284 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
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
The aerodynamic design and optimization of a wing-fuselage junction fillet as part of a multi-disciplinary optimization process during the early aircraft design stages
No full textAn attempt to minimize interference drag in a wing-fuselage junction by means
of inserting a fillet is presented in this thesis. The case of a low-wing com-
mercial transport aicraft at cruise conditions is examined. Due to the highly
three dimensional behaviour of the flow field around the junction, a thin-layer
Navier-Stokes code was implemented to estimate the drag forces at the junc-
tion. Carefully selected design variable combinations based on-the theory of
Design of Experiments constituted the initial group of feasible cases for which
the flow solver had to be run. The drag values of these feasible cases were then
used to create a second order response surface which could predict with rea-
sonable accuracy the interference drag given the value of the design variables
within the feasible region. A further optimization isolated the minimum in-
terference drag combination of design variable values within the design space.
The minimurn interference drag combination of design variable values was eval-
uated numerically by the flow solver. The prediction of the response surface
and the numerical value obtained by the flow solver for the interference drag
of the optimal wing-fuselage combination differed by less than five percent. To demonstrate the ability of the method to be used in an interdisciplinary
analysis and optimization program, a landing gear design module is included
which provides volume constraints on the fillet geometry during the fillet sur-
face definition phase.
The Navier Stokes flow analyses were performed on the Cranfield Cray su-
percomputer. Each analysis required between eight to twelve CPU hours, and
the total CPU time required for the optimization of the six variable model
described in the thesis required thirty Navier Stokes runs implementing the
Design of Experimens and Surface Response Methodology implementation.
For comparison, a typical optimization implementing a classical conjugate di-
rections optimizer with no derivative information available would probably
require more than forty iterations.
Both the optimization and the flow solver results are discussed and some
recommendations for improving the efficiency of the code and for further ap-
plications of the method are given
Pseudopelmatops continentalis Zia & Chen
No full text<i>Pseudopelmatops continentalis</i> Zia & Chen <p>(Figs. 6, 15, 25, 30, 39, 42, 47)</p> <p> <i>Pseudopelmatops nigricostalis continentalis</i> Zia & Chen, 1954: 310. Type-locality: Tianmushan, Zhejiang; Chongan [not Shao-Woo as originally recorded by Zia & Chen (1954)], Fujian, China. Lectotype male and three paralectotypes designated by Wang, 1996 in IZCAS. <i>—</i> Hardy, 1977: 76. — Wang, 1996: 112.</p> <p> <b>Diagnosis.</b> This species is similar to <i>P. nigricostalis</i> Shiraki in wing markings, but differs by lacking frontal and postsutural supra-alar setae; and femora yellow except the basal 1/2–3/5 dark brown. It also closely resembles <i>P. angustifasciatus</i> in body coloration and chaetotaxy of the head and thorax, but is easily distinguished by having a much broader brownish-black costal band extending proximally to the base of cell r 1 (Fig. 30).</p> <p> <b>Description.</b> Body length 13.5–16.0 mm; wing length 10.5–13.0 mm. The body usually predominantly dark brown to black and sub-shining (Fig. 6).</p> <p> Head (Figs. 15, 25): dark brown to black except the middle of frons with a very narrow yellow longitudinal stripe; ventral 1/2 of face, parafacial and palpus yellow to yellow-brown. Palpus narrow, parallelsided and densely covered with strong, black setulae. Chaetotaxy reduced: head with orbital, medial vertical and genal setae present; postocellar, lateral vertical, ocellar, and frontal setae absent. Antenna almost equal to face, with 1 st flagellomere about 1/4–1/3 as wide as long, and 1 st flagellomere dorsoapically slightly sharp; arista plumose, longest ray slightly shorter or about equal to width of 1 st flagellomere.</p> <p>Thorax entirely dark brown to black except for scutum with two slightly broad grayish-white microtrichose longitudinal stripes, halter yellow. Chaetotaxy reduced: only 1 notopleural, 1 postalar and 1 apical scutellar setae present.</p> <p> Wing (Fig. 30). Largely hyaline with a broad brownish-black costal band extending from the base of cell r 1 to the wing tip, all the posterior margin in the cells br and r 4+5; pterostigma yellow-brown, narrow and long, about 0.97–1.00 times as long as cell c. Vein R 4+5 bare.</p> <p>Legs. Slender and long. Coxa, trochanter and the basal 2/3 of femora dark brown, other parts yellow brown.</p> <p>Abdomen elongate with tergites yellow-brown to dark brown; tergites 1–2 combined nearly parallel-sided and almost as long as tergites 3 and 4 combined.</p> <p>Male terminalia: Epandrium large and broad, rounded in posterior view (Fig. 39); lateral surstylus small and short, apex rounded in lateral view (Fig. 42); medial surstylus with 1 black prensiseta. Glans slightly expanded medially, without distinct acrophallus and membranous subapical lobe (Fig. 47).</p> <p>Female. Unknown.</p> <p> <b>Distribution.</b> China (Hunan, Hubei, Zhejiang, Fujian, Sichuan, Yunnan). Hunan and Hubei are new province records for this species.</p> <p> <b>Type data.</b> Lectotype ♂ (IZCAS), CHINA: Zhejiang: Tianmushan, 8. July 1936 (examined); paraletotypes: 1 ♂, same data with lectotype (examined); 1 ♂, same locality as lectotype, 20 July 1936 (examined); 1 ♂ (IZCAS), CHINA: Fujian: Chongan, 24 July 1944 (examined).</p> <p> <b>Other specimens examined.</b> CHINA: Hunan: Sangzhi, 1200m, 14 August 2001, J. Wen & N.T. Huang, 1 ♁ (IZCAS). Hubei: Shennongjia, 900m, 11 August 2004, Z. Wang, 1♁ (IZCAS). Sichuan: Mt. Emei, 27 July 1957, Y. C. Lu, 1♁ (IZCAS). Yunnan: Kunming, 1200 m, 7 July 1956, K. R. Huang, 1♁ (IZCAS).</p> <p> <b>Remark.</b> The type specimens of <i>Ps. angustifasciatus</i> (females) and <i>Ps. continentalis</i> (males) were collected in the same days and locality. Considering sexually dimorphic of wing pattern in this group, a possibility that they are conspecific has been considered seriously. However, their unpublished DNA sequence data from author’s recent molecular experiment didn’t support this suppose so far.</p>Published as part of <i>Chen, Xiaolin, Zhang, Yanzhou, Li, Jie & Zhu, Chaodong, 2010, A review of stalk-eyed fruit flies (Diptera: Tephritidae: Trypetinae), pp. 1-16 in Zootaxa 2654 (1)</i> on pages 9-12, DOI: 10.11646/zootaxa.2654.1.1, <a href="http://zenodo.org/record/5301417">http://zenodo.org/record/5301417</a>
Largusoperla dewalti Chen 2018
No full textLargUSoperla dewaltI Chen, sp. nov. Figs. 1–4. Description. Macropterous; body length (excluding antennae and cerci) ca. 9.1 mm, generally brown (Figs. 1, 2). Head (Figs. 1–3): Head oblate, mostly covered with a dark stigma, compound eyes dark. Antennae hairy and dark brown, with at least 29 segments. Maxillary palps not preserved; labial palps three-segmented, basal segment thickest. Pronotum (Fig. 3): Pronotum nearly trapezoidal, rugose and mostly brown, much narrower than head, anterior margin wider than posterior margin, median area not visible. Meso- and metathorax sclerotized, nearly as wide as pronotum. Legs mostly dark brown except for the pale joints; tibia with several thick ventral spines, the paired tibial spurs present; first two tarsal segments shortest with conspicuous euplantulae; apex of the claw dark sclerotized. Wings (Figs. 1–2): Wings hyaline, veins dark brown. Left forewing: length ca. 11.0 mm; ScP about threefourth of forewing length, reaching ScP+RA beyond ra-rp; apical area between anterior margin and RA with one crossvein; about nine crossveins present between ScP and the anterior margin; RP originated from about one-third of RA and with three branches; M forked at near half of the wing length; ra-rp not connected with the opposite crossvein rp-ma; CuA forked basal to the fork of M, with three branches; CuP simple; area between M and CuA with six crossveins; area between CuA and CuP with five crossveins; AA1 simple, AA2 forked. Hind wings covered by forewings, veins not visible. Abdomen (Fig. 4): Abdomen approximately ½ length of the body, generally brown, laterally with dark marks; sterna 6-8 with a pale oval mark; posterolateral margins of each segment slightly extruded. Sternum 9 strongly extended backwards, posteromedially with an elliptical hammer. Paraproct thick, hairy and finger-shaped, unevenly sclerotized with a banded pattern, apex rounded. Cerci hairy and pale,10-segmented, each segment with several dark apical bristles. Type material. Holotype male, No. CZT-PLE-MA3. This specimen is relatively well preserved except for the apex of the antennae, forelegs and right mid-leg, and the maxillary palps. The dorsal aspect of abdomen is not clear; wings are overlapping with only the left forewing clearly visible. Etymology. The new species is named in honor of Dr. R. Edward DeWalt, Illinois Natural History Survey, Champaign, Illinois, USA for his enthusiasm for the study of the Plecoptera and for his generous assistance to the author. Syninclusions. Plant remains and unknown organisms. Remarks. The new species exhibits typical head pattern, body color, similar wing venation and terminalia structures of other known species of Largusoperla but L. dewalti is easily distinguished by the finger-shaped and banded paraprocts.Published as part of Chen, Zhi-Teng, 2018, Key to the fossil genus Largusoperla (Plecoptera: Perlidae), with description of two new species from mid-Cretaceous Burmese amber, pp. 495-500 in Zootaxa 4450 (4) on page 496, DOI: 10.11646/zootaxa.4450.4.8, http://zenodo.org/record/144498
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
Effectiveness of Thrust Vectoring Control for Longitudinal Trim of a Blended Wing Body Aircraft
No full textThe application of thrust vectoring on civil transport aircraft has only been studied by a few individuals. Quantified investigations need to be carried out to search for the potential benefits of the application of thrust vectoring control on a civil transport aircraft. Blended Wing Body configuration is a novel aircraft concept. Due to the absence of conventional tails longitudinal controllability become part of the key challenges of this configuration. It is therefore the objective of this thesis project to carry out quantified flight mechanics analyses on the effectiveness of controlling a Blended Wing Body aircraft with vectoring thrust. As a starting point flight mechanics simulations under steady level flight conditions in longitudinal plane are conducted in this project. Through this project a thrust vectoring model, which contains the calculation of nozzle deflection angles based on nozzle deflection controls and the calculation of engine thrust loss due to nozzle deflections, is developed and embedded in a flight mechanics toolbox used for the flight mechanics simulations. The flight mechanics simulations of thrust vectoring control are then carried out with a series of nozzle deflections, flight conditions, aircraft mass and CG locations. From the simulation results it is investigated that for the Blended Wing Body configuration tested in this project, thrust vectoring control under steady level flight conditions is much less effective than the conventional aerodynamic control surfaces. The maximum effectiveness ratio between thrust vectoring control and conventional aerodynamic control surfaces obtained in this project is about 11.2%. With extensive flight mechanics simulations, the way that aircraft flight conditions, mass and CG locations affect the effectiveness of thrust vectoring control is analysed through this project.Flight Performance and PropulsionAerospace Engineerin
Flapping wing mechanism for micro aerial vehicles
No full textMicro aerial vehicles (MAVs) are defined as vehicles capable of flight not exceeding 15 cm in max dimensions. In recent times, interest in unmanned aerial vehicles of relative smaller dimensions – micro aerial vehicles have spurned a trend in the development of suitable propulsion platforms. Many have looked to nature for an answer, as the flapping flight ability of birds and insects continue to captivate biological scientists and researchers. One of the more promising propulsion mechanisms identified is that of flapping wings in plunging motions with restricted oscillatory movements. Whilst extensive research has been done on the applicability of a bi-plane configured flapping wing mechanism on micro-aerial vehicles, the majority of this work has been concentrated solely on the computational aspects. Experimental research is limited to the pioneers of the bi-plane flapping wing design: KD Jones and team. It is with this mindset that the author has chosen this project where the design, manufacture and experimental testing of a bi-plane configured flapping wing propulsion mechanism are successfully accomplished.In this report, the design and manufacture of a bi-plane configured flapping wing propulsion mechanism capable of flapping in counter-phase and in perfect symmetry is described. The thrust generation ability of this flapping wing propulsion mechanism is obtained with different sets of airfoils under varying flapping frequencies. Finally, the wake velocity profiles generated by the different set of airfoils under varying flapping frequencies are plotted and analysed. A correlation between the thrust generated and the wake velocity profile generated is drawn and the suitability of such a mechanism as a propulsion platform in MAVs is assessed.Bachelor of Engineering (Aerospace Engineering
CUHK electronic theses & dissertations collection
No full textChen, Junyu.Thesis M.Phil. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 56-61).Abstracts also in Chinese.Title from PDF title page (viewed on 25, October, 2016)
Simulation studies on the design of optimum PID controllers to suppress chaotic oscillations in a family of Lorenz-like multi-wing attractors
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Multi-wing chaotic attractors are highly complex nonlinear dynamical systems with higher number of index-2 equilibrium points. Due to the presence of several equilibrium points, randomness and hence the complexity of the state time series for these multi-wing chaotic systems is much higher than that of the conventional double-wing chaotic attractors. A real-coded Genetic Algorithm (GA) based global optimization framework has been adopted in this paper as a common template for designing optimum Proportional-Integral-Derivative (PID) controllers in order to control the state trajectories of four different multi-wing chaotic systems among the Lorenz family viz. Lu system, Chen system, Rucklidge (or Shimizu Morioka) system and Sprott-1 system. Robustness of the control scheme for different initial conditions of the multi-wing chaotic systems has also been shown
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