bluuebunny/crossref_metadata_2025 huggingface dataset:
Thwarting location privacy protection in location‐based social discovery services
Authors: Xue Minhui , Liu Yong , Ross Keith W. , Qian Haifeng
Published: February 2016

Location‐based social discovery (LBSD) services enable users to discover their geographic neighborhoods to make new friends. Original LBSD services were designed to provide the exact distances to nearby users. It has been shown that it is easy to pinpoint any target user's location by using trilateration based on the exact distances from three fake Global Positioning System locations to the target user. To defend against the trilateration attack, contemporary LBSD services then began to report distances of nearby users in concentric bands, for example, bands of 100 meters, rather than exact distances. In this paper, we investigate the user location privacy leakage problem in LBSD services reporting distances in discrete bands. Using number theory, we analytically show that by strategically placing multiple virtual probes with fake Global Positioning System locations, one can nevertheless localize user locations in band‐based LBSD. Our methodology is guaranteed to localize any reported user within a circle of radius no greater than one meter, even for LBSD services using large bands (such as 100 m as used by WeChat). Eventually, countermeasures are proposed to reduce location privacy leakage to the very minimum. To the best of our knowledge, this is the first work that explicitly exploits and quantifies user location privacy leakage in band‐based LBSD services. We expect our study to draw more public attention to this serious privacy issue and expectantly motivate better privacy preserving LBSD designs. Copyright © 2016 John Wiley & Sons, Ltd.
Hartung–Knapp method is not always conservative compared with fixed‐effect meta‐analysis
Authors: Wiksten Anna , Rücker Gerta , Schwarzer Guido
Published: February 2016

A widely used method in classic random‐effects meta‐analysis is the DerSimonian–Laird method. An alternative meta‐analytical approach is the Hartung–Knapp method. This article reports results of an empirical comparison and a simulation study of these two methods and presents corresponding analytical results. For the empirical evaluation, we took 157 meta‐analyses with binary outcomes, analysed each one using both methods and performed a comparison of the results based on treatment estimates, standard errors and associated P‐values. In several simulation scenarios, we systematically evaluated coverage probabilities and confidence interval lengths. Generally, results are more conservative with the Hartung–Knapp method, giving wider confidence intervals and larger P‐values for the overall treatment effect. However, in some meta‐analyses with very homogeneous individual treatment results, the Hartung–Knapp method yields narrower confidence intervals and smaller P‐values than the classic random‐effects method, which in this situation, actually reduces to a fixed‐effect meta‐analysis. Therefore, it is recommended to conduct a sensitivity analysis based on the fixed‐effect model instead of solely relying on the result of the Hartung–Knapp random‐effects meta‐analysis. Copyright © 2016 John Wiley & Sons, Ltd.
Concise Review: Cell Therapies for Stroke and Traumatic Brain Injury: Targeting Microglia
Authors: Savitz Sean I. , Cox Charles S.
Published: February 2016

We present a model hypothesis of how several types of cell therapies may target microglia as one of the principal cell types contributing to the inflammatory response after brain injury and discuss how imaging of brain inflammation could potentially be applied to develop biomarkers in patients with stroke and TBI enrolled into stem cell clinical trials.
Channel modeling for visible light communications—a survey
Authors: Qiu Yang , Chen Hsiao‐Hwa , Meng Wei‐Xiao
Published: February 2016

Visible light communication (VLC) is a newly emerging technology, which integrates communications and lighting purposes, and has become a very active research topic in the areas of wireless communications. It is expected to become an important part of the next generation wireless communications because of its unique features in using unlicensed spectrum, support of high data rate, and its resistance to electromagnetic interferences. In this survey paper, we begin with a review on the basis of photometry, which is used to establish channel models of VLC systems. Then, we will continue to address various issues on the fundamental characteristic features of VLC systems, the impact of indoor environments on system performance, and the analysis and discussions of five different types of typical VLC channel models and other related parameters in VLC channel models. Finally, in terms of the future works, we will show the possible follow‐up research focuses and directions as an effort to identify some new research topics on VLCs. Copyright © 2016 John Wiley & Sons, Ltd.
GPS-Tracking in touristischen Destinationen – Neue Software-Anwendung zur Erfassung des Mobilitätsverhaltens am Beispiel von Wanderern im Harz
Authors: Groß Sven , Menzel Anne
Published: February 2016

There is a variety of quantitative and qualitative methods available to analyze the mobility behavior of people, and GPS tracking has evolved into a major tool to investigate tourism mobility behavior. For example, the use of GPS data loggers enables the recording and analysis of routes and time-space movements of participants. Through the combination of research tools, additional data can be collected, such as activities at the Point of Interest (PoI), motivations (e.g., for spending time at a specific PoI), demographic data and visitor satisfaction. An Android Application for tablets developed by the Harz University allows the link between complementary data-collection tools: GPS tracking and face-to-face surveys. The software GimToP (GTK) enables the researcher to collect data in-situ, and subsequently displays specific results (e.g., track, distance, breaks) in an interactive map. This way, respondents can be asked to provide data during their experience at various track points, which represents a new and significant tool to understand the mobility and space-time behavior of a variety of respondent groups, such as hikers, city tourists, as well as visitors of leisure facilities or tourist attractions. This presentation will introduce the most important goals and opportunities of this new software, underpinned by a case study presenting the used GTK for hikers in the Harz Mountains.
Periodontal disease's contribution to Alzheimer's disease progression in Down syndrome
Authors: Kamer Angela R. , Fortea Juan O. , Videla Sebastià , Mayoral Angela , Janal Malvin , Carmona‐Iragui Maria , Benejam Bessy , Craig Ronald G. , Saxena Deepak , Corby Patricia , Glodzik Lidia , Annam Kumar Raghava Chowdary , Robbins Miriam , de Leon Mony J.
Published: February 2016

People with Down syndrome (DS) are at an increased risk for Alzheimer's disease (AD). After 60 years of age, >50% of DS subjects acquire dementia. Nevertheless, the age of onset is highly variable possibly because of both genetic and environmental factors. Genetics cannot be modified, but environmental risk factors present a potentially relevant intervention for DS persons at risk for AD. Among them, inflammation, important in AD of DS type, is potential target. Consistent with this hypothesis, chronic peripheral inflammation and infections may contribute to AD pathogenesis in DS. People with DS have an aggressive form of periodontitis characterized by rapid progression, significant bacterial and inflammatory burden, and an onset as early as 6 years of age. This review offers a hypothetical mechanistic link between periodontitis and AD in the DS population. Because periodontitis is a treatable condition, it may be a readily modifiable risk factor for AD.
Subjective memory decline predicts greater rates of clinical progression in preclinical Alzheimer's disease
Authors: Buckley Rachel F. , Maruff Paul , Ames David , Bourgeat Pierrick , Martins Ralph N. , Masters Colin L. , Rainey‐Smith Stephanie , Lautenschlager Nicola , Rowe Christopher C. , Savage Greg , Villemagne Victor L. , Ellis Kathryn A. ,   AIBL study
Published: February 2016

Introduction

The objective of this study was to determine the utility of subjective memory decline (SMD) to predict episodic memory change and rates of clinical progression in cognitively normal older adults with evidence of high β‐amyloid burden (CN Aβ+).

Methods

Fifty‐eight CN Aβ+ participants from the Australian Imaging, Biomarkers, and Lifestyle study responded to an SMD questionnaire and underwent comprehensive neuropsychological assessments. Participant data for three follow‐up assessments were analyzed.

Results

In CN Aβ+, subjects with high SMD did not exhibit significantly greater episodic memory decline than those with low SMD. High SMD was related to greater rates of progression to mild cognitive impairment or Alzheimer's disease (AD) dementia (hazard ratio = 5.1; 95% confidence interval, 1.4–20.0, P = .02) compared with low SMD. High SMD was associated with greater depressive symptomatology and smaller left hippocampal volume.

Discussion

High SMD is a harbinger of greater rates of clinical progression in preclinical AD. Although SMD reflects broader diagnostic implications for CN Aβ+, more sensitive measures may be required to detect early subtle cognitive change.
Health-Related Quality of Life, Psychological Distress, and Sexual Changes Following Prostate Cancer: A Comparison of Gay and Bisexual Men with Heterosexual Men
Authors: Ussher Jane M. , Perz Janette , Kellett Andrew , Chambers Suzanne , Latini David , Davis Ian D. , Rose Duncan , Dowsett Gary W. , Williams Scott
Published: February 2016

Introduction

Decrements in health-related quality of life (HRQOL) and sexual difficulties are a recognized consequence of prostate cancer (PCa) treatment. However little is known about the experience of gay and bisexual (GB) men.

Aim

HRQOL and psychosexual predictors of HRQOL were examined in GB and heterosexual men with PCa to inform targeted health information and support.

Method

One hundred twenty-four GB and 225 heterosexual men with PCa completed a range of validated psychosexual instruments.

Main outcome measure

Functional Assessment of Cancer Therapy – Prostate (FACT-P) was used to measure HRQOL, with validated psychosexual measures, and demographic and treatment variables used as predictors.

Results

GB men were significantly younger (64.25 years) than heterosexual men (71.54 years), less likely to be in an ongoing relationship, and more likely to have casual sexual partners. Compared with age-matched population norms, participants in both groups reported significantly lower sexual functioning and HRQOL, increased psychological distress, disruptions to dyadic sexual communication, and lower masculine self-esteem, sexual confidence, and sexual intimacy. In comparison with heterosexual men, GB men reported significantly lower HRQOL (P = .046), masculine self-esteem (P < .001), and satisfaction with treatment (P = .013); higher psychological distress (P = .005), cancer related distress (P < .001) and ejaculatory concern (P < .001); and higher sexual functioning (P < .001) and sexual confidence (P = .001). In regression analysis, psychological distress, cancer-related distress, masculine self-esteem, and satisfaction with treatment were predictors of HRQOL for GB men (R2Adj = .804); psychological distress and sexual confidence were predictors for heterosexual men (R2Adj = .690).

Conclusion

These findings confirm differences between GB and heterosexual men in the impact of PCa on HRQOL across a range of domains, suggesting there is a need for GB targeted PCa information and support, to address the concerns of this “hidden population” in PCa care.
Beyond Anal Sex: Sexual Practices of Men Who Have Sex with Men and Associations with HIV and Other Sexually Transmitted Infections
Authors: Rice Cara E. , Maierhofer Courtney , Fields Karen S. , Ervin Melissa , Lanza Stephanie T. , Turner Abigail Norris
Published: February 2016

Introduction

Unprotected anal intercourse is often used as a single indicator of risky behavior in men who have sex with men (MSM), yet MSM engage in a variety of behaviors that have unknown associations with sexually transmitted infection (STI) and HIV.

Aim

To assess the prevalence of a wide range of sexual behaviors and their associations with prevalent STI and HIV.

Methods

We used a standardized, self-administered survey to collect behavioral data for this cross-sectional study of 235 MSM seeking care in a public clinic for sexually transmitted diseases.

Mean Outcome Measures

Using modified Poisson regression, we generated unadjusted and adjusted prevalence ratios (PRs) to characterize associations between recent participation in each behavior and prevalent STI and HIV.

Results

Participants' median age was 26 years. One third (35%) were positive for STI. STI prevalence was significantly associated with using sex slings (adjusted PR [aPR] = 2.35), felching (aPR = 2.22), group sex (aPR = 1.86), fisting (aPR = 1.78), anonymous sex (aPR = 1.51), and sex toys (aPR = 1.46). HIV prevalence was 17% and was significantly associated with fisting (aPR = 4.75), felching (aPR = 4.22), enemas (aPR = 3.65), and group sex (aPR = 1.92).

Conclusion

Multiple behaviors were significantly associated with prevalent STI and HIV in adjusted analyses. To provide a more comprehensive understanding of sexual risk in MSM, prospective studies are needed to examine whether these behaviors are causally associated with HIV and STI acquisition.
Triumphant memory of the perpetrators: Putin’s politics of re-Stalinization
Authors: Khapaeva Dina
Published: February 2016

In this article, I explore the interconnection between Putin’s politics of re-Stalinization, historical memory, and a specific version of the post-Soviet neo-medievalism. I show that re-Stalinization is a mass movement that is grounded in the unprocessed memory of Soviet crimes and atrocities. The popular myth of the “Great Patriotic War” and the myth of Stalinism as the Golden Age exploited by Putin’s memory politics became a gold mine for Putin’s kleptocracy. I argue that re-Stalinization and the Kremlin-sponsored ideology of Eurasianism represents two interrelated trends of a complex ideological process. Eurasianism combines Soviet denial of individuality with the idea of a state-dependent patriarchal society and Russian historical messianism. It glorifies the reign of Ivan the Terrible and Stalin. The ‘medievalist’ discourse of Eurasian ideologists, which advocates a return to the medieval society of orders, on the one hand, and the Gothic monsters populating post- Soviet film and fiction, on the other, creates a political language that expresses new attitudes to people in post-Soviet Russia. They depict a new social contract that reconsiders the modern concept of citizenship, and creates a social basis for the criminalization and militarization of Russian society.
Evolution of the rhytidectomy
Authors: Barrett Dane M. , Casanueva Fernando J. , Wang Tom D.
Published: February 2016

Since the advent of facelift surgery, there has been a progressive evolution in technique. Methods of dissection trended towards progressively aggressive surgery with deeper dissection for repositioning of ptotic facial tissues. In recent decades, the pendulum has swung towards more minimally invasive options. Likewise, there has been a shift in focus from repositioning alone to the addition of volumization for facial rejuvenation. The techniques in this article are reviewed in a chronologic fashion with a focus on historical development as well as brief discussion on efficacy in relation to the other existing options. There is currently no gold standard technique with a plethora of options with comparable efficacy. There is controversy over which approach is optimal and future research is needed to better delineate optimal treatment options, which may vary based on the patient.
Virtual manufacturing of composite aerostructures
Authors: D’Mello R. J. , Maiarù M. , Waas A. M.
Published: February 2016

The past century has witnessed the rise and maturity of the flying machine, starting with the Wright brothers flyer to today’s modern passenger aircrafts and warfighters. At the start of this century, yet another achievement in flying vehicle technology was seen with the launch of the Boeing 787 aircraft, which has a significant portion by weight of polymer matrix fibre composites. This paper, therefore, addresses the effects of the manufacturing process of fibre reinforced polymer matrix composites on mechanical performance. Computations are carried out using the Finite Element (FE) method at the microscale where Representative Volume Elements (RVEs) are analysed with Periodic Boundary Conditions (PBCs). Straight fibre pre-preg-based composites and textile composites are considered. The commercial code ABAQUS is used as the solver for the FE equations, supplemented by user-written subroutines. The transition from a continuum to damage/failure is effected by using the Bažant-Oh crack band model, which preserves mesh objectivity. Results are presented for RVEs that are first subjected to curing and subsequently to mechanical loading. The effect of the fibre packing randomness on the microstructure is examined by considering multifibre RVEs where fibre volume fraction is held constant but with random packing of fibres. Plain weave textile composites are also cured first and then subjected to mechanical loads. The possibility of failure is accommodated throughout the analysis – failure can take place during the curing process even prior to the application of in-service mechanical loads. The analysis shows the differences in both the cured RVE strength and stiffness, when cure-induced damage has and has not been taken into account.
Aircraft engines: a proud heritage and an exciting future
Authors: Parker R. , Fedder G.
Published: February 2016

The 150th anniversary of the Royal Aeronautical Society has seen Rolls-Royce become a global player in aerospace and a champion of British industry. Its products vary from the nimble RR300, powering two-seater helicopters, all the way to the 97,000-pound thrust Trent XWB, powering future variants of the Airbus A350, and the MT30, which provides the propulsion for the Royal Navy's new Queen Elizabeth class aircraft carriers. It has built this range of products derived from the vision and innovation of its talented engineers, spurred on by the guiding principles provided by Henry Royce. This has seen it through times of war, hardship, bankruptcy and fierce competition to emerge as the leading manufacturer of aircraft engines and a provider of power across land and sea. Alongside its products, it has developed pioneering services to support its customers, analysing real-time data to improve the reliability and efficiency of its engines. In keeping with its tradition of innovation, the company is continuing to develop new products and services for the next generation of power systems for land, sea and air.
Setting an Agenda for the Socio-Legal Study of Contemporary Buddhism
Authors: SCHONTHAL Benjamin , GINSBURG Tom
Published: February 2016

This introduction to the special issue on Buddhism and law lays out an agenda for the socio-legal study of contemporary Buddhism. We identify lacunae in the current literature and call for further work on four themes: the relations between monastic legal practice and state law; the formations of Buddhist constitutionalism; Buddhist legal activism and Buddhist-interest litigation; and Buddhist moral critiques of law. We argue that this agenda is important for advancing Buddhist studies and for the comparative study of law and legal institutions.
Engaging Active Bystanders in Mass Casualty Events and Other Life-Threatening Emergencies: A Pilot Training Course Demonstration
Authors: Smith Tracey O. , Baker Susan D. , Roberts Kathryn , Payne Skip A.
Published: February 2016

Emerging research indicates the critical role members of the public can play in saving lives and reducing morbidity at the scene in the immediate aftermath of a disaster. It is anticipated that with training, more members of the public will be ready and able to assist should they be present at mass casualty events or other circumstances in which there are serious injuries or potential loss of life. This article describes a training course developed by multiple federal and nonfederal partners aimed at preparing the public to become “active bystanders” followed by a pilot demonstration project conducted by Medical Reserve Corps Units. The outcomes of the project indicated that the training was comprehensive and appropriate for members of the public with little or no first aid knowledge. National availability of the “Becoming an Active Bystander” training course is currently being planned. (Disaster Med Public Health Preparedness. 2016;10:286–292).
Momentum transport in Taylor–Couette flow with vanishing curvature
Authors: Brauckmann Hannes J. , Salewski Matthew , Eckhardt Bruno
Published: February 2016

We numerically study turbulent Taylor–Couette flow (TCF) between two independently rotating cylinders and the transition to rotating plane Couette flow (RPCF) in the limit of infinite radii. By using the shear Reynolds number$Re_{S}$and rotation number$R_{{\it\Omega}}$as dimensionless parameters, the transition from TCF to RPCF can be studied continuously without singularities. Already for radius ratios${\it\eta}\geqslant 0.9$we find that the simulation results for various radius ratios and for RPCF collapse as a function of$R_{{\it\Omega}}$, indicating a turbulent behaviour common to both systems. We observe this agreement in the torque, mean momentum transport, mean profiles and turbulent fluctuations. Moreover, in TCF and RPCF for$R_{{\it\Omega}}>0$, the profiles in the central region are found to conform with inviscid neutral stability. Intermittent bursts, that have been observed in the outer boundary layer and have been linked to the formation of a torque maximum for counter-rotation, are shown to disappear as${\it\eta}\rightarrow 1$. The corresponding torque maximum disappears as well. Instead, two new maxima of different origin appear for${\it\eta}\geqslant 0.9$and RPCF, a broad and a narrow one, in contrast to the results for smaller${\it\eta}$. The broad maximum at$R_{{\it\Omega}}=0.2$is connected with a strong vortical flow and can be reproduced by streamwise-invariant simulations. The narrow maximum at$R_{{\it\Omega}}=0.02$only emerges with increasing$Re_{S}$and is accompanied by an efficient and correlated momentum transport by the mean flow. Since the narrow maximum is of larger amplitude for$Re_{S}=2\times 10^{4}$, our simulations suggest that it will dominate at even higher$Re_{S}$.
Numerical investigation of near-wake characteristics of cavitating flow over a circular cylinder
Authors: Gnanaskandan Aswin , Mahesh Krishnan
Published: February 2016

A homogeneous mixture model is used to study cavitation over a circular cylinder at two different Reynolds numbers ($Re=200$and 3900) and four different cavitation numbers (${\it\sigma}=2.0$, 1.0, 0.7 and 0.5). It is observed that the simulated cases fall into two different cavitation regimes: cyclic and transitional. Cavitation is seen to significantly influence the evolution of pressure, boundary layer and loads on the cylinder surface. The cavitated shear layer rolls up into vortices, which are then shed from the cylinder, similar to a single-phase flow. However, the Strouhal number corresponding to vortex shedding decreases as the flow cavitates, and vorticity dilatation is found to play an important role in this reduction. At lower cavitation numbers, the entire vapour cavity detaches from the cylinder, leaving the wake cavitation-free for a small period of time. This low-frequency cavity detachment is found to occur due to a propagating condensation front and is discussed in detail. The effect of initial void fraction is assessed. The speed of sound in the free stream is altered as a result and the associated changes in the wake characteristics are discussed in detail. Finally, a large-eddy simulation of cavitating flow at$Re=3900$and${\it\sigma}=1.0$is studied and a higher mean cavity length is obtained when compared to the cavitating flow at$Re=200$and${\it\sigma}=1.0$. The wake characteristics are compared to the single-phase results at the same Reynolds number and it is observed that cavitation suppresses turbulence in the near wake and delays three-dimensional breakdown of the vortices.
A multidisciplinary robust optimisation framework for UAV conceptual design
Authors: Van Nguyen N. , Lee J.-W. , Lee Y.-D. , Park H.-U.
Published: February 2016

This paper describes a multidisciplinary robust optimisation framework for UAV conceptual design. An in-house configuration designer system is implemented to generate the full sets of configuration data for a well-developed advanced UAV analysis tool. A fully integrated configuration designer along with the UAV analysis tool ensures that full sets of configuration data are provided simultaneously while the UAV configuration changes during optimisation. The computational strategy for probabilistic analysis is proposed by implementing a central difference method and fitting distribution for a reduced number of Monte Carlo Simulation sampling points. The minimisation of a new robust design objective function helps to enhance the reliability while other UAV performance criteria are satisfied. In addition, the fully integrated process and a probabilistic analysis strategy method demonstrate a reduction in the probability of failure under noise factors without any noticeable increase in design turnaround time. The proposed robust optimisation framework for UAV conceptual design case study yields a more trustworthy prediction of the optimal configuration and is preferable to the traditional deterministic design approach. The high fidelity analysis ANSYS Fluent 13 is performed to demonstrate the accuracy of proposed framework on baseline, deterministic and RDO configuration.
Simulation modelling of runway capacity for flight training airports
Authors: Cetek F. A. , Cetek C.
Published: February 2016

This study aims to develop a practical discrete-event simulation model to analyse the single runway capacity of airports serving training flights under various operational scenarios. The number of operations per hour, average airborne and ground delays, queue lengths and runway utilisation are selected as performance measures for the analysis. The simulation model has been developed in ARENA in order to obtain a practical yet accurate analysis. The model can contribute to the efficient use of runway capacity as well as effective planning of flight training at airports.
Investigation of flow asymmetry around axi-symmetric spiked blunt bodies in hypersonic speeds
Authors: Ahmed Mahmoud Y. M. , Qin N.
Published: February 2016

The assumption that a zero-incidence flow around bodies of revolution is axisymmetric has been broadly adopted by many researchers, even for cases where the flow around such bodies becomes unstable. In this study, the validity of this assumption is revisited using CFD simulation. As a case study, the simulations of both stable and unstable hypersonic flows around spiked blunt bodies in 2D axisymmetric and full 3D computational domains are compared. It is found that, for the stable flow cases, the main flow features are apparently axisymmetric and the assumption is generally acceptable. However, some degree of asymmetry can be observed inside the shear layer in the separated region, causing small variation in the drag coefficient. For the unstable flow cases, the asymmetry of the flow features is much more significant. More importantly, the assumption that the flow is axisymmetric is found to overestimate the level of flow unsteadiness. The amplitude of temporal drag variation as predicted by the axisymmetric solution is higher than that predicted by the full 3D solution.
Airspace sectorisation via a weighted graph model
Authors: Zhang D.F. , chen Y.Z.
Published: February 2016

With the development of air traffic, flight delays happen frequently due to bad weather and traffic congestion. The problem can be solved partly by certain strategies, such as changing air routes. However, rerouting leads to a global imbalance in controller workload of current sectors and to an increase in co-ordination workload, and the workloads of some sectors may be beyond the controller’s ability to manage. Thus, airspace sectorisation is expected to migrate from the current static sectors to dynamically-changing ones capable of adapting to traffic demand. Besides addressing imbalance and controlling the increase in workload, the sectorisation has to meet additional geometric constraints such as convexity, connectivity, and minimum distance constraint.
Computational aeroelastic analysis of slowed rotors at high advance ratios
Authors: de Montaudouin J. , Reveles N. , Smith M. J.
Published: February 2016

The aerodynamic and aeroelastic behaviour of a rotor become more complex as advance ratios increase to achieve high-speed forward fight. As the rotor blades encounter large regions of cross and reverse flows during each revolution, strong variations in the local Mach regime are encountered, inducing complex elastic blade deformations. In addition, the wake system may remain in the vicinity of the rotor, adding complexity to the blade loading. The aeroelastic behaviour of a model rotor with advance ratios ranging from 0·5 to 2·0 has been evaluated with aerodynamics provided via a computational fluid dynamics (CFD) method. Significant radial blade-vortex interaction can occur at a high advance ratio; the advance ratio at which this occurs is dependent on the rotor configuration. This condition is accompanied by high vibratory loads, peak negative torsion, and peak torsion and in-plane loads. The high vibratory loading increases the sensitivity of the trim model, so that at some high advance ratios the vibratory loads must be filtered to achieve a trimmed state.
Numerical investigation of separation pattern and separation pattern transition in overexpanded single expansion ramp nozzle
Authors: Yu Y. , Xu J. , Mo J. , Wang M.
Published: February 2016

Flow separation results in many problems to single expansion ramp nozzle (SERN) and hypersonic vehicle. However, little research has been conducted on the separation patterns and their effects on SERN’s performance. In the present paper, the numerical simulation is adopted to get the intuitive results and help to analyse the separation phenomena in SERN thoroughly. The main separation pattern is the restricted shock separation (RSS) in SERN, and the free shock separation (FSS) only appears in a small range of the nozzle pressure ratio (NPR), which is much different from the axisymmetric rocket nozzle. Further CFD results show that the separation pattern transition makes great effects on the performance of SERN, especially the lift. Moreover, the performance of SERN has an extreme in the separation pattern transition because of the main jet impinging on the expansion ramp. The transitions occur in both the startup and shutdown processes but the critical nozzle pressure ratios of the separation pattern transitions are different, which leads to a hysteresis loop of SERN performance.
Neurally-augmented immunity-based detection and identification of aircraft sub-system failures
Authors: Perhinschi M. G. , Moncayo H. , Wilburn B. , Wilburn J. , Karas O. , Bartlett A.
Published: February 2016

This paper presents the development and testing through simulation of an integrated scheme for aircraft sub-system failure detection and identification (FDI) based on the artificial immune system (AIS) paradigm augmented with artificial neural networks. The features that define the self within the AIS paradigm include neural estimates of the angular accelerations produced by the abnormal conditions. The simulation environment integrates the NASA Generic Transport Model interfaced with FlightGear. A hierarchical multi-self strategy was investigated for developing FDI schemes capable of handling malfunctions of a variety of aircraft sub-systems. The performance of the FDI scheme has been evaluated in terms of false alarms and successful detection and identification over a wide flight envelope and for several actuator and aerodynamic surface failures. For all cases considered, the performance was very good, confirming the potential of the AIS paradigm augmented with the proposed neural network-based approach for feature definition to offer a comprehensive solution to the aircraft sub-system FDI problem.
Scale effects on a single-element inverted wing in ground effect
Authors: Correia J. , Roberts L. S. , Finnis M. V. , Knowles K.
Published: February 2016

A study was conducted on a GA(W)-1 wing in order to investigate the effect of testing inverted wings in ground effect at low Reynolds numbers. The wing was tested at a range of ground clearances and Reynolds numbers and results showed that the wing’s performance was dependent on both these parameters. Surface flow-visualisation and numerical simulation results highlighted the existence of a laminar separation bubble on the wing’s suction surface. The results also indicated that both the bubble’s length and the onset of separation were sensitive to ground clearance and Reynolds number. Attempts were made to minimise the wing’s Reynolds number dependency by using transition strips on the suction surface. The transition strip results highlighted the influence that a laminar separation bubble has on the overall performance of the wing and how its presence alters the force enhancement and reduction mechanisms on an inverted wing in ground effect.
Riveted patch repairs for helicopter tail drive shafts with battle damage
Authors: Wang J. , Baker A. A. , Bitton D.
Published: February 2016

The ability to repair battle damage in a helicopter tail drive shaft (TDS) caused by small arms fire is a very important capability. A successful repair will enable the helicopter to continue its mission or at least allow it to return safely to base. This paper describes assessment of conventional and novel repair techniques using riveted metallic patches to restore the balance and strength of a damaged TDS. Analytical approaches are provided for the design of the repair. Modal analyses indicated that the effect of repair on change of the natural frequency of the TDS was negligible. An experimental testing program was conducted to validate the proposed repair methods. It has been demonstrated that the proposed repair methods achieved sufficient balance restoration by a defined repair procedure, assuming the unbalance could not be measured during a repair in the field. The conventional thin, single aluminium sheet, riveted repair significantly restored static strength. However, it only gave a fatigue life of 15hrs, and thus the repaired shaft may only be used for limited time for a military mission. The improved thick, two-half aluminium shell, riveted repair had sufficient static strength and met the 100-hour fatigue requirement.
Taranis and beyond: inspiring aerodynamic capability
Authors: Lee C.
Published: February 2016

In his 1916 book,Aircraft in Warfare, the Dawn of the Fourth Arm, F.W. Lanchester wrote:

“The supremacy of British aircraft can only be maintained by the adoption of a thoroughly progressive constructional policy, guided constantly by the most recent scientific discovery and research, and by utilising to the full information and experience gained in the Services.”

The recent successful flight trials of the Taranis low-observable unmanned demonstrator aircraft provide the latest evidence of the UK’s continued capacity for the entire design, development, manufacture, and flight testing of world-leading combat aircraft, particularly with regard to Aerodynamics. Taranis is both the culmination of many years’ research and development in the UK and a starting-point for the next generation of UK combat air systems.

In this lecture, Taranis is reviewed, in such detail as current sensitivities will allow, in the wider context of UK combat aircraft aerodynamic capability, exemplified by the leading roles taken by the UK in the Tornado and Typhoon programmes and the important contribution made to the development of the F-35 Lightning II Joint Strike Fighter.

The immediate technical challenges associated with the aerodynamic design and qualification of a low-observable air vehicle are considerable. In this instance they have been compounded by the balanced view taken within the project of trade-offs against many parameters. However, the UK aerodynamics community faces equally stringent challenges in terms of the identification and delivery of the most appropriate future systems; increasingly complex and demanding operational and functional requirements; and, perhaps most of all, maintaining an affordable and cost-effective capability in the face of strict budgetary pressures and austere economic conditions.

Nevertheless, those challenges are accompanied by a wide range of opportunities, namely for national and international partnership; radically innovative engineering solutions and approaches; new thinking; and the engagement of the best minds and ideas in the UK academic community.

Taranis represented a big integration task, requiring a particular set of skills to pull together the total package, resting on a bedrock of mastery of the technical issues. It has been an inspirational experience for those of us who have worked on it. It has demonstrated that the UK is capable of achieving the most demanding current and anticipated military aerodynamic requirements and has signposted the way to an exciting and nationally important future.
Diagonally dominant backstepping autopilot for aircraft with unknown actuator failures and severe winds
Authors: Ismail S. , Pashilkar A. A. , Ayyagari R. , Sundararajan N.
Published: February 2016

A novel formulation of the flight dynamic equations is presented that permits a rapid solution for the design of trajectory following autopilots for nonlinear aircraft dynamic models. A robust autopilot control structure is developed based on the combination of the good features of the nonlinear dynamic inversion (NDI) method, integrator backstepping method, time scale separation and control allocation methods. The aircraft equations of motion are formulated in suitable variables so that the matrices involved in the block backstepping control design method are diagonally dominant. This allows us to use a linear controller structure for a trajectory following autopilot for the nonlinear aircraft model using the well known loop by loop controller design approach. The resulting autopilot for the fixed-wing rigid-body aircraft with a cascaded structure is referred to as the diagonally dominant backstepping (DDBS) controller. The method is illustrated here for an aircraft auto-landing problem under unknown actuator failures and severe winds. The requirement of state and control surface limiting is also addressed in the context of the design of the DDBS controller.
On the compensation and damping of roll induced by wake vortices
Authors: Campos L. M. B. C. , Marques J. M. G.
Published: February 2016

The effect of the wake of a leading aircraft on a following aircraft is demonstrated by calculating the rolling motion consisting of three terms: (i) the free rolling motion due to initial bank angle and roll rate; (ii) the forced wake response due the rolling moment induced by the wake encounter; (iii) the forced control response due to aileron deflection to counter the wake vortex effects. It is shown that in the absence of control action, the roll rate of the following aircraft goes through a peak, and then decays, leading to a constant asymptotic bank angle; the latter is a measure of the magnitude of the wake effect, e.g. is larger for weaker damping. The exact analytical solution of the roll equation appears as a power series of a damping factor, whose coefficients are exponential integrals of time; it is shown that the first two terms give an accuracy better than 2%. The theory is used to simulate 15 combinations of wake vortex encounters between leading and following aircraft in the five ICAO/FAA weight categories: light, medium, heavy, special (B757) and very large (A380).
Vibration analyses of an equivalent plate wing with an external store
Authors: Na Y.-H. , Kim J.-H. , Shin S.-J.
Published: February 2016

Generally, pylon-mounted external stores significantly affect the aerodynamic characteristics of the aircraft due to their flexibility. Therefore, many investigations upon the dynamic and aeroelastic characteristics of an aircraft wing with external stores have been done over the last few decades Recently, a study was carried out regarding the aeroelastic effects on wings by the engine placement For severe operation conditions, classical linear theory with a small amount of amplitude vibration may not be an appropriate analysis. Nonlinear vibration analysis will be required, especially when the amplitude of the vibration is larger than the wing thickness. Chia performed static, dynamic, and post-buckling analyses of various isotropic and composite plates for that purpose. Dumir and Bhaskar derived finite element formulations to analyse the nonlinear vibration of beams and plates. Moreover, the variational-asymptotic plate formulation and the accompanying equations for the global analysis for the plates have been studied. That approach accounted every possible geometrical non-linearity associated with large displacement and small strain.
Progress in aerodynamic and aeroacoustic integration of CROR propulsion systems
Authors: Stuermer A. , Yin J. , Akkermans R.
Published: February 2016

Contra-Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as an economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the past five years, DLR’s Institute of Aerodynamics and Flow Technology has performed a number of numerical studies investigating important aspects relating to engine-airframe integration of CROR engines. In this article an overview of coupled aerodynamic and aeroacoustic simulations investigating representative pusher-configuration CROR engines will be given, focusing on the impact on aerodynamic performance and aeroacoustics caused by the presence of a pylon, the potential for noise reduction by employing trailing-edge blowing at the pylon trailing edge as well as the performance and noise variations caused by different senses of rotation of the rotors. It is shown that the interaction with the pylon strongly impacts blade performance and front rotor noise emissions but that the use of active flow control in the form of pylon trailing-edge blowing can alleviate these adverse installation effects to a notable extent.
Performance prediction and progress towards multi-disciplinary design of contra-rotating open rotors
Authors: Guérin S. , Schnell R. , Becker R. G.
Published: February 2016

At DLR’s Institute of Propulsion Technology, the prediction tools and multi-disciplinary optimisation strategies developed for turbofan engines have been extended to contra-rotating open rotors (CROR). Thereby the objective has been to appraise and improve the performance of CROR engines and thus to reduce their environmental impact. The present paper reviews the intermediate progress achieved in this scope. The prediction is based on analytical and CFD methods and covers the fields of engine performance analysis, aerodynamics and acoustics. The aerodynamic and acoustic results could be partly validated through the comparison to experimental data obtained from wind-tunnel tests. In a multi-disciplinary approach the aforementioned aspects are optimised together. First results of an aero-acoustic optimisation are presented. Furthermore this paper undertakes some comparison between high-bypass ratio turbofan engines and open-rotor concepts.
Progress in open rotor propulsors: The FAA/GE/NASA open rotor test campaign
Authors: Van Zante D. E. , Collier F. , Orton A. , Khalid S. Arif , Wojno J. P. , Wood T. H.
Published: February 2016

Model scale tests of modern ‘open rotor’ propulsor concepts that have potential for significant fuel burn reduction for aircraft applications were completed at NASA Glenn Research Center. The recent test campaign was a collaboration between NASA, FAA, and General Electric (GE). GE was the primary industrial partner, but other organisations were involved such as Boeing and Airbus who provided additional hardware for fuselage simulations. The open rotor is a modern version of the UnDucted Fan (UDF®) that was flight tested in the late 1980s through a partnership between NASA and GE. The UDF® was memorable for its scimitar shaped propeller blades and its unique noise signature. Design methods of the time were not able to optimise for both high aerodynamic efficiency and low noise simultaneously. Contemporary CFD/CAA based design methods can produce open rotor blade designs that maintain efficiency with acceptable acoustic signatures. Tests of two generations of new open rotor designs were conducted in the 9’ × 15’ Low Speed Wind Tunnel and the 8’ × 6’ Supersonic Wind Tunnel starting in late 2009 and completed in early 2012. Aerodynamic performance and acoustic data were obtained for take-off, approach and cruise conditions in isolated and semi-installed configurations. Additional detailed flow diagnostic measurements and acoustic measurements, including canonical shielding configurations, were obtained by NASA. NASA and GE conducted joint systems analysis to evaluate the performance of the new blade designs on a Boeing 737 class aircraft. The program demonstrated a 2-3% improvement in overall net efficiency relative to the best efficiency designs of the 1980s while nominally achieving 15-17 EPNdB noise margin to Chapter 4 (at a Technology Readiness Level of 5) for a notional aircraft system defined by NASA.
Conceptual stage separation from widebody subsonic carrier aircraft for space access
Authors: Mehta U. , Bowles J. , Pandya S. , Melton J. , Huynh L. , Kless J. , Hawke V.
Published: February 2016

Stage separation is a critical technical issue for developing two-stage-to-orbit (TSTO) launch systems with widebody carrier aircraft that use air-breathing propulsion and launch vehicle stages that use rocket propulsion. During conceptual design phases, this issue can be addressed with a combination of engineering methods, computational fluid dynamics simulations, and trajectory analysis of the mated system and the launch vehicle after staging. The outcome of such analyses helps to establish the credibility of the proposed TSTO system and formulate a ground-based test programme for the preliminary design phase. This approach is demonstrated with an assessment of stage separation from the shuttle carrier aircraft. Flight conditions are determined for safe mated flight, safe stage separation, and for the launch vehicle as it commences ascending flight. Accurate assessment of aerodynamic forces and moments is critical during staging to account for interference effects from the proximities of the two large vehicles. Interference aerodynamics have a modest impact on the separation conditions and separated flight trajectories, but have a significant impact on the interaction forces.