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D. K. Haldar

Bio: D. K. Haldar is an academic researcher from University of Calcutta. The author has contributed to research in topics: Schumann resonances & Solar eclipse. The author has an hindex of 6, co-authored 30 publications receiving 104 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the variation of the first Schumann resonance (SR) frequency spectra observed from the recorded data over Kolkata (22.56°N, 88.5°E) during a solar proton event (SPE) on July 14, 2000 has been presented.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of the solar eclipse on Fair Weather Field (FWF) and VLF amplitude and phase were investigated at Kolkata (latitude: 22°34′N, longitude: 88°30′E).
Abstract: Several experiments were undertaken at Kolkata (latitude: 22°34′N, longitude: 88°30′E) on the solar eclipse day of August 1, 2008 to observe the effects of the solar eclipse on Fair Weather Field (FWF) and VLF amplitude and phase. The experimental results presented here show significant deviations of the observed parameters from their normal values, as they are determined by the average of the records obtained on 5 days adjacent to the day of the solar eclipse.

12 citations

Journal ArticleDOI
TL;DR: In this paper, an analysis of the sub-inospheric VLF signals at 19.8 kHz and 40 kHz was performed during the occurrence of two earthquakes at Andaman Island and South Coast of Honsu, Japan.
Abstract: Some anomalies are observed in the subinospheric VLF electromagnetic (EM) signals at 19.8 kHz transmitted from North West Cape, Australia (lat: 21.82° S; long: 114.16° E) and 40 kHz from Fukushima, Japan (lat: 36.18° N, long: 139.85° E), recorded by VLF receivers near Kolkata (lat: 22.56° N, long: 88.5° E) during the occurrence of the two earthquakes at Andaman Island (lat:14.018° N, long: 92.92° E), India and other at South Coast of Honsu (lat: 34.78° N, long: 138.27° E), Japan. The analyses of these seismo-ionospheric VLF EM anomalies at these two frequencies during some days before and after the occurrence of earthquake on August 11, 2009 will be presented here. VLF-LF transient variations of significant magnitude in the form of spikes are observed few days prior to the day of occurrence of the earthquakes that continued several days more, then decaying gradually and finally ceased. Signals are examined to describe their connectivity with earthquakes. The enhancements of the amplitude and frequency of the fourth mode of Schumann resonance spectra have been detected during the occurrence of the two earthquakes, which will also be reported here.

11 citations

Journal ArticleDOI
TL;DR: In this article, the results of some analyses of electromagnetic emissions recorded by VLF receivers at 6 kHz and 9 kHz over Agartala, Tripura, the North-Eastern state of India (Lat. 34.53° N, Long. 73.58° E) at Kashmir under Pakistan have been presented.
Abstract: . The outcome of the results of some analyses of electromagnetic emissions recorded by VLF receivers at 6 kHz and 9 kHz over Agartala, Tripura, the North-Eastern state of India (Lat. 23° N, Long. 91.4° E) during the large earthquake at Muzaffarabad (Lat. 34.53° N, Long. 73.58° E) at Kashmir under Pakistan have been presented here. Spiky variations in integrated field intensity of atmospherics (IFIA) at 6 and 9 kHz have been observed 10 days prior (from midnight of 28 September 2005) to the day of occurrence of the earthquake on 8 October 2005 and the effect continued, decayed gradually and eventually ceased on 16 October 2005. The spikes distinctly superimposed on the ambient level with mutual separation of 2–5 min. Occurrence number of spikes per hour and total duration of their occurrence have been found remarkably high on the day of occurrence of the earthquake. The spike heights are higher at 6 kHz than at 9 kHz. The results have been explained on the basis of generation of electromagnetic radiation associated with fracture of rocks, their subsequent penetration into the Earth's atmosphere and finally their propagation between Earth-ionosphere waveguide. The present observation shows that VLF anomaly is well-confined between 6 and 9 kHz.

9 citations

01 Aug 2009
TL;DR: In this article, the amplitude and frequency fluctuations along with some aspects of Schumann Resonance (SR) during the period are investigated and the variation of global thunderstorm activity as inferred from monthly intensity fluctuations of global SR signals over Kolkata and Modra (Latitude 48.61oN) is presented and the observed difference has been interpreted.
Abstract: The paper deals with the study of Schumann resonance data set recorded at Kolkata (Latitude 22.56oN). The results of analyses are confined to a period of one year (January to December 2000). The amplitude and frequency fluctuations along with some aspects of Schumann resonances (SR) during the period are investigated. The variation of global thunderstorm activity as inferred from monthly intensity fluctuations of global SR signals over Kolkata and Modra (Latitude 48.61oN) is presented and the observed difference has been interpreted.

8 citations


Cited by
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09 Mar 2012
TL;DR: Artificial neural networks (ANNs) constitute a class of flexible nonlinear models designed to mimic biological neural systems as mentioned in this paper, and they have been widely used in computer vision applications.
Abstract: Artificial neural networks (ANNs) constitute a class of flexible nonlinear models designed to mimic biological neural systems. In this entry, we introduce ANN using familiar econometric terminology and provide an overview of ANN modeling approach and its implementation methods. † Correspondence: Chung-Ming Kuan, Institute of Economics, Academia Sinica, 128 Academia Road, Sec. 2, Taipei 115, Taiwan; ckuan@econ.sinica.edu.tw. †† I would like to express my sincere gratitude to the editor, Professor Steven Durlauf, for his patience and constructive comments on early drafts of this entry. I also thank Shih-Hsun Hsu and Yu-Lieh Huang for very helpful suggestions. The remaining errors are all mine.

2,069 citations

Journal ArticleDOI
TL;DR: Comparison of methods to prevent multi-layer perceptron neural networks from overfitting of the training data in the case of daily catchment runoff modelling shows that the elaborated noise injection method may prevent overfitting slightly better than the most popular early stopping approach.

198 citations

20 Nov 1991
TL;DR: In this paper, a statistical point-process model is derived to describe the standard activity of earthquake occurrences by assuming that general seismicity is given by the superposition of aftershock sequences.
Abstract: A statistical point-process model is derived to describe the standard activity of earthquake occurrences by assuming that general seismicity is given by the superposition of aftershock sequences. The parameters are estimated ty the maximum likelihood method. Using the estimated model, the “residual point process” of the data is defined and used to find the anomalies which are included in the data set but not captured in the considered model for the standard seismicity. For instance, seismic quiescences can be measured quantitatively by using the residual process. Some examples are provided to illustrate such analyses. Furthermore, a time series of the magnitudes on the residual point process is considered, to investigate its dependence either on the time or on the history of the seismicity. By assuming the exponential distribution at each time and modelling of the b- value , we can examine such dependences and estimate them. Two practical examples are shown.

146 citations

Journal ArticleDOI
TL;DR: The overall performance of the Levenberg–Marquardt algorithm and the DE with Global and Local Neighbors method for neural networks training turns out to be superior to other Evolutionary Computation-based algorithms.

104 citations

Journal ArticleDOI
Colin Price1
TL;DR: In the extremely low frequency (ELF) range below 100 Hz, the global Schumann Resonance (SR) are excited at frequencies of 8 Hz, 14 Hz, 20 Hz, etc as mentioned in this paper.
Abstract: Lightning produces electromagnetic fields and waves in all frequency ranges. In the extremely low frequency (ELF) range below 100 Hz, the global Schumann Resonances (SR) are excited at frequencies of 8 Hz, 14 Hz, 20 Hz, etc. This review is aimed at the reader generally unfamiliar with the Schumann Resonances. First some historical context to SR research is given, followed by some theoretical background and examples of the extensive use of Schumann resonances in a variety of lightning-related studies in recent years, ranging from estimates of the spatial and temporal variations in global lighting activity, connections to global climate change, transient luminous events and extraterrestrial lightning. Both theoretical and experimental results of the global resonance phenomenon are presented. It is our hope that this review will increase the interest in SR among researchers previously unfamiliar with this phenomenon.

68 citations