Cavity pulling in Galileo Passive Hydrogen Maser

Multipath fading in HF channels causes time-delay spread that limits the maximum symbol rate, and frequency selective fading that attenuates some frequency bands compared to others. Multi-carrier modulation techniques, multi-carrier ASK (MCASK) and multi-carrier PSK (MCPSK), can be used to ensure reliability of transmission and high data transmission rate. The bit-error rate (BER) performance is compared between single frequency modulation such as amplitude shift-keying (ASK) or phase shift-keying (PSK) and the multi-carrier modulation in the presence of additive white Gaussian noise and a combination of multipath fading and additive white Gaussian noise. On the average, the BER performance is better for the multi-carrier modulation compared to the single carrier modulation under multipath fading conditions.

被动型氢原子钟单频调制的鉴频特性研究

Substantial progress in the field of light spectroscopy and imaging of tissues was achieved when the group of Chance, Patterson and Wilson showed that the optical parameters of a turbid medium can be obtained from time resolved measurements of short light pulses propagating in the medium (Patterson et al, 1991a). Essentially, a fit of the intensity as a function of time, measured at some distance from the source, can provide separately the values of the absorption and of the reduced scattering coefficients. This demonstration was important because the focus was shifted from attempts to separate the scattering from absorption, using empirical corrections to the Beer-Lambert law, to a rigorous application of a physical model. During the same period, our lab proposed employing the Fourier transform equivalent concept using an intensity modulated light source (Gratton et al, 1990). Since frequency domain methods have better resolution and sensitivity and are much faster than the time domain methods, our proposal was followed by many others including Chance, Patterson and Wilson (Boas et al, 1993, 1994; Cui and Ostrander, 1993; Duncan et al, 1993; Kaltenbach and Kaschke, 1993; O’Leary et al, 1992; Patterson et al, 1991b; Tromberg et al, 1993). It is well known that time domain and frequency domain measurements are mathematically equivalent, when the frequency domain measurement is carried out using a wide range of modulation frequencies (Gratton et al, 1983; Alcala et al, 1984). However, frequency domain measurements can be made at a single modulation frequency, thereby sacrificing some of the information. The advantage of measurements at a single frequency is that they can be very fast, accurate and have an excellent signal-to-noise ratio.

We present a distributed optical fiber sensor based on a hybrid Brillouin optical frequency/correlation-domain analysis (BOFDA/BOCDA) configuration for both static and dynamic strain measurements. Distributed static strain (or temperature) measurements are realized using the conventional BOFDA method, i.e., acquiring the baseband transfer function of the fiber through a vector network analyzer (VNA). With little modifications, the same setup can perform dynamic, position-selective measurements synthesizing a correlation peak through a frequency modulation of the laser source while operating the VNA at a single modulation frequency. Experimental tests, carried out at a sampling frequency up to 40 Hz and a spatial resolution of ≈5 cm, demonstrate the validity of the proposed approach.

The single frequency dithering technique for coherent beam combination with one single modulation frequency and without a reference beam is presented for the first time to our knowledge. Coherent beam combination of four fiber amplifiers is successfully demonstrated by using the single-dithering technique. When the phase control system is in the closed loop, the fringe contrast of far-field intensity pattern is improved by more than 85% from 8% in open loop, and the residual phase error is less than lambda/20. Experimental results reveal that the single-dithering technique has great potential in scaling to a large number of beamlets with a simple phase control system and low cost.

Analysis of multi-component fluorescence emission by phase-sensitive detection using one modulation frequency

We present a novel phase unwrapping framework for the Time-of-Flight sensor that can match the performance of systems using two modulation frequencies, within a single shot. Our framework is based on an interleaved pixel arrangement, where a pixel measures phase at a different modulation frequency from its neighboring pixels. We demonstrate that: (1) it is practical to capture ToF images that contain phases from two frequencies in a single shot, with no loss in signal fidelity, (2) phase unwrapping can be effectively performed on such an interleaved phase image, and (3) our method preserves the original spatial resolution. We find that the output of our framework is comparable to results using two shots under separate modulation frequencies, and is significantly better than using a single modulation frequency.

Analytic Mode Decomposition and Windowed Three-Point Interpolated Chirp-Z Transform for Voltage Flicker Components Detection

A systematic evaluation of the selection criteria of non-aqueous phases in two liquid phase bioreactors (TLPBs), also named two-phase partitioning bioreactors (TPPBs), was carried out using the biodegradation of alpha-pinene by Pseudomonas fluorescens NCIMB 11671 as a model process. A preliminary solvent screening was thus carried out among the most common non-aqueous phases reported in literature for volatile organic contaminants biodegradation in TLPBs: silicon oil, paraffin oil, hexadecane, diethyl sebacate, dibutyl-phtalate, FC 40, 1,1,1,3,5,5,5-heptamethyltrisiloxane (HMS), and 2,2,4,4,6,8,8-heptamethylnonane (HMN). FC 40, silicone oil, HMS, and HMN were first selected based on its biocompatibility, resistance to microbial attack, and alpha-pinene mass transport characteristics. FC 40, HMS, HMN, and silicone oil at 10% (v/v) enhanced alpha-pinene mass transport from the gas to the liquid phase by a factor of 3.8, 14.8, 11.4, and 8.6, respectively, compared to a single-phase aqueous system. FC 40 and HMN were finally compared for their ability to enhance alpha-pinene biodegradation in a mechanically agitated bioreactor. The use of FC 40 or HMN (both at 10% v/v) sustained non-steady state removal efficiencies (RE) and elimination capacities (EC) approximately 7 and 12 times higher than those achieved in the system without an organic phase, respectively. In addition, preliminary results showed that P fluorescens could uptake and mineralize alpha-pinene directly from the non aqueous phase.

For targets with complex motion, such as ships fluctuating with oceanic waves and high maneuvering airplanes, azimuth echo signals can be modeled as multicomponent quadratic frequency modulation (QFM) signals after migration compensation and phase adjustment. For the QFM signal model, the chirp rate (CR) and the quadratic chirp rate (QCR) are two important physical quantities, which need to be estimated. For multicomponent QFM signals, the cross terms create a challenge for detection, which needs to be addressed. In this paper, by employing a novel multi-scale parametric symmetric self-correlation function (PSSF) and modified scaled Fourier transform (mSFT), an effective parameter estimation algorithm is proposed—referred to as the Two-Dimensional product modified Lv’s distribution (2D-PMLVD)—for QFM signals. The 2D-PMLVD is simple and can be easily implemented by using fast Fourier transform (FFT) and complex multiplication. These measures are analyzed in the paper, including the principle, the cross term, anti-noise performance, and computational complexity. Compared to the other three representative methods, the 2D-PMLVD can achieve better anti-noise performance. The 2D-PMLVD, which is free of searching and has no identifiability problems, is more suitable for multicomponent situations. Through several simulations and analyses, the effectiveness of the proposed estimation algorithm is verified.

Speech recognition performance in noise was examined in children with cochlear implants (CIs) when using (a) a second CI (bilateral group), (b) a hearing aid (HA) on the nonimplant ear (bimodal group), and (c) a frequency modulation (FM) system on 1 or both sides. While always maintaining use of the first CI, 2 groups participated in 6 conditions each using various listening arrangements with the second CI, HA, or FM system. Speech-in-noise thresholds were determined using simple phrases, classroom noise, and a method-of-limits approach. No group differences were detected across any conditions. In the no-FM-system conditions, no significant benefit of bilateral or bimodal input was found relative to a single CI. In the FM-system conditions, thresholds were significantly lower (up to 20 dB) relative to all other conditions when FM-system input was provided to the first-implanted side or to both sides simultaneously. Children's speech-in-noise thresholds did not improve when providing input to the second side with a CI or an HA relative to a single CI. However, children with CIs had better speech recognition in noise with the use of an FM system on one or both sides relative to the conditions with no FM system. Binaural conditions with a single FM receiver on the second CI or HA yielded significantly poorer performance than any other FM condition.

We report a new mechanism of direct frequency modulation, the cavity-mode enhanced frequency modulation (CME-FM), using the newly developed cleaved-coupled-cavity (C3) semiconductor laser. In this operation, one of the diode of the C3 laser was operated as a laser, while the other diode was operated as a frequency modulator. It was shown that a very large frequency excursion of 150 Å and frequency tuning rate of 10 Å/mA have been obtained with a C3 GaInAsP crescent laser operating at 1.3 μm. Time-resolved spectral and spectral-resolved pulse response measurements also showed that such C3 lasers operated in highly stable single-longitudinal mode at all times even under high-speed direct frequency modulation. In addition to the important application as the optical source in FM optical communication systems, the present CME-FM C3 laser can also be used as the optical source in wavelength-division multiplexing systems. Further, it opens the possibility of ultrahigh capacity multilevel optical FM information transmission systems.

Single and multiple period modulation doped GaAs–Ga1-xAlxAs heterostructures have been grown by atmospheric pressure metalorganic vapour phase epitaxy (AP-MOVPE). Single period structures exhibit electron mobilities of 6700, 80000 and 90000 cm2·V-1·s-1 at 300 K, 77 K, and 4 K for a sheet carrier concentration of 7.4×1011 cm-2, 8.3×1011 cm-2 and 3.9×1011 cm-2 respectively. To our knowledge, these values represent the best mobilities reported in this structure grown by AP-MOVPE. Preliminary results on field effect transistors show a three fold increase of transconductance as temperature decreases from ambient to 77 K. Furthermore, we report mobility enhancement in “inverted” structures in which the conducting accumulation layers are located at the interfaces formed by growth of GaAs on top of (Ga, Alcp)As.

1038. Lentiviral Gene Transfer into HSC Is Enhanced by Early-Acting Cytokines without Impairing Stem Cell Properties and Involves Cellular Responses Distinct from Cell Cycle Control

T Targeted at the existing complex structure, numerous switching components and high control difficulty of existing equalization circuit of lithium-ion battery series, this paper proposes an active equalization topology circuit based on multi-input transformer. The equalization circuit is composed of battery module, fly-wheel diode, MOS transistor and transformer. Based on the classification and summary of battery equalization topology, this paper analyzes and studies the principle of active equalization topology based on multi-input transformers. The working principle is simple, with the use of fewer devices. Matlab/Simulink is applied to build a model for simulation analysis, and the simulation results show that switching frequency and series module capacity have an impact on the equalization effects. The equalization comparison rate simulation of the series capacitor module and the single module indicates that the proposed topology has a faster equalization speed for multiple modules. The simulation results verify the validity of the proposed topology in voltage equalization between different modules.