177,373 research outputs found
General -- July-December,1961 -- Correspondence, OPV Miscellaneous -- letter, 1961-07-31
No full textLetter from Toth, Robert C. to Sabin, Albert B. dated 1961-07-31.Sabin Collection Fair Use Policy</a
On a problem of G Fejes Toth
No full textA solution is given for the following Problem of G Fejes Toth: In 3-space find the thinnest lattice of balls such that every straight line meets one of the balls
Il dibattito sulla sostenibilità del SSN
No full textIl progressivo invecchiamento della popolazione e i recenti tagli al fondo sanitario nazionale mettono in dubbio la sostenibilità futura del Servizio sanitario nazionale. L'adozione di nuovi modelli organizzativi e l'utilizzo delle tecnologie informatiche possono costituire una risposta a tali problemi
On a problem of G Fejes Toth
No full textA solution is given for the following Problem of G Fejes Toth: In 3-space find the thinnest lattice of balls such that every straight line meets one of the balls
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
TOX3_TOX4_TOX5 generated data
No full textThe TOX3, TOX4 and TOX5 datasets are QSAR ones published by Gramatica et al. In their paper the experimental EC50 values (growth inhibition with respect to algea species Pseudokirchneriella subcapitata) of 35 triazole or benzo-triazole derivatives were used as training set. In the original article three linear QSAR models were developed using these 35 compounds (models A, B and C). Thereafter, the models were used on further 369 compounds, but for these no experimental data were available. In our calculation three datasets were formed. Each set contained the merged set of cases with altogether 404 molecules and the corresponding descriptor values of the given model. The response values were calculated in a quasi-independent way. For example, the response values for set TOX3 were defined as the averages of the response values calculated according to models B and C. For TOX4 the average responses of models A and C and for TOX5 the average responses of A and B were used. All responses were calculated in this way. We know that the generation procedure of TOX3-TOX5 datasets regularized the responses and probably eliminated the outliers. The original data were downloaded from the qsardb repository.
P. Gramatica, S. Cassani, P.P. Roy, S. Kovarich, C.W. Yap, E. Papa, QSAR Modeling is not “Push a Button and Find a Correlation”: A Case Study of Toxicity of (Benzo-)triazoles on Algae, Mol. Inform. 31 (2012) 817-835. http://dx.doi.org/10.1002/minf.201200075
V. Ruusmann, S. Sild, U. Maran, QSAR DataBank repository: open and linked qualitative and quantitative structure–activity relationship models. J. Cheminf. 7 (2015) 32. https://doi.org/10.1186/s13321-015-0082-6, http://www.qsardb.org
TOX3 multivariate linear regression R2 on total set
404 cases 3 descriptors 1 response 0.75
TOX4 multivariate linear regression
404 cases 3 descriptors 1 response 0.80
TOX5 multivariate linear regression
404 cases 3 descriptors 1 response 0.8
Remarks on a conjecture of Barat and Toth
No full textIn 2010, Barat and Toth verified that any r-critical graph with at most r + 4 vertices has a subdivision of K-r. Based in this result, the authors conjectured that, for every positive integer c, there exists a bound r(c) such that for any r, where r >= r(c), any r-critical graph on r + c vertices has a subdivision of K-r. In this note, we verify the validity of this conjecture for c = 5, and show counterexamples for all c >= 6211FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP12/16118-1Natural Sciences and Engineering Research Council of Canad
The Time Dependent Traveling Salesman Planning Problem in Controlled Airspace
No full textThe integration of drones into civil airspace is one of the most challenging problems for the automation of the controlled airspace, and the optimization of the drone route is a key step for this process. In this paper, we optimize the route planning of a drone mission that consists of departing from an airport, flying over a set of mission way points and coming back to the initial airport. We assume that during the mission a set of piloted aircraft flies in the same airspace and thus the cost of the drone route depends on the air traffic and on the avoidance maneuvers used to prevent possible conflicts. Two air traffic management techniques, i.e., routing and holding, are modeled in order to maintain a minimum separation between the drone and the piloted aircraft. The considered problem, called the Time Dependent Traveling Salesman Planning Problem in Controlled Airspace (TDTSPPCA), relates to the drone route planning phase and aims to minimize the total operational cost. Two heuristic algorithms are proposed for the solution of the problem. A mathematical formulation based on a particular version of the Time Dependent Traveling Salesman Problem, which allows holdings at mission way points, and a Branch and Cut algorithm are proposed for solving the TDTSPPCA to optimality. An additional formulation, based on a Travelling Salesman Problem variant that uses specific penalties to model the holding times, is proposed and a Cutting Plane algorithm is designed. Finally, computational experiments on real-world air traffic data from Milano Linate Terminal Maneuvering Area are reported to evaluate the performance of the proposed formulations and of the heuristic algorithms
Models and algorithms for the Traveling Salesman Problem with Time-dependent Service times
No full textThe Traveling Salesman Problem with Time-dependent Service times (TSP-TS) is a generalization of the Asymmetric TSP, in which the service time at each customer is given by a (linear or quadratic) function of the corresponding start time of service. TSP-TS calls for determining a Hamiltonian tour (i.e. a tour visiting each customer exactly once) that minimizes the total tour duration, given by the sum of travel and service times. We propose a new Mixed Integer Programming model for TSP-TS, that is enhanced by lower and upper bounds that improve previous bounds from the literature, and by incorporating exponentially many subtour elimination constraints, that are separated in a dynamic way. In addition, we develop a multi-operator genetic algorithm and two Branch-and-Cut methods, based on the proposed model. The algorithms are tested on benchmark symmetric instances from the literature, and compared with an existing approach. The computational results show that the proposed exact methods are able to prove the optimality of the solutions found for a larger set of instances in shorter computing times. We also tested the Branch-and-Cut algorithms on larger size symmetric instances with up to 58 nodes and on asymmetric instances with up to 45 nodes, demonstrating the effectiveness of the proposed algorithms. In addition, we tested the genetic algorithm on symmetric and asymmetric instances with up to 200 nodes
An Iterated Local Search for the Traveling Salesman Problem with Pickup, Delivery and Handling Costs
No full textIn this paper the Traveling Salesman Problem with pickup, delivery and handling costs is studied. We have to find a route from a depot to a set of customers, each of which requires a pickup and delivery service the goal is to minimize the global routing and handling cost. We have developed an Iterated Local Search for this problem combining different heuristics of the Traveling Salesman Problem, and using frequency of improvements and a perturbation with memory the proposed algorithm is tested on different benchmark instances from the literature with up to 200 vertices, obtaining high quality solutions in reasonable computing times
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