93,678 research outputs found

    No. 26: Social Media, The Internet and Diasporas for Development

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    The recent focus on diasporas by policy-makers researchers has highlighted the rich potential of migrants as a force for shaping development activities in their countries of origin. The study of diasporas in development presents researchers a number of significant challenges. As Vertovec and Cohen suggest, ‘one of the major changes in migration patterns is the growth of populations anchored … neither at their places of origin nor at their places of destination’. The fluid, multi-sited and multi-generational nature of diaspora groupings poses considerable methodological challenges of definition, identification, location, sampling and interviewing. As the nature of African diasporas are constantly in flux so too should the methodologies we use to study them. In practice, traditional approaches lead to the same methodological roadblocks. Census and immigration data (particularly from destination countries) can provide an overall picture of diaspora stocks, flows and locations. However, privacy issues generally preclude these sources from providing disaggregated data at the level of the individual migrant or migrant household. Surveys of diaspora members have therefore become the standard means of collecting information on diaspora characteristics, identities, activities and linkages. This immediately raises a set of problems and challenges. Census data can tell us the size of the population to sample but not who the individuals are, where they live and how to contact them. Without a sampling frame, researchers tend to rely instead on ‘snowball’, ‘purposive’ or ‘convenience’ sampling. This has produced a disproportionate number of studies that rely on key informant and focus group interviews in order to create a profile of diasporas and their development-related activities. Diasporas are often geographically dispersed within a country and across different countries. Cost and time constraints and the bias of snowball and convenience sampling lead to a focus on sub-sets. Studies of diaspora members in particular cities or regions are especially common. While sample sizes vary considerably, there is a marked reliance on very small samples, which raises obvious questions about the representativeness and generalizability of the findings. The mail-out survey is still the preferred method of reaching members of a geographically dispersed diaspora, although response rates remain stubbornly low. To contact members of the diaspora, mailing lists are compiled from organizations that keep, and are willing to share, membership lists (such as diaspora organizations, embassies, alumni associations, immigrant service agencies and religious organizations). However, this means an inherent sampling bias since data collected from these individuals and groups has the potential to be skewed towards diaspora members actively engaged with their origin country. This method of ‘accessing the diaspora through the diaspora’ is also unlikely to provide much information on ‘hidden’ members of a diaspora whose immigration status may be undocumented or uncertain and who are wary of disclosing personal information directly to researchers. Researchers have also noted that members of vulnerable populations such as asylum seekers and refugees might be reluctant to provide personal information due to fear and trust issues. To identify and connect with larger numbers, different strategies need to be adopted. In this context, the potential of the internet has rarely been considered. Since the advent of the internet age, more than one billion people have become connected to the World Wide Web (WWW), creating seemingly limitless opportunities for communication. The past decade has also seen a major increase in the use of the internet by diaspora individuals and groupings. The internet has not only facilitated remittance transfers, but has increased communication among and between diasporas and influenced the formation of diasporic identities. In this context, the potential of web-based methodologies in diaspora research appears promising. The aim of this paper is twofold. First, we argue for supplementing conventional approaches with new methodologies that embrace the connectivity of diasporas, the emergence of social media and the potential of online surveys. Second, we illustrate the potential of this approach through discussion of the methods adopted in our current research on the African diaspora in Canada

    Analysis of dependence among size, rate and duration in internet flows

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    In this paper we examine rigorously the evidence for dependence among data size, transfer rate and duration in Internet flows. We emphasize two statistical approaches for studying dependence, including Pearson's correlation coefficient and the extremal dependence analysis method. We apply these methods to large data sets of packet traces from three networks. Our major results show that Pearson's correlation coefficients between size and duration are much smaller than one might expect. We also find that correlation coefficients between size and rate are generally small and can be strongly affected by applying thresholds to size or duration. Based on Transmission Control Protocol connection startup mechanisms, we argue that thresholds on size should be more useful than thresholds on duration in the analysis of correlations. Using extremal dependence analysis, we draw a similar conclusion, finding remarkable independence for extremal values of size and rate.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS268 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Transport on complex networks: Flow, jamming and optimization

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    Many transport processes on networks depend crucially on the underlying network geometry, although the exact relationship between the structure of the network and the properties of transport processes remain elusive. In this paper we address this question by using numerical models in which both structure and dynamics are controlled systematically. We consider the traffic of information packets that include driving, searching and queuing. We present the results of extensive simulations on two classes of networks; a correlated cyclic scale-free network and an uncorrelated homogeneous weakly clustered network. By measuring different dynamical variables in the free flow regime we show how the global statistical properties of the transport are related to the temporal fluctuations at individual nodes (the traffic noise) and the links (the traffic flow). We then demonstrate that these two network classes appear as representative topologies for optimal traffic flow in the regimes of low density and high density traffic, respectively. We also determine statistical indicators of the pre-jamming regime on different network geometries and discuss the role of queuing and dynamical betweenness for the traffic congestion. The transition to the jammed traffic regime at a critical posting rate on different network topologies is studied as a phase transition with an appropriate order parameter. We also address several open theoretical problems related to the network dynamics

    ITS implementation plan for the Gold Coast area

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    ITS needs to be used to reinforce the planned major changes to the road functional hierarchy in the District, namely: • the use of Southport-Burleigh Rd. (SBR) as the major regional corridor; • the removal of through traffic from the GCH; • the use of Oxley Dr./Olsen Av./Ross St./NBR as another major north-south by-pass; • the use of Smith St.; NSR/Queen St.; NBR and Reedy Creek Rd. – West Burleigh Road as the major east-west access corridors. There is a need to integrate the proposed ITS measures into the current related plans for the Pacific Motorway and into the overall traffic control strategies for the area as a whole. In addition, the staging of the proposed plan needs to take into account the planned DMR capital Works Program. An index representing the degree of priority to be attached to each network link was developed to assist in the phased implementation of ITS technologies over the next 5 years. 'ITS Index' is made up of five variables, namely: • Accident rate factor • AADT • Volume/Capacity ratio • Delay • % Commercial Vehicles The main components of the ITS plan are shown diagrammatically in Figure 1. The latter assumes that the high level of ITS implementation on the Pacific Motorway will be extended in time to the remainder of that Highway. To assist in the implementation of the road hierarchy system, a new static signage plan should be implemented. This plan needs to reinforce the changes by clearly assigning single road names to corridors and by placing new signs at appropriate locations. Capturing Traffic Data The following corridors should be equipped with automatic traffic monitoring capability in priority order: High Priority ? SBR corridor from Smith St. connection to Reedy Creek Rd. ? Smith St. from Pacific Highway to High St. ? GCH from Pacific Highway to North St. Medium Priority ? Nerang-Broadbeach Rd/Ross St. to Nerang-Southport Rd. ? Nerang-Southport Rd from Pacific Highway to SBR ? Nerang-Broadbeach Rd from Pacific Highway to SBR The Smith St. link from the Pacific Motorway to Olsen Ave. should be considered as a freeway for monitoring purposes. The GCH along the coastal strip needs to be treated as a local distributor rather than as the major corridor. As a result, the future traffic surveillance priority should be low. At least one permanent environmental (vehicle emissions) monitoring station should be set up as part of the ITS plan. The most appropriate site for such a station would seem to be on the SBR corridor at the vicinity of Hooker Blv. intersection. Pacific Highway The Pacific Motorway project will set the benchmark for freeway incident detection and traffic management in the State. The high level of ITS implementation on the Motorway section will create a significant gap in performance and expectation, relative to the remainder of the Highway. It is recommended that the southern sections of the Pacific Highway be equipped to the equivalent level of traffic data collection and surveillance as the newly upgraded Motorway section, under a staged program. Travel Time Savings The travel time benefits of the full implementation of ITS over the network are likely to be of the order of at least 5 percent of vehicle-hours travelled on the affected links. At a discount rate of 6 percent, the total present value of the gross travel time benefit over 10 years is of the order of $200 million

    The Changing Demographic Profile of the United States

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    [Excerpt] The United States, the third most populous country globally, accounts for about 4.5% of the world’s population. The U.S. population—currently estimated at 308.7 million persons—has more than doubled since its 1950 level of 152.3 million. More than just being double in size, the population has become qualitatively different from what it was in 1950. As noted by the Population Reference Bureau, “The U.S. is getting bigger, older, and more diverse.” The objective of this report is to highlight some of the demographic changes that have already occurred since 1950 and to illustrate how these and future trends will reshape the nation in the decades to come (through 2050). The United States Is Getting Bigger. U.S. population growth is due to the trends over time in the interplay of increased births, decreased deaths, and increased net immigration. The United States Is Getting Older. Aside from the total size, one of the most important demographic characteristics of a population for public policy is its age and sex structure. This report illustrates how the United States has been in the midst of a profound demographic change: the rapid aging of its population, as reflected by an increasing proportion of persons aged 65 and older, and an increasing median age in the population. The United States Is Becoming More Racially and Ethnically Diverse, reflecting the major influence that immigration has had on both the size and the age structure of the U.S. population. This section considers the changing profile of the five major racial groups in the United States. In addition, trends in the changing ethnic composition of the Hispanic or Latino Origin population are discussed. Although this report will not specifically discuss policy options to address the changing demographic profile, it is important to recognize that the inexorable demographic momentum will have important implications for the economic and social forces that will shape future societal well-being. There is ample reason to believe that the United States will be able to cope with the current and projected demographic changes if policymakers accelerate efforts to address and adapt to the changing population profile as it relates to a number of essential domains, such as work, retirement, and pensions; private wealth and income security; the federal budget and intergenerational equity; health, healthcare, and health spending; and the health and well-being of the aging population. These topics, among others, are discussed briefly in the final section of this report. This report will be updated as needed

    Point process model of 1/f noise versus a sum of Lorentzians

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    We present a simple point process model of 1/fβ1/f^{\beta} noise, covering different values of the exponent β\beta. The signal of the model consists of pulses or events. The interpulse, interevent, interarrival, recurrence or waiting times of the signal are described by the general Langevin equation with the multiplicative noise and stochastically diffuse in some interval resulting in the power-law distribution. Our model is free from the requirement of a wide distribution of relaxation times and from the power-law forms of the pulses. It contains only one relaxation rate and yields 1/fβ1/f^ {\beta} spectra in a wide range of frequency. We obtain explicit expressions for the power spectra and present numerical illustrations of the model. Further we analyze the relation of the point process model of 1/f1/f noise with the Bernamont-Surdin-McWhorter model, representing the signals as a sum of the uncorrelated components. We show that the point process model is complementary to the model based on the sum of signals with a wide-range distribution of the relaxation times. In contrast to the Gaussian distribution of the signal intensity of the sum of the uncorrelated components, the point process exhibits asymptotically a power-law distribution of the signal intensity. The developed multiplicative point process model of 1/fβ1/f^{\beta} noise may be used for modeling and analysis of stochastic processes in different systems with the power-law distribution of the intensity of pulsing signals.Comment: 23 pages, 10 figures, to be published in Phys. Rev.
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