bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Part Played by Wind Tunnels in Modern Aeronautics
Authors: Lilley G. M. 
Published: July 2016

Summary:The wind tunnel has been the main instrument for experimental research in aeronautics since the turn of the century and its history is as brief as powered flight itself. It has always played a leading rdle in aeronautics right from the time of the Wright Brothers to the present day.The early form of wind tunnels as developed at the National Physical Laboratory and other research establishments have been replaced over the years by larger and more elaborate facilities, each having a particular speed range and specific role in aeronautical research and development. Modern wind tunnels having continuous operation of the type installed at the Royal Aircraft Establishment involve powers of up to 100 000 h.p. and cost in the neighbourhood of £10 000 000. In spite of this cost it is a sobering thought that, if anything, the overall cost of each data point is less today than it was in the early days of aeronautics. Such tunnels are highly complex instruments for research and development and although they play a rôle similar in many respects to that of a computer, they have the advantage of always dealing with a real fluid. Indeed no known computer could cope with the range of problems that can be solved in a wind tunnel, ranging from such complex problems as the structure of turbulent flow to the pressures in separated flow regimes, to quote just two examples. This fact must always be kept in perspective when arguments are presented for more and more work on digital computers to solve basic fluid motion problems. Of course we cannot overlook the problems of interpretation of wind tunnel data and the difficulties encountered in extrapolating these data to flight conditions.The development of theories for such problems together with answers is of ever increasing importance, especially as the problems in aeronautics are becoming more and more complex. These solutions have the important function not only of high-lighting certain aspects of the flow, but of pin-pointing the important parameters in a problem together with providing better than order of magnitude results. However, theories must be based on physical facts and these can only be determined in the final analysis from experiments.The wind tunnel has three highly significant roles in modern aeronautics:(i) Experimental research as a forerunner to future theoretical research.(ii) Experimental research as a confirmation and extension of theory.(iii) Current research and development work on a given aircraft.The current trend in bringing strong theoretical and experimental groups together, plus the employment of rapid measurement techniques in wind tunnels, promises the greatest possible productive utilisation of these highly important and expensive facilities. In most cases today they are playing a strong, if not the leading, role in aeronautical development.
The First Short Brothers Commemorative Lecture
Authors: Lankester Parker J. 
Published: July 2016

The Short Brothers were well known to me by name for a good many years before I had the pleasure of meeting any of them personally. That was when I joined the Company in the middle of 1916. It must I think, therefore, seem strange to you that the honour, a very real one to me, of being invited to give this first lecture to commemorate their great pioneering work, should fall to me.A big part of the span of man's life has passed since they began their activities; many of their contemporaries and friends of those early days have either passed on or have reached a ripe old age. It may well be that I know the brothers personally better than any one else living. Be that as it may, I am quite sure that none holds them in greater esteem.
Cabotage in Civil Aviation
Authors: Agostini Carl 
Published: July 2016

In presenting this paper I shall take but a brief look at a rather interesting subject, the impact of which, on our business in aviation, has doubtlessly touched each and everyone of us. I refer to the subject of Cabotage—an old term which like so many others in human affairs has taken on a new meaning in a world shrunken by our own specialised activity of aviation.Cabotage in its original maritime usage referred to carriage between two places within a geographical unit by earthbound vehicles. The essence of this cabotage however, was its parochial as opposed to international application and this was based on the recognised right of a State to reserve such carriage to its own ships. This restrictive nature of cabotage in maritime law is an exception to the general rule of the freedom of the seas.
The Society and Lighter-than-Air
Authors: Ventry Lord 
Published: July 2016

In the past, the Society did much for Lighter-than-Air, through its lectures, most of which I was able to attend. I well remember that anti-airship man, E. F. Spanner, who used to face a basically hostile audience, and the fighting speeches from that great protagonist for airships, the late Captain Boothby.The first, I think, to give lectures on airships was the late Colonel Waterlow in 1912 and 1913, but I was at Wellington then, and so was not present. Nobody fought harder than he did for airships, and he was very helpful to me when I used to visit the airship station at Wormwood Scrubbs.
Cloud Flying in the First World War
Authors: Melvill Jones B. 
Published: July 2016

I will describe some interesting work that was done in the First World War by S. Keith-Lucas who, like many of us, had been called up from his university to work, during the war, in what is now known as the Royal Aircraft Establishment, at Farnborough.After doing some experiments in flight, with ordinary compasses, he designed a special compass with which pilots could maintain a straight course and navigate, quite accurately, in clouds.It was early in the war that many pilots told us that, in clouds, their compasses went all wrong and pointed in almost any direction.
The Contribution of Radio Telephony, Telegraphy and the Later Electronic Techniques to Aviation
Authors: Barton F. S. , Cox Walker N. 
Published: July 2016

The Royal Flying Corps and the Royal Naval Air Service, which were combined in 1918 to form the Royal Air Force, both ended the First World War with radio communication by telegraphy and telephony between aircraft and ground stations and between actual aircraft.The equipment to achieve this was the result of research and development carried out for the Royal Flying Corps at various military establishments such as the Signals Experimental Establishment at Woolwich and for the Royal Naval Air Service, first at Eastchurch, Isle of Sheppey, and latterly at Cranwell.
Approximate entropy for testing randomness
Authors: Rukhin Andrew L. 
Published: July 2016

This paper arose from interest in assessing the quality of random number generators. The problem of testing randomness of a string of binary bits produced by such a generator gained importance with the wide use of public key cryptography and the need for secure encryption algorithms. All such algorithms are based on a generator of (pseudo) random numbers; the testing of such generators for randomness became crucial for the communications industry where digital signatures and key management are vital for information processing.
The concept of approximate entropy has been introduced in a series of papers by S. Pincus and co-authors. The corresponding statistic is designed to measure the degree of randomness of observed sequences. It is based on incremental contrasts of empirical entropies based on the frequencies of different patterns in the sequence. Sequences with large approximate entropy must have substantial fluctuation or irregularity. Alternatively, small values of this characteristic imply strong regularity, or lack of randomness, in a sequence. Pincus and Kalman (1997) evaluated approximate entropies for binary and decimal expansions of e, π, √2 and √3 with the surprising conclusion that the expansion of √3 demonstrated much less irregularity than that of π. Tractable small sample distributions are hardly available, and testing randomness is based, as a rule, on fairly long strings. Therefore, to have rigorous statistical tests of randomness based on this approximate entropy statistic, one needs the limiting distribution of this characteristic under the randomness assumption. Until now this distribution remained unknown and was thought to be difficult to obtain. To derive the limiting distribution of approximate entropy we modify its definition. It is shown that the approximate entropy as well as its modified version converges in distribution to a χ2-random variable. The P-values of approximate entropy test statistics for binary expansions of e, π and √3 are plotted. Although some of these values for √3 digits are small, they do not provide enough statistical significance against the randomness hypothesis.
Explicit sufficient invariants for an interacting particle system
Authors: Itoh Yoshiaki , Mallows Colin , Shepp Larry 
Published: July 2016

We introduce a new class of interacting particle systems on a graph G. Suppose initially there are N

i
(0) particles at each vertex i of G, and that the particles interact to form a Markov chain: at each instant two particles are chosen at random, and if these are at adjacent vertices of G, one particle jumps to the other particle's vertex, each with probability 1/2. The process
N
enters a death state after a finite time when all the particles are in some independent subset of the vertices of G, i.e. a set of vertices with no edges between any two of them. The problem is to find the distribution of the death state, η
i
= N

i
(∞), as a function of N

i
(0).
We are able to obtain, for some special graphs, the limiting distribution of N

i
if the total number of particles N → ∞ in such a way that the fraction, N

i
(0)/S = ξ
i
, at each vertex is held fixed as N → ∞. In particular we can obtain the limit law for the graph S
2, the two-leaf star which has three vertices and two edges.
Bounds for the total variation distance between the binomial and the Poisson distribution in case of medium-sized success probabilities
Authors: Weba Michael 
Published: July 2016

In applied probability, the distribution of a sum of n independent Bernoulli random variables with success probabilities p
1,p
2,…, p

n
is often approximated by a Poisson distribution with parameter λ = p
1 + p
2 + p

n
. Popular bounds for the approximation error are excellent for small values, but less efficient for moderate values of p
1,p
2,…,p

n
.
Upper bounds for the total variation distance are established, improving conventional estimates if the success probabilities are of medium size. The results may be applied directly, e.g. to approximation problems in risk theory.
A service model in which the server is required to search for customers
Authors: Neuts Marcel F. , Ramalhoto M. F. 
Published: July 2016

Customers enter a pool according to a Poisson process and wait there to be found and processed by a single server. The service times of successive items are independent and have a common general distribution. Successive services are separated by seek phases during which the server searches for the next customer. The search process is Markovian and the probability of locating a customer in (t, t + dt) is proportional to the number of customers in the pool at time t. Various stationary probability distributions for this model are obtained in explicit forms well-suited for numerical computation.
Under the assumption of exponential service times, corresponding results are obtained for the case where customers may escape from the pool.
A recursion theorem on solving differential-difference equations and applications to some stochastic processes
Authors: Severo Norman C. 
Published: July 2016

Summary
A recursive procedure leading to the solution of triangular systems of differential-difference equations is presented. It is shown that the equations for special families of multi-dimensional pure birth processes and pure death processes can be represented as such a system. The theory is used to resolve a difficult problem of stochastic cross-infection among groups. Additional applications to problems in epidemic theory are discussed.
On the equivalence of flows in networks of queues
Authors: Walrand J. 
Published: July 2016

Consider a network of queues in equilibrium. When are the flows observed on two given links of that network equivalent, i.e., when do they have the same law?
The verification of the equivalence of two such point processes is first reduced to an algebraic problem by a technique based on the filtering theory.
This method is then used to show that the arrival and departure processes at an M/M/1 node in a Jackson network are not always equivalent, thereby contradicting a conjecture made in [8]. An example where that equivalence holds is also given; it provides new results on the time reversibility of some familiar processes.
Smooth first-passage densities for one-dimensional diffusions
Authors: Pauwels E. J. 
Published: July 2016

The purpose of this paper is to show that smoothness conditions on the diffusion and drift coefficient of a one-dimensional stochastic differential equation imply the existence and smoothness of a first-passage density.
In order to be able to prove this, we shall show that Brownian motion conditioned to first hit a point at a specified time has the same distribution as a Bessel (3)-process with changed time scale.
The impact of the composition of the customer base in general queueing models
Authors: Federgruen A. , Groenevelt H. 
Published: July 2016

We consider general queueing models dealing with multiple classes of customers and address the question under what conditions and in what (stochastic) sense the marginal increase in various performance measures, resulting from the addition of a new class of customers to an existing system, is larger than if the same class were added to a system dealing with only a subset of its current customer base.
Our results enhance our understanding of the dependence of various performance measures with respect to the composition of the customer base. In addition they translate readily into convexity results in an (appropriately defined) arrival rate.
Single server queue with uniformly bounded virtual waiting time
Authors: Cohen J. W. 
Published: July 2016

Summary
In a previous paper [4] the author studied the stochastic process {wn
, n = 1,2, …}, recursively defined by

with K a positive constant, τ1, τ2, … σ1, σ2, …, independent, nonnegative stochastic variables. τ1,τ2…, are identically distributed, and σ1,σ2,…, are also identically distributed variables. For this process the generating function of the Laplace-Stieltjes transforms of the joint distribution of Wn
, σ2 + … + σ
n
and τ1 + … + τ
n−1
has been obtained. Closely related to the process {wn
, n = 1, 2,…} is the process {un
, n = 1, 2,…} with {un
= K + [wn
+ τ
n
− K]−, n = 1,2,…; these are dual processes.
In the present paper we study the stationary distributions of the processes {wn
, n= 1,2, …} and {un
, n = 1,2, …}, and the distributions ot the entrance times and return times of the events “wn
, n = 0” and “un
= K” for some n, for discrete as well as for continuous time. For these events various taboo probabilities are also investigated. The mathematical descri ption of the processes {wn
, n = 1,2, …} and {un
, n= 1,2, …} gives all the necessary information about the time-dependent behaviour for the general dam model with finite capacity K, since the process {wn
, n= 1,2, …} is the basic process for such dam models. In Sections 5, 6 and 7 the general theory is applied to the models M/G/1 and G/M/1. Complete explicit solutions are obtained for these models.
The present theory also leads to new and important results for the queueing system or dam model G/G/1 with infinite capacity. For instance the joint distribution of the busy period (or wet period) and of the supremum of the dam content dunng this period is obtained.
Two queues in series with a finite, intermediate waitingroom
Authors: Neuts Marcel F. 
Published: July 2016

A service unit I, with Poisson input and general service times is in series with a unit II, with negative-exponential service times. The intermediate waitingroom can accomodate at most k persons and a customer cannot leave unit I when the waitingroom is full.
The paper shows that this system of queues can be studied in terms of an imbedded semi-Markov process. Equations for the time dependent distributions are given, but the main emphasis of the paper is on the equilibrium conditions and on asymptotic results.
A new family of life distributions
Authors: Birnbaum Z.W. , Saunders S.C. 
Published: July 2016

Summary
A new two parameter family of life length distributions is presented which is derived from a model for fatigue. This derivation follows from considerations of renewal theory for the number of cycles needed to force a fatigue crack extension to exceed a critical value. Some closure properties of this family are given and some comparisons made with other families such as the lognormal which have been previously used in fatigue studies.
A diffusion process model for the optimal investment strategies of an R & D project
Authors: Zuckerman Dror 
Published: July 2016

In this article we examine an R &amp; D project in which the project status changes according to a diffusion process. The decision variables include a resource expenditure strategy and a stopping policy which determines when the project should be terminated. The drift and the diffusion parameters of the project status process are assumed to be functions of the resource expenditure rate.
The terminal reward from the project is a non-decreasing function of the project status. Our purpose is to select optimal investment strategies under the discounted return criterion.
The value of the project is shown to be a solution of a second order, non-linear differential equation. Finally, we derive the optimal investment strategies for an R &amp; D project in which the project status changes according to a non-homogeneous compound Poisson process by using diffusion approximation.
The multi-type Galton-Watson process with immigration
Authors: Quine M. P. 
Published: July 2016

Summary
We consider the limiting behaviour of a k-type (k &lt; ∞) Galton-Watson process which is augmented at each generation by a stochastic immigration component. In Section 2, conditions for ergodicity are found for a subclass of such processes. In Section 3, expressions are derived for the first two moments of the nth generation (by way of a recurrence relation) and for the first two asymptotic moments, in a manner which to some extent generalises previous results.
Moments in Markovian systems with lumped states
Authors: Taylor G. C. 
Published: July 2016

In dealing with Markov chains, we are sometimes forced by circumstances to make observations on lumped states. We may wish, however, to deal with a random variable which is a function of the numbers in the various (unlumped) states at various times and whose moments, therefore, will involve the probabilities of transition between the unlumped states.
This paper demonstrates that, although these probabilities are immeasurable directly, we can, provided that we restrict our attention to a certain well-defined class of functions as our random variables, reduce all moments and product-moments of such random variables to functions of lumped state probabilities.
Optimal stationary strategies in leavable Markov decision processes
Authors: Fassbender Matthias 
Published: July 2016

This paper establishes the existence of an optimal stationary strategy in a leavable Markov decision process with countable state space and undiscounted total reward criterion.
Besides assumptions of boundedness and continuity, an assumption is imposed on the model which demands the continuity of the mean recurrence times on a subset of the stationary strategies, the so-called ‘good strategies'. For practical applications it is important that this assumption is implied by an assumption about the cost structure and the transition probabilities. In the last part we point out that our results in general cannot be deduced from related works on bias-optimality by Dekker and Hordijk, Wijngaard or Mann.
Convexity results for single-server queues and for multiserver queues with constant service times
Authors: Harel Arie 
Published: July 2016

We show that the waiting time in queue and the sojourn time of every customer in the G/G/1 and G/D/c queue are jointly convex in mean interarrival time and mean service time, and also jointly convex in mean interarrival time and service rate. Counterexamples show that this need not be the case, for the GI/GI/c queue or for the D/GI/c queue, for c ≧ 2. Also, we show that the average number of customers in the M/D/c queue is jointly convex in arrival and service rates.
These results are surprising in light of the negative result for the GI/GI/2 queue (Weber (1983)).
Processes with associated increments
Authors: Glasserman Paul 
Published: July 2016

We derive conditions under which the increments of a vector process are associated — i.e. under which all pairs of increasing functions of the increments are positively correlated. The process itself is associated if it is generated by a family of associated and monotone kernels. We show that the increments are associated if the kernels are associated and, in a suitable sense, convex. In the Markov case, we note a connection between associated increments and temporal stochastic convexity.
Our analysis is motivated by a question in variance reduction: assuming that a normalized process and its normalized compensator converge to the same value, which is the better estimator of that limit? Under some additional hypotheses we show that, for processes with conditionally associated increments, the compensator has smaller asymptotic variance.
On distributions having the almost-lack-of-memory property
Authors: Chukova S. , Dimitrov B. 
Published: July 2016

It is shown that random variables X exist, not exponentially or geometrically distributed, such that

P{X – b ≧ x | X ≧ b} = P{X ≧ x}
for all x &gt; 0 and infinitely many different values of b. A class of distributions having the given property is exhibited. We call them ALM distributions, since they almost have the lack-of-memory property. For a given subclass of these distributions some phenomena relating to service by an unreliable server are discussed.
Distribution of the number of alleles in multigene families
Authors: Griffiths R. C. 
Published: July 2016

The distribution of the number of alleles in samples from r chromosomes is studied. The stochastic model used includes gene conversion within chromosomes and mutation at loci on the chromosomes. A method is described for simulating the distribution of alleles and an algorithm given for computing lower bounds for the mean number of alleles.
A formula is derived for the expected number of samples from r chromosomes which contain the allele type of a locus chosen at random.
On closed ring queueing networks
Authors: Bambos Nicholas 
Published: July 2016

In this paper we first study ring structured closed queueing networks with distinguishable jobs. Under assumptions of periodicity and ergodicity of the service times, essentially the most general, it is shown that the limits defining the average flows of the jobs exist almost surely, and methods for their estimation by simulation are given. However, it turns out that the values of the flows depend on the initial positions of the jobs, due to the emergence of distinct persistent blocking modes. The effect of these modes on the behavior of general networks with queueing loops is examined.
For independent and identically distributed service times, conditions are specified for the network to asymptotically approach a steady state at large times.
Finally, we study the special case of ring networks with indistinguishable items and stationary and ergodic service times. It is shown that as the number of jobs in the network increases towards infinity, the average circulation time converges to the maximum of the expectations of the service times.