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Sample records for frequency shift keying

  1. Frequency shift keying by current modulation in a MTJ-based STNO with high data rate

    Science.gov (United States)

    Ruiz-Calaforra, A.; Purbawati, A.; Brächer, T.; Hem, J.; Murapaka, C.; Jiménez, E.; Mauri, D.; Zeltser, A.; Katine, J. A.; Cyrille, M.-C.; Buda-Prejbeanu, L. D.; Ebels, U.

    2017-08-01

    Spin torque nano-oscillators are nanoscopic microwave frequency generators which excel due to their large frequency tuning range and agility for amplitude and frequency modulation. Due to their compactness, they are regarded as suitable candidates for applications in wireless communications, where cost-effective and complementary metal-oxide semiconductor-compatible standalone devices are required. In this work, we study the ability of a magnetic-tunnel-junction based spin torque nano-oscillator to respond to a binary input sequence encoded in a square-shaped current pulse for its application as a frequency-shift-keying (FSK) based emitter. We demonstrate that below the limit imposed by the spin torque nano-oscillator intrinsic relaxation frequency, an agile variation between discrete oscillator states is possible. For this kind of devices, we demonstrate FSK up to data rates of 400 Mbps, which is well suited for the application of such oscillators in wireless networks.

  2. BLIND CHANNEL ESTIMATION OF SPACE-TIME FREQUENCY-SHIFT KEYING

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The decoupled coherent Maximum Likelihood (ML) detection algorithm presented in this lettercan sharply reduce the complexity of the receiver as well as provide better error performance under the pre-condition that channel should be estimated first. Considering the bandwidth inefficiency of Frequency ShiftKeying (FSK), the acquisition of channel state information through training sequences will further decreasethe transmission efficiency. This letter presents a blind channel estimation algorithm based on noise subspacetheory which can acquire channel information without any training symbols. The simulation shows that thealgorithm brings about fewer channel estimation errors while the frequency efficiency can be increased.

  3. Multiple symbols soft-decision metrics for coded frequency-shift keying signals

    Institute of Scientific and Technical Information of China (English)

    MA Zheng; PERSSON Danie; LARSSON Erik G.; FAN PingZhi

    2013-01-01

    This paper derives a novel multiple symbols soft-decision metrics for frequency-shift keying signals which are affected by additive symmetric α -stable (S α S) noise and fading. The approximate metric, which is for the case where channel state information (phases, amplitudes, and noise dispersion parameter) is unknown is obtained based on a generalized-likelihood ratio (GLR) approach. The metric is obtained in closed form and proved to be effective. The performances of the multiple symbols soft-decision metrics are compared numerically for a turbo-coded system. The proposed multiple symbols metric provides substantial improvement over earlier single-symbol metrics.

  4. An ultraviolet laser communication system using frequency-shift keying modulation scheme

    Science.gov (United States)

    Peng, Di-yong; Shi, Jun; Peng, Guang-hui; Xiao, Sha-li; Xu, Shan-he; Wang, Shan; Liu, Feng

    2015-01-01

    A communication system based on an ultraviolet (UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying (FSK) modulation scheme is studied and improved in order to reduce the bit error rate (BER), and is put into practice on a field programmable gate array (FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10-7 at distance of 300 m in line-of-sight (LOS) communication model and to be less than 10-6 at distance of 80 m in non-line-of-sight (NLOS) communication model.

  5. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

    Directory of Open Access Journals (Sweden)

    Laurent Segers

    2015-07-01

    Full Text Available This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.

  6. A design for LED's frequency shift keying drive circuit%LED移频键控信号驱动电路的设计

    Institute of Scientific and Technical Information of China (English)

    李绍铭; 刘晓东

    2012-01-01

    提出了一种新的推挽功率管驱动信号的死区加入方法,并结合负压电荷泵理论设计了一种通过移频键控控制信号实现LED准恒流调节的方法。该方法可以实现对电流的线性调节,满足中小功率LED对于能量利用效率和延长使用寿命的要求。%This paper proposes a new kind of method to insert dead time to the signals which control the push-pull tube. Combining with the charge pump theory and frequency shift keying, a new method to realize LED constant-current drive is designed. The circuit can realize nonlinear control to the current efficiently without the feedback branch. The circuit can realize linear control to the current. So it can meet the requirements that energy should be used efficiently and that the LED's using life should be extended effectively.

  7. Frequency shifts in gravitational resonance spectroscopy

    CERN Document Server

    Baeßler, S; Pignol, G; Protasov, K V; Rebreyend, D; Kupriyanova, E A; Voronin, A Yu

    2015-01-01

    Quantum states of ultracold neutrons in the gravitational field are to be characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts, which we call Stern-Gerlach shift, interference shift, and spectator state shift, appear in conceivable measurement schemes and have general importance. These shifts have to be taken into account in precision experiments.

  8. Hippocampal theta frequency shifts and operant behaviour

    NARCIS (Netherlands)

    Lopes da Silva, F.H.; Kamp, A.

    1. 1. A shift of hippocampal dominant theta frequency to 6 c/sec has been demonstrated in the post-reward period in two dogs, which occurs consistently related in time to a well defined behavioural pattern in the course of an operant conditioning paradigm. 2. 2. The frequency shift was detected and

  9. Hippocampal frequency shifts in different behavioural situations

    NARCIS (Netherlands)

    Kamp, A.; Lopes da Silva, F.H.; Storm van Leeuwen, W.

    1971-01-01

    Electrical activity of the dog's hippocampus was recorded in (a) an operant behaviour situation, and (b) a field situation by a radio-telemetering system. The dominant frequency of the theta rhythm shifted consistently from 4–5 c/sec to 6–7 c/sec when a dog (a) withdrew from a pedal after being rewa

  10. On the frequency shift of gravitational waves

    CERN Document Server

    De Sousa, C M G

    2002-01-01

    Considering plane gravitational waves propagating through flat spacetime, it is shown that curvatures experienced both in the starting point and during their arrival at the earth can cause a considerable shift in the frequencies as measured by earth and space-based detectors.

  11. Damage detection using frequency shift path

    Science.gov (United States)

    Wang, Longqi; Lie, Seng Tjhen; Zhang, Yao

    2016-01-01

    This paper introduces a novel concept called FREquency Shift (FRESH) path to describe the dynamic behavior of structures with auxiliary mass. FRESH path combines the effects of frequency shifting and amplitude changing into one space curve, providing a tool for analyzing structure health status and properties. A damage index called FRESH curvature is then proposed to detect local stiffness reduction. FRESH curvature can be easily adapted for a particular problem since the sensitivity of the index can be adjusted by changing auxiliary mass or excitation power. An algorithm is proposed to adjust automatically the contribution from frequency and amplitude in the method. Because the extraction of FRESH path requires highly accurate frequency and amplitude estimators; therefore, a procedure based on discrete time Fourier transform is introduced to extract accurate frequency and amplitude with the time complexity of O (n log n), which is verified by simulation signals. Moreover, numerical examples with different damage sizes, severities and damping are presented to demonstrate the validity of the proposed damage index. In addition, applications of FRESH path on two steel beams with different damages are presented and the results show that the proposed method is valid and computational efficient.

  12. Precoded generalized space shift keying for indoor visible light communications

    KAUST Repository

    Kadampot, Ishaque Ashar

    2014-09-01

    We consider a visible light communication system with 2 transmit light emitting diodes (LED) and nr receive photodiodes. An optical generalized space shift keying modulation scheme is considered for the transmission of bits where each LED can be either in ON state or OFF state at a given time. With this set-up, we design in this paper a precoder for this modulation scheme given the channel state information to improve the bit error rate performance of the system. As conventional precoding techniques for radio frequency at the transmitter cannot be applied to the optical intensity channel, we formulate an optimization problem with constraints for this specific channel. An analytical solution for the precoder is derived and the system performance is compared with and without precoder.

  13. Quantum Key Distribution Network Based on Differential Phase Shift

    Institute of Scientific and Technical Information of China (English)

    WANG Wan-Ying; WANG Chuan; WEN Kai; LONG Gui-Lu

    2007-01-01

    Using a series of quantum correlated photon pairs, we propose a theoretical scheme for any-to-any multi-user quantum key distribution network based on differential phase shift. The differential phase shift and the different detection time slots ensure the security of our scheme against eavesdropping. We discuss the security under the intercept-resend attack and the source replacement attack.

  14. Cyclotron mode frequency shifts in multi-species ion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Affolter, M.; Anderegg, F.; Dubin, D.H.E.; Driscoll, C.F.

    2014-06-27

    In trapped plasmas, electric fields and collective effects shift the cyclotron mode frequencies away from the “bare” cyclotron frequency for each species s. Here, these shifts are measured on a set of cyclotron modes (m=0,1, and 2) with cos(mθ) azimuthal dependence in near rigid-rotor multi-species ion plasmas. We observe that these frequency shifts are dependent on the plasma density, through the E×B rotation frequency f{sub E}, and on the “local” charge concentration δ{sub s} of species s, in close agreement with theory. - Highlights: • Cyclotron modes varying as sin(mθ) with m=0,1and2 are detected. • These mode frequencies shift by factors of the ExB rotation frequency. • These frequency shifts depend on the species charge fraction and radial distribution. • Centrifugal separation of species can greatly modify these frequency shifts.

  15. Auto-compensating differential phase shift quantum key distribution

    CERN Document Server

    Han, X; Zhou, C; Zeng, H; Han, Xiaohong; Wu, Guang; Zhou, Chunyuan; Zeng, Heping

    2005-01-01

    We propose an auto-compensating differential phase shift scheme for quantum key distribution with a high key-creation efficiency, which skillfully makes use of automatic alignment of the photon polarization states in optical fiber with modified Michelson interferometers composed of unequal arms with Faraday mirrors at the ends. The Faraday-mirrors-based Michelson interferometers not only function as pulse splitters, but also enable inherent compensation of polarization mode dispersion in the optic-fiber paths at both Alice's and Bob's sites. The sequential pulses encoded by differential phase shifts pass through the quantum channel with the same polarization states, resulting in a stable key distribution immune to the polarization mode dispersion in the quantum channel. Such a system features perfect stability and higher key creation efficiency over traditional schemes.

  16. Frequency-coded quantum key distribution.

    Science.gov (United States)

    Bloch, Matthieu; McLaughlin, Steven W; Merolla, Jean-Marc; Patois, Frédéric

    2007-02-01

    We report an intrinsically stable quantum key distribution scheme based on genuine frequency-coded quantum states. The qubits are efficiently processed without fiber interferometers by fully exploiting the nonlinear interaction occurring in electro-optic phase modulators. The system requires only integrated off-the-shelf devices and could be used with a true single-photon source. Preliminary experiments have been performed with weak laser pulses and have demonstrated the feasibility of this new setup.

  17. Phase shifting in the spatial frequency domain

    Science.gov (United States)

    Yazdani, Roghayeh; Petsch, Sebastian; Fallah, Hamidreza; Hajimahmoodzadeh, Morteza; Zappe, Hans

    2016-03-01

    We present a simple mathematical method for phase shifting that overcomes some phase shift errors and limitations of commonly used methods. The method is used to generate a sequence of phase-shifted interferograms from a single interferogram. The generated interferograms are employed to reconstruct the wavefront aberrations, as an application. The approach yields results with only very small deviations compared to both simulated wavefront aberrations, including the first 25 Zernike polynomials (0.05%) and those measured with a Shack-Hartmann sensor (0.5%).

  18. Improvement of Amplitude-Shift-Keying Signal Quality by Employing an Effective Spectrum Equalization Method in a Combined FSK/ASK Modulation Scheme

    Institute of Scientific and Technical Information of China (English)

    XIN Xiang-Jun; P. S. André; A. L. J. Teixeira; YU Chong-Xiu; Ana Ferreira; Tiago Silveira; P. M. Monteiro; F. da Rocha; J. L. Pinto

    2005-01-01

    @@ A simple, economical and applicable spectrum equalization method is implemented by employing a reshaping filter in the combined frequency-shift-keying/amplitude-shift-keying modulation scheme to improve the quality of amplitude-shift-keying optical signal. The 3-dB improvement for eye diagram height is experimentally demonstrated.

  19. Atomic frequency standard relativistic Doppler shift experiment

    Science.gov (United States)

    Peters, H. E.; Reinhardt, V. S.

    1974-01-01

    An experiment has been performed to measure possible space anisotropy as it would effect the frequency of a cesium atomic beam standard clock in a laboratory on earth due to motion relative to external coordinate frames. The cesium frequency was measured as a function of orientation with respect to an atomic hydrogen maser standard. Over a period of 34 days 101 measurements were made. The results are consistent with a conclusion that no general orientation dependance attributable to spacial anisotropy was observed. It is shown that both the airplane clock results, and the null results for the atomic beam clock, are consistent with Einstein general or special relativity, or with the Lorentz transformations alone.

  20. Laser frequency stabilization and shifting by using modulation transfer spectroscopy

    Science.gov (United States)

    Cheng, Bing; Wang, Zhao-Ying; Wu, Bin; Xu, Ao-Peng; Wang, Qi-Yu; Xu, Yun-Fei; Lin, Qiang

    2014-10-01

    The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 → F' = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro—optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.

  1. Optimization of Key Parameters in 622-Mb/s Amplitude Shift Keying Labeled 40-Gb/s Return to Zero Differential Phase Shift Keying Optical Switching Network

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun-yan; XIN Xiang-jun; YU Chong-xiu; XU Da-xiong

    2008-01-01

    Optimized are the label extinction ratio and dispersion compensation of an optical label switching transmission system, which employs 40-Gb/s return to zero differential phase shift keying(RZ-DPSK) payload labeled with 622-Mb/s amplitude shift keying(ASK) control data. In our scheme, the receiver sensitivities of payload and label achieves -27.8 dBm and -33.5 dBm, respectively. After transmitted over 40 km, 60 km and 80 km single mode fiber(SMF)(with dispersion compensation) respectively, the payload can be recovered with no power penalty, while the label can be recovered with less than 2 dB penalty.

  2. The frequency crossover for the Goos-Hanchen shift

    OpenAIRE

    Araujo, Manoel; Carvalho, Silvania; De Leo, Stefano

    2014-01-01

    For total reflection, the Goos-Hanchen (GH) shift is proportional to the wavelength of the laser beam. At critical angles, such a shift is instead proportional to the square root of the product of the beam waist and wavelength. By using the stationary phase method (SPM) and, when necessary, numerical calculations, we present a detailed analysis of the frequency crossover for the GH shift. The study, done in different incidence regions, sheds new light on the validity of the analytic formulas ...

  3. Comment on "Frequency shifts in NIST Cs primary frequency standards due to transverse rf field gradients"

    CERN Document Server

    Gibble, Kurt

    2015-01-01

    We discuss the theoretical treatment of the microwave lensing frequency shift of the NIST-F1 and F2 atomic fountain clocks by Ashby et al. [Phy. Rev. A. 91, 033624 (2015)]. The shifts calculated by NIST are much smaller than the previously evaluated microwave lensing frequency shifts of other clocks contributing to International Atomic Time. We identify several fundamental problems in the NIST treatment and demonstrate that each significantly affects their results. We also show a smooth transition of microwave lensing frequency shifts to the photon recoil shift for large wave packets.

  4. Frequency Constrained ShiftCP Modeling of Neuroimaging Data

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai; Madsen, Kristoffer H.

    2011-01-01

    The shift invariant multi-linear model based on the CandeComp/PARAFAC (CP) model denoted ShiftCP has proven useful for the modeling of latency changes in trial based neuroimaging data[17]. In order to facilitate component interpretation we presently extend the shiftCP model such that the extracted...... components can be constrained to pertain to predefined frequency ranges such as alpha, beta and gamma activity. To infer the number of components in the model we propose to apply automatic relevance determination by imposing priors that define the range of variation of each component of the shiftCP model...

  5. Frequency shift in high order harmonic generation from isotopic molecules

    CERN Document Server

    He, Lixin; Zhai, Chunyang; Wang, Feng; Shi, Wenjing; Zhang, Qingbin; Zhu, Xiaosong; Lu, Peixiang

    2016-01-01

    We report the first experimental observation of frequency shift in high order harmonic generation (HHG) from isotopic molecules H2 and D2 . It is found that harmonics generated from the isotopic molecules exhibit obvious spectral red shift with respect to those from Ar atom. The red shift is further demonstrated to arise from the laser-driven nuclear motion in isotopic molecules. By utilizing the red shift observed in experiment, we successfully retrieve the nuclear vibrations in H2 and D2, which agree well with the theoretical calculations from the time-dependent Schrodinger equation (TDSE) with Non-Born-Oppenheimer approximation. Moreover, we demonstrate that the frequency shift can be manipulated by changing the laser chirp.

  6. Systematic Shifts for Ytterbium-ion Optical Frequency Standards

    CERN Document Server

    Batra, N; Gupta, A Sen; Singh, Sukhjit; Arora, Amisha; Arora, Bindiya

    2014-01-01

    The projected systematic uncertainties of single trapped Ytterbium-ion optical frequency standards are estimated for the quadrupole and octupole transitions which are at wavelengths 435.5 nm and 467 nm, respectively. Finite temperature of the ion and its interaction with the external fields introduce drift in the measured frequency compared to its absolute value. Frequency shifts due to electric quadrupole moment, induced polarization and excess micromotion of the ion depend on electric fields, which are estimated in this article. Geometry of the trap electrodes also result in unwanted electric fields which have been considered in our calculation. Magnetic field induced shift and Stark shifts due to electro-magnetic radiation at a surrounding temperature are also estimated. At CSIR-NPL, we are developing a frequency standard based on the octupole transition for which the systematic uncertainties are an order of magnitude smaller than that using the quadrupole transition, as described here.

  7. Resonance frequency shift of strongly heated micro-cantilevers

    CERN Document Server

    Sandoval, Felipe Aguilar; Bertin, Éric; Bellon, Ludovic

    2015-01-01

    In optical detection setups to measure the deflection of micro-cantilevers, part of the sensing light is absorbed, heating the mechanical probe. We present experimental evidences of a frequency shift of the resonant modes of a cantilever when the light power of the optical measurement set-up is increased. This frequency shift is a signature of the temperature rise, and presents a dependence on the mode number. An analytical model is derived to take into account the temperature profile along the cantilever, it shows that the frequency shifts are given by an average of the profile weighted by the local curvature for each resonant mode. We apply this framework to measurements in vacuum and demonstrate that huge temperatures can be reached with moderate light intensities: a thousand {\\textdegree}C with little more than 10 mW. We finally present some insight into the physical phenomena when the cantilever is in air instead of vacuum.

  8. Nature of the Frequency Shift of Hydrogen Valence Vibrations

    CERN Document Server

    Zhyganiuk, I V

    2015-01-01

    The physical nature of a frequency shift of hydrogen valence vibrations in a water molecule due to its interaction with neighbor molecules has been studied. Electrostatic forces connected with the multipole moments of molecules are supposed to give a dominating contribution to the intermolecular interaction. The frequency shift was calculated in the case where two neighbor molecules form a dimer. The obtained result is in qualitative agreement with the frequency shifts observed for water vapor, hexagonal ice, and liquid water, as well as for aqueous solutions of alcohols. This fact testifies to the electrostatic nature of H-bonds used to describe both the specific features of the intermolecular interaction in water and the macroscopic properties of the latter.

  9. The frequency crossover for the Goos-Hanchen shift

    CERN Document Server

    Araujo, Manoel; De Leo, Stefano

    2014-01-01

    For total reflection, the Goos-Hanchen (GH) shift is proportional to the wavelength of the laser beam. At critical angles, such a shift is instead proportional to the square root of the product of the beam waist and wavelength. By using the stationary phase method (SPM) and, when necessary, numerical calculations, we present a detailed analysis of the frequency crossover for the GH shift. The study, done in different incidence regions, sheds new light on the validity of the analytic formulas found in literature.

  10. Frequency-Shift of a Frequency Stabilized Laser Based on Zeeman Effect

    Institute of Scientific and Technical Information of China (English)

    魏荣; 邓见辽; 钱勇; 张宇; 王育竹

    2003-01-01

    We introduce a new method of frequency-shifting for a diode laser in laser cooling experiments, the method is based on the Zeeman effect of 87Rb atoms. The laser frequency is stabilized by absorption spectrum line of atoms in magnetic field. We show that a magnetic field can be added up to 10-2T. The corresponding frequency shift is 102MHz and the response time is about 1 ms. The large range of the frequency shift is sufficient for laser-cooling experiments.

  11. Melanosome evolution indicates a key physiological shift within feathered dinosaurs.

    Science.gov (United States)

    Li, Quanguo; Clarke, Julia A; Gao, Ke-Qin; Zhou, Chang-Fu; Meng, Qingjin; Li, Daliang; D'Alba, Liliana; Shawkey, Matthew D

    2014-03-20

    Inference of colour patterning in extinct dinosaurs has been based on the relationship between the morphology of melanin-containing organelles (melanosomes) and colour in extant bird feathers. When this relationship evolved relative to the origin of feathers and other novel integumentary structures, such as hair and filamentous body covering in extinct archosaurs, has not been evaluated. Here we sample melanosomes from the integument of 181 extant amniote taxa and 13 lizard, turtle, dinosaur and pterosaur fossils from the Upper-Jurassic and Lower-Cretaceous of China. We find that in the lineage leading to birds, the observed increase in the diversity of melanosome morphologies appears abruptly, near the origin of pinnate feathers in maniraptoran dinosaurs. Similarly, mammals show an increased diversity of melanosome form compared to all ectothermic amniotes. In these two clades, mammals and maniraptoran dinosaurs including birds, melanosome form and colour are linked and colour reconstruction may be possible. By contrast, melanosomes in lizard, turtle and crocodilian skin, as well as the archosaurian filamentous body coverings (dinosaur 'protofeathers' and pterosaur 'pycnofibres'), show a limited diversity of form that is uncorrelated with colour in extant taxa. These patterns may be explained by convergent changes in the key melanocortin system of mammals and birds, which is known to affect pleiotropically both melanin-based colouration and energetic processes such as metabolic rate in vertebrates, and may therefore support a significant physiological shift in maniraptoran dinosaurs.

  12. Anomalously small BBR shift in Tl^+ frequency standard

    Science.gov (United States)

    Zuhrianda, Z.; Safronova, Marianna; Kozlov, Mikhail

    2012-06-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. In the present work, we have used configuration interaction + coupled-cluster method to evaluate polarizabilities of the 6s^2 ^1S0 and 6s6p ^3P0 states of Tl^+; α0(^1S0)=19.5 a.u. and α0(^3P0)=21.4 a.u.. We find dynamic correction to the BBR shift to be negligible. The resulting BBR shift at 300 K is δνBBR=-0.0166(17) Hz. This result demonstrates that near cancelation of the ^1S0 and ^3P0 state polarizabilities in monovalent B^+, Al^+, In^+ ions of group 13 [Safronova et al., PRL 107, 143006 (2011)] continues for much heavier Tl^+, leading to anomalously small BBR shift for this system. The corresponding relative BBR shift at 300 K is |δνBBR/ν0|=1.1(1)x10-17. This calculation demonstrates that the BBR contribution to the fractional frequency uncertainty of the Tl^+ frequency standard at 300 K is 1x10-18.

  13. Frequency-shift vs phase-shift characterization of in-liquid quartz crystal microbalance applications

    Energy Technology Data Exchange (ETDEWEB)

    Montagut, Y. J.; Garcia, J. V.; Jimenez, Y.; Arnau, A. [Grupo de Fenomenos Ondulatorios, Departamento de Ingenieria Electronica, Universitat Politecnica de Valencia (Spain); March, C.; Montoya, A. [Instituto Interuniversitario de Investigacion en Bioingenieria y Tecnologia Orientada al Ser Humano, Universitat Politecnica de Valencia (Spain)

    2011-06-15

    The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed.

  14. Frequency shifts of radiating particle moving in EIT metamaterial

    CERN Document Server

    Zielińska-Raczyńska, S

    2015-01-01

    Nowadays, there is considerable interest in metamaterials which realize the electromagnetically induced transparency in a classical system. We consider the frequency shifts of particle moving in metamaterials exhibiting electromagnetically induced transparency effect. The dramatic change of the material dispersion due to the EIT influences the conditions for signal propagation in the medium and has a significant impact on the Doppler effect, possibly leading to the optical control over this phenomenon. The dependence of the Doppler shift to the source frequency and velocity and radiation spectra on external parameters is examined. It was found that for source frequencies fitting transparency window for particular range of source velocities cutoffs appear, i.e. the radiation is not emitted. Our theoretical findings are proved analytically and confirmed by numerical simulations based on finite-difference time-domain method.

  15. Blackbody radiation shift in 87Rb frequency standard

    CERN Document Server

    Safronova, M S; Safronova, U I

    2010-01-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in 87Rb using the relativistic all-order method and carried out detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly-excited states. Our predicted value for the Stark coefficient, k_S=-1.240(4)\\times 10^{-10}\\text{Hz/(V/m)}^{2} is three times more accurate than the previous calculation [1].

  16. Blackbody radiation shift in ^87Rb frequency standard

    Science.gov (United States)

    Safronova, Marianna; Safronova, U. I.

    2010-03-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in ^87Rb using the relativistic all-order method and evaluated the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly-excited states. Various Rb atomic properties, including E1, E2, and E3 ground state polarizabilities, np and nd E1 polarizabilities, and hyperfine constants are also calculated. The results are compared with experiment and other theory where available.

  17. Noise-free quantum optical frequency shifting driven by mechanics

    CERN Document Server

    Fan, Linran; Poot, Menno; Cheng, Risheng; Guo, Xiang; Han, Xu; Tang, Hong X

    2016-01-01

    The ability to manipulate single photons is of critical importance for fundamental quantum optics studies and practical implementations of quantum communications. While extraordinary progresses have been made in controlling spatial, temporal, spin and orbit angular momentum degrees of freedom, frequency-domain control of single photons so far relies on nonlinear optical effects, which have faced obstacles such as noise photons, narrow bandwidth and demanding optical filtering. Here we demonstrate the first integrated near-unity efficiency frequency manipulation of single photons, by stretching and compressing a waveguide at 8.3 billion cycles per second. Frequency shift up to 150 GHz at telecom wavelength is realized without measurable added noise and the preservation of quantum coherence is verified through quantum interference between twin photons of different colors. This single photon frequency control approach will be invaluable for increasing the channel capacity of quantum communications and compensati...

  18. Atomic resolution in noncontact AFM by probing cantilever frequency shifts

    Institute of Scientific and Technical Information of China (English)

    Hong Yong Xie

    2007-01-01

    Rutile TiO2(001) quantum dots (or nano-marks) in different shapes were used to imitate uncleaved material surfaces or materials with rough surfaces. By numerical integration of the equation of motion of cantilever for silicon tip scanning along the [110] direction over the rutile TiO2 (001) quantum dots in ultra high vacuum (UHV), scanning routes were explored to achieve atomic resolution from frequency shift image. The tip-surface interaction forces were calculated from Lennard-Jones (12-6) potential by the Hamaker summation method. The calculated results showed that atomic resolution could be achieved by frequency shift image for TiO2 (001) surfaces of rhombohedral quantum dot scanning in a vertical route, and spherical cap quantum dot scanning in a superposition route.

  19. Tapered amplifier laser with frequency-shifted feedback

    CERN Document Server

    Bayerle, A; Vlaar, P; Pasquiou, B; Schreck, F

    2016-01-01

    We present a frequency-shifted feedback (FSF) laser based on a tapered amplifier. The laser operates as a coherent broadband source with up to 370GHz spectral width and 2.3us coherence time. If the FSF laser is seeded by a continuous-wave laser a frequency comb spanning the output spectrum appears in addition to the broadband emission. The laser has an output power of 280mW and a center wavelength of 780nm. The ease and flexibility of use of tapered amplifiers makes our FSF laser attractive for a wide range of applications, especially in metrology.

  20. Damping and Frequency Shift of Large Amplitude Electron Plasma Waves

    DEFF Research Database (Denmark)

    Thomsen, Kenneth; Juul Rasmussen, Jens

    1983-01-01

    The initial evolution of large-amplitude one-dimensional electron waves is investigated by applying a numerical simulation. The initial wave damping is found to be strongly enhanced relative to the linear damping and it increases with increasing amplitude. The temporal evolution of the nonlinear...... damping rate γ(t) shows that it increases with time within the initial phase of propagation, t≲π/ωB (ωB is the bounce frequency), whereafter it decreases and changes sign implying a regrowth of the wave. The shift in the wave frequency δω is observed to be positive for t≲π/ωB; then δω changes sign...

  1. Anomalously small blackbody radiation shift in the Tl+ frequency standard

    Science.gov (United States)

    Zuhrianda, Z.; Safronova, M. S.; Kozlov, M. G.

    2012-02-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. In the present work, we used configuration interaction + coupled-cluster method to evaluate polarizabilities of the 6s21S0 and 6s6p3P0 states of the Tl+ ion; we find α0(1S0)=19.6 a.u. and α0(3P0)=21.4 a.u. The resulting BBR shift of the 6s6p3P0-6s21S0 Tl+ transition at 300 K is ΔνBBR=-0.0157(16) Hz. This result demonstrates that near cancellation of the 1S0 and 3P0 state polarizabilities in divalent B+, Al+, and In+ ions of group IIIB [M. S. Safronova , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.143006 107, 143006 (2011)] continues for much heavier Tl+, leading to anomalously small BBR shift for this system. This calculation demonstrates that the BBR contribution to the fractional frequency uncertainty of the Tl+ frequency standard at 300 K is 1×10-18. We find that Tl+ has the smallest fractional BBR shift among all present or proposed frequency standards with the exception of Al+.

  2. Modeling of Doppler frequency shift in multipath radiochannels

    Science.gov (United States)

    Penzin, Maksim; Iyin, Nikolay

    2016-06-01

    We discuss the modeling of propagation of a quasi-monochromatic radio signal, represented by a coherent pulse sequence, in a non-stationary multipath radio channel. In such a channel, signal propagation results in the observed frequency shift for each ray (Doppler effect). The modeling is based on the assumption that during propagation of a single pulse a channel can be considered stationary. A phase change in the channel transfer function is shown to cause the observed frequency shift in the received signal. Thus, instead of measuring the Doppler frequency shift, we can measure the rate of change in the mean phase of one pulse relative to another. The modeling is carried out within the framework of the method of normal waves. The method enables us to model the dynamics of the electromagnetic field at a given point with the required accuracy. The modeling reveals that a local change in ionospheric conditions more severely affects the rays whose reflection region is in the area where the changes occur.

  3. Direct Derivation of the Gravitational Red Shift (Einstein Shift) with the frequency dependent Gall metric

    Science.gov (United States)

    Gall, Clarence A.

    1999-05-01

    When an electromagnetic radiation (EMR) source is in uniform motion with respect to an observer, a spectral (Doppler) shift in frequency is seen (blue as it approaches, red as it recedes). Since special relativity is limited to coordinate systems in uniform relative motion, this theory should be subject to this condition. On the other hand, the gravitational red shift (Einstein; Relativity: The Special and the General Theory, Crown,(1961), p.129) claims that EMR frequency decreases as the gravitational field, where the source is located, increases. As a gravitational effect, one would expect its derivation from a solution of the general relativistic field equations (R_μσ=0). Up to now, it has only been possible to derive it indirectly, by comparing the gravitational field to a (centrifugal) field produced by coordinate systems in relative rotational motion as an approximation of special relativity. Since rotation implies acceleration, it does not meet the conditions of special relativity so this is unsatisfactory. This work shows that the problem lies in the Schwarzschild metric which is independent of EMR frequency. By contrast it is easy to deduce the gravitational red shift from the frequency dependent Gall metric (Gall in AIP Conference Proceedings 308, The Evolution of X-Ray Binaries,(1993), p. 87).

  4. 60-GHz integrated-circuit high data rate quadriphase shift keying exciter and modulator

    Science.gov (United States)

    Grote, A.; Chang, K.

    1984-01-01

    An integrated-circuit quadriphase shift keying (QPSK) exciter and modulator have demonstrated excellent performance directly modulating a carrier frequency of 60 GHz with an output phase error of less than 3 degrees and maximum amplitude error of 0.5 dB. The circuit consists of a 60-GHz Gunn VCO phase-locked to a low-frequency reference source, a 4th subharmonic mixer, and a QPSK modlator packaged into a small volume of 1.8 x 2.5 x 0.35 in. The use of microstrip has the advantages of small size, light-weight, and low-cost fabrication. The unit has the potential for multigigabit data rate applications.

  5. Self-Frequency Shift of Cavity Soliton in Kerr Frequency Comb

    CERN Document Server

    Zhang, Lin; Kimerling, Lionel C; Michel, Jurgen

    2014-01-01

    We show that the ultrashort cavity soliton in octave-spanning Kerr frequency comb generation exhibits striking self-adaptiveness and robustness to external perturbations, resulting in a novel frequency shifting/cancellation mechanism and gigantic dispersive wave generation in response to the strong frequency dependence of Kerr nonlinearity, Raman scattering, chromatic dispersion, and cavity Q. These observations open up a great avenue towards versatile manipulation of nonlinear soliton dynamics, flexible spectrum engineering of mode-locked Kerr frequency combs, and highly efficient frequency translation of optical waves.

  6. Frequency shifting approach towards textual transcription of heartbeat sounds

    Directory of Open Access Journals (Sweden)

    Safar Khorasani Ehsan

    2011-10-01

    Full Text Available Abstract Auscultation is an approach for diagnosing many cardiovascular problems. Automatic analysis of heartbeat sounds and extraction of its audio features can assist physicians towards diagnosing diseases. Textual transcription allows recording a continuous heart sound stream using a text format which can be stored in very small memory in comparison with other audio formats. In addition, a text-based data allows applying indexing and searching techniques to access to the critical events. Hence, the transcribed heartbeat sounds provides useful information to monitor the behavior of a patient for the long duration of time. This paper proposes a frequency shifting method in order to improve the performance of the transcription. The main objective of this study is to transfer the heartbeat sounds to the music domain. The proposed technique is tested with 100 samples which were recorded from different heart diseases categories. The observed results show that, the proposed shifting method significantly improves the performance of the transcription.

  7. Anomalously small blackbody radiation shift in Tl+ frequency standard

    CERN Document Server

    Zuhrianda, Z; Kozlov, M G

    2012-01-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. In the present work, we used configuration interaction + coupled-cluster method to evaluate polarizabilities of the $6s^2 ^1S_0$ and $6s6p ^3P_0$ states of Tl$^+$ ion; we find $\\alpha_0(^1S_0)=19.6$ a.u. and $\\alpha_0(^3P_0)=21.4$ a.u.. The resulting BBR shift of the $6s6p ^3P_0 - 6s^2 ^1S_0$ Tl$^+$ transition at $300 K$ is $\\Delta \

  8. Frequency shifting approach towards textual transcription of heartbeat sounds.

    Science.gov (United States)

    Arvin, Farshad; Doraisamy, Shyamala; Safar Khorasani, Ehsan

    2011-10-04

    Auscultation is an approach for diagnosing many cardiovascular problems. Automatic analysis of heartbeat sounds and extraction of its audio features can assist physicians towards diagnosing diseases. Textual transcription allows recording a continuous heart sound stream using a text format which can be stored in very small memory in comparison with other audio formats. In addition, a text-based data allows applying indexing and searching techniques to access to the critical events. Hence, the transcribed heartbeat sounds provides useful information to monitor the behavior of a patient for the long duration of time. This paper proposes a frequency shifting method in order to improve the performance of the transcription. The main objective of this study is to transfer the heartbeat sounds to the music domain. The proposed technique is tested with 100 samples which were recorded from different heart diseases categories. The observed results show that, the proposed shifting method significantly improves the performance of the transcription.

  9. Blackbody radiation shift in the Rb87 frequency standard

    Science.gov (United States)

    Safronova, M. S.; Jiang, Dansha; Safronova, U. I.

    2010-08-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature, of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in Rb87 using the relativistic all-order method and carried out a detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly excited states. Our predicted value for the Stark coefficient, kS=-1.240(4)×10-10Hz/(V/m)2, is three times more accurate than the previous calculation [E. J. Angstman, V. A. Dzuba, and V. V. Flambaum, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.74.023405 74, 023405 (2006)].

  10. Raman induced soliton self-frequency shift in microresonator Kerr frequency combs

    CERN Document Server

    Karpov, Maxim; Kordts, Arne; Brasch, Victor; Pfeiffer, Martin; Zervas, Michail; Geiselmann, Michael; Kippenberg, Tobias J

    2015-01-01

    The formation of temporal dissipative solitons in continuous wave laser driven microresonators enables the generation of coherent, broadband and spectrally smooth optical frequency combs as well as femtosecond pulses with compact form factor. Here we report for the first time on the observation of a Raman-induced soliton self-frequency shift for a microresonator soliton. The Raman effect manifests itself in amorphous SiN microresonator based single soliton states by a spectrum that is hyperbolic secant in shape, but whose center is spectrally red-shifted (i.e. offset) from the continuous wave pump laser. The Raman induced spectral red-shift is found to be tunable via the pump laser detuning and grows linearly with peak power. The shift is theoretically described by the first order shock term of the material's Raman response, and we infer a Raman shock time of 20 fs for amorphous SiN. Moreover, we observe that the Raman induced frequency shift can lead to a cancellation or overcompensation of the soliton recoi...

  11. Frequency-Shift Detectors Bind Binaural as Well as Monaural Frequency Representations

    Science.gov (United States)

    Carcagno, Samuele; Semal, Catherine; Demany, Laurent

    2011-01-01

    Previous psychophysical work provided evidence for the existence of automatic frequency-shift detectors (FSDs) that establish perceptual links between successive sounds. In this study, we investigated the characteristics of the FSDs with respect to the binaural system. Listeners were presented with sound sequences consisting of a chord of pure…

  12. Acoustic hologram formation with a frequency shifted reference beam.

    Science.gov (United States)

    Whitman, R L

    1970-06-01

    This paper discusses an interference technique that makes it possible to directly observe and record the usually very weak light diffracted by an acoustical surface perturbation. This is accomplished by using spatial filtering techniques in combination with a frequency shifted reference beam. It is shown that the acoustically diffracted light may be visualized even in the presence of statically scattered light of much higher intensity. An experiment is described in which this technique is used to view the surface perturbations of piezoelectric ceramic material caused by acoustic surface waves. The application of this system to acoustic holography is discussed in detail. This application makes use of the fact that bulk acoustic waves in a material, upon striking the surface at some acute angle, cause surface ripple patterns which form a dynamic hologram of the acoustic field. A photographic image of this hologram frozen in time may then be recorded using the process discussed above.

  13. Cardiac frequency throughout a working shift in coal miners.

    Science.gov (United States)

    Montoliu, M A; Gonzalez, V; Palenciano, L

    1995-06-01

    Despite the ever-increasing mechanization of industrial activities, coal mining still remains a physically demanding occupation as it is not always possible to extensively mechanize the extraction process. To estimate the physical effort necessary to sustain coal mining activities in a poorly-mechanized mine, cardiac frequency (fc) was measured throughout the working shift with a Sport-Tester PE3000 (Polar Electro OY, Finland) in a representative sample of 73 Asturian miners engaged in a full spectrum of underground work. The mean +/- SD of the overall fc values measured in miners working at the coal face (Group 1, 33 subjects, mean age 32.7 years, age range 21-48 years) was 106.5 +/- 18.2 beats.min-1. In other miners (Group 2, 40 subjects, mean age 34.6 years, age range 23-48 years) corresponding figures were 103.1 +/- 17.7 beats.min-1 (p mechanized mines. However, average working-shift fc differs considerably from subject to subject and is largely unpredictable.

  14. Evaluation of Light Frequency Shift in a Cesium Beam Frequency Standard with Sharp Angle Incident Detecting Laser

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun-Hai; WANG Feng-Zhi; WANG Yi-Qiu; YANG Dong-Hai

    2004-01-01

    @@ Light frequency shift measured in a smalloptically pumped caesium beam frequency standard is reported and analysed. Two light sources, the diffused laser light scattered from the caesium beam tube parts and the fluorescence light from the beam atoms excited by the laser light, for the light frequency shift are discussed.

  15. Frequency shifts in NIST Cs Primary Frequency Standards due To Transverse RF Field Gradients

    CERN Document Server

    Ashby, Neil; Heavner, Thomas; Jefferts, Steven

    2014-01-01

    A single-particle Green's function (propagator) is introduced to study the detection of laser-cooled Cesium atoms in an atomic fountain due to RF ?field gradients in the Ramsey TE011 cavity. The detection results in a state-dependent loss of atoms at apertures in the physics package, resulting in a frequency bias. A model accounting only for motion in one dimension transverse to the symmetry axis of the fountain is discussed in detail and then generalized to two transverse dimensions. Results for fractional frequency shifts due to transverse field gradients are computed for NIST F-1 and F-2 Cesium fountains. The shifts are found to be negligible except in cases of higher RF power applied to the cavities.

  16. Orthogonal Frequency-Division Multiplexed Quantum Key Distribution

    Science.gov (United States)

    Bahrani, Sima; Razavi, Mohsen; Salehi, Jawad A.

    2015-12-01

    We propose orthogonal frequency division multiplexing (OFDM), as a spectrally efficient multiplexing technique, for quantum key distribution (QKD) at the core of trustednode quantum networks. Two main schemes are proposed and analyzed in detail, considering system imperfections, specifically, time misalignment issues. It turns out that while multiple service providers can share the network infrastructure using the proposed multiplexing techniques, no gain in the total secret key generation rate is obtained if one uses conventional all-optical passive OFDM decoders. To achieve a linear increase in the key rate with the number of channels, an alternative active setup for OFDM decoding is proposed, which employs an optical switch in addition to conventional passive circuits. We show that by using our proposed decoder the bandwidth utilization is considerably improved as compared to conventional wavelength division multiplexing techniques.

  17. Frequency-shift vibro-acoustic modulation driven by low-frequency broadband excitations in a bistable cantilever oscillator

    Science.gov (United States)

    He, Qingbo; Xu, Yanyan; Lu, Siliang; Shao, Yong

    2017-03-01

    This paper reports a frequency-shift vibro-acoustic modulation (VAM) effect in a bistable microcracked cantilever oscillator. Low-frequency broadband excitations induced a VAM effect with a shifted modulation frequency through involving a microcracked metal beam in a bistable oscillator model. We used nonlinear dynamics equations and principles to describe the mechanism of a bistable oscillator whose natural frequency varied as the oscillation amplitude increased. We demonstrated this frequency-shift VAM effect using a prototype bistable oscillator model designed to efficiently detect microcracks in solid materials via the VAM effect using ambient vibration excitations.

  18. The application of sample-and-hold circuits in the laser frequency-shifting

    Institute of Scientific and Technical Information of China (English)

    Shuyu Zhou; Shanyu Zhou; Yuzhu Wang

    2005-01-01

    @@ A new method of frequency-shifting for a diode laser is realized. Using a sample-and-hold circuit, the error signal can be held by the circuit during frequency shifting. It can avoid the restraint of locking or even lock-losing caused by the servo circuit when we input a step-up voltage into piezoelectric transition (PZT)to achieve laser frequency-shifting.

  19. Optical differential phase-shift keyed signal generation, transmission and detection

    Science.gov (United States)

    Lize, Yannick Keith

    When encoding information on an electromagnetic wave such as infrared light, to be transmitted through an optical fibre in telecommunication networks, any of the physical properties of light can be modulated. Light has a frequency, intensity, polarization and a phase. Until recently, optical communication systems strictly employed conventional intensity (IM) modulation signals in either non return-to-zero (NRZ) or return-to-zero (RZ) format. But a number of advanced optical modulation formats have attracted increasing attention in the last few years. One prime example is the phase-shift-keyed (PSK) family of formats which carry the information on the optical phase. Since absolute phase is not easily detected through coherent demodulation, differential encoding in which the phase of the preceding bit is used as a relative phase reference for demodulation has become a method of choice for phase modulated signals. The result in the differential-phase-shift-keyed (DPSK) formats, which carry the information in the difference in optical phase between successive bits. In this thesis by article, composed of six papers, we investigate the generation, transmission and demodulation of DPSK in optical fibre transmission systems. We propose a novel way to encode optical packets using DPSK in our investigation of the generation. We also investigate transmission effects monitoring using a novel partial-bit delay interferometer-assisted clock tone monitoring method for sensitive optical-signal-to-noise ratio (OSNR), chromatic dispersion and polarization mode dispersion monitoring. Then we look at the demodulation of DPSK, first investigating the reduced tolerances and power penalties of DPSK demodulation when more than one bit delay is used in the interferometer. We also propose an optical error correction method combining DPSK optical logic gates with electronic logic gates to improve receiver sensitivity and transmission impairment tolerances. Finally we redefine the previously

  20. Resonances in BSO with frequency shifted input beams

    DEFF Research Database (Denmark)

    Buchhave, Preben; Vasnetsov, M.; Lyuksyutov, S.

    1996-01-01

    In this publication we report experiments with a frequency modulated offset frequency, which illustrate in which situations the problem may be considered linear, and in which it may not. Surprisingly we find, that even in the region of subharmonic generation, the space-charge field of the primary...... frequencies. We also report how resonances, forced by even a weak modulation of the frequency detuning may cause the suppression of the subharmonic generation....

  1. Electrostatics determine vibrational frequency shifts in hydrogen bonded complexes.

    Science.gov (United States)

    Dey, Arghya; Mondal, Sohidul Islam; Sen, Saumik; Ghosh, Debashree; Patwari, G Naresh

    2014-12-14

    The red-shifts in the acetylenic C-H stretching vibration of C-H∙∙∙X (X = O, N) hydrogen-bonded complexes increase with an increase in the basicity of the Lewis base. Analysis of various components of stabilization energy suggests that the observed red-shifts are correlated with the electrostatic component of the stabilization energy, while the dispersion modulates the stabilization energy.

  2. Frequency Shift of Carbon-Nanotube-Based Mass Sensor Using Nonlocal Elasticity Theory

    Directory of Open Access Journals (Sweden)

    Lee Haw-Long

    2010-01-01

    Full Text Available Abstract The frequency equation of carbon-nanotube-based cantilever sensor with an attached mass is derived analytically using nonlocal elasticity theory. According to the equation, the relationship between the frequency shift of the sensor and the attached mass can be obtained. When the nonlocal effect is not taken into account, the variation of frequency shift with the attached mass on the sensor is compared with the previous study. According to this study, the result shows that the frequency shift of the sensor increases with increasing the attached mass. When the attached mass is small compared with that of the sensor, the nonlocal effect is obvious and increasing nonlocal parameter decreases the frequency shift of the sensor. In addition, when the location of the attached mass is closer to the free end, the frequency shift is more significant and that makes the sensor reveal more sensitive. When the attached mass is small, a high sensitivity is obtained.

  3. Cylindrical PVF2 film based fiber optic phase modulator - Phase shift nonlinearity and frequency response

    Science.gov (United States)

    Sudarshanam, V. S.; Claus, Richard O.

    1993-03-01

    A new cylindrical coil configuration for polyvinylidene flouride (PVF2) film based fiber optic phase modulator is studied for the frequency response and nonlinearity of phase shift at the resonance frequency. This configuration, hitherto unapproached for PVF2 film modulators, offers resonance at well defined, controllable and higher frequencies than possible for the flat-strip configuration. Two versions of this configuration are presented that differ strongly in both the resonance frequency and the phase shift nonlinearity coefficient.

  4. 16-level differential phase shift keying (D16PSK) in direct detection optical communication systems

    DEFF Research Database (Denmark)

    Sambaraju, R.; Tokle, Torger; Jensen, J.B.;

    2006-01-01

    Optical 16-level differential phase shift keying (D16PSK) carrying four bits for every symbol is proposed for direct detection optical communication systems. Transmitter and receiver schematics are presented, and the receiver sensitivity is discussed. We numerically investigate the impact...

  5. Quantum displacement receiver for M-ary phase-shift-keyed coherent states

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, Shuro [National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan and Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takeoka, Masahiro; Fujiwara, Mikio; Sasaki, Masahide [National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 (Japan); Pozza, Nicola Dalla; Assalini, Antonio [Department of Information Engineering, University of Padua, Via Gradenigo 6/B, 35131, Padova (Italy); Ema, Kazuhiro [Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2014-12-04

    We propose quantum receivers for 3- and 4-ary phase-shift-keyed (PSK) coherent state signals to overcome the standard quantum limit (SQL). Our receiver, consisting of a displacement operation and on-off detectors with or without feedforward, provides an error probability performance beyond the SQL. We show feedforward operations can tolerate the requirement for the detector specifications.

  6. Quadrature phase shift keying coherent state discrimination via a hybrid receiver

    DEFF Research Database (Denmark)

    Müller, C. R.; Castaneda, Mario A. Usuga; Wittmann, C.;

    2012-01-01

    We propose and experimentally demonstrate a near-optimal discrimination scheme for the quadrature phase shift keying (QPSK) protocol. We show in theory that the performance of our hybrid scheme is superior to the standard scheme—heterodyne detection—for all signal amplitudes and underpin the pred...

  7. High-resolution temperature sensor through measuring the frequency shift of single-frequency Erbium-doped fiber ring laser

    Science.gov (United States)

    Zhang, Haiwei; Shi, Wei; Duan, Liangcheng; Fu, Shijie; Sheng, Quan; Yao, Jianquan

    2017-02-01

    We propose a principle to achieve a high-resolution temperature sensor through measuring the central frequency shift in the single-frequency Erbium-doped fiber ring laser induced by the thermal drift via the optical heterodyne spectroscopy method. We achieve a temperature sensor with a sensitivity about 9.7 pm/°C and verify the detection accuracy through an experiment. Due to the narrow linewidth of the output singlefrequency signal and the high accuracy of the optical heterodyne spectroscopy method in measuring the frequency shift in the single-frequency ring laser, the temperature sensor can be employed to resolve a temperature drift up to 5.5×10-6 °C theoretically when the single-frequency ring laser has a linewidth of 1 kHz and 10-kHz frequency shift is achieved from the heterodyne spectra.

  8. Microwave lensing frequency shift of the PHARAO laser-cooled microgravity atomic clock

    Science.gov (United States)

    Peterman, Phillip; Gibble, Kurt; Laurent, Phillipe; Salomon, Christophe

    2016-04-01

    We evaluate the microwave lensing frequency shift of the microgravity laser-cooled caesium clock PHARAO. We find microwave lensing frequency shifts of δν/ν  =  11  ×  10-17 to 13  ×  10-17, larger than the shift of typical fountain clocks. The shift has a weak dependence on PHARAO parameters, including the atomic temperature, size of the atomic cloud, detection laser intensities, and the launch velocity. We also find the lensing frequency shift to be insensitive to selection and detection spatial inhomogeneities and the expected low-frequency vibrations. We conservatively assign a nominal microwave lensing frequency uncertainty of  ±4  ×  10-17.

  9. Experimental Passive Round-Robin Differential Phase-Shift Quantum Key Distribution

    Science.gov (United States)

    Guan, Jian-Yu; Cao, Zhu; Liu, Yang; Shen-Tu, Guo-Liang; Pelc, Jason S.; Fejer, M. M.; Peng, Cheng-Zhi; Ma, Xiongfeng; Zhang, Qiang; Pan, Jian-Wei

    2015-05-01

    In quantum key distribution (QKD), the bit error rate is used to estimate the information leakage and hence determines the amount of privacy amplification—making the final key private by shortening the key. In general, there exists a threshold of the error rate for each scheme, above which no secure key can be generated. This threshold puts a restriction on the environment noises. For example, a widely used QKD protocol, the Bennett-Brassard protocol, cannot tolerate error rates beyond 25%. A new protocol, round-robin differential phase-shifted (RRDPS) QKD, essentially removes this restriction and can in principle tolerate more environment disturbance. Here, we propose and experimentally demonstrate a passive RRDPS QKD scheme. In particular, our 500 MHz passive RRDPS QKD system is able to generate a secure key over 50 km with a bit error rate as high as 29%. This scheme should find its applications in noisy environment conditions.

  10. On the contribution of sunspots to the observed frequency shifts of solar acoustic modes

    CERN Document Server

    Santos, A R G; Avelino, P P; Chaplin, W J; Campante, T L

    2016-01-01

    Activity-related variations in the solar oscillation properties have been known for 30 years. However, the relative importance of the different contributions to the observed variations is not yet fully understood. Our goal is to estimate the relative contribution from sunspots to the observed activity-related variations in the frequencies of the acoustic modes. We use a variational principle to relate the phase differences induced by sunspots on the acoustic waves to the corresponding changes in the frequencies of the global acoustic oscillations. From the sunspot properties (area and latitude as a function of time), we are able to estimate the spot-induced frequency shifts. These are then combined with a smooth frequency shift component, associated with long-term solar-cycle variations, and the results compared with the frequency shifts derived from the Global Oscillation Network Group (GONG) data. The result of this comparison is consistent with a sunspot contribution to the observed frequency shifts of rou...

  11. A full-duplex radio-over-fiber system with differential phase-shift keying signals

    Energy Technology Data Exchange (ETDEWEB)

    He Jing; Yang Dong; Chen Lin, E-mail: hnu_jhe@hotmail.com [School of Computer and Communication, Hunan University, Changsha 410082 (China)

    2011-02-01

    We propose a full-duplex radio-over-fiber (ROF) system transmitting 2.5 Gb/s differential phase-shift keying (DPSK) signals with 40GHz optical millimeter-wave as downlink. Meanwhile it can be reused central wavelength as uplink connection for transmitting 2.5 Gb/s on-off keying (OOK) signals. The experimental and simulation results show that the downstream 2.5Gb/s DPSK data and the upstream 2.5Gb/s OOK data can transmit 40km single-mode fiber successfully.

  12. Differential-phase-shift quantum key distribution using heralded narrow-band single photons.

    Science.gov (United States)

    Liu, Chang; Zhang, Shanchao; Zhao, Luwei; Chen, Peng; Fung, C-H F; Chau, H F; Loy, M M T; Du, Shengwang

    2013-04-22

    We demonstrate the first proof of principle differential phase shift (DPS) quantum key distribution (QKD) using narrow-band heralded single photons with amplitude-phase modulations. In the 3-pulse case, we obtain a quantum bit error rate (QBER) as low as 3.06% which meets the unconditional security requirement. As we increase the pulse number up to 15, the key creation efficiency approaches 93.4%, but with a cost of increasing the QBER. Our result suggests that narrow-band single photons maybe a promising source for the DPS-QKD protocol.

  13. Simultaneous all-optical AND and NOR gates for NRZ differential phase-shift-keying signals

    DEFF Research Database (Denmark)

    Xu, Jing; Zhang, X.; Dong, J.

    2008-01-01

    A scheme for realizing all-optical logic AND and NOR gates simultaneously for nonreturn-to-zero differential phase-shift-keying signals is proposed and demonstrated based on a delayed interferometer and two semiconductor optical amplifiers. Experimental demonstration at 20 Gb/s verifies the logic...... integrity of this scheme. The final results are derived in the ON–OFF keying format with clear open eyes and extinction ratios over 10 dB. The proposed scheme can be expanded to realize arbitrary logic gate....

  14. Variable-length balanced codes for quadrature phase shift keyed systems

    Directory of Open Access Journals (Sweden)

    Xin Tu

    2015-10-01

    Full Text Available The authors outline an approach to construct capacity-approaching balanced quadrature phase shift keyed (QPSK codes. These codes ensure an equal number of different symbol values and many symbol transitions in the encoded sequence in order to assist practical demodulators to accurately recover symbol values. Their codes are comprised of instantaneously decodable variable-length codewords that exhibit excellent performance with average code rates higher than previously reported fixed-length balanced QPSK codes.

  15. Noise suppression properties of an interferometer-based regenerator for differential phase-shift keying data.

    Science.gov (United States)

    Elschner, Robert; de Melo, Alessandro Marques; Bunge, Christian-Alexander; Petermann, Klaus

    2007-01-15

    We studied the amplitude and phase noise suppression properties of an all-optical regenerator for differential phase-shift keying data. A detailed analytical investigation is performed and compared with numerical simulations for different working points. The results show that both amplitude and phase can be regenerated. However, simultaneous amplitude and phase noise suppression is possible only if the phase degradation is stronger than the amplitude degradation, for instance, due to nonlinear phase noise.

  16. Differential effects of frequency shifted feedback between child and adult stutterers.

    Science.gov (United States)

    Howell, Peter; Sackin, Stevie; Williams, Roberta

    1999-01-01

    It has been reported previously that presentation of an altered form of the voice enhances the fluency of people who stutter. One of these forms of alteration is frequency shifted feedback. The effects of frequency shifted feedback was compared between two speaker groups that differed in age. The fluency enhancing effects of frequency shifted feedback was greater for adult speakers (mean age 21;3) than for children (mean age 9;11). The results are discussed in terms of their implications for theory and treatment.

  17. Labile cochlear tuning in the mustached bat. I. Concomitant shifts in biosonar emission frequency.

    Science.gov (United States)

    Huffman, R F; Henson, O W

    1993-01-01

    The cochlea of the mustached bat (Pteronotus parnellii) has sharp tuning characteristics and pronounced resonance within a narrow band near the second harmonic, constant frequency (CF2) component of the animal's biosonar signals. That fine frequency discrimination occurs within this narrow band is evident from Doppler-shift compensation, whereby bats in flight lower the frequency of emitted CF2s to maintain returning echoes within this band. This study examined various factors capable of producing shifts in both the cochlear resonance frequency (CRF) and CF2s emitted by stationary bats and bats actively Doppler-shift compensating on a pendulum. Each of three experimental factors shifted the CRF in a reversible manner. Changes in body temperature produced an average CRF shift of 39 +/- 18 Hz/degrees C. The CRF increased with flight by 150 +/- 100 Hz and returned to baseline values within 10 min after flight. Contralateral sound exposure produced smaller (100 +/- 20 Hz), rapid shifts in the CRF, suggesting that a mechanism different from the temperature- and flight-related shifts was involved. Changes in the CRF induced by temperature and flight were accompanied by shifts in the emitted CF2 of stationary and moving bats. Coupled with a companion study of associated shifts in neural tuning, the concomitant changes in CRF and CF2 provide evidence of cochlear tuning lability in the mustached bat.

  18. Frequencies Shift in Relativistic Binary System (Theoretical Study)

    Science.gov (United States)

    El Fady Morcos, Abd

    2016-07-01

    A generalized formula for Kermack, McCrea and Whittaker (KMW), has been derived by the author and et al., to study the limb effect of massive rapidly rotating stars. In this work a modified Curzon exact solution for Einstein's field equations has been used to study the variation in the frequencies of signals' carriers from a relativistic binary system. The primary star is assumed to be massive with respect to the secondary one. The center of mass is considered to be coincident to the center of rotating polar coordinate system. The rotation of the secondary star around the primary star and Earth's observer rotates with the Earth are considered in our calculation. A general theoretical formula for the variation in the frequencies of the signals' carriers from a binary system is obtained

  19. Type WYZ-97 Eighteen-information Noninsulate Frequency-shift Automatic Blocking System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Type WYZ-97 eighteen-information noninsulate frequency-shift automatic blocking system is the most advanced railroad signaling system in China nowadays.The article introduced its principles,technical targets,features and the applications.

  20. Frequency-Shift a way to Reduce Aliasing in the Complex Cepstrum

    DEFF Research Database (Denmark)

    Bysted, Tommy Kristensen

    1998-01-01

    The well-known relation between a time signal and its frequency-shifted spectrum is introduced as an excellent tool for reduction of aliasing in the complex cepstrum. Using N points DFTs the frequency-shift property, when used in the right way, will reduce the aliasing error to a size which on av...... on average is identical to the one normally requiring 2N points DFTs. The cost is an insignificant increase in the number of operations compared to the total number needed for the transformation to the complex cepstrum domain......The well-known relation between a time signal and its frequency-shifted spectrum is introduced as an excellent tool for reduction of aliasing in the complex cepstrum. Using N points DFTs the frequency-shift property, when used in the right way, will reduce the aliasing error to a size which...

  1. Multi-pulse frequency shifted (MPFS) multiple access modulation for ultra wideband

    Science.gov (United States)

    Nekoogar, Faranak [San Ramon, CA; Dowla, Farid U [Castro Valley, CA

    2012-01-24

    The multi-pulse frequency shifted technique uses mutually orthogonal short duration pulses o transmit and receive information in a UWB multiuser communication system. The multiuser system uses the same pulse shape with different frequencies for the reference and data for each user. Different users have a different pulse shape (mutually orthogonal to each other) and different transmit and reference frequencies. At the receiver, the reference pulse is frequency shifted to match the data pulse and a correlation scheme followed by a hard decision block detects the data.

  2. Influence of Two Photon Absorption on Soliton Self-Frequency Shift

    DEFF Research Database (Denmark)

    Steffensen, Henrik; Rottwitt, Karsten; Jepsen, Peter Uhd;

    2011-01-01

    The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect.......The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect....

  3. Resonance frequency shift in a cavity with a thin conducting film near a conducting wall

    Energy Technology Data Exchange (ETDEWEB)

    Braggio, C. [Dipartimento di Fisica, Universita di Ferrara and INFN, Via del Paradiso 12, 44100 Ferrara (Italy)]. E-mail: caterina.braggio@lnl.infn.it; Bressi, G. [INFN, Sezione di Pavia, Via Bassi 6, 27100 Pavia (Italy); Carugno, G. [INFN, Sezione di Padova, Via F. Marzolo 8, 35131 Padova (Italy); Dodonov, A.V. [Departamento de Fisica, Universidade Federal de Sao Carlos, Via Washington Luiz, Km 235, Sao Carlos 13565-905, SP (Brazil); Dodonov, V.V. [Instituto de Fisica, Universidade de Brasilia, Caixa Postal 04455, 70910-900 Brasilia, DF (Brazil)]. E-mail: vdodonov@fis.unb.br; Galeazzi, G. [INFN, LNL, Viale dell' Universita 2, 35020 Legnaro (Italy); Ruoso, G. [INFN, LNL, Viale dell' Universita 2, 35020 Legnaro (Italy); Zanello, D. [INFN, Sezione di Roma, Piazzale A. Moro 2, 00185 Roma (Italy)

    2007-03-19

    We show that a very thin conducting film (whose thickness can be much smaller than the skin depth), placed nearby a wall of an electromagnetic cavity, can produce the same shift of the resonance frequency as a bulk conducting slab, provided the displacement of the film from the wall is much bigger than the skin depth. We derive a simple analytical formula for the frequency shift and compare it with exact numerical calculations and experimental data.

  4. Analytical and experimental comparisons between the frequency-modulated–frequency-shift measurement and the pulsed-wave–time-shift measurement Doppler systems

    DEFF Research Database (Denmark)

    Wilhjelm, Jens Erik; Pedersen, P. C.

    1996-01-01

    In previous publications, a new echo-ranging Doppler system based on transmission of repetitive coherent frequency modulated (FM) sinusoids in two different implementations was presented. One of these implementations, the Frequency Modulated - frequency shift measurement (FM-fsm) Doppler system...... is in this paper compared with its PW counterpart, the Pulsed Wave - time shift measurement (PW-tsm) Doppler system. When using transmitted PW and FM signals with a Gaussian envelope, the parallelism between the two systems can be stated explicitly, and comparison be made between the main performance indices...... for the two Doppler systems. The performance of the FM and PW Doppler systems is evaluated by means of numerical simulation and measurements of actual flow profiles. The results indicate that the two Doppler systems have very similar levels of performance....

  5. Task shifting: A key strategy in the multipronged approach to reduce maternal mortality in India.

    Science.gov (United States)

    Bhushan, Himanshu; Bhardwaj, Ajey

    2015-10-01

    Task shifting from specialist to nonspecialist doctors (NSDs) is an important strategy that has been implemented in India to overcome the critical shortage of healthcare workers by using the human resources available to serve the vast population, particularly in rural areas. A competency-based training program in comprehensive emergency obstetric care was implemented to train and certify NSDs. Trained NSDs were able to provide key services in maternal health, which contribute toward reductions in maternal morbidity and mortality. The present article provides an overview of the maternal health challenges, shares important steps in program implementation, and shows how challenges can be overcome. The lessons learned from this experience contribute to understanding how task shifting can be used to address large-scale public health issues in low-resource countries and in particular solutions to address maternal health issues.

  6. Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave

    Science.gov (United States)

    Wen, Biyang; Li, Ke

    2016-08-01

    Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity.

  7. Vortex precession frequency and its amplitude-dependent shift in cylindrical nanomagnets

    Energy Technology Data Exchange (ETDEWEB)

    Metlov, Konstantin L., E-mail: metlov@fti.dn.ua [Donetsk Institute for Physics and Technology NAS, Donetsk 83114 (Ukraine)

    2013-12-14

    Frequency of free magnetic vortex precession in circular soft ferromagnetic nano-cylinders (magnetic dots) of various sizes is an important parameter, used in design of spintronic devices (such as spin-torque microwave nano-oscillators) and characterization of magnetic nanostructures. Here, using a recently developed collective-variable approach to non-linear dynamics of magnetic textures in planar nano-magnets, this frequency and its amplitude-dependent shift are computed analytically and plotted for the full range of cylinder geometries. The frequency shift is positive in large planar dots, but becomes negative in smaller and more elongated ones. At certain dot dimensions, a zero frequency shift is realized, which can be important for enhancing frequency stability of magnetic nano-oscillators.

  8. Optical code division multiple access secure communications systems with rapid reconfigurable polarization shift key user code

    Science.gov (United States)

    Gao, Kaiqiang; Wu, Chongqing; Sheng, Xinzhi; Shang, Chao; Liu, Lanlan; Wang, Jian

    2015-09-01

    An optical code division multiple access (OCDMA) secure communications system scheme with rapid reconfigurable polarization shift key (Pol-SK) bipolar user code is proposed and demonstrated. Compared to fix code OCDMA, by constantly changing the user code, the performance of anti-eavesdropping is greatly improved. The Pol-SK OCDMA experiment with a 10 Gchip/s user code and a 1.25 Gb/s user data of payload has been realized, which means this scheme has better tolerance and could be easily realized.

  9. A novel modulation and direct detection scheme of optical phase shift keying

    Institute of Scientific and Technical Information of China (English)

    Yongcai Yang(杨永才); Wolfgang Vogel

    2004-01-01

    This paper introduces a new modulation and direct detection scheme of optical phase shift keying (PSK)which is simple and practical in fiber optical communication. A phase modulator is used to modulate a continuous wave (CW) laser source and return-to-zero (RZ) signal that is changed from the initial transmitting information is used to control a phase modulator to form a optical PSK signal. In the receiver terminal, just add a signal delayed a half of one bit to itself so that the initial information can be restored.

  10. Binary polarization-shift-keyed modulation for interplanetary CubeSat optical communications

    Science.gov (United States)

    Peng, Michael Y.; Farr, William H.; Borden, Michael B.; Biswas, Abhijit; Kovalik, Joseph M.

    2017-02-01

    Recent developments for laser communication on CubeSats across interplanetary distances will be presented. A binary polarization-shift-keyed modulation scheme using dual gain-switched diode lasers is developed and demonstrated within an end-to-end link testbed to achieve signal acquisition under extremely poor signal-to-noise conditions (-43.5 dB average signal-to-noise power ratio at a 1-MHz symbol rate) to simulate direct-to-Earth links, while simultaneously targeting a limited SWaP footprint (1.5U envelope). Additional system design and constraints for the compact laser transmitter will be discussed.

  11. Trustworthiness of measurement devices in round-robin differential-phase-shift quantum key distribution

    Science.gov (United States)

    Cao, Zhu; Yin, Zhen-Qiang; Han, Zheng-Fu

    2016-02-01

    Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) has been proposed to raise the noise tolerability of the channel. However, in practice, the measurement device in RRDPS QKD may be imperfect. Here, we show that, with these imperfections, the security of RRDPS may be damaged by proposing two attacks for RRDPS systems with uncharacterized measurement devices. One is valid even for a system with unit total efficiency, while the other is valid even when a single-photon state is sent. To prevent these attacks, either security arguments need to be fundamentally revised or further practical assumptions on the measurement device should be put.

  12. Practical round-robin differential phase-shift quantum key distribution

    Science.gov (United States)

    Zhang, Ying-Ying; Bao, Wan-Su; Zhou, Chun; Li, Hong-Wei; Wang, Yang; Jiang, Mu-Sheng

    2016-09-01

    To overcome the signal disturbance from the transmission process, recently, a new type of protocol named round-robin differential-phase-shift(RRDPS) quantum key distribution[Nature 509, 475(2014)] is proposed. It can estimate how much information has leaked to eavesdropper without monitoring bit error rates. In this paper, we compare the performance of RRDPS using different sources without and with decoy-state method, such as weak coherent pulses(WCPs) and heralded single photon source(HSPS). For practical implementations, we propose finite decoy-state method for RRDPS, the performance of which is close to the infinite one. Taking WCPs as an example, the three-intensity decoystate protocol can distribute secret keys over a distance of 128 km when the length of pulses packet is 32, which confirms the great practical interest of our method.

  13. Quantum hacking: Experimental demonstration of time-shift attack against practical quantum-key-distribution systems

    Science.gov (United States)

    Zhao, Yi; Fung, Chi-Hang F.; Qi, Bing; Chen, Christine; Lo, Hoi-Kwong

    2009-03-01

    Quantum key distribution (QKD) systems can send signals over more than 100 km standard optical fiber and are widely believed to be secure. Here, we show experimentally for the first time a technologically feasible attack, namely the time-shift attack, against a commercial QKD system. Our result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability (˜4%) to break the security of the system. Eve's success is due to the well-known detection efficiency loophole in the experimental testing of Bell inequalities. Therefore, the detection efficiency loophole plays a key role not only in fundamental physics, but also in technological applications such as QKD. Our work is published in [1]. [4pt] [1] Y. Zhao, C.-H. F. Fung, B. Qi, C. Chen, and H.-K. Lo, Phys. Rev. A, 78:042333 (2008).

  14. Analyzing the frequency shift of physi-adsorbed CO2 in metal organic framework materials

    Science.gov (United States)

    Yao, Yanpeng; Nijem, Nour; Li, Jing; Chabal, Yves; Langreth, David; Thonhauser, Timo

    2012-02-01

    Combining first-principles density functional theory simulations with IR and Raman experiments, we determine the frequency shift of vibrational modes of CO2 when physi-adsorbed in the iso-structural metal organic framework materials Mg-MOF74 and Zn-MOF74. Surprisingly, we find that the resulting change in shift is rather different for these two systems and we elucidate possible reasons. We explicitly consider three factors responsible for the frequency shift through physi-absorption, namely (i) the change in the molecule length, (ii) the asymmetric distortion of the CO2 molecule, and (iii) the direct influence of the metal center. The influence of each factor is evaluated separately through different geometry considerations, providing a fundamental understanding of the frequency shifts observed experimentally.

  15. Observation of Hysteresis between Solar Activity Indicators and -mode Frequency Shifts for Solar Cycle 22

    Indian Academy of Sciences (India)

    S. C. Tripathy; Brajesh Kumar; Kiran Jain; A. Bhatnagar

    2000-09-01

    Using intermediate degree p-mode frequency data sets for solar cycle 22, we find that the frequency shifts and magnetic activity indicators show a ``hysteresis" phenomenon. It is observed that the magnetic indices follow different paths for the ascending and descending phases of the solar cycle while for radiative indices, the separation between the paths are well within the error limits.

  16. Practical round-robin differential-phase-shift quantum key distribution

    Science.gov (United States)

    Zhang, Zhen; Yuan, Xiao; Cao, Zhu; Ma, Xiongfeng

    2017-03-01

    The security of quantum key distribution (QKD) relies on the Heisenberg uncertainty principle, with which legitimate users are able to estimate information leakage by monitoring the disturbance of the transmitted quantum signals. Normally, the disturbance is reflected as bit flip errors in the sifted key; thus, privacy amplification, which removes any leaked information from the key, generally depends on the bit error rate. Recently, a round-robin differential-phase-shift QKD protocol for which privacy amplification does not rely on the bit error rate (Sasaki et al 2014 Nature 509 475) was proposed. The amount of leaked information can be bounded by the sender during the state-preparation stage and hence, is independent of the behavior of the unreliable quantum channel. In our work, we apply the tagging technique to the protocol and present a tight bound on the key rate and employ a decoy-state method. The effects of background noise and misalignment are taken into account under practical conditions. Our simulation results show that the protocol can tolerate channel error rates close to 50% within a typical experiment setting. That is, there is a negligible restriction on the error rate in practice.

  17. Differential phase shift quantum key distribution experiment over 105 km fibre

    CERN Document Server

    Takesue, H; Honjo, T; Langrock, C; Fejer, M M; Inoue, K; Yamamoto, Y

    2005-01-01

    Since several papers appeared in 2000, the quantum key distribution (QKD) community has been well aware that photon number splitting (PNS) attack by Eve severely limits the secure key distribution distance in BB84 QKD systems with Poissonian photon sources. In attempts to solve this problem, entanglement-based QKD, single-photon based QKD, and entanglement swapping-based QKD, have been studied in recent years. However, there are many technological difficulties that must be overcome before these schemes can become practical systems. Here we report a very simple QKD system, in which secure keys were generated over >100 km fibre for the first time. We used an alternative protocol of differential phase shift keying (DPSK) but with a Poissonian source. We analysed the security of the DPSK protocol and showed that it is robust even against hybrid attacks including collective PNS attack over consecutive pulses, intercept-and-resend (I-R) attack and beamsplitting (BS) attack, because of the non-deterministic collapse...

  18. Round-robin differential quadrature phase-shift quantum key distribution

    Science.gov (United States)

    Zhou, Chun; Zhang, Ying-Ying; Bao, Wan-Su; Li, Hong-Wei; Wang, Yang; Jiang, Mu-Sheng

    2017-02-01

    Recently, a round-robin differential phase-shift (RRDPS) protocol was proposed [Nature 509, 475 (2014)], in which the amount of leakage is bounded without monitoring the signal disturbance. Introducing states of the phase-encoded Bennett–Brassard 1984 protocol (PE-BB84) to the RRDPS, this paper presents another quantum key distribution protocol called round-robin differential quadrature phase-shift (RRDQPS) quantum key distribution. Regarding a train of many pulses as a single packet, the sender modulates the phase of each pulse by one of {0, π/2, π, 3π/2}, then the receiver measures each packet with a Mach–Zehnder interferometer having a phase basis of 0 or π/2. The RRDQPS protocol can be implemented with essential similar hardware to the PE-BB84, so it has great compatibility with the current quantum system. Here we analyze the security of the RRDQPS protocol against the intercept-resend attack and the beam-splitting attack. Results show that the proposed protocol inherits the advantages arising from the simplicity of the RRDPS protocol and is more robust against these attacks than the original protocol. Project supported by the National Natural Science Foundation of China (Grant Nos. 61505261 and 11304397) and the National Basic Research Program of China (Grant No. 2013CB338002)

  19. Ranging with frequency-shifted feedback lasers: from μm-range accuracy to MHz-range measurement rate

    Science.gov (United States)

    Kim, J. I.; Ogurtsov, V. V.; Bonnet, G.; Yatsenko, L. P.; Bergmann, K.

    2016-12-01

    We report results on ranging based on frequency-shifted feedback (FSF) lasers with two different implementations: (1) An Ytterbium-fiber system for measurements in an industrial environment with accuracy of the order of 1 μm, achievable over a distance of the order of meters with potential to reach an accuracy of better than 100 nm; (2) A semiconductor laser system for a high rate of measurements with an accuracy of 2 mm @ 1 MHz or 75 μm @ 1 kHz and a limit of the accuracy of ≥10 μm. In both implementations, the distances information is derived from a frequency measurement. The method is therefore insensitive to detrimental influence of ambient light. For the Ytterbium-fiber system, a key feature is the injection of a single-frequency laser, phase modulated at variable frequency Ω, into the FSF-laser cavity. The frequency Ω_{max} at which the detector signal is maximal yields the distance. The semiconductor FSF-laser system operates without external injection seeding. In this case, the key feature is frequency counting that allows convenient choice of either accuracy or speed of measurements simply by changing the duration of the interval during which the frequency is measured by counting.

  20. Distributed cavity phase frequency shifts of the caesium fountain PTB-CSF2

    CERN Document Server

    Weyers, S; Nemitz, N; Li, R; Gibble, K

    2011-01-01

    We evaluate the frequency error from distributed cavity phase in the caesium fountain clock PTB-CSF2 at the Physikalisch-Technische Bundesanstalt with a combination of frequency measurements and ab initio calculations. The associated uncertainty is 1.3E-16, with a frequency bias of 0.4E-16. The agreement between the measurements and calculations explains the previously observed frequency shifts at elevated microwave amplitude. We also evaluate the frequency bias and uncertainty due to the microwave lensing of the atomic wavepackets. We report a total PTB-CSF2 systematic uncertainty of 4.1E-16.

  1. Decision-directed automatic gain control for MAPSK systems. [M-ary Amplitude and Phase Shift Keying

    Science.gov (United States)

    Weber, W. J., III

    1974-01-01

    An automatic gain control (AGC) loop is presented for use with M-ary amplitude and phase shift keying (MAPSK) systems. The gain control amplifier is regulated by an error signal formed by the difference between the estimated amplitude level and the received amplitude level. The AGC performance is thus independent of the short-term average received signal energy. AGC loop analysis and simulation is presented for M-ary amplitude shift keying and quadrature amplitude shift keying. The AGC is shown to have a negligible degradation on the symbol probability of error for most practical cases. A generalized AGC for an arbitrary MAPSK system is presented.

  2. Displacement damage in bit error ratio performance of on-off keying, pulse position modulation, differential phase shift keying, and homodyne binary phase-shift keying-based optical intersatellite communication system.

    Science.gov (United States)

    Liu, Yun; Zhao, Shanghong; Gong, Zizheng; Zhao, Jing; Dong, Chen; Li, Xuan

    2016-04-10

    Displacement damage (DD) effect induced bit error ratio (BER) performance degradations in on-off keying (OOK), pulse position modulation (PPM), differential phase-shift keying (DPSK), and homodyne binary phase shift keying (BPSK) based systems were simulated and discussed under 1 MeV neutron irradiation to a total fluence of 1×1012  n/cm2 in this paper. Degradation of main optoelectronic devices included in communication systems were analyzed on the basis of existing experimental data. The system BER degradation was subsequently simulated and the variations of BER with different neutron irradiation location were also achieved. The result shows that DD on an Er-doped fiber amplifier (EDFA) is the dominant cause of system degradation, and a BPSK-based system performs better than the other three systems against DD. In order to improve radiation hardness of communication systems against DD, protection and enhancement of EDFA are required, and the use of a homodyne BPSK modulation scheme is a considered choice.

  3. Frequency Shifts of Micro and Nano Cantilever Beam Resonators Due to Added Masses

    KAUST Repository

    Bouchaala, Adam M.

    2016-03-21

    We present analytical and numerical techniques to accurately calculate the shifts in the natural frequencies of electrically actuated micro and nano (carbon nanotubes (CNTs)) cantilever beams implemented as resonant sensors for mass detection of biological entities, particularly Escherichia coli (E. coli) and prostate specific antigen (PSA) cells. The beams are modeled as Euler-Bernoulli beams, including the nonlinear electrostatic forces and the added biological cells, which are modeled as discrete point masses. The frequency shifts due to the added masses of the cells are calculated for the fundamental and higher-order modes of vibrations. Analytical expressions of the natural frequency shifts under a direct current (DC) voltage and an added mass have been developed using perturbation techniques and the Galerkin approximation. Numerical techniques are also used to calculate the frequency shifts and compared with the analytical technique. We found that a hybrid approach that relies on the analytical perturbation expression and the Galerkin procedure for calculating accurately the static behavior presents the most computationally efficient approach. We found that using higher-order modes of vibration of micro-electro-mechanical-system (MEMS) beams or miniaturizing the sizes of the beams to nanoscale leads to significant improved frequency shifts, and thus increased sensitivities. © 2016 by ASME.

  4. Investigation of the Frequency Shift of a SAD Circuit Loop and the Internal Micro-Cantilever in a Gas Sensor

    Directory of Open Access Journals (Sweden)

    Zheng You

    2010-07-01

    Full Text Available Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.

  5. Experimental round-robin differential phase-shift quantum key distribution

    Science.gov (United States)

    Li, Yu-Huai; Cao, Yuan; Dai, Hui; Lin, Jin; Zhang, Zhen; Chen, Wei; Xu, Yu; Guan, Jian-Yu; Liao, Sheng-Kai; Yin, Juan; Zhang, Qiang; Ma, Xiongfeng; Peng, Cheng-Zhi; Pan, Jian-Wei

    2016-03-01

    In conventional quantum key distribution (QKD) protocols, security is guaranteed by estimating the amount of leaked information. Such estimation tends to overrate, leading to a fundamental threshold of the bit error rate, which becomes a bottleneck of practical QKD development. This bottleneck is broken through by the recent work of round-robin differential phase-shift (RRDPS) protocol, which eliminates the fundamental threshold of the bit error rate. The key challenge for the implementation of the RRDPS scheme lies in the realization of a variable-delay Mach-Zehnder interferometer, which requires active and random choice of many delays. By designing an optical system with multiple switches and employing an active phase stabilization technology, we successfully construct a variable-delay interferometer with 127 actively selectable delays. With this measurement, we experimentally demonstrate the RRDPS protocol and obtain a final key rate of 15.54 bps with a total loss of 18 dB and an error rate of 8.9%.

  6. Round-robin differential-phase-shift quantum key distribution with heralded pair-coherent sources

    Science.gov (United States)

    Wang, Le; Zhao, Shengmei

    2017-04-01

    Round-robin differential-phase-shift (RRDPS) quantum key distribution (QKD) scheme provides an effective way to overcome the signal disturbance from the transmission process. However, most RRDPS-QKD schemes use weak coherent pulses (WCPs) as the replacement of the perfect single-photon source. Considering the heralded pair-coherent source (HPCS) can efficiently remove the shortcomings of WCPs, we propose a RRDPS-QKD scheme with HPCS in this paper. Both infinite-intensity decoy-state method and practical three-intensity decoy-state method are adopted to discuss the tight bound of the key rate of the proposed scheme. The results show that HPCS is a better candidate for the replacement of the perfect single-photon source, and both the key rate and the transmission distance are greatly increased in comparison with those results with WCPs when the length of the pulse trains is small. Simultaneously, the performance of the proposed scheme using three-intensity decoy states is close to that result using infinite-intensity decoy states when the length of pulse trains is small.

  7. Round-robin differential-phase-shift quantum key distribution with a passive decoy state method

    Science.gov (United States)

    Liu, Li; Guo, Fen-Zhuo; Qin, Su-Juan; Wen, Qiao-Yan

    2017-02-01

    Recently, a new type of protocol named Round-robin differential-phase-shift quantum key distribution (RRDPS QKD) was proposed, where the security can be guaranteed without monitoring conventional signal disturbances. The active decoy state method can be used in this protocol to overcome the imperfections of the source. But, it may lead to side channel attacks and break the security of QKD systems. In this paper, we apply the passive decoy state method to the RRDPS QKD protocol. Not only can the more environment disturbance be tolerated, but in addition it can overcome side channel attacks on the sources. Importantly, we derive a new key generation rate formula for our RRDPS protocol using passive decoy states and enhance the key generation rate. We also compare the performance of our RRDPS QKD to that using the active decoy state method and the original RRDPS QKD without any decoy states. From numerical simulations, the performance improvement of the RRDPS QKD by our new method can be seen.

  8. Nonlinear modification of the laser noise power spectrum induced by a frequency-shifted optical feedback

    CERN Document Server

    Lacot, Eric; Girardeau, Vadim; Hugon, Olivier; Jacquin, Olivier

    2016-01-01

    In this article, we study the non-linear coupling between the stationary (i.e. the beating modulation signal) and transient (i.e. the laser quantum noise) dynamics of a laser subjected to frequency shifted optical feedback. We show how the noise power spectrum and more specifically the relaxation oscillation frequency of the laser are modified under different optical feedback condition. Specifically we study the influence of (i) the amount of light returning to the laser cavity and (ii) the initial detuning between the frequency shift and intrinsic relaxation frequency. The present work shows how the relaxation frequency is related to the strength of the beating signal and the shape of the noise power spectrum gives an image of the Transfer Modulation Function (i.e. of the amplification gain) of the nonlinear-laser dynamics.The theoretical predictions, confirmed by numerical resolutions, are in good agreements with the experimental data.

  9. Key parameters of efficient phosphor-filled luminescent down-shifting layers for photovoltaics

    Science.gov (United States)

    Solodovnyk, Anastasiia; Lipovšek, Benjamin; Riedel, Daniel; Forberich, Karen; Stern, Edda; Batentschuk, Miroslaw; Krč, Janez; Topič, Marko; Brabec, Christoph J.

    2017-09-01

    Spectral management is one of the promising ways to increase the efficiency of modern photovoltaic devices. We study the performance of phosphor-filled luminescent down-shifting (LDS) layers. We focus on four powder phosphors with refractive indices in the range of 1.66-1.84 and similar particle size distributions. Using experimental characterization as well as 3D optical simulations, we identify key parameters of the phosphor particles and LDS layers that primarily affect the optical transmittance, absorptance, and photoluminescence quantum yield of the layers. We investigate the influence of the medium located beneath the LDS layer and reveal a strong increase in the performance when the layer is applied directly onto the solar cell. Finally, the optimal combination of the particle, binder and layer parameters that render the highest performance of the LDS layers are also indicated and discussed.

  10. Shifting the Climate Finance Paradigm: Nine Key Challenges for Developed Countries

    Energy Technology Data Exchange (ETDEWEB)

    Curtin, Joseph

    2013-03-13

    In 2009, developed countries committed to part-funding the cost of adapting to the impacts of climate change and of low carbon development in developing countries. From 2010 to 2012, fast start finance began to flow from developed country exchequers. However, the climate finance paradigm is now shifting. A transition from loans and grants provided from scarce exchequer resources to innovative instruments for leveraging private capital and mitigating investment risk is required in the coming period. But what are the implications for developed countries? This policy brief explores the policy context defining the current climate finance debate; examines the extent to which commitments have been met; and identifies nine key challenges for developed countries as they enter the new climate finance paradigm, drawing on the lessons of the fast start finance period. This is the second in a series of Environment Nexus policy briefs by leading experts in the fields of agriculture, energy, climate change and water.

  11. Cochannel and Adjacent-Channel Interference in Nonlinear Minimum-Shift-Keyed Satellite System

    Science.gov (United States)

    Yu, John

    1995-01-01

    The interference susceptibility of a serial-minimum-shift-keyed (SMSK) modulation system to an interfering signal transmitted through a satellite link with cascaded nonlinear elements was investigated through computer simulation. The satellite link evaluated in this study represented NASA's Advanced Communications Technology Satellite (ACTS) system. Specifically, nonlinear characteristics were used that had specified amplitude-modulation to amplitude-modulation and amplitude-modulation to phase-modulation transfer characteristics obtained from the actual ACTS hardware. Two measurement scenarios were analyzed: degradation of an MSK satellite link from cochannel interference and from adjacent-channel interference. Interference was evaluated in terms of the probability of bit error rate (BER) versus energy per bit over noise power density Eb/No.

  12. Principle of Quantum Key Distribution on an Optical Fiber Based on Time Shifts of TB Qubits

    Science.gov (United States)

    Zadorin, A. S.; Makhorin, D. A.

    2016-07-01

    The possibility of the physical realization of a quantum key distribution scheme in an optical-fiber communication channel based on time coding of two- and three-level single-photon quantum states is demonstrated. It is proposed to employ shifts of TB qubits (time-bin qubits) as protected code combinations, transmitted over a quantum channel, and for registering individual photons - the corresponding qutrits prepared in unbalanced Mach-Zehnder interferometers. The possibility of enhancing the level of protection of the code combinations as a result of taking into account information about qubit basis states and their statistics is indicated. A computer model of the time coding of TB qubits based on the BB84 protocol is developed, and results of calculations confirming the realizability of the indicated principle are presented.

  13. Qualitative analysis of collective mode frequency shifts in L-alanine using terahertz spectroscopy.

    Science.gov (United States)

    Taulbee, Anita R; Heuser, Justin A; Spendel, Wolfgang U; Pacey, Gilbert E

    2009-04-01

    We have observed collective mode frequency shifts in deuterium-substituted L-alanine, three of which have previously only been calculated. Terahertz (THz) absorbance spectra were acquired at room temperature in the spectral range of 66-90 cm(-1), or 2.0-2.7 THz, for L-alanine (L-Ala) and four L-Ala compounds in which hydrogen atoms (atomic mass = 1 amu) were substituted with deuterium atoms (atomic mass = 2 amu): L-Ala-2-d, L-Ala-3,3,3-d(3), L-Ala-2,3,3,3-d(4), and L-Ala-d(7). The absorbance maxima of two L-Ala collective modes in this spectral range were recorded for multiple spectral measurements of each compound, and the magnitude of each collective mode frequency shift due to increased mass of these specific atoms was evaluated for statistical significance. Calculations were performed which predict the THz absorbance frequencies based on the estimated reduced mass of the modes. The shifts in absorbance maxima were correlated with the location(s) of the substituted deuterium atom(s) in the L-alanine molecule, and the atoms contributing to the absorbing delocalized mode in the crystal structure were deduced using statistics described herein. The statistical analyses presented also indicate that the precision of the method allows reproducible frequency shifts as small as 1 cm(-1) or 0.03 THz to be observed and that these shifts are not random error in the measurement.

  14. Continuous wave operation of quantum cascade lasers with frequency-shifted feedback

    Energy Technology Data Exchange (ETDEWEB)

    Lyakh, A., E-mail: arkadiy.lyakh@ucf.edu [Pranalytica, Inc., 1101 Colorado Ave., Santa Monica, CA 90401 (United States); NanoScience Technology Center, University of Central Florida, 12424 Research Pkwy, Orlando, FL 32826 (United States); College of Optics and Photonics, University of Central Florida, 304 Scorpius St, Orlando, FL 32826 (United States); Barron-Jimenez, R.; Dunayevskiy, I.; Go, R.; Tsvid, G.; Patel, C. Kumar N., E-mail: patel@pranalytica.com [Pranalytica, Inc., 1101 Colorado Ave., Santa Monica, CA 90401 (United States)

    2016-01-15

    Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm{sup −1} for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep times, consistent with sound wave grating period variation across the illuminated area on the acousto-optic modulator. Standoff detection capability of the AOM-based QCL setup was demonstrated for several solid materials.

  15. New method for lens thickness measurement by the frequency-shifted confocal feedback

    Science.gov (United States)

    Tan, Yidong; Zhu, Kaiyi; Zhang, Shulian

    2016-12-01

    We describe a new method for lens thickness and air gap measurement based on the frequency-shifted confocal feedback. The light intensity fluctuation is eliminated by the heterodyne modulation and the detection sensitivity is improved prominently by the frequency-shifted feedback effect. The measurement results for different materials and kinds of lenses are presented in the paper, including K9 plain glasses, fused silica plain glass, and K9 biconvex lens. The uncertainty of the axial positioning is better than 0.0005 mm and the accuracy reaches micron range. It is promising to be applied in the multi-layer interface positioning and measurement area.

  16. Wide tunable shift of the reflection band in dual frequency cholesteric liquid crystals.

    Science.gov (United States)

    Oton, Eva; Netter, Estelle

    2017-06-12

    Technologies featuring external control of reflected and transmitted light are lately being explored for a wide range of optical and photonic applications. Yet, the options for spectral band tuning are scarce, especially if dynamic control of either reflected or transmitted light is required. In this work we demonstrate a tunable device capable of shifting the reflected light spectrum of an impinging light using dual frequency cholesteric liquid crystals. Modulating the frequency of the applied signal, the Bragg reflection can be dynamically shifted over a wide spectral range and also switched off. This feature can be applied to color filters, augmented reality, multi-color lasers or tunable windows.

  17. A New High Frequency Injection Method Based on Duty Cycle Shifting without Maximum Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2015-01-01

    The conventional high frequency signal injection method is to superimpose a high frequency voltage signal to the commanded stator voltage before space vector modulation. Therefore, the magnitude of the voltage used for machine torque production is limited. In this paper, a new high frequency...... injection method, in which high frequency signal is generated by shifting the duty cycle between two neighboring switching periods, is proposed. This method allows injecting a high frequency signal at half of the switching frequency without the necessity to sacrifice the machine fundamental voltage...... amplitude. This may be utilized to develop new position estimation algorithm without involving the inductance in the medium to high speed range. As an application example, a developed inductance independent position estimation algorithm using the proposed high frequency injection method is applied to drive...

  18. Demodulation of acoustic telemetry binary phase shift keying signal based on high-order Duffing system

    Science.gov (United States)

    Yan, Bing-Nan; Liu, Chong-Xin; Ni, Jun-Kang; Zhao, Liang

    2016-10-01

    In order to grasp the downhole situation immediately, logging while drilling (LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is critical for acoustic telemetry technology that the signal is successfully transmitted to the ground. In this paper, binary phase shift keying (BPSK) is used to modulate carrier waves for the transmission and a new BPSK demodulation scheme based on Duffing chaos is investigated. Firstly, a high-order system is given in order to enhance the signal detection capability and it is realized through building a virtual circuit using an electronic workbench (EWB). Secondly, a new BPSK demodulation scheme is proposed based on the intermittent chaos phenomena of the new Duffing system. Finally, a system variable crossing zero-point equidistance method is proposed to obtain the phase difference between the system and the BPSK signal. Then it is determined that the digital signal transmitted from the bottom of the well is ‘0’ or ‘1’. The simulation results show that the demodulation method is feasible. Project supported by the National Natural Science Foundation of China (Grant No. 51177117) and the National Key Science & Technology Special Projects, China (Grant No. 2011ZX05021-005).

  19. Multi-format receiver for non-return-to-zero binary-phase-shift-keyed and non-return-to-zero amplitude-shit-keyed signals.

    Science.gov (United States)

    Liu, Zhixin; Xiao, Shilin; Cai, Lei; Liang, Zheng

    2009-02-16

    A Multi-format receiver for both non-return-to-zero binary-phase- shift-keyed (NRZ-BPSK) signal and non-return-to-zero amplitude-shift- keyed (NRZ-ASK) signal is demonstrated. Multi-format signal detection is based on incoherent BPSK demodulation and ASK-BPSK format conversion. Incoherent BPSK demodulation is realized by a Mach- Zehnder delay interferometer (MZDI) and a feedback decoder. Transmission experiments validate the feasibility of multi-format receiver. This receiver has potential to serve as a useful terminal block for all-optical wavelength division-multiplexed (WDM) networks.

  20. Prediction of spectral shifts proportional to source distances by time-varying frequency or wavelength selection

    CERN Document Server

    Guruprasad, V

    2008-01-01

    Any frequency selective device with an ongoing drift will cause observed spectra to be variously and simultaneously scaled in proportion to their source distances. The reason is that detectors after the drifting selection will integrate instantaneous electric or magnetic field values from successive sinusoids, and these sinusoids would differ in both frequency and phase. Phase differences between frequencies are ordinarily irrelevant, and recalibration procedures at most correct for frequency differences. With drifting selection, however, each integrated field value comes from *the sinusoid of the instantaneously selected frequency at its instantaneous received phase*, hence the waveform constructed by the integration will follow the drifting selection with a phase acceleration given by the drift rate times the slope of the received phase spectrum. A phase acceleration is literally a frequency shift, and the phase spectrum slope of a received waveform is an asymptotic measure of the source distance, as the pa...

  1. Tracing part-per-billion line shifts with direct-frequency-comb Vernier spectroscopy

    Science.gov (United States)

    Siciliani de Cumis, M.; Eramo, R.; Coluccelli, N.; Cassinerio, M.; Galzerano, G.; Laporta, P.; De Natale, P.; Cancio Pastor, P.

    2015-01-01

    Accurate frequency measurements of molecular transitions around 2 μ m are performed by using a direct-frequency-comb spectroscopy approach that combines an Er+ frequency-comb oscillator at 1.5 μ m , a Tm-Ho fiber amplifier, and a Fabry-Perot-filter, high-resolution dispersive spectrometer optical multiplex-detection system. This apparatus has unique performances in terms of a wide dynamic range to integrate the intensity per comb mode, which allows one to measure molecular absorption profiles with high precision. Spectroscopic information about transition frequencies and linewidths is very accurately determined. Relative frequency uncertainties of the order of a few parts in 10-9 are achieved for rovibrational transitions of the CO2 molecule around 5100 cm-1. Moreover, tiny frequency shifts due to molecular collisions and interacting laser power using direct comb spectroscopy are investigated in a systematic way.

  2. Investigation of the Phonon Frequency Shifts in ZnO Quantum Dots

    Science.gov (United States)

    Alim, Khan A.

    2005-03-01

    Nanostructures made of ZnO have recently attracted attention due to their proposed applications in low-voltage and short-wavelength electro-optical devices. However, the origin of the observed phonon frequency shifts in such nanostructures is not always understood. We carried out both resonant and non-resonant Raman measurements for 20 nm-diameter ZnO quantum dots (QDs) and bulk ZnO reference samples [1]. A comparison with a recently developed theory [2], allowed us to clarify the origin of the phonon frequency shifts in ZnO QDs. It was found that the phonon confinement results in phonon frequency shifts of only few cm-1. At the same time, the UV laser heating of the QD ensemble was found to induce a large red shift of phonon frequencies for up to 14 cm-1. The authors acknowledge the support of MARCO and its Functional Engineered Nano Architectonics (FENA) Focus Center. [1] K.A. Alim, V.A. Fonoberov, and A.A. Balandin, Appl. Phys. Lett., in review (2004). [2] V.A. Fonoberov and A.A. Balandin, Phys. Stat. Solidi C 1, 2650 (2004); cond-mat/0405681; cond-mat/0411742.

  3. Time and frequency characteristics of temporary threshold shifts caused by pure tone exposures

    DEFF Research Database (Denmark)

    Ordoñez, Rodrigo Pizarro; Hammershøi, Dorte

    2011-01-01

    The time-frequency characteristics of Temporary Threshold Shifts (TTS) caused by pure tones were determined using the Békésy audiometric method with narrow-band noise of short duration as the probe stimuli. Two experiments were done using exposures of 3 min at 100 dB above threshold. In the first...

  4. Origin of the frequency shift of Raman scattering in chalcogenide glasses

    DEFF Research Database (Denmark)

    Han, X.C.; Tao, H.Z.; Gong, L.J.;

    2014-01-01

    Raman scattering is a sensitive method for probing the structural evolution in glasses, especially in covalent ones. Usually the main Raman scattering frequency shifts with composition for Gesingle bondSe chalcogenide glasses. However, it has not been well established whether and how the dependen...

  5. Raman Self-Frequency Shift of Dissipative Kerr Solitons in an Optical Microresonator.

    Science.gov (United States)

    Karpov, Maxim; Guo, Hairun; Kordts, Arne; Brasch, Victor; Pfeiffer, Martin H P; Zervas, Michail; Geiselmann, Michael; Kippenberg, Tobias J

    2016-03-11

    The formation of temporal dissipative Kerr solitons in microresonators driven by a continuous-wave laser enables the generation of coherent, broadband, and spectrally smooth optical frequency combs as well as femtosecond pulse sources with compact form factors. Here we report the observation of a Raman-induced soliton self-frequency shift for a microresonator dissipative Kerr soliton also referred to as the frequency-locked Raman soliton. In amorphous silicon nitride microresonator-based single soliton states the Raman effect manifests itself by a spectrum that is sech^{2} in shape and whose center is spectrally redshifted from the continuous wave pump laser. The shift is theoretically described by the first-order shock term of the material's Raman response, and we infer a Raman shock time of ∼20  fs for amorphous silicon nitride. Moreover, we observe that the Raman-induced frequency shift can lead to a cancellation or overcompensation of the soliton recoil caused by the formation of a coherent dispersive wave. The observations are in agreement with numerical simulations based on the Lugiato-Lefever equation with a Raman shock term. Our results contribute to the understanding of Kerr frequency combs in the soliton regime, enable one to substantially improve the accuracy of modeling, and are relevant to the understanding of the fundamental timing jitter of microresonator solitons.

  6. From frequency to time-average-frequency a paradigm shift in the design of electronic system

    CERN Document Server

    Xiu, Liming

    2015-01-01

    Written in a simple, easy to understand style, this book will teach PLL users how to use new clock technology in their work in order to create innovative applications.       Investigates the clock frequency concept from a different perspective--at an application level       Teaches engineers to use this new clocking technology to create innovations in chip/system level, through real examples extracted from commercial products  

  7. Matrix method for the solution of RF field perturbations due to local frequency shifts

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-Rui; PENG Jun; FU Shi-Nian

    2009-01-01

    To tune the accelerating field to the design value in a periodical radio frequency accelerating structure, Slater's perturbation theorem is commonly used. This theorem solves a second-order differential equation to obtain the electrical field variation due to a local frequency shift. The solution becomes very difficult for a complex distribution of the local frequency shifts. Noticing the similarity between the field perturbation equation and the equation describing the transverse motion of a particle in a quadrupole channel, we propose in this paper a new method in which the transfer matrix method is applied to the field calculation instead of directly solving the differential equation. The advantage of the matrix method is illustrated in examples.

  8. Coherent Detection of Optical Quadrature Phase-Shift Keying Signals With Carrier Phase Estimation

    Science.gov (United States)

    Ly-Gagnon, Dany-Sebastien; Tsukamoto, Satoshi; Katoh, Kazuhiro; Kikuchi, Kazuro

    2006-01-01

    This paper describes a coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK) signals. At the receiver, a phase-diversity homodyne detection scheme is employed without locking the phase of the local oscillator (LO). To handle the carrier phase drift, the carrier phase is estimated with digital signal processing (DSP) on the homodyne-detected signal. Such a scheme presents the following major advantages over the conventional optical differential detection. First, its bit error rate (BER) performance is better than that of differential detection. This higher sensitivity can extend the reach of unrepeated transmission systems and reduce crosstalk between multiwavelength channels. Second, the optoelectronic conversion process is linear, so that the whole optical signal information can be postprocessed in the electrical domain. Third, this scheme is applicable to multilevel modulation formats such as M-array PSK and quadrature amplitude modulation (QAM). The performance of the receiver is evaluated through various simulations and experiments. As a result, an unrepeated transmission over 210 km with a 20-Gb/s optical QPSK signal is achieved. Moreover, in wavelength-division multiplexing (WDM) environment, coherent detection allows the filtering of a desired wavelength channel to reside entirely in the electrical domain, taking advantage of the sharp cutoff characteristics of electrical filters. The experiments show the feasibility to transmit polarization-multiplexed 40-Gb/s QPSK signals over 200 km with channel spacing of 16 GHz, leading to a spectral efficiency as high as 2.5 b/s/Hz.

  9. Locality of Area Coverage on Digital Acoustic Communication in Air using Differential Phase Shift Keying

    Science.gov (United States)

    Mizutani, Keiichi; Ebihara, Tadashi; Wakatsuki, Naoto; Mizutani, Koichi

    2009-07-01

    We experimentally evaluate the locality of digital acoustic communication in air. Digital acoustic communication in air is suitable for a small cell system, because acoustic waves have a short propagation distance in air. In this study, optimal cell size is experimentally evaluated. Each base station (BS) transmits different commands. In our experiment, differential phase shift keying (DPSK), especially binary DPSK (DBPSK), is adopted as a modulation and demodulation scheme. The evaluated system consists of a personal computer (PC), a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a loud speaker (SP), a microphone (MIC), and transceiver software. All experiments are performed in an anechoic room. The cell size of the transmitter can be limited under low signal-to-noise ratio (SNR) condition. If another transmitter works, cell size is limited by the effect of the interference from that transmitter. The cell size-to-distance ratio of transmitter A to transmitter B is 37.5%, if cell edge bit-error-rate (BER) is taken as 10-3.

  10. Time and Frequency Domain Optimization with Shift, Convolution and Smoothness in Factor Analysis Type Decompositions

    DEFF Research Database (Denmark)

    Madsen, Kristoffer Hougaard; Hansen, Lars Kai; Mørup, Morten

    2009-01-01

    We propose the Time Frequency Gradient Method (TFGM) which forms a framework for optimization of models that are constrained in the time domain while having efficient representations in the frequency domain. Since the constraints in the time domain in general are not transparent in a frequency...... representation we demonstrate how the class of objective functions that are separable in either time or frequency instances allow the gradient in the time or frequency domain to be converted to the opposing domain. We further demonstrate the usefulness of this framework for three different models; Shifted Non......-negative Matrix Factorization, Convolutive Sparse Coding as well as Smooth and Sparse Matrix Factorization. Matlab implementation of the proposed algorithms are available for download at www.erpwavelab.org....

  11. Stabilization and Shift of Frequency in an External Cavity Diode Laser with Solenoid-Assisted Saturated Absorption

    Institute of Scientific and Technical Information of China (English)

    HAN Shun-Li; CHENG Bing; ZHANG Jing-Fang; XU Yun-Fei; WANG Zhao-Ying; LIN Qiang

    2009-01-01

    A simple method to realize both stabilization and shift of the frequency in an external cavity diode laser (ECDL) is reported.Due to the Zeeman effect,the saturated absorption spectrum of Rb atoms in a magnetic field is shifted.This shift can be used to detune the frequency of the ECDL,which is locked to the saturated absorption spectrum.The frequency shift amount can be controlled by changing the magnetic field for a specific polarization state of the laser beam.The advantages of this tunable frequency lock include low laser power requirement,without additional power loss,cheapness,and so on.

  12. Analysis of the influence of various effects on frequency shifts of the acetylene saturated absorption lines

    Institute of Scientific and Technical Information of China (English)

    Dong Lei; Zhang Lei; Dou Hai-Peng; Yin Wang-Bao; Jia Suo-Tang

    2008-01-01

    Frequency shifts of the acetylene saturated absorption lines at 1.5μm with temperature,gas pressure and laser power have been investigated in detail.The second-order Doppler effect,the recoil effect,the Zeeman effect,the pressure shift and the power shift are taken into consideration.The magnitudes of those shifts caused by various effects are evaluated.In order to reproduce the stability of 5.7 x 10-14 obtained by Edwards,all necessary conditions are given.The results show that when there is a larger external magnetic field,the Zeeman shift could not be neglected,so that the shield should be employed.And the design of a long cavity is advantageous to reduce the influence of the second-order Doppler effect.The results also show that at least ±2.5°C temperature control for cavity can effectively prevent several effects and improve the frequency stability.

  13. Lattice Induced Frequency Shifts in Sr Optical Lattice Clocks at the $10^{-17}$ Level

    CERN Document Server

    Westergaard, Philip G; Lorini, Luca; Lecallier, Arnaud; Burt, Eric; Zawada, Michal; Millo, Jacques; Lemonde, Pierre

    2011-01-01

    We present a comprehensive study of the frequency shifts associated with the lattice potential for a Sr lattice clock. By comparing two such clocks with a frequency stability reaching $5\\times 10^{-17}$ after a one hour integration time, and varying the lattice depth up to $U_0=900 \\, E_r$ with $E_r$ being the recoil energy, we evaluate lattice related shifts with an unprecedented accuracy. We put the first experimental upper bound on the recently predicted frequency shift due to the magnetic dipole (M1) and electric quadrupole (E2) interactions. This upper bound is significantly smaller than the theoretical upper limit. We also give a new upper limit on the effect of hyperpolarizability with an improvement by more than one order of magnitude. Finally, we report the first observation of the vector and tensor shifts in a lattice clock. Combining these measurements, we show that all known lattice related perturbation will not affect the clock accuracy down to the $10^{-17}$ level, even for very deep lattices, u...

  14. Ranging with frequency-shifted feedback lasers: from $\\mu$m-range accuracy to MHz-range measurement rate

    CERN Document Server

    Kim, J I; Bonnet, G; Yatsenko, L P; Bergmann, K

    2016-01-01

    We report results on ranging based on frequency shifted feedback (FSF) lasers with two different implementations: (1) An Ytterbium-fiber system for measurements in an industrial environment with accuracy of the order of 1 $\\mu$m, achievable over a distance of the order of meters with potential to reach an accuracy of better than 100 nm; (2) A semiconductor laser system for a high rate of measurements with an accuracy of 2 mm @ 1 MHz or 75 $\\mu$m @ 1 kHz and a limit of the accuracy of $\\geq $ 10 $\\mu$m. In both implementations, the distances information is derived from a frequency measurement. The method is therefore insensitive to detrimental influence of ambient light. For the Ytterbium-fiber system a key feature is the injection of a single frequency laser, phase modulated at variable frequency $\\Omega$, into the FSF-laser cavity. The frequency $\\Omega_{max}$ at which the detector signal is maximal yields the distance. The semiconductor FSF laser system operates without external injection seeding. In this c...

  15. Linking global-change induced shifts in soil nitrogen cycling with the abundance of key microorganisms

    Science.gov (United States)

    Carey, C.; Eviner, V.; Beman, M.; Hart, S. C.

    2013-12-01

    Since western colonization, the ecology of California has seen marked transformations. In particular, invasion of terrestrial ecosystems by exotic plants has altered plant community composition, disturbances, soil hydrologic regimes, and nutrient cycling. In addition, as a result of fertilization and combustion of fossil fuels, California experiences some of the highest nitrogen (N) deposition rates in the country. Land use has also changed with the introduction of domestic livestock grazing about 250 years ago. Currently, approximately 32% of land in California experiences grazing pressure. These ecological changes likely affect the ecosystems of California simultaneously. However, with multifactor global change experiments in their infancy, little is known about potential interactive effects on ecosystem structure and function. Our study measured the response of soil N dynamics to a unique combination of treatments: invasion by exotic plants (Aegilops triuncialis and Taeniatherum caput-medusae), elevated N additions, and simulated cattle grazing (aboveground vegetation removal). In addition, we quantified the abundance of key functional genes involved in nitrification (amoA) and denitrification (nirS/nirK) in order to gain a mechanistic insight into changes in ecosystem functioning. We found that, while responses of soil N pools and processes to global change factors tend to be dominated by main effects, interactions among factors can substantially alter the overall response of the ecosystem. For instance, N additions increased potential nitrification and pools of total inorganic N (TIN; NH4+ and NO3-); when N additions and grazing were combined, however, nitrification potentials and TIN decreased to those of ambient N (control) levels. Additionally, neither N additions nor simulated grazing independently affected soil microbial biomass of invaded plots; yet, when combined, the microbial biomass increased significantly. Our results help to provide a better

  16. Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction

    Institute of Scientific and Technical Information of China (English)

    K.V. Priyesh; Ramesh Babu Thayyullathil

    2012-01-01

    We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings model. Here the frequency of the interacting field is sinusoidally varying with time with a constant phase. Due to the presence of phase in the frequency modulation, the variation of population inversion with time is different from the standard case. There are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with time. In coherent field atom interaction the population inversion behaves as in the case of Fock state atom interaction, when frequency modulation with a non zero phase is applied. The study done with squeezed field has shown the same behavior of the population inversion.

  17. Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System

    Science.gov (United States)

    Ruesink, Freek; Doeleman, Hugo M.; Hendrikx, Ruud; Koenderink, A. Femius; Verhagen, Ewold

    2015-11-01

    The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.

  18. The Coefficient of the Voltage Induced Frequency Shift Measurement on a Quartz Tuning Fork

    Directory of Open Access Journals (Sweden)

    Yubin Hou

    2014-11-01

    Full Text Available We have measured the coefficient of the voltage induced frequency shift (VIFS of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built.

  19. Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system

    CERN Document Server

    Ruesink, Freek; Hendrikx, Ruud; Koenderink, A Femius; Verhagen, Ewold

    2015-01-01

    The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a non-trivial phase relation between cavity and nanoparticle radiation, allowing back-action via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.

  20. Electric dipole moment searches: reexamination of frequency shifts for particles in traps

    CERN Document Server

    Pignol, Guillaume

    2012-01-01

    In the context of the search for electric dipole moments, a proper theory describing frequency shifts for particles precessing in traps is needed to evaluate the systematic effects. We present here such a theory, valid in the ballistic regime and in the nonadiabatic limit. It permits the calculation of the frequency shifts for arbitrary geometry of the confinement cell as well as for arbitrary shape of the magnetic field, such as those induced by localized magnetic impurities. Our improved theory is especially relevant for experiments measuring the neutron electric dipole moment with an atomic magnetometer. Indeed, the main systematic effects of performed, on-going and future experiments can be assessed with increased confidence and precision.

  1. Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Han-Chun; Ye, Tianyu; Mani, R. G. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Wegscheider, W. [Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich (Switzerland)

    2015-02-14

    Linear polarization angle, θ, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, R{sub xx}, in high mobility GaAs/AlGaAs 2D electron devices have shown a θ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, θ{sub 0}. Here, we suggest a microwave frequency dependence of θ{sub 0}(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.

  2. THz radiation by the frequency down-shift of Nd:YAG lasers

    CERN Document Server

    Son, S; Park, J Y

    2013-01-01

    The interaction between an intense laser and a relativistic dense electron beam propagating in the same direction could down-shift the laser frequency. This process, which can be used to generate a coherent THz radiation, is theoretically analyzed. With a set of practically relevant parameters, it is suggested that the radiation energy could reach the order of 1 mJ per shot in the duration of 100 pico-second, or the temporal radiation power of 10 MW.

  3. Nonlinear frequency shift in Raman backscattering and its implications for plasma diagnostics

    Science.gov (United States)

    Kaganovich, D.; Hafizi, B.; Palastro, J. P.; Ting, A.; Helle, M. H.; Chen, Y.-H.; Jones, T. G.; Gordon, D. F.

    2016-12-01

    Raman backscattered radiation of intense laser pulses in plasmas is investigated for a wide range of intensities relevant to laser wakefield acceleration. The weakly nonlinear dispersion relation for Raman backscattering predicts an intensity and density dependent frequency shift that is opposite to that suggested by a simple relativistic consideration. This observation has been benchmarked against experimental results, providing a novel diagnostic for laser-plasma interactions.

  4. Nonlinear Frequency Shift in Raman Backscattering and its Implications for Plasma Diagnostics

    CERN Document Server

    Kaganovich, D; Palastro, J P; Ting, A; Helle, M H; Chen, Y -H; Jones, T G; Gordon, D F

    2016-01-01

    Raman backscattered radiation of intense laser pulses in plasma is investigated for a wide range of intensities relevant to laser wakefield acceleration. The weakly nonlinear dispersion relation for Raman backscattering predicts an intensity and density dependent frequency shift that is opposite to that suggested by a simple relativistic consideration. This observation has been benchmarked against experimental results, providing a novel diagnostic for laser-plasma interactions.

  5. Control of the soliton self-frequency shift dynamics using topographic optical fibers.

    Science.gov (United States)

    Bendahmane, A; Vanvincq, O; Mussot, A; Kudlinski, A

    2013-09-01

    We demonstrate that the dynamics of the soliton self-frequency shift can be accurately controlled by using tapered optical fibers with optimized longitudinal profile shape (that we term topographic fibers). The tapering profiles tailored for a targeted soliton spectral trajectory through dispersion and nonlinearity management are determined by an inverse algorithm. This control is demonstrated experimentally with topographic photonic crystal fibers fabricated directly on a drawing tower.

  6. Gear Fault Diagnosis Based on Narrowband Demodulation with Frequency Shift and Spectrum Edit

    Directory of Open Access Journals (Sweden)

    Yu Guo

    2016-09-01

    Full Text Available To address the difficulties on the vibration feature extraction of gear localized faults for rotating machinery under varying speed conditions, an improved narrowband demodulation method with spectrum edit and frequency shift is proposed in the paper. The vibration signal is acquired and resampled at constant angle increments at first, by which the non-stationary signal is converted into a quasi-stationary signal in the angular domain to reduce the distortions caused by the speed fluctuations. Subsequently, the signal in the angular domain is processed by a synchronous average algorithm, where the noises can be eliminated effectively and the order components corresponding to the gear faults become prominent. Finally, the narrowband demodulation scheme with the spectrum edit and frequency shift is applied on the averaged signal. By using the spectrum edit, most of unconcerned components can be filtered out effectively. Moreover, the frequency shift property of the Fourier transform is employed in the proposed demodulation scheme to obtain a better phase demodulation result. Simulations and experiments support the proposed scheme positively.

  7. Are Gaze Shifts a Key to a Translator’s Text Segmentation?

    DEFF Research Database (Denmark)

    Lykke Jakobsen, Arnt

    2016-01-01

    the feasibility of identifying segments, understood as processing units, on the basis of gaze shifts, and to inquire into what motivates gaze shifts. It also seeks to illustrate how much our interpretation of gaze representations, not least suboptimal representations, depend on a theory of reading.......? And do such shifts give us more accurate information about segmentation or more information than keystroke intervals? Using a rather poorly calibrated recording of just one translator’s translation of a single sentence (within a longer task) for illustration, the paper seeks to tentatively explore...

  8. Frequency-shift low-pass filtering and least mean square adaptive filtering for ultrasound imaging

    Science.gov (United States)

    Wang, Shanshan; Li, Chunyu; Ding, Mingyue; Yuchi, Ming

    2016-04-01

    Ultrasound image quality enhancement is a problem of considerable interest in medical imaging modality and an ongoing challenge to date. This paper investigates a method based on frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for ultrasound image quality enhancement. FSLF is used for processing the ultrasound signal in the frequency domain, while LMSAPF in the time domain. Firstly, FSLF shifts the center frequency of the focused signal to zero. Then the real and imaginary part of the complex data are filtered respectively by finite impulse response (FIR) low-pass filter. Thus the information around the center frequency are retained while the undesired ones, especially background noises are filtered. Secondly, LMSAF multiplies the signals with an automatically adjusted weight vector to further eliminate the noises and artifacts. Through the combination of the two filters, the ultrasound image is expected to have less noises and artifacts and higher resolution, and contrast. The proposed method was verified with the RF data of the CIRS phantom 055A captured by SonixTouch DAQ system. Experimental results show that the background noises and artifacts can be efficiently restrained, the wire object has a higher resolution and the contrast ratio (CR) can be enhanced for about 12dB to 15dB at different image depth comparing to delay-and-sum (DAS).

  9. Calculations of the vibrational frequency and isotopic shift of UF6 and U2F6

    Institute of Scientific and Technical Information of China (English)

    Zhang Yun-Guang; Zha Xin-Wei

    2012-01-01

    Molecular structure,vibrational frequency and infrared intensity of UF6 are investigated by using the revised Perdew-Burke-Enzerhof function with the triple-zeta polarized basis set.The calculation results are in good agreement with the experimental values and indicate the existence of a stable U2F6 molecule with a multiple bonded U2 unit.The calculation results also predict that the D3d symmetry of U2F6 is more stable than D3h.The optimized geometries,vibrational frequencies,and infrared intensities are also reported for U2F6 molecules in D3d symmetry.In addition,the isotopic shift of vibrational frequencies of the two molecules under isotopic substitution of uranium atom are also investigated with the same method.The U2F6 molecule is predicted to be better than UF6 for laser uranic isotope separation.

  10. FREQUENCY SHIFTS OF RESONANT MODES OF THE SUN DUE TO NEAR-SURFACE CONVECTIVE SCATTERING

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, J.; Hanasoge, S.; Antia, H. M. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai-400005 (India)

    2015-06-20

    Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the “surface term.” The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun. We show that the full oscillation equations, in the presence of temporally stationary three-dimensional (3D) flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt–Väisäla frequency, and Lamb frequency. We derive the modified equation and relations for the appropriate averaging of 3D flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from 3D numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.

  11. A Design of Frequency Shifting GoTa Terminal%一种GoTa移频终端的设计方案

    Institute of Scientific and Technical Information of China (English)

    吕国栋; 白灵; 宋滔

    2013-01-01

    GoTa数字集群通信系统是应用范围最广和国际化程度最高的国产数字集群系统。将GoTa系统移频应用,使其能够突破频段限制,满足更多用户的集群调度通信需求。移频终端是GoTa集群通信系统移频应用的重要设备,主要由主控模块、移频模块、GoTa模块等构成。介绍了GoTa系统移频应用的工作原理,提出了一种GoTa移频终端解决方案。并给出了移频模块、接收待机等技术难点的解决方法。样机通过系统测试,实现非标准频段下的GoTa集群功能。%GoTa(Global Open Trunking Architecture) is a typical domestic digital trunking system with independent intellectual property right and also a well-known system all over the world. And it is widely used and has a huge amount of users. By breaking through the limitation of working frequency and expanding the working frequency to a broad band, the frequency shifting application of GoTa could be done, thus to meet the demands of more users. The terminal of frequency shifting GoTa system, as a very important equipment, is mainly composed of central control module, frequency shifting RF module and basic GoTa module. This paper, based on the working principle of GoTa frequency shifting application, proposes a novel solution for the design of frequency shifting terminal, gives a detailed analysis of the key issues, including the frequency shifting RF module and the power management of receiver. Finally, the experiment on prototype frequency shifting GoTa system indicates that the scheme is feasible and effective and that all the functions of frequency shifting GoTa terminal could work well.

  12. Drought-induced vegetation shifts in terrestrial ecosystems: The key role of regeneration dynamics

    Science.gov (United States)

    Martínez-Vilalta, Jordi; Lloret, Francisco

    2016-09-01

    Ongoing climate change is modifying climatic conditions worldwide, with a trend towards drier conditions in most regions. Vegetation will respond to these changes, eventually adjusting to the new climate. It is unclear, however, how close different ecosystems are to climate-related tipping points and, thus, how dramatic these vegetation changes will be in the short- to mid-term, given the existence of strong stabilizing processes. Here, we review the published evidence for recent drought-induced vegetation shifts worldwide, addressing the following questions: (i) what are the necessary conditions for vegetation shifts to occur? (ii) How much evidence of drought-induced vegetation shifts do we have at present and where are they occurring? (iii) What are the main processes that favor/oppose the occurrence of shifts at different ecological scales? (iv) What are the complications in detecting and attributing drought-induced vegetation shifts? (v) What ecological factors can interact with drought to promote shifts or stability? We propose a demographic framework to classify the likely outcome of instances of drought-induced mortality, based upon the survival of adults of potential replacement species and the regeneration of both formerly dominant affected species and potential replacement species. Out of 35 selected case studies only eight were clearly consistent with the occurrence of a vegetation shift (species or biome shift), whereas three corresponded to self-replacements in which the affected, formerly dominant species was able to regenerate after suffering drought-induced mortality. The other 24 cases were classified as uncertain, either due to lack of information or, more commonly, because the initially affected and potential replacement species all showed similar levels of regeneration after the mortality event. Overall, potential vegetation transitions were consistent with more drought-resistant species replacing less resistant ones. However, almost half (44

  13. Shifting of wrapped phase maps in the frequency domain using a rational number

    Science.gov (United States)

    Gdeisat, Munther A.; Burton, David R.; Lilley, Francis; Arevalillo-Herráez, Miguel; Abushakra, Ahmad; Qaddoura, Maen

    2016-10-01

    The number of phase wraps in an image can be either reduced, or completely eliminated, by transforming the image into the frequency domain using a Fourier transform, and then shifting the spectrum towards the origin. After this, the spectrum is transformed back to the spatial domain using the inverse Fourier transform and finally the phase is extracted using the arctangent function. However, it is a common concern that the spectrum can be shifted only by an integer number, meaning that the phase wrap reduction is often not optimal. In this paper we propose an algorithm than enables the spectrum to be frequency shifted by a rational number. The principle of the proposed method is confirmed both by using an initial computer simulation and is subsequently validated experimentally on real fringe patterns. The technique may offer in some cases the prospects of removing the necessity for a phase unwrapping process altogether and/or speeding up the phase unwrapping process. This may be beneficial in terms of potential increases in signal recovery robustness and also for use in time-critical applications.

  14. [Research on explosive temperature network monitoring system based on the linear frequency shift of spectrum].

    Science.gov (United States)

    Wen, Qiang; Lian, Su-Jie; Zhang, Chen; Zhao, Hui; Zhao, Yu; Wang, Gao; Xu, De-Gang; Yao, Jian-Quan

    2014-03-01

    In order to obtain the different position temperature changes in the process of explosive casting accurate, stability and comprehensive, we designed the temperature monitoring system based on fiber Bragg grating spectral shift. Through the fiberoptic network, the system can monitor the different point temperature of melt-cast explosive real-time. According to the function of linear frequency shift of fiber Bragg grating wavelength with the grating of temperature, we get the temperature of different positions. Four channels share a broadband light source with a coupler. The Bragg wavelengths of the 5 gratings of each fiber are separated from each other. Using the gratings designed, spliced and packaged by our own, we can obtain temperature data through the demodulator. The temperature data was processed by the Origin to draw diagram time-temperature curve. The results show that the measured temperature data of the fiber Bragg grating can meet the requirements of experiment.

  15. Detection of damaged supports under railway track based on frequency shift

    Science.gov (United States)

    Wang, Longqi; Zhang, Yao; Lie, Seng Tjhen

    2017-03-01

    In railway transportation systems, the tracks are usually fastened on sleepers which are supported by the ballast. A lot of research has been conducted to guarantee the safety of railway track because of its importance, and more concern is expressed about monitoring of track itself such as railway level and alignment. The ballast and fasteners which provide strong support to the railway track are important as well whereas the detection of loose or missing fasteners and damaged ballast mainly relies on visual inspection. Although it is reliable when the fastener is missing and the damaged ballast is on the surface, it provides less help if the fastener is only loose and the damaged ballast is under the sleepers, which are however frequently observed in practice. This paper proposes an approach based on frequency shift to identify the damaged supports including the loose or missing fasteners and damaged ballast. In this study, the rail-sleeper-ballast system is modeled as an Euler beam evenly supported by a series of springs, the stiffness of which are reduced when the fastener is loose or missing and the ballast under the sleepers is damaged. An auxiliary mass is utilized herein and when it is mounted on the beam, the natural frequencies of the whole system will change with respect to the location of the auxiliary mass. The auxiliary mass induced frequency shift is analyzed and it is found the natural frequencies change periodically when the supports are undamaged, whereas the periodicity will be broken due to damaged supports. In fact, the natural frequencies drop clearly when the auxiliary mass moves over the damaged support. A special damage index only using the information of the damaged states is proposed and both numerical and experimental examples are carried out to validate the proposed method.

  16. Are Gaze Shifts a Key to a Translator’s Text Segmentation?

    DEFF Research Database (Denmark)

    Lykke Jakobsen, Arnt

    2016-01-01

    Keystroke logging has demonstrated that a translator’s text production can be broken down into units separated by pause boundaries (Dragsted 2004, 2005, 2010). Reading research has not identified analogous boundaries, as the only interruptions in a reader’s visual attention to a text are often only...... blinks. However, in an experimental setup with tracking of a translator’s gaze movements across a screen showing the source text and (emerging) target text, gaze data show the translator’s shifts of visual attention between the two texts. Can such shifts be seen as an index of content processing units...

  17. Cloud Storage Vendors Wide Support and Security Key Features for Shifting Towards Business Perspective

    Directory of Open Access Journals (Sweden)

    T Prasath

    2014-02-01

    Full Text Available The emerging trends that suits well with the shifting terminologies of computational environment. The cloud computing plays the vital role in today’s business activities. The essential fact of computing rapid technological shift towards cloud.  The storage medium of cloud provides common public spacing, privatized infrastructure, and other platform supports are facilitated. Here in this paper a brief scrutiny  under gone on various cloud storage vendors. The various cloud storage vendors provides data storage, space availability, scaling, sharing, secure transmission between cloud storage medium. Here different vendors wide data storage mediums are discussed with their security features and data access managing capabilities are rendered.

  18. Narrow-linewidth chirped frequency comb from a frequency-shifted feedback Ti:sapphire laser seeded by a phase-modulated single-frequency fiber laser.

    Science.gov (United States)

    Brandl, Matthias F; Mücke, Oliver D

    2010-12-15

    Frequency-shifted feedback (FSF) lasers have emerged as powerful tools for precision distance metrology. At the output of a Michelson interferometer, the detected rf spectra of the FSF laser light contain a length-dependent heterodyne beat signal whose linewidth ultimately limits the achievable accuracy of length measurements. Here, we demonstrate a narrow-linewidth chirped frequency comb from an FSF Ti:sapphire ring laser seeded by a phase-modulated, ultra-low-phase-noise, single-frequency fiber laser. We experimentally investigate the influence of the seed laser linewidth on the resulting width and shape of the length-dependent rf beat signal. An ultranarrow heterodyne beat linewidth of <20 Hz is observed.

  19. Wideband multiwavelength erbium-doped fiber ring laser with frequency shifted feedback

    Science.gov (United States)

    Kim, Seung Kwan; Chu, Moo Jung; Lee, Jong Hyun

    2001-04-01

    Wideband multiwavelength erbium-doped fiber ring lasers with frequency shifted feedback are described. The use of an intra-cavity gain flattening filter (GFF) was proposed in order to increase the lasing spectral bandwidth, leading to a demonstration of 34 lasing wavelengths in 28 nm bandwidth in C-band. The GFF induced spectral output power fluctuation is discussed. Multiwavelength operation was also demonstrated for the first time in L-band, where wideband laser operation was obtained without a GFF. Optical bistability and Kerr effect induced pulsation were determined to be limiting factors to stable operation range in this kind of multiwavelength lasers.

  20. Optimization of the soliton self-frequency shift in a tapered photonic crystal fiber

    DEFF Research Database (Denmark)

    Judge, A.C.; Bang, Ole; Eggleton, B.J.

    2009-01-01

    Soliton propagation is modeled in a tapered photonic crystal fiber for various taper profiles with the purpose of optimizing the soliton self-frequency shift (SSFS) in such geometries. An optimal degree of tapering is found to exist for tapers with an axially uniform waist. In the case of axially...... of dispersive waves. In doing so, the increased nonlinearity and dispersion engineering afforded by the reduction of the core size are exploited while circumventing the limitation imposed on the soliton redshift by the associated shortening of the red zero-dispersion wavelength....

  1. Analysis of soliton self-frequency shift in ZBLAN fiber as a broadband supercontinuum medium

    Science.gov (United States)

    Yan, Xin; Liao, Meisong; Suzuki, Takenobu; Ohishi, Yasutake

    2013-03-01

    In this paper, Soliton self-frequency shift (SSFS) in ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) is investigated based on Raman gain coefficients and generalized nonlinear SchrÖdinger equation. We have measured the Raman gain coefficient spectrum of a fluoride ZBLAN glass. The Raman response function and Raman fraction of ZBLAN fibers are obtained from the actual Raman gain spectrum. The enhanced SSFS in the ZBLAN fiber under investigation as compared to the silica fiber is mainly due to the combination of nonlinear coefficient and Raman response function enhancement. Therefore, ZBLAN fiber is promising materials for SSFS.

  2. Frequency Shifts Induced by Field Gradients in Muon $g-2$ Experiments

    CERN Document Server

    Nouri, N; Golub, R; Plaster, B

    2016-01-01

    Two prominent efforts aimed at probing beyond Standard Model physics, searches for a neutron electric dipole moment (EDM) and measurements of the muon $g-2$ anomalous magnetic moment, employ spin precession techniques. In the most recent neutron EDM experiment, frequency shifts induced by magnetic field gradients and $\\mathbf{E} \\times \\mathbf{v}$ motional fields were a significant source of systematic error. We consider the possibility of a similar effect in the most recent muon $g-2$ experiment, and find that such an effect could potentially be as large as $\\sim 1$ ppm fractional error, to be compared with the reported $\\sim 0.5$ ppm error.

  3. Measurements of quadrupole frequency shift in the SPS at 26 GeV/c

    CERN Document Server

    Bohl, T; Shaposhnikova, E; Tückmantel, Joachim; CERN. Geneva. AB Department

    2008-01-01

    Measurements of the quadrupole frequency shift with intensity at 26 GeV/c using the peak detected signal were performed in the SPS from 1999 to monitor the evolution of the low-frequency longitudinal impedance [1]. While the large changes, first, due to the impedance reduction and then due to the re-installation of the MKE kickers,are easy to see, to observe small variations of impedance (as shielding or removal of a few kickers) much higher accuracy of measurements is required. This was difficult to achieve so far, mainly due to the insufficient reproducibility of the longitudinal parameters of the injected beam for different intensities as well as for different MDs. In this Note the important role of longitudinal emittance in addition to the bunch length is also revealed.

  4. Frequency-Shifted Interferometry — A Versatile Fiber-Optic Sensing Technique

    Directory of Open Access Journals (Sweden)

    Fei Ye

    2014-06-01

    Full Text Available Fiber-optic sensing is a field that is developing at a fast pace. Novel fiber-optic sensor designs and sensing principles constantly open doors for new opportunities. In this paper, we review a fiber-optic sensing technique developed in our research group called frequency-shifted interferometry (FSI. This technique uses a continuous-wave light source, an optical frequency shifter, and a slow detector. We discuss the operation principles of several FSI implementations and show their applications in fiber length and dispersion measurement, locating weak reflections along a fiber link, fiber-optic sensor multiplexing, and high-sensitivity cavity ring-down measurement. Detailed analysis of FSI system parameters is also presented.

  5. Magnetic resonance spectral reconstruction using frequency-shifted and summed Fourier transform processing

    Science.gov (United States)

    Clark, W. G.; Hanson, M. E.; Lefloch, F.; Ségransan, P.

    1995-03-01

    A novel method of Fourier transform spectroscopy of the transient signals from wide, inhomogeneously broadened magnetic resonance spectra is described and analyzed. It has the advantages of high resolution, high sensitivity, and freedom from the distortions introduced by the finite amplitude of the pulsed rf magnetic field and the finite bandwidth of the receiving system. It consists of recording the transient signal at a series of magnetic fields, shifting the frequency of the transient by the corresponding field step for each point, and summing the corresponding Fourier transformed signals. Although the primary emphasis is on pulsed NMR, the analysis also applies to pulsed ESR. Criteria for the range and step interval of the magnetic field variation are discussed. The accuracy and sensitivity of the method are compared with earlier methods of spin echo spectroscopy. A description of the corresponding measurement of NQR, NMR, and ESR spectra obtained by stepping the frequency of the spectrometer is also presented.

  6. Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis

    CERN Document Server

    Wilhelm, Matthias; Schmitt, Jens B

    2010-01-01

    Key management in wireless sensor networks faces several new challenges. The scale, resource limitations, and new threats such as node capture necessitate the use of an on-line key generation by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The practical advantage of this approach is that we do not require node movement. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the...

  7. Performance of Differential-Phase-Shift Keying Protocol Applying 1310 nm Up-Conversion Single-Photon Detector

    Institute of Scientific and Technical Information of China (English)

    FENG Chen-Xu; JIAO Rong-Zhen; ZHANG Wen-Han

    2008-01-01

    The performance of the differential-phase-shift keying (DPSK) protocol applying a 1310nm up-conversion single-photon detector is analysed. The error rate and the communication rate as a function of distance for three quantum key distribution protocols, the Bennett-Brassard 1984, the Bennett-Brassard-Mermin 1992, and the DPSK, are presented. Then we compare the performance of these three protocols using the 1310 nm up-conversion detector. We draw the conclusion that the DPSK protocol applying the detector has significant advantage over the other two protocols. Longer transmission distance and lower error rate can be achieved.

  8. DIFFERENTIAL AMPLITUDE PHASE SHIFT KEYING:A NEW MODULATION METHOD FOR TURBO CODE IN DIGITAL RADIO BROADCASTING

    Institute of Scientific and Technical Information of China (English)

    Khalid H. Sayhood; Wu Lenan

    2003-01-01

    The multilevel modulation techniques of M-Differential Amplitude Phase Shift Keying (DAPSK) have been proposed in combination with Turbo code scheme for digital radio broadcasting bands below 30 MHz radio channel. Comparison of this modulation method with channel coding in an Additive White Gaussian Noise (AWGN) and multi-path fading channels has been presented. The analysis provides an iterative decoding of the Turbo code.

  9. Frequency shifts in an optical lattice clock due to magnetic-dipole and electric-quadrupole transitions.

    Science.gov (United States)

    Taichenachev, A V; Yudin, V I; Ovsiannikov, V D; Pal'chikov, V G; Oates, C W

    2008-11-01

    We report a hitherto undiscovered frequency shift for forbidden J = 0-->J = 0 clock transitions excited in atoms confined to an optical lattice. These shifts result from magnetic-dipole and electric-quadrupole transitions, which have a spatial dependence in an optical lattice that differs from that of the stronger electric-dipole transitions. In combination with the residual translational motion of atoms in an optical lattice, this spatial mismatch leads to a frequency shift via differential energy level spacing in the lattice wells for ground state and excited state atoms. We estimate that this effect could lead to fractional frequency shifts as large as 10(-16), which might prevent lattice-based optical clocks from reaching their predicted performance levels. Moreover, these effects could shift the magic wavelength in lattice clocks in three dimensions by as much as 100 MHz, depending on the lattice configuration.

  10. Wavelength conversion through soliton self-frequency shift in tellurite microstructured fiber with picosecond pump pulse

    Science.gov (United States)

    Bi, Wanjun; Li, Xia; Xing, Zhaojun; Zhou, Qinling; Fang, Yongzheng; Gao, Weiqing; Xiong, Liangming; Hu, Lili; Liao, Meisong

    2016-01-01

    Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the soliton self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the soliton to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large soliton number N, the pulse width of the first split fundamental soliton is approximately 40 fs, producing a pulse compression factor of ˜38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous soliton shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.

  11. State-dependent alpha peak frequency shifts: Experimental evidence, potential mechanisms and functional implications.

    Science.gov (United States)

    Mierau, Andreas; Klimesch, Wolfgang; Lefebvre, Jérémie

    2017-09-30

    Neural populations produce complex oscillatory patterns thought to implement brain function. The dominant rhythm in the healthy adult human brain is formed by alpha oscillations with a typical power peak most commonly found between 8 and 12Hz. This alpha peak frequency has been repeatedly discussed as a highly heritable and stable neurophysiological "trait" marker reflecting anatomical properties of the brain, and individuals' general cognitive capacity. However, growing evidence suggests that the alpha peak frequency is highly volatile at shorter time scales, dependent on the individuals' "state". Based on the converging experimental and theoretical results from numerous recent studies, here we propose that alpha frequency variability forms the basis of an adaptive mechanism mirroring the activation level of neural populations which has important functional implications. We here integrate experimental and computational perspectives to shed new light on the potential role played by shifts in alpha peak frequency and discuss resulting implications. We further propose a potential mechanism by which alpha oscillations are regulated in a noisy network of spiking neurons in presence of delayed feedback. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity.

    Science.gov (United States)

    Zhang, Haiyang; Brunel, Marc; Romanelli, Marco; Vallet, Marc

    2016-04-01

    This paper investigates the radio frequency (RF) up-conversion properties of a frequency-shifting external cavity on a laser beam. We consider an infrared passively Q-switched pulsed laser whose intensity modulation results from the multiple round-trips in the external cavity, which contains a frequency shifter. The output beam undergoes optical second-harmonic generation necessary to reach the green wavelength. We model the pulse train using a rate-equation model to simulate the laser pulses, together with a time-delayed interference calculation taking both the diffraction efficiency and the Gaussian beam propagation into account. The predictions are verified experimentally using a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG whose pulse train makes multiple round-trips in a mode-matched external cavity containing an acousto-optic frequency shifter driven at 85 MHz. Second-harmonic generation is realized in a KTP crystal, yielding RF-modulated pulses at 532 nm with a modulation contrast of almost 100%. RF harmonics up to the 6th order (1.020 GHz) are observed in the green output pulses. Such a RF-modulated green laser may find applications in underwater detection and ranging.

  13. Performance of Coded Offset Quadrature Phase-Shift Keying (OQPSK) and MIL-STD Shaped OQPSK (SOQPSK) with Iterative Decoding

    Science.gov (United States)

    Li, L.; Simon, M. K.

    2004-02-01

    We show that, similar to the trellis-coded modulation representation of MIL-STD shaped offset quadrature phase-shift keying (SOQPSK), offset quadrature phase-shift keying (OQPSK) can be decomposed into a "degraded" trellis encoder and a memoryless mapper. Based on the representations of OQPSK and MIL-STD SOQPSK as trellis-coded modulations, we investigate the potential coding gains achievable from the application of simple outer codes to form a concatenated coding structure with iterative decoding. For MIL-STD SOQPSK, we describe the optimum receiver corresponding to its trellis-coded modulation form and then propose a simplified receiver. The bit-error-rate (BER) performances of both receivers for uncoded and coded MIL-STD SOQPSK are simulated and compared to those of OQPSK and Feher-patented quadrature phase-shift keying (FQPSK). The asymptotic BER performance of MIL-STD SOQPSK also is analyzed and compared to that of OQPSK and FQPSK. Simulation results show that, compared to their uncoded systems, both OQPSK and MIL-STD SOQPSK obtain significant coding gains by applying iterative decoding to either the parallel concatenated coding scheme or the serial one, even when very simple outer codes are used.

  14. Mathematical model for the adsorption-induced nonlocal frequency shift in adatoms-nanobeam system

    Science.gov (United States)

    Bourouina, Hicham; Yahiaoui, Réda; Kerid, Rachid; Amine Benamar, Mohammed El; Brioua, Fathi

    2017-09-01

    This paper models and investigates the resonance frequency shift induced by the adsorption phenomena for an adatoms-nanobeam system including the small scale effect as well as rotary inertia and shear distortion effects. The Lennard-Jones (6-12) type potential is used to determine the adsorption-induced energy owing van der Waals (vdW) interaction mechanism between adatom-adatom and adatom-substrate. The small scale effect is introduced by using Eringen's nonlocal elasticity theory while the explicit expressions of inertia moment and shear force are derived from the standard Timoshenko beam equations in which the residual stress effect is accounted as an additive axial load. Numerical results showed that the resonance frequency shift is depended on each of the adsorption density, mode number and small scale effects. Thus, numerical results are discussed in detail for a proper analysis of dynamic vibration behavior of adatoms-nanobeam systems which are of interest in the development of mass sensing devices.

  15. An improved Q estimation approach: the weighted centroid frequency shift method

    Science.gov (United States)

    Li, Jingnan; Wang, Shangxu; Yang, Dengfeng; Dong, Chunhui; Tao, Yonghui; Zhou, Yatao

    2016-06-01

    Seismic wave propagation in subsurface media suffers from absorption, which can be quantified by the quality factor Q. Accurate estimation of the Q factor is of great importance for the resolution enhancement of seismic data, precise imaging and interpretation, and reservoir prediction and characterization. The centroid frequency shift method (CFS) is currently one of the most commonly used Q estimation methods. However, for seismic data that contain noise, the accuracy and stability of Q extracted using CFS depend on the choice of frequency band. In order to reduce the influence of frequency band choices and obtain Q with greater precision and robustness, we present an improved CFS Q measurement approach—the weighted CFS method (WCFS), which incorporates a Gaussian weighting coefficient into the calculation procedure of the conventional CFS. The basic idea is to enhance the proportion of advantageous frequencies in the amplitude spectrum and reduce the weight of disadvantageous frequencies. In this novel method, we first construct a Gauss function using the centroid frequency and variance of the reference wavelet. Then we employ it as the weighting coefficient for the amplitude spectrum of the original signal. Finally, the conventional CFS is adopted for the weighted amplitude spectrum to extract the Q factor. Numerical tests of noise-free synthetic data demonstrate that the WCFS is feasible and efficient, and produces more accurate results than the conventional CFS. Tests for noisy synthetic data indicate that the new method has better anti-noise capability than the CFS. The application to field vertical seismic profile (VSP) data further demonstrates its validity5.

  16. The effect of diurnal variations of ionospheric parameters on Doppler frequency shift on the Boulder-Havana path

    Science.gov (United States)

    Laso, B.; Potapova, N. I.; Freizon, I. A.; Shapiro, B. S.

    1981-08-01

    An analysis of vertical-sounding and Doppler-shift data at 10 and 15 MHz obtained for the Boulder-Havana path indicates that the influence of critical frequencies is primarily manifested in variations of propagation modes and associated variations of Doppler shift. Variations of layer height are shown to have a considerable effect on the morning peak and to primarily determine the magnitude of Doppler shift during disturbed nighttime periods.

  17. Regime shifts in annual maximum rainfall across Australia - implications for intensity-frequency-duration (IFD) relationships

    Science.gov (United States)

    Verdon-Kidd, D. C.; Kiem, A. S.

    2015-12-01

    Rainfall intensity-frequency-duration (IFD) relationships are commonly required for the design and planning of water supply and management systems around the world. Currently, IFD information is based on the "stationary climate assumption" that weather at any point in time will vary randomly and that the underlying climate statistics (including both averages and extremes) will remain constant irrespective of the period of record. However, the validity of this assumption has been questioned over the last 15 years, particularly in Australia, following an improved understanding of the significant impact of climate variability and change occurring on interannual to multidecadal timescales. This paper provides evidence of regime shifts in annual maximum rainfall time series (between 1913-2010) using 96 daily rainfall stations and 66 sub-daily rainfall stations across Australia. Furthermore, the effect of these regime shifts on the resulting IFD estimates are explored for three long-term (1913-2010) sub-daily rainfall records (Brisbane, Sydney, and Melbourne) utilizing insights into multidecadal climate variability. It is demonstrated that IFD relationships may under- or over-estimate the design rainfall depending on the length and time period spanned by the rainfall data used to develop the IFD information. It is recommended that regime shifts in annual maximum rainfall be explicitly considered and appropriately treated in the ongoing revisions of the Engineers Australia guide to estimating and utilizing IFD information, Australian Rainfall and Runoff (ARR), and that clear guidance needs to be provided on how to deal with the issue of regime shifts in extreme events (irrespective of whether this is due to natural or anthropogenic climate change). The findings of our study also have important implications for other regions of the world that exhibit considerable hydroclimatic variability and where IFD information is based on relatively short data sets.

  18. Drive Signal Frequency-Lock Method Based on 90° Phase Shift for Quartz Angular-Rate Sensor

    Institute of Scientific and Technical Information of China (English)

    LIAO Xing-cai; SUN Yu-nan; TANG Qiong; CUI Fang

    2005-01-01

    A drive signal frequency-lock method for quartz angular-rate sensor is presented. The calculation result obtained by the equivalent volume force analytic method indicated that when taking the inherent frequency of the drive tines as the drive signal frequency the phase of the reference vibration is 90° behind that of the drive signal, and the square of amplitude is less than that of the maximal amplitude by 1/(4Q2d) merely. The curves derived from the finite element analytic method proved that near the inherent frequency the phase shift of the feedback voltage is identical to that of the reference vibration, and the amplitude is proportional to that of the reference vibration, and the phase shift is linear approximatively with the frequency shift. The frequency shift could be calculated according to the phase shift obtained by quadrature correlation detection, so the drive signal frequency could be locked at the inherent frequency of the drive tines by means of iteration.

  19. Ultrahigh-frequency microwave phase shifts mediated by ultrafast dynamics in quantum-dot semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2010-01-01

    We present a novel scheme to achieve tunable microwave phase shifts at frequencies exceeding 100 GHz based on wavelength conversion induced by high-speed cross-gain modulation in quantum-dot semiconductor optical amplifiers.......We present a novel scheme to achieve tunable microwave phase shifts at frequencies exceeding 100 GHz based on wavelength conversion induced by high-speed cross-gain modulation in quantum-dot semiconductor optical amplifiers....

  20. The Low-Frequency Array (LOFAR) and EoR Key-Science Project

    NARCIS (Netherlands)

    Brentjens, Michiel; Koopmans, L. V. E.; de Bruyn, A. G.; Zaroubi, S.

    The Low-Frequency ARray (LOFAR) is a novel radio-telescope facility with its core and operation center in the Netherlands. LOFAR is one of several current pathfinders toward SKA. One of LOFAR's key science projects is the detection and characterization of the redshifted 21-cm emission from neutral

  1. Frequency Shift and Sub-band Effect in Pair-Production Process Under Adiabatic Closing the External Field

    Science.gov (United States)

    Song, Xinfang; Wang, Wenyuan; Fu, Libin

    2016-09-01

    Oscillating electric field is chosen to investigate the electron-positron pair production process by using a quantum kinetic theory and the effective mass model [Phys. Rev. Lett. 112, 050402 (2014)]. The particle yield exhibits a characteristic oscillatory structure which is related to the multi-photon thresholds. The true peak positions are typically slightly above the naive threshold estimate, which is defined as frequency shift. During the numerical calculations, we find the frequency shift can be affected by the system parameters under adiabatic closing the external field, it is worthwhile to study in detail. In this paper, we investigate the frequency shift and the sub-band effect in electron-positron pair production with oscillating electric field. First, a quantum kinetic theory and the effective mass are presented to obtain the frequency shift, the results are fitted very well. And we find the frequency shift and the sub-band effect can be influenced by pulse duration, photon number, and strength of the external field. The frequency shift becomes evident as increases of photon number and the external field strength. The sub-band width is relatively lower at longer pulse duration, higher photon number region, and weaker external field. The results shown in the paper are helpful for understanding multi-photon pair production process in the strong field.

  2. Frequency-Shift Zero-Forcing Time-Varying Equalization for Doubly Selective SIMO Channels

    Directory of Open Access Journals (Sweden)

    Verde Francesco

    2006-01-01

    Full Text Available This paper deals with the problem of designing linear time-varying (LTV finite-impulse response zero-forcing (ZF equalizers for time- and frequency-selective (so-called doubly selective single-input multiple-output (SIMO channels. Specifically, relying on a basis expansion model (BEM of the rapidly time-varying channel impulse response, we derive the canonical frequency-domain representation of the minimal norm LTV-ZF equalizer, which allows one to implement it as a parallel bank of linear time-invariant filters having, as input signals, different frequency-shift (FRESH versions of the received data. Moreover, on the basis of this FRESH representation, we propose a simple and effective low-complexity version of the minimal norm LTV-ZF equalizer and we discuss the relationships between the devised FRESH equalizers and a LTV-ZF equalizer recently proposed in the literature. The performance analysis, carried out by means of computer simulations, shows that the proposed FRESH-LTV-ZF equalizers significantly outperform their competitive alternative.

  3. A New Quantum Key Distribution Scheme Based on Frequency and Time Coding

    Institute of Scientific and Technical Information of China (English)

    ZHU Chang-Hua; PEI Chang-Xing; QUAN Dong-Xiao; GAO Jing-Liang; CHEN Nan; YI Yun-Hui

    2010-01-01

    @@ A new scheme of quantum key distribution (QKD) using frequency and time coding is proposed,in which the security is based on the frequency-time uncertainty relation.In this scheme,the binary information sequence is encoded randomly on either the central frequency or the time delay of the optical pulse at the sender.The central frequency of the single photon pulse is set as ω1 for bit 0 and set as ω2 for bit 1 when frequency coding is selected.However,the single photon pulse is not delayed for bit 0 and is delayed in T for 1 when time coding is selected.At the receiver,either the frequency or the time delay of the pulse is measured randomly,and the final key is obtained after basis comparison,data reconciliation and privacy amplification.With the proposed method,the effect of the noise in the fiber channel and environment on the QKD system can be reduced effectively.

  4. Frequency Shifts of Luminescence for ZnO Nanoparticles in Porous Alumina Template

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    ZnO nanoparticles in porous anodized alumina were fabricated by sol-gel method. The PL spectra of pure ZnO nanoparticles, porous alumina template and the ZnO/PAA composite system were investigated after annealed at different temperatures. The annealing of ZnO/PAA composite system displays very complicated behavior, where changing of luminescence intensity and a "red shift" of emission frequency were observed at less or higher than 500 ℃ of the annealing temperature, respectively. To explain the phenomenon, it is considered that the emission origin of the green luminescence of ZnO nanoparticles came from OZn. It is suggested that the ZnO/PAA composite system should be annealed at the temperature above 500 ℃ in order to get intense luminescence of ZnO nanoparticle.

  5. Theoretical analyses of resonant frequency shift in anomalous dispersion enhanced resonant optical gyroscopes

    Science.gov (United States)

    Lin, Jian; Liu, Jiaming; Zhang, Hao; Li, Wenxiu; Zhao, Lu; Jin, Junjie; Huang, Anping; Zhang, Xiaofu; Xiao, Zhisong

    2016-12-01

    Rigorous expressions of resonant frequency shift (RFS) in anomalous dispersion enhanced resonant optical gyroscopes (ADEROGs) are deduced without making approximation, which provides a precise theoretical guidance to achieve ultra-sensitive ADEROGs. A refractive index related modification factor is introduced when considering special theory of relativity (STR). We demonstrate that the RFS will not be ”infinitely large” by using critical anomalous dispersion (CAD) and negative modification does not exist, which make the mechanism of anomalous dispersion enhancement clear and coherent. Although step change of RFS will happen when the anomalous dispersion condition varies, the amplification of RFS is limited by attainable variation of refractive index in practice. Moreover, it is shown that the properties of anomalous dispersion will influence not only the amplification of RFS, but also the detection range of ADEROGs.

  6. Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus

    Directory of Open Access Journals (Sweden)

    Elena T. Herruzo

    2012-03-01

    Full Text Available Bimodal atomic force microscopy is a force-microscopy method that requires the simultaneous excitation of two eigenmodes of the cantilever. This method enables the simultaneous recording of several material properties and, at the same time, it also increases the sensitivity of the microscope. Here we apply fractional calculus to express the frequency shift of the second eigenmode in terms of the fractional derivative of the interaction force. We show that this approximation is valid for situations in which the amplitude of the first mode is larger than the length of scale of the force, corresponding to the most common experimental case. We also show that this approximation is valid for very different types of tip–surface forces such as the Lennard-Jones and Derjaguin–Muller–Toporov forces.

  7. Classical calculation of relativistic frequency-shifts in an ideal Penning trap

    CERN Document Server

    Ketter, Jochen; Höcker, Martin; Schuh, Marc; Streubel, Sebastian; Blaum, Klaus

    2013-01-01

    The ideal Penning trap consists of a uniform magnetic field and an electrostatic quadrupole potential. In the classical low-energy limit, the three characteristic eigenfrequencies of a charged particle trapped in this configuration do not depend on the amplitudes of the three eigenmotions. No matter how accurate the experimental realization of the ideal Penning trap, its harmonicity is ultimately compromised by special relativity. Using a classical formalism of first-order perturbation theory, we calculate the relativistic frequency-shifts associated with the motional degrees of freedom for a spinless particle stored in an ideal Penning trap, and we compare the results with the simple but surprisingly accurate model of relativistic mass-increase.

  8. Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps

    Directory of Open Access Journals (Sweden)

    Katarzyna Krupa

    2012-01-01

    Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.

  9. On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23

    CERN Document Server

    Santos, A R G; Avelino, P P; Chaplin, W J; Campante, T L

    2016-01-01

    The activity-related variations in the solar acoustic frequencies have been known for 30 years. However, the importance of the different contributions is still not well established. With this in mind, we developed an empirical model to estimate the spot-induced frequency shifts, which takes into account the sunspot properties, such as area and latitude. The comparison between the model frequency shifts obtained from the daily sunspot records and those observed suggests that the contribution from a stochastic component to the total frequency shifts is about 30%. The remaining 70% is related to a global, long-term variation. We also propose a new observable to investigate the short- and mid-term variations of the frequency shifts, which is insensitive to the long-term variations contained in the data. On the shortest time scales the variations in the frequency shifts are strongly correlated with the variations in the total area covered by sunspots. However, a significant loss of correlation is still found, whic...

  10. A Study of Shift-Frequency Jamming to LPI Radar%一种低截获概率雷达的移频干扰研究

    Institute of Scientific and Technical Information of China (English)

    吕亚昆; 杨承志; 芦建辉; 张晓杰

    2014-01-01

    A combined modulation LPI radar signal-frequency modulated continuous wave-phase shift keying (FMCW-PSK) was designed ,and the effect to matched filtering of the two characteristics ,carrier frequency and frequency rate of the signal were analyzed .Starting from these two characteristic ,their changes on the radar signal's jamming were studied .The false Doppler shift-frequency jamming on radar signals influence and jamming effects were analyzed in detail .Based on this an improved method was proposed ,which was sawtooth wave frequency-shift jamming ,and a detailed theoretical analysis and simulation was given .The results showed that the jamming can achieve better results ,verified the shift frequency jamming was an effective jamming method to the low probability of intercept radar .%设计了一种调频连续波-相移键控复合调制的低截获概率雷达信号,并分析了频率、调频斜率两个特征对信号匹配滤波的影响。从这两个特征入手研究利用特征变化对雷达信号的干扰。详细分析了假多普勒移频干扰对雷达信号的影响和干扰效果,在此基础上提出了锯齿波移频改进干扰方法,并给出了仿真实验,结果表明可以实现较好的干扰效果,验证了移频干扰是对低截获概率雷达的一种有效干扰。

  11. Using noncontact AFM frequency shifts to determine stereocilia bundle stiffness and tension in the developing cochlear sensory epithelium

    Science.gov (United States)

    Chadwick, Richard S.; Cartagena-Rivera, Alexander X.

    2015-12-01

    Measurement of frequency shifts of cantilevers having an attached microsphere oscillating at acoustic frequencies can be used to assess mechanical properties of cochlear structures. The method has already been reported for measuring elastic and viscous properties of the tectorial membrane. We describe here how the method can be used to examine other cochlear structures. Theory and formulas for relating hair bundle stiffness and tension in the developing cochlear sensory epithelium to measured frequency shifts are given to estimate the expected frequency shifts and show feasibility of the measurements. We show through a molecular model of myosin II located along the edges of confluent hexagons that myosin contractile forces are balanced by isotropic tension in the developing confluent sheet of cells.

  12. Measurement of Frequency Shift Characteristics Based on LiNbO3 Waveguide Electro-Optic Intensity Modulator

    Institute of Scientific and Technical Information of China (English)

    Zhou Meng; Hui-Juan Zhou; Yi Liao; Qiong Yao

    2008-01-01

    High-speed and wide-band LiNbO3 waveguide electro-optic intensity modulator has drawn great attention in the field of optical fiber communi-cation and sensor. This paper reports the research results on the measurement of frequency shift character-istics of Mach-Zehnder electro-optic intensity modulator. Two measurement methods of frequency shift character-istics for high and low frequency modulations are studied in theory and experiment and demonstrate different results. The realization of a multi-wavelength optical source based on Mach-Zehnder electro-optic intensity modulator has been introduced. The technique to reach the maximum intensity for interesting shift frequency, particularly for heterodyne detection of Brillouin distributed optical fiber sensing, has been given.

  13. Intercomparison of Methods for Determination of Resonant Frequency Shift of a Microstrip Patch Antenna Loaded with Hevea Rubber Latex

    Directory of Open Access Journals (Sweden)

    Nor Zakiah Yahaya

    2014-01-01

    Full Text Available This paper presents an intercomparison between the finite element method, method of moment, and the variational method to determine the effect of moisture content on the resonant frequency shift of a microstrip patch loaded with wet material. The samples selected for this study were Hevea rubber latex with different percentages of moisture content from 35% to 85%. The results were compared with the measurement data in the frequency range between 1 GHz and 4 GHz. It was found that the finite element method is the most accurate among all the three computational techniques with 0.1 mean error when compared to the measured resonant frequency shift. A calibration equation was obtained to predict moisture content from the measured frequency shift with an accuracy of 2%.

  14. PDF neuron firing phase-shifts key circadian activity neurons in Drosophila.

    Science.gov (United States)

    Guo, Fang; Cerullo, Isadora; Chen, Xiao; Rosbash, Michael

    2014-06-17

    Our experiments address two long-standing models for the function of the Drosophila brain circadian network: a dual oscillator model, which emphasizes the primacy of PDF-containing neurons, and a cell-autonomous model for circadian phase adjustment. We identify five different circadian (E) neurons that are a major source of rhythmicity and locomotor activity. Brief firing of PDF cells at different times of day generates a phase response curve (PRC), which mimics a light-mediated PRC and requires PDF receptor expression in the five E neurons. Firing also resembles light by causing TIM degradation in downstream neurons. Unlike light however, firing-mediated phase-shifting is CRY-independent and exploits the E3 ligase component CUL-3 in the early night to degrade TIM. Our results suggest that PDF neurons integrate light information and then modulate the phase of E cell oscillations and behavioral rhythms. The results also explain how fly brain rhythms persist in constant darkness and without CRY.

  15. PDF neuron firing phase-shifts key circadian activity neurons in Drosophila

    Science.gov (United States)

    Guo, Fang; Cerullo, Isadora; Chen, Xiao; Rosbash, Michael

    2014-01-01

    Our experiments address two long-standing models for the function of the Drosophila brain circadian network: a dual oscillator model, which emphasizes the primacy of PDF-containing neurons, and a cell-autonomous model for circadian phase adjustment. We identify five different circadian (E) neurons that are a major source of rhythmicity and locomotor activity. Brief firing of PDF cells at different times of day generates a phase response curve (PRC), which mimics a light-mediated PRC and requires PDF receptor expression in the five E neurons. Firing also resembles light by causing TIM degradation in downstream neurons. Unlike light however, firing-mediated phase-shifting is CRY-independent and exploits the E3 ligase component CUL-3 in the early night to degrade TIM. Our results suggest that PDF neurons integrate light information and then modulate the phase of E cell oscillations and behavioral rhythms. The results also explain how fly brain rhythms persist in constant darkness and without CRY. DOI: http://dx.doi.org/10.7554/eLife.02780.001 PMID:24939987

  16. Orthogonal frequency division multiplexed quantum key distribution in the presence of Raman noise

    Science.gov (United States)

    Bahrani, Sima; Razavi, Mohsen; Salehi, Jawad A.

    2016-04-01

    In this paper, we investigate the performance of orthogonal frequency division multiplexed quantum key distribution (OFDM-QKD) in an integrated quantum-classical wavelength-division-multiplexing system. The presence of an intense classical signal alongside the quantum one generates Raman background noise. Noise reduction techniques should, then, be carried out at the receiver to suppress this crosstalk noise. In this work, we show that OFDM-QKD enables efficient filtering, in time and frequency domains, making it an attractive solution for the high-rate links at the core of quantum-classical networks.

  17. Robustness of the round-robin differential-phase-shift quantum-key-distribution protocol against source flaws

    Science.gov (United States)

    Mizutani, Akihiro; Imoto, Nobuyuki; Tamaki, Kiyoshi

    2015-12-01

    Recently, a new type of quantum key distribution, called the round-robin differential-phase-shift (RRDPS) protocol [T. Sasaki et al., Nature (London) 509, 475 (2014), 10.1038/nature13303], was proposed, where the security can be guaranteed without monitoring any statistics. In this Rapid Communication, we investigate source imperfections and side-channel attacks on the source of this protocol. We show that only three assumptions are needed for the security, and no detailed characterizations of the source or the side-channel attacks are needed. This high robustness is another striking advantage of the RRDPS protocol over other protocols.

  18. Practical Quantum Private Database Queries Based on Passive Round-Robin Differential Phase-shift Quantum Key Distribution

    Science.gov (United States)

    Li, Jian; Yang, Yu-Guang; Chen, Xiu-Bo; Zhou, Yi-Hua; Shi, Wei-Min

    2016-08-01

    A novel quantum private database query protocol is proposed, based on passive round-robin differential phase-shift quantum key distribution. Compared with previous quantum private database query protocols, the present protocol has the following unique merits: (i) the user Alice can obtain one and only one key bit so that both the efficiency and security of the present protocol can be ensured, and (ii) it does not require to change the length difference of the two arms in a Mach-Zehnder interferometer and just chooses two pulses passively to interfere with so that it is much simpler and more practical. The present protocol is also proved to be secure in terms of the user security and database security.

  19. Vibrational dephasing and frequency shifts of hydrogen-bonded pyridine-water complexes

    Science.gov (United States)

    Kalampounias, A. G.; Tsilomelekis, G.; Boghosian, S.

    2015-01-01

    In this paper we present the picosecond vibrational dynamics and Raman shifts of hydrogen-bonded pyridine-water complexes present in aqueous solutions in a wide concentration range from dense to extreme dilute solutions. We studied the vibrational dephasing and vibrational frequency modulation by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The concentration induced variations in bandwidths, band frequencies and characteristic dephasing times have been estimated and interpreted as effects due to solute-solvent interactions. The time-correlation functions of vibrational dephasing were obtained for the ring breathing mode of both "free" and hydrogen-bonded pyridine molecules and it was found that sufficiently deviate from the Kubo model. There is a general agreement in the whole concentration range with the modeling proposed by the Rothschild approach, which applies to complex liquids. The results have shown that the reorientation of pyridine aqueous solutions is very slow and hence in both scattering geometries only vibrational dephasing is probed. It is proposed that the spectral changes depend on the perturbations induced by the dynamics of the water molecules in the first hydration cell and water in bulk, while at extreme dilution conditions, the number of bulk water molecules increases and the interchange between molecules belonging to the first hydration cell may not be the predominant modulation mechanism. The evolution of several parameters, such as the characteristic times, the percentage of Gaussian character in the peak shape and the a parameter are indicative of drastic variations at extreme dilution revealing changes in the vibrational relaxation of the pyridine complexes in the aqueous environment. The higher dilution is correlated to diffusion of water molecules into the reference pyridine system in agreement with the jump diffusion model, while at extreme dilutions, almost all pyridine molecules are

  20. Vibrational dephasing and frequency shifts of hydrogen-bonded pyridine-water complexes.

    Science.gov (United States)

    Kalampounias, A G; Tsilomelekis, G; Boghosian, S

    2015-01-25

    In this paper we present the picosecond vibrational dynamics and Raman shifts of hydrogen-bonded pyridine-water complexes present in aqueous solutions in a wide concentration range from dense to extreme dilute solutions. We studied the vibrational dephasing and vibrational frequency modulation by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The concentration induced variations in bandwidths, band frequencies and characteristic dephasing times have been estimated and interpreted as effects due to solute-solvent interactions. The time-correlation functions of vibrational dephasing were obtained for the ring breathing mode of both "free" and hydrogen-bonded pyridine molecules and it was found that sufficiently deviate from the Kubo model. There is a general agreement in the whole concentration range with the modeling proposed by the Rothschild approach, which applies to complex liquids. The results have shown that the reorientation of pyridine aqueous solutions is very slow and hence in both scattering geometries only vibrational dephasing is probed. It is proposed that the spectral changes depend on the perturbations induced by the dynamics of the water molecules in the first hydration cell and water in bulk, while at extreme dilution conditions, the number of bulk water molecules increases and the interchange between molecules belonging to the first hydration cell may not be the predominant modulation mechanism. The evolution of several parameters, such as the characteristic times, the percentage of Gaussian character in the peak shape and the a parameter are indicative of drastic variations at extreme dilution revealing changes in the vibrational relaxation of the pyridine complexes in the aqueous environment. The higher dilution is correlated to diffusion of water molecules into the reference pyridine system in agreement with the jump diffusion model, while at extreme dilutions, almost all pyridine molecules are

  1. Evaluation of quadrature-phase-shift-keying signal characteristics in W-band radio-over-fiber transmission using direct in-phase/quadrature-phase conversion technique

    Science.gov (United States)

    Suzuki, Meisaku; Kanno, Atsushi; Yamamoto, Naokatsu; Sotobayashi, Hideyuki

    2016-02-01

    The effects of in-phase/quadrature-phase (IQ) imbalances are evaluated with a direct IQ down-converter in the W-band (75-110 GHz). The IQ imbalance of the converter is measured within a range of +/-10 degrees in an intermediate frequency of DC-26.5 GHz. 1-8-G-baud quadrature phase-shift keying (QPSK) signals are transmitted successfully with observed bit error rates within a forward error correction limit of 2×10-3 using radio over fiber (RoF) techniques. The direct down-conversion technique is applicable to next-generation high-speed wireless access communication systems in the millimeter-wave band.

  2. Soliton self-frequency blue-shift in gas-filled hollow-core photonic crystal fibers

    CERN Document Server

    Saleh, Mohammed F; Hoelzer, Philipp; Nazarkin, Alexander; Travers, John C; Joly, Nicolas Y; Russell, Philip St J; Biancalana, Fabio

    2011-01-01

    We show theoretically that the photoionization process in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas leads to a constant acceleration of solitons in the time domain with a continuous shift to higher frequencies, limited only by ionization loss. This phenomenon is opposite to the well-known Raman self-frequency red-shift of solitons in solid-core glass fibers. We also predict the existence of unconventional long-range non-local soliton interactions leading to spectral and temporal soliton clustering. Furthermore, if the core is filled with a Raman-active molecular gas, spectral transformations between red-shifted, blue-shifted and stabilized solitons can take place in the same fiber.

  3. Analytical study of the frequency shifts of micro and nano clamped–clamped beam resonators due to an added mass

    KAUST Repository

    Bouchaala, Adam M.

    2016-03-18

    We present analytical formulations to calculate the induced resonance frequency shifts of electrically actuated clamped–clamped micro and nano (Carbon nanotube) beams due to an added mass. Based on the Euler–Bernoulli beam theory, we investigate the linear dynamic responses of the beams added masses, which are modeled as discrete point masses. Analytical expressions based on perturbation techniques and a one-mode Galerkin approximation are developed to calculate accurately the frequency shifts under a DC voltage as a function of the added mass and position. The analytical results are compared to numerical solution of the eigenvalue problem. Results are shown for the fundamental as well as the higher-order modes of the beams. The results indicate a significant increase in the frequency shift, and hence the sensitivity of detection, when scaling down to nano scale and using higher-order modes. © 2016 Springer Science+Business Media Dordrecht

  4. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. H.; Luo, H.; Qu, T. L., E-mail: qutianliang@nudt.edu.cn; Yang, K. Y.; Ding, Z. C. [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2015-10-15

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  5. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    Directory of Open Access Journals (Sweden)

    X. H. Liu

    2015-10-01

    Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  6. Exploring the sources of p-mode frequency shifts in the CoRoT target HD 49933

    CERN Document Server

    Liu, Zhie; Yang, Wuming; Li, Tanda; Liu, Kang; Tian, Zhijia; Ge, Zhishuai; Yu, Jie

    2014-01-01

    The oscillations of the solar-like star HD 49933 have been observed thoroughly by CoRot. Two dozens of frequency shifts, which are closely related with the change in magnetic activity, have been measured. To explore the effects of the magnetic activity on the frequency shifts, we calculate frequency shifts for the radial and $l = 1$ p-modes of HD 49933 with the general variational method, which evaluates the shifts using a spatial integral of the product of a kernel and some sources. The theoretical frequency shifts well reproduce the observation. The magnitudes and positions of the sources are determined according to the $\\chi^2$ criterion. We predict the source that contributes to both $l = 0$ and $l = 1$ modes is located at $0.48 - 0.62$Mm below the stellar surface. In addition, based on the assumption that $A_{0}$ is proportional to the change in the MgII activity index $\\Delta{i}_{MgII}$, we obtained that the change of MgII index between minimum and maximum of HD 49933 cycle period is about 0.665. The ma...

  7. Analytical calculation of the frequency shift in phase oscillators driven by colored noise: implications for electrical engineering and neuroscience.

    Science.gov (United States)

    Galán, Roberto F

    2009-09-01

    We provide an analytical expression for the mean frequency shift in phase oscillators as a function of the standard deviation, sigma and the autocorrelation time, tau of small random perturbations. We show that the frequency shift is negative and proportional to sigma;{2} . Its absolute value increases monotonically with tau , approaching an asymptote determined by the L2 -norm of the phase-response curve. We validate our theoretical predictions with computer simulations and discuss their implications for the design of electronic oscillators and for the encoding of information in biological neural networks.

  8. Soliton self-frequency blue-shift in gas-filled hollow-core photonic crystal fibers

    OpenAIRE

    2011-01-01

    We show theoretically that the photoionization process in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas leads to a constant acceleration of solitons in the time domain with a continuous shift to higher frequencies, limited only by ionization loss. This phenomenon is opposite to the well-known Raman self-frequency red-shift of solitons in solid-core glass fibers. We also predict the existence of unconventional long-range non-local soliton interactions leading to s...

  9. Optimal spectral filtering in soliton self-frequency shift for deep-tissue multiphoton microscopy

    Science.gov (United States)

    Wang, Ke; Qiu, Ping

    2015-05-01

    Tunable optical solitons generated by soliton self-frequency shift (SSFS) have become valuable tools for multiphoton microscopy (MPM). Recent progress in MPM using 1700 nm excitation enabled visualizing subcortical structures in mouse brain in vivo for the first time. Such an excitation source can be readily obtained by SSFS in a large effective-mode-area photonic crystal rod with a 1550-nm fiber femtosecond laser. A longpass filter was typically used to isolate the soliton from the residual in order to avoid excessive energy deposit on the sample, which ultimately leads to optical damage. However, since the soliton was not cleanly separated from the residual, the criterion for choosing the optimal filtering wavelength is lacking. Here, we propose maximizing the ratio between the multiphoton signal and the n'th power of the excitation pulse energy as a criterion for optimal spectral filtering in SSFS when the soliton shows dramatic overlapping with the residual. This optimization is based on the most efficient signal generation and entirely depends on physical quantities that can be easily measured experimentally. Its application to MPM may reduce tissue damage, while maintaining high signal levels for efficient deep penetration.

  10. Dependence of Brillouin frequency shift on water absorption ratio in polymer optical fibers

    Science.gov (United States)

    Minakawa, Kazunari; Koike, Kotaro; Hayashi, Neisei; Koike, Yasuhiro; Mizuno, Yosuke; Nakamura, Kentaro

    2016-06-01

    We studied the dependence of the Brillouin frequency shift (BFS) on the water-absorption ratio in poly(methyl methacrylate)-based polymer optical fibers (POFs) to clarify the effect of the humidity on POF-based Brillouin sensors. The BFS, deduced indirectly using an ultrasonic pulse-echo technique, decreased monotonically as the water absorption ratio increased, mainly because of the decrease in the Young's modulus. For the same water absorption ratio, the BFS change was larger at a higher temperature. The maximal BFS changes (absolute values) at 40, 60, and 80 °C were 158, 285, and 510 MHz, respectively (corresponding to the temperature changes of ˜9 °C, ˜16 °C, and ˜30 °C). Thus, some countermeasure against the humidity is indispensable in implementing strain/temperature sensors based on Brillouin scattering in POFs, especially at a higher temperature. On the other hand, Brillouin-based distributed humidity sensors might be developed by exploiting the BFS dependence on water absorption in POFs.

  11. Modified reverse tapering method to prevent frequency shift of the radiation in the planar undulator

    Science.gov (United States)

    Shim, Chi Hyun; Ko, In Soo; Parc, Yong Woon

    2017-03-01

    This paper presents a modified reverse tapering method to generate a polarized soft x ray in x-ray free-electron lasers (XFELs) with a higher photon power and a shorter undulator length than the simple linear reverse tapering method. In the proposed method, a few untapered planar undulators are added before the simple linear reverse tapering section of the undulator line. This simple modification prevents the frequency shift of the radiation that occurs when the simple linear reverse tapering method is applied to planar undulators. In the proposed method, the total length of planar undulators decreased in spite of the additional untapered undulators. When the modified reverse tapering method is used with four untapered planar undulators, the total length of the planar undulators is 64.6 m. On the other hand, the required length of the planar undulators is 94.6 m when the simple linear reverse tapering method is used. The proposed method gives us a way to generate a soft x-ray pulse (1.24 keV) with a high degree of polarization (>0.99 ) and radiation power (>30 GW ) at the new undulator line with a 10-GeV electron beam in the Pohang Accelerator Laboratory X-ray Free-Electron Laser. This method can be applied in the existing XFELs in the world without any change in the undulator lines.

  12. 25 Gbit/s differential phase-shift-keying signal generation using directly modulated quantum-dot semiconductor optical amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Zeghuzi, A., E-mail: zeghuzi@mailbox.tu-berlin.de; Schmeckebier, H.; Stubenrauch, M.; Bimberg, D. [Department of Solid-State Physics, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Meuer, C.; Schubert, C. [Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, Einsteinufer 37, 10587 Berlin (Germany); Bunge, C.-A. [Hochschule fuer Telekommunikation Leipzig (HfTL), Gustav-Freytag-Str. 43-45, 04277 Leipzig (Germany)

    2015-05-25

    Error-free generation of 25-Gbit/s differential phase-shift keying (DPSK) signals via direct modulation of InAs quantum-dot (QD) based semiconductor optical amplifiers (SOAs) is experimentally demonstrated with an input power level of −5 dBm. The QD SOAs emit in the 1.3-μm wavelength range and provide a small-signal fiber-to-fiber gain of 8 dB. Furthermore, error-free DPSK modulation is achieved for constant optical input power levels from 3 dBm down to only −11 dBm for a bit rate of 20 Gbit/s. Direct phase modulation of QD SOAs via current changes is thus demonstrated to be much faster than direct gain modulation.

  13. Numerical analysis for four-wave mixing based wavelength conversion of differential phase-shift keying signals

    Institute of Scientific and Technical Information of China (English)

    Liang Jia; Fan Zhang; Ming Li; Yuliang Liu; Zhangyuan Chen

    2009-01-01

    We numerically investigate the main constrains for high efficiency wavelength conversion of differential phase-shift keying (DPSK) signals based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF). Using multi-tone pump phase modulation techniques, high efficiency wavelength conversion of DPSK signals is achieved with the stimulated Brillouin scattering (SBS) effects effectively suppressed. Our analysis shows that there is a compromise between conversion efficiency and converted idler degradation. By optimizing the pump phase modulation configuration, the converted DPSK idler's degradation can be dramatically decreased through balancing SBS suppression and pump phase modulation degradation. Our simulation results also show that these multi-tone pump phase modulation techniques are more appropriate for the future high bit rate systems.

  14. Optical encryption of parallel quadrature phase shift keying signals based on nondegenerate four-wave mixing in highly nonlinear fiber

    Science.gov (United States)

    Cui, Yue; Zhang, Min; Zhan, Yueying; Wang, Danshi; Huang, Shanguo

    2016-08-01

    A scheme for optical parallel encryption/decryption of quadrature phase shift keying (QPSK) signals is proposed, in which three QPSK signals at 10 Gb/s are encrypted and decrypted simultaneously in the optical domain through nondegenerate four-wave mixing in a highly nonlinear fiber. The results of theoretical analysis and simulations show that the scheme can perform high-speed wiretapping against the encryption of parallel signals and receiver sensitivities of encrypted signal and the decrypted signal are -25.9 and -23.8 dBm, respectively, at the forward error correction threshold. The results are useful for designing high-speed encryption/decryption of advanced modulated signals and thus enhancing the physical layer security of optical networks.

  15. Broadband-tunable LP$_{01}$ mode frequency shifting by Raman coherence waves in H$_2$-filled hollow-core PCF

    CERN Document Server

    Bauerschmidt, S T; Abdolvand, Amir; Russell, Philip S J

    2015-01-01

    When a laser pump beam of sufficient intensity is incident on a Raman-active medium such as hydrogen gas, a strong Stokes signal, red-shifted by the Raman transition frequency {\\Omega}$_R$, is generated. This is accompanied by the creation of a "coherence wave" of synchronized molecular oscillations with wavevector {\\Delta}{\\beta} determined by the optical dispersion. Within its lifetime, this coherence wave can be used to shift by {\\Omega}$_R$ the frequency of a third "mixing" signal, provided phase-matching is satisfied, i.e., {\\Delta}{\\beta} is matched. Conventionally this can be arranged using non-collinear beams or higher-order waveguide modes. Here we report collinear phase-matched frequency shifting of an arbitrary mixing signal using only the fundamental LP$_{01}$ modes of a hydrogen-filled hollow-core PCF. This is made possible by the S-shaped dispersion curve that occurs around the pressure-tunable zero dispersion point. Phase-matched frequency shifting by 125 THz is possible from the UV to the near...

  16. Ultrafast OH-stretching frequency shifts of hydrogen- bonded 2-naphthol photoacid-base complexes in solution

    Directory of Open Access Journals (Sweden)

    Batista VictorS.

    2013-03-01

    Full Text Available We characterize the transient solvent-dependent OH-stretching frequency shifts of photoacid 2-naphthol hydrogen-bonded with CH3CN in the S0- and S1-states using a combined experimental and theoretical approach, and disentangle specific hydrogen-bonding contributions from nonspecific dielectric response.

  17. The effects of relativistic broadening and frequency down-shift on electron-cyclotron emission measurements in EAST

    Institute of Scientific and Technical Information of China (English)

    Liu Yong; Han Xiang; Ti Ang; Wang Yu-Min; Ling Bi-Li; Hu Li-Qun; Gao Xiang

    2012-01-01

    This paper presents a theoretical calculation of the effects of relativistic broadening and frequency down-shift on the electron cyclotron emission measurements for a wide range of plasma parameters in the Experimental Advanced Superconducting Tokamak (EAST).The calculation is based on the radiation transfer equation,with the reabsorption and reemission processes taken into account.The broadening effect contributes to the radial resolution of the measurement,and the calculation results indicate that it is ~ 2 cm in the case of the central electron temperature 10 keV.A pseudo radial displacement of the obtained electron temperature profile occurs if the relativistic frequency down-shift effect is not taken into account in the determination of the emission layer position.The shift could be a few centimeters as the electron temperature increases,and this effect should be taken into account.

  18. A calibration concept for passive MW imaging using beam steering by frequency shift and aperture synthesis

    Science.gov (United States)

    Schreiber, Eric; Peichl, Markus; Jirousek, Matthias

    2013-10-01

    Passive microwave (MW) remote sensing is used in Earth observation missions for example to estimate the salinity of oceans or the soil moisture of landscapes. In these cases the absolute brightness temperature numbers are important for sufficient accuracy of the estimated geo-physical parameters. Consequently a suitable system calibration network is required. At DLR a radiometric demonstrator for fully-electronic MW imaging was set up at Ka-band, which is based on a combination of beam steering by frequency shift using a broadband slotted-waveguide antenna for one scanning direction, and the application of aperture synthesis for the other direction. Aperture synthesis is well known from radio astronomy, but it is still a new imaging principle for Earth observation or security applications. Hence as well new calibration techniques have to be developed for this kind of scanning mechanism. In this paper a novel approach for a noise-source based calibration method taking into account the antenna losses will be introduced. When using aperture synthesis techniques to determine the absolute brightness temperature values, it is very important, among other things, to know the exact phase transfer function of the system in order to achieve the desired radiometric resolution. Consequently our approach enables phase calibration as well. The paper outlines a proof of concept for this calibration method using a two-element interferometer called VESAS (Voll Elektronischer Scanner mit AperturSynthese) as a demonstrator. The functionality of the demonstrator and the proof of concept of the imaging principle mentioned before are written in detail in [1].

  19. The Effect of Doppler Frequency Shift, Frequency Offset of the Local Oscillators, and Phase Noise on the Performance of Coherent OFDM Receivers

    Science.gov (United States)

    Xiong, Fuqin; Andro, Monty

    2001-01-01

    This paper first shows that the Doppler frequency shift affects the frequencies of the RF carrier, subcarriers, envelope, and symbol timing by the same percentage in an Orthogonal Frequency Division Multiplexing (OFDM) signal or any other modulated signals. Then the SNR degradation of an OFDM system due to Doppler frequency shift, frequency offset of the local oscillators and phase noise is analyzed. Expressions are given and values for 4-, 16-, 64-, and 256-QAM OFDM systems are calculated and plotted. The calculations show that the Doppler shift of the D3 project is about 305 kHz, and the degradation due to it is about 0.01 to 0.04 dB, which is negligible. The degradation due to frequency offset and phase noise of local oscillators will be the main source of degradation. To keep the SNR degradation under 0.1 dB, the relative frequency offset due to local oscillators must be below 0.01 for the 16 QAM-OFDM. This translates to an offset of 1.55 MHz (0.01 x 155 MHz) or a stability of 77.5 ppm (0.01 x 155 MHz/20 GHz) for the DI project. To keep the SNR degradation under 0.1 dB, the relative linewidth (0) due to phase noise of the local oscillators must be below 0.0004 for the 16 QAM-OFDM. This translates to a linewidth of 0.062 MHz (0.0004 x 155 MHz) of the 20 GHz RIF carrier. For a degradation of 1 dB, beta = 0.04, and the linewidth can be relaxed to 6.2 MHz.

  20. Application of the light-shift effect to laser frequency stabilization with reference to a microwave frequency standard

    Energy Technology Data Exchange (ETDEWEB)

    Arditi, M. (Univ. of Paris, Orsay, France); Picque, J.L.

    1975-10-01

    A new method allowing laser frequency stabilization with reference to a microwave oscillator, independently of the laser intensity, is described. The method makes use of the dependence of the ground-state HF transition frequency on the optical radiation frequency in alkali atoms irradiated by quasi-resonant light. Preliminary experimental investigations are reported in the case of a cw CaAs diode laser tuned to the D2 absorption line in a cesium gas cell. The absolute laser frequency exhibited variations of 1.4 MHz rms around an average value determined to within 2 parts in 100 billions for a period of 5 min. The possibility of defining a cesium beam, reference wavelength connected with the time standard is discussed.

  1. A dual-frequency online PMP method with phase-shifting parallel to moving direction of measured object

    Science.gov (United States)

    Peng, Kuang; Cao, Yiping; Wu, Yingchun; Chen, Cheng; Wan, Yingying

    2017-01-01

    A dual-frequency online phase measurement profilometry (PMP) method with phase-shifting parallel to moving direction of measured object is proposed in this paper. The high-frequency fringe is used for the better modulation patterns in pixel matching and it is not modified by the measured object's surface. Based on the relative positive between the moving measured object and digital light processing (DLP), the high-frequency fringe in each dual-frequency deformed pattern after pixel matching is the same. As a result, the phase can be calculated directly by the improved Stoilov algorithm without filtering out the low-frequency component containing the measured object's height information. As there is no filtering process in phase calculation, the valid information loss can be avoided so that the accuracy of the proposed method can be guaranteed. Simulations and experiments prove the method's feasibility and precision.

  2. Employing circle polarization shift keying in free space optical communication with gamma-gamma atmospheric turbulence channel

    Science.gov (United States)

    Wang, Yi; Du, Fan; Ma, Jing; Tan, Liying

    2014-12-01

    A novel theoretical model of a circular polarization shift keying (CPolSK) system for free space optical links through an atmospheric turbulence channel, is proposed. Intensity scintillation and phase fluctuation induced in atmospheric turbulence, from weak to strong levels, are specifically researched with respect to circular polarization control error caused by the system design. We derive closed form expressions of the bit error rate (BER) and outage probability for evaluating the BER performance and communication interruption in the Gamma-Gamma distributed channel model. Simulation results show that atmospheric turbulence and circular polarization control error have significant effects on the BER performance and interruption of communication in the CPolSK system. The deterioration in BER performance, caused by intensity scintillation and phase fluctuation, is augmented by the power penalty conditioned by the circular polarization control error. This consequently adds to the demand for emissive power from the CPolSK system. Furthermore, we demonstrate that controlling the circular polarization control error below 8° as well as the normalized threshold within 8 dB, 9 dB and 10 dB in turbulent scenarios from weak to strong levels can significantly reduce the probability of communication interruption occurring. This study provides reference material for further design of the CPolSK system.

  3. Modulation Depth Based on Frequency-shift Characteristic of LiNbO3 Waveguide Electro-optic Intensity Modulator

    Institute of Scientific and Technical Information of China (English)

    Hui-juan ZHOU; Zhou MENG; Yi LIAO

    2010-01-01

    The modulation depth,defined according to practical mod-ulation results,which changes with the microwave power and its fre-quency,is significant for systems utilizing the frequency-shift charac-teristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator (EOIM).By analyzing the impedance mismatch between the micro-wave source and the EOIM,the effective voltage applied to the RF port of the EOIM is deprived frcm the microwave power and its fre-quency.Associating with analyses of the phase velocity mismatch be-tween the microwave and the optical wave,the theoretical modulation depth has been obtained,which is verified by experimental results.We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias far the system based an the frequency-shift characteristic of the EOIM.

  4. Nonlinear frequency shift of electrostatic waves in general collisionless plasma: unifying theory of fluid and kinetic nonlinearities

    CERN Document Server

    Liu, Chang

    2015-01-01

    The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the ?first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.

  5. Impact of frequency modulation ratio on capacitor cells balancing in phase-shifted PWM based chain-link STATCOM

    DEFF Research Database (Denmark)

    Behrouzian, Ehsan; Bongiorno, Massimo; Teodorescu, Remus

    2014-01-01

    The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power that flows in the cells of a chain-link based STATCOM when using Phase-Shifted PWM. Two different cases are investigated for the converter cells: low, and high switching frequency. It is shown...... distribution among cells of the same phase leg, thus contributing to the capacitors balancing. Theoretical conclusions are validated through PSCAD simulation results....

  6. Multivariate analysis of spectral data with frequency shifts: application to temperature dependent infrared spectra of peptides and proteins.

    Science.gov (United States)

    Kubelka, Jan

    2013-10-15

    Changes in the amide I' IR band with temperature are widely used for elucidation of peptide and protein conformational transitions and folding equilibria. Since amide I' exhibits inherent temperature dependent frequency shifts, standard mixture analysis methods are not applicable. To reliably extract the true thermodynamic states, frequency shifts of the component spectra must be explicitly taken into account. For this purpose, new methods termed shifted multivariate spectra analysis (SMSA) and parametric SMSA (pSMSA) are developed and tested on sets of synthetic data as well as real experimental amide I' spectra for thermal unfolding of an α-helical peptide. SMSA uses no specific functional form for the transition (soft modeling), while the parametric variant (pSMSA) assumes a thermodynamic model (hard modeling). The implementation is optimized specifically for amide I' IR in that it takes advantage of known, linear dependence of the frequencies as well as intensities on temperature. The synthetic data tests demonstrate the robustness of the methods; the initial test parameters are recovered with a high degree of reliability, although the nonparameteric SMSA is subject to the rotational ambiguity. Application to the peptide experimental amide I' data illustrates additional complications encountered with the analysis of real systems, such as correction for the side-chain spectra and interference of spectral shape changes. Nevertheless, the results are in excellent agreement with the independent control using circular dichroism (CD) data. The general applicability and limitations of the methods are discussed along with potential extensions.

  7. Magnetic susceptibility induced white matter MR signal frequency shifts--experimental comparison between Lorentzian sphere and generalized Lorentzian approaches.

    Science.gov (United States)

    Luo, J; He, X; Yablonskiy, D A

    2014-03-01

    The nature of the remarkable phase contrast in high-field gradient echo MRI studies of human brain is a subject of intense debates. The generalized Lorentzian approach (He and Yablonskiy, Proc Natl Acad Sci USA 2009;106:13558-13563) provides an explanation for the anisotropy of phase contrast, the near absence of phase contrast between white matter and cerebrospinal fluid, and changes of phase contrast in multiple sclerosis. In this study, we experimentally validate the generalized Lorentzian approach. The Generalized Lorentzian Approach suggests that the local contribution to frequency shifts in white matter does not depend on the average tissue magnetic susceptibility (as suggested by Lorentzian sphere approximation), but on the distribution and symmetry of magnetic susceptibility inclusions at the cellular level. We use ex vivo rat optic nerve as a model system of highly organized cellular structure containing longitudinally arranged myelin and neurofilaments. The nerve's cylindrical shape allowed accurate measurement of its magnetic susceptibility and local frequency shifts. We found that the volume magnetic susceptibility difference between nerve and water is -0.116 ppm, and the magnetic susceptibilities of longitudinal components are -0.043 ppm in fresh nerve, and -0.020 ppm in fixed nerve. The frequency shift observed in the optic nerve as a representative of white matter is consistent with generalized Lorentzian approach but inconsistent with Lorentzian sphere approximation. Copyright © 2013 Wiley Periodicals, Inc.

  8. Study on self-frequency-shift of femtosecond pulse in nonlinear dispersion medium using time-resolved cross-phase modulation method

    Institute of Scientific and Technical Information of China (English)

    赵应桥; 朱鹤元; 刘建华; 孙迭篪; 李富铭

    1997-01-01

    A time-resolved cross-phase modulation method combined with a modified nonlinear Schrodinger equation is used to study the effects of nonlinear response time on the propagation of ultrashort pulses in nonlinear dispersion media. Evolution of cross-phase modulation spectrum with the different time delay between the probe pulse and pump pulse is simulated using split-step Fourier method. It is shown that both normal self-frequency-shift-red-shift and abnormal self-frequency-shift-blue-shift can occur in the frequency domain for the probe pulse, and a satisfactory theoretical interpretation is given.

  9. Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers.

    Science.gov (United States)

    Kuzin, Evgeny; Mendoza-Vazquez, Sergio; Gutierrez-Gutierrez, Jaime; Ibarra-Escamilla, Baldemar; Haus, Joseph; Rojas-Laguna, Roberto

    2005-05-02

    We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

  10. Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers

    Science.gov (United States)

    Kuzin, Evgeny A.; Mendoza-Vazquez, Sergio; Gutierrez-Gutierrez, Jaime; Ibarra-Escamilla, Baldemar; Haus, Joseph W.; Rojas-Laguna, Roberto

    2005-05-01

    We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

  11. Shifted coupling of EEG driving frequencies and fMRI resting state networks in schizophrenia spectrum disorders.

    Directory of Open Access Journals (Sweden)

    Nadja Razavi

    Full Text Available INTRODUCTION: The cerebral resting state in schizophrenia is altered, as has been demonstrated separately by electroencephalography (EEG and functional magnetic resonance imaging (fMRI resting state networks (RSNs. Previous simultaneous EEG/fMRI findings in healthy controls suggest that a consistent spatiotemporal coupling between neural oscillations (EEG frequency correlates and RSN activity is necessary to organize cognitive processes optimally. We hypothesized that this coupling is disorganized in schizophrenia and related psychotic disorders, in particular regarding higher cognitive RSNs such as the default-mode (DMN and left-working-memory network (LWMN. METHODS: Resting state was investigated in eleven patients with a schizophrenia spectrum disorder (n = 11 and matched healthy controls (n = 11 using simultaneous EEG/fMRI. The temporal association of each RSN to topographic spectral changes in the EEG was assessed by creating Covariance Maps. Group differences within, and group similarities across frequencies were estimated for the Covariance Maps. RESULTS: The coupling of EEG frequency bands to the DMN and the LWMN respectively, displayed significant similarities that were shifted towards lower EEG frequencies in patients compared to healthy controls. CONCLUSIONS: By combining EEG and fMRI, each measuring different properties of the same pathophysiology, an aberrant relationship between EEG frequencies and altered RSNs was observed in patients. RSNs of patients were related to lower EEG frequencies, indicating functional alterations of the spatiotemporal coupling. SIGNIFICANCE: The finding of a deviant and shifted coupling between RSNs and related EEG frequencies in patients with a schizophrenia spectrum disorder is significant, as it might indicate how failures in the processing of internal and external stimuli, as commonly seen during this symptomatology (i.e. thought disorders, hallucinations, arise.

  12. Frequency shifts of resonant modes of the Sun due to near-surface convective scattering

    CERN Document Server

    Bhattacharya, Jishnu; Antia, H M

    2015-01-01

    Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the "surface term." The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun....

  13. Complex hydrologic changes in frequency-magnitude response due to shifting agricultural practices in the Midwestern U.S.

    Science.gov (United States)

    Takbiri, Z.; Czuba, J. A.; Foufoula-Georgiou, E.

    2014-12-01

    Hydrologic change is occurring in many basins throughout the Midwestern U.S. not only in the mean annual streamflow but across a spectrum of magnitudes and frequencies. Disentangling the causative mechanisms responsible for these changes such as anthropogenic factors, e.g., artificial drainage to increase agricultural productivity, and climatic shifts in precipitation patterns is important for planning effective mitigation strategies. We have begun unraveling these changes in a human impacted agricultural landscape in the Midwestern U.S., specifically two subbasins of the Minnesota River Basin in Minnesota: the Redwood and Whetstone River Basins, where there has been a shift in agriculture from small grains to soybeans. This shift occurred at different times for each basin (1976 and 1991, respectively) and when soy covered about 20% of the basin area an apparent shift in the hydrologic regime also occurred as evidence by visual inspection of the hydrographs. Precisely quantifying the nature of this hydrologic regime shift however is a challenge and this work adds in this direction. Using Copulas and the joint probability distribution of daily precipitation and streamflow, we quantified a significantly higher dependence between precipitation and streamflow increments in the mid-quantiles (0.1-0.6; attributed to the artificial drainage to the stream rather than the slower infiltration and subsurface runoff) and no significant change for high quantiles (because for extreme storms the artificially fast drainage does not differ much hydrologically from the naturally fast overland flow). We further performed a multi-scale analysis of streamflow increments via wavelets to quantify the changes in the magnitude and frequency of the rising and falling limbs of hydrographs, confirming the above findings. Since precipitation changes were confirmed not to be significant, it is suggested that streamflow changes are largely driven by a change in land use and not climate in these

  14. Hyperfine-frequency shifts of alkali-metal atoms during long-range collisions

    CERN Document Server

    McGuyer, B H

    2013-01-01

    Collisions with chemically inert atoms or molecules change the hyperfine coupling of an alkali-metal atom through the hyperfine-shift interaction. This interaction is responsible for the pressure shifts of the microwave resonances of alkali-metal atoms in buffer gases, is an important spin interaction in alkali-metal--noble-gas van der Waals molecules, and is anticipated to enable the magnetoassociation of ultracold molecules such as RbSr. An improved estimate is presented for the long-range asymptote of this interaction for Na, K, Rb, and Cs. To test the results, the change in hyperfine coupling due to a static electric field is estimated and reasonable agreement is found.

  15. Signal processing method based on group delay calculation for distributed Bragg wavelength shift in optical frequency domain reflectometry.

    Science.gov (United States)

    Wada, Daichi; Igawa, Hirotaka; Murayama, Hideaki; Kasai, Tokio

    2014-03-24

    A signal processing method based on group delay calculations is introduced for distributed measurements of long-length fiber Bragg gratings (FBGs) based on optical frequency domain reflectometry (OFDR). Bragg wavelength shifts in interfered signals of OFDR are regarded as group delay. By calculating group delay, the distribution of Bragg wavelength shifts is obtained with high computational efficiency. We introduce weighted averaging process for noise reduction. This method required only 3.5% of signal processing time which was necessary for conventional equivalent signal processing based on short-time Fourier transform. The method also showed high sensitivity to experimental signals where non-uniform strain distributions existed in a long-length FBG.

  16. Determination of pressure from measured Raman frequency shifts of anhydrite and its application in fluid inclusions and HDAC experiments

    Science.gov (United States)

    Yuan, Xueyin; Mayanovic, Robert A.; Zheng, Haifei

    2016-12-01

    A new geobarometry was derived from the quantified relationships among Raman vibrational frequencies of anhydrite, pressure and temperature, as determined from in-situ micro-Raman spectroscopy of natural anhydrite crystals measured at p-T conditions up to 560 °C and 1400 MPa by using a hydrothermal diamond anvil cell (HDAC). With this geobarometry, the pressure in HDAC experiments and in anhydrite-bearing fluid inclusions can be determined directly from the ν1, 1016, ν3, 1128 and ν3, 1160 Raman frequency shifts of anhydrite at high p-T conditions relative to their values measured at ambient conditions. The pressure can be determined to an accuracy of better than 30 MPa based on the attainable accuracy of ±0.1 cm-1 for the fitted ν1 Raman peak positions, provided the measured spectra are calibrated using the emission peak of an external fluorescent light source. The feasibility and reliability of this geobarometry were verified by rebuilding the p-T history of two fluid inclusions from the ν1 frequency shifts of anhydrite daughter minerals from room to high temperatures, and by measuring the phase-transition pressures of calcite-CaCO3(II)-CaCO3(III) sequence at ambient temperature in a HDAC experiment using anhydrite as a Raman pressure sensor.

  17. Measurement of air-refractive-index fluctuation from laser frequency shift with uncertainty of order 10-9

    Science.gov (United States)

    Banh Quoc, Tuan; Ishige, Masashi; Ohkubo, Yuria; Aketagawa, Masato

    2009-12-01

    In the previous work (Ishige et al 2009 Meas. Sci. Technol. 20 084019), we presented a method of measuring the relative air-refractive-index fluctuation (Δnair) from the laser frequency shift with the measurement uncertainty of order 10-8 using a phase modulation homodyne interferometer (Basile et al 1991 Metrologia 28 455), which was supported by an ultralow thermal expansion material (ULTEM) and an external cavity laser diode (ECLD). In this paper, an improvement in the uncertainty of the Δnair measurement is presented. The improvement method is based on a Fabry-Perot cavity constructed on the ULTEM, which has a thermal expansion coefficient of 2 × 10-8 K-1 and an ECLD. The Pound-Drever-Hall method (Drever et al 1983 Appl. Phys. B 31 97) is also used to control the ECLD frequency to track the resonance of the cavity. Δnair can be derived from the ECLD frequency shift. The estimated measurement uncertainty of Δnair for a short time (~150 s) in the experiment is of order 2.5 × 10-9 or less.

  18. MRI thermometry in phantoms by use of the proton resonance frequency shift method: application to interstitial laser thermotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Olsrud, Johan; Wirestam, Ronnie; Brockstedt, Sara; Persson, Bertil R.R. [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Nilsson, Annika M.K. [Department of Physics, Lund Institute of Technology, SE-221 00 Lund (Sweden); Tranberg, Karl-Goeran [Department of Surgery, Lund University Hospital, SE-221 85 Lund (Sweden); Staahlberg, Freddy [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Department of Diagnostic Radiology, Lund University Hospital, SE-221 85 Lund (Sweden)

    1998-09-01

    In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 deg. C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 deg. C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approximately linear relationship (0.0085 ppm deg. C{sup -1}) between proton resonance frequency shift and temperature change was found for agarose gel, whereas deviations from a linear relationship were observed for porcine liver. The optically tissue-like agarose gel allowed reliable MRI temperature monitoring, and the MR relaxation times (T{sub 1} and T{sub 2}) and the optical properties were found to be independently alterable. Temperature distributions around a diffusing laser fibre, during irradiation and subsequent cooling, were assessed with high spatial resolution (voxel size = 4.3 mm{sup 3}) and with random uncertainties ranging from 0.3 deg. C to 1.4 deg. C (1 SD) with a 40 s scan time. (author)

  19. DEFORMATION MEASUREMENT USING DUAL-FREQUENCY PROJECTION GRATING PHASE-SHIFT PROFILOMETRY

    Institute of Scientific and Technical Information of China (English)

    Yanming Chen; Yuming He; Eryi Hu; Hongmao Zhu

    2008-01-01

    2π phase ambiguity problem is very important in phase measurement when a deformed object has a large out of plane displacement. The dual-frequency projection grating phaseshifting profilometry (PSP) can be used to solve such an issue. In the measurement, two properchosen frequency gratings are utilized to synthesize an equivalent wavelength grating which ensures the computed phase in a principal phase range. Thus, the error caused by the phase unwrapping process with the conventional phase reconstruct algorithm can be eliminated. Finally, experimental result of a specimen with large plastic deformation is given to prove that the proposed method is effective to handle the phase discontinuity.

  20. Effect of Two-Photon Stark Shift on the Multi-Frequency Raman Spectra

    Directory of Open Access Journals (Sweden)

    Hao Yan

    2014-09-01

    Full Text Available High order Raman generation has received considerable attention as a possible method for generating ultrashort pulses. A large number of Raman orders can be generated when the Raman-active medium is pumped by two laser pulses that have a frequency separation equal to the Raman transition frequency. High order Raman generation has been studied in the different temporal regimes, namely: adiabatic, where the pump pulses are much longer than the coherence time of the transition; transient, where the pulse duration is comparable to the coherence time; and impulsive, where the bandwidth of the ultrashort pulse is wider than the transition frequency. To date, almost all of the work has been concerned with generating as broad a spectrum as possible, but we are interested in studying the spectra of the individual orders when pumped in the transient regime. We concentrate on looking at extra peaks that are generated when the Raman medium is pumped with linearly chirped pulses. The extra peaks are generated on the low frequency side of the Raman orders. We discuss how linear Raman scattering from two-photon dressed states can lead to the generation of these extra peaks.

  1. Center of Mass Estimation for a Spinning Spacecraft Using Doppler Shift of the GPS Carrier Frequency

    Science.gov (United States)

    Sedlak, Joseph E.

    2016-01-01

    A sequential filter is presented for estimating the center of mass (CM) of a spinning spacecraft using Doppler shift data from a set of onboard Global Positioning System (GPS) receivers. The advantage of the proposed method is that it is passive and can be run continuously in the background without using commanded thruster firings to excite spacecraft dynamical motion for observability. The NASA Magnetospheric Multiscale (MMS) mission is used as a test case for the CM estimator. The four MMS spacecraft carry star cameras for accurate attitude and spin rate estimation. The angle between the spacecraft nominal spin axis (for MMS this is the geometric body Z-axis) and the major principal axis of inertia is called the coning angle. The transverse components of the estimated rate provide a direct measure of the coning angle. The coning angle has been seen to shift slightly after every orbit and attitude maneuver. This change is attributed to a small asymmetry in the fuel distribution that changes with each burn. This paper shows a correlation between the apparent mass asymmetry deduced from the variations in the coning angle and the CM estimates made using the GPS Doppler data. The consistency between the changes in the coning angle and the CM provides validation of the proposed GPS Doppler method for estimation of the CM on spinning spacecraft.

  2. Effect of Shift Work on the Frequency of Depression in Nursing Staff of Yazd University of Medical Sciences

    Directory of Open Access Journals (Sweden)

    Gholam Hossein Halvani

    2012-12-01

    Full Text Available Introduction: Depression as a disorder is relatively common in all societies; several factors are involved in depression development, that shift work is one of these factors. This study compared the frequency of depression in different shifts of nurses in hospitals of Yazd University of medical sciences. Materials & Methods: This study is a descriptive analytical study. Based on statistical methods, 150 nurses participated in this study. The research tool was a questionnaire that included 15 personal questions and 21 questions related to Beck test. The results were analysed by SPSS software. Results: 13.3% of all subjects were males and 86.7% were females. Results showed that, there is no significant relationship between gender, education, type of job, employment status and satisfaction levels of income with depression. Marital status (P-Value = 0.009 and F = 6.93, shift work (day working and shift work (P-Value = 0.032 and F = 1.11, job satisfaction (P-Value = 0.000 and F = 7.641 and the satisfaction of the employer (P-Value = 0.001 and F = 5.414 were significantly associated with depression. 3.49% of the nurses were in normal status, 7.26% had mild depression, 3.9% required consultation with the psychiatrist,% 7.8% suffered from moderate depression, 75.4% from severe depression and 3.1% from very severe depression. Conclusion: It seems that shift work can not cause depression alone, but depression is the result of the interaction of several factors.

  3. Spin 1/2 systems perturbed by fluctuating, arbitrary fields; relaxation and frequency shifts, a new approach to Redfield theory

    CERN Document Server

    Golub, Robert

    2014-01-01

    The usual approach to considerations of apin relaxation and frequency shifts due to fluctuating fields is through the density matrix Slichter. Here we treat the problem of the influence of fluctuating fields on a spin 1/2 system based on direct solution of the Schroedinger equation in contrast to the usual treatment. Our results are seen to be in agreement with the known results in the literature McGregor, Slichter, Red2, CSH, as they must, but our derivation directly from the Schroedinger equation allows us to see the role of the necessary assumptions in a somewhat clearer way.

  4. Method of shifting and fixing optical frequency of an optical resonator, and optical resonator made by same

    Science.gov (United States)

    Savchenkov, Anatoliy A. (Inventor); Strekalov, Dmitry V. (Inventor); Maleki, Lute (Inventor); Matsko, Andrey B. (Inventor); Iltchenko, Vladimir S. (Inventor); Martin, Jan M. (Inventor)

    2010-01-01

    A method of shifting and fixing an optical frequency of an optical resonator to a desired optical frequency, and an optical resonator made by such a method are provided. The method includes providing an optical resonator having a surface and a refractive index, and obtaining a coating composition having a predetermined concentration of a substance and having a refractive index that is substantially similar to the refractive index of the optical resonator. The coating composition inherently possesses a thickness when it is applied as a coating. The method further includes determining a coating ratio for the surface of the optical resonator and applying the coating composition onto a portion of the surface of the optical resonator based upon the determined coating ratio.

  5. Amplitude and Frequency Control: Stability of Limit Cycles in Phase-Shift and Twin-T Oscillators

    Directory of Open Access Journals (Sweden)

    J. P. Dada

    2008-01-01

    Full Text Available We show a technique for external direct current (DC control of the amplitudes of limit cycles both in the Phase-shift and Twin-T oscillators. We have found that amplitudes of the oscillator output voltage depend on the DC control voltage. By varying the total impedance of each oscillator oscillatory network, frequencies of oscillations are controlled using potentiometers. The main advantage of the proposed circuits is that both the amplitude and frequency of the waveforms generated can be independently controlled. Analytical, numerical, and experimental methods are used to determine the boundaries of the states of the oscillators. Equilibrium points, stable limit cycles, and divergent states are found. Analytical results are compared with the numerical and experimental solutions, and a good agreement is obtained.

  6. Resonance frequency shifts due to quantized electronic states in atomically thin NEMS

    Science.gov (United States)

    Chen, Changyao; Deshpande, Vikram; Koshino, Mikito; Lee, Sunwoo; Gondarenko, Alexander; MacDonald, Allan; Kim, Philip; Hone, James

    The classic picture of the force exerted on a parallel plate capacitor assumes infinite density of states (DOS), which implies identical electrochemical and electrostatic potential. However, such assumption can breakdown in low-dimensional devices where the DOS is finite or quantized. Here we consider the mechanical resonance shift of a nanoelectromechanical (NEMS) resonator with small DOS, actuated and detected capacitively at fixed electrochemical potential. We found three leading correction terms to the classical picture: the first term leads to the modulation of static force due to the variation in chemical potential, and the second and third terms are related to the static and dynamic changes in spring constants, caused by quantum capacitance. The theory agrees well with recent experimental findings from graphene resonator in quantum Hall regimes, where the chemical potential and quantum capacitance are tuned by magnetic field, while the gate voltage is kept constant.

  7. Relativistic down-shift frequency effect on the application of electron cyclotron emission measurements to JT-60U tokamak plasmas. Second harmonics

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Masayasu; Isei, Nobuaki; Ishida, Sinichi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1995-11-01

    Effect of relativistic frequency down-shift on the determination of the electron temperature profile from electron cyclotron emission(ECE) in JT-60U tokamak plasmas is studied. The radial shift of the electron temperature profile due to the effects is not negligible, compared with the spatial resolution of ECE measurement systems of JT-60U. Therefore it is necessary to correct the effect for precise measurement of the electron temperature profile. Dependencies of the shifted frequency on the electron density, electron temperature and toroidal magnetic field are studied for the uniform electron density and parabolic electron temperature profile in JT-60U. It is revealed to be necessary for the estimation of shift due to the relativistic down-shift frequency to take into account of the optical thickness. (author).

  8. Fluid nonlinear frequency shift of nonlinear ion acoustic waves in multi-ion species plasmas in small wave number region

    CERN Document Server

    Feng, Q S; Wang, Q; Zheng, C Y; Liu, Z J; Cao, L H; He, X T

    2016-01-01

    The properties of the nonlinear frequency shift (NFS) especially the fluid NFS from the harmonic generation of the ion-acoustic wave (IAW) in multi-ion species plasmas have been researched by Vlasov simulation. The pictures of the nonlinear frequency shift from harmonic generation and particles trapping are shown to explain the mechanism of NFS qualitatively. The theoretical model of the fluid NFS from harmonic generation in multi-ion species plasmas is given and the results of Vlasov simulation are consistent to the theoretical result of multi-ion species plasmas. When the wave number $k\\lambda_{De}$ is small, such as $k\\lambda_{De}=0.1$, the fluid NFS dominates in the total NFS and will reach as large as nearly $15\\%$ when the wave amplitude $|e\\phi/T_e|\\sim0.1$, which indicates that in the condition of small $k\\lambda_{De}$, the fluid NFS dominates in the saturation of stimulated Brillouin scattering especially when the nonlinear IAW amplitude is large.

  9. Relativistic Tennis with Photons: Frequency Up-Shifting, Light Intensification and Ion Acceleration with Flying Mirrors

    Science.gov (United States)

    Bulanov, S. V.; Esirkepov, T. Zh.; Kando, M.; Koga, J. K.; Pirozhkov, A. S.; Rosanov, N. N.; Zhidkov, A. G.

    2011-01-01

    We formulate the Flying Mirror Concept for relativistic interaction of ultra-intense electromagnetic waves with plasmas, present its theoretical description and the results of computer simulations and laboratory experiments. In collisionless plasmas, the relativistic flying mirrors are thin and dense electron or electron-ion layers accelerated by the high intensity electromagnetic waves up to velocity close to the speed of light in vacuum; in nonlinear-media and in nonlinear vacuum they are the ionization fronts and the refraction index modulations induced by a strong electromagnetic wave. The reflection of the electromagnetic wave at the relativistic mirror results in its energy and frequency change due to the double Doppler effect. In the co-propagating configuration, in the radiation pressure dominant regime, the energy of the electromagnetic wave is transferred to the ion energy providing a highly efficient acceleration mechanism. In the counter-propagation configuration the frequency of the reflected wave is multiplied by the factor proportional to the gamma-factor squared. If the relativistic mirror performs an oscillatory motion as in the case of the electron motion at the plasma-vacuum interface, the reflected light spectrum is enriched with high order harmonics.

  10. Enhancing the secure key rate in a quantum-key-distribution system using discrete-variable, high-dimensional, time-frequency states

    Science.gov (United States)

    Islam, Nurul T.; Cahall, Clinton; Aragoneses, Andrés.; Lim, Charles Ci Wen; Allman, Michael S.; Verma, Varun; Nam, Sae Woo; Kim, Jungsang; Gauthier, Daniel J.

    2016-10-01

    High-dimensional (dimension d > 2) quantum key distribution (QKD) protocols that encode information in the temporal degree of freedom promise to overcome some of the challenges of qubit-based (d = 2) QKD systems. In particular, the long recovery time of single-photon detectors and large channel noise at long distance both limit the rate at which a final secure key can be generated in a low-dimension QKD system. We propose and demonstrate a practical discrete-variable time-frequency protocol with d = 4 at a wavelength of 1550 nm, where the temporal states are secured by transmitting and detecting their dual states under Fourier transformation, known as the frequency-basis states, augmented by a decoy-state protocol. We show that the discrete temporal and frequency states can be generated and detected using commercially-available equipment with high timing and spectral efficiency. In our initial experiments, we only have access to detectors that have low efficiency (1%) at 1550 nm. Together with other component losses, our system is equivalent to a QKD system with ideal components and a 50-km-long optical-fiber quantum channel. We find that our system maintains a spectral visibility of over 99.0% with a quantum bit error rate of 2.3%, which is largely due to the finite extinction ratio of the intensity modulators used in the transmitter. The estimated secure key rate of this system is 7.7×104 KHz, which should improve drastically when we use detectors optimized for 1550 nm.

  11. Stabilized soliton self-frequency shift and 0.1- PHz sideband generation in a photonic-crystal fiber with an air-hole-modified core.

    Science.gov (United States)

    Liu, Bo-Wen; Hu, Ming-Lie; Fang, Xiao-Hui; Li, Yan-Feng; Chai, Lu; Wang, Ching-Yue; Tong, Weijun; Luo, Jie; Voronin, Aleksandr A; Zheltikov, Aleksei M

    2008-09-15

    Fiber dispersion and nonlinearity management strategy based on a modification of a photonic-crystal fiber (PCF) core with an air hole is shown to facilitate optimization of PCF components for a stable soliton frequency shift and subpetahertz sideband generation through four-wave mixing. Spectral recoil of an optical soliton by a red-shifted dispersive wave, generated through a soliton instability induced by high-order fiber dispersion, is shown to stabilize the soliton self-frequency shift in a highly nonlinear PCF with an air-hole-modified core relative to pump power variations. A fiber with a 2.3-microm-diameter core modified with a 0.9-microm-diameter air hole is used to demonstrate a robust soliton self-frequency shift of unamplified 50-fs Ti: sapphire laser pulses to a central wavelength of about 960 nm, which remains insensitive to variations in the pump pulse energy within the range from 60 to at least 100 pJ. In this regime of frequency shifting, intense high- and low-frequency branches of dispersive wave radiation are simultaneously observed in the spectrum of PCF output. An air-hole-modified-core PCF with appropriate dispersion and nonlinearity parameters is shown to provide efficient four-wave mixing, giving rise to Stokes and anti-Stokes sidebands whose frequency shift relative to the pump wavelength falls within the subpetahertz range, thus offering an attractive source for nonlinear Raman microspectroscopy.

  12. Relative phase noise induced impairment in M-ary phase-shift-keying coherent optical communication system using distributed fiber Raman amplifier.

    Science.gov (United States)

    Cheng, Jingchi; Tang, Ming; Fu, Songnian; Shum, Perry Ping; Liu, Deming

    2013-04-01

    We show for the first time, to the best of our knowledge, that, in a coherent communication system that employs a phase-shift-keying signal and Raman amplification, besides the pump relative intensity noise (RIN) transfer to the amplitude, the signal's phase will also be affected by pump RIN through the pump-signal cross-phase modulation. Although the average pump power induced linear phase change can be compensated for by the phase-correction algorithm, a relative phase noise (RPN) parameter has been found to characterize pump RIN induced stochastic phase noise. This extra phase noise brings non-negligible system impairments in terms of the Q-factor penalty. The calculation shows that copumping leads to much more stringent requirements to pump RIN, and relatively larger fiber dispersion helps to suppress the RPN induced impairment. A higher-order phase-shift keying (PSK) signal is less tolerant to noise than a lower-order PSK.

  13. Broadly wavelength- and pulse width-tunable high-repetition rate light pulses from soliton self-frequency shifting photonic crystal fiber integrated with a frequency doubling crystal.

    Science.gov (United States)

    Lanin, Aleksandr A; Fedotov, Andrei B; Zheltikov, Aleksei M

    2012-09-01

    Soliton self-frequency shift (SSFS) in a photonic crystal fiber (PCF) pumped by a long-cavity mode-locked Cr:forsterite laser is integrated with second harmonic generation (SHG) in a nonlinear crystal to generate ultrashort light pulses tunable within the range of wavelengths from 680 to 1800 nm at a repetition rate of 20 MHz. The pulse width of the second harmonic output is tuned from 70 to 600 fs by varying the thickness of the nonlinear crystal, beam-focusing geometry, and the wavelength of the soliton PCF output. Wavelength-tunable pulses generated through a combination of SSFS and SHG are ideally suited for coherent Raman microspectroscopy at high repetition rates, as verified by experiments on synthetic diamond and polystyrene films.

  14. 主动频移孤岛检测的抗干扰测频算法%Anti-interference frequency detection algorithm of active frequency shift islanding detection

    Institute of Scientific and Technical Information of China (English)

    陈运运; 吴军基; 应展烽; 万萌

    2012-01-01

    针对并网光伏发电系统主动频移孤岛检测中,并网侧待测信号在过零点附近存在的噪声干扰,对过零测频法和锁相环测频法精度带来的不良影响,提出了一种具有噪声抑制功能的三角变换测频法.通过对最优检测点间隔进行估计和少数频率奇异点的剔除,即使并网光伏发电系统主动频移孤岛检测中并网侧待测信号受噪声干扰,带噪声抑制的三角变换测频法也能避免孤岛效应误判现象,提高了系统运行的可靠性.在MATLAB/Simulink下进行了建模和仿真,验证了该三角变换测频算法的正确性.%Aimed at the active frequency shift islanding detection of grid-connected PV generation system, the noise interference nearby zero crossing point of grid connected side signal to be measured brought adverse effects on the precision, of zero-crossing measurement and PLL (phase-locked loop) frequency detection method, a triangle transformation frequency detection method with the function of noise suppression was proposed. Through optimal detction point interval evaluation and eliminating frequency singularity, the proposed method could avoid islanding misjudgement although grid connected side signal to be measured is interfered by the noise,system operation reliability was improved. The simulation model of system was established, which verified the the correctness of the method.

  15. Ultrasound computed tomography by frequency-shift low-pass filtering and least mean square adaptive filtering

    Science.gov (United States)

    Wang, Shanshan; Song, Junjie; Peng, Yang; Zhou, Liang; Ding, Mingyue; Yuchi, Ming

    2017-03-01

    In recent years, many research studies have been carried out on ultrasound computed tomography (USCT) for improving the detection and management of breast cancer. This paper investigates a signal pre-processing method based on frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for USCT image quality enhancement (proposed in our previous work). FSLF is designed base on Zoom Fast Fourier Transform algorithm (ZFFT) for processing the ultrasound signals in the frequency domain, while LMSAPF is based on the least mean square (LMS) algorithm in the time domain. Through the combination of the two filters, the ultrasound image is expected to have less noises and artifacts, and higher resolution and contrast. The proposed method was verified with the radio-frequency (RF) data of the nylon threads and the breast phantom captured by the USCT system developed in the Medical Ultrasound Laboratory. Experimental results show that the reconstructed images of nylon threads by the proposed method had narrower main lobe width and lower side lobe level comparing to the delay-and-sum (DAS). The background noises and artifacts could also be efficiently restrained. The reconstructed image of breast phantom by the proposed method had a higher resolution and the contrast ratio (CR) could be enhanced for about 12dB to 18dB at different region of interest (ROI).

  16. M元码元移位键控扩频水声通信%M-ary code shift keying spread spectrum underwater acoustic communication

    Institute of Scientific and Technical Information of China (English)

    于洋; 周锋; 乔钢

    2012-01-01

    Aiming at the low data rate of traditional direct sequence spread spectrum, M-ary spread spectrum and code shift keying un- derwater acoustic spread spectrum communication, a new combine method of M-ary code shift keying underwater acoustic spread spectrum communication is proposed based on the small Kasami sequence with good self and mutual correlation. Different sequence information and the same sequence code phase information are used in this method. The influences of self and mutual correlation func- tion on M-ary code shift keying underwater acoustic spread spectrum communication over gaussian and fading channel are analyzed. The performances under the two kinds of channels are simulated. The simulation shows that the ability for M-ary code shift spread spectrum to overcome the noise is better than for the direct sequence spread spectrum, M-ary spread spectrum and code shift keying spread spectrum. The comparative experiment is conducted to compare the M-ary spread spectrum, code shift keying spread spectrum and M-ary code shift keying spread spectrum in the pool. The M-ary code shift keying communication rate of 256.3 bps with no transmitting error in 104 bit data volume is realized.%针对传统直接序列扩频、M元扩频和码元移位键控扩频水声通信速率低的问题,基于小Kasami序列优良的自相关和互相关特性,提出了M元扩频和码元移位键控扩频两者相结合的水声扩频通信新方法.不仅利用了不同的序列信息,还利用了相同序列的扩频码相位信息.对于白相关和互相关函数在加性高斯白噪声和衰落信道下对M元码元移位键控扩频这种水声通信方法的影响进行了分析,并分别在两种信道下对其性能进行仿真,仿真结果表明在同等通信速率下M元码元移位键控扩频的抗噪声能力要高于直接序列扩频、M元扩频和码元移位键控扩频.在水池对M元扩频、码元移位键控扩频和M元码元移位键

  17. Derivation of the shear compliance of thin films on quartz resonators from comparison of the frequency shifts on different harmonics: A perturbation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Johannsmann, Diethelm

    2001-06-01

    Viscoelastic effects contribute to the shift in resonance frequency of quartz crystal resonators induced by deposition of thin films on the resonator surface. In turn, the mechanical stiffness of the film can be experimentally determined from a comparison of the resonance shifts on different harmonics. When the film is much thinner than the wavelength of shear sound, a series expansion of the viscoelastic effects to third order in film thickness leads to rather simple equations. When plotting the normalized frequency shift {delta}f/f versus the square of the overtone order n{sup 2} one finds a linear relationship, where the slope is determined by the film{close_quote}s elastic compliance. When the same analysis is carried out on the resonance bandwidths rather than the frequency shifts the viscous compliance is obtained. The effects of asymmetric coatings, electrodes, and liquid media are discussed. {copyright} 2001 American Institute of Physics.

  18. Asynchronous, all-optical signal processing based on the self-frequency shift of a gigahertz Raman soliton.

    Science.gov (United States)

    Kato, Masao; Fujiura, Kazuo; Kurihara, Takashi

    2005-03-10

    Ultrafast asynchronous all-optical signal processing is experimentally demonstrated. It is based on the intensity-dependent, self-frequency shift of a gigahertz Raman soliton. We demonstrate error-free, asynchronous, all-optical, bit-by-bit, self-signal recognition and demultiplexing from contended optical packets without use of an optical buffer, control pulse, or bit-phase synchronization. Fourfold, contended, 9.95-Gbit/s optical packets are transmitted through a conventional repeater span of 80 km and simultaneously demultiplexed to multiwavelength 9.95-Gbit/s optical packets with 0.5-dB processing sensitivity. Furthermore, we successfully accomplish demultiplexing from overlapping signals in contended optical packets with better than 3-dB recognition sensitivity. We confirm the capability of realizing a 3x cascade operation from bit-error-rate measurements.

  19. Three-dimensional surface imaging by multi-frequency phase shift profilometry with angle and pattern modeling for system calibration

    Science.gov (United States)

    Wang, Zhenzhou

    2016-08-01

    In this paper, we present a 3D surface imaging system based on the well-known phase shift profilometry. To yield the analytical solutions, four shifted phases and three high carrier frequencies are used to compute the phase map and reduce the noises that are caused by the inherent optical aberrations and external influences, e.g. different illumination light sources, uneven intensity distribution and automatic image processing algorithms. To reduce the system noise, we propose to model the pattern of the calibration grid in a virtual space. To obtain the modeled pattern, we use a plane to intercept the rays that are modeled by the proposed angle modeling method. In the world coordinate system, the angle and the pattern are computed based on the calibration data. A registration method is used to transform the modeled pattern in the virtual space to the ideal pattern in the world coordinate system by computing the least squared errors between the true points in the modeled pattern and the measured points in the practical pattern. The modeled (true) points are used for re-calibration of the 3D imaging system. Experimental results showed that the measurement accuracy increases considerably and the MSE is reduced from 0.95 mm to 0.65 mm (32% average error decrease) after replacing the measured points with the true points for calibration.

  20. Genetic Adaptation to Climate in White Spruce Involves Small to Moderate Allele Frequency Shifts in Functionally Diverse Genes.

    Science.gov (United States)

    Hornoy, Benjamin; Pavy, Nathalie; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-11-11

    Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to nonmodel species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome.Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs.Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular

  1. Multi-carrier chaotic shift keying chaotic communications under MIMO multipath fading channels%MIMO 多径衰落信道下的多载波混沌键控混沌通信

    Institute of Scientific and Technical Information of China (English)

    王世练; 胡登鹏; 张智力; 卢树军

    2015-01-01

    为提高差分混沌键控的传输效率及其在衰落信道下的传输性能,提出了多载波混沌键控及类差分混沌键控检测方法,发射端每隔 M个 OFDM符号间隔插入由混沌参考信号构成的“导频”,在此间隔内其他 M-1个 OFDM符号即以此混沌参考信号生成的混沌键控信号,接收端提取“导频”并将之与其他 OFDM符号进行相关积分,恢复出 M-1比特信息。进一步给出了 MIMO 多径衰落信道下的多载波混沌键控分集发射与接收方法,发射端采用不同混沌信号以获得一定的发射分集增益,接收端不需要任何信道先验信息,对各天线的相关积分输出进行等增益合并,可获得空间分集增益和频域分集增益。性能分析和计算机仿真表明,在“导频”插入间隔大于2的情况下,多载波混沌键控的功率效率大于差分混沌键控,且传输性能优于差分混沌键控。%To improve the frequency efficiency and the transmission performance of differential chaos shift keying under wireless fading channel,a multi-carrier chaotic shift keying communication scheme is proposed.In each block size of MOFDMsymbols,one pilot OFDMsymbol inserted time-spaced in all-frequency is used to transmit the reference chaotic signal and the other M-1 OFDM symbols is used to transmit the information-bearing signals,which spread by the reference chaotic signal.At the receiver,a differential detector is constructed and the information bits from the correlations between the pilot OFDMsymbol and the other M-1 OFDMsymbols in each block size of Mare recovered.A multi-carrier chaotic shift keying transceiver under MIMO multipath fading channels with no channel state information is presented,in which a distinct chaotic sequence at each transmit antenna is used to spread the same data symbol and the detection statistics at each receive antenna are combined with equal gain for symbol detection.Both performance analysis

  2. A Joint Doppler Frequency Shift and DOA Estimation Algorithm Based on Sparse Representations for Colocated TDM-MIMO Radar

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2014-01-01

    Full Text Available We address the problem of a new joint Doppler frequency shift (DFS and direction of arrival (DOA estimation for colocated TDM-MIMO radar that is a novel technology applied to autocruise and safety driving system in recent years. The signal model of colocated TDM-MIMO radar with few transmitter or receiver channels is depicted and “time varying steering vector” model is proved. Inspired by sparse representations theory, we present a new processing scheme for joint DFS and DOA estimation based on the new input signal model of colocated TDM-MIMO radar. An ultracomplete redundancy dictionary for angle-frequency space is founded in order to complete sparse representations of the input signal. The SVD-SR algorithm which stands for joint estimation based on sparse representations using SVD decomposition with OMP algorithm and the improved M-FOCUSS algorithm which combines the classical M-FOCUSS with joint sparse recovery spectrum are applied to the new signal model’s calculation to solve the multiple measurement vectors (MMV problem. The improved M-FOCUSS algorithm can work more robust than SVD-SR and JS-SR algorithms in the aspects of coherent signals resolution and estimation accuracy. Finally, simulation experiments have shown that the proposed algorithms and schemes are feasible and can be further applied to practical application.

  3. Sensing Escherichia coli O157:H7 via frequency shift through a self-assembled monolayer based QCM immunosensor

    Institute of Scientific and Technical Information of China (English)

    Li-jiang WANG; Chun-sheng WU; Zhao-ying HU; Yuan-fan ZHANG; Rong LI; Ping WANG

    2008-01-01

    By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157:H7 detection was developed in this work. As a suitable surfactant, 16-mercaptohexadecanoic acid (MHDA) was introduced onto the Au surface of QCM, and then self-assembled with N-hydroxysuccinimide (NHS) raster as a reactive intermediate to provide an active interface for the specific antibody immobilization. The binding of target bacteria with the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of the electrochemical techniques. Using the immersion-dry-immersion procedure, this QCM biosensor could detect 2.0×102 colony forming units (CFU)/ml E. coli O157:H7. In order to reduce the fabrication time, a polyelectrolyte layer-by-layer self-assembly (LBL-SA) method was adopted for fast construction. Finally, the reproducibility of this biosensor was discussed.

  4. Modeling and Simulation of a Non-Coherent Frequency Shift Keying Transceiver Using a Field Programmable Gate Array (FPGA)

    Science.gov (United States)

    2008-09-01

    where {1 00 0( ) if nif nnδ =≠= . The initialization block, as in the case of the block ‘Mcode1’ of the transmitter, is used only to prevent the...Xilinx online documentation, ISE Design Suite 10.1 – ISE Foundation, http://www.xilinx.com/publications/prod_mktg/pn0010867. pdf (Accessed September 17...http://www.ux.uis.no/~karlsk/MIK200/dok/P160Analog_UserGuide_1_2. pdf (Accessed September 17, 2008). [19] Xilinx Online Documentation, Manuals and

  5. A comparison of two 40Ca+ single-ion optical frequency standards at the 5 × 10-17 level and an evaluation of systematic shifts

    Science.gov (United States)

    Huang, Y.; Guan, H.; Bian, W.; Ma, L.; Liang, K.; Li, T.; Gao, K.

    2017-05-01

    A comparison of two optical frequency standards and a detailed study of the systematic frequency shifts of each 40Ca+ single-ion optical frequency standard is presented. The methods used for the systematic shift evaluation of the comparison measurements are also provided. One of the ion traps runs at a chosen operating frequency of 24.7 MHz, determined by the differential scalar polarizability of the clock transition, at which frequency the rf-induced Stark shifts and second-order Doppler shifts cancel each other, yielding a great suppression in the combined micromotion shifts. After compensating for the micromotion, the two optical frequency standards both reach an uncertainty level of a few parts in 10-17, which is more than an order of magnitude smaller compared to a few years ago. The dominant source of uncertainty is the blackbody radiation shift after minimizing the micromotion-induced shifts. The blackbody radiation shift is evaluated by controlling and measuring the temperature at the trap center. With a measurement over one month, the frequency difference between the two clocks is measured to be 3.2 × 10-17 with a measurement uncertainty of 5.5 × 10-17, considering both the statistical (1.9 × 10-17) and the systematic (5.1 × 10-17) uncertainties. Due to improvement of the clock laser and better control of the optical and electromagnetic field geometry and the laboratory conditions, a fractional stability of 7 × 10-17 in 20,000 s of averaging time is achieved. The absolute frequency of the 40Ca+ 4 s2S1/2-3d 2D5/2 clock transition is measured as 411 042 129 776 401.7 (1.1) Hz, with a fractional uncertainty of 2.7 × 10-15 using the GPS satellites as a link to the SI second. Details of the method used for the systematic shift evaluation of the measurements are given.

  6. The giant frequency shift of intramolecular O-H vibration band in the raman spectra of water on the silver surface

    CERN Document Server

    Kompan, Mikhail

    2016-01-01

    The giant frequency shift was observed in Raman spectra for inramolecular O-H vibration band. The effect was observed in SERS-condition experiment, when exciting light was focused by short-focus objective on the Ag-surface, merged in water. The shift was detected relatively to the regularl position of band, measured from the bulk of water under the same other conditions.

  7. First-order perturbative calculation of the frequency-shifts caused by static cylindrically-symmetric electric and magnetic imperfections of a Penning trap

    CERN Document Server

    Ketter, Jochen; Höcker, Martin; Streubel, Sebastian; Blaum, Klaus

    2014-01-01

    The ideal Penning trap consists of a uniform magnetic field and an electrostatic quadrupole potential. Cylindrically-symmetric deviations thereof are parametrized by the coefficients Bn and Cn, respectively. Relativistic mass-increase aside, the three characteristic eigenfrequencies of a charged particle stored in an ideal Penning trap are independent of the three motional amplitudes. This three-fold harmonicity is a highly-coveted virtue for precision experiments that rely on the measurement of at least one eigenfrequency in order to determine fundamental properties of the stored particle, such as its mass. However, higher-order contributions to the ideal fields result in amplitude-dependent frequency-shifts. In turn, these frequency-shifts need to be understood for estimating systematic experimental errors, and eventually for correcting them by means of calibrating the imperfections. The problem of calculating the frequency-shifts caused by small imperfections of a near-ideal trap yields nicely to perturbat...

  8. The Effect of an Added Mass on the Frequency Shifts of a Clamped-Clamped Microbeam for Bio-Mass Detection

    KAUST Repository

    Bouchaala, Adam M.

    2016-12-05

    We present analytical formulations to calculate the induced resonance frequency shifts of electrically actuated clamped-clamped microbeams due to an added mass. Based on the Euler-Bernoulli beam theory, we investigate the linear dynamic responses of the beams added masses, which are modeled as discrete point masses. Analytical expressions based on perturbation techniques and a one-mode Galerkin approximation are developed to calculate accurately the frequency shifts under a DC voltage as a function of the added mass and position. The analytical results are compared to numerical solution of the eigenvalue problem. Results are shown for the fundamental as well as the higher-order modes of the beams. The results indicate a significant increase in the frequency shift, and hence the sensitivity of detection, when scaling down to nano scale and using higher-order modes.

  9. COLLABORATE©: a universal competency-based paradigm for professional case management, Part III: key considerations for making the paradigm shift.

    Science.gov (United States)

    Treiger, Teresa M; Fink-Samnick, Ellen

    2014-01-01

    The purpose of the third of this 3-article series is to provide context and justification for a new paradigm of case management built upon a value-driven foundation that * improves the patient's experience of health care delivery, * provides consistency in approach applicable across health care populations, and * optimizes the potential for return on investment. Applicable to all health care sectors where case management is practiced. In moving forward the one fact that rings true is there will be constant change in our industry. As the health care terrain shifts and new influences continually surface, there will be consequences for case management practice. These impacts require nimble clinical professionals in possession of recognized and firmly established competencies. They must be agile to frame (and reframe) their professional practice to facilitate the best possible outcomes for their patients. Case managers can choose to be Gumby or Pokey. This is exactly why the definition of a competency-based case management model's time has come, one sufficiently fluid to fit into any setting of care. The practice of case management transcends the vast array of representative professional disciplines and educational levels. A majority of current models are driven by business priorities rather than the competencies critical to successful practice and quality patient outcomes. This results in a fragmented professional case management identity. While there is inherent value in what each discipline brings to the table, this advanced model unifies behind case management's unique, strengths-based identity instead of continuing to align within traditional divisions (e.g., discipline, work setting, population served). This model fosters case management's expanding career advancement opportunities, including a reflective clinical ladder.

  10. A FIRST APPROACH TO THE LEXICAL PROFILE OF TELECOMMUNICATION ENGLISH: FREQUENCY, DISTRIBUTION, RESTRICTION AND KEYNESS

    Directory of Open Access Journals (Sweden)

    Camino Rea Rizzo

    2009-10-01

    Full Text Available This corpus-based study is conducted to gain an insight into the lexis of Telecommunication English, with the aim of characterizing the lexical profile of this specialized language. The applied methodology integrates quantitative techniques and qualitative interpretations to perform an analysis from two different perspectives, and according to two parameters: restriction and keyness. The first approach is focused on the lexical behaviour and the extent that a word is restricted to the constituent areas of a domain, whereas the second approach is directed towards the extent that a word is significant in the domain, regardless of lexical category. The set of empirical and statistical data obtained contribute to map the lexical profile and will serve as a baseline for future studies.

  11. Experimental transmission of quantum digital signatures over 90 km of installed optical fiber using a differential phase shift quantum key distribution system

    Science.gov (United States)

    Collins, Robert J.; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Andersson, Erika; Buller, Gerald S.; Sasaki, Masahide

    2016-11-01

    Quantum digital signatures apply quantum mechanics to the problem of guaranteeing message integrity and non-repudiation with information-theoretical security, which are complementary to the confidentiality realized by quantum key distribution. Previous experimental demonstrations have been limited to transmission distances of less than 5-km of optical fiber in a laboratory setting. Here we report the first demonstration of quantum digital signatures over installed optical fiber as well as the longest transmission link reported to date. This demonstration used a 90-km long differential phase shift quantum key distribution system to achieve approximately one signed bit per second - an increase in the signature generation rate of several orders of magnitude over previous optical fiber demonstrations.

  12. Small-Signal Analysis of Single-Phase and Three-phase DC/AC and AC/DC PWM Converters with the Frequency-Shift Technique

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Aquila, A. Dell’; Liserre, Marco;

    2004-01-01

    A systematic approach to study dc/ac and ac/dc converters without the use of synchronous transformation is proposed. The use of a frequency-shift technique allows a straightforward analysis of single-phase and three-phase systems. The study of dc/ac and of ac/dc converters is reported to the study...... of dc/dc converters via a 50 Hz frequency-shift. The input admittance is calculated and measured for two study examples (a three-phase active rectifier and a single-phase photovoltaic inverter). These examples show that the purpose of a well designed controller for grid-connected converters...

  13. The static and dynamic polarisability, and the Stark and black-body radiation frequency shifts of the molecular hydrogen ions H2+, HD+, and D2+

    CERN Document Server

    Schiller, Stephan; Bekbaev, Ashat K; Korobov, Vladimir I

    2014-01-01

    We calculate the DC Stark effect for three molecular hydrogen ions in the non-relativistic approximation. The effect is calculated both in dependence on the rovibrational state and in dependence on the hyperfine state. We discuss special cases and approximations. We also calculate the AC polarisabilities for several rovibrational levels, and therefrom evaluate accurately the black-body radiation shift, including the effects of excited electronic states. The results enable the detailed evaluation of certain systematic shifts of the transitions frequencies for the purpose of ultra-high-precision optical, microwave or radio-frequency spectroscopy in ion traps.

  14. Static and dynamic polarizability and the Stark and blackbody-radiation frequency shifts of the molecular hydrogen ions H2+, HD+, and D2+

    Science.gov (United States)

    Schiller, S.; Bakalov, D.; Bekbaev, A. K.; Korobov, V. I.

    2014-05-01

    We calculate the dc Stark effect for three molecular hydrogen ions in the nonrelativistic approximation. The effect is calculated both in dependence on the rovibrational state and in dependence on the hyperfine state. We discuss special cases and approximations. We also calculate the ac polarizabilities for several rovibrational levels and therefrom evaluate accurately the blackbody radiation shift, including the effects of excited electronic states. The results enable the detailed evaluation of certain systematic shifts of the transitions frequencies for the purpose of ultrahigh-precision optical, microwave, or radio-frequency spectroscopy in ion traps.

  15. Shifts in Köppen-Geiger climate zones over southern Africa in relation to key global temperature goals

    Science.gov (United States)

    Engelbrecht, Christien J.; Engelbrecht, Francois A.

    2016-01-01

    Potential changes in Köppen-Geiger climate zones over southern Africa (Africa south of 22 °S) under future climate change are investigated using an ensemble of high-resolution projections of a regional climate model. The projections are performed under the A2 scenario of the Special Report on Emission Scenarios (SRES), and changes are presented for those times in the future when the increase in global average surface temperature reaches thresholds of 1, 2, and 3 °C, relative to the present-day baseline climatology. Widespread shifts in climate regimes are projected, of which the southern and eastern expansion of the hot desert and hot steppe zones is the most prominent. From occupying 33.1 and 19.4 % of southern Africa under present-day climate, these regions are projected to occupy between 47.3 and 59.7 % (hot desert zone) and 24.9 and 29.9 % (hot steppe zone) of the region in a future world where the global temperature has increased by 3 °C. The cold desert and cold steppe zones are projected to decrease correspondingly. The temperate regions of eastern South Africa, the Cape south coast, and winter rainfall region of the southwestern Cape are also projected to contract. An expansion of the hot steppe zone into the cold steppe and temperate zones may favor the intrusion of trees (and therefore the savanna biome) into the most pristine grasslands of southern Africa. However, the correlative climate-vegetation approach of using projected changes in Köppen-Geiger zones to infer future vegetation patterns is of limited value in the savanna complex of southern Africa, where complex feedbacks occur between carbon dioxide (CO2) concentrations, trees, C4 grasses, fire, and climate. The present-day temperate Cape Fynbos regime may come under increasing pressure as the encompassing temperate zone is invaded mainly from the east by the hot steppe climate regime under climate change, with the incidence of Fynbos fires also becoming more likely in a generally warmer and

  16. Investigation of the mechanical bending and frequency shift induced by adsorption and temperature using micro- and nanocantilever sensors

    Science.gov (United States)

    Feng, Lu; Gao, Fengling; Liu, Meihua; Wang, Shibin; Li, Linan; Shen, Min; Wang, Zhiyong

    2012-07-01

    The marked progress in MEMS/NEMS technology has demanded the development of a fundamental understanding of cantilever-based sensing principles. One of the challenges of cantilever-based detection is identifying and discerning the most influenced parameters responsible for the observed changes in the cantilever response. For example, effects of various force fields such as those induced by atom/molecular adsorption and variations in temperature may occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of sensors. In this paper, we, therefore, systematically investigate the interplay between these two distinctly different mechanisms and attendant mechanical response. To this end, a theory model is proposed to predict the mechanical bending and resonance frequency shift of micro- and nanocantilevers taking into account atom/molecular adsorption and variations in temperature at the same time. The adsorption induced mechanical responses of microcantilevers are modeled for the van der Waals interaction in presence of surface effect. Thermal effects addressed here include the thermal mismatch between the substrate and coating layer owing to different thermal expansion coefficients and the temperature-dependent material properties. The theoretical and computational model developed here will allow one to gain an insight into not only the mechanical responses observed experimentally but also the fundamental, novel detection principles for sensing applications.

  17. Recovery model of temporary threshold shifts from exposures with the same L_Aeq,T and different frequency components

    DEFF Research Database (Denmark)

    Ordonez, Rodrigo; Hammershøi, Dorte

    2005-01-01

    Temporary Threshold Shifts (TTS) were determined for 9 subjects exposed to three different band-passed signals taken from one channel of a binaural recording of an industrial mill. The three 2-octave bands were: Low (125 to 500 Hz), mid (500 Hz to 2 kHz), and high (2 kHz to 8 kHz). The band-passe...... signals may not be well characterised by the A-weighting curve. The present paper presents the recovery model and discusses the application of the model to the present TTS data.......-passed signals were adjusted to give the same equivalent A-weighted sound exposure according to ISO-1999 (1990) and were presented to one ear of the subjects in three separate experimental sessions. The results were used in a recovery model based on a least-squares fit of the data to a superposition...... of exponential functions. The recovery model showed good agreement with the average TTS across subjects and confirms that the high band caused the greatest TTS. The difference between the TTS caused by exposures with the same A-weighted equivalent level, suggests that the frequency characteristics of exposure...

  18. Doppler Frequency Shift in Ocean Wave Measurements: Frequency Downshift of a Fixed Spectral Wave Number Component by Advection of Wave Orbital Velocity

    National Research Council Canada - National Science Library

    Hwang, Paul

    2006-01-01

    ... expected intrinsic frequency in the frequency spectrum measured by a stationary probe. The advection of the wave number component by the orbital current of background waves produces a net downshift in the encounter frequency...

  19. Mid-frequency range modes computation based on component mode synthesis and frequency shifting%基于模态综合和移频方法的中频段模态计算

    Institute of Scientific and Technical Information of China (English)

    李兴泉; 邓兆祥; 李英强; 章竟成; 王腾腾

    2013-01-01

    The component mode synthesis method was used to compute structural mid-frequency range modes,and the characteristic constraint mode was used for reducing interface DOFs.The frequency shifting technique was induced to cut off lower frequency characteristic constraint modes.The influence of lower frequency characteristic constraint modes on structural mid-frequency range modes was studied.The results showed that before frequency shifting,the lower frequency characteristic constraint modes have an important influence on the mid-frequency range modes of a system,the former can not be cut off; but after frequency shifting,the former can be cut off.The frequency shifting technique was used to compute a prototype vehicle modes in a frequency range of 250 ~300 Hz.The results showed that the lower frequency characteristic constraint modes can be cut off after frequency shifting,the computation needs less time; it means this technique can improve the computational efficiency for mid-frequency range modes of a complex structure.%采用基于特征约束模态降阶的模态综合方法计算结构中频段振动特性时,针对低阶特征约束模态不能截断的问题,引入了移频方法对子结构动力学方程进行变换,并推导了移频后低阶特征约束模态与系统中频段模态的关系,结果表明:采用移频方法后,低阶特征约束模态可以截断.采用该方法计算了某白车身有限元模型160 ~190Hz频段内的振动特性,结果表明:采用移频方法后,保留的特征约束模态阶数较少,系统振动特性的计算时间较短,说明该方法有助于提高复杂结构中频段振动特性的计算效率.

  20. Optical Solitary Waves in Fourth-Order Dispersive Nonlinear Schr(o)dinger Equation with Self-steepening and Self-frequency Shift

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    By making use of the generalized sine-Gordon equation expansion method, we find cnoidal periodic wave solutions and fundamental bright and dark optical solitarywave solutions for the fourth-order dispersive and the quintic nonlinear Schrodinger equation with self-steepening, and self-frequency shift. Moreover, we discuss the formation conditions of the bright and dark solitary waves.

  1. (H2O)2(g): Monomer/dimer vibrational frequency shifts in Bopp-Jancsó-Heinzinger- and Matsuoka-Clementi-Yoshimine-Lie-type flexible potentials

    Science.gov (United States)

    Slanina, Zdeněk

    1991-01-01

    Harmonic vibrational analysis of the water dimer is reported for four BJH- and four MCYL-type flexible water-water potentials. The calculated monomer/dimer frequency shifts correspond reasonably well to the available observed terms, the BJH-type flexible potentials (with the gas-phase intramolecular potential) yielding a slightly better agreement.

  2. Evaluation of trap-induced systematic frequency shifts for a multi-ion optical clock at the $10^{-19}$ level

    CERN Document Server

    Keller, J; Kalincev, D; Kiethe, J; Mehlstäubler, T E

    2015-01-01

    In order to improve the short-term stability of trapped-ion optical clocks, we are developing a frequency standard based on ${}^{115}$In${}^+$ / ${}^{172}$Yb${}^+$ Coulomb crystals. For this purpose, we have developed scalable segmented Paul traps which allow a high level of control for multiple ion ensembles. In this article, we detail on our recent results regarding the reduction of the leading sources of frequency uncertainty introduced by the ion trap: 2nd-order Doppler shifts due to micromotion and the heating of secular motion, as well as the black-body radiation shift due to warming of the trap. We show that the fractional frequency uncertainty due to each of these effects can be reduced to well below $10^{-19}$.

  3. A Cross-Correlated Trellis-Coded Quadrature Modulation Representation of MIL-STD Shaped Offset Quadrature Phase-Shift Keying

    Science.gov (United States)

    Simon, M. K.; Li, L.

    2003-08-01

    We show that MIL-STD shaped offset quadrature phase-shift keying (SOQPSK), a highly bandwidth-efficient constant-envelope modulation, can be represented in the form of a cross-correlated trellis-coded quadrature modulation, a generic structure containing both memory and cross-correlation between the in-phase and quadrature-phase channels. Such a representation allows identification of the optimum form of receiver for MIL-STD SOQPSK and at the same time, through modification of the equivalent I and Q encoders to recursive types, allows for it to be embedded as the inner code of a serial or parallel (turbo-like) concatenated coding structure together with iterative decoding.

  4. Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

    Science.gov (United States)

    Goto, Nobuo; Miyazaki, Yasumitsu

    2014-06-01

    Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

  5. Reconfigurable all-optical dual-directional half-subtractor for high-speed differential phase shift keying signal based on semiconductor optical amplifiers

    Institute of Scientific and Technical Information of China (English)

    Zhang Yin; Dong Jian-Ji; Lei Lei; Zhang Xin-Liang

    2012-01-01

    All-optical digital logic elementary circuits are the building blocks of many important computational operations in future high-speed all-optical networks and computing systems.Multifunctional and reconfigurable logic units are essential in this respect.Employing the demodulation properties of delay interferometers for input differential phase shift keying signals and the gain saturation effect in two parallel semiconductor optical amplifiers,a novel design of 40 Gbit/s reconfigurable all-optical dual-directional half-subtractor is proposed and demonstrated.All output logic results show that the scheme achieves over 11=dB extinction ratio,clear and wide open eye diagram,as well as low polarization dependence (< 1 dB),without using any additional input light beam.The scheme may provide a promising candidate for future ultrafast all-optical signal processing applications.

  6. Experimental transmission of quantum digital signatures over 90  km of installed optical fiber using a differential phase shift quantum key distribution system.

    Science.gov (United States)

    Collins, Robert J; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Andersson, Erika; Buller, Gerald S; Sasaki, Masahide

    2016-11-01

    Quantum digital signatures (QDSs) apply quantum mechanics to the problem of guaranteeing message integrity and non-repudiation with information-theoretical security, which are complementary to the confidentiality realized by quantum key distribution (QKD). Previous experimental demonstrations have been limited to transmission distances of less than 5 km of optical fiber in a laboratory setting. Here we report, to the best of our knowledge, the first demonstration of QDSs over installed optical fiber, as well as the longest transmission link reported to date. This demonstration used a 90 km long differential phase shift QKD to achieve approximately one signed bit per second, an increase in the signature generation rate of several orders of magnitude over previous optical fiber demonstrations.

  7. Hybrid pulse position modulation and binary phase shift keying subcarrier intensity modulation for free space optics in a weak and saturated turbulence channel.

    Science.gov (United States)

    Faridzadeh, Monire; Gholami, Asghar; Ghassemlooy, Zabih; Rajbhandari, Sujan

    2012-08-01

    In this paper a hybrid modulation scheme based on pulse position modulation (PPM) and binary phase shift keying subcarrier intensity modulation (BPSK-SIM) schemes for free-space optical communications is proposed. The analytical bit error rate (BER) performance is investigated in weak and saturated turbulence channels and results are verified with the simulation data. Results show that performance of PPM-BPSK-SIM is superior to BPSK-SIM in all turbulence regimes; however, it outperforms 2-PPM for the turbulence variance σ(1)(2)>0.2. PPM-BPSK-SIM offers a signal-to-noise ratio (SNR) gain of 50 dB in the saturation regime compared to BPSK at a BER of 10(-6). The SNR gain in comparison to PPM improves as the strength of the turbulence level increases.

  8. Quadrature Phase Shift Keying (QPSK Modulator Design using Multi-Port Network in Multilayer Microstrip-Slot Technology for Wireless Communication Applications

    Directory of Open Access Journals (Sweden)

    N. Seman

    2015-06-01

    Full Text Available The design of the quadrature phase shift keying (QPSK modulator by using a multi-port network is proposed in this article for the use in wireless communication applications. The multi-port network is in the form of multilayer microstrip-slot technology. This multi-port network is composed of three 3-dB rectangular-shaped directional couplers with virtual stubs and an equal power division divider with in-phase characteristic. The design is performed by applying a full-wave electromagnetic simulation software, CST Microwave Studio (CST MWS. Keysight’s Advanced Design System (ADS is applied in analyzing and evaluating the QPSK constellation of the proposed modulator. This comparatively small size of proposed design has been fabricated, and its wideband performance of 2 to 6 GHz is verified.

  9. High-Frequency (1)H NMR Chemical Shifts of Sn(II) and Pb(II) Hydrides Induced by Relativistic Effects: Quest for Pb(II) Hydrides.

    Science.gov (United States)

    Vícha, Jan; Marek, Radek; Straka, Michal

    2016-10-17

    The role of relativistic effects on (1)H NMR chemical shifts of Sn(II) and Pb(II) hydrides is investigated by using fully relativistic DFT calculations. The stability of possible Pb(II) hydride isomers is studied together with their (1)H NMR chemical shifts, which are predicted in the high-frequency region, up to 90 ppm. These (1)H signals are dictated by sizable relativistic contributions due to spin-orbit coupling at the heavy atom and can be as large as 80 ppm for a hydrogen atom bound to Pb(II). Such high-frequency (1)H NMR chemical shifts of Pb(II) hydride resonances cannot be detected in the (1)H NMR spectra with standard experimental setup. Extended (1)H NMR spectral ranges are thus suggested for studies of Pb(II) compounds. Modulation of spin-orbit relativistic contribution to (1)H NMR chemical shift is found to be important also in the experimentally known Sn(II) hydrides. Because the (1)H NMR chemical shifts were found to be rather sensitive to the changes in the coordination sphere of the central metal in both Sn(II) and Pb(II) hydrides, their application for structural investigation is suggested.

  10. Optimum Jamming Effects on Frequency-Hopping M-ary FSK (Frequency-Shift Keying) Systems under Certain ECCM (Electronic Counter-Countermeasures) Receiver Design Strategies.

    Science.gov (United States)

    1984-10-01

    2 to 4 from attaining a net improvement. We note that for band multitone jamming with n = I the minimum realizable value of y is y = 1/2400 when just...common to all values of M considered. The seventh value is y = 1/M, which is the maximum realizable value for barrage jamming with tone spacing n = M

  11. Doppler-shifting effects on frequency spectra of gravity waves observed near the summer mesopause at high latitude

    Science.gov (United States)

    Fritts, David C.; Wang, Ding-Yi

    1991-01-01

    Results are presented of radar observations of horizontal and vertical velocities near the summer mesopause at Poker Flat (Alaska), showing that the observed vertical velocity spectra were influenced strongly by Doppler-shifting effects. The horizontal velocity spectra, however, were relatively insensitive to horizontal wind speed. The observed spectra are compared with predicted spectra for various models of the intrinsic motion spectrum and degrees of Doppler shifting.

  12. Speech Signal Encryption Based on Frequency Shift Function%基于移频函数的语音信号加密

    Institute of Scientific and Technical Information of China (English)

    闫应天

    2015-01-01

    Aiming at the problem of encryption of speech signal, based on MATLAB software programming, using frequency shift function to shift frequency encryption, and on this basis, an improved method is presented to segment a speech signal into encryption, so as to improve the effect of encryption.%针对语音信号的加密问题,基于MATLAB软件编程,利用移频函数对语音信号进行移频加密,并在此基础上给出了一种改进方法,将一个语音信号进行分割加密,从而提高加密的效果.

  13. Mitigation of nonlinear effects through frequency shift free mid-span spectral inversion using counter-propagating dual pumped FWM in fiber

    Science.gov (United States)

    Anchal, Abhishek; Kumar, Pradeep; Landais, Pascal

    2016-10-01

    We propose and numerically verify a scheme of frequency-shift free mid-span spectral inversion (MSSI) for nonlinearity mitigation in an optical transmission system. Spectral inversion is accomplished by optical phase conjugation, realized by counter-propagating dual pumped four-wave mixing in a highly nonlinear fiber. We examine the performance of MSSI due to critical parameters such as nonlinear fiber length, pump and signal power. We demonstrate the near complete nonlinearity mitigation of 40 Gbps DQPSK modulated data transmitted over 1000 km standard single mode fiber using our method of MSSI. We perform simulation of bit-error rate as a function of optical signal to noise ratio to corroborate the effect of frequency-shift free MSSI.

  14. Modified Pippard relationship describing the Raman frequency shifts of the rotatory lattice mode of ammonia solid II in the vicinity of its melting point

    Indian Academy of Sciences (India)

    H Karacali; H Yurtseven

    2005-11-01

    We relate in this study the thermal expansivity, , to the Raman frequency shift (1/)( /) for the rotatory lattice (librational) mode in ammonia solid II near its melting point. We have used our calculated Raman frequencies of this mode for pressures of 3.65, 5.02 and 6.57 kbars for this crystalline system. The values of the slope, d/d, which we deduced from our spectroscopic relation, are compared with those obtained experimentally. In particular, our computed slope value for the pressure of 5.02 kbar is in very good agreement with the empirical result.

  15. Analysis of the resonance frequency shift in cylindrical cavities containing a sphere and its prediction based on the Boltzmann-Ehrenfest principle

    DEFF Research Database (Denmark)

    Orozco Santillán, Arturo; Cutanda Henriquez, Vicente

    2008-01-01

    of the cavity due to the presence of the levitated object. The Boltzmann-Ehrenfest principle has been used to obtain an analytical expression for the resonance frequency shift in a cylindrical cavity produced by a small sphere, with kR .... The validity of the Boltzmann-Ehrenfest method has been investigated by means of the Boundary Element Method (BEM) and confirmed with experiments....

  16. Wearable slot antenna at 2.45 GHz for off-body radiation: Analysis of efficiency, frequency shift, and body absorption.

    Science.gov (United States)

    Fernandez, Marta; Espinosa, Hugo G; Thiel, David V; Arrinda, Amaia

    2017-09-12

    The interaction of body-worn antennas with the human body causes a significant decrease in antenna efficiency and a shift in resonant frequency. A resonant slot in a small conductive box placed on the body has been shown to reduce these effects. The specific absorption rate is less than international health standards for most wearable antennas due to small transmitter power. This paper reports the linear relationship between power absorbed by biological tissues at different locations on the body and radiation efficiency based on numerical modeling (r = 0.99). While the -10 dB bandwidth of the antenna remained constant and equal to 12.5%, the maximum frequency shift occurred when the antenna was close to the elbow (6.61%) and on the thigh (5.86%). The smallest change was found on the torso (4.21%). Participants with body-mass index (BMI) between 17 and 29 kg/m(2) took part in experimental measurements, where the maximum frequency shift was 2.51%. Measurements showed better agreement with simulations on the upper arm. These experimental results demonstrate that the BMI for each individual had little effect on the performance of the antenna. Bioelectromagnetics. 2017;9999:XX-XX. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  17. An Estimation Method for number of carrier frequency

    Directory of Open Access Journals (Sweden)

    Xiong Peng

    2015-01-01

    Full Text Available This paper proposes a method that utilizes AR model power spectrum estimation based on Burg algorithm to estimate the number of carrier frequency in single pulse. In the modern electronic and information warfare, the pulse signal form of radar is complex and changeable, among which single pulse with multi-carrier frequencies is the most typical one, such as the frequency shift keying (FSK signal, the frequency shift keying with linear frequency (FSK-LFM hybrid modulation signal and the frequency shift keying with bi-phase shift keying (FSK-BPSK hybrid modulation signal. In view of this kind of single pulse which has multi-carrier frequencies, this paper adopts a method which transforms the complex signal into AR model, then takes power spectrum based on Burg algorithm to show the effect. Experimental results show that the estimation method still can determine the number of carrier frequencies accurately even when the signal noise ratio (SNR is very low.

  18. Finite element analysis and frequency shift studies for the bridge coupler of the coupled cavity linear accelerator of the spallation neutron source.

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z. (Zukun)

    2001-01-01

    The Spallation Neutron Source (SNS) is an accelerator-based neutron scattering research facility. The linear accelerator (linac) is the principal accelerating structure and divided into a room-temperature linac and a superconducting linac. The normal conducting linac system that consists of a Drift Tube Linac (DTL) and a Coupled Cavity Linac (CCL) is to be built by Los Alamos National Laboratory. The CCL structure is 55.36-meters long. It accelerates H- beam from 86.8 Mev to 185.6 Mev at operating frequency of 805 MHz. This side coupled cavity structure has 8 cells per segment, 12 segments and 11 bridge couplers per module, and 4 modules total. A 5-MW klystron powers each module. The number 3 and number 9 bridge coupler of each module are connected to the 5-MW RF power supply. The bridge coupler with length of 2.5 {beta}{gamma} is a three-cell structure and located between the segments and allows power flow through the module. The center cell of each bridge coupler is excited during normal operation. To obtain a uniform electromagnetic filed and meet the resonant frequency shift, the RF induced heat must be removed. Thus, the thermal deformation and frequency shift studies are performed via numerical simulations in order to have an appropriate cooling design and predict the frequency shift under operation. The center cell of the bridge coupler also contains a large 4-inch slug tuner and a tuning post that used to provide bulk frequency adjustment and field intensity adjustment, so that produce the proper total field distribution in the module assembly.

  19. Research on the system performance evaluation of minimum-shift keying in uplink ground-to-satellite with gamma-gamma distribution

    Science.gov (United States)

    Wang, Yi; Zhang, Ao; Ma, Jing

    2017-07-01

    Minimum-shift keying (MSK) has the advantages of constant envelope, continuous phase, and high spectral efficiency, and it is applied in radio communication and optical fiber communication. MSK modulation of coherent detection is proposed in the ground-to-satellite laser communication system; in addition, considering the inherent noise of uplink, such as intensity scintillation and beam wander, the communication performance of the MSK modulation system with coherent detection is studied in the uplink ground-to-satellite laser. Based on the gamma-gamma channel model, the closed form of bit error rate (BER) of MSK modulation with coherent detection is derived. In weak, medium, and strong turbulence, the BER performance of the MSK modulation system is simulated and analyzed. To meet the requirements of the ground-to-satellite coherent MSK system to optimize the parameters and configuration of the transmitter and receiver, the influence of the beam divergence angle, the zenith angle, the transmitter beam radius, and the receiver diameter are studied.

  20. Reply to Comment on ‘Roles of interbasin frequency changes in the poleward shifts of maximum intensity location of tropical cyclones’

    Science.gov (United States)

    Moon, Il-Ju; Kim, Sung-Hun; Klotzbach, Phil; Chan, Johnny C. L.

    2016-06-01

    Recently a pronounced global poleward shift in the latitude at which the maximum intensities of tropical cyclones (TC) occur has been identified. Moon et al (2015 Environ. Res. Lett. 10 104004) reported that the poleward migration is significantly influenced by changes in interbasin frequency. These frequency changes are a larger contributor to the poleward shift than the intrabasin migration component. The strong role of interbasin frequency changes in the poleward migration also suggest that the poleward trend could be changed to an opposite equatorward trend in the future due to multi-decadal variability that significantly impacts Northern Hemisphere TC frequency. In the accompanying comment, Kossin et al (2016 Environ. Res. Lett. 11 068001) questioned the novelty and robustness of our results by raising issues associated with subsampling, contributions from some basins to poleward migration, and data dependency. Here, we explain the originality and importance of our main findings, which are different from those of Kossin et al (2014 Nature 509 349-52) and reaffirm that our conclusions are maintained regardless of the issues that were raised.

  1. Temperature Compensated Crystal Oscillator (TCXO) Design Aids: Frequency-Temperature Resonator Characteristics as Shifted by Series Capacitors

    Science.gov (United States)

    1977-05-01

    and 6() in place of the corresponding resonance quantities. In the limit o - I (CL - o), the load frequencies approach the antiresonance frequencies...while the limit a o (CL c) reduces the frequencies to the resonances. 2 Cu. Y+ _II ZL w NOW"z CZ) LUL Lu Ul- CD 0 LU OD (D qt 6 0 OD (D I* N -00 0 0 0...2. The quantity multiplying Tk in (40) is called the Onoe funcion : 46 G (M) = +2k2/D. is plotted versus 0 for various k values and for M = 1, 3, and

  2. The asteroseismic surface effect from a grid of 3D convection simulations - I. Frequency shifts from convective expansion of stellar atmospheres

    DEFF Research Database (Denmark)

    Trampedach, Regner; Aarslev, Magnus J.; Houdek, Günter

    2017-01-01

    We analyse the effect on adiabatic stellar oscillation frequencies of replacing the near-surface layers in 1D stellar structure models with averaged 3D stellar surface convection simulations. The main difference is an expansion of the atmosphere by 3D convection, expected to explain a major part...... of the asteroseismic surface effect; a systematic overestimation of p-mode frequencies due to inadequate surface physics. We employ pairs of 1D stellar envelope models and 3D simulations from a previous calibration of the mixing-length parameter, alpha. That calibration constitutes the hitherto most consistent...... matching of 1D models to 3D simulations, ensuring that their differences are not spurious, but entirely due to the 3D nature of convection. The resulting frequency shift is identified as the structural part of the surface effect. The important, typically non-adiabatic, modal components of the surface...

  3. Isotope shifts and transition frequencies for the S and P states of lithium: Bethe logarithms and second-order relativistic recoil

    Science.gov (United States)

    Wang, L. M.; Li, Chun; Yan, Z.-C.; Drake, G. W. F.

    2017-03-01

    Isotope shifts and total transition frequencies are calculated for the 2 2S-3 2S transition of the lithium isotopes 6Li, 7Li, 8Li, 9Li, and the halo nucleus 11Li. The accuracy is improved for previously calculated relativistic and quantum electrodynamic corrections, and in particular a disagreement for the Bethe logarithm is resolved for the ground 2S state. Our previous result is confirmed for the 2 2P state. We use the pseudostate expansion method to perform the sum over virtual intermediate states. Results for the second-order relativistic recoil term of order α2(μ/M ) 2 Ry are shown to make a significant contribution relative to the theoretical uncertainty, but because of accidental cancellations the final result for the isotope shift is nearly unchanged. However, the spin-orbit term makes an unexpectedly large contribution to the splitting isotope shift (SIS) for the 2 1/2 2P -2 3/2 2P fine structure, increasing the theoretical value for the 6Li-7Li isotopes to 0.556 31 (7 )±0.001 MHz. A comparison is made with high-precision measurements and other calculations for the SIS and for the total 2 2S-3 2S transition frequency.

  4. Solid state NMR of proteins at high MAS frequencies: symmetry-based mixing and simultaneous acquisition of chemical shift correlation spectra

    Energy Technology Data Exchange (ETDEWEB)

    Bellstedt, Peter [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany); Herbst, Christian [Ubon Ratchathani University, Department of Physics, Faculty of Science (Thailand); Haefner, Sabine; Leppert, Joerg; Goerlach, Matthias; Ramachandran, Ramadurai, E-mail: raman@fli-leibniz.de [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany)

    2012-12-15

    We have carried out chemical shift correlation experiments with symmetry-based mixing sequences at high MAS frequencies and examined different strategies to simultaneously acquire 3D correlation spectra that are commonly required in the structural studies of proteins. The potential of numerically optimised symmetry-based mixing sequences and the simultaneous recording of chemical shift correlation spectra such as: 3D NCAC and 3D NHH with dual receivers, 3D NC Prime C and 3D C Prime NCA with sequential {sup 13}C acquisitions, 3D NHH and 3D NC Prime H with sequential {sup 1}H acquisitions and 3D CANH and 3D C'NH with broadband {sup 13}C-{sup 15}N mixing are demonstrated using microcrystalline samples of the {beta}1 immunoglobulin binding domain of protein G (GB1) and the chicken {alpha}-spectrin SH3 domain.

  5. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study

    Directory of Open Access Journals (Sweden)

    Federica Villa

    2016-05-01

    Full Text Available Bioelectrical Impedance Spectroscopy (BIS allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously.

  6. "Hot moments" of carbon and nitrogen in streams: Key insights from in-situ, high-frequency optical sensors from the North East Water Resources Network (NEWRnet)

    Science.gov (United States)

    Inamdar, S. P.; Vaughan, M.; Rowland, R. D.; Winters, C. G.; Addy, K.; Schroth, A. W.; Gold, A.; Bowden, W. B.; Vermilyea, A.; Parr, T. B.; Andres, S.; Levia, D. F., Jr.

    2015-12-01

    Sharp or unexpected changes in stream water solute concentrations and fluxes can often provide important insights into potential sources, supply versus transport controls, and threshold behavior in watersheds. Identifying these "hot moments" is critical for furthering our understanding of biogeochemical processes and for developing accurate mechanistic models to manage water quality. Use of in-situ, high-frequency optical sensors, while in its infancy, has shown considerable promise in capturing fine resolution time series data on solute concentrations. Here, we highlight key lessons from the North East Water Resources Network (NEWRnet), a regional water quality network (Delaware, Rhode Island and Vermont) instrumented with optical sensors on a suite of stream sites (forested, agricultural, and urban watersheds in each state). Sensor data is coupled with traditional hydrologic and water chemistry sampling for baseflow and storms, laboratory-based UV and fluorescence excitation-emission matrices (EEMs) to characterize organic matter composition, and stable carbon (C) and nitrogen (N) isotopes to identify solute sources. Both dissolved and particulate forms of C and N are being studied. Sampling is performed throughout the year with special attention to large storm events, droughts, diel variations, and key seasonal transitions including snowmelt and autumn leaf fall. We leverage these complimentary data to reveal both - process controls on C and N as well as methodological constraints and challenges with the sensors. Particulate and dissolved concentrations of C and N are compared for large storm events to disentangle supply and transport controls. Simultaneously, the accuracy of sensors is evaluated for interferences from varying particle size classes. Coupled changes in C and N concentrations and shifts in C composition during autumn leaf fall and snowmelt are investigated to identify biogeochemical/ecological controls. However, we also investigate how variability

  7. Recovery model of temporary threshold shifts from exposures with the same L_Aeq,T and different frequency components

    DEFF Research Database (Denmark)

    Ordonez, Rodrigo; Hammershøi, Dorte

    2005-01-01

    Temporary Threshold Shifts (TTS) were determined for 9 subjects exposed to three different band-passed signals taken from one channel of a binaural recording of an industrial mill. The three 2-octave bands were: Low (125 to 500 Hz), mid (500 Hz to 2 kHz), and high (2 kHz to 8 kHz). The band......-passed signals were adjusted to give the same equivalent A-weighted sound exposure according to ISO-1999 (1990) and were presented to one ear of the subjects in three separate experimental sessions. The results were used in a recovery model based on a least-squares fit of the data to a superposition...

  8. On a simple attack, limiting the range transmission of secret keys in a system of quantum cryptography based on coding in a sub-carrier frequency

    Science.gov (United States)

    Klimov, A. N.; Kulik, S. P.; Molotkov, S. N.; Potapova, T. A.

    2017-03-01

    In the paper by Gleim et al (2016 Opt. Express 24 2619), it was declared that the system of quantum cryptography, exploiting quantum key distribution (QKD) protocol BB84 with the additional reference state and encoding in a sub-carrier, is able to distribute secret keys at a distance of 210 km. The following shows that a simple attack realized with a beam splitter results in a loss of privacy of the keys over substantially smaller distances. It turns out that the actual length of the secret key transmission for the QKD system encoding in the sub-carrier frequency is ten times less than that declared in Gleim et al (2016 Opt. Express 24 2619). Therefore it is impossible to safely use the keys when distributed at a larger length of the communication channel than shown below. The maximum communication distance does not exceed 22 km, even in the most optimistic scenario.

  9. 大气激光通信系统偏振移位键控调制技术%Polarization shift keying modulation technology in atmospheric laser communication

    Institute of Scientific and Technical Information of China (English)

    王璞瑶; 刘丹; 赵怡春; 刘智; 付强; 刘建华

    2012-01-01

    为了实现自由空间高速激光通信,对基于偏振移位键控的激光通信调制和解调技术进行了研究.介绍了一种基于PolSK的调制与差分解调方法,对实现大气信道中高速激光通信的调制与解调方法进行了研究,并通过理论推导及计算机仿真验证了其可行性.仿真研究结果表明:虽然大气信道对激光的传输特性有一定的影响,但利用以左右旋圆偏振光调制为基础的偏振态移位键控方法实现数据调制传输,并采用差分探测解调技术,可以实现传输速率为2.5 Gb/s、传输距离为20 km的低误码率数据传输.基本满足了空间激光通信系统的稳定可靠性、简便易实现、抗干扰能力强等要求.%In order to achieve the high-speed FSO communication, the technology of modulation and demodulation on polarization shift keying (PolSK) was studied. A modulation and differential demodulation method based on PolSK was introduced and the method of modulation and demodulation in high speed laser communications through atmosphere channel was studied, and its feasibility by theoretical analysis and computer simulation was validated. The simulation result shows that although the atmospheric channel may affect the laser transmission characteristics, data transmission and modulation based on right/left circle polarization technology using differential detection demodulation technology, can transmit for 20 km at the speed of 2.5 Gb/s with a low BER. It meets the basic requirement of space laser communication system which is stability and reliability, simple and easy realization, and anti-interference ability.

  10. Time dependent Doppler shifts in high-order harmonic generation in intense laser interactions with solid density plasma and frequency chirped pulses

    Energy Technology Data Exchange (ETDEWEB)

    Welch, E. C.; Zhang, P.; He, Z.-H. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Dollar, F. [JILA, University of Colorado, Boulder, Colorado 80309 (United States); Krushelnick, K.; Thomas, A. G. R., E-mail: agrt@umich.edu [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States)

    2015-05-15

    High order harmonic generation from solid targets is a compelling route to generating intense attosecond or even zeptosecond pulses. However, the effects of ion motion on the generation of harmonics have only recently started to be considered. Here, we study the effects of ion motion in harmonics production at ultrahigh laser intensities interacting with solid density plasma. Using particle-in-cell simulations, we find that there is an optimum density for harmonic production that depends on laser intensity, which scales linearly with a{sub 0} with no ion motion but with a reduced scaling if ion motion is included. We derive a scaling for this optimum density with ion motion and also find that the background ion motion induces Doppler red-shifts in the harmonic structures of the reflected pulse. The temporal structure of the Doppler shifts is correlated to the envelope of the incident laser pulse. We demonstrate that by introducing a frequency chirp in the incident pulse we are able to eliminate these Doppler shifts almost completely.

  11. A novel femtosecond-gated, high-resolution, frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Feister, S., E-mail: feister.7@osu.edu; Orban, C. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Nees, J. A. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Center for Ultra-Fast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Morrison, J. T. [Fellow, National Research Council, Washington, D.C. 20001 (United States); Frische, K. D. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Chowdhury, E. A. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Intense Energy Solutions, LLC., Plain City, Ohio 43064 (United States); Roquemore, W. M. [Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

    2014-11-15

    Ultra-intense laser-matter interaction experiments (>10{sup 18} W/cm{sup 2}) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the main ultra-intense pulse. These system-dependent pre-pulses in the nanosecond and/or picosecond regimes are often intense enough to modify the target significantly by ionizing and forming a plasma layer in front of the target before the arrival of the main pulse. Time resolved interferometry offers a robust way to characterize the expanding plasma during this period. We have developed a novel pump-probe interferometry system for an ultra-intense laser experiment that uses two short-pulse amplifiers synchronized by one ultra-fast seed oscillator to achieve 40-fs time resolution over hundreds of nanoseconds, using a variable delay line and other techniques. The first of these amplifiers acts as the pump and delivers maximal energy to the interaction region. The second amplifier is frequency shifted and then frequency doubled to generate the femtosecond probe pulse. After passing through the laser-target interaction region, the probe pulse is split and recombined in a laterally sheared Michelson interferometer. Importantly, the frequency shift in the probe allows strong plasma self-emission at the second harmonic of the pump to be filtered out, allowing plasma expansion near the critical surface and elsewhere to be clearly visible in the interferograms. To aid in the reconstruction of phase dependent imagery from fringe shifts, three separate 120° phase-shifted (temporally sheared) interferograms are acquired for each probe delay. Three-phase reconstructions of the electron densities are then inferred by Abel inversion. This interferometric system delivers precise measurements of pre-plasma expansion that can identify the condition of the target at the moment that the ultra-intense pulse arrives. Such measurements are indispensable for correlating laser pre-pulse measurements

  12. Detailed discussion of a linear electric field frequency shift induced in confined gases by a magnetic field gradient: Implications for neutron electric-dipole-moment experiments

    Science.gov (United States)

    Lamoreaux, S. K.; Golub, R.

    2005-03-01

    The search for particle electric dipole moments (EDM’s) is one of the best places to look for physics beyond the standard model of electroweak interaction because the size of time reversal violation predicted by the standard model is incompatible with present ideas concerning the creation of the baryon-antibaryon asymmetry. As the sensitivity of these EDM searches increases more subtle systematic effects become important. We develop a general analytical approach to describe a systematic effect recently observed in an electric dipole moment experiment using stored particles [J. M. Pendlebury , Phys. Rev. A 70, 032102 (2004)]. Our approach is based on the relationship between the systematic frequency shift and the velocity autocorrelation function of the resonating particles. Our results, when applied to well-known limiting forms of the correlation function, are in good agreement with both the limiting cases studied in recent work that employed a numerical and heuristic analysis. Our general approach explains some of the surprising results observed in that work and displays the rich behavior of the shift for intermediate frequencies, which has not been studied previously.

  13. Colloquium paper: human adaptations to diet, subsistence, and ecoregion are due to subtle shifts in allele frequency.

    Science.gov (United States)

    Hancock, Angela M; Witonsky, David B; Ehler, Edvard; Alkorta-Aranburu, Gorka; Beall, Cynthia; Gebremedhin, Amha; Sukernik, Rem; Utermann, Gerd; Pritchard, Jonathan; Coop, Graham; Di Rienzo, Anna

    2010-05-11

    Human populations use a variety of subsistence strategies to exploit an exceptionally broad range of ecoregions and dietary components. These aspects of human environments have changed dramatically during human evolution, giving rise to new selective pressures. To understand the genetic basis of human adaptations, we combine population genetics data with ecological information to detect variants that increased in frequency in response to new selective pressures. Our approach detects SNPs that show concordant differences in allele frequencies across populations with respect to specific aspects of the environment. Genic and especially nonsynonymous SNPs are overrepresented among those most strongly correlated with environmental variables. This provides genome-wide evidence for selection due to changes in ecoregion, diet, and subsistence. We find particularly strong signals associated with polar ecoregions, with foraging, and with a diet rich in roots and tubers. Interestingly, several of the strongest signals overlap with those implicated in energy metabolism phenotypes from genome-wide association studies, including SNPs influencing glucose levels and susceptibility to type 2 diabetes. Furthermore, several pathways, including those of starch and sucrose metabolism, are enriched for strong signals of adaptations to a diet rich in roots and tubers, whereas signals associated with polar ecoregions are overrepresented in genes associated with energy metabolism pathways.

  14. Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method

    Directory of Open Access Journals (Sweden)

    Weifang Sun

    2017-08-01

    Full Text Available Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.

  15. Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method.

    Science.gov (United States)

    Sun, Weifang; Yao, Bin; He, Yuchao; Chen, Binqiang; Zeng, Nianyin; He, Wangpeng

    2017-08-09

    Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.

  16. The asteroseismic surface effect from a grid of 3D convection simulations. I. Frequency shifts from convective expansion of stellar atmospheres

    CERN Document Server

    Trampedach, Regner; Houdek, Günter; Collet, Remo; Christensen-Dalsgaard, Jørgen; Stein, Robert F; Asplund, Martin

    2016-01-01

    We analyse the effect on adiabatic stellar oscillation frequencies of replacing the near-surface layers in 1D stellar structure models with averaged 3D stellar surface convection simulations. The main difference is an expansion of the atmosphere by 3D convection, expected to explain a major part of the asteroseismic surface effect; a systematic overestimation of p-mode frequencies due to inadequate surface physics. We employ pairs of 1D stellar envelope models and 3D simulations from a previous calibration of the mixing-length parameter, alpha. That calibration constitutes the hitherto most consistent matching of 1D models to 3D simulations, ensuring that their differences are not spurious, but entirely due to the 3D nature of convection. The resulting frequency shift is identified as the structural part of the surface effect. The important, typically non-adiabatic, modal components of the surface effect are not included in the present analysis, but relegated to future papers. Evaluating the structural surfac...

  17. The present is the key to the past: linking regime shifts in kelp beds to the distribution of deep-living sea urchins.

    Science.gov (United States)

    Filbee-Dexter, Karen; Scheibling, Robert E

    2017-01-01

    Understanding processes that drive sudden shifts in ecosystem structure and function has become an important research focus for coastal management. In kelp bed ecosystems, regime shifts occur when high densities of sea urchins destructively graze kelp and create coralline algal barrens. While the importance of predation and disease in mediating shifts between kelp beds and barrens on shallow rocky reefs has been well documented, little is known about the role of deep-living urchins in these alternative stable-state dynamics. In this study, we test the hypothesis that deep-living urchins along the central Atlantic coast of Nova Scotia move onshore and trigger shifts from kelp beds to barrens on shallow rocky reefs. We documented urchin distribution and abundance using tow-camera surveys down to 140 m depth and spanning 140 km of coast and created a predictive species-distribution model using these observations and spatial data on environmental factors that likely delineate suitable habitat for urchins. We used a random forest model to generate our predictions, which correctly classified 91% of observations into a positive or negative occurrence of urchins. Sea urchins predominantly occurred within 1.5 km of shore, in depressions and flat habitats between 40 and 85 m depth. We found that shallow regions where destructive grazing fronts have been documented over the past four decades were closer to deep-living sea urchin habitats compared to regions that remained in a kelp bed state during the same period. This supports our prediction that deep-living urchins play an important role in driving shallow regime shift dynamics, and indicates that their distribution can help identify areas of coast that are most vulnerable to a collapse to barrens.

  18. LINE SHAPES OF DOPPLER-FREE RESONANCE IN SRFM: STRONG ATOM-WALL INTERACTION AND PRESSURE EFFECT ON THE FREQUENCY SHIFT OF AN ALKALI VAPOR

    Directory of Open Access Journals (Sweden)

    B BOUHAFS

    2003-12-01

    Full Text Available The attractive potential energy between the atoms of rubidium vapor and a dielectric wall has been investigated by monitoring the reflection light at the interface. The atom- wall interaction potential of the form V(z = - C /z3 (z: atom-wall allows to predict experimental results only for weak regime, i.e., where C<< 0.2 kHzmm3. In the strong interaction case, the dispersive line shape is turned into an absorption-type line shape. The influence of atomic density on the shift of  the selective reflection resonance  relatively to the frequency of unperturbed atomic transition is found to be red with a negative slope. This technique opens the way to characterize the windows made of different materials thin films.

  19. Geometric frequency shift for electric dipole searches with trapped spin-1/2 particles in general fields and measurement cells of arbitrary shape with smooth or rough walls

    CERN Document Server

    Steyerl, A; Müller, G; Golub, R

    2015-01-01

    The important role of geometric phases in searches for a permanent electric dipole moment of the neutron, using Ramsey separated oscillatory field nuclear magnetic resonance, was first investigated by Pendlebury $\\textit{et al.}$ [Phys. Rev. A $\\mathbf{70}$, 032102 (2004)]. Their analysis was based on the Bloch equations. In subsequent work using the spin density matrix Lamoreaux and Golub [Phys. Rev. A $\\mathbf{71}$, 032104 (2005)] showed the usual relation between the frequency shifts and the correlation functions of the fields seen by trapped particles in general fields (Redfield theory). More recently we presented a solution of the Schr\\"odinger equation for spin-$1/2$ particles in circular cylindrical traps with smooth walls and exposed to arbitrary fields [Steyerl $\\textit{et al.}$, Phys.Rev. A $\\mathbf{89}$, 052129 (2014)]. Here we extend this work to show how the Redfield theory follows directly from the Schr\\"odinger equation solution and include wall roughness, cylindrical trap geometry with arbitra...

  20. Synthesis of multi-wavelength temporal phase-shifting algorithms optimized for high signal-to-noise ratio and high detuning robustness using the frequency transfer function

    CERN Document Server

    Servin, Manuel; Garnica, Guillermo

    2016-01-01

    Synthesis of single-wavelength temporal phase-shifting algorithms (PSA) for interferometry is well-known and firmly based on the frequency transfer function (FTF) paradigm. Here we extend the single-wavelength FTF-theory to dual and multi-wavelength PSA-synthesis when several simultaneous laser-colors are present. The FTF-based synthesis for dual-wavelength PSA (DW-PSA) is optimized for high signal-to-noise ratio and minimum number of temporal phase-shifted interferograms. The DW-PSA synthesis herein presented may be used for interferometric contouring of discontinuous industrial objects. Also DW-PSA may be useful for DW shop-testing of deep free-form aspheres. As shown here, using the FTF-based synthesis one may easily find explicit DW-PSA formulae optimized for high signal-to-noise and high detuning robustness. To this date, no general synthesis and analysis for temporal DW-PSAs has been given; only had-hoc DW-PSAs formulas have been reported. Consequently, no explicit formulae for their spectra, their sign...

  1. Automatic oscillator frequency control system

    Science.gov (United States)

    Smith, S. F. (Inventor)

    1985-01-01

    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.

  2. A Novel Femtosecond-Gated, High-Resolution, Frequency-Shifted Shearing Interferometry Technique for Probing Pre-Plasma Expansion in Ultra-Intense Laser Experiments

    CERN Document Server

    Feister, S; Morrison, J T; Frische, K D; Orban, C; Chowdhury, E A; Roquemore, W M

    2014-01-01

    Ultra-intense laser-matter interaction experiments (>10$^{18}$ W/cm$^{2}$) with dense targets are highly sensitive to the effect of laser "noise" (in the form of pre-pulses) preceding the main ultra-intense pulse. These system-dependent pre-pulses in the nanosecond and/or picosecond regimes are often intense enough to modify the target significantly by ionizing and forming a plasma layer in front of the target. Time resolved interferometry offers a robust way to characterize the expanding plasma during this period. We have developed a novel pump-probe interferometry system for an ultra-intense laser experiment that uses two short-pulse amplifiers synchronized by one ultra-fast seed oscillator to achieve 40-femtosecond time resolution over hundreds of nanoseconds, using a variable delay line and other techniques. The first of these amplifiers acts as the pump and delivers maximal energy to the interaction region. The second amplifier is frequency shifted and then frequency doubled to generate the femtosecond p...

  3. An estimation of the influence of force decrease on the mean power spectral frequency shift of the EMG during repetitive maximum dynamic knee extensions.

    Science.gov (United States)

    Karlsson, J S; Ostlund, N; Larsson, B; Gerdle, B

    2003-10-01

    Frequency analysis of myoelectric (ME) signals, using the mean power spectral frequency (MNF), has been widely used to characterize peripheral muscle fatigue during isometric contractions assuming constant force. However, during repetitive isokinetic contractions performed with maximum effort, output (force or torque) will decrease markedly during the initial 40-60 contractions, followed by a phase with little or no change. MNF shows a similar pattern. In situations where there exist a significant relationship between MNF and output, part of the decrease in MNF may per se be related to the decrease in force during dynamic contractions. This study estimated force effects on the MNF shifts during repetitive dynamic knee extensions. Twenty healthy volunteers participated in the study and both surface ME signals (from the right vastus lateralis, vastus medialis, and rectus femoris muscles) and the biomechanical signals (force, position, and velocity) of an isokinetic dynamometer were measured. Two tests were performed: (i) 100 repetitive maximum isokinetic contractions of the right knee extensors, and (ii) five gradually increasing static knee extensions before and after (i). The corresponding ME signal time-frequency representations were calculated using the continuous wavelet transform. Compensation of the MNF variables of the repetitive contractions was performed with respect to the individual MNF-force relation based on an average of five gradually increasing contractions. Whether or not compensation was necessary was based on the shape of the MNF-force relationship. A significant compensation of the MNF was found for the repetitive isokinetic contractions. In conclusion, when investigating maximum dynamic contractions, decreases in MNF can be due to mechanisms similar to those found during sustained static contractions (force-independent component of fatigue) and in some subjects due to a direct effect of the change in force (force-dependent component of fatigue

  4. Mathematical model of the laser frequency shift modulated by small signal low frequency current%小信号低频电流调制下激光频移数学模型

    Institute of Scientific and Technical Information of China (English)

    阎得科; 钟镇; 孙传东

    2011-01-01

    激光通过光纤传输时,线宽越窄,受激布里渊散射的阈值就越低.高功率激光很容易产生受激布里渊散射,影响光信号的传输.对大功率半导体激光器进行小信号电流调制是解决这一问题的方法之一.在正弦小信号调制电流作用下,分布反馈式半导体激光器(DFB-SLD)输出的激光会发生频率偏移,光源线宽展宽,从而可以提高受激散射阈值,进而降低传输损耗.通过理论分析,给出了在正弦小信号低频调制电流作用下激光频率偏移量与调制电流幅度和频率关系的数学模型,进而设计相应的光路和电路进行实验测量,并借助数据拟合的方法给出了数学模型中的参数值.%When laser transmits through the fiber, the more narrow of the laser spectral line width is, the more lower of the threshold for the stimulated Brillouin scattering is. High power laser tends to bring stimulated Brillouin scattering, thereby affecting the laser transmission. Modulating the high power laser diode by small signal current is one of the means for solving this problem. Effected by the sine small signal modulating current, the output laser of the distributed feedback semiconductor laser diode could produce frequency shift and broaden the spectral line width. Accordingly, it could increase the threshold of stimulated Brillouin scattering and reduce the transmission loss. It was shown that the mathematical expression for the laser frequency shift associated with modulating current's amplitude and frequency on the condition of sine small signal low frequency modulating current. Then, the relative electro-optical system was also designed for the experiment. And then, the parameters of the mathematical model were obtained by data fitting.

  5. Final report of key comparison AFRIMETS.AUV.A-K5: primary pressure calibration of LS1P microphones according to IEC 61094-2, over the frequency range 2 Hz to 10 kHz.

    Science.gov (United States)

    Nel, R.; Avison, J.; Harris, P.; Blabla, M.; Hämäläinen, J.

    2017-01-01

    The degrees of equivalence of the AFRIMETS.AUV.A-K5 regional key comparison are reported here as the final report. The scope of the comparison covered the complex pressure sensitivities of two LS1P microphones over the frequency range 2 Hz to 10 kHz in accordance with IEC 61094-2: 2009. Four national metrology institutes from two different regional metrology organisations participated in the comparison. Two LS1P microphones were circulated simultaneously to all the participants in a circular configuration. One of the microphones sensitivity shifted and all results associated with this microphone were subsequently excluded from further analysis and linking. The AFRIMETS.AUV.A-K5 comparison results were linked to the CCAUV.A-K5 comparison results via dual participation in the CCAUV.A-K5 and AFRIMETS.AUV.A-K5 comparisons. The degrees of equivalence, linked to the CCAUV.A-K5 comparison, were calculated for all participants of this comparison. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  6. Tryptophan as key biomarker to detect gastrointestinal tract cancer using non-negative biochemical analysis of native fluorescence and Stokes Shift spectroscopy

    Science.gov (United States)

    Wang, Leana; Zhou, Yan; Liu, Cheng-hui; Zhou, Lixin; He, Yong; Pu, Yang; Nguyen, Thien An; Alfano, Robert R.

    2015-03-01

    The objective of this study was to find out the emission spectral fingerprints for discrimination of human colorectal and gastric cancer from normal tissue in vitro by applying native fluorescence. The native fluorescence (NFL) and Stokes shift spectra of seventy-two human cancerous and normal colorectal (colon, rectum) and gastric tissues were analyzed using three selected excitation wavelengths (e.g. 300 nm, 320 nm and 340 nm). Three distinct biomarkers, tryptophan, collagen and reduced nicotinamide adenine dinucleotide hydrate (NADH), were found in the samples of cancerous and normal tissues from eighteen subjects. The spectral profiles of tryptophan exhibited a sharp peak in cancerous colon tissues under a 300 nm excitation when compared with normal tissues. The changes in compositions of tryptophan, collagen, and NADH were found between colon cancer and normal tissues under an excitation of 300 nm by the non-negative basic biochemical component analysis (BBCA) model.

  7. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Frederik Freudenstein

    2015-01-01

    Full Text Available The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one’s own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed.

  8. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields

    Science.gov (United States)

    Freudenstein, Frederik; Wiedemann, Peter M.; Brown, Tim W. C.

    2015-01-01

    The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed. PMID:26229540

  9. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields.

    Science.gov (United States)

    Freudenstein, Frederik; Wiedemann, Peter M; Brown, Tim W C

    2015-01-01

    The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed.

  10. Mitigating Doppler shift effect in HF multitone data modem

    Science.gov (United States)

    Sonlu, Yasar

    1989-09-01

    Digital communications over High Frequency (HF) radio channels are getting important in recent years. Current HF requirements are for data transmission at rates 2.4 kbps or more to accommodate computer data links and digital secure voice. HF modems which were produced to meet these speeds are, serial modems and parallel modems. On the other hand, the HF sky-wave communication medium, the ionosphere, has some propagation problems such as multipath and Doppler shift. The effect of Doppler shift in a parallel modem which employs Differential Quadrature Phase Shift Keying (DQPSK) modulation is considered and a correction method to mitigate the Doppler Shift effect is introduced.

  11. Final report on key comparison CCAUV.A-K5: pressure calibration of laboratory standard microphones in the frequency range 2 Hz to 10 kHz

    Science.gov (United States)

    Avison, Janine; Barham, Richard

    2014-01-01

    This document and the accompanying spreadsheets constitute the final report for key comparison CCAUV.A-K5 on the pressure calibration of laboratory standard microphones in the frequency range from 2 Hz to 10 kHz. Twelve national measurement institutes took part in the key comparison and the National Physical Laboratory piloted the project. Two laboratory standard microphones IEC type LS1P were circulated to the participants and results in the form of regular calibration certificates were collected throughout the project. One of the microphones was subsequently deemed to have compromised stability for the purpose of deriving a reference value. Consequently the key comparison reference value (KCRV) has been made based on the weighted mean results for sensitivity level and for sensitivity phase from just one of the microphones. Corresponding degrees of equivalence (DoEs) have also been calculated and are presented. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  12. Continuously adjustable phase shifting circuit from module integration of high frequency induction heating power%高频感应加热电源模数结合连续可调移相电路研究

    Institute of Scientific and Technical Information of China (English)

    王世明; 梅志千; 于海龙; 厉娟

    2012-01-01

    Generally, to reduce switch loss and prevent damage of switch tube, high frequency induction heating equipments are required to work in weak perceptual state, so phase leads or lags circuit adjustment must be introduced in its feedback loops, On one hand, the traditional high frequency analog phase shifting circuit has shortcomings that phase angle moving with input signal frequency changes. On the other hand, high frequency digital phase shifting circuit has difficulty to achieve frequency doubling in high accuracy phase shifting demand . Therefore, two practical high frequency module integration phase shifting circuit are put forward, and they can achieve continuously adjustable phase angle at any desired angle range. In the experiment of photovohaic cells components welding with 1 MHz of high frequency induction, it has a perfect phase shifting effect.%为减小开关损耗和防止开关管损坏,通常要求高频感应加热设备工作在弱感性状态,为此必须在反馈回路进行相位的超前、滞后调节。传统的高频模拟移相电路存在移相角随输入信号频率变化时刻发生变化的缺点,而高频数字移相电路在移相精度要求较高时倍频难以实现。为此,文中提出了两种实用的高频模数结合移相电路实现移相角在任意需要角度范围内连续可调移相。经实验,在光伏电池片组件1MHz高频感应焊接时满足移相要求,移相效果好。

  13. Performance of a Spectrally Encoded Multi-Carrier Phase Shift Keying Communications System in a Frequency-Selective, Slowly-Fading Multipath Channel

    Science.gov (United States)

    2005-03-01

    Wright-Patterson AFB OH, March 2004. AFIT/GE/ENG/04-20. 7. Papoulis, Athanasios and S. Unnikrishna Pillai . Probability, Random Variables, and...Upper Saddle River, New Jersey 07458, 2001. 129 13. Swackhammer, Patrick J. Design and Simulation of a Multiple Access Trans- form Domain Communication

  14. WDM Transmission over 320 km EDFA-Amplified SSMF Using 30 Gb/s Return-to-Zero Optical Differential 8-Level Phase-Shift Keying (OD8PSK).

    Science.gov (United States)

    Kim, Cheolhwan; Goldfarb, Gilad; Han, Yan; Li, Zhihong; Li, Xiaoxu; Li, Guifang

    2005-05-30

    Fiber transmission of optical differential 8-level phase-shift keying (OD8PSK) signals is demonstrated for the first time. Co-polarized 8 WDM channels of 10 Giga-symbol/s or 30 Gb/s return-to-zero (RZ) OD8PSK signals with a channel spacing of 50 GHz were transmitted over 320 km of standard single mode fiber (SSMF) with an EDFA spacing of 80 km. The BER of the worst WDM channel after transmission of 320 km was 2.3x10-5.

  15. Is the Frequency in Somatosensory Electrical Stimulation the Key Parameter in Modulating the Corticospinal Excitability of Healthy Volunteers and Stroke Patients with Spasticity?

    Directory of Open Access Journals (Sweden)

    Marco Antonio Cavalcanti Garcia

    2016-01-01

    Full Text Available Somatosensory electrical stimulation (SES has been proposed as an approach to treat patients with sensory-motor impairment such as spasticity. However, there is still no consensus regarding which would be the adequate SES parameters to treat those deficits. Therefore, the aim of this study was to evaluate the effects of applying SES over the forearm muscles at four different frequencies of stimulation (3, 30, 150, and 300 Hz and in two intervals of time (5′ and 30′ by means of transcranial magnetic stimulation and Hoffmann’s reflex (H-reflex in healthy volunteers (Experiments  I and II. A group of stroke patients (Experiment  III was also preliminary evaluated to ascertain SES effects at a low frequency (3 Hz applied for 30′ over the forearm spastic flexors muscles by measuring the wrist joint passive torque. Motor evoked potentials and the H-reflex were collected from different forearm and hand muscles immediately before and after SES and up to 5′ (Experiment  I and 10′ (Experiments  I and II later. None of the investigated frequencies of SES was able to operate as a key in switching modulatory effects in the central nervous system of healthy volunteers and stroke patients with spasticity.

  16. Is the Frequency in Somatosensory Electrical Stimulation the Key Parameter in Modulating the Corticospinal Excitability of Healthy Volunteers and Stroke Patients with Spasticity?

    Science.gov (United States)

    Garcia, Marco Antonio Cavalcanti; Catunda, João Marcos Yamasaki; de Souza, Marcio Nogueira; Fontana, Ana Paula; Vargas, Claudia D.

    2016-01-01

    Somatosensory electrical stimulation (SES) has been proposed as an approach to treat patients with sensory-motor impairment such as spasticity. However, there is still no consensus regarding which would be the adequate SES parameters to treat those deficits. Therefore, the aim of this study was to evaluate the effects of applying SES over the forearm muscles at four different frequencies of stimulation (3, 30, 150, and 300 Hz) and in two intervals of time (5′ and 30′) by means of transcranial magnetic stimulation and Hoffmann's reflex (H-reflex) in healthy volunteers (Experiments  I and II). A group of stroke patients (Experiment  III) was also preliminary evaluated to ascertain SES effects at a low frequency (3 Hz) applied for 30′ over the forearm spastic flexors muscles by measuring the wrist joint passive torque. Motor evoked potentials and the H-reflex were collected from different forearm and hand muscles immediately before and after SES and up to 5′ (Experiment  I) and 10′ (Experiments  I and II) later. None of the investigated frequencies of SES was able to operate as a key in switching modulatory effects in the central nervous system of healthy volunteers and stroke patients with spasticity. PMID:26881102

  17. Hybrid approaches to magnetic resonance thermometry using the proton resonance frequency shift and the spin-lattice relaxation time T1

    Science.gov (United States)

    Diakite, Mahamadou

    Minimally invasive thermal therapy under Magnetic Resonance Imaging (MRI) guidance is becoming popular with several applications in the process of getting FDA approval. The ability to determine in near real-time the temperature map of a tumor and its surrounding tissue makes MR thermometry very attractive and well suited for thermal treatment. The proton resonance frequency shift (PRF) is currently the gold standard method for temperature monitoring using MRI. However, its incapacity to measure temperature in fatty tissue limits the scope of its applicability. The spin lattice relaxation time T1, on the other hand, has shown good temperature sensitivity and works well in all types of tissues. In this dissertation, we have addressed a number of challenges currently affecting MRI thermometry. A non-CPMG Turbo Spin Echo (TSE) sequence has been implemented to monitor the temperature rise due to the high RF power deposition inherent to this sequence at high field (3T and higher). This new implementation allows TSE sequences to be used safely without altering their high contrast properties which make them appealing in clinical settings. Tissue damage assessment during thermal therapy is critical for the safety of the patient. We have developed a new hybrid PRF-T1 sequence that has the capability to provide simultaneously in near real-time the temperature map and T1 information, which is a good indication of the state of the tissue. The simplicity and the real-time capability of the newly developed sequence make it an ideal tool for tissue damage assessment. Temperature monitoring during thermal therapy in organs with large fat content have been hindered by the lack of an MRI thermometry method that can provide simultaneous temperature in fat and aqueous tissue. A new sequence and acquisition scheme have been developed to address this issue. In sum, this dissertation proposed several pulse sequence implementation techniques and an acquisition scheme to overcome some of

  18. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study

    National Research Council Canada - National Science Library

    Villa, Federica; Magnani, Alessandro; Maggioni, Martina A; Stahn, Alexander; Rampichini, Susanna; Merati, Giampiero; Castiglioni, Paolo

    2016-01-01

    .... However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments...

  19. Faster Estimation and Analysis of Doppler Frequency Shift from Medium Elliptic Orbit Satellites%中椭圆轨道卫星多普勒频移快速估计及分析

    Institute of Scientific and Technical Information of China (English)

    乔文龙; 章坚武; 包建荣; 姜斌

    2016-01-01

    卫星通信中,星地双方高速移动及快速角度变化等因素,将造成较大多普勒频移及频谱扩展等现象,恶化星地通信性能.在Walker星座计算多普勒频移算法的基础上,提出了改进的中椭圆轨道卫星多普勒频移的快速简化计算方法.相对于传统卫星在宇宙空间的三维坐标复杂公式计算方法,所提方法通过长半轴、偏心率等参数直接计算卫星半径,较大降低了计算复杂度.最后,仿真对比和分析高椭圆轨道通信卫星的多普勒频移曲线,较好地解释了中椭圆轨道多普勒频移特性.同时,仿真星地在相对运动情况下的多普勒频移特性,验证了其有效性,以便于实际卫星通信场合快速估计多普勒频移而有效辅助信号接收.%In satellite communications, the high-speed movement, the rapid angle change and some other factors of between the satellites and the ground stations would usually, cause fairly large Doppler frequency shifting, spectrum spreading, and other phenomena, thus deteriorating the satellite-ground communication performance. Based on the Doppler frequency shift algorithm under the Walker constellation a modified calculation method of the Doppler shift in the medium elliptical orbit satellite is proposed. Compared with traditional formula methods needing to know three-dimensional coordinates of the satellites in space, the computational complexity is greatly reduced through directly calculating the radius of the satellite by the semi-major axis of ellipse, eccentricity and other parameters. Finally, simulation comparison and analysis of the Doppler frequency shift curves in high elliptical orbit communication satellites fairly interprets the characteristics of medium elliptical orbit Doppler frequency shift. In addition, simulation on the characteristics of medium elliptical orbit Doppler frequency shift for the relative motion of between satellite and ground station indicates the effectiveness of this

  20. Quantized beam shifts

    CERN Document Server

    Kort-Kamp, W J M; Dalvit, D A R

    2015-01-01

    We predict quantized Imbert-Fedorov, Goos-H\\"anchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant $\\alpha$, while the Goos- H\\"anchen ones in multiples of $\\alpha^2$. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  1. Key Techniques of Frequency Synthesizer for WLAN Receivers%无线局域网接收机用频率综合器的关键技术

    Institute of Scientific and Technical Information of China (English)

    唐路; 王志功; 徐勇; 李智群

    2007-01-01

    对无线局域网接收机用锁相环型频率综合器的几项关键技术进行了研究.首先分析了锁相环型频率综合器的结构并提出了系统的主要参数.采用TSMC 0.18μm射频CMOS工艺设计了一个具有低相位噪声的单片LC调谐型压控振荡器.其在4.189GHz频点上4MHz频偏处所测得的相位噪声为-117dBc/Hz.采用TSMC 0.18μm混合信号CMOS工艺实现了具有低功耗的下变频模块电路.该电路在1.8V电源供电下可正常工作,功耗为13mW.%Several key techniques for a PLL-type frequency synthesizer for WLAN receivers are studied. Its structure is analyzed and the main parameters are proposed. A monolithic LC-tuned voltage controlled oscillator (LCVCO) with low phase noise is fabricated with TSMC 0.18μm RF (radio frequency) CMOS technology. The measured phase noise is - 117dBc/Hz at 4MHz off the center frequency of 4. 189GHz. A down-scaling circuit with low power dissipation was fabricated in a TSMC 0.18μm mixed-signal CMOS process. The measured results show that the IC can work well under a 1.8V power supply. Its total power dissipation is only 13mW.

  2. Generalized minimum shift-keying modulation techniques

    Science.gov (United States)

    Sadr, Ramin; Omura, Jim K.

    1988-01-01

    The simultaneous data demodulation and phase tracking of an MSK signal using the Viterbi algorithm is described and two variations of MSK modulation are studied. The MSK with overlay is a dual rate modulation technique where low-and high-rate data are superimposed on an MSK signal. Here the demodulator uses the Viterbi algorithm to estimate both the low-and high-rate data simultaneously. The MSK with pseudorandom sequence spreading combats intentional or unintentional jamming. A simplified receiver for these spread spectrum MSK signals is found, which takes into consideration the effect of random phase perturbations. The performance of these demodulators is evaluated using transfer function bounds for the bit error probability. It is shown that with a reasonable short overlay period, at a relatively high signal-to-noise ratio (13 dB), there is a small (0.7 dB) loss of performance. For demodulation of the spread spectrum MSK signal, a simplified receiver is derived, and its performance in the presence of continuous jamming is evaluated.

  3. 空间相干光通信中基于DSP的多普勒频移补偿技术%Compensation technology of Doppler frequency shift in space coherent optical communication using DSP

    Institute of Scientific and Technical Information of China (English)

    向劲松; 潘乐春; 张苗苗; 张孝雷

    2011-01-01

    Optical phase-locked loop(OPLL) is often used in space coherent optical communication as the traditional way to achieve the phase synchronous. But the OPLL is affected by the Doppler frequency shift, so in this paper, we use an open-loop compensation technology based on DSP to compensate the Doppler frequency shift, and apply it to a recursive demodulate system, demodulating the next data according to the previous data information. Simulation results show that the open-loop compensation technology based on DSP is able to compensate the Doppler frequency shift, and allow the space coherent optical communication system to demodulate without any optical phase-locked loop, and the performance of the system can approach the ideal status which Doppler frequency shift is completely compensated.%目前通常采用光锁相环(optical phase-locked loop,OPLL)完成空间相干光通信中的相位同步.针对光锁相环性能受空间通信终端间多普勒频移影响的不足,采用基于数字信号处理(digital singnal procesor,DSP)的开环方法补偿多普勒频移,并将开环补偿方法应用于一种递推解调系统中,根据前一时刻的数据信息进行后一时刻的数据解调.仿真结果表明:采用基于DSP的开环补偿方法可以补偿多普勒频移,使空间相干光通信系统不使用光锁相环,且性能接近多普勒频移被完全补偿的理想状态.

  4. Vapor-solvent shift of the lowest frequency vibration of p-benzoquinone and toluquinone and the consequences for the vibrational and electronic spectral assignments

    NARCIS (Netherlands)

    Trommsdorff, H.P.; Zelsmann, H.R.

    1985-01-01

    Far-infrared (20–230 cm–1) absorption spectra of p-benzoquinone-h4,-d4 and of toluquinone have been measured. In the vapor phase, the lowest frequency vibration of these three compounds is found at 88.9, 87.5, and 82.3 cm–1, respectively. In the condensed phase the frequency increases by

  5. Vapor-solvent shift of the lowest frequency vibration of p-benzoquinone and toluquinone and the consequences for the vibrational and electronic spectral assignments

    NARCIS (Netherlands)

    Trommsdorff, H.P.; Zelsmann, H.R.

    1985-01-01

    Far-infrared (20–230 cm–1) absorption spectra of p-benzoquinone-h4,-d4 and of toluquinone have been measured. In the vapor phase, the lowest frequency vibration of these three compounds is found at 88.9, 87.5, and 82.3 cm–1, respectively. In the condensed phase the frequency increases by approximate

  6. Pressure-induced basilar membrane position shifts and the stimulus-evoked potentials in the low-frequency region of the guinea pig cochlea

    NARCIS (Netherlands)

    Fridberger, A; vanMaarseveen, JTPW; Scarfone, E; Ulfendahl, M; Flock, B; Flock, A

    1997-01-01

    We have used the guinea pig isolated temporal bone preparation to investigate changes in the nonlinear properties of the tone-evoked cochlear potentials during reversible step displacements of the basilar membrane towards either the scala tympani or the scala vestibuli. The position shifts were prod

  7. Frequency noise in frequency swept fiber laser

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-01-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto...

  8. Frequency noise in frequency swept fiber laser.

    Science.gov (United States)

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-04-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto- optical modulators and forward propagating Brillouin scattering appear in the spectrum.

  9. Shifting Attention

    Science.gov (United States)

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  10. Shifting Attention

    Science.gov (United States)

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  11. Tough Shift

    DEFF Research Database (Denmark)

    Brewer, Robert S.; Verdezoto, Nervo; Holst, Thomas;

    2015-01-01

    in a student dormitory and found that players did not shift their electricity use, because they were unwilling to change their schedules and found it easier to focus on reducing electricity use. Based on our findings, we discuss the implications for encouraging shifting, and also the challenges of integrating...

  12. Fermi resonance and solvent dependence of the vC=O frequency shifts of Raman spectra: cyclohexanone and 2-cyclohexene-1-one

    CERN Document Server

    Nam, S I; Lee, M S; Jung, Y M

    2001-01-01

    The carbonyl stretching vibration, vC=O of 2-cyclohexene-1-one , is in Fermi resonance with a combination tone. The amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/solvent interaction due to hydrogen bonding between the carbonyl oxygen and the solvent proton. The corrected vC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed vC=O mode of cyclohexanone, possibly caused by expanded conjugation effects. The carbonyl stretching modes of cyclic ketones were also affected by interaction with the ROH/CCl sub 4 mixed solvent system.

  13. 数字移相在原子频标领域中的应用%Application of Digital Phase Shift in the Field of Atomic Frequency Standard

    Institute of Scientific and Technical Information of China (English)

    雷海东

    2012-01-01

    在被动型原子频标中,由于相位延时及系统驰豫时间的影响,给伺服环路的同步鉴相环节带来不便,进而会影响系统的指标。从整机系统中参与同步鉴相的两路低频方波信号出发,通过综合器模块中的DDS的FSK模式来调整两路方波信号的相位,使其满足同步鉴相的要求,并给出了调整后系统稳定度指标改善的实验结果。%The stability of the passive atomic frequency standard can be influenced by the phase delay and system relaxation time.In the servo loop of the synchronization phase discrimination,we can realize the system locked based on the synchronous pulse signal of low frequency.In this paper,the phases of two square waves are adjusted by FSK mode of DDS,in order to satisfy the requirements of synchronous phase discrimination,and the improved experimental results are list out.

  14. Solvent-induced red-shifts for the proton stretch vibrational frequency in a hydrogen-bonded complex. 1. A valence bond-based theoretical approach.

    Science.gov (United States)

    Kiefer, Philip M; Pines, Ehud; Pines, Dina; Hynes, James T

    2014-07-17

    A theory is presented for the proton stretch vibrational frequency νAH for hydrogen (H-) bonded complexes of the acid dissociation type, that is, AH···B ⇔ A(-)···HB(+)(but without complete proton transfer), in both polar and nonpolar solvents, with special attention given to the variation of νAH with the solvent's dielectric constant ε. The theory involves a valence bond (VB) model for the complex's electronic structure, quantization of the complex's proton and H-bond motions, and a solvent coordinate accounting for nonequilibrium solvation. A general prediction is that νAH decreases with increasing ε largely due to increased solvent stabilization of the ionic VB structure A(-)···HB(+) relative to the neutral VB structure AH···B. Theoretical νAH versus 1/ε slope expressions are derived; these differ for polar and nonpolar solvents and allow analysis of the solvent dependence of νAH. The theory predicts that both polar and nonpolar slopes are determined by (i) a structure factor reflecting the complex's size/geometry, (ii) the complex's dipole moment in the ground vibrational state, and (iii) the dipole moment change in the transition, which especially reflects charge transfer and the solution phase proton potential shapes. The experimental proton frequency solvent dependence for several OH···O H-bonded complexes is successfully accounted for and analyzed with the theory.

  15. Analytic Morse/long-range potential energy surfaces and predicted infrared spectra for CO-H2 dimer and frequency shifts of CO in (para-H2)N N = 1-20 clusters

    Science.gov (United States)

    Li, Hui; Zhang, Xiao-Long; Le Roy, Robert J.; Roy, Pierre-Nicholas

    2013-10-01

    A five-dimensional ab initio potential energy surface (PES) for CO-H2 that explicitly incorporates dependence on the stretch coordinate of the CO monomer has been calculated. Analytic four-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for vCO = 0 and 1 to the Morse/long-range potential function form. These fits to 30 206 points have root-mean-square (RMS) deviations of 0.087 and 0.082 cm-1, and require only 196 parameters. The resulting vibrationally averaged PESs provide good representations of the experimental infrared data: for infrared transitions of para H2-CO and ortho H2-CO, the RMS discrepancies are only 0.007 and 0.023 cm-1, which are almost in the same accuracy as those values of 0.010 and 0.018 cm-1 obtained from full six-dimensional ab initio PESs of V12 [P. Jankowski, A. R. W. McKellar, and K. Szalewicz, Science 336, 1147 (2012)]. The calculated infrared band origin shift associated with the fundamental of CO is -0.179 cm-1 for para H2-CO, which is the same value as that extrapolated experimental value, and slightly better than the value of -0.176 cm-1 obtained from V12 PESs. With these potentials, the path integral Monte Carlo algorithm and a first order perturbation theory estimate are used to simulate the CO vibrational band origin frequency shifts of CO in (para H2)N-CO clusters for N = 1-20. The predicted vibrational frequency shifts are in excellent agreement with available experimental observations. Comparisons are also made between these model potentials.

  16. 傅里叶望远镜中激光频移误差对成像质量影响的分析%Effect Analysis of Laser Frequency-Shift Error on Imaging Quality in Fourier Telescope

    Institute of Scientific and Technical Information of China (English)

    孔新新; 黄旻; 张文喜

    2012-01-01

    傅里叶望远镜成像技术,综合了激光主动成像技术、光学合成孔径技术和相位闭合技术是一种新的高分辨率成像探测技术.激光频移的效果是影响傅里叶望远镜成像质量的重要因素,特别是使用大功率、宽光束和宽调制带宽激光的系统.构建了不同的误差模型,推导了频移误差在系统中的传递函数,利用仿真实验分析其对系统成像的影响,得到了对应的误差影响分析.结果表明,频移精度和稳定度严重影响到系统的成像效果,部分情况下含有误差的反演图像与理论反演图像的施特雷尔值已降到0.2,因此合理的设计和选择声光频移器是改善系统成像的一个关键因素.%Fourier telescopy (FT) is a sort of high-resolution imaging technology, which integrates laser initiative imaging technology, optical synthetic aperture technology and phase close technology. The effect of frequency shifting of laser is one of the most important factors to influence imaging quality of the FT system, especially in the situation of high power, broad beam and large modulation bandwidth. Various frequency-shifting error models are proposed, the transfer function of error in system is built, the effect of which on imaging of the system is researched by simulation, error analysis results of the various models are obtained. According to the results, the image quality of the system is directly influenced by the frequency shift accuracy and stability, the value of Strehl between the inverted image with error and the theoretically inverted image is below 0. 2 in some of the models. As indicated, the reasonable design of acousto-optical frequency shifter and the driver circuit is an important way to improve the imaging of the system.

  17. Power Shift

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ "We are entering a new era of world history: the end of Western domination and the arrival of the Asian century. The question is: will Washington wake up to this reality?" This is the central premise of Kishore Mahbubani's provocative new book The New Asian Hemisphere: The Irresistible Shift of Global Power to the East.

  18. The ratio of the kinetic inductance to the geometric inductance: a key parameter for the frequency tuning of the THz semiconductor split-ring resonator.

    Science.gov (United States)

    Cong, Jiawei; Yun, Binfeng; Cui, Yiping

    2013-08-26

    By introducing the frequency tuning sensitivity, an analytical model based on equivalent LC circuit is developed for the relative frequency tuning range of THz semiconductor split-ring resonator (SRR). And the model reveals that the relative tuning range is determined by the ratio of the kinetic inductance to the geometric inductance (RKG). The results show that under the same carrier density variation, a larger RKG results in a larger relative tuning range. Based on this model, a stacked SRR-dimer structure with larger RKG compared to the single SRR due to the inductive coupling is proposed, which improves the relative tuning range effectively. And the results obtained by the simple analytical model agree well with the numerical FDTD results. The presented analytical model is robust and can be used to analyze the relative frequency tuning of other tunable THz devices.

  19. 氢键复合物中键长变化与振动频率移动相关性重访%Correlation between Bond-Length Change and Vibrational Frequency Shift in Hydrogen-Bonded Complexes Revisited

    Institute of Scientific and Technical Information of China (English)

    张愚; 马宁; 王伟周

    2012-01-01

    X—H…Y(Y为电子供体)型氢键形成时,X-H键长伸长或缩短与相应的X-H伸缩振动频率红移或蓝移存在较强的相关性,这也是氢键光谱检测和研究的基础.但是,最近的理论研究却推翻了这一观点,认为X-H键长变化和相应的X-H伸缩振动频率移动在有些氢键体系中并不存在相关性(McDowell,S.A.C.;Buckingham,A.D.J.Am.Chem.Soc.2005,127,15515.).本文中,我们采用更为可信的计算方法,对这一问题进行再研究.结果表明是错误的计算方法导致了McDowell和Buckingham得出错误的结论.在McDowell和Buckingham所研究的氢键体系中,X-H键长变化和相应的X-H伸缩振动频率移动仍存在较强的相关性.%The correlation between the X-H bond-length change and the corresponding X-H stretching frequency shift upon X - H … Y (Y is an electron donor) hydrogen bond formation is the basis for the spectroscopic detection and investigation of the hydrogen bond.However,this view has been questioned in a recent report,suggesting that the widely accepted correlation between the bond-length change and the frequency shift in hydrogen-bonded complexes is unreliable (McDowell,S.A.C.; Buckingham,A.D.J.Am.Chem.Soc.2005,127,15515.).In this work,several robust computational methods have been used to investigate this issue.The results clearly show that a computational artifact leads to the conclusion incorrectly reported by McDowell and Buckingham and that the correlation between the X- H bond-length change and the corresponding X- H stretching frequency shift is still very good in the hydrogen-bonded complexes studied.

  20. Quantized beam shifts in graphene

    Energy Technology Data Exchange (ETDEWEB)

    de Melo Kort-Kamp, Wilton Junior [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sinitsyn, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalvit, Diego Alejandro Roberto [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-08

    We predict the existence of quantized Imbert-Fedorov, Goos-Hanchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant α, while the Goos-Hanchen ones in multiples of α2. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  1. 用李萨如图形变化的快慢测多普勒效应中的频率差(测速)%Measuring frequency shift (speed) in Doppler effect through the variation of Lissajous figures

    Institute of Scientific and Technical Information of China (English)

    周珺; 王婷; 郭鹏

    2013-01-01

    The measurement of frequency shift was difficult in speedometer system based on Doppler effect .The application of Lissajous figures in the system was introduced .The experiment was more practical because a remote controlled toy car was used to simulate real vehicle .%针对当前利用多普勒效应测速实验中的测量频率差难的问题,通过实验发现利用李萨如图形变化的快慢测多普勒效应中的频率差,效果很好。实验中设计了使用遥控赛车模拟现实中的车辆,实验更具现实性。

  2. 基于布里渊载波相移的宽带可调谐二倍频微波信号生成*%Widely tunable frequency-doubling microwaves generated using Brillouin-assisted carrier phase shift

    Institute of Scientific and Technical Information of China (English)

    郑狄; 潘炜; 闫连山; 罗斌; 邹喜华; 刘新开; 易安林

    2014-01-01

    本文提出并实验验证了一种基于光纤中受激布里渊散射效应的光子二倍频微波信号生成技术。利用布里渊增益谱内的强色散特性,对光强度调制器产生的双边带调制信号的载波进行π/2相移,可实现载波与±1阶边带拍频仅生成二倍频微波信号。由于光纤中受激布里渊散射的窄带特性以及仅对双边带调制信号的载波进行相移,不影响调制信号两个边带的幅值和相位,因而生成的二倍频微波信号可实现宽带调谐,调谐范围仅受其他光器件的工作带宽限制。此外,信号光和产生受激布里渊散射的抽运光均来自同一光源,因而不受波长漂移的影响,系统具良好的稳定性。%An optically tunable frequency-doubling microwave generation technique based on stimulated Brillouin scattering (SBS) in optical fibers is proposed and experimentally demonstrated. Due to the strong dispersion characteristics in SBS, when a π/2 phase shift is imposed on the optical carrier of an amplitude-modulated signal by SBS, only a frequency-doubling microwave signal from the beating between the optical carrier and the ±1st sidebands is generated. Due to the inherent narrowband character of SBS and the phase shift being only imported on to the optical carrier while the sidebands are kept unchanged, the frequency-doubling with large frequency tunability is realized, the operational bandwidth is just limited by other optical device deployed. In addition, all the required optical signals and pumps can be generated from the same laser source, the influence from the wavelength drifting is eliminated, so the stability of the system is established.

  3. 罗丹明6G在醇溶液中的荧光频移特性分析%Analysis of Fluorescence Frequency Shift of Rhodamine 6G in Alcohol Solution

    Institute of Scientific and Technical Information of China (English)

    付静; 高洁; 杨雪芹; 马小虎

    2016-01-01

    Rhodamine 6G in methanol, ethanol, ethylene glycol solution are all issue a strong fluorescence. When the concentration of alcohol is 33.3%,there is no frequency shift,when alcohol concentration is 99.7%and fluorescence summit occurs redshift or blueshift.The analysis shows that the frequency shift is composed of Rhodamine 6G and alcohols interactions (such as hydrogen bonding,electrostatic attraction)lead to excited state energy increased and thus fluorescence peak occurs blueshift,and alcohols in the hydroxyl OH solitary on the electron transition leads to lower fluorescence energy,and thus fluorescence peak occurs redshift,and in high concentration alcohol solution,the more the hydroxyl OH,the redshift more obvious.%罗丹明6G在甲醇、乙醇、乙二醇溶液中均发出较强的荧光。当醇溶液浓度为33.3%时,基本不存在频移现象。当醇溶液浓度为99.7%时,荧光峰发生蓝移或红移,分析认为该频移是由罗丹明6G和醇类物质分子相互作用(如氢键、静电吸引)导致激发态能量升高、荧光峰蓝移,与醇类物质分子中羟基OH的孤对电子跃迁导致荧光能量降低、荧光峰红移,这两种因素相互竞争的结果,且在高浓度醇溶液中,羟基OH数量越多,红移越明显。

  4. 基于改进移频变尺度随机共振的齿轮故障诊断%Improved frequency-shifted and re-scaling stochastic resonance for gear fault diagnosis

    Institute of Scientific and Technical Information of China (English)

    谢有浩; 刘晓乐; 刘后广; 程刚; 陈曦晖

    2016-01-01

    With the progress of agricultural technology, agricultural machinery is developing towards the direction of large power, high speed and high efficiency. Due to structural complexity and harsh working conditions, the gear in the agricultural machinery is prone to failure. If the fault cannot be detected accurately, it will result in great economic losses and even much more serious casualties. Yet, the fault feature information is not only weak, but also usually drowned in strong background noise. As a result, it is a challenging project to extract the fault feature information precisely. Different from the traditional de-noising method, the traditional frequency-shifted and re-scaling stochastic resonance method can divert the noise energy to the weak characteristic signal. So it can make the weak characteristic signal increased when the noise was reduced. Then it can precisely realize the aim of detecting the weak characteristic signal which is drowned in strong background noise. Meanwhile, it breaks the limitation of the traditional stochastic resonance due to the frequency-shifted and re-scaling method involved. So, it can be applied under the conditions of large parameters. However, the traditional frequency-shifted and re-scaling stochastic resonance method just does the optimization on the single parameter and neglects the interaction between individual parameter. It cannot sufficiently make full use of the advantages of stochastic resonance in the weak feature signal extraction. So an improved frequency-shifted and re-scaling stochastic resonance method is proposed in this paper. In the proposed method, the signal-noise ratio (SNR) is chosen as the optimization objective, and the improved fish swarm algorithm is used for synchronous optimizationof the frequency-shifted and re-scaling stochastic resonance system parameters. With the progress of the optimization, the precision and speed of the traditional fish swarm algorithm will become lower and lower due to

  5. Frequency shift due to blackbody radiation in a cesium atomic fountain and improvement of the clock performances; Deplacement de frequence du au rayonnement du corps noir dans une fontaine atomique a cesium et amelioration des performances de l'horloge

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S

    2004-07-01

    FO1 was the first caesium fountain primary frequency standard in the world. The most recent evaluation in 2002 before improvement reached an accuracy of 1*10{sup -15} when operated with optical molasses. Working as an extremely precise and stable instrument, FO1 has contributed to fundamental physics and technical measurements: - Frequency comparison between Cs and Rb fountains over an interval of 5 years sets an upper limit for a possible variation of the fine structure constant as |alpha/alpha| < 2*10{sup -15}/y. The resolution is about 5 times better than the previous test in our laboratory. The projected accuracy of the space clock PHARAO is 1*10{sup -16}. We confirmed its Ramsey cavity performance by testing the phase difference between the two interaction zones in FO1. The measured temperature T dependent frequency shift of the Cs clock induced by the blackbody radiation field is given as nu(T)=154(6)*10{sup -6}*(T/300){sup 4}[1+{epsilon}(T/300){sup 2}] Hz with the theoretical value {epsilon} = 0,014. The obtained accuracy represents a 3 times improvement over the previous measurement by the PTB group. Some improvements have been carried out on FO1. The new FO1 version works directly with optical molasses loaded by a laser slowed atomic beam. The application of the adiabatic passage method to perform the state selection allows us to determine the atom number dependent frequency shifts due to the cold collision and cavity pulling effects at a level of of 10{sup -16}. Recently, the obtained frequency stability is 2,8*10{sup -14}*{tau}{sup -1/2} for about 4*10{sup 6} detected atoms. The accuracy is currently under evaluation, the expected value is a few times 10{sup -16}. (author)

  6. A new UK Greenhouse Gas measurement network providing ultra high-frequency measurements of key radiatively active trace gases taken from a network of tall towers

    Science.gov (United States)

    Grant, A.; O'Doherty, S.; Manning, A. J.; Simmonds, P. G.; Derwent, R. G.; Moncrieff, J. B.; Sturges, W. T.

    2012-04-01

    Monitoring of atmospheric concentrations of gases is important in assessing the impact of international policies related to the atmospheric environment. The effects of control measures on greenhouse gases introduced under the Montreal and Kyoto Protocols are now being observed. Continued monitoring is required to assess the overall success of the Protocols. For over 15 years the UK Government have funded high-frequency measurements of greenhouse gases and ozone depleting gases at Mace Head, a global background measurement station on the west coast of Ireland. These continuous, high-frequency, high-precision measurements are used to estimate regional (country-scale) emissions of greenhouse gases across the UK using an inversion methodology (NAME-Inversion) that links the Met Office atmospheric dispersion model (Numerical Atmospheric dispersion Modelling Environment - NAME) with the Mace Head observations. This unique inversion method acts to independently verify bottom up emission estimates of radiatively active and ozone-depleting trace gases. In 2011 the UK government (DECC) funded the establishment and integration of three new tall tower measurements stations in the UK, to provide enhanced resolution emission maps and decrease uncertainty of regional emission estimates produced using the NAME-Inversion. One station included in this new UK network was already established in Scotland and was used in collaboration with Edinburgh University. The two other new stations are in England and were set-up early in 2012, they contain brand new instrumentation for measurements of greenhouse gases. All three additional stations provide ultra high-frequency (1 sec) data of CO2 and CH4 using the Picarro© Cavity Ring Down Spectrometer and high frequency (20 min) measurements of N2O and SF6 from custom built sample modules with GC-ECD. We will present the new tall tower UK measurement network in detail. Using high-frequency measurements at new operational sites, including Mace

  7. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; Liu, J.; Macias, B.; Martin, D. S.; Minkoff, L.; Ploutz-Snyder, R.; Ribeiro, L. C.; Sargsyan, A.; Smith, S. M.

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  8. Methods and apparatuses for self-generating fault-tolerant keys in spread-spectrum systems

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Hussein; Farhang, Behrouz; Subramanian, Vijayarangam

    2015-12-15

    Self-generating fault-tolerant keys for use in spread-spectrum systems are disclosed. At a communication device, beacon signals are received from another communication device and impulse responses are determined from the beacon signals. The impulse responses are circularly shifted to place a largest sample at a predefined position. The impulse responses are converted to a set of frequency responses in a frequency domain. The frequency responses are shuffled with a predetermined shuffle scheme to develop a set of shuffled frequency responses. A set of phase differences is determined as a difference between an angle of the frequency response and an angle of the shuffled frequency response at each element of the corresponding sets. Each phase difference is quantized to develop a set of secret-key quantized phases and a set of spreading codes is developed wherein each spreading code includes a corresponding phase of the set of secret-key quantized phases.

  9. 基于调频率捷变的抗移频干扰 SAR 成像方法%SAR Imaging Method of Shift-Frequency Anti-Jamming Based on Chirp Rate Agility

    Institute of Scientific and Technical Information of China (English)

    蒋思源; 吕幼新

    2015-01-01

    针对固定移频 SAR 干扰,提出一种基于调频率极性捷变的抗干扰处理方法,通过改变发射信号中的调频率,改变信号波形,使干扰机很难使用先前侦获的雷达信号参数来干扰雷达工作。理论分析表明,该方法可以有效抑制固定移频干扰对合成孔径雷达带来的影响。在高干信比的情况下,还可以采用调频率极性捷变与限幅相结合的方法来提高抗干扰性能,该方法在处理流程上仅对距离脉冲压缩进行改变,在成像算法中需要对二维频域使用调频率极性捷变与幅度限制相结合的方法。仿真结果表明,事先在雷达发射信号中改变发射信号的调频率,通过改变信号波形进行抗干扰是能达到抗干扰目的的。%Aiming at fixed-shift-frequency SAR jamming,an anti-jamming processing method based on chirp rate polarity agility has been proposed.Through changing the chirp rate of transmit signal to change signal waveform,the difficulty is increased for jammer using the previous radar signal parameters to interfere the radar.Theoretical analysis shows that the method can restrain the influence of fixed-shift-frequency jamming on synthetic aperture radar effectively.In high jamming-to-signal ratio circumstance,using the method of chirp rate polarity agility and combing with amplitude limitation can improve anti-jamming performance.The meth-od only makes change in range pulse compression and uses an imaging algorithm combing chirp rate polarity agility and amplitude limitation in two-dimensional frequency domain.Simulation result shows that through changing chirp rate of transmit signal to change waveform in advance can achieve the target of anti-jamming.

  10. Spread Spectrum Communication with Chaotic Frequency Modulation

    Science.gov (United States)

    Volkovskii, Alexander R.; Tsimring, Lev S.; Rulkov, Nikolai F.; Langmore, Ian; Young, Stephen C.

    We describe two different approaches to employ chaotic signals in spread-spectrum (SS) communication systems with phase and frequency modulation. In the first one a chaotic signal is used as a carrier. We demonstrate that using a feedback loop controller, the local chaotic oscillator in the receiver can be synchronized to the transmitter. The information can be transmitted using phase or frequency modulation of the chaotic carrier signal. In the second system the chaotic signal is used for frequency modulation of a voltage controlled oscillator (VCO) to provide a SS signal similar to frequency hopping systems. We show that in a certain parameter range the receiver VCO can be synchronized to the transmitter VCO using a relatively simple phase lock loop (PLL) circuit. The same PLL is used for synchronization of the chaotic oscillators. The information signal can be transmitted using a binary phase shift key (BPSK) or frequency shift key (BFSK) modulation of the frequency modulated carrier signal. Using an experimental circuit operating at radio frequency band and a computer modeling we study the bit error rate (BER) performance in a noisy channel as well as multiuser capability of the system.

  11. Islanding Detection for PV Grid-connected System Based on Improved Slip-mode Frequency Shift%基于改进滑模频率偏移法的光伏孤岛检测研究

    Institute of Scientific and Technical Information of China (English)

    肖龙; 杨国华; 鲍丽芳; 智腾飞; 韩世军; 王金梅

    2012-01-01

    孤岛检测是光伏并网系统的必备功能之一,检测性能的优劣直接关系到设备的安全运行,在总结现有孤岛检测方法的基础上,针对传统滑模频率偏移法有检测失败的可能,提出一种改进型算法.首先阐述了改进型滑模频率偏移算法的工作原理,其次进行了改进型滑模频率偏移算法的参数优化和盲区分析,最后在考虑不同负载情形下,利用Matlab/Simulink搭建了5kW光伏并网孤岛检测模型并进行了仿真,结果表明改进型算法不仅能快速准确地检测出孤岛,而且减小了检测盲区.%Islanding detection is one of the essential functions for PV grid-connected system, the advantage and disadvantage of the detection performance directly relate to equipment safety. On the basis of summing up the current detection methods, aiming at the possibility of failure detection of Slip-Mode Frequency Shift (SMS), an improved Slip-Mode Frequency Shift (IM-SMS) algorithm is proposed. At first, the working principle of the IM-SMS algorithm is illustrated, then the parameter of IM-SMS algorithm is optimized and non-detection zone (NDZ) is analyzed. In the end, considering the impacts of different local load on islanding detection, Matlah/Simulink is used for setting up 5kW PV grid-connected system, and simulation study is processed afterward. The experimental results show that the proposed method can not only detect the islanding fast and accurate, but also reduce the NDZ.

  12. Opportunistic Access in Frequency Hopping Cognitive Radio Networks

    Science.gov (United States)

    2014-03-27

    Modulator ib X c(t) s(t) Figure 3.4: Transmitter function model. + s(t) n(t) i(t) X c(t) MFSK Demod îb Figure 3.5: Receiver function model...Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x I. Introduction...thresholding MA multiple access MFSK M-ary frequency shift keying MIMO multiple-input/multiple-output OFDM orthogonal frequency-division multiplexing x

  13. Roller Bearing Health Monitoring Using CPLE Frequency Analysis Method

    Science.gov (United States)

    Jong, Jen-Yi; Jones, Jess H.

    2007-01-01

    This paper describes a unique vibration signature analysis technique Coherence Phase Line Enhancer (CPLE) Frequency Analysis - for roller bearing health monitoring. Defects of roller bearing (e.g. wear, foreign debris, crack in bearing supporting structure, etc.) can cause small bearing characteristic frequency shifts due to minor changes in bearing geometry. Such frequency shifts are often too small to detect by the conventional Power Spectral Density (PSD) due to its frequency bandwidth limitation. This Coherent Phase Line Enhancer technology has been evolving over the last few years and has culminated in the introduction of a new and novel frequency spectrum which is fully described in this paper. This CPLE technology uses a "key phasor" or speed probe as a preprocessor for this analysis. With the aid of this key phasor, this CPLE technology can develop a two dimensional frequency spectrum that preserves both amplitude and phase that is not normally obtained using conventional frequency analysis. This two-dimensional frequency transformation results in several newly defined spectral functions; i. e. CPLE-PSD, CPLE-Coherence and the CPLE-Frequency. This paper uses this CPLE frequency analysis to detect subtle, low level bearing related signals in the High Pressure Fuel Pump (HPFP) of the Space Shuttle Main Engine (SSME). For many rotating machinery applications, a key phasor is an essential measurement that is used in the detection of bearing related signatures. There are times however, when a key phasor is not available; i. e. during flight of any of the SSME turbopumps or on the SSME High Pressure Oxygen Turbopump (HPOTP) where no speed probe is present. In this case, the CPLE analysis approach can still be achieved using a novel Pseudo Key Phasor (PKP) technique to reconstruct a 1/Rev PKP signal directly from external vibration measurements. This paper develops this Pseudo Key Phasor technique and applies it to the SSME vibration data.

  14. Development of high precision digital driver of acoustic-optical frequency shifter for ROG

    Science.gov (United States)

    Zhang, Rong; Kong, Mei; Xu, Yameng

    2016-10-01

    We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.

  15. Generation and extraction of second pitch-shift from cochlear biophysics

    CERN Document Server

    Gomez, Florian

    2013-01-01

    It has been long known that the perceived pitch of a complex harmonic sound changes if the partials of the sound are shifted in frequency by a fixed amount. Rules that this pitch-shift can be expected to follow can be derived from simple nonlinear modeling (first pitch-shift), but clear deviations were observed in corresponding psychoacoustic experiments (second pitch-shift effects). This raises the question of whether these deviations are due to the biophysics of the nonlinear hearing sensor, the cochlea, or are an artifact generated higher up in the auditory pathway. In this article, we explicitly confirm that the second pitch-shift originates in the cochlea, and that the key factors responsible for the phenomenon are combination-tone generation, low-pass filtering and feed-forward coupling in the cochlea. We find, in particular, that the scaling laws of Hopf cochlea combination tones fully explain the psychoacoustical pitch data of G.F. Smoorenburg (1970).

  16. 高频电刀使用安全与质量控制中关键因素的分析%Analysis on key factors of safety in use and quality control for high frequency surgical unit

    Institute of Scientific and Technical Information of China (English)

    徐恒; 田金; 许锋

    2014-01-01

    Objective: To analysis the key factors of quality control for high frequency surgical unit to provide reference to ensure accurate and standard. Methods:To analysis the details of quality control on protective earth impendence, resistor-capacitor network, test error on definition, structure, magnitude and other aspects. Results:To master the key factors of quality control is important for the promotion of operability of the quality control work and decrease the using risk, and then to improve the quality of medical services ensure the safety of patients and medical staff. Conclusion: To analysis the each key factor is important significance to the quality control for high frequency surgical unit.%目的:分析高频电刀质量控制中的各个关键因素,为质量控制工作提供具体参考,以保证质量控制的准确和规范。方法:从保护接地阻抗、阻容网络及测试误差等因素的定义、结构、量值及其他方面分析质量控制细节。结果:掌握高频电刀质量控制中的各个关键因素后,提高其可操作性,有效降低使用风险,提高医疗服务质量,保障患者和使用人员安全。结论:分析各个关键因素,对全面深入地做好高频电刀的质量控制工作具有重要意义。

  17. The Shift Needed for Sustainability

    Science.gov (United States)

    Smith, Peter A. C.; Sharicz, Carol

    2011-01-01

    Purpose: The purpose of this action research is to begin to assess to what extent organizations have in practice begun to make the shift towards triple bottom line (TBL) sustainability. Design/methodology/approach: A definition of TBL sustainability is provided, and key elements of TBL sustainability considered necessary to success are identified…

  18. Recognition of Bread Key Odorants by Using Polymer Coated QCMs

    Science.gov (United States)

    Nakai, Takashi; Kouno, Shinji; Hiruma, Naoya; Shuzo, Masaki; Delaunay, Jean-Jacques; Yamada, Ichiro

    Polyisobutylene (PIB) polymer and methylphenylsiloxane (25%) diphenylsiloxane (75%) copolymer (OV25) were coated on Quartz Crystal Microbalance (QCM) sensors and used in recognition of bread key odorants. Representative compounds of key roasty odorants of bread were taken as 3-acetylpyridine and benzaldehyde, and representative key fatty odorants were hexanal and (E)-2-nonenal. Both OV25- and PIB-coated QCM fabricated sensors could detect concentration as low as 0.9 ppm of 3-acetylpyridine and 1.2 ppm of (E)-2-nonenal. The sensitivity to 3-acetylpyridine of the OV25-coated QCM was about 1000 times higher than that of ethanol, the major interference compound in bread key odorant analysis. Further, the OV25-coated QCM response was 5-6 times and 2-3 times larger than that of the PIB-coated QCM when exposed to roasty odorants and to fatty odorants, respectively. The difference in sensitivity of the OV25- and PIB-coated QCMs we fabricated made possible to discriminate roasty from fatty odorants as was evidenced by the odor recognition map representing the frequency shifts of the OV25-coated QCM against the frequency shift of the PIB-coated QCM. In conclusion, we found that the combination of an OV25-coated QCM and a PIB-coated QCM was successful in discriminating roasty odorants from fatty odorants at the ppm level.

  19. 基于非线性滤波估计的北斗B1 QPSK信号跟踪方法%BeiDou B1 quadrature phase shift keying carrier tracking method based on nonlinear Kalman filter

    Institute of Scientific and Technical Information of China (English)

    李荣冰; 黄隽祎; 刘建业; 谢非

    2014-01-01

    Doppler shift and signal power attenuation in the complex environment both can make damage in the accuracy of carrier tracking. Therefore, the non-linear Kalman filter for carrier tracking is designed, which makes correlated observations in the EKF and UKF model based on the analysis of the structure of BeiDou B1 signal. By using measurements from the estimation of filtering in feedback control of the carrier tracking loop, higher and more stable performance can be given in high dynamic and weak signal environments. Finally, the test results show that the feedback control-based EKF and UKF model can perform precise carrier tracking, and make a good limitation of loop error, both of which lead to realization of high performance of signal tracking.%复杂环境下的多普勒频移变化及信号功率衰减均会对载波准确跟踪造成影响。在研究北斗卫星B1频点信号结构的基础上,建立以环路中相关积分值为观测量的非线性EKF模型和UKF模型,并提出利用滤波估计状态量进行状态反馈控制的方法,从而解决了载波跟踪环路在高动态及弱信号环境中难以高性能工作的问题。实验结果表明,状态反馈控制的EKF模型和UKF滤波模型能准确地跟踪弱信号及高动态下的信号变化,从而有效控制跟踪误差,为实现快速准确的载波跟踪奠定了基础。

  20. Repetition and Translation Shifts

    Directory of Open Access Journals (Sweden)

    Simon Zupan

    2006-06-01

    Full Text Available Repetition manifests itself in different ways and at different levels of the text. The first basic type of repetition involves complete recurrences; in which a particular textual feature repeats in its entirety. The second type involves partial recurrences; in which the second repetition of the same textual feature includes certain modifications to the first occurrence. In the article; repetitive patterns in Edgar Allan Poe’s short story “The Fall of the House of Usher” and its Slovene translation; “Konec Usherjeve hiše”; are compared. The author examines different kinds of repetitive patterns. Repetitions are compared at both the micro- and macrostructural levels. As detailed analyses have shown; considerable microstructural translation shifts occur in certain types of repetitive patterns. Since these are not only occasional; sporadic phenomena; but are of a relatively high frequency; they reduce the translated text’s potential for achieving some of the gothic effects. The macrostructural textual property particularly affected by these shifts is the narrator’s experience as described by the narrative; which suffers a reduction in intensity.

  1. New Iterated Decoding Algorithm Based on Differential Frequency Hopping System

    Institute of Scientific and Technical Information of China (English)

    LIANG Fu-lin; LUO Wei-xiong

    2005-01-01

    A new iterated decoding algorithm is proposed for differential frequency hopping (DFH) encoder concatenated with multi-frequency shift-key (MFSK) modulator. According to the character of the frequency hopping (FH) pattern trellis produced by DFH function, maximum a posteriori (MAP) probability theory is applied to realize the iterate decoding of it. Further, the initial conditions for the new iterate algorithm based on MAP algorithm are modified for better performance. Finally, the simulation result compared with that from traditional algorithms shows good anti-interference performance.

  2. ROBUST MODULATION CLASSIFIER BASED ON CUMULANTS FOR MDPSK WITH FREQUENCY OFFSET

    Institute of Scientific and Technical Information of China (English)

    Han Gang; Li Jiandong; Chen Chen

    2004-01-01

    This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on cumulant. The feature proposed in the algorithm is invariant with respect to constellation scale, rotation, the shift and the carrier frequency offset between transmitter and receiver. The invariant property is proved theoretically. Through computer simulation the performance is evaluated and the results show that the improved classification algorithm is better and valuable in practice.

  3. Depth keying

    Science.gov (United States)

    Gvili, Ronen; Kaplan, Amir; Ofek, Eyal; Yahav, Giora

    2003-05-01

    We present a new solution to the known problem of video keying in a natural environment. We segment foreground objects from background objects using their relative distance from the camera, which makes it possible to do away with the use of color for keying. To do so, we developed and built a novel depth video camera, capable of producing RGB and D signals, where D stands for the distance to each pixel. The new RGBD camera enables the creation of a whole new gallery of effects and applications such as multi-layer background substitutions. This new modality makes the production of real time mixed reality video possible, as well as post-production manipulation of recorded video. We address the problem of color spill -- in which the color of the foreground object is mixed, along its boundary, with the background color. This problem prevents an accurate separation of the foreground object from its background, and it is most visible when compositing the foreground objects to a new background. Most existing techniques are limited to the use of a constant background color. We offer a novel general approach to the problem with enabling the use of the natural background, based upon the D channel generated by the camera.

  4. Compressive Shift Retrieval

    Science.gov (United States)

    Ohlsson, Henrik; Eldar, Yonina C.; Yang, Allen Y.; Sastry, S. Shankar

    2014-08-01

    The classical shift retrieval problem considers two signals in vector form that are related by a shift. The problem is of great importance in many applications and is typically solved by maximizing the cross-correlation between the two signals. Inspired by compressive sensing, in this paper, we seek to estimate the shift directly from compressed signals. We show that under certain conditions, the shift can be recovered using fewer samples and less computation compared to the classical setup. Of particular interest is shift estimation from Fourier coefficients. We show that under rather mild conditions only one Fourier coefficient suffices to recover the true shift.

  5. Modification and Performance Analysis of a Multiple-Symbol-Observation Based MDPSK Demodulator Under Frequency Offset

    Institute of Scientific and Technical Information of China (English)

    LIANGXin; HANGQinglin; XUWenlong

    2004-01-01

    With frequency offset being taken into account, the performance of an existing coherent M-ary differential phase shift keying (MDPSK) demodulator, which bases on multiple symbols observation, is analyzed in this paper. It is revealed that the frequency offset will induce phase offset in proportion to the frequency offset in recovered carrier, and degrade the performance of demodulation. Aiming at this, a simple modified scheme is proposed to compensate for the phase offset; and theoretical performance analysis and simulation are also provided to show good agreement. Both theoretical and simulation results show that the modified scheme is superior to the original one under frequency offset.

  6. Directional Time-frequency Analysis via Continuous Frames

    DEFF Research Database (Denmark)

    Christensen, Ole; Forster, Birgitte; Massopust, Peter

    2015-01-01

    Grafakos and Sansing [‘Gabor frames and directional time–frequency analysis’, Appl. Comput. Harmon. Anal.25 (2008), 47–67] have shown how to obtain directionally sensitive time–frequency decompositions in L2(Rn) based on Gabor systems in L2(R). The key tool is the ‘ridge idea’, which lifts...... spaces. The first step allows us to apply the theory to several other classes of frames, for example wavelet frames and shift-invariant systems, and the second one significantly extends the class of examples and applications. We consider applications to the Meyer wavelet and complex B...

  7. Optical Doppler shift with structured light

    OpenAIRE

    2011-01-01

    When a light beam with a transverse spatially varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler frequency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears associated to the motion of the scatterer in the plane perpendicular to the beam axis. We discuss here how this new effect can be used to enhance the current capabilities of optical measurement system...

  8. Design principles for shift current photovoltaics.

    Science.gov (United States)

    Cook, Ashley M; M Fregoso, Benjamin; de Juan, Fernando; Coh, Sinisa; Moore, Joel E

    2017-01-25

    While the basic principles of conventional solar cells are well understood, little attention has gone towards maximizing the efficiency of photovoltaic devices based on shift currents. By analysing effective models, here we outline simple design principles for the optimization of shift currents for frequencies near the band gap. Our method allows us to express the band edge shift current in terms of a few model parameters and to show it depends explicitly on wavefunctions in addition to standard band structure. We use our approach to identify two classes of shift current photovoltaics, ferroelectric polymer films and single-layer orthorhombic monochalcogenides such as GeS, which display the largest band edge responsivities reported so far. Moreover, exploring the parameter space of the tight-binding models that describe them we find photoresponsivities that can exceed 100 mA W(-1). Our results illustrate the great potential of shift current photovoltaics to compete with conventional solar cells.

  9. Design principles for shift current photovoltaics

    Science.gov (United States)

    Cook, Ashley M.; M. Fregoso, Benjamin; de Juan, Fernando; Coh, Sinisa; Moore, Joel E.

    2017-01-01

    While the basic principles of conventional solar cells are well understood, little attention has gone towards maximizing the efficiency of photovoltaic devices based on shift currents. By analysing effective models, here we outline simple design principles for the optimization of shift currents for frequencies near the band gap. Our method allows us to express the band edge shift current in terms of a few model parameters and to show it depends explicitly on wavefunctions in addition to standard band structure. We use our approach to identify two classes of shift current photovoltaics, ferroelectric polymer films and single-layer orthorhombic monochalcogenides such as GeS, which display the largest band edge responsivities reported so far. Moreover, exploring the parameter space of the tight-binding models that describe them we find photoresponsivities that can exceed 100 mA W-1. Our results illustrate the great potential of shift current photovoltaics to compete with conventional solar cells.

  10. Implementing OpenShift

    CERN Document Server

    Miller, Adam

    2013-01-01

    A standard tutorial-based approach to using OpenShift and deploying custom or pre-built web applications to the OpenShift Online cloud.This book is for software developers and DevOps alike who are interested in learning how to use the OpenShift Platform-as-a-Service for developing and deploying applications, how the environment works on the back end, and how to deploy their very own open source Platform-as-a-Service based on the upstream OpenShift Origin project.

  11. The Keys to the White House

    Science.gov (United States)

    Lichtman, Allan J.

    2012-01-01

    The Keys to the White House is a historically-based system for predicting the result of the popular vote in American presidential elections. The Keys system tracks the big picture of how well the party holding the White House has governed and does not shift with events of the campaign. This model gives specificity to the idea that it is…

  12. OpenShift cookbook

    CERN Document Server

    Gulati, Shekhar

    2014-01-01

    If you are a web application developer who wants to use the OpenShift platform to host your next big idea but are looking for guidance on how to achieve this, then this book is the first step you need to take. This is a very accessible cookbook where no previous knowledge of OpenShift is needed.

  13. Shifting employment revisited

    NARCIS (Netherlands)

    Cremers, Jan; Gramuglia, Alessia

    2014-01-01

    The CLR-network examined in 2006 the phenomenon of undeclared labour, with specific regard to the construction sector. The resulting study, Shifting Employment: undeclared labour in construction (Shifting-study hereafter), gave evidence that this is an area particularly affected by undeclared activi

  14. Making Shifts toward Proficiency

    Science.gov (United States)

    McGatha, Maggie B.; Bay-Williams, Jennifer M.

    2013-01-01

    The Leading for Mathematical Proficiency (LMP) Framework (Bay-Williams et al.) has three components: (1) The Standards for Mathematical Practice; (2) Shifts in classroom practice; and (3) Teaching skills. This article briefly describes each component of the LMP framework and then focuses more in depth on the second component, the shifts in…

  15. Shifted Independent Component Analysis

    DEFF Research Database (Denmark)

    Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai

    2007-01-01

    Delayed mixing is a problem of theoretical interest and practical importance, e.g., in speech processing, bio-medical signal analysis and financial data modelling. Most previous analyses have been based on models with integer shifts, i.e., shifts by a number of samples, and have often been carrie...

  16. Characteristics of Menstrual Cycle in Shift Workers

    Science.gov (United States)

    Attarchi, Mirsaeed; Darkhi, Hamidreza; Kashanian, Maryam; khodarahmian, Mahshad; Dolati, Mandana; Ghaffari, Mostafa; Mirzamohammadi, Elham; Mohammadi, Saber

    2013-01-01

    Background: In this study, the characteristics of menstrual cycle in shift workers employed in the pharmaceutical industry are investigated. Method: This study was conducted in a pharmaceutical industrial complex in Tehran in 2012. 406 female workers in packaging units were studied on the menstrual cycle characteristics. The studied workers were divided into two groups of shift workers and non-shift workers and were compared in terms of the frequency of menstrual disorder (short-term cycle, long-term cycle, irregular cycle and bleeding during menstrual cycle) as well as hormonal values (FSH, LH, TSH, and Prolactin). Results: The odds ratio (OR) for menstrual disorder in the shift workers was 5.54 (95% CI=2.78-11.02) compared to the non-shift workers. The mean difference of hormonal values (except prolactin) between shift workers and non-shift workers was not significant (P> 0.05). Conclusion: This study suggests that shift work may disrupt the menstrual cycle. PMID:23618486

  17. Frequency scanning microstrip antennas

    DEFF Research Database (Denmark)

    Danielsen, Magnus; Jørgensen, Rolf

    1979-01-01

    The principles of using radiating microstrip resonators as elements in a frequency scanning antenna array are described. The resonators are cascade-coupled. This gives a scan of the main lobe due to the phase-shift in the resonator in addition to that created by the transmission line phase...

  18. Influence of frequency offset on the reception of OFDM/QPSK signal using MBDD algorithm

    Directory of Open Access Journals (Sweden)

    N. Milošević

    2011-11-01

    Full Text Available In this paper we present the basic characteristics of Orthogonal Frequency Division Multiplex (OFDM systems with quadrature phase shift keying (QPSK modulation and multi-bit differential detection (MBDD. In the simulation environment designed for this purpose, we analyze the effects of frequency offset on the performances of OFDM digital communications. We also analyze the influence of OFDM system parameters on system performances for various values of frequency offset, number of bits for multi-bit detection and the number of subcarriers. We have shown the advantages and disadvantages of using MBDD in the OFDM systems.

  19. Shifted Non-negative Matrix Factorization

    DEFF Research Database (Denmark)

    Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai

    2007-01-01

    where a shift in onset of frequency profile can be induced by the Doppler effect. However, the model is also relevant for biomedical data analysis where the sources are given by compound intensities over time and the onset of the profiles have different delays to the sensors. A simple algorithm based...

  20. Atomic clocks with suppressed blackbody radiation shift

    CERN Document Server

    Yudin, V I; Okhapkin, M V; Bagayev, S N; Tamm, Chr; Peik, E; Huntemann, N; Mehlstaubler, T E; Riehle, F

    2011-01-01

    We develop a nonstandard concept of atomic clocks where the blackbody radiation shift (BBRS) and its temperature fluctuations can be dramatically suppressed (by one to three orders of magnitude) independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies $\

  1. 防爆变频器在煤矿应用中的关键技术%Key Technologies of Explosion-proof Frequency Converter Applied in Coal Mine

    Institute of Scientific and Technical Information of China (English)

    祝龙记; 张旭立

    2012-01-01

    分析了防爆变频器在煤矿井下使用过程中存在的电压等级、散热、电磁兼容性、逆变器转换效率等问题,详细介绍了解决这些问题的方法,即通过采用隔爆兼本质安全型技术和热管散热技术解决变频器的防爆和散热问题,使防爆变频器具有性能高、功能强、噪音低等特点;通过改变变频器的电路拓扑结构、改进控制策略等技术手段解决变频器的电磁兼容性和能耗问题,使防爆变频器满足煤矿生产的现代化要求.%The paper analyzed problems of voltage level, heat dissipation, EMC and conversion efficiency of inverter existed in using process of explosion-proof frequency converter in coal mine underground, and introduced methods of solving these problems in details, namely using technologies of flameproof and intrinsic safety and heat dissipation with heat pipes to solve problems of explosion-proof and heat dissipation of frequency converter, which can make explosion-proof frequency converter has characteristics of high performance, strong functions and low noise; using technical means of changing circuit topology and improving control strategy of frequency converter to solve problems of EMC and energy consumption of frequency converter, which can make explosion-proof frequency converter meet with requirements of modernization of coal mine production.

  2. Using LEADS to shift to high performance.

    Science.gov (United States)

    Fenwick, Shauna; Hagge, Erna

    2016-03-01

    Health systems across Canada are tasked to measure results of all their strategic initiatives. Included in most strategic plans is leadership development. How to measure leadership effectiveness in relation to organizational objectives is key in determining organizational effectiveness. The following findings offer considerations for a 21(st)-century approach to shifting to high-performance systems.

  3. Shift Verification and Validation

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Tara M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Evans, Thomas M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Gregory G [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Seth R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Godfrey, Andrew T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-07

    This documentation outlines the verification and validation of Shift for the Consortium for Advanced Simulation of Light Water Reactors (CASL). Five main types of problems were used for validation: small criticality benchmark problems; full-core reactor benchmarks for light water reactors; fixed-source coupled neutron-photon dosimetry benchmarks; depletion/burnup benchmarks; and full-core reactor performance benchmarks. We compared Shift results to measured data and other simulated Monte Carlo radiation transport code results, and found very good agreement in a variety of comparison measures. These include prediction of critical eigenvalue, radial and axial pin power distributions, rod worth, leakage spectra, and nuclide inventories over a burn cycle. Based on this validation of Shift, we are confident in Shift to provide reference results for CASL benchmarking.

  4. Shift Verification and Validation

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Tara M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Evans, Thomas M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Gregory G [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Seth R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Godfrey, Andrew T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-07

    This documentation outlines the verification and validation of Shift for the Consortium for Advanced Simulation of LightWater Reactors (CASL). Fivemain types of problems were used for validation: small criticality benchmark problems; full-core reactor benchmarks for light water reactors; fixed source coupled neutron-photon dosimetry benchmarks; depletion/burnup benchmarks; and full-core reactor performance benchmarks. We compared Shift results to measured data and other simulated Monte Carlo radiation transport code results and found very good agreement in a variety of comparison measures. These include prediction of critical eigenvalue, radial and axial pin power distributions, rod worth, leakage spectra, and nuclide inventories over a burn cycle. Based on this validation of Shift, we are confident in Shift to provide reference results for CASL benchmarking.

  5. Progress of the NTSC-F1 primary frequency standard

    Institute of Scientific and Technical Information of China (English)

    RUAN; Jun; WANG; Xinliang; LIU; Dandan; GUAN; Yong; ZHANG; Hui; CHEN; Jiang; LIN; Rui; YU; Fengxiang; SHI; Junru; ZHANG; Shougang

    2015-01-01

    The SI "second"is realized by caesium primary frequency standards( PFSs) using laser cooled atoms in a fountain configuration. Four sub systems and operation procedure of the NTSC-F1 primary frequency standard are introduced in the paper.The frequency stability of NTSC-F1 is 3.0×10-13/ τ-1 / 2compared to hydrogen maser. Four terms of frequency shift and uncertainty including second order Zeeman frequency shift,cold collision shift,gravity shift and blackbody shift are evaluated. The improvement of NTSC-F1 is introduced.

  6. A paradigm shift in patterning foundation from frequency multiplication to edge-placement accuracy: a novel processing solution by selective etching and alternating-material self-aligned multiple patterning

    Science.gov (United States)

    Han, Ting; Liu, Hongyi; Chen, Yijian

    2016-03-01

    Overlay errors, cut/block and line/space critical-dimension (CD) variations are the major sources of the edge-placement errors (EPE) in the cut/block patterning processes of complementary lithography when IC technology is scaled down to sub-10nm half pitch (HP). In this paper, we propose and discuss a modular technology to reduce the EPE effect by combining selective etching and alternating-material (dual-material) self-aligned multiple patterning (altSAMP) processes. Preliminary results of altSAMP process development and material screening experiment are reported and possible material candidates are suggested. A geometrical cut-process yield model considering the joint effect of overlay errors, cut-hole and line CD variations is developed to analyze its patterning performance. In addition to the contributions from the above three process variations, the impacts of key control parameters (such as cut-hole overhang and etching selectivity) on the patterning yield are examined. It is shown that the optimized altSAMP patterning process significantly improves the patterning yield compared with conventional SAMP processes, especially when the half pitch of device patterns is driven down to 7 nm and below.

  7. Research on Dynamic Performance of Power Shift Clutch

    Directory of Open Access Journals (Sweden)

    Wang Li

    2016-01-01

    Full Text Available Smooth shift and low shift shock are needed to improve power shift quality and comfort of construction vehicle. And higher dynamic performance of power shift clutch is needed. In this paper, the dynamic mathematical model and simulation model of the clutch engagement process were established, the factors affecting the shift quality were analyzed qualitatively and quantitatively. The simulation model of the transmission system was established based on the software AMESim, the corresponding vehicle tests were performed, and the shifting quality was improved by changing key parameters. Analysis results illustrate that the proposed mathematical model and simulation model are correct and effective and can be used to predict and evaluate construction vehicle shift-feel, which are the theoretical basis for analysis and research on the static and dynamic characteristics of the dynamic shifting process in the future.

  8. Expert system application for prioritizing preventive actions for shift work: shift expert.

    Science.gov (United States)

    Esen, Hatice; Hatipoğlu, Tuğçen; Cihan, Ahmet; Fiğlali, Nilgün

    2017-09-19

    Shift patterns, work hours, work arrangements and worker motivations have increasingly become key factors for job performance. The main objective of this article is to design an expert system that identifies the negative effects of shift work and prioritizes mitigation efforts according to their importance in preventing these negative effects. The proposed expert system will be referred to as the shift expert. A thorough literature review is conducted to determine the effects of shift work on workers. Our work indicates that shift work is linked to demographic variables, sleepiness and fatigue, health and well-being, and social and domestic conditions. These parameters constitute the sections of a questionnaire designed to focus on 26 important issues related to shift work. The shift expert is then constructed to provide prevention advice at the individual and organizational levels, and it prioritizes this advice using a fuzzy analytic hierarchy process model, which considers comparison matrices provided by users during the prioritization process. An empirical study of 61 workers working on three rotating shifts is performed. After administering the questionnaires, the collected data are analyzed statistically, and then the shift expert produces individual and organizational recommendations for these workers.

  9. Influences on Dietary Choices during Day versus Night Shift in Shift Workers: A Mixed Methods Study

    Directory of Open Access Journals (Sweden)

    Emily K. Bonnell

    2017-02-01

    Full Text Available Shift work is associated with diet-related chronic conditions such as obesity and cardiovascular disease. This study aimed to explore factors influencing food choice and dietary intake in shift workers. A fixed mixed method study design was undertaken on a convenience sample of firefighters who continually work a rotating roster. Six focus groups (n = 41 were conducted to establish factors affecting dietary intake whilst at work. Dietary intake was assessed using repeated 24 h dietary recalls (n = 19. Interviews were audio recorded, transcribed verbatim, and interpreted using thematic analysis. Dietary data were entered into FoodWorks and analysed using Wilcoxon signed-rank test; p < 0.05 was considered significant. Thematic analysis highlighted four key themes influencing dietary intake: shift schedule; attitudes and decisions of co-workers; time and accessibility; and knowledge of the relationship between food and health. Participants reported consuming more discretionary foods and limited availability of healthy food choices on night shift. Energy intakes (kJ/day did not differ between days that included a day or night shift but greater energy density (EDenergy, kJ/g/day of the diet was observed on night shift compared with day shift. This study has identified a number of dietary-specific shift-related factors that may contribute to an increase in unhealthy behaviours in a shift-working population. Given the increased risk of developing chronic diseases, organisational change to support workers in this environment is warranted.

  10. Protein Chemical Shift Prediction

    CERN Document Server

    Larsen, Anders S

    2014-01-01

    The protein chemical shifts holds a large amount of information about the 3-dimensional structure of the protein. A number of chemical shift predictors based on the relationship between structures resolved with X-ray crystallography and the corresponding experimental chemical shifts have been developed. These empirical predictors are very accurate on X-ray structures but tends to be insensitive to small structural changes. To overcome this limitation it has been suggested to make chemical shift predictors based on quantum mechanical(QM) calculations. In this thesis the development of the QM derived chemical shift predictor Procs14 is presented. Procs14 is based on 2.35 million density functional theory(DFT) calculations on tripeptides and contains corrections for hydrogen bonding, ring current and the effect of the previous and following residue. Procs14 is capable at performing predictions for the 13CA, 13CB, 13CO, 15NH, 1HN and 1HA backbone atoms. In order to benchmark Procs14, a number of QM NMR calculatio...

  11. Peakfitter — an integrated Excel-based Visual Basic program for processing multiple skewed and shifting Gaussian-like spectral peaks simultaneously: application to radio frequency glow discharge ion trap mass spectrometry

    Science.gov (United States)

    Eanes, Ritchie C.; Marcus, R. Kenneth

    2000-04-01

    This article is an electronic publication in Spectrochimica Acta Electronica (SAE), a section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by an electronic archive, stored on the SAE homepage at (http://www.elsevier.nl/locate/sabe). The archive contains program and data files. The main article discusses the scientific spectroscopic and instrumental aspects of the subject and explains the purpose of the program and data files. The work deals with a Microsoft Excel Visual Basic program, Peakfitter, which can process multiple Gaussian-shaped spectral peaks quickly and easily. The program employs Microsoft Excel Solver to process any Gaussian-like spectra that can be opened in Microsoft Excel 97. Up to three peaks in one to 225 spectra, each containing up to 2000 data points can be processed per data file to give background corrected peak areas for both raw data and its associated fit data as calculated by the trapezoidal method or by simple successive addition of channel intensities across each peak. Concurrently output also includes fit peak heights for Gaussian-shaped spectral peaks. Use of other statistical distributions such as the Lorentzian model requires only slight modification to a template file. Hence, Peakfitter was actually written as two application programs, 'Gaussfitter' and 'Lorenfitter' to accommodate spectra of Gaussian or Lorentzian character, respectively. Written initially to process data from a radio frequency glow discharge ion trap mass spectrometer (rf-GD/ITMS), the program is useful for processing sequentially acquired spectra, which have a limited number of data points across each peak. The user may examine and manipulate program variables in cases where the raw data is skewed with respect to the fit data. An assessment of Peakfitter is given using rf-GD/ITMS elemental analysis and ion-molecule reaction data. Peakfitter's (i.e. 'Gaussfitter's) utility in processing rf-GD/ITMS spectra is characterized by a slight

  12. SELECTION OF BRILLOUIN SHIFT DISCRIMINATOR FOR BRILLOUIN LIDAR

    Institute of Scientific and Technical Information of China (English)

    吴东; 刘智深

    2002-01-01

    For the measurement of vertical profiles of sound speed in the sea using laser excited Brillouin scattering, a high-resolution measurement of Brillouin frequency shift is required. In this work, a molecular absorption cell was selected as the frequency shift discriminator and several kinds of absorption gases were tried. It was found that the strong line ( # 1095) of 127 I2 at 18783. 3297 cm-1 and two absorption lines of 129 I2 located at the two sides of the # 1095 line of 127 I2 could be used as frequency shift discriminator to detect the changes of the Brillouin frequency shift. This selection is the best one within the range from 532.0131 run to 532.5154 nm. But it is not perfect and there is a lot of work to do before its practical application.

  13. Core shifts in blazar jets

    CERN Document Server

    Zdziarski, Andrzej A; Pjanka, Patryk; Tchekhovskoy, Alexander

    2014-01-01

    We study the effect of core shift in jets, which is the dependence of the position of the jet radio core on the frequency. We derive a new method to measure the jet magnetic field based on both the value of the shift and the observed flux, which compliments the standard method assuming equipartition. Using both methods, we re-analyse the blazar sample of Zamaninasab et al. We find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, $\\simeq$0.1--0.2 divided by the bulk Lorentz factor, $\\Gamma_{\\rm j}$. Larger values, e.g., $1/\\Gamma_{\\rm j}$, would imply very strong departures from equipartition. A small jet opening angle implies in turn the magnetization parameter of $\\ll 1$. We determine the jet magnetic flux taking this effect into account. We find that the average jet magnetic flux is compatible with the model of jet formation due to black-hole spin energy extraction and accretion being magnetically arrested. We calculate the ...

  14. 基于FPGA的卫星数字频率信号处理关键技术研究与实现%Research and implementation of key technologies about satellite digital frequency signal processing based on FPGA

    Institute of Scientific and Technical Information of China (English)

    罗来金; 曾连荪

    2011-01-01

    This paper introduced how to use ALTERA Cyclone II series FPGA EP2C70F896C6N with equal precision frequency measurement method and corresponding digital signal processing IP core,and then completed design of the measurements and processing system about three directions angular velocity and temperature signals of a certain type satellite's Gyro X,Y,Z axis.Experimental results show that the FPGA-based digital frequency signal processing system has a high accuracy,high integration,high-speed and high reliability features compared with the previous digital frequency signal processing circuit,meets the signal processing circuit design for high standards in space systems.%采用等精度测频法及相应的数字信号处理IP核,以ALTERA公司Cyclone II系列EP2C70F896C6N FPGA为核心实现了某型卫星陀螺组合X、Y、Z轴3个方向上的角速度信号、温度信号的测量处理系统的设计。实验结果表明基于FPGA的数字频率信号处理系统相对于以往数字频率信号处理电路具有高精度、高集成度、高速和高可靠性的特点,满足航天系统对信号处理电路设计高标准的要求。

  15. Optical Doppler shift with structured light.

    Science.gov (United States)

    Belmonte, Aniceto; Torres, Juan P

    2011-11-15

    When a light beam with a transverse spatially varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler frequency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears associated to the motion of the scatterer in the plane perpendicular to the beam axis. We discuss here how this new effect can be used to enhance the current capabilities of optical measurement systems, adding the capacity to detect more complex movements of scatters.

  16. Shift Work Disorder and Mental and Physical Effects of Shift Work

    Directory of Open Access Journals (Sweden)

    Pinar Guzel Ozdemir

    2018-03-01

    Full Text Available With the growing prevalence of shift work all over the the world, the relationship between the daily lives of irregular lifestyles and rhythms is being investigated for those working as shift workers and their families. The effect of shift work on physical and mental health is a very important field of research in recent years. The onset and persistence of medical complications in shift workers includes impaired synchronization between work schedule rhythms and circadian clock. In this context, studies have been carried out showing the increased risk of sleep-wake disorders, gastrointestinal problems, and cardiovascular diseases. There is little information about the actual frequency, effect on health and treatment of shift work disorder, known as circadian rhythm sleep disorder. Shift work disorder includes insomnia and/or excessive sleepiness related with the work schedule. The aim of this rewiev, mentioning about the physical and mental effects of shift work, and to provide information about the diagnosis, clinic and treatment methods of shift-work disorder.

  17. A Shift of Power

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Administrative reforms are shifting prefecture government powers to the county level in an effort to boost local economies on July 8, the government of China’s southernmost Hainan Province announced that it was to hand over 177 of its administrative powers to county-level governments. The move practically dismantled the powers of the

  18. Metrology on phase-shift masks

    Science.gov (United States)

    Roeth, Klaus-Dieter; Maurer, Wilhelm; Blaesing-Bangert, Carola

    1992-06-01

    In the evaluation of new manufacturing processes, metrology is a key function, beginning with the first step of process development through the final step of everyday mass production at the fabrication floor level. RIM-type phase shift masks are expected to be the first application of phase shift masks in high volume production, since they provide improved lithography process capability at the expense of only moderate complexity in their manufacturing. Measurements of critical dimension (CD) and pattern position (overlay) on experimental rim-type and chromeless phase shift masks are reported. Pattern placement (registration) was measured using the Leitz LMS 2000. The overall design and important components were already described. The pattern placement of the RIM type phase shift structures on the photomask described above was determined within a tolerance of 25 nm (3s); nominal accuracy was within 45 nm (3s). On the chromeless phase shift mask the measurement results were easily obtained using a wafer intensity algorithm available with the system. The measurement uncertainties were less than 25 nm and 50 nm for precision and nominal accuracy respectively. The measurement results from the Leitz CD 200 using transmitted light were: a CD- distribution of 135 nm (3s) on a typical 6 micrometers structure all over the mask; the 0.9 micrometers RIM structure had a distribution of 43 nm (3s). Typical long term precision performance values for the CD 200 on both chrome and phase shift structures have been less than 15 nm.

  19. Core shift effect in blazars

    Science.gov (United States)

    Agarwal, A.; Mohan, P.; Gupta, Alok C.; Mangalam, A.; Volvach, A. E.; Aller, M. F.; Aller, H. D.; Gu, M. F.; Lähteenmäki, A.; Tornikoski, M.; Volvach, L. N.

    2017-07-01

    We studied the pc-scale core shift effect using radio light curves for three blazars, S5 0716+714, 3C 279 and BL Lacertae, which were monitored at five frequencies (ν) between 4.8 and 36.8 GHz using the University of Michigan Radio Astronomical Observatory (UMRAO), the Crimean Astrophysical Observatory (CrAO) and Metsähovi Radio Observatory for over 40 yr. Flares were Gaussian fitted to derive time delays between observed frequencies for each flare (Δt), peak amplitude (A) and their half width. Using A ∝ να, we infer α in the range of -16.67-2.41 and using Δ t ∝ ν ^{1/k_r}, we infer kr ∼ 1, employed in the context of equipartition between magnetic and kinetic energy density for parameter estimation. From the estimated core position offset (Ωrν) and the core radius (rcore), we infer that opacity model may not be valid in all cases. The mean magnetic field strengths at 1 pc (B1) and at the core (Bcore) are in agreement with previous estimates. We apply the magnetically arrested disc model to estimate black hole spins in the range of 0.15-0.9 for these blazars, indicating that the model is consistent with expected accretion mode in such sources. The power-law-shaped power spectral density has slopes -1.3 to -2.3 and is interpreted in terms of multiple shocks or magnetic instabilities.

  20. Phase Analysis for Frequency Standards in the Microwave and Optical Domains

    CERN Document Server

    Kazda, M; Huntemann, N; Lipphardt, B; Weyers, S

    2015-01-01

    Coherent manipulation of atomic states is a key concept in high-precision spectroscopy and used in atomic fountain clocks and a number of optical frequency standards. Operation of these standards can involve a number of cyclic switching processes, which may induce cycle synchronous phase excursions of the interrogation signal and thus lead to shifts in the output of the frequency standard. We have built a FPGA-based phase analyzer to investigate these effects and conducted measurements on two frequency standards. For the caesium fountain PTB-CSF2 we were able to exclude phase variations of the microwave source at the level of a few $\\mu$rad, corresponding to relative frequency shifts of less than 10$^{-16}$. In the optical domain, we investigated phase variations in PTB's Yb$^+$ optical frequency standard and made detailed measurements of AOM chirps and their scaling with duty cycle and driving power. We ascertained that cycle-synchronous as well as long-term phase excursion do not cause frequency shifts larg...

  1. Phase Analysis for Frequency Standards in the Microwave and Optical Domains.

    Science.gov (United States)

    Kazda, Michael; Gerginov, Vladislav; Huntemann, Nils; Lipphardt, Burghard; Weyers, Stefan

    2016-07-01

    Coherent manipulation of atomic states is a key concept in high-precision spectroscopy and used in atomic fountain clocks and a number of optical frequency standards. Operation of these standards can involve a number of cyclic switching processes, which may induce cycle-synchronous phase excursions of the interrogation signal and thus lead to shifts in the output of the frequency standard. We have built a field-programmable gate array (FPGA)-based phase analyzer to investigate these effects and conducted measurements on two kinds of frequency standards. For the caesium fountains PTB-CSF1 and PTB-CSF2, we were able to exclude phase variations of the microwave source at the level of a few microradians, corresponding to relative frequency shifts of less than [Formula: see text]. In the optical domain, we investigated phase variations in PTB's Yb (+) optical frequency standard and made detailed measurements of acousto-optic modulator (AOM) chirps and their scaling with duty cycle and driving power. We ascertained that cycle-synchronous as well as long-term phase excursion do not cause frequency shifts larger than [Formula: see text].

  2. The LOFAR Transients Key Science Project

    NARCIS (Netherlands)

    Stappers, B.; Fender, R.; Wijers, R.

    2009-01-01

    The Transients Key Science Project (TKP) is one of six Key Science Projects of the next generation radio telescope LOFAR. Its aim is the study of transient and variable low-frequency radio sources with an extremely broad science case ranging from relativistic jet sources to pulsars, exoplanets,

  3. On the Lamb shift

    Energy Technology Data Exchange (ETDEWEB)

    Villarroel, D. [Av. Tobalaba 3696, Puente Alto, Santiago, Metropolitana (Chile)

    2008-02-15

    The Lamb shift is calculated, in an approximate way, considering the hydrogen atom as an isolated physical system; the quantized radiation field does not play any role in the present approach. Our formalism is based on the generalization of the Dirac wave equation that incorporates the effects of the electron self-fields directly into it. Both the physical picture as well as the mathematical formalism have their roots in the classical theory of the electron. (author)

  4. Collisionally induced atomic clock shifts and correlations

    Energy Technology Data Exchange (ETDEWEB)

    Band, Y. B.; Osherov, I. [Departments of Chemistry and Electro-Optics and the Ilse Katz Center for Nano-Science, Ben-Gurion University, Beer-Sheva 84105 (Israel)

    2011-07-15

    We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

  5. Frequency scaling for angle gathers

    KAUST Repository

    Zuberi, M. A H

    2014-01-01

    Angle gathers provide an extra dimension to analyze the velocity after migration. Space-shift and time shift-imaging conditions are two methods used to obtain angle gathers, but both are reasonably expensive. By scaling the time-lag axis of the time-shifted images, the computational cost of the time shift imaging condition can be considerably reduced. In imaging and more so Full waveform inversion, frequencydomain Helmholtz solvers are used more often to solve for the wavefields than conventional time domain extrapolators. In such cases, we do not need to extend the image, instead we scale the frequency axis of the frequency domain image to obtain the angle gathers more efficiently. Application on synthetic data demonstrate such features.

  6. The cooperative Lamb shift in an atomic nanolayer

    CERN Document Server

    Keaveney, James; Krohn, Ulrich; Hughes, Ifan G; Sarkisyan, David; Adams, Charles S

    2012-01-01

    We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using an atomic nanolayer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift which has a spatial frequency equal to $2k$, i.e. twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for non-linear optics.

  7. Molecular profiling of gene copy number abnormalities in key regulatory genes in high-risk B-lineage acute lymphoblastic leukemia: frequency and their association with clinicopathological findings in Indian patients.

    Science.gov (United States)

    Bhandari, Prerana; Ahmad, Firoz; Das, Bibhu Ranjan

    2017-05-01

    Genes related to key cellular pathways are frequently altered in B cell ALL and are associated with poor survival especially in high-risk (HR) subgroups. We examined gene copy number abnormalities (CNA) in 101 Indian HR B cell ALL patients and their correlation with clinicopathological features by multiplex ligation-dependent probe amplification. Overall, CNA were detected in 59 (59%) cases, with 26, 10 and 23% of cases harboring 1, 2 or +3 CNA. CNA were more prevalent in BCR-ABL1 (60%), pediatric (64%) and high WCC (WBC count) (63%) patients. Frequent genes deletions included CDNK2A/B (26%), IKZF1 (25%), PAX5 (14%), JAK2 (7%), BTG1 (6%), RB1 (5%), EBF1 (4%), ETV6 (4%), while PAR1 region genes were predominantly duplicated (20%). EBF1 deletions selectively associated with adults, IKZF1 deletions occurred frequently in high WCC and BCR-ABL1 cases, while PAR1 region gains significantly associated with MLL-AF4 cases. IKZF1 haploinsufficiency group was predominant, especially in adults (65%), high WCC (60%) patients and BCR-ABL1-negative (78%) patients. Most cases harbored multiple concurrent CNA, with IKZF1 concomitantly occurring with CDNK2A/B, PAX5 and BTG1, while JAK2 occurred with CDNK2A/B and PAX5. Mutually exclusive CNA included ETV6 and IKZF1/RB1, and EBF1 and JAK2. Our results corroborate with global reports, aggregating molecular markers in Indian HR B-ALL cases. Integration of CNA data from rapid methods like MLPA, onto background of existing gold-standard methods detecting significant chromosomal abnormalities, provides a comprehensive genetic profile in B-ALL.

  8. Quantum key management

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  9. Quantum key management

    Science.gov (United States)

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  10. Increased diversification rates follow shifts to bisexuality in liverworts

    DEFF Research Database (Denmark)

    Laenen, Benjamin; Machac, Antonin; Gradstein, S. Robbert

    2016-01-01

    Shifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts. We investigate whether...

  11. Group key management

    Energy Technology Data Exchange (ETDEWEB)

    Dunigan, T.; Cao, C.

    1997-08-01

    This report describes an architecture and implementation for doing group key management over a data communications network. The architecture describes a protocol for establishing a shared encryption key among an authenticated and authorized collection of network entities. Group access requires one or more authorization certificates. The implementation includes a simple public key and certificate infrastructure. Multicast is used for some of the key management messages. An application programming interface multiplexes key management and user application messages. An implementation using the new IP security protocols is postulated. The architecture is compared with other group key management proposals, and the performance and the limitations of the implementation are described.

  12. The shifting beverage landscape.

    Science.gov (United States)

    Storey, Maureen

    2010-04-26

    STOREY, M.L. The shifting beverage landscape. PHYSIOL BEHAV, 2010. - Simultaneous lifestyle changes have occurred in the last few decades, creating an imbalance in energy intake and energy expenditure that has led to overweight and obesity. Trends in the food supply show that total daily calories available per capita increased 28% since 1970. Total energy intake among men and women has also increased dramatically since that time. Some have suggested that intake of beverages has had a disproportional impact on obesity. Data collected by the Beverage Marketing Corporation between 1988-2008 demonstrate that, in reality, fewer calories per ounce are being produced by the beverage industry. Moreover, data from the National Cancer Institute show that soft drink intake represents 5.5% of daily calories. Data from NHANES 1999-2003 vs. 2003-06 may demonstrate a shift in beverage consumption for age/gender groups, ages 6 to>60years. The beverages provided in schools have significantly changed since 2006 when the beverage industry implemented School Beverage Guidelines. This voluntary action has removed full-calorie soft drinks from participating schools across the country. This shift to lower-calorie and smaller-portion beverages in school has led to a significant decrease in total beverage calories in schools. These data support the concept that to prevent and treat obesity, public health efforts should focus on energy balance and that a narrow focus on sweetened beverages is unlikely to have any meaningful impact on this complex problem. Copyright 2010 Elsevier Inc. All rights reserved.

  13. A computational investigation of the red and blue shifts in hydrogen bonded systems

    Indian Academy of Sciences (India)

    MITRADIP DAS; SWAPAN K GHOSH

    2017-07-01

    The presentwork reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters are proposed, thereby generating new insight into both types of the frequency shifts. Thus, the frequency shifts in X—H—-Y hydrogen bonded systems at differentH—Ydistances are shown to correlate well with the Mullikencharges on H and Y, with the positive and negative charges on Y correlating with the blue and red shift of the frequency of X—H vibration, respectively. The role played by charge transfers at other parts of the interacting system is also discussed.

  14. Catastrophic shifts in ecosystems

    Science.gov (United States)

    Scheffer, Marten; Carpenter, Steve; Foley, Jonathan A.; Folke, Carl; Walker, Brian

    2001-10-01

    All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

  15. Terrestrial Digital Television Broadcast Single Frequency Network (SFN) Group Gateway Key Technologies and Test Methods%地面数字电视广播单频网(SFN)组网关键技术与测试方法

    Institute of Scientific and Technical Information of China (English)

    杨延冬; 呼和; 黄艳萍; 吕倩

    2014-01-01

    TV with the single frequency network will also DTMB standard promotion and inter-nationalization have been adopted by other more countries and regions , its promotion prospects .

  16. SELECTION OF BRILLOUIN SHIFT DISCRIMINATOR FOR BRILLOUIN LIDAR

    Institute of Scientific and Technical Information of China (English)

    吴东; 刘智深

    2002-01-01

    For the measurement of vertical profiles of sound speed in the sea using laser excited Brillouin scattering, a high-resolution measurement of Brillouin frequency shift is required. In this work, a molecular absorption cell was selec ted as the frequency shift discriminator and several kinds of absorption gases were tri ed. It was found that the strong line (#1095) of 127I2 at 18783.3297 cm-1 and two absorption lines of 129I2 located at the two sides of the #1095 line of 127 I2 could be used as frequency shift discriminator to detect the changes of the Brillouin frequency s hift. This selection is the best one within the range from 532.0131 nm to 532.5154 nm. But it is not perfect and there is a lot of work to do before its practical application.

  17. Climate Smart Agriculture (CSA) : Key messages - What is it about?

    NARCIS (Netherlands)

    Verhagen, A.; Neijenhuis, F.; Jarvis, T.; Jackson, L.; Caron, P.; Lipper, L.; Fernandes, E.; Entsuah-Mensa, R.; Vermeulen, S.

    2014-01-01

    Climate change fundamentally shifts the agricultural development agenda. Changing temperature and precipitation, sea level rise, and the rising frequency of extreme climate events will significantly reduce global food production in this century unless action is taken. Major investments, private and

  18. Cooperative Lamb shift in a quantum emitter array

    CERN Document Server

    Meir, Ziv; Shahmoon, Ephraim; Oron, Dan; Ozeri, Roee

    2013-01-01

    Whenever several quantum light emitters are brought in proximity with one another, their interaction with common electromagnetic fields couples them, giving rise to cooperative shifts in their resonance frequency. Such collective line shifts are central to modern atomic physics, being closely related to superradiance on one hand and the Lamb shift on the other. Although collective shifts have been theoretically predicted more than fifty years ago, the effect has not been observed yet in a controllable system of a few isolated emitters. Here, we report a direct spectroscopic observation of the cooperative shift of an optical electric dipole transition in a system of up to eight Sr ions suspended in a Paul trap. We study collective resonance shift in the previously unexplored regime of far-field coupling, and provide the first observation of cooperative effects in an array of quantum emitters. These results pave the way towards experimental exploration of cooperative emission phenomena in mesoscopic systems.

  19. Quantum Key Distribution

    Science.gov (United States)

    Seshu, Ch.

    Quantum Key Distribution (QKD) uses Quantum Mechanics to guarantee secure communication. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt messages.

  20. Public Key Cryptography.

    Science.gov (United States)

    Tapson, Frank

    1996-01-01

    Describes public key cryptography, also known as RSA, which is a system using two keys, one used to put a message into cipher and another used to decipher the message. Presents examples using small prime numbers. (MKR)

  1. Key Management Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides a secure environment to research and develop advanced electronic key management and networked key distribution technologies for the Navy and DoD....

  2. Quantum dense key distribution

    CERN Document Server

    Degiovanni, I P; Castelletto, S; Rastello, M L; Bovino, F A; Colla, A M; Castagnoli, G C

    2004-01-01

    This paper proposes a new protocol for quantum dense key distribution. This protocol embeds the benefits of a quantum dense coding and a quantum key distribution and is able to generate shared secret keys four times more efficiently than BB84 one. We hereinafter prove the security of this scheme against individual eavesdropping attacks, and we present preliminary experimental results, showing its feasibility.

  3. LOCKS AND KEYS SERVICE

    CERN Multimedia

    Locks and Keys Service

    2002-01-01

    The Locks and Keys service (ST/FM) will move from building 55 to building 570 from the 2nd August to the 9th August 2002 included. During this period the service will be closed. Only in case of extreme urgency please call the 164550. Starting from Monday, 12th August, the Locks and Keys Service will continue to follow the activities related to office keys (keys and locks) and will provide the keys for furniture. The service is open from 8h30 to 12h00 and from 13h00 to 17h30. We remind you that your divisional correspondents can help you in the execution of the procedures. We thank you for your comprehension and we remain at your service to help you in solving all the matters related to keys for offices and furniture. Locks and Keys Service - ST Division - FM Group

  4. Frequency standards

    CERN Document Server

    Riehle, Fritz

    2006-01-01

    Of all measurement units, frequency is the one that may be determined with the highest degree of accuracy. It equally allows precise measurements of other physical and technical quantities, whenever they can be measured in terms of frequency.This volume covers the central methods and techniques relevant for frequency standards developed in physics, electronics, quantum electronics, and statistics. After a review of the basic principles, the book looks at the realisation of commonly used components. It then continues with the description and characterisation of important frequency standards

  5. Michelson interferometer based spatial phase shift shearography.

    Science.gov (United States)

    Xie, Xin; Yang, Lianxiang; Xu, Nan; Chen, Xu

    2013-06-10

    This paper presents a simple spatial phase shift shearography based on the Michelson interferometer. The Michelson interferometer based shearographic system has been widely utilized in industry as a practical nondestructive test tool. In the system, the Michelson interferometer is used as a shearing device to generate a shearing distance by tilting a small angle in one of the two mirrors. In fact, tilting the mirror in the Michelson interferometer also generates spatial frequency shift. Based on this feature, we introduce a simple Michelson interferometer based spatial phase shift shearography. The Fourier transform (FT) method is applied to separate the spectrum on the spatial frequency domain. The phase change due to the loading can be evaluated using a properly selected windowed inverse-FT. This system can generate a phase map of shearography by using only a single image. The effects of shearing angle, spatial resolution of couple charge device camera, and filter methods are discussed in detail. The theory and the experimental results are presented.

  6. Key Aspects of Wave Energy

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Nørgaard, Jørgen Harck

    2012-01-01

    Diversification of renewable energy sources is fundamental to ensure sustainability. In this contest, wave energy can provide a substantial contribution as soon as the sector breaks into the market. In order to accelerate shift from a technology to a market focus and reduce technical and non...... be used as a breakwater therefore providing a solid structure for harbor protection; the Wave Star can be used as a base for offshore wind and photovoltaic installation in the middle of the sea, realizing an hybrid renewable energy platform. It is the authors´ believe that taking wave energy devices......-technical risks, it is critical to provide comprehensive and reliable information on the technologies without neglecting attractive advantages. It is possible to underline a different key of lecture of wave energy performance by considering efficiency and power production as well as device versatility...

  7. Frequency Offset Influence on MDPSK Signal Reception in Fading Channel

    Directory of Open Access Journals (Sweden)

    S. N. Stošović

    2013-11-01

    Full Text Available The symbol error probability of M-ary differential phase shift keying (MDPSK receiver, in the presence of carrier frequency offset, is analysed in this paper. The paper proposes a novel multiple symbol differential detection (MSDD receiver. The influence of various receiver’s parameters on the error probability is analysed. The theoretical symbol error probability is derived and compared to the Monte-Carlo simulation results, for an AWGN channel. The analysis shows a good agreement between the theoretical and simulation results. The influence of the frequency offset in the Rician fading channel, using Monte-Carlo simulation, is also considered for the same receiver’s parameters as in the AWGN channel. Simulation results show good system performances in the case of Rician fading channel, also.

  8. The Homomorphic Key Agreement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    There are various challenges that are faced in group communication, so it is necessary to ensure session key. Key agreement is the fundamental cryptographic primitive for establishing a secure communication. It is a process of computing a shared secret contributed by two or more entities such that no single node can predetermine the resulting value. An authenticated key agreement is attained by combining the key agreement protocol with digital signatures. After a brief introduction to existing key agreement in group communication, Making use of the additive-multiplicative homomorphism in the integer ring defined by Sander and Tschudin: A new protocols, called the homomorphism key agreement, was designed, which can be self-contributory, robust, scalable and applicable in group communication.

  9. Frequency synthesiser

    NARCIS (Netherlands)

    Drago, Salvatore; Sebastiano, Fabio; Leenaerts, Dominicus Martinus Wilhelmus; Breems, Lucien Johannes; Nauta, Bram

    2016-01-01

    A low power frequency synthesiser circuit (30) for a radio transceiver, the synthesiser circuit comprising: a digital controlled oscillator configured to generate an output signal having a frequency controlled by an input digital control word (DCW); a feedback loop connected between an output and an

  10. Robust laser frequency stabilization by serrodyne modulation

    CERN Document Server

    Kohlhaas, Ralf; Bernon, Simon; Bertoldi, Andrea; Landragin, Arnaud; Bouyer, Philippe

    2011-01-01

    We report the frequency stabilization of a distributed feedback erbium-doped fiber laser on an optical cavity by serrodyne frequency shifting. A correction bandwidth of 2.4 MHz and a dynamic range of 220 MHz are achieved, which leads to a strong robustness against large disturbances up to high frequencies. Serrodyne frequency shifting allows to use an electro-optical modulator as a fast external transducer with a correction range which exceeds the one of acousto-optical modulators by at least one order of magnitude.

  11. A Hardware Transverse Beam Frequency Response Simulator

    CERN Document Server

    Ning, Jia

    2005-01-01

    We build an electronical instrument to get the frequency response close to the pattern of transverse beam frequency response. The method is to apply 1)a time delay circuit with ADC, FIFO RAM and DAC; 2)a phase shift circuit which is an all pass filter with adjustable phase shift in the frequency range of 25kHz to 30kHz; in a feedback loop of 3)a commutating filter which is a high Q band pass filter. We can dynamically adjust the center frequency, the side band distance during the testing. With this instrument, some beam instruments can be tested without using the real beam.

  12. Research on fiber-optic interferometric hydrophone array using frequency division multiplying technique

    Institute of Scientific and Technical Information of China (English)

    CAO Jianian; LI Xuyou; WANG Zhaoxia; LUO Jicheng; FU Lintai

    2001-01-01

    From the point of view of system design, a configuration of fiber-optic interferometric hydrophone array and its modulation and demodulation approach using frequency division multiplexing technique based on Phase Generated Carrier (PGC) is introduced. And the emphasis on demonstrating the relationship among the number of units N, the detectable signal amplitude D and the detectable frequency ωs through analyzing the frequency spectrum of the output signal of the J × K array and the key factor which restricts N, D, ωo for increasing are presented. The maximum phase shift and the law of its variation according to frequency are specially analyzed. The results induced from some relative theory were verified by experiments.

  13. Key Account Management

    OpenAIRE

    Dvořák, Dalibor

    2007-01-01

    This note tries to explain concept of key account management (KAM), factors leading to importance of this emerging concept, criteria to determine key accounts from customer base, benefits to both buyers and sellers agreeing to practice it, stages of KAM relationship, conditions under which power lies with buyer or seller, outlines risks faced by both the parties, key success factors, challenges faced in implementing this concept and relevance to infrastructure sector.

  14. Metacognitive Instruction: Global and Local Shifts in Considering Listening Input

    Directory of Open Access Journals (Sweden)

    Hossein Bozorgian

    2013-01-01

    Full Text Available A key shift of thinking for effective learning and teaching of listening input has been seen and organized in education locally and globally. This study has probed whether metacognitive instruction through a pedagogical cycle shifts high-intermediate students' English language learning and English as a second language (ESL teacher's teaching focus on listening input. Twenty male Iranian students with an age range of 18 to 24 received a guided methodology including metacognitive strategies (planning, monitoring, and evaluation for a period of three months. This study has used the strategies and probed the importance of metacognitive instruction through interviewing both the teacher and the students. The results have shown that metacognitive instruction helped both the ESL teacher's and the students' shift of thinking about teaching and learning listening input. This key shift of thinking has implications globally and locally for classroom practices of listening input.

  15. Bethe logarithm and QED shift for lithium.

    Science.gov (United States)

    Yan, Zong-Chao; Drake, G W F

    2003-09-12

    A novel finite basis set method is used to calculate the Bethe logarithm for the ground 2 (2)S(1/2) and excited 3 (2)S(1/2) states of lithium. The basis sets are constructed to span a huge range of distance scales within a single calculation, leading to well-converged values for the Bethe logarithm. The results are used to calculate an accurate value for the complete quantum electrodynamic energy shift up to order alpha(3) Ry. The calculated 3 (2)S(1/2)-2 (2)S(1/2) transition frequency for 7Li is 27 206.092 6(9) cm(-1), and the ionization potential for the 2 (2)S(1/2) state is 43 487.158 3(6) cm(-1). The 7Li-6Li isotope shift is also considered, and all the results compared with experiment.

  16. Shape-shifting colloids via stimulated dewetting

    Science.gov (United States)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-07-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly.

  17. Widely-tunable mid-infrared frequency comb source based on difference frequency generation

    NARCIS (Netherlands)

    Ruehl, A.; Gambetta, A.; Hartl, I.; Fermann, M.E.; Eikema, K.S.E.; Marangoni, M.

    2012-01-01

    We report on a mid-IR frequency comb source of unprecedented tunability covering the entire 3-10 mu m molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman-shifted solitons

  18. When teams shift among processes: insights from simulation and optimization.

    Science.gov (United States)

    Kennedy, Deanna M; McComb, Sara A

    2014-09-01

    This article introduces process shifts to study the temporal interplay among transition and action processes espoused in the recurring phase model proposed by Marks, Mathieu, and Zacarro (2001). Process shifts are those points in time when teams complete a focal process and change to another process. By using team communication patterns to measure process shifts, this research explores (a) when teams shift among different transition processes and initiate action processes and (b) the potential of different interventions, such as communication directives, to manipulate process shift timing and order and, ultimately, team performance. Virtual experiments are employed to compare data from observed laboratory teams not receiving interventions, simulated teams receiving interventions, and optimal simulated teams generated using genetic algorithm procedures. Our results offer insights about the potential for different interventions to affect team performance. Moreover, certain interventions may promote discussions about key issues (e.g., tactical strategies) and facilitate shifting among transition processes in a manner that emulates optimal simulated teams' communication patterns. Thus, we contribute to theory regarding team processes in 2 important ways. First, we present process shifts as a way to explore the timing of when teams shift from transition to action processes. Second, we use virtual experimentation to identify those interventions with the greatest potential to affect performance by changing when teams shift among processes. Additionally, we employ computational methods including neural networks, simulation, and optimization, thereby demonstrating their applicability in conducting team research.

  19. Financial Key Ratios

    Directory of Open Access Journals (Sweden)

    Tănase Alin-Eliodor

    2014-08-01

    Full Text Available This article focuses on computing techniques starting from trial balance data regarding financial key ratios. There are presented activity, liquidity, solvency and profitability financial key ratios. It is presented a computing methodology in three steps based on a trial balance.

  20. The compact key

    NARCIS (Netherlands)

    NN,

    1966-01-01

    Here is given a sample of a new sort of identification key, recently developed by Dr. P. W. Leenhouts of the Rijksherbarium. Having to sort many specimens of Sapindaceae into genera, he became dissatisfied with the common dichotomous key, which too often does not work when the material is not comple

  1. Evaluation of Audiometric Threshold Shift Criteria for Ototoxicity Monitoring

    Science.gov (United States)

    Konrad-Martin, Dawn; James, Kenneth E.; Gordon, Jane S.; Reavis, Kelly M.; Phillips, David S.; Bratt, Gene W.; Fausti, Stephen A.

    2017-01-01

    Background There is disagreement about ototoxicity monitoring methods. Controversy exists about what audiometric threshold shift criteria should be used, which frequencies should be tested, and with what step size. An evaluation of the test performance achieved using various criteria and methods for ototoxicity monitoring may help resolve these issues. Purpose (1) Evaluate test performance achieved using various significant threshold shift (STS) definitions for ototoxicity monitoring in a predominately veteran population; and (2) determine whether testing in ⅙- or ⅓-octave steps improves test performance compared to ½-octave steps. Research Design A prospective, observational study design was used in which STSs were evaluated at frequencies within an octave of each subject’s high-frequency hearing limit at two time points, an early monitoring test and the final monitoring test. Study Sample Data were analyzed from 78 ears of 41 patients receiving cisplatin and from 53 ears of 28 hospitalized patients receiving nonototoxic antibiotics. Cisplatin-treated subjects received a cumulative dosage ≥350 mg by the final monitoring test. Testing schedule, age, and pre-exposure hearing characteristics were similar between the subject groups. Data Collection and Analysis Threshold shifts relative to baseline were examined to determine whether they met criteria based on magnitudes of positive STS (shifts of ≥5, 10, 15, or 20 dB) and numbers of frequencies affected (shifts at ≥1, 2, or 3 adjacent frequencies) for data collected using approximately ⅙-, ⅓-, or ½-octave steps. Thresholds were confirmed during monitoring sessions in which shifts were identified. Test performance was evaluated with receiver operating characteristic (ROC) curves developed using a surrogate “gold standard”; true positive (TP) rates were derived from the cisplatin-exposed group and false positive (FP) rates from the nonexposed, control group. Best STS definitions were identified

  2. Slow light based optical frequency shifter

    CERN Document Server

    Li, Qian; Thuresson, Axel; Nilsson, Adam N; Rippe, Lars; Kröll, Stefan

    2016-01-01

    We demonstrate experimentally and theoretically a controllable way of shifting the frequency of an optical pulse by using a combination of spectral hole burning, slow light effect, and linear Stark effect in a rare-earth-ion doped crystal. We claim that the solid angle of acceptance of a frequency shift structure can be close to $2\\pi$, which means that the frequency shifter could work not only for optical pulses propagating in a specific spatial mode but also for randomly scattered light. As the frequency shift is controlled solely by an external electric field, it works also for weak coherent light fields, and can e.g. be used as a frequency shifter for quantum memory devices in quantum communication.

  3. Improved chemical shift prediction by Rosetta conformational sampling

    Energy Technology Data Exchange (ETDEWEB)

    Tian Ye [Sanford Burnham Medical Research Institute (United States); Opella, Stanley J. [University of California San Diego, Department of Chemistry and Biochemistry (United States); Marassi, Francesca M., E-mail: fmarassi@sbmri.org [Sanford Burnham Medical Research Institute (United States)

    2012-11-15

    Chemical shift frequencies represent a time-average of all the conformational states populated by a protein. Thus, chemical shift prediction programs based on sequence and database analysis yield higher accuracy for rigid rather than flexible protein segments. Here we show that the prediction accuracy can be significantly improved by averaging over an ensemble of structures, predicted solely from amino acid sequence with the Rosetta program. This approach to chemical shift and structure prediction has the potential to be useful for guiding resonance assignments, especially in solid-state NMR structural studies of membrane proteins in proteoliposomes.

  4. Early dynamics of the semantic priming shift

    Science.gov (United States)

    Lavigne, Frédéric; Chanquoy, Lucile; Dumercy, Laurent; Vitu, Françoise

    2013-01-01

    Semantic processing of sequences of words requires the cognitive system to keep several word meanings simultaneously activated in working memory with limited capacity. The real- time updating of the sequence of word meanings relies on dynamic changes in the associates to the words that are activated. Protocols involving two sequential primes report a semantic priming shift from larger priming of associates to the first prime to larger priming of associates to the second prime, in a range of long SOAs (stimulus-onset asynchronies) between the second prime and the target. However, the possibility for an early semantic priming shift is still to be tested, and its dynamics as a function of association strength remain unknown. Three multiple priming experiments are proposed that cross-manipulate association strength between each of two successive primes and a target, for different values of short SOAs and prime durations. Results show an early priming shift ranging from priming of associates to the first prime only to priming of strong associates to the first prime and all of the associates to the second prime. We investigated the neural basis of the early priming shift by using a network model of spike frequency adaptive cortical neurons (e.g., Deco & Rolls, 2005), able to code different association strengths between the primes and the target. The cortical network model provides a description of the early dynamics of the priming shift in terms of pro-active and retro-active interferences within populations of excitatory neurons regulated by fast and unselective inhibitory feedback. PMID:23717346

  5. Beam shifts and distribution functions

    CERN Document Server

    Aiello, Andrea

    2011-01-01

    When a beam of light is reflected by a smooth surface its behavior deviates from geometrical optics predictions. Such deviations are quantified by the so-called spatial and angular Goos-Haenchen (GH) and Imbert-Fedorov (IF) shifts of the reflected beam. These shifts depend upon the shape of the incident beam, its polarization and on the material composition of the reflecting surface. In this article we suggest a novel approach that allows one to unambiguously isolate the beam-shape dependent aspects of GH and IF shifts. We show that this separation is possible as a result of some universal features of shifted distribution functions which are presented and discussed.

  6. Ecohydrology by thinking outside the bog: Shifting paradigms in an era of shifting peatland ecosystems

    Science.gov (United States)

    Waddington, James; Moore, Paul

    2016-04-01

    Large shifts in vegetation distributions are occurring worldwide and at unprecedented rates. The most extreme of these regime shifts are expected to occur at ecosystem boundaries of both semi-arid and semi-humid landscapes. Despite extensive hydrological research on the interactions between water and semi-arid ecosystems, research in peatlands on the wet end of ecosystem continuum has been "bogged down" (pun fully intended) by the traditional conceptual models (paradigms?) of peatland hydrology and ecology. The consequences of this "thinking" are large given that northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). This is especially true because peatlands face increases in the severity, areal extent, and frequency of climate-mediated (e.g., wildfire, drought) and land-use change (e.g., drainage, flooding, and mining) disturbances placing the future security of these critical ecosystem services in doubt. We use the word doubt because while numerical modelling studies predict peatland regime shifts and the demise of global peat stocks, there is growing evidence that peatlands are self-regulating ecosystems dominated by negative ecohydrological feedbacks that stabilize the aforementioned ecosystem services through high ecosystem resilience to disturbance. This raises several important hydrological questions? "Is there field evidence of peatland regime shifts? If so, what are the potential impacts of these shifts on water resources and watershed management? If not, are researchers actually looking in the right places (or times)? In this presentation we explore the need for a "thinking outside the bog" in order to understand the ecohydrological consequences of transformative landscape change caused by peatland regime shifts. With reference to over two decades of field research, recent advances with our Peatland Hydrological Impacts model and recent research examining primary peat formation, we

  7. A new image cipher in time and frequency domains

    Science.gov (United States)

    Abd El-Latif, Ahmed A.; Niu, Xiamu; Amin, Mohamed

    2012-10-01

    Recently, various encryption techniques based on chaos have been proposed. However, most existing chaotic encryption schemes still suffer from fundamental problems such as small key space, weak security function and slow performance speed. This paper introduces an efficient encryption scheme for still visual data that overcome these disadvantages. The proposed scheme is based on hybrid Linear Feedback Shift Register (LFSR) and chaotic systems in hybrid domains. The core idea is to scramble the pixel positions based on 2D chaotic systems in frequency domain. Then, the diffusion is done on the scrambled image based on cryptographic primitive operations and the incorporation of LFSR and chaotic systems as round keys. The hybrid compound of LFSR, chaotic system and cryptographic primitive operations strengthen the encryption performance and enlarge the key space required to resist the brute force attacks. Results of statistical and differential analysis show that the proposed algorithm has high security for secure digital images. Furthermore, it has key sensitivity together with a large key space and is very fast compared to other competitive algorithms.

  8. Measurement of the Microwave Lensing shift in NIST-F1 and NIST-F2

    Science.gov (United States)

    Jefferts, S. R.; Heavner, T. P.; Barlow, S. E.; Ashby, N.

    2016-06-01

    With several Primary Frequency Standards (PFS) across the world demonstrating systematic fractional frequency uncertainties on order of 1 x 10-16, it is crucial to accurately measure or model even small frequency shifts that could affect the ultimate PFS uncertainty, and thus ultimately impact the rate of Coordinated Universal Time (UTC) which relies on precision PFS measurements. Recently there has been controversy about the physical causes and size of PFS frequency shifts due to microwave lensing effects. We present here the first measurements of microwave lensing frequency shifts in the PFS NIST-F1 and NIST-F2. The measured frequency shifts agree well with the recent theory of Ashby et al [1].

  9. An Alternative to Keys

    Science.gov (United States)

    O'Hagan, James

    1977-01-01

    For the secondary school, the author discourages the use of dichotomous keys in favor of a punch-card system. The system is readily constructed by students for use in plant and animal classification. (CP)

  10. Constant frequency pulsed phase-locked loop measuring device

    Science.gov (United States)

    Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

    1993-01-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  11. Constant frequency pulsed phase-locked loop measuring device

    Science.gov (United States)

    Yost, William T.; Kushnick, Peter W.; Cantrell, John H.

    1993-06-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  12. Constant frequency pulsed phase-locked loop measuring device

    Science.gov (United States)

    Yost, William T.; Kushnick, Peter W.; Cantrell, John H.

    1991-08-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  13. Keys to the City

    DEFF Research Database (Denmark)

    Monsson, Christian Kjær

    2014-01-01

    Review of: Keys to the City: How Economics, Institutions, Social Interaction, and Politics Shape Development / Michael Storper Princeton University Press, Princeton, NJ, 2013, 288 pp., $39.95/£27.95 (cloth), ISBN 9780691143118......Review of: Keys to the City: How Economics, Institutions, Social Interaction, and Politics Shape Development / Michael Storper Princeton University Press, Princeton, NJ, 2013, 288 pp., $39.95/£27.95 (cloth), ISBN 9780691143118...

  14. Key concepts in energy

    CERN Document Server

    Madureira, Nuno Luis

    2014-01-01

    Highlights how key energy concepts surfaced, tracing their evolution throughout history to encompasses four economic concepts and four technological-engineering concepts developed through their history to conclude with current economic and environmental sciences Considers the process of energy-substitutions through complementary usages, hybridization and technological mixes Combines a conceptual approach with key theoretical concepts from engineering, geological and economic sciences providing cross disciplinary overview of energy fundamentals in a short and focused reading

  15. Secret Key Crypto Implementations

    Science.gov (United States)

    Bertoni, Guido Marco; Melzani, Filippo

    This chapter presents the algorithm selected in 2001 as the Advanced Encryption Standard. This algorithm is the base for implementing security and privacy based on symmetric key solutions in almost all new applications. Secret key algorithms are used in combination with modes of operation to provide different security properties. The most used modes of operation are presented in this chapter. Finally an overview of the different techniques of software and hardware implementations is given.

  16. Regime shifts in resource management

    NARCIS (Netherlands)

    de Zeeuw, A.J.

    2014-01-01

    Resource management has to take account of the possibility of tipping points and regime shifts in ecological systems that provide the resources. This article focuses on the typical model of regime shifts in the ecological literature and analyzes optimal management and common-property issues when tra

  17. Work shifts in Emergency Medicine

    Directory of Open Access Journals (Sweden)

    Roberto Recupero

    2007-06-01

    Full Text Available Emergency Medicine is known as a high stress specialty. The adverse effect of constantly rotating shifts is the single most important reason given for premature attrition from the field. In this work problems tied with night shift work will be taken into account and some solutions to reduce the impact of night work on the emergency physicians will be proposed.

  18. Privacy for Key-Trees with Adaptive Adversaries

    NARCIS (Netherlands)

    Beye, M.; Veugen, P.J.M.

    2011-01-01

    Hash-lock authentication protocols for Radio Frequency IDentification (RFID) tags incur heavy search on the server. Key-trees have been proposed as a way to reduce search times, but because partial keys in such trees are shared, key compromise affects several tags. Butty´an [3] and Beye and Veugen [

  19. Anonymity for key-trees with adaptive adversaries

    NARCIS (Netherlands)

    Beye, M.; Veugen, P.J.M.

    2012-01-01

    Hash-lock authentication protocols for Radio Frequency IDentification (RFID) tags incur heavy search on the server. Key-trees have been proposed as a way to reduce search times, but because partial keys in such trees are shared, key compromise affects several tags. Buttyán [4] and Beye and Veugen [3

  20. Metabolic impact of shift work.

    Science.gov (United States)

    Zimberg, Ioná Zalcman; Fernandes Junior, Silvio A; Crispim, Cibele Aparecida; Tufik, Sergio; de Mello, Marco Tulio

    2012-01-01

    In developing countries, shift work represents a considerable contingent workforce. Recently, studies have shown that overweight and obesity are more prevalent in shift workers than day workers. In addition, shift work has been associated with a higher propensity for the development of many metabolic disorders, such as insulin resistance, diabetes, dislipidemias and metabolic syndrome. Recent data have pointed that decrease of the sleep time, desynchronization of circadian rhythm and alteration of environmental aspects are the main factors related to such problems. Shortened or disturbed sleep is among the most common health-related effects of shift work. The plausible physiological and biological mechanisms are related to the activation of the autonomic nervous system, inflammation, changes in lipid and glucose metabolism, and related changes in the risk for atherosclerosis, metabolic syndrome, and type II diabetes. The present review will discuss the impact of shift work on obesity and metabolic disorders and how disruption of sleep and circadian misalignment may contribute to these metabolic dysfunctions.

  1. The LOFAR Magnetism Key Science Project

    NARCIS (Netherlands)

    Anderson, James; Beck, Rainer; Bell, Michael; de Bruyn, Ger; Chyzy, Krzysztof; Eislöffel, Jochen; Enßlin, Torsten; Fletcher, Andrew; Haverkorn, Marijke; Heald, George; Horneffer, Andreas; Noutsos, Aris; Reich, Wolfgang; Scaife, Anna; the LOFAR collaboration, [No Value

    2012-01-01

    Measuring radio waves at low frequencies offers a new window to study cosmic magnetism, and LOFAR is the ideal radio telescope to open this window widely. The LOFAR Magnetism Key Science Project (MKSP) draws together expertise from multiple fields of magnetism science and intends to use LOFAR to tac

  2. Dependence of synchronization frequency of Kuramoto oscillators on symmetry of intrinsic frequency in ring network

    Indian Academy of Sciences (India)

    Arindam Saha; R E Amritkar

    2014-12-01

    Kuramoto oscillators have been proposed earlier as a model for interacting systems that exhibit synchronization. In this article, we study the difference between networks with symmetric and asymmetric distribution of natural frequencies. We first indicate that synchronization frequency of oscillators in a completely connected network is always equal to the mean of the natural frequency distribution. In particular, shape of the natural frequency distribution does not affect the synchronization frequency in this case. Then, we analyse the case of oscillators in a directed ring network, where asymmetry in the natural frequency distribution is seen to shift the synchronization frequency of the network. We also present an estimate of the shift in the frequencies for slightly asymmetric distributions.

  3. Seasonal and regional variations in extreme precipitation event frequency using CMIP5

    Science.gov (United States)

    Janssen, E.; Sriver, R. L.; Wuebbles, D. J.; Kunkel, K. E.

    2016-05-01

    Understanding how the frequency and intensity of extreme precipitation events are changing is important for regional risk assessments and adaptation planning. Here we use observational data and an ensemble of climate change model experiments (from the Coupled Model Intercomparison Project Phase 5 (CMIP5)) to examine past and potential future seasonal changes in extreme precipitation event frequency over the United States. Using the extreme precipitation index as a metric for extreme precipitation change, we find key differences between models and observations. In particular, the CMIP5 models tend to overestimate the number of spring events and underestimate the number of summer events. This seasonal shift in the models is amplified in projections. These results provide a basis for evaluating climate model skill in simulating observed seasonality and changes in regional extreme precipitation. Additionally, we highlight key sources of variability and uncertainty that can potentially inform regional impact analyses and adaptation planning.

  4. Reweighted ℓ1 referenceless PRF shift thermometry.

    Science.gov (United States)

    Grissom, William A; Lustig, Michael; Holbrook, Andrew B; Rieke, Viola; Pauly, John M; Butts-Pauly, Kim

    2010-10-01

    Temperature estimation in proton resonance frequency (PRF) shift MR thermometry requires a reference, or pretreatment, phase image that is subtracted from image phase during thermal treatment to yield a phase difference image proportional to temperature change. Referenceless thermometry methods derive a reference phase image from the treatment image itself by assuming that in the absence of a hot spot, the image phase can be accurately represented in a smooth (usually low order polynomial) basis. By masking the hot spot out of a least squares (ℓ(2)) regression, the reference phase image's coefficients on the polynomial basis are estimated and a reference image is derived by evaluating the polynomial inside the hot spot area. Referenceless methods are therefore insensitive to motion and bulk main field shifts, however, currently these methods require user interaction or sophisticated tracking to ensure that the hot spot is masked out of the polynomial regression. This article introduces an approach to reference PRF shift thermometry that uses reweighted ℓ(1) regression, a form of robust regression, to obtain background phase coefficients without hot spot tracking and masking. The method is compared to conventional referenceless thermometry, and demonstrated experimentally in monitoring HIFU heating in a phantom and canine prostate, as well as in a healthy human liver.

  5. Scientific evidence contradicts findings and assumptions of Canadian Safety Panel 6: microwaves act through voltage-gated calcium channel activation to induce biological impacts at non-thermal levels, supporting a paradigm shift for microwave/lower frequency electromagnetic field action.

    Science.gov (United States)

    Pall, Martin L

    2015-01-01

    This review considers a paradigm shift on microwave electromagnetic field (EMF) action from only thermal effects to action via voltage-gated calcium channel (VGCC) activation. Microwave/lower frequency EMFs were shown in two dozen studies to act via VGCC activation because all effects studied were blocked by calcium channel blockers. This mode of action was further supported by hundreds of studies showing microwave changes in calcium fluxes and intracellular calcium [Ca2+]i signaling. The biophysical properties of VGCCs/similar channels make them particularly sensitive to low intensity, non-thermal EMF exposures. Non-thermal studies have shown that in most cases pulsed fields are more active than are non-pulsed fields and that exposures within certain intensity windows have much large biological effects than do either lower or higher intensity exposures; these are both consistent with a VGCC role but inconsistent with only a heating/thermal role. Downstream effects of VGCC activation include calcium signaling, elevated nitric oxide (NO), NO signaling, peroxynitrite, free radical formation, and oxidative stress. Downstream effects explain repeatedly reported biological responses to non-thermal exposures: oxidative stress; single and double strand breaks in cellular DNA; cancer; male and female infertility; lowered melatonin/sleep disruption; cardiac changes including tachycardia, arrhythmia, and sudden cardiac death; diverse neuropsychiatric effects including depression; and therapeutic effects. Non-VGCC non-thermal mechanisms may occur, but none have been shown to have effects in mammals. Biologically relevant safety standards can be developed through studies of cell lines/cell cultures with high levels of different VGCCs, measuring their responses to different EMF exposures. The 2014 Canadian Report by a panel of experts only recognizes thermal effects regarding safety standards for non-ionizing radiation exposures. Its position is therefore contradicted by each

  6. Nonlocal optical effects on the Goos-Hänchen shifts at multilayered hyperbolic metamaterials

    Science.gov (United States)

    Chen, Chih-Wei; Bian, Tingting; Chiang, Hai-Pang; Leung, P. T.

    2016-02-01

    The lateral beam shift of light incident on a multilayered hyperbolic metamaterial (HMM) is investigated using a theoretical model which emphasizes the nonlocal optical response of the indefinite material. By applying an effective local response theory formulated recently in the literature, it is found that nonlocal effects only affect p polarized light in this Goos-Hänchen (GH) shift of the incident beam; leading to a blue-shifted peak for positive shifts at high frequencies and red-shifted dip for negative shifts at low frequencies in the GH shift spectrum. An account for the observed phenomenon is given by referring to the ‘Brewster condition’ for the reflected wave from the HMM. This observation thus provides a relatively direct probe for the nonlocal response of the HMM.

  7. Constant-Frequency Pulsed Phase-Locked-Loop Measuring Device

    Science.gov (United States)

    Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

    1992-01-01

    Constant-frequency pulsed phase-locked-loop measuring device is sensitive to small changes in phase velocity and easily automated. Based on use of fixed-frequency oscillator in measuring small changes in ultrasonic phase velocity when sample exposed to such changes in environment as changes in pressure and temperature. Automatically balances electrical phase shifts against acoustical phase shifts to obtain accurate measurements of acoustical phase shifts.

  8. The study of key issues about integration of GNSS and strong-motion records for real-time earthquake monitoring

    Science.gov (United States)

    Tu, Rui; Zhang, Pengfei; Zhang, Rui; Liu, Jinhai

    2016-08-01

    This paper has studied the key issues about integration of GNSS and strong-motion records for real-time earthquake monitoring. The validations show that the consistence of the coordinate system must be considered firstly to exclude the system bias between GNSS and strong-motion. The GNSS sampling rate is suggested about 1-5 Hz, and we should give the strong-motion's baseline shift with a larger dynamic noise as its variation is very swift. The initialization time of solving the baseline shift is less than one minute, and ambiguity resolution strategy is not greatly improved the solution. The data quality is very important for the solution, we advised to use multi-frequency and multi-system observations. These ideas give an important guide for real-time earthquake monitoring and early warning by the tight integration of GNSS and strong-motion records.

  9. Time-frequency analysis of the bistatic acoustic scattering from a spherical elastic shell.

    Science.gov (United States)

    Anderson, Shaun D; Sabra, Karim G; Zakharia, Manell E; Sessarego, Jean-Pierre

    2012-01-01

    The development of low-frequency sonar systems, using, for instance, a network of autonomous systems in unmanned vehicles, provides a practical means for bistatic measurements (i.e., when the source and receiver are widely separated) allowing for multiple viewpoints of the target of interest. Time-frequency analysis, in particular, Wigner-Ville analysis, takes advantage of the evolution time dependent aspect of the echo spectrum to differentiate a man-made target, such as an elastic spherical shell, from a natural object of the similar shape. A key energetic feature of fluid-loaded and thin spherical shell is the coincidence pattern, also referred to as the mid-frequency enhancement (MFE), that results from antisymmetric Lamb-waves propagating around the circumference of the shell. This article investigates numerically the bistatic variations of the MFE with respect to the monostatic configuration using the Wigner-Ville analysis. The observed time-frequency shifts of the MFE are modeled using a previously derived quantitative ray theory by Zhang et al. [J. Acoust. Soc. Am. 91, 1862-1874 (1993)] for spherical shell's scattering. Additionally, the advantage of an optimal array beamformer, based on joint time delays and frequency shifts is illustrated for enhancing the detection of the MFE recorded across a bistatic receiver array when compared to a conventional time-delay beamformer.

  10. Probe light-shift elimination in generalized hyper-Ramsey quantum clocks

    Science.gov (United States)

    Zanon-Willette, T.; de Clercq, E.; Arimondo, E.

    2016-04-01

    We present an interrogation scheme for the next generation of quantum clocks to suppress frequency shifts induced by laser probing fields that are themselves based on generalized hyper-Ramsey resonances. Sequences of composite laser pulses with a specific selection of phases, frequency detunings, and durations are combined to generate a very efficient and robust frequency locking signal with an almost perfect elimination of the light shift from off-resonant states and to decouple the unperturbed frequency measurement from the laser's intensity. The frequency lock point generated from synthesized error signals using either π /4 or 3 π /4 laser phase steps during the intermediate pulse is tightly protected against large laser-pulse area variations and errors in potentially applied frequency shift compensations. Quantum clocks based on weakly allowed or completely forbidden optical transitions in atoms, ions, molecules, and nuclei will benefit from these hyperstable laser frequency stabilization schemes to reach relative accuracies below the 10-18 level.

  11. Keys through ARQ

    CERN Document Server

    Latif, Mohamed Abdel; Gamal, Hesham El

    2009-01-01

    This paper develops a novel framework for sharing secret keys using the well-known Automatic Repeat reQuest (ARQ) protocol. The proposed key sharing protocol does not assume any prior knowledge about the channel state information (CSI), but, harnesses the available opportunistic secrecy gains using only the one bit feedback, in the form of ACK/NACK. The distribution of key bits among multiple ARQ epochs, in our approach, allows for mitigating the secrecy outage phenomenon observed in earlier works. We characterize the information theoretic limits of the proposed scheme, under different assumptions on the channel spatial and temporal correlation function, and develop low complexity explicit implementations. Our analysis reveals a novel role of "dumb antennas" in overcoming the negative impact of spatial correlation, between the legitimate and eavesdropper channels, on the achievable secrecy rates. We further develop an adaptive rate allocation policy which achieves higher secrecy rates by exploiting the channe...

  12. Progress towards primary frequency standard%时间频率基准装置的研制现状∗

    Institute of Scientific and Technical Information of China (English)

    阮军; 王叶兵; 常宏; 姜海峰; 刘涛; 董瑞芳; 张首刚

    2015-01-01

    The cesium fountain clock as primary frequency standard is widely used in the areas, such as time-keeping system, satellite navigation, fundamental physics research, etc. The principle of operation of cesium fountain clock is introduced. The noise source and frequency shift term are ananlyzed. The major noise source influencing frequency stability are cold atom loading time, microwave phase noise related to Dick effect, and detection laser frequency noise. The major frequency bias influencing frequency uncertainty is blackbody radiation frequency shift,cold atom collision frequency shift,distributed cavity phase frequency shift and microwave leakage frequency shift.The key technique to achieve high-performance cesium fountain clock is sumerized. The application of cesium fountain clock is presented. The status of space cesium clock and future primary frequency standard of optical clock are shown.%时间频率基准装置——铯原子喷泉钟,在标准时间产生和保持、基础物理研究中发挥了重要的作用。介绍了铯原子喷泉钟的工作原理,对影响其性能的各项噪声源和频移项给出了分析,影响频率稳定度性能的主要因素为Dick效应相关的原子团装载时间、微波激励源相位噪声和探测激光的频率噪声,影响频率不确定性能主要频移项为:黑体辐射频移、冷原子碰撞频移、腔相位分布频移和微波泄露频移;总结和比较了当前具有先进性能的铯原子喷泉钟采用的技术;介绍了铯原子喷泉钟的主要应用方向、空间冷原子铯钟的研制情况和光学频率原子钟进展。

  13. A Novel Method for Generating Encryption Keys

    Directory of Open Access Journals (Sweden)

    Dascalescu Ana Cristina

    2009-12-01

    Full Text Available The development of the informational society, which has led to an impressive growth of the information volume circulating in the computer networks, has accelerated the evolution and especially the use of modern cryptography instruments. Today, the commercial products use standard cryptographic libraries that implement certified and tested cryptographic algorithms. Instead, the fragility ofencryption algorithms is given by compositional operations like key handling or key generation. In this sense, the article proposes an innovative method to generate pseudorandom numbers which can be used for the construction of secure stream encryption keys. The proposed method is based on the mathematical complements based on the algebra of the finite fields and uses a particularized structure of the linear feedback shift registers.

  14. Explaining (Missing) Regulator Paradigm Shifts

    DEFF Research Database (Denmark)

    Wigger, Angela; Buch-Hansen, Hubert

    2014-01-01

    of competition regulation is heaving into sight. It sets out to explain this from the vantage point of a critical political economy perspective, which identifies the circumstances under which a crisis can result in a regulatory paradigm shift. Contrasting the current situation with the shift in EC/EU competition...... capitalism; the social power configuration underpinning the neoliberal order remains unaltered; no clear counter-project has surfaced; the European Commission has been (and remains) in a position to oppose radical changes; and finally, there are no signs of a wider paradigm shift in the EU's regulatory...

  15. Key World Energy Statistics

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-07-01

    The IEA produced its first handy, pocket-sized summary of key energy data in 1997. This new edition responds to the enormously positive reaction to the book since then. Key World Energy Statistics produced by the IEA contains timely, clearly-presented data on supply, transformation and consumption of all major energy sources. The interested businessman, journalist or student will have at his or her fingertips the annual Canadian production of coal, the electricity consumption in Thailand, the price of diesel oil in Spain and thousands of other useful energy facts. It exists in different formats to suit our readers' requirements.

  16. Requirements: The Key to Sustainability

    OpenAIRE

    2016-01-01

    Software's critical role in society demands a paradigm shift in the software engineering mind-set. This shift's focus begins in requirements engineering. This article is part of a special issue on the Future of Software Engineering.

  17. Light-shift measurement and suppression in atomic spin gyroscope.

    Science.gov (United States)

    Fang, Jiancheng; Wan, Shuangai; Chen, Yao; Li, Rujie

    2012-11-01

    We present a method to determine and suppress the light shift in an atomic spin gyroscope. This method doesn't require additional drive source or frequency modulation, and it is based on the dynamics of an atomic spin gyroscope to determine a clean curve as a function of the frequency of the pump beam that predicts the zero light shift. We experimentally validate the method in a Cs-(129)Xe atomic spin gyroscope and verify the results through numerical simulations. This method can also be applied to an atomic spin magnetometer based on the spin-exchange relaxation-free exchange that experiences light shift. The method is useful for atomic spin devices because it can improve long-term performance and reduce the influence of the laser.

  18. Analytical bit error rate performance evaluation of an orthogonal frequency division multiplexing power line communication system impaired by impulsive and Gaussian channel noise

    OpenAIRE

    Munshi Mahbubur Rahman; Satya Prasad Majumder

    2015-01-01

    An analytical approach is presented to evaluate the bit error rate (BER) performance of a power line (PL) communication system considering the combined influence of impulsive noise and background PL Gaussian noise. Middleton class-A noise model is considered to evaluate the effect of impulsive noise. The analysis is carried out to find the expression of the signal-to-noise ratio and BER considering orthogonal frequency division multiplexing (OFDM) with binary phase shift keying modulation wit...

  19. Reed Solomon Coding for Frequency Hopping Spread Spectrum in Jamming Environment

    Directory of Open Access Journals (Sweden)

    Othman Sidek

    2008-01-01

    Full Text Available Frequency hopping spread spectrum with noncoherent M-ary frequency shift keying system is considered. In this study Reed Solomon codes RS (255, 223 are employed in a standard error correction role to provide some Anti-Jamming (AJ capability with 8-bit symbols. Noise has been added to RS encoded data, which is demodulated at RS decoder perfectly. Matlab simulations have been implemented for numerical results. Graphical results have been plotted between the probability of an erasure versus ρ using RS (255, 223 code for 1 and 2 kHz frequencies. The simulation results have proved that system having RS (255, 223 code with M = 32 require substantially less signal to jammer power ratio to achieve the same bit error probability.

  20. Locks and Keys Service

    CERN Multimedia

    Claude Ducastel

    The GS-LS-SEM section is pleased to inform you that as from Monday 30 November 2009, the opening hours of the Locks and Keys service will be the following: 08h30 - 12h30 / 13h30 - 16:30, Mondays to Fridays. GS-SEM-LS 73333