Multi-aircraft conflict detection and resolution based on probabilistic reach sets

In this brief, a novel scheme to multi-aircraft conflict detection and resolution is introduced. A key feature of the proposed scheme is that uncertainty affecting the aircraft future positions along some look-ahead prediction horizon is accounted for via a probabilistic reachability analysis approach. In particular, ellipsoidal probabilistic reach sets are determined by formulating a chance-constrained optimization problem and solving it via a simulation-based method called scenario approach. Conflict detection is then performed by verifying if the ellipsoidal reach sets of different aircraft intersect. If a conflict is detected, then the aircraft flight plans are redesigned by solving a second-order cone program resting on the approximation of the ellipsoidal reach sets with spheres with constant radius along the look-ahead horizon. A bisection procedure allows one to determine the minimum radius such that the ellipsoidal reach sets of different aircraft along the corresponding new flight plans do not intersect. Some numerical examples are presented to show the efficacy of the proposed scheme

Kesediaan pelajar dari aspek kemahiran teknikal terhadap pembentukan kebolehkerjaan di Kolej Vokasional Wilayah Selatan

Graduan yang menganggur terus menjadi masalah yang semakin meruncing di Malaysia. Terdapat majikan yang menganggap kompetensi akademik sahaja tidak mencukupi dan mula meminta institusi pendidikan tinggi untuk menghasilkan graduan yang dilengkapi dengan kemahiran teknikal. Kajian ini merupakan satu kajian untuk mengenalpasti kesediaan pelajar dari aspek kemahiran teknikal terhadap pembentukan kebolehkerjaan di kolej vokasional wilayah selatan. Seramai 113 responden telah dipilih sebagai sampel kajian. Instrumen kajian yang digunakan dalam kajian ini ialah borang soal selidik yang mengandungi 60 item. Kajian rintis dijalankan untuk mendapatkan nilai alpha bagi instrument kajian di mana nilai alpha bagi aspek kemahiran teknikal adalah α = 0.962 dan bagi aspek kebolehkerjaan adalah α = 0.954 . Data yang diperoleh dianalisis dengan menggunakan Statistical Package for Social Science Version 20 (SPSS 20). Analisis deskriptif dalam bentuk skor min digunakan untuk melihat kesediaan pelajar. Hasil kajian mendapati bahawa tahap kesediaan pelajar dari aspek kemahiran teknikal terhadap pembentukan kebolehkerjaan di Kolej Vokasional Kluang, Kolej Vokasional Batu Pahat dan Kolej Vokasional Muar berada pada tahap tinggi. Hasil kajian juga menunjukkan terdapat perbezaan antara jantina pelajar dari aspek kemahiran teknikal yang mempengaruhi kesediaan pelajar terhadap pembentukan kebolehkerjaa

Optimisation of Low-Thrust and Hybrid Earth-Moon Transfers

This paper presents an optimization procedure to generate fast and low-∆v Earth-Moon transfer trajectories, by exploiting the multi-body dynamics of the Sun-Earth-Moon system. Ideal (first-guess) trajectories are generated at first, using two coupled planar circular restricted three-body problems, one representing the Earth-Moon system, and one representing the Sun-Earth. The trajectories consist of a first ballistic arc in the Sun-Earth system, and a second ballistic arc in the Earth-Moon system. The two are connected at a patching point at one end (with an instantaneous ∆v), and they are bounded at Earth and Moon respectively at the other end. Families of these trajectories are found by means of an evolutionary optimization method. Subsequently, they are used as first-guess for solving an optimal control problem, in which the full three-dimensional 4-body problem is introduced and the patching point is set free. The objective of the optimisation is to reduce the total ∆v, and the time of flight, together with introducing the constraints on the transfer boundary conditions and of the considered propulsion technology. Sets of different optimal trajectories are presented, which represents trade-off options between ∆v and time of flight. These optimal transfers include conventional solar-electric low-thrust and hybrid chemical/solar-electric high/low-thrust, envisaging future spacecraft that can carry both systems. A final comparison is made between the optimal transfers found and only chemical high-thrust optimal solutions retrieved from literature

Airplane wing leading edge variable camber flap

The invention and design of an aerodynamic high lift device which provided a solution to an aircraft performance problem are described. The performance problem of converting a high speed cruise airfoil into a low speed aerodynamic shape that would provide landing and take-off characteristics superior to those available with contemporary high lift devices are addressed. The need for an improved wing leading edge device that would complement the high lift performance of a triple slotted trailing edge flap is examined. The mechanical and structural aspects of the variable camber flap are discussed and the aerodynamic performance aspects only as they relate to the invention and design of the device are presented

Leading edge curvature based on convective heating Patent

Construction of leading edges of surfaces for aerial vehicles performing from subsonic to above transonic speed

Refraction-corrected ray-based inversion for three-dimensional ultrasound tomography of the breast

Ultrasound Tomography has seen a revival of interest in the past decade, especially for breast imaging, due to improvements in both ultrasound and computing hardware. In particular, three-dimensional ultrasound tomography, a fully tomographic method in which the medium to be imaged is surrounded by ultrasound transducers, has become feasible. In this paper, a comprehensive derivation and study of a robust framework for large-scale bent-ray ultrasound tomography in 3D for a hemispherical detector array is presented. Two ray-tracing approaches are derived and compared. More significantly, the problem of linking the rays between emitters and receivers, which is challenging in 3D due to the high number of degrees of freedom for the trajectory of rays, is analysed both as a minimisation and as a root-finding problem. The ray-linking problem is parameterised for a convex detection surface and three robust, accurate, and efficient ray-linking algorithms are formulated and demonstrated. To stabilise these methods, novel adaptive-smoothing approaches are proposed that control the conditioning of the update matrices to ensure accurate linking. The nonlinear UST problem of estimating the sound speed was recast as a series of linearised subproblems, each solved using the above algorithms and within a steepest descent scheme. The whole imaging algorithm was demonstrated to be robust and accurate on realistic data simulated using a full-wave acoustic model and an anatomical breast phantom, and incorporating the errors due to time-of-flight picking that would be present with measured data. This method can used to provide a low-artefact, quantitatively accurate, 3D sound speed maps. In addition to being useful in their own right, such 3D sound speed maps can be used to initialise full-wave inversion methods, or as an input to photoacoustic tomography reconstructions