scholarly journals A Traceable High-Accuracy Velocity Measurement by Electro-Optic Dual-Comb Interferometry

2019 ◽  
Vol 9 (19) ◽  
pp. 4118 ◽  
Author(s):  
Bin Xue ◽  
Haoyun Zhang ◽  
Tuo Zhao ◽  
Haoming Jing
Keyword(s):  
Velocity Measurement ◽  
Atomic Clock ◽  
Microwave Frequency ◽  
High Accuracy ◽  
Repetition Frequency ◽  
Maximum Deviation ◽  
Phase Modulators ◽  
Electro Optic ◽  
Wide Range ◽  
Rubidium Clock

An electro-optic dual-comb Doppler velocimeter for high-accuracy velocity measurement is presented in this paper. The velocity information of the object can be accurately extracted from the change of repetition frequency, which is in the microwave frequency domain and can be locked to an atomic clock. We generate two optical combs by electro-optic phase modulators and trace their repetition frequencies to the rubidium clock. One functions as the measurement laser and the other the reference. Experimentally, we verify its high accuracy in the range of 100–300 mm/s with a maximum deviation of 0.44 mm/s. The proposed velocimeter combines the merits of high accuracy and wide range. In addition, since the repetition frequency used for the measurement is traceable to the rubidium clock, its potential superiority in traceability can be utilized in velocity metrology.

NORMAL-INCIDENCE INTERSUBBAND TRANSITIONS FOR INFRARED ELECTRO-OPTICAL MODULATION AND SECOND-HARMONIC GENERATION

1995 ◽  
Vol 04 (02) ◽  
pp. 337-361 ◽  
Author(s):  
H. XIE ◽  
W. I. WANG ◽  
J. R. MEYER ◽  
C. A. HOFFMAN ◽  
L. R. RAM-MOHAN
Keyword(s):  
Effective Mass ◽  
Second Harmonic ◽  
Normal Incidence ◽  
Growth Direction ◽  
Intersubband Transitions ◽  
Frequency Converters ◽  
Phase Modulators ◽  
Electro Optic ◽  
Wide Range ◽  
Infrared Wavelengths

We have developed a fundamental theory for electro-optical and nonlinear optical processes involving intersubband transitions in conduction valleys with arbitrary effective-mass anisotropy and orientation. New classes of amplitude and phase modulators, as well as frequency converters employing L-valley interactions in GaSb/AlSb-based quantum well systems are proposed. Key advantages of these devices include operation at normal incidence (enabled by the L-valley effective-mass anisotropy and tilted growth direction with respect to the L-valley constant energy ellipsoids) and adaptability to a wide range of infrared wavelengths (as short as 1.5 μm, made possible by the large band offsets). The electro-optic coefficients and second-order nonlinear susceptibilities derived from our modeling are larger than any measured or predicted to date for conventional Γ-valley processes.

Wide-range, high-accuracy multiple microwave frequency measurement by frequency-to-phase-slope mapping

2020 ◽  
Vol 123 ◽  
pp. 105895
Author(s):  
Di Wang ◽  
Cong Du ◽  
Yuchen Yang ◽  
Weinan Zhou ◽  
Tong Meng ◽  
...  
Keyword(s):  
Microwave Frequency ◽  
Frequency Measurement ◽  
High Accuracy ◽  
Phase Slope ◽  
Wide Range

Epitaxial ferroelectric thin films

1994 ◽  
Vol 52 ◽  
pp. 572-573
Author(s):  
S. G. Ghonge ◽  
E. Goo ◽  
R. Ramesh ◽  
R. Haakenaasen ◽  
D. K. Fork
Keyword(s):  
Single Crystal ◽  
Work Function ◽  
Nonvolatile Memory ◽  
Ferroelectric Properties ◽  
Electrical Contact ◽  
Memory Devices ◽  
Ferroelectric Films ◽  
Si Substrates ◽  
Electro Optic ◽  
Wide Range

Microstructure of epitaxial ferroelectric/conductive oxide heterostructures on LaAIO3(LAO) and Si substrates have been studied by conventional and high resolution transmission electron microscopy. The epitaxial films have a wide range of potential applications in areas such as non-volatile memory devices, electro-optic devices and pyroelectric detectors. For applications such as electro-optic devices the films must be single crystal and for applications such as nonvolatile memory devices and pyroelectric devices single crystal films will enhance the performance of the devices. The ferroelectric films studied are Pb(Zr0.2Ti0.8)O3(PLZT), PbTiO3(PT), BiTiO3(BT) and Pb0.9La0.1(Zr0.2Ti0.8)0.975O3(PLZT).Electrical contact to ferroelectric films is commonly made with metals such as Pt. Metals generally have a large difference in work function compared to the work function of the ferroelectric oxides. This results in a Schottky barrier at the interface and the interfacial space charge is believed to responsible for domain pinning and degradation in the ferroelectric properties resulting in phenomenon such as fatigue.

scholarly journals A Novel Ultrasonic TOF Ranging System Using AlN Based PMUTs

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 284
Author(s):  
Yihsiang Chiu ◽  
Chen Wang ◽  
Dan Gong ◽  
Nan Li ◽  
Shenglin Ma ◽  
...  
Keyword(s):  
Clock Cycle ◽  
High Accuracy ◽  
Ultrasonic Waves ◽  
Oxide Semiconductor ◽  
Average Error ◽  
Cmos Process ◽  
Clock Frequency ◽  
Time Frequency ◽  
Range Finding ◽  
Wide Range

This paper presents a high-accuracy complementary metal oxide semiconductor (CMOS) driven ultrasonic ranging system based on air coupled aluminum nitride (AlN) based piezoelectric micromachined ultrasonic transducers (PMUTs) using time of flight (TOF). The mode shape and the time-frequency characteristics of PMUTs are simulated and analyzed. Two pieces of PMUTs with a frequency of 97 kHz and 96 kHz are applied. One is used to transmit and the other is used to receive ultrasonic waves. The Time to Digital Converter circuit (TDC), correlating the clock frequency with sound velocity, is utilized for range finding via TOF calculated from the system clock cycle. An application specific integrated circuit (ASIC) chip is designed and fabricated on a 0.18 μm CMOS process to acquire data from the PMUT. Compared to state of the art, the developed ranging system features a wide range and high accuracy, which allows to measure the range of 50 cm with an average error of 0.63 mm. AlN based PMUT is a promising candidate for an integrated portable ranging system.

Measurement of Unsteady Flow in Pump-Turbine for Hydropower Using PIV Method

2009 ◽  
Author(s):  
Nobuhiko Fukuda ◽  
Satoshi Someya ◽  
Koji Okamoto
Keyword(s):  
Rotational Speed ◽  
Velocity Measurement ◽  
Numerical Procedure ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
High Time ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Runner Blade ◽  
Wide Range

It is thought that the pressure fluctuation can occur due to the interaction between flow through guide vanes and flow into runner blades, resulting in a vibration of turbine and a blade cracking, in a hydraulic turbine operated in a wide range for flexible power demand. High accurate velocity measurement with high time/spatial resolution can help to clarify the mechanism of the interaction and to provide good experimental data for the validation of numerical procedure. So the aim of present study is to estimate the unstable velocity field quantitatively in the area between guide vanes and runner blades, using high time-resolved particle image velocimetry (PIV). Two types of velocity measurements were carried out, i.e., phase-locked measurement and high time sequential velocity measurement, in a pump-turbine model with 20 guide vanes and 6 runner blades. The characteristic of the flow field varied corresponding to the operating conditions such as flow rate and rotational speed. Opening angles of guide vanes were kept uniform. A clockwise vortex was generated at inside of the runner blade under smaller rotational speed. A counterclockwise vortex was separated at the backside of the runner blade under higher rotational speed. At any operating conditions, the velocity between guide vanes and runner blades oscillated periodically at the blade passing frequency.

scholarly journals Selective 13C labelling reveals the electronic structure of flavocoenzyme radicals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Erik Schleicher ◽  
Stephan Rein ◽  
Boris Illarionov ◽  
Ariane Lehmann ◽  
Tarek Al Said ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Blue Light ◽  
Density Functional ◽  
Double Resonance ◽  
Density Functional Theory Calculations ◽  
Microwave Frequency ◽  
Fine Tuning ◽  
Electron Nuclear Double Resonance ◽  
Intermediate Radical ◽  
Wide Range

AbstractFlavocoenzymes are nearly ubiquitous cofactors that are involved in the catalysis and regulation of a wide range of biological processes including some light-induced ones, such as the photolyase-mediated DNA repair, magnetoreception of migratory birds, and the blue-light driven phototropism in plants. One of the factors that enable versatile flavin-coenzyme biochemistry and biophysics is the fine-tuning of the cofactor’s frontier orbital by interactions with the protein environment. Probing the singly-occupied molecular orbital (SOMO) of the intermediate radical state of flavins is therefore a prerequisite for a thorough understanding of the diverse functions of the flavoprotein family. This may be ultimately achieved by unravelling the hyperfine structure of a flavin by electron paramagnetic resonance. In this contribution we present a rigorous approach to obtaining a hyperfine map of the flavin’s chromophoric 7,8-dimethyl isoalloxazine unit at an as yet unprecedented level of resolution and accuracy. We combine powerful high-microwave-frequency/high-magnetic-field electron–nuclear double resonance (ENDOR) with 13C isotopologue editing as well as spectral simulations and density functional theory calculations to measure and analyse 13C hyperfine couplings of the flavin cofactor in DNA photolyase. Our data will provide the basis for electronic structure considerations for a number of flavin radical intermediates occurring in blue-light photoreceptor proteins.

scholarly journals Spatial analysis of phylogenetic community structure: New version of a classical method

2015 ◽  
Author(s):  
Carlo Ricotta ◽  
Eszter EA Ari ◽  
Giuliano Bonanomi ◽  
Francesco Giannino ◽  
Duncan Heathfield ◽  
...  
Keyword(s):  
Community Structure ◽  
Spatial Scales ◽  
Point Pattern ◽  
Maximum Deviation ◽  
Individual Plant ◽  
Phylogenetic Distance ◽  
Phylogenetic Structure ◽  
Phylogenetic Community Structure ◽  
Point Patterns ◽  
Wide Range

The increasing availability of phylogenetic information facilitates the use of evolutionary methods in community ecology to reveal the importance of evolution in the species assembly process. However, while several methods have been applied to a wide range of communities across different spatial scales with the purpose of detecting non-random phylogenetic patterns, the spatial aspects of phylogenetic community structure have received far less attention. Accordingly, the question for this study is: can point pattern analysis be used for revealing the phylogenetic structure of multi-species assemblages? We introduce a new individual-centered procedure for analyzing the scale-dependent phylogenetic structure of multi-species point patterns based on digitized field data. The method uses nested circular plots with increasing radii drawn around each individual plant and calculates the mean phylogenetic distance between the focal individual and all individuals located in the circular ring delimited by two successive radii. This scale-dependent value is then averaged over all individuals of the same species and the observed mean is compared to a null expectation with permutation procedures. The method detects particular radius values at which the point pattern of a single species exhibits maximum deviation from the expectation towards either phylogenetic aggregation or segregation. Its performance is illustrated using data from a grassland community in Hungary and simulated point patterns. The proposed method can be extended to virtually any distance function for species pairs, such as functional distances.

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