945 resultados para second-order planning
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A fourth-order numerical method for solving the Navier-Stokes equations in streamfunction/vorticity formulation on a two-dimensional non-uniform orthogonal grid has been tested on the fluid flow in a constricted symmetric channel. The family of grids is generated algebraically using a conformal transformation followed by a non-uniform stretching of the mesh cells in which the shape of the channel boundary can vary from a smooth constriction to one which one possesses a very sharp but smooth corner. The generality of the grids allows the use of long channels upstream and downstream as well as having a refined grid near the sharp corner. Derivatives in the governing equations are replaced by fourth-order central differences and the vorticity is eliminated, either before or after the discretization, to form a wide difference molecule for the streamfunction. Extra boundary conditions, necessary for wide-molecule methods, are supplied by a procedure proposed by Henshaw et al. The ensuing set of non-linear equations is solved using Newton iteration. Results have been obtained for Reynolds numbers up to 250 for three constrictions, the first being smooth, the second having a moderately sharp corner and the third with a very sharp corner. Estimates of the error incurred show that the results are very accurate and substantially better than those of the corresponding second-order method. The observed order of the method has been shown to be close to four, demonstrating that the method is genuinely fourth-order. © 1977 John Wiley & Sons, Ltd.
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In this work we study a Hořava-like 5-dimensional model in the context of braneworld theory. The equations of motion of such model are obtained and, within the realm of warped geometry, we show that the model is consistent if and only if λ takes its relativistic value 1. Furthermore, we show that the elimination of problematic terms involving the warp factor second order derivatives are eliminated by imposing detailed balance condition in the bulk. Afterwards, Israel's junction conditions are computed, allowing the attainment of an effective Lagrangian in the visible brane. In particular, we show that the resultant effective Lagrangian in the brane corresponds to a (3 + 1)-dimensional Hořava-like model with an emergent positive cosmological constant but without detailed balance condition. Now, restoration of detailed balance condition, at this time imposed over the brane, plays an interesting role by fitting accordingly the sign of the arbitrary constant β, insuring a positive brane tension and a real energy for the graviton within its dispersion relation. Also, the brane consistency equations are obtained and, as a result, the model admits positive brane tensions in the compactification scheme if, and only if, β is negative and the detailed balance condition is imposed. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.
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Pós-graduação em Agronomia (Ciência do Solo) - FCAV
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Pós-graduação em Agronomia (Produção Vegetal) - FCAV
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Pós-graduação em Educação - FFC
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Relativistic effects need to be considered in quantum-chemical calculations on systems including heavy elements or when aiming at high accuracy for molecules containing only lighter elements. In the latter case, consideration of relativistic effects via perturbation theory is an attractive option. Among the available techniques, Direct Perturbation Theory (DPT) in its lowest order (DPT2) has become a standard tool for the calculation of relativistic corrections to energies and properties.In this work, the DPT treatment is extended to the next order (DPT4). It is demonstrated that the DPT4 correction can be obtained as a second derivative of the energy with respect to the relativistic perturbation parameter. Accordingly, differentiation of a suitable Lagrangian, thereby taking into account all constraints on the wave function, provides analytic expressions for the fourth-order energy corrections. The latter have been implemented at the Hartree-Fock level and within second-order Møller-Plesset perturbaton theory using standard analytic second-derivative techniques into the CFOUR program package. For closed-shell systems, the DPT4 corrections consist of higher-order scalar-relativistic effects as well as spin-orbit corrections with the latter appearing here for the first time in the DPT series.Relativistic corrections are reported for energies as well as for first-order electrical properties and compared to results from rigorous four-component benchmark calculations in order to judge the accuracy and convergence of the DPT expansion for both the scalar-relativistic as well as the spin-orbit contributions. Additionally, the importance of relativistic effects to the bromine and iodine quadrupole-coupling tensors is investigated in a joint experimental and theoretical study concerning the rotational spectra of CH2BrF, CHBrF2, and CH2FI.
On degeneracy and invariances of random fields paths with applications in Gaussian process modelling
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We study pathwise invariances and degeneracies of random fields with motivating applications in Gaussian process modelling. The key idea is that a number of structural properties one may wish to impose a priori on functions boil down to degeneracy properties under well-chosen linear operators. We first show in a second order set-up that almost sure degeneracy of random field paths under some class of linear operators defined in terms of signed measures can be controlled through the two first moments. A special focus is then put on the Gaussian case, where these results are revisited and extended to further linear operators thanks to state-of-the-art representations. Several degeneracy properties are tackled, including random fields with symmetric paths, centred paths, harmonic paths, or sparse paths. The proposed approach delivers a number of promising results and perspectives in Gaussian process modelling. In a first numerical experiment, it is shown that dedicated kernels can be used to infer an axis of symmetry. Our second numerical experiment deals with conditional simulations of a solution to the heat equation, and it is found that adapted kernels notably enable improved predictions of non-linear functionals of the field such as its maximum.
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A three-level satellite to ground monitoring scheme for conservation easement monitoring has been implemented in which high-resolution imagery serves as an intermediate step for inspecting high priority sites. A digital vertical aerial camera system was developed to fulfill the need for an economical source of imagery for this intermediate step. A method for attaching the camera system to small aircraft was designed, and the camera system was calibrated and tested. To ensure that the images obtained were of suitable quality for use in Level 2 inspections, rectified imagery was required to provide positional accuracy of 5 meters or less to be comparable to current commercially available high-resolution satellite imagery. Focal length calibration was performed to discover the infinity focal length at two lens settings (24mm and 35mm) with a precision of O.1mm. Known focal length is required for creation of navigation points representing locations to be photographed (waypoints). Photographing an object of known size at distances on a test range allowed estimates of focal lengths of 25.lmm and 35.4mm for the 24mm and 35mm lens settings, respectively. Constants required for distortion removal procedures were obtained using analytical plumb-line calibration procedures for both lens settings, with mild distortion at the 24mm setting and virtually no distortion found at the 35mm setting. The system was designed to operate in a series of stages: mission planning, mission execution, and post-mission processing. During mission planning, waypoints were created using custom tools in geographic information system (GIs) software. During mission execution, the camera is connected to a laptop computer with a global positioning system (GPS) receiver attached. Customized mobile GIs software accepts position information from the GPS receiver, provides information for navigation, and automatically triggers the camera upon reaching the desired location. Post-mission processing (rectification) of imagery for removal of lens distortion effects, correction of imagery for horizontal displacement due to terrain variations (relief displacement), and relating the images to ground coordinates were performed with no more than a second-order polynomial warping function. Accuracy testing was performed to verify the positional accuracy capabilities of the system in an ideal-case scenario as well as a real-world case. Using many welldistributed and highly accurate control points on flat terrain, the rectified images yielded median positional accuracy of 0.3 meters. Imagery captured over commercial forestland with varying terrain in eastern Maine, rectified to digital orthophoto quadrangles, yielded median positional accuracies of 2.3 meters with accuracies of 3.1 meters or better in 75 percent of measurements made. These accuracies were well within performance requirements. The images from the digital camera system are of high quality, displaying significant detail at common flying heights. At common flying heights the ground resolution of the camera system ranges between 0.07 meters and 0.67 meters per pixel, satisfying the requirement that imagery be of comparable resolution to current highresolution satellite imagery. Due to the high resolution of the imagery, the positional accuracy attainable, and the convenience with which it is operated, the digital aerial camera system developed is a potentially cost-effective solution for use in the intermediate step of a satellite to ground conservation easement monitoring scheme.
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No tenemos conocimiento de ninguna red de caminos prerromanos que sirvieran como base de una posible malla territorial de España. Sin embargo, una sociedad prerromana sin caminos, por muy fragmentada y aislada que fuera, es algo improbable y mucho menos en la Edad del Hierro. Por eso en época prerromana existían infinidad de caminos, muchos de los cuales hoy han desaparecido y otros han sobrevivido, casi siempre con sus recorridos mejorados. Los pueblos prerromanos aprovecharon vías naturales de comunicación (ríos, vados, valles, puertos naturales, llanuras, etc.) para tender sus caminos. En sus orígenes no siguieron pautas concretas, si no que los caminos se originaban por el tránsito (de personas, ganados, mercancías, etc.) de un lugar a otro. De este modo la red viaria prerromana era caótica y anárquica: todo camino tenía numerosos ramales y variantes, según las necesidades. Pendientes excesivas, anchuras variables, etc., en decir eran vías espontáneas, surgidas sin ninguna planificación aparente. Los recorridos en general eran cortos, aunque algunas investigaciones actuales están demostrando que algunas de las cañadas ganaderas más importantes, como la Galiana, y de largo recorrido, eran de origen prerromano. En el caso de la península Ibérica, y más concretamente en el caso de la Meseta, el territorio estaba fragmentado en diversos pueblos y tribus, agrupados según criterios étnicos y culturales y con contactos con los pueblos próximos que motivan la preponderancia de caminos de recorrido cortos. Solo la necesidad de llevar los rebaños (de cabras y ovejas sobre todo) desde las serranías en verano a las llanuras en invierno, motivaría viajes más largos en los que algunas cañadas ganaderas jugarían un papel más importante. Con la llegada de los romanaos, se implantó en Hispania una densa red viaria, cuya construcción se prolongó durante toda la dominación romana, siendo reparadas muchas calzadas y vías en varias ocasiones. En época romana la red caminera era variada y estaba constituida por “las calzadas” que comunicaban puntos importantes, eran muy transitadas, de ahí que la administración romana las mantuviera siempre en buen estado, para asegurar el intercambio comercial entre zonas distintas, cobro de impuestos, etc. “Los caminos de tierra (viae terrenae)” que además de las calzadas, que podemos asemejar a las actuales carreteras de primer y segundo orden, constituían la infinidad de caminos locales y comarcales. Los trazados se realizaron unos en época romana, y otros muchos apoyándose en los caminos de la época prerromana, éstas vías no se realizaban buscando el recorrido más corto entre dos puntos, ni tampoco el más cómodo y con un firme estructural de menor importancia que en las calzadas. Tampoco estaban hechos para un tipo concreto de transporte, por lo que nos encontraríamos algunos que por su anchura permitían el paso de carros, y otros que sólo permitirían el paso a pie, a caballo o en burro. Solían ser, como hemos indicado, caminos de tierra con acabados en zahorras y recorridos en su mayor parte cortos y medianos. Dentro de la malla territorial de España las calzadas constituirían las denominadas “viae publicae” que constituían la red principal y esqueleto vertebrador de Hispania. Los caminos de tierra constituirían los denominados “actus” caminos de carácter regional que configuraban la mayor parte de la red. Muchas de las “viae publicae” y de los “actus” tendrían su origen en las “viae militares” que habrían sido los primeros construidos, apoyándose en muchas ocasiones en los caminos prerromanos, por los romanos para realizar la conquista de Hispania y que luego con la Paz romana habrían tenido otro tipo de uso. Dentro de estas “viae militares” tuvieron una importancia relevancia aquellas que se utilizaron en la conquista de la Celtiberia, culminada con la caída de Numantia. Dentro de ellas tuvo una importancia fundamental la vía romana del río Alhama, objeto de esta Tesis, que facilitaría el desplazamiento de los ejércitos romanos desde Graccurris, primera ciudad romana fundada en el Ebro medio, hasta Numantia. Desde la época Augusta, la vía romana del río Alhama, pasaría a formar parte de los denominados “actus” formando parte de la malla territorial de la Península Ibérica como vía de comunicación entre la Meseta y el Ebro Medio. We do not have knowledge of any network of ways prerromanos that were serving as base of a possible territorial mesh of Spain. Nevertheless, a company prerromana without ways, for very fragmented and isolated that was, is something improbable and great less in the Age of the Iron. Because of it in epoch prerromana existed infinity of ways, many of which today have disappeared and others have survived, almost always with his improved tours. The people prerromanos took advantage of natural routes of communication (rivers, fords, valleys, natural ports, plains, etc.) to stretch his ways. In his origins concrete guidelines did not continue, if not that the ways were originating for the traffic (of persons, cattle, goods, etc.) to and from. Thus the network viaria prerromana was chaotic and anarchic: all way had numerous branches and variants, according to the needs. Excessive slopes, variable widths, etc., in saying were spontaneous routes arisen without no apparent planning. The tours in general were short, though some current investigations are demonstrating that some of the most important cattle glens, as the Galiana, and of crossed length, were of origin prerromano. In case of the Iberian Peninsula, and more concretely in case of the Plateau, the territory was fragmented in diverse peoples and tribes, grouped according to ethnic and cultural criteria and with contacts with the near peoples that motivate the prevalence of short ways of tour. Only the need to take the flocks (of goats and sheeps especially) from the mountainous countries in summer to the plains in winter, would motivate longer trips in which some cattle glens would play a more important paper. With the arrival of the romanos, a dense network was implanted in Roman Spain viaria, whose construction extended during the whole Roman domination, being repaired many causeways and routes in several occasions. In Roman epoch the pertaining to roads network was changed and constituted by " the causeways " that were communicating important points, they were very travelled, of there that the Roman administration was supporting always in good condition, to assure the commercial exchange between different zones, collection of taxes, etc. "The dirt tracks (viae terrenae)" that besides the causeways, which we can make alike to the current roads of the first and second order, were constituting the infinity of local and regional ways. The tracings were realized some in Roman epoch, and great others resting on the ways of the epoch prerromana, these routes were not realized looking for the most short tour neither between points, two nor neither most comfortable and with a structural road surface of minor importance that in the causeways. They were not also done for a concrete type of transport, for what some of us would think that for his width they were allowing the step of cars, and others that only would allow the step afoot, astride or in donkey. They were in the habit of being, since we have indicated, dirt tracks with ended in zahorras and tours in his most short and medium. Inside the territorial mesh of Spain the causeways would constitute the called ones "viae publicae" that constituted the principal network and skeleton vertebrador of Roman Spain. The dirt tracks would constitute the "actus” called ways of regional character that were forming most of the network. Many of "viae publicae" and of the "actus" they would have his origin in " viae military" that would have been the first ones constructed, resting on many occasions on the ways prerromanos, for the Romans to realize the conquest of Roman Spain and that then with the Roman Peace they would have had another type of use. Inside these "viae military" had an importance relevancy those that were in use in the conquest of the Celtiberia, reached with Numantia's fall. Inside them a fundamental importance had the Roman route of the river Alhama, object of this Thesis, which would facilitate the displacement of the Roman armies from Graccurris, the first Roman city been founded on the average Ebro, up to Numantia. From the August epoch, the Roman route of the river Alhama, would happen to form a part of the "actus” forming a part of the territorial mesh of the Iberian Peninsula as road link between the Plateau and the Average Ebro.
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La presente investigación tiene como objetivo el desarrollo de una metodología que favorezca la innovación en las empresas a través de la actividad directiva, analizando a su vez, su influencia a nivel macro, en los sistemas de innovación, en las políticas de innovación y en el capital intelectual y a nivel micro, en la innovación, en el desempeño y en el clima organizacional. Se estima importante realizar un estudio sobre este tema debido a que la innovación se considera un pilar crítico para el desarrollo social a través de la competitividad de las empresas, así como, una fuente importante de ventaja competitiva. Existe abundante literatura sobre la influencia de la innovación en la gestión empresarial y el papel que el liderazgo desempeña en términos generales. Sin embargo, la literatura presenta diversos estilos de liderazgo sin mostrar una línea consistente de interrelación entre ellos, por lo que finalmente no existe una relación sólida entre el liderazgo, la gestión empresarial y la innovación. Este hecho se debe, como se muestra en la tesis, a que la literatura analiza las organizaciones y el liderazgo desde una perspectiva sociológica u organizacional, y otra desde la perspectiva psicológica sin aportar una línea de articulación entre ambas. Es decir, la literatura analiza el comportamiento organizacional pero no su causa. A lo largo de la tesis se van desarrollando diferentes líneas de trabajo que se convierten en aportaciones empíricas y académicas. Así, una de las aportaciones de la tesis es la sustitución de la figura del líder como persona, por la de un directivo con una doble función; por un lado, la función de liderazgo cuyo objetivo es generar cambio y por el otro, la función de gestionar el día a día o desempeño. Sustituir la figura del líder por una doble funcionalidad directiva facilita la comprensión del concepto liderazgo, lo que permite a su vez, establecer estrategias para su desarrollo, haciendo una realidad el que el liderazgo puede ser aprendido. Este resultado constituye la primera aportación de la tesis. Así mismo, a través de un exhaustivo análisis de la literatura, se desarrolla una propuesta de liderazgo integrado de acuerdo con el modelo Stuart-Kotze, el cual se describe también ampliamente. Encontrar un modelo único de liderazgo supone la piedra angular para el desarrollo de la metodología. Esta propuesta de liderazgo integrado da lugar a la segunda aportación de la tesis. Del mismo modo, se realiza un estudio en profundidad de la perspectiva psicológica de las organizaciones desarrollando el constructo Miedo al Error (ME) que resulta ser un rasgo de la personalidad existente en todos los seres humanos y que presenta una influencia negativa tanto en el desempeño, como en la innovación empresarial. Este resultado permite identificar cuales son las verdaderas barreras para el ejercicio del liderazgo, señalando que la disminución del ME debe ser considerada como una competencia de la Inteligencia Emocional a ser desarrollada por los directivos. Este resultado constituye la tercera aportación de la tesis. Una vez desarrollado el modelo de gestión empresarial expuesto, se procede a su validación, analizando la relación entre los constructos que definen el modelo de gestión: el desempeño, la innovación y el ME. Para identificar las influencias o relaciones de causalidad que subyacen entre los constructos, se utilizó la técnica del modelo de ecuaciones estructurales (SEM). La población objeto de estudio estuvo constituida por 350 profesionales con responsabilidad directiva, procedentes de empresas del sector servicios repartidas por toda la geografía española. Como fuente primaria de recolección de información se utilizó el cuestionario desarrollado por Stuart-Kotze M-CPI (Momentum Continuous Performance Improvement). En primer lugar se procedió a evaluar las propiedades psicométricas del modelo de medida, llevándose a cabo un análisis factorial exploratorio (AFE) y un análisis factorial confirmatorio (AFC) de segundo orden. Los resultados obtenidos ponen de manifiesto que el constructo desempeño (D) viene determinado por dos dimensiones, (DOP), desempeño orientado hacia la planificación y (DORT), desempeño orientado hacia la realización de la tarea. Es decir, la muestra de directivos no percibe que la planificación en el día a día y la realización de la tarea estén articuladas. Posteriormente se procede a realizar el contraste del modelo a través del método de ecuaciones estructurales. Los resultados muestran que la relación de influencia de la dimensión DOP no es significativa, por lo que el constructo D queda representado únicamente por la dimensión DORT. Los resultados de la investigación proporcionan conclusiones e hipótesis para futuras investigaciones. Si bien la muestra de directivos realiza un plan estratégico, éste no se tiene en cuenta en el día a día. Este hecho podría explicar el alto grado de administración por crisis tan frecuente en la empresa española. A su vez, el ME presenta una influencia negativa en la innovación, lo que concuerda con la literatura. Al respecto, considerar el ME como un rasgo de la personalidad, presente tanto en directivos como en colaboradores, facilita la comprensión de las barreras de la organización hacia la comunicación abierta a la vez, que una dirección de trabajo para la mejora de la capacidad innovadora de la organización. Por último, los resultados establecen la existencia de una relación causal entre el desempeño diario y la innovación. Con respecto a este segundo resultado y analizando los comportamientos que identifican el constructo D surgen también varias conclusiones e hipótesis para futuras investigaciones. Los resultados ponen de manifiesto que la muestra de directivos genera iniciativas de cambio con la finalidad de que el trabajo diario salga adelante según los estándares de calidad definidos. Sin embargo, estas iniciativas sólo proceden de los directivos, sin participación alguna de los colaboradores, los cuales son sólo responsables de la implementación produciéndose la consiguiente desmotivación y pérdida de oportunidades. Esta conclusión pone de manifiesto que la innovación de las empresas de la muestra sucede para garantizar la eficiencia de los procesos existentes, pero en ningún caso surge de la iniciativa de buscar una mejor eficacia empresarial. Este hecho plantea un origen doble de la innovación en los procesos. La innovación proactiva que buscaría la mejora de la eficacia de la organización y una innovación de carácter reactiva que buscaría la salvaguarda de la eficiencia. Quizás sea esta la causa del gap existente entre la innovación en España y la innovación de los países que ocupan los primeros puestos en el ranking de producción de innovación lo que constituye un importante punto de partida para una investigación futura. ABSTRACT This research aims to develop a methodology that supports innovation in companies through the managers’ activity, analysing in turn its influence at the macro level: innovation systems, innovation policies and Intellectual capital and at the micro level: innovation itself, performance and organizational climate. It is considered important to conduct a study on this subject due to the fact that innovation is considered a critical pillar for the development and future of the enterprise and an important source of competitive advantage. There is abundant literature about the influence of innovation in business management and the role that leadership plays in general terms. However, the literature presents various styles of leadership without showing a consistent relationship among them, so finally there is not a strong relationship among leadership, business management and innovation. As shown in the thesis, this is due to the fact that the literature analyses organizations and leadership from a sociological or organizational perspective and from a psychological perspective, without providing a hinge line between the two. That is, the existing literature discusses organizational behaviour but not its cause. Throughout the thesis, different lines of work that become empirical and academic contributions have been developed. Thus, one of the contributions of the thesis is replacing the figure of the leader as a person, by a manager with a dual function. Firstly, we have the leadership role which aims to generate change and, on the other hand, the function to manage the day-to-day task or performance. Replacing the figure of the leader by a dual managerial functionality facilitates the understanding of the leadership concept, allowing in turn, to establish development strategies and making true that leadership can be learned. This outcome is the first contribution of the thesis. Likewise, through a comprehensive literature review, an integrated leadership proposal is developed, according to the Kotze model, which is also described widely. Finding a specific leadership model represents the cornerstone for the development of the methodology. This integrated leadership proposal leads to the second contribution of the thesis. Similarly, an in-depth study was conducted about the psychological perspective of the organizations disclosing the construct Fear of Failure. This construct is a personality trait that exists in all human beings and has a negative influence on both performance and business innovation. This outcome allows identifying which are the real barriers to the exercise of leadership, noting that the decrease in fear of failure must be considered as an Emotional Intelligence competence to be developed by managers. This outcome represents the third contribution of the thesis. Once a business management model has been developed, we proceed to its validation by analysing the relationship among the model constructs: management, innovation and fear of failure. To identify the influence or causal relationships underlying the constructs, a structural equation model (SEM) technique was used. The study population consisted of 350 professionals with managerial responsibility, from companies in the services sector scattered throughout the Spanish geography. As a primary source for gathering information a questionnaire developed by Kotze M-CPI (Continuous Performance Improvement Momentum) was used. First we proceeded to evaluate the psychometric properties of the measurement model, carrying out an exploratory factorial analysis (EFA) and a confirmatory factorial analysis (CFA) of second order. The results show that the performance construct D is determined by two-dimensions (DOP: performance oriented to planning) and (DORT: aiming at the realization of the task). That is, the sample of managers does not perceive that planning and the daily task are articulated. Then, we proceeded to make the contrast of the model through a structural equation model SEM. The results show that the influence of the DOP dimension is not significant, so that only the DORT dimension finally represents the construct D. The research outcomes provide conclusions and hypotheses for future research. Although the managers in the sample develop a strategic plan, it seems that managers do not take it into account in their daily tasks. This could explain the high degree of crisis management so prevalent in the Spanish companies. In turn, the fear of failure has a negative influence on innovation, consistent with the literature. In this regard, the fear of failure is considered as a personality trait, present in both managers and employees, which enables the understanding of organizational barriers to open communication and provides a direction to improve the organization’s innovative capacity as well. Finally, the results establish a causal relationship between daily performance and innovation. Regarding this second outcome and analysing the behaviours that identify the construct D, several conclusions and hypotheses for future research arise as well. The results show that the managers in the sample show initiatives of change in order to make everyday work go ahead, according to defined quality standards. However, these initiatives only come from managers without any participation of coworkers, which are only responsible for the implementation, and this produces discouragement and loss of opportunities. This finding shows that the innovation by the companies in the sample happens to guarantee the efficiency of existing processes, but do not arise from an initiative that seeks better business efficacy. This raises two sources of innovation in processes. The first source would be a proactive innovation that would seek improved organizational efficacy. The second one is a reactive innovation that would seek to safeguard efficiency. Perhaps this is the cause of the existing gap between the innovation activity in Spain and the innovation activity in those countries that occupy the top positions in the ranking of innovation outcomes. The Spanish companies seek process efficiency and the top innovators business efficacy. This is an important starting point for future research.
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A first-order Lagrangian L ∇ variationally equivalent to the second-order Einstein- Hilbert Lagrangian is introduced. Such a Lagrangian depends on a symmetric linear connection, but the dependence is covariant under diffeomorphisms. The variational problem defined by L ∇ is proved to be regular and its Hamiltonian formulation is studied, including its covariant Hamiltonian attached to ∇ .
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Graphs of second harmonic generation coefficients and electro-optic coefficients (measured by ellipsometry, attenuated total reflection, and two-slit interference modulation) as a function of chromophore number density (chromophore loading) are experimentally observed to exhibit maxima for polymers containing chromophores characterized by large dipole moments and polarizabilities. Modified London theory is used to demonstrated that this behavior can be attributed to the competition of chromophore-applied electric field and chromophore–chromophore electrostatic interactions. The comparison of theoretical and experimental data explains why the promise of exceptional macroscopic second-order optical nonlinearity predicted for organic materials has not been realized and suggests routes for circumventing current limitations to large optical nonlinearity. The results also suggest extensions of measurement and theoretical methods to achieve an improved understanding of intermolecular interactions in condensed phase materials including materials prepared by sequential synthesis and block copolymer methods.
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We present the first detailed numerical study in three dimensions of a first-order phase transition that remains first order in the presence of quenched disorder (specifically, the ferromagnetic-paramagnetic transition of the site-diluted four states Potts model). A tricritical point, which lies surprisingly near the pure-system limit and is studied by means of finite-size scaling, separates the first-order and second-order parts of the critical line. This investigation has been made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that plague the standard approach. Entropy, rather than free energy, is the basic object in this approach that exploits a recently introduced microcanonical Monte Carlo method.
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We present a detailed numerical study on the effects of adding quenched impurities to a three dimensional system which in the pure case undergoes a strong first order phase transition (specifically, the ferromagnetic/paramagnetic transition of the site-diluted four states Potts model). We can state that the transition remains first-order in the presence of quenched disorder (a small amount of it) but it turns out to be second order as more impurities are added. A tricritical point, which is studied by means of Finite-Size Scaling, separates the first-order and second-order parts of the critical line. The results were made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that arise using the standard methodology. We also made use of a recently proposed microcanonical Monte Carlo method in which entropy, instead of free energy, is the basic quantity.
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1/2-meter resolution 1:5,000 orthophoto image of the Boston region from April 2001. This datalayer is a subset (covering only the Boston region) of the Massachusetts statewide orthophoto image series available from MassGIS. It consists of 23 orthophoto quads mosaicked together (MassGIS orthophoto quad ID: 229890, 229894, 229898, 229902, 233886, 233890, 233894, 233898, 233902, 233906, 233910, 237890, 237894, 237898, 237902, 237906, 237910, 241890, 241894, 241898, 241902, 245898, 245902). These medium resolution true color images are considered the new "basemap" for the Commonwealth by MassGIS and the Executive Office of Environmental Affairs (EOEA). MassGIS/EOEA and the Massachusetts Highway Department jointly funded the project. The photography for the mainland was captured in April 2001 when deciduous trees were mostly bare and the ground was generally free of snow. The geographic extent of this dataset is the same as that of the MassGIS dataset: Boston, Massachusetts Region LIDAR First Return Elevation Data, 2002 [see cross references].