Self-assessment and peer assignment have clear advantages for the training of responsible, critical, and reflective professionals. In recent years, self and peer evaluation have also been shown to be ...even more effective than lecturer evaluation when we assure anonymity through online platforms learning tools. Therefore, self and peer assessments are to become a core aspect of student-centred evaluation processes in Higher Education. Besides, a high concordance with lecturer evaluation may allow lecturers to also benefit from self and peer evaluation without an increase in their workload. In the present work, we compare the formative evaluation from the lecturer with the self and peer assessments through a virtual learning environment. The subject of study if formed by assessments prepared by students in a first-year course in a Social Sciences degree at the Universidade de Vigo, Spain. We find a strong concordance between peer assessment and lecturer assignment, and a moderate agreement between self-assessment and lecturer assignment. These results show that students perform well as peer evaluators, with peer assignment being a procedure with high validity and reliability.
We consider a cost allocation problem arising from a hub network problem design. Finding an optimal hub network is NP-hard, so we start with a hub network that could be optimal or not. Our main ...objective is to divide the maintenance and/or building cost of such network among the nodes. We consider two cases. In the one-way flow case, we assume that the cost paid by a set of nodes depends only on the flow they send to other nodes (including nodes outside the set), but not on the flow they receive from nodes outside. In the two-way flow case, we assume that the cost paid by a set of nodes depends on the flow they send to other nodes (including nodes outside the set) and also on the flow they receive from nodes outside. In both cases, we study the core and the Shapley value of the corresponding cost game.
We study minimum cost spanning tree problems and define a cost sharing rule that satisfies many more properties than other rules in the literature. Furthermore, we provide an axiomatic ...characterization based on monotonicity properties.
Proper tuning of hyper-parameters is essential to the successful application of SVM-classifiers. Several methods have been used for this problem: grid search, random search, estimation of ...distribution Algorithms (EDAs), bio-inspired metaheuristics, among others. The objective of this paper is to determine the optimal method among those that recently reported good results: Bat algorithm, Firefly algorithm, Fruit-fly optimization algorithm, particle Swarm optimization, Univariate Marginal Distribution Algorithm (UMDA), and Boltzmann-UMDA. The criteria for optimality include measures of effectiveness, generalization, efficiency, and complexity. Experimental results on 15 medical diagnosis problems reveal that EDAs are the optimal strategy under such criteria. Finally, a novel performance index to guide the optimization process, that improves the generalization of the solutions while maintaining their effectiveness, is presented.
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•Hardmetal with less toxic and more economical alternative binder to Co.•Nanostructured and highly homogeneous hardmetal powder obtained by HEBM.•Nanopowder with early densification ...and large contribution of solid state sintering.
WC cemented carbides with a greener alternative binder to Co, AISI 304 stainless steel (SS), were processed through high energy ball milling (HEBM). The milling parameters, such as rotation speed, ball-to-powder ratio and milling time were investigated. Selected milling conditions were applied to obtain a nanosized powder of WC-12 wt% SS with a highly uniform distribution of the ductile phase. For comparison, a conventionally wet milled powder was also prepared. Both powders were thermally characterized by dilatometry, up to 1450 °C, using vacuum atmosphere, and structural and microstructural analysis were performed in the sintered samples. The nanometric size of the HEBM powder particles markedly affected its densification and thermal reactivity; when compared with the micrometric powder obtained from conventional milling, early starting densification, with a greater contribution of solid state sintering, and increased reactivity, with formation of a larger amount of (M,W)6C phase, was noticed during sintering of HEBM powder compacts.
Schedule‐induced polydipsia (SIP) is an animal model of compulsive drinking that selects for individual differences and varies across rat strains. The aim of this study was to investigate excessive ...habit formation by analyzing the SIP licking microstructure among rat strains, and to compare the brain areas activated by SIP in different populations. Wistar, Long Evans and Roman High‐ and Low‐Avoidance rat strains were compared using a cluster analysis of 2 main variables, that is, frequency of licking (percentage of interpellet intervals with drinking episodes) and intensity of licking (mean number of licks per interpellet interval), and were found to exhibit high intensity and frequent licking (compulsive drinkers, CD), low intensity but frequent licking (habitual drinkers, HD), and low intensity and low‐frequency licking (low drinkers, LD). The Wistar strain showed a higher frequency and intensity of licking, and had the largest group of CD rats when compared with the other strains. Regarding the acquisition of SIP, CD rats showed a higher intensity of licking when compared with the HD and LD rats. Moreover, c‐Fos quantification revealed that rats in the CD group showed hyperactivity in the lateral orbitofrontal cortex and basolateral amygdala when compared with the LD group. Analyzing the SIP microstructure could be a valuable tool for understanding the role of excessive habit formation in the development of compulsive drinking and its underpinning neurobiological mechanisms.
Excessive habit formation measured by frequency and intensity of licking in schedule‐induce polydipsia among rat strains
Glaciers supply multiple ecosystem services that are threatened by climate change. The retreat and disappearance of tropical glaciers is an important dynamic that affects ecosystems and local ...communities. The knowledge of the impacts of this land-change dynamics on the supply of ecosystem services is lacking. In that sense, the assessment developed can provide evidence about the costs and benefits of promoting conservation and human well-being at the same time. Then, the main objective of this research is to determine the spatial–temporal changes and their effects on the economic value of ecosystem services in a glacial retreat environment. We selected the Marangani district as a study area. It comprises the La Raya Mountain range in the Andes. The assessments were carried out across two scales of observation: the municipality and the watershed level. Here, we process spectral information from Landsat Sensor using the Random Forest algorithm in the Google Earth Engine platform to classify 10 biomes. It was carried out over more than 30 years (from 1986 to 2019). After that, ecosystem services provided by the biomes were valued using the transfer method. This research shows that at the municipality level, almost all the LULCs faced variations over time, and the glaciers had the highest change, accumulating a ratio of –85.51%, whereas at the watershed level, a higher tendency of land changes is observed in the areas without glaciers, and those with glacier areas count on permanent larger bofedales. At the municipality level, the economic value of ecosystems shows that bofedales and water surfaces are the LULCs that supply the highest ecosystem services (∼33,000 USD ha
−1
yr
−1
each). In addition, without the inflation adjustment, the total ESV is on a trajectory of losing ESV (–$9.67 × 10
6
). In the watersheds with glacier retreat, significant quantity of bofedales and natural grasslands controls the fluctuations of ESV. These high-mountain watersheds play an essential role in providing benefits and value to local communities. In general, the municipality level indicates the trajectory of changes in the district, whereas the watershed scale shows the urgency for implementing spatial conservation actions.
Estimation of Distribution Algorithms (EDAs) maintain and iteratively update a probabilistic model to tackle optimization problems. The Boltzmann Probability Distribution Function (Boltzmann-PDF) ...provides advantages when used in energy based EDAs. However, direct sampling from the Boltzmann-PDF to update the probabilistic model is unpractical, and several EDAs employ an approximation to the Boltzmann-PDF by means of a Gaussian distribution that is usually derived by the minimization of the Kullback-Leibler divergence (KL-divergence) computed between the Gaussian and the Boltzmann-PDFs. The KL-divergence measure is not symmetric, and this causes the Gaussian approximation to fail at correctly modeling the target function for the EDAs, because the parameters of the Gaussian are not optimally estimated. In this paper, we derive an approximation to the Boltzmann-PDF using Jeffreys' divergence (a symmetric measure) in lieu of the KL-divergence and thus improve the performance of the optimization algorithm. Our approach is termed Symmetric-approximation Energy-based Estimation of Distribution (SEED) algorithm. The SEED algorithm is experimentally compared under a univariate approach against two other EDAs (UMDAc and BUMDA) on several benchmark optimization problems. The results show that the SEED algorithm is more effective and more efficient than the other algorithms.
Pulmonary ventricle (PV) to pulmonary artery (PA) conduits have made possible the correction of many complex congenital cardiac anomalies.
Between April 1964 and January 2001, 1270 patients underwent ...operation with conduit placement from the PV to PA. The present study evaluates late outcome of 1095 patients (612 males, 483 females) having an operation before July 1992. Mean age was 9.6 ± 8.2 years old. Diagnoses included pulmonary atresia/tetralogy of Fallot (459), transposition of the great arteries (TGA) (232), truncus arteriosus (193), double outlet right ventricle (DORV) (121), corrected TGA (49), septated univentricular heart (36), and other (5). A porcine-valved Dacron conduit was used in 730, homograft in 239, and non-valved conduit in 126.
Early mortality decreased from 23.5% prior to 1980 to 3.7% for the most recent decade. Mean follow-up was 10.9 years (maximum, 29 years). Actuarial survival for early survivors at 10 and 20 years was 77.0% ± 1.5% and 59.5% ± 2.6%. On univariate analysis, clinical and hemodynamic factors associated with late mortality were male gender, older age at operation, higher post-repair PV/systemic ventricle (SV) pressure ratio, higher distal PA pressure, and longer bypass time (
p ≤ 0.01 for all). On multivariate analysis, independent risk factors for late mortality were male gender, older age at operation, diagnosis of TGA, corrected TGA, truncus, or univentricular heart, and PV/SV pressure ratio ≥ 0.72 (
p ≤ 0.03 for all). Freedom from reoperation for conduit failure at 10 and 20 years was 55.5% ± 2.0% and 31.9% ± 2.7%. On multivariate analysis, independent risk factors for conduit failure were homograft conduit, diagnosis of TGA, younger age at operation, and smaller conduit size (
p ≤ 0.007 for all). Reoperation for one conduit replacement was performed in 306 patients, two conduit replacements in 55 patients, three in 6 patients, and four in 3 patients. Overall early mortality for conduit replacement in this series was 4.9%; it was 1.7% for patients operated on from 1989 through 1992. At follow-up, 84% of survivors were in NYHA class I or II.
Operations that include conduit placement and replacement can be performed with low early mortality. Younger age at operation was associated with improved late survival. The diagnosis of TGA was associated with increased risk for conduit failure, and the durability of the homograft, in this series, was inferior to the porcine-valved Dacron conduit. Quality of life was excellent for most patients despite the need for reoperation.
In this work, we focus on the problem of selecting low-level heuristics in a hyperheuristic approach with offline learning, for the solution of instances of different problem domains. The objective ...is to improve the performance of the offline hyperheuristic approach, identifying equivalence classes in a set of instances of different problems and selecting the best performing heuristics in each of them. A methodology is proposed as the first step of a set of instances of all problems, and the generic characteristics of each instance and the performance of the heuristics in each one of them are considered to define the vectors of characteristics and make a grouping of classes. Metalearning with statistical tests is used to select the heuristics for each class. Finally, we used the Naive Bayes to test the set instances with k-fold cross-validation, and we compared all results statistically with the best-known values. In this research, the methodology was tested by applying it to the problems of capacitated vehicle routing (CVRP) and graph coloring (GCP). The experimental results show that the proposed methodology can improve the performance of the offline hyperheuristic approach, correctly identifying the classes of instances and applying the appropriate heuristics in each case. This is based on the statistical comparison of the results obtained with those of the state of the art of each instance.
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