Bounded Error Identification of Systems With Time-Varying Parameters

This note presents a new approach to guaranteed system identification for time-varying parameterized discrete-time systems. A bounded description of noise in the measurement is considered. The main result is an algorithm to compute a set that contains the parameters consistent with the measured output and the given bound of the noise. This set is represented by a zonotope, that is, an affine map of a unitary hypercube. A recursive procedure minimizes the size of the zonotope with each noise corrupted measurement. The zonotopes take into account the time-varying nature of the parameters in a nonconservative way. An example has been provided to clarify the algorithm

Robust MPC of constrained nonlinear systems based on interval arithmetic

A robust MPC for constrained discrete-time nonlinear systems with additive uncertainties is presented. The proposed controller is based on the concept of reachable sets, that is, the sets that contain the predicted evolution of the uncertain system for all possible uncertainties. If processes are nonlinear these sets are very difficult to compute. A conservative approximation based on interval arithmetic is proposed for the online computation of these sets. This technique provides good results with a computational effort only slightly greater than the one corresponding to the nominal prediction. These sets are incorporated into the MPC formulation to achieve robust stability. By choosing a robust positively invariant set as a terminal constraint, a robustly stabilising controller is obtained. Stability is guaranteed in the case of suboptimality of the computed solution. The proposed controller is applied to a continuous stirred tank reactor with an exothermic reaction.Ministerio de Ciencia y Tecnología DPI-2001-2380-03- 01Ministerio de Ciencia y Tecnología DPI-2002-4375-C02-0

Understanding how customers engage with social tourism websites

Purpose: This paper aims to analyse the effect of technology acceptance variables on customer attitude and customer engagement behaviours (CEB) with social tourism websites (STWs). Design/methodology/approach: An empirical study was carried out with 346 customers. A model was developed to analyse the relationships between CEB and their determinants. Partial least squares – structural equation modelling was used to test the model. Findings: Customers’ perceptions of enjoyment, ease of use, usefulness and trustworthiness positively influence their attitude towards STWs and their subsequent engagement behaviours [purchases, word of mouth (WOM) and referrals]. Originality/value: This study develops and empirically tests a model that analyses the impact of technology acceptance model variables on CEB, both transactional (customer purchases) and non-transactional (customer WOM, referrals and feedback), in the context of STWs

Effects of internal brand knowledge dissemination on the employee

Purpose: This study aims to examine the internal brand knowledge dissemination process in the banking sector and its effects on employees. Specifically, it focuses on the key roles of employee identification with both the organization and with the customer as antecedents of behaviors supportive of the brand, i.e. employee citizenship behaviors and recommendation behaviors. Design/methodology/approach: An empirical study was carried out in a major Spanish bank. Data gathered from a survey of 315 employees were analyzed through structural equation modeling. Findings: The results showed that employees'' perceptions of brand value congruence are key in explaining their identification with both the organization and with the customer. However, the employees'' perceptions of the brand''s authenticity explained only their recommendations of the bank as a good place to work. Originality/value: These findings contribute to the advance in the current knowledge of the role of variables such as brand authenticity and employee–customer identification in internal brand management. From a managerial viewpoint, the results provide insights into the importance of employees'' perceptions and attitudes when it comes to brand knowledge dissemination. © 2021, Emerald Publishing Limited

Effects of service experience on customer responses to a hotel chain

Purpose: This paper aims to analyse customer experience in a hotel and its impact on customer attitudes to both the individual hotel and the hotel chain. Specifically, the study focuses on the effects of service perceptions on emotions, satisfaction, attitude to hotel chain, intention to return, scepticism towards negative information and Word of Mouth (WOM). Design/methodology/approach: An empirical study was carried out on a sample of 300 individuals. Data were analysed through structural equation modelling. Findings: Service perceptions and emotions elicited by an individual hotel influence the customer response towards the hotel chain. Among all the outcomes considered, the strongest effects are found on WOM. Originality/value: This paper develops and empirically tests an original model that integrates the customer experience in an individual hotel and the customer response to the hotel chain. This model includes variables that have recently been considered in the literature, such as scepticism towards negative information, in combination with more traditional outcomes such as intention to return or WOM

Isolation and characterization of phenanthrene degrading bacteria from diesel fuel-contaminated Antarctic soils

Indexación: Scopus.Antarctica is an attractive target for human exploration and scientific investigation, however the negative effects of human activity on this continent are long lasting and can have serious consequences on the native ecosystem. Various areas of Antarctica have been contaminated with diesel fuel, which contains harmful compounds such as heavy metals and polycyclic aromatic hydrocarbons (PAH). Bioremediation of PAHs by the activity of microorganisms is an ecological, economical, and safe decontamination approach. Since the introduction of foreign organisms into the Antarctica is prohibited, it is key to discover native bacteria that can be used for diesel bioremediation. By following the degradation of the PAH phenanthrene, we isolated 53 PAH metabolizing bacteria from diesel contaminated Antarctic soil samples, with three of these isolates exhibiting a high phenanthrene degrading capacity. In particular, the Sphingobium xenophagum D43FB isolate showed the highest phenanthrene degradation ability, generating up to 95% degradation of initial phenanthrene. D43FB can also degrade phenanthrene in the presence of its usual co-pollutant, the heavy metal cadmium, and showed the ability to grow using diesel-fuel as a sole carbon source. Microtiter plate assays and SEM analysis revealed that S. xenophagum D43FB exhibits the ability to form biofilms and can directly adhere to phenanthrene crystals. Genome sequencing analysis also revealed the presence of several genes involved in PAH degradation and heavy metal resistance in the D43FB genome. Altogether, these results demonstrate that S. xenophagum D43FB shows promising potential for its application in the bioremediation of diesel fuel contaminated-Antarctic ecosystems.https://www.frontiersin.org/articles/10.3389/fmicb.2017.01634/ful

Vulnerability and Resilience Assessment of Power Systems: From Deterioration to Recovery via a Topological Model based on Graph Theory

Traditionally, vulnerability is the level of degradation caused by failures or disturbances, and resilience is the ability to recover after a high-impact event. This paper presents a topological procedure based on graph theory to evaluate the vulnerability and resilience of power grids. A cascading failures model is developed by eliminating lines both deliberately and randomly, and four restoration strategies inspired by the network approach are proposed. In the two cases, the degradation and recovery of the electrical infrastructure are quantified through four centrality measures. Here, an index called flow-capacity is proposed to measure the level of network overload during the iterative processes. The developed sequential framework was tested on a graph of 600 nodes and 1196 edges built from the 400 kV high-voltage power system in Spain. The conclusions obtained show that the statistical graph indices measure different topological aspects of the network, so it is essential to combine the results to obtain a broader view of the structural behaviour of the infrastructure

Estimation of PCBs content in agricultural soils associated with long-term fertilization with organic waste

Polychlorinated biphenyl (PCB) pollution related to the use of organic waste as fertilizers in agricultural soils is a cause of major concern. In the study presented herein, PCB concentration was studied through a field trial conducted in two agricultural soils in the province of Palencia (Spain) over a 4-year period, assessing the impact of irrigation and of different types of organic waste materials. The amounts of organic waste added to the soil were calculated according to the nitrogen needs of the crop, and the concentration of PCBs was determined before and after the application of the organic waste. The resulting persistence of the total PCB content in the agricultural soils, compared with the PCB concentration in the original soils, ranged from 27% to 90%, with the lowest value corresponding to irrigated soils treated with municipal solid waste compost (MSWC) and the highest value to non-irrigated soils treated with composted sewage sludge (CSS). An estimate of the PCB content in agricultural soils after the application of organic waste materials until year 2050 was obtained, resulting in a value below 5 ng·g-1, considered a background value for soils in sites far away from potential pollution sources

Encuesta nacional sobre las Unidades de Cirugía Pancreática

Introducción: Las características técnicas, humanas, científicas y asistenciales de las Unidades que atienden una patología compleja son poco estudiadas y conocidas. Métodos: Estudio descriptivo multiinstitucional (encuesta) desarrollado conjuntamente por la sección Hepatobiliopancreática de la Asociación Española de Cirujanos y el capítulo español de la IHPBA (Asociación Internacional Hepatopancreatobiliar) sobre las características de las Unidades donde se realiza cirugía pancreática en España. Resultados: Se enviaron 82 encuestas. Respondieron 69 centros (84%) pertenecientes a 16 comunidades autónomas. La suma de habitantes de las áreas propias fue 23.183.262. El número medio de camas por hospital fue 673. La Unidad que realiza la cirugía pancreática es la Unidad de Cirugía Hepatobiliopancreática o Cirugía HPB y Trasplante Hepático en 56 hospitales (77%). El número medio de cirujanos es 4, 5 por Unidad. Cincuenta y cinco Unidades (80%) carecen de anestesistas específicos. El número de pancreatectomías realizadas durante 2017 en los centros encuestados fue 1.315 duodenopancreatectomías cefálicas (DPC), 566 pancreatectomías distales (PD) y 178 duodenopancreatectomías totales (DPT). La media por centro fueron 19, 1 DPC, 8, 2 PD y 2, 6 DPT. La DPC más habitual se realiza mediante abordaje clásico, con pancreatoyeyunostomía, montaje en un asa, con gastroyeyunostomía antecólica y 2 drenajes. Solo 7 Unidades efectúan la DPC por laparoscopia y solamente 13 Unidades no realizan PD laparoscópica. Conclusiones: Esta encuesta proporciona información actualizada del trabajo asistencial y científico de un gran porcentaje de las Unidades donde se realiza cirugía pancreática en España, y además puede servir de punto de partida a trabajos multicéntricos prospectivos. Introduction: The technical, human, scientific and treatment characteristics of the Units that manage complex pathologies have not been studied in depth. Methods: Multi-institutional descriptive study (survey) developed jointly by the Hepatobiliary-Pancreatic Division of the Spanish Association of Surgeons and the Spanish Chapter of the IHPBA (International Hepatopancreatobiliary Association) on the characteristics of the Units where pancreatic surgery is performed in Spain. Results: 82 surveys were sent. 69 medical centers responded (84%), belonging to 16 autonomous regions of Spain. The total population of these regions was 23, 183, 262 (50% of the Spanish population). The average number of beds per hospital was 673. The unit that performs pancreatic surgery is a Hepatobiliary-Pancreatic Surgery Unit or HPB and Liver Transplant Surgery Unit in 56 hospitals (77%). The average number of surgeons is 4.5 per Unit. Fifty-five Units (80%) lack specific anesthetists. The number of pancreatectomies performed during 2017 at the hospitals surveyed was 1, 315 pancreaticoduodenectomies (PD), 566 distal pancreatectomies (DP) and 178 total pancreaticoduodenectomies (TPD). The mean per hospital was 19.1 PD, 8.2 DP and 2.6 TPD. PD was usually performed using a classic approach, with pancreatojejunostomy, single-loop technique, antecolic gastrojejunostomy and using two drain tubes. Only 7 Units performed PD laparoscopically and only 13 units did not perform laparoscopic DP. Conclusions: This survey provides updated information about the majority of the Units where pancreatic surgery is performed in Spain and could also serve as a starting point for prospective multicenter studies