Barin Kumar De | Tripura University (original) (raw)

Papers by Barin Kumar De

SPIE Proceedings, 2016

Facial expressions in infrared imaging have been introduced to solve the problem of illumination,... more Facial expressions in infrared imaging have been introduced to solve the problem of illumination, which is an integral constituent of visual imagery. The paper investigates facial skin temperature distribution on mixed thermal facial expressions of our created face database where six are basic expressions and rest 12 are a mixture of those basic expressions. Temperature analysis has been performed on three facial regions of interest (ROIs); periorbital, supraorbital and mouth. Temperature variability of the ROIs in different expressions has been measured using statistical parameters. The temperature variation measurement in ROIs of a particular expression corresponds to a vector, which is later used in recognition of mixed facial expressions. Investigations show that facial features in mixed facial expressions can be characterized by positive emotion induced facial features and negative emotion induced facial features. Supraorbital is a useful facial region that can differentiate basic expressions from mixed expressions. Analysis and interpretation of mixed expressions have been conducted with the help of box and whisker plot. Facial region containing mixture of two expressions is generally less temperature inducing than corresponding facial region containing basic expressions.

The paper reports the experimental observations of isolated short period enhancements in amplitud... more The paper reports the experimental observations of isolated short period enhancements in amplitude of 40 kHz radio signal transmitted from Sanwa, Japan to KLolkata, India m relation to solar radio bursts having peak flux greater than 1000 m the unit of 10 * ' Wm ^ Hz ' The delay between commencements of signal amplitude and solar radio bursts lies between 3 and 12 minutes The signal Liilianccmcnt in dB exhibits linear increase with increase of solar radio flux up to 8000 flux unit The emission of hard X-rays associated with solar radii) hursts can cause extra ionization in the D-region of ionosphere As a result, conductivity parameter in wave guide mode theory is changed to allow better reflection This fact is the cause of enhancement of signal amplitude Keywords Solar radio emission and X-rays, radio propagation, ionosphere.

Annals of Geophysics, 2009

Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at ... more Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at Kolkata (latitude: 22°34lN) to observe the effect, if any, of transit of Venus on FWF, ELF and VLF amplitudes. The result shows a good correlation between their temporal variations during the transit. The observation was unbelievable as the Venus subtends only 1/32th of the cone subtended by Sun on Earth. This anomaly may be explained on the assumption that the height of Venusian atmosphere with high content of CO2, and nitrogen which absorbs electromagnetic and corpuscular radiations from Sun, depleting the solar radiation reaching the Earth to a considerable extent. As a result, relevant parameters of Earth's atmosphere are modulated and here we show how these changes are reflected in identical behaviour of fair weather field and ELF and VLF spectra.

Advances in Space Research, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Comments on the percentage of occurrence methodology used in "A study of L band scintillations during the initial phase of rising solar activity at an Indian low latitude station" by H

Non-linear interaction between Schumann resonances (SR) and high frequency round-the-world signal... more Non-linear interaction between Schumann resonances (SR) and high frequency round-the-world signals (RWS) in the lower ionosphere yields the ELF spectra that correspond to the three first modes of Schumann resonances. The phenomenon resembles Luxembourg effect between Schumann resonances and HF signals. The intensity of natural electromagnetic field (SR field) produced by thunderstorm activity is strong enough to give rise to non-linear effects in the 0-layer. As a result, there will be heating of electrons by the ELF oscillations of SR fields (£,). The fair-weather electric field (£ 0) also initiates the process of heating in the 0-layer. The influence of this field gives a linear dependence of electron temperature fluctuations on the field strength on SR. These lead to non-linear effects comprising the variations of electron temperature, effective collision frequency and conductivity of the medium. Also, there will be modulation of HF waves by ELF signals.

Bulletin of The Astronomical Society of India - BULL ASTRON SOC INDIA, 2004

A statistical study has been done on soft x-ray (SXR) flares, the data of which were collected by... more A statistical study has been done on soft x-ray (SXR) flares, the data of which were collected by Geostationary Operational Environmental Satellites (GOES) during the period July 1993-June 1994. From the analysis different distribution functions were obtained empirically which give the number of SXR flares per unit interval of intensity and asymmetry in duration and angular interval of longitude. These distribution functions have been used for evaluating the center to limb variation of optical thickness for SXR flares.

Pure and Applied Geophysics, 2009

Several experiments were undertaken at Kolkata (latitude: 22°34 0 N, longitude: 88°30 0 E) on the... more Several experiments were undertaken at Kolkata (latitude: 22°34 0 N, longitude: 88°30 0 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.

Studies have been made on the solar X-ray flares observed by GOES during the period July 1993 - J... more Studies have been made on the solar X-ray flares observed by GOES during the period July 1993 - June 1994, which encompasses the post-maximum phase of 22nd solar cycle. It has been examined that N-S asymmetry remains positive in respect of both latitudinal position and intensity of X-ray flares and increases with the increase of intensity. The E-W asymmetry is found to be zero, when longitudinal distribution is considered; but it remains positive up to a certain intensity value above which it becomes negative. The duration and rise time lie respectively in the ranges of values 5 - 15 min and 0 - 5 min. The distribution of impulsiveness of X-ray flares follows an almost binomial distribution pattern peaking around 0.45.

Annales Geophysicae, 1994

. The statistical behaviour of the sudden enhancement in signal strength (SES) in relation to sol... more . The statistical behaviour of the sudden enhancement in signal strength (SES) in relation to solar X-ray flares has been studied for the near east-west propagation of 40 kHz radio waves from Sanwa (36°11'N; 139°51'E) in Japan to Calcutta (22°34'N; 88°24'E) over a long distance path of 5100 km for a period of two years. The period has been divided into four phases - P1, P2, P3 and P4, according to the position of the overhead sun. The change in signal strength during X-ray flares is dependent on the solar zenith angle and climatic conditions. The statistical modal values of the time lag of the SES peak with respect to that solar X-ray flare is found to increase as solar zenith angle increases. The relative rates of increase and decrease of the signal strength (RRISS and RRDSS respectively) have been evaluated for a number of SES which are related to large X-ray flares. Their characteristics have also been investigated. The modal values of the relaxation time have been found to be highly correlated with climatic conditions like temperature and humidity of the propagation path.

nopr.niscair.res.in

SS De1,$,*, BK De2, BK Sarkar1, B Bandyopadhyay1, DK Haldar1, Suman Paul1 & S Barui1 1Centre of A... more SS De1,$,*, BK De2, BK Sarkar1, B Bandyopadhyay1, DK Haldar1, Suman Paul1 & S Barui1 1Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009, India 2Department of Physics, Tripura University, Tripura 799 130, India $ ...

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019

The effect of the rocket exhaust products on the D-region of the ionosphere is investigated with ... more The effect of the rocket exhaust products on the D-region of the ionosphere is investigated with the help of Very Low Frequency (VLF) electromagnetic wave along the Earth-ionosphere waveguide. VLF is a very useful tool to study the Earth’s lower ionospheric disturbances. The changes in the electron density profile are computed from the observed VLF signal perturbations after the rocket launch. We report the effect of the rocket exhaust on the lower ionosphere at an altitude around 58 km. The effect is primarily caused by localized free-electron depletion by water molecules by the process of attachment, decreasing the electrical conductivity of the ionosphere. The electron depletion is supposed to be formed by the rocket exhaust products of the 1st stage burn of Geosynchronous Launch Vehicle (GSLV) rocket launched from Sriharikota, India, on 27th August 2015 at 11:22 UT (16:52 IST). A Long Wave Propagation Capability (LWPC) model study also supports our findings.

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019

The high latitude southern polar cap ionospheric irregularities observed during the St. Patrick’s... more The high latitude southern polar cap ionospheric irregularities observed during the St. Patrick’s Day 2015 severe geomagnetic storm is reported using Total Electron Content (TEC) data of network of International Ground Stations (IGS) GPS receivers McMurdo-MCM4(-77.83⁰ S, 166.66⁰ E), Casey-CAS1 (-66.28⁰ S, 110.52⁰ E), Davis-DAV 1 (68.58⁰ S, 77.97⁰ E), Mawson-MAW1 (-77.83⁰ S, 166.66⁰ E), East Ongle Island-SYOG Mawson-MAW1 (-67.61⁰ S, 62.87⁰ E) and Rothera-ROTH (-67.57⁰ N, 68.13⁰ E), in the Antarctic Circle. The irregularities of TEC phase fluctuation i.e. Rate of TEC (ROT) and TEC rate index (ROTI) expressed in TECU/min was estimated during the period of 16-18 March, 2015.

Archives for Meteorology, Geophysics, and Bioclimatology Series A, 1985

Studies have been made over a two-year period from April 1981 to March 1983 on an approximately e... more Studies have been made over a two-year period from April 1981 to March 1983 on an approximately east-west propagation of a long distant (5100 kin) radio wave at 40 kHz from Sanwa, Japan to Calcutta. Besides ionospheric effects, the seasonal variations of the amplitude of the received signal have been carefully examined in this paper. The regular amplitude of the signal shows that the sunrise fade minimum lags well behind the ionospheric sunrise and it varies from season to season. Along the path of propagation which is very close to the tropic of cancer, the four important meteorological seasons are pre-monsoon (March-June), monsoon (July-September), post-monsoon (October-November) and winter (December-February), and the meteorological parameters of these seasons have been found to impress the signal amplitude. The signal amplitude has been found to be remarkably related to the product of the temperature and relative humidity. The correlation lies on the fact that humid air possesses a finite conductivity which controls the attenuation of the long wave while passing through the tropospheric regions in multiple paths. Zusammenfassung Meteorologische Effekte bei der Obertragung eines 40 kHz Signals auf langer Distanz Die vorliegende Arbeit besch~iftigt sich mit der Obertragung eines 40 kHz Signals auf 1anger Distanz, ungefiihr yon Osten nach Westen. Die Obertragungsstrecke betlug 5100 km und reichte yon Sanwa in Japan bis nach Kalkutta in Indien. Dabei wurden Beobachtungen vom April 1981 bis M~irz 1983 ausgewertet und neben den ionosphiirischen Effekten auc h die jahreszeitlichen Schwankungen der Amplitude des empfangenen Signals sorgfiiltig untersucht. Der Amplitudenschwund zu Sonnenaufgang bleibt klar gegeniiber dem ionosph/irischen Sonnenaufgang zuriick und ist einer jahreszeitlichen Variation unterworfen. Entlang des Ausbreitungsweges, der ann~ihernd dem n6rdlichen Wendekreis folgt, sind die meteorologischen Jahreszeiten dutch die Volmonsunperiode (Miirz-Juni), dutch den Monsun (Juli-September), der Nachmonsunperiode (Oktober-366 S.K. Sarkar and B. K. De November) und dutch den Winter geprggt. Die meteorologischen Parameter dieser Jahreszeiten driicken den Signalamplituden ihren Stempel auf. Diese sind bemerkenswert gut mit dem Produkt aus der Temperatur und relativer Feuchte korreliert, was auf die endliche Leitfahigkeit der feuchten Luft zuriickzufiihren ist, die die D~mpfung der Langwelten w~hrend ihrer multiplen Wege durch die Troposphgre kontrolliert.

Earth, Moon, and Planets, 2009

Abstract The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiati... more Abstract The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiation spectra in Tripura (23.50° N, 91.25° E), India, is presented here. The field experiments were performed during 12–17th December, 2007 inside Tripura University campus ...

… and Devices for …, 2010

Abstract— Electromagnetic fields due to earthquake have been studied in this presentation through... more Abstract— Electromagnetic fields due to earthquake have been studied in this presentation through some model calculations. The expressions of the variation of electron concentration and electron temperature as the ionospheric precursors of earthquake have been deduced in this ...

… and Devices for …, 2010

Abstract— Some experiments on July 22, 2009, the day of solar eclipse, were undertaken at Kolkata... more Abstract— Some experiments on July 22, 2009, the day of solar eclipse, were undertaken at Kolkata (latitude: 22.56° N, longitude: 88.5° E) to observe the effect of solar eclipse on various parameters of the atmospheric electricity which are directly related to global thunderstorm ...

Acta Geophysica, 2011

Autoregressive neural network (AR-NN) models of various orders have been generated in this work f... more Autoregressive neural network (AR-NN) models of various orders have been generated in this work for the daily total ozone (TO) time series over Kolkata (22.56°N, 88.5°E). Artificial neural network in the form of multilayer perceptron (MLP) is implemented in order to generate the AR-NN models of orders varying from 1 to 13. An extensive variable selection method through multiple linear regression (MLR) is implemented while developing the AR-NNs. The MLPs are characterized by sigmoid non-linearity. The optimum size of the hidden layer is identified in each model and prediction are produced by validating it over the test cases using the coefficient of determination (R 2) and Willmott’s index (WI). It is observed that AR-NN model of order 7 having 6 nodes in the hidden layer has maximum prediction capacity. It is further observed that any increase in the orders of AR-NN leads to less accurate prediction.

SPIE Proceedings, 2016

Facial expressions in infrared imaging have been introduced to solve the problem of illumination,... more Facial expressions in infrared imaging have been introduced to solve the problem of illumination, which is an integral constituent of visual imagery. The paper investigates facial skin temperature distribution on mixed thermal facial expressions of our created face database where six are basic expressions and rest 12 are a mixture of those basic expressions. Temperature analysis has been performed on three facial regions of interest (ROIs); periorbital, supraorbital and mouth. Temperature variability of the ROIs in different expressions has been measured using statistical parameters. The temperature variation measurement in ROIs of a particular expression corresponds to a vector, which is later used in recognition of mixed facial expressions. Investigations show that facial features in mixed facial expressions can be characterized by positive emotion induced facial features and negative emotion induced facial features. Supraorbital is a useful facial region that can differentiate basic expressions from mixed expressions. Analysis and interpretation of mixed expressions have been conducted with the help of box and whisker plot. Facial region containing mixture of two expressions is generally less temperature inducing than corresponding facial region containing basic expressions.

The paper reports the experimental observations of isolated short period enhancements in amplitud... more The paper reports the experimental observations of isolated short period enhancements in amplitude of 40 kHz radio signal transmitted from Sanwa, Japan to KLolkata, India m relation to solar radio bursts having peak flux greater than 1000 m the unit of 10 * ' Wm ^ Hz ' The delay between commencements of signal amplitude and solar radio bursts lies between 3 and 12 minutes The signal Liilianccmcnt in dB exhibits linear increase with increase of solar radio flux up to 8000 flux unit The emission of hard X-rays associated with solar radii) hursts can cause extra ionization in the D-region of ionosphere As a result, conductivity parameter in wave guide mode theory is changed to allow better reflection This fact is the cause of enhancement of signal amplitude Keywords Solar radio emission and X-rays, radio propagation, ionosphere.

Annals of Geophysics, 2009

Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at ... more Some experiments on June 8, 2004, the day of transit of Venus across the Sun, were undertaken at Kolkata (latitude: 22°34lN) to observe the effect, if any, of transit of Venus on FWF, ELF and VLF amplitudes. The result shows a good correlation between their temporal variations during the transit. The observation was unbelievable as the Venus subtends only 1/32th of the cone subtended by Sun on Earth. This anomaly may be explained on the assumption that the height of Venusian atmosphere with high content of CO2, and nitrogen which absorbs electromagnetic and corpuscular radiations from Sun, depleting the solar radiation reaching the Earth to a considerable extent. As a result, relevant parameters of Earth's atmosphere are modulated and here we show how these changes are reflected in identical behaviour of fair weather field and ELF and VLF spectra.

Advances in Space Research, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Comments on the percentage of occurrence methodology used in "A study of L band scintillations during the initial phase of rising solar activity at an Indian low latitude station" by H

Non-linear interaction between Schumann resonances (SR) and high frequency round-the-world signal... more Non-linear interaction between Schumann resonances (SR) and high frequency round-the-world signals (RWS) in the lower ionosphere yields the ELF spectra that correspond to the three first modes of Schumann resonances. The phenomenon resembles Luxembourg effect between Schumann resonances and HF signals. The intensity of natural electromagnetic field (SR field) produced by thunderstorm activity is strong enough to give rise to non-linear effects in the 0-layer. As a result, there will be heating of electrons by the ELF oscillations of SR fields (£,). The fair-weather electric field (£ 0) also initiates the process of heating in the 0-layer. The influence of this field gives a linear dependence of electron temperature fluctuations on the field strength on SR. These lead to non-linear effects comprising the variations of electron temperature, effective collision frequency and conductivity of the medium. Also, there will be modulation of HF waves by ELF signals.

Bulletin of The Astronomical Society of India - BULL ASTRON SOC INDIA, 2004

A statistical study has been done on soft x-ray (SXR) flares, the data of which were collected by... more A statistical study has been done on soft x-ray (SXR) flares, the data of which were collected by Geostationary Operational Environmental Satellites (GOES) during the period July 1993-June 1994. From the analysis different distribution functions were obtained empirically which give the number of SXR flares per unit interval of intensity and asymmetry in duration and angular interval of longitude. These distribution functions have been used for evaluating the center to limb variation of optical thickness for SXR flares.

Pure and Applied Geophysics, 2009

Several experiments were undertaken at Kolkata (latitude: 22°34 0 N, longitude: 88°30 0 E) on the... more Several experiments were undertaken at Kolkata (latitude: 22°34 0 N, longitude: 88°30 0 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.

Studies have been made on the solar X-ray flares observed by GOES during the period July 1993 - J... more Studies have been made on the solar X-ray flares observed by GOES during the period July 1993 - June 1994, which encompasses the post-maximum phase of 22nd solar cycle. It has been examined that N-S asymmetry remains positive in respect of both latitudinal position and intensity of X-ray flares and increases with the increase of intensity. The E-W asymmetry is found to be zero, when longitudinal distribution is considered; but it remains positive up to a certain intensity value above which it becomes negative. The duration and rise time lie respectively in the ranges of values 5 - 15 min and 0 - 5 min. The distribution of impulsiveness of X-ray flares follows an almost binomial distribution pattern peaking around 0.45.

Annales Geophysicae, 1994

. The statistical behaviour of the sudden enhancement in signal strength (SES) in relation to sol... more . The statistical behaviour of the sudden enhancement in signal strength (SES) in relation to solar X-ray flares has been studied for the near east-west propagation of 40 kHz radio waves from Sanwa (36°11'N; 139°51'E) in Japan to Calcutta (22°34'N; 88°24'E) over a long distance path of 5100 km for a period of two years. The period has been divided into four phases - P1, P2, P3 and P4, according to the position of the overhead sun. The change in signal strength during X-ray flares is dependent on the solar zenith angle and climatic conditions. The statistical modal values of the time lag of the SES peak with respect to that solar X-ray flare is found to increase as solar zenith angle increases. The relative rates of increase and decrease of the signal strength (RRISS and RRDSS respectively) have been evaluated for a number of SES which are related to large X-ray flares. Their characteristics have also been investigated. The modal values of the relaxation time have been found to be highly correlated with climatic conditions like temperature and humidity of the propagation path.

nopr.niscair.res.in

SS De1,$,*, BK De2, BK Sarkar1, B Bandyopadhyay1, DK Haldar1, Suman Paul1 & S Barui1 1Centre of A... more SS De1,$,*, BK De2, BK Sarkar1, B Bandyopadhyay1, DK Haldar1, Suman Paul1 & S Barui1 1Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009, India 2Department of Physics, Tripura University, Tripura 799 130, India $ ...

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019

The effect of the rocket exhaust products on the D-region of the ionosphere is investigated with ... more The effect of the rocket exhaust products on the D-region of the ionosphere is investigated with the help of Very Low Frequency (VLF) electromagnetic wave along the Earth-ionosphere waveguide. VLF is a very useful tool to study the Earth’s lower ionospheric disturbances. The changes in the electron density profile are computed from the observed VLF signal perturbations after the rocket launch. We report the effect of the rocket exhaust on the lower ionosphere at an altitude around 58 km. The effect is primarily caused by localized free-electron depletion by water molecules by the process of attachment, decreasing the electrical conductivity of the ionosphere. The electron depletion is supposed to be formed by the rocket exhaust products of the 1st stage burn of Geosynchronous Launch Vehicle (GSLV) rocket launched from Sriharikota, India, on 27th August 2015 at 11:22 UT (16:52 IST). A Long Wave Propagation Capability (LWPC) model study also supports our findings.

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019

The high latitude southern polar cap ionospheric irregularities observed during the St. Patrick’s... more The high latitude southern polar cap ionospheric irregularities observed during the St. Patrick’s Day 2015 severe geomagnetic storm is reported using Total Electron Content (TEC) data of network of International Ground Stations (IGS) GPS receivers McMurdo-MCM4(-77.83⁰ S, 166.66⁰ E), Casey-CAS1 (-66.28⁰ S, 110.52⁰ E), Davis-DAV 1 (68.58⁰ S, 77.97⁰ E), Mawson-MAW1 (-77.83⁰ S, 166.66⁰ E), East Ongle Island-SYOG Mawson-MAW1 (-67.61⁰ S, 62.87⁰ E) and Rothera-ROTH (-67.57⁰ N, 68.13⁰ E), in the Antarctic Circle. The irregularities of TEC phase fluctuation i.e. Rate of TEC (ROT) and TEC rate index (ROTI) expressed in TECU/min was estimated during the period of 16-18 March, 2015.

Archives for Meteorology, Geophysics, and Bioclimatology Series A, 1985

Studies have been made over a two-year period from April 1981 to March 1983 on an approximately e... more Studies have been made over a two-year period from April 1981 to March 1983 on an approximately east-west propagation of a long distant (5100 kin) radio wave at 40 kHz from Sanwa, Japan to Calcutta. Besides ionospheric effects, the seasonal variations of the amplitude of the received signal have been carefully examined in this paper. The regular amplitude of the signal shows that the sunrise fade minimum lags well behind the ionospheric sunrise and it varies from season to season. Along the path of propagation which is very close to the tropic of cancer, the four important meteorological seasons are pre-monsoon (March-June), monsoon (July-September), post-monsoon (October-November) and winter (December-February), and the meteorological parameters of these seasons have been found to impress the signal amplitude. The signal amplitude has been found to be remarkably related to the product of the temperature and relative humidity. The correlation lies on the fact that humid air possesses a finite conductivity which controls the attenuation of the long wave while passing through the tropospheric regions in multiple paths. Zusammenfassung Meteorologische Effekte bei der Obertragung eines 40 kHz Signals auf langer Distanz Die vorliegende Arbeit besch~iftigt sich mit der Obertragung eines 40 kHz Signals auf 1anger Distanz, ungefiihr yon Osten nach Westen. Die Obertragungsstrecke betlug 5100 km und reichte yon Sanwa in Japan bis nach Kalkutta in Indien. Dabei wurden Beobachtungen vom April 1981 bis M~irz 1983 ausgewertet und neben den ionosphiirischen Effekten auc h die jahreszeitlichen Schwankungen der Amplitude des empfangenen Signals sorgfiiltig untersucht. Der Amplitudenschwund zu Sonnenaufgang bleibt klar gegeniiber dem ionosph/irischen Sonnenaufgang zuriick und ist einer jahreszeitlichen Variation unterworfen. Entlang des Ausbreitungsweges, der ann~ihernd dem n6rdlichen Wendekreis folgt, sind die meteorologischen Jahreszeiten dutch die Volmonsunperiode (Miirz-Juni), dutch den Monsun (Juli-September), der Nachmonsunperiode (Oktober-366 S.K. Sarkar and B. K. De November) und dutch den Winter geprggt. Die meteorologischen Parameter dieser Jahreszeiten driicken den Signalamplituden ihren Stempel auf. Diese sind bemerkenswert gut mit dem Produkt aus der Temperatur und relativer Feuchte korreliert, was auf die endliche Leitfahigkeit der feuchten Luft zuriickzufiihren ist, die die D~mpfung der Langwelten w~hrend ihrer multiplen Wege durch die Troposphgre kontrolliert.

Earth, Moon, and Planets, 2009

Abstract The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiati... more Abstract The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiation spectra in Tripura (23.50° N, 91.25° E), India, is presented here. The field experiments were performed during 12–17th December, 2007 inside Tripura University campus ...

… and Devices for …, 2010

Abstract— Electromagnetic fields due to earthquake have been studied in this presentation through... more Abstract— Electromagnetic fields due to earthquake have been studied in this presentation through some model calculations. The expressions of the variation of electron concentration and electron temperature as the ionospheric precursors of earthquake have been deduced in this ...

… and Devices for …, 2010

Abstract— Some experiments on July 22, 2009, the day of solar eclipse, were undertaken at Kolkata... more Abstract— Some experiments on July 22, 2009, the day of solar eclipse, were undertaken at Kolkata (latitude: 22.56° N, longitude: 88.5° E) to observe the effect of solar eclipse on various parameters of the atmospheric electricity which are directly related to global thunderstorm ...

Acta Geophysica, 2011

Autoregressive neural network (AR-NN) models of various orders have been generated in this work f... more Autoregressive neural network (AR-NN) models of various orders have been generated in this work for the daily total ozone (TO) time series over Kolkata (22.56°N, 88.5°E). Artificial neural network in the form of multilayer perceptron (MLP) is implemented in order to generate the AR-NN models of orders varying from 1 to 13. An extensive variable selection method through multiple linear regression (MLR) is implemented while developing the AR-NNs. The MLPs are characterized by sigmoid non-linearity. The optimum size of the hidden layer is identified in each model and prediction are produced by validating it over the test cases using the coefficient of determination (R 2) and Willmott’s index (WI). It is observed that AR-NN model of order 7 having 6 nodes in the hidden layer has maximum prediction capacity. It is further observed that any increase in the orders of AR-NN leads to less accurate prediction.