scholarly journals Modulation above Pump Beam Energy in Photoreflectance

2017 ◽  
Vol 2017 ◽  
pp. 1-4 ◽  
Author(s):  
D. Fuertes Marrón
Keyword(s):  
Probe Beam ◽  
Critical Points ◽  
Pump Beam ◽  
Lower Energy ◽  
High Energy ◽  
Pump Light ◽  
Spectral Content ◽  
Bulk Gaas ◽  
Upper Limit ◽  
Set Up

Photoreflectance is used for the characterisation of semiconductor samples, usually by sweeping the monochromatized probe beam within the energy range comprised between the highest value set up by the pump beam and the lowest absorption threshold of the sample. There is, however, no fundamental upper limit for the probe beam other than the limited spectral content of the source and the responsivity of the detector. As long as the modulation mechanism behind photoreflectance does affect the complete electronic structure of the material under study, sweeping the probe beam towards higher energies from that of the pump source is equally effective in order to probe high-energy critical points. This fact, up to now largely overseen, is shown experimentally in this work. E1 and E0 + Δ0 critical points of bulk GaAs are unambiguously resolved using pump light of lower energy. This type of upstream modulation may widen further applications of the technique.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

The Tahaddart estuary, NW of Morocco: evidence of marine submersion events during the last 3500 years 

2021 ◽  
Author(s):  
Otmane Khalfaoui ◽  
laurent Dezileau ◽  
Jean-Philippe Degeai ◽  
Maria Snoussi
Keyword(s):  
Late Holocene ◽  
Atlantic Coast ◽  
High Energy ◽  
Mitigation Strategies ◽  
Spatial And Temporal Variability ◽  
Progressive Change ◽  
Marine Facies ◽  
Set Up ◽  
Long Term Studies

<p>The Atlantic coast of Morocco has been confronted with several marine submersion events. Historically, some of them have resulted in significant economic and human damage, including the 1755 AD event (known as the tsunami of Lisbon). This indicates the need to implement adaptation and mitigation strategies, based on long-term studies of these extreme events to deduce their spatial and temporal variability. Using two cores (TAH17-1 and TAH17-3) collected from the Tahaddart estuary (NW of Morocco), this work aims to identify deposits, set up by these high energy events during the mid to late Holocene period. The sedimentological, geochemical and geochronological analyses carried out on these geological archives show two fining-upward sequences, indicating a progressive change from a purely sandy marine facies, between 6500 and 3500 BP, to another finer and more terrigenous one. The fine sedimentation, which has dominated in the estuary during the last 3500 years, has facilitated the recording of several marine submersion events in the form of isolated sandy layers. Chronological data have made it possible to date four deposits. Two (1-E1 and 3-E1) were put in place about 250 years ago, which corresponds, according to historical records, to the 1755 AD Lisbon tsunami. Two other deposits (1-E13 and 1-E14) are dated around 3200 BP and represent unknown submersion events on the Moroccan Atlantic coast.</p>

Implementation of a high energy 4ω probe beam on the Omega laser

2004 ◽  
Vol 75 (10) ◽  
pp. 3906-3908 ◽  
Author(s):  
A. J. Mackinnon ◽  
S. Shiromizu ◽  
G. Antonini ◽  
J. Auerbach ◽  
K. Haney ◽  
...  
Keyword(s):  
Probe Beam ◽  
High Energy ◽  
Omega Laser

scholarly journals FIELD MEASUREMENTS AND MODELLING OF NEARSHORE CURRENTS AT A HIGH-ENERGY GEOLOGICALLY-CONSTRAINED BEACH

2020 ◽  
pp. 18
Author(s):  
Arthur Mouragues ◽  
Philippe Bonneton ◽  
Bruno Castelle ◽  
Vincent Marieu
Keyword(s):  
Surf Zone ◽  
Low Frequency ◽  
Field Measurements ◽  
High Energy ◽  
Oblique Wave ◽  
Wave Forcing ◽  
Circulation Patterns ◽  
Wave Conditions ◽  
Nearshore Currents ◽  
Set Up

We present field measurements of nearshore currents at a high-energy mesotidal beach with the presence of a 500-m headland and a submerged reef. Small changes in wave forcing and tide elevation were found to largely impact circulation patterns. In particular, under 4-m oblique wave conditions, our measurements indicate the presence of an intense low-frequency fluctuating deflection rip flowing against the headland and extending well beyond the surf zone. An XBeach model is further set up to hindcast such flow patterns.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/EiqnjBIkWJE

Implementing effective animal-based measurements for assessing animal welfare on farms and slaughter plants.

2021 ◽  
pp. 60-83
Author(s):  
Temple Grandin
Keyword(s):  
Cold Stress ◽  
Animal Welfare ◽  
Body Condition ◽  
Critical Points ◽  
Heat And Cold Stress ◽  
Standards And Guidelines ◽  
The Difference ◽  
Set Up ◽  
Animal Handling ◽  
Input Resource

Abstract This chapter describes how to write clear animal welfare standards and guidelines that will be interpreted the same way by different people; the difference between animal-based outcome measures and input resource-based standards; how to determine the most important core criteria or critical points to prevent abuse or neglect; easy-to-use measures for assessing body condition, lameness, injuries, condition of haircoat/feathers, animal handling, hygiene, heat and cold stress and the presence of abnormal behaviour and how to set up effective animal welfare auditing programmes.

Linear model predictive control for vision-based UAV pursuit

2020 ◽  
Vol 8 (4) ◽  
pp. 334-363 ◽  
Author(s):  
Christopher C. Surma ◽  
Martin Barczyk
Keyword(s):  
Model Predictive Control ◽  
Linear Model ◽  
Predictive Control ◽  
High Energy ◽  
Aerial Videography ◽  
Combined Control ◽  
Communication Devices ◽  
Laser Systems ◽  
Commercial Off The Shelf ◽  
Set Up

This article develops and implements a vision-based unmanned aerial vehicle (UAV)-to-UAV pursuit system using a commercial off-the-shelf Parrot AR.Drone 2.0 quadrotor. This technology is intended as a countermeasure to rogue drones carrying out activities such as flying in restricted airspace, performing unauthorized aerial videography, transporting contraband and other criminal activities, or being used as improvised weapons. The proposed approach offers benefits over other current solutions, such as wide-area radio-frequency jamming that interferes with regular communication devices or high-energy military laser systems that are expensive and time consuming to set up. A linear dynamics model of the AR.Drone 2.0 vehicle stabilized by its onboard feedback control system is derived, and its parameters are experimentally identified. A linear model predictive control is developed to track specified flight trajectories, then implemented and validated in hardware flight tests. Detection and ranging of the target UAV from the pursuer UAV’s onboard monocular camera are performed using the YOLO v2 convolutional neural network algorithm. The combined control and vision design is implemented in hardware and tested quantitatively in flight experiments.

scholarly journals Estimation of the combustion products from the cylinder of the petrol engine and its relation to "knock"

1935 ◽  
Vol 234 (744) ◽  
pp. 433-521 ◽  
Keyword(s):  
High Pressure ◽  
Experimental Evidence ◽  
Combustion Products ◽  
High Energy ◽  
High Pressure And Temperature ◽  
Engine Cylinder ◽  
Engine Knock ◽  
Slow Combustion ◽  
Set Up ◽  
Exhaust Valves

As a result of a variety of experiments it was suggested in 1928 that engine “knock” “appears to be due to inequality in the condition of the charge (in the engine cylinder) set up, particularly in regions of high pressure and temperature as in the neighbourhood of hot exhaust valves. This inequality provides regions of high energy containing molecules in high energy states where reaction can spread more quickly.” This view was a little vague, and was arrived at from indirect experimental evidence. It was with a view to obtaining more precise evidence that knock was occasioned in the flame as the result of processes of slow combustion occurring in the gaseous charge prior to its arrival that the present work was undertaken. Callendar and those working with him had simultaneously arrived at the conclusion that “knock” was occasioned in much the same manner, but they adopted the more definite view that peroxides of the hydrocarbons were formed and stored in the gas, and then suddenly detonated, so igniting a whole region of the gas simultaneously. This view had also been advanced by Moureu and Dufraisse.

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