68,402 research outputs found
Pterodactyl: The Development and Performance of Guidance Algorithms for a Mechanically Deployed Entry Vehicle
Pterodactyl is a NASA Space Technology Mission Directorate (STMD) project focused on developing a design capability for optimal, scalable, Guidance and Control (G&C) solutions that enable precision targeting for Deployable Entry Vehicles (DEVs). This feasibility study is unique in that it focuses on the rapid integration of targeting performance analysis with structural & packaging analysis, which is especially challenging for new vehicle and mission designs. This paper will detail the guidance development and trajectory design process for a lunar return mission, selected to stress the vehicle designs and encourage future scalability. For the five G&C configurations considered, the Fully Numerical Predictor-Corrector Entry Guidance (FNPEG) was selected for configurations requiring bank angle guidance and FNPEG with Uncoupled Range Control (URC) was developed for configurations requiring angle of attack and sideslip angle guidance. Successful G&C configurations are defined as those that can deliver payloads to the intended descent and landing initiation point, while abiding by trajectory constraints for nominal and dispersed trajectories
Towards Structural Classification of Proteins based on Contact Map Overlap
A multitude of measures have been proposed to quantify the similarity between
protein 3-D structure. Among these measures, contact map overlap (CMO)
maximization deserved sustained attention during past decade because it offers
a fine estimation of the natural homology relation between proteins. Despite
this large involvement of the bioinformatics and computer science community,
the performance of known algorithms remains modest. Due to the complexity of
the problem, they got stuck on relatively small instances and are not
applicable for large scale comparison. This paper offers a clear improvement
over past methods in this respect. We present a new integer programming model
for CMO and propose an exact B &B algorithm with bounds computed by solving
Lagrangian relaxation. The efficiency of the approach is demonstrated on a
popular small benchmark (Skolnick set, 40 domains). On this set our algorithm
significantly outperforms the best existing exact algorithms, and yet provides
lower and upper bounds of better quality. Some hard CMO instances have been
solved for the first time and within reasonable time limits. From the values of
the running time and the relative gap (relative difference between upper and
lower bounds), we obtained the right classification for this test. These
encouraging result led us to design a harder benchmark to better assess the
classification capability of our approach. We constructed a large scale set of
300 protein domains (a subset of ASTRAL database) that we have called Proteus
300. Using the relative gap of any of the 44850 couples as a similarity
measure, we obtained a classification in very good agreement with SCOP. Our
algorithm provides thus a powerful classification tool for large structure
databases
A Multi Hidden Recurrent Neural Network with a Modified Grey Wolf Optimizer
Identifying university students' weaknesses results in better learning and
can function as an early warning system to enable students to improve. However,
the satisfaction level of existing systems is not promising. New and dynamic
hybrid systems are needed to imitate this mechanism. A hybrid system (a
modified Recurrent Neural Network with an adapted Grey Wolf Optimizer) is used
to forecast students' outcomes. This proposed system would improve instruction
by the faculty and enhance the students' learning experiences. The results show
that a modified recurrent neural network with an adapted Grey Wolf Optimizer
has the best accuracy when compared with other models.Comment: 34 pages, published in PLoS ON
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