Using the Risk Function in the Problem of Detection of Radiophysical Sounding Signals

© 2017 Springer Science+Business Media New YorkWe propose a model of a two-component mixture for the statistical description of a radiophysical sounding signal at the output of the receiver of a signal with linear frequency modulation. Within this framework, it is found that the risk function can be used to detect readings of the second component in the mixture for small reading amounts. The method for detection of the second mixture component by using the risk function of the mixture on the basis of learning samples is proposed and tested experimentally for the first time

Use of Hazard Function for Signal Detection on Ionograms

© 2004-2012 IEEE. This letter considers a new method for sample detection of ionospheric propagation modes at the receiver output of a chirp ionosonde. The method is based on the use of the hazard function. Within the framework of the two-component mixture model, it is shown that the hazard function can be used to detect samples of the second component in the mixture when the corresponding fraction of samples in the total number is small. The implementation of the method is carried out using training sets. An average normalized hazard function is constructed for the training set not containing the signal. Normalization is carried out in such a way that the hazard function can be considered as a probability density function of a certain random variable. We used Pearson's statistic to test the agreement between the average normalized hazard function of samples that do not contain the signal and an arbitrary normalized hazard function. The critical value of the statistic was determined using the Neyman-Pearson criterion. The effectiveness of the proposed method has been tested for the determination of the lowest and maximum observed frequencies of radio paths from oblique ionospheric sounding ionograms obtained in the Russian network of circumpolar radio paths. The method suggested in this letter can be used not only when processing ionograms but also for the detection of samples of signals of arbitrary nature against a background noise, provided that statistical signal-to-noise ratios are similar to those considered here

Impact of a Strong Magnetic Storm and Two X-Ray Flares on the Ionospheric HF Channel in the Summer Solstice of 2015 According to Oblique Sounding in the Eurasian Region

© 2017, Springer Science+Business Media, LLC. We present the results of observations of the impact a strong magnetic storm and two X-ray flares in the summer solstice of 2015 on the HF signal characteristics during oblique sounding of the ionosphere in the Eurasian region. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, up to a long blackout on the paths adjacent to the subauroral latitudes. On the midlatitude paths, a decrease in the maximum observable frequency of the F layer reached 50% with respect to the average values for an undisturbed ionosphere. The propagation velocity of the negative phase of a disturbance from the subauroral to the midlatitude ionosphere is determined (it is equal to about 100 m/s). It is shown that during a magnetic storm the least observable frequency and the average signal-to-noise ratio for the propagation mode via the sporadic E s layer correlate well with the auroral AE index. Anomalous signals were detected in the main phase of the magnetic storm on the Cyprus—Rostov-on-Don path when a chirp ionosonde–radio direction finder was operated in the over-the-horizon HF radar mode. On the basis of modeling and comparison with experimental data, it is shown that the anomalous signals are due to scattering of radio waves by small-scale irregularities located in the subauroral ionospheric F region

Impact of a Strong Magnetic Storm and Two X-Ray Flares on the Ionospheric HF Channel in the Summer Solstice of 2015 According to Oblique Sounding in the Eurasian Region

© 2017 Springer Science+Business Media, LLC We present the results of observations of the impact a strong magnetic storm and two X-ray flares in the summer solstice of 2015 on the HF signal characteristics during oblique sounding of the ionosphere in the Eurasian region. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, up to a long blackout on the paths adjacent to the subauroral latitudes. On the midlatitude paths, a decrease in the maximum observable frequency of the F layer reached 50% with respect to the average values for an undisturbed ionosphere. The propagation velocity of the negative phase of a disturbance from the subauroral to the midlatitude ionosphere is determined (it is equal to about 100 m/s). It is shown that during a magnetic storm the least observable frequency and the average signal-to-noise ratio for the propagation mode via the sporadic E s layer correlate well with the auroral AE index. Anomalous signals were detected in the main phase of the magnetic storm on the Cyprus—Rostov-on-Don path when a chirp ionosonde–radio direction finder was operated in the over-the-horizon HF radar mode. On the basis of modeling and comparison with experimental data, it is shown that the anomalous signals are due to scattering of radio waves by small-scale irregularities located in the subauroral ionospheric F region

Impact of heliogeophysical disturbances on ionospheric HF channels

© 2017 COSPAR. The article presents the results of the observation of a strong magnetic storm and two X-ray flares during the summer solstice in 2015, and their impact on the HF signals characteristics in ionospheric oblique sounding. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, ultimately causing a long blackout on paths adjacent to subauroral latitudes. On mid-latitude paths, the decrease in 1FMOF reached ∼50% relative to the average values for the quiet ionosphere. It is shown that the propagation conditions via the sporadic Es layer during the magnetic storm on a subauroral path are substantially better than those for F-mode propagation via the upper ionosphere. The delay of the sharp decrease in 1FMOF during the main phase of the magnetic storm allowed us to determine the propagation velocity of the negative phase disturbances (∼100. m/s) from subauroral to mid-latitude ionosphere along two paths: Lovozero - Yoshkar-Ola and Cyprus - Nizhny Novgorod. It is shown that both the LOF and the signal/noise ratio averaged over the frequency band corresponding to the propagation mode via the sporadic Es layer correlate well with the auroral AE index. Using an over-the-horizon chirp radar with a bistatic configuration on the Cyprus - Rostov-on-Don path, we located small-scale scattering irregularities responsible for abnormal signals in the region of the equatorial boundary of the auroral oval

Сравнительный анализ диагностической ценности систем компьютерного анализа маммограмм I и II поколений

Aim: to compare the diagnostic efficacy of generation I and II computer aided detection (CAD) systems for mammography of our own design using the large set of unselect ed mammography images obtained in a routine clinical practice settings. Material and methods. Both CADs were tested on the set of 1532 mammography images of 356 women with confirmed breast cancer (BC). We assessed their value in the detection of suspicious areas with various characteristics located on the different density background. Size of BC lesions varied from 4 to 35 mm (mean – 13,4 ± 6,3 mm). We excluded BC representing only with microcalcification clusters from this analysis, because this task is solved using the separate universal module compatible with both CADs.Results. For I and II generation CADs we obtained the following results: detection of small nodular BCs (≤10 mm) – 41 of 52 (78.85%) and 48 of 52 (92.31%; p > 0.05), respectively; detection of BCs visible as asymmetric areas – 18 of 18 (100%) and 13 of 18 (72.2%; p > 0.05), respectively; detection of only partially visible masses – 15 of 18 (83.3%) and 17 of 18 (94.4%; p > 0.05); detection of lesions poorly visible or invisible on standard mammography images due to the high density background (C-D types according to the ACR 2013 classification) – 9 of 16 (56.3%) and 7 of 16 (70.0%; p = 0.046). Total detection rate was 88.76% (316 of 356 cases) – for CAD I and 90.73% (323 of 356 cases; р > 0.05) – for CAD II. Mean false positive marks rate was 1.8 and 1.3 per image, respectively, – for ACR А-В images and 2.6 and 1.8 per image, respectively – for ACR C-D images (p < 0.05).Conclusion. Generally the diagnostic value of CAD II is not inferior that of CAD I in all analyzed situations, except the poorly visible or invisible lesions on the dense breast background. Moreover, CAD II is probably superior CAD I in the detection of spiculated small masses. The rate of false positive marks was significantly higher for CAD I.Цель исследования: сравнительная оценка эффективности работы систем компьютерного анализа (CAD) I и II поколений собственной разработки на обширной базе неотобранных маммографических изображений, полученных в условиях рутинной клинической практики.Материал и методы. Обе системы были протестированы на наборе из 1532 маммограмм 356 пациенток с верифицированным раком молочной железы (РМЖ) на способность обнаруживать подозрительные области с различными характеристиками на маммограммах различной степени плотности. Размер образований, соответствовавших РМЖ, варьировал от 4 до 35 мм (средний – 13,4 ± 6,3 мм). Исключали случаи РМЖ, проявлявшиеся только в виде скоплений микрокальцинатов, поскольку данная задача решается с использованием отдельного универсального блока.Результаты. При использовании систем I и II поколения были получены следующие результаты соответственно: обнаружение малых раков (до 10 мм) с очаговым ростом – 41 (78,85%) из 52 и 48 (92,31%; p > 0,05) из 52; обнаружение РМЖ, проявляющегося в виде асимметрии, – 18 (100%) из 18 и 13 (72,2%; p > 0,05) из 18; обнаружение частично срезанных образований – 15 (83,3%) из 18 и 17 (94,4%; p > 0,05) из 18; обнаружение образований, плохо видимых или вообще невидимых на стандартных маммограммах ввиду плотной паренхимы МЖ (типы C-D согласно ACR 2013), – 9 (56,3%) из 16 и 7 (70,0%; p = 0,046) из 16. Общая частота обнаружения подозрительных образований составила 88,76% (316 из 356 случаев) – для CAD I и 90,73% (323 из 356 случаев; р>0,05) – для CAD II. Частота ложноположительных меток составила в среднем 1,8 и 1,3 соответственно на маммограмму при типах ACR А–В и 2,6 и 1,8 соответственно – при типах ACR C–D (p < 0,05).Выводы. Эффективность CAD II сравнима с таковой CAD I во всех ситуациях, за исключением выявления плохо видимых и невидимых образований вследствие плотной паренхимы МЖ. Кроме того, CAD II, вероятно, превосходит CAD I в выявлении спикулизированных образований малых размеров. Частота ложноположительных меток при использовании CAD I была достоверно выше

Use of Hazard Function for Signal Detection on Ionograms

© 2004-2012 IEEE. This letter considers a new method for sample detection of ionospheric propagation modes at the receiver output of a chirp ionosonde. The method is based on the use of the hazard function. Within the framework of the two-component mixture model, it is shown that the hazard function can be used to detect samples of the second component in the mixture when the corresponding fraction of samples in the total number is small. The implementation of the method is carried out using training sets. An average normalized hazard function is constructed for the training set not containing the signal. Normalization is carried out in such a way that the hazard function can be considered as a probability density function of a certain random variable. We used Pearson's statistic to test the agreement between the average normalized hazard function of samples that do not contain the signal and an arbitrary normalized hazard function. The critical value of the statistic was determined using the Neyman-Pearson criterion. The effectiveness of the proposed method has been tested for the determination of the lowest and maximum observed frequencies of radio paths from oblique ionospheric sounding ionograms obtained in the Russian network of circumpolar radio paths. The method suggested in this letter can be used not only when processing ionograms but also for the detection of samples of signals of arbitrary nature against a background noise, provided that statistical signal-to-noise ratios are similar to those considered here

Using the Risk Function in the Problem of Detection of Radiophysical Sounding Signals

© 2017 Springer Science+Business Media New YorkWe propose a model of a two-component mixture for the statistical description of a radiophysical sounding signal at the output of the receiver of a signal with linear frequency modulation. Within this framework, it is found that the risk function can be used to detect readings of the second component in the mixture for small reading amounts. The method for detection of the second mixture component by using the risk function of the mixture on the basis of learning samples is proposed and tested experimentally for the first time

Using the Risk Function in the Problem of Detection of Radiophysical Sounding Signals

© 2017 Springer Science+Business Media New YorkWe propose a model of a two-component mixture for the statistical description of a radiophysical sounding signal at the output of the receiver of a signal with linear frequency modulation. Within this framework, it is found that the risk function can be used to detect readings of the second component in the mixture for small reading amounts. The method for detection of the second mixture component by using the risk function of the mixture on the basis of learning samples is proposed and tested experimentally for the first time

Application of a mixture model of probability distributions when detecting radiophysical signals

© 2019 IEEE. The paper shows the effectiveness of using a mixture model of probability distributions when detecting signals of radiophysical sounding. By simulating characteristics of the mixture of noise samples and a emitted signal, it was established that the hazard function can be used as an integral characteristic of the mixture, which indicates the presence of signal samples. The method of using the hazard function for signal detection is given. The results of experimental approbation of the proposed method are carried out