Deposition of hafnium silicate films by liquid injection MOCVD using a single source or dual source approach

2004 ◽  
Vol 14 (3) ◽  
pp. 391 ◽  
Author(s):  
John L. Roberts ◽  
Paul A. Marshall ◽  
Anthony C. Jones ◽  
Paul R. Chalker ◽  
Jamie F. Bickley ◽  
...  
Keyword(s):  
Single Source ◽  
Hafnium Silicate ◽  
Liquid Injection ◽  
Dual Source

Thermal stability of hafnium silicate dielectric films deposited by a dual source liquid injection MOCVD

2004 ◽  
Vol 15 (11) ◽  
pp. 711-714 ◽  
Author(s):  
Paul R. Chalker ◽  
Paul A. Marshall ◽  
Richard J. Potter ◽  
Timothy B. Joyce ◽  
Anthony C. Jones ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Dielectric Films ◽  
Hafnium Silicate ◽  
Liquid Injection ◽  
Dual Source ◽  
Thermal Stability Of

Dose performance and image quality: Dual source CT versus single source CT in cardiac CT angiography

2009 ◽  
Vol 72 (3) ◽  
pp. 396-400 ◽  
Author(s):  
Min Wang ◽  
Heng-Tao Qi ◽  
Xi-Ming Wang ◽  
Tao Wang ◽  
Jiu-Hong Chen ◽  
...  
Keyword(s):  
Image Quality ◽  
Ct Angiography ◽  
Cardiac Ct ◽  
Dual Source Ct ◽  
Single Source ◽  
Cardiac Ct Angiography ◽  
Dual Source

scholarly journals On the Impact and Mitigation of Signal Crosstalk in Ground-Based and Low Altitude Airborne GNSS-R

2021 ◽  
Vol 13 (6) ◽  
pp. 1085
Author(s):  
Corentin Lubeigt ◽  
Lorenzo Ortega ◽  
Jordi Vilà-Valls ◽  
Laurent Lestarquit ◽  
Eric Chaumette
Keyword(s):  
Specular Reflection ◽  
Signal Amplitude ◽  
Satellite System ◽  
Mitigation Strategies ◽  
Variance Estimator ◽  
Single Source ◽  
Dual Source ◽  
Reflected Signal ◽  
The Impact ◽  
Signal Crosstalk

Global Navigation Satellite System Reflectometry (GNSS-R) is a powerful way to retrieve information from a reflecting surface by exploiting GNSS as signals of opportunity. In dual antenna conventional GNSS-R architectures, the reflected signal is correlated with a clean replica to obtain the specular reflection point delay and Doppler estimates, which are further processed to obtain the GNSS-R product of interest. An important problem that may appear for low elevation satellites is signal crosstalk, that is the direct line-of-sight signal leaks into the antenna dedicated to the reflected signal. Such crosstalk may degrade the overall system performance if both signals are very close in time, similar to multipath in standard GNSS receivers, the reason why mitigation strategies must be accounted for. In this article: (i) we first provide a geometrical analysis to justify that the estimation performance is only affected for low height receivers; (ii) then, we analyze the impact of crosstalk if not taken into account, by comparing the single source conditional maximum likelihood estimator (CMLE) performance in a dual source context with the corresponding Cramér–Rao bound (CRB); (iii) we discuss dual source estimators as a possible mitigation strategy; and (iv) we investigate the performance of the so-called variance estimator, which is designed to eliminate the coherent signal part, compared to both the CRB and non-coherent dual source estimators. Simulation results are provided for representative GNSS signals to support the discussion. From this analysis, it is found that: (i) for low enough reflected-to-direct signal amplitude ratios (RDR), the crosstalk has no impact on standard single source CMLEs; (ii) for high enough signal-to-noise ratios (SNR), the dual source estimators are efficient irrespective of the RDR, then being a promising solution for any reflected signal scenario; (iii) non-coherent dual source estimators are also efficient at high SNR; and (iv) the variance estimator is efficient as long as the non-coherent part of the signal is dominant.

scholarly journals Data-Driven Tuning of PID Controlled Piezoelectric Ultrasonic Motor

Actuators ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 148
Author(s):  
Sarah Makarem ◽  
Bülent Delibas ◽  
Burhanettin Koc
Keyword(s):  
Genetic Algorithm ◽  
Pid Controller ◽  
Good Alternative ◽  
Data Driven ◽  
Grid Search ◽  
Single Source ◽  
Dual Frequency ◽  
Dual Source ◽  
Stage System ◽  
Piezoelectric Ultrasonic Motor

Ultrasonic motors employ resonance to amplify the vibrations of piezoelectric actuator, offering precise positioning and relatively long travel distances and making them ideal for robotic, optical, metrology and medical applications. As operating in resonance and force transfer through friction lead to nonlinear characteristics like creep and hysteresis, it is difficult to apply model-based control, so data-driven control offers a good alternative. Data-driven techniques are used here for iterative feedback tuning of a proportional integral derivative (PID) controller parameters and comparing between different motor driving techniques, single source and dual source dual frequency (DSDF). The controller and stage system used are both produced by the company Physik Instrumente GmbH, where a PID controller is tuned with the help of four search methods: grid search, Luus–Jaakola method, genetic algorithm, and a new hybrid method developed that combines elements of grid search and Luus–Jaakola method. The latter method was found to be quick to converge and produced consistent result, similar to the Luus–Jaakola method. Genetic Algorithm was much slower and produced sub optimal results. The grid search has also proven the DSDF driving method to be robust, less parameter dependent, and produces far less integral position error than the single source driving method.

Assessment of image quality of 64-row Dual Source versus Single Source CT coronary angiography on heart rate: A phantom study

2009 ◽  
Vol 70 (1) ◽  
pp. 61-68 ◽  
Author(s):  
R. Dikkers ◽  
M.J.W. Greuter ◽  
W. Kristanto ◽  
P.M.A. van Ooijen ◽  
P.E. Sijens ◽  
...  
Keyword(s):  
Heart Rate ◽  
Image Quality ◽  
Coronary Angiography ◽  
Ct Coronary Angiography ◽  
Phantom Study ◽  
Single Source ◽  
Dual Source

Radiation Dose at Coronary CT Angiography: Second-Generation Dual-Source CT Versus Single-Source 64-MDCT and First-Generation Dual-Source CT

2011 ◽  
Vol 196 (5) ◽  
pp. W550-W557 ◽  
Author(s):  
Christian Fink ◽  
Radko Krissak ◽  
Thomas Henzler ◽  
Ursula Lechel ◽  
Gunnar Brix ◽  
...  
Keyword(s):  
Radiation Dose ◽  
Ct Angiography ◽  
Coronary Ct Angiography ◽  
First Generation ◽  
Second Generation ◽  
Dual Source Ct ◽  
Single Source ◽  
Coronary Ct ◽  
Dual Source

Using Active and Passive Near-Field Hydrophones to Image the Near-Surface in Ultra-Shallow Waters Offshore Abu Dhabi

2021 ◽  
Author(s):  
Oleg Khakimov ◽  
Yaser Gholami ◽  
Bertrand Tertrais ◽  
Guillaume Cambois ◽  
Mohamed Mahgoub
Keyword(s):  
Near Field ◽  
Abu Dhabi ◽  
Shallow Waters ◽  
Surface Imaging ◽  
Single Source ◽  
Near Surface ◽  
Seismic Surveys ◽  
Site Survey ◽  
Dual Source ◽  
Water Bottom

Abstract Seismic surveys are generally designed to image deep reservoirs, which leaves the near-surface woefully under-sampled. This is particularly a challenge offshore Abu Dhabi, where a complex near-surface – with karstic collapses and meandering channels – contaminates the seismic image with strong footprints. To mitigate these effects, we use near-field hydrophone data, primarily designed to QC the airgun source, for near-surface imaging. Near-field hydrophones (NFH) are positioned about a meter above each airgun and are designed to record the source near-field pressure. They immediately capture dysfunctional or out-of-spec guns, which alerts the recording crew. Yet, in a shallow water environment, they unintentionally record seismic reflections from the near-surface, which we will use for seismic imaging. Streamer vessels usually use two source arrays, 50 meters apart, which shoot in a flip-flop mode. The active NFH refer to the recordings directly above the shooting guns, while the passive NFH refer to the recordings from the array that is not shooting. Because the passive NFH are less contaminated by the source near-field, they are typically the preferred choice for near-surface imaging. Waters are too shallow in offshore Abu Dhabi to use streamer vessels. Instead, seismic surveys involve ocean-bottom cables (OBC) or nodes (OBN) and smaller airgun arrays. The shooting vessels can be single-source or dual-source. While a single source vessel has only active NFH, a dual source vessel has both active and passive NFH. However, even if a dual-source vessel is used, the 50 m distance between the shooting source array and the passive NFH is too large to capture the water-bottom reflection for water-depths shallower than 25 m. For these reasons, we propose to combine both measurements, using active NFH for the very shallow section and passive NFH for the deeper section. We have applied this technique to a recent node survey acquired offshore Abu Dhabi. By combining the active and passive NFH, a very high-resolution shallow image was obtained, which allows the interpretation of geological layers just below the water bottom. Comparisons with high resolution 2D site survey images show good agreement. Given the NFH do not require any additional acquisition and are delivered as a byproduct of standard seismic surveys, we have demonstrated that proper use of NFH can provide high quality images for pre-site survey interpretation, which reduces the need for additional – and expensive – geotechnical surveys. This is the first published use of combined active and passive NFH in Abu Dhabi shallow waters for the purpose of imaging. The resolution of the shallow formation images allows detailed interpretation not achievable using conventional seismic data. In the long term, this technique may reduce the need for additional site survey acquisitions.

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