1,479 research outputs found
No easy thing: Senior Command in the Canadian Army, 1939–1945
There is relatively little Canadian military history which looks specifically at the questions and themes surrounding senior command (commanders of large formations of troops—normally generals or lieutenant–generals). Current interpretations call for a trilogy of abilities: the ability to defend national interests in the highest military (and often political) circles; the ability to organize and manage forces both before and during combat; and the ability to lead both directly and indirectly those who have to implement the plans. Were Canadians then, and are historians today, right to apply this multiple standard? This article looks at the three officers who commanded First Canadian Army during the Second World War: Generals A.G.L. McNaughton, H.D.G. Crerar and G.G. Simonds. Where these comanders might well possess one or two of these abilities they could as easily have little competence in the third. Overall Crerar comes out the best of the three
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Evolutionary optimization within an intelligent hybrid system for design integration
An intelligent hybrid approach has been developed to integrate various stages in total design, including formulation of product design specifications, conceptual design, detail design, and manufacture. The integration is achieved by blending multiple artificial intelligence (AI) techniques and CAD/CAE/CAM into a single environment. It has been applied into power transmission system design. In addition to knowledge-based systems and artificial neural networks, another AI technique, genetic algorithms (GAs), are involved in the approach. The GA is used to conduct optimization tasks: (1) searching the best combination of design parameters to obtain optimum design of gears, and (2) optimization of the architecture of the artificial neural networks used in the hybrid system. In this paper, after a brief overview of the intelligent hybrid system, the GA applications are described in detail
Chemical sensitivity to the ratio of the cosmic-ray ionization rates of He and H2 in dense clouds
Aim: To determine whether or not gas-phase chemical models with homogeneous
and time-independent physical conditions explain the many observed molecular
abundances in astrophysical sources, it is crucial to estimate the
uncertainties in the calculated abundances and compare them with the observed
abundances and their uncertainties. Non linear amplification of the error and
bifurcation may limit the applicability of chemical models. Here we study such
effects on dense cloud chemistry. Method: Using a previously studied approach
to uncertainties based on the representation of rate coefficient errors as log
normal distributions, we attempted to apply our approach using as input a
variety of different elemental abundances from those studied previously. In
this approach, all rate coefficients are varied randomly within their log
normal (Gaussian) distribution, and the time-dependent chemistry calculated
anew many times so as to obtain good statistics for the uncertainties in the
calculated abundances. Results: Starting with so-called ``high-metal''
elemental abundances, we found bimodal rather than Gaussian like distributions
for the abundances of many species and traced these strange distributions to an
extreme sensitivity of the system to changes in the ratio of the cosmic ray
ionization rate zeta\_He for He and that for molecular hydrogen zeta\_H2. The
sensitivity can be so extreme as to cause a region of bistability, which was
subsequently found to be more extensive for another choice of elemental
abundances. To the best of our knowledge, the bistable solutions found in this
way are the same as found previously by other authors, but it is best to think
of the ratio zeta\_He/zeta\_H2 as a control parameter perpendicular to the
''standard'' control parameter zeta/n\_H.Comment: Accepted for publicatio
Sensitivity analyses of dense cloud chemical models
Because of new telescopes that will dramatically improve our knowledge of the
interstellar medium, chemical models will have to be used to simulate the
chemistry of many regions with diverse properties. To make these models more
robust, it is important to understand their sensitivity to a variety of
parameters. In this article, we report a study of the sensitivity of a chemical
model of a cold dense core, with homogeneous and time-independent physical
conditions, to variations in the following parameters: initial chemical
inventory, gas temperature and density, cosmic-ray ionization rate, chemical
reaction rate coefficients, and elemental abundances. From the results of the
parameter variations, we can quantify the sensitivity of the model to each
parameter as a function of time. Our results can be used in principle with
observations to constrain some parameters for different cold clouds. We also
attempted to use the Monte Carlo approach with all parameters varied
collectively. Within the parameter ranges studied, the most critical parameters
turn out to be the reaction rate coefficients at times up to 4e5 yr and
elemental abundances at later times. At typical times of best agreement with
observation, models are sensitive to both of these parameters. The models are
less sensitive to other parameters such as the gas density and temperature. The
improvement of models will require that the uncertainties in rate coefficients
of important reactions be reduced. As the chemistry becomes better understood
and more robust, it should be possible to use model sensitivities concerning
other parameters, such as the elemental abundances and the cosmic ray
ionization rate, to yield detailed information on cloud properties and history.
Nevertheless, at the current stage, we cannot determine the best values of all
the parameters simultaneously based on purely observational constraints.Comment: Accepted for publication in Astronomy & Astrophysic
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Integration of knowledge-based system, artificial neural networks and multimedia for gear design
Design is a complicated area consisting of a combination of rules, technical information and personal judgement. The quality of design depends highly on the designer's knowledge and experience. This system attempts to simulate the design process and to capture design expertise by combining artificial neural networks (ANNs) and knowledge based system (KBS) together with multi-media (MM). It has been applied to the design of gears. Within the system the knowledge based system handles clearly defined design knowledge, the artificial neural networks capture knowledge which is difficult to quantify and multi-media provides a user-friendly interface prompting the user to input information and to retrieve results during design process. The finished system illustrates how features of different Artificial Intelligence techniques, KBS, ANNs and MM, are combined in a hybrid manner to conduct complicated design tasks
Sulfur chemistry: 1D modeling in massive dense cores
The main sulfur-bearing molecules OCS, H2S, SO, SO2, and CS have been
observed in four high mass dense cores (W43-MM1, IRAS 18264, IRAS 05358, and
IRAS 18162). Our goal is to put some constraints on the relative evolutionary
stage of these sources by comparing these observations with time-dependent
chemical modeling. We used the chemical model Nahoon, which computes the
gas-phase chemistry and gas-grain interactions of depletion and evaporation.
Mixing of the different chemical compositions shells in a 1D structure through
protostellar envelope has been included since observed lines suggest nonthermal
supersonic broadening. Observed radial profiles of the temperature and density
are used to compute the chemistry as a function of time. With our model, we
underproduce CS by several orders of magnitude compared to the other S-bearing
molecules, which seems to contradict observations, although some uncertainties
in the CS abundance observed at high temperature remain. The OCS/SO2, SO/SO2,
and H2S/SO2 abundance ratios could in theory be used to trace the age of these
massive protostars since they show a strong dependence with time, but the
sources are too close in age compared to the accuracy of chemical models and
observations. Our comparison between observations and modeling may, however,
indicate that W43-MM1 could be chemically younger than the three other sources.
Turbulent diffusivity through the protostellar envelopes has to be less
efficient than 2e14 cm2s-1. Otherwise, it would have smoothed out the abundance
profiles, and this would have been observed. The sulfur chemistry depends
strongly on the 1D physical conditions. In our case, no conclusion can be given
on the relative age of IRAS 18264, IRAS 18162 and IRAS 05358 except that they
are very close. W43-MM1 seems younger than the other sources.Comment: Accepted for publication to A&
The interstellar gas-phase chemistry of HCN and HNC
We review the reactions involving HCN and HNC in dark molecular clouds to
elucidate new chemical sources and sinks of these isomers. We find that the
most important reactions for the HCN-HNC system are Dissociative Recombination
(DR) reactions of HCNH+ (HCNH+ + e-), the ionic CN + H3+, HCN + C+, HCN and HNC
reactions with H+/He+/H3+/H3O+/HCO+, the N + CH2 reaction and two new
reactions: H + CCN and C + HNC. We test the effect of the new rate constants
and branching ratios on the predictions of gas-grain chemical models for dark
cloud conditions. The rapid C + HNC reaction keeps the HCN/HNC ratio
significantly above one as long as the carbon atom abundance remains high.
However, the reaction of HCN with H3+ followed by DR of HCNH+ acts to isomerize
HCN into HNC when carbon atoms and CO are depleted leading to a HCN/HNC ratio
close to or slightly greater than 1. This agrees well with observations in
TMC-1 and L134N taking into consideration the overestimation of HNC abundances
through the use of the same rotational excitation rate constants for HNC as for
HCN in many radiative transfer models.Comment: Accepted for publication in MNRA
Developing an agent-based simulation model of software evolution
Context In attempt to simulate the factors that affect the software evolution behaviour and possibly predict it, several simulation models have been developed recently. The current system dynamic (SD) simulation model of software evolution process was built based on actor-network theory (ANT) of software evolution by using system dynamic environment, which is not a suitable environment to reflect the complexity of ANT theory. In addition the SD model has not been investigated for its ability to represent the real-world process of software evolution. Objectives This paper aims to re-implements the current SD model to an agent-based simulation environment ‘Repast’ and checks the behaviour of the new model compared to the existing SD model. It also aims to investigate the ability of the new Repast model to represent the real-world process of software evolution. Methods a new agent-based simulation model is developed based on the current SD model's specifications and then tests similar to the previous model tests are conducted in order to perform a comparative evaluation between of these two results. In addition an investigation is carried out through an interview with an expert in software development area to investigate the model's ability to represent real-world process of software evolution. Results The Repast model shows more stable behaviour compared with the SD model. Results also found that the evolution health of the software can be calibrated quantitatively and that the new Repast model does have the ability to represent real-world processes of software evolution. Conclusion It is concluded that by applying a more suitable simulation environment (agent-based) to represent ANT theory of software evolution, that this new simulation model will show more stable bahaviour compared with the previous SD model; And it will also shows the ability to represent (at least quantatively) the real-world aspect of software evolution.Peer reviewedFinal Accepted Versio
The collection, analysis and exploitation of footballer attributes: A systematic review
© 2022 – The authors. Published by IOS Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Non Commercial License (CC BY-NC 4.0)There is growing on-going research into how footballer attributes, collected prior to, during and post-match, may address the demands of clubs, media pundits and gaming developers. Focusing upon individual player performance analysis and prediction, we examined the body of research which considers different player attributes. This resulted in the selection of 132 relevant papers published between 1999 and 2020. From these we have compiled a comprehensive list of player attributes, categorising them as static, such as age and height, or dynamic, such as pass completions and shots on target. To indicate their accuracy, we classified each attribute as objectively or subjectively derived, and finally by their implied accessibility and their likely personal and club sensitivity. We assigned these attributes to 25 logical groups such as passing, tackling and player demographics. We analysed the relative research focus on each group and noted the analytical methods deployed, identifying which statistical or machine learning techniques were used. We reviewed and considered the use of character trait attributes in the selected papers and discuss more formal approaches to their use. Based upon this we have made recommendations on how this work may be developed to support elite clubs in the consideration of transfer targets.Peer reviewedFinal Published versio
Reactions forming C(0,+)n=2,10, Cn=2,4H(0,+) and C3H(0,+) in the gas phase: semi empirical branching ratios
The aim of this paper is to provide a new set of branching ratios for
interstellar and planetary chemical networks based on a semi empirical model.
We applied, instead of zero order theory (i.e. only the most exoergic decaying
channel is considered), a statistical microcanonical model based on the
construction of breakdown curves and using experimental high velocity collision
branching ratios for their parametriza- tion. We applied the model to
ion-molecule, neutral-neutral, and ion-pair reactions implemented in the few
popular databases for astrochemistry such as KIDA, OSU and UMIST. We studied
the reactions of carbon and hydrocarbon species with electrons, He+, H+, CH+,
CH, C, and C+ leading to intermediate complexes of the type Cn=2,10, Cn=2,4 H,
C3 H2, C+n=2,10, Cn=2,4 H+, or C3 H+2 . Comparison of predictions with
measurements supports the validity of the model. Huge deviations with respect
to database values are often obtained. Effects of the new branching ratios in
time dependant chemistry for dark clouds and for photodissociation region
chemistry with conditions similar to those found in the Horsehead Nebula are
discussed
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