308 research outputs found
An evolutionary algorithm for a real vehicle routing problem
No full textThe NP-hard Vehicle Routing Problem (VRP) is central in the optimisation of distribution networks. Its main objective is to determine a set of vehicle trips of minimum total cost. The ideal schedule will efficiently exploit the company's recourses, service all customers and satisfy the given (mainly daily) constraints. There have been many attempts to solve this problem with conventional techniques but applied to small-scale simplified problems. This is due to the complexity of the problem and the large volume of data to be processed. Evolutionary Algorithms are search and optimization techniques that are capable of confronting that kind of problems and reach a good feasible solution in a reasonable period of time. In this paper we develop an Evolutionary Algorithm in order to solve the VRP of a specific transportation company in Volos, Greece with different vehicle capacities. The algorithm has been tested with different configurations and constraints, and proved to be effective in reaching a satisfying solution for the company's needs
Leg extension test, semg and vibratory stimuli to assess functional recovery following knee joint surgery
No full textObjective: the purpose of this study was to introduce new procedure to determine the magnitude of functional recovery after knee surgery. Design: we compared the performance in the leg extension test and the response in the sEMG activity to vibration in the operated to the non-operated leg. Thirty-eight patients with knee operation and 14 healthy subjects participated in these experiments. Results: during leg extension test, the mechanical power of the operated leg showed a lower value (P<0.001) than the contralateral one, while no differences were noted in the sEMG activity. The sEMG activity during vibration treatment was higher in the operated compared to non-operated leg (P<0.001). It has been suggested that the reduced motility trigger functional adaptations that are exhibited via the vibration test. Conclusions: results of our study suggest that combination of vibration and sEMG recordings may detect the impairment as well as monitoring progress of the rehabilitation program
On the parallelization of artificial neural networks and genetic algorithms
No full textΔημοσιεύσεις μελών--ΣΤΕΦ--Τμήμα Μηχανικών Πληροφορικής, 1998Simulating an ANN or a genetic algorithm on a parallel processing system one can use several techniques. This paper presents two methods on implementing parallel simulations of Artificial Neural Networks (ANNs) on Transputer Based Systems, using the C programming language under Helios O.S. and Component Distribution Language (CDL) or, alternatively, the 3L Parallel C language. The Processor Farm topology is used for the parallel implementation of Back-Propagation and Multi-Layered Feed-Forward ANNs. A transputer system was also used to implement a simulation of an island parallel genetic algorithm (PGA) and a new optimization method based on PGAs. The method, called Co-operating Populations with Different Evolution Behaviours (CoPDEB), is independent of the machine architecture. It allows the populations to exhibit different evolution behaviours by using a variety of selection mechanisms, operators, communication methods, and parameters as explained in the sequel
Expression of immunohistochemical markers in lupus nephritis and association with clinical data
No full textPURPOSE: The aim of this study was to examine the expression of metalloproteinases (MMPs) MMP-1, MMP-2, MMP-3, MMP-9 and their specific tissue inhibitor TIMP-1 in kidney biopsies of patients with Lupus Nephritis (LN) and to investigate the relationship between MMPs, activity index and renal function at the time of kidney biopsy. METHODS: We performed immunohistochemistry with monoclonal antibodies against MMP-1, MMP-2, MMP-3, MMP-9, and TIMP-1 in 58 kidney-biopsy specimens with LN (according the 2004 ISN/RPS classification) and 8 specimens from normal kidney tissue. We used clinical data of 36 patients at the time of kidney biopsy to evaluate the association between MMPs expression and renal function. RESULTS: We found increased MMP-1, MMP-2 and MMP-3 expression in LN glomeruli and a significant correlation with the activity features, with higher activity index score and worse renal function (p<0.001). In particular, we have noticed a significant correlation of MMP-1 with leukocyte influx (OR:16,5 95%CI 4,3-62,5 p<0,001), and MMP-3 with glomerular hypercellularity (OR:18,6 95%CI 4,8-72,8 p<0,001). Moreover, we found a strong correlation of MMP-2 expression with fibrinoid necrosis and cellular crescents formation (OR:17,1 95%CI 4,3-67,7 p<0,001). CONCLUSION: MMP expression in renal biopsy of patients with LN is increased and directly related to a highly active inflammatory response. Moreover, stronger MMP expression is associated with higher activity index and a more profound renal dysfunction.ΣΚΟΠΟΣ: Η μελέτη είχε στόχο να ερευνήσει την σπειραματική έκφραση των μεταλλοπρωτεϊνασών (ΜΜΡs) MMP-1, MMP-2, MMP-3, MMP-9 και του αναστολέα τους ΤΙΜΡ-1 σε περιπτώσεις σπειραματονεφρίτιδας ασθενών με Συστηματικό Ερυθηματώδη Λύκο (ΣΕΛ) και να μελετήσει τη συσχέτισή τους με συγκεκριμένους δείκτες ενεργότητας καθώς και με την νεφρική λειτουργία, τη στιγμή της διενέργειας της νεφρικής βιοψίας. ΜΕΘΟΔΟΣ: Η αξιολόγηση της έκφρασης των ΜΜΡ έγινε με ανοσοϊστοχημεία. Για τις χρώσεις χρησιμοποιήθηκαν μονοκλωνικά αντισώματα έναντι των MMP-1, MMP-2, MMP-3, MMP-9 και TIMP-1 σε 58 περιπτώσεις βιοψίας νεφρού ασθενών με ΣΕΛ νεφρίτιδα. Η αξιολόγηση των βιοψιών έγινε με βάση το σύστημα κατάταξης 2004 ISN/RPS. Ως μάρτυρες χρησιμοποιήθηκαν 8 δείγματα φυσιολογικού νεφρικού παρεγχύματος από περιπτώσεις νεφρεκτομής λόγω τραυματισμού ή νεοπλασίας. Για τη συσχέτιση με τη νεφρική λειτουργία χρησιμοποιήθηκαν κλινικά και εργαστηριακά δεδομένα από 36 ασθενείς. ΑΠΟΤΕΛΕΣΜΑΤΑ: Στη μελέτη φάνηκε ισχυρή συσχέτιση της σπειραματικής έκφρασης των ΜΜΡ-1, ΜΜΡ-2 και ΜΜΡ-3 με τους περισσότερους επιμέρους δείκτες ενεργότητας, με υψηλότερο συνολικό δείκτη ενεργότητας και με χειρότερη νεφρική λειτουργία κατά τη στιγμή της διενέργειας της νεφρικής βιοψίας (p<0.001). Ιδιαίτερη συσχέτιση διαπιστώθηκε μεταξύ της έκφρασης της ΜΜΡ-1 και της λευκοκυτταρικής διήθησης (OR:16,5 95%CI 4,3-62,5 p<0,001) καθώς και της έκφρασης της ΜΜΡ-3 με την ενδοτριχοειδική κυτταροβρίθεια (OR:18,6 95%CI 4,8-72,8 p<0,001). Επίσης, ισχυρή συσχέτιση διαπιστώθηκε μεταξύ της έκφρασης της ΜΜΡ-2 και της παρουσίας ινιδοειδούς νέκρωσης και κυτταρικών μηνοειδών σχηματισμών (OR:17,1 95%CI 4,3-67,7 p<0,001), η οποία παρουσίασε ιδιαίτερο ενδιαφέρον. ΣΥΜΠΕΡΑΣΜΑ: Στη σπειραματονεφρίτιδα του ΣΕΛ παρατηρείται αυξημένη έκφραση των μεταλλοπρωτεϊνασών, η οποία παρουσιάζει σημαντική συσχέτιση με τις επιμέρους παραμέτρους ενεργότητας καθώς και το συνολικό δείκτη ενεργότητας. Το φαινόμενο αυτό σχετίζεται με εντονότερη φλεγμονώδη αντίδραση, σημαντικότερη παρεγχυματική βλάβη και με χειρότερη νεφρική λειτουργία κατά τη στιγμή της διενέργειας της βιοψίας
Model-based Search for Combinatorial Optimization: A Comparative Study
No full textIn this paper we introduce model-based search as a unifying framework accommodating some recently proposed heuristics for combinatorial optimization such as ant colony optimization, stochastic gradient ascent, cross-entropy and estimation of distribution methods. We discuss similarities as well as distinctive features of each method, propose some extensions and present a comparative experimental study of these algorithms.Proceedings of PPSN VII – Seventh International Conference on Parallel Problem Solving From Nature, J. J. Merelo, P. Adamidis, H.-G. Beyer, J.-L. Fernández-Villacanas & H.-P. Schwefel (Eds.)SCOPUS: cp.kinfo:eu-repo/semantics/publishe
State parameter for partially drained paths using a SANISAND model
No full textThe state parameter is a fundamental component of critical state compatible, bounding surface plasticity models. Several definitions for the state parameter exist, expressing how far the current state is from critical. However, there is rarely the opportunity to directly assess the chosen state parameter definition within a given model. Here, we use a plasticity model of the SANISAND family to simulate partially drained paths in triaxial space, by imposing a constant ratio of volumetric to axial strain. We show that for such paths, the locus of post-phase transformation and post-peak stress ratio points where instability is triggered represents a constant state parameter curve in e−p′ space. We then present results from a series of partially drained triaxial compression experiments on Hostun sand, where volumetric and axial strains are coupled. We demonstrate that the chosen constitutive model does not recreate the experimentally observed paths well and more specifically is unable to match the experimentally obtained locus of constant state instability points. Consequently, we propose an updated state parameter definition through which the selected bounding surface plasticity model is shown to not only capture the desired locus of instability points, but to also achieve an overall improved performance in simulating partially drained paths
- …
