A Network Recovery Strategy Scheme Based on Network Failure Scenarios and Topologies

Network failures happen frequently. There is a need for recovery mechanisms to reduce service interruption. Recovery mechanismsâ advantages and disadvantages are described extensively based on their characteristics and performances. However, it is more desirable that network recovery strategies are chosen based on failure scenarios and topologies. In this paper, we propose a recovery scheme and focus on networks whose paths and resources from source to destination nodes are computed and negotiated primarily at source nodes, Ingress Label Switched Router (LSR), which are the case for Generalized Multiprotocol Label Switching (GMPLS) networks. Choosing proper network recovery mechanisms depends on many parameters such as distance of failure from source node, degree distribution of nodes, availabilities of alternative paths, and maximum allowed-hopcount increase in alternative paths. Three recovery mechanisms: Haskin, Global and Local Protection are compared with the proposed restoration scheme. By changing parameters on appropriate ranges and by using probability of received data packet at the destination node, e.g. probability of error as one of the performance criteria, we can make a fair judgment on choosing a network strategy by considering available network parameters and topology

Prevalence of Cryptosporidium Infection in Immunocompromised Patients, In South-West of Iran, 2009–10

Background: Cryptosporidium is a protozoan parasite with worldwide distribution. The aim of this study was to estimate the prevalence of Cryptosporidium infection by antigen detection in faeces among immunocompromised patients referred to educational hospitals of Ahvaz City, South-West of Iran, 2009-2010.Methods: Fecal samples from 176 immunocompromised patients were collected and Cryptosporid­ium coproantigen test was performed using ELISA method (DRG kit, Germany). A questionnaire was completed for each case and the results were analyzed using descriptive and Chi-Square tests, by SPSS statistical software (15th version).Results: Our study indicated 5.1% Cryptosporidium infection prevalence in the immunocompro­mised participated population. Furthermore, 4.2 %, 4%, 4.5 % and 9.1% infection rates were identi­fied in children suffered from hematopoietic malignancy, adult cancer patients, renal trans­plant recipients, and HIV+ cases, respectively. There was not significant correlation between the infection and age and gender (P>0.05). Infection was most frequent among HIV+ patients.Conclusion: The present study confirmed the high prevalence of Cryptosporidium antigen in fe­cal samples of immunocompromised patients in the region. As no chemotherapeutic agents have yet proven, especially in immunosuppressed patients, therefore our results highlight the impor­tance of preventive intervention in these groups

A geometrical sink-based cooperative coverage hole recovery strategy for WSNs

© 2015 IEEE. Unlike sporadic node failures, coverage holes emerging from multiple temporally-correlated node failures can severely affect quality of service in a network and put the integrity of entire wireless sensor networks at risk. Conventional topology control schemes addressing such undesirable topological changes have usually overlooked the status of participating nodes in the recovery process with respect to the deployed sink node(s) in the network. In this paper, a cooperative coverage hole recovery model is proposed which utilises the simple geometrical procedure of circle inversion. In this model, autonomous nodes consider their distances to the deployed sink node(s) in addition to their local status, while relocating towards the coverage holes. By defining suitable metrics, the performance of our proposed model performance is compared with a force-based approach