Synchronization in Dual Delay Line SAW Sensors

2004 ◽  
Author(s):  
Duck-Bong Seo ◽  
Z. C. Feng
Keyword(s):  
Delay Line ◽  
Phase Measurement ◽  
Surface Adsorption ◽  
Propagation Speed ◽  
Frequency Measurement ◽  
Frequency Change ◽  
Averaged Equations ◽  
Excited Oscillation ◽  
The Difference ◽  
Delay Differential

Surface acoustic wave (SAW) sensors are self-excited oscillators. Self-excitation is a consequence of the finite amount of delay in the circuit. The oscillation frequency is affected by the wave propagation speed which further depends on surface adsorption. Therefore, measurement on the surface adsorption is done by measuring the frequency change of the self-excited oscillation. In dual delay line oscillators the difference between the surface physical conditions is reflected through the difference in oscillation frequencies. Delay differential equations are used to model the sensor. Bifurcation analysis of the averaged equations indicates the presence of synchronization. The occurrence of synchronization is further demonstrated through numerical simulations. Synchronization makes the frequency measurement irrelevant. We propose phase measurement as an alternative in the presence of strong coupling between the two oscillators.

scholarly journals Influence of the mode of reproduction on dispersal evolution during species invasion

2020 ◽  
Vol 67 ◽  
pp. 120-134
Author(s):  
Vincent Calvez ◽  
Joachim Crevat ◽  
Léonard Dekens ◽  
Benoit Fabrèges ◽  
Frédéric Kuczma ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Formal Analysis ◽  
Propagation Speed ◽  
Reaction Diffusion ◽  
Equation Modeling ◽  
Asexual Population ◽  
Acceleration Rate ◽  
Non Local ◽  
The Difference ◽  
Dispersal Evolution

We consider a reaction-diffusion-reproduction equation, modeling a population which is spatially heterogeneous. The dispersion of each individuals is influenced by its phenotype. In the literature, the asymptotic propagation speed of an asexual population has already been rigorously determined. In this paper we focus on the difference between the asexual reproduction case, and the sexual reproduction case, involving a non-local term modeling the reproduction. This comparison leads to a different invasion speed according to the reproduction. After a formal analysis of both cases, leading to a heuristic of the asymptotic behaviour of the invasion fronts, we give some numerical evidence that the acceleration rate of the spatial spreading of a sexual population is slower than the acceleration rate of an asexual one. The main difficulty to get sharper results on a transient comes from the non-local sexual reproduction term.

Diurnal Variations of Warm-Season Precipitation East of the Tibetan Plateau over China

2011 ◽  
Vol 139 (9) ◽  
pp. 2790-2810 ◽  
Author(s):  
Xinghua Bao ◽  
Fuqing Zhang ◽  
Jianhua Sun
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Propagation Speed ◽  
Western Pacific Subtropical High ◽  
Diurnal Variations ◽  
The Tibetan Plateau ◽  
Diurnal Cycles ◽  
Thermally Driven ◽  
The Difference ◽  
Precipitation Cycle

This study explores the diurnal variations of the warm-season precipitation to the east of the Tibetan Plateau over China using the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation data and the Global Forecast System (GFS) gridded analyses during mid-May to mid-August of 2003–09. Complementary to the past studies using satellite or surface observations, it is found that there are strong diurnal variations in the summertime precipitation over the focus domain to the east of the Tibetan Plateau. These diurnal precipitation cycles are strongly associated with several thermally driven regional mountain–plains solenoids due to the differential heating between the Tibetan Plateau, the highlands, the plains, and the ocean. The diurnal cycles differ substantially from region to region and during the three different month-long periods: the pre-mei-yu period (15 May–15 June), the mei-yu period (15 June–15 July), and the post-mei-yu period (15 July–15 August). In particular, there is a substantial difference in the propagation speed and eastward extent of the peak phase of the dominant diurnal precipitation cycle that is originated from the Tibetan Plateau. This diurnal peak has a faster (slower) eastward propagation speed, the more (less) coherent propagation duration, and thus covers the longest (shortest) distance to the east during the pre-mei-yu (post-mei-yu) period than that during the mei-yu period. The differences in the mean midlatitude westerly flow and in the positioning and strength of the western Pacific subtropical high during different periods are the key factors in explaining the difference in the propagation speed and the eastward extent of this dominant diurnal precipitation cycle.

Comparison of Ground-Based Radar and Geosynchronous Satellite Climatologies of Warm-Season Precipitation over the United States

2008 ◽  
Vol 47 (12) ◽  
pp. 3264-3270 ◽  
Author(s):  
John D. Tuttle ◽  
Richard E. Carbone ◽  
Phillip A. Arkin
Keyword(s):  
United States ◽  
Brightness Temperature ◽  
Satellite Data ◽  
Warm Season ◽  
Propagation Speed ◽  
Radar Data ◽  
The United States ◽  
Temperature Threshold ◽  
Brightness Temperatures ◽  
The Difference

Abstract Studies in the past several years have documented the climatology of warm-season precipitation-episode statistics (propagation speed, span, and duration) over the United States using a national composited radar dataset. These climatological studies have recently been extended to other continents, including Asia, Africa, and Australia. However, continental regions outside the United States have insufficient radar coverage, and the newer studies have had to rely on geostationary satellite data at infrared (IR) frequencies as a proxy for rainfall. It is well known that the use of IR brightness temperatures to infer rainfall is subject to large errors. In this study, the statistics of warm-season precipitation episodes derived from radar and satellite IR measurements over the United States are compared and biases introduced by the satellite data are evaluated. It is found that the satellite span and duration statistics are highly dependent upon the brightness temperature threshold used but with the appropriate choices of thresholds can be brought into good agreement with those based upon radar data. The propagation-speed statistics of satellite events are on average ∼4 m s−1 faster than radar events and are relatively insensitive to the brightness temperature threshold. A simple correction procedure based upon the difference between the steering winds for the precipitation core and the winds at the level of maximum anvil outflow is developed.

scholarly journals The Accuracy of Ground-Based Optical Interferometry Observations

2000 ◽  
Vol 180 ◽  
pp. 47-56
Author(s):  
Donald J. Hutter
Keyword(s):  
Delay Line ◽  
Wide Angle ◽  
Actual Situation ◽  
Optical Interferometer ◽  
Beam Combination ◽  
The Status ◽  
The Difference ◽  
Path Lengths ◽  
Optical Paths ◽  
Star Position

AbstractThe problem of wide-angle astrometry via interferometry is to recover the two coordinates for each star from the observed delays. In the absence of atmospheric turbulence, the geometrical delay can be defined as: dG, ij(t) ≡ dj(t) ‒ di(t) = Bij(t)·ŝ0 ‒ Cij. Here the geometrical delay is the difference between the delay line lengths di and dj that is required to equalize the effective optical paths from the star to the point of beam combination via each of two apertures i and j. Bij(t) is the baseline between the apertures, ŝ0 is the star position, and Cij is the difference between the ‘fixed’ internal optical path lengths Ci and Cj within the instrument. In principle, sufficient delay measurements would allow solution for the baseline vectors and the delay constants, as well as the positions of the stars. However, the actual situation is greatly complicated by the presence of the atmosphere and the fact that neither the delay ‘constants’ Cij nor the baseline vectors are stable over time. The design of, and the analysis of the data from, any ground-based optical interferometer must overcome all three of these effects. The design, operation, and the analysis of data from the Navy Prototype Optical Interferometer (NPOI) are presented here as examples of how to overcome the effects of the atmosphere and the instrumental instabilities in order to achieve accurate wide-angle astrometry. The status of the implementation of these techniques at the NPOI is presented.

Micro Flow Sensor Based on Frequency Measurement of Micro Whistles

2012 ◽  
Vol 468-471 ◽  
pp. 2061-2064
Author(s):  
Yan Bin Di ◽  
Ying Miao
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Flow Rate ◽  
Frequency Measurement ◽  
Flow Sensor ◽  
Fluid Properties ◽  
Micro Flow ◽  
The Difference ◽  
Rate Frequency ◽  
Geometrical Dimensions

In this work, several millimeter sized micro whistles have been tested as potential frequency analog gas flow sensors. The characteristic curves of the whistles were systematically investigated as a function of geometrical dimensions, the kind of gas applied, and temperature. Both a micro¬phone and a PVDF foil were employed to record the frequencies. The relation be¬tween oscillation frequency and volume flow rate only shows a weak function of fluid properties and temperature. At a given flow rate, the difference of argon and nitrogen is 120 Hz on average, which is corresponding to 1.4 %. For air flow at a given flow rate, frequency rises approximately 380 Hz (2.73 %) per 10 °C. This kind of micro whistle could be employed as gas flow sensor which is insensitive to fluid properties.

scholarly journals Optimal monodomain approximations of the bidomain equations used in cardiac electrophysiology

2014 ◽  
Vol 24 (06) ◽  
pp. 1115-1140 ◽  
Author(s):  
Yves Coudière ◽  
Yves Bourgault ◽  
Myriam Rioux
Keyword(s):  
Boundary Conditions ◽  
Cardiac Electrophysiology ◽  
Propagation Speed ◽  
Neumann Boundary ◽  
Test Cases ◽  
Bidomain Model ◽  
Bidomain Equations ◽  
Monodomain Model ◽  
The Difference ◽  
Computationally Intensive

The bidomain model is the current most sophisticated model used in cardiac electrophysiology. The monodomain model is a simplification of the bidomain model that is less computationally intensive but only valid under equal conductivity ratio. We propose in this paper optimal monodomain approximations of the bidomain model. We first prove that the error between the bidomain and monodomain solutions is bounded by the error ‖B - A‖ between the bidomain and monodomain conductivity operators. Optimal monodomain approximations are defined by minimizing the distance ‖B - A‖, which reduces for solutions over all ℝd to minimize the Lp norm of the difference between the operator symbols. Similarly, comparing the symbols pointwise amounts to compare the propagation of planar waves in the bidomain and monodomain models. We prove that any monodomain model properly propagates at least d planar waves in ℝd. We next consider and solve the optimal problem in the L∞ and L2 norms, the former providing minimal propagation error uniformly over all directions. The quality of these optimal monodomain approximations is compared among themselves and with other published approximations using two sets of test cases. The first one uses periodic boundary conditions to mimic propagation in ℝd while the second is based on a square domain with common Neumann boundary conditions. For the first test cases, we show that the error on the propagation speed is highly correlated with the error on the symbols. The second test cases show that domain boundaries control propagation directions, with only partial impact from the conductivity operator used.

Bifurcation to fronts due to delay

2010 ◽  
Vol 368 (1911) ◽  
pp. 483-493 ◽  
Author(s):  
T. Erneux ◽  
G. Kozyreff ◽  
M. Tlidi
Keyword(s):  
Global Bifurcation ◽  
Propagation Speed ◽  
Radial Symmetry ◽  
Delayed Feedback Control ◽  
The Past ◽  
The Difference ◽  
The Stability ◽  
System Variables ◽  
Time Delayed Feedback ◽  
Moving Front

The stability of a steady-state front (kink) subject to a time-delayed feedback control (TDFC) is examined in detail. TDFC is based on the use of the difference between system variables at the current moment of time and their values at some time in the past. We first show that there exists a bifurcation to a moving front. We then investigate the limit of large delays but weak feedback and obtain a global bifurcation diagram for the propagation speed. Finally, we examine the case of a two-dimensional front with radial symmetry and determine the critical radius above which propagation is possible.

Averaged equations for inviscid disperse two-phase flow

1994 ◽  
Vol 267 ◽  
pp. 185-219 ◽  
Author(s):  
D. Z. Zhang ◽  
A. Prosperetti
Keyword(s):  
Ad Hoc ◽  
Volume Fraction ◽  
Detailed Comparison ◽  
Momentum Equation ◽  
Average Pressure ◽  
Rigid Spheres ◽  
Two Phase ◽  
Averaged Equations ◽  
Mass Coefficient ◽  
The Difference

Averaged equations governing the motion of equal rigid spheres suspended in a potential flow are derived from the equation for the probability distribution. A distinctive feature of this work is the derivation of the disperse-phase momentum equation by averaging the particle equation of motion directly, rather than the microscopic equation for the particle material. This approach is more flexible than the usual one and leads to a simpler and more fundamental description of the particle phase. The model is closed in a systematic way (i.e. with no ad hoc assumptions) in the dilute limit and in the linear limit. One of the closure quantities is related to the difference between the gradient of the average pressure and the average pressure gradient, a well-known problem in the widely used two-fluid engineering models. The present result for this quantity leads to the introduction of a modified added mass coefficient (related to Wallis's ‘exertia’) that remains very nearly constant with changes in the volume fraction and densities of the phases. Statistics of this coefficient are provided and exhibit a rather strong variability of up to 20% among different numerical simulations. A detailed comparison of the present results with those of other investigators is given in § 10.As a further illustration of the flexibility of the techniques developed in the paper, in Appendix C they are applied to the calculation of the so-called ‘particle stress’ tensor. This derivation is considerably simpler than others available in the literature.

scholarly journals Acoustical Slot Mode Sensor for the Rapid Coronaviruses Detection

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1822 ◽  
Author(s):  
Olga Guliy ◽  
Boris Zaitsev ◽  
Andrey Teplykh ◽  
Sergey Balashov ◽  
Alexander Fomin ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Rapid Detection ◽  
Delay Line ◽  
Virus Detection ◽  
Transmissible Gastroenteritis Virus ◽  
Acoustic Sensor ◽  
Viral Particles ◽  
Before And After ◽  
The Difference ◽  
Transmissible Gastroenteritis

A method for the rapid detection of coronaviruses is presented on the example of the transmissible gastroenteritis virus (TGEV) directly in aqueous solutions with different conductivity. An acoustic sensor based on a slot wave in an acoustic delay line was used for the research. The addition of anti-TGEV antibodies (Abs) diluted in an aqueous solution led to a change in the depth and frequency of resonant peaks on the frequency dependence of the insertion loss of the sensor. The difference in the output parameters of the sensor before and after the biological interaction of the TGE virus in solutions with the specific antibodies allows drawing a conclusion about the presence/absence of the studied viruses in the analyzed solution. The possibility for virus detection in aqueous solutions with the conductivity of 1.9–900 μs/cm, as well as in the presence of the foreign viral particles, has been demonstrated. The analysis time did not exceed 10 min.

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