Near-Field and Far-Field Sampling of Aerosol Plumes to Evaluate Particulate Emission Rates From a Falling Particle Receiver During On-Sun Testing

Abstract High-temperature falling particle receivers are being investigated for next-generation concentrating solar power applications. Small sand-like particles are released into an open-cavity receiver and are irradiated by concentrated sunlight from a field of heliostats. The particles are heated to temperatures over 700 °C and can be stored to produce heat for electricity generation or industrial applications when needed. As the particles fall through the receiver, particles and particulate fragments in the form of aerosolized dust can be emitted from the aperture, which can lower thermal efficiency, increase costs of particle replacement, and pose a particulate matter (PM) inhalation risk. This paper describes sampling methods that were deployed during on-sun tests to record near-field (several meters) and far-field (tens to hundreds of meters) concentrations of aerosol particles within emitted plumes. The objective was to quantify the particulate emission rates and loss from the falling particle receiver in relation to OSHA and EPA National Ambient Air Quality Standards (NAAQS). Near-field instrumentation placed on the platform in proximity to the receiver aperture included several real-time aerosol size distribution and concentration measurement techniques, including a TSI Aerodynamic Particle Sizers (APS), TSI DustTraks, Handix Portable Optical Particle Spectrometers (POPS), Alphasense Optical Particle Counters (OPC), TSI Condensation Particle Counters (CPC), Cascade Particle Impactors, 3D-printed prototype tipping buckets, and meteorological instrumentation. Far-field particle sampling techniques utilized multiple tethered balloons located upwind and downwind of the particle receiver to measure the advected plume concentrations using a suite of airborne aerosol and meteorological instruments including POPS, CPCs, OPCs and cascade impactors. The combined aerosol size distribution for all these instruments spanned particle sizes from 0.02 μm – 500 μm. Results showed a strong influence of wind direction on particle emissions and concentration, with preliminary results showing representative concentrations below both the OSHA and NAAQS standards.

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Hybrid multilevel plane wave based near-field far-field transformation utilising combined near- and far-field translations

Advances in Radio Science ◽

10.5194/ars-7-17-2009 ◽

2009 ◽

Vol 7 ◽

pp. 17-22 ◽

Cited By ~ 1

Author(s):

C. H. Schmidt ◽

T. F. Eibert

Keyword(s):

Near Field ◽

Measurement Techniques ◽

Plane Waves ◽

Low Complexity ◽

Far Field ◽

Computation Complexity ◽

Low Frequencies ◽

Field Transformation ◽

Translation Operators ◽

Equivalent Sources

Abstract. The radiation of large antennas and those operating at low frequencies can be determined efficiently by near-field measurement techniques and a subsequent near-field far-field transformation. Various approaches and algorithms have been researched but for electrically large antennas and irregular measurement contours advanced algorithms with low computation complexity are required. In this paper an algorithm employing plane waves as equivalent sources and utilising efficient diagonal translation operators is presented. The efficiency is further enhanced using simple far-field translations in combination with the expensive near-field translations. In this way a low complexity near-field transformation is achieved, which works for arbitrary sample point distributions and incorporates a full probe correction without increasing the complexity.

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Femtosecond Laser Precision Engineering: From Micron, Submicron, to Nanoscale

Ultrafast Science ◽

10.34133/2021/9783514 ◽

2021 ◽

Vol 2021 ◽

pp. 1-22

Author(s):

Zhenyuan Lin ◽

Minghui Hong

Keyword(s):

Femtosecond Laser ◽

High Efficiency ◽

Near Field ◽

Ambient Air ◽

Optical Microscope ◽

Far Field ◽

Large Area ◽

Precision Engineering ◽

Processing Strategies ◽

Near Field Effect

As a noncontact strategy with flexible tools and high efficiency, laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication, especially to achieve novel functional photoelectric structures and devices. For the microscale creation, several femtosecond laser fabrication methods, including multiphoton absorption, laser-induced plasma-assisted ablation, and incubation effect have been developed. Meanwhile, the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales. Down to nanoscale feature sizes, advanced processing strategies, such as near-field scanning optical microscope, atomic force microscope, and microsphere, are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to ~25 nm due to near-field effect. The most fascinating femtosecond laser precision engineering is the possibility of large-area, high-throughput, and far-field nanofabrication. In combination with special strategies, including dual femtosecond laser beam irradiation, ~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air. The challenges and perspectives in the femtosecond laser precision engineering are also discussed.

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Non-redundant Spherical Near-Field to Far-Field Transformation for a Volumetric Antenna in Offset Configuration

The Open Electrical & Electronic Engineering Journal ◽

10.2174/1874129001913010019 ◽

2019 ◽

Vol 13 (1) ◽

pp. 19-29 ◽

Cited By ~ 3

Author(s):

Francesco D’Agostino ◽

Flaminio Ferrara ◽

Claudio Gennarelli ◽

Rocco Guerriero ◽

Massimo Migliozzi

Keyword(s):

Near Field ◽

Measurement Techniques ◽

Data Gathering ◽

Experimental Tests ◽

Precise Determination ◽

Far Field ◽

Interpolation Algorithm ◽

Classical Technique ◽

Field Transformation

Background: The development of fast Near-Field (NF) measurement techniques allowing the precise determination of the Far-Field (FF) radiation features of an antenna is becoming more and more challenging nowadays. Objective: The goal of the article is the development of an NF To FF Transformation (NFTFFT) with spherical scan for offset mounted volumetric Antennas Under Tests (AUTs) requiring, unlike the classical technique, a reduced set of NF data, that is of the same amount as for the onset mounting case, thus making data gathering faster. In fact, the number of NF data needed by the standard approach may considerably increase in this case, since the size of the smallest sphere surrounding the AUT and centered at the center of the measurement sphere rises. Methods: This goal has been achieved by profitably exploiting the non-redundant sampling representation of electromagnetic field and assuming a volumetric AUT as contained in a sphere. An optimal sampling interpolation algorithm is then employed to precisely reconstruct the input NF data for the traditional spherical NFTFFT from the reduced set of the collected ones. Conclusion: The numerical simulations and experimental tests demonstrate the effectiveness of the developed approach accounting for an offset mounting of the AUT.

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Influence of semi-volatile aerosols on physical and optical properties of aerosols in the Kathmandu Valley

10.5194/acp-2017-287 ◽

2017 ◽

Cited By ~ 2

Author(s):

Sujan Shrestha ◽

Siva Praveen Puppala ◽

Bhupesh Adhikary ◽

Kundan Lal Shrestha ◽

Arnico K. Panday

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Room Temperature ◽

Ambient Air ◽

Aerosol Size Distribution ◽

Volatile Fraction ◽

Kathmandu Valley ◽

Effective Diameter ◽

Distribution Analysis ◽

Aerosol Fraction

Abstract. A field study was conducted in the urban atmosphere of the Kathmandu Valley to study influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. The study was carried out during the pre-monsoon season of 2015. Our experimental setup consisted of a single ambient air inlet from which the flow was split into two sets of identical sampling instruments; the first set was connected directly with an ambient sample while the second set received the air sample through a thermodenuder (TDD). Four sets of experiments were conducted for our study to understand aerosol number, size distribution, absorption, and scattering properties using Condensation Particle Counter (CPC), Scanning Mobility Particle Sizer (SMPS), Aethalometer (AE33) and Nephelometer respectively. The influence of semi-volatile aerosols were calculated based on the difference of aerosol properties at room temperature, 50 °C, 100 °C, 150 °C, 200 °C, 250 °C and 300 °C through set TDD temperatures to ambient sample. Our results show that with increasing TDD temperature, the evaporated fraction of semi-volatile aerosols also increased. At room temperature the semi-volatile fraction of aerosol number was 12 %, while at 300 °C it was as high as 49 % of ambient aerosol. Aerosol size distribution analysis from SMPS shows that with an increase in temperature from 50 °C to 300 °C, the peak mobility diameter of particles shifted from around 60 nm to 40 nm. However, no distinct change in the effective diameter of the aerosol size distribution was observed with increase in set TDD temperature. The change in size of aerosols due to loss of semi-volatile component had a stronger influence (~ 70 %) at larger size bins when compared to (~ 20 %) at smaller bins of SMPS. At 300 °C, the semi-volatile aerosols amplified BC absorption by approximately 28 % while scattering by the semi-volatile aerosols contributed up to 71 % of total scattering. The Scattering Angstrom Exponent (SAE) of the semi-volatile aerosol fraction was found to be more sensitive at lower temperatures (

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Comparison of pipette method and state of the art analytical techniques to determine granulometric properties of sediments and soils

Hungarian Geographical Bulletin ◽

10.15201/hungeobull.69.1.3 ◽

2020 ◽

Vol 69 (1) ◽

pp. 27-39

Author(s):

Fruzsina Gresina

Keyword(s):

Earth Sciences ◽

Particle Size ◽

Grain Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Measurement Techniques ◽

Industrial Applications ◽

Laser Diffraction ◽

Cement Industry ◽

Coarse Grained

The determination of particle size distribution is a crucial issue in various fields of earth sciences (e.g., Quaternary research, sedimentology, stratigraphy, structural geology, volcanology), environmental sciences as well as diverse industrial applications (e.g., pharmaceuticals, cement industry). New measurement techniques developed as a result of industrial demands have also gained ground in environmental and Earth sciences research. The new techniques (especially laser diffraction) have enabled the particle characterisation in the broader size-range with a more detailed resolution. Still, they have to be compared with data obtained by classical methods. In light of the above, the primary aim of our research is to examine the methods of particle size determination critically. Excessive oversimplifications of particle size analyses routinely have used in paleo-environmental and paleo-climatological reconstructions, and other sedimentary studies, as well as insufficient knowledge of the background of the applied methods, distort the interpretation of the results. Over the past four decades, laser diffraction particle size analysers have proven to be practical tools of particle size characterisation. However, the shape of the natural sediment and soil particles are irregular and, therefore, affects the particle size distribution results obtained by different methods. The results of the traditional pipette method differed from laser diffraction results. The presence or absence of the pretreatments did control the differences between the two techniques. The results of Fraunhofer optical method were significantly different from Mie theory because it can detect much lower volume percentages of finer particles. Grain size results of coarse-grained samples measured by different laser diffraction devices were more comparable than the results of more clayey samples. The ratios of different sizes were changed due to the hydrochloric acid and hydrogen peroxide pretreatments. The comparison of different techniques is necessary to revaluate standards in grain size measurements which can enable the shift from conventional methods to more productive and reproducible methods. Still, light scattering techniques have not yet been able to displace classical methods in Earth sciences completely, in contrast to industrial applications.

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