirm that rotation cannot account for the presence of low frequencies. We calculated a large variety of standard pulsation models with different metal and helium abundances, but were unable to obtain unstable low-frequency modes driven by the kappa mechanism in any model. We also constructed models with modified opacities in the envelope. Increasing the opaci...

  10. Radio Frequency Power Load and Associated Method

    NASA Technical Reports Server (NTRS)

    Srinivasan, V. Karthik (Inventor); Freestone, Todd M. (Inventor); Sims, William Herbert, III (Inventor)

    2014-01-01

    A radio frequency power load and associated method. A radio frequency power load apparatus may include a container with an ionized fluid therein. The apparatus may include one conductor immersed in a fluid and another conductor electrically connected to the container. A radio frequency transmission system may include a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus may include a fluid having an ion source therein, one conductor immersed in a fluid, and another conductor electrically connected to the container. A method of dissipating power generated by a radio frequency transmission system may include constructing a waveguide with ionized fluid in a container and connecting the waveguide to an amplifier of the transmission system.

  11. Variable frequency microwave heating of food.

    PubMed

    Bows, J R

    1999-01-01

    Industrial microwave food processing is universally based on single frequency microwave sources. With the emergence of variable frequency microwave ovens, it is possible to exploit the frequency dependence of a food's permittivity and/or choice of heating frequency, for example as a new route to achieving targeted heating. Variable frequency heating procedures are developed to overcome the geometry of a roughly spherical foodstuff dominating the heating pattern when heated in fixed frequency applicators. Target mean temperatures of 55, 75 and 90 degrees C within 2 minutes and without physical damage were set; means of 54.5 +/- 4.1, 75.1 +/- 4.7 and 87.6 +/- 3.5 degrees C respectively were achieved within the time constraint and with no major physical damage, based on combining 8 discrete frequencies between 2.4 and 6.2 GHz. PMID:10687155

  12. Dual frequency launcher for circularly polarized antenna

    NASA Astrophysics Data System (ADS)

    Chen, Ming H.

    1989-10-01

    A dual frequency antenna feed is formed from a central, circular waveguide connected to the flat boundry of circular, disk-shaped resonant cavity. A second circular waveguide is connected one end of a disk-shaped resonant cavity. Energy of one frequency enters and exits the cavity along the common axis of the waveguides. Energy of the second frequency is introduced to the same resonant cavity by way of a plurality of bandpass filters, also connected to the cavity. This energy enters by way of slots in the cylindrical walls of the cavity. The central circular waveguide is propagating at one frequency but cut off at the second frequency. These bandpass filters are at this pass band for the second frequency, but at the rejection band for the first frequency. Therefore, the isolation between these two input ports are obtained.

  13. On the Carrier Frequency Offset Estimation for Frequency Hopping Burst Mode Mobile Radio

    E-print Network

    Yýlmaz, Özgür

    On the Carrier Frequency Offset Estimation for Frequency Hopping Burst Mode Mobile Radio G¨okhan M to the number of radio frequency bursts (RFB) used, constellation and SNR level, and is an important measure a message over multiple radio frequency bursts (RFB) to increase the robustness of the system against

  14. On Phase Noise and Frequency Offsets in the Reception of Frequency Dehopped Mary FSK

    Microsoft Academic Search

    P. H. Wittke; P. J. McLane; P. Ma

    1983-01-01

    We consider the error performance of frequency dehopped, noncoherent, M-ary FSK when the receiver is a bank of energy detectors. The effects of phase noise and frequency offset are included in the analysis as our application is for the EHF band with fast-frequency hopping. Our result on the effect of frequency offsets on the bit error rate (BER) is the

  15. Estimating the number of frequency hopping interferers using spectral sensing with time and frequency offset measurements

    Microsoft Academic Search

    A. Gok; Shaunak Joshi; John Villasenor; Danijela Cabric

    2009-01-01

    A critical aspect of spectrum sensing involves determining the number and type of transmitters in the band of interest. We present a technique that exploits a combination of temporal and frequency-based analysis to enable significantly more accurate frequency offset measurements than would be possible with frequency domain measurements alone, thus enabling improved RF fingerprinting for frequency hopping devices.

  16. A new frequency synthesizer for coherent communication in frequency hopping spread spectrum multiple access communication systems

    Microsoft Academic Search

    Hisayoshi Sugiyama; Yoshifumi Amemiya

    1983-01-01

    In Spread Spectrum Multiple Access (SSMA) communications systems, the narrow band information spectrum is uniformly spread over the communication bandwidth, and plural communication parties share the same frequency band at the same time. Frequency-Hopping SSMA (FH-SSMA) involves the generation of pseudonoise signals, for spectrum spreading of the information signal, by means of a frequency synthesizer. Conventional frequency synthesizers, howewver, cannot

  17. Differential Roles of Frequency-following and Frequency-doubling Visual Responses

    E-print Network

    Reber, Paul J.

    Differential Roles of Frequency-following and Frequency-doubling Visual Responses Revealed revealed the spatial and functional segregation of frequency-following (the first harmonic) and frequency, a divergence not attributable to absolute response fre- quency. Functionally, voluntary visual­spatial

  18. Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb

    E-print Network

    Washburn, Brian

    a 1532 nm CW laser stabilized to an acetylene-filled kagome photonic crystal fiber infrared reference [5Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb Jinkang@phys.ksu.edu Abstract: The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using

  19. Space-frequency correlation of classical waves in disordered media: High-frequency and

    E-print Network

    Fannjiang, Albert

    OFFPRINT Space-frequency correlation of classical waves in disordered media: High-frequency) 14005 www.epljournal.org doi: 10.1209/0295-5075/80/14005 Space-frequency correlation of classical waves in disordered media: High-frequency and small-scale asymptotics A. C. Fannjiang Department of Mathematics

  20. Elimination of pump-induced frequency jitter on fiber-laser frequency combs

    E-print Network

    Washburn, Brian

    Elimination of pump-induced frequency jitter on fiber-laser frequency combs J. J. McFerran, W. C. ID 68330) Optical frequency combs generated by femtosecond fiber lasers typically exhibit significant frequency noise that causes broad optical linewidths, particularly in the comb wings and in the carrier

  1. Frequency domain optical parametric amplification

    PubMed Central

    Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

    2014-01-01

    Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43?mJ two-cycle pulses at 1.8??m wavelength. PMID:24805968

  2. Biomechanics of Fundamental Frequency Regulation

    PubMed Central

    Chan, Roger W.; Siegmund, Thomas; Zhang, Kai

    2009-01-01

    Accurate characterization of biomechanical characteristics of the vocal fold is critical for understanding the regulation of vocal fundamental frequency (F0), which depends on the active control of the intrinsic laryngeal muscles as well as the passive biomechanical response of the vocal fold lamina propria. Specifically, the tissue stress-strain response and viscoelastic properties under cyclic tensile deformation are relevant, when the vocal folds are subjected to length and tension changes due to posturing. This paper describes a constitutive modeling approach quantifying the relationship between vocal fold stress and strain (or stretch), and establishes predictions of F0 with the string model of phonation based on the constitutive parameters. Results indicated that transient and time-dependent changes in F0, including global declinations in declarative sentences, as well as local F0 overshoots and undershoots, can be partially attributed to the time-dependent viscoplastic response of the vocal fold cover. PMID:19415568

  3. Lightweight, high-frequency transformers

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.

    1983-01-01

    The 25-kVA space transformer was developed under contract by Thermal Technology Laboratory, Buffalo, N. Y. The NASA Lewis transformer technology program attempted to develop the baseline technology. For the 25-kVA transformer the input voltage was chosen as 200 V, the output voltage as 1500 V, the input voltage waveform as square wave, the duty cycle as continuous, the frequency range (within certain constraints) as 10 to 40 kHz, the operating temperatures as 85 deg. and 130 C, the baseplate temperature as 50 C, the equivalent leakage inductance as less than 10 micro-h, the operating environment as space, and the life expectancy as 10 years. Such a transformer can also be used for aircraft, ship and terrestrial applications.

  4. Frequency stabilization of algaas lasers

    SciTech Connect

    Ohtsu, M.; Tsuchida, H.; Tako, T.

    1982-01-01

    Performances of semiconductor lasers have been remarkably improved by the demand of the optical communications industry. Recently, a single longitudinal mode, CW oscillation at room temperature has been realized. The price of each laser has been reduced as low as $250. These lasers are mostly oscillated in the near-infrared, and the coherent lights of 0.83 micrometers and 1.3-1.6 micrometers in wavelengths are obtained by AlGaAs lasers and InGaAsP lasers, respectively. Since few number of other kind of lasers oscillates in these wavelength regions, these semiconductor lasers could be conveniently used not only in optical communications but in many fields of application, e.g., laser spectroscopy, optical pumping, frequency and length standards, laser radar, air-borne gyroscope, etc.

  5. Modulating action of low frequency oscillations on high frequency instabilities in Hall thrusters

    NASA Astrophysics Data System (ADS)

    Liqiu, Wei; Liang, Han; Ziyi, Yang; Jing, Li; Yong, Cao; Daren, Yu; Jianhua, Du

    2015-02-01

    It is found that the low frequency oscillations have modulating action on high frequency instabilities in Hall thrusters. The physical mechanism of this modulation is discussed and verified by numerical simulations. Theoretical analyses indicate that the wide-range fluctuations of plasma density and electric field associated with the low frequency oscillations affect the electron drift velocity and anomalous electron transport across the magnetic field. The amplitude and frequency of high frequency oscillations are modulated by low frequency oscillations, which show the periodic variation in the time scale of low frequency oscillations.

  6. Single-frequency approximation of the coupling ray theory

    E-print Network

    Cerveny, Vlastislav

    Single-frequency approximation of the coupling ray theory Ludek Klimes & Petr Bulant Department­ray­theory Green tensor is frequency dependent, and is usually calculated for many frequencies. This frequency this frequency dependence. In the vicinity of a given prevailing frequency, we approximate the frequency­ domain

  7. The characteristics of atmospheric radio frequency discharges with frequency increasing at a constant power density

    SciTech Connect

    Zhang Yuantao; Li Qingquan; Lou Jie; Li Qingmin [School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China)

    2010-10-04

    A computational model is used to investigate the characteristics of atmospheric radio frequency discharges by increasing frequency from 20 to 100 MHz at a constant power density. The simulation results show that increasing frequency can effectively enhance electron density before the transition frequency but after it the ignition is quenched then the electron density decreases. However this simulation also indicates the maximum time-averaged electron energy reduces monotonically with the excitation frequency increasing at a constant power density.

  8. Noncoherent fast frequency hopped\\/joint frequency-phase modulation over Rayleigh fading channels

    Microsoft Academic Search

    Ibrahim Ghareeb; A. Yongacoglu

    1994-01-01

    The performance of a fast frequency hopped spread spectrum system is studied. The frequency hopped signal is a combination of multi frequency-multi phase signals and is referred to as fast frequency hopped\\/joint frequency-phase modulation (FFH\\/JFPM). A noncoherent receiver for the FFH\\/JFPM signals is introduced and an exact expression for the bit error is obtained. A performance analysis of this system

  9. Frequency comparison and absolute frequency measurement of I 2-stabilized lasers at 532 nm

    Microsoft Academic Search

    A. Yu. Nevsky; R. Holzwarth; J. Reichert; Th. Udem; T. W. Hänsch; J. von Zanthier; H. Walther; H. Schnatz; F. Riehle; P. V. Pokasov; M. N. Skvortsov; S. N. Bagayev

    2001-01-01

    A frequency comparison and an absolute frequency measurement of iodine stabilized frequency-doubled Nd:YAG lasers at 532 nm has been performed at the Max-Planck-Institute for Quantum Optics. Two independent I2-stabilized laser systems, one assembled at the Institute of Laser Physics, Novosibirsk, Russia, the other at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany were investigated. Using a phase-coherent frequency chain, the absolute frequency of

  10. VCO PLL Frequency Synthesizers for Spacecraft Transponders

    NASA Technical Reports Server (NTRS)

    Smith, Scott; Mysoor, Narayan; Lux, James; Cook, Brian

    2007-01-01

    Two documents discuss a breadboard version of advanced transponders that, when fully developed, would be installed on future spacecraft to fly in deep space. These transponders will be required to be capable of operation on any deepspace- communications uplink frequency channel between 7,145 and 7,235 MHz, and any downlink frequency channel between 8,400 and 8,500 MHz. The document focuses on the design and operation of frequency synthesizers for the receiver and transmitter. Heretofore, frequency synthesizers in deep-space transponders have been based on dielectric resonator oscillators (DROs), which do not have the wide tuning bandwidth necessary to tune over all channels in the uplink or downlink frequency bands. To satisfy the requirement for tuning bandwidth, the present frequency synthesizers are based on voltage-controlled-oscillator (VCO) phase-locked loops (PLLs) implemented by use of monolithic microwave integrated circuits (MMICs) implemented using inGaP heterojunction bipolar transistor (HBT) technology. MMIC VCO PLL frequency synthesizers similar to the present ones have been used in commercial and military applications but, until now, have exhibited too much phase noise for use in deep-space transponders. The present frequency synthesizers contain advanced MMIC VCOs, which use HBT technology and have lower levels of flicker (1/f) phase noise. When these MMIC VCOs are used with high-speed MMIC frequency dividers, it becomes possible to obtain the required combination of frequency agility and low phase noise.

  11. Simulation of multi-frequency ECRH

    SciTech Connect

    Rognlien, T.D.

    1981-11-23

    We use a test particle simulation code to investigate electron cyclotron heating in a magnetic mirror well. A comparison is made between heating with one frequency and heating with two closely spaced frequencies. The code follows electron orbits in the presence of one or two monochromatic ECRH waves using guiding center equations and an equation for the electron gyrophase. Coulomb collisions with electrons and ions are simulated as a Monte Carlo scattering process. We find for the parameters of SM-1 that at the fundamental resonance the heating rate, or velocity rf diffusion coefficient, begins to decrease significantly from the quasilinear value for epsilon/sub e/ greater than or equal to 10 keV due to superadiabatic effects. As suggested by Howard et al., using multiple frequencies pushes the superadiabatic boundary to higher energies. For a given energy, the optimum frequency separations for two frequencies are those which cause the axial bounce resonances to interlace; i.e., odd multiples of the bounce frequency, ..omega../sub b/. This interlacing increases the chance of resonance overlap and thus stochasticity. If the frequency difference is equal to an even multiple of ..omega../sub b/, the diffusion coefficient returns to near its one frequency value. More generally, for more than two frequencies one should choose the frequency separation such that the bounce resonances interlace evenly. Detailed calculations are presented for SM-1 parameters.

  12. 47 CFR 80.1165 - Assignment and use of frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...MARITIME SERVICES Voluntary Radio Installations Voluntary Telephony...1165 Assignment and use of frequencies. Frequencies for general radiotelephone...available to ships in three radio frequency bands. Use of...

  13. 47 CFR 80.1165 - Assignment and use of frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...MARITIME SERVICES Voluntary Radio Installations Voluntary Telephony...1165 Assignment and use of frequencies. Frequencies for general radiotelephone...available to ships in three radio frequency bands. Use of...

  14. 47 CFR 80.1165 - Assignment and use of frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...MARITIME SERVICES Voluntary Radio Installations Voluntary Telephony...1165 Assignment and use of frequencies. Frequencies for general radiotelephone...available to ships in three radio frequency bands. Use of...

  15. 47 CFR 80.1165 - Assignment and use of frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...MARITIME SERVICES Voluntary Radio Installations Voluntary Telephony...1165 Assignment and use of frequencies. Frequencies for general radiotelephone...available to ships in three radio frequency bands. Use of...

  16. 47 CFR 80.1165 - Assignment and use of frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...MARITIME SERVICES Voluntary Radio Installations Voluntary Telephony...1165 Assignment and use of frequencies. Frequencies for general radiotelephone...available to ships in three radio frequency bands. Use of...

  17. Frequency Comb Generation in Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Pappas, David; Erickson, Robert; Vissers, Michael; Ku, Hsiang-Sheng

    2015-03-01

    We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? = 2 resonators at T =3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 108 The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves. Generation of combs in this frequency range allows for unprecedented analysis of this non-linear phenomena in the time domain. We acknowledge DARPA and the NIST Quantum Information program.

  18. Compact stabilized semiconductor laser for frequency metrology.

    PubMed

    Liang, Wei; Ilchenko, Vladimir S; Eliyahu, Danny; Dale, Elijah; Savchenkov, Anatoliy A; Seidel, David; Matsko, Andrey B; Maleki, Lute

    2015-04-10

    We report on the development of a frequency modulatable 795 nm semiconductor laser based on self-injection locking to a high-quality-factor whispering-gallery-mode microresonator. The laser is characterized by residual amplitude modulation below -80??dB and frequency noise better than 300??Hz/Hz1/2 at offset frequencies ranging from 100 Hz to 10 MHz. The frequency modulation speed and span of the laser exceed 1 MHz and 4 GHz, respectively. Locking of the laser to the Doppler-free saturated absorption resonance of the Rb87D1 line is demonstrated and relative frequency stability better than 10-12 is measured for integration time spanning from 1 s to 1 day. The architecture demonstrated in this study is suitable for the realization of frequency modulatable lasers at any wavelength. PMID:25967323

  19. Power Supply for Variable Frequency Induction Heating Using MERS Soft-Switching High Frequency Inverter

    NASA Astrophysics Data System (ADS)

    Isobe, Takanori; Kitahara, Tadayuki; Fukutani, Kazuhiko; Shimada, Ryuichi

    Variable frequency induction heating has great potential for industrial heating applications due to the possibility of achieving heating distribution control; however, large-scale induction heating with variable frequency has not yet been introduced for practical use. This paper proposes a high frequency soft-switching inverter for induction heating that can achieve variable frequency operation. One challenge of variable frequency induction heating is increasing power electronics ratings. This paper indicates that its current source type dc-link configuration and soft-switching characteristics can make it possible to build a large-scale system with variable frequency capability. A 90-kVA 150-1000Hz variable frequency experimental power supply for steel strip induction heating was developed. Experiments confirmed the feasibility of variable frequency induction heating with proposed converter and the advantages of variable frequency operation.

  20. High-frequency nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Bimberg, D.; Fiol, G.; Meuer, C.; Laemmlin, M.; Kuntz, M.

    2007-02-01

    Recent results on GaAs-based high-speed mode-locked quantum dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode-locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultra-low timing jitter down to 190 fs, high output peak power beyond 1 W and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of quantum dot semiconductor optical amplifiers are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multi-wavelength amplification of three CWDM wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultra-fast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.

  1. [Low-Frequency Flow Oscillation

    NASA Technical Reports Server (NTRS)

    Bragg, Michael B.

    1997-01-01

    The results of the research conducted under this grant are presented in detail in three Master theses, by Heinrich, Balow, and Broeren. Additional analysis of the experimental data can be found in two AIAA Journal articles and two conference papers. Citations for all of the studies' publications can be found in the bibliography which is attached. The objective of Heinrich's study was to document the low-frequency flow oscillation on the LRN-1007 airfoil, which had been previously observed at low Reynolds number, to determine its origin, and explore the phenomenon at higher Reynolds number. Heinrich performed detailed flow visualization on the airfoil using surface fluorescent oil and laser-sheet off-body visualization. A large leading-edge separation bubble and trailing-edge separation was identified on the airfoil just prior to the onset of the unsteady stall flow oscillation. From the laser-sheet data, the unsteady flow appeared as a massive boundary-layer separation followed by flow reattachment. Hot-wire data were taken in the wake to identify the presence of the flow oscillation and the dominant frequency. The oscillation was found in the flow from a Reynolds number of 0.3 to 1.3 x 10 exp 6. The Strouhal number based on airfoil projected height was nominally 0.02 and increased slightly with increasing Reynolds number and significantly with increasing airfoil angle of attack. Balow focused his research on the leading-edge separation bubble which was hypothesized to be the origin of the low-frequency oscillation. Initially, experimental measurements in the bubble at the onset of the low-frequency oscillation were attempted to study the characteristics of the bubble and explain possible relationships to the shear-layer-flapping phenomena. Unfortunately, the bubble proved to be extremely sensitive to the probe interference and it drastically reduced the size of the bubble. These detailed measurements were then abandoned by Balow. However, this led to a series of tests where the leading-edge bubble and trailing-edge separation were altered and the affect on the flow-oscillation studied. Balow found that by tripping the airfoil boundary-layer with "zigzag" tape ahead of bubble separation, the bubble was effectively eliminated mid the oscillation suppressed. Wake survey drag measurements showed a drastic reduction in airfoil drag when the bubble and oscillation were eliminated. Using the "zigzag" tape, the trailing-edge separation was moved downstream approximately 5 percent chord. This was found to reduce the amplitude of the oscillation, particularly in the onset stage at low angle of attack (around 14 degrees). Through detailed analysis of the wake behind the airfoil during the unsteady flow oscillation, Balow provided a better understanding of the wake flowfield. Broeren studied the oscillating flowfield in detail at Reynolds number equal 3 x 10 exp 5 and an angle of attack of 15 degrees using laser Doppler velocimetry (LDV). Two-dimensional LDV data were acquired at 687 grid points above the model upper surface while hot-wire data were taken simultaneously in the wake. Using the hot-wire signal, the LDV data were phase averaged into 24 bins to represent a single ensemble average of one oscillation cycle. The velocity data showed a flowfield oscillation that could be divided into three flow regimes. In the first regime, the flow over the airfoil was completely separated initially, the flowfield reattached from the leading edge and the reattachment point moved downstream with increasing time or phase. Broeren referred to this as the reattachment regime. The bubble development regime followed, where a leading-edge separation bubble formed at the leading edge and grew with increasing time. During the initial part of this regime the trailing-edge separation continued to move downstream. However, during the last 30 degrees of phase the trailing-edge separation moved rapidly forward and appeared to merge with the leading-edge bubble. During the third regime, the separation regime, the flow was segmented f

  2. Microflare Statistics and Frequency Distribution

    NASA Astrophysics Data System (ADS)

    Christe, S. D.; Hannah, I.; Rauscher, E.; Krucker, S.; McTiernan, J.; Lin, R. P.

    2005-05-01

    RHESSI is uniquely suited to observe solar microflares due to its unique sensitivity in the 3-15 keV energy range (up to ~100 times better than previous solar instruments). As such, it provides new information on these low level transients. Initial results (Krucker et al 2002, Benz & Grigis 2002) suggest that microflares are different from larger flares. They are more often associated with steep nonthermal spectra (power law index -5 to -7). In this study, we present microflare statistics from times of low activity. A list of microflares was created by applying the standard RHESSI flare-finding algorithm to the lower 6-12 keV energy range (~10,000 events). Imaging was used in order to obtain positions of solar events and reject non-solar events. These solar events were then each spectrally analyzed. We present microflare statistics, including active region productivity, and the microflare frequency distribution. This work was supported by NASA contract NAS5-98033.

  3. Operation of Graphene Transistors at Gigahertz Frequencies

    Microsoft Academic Search

    Yu-Ming Lin; Keith A. Jenkins; Alberto Valdes-Garcia; Joshua P. Small; Damon B. Farmer; Phaedon Avouris

    2009-01-01

    Top-gated graphene transistors operating at high frequencies (GHz) have been fabricated and their characteristics analyzed. The measured intrinsic current gain shows an ideal 1\\/f frequency dependence, indicating an FET-like behavior for graphene transistors. The cutoff frequency fT is found to be proportional to the dc transconductance gm of the device. The peak fT increases with a reduced gate length, and

  4. High-frequency breakdown and paschen law

    Microsoft Academic Search

    J. C. Biswas; Ved Mitra

    1979-01-01

    In the present paper an attempt has been made to draw theoretically a correlation between the well-known Paschen curve and\\u000a the high-frequency breakdown characteristic of a gas device by interpreting electron mean free path in terms of the frequency\\u000a of the applied field. The analytical high-frequency breakdown characteristic, so obtained, agree fairly well with the experimental\\u000a results.

  5. Biorthogonal frequency-varying modulated lapped transform

    Microsoft Academic Search

    Yixin Gao; Guizhong Liu

    2009-01-01

    In this paper we introduce a biorthogonal frequency-varying modulated lapped transform (BFV-MLT) with flexible tiling behavior of time-frequency plane and attenuation of ringing artifacts. Biorthogonality allows accessorial freedom in designing the analysis and synthesis filter-banks and FVMLT provides nonuniform decomposition of signals with ideal time or frequency resolutions. By constructing a new approach to FV-MLT, we incorporate biorthogonality into FV-MLT

  6. Apparatus for measuring high frequency currents

    NASA Technical Reports Server (NTRS)

    Hagmann, Mark J. (Inventor); Sutton, John F. (Inventor)

    2003-01-01

    An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents.

  7. Frequency-offset insensitive digital modem techniques

    NASA Technical Reports Server (NTRS)

    Dutta, S.; Nicholas, D. C.

    1990-01-01

    Conventional DPSK systems are adversely affected by transmitter/receiver frequency offsets due to frequency reference errors and Doppler shifts. Two DPSK modem concepts are presented which avoid the long frequency acquisition process of conventional DPSK. One technique involves a modified demodulator for conventional DPSK signals, while the other involves making minor changes to both the modulator and demodulator. Simulation results are provided showing performance relative to conventional DPSK.

  8. Frequency modulation drive for a piezoelectric motor

    DOEpatents

    Mittas, Anthony (Albuquerque, NM)

    2001-01-01

    A piezoelectric motor has peak performance at a specific frequency f.sub.1 that may vary over a range of frequencies. A drive system is disclosed for operating such a motor at peak performance without feedback. The drive system consists of the motor and an ac source connected to power the motor, the ac source repeatedly generating a frequency over a range from f.sub.1 -.DELTA.x to f.sub.1 +.DELTA.y.

  9. Laser frequency stabilization using Zeeman effect

    Microsoft Academic Search

    B. Chéron; H. Gilles; J. Hamel; O. Moreau; H. Sorel

    1994-01-01

    We describe a new and easy to handle method to stabilize the laser frequency on an atomic transition. This method, based on Zeeman effect, involves the circular dichroism of an atomic vapour submitted to a magnetic field. It is applied to the frequency stabilization of a single frequency LNA laser on (2 (2 ^3S1-2 ^3P0) helium transition. Nous décrivons une

  10. Floodflow frequency model selection in Australia

    Microsoft Academic Search

    Richard M. Vogel; Thomas A. McMahon; Francis H. S. Chiew

    1993-01-01

    Vogel, R.M., McMahon, T.A. and Chiew, F.H.S., 1993. Floodflow frequency model selection in Australia. J. Hydrol., 146: 421~49. Uniform flood frequency guidelines in Australia and the United States recommend the use of the log Pearson type 3 (LP3) distribution in flood frequency investigations. Many investigators have suggested alternate models such as the Generalized Extreme Value (GEV) distribution as an improvement

  11. Beat frequency interference pattern characteristics study

    NASA Technical Reports Server (NTRS)

    Ott, J. H.; Rice, J. S.

    1981-01-01

    The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.

  12. Precision frequency measurements with entangled states

    E-print Network

    C. F. Roos

    2005-08-19

    We demonstrate how quantum entanglement can be used for precision frequency measurements with trapped ions. In particular, we show how to suppress linear Zeeman shifts in optical frequency measurements by using maximally entangled states of two ions even if the individual ions do not have any field-independent transition. In addition, this technique allows for an accurate measurement of small external field frequency shifts such as the electric quadrupole shift which are important for ion clock experiments.

  13. Broadband midinfrared frequency comb with tooth scanning

    NASA Astrophysics Data System (ADS)

    Lee, Kevin F.; Mas?owski, P.; Mills, A.; Mohr, C.; Jiang, Jie; Schunemann, Peter G.; Fermann, M. E.

    2015-03-01

    Frequency combs are a massively parallel source of extremely accurate optical frequencies. Frequency combs generally operate at the visible or near-infrared wavelengths, but fundamental molecular vibrations occur at midinfrared wavelengths. We demonstrate an optically-referenced, broadband midinfrared frequency comb based on a doublyresonant optical parametric oscillator (OPO). By tuning the wavelength of the reference laser, the comb line frequencies are tuned as well. By scanning the reference wavelength, any frequency can be accessed, not just the frequencies of the base comb. Combined with our comb-resolving Fourier transform spectrometer, we can measure 200 wavenumber wide broadband absorption spectra with 200 kHz linewidth comb teeth. Our OPO is pumped by an amplified Tm fiber frequency comb, with phase-locked carrier envelope offset frequency, and repetition rate fixed by phase-locking a frequency comb line to a narrow linewidth diode laser at a telecom channel. The frequency comb is referenced to GPS by long-term stabilization of the repetition rate to a selected value using the temperature of the reference laser as the control. The resulting pump comb is about 3W of 100 fs pulses at 418 MHz repetition rate at 1950 nm. Part of the comb is used for supercontinuum generation for frequency stabilization, and the rest pumps an orientation-patterned gallium arsenide (OP-GaAs) crystal in a doubly-resonant optical parametric oscillator cavity, yielding collinear signal and idler beams from about 3 to 5.5 ?m. We verify comb scanning by resolving the 200 MHz wide absorption lines of the entire fundamental CO vibrational manifold at 11 Torr pressure.

  14. Subjective Frequency Ratings for 432 ASL Signs

    PubMed Central

    Mayberry, Rachel I.; Hall, Matthew L.; Zvaigzne, Meghan

    2013-01-01

    Given the importance of lexical frequency for psycholinguistic research, and the lack of comprehensive frequency data for sign languages, we collected subjective estimates of lexical frequency for 432 signs in American Sign Language. Participants were 59 deaf signers who first began to acquire ASL at ages ranging from birth to 14 years with a minimum of 10 years experience. Subjective frequency estimates were made on a scale ranging from 1 = rarely see the sign to 7 = always see the sign. Mean subjective frequency ratings for individual signs did not vary in relation to age of sign language exposure (AoLE), chronological age, or length of ASL experience. Nor did AoLE show significant effects on response time for making the ratings. However, RT was highly correlated with mean frequency rating. These results suggest that the distributions of subjective lexical frequencies are consistent across signers with varying AoLE. The implications for research practice are that subjective frequency ratings from random samples of highly experienced deaf signers can provide a reasonable measures of lexical control in sign language experiments. The appendix gives the mean and median subjective frequency rating, and the median and mean log(RT) for the ASL signs for the entire sample; the supplemental material gives these measures for three AoLE groups, Native, Early, and Late. PMID:23943581

  15. 23 CFR 650.311 - Inspection frequency.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

  16. 23 CFR 650.311 - Inspection frequency.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

  17. 23 CFR 650.311 - Inspection frequency.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

  18. Frequency-Diversity Reception for Phase Modulation

    NASA Technical Reports Server (NTRS)

    Brockman, M. H.

    1984-01-01

    Signal-to-noise ratio improved. System receives phase modulation transmitted simultaneously on different carrier frequencies. Used for carriers received through different antennas or through same antenna.

  19. Frequency doubled, cavity dumped feedback laser

    NASA Technical Reports Server (NTRS)

    Sipes, Jr., Donald L. (Inventor); Robinson, Deborah L. (Inventor)

    1989-01-01

    Higher efficiency in cavity dumping and frequency doubling in a laser used to produce modulated output beam pulses is achieved by deflecting light out of the resonant cavity to a third mirror through a frequency doubler using an electro-optic modulator and a polarizing beamsplitter in the resonant cavity, or using just an acousto-optic modulator to deflect light out of the laser cavity in response to a control signal (electric or acoustic). The frequency doubler in front of the third mirror rotates the frequency doubled light so that it will pass out of the laser cavity through the polarizing beamsplitter, while undoubled frequency light is reflected by the polarizing beamsplitter back into the gain medium of the laser. In the case of using a type-II frequency doubler, a dichroic beamsplitter deflects out the frequency doubled light and passes the undoubled frequency light to the polarizing beamsplitter for return to the laser gain medium. If an acousto-optic modulator is used, it deflects light out of the primary laser cavity, so a polarizing beamsplitter is not needed, and only a dichroic beamsplitter is needed to separate frequency doubled light out of the path from the third mirror.

  20. 47 CFR 87.279 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Enroute and Aeronautical Fixed Stations Aeronautical Fixed Stations § 87.279 Frequencies. (a) United States (except...

  1. 47 CFR 87.279 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Enroute and Aeronautical Fixed Stations Aeronautical Fixed Stations § 87.279 Frequencies. (a) United States (except...

  2. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency...

  3. Optimum Detection of Frequency-Hopped Signals

    NASA Technical Reports Server (NTRS)

    Cheng, Unjeng; Levitt, Barry; Polydoros, Andreas; Simon, Marvin K.

    1992-01-01

    This paper derives and analyzes optimum and near-optimum structures for detecting frequency-hopped (FH) signals with arbitrary modulation in additive white Gaussian noise. The principalmodulation formats considered are M-ary frequency-shift-keying (MFSK) with fast frequency hopping(FFH) wherein a single tone is transmitted per hop, and slow frequency hopping (SFH) with multipleMFSK tones (data symbols) per hop. The SFH detection category has not previously been addressedin the open literature and its analysis is generally more complex than FFH.

  4. Hermetic optical-fiber iodine frequency standard.

    PubMed

    Light, Philip S; Anstie, James D; Benabid, Fetah; Luiten, Andre N

    2015-06-15

    We have built an optical-frequency standard based on interrogating iodine vapor that has been trapped within the hollow core of a hermetically sealed kagome-lattice photonic crystal fiber. A frequency-doubled Nd:YAG laser locked to a hyperfine component of the P(142)37-0 I2127 transition using modulation transfer spectroscopy shows a frequency stability of 3×10-11 at 100 s. We discuss the impediments in integrating this all-fiber standard into a fully optical-fiber-based system, and suggest approaches that could improve performance of the frequency standard substantially. PMID:26076241

  5. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

  6. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

  7. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

  8. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

  9. 47 CFR 87.195 - Frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

  10. (14) N nuclear quadrupole resonance study of piroxicam: confirmation of new polymorphic form v.

    PubMed

    Lavri?, Zoran; Pirnat, Janez; Lužnik, Janko; Puc, Uroš; Trontelj, Zvonko; Sr?i?, Stane

    2015-06-01

    A new polymorphic crystal form of piroxicam was discovered while preparing crystalline samples of piroxicam for (14) N nuclear quadrupole resonance (NQR) analysis. The new crystal form, designated as V, was prepared by evaporative recrystallization from dichloromethane. Three known polymorphic forms (I, II, and III) were also prepared. Our aim was to apply (14) N NQR to characterize the new polymorphic form of piroxicam and compare the results with those of the other known polymorphic forms. Additional analytical methods used for characterization were X-ray powder diffraction (XRPD), thermal analysis, and vibrational spectroscopy. For the first time, a complete set of nine characteristic (14) N NQR frequencies was found for each prepared polymorph of piroxicam. The consistent set of measured frequencies and calculated characteristic quadrupole parameters found for the new polymorphic form V is a convincing evidence that we are dealing with a new form. The already known piroxicam polymorphic forms were characterized similarly. The XRPD results were in accordance with the conclusions of (14) N NQR analysis. The performed study clearly demonstrates a strong potential of (14) N NQR method to be applied as a highly discriminative spectroscopic analytical tool to characterize polymorphic forms. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1909-1918, 2015. PMID:25776345

  11. Magnetic field-cycling NMR and 14N, 17O quadrupole resonance in the explosive pentaerythritol tetranitrate (PETN)

    Microsoft Academic Search

    John A. S. Smith; Timothy J. Rayner; Michael D. Rowe; Jamie Barras; Neil F. Peirson; Andrew D. Stevens; Kaspar Althoefer

    2010-01-01

    The explosive pentaerythritol tetranitrate (PETN) C(CH2–O–NO2)4 has been studied by 1H NMR and 14N NQR. The 14N NQR frequency and spin–lattice relaxation time T1Q for the ?+ line have been measured at temperatures from 255 to 325K. The 1H NMR spin–lattice relaxation time T1 has been measured at frequencies from 1.8kHz to 40MHz and at temperatures from 250 to 390K.

  12. Magnetic field-cycling NMR and 14N, 17O quadrupole resonance in the explosive pentaerythritol tetranitrate (PETN)

    Microsoft Academic Search

    John A. S. Smith; Timothy J. Rayner; Michael D. Rowe; Jamie Barras; Neil F. Peirson; Andrew D. Stevens; Kaspar Althoefer

    2010-01-01

    The explosive pentaerythritol tetranitrate (PETN) C(CH2-O-NO2)4 has been studied by 1H NMR and 14N NQR. The 14N NQR frequency and spin-lattice relaxation time T1Q for the nu+ line have been measured at temperatures from 255 to 325 K. The 1H NMR spin-lattice relaxation time T1 has been measured at frequencies from 1.8 kHz to 40 MHz and at temperatures from

  13. 47 CFR 80.377 - Frequencies for ship earth stations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

  14. 47 CFR 80.377 - Frequencies for ship earth stations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

  15. 47 CFR 80.377 - Frequencies for ship earth stations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

  16. 47 CFR 90.214 - Transient frequency behavior.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Transient frequency behavior. 90.214 Section...General Technical Standards § 90.214 Transient frequency behavior. Transmitters...421-512 MHz frequency bands must maintain transient frequencies within the maximum...

  17. 47 CFR 90.214 - Transient frequency behavior.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Transient frequency behavior. 90.214 Section...General Technical Standards § 90.214 Transient frequency behavior. Transmitters...421-512 MHz frequency bands must maintain transient frequencies within the maximum...

  18. 47 CFR 90.214 - Transient frequency behavior.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Transient frequency behavior. 90.214 Section...General Technical Standards § 90.214 Transient frequency behavior. Transmitters...421-512 MHz frequency bands must maintain transient frequencies within the maximum...

  19. 47 CFR 90.214 - Transient frequency behavior.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Transient frequency behavior. 90.214 Section...General Technical Standards § 90.214 Transient frequency behavior. Transmitters...421-512 MHz frequency bands must maintain transient frequencies within the maximum...

  20. 47 CFR 90.214 - Transient frequency behavior.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Transient frequency behavior. 90.214 Section...General Technical Standards § 90.214 Transient frequency behavior. Transmitters...421-512 MHz frequency bands must maintain transient frequencies within the maximum...

  1. A precision millimeter-wave measurement of the Rydberg frequency

    E-print Network

    De Vries, Joel Christopher, 1971-

    2002-01-01

    The Rydberg frequency, cR[infinity], sets the frequency scale for the spectrum of hydrogen atoms. From a frequency measurement of one transition in hydrogen, cR[infinity] can be extracted and the frequency of any other ...

  2. Visible-frequency hyperbolic metasurface.

    PubMed

    High, Alexander A; Devlin, Robert C; Dibos, Alan; Polking, Mark; Wild, Dominik S; Perczel, Janos; de Leon, Nathalie P; Lukin, Mikhail D; Park, Hongkun

    2015-06-11

    Metamaterials are artificial optical media composed of sub-wavelength metallic and dielectric building blocks that feature optical phenomena not present in naturally occurring materials. Although they can serve as the basis for unique optical devices that mould the flow of light in unconventional ways, three-dimensional metamaterials suffer from extreme propagation losses. Two-dimensional metamaterials (metasurfaces) such as hyperbolic metasurfaces for propagating surface plasmon polaritons have the potential to alleviate this problem. Because the surface plasmon polaritons are guided at a metal-dielectric interface (rather than passing through metallic components), these hyperbolic metasurfaces have been predicted to suffer much lower propagation loss while still exhibiting optical phenomena akin to those in three-dimensional metamaterials. Moreover, because of their planar nature, these devices enable the construction of integrated metamaterial circuits as well as easy coupling with other optoelectronic elements. Here we report the experimental realization of a visible-frequency hyperbolic metasurface using single-crystal silver nanostructures defined by lithographic and etching techniques. The resulting devices display the characteristic properties of metamaterials, such as negative refraction and diffraction-free propagation, with device performance greatly exceeding those of previous demonstrations. Moreover, hyperbolic metasurfaces exhibit strong, dispersion-dependent spin-orbit coupling, enabling polarization- and wavelength-dependent routeing of surface plasmon polaritons and two-dimensional chiral optical components. These results open the door to realizing integrated optical meta-circuits, with wide-ranging applications in areas from imaging and sensing to quantum optics and quantum information science. PMID:26062510

  3. Gradual adaptation to auditory frequency mismatch.

    PubMed

    Svirsky, Mario A; Talavage, Thomas M; Sinha, Shivank; Neuburger, Heidi; Azadpour, Mahan

    2015-04-01

    What is the best way to help humans adapt to a distorted sensory input? Interest in this question is more than academic. The answer may help facilitate auditory learning by people who became deaf after learning language and later received a cochlear implant (a neural prosthesis that restores hearing through direct electrical stimulation of the auditory nerve). There is evidence that some cochlear implants (which provide information that is spectrally degraded to begin with) stimulate neurons with higher characteristic frequency than the acoustic frequency of the original stimulus. In other words, the stimulus is shifted in frequency with respect to what the listener expects to hear. This frequency misalignment may have a negative influence on speech perception by CI users. However, a perfect frequency-place alignment may result in the loss of important low frequency speech information. A trade-off may involve a gradual approach: start with correct frequency-place alignment to allow listeners to adapt to the spectrally degraded signal first, and then gradually increase the frequency shift to allow them to adapt to it over time. We used an acoustic model of a cochlear implant to measure adaptation to a frequency-shifted signal, using either the gradual approach or the "standard" approach (sudden imposition of the frequency shift). Listeners in both groups showed substantial auditory learning, as measured by increases in speech perception scores over the course of fifteen one-hour training sessions. However, the learning process was faster for listeners who were exposed to the gradual approach. These results suggest that gradual rather than sudden exposure may facilitate perceptual learning in the face of a spectrally degraded, frequency-shifted input. This article is part of a Special Issue entitled . PMID:25445816

  4. Phase-stabilized 167 MHz repetition frequency carbon nanotube fiber laser frequency comb

    Microsoft Academic Search

    Jinkang Lim; Kevin Knabe; Yishan Wang; Rodrigo Amezcua-Correa; François Couny; Philip S. Light; Fetah Benabid; Jonathan C. Knight; Kristan L. Corwin; Jeffrey W. Nicholson; Brian R. Washburn

    2009-01-01

    The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using carbon nanotube saturable absorber is phase-stabilized for the first time. The comb's stability is compared a photonic crystal fiber acetylene reference.

  5. Multi-dimensional ultra-high frequency passive radio frequency identification tag antenna designs

    E-print Network

    Delichatsios, Stefanie Alkistis

    2006-01-01

    In this thesis, we present the design, simulation, and empirical evaluation of two novel multi-dimensional ultra-high frequency (UHF) passive radio frequency identification (RFID) tag antennas, the Albano-Dipole antenna ...

  6. Fundamental Frequency Estimation in the SMS Analysis

    Microsoft Academic Search

    Pedro Cano

    1998-01-01

    This paper deals with the fundamental frequency estimation for monophonic sounds in the SMS analysis environment. The importance of the fundamental frequency as well as some uses in SMS is commented. The particular method of F0 estimation based on a two-way mismatched measure is described as well as some modifications. Finally we explain how pitch -unpitched decision is performed.

  7. Frequency tuning of THz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Qian, Xifeng; Danylov, Andriy A.; Light, Alexander R.; Waldman, Jerry; Erickson, Neal

    2015-03-01

    This paper introduces the continuously tunable THz radiation through sideband generation of a free running and solidnitrogen- cooled THz quantum cascade laser. The 2.324 THz QCL operating in a single longitudinal mode (SLM) in continuous-wave (cw) was mixed with a swept synthesized microwave signal by a THz Schottky-diode-balanced mixer. Through sideband generation, two frequency branches were observed at low and high frequency, characterized with a Fourier-transform spectrometer. At low frequency, the sideband generates frequencies from -50 GHz to +50 GHz. At high frequency, it generates sideband frequencies from 70 GHz to 115 GHz. The total +/-100 GHz tuning range can be further expanded with higher frequency millimeter wave amplifier/multiplier source. The sideband generates total 1 ?W of output power at both upper and lower frequency with 200 ?W of driven power from the THz QCL, showing a power conversion efficiency of 5 × 10-3. The demonstration of this SM, continuously tunable THz source enables its applications where SM, spatially coherent beam is required.

  8. 47 CFR 90.715 - Frequencies available.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequencies available. 90.715 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band...

  9. 47 CFR 90.715 - Frequencies available.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Frequencies available. 90.715 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band...

  10. 47 CFR 90.715 - Frequencies available.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Frequencies available. 90.715 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band...

  11. 47 CFR 90.715 - Frequencies available.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Frequencies available. 90.715 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band...

  12. 47 CFR 90.715 - Frequencies available.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequencies available. 90.715 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band...

  13. Radio Propagation at Frequencies above 30 Megacycles

    Microsoft Academic Search

    K. Bullington

    1947-01-01

    Radio propagation is affected by many factors, including the frequency, distance, antenna heights, curvature of the earth, atmospheric conditions, and the presence of hills and buildings. The influence of each of these factors at frequencies above about 30 megacycles is discussed, with most of the quantitative data being presented in a series of nomograms. By means of three or four

  14. Robust frequency and timing synchronization for OFDM

    Microsoft Academic Search

    Timothy M. Schmidl; Donald C. Cox

    1997-01-01

    A rapid synchronization method is presented for an orthogonal frequency-division multiplexing (OFDM) system using either a continuous transmission or a burst operation over a frequency-selective channel. The presence of a signal can be detected upon the receipt of just one training sequence of two symbols. The start of the frame and the beginning of the symbol can be found, and

  15. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Low Power TV, TV Translator, and TV Booster Stations § 74.762 Frequency measurements...TV station, a TV translator, or a TV booster station must measure the carrier frequencies...a low power TV, TV translator, or TV booster station is found to be operating...

  16. A New Frequency-Stabilized Oscillator System

    Microsoft Academic Search

    R. Gunn

    1930-01-01

    A new vacuum-tube self-oscillating system having extraordinary frequency stability is described which depends on the reëntrant circulation of oscillations through tuned filter or coupling units. The reëntrant circulation through the filter sections attenuates all but a single frequency in a manner analogous to the attenuation produced by a filter system having an infinite number of sections. The unattenuated component having

  17. Small signal frequency characteristic of electroluminescent diodes

    Microsoft Academic Search

    L. Kucera; V. Snejdar; H. Barankova

    1979-01-01

    Under simplifying assumptions the small signal frequency characteristic of the planar geometry electroluminescent diode is derived. It has been found that it is generally determined by the diode impedance, by transit-time phenomena of injected carriers and by absorption losses, which depend on the a.c. photon generation rate distribution in the diode volume. The dependence of the frequency characteristic on the

  18. Managing the frequency resource today and tomorrow

    Microsoft Academic Search

    P. A. Major

    1994-01-01

    Frequency-resource management is the judicious use of the electromagnetic spectrum to accomplish the mission or objective of the user with little or no impact on other users of the spectrum. One mission of military frequency management is to support command and control (C2), which is crucial to executing the operational plans of the commanders. Effective C2 is impossible without communications

  19. Frequency correction device uses digital circuitry

    NASA Technical Reports Server (NTRS)

    Schaefer, D.

    1965-01-01

    Signal acquisition and tracking system covering a wide range of frequencies uses a digital circuit to sample the frequency of an incoming signal and provide correction pulses to the voltage-controlled oscillator. The circuit can also sense the presence of a signal on any one of the input lines.

  20. Radar scattering: a time-frequency perspective

    Microsoft Academic Search

    H. N. Kritikos

    1997-01-01

    Time-frequency analysis is used to study electromagnetic scattering from canonical objects leading to the detection, localization and extraction of response features that result from the object's physical attributes. The time-frequency analysis techniques are motivated by signal representation in phase space, and are formulated using the Bargman transform. Bargman transform techniques allow the phase space to be parametrically represented in terms

  1. Optimizing frequency planning in the GSM system

    Microsoft Academic Search

    Andrea De Pasquale; N. P. Magnani; Paolo Zanini

    1998-01-01

    Frequency planning is an important process in planning and optimising second generation TDMA mobile networks. For the GSM system, frequency planning is usually performed by controlling only the downlink estimated quality in the territory. In this paper, by means of simulation results, field measurements and theoretical analysis, we verify that the uplink and downlink in the GSM system experience a

  2. CMOS ring oscillators with enhanced frequency operation

    Microsoft Academic Search

    A. El mourabit; Guo-Neng Lu; Ming Zhang; P. Pittet; Y. Birjali; F. Lahjoumri

    2010-01-01

    This paper presents a new technique to improve frequency performance of CMOS ring oscillator. It is based on the adding of a CR differentiators-based MOS transistor to boost switching speed of the oscillator delay cell. The method can be used for simple and differential oscillator and offers a simple way to implement frequency tuning without introduction of any additional phase

  3. Empirical Limitations on High Frequency Trading Profitability

    E-print Network

    Plotkin, Joshua B.

    Empirical Limitations on High Frequency Trading Profitability Michael Kearns, Alex Kulesza, Yuriy examination of high-frequency trading practices in financial markets, we report the results of an extensive, and arrive at figures that are surprisingly modest. By "aggressive" we mean any trading strategy employing

  4. Frequency chirp effects in electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Davis, J. P.; Narducci, F. A.

    We consider the effects of the time-dependence of the frequency of a probe field in a three-level system when the probe field is scanned in frequency. We find that, under conditions of weak coupling and probe fields, the resonance can show ringing when the scan rate is greater than the ground state recovery time.

  5. 47 CFR 101.803 - Frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

  6. 47 CFR 101.803 - Frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

  7. 47 CFR 101.803 - Frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

  8. The Distribution of Annual Tropical Cyclone Frequency

    Microsoft Academic Search

    H. C. S. Thom

    1960-01-01

    In preparation for studying and fitting tropical cyclone frequency distributions certain time trends in the climatological series are tested statistically and explanations of their possible cause proposed. The annual frequency of tropical cyclones and hurricanes is hypo- thesized to be a rare-event type of series. On the basis of physical and statistical principles it is shown how the Poisson and

  9. LOFAR, a new low frequency radio telescope

    Microsoft Academic Search

    Huub Röttgering

    2003-01-01

    LOFAR, the Low Frequency Array, is a large radio telescope consisting of approximately 100 soccer-field sized antenna stations spread over a region of 400 km in diameter. It will operate at frequencies from ?10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for studies of a broad range of

  10. Operating Frequencies for Educational Satellite Services.

    ERIC Educational Resources Information Center

    Singh, Jai P.

    Part of a continuing study of application of communication satellites for helping to meet educational needs, this memorandum discusses operating frequencies for educational satellite services. Each of the factors affecting choice of transmission frequencies is identified and discussed in a separate section. Included among these factors are…

  11. 47 CFR 95.1511 - Frequencies available.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Communications Service On-Board Units (DSRCS-OBUs) § 95.1511 Frequencies available...5850-5925 MHz band for On-Board Units (OBUs): 1 Channel No. Channel use Frequency...maximum output power for portable DSRCS-OBUs is 1.0 mW. See §...

  12. 47 CFR 95.1511 - Frequencies available.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Communications Service On-Board Units (DSRCS-OBUs) § 95.1511 Frequencies available...5850-5925 MHz band for On-Board Units (OBUs): 1 Channel No. Channel use Frequency...maximum output power for portable DSRCS-OBUs is 1.0 mW. See §...

  13. Detection and frequency tracking of chirping signals

    SciTech Connect

    Elliott, G.R.; Stearns, S.D.

    1990-08-01

    This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate. Frequency tracking and behavior in the presence of varying levels of noise are illustrated in examples. 11 refs., 29 figs.

  14. The Frequency Shifting of Femtosecond Laser Pulses

    Microsoft Academic Search

    Glenn Bryant Focht

    1990-01-01

    Two new and widely applicable methods of shifting the frequency of femtosecond laser pulses have been developed experimentally and theoretically analyzed: (1) intracavity frequency doubling, for low energy (nanojoule) pulses, and (2) blue shifting in a laser-produced plasma, for high energy (millijoule) pulses. For the first method, we efficiently extract an ultraviolet femtosecond pulse train of milliwatt average power and

  15. Multi-Frequency Band Pyroelectric Sensors

    PubMed Central

    Hsiao, Chun-Ching; Liu, Sheng-Yi

    2014-01-01

    A methodology is proposed for designing a multi-frequency band pyroelectric sensor which can detect subjects with various frequencies or velocities. A structure with dual pyroelectric layers, consisting of a thinner sputtered ZnO layer and a thicker aerosol ZnO layer, proved helpful in the development of the proposed sensor. The thinner sputtered ZnO layer with a small thermal capacity and a rapid response accomplishes a high-frequency sensing task, while the thicker aerosol ZnO layer with a large thermal capacity and a tardy response is responsible for low-frequency sensing tasks. A multi-frequency band pyroelectric sensor is successfully designed, analyzed and fabricated in the present study. The range of the multi-frequency sensing can be estimated by means of the proposed design and analysis to match the thicknesses of the sputtered and the aerosol ZnO layers. The fabricated multi-frequency band pyroelectric sensor with a 1 ?m thick sputtered ZnO layer and a 20 ?m thick aerosol ZnO layer can sense a frequency band from 4000 to 40,000 Hz without tardy response and low voltage responsivity. PMID:25429406

  16. Ac electronic tunneling at optical frequencies

    NASA Technical Reports Server (NTRS)

    Faris, S. M.; Fan, B.; Gustafson, T. K.

    1974-01-01

    Rectification characteristics of non-superconducting metal-barrier-metal junctions deduced from electronic tunneling have been observed experimentally for optical frequency irradiation of the junction. The results provide verification of optical frequency Fermi level modulation and electronic tunneling current modulation.

  17. Digital Frequency Synthesizer For Radar Astronomy

    NASA Technical Reports Server (NTRS)

    Sadr, Ramin; Satorius, Edgar; Robinett, J. Loris, Jr.; Olson, Erlend

    1992-01-01

    Report discusses conceptual digital frequency synthesizer part of programmable local oscillator in radar-astronomy system. Phase must remain continuous during adjustments of frequency, phase noise must be low, and spectral purity must be high. Discusses theory of operation in some mathematical detail and presents new analysis of spectral purity of output.

  18. Spatial frequency response of thermoplastic films

    Microsoft Academic Search

    D. S. Lo; L. H. Johnson; R. W. Honebrink

    1975-01-01

    The spatial frequency response is investigated using a multilayer device that consists of a PVK-TNF photoconductor layer, a polystyrene thermoplastic layer, and an InO transparent layer on a glass substrate. To determine the frequency response, the diffraction efficiency (ratio of the intensity of the light diffracted by the hologram during readout to the intensity of the readout light) is measured

  19. Spatial frequency response for an optical profiler

    Microsoft Academic Search

    R. A. Auriemma; Joseph R. Bietry; Thomas C. Bristow; Gary Wagner

    1992-01-01

    This paper presents a general method for measuring the frequency response of a surface profiling instrument. One important consequence of this work is the discussion of the importance of the modification of surface spatial frequencies by the measuring instrument. The method uses a step height sample to characterize the impulse instrument, and power spectrum response. Experimental measurements are shown for

  20. Circular-edge spatial frequency response test

    Microsoft Academic Search

    Richard L. Baer

    2003-01-01

    A new method for testing the resolution of digital cameras has been developed. The new method is an extension of the ISO 12233 Slanted-edge Spatial Frequency Response test. The new method computes the spatial frequency response along the edge of a circle. It is especially well adapted to inexpensive imaging systems with rotationally symmetric blur and lens distortion. In addition