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101.
102.
Very high spatial and temporal resolution remote sensing data facilitate mapping highly complex and diverse urban environments. This study analyzed and demonstrated the usefulness of combined high-resolution aerial digital images and elevation data, and its processing using object-based image analysis for mapping urban land covers and quantifying buildings. It is observed that mapping heterogeneous features across large urban areas is time consuming and challenging. This study presents and demonstrates an approach for formulating an optimal land cover classification rule set over small representative training urban area image, and its subsequent transfer to the multisensor, multitemporal images. The classification results over the training area showed an overall accuracy of 96%, and the application of rule set to different sensor images of other test areas resulted in reduced accuracies of 91% for the same sensor, 90% and 86% for the different sensors temporal data. The comparison of reference and classified buildings showed ±4% detection errors. Classification through a transferred rule set reduced the classification accuracy by about 5%–10%. However, the trade-off for this accuracy drop was about a 75% reduction in processing time for performing classification in the training area. The factors influencing the classification accuracies were mainly the shadow and temporal changes in the class characteristics. 相似文献
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F. Akbar Jan Sabir Khan M. Ishaq M. Naeem I. Ahmad Sajjad Hussain 《Arabian Journal of Geosciences》2014,7(1):13-19
The purpose of the present study was to investigate the effects of brick kiln exhaust on the quantity of polycyclic aromatic hydrocarbons in surrounding soils and plants. In Pakistan, a big problem is the rapid conglomeration of the brick kilns in out skirt of nearly all urban centers to cope with the rapid construction work in big cities. A huge amount of low-grade coal, rubber, tires is used in non-scientific manner. The study was conducted in the City of Peshawar the capital of Kyber Pakhtunkhwa where many brick kilns are located in the periurban areas. Soil and medicinal plants samples were collected from different locations around the bricks kiln and were analyzed for selected polycyclic aromatic hydrocarbons (PAHs), i.e., benzo(a)pyrene, anthracene, chrysene, flourene, flouranthene, phenanthrene, naphthalene, and acenapthylene. Quantitative and qualitative analysis was carried out by UV spectrophotometer and high-performance liquid chromatography. Benzo[a]pyren and Chrysene were found to be the most abundant compounds. The total load of PAHs in the central location was found to be 0.4014 mg/kg. General trend of PAHs distribution was such that the concentration of individual PAHs was found to increase with depth clearly indicating their absorption in the soil. PAHs concentration increased with the distance up to 300 m and then gradual decreased which showed their movement with the water and air. The PAHs load was found high in the leaves as compared to stem and roots. This high load in the aerial parts indicated their excretion route as well as air deposition. 相似文献
105.
A rigorous theoretical investigation is carried out in analyzing the excitation of electrostatic ion acoustic (IA) solitary wave (SW) structures in two dimensional negative ion magneto-plasmas with superthermal electrons (following κ type distribution). The Zakharov-Kuznetsov (ZK) equation is derived by employing the well known reductive perturbation method, and the analytical solution of ZK equation assists to find out the SW profiles along with their properties. The consequences of different plasma parameters (regarding our considered plasma system) variation on SW structures has been studied. It is found that magnetic field intensity, superthermal parameter κ and temperature of positive and negative ions as well as their densities significantly modify the basic characteristics (amplitude, width, etc.) of the SW waves. A comparison of the SW structures is also presented when the electrons are Maxwellian to when they are superthermal. The relevance of the findings of this work with astrophysical plasmas is briefly pointed out. 相似文献
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107.
S. V. Jeffers J. P. Aufdenberg G. A. J. Hussain A. Collier Cameron V. R. Holzwarth 《Monthly notices of the Royal Astronomical Society》2006,367(3):1308-1316
The variation of the specific intensity across the stellar disc is an essential input parameter in surface brightness reconstruction techniques such as Doppler imaging, where the relative intensity contributions of different surface elements are important in detecting star-spots. We use phoenix and atlas model atmospheres to model light curves derived from high precision (signal-to-noise ratio ≃ 5000) Hubble Space Telescope ( HST ) data of the eclipsing binary SV Cam (F9V+K4V), where the variation of specific intensity across the stellar disc will determine the contact points of the binary system light curve. For the first time, we use χ2 comparison fits to the first derivative profiles to determine the best-fitting model atmosphere. We show the wavelength dependence of the limb darkening and that the first derivative profile is sensitive to the limb-darkening profile very close to the limb of the primary star. It is concluded that there is only a marginal difference (<1σ) between the χ2 comparison fits of the two model atmospheres to the HST light curve at all wavelengths. The usefulness of the second derivative of the light curve for measuring the sharpness of the primary's limb is investigated, but we find that the data are too noisy to permit a quantitative analysis. 相似文献
108.
The coronal structure of AB Doradus determined from contemporaneous Doppler imaging and X-ray spectroscopy 总被引:1,自引:0,他引:1
109.
Nonlinear cylindrical and spherical ion acoustic shocks have been studied in unmagnetized dissipative non-Maxwellian electron-positron-ion (e-p-i) plasmas. Modified Korteweg-de Vries Burgers (mKdVB) has been derived by using reductive perturbation method. Two level finite difference scheme is used with the help of Runge Kutta method to simulate the mKdVB. It is noticed that positron concentration, spectral indices of electrons and positrons, kinematic viscosity of ions significantly modifies the strength of shocks in cylindrical and spherical geometries. 相似文献
110.