Survivability in hierarchical telecommunications networks under dual homing

Cataloged from PDF version of article.The motivation behind this study is the essential need for survivability in the telecommunications networks. An optical signal should find its destination even if the network experiences an occasional fiber cut. We consider the design of a two-level survivable telecommunications network. Terminals compiling the access layer communicate through hubs forming the backbone layer. To hedge against single link failures in the network, we require the backbone subgraph to be two-edge connected and the terminal nodes to connect to the backbone layer in a dual-homed fashion, i.e., at two distinct hubs. The underlying design problem partitions a given set of nodes into hubs and terminals, chooses a set of connections between the hubs such that the resulting backbone network is two-edge connected, and for each terminal chooses two hubs to provide the dual-homing backbone access. All of these decisions are jointly made based on some cost considerations. We give alternative formulations using cut inequalities, compare these formulations, provide a polyhedral analysis of the smallsized formulation, describe valid inequalities, study the associated separation problems, and design variable fixing rules. All of these findings are then utilized in devising an efficient branch-and-cut algorithm to solve this network design problem

Analysis of design parameters in SIL-4 safety-critical computer

Nowadays, Safety-critical computers are extensively used in may civil domains like transportation including railways, avionics and automotive. We noticed that in design of some previous works, some critical safety design parameters like failure diagnostic coverage (DC) or common cause failure (CCF) ratio have not been seriously taken into account. Moreover, in some cases safety has not been compared with standard safety levels (IEC-61508 SIL1-SIL4) or even have not met them. Most often, it is not very clear that which part of the system is the Achilles' heel and how design can be improved to reach standard safety levels. Motivated by such design ambiguities, we aim to study the effect of various design parameters on safety in some prevalent safety configurations: 1oo2 and 2oo3. 1oo1 is also used as a reference. By employing Markov modeling, sensitivity of safety to each of the following critical design parameters is analyzed: failure rate of processing element, failure diagnostics coverage, common cause failures and repair rates. This study gives a deeper sense regarding influence of variation in design parameters over safety. Consequently, to meet appropriate safety integrity level, instead of improving some system parts blindly, it will be possible to make an informed decision on more relevant parameters. © 2017 IEEE

Effect of lactic acid bacteria and the potential probiotic Hafnia alvei on growth and survival rates of narrow clawed crayfish (Astacus leptodactylus Esch., 1823) stage II juveniles

The aim of this study was to screen potential probiotic bacteria against Aeromonas hydrophila and determine the effects of antagonistic bacteria and a commercial product containing lactic acid bacteria on the survival and growth of stage II Astacus leptodactylus juveniles. For this purpose, a total of 110 bacterial strains were isolated from adult, stage II crayfish juveniles and rearing water screened for antagonistic activities against A. hydrophila with well diffusion agar assay. Hafnia alvei strain from stage II crayfish juveniles displayed the inhibition zone (10mm) against A. hydrophila. The experiment was conducted in a completely randomized design with four treatments for 60 days: (I) crayfish fed with live food without probiotics (control group); (II) crayfish fed with live food enriched with lactic acid bacteria (0.015 gL^-1); (III) crayfish fed with live food enriched with Hafnia alvei (10^6 CFU mL^−1); (IV) crayfish fed with control diet and H. alvei added to rearing water (10^6 CFU mL^−1). As a result of this study, lactic acid bacteria and Hafnia alvei applications did not positively affect growth and survival of stage II A. leptodactylus juveniles. In the future, studies on screening potential probiotic bacteria should be used in vitro and in vivo tests. In addition, it will be useful to investigate the lactic acid bacteria and Bacillus spp. from indigenous microflora of crayfish

Modeling Measurement as a Sequential Process: Autoregressive Confirmatory Factor Analysis (AR-CFA)

To model data from multi-item scales, many researchers default to a confirmatory factor analysis (CFA) approach that restricts cross-loadings and residual correlations to zero. This often leads to problems of measurement-model misfit while also ignoring theoretically relevant alternatives. Existing research mostly offers solutions by relaxing assumptions about cross-loadings and allowing residual correlations. However, such approaches are critiqued as being weak on theory and/or indicative of problematic measurement scales. We offer a theoretically-grounded alternative to modeling survey data called an autoregressive confirmatory factor analysis (AR-CFA), which is motivated by recognizing that responding to survey items is a sequential process that may create temporal dependencies among scale items. We compare an AR-CFA to other common approaches using a sample of 8,569 people measured along five common personality factors, showing how the AR-CFA can improve model fit and offer evidence of increased construct validity. We then introduce methods for testing AR-CFA hypotheses, including cross-level moderation effects using latent interactions among stable factors and time-varying residuals. We recommend considering the AR-CFA as a useful complement to other existing approaches and treat AR-CFA limitations

Postoperative Radiotherapy in the Management of Resected Non-Small-Cell Lung Carcinoma: 10 Years' Experience in a Single Institute

PubMed ID: 19386425Purpose: This study reports the long term outcomes of postoperative radiotherapy in patients with resection for non-small-cell lung cancer (NSCLC). Methods and Materials: A total of 98 patients with resected NSCLC who received postoperative radiotherapy (PORT) between January 1994 and December 2004 were retrospectively analyzed. The most frequently performed surgical procedure was lobectomy (59 patients), followed by pneumonectomy (25), wedge resection (8), and bilobectomy (6). Postoperative radiotherapy was delivered as an adjuvant treatment in 71 patients, after a wedge resection in 8 patients, and after an R1 resection in 19 patients. The PORT was administered using a Co-60 source in 86 patients and 6-MV photons in 12 patients. A Kaplan-Meier estimate of overall survival, locoregional control, and distant metastasis-free survival were calculated. Results: Stages included I (n =13), II (n = 50), IIIA (n = 29), and IIIB (n = 6). After a median follow-up of 52 months median survival was 61 months. The 5-year overall survival, locoregional control, and distant metastasis-free survival rates for the whole group were 50%, 78%, and 55% respectively. The RT dose, Karnofsky performance status, age, lateralization of the tumor, and pneumonectomy were independent prognostic factors for OAS; anemia and the number of involved lymph nodes were independent prognostic factors for LC. Conclusions: Doses of PORT of greater than 54 Gy were associated with higher death rate in patients with left-sided tumor, which may indicate a risk of radiation-induced cardiac mortality. © 2010 Elsevier Inc