190 research outputs found
Optimal design of a composite wing structure for a flying-wing aircraft subject to multi-constraint
No full textThis thesis presents a research project and results of design and optimization of a composite wing structure for a large aircraft in flying wing configuration. The design process started from conceptual design and preliminary design, which includes initial sizing and stressing followed by numerical modelling and analysis of the wing structure. The research was then focused on the minimum weight optimization of the /composite wing structure /subject to multiple design /constraints. The modelling, analysis and optimization process has been performed by using the NASTRAN code. The methodology and technique not only make the modelling in high accuracy, but also keep the whole process within one commercial package for practical application.
The example aircraft, called FW-11, is a 250-seat commercial airliner of flying wing configuration designed through our MSc students Group Design Project (GDP) in Cranfield University. Started from conceptual design in the GDP, a high-aspect-ratio and large sweepback angle flying wing configuration has been adopted. During the GDP, the author was responsible for the structural layout design and material selection. Composite material has been chosen as the preferable material for both the inner and outer wing components. Based on the derivation of structural design data in the conceptual phase, the author continued with the preliminary design of the outer wing airframe and then focused on the optimization of the composite wing structure. Cont/d
Preliminary fuselage structural configuration of a flying-wing type airline
No full textThe flying-wing is a type of configuration which is a tailless airplane accommodating all of its parts within the outline of a single airfoil. Theoretically, it has the most aerodynamic efficiency. The fuel consumption can be more efficient than the existed conventional airliner. It seems that this configuration can achieve the above mentioned requirements.
According to these outstanding advantages, many aircraft companies did a great deal of projects on the flying-wing concept. However, the application was only for sport and military use; for airliner, none of them entered production.
FW-11 is a flying-wing configuration airliner which is a design cooperation between Cranfield University and Aviation Industry Corporation of China (AVIC). Aiming the spatial economic and environmental needs, this 200-seat airliner would attract attention from airline companies for cost saving and environmental protection.
Before start, this program is designated for a new generation commercial aircraft to compete with the existing same capability airliner, such as Airbus A320 and Boeing 767. As the first team of this program, the aim is to finish the conceptual design and prepare the relevant document for next two teams that will perform preliminary and detail design.
As a member of FW-11 program and as part of the GDP, the author has been through the four conceptual design stages: engine manufacturers, aircraft family issues, structure design and the establishment of 3-D CAD model.
The aim of IRP study is to focus on the initial fuselage design
Influence of wing kinematics on aerodynamic performance in hovering insect flight
No full textThe influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied. The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.Aerospace Design, Integration and OperationsAerospace Engineerin
Analysis of composite wing structures with a morphing leading edge
No full textOne of the main challenges for the civil aviation industry is the reduction of its environmental impact. Over the past years, improvements in performance efficiency have been achieved by simplifying the design of the structural components and using composite materials to reduce the overall weight. These approaches however, are not sufficient to meet the current demanding requirements set for a „greener‟ aircraft.
Significant changes in drag reduction and fuel consumption can be obtained by using new technologies, such as smart morphing structures. These concepts will in fact help flow laminarisation, which will increase the lift to drag ratio. Furthermore, the capability to adapt the wing shape will enable to optimise the aerodynamic performance not only for a single flight condition but during the entire mission. This will significantly improve the aircraft efficiency.
The current research work has been carried out as part of the European Commission founded Seventh Framework Program called „Smart High Lift Device for the Next Generation Wing‟ (SADE), which main aim is to develop and study morphing high lift devices. The author‟s investigation focused on developing a design concept for the actuation mechanism of a morphing leading edge device. A detailed structural analysis has been carried out in order to demonstrate its feasibility.In the first phase of the research the attention was directed on the preliminary design and analysis of the composite wing box. The parameters of the key structural components, such as skin, spars, ribs and stringers were set to satisfy the static stress and buckling requirements. Moreover, numerical and experimental studies were conducted to analyse the static failure and buckling behaviour of two typical composite wing structural components: a spar section and a web and base joint assembly.
In the second stage of the research, a design for the morphing leading edge actuation mechanism was developed. The actuation system was designed in such a way that the target shape was reached with minimum actuation force demand. A geometrical nonlinear FE analysis was conducted to simulate the leading edge morphing deflection and ensure that structural strength requirements were satisfied. Furthermore, the behaviour of the skin integrated with the internal actuation mechanism was modelled under the aerodynamic pressure, at different flight conditions and gust loads, in order to prove that the proposed actuation system can compete with the conventional rigid rib.
This study demonstrated that a feasible morphing leading edge design for a next generation large aircraft wing can be achieved. Developing the readiness of this technology will have a significant impact on aircraft efficiency and considerable contribution towards a more environmental friendly aviation
Effects of repetitive transcranial magnetic stimulation on improvement of cognition in elderly patients with cognitive impairment: A systematic review and meta-analysis
No full textThe study aimed to examine the effects of repetitive transcranial magnetic stimulation (rTMS) on cognitive function in elderly patients with cognitive impairment
Investigation of wing rock on delta wing part 1 : flow field and hydrodynamic force analysis
No full textAll modern fighter jets incorporate the use of the delta wing in the aircraft design to reduce wave drag and enhance flight performance at supersonic speeds. Delta wings are capable of providing increased lift compared to conventional airfoils due to the suction force generated by the leading edge vortices. However, at high angles of attack, delta wings are also prone to a phenomenon known as wing rock which can occur at high angles of attack and subsonic speeds.
This final year project focuses on the study of wing rock of delta wings at high angles of attack in a water tunnel. In the experiment, the hydrodynamic force generated by the delta wing is measured using a force-moment transducer, and the flow visualization is carried out with a dye probe, video camera and a digital SLR. Four delta wings, one Free To Roll device (FTR) and numerous angled joints were designed specifically for this experiment. Special attention was dedicated to the FTR device such that it only allowed movement around the longitudinal axis of the delta wing, and that special water-proof bearings were used to withstand the testing conditions.
Experimental data suggests that the wing rock motion is dependent on asymmetrical vortex breakdown over the wing. Discrepancies with other studies could be due to different friction used between systems, which can have a significant on the propagation of wing rock. The conclusion from this study is that there is good correlation between angle of attack, delta wing sweep angle, Reynolds number and the vortex breakdown behavior. In addition, dye flow visualization results show that the asymmetric vortex breakdown occurs at certain conditions.Bachelor of Engineering (Aerospace Engineering
The role of dopamine dysregulation and evidence for the transdiagnostic nature of elevated dopamine synthesis in psychosis: a positron emission tomography (PET) study comparing schizophrenia, delusional disorder, and other psychotic disorders
No full textThere have been few studies performed to examine the pathophysiological differences between different types of psychosis, such as between delusional disorder (DD) and schizophrenia (SZ). Notably, despite the different clinical characteristics of DD and schizophrenia (SZ), antipsychotics are deemed equally effective pharmaceutical treatments for both conditions. In this context, dopamine dysregulation may be transdiagnostic of the pathophysiology of psychotic disorders such as DD and SZ. In this study, an examination is made of the dopamine synthesis capacity (DSC) of patients with SZ, DD, other psychotic disorders, and the DSC of healthy subjects. Fifty-four subjects were recruited to the study, comprising 35 subjects with first-episode psychosis (11 DD, 12 SZ, 12 other psychotic disorders) and 19 healthy controls. All received an 18F-DOPA positron emission tomography (PET)/magnetic resonance (MR) scan to measure DSC (Kocc;30-60 value) within 1 month of starting antipsychotic treatment. Clinical assessments were also made, which included Positive and Negative Syndrome Scale (PANSS) measurements. The mean Kocc;30-60 was significantly greater in the caudate region of subjects in the DD group (ES = 0.83, corrected p = 0.048), the SZ group (ES = 1.40, corrected p = 0.003) and the other psychotic disorder group (ES = 1.34, corrected p = 0.0045), compared to that of the control group. These data indicate that DD, SZ, and other psychotic disorders have similar dysregulated mechanisms of dopamine synthesis, which supports the utility of abnormal dopamine synthesis in transdiagnoses of these psychotic conditions
Minimum Dominating Sets of Intervals on Lines
No full textWe study the problem of computing minimum dominating sets of n intervals on lines in three cases: (1) the lines intersect at a single point, (2) all lines except one are parallel, and (3) one line with t weighted points on it and the minimum dominating set must maximize the sum of the weights of the points covered. We propose polynomial-time algorithms for the first two problems, which are special cases of the minimum dominating set problem for path graphs which is known to be NP-hard. The third problem requires identifying the structure of minimum dominating sets of intervals on a line so as to be able to select one that maximizes the weight sum of the weighted points covered. Assuming that presorting has been performed, the first problem has an O(n) time solution, while the second and the third problems are solved by dynamic programming algorithms, requiring O(n log n) and O(n + t) time, respectively. Contact author: Siu-Wing Cheng, email [email protected] y Research partially sup..
, 062007 (2021)]
No full textThis article was originally published online on 17 June 2021 with an error in the author list. Alan Chen Hou Tsang should have appeared as Alan Cheng Hou Tsang. The author list is correct as it appears above. All online versions of the article were corrected on 18 June 2012; the article is correct as it appears in the printed version of the journal
A Fast Algorithm for Computing Optimal Rectilinear Steiner Trees for Extremal Point Sets (Extended Abstract)
No full textSiu-Wing Cheng and Chi-Keung Tang Department of Computer Science The Hong Kong University of Science and Technology Clear Water Bay, Hong Kong Contact author e-mail: [email protected]. Abstract. We present a fast algorithm to compute an optimal rectilinear Steiner tree for extremal point sets. A point set is extremal if each point lies on the boundary of a rectilinear convex hull of the point set. Our algorithm can be used in homotopic routing in VLSI layout design and it runs in O(k 2 n) time, where n is the size of the point set and k is the size of its rectilinear convex hull. 1 Introduction Routing in VLSI layout design calls for connecting terminals in the same plane with horizontal and vertical wiring. The terminals are points that sit on the boundaries of isothetic modules which are impenetrable rectilinear polygons. The terminals are divided into groups known as nets [9] and the terminals in each net are to be wired together in the routing region outside the modules. The con..
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