•A novel 2D chaotic system based on the Schaffer function is conceived.•The Shaffer function is a tough optimization testing function.•The chaotic performance of the Schaffer map is evaluated through ...chaos indicators.•The 2D Schaffer map is validated by comparison with the existing chaotic systems.•The 2D Schaffer map is corroborated by implementing it to image encryption.
Chaotic systems are the most essential tools for wide range of applications such as communication, watermarking, data compression and multimedia encryption. However, the existing chaotic systems suffer from low complexity and randomness. In this study, a novel 2D hyperchaotic system denoted as Schaffer map is conceived for high complexity required applications. It is inspired by the Schaffer function mostly used as optimization benchmark function to exploit its strict oscillation properties. The chaotic performance of 2D Schaffer map is evaluated over rigorous chaos indicators such as bifurcation and phase space trajectory diagrams, Lyapunov exponent (LE), sample entropy (SE), permutation entropy (PE), 0-1 test, correlation dimension (CD) and Kolmogorov entropy (KE). The proposed chaotic system is verified through comparison with its recent counterparts. The 2D Schaffer map manifests the best ergodicity and erraticity characteristics. In addition, the applicability of the 2D Schaffer map is tested by implementing it to image encryption. The results show that the proposed 2D Schaffer map has excellent hyperchaotic performance thanks to its diversity property.
This paper proposes a geometric-based method of the ground-point visibility from a satellite or satellite constellation in elliptical orbit considering the J 2 perturbation. First, the field-element ...equations describing the relationship between the elliptical satellite orbit, field parameters, and ground point are introduced and can be solved semi-analytically. Also, using a two-dimensional map composed of the mean argument of latitude and geographic longitude of the ascending node, the problem of calculating visible intervals is transformed into a simple intersection problem of a group of parallel lines and a time-invariant region generated by the field-element equations. Furthermore, based on the geometric relationship between any two satellites, the relative field mapping and constellation field mapping are described, which can simplify the multi-satellite coverage problem to a single-satellite coverage problem and can be used to obtain the coverage performance of the constellation analytically and rapidly for the target. The simulation results demonstrate that the proposed method is rapid, efficient, intuitive, and accurate, suggesting its wide applications in constellation studies .
To efficiently and accurately design satellite constellations equipped with Reentry Glide Vehicles (RGVs), new analytical solutions are developed for calculating their coverage performance. ...Specifically, a new coverage model is established by approximating the Reentry Reachable Domain (RRD). However, the computation of real-time relative distances between satellites and targets, which is essential for coverage analysis based on this model, imposes a significant computational burden. To address this challenge, a coverage analysis method based on two-dimensional map theory is proposed. This method represents the coverage conditions of a target as a fixed area on a two-dimensional map and transforms the satellite trajectory into a series of parallel lines. By determining the intersection points between these lines and the area boundaries, the coverage analytical solutions for a target point are derived. On this basis, coverage theorems are presented for rapid calculation of the constellation coverage performance for an area. Simulation results demonstrate the effectiveness and high precision of the proposed analytical solutions.
In a lecture that J.K.Moser gave in 1968, he pointed out the possibility that the periodic orbit with period q=3 (period-3 orbit) appears through anomalous rotation bifurcation (ARB). There are two ...different types of rotation bifurcation, the ordinary rotation bifurcation (ORB) and ARB. In order to study ORB and ARB, the map Tm (yn+1=yn+a(xn−xnm), xn+1=xn+yn+1 (a≥0, m≥2)) is introduced. It is proved that the period-3 orbit in Tm (m≥2) and the period-4 orbit in Tm (m≥3) appear through ARB and the period-4 orbit in T2 appears through ORB.
This article proposes a modified 2-D coverage method for satellite coverage analysis considering various perturbations. First, the basic mathematical model, including the standard 2-D field-mapping ...method and frequently used perturbation model, is introduced. Then, based on the osculating orbital elements, a modified 2-D field-mapping method is presented for calculating visible intervals between a satellite and a target accurately and efficiently. Furthermore, based on the analytical partial differential of the field-element equations with respect to the orbital elements, the maximum error of the proposed method is calculated to estimate its accuracy. The simulation results demonstrate that the proposed method is accurate and effective, indicating its wide application prospect in coverage analysis involving various perturbations.
Coverage analysis is an essential process when designing a satellite constellation, and the variations of global revisit characteristics are usually elusive in discontinuous coverage problems. In ...dealing with this, a general method for analyzing the global revisit characteristics of constellations with repeating ground track orbits is proposed in this paper. Firstly, a two-dimensional map based analytical model for the point coverage of constellations is introduced. Then, the variations of revisit characteristics along both the parallel and meridian are analyzed based on the presented analytical model. Finally, numerical examples are carried out. On the one hand, the proposed analytical model for point coverage is demonstrated to be of high precision. On the other hand, all possible positions where the discontinuous changes of revisit characteristics occur can be analytically obtained, which can reveal the discontinuous variations of revisit characteristics along both the parallel and meridian, and can also ensure that all possible global or regional revisit characteristics are counted for a given constellation. The proposed method can contribute to constellation design and coverage performance analysis.
•An analytical model for the coverage calculation of satellite constellations is developed.•Conditions for the appearance of the discontinuous changes of global revisit characteristics are deduced analytically.•Variations of the revisit characteristics of satellite constellations along both the parallel and meridian are revealed.
Based on the different combinations of mercapto, amino and carboxyl groups of biothiols (mercapto for Hcy, mercapto and amino for Cys, and mercapto and carboxyl for GSH) that participate in the ...interaction with BTHA, BTHA should has the potential ability of simultaneous detecting GSH/Cys/Hcy.
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•A simple acrylate-substituted fluorescent sensor BTHA was synthesized for simultaneous discrimination of GSH, Cys and Hcy.•BTHA showed ratiometric fluorescence response to GSH through carboxyl assisted interactions.•BTHA can detect exogenous and endogenous GSH with ratiometric fluorescence response in live cells.
Simultaneous detection of biothiols would be helpful for understanding their biological functions and pathological study of related diseases. The structural similarities of biothiols present a great challenge to achieve their selective detection. Herein, we report a simple acrylate-substituted fluorescent sensor BTHA with one recognition site and an assisted neighboring hydroxy group for this purpose. BTHA exhibited an emission band at 507 nm with a 147 nm Stokes shift. Upon addition of glutathione (GSH) or cysteine (Cys), deacrylate product was obtained and new fluorescent band at 459 nm occurred. The addition reaction product with decreased fluorescence was achieved as BTHA was treated with homocysteine (Hcy). BTHA acts with the mercapto group of Cys, the mercapto and amino group of Hcy, and the mercapto and carboxyl group of GSH, respectively. Correspondingly, different ratiometric fluorescence changes (I459/I507) with these biothiols was produced. Using the two-dimensional map with two channel signals, BTHA can simultaneous distinguish GSH, Cys and Hcy. The sensor BTHA can also be used for exogenous and endogenous GSH imaging with ratiometric fluorescence response in live cells.
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