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Artigos de revistas sobre o tema "Ultra Stable Oscillator"

Autor: Grafiati

Publicado: 7 de dezembro de 2024

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1

Liu, Anni, Jian Dai e Kun Xu. "Stable and Low-Spurs Optoelectronic Oscillators: A Review". Applied Sciences 8, n.º 12 (14 de dezembro de 2018): 2623. http://dx.doi.org/10.3390/app8122623.

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An optoelectronic oscillator (OEO) is an optoelectronic hybrid oscillator which utilizes ultra-low loss fiber as an electro-magnetic energy storage element, overcoming the limits of traditional microwave oscillators in phase noise performance. Due to their ability to generate ultra-low phase noise microwave signal, optoelectronic oscillators have attracted considerable attentions and are becoming one of the most promising and powerful microwave signal sources. In this paper, we briefly introduce the operation principle and discuss current research on frequency stability and spurious suppression of optoelectronic oscillators.

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Luiten, A. N., A. G. Mann, A. J. Giles e D. G. Blair. "Ultra-stable sapphire resonator-oscillator". IEEE Transactions on Instrumentation and Measurement 42, n.º 2 (abril de 1993): 439–43. http://dx.doi.org/10.1109/19.278600.

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3

Liu, Rui Hong, e Chih Hsiung Shen. "A High Resolution Vernier Ring Oscillator with Ultra-Low Temperature Drift". Advanced Materials Research 542-543 (junho de 2012): 795–99. http://dx.doi.org/10.4028/www.scientific.net/amr.542-543.795.

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Nowadays, the precise measurement of the time interval between two events with very fine timing resolution is common challenge in the test and measurement instrumentation. This paper present a new high resolution vernier ring oscillator(VRO), which can measures the clock jitter as the operation temperature rises.The goal of this work focuses on the design of a TDC of temperature stable oscillator and we propose an ultra-low temperature drift of a differential delay cell oscillator based on a proportional to absolute temperature(PTAT) compensation methodology. It is very desirable to have a single integrated circuit producing a stable high resolution timing circuit over a wide temperature range developed in a standard CMOS process. By the simple concept of vernier delay line and two ring oscillators, the proposed can achieve a fine time resolution with wide working temperature. For each channel of ring oscillator, the relative delay time is fine tuned by an external VBIAS input. From 25°Cto 45°C, the maximum error percent of delay time without compensation circuits is more than 2.9%, but it with compensation circuits is less than 0.3%. The different operating temperature will affect entire circuit and the delay time of ring oscillator. A compensation circuit to reduce the variety of ring oscillator is also added. The new architecture of high resolution TDC with temperature compensated circuit is proven to be applicable in high precision clock applications which is analyzed and implemented in a CMOS 0.18μm 1P6M process.

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4

Salzenstein, Patrice, Nathalie Cholley, Alexander Kuna, Philippe Abbé, Franck Lardet-Vieudrin, Ludvík Šojdr e Jacques Chauvin. "Distributed amplified ultra-stable signal quartz oscillator based". Measurement 45, n.º 7 (agosto de 2012): 1937–39. http://dx.doi.org/10.1016/j.measurement.2012.03.035.

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5

Galliou, S., e M. Mourey. "Temperature processing of an ultra stable quartz oscillator". IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 48, n.º 6 (novembro de 2001): 1539–46. http://dx.doi.org/10.1109/58.971705.

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6

Fluhr, C., B. Dubois, S. Grop, J. Paris, G. Le Tetû e V. Giordano. "A low power cryocooled autonomous ultra-stable oscillator". Cryogenics 80 (dezembro de 2016): 164–73. http://dx.doi.org/10.1016/j.cryogenics.2016.10.007.

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7

Bourgeois, P. Y., Y. Kersalé, N. Bazin, M. Chaubet e V. Giordano. "Cryogenic opened cavity sapphire resonator for ultra-stable oscillator". Electronics Letters 39, n.º 10 (2003): 780. http://dx.doi.org/10.1049/el:20030509.

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8

Galliou, Serge, e Marc Mourey. "Electro-thermal simulation of an ultra stable quartz oscillator". International Journal of Thermal Sciences 41, n.º 2 (fevereiro de 2002): 173–81. http://dx.doi.org/10.1016/s1290-0729(01)01295-9.

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9

IKEGAMI, Takeshi, e Ken-ichi WATABE. "An Ultra-Stable Microwave Oscillator using a Cryogenic Sapphire Crystal Towards the Most Stable Oscillator on Earth". TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan) 50, n.º 6 (2015): 322–29. http://dx.doi.org/10.2221/jcsj.50.322.

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10

Peng, Jiankang, Liufeng Li e Lisheng Chen. "A spaceborne neodymium-doped yttrium aluminum garnet laser with nonplanar-ring-oscillator configuration". International Journal of Modern Physics A 36, n.º 11n12 (22 de março de 2021): 2140007. http://dx.doi.org/10.1142/s0217751x21400078.

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Due to their excellent noise performance and technical maturity, ultra-stable continuous-wave neodymium-doped yttrium aluminum garnet lasers are one of the major light sources in a series of precision measurements such as ground and space-based gravitational wave detection, inter-satellite laser ranging and coherent optical communication. As the first step of developing an ultra-stable spaceborne laser, we carried out the design, development and environmental test of an all-solid-state Nd:YAG NPRO spaceborne laser. The laser deliveries 11.48 mW of optical power at 1064.405 nm, exhibits intensity and frequency noises less than 1 × 10[Formula: see text]/[Formula: see text]Hz and 1 MHz/[Formula: see text]Hz (Fourier frequencies [Formula: see text] 10 mHz), respectively, passed environmental tests and has been onboard the first satellite of the Taiji program for one year. The work laid a solid foundation for realizing ultra-stable lasers for the Taiji program as well as being used in many space applications.

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11

kumari B.S, Priyanka, e Dr Sobhit Saxena. "Design and Analysis of Ultra-low Power Voltage Controlled Oscillator in Nanoscale Technologies". International Journal of Electrical and Electronics Research 12, n.º 1 (15 de janeiro de 2024): 12–19. http://dx.doi.org/10.37391/ijeer.120103.

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In latest wired and wireless communication equipment, VCO (voltage-controlled oscillator) is the major building block and particularly used as the stable high frequency clock generator. VCO performance is measured through frequency range, power supply used, area occupied, power consumption, delay, and phase noise. VCO is the cascaded of odd number of inverter stages in a ring format, hence it is also articulated as a ring oscillator. Today’s portable communication devices are battery operated. Hence, low power and area efficient designs play a key role in battery life enhancement and device size reduction. Device scaling improves the effective silicon area utilization, but it leads to more leakages. Therefore, low power techniques along with the technology scaling is the best way of low power designs. In this article, discussed various low power schemes. The ring oscillator designs are carried out in various nano meter scaled technologies such as 180nm, 90nm,65nm and 45nm. A 5-stage ring oscillator is implemented in each technology along with low power schemes, simulated in Cadence virtuoso, and noted power, delay, and area. Observed that the proposed ring oscillator with sleepy keeper technique generated a stable frequency of oscillations in the range of 1GHz-2GHz. A control voltage of 1.8V to 0.4V is applied and targeted the power less than 30mW and delay in 0.25p sec.

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Rabbi, Md Hasnat, Arqum Ali, Jinbaek Bae, Abul Tooshil, Chanju Park e Jin Jang. "P‐28: High‐speed Oscillator using Polycrystalline InGaO TFTs by Spray Pyrolysis on Polyimide Substrate for Flexible Electronics". SID Symposium Digest of Technical Papers 55, n.º 1 (junho de 2024): 1463–66. http://dx.doi.org/10.1002/sdtp.17827.

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We demonstrate high‐performance coplanar thin film transistors (TFTs) on polyimide (PI) substrate, with very thin polycrystalline InGaO (poly‐IGO) thin films deposited by spray‐pyrolysis. The TFTs exhibit saturation mobility (µSAT) of ~39.25 ± 0.73 cm2 V−1 s−1, with excellent uniformity and stable bias stabilities (ΔVTH = +0.3 V for PBTS, ΔVTH = −0.3 V for NBTS). The 7‐stage ring oscillator made of the corresponding TFTs exhibits a very high oscillation frequency of 9.09 MHz at VDD of 15 V with ultra‐low propagation delay time of 7.86 ns/stage.

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13

Zhenghua, Zhou, Yang Chun, Cao Zhewei, Chong Yuhua e Li Xianghua. "An Ultra-Low Phase Noise and Highly Stable Optoelectronic Oscillator Utilizing IL-PLL". IEEE Photonics Technology Letters 28, n.º 4 (15 de fevereiro de 2016): 516–19. http://dx.doi.org/10.1109/lpt.2015.2501369.

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14

Raut, Nabin K., Jeffery Miller e Jay Sharping. "Progress in Optoelectronic Oscillators". Journal of Institute of Science and Technology 24, n.º 1 (26 de junho de 2019): 26–33. http://dx.doi.org/10.3126/jist.v24i1.24625.

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An optoelectronic oscillator (OEO) generates a spectrally pure and ultra-stable radio frequency signal from a continuous wave laser source (Yao et al. 2004). In a conventional electrical oscillator, the energy storage capacity is limited, which compromises stability of the signal. To address this issue, Yao and Maleki invented the optoelectronic oscillator in 1996. This novel oscillator uses low-loss optical fiber to extend the length of the oscillator and thereby increases the amount of energy that can be stored (Madjar & Tibor 2006). Due to this additional energy storing component in the system, the purity and stability of the signal increase significantly. Following their invention, many modifications have been made over the years to improve the frequency stability of OEOs (lower phase noise and timing jitter). This review article discusses some of those key developments and then introduces some ongoing work devoted to understanding the impact of using electrical filters with Q >109.

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15

Dick, G. J., D. G. Santiago e R. T. Wang. "Temperature-compensated sapphire resonator for ultra-stable oscillator capability at temperatures above 77 K". IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 42, n.º 5 (setembro de 1995): 812–19. http://dx.doi.org/10.1109/58.464836.

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16

Liu, Jianguo, Gregory S. Kanter, Shawn X. Wang e Prem Kumar. "10GHz ultra-stable short optical pulse generation via phase-modulation enhanced dual-loop optoelectronic oscillator". Optics Communications 285, n.º 6 (março de 2012): 1035–38. http://dx.doi.org/10.1016/j.optcom.2011.11.053.

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17

Fu, Hailing, Stephanos Theodossiades, Ben Gunn, Imad Abdallah e Eleni Chatzi. "Ultra-low frequency energy harvesting using bi-stability and rotary-translational motion in a magnet-tethered oscillator". Nonlinear Dynamics 101, n.º 4 (setembro de 2020): 2131–43. http://dx.doi.org/10.1007/s11071-020-05889-9.

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Abstract Harvesting ultra-low frequency random vibration, such as human motion or turbine tower oscillations, has always been a challenge, but could enable many potential self-powered sensing applications. In this paper, a methodology to effectively harness this type of energy is proposed using rotary-translational motion and bi-stability. A sphere rolling magnet is designed to oscillate in a tube with two tethering magnets underneath the rolling path, providing two stable positions for the oscillating magnet. The generated magnetic restoring forces are of periodic form with regard to the sphere magnet location, providing unique nonlinear dynamics and allowing the harvester to operate effectively at ultra-low frequencies (< 1 Hz). Two sets of coils are mounted above the rolling path, and the change of magnetic flux within the coils accomplishes the energy conversion. A theoretical model, including the magnetic forces, the electromagnetic conversion and the occurring bi-stability, is established to understand the electromechanical dynamics and guide the harvester design. End linear springs are designed to maintain the periodic double-well oscillation when the excitation magnitude is high. Parametric studies considering different design factors and operation conditions are conducted to analyze the nonlinear electromechanical dynamics. The harvester illustrates its capabilities in effectively harnessing ultra-low frequency motions over a wide range of low excitation magnitudes.

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18

Shang, Yaping, Jiangming Xu, Peng Wang, Xiao Li, Pu Zhou e Xiaojun Xu. "Ultra-stable high-power mid-infrared optical parametric oscillator pumped by a super-fluorescent fiber source". Optics Express 24, n.º 19 (9 de setembro de 2016): 21684. http://dx.doi.org/10.1364/oe.24.021684.

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19

Maciuk e Lewińska. "High-Rate Monitoring of Satellite Clocks Using Two Methods of Averaging Time". Remote Sensing 11, n.º 23 (22 de novembro de 2019): 2754. http://dx.doi.org/10.3390/rs11232754.

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Knowledge of the global navigation satellite system (GNSS) satellite clock error is crucial in real-time precise point positioning (PPP), seismology, and many other high-rate GNSS applications. In this work, the authors show the characterisation of the atomic GNSS clock’s stability and its dependency on the adopted orbit type using Allan deviation with two methods of averaging time. Four International GNSS Service (IGS) orbit types were used: broadcast, ultra-rapid, rapid and final orbit. The calculations were made using high-rate 1 Hz observations from the IGS stations equipped with external clocks (oscillators). The most stable receiver oscillator was chosen as a reference clock. The results show the advantage of the newest GPS satellite block with respect to the other satellites. Significant differences in the results based on the orbit type used have not been recorded. Many averaging time methods used in Allan deviation (ADEV) show the clock’s fluctuations, usually smoothed in 2n s averaging times.

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20

Fu, Zhenwei, Zhen Zeng, Huan Tian, Weiqiang Lyu, Lingjie Zhang, Yaowen Zhang, Zhiyao Zhang et al. "Phase-locked dual-frequency microwave signal generation in an optoelectronic oscillator based on frequency mixing mutual injection". Optics Express 32, n.º 8 (29 de março de 2024): 13825. http://dx.doi.org/10.1364/oe.520158.

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An approach to generating stable phase-locked dual-frequency microwave signals is proposed and demonstrated based on a dual-passband optoelectronic oscillator (OEO). Mode gain competition is broken by employing frequency mixing mutual injection effect to realize phase locking between the two oscillation signals, which is achieved by applying a single-tone signal to a microwave mixer in the OEO cavity. In addition, a dual-loop configuration with balanced detection is utilized to ensure a high side mode suppression ratio (SMSR) and ultra-low phase noise, which also enhances the stability of the generated signal. In the experiment, a phase-locked dual-frequency microwave signal at 9.9982 GHz and 10.1155 GHz is generated by using the proposed OEO scheme. The SMSR and the phase noise are 75 dB and –141 dBc/Hz@10 kHz, respectively. Additionally, the Allan deviation of the generated signal is in the order of 10−11@1 s. These parameters are superior to those based on the same OEO but with a single-loop configuration, which are also compared in detail.

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21

Hua, Yi, Henrik Tünnermann, Caterina Vidoli, Haydar Sarper Salman, Yuxuan Ma, Uwe Grosse-Wortmann, Lutz Winkelmann e Ingmar Hartl. "Packaging of an ultra-stable all-fiber-integrated NALM oscillator at 1 μm center wavelength for FEL facilities". EPJ Web of Conferences 267 (2022): 02034. http://dx.doi.org/10.1051/epjconf/202226702034.

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22

Nand, Nitin R., John G. Hartnett, Eugene N. Ivanov e Giorgio Santarelli. "Ultra-Stable Very-Low Phase-Noise Signal Source for Very Long Baseline Interferometry Using a Cryocooled Sapphire Oscillator". IEEE Transactions on Microwave Theory and Techniques 59, n.º 11 (novembro de 2011): 2978–86. http://dx.doi.org/10.1109/tmtt.2011.2166976.

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23

NAKAZAWA, M., M. YOSHIDA e T. HIROOKA. "Ultra-Stable Regeneratively Mode-Locked Laser as an Opto-Electronic Microwave Oscillator and Its Application to Optical Metrology". IEICE Transactions on Electronics E90-C, n.º 2 (1 de fevereiro de 2007): 443–49. http://dx.doi.org/10.1093/ietele/e90-c.2.443.

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Wang, Wenxuan, Yi Liu, Xinwei Du, Xiaoxuan Zhong, Changyuan Yu e Xiangfei Chen. "Ultra-Stable and Real-Time Demultiplexing System of Strong Fiber Bragg Grating Sensors Based on Low-Frequency Optoelectronic Oscillator". Journal of Lightwave Technology 38, n.º 4 (15 de fevereiro de 2020): 981–88. http://dx.doi.org/10.1109/jlt.2019.2949682.

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Ruan, Jun, Xinliang Wang, Hui Zhang, Dandan Liu, Yong Guan, Junru Shi, Yang Bai et al. "Atom Fountains at NTSC". Journal of Physics: Conference Series 2889, n.º 1 (1 de novembro de 2024): 012037. http://dx.doi.org/10.1088/1742-6596/2889/1/012037.

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Abstract Atom fountains as primary frequency standard (PFS) and continuously operated clocks have been developed to improve the local time scale at the National Time Service Center (NTSC), Chinese Academy of Sciences. Cesium fountain NTSC-CsF2 as PFS showed that the type B uncertainty was evaluated at 4.3 × 10−16. Frequency comparisons were completed between NTSC-CsF2 and the SI second through a GNSS link for 14 months, the results of which were consistent with those of the other fountains within the uncertainty. A cryogenic Cs fountain is being developed to reduce the blackbody radiation shift (BBR) and verify the BBR theory. An Rb fountain clock NTSC-RbF1 was operated to generate local and EAL time scale. The frequency drift was reduced by maintaining a stable vapor pressure. NTSC-RbF2 features a more robust optical system consisting of all fiber-optical components and an ultra-stable OCXO as a local oscillator. An instability time scale below 100 ps is expected based on the Rb atom fountain clocks.

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Mrad, Mohamad, Ahmad Tarhini, Pierre-Yves Bourgeois e Vincent Giordano. "Physics of the sapphire whispering-gallery-mode solid-state MASER oscillator". European Physical Journal Applied Physics 91, n.º 3 (setembro de 2020): 31001. http://dx.doi.org/10.1051/epjap/2020200107.

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The Cryogenic Sapphire Oscillator (CSO) is currently the best available technology that can provide a relative frequency stability better than 10−15 with integration times between 1 s and 10,000 s. But, the CSO remains a complex instrument that requires multiple loop controls to achieve the best frequency stability. The possibility to use the sapphire resonator in a self-sustained MASER oscillator presents an elegant alternative to the CSO. Here, sustaining the amplification is achieved through the interaction between a high-Q factor whispering gallery mode and the paramagnetic Fe3+ ions, which are present in small concentration in the sapphire crystal. The Fe3+ ion exhibits three energy states enabling to realize a self-sustaining solid-state maser. Although, this principle has been already experimentally demonstrated few years ago, its development as a truly usable ultra-stable source has not yet been completed, mainly due to the lack of control of the complex physical phenomena involved. This paper complements the previous theoretical work based on the rate equations model. Here we derive the full quantum equations describing the evolution of the Fe3+ ions inside the sapphire lattice and submitted to a pump and a maser signal. The influence of the ions concentration and spin-spin relaxation time will be pointed out.

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Jalabert, Eva, e Flavien Mercier. "Analysis of South Atlantic Anomaly perturbations on Sentinel-3A Ultra Stable Oscillator. Impact on DORIS phase measurement and DORIS station positioning". Advances in Space Research 62, n.º 1 (julho de 2018): 174–90. http://dx.doi.org/10.1016/j.asr.2018.04.005.

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Rasch, Joel, Anders Carlström, Jacob Christensen e Thomas Liljegren. "The GRAS-2 radio occultation mission". Atmospheric Measurement Techniques 17, n.º 20 (24 de outubro de 2024): 6213–22. http://dx.doi.org/10.5194/amt-17-6213-2024.

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Abstract. The second generation of the Global navigation satellite system Receiver for Atmospheric Sounding (GRAS-2) is a radio occultation (RO) instrument which is capable of providing 2000 atmospheric profiles per day. The instrument is hosted on all satellites in the MetOp Second Generation (MetOp-SG) series for polar orbit operation. The GRAS-2 instruments provide occultation measurements from the Galileo, GPS, and BeiDou satellites at their common frequencies centred at 1575.42 MHz (L1) and 1176.45 MHz (L5). Using high-gain antennas and an ultra-stable oscillator, neutral bending angles are measured at an unprecedented accuracy of 0.3–0.4 µrad, which is better than the requirement of less than 0.5 µrad. The RO signal will be measured deep into the troposphere using a novel open-loop tracking scheme utilizing multiple correlator outputs for operation with a tailored ground processing algorithm optimized for extracting signals with low amplitudes, approaching the noise floor limitation. Ionosphere measurements to an altitude of 600 km are also acquired.

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Ishak, S. N., J. Sampe, N. A. Nayan e Z. Yusoff. "A Fast Digital Phase Frequency Detector with Preset Word Frequency Searching in ADPLL for a UHF RFID Reader". Engineering, Technology & Applied Science Research 12, n.º 5 (2 de outubro de 2022): 9379–87. http://dx.doi.org/10.48084/etasr.5202.

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An All-Digital Phase-Locked Loop (ADPLL) is an architecture that is widely employed in the communication system due to the advancement of the Complementary Metal-Oxide-Semiconductor (CMOS) technology process. A 2.4GHz Radio Frequency Identification (RFID) system needs a frequency synthesizer in the local oscillator architecture of the transceiver to generate a stable frequency tuning range Therefore, in this paper, a Digital Phase-Frequency Detector (DPFD) is designed to achieve the phase and frequency acquisition in the ADPLL system. The proposed DPFD is divided into two main parts, the first is the Phase Detector (PD) and the second is the Frequency Detector (FD). The PD has managed to detect the presence of the phase difference by recognizing two different input signals. The FD, on the other hand, is capable to detect the higher frequency by identifying the output signals from the PD in digital formation. In addition, a control unit module is developed to control and adjust the Preset Word (PW) for the system by using a binary search scheme. Comparison results show that the final value of the PW from the simulation is the same as from the manual calculation (theoretical values). The digital PFD and the PW control modules are designed and simulated by using Verilog HDL code. These two designed modules will be integrated into the targeted ADPLL to achieve fast locking performance and ultra-low power for Ultra-High Frequency (UHF) RFID applications.

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Belli, Alexandre, P. Exertier, E. Samain, C. Courde, F. Vernotte, C. Jayles e A. Auriol. "Temperature, radiation and aging analysis of the DORIS Ultra Stable Oscillator by means of the Time Transfer by Laser Link experiment on Jason-2". Advances in Space Research 58, n.º 12 (dezembro de 2016): 2589–600. http://dx.doi.org/10.1016/j.asr.2015.11.025.

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Wang, Kai, Bai-Ke Lin, You-Jian Song, Fei Meng, Yi-Ge Lin, Shi-Ying Cao, Ming-Lie Hu e Zhan-Jun Fang. "Low-noise microwave generation based on optical-microwave synchronization". Acta Physica Sinica 71, n.º 4 (2022): 044204. http://dx.doi.org/10.7498/aps.71.20211253.

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Low-noise microwave signals are of vital importance in fields such as cold atomic optical clocks, photon radars, and remote synchronization at large facilities. Here, we report a compact all-optical-fiber method to generate a low noise microwave signal, in which the fiber loop optical-microwave phase detector is used to coherently transfer the frequency stability of the ultra-stable laser to the microwave. Combining a narrow linewidth optical frequency comb and a fiber loop optical-microwave phase discriminator, a tight phase-lock between 7 GHz dielectric oscillator and optical frequency comb is achieved, the remaining phase noise of the synchronized optical pulse sequence and the microwave signal is –100 dBc/Hz@1 Hz, and the timing jitter is 8.6 fs (1 Hz—1.5 MHz); by building two sets of low-noise microwave generation systems, the measured residual phase noise of the 7 GHz microwave is –90 dBc/Hz@1 Hz, and the corresponding frequency stability is 4.8 × 10<sup>–15</sup>@1 s. These results provide a novel idea for generating the low-noise microwaves based on optical coherent frequency division.

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Allahvirdi-Zadeh, Amir, Joseph Awange, Ahmed El-Mowafy, Tong Ding e Kan Wang. "Stability of CubeSat Clocks and Their Impacts on GNSS Radio Occultation". Remote Sensing 14, n.º 2 (13 de janeiro de 2022): 362. http://dx.doi.org/10.3390/rs14020362.

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Global Navigation Satellite Systems’ radio occultation (GNSS-RO) provides the upper troposphere-lower stratosphere (UTLS) vertical atmospheric profiles that are complementing radiosonde and reanalysis data. Such data are employed in the numerical weather prediction (NWP) models used to forecast global weather as well as in climate change studies. Typically, GNSS-RO operates by remotely sensing the bending angles of an occulting GNSS signal measured by larger low Earth orbit (LEO) satellites. However, these satellites are faced with complexities in their design and costs. CubeSats, on the other hand, are emerging small and cheap satellites; the low prices of building them and the advancements in their components make them favorable for the GNSS-RO. In order to be compatible with GNSS-RO requirements, the clocks of the onboard receivers that are estimated through the precise orbit determination (POD) should have short-term stabilities. This is essential to correctly time tag the excess phase observations used in the derivation of the GNSS-RO UTLS atmospheric profiles. In this study, the stabilities of estimated clocks of a set of CubeSats launched for GNSS-RO in the Spire Global constellation are rigorously analysed and evaluated in comparison to the ultra-stable oscillators (USOs) onboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC-2) satellites. Methods for improving their clock stabilities are proposed and tested. The results (i) show improvement of the estimated clocks at the level of several microseconds, which increases their short-term stabilities, (ii) indicate that the quality of the frequency oscillator plays a dominant role in CubeSats’ clock instabilities, and (iii) show that CubeSats’ derived UTLS (i.e., tropopause) atmospheric profiles are comparable to those of COSMIC-2 products and in situ radiosonde observations, which provided external validation products. Different comparisons confirm that CubeSats, even those with unstable onboard clocks, provide high-quality RO profiles, comparable to those of COSMIC-2. The proposed remedies in POD and the advancements of the COTS components, such as chip-scale atomic clocks and better onboard processing units, also present a brighter future for real-time applications that require precise orbits and stable clocks.

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Nguyen, Viet Khoi, Adria Rovira-Garcia, José Miguel Juan, Jaume Sanz, Guillermo González-Casado, The Vinh La e Tung Hai Ta. "Measuring phase scintillation at different frequencies with conventional GNSS receivers operating at 1 Hz". Journal of Geodesy 93, n.º 10 (outubro de 2019): 1985–2001. http://dx.doi.org/10.1007/s00190-019-01297-z.

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Abstract Ionospheric scintillation causes rapid fluctuations of measurements from Global Navigation Satellite Systems (GNSSs), thus threatening space-based communication and geolocation services. The phenomenon is most intense in equatorial regions, around the equinoxes and in maximum solar cycle conditions. Currently, ionospheric scintillation monitoring receivers (ISMRs) measure scintillation with high-pass filter algorithms involving high sampling rates, e.g. 50 Hz, and highly stable clocks, e.g. an ultra-low-noise Oven-Controlled Crystal Oscillator. The present paper evolves phase scintillation indices implemented in conventional geodetic receivers with sampling rates of 1 Hz and rapidly fluctuating clocks. The method is capable to mitigate ISMR artefacts that contaminate the readings of the state-of-the-art phase scintillation index. Our results agree in more than 99.9% within ± 0.05 rad (2 mm) of the ISMRs, with a data set of 8 days which include periods of moderate and strong scintillation. The discrepancies are clearly identified, being associated with data gaps and to cycle-slips in the carrier-phase tracking of ISMR that occur simultaneously with ionospheric scintillation. The technique opens the door to use huge databases available from the International GNSS Service and other centres for scintillation studies. This involves GNSS measurements from hundreds of worldwide-distributed geodetic receivers over more than one Solar Cycle. This overcomes the current limitations of scintillation studies using ISMRs, as only a few tens of ISMRs are available and their data are provided just for short periods of time.

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Choi, Jeong-Ryeol. "Characterizing Quantum Effects in Optically Induced Nanowire Self-Oscillations: Coherent Properties". Photonics 8, n.º 7 (25 de junho de 2021): 237. http://dx.doi.org/10.3390/photonics8070237.

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Mechanical properties of metallic-nanowire self-oscillations are investigated through a coherent-state analysis. We focus on elucidating the time behavior of quantum energy in such oscillations, in addition to the analysis of fluctuations, evolution of eigenstates, and oscillatory trajectories. The quantum energy varies somewhat randomly at first, but, at a later time, it undergoes a stable periodical oscillation; the mean energy in the stabilized motion is large when the frequency of the driving force is resonated with that of the intrinsic oscillation of the nanowire. We confirmed that when the oscillatory amplitude is sufficiently low, the quantum energy is quite different from the classical one due to zero-point energy, which appears in the quantum regime. Because the power in such an oscillation is typically ultra low, quantum effects in the nanowire oscillations are non-negligible. Detailed analysis for the evolution of the probability densities and their relation with the oscillation trajectories of the nanowire are also carried out. Characterizing quantum effects in the actual oscillatory motions and clarifying their difference from the classical ones are important in understanding nanowire self-oscillations.

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Giordano, V., P. Y. Bourgeois, Y. Gruson, N. Boubekeur, R. Boudot, E. Rubiola, N. Bazin e Y. Kersalé. "New advances in ultra–stable microwave oscillators". European Physical Journal Applied Physics 32, n.º 2 (26 de outubro de 2005): 133–41. http://dx.doi.org/10.1051/epjap:2005078.

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Wang, Kan, Ahmed El-Mowafy e Xuhai Yang. "LEO Satellite Clock Modeling and Its Benefits for LEO Kinematic POD". Remote Sensing 15, n.º 12 (16 de junho de 2023): 3149. http://dx.doi.org/10.3390/rs15123149.

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High-accuracy Low Earth Orbit (LEO) satellite clock and orbital products are preconditions to realize LEO augmentation for high-accuracy GNSS-based positioning on the ground. There is a high correlation between the orbit and clock parameters in the kinematic Precise Orbit Determination (POD) process. While future LEO satellites are planned to be equipped with better clocks, the benefits of modeling high-stability LEO satellite clocks are not yet thoroughly investigated, particularly when mid- to long-term systematic effects induced by the complex LEO relativistic effects and the external environment remain in the clocks. Through clock modeling, this study attempts to reduce not only the short-term noise of radial kinematic orbits, but also mis-modeled effects caused by, e.g., real-time GNSS orbital and clock errors. To explore the benefits of clock modeling, the clocks need to be first detrended by the mid- to long-term systematic effects. While over-detrending limits the orbital improvements, weak detrending would also hamper strong clock modeling and easily lead to performance degradations. A balance between the strengths of the detrending and the model thus needs to be investigated for different clock types. In this study, the Piece-Wise Linear (PWL) model of different time lengths and a 2.5-state filter with different strengths (h values) are tested using real data from GRACE FO-1 with an Ultra-Stable Oscillator (USO) on board. Using the CNES real-time GPS products, it was found that when detrending the clocks with a smoothing window of 300 to 500 s, one could generally expect an improvement larger than 10% in the estimation of radial orbits when applying a PWL model with a length from 300 to 1200 s. Improvements of this size can also be expected when using the 2.5-state model with h−1 (for Flicker Frequency Noise) from 10−28 to 10−30.

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Zhu, Zong Jiu, Yuan Yuan Niu, Jia Xing Cai e Peng Cheng Yan. "Experiment Studying of Multiwavelength Erbium-Doped Fiber Laser with Ultra-Small Wavelength Spacing". Applied Mechanics and Materials 333-335 (julho de 2013): 2479–83. http://dx.doi.org/10.4028/www.scientific.net/amm.333-335.2479.

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The configurations of Erbium-doped fiber laser and comb filter that work stably have been designed. The stable multiwavelength oscillation of erbium-doped fiber laser with wavelength spacing 0.20nm in 1532nm band had been obtained at liquid nitrogen temperature by optimizing length of erbium-doped fiber and loss of cavity. The experimental results show that, the erbium-doped fiber exhibits obviously different inhomogeneous gain broadening in different band.

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38

Bai, Weihua, Congliang Liu, Xiangguang Meng, Yueqiang Sun, Gottfried Kirchengast, Qifei Du, Xianyi Wang et al. "Evaluation of atmospheric profiles derived from single- and zero-difference excess phase processing of BeiDou radio occultation data from the FY-3C GNOS mission". Atmospheric Measurement Techniques 11, n.º 2 (13 de fevereiro de 2018): 819–33. http://dx.doi.org/10.5194/amt-11-819-2018.

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Abstract. The Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) is one of the new-generation payloads onboard the Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth's neutral atmosphere and ionosphere. The GNOS was designed for acquiring setting and rising radio occultation (RO) data by using GNSS signals from both the Chinese BeiDou System (BDS) and the US Global Positioning System (GPS). An ultra-stable oscillator with 1 s stability (Allan deviation) at the level of 10−12 was installed on the FY-3C GNOS, and thus both zero-difference and single-difference excess phase processing methods should be feasible for FY-3C GNOS observations. In this study we focus on evaluating zero-difference processing of BDS RO data vs. single-difference processing, in order to investigate the zero-difference feasibility for this new instrument, which after its launch in September 2013 started to use BDS signals from five geostationary orbit (GEO) satellites, five inclined geosynchronous orbit (IGSO) satellites and four medium Earth orbit (MEO) satellites. We used a 3-month set of GNOS BDS RO data (October to December 2013) for the evaluation and compared atmospheric bending angle and refractivity profiles, derived from single- and zero-difference excess phase data, against co-located profiles from European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. We also compared against co-located refractivity profiles from radiosondes. The statistical evaluation against these reference data shows that the results from single- and zero-difference processing are reasonably consistent in both bias and standard deviation, clearly demonstrating the feasibility of zero differencing for GNOS BDS RO observations. The average bias (and standard deviation) of the bending angle and refractivity profiles were found to be about 0.05 to 0.2 % (and 0.7 to 1.6 %) over the upper troposphere and lower stratosphere. Zero differencing was found to perform slightly better, as may be expected from its lower vulnerability to noise. The validation results indicate that GNOS can provide, on top of GPS RO profiles, accurate and precise BDS RO profiles both from single- and zero-difference processing. The GNOS observations by the series of FY-3 satellites are thus expected to provide important contributions to numerical weather prediction and global climate change analysis.

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Rubiola, E., Y. Gruson e V. Giordano. "On the flicker noise of ferrite circulators for ultra-stable oscillators". IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 51, n.º 8 (agosto de 2004): 957–63. http://dx.doi.org/10.1109/tuffc.2004.1324399.

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Rubiola, E., e V. Giordano. "On the 1/f frequency noise in ultra-stable quartz oscillators". IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 54, n.º 1 (janeiro de 2007): 15–22. http://dx.doi.org/10.1109/tuffc.2007.207.

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Watanabe, Yasuaki, Naoto Fujita, Kazuhide Shimizu, Shigeyoshi Goka e Hitoshi Sekimoto. "Experimental Study on Long-Term Frequency Drift Factors in Ultra-Stable Crystal Oscillators". IEEJ Transactions on Electronics, Information and Systems 119, n.º 7 (1999): 810–14. http://dx.doi.org/10.1541/ieejeiss1987.119.7_810.

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Giordano, Vincent, Christophe Fluhr, Serge Grop e Benoit Dubois. "Tests of Sapphire Crystals Manufactured With Different Growth Processes for Ultra-Stable Microwave Oscillators". IEEE Transactions on Microwave Theory and Techniques 64, n.º 1 (janeiro de 2016): 78–85. http://dx.doi.org/10.1109/tmtt.2015.2503748.

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Xing, Chao, Mingqun Liu, Junzhen Peng, Yuhong Wang, Yichen Zhou, Zongsheng Zheng, Shilin Gao e Jianquan Liao. "FLC-Based Ultra-Low-Frequency Oscillation Suppression Scheme for Interconnected Power Grids". Energies 17, n.º 6 (8 de março de 2024): 1300. http://dx.doi.org/10.3390/en17061300.

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The appearance of ultra-low-frequency oscillations in the grid at the sending end, after asynchronous grid interconnection, poses a significant threat to the stable operation of the system. For post-asynchronous interconnection in a multi-DC transmission system, an investigation is conducted to analyze the causes of ultra-low-frequency oscillations and the utilization of a Frequency Limit Controller (FLC) which aims to suppress these oscillations. Furthermore, a method is developed to rank DC sensitivity, considering the hydroelectric distribution in the sending-end grid, by combining the DC FLC impact factor and DC control sensitivity. Subsequently, a novel approach for ultra-low-frequency oscillation suppression is proposed. This approach employs the stochastic subspace method for parameter estimation and the NSGA-II optimization algorithm to convert the multi-DC optimization challenge into multiple sequential cyclic optimization problems, each focusing on a single DC, ensuring a more effective suppression of ultra-low-frequency oscillations. The proposed scheme’s effectiveness is validated through simulations using a specific locations’ interconnected power grid.

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Su, Ziyi, Wenquan Yang e Jianlong Wan. "Ultra-lean dynamics of holder-stabilized hydrogen-enriched flames in a preheated mesoscale combustor near the laminar critical limit". Physics of Fluids 34, n.º 10 (outubro de 2022): 107117. http://dx.doi.org/10.1063/5.0111041.

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This work experimentally investigates the ultra-lean dynamics of a 40% H2–60% CH4 flame near the laminar critical limit in a preheated mesoscale combustor with a flame holder. These experiments are conducted to verify a conjecture we proposed in a previous publication and reveal the ultra-lean flame dynamics under the synergistic effects of heat and flow recirculation. Notably, not only is our conjecture confirmed, but also some novel flame behaviors are found. As the equivalence ratio ϕ is decreased from 0.500 to 0.320, the conventional stable flame, stable residual flame, periodic residual flame with repetitive local extinction and re-ignition (periodic RFRER), and periodic oscillating residual flame are observed in sequence. For the stable residual flame (0.370 ≥ ϕ ≥ 0.355), the left and right flame roots reside directly behind the flame holder, and the flame tip stays near the combustor exit. For the periodic RFRER (0.350 ≥ ϕ ≥ 0.340), observed experimentally for the first time, the flame roots reside at almost the same location, but the flame tip oscillates up and down over time with pinch-off events. For the periodic oscillating residual flame (0.335 ≥ ϕ ≥ 0.320), found for the first time, the stable flame roots also reside at almost the same location, but the residual flame tip oscillates up and down over time without a pinch-off event. When ϕ decreases to 0.315, the oscillating residual flame extinguishes, and its blow-off dynamics are revealed in detail.

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Авдєєнко, Гліб Леонідович, Сергій Георгійович Бунін e Теодор Миколайович Наритник. "ТЕРАГЕРЦОВІ ТЕХНОЛОГІЇ В ТЕЛЕКОМУНІКАЦІЙНИХ СИСТЕМАХ. ЧАСТИНА 1. ОБҐРУНТУВАННЯ ЧАСТОТНОГО ДІАПАЗОНУ, ПРОЕКТУВАННЯ ФУНКЦІОНАЛЬНИХ ВУЗЛІВ ТЕЛЕКОМУНІКАЦІЙНИХ СИСТЕМ ТЕРАГЕРЦОВОГО ДІАПАЗОНУ". Aerospace technic and technology, n.º 4 (14 de outubro de 2018): 72–91. http://dx.doi.org/10.32620/aktt.2018.4.10.

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The article presented results of researches conducted by the team of authors devoted to the possibilities of creation for the first time in Ukraine the real prerequisites for solving the fundamental problem of constructing digital telecommunication systems with the use of terahertz technologies. The necessity of transition to the use of the terahertz frequency range substantiated during the deployment of future telecommunication systems of ultra-high bandwidth. The analysis of characteristics of the path of signal propagation and determination of signal losses in conditions of operation of the radio relay system in the terahertz frequency range is carried out. The conducted analysis has shown that in the frequency range of 30-300 GHz, the most important types of fading that should consider during the design are fading due to the easing of the signal by hydrometeors and fading due to the absorption of the radio signal in gases, fading due to the influence of the antenna pattern. It determined that the work of the radio relay lines in the terahertz range allows practically not to take into consideration the refraction and interference of electromagnetic waves reflected from interference in the zone of radio signal propagation, which arises especially in conditions of dense urban development. This is due primarily to the fact that the terahertz waves have a low ability to "bend" the noise, and secondly, at the current frequency of 30 to 300 Hz apply at relatively small distances (up to 5 km), which allows for avoiding spatial planning interference to the zone of direct visibility of antennas and the first Fresnel zone. It considered the main factors that lead to the emergence of fading in radio relay communication lines. It is shown that in the terahertz range the greatest influence on the energy potential of the radio-relay lines is attenuating in hydro meteors and gases. The terahertz frequency range areas allocated that is most suitable for application in radio relay communication lines. The principles of formation of signal-code construction considered methods and new technical solutions for choosing the type of signal construction proposed in order to achieve the best bandwidth and performance in the channel of communication of a wireless gigabit system of transmission in the terahertz range. The physical simulation of the ultra high-speed shaper based on multifrequency multiplexing of the modulated OFDM digital streams has been carried out, bench tests and optimization have been carried out to achieve the maximum bandwidth of the digital data transmission channel in the Ethernet format using the developed software. The developed software and hardware allowed for the first time to reach the overall channel speed with a full duplex up to 1.2 Gb / s. On the basis of the generalization of the results of theoretical research and experimental work, the analysis of the existing radio relay element base, the design of the main nodes of the receiving and transmitting parts of a telecommunication system with a gigabit throughput in the frequency range 130-134 GHz, the structural scheme of the transmitting and receiving system of the system is developed: frequency mixer with subharmonic pumping, the heterodyne, which uses a highly stable reference quartz oscillator with a subsequent chain of multiplication and under power stage, bandpass filter using a thin metal plate in the E-plane of the waveguide channel 1.6x0.8 mm, horn antenna. It is presented the results of experimental studies of the main nodes of the receiving and transmitting parts of a telecommunication system with a gigabit throughput in the frequency range 130-134 GHz. Scientific novelty of the work consists in generalization and development of the theory of distribution, generation and measurement of terahertz signals, in the development of the method of multiple frequency multiplexing and generation of modulated OFDM digital streams in the terahertz frequency range and the development of the principles of functional design of the receiving and transmitting parts of a telecommunication system with a gigabit throughput in terahertz frequency range

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Li, Liufeng, Hui Shen, Jin Bi, Chun Wang, Shasha Lv e Lisheng Chen. "Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation". Applied Physics B 117, n.º 4 (14 de setembro de 2014): 1025–33. http://dx.doi.org/10.1007/s00340-014-5923-x.

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Pokharel, A., F. Sthal, J. Imbaud, S. Ghosh, M. Devel, F. X. Esnault e G. Cibiel. "Flicker Noise in Quartz Crystal Resonator at 353K as a Function of Q-Factor of Overtones and Anharmonic Modes at 4K". Fluctuation and Noise Letters 17, n.º 03 (setembro de 2018): 1871002. http://dx.doi.org/10.1142/s0219477518710025.

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The unclear physical origin of flicker noise in ultra-stable quartz oscillators is still limiting some practical metrological applications. In this paper, we study experimentally the possible correlations between Q-factor measurements at low temperature (4[Formula: see text]K) and the level of flicker noise at nominal operating temperature (353[Formula: see text]K). Results for 10 Stress-Compensated-cut (SC-cut) resonators with a 5[Formula: see text]MHz resonant frequency and different noise levels (some excellent) are presented and commented, for several overtones and anharmonic modes.

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Xu, Jinliang, Xiongjiang Yu e Wu Jin. "Porous-wall microchannels generate high frequency “eye-blinking” interface oscillation, yielding ultra-stable wall temperatures". International Journal of Heat and Mass Transfer 101 (outubro de 2016): 341–53. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.05.039.

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Wang, Min, e Dan Zhen Gu. "The Application Research of HVDC & FACTS to Suppress the Power System Low-Frequency Oscillation". Applied Mechanics and Materials 704 (dezembro de 2014): 190–94. http://dx.doi.org/10.4028/www.scientific.net/amm.704.190.

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With the widely application use of UHV（ultra- high- voltage） transmission，increased the system low frequency oscillations，and flexible application of high-voltage direct current transmission (HVDC) and flexible ac transmission system (FACTS) can improve the system damping oscillation inhibition. This paper Based on the research results in recent years, classify& summarize HVDC and FACTS devices the theoretical basis and the main application places, and according to the way of access system of parallel, series and parallel hybrid FACTS devices stable controller design and optimization are summarized and classified.

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Wan, Jianlong, e Ziyi Su. "Ultra-lean dynamics of a holder-stabilized hydrogen enriched flames in a preheated mesoscale combustor". Physics of Fluids 34, n.º 5 (maio de 2022): 057108. http://dx.doi.org/10.1063/5.0091039.

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To provide the theoretical basis to suppress the unstable flames under the coupling effect of flow and heat recirculation, the present work experimentally studies the ultra-lean dynamics of a holder stabilized 40%H2–60%CH4–air premixed flame in a preheated mesoscale combustor. The regime diagram of the flame behaviors at various operating conditions is obtained. It is observed that the blow-off limit first increases slightly and then decreases sharply (the anomalous blow-off limit) with the decreased Re value. Three types of the flame behaviors (i.e., the conventional stable flame, the stable residual flame, and the periodic oscillating residual flame) are found before the flame blow-off. In addition, with the decreased Reynolds number, the operating range for the stable residual flame broadens first and then narrows, but that of the periodic oscillating residual flame decreases monotonically, which are observed for the first time. The results show that, with the decreased Reynolds number, the flame root of the conventional stable flame anchors almost at the same location right behind the holder, while the flame tips obviously shift upstream. With the decreased equivalence ratio, the left and right flame tips in the downstream channel shift toward each other and finally merge into a single flame tip, which results in the formation of the stable residual flame. When the equivalence ratio decreases further, the periodic oscillating residual flame occurs. The flame tip periodically oscillates up and down over time. In the end, the blow-off dynamics of the stable residual flame and periodic oscillating residual flame are revealed.

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