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Artykuły w czasopismach na temat "DUST ACCUMULATION LEVELS"
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Perez-Anaya, Eduardo, David A. Elvira-Ortiz, Roque A. Osornio-Rios i Jose A. Antonino-Daviu. "Methodology for the Identification of Dust Accumulation Levels in Photovoltaic Panels Based in Heuristic-Statistical Techniques". Electronics 11, nr 21 (28.10.2022): 3503. http://dx.doi.org/10.3390/electronics11213503.
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The use of renewable energies is increasing around the world in order to deal with the environmental and economic problems related with conventional generation. In this sense, photovoltaic generation is one of the most promising technologies because of the high availability of sunlight, the easiness of maintenance, and the reduction in the costs of installation and production. However, photovoltaic panels are elements that must be located outside in order to receive the sun radiation and transform it into electricity. Therefore, they are exposed to the weather conditions and many environmental factors that can negatively affect the output delivered by the system. One of the most common issues related to the outside location is the dust accumulation in the surface of the panels. The dust particles obstruct the passage of the sunlight, reducing the efficiency of the generation process and making the system prone to experimental long-term faults. Thus, it is necessary to develop techniques that allow us to assess the level of dust accumulation in the panel surface in order to schedule a proper maintenance and avoid losses associated with the reduction of the delivered power and unexpected faults. In this work, we propose a methodology that uses a machine learning approach to estimate different levels of dust accumulation in photovoltaic panels. The developed method takes the voltage, current, temperature, and sun radiance as inputs to perform a statistical feature extraction that describes the behavior of the photovoltaic system under different dust conditions. In order to retain only the relevant information, a genetic algorithm works along with the principal component analysis technique to perform an optimal feature selection. Next, the linear discrimination analysis is carried out using the optimized dataset to reduce the problem dimensionality, and a multi-layer perceptron neural network is implemented as a classifier for discriminating among three different conditions: clean surface, slight dust accumulation, and severe dust accumulation. The proposed methodology is implemented using real signals from a photovoltaic installation, proving to be effective not only to determine if a dust accumulation condition is present but also when maintenance actions must be performed. Moreover, the results demonstrate that the accuracy of the proposed method is always above 94%.
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Shaaban, Mostafa F., Amal Alarif, Mohamed Mokhtar, Usman Tariq, Ahmed H. Osman i A. R. Al-Ali. "A New Data-Based Dust Estimation Unit for PV Panels". Energies 13, nr 14 (13.07.2020): 3601. http://dx.doi.org/10.3390/en13143601.
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Solar photovoltaic (PV) is playing a major role in the United Arab Emirates (UAE) smart grid infrastructure. However, one of the challenges facing PV-based energy systems is the dust accumulation on solar panels. Dust accumulation on solar panels results in a high degradation in the output power. The UAE has low intensity rainfall and wind velocity; therefore solar panels must be cleaned manually or using automated cleaning methods. Estimating dust accumulation on solar panels will increase the output power and reduce maintenance costs by initiating cleaning actions only when required. In this paper, the impact of natural dust accumulation on solar panels is investigated using field measurements and regression modeling. Experimental data were collected under various real weather conditions and controlled levels of dust. Moreover, this paper proposes a data-driven approach based on machine learning to estimate the accumulated dust level on solar panels. In this approach, a dust estimation unit based on a regression tree model has been developed to estimate the dust accumulation. This unit is trained using experimental records of solar irradiance, ambient temperature, and the output power generated from solar panels as well as the amount of dust at these conditions. The proposed unit is evaluated through different case studies with a random amount of dust applied to the solar panels to demonstrate the accurate performance of the proposed unit.
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Pan, Huiyun, Xinwei Lu i Kai Lei. "Contamination Identification of Trace Metals in Roadway Dust of a Typical Mountainous County in the Three Gorges Reservoir Region, China, and its Relationships with Socio-Economic Factors". Sustainability 12, nr 14 (13.07.2020): 5624. http://dx.doi.org/10.3390/su12145624.
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Trace metal contamination in urban road dust has attracted global concern due to its potential risk to the urban environment and human health. Compared to big cities, relative studies in counties and small towns have not been well quantified. This research identified the trace metal contamination characteristics and possible sources in the road dust of a typical mountainous county and a town in the Three Gorges Reservoir region, southwest China, and their associations with major regional socio-economic factors. The trace metal concentrations were determined, and the contamination levels were assessed. Concentrations of Zn, Pb, and Cu were relatively high in both locations, and a significant accumulation of them was confirmed by the geo-accumulation method. Multivariate analysis and geographic information system (GIS) mapping were combined to explore the sources of trace metals in the investigated area. Anthropogenic activities predominantly affected the contamination levels of Zn, Pb, Cu, and Co, and traffic emission, agricultural activities, and fossil fuel combustion were their main sources. The significant accumulation of Zn should attract special concern for its wide use in industrial and agricultural activities. Population and vehicle density were the main factors that controlled the trace metal contamination levels in the roadway dust. Rapid urbanizing promoted trace metal accumulation in counties and towns. Therefore, it is urgent to make appropriate strategies for trace metal pollution mitigation in the process of urbanization.
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Bezberdaya, Liliya, Natalia Kosheleva, Olga Chernitsova, Mikhail Lychagin i Nikolay Kasimov. "Pollution Level, Partition and Spatial Distribution of Benzo(a)pyrene in Urban Soils, Road Dust and Their PM10 Fraction of Health-Resorts (Alushta, Yalta) and Industrial (Sebastopol) Cities of Crimea". Water 14, nr 4 (12.02.2022): 561. http://dx.doi.org/10.3390/w14040561.
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Polycyclic aromatic hydrocarbons (PAHs), in particular benzo(a)pyrene (BaP), are priority organic pollutants coming from various anthropogenic sources. The levels of accumulation and the spatial distribution of BaP in urban soils, road dust and their PM10 particles (with a diameter of less than 10 microns) were for the first time determined for various land use zones and roads of different size in the cities of Crimea—Alushta, Yalta and Sebastopol. The average content of BaP in soils and road dust in Alushta is 60 and 97 ng/g, in Yalta—139 and 64 ng/g, in Sebastopol—260 and 89 ng/g, respectively, which considerably exceeds the background level (1 ng/g). The BaP concentrations in PM10 particles of soils and dust are up to 11 and four times higher, respectively, than the total contents; they concentrate 35–70% of amount of the pollutant. The accumulation of BaP in soils and dust depends on the type of land use and size of roads. The exceedance of BaP standards in soils and road dust indicates a hazardous environmental situation in three cities of Crimea. The most dangerous are PM10 particles, which form anomalies with extreme levels of BaP contamination.
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Brodny, Jarosław, i Magdalena Tutak. "Exposure to Harmful Dusts on Fully Powered Longwall Coal Mines in Poland". International Journal of Environmental Research and Public Health 15, nr 9 (27.08.2018): 1846. http://dx.doi.org/10.3390/ijerph15091846.
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The mining production process is exposed to a series of different hazards. One of them is the accumulation of dust which can pose a serious threat to the life and health of mine workers. The analysis of dust hazard in hard coal mining should include two aspects. One is the risk of coal dust explosions, which poses a direct risk of injury or even loss of life, the second is the risk of harmful dust, associated with the possibility of negative health effects as a result of long-term exposure to dust in the worker’s body. The technologies currently applied in underground mining produce large amounts of coal and stone dust. Long-term exposure to dust and crystalline silica may cause chronic respiratory disease. The article presents the results of tests on the dust levels in the area of a fully-powered longwall. The tests were conducted for five longwalls from different hard coal mines. In each of them, the average values of inhalable and respirable dust as well as the percentage content of free silica in the dust were determined in ten selected working positions. Additionally, for the longwall with the highest dust concentration, the levels of dust were determined for the basic activities related to the phases of the technological cycle. The comparative analysis conducted and the results obtained demonstrate large variations in the dust levels in the different areas. The permissible values were significantly exceeded in a number of cases. This poses a great threat to the health of Polish miners. The results obtained indicate that it is necessary to undertake more effective measures in order to improve the working environment of the crew in hard coal mines.
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Lin, Wenpeng, Xumiao Yu, Di Xu, Tengteng Sun i Yue Sun. "Effect of Dust Deposition on Chlorophyll Concentration Estimation in Urban Plants from Reflectance and Vegetation Indexes". Remote Sensing 13, nr 18 (8.09.2021): 3570. http://dx.doi.org/10.3390/rs13183570.
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Using reflectance spectroscopy to monitor vegetation pigments is a crucial method to know the nutritional status, environmental stress, and phenological phase of vegetation. Defining cities as targeted areas and common greening plants as research objects, the pigment concentrations and dust deposition amounts of the urban plants were classified to explore the spectral difference, respectively. Furthermore, according to different dust deposition levels, this study compared and discussed the prediction models of chlorophyll concentration by correlation analysis and linear regression analysis. The results showed: (1) Dust deposition had interference effects on pigment concentration, leaf reflectance, and their correlations. Dust was an essential factor that must be considered. (2) The influence of dust deposition on chlorophyll—a concentration estimation was related to the selected vegetation indexes. Different modeling indicators had different sensitivity to dust. The SR705 and CIrededge vegetation indexes based on the red edge band were more suitable for establishing chlorophyll-a prediction models. (3) The leaf chlorophyll concentration prediction can be achieved by using reflectance spectroscopy data. The effect of the chlorophyll estimation model under the levels of “Medium dust” and “Heavy dust” was worse than that of “Less dust”, which meant the accumulation of dust had interference to the estimation of chlorophyll concentration. The quantitative analysis of vegetation spectrum by reflectance spectroscopy shows excellent advantages in the research and application of vegetation remote sensing, which provides an important theoretical basis and technical support for the practical application of plant chlorophyll content prediction.
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Song, Yuhang, Chengzhi Xing, Cheng Liu, Jinan Lin, Hongyu Wu, Ting Liu, Hua Lin i in. "Evaluation of transport processes over North China Plain and Yangtze River Delta using MAX-DOAS observations". Atmospheric Chemistry and Physics 23, nr 3 (2.02.2023): 1803–24. http://dx.doi.org/10.5194/acp-23-1803-2023.
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Abstract. Pollutant transport has a substantial impact on the atmospheric environment in megacity clusters. However, owing to the lack of knowledge of vertical pollutant structure, quantification of transport processes and understanding of their impacts on the environment remain inadequate. In this study, we retrieved the vertical profiles of aerosols, nitrogen dioxide (NO2), and formaldehyde (HCHO) using multi-axis differential optical absorption spectroscopy (MAX-DOAS) and analyzed three typical transport phenomena over the North China Plain (NCP) and Yangtze River Delta (YRD). We found the following: (1) the main transport layers (MTL) of aerosols, NO2, and HCHO along the southwest–northeast transport pathway in the Jing-Jin-Ji region were approximately 400–800, 0–400, and 400–1200 m, respectively. The maximum transport flux of HCHO appeared in Wangdu (WD), and aerosol and NO2 transport fluxes were assumed to be high in Shijiazhuang (SJZ), both urban areas being significant sources feeding regional pollutant transport pathways. (2) The NCP was affected by severe dust transport on 15 March 2021. The airborne dust suppressed dissipation and boosted pollutant accumulation, decreasing the height of high-altitude pollutant peaks. Furthermore, the dust enhanced aerosol production and accumulation, weakening light intensity. For the NO2 levels, dust and aerosols had different effects. At the SJZ and Dongying (DY) stations, the decreased light intensity prevented NO2 photolysis and favored NO2 concentration increase. In contrast, dust and aerosols provided surfaces for heterogeneous reactions, resulting in reduced NO2 levels at the Nancheng (NC) and Xianghe (XH) stations. The reduced solar radiation favored local HCHO accumulation in SJZ owing to the dominant contribution of the primary HCHO. (3) Back-and-forth transboundary transport between the NCP and YRD was found. The YRD-to-NCP and NCP-to-YRD transport processes mainly occurred in the 500–1500 and 0–1000 m layers, respectively. This transport, accompanied by the dome effect of aerosols, produced a large-scale increase in PM2.5, further validating the haze-amplifying mechanism.
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Roumpakias, Elias, i Tassos Stamatelos. "Surface Dust and Aerosol Effects on the Performance of Grid-Connected Photovoltaic Systems". Sustainability 12, nr 2 (11.01.2020): 569. http://dx.doi.org/10.3390/su12020569.
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A large number of grid-connected Photovoltaic parks of different scales have been operating worldwide for more than two decades. Systems’ performance varies with time, and an important factor that influences PV performance is dust and ambient aerosols. Dust accumulation has significant effects depending the region, and—on the other hand—understanding the role of absorption or scattering in particular wavelengths from aerosols is a challenging task. This paper focuses on performance analysis of a grid-connected PV system in Central Greece, aiming to study these effects. The methodology of analysis follows three directions, namely, PR computations, use of mathematical model’s prediction as reference value, and normalized efficiency calculation. These metrics are correlated with the levels of dust accumulation on PV panels’ surfaces and the ambient aerosol mass concentration. The results show that only heavily soiled surfaces have significant impact on PV performance and, particularly, a decrease of 5.6%. On the other hand, light or medium soiling have negligible impact on PV performance. On the other hand, the impact of ambient aerosol concentration levels on PV efficiency is more complex and requires further study. Aerosol scattering of different wavelengths can possibly affect PV efficiency, however, this fact may be related to the specific spectral response of PV cells.
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Qusay Kamil Jasim. "Effect of The Different Types of Dust on The Performance of Photovoltaic Panels in Iraq". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 100, nr 3 (31.12.2022): 1–10. http://dx.doi.org/10.37934/arfmts.100.3.110.
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Iraq is characterized by an atmosphere that contains dust particles most of the time. In this study, a detailed investigation was conducted on the effect of dust particles of different types on the performance of the photovoltaic (PV) model. Data were collected for samples of four types of dust (chalk powder, brick powder, Sand, Cool powder) and different weights (30,60,90 and 120 g/m2) with the change in the energy loss of the PV module at four levels of solar radiation (500, 600, 700 and 800 W/m2). In this study the effect of environmental dust particles on energy loss as well as electrical efficiency was evaluated. The minimum and maximum power value of (43.58, 101.95W) respectively, was observed during dust accumulation on the photovoltaic unit. It was also noted that the efficiency and power were inversely proportional to the increase in weight and directly to the size of the dust particles.
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Choi, Soo-Min, i Hyo Choi. "Statistical Modeling for PM10, PM2.5 and PM1 at Gangneung Affected by Local Meteorological Variables and PM10 and PM2.5 at Beijing for Non- and Dust Periods". Applied Sciences 11, nr 24 (15.12.2021): 11958. http://dx.doi.org/10.3390/app112411958.
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Multiple statistical prediction modeling of PM10, PM2.5 and PM1 at Gangneung city, Korea, was performed in association with local meteorological parameters (air temperature, wind speed and relative humidity) and PM10 and PM2.5 concentrations of an upwind site in Beijing, China, in the transport route of Chinese yellow dusts which originated from the Gobi Desert and passed through Beijing to the city from 18 March to 27 March 2015. Before and after the dust periods, the PM10, PM2.5 and PM1 concentrations showed as being very high at 09:00 LST (the morning rush hour) by the increasing emitted pollutants from vehicles and flying dust from the road and their maxima occurred at 20:00 to 22:00 LST (the evening departure time) from the additional pollutants from resident heating boilers. During the dust period, these peak trends were not found due to the persistent accumulation of dust in the city from the Gobi Desert through Beijing, China, as shown in real-time COMS-AI satellite images. Multiple correlation coefficients among PM10, PM2.5 and PM1 at Gangneung were in the range of 0.916 to 0.998. Multiple statistical models were devised to predict each PM concentration, and the significant levels through multi-regression analyses were p < 0.001, showing all the coefficients to be significant. The observed and calculated PM concentrations were compared, and new linear regression models were sequentially suggested to reproduce the original observed PM values with improved correlation coefficients, to some extent.
Rozprawy doktorskie na temat "DUST ACCUMULATION LEVELS"
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SINGH, KOMAL. "AI BASED APPROACH FOR POWER PREDICTION AND PERFORMANCE EVALUATION OF THE SOLAR PV MODULES WITH VARYING DUST ACCUMULATION LEVELS". Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19994.
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Solar energy has shown to be the undisputed leader among renewable energy
sources since it is clean and environmentally benign. A photovoltaic module's output
power and longevity are controlled by a number of parameters, including solar
insolation, clouds, cell temperature and other shading effects such as dust deposition,
meteorological conditions, geographical location, module orientation, and so on.
Energy demand and concerns over greenhouse gases have made the integration of
solar PV into the grid imperative. Solar power forecasting models must have a high
prediction accuracy to address the intermittent nature of solar irradiation. Solar PV
power is significantly affected by the dust deposited on the PV panel surface.
The impact of dust collection on the operation of the 5 kW photovoltaic system set
up on the rooftop of the UEE laboratory at Delhi Technological University is initially
investigated in this work. The performance of the 5 kW photovoltaic system is
evaluated for 62 days, with the panels left naturally uncleaned for the first 31 days and
then cleaned on a regular basis for the next 31 days. The performance ratio, capacity
factor, system energy yield, and reference energy yield are all calculated. The
pragmatic 5 kW system's performance analysis results were afterwards compared to
the PVsyst software results.
Later on, the amount of dust deposited on PV panel as one of the input parameters
to predict solar PV power and solar irradiation is also studied. Multivariate analysis of
three deep learning techniques that is LSTM (Long short-term memory), 1D CNN
(Convolution Neural Network) and BilSTM (Bidirectional Long short-term memory)
to predict the solar PV power and solar irradiation with varying dust accumulated
levels for the 335-watt PV module set up on the rooftop of the lab at Delhi
Technological University is presented. An artificial dust scenario is created by
continually incrementing the dust level by 1.258 mg/cm2
.
Części książek na temat "DUST ACCUMULATION LEVELS"
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Gough, L. P., i W. C. Day. "Cadmium Accumulation in Browse Vegetation, Alaska — Implications for Animal Health". W Geology and Health. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195162042.003.0018.
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We conducted biogeochemical investigations of Cd transport and uptake by vegetation over a metamorphic and intrusive terrane in the Fortymile River watershed and Mining District, east-central Alaska. The occurrence of Cd in eolian-dominated sub-arctic soils developed over five major rock units was examined, as well as its relative bioaccumulation in willow. Although the bioaccumulation of Cd by willow (Salix spp.) has been known for some time (Gough 1991), the connection to adverse animal health, under natural (geogenic) conditions, has only recently been demonstrated (Larison et al. 2000, Mykelbust and Pederson 1999). We present Cd data for three soil horizons and the leaf and twig material of Salix glauca L. (grayleaf willow) collected at sites within defined rock units. The cycling of Cd and its bioaccumulation in willow are compared among rock types and soil horizons. Cadmium in study area soils is derived from aeolian dust (loess) and the weathering of the primary bedrock. Plots of rare earth elements (REE, normalized to chondrite abundance’s) in samples of A, B, and C soil horizon soils were similar to REE patterns in regional loess samples and did not correspond to bedrock patterns. Not surprisingly, therefore, we found essentially no difference in the concentration of Cd in soils developed over different lithologic units. In addition, the anthropogenic input (from mining) at sites we sampled was found to be minimal. Cadmium levels in soil are generally higher than that found in the study area rock types (~2ppm)(Day2000). In our acidic soils (pH 4.5-6.0), Cd should be mobile (readily leached), and should tend to form complexes with carbonates, hydroxides, and phosphates. Interestingly, Cd concentrations decrease with increasing soil depth — a trend directly proportional to soil organic matter content. Enrichment factors (EF), a measure of the relative uptake by a plant of an element from its substrate — a sort of “bioavailability” assessment, are presented in Figure 12.2 for Cd in willow leaf material. This procedure normalizes the data, with respect to a geochemical reference element (in this case Ce), for each of the soil horizons developed over the five major rock units.
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Montanari, Alessandro, Marco Peter Ferretti, Maurizio Mainiero, David McGee, Gaia Pignocchi, Stefano Recanatini i Roberto Zorzin. "Revisiting the archaeological site of Grotta dei Baffoni Cave (Frasassi Gorge, Italy): Integrated stratigraphy, archaeometry, and geochronology of upper Pleistocene–Holocene cave sediments". W From the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid: Honoring the Career of Walter Alvarez. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2557(28).
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ABSTRACT In this paper, we present old and new data about our integrated interdisciplinary stratigraphic study of sedimentary deposits preserved in the Grotta dei Baffoni Cave of the Frasassi hypogenic cave complex, including sedimentological, paleontological, archaeometric, and radiometric analyses. This research work allowed us to reconstruct the geologic, environmental, and human history of this part of the northeastern Apennines of Italy for the past 200,000 years, from the late Middle Pleistocene to the Present. Accumulation of alluvial sediment began in this cave ~200,000 years ago, when an entrance was breached by the Sentino River during its process of incision and deepening of the Frasassi Gorge coupled with regional tectonic uplift. Flooding of the cave went on until the entrance sill of the cave was lifted up to an elevation that could no longer be reached by the river, sometime in the mid–Late Pleistocene. After this, windblown dust (i.e., loess) and coarser carbonate clasts derived from the disintegration of the vaults due to cryogenic processes and/or seismically induced collapses of the limestone vaults, accumulated on this now-dry underground environment. The stratigraphy of an ~4-m-thick sedimentary deposit accumulated in the vast atrium room of the cave was measured, sampled, and documented in two excavation trenches in 1952 by archaeologist Anton Mario Radmilli. By collecting a dozen stratigraphically located osteological finds for 14C dating, and revisiting artifacts collected by Radmilli, which are archived respectively in the Museum of Natural History of Verona and in the National Museum of Archaeology of Ancona, we assessed that the cave was frequented by wild animals, such as cave bear and ibex, starting in the mid–Late Pleistocene. Dating of charcoal particles from subsurface sediments in the inner part of the cave suggested that fires were lit in this cave by Epigravettian visitors during the Younger Dryas cold period. Scarce archaeological evidence nevertheless suggests that man began using this underground environment for worship practices probably in the early Neolithic. Human bones in the lower part of one of Radmilli’s excavations yielded early Eneolithic ages. No other human bones were found in overlying levels of this excavation, but the typology of animal bones and associated ceramic artifacts, corroborated by our 14C dates, suggest that this cave was utilized as a worship or ritual place until the early Middle Bronze Age. After that, the cave was sporadically used as a shelter for herders until recent times.
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"Soil Pollution by Lead in Sub-Saharan Africa". W Global Industrial Impacts of Heavy Metal Pollution in Sub-Saharan Africa, 161–77. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-7116-6.ch007.
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This chapter discusses the anthropic sources of lead and its subsequent pollution to soils of sub-Saharan Africa (SSA) region. Using examples of east, west, and south African empirical studies, industrial activities characterized by cottage industries involved in paint use, electrical appliance and motor vehicle repair, hairdressing, and scrap metal recycling were associated with Pb introduction in soils leading to their contamination. The use of leaded petrol and manufacture and recycling of Pb- based batteries were additional causes of metal pollution in soils. The contaminant is introduced to soils via Pb-containing dusts, emissions, particulate matter, solid wastes, and effluents. Subsequent transfer to trophic levels is via ingestion, inhalation, and consumption of contaminated soils and food crops. It is essential to manage the sources of Pb to control and manage its accumulation in soil.
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Reddy, Ashvini K., i Kimberly G. Yen. "Management of Pediatric Nasolacrimal Duct Obstruction". W Surgery of the Eyelid, Lacrimal System, and Orbit. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780195340211.003.0020.
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Tearing is a common presenting complaint in infants referred to an ophthalmologist and may be the first sign of something as benign as an impermanent anatomic defect or as grave as congenital glaucoma. When tearing is chronic, parents of an affected infant are often frustrated by the persistent accumulation of fluid and mucopurulent material in the eye and on the eyelids and anxious that the condition may be a sign of a more serious problem. The best initial management of tearing in an infant is to take a detailed history, which often provides important clues as to the cause of tearing, and then to perform a thorough, systematic ophthalmic examination. Tears serve four main functions: (1) they form a tear film to keep the eye moist, (2) they lubricate the eye, (3) they keep the eye clear of particulate matter and debris, and (4) they provide a refractive surface on the corneal epithelium. The tear film comprises three layers: a thin inner layer of proteinaceous mucin coats and protects the eye, an aqueous layer keeps the eye moist and lubricated, and an outer lipid layer slows evaporation of the aqueous layer. Basal tears are produced by the accessory lacrimal glands located in the conjunctiva and keep the eye moist under steady-state conditions; normal patients have a tear meniscus (or “tear lake”) visible along the inner lower eyelid as a result of basal tear production. Irritation or emotional extremes can trigger reflex tear production by the main lacrimal gland in the superotemporal quadrant of the orbit, “flooding” the tear lake. The level of the tear lake is highest when the rate of tear production by the lacrimal glands exceeds the rate of tear drainage into the nasolacrimal system. Tears normally drain out of the eye through puncta located on the nasal portion of the upper and lower eyelids. They then enter the upper and lower canaliculi, which run inferiorly and medially before joining to form the common canaliculus, which conducts tears through the valve of Rosenmuller and into the lacrimal sac.
Streszczenia konferencji na temat "DUST ACCUMULATION LEVELS"
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Singh, Komal, i M. Rizwan. "AI based Approach for Solar PV Power Prediction with Varying Dust Accumulation Levels". W 2023 International Conference on Recent Advances in Electrical, Electronics & Digital Healthcare Technologies (REEDCON). IEEE, 2023. http://dx.doi.org/10.1109/reedcon57544.2023.10150800.
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Ramirez, Juan C., Russell A. Ogle i Andrew R. Carpenter. "Risk Evaluation and the NFPA 654 Layer Depth Criteria for Dust Explosion and Flash Fire Hazards". W ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52155.
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What is an acceptable thickness of accumulated combustible dust in an industrial facility? Combustible dusts present both flash fire and explosion hazards. Companies which generate, handle, process, store, or distribute combustible dusts need to cost-effectively manage these hazards. In the United States, the Occupational Health and Safety Administration (OSHA) has stepped up its enforcement activity and is conducting inspections at these locations to verify that the facility is being operated in accordance with recognized and generally accepted good engineering practices (RAGAGEP). The combustible dust safety standard from the National Fire Protection Association, NFPA 654 (1) is often cited as the RAGAGEP for combustible dust risk management. One aspect of combustible dust risk management is the monitoring and control of fugitive dust accumulation on horizontal surfaces. NFPA 654 gives specific guidance on how to determine an acceptable level of combustible dust accumulation using different risk scenarios. These acceptable levels or thresholds were only recently added as requirements in the 2013 edition of NFPA 654 and there is debate as to whether they are accurate. An examination of this guidance reveals that it is very conservative because it omits consideration of several distinct events necessary for a dust deflagration or flash fire to occur. NFPA 654, 2013 edition presents four techniques to determine if a flash fire or explosion hazard exists in a building or enclosure. These are: the layer depth criterion, Mass Method A, Mass method B, and Risk Evaluation. The standard gives explicit directions on how to calculate critical layer thickness using the first three methods. The standard does not give guidance on how to conduct a risk evaluation. In this paper we present a risk evaluation based on the NFPA 654 layer depth criteria. We formulate the dust accumulation scenario as a sequence of distinct events, estimate probabilities for each event, and illustrate how the NFPA 654 guidelines generally skew the layer depth criteria towards lower values. It is argued that the NFPA 654 guidance may result in layer depth criteria that are too conservatively low for facilities that manage marginally combustible dusts. In those facilities a more quantitative risk analysis will likely yield better, i.e., more practical criteria.
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McCormick, F. B., F. A. P. Tooley, A. L. Lentine, R. L. Morrison, R. A. Novotny i T. J. Cloonan. "Optical and mechanical issues in free-space digital optical logic systems". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.fii1.
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Three-dimensional array logic was recently demonstrated by optically interconnecting two-dimensional arrays of symmetric self-electro-optic effect devices (S-SEEDs).1 As in the operation of electronic logic, logiclevel uniformity of the optical input signals to each optical logic gate is necessary. As the outputs of one optical-logic-device array propagate to the next array, spatial variations of the logic levels can be introduced. Logic-level nonuniformity can accumulate from optical sources (spot-array generation, geometric aberration, and polarization effects), mechanical sources (misalignment and lack of stability), image plane sources (dust, damage, and device nonuniformity), and laser sources (wavelength and mode variations). We have found that although individual nonuniformity contributions can be kept to less than 10%, in complex systems the total accumulation of nonuniformity errors can exceed ±40%. These large variations of the input logic levels introduce errors in the desired logical decisions. The system constraints and limitations brought about by these nonuniformity contributions will be discussed, and experimental results will be presented.
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Cory, Trevor M., Karen A. Thole, Kathryn L. Kirsch, Ryan Lundgreen, Robin Prenter i Stephen Kramer. "Impact of Dust Feed on Capture Efficiency and Deposition Patterns in a Double-Walled Liner". W ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90981.
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Abstract The introduction of particulates into gas turbine engines poses a serious threat to component durability. Particles drawn from the environment, such as ash or sand, can be introduced into the air system used to cool hot section components and drastically diminish cooling performance. In the current study, a dirt-laden coolant stream impinged on a double-walled cooling configuration, which was comprised of an impingement plate followed by an effusion-cooled plate. Experiments were conducted at both room temperature and at temperatures in excess of 750°C; flow conditions were varied to achieve different pressure ratios across the cooling configuration. Dirt particles were introduced into the coolant using two different methods: in discrete bursts, called slugs; or in a continuous feed ensuring a constant stream of particles. This continuous feed mechanism is at the crux of a new test facility created to introduce flexibility and precision in the control of dirt feed rates, particularly for very small (< 50 mg) amounts of dirt. The difference in capture efficiency and in dirt patterns between the two feed methods showed measurably different dirt accumulation levels on the cold side of the effusion plate at the same test conditions. Results show that the slug feed method caused higher capture efficiency and thicker dirt deposition on the effusion plate compared to the continuous feed.
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Hillegass, Matthew J., i Eric L. Rabeno. "Seeded Fault Testing of Military Ground Vehicles as a Pathway to Condition Based Maintenance". W ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28039.
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The performance of military ground vehicle systems is being degraded due to high operation tempo and exposure to extreme environments while performing in-theater service. To address this issue, the US Army is implementing a policy of Condition Based Maintenance which is supported by the Army Material System Analysis Activity (AMSAA). The vision of this policy is to base the maintenance of systems upon the actual condition of the system and not upon time- or distance-based schedules. This capability will be enabled by the application of usage, diagnostic and prognostic processes executed on a Health and Usage Monitoring System (HUMS) installed on these vehicle systems. A thorough understanding of the ways in which the system condition is degenerated and the ability of the HUMS to detect, identify, and communicate all conditions that require maintenance in a timely manner are key requirements of these processes. Seeded Fault Testing is the critical means of fulfilling these requirements. A joint Seeded Fault Testing project between AMSAA and the US Army Aberdeen Test Center (ATC) has been initiated to gain a thorough understanding of ground vehicle system condition degeneration and HUMS implementation of products and processes that can accurately identify and communicate it. A military vehicle underwent exhaustive testing in support of this project. The vehicle was subjected to specific use scenarios while carefully controlled faults are induced in engine, transmission, and other key mechanical subsystems that would degrade vehicle performance and degenerate system condition. The vehicle’s induced faults included lowered coolant levels to simulate leakage, restriction of air flow across radiators and filters to simulate dust and debris accumulation, and lowered transmission and engine oil levels to simulate leakage and usage. The objective of this project was to use the results from the seeded fault tests to establish critical thresholds, trends, and patterns that will be the basis of the creation and implementation of real-time HUMS-based algorithms that predict faults, warn operators and maintainers of imminent failures, and provide a sound foundation for Condition Based Maintenance.
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Pal, S., Leonard Peltier, Mitchell Krasnopoler, Kelly J. Knight i Jonathan Berkoe. "Predicting Fly Ash Accumulation in a Fossil Power Plant Flue Gas Duct Using Computational Fluid Dynamics". W ASME 2011 Power Conference collocated with JSME ICOPE 2011. ASMEDC, 2011. http://dx.doi.org/10.1115/power2011-55077.
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During the startup of a new fossil power plant, a high level of fly ash accumulation (higher than predicted) was encountered in the flue gas ducting upstream of a fluidized bed scrubber. The level of fly ash accumulation made it necessary to manually withdraw fly ash using a vacuum truck after short periods of operation, at less than 80% maximum continuous rating (MCR). This paper presents a simple method for rapid assessment of fly ash accumulation in flue gas ducts using steady state single phase Computational Fluid Dynamics (CFD) simulation of flue gas flow. The propensity for fly ash accumulation in a duct is predicted using calculated wall shear stresses from CFD coupled with estimates for the critical shear stresses required for mobilization of settled solids. Critical values for the mobilization stresses are determined from the Shields relations for incipient motion of particles in a packed bed with given fly ash particle size and density as inputs. Solids accumulation is possible where the wall shear stress magnitude is less than the critical shear stress for mobilization calculated from the Shields relations. Predictions of incipient fly ash accumulation based on the coupled CFD/Shields relations model correlate well with plant startup field observations. Fly ash accumulation was not observed in a related physical scale model test. A separate CFD/Shields relation analysis of the scale model physical tests show that the wall shear stresses in the scale model are several times larger than the critical value required for the mobilization of the fly ash simulant. This study demonstrates that a simple steady state, single phase CFD analysis of flue gas flow can be used to rapidly identify and address fly ash accumulation concerns in flue gas duct designs. This approach is much simpler and computationally inexpensive compared to a transient Eulerian multiphase simulation of particle laden flow involving handling the dense phase in regions of ash accumulation. Further, this study shows that physical model tests will be accurate for predicting fly ash accumulation, only if, the scaling maintains the proper ratio of wall shear stress to critical remobilization stress.
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Miyoshi, Masahiro, Tetsuharu Kawasaki, Satoru Takahashi i Hironori Mine. "90mm Magneto-Optical Disk Drive With Digital Servo". W Optical Data Storage. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/ods.1991.me1.
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As personal computers and OA machines with higer level functions continue decrease in size recently, the requirements for external storage devices are becoming exacting. The 130mm magneto-optical disk drives presently used cannot necessarily meet those requirements. We have developed a 90mm magneto-optical disk drive, aiming at higher performance, small size and lower power dissipation, as well as higher reliability. The target of lower power dissipation is important in order to prevent a rise in temperature inside the drive, to realize higher-density packaging and to decrease the quantity of cooling airflow which causes the accumulation of dust.
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Nakayama, Jiro, i Masahiro Yoshioka. "Experience of Glass Melter Operation in Tokai Vitrification Facility". W ASME 2001 8th International Conference on Radioactive Waste Management and Environmental Remediation. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/icem2001-1276.
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Abstract Tokai Vitrification Facility (TVF) is the first plant in Japan to immobilize the High-Level Liquid Waste (HLLW) transferred from Tokai Reprocessing Plant (TRP) to the borosilicate glass. Two problems happened through the plant operation, and the investigations to solve them are being carried on. One is the deposit that is caused by the cohesion of the dust inside the air-film cooler (a type of the exhaust pipe) of the glass melter and the other is the accumulation of noble metal elements in the HLLW on the melter bottom. The countermeasure for the former is the water injection system and for the latter is the reform of the melter bottom structure.
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Stepanova, Natalya, Emiliya Valeeva, Amr S. Elbahnasawy, Oxana Sinitsyna, Suryana Fomina i Aizat Basyyrov. "THREE-DIMENSIONAL ANALYSIS OF THE CITY ENVIRONMENT CONTAMINATION WITH HEAVY METALS BASED ON THE FINDINGS OF THE SNOW COVER STUDY". W 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022v/4.2/s19.56.
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Analysis of the air environment and atmospheric emissions is an efficient method for assessing the ecological situation in cities. Assessment of the chemical composition of deposit environments (soil, snow) shows long-term contamination. The snow cover (SC), being a natural accumulating plate, reflects environmental contamination with heavy metals (HM) caused by entry from various sources. The work aims to study the three-dimensional dynamics of large city contamination with HM. Sampling (in 2019 - 100, in 2020-100, in 2021 - 280) was performed in the first decade of March. The samples were analyzed for the HM content by atomic absorption method on apparatus AAS 3. Simultaneously, the content of Cd, Cu, Zn,/, Ni, and Mn in the solid residue (mg/kg of dust), along with the HM fallout density per unit area for dissolved and solid phases (mg/m2) during winter period were calculated. The average daily dust load on the city territory was confirmed by relatively weak temporal variation, the difference in dust release during the winter seasons of the years 2019-2021 did not increase by 20%. In 2019, the SC dust level was characterized mainly as low (85.5 kg/km2/day). High dust level was observed only at the sites adjacent to large industrial enterprises (816 kg/km2 -day). In 2020, the dust level of the city of SC was the lowest (40.8 kg/km2/day). Along with the decrease of the total dust weight, which entered the SC, a decrease of HM entry as part of dust was registered too. The element-by-element analysis showed that Fe (80-87%), Zn (5-6.8%), Mn (3.45-3.6%), and Cu (1.3-2.7%) made the highest proportion in the dust. Ranking in value of the concentration coefficient (C-) was as follows: Cd 327 > -u 51 > Zn 38 > / 18 > / 13 > Ni 11 > n 1.3. The spread of Cd data in selected measurement points in dust fallouts on SC was achieved 900 times. In urbanized systems, the Cd behavior is regulated by the transformation of hydrocarbons, which involves the structure of atmospheric emissions in the city of Kazan. Correlation between the HM content as part of liquid and solid phases of the city SC indicates a statistically significant relationship with their technogenic entry into the atmosphere from one or several sources, and the composition of HM geochemical association in SC depends largely on the set and relationship of elements in other components of the urban environment. The assumption of the integrity of -d, Pb, Cu, and Zn source of entry (Spearman correlation coefficient 0.55-0.92) was confirmed. Data on the SC contamination not only deepen our knowledge, reflecting peculiarities of the atmospheric pollution spread, but also allow preventing the contamination of water bodies and soils.
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Radmehr, Ahmad, Arash Hosseinian Ahangarnejad, Ali Tajaddini i Mehdi Ahmadian. "Surface Profile and Third-Body Layer Accumulation Measurement Using a 3D Laser Profiler". W 2020 Joint Rail Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/jrc2020-8041.
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Abstract The surface profile wear and the resulting third-body layer accumulation are investigated on the Virginia Tech-Federal Railroad Administration Roller Rig (VT-FRA Roller Rig), using a high-precision 3D laser profiler by Keyence. It is observed that the wheel surface gradually wears and the fine worn material accumulates on the running surfaces. It is further observed that with the progression of the wear and accumulation of a powder-like material at running surface, a preocular change in wheel-rail traction occurs. The first step in exploring the physics of the changes in traction is quantifying, precisely, the micron-sized surface finish changes and wear material accumulation. This paper provides the process of choosing a suitable surface profiler for the VT-FRA roller rig adaptation, and the results of a series of tests under various wheel load and contact configurations. A baseline experiment is conducted to evaluate the wheel wear and the accumulation of the naturally-generated third body layer (the worn material) on the wheel’s running surface. Before each series of experiments, the wheel and roller running surfaces were polished and thoroughly cleaned to make sure that they are perfectly smooth (finished) and free of any debris or dust. The wheel surface profile is measured in the perfectly cleaned condition using the 3D laser scanner. Time controlled experiments are run with different wheel loads, % slippage, and angle of attack (AoA) for 500 seconds. For each run, the change with surface finish and accumulated third body layer build up is measured. It is consistently observed that the traction forces increase gradually with time until they reach a stable level, presented by a plateau in the traction-slippage curves. The time to reach the plateau is directly related to wheel’s dynamic conditions including load, %slippage, and AOA. For some of the conditions, such as wheel load, the relationship is linear and for others (such as AOA) it is nonlinear. Concentrating on the analysis of the baseline results, it is observed that the change in surface finish and the third body layer that naturally accumulates at the running surface — hence, referred to as “natural third body layer” or “NTBL” — is directly correlated and somewhat linearly with NTBL and change in the running surface from smooth to rough. The correlation is most noticeable for the NTBL. With increasing NTBL, traction increases rapidly until the running surface is saturated with the accumulated wear material, presumably a ferrous oxide. There is far weaker correlation between the change in surface finish and traction variations. It is noticed that the surface finish continues to change beyond the time that the traction forces reach their plateau, and its effect remains far more gradual than NTBL.