Anomalous geomagnetic variations and possible causative structures along foothills of Himachal Pradesh-Kumaun-Himalaya     

M. V. Mahashabde  S. Y. Waghmare  B. R. Arora 《Journal of Earth System Science》1989,98(4):319-326

This paper presents the results of a magnetometer array study covering Kangra region to supplement information already available on the nature of geoelectrical structure at the foothills of Himachal Pradesh-Kumaun-Himalaya. The observed induction pattern across the Himalayan frontal fault is found to be the expression of a psuedo-geomagnetic coast effect associated with the edge of sheet current flowing in the sediments of the IndoGangetic Plains. An additional conductive sheet that is required beneath the frontal folded belt may represent increased hydration of certain sedimentary layers.  相似文献   

Effects of Chronic Exposure to Sublethal Doses of Two Pesticides on Alkaline and Acid Phosphatase Activities in the Intestine of a Fresh Water Teleost,Channa striatus BL. (Channidae)     

N. Arora  S. K. Kulshrestha 《洁净——土壤、空气、水》1985,13(5):619-624

The effects of chronic exposures to sublethal concentration of two pesticides Carbaryl and Endosulfan on alkaline and acid phosphatase activities in the intestine of a fresh water teleost Channa striatus have been observed by exposing the fish for a period of two to thirty days to 10 ppm and 20 ppm of Carbaryl and 0.00075 and 0.001 ppm of Endosulfan. The inhibition of alkaline phosphatase activity has been dependent on the duration of exposure, concentration and the type of pesticide used. The acid phosphatase activity increased with the duration of exposure in higher concentration of Carbaryl and both the concentrations of Endosulfan. Endosulfan produced more pronounced effects than Carbaryl.  相似文献   

Delineation of long-wavelength magnetic anomalies over central India by rectangular harmonic analysis     

B. R. Arora  S. Y. Waghmare 《Journal of Earth System Science》1984,93(4):353-362

The method of rectangular harmonic analysis is applied to the geomagnetic field data from central India to isolate long wavelength magnetic anomalies associated with largescale crustal structures. The long-wavelength anomalies have accounted for approximately 20 % of the spatial variability of the residual magnetic field over the International Geomagnetic Reference Field. On the magnetic anomaly map, reflecting the surface expression of longwavelength anomalies, the Tapi-Narmada-Son zone is characterized by a feeble positive anomaly bounded by a strong negative anomaly. The anomaly pattern is believed to be caused by the large-scale undulation in Moho and related variations in the thickness of the lower (basaltic) crust. The other two prominent anomalies, the magnetic low striking northwest and the magnetic high trending east-northeast, appear to be related to the deep structural feature of the Godavari graben and the eastern Rajasthan lineament respectively.  相似文献   

Geomagnetic solar and lunar daily variations at Alibag,India     

B. R. Arora  D. R. K. Rao  N. S. Sastri 《Pure and Applied Geophysics》1984,122(1):89-109

Geomagnetic solar and lunar daily variationsS andL, at Alibag, India are derived, by the well-known Chapman-Miller method, from the series of homogeneous mean hourly magnetic data of the years 1932 to 1972. The data for all the three elements — declinationD and horizontal and vertical intensitiesH andZ — are analysed, by dividing the data suitably for a study of the seasonal variations, the effect of the changes in the solar and magnetic activities onS andL, the oceanic dynamo contribution toL, and their interactions with each other. The main results are as follows.

1. ForS the daily pattern and its seasonal progression conform to the type expected from a northern-hemisphere station. On the other hand, the amplitudes of all the four harmonics ofL systematically have higher values in winter, and inD andZ the harmonics show large phase differences between summer and winter. The pattern ofL in winter suggests that the lunar current system consists of a single set of vortices in the summer hemisphere rather than the conventional vortices, one set in each of the hemispheres.
2. Solar-cycle modulation on the solar ranges as well as on the amplitudes of the first three harmonics ofS is greater than that expected solely from the increase in E-region conductivity, whereas the corresponding modulation onL is comparable to that on the E-region conductivity.
3. With increasing magnetic activity the first harmonic ofS shows an increase, and the first three harmonics ofL indicate a general decrease, in amplitude.
4. Of the variability inS 96%, but inL only 32%, is found to be accounted for by the combined effect of the variations in the solar and magnetic activities.

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Indices of equatorial electrojet and counter-electrojet in the Indian region: Evolution of the indices and their authenticity     

B N Bhargava  B R Arora  N S Sastri 《Journal of Earth System Science》1983,92(1):45-55

Indices of the equatorial electrojet and counter-electrojet in the Indian region have been evolved based on certain reasonable assumptions, by a criterion depending on the difference in the horizontal field strength between a station under the electrojet axis (Trivandrum) and a station outside the jet influence (Alibag). The indices enable one to characterize each day of the year by an appropriate index. Distribution, in the months, seasons and over the years, of the electrojet and counter-electrojet frequencies at Trivandrum during a 20-year period, 1959–78, is examined. The salient features of the distributions are: (i) Strong electrojets (range 50 nT) and the afternoon counter-electrojets occur, on an average, on about 50% of the days in the year; (ii) For the counter-electrojet, the monthly frequencies show an annual variation with a summer maximum, and for the strong electrojet, a semi-annual variation with maxima in the equinoxes; (iii) A secondary maximum is noted in January in the occurrence frequency of both counter-electrojet and strong electrojet events; (iv) Intense electrojets occur with greater frequency in September.  相似文献   

A comparative study of conventional, ANN black box, fuzzy and combined neural and fuzzy weighting procedures for landslide susceptibility zonation in Darjeeling Himalayas   总被引：7，自引：0，他引：7  

D.P. Kanungo  M.K. Arora  S. Sarkar  R.P. Gupta   《Engineering Geology》2006,85(3-4):347-366

Landslides are one of the most destructive phenomena of nature that cause damage to both property and life every year, and therefore, landslide susceptibility zonation (LSZ) is necessary for planning future developmental activities. In this paper, apart from conventional weighting system, objective weight assignment procedures based on techniques such as artificial neural network (ANN), fuzzy set theory and combined neural and fuzzy set theory have been assessed for preparation of LSZ maps in a part of the Darjeeling Himalayas. Relevant thematic layers pertaining to the causative factors have been generated using remote sensing data, field surveys and Geographic Information System (GIS) tools. In conventional weighting system, weights and ratings to the causative factors and their categories are assigned based on the experience and knowledge of experts about the subject and the study area to prepare the LSZ map (designated here as Map I). In the context of objective weight assignments, initially the ANN as the black box approach has been used to directly produce an LSZ map (Map II). In this approach, however, the weights assigned are hidden to the analyst. Next, the fuzzy set theory has then been implemented to determine the membership values for each category of the thematic layer using the cosine amplitude method (similarity method). These memberships are used as ratings for each category of the thematic layer. Assuming weights of each thematic layer as one (or constant), these ratings of the categories are used for the generation of another LSZ map (Map III). Subsequently, a novel weight assignment procedure based on ANN is implemented to assign the weights to each thematic layer objectively. Finally, weights of each thematic layer are combined with fuzzy set derived ratings to produce another LSZ map (Map IV). The maps I–IV have been evaluated statistically based on field data of existing landslides. Amongst all the procedures, the LSZ map based on combined neural and fuzzy weighting (i.e., Map IV) has been found to be significantly better than others, as in this case only 2.3% of the total area is found to be categorized as very high susceptibility zone and contains 30.1% of the existing landslide area.  相似文献   

Logistic Regression for Feature Selection and Soft Classification of Remote Sensing Data   总被引：2，自引：0，他引：2  

Cheng  Q. Varshney  P.K. Arora  M.K. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(4):491-494

Feature selection is a key task in remote sensing data processing, particularly in case of classification from hyperspectral images. A logistic regression (LR) model may be used to predict the probabilities of the classes on the basis of the input features, after ranking them according to their relative importance. In this letter, the LR model is applied for both the feature selection and the classification of remotely sensed images, where more informative soft classifications are produced naturally. The results indicate that, with fewer restrictive assumptions, the LR model is able to reduce the features substantially without any significant decrease in the classification accuracy of both the soft and hard classifications  相似文献   

Modulation of Geomagnetic Lunar Daily Variation in H at Alibag with Lunar Distance     

B. R. Arora  D. R. K. Rao 《Geophysical Journal International》1975,43(2):627-633

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Current Status and Future Challenges of Weather Radar Polarimetry: Bridging the Gap between Radar Meteorology/Hydrology/Engineering and Numerical Weather Prediction     

Guifu ZHANG  Vivek N.MAHALE  Bryan J.PUTNAM  Youcun QI  Qing CAO  ANDrew D.BYRD  Petar BUKOVCIC  Dusan S.ZRNIC  Jidong GAO  Ming XUE  Youngsun JUNG  Heather D.REEVES  Pamela L.HEINSELMAN  AlexANDer RYZHKOV  Robert D.PALMER  Pengfei ZHANG  Mark WEBER  Greg M.MCFARQUHAR  Berrien MOORE III  Yan ZHANG  Jian ZHANG  J.VIVEKANANDAN  Yasser AL-RASHID  Richard L.ICE  Daniel S.BERKOWITZ  Chong-chi TONG  Caleb FULTON  Richard J.DOVIAK 《大气科学进展》2019,36(6):571-588

After decades of research and development, the WSR-88 D(NEXRAD) network in the United States was upgraded with dual-polarization capability, providing polarimetric radar data(PRD) that have the potential to improve weather observations,quantification, forecasting, and warnings. The weather radar networks in China and other countries are also being upgraded with dual-polarization capability. Now, with radar polarimetry technology having matured, and PRD available both nationally and globally, it is important to understand the current status and future challenges and opportunities. The potential impact of PRD has been limited by their oftentimes subjective and empirical use. More importantly, the community has not begun to regularly derive from PRD the state parameters, such as water mixing ratios and number concentrations, used in numerical weather prediction(NWP) models.In this review, we summarize the current status of weather radar polarimetry, discuss the issues and limitations of PRD usage, and explore potential approaches to more efficiently use PRD for quantitative precipitation estimation and forecasting based on statistical retrieval with physical constraints where prior information is used and observation error is included. This approach aligns the observation-based retrievals favored by the radar meteorology community with the model-based analysis of the NWP community. We also examine the challenges and opportunities of polarimetric phased array radar research and development for future weather observation.  相似文献   

A nonlinear criterion for triaxial strength of inherently anisotropic rocks   总被引：3，自引：2，他引：1  

Mahendra Singh  N. K. Samadhiya  Ajit Kumar  Vivek Kumar  Bhawani Singh 《Rock Mechanics and Rock Engineering》2015,48(4):1387-1405

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