bluuebunny/crossref_metadata_2025 huggingface dataset:
A secure authentication scheme with provable correctness for pay‐TV systems
Authors: Wu Hsiao‐Ling , Chang Chin‐Chen , Sun Chin‐Yu
Published: February 2016

In traditional television (TV) systems, users have to pay for all of the channels provided by the TV service server. However, usually, users are not interested in all of the channels, so they waste money by paying for all of the channels. For this reason, the concept of “pay‐TV” has been developed. A pay‐TV system allows the subscribers to pay for the specific channels they want to watch. If we consider that m users subscribe to n channels in traditional schemes for pay‐TV, the time complexity will be O(mn). It is lower efficiency for user on the pay‐TV system. But, in this paper, we proposed a novel authentication scheme for pay‐TV systems based on Chebyshev chaotic maps, and the time complexity only needs O(m). The purpose of our scheme is focus on efficiency and security. The security and performance analyses showed that our proposed scheme satisfies the essential functionality requirements, withstands potential attacks, and is suitable for real‐world practical implementation. Furthermore, the Burrows–Abadi–Needham logic model was used to prove the correctness of our proposed scheme for the mutual authentication between users and the server. Copyright © 2016 John Wiley & Sons, Ltd.
Variable selection for distribution‐free models for longitudinal zero‐inflated count responses
Authors: Chen Tian , Wu Pan , Tang Wan , Zhang Hui , Feng Changyong , Kowalski Jeanne , Tu Xin M.
Published: February 2016

Zero‐inflated count outcomes arise quite often in research and practice. Parametric models such as the zero‐inflated Poisson and zero‐inflated negative binomial are widely used to model such responses. Like most parametric models, they are quite sensitive to departures from assumed distributions. Recently, new approaches have been proposed to provide distribution‐free, or semi‐parametric, alternatives. These methods extend the generalized estimating equations to provide robust inference for population mixtures defined by zero‐inflated count outcomes. In this paper, we propose methods to extend smoothly clipped absolute deviation (SCAD)‐based variable selection methods to these new models. Variable selection has been gaining popularity in modern clinical research studies, as determining differential treatment effects of interventions for different subgroups has become the norm, rather the exception, in the era of patent‐centered outcome research. Such moderation analysis in general creates many explanatory variables in regression analysis, and the advantages of SCAD‐based methods over their traditional counterparts render them a great choice for addressing this important and timely issues in clinical research. We illustrate the proposed approach with both simulated and real study data. Copyright © 2016 John Wiley & Sons, Ltd.
Small is Beautiful: Challenges and Perspectives of Nano/Meso/Microscience
Authors: Antonietti Markus
Published: February 2016

This article gives a personal view on the development of our discipline, but also tries to elaborate some of the current and future trends to illustrate why “Small science” is at the core of the current scientific development of chemistry and physics. Topics such as the limits of ‘small’, new modes of self‐organization, pattern recognition, self‐repair, encoding of structures, and the appropriate handling of complexity are discussed along these lines.
Experimental study and associated numerical simulation of horizontally connected precast shear wall assembly
Authors: Sun Jian , Qiu Hongxing , Lu Yong
Published: February 2016

This paper is concerned about precast reinforced concrete shear walls and the methods of assembling shear wall panels to form a reliable load transfer system. An assembling method is proposed using dry connection through a horizontal steel connector (H‐connector) and high‐strength bolts. To investigate the effectiveness and the design of such a connection method, three wall‐connector assembly specimens with different connection details have been constructed and tested under monotonic loading while subjected to a constant vertical compression. The test results provided comprehensive data regarding the progressive transition of the load transfer mechanisms and showed that the performance of the shear wall assembly was generally satisfactory in terms of ensuring the full development of the shear wall strength and ductility. To assist in the interpretation of the experimental results and enable further parametric analysis, a detailed finite element model has been developed with incorporation of the main load transfer mechanisms, in addition to the description of the nonlinear behavior of the shear wall. The finite element model has been verified to represent well the actual behavior of the shear wall assembly, and it has provided further insight into the occurrence of slippage at the connection, the development of the bearing resistance of the bolts and the compression load transfer through contact in the later stage of the response. Copyright © 2016 John Wiley & Sons, Ltd.
Challenges in preclinical to clinical translation for anticancer carrier‐mediated agents
Authors: Lucas Andrew T. , Madden Andrew J. , Zamboni William C.
Published: February 2016

Major advances in carrier‐mediated agents (CMAs), which include nanoparticles and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages over their small‐molecule counterparts, there is substantial variability in how individual CMA formulations and patient characteristics affect the pharmacology, pharmacokinetics (PK), and pharmacodynamics (PD) (efficacy and toxicity) of these agents. Development or selection of animal models is used to predict the effects within a particular human disease. A breadth of studies have begun to emphasize the importance of preclinical animal models in understanding and evaluating the interaction between CMAs and the immune system and tumor matrix, which ultimately influences CMA PK (clearance and distribution) and PD (efficacy and toxicity). It is fundamental to study representative preclinical tumor models that recapitulate patients with diseases (e.g., cancer) and evaluate the interplay between CMAs and the immune system, including the mononuclear phagocyte system (MPS), chemokines, hormones, and other immune modulators. Furthermore, standard allometric scaling using body weight does not accurately predict drug clearance in humans. Future studies are warranted to better understand the complex pharmacology and interaction of CMA carriers within individual preclinical models and their biological systems, such as the MPS and tumor microenvironment, and their application to allometric scaling across species. WIREs Nanomed Nanobiotechnol 2016, 8:642–653. doi: 10.1002/wnan.1394

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials
Which stocks drive the size, value, and momentum anomalies and for how long? Evidence from a statistical leverage analysis
Authors: Aretz Kevin , Aretz Marc
Published: February 2016

A large number of neoclassical, behavioral, and bias-based theories try to explain the tendency of small, value, and winner stocks to outperform big, growth, and loser stocks, three well-known characteristic anomalies. Because the theories often predict similar relationships between a stock’s propensity to contribute to the anomalies and a set of correlated firm characteristics, existing studies focusing on single theories do not tell us which theory is most successful in explaining the anomalies. To fill this gap, we use a new non-parametric methodology to run a horse race between the theories. In the first step, we use statistical leverage analysis to find out which stocks are ultimately responsible for the anomalies. In the second, we use the firm characteristics suggested by the theories to forecast the identity of the anomaly drivers, with the purpose of determining which theory is most supported by the data. We find that behavioral theories are most convincing in explaining the size and book-to-market anomalies, while no theory is convincing in explaining the momentum anomaly.
Inpatient Rehabilitation of Patients with Cancer: Efficacy and Treatment Considerations
Authors: Huang Mark E. , Sliwa James A.
Published: February 2016

Although cancer can affect a great number of individuals and is the second leading cause of death in the United States, the number of individuals admitted to acute inpatient rehabilitation units with impairments primarily as the result of cancer diagnoses remains small. There is a lack of awareness among health care providers as to the functional loss that can be associated with cancer and the potential benefits of inpatient rehabilitation. Furthermore, financial pressures from third‐party payors may dissuade the admission of patients with cancer for inpatient rehabilitation. This is a narrative review of the literature with respect to the efficacy and potential benefits of inpatient rehabilitation for patients with cancer. The findings of studies on the rehabilitation of general cancer populations are presented, with a focus on functional outcomes, medical complications and transfer rates, and common symptoms encountered during inpatient rehabilitation. Studies that focus on tumors involving the brain and spinal cord are separately analyzed. Functional outcomes by tumor location are reviewed with respect to tumor type, recurrence, and comparison with nontumor diagnoses. In addition, the effects of concomitant treatments on functional outcomes and possible correlations of survival with functional outcome are presented. Justification for admission of patients with cancer diagnoses to inpatient rehabilitation units, as well as implications for management of these patients during their rehabilitation stay, will be summarized.
The Problem of High Temperature Alloys for Gas Turbines
Authors: Griffiths William T.
Published: February 2016

It is now a matter of history that the development of an efficient gas turbine for use in aircraft engines had to await the availability of materials with the properties which would give an adequate life under the conditions which have to be imposed for efficient and economic service. These conditions are, of their type, more severe than any so far imposed on materials in other mechanical equipment. For efficient operation the gases employed in the turbine must be at a high temperature and the flow of gas passing through must be large. In aircraft engines also, the turbine must operate at high speed, with the resulting accompaniment of high stresses. It was to the metallurgist that the engineer naturally turned first for materials to meet these conditions of high temperatures and high stresses and, although some attention has been given to non-metallic substances, the problem still remains essentially a metallurgical one.
Load alleviation in tilt rotor aircraft through active control; modelling and control concepts
Authors: Manimala B. , Padfield G. D. , Walker D. , Naddei M. , Verde L. , Ciniglio U. , Rollet P. , Sandri F.
Published: February 2016

This paper presents the first results from research into active control of structural load alleviation (SLA) for tiltrotor aircraft carried out in the European ‘critical technology’ RHILP project. The importance of and the need for SLA in tiltrotors are discussed, drawing on previous US experience reported in the open literature. The paper addresses the modelling aspects in some detail; hence forming the foundation for both the FLIGHTLAB simulated XV-15 and EUROTILT configurations. The primary focus of attention is the suppression of in-plane rotor yoke loads for pitch manoeuvres in airplane mode; without suppression these loads would result in a very high level of fatigue damage. Multi-variable control law design methods are used to develop controller schemes and load suppression of 80-90% is demonstrated using rotor cyclic control, albeit at a 20-30% performance penalty. However, rotor flapping transients tend to increase by the action of the SLA system. A dual-objective control design approach demonstrates the effectiveness of suppressing both loads and flapping simultaneously.
Fuel sensitivity analyses for active drag reduction systems
Authors: Young T. M.
Published: February 2016

Active drag reduction systems, such as hybrid laminar flow control (HLFC), have the potential for significant fuel savings; however, this is at the expense of an increase in aircraft weight and engine power off-take. A computer program – capable of accurately determining the trip fuel for a given mission profile – has been developed. The program was validated against manufacturer’s payload-range data, and then modified to emulate the installation of an active drag reduction system, by incorporating changes to the drag polars, specific fuel consumption (SFC) data and operating empty weight (OEW). Results of sensitivity studies are presented that enable the reduction in trip fuel to be determined for given changes in CD, SFC and OEW. The underlying assumption of linear independence of the three parameters is explored. The linearised method was observed to underestimate the fuel savings of the HLFC aircraft by approximately 0·6% compared to an analysis which took into account the coupling between the parameters. A mathematical relationship has been established to estimate the impact on cruise fuel burn arising from relative changes to the aircraft’s mass, lift-to-drag ratio and SFC.
Supersonic transport aircraft longitudinal flight control law design
Authors: Steer A. J.
Published: February 2016

Modern civil transport aircraft utilise increasingly complex command and stability augmentation systems to restore stability, optimise aerodynamic performance and provide the pilot with the optimum handling qualities. Provided it has sufficient control power a second generation fly-by-wire supersonic transport aircraft should be capable of exhibiting similarly desirable low-speed handling qualities. However, successful flight control law design requires identification of the ideal command response type for a particular phase of flight, a set of valid handling quality design criteria and piloted simulation evaluation tasks and metrics. A non-linear mathematical model of the European supersonic transport aircraft has been synthesized on the final approach to land. Specific handling quality design criteria have been proposed to enable the non-linear dynamic inversion flight control laws to be designed, with piloted simulation used for validation. A pitch rate command system, with dynamics matched to the aircraft’s flight path response, will consistently provide Level 1 handling qualities. Nevertheless, pre-filtering the pilot’s input to provide a second order pitch rate response, using the author’s suggested revised constraints on the control anticipation parameter will generate the best handling qualities during the terminal phase of flight. The resulting pre-filter can be easily applied to non-linear dynamic inversion inner loop controllers and has simple and flight proven sensor requirements.
Aeroelastically adaptive propeller using blades’ root flexibility
Authors: Sandak Y. , Rosen A.
Published: February 2016

Usually a fixed pitch propeller is designed to be optimal at cruise speeds. Thus the efficiency is quite low at takeoff or low speeds, as well as during other flight regimes. The present paper shows that by introducing a flexible element into the blade root, the propeller efficiency can be improved over a wide range of velocities. The flexible element reacts to root flap or torsion moments by changing the blade pitch at the root. The root flexibility and the pitch angles at the root at zero loads are chosen such that efficiency will increase during problematic regimes without decreasing the propeller thrust. In the case of straight blades the torsional moment at the root is too small to be used. In the case of swept blades this moment component is significantly increased and can contribute to the design of an optimal aeroelastically adaptive propeller.
Vortex breakdown location over 65° delta wings empiricism and experiment
Authors: Jobe C. E.
Published: February 2016

Thirty-eight data sets from static tests of various 65° delta wings in many water and wind tunnels are compared with four empirical vortex breakdown location prediction methods and the results of two Navier-Stokes computations to assess their range of validity in pitch. Vortex breakdown is the sudden expansion and subsequent chaotic evolution of the otherwise orderly, spiraling, leading-edge vortex flow over the upper surface. Large fluctuations occur in vortex breakdown location at static test conditions making accurate experimental determination difficult.

The prediction methods do not account for the seemingly minor geometric details that vary between the models such as thickness, leading-edge bevel angle and radius, trailing-edge bevel angle, sting mounting, instrument housings, etc. These geometric variations significantly affect the position of vortex breakdown and degrade the accuracy of the predictions. The large changes in the flow produced by small geometric changes indicate that an efficient flow control strategy may be possible. Many of the data sets are not corrected for tunnel wall effects, which may account for some of the differences. Data presented herein are as published by the original authors, without additional corrections.
Application of generic algorithms in aerodynamic optimisation design procedures
Authors: Clayton R. P. , Martinez-Botas R. F.
Published: February 2016

Direct optimisation techniques using different methods are presented and compared for the solution of two common flows: a two dimensional diffuser and a drag minimisation problem of a fixed area body. The methods studied are a truncated Newton algorithm (gradient method), a simplex approach (direct search method) and a genetic algorithm (stochastic method). The diffuser problem has a known solution supported by experimental data, it has one design performance measure (the pressure coefficient) and two design variables. The fixed area body also has one performance measure (the drag coefficient), but this time there are four design variables; no experimental data is available, this computation is performed to assess the speed/progression of solution.

In all cases the direct search approach (simplex method) required significantly smaller number of evaluations than the generic algorithm method. The simplest approach, the gradient method (Newton) performed equally to the simplex approach for the diffuser problem but it was unable to provide a solution to the four-variable problem of a fixed area body drag minimisation. The level of robustness obtained by the use of generic algorithm is in principle superior to the other methods, but a large price in terms of evaluations has to be paid.
Polynomial series expansion for optimisation of wing plane structures in idealised critical flutter conditions
Authors: Tizzi S.
Published: February 2016

A numerical procedure, which utilises polynomial power series expansions for the optimisation of multipanel wing structures in idealised critical flutter conditions, is introduced and developed. It arises from the Rayleigh-Ritz method and employes trial polynomial describing functions both for the flexural displacement and for the thickness variation over the multipanel surface. An idealised structural plate model, according to the Kirchhoff’s theory, together with a linearised supersonic aerodynamic approach, are supposed. The classical Euler-Lagrange optimality criterion, based on variational principles, has been utilised for the optimisation operations, where by imposing the stationary conditions of the Lagrangian functional expression, a nonlinear algebraic equations system is obtained, whose solution is found by an appropriate algorithm. By utilising an iterative process it is possible to reach the reference structure critical conditions, with an optimised thickness distribution throughout the multipanel surface. The final part of the work consists in searching the minimum weight of the multipanel planform wing structure with optimised thickness profilevsthe flutter frequency, considered as a variable imput parameter, for fixed flutter speed and equal to the critical one of the reference uniform structure.
Evaluation of CFD methods for transport aircraft high lift systems
Authors: Rudnik R. , Eliasson P. , Perraud J.
Published: February 2016

Major results and findings of the numerical work package of the European high lift programme EUROLIFT are outlined. The main objective of these studies is to validate and test numerical methods for the prediction of high lift flows for transport aircraft configurations. The activities comprise the assessment of current CFD methods for 3D flows, evaluation of means for code improvement, and transition prediction. All aspects are especially devoted to high lift flow problems. A general capability to predict maximum lift on a simplified wing/fuselage high lift configuration is demonstrated by a variety of different numerical approaches. In general, major shortcomings are the reliability and the accurate simulation of large separation areas and the turn-around time to compute 3D lift polars. Advanced turbulence modelling and numerical solver features, such as the preconditioning technique, show a potential to overcome these deficiencies. Promising results with respect to transition prediction were obtained on a swept high lift wing using a database method. The results obtained in the numerical activities represent major ingredients on the way to a consistent numerical approach for the simulation of transport aircraft high lift configurations including all maximum lift determining effects.
Experimental investigation of the effect of nozzle shape and test section perforation on the stationary and non-stationary characteristics of flow field in the large transonic TsAGI T-128 Wind tunnel
Authors: Biryukov V. I. , Glazkov S. A. , Gorbushin A. R. , Ivanov A. I. , Semenov A. V.
Published: February 2016

The results are presented for a cycle of experimental investigations of flow field characteristics (static pressure distribution, static pressure fluctuations, upwash, boundary-layer parameters) in the perforated test section of the transonic TsAGI T-128 Wind Tunnel. The investigations concern the effect of nozzle shape, wall open-area ratio, Mach and Reynolds numbers on the above-outlined flow characteristics. During the tests, the main Wind-tunnel drive power is measured. Optimal parameters of the nozzle shape and test section perforation are obtained to minimise acoustic perturbations in the test section and their non-uniformity in frequency, static pressure field non-uniformity, nozzle and test section drag and, accordingly, required main Wind-tunnel drive power.
Dye visualisation of inclined and skewed synthetic jets in a cross flow
Authors: Zhong S. , Garcillan L. , Wood N. J
Published: February 2016

Dye visualisation of both inclined synthetic jets and skewed synthetic jets was undertaken in a cross-flow experiment and the results were compared with those of normal synthetic jets. The process of vortex roll-up near the orifice exit and how the structure develops and interacts with the cross-flow as it propagates downstream was investigated so as to obtain an understanding of the effect of orifice orientation on the behaviour of synthetic jets. The effects of varying Reynolds number, velocity ratio and Strouhal number due to changes in diaphragm displacements and freestream velocities on the characteristics of synthetic jets were also examined. It is observed that in comparison to the normal jets vortical structures produced by both inclined and skewed jets tend to stay closer to the near wall region where maximum flow control effect is required. In both cases, at a relatively low Reynolds number and velocity ratio the active structures produced by the synthetic jet appear to be hairpin vortices which turn into vortex rings that migrate away from the wall as the Reynolds number and velocity ratio increase. These hairpin vortices are persistent in the near wall region hence are believed to be desirable structures for delaying flow separation.
Trade disputes in the commercial aircraft industry: A background note
Authors: Hayward K.
Published: February 2016

The long-running debate between the US and the EU over government supports for large commercial aircraft has recently boiled over into a major dispute involving the World Trade Organisation (WTO). While the two sides have currently backed off from what could be a very damaging WTO outcome, there are still wide differences over the legitimacy of government supports (direct or indirect) for Airbus and Boeing airliners. This paper:

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Describes the background to the current dispute.

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Analyses the 1992 US–EU Agreement on Large Aircraft Subsidies.

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Outlines the WTO Agreement on Subsidies and Countervailing Measures and the decision by the US to mount an action under the WTO complaints procedures against launch investment for Airbus and the EU’s counter claim against Boeing.

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Considers the precedents set by the WTO rulings on the Brazilian–Canadian dispute over regional jet supports.

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Summarises the US–EU complaints to the WTO.

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Considers potential outcomes and the implications for the civil aerospace industry on both sides of the Atlantic.

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Analyses the wider issues surrounding government intervention in the aerospace sector.

The paper views the dispute as a reflection of fundamental differences, based primarily on divergent economic doctrines and values, between the US and the EU states. There could be especially damaging consequences for the EU should the WTO rule against the systems of repayable launch investment used by the Airbus governments. But both sides could lose heavily from the affair and there is a good case for maintaining some form of direct government intervention in civil aerospace technology acquisition, even near market research, in support of environmental sustainability objectives.
Kite performance testing by flying in a circle
Authors: Stevenson J. , Alexander K. , Lynn P.
Published: February 2016

With the advent of recreational sports like kite surfing and buggying, the performance of kites has become a market driven item. Producers increasingly require methods to measure and improve the performance of the kites they manufacture. The Mechanical Engineering Department at the University of Canterbury has been working with a local kite producer to develop testing procedures suitable for kite manufacturers. The primary performance measurement is the lift to drag ratio. An early test rig was mounted in the top of a car, but limitations inherent in the design meant that it lost precision as the lift to drag ratio approached that of more advanced kites. This led the investigators to look for alternatives, and resulted in the development of the circular flight method. This method allows the test apparatus to be tuned to the performance of each kite, significantly improving the precision of the results while reducing the time taken for each test. In their raw form, the L/D results are not quite the same as those of the more traditional methods. But they reflect the underlying aerodynamic characteristics, and when used comparatively they can be used in the kite development process. Alternatively, with suitable processing the circular flight results can be converted to the traditional forms.
Semi–optimal co–ordinated manoeuvres for aircraft conflict resolution
Authors: Parastari J. , Malaek M. B.
Published: February 2016

In this manuscript, a new concept of 2D-semi-optimal-circular-3-arced-path manoeuvres with constant speed for multiple aircraft cooperative conflict resolution is presented. This type of manoeuvres is based on appropriate commands to heading, speed and manoeuvreing time. According to aircraft turning dynamics, each aircraft manoeuvre is composed of three tangent circular arcs. The optimality of manoeuvres is based on the minimisation of weighted sum of kinetic energy for aircraft two-legged manoeuvres. In comparison, aircraft with lower weight factors bear more responsibility to resolve the conflicts. The effectiveness of the proposed algorithm for real time conflict resolution is guaranteed, where the number of encountering aircraft is less than five. Otherwise, the current method could also be jointed to one of the fast resolution methods, like probabilistic resolution algorithm or genetic algorithm – as a tool to choose the convex domain – to become more computationally effective. Considerable number of case studies has been done to evaluate the effectiveness of the proposed methodology, while some are presented in the paper.
Effects of leading-edge bevel angle on the aerodynamic forces of a non-slender 50° delta wing
Authors: Wang J. J. , Lu S. F.
Published: February 2016

The aerodynamic performances of a non-slender 50° delta wing with various leading-edge bevels were measured in a low speed wind tunnel. It is found that the delta wing with leading-edge bevelled leeward can improve the maximum lift coefficient and maximum lift to drag ratio, and the stall angle of the wing is also delayed. In comparison with the blunt leading-edge wing, the increment of maximum lift to drag ratio is 200%, 98% and 100% for the wings with relative thickness t/c = 2%, t/c = 6.7% and t/c = 10%, respectively.
Progress toward CFD for full flight envelope
Authors: Tinoco E. N. , Bogue D. R. , Kao T-J. , Yu N. J. , Li P. , Ball D. N.
Published: February 2016

The value of computational fluid dynamics, CFD, delivered to date has mainly been related to its application to high-speed cruise design. To increase its applicability CFD must apply to the full flight envelope frequently characterised by large regions of separated flows. These flows are encountered by transport aircraft at low speed with deployed high lift devices, at their structural design loads conditions, or subjected to in-flight upsets that expose them to speed and/or angle-of-attack conditions outside the envelope of normal flight conditions to name a few. Such flows can only be characterised by the Navier-Stokes equations. This paper will report the progress toward CFD for full flight envelope. The CFD methods in use at Boeing will be described. Examples presented will address high-lift, loads and stability and control concerns including Reynolds scaling from wind tunnel to flight, vortex generator simulation, spoiler and horizontal tail effectiveness. In general, results shown are in ‘good enough’ agreement with experimental data. Deficiencies and the need for further algorithm and process improvement are noted. The need for automation to enable the large scale use of CFD will also be discussed.
Normal shock wave/turbulent boundary-layer interaction control using ‘smart’ piezoelectric actuators
Authors: Couldrick J. S. , Gai S. L. , Milthorpe J. F. , Shankar K.
Published: February 2016

This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a plenum chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer.

The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
Fracture of layered composites by internal fibre instability: effect of interfacial adhesion
Authors: Soutis C. , Guz I. A.
Published: February 2016

In this paper, a mechanism of compressive fracture for elastic and elastic-plastic composite materials with interfacial adhesion defects is investigated. A classification of different approaches in modelling compressive response of layered materials is given. The analysis finds the upper and the lower bounds for the critical load. In order to achieve this, the problem of the internal fibre (layer) instability is considered within the scope of the exact statement based on the application of the model of a piecewise-homogeneous medium and the equations of the three-dimensional (3D) stability theory. The solution of the 3D problem is found for the most general case accounting for the bi-axiality of compressive loads. The characteristic determinants are derived for the first four fibre instability (microbuckling) modes, which are more commonly observed. Special attention is given to the calculation of critical loads for practical elastic and elastic-plastic layered materials.
Sub boundary-layer vortex generators for the control of shock induced separation
Authors: Cohen G. S. , Motallebi F.
Published: February 2016

The results of an investigation into the effects that sub-boundary layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation are presented. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Total pressure profiles, static pressure distributions, surface total pressure distributions, oil flow visualisation and Schlieren photographs were used in the results analysis. The effects of SBVG height, lateral spacing and location upstream of the shock were investigated. A novel curved shape SBVG was also evaluated and comparisons against the conventional flat vane type were made. The results show that in all but two cases, separation was completely eliminated. As expected, the largest SBVGs with height,h= 55%δ, provided the greatest pressure recovery and maximum mixing. However, the shock pressure rise was highest for this case. The experiments showed that the mid height SBVG array with the largest spacing provided similar results to the SBVG array with the largest height. Reducing the distance to shock to 10δ upstream also showed some improvement over the SBVG position of 18δ upstream. It was suggested that total elimination of the separated region may not be required to achieve a balance of improved static pressure recovery whilst minimising the pressure rise through the shock. The effect of curving the SBVGs provided an improved near wall mixing with an improved static and surface total pressure recovery downstream of the separation line. The optimum SBVG for the current flow conditions was found to be the curved vanes ofh= 40%δ, with the largest spacing, located at 18δ upstream of the shock. Overall, it was apparent from the results that in comparison to larger vortex generators with a height comparable to δ, for SBVGs the parameters involved become more important in order to obtain the highest degree of mixing from a given SBVG configuration.
Impacts of low-pressure (LP) compressor’s deterioration upon an aero-engine’s high-pressure (HP) turbine blade’s life consumption
Authors: Naeem M.
Published: February 2016

Some in-service deterioration in any mechanical device, such as an aero-engine, is inevitable. As a result of experiencing a deterioration of efficiency and/or mass flow, an aero-engine will automatically adjust to a different set of operating characteristics; thereby frequently resulting in changes of rpm and/or turbine entry temperature in order to provide the same thrust. Rises in the turbine entry-temperatures and the high-pressure turbine’s rotational speed result in greater rates of creep and fatigue damage being incurred by the hot-end components and thereby higher engine’s life cycle costs. Possessing a better knowledge of the effects of engine deterioration upon the aircraft’s performance, as well as fuel and life usages, helps the users to take wiser management decisions and hence achieve improved engine utilisation. For a military aircraft, using a computer performance simulation, the consequences of low-pressure (LP) compressor’s deterioration upon an aero-engine high-pressure (HP) turbine blade’s life-consumption have been predicted.
Comparison of experimental and numerical investigation on a jet in a supersonic cross-flow
Authors: Kovar A. , Schülein E.
Published: February 2016

Flow interaction of three different jet configurations ejecting air from a flat plate into a supersonic cross flow were investigated experimentally and numerically. The test conditions encompassed a jet pressure ratio of Poj, P∞ = 100 at a Mach number of M∞ = 5 and Reynolds number of about Re∞ = 25 × 106 based on the length of the flat plate. The investigated test cases are: a) single jet; b) four jets positioned in-line in main flow direction; c) four jets positioned side-by-side in spanwise direction. The prediction of the overall flow phenomena as occurring within the interaction area was in fair agreement with the experiments, although quantitatively differences occur that will be discussed in the paper.

The results of the comparison are presented and the experimental data are used to validate the applied code.
Boundary condition effects on the evolution of a train of vortex pairs in still air
Authors: Yehoshua T. , Seifert A.
Published: February 2016

Effects of boundary conditions on the performance of compact oscillatory momentum and vorticity generators, commonly known as ‘synthetic jet’, ejecting a train of vortex-pairs into still air, were studied experimentally. The different boundary conditions altered the near-device entrainment process of the zero-net-mass-flux actuator. The measurements included hot-wire and Particle Image Velocimetry, cavity pressures and temperatures.

When the actuator operates in still air, a quasi-2D vortex pair is generated due to the extreme shear at the edges of the fluid slug ejected during the blowing stage of each excitation cycle. The vorticity flux exiting the slot determines the resulting vortex-pair circulation. The threshold slot exit velocity, for the current configuration and operating conditions, determines if the vortices will be sucked into the actuator’s cavity or be released. Once released, the vortex convection speed approximately scales with the peak velocity at the slot exit. However, the normalised convection velocity increases with the slot Reynolds number.

When even a very short extension is attached to one ‘lip’ of the actuator exit, the jet is deflected in the direction opposite the extended lip, due to the restriction on the entrainment process. When long, one ‘lip’ extension is attached, such that the vortex pair is ejected parallel to a plate, the coherence of the vortices improve, their phase speed and magnitude decrease.

The effects of high-frequency excitation, ejected perpendicular to a wall into still air, were also investigated. It was found that the presence of the plate does not have a measurable effect on the wall normal excitation, indicating that the majority of the entrainment is taking place from the forward 180° of the actuator exit plane. When the slot is inclined to the surface at a shallow angle of 30 degrees, an unsteady wall jet is formed, transferring momentum along the wall. This is a direct result of the symmetry break, altering the relative magnitudes of the vortex pair.
Towards a silent aircraft
Authors: Dowling A.P. , Hynes T.
Published: February 2016

We set a target for a ‘Silent’ aircraft to be imperceptible outside the airfield perimeter in an urban environment, and then address conceptual designs to meet this requirement. Avoiding some traditional aircraft noise sources requires a radical rethink about the configuration. An all-lifting design has many benefits, enabling a closer integration of airframe and engine than the traditional ‘tube and wing’. Low-noise design includes taking advantage of shielding of engine noise by the airframe; low-noise engines with large, low speed jets; an order of magnitude increase in absorption by liners; and operations for low-noise informing the design. Progress to date on the Silent Aircraft Initiative is presented, along with some conceptual aircraft and engine designs. The further work needed to develop these into viable future aircraft is discussed.
Efficiency parameters for modern commercial aircraft
Authors: Nangia R. K.
Published: February 2016

Currently, there is great emphasis, worldwide, on environmental issues. This will have an impact on civil aircraft design, manufacture and operation.

Since the advent of the jet engine and swept wing aircraft, the trends have naturally tended towards greater productivity through increasing speed and payload. The cruise speed of conventional civil aircraft is unlikely to increase beyond current levels. Further increases in productivity are achieved by increasing payloads. This has led towards larger aircraft with the capability for increased ranges. It is shown that designing aircraft for longer ranges increases fuel burn significantly.

A series of aircraft operational parameters have been analysed. Selected data and established trends for current and future aircraft are presented. The data has been interpreted into efficiency terms, relating payload, range, fuel consumed and a measure of unit costs. It is shown that ‘value’ (cost) and noise effective efficiencies decrease dramatically with increasing range.

Environmental and economic considerations, in the future, may well demand greater efficiency in preference to productivity. One solution for long-range services is to use short-range hops. Another is via air-to-air refuelling. This will be addressed, in more detail, in a future paper.
Aerodynamic effectiveness of the flow of exhaust gases in a generic formula one car configuration
Authors: Parra F. L. , Kontis K.
Published: February 2016

The effects of the flow of exhaust gases intentionally orientated on the rear wing element of a generic Formula One car body have been studied. A qualitative analysis of the effectiveness of a cold nitrogen jet on a NACA 0012 type of aerofoil has been conducted. The Reynolds number of the jet was 13,000, based on the jet velocity and diameter, and of the bodywork was 54,000, based on the free stream velocity and bodywork length. The lift coefficient was measured via a three-component strain-gauge force balance at four different ground-to-aerofoil heights (32, 45, 60 and 90mm) and incidence range –20 to +20 degrees. The surface flow patterns were visualised using the oil flow technique and were compared with numerical simulations. Pressure measurements were conducted using pressure tappings. The CFD solver was FLUENT. The RNGk-ε model was selected to solve the turbulent flow transport equations. The numerical study also comprised the investigation of the aspiration generated by exhaust gases when these are ejected inside a duct of greater diameter. A parametric investigation relating the relative diameter of exhaust pipe and outer duct and the relative overlap between the sides of the duct and the exhaust pipe was performed.
Research initiatives for improving the safety of offshore helicopter operations
Authors: Howson D. A.
Published: February 2016

Since the late 1980s, the UK Civil Aviation Authority (CAA) has been leading a programme of research aimed at improving the safety of offshore helicopter operations. The motivation for this initiative came from a major joint CAA/Industry review of helicopter airworthiness, commissioned in 1982. This study led to a number of research projects and other reviews which, in turn, led to further research projects. A total of over 20 projects have been undertaken covering airworthiness and operational issues, and covering helicopters and helidecks. This programme of work has been jointly funded and monitored by the UK CAA-run Helicopter Safety Research Management Committee (HSRMC). This paper provides a top-level summary of current activities on the seven main ‘live’ research projects.
3D numerical simulation of the supersonic combustion of H2
Authors: Dinde Prashant , Rajasekaran A. , Babu V.
Published: February 2016

Results from numerical simulations of supersonic combustion of H2 are presented. The combustor has a single stage fuel injection parallel to the main flow from the base of a wedge. The simulations have been performed using FLUENT. Realisable k-ε model has been used for modelling turbulence and single step finite rate chemistry has been used for modelling the H2-Air kinetics. All the numerical solutions have been obtained on grids with average value for wall y+ less than 40. Numerically predicted profiles of static pressure, axial velocity, turbulent kinetic energy and static temperature for both non-reacting as well as reacting flows are compared with the experimental data. The RANS calculations are able to predict the mean and fluctuating quantities reasonably well in most regions of the flow field. However, the single step kinetics predicts heat release much more rapid than what was seen in the experiments. Nonetheless, the overall pressure rise in the combustor due to combustion is predicted well. Also, the k-ε model is not able to predict the fluctuating quantities in the base region of the wedge where there is strong anisotropy in the presence of combustion.
Waypoint navigation for a micro air vehicle using vision-based attitude estimation
Authors: Kehoe J. J. , Causey R. S. , Abdulrahim M. , Lind R.
Published: February 2016

Missions envisioned for micro air vehicles may require a high degree of autonomy to operate in unknown environments. As such, vision is a critical technology for mission capability. This paper discusses an autopilot that uses vision coupled with GPS and altitude sensors for waypoint navigation. The vision processing analyses a horizon to estimate roll and pitch information. The GPS and altitude sensors then command values to roll and pitch for navigation between waypoints. A flight test of a MAV using this autopilot demonstrates the resulting closed-loop system is able to autonomously reach several waypoints. The vehicle actually uses a telemetry link to a ground station on which all vision processing and related guidance and control is performed. Several issues, such as estimating heading to account for slow updates, are investigated to increase performance.
Rotorcraft simulation modelling and validation for control law design
Authors: Manimala B. J. , Walker D. J. , Padfield G. D. , Voskuijl M. , Gubbels A. W.
Published: February 2016

This paper describes the development and validation of a high fidelity simulation model of the Bell 412 helicopter for handling qualities and flight control investigations. The base-line model features a rigid, articulated blade-element formulation of the main rotor, with flap and lag degrees of freedom. The Bell 412 HP engine/governor dynamics are represented by a second-order system. Other key features of the base-line model include a finite-state dynamic inflow model and lag damper dynamics. The base-line model gives excellent agreement with flight-test data over the speed range 15-120kt for on-axis responses. Prediction of off-axis responses is less accurate. Several model enhancement options were introduced to obtain an improved off-axis response. It is shown that the pitch/roll off-axis responses in transient manoeuvres can be improved significantly by including wake geometry distortion effects in the Peters-He finite-state dynamic inflow model.
Design and performance of thin, circular arc, wind-tunnel turning vanes
Authors: Johl G. , Passmore M. , Render P.
Published: February 2016

Although test rig data exists for ¼ circle turning vanes, the actual performance of these vanes once installed in a wind tunnel, and the extent to which test rig results are replicated, is rarely known. This paper compares pressure loss coefficient and velocity profile data from a vane test module with measurements taken in the low speed wind tunnel described in Ref. 1.