An Image Preprocessing Model of Coal and Gangue in High Dust and Low Light Conditions Based on the Joint Enhancement Algorithm

The lighting facilities are affected due to conditions of coal mine in high dust pollution, which bring problems of dim, shadow, or reflection to coal and gangue images, and make it difficult to identify coal and gangue from background. To solve these problems, a preprocessing model for low-quality images of coal and gangue is proposed based on a joint enhancement algorithm in this paper. Firstly, the characteristics of coal and gangue images are analyzed in detail, and the improvement ways are put forward. Secondly, the image preprocessing flow of coal and gangue is established based on local features. Finally, a joint image enhancement algorithm is proposed based on bilateral filtering. In experimental, K-means clustering segmentation is used to compare the segmentation results of different preprocessing methods with information entropy and structural similarity. Through the simulation experiments for six scenes, the results show that the proposed preprocessing model can effectively reduce noise, improve overall brightness and contrast, and enhance image details. At the same time, it has a better segmentation effect. All of these can provide a better basis for target recognition.

Graphene spin-coated electrode for polyacrylonitrile acoustic nanogenerators

In recent years piezoelectric nanogenerators, due to their more durability in high dust or humidity are more attractive than triboelectric ones. So, increasing their outputs is the subject of much researches. I focused on electrodes of the acoustic nanofibers nanogenerators for the first time. Here, I introduced a new electrode that is cheaper and does not result in lower outputs. Here for the first time graphene spin-coated ink was used for polyacrylonitrile-based acoustic nanogenerator. The results of the tests compared with the in-situ synthesis of nickel nanoparticles on the layer and using graphene spin-coated screen ink and conductive tapes. Finally, producing sound by this graphene ink was done too.

The dust and gas environment of comet 8P/Tuttle

ABSTRACT Comet 8P/Tuttle has been selected as a possible backup target for the Comet Interceptor mission (ESA). This comet was observed intensively during its previous perihelion passage, in 2008 January. From those observations, important information was obtained about the physical properties of the nucleus and coma. This study focuses on the coma of 8P/Tuttle using visible spectra and images to derive gas and dust production rates. The production rates obtained suggest that this comet can be considered as ‘typical’ concerning the C2/CN and C3/CN ratios, although, depending on the criteria adopted, it could be defined as C3 depleted. NH2 production rates suggest an enrichment of this molecule. Visible and infrared images have been analysed using a Monte Carlo dust tail model. At comparatively large heliocentric distances, the coma is characterized by a dust-to-water ratio around or less than 1. Nevertheless, when the comet approaches perihelion, and the subsolar latitude crosses the equator, the coma dust-to-water ratio increases significantly, reaching values larger than six. Such a high dust-to-gas ratio around perihelion suggests that the nucleus of 8P/Tuttle is also ‘typical’ regarding the refractory content, considering the comparatively high values of that magnitude estimated for different comets.

Recent dust variability over South Asia controlled by North Atlantic SST anomalies

<p>Several studies have associated high dust years over South Asia to warming of the central or eastern equatorial Pacific Ocean (El Nino conditions) and the resulting weakening of the summer monsoon. Using satellite aerosol data for 2001-2018, we show that there has been a departure from this relation since the second decade of the 21st century with the North Atlantic Ocean emerging as a major driver of interannual variability of dust over South Asia. This change in relation coincides with the end of the global warming hiatus and a shift towards persistent positive phase of the winter North Atlantic Oscillation (NAO). Positive phase of the NAO induces cold phase of the spring/summer North Atlantic sea surface temperature (SST) tripole pattern. We show here that high dust activity during 2011-2018 is associated with positive SST anomaly over the mid-latitude North Atlantic and negative SST anomaly over the sub-tropical North Atlantic: the two southern arms of the SST tripole pattern. Interestingly, the relation between NAO and these two southern arms of the SST tripole has undergone changes in recent years, which has impacted the South Asian monsoon. The result is general drying over South Asia and an increase in the strength of the dust-carrying northwesterlies. Simulations with the Community Earth System Model (CESM) shows that SST tripole-like anomalies recorded during 2011-2018 over the North Atlantic can generate mid-latitude wave train that weakens the South Asian monsoon circulation, leads to surface high pressure anomalies and increase in dust emission and transport over northwest India and Pakistan. Most of the increase in the dust load can be attributed to enhanced transport at 800 hPa pressure level during May-June, which can lead to ~40-50% increase in dust concentrations at this level.</p>

Simulated regional dust cycle in the Carpathian Basin and the Adriatic Sea region during the Last Glacial Maximum

<p>Different climate and environmental conditions dominated in the Carpathian Basin and the adjacent northern Italy/Adriatic region during the Last Glacial Maximum (LGM), as compared to today. For instance, high dust accumulation rates recorded in loess deposits point to an active dust cycle during the LGM. We investigated the climate conditions and regional dust cycle based on high-resolution (grid spacing of ~8.5 km) regional climate simulations for LGM conditions. The model output is in good agreement with proxy data, reproducing cold and dry conditions for the LGM. Highest dust emissions are simulated to the east of the Alpine ice sheet and in the Kvarner Bay region. While simulated dust deposition plumes in the northern Carpathian Basin indicate prevailing northerly (NW, N and NE) winds during dust events, strong Bora winds flowing down the slopes of the Dinaric Alps appear to play a major role in the local to regional dust cycle in the northern Adriatic region. From a seasonal perspective, the simulated dust cycle is most active during late winter and spring. A detailed analysis of climate and environmental conditions at key areas reveals that high wind speeds and low precipitation rates during late winter and spring correlate well with high dust emissions. In contrast, lower wind speeds, increasing precipitation, and the greening of vegetation prevent high dust emissions during summer and autumn. The occurrence of cyclonic circulation patterns in the Adriatic shelf region reveals that individual cyclones played an important role in transporting dust particles from the alluvial Po plain towards the eastern Adriatic loess deposition sites.</p>

Atmospheric circulation and meteorological conditions during dust aerosol episodes over the broader Mediterranean Basin. The case of 16 June 2016

<p>Mediterranean Basin (MB), due to its position near to the greatest world deserts (the Sahara Desert in North Africa and the deserts of Middle East), is frequently affected by dust transport. This results in dust episodes, associated with high Dust Aerosol (DA) loads reaching the northern parts of MB, taking place every year with different intensity, but with specific seasonal and spatial characteristics. The seasonal and spatial characteristics of Dust Aerosol Episodes (DAEs) in the region are connected to specific atmospheric conditions that favor the injection of DA into the region’s atmosphere, as well as to specific atmospheric circulation characteristics favoring the transport to the MB.</p><p>DA not only are affected by, but they also can affect the atmospheric conditions and thus the regional weather and climate regime. Specifically, due to their ability to absorb the shortwave, but also the longwave, radiation, DA can modify the temperature structure of the atmosphere as well as the radiative budget. In addition, DA are effective Ice Nuclei (IN), and also, under mature stages, Cloud Condensation Nuclei (CCN), thus affecting cloud properties. These effects of DA become more important, but also complicated, when high dust loads are associated with other aerosol types, e.g. sea-salt (SS) and biomass burning (BB) over a region with high solar radiation, diverse topography and cloud regimes such as the MB.</p><p>In the present study, the atmospheric circulation (geopotential height and mean sea level pressure), as well as the meteorological conditions (cloud fraction, cloud optical thickness, cloud phase, temperature and humidity profiles and vertical velocity) before, during and after an extreme Dust Aerosol Episode Case (DAEC) that took place over the western MB on June 16, 2016 are examined. The studied DAEC is identified using a satellite algorithm, which uses MODIS C6.1 and OMI OMAERUV derived aerosol optical properties.  Emphasis is given to the understanding of the 3-D structure of the episode and its possible effects on the atmospheric temperature and humidity regime, as well as on cloud properties. For this reason, different reanalyses and satellite data, namely from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis Project), MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, Version 2) and MODIS databases, are analyzed. In addition, the vertical aerosol profile is obtained from MERRA-2 data.</p>

Reduction of Dust in the Longwall Faces of Coal Mines: Problems and Perspective Solutions

Despite the increasing reliance on alternative and renewable energy sources in recent years, coal is set to continue being the most vital element of the global energy sector. The world coal supply (1,070 billion tons) shall last for 130 years with the current mining levels. In contrast to some large countries (such as the USA and Germany) reducing their coal production and consumption, Russia plans to increase the coal production levels as part of its strategy regarding the future of the coal mining industry. The annual volume of coal output is more than 440 million tons, 1/3 of which is extracted underground. The current and projected levels of underground coal mining present a set of issues pertaining to elevated dust concentration in the air and increased dust dispersion. High dust concentration in the air leads to damage to the skin, mucous membranes and respiratory organs of workers. Also, with high dust content, visibility in the longwalls decreases, the risk of injury and accidents increases. The present article deals with the formation of detrimental dust conditions that happen in the course of cleaning and preparatory mining operations in coal mines. The article reviews the international practices on dust reduction in coal mining operations and provides an overview of studies on dustiness levels and airborne dust composition in longwall faces of coal mines. It also presents mathematical models dealing with projections on dust composition, including projections on most hazardous dust particles the size of 0.1-10 and 0.1-35 μm. The article also presents a newly developed wetting method showing increased effectiveness.

A 15-Year Climatology of Desert Dust Episodes in the Broader Mediterranean Basin

In the present study, dust aerosol episodes (DAEs) in the broader Mediterranean Basin (MB) are investigated over a 15-year (2005–2019) period using contemporary MODIS Collection 6.1 and OMI OMAERUV satellite data and a satellite algorithm applying a thresholding technique on selected aerosol optical properties. The algorithm operates on a daily and 1° × 1° pixel level basis, first identifying the presence of dust, and consequently requiring the presence of unusually high dust loads, i.e., dust episodes. Apart from the presence of pixel-level DAEs, an extended spatial coverage of dust is also required. Thus, a specific day is characterized as a Dust Aerosol Episode Day (DAED), when at least 30 episodic pixels exist over Mediterranean Basin (MB). According to the algorithm results, 166 DAEDs (116 strong and 50 extreme) took place in the MB from 2005 to 2019. Most DAEDs occurred in spring (47%) and summer (38%), while a different seasonality is observed for strong and extreme episodes. The interannual variability of DAEDs reveal a decreasing trend, which is however not statistically significant.

UV dust attenuation as a function of stellar mass and its evolution with redshift

ABSTRACT Studying the ultraviolet dust attenuation, as well as its relation to other galaxy parameters such as the stellar mass, plays an important role in multiwavelength research. This work relates the dust attenuation to the stellar mass of star-forming galaxies, and its evolution with redshift. A sample of galaxies with an estimate of the dust attenuation computed from the infrared excess was used. The dust attenuation versus stellar mass data, separated in redshift bins, was modelled by a single parameter linear function, assuming a non-zero constant apparent dust attenuation for low-mass galaxies. But the origin of this effect is still to be determined and several possibilities are explored (actual high dust content, variation of the dust-to-metal ratio, variation of the stars–dust geometry). The best-fitting parameter of this model is then used to study the redshift evolution of the cosmic dust attenuation and is found to be in agreement with results from the literature. This work also gives evidence to a redshift evolution of the dust attenuation–stellar mass relationship, as is suggested by recent works in the highest redshift range.