The higher the pointing accuracy of the radio telescope, the more obvious the influence of wind disturbance on antenna performance. Taking the site of the 110 m aperture QiTai radio Telescope (QTT) as an example, the terrain and air flow characteristics of the site are studied. It is found that the wind direction with high incoming wind frequency and relatively high speed is mostly located in the mountain gap on the periphery of the antenna. If the wind resistance facilities are precisely arranged in the upstream tuyere, the wind speed in the antenna area can be effectively reduced. This study proposes a method to control the wind flow at a telescope site based on the precise arrangement of the windbreak fence. The windbreak fence simulation model is constructed using the theory of porous jump. The mean error of the simulation results is less than 14% compared to the wind tunnel measured data, indicating that the constructed windbreak fence model has high reliability. The computational domain model of the working conditions for the site is constructed. The extreme condition of the windbreak fence arrangement is considered, and the simulation results show that the wind speed in the antenna area can be reduced by more than 30% through the control of the windbreak fence. It verifies the feasibility of the method of controlling the wind flow by the windbreak fence for the site which provides a reference for the subsequent research on the precise arrangement of the windbreak fence.
{"title":"Research on Wind Flow Control by Windbreak Fence for a Large Radio Telescope Site Based on Numerical Simulations","authors":"Feilong He, Qian Xu, Na Wang","doi":"10.1155/2023/5257749","DOIUrl":"https://doi.org/10.1155/2023/5257749","url":null,"abstract":"The higher the pointing accuracy of the radio telescope, the more obvious the influence of wind disturbance on antenna performance. Taking the site of the 110 m aperture QiTai radio Telescope (QTT) as an example, the terrain and air flow characteristics of the site are studied. It is found that the wind direction with high incoming wind frequency and relatively high speed is mostly located in the mountain gap on the periphery of the antenna. If the wind resistance facilities are precisely arranged in the upstream tuyere, the wind speed in the antenna area can be effectively reduced. This study proposes a method to control the wind flow at a telescope site based on the precise arrangement of the windbreak fence. The windbreak fence simulation model is constructed using the theory of porous jump. The mean error of the simulation results is less than 14% compared to the wind tunnel measured data, indicating that the constructed windbreak fence model has high reliability. The computational domain model of the working conditions for the site is constructed. The extreme condition of the windbreak fence arrangement is considered, and the simulation results show that the wind speed in the antenna area can be reduced by more than 30% through the control of the windbreak fence. It verifies the feasibility of the method of controlling the wind flow by the windbreak fence for the site which provides a reference for the subsequent research on the precise arrangement of the windbreak fence.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46426983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The restricted concave kite five-body problem is a problem in which four positive masses, called the primaries, rotate in the concave kite configuration with a mass at the center of the triangle formed by three of the primaries. The fifth body has negligible mass and does not influence the motion of the four primaries. It is assumed that the fifth mass is in the same plane of the primaries and that the masses of the primaries are m 1 , m 2 , m 3 , and m 4 , respectively. Three different types of concave kite configurations are considered based on the masses of the primaries. In case I, one pair of primaries has equal masses; in case II, two pairs of primaries have equal masses; in case III, three of the primaries have equal masses. For all three cases, the regions of central configuration are obtained using both analytical and numerical techniques. The existence and uniqueness of equilibrium positions of the infinitesimal mass are investigated in the gravitational field of the four primaries. It is numerically confirmed that none of the equilibrium points are linearly stable. The Jacobian constant C is used to investigate the regions of possible motion of the infinitesimal mass.
{"title":"Restricted Concave Kite Five-Body Problem","authors":"A. Kashif, M. Shoaib","doi":"10.1155/2023/9434141","DOIUrl":"https://doi.org/10.1155/2023/9434141","url":null,"abstract":"The restricted concave kite five-body problem is a problem in which four positive masses, called the primaries, rotate in the concave kite configuration with a mass at the center of the triangle formed by three of the primaries. The fifth body has negligible mass and does not influence the motion of the four primaries. It is assumed that the fifth mass is in the same plane of the primaries and that the masses of the primaries are \u0000 \u0000 \u0000 \u0000 m\u0000 \u0000 \u0000 1\u0000 \u0000 \u0000 \u0000 , \u0000 \u0000 \u0000 \u0000 m\u0000 \u0000 \u0000 2\u0000 \u0000 \u0000 \u0000 , \u0000 \u0000 \u0000 \u0000 m\u0000 \u0000 \u0000 3\u0000 \u0000 \u0000 \u0000 , and \u0000 \u0000 \u0000 \u0000 m\u0000 \u0000 \u0000 4\u0000 \u0000 \u0000 \u0000 , respectively. Three different types of concave kite configurations are considered based on the masses of the primaries. In case I, one pair of primaries has equal masses; in case II, two pairs of primaries have equal masses; in case III, three of the primaries have equal masses. For all three cases, the regions of central configuration are obtained using both analytical and numerical techniques. The existence and uniqueness of equilibrium positions of the infinitesimal mass are investigated in the gravitational field of the four primaries. It is numerically confirmed that none of the equilibrium points are linearly stable. The Jacobian constant \u0000 \u0000 C\u0000 \u0000 is used to investigate the regions of possible motion of the infinitesimal mass.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42563627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There are many factors that cause pointing errors in radio telescopes. As one of the motion positioning mechanisms of the radio telescope, the error caused by the elevation mechanism cannot be ignored. The source of error in the elevation mechanism comes mainly from the key transmission components and the support structure. Accurate measurement of the errors caused by them is the key to analyzing their law of change. Aiming at the main error factors in the antenna elevation mechanism, this study builds a scaled-down experimental platform for the elevation mechanism and proposes an error measurement method based on multiencoder information sources. The method compares the error law of change of the antenna elevation mechanism under different driving modes, different centerline deviations of the bearings, and different backlashes and designs error measurement experiments for the abovementioned operating conditions. The results show that the error measurement method based on multiencoder information sources can accurately measure the error of the antenna elevation mechanism under different driving modes. The method can also accurately reflect the law of change in transmission error when the backlash of the elevation mechanism and the centerline deviation of the bearings increase. The final experimental measurement shows that the driving mode of the dual-motor can eliminate about 70% of the mechanism error caused by the backlash. The average value of the error increases by a factor of 1.9 when the backlash increases from 0.1 mm to 1.26 mm. The average value of the error increases by a factor of 5 when the centerline deviation of the bearings increases from 0 to 1.5 mm. This has a good reference value to correct for the pointing error of a radio telescope.
{"title":"Measuring Antenna Elevation Mechanism Pointing Errors with Multiencoder Information Sources","authors":"Duoxiang Xu, Qian Xu, Na Wang, Fei Xue","doi":"10.1155/2023/3527106","DOIUrl":"https://doi.org/10.1155/2023/3527106","url":null,"abstract":"There are many factors that cause pointing errors in radio telescopes. As one of the motion positioning mechanisms of the radio telescope, the error caused by the elevation mechanism cannot be ignored. The source of error in the elevation mechanism comes mainly from the key transmission components and the support structure. Accurate measurement of the errors caused by them is the key to analyzing their law of change. Aiming at the main error factors in the antenna elevation mechanism, this study builds a scaled-down experimental platform for the elevation mechanism and proposes an error measurement method based on multiencoder information sources. The method compares the error law of change of the antenna elevation mechanism under different driving modes, different centerline deviations of the bearings, and different backlashes and designs error measurement experiments for the abovementioned operating conditions. The results show that the error measurement method based on multiencoder information sources can accurately measure the error of the antenna elevation mechanism under different driving modes. The method can also accurately reflect the law of change in transmission error when the backlash of the elevation mechanism and the centerline deviation of the bearings increase. The final experimental measurement shows that the driving mode of the dual-motor can eliminate about 70% of the mechanism error caused by the backlash. The average value of the error increases by a factor of 1.9 when the backlash increases from 0.1 mm to 1.26 mm. The average value of the error increases by a factor of 5 when the centerline deviation of the bearings increases from 0 to 1.5 mm. This has a good reference value to correct for the pointing error of a radio telescope.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45210851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Considering the stringent requirement of the pointing accuracy up to 2.5″ of the world’s largest full steerable radio telescope, this paper studies the welding experiment of the azimuth track of the antenna. First, the opposite deformation jig and welding process were designed for the QTT’s azimuth track. Then, the welding process was numerically simulated using a finite element model. The simulation results show that a better welding effect will be obtained by appropriately reducing the opposite force on the basis of the original. The three deformation processes of the track are regulated by the opposite deformation jig. The results show that the opposite deformation jig designed for QTT’s azimuth track can make the amount of deformation and flatness meet the design requirements. Finally, nondestructive testing was carried out to check the welding quality of the track surface and interior. The results show that there are no obvious defects in the welds of the azimuth track. The constraint jig and welding processes designed for QTT are effective and feasible.
{"title":"Numerical Simulation and Test Study on Track Welding of QTT","authors":"Duoxiang Xu, Qian Xu, Lin Li, Hui Wang, Na Wang","doi":"10.1155/2023/5525558","DOIUrl":"https://doi.org/10.1155/2023/5525558","url":null,"abstract":"Considering the stringent requirement of the pointing accuracy up to 2.5″ of the world’s largest full steerable radio telescope, this paper studies the welding experiment of the azimuth track of the antenna. First, the opposite deformation jig and welding process were designed for the QTT’s azimuth track. Then, the welding process was numerically simulated using a finite element model. The simulation results show that a better welding effect will be obtained by appropriately reducing the opposite force on the basis of the original. The three deformation processes of the track are regulated by the opposite deformation jig. The results show that the opposite deformation jig designed for QTT’s azimuth track can make the amount of deformation and flatness meet the design requirements. Finally, nondestructive testing was carried out to check the welding quality of the track surface and interior. The results show that there are no obvious defects in the welds of the azimuth track. The constraint jig and welding processes designed for QTT are effective and feasible.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43359903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The distribution of the spin directions of spiral galaxies in the Sloan Digital Sky Survey has been a topic of debate in the past two decades, with conflicting conclusions reported even in cases where the same data were used. Here, we follow one of the previous experiments by applying the SpArcFiRe algorithm to annotate the spin directions in an original dataset of Galaxy Zoo 1. The annotation of the galaxy spin directions is carried out after the first step of selecting the spiral galaxies in three different manners: manual analysis by Galaxy Zoo classifications, by a model-driven computer analysis, and with no selection of spiral galaxies. The results show that when spiral galaxies are selected by Galaxy Zoo volunteers, the distribution of their spin directions as determined by SpArcFiRe is not random, which agrees with previous reports. When selecting the spiral galaxies using a model-driven computer analysis or without selecting the spiral galaxies at all, the distribution is also not random. Simple binomial distribution analysis shows that the probability of the parity violation to occur by chance is lower than 0.01. Fitting the spin directions as observed from the Earth to cosine dependence exhibits a dipole axis with statistical strength of 2.33 σ to 3.97 σ . These experiments show that regardless of the selection mechanism and the analysis method, all experiments show similar conclusions. These results are aligned with previous reports using other methods and telescopes, suggesting that the spin directions of spiral galaxies as observed from the Earth exhibit a dipole axis formed by their spin directions. Possible explanations can be related to the large-scale structure of the universe or to the internal structure of galaxies. The catalogs of annotated galaxies generated as part of this study are available.
{"title":"Reanalysis of the Spin Direction Distribution of Galaxy Zoo SDSS Spiral Galaxies","authors":"Darius Mcadam, L. Shamir","doi":"10.1155/2023/4114004","DOIUrl":"https://doi.org/10.1155/2023/4114004","url":null,"abstract":"The distribution of the spin directions of spiral galaxies in the Sloan Digital Sky Survey has been a topic of debate in the past two decades, with conflicting conclusions reported even in cases where the same data were used. Here, we follow one of the previous experiments by applying the SpArcFiRe algorithm to annotate the spin directions in an original dataset of Galaxy Zoo 1. The annotation of the galaxy spin directions is carried out after the first step of selecting the spiral galaxies in three different manners: manual analysis by Galaxy Zoo classifications, by a model-driven computer analysis, and with no selection of spiral galaxies. The results show that when spiral galaxies are selected by Galaxy Zoo volunteers, the distribution of their spin directions as determined by SpArcFiRe is not random, which agrees with previous reports. When selecting the spiral galaxies using a model-driven computer analysis or without selecting the spiral galaxies at all, the distribution is also not random. Simple binomial distribution analysis shows that the probability of the parity violation to occur by chance is lower than 0.01. Fitting the spin directions as observed from the Earth to cosine dependence exhibits a dipole axis with statistical strength of 2.33\u0000 \u0000 σ\u0000 \u0000 to 3.97\u0000 \u0000 σ\u0000 \u0000 . These experiments show that regardless of the selection mechanism and the analysis method, all experiments show similar conclusions. These results are aligned with previous reports using other methods and telescopes, suggesting that the spin directions of spiral galaxies as observed from the Earth exhibit a dipole axis formed by their spin directions. Possible explanations can be related to the large-scale structure of the universe or to the internal structure of galaxies. The catalogs of annotated galaxies generated as part of this study are available.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45460538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Santhi, T. Chinnappalanaidu, S. S. Madhu, Daba Meshesha Gusu
<jats:p>In this article, we analyze Bianchi type–II, VIII, and IX spatially homogeneous and anisotropic space-times in the background of the Brans–Dicke theory of gravity within the framework of viscous holographic dark energy. To solve the field equations, we have used the relation between the metric potentials as <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"> <mi>R</mi> <mo>=</mo> <msup> <mrow> <mi>S</mi> </mrow> <mrow> <mi>n</mi> </mrow> </msup> </math> </jats:inline-formula> and the relation between the scalar field <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2"> <mi>ϕ</mi> </math> </jats:inline-formula> and the scale factor <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3"> <mi>a</mi> </math> </jats:inline-formula> as <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4"> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mi>a</mi> </mrow> <mrow> <mi>m</mi> </mrow> </msup> </math> </jats:inline-formula>. Also, we have discussed some of the dynamical parameters of the obtained models, such as the deceleration parameter <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M5"> <mfenced open="(" close=")" separators="|"> <mrow> <mi>q</mi> </mrow> </mfenced> </math> </jats:inline-formula>, the jerk parameter <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M6"> <mfenced open="(" close=")" separators="|"> <mrow> <mo> </mo> <mi>j</mi> </mrow> </mfenced> </math> </jats:inline-formula>, the EoS parameter <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7"> <mfenced open="(" close=")" separators="|">
本文在粘性全息暗能量的框架下，以Brans-Dicke引力理论为背景，分析了Bianchi型ii、VIII和IX型空间均质和各向异性时空。为了解场方程，我们使用了度量势之间的关系R = S n和标量场φ之间的关系比例因子a是φ = m。此外，我们还讨论了得到的模型的一些动力学参数，如减速参数q，抖动参数j，EoS参数ω v h d e,密度参数Ω vhde, Om-diagnostic，声速的平方v s 2，EoS平面ω v h d e−ω v h d e '，以及通过图形表示的寻态平面r - s，这在宇宙学的讨论中具有重要意义。此外，所有获得的模型和图形都显示了一个膨胀和加速的宇宙，这与最新的实验数据更吻合。粘性全息暗能量模型与解释当前的宇宙加速膨胀是相容的。
{"title":"Some Bianchi Type Viscous Holographic Dark Energy Cosmological Models in the Brans–Dicke Theory","authors":"M. Santhi, T. Chinnappalanaidu, S. S. Madhu, Daba Meshesha Gusu","doi":"10.1155/2022/5364541","DOIUrl":"https://doi.org/10.1155/2022/5364541","url":null,"abstract":"<jats:p>In this article, we analyze Bianchi type–II, VIII, and IX spatially homogeneous and anisotropic space-times in the background of the Brans–Dicke theory of gravity within the framework of viscous holographic dark energy. To solve the field equations, we have used the relation between the metric potentials as <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M1\">\u0000 <mi>R</mi>\u0000 <mo>=</mo>\u0000 <msup>\u0000 <mrow>\u0000 <mi>S</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>n</mi>\u0000 </mrow>\u0000 </msup>\u0000 </math>\u0000 </jats:inline-formula> and the relation between the scalar field <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M2\">\u0000 <mi>ϕ</mi>\u0000 </math>\u0000 </jats:inline-formula> and the scale factor <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M3\">\u0000 <mi>a</mi>\u0000 </math>\u0000 </jats:inline-formula> as <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M4\">\u0000 <mi>ϕ</mi>\u0000 <mo>=</mo>\u0000 <msup>\u0000 <mrow>\u0000 <mi>a</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>m</mi>\u0000 </mrow>\u0000 </msup>\u0000 </math>\u0000 </jats:inline-formula>. Also, we have discussed some of the dynamical parameters of the obtained models, such as the deceleration parameter <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M5\">\u0000 <mfenced open=\"(\" close=\")\" separators=\"|\">\u0000 <mrow>\u0000 <mi>q</mi>\u0000 </mrow>\u0000 </mfenced>\u0000 </math>\u0000 </jats:inline-formula>, the jerk parameter <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M6\">\u0000 <mfenced open=\"(\" close=\")\" separators=\"|\">\u0000 <mrow>\u0000 <mo> </mo>\u0000 <mi>j</mi>\u0000 </mrow>\u0000 </mfenced>\u0000 </math>\u0000 </jats:inline-formula>, the EoS parameter <jats:inline-formula>\u0000 <math xmlns=\"http://www.w3.org/1998/Math/MathML\" id=\"M7\">\u0000 <mfenced open=\"(\" close=\")\" separators=\"|\">\u0000 ","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45546215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of the 15th January 2010 annular solar eclipse on traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) is studied using data from six global navigation and satellite system (GNSS) receivers spread across the path of annularity over the low latitude region of East Africa. The GNSS receivers are stationed at Nairobi (RCMN), Malindi (MAL2), and Eldoret (MOIU) in Kenya; Mbarara (MBAR) in Uganda; Kigali (NURK) in Rwanda; and Mtwara (MTWA) in Tanzania. The study period ranges from 12th to 18th January 2010, three days before and after the 15th January 2010 annular solar eclipse. The year 2010 marked the beginning phase of solar cycle 24, evidently observed in low total electron content (TEC) values and the disturbed storm time index (Dst). The eclipse started at 7 : 06 LT and ended at 10 : 14 LT, with MOIU and RCMN experiencing eclipse magnitudes of 0.946 and 0.93, respectively. The maximum obscuration occurred between 8 : 21 LT and 8 : 34 LT across most of the stations. A detrending on vertical TEC (VTEC) derived from GNSS receivers across or close to the path of totality revealed a reduction of ∼2-3 TECU during the maximum phase of the eclipse. The level of reduction was highly close to the totality path and decreased smoothly away from the totality path. Using a background polynomial fitting technique on diurnal TEC, we analyzed TIDs along NURK-MBAR-MOIU and MOIU-RCMN-MAL2 GPS arrays. The results revealed a wavelike perturbation with a virtual horizontal velocity of 830m/s and ∼1 TECU amplitude propagating eastward along the MOIU-RCMN-MAL2 GPS array. The study reports a moderate scintillation activity of 0.5 ≤ ROTI ≤ 0.9 values, demonstrating the presence of few EPBs over the region. The results show a latitudinal variation in GPS-TEC scintillation activities and suggest a possible influence of the eclipse on the observed increase in average scintillation levels across East Africa.
{"title":"Effects of 15th January 2010 Annular Solar Eclipse on Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles over Low Latitude Regions of East Africa","authors":"Davis Odhiambo Athwart, B. Ndinya, P. Baki","doi":"10.1155/2022/5263997","DOIUrl":"https://doi.org/10.1155/2022/5263997","url":null,"abstract":"The influence of the 15th January 2010 annular solar eclipse on traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) is studied using data from six global navigation and satellite system (GNSS) receivers spread across the path of annularity over the low latitude region of East Africa. The GNSS receivers are stationed at Nairobi (RCMN), Malindi (MAL2), and Eldoret (MOIU) in Kenya; Mbarara (MBAR) in Uganda; Kigali (NURK) in Rwanda; and Mtwara (MTWA) in Tanzania. The study period ranges from 12th to 18th January 2010, three days before and after the 15th January 2010 annular solar eclipse. The year 2010 marked the beginning phase of solar cycle 24, evidently observed in low total electron content (TEC) values and the disturbed storm time index (Dst). The eclipse started at 7 : 06 LT and ended at 10 : 14 LT, with MOIU and RCMN experiencing eclipse magnitudes of 0.946 and 0.93, respectively. The maximum obscuration occurred between 8 : 21 LT and 8 : 34 LT across most of the stations. A detrending on vertical TEC (VTEC) derived from GNSS receivers across or close to the path of totality revealed a reduction of ∼2-3 TECU during the maximum phase of the eclipse. The level of reduction was highly close to the totality path and decreased smoothly away from the totality path. Using a background polynomial fitting technique on diurnal TEC, we analyzed TIDs along NURK-MBAR-MOIU and MOIU-RCMN-MAL2 GPS arrays. The results revealed a wavelike perturbation with a virtual horizontal velocity of 830m/s and ∼1 TECU amplitude propagating eastward along the MOIU-RCMN-MAL2 GPS array. The study reports a moderate scintillation activity of 0.5 ≤ ROTI ≤ 0.9 values, demonstrating the presence of few EPBs over the region. The results show a latitudinal variation in GPS-TEC scintillation activities and suggest a possible influence of the eclipse on the observed increase in average scintillation levels across East Africa.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47346289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work studies the possibility of generating artificial collinear liberation points for the planar circular restricted three-body problem using Lorentz force affecting a charged spacecraft due to the magnetic field of a planet. It is considered to be a magnetic dipole inclined by angle α with the spin axis of the planet. The acceleration components for Lorentz force are first derived in an inertial planet-center coordinate system. Then, they are transformed into the rotating coordinate system of the three-body system, with the planet naturally the smaller primary in a planet-Sun system. The equations for the liberation points are derived including the charge per unit mass as the controlling parameter. Finally, the values of the charge per unit mass required for controlling the collinear liberation point positions are derived. A numerical application for the Sun-Jupiter system is introduced and the relation between the position of the artificial liberation point and the charge per unit mass is presented graphically.
{"title":"Artificial Controlling of the Collinear Liberation Points Using Lorentz Force in the Restricted Three-Body Problem","authors":"M. El-Saftawy, M. A. Yousef, A. Mostafa","doi":"10.1155/2022/1445354","DOIUrl":"https://doi.org/10.1155/2022/1445354","url":null,"abstract":"This work studies the possibility of generating artificial collinear liberation points for the planar circular restricted three-body problem using Lorentz force affecting a charged spacecraft due to the magnetic field of a planet. It is considered to be a magnetic dipole inclined by angle α with the spin axis of the planet. The acceleration components for Lorentz force are first derived in an inertial planet-center coordinate system. Then, they are transformed into the rotating coordinate system of the three-body system, with the planet naturally the smaller primary in a planet-Sun system. The equations for the liberation points are derived including the charge per unit mass as the controlling parameter. Finally, the values of the charge per unit mass required for controlling the collinear liberation point positions are derived. A numerical application for the Sun-Jupiter system is introduced and the relation between the position of the artificial liberation point and the charge per unit mass is presented graphically.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48757401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shangmin Lin, Wei Wang, Hu Wang, Yang Song, Yue Pan, Jiang Qiao, Yaoke Xue, Qinfang Chen, Meiying Liu, Yang Shen, Jie Liu, Yang Liu, Yongjie Xie, Canglong Zhou
Subreflector misalignment of a large steerable radio telescope induces a pointing error and reduces the gain of the antenna system. To improve the antenna’s operational efficiency, it is necessary to measure and adjust the position and attitude of the subreflector in real time. In this paper, a method based on a position sensitive detector (PSD) and laser array without an optical system is proposed to measure the six degree-of-freedom (DOF) poses of the subreflector. The laser emitted by the laser module array ensures that the PSD can be covered as it moves with the subreflector, and the PSD can obtain more than three laser beams. These ensure the measurement of all attitude changes of a large-aperture antenna subreflector. The two-dimensional coordinates of the centroids of three laser spots are extracted using the PSD, and then the bursa model is established to complete the coordinate transformation. Finally, the 6-DOF attitude information of the antenna subreflector is obtained. The results of a 6.05 m measurement simulation show that it can obtain high 6-DOF PSD attitude information. The experimental results show that the 6-DOF position and attitude information of the subreflector at a distance of 5.78 m can be obtained within seconds. Moreover, the error of the translation is within 0.014 mm and the error of the rotation is within 0.37°. This method can meet the pose measurement requirements of the subreflector.
{"title":"A High-Precision Dynamic Six Degree-of-Freedom Pose Measurement of the Subreflectors of Large Antennas Based on a Position Sensitive Detector and Laser Array","authors":"Shangmin Lin, Wei Wang, Hu Wang, Yang Song, Yue Pan, Jiang Qiao, Yaoke Xue, Qinfang Chen, Meiying Liu, Yang Shen, Jie Liu, Yang Liu, Yongjie Xie, Canglong Zhou","doi":"10.1155/2022/3255088","DOIUrl":"https://doi.org/10.1155/2022/3255088","url":null,"abstract":"Subreflector misalignment of a large steerable radio telescope induces a pointing error and reduces the gain of the antenna system. To improve the antenna’s operational efficiency, it is necessary to measure and adjust the position and attitude of the subreflector in real time. In this paper, a method based on a position sensitive detector (PSD) and laser array without an optical system is proposed to measure the six degree-of-freedom (DOF) poses of the subreflector. The laser emitted by the laser module array ensures that the PSD can be covered as it moves with the subreflector, and the PSD can obtain more than three laser beams. These ensure the measurement of all attitude changes of a large-aperture antenna subreflector. The two-dimensional coordinates of the centroids of three laser spots are extracted using the PSD, and then the bursa model is established to complete the coordinate transformation. Finally, the 6-DOF attitude information of the antenna subreflector is obtained. The results of a 6.05 m measurement simulation show that it can obtain high 6-DOF PSD attitude information. The experimental results show that the 6-DOF position and attitude information of the subreflector at a distance of 5.78 m can be obtained within seconds. Moreover, the error of the translation is within 0.014 mm and the error of the rotation is within 0.37<sup>°</sup>. This method can meet the pose measurement requirements of the subreflector.","PeriodicalId":48962,"journal":{"name":"Advances in Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138537761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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