bluuebunny/crossref_metadata_2025 huggingface dataset:
On mechanisms that determine synoptic time scale convection over East Africa
Authors: Mekonnen Ademe , Thorncroft Chris D.
Published: February 2016

This study explores potential mechanisms to explain the marked synoptic scale variability in convection seen over East Africa during the July–September season. Regression composites based on analysis of 22 years of brightness temperature and reanalysis datasets highlights a complicated evolution for this synoptic convection. Active convection in the region is typically preceded by a coherent eastward moving convective signal that is followed by a period with a prominent westward moving convective signal away from the region. Results suggest that this sequence is associated with eastward propagation of convectively coupled Kelvin waves (CCKWs) that subsequently trigger westward‐moving African easterly waves (EWs). Results also indicate that synoptic convection in the East African region is impacted by westward moving upper tropospheric EWs originating on the tropical easterly jet in the South Asian region. These upper EWs propagate through East Africa with about a 4‐day period, consistent with the synoptic convection variability observed over East Africa. Consistent with local forecaster experience, analysis of the regional spatial patterns of convection and associated moisture flux convergence show that a coherent signal propagates northeastwards from the equatorial Congo region to East Africa on synoptic timescales. The evolution resembles the CCKW‐associated signal suggesting that CCKWs contribute to this synoptic variability.
Does microscopically involved margin increase disease recurrence after curative surgery in papillary thyroid carcinoma?
Authors: Lang Brian Hung‐Hin , Shek Tony W.H. , Wan Koon Yat
Published: February 2016

Background

The prognostic significance of microscopically involved margin in papillary thyroid carcinoma (PTC) following curative surgery remains unclear. We aimed to evaluate the impact of an involved margin and its location (anterior vs. posterior) on disease recurrence.

Methods

Of the 638 eligible patients, 538 (85.9%) did not have an involved margin (group I) while 100 (14.1%) did (group II). The latter group was further classified according to its location relative to the surface of the thyroid gland (anterior or posterior). A multivariate analysis was conducted to identify independent factors for recurrence risk.

Results

After a mean of 130.1 ± 93.5 months, 22 patients had disease recurrence. The 10‐year disease‐free survival (DFS) was significantly worse in group II (95.0% vs. 97.0%, P = 0.011). After adjusting other significant factors, involved margin was not an independent risk factor for disease recurrence (P = 0.358). Compared to a negative margin, an anterior involved margin did not pose increased recurrence risk (HR = 1.21, 95%CI = 0.93–500.00, P = 0.368), whereas a posterior involved margin had almost 23 times higher recurrence risk (HR = 22.95; 95%CI = 4.33–121.70, P < 0.001).

Conclusions

Overall, a microscopically involved margin was not an independent factor for DFS. However, although an anterior involved margin itself did not increase disease recurrence, a posterior involved margin did. J. Surg. Oncol. 2016;113:635–639. © 2016 Wiley Periodicals, Inc.
Identification, characterization, and high‐performance liquid chromatography quantification of process‐related impurities in vonoprazan fumarate
Authors: Liu Lei , Cao Na , Ma Xingling , Xiong Kaihe , Sun Lili , Zou Qiaogen
Published: February 2016

High‐performance liquid chromatography analysis of vonoprazan fumarate, a novel proton pump inhibitor drug revealed six impurities. These were identified by liquid chromatography with mass spectrometry. Further, the structures of the impurities were confirmed by synthesis followed by characterization by mass spectrometry, NMR spectroscopy, and infrared spectroscopy. On the basis of these data and knowledge of the synthetic scheme of vonoprazan fumarate, the previously unknown impurity was identified as 1‐[5‐(2‐fluorophenyl)‐1‐(pyridin‐3‐ylsulfonyl)‐1H‐pyrrol‐3‐yl]‐N‐methyldimethylamine, which is a new compound. The possible mechanisms by which these impurities were formed were also discussed. A high‐performance liquid chromatography method was optimized in order to separate, selectively detect, and quantify all process‐related impurities of vonoprazan fumarate. The presented method has been validated in terms of linearity, limits of detection, and quantification, and response factors and, therefore, is highly suitable for routine analysis of vonoprazan fumarate related substances as well as stability studies.
The epidemiology of the human papillomavirus related to oropharyngeal head and neck cancer
Authors: Gooi Zhen , Chan Jason Y. K. , Fakhry Carole
Published: February 2016

Objective

To summarize the epidemiology of human papillomavirus (HPV)‐related oropharyngeal squamous cell carcinomas (OSCC).

Data Sources

Articles in the English language referenced in MEDLINE/PubMed from the year 2000 onward.

Review Methods

Relevant articles pertaining to the epidemiology of HPV‐related OSCC were selected for review, with a particular preference for articles from 2008 onward.

Results

The incidence of HPV‐related OSCC continues to increase in North America and Western Europe, with up to 70% of new oropharyngeal cancer cases being attributed to HPV, whereas data from the developing world remain lacking. There is evidence to support distinct risk factors for HPV‐related OSCC as compared with HPV‐unrelated OSCC. The long‐term natural history of HPV infections remains unknown. HPV‐related OSCC are associated with an improved prognosis both at the time of primary diagnosis and disease progression. There is preliminary evidence to show that HPV vaccination initiatives are effective in preventing HPV cervical infections, although data related to oral HPV infections are lacking.

Conclusion

The epidemiology of HPV‐related OSCC is evolving. Further efforts are needed to characterize the natural history of oral HPV infection and its relationship with the eventual development of HPV‐associated OSCC to develop effective tools for secondary prevention.

Level of Evidence

NA Laryngoscope, 126:894–900, 2016
Impaired Left Ventricular Reserve in Childhood Cancer Survivors Treated With Anthracycline Therapy
Authors: Kaneko Sachie , Tham Edythe B. , Haykowsky Mark J. , Spavor Maria , Khoo Nee S. , Mackie Andrew S. , Smallhorn Jeffrey F. , Thompson Richard B. , Nelson Michael D.
Published: February 2016

Background

Childhood cancer survivors show evidence of diffuse myocardial fibrosis that is related to exercise capacity. The mechanism of reduced exercise tolerance in anthracycline cardiotoxicity remains unclear. We explored the determinants of exercise intolerance by evaluating left ventricular (LV) distensibility and functional reserve.

Methods

Patients (n = 22) and healthy controls (n = 10) underwent two‐dimensional echocardiography while supine, upright, and during cycle exercise. LV distensibility was measured as the change in end‐diastolic cavity area (EDCA) from supine to the upright position. LV functional reserve was assessed during peak exercise, and measured as the exercise‐induced change in systolic circumferential strain rate (SR) and early‐diastolic SR (EDSR). The peak rate of oxygen consumption was measured by indirect calorimetry.

Results

Median age of patients was 16 years (range 8–19) and controls 14 years (range 8–19). Median time since anthracycline therapy was 6 years (range 2–16). Peak oxygen consumption was significantly lower in patients compared to controls (35 ml/kg/min [28–60] vs. 45 ml/kg/min [44–53], P = 0.005). Transitioning from the supine position to the upright position caused a similar reduction in LV EDCA, suggesting similar LV distensibility between patients (–22% [–46 to –4]) and controls (–20% [–46 to –3], P = 0.3). However, during exercise, both systolic SR and EDSR reserve were significantly impaired in patients (∆SR: 93% [14–308], ∆EDSR: –4.5% [–88 to 121]) compared to controls (∆SR: 128% [54–230], P = 0.046; ∆EDSR: 74% [22–234], P = 0.02).

Conclusions

Our findings suggest that impaired LV contractility and functional reserve play a role in the reduced exercise capacity in anthracycline cardiotoxicity rather than LV distensibility.
Incidental detection of familial APP duplication: an unusual reason for a false positive NIPT result of trisomy 21
Authors: Meschino Wendy S. , Miller Kristen , Bedford H. Melanie
Published: February 2016

What's Already Known About This Topic?

Incidental findings such as maternal malignancies and maternal chromosome abnormalities, in particular sex chromosome mosaicism, have been detected by NIPT, but there are no previous reports of detection of late‐onset single gene disorders for the fetus and/or mother.

What Does This Study Add?

This report highlights the potential for NIPT to predict late-onset genetic conditions for both fetus and mother.
Prenatal prediction of neonatal death in single ventricle congenital heart disease
Authors: Lee Seung Mi , Kwon Jeong Eun , Song Sang Hoon , Kim Gi. Beom , Park Jung Yeon , Kim Byoung Jae , Lee Joon Ho , Park Chan‐Wook , Park Joong Shin , Jun Jong Kwan
Published: February 2016

Objective

The objective of this study was to determine whether prenatal ultrasound findings and cord blood N‐terminal pro‐B‐type natriuretic peptide (NT pro‐BNP) and cardiac troponin T (cTnT) can predict neonatal mortality in single ventricle congenital heart disease.

Methods

The association between neonatal mortality and prenatal ultrasound findings/cord blood biomarkers was evaluated in neonates delivered with a diagnosis of single ventricle congenital heart disease. The presence of prenatal ultrasound findings suggesting systemic outflow obstruction (ascending aorta <2.5 percentile) or ventricular dysfunction (the presence of cardiomegaly or hydrops) was evaluated, and the total number of abnormal findings was converted to a numeric score called the ‘single ventricle score’. In addition, NT pro‐BNP and cTnT were measured in cord blood taken at the time of delivery.

Results

A total of 48 cases of single ventricle congenital heart disease were included. The rate of neonatal mortality was 31% (15/48). The presence of either abnormal ultrasound findings(single ventricle score ≥ 2) or elevated concentrations of NT pro‐BNP or cTnT was associated with increased risk of neonatal death.

Conclusion

The presence of either abnormal prenatal ultrasound findings or increased cord blood NT pro‐BNP and cTnT concentrations was associated with the risk of neonatal death in single ventricle congenital heart disease. © 2016 John Wiley & Sons, Ltd.
Carrying out a structured medication review
Authors: Coane Sharon , Payne Rosalyne
Published: February 2016

As part of our series on the NICE guideline on Medicines Optimisation, Sharon Coane and Rosalyne Payne discuss the NICE recommendations relating to medication review and how to put these into practice effectively.
Topical treatments for scalp psoriasis: evidence‐based guide
Authors: Jheeta Anup , Fawcett Joanna M , de Berker David
Published: February 2016

Scalp psoriasis can significantly affect quality of life and its treatment presents unique challenges. This article provides an overview of the evidence‐based management of scalp psoriasis in primary care, with an emphasis on topical treatments.
A New Nonparametric Control Chart for Monitoring Variability
Authors: Zhou Maoyuan , Zhou Qin , Geng Wei
Published: February 2016

Statistical process control is widely used in industrial processes, service fields, among others. While parametric control charts are useful in certain processes, there is often a lack of enough knowledge about the process distribution. So, nonparametric control charts are needed in such situations. This paper develops a new nonparametric control chart based on the Ansari–Bradley nonparametric test and the effective change point model. Simulation results show that our proposed control chart is superior to other nonparametric control charts in monitoring process variability for most cases. Our proposed control chart is easy in computation, and powerful for monitoring process variability. Copyright © 2016 John Wiley & Sons, Ltd.
Die großen Apophysen
Authors: Heimkes B.
Published: February 2016

Hintergrund

Apophysen und Apophysenfugen unterscheiden sich in ihrem Aufbau nicht wesentlich von Epiphysen und Epiphysenfugen, im Gegensatz zu diesen tragen sie jedoch nicht zum Längenwachstum der Extremitäten bei. Sie sind den jeweilig benachbarten Gelenken zugeordnet. Das apophysäre Wachstum bestimmt hierbei Hebellängen und beeinflusst die Gelenkform und -struktur. Der formative Reiz hierzu geht von Muskeln aus, die sehnig an den Apophysen inserieren oder diese überwölben.

Apophyse des Trochanter major

Die Apophyse des Trochanter major trägt wesentlich zur Kraftarmlänge des Hüftgelenkes bei. Ihre Wachstumsleistung bestimmt, ob sich der Schenkelhals valgisch oder varisch entwickelt, letztendlich hängt davon auch ab, ob eine Hüfte dezentriert oder nicht.

Tibiaapophyse

Die Tibiaapophyse gibt vor, wie stark das Tibiaplateau nach ventral oder dorsal geneigt ist (tibialer Slope) und beeinflusst somit die sagittale Stabilität des Kniegelenkes. Ist sie verletzt, dann entwickelt sich ein schwierig zu behandelndes Genu recurvatum.

Calcaneusapophyse

Die Calcaneusapophyse gibt die Länge und Stellung des Fersenbeines vor und trägt hiermit entscheidend zum Drehmoment des oberen Sprunggelenkes bei.

Zusammenfassend lässt sich sagen, dass Apophysen als Stellschrauben angesehen werden können, welche das Wachstum, die Form und Struktur ihrer benachbarten Gelenke lenken.
A randomized trial to assess the efficacy of a psychoeducational intervention on caregiver burden in schizophrenia
Authors: Martín-Carrasco M. , Fernández-Catalina P. , Domínguez-Panchón A.I. , Gonçalves-Pereira M. , González-Fraile E. , Muñoz-Hermoso P. , Ballesteros J. ,   the EDUCA-III group
Published: February 2016

Background

Patient's relatives usually care for patients with schizophrenia, and as informal caregivers they experience negative consequences. The aim of the EDUCA-III trial is to test the efficacy of a psychoeducational intervention program (PIP) versus standard care to reduce the caregiver burden at post-intervention (4 months), and at follow-up (8 months).

Method

A two-arm, evaluator blind, multicentre, randomized controlled trial. The PIP group had 12 weekly group sessions. The control intervention group had the usual support and standard care. Primary outcomes were change scores since baseline on the Zarit Burden Interview (ZBI) and the Involvement Evaluation Questionnaire (IEQ).

Results

One hundred and nine caregivers were randomized to PIP and 114 to control condition from 23 research sites. The decrease of ZBI scores was significantly higher on the PIP arm at 4 months (mean difference [MD] = −4.33; 95% CI −7.96, −0.71), and at 8 months (MD = −4.46; 95% CI −7.79, −1.13). There were no significant decreases in the IEQ scores (MD at 4 months = −2.80; 95% CI −6.27, 0.67; MD at 8 months = −2.85; 95% CI −6.51, 0.81).

Conclusions

The PIP condition seems to reduce caregiver burden.

Trial registration

ISRCTN32545295.
Active flow control for high lift with steady blowing
Authors: Radespiel R. , Burnazzi M. , Casper M. , Scholz P.
Published: February 2016

The general picture of research in active flow control for aircraft applications has been continuously changing over the last 20 years. Researchers can now obtain design sensitivities by using numerical flow simulations, and new optical experimental methods can be used that measure flow field data non-intrusively in planes and volumes. These methodological advances enabled significant knowledge increase. The present paper reviews recent progress in active flow control by steady blowing. It appears that two strategies of blowing deserve particular attention. The first uses tangential blowing of thin wall jets to overcome the adverse pressure gradients from locally very large flow turning rates. This approach exploits the potentials of the Coanda effect. The second strategy employs oblique blowing of air jets designed to generate longitudinal vortices in the boundary layer. The longitudinal vortices provide convective redistribution of momentum in the boundary layer, and they also enhance turbulent momentum transport. The sensitivities of these two approaches as observed in fundamental flow investigations and in applications to high-lift aerofoils are described and suited efficiency parameters of blowing are analysed.
Space in 150 years: from Fantasy through fiction to fact and function
Authors: Southwood D.
Published: February 2016

In the last century and a half, space has moved from the realm of fantasy to everyday reality. In parallel, the way space has been regarded by the person in the street and the ideas of what access to space might be used for have evolved extraordinarily.
At the intersection of lay and professional social networks: how community ties shape perceptions of mental health treatment providers
Authors: Perry B. L. , Pullen E. , Pescosolido B. A.
Published: February 2016

Background.

The therapeutic alliance is a critical determinant of individuals’ persistence and outcomes in mental health treatment. Simultaneously, individuals’ community networks shape decisions about whether, when, and what kind of treatment are used. Despite the similar focus on social relationship influence for individuals with serious mental illness, each line of research has maintained an almost exclusive focus on either ‘inside’ (i.e. treatment) networks or ‘outside’ (i.e. community) networks, respectively.

Method.

For this study, we integrate these important insights by employing a network-embedded approach to understand the therapeutic alliance. Using data from the Indianapolis Network Mental Health Study (INMHS, n = 169, obs = 2206), we target patients experiencing their first major contact with the mental health treatment system. We compare patients’ perceptions of support resources available through treatment providers and lay people, and ask whether evaluations of interpersonal dimensions of the therapeutic alliance are contingent on characteristics of community networks.

Results.

Analyses reveal that providers make up only 9% of the whole social network, but are generally perceived positively. However, when community networks are characterized by close relationships and frequent contact, patients are significantly more likely to report that treatment providers offer useful advice and information. Conversely, when community networks are in conflict, perceptions of treatment providers are more negative.

Conclusion.

Community-based social networks are critical for understanding facilitators of and barriers to effective networks inside treatment, including the therapeutic alliance. Implications for community-based systems of care are discussed in the context of the USA and global patterns of deinstitutionalization and community reintegration.
Infections in Australian Aged-Care Facilities: Evaluating the Impact of Revised McGeer Criteria for Surveillance of Urinary Tract Infections
Authors: Bennett Noleen J. , Johnson Sandra A. , Richards Michael J. , Smith Mary A. , Worth Leon J.
Published: February 2016

Our survey of 112 Australian aged-care facilities demonstrated the prevalence of healthcare-associated infections to be 2.9%. Urinary tract infections (UTIs) defined by McGeer criteria comprised 35% of all clinically defined UTIs. To estimate the infection burden in these facilities where microbiologic testing is not routine, modified surveillance criteria for UTIs are necessary.

Infect Control Hosp Epidemiol 2016;37:610–612
Reduced order system identification for UAVs
Authors: Jameson P-D. , Cooke A. K.
Published: February 2016

Reduced order models representing the dynamic behaviour of symmetric aircraft are well known and can be easily derived from the standard equations of motion. In flight testing, accurate measurements of the dependent variables which describe the linearised reduced order models for a particular flight condition are vital for successful system identification. However, not all the desired measurements such as the rate of change in vertical velocity (Ẇ) can be accurately measured in practice. In order to determine such variables two possible solutions exist: reconstruction or differentiation. This paper addresses the effect of both methods on the reliability of the parameter estimates. The methods are used in the estimation of the aerodynamic derivatives for the Aerosonde UAV from a recreated flight test scenario in Simulink. Subsequently, the methods are then applied and compared using real data obtained from flight tests of the Cranfield University Jetstream 31 (G-NFLA) research aircraft.
Fixed-wing approach techniques for complex environments
Authors: Thomas P. R. , Bullock S. , Bhandari U. , Richardson T. S.
Published: February 2016

The landing approach for fixed-wing small unmanned air vehicles (SUAVs) in complex environments such as urban canyons, wooded areas, or any other obscured terrain is challenging due to the limited distance available for conventional glide slope descents. Alternative approach methods, such as deep stall and spin techniques, are beneficial for such environments but are less conventional and would benefit from further qualitative and quantitative understanding to improve their implementation. Flight tests of such techniques, with a representative remotely piloted vehicle, have been carried out for this purpose and the results are presented in this paper. Trajectories and flight data for a range of approach techniques are presented and conclusions are drawn as to the potential benefits and issues of using such techniques for SUAV landings. In particular, the stability of the vehicle on entry to a deep stall was noticeably improved through the use of symmetric inboard flaps (crow brakes). Spiral descent profiles investigated, including spin descents, produced faster descent rates and further reduced landing space requirements. However, sufficient control authority was maintainable in a spiral stall descent, whereas it was compromised in a full spin.
A hybrid approach for aircraft fault diagnosis based on fault inference and fault identification
Authors: Liu X. , Liu Z.
Published: February 2016

A cockpit instrumentation system provides various elements of information for pilots. However, logical inference based on a cockpit instruments fault tree (FT) and reliability sometimes cannot give a correct diagnosis of failures. In addition, in flight control systems (FCS), a fault identification method based on the multiple-model (MM) estimator cannot find the basic fault cause. To deal with these problems, a hybrid approach which is capable of integrating inference and fault identification is proposed. In this approach, the event nodes of the FT which have correlations to the FCS are separated into modules. Each module corresponds to a fault mode of the FCS. To use these correlations, fault inference and the MM estimator can share fault diagnosis information. Simulation results show that the proposed approach is helpful in detecting the root cause of failure and is more correct than single fault diagnosis method.
An analysis approach toward FAA certification for damage tolerance of aircraft components
Authors: Abdi F. , Xue Y. , Garg M. , Farahmand B. , Housner J. , Nikbin K.
Published: February 2016

This paper presents a novel analysis approach by considering multiple crack interaction in achieving FAA certification for durability and damage tolerance of exterior attachment installations on an aircraft fuselage according to FAA policy on Certification by Analysis-Supported-by-Test (CAST). Durability and damage tolerance evaluation of an aircraft component requires assessment of damage initiation and fatigue crack propagations under service loading, which consists of complex loading types, paths and variable amplitudes. Both simulation and service experience showed that multiple cracks developed in the fuselage skin and doublers that are made of wrought aluminum alloys. Progressive failure analysis (PFA) tool was used to simulate the fatigue damage initiation life using a scale-down stress-life property. A virtual crack closure technique (VCCT) was implemented to evaluate fatigue crack growth with interactions between cracks from different parts in a component, which preserves conservativeness. The fatigue crack growth data is obtained uniquely from an analytical extension of fatigue crack growth data of thin aluminum sheet. Fatigue crack growth analysis showed that only a few initiated cracks propagated steadily before a crack became visible under inspection, which was validated by comparison to service history. Eventually one crack became dominate in the fracturing process thereby setting an inspection time. Analysis also showed that fatigue damage state in the components at the designed operational life will not exceed the static safety requirements. Therefore, FAA accepted the damage tolerance analysis and the aircraft retained certification with no need for repair.
Topology optimisation via the moving iso-surface threshold method: implementation and application
Authors: Vasista S. , Tong L.
Published: February 2016

Topology optimisation is a useful tool for the design of aircraft structures. This work details how the new moving iso-surface threshold (MIST) topology optimisation method works and how it can be applied to aircraft structural design. This method has been coupled with commercial finite element analysis software in a simple manner without requiring the modification of the commercial software source code. In this way the user is able to take advantage of the finite element analysis tools such as automatic mesh generation and efficient solving. The extension of the method to 3D designs is also presented. The topology results of a 2D leading-edge rib for stiffness, stress and morphing objectives and a 3D wing skin stringer for stress design demonstrate the functionality of this method.
Improved sliding mode guidance law based on fuzzy variable coefficients strategy
Authors: Xiong J.H. , Tang S.J. , Guo J. , Wang T.N.
Published: February 2016

An adaptive sliding mode guidance law guiding the line-of-sight angular rate to converge to zero was highly appraised. However, compared with the conventional proportional navigation law, adaptive sliding mode guidance law leads to large acceleration demand of the interceptor before the line-of-sight angular rate converging to zero, especially in a situation where the target has strong manoeuvrability as well as high velocity. In this paper, a strategy making the coefficients of the guidance law vary according to a fuzzy rule is proposed. Smaller guidance coefficients are selected at the beginning of the terminal guidance. Therefore, the guidance command is reduced and a smaller acceleration of the interceptor is incurred. As the coefficients grow to the fixed and desired values, the line-of-sight angular rate converges to zero rapidly, so that the convergence to the sliding surface is guaranteed. It is concluded that the fuzzy variable coefficients strategy is highly effective for tail-chase, head-on interception and head pursuit engagements as shown in the simulations.
Evaluating a set of stall recovery actions for single engine light aeroplanes
Authors: Gratton G. B. , Hoff R. I. , Rahman A. , Harbour C. , Williams S. , Bromfield M.
Published: February 2016

This paper considers four alternative sets of actions that a pilot may use to recover an aeroplane from the stall. These actions: those published by the UK CAA and the US FAA, as well as a power delayed sequence and a pitch delayed sequence, were evaluated on 14 single engine piston aeroplane types. In a limited number of types (five in cruise configuration, two in landing configuration) the pitch delayed recovery gave a safe response and least height loss, but in a greater number of types (six and eight in cruise and landing configurations respectively) it resulted in further post-stall uncommanded motion. The other sets of actions all gave a consistent recovery from the stall, but the least height loss in recovery was also consistently the CAA sequence of simultaneous full power and nose-down pitching input, which normally resulted in approximately two thirds the height loss of the FAA’s pitch first then power method, which in turn resulted in about 90% of the height loss of the trialled power delayed recovery. Additionally the CAA recovery gave the least variation in height loss during stall recovery. It was also found that all of the aeroplane types evaluated except for one microlight aeroplane of unusual design, displayed a pitch-up with increased power in the normal (pre-stall) flight regime. Reducing this to separate components it was therefore shown that pitch control is of primary importance and should be used to provide immediate stall recovery. The thrust control can additionally be used as early as possible to minimise height loss, but if the thrust control is used before the pitch control in the stall or post-stall flight regime, there is some risk of subsequent loss of control. Finally, from the discussion on stall recovery methods, questions for Regulatory Authorities are put forward that should address the current practices.
Flapping wings in line formation flight: a computational analysis
Authors: Ghommem M. , Calo V. M.
Published: February 2016

The current understanding of the aerodynamics of birds in formation flights is mostly based on field observations. The interpretation of these observations is usually made using simplified aerodynamic models. Here, we investigate the aerodynamic aspects of formation flights. We use a potential flow solver based on the unsteady vortex lattice method (UVLM) to simulate the flow over flapping wings flying in grouping arrangements and in proximity of each other. UVLM has the capability to capture unsteady effects associated with the wake. We demonstrate the importance of properly capturing these effects to assess aerodynamic performance of flapping wings in formation flight. Simulations show that flying in line formation at adequate spacing enables significant increase in the lift and thrust and reduces power consumption. This is mainly due to the interaction between the trailing birds and the previously-shed wake vorticity from the leading bird. Moreover, enlarging the group of birds flying in formation further improves the aerodynamic performance for each bird in the flock. Therefore, birds get significant benefit of such organised patterns to minimise power consumption while traveling over long distances without stop and feeding. This justifies formation flight as being beneficial for bird evolution without regard to potential social benefits, such as, visual and communication factors for group protection and predator evasion.
Constrained optimal terrain following/threat avoidance trajectory planning using network flow
Authors: Zardashti R. , Nikkhah A. A. , Yazdanpanah M. J.
Published: February 2016

This paper focuses on the trajectory planning for a UAV on a low altitude terrain following/threat avoidance (TF/TA) mission. Using a grid-based approximated discretisation scheme, the continuous constrained optimisation problem into a search problem is transformed over a finite network. A variant of the Minimum Cost Network Flow (MCNF) to this problem is then applied. Based on using the Digital Terrain Elevation Data (DTED) and discrete dynamic equations of motion, the four-dimensional (4D) trajectory (three spatial and one time dimensions) from a starting point to an end point is obtained by minimising a cost function subject to dynamic and mission constraints of the UAV. For each arc in the grid, a cost function is considered as the combination of the arc length, fuel consumption and flight time. The proposed algorithm which considers dynamic and altitude constraints of the UAV explicitly is then used to obtain the feasible trajectory. The resultant trajectory can increase the survivability of the UAV using the threat region avoidance and the terrain masking effect. After obtaining the feasible trajectory, an improved algorithm is proposed to smooth the trajectory. The numeric results are presented to verify the capability of the proposed approach to generate admissible trajectory in minimum possible time in comparison to the previous works.
Initial conceptual design and wing aerodynamic analysis of a solar power-based UAV
Authors: Harasani W. , Khalid M. , Arai N. , Fukuda K. , Hiraoka K.
Published: February 2016

King Abdul Aziz University of Saudi Arabia (KAU) and Tokai University in Japan have collaborated to design and manufacture a solar powered unmanned air vehicle (UAV), Sun Falcon, which has capability of continuous one day fight with intended design extension towards night flight. The project is a student-driven endeavour involving some 30 students. Both universities are equally involved in the actual design studies of the performance characteristics, aerodynamic design, propulsion and structural analysis. Tokai University is in charge of the actual on-site supervision and examination of on-going manufacturing processes and ultimate fabrication of the prototype model.

The conceptual design of the Sun Falcon was meticulously worked out in consideration of the operational mission, which included such flight characteristics as the cruising velocity, flight altitude, payload, flight time, rate of climb, power requirements and so on. The weather condition patterns in Saudi Arabia, which remained fairly supportive of the solar cell performance, were also deemed crucial in the design process. However, the design of a solar plane had other challenges in terms of power unit accommodation and payload consideration in comparison to other conventional UAVs. In this paper, an outline of the design features of the Sun Falcon is presented and other notable design features particular to solar UAVs are discussed. It was learnt in this exercise that the selection of the base aerofoil is perhaps one of the most important design items, as the Reynolds number for such UAVs understandably drops notably lower than conventional aeroplanes and such features as the camber curvature and wing area must cater for the installation of solar panels whose size, strength and quantity must respect local weather conditions. For the Sun Falcon, the actual design process examined two candidate aerofoils FX74-CL5-140 (FX74) and SD7037-092-88(SD7037) both of which were abundantly suitable for furnishing the required aerodynamic characteristics. SD7037 was ultimately chosen as it provided the best geometry and camber line in terms of accommodation and placement of the solar panels. Further scrutiny demonstrated that this latter aerofoil provided better take-off performance and superior L/D behaviour under cruise conditions. In order to check out the aerodynamic performance in general and overall stability and control characteristics, a preflight test under battery power (a 2,500 mAh li-po 4-cell 14·8v) was achieved on 4 June 2013. Other solar powered based tests are currently under way at present.
The aerodynamic challenges of aeroengine gas-turbine combustion systems
Authors: McGuirk J. J.
Published: February 2016

The components of an aeroengine gas-turbine combustor have to perform multiple tasks – control of external and internal air distribution, fuel injector feed, fuel/air atomisation, evaporation, and mixing, flame stabilisation, wall cooling, etc. The ‘rich-burn’ concept has achieved great success in optimising combustion efficiency, combustor life, and operational stability over the whole engine cycle. This paper first illustrates the crucial role of aerodynamic processes in achieving these performance goals. Next, the extra aerodynamic challenges of the ‘lean-burn’ injectors required to meet the ever more stringent NOx emissions regulations are introduced, demonstrating that a new multi-disciplinary and ‘whole system’ approach is required. For example, high swirl causes complex unsteady injector aerodynamics; the threat of thermo-acoustic instabilities means both aerodynamic and aeroacoustic characteristics of injectors and other air admission features must be considered; and high injector mass flow means potentially strong compressor/combustor and combustor/turbine coupling. The paper illustrates how research at Loughborough University, based on complementary use of advanced experimental and computational methods, and applied to both isolated sub-components and fully annular combustion systems, has improved understanding and identified novel ideas for combustion system design.
Aerodynamic study of aerofoil and wing in simulated rain environment via a two-way coupled Eulerian-Lagrangian approach
Authors: Wu Z. , Cao Y.
Published: February 2016

Aerodynamic performance degradation has been considered a critical hazard to aircraft due to flying in heavy rain. In this work, a two-way momentum coupled Eulerian-Lagrangian approach is developed to study the aerodynamic performance of a two-dimensional (2D) transport-type NACA 64-210 cruise and landing configuration aerofoil as well as a three-dimensional (3D) NACA 64-210 cruise configuration rectangular wing in heavy rain environment. Raindrop impacts, splashback and formed water film are modeled. The steady-state incompressible air flow field and the raindrop trajectory are calculated alternately by incorporating an interphase momentum coupling term through a curvilinear body-fitted grid surrounding the aerofoil/wing. Our simulation results agree well with the experimental results and show significant aerodynamic penalties for all the test cases in heavy rain. Rain-induced premature boundary-layer transition and separation are observed and details of the raindrop splashback effect on the boundary layer are examined. A 1° rain-induced decrease in stall angle-of-attack is predicted. An uneven water film upon the wing surface is observed and its effect on the wing surface roughness is also examined.
Multi-body dynamic modelling and flight control for an asymmetric variable sweep morphing UAV
Authors: Tong L. , Ji H.
Published: February 2016

In this paper, the multi-body dynamic model of an asymmetric variable sweep wing morphing UAV is built based on Kane’s method. This model describes the UAV’s transient behaviour during morphing process and the dynamic characteristic of the variable sweep wings. An integrated design of trajectory tracking control via constrained backstepping method is presented then. The idea of aircraft roll control through asymmetric wing sweep angle changes rather than traditional aileron is explored and used in the fight control design. The control of variable sweep wings is designed as well based on the presented dynamic model. Command filters are used in the backstepping design procedure to accommodate magnitude, rate and bandwidth constraints on virtual states and actuator signals. Stability of the closed-loop system can be proved in the sense of Lyapunov. Simulation of tracking a desired trajectory which contains two manoeuvres demonstrates the feasibility of the proposed protocol and the morphing wing roll controller.
The Ornicopter – a tailless helicopter with active flapping blades
Authors: Wan J. , Pavel M. D.
Published: February 2016

The ‘Ornicopter’ is a single-rotor helicopter without anti-torque rotor developed since 2002 at Delft University of Technology in The Netherlands. The Ornicopter’s principle is similar to the movement of a bird’s wing and is based on actively flapping the blades up and down while rotating them around a shaft to generate both the required lift and the propulsive force. The shaft torque is no longer needed and thus the anti-torque rotor is redundant. The present paper describes the basic principles of the Ornicopter’s forced flapping, discussing the feasibility of the Ornicopter concept with respect to the power required, performance, stability, and vibratory loads. On the one side it is shown that the Ornicopter has a similar power requirement to a conventional helicopter, as well as very similar longitudinal and lateral stability and controllability characteristics to a conventional helicopter. On the other side, the Ornicopter generates higher vibratory loads than in a conventional helicopter, and its performance is strongly limited by the stall effect.
Lagrangian formulation for the rapid estimation of helicopter rotor blade vibration characteristics
Authors: Goulos I. , Pachidis V. , Pilidis P.
Published: February 2016

This paper presents a numerical formulation targeting the rapid estimation of natural vibration characteristics of helicopter rotor blades. The proposed method is based on application of Lagrange’s equation of motion to the kinematics of blade flap/lag bending and torsion. Modal properties obtained from Bernoulli-Euler beam and classical torsional vibration theory, are utilised as assumed deformation functions in order to estimate the time variations of strain and kinetic energy for each degree of freedom. Integral expressions are derived, describing the generalised centrifugal force and torsional moment acting on the blade in terms of normal coordinates, for flap/lag transverse displacement and torsional deformation. Closed form expressions are provided for the direct analysis of hingeless, freely-hinged and spring-hinged articulated rotor blades. Results are presented in terms of natural frequencies and mode shapes for two small-scale rotor blade models. Extensive comparisons are carried out with experimental measurements and nonlinear finite element analysis. Predictions of resonant frequencies are also presented for two full-scale rotor blade models and the results are compared with established multi-body dynamics analysis methods. It is shown that, the proposed approach exhibits excellent numerical behaviour with low computational cost and definitive convergence characteristics. The comparisons suggest very good and in some cases excellent accuracy levels, especially considering the method’s simplicity, computational efficiency, and ease of implementation.
Prediction of warning level in aircraft accidents using data mining techniques
Authors: Christopher A. B. Arockia , Balamurugan S. Appavu alias
Published: February 2016

Data mining is a data analysis process which is designed for large amounts of data. It proposes a methodology for evaluating risk and safety and describes the main issues of aircraft accidents. We have a huge amount of knowledge and data collection in aviation companies. This paper focuses on different feature selectwindion techniques applied to the datasets of airline databases to understand and clean the dataset. CFS subset evaluator, consistency subset evaluator, gain ratio feature evaluator, information gain attribute evaluator, OneR attribute evaluator, principal components attribute transformer, ReliefF attribute evaluatoboundar and symmetrical uncertainty attribute evaluator are used in this study in order to reduce the number of initial attributes. The classification algorithms, such as DT, KNN, SVM, NN and NB, are used to predict the warning level of the component as the class attribute. We have explored the use of different classification techniques on aviation components data. For this purpose Weka software tools are used. This study also proves that the principal components attribute with decision tree classifier would perform better than other attributes and techniques on airline data. Accuracy is also very highly improved. This work may be useful for an aviation company to make better predictions. Some safety recommendations are also addressed to airline companies.
A rating scale for the subjective assessment of simulation fidelity
Authors: Perfect P. , Timson E. , White M. D. , Padfield G. D. , Erdos R. , Gubbels A. W.
Published: February 2016

A new rating scale for capturing pilot subjective assessment of simulation fidelity is described in this paper. The scale has been developed through a series of flight and simulation trials using six test pilots from a variety of backgrounds, and is based on the methodology utilised with the Cooper-Harper Handling Qualities Rating scale and the concepts of transfer of training, comparative task performance and task strategy adaptation. The development of the new rating scale has been undertaken using simulations of rotary-wing aircraft on the University of Liverpool’s HELIFLIGHT-R research simulator, in conjunction with the Canadian Flight Research Laboratory’s Bell 412 ASRA in-flight simulator. The utility of the scale applied to locating fidelity boundaries for quantitative metrics is illustrated for an inter-axis coupling criterion. The work described in this paper is preliminary in nature, and research activities are on-going to continue the validation of the fidelity rating scale.
Aeroelastic effects of battens on the flight dynamics of a MAV
Authors: Babcock J. , Lind R.
Published: February 2016

Wing flexibility is well established as providing gust rejection and delayed onset of stall for micro air vehicles. As such, many designs adopt wings of a flexible material mounted onto a skeleton comprised of a stiff leading-edge spar and stiff chordwise strips, called battens. These battens are shown to provide additional strength at localised regions of the wing and thus improve the gust rejection and delay stall; however, their effect on the flight dynamics is less studied. Using a numerical modeling approach, this paper explores a design space of vehicles with a varied number of wing battens mounted onto a baseline vehicle with a flexible wing. The battens are modelled as stepwise changes in torsional stiffness along the wing span. The resulting trim characteristics, static stability metrics and flight dynamics are evaluated. The battens are shown to improve gust rejection but otherwise have a complicated effect across the design space. A reduction in the number of battens improves the longitudinal static stability derivative slightly but lowers the lateral and directional static stability. The damping is decreased for the short period mode and increased for the phugoid and dutch roll modes as the number of battens is reduced.