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1.
Identification of sharp and discontinuous lithological boundaries from well log signal stemming from heterogeneous subsurface structures assumes a special significance in geo-exploration studies. Well log data acquired from various geological settings generally display nonstationary/nonlinear characteristics with varying wavelengths and frequencies. Modelling of such complex well-log signals using the conventional signal processing techniques either fails to catch-up abrupt boundaries or at the best, do not provide precise information on insidious lithological discontinuities. In this paper, we have proposed a new wavelet transform-based algorithm to model the abrupt discontinuous changes from well log data by taking care of nonstationary characteristics of the signal. Prior to applying the algorithm on the geophysical well data, we analyzed the distribution of wavelet coefficients using synthetic signal generated by the first order nonstationary auto-regressive model and then applied the method on actual well log dataset obtained from the KTB bore hole, Germany. Besides identifying the formation of layered boundaries, the underlying method also maps some additional formation boundaries, which were hitherto undetected at the KTB site. The results match well with known geological lithostratigraphy and will be useful for constraining the future model of KTB bore hole data. 相似文献
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Yadav Ganesh Singh R. B. Anand Subhash Pandey B. W. Mohanty Ashutosh Dash Sushree Sangita 《GeoJournal》2021,87(4):469-483
Ambient air pollution, particularly in the urban environment of developing countries, has turned out to be a major health risk factor. We explore the compounded impact of age sensitivity, exposure, poverty, co-morbidity, etc., along with composite air pollution in determining morbidity and health burden of people in Lucknow, India. This cross-sectional study is confined to analyse respiratory health status across different socio-economic and geographic locations using n = 140 in-depth questionnaire method. We used mean daily ambient air pollution data of PM10, PM2.5, SO2, and NO2 for the 2008–2018 period. We used the ecological model framework to assess the risk at different hierarchical levels and compounded severity on a spatial scale. We also used Logistic regression model with log odds and odds ratio to analyze the association of risks outcomes with composite air pollution scores calculated using the principal component analysis method. There is a strong association of location-specific respiratory disease prevalence with an overall 32 percent prevalence. The prevalence of ecological model 1 (individual domain) is 4.3 percent, while ecological model 2 (community domain) has the highest prevalence at 32.4 percent. The logistic regression model shows that respiratory disease load is positively associated with age sensitivity (P < .001) and composite pollution level (P < .001). For another model with suffocation as the outcome variable, composite pollution level (P < .001) and exposure (P < .001) are positively associated. Optimum interventions are required at Ecological models 1, 2, and 3 levels for better respiratory health outcomes.
相似文献4.
K.O. Buesseler S. Pike K. Maiti C.H. Lamborg D.A. Siegel T.W. Trull 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(7):1143-1167
An extensive 234Th data set was collected at two sites in the North Pacific: ALOHA, an oligotrophic site near Hawaii, and K2, a mesotrophic HNLC site in the NW Pacific as part of the VERTIGO (VERtical Transport In the Global Ocean) study. Total 234Th:238U activity ratios near 1.0 indicated low particle fluxes at ALOHA, while 234Th:238U ～0.6 in the euphotic zone at K2 indicated higher particle export. However, spatial variability was large at both sites—even greater than seasonal variability as reported in prior studies. This variability in space and time confounds the use of single profiles of 234Th for sediment trap calibration purposes. At K2, there was a decrease in export flux and increase in 234Th activities over time associated with the declining phase of a summer diatom bloom, which required the use of non-steady state models for flux predictions. This variability in space and time confounds the use of single profiles of 234Th for sediment trap calibration purposes. High vertical resolution profiles show narrow layers (20–30 m) of excess 234Th below the deep chlorophyll maximum at K2 associated with particle remineralization resulting in a decrease in flux at depth that may be missed with standard sampling for 234Th and/or with sediment traps. Also, the application of 234Th as POC flux tracer relies on accurate sampling of particulate POC/234Th ratios and here the ratio is similar on sinking particles and mid-sized particles collected by in-situ filtration (>10–50 μm at ALOHA and >5–350 μm at K2). To further address variability in particle fluxes at K2, a simple model of the drawdown of 234Th and nutrients is used to demonstrate that while coupled during export, their ratios in the water column will vary with time and depth after export. Overall these 234Th data provide a detailed view into particle flux and remineralization in the North Pacific over time and space scales that are varying over days to weeks, and 10's–100's km at a resolution that is difficult to obtain with other methods. 相似文献
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Narendra K. Meena Sabyasachi Maiti Ankush Shrivastava 《Journal of Applied Geophysics》2011,73(2):121-129
In this paper magnetic property of the Delhi topsoil has been used to characterize the potentially polluted areas in terms of magnetic minerals and grain (Magnetic Domain) concentration as a factor of toxic metals and other mutagenic pollutant concentration. The Saturation magnetisation (Ms) and Saturation remanence (Mrs) has been taken as proxy for ferrimagnetic mineral concentration. However, delineation of anthropogenic magnetic fraction from lithogenic (geogenic) magnetic fraction has been done by the paramagnetic/diamagnetic contribution of soil with the fact that the fresh soil contains higher paramagnetic and diamagnetic minerals than polluted. Predominantly, the topsoils of Delhi are dominated with ferrimagnetic minerals (Magnetite and Maghemite phase). Significantly the industrial areas contain highest concentration of the ferrimagnetic minerals with negligible paramagnetic/diamagnetic fraction which leads to anthropogenic contribution. Heavy traffic and densely populated areas of the Delhi exhibit moderate to low soil pollution while green areas show lowest with higher paramagnetic/diamagnetic contribution. The soils in Delhi are dominated with Pseudo-Single Domain (PSD) magnetic grain, though the industrial areas in Delhi show coarser Multidomain (MD) grains in comparison to Stable Single Domain (SSD) in forest areas. Our study reveals that the fine grain particle does not show significant link with higher concentration of ferrimagnetic minerals at least in soils. The presence of the lithogenic magnetite crystal in the forest soil and anthropogenically produced spherules in industrial areas and higher concentration of the heavy metal in Delhi soil strengthen our findings. 相似文献
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Kanchan Maiti Claudia R. Benitez-Nelson Yoshimi Rii Robert Bidigare 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1445
Mesoscale eddies may enhance primary production (PP) in the open ocean by bringing nutrient-rich deep waters into the euphotic zone, potentially leading to increased transport of particles to depth. This hypothesis remains controversial, however, due to a paucity of direct particle export measurements. In this study, we investigated particle dynamics using 234Th–238U disequilibria within a mesoscale cold-core eddy, Cyclone Opal, which formed in the lee of the Hawaiian Islands. 234Th samples were collected along two transects across Cyclone Opal as well as during a time-series within the eddy core during a decaying diatom bloom. Particulate carbon (PC), particulate nitrogen (PN) and biogenic silica (bSiO2) fluxes at 150 m varied spatially and temporally within the eddy and strongly depended on the 234Th model formulation used (e.g., steady state versus non-steady state, inclusion of upwelling, etc.). Particle fluxes estimated from a steady state model assuming an upwelling rate of 2 m day−1 yielded the best fit to sediment-trap data. These 234Th-derived particle fluxes ranged from 332±14 to 1719±53 μmol C m−2 day−1, 27±3 to 114±12 μmol N m−2 day−1, and 33±20 to 309±73 μmol Si m−2 day−1. Although PP rates within Cyclone Opal were elevated by a factor of 2–3, PC and PN fluxes were the same, within error, inside and outside of Cyclone Opal. The ratio of PC export to PP remained surprisingly low at <0.03 and similar to those measured in surrounding waters. In contrast, bSiO2 fluxes within the eddy core were three times higher. Detailed analyses of 234Th depth profiles consistently showed excess 234Th at 100–175 m, associated with the remineralization and possible accumulation of suspended and dissolved organic matter from the surface. We suggest that strong microzooplankton grazing facilitated particulate organic matter recycling and resulted in the export of empty diatom frustules. Thus, while eddies may increase PP, they do not necessarily increase PC and PN export to deep waters. This may be a general characteristic of wind-driven cyclonic eddies of the North Pacific Subtropical Gyre and suggests that eddies may preferentially act as a silica pump, thereby playing an important role in promoting silicic-acid limitation in the region. 相似文献
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A numerical time-simulation algorithm for analysing highly nonlinear solitary waves interacting with plane gentle and steep slopes is described by employing a mixed Eulerian–Lagrangian method. The full nonlinear free surface conditions are considered here in a Lagrangian frame of reference without any analytical approximations, and thus the method is valid for very steep waves including overturning. It is found that the runup height is crucially dependent on the wave steepness and the slope of the plane. Pressures and forces exerted on impermeable walls of different inclinations (slopes) by progressive shallow water solitary waves are studied. Strong nonlinear features in the form of pronounced double peaks are visible in the time history of pressure and force signals with increasing heights of the oncoming solitary waves. The effect of nonlinearity is less pronounced as the inclination of the wall decreases with respect to the bottom surface. 相似文献
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１９９８年５月２９日皮山县发生６．２级地震,震中距皮山县城约３９ｋｍ,震源深度为３２ｋｍ,烈度分布区为北西－南东走向的椭圆形,极震区烈度为Ⅶ度,个别点为Ⅷ度,地震使皮山县县城,９个乡,２个镇,２个农场,墨玉县部分地区遭到不同程度的损失。共计受伤人数为２６人,其中重伤为２人,无家可归者人数为５５６６人,１３９２户,牲畜死亡４４５４头。地震造成的直接经济损失达５４８６．７５万元。 相似文献
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The nonlinear diffraction of 2D single and twin hulls are studied by employing a mixed Eulerian–Lagrangian model based on a higher-order cubic-spline boundary element solver. Two types of simulations are considered. In the first, waves are generated by a piston-type wave-maker in a rectangular tank and in the second case a nonlinear incident wave is assumed to exist in the tank in which the body is introduced. For the application of this model, the full nonlinear diffraction problem is recast in terms of a perturbation wave-field. Computations are performed for rectangular and triangular hull geometries. Computed results show significant nonlinearities, particularly in the heave force. The twin hull results show the influence of wave interference on the diffraction forces. This interference influences the surge force considerably, but heave force is less affected. 相似文献
10.
Summary ?The paper considers a meso-scale, adiabatic, inviscid and Boussisnesq flow of a stably stratified fluid over a three-dimensional
(3-D) meso-scale orographic barrier with elliptic contour, with special reference to a part of the Western ghats mountain
along west coast of India and on the Khasi-Jayantia hill in the northeast India. The airstream characteristics are simplified
by assuming that the upstream wind velocity (U) and buoyancy frequency (N) are constant with height. Solutions for perturbation vertical velocity (w′) and streamline displacement (η′) are expressed in terms of double integrals. These integrals cannot be evaluated exactly,
hence they have been approximated by asymptotic expansion method. Side by side solutions using numerical method have also
been obtained. The results of the study indicate that the updraft regions in the asymptotic solution are crescent shaped,
symmetrical about the axis y = 0, tilting upwind and spreading laterally with height. The study also shows that in both asymptotic solution and numerical
solution w′ and η′ fall off down wind of the barrier in the central plane (y = 0), further more in the asymptotic solution w′ and η′ fall off as x
−1. The study also indicates that the discrete updraft regions obtained in the numerical solution, when joined, take a crescent
shape.
Received November 26, 2001; accepted February 27, 2002 相似文献