1,838 research outputs found
Performance and operational economics estimates for a coal gasification combined-cycle cogeneration powerplant
A performance and operational economics analysis is presented for an integrated-gasifier, combined-cycle (IGCC) system to meet the steam and baseload electrical requirements. The effect of time variations in steam and electrial requirements is included. The amount and timing of electricity purchases from sales to the electric utility are determined. The resulting expenses for purchased electricity and revenues from electricity sales are estimated by using an assumed utility rate structure model. Cogeneration results for a range of potential IGCC cogeneration system sizes are compared with the fuel consumption and costs of natural gas and electricity to meet requirements without cogeneration. The results indicate that an IGCC cogeneration system could save about 10 percent of the total fuel energy presently required to supply steam and electrical requirements without cogeneration. Also for the assumed future fuel and electricity prices, an annual operating cost savings of 21 percent to 26 percent could be achieved with such a cogeneration system. An analysis of the effects of electricity price, fuel price, and system availability indicates that the IGCC cogeneration system has a good potential for economical operation over a wide range in these assumptions
Social Ranking Techniques for the Web
The proliferation of social media has the potential for changing the
structure and organization of the web. In the past, scientists have looked at
the web as a large connected component to understand how the topology of
hyperlinks correlates with the quality of information contained in the page and
they proposed techniques to rank information contained in web pages. We argue
that information from web pages and network data on social relationships can be
combined to create a personalized and socially connected web. In this paper, we
look at the web as a composition of two networks, one consisting of information
in web pages and the other of personal data shared on social media web sites.
Together, they allow us to analyze how social media tunnels the flow of
information from person to person and how to use the structure of the social
network to rank, deliver, and organize information specifically for each
individual user. We validate our social ranking concepts through a ranking
experiment conducted on web pages that users shared on Google Buzz and Twitter.Comment: 7 pages, ASONAM 201
Voter model with non-Poissonian interevent intervals
Recent analysis of social communications among humans has revealed that the
interval between interactions for a pair of individuals and for an individual
often follows a long-tail distribution. We investigate the effect of such a
non-Poissonian nature of human behavior on dynamics of opinion formation. We
use a variant of the voter model and numerically compare the time to consensus
of all the voters with different distributions of interevent intervals and
different networks. Compared with the exponential distribution of interevent
intervals (i.e., the standard voter model), the power-law distribution of
interevent intervals slows down consensus on the ring. This is because of the
memory effect; in the power-law case, the expected time until the next update
event on a link is large if the link has not had an update event for a long
time. On the complete graph, the consensus time in the power-law case is close
to that in the exponential case. Regular graphs bridge these two results such
that the slowing down of the consensus in the power-law case as compared to the
exponential case is less pronounced as the degree increases.Comment: 18 pages, 8 figure
Multiple agency perspective, family control, and private information abuse in an emerging economy
Using a comprehensive sample of listed companies in Hong Kong this paper investigates how family control affects private information abuses and firm performance in emerging economies. We combine research on stock market microstructure with more recent studies of multiple agency perspectives and argue that family ownership and control over the board increases the risk of private information abuse. This, in turn, has a negative impact on stock market performance. Family control is associated with an incentive to distort information disclosure to minority shareholders and obtain private benefits of control. However, the multiple agency roles of controlling families may have different governance properties in terms of investors’ perceptions of private information abuse. These findings contribute to our understanding of the conflicting evidence on the governance role of family control within a multiple agency perspectiv
Size-Dependent Surface Plasmon Dynamics in Metal Nanoparticles
We study the effect of Coulomb correlations on the ultrafast optical dynamics
of small metal particles. We demonstrate that a surface-induced dynamical
screening of the electron-electron interactions leads to quasiparticle
scattering with collective surface excitations. In noble-metal nanoparticles,
it results in an interband resonant scattering of d-holes with surface
plasmons. We show that this size-dependent many-body effect manifests itself in
the differential absorption dynamics for frequencies close to the surface
plasmon resonance. In particular, our self-consistent calculations reveal a
strong frequency dependence of the relaxation, in agreement with recent
femtosecond pump-probe experiments.Comment: 8 pages + 4 figures, final version accepted to PR
Collective Decision Dynamics in the Presence of External Drivers
We develop a sequence of models describing information transmission and
decision dynamics for a network of individual agents subject to multiple
sources of influence. Our general framework is set in the context of an
impending natural disaster, where individuals, represented by nodes on the
network, must decide whether or not to evacuate. Sources of influence include a
one-to-many externally driven global broadcast as well as pairwise
interactions, across links in the network, in which agents transmit either
continuous opinions or binary actions. We consider both uniform and variable
threshold rules on the individual opinion as baseline models for
decision-making. Our results indicate that 1) social networks lead to
clustering and cohesive action among individuals, 2) binary information
introduces high temporal variability and stagnation, and 3) information
transmission over the network can either facilitate or hinder action adoption,
depending on the influence of the global broadcast relative to the social
network. Our framework highlights the essential role of local interactions
between agents in predicting collective behavior of the population as a whole.Comment: 14 pages, 7 figure
The Movement Imagery Questionnaire-Revised, Second Edition (MIQ-RS) Is a Reliable and Valid Tool for Evaluating Motor Imagery in Stroke Populations
Mental imagery can improve motor performance in stroke populations when combined with physical therapy. Valid and reliable instruments to evaluate the imagery ability of stroke survivors are needed to maximize the benefits of mental imagery therapy. The purposes of this study were to: examine and compare the test-retest intra-rate reliability of the Movement Imagery Questionnaire-Revised, Second Edition (MIQ-RS) in stroke survivors and able-bodied controls, examine internal consistency of the visual and kinesthetic items of the MIQ-RS, determine if the MIQ-RS includes both the visual and kinesthetic dimensions of mental imagery, correlate impairment and motor imagery scores, and investigate the criterion validity of the MIQ-RS in stroke survivors by comparing the results to the KVIQ-10. Test-retest analysis indicated good levels of reliability (ICC range: .83–.99) and internal consistency (Cronbach α: .95–.98) of the visual and kinesthetic subscales in both groups. The two-factor structure of the MIQ-RS was supported by factor analysis, with the visual and kinesthetic components accounting for 88.6% and 83.4% of the total variance in the able-bodied and stroke groups, respectively. The MIQ-RS is a valid and reliable instrument in the stroke population examined and able-bodied populations and therefore useful as an outcome measure for motor imagery ability
Cascades on clique-based graphs
peer-reviewedWe present an analytical approach to determining the expected cascade size in a broad range of dynamical models on the class of highly clustered random graphs introduced by Gleeson [J. P. Gleeson, Phys. Rev. E 80, 036107 (2009)]. A condition for the existence of global cascades is also derived. Applications of this approach include analyses of percolation, and Watts's model. We show how our techniques can be used to study the effects of in-group bias in cascades on social networks.PUBLISHEDpeer-reviewe
An Exploration of Fetish Social Networks and Communities
Online Social Networks (OSNs) provide a venue for virtual interactions and relationships between individuals. In some communities, OSNs also facilitate arranging offline meetings and relationships. FetLife, the world’s largest anonymous social network for the BDSM, fetish and kink communities, provides a unique example of an OSN that serves as an interaction space, community organizing tool, and sexual market. In this paper, we present a first look at the characteristics of European members of Fetlife, comprising 504,416 individual nodes with 1,912,196 connections. We looked at user characteristics in terms of gender, sexual orientation, and preferred role. We further examined the homophilic communities and find that women in particular are far more platonically involved on the site than straight males. Our results suggest there are important differences between the FetLife community and conventional OSNs
Women’s experiences of wearing therapeutic footwear in three European countries
Background: Therapeutic footwear is recommended for those people with severe foot problems associated with
rheumatoid arthritis (RA). However, it is known that many do not wear them. Although previous European studies
have recommended service and footwear design improvements, it is not known if services have improved or if this
footwear meets the personal needs of people with RA. As an earlier study found that this footwear has more
impact on women than males, this study explores women’s experiences of the process of being provided with it
and wearing it. No previous work has compared women’s experiences of this footwear in different countries,
therefore this study aimed to explore the potential differences between the UK, the Netherlands and Spain.
Method: Women with RA and experience of wearing therapeutic footwear were purposively recruited. Ten women
with RA were interviewed in each of the three countries. An interpretive phenomenological approach (IPA) was
adopted during data collection and analysis. Conversational style interviews were used to collect the data.
Results: Six themes were identified: feet being visibly different because of RA; the referring practitioners’ approach
to the patient; the dispensing practitioners’ approach to the patient; the footwear being visible as different to
others; footwear influencing social participation; and the women’s wishes for improved footwear services. Despite
their nationality, these women revealed that therapeutic footwear invokes emotions of sadness, shame and anger
and that it is often the final and symbolic marker of the effects of RA on self perception and their changed lives.
This results in severe restriction of important activities, particularly those involving social participation. However,
where a patient focussed approach was used, particularly by the practitioners in Spain and the Netherlands, the
acceptance of this footwear was much more evident and there was less wastage as a result of the footwear being
prescribed and then not worn. In the UK, the women were more likely to passively accept the footwear with the
only choice being to reject it once it had been provided. All the women were vocal about what would improve
their experiences and this centred on the consultation with both the referring practitioner and the practitioner that
provides the footwear.
Conclusion: This unique study, carried out in three countries has revealed emotive and personal accounts of what
it is like to have an item of clothing replaced with an ‘intervention’. The participant’s experience of their
consultations with practitioners has revealed the tension between the practitioners’ requirements and the women’s
‘social’ needs. Practitioners need greater understanding of the social and emotional consequences of using
therapeutic footwear as an intervention
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