Perceptions of work engagement of nurses in Taiwan

Purpose. The purpose of this study was to determine the perceptions of work engagement of Taiwanese nurses with 3 specific aims: (1) understand Taiwanese nurses' perceptions of work engagement; (2) explore the factors influencing work engagement, and (3) examine how work engagement impacts nursing care for patients. ^ Design. The study used an ethnographic approach with participant observation and semi-structured interviews with RNs. ^ Setting. The study was conducted in the highest and lowest nurse turnover medical surgical units at a regional teaching hospital in southwestern Taiwan. ^ Sample. Purposive sampling resulted in 28 formal interviews with RNs who provided direct patient care, had at least 3 months experience in nursing, and were full-time employees. ^ Methods. Descriptive data were collected through participant observation in each unit. Observations were made while attending meetings, continuing education sessions, and informal conversations with RNs. Field notes and audio recorded semi-structured interviews were analyzed using qualitative thematic analytic techniques. ^ Findings. Findings revealed perceptions of work engagement spanned four domains: patients ("wholehearted care"), work (positive attitude), self (fulfillment and happiness), and others (relationships with colleagues). Providing "wholehearted care" toward patients was the foundation of work engagement for nurses in Taiwan. Engaged nurses felt fulfilled, happy, and found "meaning" through the process of patient care. The study revealed five factors that influenced work engagement: personal, organizational, social, patient, and professional. The impact of work engagement on nurse and patient outcomes are confirmed. ^ Conclusions. Taiwanese nurses connect work engagement with patients, the job, oneself, and colleagues. "Wholehearted patient care" is the core manifestation of work engagement among these nurses. In contrast, studies in western business only focused on work attitudes. Losing interest and "heart" lead to work routines which can lead to individual unhappiness. Findings from this study validate the multiple factors contributing to work engagement of nurses. Job demands and resources can only partially explain what hinders work engagement. Work disengagement and burnout share some commonality but should be measured differently. An understanding of RNs' perceptions of work engagement may provide direction for strategies that improve work engagement leading to decreased RN turnover. ^

Process and outcome evaluation of the hepatitis B perinatal vaccination program in Houston, Texas, 1991--1993

A retrospective cohort study was designed to evaluate the compliance of vaccination dose schedules and vaccination effectiveness at 12 months of age among a total of 226 high-risk infants born to HBsAg-positive pregnant women who participated in the HBV Perinatal Vaccination Program in Houston, Texas, 1991-1993.^ The seroprevalence of HBsAg-positivity was 0.5% among pregnant women who attended prenatal clinics in Houston, Texas, 1991-1993. The Asian women had the highest seroprevalence rate (5.9%), followed by black (1.9%), white (0.7%), and Hispanic women (0.3%). The seroprevalence of HBsAg increased with age (p =.02); the highest seroprevalence rate found among the $>$40 group (5.4%), followed by the 20-40 age group, and the $<$20 age. A steady increase was observed in the number of infants, from 45 in 1991, to 103 in 1993. The majority of these infants were black (58.0%), followed by Hispanic (28.8%), Asian (8.4%), and white infants (4.0%). Significant increases were observed from 1991 to 1993 in the number of infants who initiated vaccination (86.7% to 98.1%, p =.02) and in those infants who were post-tested at 12 months of age (24.4% to 44.7%, p =.04). During the same period an increase was also observed in the number of infants who completed the vaccination dose schedules (62.2% to 72.8%, p =.37). The compliance rates were not statistically significant regarding gender, race or ethnicity, health service area, medical referral source, and residential geographic areas. About 56.0% of the reasons cited for non-compliance among the 144 infants who neither completed the vaccination dose schedules nor received the 12-month post-test were "moved," and "no response/not at home." A total of 82 infants completed the vaccination dose schedules and were post-tested at 12 months of age for anti-HBs-positivity, and 96.3% of these infants seroconverted. A race-specific statistically significant seroconversion difference was found among infants who received all vaccination doses and were post-tested at 12 months of age (100% for the black and the white, 96.3% for the Hispanic, and 80.0% for the Asians infants, p =.05).^ From a public health perspective, the HBV Perinatal Vaccination Program improved during its first three years (1991-1993). It was effective in preventing perinatal HBV infection in almost 97.0% of infants who were vaccinated and post-tested. To increase the efficiency and efficacy of the program, the following recommendations are proposed: (1) Increase the vaccination compliance rate by educating and improving the tracking, communication and coordination channels with those individuals involved in the process and by increasing staff resources. (2) Reduce the post-test vaccination non-compliance by post-testing infants simultaneously with third vaccination dose at 6 months of age, and only post-test those infants who are anti-HBs-negative at 9-12 months of age. (Abstract shortened by UMI.) ^

La vida cultural de las políticas públicas : un análisis de los conflictos por el uso del agua en el contexto neoliberal

La descentralización en el marco de las políticas neoliberales se concibió como una reforma política-administrativa para minimizar el rol del Estado postulando como bastión clave "La participación local". Sin embargo ésta sólo se queda en los ámbitos formales. El caso particular de las políticas de descentralización del riego en la provincia de Mendoza no es una excepción. Lo que nos lleva a analizar su microcosmos y las redes sociales informales que dan cuenca de la desigual participación de los distintos usuarios del agua de riego en las decisiones en torno a este recurso, según sus trayectorias y sus capitales sociales, económicos y culturales.

Lógicas y tendencias de la expansión residencial en áreas periurbanas. El Partido de La Plata, Buenos Aires, Argentina, entre 1990 y 2010

Con el propósito de contribuir al conocimiento de las lógicas y tendencias de la expansión residencial en áreas periurbanas y su impronta en la organización futura de las ciudades medias, tendiente al logro de una relación armónica entre la actividad residencial y las otras actividades socioeconómicas que se presentan en dichas áreas, en la presente Tesis doctoral se aborda el estudio del proceso de expansión residencial que se han venido desarrollando en el espacio periurbano del Partido de La Plata desde principios de los años '90 hasta nuestros días. Para tal fin, se profundiza en el estudio de espacios periurbanos, caracterizados por su dinamismo, heterogeneidad y complejidad. En relación a los espacios residenciales que se desarrollan en estas áreas periféricas del Partido, fueron reconocidas tres tendencias diferenciadas: a) el proceso de urbanización cerrada, con tendencias al aislamiento de viviendas y complejos habitacionales, b) la "producción de periferia" relacionada con los sectores de población que no consiguen acceder al mercado formal de la tierra y la vivienda, asociada por lo general a modalidades de asentamiento espontáneo; y c) la ocupación gradual de baldíos urbanos con escasa o nula provisión de servicios y redes de infraestructura. En la presente Tesis se profundizará en las dos primeras de estas modalidades expansivas, indagándose en las lógicas de los distintos actores -sociales, políticos y económicos- que intervienen en el proceso urbano expansivo que hemos denominado "formal cerrado" e "informal abierto", respectivamente. La hipótesis que guía nuestro trabajo plantea que la expansión urbana en el Partido de La Plata trae aparejada una competencia por el territorio entre diferentes usos del suelo y actividades, con el consecuente incremento en los precios de la tierra, abandono de los sectores de bajos ingresos como habitantes originales y disminución del uso de tierra rural. Para dar respuesta a los objetivos e hipótesis planteados en nuestra Tesis, los criterios metodológicos adoptados parten de considerar al territorio como un sistema complejo. En este marco, el abordaje desde una visión sistémica y de la complejidad de nuestro objeto de estudio necesita de un abordaje dialéctico y de la convergencia metodológica para obtener distintos puntos de vista sobre el mismo. En el desarrollo de esta Tesis se han utilizado como herramientas de investigación: el método del estudio de caso, la construcción tipológica, la realización de entrevistas semiestructuradas y en profundidad, la utilización de modelos y la construcción de escenarios urbanos. Finalmente, producto de estos años de investigación en la temática, se arribó a las siguientes conclusiones, que han sido estructuradas en cinco apartados principales en función de su carácter predominantemente teórico, empírico, metodológico y/o propositivo, a saber: 1. el periurbano: ¿espacio de competencia o complementariedad?; 2. la construcción de tipologías como camino explicativo en materia de espacios periurbanos; 3. las lógicas residenciales periféricas: la "privatópolis" y la "precariópolis"; 4. las tendencias residenciales periféricas y los desafíos de la planificación urbana, y 5. nuevos interrogantes y perspectivas surgidos de esta Tesis.

Lógicas y tendencias de la expansión residencial en áreas periurbanas. El Partido de La Plata, Buenos Aires, Argentina, entre 1990 y 2010

Con el propósito de contribuir al conocimiento de las lógicas y tendencias de la expansión residencial en áreas periurbanas y su impronta en la organización futura de las ciudades medias, tendiente al logro de una relación armónica entre la actividad residencial y las otras actividades socioeconómicas que se presentan en dichas áreas, en la presente Tesis doctoral se aborda el estudio del proceso de expansión residencial que se han venido desarrollando en el espacio periurbano del Partido de La Plata desde principios de los años '90 hasta nuestros días. Para tal fin, se profundiza en el estudio de espacios periurbanos, caracterizados por su dinamismo, heterogeneidad y complejidad. En relación a los espacios residenciales que se desarrollan en estas áreas periféricas del Partido, fueron reconocidas tres tendencias diferenciadas: a) el proceso de urbanización cerrada, con tendencias al aislamiento de viviendas y complejos habitacionales, b) la "producción de periferia" relacionada con los sectores de población que no consiguen acceder al mercado formal de la tierra y la vivienda, asociada por lo general a modalidades de asentamiento espontáneo; y c) la ocupación gradual de baldíos urbanos con escasa o nula provisión de servicios y redes de infraestructura. En la presente Tesis se profundizará en las dos primeras de estas modalidades expansivas, indagándose en las lógicas de los distintos actores -sociales, políticos y económicos- que intervienen en el proceso urbano expansivo que hemos denominado "formal cerrado" e "informal abierto", respectivamente. La hipótesis que guía nuestro trabajo plantea que la expansión urbana en el Partido de La Plata trae aparejada una competencia por el territorio entre diferentes usos del suelo y actividades, con el consecuente incremento en los precios de la tierra, abandono de los sectores de bajos ingresos como habitantes originales y disminución del uso de tierra rural. Para dar respuesta a los objetivos e hipótesis planteados en nuestra Tesis, los criterios metodológicos adoptados parten de considerar al territorio como un sistema complejo. En este marco, el abordaje desde una visión sistémica y de la complejidad de nuestro objeto de estudio necesita de un abordaje dialéctico y de la convergencia metodológica para obtener distintos puntos de vista sobre el mismo. En el desarrollo de esta Tesis se han utilizado como herramientas de investigación: el método del estudio de caso, la construcción tipológica, la realización de entrevistas semiestructuradas y en profundidad, la utilización de modelos y la construcción de escenarios urbanos. Finalmente, producto de estos años de investigación en la temática, se arribó a las siguientes conclusiones, que han sido estructuradas en cinco apartados principales en función de su carácter predominantemente teórico, empírico, metodológico y/o propositivo, a saber: 1. el periurbano: ¿espacio de competencia o complementariedad?; 2. la construcción de tipologías como camino explicativo en materia de espacios periurbanos; 3. las lógicas residenciales periféricas: la "privatópolis" y la "precariópolis"; 4. las tendencias residenciales periféricas y los desafíos de la planificación urbana, y 5. nuevos interrogantes y perspectivas surgidos de esta Tesis.

Lógicas y tendencias de la expansión residencial en áreas periurbanas. El Partido de La Plata, Buenos Aires, Argentina, entre 1990 y 2010

Con el propósito de contribuir al conocimiento de las lógicas y tendencias de la expansión residencial en áreas periurbanas y su impronta en la organización futura de las ciudades medias, tendiente al logro de una relación armónica entre la actividad residencial y las otras actividades socioeconómicas que se presentan en dichas áreas, en la presente Tesis doctoral se aborda el estudio del proceso de expansión residencial que se han venido desarrollando en el espacio periurbano del Partido de La Plata desde principios de los años '90 hasta nuestros días. Para tal fin, se profundiza en el estudio de espacios periurbanos, caracterizados por su dinamismo, heterogeneidad y complejidad. En relación a los espacios residenciales que se desarrollan en estas áreas periféricas del Partido, fueron reconocidas tres tendencias diferenciadas: a) el proceso de urbanización cerrada, con tendencias al aislamiento de viviendas y complejos habitacionales, b) la "producción de periferia" relacionada con los sectores de población que no consiguen acceder al mercado formal de la tierra y la vivienda, asociada por lo general a modalidades de asentamiento espontáneo; y c) la ocupación gradual de baldíos urbanos con escasa o nula provisión de servicios y redes de infraestructura. En la presente Tesis se profundizará en las dos primeras de estas modalidades expansivas, indagándose en las lógicas de los distintos actores -sociales, políticos y económicos- que intervienen en el proceso urbano expansivo que hemos denominado "formal cerrado" e "informal abierto", respectivamente. La hipótesis que guía nuestro trabajo plantea que la expansión urbana en el Partido de La Plata trae aparejada una competencia por el territorio entre diferentes usos del suelo y actividades, con el consecuente incremento en los precios de la tierra, abandono de los sectores de bajos ingresos como habitantes originales y disminución del uso de tierra rural. Para dar respuesta a los objetivos e hipótesis planteados en nuestra Tesis, los criterios metodológicos adoptados parten de considerar al territorio como un sistema complejo. En este marco, el abordaje desde una visión sistémica y de la complejidad de nuestro objeto de estudio necesita de un abordaje dialéctico y de la convergencia metodológica para obtener distintos puntos de vista sobre el mismo. En el desarrollo de esta Tesis se han utilizado como herramientas de investigación: el método del estudio de caso, la construcción tipológica, la realización de entrevistas semiestructuradas y en profundidad, la utilización de modelos y la construcción de escenarios urbanos. Finalmente, producto de estos años de investigación en la temática, se arribó a las siguientes conclusiones, que han sido estructuradas en cinco apartados principales en función de su carácter predominantemente teórico, empírico, metodológico y/o propositivo, a saber: 1. el periurbano: ¿espacio de competencia o complementariedad?; 2. la construcción de tipologías como camino explicativo en materia de espacios periurbanos; 3. las lógicas residenciales periféricas: la "privatópolis" y la "precariópolis"; 4. las tendencias residenciales periféricas y los desafíos de la planificación urbana, y 5. nuevos interrogantes y perspectivas surgidos de esta Tesis.

Narwhal (Monodon monoceros) sightings and population estimates for the Canadian High Arctic 2002-2004

Aerial surveys of narwhals (Monodon monoceros) were conducted in the Canadian High Arctic during the month of August from 2002 to 2004. The surveys covered the waters of Barrow Strait, Prince Regent Inlet, the Gulf of Boothia, Admiralty Inlet, Eclipse Sound, and the eastern coast of Baffin Island, using systematic sampling methods. Fiords were flown along a single transect down the middle. Near-surface population estimates increased by 1.9%-8.7% when corrected for perception bias. The estimates were further increased by a factor of approximately 3, to account for individuals not seen because they were diving when the survey plane flew over (availability bias). These corrections resulted in estimates of 27 656 (SE = 14 939) for the Prince Regent and Gulf of Boothia area, 20 225 (SE = 7285) for the Eclipse Sound area, and 10 073 (SE = 3123) for the East Baffin Island fiord area. The estimate for the Admiralty Inlet area was 5362 (SE = 2681) but is thought to be biased. Surveys could not be done in other known areas of occupation, such as the waters of the Cumberland Peninsula of East Baffin, and channels farther west of the areas surveyed (Peel Sound, Viscount Melville Sound, Smith Sound and Jones Sound, and other channels of the Canadian Arctic archipelago). Despite these probable biases and the incomplete coverage, results of these surveys show that the summering range of narwhals in the Canadian High Arctic is vast. If narwhals are philopatric to their summering areas, as they appear to be, the total population of that range could number more than 60 000 animals. The largest numbers are in the western portion of their summer range, around Somerset Island, and also in the Eclipse Sound area. However, these survey estimates have large variances due to narwhal aggregation in some parts of the surveyed areas.

Nutrients and oxygen concentrations measured in water samples from the North Atlantic during the James Cook cruise JC087 in March 2013

Analysis for micro-molar concentrations of nitrate and nitrite, nitrite, phosphate, silicate and ammonia was undertaken on a SEAL Analytical UK Ltd, AA3 segmented flow autoanalyser following methods described by Kirkwood (1996). Samples were drawn from Niskin bottles on the CTD into 15ml polycarbonate centrifuge tubes and kept refrigerated at approximately 4oC until analysis, which generally commenced within 30 minutes. Overall 23 runs with 597 samples were analysed. This is a total of 502 CTD samples, 69 underway samples and 26 from other sources. An artificial seawater matrix (ASW) of 40g/litre sodium chloride was used as the inter-sample wash and standard matrix. The nutrient free status of this solution was checked by running Ocean Scientific International (OSI) low nutrient seawater (LNS) on every run. A single set of mixed standards were made up by diluting 5mM solutions made from weighed dried salts in 1litre of ASW into plastic 250ml volumetric flasks that had been cleaned by washing in MilliQ water (MQ). Data processing was undertaken using SEAL Analytical UK Ltd proprietary software (AACE 6.07) and was performed within a few hours of the run being finished. The sample time was 60 seconds and the wash time was 30 seconds. The lines were washed daily with wash solutions specific for each chemistry, but comprised of MQ, MQ and SDS, MQ and Triton-X, or MQ and Brij-35. Three times during the cruise the phosphate and silicate channels were washed with a weak sodium hypochlorite solution.

Medem Channel profiles based on stand-alone model simulation and corrections with nudging

State-of-the-art process-based models have shown to be applicable to the simulation and prediction of coastal morphodynamics. On annual to decadal temporal scales, these models may show limitations in reproducing complex natural morphological evolution patterns, such as the movement of bars and tidal channels, e.g. the observed decadal migration of the Medem Channel in the Elbe Estuary, German Bight. Here a morphodynamic model is shown to simulate the hydrodynamics and sediment budgets of the domain to some extent, but fails to adequately reproduce the pronounced channel migration, due to the insufficient implementation of bank erosion processes. In order to allow for long-term simulations of the domain, a nudging method has been introduced to update the model-predicted bathymetries with observations. The model-predicted bathymetry is nudged towards true states in annual time steps. Sensitivity analysis of a user-defined correlation length scale, for the definition of the background error covariance matrix during the nudging procedure, suggests that the optimal error correlation length is similar to the grid cell size, here 80-90 m. Additionally, spatially heterogeneous correlation lengths produce more realistic channel depths than do spatially homogeneous correlation lengths. Consecutive application of the nudging method compensates for the (stand-alone) model prediction errors and corrects the channel migration pattern, with a Brier skill score of 0.78. The proposed nudging method in this study serves as an analytical approach to update model predictions towards a predefined 'true' state for the spatiotemporal interpolation of incomplete morphological data in long-term simulations.

Response threshold models, stochastic learning automata and ant colony optimization-based decentralized self-coordination algorithms for heterogeneous multi-tasks distribution in multi-robot systems

In recent decades, there has been an increasing interest in systems comprised of several autonomous mobile robots, and as a result, there has been a substantial amount of development in the eld of Articial Intelligence, especially in Robotics. There are several studies in the literature by some researchers from the scientic community that focus on the creation of intelligent machines and devices capable to imitate the functions and movements of living beings. Multi-Robot Systems (MRS) can often deal with tasks that are dicult, if not impossible, to be accomplished by a single robot. In the context of MRS, one of the main challenges is the need to control, coordinate and synchronize the operation of multiple robots to perform a specic task. This requires the development of new strategies and methods which allow us to obtain the desired system behavior in a formal and concise way. This PhD thesis aims to study the coordination of multi-robot systems, in particular, addresses the problem of the distribution of heterogeneous multi-tasks. The main interest in these systems is to understand how from simple rules inspired by the division of labor in social insects, a group of robots can perform tasks in an organized and coordinated way. We are mainly interested on truly distributed or decentralized solutions in which the robots themselves, autonomously and in an individual manner, select a particular task so that all tasks are optimally distributed. In general, to perform the multi-tasks distribution among a team of robots, they have to synchronize their actions and exchange information. Under this approach we can speak of multi-tasks selection instead of multi-tasks assignment, which means, that the agents or robots select the tasks instead of being assigned a task by a central controller. The key element in these algorithms is the estimation ix of the stimuli and the adaptive update of the thresholds. This means that each robot performs this estimate locally depending on the load or the number of pending tasks to be performed. In addition, it is very interesting the evaluation of the results in function in each approach, comparing the results obtained by the introducing noise in the number of pending loads, with the purpose of simulate the robot's error in estimating the real number of pending tasks. The main contribution of this thesis can be found in the approach based on self-organization and division of labor in social insects. An experimental scenario for the coordination problem among multiple robots, the robustness of the approaches and the generation of dynamic tasks have been presented and discussed. The particular issues studied are: Threshold models: It presents the experiments conducted to test the response threshold model with the objective to analyze the system performance index, for the problem of the distribution of heterogeneous multitasks in multi-robot systems; also has been introduced additive noise in the number of pending loads and has been generated dynamic tasks over time. Learning automata methods: It describes the experiments to test the learning automata-based probabilistic algorithms. The approach was tested to evaluate the system performance index with additive noise and with dynamic tasks generation for the same problem of the distribution of heterogeneous multi-tasks in multi-robot systems. Ant colony optimization: The goal of the experiments presented is to test the ant colony optimization-based deterministic algorithms, to achieve the distribution of heterogeneous multi-tasks in multi-robot systems. In the experiments performed, the system performance index is evaluated by introducing additive noise and dynamic tasks generation over time.

Developmental Expression of Kv Potassium Channels at the Axon Initial Segment of Cultured Hippocampal Neurons

Axonal outgrowth and the formation of the axon initial segment (AIS) are early events in the acquisition of neuronal polarity. The AIS is characterized by a high concentration of voltage-dependent sodium and potassium channels. However, the specific ion channel subunits present and their precise localization in this axonal subdomain vary both during development and among the types of neurons, probably determining their firing characteristics in response to stimulation. Here, we characterize the developmental expression of different subfamilies of voltage-gated potassium channels in the AISs of cultured mouse hippocampal neurons, including subunits Kv1.2, Kv2.2 and Kv7.2. In contrast to the early appearance of voltage-gated sodium channels and the Kv7.2 subunit at the AIS, Kv1.2 and Kv2.2 subunits were tethered at the AIS only after 10 days in vitro. Interestingly, we observed different patterns of Kv1.2 and Kv2.2 subunit expression, with each confined to distinct neuronal populations. The accumulation of Kv1.2 and Kv2.2 subunits at the AIS was dependent on ankyrin G tethering, it was not affected by disruption of the actin cytoskeleton and it was resistant to detergent extraction, as described previously for other AIS proteins. This distribution of potassium channels in the AIS further emphasizes the heterogeneity of this structure in different neuronal populations, as proposed previously, and suggests corresponding differences in action potential regulation.

The city as a learning gamified platform

The area of mobile city guides has grown really fast in the last years based on new mobile capabilities. This growth has been fostered by the evolution of ubiquitous systems and the great penetration of smartphones in the society. In this paper we propose a generic model to support a new way of visiting the city: instead of as a place for tourism, we see it as a place for learning in which located educational resources are available for end users. The model has been conceived as a way to encourage them to create their own educational tours, in which Learning Points Of Interest are set up to be discovered. Two main use cases are supported by the model: formal (conducted by a teacher) and informal (no educator is related to the learning experience) outdoor mobile learning. Details about the impact of the conjunction of tourism, learning and gamification dimensions in the model design, as well as about the model itself are provided. Finally, a mobile application prototype developed in the context of the FI-CONTENT European project is presented as a proof of concept of the model.

Microfabrication processes for microfluidic devices on a single laser Workstation: direct writing lithography on SU-8, laser ablation on polymers and mask manufacturing

We demonstrate the capability of a laser micromachining workstation for cost-effective manufacturing of a variety of microfluidic devices, including SU-8 microchannels on silicon wafers and 3D complex structures made on polyimide Kapton® or poly carbonate (PC). The workstation combines a KrF excimer laser at 248 nm and a Nd3+:YVO4 DPSS with a frequency tripled at 355 nm with a lens magnification 10X, both lasers working at a pulsed regime with nanoseconds (ns) pulse duration. Workstation also includes a high-resolution motorized XYZ-tilt axis (~ 1 um / axis) and a Through The Lens (TTL) imaging system for a high accurate positioning over a 120 x 120 mm working area. We have surveyed different fabrication techniques: direct writing lithography,mask manufacturing for contact lithography and polymer laser ablation for complex 3D devices, achieving width channels down to 13μ m on 50μ m SU-8 thickness using direct writing lithography, and width channels of 40 μm for polyimide on SiO2 plate. Finally, we have tested the use of some devices for capillary chips measuring the flow speed for liquids with different viscosities. As a result, we have characterized the presence of liquid in the channel by interferometric microscopy.

Electronic and optical properties of substitutional V, Cr and Ir impurities in Cu2ZnSnS4

The substitution of cation atoms by V, Cr and It in the natural and synthetic quaternary Cu2ZnSnS4 semiconductor is analyzed using first-principles methods. In most of the substitutions, the electronic structure of these modified CZTS is characterized for intermediate bands with different occupation and position within of the energy band gap. A study of the symmetry and composition of these intermediate bands is carried out for all substitutions. These bands permit additional photon absorption and emission channels depending on their occupation. The optical properties are obtained and analyzed. The absorption coefficients are split into contributions from the different absorption channels and from the inter- and intra-atomic components. The sub bandgap transitions are significant in many cases because the anion states contribute to the valence, conduction and intermediates bands. These properties could therefore be used for novel optoelectronic devices.

Optimization of the Integrated Guidance and Control for a Dual Aerodynamic Control Missile

Las futuras misiones para misiles aire-aire operando dentro de la atmósfera requieren la interceptación de blancos a mayores velocidades y más maniobrables, incluyendo los esperados vehículos aéreos de combate no tripulados. La intercepción tiene que lograrse desde cualquier ángulo de lanzamiento. Una de las principales discusiones en la tecnología de misiles en la actualidad es cómo satisfacer estos nuevos requisitos incrementando la capacidad de maniobra del misil y en paralelo, a través de mejoras en los métodos de guiado y control modernos. Esta Tesis aborda estos dos objetivos simultáneamente, al proponer un diseño integrando el guiado y el control de vuelo (autopiloto) y aplicarlo a misiles con control aerodinámico simultáneo en canard y cola. Un primer avance de los resultados obtenidos ha sido publicado recientemente en el Journal of Aerospace Engineering, en Abril de 2015, [Ibarrondo y Sanz-Aranguez, 2015]. El valor del diseño integrado obtenido es que permite al misil cumplir con los requisitos operacionales mencionados empleando únicamente control aerodinámico. El diseño propuesto se compara favorablemente con esquemas más tradicionales, consiguiendo menores distancias de paso al blanco y necesitando de menores esfuerzos de control incluso en presencia de ruidos. En esta Tesis se demostrará cómo la introducción del doble mando, donde tanto el canard como las aletas de cola son móviles, puede mejorar las actuaciones de un misil existente. Comparado con un misil con control en cola, el doble control requiere sólo introducir dos servos adicionales para accionar los canards también en guiñada y cabeceo. La sección de cola será responsable de controlar el misil en balanceo mediante deflexiones diferenciales de los controles. En el caso del doble mando, la complicación añadida es que los vórtices desprendidos de los canards se propagan corriente abajo y pueden incidir sobre las superficies de cola, alterando sus características de control. Como un primer aporte, se ha desarrollado un modelo analítico completo para la aerodinámica no lineal de un misil con doble control, incluyendo la caracterización de este efecto de acoplamiento aerodinámico. Hay dos modos de funcionamiento en picado y guiñada para un misil de doble mando: ”desviación” y ”opuesto”. En modo ”desviación”, los controles actúan en la misma dirección, generando un cambio inmediato en la sustentación y produciendo un movimiento de translación en el misil. La respuesta es rápida, pero en el modo ”desviación” los misiles con doble control pueden tener dificultades para alcanzar grandes ángulos de ataque y altas aceleraciones laterales. Cuando los controles actúan en direcciones opuestas, el misil rota y el ángulo de ataque del fuselaje se incrementa para generar mayores aceleraciones en estado estacionario, aunque el tiempo de respuesta es mayor. Con el modelo aerodinámico completo, es posible obtener una parametrización dependiente de los estados de la dinámica de corto periodo del misil. Debido al efecto de acoplamiento entre los controles, la respuesta en bucle abierto no depende linealmente de los controles. El autopiloto se optimiza para obtener la maniobra requerida por la ley de guiado sin exceder ninguno de los límites aerodinámicos o mecánicos del misil. Una segunda contribución de la tesis es el desarrollo de un autopiloto con múltiples entradas de control y que integra la aerodinámica no lineal, controlando los tres canales de picado, guiñada y cabeceo de forma simultánea. Las ganancias del autopiloto dependen de los estados del misil y se calculan a cada paso de integración mediante la resolución de una ecuación de Riccati de orden 21x21. Las ganancias obtenidas son sub-óptimas, debido a que una solución completa de la ecuación de Hamilton-Jacobi-Bellman no puede obtenerse de manera práctica, y se asumen ciertas simplificaciones. Se incorpora asimismo un mecanismo que permite acelerar la respuesta en caso necesario. Como parte del autopiloto, se define una estrategia para repartir el esfuerzo de control entre el canard y la cola. Esto se consigue mediante un controlador aumentado situado antes del bucle de optimización, que minimiza el esfuerzo total de control para maniobrar. Esta ley de alimentación directa mantiene al misil cerca de sus condiciones de equilibrio, garantizando una respuesta transitoria adecuada. El controlador no lineal elimina la respuesta de fase no-mínima característica de la cola. En esta Tesis se consideran dos diseños para el guiado y control, el control en Doble-Lazo y el control Integrado. En la aproximación de Doble-Lazo, el autopiloto se sitúa dentro de un bucle interior y se diseña independientemente del guiado, que conforma el bucle más exterior del control. Esta estructura asume que existe separación espectral entre los dos, esto es, que los tiempos de respuesta del autopiloto son mucho mayores que los tiempos característicos del guiado. En el estudio se combina el autopiloto desarrollado con una ley de guiado óptimo. Los resultados obtenidos demuestran que se consiguen aumentos muy importantes en las actuaciones frente a misiles con control canard o control en cola, y que la interceptación, cuando se lanza cerca del curso de colisión, se consigue desde cualquier ángulo alrededor del blanco. Para el misil de doble mando, la estrategia óptima resulta en utilizar el modo de control opuesto en la aproximación al blanco y utilizar el modo de desviación justo antes del impacto. Sin embargo la lógica de doble bucle no consigue el impacto cuando hay desviaciones importantes con respecto al curso de colisión. Una de las razones es que parte de la demanda de guiado se pierde, ya que el misil solo es capaz de modificar su aceleración lateral, y no tiene control sobre su aceleración axial, a no ser que incorpore un motor de empuje regulable. La hipótesis de separación mencionada, y que constituye la base del Doble-Bucle, puede no ser aplicable cuando la dinámica del misil es muy alta en las proximidades del blanco. Si se combinan el guiado y el autopiloto en un único bucle, la información de los estados del misil está disponible para el cálculo de la ley de guiado, y puede calcularse la estrategia optima de guiado considerando las capacidades y la actitud del misil. Una tercera contribución de la Tesis es la resolución de este segundo diseño, la integración no lineal del guiado y del autopiloto (IGA) para el misil de doble control. Aproximaciones anteriores en la literatura han planteado este sistema en ejes cuerpo, resultando en un sistema muy inestable debido al bajo amortiguamiento del misil en cabeceo y guiñada. Las simplificaciones que se tomaron también causan que el misil se deslice alrededor del blanco y no consiga la intercepción. En nuestra aproximación el problema se plantea en ejes inerciales y se recurre a la dinámica de los cuaterniones, eliminado estos inconvenientes. No se limita a la dinámica de corto periodo del misil, porque se construye incluyendo de modo explícito la velocidad dentro del bucle de optimización. La formulación resultante en el IGA es independiente de la maniobra del blanco, que sin embargo se ha de incluir en el cálculo del modelo en Doble-bucle. Un típico inconveniente de los sistemas integrados con controlador proporcional, es el problema de las escalas. Los errores de guiado dominan sobre los errores de posición del misil y saturan el controlador, provocando la pérdida del misil. Este problema se ha tratado aquí con un controlador aumentado previo al bucle de optimización, que define un estado de equilibrio local para el sistema integrado, que pasa a actuar como un regulador. Los criterios de actuaciones para el IGA son los mismos que para el sistema de Doble-Bucle. Sin embargo el problema matemático resultante es muy complejo. El problema óptimo para tiempo finito resulta en una ecuación diferencial de Riccati con condiciones terminales, que no puede resolverse. Mediante un cambio de variable y la introducción de una matriz de transición, este problema se transforma en una ecuación diferencial de Lyapunov que puede resolverse mediante métodos numéricos. La solución resultante solo es aplicable en un entorno cercano del blanco. Cuando la distancia entre misil y blanco es mayor, se desarrolla una solución aproximada basada en la solución de una ecuación algebraica de Riccati para cada paso de integración. Los resultados que se han obtenido demuestran, a través de análisis numéricos en distintos escenarios, que la solución integrada es mejor que el sistema de Doble-Bucle. Las trayectorias resultantes son muy distintas. El IGA preserva el guiado del misil y consigue maximizar el uso de la propulsión, consiguiendo la interceptación del blanco en menores tiempos de vuelo. El sistema es capaz de lograr el impacto donde el Doble-Bucle falla, y además requiere un orden menos de magnitud en la cantidad de cálculos necesarios. El efecto de los ruidos radar, datos discretos y errores del radomo se investigan. El IGA es más robusto, resultando menos afectado por perturbaciones que el Doble- Bucle, especialmente porque el núcleo de optimización en el IGA es independiente de la maniobra del blanco. La estimación de la maniobra del blanco es siempre imprecisa y contaminada por ruido, y degrada la precisión de la solución de Doble-Bucle. Finalmente, como una cuarta contribución, se demuestra que el misil con guiado IGA es capaz de realizar una maniobra de defensa contra un blanco que ataque por su cola, sólo con control aerodinámico. Las trayectorias estudiadas consideran una fase pre-programada de alta velocidad de giro, manteniendo siempre el misil dentro de su envuelta de vuelo. Este procedimiento no necesita recurrir a soluciones técnicamente más complejas como el control vectorial del empuje o control por chorro para ejecutar esta maniobra. En todas las demostraciones matemáticas se utiliza el producto de Kronecker como una herramienta practica para manejar las parametrizaciones dependientes de variables, que resultan en matrices de grandes dimensiones. ABSTRACT Future missions for air to air endo-atmospheric missiles require the interception of targets with higher speeds and more maneuverable, including forthcoming unmanned supersonic combat vehicles. The interception will need to be achieved from any angle and off-boresight launch conditions. One of the most significant discussions in missile technology today is how to satisfy these new operational requirements by increasing missile maneuvering capabilities and in parallel, through the development of more advanced guidance and control methods. This Thesis addresses these two objectives by proposing a novel optimal integrated guidance and autopilot design scheme, applicable to more maneuverable missiles with forward and rearward aerodynamic controls. A first insight of these results have been recently published in the Journal of Aerospace Engineering in April 2015, [Ibarrondo and Sanz-Aránguez, 2015]. The value of this integrated solution is that it allows the missile to comply with the aforementioned requirements only by applying aerodynamic control. The proposed design is compared against more traditional guidance and control approaches with positive results, achieving reduced control efforts and lower miss distances with the integrated logic even in the presence of noises. In this Thesis it will be demonstrated how the dual control missile, where canard and tail fins are both movable, can enhance the capabilities of an existing missile airframe. Compared to a tail missile, dual control only requires two additional servos to actuate the canards in pitch and yaw. The tail section will be responsible to maintain the missile stabilized in roll, like in a classic tail missile. The additional complexity is that the vortices shed from the canard propagate downstream where they interact with the tail surfaces, altering the tail expected control characteristics. These aerodynamic phenomena must be properly described, as a preliminary step, with high enough precision for advanced guidance and control studies. As a first contribution we have developed a full analytical model of the nonlinear aerodynamics of a missile with dual control, including the characterization of this cross-control coupling effect. This development has been produced from a theoretical model validated with reliable practical data obtained from wind tunnel experiments available in the scientific literature, complement with computer fluid dynamics and semi-experimental methods. There are two modes of operating a missile with forward and rear controls, ”divert” and ”opposite” modes. In divert mode, controls are deflected in the same direction, generating an increment in direct lift and missile translation. Response is fast, but in this mode, dual control missiles may have difficulties in achieving large angles of attack and high level of lateral accelerations. When controls are deflected in opposite directions (opposite mode) the missile airframe rotates and the body angle of attack is increased to generate greater accelerations in steady-state, although the response time is larger. With the aero-model, a state dependent parametrization of the dual control missile short term dynamics can be obtained. Due to the cross-coupling effect, the open loop dynamics for the dual control missile is not linearly dependent of the fin positions. The short term missile dynamics are blended with the servo system to obtain an extended autopilot model, where the response is linear with the control fins turning rates, that will be the control variables. The flight control loop is optimized to achieve the maneuver required by the guidance law without exceeding any of the missile aerodynamic or mechanical limitations. The specific aero-limitations and relevant performance indicators for the dual control are set as part of the analysis. A second contribution of this Thesis is the development of a step-tracking multi-input autopilot that integrates non-linear aerodynamics. The designed dual control missile autopilot is a full three dimensional autopilot, where roll, pitch and yaw are integrated, calculating command inputs simultaneously. The autopilot control gains are state dependent, and calculated at each integration step solving a matrix Riccati equation of order 21x21. The resulting gains are sub-optimal as a full solution for the Hamilton-Jacobi-Bellman equation cannot be resolved in practical terms and some simplifications are taken. Acceleration mechanisms with an λ-shift is incorporated in the design. As part of the autopilot, a strategy is defined for proper allocation of control effort between canard and tail channels. This is achieved with an augmented feed forward controller that minimizes the total control effort of the missile to maneuver. The feedforward law also maintains the missile near trim conditions, obtaining a well manner response of the missile. The nonlinear controller proves to eliminate the non-minimum phase effect of the tail. Two guidance and control designs have been considered in this Thesis: the Two- Loop and the Integrated approaches. In the Two-Loop approach, the autopilot is placed in an inner loop and designed separately from an outer guidance loop. This structure assumes that spectral separation holds, meaning that the autopilot response times are much higher than the guidance command updates. The developed nonlinear autopilot is linked in the study to an optimal guidance law. Simulations are carried on launching close to collision course against supersonic and highly maneuver targets. Results demonstrate a large boost in performance provided by the dual control versus more traditional canard and tail missiles, where interception with the dual control close to collision course is achieved form 365deg all around the target. It is shown that for the dual control missile the optimal flight strategy results in using opposite control in its approach to target and quick corrections with divert just before impact. However the Two-Loop logic fails to achieve target interception when there are large deviations initially from collision course. One of the reasons is that part of the guidance command is not followed, because the missile is not able to control its axial acceleration without a throttleable engine. Also the separation hypothesis may not be applicable for a high dynamic vehicle like a dual control missile approaching a maneuvering target. If the guidance and autopilot are combined into a single loop, the guidance law will have information of the missile states and could calculate the most optimal approach to the target considering the actual capabilities and attitude of the missile. A third contribution of this Thesis is the resolution of the mentioned second design, the non-linear integrated guidance and autopilot (IGA) problem for the dual control missile. Previous approaches in the literature have posed the problem in body axes, resulting in high unstable behavior due to the low damping of the missile, and have also caused the missile to slide around the target and not actually hitting it. The IGA system is posed here in inertial axes and quaternion dynamics, eliminating these inconveniences. It is not restricted to the missile short term dynamic, and we have explicitly included the missile speed as a state variable. The IGA formulation is also independent of the target maneuver model that is explicitly included in the Two-loop optimal guidance law model. A typical problem of the integrated systems with a proportional control law is the problem of scales. The guidance errors are larger than missile state errors during most of the flight and result in high gains, control saturation and loss of control. It has been addressed here with an integrated feedforward controller that defines a local equilibrium state at each flight point and the controller acts as a regulator to minimize the IGA states excursions versus the defined feedforward state. The performance criteria for the IGA are the same as in the Two-Loop case. However the resulting optimization problem is mathematically very complex. The optimal problem in a finite-time horizon results in an irresoluble state dependent differential Riccati equation with terminal conditions. With a change of variable and the introduction of a transition matrix, the equation is transformed into a time differential Lyapunov equation that can be solved with known numerical methods in real time. This solution results range limited, and applicable when the missile is in a close neighborhood of the target. For larger ranges, an approximate solution is used, obtained from solution of an algebraic matrix Riccati equation at each integration step. The results obtained show, by mean of several comparative numerical tests in diverse homing scenarios, than the integrated approach is a better solution that the Two- Loop scheme. Trajectories obtained are very different in the two cases. The IGA fully preserves the guidance command and it is able to maximize the utilization of the missile propulsion system, achieving interception with lower miss distances and in lower flight times. The IGA can achieve interception against off-boresight targets where the Two- Loop was not able to success. As an additional advantage, the IGA also requires one order of magnitude less calculations than the Two-Loop solution. The effects of radar noises, discrete radar data and radome errors are investigated. IGA solution is robust, and less affected by radar than the Two-Loop, especially because the target maneuvers are not part of the IGA core optimization loop. Estimation of target acceleration is always imprecise and noisy and degrade the performance of the two-Loop solution. The IGA trajectories are such that minimize the impact of radome errors in the guidance loop. Finally, as a fourth contribution, it is demonstrated that the missile with IGA guidance is capable of performing a defense against attacks from its rear hemisphere, as a tail attack, only with aerodynamic control. The studied trajectories have a preprogrammed high rate turn maneuver, maintaining the missile within its controllable envelope. This solution does not recur to more complex features in service today, like vector control of the missile thrust or side thrusters. In all the mathematical treatments and demonstrations, the Kronecker product has been introduced as a practical tool to handle the state dependent parametrizations that have resulted in very high order matrix equations.