Analysis of the effect of clock drifts on frequency regulation and power sharing in inverter-based islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.Peer ReviewedPostprint (author's final draft

Robust Single Object Tracking and Following by Fusion Strategy

Single Object Tracking methods are yet not robust enough because they may lose the target due to occlusions or changes in the target’s appearance, and it is difficult to detect automatically when they fail. To deal with these problems, we design a novel method to improve object tracking by fusing complementary types of trackers, taking advantage of each other’s strengths, with an Extended Kalman Filter to combine them in a probabilistic way. The environment perception is performed with a 3D LiDAR sensor, so we can track the object in the point cloud and also in the front-view image constructed from the point cloud. We use our tracker-fusion method in a mobile robot to follow pedestrians, also considering the dynamic obstacles in the environment to avoid them. We show that our method allows the robot to follow the target accurately during long experimental sessions where the trackers independently fail, demonstrating the robustness of our tracker-fusion strategy.This work has been supported by the Ministry of Science and Innovation of the Spanish Government through the research project PID2021-122685OB-I00 and through the Formación del Personal Investigador [Research Staff Formation (FPI)] under Grant PRE2019-088069

El cluster turístico de un destino cultural en México: su ciclo de vida y la red de actores

En este artículo, se analiza el grado de conformación del clúster del destino turístico de la ciudad de Oaxaca, México. Un elemento central en este ciclo es el grado de consolidación de las relaciones entre los actores que en él participan, por lo cual se analizan las redes sociales para determinar la fase del ciclo de vida del cluster. La hipótesis propuesta es que el grado de desarrollo del clúster de este destino es de gestación debido a la escasa vinculación entre los actores que lo conforman, la cual se confirma con los resultados empíricos que reflejan una red de baja densidad

Inferior alveolar nerve trajectory, mental foramen location and incidence of mental nerve anterior loop

Background: Injury of the inferior alveolar nerve (IAN) is a serious intraoperative complication that may occur during routine surgical procedures, such as dental implant placement or extraction of impacted teeth. Thus, the purpose of this study was to analyze the trajectory of the mandibular canal (MC), the location of the mental foramen (MF) and the presence and extension of an anterior loop of the mental nerve (AL). Study Design: In this cross-sectional study, a total of 348 CBCTs were analyzed. Distances from MC to the surface of the basal, medial and lateral cortical of the mandible were measured at the level of the second molar, first molar and second premolar. Location of the MF relative to the apices of the premolars, as well as incidence and anterior extent of the AL were also determined. Results: Significant and clinically relevant correlations were found between the position of the MC in women, which was located more caudal (r=-0.219, p=0.007; r=-0.276, p<0.001; right and left, respectively) and lateral (r=-0.274, p=0.001; r=-0.285, p<0.001; right and left, respectively), particularly at the level of the premolars. Additionally, the presence (r=-0.181, p=0.001; r=-0.163, p=0.002; right and left, respectively) and anterior extension (r=-0.180, p=0.009; r=-0.285, p=0.05; right and left, respectively) of the AL was found to be inversely correlated with the age of the patient. Conclusions: This analysis of a Caucasian population has found that the older the patient, the lower the incidence of the loop and the shorter its anterior extension. Key words:Cone-beam computed tomography, mandibular nerve, mental foramen

General anesthesia for oral and dental care in paediatric patients with special needs : a systematic review

Background: The objective of this study is to conduct a systematic review of the literature on the characteristics, needs and current situation of dental care for pediatric patients with special needs. Material and Methods: An exhaustive search for literature published until June 1, 2020. It was carried out using PubMed, Web of Science, Scopus, Cochrane and EBSCO, with the following keywords: Oral Surgical Procedures and Dentistry, Operational and Anesthesia, General Y (Spanish[lang] or English[lang] ) Y (infant[MeSH] Or child[MeSH] Or adolescent[MeSH]). The research was carried out following the PRISMA research methodology. Results: The most common indication for general anesthesia (GA) was tooth decay in 16 studies (6.5-90.8% of patients), followed by lack of cooperation and/or fear of dental professionals performing dental procedures in 8 studies. There is a higher prevalence of treatment in the group of patients with special needs, reaching 87.7% compared to 69.9% in healthy patients. Conclusions: In paediatric patients with special needs the use of GA is increasing, monitoring and preventive care are insufficient and withdrawal rates are high

Dynamically Weighted Factor-Graph for Feature-based Geo-localization

Feature-based geo-localization relies on associating features extracted from aerial imagery with those detected by the vehicle's sensors. This requires that the type of landmarks must be observable from both sources. This no-variety of feature types generates poor representations that lead to outliers and deviations, produced by ambiguities and lack of detections respectively. To mitigate these drawbacks, in this paper, we present a dynamically weighted factor graph model for the vehicle's trajectory estimation. The weight adjustment in this implementation depends on information quantification in the detections performed using a LiDAR sensor. Also, a prior (GNSS-based) error estimation is included in the model. Then, when the representation becomes ambiguous or sparse, the weights are dynamically adjusted to rely on the corrected prior trajectory, mitigating in this way outliers and deviations. We compare our method against state-of-the-art geo-localization ones in a challenging ambiguous environment, where we also cause detection losses. We demonstrate mitigation of the mentioned drawbacks where the other methods fail.Comment: This paper is under review at the journal "IEEE Robotics and Automation Letters

Geo-Localization Based on Dynamically Weighted Factor-Graph

Feature-based geo-localization relies on associating features extracted from aerial imagery with those detected by the vehicle's sensors. This requires that the type of landmarks must be observable from both sources. This lack of variety of feature types generates poor representations that lead to outliers and deviations produced by ambiguities and lack of detections, respectively. To mitigate these drawbacks, in this letter, we present a dynamically weighted factor graph model for the vehicle's trajectory estimation. The weight adjustment in this implementation depends on information quantification in the detections performed using a LiDAR sensor. Also, a prior (GNSS-based) error estimation is included in the model. Then, when the representation becomes ambiguous or sparse, the weights are dynamically adjusted to rely on the corrected prior trajectory, mitigating outliers and deviations in this way. We compare our method against state-of-the-art geo-localization ones in a challenging and ambiguous environment, where we also cause detection losses. We demonstrate mitigation of the mentioned drawbacks where the other methods fail.This work was supported in part by Regional Valencian Community Government and the European Union under Project PROMETEO/2021/075 and in part by Spanish Government under Grant PRE2019-088069, Grant PRE2022-101680, and Project PID2021-122685OB-I00

LiLO: Lightweight and low-bias LiDAR Odometry method based on spherical range image filtering

In unstructured outdoor environments, robotics requires accurate and efficient odometry with low computational time. Existing low-bias LiDAR odometry methods are often computationally expensive. To address this problem, we present a lightweight LiDAR odometry method that converts unorganized point cloud data into a spherical range image (SRI) and filters out surface, edge, and ground features in the image plane. This substantially reduces computation time and the required features for odometry estimation in LOAM-based algorithms. Our odometry estimation method does not rely on global maps or loop closure algorithms, which further reduces computational costs. Experimental results generate a translation and rotation error of 0.86\% and 0.0036{\deg}/m on the KITTI dataset with an average runtime of 78ms. In addition, we tested the method with our data, obtaining an average closed-loop error of 0.8m and a runtime of 27ms over eight loops covering 3.5Km.Comment: This paper is under review at the journal "Autonomous Robots" (Springer

Maxillary sinus dimensions with respect to the posterior superior alveolar artery decrease with tooth loss

Background: The posterior superior alveolar (PSA) artery is frequently encountered in the area where the lateral osteotomy is performed during direct sinus augmentation procedures. Objective: To investigate the correlation between patient-dependent variables and measurements related to PSA using cone beam computed tomography (CBCT) data. Methods: Three hundred ninety-four CBCT scans were evaluated to assess the PSA artery diameter and distances to the sinus floor and to alveolar crest. Patient's age, gender, and edentulism status were recorded. Results: The PSA artery tends to be wider in older patients. Distances to the sinus floor or the alveolar crest tend to be shorter in women and in partially and completely edentulous patients. Also, as those distances decrease, the mediolateral width of the sinus increases. Conclusion: Tooth loss leads to maxillary sinus vertical collapse with respect to the PSA artery. The position of the artery is stable; so, the mediolateral dimensions at different heights from the floor increase. Practical implications: The reduced distances from the PSA to the sinus floor and the alveolar crest in edentulous patients potentially increase the risk of injury during maxillary sinus lift. Additionally, when the distance to the sinus floor decreases, the mediolateral dimensions of the sinus at different heights increase, which may complicate the technique and challenge the outcomes.Junta de Andalucía #CTS-138 and #CTS-58

The regional impact of tourism in sustainable development: the case of the regions of Mexico 2000-2010

El presente artículo analiza la relación existente entre desarrollo regional sostenible y competitividad turística en las regiones de México durante el periodo 2000-2010. Supone que la competitividad es un factor importante para la promoción del desarrollo, es decir, a mayor competitividad turística mayor desarrollo sostenible existe en una región. Sin embargo, al interrelacionar estas variables se encontró entre ellas una muy baja correlación. Pero los mismos indicadores para los estados del país indican una alta correlación. Esto sugiere que entre más amplio sea el espacio en el cual se aplica, menor es el impacto del turismo en el desarrollo; en otras palabras, el artículo concluye que el turismo tiene un impacto local, pero no regional en el impulso al desarrollo.This article analyzes the relationship between sustainable regional development and tourism competitiveness in the regions of Mexico during the period 2000-2010. Assumes that competitiveness is an important factor in promoting development, i.e., greater competitiveness of tourism more sustainable development exists in a region. However, the interrelation between these variables was found very low correlation them. But the same indicators for states indicate a high correlation. This suggests that the larger the space in which it is applied, the less impact on the development of tourism in other words, the article concludes that tourism has a local impact, but not in boosting regional development