Article
Automation & Control Systems
Hao Ding, Quanjie Li, Xiaoqiang Guo, Yong Yang, Zhigang Lu
Summary: DC-link current ripple is an important performance indicator of a current-source converter and is closely related to the modulation strategy. Excessive ripple reduces system efficiency, increases total harmonic distortion of grid current, and causes electromagnetic interference. In this article, a novel modulation strategy is proposed to reduce ripple by optimizing the switching sequence according to the modulation index. The proposed strategy effectively reduces current ripple across the modulation index range without increasing switching frequency or inductor, and experimental results confirm its validity.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2023)
Article
Engineering, Electrical & Electronic
Faxing Zuo, Zufeng Chen, Liang Hu, Jianping Chen, Yi Jin, Guiling Wu
Summary: This article proposes a multiple-node fiber-optic time synchronization scheme based on BWDM transmission, which achieves accurate synchronization and effectively suppresses the impact of wavelength asymmetry on time synchronization accuracy. Experimental results show that stable time synchronization can be achieved for all nodes in the hybrid star and bus fiber network.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2021)
Article
Engineering, Electrical & Electronic
Adrien Meynard, Hau-Tieng Wu
Summary: This study introduces an effective method to reduce the boundary effects in time-frequency representations of time series, which is suitable for real-time acquisition of information from nonstationary oscillatory time series. The theoretical guarantee of the method's performance is provided through the study of locally oscillating signals and its effectiveness is validated by implementing it on biomedical signals after numerical verification of algorithmic performance.
IEEE TRANSACTIONS ON SIGNAL PROCESSING
(2021)
Article
Instruments & Instrumentation
Bin Jian, John Bernard, Marina Gertsvolf, Pierre Dube
Summary: We have improved the absolute frequency measurement of a single trapped strontium ion's 5s2S1/2-4d2D5/2 optical transition using a Global Positioning System (GPS) link to the SI second. The systematic uncertainty of the optical clock has been reduced from 1.5 x 10(-17) to 1.2 x 10(-17) compared to previous measurements. The traceability to the SI second through International Atomic Time was achieved using a GPS link and the Precise Point Positioning method. The measured frequency of the 88Sr+ ion 5s2S1/2-4d2D5/2 transition is 444779044095485.49(19) Hz, with the uncertainty reduced by almost a factor of four compared to previous measurements.
Article
Optics
Martin Cizek, Lenka Pravdova, Tuan Minh Pham, Adam Lesundak, Jan Hrabina, Josef Lazar, Thomas Pronebner, Elke Aeikens, Jorg Premper, Ondrej Havlis, Radek Velc, Vladimir Smotlacha, Lada Altmannova, Thorsten Schumm, Josef Vojtech, Anton Niessner, Ondrej Cip
Summary: Challenging experiments in fundamental physics require highly coherent optical frequency references with suppressed phase noise. This study presents a path to realize a delocalized optical frequency reference for spectroscopy of the isomeric state of Thorium-229 atom, which is crucial for the development of the next generation nuclear clock. A 235 km long phase-coherent stabilized cross-border fibre link has been established, connecting two metrology laboratories and using optical frequency combs to discipline highly-coherent lasers. The deployment of digital signal processing techniques and measurement of phase noise power spectral density demonstrate the functionality and reliability of the link.
Article
Engineering, Electrical & Electronic
Jeffrey Rodriguez, Michael J. Benker, Jason Poirier, Robert Dougenik, Yifei Li
Summary: The paper proposes a coherent amplitude-modulated link with optical down-conversion, achieving high dynamic range by utilizing a receiver with balanced detection and digital linearization. Experimental results demonstrate notable dynamic range enhancements in down-conversion RF photonic links compared to prior arts.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2021)
Article
Engineering, Multidisciplinary
Maria Almeida Silva, Conceicao Amado, Alvaro Ribeiro, Dalia Loureiro
Summary: Data quality is crucial in modeling, and uncertainty evaluation methods are lacking for time-dependent measurements. This study proposes a general methodology to assess the uncertainty of such measurements and validates its effectiveness through experiments.
Article
Management
Gerald Oeser, Pietro Romano
Summary: The study found that applying risk pooling methods in healthcare can reduce economic losses, with inventory pooling, transshipments, and product substitution being the most effective in improving the economic situation of hospitals. However, form postponement may not be suitable for hospitals due to required efforts, delays in treatment, and liability issues.
OPERATIONS MANAGEMENT RESEARCH
(2021)
Article
Engineering, Electrical & Electronic
Lu Wang, Tengfei Hao, Mengyuan Guan, Guangyi Li, Ming Li, Ninghua Zhu, Wei Li
Summary: A microwave photonic frequency measurement scheme is proposed based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) and frequency-to-time mapping. The use of a single modulator guarantees a compact frequency measurement system, and the principle of frequency-to-time mapping enables multi-tone measurement capability. In the proposed scheme, the unknown microwave signal is mixed with a linearly chirped microwave signal using the DP-DDMZM, and the resulting mixed signal is selected by an electrical bandpass filter for frequency-to-time mapping. Single and multi-tone microwave frequency measurements are successfully demonstrated in the experiment, with measurement errors less than +/- 3 MHz.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2022)
Article
Acoustics
L. Sliwczynski, P. Krehlik, L. Buczek, H. Schnatz
Summary: This article addresses the issue of a systematic frequency error in semiconductor-laser frequency synchronization circuits. The error occurs when the power of the reference laser is below a certain level, resulting in a significant frequency error that is independent of the laser frequency difference. The article presents theoretical models and simulations that accurately predict the error value and discusses the potential mitigation of the error through polarization scrambling.
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
(2023)
Article
Engineering, Electrical & Electronic
Lukasz Sliwczynski, Przemyslaw Krehlik, Lukasz Buczek, Harald Schnatz
Summary: This paper focuses on the circuits for active stabilization of the frequency offset between two semiconductor ultra-accurate fiber optic time transfer systems. It discusses the general frequency accuracy and stability required for the stabilization circuit. The technical details of the essential building block of the system are analyzed. Experimental circuits using commercially available millimeter wave integrated circuits are tested, and it is found that the stabilization circuits can cause systematic errors that need to be addressed.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2022)
Article
Chemistry, Analytical
Anne Pallares, Philippe Schmitt, Wilfried Uhring
Summary: Environmental water monitoring requires estimation of suspended solids load. This paper compares concentration ranges accessible through optical turbidity, acoustic backscattering and time resolved optical turbidity techniques in laboratory measurements. The study finds that time resolved optical turbidity shows clear advantage over other methods across different particle types.
Article
Instruments & Instrumentation
Masato Wada, Hajime Inaba
Summary: The definition of the second in the International System of Units (SI) is likely to be redefined in the optical frequency region, and reducing uncertainty in the frequency link is crucial for numerical determination and International Atomic Time operation. Researchers have evaluated and minimized uncertainty factors, achieving the lowest reported uncertainty yet. The validity of the frequency link has been confirmed through simultaneous measurements and is consistent with the evaluated uncertainty.
Article
Engineering, Electrical & Electronic
Xianbo Li, Derun Li, Chao Tang, Shaoxian Liu
Summary: This paper presents the design and characterization of a fully-integrated receiver based on single-photon avalanche diodes (SPADs) with nanosecond dead time for high-speed high-sensitivity optical wireless communication (OWC). The receiver consists of a 4x4 SPAD array that is based on a p-well/deep n-well (DNW) structure, and each SPAD is integrated with a tunable front-end circuit to perform quench and reset. In addition, an OR tree is designed to combine the 16 channels of output from the front-end circuits to generate a single data stream for signal processing, and an output buffer is implemented as the interface to drive 50-omega loading for testing purpose. Fabricated in a standard 180 nm CMOS process, the receiver achieves a minimum dead time of about 2.5 ns. Bit error rate (BER) measurement of the implemented receiver indicates a sensitivity of -31.6 dBm at 100 Mb/s for a BER of 2 x 10(-3) and a wavelength of 520 nm, where on-off keying (OOK) modulation and a 2(15)-1 pseudorandom binary sequence (PRBS-15) are employed. To recover the transmitted data stream from the received signal, a signal processing flow specific for SPAD-based receivers is proposed and implemented.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2023)
Article
Geosciences, Multidisciplinary
Kristina Collins, John Gibbons, Nathaniel Frissell, Aidan Montare, David Kazdan, Darren Kalmbach, David Swartz, Robert Benedict, Veronica Romanek, Rachel Boedicker, William Liles, William Engelke, David G. McGaw, James Farmer, Gary Mikitin, Joseph Hobart, George Kavanagh, Shibaji Chakraborty
Summary: This study measures the measurable effects of ionospheric variability on the Doppler shift of HF skywave signals using low-cost equipment. It presents a modular network called PSWS that measures Doppler shift in carrier signals and serves as a building block for a large-scale ionospheric and HF propagation measurement network. The study also provides software tools for data visualization and analysis and demonstrates the use of the data in event-based analyses and accuracy assessment of ionospheric models.
EARTH SYSTEM SCIENCE DATA
(2023)
