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1

35 Cl NQR spectra of group 1 and silver dichloromethanesulfonates  

Microsoft Academic Search

The dichloromethanesulfonates of silver and other +1-charged cations, M\\u000a ?+?(Cl2CHSO (M = Ag, Tl, Li, Na, K, Rb, Cs) were synthesized and studied by 35Cl NQR. Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, and was then neutralized\\u000a with the carbonates of the +1-charged cations to produce the corresponding dichloromethanesulfonate salt. This NQR study completed\\u000a the investigation of

Gabriel Gillette; Gary Wulfsberg

2008-01-01

2

35Cl NQR spectra of group 1 and silver dichloromethanesulfonates  

NASA Astrophysics Data System (ADS)

The dichloromethanesulfonates of silver and other +1-charged cations, M + (Cl2CHSO3-) ( M = Ag, Tl, Li, Na, K, Rb, Cs) were synthesized and studied by 35Cl NQR. Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, and was then neutralized with the carbonates of the +1-charged cations to produce the corresponding dichloromethanesulfonate salt. This NQR study completed the investigation of the chloroacetates and chloromethanesulfonates of silver, Ag + (Cl x CH3 - x SO3-) and Ag + (Cl x CH3 - x CO2-), and suggests (1) that the ability of organochlorine atoms to coordinate to silver decreases as the number of electron-withdrawing groups (Cl, SO3-, CO2-) attached to the carbon atom increases; (2) that the unusually large NQR spectral width found among M + (Cl2CHCO2-) salts is not present among M + (Cl2CHSO3-) salts, and therefore is not generally characteristic of the dichloromethyl group in salts.

Gillette, Gabriel; Wulfsberg, Gary

2008-01-01

3

35Cl NQR spectra of group 1 and silver dichloromethanesulfonates  

NASA Astrophysics Data System (ADS)

The dichloromethanesulfonates of silver and other +1-charged cations, M +(Cl2CHSO{3/-}) (M=Ag, Tl, Li, Na, K, Rb, Cs) were synthesized and studied by 35Cl NQR. Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, and was then neutralized with the carbonates of the +1-charged cations to produce the corresponding dichloromethanesulfonate salt. This NQR study completed the investigation of the chloroacetates and chloromethanesulfonates of silver, Ag+(Cl x CH3-x SO{3/-}) and Ag+(Cl x CH3-x CO{2/-}), and suggests (1) that the ability of organochlorine atoms to coordinate to silver decreases as the number of electron-withdrawing groups (Cl, SO{3/-} CO{2/-}) attached to the carbon atom increases; (2) that the unusually large NQR spectral width found among M+(Cl2CHCO{2/-}) salts is not present among M+(Cl2CHS0{3/-}) salts, and therefore is not generally characteristic of the dichloromethyl group in salts.

Gillette, Gabriel; Wulfsberg, Gary

4

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

SciTech Connect

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.

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

5

35Cl-NQR and DFT study of electronic structure of amlodipine and felodipine vascular-selective drugs from the dihydropyridine Ca ++ antagonists group  

NASA Astrophysics Data System (ADS)

Amlodipine (AM) and felodipine (FL) have been studied in solid state by the nuclear quadrupole resonance (NQR) and density functional theory (DFT). The results have shown that NQR data do not permit a differentiation between R and S enantiomers, which is a consequence of the symmetry of the 4-aryl ring, whereas they permit a differentiation between free bases and salts. The HOMO-LUMO gap is smaller for AM than for FL, which suggests smaller energy of excitation for AM. The absolute hardness, chemical potential and electrophilicity of both AM enantiomers are lower than the corresponding values for FL enantiomers, suggesting that AM should be more reactive than FL in unimolecular reactions.

Latosi?ska, J. N.; Latosi?ska, M.; Kasprzak, J.

2008-09-01

6

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

NASA Astrophysics Data System (ADS)

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.

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

1980-11-01

7

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)

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.

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

2009-07-01

8

Compound model-morphed potentials contrasting OC-79Br35Cl with the halogen bonded OC-35Cl2 and hydrogen-bonded OC-HX (X = 19F, 35Cl, 79Br)  

NASA Astrophysics Data System (ADS)

A five-dimensional compound-model morphed (CMM) potential has been generated for the halogen bonded intermolecular interaction 16O12C-79Br35Cl based on a fit to the currently generated infrared and previously available microwave spectroscopic data. The experimentally determined blue frequency shift of the 16O12C stretching frequency on complexation with 79Br35Cl is found to be ?? = 12.89643(28) cm-1 indicating a more strongly bound complex than in OC-35Cl2. Re center-of-mass to center-of-mass distance of 4.270(7) Å and dissociation energies De = 778(70) cm-1 and D0 = 605(70) cm-1 are predicted from the CMM potential and also compared with the corresponding values of Re = 4.742(3) Å and De = 544(5) cm-1 and D0 = 397(5) cm-1 for 16O12C-35Cl2. The molecular dynamics, binding energy and other molecular parameters of OC-BrCl are also compared with the hydrogen bonded dimers OC-HX (X = F, Cl, Br) giving further insight into the characteristics of the complex.

Rivera-Rivera, Luis A.; Scott, Kevin W.; McElmurry, Blake A.; Lucchese, Robert R.; Bevan, John W.

2013-11-01

9

NQR studies of gallium and bismuth trichlorides complexes with n- and ? -donors.  

NASA Astrophysics Data System (ADS)

The 35,37C1, 69,71Ga and 209Bi NQR spectra of the charge-transfer complexes of GaCl 3 with ketones, nitriles and BiCl 3 with methyl substituted derivatives of benzene at 77K have been investigated. The complexing of BiCl 3 with methyl substituted derivatives of benzene leads to an increase in 209Bi Quadrupole Coupling Constant (QCC) along the direction of the maximum field gradient of e 2Qq zzh. The nature of the frequency changes of 35,37 Cl in the acceptor molecule is different for axial and equatorial chlorine atoms. There is a correlation between the QCC 14N of the nitriles and the shifts of the 69Ga on complexing and also between shifts of the 35Cl and 69 Ga frequencies on complexing.

Popkova, L. A.; Guryanova, E. N.; Volkov, A. F.

10

Landmine detection using feedback NQR  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) is well suited for detecting land mines with non-metallic cases. It provides both spatial localization and chemical identification of explosives. A search coil produces a train of radio frequency (RF) magnetic pulses that perturb the orientation of nitrogen nuclei contained within the explosive material. Following each RF pulse, the nuclei rotate back to orientations of lower

Andrew J. Blauch; Jeffrey L. Schiano; Mark D. Ginsberg

1999-01-01

11

14N NQR in the tetrazole family  

NASA Astrophysics Data System (ADS)

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.

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

2009-10-01

12

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

PubMed

A low frequency (0.5-5MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5W and a total mass of about 3kg aimed at detecting (14)N 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 (14)N 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 (14)N NQR based detection device. PMID:25233110

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

2014-10-01

13

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

14

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

SciTech Connect

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.

Ziegeweid, M.A.

1995-11-29

15

Two-dimensional NQR using ultra-broadband electronics  

NASA Astrophysics Data System (ADS)

We have recently developed an ultra-broadband instrument that can effectively excite and detect NMR and NQR signals over a wide frequency range. Our current system operates between 100 kHz and 3.2 MHz using an un-tuned sample coil. The major benefits of this instrument compared to conventional NQR/NMR systems include increased robustness, ease of use (in particular for multi-frequency experiments), and elimination of the need for tuning adjustments in the hardware. Here we describe its use for performing two-dimensional (2D) scans, which allow improved interpretation of complex NQR spectra by detecting the connected resonances. Our method relies on population transfers between the three energy levels of spin-1 nuclei (such as 14N) by using multi-frequency excitation and a single RF coil. Experimental results on pure samples and mixtures are also presented.

Mandal, S.; Song, Y.-Q.

2014-03-01

16

Two-dimensional NQR using ultra-broadband electronics.  

PubMed

We have recently developed an ultra-broadband instrument that can effectively excite and detect NMR and NQR signals over a wide frequency range. Our current system operates between 100 kHz and 3.2 MHz using an un-tuned sample coil. The major benefits of this instrument compared to conventional NQR/NMR systems include increased robustness, ease of use (in particular for multi-frequency experiments), and elimination of the need for tuning adjustments in the hardware. Here we describe its use for performing two-dimensional (2D) scans, which allow improved interpretation of complex NQR spectra by detecting the connected resonances. Our method relies on population transfers between the three energy levels of spin-1 nuclei (such as (14)N) by using multi-frequency excitation and a single RF coil. Experimental results on pure samples and mixtures are also presented. PMID:24495675

Mandal, S; Song, Y-Q

2014-03-01

17

Dissociation dynamics of higher-order He2···I35Cl(B,v? = 3) complexes  

NASA Astrophysics Data System (ADS)

The dissociation dynamics of He2···I35Cl complexes prepared with varying amounts of intermolecular vibrational excitation within the 2He + I35Cl(B,v? = 3) potential energy surface are reported. For the intermolecular level associated with one He atom in an energetically excited, delocalized state and the other localized in the lowest-energy, T-shaped potential minimum, the higher-energy He atom dissociates preferentially. The binding energy of the ground-state He2···I35Cl(X,v? = 0) conformer with a police nightstick geometry (one He atom in the T-shaped minimum and the second in the linear well) is measured to be 38.6(9) cm-1.

Darr, Joshua P.; Loomis, Richard A.

2013-10-01

18

Local electric state of noncentrosymmetric superconductor Mo3Al2C revealed by Mo NQR and NMR experiments  

NASA Astrophysics Data System (ADS)

Mo nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements were performed on a noncentrosymmetric superconductor Mo3Al2C to investigate the local electronic state at Mo nuclei, which carries the electrons responsible for superconductivity. The NQR frequency, which is linked to the electric field gradient at Mo site, was determined from 95Mo NMR spectrum and the result was verified by the independent 97Mo NQR measurement. The experimentally obtained value is compared to the result of a point charge calculation to extract the EFG induced by conduction electrons and reveal the local electronic state.

Ihara, Y.; Kimura, Y.; Kumagai, K.; Bauer, E.; Rogl, G.; Rogl, P.

2012-12-01

19

Explosives detection by nuclear quadrupole resonance (NQR)  

Microsoft Academic Search

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

Allen N. Garroway; M. L. Buess; J. P. Yesinowski; J. B. Miller; Ronald A. Krauss

1994-01-01

20

Gamma-ray energies from the reaction 35Cl(n,?)  

NASA Astrophysics Data System (ADS)

A two-axis flat-crystal spectrometer has been used to measure accurately gamma-ray energies up to 2 MeV from the reaction 35Cl(n,?). This represents a fourfold extension of the range of direct optically based gamma-ray energies. The crystals and spectrometer have performed in a manner which demonstrates that sub-ppm measurements are possible at energies >~2 MeV. The reported transition energies (in eV) are 517 077.41+/-0.23, 786 311.32+/-0.38, 788 437.43+/-0.44, 1 164 885.74+/-0.48, 1 951 197.06+/-0.58, and 1 959 413.45+/-8.45. The sum rule is satisfied by three of the lines (786 keV+1165 keV=1951 keV) within an uncertainty of ~1 ppm.

Kessler, E. G., Jr.; Greene, G. L.; Deslattes, R. D.; Börner, H. G.

1985-08-01

21

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.  

PubMed

Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined ?iso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and ?33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (?11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. PMID:24581866

Peri?, Berislav; Gautier, Régis; Pickard, Chris J; Bosio?i?, Marko; Grbi?, Mihael S; Požek, Miroslav

2014-01-01

22

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

E-print Network

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.

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

23

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

SciTech Connect

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.

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

1993-07-01

24

NQR investigation and characterization of cocrystals and crystal polymorphs  

NASA Astrophysics Data System (ADS)

The application of 14N NQR to the study of cocrystals and crystal polymorphs is reviewed. In ferroelectric and antiferroelectric organic cocrystals 14N NQR is used to determine proton position in an N-H...O hydrogen bond and proton displacement below TC. In cocrystal isonicitinamide - oxalic acid (2:1) 14N NQR is used to distinguish between two polymorphs and to determine the type of the hydrogen bond (N-...H-O). The difference in the 14N NQR spectra of cocrystal formers and cocrystal is investigated in case of carbamazepine, saccharin and carbamazepine - saccharin (1:1). The experimental resolution allows an unambiguous distinction between the 14N NQR spectrum of the cocrystal and the 14N NQR spectra of the cocrystal formers. The possibility of application of NQR and double resonance for the determination of the inhomogeneity of the sample and for the study of the life time of an unstable polymorph is discussed.

Seliger, Janez; Žagar, Veselko; Asaji, Tetsuo

2013-05-01

25

133Cs and 35Cl NMR spectroscopy and molecular dynamics modeling of Cs + and Cl ? complexation with natural organic matter  

Microsoft Academic Search

Interaction of dissolved aqueous species with natural organic matter (NOM) is thought to be important in sequestering some species and enhancing the transport of others, but little is known about these interactions on a molecular scale. This paper describes a combined experimental 133Cs and 35Cl nuclear magnetic resonance (NMR) and computational molecular dynamics (MD) modeling study of the interaction of

Xiang Xu; Andrey G. Kalinichev; R. James Kirkpatrick

2006-01-01

26

Fragmentation Cross Sections of Medium-Energy 35Cl, 40Ar, and 48TiBeams on Elemental Targets  

SciTech Connect

Charge-changing and fragment production cross sections at 0degrees have been obtained for interactions of 290, 400, and 650MeV/nucleon 40Ar beams, 650 and 1000 MeV/nucleon 35Cl beams, and a 1000MeV/nucleon 48Ti beam. Targets of C, CH2, Al, Cu, Sn, and Pb were used.Using standard analysis methods, we obtain fragment cross sections forcharges as low as 8 for Cl and Ar beams, and as low as 10 for the Tibeam. Using data obtained with small-acceptance detectors, we reportfragment production cross sections for charges as low as 5, corrected foracceptance using a simple model of fragment angular distributions. Withthe lower-charged fragment cross sections, we cancompare the data topredictions from several models (including NUCFRG2, EPAX2, and PHITS) ina region largely unexplored in earlier work. As found in earlier workwith other beams, NUCFRG2 and PHITS predictions agree reasonably wellwith the data for charge-changing cross sections, but do not accuratelypredict the fragment production cross sections. The cross sections forthe lightest fragments demonstrate the inadequacy of several models inwhich the cross sections fall monotonically with the charge of thefragment. PHITS, despite not agreeing particularly well with the fragmentproduction cross sections on average, nonetheless qualitativelyreproduces somesignificant features of the data that are missing from theother models.

Zeitlin, C.; Guetersloh, S.; Heilbronn, L.; Miller, J.; Fukumura,A.; Iwata, Y.; Murakami, T.; Sihver, L.; Mancusi, D.

2007-12-08

27

Three-dimensional high-inductance birdcage coil for NQR applications.  

PubMed

A birdcage coil capable of operating simultaneously and independently in three orthogonal dimensions has been developed. A co-rotational end-ring mode producing an RF field in the longitudinal direction was utilized in addition to the two common transverse orthogonal modes. Two conductor turns were used for each of the coil's windows, increasing its inductance by a factor of four, thereby, making the coil suitable for low-frequency applications. Two or three-frequency detection can be easily carried out with this device. Orthogonality of the coil's channels allows arbitrarily close frequency positioning of each resonant mode, potentially useful in wide-line NQR studies, in which simultaneous excitation/detection of signals from three adjacent regions of a single wide line can be performed. The coil's performance was evaluated using a three-dimensional scheme, in which a circularly polarized experiment was combined with a linearly polarized measurement at another frequency, resulting in SNR improvement by 55%. PMID:16584871

Peshkovsky, A S; Cerioni, L; Osan, T M; Avdievich, N I; Pusiol, D J

2006-09-01

28

Rapid detection of arsenic minerals using portable broadband NQR  

NASA Astrophysics Data System (ADS)

remote real-time detection of specific arsenic species would significantly benefit in minerals processing to mitigate the release of arsenic into aquatic environments and aid in selective mining. At present, there are no technologies available to detect arsenic minerals in bulk volumes outside of laboratories. Here we report on the first room-temperature broadband 75As nuclear quadrupole resonance (NQR) detection of common and abundant arsenic ores in the Earth crust using a large sample (0.78 L) volume prototype sensor. Broadband excitation aids in detection of natural minerals with low crystallinity. We briefly discuss how the proposed NQR detector could be employed in mining operations.

Lehmann-Horn, J. A.; Miljak, D. G.; O'Dell, L. A.; Yong, R.; Bastow, T. J.

2014-10-01

29

Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z=0.89 toward PKS1830-211  

E-print Network

We report the first extragalactic detection of chloronium (H2Cl+), in the z=0.89 absorber in front of the lensed blazar PKS1830-211. The ion is detected through its 1_11-0_00 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 H2^35Cl+ and H2^37Cl+ 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.

Muller, S; Guelin, M; Henkel, C; Combes, F; Gerin, M; Aalto, S; Beelen, A; Darling, J; Horellou, C; Martin, S; Menten, K M; Dinh-V-Trung,; Zwaan, M A

2014-01-01

30

The two-frequency nuclear quadrupole resonance for explosives detection  

Microsoft Academic Search

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

G. V. Mozjoukhine

2000-01-01

31

Probing midrapidity source characteristics with charged particles and neutrons in the 35Cl+natTa reaction at 43 MeV\\/nucleon  

Microsoft Academic Search

The characteristics of the midrapidity and target sources (apparent temperatures, velocities, and neutron multiplicities) extracted from the neutron energy spectra, have been measured for various quasiprojectile (QP) excitation energies, reconstructed from charged particles of well defined peripheral events in the 35Cl+natTa reaction at 43 MeV\\/nucleon. The reconstructed excitation energy of the QP is always smaller than the excitation energy calculated

Y. Larochelle; C. St-Pierre; L. Beaulieu; N. Colonna; L. Gingras; G. C. Ball; D. R. Bowman; M. Colonna; G. D'erasmo; E. Fiore; D. Fox; A. Galindo-Uribarri; E. Hagberg; D. Horn; R. Laforest; A. Pantaleo; R. Roy; G. Tagliente

1999-01-01

32

Improved line parameters for the Chi 2Pi-Chi 2Pi (1-0) bands of (35)ClO and (37)ClO  

NASA Technical Reports Server (NTRS)

Improved line parameters at 296 K for the Chi 2Pi-Chi 2Pi (1-0) bands of (35)ClO and (37)ClO have been calculated with J up to 43.5. The integrated intensity for the 2048 lines in the main and satellite bands has been normalized to 9.68-sq cm/atm at 296K.

Goldman, Aaron; Gillis, James R.; Rinsland, Curtis P.; Burkholder, James B.

1994-01-01

33

A search for P-odd and P-even correlations in the 35Cl(n,p) 35S reaction  

NASA Astrophysics Data System (ADS)

The experiment of the forward-backward asymmetry ? FB in the 35Cl(n,p) 35S reaction has been carried out with resonance neutrons up to 1 keV. Starting from the theoretical background the cross section and the asymmetry coefficients have been calculated and analyzed together with the experimental values of the p-odd (? PN) and left-right (? LR) asymmetry observed in the capture reaction of polarized thermal neutrons.

Gledenov, Yu. M.; Machrafi, R.; Oprea, A. I.; Salatski, V. I.; Sedyshev, P. V.; Szalanski, P. I.; Vesna, V. A.; Okunev, I. S.

34

27Al-NQR\\/NMR Study of Kondo Semiconductor CeFe2Al10  

Microsoft Academic Search

27Al-NQR\\/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1\\/T1 above about 20

Yukihiro Kawamura; Shingo Edamoto; Tomoaki Takesaka; Takashi Nishioka; Harukazu Kato; Masahiro Matsumura; Yo Tokunaga; Shinsaku Kambe; Hiroshi Yasuoka

2010-01-01

35

Beta-detected NQR in zero field with a low energy beam of 8Li+  

NASA Astrophysics Data System (ADS)

Beta-detected nuclear quadrupole resonances ( ?-NQR) in zero field are observed using a beam of low energy highly polarized radioactive Li+8. The resonances were detected in SrTiO 3, Al 2O 3 and Sr 2RuO 4 single crystals by monitoring the beta-decay anisotropy as a function of a small audio frequency magnetic field. The resonances show clearly that Li+8 occupies one site with non-cubic symmetry in SrTiO 3, two in Al 2O 3 and three sites in Sr 2RuO 4. The resonance amplitude and width are surprisingly large compared to the values expected from transitions between the |±2>?|±1> spin states, indicating a significant mixing between the |±m> quadrupolar split levels.

Salman, Z.; Kiefl, R. F.; Chow, K. H.; MacFarlane, W. A.; Kreitzman, S. R.; Arseneau, D. J.; Daviel, S.; Levy, C. D. P.; Maeno, Y.; Poutissou, R.

2006-03-01

36

Part I. Analyzing the distribution of gas law questions in chemistry textbooks. Part II. Chlorine-35 NQR spectra of group 1 and silver dichloromethanesulfonates  

NASA Astrophysics Data System (ADS)

Part I. Two studies involving the gas law questions in eight high school and Advanced Placement/college chemistry textbooks were performed using loglinear analysis to look for associations among six variables. These variables included Bloom's Taxonomy (higher-order, lower-order), Book Type (high school, college), Question Format (multiple-choice, problem, short answer), Question Placement (in-chapter, end-of-chapter, test bank), Representation (macroscopic, microscopic, symbolic), and Arkansas Science Standard (conceptual, mathematical; gas laws, pressure conversion, stoichiometry). The first study, involving the conceptual gas law questions, found the Book Type and Question Placement variables had the biggest impact, each appearing in 5 of the 11 significant associations. The second study, involving the mathematical gas law questions, found the Question Placement had the biggest impact, appearing in 7 of the 11 significant associations, followed by Book Type and the Arkansas Science Standard variables, which appeared in 5 of the 11 significant associations. These studies showed that compared to the high school books, college books have fewer multiple-choice questions (compared to short-answer and problem questions), fewer in-chapter questions (compared to end-of-chapter and test bank questions), fewer questions in the chapters and more questions at the end of the chapters and fewer multiple-choice questions in and at the end of the books and more multiple-choice questions in the test banks. Part II. The dichloromethanesulfonate salts of several +1 charged cations, M+Cl2CHSO3 - (M = Li, Na, K, Rb Ag, Cs Tl) were synthesized and studied by 35Cl nuclear quadrupole resonance (NQR). Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, which was neutralized with the metal carbonates to produce the corresponding metal dichloromethanesulfonate salts. This study completed the NQR investigation of the family of chloroacetates and chloromethanesulfonates of silver. The study suggests that the ability of organochlorine atoms to coordinate to silver ions decreases as the number of electron-withdrawing groups attached to carbon atom bound to the coordinating chlorine atom increases. The unusually large NQR spectral width found among M+Cl2CHCO2 - salts are not present among M+Cl2CHSO 3- salts and does not appear to be generally characteristic of the dichloromethyl family of salts.

Gillette, Gabriel

37

Quadrupole coupling parameters and structural aspects of crystalline and amorphous solids by NMR and NQR  

SciTech Connect

NMR and NQR techniques were 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. {sup 71}Ga and {sup 69}Ga NMR was used to study crystalline {beta}-Ga{sub 2}O{sub 3} and several gallate glasses. Quadrupole parameters were acquired for GaO{sub 6} and GaO{sub 4} units in {beta}-Ga{sub 2}O{sub 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. {sup 51}V (I = 7/2) NQR resonances below 850 kHz were detected for several metavanadates at both room temperature and liquid nitrogen temperature. Two methods, Zeeman perturbed NQR powder pattern and {sup 10}B NQR, can be employed to obtain both Qcc and {eta}. With a double coil tank circuit design, pure {sup 11}B NQR was used to determine the fraction of borons in BO{sub 3} and BO{sub 4} configurations in hydrated zinc borates. {sup 11}B NMR and NQR were also used to study lead borate glasses.

Mao, Degen.

1991-01-01

38

Investigation of structural information for boron-rich solids and aluminates via NMR and NQR studies  

SciTech Connect

Along with NMR, Nuclear Quadrupole Resonance (NQR) has become important recently for obtaining structural information from oxide glasses. The NQR studies prove in this thesis that they provide more accurate structural information than the NMR studies have done. This study presents boron and aluminum NMR, and NQR studies for some borate glasses and compounds, icosahedral boron-rich solids, some crystalline aluminosilicates. Various borates were employed to acquire structural information as well as to determine the quadrupole parameters (the quadrupole coupling constant Qcc and the asymmetry parameter {eta}) using NQR under a guidance of NMR or vice versa. By NQR a previously unknown boron site was observed for vitreous Li{sub 2}O{center dot}B{sub 2}O{sub 3}. The NMR and NQR studies were performed on some icosachedral boron-rich solids: {alpha}-rhombohedral boron (B{sub 12}), {beta}-boron (B{sub 105}) and boron carbide (B{sub 12}C{sub 3}). Three different forms of crystalline aluminosilicate (Al{sub 2}SiO{sub 5}) were studied by NQR. The NQR study yielded more accurate values of the quadrupole parameters for {sup 27}Al than the previous NMR single crystal study did.

Lee, D.

1991-01-01

39

Relative intensities of prompt ?-rays from the 35Cl(n,?)36Cl reaction with thermal neutrons as secondary ?-ray intensity standards.  

PubMed

The relative intensities of 16 prompt ?-rays from the (35)Cl(n,?)(36)Cl reaction with a thermal neutron were precisely determined as secondary ?-ray intensity standards with HPGe detectors. The detection efficiencies were calibrated from 0.2 to 10.8 MeV using the standard sources (152)Eu and (56)Co and the (14)N(n,?)(15)N reaction. We performed appropriate analyses for the evaluation of doublet peaks, subtraction of mixing with escape ?-rays and other corrections; consequently, the values were determined within 1% accuracy. Relative intensities in the range of 0.7 to 8.6 MeV are proposed as reliable secondary standards for 16 ?-rays. PMID:23287705

Shibata, Michihiro; Tojo, Akinori; Miyazaki, Itaru; Furuta, Masataka; Hayashi, Hiroaki; Kojima, Yasuaki; Shima, Yosuke; Taniguchi, Akihiro

2013-03-01

40

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

NASA Astrophysics Data System (ADS)

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.

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

41

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)

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.

Cheng, Show-Jye

42

27Al-NQR Study on Novel Phase Transition in CeOs2Al10  

NASA Astrophysics Data System (ADS)

We have performed 27Al-NQR measurements in CeOs2Al10 which exhibits a novel phase transition at T0=29 K The NQR parameters determined for all the Al sites in ambient pressure were compared with those in CeRu2Al10 with T0=27 K and CeFe2Al10 with no phase transition. The distinct NQR splitting just below T0=32.5 K under pressure 0.66 GPa ensures an enhancement of T0 and a homogeneous transition. Despite the increase of T0, the nuclear spin-lattice relaxation rate 1/Tl is suppressed over whole range of temperature than in ambient pressure. The characteristic features of no critical slowing down at T0 and of the remarkable decrease of 1/T1T starting at T > T0 become prominent under pressure, suggesting an approach to Kondo semiconductor in a valence fluctuation regime.

Matsumura, M.; Inagaki, T.; Kato, H.; Nishioka, T.; Tanida, H.; Sera, M.

2012-12-01

43

Unconventional superconductivity near quantum critical point revealed by Co-NQR measurements on Nax(H3O)CoO2·yH2O  

NASA Astrophysics Data System (ADS)

The nuclear quadrupole resonance (NQR) frequency of Co nuclei and the nuclear spin lattice relaxation rate 1/T1 were measured on several bilayered hydrate (BLH) Nax(H3O)CoO2·yH2O (y˜1.3) with variety of superconducting (SC) and magnetic transition temperatures, Tc and TM, together with non-SC mono-layered hydrate (MLH) Nax(H3O)CoO2·yH2O (y˜0.7). In the high temperature region above 70 K, 1/T1T in all the samples follows the same temperature dependence which is interpreted as the pseudogap behavior. In the BLH compounds, 1/T1T increases with decreasing temperature below 70 K, and the values of 1/T1T at Tc are large in high-Tc samples. The magnetic ordering is ascertained from the observation of the prominent divergence of 1/T1T at TM in the samples whose NQR frequency is higher than 12.5 MHz. The temperature dependence of 1/T1T is found to be consistently expressed by a unique function with two fitting parameters. We analyze the temperature dependence of 1/T1T on the basis of this function, and investigate the relationship between the magnetic fluctuations and superconductivity in the BLH compounds.

Ihara, Y.; Takeya, H.; Ishida, K.; Michioka, C.; Yoshimura, K.; Takada, K.; Sasaki, T.; Sakurai, H.; Takayama-Muromachi, E.

2007-11-01

44

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

E-print Network

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance S 20 November 2006 A radio-frequency tunable atomic magnetometer is developed for detection of nuclearHz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection

Romalis, Mike

45

Low-frequency nuclear quadrupole resonance with a dc SQUID  

SciTech Connect

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.

Chang, J.W.

1991-07-01

46

Nuclear electric quadrupole moment of 9Li using zero-field ?-detected NQR  

NASA Astrophysics Data System (ADS)

A ?-detected nuclear quadrupole resonance (NQR) spectrometer becomes a powerful tool to study changes in nuclear ground-state properties along isotopic chains when coupled to a laser excitation beamline to polarize the nuclei of interest. Recently, the ?-NQR technique in a zero magnetic field has been applied for the first time to measure the ratio of static nuclear quadrupole moments of 8, 9Li, Q9/Q8 = 0.966 75(9) denoted by Q8 for 8Li and Q9 for 9Li, respectively. This shows agreement with present literature values but with significantly improved precision. Based on the literature, the quadrupole moment for 8Li has been re-evaluated to be |Q8| = 32.6(5) mb. From this, the quadrupole moment for 9Li is calculated as |Q9| = 31.5(5) mb with the error being dominated by the error of Q8.

Voss, A.; Pearson, M. R.; Billowes, J.; Buchinger, F.; Chow, K. H.; Crawford, J. E.; Hossein, M. D.; Kiefl, R. F.; Levy, C. D. P.; MacFarlane, W. A.; Mané, E.; Morris, G. D.; Parolin, T. J.; Saadaoui, H.; Salman, Z.; Smadella, M.; Song, Q.; Wang, D.

2011-07-01

47

Structure-activity study of thiazides by magnetic resonance methods (NQR, NMR, EPR) and DFT calculations.  

PubMed

The paper presents a comprehensive analysis of the relationship between the electronic structure of thiazides and their biological activity. The compounds of interest were studied in solid state by the resonance methods nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) and quantum chemistry (ab inito and DFT) methods. Detailed parallel analysis of the spectroscopic parameters such as quadrupole coupling constant (QCC) NQR chemical shift (delta), chemical shift anisotropy (CSA), asymmetry parameter (eta), NMR and hyperfine coupling constant (A), EPR was performed and the electronic effects (polarisation and delocalisation) were revealed and compared. Biological activity of thiazides has been found to depend on many factors, but mainly on the physico-chemical properties whose assessment was possible on the basis of electron density determination in the molecules performed by experimental and theoretical methods. PMID:15670953

Latosi?ska, J N

2005-01-01

48

Addition compounds of antimony trichloride and tribromide. Crystal structure and charge transfer from NQR data  

NASA Astrophysics Data System (ADS)

The correlation analysis of the quadrupcle coupling constants(QCC) for the antimony nuclei in the intermolecular compounds of SbCl 3 and SbBr 3 with aromatic hydrocarbons is carried out. The results confirm a supposition about the general similarity of the crystal structures of these complexes. The correlative dependence between the antimony QCC values and also the results of the chlorine and bromine NQR spectra Investigation permit the evaluation of the relative acceptor strength of the antimony trihalide molecules.

Kjuntsel, I. A.; Gordeev, A. D.

49

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

NASA Astrophysics Data System (ADS)

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.

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

2004-07-01

50

27Al-NQR/NMR Study of Kondo Semiconductor CeFe2Al10  

NASA Astrophysics Data System (ADS)

27Al-NQR/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1/T1 above about 20 K, following the Korringa law (T1T = const.) below 20 K, indicates a pseudogap opening near the Fermi level. The gap magnitude of 70 K with a mid-gap state of 42% is estimated based on a rectangular density of states. The gap magnitude is much larger than the gap of 15 K evaluated previously from the electrical resistivity, which suggests CeFe2Al10 to be a Kondo semiconductor with a Kondo temperature much higher than 300 K.

Kawamura, Yukihiro; Edamoto, Shingo; Takesaka, Tomoaki; Nishioka, Takashi; Kato, Harukazu; Matsumura, Masahiro; Tokunaga, Yo; Kambe, Shinsaku; Yasuoka, Hiroshi

2010-10-01

51

The development of pure ?-NQR techniques for measurements of nuclear ground state quadrupole moments in lithium isotopes  

NASA Astrophysics Data System (ADS)

A ?-NQR spectrometer becomes a powerful tool to study changes in nuclear ground state properties along isotopic chains when coupled to a laser excitation beamline to polarise the nuclei of interest. Recently, the ?-NQR technique in a zero magnetic field has been applied for the first-time to measure ratios of static nuclear quadrupole moments of, Li. Preliminary results of the experiment determining the ratios Q9/Q8 and Q11/Q9 show agreement with present literature values with improved precision.

Voss, A.; Pearson, M. R.; Billowes, J.; Buchinger, F.; Chow, K. H.; Crawford, J. E.; Hossein, M. D.; Kiefl, R. F.; Levy, C. D. P.; MacFarlane, W. A.; Mané, E.; Morris, G. D.; Parolin, T. J.; Saadaoui, H.; Salman, Z.; Smadella, M.; Song, Q.; Wang, D.

2011-09-01

52

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

PubMed Central

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

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

2014-01-01

53

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

PubMed

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

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

54

Heteronuclear and quadrupolar second moment determination of the NQR line of 127I in NaIO4.  

PubMed

This work reports on a theoretical expression of the heteronuclear dipolar second moment (M2IS) of a NQR line of spin 5/2 nuclei. The result is applied to obtain M2IS for the resonance line of 127I in NaIO4, and in addition, an indirect determination of the quadrupolar second moment is given. PMID:10023847

Azurmendi, H F; Nagel, O A; Ramia, M E

1998-12-01

55

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

SciTech Connect

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.

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

1980-12-01

56

arXiv:physics/0609196v122Sep2006 Detection of radio frequency magnetic fields using nonlinear magneto-optical rotation  

E-print Network

magneto-optical rotation M. P. Ledbetter, V. M. Acosta, S. M. Rochester, and D. Budker Department for detection of small, high frequency magnetic fields. The magnetometer operates by detecting optical rotation), magnetic resonance imaging (MRI), nuclear quadrupole resonance (NQR) [1] and has been used in tests

57

Ab initio DFT study of bisphosphonate derivatives as a drug for inhibition of cancer: NMR and NQR parameters.  

PubMed

DFT computations were carried out to characterize the (17)Oand (2)H electric field gradient, EFG, in various bisphosphonate derivatives. The computations were performed at the B3LYP level with 6-311++G (d,P) standard basis set. Calculated EFG tensors were used to determine the (17)O and (2)H nuclear quadrupole coupling constant, ? and asymmetry parameter, ?. For better understanding of the bonding and electronic structure of bisphosphonates, isotropic and anisotropic NMR chemical shieldings were calculated for the (13)C, (17)O and (31)P nuclei using GIAO method for the optimized structure of intermediate bisphosphonates at B3LYP level of theory using 6-311++G (d, p) basis set. The results showed that various substituents have a strong effect on the nuclear quadrupole resonance (NQR) parameters (?, ?) of (17)O in contrast with (2)H NQR parameters. The NMR and NQR parameters were studied in order to find the correlation between electronic structure and the activity of the desired bisphosphonates. In addition, the effect of substitutions on the bisphosphonates polarity was investigated. Molecular polarity was determined via the DFT calculated dipole moment vectors and the results showed that substitution of bromine atom on the ring would increase the activity of bisphosphonates. PMID:21633790

Aghabozorg, Hussein; Sohrabi, Beheshteh; Mashkouri, Sara; Aghabozorg, Hamid Reza

2012-03-01

58

Structure of the Cu-NQR Spectrum in Hg-1223 Between 4.2 K and 145 K  

NASA Astrophysics Data System (ADS)

An extremely low noise RF preamplifier cooled with liquid helium has been developed and is used to perform Cu-NQR measurements for Hg-1223 (Tc=134 K) at temperatures from 4.2 K to 145 K. At temperatures from 4.2 K to 20 K the spectra are centered at 15 MHz with a spectral width of approximately 2 MHz, similar to the Cu-NQR spectra of the other members of the HgBa2Can-1CunO2n+2+? series. The Cu-NQR spectra in this temperature range exhibit some features indicating an unresolved splitting but they can still be fitted quite well by a set of two pairs of 63/65Cu lines, as expected for the 1223 structure. The spectra at 40 K and above clearly show a structure that can not be fitted suitable by a set of two pairs of 63/65Cu lines. However, a fit with a set of four pairs of 63/65Cu lines is in good agreement with the experimental results. Furthermore, the spectra at 80 K, 85 K and 90 K show a strong variation with respect to each other which might indicate a structural change like the formation of a superstructure, as discussed for other high-Tc compounds, instead of a simple disorder in the crystal lattice.

Breitzke, H.; Lüders, K.; Gippius, A. A.; Antipov, E. V.

59

Mutual influence of axial and equatorial PCl bonds in the molecular forms of pentachlorophosphorane, their lengths in gaseous and crystalline states  

Microsoft Academic Search

The quantum-chemical calculations by RHF\\/6-31G(d), MR2\\/6-31G(d) and MP2\\/6-31+G(d) methods of molecular forms of pentachlorophosphorane\\u000a with the complete geometry optimization at the different lengths of P-Cl bonds are performed. The results of the calculations\\u000a are used for estimation of respective 35Cl NQR frequencies. The lengths of axial (2.05 Å) and equatorial (2.01 Å) P-Cl bonds are found, when the calculated NQR

V. P. Feshin; E. V. Feshina

2009-01-01

60

Central role of the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) in sodium bioenergetics of Vibrio cholerae.  

PubMed

Abstract Vibrio cholerae is a Gram-negative bacterium that lives in brackish or sea water environments. Strains of V. cholerae carrying the pathogenicity islands infect the human gut and cause the fatal disease cholera. Vibrio cholerae maintains a Na+ gradient at its cytoplasmic membrane that drives substrate uptake, motility, and efflux of antibiotics. Here, we summarize the major Na+-dependent transport processes and describe the central role of the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR), a primary Na+ pump, in maintaining a Na+-motive force. The Na+-NQR is a membrane protein complex with a mass of about 220 kDa that couples the exergonic oxidation of NADH to the transport of Na+ across the cytoplasmic membrane. We describe the molecular architecture of this respiratory complex and summarize the findings how electron transport might be coupled to Na+-translocation. Moreover, recent advances in the determination of the three-dimensional structure of this complex are reported. PMID:25205724

Steuber, Julia; Halang, Petra; Vorburger, Thomas; Steffen, Wojtek; Vohl, Georg; Fritz, Günter

2014-12-01

61

Staggered magnetization in La2-xSrxCuO4 from 139La NQR and muSR: Effects of Sr doping in the range 0  

Microsoft Academic Search

We have used 139La nuclear quadrupole resonance (NQR) and positive muon spin rotation (muSR) measurements to probe the weakly doped antiferromagnetic (AF) region (x<0.02) of the La2-xSrxCuO4 system below the three-dimensional (3D) AF ordering (Néel) temperature TN(x). From these measurements, our previous 139La NQR measurements [F. C. Chou et al., Phys. Rev. Lett. 71, 2323, (1993)], and auxiliary 139La nuclear

F. Borsa; P. Carreta; J. H. Cho; F. C. Chou; Q. Hu; D. C. Johnston; A. Lascialfari; D. R. Torgeson; R. J. Gooding; N. M. Salem; K. J. E. Vos

1995-01-01

62

Noise-resilient multi-frequency surface sensor for nuclear quadrupole resonance.  

PubMed

A planar nuclear quadrupole resonance (NQR) sensor has been developed. The sensor is resilient to environmental noise and is capable of simultaneous independent multi-frequency operation. The device was constructed as an open multimodal birdcage structure, in which the higher modes, generally not used in magnetic resonance, are utilized for NQR detection. These modes have smooth distributions of the amplitudes of the corresponding radiofrequency magnetic fields everywhere along the sensor's surface. The phases of the fields, on the other hand, are cyclically shifted across the sensor's surface. Noise signals coming from distant sources, therefore, induce equal-magnitude cyclically phase-shifted currents in different parts of the sensor. When such cyclically phase-shifted currents arrive at the mode connection point, they destructively interfere with each other and are cancelled out. NQR signals of polycrystalline or disordered substances, however, are efficiently detected by these modes because they are insensitive to the phases of the excitation/detection. No blind spots exist along the sensor's surface. The sensor can be used for simultaneous detection of one or more substances in locations with environmental noise. PMID:18667343

Peshkovsky, A S; Cattena, C J; Cerioni, L M; Osán, T M; Forguez, J G; Peresson, W J; Pusiol, D J

2008-10-01

63

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

NASA Technical Reports Server (NTRS)

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.

Borsa, F.; Rigamonti, A.

1991-01-01

64

Synthesis, structure, and photoluminescence properties of a novel 3D 3 d -4 f heterometallic polymer: Pr 4 (H 2 O) 9 Cu 3.5 Cl 0.5 (Bpdc) 6.5 (OH) 2 · 5H 2 O (H 2 Bpdc = 2,2?-bipyridyl-5,5-dicarboxylic acid)  

Microsoft Academic Search

A novel 3D 3d–4f heterometallic polymer Pr4(H2O)9Cu3.5Cl0.5(Bpdc)6.5(OH)2 · 5H2O (I) (H2Bpdc = 2,2?-bipyridyl-5,5?-dicarboxylic acid) has been hydrothermally synthesized by the reaction of CuCl2 · 2H2O, PrCl3, H2Bpdc, TAA (TAA = 1H-tetrazolyl-1-acetic acid) and glacial acetic acid and characterized by elemental analysis, IR spectroscopy,\\u000a and single-crystal X-ray diffraction. Single-crystal structural analysis shows that I displays an interesting heterometallic 3D coordination framework

H. L. Cheng; D. Y. Shi; J. W. Zhao; Z. D. Geng; L. J. Chen; P. T. Ma; J. Y. Niu

2011-01-01

65

An ultra-broadband low-frequency magnetic resonance system.  

PubMed

MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3MHz frequency range without using conventional resonant circuits for either transmission or reception. This "non-resonant" approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range. PMID:24632101

Mandal, S; Utsuzawa, S; Cory, D G; Hürlimann, M; Poitzsch, M; Song, Y-Q

2014-05-01

66

Direct current superconducting quantum interference device spectrometer for pulsed nuclear magnetic resonance and nuclear quadrupole resonance at frequencies up to 5 MHz  

NASA Astrophysics Data System (ADS)

A spectrometer based on a dc superconducting quantum interference device (SQUID) has been developed for the direct detection of nuclear magnetic resonance (NMR) or nuclear quadrupole resonance (NQR) at frequencies up to 5 MHz. The sample is coupled to the input coil of the niobium-based SQUID via a nonresonant superconducting circuit. The flux locked loop involves the direct offset integration technique with additional positive feedback in which the output of the SQUID is coupled directly to a low-noise preamplifier. Precession of the nuclear quadrupole spins is induced by a magnetic field pulse with the feedback circuit disabled; subsequently, flux locked operation is restored and the SQUID amplifies the signal produced by the nuclear free induction signal. The spectrometer has been used to detect 27Al NQR signals in ruby (Al2O3[Cr3+]) at 359 and 714 kHz.

TonThat, Dinh M.; Clarke, John

1996-08-01

67

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

NASA Technical Reports Server (NTRS)

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.

Borsa, F.; Rigamonti, A.

1990-01-01

68

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

NASA Technical Reports Server (NTRS)

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. We will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in our laboratory. In particular, we will deal with Knight shift and relaxation studies of copper and oxygen. We will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-01-01

69

Field-tuned critical fluctuations in YFe2Al10: Evidence from magnetization, 27Al NMR, and NQR investigations  

NASA Astrophysics Data System (ADS)

We report magnetization, specific heat, and NMR investigations on YFe2Al10 over a wide range of temperature and magnetic field and zero field (NQR) measurements. Magnetic susceptibility, specific heat, and spin-lattice relaxation rate divided by T(1/T1T) follow a weak power law (˜T-0.4) temperature dependence, which is a signature of the critical fluctuations of Fe moments. The value of the Sommerfeld-Wilson ratio and the linear relation between 1/T1T and ? suggest the existence of ferromagnetic correlations in this system. No magnetic ordering down to 50 mK in Cp(T)/T and the unusual T and H scaling of the bulk and NMR data are associated with a magnetic instability which drives the system to quantum criticality. The magnetic properties of the system are tuned by field wherein ferromagnetic fluctuations are suppressed and a crossover from quantum critical to Fermi-liquid behavior is observed with increasing magnetic field.

Khuntia, P.; Strydom, A. M.; Wu, L. S.; Aronson, M. C.; Steglich, F.; Baenitz, M.

2012-12-01

70

IMPLEMENTATION OF A -NQR SYSTEM AT THE NSCL FOR GROUND STATE QUADRUPOLE MOMENT  

E-print Network

of multi-radio frequencies, high rf magnetic field strength, short rf application time due to the short.2 Implantation of nuclei and preservation of polarization in a host crystal 13 2.3 Hyperfine interactions

Mantica, Paul F.

71

Distinctive features of the electronic structure of tetrachloride titanium complexes  

NASA Astrophysics Data System (ADS)

The paper reports results of measurements of the ClK? shifts in the X-ray fluorescence spectra and 35Cl-NQR frequency for a group of tetrachloride titanium complexes. The experimental ClK? shifts were correlated with the parameters describing donor properties of ligands such as ligand strength (DN), ionisation potential (IP) or parameters of influence (P). Analysis of the correlation dependencies has indicated that changes in the electronic density on the chloride atom of the acceptor, taking place upon complexation, are determined by the polarisation effects.

Dolenko, G. N.; Poleshchuk, O. Kh; Gostewskii, B. A.; Latosinska, J. N.; Ostafin, M.

2000-04-01

72

Intermetallic solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3}: Synthesis, structure, NQR study and electronic band structure calculations  

SciTech Connect

Unlimited solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3} was prepared from Ga flux. Its crystal structure was refined for Fe{sub 0.5}Co{sub 0.5}Ga{sub 3} (P4{sub 2}/mnm, a=6.2436(9), c=6.4654(13), Z=4) and showed no ordering of the metal atoms. A combination of the electronic band structure calculations within the density functional theory (DFT) approach and {sup 69,71}Ga nuclear quadrupole resonance (NQR) spectroscopy clearly shows that the Fe-Fe and Co-Co dumbbells are preferred to the Fe-Co dumbbells in the crystals structure. The band structure features a band gap of about 0.4 eV, with the Fermi level crossing peaks of a substantial density of electronic states above the gap for x>0. The solid solution is metallic for x>0.025. The study of the nuclear spin-lattice relaxation shows that the rate of the relaxation, 1/T{sub 1}, is very sensitive to the Co concentration and correlates well with the square of the density of states at the Fermi level, N{sup 2}(E{sub F}). - Graphical abstract: Rate of the nuclear spin-lattice relaxation, 1/T{sub 1}, observed in the {sup 69}Ga NQR experiments for the intermetallic solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3} is the highest for x=0.25 with the highest calculated density of electronic states at the Fermi level, N(E{sub F}); in general, 1/T{sub 1} correlates with N{sup 2}(E{sub F}). Highlights: Black-Right-Pointing-Pointer Fe{sub 1-x}Co{sub x}Ga{sub 3} solid solution is prepared in single crystalline form from Ga flux. Black-Right-Pointing-Pointer In the crystal structure Fe-Fe and Co-Co dumbbells are preferred to Fe-Co dumbbells. Black-Right-Pointing-Pointer Metal-to-semiconductor transition occurs at 0NQR spectra efficiently probe local environment of two independent Ga atoms. Black-Right-Pointing-Pointer Rate of nuclear spin-lattice relaxation follows squared DOS at the Fermi level.

Verchenko, V.Yu.; Likhanov, M.S.; Kirsanova, M.A. [Department of Chemistry, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)] [Department of Chemistry, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Gippius, A.A; Tkachev, A.V.; Gervits, N.E. [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation) [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); A.V. Shubnikov Institute of Crystallography, Moscow 119333 (Russian Federation); Galeeva, A.V. [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)] [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Buettgen, N.; Kraetschmer, W. [Institut fuer Physik, University of Augsburg, Augsburg D-86135 (Germany)] [Institut fuer Physik, University of Augsburg, Augsburg D-86135 (Germany); Lue, C.S. [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)] [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Okhotnikov, K.S. [Materials and Environmental Chemistry, Stockholm University, Stockholm (Sweden)] [Materials and Environmental Chemistry, Stockholm University, Stockholm (Sweden); Shevelkov, A.V., E-mail: shev@inorg.chem.msu.ru [Department of Chemistry, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

2012-10-15

73

Suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by As75 NMR/NQR measurements  

NASA Astrophysics Data System (ADS)

The static and the dynamic spin correlations in the low-temperature collapsed tetragonal and the high-temperature tetragonal phase in CaFe2As2 have been investigated by As75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. Through the temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic (AFM) spin correlations are realized in the high-temperature tetragonal phase, no trace of the AFM spin correlations can be found in the nonsuperconducting, low-temperature, collapsed tetragonal (cT) phase. Given that there is no magnetic broadening in As75 NMR spectra, together with the T-independent behavior of magnetic susceptibility ? and the T dependence of 1/T1T?, we conclude that Fe spin correlations are completely quenched statically and dynamically in the nonsuperconducting cT phase in CaFe2As2.

Furukawa, Y.; Roy, B.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.

2014-03-01

74

Intensity of N and P signals of a two dimensional two-particle NQR spectrum (J=1)  

SciTech Connect

We calculate the intensities and phases of the N and P peaks of a 2D NMR spectrum under two-frequency excitation during preparation and mixing by means of simultaneous radio-frequency pulses with repetition frequencies close to those of adjacent transitions of the nuclear species studied. The 2D spectrum is shown to contain up to four cross-peaks, in addition to the two diagonal peaks.

Sinyavskii, N.A.; Grechishkin, V.S.; Shelukhina, S.F. [Kaliningrad State Univ. (Russian Federation)

1995-12-01

75

^7Li NMR and ^139L NQR in La_2Cu_1.985Li_0.015Cu0_4  

NASA Astrophysics Data System (ADS)

In Li doped La_2CuO4 the Li substitutes in the Cu site and introduces holes which, unlike the Sr doping, are localized. However, the effect of Li doping on the antiferromagnetic transition is much like that of Sr in that the transition is rapidly depressed at low doping concentrations and disappears at 3-4been measured in a 1.5line shows only a small increase in T2 below the transition over that at 300 K, considerably less than the nearest neighbor dipole contribution. The values of T1 also show no dramatic difference above and below the transition. However, the ^139La NQR data show the expected splitting by an internal field below the ordering temperature. This is consistent with the possibility that the the exchange coupling between nearest neighbor Cu's is modified to the extent that they do not participate in the antiferromagnetic order. Complete temperature dependent data of T1 and T2 will be presented.

Kleinhammes, A.; Kuhns, P. L.; Moulton, W. G.; Sarrao, J. L.; Fisk, Cassidy; Sullivan, Z.

1996-03-01

76

Supramolecular synthon pattern in solid clioquinol and cloxiquine (APIs of antibacterial, antifungal, antiaging and antituberculosis drugs) studied by ³?Cl NQR, ¹H-¹?O and ¹H-¹?N NQDR and DFT/QTAIM.  

PubMed

The quinolinol derivatives clioquinol (5-chloro-7-iodo-8-quinolinol, Quinoform) and cloxiquine (5-chloro-8-quinolinol) were studied experimentally in the solid state via ³?Cl NQR, ¹H-¹?O and ¹H-¹?N NQDR spectroscopies, and theoretically by density functional theory (DFT). The supramolecular synthon pattern of O-H···N hydrogen bonds linking dimers and ?-? stacking interactions were described within the QTAIM (quantum theory of atoms in molecules) /DFT (density functional theory) formalism. Both proton donor and acceptor sites in O-H···N bonds were characterized using ¹H-¹?O and ¹H-¹?N NQDR spectroscopies and QTAIM. The possibility of the existence of O-H···H-O dihydrogen bonds was excluded. The weak intermolecular interactions in the crystals of clioquinol and cloxiquine were detected and examined. The results obtained in this work suggest that considerable differences in the NQR parameters for the planar and twisted supramolecular synthons permit differentiation between specific polymorphic forms, and indicate that the more planar supramolecular synthons are accompanied by a greater number of weaker hydrogen bonds linking them and stronger ?···? stacking interactions. PMID:21080020

Latosi?ska, Jolanta Natalia; Latosi?ska, Magdalena; Tomczak, Marzena Agnieszka; Seliger, Janez; Zagar, Veselko

2011-07-01

77

Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study  

Microsoft Academic Search

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for

Travis O. Sandland; Lin-Shu Du; Jonathan F. Stebbins; James D. Webster

2004-01-01

78

Unsupervised frequency selection†  

Microsoft Academic Search

The paper describes an algorithm for the unsupervised selection of frequencies for Bode or Nyquist frequency analyses. The algorithm includes phase crossovers, gain crossovers, bounds on the frequency range, critical points, and a multiplicative increment.

RICHARD A. NORTHOUSE

1972-01-01

79

HIV Testing Frequency  

MedlinePLUS

... HIV Testing Frequency Translate Text Size Print Share HIV Testing Frequency Testing Frequency How often should you ... local health department for proper care and information. HIV Testing HIV Test Locations HIV Test Types HIV ...

80

Frequency Measurement & Analysis Service  

E-print Network

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

Magee, Joseph W.

81

Generalized frequency modulation  

E-print Network

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 ...

Torres, Wade Patrick

2001-01-01

82

Frequency comb swept lasers  

E-print Network

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 ...

Tsai, Tsung-Han

83

Eastern Frequency Response Study  

SciTech Connect

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.

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

2013-05-01

84

Spin diffusion of dipolar energy in NQR.  

PubMed

The theory of spin diffusion was extended to the case of nuclear dipolar order in solids containing paramagnetic impurities and nuclei with spin I > 1/2 having nuclear quadrupole moment. We show that spin diffusion process of dipolar order takes place in solids containing paramagnetic impurities. At the start of relaxation process, the direct relaxation regime is realized with non-exponential time dependence. Then the relaxation regime will be changed to diffusion-limited one. Using obtained expressions for the spin lattice relaxation times for these two relaxation regimes, the diffusion coefficient of the dipolar order in nuclear quadrupole resonance can be estimated from experimental data. PMID:10868572

Furman, G B; Goren, S D

2000-06-01

85

Frequency Bin Entangled Photons  

E-print Network

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.

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

2009-10-07

86

Radio frequency detection assembly and method for detecting radio frequencies  

DOEpatents

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.

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

2010-03-16

87

Frequency invariant interferometry  

NASA Astrophysics Data System (ADS)

This paper discusses frequency-independent phase comparison interferometry as a method of direction finding. Theoretical relationships are derived that show the electrical phase between two elements of an array can remain approximately constant over frequency. The theory is developed for log-periodic dipole arrays. Design and fabrication of a two-element interferometer using log-periodic antennas are discussed. Experimental results are presented which show that this array remains frequency independent over a three-octave bandwidth.

Musselman, Randall L.; Norgard, John D.

1992-05-01

88

Nonlinear Frequency Compression  

PubMed Central

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

Scollie, Susan; Glista, Danielle; Seelisch, Andreas

2013-01-01

89

Frequencies of solar oscillations  

NASA Technical Reports Server (NTRS)

Solar oscillations have been observed at three different spatial scales at Big Bear Solar Observatory during 1986-1987 and, using three data sets, a new and more accurate table of solar oscillation frequencies has been compiled. The oscillations, which are presented as functions of radial order n and spherical harmonic degree l, are averages over azimuthal order and therefore approximate the normal mode frequencies of a nonrotating, spherically symmetric sun, near solar minimum. The table contains frequencies for most of the solar p and f modes with l between 0 and 1860, n between 0 and 26, and oscillation mode frequencies between 1.0 and 5.3.

Libbrecht, K. G.; Woodard, M. F.; Kaufman, J. M.

1990-01-01

90

Electrophysiological Low-Frequency Coherence and Cross-Frequency Coupling  

E-print Network

to interareal BOLD correlations. The low-frequency oscillations also influenced local pro- cessing by modulatingNeuron Article Electrophysiological Low-Frequency Coherence and Cross-Frequency Coupling Contribute in the task-free state. Low-frequency oscillations (

Kastner, Sabine

91

Frequency modulated oscillator  

NASA Technical Reports Server (NTRS)

A frequency modulated push-pull oscillator in which the non-linear characteristic of varactors producing frequency modulation is compensated for by an opposite non-linear characteristic of a field effect transistor providing modulating bias to the varactors is described.

Honnell, M. A. (inventor)

1977-01-01

92

Stabilized radio frequency quadrupole  

DOEpatents

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.

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

1984-01-01

93

Microfabricated ion frequency standard  

DOEpatents

A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

Schwindt, Peter (Albuquerque, NM); Biedermann, Grant (Albuquerque, NM); Blain, Matthew G. (Albuquerque, NM); Stick, Daniel L. (Albuquerque, NM); Serkland, Darwin K. (Albuquerque, NM); Olsson, III, Roy H. (Albuquerque, NM)

2010-12-28

94

Precision frequency synthesizing sources with excellent time/frequency performances  

NASA Technical Reports Server (NTRS)

Precision frequency synthesizing sources are needed in the time / frequency measuring system, atomic frequency standards, telemetry, communication, and radar systems. This kind of frequency synthesizing source possesses high frequency accuracy and excellent long term and short term frequency stability. Several precision frequency synthesizing sources developed by Beijing Institute of Radio Metrology and Measurement (BIRMM) which have been successfully applied to the time / frequency measuring system, atomic frequency standards system, and radar system are described. In addition, the working principle, implementation approach, and the main technical specifications of the frequency synthesizing sources are also given.

Zhou, Liren; Lin, Hai

1994-01-01

95

Squeezing frequency combs  

E-print Network

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.

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

2006-05-15

96

Radio frequency strain monitor  

NASA Technical Reports Server (NTRS)

A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

1989-01-01

97

Quantum frequency downconversion experiment  

E-print Network

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.

Hiroki Takesue

2010-06-02

98

Graphene Frequency Multipliers  

E-print Network

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 ...

Wang, Han

99

A digital frequency synthesizer  

Microsoft Academic Search

A digital frequency synthesizer has been designed and constructed based on generating digital samples ofexp [j(2^{pi}nk\\/N)]at timenT. The real and imaginary parts of this exponential form samples of quadrature sinusoids where the frequency indexkis allowed to vary(-N\\/4) leq K < (N\\/4). The digital samples drive digital to analog converters followed by low-pass interpolating filters to produce analog sinusoids. The method

JOSEPH TIERNEY; CHARLES M. RADER; B. Gold

1971-01-01

100

Metamaterials at zero frequency.  

PubMed

We investigate the problem of designing metamaterial structures which operate at very low frequencies. As an example, we consider the case of a DC magnetic cloak, which requires a variable, anisotropic magnetic permeability with both paramagnetic and diamagnetic components. We show that a structure based on superconducting components is the key to diamagnetism at low frequencies, and present a metamaterial design which meets the requirements of the cloak. PMID:22251595

Wood, B; Pendry, J B

2007-02-21

101

Frequency domain measurement systems  

NASA Technical Reports Server (NTRS)

Stable frequency sources and signal processing blocks were characterized by their noise spectra, both discrete and random, in the frequency domain. Conventional measures are outlined, and systems for performing the measurements are described. Broad coverage of system configurations which were found useful is given. Their functioning and areas of application are discussed briefly. Particular attention is given to some of the potential error sources in the measurement procedures, system configurations, double-balanced-mixer-phase-detectors, and application of measuring instruments.

Eischer, M. C.

1978-01-01

102

Studies of low-frequency intermolecular hydrogen-bonded vibrations using a continuous supersonic slit jet mid-infrared quantum cascade laser spectrometer  

NASA Astrophysics Data System (ADS)

Rovibrational manifolds in low frequency intermolecular vibrations of prototypical hydrogen-bonded interactions OC-HX (X = F, Cl, CN) are reported using a near infrared quantum cascade cw supersonic jet spectrometer. (i) OC-HCl is studied to evaluate future capabilities of the QCL spectrometer. (ii) Analysis of OC-HF demonstrates applicability to vibrations greater than 80 cm-1 above the ground state. ?51 band origins in OC-1H35Cl and OC-1H19F are 48.9944(2) and 81.96825(12) cm-1 respectively. (iii) The corresponding intermolecular ?71 band origin of OC-HCN is 34.63742(18) cm-1 and its corresponding rovibrational spectrum made available for attempted detection in interstellar space. Analysis of ?2, ?2+?71-?71, ?2+?71, and ?2+?61 vibrations in OC-HCN also enables generation of its 5-dimensional semi-empirical intermolecular potential. Structural and other properties of OC-HCN are then compared with corresponding properties predicted using morphed potentials for the homologous series OC-HX (X = F, Cl, Br, I). These results permit investigation of blue shifts in OC vibrations for this homologous series.

McElmurry, B. A.; Rivera-Rivera, L. A.; Scott, K. W.; Wang, Z.; Leonov, I. I.; Lucchese, R. R.; Bevan, J. W.

2012-12-01

103

Frequency Standards and Metrology  

NASA Astrophysics Data System (ADS)

Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and imaging an event horizon (Invited) / S. Doeleman. Optically-pumped space cesium clock for Galileo: results of the breadboard / R. Ruffieux ... [et al.] -- pt. IV. Optical clocks I: lattice clocks. Optical lattice clock: seven years of progress and next steps (Invited) / H. Katori, M. Takamoto and T. Akatsuka. The Yb optical lattice clock (Invited) / N. D. Demke ... [et al.]. Optical Lattice clock with Sr atoms (Invited) / P. G. Westergaard ... [et al.]. Development of an optical clock based on neutral strontium atoms held in a lattice trap / E. A. Curtis ... [et al.]. Decoherence and losses by collisions in a [symbol]Sr lattice clock / J. S. R. Vellore Winfred ... [et al.]. Lattice Yb optical clock and cryogenic Cs fountain at INRIM / F. Levi ... [et al.] -- pt. V. Optical clocks II: ion clocks. [Symbol]Yb+ single-ion optical frequency standards (Invited) / Chr. Tamm ... [et al.]. An optical clock based on a single trapped [symbol]Sr+ ion (Invited) / H. S. Margolis ... [et al.]. A trapped [symbol]Yb+ ion optical frequency standard based on the [symbol] transition (Invited) / P. Gill ... [et al.]. Overview of highly accurate RF and optical frequency standards at the National Research Council of Canada (Invited) / A. A. Madej ... [et al.] -- pt. VI. Optical frequency combs. Extreme ultraviolet frequency combs for spectroscopy (Invited) / A. Ozawa ... [et al.]. Development of an optical clockwork for the single trapped strontium ion standard at 445 THz / J. E. Bernard ... [et al.]. A phase-coherent link between the visible and infrared spectral ranges using a combination of CW OPO and femtosecond laser frequency comb / E. V. Kovalchuk and A. Peters. Improvements to the robustness of a TI: sapphire-based femtosecond comb at NPL / V. Tsatourian ... [et al.] -- pt. VII. Atomic microwave standards. NIST FI and F2 (Invited) / T. P. Heavner ... [et al.]. Atomic fountains for the USNO master clock (Invited) / C. Ekstrom ... [et al.]. The transportable cesium fountain clock NIM5: its construction and performance (Invited) / T. Li ... [et al.].Compensated multi-pole merc

Maleki, Lute

2009-04-01

104

Monolithic THz Frequency Multipliers  

NASA Technical Reports Server (NTRS)

Frequency multipliers are required as local oscillator sources for frequencies up to 2.7 THz for FIRST and airborne applications. Multipliers at these frequencies have not previously been demonstrated, and the object of this work was to show whether such circuits are really practical. A practical circuit is one which not only performs as well as is required, but also can be replicated in a time that is feasible. As the frequency of circuits is increased, the difficulties in fabrication and assembly increase rapidly. Building all of the circuit on GaAs as a monolithic circuit is highly desirable to minimize the complexity of assembly, but at the highest frequencies, even a complete monolithic circuit is extremely small, and presents serious handling difficulty. This is compounded by the requirement for a very thin substrate. Assembly can become very difficult because of handling problems and critical placement. It is very desirable to make the chip big enough to that it can be seen without magnification, and strong enough that it may be picked up with tweezers. Machined blocks to house the chips present an additional challenge. Blocks with complex features are very expensive, and these also imply very critical assembly of the parts. It would be much better if the features in the block were as simple as possible and non-critical to the function of the chip. In particular, grounding and other electrical interfaces should be done in a manner that is highly reproducible.

Erickson, N. R.; Narayanan, G.; Grosslein, R. M.; Martin, S.; Mehdi, I.; Smith, P.; Coulomb, M.; DeMartinez, G.

2001-01-01

105

High frequency energy measurements  

SciTech Connect

High-frequency (> 100 MHz) energy measurements present special problems to the experimenter. Environment or available electronics often limit the applicability of a given detector type. The physical properties of many detectors are frequency dependent and in some cases, the physical effect employed can be frequency dependent. State-of-the-art measurements generally involve a detection scheme in association with high-speed electronics and a method of data recording. Events can be single or repetitive shot requiring real time, sampling, or digitizing data recording. Potential modification of the pulse by the detector and the associated electronics should not be overlooked. This presentation will review typical applications, methods of choosing a detector, and high-speed detectors. Special considerations and limitations of some applications and devices will be described.

Stotlar, S.C.

1981-01-01

106

Hg(+) Frequency Standards  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

107

Frequency division multiplex technique  

NASA Technical Reports Server (NTRS)

A system for monitoring a plurality of condition responsive devices is described. It consists of a master control station and a remote station. The master control station is capable of transmitting command signals which includes a parity signal to a remote station which transmits the signals back to the command station so that such can be compared with the original signals in order to determine if there are any transmission errors. The system utilizes frequency sources which are 1.21 multiples of each other so that no linear combination of any harmonics will interfere with another frequency.

Brey, H. (inventor)

1973-01-01

108

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).

2011-05-25

109

HF (High Frequency) Communications Frequency-Management Procedure for Forecasting the Frequency of Optimum Transmission.  

National Technical Information Service (NTIS)

This report describes a procedure for forecasting the Frequency of Optimum Transmission (FOT) on a high-frequency communications path when the Maximum Observable Frequency (MOF) on another path and an historical record of the correlations of MOFs measured...

M. Daehler

1984-01-01

110

Low frequency phase signal measurement with high frequency squeezing  

E-print Network

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.

Zehui Zhai; Jiangrui Gao

2011-01-14

111

Coherent frequency combs and spectroscopy  

Microsoft Academic Search

Optical frequency combs possessing precise phase coherence across the entire visible spectrum have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic

Jun Ye

2010-01-01

112

Judged frequency of lethal events  

Microsoft Academic Search

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

Sarah Lichtenstein; Baruch Fischhoff; Mark Layman; Barbara Combs

1978-01-01

113

Optimization of frequency assignment  

NASA Astrophysics Data System (ADS)

A systematic method of determining carrier frequency assignment is proposed to minimize the cochannel interference in satellite communication systems. For the mathematical treatment of the problem, discrete positioning of carriers is introduced to avoid the nonlinear expression inherent in interference evaluation. The proposed method converts this nonlinear problem into the well-known assignment problem and enables the development of an algorithm based on the branch-and-bound method. Extended models of the proposed method are presented for practical application. To demonstrate the effectiveness of the method, computation results are shown for two typical problems. In both of the examples, cochannel interference is significantly reduced as the result of optimization of frequency assignment.

Mizuike, Takeshi; Ito, Yasuhiko

1989-10-01

114

High frequency reference electrode  

DOEpatents

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.

Kronberg, James W. (Aiken, SC)

1994-01-01

115

Micro ion frequency standard  

NASA Astrophysics Data System (ADS)

We are developing a highly miniaturized trapped ion clock to probe the 12.6 GHz hyperfine transition in the 171Yb+ ion. The clock development is being funded by the Integrated Micro Primary Atomic Clock Technology (IMPACT) program from DARPA where the stated goals are to develop a clock that consumes 50 mW of power, has a size of 5 cm3, and has a long-term frequency stability of 10-14 at one month. One of the significant challenges will be to develop miniature single-frequency lasers at 369 nm and 935 nm and the optical systems to deliver light to the ions and to collect ion fluorescence on a detector.

Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; Serkland, Darwin K.; Boye, Robert; Fang, Lu; Casias, Adrian; Manginell, Ronald P.; Moorman, Matthew; Prestage, John; Yu, Nan

2011-06-01

116

Flood Frequency Analysis  

NSDL National Science Digital Library

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.

Comet

2006-10-10

117

Variable Frequency Pump Drives  

E-print Network

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... is about to have a dramatic effect on many basic applications that exist for centrifugal pumps and their future standardization. VARIABLE SPEED PUMP OPERATION Changing the speed of the centrifugal pump driver is not a new development. Its advantages...

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

118

Rapid frequency scan EPR  

NASA Astrophysics Data System (ADS)

In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x, y plane decays to baseline at the end of the scan, which typically is about 5 T2 after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5 T2. However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5 T2, even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B1, periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation.

Tseitlin, Mark; Rinard, George A.; Quine, Richard W.; Eaton, Sandra S.; Eaton, Gareth R.

2011-08-01

119

Low frequency cavitation erosion  

NASA Astrophysics Data System (ADS)

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.

Pardue, Sally J.; Chandekar, Gautam

2002-11-01

120

Pronunciation and the Frequency Meaningfulness Effect in Children's Frequency Discrimination.  

ERIC Educational Resources Information Center

In an absolute frequency judgment task, 130 sixth graders received either high-frequency (Hi-F), low-frequency, high-meaningfulness (Lo-F/Hi-M), or low-frequency, low-meaningfulness (Lo-F/Lo-M) words selected from the 1944 Thorndike-Lorge list. Subjects were asked to either pronounce the words aloud, listen to the examiner prounounce the written…

Ghatala, Elizabeth S.; And Others

121

Modeling Infrared Frequency Selective Surfaces with Frequency Dependent Materials  

Microsoft Academic Search

With the emergence of infrared frequency selective surfaces (FSS), the increasing need for accurate characterization using numerical modeling prior to device fabrication has exposed limitations in the t raditional modeling procedures used for lower frequency FSS designs. To impr ove full-wave FSS models at IR, a procedure to measure and integrate frequency dependent material properties in modeling is described. Measured

James Ginn; Brian Lail; David Shelton; Jeffrey Tharp; William Folks; Glenn Boreman

122

High-frequency ECG  

NASA Technical Reports Server (NTRS)

The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire ventricular surface and were signal-averaged and filtered in the 30-250 Hz frequency range. The results showed that the decrease noted in the HF-QRS correlated linearly with the local conduction delay. The results suggest that HF-QRS is a potent indicator of disturbed local conduction. An alternative theory is that HF-QRS reflect the shape of the original electrocardiographic signal. Bennhagen et al showed that root mean square (RMS) voltage values of the depolarization signal correlate poorly with the signal amplitude but highly with the first and second derivatives, i.e. the velocity and the acceleration of the signal. It has also been suggested that the autonomic nervous system affects HF-QRS. For example, sitting up causes significant changes in HF-QRS in some leads compared to the supine position [Douglas et al., 2006]. Unpublished results indicate that familial dysautonomic patients (both vagal and sympathetic degeneration) have very little Reduced Amplitude Zones (RAZ) formation . Athletic individuals, especially elite athletes, who have vagally-mediated changes on the conventional ECG (i.e. early repolarization, bradycardia) have increased RAZ formation. Further electrophysiological studies are needed, however, to better understand the underlying mechanisms of HF-QRS. Several investigators have studied HF-QRS in different cardiac conditions, including acute myocardial ischemia and myocardial infarction (MI). However, in order for clinicians to confidently use HF-QRS as an adjunct to standard ECG, more knowledge about the characteristics of HF-QRS is needed.

Tragardh, Elin; Schlegel, Todd T.

2006-01-01

123

Dual-frequency patch antennas  

Microsoft Academic Search

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency

S. Maci; G. BifJi Gentili

1997-01-01

124

Frequency entrainment for micromechanical oscillator  

Microsoft Academic Search

We demonstrate synchronization of laser-induced self-sustained vibrations of radio-frequency micromechanical resonators by applying a small pilot signal either as an inertial drive at the natural frequency of the resonator or by modulating the stiffness of the oscillator at double the natural frequency. By sweeping the pilot signal frequency, we demonstrate that the entrainment zone is hysteretic and can be as

M. Zalalutdinov; K. L. Aubin; M. Pandey; A. T. Zehnder; R. H. Rand; H. G. Craighead; J. M. Parpia; B. H. Houston

2003-01-01

125

Binaural Beats at High Frequencies  

Microsoft Academic Search

Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other

Dennis McFadden; Edward G. Pasanen

1975-01-01

126

Terahertz laser frequency combs  

NASA Astrophysics Data System (ADS)

Terahertz light can be used to identify numerous complex molecules, but has traditionally remained unexploited due to the lack of powerful broadband sources. Pulsed lasers can be used to generate broadband radiation, but such sources are bulky and produce only microwatts of average power. Conversely, although terahertz quantum cascade lasers are compact semiconductor sources of high-power terahertz radiation, their narrowband emission makes them unsuitable for complex spectroscopy. In this work, we demonstrate frequency combs based on terahertz quantum cascade lasers, which combine the high power of lasers with the broadband capabilities of pulsed sources. By fully exploiting the quantum-mechanically broadened gain spectrum available to these lasers, we can generate 5 mW of terahertz power spread across 70 laser lines. This radiation is sufficiently powerful to be detected by Schottky-diode mixers, and will lead to compact terahertz spectrometers.

Burghoff, David; Kao, Tsung-Yu; Han, Ningren; Chan, Chun Wang Ivan; Cai, Xiaowei; Yang, Yang; Hayton, Darren J.; Gao, Jian-Rong; Reno, John L.; Hu, Qing

2014-06-01

127

Frequency mixing crystal  

DOEpatents

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.

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

1992-01-01

128

Matsubara Frequency Sums  

E-print Network

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.

Alok Kumar

2010-02-25

129

Radio frequency coaxial feedthrough  

DOEpatents

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.

Owens, Thomas L. (Kingston, TN)

1989-01-17

130

[High frequency jet ventilation].  

PubMed

High frequency jet ventilation (HFJV) is a new ventilation technique which ensures satisfactory gas exchanges with tidal volumes of about 2 ml . kg-1. A gas mixture under high pressure is "chopped up" by an electrically-controlled solenoid valve and delivered to the patient by an injection system. A specific heater-humidifier is required for optimal humidity and warmth of the gas mixture. HFJV creates a positive end-expiratory pressure effect in the alveoles, and the increase of mean intratracheal pressure observed accurately reflects the increase of mean alveolar pressure. Convection by direct alveolar ventilation plays a determinant role in CO2 clearance under HFJV, the other gas transport mechanisms being accessory. In respiratory failure with shock HFJV is better tolerated haemodynamically than conventional ventilation. The main indications of the new technique are ENT surgery, thoracic and tracheal surgery, lithotripsy, broncho-pleural and oesophago-tracheal fistulae and circulatory shock. PMID:2958820

Rouby, J J; Viars, P

1987-09-26

131

Frequency doubling crystals  

DOEpatents

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.

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

1989-01-01

132

High frequency nanotube oscillator  

DOEpatents

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.

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

2012-02-21

133

Frequency dependence of organic magnetoresistance  

NASA Astrophysics Data System (ADS)

Organic magnetoresistive (OMAR) devices show a large enough magnetoresistive response (typically 10%) for potential applications as magnetic field sensors. However, applications often require sensing high frequency magnetic fields, and the examination of the frequency-dependent magnetoresistive response is therefore required. Analysis of time constants that limit the frequency response may also shed light on the mechanism behind the OMAR effect, because different OMAR mechanisms occur at different time scales In our experiments, the AC magnetic field is supplied by a coil with a ferrite core which is driven by a function generator The AC magnet shows a frequency response that is almost flat up to 1MHz. We found that the OMAR frequency limit is about 10 kHz for a typical organic semiconductor device and at least 100 kHz for devices made from a doped polymer film. We also performed capacitance and conductance vs. frequency measurements to understand the origin of the observed limit frequencies.

Wang, Fujian; Rybicki, James; Lin, Ran; Hutchinson, Kent; Hou, Jia; Wohlgenannt, Markus

2011-03-01

134

Radio Frequency Identification  

NSDL National Science Digital Library

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.

Leske, Cavin.

135

Towards VECSEL frequency combs  

NASA Astrophysics Data System (ADS)

Significant progress has been made over the last year towards generating frequency combs using VECSELs. Here, I will discuss recent progress made generating < 4kW peak power femtosecond pulse VECSELs, where we have achieved 3.3 W average power with 400 fs pulse duration at 1.7 GHz repetition rate. This has been achieved by exploiting the rapid power scaling progress made in the field of CW VECSELs [1]. The gain structure used here is grown and processed by the University of Marburg, and the window layer is etched for anti-resonance to increase the gain bandwidth and reduce the dispersion [2]. We have used this to generate supercontinuum, achieving 45 % throughput in a 2.2 micron core photonic crystal fiber when the VECSEL produced 1 W average output power. A continuum with a width of 175 nm is generated. At higher average powers heating of the fiber tip reduces coupling efficiency which limits the supercontinuum bandwidth and we will discuss measures to avoid this. Finally, I will outline approaches to further reduce the pulse length, whilst maintaining the average power, to a point where generating coherent octave spanning supercontinuum, suitable for F-2F stabilization should become a reality.

Wilcox, Keith G.

2013-02-01

136

A Biochemical Magic Frequency  

NASA Technical Reports Server (NTRS)

Life is composed principally of four classes of biomolecules - protein, nucleic acid, polysaccharide and lipid. Using 1) estimates of the reducing equivalents (electron pairs) needed to synthesize these biomolecules from carbon dioxide, and 2) measurements of the molecular composition of different organisms, we calculated the average number of electron pairs required for the reduction of carbon dioxide to biological carbon (electron pairs/carbon atom). These calculations showed that the carbon of the Earths biosphere is at the reduction level of formaldehyde that requires 2 electron pairs/carbon atom to be synthesized from carbon dioxide. This was also the reduction level of carbon of individual organisms, except for those that stored large amounts of fuel as lipid. Since this chemical property of life is easily discovered and probably universal, it's most likely known by other intelligent life in the universe. It could be the one thing we know about other carbon-based life in the universe, and the one thing that other intelligent life knows about us. We believe this common knowledge that formaldehyde represents the reduction level of life's carbon could lead to the selection of the 72.83814 GHz line of the 0,0,0,1,0,1 ground-state rotational transition of formaldehyde as a frequency for interstellar communication.

Weber, Arthur L.

1993-01-01

137

High frequency ultrasound torturer.  

PubMed

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

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

2009-12-01

138

A technique for orthogonal frequency division multiplexing frequency offset correction  

Microsoft Academic Search

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,

P. H. Moose

1994-01-01

139

Operational frequency stability of rubidium and cesium frequency standards  

NASA Technical Reports Server (NTRS)

The frequency stabilities under operational conditions of several commercially available rubidium and cesium frequency standards were determined from experimental data for frequency averaging times from 10 to the 7th power s and are presented in table and graph form. For frequency averaging times between 10 to the 5th power and 10 to the 7th power s, the rubidium standards tested have a stability of between 10 to the minus 12th power and 5 x 10 to the minus 12th power, while the cesium standards have a stability of between 2 x 10 to the minus 13th power and 5 x 10 to the minus 13th power.

Lavery, J. E.

1973-01-01

140

An assessment of derived flood frequency distributions  

E-print Network

Flood Frequency Curve - Turtle Creek. . . FIG. 9. Statistical Flood Frequency Curve - Halls Bayou . . . . . . 51 . . . 51 FIG. 10. Derived Flood Frequency Curves ? South Rocky Creek. . . . . . 53 FIG. 11. Derived Flood Frequency Curves - Briar Creek... . . FIG. 12, Derived Flood Frequency Curves - Turtle Creek. . . FIG. 13. Derived Flood Frequency Curves - Halls Bayou. . . . . . . . . . . . . . FIG. 14. Simulation Flood Frequency Curve ? South Rocky Creek. . . . . . 54 . . . 56 FIG. 15. Simulation...

Raines, Timothy Howard

2012-06-07

141

A fiber optic frequency shifter  

NASA Astrophysics Data System (ADS)

A fiber optic frequency shifter capable of shifting the frequency of light traveling through the fiber has been designed, constructed, and tested. The frequency of the transmitted light is shifted by stretching and contracting the optical fiber that is wound around two piezoelectric ceramic tubes. The frequency of the light is shifted by linearly changing the path length along which the light must travel. The diameters of two piezoelectric ceramic tubes are changed when a linearly increasing electric field is applied to the tubes. A servo control system is used to correct and compensate for nonlinearity of the piezoelectric material and assembly. A frequency shift of up to 305 Hz for up to 2.5 s with a linewidth of less than 1 Hz is achieved with the present setup. This frequency shifter has been successfully applied to a laser light scattering apparatus for which heterodyne experiments are made for particle electrophoretic mobility and zeta potential measurements.

Xu, Renliang; Schmitz, Brian; Lynch, Martin

1997-05-01

142

Frequency entrainment for micromechanical oscillator  

NASA Astrophysics Data System (ADS)

We demonstrate synchronization of laser-induced self-sustained vibrations of radio-frequency micromechanical resonators by applying a small pilot signal either as an inertial drive at the natural frequency of the resonator or by modulating the stiffness of the oscillator at double the natural frequency. By sweeping the pilot signal frequency, we demonstrate that the entrainment zone is hysteretic and can be as wide as 4% of the natural frequency of the resonator, 400 times the 1/Q˜10-4 half-width of the resonant peak. Possible applications are discussed based on the wide range of frequency tuning and the power gain provided by the large amplitude of self-oscillations (controlled by a small pilot signal).

Zalalutdinov, M.; Aubin, K. L.; Pandey, M.; Zehnder, A. T.; Rand, R. H.; Craighead, H. G.; Parpia, J. M.; Houston, B. H.

2003-10-01

143

Frequency-Shift Hearing Aid  

NASA Technical Reports Server (NTRS)

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.

Weinstein, Leonard M.

1994-01-01

144

Flood Frequency Analysis: International Edition  

NSDL National Science Digital Library

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.

Comet

2010-08-31

145

Effective switching frequency multiplier inverter  

DOEpatents

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.

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

2007-08-07

146

Automatic oscillator frequency control system  

NASA Technical Reports Server (NTRS)

A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

Smith, S. F. (inventor)

1985-01-01

147

Binaural beats at high frequencies.  

PubMed

Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other--that is, that there be a small interaural difference in the envelope periodicities. This finding is in accord with other recent demonstrations that the auditory system is not deaf to interaural time differences at high frequencies. PMID:1179219

McFadden, D; Pasanen, E G

1975-10-24

148

Nuclear Quadrupole Resonance Study of the Nitrogen Mustards and Local Anesthetics.  

NASA Astrophysics Data System (ADS)

The density matrix description of pulsed nitrogen -14 nuclear quadrupole resonance (NQR) spin-echoes is presented. The parallel between this problem, when formulated in terms of the fictitious spin- 1/2 operators, and that of spin - 1/2 NMR spin-echoes in liquids is discussed along with the complications which arise in multiple-pulse NQR experiments in powders due to the random orientation of the electric field gradient tensors. The equipment and procedures involved in searching for, detecting and identifying NQR resonances using pulsed techniques are described. The ('14)N NQR spectra of several nitrogen mustard compounds in the solid state are reported and analyzed in the framework of the Townes and Dailey theory. For the aniline derivatives, a correlation exists between l -(sigma), l being the nitrogen lone-pair electron density and (sigma) the average N-C sigma bond electron density, and the enhanced Hammett sigma constant (sigma)('-). An improved correlation is obtained between l-(sigma) and (sigma)(,R)('-), which emphasizes the importance of resonance effects in determining l-(sigma). The increase of hydrolysis and alkylation rates with increasing values of l-(sigma) is in agreement with the identification of the cyclic immonium ion as the intermediate in the hydrolysis and alkylation processes of the aromatic nitrogen mustards. A possible correlation is noted between the ('35)Cl NQR spectra for some of the mustards and measures of toxic and antitumor activity. ('14)N NQR spectra for several local anesthetics in the solid state are also reported and analyzed using the Townes and Dailey approach. The changes in the electron distributions at various nitrogen sites, produced by protonating the tertiary amino nitrogen, are discussed and shown to be in general agreement with expectations bases on the increased electrophilic character of the protonated amino group.

Buess, Michael Lee

149

New ?-? voltage to frequency converter  

Microsoft Academic Search

The voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to the control voltage. There are two common VFC architectures: the current steering multivibrator and the charge-balance VFC. For higher linearity, the charge-balancing method is preferred. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or \\

Milan Stork

2002-01-01

150

Disclosure frequency and earnings management  

Microsoft Academic Search

We examine the relation between disclosure frequency and earnings management, and the impact of this relation on post-issue performance, for a sample of seasoned equity offerings (SEOs). We contend that firms with extensive disclosure are less likely to face information problems, leading to less earnings management and better post-issue performance. Our results confirm that disclosure frequency is inversely related to

Hoje Jo; Yongtae Kim

2007-01-01

151

Frequency-controlled voltage regulator  

NASA Technical Reports Server (NTRS)

Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

Mclyman, W. T.

1980-01-01

152

Frequency tuning in animal locomotion  

Microsoft Academic Search

In locomotion that involves repetitive motion of propulsive structures (arms, legs, fins, wings) there are resonant frequencies f* at which the energy consumption is a minimum. As animals need to change their speed, they can maintain this energy minimum by tuning their body resonances. We discuss the physical principles of frequency tuning, and how it relates to forces, damping, and

Boye K. Ahlborn; Robert W. Blake; William M. Megill

2006-01-01

153

Gaming Frequency and Academic Performance  

ERIC Educational Resources Information Center

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…

Ip, Barry; Jacobs, Gabriel; Watkins, Alan

2008-01-01

154

Spatial frequency in speckle metrology  

Microsoft Academic Search

Speckle metrology, as applied to whole-field displacement measurements, has been reviewed from the point of view of the relevant frequency domain. It is shown that spatial frequency defines sensitivity and resolution for both pointwise and whole-field analysis. Theory and experimental results indicate several ways in which sensitivity can be increased to values comparable with those obtained with moire interferometry. Grating

Meirong Tu; Peter J. Gielisse

1990-01-01

155

Frequency Discrimination in Young Infants.  

ERIC Educational Resources Information Center

Frequency difference thresholds were determined for fourteen 4- to 9-month-old infants (mean age, 6 months 10 days) using a discrimination learning paradigm, following a one-up, two-down staircase procedure. The subject heard 500 msec tone bursts repeated at a rate of one per sec, with a fixed standard frequency. At various points in this pulse…

Olsho, Lynne Werner; And Others

156

Frequency Conversion of Entangled State  

E-print Network

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.

Aihong Tan; Xiaojun Jia; Changde Xie

2006-03-01

157

Laser frequency stabilization for LISA  

NASA Technical Reports Server (NTRS)

The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

Mueller, Guido; McNamara, Paul; Thorpe, Ira; Camp, Jordan

2005-01-01

158

Frequency dependence of organic magnetoresistance  

NASA Astrophysics Data System (ADS)

To identify the microscopic mechanisms of organic magnetoresistance (OMAR), the dependency on the frequency of the applied magnetic field is explored, which consists of a dc and ac component. The measured magnetoconductance decreases when the frequency is increased. The decrease is stronger for lower voltages, which is shown to be linked to the presence of a negative capacitance, as measured with admittance spectroscopy. The negative capacitance disappears when the frequency becomes comparable to the inverse transit time of the minority carriers. These results are in agreement with recent interpretations that magnetic field effects on minority carrier mobility dominate OMAR.

Wagemans, W.; Janssen, P.; van der Heijden, E. H. M.; Kemerink, M.; Koopmans, B.

2010-09-01

159

Spectrally resolved frequency comb interferometry  

NASA Astrophysics Data System (ADS)

In this contribution a novel method for interferometric distance measurement is presented, that is based on unraveling the spectrum of a femtosecond frequency comb. The light of a frequency comb is sent into a Michelson interferometer. The output of the interferometer is analyzed by a high-resolution spectrometer, resolving the individual comb modes. The path-length difference between the two arms is determined on the level of tens of nm, by utilizing the wealth of information present in the unraveled spectrum, showing homodyne interference for each individual frequency comb mode. The measurement method allows for high-accuracy measurements in combination with a large range of non-ambiguity.

van den Berg, S.

2014-04-01

160

Pulsed optically pumped frequency standard  

SciTech Connect

We reconsider the idea of a pulsed optically pumped frequency standard conceived in the early 1960s to eliminate the light-shift effect. The development of semiconductor lasers and of pulsed electronic techniques for atomic fountains and new theoretical findings allow an implementation of this idea which may lead to a frequency standard whose frequency stability is limited only by the thermal noise in the short term and by the temperature drift in the long term. We shall also show both theoretically and experimentally the possibility of doubling the atomic quality factor with respect to the classical Ramsey technique approach.

Godone, Aldo; Micalizio, Salvatore; Levi, Filippo [Istituto Elettrotecnico Nazionale Galileo Ferraris, Strada delle Cacce 91, 10135 Torino (Italy)

2004-08-01

161

Instantaneous Frequency Stock Market Model  

NSDL National Science Digital Library

The Instantaneous Frequency Stock Model estimates a stock's cyclical fluctuations over a three-day period to determine how fast the market is moving. The instantaneous frequency of an input signal is calculated by modeling an input function's most recent data points as a sin wave and performing a Fourier transform to derive the function's frequency. This model implements different velocity indicators on daily closing prices of a few common companies, and allows the user to compare values of the indicators at different times. The Instantaneous Frequency model was developed by Matt Mohorn using the Easy Java Simulations (EJS) modeling tool.  You can examine and modify the physical model for this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu. 

Mohorn, Matthew

2013-05-17

162

Coherent frequency combs and spectroscopy  

NASA Astrophysics Data System (ADS)

Optical frequency combs maintain precise phase coherence across the entire visible spectrum and they have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic approach that realizes simultaneously broad spectral coverage, high spectral resolution, many parallel detection channels, ultrahigh sensitivity, and real-time analysis [2]. These powerful capabilities have been demonstrated in a series of experiments where identification and quantification of many different molecular states or species are achieved in a massively parallel fashion [3].[4pt] [1] A. Marian et al., Science 306, 2063 (2004). [0pt] [2] M. J. Thorpe et al., Science 311, 1595 (2006). [0pt] [3] M. J. Thorpe & J. Ye, Appl. Phys. B 91, 397 (2008).

Ye, Jun

2010-03-01

163

Coherent frequency combs and spectroscopy  

NASA Astrophysics Data System (ADS)

Optical frequency combs possessing precise phase coherence across the entire visible spectrum have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic approach that embraces simultaneously broad spectral coverage, fine spectral resolution, numerous detection channels, ultrahigh sensitivity, and real-time analysis [2]. These powerful capabilities have been demonstrated in a series of experiments where identification and quantification of many different molecular states or species are achieved in a massively parallel fashion [3]. A range of interesting scientific applications will be discussed. [4pt] [1] A. Marian et al., Science 306, 2063 (2004). [0pt] [2] M. J. Thorpe et al., Science 311, 1595 (2006). [0pt] [3] M. J. Thorpe & J. Ye, Appl. Phys. B 91, 397 (2008).

Ye, Jun

2010-03-01

164

Frequency coded sensors incorporating tapers  

NASA Technical Reports Server (NTRS)

A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.

Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor)

2010-01-01

165

Foreign Voltages and Frequencies Guide.  

National Technical Information Service (NTIS)

Foreign countries around the world use different electrical standards for voltage and frequency than those of the United States. Electrical equipment designed for 60 Hertz may or may not operate properly in a 50 Hertz environment. Similarly, electrical eq...

L. M. Windingland, S. A. Steele, K. K. Heyen, H. T. Maase, F. H. Holcomb

1997-01-01

166

High Frequency Electronic Packaging Technology  

NASA Technical Reports Server (NTRS)

Commercial and government communication, radar, and information systems face the challenge of cost and mass reduction via the application of advanced packaging technology. A majority of both government and industry support has been focused on low frequency digital electronics.

Herman, M.; Lowry, L.; Lee, K.; Kolawa, E.; Tulintseff, A.; Shalkhauser, K.; Whitaker, J.; Piket-May, M.

1994-01-01

167

Extreme ultraviolet frequency comb metrology.  

PubMed

The remarkable precision of frequency-comb (FC) lasers is transferred to the extreme ultraviolet (XUV, wavelengths shorter than 100 nm), a frequency region previously not accessible to these devices. A frequency comb at XUV wavelengths near 51 nm is generated by amplification and coherent up-conversion of a pair of pulses originating from a near-infrared femtosecond FC laser. The phase coherence of the source in the XUV is demonstrated using helium atoms as a ruler and phase detector. Signals in the form of stable Ramsey-like fringes with high contrast are observed when the FC laser is scanned over P states of helium, from which the absolute transition frequency in the XUV can be extracted. This procedure yields a (4)He ionization energy at h×5?945?204?212(6)??MHz, improved by nearly an order of magnitude in accuracy, thus challenging QED calculations of this two-electron system. PMID:20867977

Kandula, Dominik Z; Gohle, Christoph; Pinkert, Tjeerd J; Ubachs, Wim; Eikema, Kjeld S E

2010-08-01

168

Very low frequency radio astronomy  

NASA Astrophysics Data System (ADS)

Very low frequency (VLF) radio astronomy covers the frequency range below about 30 MHz (or the wavelength range above 10 m). This is the last window of the electromagnetic spectrum never to have been observed with spatial resolution. This is a range over which the Earth's ionosphere transmits either poorly or not at all. In this paper, we describe some means to observe this frequency range and we review what can be expected from exploring the astrophysics of the universe at very low radio frequencies. We present the scientific case for a large array to be set up on the far side of the Moon. This would open an entirely new field of remote probing of astrophysical plasmas in the Universe.

Bougeret, J.-L.

169

AUTO ID FUTURE - FREQUENCY AGNOSTIC  

E-print Network

Identification of information is one key to the development of intelligent decision systems of the future. Frequency agnostic automatic identification is only one step in the physical world to make physical objects identify ...

DATTA, SHOUMEN

170

Low-Frequency Radioastronomy Basics  

NASA Astrophysics Data System (ADS)

With the many large instruments in construction or in project, the present epoch corresponds to a renewal of low-frequency radioastronomy. The field will attract new researchers and students not expert of the radioastronomy techniques. With this audience in mind, we present here a very brief introduction to radioastronomy basics, including propagation and polarization of low-frequency radio waves as well as instrumental aspects. Basic formulas are given. The references and internet links will allow the interested reader to go further.

Zarka, P.

2011-04-01

171

Sentence-frame frequency effects  

Microsoft Academic Search

This study investigates how sentences of subject-verb-object type are comprehended. We adopted a usage-based approach by first selecting a high frequency and a low frequency sentence frame (SF) determined by the same verb, each SF being characterised by its subject and object belonging to some semantic categories for a specific verb. It was observed in Experiment 1 that the time

Liu In-mao; Sue Iue-ruey; Chen Sau-chin; Chou Ting-hsi

2007-01-01

172

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

173

Prospects for atomic frequency standards  

NASA Technical Reports Server (NTRS)

The potentialities of different atomic frequency standards which are not yet into field operation, for most of them, but for which preliminary data, obtained in laboratory experiments, give confidence that they may improve greatly the present state of the art are described. The review will mainly cover the following devices: (1) cesium beam frequency standards with optical pumping and detection; (2) optically pumped rubidium cells; (3) magnesium beam; (4) cold hydrogen masers; and (5) traps with stored and cooled ions.

Audoin, C.

1984-01-01

174

Frequency tuning in animal locomotion.  

PubMed

In locomotion that involves repetitive motion of propulsive structures (arms, legs, fins, wings) there are resonant frequencies f(*) at which the energy consumption is a minimum. As animals need to change their speed, they can maintain this energy minimum by tuning their body resonances. We discuss the physical principles of frequency tuning, and how it relates to forces, damping, and oscillation amplitude. The resonant frequency of pendulum-type oscillators (e.g. swinging arms and legs) may be changed by varying the mass moment of inertia, or the vertical acceleration of the pendulum pivot. The frequency of elastic vibrations (e.g. the bell of a jellyfish) can be tuned with a non-linear modulus of elasticity: soft for low deflection amplitudes (low resonant frequency), and stiff for large displacements (high resonant frequency). Tuning of elastic oscillations can also be achieved by changing the effective length or cross-sectional area of the elastic members, or by allowing springs in parallel or in series to become active. We propose that swimming and flying animals generate oscillating propulsive forces from precisely placed shed vortices and that these tuned motions can only occur when vortex shedding and the simple harmonic motion of the elastic elements of the propulsive structures are in resonance. PMID:16403613

Ahlborn, Boye K; Blake, Robert W; Megill, William M

2006-01-01

175

Frequency Stability of Atomic Frequency Standards beyond Quantum Projection Noise  

E-print Network

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.

G. M. Saxena

2011-04-07

176

Variable frequency drive applications guide  

SciTech Connect

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.

Laloudakis, D.J.

1991-10-01

177

Active Faraday optical frequency standards  

E-print Network

We propose the mechanism of active Faraday optical clock, and experimentally demonstrate active Faraday optical frequency standards based on 852 nm 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 standards 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 996(26) Hz, which is 5.3 $\\times$ 10$^{3}$ times smaller than the natural linewidth of the cesium 852 nm transition line. The maximum emitted light power reaches 75 $\\upmu$W. The active Faraday optical frequency standards reported here have 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...

Zhuang, Wei

2014-01-01

178

Skewed Frequency Selective Surface Absorber  

NASA Astrophysics Data System (ADS)

In this paper, a skewed Frequency Selective Surface (FSS) absorber based on cross-dipole elements is presented. The proposed FSS design provides good frequency stability for oblique incidences. It provides better absorption rate for 5-GHz WLAN frequency band and allow other communication bands to pass through it. Also, the absorption in the stop-band reduces multipath fading of additional WLAN signals which occurred due to the placement of conducting/reflecting FSS. The FSS design consists of two layers; first layer consists of conducting cross-dipole and second layer consists of resistive cross-dipole placed in-front of the first layer. The periodicity of both elements is same. Asymmetric property is applied to FSS elements by taking a reference of central element. This technique leads to achieve a maximum stability in the stop-band. Simulated results demonstrated that the proposed FSS design has a stable frequency response for 5-GHz frequency band for both horizontal (TE) and vertical (TM) polarizations when the incident wave angle varied from 0 0 to 45 0.

Rafique, Umair; Khan, M. Arif; Afzal, M. Tausif; Malik, Fahad; Qasim, Shahzaib

2012-12-01

179

Active Faraday optical frequency standard.  

PubMed

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 S1/22F=4 to 6 P3/22F'=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 1.9×104 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

Zhuang, Wei; Chen, Jingbiao

2014-11-01

180

Spatial frequencies and emotional perception.  

PubMed

It has been suggested that, during evolution, specific mechanisms developed in order to optimize the detection of threats and opportunities even in perceptually degraded conditions. A naturalistic example of perceptual degradation can be found in blurry images, which contain the coarsest elements of a scene (low spatial frequencies) but lack the fine-grained details (high spatial frequencies). In the past decade, several studies have examined the relation between spatial frequencies and emotions, using a variety of methods, stimuli, and rationales. Here, we conduct a literature survey on the studies that have examined the relation between emotion and spatial frequencies. Some studies have suggested that the low spatial frequencies of emotional stimuli may be processed by a subcortical neural pathway, eventually eliciting emotional responses. However, the evidence provided by the reviewed studies does not support this possibility, for conceptual and methodological reasons (e.g., mistaking the processing of a fuzzy stimulus for subcortical processing). Here, the conceptual and methodological problems present in the reviewed studies are analyzed and discussed, along with suggestions for future research. PMID:23183741

De Cesarei, Andrea; Codispoti, Maurizio

2013-01-01

181

Frequency response of ice streams  

PubMed Central

Changes at the grounding line of ice streams have consequences for inland ice dynamics and hence sea level. Despite substantial evidence documenting upstream propagation of frontal change, the mechanisms by which these changes are transmitted inland are not well understood. In this vein, the frequency response of an idealized ice stream to periodic forcing in the downstream strain rate is examined for basally and laterally resisted ice streams using a one-dimensional, linearized membrane stress approximation. This reveals two distinct behavioural branches, which we find to correspond to different mechanisms of upstream velocity and thickness propagation, depending on the forcing frequency. At low frequencies (centennial to millennial periods), slope and thickness covary hundreds of kilometres inland, and the shallow-ice approximation is sufficient to explain upstream propagation, which occurs through changes in grounding-line flow and geometry. At high frequencies (decadal to sub-decadal periods), penetration distances are tens of kilometres; while velocity adjusts rapidly to such forcing, thickness varies little and upstream propagation occurs through the direct transmission of membrane stresses. Propagation properties vary significantly between 29 Antarctic ice streams considered. A square-wave function in frontal stress is explored by summing frequency solutions, simulating some aspects of the dynamical response to sudden ice-shelf change. PMID:23197934

Williams, C. Rosie; Hindmarsh, Richard C. A.; Arthern, Robert J.

2012-01-01

182

Variable frequency microwave heating apparatus  

DOEpatents

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).

Bible, Don W. (Clinton, TN); Lauf, Robert J. (Oak Ridge, TN); Johnson, Arvid C. (Lake in the Hills, IL); Thigpen, Larry T. (Angier, NC)

1999-01-01

183

Frequency-chirped subwavelength nanoantennas.  

PubMed

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

Yaacobi, Ami; Watts, Michael R

2012-12-01

184

Swept Frequency Laser Metrology System  

NASA Technical Reports Server (NTRS)

A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

Zhao, Feng (Inventor)

2010-01-01

185

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2013-10-01

186

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2013-10-01

187

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2011-10-01

188

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2012-10-01

189

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2010-10-01

190

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

191

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

192

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...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...

2010-10-01

193

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

194

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

195

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...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...

2010-10-01

196

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2010-10-01

197

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2011-10-01

198

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

199

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2010-10-01

200

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

201

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2012-10-01

202

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2013-10-01

203

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2011-10-01

204

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2012-10-01

205

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency coordination. 74.638 Section 74.638 Telecommunication...Auxiliary Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for...

2011-10-01

206

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency coordination. 74.638 Section 74.638 Telecommunication...Auxiliary Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for...

2010-10-01

207

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency coordination. 74.638 Section 74.638 Telecommunication...Auxiliary Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for...

2012-10-01

208

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency coordination. 74.638 Section 74.638 Telecommunication...Auxiliary Stations § 74.638 Frequency coordination. (a) Coordination of all frequency assignments for...

2013-10-01

209

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2012-10-01

210

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2011-10-01

211

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2010-10-01

212

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Frequency stability. 5.101 Section...Requirements § 5.101 Frequency stability. Experimental...remain within the authorized frequency band under normal operating...degrees Celsius with an input voltage variation of 85% to...

2013-10-01

213

Bichromatically pumped microresonator frequency combs  

NASA Astrophysics Data System (ADS)

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.

Hansson, T.; Wabnitz, S.

2014-07-01

214

OPTIMUM FREQUENCY OF CALIBRATION MONITORING  

EPA Science Inventory

The paper develops an algorithm by which to compute the optimal frequency of calibration monitoring to minimize the total cost of analyzing a set of samples and the required calibration standards. Optimum calibration monitoring is needed because of the high cost and calibration d...

215

Variable frequency microwave moisture leveling  

SciTech Connect

A variable frequency microwave system was examined to replace an existing carousel resistance heating line as the method for drying of mouth swabs for the pharmaceutical industry. A pharmaceutical manufacturer located in Northern Illinois had a resistive heating system that was not drying product satisfactorily, thus requiring additional ambient drying time even after a 30-minute drying cycle. Since the swabs are used for the healthcare industry, the amount of moisture present after drying was critical to avoid the formation of mold on the product that could have lead to dissatisfied customers. Variable frequency microwave moisture leveling allowed better product quality while turning the manufacturing operation into just in time delivery. During pilot scale testing, a 300 times cycle improvement was realized for variable frequency microwave compared to the conventional carousel resistive drying unit (24 hours to 5 minutes). The projected total cost of the variable frequency microwave system is $1 million, with 25% of the cost in the microwave unit and 70% of the cost in a new autobagging system. The author projected a $0.58 million saving per year in reduced operational costs with productivity increases. Although the project would have had a 1.8 year payback time, it was not implemented due to the capital expense and risk of an unknown technology.

Hamann, M.R.

1999-07-01

216

Frequency Effects, Noticing, and Creativity  

ERIC Educational Resources Information Center

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…

Tarone, Elaine

2002-01-01

217

High-frequency welding trials.  

PubMed

The high-frequency weldability of a new family of polyolefin films is compared with that of conventional films made of other polymers. A comparison of the optimum weld parameters of all the films and the results of performance testing of all the pouches produced are reported. PMID:15326740

Kelch, R

2000-09-01

218

High frequency carbon nanotube devices  

NASA Astrophysics Data System (ADS)

We investigate high frequency electrical and mechanical performances of carbon nanotube based devices. Using configurations with multiple single-wall nanotubes in parallel, we show that HF nanotube transistors with intrinsic cut-off frequencies as high as 30 GHz can be obtained on rigid substrates. Adapting our process to plastic substrates, we also obtained highly flexible HF transistors showing constant transconductances up to at least 6 GHz, as-measured cut-off frequencies as high as 1 GHz (5-8 GHz after de-embedding) and stable DC performances upon bending. We probed electromechanical properties of individual suspended carbon multiwall nanotubes by using a modified AFM. DC deflection measurements on different devices are in agreement with a continuum model prediction and consistent with a Young's modulus of 0.4 TPa. Preliminary HF measurements on a doubly clamped device showed a resonant frequency of 200MHz consistent with a Young's modulus of 0.43 TPa. This implies that built-in mechanical stress in the case of MWNTs is negligeable.

Goffman, M. F.; Chimot, N.; Mile, E.; Monteverde, M. C.; Bourgoin, J.-P.; Derycke, V.

2008-08-01

219

Extension of the frequency limit of an electronic-counter frequency meter  

Microsoft Academic Search

Description of the structural scheme of an automatic frequency carrier designed to broaden the frequency range of an electronic-counter frequency meter. The structure and special features of certain units of a device which employs automatic phase locking to stabilize the intermediate frequency during automatic frequency measurement are described, and the construction of a device which broadens the frequency range of

V. V. Imshenetskii; M. S. Martyniv

1974-01-01

220

Low frequency and high-frequency cochlear nonlinearity in humans  

PubMed Central

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

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

2008-01-01

221

On E-Pólya frequency functions  

NASA Astrophysics Data System (ADS)

Let E be a subset of . We say that is an E-Pólya frequency function if the kernel f(u-x) is totally positive on and f is integrable on . In this paper, we show that under some conditions on E, an E-Pólya frequency function is a Pólya frequency function. This strengthens Schoenberg's result on Pólya frequency functions.

Ganzburg, Michael I.

2008-10-01

222

HELIOS dual swept frequency radiometer  

NASA Technical Reports Server (NTRS)

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.

White, J. R.

1975-01-01

223

Radio frequency coaxial feedthrough device  

DOEpatents

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.

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

224

Polarimetric time-frequency ESPRIT  

Microsoft Academic Search

An ESPRIT (estimation of signal parameters via rotational invariance techniques) like algorithm for estimating the direction-of-arrival (DOA) of nonstationary polarized signals is developed. This algorithm relies on the recently introduced spatial polarimetric time-frequency distributions (SPTFD) as a platform to provide low computational, high resolution direction finding. The use of dual polarizations empowers the SPTFD with additional degrees-of-freedom, and improves the

Baha A. Obeidat; Yimin Zhang; Moeness G. Amin

2003-01-01

225

Frequency chirped differential absorption LIDAR  

NASA Astrophysics Data System (ADS)

We present a novel concept design of a differential absorption LIDAR for open path trace gas sensing in the atmosphere. To perform a range-resolved gas sensing we propose to arrange a set of retroreflectors in the laser beam path to measure a differential absorption in adjacent sections. In validation experiments we used a pulsed DFB quantum cascade laser fabricated by Alpes Lasers. The laser was excited with 200-ns current pulses with a repetition rate of 10 kHz. The frequency chirp rate was found to increase from 7.7 to 1.0 cm -1/?s as peak injection current was increased from 7.1, to 7.8 A. We utilized the frequency chirp at laser substrate temperature of 24.0 °C to scan the 967.0 - 968.5 cm -1 spectral interval containing the absorption lines of CO II and NH3. We detected ~ 0.25 ppmv of NH 3 in nitrogen at atmospheric pressure using a double-pass gas cell with an effective absorption path of 2.4 m. Digital filtering of the spectra was shown to be effective in eliminating a high-frequency noise. To demonstrate range-resolved capabilities of the sensor we used two retroreflectors inserted into the laser beam. A differential absorption of CO II at 967.7 cm -1 was measured with the gas cell placed in one of the sections. Our experiments indicate that the frequency chirped LIDAR can be used for open path spectroscopy of NH 3 over the ranges up to ~ 1 km with a spatial resolution of ~ 30 m and detection limit of ~ 20 ppbv per a 30-m section.

Lytkine, A.; Jäger, W.; Tulip, J.

2006-09-01

226

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

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.

Padamsee, Hasan S.

2014-10-01

227

Low Frequency Radio Experiment (LORE)  

NASA Astrophysics Data System (ADS)

High temporal and frequency resolution observations of solar generated disturbances below 15 MHz in the near-Sun region and at Sun-Earth distances in conjunction with optical and high energy observations of Sun are essential to understand the structure and evolution of eruptions, such as, flares, coronal mass ejections (CMEs), and their associated solar wind disturbances at heights above the photosphere and their consequences in the interplanetary medium. This talk presents a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii below 30 MHz. The LORE, although not part of Aditya-L1 mission, can be complimentary to planned Aditya-L1 coronagraph and its other on-board payloads as well as synergistic to ground based observations, which are routinely carried out by Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and it is particularly suitable for providing data on the detailed time and frequency structure of fast drifting Type-III and slow drifting Type-II radio bursts with unprecedented time and frequency resolution as well as goniopolarimetry, made possible with better designed antennas and state-of-art electronics, employing FPGAs and an intelligent data management system. This would enable wide ranging studies such as studies of nonlinear plasma processes, CME in-situ radio emission, CME driven phenomena, interplanetary CME driven shocks, ICMEs driven by decelerating IP shocks and space weather effects of Solar Wind interaction regions. The talk will highlight the science objectives as well as the proposed technical design features.

Manoharan, Periasamy K.; Joshi, Bhal Chandra; Naidu, Arun Kumar

228

Frequency estimation by linear prediction  

Microsoft Academic Search

The application of linear prediction to frequency estimation for sinusoidal signals in noise is investigated. It is shown that improved performance is obtained by processing a complex-valued version of the real-valued input signal, with the corresponsing sampling rate reduced by one-half. The case of a single sinusoid in white noise is studied in detail, including the eigenvalues of the covariance

Leland B. Jackson; Donald W. Tufts; Frank K. Soong; Rahul M. Rao

1978-01-01

229

Phase and Frequency Noise Metrology  

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

230

Automatic frequency control for FM transmitter  

NASA Technical Reports Server (NTRS)

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.

Honnell, M. A. (inventor)

1974-01-01

231

Mid-IR frequency measurement using an optical frequency comb and a long-distance remote frequency reference  

E-print Network

We have built a frequency chain which enables to measure the absolute frequency of a laser emitting in the 28-31 THz frequency range and stabilized onto a molecular absorption line. The set-up uses an optical frequency comb and an ultrastable 1.55 $\\mu$m frequency reference signal, transferred from LNE-SYRTE to LPL through an optical link. We are now progressing towards the stabilization of the mid-IR laser via the frequency comb and the extension of this technique to quantum cascade lasers. Such a development is very challenging for ultrahigh resolution molecular spectroscopy and fundamental tests of physics with molecules.

Bruno Chanteau; Olivier Lopez; Wei Zhang; Giorgio Santarelli; Yann Le Coq; Frédéric Auguste; Benoît Darquié; Christian Chardonnet; Anne Amy-Klein

2012-10-13

232

Low Radio Frequency Picosatellite Missions  

NASA Astrophysics Data System (ADS)

The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Jones, Dayton L.

2014-06-01

233

Frequency dependent polarization in blazars.  

NASA Astrophysics Data System (ADS)

It is argued that the observed properties of the intrinsically frequency-dependent polarization (FDP) in blazars suggest a one - rather than a multi - component source model. Assuming a synchrotron origin of the emitted radiation, a well ordered magnetic field and a sharp break or cutoff in the electron distribution are both obligatory in such models; non-uniform pitch angle distribution or synchrotron losses enhance the resulting FDP. It is emphasized that the existence of such conditions in blazars finds observational support. Furthermore, a specific model is presented in order to illustrate the salient features of one-component models.

Björnsson, C.-I.

234

Radio Frequency (RF) strain monitor  

NASA Technical Reports Server (NTRS)

This invention relates to an apparatus for measuring strain in a structure. In particular, the invention detects strain in parts per million to over ten percent along an entire length (or other dimension) of a structure measuring a few millimeters to several kilometers. By using a propagation path bonded to the structure, the invention is not limited by the signal attenuation characteristics of the structure and thus frequencies in the megahertz to gigahertz range may be used to detect strain in part per million to over ten percent with high precision.

Heyman, Joseph S. (inventor); Rogowski, Robert S. (inventor); Holben, Milford S., Jr. (inventor)

1988-01-01

235

Intelligent Radio Frequency (RF) Monitoring  

E-print Network

? 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... day Weeks a Year 52 week Total Hours 8760 hr/hr *Max Flow Thru is Calculated Using a 7/64" Orifice @ 200 psig for Each Application Listed Above & Blow 1 Hour 1 Day 1 Week 1 Month 3 Months 1 Year Drip 97 2,328 16,296 69,840 209,520 849,720 Tracer...

Kimbrough, B.

236

Radio-Frequency Strain Monitor  

NASA Technical Reports Server (NTRS)

Radio-frequency (RF) strain monitor developed to measure lengths of objects. RF waveguide or cable bonded to structure monitored. Propagation of RF signal along waveguide results in phase shift proportional to length of path traveled. Impedance mismatches placed in RF cable at nodes of structure. Records mismatches and detects overall length of line and lengths of intervals between nodes. Used to detect changes in elements of large structure with single cable. Monitor has potential for many applications, including monitoring stability of such large structures as aircraft, bridges, and buildings in Earthquake zones.

Heyman, Joseph S.; Rogowski, Robert S.; Holben, Milford S., Jr.

1988-01-01

237

Multi-frequency imaging in VLBI  

E-print Network

The new technique, multi-frequency imaging (MFI) is developed. In VLBI, Multi-Frequency Imaging (MFI) consists of multi-frequency synthesis (MFS) and multi-frequency analysis (MFA) of the VLBI data obtained from observations on various frequencies. A set of linear deconvolution MFI algorithms is described. The algorithms make it possible to obtain high quality images interpolated on any given frequency inside any given bandwidth, and to derive reliable estimates of spectral indexes for radio sources with continuum spectrum. Thus MFI approach makes it is possible not only to improve the quality and fidelity of the images and also essentially to derive the morphology of the observed radio sources.

S. Likhachev

2004-12-17

238

Low frequency AC waveform generator  

DOEpatents

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.

Bilharz, Oscar W. (Scotia, NY)

1986-01-01

239

Low frequency ac waveform generator  

DOEpatents

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.

Bilharz, O.W.

1983-11-22

240

Frequency Responses Of Hot-Wire Anemometers  

NASA Technical Reports Server (NTRS)

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.

Watmuff, Jonathan H.

1992-01-01

241

Frequency synthesis using MEMS piezoelectric resonators  

E-print Network

(cont.) Ultimately, this thesis presents two approaches to frequency synthesizer design. The first uses frequency windows of approximately 200 MHz. The 800 MHz to 1 GHz matching network is presented in detail along with ...

Calhoun, Paul Jacob, 1979-

2004-01-01

242

Diagnosing transformer faults using frequency response analysis  

Microsoft Academic Search

This technique measures the impedance of transformer windings over a wide frequency range and compares the results with reference data. The author used a network analyzer to sweep the frequency range, make the measurements, and analyze the results.

S. A. Ryder

2003-01-01

243

Radio frequency power load and associated method  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

244

Binaural beats and frequency-coding  

Microsoft Academic Search

Binaural beats were studied before and during a situation of temporary threshold shift, and no frequency shift could be found. In contrast, subjective binaural frequency comparison revealed a distinct shift. These findings demonstrate the two known modes of perception.

W. Fritze; W. Köhler

1986-01-01

245

47 CFR 101.505 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...101.505 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.505 Frequencies. Frequencies, and...

2010-10-01

246

Substructure coupling in the frequency domain  

NASA Technical Reports Server (NTRS)

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.

1985-01-01

247

47 CFR 80.1077 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Global Maritime Distress and Safety System (GMDSS) General Provisions § 80.1077 Frequencies. The following table describes the frequencies used in the Global...

2012-10-01

248

47 CFR 80.1077 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Global Maritime Distress and Safety System (GMDSS) General Provisions § 80.1077 Frequencies. The following table describes the frequencies used in the Global...

2013-10-01

249

47 CFR 80.1077 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Global Maritime Distress and Safety System (GMDSS) General Provisions § 80.1077 Frequencies. The following table describes the frequencies used in the Global...

2011-10-01

250

47 CFR 80.1077 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Global Maritime Distress and Safety System (GMDSS) General Provisions § 80.1077 Frequencies. The following table describes the frequencies used in the Global...

2010-10-01

251

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

SciTech Connect

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{sub 0}/2Q, where f{sub 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{sub 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.

Kobayashi, Kei [Office of Society-Academia Collaboration for Innovation, Kyoto University, Katsura, Nishikyo, Kyoto 615-8520 (Japan); Yamada, Hirofumi; Matsushige, Kazumi [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan)

2011-03-15

252

Latency represents sound frequency in mouse IC  

Microsoft Academic Search

Frequency is one of the fundamental parameters of sound. The frequency of an acoustic stimulus can be represented by a neural\\u000a response such as spike rate, and\\/or first spike latency (FSL) of a given neuron. The spike rates\\/frequency function of most\\u000a neurons changes with different acoustic amplitudes, whereas FSL\\/frequency function is highly stable. This implies that FSL\\u000a might represent the

Qiang Qiu; Jie Tang; ZuLin Yu; Juan Zhang; YingJie Zhou; ZhongJu Xiao; JunXian Shen

2007-01-01

253

Predicting Fire Frequency with Chemistry and Climate  

E-print Network

Predicting Fire Frequency with Chemistry and Climate Richard P. Guyette,1 * Michael C. Stambaugh,1 frequency was developed from theories and data in physical chemistry, ecosystem ecology, and climatology. We refer to this equation as the Physical Chemistry Fire Frequency Model (PC2FM). The equation was cal

254

Lecture 2: Fourier transforms and frequency response  

E-print Network

Lecture 2: Fourier transforms and frequency response Course at a glance Discrete-time signals and systems Fourier-domain representation DFT/FFT System structures Filter structures Filter design Filter z-transform Sampling and reconstruction System analysis System Fourier transforms and frequency response Frequency

Fan, Xingzhe

255

Measurements of Low Frequency Electromagnetic Instabilities  

Microsoft Academic Search

Very low frequency, below 10 kHz, weak, electromagnetic instabilities are difficult to measure in plasmas because the typical diagnostic, a magnetic sense coil, has a frequency dependent sensitivity. The sensitivity of a magnetic sense coil can be increased by increasing the number of turns on the coil, but at the expense of size and high frequency response. As an alternative

Brendan McGeehan; Anna Zaniewski; Costel Biloiu; Earl Scime

2003-01-01

256

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2010-10-01

257

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

258

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2012-10-01

259

High Frequency Microphone Measurements for Transition Detection  

E-print Network

! High Frequency Microphone Measurements for Transition Detection on Airfoils Mads Døssing Risø Døssing Risø­R­1645(EN) Title: High Frequency Microphone Measurements for Transition Detection on Airfoils of pressure fluctuations has been obtained using high frequency microphones distributed over the surface

260

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2012-10-01

261

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2011-10-01

262

47 CFR 74.402 - Frequency assignment.  

Code of Federal Regulations, 2013 CFR

...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,...

2013-10-01

263

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

264

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

265

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2013-10-01

266

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2011-10-01

267

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 758-775 and 788-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2013-10-01

268

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2010-10-01

269

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Frequency capability. 95.655 Section 95.655 Telecommunication...Requirements § 95.655 Frequency capability. (a) No transmitter will be certificated...service if it is equipped with a frequency capability not listed in § 95.625, and...

2010-10-01

270

STABILIZED FIBER OPTIC FREQUENCY DISTRIBUTION SYSTEM  

Microsoft Academic Search

A technique for stabilizing reference frequencies transmitted over flber optic cable in a frequency distribution system is discussed. The distribution system utilizes fiber optic cable as the transmission medium to dietribute precise reference signals from a frequency standard to remote users. The stability goal of the distribution system is to transmit a 100 MH5 signal over a 22 km fiber

Lori E. Primas; George F. Lutes; Richard L. Sydnor

271

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2011-10-01

272

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2013-10-01

273

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2010-10-01

274

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2012-10-01

275

Neural analysis of sound frequency in insects  

E-print Network

Neural analysis of sound frequency in insects Gerald S. Pollack* and Kazuo Imaizumi Summary Insects appropriately. One parameter of sound that carries information is its frequency content. Insects analyze sound and prey. We review how frequency is analyzed in the insect nervous system, focusing on two taxa in which

Pollack, Gerald

276

High frequency-heated air turbojet  

NASA Technical Reports Server (NTRS)

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.

Miron, J. H. D.

1986-01-01

277

On the Probability Distribution of Typological Frequencies  

Microsoft Academic Search

Some language types are more frequent among the world's languages than others, and the eld of linguistic typology attempts to elucidate the reasons for such dierences in type frequency. However, there is no consensus in that eld about the stochastic processes that shape these frequencies, and there is thus likewise no agreement about the expected probability distribution of typological frequencies.

Michael Cysouw; Max Planck

2009-01-01

278

Frequency Characterization of Blood Glucose Dynamics  

Microsoft Academic Search

Examples of the frequency range of blood glucose dynamics of normal subjects and subjects with diabetes are reported here, based on data from the literature. The frequency band edge was determined from suitable, frequently sampled blood glucose recordings using two methods: frequency domain estimation and signal reconstruction. The respective maximum acceptable sampling intervals, or Nyquist sampling periods (NSP), required to

David A. Gough; Kenneth Kreutz-Delgado; Troy M. Bremer

2003-01-01

279

Derivational Morphology and Base Morpheme Frequency  

ERIC Educational Resources Information Center

Morpheme frequency effects for derived words (e.g. an influence of the frequency of the base "dark" on responses to "darkness") have been interpreted as evidence of morphemic representation. However, it has been suggested that most derived words would not show these effects if family size (a type frequency count claimed to reflect semantic…

Ford, M. A.; Davis, M. H.; Marslen-Wilson, W. D.

2010-01-01

280

Heterodyne laser instantaneous frequency measurement system  

DOEpatents

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.

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

1990-01-01

281

Frequency domain optical parametric amplification  

PubMed Central

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

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

2014-01-01

282

A radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feedthrough is 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 reflection 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 the voltage and power handling capabilities of a feedthrough.

Owens, T.L.

1987-12-07

283

Frequency stabilization of algaas lasers  

SciTech Connect

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.

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

1982-01-01

284

Coping with Radio Frequency Interference  

NASA Astrophysics Data System (ADS)

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

Lewis, B. M.

2009-01-01

285

Frequency Comb Generation in Superconducting Resonators  

NASA Astrophysics Data System (ADS)

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 1 08. The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves.

Erickson, R. P.; Vissers, M. R.; Sandberg, M.; Jefferts, S. R.; Pappas, D. P.

2014-10-01

286

FREQUENCY CONTROL OF CELL CYCLE OSCILLATORS  

PubMed Central

SUMMARY The cell cycle oscillator, based on a core negative feedback loop and modified extensively by positive feedback, cycles with a frequency that is regulated by environmental and developmental programs to encompass a wide range of cell cycle times. We discuss how positive feedback allows frequency tuning, how size and morphogenetic checkpoints regulate oscillator frequency, and how extrinsic oscillators such as the circadian clock gate cell cycle frequency. The master cell cycle regulatory oscillator in turn controls the frequency of peripheral oscillators controlling essential events. A recently proposed phase-locking model accounts for this coupling. PMID:20851595

Oikonomou, Catherine; Cross, Frederick R.

2010-01-01

287

Time domain characterization of oscillating sensors: Application of frequency counting to resonance frequency determination  

Microsoft Academic Search

A frequency counting technique is described for determining the resonance frequency of a transiently excited sensor; the technique is applicable to any sensor platform where the characteristic resonance frequency is the parameter of interest. The sensor is interrogated by a pulse-like excitation signal, and the resonance frequency of the sensor subsequently determined by counting the number of oscillations per time

Kefeng Zeng; Keat G. Ong; Casey Mungle; Craig A. Grimes

2002-01-01

288

Frequency / Duty Cycle Control of LCC Resonant Converter Supplying High Voltage Very Low Frequency Test Systems  

E-print Network

Frequency / Duty Cycle Control of LCC Resonant Converter Supplying High Voltage Very Low Frequency», «Resonant converter», «Soft switching» Abstract Very low frequency (VLF) high-voltage (HV) sinusoidal test waves. Due to the wide ranges of output voltage and output load, both the switching frequency

Paderborn, Universität

289

Dual-frequency Brillouin fiber laser for optical generation of tunable low-noise radio frequency/microwave frequency.  

PubMed

We demonstrate a new approach, i.e., a cw dual-frequency Brillouin fiber laser pumped by two independent single-frequency Er-doped fiber lasers, for the generation of tunable low-noise rf/microwave optical signals. Its inherent features of both linewidth narrowing effect in a Brillouin fiber cavity and common mode noise cancellation between two laser modes sharing a common cavity allow us to achieve high frequency stability without using a supercavity. Beat frequency of the dual-frequency Brillouin fiber laser can be tuned from tens of megahertz up to 100 GHz by thermally tuning the wavelengths of the two pump lasers with tuning sensitivity of approximately 1.4 GHz/ degrees C. Allan variance measurements show the beat signals have the hertz-level frequency stability. PMID:18157243

Geng, Jihong; Staines, Sean; Jiang, Shibin

2008-01-01

290

Planck high-frequency instrument  

NASA Astrophysics Data System (ADS)

The High Frequency Instrument of the Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB). Its main goal is to map the CMB with a sensitivity of ?T/T=2.10-6 and an angular resolution of 5 arcmin in order to constrain cosmological parameters. Planck is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The architecture of the satellite is driven by the thermal requirements resulting from the search for low photon noise. Especially, the passively cooled telescope should be at less than 50K, while a cascade of cryo-coolers will ensure the cooling of the HFI bolometers down to 0.1K. This last temperature will be produced by a gravity insensitive 3He/4He dilution cooler. This will be achieved at the L2 Lagrangian point of the Sun-Earth system. The whole sky will be observed two times in the 14 months mission with a scanning strategy based on a 1RPM rotation of the satellite. In addition to the cosmological parameters that can be derived from the CMB maps, Planck will deliver nine high sensitivity submillimeter maps of the whole sky that will constitute unique data available to the whole astronomical community.

Lamarre, Jean-Michel; Puget, Jean L.; Piat, M.; Ade, Peter A. R.; Lange, Andrew E.; Benoit, Alain; De Bernardis, Pierluigi; Bouchet, F. R.; Bock, James J.; Desert, F. X.; Emery, Roger J.; Giard, Martin; Maffei, Bruno; Murphy, J. A.; Torre, Jean-Pierre; Bhatia, Ravinder; Sudiwala, Rashmi V.; Yourchenko, V.

2003-03-01

291

Nonlinear cloaking at microwave frequencies  

NASA Astrophysics Data System (ADS)

The ideas of employing the unique properties of metamaterials for cloaking and invisibility applications has been recently suggested and investigated by several groups, because they may find numerous applications in physics and technology. While many of the recent designs of the cloaking structures are based on the transformation optics and exact formulas, the original concept suggested by Tretyakov employed the periodical set of parallel-plate waveguides with the height smoothly varying from H to h in order to reduce drastically the total scattering cross-section of a given object and to obtain broadband cloaking effect. Our paper is devoted to improvement of this design to make tunability and nonlinear effect. The Tretyakov's design was scaled for Ku-band frequencies and the cloak was placed into rectangular waveguide. The broad transmission band ("invisibility region") was obtained. The tunability of transmission band was realized by addition the capacitors into the cloak, between metallic plates. The cloaking system was simulated numerically by CST Microwave Studio. The possibility of invisibility switching on/off was shown by changing of capacity of varactor diodes from 0.4 to 3.4 pF by incident power. The nonlinear cloak behavior was shown at microwaves.

Gurvitz, E. A.; Sedykh, E. A.; Khodzitskiy, M. K.

292

High-frequency nanophotonic devices  

NASA Astrophysics Data System (ADS)

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.

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

2007-02-01

293

Integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.

Abbott, Steven R. (Concord, CA)

1989-01-01

294

High-Frequency Surface-Wave Radar Real Time Frequency Selecting Based on Frequency Randomly Hopping Signal  

Microsoft Academic Search

Serious radio interferences are distributed in the operating frequency band of High-frequency surface-wave radar (HFSWR) which makes it difficult to find silent bandwidth especially at night to work, the performance of HFSWR is decreased greatly. Frequency randomly hopping signal which breakthrough the restriction of continual spectrum has become an effective anti-jamming method. Based on the study of HF spectrum forecasting

Xu Liu; Changjun Yu

2008-01-01

295

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

SciTech Connect

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.

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

2010-10-04

296

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

SciTech Connect

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee [Division of Physical Metrology, Korea Research Institute of Standards and Science, 209 Gajeongno, Yuseong-gu, Daejeon 305-340 (Korea, Republic of); Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Moon, S. Y. [LG Electronics Advanced Research Institute, 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724 (Korea, Republic of)

2011-04-15

297

Single-frequency approximation of the coupling ray theory  

E-print Network

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

Cerveny, Vlastislav

298

Cavity-enhanced direct frequency comb spectroscopy  

E-print Network

Cavity-enhanced direct frequency comb spectroscopy combines broad spectral bandwidth, high spectral resolution, precise frequency calibration, and ultrahigh detection sensitivity, all in one experimental platform based on an optical frequency comb interacting with a high-finesse optical cavity. Precise control of the optical frequency comb allows highly efficient, coherent coupling of individual comb components with corresponding resonant modes of the high-finesse cavity. The long cavity lifetime dramatically enhances the effective interaction between the light field and intracavity matter, increasing the sensitivity for measurement of optical losses by a factor that is on the order of the cavity finesse. The use of low-dispersion mirrors permits almost the entire spectral bandwidth of the frequency comb to be employed for detection, covering a range of ~10% of the actual optical frequency. The light transmitted from the cavity is spectrally resolved to provide a multitude of detection channels with spectral ...

Thorpe, Michael J

2008-01-01

299

Frequency Control Performance Measurement and Requirements  

SciTech Connect

Frequency control is an essential requirement of reliable electric power system operations. Determination of frequency control depends on frequency measurement and the practices based on these measurements that dictate acceptable frequency management. This report chronicles the evolution of these measurements and practices. As technology progresses from analog to digital for calculation, communication, and control, the technical basis for frequency control measurement and practices to determine acceptable performance continues to improve. Before the introduction of digital computing, practices were determined largely by prior experience. In anticipation of mandatory reliability rules, practices evolved from a focus primarily on commercial and equity issues to an increased focus on reliability. This evolution is expected to continue and place increased requirements for more precise measurements and a stronger scientific basis for future frequency management practices in support of reliability.

Illian, Howard F.

2010-12-20

300

Precision frequency measurements with entangled states  

E-print Network

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.

C. F. Roos

2005-08-19

301

Precision frequency measurements with interferometric weak values  

E-print Network

We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 kHz per root Hz with only 2 mW of continuous wave, single mode input power. We describe the measurement of a weak value and show how even higher frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.

David J. Starling; P. Ben Dixon; Andrew N. Jordan; John C. Howell

2011-01-07

302

An accurate voltage-to-frequency converter  

Microsoft Academic Search

A current- or voltage-to-frequency converter is described for converting analogue signals into a pulse form in which the pulse repetition frequency is proportional to the instantaneous signal amplitude. The conversion is linear to within 0·01% over the frequency range 0-10 kHz (or 0-1 kHz), and to within 0·1% up to 50 kHz. Thermal stability is comparable.The circuit action is based

P J Unsworth

1969-01-01

303

Stabilized fiber-optic frequency distribution system  

Microsoft Academic Search

A technique for stabilizing reference frequencies transmitted over fiber-optic cable in a frequency distribution system is discussed. The distribution system utilizes fiber-optic cable as the transmission medium to distribute precise reference signals from a frequency standard to remote users. The stability goal of the distribution system is to transmit a 100-MHz signal over a 22-km fiber-optic cable and maintain a

L. E. Primas; G. F. Lutes; R. L. Sydnor

1989-01-01

304

Frequency modulation drive for a piezoelectric motor  

SciTech Connect

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.

Mittas, Anthony (Albuquerque, NM)

2001-01-01

305

Optical multimode frequency-domain reflectometer.  

PubMed

A multimode laser can instantaneously generate a carrier frequency of significantly wide band. The proposed systems, composed of a free-running multimode laser diode, an optical spectrometer, and a computing system for fast Fourier transformation, can easily provide the potential for ultrahigh resolution of the order of 10 microm without scanning frequencies as in frequency-domain reflectometers of either the continuously or the stepwise-swept variety. PMID:19844381

Tan-No, N; Ichimura, T; Funaba, T; Anndo, N; Odagiri, Y

1994-04-15

306

High Frequency AC Power Distribution Platforms  

Microsoft Academic Search

High Frequency AC (HFAC) power distribution system concerns the delivery of power at multi-kHz frequency via electric cables.\\u000a Early work on HFAC has demonstrated the many potential benefits of HFAC systems in terms of flexibility to meet loads at different\\u000a voltage levels, ease of electrical isolation using compact high frequency transformers, and the prospect of significant savings\\u000a in component count

Patrick Chi-Kwong Luk; Andy Seng Yim Ng

307

An ultra-miniature rubidium frequency standard  

Microsoft Academic Search

An ultra-miniature, general-purpose rubidium gas cell frequency standard with a two-cell scheme has been successfully developed, with the aim of developing one of the smallest atomic frequency standards in the world. The target volume of the new rubidium frequency standard is less than 100 cm3. It is assumed that the shape of oscillator enables to mount on a printed circuit

Y. Koyama; H. Matsuura; K. Atsumi; K. Nakamuta; M. Sakai; I. Maruyama

2000-01-01

308

Instantaneous frequency based newborn EEG seizure characterisation  

NASA Astrophysics Data System (ADS)

The electroencephalogram (EEG), used to noninvasively monitor brain activity, remains the most reliable tool in the diagnosis of neonatal seizures. Due to their nonstationary and multi-component nature, newborn EEG seizures are better represented in the joint time-frequency domain than in either the time domain or the frequency domain. Characterising newborn EEG seizure nonstationarities helps to better understand their time-varying nature and, therefore, allow developing efficient signal processing methods for both modelling and seizure detection and classification. In this article, we used the instantaneous frequency (IF) extracted from a time-frequency distribution to characterise newborn EEG seizures. We fitted four frequency modulated (FM) models to the extracted IFs, namely a linear FM, a piecewise-linear FM, a sinusoidal FM, and a hyperbolic FM. Using a database of 30-s EEG seizure epochs acquired from 35 newborns, we were able to show that, depending on EEG channel, the sinusoidal and piecewise-linear FM models best fitted 80-98% of seizure epochs. To further characterise the EEG seizures, we calculated the mean frequency and frequency span of the extracted IFs. We showed that in the majority of the cases (>95%), the mean frequency resides in the 0.6-3 Hz band with a frequency span of 0.2-1 Hz. In terms of the frequency of occurrence of the four seizure models, the statistical analysis showed that there is no significant difference( p = 0.332) between the two hemispheres. The results also indicate that there is no significant differences between the two hemispheres in terms of the mean frequency ( p = 0.186) and the frequency span ( p = 0.302).

Mesbah, Mostefa; O'Toole, John M.; Colditz, Paul B.; Boashash, Boualem

2012-12-01

309

Microwave Synthesisers for Atomic Frequency Standards  

Microsoft Academic Search

Following our earlier work on a new approach to synthesising the Cs hyperfme frequency of 9.192 GHz, we describe developments on its further refinements. The salient feature of our design is that it is based mainly on frequency division and requires no narrow band filter stages. Tests indicate an internal fractional frequency stability of 1.5 × 10-15 at 10 s

A. Sen Gupta; J. F. Garcia Nava; C. Nelson; D. A. Howe; F. L. Walls

2002-01-01

310

Apparatus for measuring high frequency currents  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

311

47 CFR 80.381 - Frequencies for operational fixed stations.  

Code of Federal Regulations, 2010 CFR

...false Frequencies for operational fixed stations. 80...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES...SERVICES Frequencies Operational Fixed Stations § 80.381 Frequencies for operational fixed stations....

2010-10-01

312

47 CFR 95.625 - CB transmitter channel frequencies.  

Code of Federal Regulations, 2010 CFR

... false CB transmitter channel frequencies. 95.625...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...625 CB transmitter channel frequencies. (a) The CB transmitter channel frequencies are:...

2010-10-01

313

47 CFR 95.621 - GMRS transmitter channel frequencies.  

Code of Federal Regulations, 2010 CFR

...false GMRS transmitter channel frequencies. 95.621...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...621 GMRS transmitter channel frequencies. (a) The GMRS transmitter channel frequencies...

2010-10-01

314

ECOLOGY APUBLICATIONOFTHEECOLOGICALSOCIETYOFAMERICA Frequency,notrelativeabundance,oftemperatetreespeciesvariesalongclimate  

E-print Network

considerations for testing the hypothesis. Key words: adaptations; ecosystem engineering; evolution; fire ecologyECOLOGY APUBLICATIONOFTHEECOLOGICALSOCIETYOFAMERICA Reports Frequency,dynamics,andecologicalunderstanding Concepts & Synthesis Doespyrogenicityprotectburningplants? Articles

Harms, Kyle E.

315

Frequency spectrum analyzer with phase-lock  

DOEpatents

A frequency-spectrum analyzer with phase-lock for analyzing the frequency and amplitude of an input signal is comprised of a voltage controlled oscillator (VCO) which is driven by a ramp generator, and a phase error detector circuit. The phase error detector circuit measures the difference in phase between the VCO and the input signal, and drives the VCO locking it in phase momentarily with the input signal. The input signal and the output of the VCO are fed into a correlator which transfers the input signal to a frequency domain, while providing an accurate absolute amplitude measurement of each frequency component of the input signal.

Boland, Thomas J. (Idaho Falls, ID)

1984-01-01

316

47 CFR 2.1507 - Test frequencies.  

Code of Federal Regulations, 2010 CFR

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY...for Testing Class A, B and S Emergency Position Indicating Radiobeacons...may interfere with emergency communications. Therefore, all...

2010-10-01

317

47 CFR 2.1507 - Test frequencies.  

Code of Federal Regulations, 2011 CFR

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY...for Testing Class A, B and S Emergency Position Indicating Radiobeacons...may interfere with emergency communications. Therefore, all...

2011-10-01

318

47 CFR 27.54 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

319

Odd-Frequency Pairing in Superconducting Heterostructures  

NASA Astrophysics Data System (ADS)

We review the theory of odd-frequency pairing in superconducting heterostructures, where an odd-frequency pairing component is induced near interfaces. General description of superconducting proximity effect in a normal metal or a ferromagnet attached to an unconventional superconductor (S) is given within quasiclassical kinetic theory for various types of symmetry state in S. Various possible symmetry classes in a superconductor are considered, which are consistent with the Pauli principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. As an example, we consider junction between a diffusive normal metal (DN) and a p-wave superconductor (even-frequency spin-triplet odd-parity symmetry), where the pairing amplitude in DN belongs to an odd-frequency spin-triplet even-parity symmetry class. We also discuss the manifestation of odd-frequency pairing in conventional superconductor/normal (S/N) proximity systems and its relation to the classical McMillan-Rowell oscillations.

Golubov, A. A.; Tanaka, Y.; Asano, Y.; Tanuma, Y.

320

Odd-frequency pairing in superconducting heterostructures  

NASA Astrophysics Data System (ADS)

We review the theory of odd-frequency pairing in superconducting heterostructures, where an odd-frequency pairing component is induced near interfaces. A general description of the superconducting proximity effect in a normal metal or a ferromagnet attached to an unconventional superconductor (S) is given within quasiclassical kinetic theory for various types of symmetry state in S. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. As an example, we consider a junction between a diffusive normal metal (DN) and a p-wave superconductor (even-frequency spin-triplet odd-parity symmetry), where the pairing amplitude in DN belongs to an odd-frequency spin-triplet even-parity symmetry class. We also discuss the manifestation of odd-frequency pairing in conventional superconductor/normal (S/N) proximity systems and its relation to the classical McMillan-Rowell oscillations.

Golubov, A. A.; Tanaka, Y.; Asano, Y.; Tanuma, Y.

2009-04-01

321

Frequency doubled, cavity dumped feedback laser  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

322

Instantaneous frequency and wave shape functions (I)  

E-print Network

Although one can formulate an intuitive notion of instantaneous frequency, generalizing "frequency" as we understand it in e.g. the Fourier transform, a rigorous mathematical definition is lacking. In this paper, we consider a class of functions composed of waveforms that repeat nearly periodically, and for which the instantaneous frequency can be given a rigorous meaning. We shown that Synchrosqueezing can be used to determine the instantaneous frequency of functions in this class, even if the waveform is not harmonic, thus generalizing earlier results for cosine wave functions. We also provide real-life examples and discuss the advantages, for these examples, of considering such non-harmonic waveforms.

Wu, Hau-tieng

2011-01-01

323

Psychophysical tuning curves at very high frequencies  

NASA Astrophysics Data System (ADS)

For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

Yasin, Ifat; Plack, Christopher J.

2005-10-01

324

Is probability of frequency too narrow?  

SciTech Connect

Modern methods of statistical data analysis, such as empirical and hierarchical Bayesian methods, should find increasing use in future Probabilistic Risk Assessment (PRA) applications. In addition, there will be a more formalized use of expert judgment in future PRAs. These methods require an extension of the probabilistic framework of PRA, in particular, the popular notion of probability of frequency, to consideration of frequency of frequency, frequency of probability, and probability of probability. The genesis, interpretation, and examples of these three extended notions are discussed.

Martz, H.F.

1993-10-01

325

Comparison of time-frequency-based techniques for estimating instantaneous frequency parameters of nonstationary processes  

NASA Astrophysics Data System (ADS)

The aim of this work is to contrast techniques used to estimate two instantaneous frequency parameters of the surface electromyographic (EMG) signal, the instantaneous median frequency and the instantaneous mean frequency, based on their estimation error. Three methods are compared: Cohen class and Cohen-Posch class time- frequency representations are used to compute both the above- mentioned instantaneous frequency parameters, and a cross-time- frequency based technique is adopted to derive the instantaneous mean frequency. The results demonstrate that the algorithm based on Cohen-Posch class transformations leads to a standard deviation of the instantaneous frequency parameters that is smaller than that obtained using Cohen class representations. However, the cross- time-frequency estimation procedure for instantaneous mean frequency produced the smallest standard deviation compared to the other techniques. The algorithms based on Cohen class and Cohen- Posch class transformations often provided a lower bias than the cross-time-frequency based technique. This advantage was particularly evident when the instantaneous mean frequency varies non-linearly within the epochs used to derive the cross-time- frequency representation of the surface EMG signal.

Bonato, Paolo; Erim, Zeynep; Roy, Serge H.; De Luca, Carlo J.

1999-11-01

326

Generalization of Frequency Discrimination Learning Across Frequencies and Ears: Implications for Underlying Neural Mechanisms in Humans  

PubMed Central

Frequency discrimination thresholds (FDTs) at 750, 1500, 3000, and 6000 Hz were measured in 32 normal-hearing listeners before and after each listener practiced the task for 12 h at one of the above frequencies using a single ear. Marked improvements in thresholds taking place over several hours were observed during the frequency- and ear-specific training period. Comparisons between pre- and posttraining thresholds showed large improvements at the trained frequency, but also at other frequencies. The improvements were initially slightly—but significantly—larger at the trained frequency than at untrained frequencies. However, this trained-frequency advantage disappeared rapidly during the course of the two-hour multifrequency posttraining session, suggesting rapid relearning or learning generalization across frequencies. In contrast, no significant ear specificity was found, not even at early stages of the posttraining session. These findings add to earlier results suggesting that, in humans, frequency discrimination learning is only weakly frequency-specific, and they reveal that a complete generalization across frequencies can occur rapidly with little retraining at the initially untrained frequencies. Implications regarding underlying mechanisms are discussed. PMID:15834630

Delhommeau, Karine; Jouvent, Roland

2005-01-01

327

Doppler Frequency Geolocation of Uncooperative Radars  

Microsoft Academic Search

Passive geolocation of uncooperative radar emitters remains an important problem in radar electronic warfare. Several location estimation techniques have been investigated in the past. In this paper, we present a passive geolocation technique for radar emitters using Doppler frequency measurements. For uncooperative sources, neither the emitter location, nor its transmitted frequency is known a priori. The relationship between these unknowns

B. H. Lee; Y. T. Chan; F. Chan; Huai-Jing Du; Fred A. Dilkes

2007-01-01

328

Robust Frequency Estimation Using Elemental Sets  

Microsoft Academic Search

The extraction of sinusoidal signals from time-series data is a classic problem of ongoing interest in the statistics and signal processing literatures. Obtaining least squares estimates is difficult because the sum of squares has local minima O(1\\/n) apart in the frequencies. In practice the frequencies are often estimated using ad hoc and inefficient methods. Problems of data quality have received

Gordon K. Smyth; Douglas M. Hawkins

2000-01-01

329

Employing the Accident Frequency-Severity Chart.  

ERIC Educational Resources Information Center

The Accident Frequency-Severity Chart (AFSC) is a tool for correctly assessing and appropriately coping with risks inherent in adventure programs. The AFSC helps to measure risk frequency (likelihood of loss) and severity (amount of loss) of specific outdoor activities. The AFSC can also be used to compare safety records of outdoor activities and…

Priest, Simon

1996-01-01

330

He's Frequency Formulation for Nonlinear Oscillators  

ERIC Educational Resources Information Center

Based on an ancient Chinese algorithm, J H He suggested a simple but effective method to find the frequency of a nonlinear oscillator. In this paper, a modified version is suggested to improve the accuracy of the frequency; two examples are given, revealing that the obtained solutions are of remarkable accuracy and are valid for the whole solution…

Geng, Lei; Cai, Xu-Chu

2007-01-01

331

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...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...

2012-10-01

332

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...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...

2013-10-01

333

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

334

Mel Frequency Cepstral Coefficients for Music Modeling  

Microsoft Academic Search

We examine in some detail Mel Frequency Cepstral Coefficients (MFCCs) - the dominant features used for speech recognition - and investigate their applicability to modeling music. In particular, we examine two of the main assumptions of the process of forming MFCCs: the use of the Mel frequency scale to model the spectra; and the use of the Discrete Cosine Transform

Beth Logan

2000-01-01

335

Frequency response corrections for eddy correlation systems  

Microsoft Academic Search

Simplified expressions describing the frequency response of eddy correlation systems due to sensor response, path-length averaging, sensor separation and signal processing are presented. A routine procedure for estimating and correcting for the frequency response loss in flux and variance measurements is discussed and illustrated by application to the Institute of Hydrology's ‘Hydra’ eddy correlation system.

C. J. Moore

1986-01-01

336

A simple, accurate voltage to frequency converter  

Microsoft Academic Search

A simple yet accurate voltage to frequency convertor is described and its performance examined. The unit requires a stable clock frequency. Conversion is linear, predictable, and practically independent of temperature to within errors of measurement (0.05%). Power drain is low (<150 mu W).

P. J. Ross

1974-01-01

337

Exploring the limits of frequency lowering  

PubMed Central

Objective This study examined how frequency lowering affected sentence intelligibility and quality, for adults with postlingually acquired, mild-to-moderate hearing loss. Method Listeners included adults aged 60–92 years with sloping sensorineural loss and a control group of similarly-aged adults with normal hearing. Sentences were presented in quiet and babble at a range of signal-to-noise ratios. Intelligibility and quality were measured with varying amounts of frequency lowering, implemented using a form of frequency compression. Results Moderate amounts of compression, particularly with high cutoff frequencies, had minimal effects on intelligibility. Listeners with the greatest high-frequency hearing loss showed the greatest benefit. Sentence intelligibility decreased with more compression. Listeners were more affected by a given set of parameters in noise. In quiet, any amount of compression resulted in lower speech quality for most listeners, with the greatest degradation for listeners with better high-frequency hearing. Quality ratings were lower with background noise, and in noise the effect of changing compression parameters was small. Conclusions The benefits of frequency lowering in adults were affected by the compression parameters as well as individual hearing thresholds. Data are consistent with the idea that frequency lowering can be viewed in terms of an improved audibility vs increased distortion tradeoff. PMID:23785188

Souza, Pamela E.; Arehart, Kathryn H.; Kates, James M.; Croghan, Naomi B.H.; Gehani, Namita

2013-01-01

338

Single-layer dual frequency patch antenna  

Microsoft Academic Search

A configuration for a slotted patch antenna is introduced which allows two separate operating frequencies. Both of these frequencies are associated with a radiating mode almost identical to that of a standard patch. The two resonances are related to the patch width and the slot\\/patch length, respectively.

S. Maci; Gentili Biffi; G. Avitabile

1993-01-01

339

New high-frequency weldable polyolefin films.  

PubMed

There is an increasing desire for plastic films that can be sealed using high-frequency energy. Tests on new high-frequency polyolefin film structures are reported, which compare them with the characteristics and performance of poly(vinyl chloride), ethylene-vinyl acetate and thermoplastic polyurethane films. PMID:11010316

Kelch, R

2000-05-01

340

Lightning protection devices for high frequencies equipments  

SciTech Connect

Contents: Mechanism of a Lightning Stroke from Antenna to Ground; Principles of Protection Devices for Feeders; Electrical Characteristics of H.F. Protection Devices; Calculation of H.F. Protection Devices; Catalogue Devices for High Frequency Protection; Some Measurement Results for Tees; Measurement Results for Decoupling Line Devices; Installation of High Frequency Devices.

Pierre, J.

1983-01-01

341

Frequency Selective Volumes for Optical Spatial Filters  

SciTech Connect

A new model is proposed for modeling metallic losses at optical frequencies and is used in the analysis of Frequency Selective Surfaces (FSSs) and Volumes (FSVs). Conventional methods for simulating metallic losses are also outlined and a comparison with those models is given for a patch FSS. Measured data for a slot-ring FSS are also given for model validation.

E Topsakal; JL Volakis

2004-04-15

342

Frequency Estimation of Uncooperative Coherent Pulse Radars  

Microsoft Academic Search

RF Frequency estimation is required in many applications, such as Radar Electronic Warfare (REW) and telecommunications. For example, passive location estimation of uncooperative radar sites in a target area is an important military application and can be achieved by measuring the Doppler-shifted frequencies of trains of modulated pulses received by an Electronic Support Measure (ESM) receiver on-board of a moving

Jing Gai; Francois Chan; Y. T. Chan; Huai-Jing Du; Fred A. Dilkes

2007-01-01

343

Carrier Frequency Effects on Path Loss  

Microsoft Academic Search

To study the carrier frequency effects on path loss, measurements have been conducted at four discrete frequencies in the range 460-5100 MHz. The transmitter was placed on the roof of a 36 meters tall building and the receive antennas were placed on the roof of a van. Both urban and suburban areas were included in the measurement campaign. The results

Mathias Riback; Jonas Medbo; Jan-erik Berg; Fredrik Harrysson; Henrik Asplund

2006-01-01

344

Binaural beats and frequency-coding.  

PubMed

Binaural beats were studied before and during a situation of temporary threshold shift, and no frequency shift could be found. In contrast, subjective binaural frequency comparison revealed a distinct shift. These findings demonstrate the two known modes of perception. PMID:3753290

Fritze, W; Köhler, W

1986-01-01

345

Microresonator-Based Optical Frequency Combs  

E-print Network

the performance of their microwave counterparts by more than an order of magnitude (4). This development involves from the radio frequency (RF) to optical domain on a chip. Principles of Frequency Combs with respect to the car- rier phase from pulse to pulse (Fig. 1A inset), lead- ing to a global offset

346

On Resonant Heating Below the Cyclotron Frequency  

SciTech Connect

Resonant heating of particles by an electrostatic wave propagating perpendicular to a confining uniform magnetic field is examined. It is shown that, with a sufficiently large wave amplitude, significant perpendicular stochastic heating can be obtained with wave frequency at a fraction of the cyclotron frequency.

Liu Chen; Zhihong Lin; White, R.

2001-02-02

347

Electronic power generators for ultrasonic frequencies  

NASA Technical Reports Server (NTRS)

The design and construction of an ultrasonic frequency electronic power generator are discussed. The principle design elements of the generator are illustrated. The generator provides an inductive load with an output power of two kilowatts and a variable output frequency in the fifteen to thirty KiloHertz range. The method of conducting the tests and the results obtained with selected materials are analyzed.

Ciovica, D.

1974-01-01

348

Status of Galileo Frequency and Signal Design  

Microsoft Academic Search

The paper presents the status of the Galileo frequency and signal structure, status Sept. 2002. The Galileo carrier frequency, modulation scheme and data rate of all 10 navigation signals are described as well as parameters of the search and rescue service. The navigation signals will support services addressed to three different types of users. The signal performance in terms of

Guenter W. Hein; Jeremie Godet; Jean-Luc Issler; Jean-Christophe Martin; Philippe Erhard; Rafael Lucas-Rodriguez; Tony Pratt

349

Automatic frequency control of an induction furnace  

Microsoft Academic Search

Automatic frequency control enables a variable induction heating load to be driven at its resonant frequency, ensuring maximum power transfer to the load throughout the heating cycle. Analysis and experimental results of the resonance locked-loop are presented to illustrate the performance of the system

Irshad Khan; Jonathan Tapson; Ian de Vries

1999-01-01

350

Variable frequency sinusoidal oscillators based on CCII+  

Microsoft Academic Search

Using the two-integrator loop biquadratic general structure and positive second-generation current conveyor (CCII+) as the active elements, a set of variable frequency sinusoidal oscillators is synthesized. Some of the derived structures are new and three of them have been carefully analyzed because of their special interest at high frequency. Experimental results show an excellent agreement with theoretical predictions. Finally, it

P. A. Martinez; J. Sabadell; C. Aldea; S. Celma

1999-01-01

351

Gravitational Bending of Light with Frequency Shifts  

E-print Network

Non-static gravitational fields generally introduce frequency shifts when bending light. In this paper, I discuss the frequency shifts induced in the bending of light by moving masses. As examples, I treat the recently discovered high-velocity pulsar PSR 2224+65 and a typical Einstein ring.

P. D. Morley

1993-11-15

352

Resonant frequency of Hilbert curve fractal antennas  

Microsoft Academic Search

An approximate formulation for the resonant frequency of a dipole Hilbert curve fractal antenna (HCFA) is derived here. These can be used as small resonant antennas, useful in VHF\\/UHF communication. The formulas presented here can be appropriately inverted to obtain the design equations for the antenna, for a given resonant frequency

K. J. Vinoy; K. A. Jose; V. K. Varadan; V. V. Varadan

2001-01-01

353

The frequencies of conversion reaction symptoms  

Microsoft Academic Search

Compared the frequencies with which 69 conversion symptoms are described in 18 abnormal psychology and psychiatry textbooks with the frequencies with which they appeared in a sample of 40 male hysterics and a group of female conversion reactions depicted in an earlier study. The correlations were small. Results suggest that textbook descriptions do not focus on the more common conversion

Charles G. Watson; Cheryl Buranen

1979-01-01

354

Frequency agile stepped OFDM waveform for HRR  

Microsoft Academic Search

High range resolution (HRR) is an important feature for radar, aiming at target classification. The range resolution is inversely proportional to the bandwidth of the transmitted signal. Pulse burst waveforms can achieve HRR at low expenses when the carrier frequency increases from one pulse to the next, stepping and synthesizing the wide bandwidth. In such a stepped frequency approach the

Gabriel Lellouch; Radmila Pribic; Piet van Genderen

2009-01-01

355

47 CFR 2.1057 - Frequency spectrum to be investigated.  

Code of Federal Regulations, 2013 CFR

...harmonics and subharmonics of the carrier frequency as well as to those frequencies removed from the carrier by multiples of the oscillator frequency. Radiation at the frequencies of multiplier stages should also be checked. (c) The amplitude of...

2013-10-01

356

47 CFR 2.1057 - Frequency spectrum to be investigated.  

Code of Federal Regulations, 2012 CFR

...harmonics and subharmonics of the carrier frequency as well as to those frequencies removed from the carrier by multiples of the oscillator frequency. Radiation at the frequencies of multiplier stages should also be checked. (c) The amplitude of...

2012-10-01

357

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2013-10-01

358

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2012-10-01

359

Human teeth model using photoacoustic frequency response  

NASA Astrophysics Data System (ADS)

In this paper, a novel photo-acoustic technique modality utilizing a frequency- modulated Q-switch Nd:YAG laser at 1064 nm and coherent frequency domain signal processing is introduced for impulse and frequency responses of biological tissues. We present a photoacoustic technique to monitor the temporal behavior of temperature and pressure in an excised sample of human teeth after either a single laser pulse or during multiple laser pulses at pulse repetition frequencies (PRF) from 5 Hz to 100 Hz. Knowledge of the dynamic characteristics of structural elements often means the difference between normal and abnormal tissue. The determination of the resonance characteristics of structures is termed "modal analysis." The results of our study suggest that it is possible to identify the impulse, frequency response and resonance modes of simplified human teeth. This data provided a powerful tool to differentiate between normal and decay teeth.

El-Sharkawy, Yasser H.; El-Sherif, Ashraf F.

2012-03-01

360

Burst-by-burst laser frequency monitor  

NASA Astrophysics Data System (ADS)

The invention is a system for real-time frequency monitoring and display of an RF burst where the burst frequency is analyzed and displayed on a burst-by-burst basis in order to allow for frequency control. Although the invention was made for monitoring the laser frequency of a LIDAR system, it has other applications where realtime monitoring is required. The novelty of the invention resides in the use of a counter that is reset at the beginning of each unit time of monitoring and then gated for a unit of time. The invention also has an LED bar graph for displaying the measure of frequency at the end of each unit time in either a bar length mode or a moving dot mode. In the latter mode, the operator makes necessary adjustments to maintain the dot at the center of the bar graph.

Esproles, Carlos

1993-02-01

361

Burst-by-burst laser frequency monitor  

NASA Astrophysics Data System (ADS)

The invention is a system for real-time frequency monitoring and display of an RF burst where the burst frequency is analyzed and displayed on a burst-by-burst basis in order to allow for frequency control. Although the invention was made for monitoring the laser frequency of a LIDAR system, it has other applications where realtime monitoring is required. The novelty of the invention resides in the use of a counter that is reset at the beginning of each unit time of monitoring and then gated for a unit of time. The invention also has an LED bar graph for displaying the measure of frequency at the end of each unit time in either a bar length mode or a moving dot mode. In the latter mode, the operator makes necessary adjustments to maintain the dot at the center of the bar graph.

Esproles, Carlos

1994-09-01

362

Infrared Frequency-Tunable Coherent Thermal Sources  

E-print Network

In this work, we numerically demonstrate an infrared frequency-tunable selective thermal emitter made of graphene covered SiC deep gratings. Full-wave simulation shows temporally-coherent emission peak associated with magnetic polariton, whose resonance frequency can be dynamically tuned within the phonon absorption band of SiC by varying graphene chemical potential. An analytical inductor-capacitor circuit model is introduced to quantitatively predict the resonance frequency and further elucidate the mechanism for the tunable emission peak. Moreover, by depositing multiple layers of graphene sheets onto the SiC deep gratings, a large tunability of 8.5% in peak frequency can be obtained to yield the coherent emission covering a broad frequency range from 820 1/cm to 890 1/cm. The novel tunable met-amaterial could pave the way to a new class of tunable thermal sources in the infrared region.

Wang, Hao; Wang, Liping

2014-01-01

363

Frequency-Lowering Devices for Managing High-Frequency Hearing Loss: A Review  

PubMed Central

Frequency-lowering technology has been around for decades. The primary aim—namely, that of providing high-frequency information to those with severe high-frequency hearing loss—addresses a clinical need most conventional hearing devices are still unable to provide. Early studies with frequency-lowering technology reported mostly unfavorable results, and the devices never gained clinical popularity. However, as hearing aid (HA) technology becomes ever more sophisticated, it is appropriate to reconsider whether frequency-lowering HAs should be an amplification choice in those with high-frequency hearing loss. Recent research is yielding promise with people who wear frequency-lowering devices showing improved speech perception. Questions remain regarding patient candidacy and whether auditory training may result in better outcomes. The author also discusses future clinical directions and research needs for frequency lowering. PMID:19447764

Simpson, Andrea

2009-01-01

364

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

E-print Network

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 ...

Delichatsios, Stefanie Alkistis

2006-01-01

365

The frequency of planets in multiple systems  

E-print Network

The frequency of planets in binaries is an important issue in the field of extrasolar planet studies, because of its relevance in estimating of the global planet population of our Galaxy and the clues it can give to our understanding of planet formation and evolution. However, only preliminary estimates are available in the literature. We analyze and compare the frequency of planets in multiple systems to the frequency of planets orbiting single stars. We also try to highlight possible connections between the frequency of planets and the orbital parameters of the binaries (such as the periastron and mass ratio.) A literature search was performed for binaries and multiple systems among the stars of the sample with uniform planet detectability defined by Fischer & Valenti (2005), and 202 of the 850 stars of the sample turned out to be binaries, allowing a statistical comparison of the frequency of planets in binaries and single stars and a study of the run of the planet frequency as a function of the binary separation. We found that the global frequency of planets in the binaries of the sample is not statistically different from that of planets in single stars. Even conservatively taking the probable incompleteness of binary detection in our sample into account, we estimate that the frequency of planets in binaries can be no more than a factor of three lower than that of planets in single stars. There is no significant dependence of planet frequency on the binary separation, except for a lower value of frequency for close binaries. However, this is probably not as low as required to explain the presence of planets in close binaries only as the result of modifications of the binary orbit after the planet formation.

M. Bonavita; S. Desidera

2007-03-29

366

Relationship between wingbeat frequency and resonant frequency of the wing in insects.  

PubMed

In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ~ m(1/2)/Af, while the natural frequency was significantly correlated with area density (f0 ~ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports--that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy. PMID:24166827

Ha, Ngoc San; Truong, Quang Tri; Goo, Nam Seo; Park, Hoon Cheol

2013-12-01

367

Stable differential voltage to frequency converter with low supply voltage and frequency offset control  

Microsoft Academic Search

In this paper, the circuit for a new bipolar differential voltage-to-frequency converter is presented. The circuit operation and the calculation of the operating frequency are described. The circuit design is also realized using Zetex transistor array integrated circuits and a 3.3-V power supply. This circuit incorporates an adjustable operating frequency via an external capacitor. The operating frequency varied from 15

D. McDonagh; K. I. Arshak

1998-01-01

368

Digital slip frequency generator and method for determining the desired slip frequency  

DOEpatents

The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

Klein, Frederick F. (Monroeville, PA)

1989-01-01

369

Frequency synchronization algorithms for OFDM systems suitable for communication over frequency selective fading channels  

Microsoft Academic Search

In this paper, the problem of carrier synchronization of OFDM systems in the presence of a substantial frequency offset is considered. New frequency estimation algorithms for the data aided (DA) mode are presented. The resulting two stage structure is able to cope with frequency offsets in the order of multiples of the spacing between subchannels. Key features of the novel

Ferdinand Classen; Heinrich Meyr

1994-01-01

370

ADAPTIVE COMPENSATION OF FREQUENCY SELECTIVE IQ IMBALANCE AND CARRIER FREQUENCY OFFSET FOR OFDM BASED RECEIVERS  

E-print Network

],[5] etc. Hence, a lot of effort is spent in developing integrated, cost and power efficient OFDM systems the radio frequency (RF) signal directly to baseband (BB) without any intermediate frequencies (IF). However. Along with IQ imbalance, OFDM systems are also very sensitive to car- rier frequency offset (CFO

371

Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine  

E-print Network

Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine-Frequency Control (LFC) is gradually shifted to Variable Speed Wind Turbines (VSWTs). In order to equip VSWT@et.aau.dk Abstract--In near future, with high penetration of Wind Energy (WE) in power system, the burden of Load

Silva, Filipe Faria Da

372

Beyond Phonotactic Frequency: Presentation Frequency Effects Word Productions in Specific Language Impairment  

ERIC Educational Resources Information Center

Phonotactic frequency effects on word production are thought to reflect accumulated experience with a language. Here we demonstrate that frequency effects can also be obtained through short-term manipulations of the input to children. We presented children with nonwords in an experiment that systematically manipulated English phonotactic frequency

Plante, Elena; Bahl, Megha; Vance, Rebecca; Gerken, LouAnn

2011-01-01

373

Estimating minimum allele frequencies for DNA profile frequency estimates for PCR-based loci  

Microsoft Academic Search

In order that there can be confidence that DNA profile frequency estimates will not place undue bias against a defendant, 2 methods are described for estimating minimum allele frequency bounds for PCR-based loci. One approach estimates minimum allele frequencies for VNTR and STR loci using sample size and the observed heterozygosity at a locus, while the second approach, appropriate for

B. Budowle; K. L. Monson; R. Chakraborty

1996-01-01

374

Direct Frequency Comb Spectroscopy of Alkali Atoms  

NASA Astrophysics Data System (ADS)

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Pradhananga, Trinity; Palm, Christopher; Nguyen, Khoa; Guttikonda, Srikanth; Kimball, Derek Jackson

2011-11-01

375

Method and apparatus for frequency spectrum analysis  

NASA Technical Reports Server (NTRS)

A method for frequency spectrum analysis of an unknown signal in real-time is discussed. The method is based upon integration of 1-bit samples of signal voltage amplitude corresponding to sine or cosine phases of a controlled center frequency clock which is changed after each integration interval to sweep the frequency range of interest in steps. Integration of samples during each interval is carried out over a number of cycles of the center frequency clock spanning a number of cycles of an input signal to be analyzed. The invention may be used to detect the frequency of at least two signals simultaneously. By using a reference signal of known frequency and voltage amplitude (added to the two signals for parallel processing in the same way, but in a different channel with a sampling at the known frequency and phases of the reference signal), the absolute voltage amplitude of the other two signals may be determined by squaring the sine and cosine integrals of each channel and summing the squares to obtain relative power measurements in all three channels and, from the known voltage amplitude of the reference signal, obtaining an absolute voltage measurement for the other two signals by multiplying the known voltage of the reference signal with the ratio of the relative power of each of the other two signals to the relative power of the reference signal.

Cole, Steven W. (inventor)

1992-01-01

376

On zero frequency magnetic fluctuations in plasmas  

SciTech Connect

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 the energy ``lost`` by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l_angle}B{sup 2}{r_angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.

Tajima, T.; Cable, S. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Kulsrud, R.M. [Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences

1992-01-01

377

On zero frequency magnetic fluctuations in plasmas  

SciTech Connect

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 the energy lost'' by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l angle}B{sup 2}{r angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.

Tajima, T.; Cable, S. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies); Kulsrud, R.M. (Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences)

1992-01-01

378

Frequency response in short thermocouple wires  

NASA Technical Reports Server (NTRS)

Theoretical expressions are derived for the steady state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for a nonuniform wire with unequal material properties and wire diameters across the junction. The amplitude ratio at low frequency omega approaches 0 agrees with the results of Scadron and Warshawsky (1952) for a steady state temperature distribution. Moreover, the frequency response for a nonuniform wire in the limit of infinite length l approaches infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties. Theoretical expressions are also derived for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results. Experimental measurements are made for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10 pct. with the theoretical predictions of Forney and Fralick (1991). This is accomplished by choosing a natural frequency omega sub n for the wire data to correlate the first order response at large gas temperature frequencies. It is found that a large bead size, however, will increase the amplitude ratio at low frequencies but decrease the natural frequency of the wire. The phase angle data are also distorted for imperfect junctions.

Forney, L. J.; Meeks, E. L.; Ma, J.; Fralick, G. C.

1992-01-01

379

High power radio frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Quentin A. (Bloomingdale, IL); Miller, Harold W. (Winfield, IL)

1984-01-01

380

Gauribidanur Low-Frequency Solar Spectrograph  

NASA Astrophysics Data System (ADS)

A new radio spectrograph, dedicated to observe the Sun, has been recently commissioned by the Indian Institute of Astrophysics (IIA) at the Gauribidanur Radio Observatory, about 100 km North of Bangalore. The instrument, called the Gauribidanur Low-frequency Solar Spectrograph (GLOSS), operates in the frequency range?40 - 440 MHz. Radio emission in this frequency range originates close to the Sun, typically in the radial distance range r?1.1 - 2.0 R?. This article describes the characteristics of the GLOSS and the first results.

Kishore, P.; Kathiravan, C.; Ramesh, R.; Rajalingam, M.; Barve, Indrajit V.

2014-10-01

381

Multi-mode radio frequency device  

DOEpatents

A transponder device having multiple modes of operation, such as an active mode and a passive mode, wherein the modes of operation are selected in response to the strength of a received radio frequency signal. A communication system is also provided having a transceiver configured to transmit a radio frequency signal and to receive a responsive signal, and a transponder configured to operate in a plurality of modes and to activate modes of operation in response to the radio frequency signal. Ideally, each mode of operation is activated and deactivated independent of the other modes, although two or more modes may be concurrently operational.

Gilbert, Ronald W. (Morgan Hill, CA); Carrender, Curtis Lee (Morgan Hill, CA); Anderson, Gordon A. (Benton City, WA); Steele, Kerry D. (Kennewick, WA)

2007-02-13

382

NASA Radio Frequency Spectrum Management Manual  

NASA Technical Reports Server (NTRS)

The Radio Frequency (RF) Spectrum Management Manual sets forth procedures and guidelines for the management requirements for controlling the use of radio frequencies by the National Aeronautics and Space Administration. It is applicable to NASA Headquarters and field installations. NASA Management Instruction 1102.3 assigns the authority for management of radio frequencies for the National Aeronautics and Space Administration to the Associate Administrator for Space Operations, NASA Headquarters. This manual is issued in loose-leaf form and will be revised by page changes.

1989-01-01

383

Frequency Response of Pressure Sensitive Paints  

NASA Technical Reports Server (NTRS)

An experimental method for measuring the frequency response of Pressure Sensitive Paints (PSP) is presented. These results lead to the development of a dynamic correction technique for PSP measurements which is of great importance to the advancement of PSP as a measurement technique. The ability to design such a dynamic corrector is most easily formed from the frequency response of the given system. An example of this correction technique is shown. In addition to the experimental data, an analytical model for the frequency response is developed from the one dimensional mass diffusion equation.

Winslow, Neal A.; Carroll, Bruce F.; Setzer, Fred M.

1996-01-01

384

High frequency dynamic pressure calibration technique  

NASA Technical Reports Server (NTRS)

A high frequency dynamic calibration technique for pressure transducers has been developed using a siren pressure generator (SPG). The SPG is an inlet-area-modulated device generating oscillating waveforms with dynamic pressure amplitudes up to 58.6 kPa (8.5 psi) in a frequency range of 1 to 10 kHz. A description of the generator, its operating characteristics and instrumentation used for pressure amplitude and frequency measurements is given. Waveform oscillographs and spectral analysis of the pressure transducers' output signals are presented.

Davis, P. A.; Zasimowich, R. F.

1985-01-01

385

Feshbach Resonances in Kerr Frequency Combs  

E-print Network

We show that both the power and repetition rate of a frequency comb generated in a nonlinear ring resonator, pumped with continuous wave (cw) coherent light, are modulated. The modulation is brought about by the interaction of the cw background with optical pulses excited in the resonator, and occurs in resonators with nonzero high-order chromatic dispersion and wavelength-dependent quality factor. The modulation frequency corresponds to the detuning of the pump frequency from the eigenfrequency of the pumped mode in the resonator.

Matsko, Andrey B

2014-01-01

386

Effects of low-frequency biasing on spontaneous otoacoustic emissions: frequency modulation.  

PubMed

It was previously reported that low-frequency biasing of cochlear structures can suppress and modulate the amplitudes of spontaneous otoacoustic emissions (SOAEs) in humans [Bian, L. and Watts, K. L. (2008). "Effects of low-frequency biasing on spontaneous otoacoustic emissions: Amplitude modulation," J. Acoust. Soc. Am. 123, 887-898]. In addition to amplitude modulation, the bias tone produced an upward shift of the SOAE frequency and a frequency modulation. These frequency effects usually occurred prior to significant modifications of SOAE amplitudes and were dependent on the relative strength of the bias tone and a particular SOAE. The overall SOAE frequency shifts were usually less than 2%. A quasistatic modulation pattern showed that biasing in either positive or negative pressure direction increased SOAE frequency. The instantaneous SOAE frequency revealed a "W-shaped" modulation pattern within one biasing cycle. The SOAE frequency was maximal at the biasing extremes and minimized at the zero crossings of the bias tone. The temporal modulation of SOAE frequency occurred with a short delay. These static and dynamic effects indicate that modifications of the mechanical properties of the cochlear transducer could underlie the frequency shift and modulation. These biasing effects are consistent with the suppression and modulation of SOAE amplitude due to shifting of the cochlear transducer operating point. PMID:19045788

Bian, Lin

2008-11-01

387

Quantum teleportation in space and frequency using entangled pairs of photons from a frequency comb  

NASA Astrophysics Data System (ADS)

Using entangled pairs of photons from a frequency comb and wide-band frequency-resolved homodyne detection, we propose a sequential quantum teleportation protocol for continuous variables that teleports an unknown state in space and frequency. A subthreshold optical parametric oscillator (OPO) produces a comb of entangled pairs of photons separated by the free spectral range of the OPO cavity. Wide-band frequency-resolved homodyne detection enables direct access to the sum and difference of quadratures between different teeth in the comb. Such measurements are Einstein-Podolsky-Rosen nullifiers, and can be used as the basis for teleportation protocols. Our protocol for space-and-frequency teleportation effectively links arbitrary frequency channels for frequency-division multiplexing, which has applications in universal quantum computation and large-capacity quantum communication.

Song, Hongbin; Yonezawa, Hidehiro; Kuntz, Katanya B.; Heurs, Michele; Huntington, Elanor H.

2014-10-01

388

Detecting deception via eyeblink frequency modulation  

PubMed Central

To assess the efficacy of using eyeblink frequency modulation to detect deception about a third party, 32 participants were sent on a mission to deliver a package to an interviewer. 17 of the participants lied to the interviewer about the details of their mock mission and 15 responded truthfully. During the interview, eyeblink frequency data were collected via electromyography and recorded video. Liars displayed eyeblink frequency suppression while lying, while truth tellers exhibited an increase in eyeblink frequency during the mission relevant questioning period. The compensatory flurry of eyeblinks following deception observed in previous studies was absent in the present study. A discriminant function using eyeblink suppression to predict lying correctly classified 81.3% of cases, with a sensitivity of 88.2% and a specificity of 73.3%. This technique, yielding a reasonable sensitivity, shows promise for future testing as, unlike polygraph, it is compatible with distance technology. PMID:24688844

2014-01-01

389

Graphene Infrared Spectroscopy: DFT Vibrational Frequencies  

NASA Astrophysics Data System (ADS)

The band structure asymmetry in terms of positive energy solution not being equal to the negative energy solution for the electron was found by us. The experimental work shows the gap resonance and the linear Stark effect upon application of the electric field. We have calculated the vibrational frequencies by using the density functional theory LDA for various models of graphene. The bond length in a single hexagonal carbon ring is 1.376 ? and its vibrational frequency is 1062.27 cm-1. In a monolayer of 32 atoms, there are a large number of vibrations starting from 42.24 cm-1 to about 1551.32 cm-1. In another type of graphene model of 30 atoms, the frequencies calculated vary from 23.12 cm-1 to 1546.26 cm-1. In the case of the two layers of 30 atoms each, the vibrational frequencies vary from 32.55 cm-1 to 1548.23 cm-1.

Rosli, Nazrul Ahmad; Kassim, Hasan Abu; Shrivastava, Keshav N.

2010-07-01

390

Frequency References for Gravitational Wave Missions  

NASA Technical Reports Server (NTRS)

The mitigation of laser frequency noise is an important aspect of interferometry for LISA-like missions. One portion of the baseline mitigation strategy in LISA is active stabilization utilizing opto-mechanical frequency references. The LISA optical bench is an attractive place to implement such frequency references due to its environmental stability and its access to primary and redundant laser systems. We have made an initial investigation of frequency references constructed using the techniques developed for the LISA and LISA Pathfinder optical benches. Both a Mach-Zehnder interferometer and triangular Fabry-Perot cavity have been successfully bonded to a Zerodur baseplate using the hydroxide bonding method. We will describe the construction of the bench along with preliminary stability results.

Preston, Alix; Thrope, J. I.; Donelan, D.; Miner, L.

2012-01-01

391

Site frequency spectra from genomic SNP surveys.  

PubMed

Genomic survey data now permit an unprecedented level of sensitivity in the detection of departures from canonical evolutionary models, including expansions in population size and selective sweeps. Here, we examine the effects of seemingly subtle differences among sampling distributions on goodness of fit analyses of site frequency spectra constructed from single nucleotide polymorphisms. Conditioning on the observation of exactly two alleles in a random sample results in a site frequency spectrum that is independent of the scaled rate of neutral substitution (theta). Other sampling distributions, including conditioning on a single mutational event in the sample genealogy or randomly selecting a single mutation from a genealogy with multiple mutations, have distinct site frequency spectra that show highly significant departures from the predictions of the biallelic model. Some aspects of data filtering may contribute to significant departures of site frequency spectra from expectation, apart from any violation of the standard neutral model. PMID:19371756

Ganapathy, Ganeshkumar; Uyenoyama, Marcy K

2009-06-01

392

47 CFR 101.507 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...507 Section 101.507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency...

2010-10-01

393

Operating frequencies for educational satellite services  

NASA Technical Reports Server (NTRS)

The factors affecting the choice of transmission frequencies are identified. These include international radio regulations, natural environment, man-made environment, hardware considerations, and interconnection and spectrum space considerations. An analysis is presented of international radio regulations with emphasis on 1963 EARC and 1971 WARC frequency allocations, powerflux density restrictions, and resolutions concerning introduction of broadcasting-satellite systems. Natural-environmental effects were divided into two categories: (1) those due to transionospheric propagation, and (2) those that can be credited to the earth's atmosphere and its constituents. The frequency dependence of the signal attenuation, signal distortion, and contributions to system noise temperature due to environmental effects are discussed, and comparisons were made for frequencies of interest. Man-made environmental effects were examined in terms of various sharing limitations as well as the indigenous noise contribution to the overall system noise.

Singh, J. P.

1971-01-01

394

Tracing buried pipelines using multi frequency electromagnetic  

NASA Astrophysics Data System (ADS)

In this paper the application of multi frequency electromagnetic techniques to locate buried pipelines is described. The survey site has two pipelines of SUMED, one of the world chokepoints. At desert or arid areas, regular geophysical surveys usually are difficult to carry out. EM techniques could be the best among geophysical techniques to be used for this target at these conditions. The EM survey was performed using a GEM-300 multi-frequency electromagnetic profiler. It is of handheld electromagnetic induction-type that measures in-phase and quadrature terrain conductivity without electrodes or direct soil contact. An area of 60 × 15 m was surveyed, that supposed SUMED pipeline existed. Six different frequencies, typically 2025, 2875, 4125, 5875, 8425, 12,025 Hz, have been used simultaneously. The slice maps for in-phase and conductivity distribution at each frequency could help to trace the extension of the pipeline. Two pipelines were traced successfully with 20 m spacing of each others.

El-Qady, Gad; Metwaly, Mohamed; Khozaym, Ashraf

2014-06-01

395

NOVEL -MODULATORS USING FREQUENCY MODULATED INTERMEDIATE VALUES  

E-print Network

Preface i Introduction 1 Traditional delta-sigma analog-to-digital conversion .......................................... 2 The new frequency delta-sigma modulation concept........................................... 3 1.0 Conventional delta-sigma modulators 5 1.1 The first order DSM

Høvin, Mats E.

396

Very-High-Frequency Resonant Boost Converters  

E-print Network

This paper presents a resonant boost topology suitable for very-high-frequency (VHF, 30-300 MHz) DC-DC power conversion. The proposed design features low device voltage stress, high efficiency over a wide load range, and ...

Perreault, David J.

397

Tidal frequency estimation for closed basins  

NASA Technical Reports Server (NTRS)

A method was developed for determining the fundamental tidal frequencies for closed basins of water, by means of an eigenvalue analysis. The mathematical model employed, was the Laplace tidal equations.

Eades, J. B., Jr.

1978-01-01

398

Laser Doppler vibrometer employing active frequency feedback  

SciTech Connect

We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well.

Chijioke, Akobuije; Lawall, John

2008-09-20

399

Real-time, high frequency QRS electrocardiograph  

NASA Technical Reports Server (NTRS)

Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as RAZs. RAZs are displayed as go, no-go signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

2006-01-01

400

47 CFR 87.449 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Operational Fixed Stations § 87...band are assignable to operational fixed stations using...Maritime Mobile Services. Operational frequencies in the...

2010-10-01

401

High Frequency Phase Splitter Utilizing Bifilar Windings.  

National Technical Information Service (NTIS)

The transistorized inverter circuit provides first and second outputs that are balanced and opposite in phase. The circuit is particularly useful where the input voltage source is one of very high frequency.

C. E. David, R. L. Haynes

1964-01-01

402

Distributed vs. Centralized Power Systems Frequency Control  

E-print Network

Distributed vs. Centralized Power Systems Frequency Control Martin Andreasson12 , Dimos V control of electrical power systems. We propose a distributed controller which retains the reference class of large- scale systems are electrical power systems, which employ automatic generation control

Dimarogonas, Dimos

403

Casimir energy of frequency dependent interactions  

NASA Astrophysics Data System (ADS)

Vacuum polarization (or Casimir) energies can be straightforwardly computed from scattering data for static field configurations whose interactions with the fluctuating field are frequency independent. In effective theories, however, such interactions are typically frequency dependent. As a consequence, the relationship between scattering data and the Green's function is modified, which may or may not induce additional contributions to the vacuum polarization energy. We discuss several examples that naturally include frequency dependent interactions: (i) scalar electrodynamics with a static background potential, (ii) an effective theory that emerges from integrating out a heavy degree of freedom, and (iii) quantum electrodynamics coupled to a frequency dependent dielectric material. In the latter case, we argue that introducing dissipation as required by the Kramers-Kronig relations requires the consideration of the Casimir energy within a statistical mechanics formalism, while in the absence of dissipation, we can work entirely within field theory, using an alternative formulation of the energy density.

Graham, N.; Quandt, M.; Weigel, H.

2014-10-01

404

Developing high-frequency equities trading models  

E-print Network

The purpose of this paper is to show evidence that there are opportunities to generate alpha in the high frequency environment of the US equity market, using Principal Component Analysis (PCA hereafter) as a basis for short ...

Infantino, Leandro Rafael

2010-01-01

405

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...PERSONAL RADIO SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions...providers who desire to use wireless medical telemetry devices must register all devices...frequency coordinator whenever a medical telemetry device is permanently taken...

2013-10-01

406

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...is available on a secondary basis for telemetry and telecommand associated with the...following frequencies are shared with flight telemetry mobile stations: 1444.5, 1453.5...to paragraph (p ): Aeronautical telemetry operations must protect...

2011-10-01

407

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2010-10-01

408

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2012-10-01

409

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...is available on a secondary basis for telemetry and telecommand associated with the...following frequencies are shared with flight telemetry mobile stations: 1444.5, 1453.5...to paragraph (p ): Aeronautical telemetry operations must protect...

2012-10-01

410

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...PERSONAL RADIO SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions...providers who desire to use wireless medical telemetry devices must register all devices...frequency coordinator whenever a medical telemetry device is permanently taken...

2011-10-01

411

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...PERSONAL RADIO SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions...providers who desire to use wireless medical telemetry devices must register all devices...frequency coordinator whenever a medical telemetry device is permanently taken...

2012-10-01

412

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2013-10-01

413

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...is available on a secondary basis for telemetry and telecommand associated with the...following frequencies are shared with flight telemetry mobile stations: 1444.5, 1453.5...to paragraph (p ): Aeronautical telemetry operations must protect...

2013-10-01

414

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2011-10-01

415

47 CFR 87.133 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

... 13 30 Radionavigation stations 20 20 Differential GPS 2 (6) Band-137 to 470MHz: Aeronautical stations...20 Hz. (d) For radar transmitters, except non-pulse signal radio altimeters, the frequency at which maximum...

2010-10-01

416

Damped Oscillator with Delta-Kicked Frequency  

NASA Technical Reports Server (NTRS)

Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

Manko, O. V.

1996-01-01

417

Neural coding of high-frequency tones  

NASA Technical Reports Server (NTRS)

Available evidence was presented indicating that neural discharges in the auditory nerve display characteristic periodicities in response to any tonal stimulus including high-frequency stimuli, and that this periodicity corresponds to the subjective pitch.

Howes, W. L.

1976-01-01

418

Component external leakage and rupture frequency estimates  

SciTech Connect

In order to perform detailed internal flooding risk analyses of nuclear power plants, external leakage and rupture frequencies are needed for various types of components - piping, valves, pumps, flanges, and others. However, there appears to be no up-to-date, comprehensive source for such frequency estimates. This report attempts to fill that void. Based on a comprehensive search of Licensee Event Reports (LERs) contained in Nuclear Power Experience (NPE), and estimates of component populations and exposure times, component external leakage and rupture frequencies were generated. The remainder of this report covers the specifies of the NPE search for external leakage and rupture events, analysis of the data, a comparison with frequency estimates from other sources, and a discussion of the results.

Eide, S.A.; Khericha, S.T.; Calley, M.B.; Johnson, D.A.; Marteeny, M.L.

1991-11-01

419

MIMO system identification using frequency response data  

NASA Technical Reports Server (NTRS)

A solution to the problem of obtaining a multi-input, multi-output statespace model of a system from its individual input/output frequency responses is presented. The Residue Identification Algorithm (RID) identifies the system poles from a transfer function model of the determinant of the frequency response data matrix. Next, the residue matrices of the modes are computed guaranteeing that each input/output frequency response is fitted in the least squares sense. Finally, a realization of the system is computed. Results of the application of RID to experimental frequency responses of a large space structure ground test facility are presented and compared to those obtained via the Eigensystem Realization Algorithm.

Medina, Enrique A.; Irwin, R. D.; Mitchell, Jerrel R.; Bukley, Angelia P.

1992-01-01

420

Radio frequency dc-dc power conversion  

E-print Network

THIS THESIS addresses the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies. The systems architectures that are developed are structured to overcome limitations ...

Rivas, Juan, 1976-

2007-01-01

421

Low Frequency Transmission Final Project Report  

E-print Network

Low Frequency Transmission Final Project Report Power Systems Engineering Research Center Dionysios Aliprantis, Iowa State University Graduate Research Assistants: Yongnam Cho, Dongbo Zhao Distinguished Professor School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta

422

The AKR emission cone at low frequencies  

NASA Technical Reports Server (NTRS)

It is noted that certain of the ISEE-1 observations between the plasmasphere and the auroral zone have revealed the emission cone of auroral kilometric radiation (AKR) unaffected by plasmaspheric refraction. At some distance from the source, the cone produced a sharp low-frequency boundary in the AKR signals, which was displaced above the cyclotron frequency. The variation of this boundary, together with other aspects of the AKR signals, suggested that the AKR emission cone closed toward a hollow, roughly 45 deg limit cone with decreasing frequency, duplicating the behavior previously found with ISIS-1 at the opposite end of the AKR spectrum. It is pointed out that the hollow limit cone at low frequencies is a new feature, not previously reported.

Calvert, W.

1981-01-01

423

Frequency-Dependent Electro-osmosis  

E-print Network

Electro-osmosis, the movement of a fluid with respect to solid wall when an electric field is applied tangentially to the solid wall, has been studied for many years[superscript 1]. Frequency-dependent electro-osmosis ...

Reppert, Phillip M.

2002-01-01

424

SRS Process Facility Significance Fire Frequency  

SciTech Connect

This report documents the method and assumptions of a study performed to determine a site generic process facility significant fire initiator frequency and explains the proper way this value should be used.

Sarrack, A.G. [Westinghouse Savannah River Company, AIKEN, SC (United States)

1995-10-01

425

Atmospheric transmission calculations for optical frequencies  

NASA Technical Reports Server (NTRS)

A quantitative study of the transmission loss through the entire atmosphere for optical frequencies likely to be used for an earth-space communication link using existing data bases on scattering and absorption characteristics of the atmospheric constituents is presented.

Shaik, Kamran

1989-01-01

426

Terahertz Frequency Combs. Theoretical Aspects and Applications  

NASA Astrophysics Data System (ADS)

We review recent work on THz frequency combs generated by femtosecond lasers. An overview about the underlying theory and application examples for the analysis of THz signals are given. Using different optoelectronic detection methods, spatially resolved measurements of frequency, phase, and amplitude of GHz and THz emitters are presented. The measurement setup allows for high-precision measurements of the frequency (accuracy of 9 · 10- 14within a 10 s measurement interval), relative amplitude (standard deviation of the mean 0.1 %) and phase (standard deviation of the mean 0.2°). Moreover, the accuracy and invasiveness of different optoelectronic techniques are compared. The large spectral coverage provided by THz frequency combs is demonstrated by simultaneously measuring signals at 16 GHz and 28 THz.

Füser, Heiko; Bieler, Mark

2014-08-01

427

Security approaches for Radio Frequency Identification systems  

E-print Network

In this thesis, I explore the challenges related to the security of the Electronic Product Code (EPC) class of Radio Frequency Identification (RFID) tags and associated data. RFID systems can be used to improve supply chain ...

Foley, Joseph Timothy, 1976-

2007-01-01

428

47 CFR 22.355 - Frequency tolerance.  

Code of Federal Regulations, 2010 CFR

...COMMON CARRIER SERVICES PUBLIC MOBILE SERVICES Operational and Technical Requirements...each transmitter in the Public Mobile Services must be maintained within the...for Transmitters in the Public Mobile Services Frequency range (MHz)...

2010-10-01

429

Graphene mechanical oscillators with tunable frequency  

NASA Astrophysics Data System (ADS)

Oscillators, which produce continuous periodic signals from direct current power, are central to modern communications systems, with versatile applications including timing references and frequency modulators. However, conventional oscillators typically consist of macroscopic mechanical resonators such as quartz crystals, which require excessive off-chip space. Here, we report oscillators built on micrometre-size, atomically thin graphene nanomechanical resonators, whose frequencies can be electrostatically tuned by as much as 14%. Self-sustaining mechanical motion is generated and transduced at room temperature in these oscillators using simple electrical circuitry. The prototype graphene voltage-controlled oscillators exhibit frequency stability and a modulation bandwidth sufficient for the modulation of radiofrequency carrier signals. As a demonstration, we use a graphene oscillator as the active element for frequency-modulated signal generation and achieve efficient audio signal transmission.

Chen, Changyao; Lee, Sunwoo; Deshpande, Vikram V.; Lee, Gwan-Hyoung; Lekas, Michael; Shepard, Kenneth; Hone, James

2013-12-01

430

Identifying Trends in Word Frequency Dynamics  

NASA Astrophysics Data System (ADS)

The word-stock of a language is a complex dynamical system in which words can be created, evolve, and become extinct. Even more dynamic are the short-term fluctuations in word usage by individuals in a population. Building on the recent demonstration that word niche is a strong determinant of future rise or fall in word frequency, here we introduce a model that allows us to distinguish persistent from temporary increases in frequency. Our model is illustrated using a 108-word database from an online discussion group and a 1011-word collection of digitized books. The model reveals a strong relation between changes in word dissemination and changes in frequency. Aside from their implications for short-term word frequency dynamics, these observations are potentially important for language evolution as new words must survive in the short term in order to survive in the long term.

Altmann, Eduardo G.; Whichard, Zakary L.; Motter, Adilson E.

2013-04-01

431

Dual-Frequency Radar Observations of Precipitation  

Microsoft Academic Search

An equal volume, dual-frequency radar system is used to obtain a quantitative characterization of a precipitation volume. The power back-scattered is related to the rainfall rate through the use of an assumed exponential drop-size distribution and the Mie radar cross section. A method is given whereby the relative consistency of a dual-frequency radar system is aided by calibration in the

B. Walker; L. S. Lamberth; J. J. Stephens

1964-01-01

432

Spectroscopy by frequency entangled photon pairs  

E-print Network

Quantum spectroscopy was performed using the frequency-entangled broadband photon pairs generated by spontaneous parametric down-conversion. An absorptive sample was placed in front of the idler photon detector, and the frequencies of signal photons were resolved by a diffraction grating. The absorption spectrum of the sample was measured by counting the coincidences, and the result is in agreement with the one measured by a spectrophotometer with a classical light source.

Yabushita, A; Yabushita, Atsushi; Kobayashi, Takayoshi

2004-01-01

433

Spectroscopy by frequency entangled photon pairs  

E-print Network

Quantum spectroscopy was performed using the frequency-entangled broadband photon pairs generated by spontaneous parametric down-conversion. An absorptive sample was placed in front of the idler photon detector, and the frequency of signal photons was resolved by a diffraction grating. The absorption spectrum of the sample was measured by counting the coincidences, and the result is in agreement with the one measured by a conventional spectrophotometer with a classical light source.

Atsushi Yabushita; Takayoshi Kobayashi

2003-06-23

434

Multi-frequency polarimetric radar earth observations  

Microsoft Academic Search

The air-borne multi-frequency polarimetric SAR ldquoIMARCrdquo allows radar earth observation measurements at 4 frequency bands (X,L,P and VHF) and utilizes a complete set of different linear polarizations: VV, HH, VH and HV. Theoretical and experimental feasibilities have been carried out in recent years. System capabilities and potential applications have been demonstrated. Operational usage in a wide range of applications is

L. P. Ligthart; B. Kutuza

2008-01-01

435

High-Frequency Link Power Conversion  

Microsoft Academic Search

A class of electrical power conditioners incorporating an intermediate variable high-frequency link concept is introduced by considering a converter with dc source and variable voltage and frequency polyphase output, then extending the concept to polyphase ac source voltage. The ac60 Hz-achigh-freq-acoutput-freq system is essentially comprised of two cascade 12-thyristor cycloconverters separated by a parallel resonant tank circuit. The tank circuit

Paul M. Espelage; Bimal K. Bose

1977-01-01

436

Time and frequency technology at NIST  

NASA Technical Reports Server (NTRS)

The state of development of advanced timing systems at NIST is described. The work on cesium and rubidium frequency standards, stored-ion frequency standards, diode lasers used to pump such standards, time transfer, and methods for characterizing clocks, oscillators, and time distribution systems is presented. The emphasis is on NIST-developed technology rather than the general state of the art in this field.

Sullivan, D. B.

1994-01-01

437

Novel magnetic composites for high frequency applications  

Microsoft Academic Search

Magnetic materials are widely used in high frequency from radio wave and microwave range. In some cases, high loss may be desired in applications such as heating and EM wave absorption. In most applications such as power transformers, DC-DC converters, etc., low loss is required to achieve a non-dispersive (frequency-independent) permeability spectrum with high value. In this dissertation work, we

Xiaokai Zhang

2008-01-01

438

CZT-Based High Performance Frequency Estimation  

Microsoft Academic Search

Accurate and high-performance frequency estimation of a noisy sampled sinusoid sequence with short time length and adjacent overlapping has been attracting top focus in the field of signal processing. Based on the CZT of a single-tone sequence, this paper presents a novel improved Rife CZT-interpolated frequency estimator, which develops an improved Rife algorithm on the symmetry of CZT Linear Spectrum

Huang Yuchun; Huang Zailu; Huang Benxiong; Xu Shuhua

2007-01-01

439

Multiple frequency printed slot and dipole antennas  

E-print Network

fluctuation in the circuit structure's reflection coefficient between adjacent frequency points. The second type of polygon is the magnetic current polygon. This type of polygon represents the field distribution on a metallic aperture. This is a very... fluctuation in the circuit structure's reflection coefficient between adjacent frequency points. The second type of polygon is the magnetic current polygon. This type of polygon represents the field distribution on a metallic aperture. This is a very...

Kolsrud, Arild

2012-06-07

440

Improved satellite repeater amplitude-frequency measurement  

Microsoft Academic Search

After the launch of a communications satellite into geostationary orbit, satellite performance is checked by means of a series of in-orbit tests. One of the most important of these tests is the measurement of the amplitude-frequency response (in-band and out-of-band) of each satellite transponder. The present investigation is concerned with a novel satellite in-orbit amplitude-frequency measurement scheme, and the presentation

P. Daly

1983-01-01

441

Binaural Beats and the Frequency Following Response  

Microsoft Academic Search

Persistent rhythmic auditory stimuli neurologically manifest as a cortical frequency-following response (Oster 1973; Smith et al. 1975; Marsh et al. 1975; Smith et al. 1978; Hink et al. 1980). Both Oster (1973) and Hink et al. (1980) have demonstrated a frequency-following response (FFR) to binaural beating with an evoked- potential EEG protocol in the context of hearing-acuity research. This study

F. HOLMES ATWATER

442

Frequency of intercourse and contraceptive choice.  

PubMed

The effects of frequency of intercourse on perceptions of two of the most widely used contraceptive methods, the pill and condom, were assessed in 128 female college students currently involved in a sexual relationship. Intercourse frequency was found to be strongly associated with knowledge of both methods. People experiencing more frequent sexual intercourse were more favourably disposed towards the pill and less towards the condom than people experiencing intercourse less frequently. Implications of these results are discussed. PMID:2335544

Glor, J E; Severy, L J

1990-04-01

443

Calibration frequency for gas proportional counters  

Microsoft Academic Search

A laboratory that employs nuclear detectors should have a calibration procedure, and its practice is detailed in the bibliography,\\u000a but the frequency of that calibration is not settled in any case. The aim of this work is to establish an optimum frequency\\u000a for efficiency calibration in an alpha\\/beta gas proportional counter, related with the results' adequate routine controls.\\u000a The results

Margarita Herranz; Raquel Idoeta; Ainara Mira; Fernando Legarda

2007-01-01

444

Spatial-frequency requirements for reading revisited  

PubMed Central

Blur is one of many visual factors that can limit reading in both normal and low vision. Legge et al. [Legge, G. E., Pelli, D. G., Rubin, G. S., & Schleske, M. M. (1985). Psychophysics of reading. I. Normal vision. Vision Research, 25, 239–252.] measured reading speed for text that was low-pass filtered with a range of cutoff spatial frequencies. Above 2 cycles per letter (CPL) reading speed was constant at its maximum level, but decreased rapidly for lower cutoff frequencies. It remains unknown why the critical cutoff for reading speed is near 2 CPL. The goal of the current study was to ask whether the spatial-frequency requirement for rapid reading is related to the effects of cutoff frequency on letter recognition and the size of the visual span. Visual span profiles were measured by asking subjects to recognize letters in trigrams (random strings of three letters) flashed for 150 ms at varying letter positions left and right of the fixation point. Reading speed was measured with Rapid Serial Visual Presentation (RSVP). The size of the visual span and reading speed were measured for low-pass filtered stimuli with cutoff frequencies from 0.8 to 8 CPL. Low-pass letter recognition data, obtained under similar testing conditions, were available from our previous study (Kwon & Legge, 2011). We found that the spatial-frequency requirement for reading is very similar to the spatial-frequency requirements for the size of the visual span and single letter recognition. The critical cutoff frequencies for reading speed, the size of the visual span and a contrast-invariant measure of letter recognition were all near 1.4 CPL, which is lower than the previous estimate of 2 CPL for reading speed. Although correlational in nature, these results are consistent with the hypothesis that the size of the visual span is closely linked to reading speed. PMID:22521659

Kwon, MiYoung; Legge, Gordon E.

2012-01-01

445

Satellite Time- and Frequency-Transfer System  

NASA Technical Reports Server (NTRS)

Time synchronized at distant points within nanosecond. Report describes satellite-borne time-and frequency-transfer system proposed for synchronization of clocks at stations around Earth. Orbiting hydrogen-maser clock and frequency standard communicate by microwave links with Earth stations using hydrogen masers as local clocks. Pulsed-laser time-transfer sub-system also operated concurrently, either synchronized or unsynchronized with microwave subsystems.

Vessot, R. F. C.; Penfield, H.; Mattison, E.

1985-01-01

446

Oblique noise bands above local LHR frequency  

Microsoft Academic Search

The noise bands at lower hybrid resonance (LHR) frequency at a satellite position have already been observed and described. Observations onboard the MAGION 5 satellite revealed oblique noise bands above the local LHR frequency. Examples of such oblique bands, both in review (large time-scale) spectrograms, and in detailed (small time-scale) spectrograms are presented. Based on ray-tracing simulations, an explanation of

J. Chum; F. Jiricek; D. Shklyar

2003-01-01

447

Frequency-sum passive cavitation imaging.  

PubMed

Passive cavitation imaging (PCI) is a method for spatially mapping acoustic emissions caused by microbubble activity, including subharmonic and ultraharmonic emissions that denote stable cavitation. The point spread function (PSF) of passive cavitation images is diffraction limited. When typical clinical diagnostic linear arrays are used for PCI, the diffraction limit results in high azimuthal resolution but low axial resolution. Abadi et al. (2013)recently demonstrated a method called frequency-sum beamforming, which employs second-order or higher products of the acoustic emissions to manufacture higher frequencies, thereby reducing the size of the PSF. We applied this approach to cavitation emissions recorded from albumin-shelled bubbles insonified by 2 MHz ultrasound. Cavitation emissions were recorded on a 5 MHz, 128 element linear array using a Vantage scanner (Verasonics Inc.). Quadratic and fourth-order frequency-sum beamforming was applied to both harmonic and ultraharmonic cavitation emissions. Corresponding simulations were also performed to illustrate frequency-sum passive cavitation imaging of multiple bubbles. In comparison to delay-and-sum PCI, apparent areas of cavitation activity decreased when products of the emissions were used to perform frequency-sum beamforming. However, frequency-sum beamforming also produced artifacts, including the appearance of spurious emission sources. PMID:25235673

Haworth, Kevin J; Radhakrishnan, Kirthi; Mast, T Douglas

2014-04-01

448

Black phosphorus radio-frequency transistors.  

PubMed

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, which lead to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of BP field-effect transistors for the first time. The BP transistors demonstrated here show respectable current saturation with an on-off ratio that exceeds 2 × 10(3). We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cutoff frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus can be considered as a promising candidate for the future high performance thin film electronics technology for operation in the multi-GHz frequency range and beyond. PMID:25347787

Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L; Dubey, Madan; Han, Shu-Jen

2014-11-12

449

High frequency ultrasonic scattering by biological tissues  

NASA Astrophysics Data System (ADS)

High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.

Shung, K. Kirk; Maruvada, Subha

2002-05-01

450

Stabilizing Microwave Frequency of a Photonic Oscillator  

NASA Technical Reports Server (NTRS)

A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences. COEOs of various designs, at various stages of development, in some cases called by different names, have been described in a number of prior NASA Tech Briefs articles. A COEO is an optoelectronic apparatus that generates both short (picosecond) optical pulses and a steady microwave signal having an ultrahigh degree of spectral purity. The term "coupled optoelectronic" in the full name of such an apparatus signifies that its optical and electronic oscillations are coupled to each other in a single device. The present frequency-stabilization scheme is best described indirectly by describing the laboratory apparatus used to demonstrate it. The apparatus (see figure) includes a COEO that generates a comb-like optical spectrum, the various frequency components of which interfere, producing short optical pulses. This spectrum is centered at a nominal wavelength of 1,560 nm. The spectrum separation of this comb is about 10 GHz, as determined primarily by the length of an optical loop and the bandpass filter in the microwave feedback loop. The optical loop serves as microwave resonator having a very high value of the resonance quality factor (Q). The optical frequency of MLL is then stabilized by locking it to an atomic transition as described below. The COEO contains a tunable 1-nm band-pass optical filter and a piezoelectric-transducer (PZT) drum over which a stretch of fiber is wound. The 1-nm-wide pass band of the filter provides coarse tuning to overlap the frequency comb with the atomic transition frequency. Controlled stretching of the fiber by means of the PZT drum can be used in conjunction with temperature control for locking the laser frequency. To reference to an atomic resonance at 780 nm in this demonstration setup, the optical output of the COEO at 1,560 nm is fed through an erbium-doped-fiber amplifier (EDFA) to a frequency doubler in the form of a periodically poled lithium niobate (PPLN) crystal. The frequency-doubled output is combined with the output of a separate frequency-stabilized diode laser at a photodetector. As described thus far, the two 780-nm laser subsystems are nominally independent of each other and can, therefore, operate at different frequencies. Hence, at the photodetector, the two laser beams interfere, so that the output of the photodetector includes a beat note (a component at the difference between the two laser frequencies).

Maleki, Lute; Yu, Nan; Tu, Meirong

2006-01-01

451

Controlling the electromagnetically induced transparency frequency tuning range by radio-frequency field  

NASA Astrophysics Data System (ADS)

The Electromagnetically Induced Transparency (EIT) is associated with a ? three-level system and the spectral position of EIT window can be changed by varying the frequency of the coupling field, however, at large detuning the EIT will evolve into a dispersion-like feature and transparency property of EIT become less obvious. In this paper, it is shown that we can perform EIT frequency tuning by a radio-frequency (rf) field. In the cascade quasic-? four-level system, the absorption profile of probe field is calculated by solving the equations of motion of the density matrix. It is shown that the Autler-Townes doublet originates from the rf-field induced dynamic Stark effect and the spectral position of EIT window is determined by the frequency detuning of the coupling field. When the frequency detuning of the coupling field is half of the rf Rabi frequency, the EIT feature remain its absorptive profile. The frequency tuning rang of EIT is determined by the rf Rabi frequency, and can be explained using a dressed-state analysis. Therefore, frequency tuning range of EIT can be controlled by the rf Rabi frequency.

Zhang, Lianshui; Zhuang, Zhonghong; Wang, Jian; Feng, Xiaomin; Yang, Lijun

2008-01-01

452

Frequency response of lift control in Drosophila.  

PubMed

The flight control responses of the fruitfly represent a powerful model system to explore neuromotor control mechanisms, whose system level control properties can be suitably characterized with a frequency response analysis. We characterized the lift response dynamics of tethered flying Drosophila in presence of vertically oscillating visual patterns, whose oscillation frequency we varied between 0.1 and 13 Hz. We justified these measurements by showing that the amplitude gain and phase response is invariant to the pattern oscillation amplitude and spatial frequency within a broad dynamic range. We also showed that lift responses are largely linear and time invariant (LTI), a necessary condition for a meaningful analysis of frequency responses and a remarkable characteristic given its nonlinear constituents. The flies responded to increasing oscillation frequencies with a roughly linear decrease in response gain, which dropped to background noise levels at about 6 Hz. The phase lag decreased linearly, consistent with a constant reaction delay of 75 ms. Next, we estimated the free-flight response of the fly to generate a Bode diagram of the lift response. The limitation of lift control to frequencies below 6 Hz is explained with inertial body damping, which becomes dominant at higher frequencies. Our work provides the detailed background and techniques that allow optomotor lift responses of Drosophila to be measured with comparatively simple, affordable and commercially available techniques. The identification of an LTI, pattern velocity dependent, lift control strategy is relevant to the underlying motion computation mechanisms and serves a broader understanding of insects' flight control strategies. The relevance and potential pitfalls of applying system identification techniques in tethered preparations is discussed. PMID:20462877

Graetzel, Chauncey F; Nelson, Bradley J; Fry, Steven N

2010-11-01

453

The VLA Low Frequency Sky Survey  

NASA Astrophysics Data System (ADS)

We present an overview of the ongoing VLA Low-frequency Sky Survey (VLSS, formerly known as 4MASS). The VLSS will map an area of 9.1 sr covering the entire sky above a declination of -30 degrees (or 75% of the full sky), at a frequency of 74 MHz (4 meter wavelength) with an unprecedented combination of sensitivity and resolution at this low frequency. The observational challenges at this wavelength include radio frequency interference (RFI), ionospheric phase distortions and a large field of view filled with sources. These challenges have been surmounted by a variety of new algorithms. The principle data products from the survey will be a set of publicly available images along with a source catalog of approximately 80,000 objects. Thus we will create an online virtual observatory at this previously unexplored frequency which will complement other major surveys at higher frequencies such as the NVSS. From these data, statistically useful samples of extragalactic and Galactic objects, such as high redshift radio galaxies, galaxy clusters, supernova remnants and pulsars can be assembled for further study. In addition, this survey will provide a crucial calibration grid for use with next generation of large low frequency telescopes such as LWA and LOFAR. The observations are now roughly 50% complete, and we expect to observe the majority of the remaining fields by spring 2005. Current data products and more information are available on our website (URL:http://lwa.nrl.navy.mil/VLSS). Basic research in radio astronomy at the Naval Research Laboratory is supported by the office of Naval Research.

Cohen, A. S.; Lane, W. M.; Kassim, N. E.; Lazio, T. J. W.; Cotton, W. D.; Condon, J. J.; Perley, R. A.; Erickson, W. C.

2005-12-01

454

ISM band to U-NII band frequency transverter and method of frequency transversion  

DOEpatents

A frequency transverter (10) and method for enabling bi-frequency dual-directional transfer of digitally encoded data on an RF carrier by translating between a crowded or otherwise undesirable first frequency band, such as the 2.4 GHz ISM band, and a less-crowded or otherwise desirable second frequency band, such as the 5.0 GHz 6.0 GHz U-NII band. In a preferred embodiment, the transverter (10) connects between an existing data radio (11) and its existing antenna (30), and comprises a bandswitch (12); an input RF isolating device (14); a transmuter (16); a converter (18); a dual output local oscillator (20); an output RF isolating device (22); and an antenna (24) tuned to the second frequency band. The bandswitch (12) allows for bypassing the transverter (10), thereby facilitating its use with legacy systems. The transmuter (14) and converter (16) are adapted to convert to and from, respectively, the second frequency band.

Stepp, Jeffrey David (Grandview, MO); Hensley, Dale (Grandview, MO)

2006-09-12

455

ISM band to U-NII band frequency transverter and method of frequency transversion  

DOEpatents

A frequency transverter (10) and method for enabling bi-frequency dual-directional transfer of digitally encoded data on an RF carrier by translating between a crowded or otherwise undesirable first frequency band, such as the 2.4 GHz ISM band, and a less-crowded or otherwise desirable second frequency band, such as the 5.0 GHz-6.0 GHz U-NII band. In a preferred embodiment, the transverter (10) connects between an existing data radio (11) and its existing antenna (30), and comprises a bandswitch (12); an input RF isolating device (14); a transmuter (16); a converter (18); a dual output local oscillator (20); an output RF isolating device (22); and an antenna (24) tuned to the second frequency band. The bandswitch (12) allows for bypassing the transverter (10), thereby facilitating its use with legacy systems. The transmuter (14) and converter (16) are adapted to convert to and from, respectively, the second frequency band.

Stepp, Jeffrey David (Grandview, MO); Hensley, Dale (Grandview, MO)

2006-04-04

456

A center frequency adjustable narrow band filter for the detection of weak single frequency signal  

NASA Astrophysics Data System (ADS)

We describe and implement a center frequency adjustable narrow band filter based on the crystal filter for the detection of weak single frequency signal. It is formed by a multiplier, a direct digital frequency synthesizer, a multi-stage crystal bandpass filter, and a micro control unit which is used to set the center frequency of the filter. A theoretical study is proposed and experimentally validated. The test results show that the 3 db and 20 db bandwidths are 0.84 Hz and 2.73 Hz, respectively, and the filter system can effectively detect the signal with amplitude below 1 ?V and a frequency which ranges from 10 Hz to the frequency that is mainly limited by the components applied.

Xin, Yunhong; Xiang, ZhenMing; Dong, LeMing; Zhu, Bing; Cao, Hui; Fang, Yu

2014-04-01

457

Alternative solution of direct frequency conversion for AC drives  

Microsoft Academic Search

A new approach to real approximation of an ideal sinusoidal frequency conversion process is put forward. This enables the output frequency range of line-commutated direct frequency converters to be expanded up to the value of input frequency. This is achieved by the application of a low frequency value sinusoidal modulating function and the replacement of input voltage and modulating function

L. Ribickis; M. Liepins; L. Rutmanis; J. Stabulnieks

1993-01-01

458

Childhood travel frequency as a predictor of adult travel frequency: an exploratory analysis.  

E-print Network

CHILDHOOD TRAVEL FREOUENCY AS A PREDICTOR OF . ADULT TRAVEL FREQUENCY: AN EXPLORATORY ANALYSIS A Thesis DOUGLAS ROBERT HENNIG Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 1975 Ma)or Sub]ect: Recreation and Resources Development CHILDHOOD TRAVEL FREQUENCY AS A PREDICTOR OF ADULT TRAVEL FREQUENCY: AN EXPLORATORY ANALYSIS A Thesis by DOUGLAS ROBERT HENNIG Approved as to sty1e and content by...

Hennig, Douglas Robert

2012-06-07

459

Frequency response characteristic of sympathetic mediated low-frequency blood pressure fluctuations in conscious rats  

Microsoft Academic Search

A quantitative relationship between power densities of blood pressure (PBP) and sympathetic nerve activity (PSNA) in a low-frequency range (LF, 0.016–0.85Hz), expressed as PSNA=PBP×a×10b×(frequency) was proposed in pentobarbital-anesthetized rats. For evaluating the general applicability of this equation, the quantitative relationship of power density ratio H(f)=PBP\\/PSNA across frequency was tested in a conscious state. Wistar rats were chronically instrumented with a

Ruei-Feng Chen; Wan-Ting Zeng; Chen-Tung Yen; Meng-Li Tsai

2006-01-01

460

Electronic model of a neuronal sinapsis of voltage to frequency, and frequency to voltage conversion  

Microsoft Academic Search

In this work we present the results of a study of neurons with synapses of the frequency-voltage type response, and the effects of the autosynapse that give us responses of long period. We also present the effects of synapse frequency\\/voltage-voltage\\/frequency in the phenomena of autosynapse in neuron cascades. We also studied the effects of the time constant involved in the

A. Garces; S. Quintana; A. Herrera; M. Bafiuelos; J. Castillo; W. Martinez; A. Padron

1999-01-01

461

A sensitivity analysis of frequency selective surface based metamaterial at THz frequency  

NASA Astrophysics Data System (ADS)

This work presents a sensitivity analysis for the resonance frequency and bandwidth of dielectric supported Split Ring Resonator (SRR) metmaterial in THz frequency. The different designed parameters have been considered and their parametric sensitivities on resonance frequency and on bandwidth have been analyzed. The finite integral technique is used to simulate the structure and the numerical techniques are used to obtain the resonance frequency and bandwidth sensitivities as a function of the designed parameters. The analysis for sensitivity of the scattering parameters of metamaterial is especially very important in THz frequency range. The resonance frequency and the bandwidth are the main characteristics of a resonator Frequency Selective Surface (FSS). The development of FSS in mm-wave frequency range can be simplified by the knowledge of the sensitivity of their main characteristics as a function of the considered physical parameters. The FSS structure considered in this section is the square split ring resonator with copper strip lines backed by Roger 4003 C dielectric substrate. The FSS structure is simulated by using CST Microwave Studio transient solver. The resonance frequency and the bandwidth sensitivities as function structural parameters of FSS are obtained by using the simulation data. In this analysis, normal incident TE modes are considered.

Islam, S.; Stiens, J.; Vounckx, R.

2010-04-01

462

Time and Frequency Synchronization for Multicarrier Transmission on Hexagonal Time-Frequency Lattice  

NASA Astrophysics Data System (ADS)

In this paper, a novel carrier frequency offset estimation approach, including preamble structure, carrier frequency offset estimation algorithm, is proposed for hexagonal multi-carrier transmission (HMCT) system. The closed-form Cramer-Rao lower bound of the proposed carrier frequency offset estimation scheme is given. Theoretical analyses and simulation results show that the proposed preamble structure and carrier frequency offset estimation algorithm for HMCT system obtains an approximation to the Cramer-Rao lower bound mean square error (MSE) performance over the doubly dispersive (DD) propagation channel.

Xu, Kui; Xu, Youyun; Ma, Wenfeng; Xie, Wei; Zhang, Dongmei

2013-12-01

463

Blade frequency program for nonuniform helicopter rotors, with automated frequency search  

NASA Technical Reports Server (NTRS)

A computer program for determining the natural frequencies and normal modes of a lumped parameter model of a rotating, twisted beam, with nonuniform mass and elastic properties was developed. The program is used to solve the conditions existing in a helicopter rotor where the outboard end of the rotor has zero forces and moments. Three frequency search methods have been implemented. Including an automatic search technique, which allows the program to find up to the fifteen lowest natural frequencies without the necessity for input estimates of these frequencies.

Sadler, S. G.

1972-01-01

464

Multi-frequency axial transmission bone ultrasonometer.  

PubMed

The last decade has seen a surge in the development of axial transmission QUS (Quantitative UltraSound) technologies for the assessment of long bones using various modes of acoustic waves. The condition of cortical bones and the development of osteoporosis are determined by numerous mechanical, micro-structural, and geometrical or macro-structural bone properties like hardness, porosity and cortical thickness. Such complex manifestations of osteoporosis require the evaluation of multiple parameters with different sensitivities to the various properties of bone that are affected by the disease. This objective may be achieved by using a multi-frequency ultrasonic examination The ratio of the acoustic wavelength to the cortical thickness can be changed by varying the frequency of the ultrasonic pulse propagating through the long bone that results in the change in composition of the induced wave comprised of a set of numerous modes of guided, longitudinal, and surface acoustic waves. The multi-frequency axial transmission QUS method developed at Artann Laboratories (Trenton, NJ) is implemented in the Bone Ultrasonic Scanner (BUSS). In the current version of the BUSS, a train of ultrasonic pulses with 60, 100, 400, 800, and 1200 kHz frequencies is used. The developed technology was tested on a variety of bone phantoms simulating normal, osteopenic, and osteoporotic bones. The results of this study confirm the feasibility of the multi-frequency approach for the assessment of the processes leading to osteoporosis. PMID:24206675

Tatarinov, Alexey; Egorov, Vladimir; Sarvazyan, Noune; Sarvazyan, Armen

2014-07-01

465

Frequency-agile wireless sensor networks  

NASA Astrophysics Data System (ADS)

Our goal was to demonstrate a wireless communications system capable of simultaneous, high speed data communications from a variety of sensors. We have previously reported on the design and application of 2 KHz data logging transceiver nodes, however, only one node may stream data at a time, since all nodes on the network use the same communications frequency. To overcome these limitations, second generation data logging transceivers were developed with software programmable radio frequency (RF) communications. Each node contains on-board memory (2 Mbytes), sensor excitation, instrumentation amplifiers with programmable gains & offsets, multiplexer, 16 bit A/D converter, microcontroller, and frequency agile, bi-directional, frequency shift keyed (FSK) RF serial data link. These systems are capable of continuous data transmission from 26 distinct nodes (902-928 MHz band, 75 kbaud). The system was demonstrated in a compelling structural monitoring application. The National Parks Service requested a means for continual monitoring and recording of sensor data from the Liberty Bell during a move to a new location (Philadelphia, October 2003). Three distinct, frequency agile, wireless sensing nodes were used to detect visible crack shear/opening micromotions, triaxial accelerations, and hairline crack tip strains. The wireless sensors proved to be useful in protecting the Liberty Bell.

Arms, Steven W.; Townsend, Christopher P.; Churchill, David L.; Hamel, Michael J.; Galbreath, Jacob H.; Mundell, Steven W.

2004-07-01

466

Low Frequency Interstellar Scattering and Pulsar Observations  

NASA Technical Reports Server (NTRS)

Radio astronomy at frequencies from 2 to 30 MHz challenges time tested methods for extracting usable information from observations. One fundamental reason for this is that propagation effects due to the magnetoionic ionosphere, interplanetary medium, and interstellar matter (ISM) increase strongly with wavelength. The problems associated with interstellar scattering off of small scale irregularities in the electron density are addressed. What is known about interstellar scattering is summarized on the basis of high frequency observations, including scintillation and temporal broadening of pulsars and angular broadening of various galactic and extragalactic radio sources. Then those high frequency phenomena are addressed that are important or detectable at low frequencies. The radio sky becomes much simpler at low frequencies, most pulsars will not be seen as time varying sources, intensity variations will be quenched or will occur on time scales much longer than a human lifetime, and many sources will be angularly broadened and/or absorbed into the noise. Angular broadening measurements will help delineate the galactic distribution and power spectrum of small scale electron density irregularities.

Cordes, James M.

1992-01-01

467

Absolute frequency measurement of the iodine-stabilized Ar+ at 514.6 nm using a femtosecond optical frequency comb.  

E-print Network

Absolute frequency measurement of the iodine-stabilized Ar+ laser at 514.6 nm using a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) k frequency comb transfer oscillator. Secondary laser frequency references based on iodine absorption lines

Boyer, Edmond

468

High-performance iodine fiber frequency standard.  

PubMed

We have constructed a compact and robust optical frequency standard based around iodine vapor loaded into the core of a hollow-core photonic crystal fiber (HC-PCF). A 532 nm laser was frequency locked to one hyperfine component of the R(56) 32-0 (127)I(2) transition using modulation transfer spectroscopy. The stabilized laser demonstrated a frequency stability of 2.3×10(-12) at 1 s, almost an order of magnitude better than previously reported for a laser stabilized to a gas-filled HC-PCF. This limit is set by the shot noise in the detection system. We present a discussion of the current limitations to the performance and a route to improve the performance by more than an order of magnitude. PMID:22179880

Lurie, Anna; Baynes, Fred N; Anstie, James D; Light, Philip S; Benabid, Fetah; Stace, Thomas M; Luiten, Andre N

2011-12-15

469

A novel frequency-scanned reflector antenna  

NASA Astrophysics Data System (ADS)

Theoretical and experimental results are presented for a frequency-scanned antenna composed of a line source and a frequency-scanned reflection grating that is shaped to a cylindrical reflector. The principle considered is to select the grating geometry such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. An analytical solution for the cylindrical reflector geometry that gives a line focus is given. The grating structure considered consists of an array of dipoles placed over a ground plane. The design of the dipole grating for optimum blazing (i.e., for optimal power conversion from the incident wave to the diffracted wave) is discussed. For the theoretical analysis Floquet's theorem and the method of moments are used.

Johansson, F. Stefan; Josefsson, Lars G.; Lorentzon, Torlid

1989-08-01

470

Low-frequency radio navigation system  

NASA Technical Reports Server (NTRS)

A method of continuous wave navigation using four transmitters operating at sufficiently low frequencies to assure essentially pure groundwave operation is described. The transmitters are keyed to transmit constant bursts (1/4 sec) in a time-multiplexed pattern with phase modulation of at least one transmitter for identification of the transmitters and with the ability to identify the absolute phase of the modulated transmitter and the ability to modulate low rate data for transmission. The transmitters are optimally positioned to provide groundwave coverage over a service region of about 50 by 50 km for the frequencies selected in the range of 200 to 500 kHz, but their locations are not critical because of the beneficial effect of overdetermination of position of a receiver made possible by the fourth transmitter. Four frequencies are used, at least two of which are selected to provide optimal resolution. All transmitters are synchronized to an average phase as received by a monitor receiver.

Wallis, D. E. (inventor)

1983-01-01

471

Proton Assisted Recoupling at High Spinning Frequencies  

PubMed Central

We demonstrate the successful application of 13C-13C proton assisted recoupling (PAR) on [U-13C,15N] N-ƒ-MLF-OH and [U-13C,15N] protein GB1 at high magic angle spinning (MAS) frequencies (?r/2?=65 kHz). Specifically, by combining PAR mixing with low power heteronuclear decoupling (?1H/2?~16 kHz) and high spinning frequencies, we obtain high resolution 2D spectra displaying long range 13C-13C contacts from which distances can be extracted. These experiments therefore demonstrate the possibility of performing high resolution structural studies in the limit of high spinning frequency and low power 1H decoupling, a regime which optimizes resolution of protein samples and preserves their integrity. PMID:19489532

Lewandowski, Jozef R.; De Paepe, Gael; Eddy, Matthew T.; Struppe, Jochem; Maas, Werner; Griffin, Robert G.

2009-01-01

472

Anomalous frequency shifts in the solar system  

E-print Network

The improvements of the observations of the solar system allowed by the use of probes and big instruments let appear several problems: The frequencies of the radio signals received from the probes sent over 5 UA from the Sun are too high; the explanation by spicules or siphon-flows of the frequency shifts of UV emissions observed on the surface of the sun by SOHO is not satisfactory; the anisotropy of the CMB seems bound to the ecliptic. This problems are solved using a coherent optical effect, deduced from standard spectroscopy and easily observed with lasers. In a gas containing atomic hydrogen in states 2S and (or) 2P, transfers of energy between light beams, allowed by thermodynamics, produce the required frequency shifts or amplifications.

Jacques Moret-Bailly

2005-07-19

473

Frequency Scanned Interferometry for ILC Tracker Alignment  

E-print Network

In this paper, we report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. High-finesse Fabry-Perot interferometers were used to determine frequency changes during scanning. A dual-laser scanning technique was used to cancel drift errors to improve the absolute distance measurement precision. A new dual-channel FSI demonstration system is also presented which is an interim stage toward practical application of multi-channel distance measurement. Under realistic conditions, a precision of 0.3 microns was achieved for an absolute distance of 0.57 meters. A possible optical alignment system for a silicon tracker is also presented.

Hai-Jun Yang; Tianxiang Chen; Keith Riles

2011-09-12

474

Frequency dependence of the Chiral Vortical Effect  

NASA Astrophysics Data System (ADS)

We study the frequency dependence of all the chiral vortical and magnetic conductivities for a relativistic gas of free chiral fermions and for a strongly coupled conformal field theory with holographic dual in four dimensions. Both systems have gauge and gravitational anomalies, and we compute their contribution to the conductivities. The chiral vortical conductivities and the chiral magnetic conductivity in the energy current show a frequency dependence in the form of a delta centered at zero frequency. This highly discontinuous behavior is a natural consequence of the Ward identities that include the energy momentum tensor. We discuss the physical interpretation of this result and its possible implications for the quark gluon plasma as created in heavy ion collisions. In the Appendix we discuss why the chiral magnetic effect seems to vanish in the consistent current for a particular implementation of the axial chemical potential.

Landsteiner, Karl; Megías, Eugenio; Peña-Benítez, Francisco

2014-09-01

475

Frequency dependence of the Chiral Vortical Effect  

E-print Network

We study the frequency dependence of all the chiral vortical and magnetic conductivities for a relativistic gas of free chiral fermions and for a strongly coupled conformal field theory with holographic dual in four dimensions. Both systems have gauge and gravitational anomalies, and we compute their contribution to the conductivities. The chiral vortical conductivities and the chiral magnetic conductivity in the energy current show a frequency dependence in the form of a delta centered at zero frequency. This highly discontinuous behavior is a natural consequence of the Ward identities that include the energy momentum tensor. We discuss the physical interpretation of this result and its possible implications for the quark gluon plasma as created in heavy ion collisions. In the Appendix we discuss why the chiral magnetic effect seems to vanish in the consistent current for a particular implementation of the axial chemical potential.

Karl Landsteiner; Eugenio Megias; Francisco Peña Benítez

2013-12-04

476

Frequency domain state-space system identification  

NASA Technical Reports Server (NTRS)

An algorithm for identifying state-space models from frequency response data of linear systems is presented. A matrix-fraction description of the transfer function is employed to curve-fit the frequency response data, using the least-squares method. The parameters of the matrix-fraction representation are then used to construct the Markov parameters of the system. Finally, state-space models are obtained through the Eigensystem Realization Algorithm using Markov parameters. The main advantage of this approach is that the curve-fitting and the Markov parameter construction are linear problems which avoid the difficulties of nonlinear optimization of other approaches. Another advantage is that it avoids windowing distortions associated with other frequency domain methods.

Chen, Chung-Wen; Juang, Jer-Nan; Lee, Gordon

1992-01-01

477

Landslide frequency analysis in Wushe reservoir drainage  

NASA Astrophysics Data System (ADS)

The purpose of landslide hazard analysis is that predicts where, how frequently, and how large. In other words, it requires spatial probability and temporal probability. Many researches estimate spatial probability in landslide susceptibility. In temporal domain, two different approaches are used to assess the landslide frequency. One is computing the probability of failure of a slope. The other is performing in the way similar to the hydrology analysis, and the frequency of past landslide events is obtained. This study collects ten landslide inventories which cover 16 years in Wushe reservoir drainage. We assume that occurrence of landslide are randomly and independently, and the poisson distribution be used to assess the annual probability of occurrence of landslide. Finally, it is obtained the relation between frequency and magnitude.

Huang, Chuen-Ming; Lee, Ching-Fang; Lau, Der-Wei; Lee, Chyi-Tyi; Wu, Ching-Miin; Wu, Ming-Hung

2013-04-01

478

Frequency Doubling Broadband Light in Multiple Crystals  

SciTech Connect

The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth.

ALFORD,WILLIAM J.; SMITH,ARLEE V.

2000-07-26

479

47 CFR 80.393 - Frequencies for AIS stations.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Frequencies for AIS stations. 80.393 Section 80.393 Telecommunication FEDERAL COMMUNICATIONS COMMISSION...MARITIME SERVICES Frequencies Ais Stations § 80.393 Frequencies for AIS stations....

2010-10-01

480

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Frequency and wavelength bands. 2.101 Section 2.101 Telecommunication ...and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

2010-10-01

481

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Frequency and wavelength bands. 2.101 Section 2.101 Telecommunication ...and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

2011-10-01

482

47 CFR 80.387 - Frequencies for Alaska fixed stations.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Frequencies for Alaska fixed stations. 80.387 Section 80...STATIONS IN THE MARITIME SERVICES Frequencies Alaska Fixed Stations § 80.387 Frequencies for Alaska fixed stations. (a) The...

2013-10-01

483

47 CFR 80.387 - Frequencies for Alaska fixed stations.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Frequencies for Alaska fixed stations. 80.387 Section 80...STATIONS IN THE MARITIME SERVICES Frequencies Alaska Fixed Stations § 80.387 Frequencies for Alaska fixed stations. (a) The...

2011-10-01

484

47 CFR 80.387 - Frequencies for Alaska fixed stations.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Frequencies for Alaska fixed stations. 80.387 Section 80...STATIONS IN THE MARITIME SERVICES Frequencies Alaska Fixed Stations § 80.387 Frequencies for Alaska fixed stations. (a) The...

2012-10-01

485

47 CFR 80.387 - Frequencies for Alaska fixed stations.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Frequencies for Alaska fixed stations. 80.387 Section 80...STATIONS IN THE MARITIME SERVICES Frequencies Alaska Fixed Stations § 80.387 Frequencies for Alaska fixed stations. (a) The...

2010-10-01

486

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2013-10-01

487

47 CFR 80.389 - Frequencies for maritime support stations.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies for maritime support stations. 80... STATIONS IN THE MARITIME SERVICES Frequencies Maritime Support Stations § 80.389 Frequencies for maritime support stations....

2011-10-01

488

29 CFR 452.23 - Frequency of elections.  

...2014-07-01 2014-07-01 false Frequency of elections. 452.23 Section 452...LABOR-MANAGEMENT REPORTING AND DISCLOSURE ACT OF 1959 Frequency and Kinds of Elections § 452.23 Frequency of elections. The Act requires...

2014-07-01

489

47 CFR 80.391 - Frequencies for developmental stations.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies for developmental stations. 80.391... STATIONS IN THE MARITIME SERVICES Frequencies Developmental Stations § 80.391 Frequencies for developmental stations....

2012-10-01

490

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2012-10-01

491

14 CFR 398.5 - Frequency of flights.  

...2014-01-01 2014-01-01 false Frequency of flights. 398.5 Section 398...ESSENTIAL AIR SERVICE § 398.5 Frequency of flights. (a) Except in Alaska...be established with required flight frequencies changing...

2014-01-01

492

47 CFR 15.202 - Certified operating frequency range.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Certified operating frequency range. 15.202 Section 15...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices...

2011-10-01

493

47 CFR 80.381 - Frequencies for operational fixed stations.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies for operational fixed stations. 80... STATIONS IN THE MARITIME SERVICES Frequencies Operational Fixed Stations § 80.381 Frequencies for operational fixed stations....

2011-10-01

494

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2010-10-01

495

47 CFR 80.381 - Frequencies for operational fixed stations.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies for operational fixed stations. 80... STATIONS IN THE MARITIME SERVICES Frequencies Operational Fixed Stations § 80.381 Frequencies for operational fixed stations....

2012-10-01

496

47 CFR 15.202 - Certified operating frequency range.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Certified operating frequency range. 15.202 Section 15...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices...

2013-10-01

497

47 CFR 90.175 - Frequency coordinator requirements.  

Code of Federal Regulations, 2013 CFR

...5 2013-10-01 2013-10-01 false Frequency coordinator requirements. 90.175 Section...SERVICES Policies Governing the Assignment of Frequencies § 90.175 Frequency coordinator requirements. Except for...

2013-10-01

498

47 CFR 15.202 - Certified operating frequency range.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Certified operating frequency range. 15.202 Section 15...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices...

2010-10-01

499