Tesis por compendio / [ES] Comprender el comportamiento humano en situaciones de riesgo, cómo los factores individuales y externos influyen en nuestras decisiones y en qué medida es posible influir y modificar nuestros comportamientos, constituye un desafío tanto para los científicos como para la sociedad en general. Desde la perspectiva de la Seguridad y Salud en el Trabajo (SST), así como en numerosos campos como la sociología y las finanzas, este tema tiene importantes implicaciones ya que las situaciones de riesgo son un aspecto común en diversos ámbitos de nuestra vida. La toma de riesgos (TR) es parte del proceso de toma de decisiones en situaciones de incertidumbre, en las que se conoce de antemano la probabilidad de cada consecuencia positiva o negativa. Si bien el concepto de la TR está bien definido en la literatura, se ha abordado desde diferentes perspectivas, por lo que los factores que se han propuesto para explicar o moderar la TR también son muy diversos. Centrándonos en los factores individuales (procesos cognitivos y emocionales) que influyen en la TR, estos pueden afectar la forma en que se abordan las situaciones peligrosas de dos maneras diferentes. En primer lugar, pueden sesgar la percepción de una situación, de modo que no se lleve a cabo una evaluación adecuada y por tanto esto lleve a conductas sesgadas. En segundo lugar, estos factores configuran una cierta propensión general al riesgo en los seres humanos, de modo que pueden o no sentirse atraídos por situaciones potencialmente peligrosas. De la misma manera que la definición de la TR se ha abordado desde diferentes perspectivas, su evaluación también se ha tratado desde diferentes puntos de vista y constituye hoy en día un desafío para investigadores y profesionales, por lo que no se ha encontrado un consenso claro en cuanto a la existencia de una medida validada para la TR. La evaluación de la TR se ha realizado tradicionalmente mediante cuestionarios; sin embargo, se ha demostrado que estas medidas presentan diversas limitaciones que pueden conducir a resultados alterados. Las tareas comportamentales surgen como una solución alternativa capaz de superar algunas de estas barreras. En cambio, su capacidad de transferencia a situaciones de la vida real parece ser limitada. La realidad virtual (RV) permite recrear situaciones reales simuladas para realizar evaluaciones basadas en el desempeño. La RV presenta numerosas ventajas que pueden aportar beneficios para la evaluación de los comportamientos humanos, ya que aporta una mayor inmersión, fidelidad y un mayor nivel de implicación que los métodos de evaluación tradicionales, y numerosos trabajos en el campo de la psicología aplicada y la neurociencia organizacional han avalado su uso para evaluación humana. En esta investigación, proponemos la RV como tecnología capaz de facilitar el estudio de los procesos de la TR, aprovechando sus numerosas posibilidades, que se pueden resumir como: simulación de situaciones de riesgo realistas, interacciones naturales con el entorno virtual, inclusión de medidas implícitas para evaluación oculta y medición fisiológica en tiempo real. Esta tesis proporciona aportaciones a la definición de la TR, particularmente en la identificación de qué factores constituyen este complejo proceso. Además, investiga el uso de la RV inmersiva en la investigación del comportamiento humano, específicamente para la evaluación de la TR, proporcionando premisas de diseño de entornos virtuales para la evaluación de los constructos psicológicos identificados como determinantes para definir la TR. Finalmente, analiza la validez de la RV en combinación con medidas fisiológicas para la evaluación de la TR de forma implícita. / [CA] Comprendre el comportament humà en situacions de risc, com els factors individuals i externs influeixen en les nostres decisions i en quina mesura és possible influir i modificar els nostres comportaments, constitueix un desafiament tant per als científics com per a la societat en general. Des de la perspectiva de la Seguretat i Salut en el Treball (SST), així com en nombrosos camps com la sociologia i les finances, aquest tema té importants implicacions ja que les situacions de risc són un aspecte comú en diversos àmbits de la nostra vida. La presa de riscos (PR) és part del procés de presa de decisions en situacions d'incertesa, en les quals es coneix per endavant la probabilitat de cada conseqüència positiva o negativa. Si bé el concepte de la PR està ben definit en la literatura, s'ha abordat des de diferents perspectives, per la qual cosa els factors que s'han proposat per a explicar o moderar la PR també són molt diversos. Centrant-nos en els factors individuals (processos cognitius i emocionals) que influeixen en la PR, aquests poden afectar la forma en què s'aborden les situacions perilloses de dues maneres diferents. En primer lloc, poden esbiaixar la percepció d'una situació, de manera que no es duga a terme una avaluació adequada i per tant això porte a conductes esbiaixades. En segon lloc, aquests factors configuren una certa propensió general al risc en els éssers humans, de manera que poden o no sentir-se atrets per situacions potencialment perilloses. De la mateixa manera que la definició de la PR s'ha abordat des de diferents perspectives, la seua avaluació també s'ha tractat des de diferents punts de vista i constitueix hui dia un desafiament per a investigadors i professionals, per la qual cosa no s'ha trobat un consens clar quant a l'existència d'una mesura validada per a la PR. L'avaluació de la PR s'ha realitzat tradicionalment mitjançant qüestionaris; no obstant això, s'ha demostrat que aquestes mesures presenten diverses limitacions que poden conduir a resultats alterats. Les tasques comportamentals sorgeixen com una solució alternativa capaç de superar algunes d'aquestes barreres. En canvi, la seua capacitat de transferència a situacions de la vida real sembla ser limitada. La realitat virtual (RV) permet recrear situacions reals simulades per a realitzar avaluacions basades en l'acompliment. La RV presenta nombrosos avantatges que poden aportar beneficis per a l'avaluació dels comportaments humans, ja que aporta una major immersió, fidelitat i un major nivell d'implicació que els mètodes d'avaluació tradicionals, i nombrosos treballs en el camp de la psicologia aplicada i la neurociència organitzacional han avalat el seu ús per a avaluació humana. En aquesta investigació, proposem la RV com a tecnologia capaç de facilitar l'estudi dels processos de la PR, aprofitant les seues nombroses possibilitats, que es poden resumir com: simulació de situacions de risc realistes, interaccions naturals amb l'entorn virtual, inclusió de mesures implícites per a avaluació oculta i mesurament fisiològic en temps real. Aquesta tesi proporciona aportacions a la definició de la PR, particularment en la identificació de quins factors constitueixen aquest complex procés. A més, investiga l'ús de la RV immersiva en la investigació del comportament humà, específicament per a l'avaluació de la PR, proporcionant premisses de disseny d'entorns virtuals per a l'avaluació dels constructes psicològics identificats com a determinants per a definir la PR. Finalment, analitza la validesa de la RV en combinació amb mesures fisiològiques per a l'avaluació de la PR de manera implícita. / [EN] Understanding human behaviour in risk situations, how individual and external factors influence our decisions and to what extent it is possible to influence and modify our behaviours, constitutes a challenge both for scientists and for society in general. From the perspective of Occupational Safety and Health (OSH), as well as in numerous fields such as sociology of finance, this topic has important implications since risk situations are a common aspect in various domains of our lives. Risk taking (RT) is part of the decision-making process in uncertain situations, in which the probability of each positive or negative consequence is known in advance. Although the concept of RT is well defined in the literature, it has been approached from different perspectives, so that the factors that have been proposed to explain or moderate RT are also very diverse. Focusing on the individual factors - cognitive and emotional processes - that influence RT, these may affect how hazardous situations are addressed in two different ways. First, they can skew the perception of a situation, so that an adequate evaluation is not carried out and therefore this leads to biased behaviors. Second, these factors shape a certain general propensity towards risk in humans, so that they may or may not be attracted to potentially dangerous situations. In the same way that the definition of RT has been approached from different perspectives, the evaluation of RT has also been treated from different points of view and nowadays constitutes a challenge for researchers and practitioners, so that a clear consensus has not been found regarding the existence of a validated measure for RT. RT evaluation has traditionally been carried out using questionnaires; however, it has been demonstrated that these measures present various limitations that can lead to altered results. Behavioural tasks emerge as an alternative solution capable of overcoming some of these boundaries. Instead, their ability to transference to real life situations appears to be limited. Virtual reality (VR) enables recreating real-simulated situations to carry out performance-based assessments. VR presents numerous advantages that can provide benefits for the evaluation of human behaviours, since it provides greater immersion, fidelity and a higher level of involvement than traditional evaluation methods, and numerous works in the field of applied psychology and organizational neuroscience have endorsed its use for human assessment. In this investigation, we propose VR as technology capable of facilitating the study of RT processes, taking advantage of its numerous possibilities, which can be resumed as: simulation of realistic risk situations, natural interactions with the virtual environment, inclusion of implicit measures for stealth assessment and physiological real-time measurement. This thesis provides novel contributions to the definition of RT, particularly in the identification of which factors constitute this complex process. Moreover, it investigates the use of immersive VR in human behaviour research, specifically for RT assessment, providing design premises of virtual environments for the evaluation of the psychological constructs identified as determinants to define RT. Finally, it analyses the validity of VR in combination with physiological measures for the evaluation of RT in an implicit way. / Contrato predoctoral FPI (BES-2017-079857). Ministerio de Economía, Industria y Competitividad (Madrid, Spain). / Juan Ripoll, CD. (2021). Virtual reality environments for the study of decision-making processes in risky contexts through the use of physiological measures and behavioural responses [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/171236 / TESIS / Compendio

This thesis contains an introduction to anatomy and physiology of the skin highlighting its barrier function. The barrier function of the skin enables it to separate internal organism from external environment. thermore, the electrical properties of the skin are described and possibilities of skin conductance measurement are discussed. The thesis presents a design of a device for the skin conductance measurement as the method of evaluation for barrier function. Alternating current is used for measurement during iontophoresis for evaluation of skin conductance. Circuit design and circuit board are included with a list of parts. The designed device was realized and in the end it was tested and the results were discussed.

INTRODUCTION: La stimulation vestibulaire galvanique (GVS) est utilisée pour évaluer l’intégrité du système vestibulaire et améliorer notre compréhension des mécanismes de l‘équilibre. Néanmoins les réponses évoquées montrent une grande variabilité interindividuelle ce qui rend la compréhension du rôle du système vestibulaire difficile. OBJECTIF: Développer un protocole d’évaluation d’un seuil vestibulaire objectif spécifique à la personne. MÉTHODES: Dix-huit sujets sains droitiers se tenaient debout sur une plate-forme de force, les yeux fermés, la tête vers l’avant. L’accélération de la tête était enregistrée lorsque la GVS (durée: 200 ms) était appliquée à des intensités de 1 à 4,5mA. Des courbes de recrutement ont été générées afin de déterminer le seuil objectif (T). Puis, les participants ont été stimulés à différentes intensités relatives au seuil (0,5T; 0,75T; 1T et 1,5T). L’aire de l’ellipse de confiance (AE) à 95%, la vitesse de déplacement du centre de pression (CoP) et l’activité électromyographique du soléaire (SOL) ont été mesurées. RÉSULTATS: 1) Un seuil objectif a été déterminé pour chaque sujet basé sur l’accélération de la tête. 2) L’aire de l’ellipse, pendant la stimulation, corrélait avec l’intensité de stimulation (r=0,95; p=0,03). 3) L’amplitude de la 1ère phase du patron triphasique de la vitesse de déplacement du CoP corrélait aussi avec l’intensité de stimulation (r=0,98; 0,04). 4) En plus, l’amplitude de la réponse musculaire à moyenne latence induite par la GVS sur le SOL montrait une corrélation significative avec l’intensité de stimulation (r=0,7; p=0,045). DISCUSSION: Un seuil objectif vestibulaire peut être identifié par un accéléromètre. Les réponses vestibulaires mesurées par l’AE et le CoP sont proportionnelles aux intensités de stimulation relatives au seuil objectif déterminé. / INTRODUCTION: Galvanic vestibular stimulation (GVS) is used to assess the integrity of the vestibular system and to improve our understanding of the mechanisms of balance. However, the GVS-induced responses show great inter-individual variability, which makes it difficult to understand the contribution of the vestibular system in maintaining balance. OBJECTIVE: To develop a protocol identifying an objective vestibular threshold for GVS in order to limit this variability observed on GVS-induced responses. METHODS: Eighteen healthy right-handed subjects stood on a force platform, eyes closed, head forward. The head acceleration was recorded when the GVS (duration: 200 ms) was applied at intensities varying between 1 and 4.5mA. Recruitment curves were reconstructed to determine the objective threshold (T). Then, the participants were stimulated at different intensities relative to threshold (0.5T; 0.75T; 1T and 1.5T). The 95% confidence ellipse area, the velocity of the center of pressure (CoP) displacement and the electromyographic activity of the soleus muscle (SOL) were measured. RESULTS: 1) An objective threshold was determined for each subject based on the acceleration of the head. 2) The area of the ellipse, during stimulation, correlated with the stimulation intensity (r = 0.95; p = 0.03). 3) The amplitude of the 1st peak of the three-phase CoP velocity pattern also correlated with the stimulation intensity (r = 0.98; 0.04). 4) In addition, the amplitude of the medium latency response induced by the GVS on the SOL showed a significant correlation with the stimulation intensity (r = 0.7; p = 0.045). DISCUSSION: An objective vestibular threshold can be identified by an accelerometer. The vestibular responses measured by the ellipse area and the CoP are proportional to the stimulation intensities relative to the determined objective threshold.

In a variety of engineering applications, components are subjected to corrosive environment. Protective coatings are essential to improve the functional performances and/or extend the lifetime of the components. Thermal sprayingas a cost-effective coating deposition technique offers high flexibility in coatings' chemistry/morphology/microstructure design. However, the inherent pores formed during spraying limit the use of coatings for corrosion protection. The recently developed supersonic spray method, High-Velocity-Air-Fuel (HVAF), brings significant advantages in terms of cost and coating properties. Although severely reduced, the pores are not completely eliminated even with the HVAF process. In view of the above gap to have a high quality coating, bi-layer coatings have been developed to improve the corrosion resistance of the coatings. In a bi-layer coating, an intermediate layer is deposited on the substrate before spraying the coating. The electrochemical behavior of each layer is important to ensure a good corrosion protection. The corrosion behavior of the layers strongly depends on coating composition and microstructure, which are affected by feedstock material and spraying process. Therefore, the objective of the researchis to explore the relationships between feedstock material, spraying process, microstructure and corrosion behavior of bi-layer coatings. A specific motivationis to understand the corrosion mechanisms of the intermediate layer which forms the basis for developing superior protective coatings. Cr3C2-NiCr top layer and intermediate layers (Fe-, Co- and Ni-based) were sprayed by different thermal spraying processes. Microstructure analysis, as well as various corrosion tests, e.g., electrochemical, salt spray and immersion tests were performed. The results showed a direct link between the corrosion potential (Ecorr) of the intermediate layer and the corrosion mechanisms. It was found that the higher corrosion resistance of Ni-based coatings than Fe- and Co-based coatings was due to higher Ecorr of the coating in the galvanic couple with top layers. Inter-lamellar boundaries and interconnected pores reduced the corrosion resistance of intermediate layers, however a sufficient reservoir of protective scale-forming elements (such as Cr or Al) improved the corrosion behavior.

Aqueous solutions of organic or inorganic salts are used as secondary refrigerants in indirect refrigeration systems to transport and transfer heat. Water is known for its corrosive character and secondary refrigerants based on aqueous solutions have the same tendency. The least corrosive from the aqueous solutions are glycols and alcohols. Salt solutions, such as chlorides and potassium salts, are much more corrosive. Nevertheless, it is possible to minimize corrosion risks at the beginning stage while designing system. Proper design can significantly help in improving system performance against corrosion. There are several aspects which need to be taken into account while working with secondary refrigerants: design of system, selection of secondary refrigerant, proper corrosion inhibitors, compatible materials used to build the installation and proper preparation of system to operation. While choosing proper materials it is advised to avoid the formation of a galvanic couple to reduce the risk of the most dangerous type of corrosion. Oxygen present in installation is another important factor increasing the rate of corrosion. Even small amounts of oxygen can significantly affect the system lifetime. The methods of cleaning, charging the system with refrigerant, and deaeration procedures are extremely important. The purpose of this thesis work is to present the problems of corrosion occurring in the indirect systems with secondary refrigerants. The thesis describes the mechanism of corrosion and its different types, most commonly used materials in installation, different corrosion inhibitors used to protect system. This thesis also lists the available secondary refrigerants on the market and briefly describes them. Further, it describes the important aspects related with designing, preparing and maintaining of indirect systems. This thesis is giving some clues and shows what should be done in order to reduce risks of corrosion. / Effsys 2 P2 project

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