625 research outputs found
Adeste fideles [music] : with variations for piano /
No full textD. & S. 4711 (Publisher number). Cover title.; Pl. no.: D. & S. 4711.; Also available online http://nla.gov.au/nla.mus-an21640624
Resilient network design: Challenges and future directions
No full textThis paper highlights the complexity and challenges of providing reliable services in the evolving communications infrastructure. The hurdles in providing end-to-end availability guarantees are discussed and research problems identified. Avenues for overcoming some of the challenges examined are presented. This includes the use of a highly available network spine embedded in a physical network together with efficient crosslayer mapping to offer survivability and differentiation of traffic into classes of resilience. © 2013 Springer Science+Business Media New York
Spare capacity allocation using partially disjoint paths for dual link failure protection
No full textA shared backup path protection (SBPP) scheme can be used to protect dual link failures by pre-planning each traffic flow with mutually disjoint working and two backup paths while minimizing the network overbuild. However, many existing backbone networks are bi-connected without three fully disjoint paths between all node pairs. Hence in practice partially disjoint paths (PDP) have been used for backup paths instead of fully disjoint ones. This paper studies the minimum spare capacity allocation (SCA) problem using PDP within an optimization framework. This is an extension of the spare provision matrix (SPM) method for PDP. The integer linear programming (ILP) model is formulated and an approximation algorithm, Successive Survivable Routing (SSR), is extended and used in the numerical study. © 2013 Scientific Assoc for infocom
Algorithms for determining a node-disjoint path pair visiting specified nodes
No full textThe problem of calculating the shortest path that visits a given set of nodes is at least as difficult as the traveling salesman problem, and it has not received much attention. Nevertheless an efficient integer linear programming (ILP) formulation has been recently proposed for this problem. That ILP formulation is firstly adapted to include the constraint that the obtained path can be protected by a node-disjoint path, and secondly to obtain a pair of node disjoint paths, of minimal total additive cost, each having to visit a given set of specified nodes. Computational experiments show that these approaches, namely in large networks, may fail to obtain solutions in a reasonable amount of time. Therefore heuristics are proposed for solving those problems, that may arise due to network management constraints. Extensive computational results show that they are capable of finding a solution in most cases, and that the calculated solutions present an acceptable relative error regarding the cost of the obtained path or pair of paths. Further the CPU time required by the heuristics is significantly smaller than the required by the used ILP solver
A Survey of Clock Synchronization Over Packet-Switched Networks
No full textClock synchronization is a prerequisite for the realization of emerging applications in various domains such as industrial automation and the intelligent power grid. This paper surveys the standardized protocols and technologies for providing synchronization of devices connected by packet-switched networks. A review of synchronization impairments and the state-of-the-art mechanisms to improve the synchronization accuracy is then presented. Providing microsecond to sub-microsecond synchronization accuracy under the presence of asymmetric delays in a cost-effective manner is a challenging problem, and still an open issue in many application scenarios. Further, security is of significant importance for systems where timing is critical. The security threats and solutions to protect exchanged synchronization messages are also discussed
Oxidation: in the gas-phase and in solution, and with reactions of cyclopropane
No full textPART I. KINETIC STUDIES OF OXIDATION IN SOLUTION, WITH SPECIAL
REFERENCE TO THE ROLE PLAYED BY PEROXIDES AND
HVDROPEROXIDES.Paper I. The Effect of Water on the Decomposition of Benzoyl
Peroxide.
by C. F. H. Tipper.
Journal of the Chemical Society, 1952, pages 2966 -2971. •
Addèndum. The Effect of Oxygen on the. Decomposition of
Benzoyl Peroxide.
by H. Monk and C. F. H. Tipper.
Unpublished. MS. 3 quarto pages. •
Paper 2. The Decomposition of Decalin Hydroperoxide. A
Kinetic Study.
by C. F. H. Tipper.
Journal of the Chemical Society, 1953, pages 1675 -1680. •
Paper 3. Kinetics of the Decomposition of Tetralin Hydroperoxide
in Acidic and Basic Solvents.
by [Miss] J. E. Hay, [Miss] T T. H. Johnstone,
C. E. H. Tipper and R. K. Williams. .
Journal of the Chemical Society, 1954, pages 629 -634. •
Paper 4. Some Aspects of the Oxidation of Di- and
Triphenylmethane.
by D. D. K. Grant and C. F. H. Tipper.
Journal of the Chemical Society, 1955, pages 640 -646.Peroxides and hydroperoxides are important since they are the
primary products of the reaction of hydrocarbons with molecular
oxygen in solution. They then react to give the final products,
alcohols, ketones, etc. The decomposition of a typical peroxide
[benzoyl peroxide] and two typical hydroperoxides [tetralin and
decalin hydroperoxide] have been studied under a wide variety of
conditions mainly by kinetic measurements. It has been found that
the decomposition of benzoyl peroxide is more complicated than
has been suspected hitherto. Besides the main free radical chain
reaction complex side effects occur, especially in the presence
of water, which may lead to some hydrolysis. Oxygen may retard
the reaction due to the formation of a yellow secondary product,
which eliminates the induced chain decomposition. However, even
under favourable conditions, the amount of heterolytic fission of
the peroxide giving ions is small. This is in contrast to
unsymmetrical peroxides and hydroperoxides.The mechanism of the decomposition of the two hydroperoxides
is greatly affected by conditions, e.p. the solvent used. In
neutral solvents of low dielectric constant it takes place by a
chain reaction involving free -radicals produced from the
solvent, whereas in the presence of acids [and bases with the
secondary hydroperoxide from tetralin] the intermediates are
ionic, e.g. carbonium ions. It has been shown that, because
of this change in mechanism, the autoxidation of diphenylmethane
also depends on the nature of the system. In the
absence of acids autocatalysis by a first -order decomposition
of the diphenylmethylt hydroperoxide formed, initiating a
free- radical chain oxidation, occurs. In the presence of acids,
however, ionic decomposition of the hydroperoxide takes place,
leading to partial or complete retardation of the oxidation.PART II KINETIC AND ANALYTICAL STUDIES OF THE SLOW COMBUSTION OF SOME
SIMPLE ORGANIC COMPOUNDS IN THE GAS-PHASE.Paper 1. Slow Combustion of Cyclopropane.
by A. C. McEwan and C. F. H. Tipper.
Nature, 1952, vol. 170, page 462. •
Paper 2. The Slow Combustion of Cyclopropane. I. General Kinetics.
by A. C. McEwan and C. F. H. Tipper.
Proceedings of the Royal Society, 1953, A, vol. 216, pp. 280 -291. •
Paper 3. The Slow Combustion of Cyclopropane. II. Analytical Results
and Mechanism.
by A. C. McEwan and C. F. H. Tipper.
Proceedings of the Royal Society, 1953, A..vol. 220, pp. 266 -277. •
Paper 4. The Effect of Surface on the Oxidation of Cyclopropane.
by W. N. Broatch, A. C. McEwan and C. F. H. Tipper.
Transactions of the Faraday Society, 1954, vol. 50, pp. 576 -580. •
Paper 5. The Slow Combustion of Methyl Alcohol. A General Investigation.
by K. M. Bell and C. F. H. Tipper.
Proceedings of the Royal Society, 1956, A, vol. 238, pp. 256 -268. •
Paper 6. The Effect of Surface on the Slow Combustion of Methanol.
by K. M. Bell and C. F. H. Tipper.
Transactions of the Faraday Society, 1957, vol. 53, pp. 282 -290. •
Paper 7. Effect of o-Toluidine on the Gas-Phase Oxidation of Some
Aliphatic Compounds.
by K. M. Bell and C. F. H. Tipper.
Research, 1957, vol. 10, pp. 121 -122. •
Paper 8. The Slow Combustion of Cyclopentane. I. Kinetics in Coated
and Uncoated Vessels.
by I. R. McGowan and C. F. H. Tipper.
Proceedings of the Royal Society, 1958, A, vol. 246, pp. 52-63. •
Paper 9. The Slow Combustion of Cyclopentane. II. Analytical Results
and Mechanism.
by I. R. McGowan and C. F. H. Tipper.
Proceedings of the Royal Society, 1958, A, vol. 246, pp. 64-77.The reaction of hydrocarbons and their simple derivitives with
oxygen in the gas -phase has been studied for many years, but, owing
to the great complexity of such systems and the different phenomena
met with [e.g. slow combustion, cool flames, ignition] there is
still uncertainty as to the mechanism. In particular there is
still controversy over the respective roles of aldehydes and
peroxidic compounds as intermediates in the slow combstion,
especially in view of the great importance of peroxides and
hydroperoxides in hydrocarbon oxidation in solution [Part 1].
The slow combustion of three compounds, cyclopropane, cyclopentane
and methanol, has been studied in considerable detail by kinetic
and analytical methods. The effect of the nature and extent of
the surface of the reaction vessel has been particularly
investigated. This is an aspect of the subject which has been
neglected until recently. One advantage of using the cyclic
hydrocarbons is that all the C-H bonds are equivalent.The main products of the oxidations as well as carbon
monoxide and water are: methanol-formaldehyde and hydrogen peroxide;
cyclopropane-formaldehyde; cyclopentane- carbon dioxide, cyclopentene
and lower olefins, and aldehydes mainly acetaldehyde.It has been shown that aldehydes are the important intermediates,
responsible for degenerate branching, in the oxidation at "high"
temperatures [> 350°C]. Probable mechanisms of the reactions have
been deduced. These involve free-radical chains, and the rates of
the slow combustions, which vary in a complex way with pressure of
reactants, depend markedly on the termination reactions, the rates
and nature of which are affected by the temperature, wall conditions,
and the fuel. RO₂ radicals [fuel = RH] are formed and those
derived from methanol and cydopropane decompose readily to give
formaldehyde plus other radicals, rather than react with the
fuel or oxygen. Hydroperoxy [HO₂] radicals are present in the
systems and either propagate the chain by hydrogen abstraction
from fuel molecules or are destroyed at the wall. In contrast,
the cyclopentylperoxy radical [C₅H₉O₂], as well as decomposing
to give carbon dioxide, olefins or aldehydes, appears to have a
long enough life due to its complexity to be able to abstract
hydrogen from aldehyde or cyclopentane or to terminate the chains
in the gas phase by reaction with oxygen. Termination by HO₂
radicals is relatively unimportant and the hydroperoxide seems to
play only a minor role at the higher temperatures.The slow combustion of cyclopropane resembles that of methane
rather than that of propylene or higher olefins [c.f. Part III,
and see concluding remarks, page 124].PART III STUDIES OF SOME REACTIONS OF CYCLOPROPANE AND A COMPARISON
WITH THE LOWER OLEFINS.Paper 1. Some Reactions of Cyclopropane and a Comparison with the
Lower Olefins.
Part I. Introduction and Reaction with Strong Acids.
by C. D. Lawrence and C. F. H. Tipper.
Journal of the Chemical Society, 1955, pp. 713 -716. •
Paper 2. Some Reactions of Cyclopropane and.a Comparison with the .
Lower Olefins.
Part II. Some Platinous -Cyclopropane Complexes.
by C. F. H. Tipper.
Journal of the Chemical Society, 1955, pp. 2045 -2046. •
Paper 3. Some Reactions of Cyclopropane and a Comparison with the
Lower Olefins.
Part III. The Friedel -Craft Reaction.
by ,C. F. H. Tipper and D. A. Walker.
Journal of the Chemical Society, 1957, PP. 1199 -1206. •
Paper 4. The Reaction of Cyclopropane and Lithium Aluminium Hydride.
by C. F. H. Tipper and D. A. Walker.
Chemistry and Industry, 1957, page 730.In contrast to the gas -phase oxidation [Part II], in many
reactions cyclopropane behaves in a similar manner to the lower
olefins. Some physical characteristics of the cyclopropane ring,
e.g. apparent conjugation with double bonds, also indicate that
it may have some unsaturated character. This is in agreement with
wave -mechanical calculations, which suggest that there is
considerable delocalisation of the six electrons associated with
the ring.The reactions of cyclopropane with strong acids, e.g. HClO₄,
platinous salts, aromatic compounds in the presence of aluminium
chloride and lithium aluminium hydride have been studied, and it
was found to behave in a similar way to propylene. The dependence
of the rate of reaction on acid concentration is of a high
apparent order. Probably the first step is the addition of a
proton to the ring to give a n-c₃H₇⁺ ion. A co- catalyst, e.g.
water, is required for the Friedel -Craft reaction. The kinetic
results suggest that several complexes involving the various
reagents and solvent are present in the solution, and that the
A final reaction with the aromatic compound proceeds by a carbonium
ion mechanism. The strongest evidence for the unsaturated nature
of the cyclopropane ring is the fact that several complexes of
cyclopropane with platinous chloride [e.g. PtCl₂. C₃H₆], in which
the ring is intact, have been prepared. Also the reaction with
lithium aluminium hydride gives aluminium tripropyl, the initial
step in the formation of which is probably coordination of the
cyclopropane with AlH₃
Wireless network virtualization
No full textThe virtualization of wired networks and end computing systems has become one of the leading trends in networked information and communication technology (ICT) systems. In contrast relatively little virtualization has occurred in infrastructure based wireless networks, but the idea of virtualizing wireless access is gaining attention as it has the potential to improve spectrum utilization and perhaps create new services. In this paper we survey the state of the current research in virtualizing wireless networks. We define and describe possible architectures, the issues, hurdles and trends towards implementation of wireless network virtualization. © 2013 Engineering and Technology Publishing
Design of three way tipper for light truck
No full textDiplomsko delo opisuje konstruiranje in dimenzioniranje tristranega prekucnika za vozila mase
3,5 ton. Tema dela je iz podjetja Arko d. o. o.
Želja podjetja je bila izdelava lastnega prekucnika, katerega smo zmodelirali v programskem
paketu Solidworks. Opisali smo nekaj splošnih navodil glede izdelave prekucnikov in pomožnih
šasij tovornih vozil. Nato smo predstavili korake modeliranja prekucnika. Za model smo naredili
metodo končnih elementov in s tem preverili ustreznost dimenzioniranja. Opisali in ponazorili
smo izdelavo in povzeli stroške izdelavi. Analizirali smo izdelavo, modeliranje ter podali predlog
za nadaljnje delo.Diploma work describes the construct and dimension of three way tipper for vehicle up to 3,5
tonnes. The topic of the work is from Arko d.o.o. company.
The desire of the company was to produce their own tipper, which we modeled in the software
package called Solidworks. We have described some general instructions about instruction of
tippers for trucks. Then we presented steps of modeling the tipper. We made FEM analaysis
for model and relevance of dimension. We have described and illustrated the production and
summarized the manufacturing costs. We analayzed the design and modeling and made a
proposal for further work
Primary and Backup Paths Optimal Design for Traffic Engineering in Hybrid IGP/MPLS Networks
No full textThe paper describes an optimization model which aims at minimizing the maximum link utilization of IP telecommunication networks under the joint use of the traditional IGP protocols and the more sophisticated MPLS-TE technology. The survivability of the network is taken into account in the optimization process implementing the path restoration scheme. This scheme benefits of the Fast Re-Route (FRR) capability allowing service providers to offer high availability and high revenue SLAs (Service Level Agreements). The hybrid IGP/MPLS approach relies on the formulation of an innovative Linear Programming mathematical model that, while optimizing the network utilization, provides optimal user performance, efficient use of network resources, and 100% survivability in case of single link failure. The possibility of performing an optimal exploitation of the network resources throughout the joint use of the IGP and MPLS protocols provides a flexible tool for the ISP (Internet Service Provider) networks traffic engineers. The efficiency of the proposed approach is validated by a wide experimentation performed on synthetic and real networks. The obtained results show that a small number of LSP tunnels have to be set up in order to significantly reduce the congestion level of the network while at the same time guaranteeing the survivability of the network
Advanced Metering and Demand Response communication performance in Zigbee based HANs
No full textUsing IEEE 802.15.4 and Zigbee for home area networks (HANs) in the Smart Grid is becoming an increasingly prominent topic in the research area. As the standard designed for low data rate and low cost wireless personal area networks, IEEE 802.15.4 is widely employed in the construction of home sensor networks to assist with real-time environment information. For the purposes of Smart Grid the Zigbee Alliance has defined new Smart Energy Profile Protocol that leverages the existing TCP and HTTP protocols. In this paper, we provide an overview of the Smart Grid's Advanced Metering Infrastructure (AMI) and Demand Response (DR) functionalities, and the communication requirement they pose for the new SEP protocol. The discussion is followed by an evaluation of the theoretical performance bounds of the new architecture based on a analytical model. We conclude, by extending the model to account for WiFi interference which is expected to be present in home and office environments. © 2013 IEEE
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