scholarly journals Artificially Induced Phase Scintillation Observed From GLONASS Signals

2021 ◽  
Author(s):  
Abdollah Darya ◽  
Muhammad Shaikh ◽  
Ilias Fernini ◽  
Hamid AlNaimiy
Keyword(s):  
Remote Sensing ◽  
Solar Minimum ◽  
Elevated Level ◽  
The Other ◽  
Scintillation Index ◽  
Satellite Constellations ◽  
Minimum Period ◽  
Positioning Accuracy ◽  
Phase Lock ◽  
Future Studies

The phase scintillation index is a commonly used metric in the remote sensing of ionospheric irregularities. In this work, we analyze the phase scintillation index observed from the GPS, GLONASS, Galileo, and BeiDou satellite constellations, for a continuous period of three years. Our analysis reveals an elevated level of L1 phase scintillation observed from most GLONASS satellites, and non of the other GNSS constellations during the same period. This is of particular interest as the abnormality was observed during a solar minimum period, and from satellites labeled as healthy. Furthermore, the observations made were verified with data from three other receivers in different regions. This study was conducted to highlight these artificially induced phase scintillations from GLONASS satellites so that future studies can take them into considerations, especially during periods of heightened geomagnetic activity. Additionally, these artificially induced phase scintillations may result in loss of phase lock, as well as reduced positioning accuracy, which may have serious effects on the reliability and integrity of the GLONASS positioning service.

scholarly journals Artificially Induced Phase Scintillation Observed From GLONASS Signals

2021 ◽  
Author(s):  
Abdollah Darya ◽  
Muhammad Shaikh ◽  
Ilias Fernini ◽  
Hamid AlNaimiy
Keyword(s):  
Remote Sensing ◽  
Solar Minimum ◽  
Elevated Level ◽  
The Other ◽  
Scintillation Index ◽  
Satellite Constellations ◽  
Minimum Period ◽  
Positioning Accuracy ◽  
Phase Lock ◽  
Future Studies

The phase scintillation index is a commonly used metric in the remote sensing of ionospheric irregularities. In this work, we analyze the phase scintillation index observed from the GPS, GLONASS, Galileo, and BeiDou satellite constellations, for a continuous period of three years. Our analysis reveals an elevated level of L1 phase scintillation observed from most GLONASS satellites, and non of the other GNSS constellations during the same period. This is of particular interest as the abnormality was observed during a solar minimum period, and from satellites labeled as healthy. Furthermore, the observations made were verified with data from three other receivers in different regions. This study was conducted to highlight these artificially induced phase scintillations from GLONASS satellites so that future studies can take them into considerations, especially during periods of heightened geomagnetic activity. Additionally, these artificially induced phase scintillations may result in loss of phase lock, as well as reduced positioning accuracy, which may have serious effects on the reliability and integrity of the GLONASS positioning service.

scholarly journals Statistical study of the night-time F-layer dynamics at the magnetic equator in West Africa during the solar minimum period 1995–1997

2015 ◽  
Vol 33 (1) ◽  
pp. 143-157 ◽  
Author(s):  
K. S. Tanoh ◽  
B. J.-P. Adohi ◽  
I. S. Coulibaly ◽  
C. Amory-Mazaudier ◽  
A. T. Kobea ◽  
...  
Keyword(s):  
Solar Minimum ◽  
Transition Process ◽  
The Other ◽  
Winter Period ◽  
Night Time ◽  
Minimum Period ◽  
Bottom Part ◽  
Layer Height ◽  
Northern Summer ◽  
The One

Abstract. In this paper, we report on the night-time equatorial F-layer height behaviour at Korhogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, in the West African sector during the solar minimum period 1995–1997. The data were collected from quarter-hourly ionograms of an Ionospheric Prediction Service (IPS) 42-type vertical sounder. The main focus of this work was to study the seasonal changes in the F-layer height and to clarify the equinox transition process recently evidenced at Korhogo during 1995, the year of declining solar flux activity. The F-layer height was found to vary strongly with time, with up to three main phases. The night-to-night variability of these morphological phases was then analysed. The early post-sunset slow rise, commonly associated with rapid chemical recombination processes in the bottom part of the F layer, remained featureless and was observed regardless of the date. By contrast, the following event, either presented like the post-sunset height peak associated with the evening E × B drift, or was delayed to the midnight sector, thus involving another mechanism. The statistical analysis of the occurrence of these events throughout the solar minimum period 1995–1997 revealed two main F-layer height patterns, each characteristic of a specific season. The one with the post-sunset height peak was associated with the northern winter period, whereas the other, with the midnight height peak, characterized the northern summer period. The transition process from one pattern to the other took place during the equinox periods and was found to last only a few weeks. We discuss these results in the light of earlier works.

scholarly journals BeiDou Satellite Unhealthy States and the Impact on System Performance

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4196 ◽  
Author(s):  
Caibo Hu ◽  
Chuang Shi ◽  
Jinping Chen ◽  
Yidong Lou ◽  
Fei Wang
Keyword(s):  
System Performance ◽  
Satellite Orbit ◽  
Service Area ◽  
The Other ◽  
Classification Method ◽  
Positioning Accuracy ◽  
General Classification ◽  
Broadcast Ephemeris ◽  
Beidou System ◽  
The Impact

The BeiDou system satellites may be unhealthy due to many reasons, affecting system performance in different ways. Therefore, it is important to analyze the causes and characteristics of the satellites’ unhealthy states. In this study, these states are classified into five types based on the broadcast ephemeris. Three criteria are presented, based on which a general classification method is proposed. Data from July 2017 to June 2018 are analyzed to validate the method, from which we know that the average unhealthy duration due to satellite maneuvers is much longer than the duration of unhealthy states related to satellite orbit or clock anomalies, and the other unhealthy states may be caused by inbound or outbound satellites. Statistics show that most of the time, the number of unhealthy satellites is no more than two and the average positioning accuracy in the service area will decrease by no more than 0.75 and 1.2 meters when one or two BDS satellites are unhealthy, respectively.

Dreams of Truck Drivers: A Test of the Continuity Hypothesis of Dreaming

2005 ◽  
Vol 25 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Michael Schredl ◽  
Arthur Funkhouser ◽  
Nicole Arn
Keyword(s):  
Empirical Studies ◽  
Truck Drivers ◽  
The Other ◽  
Continuity Hypothesis ◽  
Future Studies ◽  
Daytime Activity ◽  
Close Relationship ◽  
The One ◽  
Dream Emotions ◽  
The Relationship

Empirical studies largely support the continuity hypothesis of dreaming. The present study investigated the frequency and emotional tone of dreams of truck drivers. On the one hand, the findings of the present study partly support the continuity regarding the time spent with driving/being in the truck and driving dreams and, on the other hand, a close relationship was found between daytime mood (feelings of stress, job satisfaction) and dream emotions, i.e., different dream characteristics were affected by different aspects of daytime activity. The results, thus, indicate that it is necessary to define very clearly how this continuity is to be conceptualized. The approach of formulating a mathematical model (cf. [1]) should be adopted in future studies in order to specify the factors and their magnitude in the relationship between waking and dreaming.

Psychophysical interactions with a double-slit interference pattern: Exploratory evidence of a causal influence

2021 ◽  
Vol 34 (1) ◽  
pp. 79-88
Author(s):  
Dean Radin ◽  
Helané Wahbeh ◽  
Leena Michel ◽  
Arnaud Delorme
Keyword(s):  
Experimental Data ◽  
Interference Pattern ◽  
Type I Error ◽  
Human Mind ◽  
The Other ◽  
Type I ◽  
Fringe Visibility ◽  
Future Studies ◽  
Before And After ◽  
Double Slit

An experiment we conducted from 2012 to 2013, which had not been previously reported, was designed to explore possible psychophysical effects resulting from the interaction of a human mind with a quantum system. Participants focused their attention toward or away from the slits in a double-slit optical system to see if the interference pattern would be affected. Data were collected from 25 people in individual half-hour sessions; each person repeated the test ten times for a total of 250 planned sessions. “Sham” sessions designed to mimic the experimental sessions without observers present were run immediately before and after as controls. Based on the planned analysis, no evidence for a psychophysical effect was found. Because this experiment differed in two essential ways from similar, previously reported double-slit experiments, two exploratory analyses were developed, one based on a simple spectral analysis of the interference pattern and the other based on fringe visibility. For the experimental data, the outcome supported a pattern of results predicted by a causal psychophysical effect, with the spectral metric resulting in a 3.4 sigma effect (p = 0.0003), and the fringe visibility metric resulting in 7 of 22 fringes tested above 2.3 sigma after adjustment for type I error inflation, with one of those fringes at 4.3 sigma above chance (p = 0.00001). The same analyses applied to the sham data showed uniformly null outcomes. Other analyses exploring the potential that these results were due to mundane artifacts, such as fluctuations in temperature or vibration, showed no evidence of such influences. Future studies using the same protocols and analytical methods will be required to determine if these exploratory results are idiosyncratic or reflect a genuine psychophysical influence.

scholarly journals Mapping the Unseen: Exploiting Super-Resolution for Semantic Segmentation in Low-Resolution Images

2020 ◽  
Author(s):  
Matheus B. Pereira ◽  
Jefersson Alex Dos Santos
Keyword(s):  
Remote Sensing ◽  
Pattern Recognition ◽  
Super Resolution ◽  
Remote Sensing Data ◽  
Semantic Segmentation ◽  
The Other ◽  
Aerial Imagery ◽  
Aerial Images ◽  
Remote Sensing Images ◽  
Low Resolution

High-resolution aerial images are usually not accessible or affordable. On the other hand, low-resolution remote sensing data is easily found in public open repositories. The problem is that the low-resolution representation can compromise pattern recognition algorithms, especially semantic segmentation. In this M.Sc. dissertation1 , we design two frameworks in order to evaluate the effectiveness of super-resolution in the semantic segmentation of low-resolution remote sensing images. We carried out an extensive set of experiments on different remote sensing datasets. The results show that super-resolution is effective to improve semantic segmentation performance on low-resolution aerial imagery, outperforming unsupervised interpolation and achieving semantic segmentation results comparable to highresolution data.

scholarly journals Examining Teachers’ Roles in Online Learning

2018 ◽  
Vol 26 (2) ◽  
pp. 3
Author(s):  
Qiang Huang
Keyword(s):  
Online Learning ◽  
Descriptive Statistics ◽  
The Other ◽  
Teacher Roles ◽  
Learning Context ◽  
Future Studies ◽  
Managerial Role ◽  
Learning Contexts ◽  
Diverse Learning ◽  
Enhanced Learning

<p>Online learning has been used in the literature to cover diverse learning contexts ranging from blended learning, distance learning, virtual learning and web-enhanced learning. Many aspects of online learning have become the focuses of research and teacher roles are one of them. The present study, therefore, intends to examine how 153 university students perceived the roles of their teachers in online learning of a blended English course by using a 27-item and 5-Likert-scale questionnaire (the STRI). Results of statistical analyses showed that the Cronbach’s Alpha value of the entire questionnaire was .955 and those of the three sub-roles were all above .891, indicating that both the questionnaire and the three factors of sub-roles were reliable and valid. Further analyses revealed that the three sub-roles of teachers, i.e., the cognitive role, the affective role and the managerial role, were significantly different from each other. Among them, the means of the managerial role was significantly higher than that of the cognitive role while the means of the affective role was the lowest. Results of descriptive statistics also revealed that keeping a record of students’ learning in the managerial role was quite notable for students. The findings suggest that the roles of teachers in online learning as a whole were reduced. However, the managerial role was more notable than the other two roles and the affective role was the least impactful in the online learning context in this study. The researcher believes that these findings may offer some insights to classroom implications and provide the basis for future studies of comparing teacher roles across different educational contexts.</p>

scholarly journals The iron-responsive genome of the chiton Acanthopleura granulata

2020 ◽  
Author(s):  
Rebecca M. Varney ◽  
Daniel I. Speiser ◽  
Carmel McDougall ◽  
Bernard M. Degnan ◽  
Kevin M. Kocot
Keyword(s):  
Iron Transport ◽  
West Indian ◽  
The Other ◽  
The West ◽  
Major Clade ◽  
Future Studies ◽  
Form And Function ◽  
Genetic Mechanisms ◽  
Molluscan Evolution ◽  
And Function

ABSTRACTMolluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the calcified teeth of their rasp-like radula with a coat of iron (as magnetite). Here we present the genome of the West Indian fuzzy chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome contains homologs of many biomineralization genes identified previously in conchiferan molluscs. We expected chitons to lack genes previously identified from pathways conchiferans use to make biominerals like calcite and nacre because chitons do not use these materials in their shells. Surprisingly, the A. granulata genome has homologs of many of these genes, suggesting that the ancestral mollusc had a more diverse biomineralization toolkit than expected. The A. granulata genome has features that may be specialized for iron biomineralization, including a higher proportion of genes regulated directly by iron than other molluscs. A. granulata also produces two isoforms of soma-like ferritin: one is regulated by iron and similar in sequence to the soma-like ferritins of other molluscs, and the other is constitutively translated and is not found in other molluscs. The A. granulata genome is a resource for future studies of molluscan evolution and biomineralization.SIGNIFICANCE STATEMENTChitons are molluscs that make shell plates, spine- or scale-like sclerites, and iron-coated teeth. Currently, all molluscs with sequenced genomes lie within one major clade (Conchifera). Sequencing the genome of a representative from the other major clade (Aculifera) helps us learn about the origins and evolution of molluscan traits. The genome of the West Indian Fuzzy Chiton, Acanthopleura granulata, reveals chitons have homologs of many genes other molluscs use to make shells, suggesting all molluscs share some shell-making pathways. The genome of A. granulata has more genes that may be regulated directly by iron than other molluscs, and chitons produce a unique isoform of a major iron-transport protein (ferritin), suggesting that chitons have genomic specializations that contribute to their production of iron-coated teeth.

Discontinuation of Somatic Medication During Psychiatric Hospitalization

2014 ◽  
Vol 48 (11) ◽  
pp. 1415-1424 ◽  
Author(s):  
Heshu Abdullah-Koolmees ◽  
Helga Gardarsdottir ◽  
Lennart J. Stoker ◽  
Judith Vuyk ◽  
Toine C. G. Egberts ◽  
...  
Keyword(s):  
Crossover Study ◽  
Confidence Intervals ◽  
Index Date ◽  
Cox Regression ◽  
Psychiatric Hospitalization ◽  
The Other ◽  
Future Studies ◽  
Time Points ◽  
Relative Risks ◽  
Health Objective

Background: Psychiatric hospitalization can increase the risk of discontinuation of pharmacotherapy, which may negatively influence patients’ health. Objective: To investigate the association between psychiatric hospitalization and discontinuation of somatic medication. Methods: A retrospective crossover study was performed in patients admitted to a psychiatric hospital (index date), who had got somatic medication dispensed during the 3 months prior to hospitalization. Discontinuation of somatic medication was investigated at the following time points: index date and 3, 6, and 9 months before the index date. Relative risks (RR) with 95% confidence intervals (95% CIs) of discontinuing somatic medication at the index date versus the time points before the index date were estimated using Cox regression. Results: In all, 471 hospitalized patients were included in the study; 38.9% of the patients were discontinuers on the index date. RR for discontinuation of ≥1 somatic medication was 1.88 (95% CI = 1.55-2.27) at the index date compared with the other time points and highest for patients <45 years (RR = 2.83; 95% CI = 1.92-4.18). Conclusions: Psychiatric hospitalization was associated with an almost doubled risk of discontinuation of somatic medication. Future studies should address the influence of discontinuation of care on patients’ health.

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