bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation control on highly-swept wings
with fixed or variable camber
Authors: Ashill P. R. , Riddle G. L. , Stanley M. J. 
Published: February 2023

AbstractThis paper describes an experimental investigation into
the effect of miniature vortex generators (VGs) on
the longitudinal aerodynamic characteristics of a
highly-swept wing with drooped leading edges. The
experiments were performed in a low-speed windtunnel
on a wing of the same delta planform as that used in
a previous study. The latter wing was of fixed
camber, while the subject of the present study was a
wing with three different leading edge droop angles.
The maximum reduction in drag due to the VGs was
found to be about half that for the fixed-camber
wing. This is reconciled with the different
behaviour of the flow on the upper surface for the
two types of wing. Without control, the drag of the
variable-droop wings is much lower than that of the
fixed-camber wing. As a result, with control, the
variable droop wings have lower drag than that of
the fixed-camber wing. Compared to that of the
variable-droop wings without control, the
fixed-camber wing, with control, has lower
lift-dependent drag for lift coefficients between
0·4 and 0·7. However, at higher lift coefficients,
the reverse applies.
Asymmetric vibration of viscoelastically
damped multilayered conical shell
Authors: Khatri K. N. 
Published: February 2023

AbstractAsymmetric vibration of multilayered conical shell with
core layers of viscoelastic material are
investigated in this paper. The analysis presented
herein considers bending, extension in plane shear
and transverse shear deformations in each of the
layers, and also includes rotary, longitudinal
translatory and transverse inertias. Appropriate
trigonometric series are used as solution functions
in the Galerkin method to reduce the governing
equations to a set of matrix equations. The
corresponding principle of linear viscoelasticity
for harmonic motion is used for evaluating the
damping effectiveness of shells with elastic and
viscoelastic layers. A computer program has been
developed for determining the resonance frequencies
and associated system loss factors for various modes
of families of asymmetric vibration of a general
multilayered conical shell consisting of an
arbitrary number of specially orthotropic material
layers. Variation of resonance frequencies and the
associated system loss factors with total thickness
parameter and circumferential modal number for
three, five and seven layered conical shells, with
three sets of classical end conditions: simply
supported at both ends, clamped-clamped and
free-free, which can be of some use to designers,
are been reported.
Structural dynamics-CFD interaction for
computation of vertical tail buffet
Authors: Kandil O. A. , Massey S. J. , Sheta E. F. 
Published: February 2023

AbstractThe multidisciplinary problem of tail buffeting is
solved using three sets of equations. The first set
is the unsteady, compressible, full Navier-Stokes
equations which are used for obtaining the flowfield
vector and the aerodynamic loads. The second set is
the coupled aeroelastic equations which are used for
obtaining the bending and torsional deflections of
the tail. The third set is the grid-displacement
equations which are used for updating the grid
coordinates due to the tail deflections. For the
computational applications, a sharp-edged delta wing
of aspect ratio one and a rectangular vertical tail
of aspect ratio one placed in the plane of geometric
symmetry behind the wing are considered. The
configuration is pitched at a critical angle of
attack (α = 38°) which produces asymmetric,
vortex-breakdown flow from the delta wing primary
vortices. The results show the effects of coupled
and uncoupled bending-torsional responses and the
effects of Reynolds number.
Aircraft dynamics optimisation via linear
matrix inequalities
Authors: Mengali G. 
Published: February 2023

AbstractThis paper deals with the problem of determining an
optimal controller which minimises the
norm of a given aircraft
while guaranteeing that an upper limit of its
norm is not exceeded. The
problem is tackled by means of a linear matrix
inequality formulation, which allows one to
constrain the eigenvalues of the model to within a
fixed region of the complex plane. Key features of
the method are the possibility of simultaneously1. keeping the maximum value of the input
demand under control2. taking flying quality requirements into
account3. assuring a minimum level of system
robustness against uncertainties of the model.The approach is simple to handle and is well suited to
the design of aircraft stability augmentation
systems. A discussion of two case studies
demonstrates the effectiveness of the procedure.
On the start condition of a second-throat
ejector-diffuser
Authors: Wang J. J. , Chen F. 
Published: February 2023

AbstractThe start condition of a second-throat ejector-diffuser
(STED) system has been studied by solving the
axisymmetric Navier-Stokes equations with a high
order conservative supra-characteristics method
(CSCM). According to the conventional concept, when
a STED is started, the flow passing through the
second-throat contraction should be supersonic so
that the normal shock swallowing condition applying
for a supersonic windtunnel holds. The present
numerical results, however, suggest that a STED can
be started with a normal shock forming ahead of the
second-throat contraction because the high speed
flow in the region close to the wall of the diffuser
serves to release the mass blocked by the normal
shock, leading to a decrease in chamber pressure as
well as the start of the system. This not only
contradicts the conventional concept of the start of
a STED, but also provides an explanation for the
experimental discrepancy between the start
conditions of a STED and a supersonic
windtunnel.
Characterisation of sandpaper roughness
under a turbulent incompressible boundary
layer
Authors: Gibbings J. C. , Al-Shukri S. M. 
Published: February 2023

AbstractThe work reported here extends the work of Nikuradse on
the categorisation of surface roughness. Nikuradse’s
work considered pipe flow, whilst in this paper
boundary layer flow is investigated. Important and
fundamental differences between these two types of
flow are shown. An experiment upon turbulent
boundary layers over sandpaper-type roughnesses
enabled a fluid-mechanic categorisation of these
surfaces to be obtained for this flow. This is
compared with some shape and size categorisations of
the roughnesses from detailed measurements.
Multi-sensor data fusion for helicopter
guidance using neuro-fuzzy estimation
algorithms
Authors: Doyle R. S. , Harris C. J. 
Published: February 2023

AbstractThe purpose of this paper is to describe an approach
which performs data fusion on the output of
multiple, spatially separate, sensors engaged in the
real time tracking of obstacles in a helicopter's
environment. The generated information can be used
either as a flight director aid or as feedback
required by an automatic collision avoidance system.
Obstacle track estimation has been commonly carried
out using the Kalman filter (KF) for linear
estimation, or the extended Kalman filter (EKF) for
use on nonlinear problems. However, certain
assumptions made in the derivation of the EKF
algorithms render it sub-optimal for aerial obstacle
track estimation. Additionally, the EKF has problems
with initialisation and divergence (stability) for
many non-linear processes.Research at the University of Southampton has
highlighted a link between fuzzy networks and
associative memory neural networks. This link is
important as it allows new learning rules to be
developed for training fuzzy rules, and learning
convergence to be proved. This paper explores
methods of fusion of estimates using neuro-fuzzy
models, and addresses some of the weakness of the
Kalman filter approximation introduced by the
assumptions made in its derivation.
Aerodynamic technology — the role of
aerodynamic technology in the design and development
of modern combat aircraft
Authors: McMichael T. , McKay K. , Walker M.J. , Fielding C. , Lockley G. , Curtis P. , Probert B. , Lee C. S. , Moretti G. 
Published: February 2023

AbstractThis paper examines the changing role aerodynamic
technology plays in the design and development of
modern combat aircraft. It reviews several aspects
of aerodynamics which contribute to aircraft
performance and handling characteristics. It
considers the importance of a range of technologies,
the contribution each makes to the final integrated
solution and comments on the compromises necessary
through the design cycle to optimise the overall
weapon system, sometimes to the cost of one of the
component technologies. The technologies discussed
are in no way exhaustive but attempt to encapsulate
the breadth of the subject, to illustrate its
diversity and to point the way for the future
development if aerodynamic technology is to continue
to make an important contribution to the design of
combat aircraft.Each of the component technologies are discussed in
terms of the contribution it makes, the tools and
techniques used to predict, analyse and interpret
the technology contribution, and the requirements
for the direction of the development of the
technology for the future.Before considering the technologies themselves it is
important to understand the environment in which
they will be used, which increasingly conditions the
manner in which they are employed and suggests the
direction for their development.This paper begins, therefore, by briefly reviewing the
changes to the environment in which the fighter
pilot operates and the manner by which his
requirements, and therefore the specification of the
aircraft, are defined before going on to look at the
overall contribution each technology makes in the
design process.
Buffeting tests in a cryogenic
windtunnel
Authors: Mabey D. G. , Boyden R. P. , Johnson W. G. 
Published: February 2023

SummaryMeasurements of wing buffeting, using root strain
gauges, were made in the Nasa Langley 0-3 m
cryogenic windtunnel to refine techniques which will
be used in larger cryogenic facilities such as the
United States National Transonic Facility (NTF) and
the European Transonic Windtunnel (ETW). The
questions addressed included the relative importance
variations in frequency parameter and Reynolds
number, the choice of model material (considering
both stiffness and damping) and the effects of
static aeroelastic distortion.The main series of tests was made on three half models
of slender 65° delta wings with a sharp leading
edge. The three delta wings had the same planform
but widely differing bending stiffnesses and
frequencies (obtained by varying both the material
and the thickness of the wings). It was known that
the steady flow on this configuration would be
insensitive to variations in Reynolds number. On
this wing at vortex breakdown the spectrum of the
unsteady excitation is unusual, having a sharp peak
at particular frequency parameter.Additional tests were made on one unswept half-wing of
aspect ratio 1·5 with an NPL 9510 aerofoil section,
known to be sensitive to variations in Reynolds
number at transonic speeds. The test Mach numbers
were M = 0·21 and 0·35 for the delta wings and to M
= 0·30 for the unswept wing. On this wing the
unsteady excitation spectrum is fairly flat (as on
most wings). Hence correct representation of the
frequency parameter is not particularly
important.
Effect of spherical roughness elements upon
transition of a 3-D boundary layer
Authors: M. Ö. Çarpinlioglu  , Ö. T. Göksel  
Published: February 2023

AbstractThe influence of isolated spherical roughness elements
upon the transition of a three-dimensional boundary
layer on a swept flat plate is discussed in this
paper. Perturbations induced by the roughness are
found to be more effective on the start of
transition rather than the crossflow of the laminar
undisturbed boundary layer at the roughness
location.
Photosynthesis rate, radiation and water use efficiencies of irrigated potato in a semi-arid climate using Eddy covariance techniques
Authors: Machakaire A. T. B. , Steyn J. M. , Franke A. C. 
Published: February 2023

AbstractUnderstanding the photosynthetic behaviour, radiation use efficiency (RUE) and water use efficiency (WUE) of potatoes in response to diurnal and seasonal fluctuations in weather, is important for optimizing growth and production. The net ecosystem exchange (NEE) of carbon dioxide (CO2), is a parameter used to measure the balance between gross CO2assimilation (also referred to as gross primary production (GPP)) and ecosystem respiration (Reco). The objectives of this study were (i) to quantify the NEE of potato grown in two contrasting agro-ecologies and partition NEE intoRecoand GPP; (ii) to describe seasonal patterns in daily photosynthesis, RUE and WUE in potato; and (iii) to analyse the variability in photosynthesis rate, RUE and WUE as affected by weather and crop growth stage. We measured CO2and water vapour fluxes using eddy covariance techniques in potato fields in two production regions of South Africa. The winter crop had higher mean RUE and WUE values, whereas the summer crop absorbed more CO2. RUE had a negative relationship with incident radiation. To optimize dry matter production, WUE and RUE, potato crops must be well established and develop a full canopy early during the season. Maintaining the crop for a longer period in the field has yield benefits, although they appear to decline over time due to reduced efficiencies as the crop matures. The RUE observed over the growing period in the present study was high, relative to findings by other field studies, despite relatively warm growing conditions that were likely sub-optimal for potato.
State of the art in assisted reproductive technologies for patients with advanced maternal age
Authors: Yurchuk Taisiia , Petrushko Marina , Fuller Barry 
Published: February 2023

SummaryAccording to the World Health Organization, the female reproductive age lasts up to 49 years, but problems with the realization of women’s reproductive rights may arise much earlier. Significant numbers of factors affect the state of reproductive health: socioeconomic, ecological, lifestyle features, the level of medical literacy, and the state of the organization and medical care quality. Among the reasons for fertility decline in advanced reproductive age are the loss of cellular receptors for gonadotropins, an increase in the threshold of sensitivity of the hypothalamic-pituitary system to the action of hormones and their metabolites, and many others. Furthermore, negative changes accumulate in the oocyte genome, reducing the possibility of fertilization, normal development and implantation of the embryo and healthy offspring birth. Another theory of ageing causing changes in oocytes is the mitochondrial free radical theory of ageing. Taking into account all these age-related changes in gametogenesis, this review considers modern technologies aimed at the preservation and realization of female fertility. Among the existing approaches, two main ones can be distinguished: methods allowing the preservation of reproductive cells at a younger age using ART intervention and cryobanking, as well as methods aimed at improving the basic functional state of advanced-age women’s oocytes and embryos.
The effects of farming system and soil management on floristic diversity in sloping olive groves
Authors: Jiménez María Noelia , Castro-Rodríguez Juan , Navarro Francisco Bruno 
Published: February 2023

Abstract
The effects of the farming system (conventional-organic-abandoned) and soil management (native cover crop vs tillage) on vascular plant species were analyzed in sloping olive groves (>20%) in 20 different locations in Andalusia, SE Spain. The soil management techniques included Organic Tillage (OT), Organic Cover Crops (OC), Conventional Tillage (CT), Conventional Non-Tillage (CNT), Abandoned Cover Crops (AC) and Abandoned Woody (AW). Data for the vascular plant species were recorded through three line transects of 30 m with a bar perpendicularly touching every 1 m of the measuring tape. Environmental variables were also recorded at plot level to assess their influence. Dependent variables, such as species abundance, richness and diversity indexes were studied using univariate analysis (one-way ANOVA, Kruskal–Wallis test) while multivariate statistics (ANOSIM, SIMPER, DCA) were used for analyzing the data matrices. We found that the different combinations of farming system and soil management affect biological diversity in terms of individual abundance, plant cover, species richness and diversity, species and family composition. Life forms and species distribution patterns are also affected. The main environmental variables affecting the plant taxa were those related with soil and climate characteristics, slope, olive age and intensive land uses at landscape level, including the percentage of artificial surfaces. The lowest levels of biodiversity (e.g., species richness) were found in the tilled olive groves (CT = 8.1 sp. ± 2.2, OT = 10.0 sp. ± 5.4). Surprisingly, the organic tilled groves (OT) were very poor in species compared to those with native plant cover (OC = 27.9 sp. ± 3.0). The latter, however, showed similar species richness to the abandoned olive groves (AC = 21.2 sp. ± 3.7, AW = 27.2 sp. ± 3.0). Possible solutions for increasingly uncompetitive sloping olive groves include conversion to organic with native plant cover or abandonment for rewilding.
Modeling Post‐Wildfire Hydrologic Response: Review and Future Directions for Applications of Physically Based Distributed Simulation
Authors: Ebel Brian A. , Shephard Zachary M. , Walvoord Michelle A. , Murphy Sheila F. , Partridge Trevor F. , Perkins Kim S. 
Published: February 2023

AbstractWildfire is a growing concern as climate shifts. The hydrologic effects of wildfire, which include elevated hazards and changes in water quantity and quality, are increasingly assessed using numerical models. Post‐wildfire application of physically based distributed models provides unique insight into the underlying processes that affect water resources after wildfire. This work reviews and synthesizes post‐wildfire applications of physically based distributed models by examining the scales and geographic/ecohydrologic distribution of model applications, hydrologic response process representation, model parameterization, and model performance metrics. Highlighted gaps and opportunities for advancing physically based distributed hydrologic response modeling after wildfire include the following: (a) applying models in under‐represented geographic (S. America, Africa, Asia) and ecohydrologic regions (arid or dry subhumid climates), (b) incorporating all four major streamflow generation mechanisms (infiltration excess, saturation excess, subsurface storm flow, and groundwater flow), (c) representing integrated vadose zone and saturated zone processes to better capture subsurface streamflow generation, (d) building new remotely sensed model parameterization methods for precipitation interception, infiltration, and overland flow that account for burn severity and recovery, (e) incorporating distributed state variables (e.g., soil moisture, groundwater levels) in model performance assessment, (f) designing model intercomparison studies, including field datasets specifically for post‐wildfire model development and validation, (g) linking mechanistic vegetation regrowth models with hydrologic models to improve simulation of process shifts as ecosystems recover, and (h) creating a new community modeling framework to integrate modeling advances across the wildfire science community.
Remarkable Changes in the Dominant Modes of North Pacific Sea Surface Temperature
Authors: Werb Benjamin E. , Rudnick Daniel L. 
Published: February 2023

AbstractThe analysis revisits the calculation of the empirical orthogonal functions (EOFs) and principal components (PCs) of sea surface temperature (SST) in the North Pacific from 1950 to 2021. The first EOF and PC of SST has proven to be such a useful metric of variability in the North Pacific that it is called the Pacific Decadal Oscillation (PDO). We find that the period of persistent marine heatwaves beginning in 2014 caused a fundamental change to the first EOF and PC of SST (calculated using data from 1950 to 2021) as compared to the established PDO spatial pattern (calculated using data from 1950 to 1993). The second EOF of SST has also changed during this period, both in spatial pattern and in the amount of variance explained. A conclusion is that the PDO and other EOF based metrics may not be as useful in the future as climate continues to change.
Persistence of Cold Wedges in the Somali Current System
Authors: Hormann Verena , Centurioni Luca R. , Paluszkiewicz Theresa 
Published: February 2023

AbstractThe Somali Current system in the western Arabian Sea reverses seasonally with the South Asian Monsoon and is associated with localized upwelling cells or cold wedges during the summer southwest monsoon. Drifter trajectories in boreal summer and fall 2014 provide rare observational evidence that the northward Somali Current and associated cold wedges can persist into the boreal fall intermonsoon period. The near‐surface circulation and sea surface temperatures further suggest that the wedge‐like surface signatures may intermittently be capped and then reappear at a later time. Our observations show that the northward Somali Current system rapidly decayed within 1 week after the onset of the winter northeast monsoon and the arrival of a cyclonic eddy at the coast in early November 2014. This eddy may not only have affected regional ocean‐atmosphere interactions but also biogeochemical processes and the marine ecosystem through the transport of water properties and locally induced upwelling.
Interannual Variability of Regional Hadley Circulation and El Niño Interaction
Authors: Li Yadi , Xie Shang‐Ping , Lian Tao , Zhang Gan , Feng Juan , Ma Jing , Peng Qihua , Wang Wenzhu , Hou Yurong , Li Xichen 
Published: February 2023

AbstractEl Niño‐Southern Oscillation (ENSO) triggers variations of the global Hadley circulation (HC), while the latter may potentially feedback to ENSO events. Previous studies mainly investigated the interactions between ENSO and the global zonal‐mean HC. Here, we present a regional perspective of HC variability by introducing zonal variations. Results show that El Niño intensifies the regional HC over the central‐eastern Pacific, while weakening the regional HC over both the Indo‐Pacific warm pool and the tropical Atlantic. The background seasonal cycle modulates the equatorial‐asymmetric component of HC, with an anticlockwise (clockwise) asymmetric circulation over the central equatorial Pacific before (after) El Niño peaks. Remarkably, the asymmetric HC in boreal spring leads ENSO with a lead correlation of up to 0.68, mediated by the wind‐evaporation‐sea surface temperature (SST) feedback and other atmosphere‐ocean dynamics. The antecedent HC anomaly may contribute to ENSO predictability.