Segmentation and classification of high spatial resolution images based on Hölder exponents and variance     

Debasish Chakraborty  Sourabh Singh  Dibyendu Dutta 《地球空间信息科学学报》2017,20(1):39-45

Pixel-based or texture-based classification technique individually does not yield an appropriate result in classifying the high spatial resolution remote sensing imagery since it comprises textured and non-textured regions. In this study, Hölder exponents (HE) and variance (VAR) are used together to transform the image for measuring texture. A threshold is derived to segment the transformed image into textured and non-textured regions. Subsequently, the original image is extracted into textured and non-textured regions using this segmented image mask. Afterward, extracted textured region is classified using ISODATA classification algorithm considering HE, VAR, and intensity values of individual pixel of textured region. And extracted non-textured region of the image is classified using ISODATA classification algorithm. In case of non-textured region, HE and VAR value of individual pixel is not considered for classification for significant textural variation is not found among different classes. Consequently, the classified outputs of non-textured and textured regions that are generated independently are merged together to get the final classified image. IKONOS 1 m PAN images are classified using the proposed algorithm, and the classification accuracy is more than 88%.  相似文献   

Understanding Diurnality and Inter-Seasonality of a Sub-tropical Urban Heat Island     

Tirthankar Chakraborty  Chandan Sarangi  Sachchida Nand Tripathi 《Boundary-Layer Meteorology》2017,163(2):287-309

We quantify the spatial and temporal aspects of the urban heat-island (UHI) effect for Kanpur, a major city in the humid sub-tropical monsoon climate of the Gangetic basin. Fixed station measurements are used to investigate the diurnality and inter-seasonality in the urban–rural differences in surface temperature (\({\Delta } T_\mathrm{s}\)) and air temperature (\({\Delta } T_\mathrm{c}\)) separately. The extent of the spatial variations of the nighttime \({\Delta } T_\mathrm{c}\) and \({\Delta } T_\mathrm{s}\) is investigated through mobile campaigns and satellite remote sensing respectively. Nighttime \({\Delta } T_\mathrm{c}\) values dominate during both the pre-monsoon (maximum of 3.6 \(^\circ \hbox {C}\)) and the monsoon (maximum of 2.0 \(^\circ \hbox {C}\)). However, the diurnality in \({\Delta } T_\mathrm{s}\) is different, with higher daytime values during the pre-monsoon, but very little diurnality during the monsoon. The nighttime \({\Delta } T_\mathrm{s}\) value is mainly associated with differences in the urban–rural incoming longwave radiative flux (\(r^{2}=0.33\) during the pre-monsoon; 0.65 during the monsoon), which, in turn, causes a difference in the outgoing longwave radiative flux. This difference may modulate the nighttime \({\Delta } T_\mathrm{c}\) value as suggested by significant correlations (\(r^{2}=0.68\) for the pre-monsoon; 0.50 for the monsoon). The magnitude of \({\Delta } T_\mathrm{c}\) may also be modulated by advection, as it is inversely related with the urban wind speed. A combination of in situ, remotely sensed, and model simulation data were used to show that the inter-seasonality in \({\Delta } T_\mathrm{s}\), and, to a lesser extent, in \({\Delta } T_\mathrm{c}\), may be related to the change in the land use of the rural site between the pre-monsoon and the monsoon periods. Results suggest that the degree of coupling of \({\Delta } T_\mathrm{s}\) and \({\Delta } T_\mathrm{c}\) may be a strong function of land use and land cover.  相似文献   

Evening twilight OH (7,2) band emission at Calcutta and its covariation with LI 6708 Å     

D. Bhaumik  J. N. Chakravorty  S. K. Midya  S. Chakraborty 《Earth, Moon, and Planets》1996,74(2):115-121

Evening twilight airglow emissions of OH (7,2) band and Li 6708 Å are observed by Dunn-Manring type photometer and following important results are obtained.

1. Intensity of OH (7,2) and Li (6708 Å) decrease exponentially during evening twilight period.
2. OH (7,2) band covaries with Li (6708 Å) during evening twilight period.
3. Empirical equations of OH (7,2) band with time is obtained.
4. Possible explanations of such type of variations is also presented.

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A study of Brans-Dicke theory in FRW-model     

Subenoy Chakraborty  Firoj Shah MD. 《Astrophysics and Space Science》1995,226(1):73-78

In FRW space time Brans-Dicke theory is developed for two cases: (i) the vacuum and (ii) the perfect fluid model. The field equations are transformed into a much simpler form under a change of time co-ordinates and then the solutions are determined for the above cases. An equation of statep =/3 (radiation) is assumed in the case of perfect fluid.  相似文献   

Tidal disruption of a disk galaxy     

Tapan K. Chatterjee  Farooq Ahmed 《Astrophysics and Space Science》1981,75(2):501-509

The tidal force effects of a spherical galaxy passing head-on through a disk galaxy have been studied for various orientations of the disk galaxy with respect to the direction of relative motion of the two galaxies. The density distribution of the spherical galaxy is taken to be that of a polytrope of indexn=4 and that of the disk galaxy is taken to be, (r)=_ce^–4r/R, where _c is the central density andR the radius of the disk. It is found that the disruptive effects due to the tidal force are minimum when the plane of the disk lies along the direction of relative motion, but are maximum when the plane of the disk is slightly inclined to this direction (about 15°). The tidal force effects at the median radius have also been computed. The tadal force effects are much higher in the interior region of the disk.  相似文献   

Whistlers as a diagnostic technique in the lower ionosphere     

G. C. Das  A. K. Sur  B. Chakraborty 《Astrophysics and Space Science》1987,129(1):159-167

We have taken a plasma model of ionosphere which is quite different from the earlier model employed by several workers to study the whistler as a diagnostic technique in the ionosphere. In contrast to the earlier model, we have considered an ionosphere that includes negative ionic species and due to which the mathematical technique loses the basic assumptions chosen earlier to derive the group travel time. We have shown that the negative ion has a significant role and without its contribution, the method to diagnose the ionospheric parameters may lead to an error. We have discussed also how to uset()= ₀ ^h dh/v _g as a diagnostic tool in determining the ionospheric parameters.  相似文献   

Phase inconsistency as a major source of error in NGFS forecast     

Singhai  Priyanshi  Balakrishnan  Shibin  Rajagopal  E. N.  Chakraborty  Arindam 《Climate Dynamics》2020,54(5):2797-2814

Climate Dynamics - South Asian monsoon exhibits multiscale spatiotemporal variability. Analyzing the nature and behavior of numerical weather forecast error associated with these space-time...  相似文献   

Probabilistic analyses of three-dimensional circular footing resting on two-layer c–ϕ soil system considering soil spatial variability     

Choudhuri  Kouseya  Chakraborty  Debarghya 《Acta Geotechnica》2022,17(12):5739-5758

Acta Geotechnica - The prime objective of this paper is to study the effect of soil spatial variability on the three-dimensional probabilistic bearing capacity of a circular footing resting on the...  相似文献   

Exposure to Hurricane Harvey flooding for subsidized housing residents of Harris County,Texas     

Chakraborty  Jayajit  McAfee  Ashley A.  Collins  Timothy W.  Grineski  Sara E. 《Natural Hazards》2021,106(3):2185-2205

Natural Hazards - This article contributes to research on social vulnerability to natural hazards by analyzing the relationship between spatial patterns of flooding caused by Hurricane Harvey and...  相似文献   

Particle creation and non-equilibrium thermodynamical prescription of dark fluids for universe bounded by an event horizon     

Subhajit Saha  Atreyee Biswas  Subenoy Chakraborty 《Astrophysics and Space Science》2015,356(1):141-147

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