A Task-Based Approach to User Interface Design for a Web-Based Hydrologic Information Systems   总被引：1，自引：0，他引：1  

Leen-Kiat Soh  Jing Zhang  Ashok Samal 《Transactions in GIS》2006,10(3):417-449

Hydroinformatics is a new and rapidly developing field that integrates knowledge and understanding of water resources with the latest developments in information technology to improve decision‐making in many critical applications. It encompasses methods for data capture, storage, processing, analysis and visualization, and the use of advanced modeling, simulation, optimization and knowledge‐based tools and systems infrastructure. Three types of hydrological data are most commonly used: flow rate in major rivers and streams, height of water in wells, and precipitation. To get a complete view of the state of water at a given point in space and time, one must analyze many different types of hydrological data together to derive information using an online GIS tool. To help use these disparate data sources more effectively and efficiently, we have built an online interface called the IJEDI WebCenter for Hydroinformatics using a task‐based approach. In this design, we first identify the tasks that users perform to study water‐related issues, then organize data for each task, and build task‐specific tools to present and analyze data and information. In a study involving both novices and experts in hydrology, we found that the both groups performed water‐related studies more effectively and efficiently than they would have without the WebCenter.  相似文献   

Emerging Flux and X-class Flares in NOAA 6555     

Debi Prasad Choudhary  Ashok Ambastha  G. Ai 《Solar physics》1998,179(1):133-140

The active region NOAA 6555 had several locations of highly sheared magnetic field structure, yet, only one of them was the site for all the five X-class flares during its disk passage in March 1991. The pre-flare observations of high-resolution H filtergrams, vector magnetograms and H Dopplergrams of the 2B/X5.3 flare on 25 March 1991 show that the flaring site was characterized by a new rising emerging flux region (EFR) near the highly sheared magnetic field configuration. The polarity axis of the emerging flux was nearly perpendicular to the pre-existing magnetic neutral line. The location of the EFR was the site of initial brightening in H. The post-flare magnetograms show higher magnetic shear at the flare location compared to the post-flare magnetograms, which might indicate that the EFR was sheared at the time of its emergence. As the new EFR coincided with the occurrence of the flare, we suggest that it might have triggered the observed flare. Observations from Big Bear Solar Observatory and Marshall Space Flight Center also show that there was emergence of new flux at the same location prior to two other X-class flares. We find that out of five observed X-class flares in NOAA 6555, at least in three cases there are clear signatures of flare-related flux emergence. Therefore, it is concluded that EFRs might play an important role in destabilizing the observed sheared magnetic structures leading to large X-class flares of NOAA 6555.  相似文献   

Infrared Observations of Comet Hale–Bopp (C/1995 O1) from Gurushikhar Observatory     

Chandrasekhar  T.  Ashok  N. M.  Tej  Anandamayee  Mondal  Soumen  Watson  P. V. 《Earth, Moon, and Planets》1998,81(2):111-121

During the recent apparition of comet Hale—Bopp (1995 O1) near infrared photometric observations were carried out in the J, H, K filter bands and also in the 3.0—3.4 μm region at the 1.2 m telescope at Gurushikkar, India. The effective temperature of the comet was substantially higher than the equilibrium blackbody temperature. A mean superheat value of 1.83 was derived in the post-perihelion phase which implies that a large fraction of the grain population are made up of small and hot grains with radii <0.5 μm. High albedo values of ∼0.4 were also derived in the scattering angle range 135° to 160° which could explain the unusual brightness of comet Hale—Bopp. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Lower Miocene (Aquitanien-Burdigalian) palaeobiogeography of the Indian subcontinent     

Dr. Ashok Sahni  Mr. Harish Chandra Mitra 《International Journal of Earth Sciences》1980,69(3):824-848

The paper analytically discusses certain palaeoecological criteria in the reconstruction of Lower Miocene (Aquitanian-Burdigalian) palaeobiogeography of the Indian subcontinent. The period is characterised by major marine transgressions and a prolific marine invertebrate and terrestrial vertebrate faunas. Faunal affinities of molluscs from western (Sind-Baluchistan) and eastern (Garo Hills) sectors are distinct and different. Molluscs of Garo Hills show affinity to Burmese species, whereas Sind-Baluchistan species shows similarity to that of the Mediterranean region. Marine molluscs resemble with the present-day taxa of the Arabian Sea and Bay of Bengal, where more than 35% species are common. This similarity is also evidenced by marine elasmobranchs, where approximately 33% species and 86% genera are similar to that of the Recent taxa. Terrestrial mammals show an intermingling of southern U.S.S.R. and African forms along with the presence of probably some groups belonging to the Indian subcontinent.Angiosperms are the dominant group. The Lower Miocene floras of the eastern and the western sectors are entirely different. The palm,Sabal major andPinus are reported from various localities. The climate in the western sector and South India was tropical, whereas in the eastern sector, it was variable.The Lower Miocene period is also marked by the contraction of Sindhu Sea, Bangla Sea and the Burmese Gulf southwards resulting in the final disappearance of the sea by the Pliocene.

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Zusammenfassung Die Paläobiogeographie des unteren Miocän (Aquitan-Burdigal) läßt sich auf dem indischen Subkontinent aus den palökologischen Daten rekonstruieren. Zu dieser Zeit gab es viele marine Invertebraten und terrestrische Vertebraten-Faunen, die große marine Transgression anzeigen. Die Mollusken des Westens (Find-Baluchistan) und Ostens (Garo-Gebirge) sind unterschiedlich. Die Mollusken des Garo-Gebirges sind mit den Spezies von Burma verwandt. Dagegen sind die Faunen von Sind-Baluchistan für die mediterrane Faunenprovinz typisch. Die marinen Mollusken sind verwandt mit den Faunen des Arabischen Meeres und der Bucht von Bengalen; etwa 35% der Spezies sind gleich. Von den marinen Elasmobranchien sind ungefähr 33 % Spezies und 86% Genera gleich wie man sie in den rezenten Faunen findet. Terrestrische Sänger zeigen eine Mischung von südlicher U.S.S.R. und Afrika mit einigen Teilen des Indischen Subkontinentes.In den Pflanzen-Gruppen herrschen die Angiospermen vor. Die Untermiocän-Flora der östlichen und westlichen Gebiete ist ganz unterschiedlich. Der Palme, dieSabal Major undPinus sind aus verschiedenen Lokalitäten bekannt. Das Klima im Westen und im Süden Indiens war tropisch, im Osten dagegen war es wechselfeucht.Das Untermiocän-Meer im Gebiet Sind, Bangladesh und Burma verschwindet vor dem Pliozän.

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Résumé Cet article analyse certains critères paléoécologiques dans la reconstitution de la paléogéographie du Miocène inférieur (Aquitanien-Burdigalien) de l'Inde subcontinentale. La période est caractérisée par de grandes transgressions marines et par des faunes abondantes d'invertébrés marins et de vertébrés terrestres. Les affinités fauniques des mollusques sont différentes dans les secteurs occidentaux (Sind-Baluchistan) et orientaux (Garo Hills). Les mollusques des Garo Hills montrent des affinités avec les espèces de Burma, tandis que les espèces de Sind-Béloutchistan montrent des similitudes avec celles de la région méditerranéenne. Les mollusques marins ont des ressemblances avec les taxons actuels de la Mer d'Arabie et du Golfe du Bengal, où plus de 35% des espèces sont les mÊmes. Cette similarité vaut aussi pour les élasmobranches marin, dont 33% des espèces et 86% des genres ressemblent aux taxons récents. Les mammifères terrestres montrent un mélange de formes du sud de l'U.S.S.R. et de formes africaines, allant de pair avec la présence de certains groupes probables appartenant au sous-continent indien.Les angiospermes forment le groupe dominant. Les formes du Miocène inférieur des secteurs orientaux et occidentaux sont entièrement différentes. Le palmier, le grand Sabal et le pin, sont connus dans différentes localités. Le climat dans le secteur occidental et dans l'Inde méridionale était tropical, tandis que dans le secteur oriental, il était variable.La période du Miocène inférieur est également marquée par le rétrécissement de la Mer de Sindhu, de la Mer de Bangla et du Golfe de Burma vers le sud, avec comme résultat la disparition finale de la mer au Pliocène.

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(Aquitanian Nurdigalian) . . (Sind- Beluchistan) (Garo Hills) . , . : 35% . Elasmobranchs 33 % 86 % . , . . , Sabal major . , , , , , — . Sindhu, .

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Luminescence chronology of late Holocene extreme hydrological events in the upper Penner River basin,South India     

Puthusserry J. Thomas  Navin Juyal  Vishwas S. Kale  Ashok K. Singhvi 《第四纪科学杂志》2007,22(8):747-753

Field stratigraphy, sedimentology and optically stimulated luminescence (OSL) dating have been used to reconstruct the southwest monsoon variability in the semi‐arid region of southern India during the late Holocene. Facies architecture and OSL dating of the water‐lain sediment suggest prevalence of a weak hydrological regime around 3 ka. Following this, a progressive strengthening of monsoon occurred till 2 ka. After 2 ka and until 1 ka fluvial activity was nearly dormant, indicating weakening of the monsoon. Presence of high‐magnitude flood deposits, overbank sedimentation and pedogenesis during 1–0.6 ka indicate intensification of the southwest monsoon in the basin. The onset of aridity was associated with episodic storm surge events that are manifested in the pond sedimentation and localised aeolian accretion. This phase is bracketed between 0.5 ka and 0.2 ka. A renewed phase of monsoonal activity was observed in the form of floodplain aggradation between 180 and 90 years ago. In the past 70 years no significant change in the monsoon performance has been observed. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Spatial pattern of languages in India: A culture-historical analysis     

Ashok K. Dutt  Chandrakanta C. Khan  Chandralekha Sangwan 《GeoJournal》1985,10(1):51-74

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Possibility of Excitation of Low-ℓ P-Modes by Energetic Solar Transients     

Ashok Ambastha  H. M. Antia 《Solar physics》2006,238(2):219-230

We examine the temporal variation of power in low-ℓ modes using GONG data for the period of May 1995–October 2005 and compare this with disk-integrated flare and CME indices. A poor correlation between the running means of Flare Index and mode power is found. A similar result is found for CME Index also. Variations in the running mean mode power corresponding to ℓ = 0 modes with different radial orders are generally stochastic in nature. This behaviour is also reflected in the distribution of mode power.  相似文献   

Decadal changes in the relationship between the Indian and Australian summer monsoons     

Karumuri Ashok  C. Nagaraju  A. Sen Gupta  D. S. Pai 《Climate Dynamics》2014,42(3-4):1043-1052

In this study, we investigate a long-term modulation in the relationship between Indian summer monsoon rainfall with the subsequent Australian summer monsoon rainfall. The two monsoon rainfall time series are significantly correlated at 0.3 at the 99 % confidence level. However, the relationship weakens during the 1932–1966 period, with the inter-monsoon correlation for the period falling below statistical significance. We find that this modulation is consistent with a breakdown of the typical El Niño-Southern Oscillation (ENSO) influence on sea surface temperature in the northern region of Australia, during this period. In addition, a change in the relative influences of ENSO and Indian Ocean Basin-wide Warming sea surface temperature anomalies on the Australian summer monsoon rainfall is also apparent across different time periods.  相似文献   

Analysing the spatio-temporal evolution of an active debris slide in Eastern Himalaya,India   总被引：1，自引：0，他引：1  

Saibal Ghosh  Anjan Bora  Sudipta Nath  Ashok Kumar 《Journal of the Geological Society of India》2014,84(3):292-302

Landslide is one of the prominent geohazards in the Himalayas where loss of lives and property are common. Owing to the complicated geomorphic and tectono-stratigraphic setting of this active Fold-thrust belt (FTB), landsliding of all possible types and spatial scales observed exhibit conspicuous spatio-temporal signatures and evolution. This evolution of landslides is commonly studied by regional assessment and by examining the multi-temporal landslide inventories of a particular area. The success of creating such multi-temporal landslide inventory depends on (i) the availability of relevant past source data (e.g., images, post event maps, air photos etc.) of suitable resolution, scale and quality, (ii) time of generation of source data with respect to the time of landsliding event, (iii) skill of the investigators in interpreting the old images, air photos etc. However, this method is of restricted use in studying the spatio-temporal evolution of a single landslide which is perennially active in the Himalayan terrain, where rapid changes in land use and land cover patterns readily obliterate the signatures of past landsliding. Moreover because of scale constraints, subtle and frequent changes in the spatial dimensions of these individual landslides, and their temporal activity become difficult to identify in such regional assessment carried out over a larger area. In this study therefore, a different approach is adopted whereby the spatio-temporal activity and style of Lanta Khola landslide, a perennially active and large (0.25 km²) debris flow in the Eastern Himalayas, has been studied in detail through detailed scale (1:1000) site-specific geological mapping in phases during the last 28 years (1983–2011). Such site-specific geological observations coupled with numerical slope stability analysis utilising the limit equilibrium method facilitate in detailed understanding of the temporal and spatial evolution and inherent mechanism of this perennial landslide.  相似文献   

The excitation mechanism of [Fe XIV] 5303 å line in the inner regions of solar corona     

K. P .Raju  J. N. Desai  T. Chandrasekhar  N. M. Ashok 《Journal of Astrophysics and Astronomy》1991,12(4):311-317

The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distancer(=R/R₀,R ₀ is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (～ 1.4R ₀). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R₀, in some of the position angles.  相似文献