bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilisation of the Aeroplane in Symmetric Flight at Zero or Very Small Air Speeds
Authors: Coleman W. S. 
Published: July 2016

SummaryThe possible use of jet thrust as a source of lift, either by deflection of the force from the normal propulsion axis, or by some other means, raises a new stability problem under conditions of hovering flight and flight at speeds for which the aerodynamic damping becomes insignificant. At the same time, despite the small dynamic pressure, the direct air loads cannot be neglected, for, due to the very large positive or negative incidences peculiar to the motion, the associated coefficients are of a compensatingly high order. Consequently, the problem retains an aerodynamic element, but is principally one of automatic stabilisation, amenable to treatment by ordinary mechanical or electrical circuit theory. The investigation has been restricted to the longitudinal-symmetric motion with virtually the only workable form of automatic control, namely, one responsive to the angular displacement and velocity in pitch, but these conditions undoubtedly embrace all the essentials of any practical application, e.g. in take-off and landing by the new technique. The solution to the stability in a gust, or in a succession of disturbances, may then be easily obtained in closed analytical form, but the more general case of unsteady motion, when the displacements are no longer purely oscillatory, necessitates, in part, the use of step-by-step integration. This arises from the added complexity of the aerodynamic terms, due to the appearance of significant changes of incidence, and to the very large and variable values of the resistance derivatives at the angles involved, so that, in the present state of knowledge, the forces determining the motion cannot be expressed functionally. The labour which such calculations entail may be considerably shortened, however, by the application of a procedure based on mean deviations, but it is also found that the conclusions to be drawn from the hovering case remain valid in a number of important respects for the general problem. This feature is demonstrated in the discussion at the end of the paper on a number of examples designed to illustrate the characteristics of the automatic control and the conditions necessary for stability in a variety of circumstances, both when the aircraft is hovering and when its displacement increases continuously with time.
Some Exploratory Three-Dimensional Jet-Flap Experiments
Authors: Williams J. , Alexander A. J. 
Published: July 2016

SummaryThis paper describes a first attempt to establish the order of magnitude of finite aspect ratio effects for jet-flap wings. Lift, pitching moment, and drag results are presented from pressure-plotting measurements on a jet-flap model of aspect ratio slightly less than three. These experiments were complementary to two-dimensional tests carried out at the National Gas Turbine Establishment.
An Approximate Method for the Calculation of Turbulent Boundary Layers in Diffusers
Authors: Norbury J. F. 
Published: July 2016

SummaryAn approximate method is described for the calculation of turbulent boundary layers in which the turbulence is developed before the commencement of the adverse pressure gradient, as in most diffuser layers. It is based on a method due to Spence which has been modified and also extended to the calculation of three-dimensional diverging layers such as occur in ducts whose breadth is increasing. The velocity profiles occurring in a diverging layer are examined and it is shown that the inner part obeys the universal logarithmic law, as in two-dimensional layers. This result is used to obtain an equation for the form parameter in diverging layers, by substitution in the equation of motion and incorporation of the equations of momentum and continuity for diverging flow. The form parameter equation contains a term involving the gradient of shear stress at y = θ and values of this term are obtained by the analysis of experimental data and the substitution of known values for all the other terms in the form parameter equation. Values of the term involving shear stress gradient are then correlated in terms of known boundary layer quantities, and the resulting correlation allows the formulation of a step-by-step method for the solution of the form parameter equation. This may be used in conjunction with the momentum equation to predict the boundary layer growth. It was not found possible to effect a satisfactory correlation for boundary layers on lifting aerofoils, in which the turbulence develops within the adverse pressure gradient, and the method cannot be used for the prediction of such layers. The results of a number of calculations are given.
Matrix Inversion by Partitioning
Authors: Kosko Eryk 
Published: July 2016

SummaryA systematic discussion of partitioning as a tool for matrix inversion is presented, together with various methods and applications which have been of help in actual computations. New concepts are introduced, among them those of super-matrix and of square partitioning. The most usual type of partitioning, that into 2x2 sub-matrices, is discussed in detail, showing the orderly arrangement of the calculations in an auxiliary matrix. Further sections deal with matrices of the continuant type, and with special types of symmetry in the arrangement of the sub-matrices. The greatest advantage of the method of partitioning for the inversion of these types (as compared with the elimination method) lies in a considerable reduction in the number of arithmetical operations.
Notes on the Mathematical Design of Nozzles and Wind Tunnel Contractions
Authors: Bloomer N. T. 
Published: July 2016

SummaryIn this work the co-ordinates of three-dimensional nozzles of several types have been obtained as explicit functions, and some shapes have been plotted. It is hoped that some of these might be of use in cases where smooth uniform fluid flow is desired. The design of a particular nozzle shape in the presence of a plane boundary is given: previously any equations obtained have been too intractable to use.
On the Generation of the Streamwise Component of Vorticity for Flows in Rotating Passages
Authors: Smith Austin G. 
Published: July 2016

SummaryA method is presented for the calculation of the streamwise component of vorticity, for flows in rotating passages. The method may be regarded as an extension of the methods applied in recent years to the calculation of secondary flows in stationary passages.Attention is concentrated on the quantityI=p+½ρV2−½ρU2,whereVis the fluid velocity relative to the rotor andUis the rotor tangential velocity.Iremains constant along a streamline in the rotor, and is found to enter into the equation for the generation of vorticity in much the same way as the total head enters for flow in stationary passages.An approximate calculation of the streamwise vorticity generated in a simple axial-flow rotor is made, and qualitative consideration is given to the flow in a centrifugal impeller. Just as for the calculation of secondary flows in stationary passages, an approximate shape of the streamline must be assumed before the secondary flows can be calculated.
On the Accuracy of the Representation of a Lifting Line by a Finite Set
of Horseshoe Vortices
Authors: Collar A. R. 
Published: July 2016

Summary
The paper examines the error involved when the continuous distribution
of lift on an unswept lifting surface is represented by a finite number of
horseshoe vortices, the strengths of which are determined by a prescribed
downwash. Attention is directed mainly to the case of elliptic loading, but
an anti-symmetrical case is also studied to ensure that the conclusions are
not peculiar to the elliptic case.
Some Identities on Structural Flexibility after Buckling
Authors: Mansfield E. H. 
Published: July 2016

Summary
This paper gives some identities concerning the flexibility of certain
elastic structures, including flat plates, at the onset of buckling and
subsequently. The identities have a useful application in determining the
flexibility and the rate of change of flexibility with load for structures
in which the mode in the buckled state changes continuously with
load.
A Note on the Drag of Wing-Body Combinations in Linearised Supersonic
Flow
Authors: Fraenkel L. E. 
Published: July 2016

Summary
In this note Ward's “area-transfer rule” is modified in order to make it
more suitable for configurations with fuselages or nacelles which are
neither slender nor smooth (although they are assumed to have small profile
slope). The body source strength of Ward's analysis, which is appropriate
only for smooth, slender bodies, is replaced by a source strength which is
valid more generally. However, the drag contributions of the body
multi-sources and of the interference field are still neglected, so that the
theory is tentative rather than rigorous.
Turbulent Shear Layer Re-Attachment with Special Emphasis on the Base Pressure Problem
Authors: McDonald H. 
Published: July 2016

SummaryAn analysis is presented which enables the boundary-layer thickness parameters of a re-attaching shear layer to be determined when the free-stream flow upstream of the base is supersonic, the base pressure is known, and die initial boundary layer is turbulent. The application of this analysis to some experimental results, on the flow behind blunt-trailing-edge wings and over a back-step where both the base pressure and the initial boundary layer are known, would appear to indicate that the re-attached profile could be specified by one parameter, namely the transformed shape parameter, the transformation used being a turbulent analogue of the well-known Stewartson-Illingworth transformation of the laminar boundary layer and where the shape parameter is defined as the ratio of boundary-layer displacement to momentum thickness. By adopting a value of the shape parameter in advance, it is possible to use the analysis to determine the base pressure by an iterative process and so, on this basis, it is suggested that this analysis is used to replace the existing recompression criterion of the Chapman-Korst model of separated flow which aims to predict base pressures and is known to be capable of improvement.As part of this investigation, an improvement had to be made to the existing compressible turbulent shear layer velocity profiles of Korst and others and this was achieved by means of the compressibility transformation.
Interaction of a Shock Wave with a Turbulent Boundary Layer Disturbed by Injection
Authors: Squire L.C. , Smith M.J. 
Published: July 2016

Summary:An experimental investigation has been made to study the interaction between an incident oblique shock wave and a turbulent boundary layer on a solid surface downstream of a porous surface with air injection through the porous surface. The results are clearly of direct interest to the design of cooled turbine blades. However, the boundary-layer profiles in the absence of the shock are similar to those in a boundary layer subjected to an adverse pressure gradient so that the results at the interaction also give some indication of the effects of an isentropic compression upstream of a shock/boundary-layer interaction. The experiments show the surprising result that the shock strength to produce incipient Separation is virtually independent of the shape of the boundary-layer profile upstream of the interaction, although the scale of the interaction increases with increase in the injection rate.
Effect of Base Slant on Flow in the Near Wake of an Axisymmetric Cylinder
Authors: Morel Thomas 
Published: July 2016

SummaryThe effects of slanting the base of a slender axisymmetric cylinder (length/diameter ratio of 9), aligned with the flow, was studied experimentally. The body was equipped with interchangeable rear ends covering a range of slant angles between 0° (vertical) and 70°. It was found that the base slant has a very dramatic effect on body drag, particularly in a relatively narrow range of slant angles where the drag coefficient exhibits a large local maximum (over-shoot). Detailed study of the flow showed that the drag overshoot is related to the existence of two very different Separation patterns on the slanted base. One pattern is similar to that found behind axisymmetric bodies with no base slant, and its main feature is the presence of a closed Separation region adjacent to the base. The other pattern is highly three-dimensional with two streamwise vortices forming along the sides of the slanted base. This pattern sets in very abruptly at a “critical” slant angle α ∼ 47°. Drag force measurements showed that, at first, the drag coefficient slowly increases with the slant angle, but then jumps suddenly upwards to more than double its baseline value (from CD = 0.24 to CD = 0.625) at the critical angle. At angles higher than that CD decreases again, and at 70° it is about equal to the baseline value. Further effects of the slant angle are the generation of a large side force and a significant increase in near-wake flow periodicity.
Changes in fruit, vegetable and juice consumption after the diagnosis of type 2 diabetes: a prospective study in men
Authors: Olofsson Camilla , Discacciati Andrea , Åkesson Agneta , Orsini Nicola , Brismar Kerstin , Wolk Alicja 
Published: July 2016

AbstractGiven the importance of prevention of complications in type 2 diabetes (T2D), we aimed to examine changes over time in consumption of fruits, vegetables and juice among men who were diagnosed with T2D in comparison with men without diabetes. The prospective Cohort of Swedish Men, aged 45–79 years in 1997, was used to examine changes in diet after diagnosis of T2D. Dietary intake was assessed using FFQ in 1997 and 2009. In all, 23 953 men who were diabetes free at baseline (1997) and completed both FFQ were eligible to participate in the study. Diagnosis of T2D was reported by subjects and ascertained through registers. Multivariable linear mixed models were used to examine changes in mean servings/week over time. In total, 1741 men developed T2D during the study period. Increased consumption of vegetables and fruits was observed among those who developed T2D (equivalent to 1·6 servings/week, 95 % CI 1·08, 2·03) and men who remained diabetes free (0·7 servings/week, 95 % CI 0·54, 0·84). Consumption of juice decreased by 0·6 servings/week (95 % CI −0·71, −0·39) among those who developed T2D and increased by 0·1 servings/week (95 % CI 0·05, 0·15) in those who were diabetes free. Changes over time and between groups were statistically significant. Although improvements in diet were observed, only 36 % of those with T2D and 35 % of those without diabetes consumed ≥5 servings of fruits and vegetables/d in 2009.
Reproducibility and validity of dietary patterns identified using factor analysis among Chinese populations
Authors: Hong Xin , Ye Qing , Wang Zhiyong , Yang Huafeng , Chen Xupeng , Zhou Hairong , Wang Chenchen , Chu Wenjie , Lai Yichao , Sun Liuyuan , Wang Youfa , Xu Fei 
Published: July 2016

AbstractIn the present study, we evaluated the reproducibility and validity of dietary patterns among Chinese adult populations. A random subsample of 203 participants (aged 31–80 years) from a community-based nutrition and health survey was enrolled. An eighty-seven-item FFQ was administered twice (FFQ1 and FFQ2) 1 year apart; four 3 consecutive day, 24-h dietary recalls (24-HDR, as a reference method) were performed between the administrations of the two FFQ every 3 months. Dietary patterns from three separate dietary sources were derived using factor analysis based on twenty-eight predefined food groups. Comparisons between dietary pattern scores were made by using Pearson’s or intraclass correlation coefficients (ICC), cross-classification analysis, weightedκstatistic and Bland–Altman plots; the four major dietary patterns identified from FFQ1, FFQ2 and 24-HDR were similar. Regarding reproducibility, ICC forz-scores between FFQ1 and FFQ2 were all >0·6 for dietary patterns. The ‘animal and plant protein’ pattern had the highest ICC of 0·870. For validity, the adjusted Pearson’s correlation coefficients for dietary patternz-scores between two FFQ and the mean of four 3 consecutive day 24-HDR ranged from 0·387 for the ‘Chinese traditional’ pattern to 0·838 for the ‘animal and plant protein’ pattern. More than 75 % of the participants were classified into the same or adjacent quartile, and <5 % were misclassified into opposite quartiles. The weightedκranged from 0·259 to 0·680. Bland–Altman plots indicated that no significant deviation was found between two dietary assessment methods. Our findings indicate a good reasonable reproducibility and a reasonable validity of dietary patterns derived by factor analysis in China.
L'analyse automatisée du ton médiatique : construction et utilisation de la version française du Lexicoder Sentiment Dictionary
Authors: Duval Dominic , Pétry François 
Published: July 2016

RésuméCet article introduit un nouveau dictionnaire permettant l'analyse automatisée du ton des médias francophones, que nous avons appelé Lexicoder Sentiment Dictionnaire Français (LSDFr) en référence au lexique anglophone de Young et Soroka (2012), Lexicoder Sentiment Dictionary (LSD) à partir duquel le LSDFr a été construit. Une fois construit, nous comparons le LSDFr au seul autre dictionnaire francophone existant de ce genre, Linguistic Inquiry and Word Count (LIWC). Nous testons ensuite la validité interne du LSDFr en le comparant avec un corpus de textes codés manuellement. Nous testons enfin la validité externe du LSDFr en mesurant jusqu'où le ton médiatique, calculé à l'aide de notre dictionnaire, prédit les intentions de vote des Québécois lors des quatre dernières campagnes électorales. En développant cet outil, notre objectif est de permettre à d'autres chercheurs d'effectuer des analyses médiatiques dans un corpus de textes comparables en français.
Uniqueness of patterns generated by repetition
Authors: Mason John 
Published: July 2016

Consider two related tasks:A) The diagram below displays a fragment of a pattern known to extend indefinitely and to be generated by an endlessly repeating pattern. What kind of shading will the 137th cell have? What number cell will the 137th white cell be in?B) What is the next term in the sequence 3, 6, 11, 18, 27, …?Tasks like the first can provide excellent experience of detecting and expressing generality as one route to algebra, but only if learners are first asked to describe a structural relationship which generates the succeeding items. Tasks like the second feature in intelligence tests, but it is well known that such tasks are mathematically incomplete.
An approximation to the arithmetic-geometric mean
Authors: Jameson G. J. O. 
Published: July 2016

Given positive numbers a > b, consider the ‘agm iteration’ given by a0 = a, b0 = b andAt each stage, the two new numbers are the arithmetic and geometric means of the previous two. It is easily seen that bn < an, (an) is decreasing, (bn) is increasing and an + 1 − bn + 1 < ½(an − bn), and hence that (an) and (bn) converge to a common limit, which is called the arithmetic-geometric mean of a and b. We will denote it by M (a, b).
Graph-theoretic models for the Fibonacci family
Authors: Koshy Thomas 
Published: July 2016

The well-known Fibonacci and Lucas numbers continue to faxcinate the mathematical community with their beauty, elegance, ubiquity, and applicability. After several centuries of exploration, they are still a fertile ground for additional activities, for Fibonacci enthusiasts and amateurs alike.Fibonacci numbers Fn and Lucas numbers Ln belong to a large integer family {xn}, often defined by the recurrence xn = xn−1 + xn−2, where x1 = a, x2 = b, and n ≥ 3. When a = b = 1, xn = Fn; and when a = 1 and b = 3, xn = Ln. Clearly, F0 = 0 and L0 = 2. They satisfy a myriad of elegant properties [1,2,3]. Some of them are:In this article, we will give a brief introduction to the Q-matrix, employ it in the construction of graph-theoretic models [4, 5], and then explore some of these identities using them.In 1960 C.H. King studied the Q-matrix
Paradoxical Euler: Integrating by Differentiating
Authors: Fabian Andrew , Nguyen Hieu D. 
Published: July 2016

Every student of calculus learns that one typically solves a differential equation by integrating it. However, as Euler showed in his 1758 paper (E236), Exposition de quelques paradoxes dans le calcul intégral (Explanation of certain paradoxes in integral calculus) [1], there are differential equations that can be solved by actually differentiating them again. This initially seems paradoxical or, as Euler describes it in the introduction of his paper:Here I intend to explain a paradox in integral calculus that will seem rather strange: this is that we sometimes encounter differential equations in which it would seem very difficult to find the integrals by the rules of integral calculus yet are still easily found. not by the method of integration. but rather in differentiating the proposed equation again; so in these cases, a repeated differentiation leads us to the sought integral.
How to choose your relations
Authors: Crilly Tony , Fletcher Colin R. 
Published: July 2016

Mathematicians are fascinated by relatios and have worked our extensive theories about them. The treatments tend to be abstract and sometimes the basic ideas are lost in the abstraction. Here we investigate some common ground between mathematical relations and down-to-earth genealogy, the study of family relations.Family relations have been studied by mathematicians, perhaps none more playfully than Thomas P. Kirkman (the nineteenth century expert in combinatorial mathematics) in his little puzzle rhyme he sent to the Educational Times [1, p.117]:Baby Tom of Bay HughThe nephew is and uncle too;In how many ways can this be true
Miscellaneous triangle properties
Authors: Scott J. A. 
Published: July 2016

In this note we will discuss five topics from triangle geometry and occasionally encounter something new. Areal coordinates (presented as Appendix A in [1]) will be used throughout, with the exception of the final section where it is advantageous to employ Cartesians.The topics are:(1) examples of collinearities where the distance ratios for important points vary with triangle shape;(2) a pencil of lines which includes the Fermat, Napoleon and Vecten axes;(3) two more circles related to the Lester circle;(4) the family of rectangular hyperbolae which circumscribe the triangle of referenceABCand whose principal member is the Kiepert hyperbola [2];(5) Cartesian coordinates leading to a solution of the ‘Euler disc problem’ [3].
Village senior centres and the living arrangements of older people in rural China: considerations of health, land, migration and intergenerational support
Authors: LIU HUIJUN , EGGLESTON KAREN N. , MIN YAN 
Published: July 2016

ABSTRACTChina is experiencing rapid urbanisation and population ageing, alongside sometimes contentious rural land consolidation. These on-going social, economic, political and demographic changes are especially problematic for older people in rural areas. In these regions, social and institutional support arrangements are less developed than in urban areas; older people have few options for re-settlement but are resistant to or incapable of adjusting to high-rise apartment living. In 2012–13, we gathered rich qualitative and quantitative data on over 600 older residents in 12 villages under the jurisdiction of City L in north-east coastal China to analyse residents’ living arrangement choices during the village renovation process. We compared villages with and without senior centres to shed light on the correlates of co-residence and independent living. Senior centres play a role in balancing the burden on rural Chinese families resulting from population ageing, smaller families, widespread migration for work, and the rapid urbanisation that is restructuring land rights and social support arrangements.