1,721,059 research outputs found
Numerical Integration of Quaternion Kinematics Using Collocation Method
No full textIn many aerospace applications, long-term attitude propagation is frequently involved. Because the integration error accumulates, the accuracy of the integration scheme is more important for the long-term attitude propagation problems. In this study, instead of explicit integration methods that have been extensively employed, the collocation method for the attitude propagation problem is studied to improve numerical integration accuracy. The closed-form solution for the collocation conditions imposed at the collocation points is derived to avoid iterative process in the collocation method. In the derivation, the operational matrix of differentiation and the Legendre-Gauss-Lobatto quadrature rule are used. Through numerical examples, the accuracy of the proposed collocation method is compared with those of the explicit methods.
Gimbal-Angle Vectors of the Nonredundant CMG Cluster
No full textThis paper deals with the method using the preferred gimbal angles of a control moment gyro (CMG) cluster for controlling spacecraft attitude. To apply the method to the nonredundant CMG cluster, analytical gimbal-angle solutions for the zero angular momentum state are derived, and the gimbal-angle vectors for the nonzero angular momentum states are studied by a numerical method. It will be shown that the number of the gimbal-angle vectors is determined from the given skew angle and the angular momentum state of the CMG cluster. Through numerical examples, it is shown that the method using the preferred gimbal-angle is an efficient approach to avoid internal singularities for the nonredundant CMG cluster.
Simple methods to determine the dissociation constant, Kd
No full textThe determination of the dissociation constant (K-d) is pivotal in biochemistry and pharmacology for understanding binding affinities in chemical reactions, which is crucial for drug development and comprehending biological systems. Here, we introduce a single-molecule fluorescence resonance energy transfer-based method for determining K-d, alongside the conventional electrophoretic mobility shift assay method of K-d, offering insights into thermodynamic interactions between proteins and substrates. The single-molecule fluorescence resonance energy transfer approach is highlighted for its ability to accurately measure binding and dissociation kinetics through fluorescence labeling and the intrinsic nature of protein-DNA interactions, representing a significant advancement in the fields of molecular biology and pharmacology. (c) 2024 The Author(s). Published by Elsevier Inc. on behalf of Korean Society for Molecular and Cellular Biology.
Spin-to-spin slew maneuvers under spherically constrained angular acceleration
No full textThis paper addresses a three-axis time-optimal attitude-control problem of rigid spacecraft. In this problem, an angular-acceleration vector lies within a spherically constrained space, and spin-to-spin boundary conditions are considered. The problem is converted into a two-point boundary-value problem by an indirect method, which is solved numerically because non-eigen-axis slew motions do not have a general analytical solution. To solve the problem, a homotopy algorithm is applied in which a discrete continuation method, closed form solutions for single-axis slew maneuvers, and a costate transformation method are included. Through numerical examples, the properties of the optimal solutions are analyzed, and the efficiency of the numerical algorithm is demonstrated.
Influence of Steering Angle Profiles on the Orbit Transfer Trajectory
No full textThis paper considers a planar orbit transfer trajectory design problem using finite thrust modeling. In this problem, the steering angles associated with the thrust direction are calculated from the predetermined profile format, and the unknown parameters in the profile are directly optimized. Three profile formats that were implemented in previous lunar exploration missions are considered. In addition, a steering angle profile defined in the rotating frame and the optimal steering angle profile are newly studied to compare the performances. To this end, the direct parameter optimization problem and the indirect optimization problem are formulated, and the characteristics of the steering angle profile and its influence on the transfer trajectory are analyzed.
Hybrid Control of Spacecraft Using Various Momentum Exchange Devices
No full textNational Research Laboratory
Program of the Ministry of science and Technology Kore
Analysis of atomic behavior of carbon during nickel silicide formation by atom probe tomography
No full text1
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