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Estimation and Assessment of Ionospheric Slant Total Electron Content (STEC) Using Dual-frequency NavIC Satellite System 利用双频导航卫星系统估算电离层倾斜总电子含量(STEC)
Pub Date : 2021-06-29 DOI: 10.13052/JGEU0975-1416.923
Sharat Chandra Bhardwaj, A. Vidyarthi, B. Jassal, A. Shukla
Many atmospheric errors affect the positional accuracy of a satellite-based navigation device, such as troposphere, ionosphere, multipath, and so on, but the ionosphere is the most significant contributor to positional error. Since the ionosphere’s dynamics are highly complex, especially in low latitude and equatorial regions, a dual-frequency approach for calculating slant total electron content (STEC) for ionospheric delay estimation performs better in these conditions. However, the STEC is ambiguous and it cannot be used directly for ionospheric delay prediction, accurate positioning purposes, or ionospheric study. As a result, STEC estimation and pre-processing are required steps prior to any positioning application. There is very little literature available for STEC pre-processing in the NavIC system, necessitating an in-depth discussion. This paper focuses on how to extract navigational data from a raw binary file obtained from the Indian NavIC satellites, estimate and pre-process STEC, and build a database for STEC. It has been found that an hourly averaged STEC data is suitable for ionospheric studies and monthly mean value can be used for ionospheric behavioral research. Furthermore, the STEC is affected by diurnal solar activity, thus, the seven-month data analysis that includes summer and winter months has been used to study ionosphere action during the summer and winter months. It has been observed that STEC values are higher during the summer months than the winter months; some seasonal characteristics are also been found.
许多大气误差影响卫星导航装置的定位精度,如对流层、电离层、多径等,但电离层是影响定位误差最大的因素。由于电离层动力学高度复杂,特别是在低纬度和赤道地区,双频方法计算倾斜总电子含量(STEC)用于电离层延迟估计在这些条件下表现更好。然而,STEC是模糊的,它不能直接用于电离层延迟预测、精确定位目的或电离层研究。因此,在任何定位应用之前,STEC估计和预处理都是必需的步骤。关于在NavIC系统中进行STEC预处理的文献很少,因此需要进行深入讨论。本文主要研究如何从印度NavIC卫星获取的原始二进制文件中提取导航数据,对STEC进行估计和预处理,并建立STEC数据库。电离层温度的小时平均值适合于电离层研究,月平均值适合于电离层行为研究。此外,STEC受太阳日活动的影响,因此,包括夏季和冬季在内的7个月数据分析已用于研究夏季和冬季的电离层作用。据观察,产气毒素含量在夏季高于冬季;还发现了一些季节性特征。
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引用次数: 1
Machine Learning Based Prediction and Impact Analysis of Various Lockdown Stages of COVID-19 Outbreak – A Case Study of India 基于机器学习的COVID-19疫情各封锁阶段预测及影响分析——以印度为例
Pub Date : 2021-06-29 DOI: 10.13052/JGEU0975-1416.922
Jaspreet Kaur, P. Chattopadhyay, L. Singh, Kausik Chattopadhyay, N. Mishra
Various measures have been taken into account for the virus outbreak. But how much it successes to control outbreak to fights against COVID-19. Machine learning is used as a tool to study these complex impacts on various stages of the epidemic. While India is forced to open up the economy after an extended lockdown, the effect of lockdown, which is critical to decide the future course of action, is yet to be understood. The study suggests Support Vector Machine (SVM) and Polynomial Regression (PR) are better suited compared to Long Short-Term Memory (LSTM) in scenarios consisting of sparse and discrete events. The time-series memory of LSTM is outperformed by the contextual hyperplanes of SVM which classifies the data even more precisely. The study suggests while phase 1 of lockdown was effective, the rest of them were not. Had India continued with lockdown 1, it would have flattened the COVID-19 infection curve by mid of May 2020. With the current rate, India will hit the 8 million mark by 23 October 2020. The SVM model is further integrated with an SIR (Susceptible, Infected and Recovered) model of epidemiology, which suggests that 70% of India’s population is infected by this pandemic during this 8 month and the peak reached in October 2020 if vaccine not found. With increasing recovery rate increases the possibility of decreasing COVID-19 cases. According to the SVM model’s prediction, 90% of cases of COVID-19 will be end in February.
针对病毒爆发采取了各种措施。但它在控制疫情方面取得了多大的成功?机器学习被用作研究疫情不同阶段这些复杂影响的工具。虽然印度在长时间的封锁后被迫开放经济,但对决定未来行动方针至关重要的封锁效果尚不清楚。研究表明,在稀疏和离散事件组成的场景中,支持向量机(SVM)和多项式回归(PR)比长短期记忆(LSTM)更适合。支持向量机的上下文超平面比LSTM的时间序列记忆性能更好,对数据的分类更加精确。研究表明,虽然第一阶段的封锁是有效的,但其他阶段的封锁却没有效果。如果印度继续实行封锁,到2020年5月中旬,COVID-19感染曲线将趋于平缓。按照目前的速度,到2020年10月23日,印度将达到800万大关。SVM模型进一步与流行病学SIR(易感、感染和恢复)模型相结合,该模型表明,在这8个月内,70%的印度人口感染了这次大流行,如果没有找到疫苗,高峰期将在2020年10月达到。随着康复率的提高,减少新冠肺炎病例的可能性也在增加。根据SVM模型的预测,90%的新冠肺炎病例将在2月份结束。
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引用次数: 0
Analysis of a Pre-Stressed Quadcopter Propeller Using Finite element Approach 预应力四轴飞行器螺旋桨有限元分析
Pub Date : 2021-06-03 DOI: 10.13052/JGEU0975-1416.921
F. Ahmad, Pushpendra Kumar, P. Patil
Quadcopter, a mechatronic device is now widely used due to its simple structure and vertical take-off and landing capability. It consists of four propellers which can lift and propelled the Quadcopter in 3-D space. The difference in angular speeds of propellers works as a steering system and responsible for attitude and altitude motion. Quadcopter self weight and pay load is carried by the propellers itself, and a bad design of the propeller may lead to crack. Quadcopter propellers are also subjected to thrust force and vibration during the flight. The main objective of this study is to find out the natural failure frequency of propeller. Two types of propellers have been designed in Creo 2.0 and analyzed in Ansys 16.2 for their vibration frequencies. Both the designs are analyzed with or without the thrust force under the vibration frequency. First six vibration modes have been calculated for both the propeller designs with Carbon Fiber Reinforced Polymer (CFRP) material. The obtained simulation results have been compared and analyzed to sustain the failure frequency.
四轴飞行器作为一种机电一体化设备,由于其结构简单,具有垂直起降能力,目前得到了广泛的应用。它由四个螺旋桨组成,可以在三维空间中提升和推进四轴飞行器。螺旋桨角速度的差异作为一个转向系统,负责姿态和高度运动。四轴飞行器的自重和有效载荷是由螺旋桨自身承担的,螺旋桨设计不良可能会导致裂纹。四轴飞行器的螺旋桨在飞行过程中也会受到推力和振动的影响。本研究的主要目的是找出螺旋桨的自然失效频率。在Creo 2.0中设计了两种螺旋桨,并在Ansys 16.2中对其振动频率进行了分析。在振动频率下,对两种设计进行了有推力和无推力的分析。对采用碳纤维增强聚合物(CFRP)材料的两种螺旋桨设计进行了前六种振动模式的计算。对得到的仿真结果进行了比较和分析,以维持故障频率。
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引用次数: 1
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Journal of Graphic Era University
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