Fluid limits for networks with bandwidth sharing and general document size distributions

We consider a stochastic model of Internet congestion control, introduced by Massouli\'{e} and Roberts [Telecommunication Systems 15 (2000) 185--201], that represents the randomly varying number of flows in a network where bandwidth is shared among document transfers. In contrast to an earlier work by Kelly and Williams [Ann. Appl. Probab. 14 (2004) 1055--1083], the present paper allows interarrival times and document sizes to be generally distributed, rather than exponentially distributed. Furthermore, we allow a fairly general class of bandwidth sharing policies that includes the weighted $\alpha$-fair policies of Mo and Walrand [IEEE/ACM Transactions on Networking 8 (2000) 556--567], as well as certain other utility based scheduling policies. To describe the evolution of the system, measure valued processes are used to keep track of the residual document sizes of all flows through the network. We propose a fluid model (or formal functional law of large numbers approximation) associated with the stochastic flow level model. Under mild conditions, we show that the appropriately rescaled measure valued processes corresponding to a sequence of such models (with fixed network structure) are tight, and that any weak limit point of the sequence is almost surely a fluid model solution. For the special case of weighted $\alpha$-fair policies, we also characterize the invariant states of the fluid model.Comment: Published in at http://dx.doi.org/10.1214/08-AAP541 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Cell Phones to Collect Pregnancy Data From Remote Areas in Liberia

Purpose: To report findings on knowledge and skill acquisition following a 3‐day training session in the use of short message service (SMS) texting with non‐ and low‐literacy traditional midwives. Design: A pre‐ and post‐test study design was used to assess knowledge and skill acquisition with 99 traditional midwives on the use of SMS texting for real‐time, remote data collection in rural Liberia, West Africa. Methods: Paired sample t‐tests were conducted to establish if overall mean scores varied significantly from pre‐test to immediate post‐test. Analysis of variance was used to compare means across groups. The nonparametric McNemar's test was used to determine significant differences between the pre‐test and post‐test values of each individual step involved in SMS texting. Pearson's chi‐square test of independence was used to examine the association between ownership of cell phones within a family and achievement of the seven tasks. Findings: The mean increase in cell phone knowledge scores was 3.67, with a 95% confidence interval ranging from 3.39 to 3.95. Participants with a cell phone in the family did significantly better on three of the seven tasks in the pre‐test: “turns cell on without help” (χ 2 (1) = 9.15, p = .003); “identifies cell phone coverage” (χ 2 (1) = 5.37, p = .024); and “identifies cell phone is charged” (χ 2 (1) = 4.40, p = .042). Conclusions: A 3‐day cell phone training session with low‐ and nonliterate traditional midwives in rural Liberia improved their ability to use mobile technology for SMS texting. Clinical Relevance: Mobile technology can improve data collection accessibility and be used for numerous health care and public health issues. Cell phone accessibility holds great promise for collecting health data in low‐resource areas of the world. Journal of Nursing Scholarship , 2012; 00:0, 1–8.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93561/1/j.1547-5069.2012.01451.x.pd

Gold, power, protest: Digital and social media and protests against large-scale mining projects in Colombia

Colombia’s Internet connectivity has increased immensely. Colombia has also ‘opened for business’, leading to an influx of extractive projects to which social movements object heavily. Studies on the role of digital media in political mobilisation in developing countries are still scarce. Using surveys, interviews, and reviews of literature, policy papers, website and social media content, this study examines the role of digital and social media in social movement organisations and asks how increased digital connectivity can help spread knowledge and mobilise mining protests. Results show that the use of new media in Colombia is hindered by socioeconomic constraints, fear of oppression, the constraints of keyboard activism and strong hierarchical power structures within social movements. Hence, effects on political mobilisation are still limited. Social media do not spontaneously produce non-hierarchical knowledge structures. Attention to both internal and external knowledge sharing is therefore conditional to optimising digital and social media use

Ionospheric coupling, especially between ionogram-recorded spread-F and sporadic-E enhancements at an equatorial-anomaly crest station, Chung-Li

[1] The analysis of ionograms recorded at Chung-Li, a station situated near the crest of the equatorial ionosphere anomaly, finds that there is coupling between the nighttime F and E layers at the onset of spread-F, as is the case in midlatitudes. The results were obtained using isolated patches of spread-F occurrence of duration 2 hours or less and for sunspot-minimum years. It is suggested that the medium-scale traveling ionospheric disturbances (TIDs), which are responsible for the spread-F occurrence, influence both the F and E levels almost simultaneously, as their travel is consistent with the evidence from these analyses, as well as that already available for midlatitudes. Some comments are made on the possibility that these medium-scale TIDs may be responsible directly for some of the small-scale irregularities observed at these equatorial latitudes. Copyright 2002 by the American Geophysical Union

A qualitative study of stakeholders' perspectives on the social network service environment

Over two billion people are using the Internet at present, assisted by the mediating activities of software agents which deal with the diversity and complexity of information. There are, however, ethical issues due to the monitoring-and-surveillance, data mining and autonomous nature of software agents. Considering the context, this study aims to comprehend stakeholders' perspectives on the social network service environment in order to identify the main considerations for the design of software agents in social network services in the near future. Twenty-one stakeholders, belonging to three key stakeholder groups, were recruited using a purposive sampling strategy for unstandardised semi-structured e-mail interviews. The interview data were analysed using a qualitative content analysis method. It was possible to identify three main considerations for the design of software agents in social network services, which were classified into the following categories: comprehensive understanding of users' perception of privacy, user type recognition algorithms for software agent development and existing software agents enhancement

Lecturers' use of Web 2.0 in the faculty of Information Science and communications at MZUZU University, Malawi

The study reported on in this article investigated the use of Web 2.0 technologies by lecturers in the Faculty of Information Science and Communications at Mzuzu University (MZUNI), Mzuzu, Malawi. By distributing a questionnaire to 19 lecturers, conducting follow-up interviews with seven lecturers and analysing the curricula, the study showed that between 10 (58.8%) and 13 (76.5%) lecturers use Wikipedia, YouTube, blogs, Google Apps and Twitter to accomplish various academic activities, such as handing out assignments to students; receiving feedback from students; uploading lecture notes; searching for content; storing lecture notes; and carrying out collaborative educational activities. The study adopted the Decomposed Theory of Planned Behaviour (Taylor and Todd 1995) and the theory's elements that strongly affected lecturers' use of the technologies according to the results included attitude and perceived behaviour control. The study also found that poor Internet access remains the key stumbling block towards a successful adoption of Web 2.0 technologies by lecturers at MZUNI. To this end, the study recommends that the newly established Department of ICT Directorate with support from MZUNI management should install campuswide Wi-Fi and improve Internet bandwidth so that lecturers' access to the Internet is not limited to their offices but rather is available in the teaching rooms across the campus.DHE