scholarly journals One- and Two-Band Sensors and Algorithms to Derive aCDOM(440) from Global Above- and In-Water Optical Observations

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5384
Author(s):  
Stanford B. Hooker ◽  
Henry F. Houskeeper ◽  
Randall N. Lind ◽  
Koji Suzuki
Keyword(s):  
Optical Sensors ◽  
Measurement Techniques ◽  
Autonomous Systems ◽  
Optical Observations ◽  
Optical Systems ◽  
Biogeochemical Processes ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Fit For Purpose ◽  
The Cost

The colored (or chromophoric, depending on the literature) dissolved organic matter (CDOM) spectral absorption coefficient, aCDOM(λ), is a variable of global interest that has broad application in the study of biogeochemical processes. Within the funding for scientific research, there is an overarching trend towards increasing the scale of observations both temporally and spatially, while simultaneously reducing the cost per sample, driving a systemic shift towards autonomous sensors and observations. Legacy aCDOM(λ) measurement techniques can be cost-prohibitive and do not lend themselves toward autonomous systems. Spectrally rich datasets carefully collected with advanced optical systems in diverse locations that span a global range of water bodies, in conjunction with appropriate quality assurance and processing, allow for the analysis of methods and algorithms to estimate aCDOM(440) from spectrally constrained one- and two-band subsets of the data. The resulting algorithms were evaluated with respect to established fit-for-purpose criteria as well as quality assured archival data. Existing and proposed optical sensors capable of exploiting the algorithms and intended for autonomous platforms are identified and discussed. One-band in-water algorithms and two-band above-water algorithms showed the most promise for practical use (accuracy of 3.0% and 6.5%, respectively), with the latter demonstrated for an airborne dataset.

scholarly journals Application of Wireless Sensor Networks to Prevent the Spread of Forest Fires

2021 ◽  
Vol 11 (11) ◽  
pp. 199-203
Author(s):  
Le Quang Bon ◽  
Keyword(s):  
Wireless Sensor Network ◽  
Sensor Network ◽  
Optical Sensors ◽  
Forest Fires ◽  
Digital Camera ◽  
Partial Solution ◽  
Optical Systems ◽  
Wireless Sensor ◽  
Network Systems ◽  
Camera Systems

The objective of this article is to identify current trends and prospects for the use of technical facilities and installations to prevent the spread of wildfires by analyzing the literature. The analysis of the literature has allowed an analysis of different ground-based wildfire detection and monitoring systems: optical sensors and digital camera systems, and wireless sensor network systems. The author concludes that the wireless sensor network can be seen as a partial solution when used in combination with other technologies. Keywords—observation towers, optical systems, optical sensors, digital cameras, wireless sensor network.

scholarly journals Investigation of Band Tailing in Sputtered ZnO:Al Thin Films Regarding Structural Properties and Impurities

2014 ◽  
Vol 1699 ◽  
Author(s):  
Steffi Schönau ◽  
Florian Ruske ◽  
Sebastian Neubert ◽  
Bernd Rech
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Pure Aluminum ◽  
Growth Conditions ◽  
Band Gap Energy ◽  
Absorption Feature ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Additional Absorption ◽  
Band Tailing

ABSTRACTThin films of pure aluminum doped ZnO and with addition of nitrogen, oxygen and hydrogen have been prepared by magnetron sputtering. The spectral absorption coefficient close to the band gap energy has been determined by spectrophotometry and analyzed regarding band tailing and creation of defect bands. We found, that an improvement of Raman crystallinity under O2- rich growth conditions is not accompanied by a suppression of band tailing as expected. An additional absorption feature evolves for layers grown in N2 containing atmosphere. Doping with hydrogen attenuates sub-band gap absorption.

Continuous measurement of pollution due to urban effluents under wet conditions using optical systems

1995 ◽  
Vol 32 (1) ◽  
pp. 241-247
Author(s):  
Gwenael Ruban
Keyword(s):  
Optical Sensors ◽  
Optical Systems ◽  
Sample Collection ◽  
Rainfall Events ◽  
Automation Systems ◽  
Calibration Sample ◽  
Long Time ◽  
Pollution Measurement ◽  
Measurement Validation ◽  
Better Than

Optical sensors appear well adapted to the pollution measurement of urban discharges during wet weather: they allow a continuous and long time investigation of sudden and highly variable phenomena such as rainfall events. They may also be connected to remote monitoring and sanitary equipment automation systems. This paper deals with the measurement principles and use of this type of equipment: adjustment and calibration, sample collection, equipment maintenance and measurement validation. Taking into account the hydraulicity (flow rate or velocity) allows one to improve appreciably the calibration for runoff waters. Calibration at the laboratory seems better than calibration using registered data on the field, as it makes it possible to eliminate the Suspended Matter under-estimation resulting from sampling/analysis.

scholarly journals Quantitative evaluation of seven optical sensors for cloud microphysical measurements at the Puy-de-Dôme Observatory, France

2015 ◽  
Vol 8 (10) ◽  
pp. 4347-4367 ◽  
Author(s):  
G. Guyot ◽  
C. Gourbeyre ◽  
G. Febvre ◽  
V. Shcherbakov ◽  
F. Burnet ◽  
...  
Keyword(s):  
Optical Properties ◽  
Wind Tunnel ◽  
Optical Sensors ◽  
Wind Direction ◽  
Total Concentration ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Number Concentration ◽  
Effective Diameter ◽  
Particle Volume

Abstract. Clouds have an important role in Earth's radiative budget. Since the late 1970s, considerable instrumental developments have been made in order to quantify cloud microphysical and optical properties, for both airborne and ground-based applications. Intercomparison studies have been carried out in the past to assess the reliability of cloud microphysical properties inferred from various measurement techniques. However, observational uncertainties still exist, especially for droplet size distribution measurements and need to be reduced. In this work, we discuss results from an intercomparison campaign, performed at the Puy de Dôme in May 2013. During this campaign, a unique set of cloud instruments was operating simultaneously in ambient air conditions and in a wind tunnel. A Particle Volume Monitor (PVM-100), a Forward Scattering Spectrometer Probe (FSSP), a Fog Monitor (FM-100), and a Present Weather Detector (PWD) were sampling on the roof of the station. Within a wind tunnel located underneath the roof, two Cloud Droplet Probes (CDPs) and a modified FSSP (SPP-100) were operating. The main objectives of this paper are (1) to study the effects of wind direction and speed on ground-based cloud observations, (2) to quantify the cloud parameters discrepancies observed by the different instruments, and (3) to develop methods to improve the quantification of the measurements. The results revealed that all instruments showed a good agreement in their sizing abilities, both in terms of amplitude and variability. However, some of them, especially the FM-100, the FSSP and the SPP, displayed large discrepancies in their capability to assess the magnitude of the total number concentration of the cloud droplets. As a result, the total liquid water content can differ by up to a factor of 5 between the probes. The use of a standardization procedure, based on data of integrating probes (PVM-100 or visibilimeter) and extinction coefficient comparison substantially enhanced the instrumental agreement. During this experiment, the total concentration agreed in variations with the visibilimeter, except for the FSSP, so a corrective factor can be applied and it ranges from 0.44 to 2.2. This intercomparison study highlights the necessity to have an instrument which provides a bulk measurement of cloud microphysical or optical properties during cloud ground-based campaigns. Moreover, the FM and FSSP orientation was modified with an angle ranging from 30 to 90° angle with wind speeds from 3 to 7 m s−1. The results show that the induced number concentration loss is between 29 and 98 % for the FSSP and between 15 and 68 % for the FM-100. In particular, FSSP experiments showed strong discrepancies when the wind speed was lower than 3 m s−1 and/or when the angle between the wind direction and the orientation of the instruments is greater than 30°. An inadequate orientation of the FSSP towards the wind direction leads to an underestimation of the measured effective diameter.

Needle Displacement Visualization With Simultaneous Measurement of Injection Rate for CR Diesel Injector: A Novel Experimental Technique

2019 ◽  
Author(s):  
Giancarlo Chiatti ◽  
Ornella Chiavola ◽  
Fulvio Palmieri
Keyword(s):  
Experimental Technique ◽  
Optical Sensors ◽  
Digital Imaging ◽  
Measurement Techniques ◽  
Combustion Process ◽  
Injection Rate ◽  
The Other ◽  
Pollutant Emissions ◽  
Injection System ◽  
Injection Strategy

Abstract The control of combustion is a key topic for diesel engine development in terms of performance and pollutant emissions. The combustion process is piloted through the proper injection strategy, which depends on the features of the injection system. Mechanical-hydraulic models of high-pressure injection systems often support the accurate tuning of the injection strategy. The higher is the accuracy in the modeling of the electro-injector behavior, the deeper is the role of the simulation. Under such a viewpoint, the validation of the models is undoubtedly fundamental. One of the most crucial information characterizing the injector relies on the measurement of the needle displacement. Needle displacement affects rate, timing and quantity of injected fuel; it also influences the flow features within the nozzle, which are then reflected by the primary atomization process. Needle is considered hardly-accessible due to the injector architecture itself, making difficult the measurement of displacement. Nevertheless, the problem has been handled in different ways and three measurement techniques have been proposed. On one side, there is the measurement based on eddy-current transducers; on the other side, there are two alternative procedures, based on the use of optical sensors. However, in all cases, the needle is traced indirectly, since the position of the control plunger of the needle is observed. The current contribution presents a novel experimental technique for the measurement of needle displacement. The method is based on the direct visualization of the needle, allowing for the detailed definition of its law of motion through digital imaging, when the injector is characterized on a test-rig under transient conditions. The paper describes the details of the diagnostic scheme, the experimental facility and the digital imaging set-up. The main features and the capabilities of the method are discussed, in comparison with the other available techniques.

scholarly journals 3D-printed automation for optimized PET radiochemistry

2019 ◽  
Vol 5 (9) ◽  
pp. eaax4762
Author(s):  
Alejandro Amor-Coarasa ◽  
James M. Kelly ◽  
John W. Babich
Keyword(s):  
Three Dimensional ◽  
Emission Tomography ◽  
Reaction Conditions ◽  
Synthesis Time ◽  
Reduce Radiation Exposure ◽  
Molar Activity ◽  
Positron Emission ◽  
3D Printed ◽  
Fit For Purpose ◽  
The Cost

Reproducible batch synthesis of radioligands for imaging by positron emission tomography (PET) in a manner that maximizes ligand yield, purity, and molar activity, and minimizes cost and exposure to radiation, remains a challenge, as new and synthetically complex radioligands become available. Commercially available automated synthesis units (ASUs) solve many of these challenges but are costly to install and cannot always accommodate diverse chemistries. Through a reiterative design process, we exploit the proliferation of three-dimensional (3D) printing technologies to translate optimized reaction conditions into ASUs composed of 3D-printed, electronic, and robotic parts. Our units are portable and robust and reduce radiation exposure, shorten synthesis time, and improve the yield of the final radiopharmaceutical for a fraction of the cost of a commercial ASU. These 3D-printed ASUs highlight the gains that can be made by designing a fit-for-purpose ASU to accommodate a synthesis over accommodating a synthesis to an unfit ASU.

Spectral Absorption Coefficient of Molten Aluminum Oxide from.0.385 to 0.780 mum

1995 ◽  
Vol 78 (3) ◽  
pp. 583-587 ◽  
Author(s):  
J. K. Richard Weber ◽  
Shankar Krishnan ◽  
Collin D. Anderson ◽  
Paul C. Nordine
Keyword(s):  
Absorption Coefficient ◽  
Aluminum Oxide ◽  
Molten Aluminum ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient
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