bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgical Methods and Experiences of Surgeons did not Significantly Affect the Recovery in Phonation Following Reconstruction of the Recurrent Laryngeal Nerve
Authors: Yoshioka Kana , Miyauchi Akira , Fukushima Mitsuhiro , Kobayashi Kaoru , Kihara Minoru , Miya Akihiro
Published: July 2016

Background

We reported phonatory recovery in the majority of 88 patients after recurrent laryngeal nerve (RLN) reconstruction. Here we analyzed factors that might influence the recovery, in a larger patient series.

Methods

At Kuma Hospital, 449 patients (354 females and 95 males) underwent RLN reconstruction with direct anastomosis, ansa cervicalis‐to‐RLN anastomosis, free nerve grafting, or vagus‐to‐RLN anastomosis; 47.4 % had vocal cord paralysis (VCP) preoperatively. Maximum phonation time (MPT) and mean airflow rate during phonation (MFR) were measured 1 year post surgery. Forty patients whose unilateral RLNs were resected and not reconstructed and 1257 normal subjects served as controls.

Results

Compared to the VCP patients, the RLN reconstruction patients had significantly longer MPTs 1 year after surgery, nearing the normal values. The MFR results were similar but less clear. Detailed analyses of 228 female patients with reconstruction for whom data were available revealed that none of the following factors significantly affected phonatory recovery: age, preoperative VCP, method of reconstruction, site of distal anastomosis, use of magnifier, thickness of suture thread, and experience of surgeon. Of these 228 patients, 24 (10.5 %) had MPTs <9 s 1 year after surgery, indicating insufficient recovery in phonation. This insufficiency was also not associated with the factors mentioned above.

Conclusions

Approximately 90 % of patients who needed resection of the RLN achieved phonatory recovery following RLN reconstruction. The recovery was not associated with gender, age, preoperative VCP, surgical method of reconstruction, or experience of the surgeon. Performing reconstruction during thyroid surgery is essential whenever the RLN is resected.
Pre-clerkship clinical skills and clinical reasoning course performance: Explaining the variance in clerkship performance: Pre-clerkship predictors of clerkship variance
Authors: LaRochelle Jeffrey S. , Dong Ting , Durning Steven J.
Published: July 2016

Introduction: Evidence suggests that pre-clerkship courses in clinical skills and clinical reasoning positively impact student performance on the clerkship. Given the increasing emphasis on reducing diagnostic reasoning errors, it is very important to develop this critical area of medical education. An integrated approach between clinical skills and clinical reasoning courses may better predict struggling learners, and better allocate scarce resources to remediate these learners before the clerkship. Methods: Pre-clerkship and clerkship outcome measures from 514 medical students graduating between 2009 and 2011were analyzed in a multiple linear regression model. Results: Learners with poor performances on integrated pre-clerkship outcome measures had a relative risk of 6.96 and 5.85 for poor performance on National Board of Medical Examiners (NBME) subject exams and clerkship performance, respectively, and explained 22 % of the variance in clerkship NBME subject exam scores and 20.2 % of the variance in clerkship grades. Discussion: Pre-clerkship outcome measures from clinical skills and clinical reasoning courses explained a significant amount of clerkship performance beyond baseline academic ability. These courses provide valuable information regarding student abilities, and may serve as an early indicator for students requiring remediation. Conclusions: Integrating pre-clerkship outcome measures may be an important aspect of ensuring the validity of this information as the pre-clerkship curriculum becomes compressed, and may serve as the basis for identifying students in need of clinical skills remediation.
Distributional properties of solutions of dV
t = V
t-dU
t + dL
t with Lévy noise
Authors: Behme Anita Diana
Published: July 2016

For a given bivariate Lévy process (U

t
, L

t
)
t≥0, distributional properties of the stationary solutions of the stochastic differential equation dV

t
= V

t-dU

t
+ dL

t
are analysed. In particular, the expectation and autocorrelation function are obtained in terms of the process (U, L) and in several cases of interest the tail behavior is described. In the case where U has jumps of size −1, necessary and sufficient conditions for the law of the solutions to be (absolutely) continuous are given.
Addendum to ‘Isotropic correlation functions ond-dimensional balls’
Authors: Gneiting Tilmann
Published: July 2016

We discuss necessary and sufficient conditions for power-law and polynomial models to be correlation functions on bounded domains. These results date back to unpublished work by Matheron (1974) and generalize the findings of Gneiting (1999).
Total variation distances and rates of convergence for ancestral coalescent processes in exchangeable population models
Authors: Möhle M.
Published: July 2016

Haploid population models with non-overlapping generations and fixed population size N are considered. It is assumed that the family sizes ν1,…,νN within a generation are exchangeable random variables. Rates of convergence for the finite-dimensional distributions of a properly time-scaled ancestral coalescent process are established and expressed in terms of the transition probabilities of the ancestral process, i.e., in terms of the joint factorial moments of the offspring variables ν1,…,νN.

The Kingman coalescent appears in the limit as the population size N tends to infinity if and only if triple mergers are asymptotically negligible in comparison with binary mergers. In this case, a simple upper bound for the rate of convergence of the finite-dimensional distributions is derived. It depends (up to some constants) only on the three factorial moments E((ν1)2), E((ν1)3) and E((ν1)2(ν2)2), where (x)k := x(x-1)…(x-k+1). Examples are the Wright-Fisher model, where the rate of convergence is of order N-1, and the Moran model, with a convergence rate of order N-2.
A general linear birth and growth model
Authors: Quine M. P. , Szczotka W.
Published: July 2016

We consider a birth and growth model where points (‘seeds’) arrive on a line randomly in time and space and proceed to ‘cover’ the line by growing at a uniform rate in both directions until an opposing branch is met; points which arrive on covered parts of the line do not contribute to the process. Existing results concerning the number of seeds assume that points arrive according to a Poisson process, homogeneous on the line, but possibly inhomogeneous in time. We derive results under less stringent assumptions, namely that the arrival process be a stationary simple point process.
Non-parametric estimation of the directional distribution of stationary line and fibre processes
Authors: Kiderlen Markus
Published: July 2016

Two non-parametric methods for the estimation of the directional measure of stationary line and fibre processes in d-dimensional space are presented. The input data for both methods are intersection counts with finitely many test windows situated in hyperplanes. The first estimator is a measure valued maximum likelihood estimator, if applied to Poisson line processes. The second estimator uses an approximation of the associated zonoid (the Steiner compact) by zonotopes. Consistency of both estimators is proved (without use of the Poisson assumption). The estimation methods are compared empirically by simulation.
Restless bandits, partial conservation laws and indexability
Authors: Niño-Mora José
Published: July 2016

We show that if performance measures in a general stochastic scheduling problem satisfy partial conservation laws (PCL), which extend the generalized conservation laws (GCL) introduced by Bertsimas and Niño-Mora (1996), then the problem is solved optimally by a priority-index policy under a range ofadmissiblelinear performance objectives, with both this range and the optimal indices being determined by a one-pass adaptive-greedy algorithm that extends Klimov's: we call such scheduling problemsPCL-indexable. We further apply the PCL framework to investigate the indexability property of restless bandits (two-action finite-state Markov decision chains) introduced by Whittle, obtaining the following results: (i) we present conditions on model parameters under which a single restless bandit is PCL-indexable, and hence indexable; membership of the class of PCL-indexable bandits is tested through a single run of the adaptive-greedy algorithm, which further computes the Whittle indices when the test is positive; this provides a tractable sufficient condition for indexability; (ii) we further introduce the subclass ofGCL-indexablebandits (including classical bandits), which are indexable under arbitrary linear rewards. Our analysis is based on the achievable region approach to stochastic optimization, as the results follow from deriving and exploiting a new linear programming reformulation for single restless bandits.
Sparse random matrices: spectral edge and statistics of rooted trees
Authors: Khorunzhy A.
Published: July 2016

Following Füredi and Komlós, we develop a graph theory method to study the high moments of large random matrices with independent entries. We apply this method to sparse N × N random matrices AN,p that have, on average, p non-zero elements per row. One of our results is related to the asymptotic behaviour of the spectral norm ∥AN,p∥ in the limit 1 ≪ p ≪ N. We show that the value pc = log N is the critical one for lim ∥AN,p/√p∥ to be bounded or not. We discuss relations of this result with the Erdős–Rényi limit theorem and properties of large random graphs. In the proof, the principal issue is that the averaged vertex degree of plane rooted trees of k edges remains bounded even when k → ∞. This observation implies fairly precise estimates for the moments of AN,p. They lead to certain generalizations of the results by Sinai and Soshnikov on the universality of local spectral statistics at the border of the limiting spectra of large random matrices.
Decay rates and cutoff for convergence and hitting times of Markov chains with countably infinite state space
Authors: Martínez Servet , Ycart Bernard
Published: July 2016

For a positive recurrent continuous-time Markov chain on a countable state space, we compare the access time to equilibrium to the hitting time of a particular state. For monotone processes, the exponential rates are ranked. When the process starts far from equilibrium, a cutoff phenomenon occurs at the same instant, in the sense that both the access time to equilibrium and the hitting time of a fixed state are equivalent to the expectation of the latter. In the case of Markov chains on trees, that expectation can be computed explicitly. The results are illustrated on the M/M/∞ queue.
The integral of geometric Brownian motion
Authors: Dufresne Daniel
Published: July 2016

This paper is about the probability law of the integral of geometric Brownian motion over a finite time interval. A partial differential equation is derived for the Laplace transform of the law of the reciprocal integral, and is shown to yield an expression for the density of the distribution. This expression has some advantages over the ones obtained previously, at least when the normalized drift of the Brownian motion is a non-negative integer. Bougerol's identity and a relationship between Brownian motions with opposite drifts may also be seen to be special cases of these results.
Conductance bounds on the L 2 convergence rate of Metropolis algorithms on unbounded state spaces
Authors: Jarner Søren F. , Yuen Wai Kong
Published: July 2016

In this paper we derive bounds on the conductance and hence on the spectral gap of a Metropolis algorithm with a monotone, log-concave target density on an interval of ℝ. We show that the minimal conductance set has measure ½ and we use this characterization to bound the conductance in terms of the conductance of the algorithm restricted to a smaller domain. Whereas previous work on conductance has resulted in good bounds for Markov chains on bounded domains, this is the first conductance bound applicable to unbounded domains. We then show how this result can be combined with the state-decomposition theorem of Madras and Randall (2002) to bound the spectral gap of Metropolis algorithms with target distributions with monotone, log-concave tails on ℝ.
Stochastic flows in fracture mechanics
Authors: Çinlar Erhan
Published: July 2016

There are two modes by which gross deformation can occur in a solid. Slips may occur along crystal planes, or the atomic planes may be torn apart and create microcracks. Both are highly stochastic phenomena requiring attention from probabilists. The present work attempts to understand the creation and growth of microcracks and their effect on the macro-level deformations.
Some comments on the cross-correlation of two processes arising from thinning a point process, with an application to queueing networks
Authors: Disney Ralph L. , Chandramohan Jagadeesh
Published: July 2016

Queueing networks continue to be of both theoretical interest and applied interest. One of the operations performed on a point process, representing customer flows in the network, thins a given process into two (or more) subprocesses each of which may thereafter be the arrival process to subsequent servers. A fair amount is known about the properties of each subprocess.
Threshing loss stochastic variabDity on combine harvesters
Authors: Glasbey C. A. , McGechan M. B.
Published: July 2016

The stochastic variability is investigated in the experimental results from an acoustic grain loss monitor and a table auger torque sensor on a combine harvester. A bivariate first-order autoregressive first-order moving-average model is identified and used to specify optimal control systems for adjusting combine forward speed to maintain constant threshing losses. These provide upper bounds on the benefits of practical forward speed control systems.
An analytically derived distribution function for mean areal rainfall
Authors: Nguyen Van-Thanh-Van
Published: July 2016

Both temporal and spatial information on rainfall distributions are important in various types of hydrologic studies concerning the determination of runoff characteristics. In reality, rainfall is measured at a point. Hence, for practical purposes, it is necessary to establish some relationships for the transformation of point rainfall at a fixed location to average rainfall over a catchment area in order to provide a more reliable input for rainfall-runoff models. The least equivocal method for deriving values of areal correction factor seems to be directly from frequency curves of areal and point rainfalls. Knowledge of the probability distribution of mean areal rainfall, therefore, is of paramount importance in solving this complex practical problem in hydrology.
Lines-of-descent and genealogical processes, and their applications in population genetics models
Authors: Tavaré Simon
Published: July 2016

This paper reviews a variety of results for genealogical (or line-of-descent) processes that arise in connection with the theory of some classical selectively neutral haploid population genetics models. While some new results and derivations are included, the principal aim of the paper is to demonstrate the central importance and simplicity of genealogical Markov chains in this theory. Considerable attention is given to ‘diffusion time scale’ approximations of such genealogical processes. A wide variety of results pertinent to (diffusion approximations of) the classical multi-allele single-locus WrightFisher model and its relatives are unified by this approach. Other examples where the genealogical process plays an explicit role (for example, the infinite-sites models) are discussed.
Laslett's line segment problem
Authors: Gill Richard D.
Published: July 2016

Consider A Stationary Line Segment Process In The Plane, Observed Through A Window W. Line Segments Which Cross The Boundary Of The Window Are Only Partially Observed. One Might Say That The Observed Lengths Of The Line Segments Are Then Censored. However, Classical Methods From The Theory Of Censored Survival Data (Kaplan-Meier Estimator) Can Be Seen To Be Inappropriate.
28th Lanchester Memorial Lecture — Experimental real-gas hypersonics
Authors: Hornung H. G.
Published: July 2016

For all who are specialists of one kind or another, it is a very healthy exercise to read books written by scientists or engineers of the calibre and breadth of F. W. Lanchester. He was at the same time truly a pioneer of flight, an expert in fluid mechanics, in flight mechanics, in the practical, and (well ahead of his time) in the military applications of flight, in the novel use of materials, and an inventor of devices and mechanisms. However, it was with particular surprise that I found, on studying the literature under the name F. W. Lanchester, a book published in 1935 entitled Relativity and two earlier papers on the subject published in 1921. Lanchester had met Minkowski in 1908 at the house of his friend Carl Runge, the applied mathematician, at Göttingen, and following a discussion with Minkowski had taken such an interest in the field that he was able to make these early English contributions.

Perhaps the most important property that makes such pioneers is the courage to think truly new thoughts. His fascination with the new philosophy in physics may be easily understood in terms of this bold style of thought.
Measurement of the drag of various three-dimensional excrescences in turbulent boundary layers
Authors: Gaudet L.
Published: July 2016

Measurements are described of the drags of various forms of three-dimensional excrescence mounted on balances installed in the walls of the working section of the RAE 8 ft x 8 ft wind tunnel. The tests cover a range of Mach numbers between 0·2 and 2·8 and a range of Reynolds number.

The excrescences tested include circular cylinders and wings mounted normal to the surface, fairing shapes and mushroom shaped rivet heads. For excrescences which were small compared with the boundary-layer thickness the scale effects were correlated in terms of the wall variables of the turbulent boundary layer. For circular cylinders and wings which protruded well into or beyond the boundary layer the drag may be determined by using a drag defect relationship. The fairings tested comprised half-bodies of revolution with pointed or rounded ends and bodies of rectangular, including square, section with pointed ends.
A review of the aerodynamics of a jet in a cross flow
Authors: Hancock G. J.
Published: July 2016

The aerodynamics of a circular jet emerging normally from a wall into a cross flow is critically assessed. Some general trends are obtained when viscous effects are neglected. But viscous effects dominate the real flow behaviour. Attempts to predict these real effects are reviewed and their anomalies highlighted. The importance of understanding and specifying the jet exit conditions is stressed, which is relevant to complete numerical solutions.
Investigation of the aerodynamic performance and noise characteristics of a 1/5th scale model of the Dowty Rotol R212 propeller
Authors: Trebble W. J. G.
Published: July 2016

An investigation of the four-bladed Dowty Rotol R212 propeller (NACA 16 sections) has been made at l/5th scale (0·7 metre diameter) in the RAE 1·5 metre acoustic tunnel. Propeller power absorption and thrust have been measured over a range of rotational speeds up to 8000 rev/min at mainstream speeds from 15 m/s to 60 m/s for a range of blade settings. Slipstream wake surveys show outward movement of the position of the peak pressure as propeller loading is increased.

Noise analysis demonstrates the predominance of multiple tones whose number and intensity increase with helical-tip Mach number. An empirical formula shows that the fundamental tone SPL varies with tip speed and power loading in an identical manner to that observed on a modern ARA-D section propeller.
The history of the Aeronautical Research Council; a personal view
Authors: Pugsley Alfred
Published: July 2016

This informal history of the ARC outlines the background to its establishment in 1909, the subsequent growth and widening of its research activities for the advancement of aircraft design and construction, particularly around the two great wars, and finally its gradual decline until brought to a close in 1980. The story is told from a personal viewpoint and touches on the many personalities involved.
Part I: Some experiences on simple panel methods applied to attached and separated flows
Authors: Tou H. B. , Hancock G. J.
Published: July 2016

Simple first order surface singularity methods based on:

(i) Smith and Hess uniform source panels plus a uniform vorticity around aerofoil profile,

(ii) piecewise linear vorticity around aerofoil profile, with different assumption for Kutta condition,

have been applied to attached flows and separated flows past an aerofoil/spoiler configuration, assuming an inviscid model.

For separated flows, piecewise linear vorticity methods give reasonable results as long as small panel elements are taken in the region of the separations at the spoiler tip and aerofoil trailing edge. The Smith and Hess method gives results which do not agree too closely with the vorticity methods. There is doubt concerning uniqueness.

Results have been compared using two different wake models; in one, the total head inside the wake is taken to be uniform, in the second, the static pressures along the separation streamlines are taken to be uniform. There appears to be a difference of about 5% in CL. It is not known why.
Vorticity measurement by a pressure probe
Authors: Freestone M. M.
Published: July 2016

An analysis is presented of the output of a pressure probe, comprised essentially of four yawmeters, which was designed to yield vorticity information.

It is shown that if the probe is utilised in flows which have vorticity dominated by variation of either the direction or the magnitude of the velocity then the probe output may be easily related to vorticity. It is argued that such flows should be readily recognised, and they include many situations of interest involving vortex flows, boundary layers and wakes.

Earlier work had already demonstrated that the probe is useful in exploring regions of predominantly streamwise vorticity. The present work shows a result with the probe used in a boundary layer flow where the vorticity is nearly normal to the local flow.

Use of the probe in unsteady flow is briefly examined.
Calculation of tunnel wall interference from wall-pressure measurements
Authors: Ashill P. R. , Keating R. F. A.
Published: July 2016

A method is described for calculating wall interference in solid-wall wind tunnels from measurements of static pressures at the walls. Since it does not require a simulation of the model flow, the technique is particularly suited to determining wall interference for complex flows such as those over VSTOL aircraft, helicopters and bluff shapes (e.g. cars and trucks). An experimental evaluation shows that the method gives wall-induced velocities which are in good agreement with those of existing methods in cases where these techniques are valid, and illustrates its effectiveness for inclined jets which are not readily modelled.
A first order theory for Newtonian flow over two-dimensional airfoils
Authors: Hemdan Hamdi T.
Published: July 2016

A simple closed-form formula for the coefficient of surface pressure, Cp is given in this paper. The formula is based on first and second approximations of the full problem and can be used for the Newtonian flow past two-dimensional thin airfoils at small angles of attack and with attached shock waves. It thus extends Cole's zero order theory to the effects of non-zero (γ – 1) and finite values of Mx where γ is the ratio of the specific heats of the gas and Mx is the free stream Mach number. The analysis presented relies on a previous recent formulation of the hypersonic small disturbance theory which has proved to be more advantageous than the hypersonic small disturbance theory. The results are compared with other approximate methods and the agreement is found to be generally good.
Some Problems of Planetary Atmosphere Entry
Authors: Julian Allen H.
Published: July 2016

Summary:—

Progress in understanding the atmosphere heating problems of space vehicles at hyperbolic entry speeds is reviewed. The various sources of aerodynamic heating are discussed along with the response of suitable heat shield materials to these inputs. It is shown that even for optimum shaped vehicles the problems are formidable at entry speeds greatly in excess of Earth parabolic speed. Much additional research, particularly of ablation materials, will be needed to effect satisfactory designs for such craft.
The Effect of Boat-Tailing on the Flow Round a Two-Dimensional Blunt-Based Aerofoil at Zero Incidence
Authors: Maull D. J. , Hoole B. J.
Published: July 2016

Some experiments on the effect of boat-tailing on the pressure distribution round blunt-based aerofoils are described. The experiments were carried out at low speeds at a Reynolds number of 1.5 X 105. The wake was investigated with attention being paid to the vortex shedding, and to the distance downstream of the base where vortices form.

It is shown that the theory due to Nash predicts the effect of boat-tailing on base pressure quite well and that a correlation of drag coefficient, Strouhal number and base pressure proposed by Bearman applies to the models tested here.
A Triangular Equilibrium Element with Linearly Varying Bending Moments for Plate Bending Problems
Authors: Morley L. S. D.
Published: July 2016

Work on the finite element analysis of flat plates in bending has been directed towards elements which satisfy kinematic conditions between the adjacent elements in conjunction with the theorem of minimum potential energy, eg Argyris, Bazeley et al, Clough and Veubeke.

The purpose of this Note is to provide the main details of a triangular element which satisfies equilibrium conditions between the adjacent elements and which is used in conjunction with the complementary energy principle. The bending moments vary linearly within the element and use is made in the derivation of the analogy (see eg Southwell, Fox, Fung and Morley that exists between problems of plane stress and plate bending. In particular, many of the present details are taken directly from the plane stress analysis of Veubeke who, along with Argyris, considers a displacement triangular element with linearly varying strain.
Optimum Tapers for Eccentrically Loaded Ties
Authors: Mansfield E. H.
Published: July 2016

Summary:—

A long untapered tie under tension exhibits localised stress concentrations when one end is subjected to a flexural rotation. These stress, concentrations can be avoided by tapering the tie. The optimum tapers for ties of circular and rectangular section are determined in this paper, and the resultant flexural stiffnesses are compared with those of untapered ties. Results are of interest in the design of certain satellite model support systems.
The Application of Circulation Control by Blowing to Helicopter Rotors
Authors: Cheeseman I. C. , Seed A. R.
Published: July 2016

A review of some methods of obtaining augmented lift coefficients in aerofoil sections precedes a description of lift by circulation control by blowing. The basic aerodynamic characteristics are considered as a prelude to a comparison of the merits of their application to helicopter rotors.

In calculating the performance of a helicopter rotor which uses high lift coefficients, the determination of the induced power has demanded an extension of the performance estimation curves normally used. A theoretical model has been developed to calculate the induced power factor which suggests a large increase in this parameter for rotor thrust coefficients above the current helicopter operating regime. Experimental results up to thrust coefficients of 0·1 which confirm the theoretical results are presented.

Some tentative ideas on the application of circulation control to produce a high speed helicopter are considered.
The Effect of Compressibility on the Maximum Lift Coefficient of Aerofoils at Subsonic Airspeeds
Authors: Wootton L. R.
Published: July 2016

It has long been known that compressibility affects the maximum lift coefficient at Mach numbers as low as 0·15. A schematic flight envelope (Fig. 1) shows that there are two main phenomena to be considered; the effects of compressibility on the low speed stall, and on the high subsonic speed stall.

In the low speed stall regime there is, in general, a decrease of the maximum lift coefficient with increasing Mach number which is appreciable even at typical aircraft landing speeds. A knowledge of the lift boundary throughout the envelope is necessary if allowances are to be made for gusts and if a safe rough-air performance is to be determined.
The Force on a Plane Screen Due to a Normal Jet
Authors: Newman B. G. , Bruce D. M.
Published: July 2016

The force on a plane wire screen at right angles to the axis of a fully-developed, turbulent and effectively two-dimensional and incompressible jet has been determined. This study was suggested by the use of perforated surfaces in the operation of aircraft. Perforated landing and takeoff pads are used to reduce adverse ground effect, and the re-ingestion of burnt gases, on VTOL aircraft with centrally-located, downward-pointing jets. Perforated baffles are occasionally used to attenuate jet speeds during ground testing of conventional jet aircraft. The study is also relevant to a process in the making of paper. The pulp and water mixture is deposited on a moving screen (Fourdrinier wire), and the jet approaches the screen at an oblique angle.
Computer Graphical Design Aids
Authors: Leslie W. H. P.
Published: July 2016

The engineering designer may not always be aware of the paramount importance of being able to sketch his ideas as a means of communicating his plans.

An example illustrates the point that drawings, graphs or diagrams convey concepts more easily than a table of figures. Table I gives a series of X and Y values describing a well-known contour, but it is not easy to determine the shape except by plotting the points. One can appreciate at a glance at Fig. 1, however, that it is a well-known shape.

Although the drawing is very graphic, the term graphic will also be taken to include alphabetical and numerical records for the purpose of this paper.
The Computer in the Stress and Design Offices
Authors: Taig I. C.
Published: July 2016

In this final presentation in this symposium I hope to relate some of the present and future developments in computer applications to the everyday world of an engineering design office. The first engineering industry to make extensive use of the computer in design was, I believe, the aircraft industry. In the late 1940's and early 50's digital and analogue computers revolutionised the treatment of aeroelasticity and since that time the spread of computer methods of analysis and design has been rapid. Until recently these developments have been erratic and badly co-ordinated and even today there is no aircraft firm to my knowledge, either in this country or the USA, which realises more than a small fraction of the potential efficiency in design which could be provided by the computers at its disposal. In the past two or three years this fact has become more widely appreciated and I believe that the really significant steps forward are being taken at this moment. The previous papers have shown clearly the possible extent of the computer revolution in the easily foreseeable future. I hope to illustrate, through a specific example, the influence of this revolution on the activities and on the men employed in an aircraft design office.
Vortex Breakdown Effects on the Low-speed Aerodynamic Characteristics of Slender Delta Wings in Symmetrical Flow
Authors: Hummel D. , Srinivasan P. S.
Published: July 2016

Even at small angles of incidence, the flow separates from the sharp leading edges of a slender wing. These flow separations usually lead to the formation of two free vortex layers, joined to the leading edges of the wing and rolling up to form spiral-shaped vortex sheets above the upper surface of the wing. This vortex formation is illustrated schematically in Fig. 1. The streamlines on the vortex sheet follow helical paths. Smoke injected near the wing apex for flow visualisation remains concentrated close to the axis of the core of the vortex sheet.
Frequency of the Karman Vortex Streets in Tube Banks
Authors: Chen Y. N.
Published: July 2016

In the note “Aerodynamically induced vibration in coolers”, by D. G. Mabey (pp 876-7, December 1965 Journal), the results of Grotz and Arnold concerning the frequency of the Karman vortex streets in tube banks, such as in heat exchangers, are mentioned, as is also the law of the linear relation between f(T—d)/V and (2T-L)/d, as found by Putnam, where

f frequency of vortex shedding

T transverse distance

L longitudinal distance between tubes

d outer diameter of tube

V mean stream velocity based on minimum flow area between the tubes

This linear relation has no theoretical justification and cannot be accurate, as is admitted by the author cited. A further investigation on a theoretical basis seems to be necessary.
On the Bending Elastic Stability of Isotropic Cylinders
Authors: Lakshmikantham C. , Gerard G.
Published: July 2016

Seide and Weingarten have, recently, shown conclusively that in isotropic cylinders, the critical stress for bending stability is essentially the same as that in the corresponding compressive stability problem although the buckle pattern is quite different. The deflection pattern obtained in ref. 1 as a result of elaborate computations presents certain interesting features. The dominant feature is that the buckle pattern is an asymmetric one, because any axisymmetric mode is incompatible with the bending problem.
A Short Proof of the Prandtl-Meyer Expansion Formula
Authors: Collar A. R.
Published: July 2016

Most teachers of gasdynamics with whom the writer has discussed the Prandtl-Meyer analysis find difficulty in giving a lucid exposition to students; the standard treatment tends to be long, and mathematical rather than physical, so that steps in the process of integration are difficult to remember. Lockwood Taylor gives a short treatment; but he begins from Ackeret's formula, which is in effect the differential equation to be treated; and he avoids the actual integration. These considerations have prompted the writer to publish the following treatment, which though self-contained is quite short, and—being mostly graphical—gives some insight into the physics of the problem.
Recent Developments in High Strength Aluminium Alloys
Authors: Baker W. A. , Bryant A. J. , Durham R. J. , Elkington R. W.
Published: July 2016

As The strength of aluminium alloys is increased, other desirable properties are increasingly sacrificed and, as with other metallic materials, a major difficulty in developing better strong alloys is to assess these other properties in terms which are satisfactory indices of service performance. This difficulty becomes more acute as strength is increased and further progress demands that supplier and user are in the closest possible agreement on methods of assessing the properties involved and on where the line must be drawn between acceptable and unacceptable material behaviour. Discussion of this aspect of strong light alloy development is always opportune and much of what is said in this paper is intended to provoke constructive discussion between supplier and user on this subject.
Ceramic Fibre Reinforced Metals
Authors: Morley J.
Published: July 2016

We want structural materials to be as strong as possible, as light as possible and as stiff as possible. For all practical applications they must be tough or resilient. We might also want them to be of use at high temperatures, to have hard surfaces, to be resistant to corrosion and to be cheap and easy to fabricate.

With all orthodox structural metals strength and stiffness are roughly in proportion to the density of the material. There is therefore not a great deal of difference between them on the basis of specific strength and specific stiffness. This is illustrated in Table I.

There are a number of ceramic substances such as silicon carbide, aluminium oxide, beryllium oxide, boron and carbon which have very high elastic modulus values coupled with low densities and high melting points.
Were the Wrights Wrong?
Authors: Hildred William
Published: July 2016

The Fourth Handley Page Memorial Lecture, “Were the Wrights Wrong?”, was given by Sir William Hildred, OBE, CB, MA, Honorary Companion of the Society, Director Emeritus of the International Air Transport Association, in the Society's Lecture Theatre on 19th May 1966. Opening the meeting the President, Mr. A. D. Baxter, MEng, CEng, FRAeS, reminded the audience that the Handley Page Memorial Lecture was arranged jointly by the Cranfield Society and the Royal Aeronautical Society. Both Societies had much reason to honour the name of Sir Frederick Handley Page and the arrangements by which they alternated in providing both venue and the lecturer had proved a happy one.

On this occasion the Royal Aeronautical Society was glad to welcome its friends from the Cranfield Society and other guests and visitors, particularly Lady Hildred. “HP’s” early reputation was built on the practical application of aerodynamic flow, but it had extended far and wide and to many fields beyond aerodynamics and even beyond aeronautics. He thought it was in this spirit of his wider service to mankind that they paid tribute that night. Certainly he felt that was the approach their lecturer had taken.

Sir William Hildred was well known to most people through his long and valued service to the International Air Transport Association. On completion of his studies at the University of Sheffield in 1914, he joined the Army and served for the duration of the 1914-18 War. In 1919 he had started his Civil Service career in the Treasury, becoming a Finance Officer, then Head of a Branch of the Ministry of Agriculture and Fisheries and later a Deputy General Manager of the Exports Guarantee Department. In 1938 he had begun his long association with civil aviation as Deputy Director General of Civil Aviation at the Air Ministry, becoming Director General in 1941. In 1946 he had joined IATA as Director General, where he had done such magnificent work ever since until his retirement only a month ago. He had received many honours, including Grand Officer of the Order of Nassau, Commander of the Order of the Crown of Belgium and, not least they hoped, Honorary Companionship of the Royal Aeronautical Society.
An Improved Displaced Frequency Method for Estimation of Dynamical Characteristics of Mechanical Systems
Authors: Simpson A.
Published: July 2016

The “displaced frequency” method is widely used in the aircraft industry for estimating the generalised masses and stiffnesses of aircraft, which are used in response and other aeroelastic calculations. The usual procedure is to measure the natural frequencies, ωi, and the associated normal modes, zi, by standard resonance testing techniques. (The number of frequencies and modes actually measured depends, of course, on the accuracy required in subsequent calculations.) A small mass, or group of masses, is then added to the structure at a convenient point or points and the resulting frequency changes, δωi noted. Now if αi and εi are generalised masses and stiffnesses respectively, then in normal co-ordinates
On the Length of Two-Dimensional Contractions
Authors: Lau W. T. F.
Published: July 2016

In a recent paper, Gibbings has made an interesting comparison of the length of two-dimensional contractions based on three criteria, namely:

(1)

the rapidity with which the boundary slope approaches its zero value;

(2)

the rapidity with which the centre-line velocity approaches its asymptotic value; and

(3)

the degree of uniformity of the velocity expressed as a percentage of its mean value.
Blackpool Aviation Meeting 18th-23rd October 1909
Authors: Boreham F. G.
Published: July 2016

Among my collection of aviation papers and souvenirs, a favourite item is the Art souvenir and programme of the 1909 Blackpool Meeting. There, as a young schoolboy, I saw for the first time an aeroplane flying in a strong, almost gale force, wind. Bleriot's successful Channel crossing and the great Aviation Week held at Rheims had stimulated organisation of the first aviation meetings to be held in England, at Blackpool and Doncaster. It was a great treat, and an exciting experience to be taken to this meeting by my father, to see the new heavier-than-air flying machines. When we arrived at the flying ground, it had turned out a wet morning, with a strong wind.
Early Flights at Farnborough
Authors: Sandison C. G.
Published: July 2016

I joined the scientific staff at Farnborough in the summer of 1915, in a very minor capacity under R. McKinnon Wood, who was in charge of the Wind Channel and Whirling Arm sections.

Now looking back to a time 50 years ago, the following names come instantly to mind: Glauert, Grinstead, Hoare, B. M. Jones, G. I. Taylor, and McKinnon Wood, and of course Miss Gilford, who sat behind glass in the office of the head of B.A. Department, always busy and helpful.

For some time Glauert and I lodged in the same house in Church Circle, and if he joined in a conversation his remarks were always worth listening to, even if he was not familiar with the subject. His comment too was always stimulating, and in spite of his brilliant intellect, he could explain in simple terms something that one had had difficulty in following.
A Journey into Aeronautics
Authors: Carter B. C.
Published: July 2016

My First attention to matters Aeronautical occurred at about the turn of the Century, when a balloon appeared over an open space at the north of Portsmouth and a parachutist came down therefrom.

Again, I remember seeing an inflated non-rigid airship exhibited in the Victoria Hall, Southsea, made by a man named Spencer.

One recollects, also, that in those pre-motoring days, it was not unusual for errand boys, on their way in the streets, to sing some music-hall ditty.
The State of Affairs in the Royal Navy
Authors: Beadon J. A.
Published: July 2016

While the subject of this colloquium is limited to reliability, I feel it is essential to put this parameter in its right context as we as users in the RN see it.

We in the RN are most concerned with the availability of our aircraft to perform the required operational task. We define availability as the percentage of a given period of time that an aircraft is either being used or is serviceable ready for use. If availability is low then we need a larger number of aircraft to meet a commitment. With the cost of current aircraft and our restrictions on carrier complements this is a vital consideration.
Present Practices and Future Requirements for the Achievement of Aircraft Reliability
Authors: Morris D. E.
Published: July 2016

No one present can be complacent about the standard of aircraft reliability and his contribution to it. This applies to all concerned, to those responsible for the requirement, those responsible for the specification, all those concerned in the design and manufacture of airframes, engines, equipments and components and finally, the user and his servicing organisation. Significant improvement in reliability will result only from a contribution by everyone involved. It seems that in recent years the attention given to reliability has been out of balance with that given to all the other desired qualities. Those responsible for the requirement must be prepared to sacrifice performance or perhaps time, or variety, or pay more, for a gain in reliability; they must be given some indication of the rate of exchange to help them in this judgment. The designer must have this problem of balance and compromise clearly in mind and must play his part in clarifying the issue. Generally we have striven after the best performance possible and because weapons systems take so long to develop this tendency is probably more pronounced. But if you cast your minds back, systems which were regarded as being designed somewhat conservatively have often, overall, given the best service. Thus my first point is that there must be a conscious compromise between performance and reliability, associated of course with the time-scale and cost of the project. The designer must give equal consideration to reliability and to maintainability (the two go together of course) as to performance and other qualities.
A Sub-Contractor's Point of View
Authors: Mullin L. R.
Published: July 2016

Previous speakers have referred to the subcontractors being responsible for most unreliability. I feel therefore I must begin by pointing out that the electronics manufacturer merely designs equipment and assembles components from sub-contractors. Nevertheless we do take the responsibility for our products.

In the post-war period there have been continuous and rapid advances in the design of aircraft. To take full advantage of the higher performance and increasing speeds offered to them, the airlines of the world have demanded smaller and lighter electronic equipment providing, at the same time, more and more facilities. The rapid increase in traffic, the higher speeds of aircraft operation and the introduction of pilot-controlled communications have demanded more complex equipment and the electronics industry has met these requirements by continuous development of both components and equipment. It is a tribute to the industry that the present day equipments, although vastly more complex, are smaller, lighter and no less reliable than their counterparts of ten years ago.
The Problems of Electronics
Authors: Smith N. J.
Published: July 2016

Failure of electronic equipment represents a significant proportion of the overall defect rate for modern aircraft. While this is not entirely surprising in view of the quantity of electronic equipment installed, and the variety and multiplicity of functions performed, it remains a serious problem.

The specific reliability of electronic equipment, in terms of separate facilities, has tended to show marked and continuous improvement, but this has been overshadowed by the increasing number of functions performed, and by greater dependance on this equipment. Most electronic failures occur without warning, and many of the remainder need delicate and complex test procedures to obtain even a few hours warning of impending failure. In some instances, particularly where electronics is used because of its rapid reaction time, a fault can, unless special precautions are taken, be a serious risk to safety, or cause other serious consequences even before there is any warning that a fault condition exists.
A Suggested Approach to Linear Aeroelasticity Theory
Authors: Bishop R. E. D.
Published: July 2016

The aeroelastic properties of modern aircraft are such that necessary calculations, of critical flutter speeds for instance, can be remarkably complicated. A flutter analyst requires an inordinate degree of skill and experience if he is to acquire a “sense of feel” in calculations. The difficulty of deciding how to adjust a critical flutter speed predictably by some structural modification is a typical outcome of this complication.
The Influence of Aviation and Astronautics on Human Affairs
Authors: Shenstone B. S.
Published: July 2016

My original title for this lecture was “Aspects of Accessibility.” Then I discovered that people assumed it concerned accessibility in connection with aircraft maintenance. That assumption implied that an engineer is expected to stick to engineering. Having written what is to follow, I wonder whether that implication might well be right, and that all I have to say could be entitled:

“Glimpses of the Obvious”

On the other hand G. K. Chesterton clearly demonstrated that when the obvious is stressed, it often turns out to have unexpected aspects.