Network Size (network + size)

Distribution by Scientific Domains

Selected Abstracts

Investigating Driver Injury Severity in Traffic Accidents Using Fuzzy ARTMAP

Hassan T. Abdelwahab
This paper applies fuzzy adaptive resonance theory MAP (fuzzy ARTMAP) neural networks to analyze and predict injury severity for drivers involved in traffic accidents. The paper presents a modified version of fuzzy ARTMAP in which the training patterns are ordered using the K,means algorithm before being presented to the neural network. The paper presents three applications of fuzzy ARTMAP for analyzing driver injury severity for drivers involved in accidents on highways, signalized intersections, and toll plazas. The analysis is based on central Florida's traffic accident database. Results showed that the ordered fuzzy ARTMAP proved to reduce the network size and improved the performance. To facilitate the application of fuzzy ARTMAP, a series of simulation experiments to extract knowledge from the models were suggested. Results of the fuzzy ARTMAP neural network showed that female drivers experience higher severity levels than male drivers. Vehicle speed at the time of an accident increases the likelihood of high injury severity. Wearing a seat belt decreases the chance of having severe injuries. Drivers in passenger cars are more likely to experience a higher injury severity level than those in vans or pickup trucks. Point of impact, area type, driving under the influence, and driver age were also among the factors that influence the severity level. [source]

Feature Extraction for Traffic Incident Detection Using Wavelet Transform and Linear Discriminant Analysis

A. Samant
To eliminate false alarms, an effective traffic incident detection algorithm must be able to extract incident-related features from the traffic patterns. A robust feature-extraction algorithm also helps reduce the dimension of the input space for a neural network model without any significant loss of related traffic information, resulting in a substantial reduction in the network size, the effect of random traffic fluctuations, the number of required training samples, and the computational resources required to train the neural network. This article presents an effective traffic feature-extraction model using discrete wavelet transform (DWT) and linear discriminant analysis (LDA). The DWT is first applied to raw traffic data, and the finest resolution coefficients representing the random fluctuations of traffic are discarded. Next, LDA is employed to the filtered signal for further feature extraction and reducing the dimensionality of the problem. The results of LDA are used as input to a neural network model for traffic incident detection. [source]

Influence of social network characteristics on cognition and functional status with aging

Ariel Frank Green
Abstract Objective To determine whether more frequent engagement in larger social networks, and more emotional support protect against cognitive and functional decline with aging. Methods We examined the influence of social networks on cognition and instrumental activities of daily living (IADLs) over a median interval of 10.9 years. Data were from the Baltimore follow-up of the Epidemiologic Catchment Area (ECA) study, a community-based sample of adults in eastern Baltimore. Eight hundred and seventy-four participants completed cognitive testing at both the third and fourth study waves (1993,1996 and 2003,2004) on the Mini-Mental State Examination (MMSE) and a delayed word recall task. Functional status at both waves was self-reported on the Lawton-Brody IADL scale. Social network characteristics, assessed at the third study wave, included network size, frequency of contact, and emotional support. Results In cross-sectional analyses at wave 3, larger networks were associated with higher MMSE and better delayed recall scores. This association persisted after adjustment for covariates. More emotional support was associated with better functional status, before and after adjustment. By contrast, social networks were not longitudinally associated with cognitive change, with two counter-intuitive exceptions: more frequent contact and more emotional support were associated with worse delayed recall and IADL scores after adjustment. Conclusions There was no evidence of a longitudinal association between social networks and cognition or IADLs, although a clear cross-sectional association exists. Together, these findings suggest the emergence of social isolation in individuals declining in cognition and functioning, rather than a protective effect of social networks. Copyright 2008 John Wiley & Sons, Ltd. [source]

Satellite rural communications: telephony and narrowband networks

Roberto Conte
Abstract Rural communications are important for large and developing countries, and telecommunications systems have been implemented depending upon the available technology at the time. Rural users do not generate the same amount of revenue as urban users do, thus lowering incentives for rural telecommunications investment with service to those regions delayed as long as possible. Voice and data communications are essential to the economic development of a region, and it has been shown that traffic increases rapidly as soon as the service is available. Satellite-based digital networks provide efficient long-distance service to rural communities at lower cost than similar land-based wired networks with acceptable quality. Small earth stations along with Wireless Local Loops can provide both local and long-distance service efficiently and at low cost, offering digital multimedia services on a global scale. This paper focuses on the description of different narrowband technologies used to service rural communities, namely basic telephone and low-bit-rate data (<64 kbps) applications through the use of satellite and terrestrial wireless systems. A basic network economic planning description is presented, and important parameters such as satellite network size, topology and multiple access are identified in order to improve the process of effective and cost-efficient rural communications network design. Copyright 2005 John Wiley & Sons, Ltd. [source]

Sexual assault history and social support: Six general population studies,

Jacqueline M. Golding
Abstract We evaluated the association of sexual assault history with later social support, operationalized as network size, marital status, presence of a partner, frequency of network contacts, and emotional support from friends and family, from spouse, and from partner. Data came from six independent general population surveys (pooled N = 9,865) whose results were summarized using meta-analysis. People who had been sexually assaulted were less likely than others to he married (OR = 0.75. 95% CI = 0.65, 0.87) or to report at least weekly contact with friends and relatives (OR = 0.48,95% CI = 0.31, 0.75), and reported less emotional support from friends and family (OR = 0.72,95% CI = 0.58,0.89) and spouse (OR = 0.67, 95% CI = 0.54, 0.82). Results were consistent across studies, genders, and ethnic groups. Circumstances of sexual assault were sometimes related to social support. [source]

Model test of the relationship between self-help-promoting nursing interventions and self-care and health status outcomes

Grace J. Kreulen
Abstract In this study of a nursing intervention outcomes model was tested. Path analysis techniques were used to examine predicted relationships between self-help-promoting interventions and patient outcomes of self-care practice and client morbidity at three times. A sample of 307 women receiving medical treatment for breast cancer provided data for the study. The average participant was White, middle-aged, married, educated, and in stage I or stage II disease. Findings support the hypothesized model linking these nursing interventions directly to self-care outcomes and self-care to client morbidity outcomes. Client factors of age, social network size, disease stage, receipt of chemotherapy, resourcefulness, and uncertainty significantly influenced predicted relationships. Examination of specific patterns of relationships for the sample revealed delayed behavioral responses to the interventions, variability in predictors of each outcome at the three measurement times and a more strongly predictive model when patient outcomes were considered within the context of client factors. 2004 Wiley Periodicals, Inc. Res Nurs Health 27:97,109, 2004 [source]

Social Networks and Collective Action

David A. Siegel
Despite growing attention to the role of social context in determining political participation, the effect of the structure of social networks remains little examined. This article introduces a model of interdependent decision making within social networks, in which individuals have heterogeneous motivations to participate, and networks are defined via a qualitative typology mirroring common empirical contexts. The analysis finds that some metrics for networks' influence,size, the prevalence of weak ties, the presence of elites,have a more complex interaction with network structure and individual motivations than has been previously acknowledged. For example, in some contexts additional network ties decrease participation. This presents the potential for selection bias in empirical studies. The model offers a fuller characterization of the role of network structure and predicts expected levels of participation across network types and distributions of motivations as a function of network size, weak and strong ties, and elite influence. [source]


Previous immigration facilitates future immigration, a phenomenon called network migration. While well recognized, previous research has mainly focused on the implications of immigrant networks on future migrants. In contrast, this paper derives a simple model from the perspective of the incumbent immigrant population by introducing sub-networks and argues that the incumbent migrants fail to achieve a Pareto optimal network size due to differences in inter- and intra-migrant group externalities and subsequently coordination failures. In short, it stresses the active role incumbents take in the provision of network effects and provides theoretical evidence that self-perpetuating and sustained immigration is not at odds with rational acting individuals. It also shows that optimally chosen migration quotas may appeal to incumbent migration cohorts and provides an alternative explanation for inter- and intra-migrant group tensions. [source]

Agglomeration Economies, Division of Labour and the Urban Land-rent Escalation: A General Equilibrium Analysis of Urbanisation

Guang-Zhen Sun
A general equilibrium model with increasing return to labour specialisation and economies of transaction agglomeration is developed to address the residential land-rent escalation associated with the urbanisation process, which is in turn endogenised as a result of the evolution of the division of labour. The interplay among the geographical pattern of transactions, trading efficiency and the network size of the division of labour plays a crucial role in our story of urbanisation. We show that: as transaction conditions are improved, the equilibrium level of division of labour and individuals specialisation levels increase; the urban land-rent increases absolutely as well as relative to that in the rural area, the relative per capita lot size of residence in the urban and rural areas decreases; the diversity of occupations in the urban area and the population share of urban residents increase; and the productivity of all goods and per capital real income increase. [source]

Adaptive zone routing protocol for ad hoc network nodes with non-uniform mobilities

Xiaofeng Zhang
Abstract In recent years, a variety of new routing protocols for mobile ad hoc wireless NETworks (MANETs) have been developed. Performance evaluation and comparison of many of these routing protocols have been performed using detailed simulation models. Zone routing protocol (ZRP) is one of these routing protocols, which is a hybrid routing protocol that proactively maintains routing information for a local neighbourhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. The studies on ZRP have assumed homogeneous scenarios where all mobile nodes have uniform mobility and are statistically identical, lacking the studies on heterogeneous scenarios where mobile nodes move with non-uniform mobilities in the same network. In this paper, we study the performance of ZRP in such scenarios. We propose an efficient scheme for ZRP to adapt to the non-uniform mobilities scenario and study its performance for different mobility scenarios, network loads and network sizes. Copyright 2003 John Wiley & Sons, Ltd. [source]