Network and service management for wide‐area electronic commerce networks

This paper focuses on the effective management of wide‐area electronic commerce networks supporting services and applications that require high availability and reliability as well as fast reconstitution time, in the event of failures. Copyright © 2001 John Wiley & Sons, Ltd.     

Dynamic market‐driven allocation of network resources using genetic algorithms in a competitive electronic commerce marketplace

In this paper, we propose a practical algorithm which finds cost‐efficient routes from Service Provider (SP) to Content Provider (CP) dynamically in a multi‐operator networking environment, using Genetic Algorithm (GA) concepts. The proposed algorithm is a kind of stochastic algorithm searching process in the solution space by emulating biological selection and reproduction. Copyright © 2001 John Wiley & Sons, Ltd.     

Numerical investigation on the start-up of methane-fueled catalytic microreactors

Transient simulations have been performed in a plane-channel, methane-fueled microreactor made of either cordierite or FeCr alloy walls and coated with a platinum catalyst. A two-dimensional model for the flow domain was used, which included detailed catalytic and gas-phase chemical reaction mechanisms. In the solid wall, axial heat conduction and surface radiation heat transfer were accounted for. Simulations were performed by varying the inlet pressure, the solid wall thermal conductivity and heat capacity, the inlet velocity, and the equivalence ratio at fuel-lean stoichiometries. The effect of solid material properties as well as the impact of gas-phase chemistry and surface radiation on the ignition (t_ig) and steady-state (t_st) microreactor times has been assessed. An increase in inlet pressure from 1 to 5 bar induced a ∼50% reduction in both t_ig and t_st owing to the enhancement of the catalytic reactivity with rising pressure. A similar behavior was also attested when increasing the equivalence ratio from 0.4 to 0.6. Reactors with low wall thermal conductivity (cordierite material) exhibited shorter ignition times compared to higher thermal conductivity ones (FeCr alloy) due to the creation of spatially localized hot spots that promoted catalytic ignition. At the same time, the ceramic material required shorter times to reach steady-state. Higher inlet velocities reduced the time required for steady-state, however, at the cost of increased cumulative reactor emissions. Surface radiation heat transfer played a key dual role in the start-up process of low thermal conductivity channels. Radiation increased t_ig by removing heat away from the initial hot spot, but from the other side it decreased t_st due to a very efficient transfer of heat from the rear to the front of the reactor. Gas-phase chemistry elongated the steady-state times for both ceramic and metallic materials and impacted the emissions of catalytic microreactors.     

Supporting multicasting in mobile ad‐hoc wireless networks: issues,challenges, and current protocols

The basic philosophy of personal communication services is to provide user‐to‐user, location independent communication services. The emerging group communication wireless applications, such as multipoint data dissemination and multiparty conferencing tools have made the design and development of efficient multicast techniques in mobile ad‐hoc networking environments a necessity and not just a desire. Multicast protocols in mobile ad‐hoc networks have been an area of active research for the past couple of years. This paper summarizes the activities and recent advances in this work‐in‐progress area by identifying the main issues and challenges that multicast protocols are facing in mobile ad‐hoc networking environments, and by surveying several existing multicasting protocols. This article presents a classification of the current multicast protocols, discusses the functionality of the individual existing protocols, and provides a qualitative comparison of their characteristics according to several distinct features and performance parameters. Furthermore, since many of the additional issues and constraints associated with the mobile ad‐hoc networks are due, to a large extent, to the attribute of user mobility, we also present an overview of research and development efforts in the area of group mobility modeling in mobile ad‐hoc networks. Copyright © 2001 John Wiley & Sons, Ltd.     

A physical picture of the mechanism of turbulent heat transfer from the wall

The present work investigates the correlation between the velocity and the temperature field in wall turbulence using direct numerical simulation of turbulent channel flow and plane Couette flow in conjunction with a Lagrangian method. Characteristic length scales for heat transfer are calculated for fluids with Prandtl numbers between 0.1 and 100. Structures of larger scales are found to contribute to the transport of heat as the distance from the wall increases. Turbulent Prandtl numbers are then calculated, showing that the turbulent Prandtl number is a function of the distance from the wall, but it does not depend on the fluid Prandtl number for high Prandtl numbers.     

Equational weighted tree transformations

We consider systems of equations of weighted tree transformations with finite support over continuous and commutative semirings. We define a weighted relation to be equational, if it is a component of the least solution of such a system of equations in a pair of algebras. In particular, we focus on equational weighted tree transformations which are equational relations obtained by considering the least solutions of such systems in pairs of term algebras. We characterize equational weighted tree transformations in terms of weighted tree transformations defined by different weighted bimorphisms. To demonstrate the robustness of equational weighted tree transformations, we give an equational definition of the class of linear and nondeleting weighted top-down tree transformations and of the class of linear and nondeleting weighted extended top-down tree transformations. Finally, we prove that a weighted relation is equational if and only if it is, roughly speaking, the morphic image of a weighted equational tree transformation.     

Amorphous carbon encapsulation of metal aerosol nanoparticles for improved collection and prevention of oxidation

A technique to encapsulate silver nanoparticles in an amorphous carbon matrix to facilitate nanoparticle collection and limit nanoparticle oxidation is presented. A carbon source added to the metal salt precursor solution decomposes to generate amorphous carbon, which forms large aggregates that are efficiently collected by filtration. The carbon matrix can be removed by oxidation with hydrogen peroxide without damaging the silver nanoparticles within it. X‐ray diffraction showed no evidence of oxidation of encapsulated particles over a two‐week period, whereas bare particles showed oxidation after 1 day. Slight oxidation was observed following carbon removal, but no further oxidation was detected over a subsequent two‐week period. Carbon encapsulation improves nanoparticle collection efficiency, relative to direct collection of unagglomerated silver nanoparticles with membrane filters. The yield of metal nanoparticles is increased by a factor 1.5 to 3 using this approach. The encapsulating carbon itself forms dendritic nanostructures that may also be of interest. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4116–4123, 2013     

Collaborative event annotation in tagged photo collections

Events constitute a significant means of multimedia content organization and sharing. Despite the recent interest in detecting events and annotating media content in an event-centric way, there is currently insufficient support for managing events in large-scale content collections and limited understanding of the event annotation process. To this end, this paper presents CrEve, a collaborative event annotation framework which uses content found in social media sites with the prime objective to facilitate the annotation of large media corpora with event information. The proposed annotation framework could significantly benefit social media research due to the proliferation of event-related user-contributed content. We demonstrate that, compared to a standard “browse-and-annotate” interface, CrEve leads to a 19% increase in the coverage of the generated ground truth in a large-scale annotation experiment. Furthermore, the paper discusses the results of a user study that quantifies the performance of CrEve and the contribution of different event dimensions in the event annotation process. The study confirms the prevalence of spatio-temporal queries as the prime option of discovering event-related content in a large collection. In addition, textual queries and social cues (content contributor) were also found to be significant as event search dimensions. Finally, it demonstrates the potential of employing automatic photo clustering methods with the goal of facilitating event annotation.