Robust DOA Estimation for Sources with Known Waveforms Against Doppler Shifts via Oblique Projection

As known, utilization of the information about signal waveform can improve the direction of arrival (DOA) estimation results. However, with a fast moving platform, Doppler effect occurs, which distorts the known waveforms and may result in large DOA estimation bias and even error for conventional DOA estimation methods for sources with known waveforms. To deal with this problem, a robust DOA estimation method for sources with known waveforms against Doppler shifts is developed. The proposed method first transforms the nonlinear mixing of Doppler shifts in the model to an approximately linear one using discrete-time Fourier transform (DTFT) and finite Taylor series expansion. Then, multiple oblique projectors are constructed to separate each component corresponding to different order of derivatives. Finally, estimations of DOAs, complex amplitudes and Doppler shifts are obtained simultaneously. Simulation results show that the proposed method has a much more robust DOA estimation performance than existing methods for sources with known waveforms

Laser frequency stabilization using folded cavity and mirror reflectivity tuning

International audienceA new method of laser frequency stabilization using polarization property of an optical cavity is proposed. In a standard Fabry–Perot cavity, the coating layers thickness of cavity mirrors is calculated to obtain the same phase shift for sand p-wave but a slight detuning from the nominal thickness can produce sand p-wave phase detuning. As a result, each wave accumulates a different round-trip phase shift and resonates at a different frequency. Using this polarization property, an error signal is generated by a simple setup consisting of a quarter wave-plate rotated at 45°, a polarizing beam splitter and two photodiodes. This method exhibits similar error signal as the Pound–Drever–Hall technique but without need for any frequency modulation. Lock theory and experimental results are presented in this paper.

ACTIVATION OF DIFFERENT CEREBRAL FUNCTIONAL REGIONS FOLLOWING ACUPUNCTURE AT BOT H TAIXI AND TAICHONG ACUPOINTS AND TAIXI ACUPOINTALONE: AN FMRI STUDY

Background: To explore the brain function regions characteristics of the acupoint combination, this study observed activity changes in the brain regions of healthy volunteers after acupuncture at both Taixi (KI3) and Taichong (LR3) (KI3 + LR3) and KI3 alone using resting-state functional magnetic resonance imaging (fMRI). Methods and Materials: 30 healthy volunteers were randomly allocated into two groups, one group received acupuncture at KI3 and LR3, the other only acupuncture at KI3, 15 cases in each group. All volunteers underwent resting-state fMRI of the brain 15 minutes before acupuncture, and which the needle was retained in place for 30 minutes; 15 minutes after withdrawing the needle underwent a further session of resting-state fMRI. The amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) were used to analyze the changes in brain regions. Results: The KI3+LR3 group compared with the KI3 group, the ALFF analysis indicated that the brain changes relatively concentrated in BA 2, 3, 7, 8, 9, 10, 18, 19, 20, 31, 32, 40, 46 and the cerebellum posterior lobe, the ReHo analysis indicated that the brain changes relatively concentrated in BA 4, 6, 7, 10, 11, 18, 19, 20, 21, 22, 31, 40 and the cerebellum posterior lobe. Conclusion: Based on this study, compared with acupuncture at KI3, acupuncture at KI3 + LR3 which could specifically influence BA 7, 10, 18, 19, 20, 31, 40 and cerebellum posterior lobe, which may be related to synergy mechanism of two acupoints combination treatment

Partial wave analysis of J/\psi \to \gamma \phi \phi

Using $5.8 \times 10^7 J/\psi$ events collected in the BESII detector, the radiative decay $J/\psi \to \gamma \phi \phi \to \gamma K^+ K^- K^0_S K^0_L$ is studied. The $\phi\phi$ invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/$c^{2}$. A partial wave analysis shows that the structure is dominated by a $0^{-+}$ state ($\eta(2225)$) with a mass of $2.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02}$ GeV/$c^{2}$ and a width of $0.19 \pm 0.03^{+0.06}_{-0.04}$ GeV/$c^{2}$. The product branching fraction is: $Br(J/\psi \to \gamma \eta(2225))\cdot Br(\eta(2225)\to \phi\phi) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}$.Comment: 11 pages, 4 figures. corrected proof for journa

Measurements of the observed cross sections for e+e−→e^+e^-\to exclusive light hadrons containing π0π0\pi^0\pi^0 at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV

By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$, $K^+K^-\pi^0\pi^0$, $2(\pi^+\pi^-\pi^0)$, $K^+K^-\pi^+\pi^-\pi^0\pi^0$ and $3(\pi^+\pi^-)\pi^0\pi^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay into these final states at 90% C.L..Comment: 7 pages, 2 figure

Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays

By analyzing about 33 $\rm pb^{-1}$ data sample collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we directly measure the branching fractions for the neutral and charged $D$ inclusive semimuonic decays to be $BF(D^0 \to \mu^+ X) =(6.8\pm 1.5\pm 0.7)$ and $BF(D^+ \to \mu^+ X) =(17.6 \pm 2.7 \pm 1.8)$, and determine the ratio of the two branching fractions to be $\frac{BF(D^+ \to \mu^+ X)}{BF(D^0 \to \mu^+ X)}=2.59\pm 0.70 \pm 0.25$

A study of charged kappa in J/ψ→K±Ksπ∓π0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0

Based on $58 \times 10^6$ $J/\psi$ events collected by BESII, the decay $J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0$ is studied. In the invariant mass spectrum recoiling against the charged $K^*(892)^{\pm}$, the charged $\kappa$ particle is found as a low mass enhancement. If a Breit-Wigner function of constant width is used to parameterize the kappa, its pole locates at $(849 \pm 77 ^{+18}_{-14}) -i (256 \pm 40 ^{+46}_{-22})$ MeV/$c^2$. Also in this channel, the decay $J/\psi \to K^*(892)^+ K^*(892)^-$ is observed for the first time. Its branching ratio is $(1.00 \pm 0.19 ^{+0.11}_{-0.32}) \times 10^{-3}$.Comment: 14 pages, 4 figure

Evolution of the nuclear spin-orbit splitting explored via the ³²Si<i>(d,p)</i>³³Si reaction using SOLARIS

The spin-orbit splitting between neutron 1p orbitals at 33Si has been deduced using the single-neutron-adding (d,p) reaction in inverse kinematics with a beam of 32Si, a long-lived radioisotope. Reaction products were analyzed by the newly implemented SOLARIS spectrometer at the reaccelerated-beam facility at the National Superconducting Cyclotron Laboratory. The measurements show reasonable agreement with shell-model calculations that incorporate modern cross-shell interactions, but they contradict the prediction of proton density depletion based on relativistic mean-field theory. The evolution of the neutron 1p-shell orbitals is systematically studied using the present and existing data in the isotonic chains of = 17, 19, and 21. In each case, a smooth decrease in the separation of the - orbitals is seen as the respective p-orbitals approach zero binding, suggesting that the finite nuclear potential strongly influences the evolution of nuclear structure in this region