The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and obli...The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and oblique backscatter detection.The ionograms obtained by these detection methods can effectively reflect a large amount of effective information in the ionosphere.The focus of this article is on the oblique backscatter ionogram obtained by oblique backscatter detection.By extracting the leading edge of the oblique backscatter ionogram,effective information in the ionosphere can be inverted.The key issue is how to accurately obtain the leading edge of the oblique backscatter ionogram.In recent years,the application of pattern recognition has become increasingly widespread,and the YOLO model is one of the best fast object detection algorithms in one-stage.Therefore,the core idea of this article is to use the newer YOLOX object detection algorithm in the YOLO family to perform pattern recognition on the F and E_(s) layers echoes in the oblique backscatter ionogram.After image processing,a single-layer oblique backscatter echoes are obtained.It can be found that the leading edge extraction of the oblique backscatter ionogram obtained after pattern recognition and image processing by the YOLOX model is more fitting to the actual oblique backscatter leading edge.展开更多
The characteristics of anomalous radio propagation in the frequency 1 - 30 MHz before and after the 2011 Tohoku-Oki earthquake are firstly revealed by using oblique ionograms for the pass from Wakkanai to Kokubunji wh...The characteristics of anomalous radio propagation in the frequency 1 - 30 MHz before and after the 2011 Tohoku-Oki earthquake are firstly revealed by using oblique ionograms for the pass from Wakkanai to Kokubunji which is closest to the epicenter. An oblique ionogram with a wavy-shape-trace was observed at 06:30 UTC on 11 March 2011 after the 2011 Tohoku-Oki earthquake. The velocity of northward-propagating disturbance caused this wavy-shape-trace is estimated to be 130 m/s. This wave-shape-trace shows very clear signature appearing in the oblique ionograms as the characteristic of strong ionospheric disturbances triggered by the earthquake. An oblique ionogram with a steep slopy-shape-trace was observed at 04:45 UTC on 11 March 2011 one hour before the 2011 Tohoku-Oki earthquake. This slopy-shape-trace is investigated as the signatures of preseismic ionospheric anomaly. This anomalous oblique ionogram with a slopy-shape-trace is examined with the slope ratio of virtual height to sweep-frequency, and the difference between monthly median foF2 and hourly value foF2 at Wakkanai and Kokubunji. These features appearing in oblique ionograms suggest that it is useful for studying the signatures of preseismic ionospheric anomaly.展开更多
The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious i...The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.展开更多
Ionograms, which were obtained from February 1995 to January 1999 by a Digisonde Portable Sounder-4 (DPS-4) at Zhongshan Station in Antarctica, have been scaled. The ionograms interpretation has shown various ionosphc...Ionograms, which were obtained from February 1995 to January 1999 by a Digisonde Portable Sounder-4 (DPS-4) at Zhongshan Station in Antarctica, have been scaled. The ionograms interpretation has shown various ionosphcric phcnomena occurred in the cusp region. They are particle precipitation effects in the E region. F region magnetic noon phenomena, slant Es phenomena and lacuna. F layer irregularity zone (FLIZ) phenomena, and auroral oval identification. Typical examples of ionograms and ionogram sequences observed at Zhongshan Station are displayed in this paper.展开更多
Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morph...Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morphological operator and inversion technique. This method is verified through the comparison of actual detecting data with statistical analysis. The results show that the proposed automatic scaling method has high acceptable rate and is suitable for scaling oblique ionogram with different high angle wave states. It is fast and precise to fit O-mode echoes in F2 layer without the influence from F1 layer. This method could be applied in real-time ionospheric oblique sounding research with high reliability and versatility.展开更多
A new method to obtain the real height profile of ionospheric electron density is described, which is called 'approximation with network'. Also it has been demonstrated how to solve the group path integral equ...A new method to obtain the real height profile of ionospheric electron density is described, which is called 'approximation with network'. Also it has been demonstrated how to solve the group path integral equation with Back Propagation(BP) neural network, and given the computation results with this method for a parabolic model.Simulation results show that the proposed method is effective.展开更多
Introduction: A higher risk of death is associated with wasting in children if it is not treated properly. The objective of this study was to investigate the ionic disorders observed in infants suffering from severe w...Introduction: A higher risk of death is associated with wasting in children if it is not treated properly. The objective of this study was to investigate the ionic disorders observed in infants suffering from severe wasting at Yalgado Ouedraogo Teaching Hospital (YO-TH) and at Charles de Gaulle Pediatric Teaching Hospital (CDG-PTH) in Ouagadougou (Burkina Faso). Methods: This was a retrospective study with a descriptive and analytical aim over the period from January 1, 2016 to December 31, 2020. Results: It concerned infants aged 6 to 24 months hospitalized at YO-TH and at CDG-PTH from Ouagadougou. We included 271 infants. The mean age of the infants was 14.48 ± 5.44 months with 42.07% which was in the age range of [12 - 18] months. On admission to the hospital, the children had an average weight, height and BMI of 6.22 ± 1.32 kg, 0.73 ± 0.07 m and 11.67 ± 1.53 kg/m<sup>2</sup>. In urban areas 56.46% of children and the main reasons for consultation were fever (88.19%), vomiting (52.80%) and diarrhea (50.20%). Electrolyte disturbances in emaciated infants affected all 8 parameters of the blood ionogram. However, the major disorders were 65.68% hyponatremia, 55.35% hypobicarbonatemia, 41.33% hypoprotidemia and 32.47% hypokalemia in infants aged 6 to 24 months. We found an association between diarrhea and residence with hypokalemia (p = 0.0000) and hypochloremia (p = 0.010), respectively. Conclusion: Severe acute wasting in infants 6 to 24 months of age remains a concern in the hospital setting. The frequency of biochemical disturbances is also high.展开更多
The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the io...The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.展开更多
The Mars Advanced Radar for Subsurface and Ionosphere Sounding(MARSIS) onboard the Mars Express(MEX) spacecraft started to collect data of the Martian topside ionosphere from May,2005.By now a large amount of ionogram...The Mars Advanced Radar for Subsurface and Ionosphere Sounding(MARSIS) onboard the Mars Express(MEX) spacecraft started to collect data of the Martian topside ionosphere from May,2005.By now a large amount of ionograms has been obtained.It is important to extract vertical ionospheric information effectively from the ionograms for further study.In this paper a new method,Object Tracking Method(OTM),is proposed to automatically extract the ionospheric electron density profiles by computer.This method is based on three algorithms,namely the Hough transform,region growing segmentation algorithm and moving objects detection method from video sequences.In processing ionosphere echoes are treated as moving objects.The identification ratio of OTM for the MARSIS ionograms is estimated to be around 90%.展开更多
The ionospheric irregularities in the East Asian sector mainly occur in the equinox months,but they also occur occasionally in the solstice months,that is,the unseasonal ionospheric irregularities.The study of the mor...The ionospheric irregularities in the East Asian sector mainly occur in the equinox months,but they also occur occasionally in the solstice months,that is,the unseasonal ionospheric irregularities.The study of the morphology and mechanism of this kind of unseasonal irregularities has been a hot topic in recent years.Using the rate of the TEC index(ROTI)map derived from the observation of multiple GNSS receiver network in China,combined with observations from four ionosondes located in Hainan and Guangzhou,the ionospheric irregularities that occurred in China's low-latitude region during the geomagnetic quiet period on July 5 and 17,2013 are studied,and their spatiotemporal evolution during these two events is provided.Unlike the irregularities in equinox months,both concerned events occurred near midnight,and when the irregularities appear above the ionosonde station,the range spread F emerges in the ionograms.Comparatively,the irregularities on July 5 mainly appear before midnight,while the irregularities on July 17 were present both before and after midnight,and the intensity and range of the irregularities on July 5 are greater than those on July 17.The irregularities can be identified as two discrete patches located on the east and west sides in both events.They initially appeared at lower latitudes and gradually drifted northeastward,roughly drifting from the region of 15°N and 105°E to the region of 25°N and 125°E.The eastward drift velocity on July 5 and 17 is estimated to be about 32 and 39 m/s,respectively.In addition,it is noted that the irregularities exhibit a little southward drifting in the final evolving stage in both events,which may be related to the meridional wind in the thermosphere.During and before the irregularities,the increase of the ionospheric foF2 and TEC is observed,but the pre-sunset reversal enhancement or the increase of hmF2 that is favorable for the development of irregularities is not observed.Considering the relatively quiet geomagnetic conditions during these two events,the reason for these two irregularities cannot be determined.展开更多
基金Supported by the National Natural Science Foundation of China(42104151,42074184,42188101,41727804)。
文摘The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and oblique backscatter detection.The ionograms obtained by these detection methods can effectively reflect a large amount of effective information in the ionosphere.The focus of this article is on the oblique backscatter ionogram obtained by oblique backscatter detection.By extracting the leading edge of the oblique backscatter ionogram,effective information in the ionosphere can be inverted.The key issue is how to accurately obtain the leading edge of the oblique backscatter ionogram.In recent years,the application of pattern recognition has become increasingly widespread,and the YOLO model is one of the best fast object detection algorithms in one-stage.Therefore,the core idea of this article is to use the newer YOLOX object detection algorithm in the YOLO family to perform pattern recognition on the F and E_(s) layers echoes in the oblique backscatter ionogram.After image processing,a single-layer oblique backscatter echoes are obtained.It can be found that the leading edge extraction of the oblique backscatter ionogram obtained after pattern recognition and image processing by the YOLOX model is more fitting to the actual oblique backscatter leading edge.
文摘The characteristics of anomalous radio propagation in the frequency 1 - 30 MHz before and after the 2011 Tohoku-Oki earthquake are firstly revealed by using oblique ionograms for the pass from Wakkanai to Kokubunji which is closest to the epicenter. An oblique ionogram with a wavy-shape-trace was observed at 06:30 UTC on 11 March 2011 after the 2011 Tohoku-Oki earthquake. The velocity of northward-propagating disturbance caused this wavy-shape-trace is estimated to be 130 m/s. This wave-shape-trace shows very clear signature appearing in the oblique ionograms as the characteristic of strong ionospheric disturbances triggered by the earthquake. An oblique ionogram with a steep slopy-shape-trace was observed at 04:45 UTC on 11 March 2011 one hour before the 2011 Tohoku-Oki earthquake. This slopy-shape-trace is investigated as the signatures of preseismic ionospheric anomaly. This anomalous oblique ionogram with a slopy-shape-trace is examined with the slope ratio of virtual height to sweep-frequency, and the difference between monthly median foF2 and hourly value foF2 at Wakkanai and Kokubunji. These features appearing in oblique ionograms suggest that it is useful for studying the signatures of preseismic ionospheric anomaly.
基金We acknowledge the Institute of Earthquake Forecasting for providing the ionosonde data.This work was supported by the National Natural Science Foundation of China(no.41604133).
文摘The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.
文摘Ionograms, which were obtained from February 1995 to January 1999 by a Digisonde Portable Sounder-4 (DPS-4) at Zhongshan Station in Antarctica, have been scaled. The ionograms interpretation has shown various ionosphcric phcnomena occurred in the cusp region. They are particle precipitation effects in the E region. F region magnetic noon phenomena, slant Es phenomena and lacuna. F layer irregularity zone (FLIZ) phenomena, and auroral oval identification. Typical examples of ionograms and ionogram sequences observed at Zhongshan Station are displayed in this paper.
基金Supported by the National Natural Science Foundation of China(59975035,41006058)the Fundamental Research Funds for the Central Universities(2014212020205)
文摘Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morphological operator and inversion technique. This method is verified through the comparison of actual detecting data with statistical analysis. The results show that the proposed automatic scaling method has high acceptable rate and is suitable for scaling oblique ionogram with different high angle wave states. It is fast and precise to fit O-mode echoes in F2 layer without the influence from F1 layer. This method could be applied in real-time ionospheric oblique sounding research with high reliability and versatility.
文摘A new method to obtain the real height profile of ionospheric electron density is described, which is called 'approximation with network'. Also it has been demonstrated how to solve the group path integral equation with Back Propagation(BP) neural network, and given the computation results with this method for a parabolic model.Simulation results show that the proposed method is effective.
文摘Introduction: A higher risk of death is associated with wasting in children if it is not treated properly. The objective of this study was to investigate the ionic disorders observed in infants suffering from severe wasting at Yalgado Ouedraogo Teaching Hospital (YO-TH) and at Charles de Gaulle Pediatric Teaching Hospital (CDG-PTH) in Ouagadougou (Burkina Faso). Methods: This was a retrospective study with a descriptive and analytical aim over the period from January 1, 2016 to December 31, 2020. Results: It concerned infants aged 6 to 24 months hospitalized at YO-TH and at CDG-PTH from Ouagadougou. We included 271 infants. The mean age of the infants was 14.48 ± 5.44 months with 42.07% which was in the age range of [12 - 18] months. On admission to the hospital, the children had an average weight, height and BMI of 6.22 ± 1.32 kg, 0.73 ± 0.07 m and 11.67 ± 1.53 kg/m<sup>2</sup>. In urban areas 56.46% of children and the main reasons for consultation were fever (88.19%), vomiting (52.80%) and diarrhea (50.20%). Electrolyte disturbances in emaciated infants affected all 8 parameters of the blood ionogram. However, the major disorders were 65.68% hyponatremia, 55.35% hypobicarbonatemia, 41.33% hypoprotidemia and 32.47% hypokalemia in infants aged 6 to 24 months. We found an association between diarrhea and residence with hypokalemia (p = 0.0000) and hypochloremia (p = 0.010), respectively. Conclusion: Severe acute wasting in infants 6 to 24 months of age remains a concern in the hospital setting. The frequency of biochemical disturbances is also high.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804042 and 41074115)the Post Doctor Foundation of China (Grant No. 200902445)the Fundamental Research Funds for the Central Universities (Grant No. 4081004)
文摘The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.
基金supported by the National Natural Science Foundation of China(Grant Nos. 10973031,2008AA12A210 and 2010AA122206)
文摘The Mars Advanced Radar for Subsurface and Ionosphere Sounding(MARSIS) onboard the Mars Express(MEX) spacecraft started to collect data of the Martian topside ionosphere from May,2005.By now a large amount of ionograms has been obtained.It is important to extract vertical ionospheric information effectively from the ionograms for further study.In this paper a new method,Object Tracking Method(OTM),is proposed to automatically extract the ionospheric electron density profiles by computer.This method is based on three algorithms,namely the Hough transform,region growing segmentation algorithm and moving objects detection method from video sequences.In processing ionosphere echoes are treated as moving objects.The identification ratio of OTM for the MARSIS ionograms is estimated to be around 90%.
基金supported by the National Natural Science Foundation of China(Grant No.42474206)the National Key Laboratory Foundation of Electromagnetic Environment(Grant No.6142403240301)+1 种基金the Specialized Research Fund for State Key Laboratory of Solar Activity and Space Weatherthe Chinese Meridian Project。
文摘The ionospheric irregularities in the East Asian sector mainly occur in the equinox months,but they also occur occasionally in the solstice months,that is,the unseasonal ionospheric irregularities.The study of the morphology and mechanism of this kind of unseasonal irregularities has been a hot topic in recent years.Using the rate of the TEC index(ROTI)map derived from the observation of multiple GNSS receiver network in China,combined with observations from four ionosondes located in Hainan and Guangzhou,the ionospheric irregularities that occurred in China's low-latitude region during the geomagnetic quiet period on July 5 and 17,2013 are studied,and their spatiotemporal evolution during these two events is provided.Unlike the irregularities in equinox months,both concerned events occurred near midnight,and when the irregularities appear above the ionosonde station,the range spread F emerges in the ionograms.Comparatively,the irregularities on July 5 mainly appear before midnight,while the irregularities on July 17 were present both before and after midnight,and the intensity and range of the irregularities on July 5 are greater than those on July 17.The irregularities can be identified as two discrete patches located on the east and west sides in both events.They initially appeared at lower latitudes and gradually drifted northeastward,roughly drifting from the region of 15°N and 105°E to the region of 25°N and 125°E.The eastward drift velocity on July 5 and 17 is estimated to be about 32 and 39 m/s,respectively.In addition,it is noted that the irregularities exhibit a little southward drifting in the final evolving stage in both events,which may be related to the meridional wind in the thermosphere.During and before the irregularities,the increase of the ionospheric foF2 and TEC is observed,but the pre-sunset reversal enhancement or the increase of hmF2 that is favorable for the development of irregularities is not observed.Considering the relatively quiet geomagnetic conditions during these two events,the reason for these two irregularities cannot be determined.
