1,721,146 research outputs found
Decision plots for preliminary design of single-shield TBMs
No full textIn this note a procedure for a back-of-the-envelope estimation of the correct length of a single-shielded TBM is reported in the context of a TBM preliminary design phase. It is based on four Decision Plots (DPs) and some associated equations, whose input data are the isotropic in-situ stress, the rock mechanical parameters, the maximum tolerated over-excavation and the shield skin friction coefficient. The essential output is the friction force the machine must overcome (the required thrust force), that can be compared with the available thrust force. The derivation of the DPs is illustrated and their practical use shown. Although the procedure involves some simplifying approximations, its performance is confirmed through two application examples and a comparison with the results obtained using design monograms of other authors
A procedure for the computation of accurate PWL approximations of nonlinear dynamical systems
No full textIn this paper we propose a variational method to find out piecewise-linear (PWL) approximations of non-linear dynamical systems in view of their circuit implementations. The method is based on some significant trajectories of the dynamical system and provides reasonably accurate PWL approximations with a relatively low number of parameters. The effectiveness of the method is validated by applying it to the approximation of limit cycles (both stable and unstable) in the Bautin system
A method for the approximate synthesis of cellular nonlinear networks - Part 1: Circuit definition
No full textIn this paper, we face the problem of the synthesis of cellular non-linear networks (CNNs) able to find approximate solutions of either partial differential equations or functional minimization problems. In particular, the paper deals with the approximate synthesis of the multi-terminal resistors that include all the non-linearities of such dynamic circuits. The proposed approximation method is based on the piecewise-linear (PWL) approach developed by Julian et al. in the last few years, but it resorts to a different definition of the inner product and hence to other PWL basis functions. The method is applied to a case-study concerning a CNN devoted to image processing
A method for the approximate synthesis of cellular nonlinear networks - Part 2: Circuit reduction
No full textIn this paper, we face the problem of model reduction in piecewise-linear (PWL) approximations of non-linear functions. The reduction procedure presented here is based on the PWL approximation method proposed in a companion paper and resorts to a strategy that exploits the orthonormality of basis functions in terms of a proper inner product. Such a procedure can be favourably applied to the synthesis of the resistive parts of cellular non-linear networks (CNNs) to reduce the complexity of the resulting circuits. As an example, the method is applied to a case study concerning a CNN for image processing
Incidence and clinical impact of chemotherapy induced myelotoxicity in cancer patients: an observational retrospective survey
No full textPurpose: To evaluate the frequency of chemotherapy-induced myelotoxicity in cancer patients, the related treatment (G-CSF, rHuEPO), and the occurrence of chemotherapy dose reductions, delays or discontinuations. Patients and methods: We retrospectively collected data from 1175 patients who completed at least four chemotherapy courses at 64 Italian Centres. Myelotoxicity was defined as anemia (Hb < 10 g/dL) and neutropenia (ANC < 1500/mm3). The study population was divided by age, in 664 adult patients aged ≤65 years and 511 elderly patients, aged >65 years. The association between events during chemotherapy and myelotoxicity indices were assessed by logistic regression. Results: The median age of the patients was 64 years. Myelotoxicity was observed in 633 patients (53.9%), anemia (<10 g/dL) in 263 (22.4%) and neutropenia in 530 (45.1%); 686 patients (58.5%) showed mild anemia (Hb < 12 g/dL). Dose reductions were observed in 199 patients (16.9%), dose delays in 338 (28.7%), and discontinuations in 157 (13.4%), with no significant difference between age groups. Myelotoxicity accounted for 20% of treatment withdrawals with no differences between age groups. G-CSF was administered to 53.4% of the neutropenic patients, and rHuEPO to 53.1% of the anemic patients. Logistic regression analyses showed a significant (P < 0.001) association between chemotherapy dose delays, dose reductions and myelotoxicity. Considering age strata, the association between dose reduction and myelotoxicity was significant. The risk of neutropenia in the adults was higher than in elderly (50.0% vs 38.7%). Conclusion: Our results show that anemia and neutropenia occur in a substantial proportion of cancer patients receiving chemotherapy, and have an impact on chemotherapy dose delivery. G-CSF and rHuEPO are treatments widely used in about one half of neutropenic and anemic patients. Particular attention should be given to elderly patients, who are at high risk of myelotoxicity and should be carefully evaluated for the prophylactic use of G-CSF and monitored for the appropriate use of rHuEPO. © 2009
A procedure for the piecewise-linear approximation of the resistive part of a cellular non-linear network
No full textThe Effect of Pseudomonas fluorescens on the Corrosion Morphology of Archaeological Tin Bronze Analogues
No full textThis work focuses on the localized forms of corrosion caused by microbiological activity, which have seldom been considered for long-term alteration processes of copper-based alloys. To reproduce a seldom-documented corrosion morphology found in some archaeological objects, called ‘tentacle like’, a Pseudomonas fluorescens strain was used on analogues of known composition in a solution containing sulfates, carbonates, nitrates and chlorides. The effect of such bacteria has already been assessed in a previous study, and a localized type of corrosion was defined. The results show that, when a biofilm grows on the surface of the samples, pits are observed under the corrosion products, while in the presence of chloride ions, these pits propagate under the metallic surface and into the matrix, forming uncommon morphologies ascribed to the type “tentacle like”
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