Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 6 Articles
Determining the effects of the formation of contrails within natural cirrus clouds has proven\nto be challenging. Quantifying any such effects is necessary if we are to properly account for\nthe influence of aviation on climate. Here we quantify the effect of aircraft on the optical\nthickness of already-existing cirrus clouds by matching actual aircraft flight tracks to satellite\nlidar measurements. We show that there is a systematic, statistically significant increase in\nnormalized cirrus cloud optical thickness inside mid-latitude flight tracks compared with\nadjacent areas immediately outside the tracks....
This paper addresses the development of the simulation of the low-level control system for the underwater remotely operated\nvehicle Visor3. The 6-DOF mathematical model of Visor3 is presented using two coordinated systems: Earth-fixed and body-fixed\nframes. The navigation, guidance, and control (NGC) structure is divided into three layers: the high level or the mission planner;\nthe mid-level or the path planner; and the low level formed by the navigation and control systems. The nonlinear model-based\nobserver is developed using the extended Kalman filter (EKF) which uses the linearization of the model to estimate the current\nstate. Thebehavior of the observer is verified through simulations using Simulink. An experiment was conducted with a trajectory\nthat describes changes in the ...
Introduction: Individuals with mobility impairments associated with lower limb disabilities often face\nenormous challenges to participate in routine activities and to move around various environments. For many,\nthe use of wheelchairs is paramount to provide mobility and social inclusion. Nevertheless, they still face a\nnumber of challenges to properly function in our society. Among the many difficulties, one in particular stands\nout: navigating in complex internal environments (indoors). The main objective of this work is to propose an\narchitecture based on Mobile Augmented Reality to support the development of indoor navigation systems\ndedicated to wheelchair users, that is also capable of recording CAD drawings of the buildings and dealing with\naccessibility issues for that population. Methods: Overall, five main functional requirements are proposed: the\nability to allow for indoor navigation by means of Mobile Augmented Reality techniques; the capacity to register\nand configure building CAD drawings and the position of fiducial markers, points of interest and obstacles\nto be avoided by the wheelchair user; the capacity to find the best route for wheelchair indoor navigation,\ntaking stairs and other obstacles into account; allow for the visualization of virtual directional arrows in the\nsmartphone displays; and incorporate touch or voice commands to interact with the application. The architecture\nis proposed as a combination of four layers: User interface; Control; Service; and Infrastructure. A proof-ofconcept\napplication was developed and tests were performed with disable volunteers operating manual and\nelectric wheelchairs. Results: The application was implemented in Java for the Android operational system.\nA local database was used to store the test building CAD drawings and the position of fiducial markers and\npoints of interest. The Android Augmented Reality library was used to implement Augmented Reality and\nthe Blender open source library handled the basis for implementing directional navigation arrows. OpenGL\nES provided support for various graphics and mathematical transformations for embedded systems, such as\nsmartphones. Experiments were performed in an academic building with various labs, classrooms and male\nand female bathrooms. Two disable volunteers using wheelchairs showed no difficulties to interact with the\napplication, either by entering touch or voice commands, and to navigate within the testing environment with\nthe help of the navigational arrows implemented by the augmented reality modules. Conclusion: The novel\nfeatures implemented in the proposed architecture, with special emphasis on the use of Mobile Augmented\nReality and the ability to identify the best routes free of potential hazards for wheelchair users, were capable of\nproviding significant benefits for wheelchair indoor navigation when compared to current techniques described\nin the literature....
Aiming at the issue of influence of blanket jamming on performances of Beidou navigation signals,\nthrough studying Beidou signals based on the BOC modulation technology, establishing a blanket\njamming mathematical model, and performing modeling and simulation on multiple jamming\ntechnologies, to attain the jamming curves of time domains and frequency domains of Beidou signals,\nand the correlation curve of the signal-to-jamming rate and the bit error rate under blanket\njamming, and thus realizing evaluation on the jamming performance....
Atomic clock is the core component of navigation satellite payload, playing a decisive role in the realization of positioning function.\nSo the monitoring for anomalies of the satellite atomic clock is very important. In this paper, a complete autonomous monitoring\nmethod for the satellite clock is put forward, which is, respectively, based on Phase-Locked Loop (PLL) and statistical principle.\nOur methods focus on anomalies in satellite clock such as phase and frequency jumping, instantaneous deterioration, stability\ndeterioration, and frequency drift-rate anomaly. Now, method based on PLL has been used successfully in China�s newest BeiDou\nnavigation satellite....
The use of the correction course option before aircraft take-off after inertial\nnavigation system (INS) inaccurate alignment based on the platform attitude-and-heading\nreference system in azimuth is considered in the paper. A course correction is performed based\non the track angle defined by the information received from the satellite navigation system\n(SNS). The course correction incudes a calculated track error definition during ground taxiing\nalong straight sections before take-off with its input in the onboard digital computational\nsystem like amendment for using in the current flight. The track error calculation is performed\nby the statistical evaluation of the track angle comparison defined by the SNS information with\nthe current course measured by INS for a given number of measurements on the realizable time\ninterval. The course correction testing results and recommendation application are given in the\npaper. The course correction based on the information from SNS can be used for improving\naccuracy characteristics for determining an aircraft path after making accelerated INS\npreparation concerning inaccurate initial azimuth alignment....
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