Analysis and Design Guidelines for Current Control Loops of Grid-Connected Converters Based on Mathematical Models

Having a method for analyzing and designing regulators of controls that contain many current loops such as active filters is not a trivial task. There can be many parameters of regulators and filters that must be carefully selected in order to fulfill certain desired requirements. For instance, these can be stability, dynamic response, robustness under uncertainty of parameters, and rejection capability to switching harmonics. Hence, this paper provides general analysis guidelines for designing current control loops by using mathematical models in an αβ reference frame. Then, by using the proposed modeling tool, a multi-objective tuning algorithm is proposed that helps obtain all the control loops’ regulator and filter parameters, meeting all the desired requirements. Thus, the proposed analysis and design methodology is illustrated by applying it to three different controls conceived in a dq rotating reference frame with PI (Proportional Integral) regulators. The first control presents two current loops (simple dq current control), the second control uses four current loops (dual vector control, for unbalanced loads), while the third control presents eight current loops (active filter controlling current harmonics). Several experimental and simulation results show the effectiveness and usefulness of the proposed method. Since the mathematical model employed is in the αβ reference frame, it can also be easily applied to controls conceived in a αβ reference frame using resonant regulators, providing also a common comparative framework

Electric Technology in Wind Turbines from a Dialectic Perspective

Wind turbines have been used by many groups of humans for many centu-ries. Wind turbines have allowed groups of humans to perform many different tasks in the past (grinding grain, pumping water, etc.). However, only a century and a half ago, they began to be used to convert the energy captured from wind into electric energy. Moreover, only approximately twenty-five years ago, we started to introduce on a massive scale the energy generated from wind turbines into the electric networks of most developed countries in the world for regular consumption. According to 2017 statistics, approximately 12 percent of the electric energy consumed in the EU is pro-duced by wind turbines. Despite the fact that wind turbines generally appear quite similar externally—i.e., a three-blade structure, a nacelle, a tower, etc.—if we care-fully examine the electric technology used within them, we find quite a wide range of technologies for energy conversion, which is a key issue in wind turbine technology. Hence, this paper adopts a dialectic perspective towards analyzing and understanding why several electric technologies coexist in wind turbine technology. We explain the specific factors that have influenced different wind turbine manufacturers to adopt dif-ferent electric technologies across the last twenty-five years. We show how their actions and the technological directions that have followed have been mutually codetermined, resulting in a technological evolution that has produced today’s wind turbine variety

Signal detection analysis of contingency assessment: Associative interference and nonreinforcement impact cue-outcome contingency sensitivity, whereas cue density affects bias

In a signal detection theory approach to associative learning, the perceived (i.e., subjective) contingency between a cue and an outcome is a random variable drawn from a Gaussian distribution. At the end of the sequence, participants report a positive cue-outcome contingency provided the subjective contingency is above some threshold. Some researchers have suggested that the mean of the subjective contingency distributions and the threshold are controlled by different variables. The present data provide empirical support for this claim. In three experiments, participants were exposed to rapid streams of trials at the end of which they had to indicate whether a target outcome O1 was more likely following a target cue X. Interfering treatments were incorporated in some streams to impend participants' ability to identify the objective X-O1 contingency: interference trials (X was paired with an irrelevant outcome O2), nonreinforced trials (X was presented alone), plus control trials (an irrelevant cue W was paired with O2). Overall, both interference and nonreinforced trials impaired participants' sensitivity to the contingencies as measured by signal detection theory's d', but they also enhanced detection of positive contingencies through a cue density effect, with nonreinforced trials being more susceptible to this effect than interference trials. These results are explicable if one assumes interference and nonreinforced trials impact the mean of the associative strength distribution, while the cue density influences the threshold. (PsycInfo Database Record (c) 2022 APA, all rights reserved)

Genetic and environmental influences on one-trial conditioned context aversion in mice

Anticipatory nausea (AN) is caused by an association between contextual cues and the experience of nausea (the side effects of chemotherapy or radiation treatment) and it develops predominantly in female patients undergoing chemotherapy. Preclinical studies in rodents show that the administration of an illness‐inducing agent in the presence of novel contextual cues can cause conditioned context aversion (CCA) and this has been proposed to model AN. The literature also suggests that brief pre‐exposure to a novel context prior to shock delivery is critical in the development of contextual fear conditioning in rodents (a phenomenon known as Immediate Shock Deficit), but this has not been assessed in CCA. The aim of present study was to develop a CCA paradigm to assess this in outbred (CD1) and inbred (C57BL/6J) mice and evaluate potential sex differences. The results revealed that a single conditioning trial in which a distinctive context was paired with LiCl‐induced illness was sufficient to elicit a conditioned response in both female and male CD1 outbred mice, but not in C57BL/6J inbred mice. In addition, CCA was facilitated when animals had prior experience with the context. Finally, outbred female mice showed longer and more robust retention of CCA than male mice, which parallels clinical findings. The results indicate the importance of using CD1 outbred mice as an animal model of AN as well as examining sex differences in the CCA paradigm. Similar findings in humans encourage the future use of this novel CCA preclinical mouse model

Safety signals as instrumental reinforcers during free-operant avoidance.

Safety signals provide "relief" through predicting the absence of an aversive event. At issue is whether these signals also act as instrumental reinforcers. Four experiments were conducted using a free-operant lever-press avoidance paradigm in which each press avoided shock and was followed by the presentation of a 5-sec auditory safety signal. When given a choice between two levers in Experiment 1, both avoiding shock, rats preferentially responded on the lever that produced the safety signal as feedback, even when footshock was omitted. Following avoidance training with a single lever in Experiment 2, removal of the signal led to a decrease in avoidance responses and an increase in responses during the safety period normally denoted by the signal. These behavioral changes demonstrate the dual conditioned reinforcing and fear inhibiting properties of the safety signal. The associative processes that support the reinforcing properties of a safety signal were tested using a novel revaluation procedure. Prior experience of systemic morphine during safety signal presentations resulted in an increased rate of avoidance responses to produce the safety signal during a drug-free extinction test, a finding not seen with d-amphetamine in Experiment 3. Morphine revaluation of the safety signal was repeated in Experiment 4 followed by a drug-free extinction test in which responses did not produce the signal for the first 10 min of the session. Instrumental avoidance in the absence of the signal was shown to be insensitive to prior signal revaluation, suggesting that the signal reinforces free-operant avoidance behavior through a habit-like mechanism.This study was supported by a Wellcome Trust Programme grant to TWR, JW Dalley, BJ Everitt, AC Roberts and BJ Sahakian (089589/z/09/z). AF was supported by an MRC Case studentship and GU was supported by a Marie Curie Fellowship. The authors would also like to thank Dr Rudolf Cardinal for his helpful comments and critiques of the manuscript. The study was completed within the Behavioural and Clinical Neuroscience Institute, supported by a joint award from the MRC and the Wellcome Trust (G00001354).This is the final published version. It's also available from the publishers at http://learnmem.cshlp.org/content/21/9/488.long

Predictive and motivational factors influencing anticipatory contrast: A comparison of contextual and gustatory predictors in food restricted and free-fed rats

In anticipation of palatable food, rats can learn to restrict consumption of a less rewarding food type resulting in an increased consumption of the preferred food when it is made available. This construct is known as anticipatory negative contrast (ANC) and can help elucidate the processes that underlie binge-like behavior as well as self-control in rodent motivation models. In the current investigation we aimed to shed light on the ability of distinct predictors of a preferred food choice to generate contrast effects and the motivational processes that underlie this behavior. Using a novel set of rewarding solutions, we directly compared contextual and gustatory ANC predictors in both food restricted and free-fed Sprague-Dawley rats. Our results indicate that, despite being food restricted, rats are selective in their eating behavior and show strong contextually-driven ANC similar to free-fed animals. These differences mirrored changes in palatability for the less preferred solution across the different sessions as measured by lick microstructure analysis. In contrast to previous research, predictive cues in both food restricted and free-fed rats were sufficient for ANC to develop although flavor-driven ANC did not relate to a corresponding change in lick patterning. These differences in the lick microstructure between context- and flavor-driven ANC indicate that the motivational processes underlying ANC generated by the two predictor types are distinct. Moreover, an increase in premature port entries to the unavailable sipper – a second measure of ANC – in all groups reveals a direct influence of response competition on ANC development

Prediction error and trace dominance determine the fate of fear memories after post-training manipulations

Different mnemonic outcomes have been observed when associative memories are reactivated by CS exposure and followed by amnestics. These outcomes include mere retrieval, destabilization- reconsolidation, a transitional period (which is insensitive to amnestics), and extinction learning. However, little is known about the interaction between initial learning conditions and these outcomes during a reinforced or nonreinforced reactivation. Here we systematically combined temporally specific memories with different reactivation parameters to observe whether these four outcomes are determined by the conditions established during training. First, we validated two training regimens with different temporal expectations about US arrival. Then, using Midazolam (MDZ) as an amnestic agent, fear memories in both learning conditions were submitted to retraining either under identical or different parameters to the original training. Destabilization (i.e., susceptibly to MDZ) occurred when reactivation was reinforced, provided the occurrence of a temporal prediction error about US arrival. In subsequent experiments, both treatments were systematically reactivated by nonreinforced context exposure of different lengths, which allowed to explore the interaction between training and reactivation lengths. These results suggest that temporal prediction error and trace dominance determine the extent to which reactivation produces the different outcomes.Fil: Alfei Palloni, Joaquin Matías. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferrer Monti, Roque Ignacio. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Molina, Victor Alejandro. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bueno, Adrián Marcelo. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Urcelay, Gonzalo Pablo. University of Cambridge; Reino Unid

Free operant observing in humans: a translational approach to compulsive certainty seeking

Excessive checking is reported in non-clinical populations and is a pervasive symptom in Obsessive Compulsive Disorder (OCD). We implemented a free-operant task in humans, previously used in rats, wherein participants can “check” to reduce uncertainty. Participants can press an observing key to ascertain which of two main keys will, if pressed, currently lead to rewards. Over a series of experiments we found that punishment robustly increased observing in non-clinical participants and that observing persisted long after punishment was removed. Moreover, participants appeared insensitive to the initial costs of checking, and a threefold increase in the effort required to observe served to deter participants only to a limited degree. We also assessed observing in OCD patients with no known comorbidities. The patients observed more than control participants and were abnormally insensitive to the introduction of punishment. These findings support the translational value of the task, with similar behaviours in humans and rodents. This paradigm may serve as a unifying platform, promoting interaction between different approaches to analyze adaptive and maladaptive certainty seeking behaviours. Specifically, we demonstrate how seemingly disparate theoretical and empirical approaches can be reconciled synergistically to promote a combined behavioural and cognitive account of certainty seeking.This research was supported by a grant from the Wellcome Trust to TW Robbins (104631/Z/14/Z)

Resultados comparativos de cirugía de Fontan en pacientes con y sin hipoplasia de corazón izquierdo

ResumenIntroducciónDurante los últimos años múltiples pacientes con diagnóstico de corazón univentricular han sido tratados quirúrgicamente en nuestra institución mediante una anastomosis cavopulmonar total, de acuerdo al protocolo de corrección quirúrgica por etapas.ObjetivoEvaluar los resultados postoperatorios y la sobrevida de pacientes con síndrome de hipoplasia de corazón izquierdo (SHCI) sometidos a la operación de Fontan en comparación con pacientes con otras formas de corazón univentricular.Pacientes y métodoCiento dos pacientes fueron sometidos a la operación de Fontan entre abril de 1996 y marzo de 2014, 25 con SHCI (grupo i) y 77 con otras formas de corazón univentricular (grupo ii). Se analizó la sobrevida, variables demográficas, estudio hemodinámico, morbimortalidad quirúrgica, ventilación mecánica, uso de drenajes, estancia postoperatoria, score de isótropos, necesidad de marcapasos y necesidad de revertir el Fontan take down.ResultadosLa mortalidad perioperatoria fue del 4% (n=1) para el grupo i y del 7,8% (n=6) para el grupo ii (p=0,451). La única diferencia encontrada fue la estancia hospitalaria, siendo de 17 días (6-47) para el grupo i y 12 (5-103) para el grupo ii(p=0,017). El seguimiento promedio fue de 4,24±2,08 años para el grupo i y de 8,7±4,67 para el grupo ii. La sobrevida a 8 años para ambos grupos fue de 88% y de 81% a 10 años para el grupo ii.ConclusionesLa cirugía de Fontan tuvo una mortalidad similar en pacientes con SHCI en comparación con aquellos con otras formas de corazón univentricular, mientras que el primer grupo tuvo una mayor estancia hospitalaria. La sobrevida a largo plazo fue similar para ambos grupos.AbstractIntroductionDuring the last few years, numerous patients with univentricular heart disease have been treated surgically with total cavopulmonary anastomosis according to a staged surgery protocol in our institution.ObjectiveTo evaluate the perioperative outcomes and survival of patients with hypoplastic left heart syndrome (HLHS) after the Fontan procedure and compare them with other types of univentricular heart disease.Patients and methodA total of 102 patients underwent a Fontan procedure between April 1996 and March 2014, 25 with HLHS (group I), and 77 patients with other types of univentricular heart disease (group II). Groups survival, demographics, hemodinamic studies, morbimortality, mechanical ventilation, surgical drains, post-operative stay, isotopes score, pacemaker use, and requiriment of Fontan takedown were analyzed.ResultsIntraoperative mortality was 4% (n=1) for group I, and 7.8% (n=6) for group II (P=.451). A difference was only found in hospital length of stay (LOS), being 17 days (6-47) for group I and 12 days (5-103) for group II (P=.017). Mean follow-up was 4.24±2.08 years for group I, and 8.7±4.67 for group II. Survival rate at 8 years for both groups was 88%, and 81% at 10 years for group II.ConclusionsThe Fontan procedure had similar mortality, but longer LOS, in patients with HLHS compared to those with another types of single ventricle anatomy. Long term survival was comparable between both groups