Direct measurements of ionospheric parameters provide accurate information about ionosphere, the most important of which are ionosonde measurements and the Langmuir Probes (LP) observations mounted on satellites. There is currently no active ionosonde station in Iran, so the observations of the Langmuir probes can greatly be helpful for ionospheric studies. This study compares and evaluates the electron density measured by Langmuir Probes on board three Swarm satellites owned by the European Space Agency and measurements of the China Seismic Electromagnetic Satellite (CSES). The global distribution of electron density derived from Swarm A and CSES satellites show good consistency for both ascending (nighttime) and descending (daytime) orbits. Correlation coefficients of electron density between these two satellites at descending and ascending orbits were calculated 0. 9268 and 0. 8171, respectively, indicating their high consistency. Evaluating of electron density behavior at the intersecting of simultaneous orbits confirmed these results. Correlation coefficients between electronic density derived from Swarm A, B and C with CSES are calculated 0. 9199, 0. 9138 and 0. 9099 for daytime and 0. 8990, 9494 and 0. 8181 for nighttime, respectively. These results reveal that the electron density observations from these satellites, especially the Swarm B with CSES, are quite correlated which could be due to the close altitudes of these two satellites. The ratio of electron density values of Swarm A to CSES show that the electron density value of Swarm A satellite is often about 4 to 7 times the values of CSES. Also, the comparison of electron density values ​​obtained from the International Reference Ionosphere model (IRI2016) with Swarm and CSES satellites show that there is no systematic and regular relationship between the, especially in nighttime but the electron density values ​​of IRI2016 model are between the values ​​of two other satellites and its values ​​are often about 1 to 3 times the values ​​of CSES.

Earth’ s upper atmosphere, called the ionosphere, is a highly variable region with complex physical characteristics in which the density of free electrons are large enough to have considerable effects on signals’ propagation travelling through this dispersive medium. As GPS signals travel through the ionosphere, they may experience rapid amplitude fluctuations or unexpected phase changes. This is referred to as ionospheric scintillation. Ionospheric scintillation which caused by small scale irregularities in the electron density, is one of the dominant propagation disturbances in radio frequency signals. These irregularities severely affect the accuracy and reliability of GPS measurements. Therefore, it is necessary to investigate ionospheric scintillation and its effects on GPS observations. Hence, the focus of this paper is to detect ionospheric scintillations over Iran’ s region and to investigate these effects on GPS observations in more details. The results will show the occurrance of this phenomenon and its effects on GPS observations.

The ionospheric plasma bubbles cause unpredictable changes in the ionospheric electron density. These variations in the ionospheric layer can cause a phenomenon known as the ionospheric scintillation. Ionospheric scintillation could affect the phase and amplitude of the radio signals traveling through this medium. This phenomenon occurs frequently around the magnetic equator and in low latitudes, mid as well as high latitude regions. ionospheric scintillation is a very complex phenomenon to be modeled. Patterns of ionospheric scintillation occurrence are depended on spatial and temporal ionospheric variabilities. Neural Network (NN) is a data-dependent method, that its performance improves with the sample size. According to the advantages of NN for large datasets and noisy data, the NN model has been implemented for predicting the occurrences of amplitude scintillations. In this paper, the GA technique was considered to obtain primary weights in the NN model in order to identify appropriate S4 values for GUAM GPS station in Guam country (latitude: 144. 8683, Longitude: 13. 5893). The modeling was carried out for the whole month of June 2017, while this model along with ionospheric physical data was used for predicting ionospheric scintillation at the first day of July 2017, the day after the modeling. The designed model has the ability to predict daily ionospheric scintillation with the accuracy of about 78%.

IntroductionThe safety of dams is directly related to the sufficiency of weir capacity. Most of the failures of dams occur due to water passing over their crests, the most important factor of which is insufficient weir capacity. Non-linear weirs can increase the discharge coefficient for a certain width without increasing the water head compared to the traditional linear weirs (such as a Ogee weirs). The hydraulics of labyrinth weirs has been investigated for the first time by Gentling (1940). Dabbling et al. (2013) investigated Labyrinth weirs with different crest height (Stage). Majediasl, et al. (2024) compared the performance of laboratory and meta-model methods to predict the discharge coefficient of labyrinth weirs. Due to the fact that in most of the previous studies, the geometric parameters have been examined separately, therefore, the purpose of this research is to investigate the simultaneous change of the geometric parameters such as the angle of the weir wall (α), the height of the weir (P), the shape of the apex, and the shape of the crest. The weir, the slope of the entrance openings and the change of the shape of the apex into a semi-circle are on the hydraulic performance of Labyrinth weirs.MethodologyThe experiments of this research were carried out in a channel with a length of 13 meters, a width of 1.2 meters and a depth of 0.8 meters with a free flow system. Weirs were installed at a distance of 5 meters from the upstream of the canal, and by establishing a steady flow, hydraulic parameters were measured. In order to check the hydraulic efficiency of Labyrinth weirs, 9 physical models have been built and a total of (196) tests have been performed on them, in which three wall angles (α = 12, 20, and 35) degrees, the height of the weirs are 10 and 11.5 centimeters (15% increase), the number of cycles in all experiments is equal to four cycles, the width of the channel is W =120 cm, the width of each cycle is w = 30 cm, the length and diameter of the apex (in the form of half circle) 2 cm and the presence or absence of slope in their entrance and exit openings (the slope of the openings 1:1:5) was investigated.Results and DiscussionThe discharge coefficient of the Labyrinth weirs with the wall angle (α=12 o) is lower than the wall angle (α=20 o) and the discharge coefficient of this wall angle is also lower than the wall angle (α=35 o). The reason for this can be stated that by increasing the angle of the wall of the cycles, the angle of approach of the flow with the wall of the cycles becomes closer to the vertical state and these weirs act like linear weirs and as a result the flow rate coefficient It becomes more. In the Labyrinth weir (α=12 o) the slope of the entrance the inlet openings of the cycles (1:1.5), the discharge coefficient has increased due to the reduction of the drop in the input flow to the Labyrinth weirs. The discharge coefficient of the Labyrinth weir (α=12 o) in the water head ratio (Ht/p=0.2) has increased by about 7.5% and with the increase of the water head ratio, the efficiency of sloping the openings decreases. In these weirs, the change of the upstream apex to a semi-circular shape has not caused a change in the discharge coefficient, which can be explained by the small length of the apex (A=2cm). Also, increasing the height by 10% and changing the shape of the crest of this weir to a quarter-circle shape has slightly increased the discharge coefficient.In the Labyrinth weir (α =35 o) the slope of the entrance of the cycles (1:1.5) and changing the upstream apex to a semi-circular shape, the discharge coefficient of the Labyrinth weirs (LW35) in all the water head ratio (Ht/p) has increased (about 8-10%). Also, increasing the height by 10% and changing the shape of the crest of this weir to a quarter-circle shape has significantly increased the discharge coefficient in the range (0.6>Ht/p>0.1).ConclusionThe purpose of this research is to investigate the change of geometrical parameters such as the angle of the weir wall (α), the height of the weir (P), the shape of the apex, the form of the weir crest and the slope of the inlet openings on the hydraulic performance of the Labyrinth weirs. By reducing the angle of the wall, the efficiency of the cycle or the efficiency of the weirs increases, and the reason for this can be stated that by reducing the angle of the walls, the length of the weir increases, and on the other hand, the discharge of the weirs has a direct relationship with the length of the weir. As a result, the flow and efficiency of the weir increases, that is, the effect of increasing the length of the weir crest is greater than the discharge coefficient.

Geomagnetic storms are one of the main causes of ionospheric perturbations in different sizes, which depending on their intensity, they can disturb the radio signals passing through this medium. On September 6-12, 2017, the sudden storm commencement (SSC) was the most massive geomagnetic storm of the year due to the X9 solar flare caused by a coronal mass ejection (CME). IMF-Bz and Dst values increased when the first SSC occurred at 23: 43 on September 6. The second SSC has a more vigorous intensity at 23: 00 on September 7 that caused a dramatic increas the other geophysical parameters such as Kp and AE. During the second SSC, Kp index reached 8, and AE reached 2500 nT. In this research, the ionospheric irregularities over OLO3 station (-2. 75E, 35. 87N, 1483. 00H) located at Arusha in Tanzania were analyzed using ground-based GNSS data and in situ measurements SWARM satellites. This procedure was applied to VTEC, signal to noise ratio (S4), and Rate of TEC Index (ROTI) values obtained from ground-based GNSS (GB-GNSS) and SWARM A & C in order to identify ionospheric perturbations during the geomagnetic storm. Furthermore, Langmuir plasma probes of SWARM satellites were implemented to recognize the rate of electron density (RODI). The results show that GB-GNSS and Swarm satellite geophysical ionospheric parameters increased during September 6-12, that indicate the effect of the geomagnetic storm on the increase of ionospheric perturbations. This work shows the potential of using space‐based in situ measurement to detect ionospheric irregularities caused by the geomagnetic storm for areas such as oceans and deserts, where ionospheric observations are hardly possible.

In this paper we are presenting a methodology, which can remove the effect of ionosphere refraction (ionosphere error) on the coordinates derived by single frequency GPS receivers up to 85 percent at a radius of 1400 km around the computational point. The method is based on the GPS observations being made at the permanent GPS stations, according to the following procedure: (i) The real-time GPS observations being made at the permanent GPS station is compared, epoch-wise, with precisely known coordinates of the permanent station and the time series of coordinate variations in x, y, and z component {∆xi, ∆x, ∆z} is derived. (ii) Fast Fourier technique is applied in order to transfer each components of the variations vector from the time domain into frequency domain. (iii) The plot of the resulted period gram provided us with the frequency vector {fx, fy, fz} of the ionosphere refraction (ionosphere error) with nearly 24 hour period. (iv) Having derived the frequency vector of the ionosphere refraction, a sinusoidal models of the form Sxi =ai0+ai1cos(wit-ψi ) (where w=2πƒ ) is fitted to the coordinate differences {∆x, ∆y, ∆z} via least squares technique. As a case study, 25 day observations of the permanent GPS station of Tehran National Cartographic Center (NCC) is used.

Objective: Evaluation of IFAT and abattoir methods for identifying and study of buffalo sarcocystosis (Sarcocystis fusiformis).Samples: A total of398 serum samples were taken from buffaloes before slaughtering for IFAT studing the rate of sarcocystis infections and the results compared with meat inspection and laboratory finding (macro and micro cyst). Procedure: Before slaughtering, blood samples were taken from jagular vein for serological examination by IFA method. After slaughtering, esophagus, diaphragm, heart and skeletal muscles were examined for macroscopic cyst of sarcocystis .For microscopic cysts, the samples were taken from each one of these tissues for impression smear (Dob smear). The macro cysts were identified as S.fusiformis. Bradizoites of this sarcocyst were used as antigen in IF AT and rabbit anti buffalo conjugated serum for this test was prepared in. central laboratory of faculty of veterinary medicine, University of Tehran (Dr.Reza Rastegar central laboratory) using standard method. Results: The results showed that macroscopic and microscopic infection rates of animals is 18.6% and 53.5% respectively. In this study, maximum rate of infection include macroscopic and microscopic finding was in eosophagus and minimum in heart muscle. Any significant differences were observed in infection rates due to sex: The infection rate in adult group was significantly more than young buffaloes. A significant correlation was observed between antibody titer and the rate of macroscopic and microscopic infection (P<0.05), increasing the antibody titer till 1:640 had positive correlation and more than this titer viceversa. All of slaughtered animals had atleast 1:40 titer and most of them were in 1:640 titer group (25.9%) and the lowest prevalence was in 1:10240 titer. (1.5%). Conclusion: According to the results, the IF AT is a suitable test for studing sarcocystosis in buffaloes and is useful for further studies about this economically important parasite in Khoozestan province.

Dynamic processes in the sun, such as solar flares, transmit plasma of charged particles, especially electron and proton, and associated fields into the earth's surroundings that cause geomagnetic disturbances on the earth's surface, called magnetic storms. On magnetic quiet days, moving charged particles, called solar wind, can restrictedly enter into the earth's atmosphere in the Polar Regions. On disturbed magnetic days, more particles at high speed can influence the earth's atmosphere and affect the ionospheric layers.During a magnetic storm, energy enters into the ionosphere at high latitudes that can change some thermospheric parameters such as atomic and molecular composition, temperature and circulation. Composition changes directly affect the electron concentration in the F2 layer, and circulation propagates the warm gas into the lower latitudes. Increasing thermospheric temperature expands the F2 layer and then the layer establishes at higher altitude and the electron concentration decreases (Campbell, 1997). The most intensive disturbances of the ionospheric layers occur during magnetic disturbances. They have a catastrophic effect in the auroral zone and the application of the normal laws is impossible. During such a disturbance, corpuscular emission, originating on the sun penetrates the atmosphere of the earth, usually in a belt between 55° to 80° of geomagnetic latitude. It generally hits the night side of the earth. Chapman and Ferraro (1930) have shown that the corpuscular emission must consist of an equal number of charges of both signs and therefore appear in general as conducting but uncharged. A magnetic disturbance in the auroral zone begins usually in the evening, with oscillations of the magnetic field. Simultaneously, aurorae borealis occur which are usually band-shaped. Strong reflections from the E-level appear in a wide frequency range often attaining 10 MHz. F-reflections do not occur since the auroral E-layer blankets the higher layers.In the course of the disturbances, the penetrating corpuscular emission often becomes harder, ionization shifts downward and the damping increases. For periods of a few minutes no reflections at all can be observed (polar blackout). Such conditions may predominate for many hours, especially during very serious disturbances. The reflections from the E-level also cease in the case of less serious disturbances shortly after midnight due to the decrease in corpuscular emission. The auroral lights diminish simultaneously and then cease entirely. During this second phase of the disturbance which lasts at least until dawn, no echoes at all can be observed. The E-reflections stop with the cessation of corpuscular emission; F-echoes also do not exist anymore as this layer was dissolved in the course of the disturbance (Rawer, 1956). In the Polar Regions the main effects of ionospheric storms are the increases in the electron concentrations in the E and D regions: they can be understood in outline in terms of the energetic electrons that also produce the aurora. At lower latitudes, however, the changes in the D region take a different form and there are conspicuous changes in the F layer.A storm usually results in significant changes in the F layer all over the world; at most latitudes the concentration of electrons is decreased, although, within a few degrees of the geomagnetic equator, it is often increased. These changes have not been properly explained. The decrease is the most surprising. One type of explanation ascribes it to an increase in the rate of loss of electrons. In the F region that loss involves reactions of the type O+N2®N+2+, with a rate k[N2][O+]: this rate could be increased during a storm either because k increases or because [N2] increases. Laboratory measurements suggest that k increases with temperature and since the temperature is known to increase during a storm the decrease of electron concentration would be explained.Those who ascribe the storm phenomenon to an increase in the concentration of molecular nitrogen suggest that during a storm the entry of particles into the low polar ionosphere excites gravity waves that then travel into the F region at lower latitudes where they mix the atmospheric constituents.Still another suggestion is that the modification of the ionospheric current system that shows itself as the polar electrojet is accompanied by an electric field that extends into the F region at lower latitudes and there causes the ionospheric plasma to move downwards to levels where the rate of loss is greater. To explain an increase in the F region electron content, of the kind that is often observed near the equator during storms, it has been suggested that at those times the ionosphere is moved upwards to places where the rate of loss of electrons is smaller. The movement might be caused by the electric field of the dynamo below, so that the F region acts like an atmospheric motor. It might also be caused by a wind in the neutral air, blowing from the poles towards the equator, so as to move the ionization upwards along the sloping lines of force (Ratcliff, 1972).