452 research outputs found
Studies in the design and implementation of programming languages for symbol manipulation
Compared with the development of computing hardware, the
development of programming languages has followed a different course.
Hardware innovations such as the use of transistors and integrated
circuitry have resulted in machines with very substantially improved
capabilities, making older machines and even comparatively modern
machines obsolescent. The programming languages currently in most
widespread use, however, remain those which were already in use as many
as ten years ago, namely HJRTRAN, ALGOL 60, and COBOL. Nevertheless,
considerable improvements can be made to these languages. The reasons
why no improvements were made appear to be primarily twofold. Firstly,
they are regarded as 'standard' languages, which in order to facilitate
transferability of programs, has made them virtually immutable.
Secondly, they can be employed in almost all programming situations
without the need for change.
Instead, very many other languages have been designed and
implemented with particular objectives in view, but which almost
invariably limit their application to a narrow field. Only recently have
attempts been made to unify some of the developments under the cloak of
a single language ( PL/1 and ALGOL 68 ). Data structures are a
particular example of what features have been incorporated. There are
still considerable omissions however. For instance, neither language has
incorporated list processing or symbol manipulation facilities within
its basic framework.
The latter seems to be most surprising. With the increased
capabilities of modern computers and the consequent broadening of their
range of application, techniques involving symbol manipulation are
becoming increasingly important. Natural language processing such as the
analysis of texts for authorship and mechanical translation, and formal
manipulations, such as those involved in mechanical theorem-proving and
algebraic formula manipulation are some obvious applications. The last
mentioned, that of algebraic manipulation of formulae, is one of the
most important applications. Several systems, notably R3RMAC, have been
developed for this purpose. With the advent of multi-access computing
systems a much greater interaction between man and machine is becoming possible, where the advantages of algebraic manipulation and
mathematical assistance packages are felt the greatest. This, further,
demonstrates the need for symbol manipulation facilities to be available
together with normal arithmetic facilities in a programming language,
for not only must the formulae be manipulated but also they must be
evaluated in normal arithmetic terns.
This combination has not completely satisfactorily been acheived in
any languages developed in the past. The present investigation is an
attempt to overcome this deficiency. A language called ASTRA has been
the result. Before discussing the design and implementation of ASTRA,
several existing languages are examined in order to discern the
desirable properties of a language for symbol manipulation. It is the
belief of the present author that the features of ASTRA described herein
represent an advance on previous languages. The methods used in the
ASTRA compiler are also described
Exploring barriers of m-commerce adoption in SMEs in the UK: Developing a framework using ISM
YesIn the modern business era, mobile commerce (m-commerce) is changing the way the business is conducted using the Internet. However, the prominence of m-commerce among small and medium-sized enterprises (SMEs) in the UK is minimal. The purpose of this study is to evaluate the existing literature and to extend the research surrounding the barriers that prevent the adoption of m-commerce amongst SMEs. The study uses an Interpretive Structural Modelling (ISM) and MICMAC approach for guiding and helping managers of SMEs. Data was collected from an expert participant group each of whom had extensive knowledge of m-commerce. The findings represent the unstable nature of variables in the context of their impact on each other, their relationships, and themselves. The listed factors in the proposed framework and the interrelationships between them highlight the multi-dimensional element of m-commerce adoption prevention. This observation proves criticality of analysing data as a collective entity rather than viewing the barriers in isolation. The findings also indicated ‘perceived risk’ being a key barrier that demonstrates how personal opinions of the concept of adoption can have a great significance on the outcome and whether other variables will come into effect
Validation of Observed Bedload Transport Pathways Using Morphodynamic Modeling
Phenomena related to braiding, including local scour and fill, channel bar development, migration
and avulsion, make numerical morphodynamic modeling of braided rivers challenging. This paper investigates
the performance of a Delft3D model, in a 2D depth-averaged formulation, to simulate the
morphodynamics of an anabranch of the Rees River (New Zealand). Model performance is evaluated using
data from field surveys collected on the falling limb of a major high flow, and using several sediment
transport formulas. Initial model results suggest that there is generally good agreement between observed and
modeled bed levels. However, some discrepancies in the bed level estimations were noticed, leading to bed
level, water depth and water velocity estimation errors
Conditions for spontaneous homogenization of the Universe
The present-day Universe appears to be homogeneous on very large scales. Yet
when the casual structure of the early Universe is considered, it becomes
apparent that the early Universe must have been highly inhomogeneous. The
current paradigm attempts to answer this problem by postulating the inflation
mechanism However, inflation in order to start requires a homogeneous patch of
at least the horizon size. This paper examines if dynamical processes of the
early Universe could lead to homogenization. In the past similar studies seem
to imply that the set of initial conditions that leads to homogenization is of
measure zero. This essay proves contrary: a set of initial conditions for
spontaneous homogenization of cosmological models can form a set of non-zero
measure.Comment: 7 pages. Fifth Award in the 2010 Gravity Research Foundation essay
competitio
Spin Transfer Measurements for (p,n) Reactions at Intermediate Energy
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Greenhouse gas and ammonia emission mitigation priorities for UK policy targets
Acknowledgements Many thanks to the Association of Applied Biologist’s for organising and hosting the ‘Agricultural greenhouse gases and ammonia mitigation: Solutions, challenges, and opportunities’ workshop. This work was supported with funding from the Scottish Government’s Strategic Research Programme (2022-2027, C2-1 SRUC) and BBSRC (BBS/E/C/000I0320 and BBS/E/C/000I0330). We also acknowledge support from UKRI694 BBSRC (United Kingdom Research and Innovation-Biotechnology and Biological Sciences 695 Research Council; United Kingdom) via grants BBS/E/C/000I0320 and BBS/E/C/000I0330. and Rothamsted Research's Science Initiative Catalyst Award (SICA) supported by BBSRC.Peer reviewedPublisher PD
Gamma-Ray Bursts: The Underlying Model
A pedagogical derivation is presented of the ``fireball'' model of gamma-ray
bursts, according to which the observable effects are due to the dissipation of
the kinetic energy of a relativistically expanding wind, a ``fireball.'' The
main open questions are emphasized, and key afterglow observations, that
provide support for this model, are briefly discussed. The relativistic outflow
is, most likely, driven by the accretion of a fraction of a solar mass onto a
newly born (few) solar mass black hole. The observed radiation is produced once
the plasma has expanded to a scale much larger than that of the underlying
``engine,'' and is therefore largely independent of the details of the
progenitor, whose gravitational collapse leads to fireball formation. Several
progenitor scenarios, and the prospects for discrimination among them using
future observations, are discussed. The production in gamma- ray burst
fireballs of high energy protons and neutrinos, and the implications of burst
neutrino detection by kilometer-scale telescopes under construction, are
briefly discussed.Comment: In "Supernovae and Gamma Ray Bursters", ed. K. W. Weiler, Lecture
Notes in Physics, Springer-Verlag (in press); 26 pages, 2 figure
Dimensionless cosmology
Although it is well known that any consideration of the variations of
fundamental constants should be restricted to their dimensionless combinations,
the literature on variations of the gravitational constant is entirely
dimensionful. To illustrate applications of this to cosmology, we explicitly
give a dimensionless version of the parameters of the standard cosmological
model, and describe the physics of Big Bang Neucleosynthesis and recombination
in a dimensionless manner. The issue that appears to have been missed in many
studies is that in cosmology the strength of gravity is bound up in the
cosmological equations, and the epoch at which we live is a crucial part of the
model. We argue that it is useful to consider the hypothetical situation of
communicating with another civilization (with entirely different units),
comparing only dimensionless constants, in order to decide if we live in a
Universe governed by precisely the same physical laws. In this thought
experiment, we would also have to compare epochs, which can be defined by
giving the value of any {\it one} of the evolving cosmological parameters. By
setting things up carefully in this way one can avoid inconsistent results when
considering variable constants, caused by effectively fixing more than one
parameter today. We show examples of this effect by considering microwave
background anisotropies, being careful to maintain dimensionlessness
throughout. We present Fisher matrix calculations to estimate how well the fine
structure constants for electromagnetism and gravity can be determined with
future microwave background experiments. We highlight how one can be misled by
simply adding to the usual cosmological parameter set
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