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排序方式: 共有219条查询结果,搜索用时 62 毫秒
51.
52.
ABSTRACTThe automated classification of ambient air pollutants is an important task in air pollution hazard assessment and life quality research. In the current study, machine learning (ML) algorithms are used to identify the inter-correlation between dominant air pollution index (API) for PM10 percentile values and other major air pollutants in order to detect the vital pollutants’ clusters in ambient monitoring data around the study area. Two air quality stations, CA0016 and CA0054, were selected for this research due to their strategic locations. Non-linear RPart and Tree model of Decision Tree (DT) algorithm within the R programming environment were adopted for classification analysis. The pollutants’ respective significance to PM10 occurrence was evaluated using Random forest (RF) of DT algorithms and K means polar cluster function identified and grouped similar features, and also detected vital clusters in ambient monitoring data around the industrial areas. Results show increase in the number of clusters did not significantly alter results. PM10 generally shows a reduction in trend, especially in SW direction and an overall minimal reduction in the pollutants’ concentration in all directions is observed (less than 1). Fluctuations were observed in the behaviors of CO and NOx during the day while NOx displayed relative stability. Results also show that a direct and positive linear relationship exists between the PM10 (target pollutant) and CO, SO2, which suggests that these pollutants originate from the same sources. A semi-linear relationship is observed between the PM10 and others (O3 and NOx) while humidity shows a negative linearity with PM10. We conclude that most of the major pollutants show a positive trend toward the industrial areas in both stations while tra?c emissions dominate this site (CA0016) for CO and NOx. Potential applications of nuggets of information derived from these results in reducing air pollution and ensuring sustainability within the city are also discussed. Results from this study are expected to provide valuable information to decision makers to implement viable strategies capable of mitigating air pollution effects. 相似文献
53.
Omar Saeed Baghabra Al-Amoudi 《Engineering Geology》1994,36(3-4):279-291
Vast expanses of arid, saline soils that occur along the Arabian Gulf seaboard and elsewhere possess a very low density and strength that necessitate improvement before any actual construction takesplace. For large-scale constructions, several field improvement techniques have recently been implemented with various degrees of success. In surficial, small-scale applications, chemical stabilization provides a potential technique to improve the inferior properties of these soils, known locally as sabkha. A literature search indicates that chemical stabilization of soils usingasphalt, lime and cement is usually conducted at lower moisture contents than the optimum. Such moisture contents are also much lower than the natural moisture content of sabkha, and if applied to sabkha in the field, this wouldrequire lowering the moisture content before any stabilization commenced; whichwould be neither feasible nor economical.
In this investigation, an eastern Saudi sabkha soil was chemically stabilized at its natural moisture level, which varies from 16% to 22%. In addition to the characterization of the soil and standard compaction tests, cement and lime sabkha mixtures were prepared at five additions and cured for up to 90 days in plastic wrap. Results indicate that cement-stabilized sabkha gained high strength with time and proved to have a potential use in construction. 相似文献
54.
The effects of foundation width on model tests for the bearing capacity of sand with geogrid reinforcement 总被引:1,自引:0,他引:1
Summary Laboratory model test results for the ultimate bearing capacity of surface strip foundations on geogrid-reinforced sand and
unreinforced sand are presented. A fine uniform sand and one type of geogrid (Tensar BX1000(SSO)) were used for the tests.
The width of the foundation and the relative density of sand were varied to determine their effects on the bearing capacity
ratio. It was found that the bearing capacity ratio of the sand-geogrid system decreased with an increase in foundation width.
However, above a certain foundation width (130–140 mm) a practically constant value of bearing capacity ratio was observed. 相似文献
55.
Summary The radon and thoron content in atmospheric air at Giza was determined through the period from January (1958 to July 1959) by using the emanometrical technique. The concentration of radon and its decay products was equal to (88±4) 10–18 Curie/c.c. and that of thoron and its decay products was equal to (51±11) 10–18 Curie/c.c. 相似文献
56.
Measurement of PM2.5 emission potential from soil using the UC Davis resuspension test chamber 总被引:2,自引:0,他引:2
Omar F. Carvacho Lowell L. Ashbaugh Michael S. Brown Robert G. Flocchini 《Geomorphology》2004,59(1-4):75
Human health effects have been linked to airborne concentrations of fine particulate matter. One source of fine particulate matter in the atmosphere is resuspended soil dust from a variety of activities, including agricultural operations. We have established a method to measure the potential of soil to emit fugitive dust in the PM10 or PM2.5 size range. The method is repeatable, and provides an index of PM10 or PM2.5 dust that is highly correlated to the soil texture. The ratio of the PM2.5 Index to the PM10 Index produced by this method is similar to field observations of ambient PM2.5 and PM10 concentrations downwind of agricultural operations in the San Joaquin Valley of California. The PM2.5 or PM10 Index will be a more useful parameter to estimate the potential of a soil to emit fugitive dust than the currently used dry silt content of soil. Research is currently underway to relate the PM10 and PM2.5 Index to measured emission factors, accounting for soil moisture and type of agricultural operation, so that a more reliable predictive equation can be developed for agricultural practices. 相似文献
57.
In the present study, the precipitation near Büyükçekmece Lake, which is one of the important drinking water sources of Istanbul city, was studied during October 2001–July 2002. Seventy-nine bulk precipitation samples were collected at two sampling stations near the Lake (41°2′35″N, 28°35′25″E and 41°5′30″N, 28°37′7″E). The study comprised the determination of H+, Cl−, NO3−, SO42−, NH4+, Na, K, Mg, Ca, Al, Ba, Fe, Cu and Mn concentrations in bulk deposition rain event samples. The average volume-weighted pH value was found to be 4.81, which points out that the rain is slightly acidic. High sulfate concentrations were observed together with high H+ ion values. Sulfur emissions were the major cause for the observed high hydrogen ion levels. On the basis of factor analysis and correlation matrix analysis, it has been found that in this region, acid neutralization is brought about by calcium rather than the ammonium ion. The varimax rotated factor analysis grouped the variables into four factors, which are crustal, marine and two anthropogenic sources. 相似文献
58.
This paper presents results of analysis of full-scale pile load test data of 14 piles embedded in either loose or medium dense
sands. The analysis was performed using two methods, p–y curve approach and a more recently developed khmax approach. Comparison of the results obtained using both the methods is also presented. A step-by-step analysis procedure
is presented for predicting lateral load deflection response of single piles in sand using the khmax approach. The results presented show that the khmax approach has promise over the p–y curve approach because of its simplicity and the fact that it provides upper- and lower-bound curves, which are valuable
guides to making engineering decisions. For loose sands, a new range of khmax values is recommended to better predict the lateral load–deflection response of single piles. 相似文献
59.
60.
Realistic models of solar prominence flux ropes are numerically constructed. The models are in 2.5 dimensions, including the effects of non-isothermal temperature, density and gravity, and pressure. Stability of the equilibria to pressure- and gravity-driven instabilities is numerically investigated, using the ballooning formalism of fusion plasma theory. The equilibrium models can become unstable to pressure- and gravity-driven modes at plasma parameters characteristic of prominences. 相似文献