911 resultados para Penrose limit and pp-wave background


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This paper presents new laboratory data on the generation of long waves by the shoaling and breaking of transient-focused short-wave groups. Direct offshore radiation of long waves from the breakpoint is shown experimentally for the first time. High spatial resolution enables identification of the relationship between the spatial gradients of the short-wave envelope and the long-wave surface. This relationship is consistent with radiation stress theory even well inside the surf zone and appears as a result of the strong nonlinear forcing associated with the transient group. In shallow water, the change in depth across the group leads to asymmetry in the forcing which generates significant dynamic setup in front of the group during shoaling. Strong amplification of the incident dynamic setup occurs after short-wave breaking. The data show the radiation of a transient long wave dominated by a pulse of positive elevation, preceded and followed by weaker trailing waves with negative elevation. The instantaneous cross-shore structure of the long wave shows the mechanics of the reflection process and the formation of a transient node in the inner surf zone. The wave run-up and relative amplitude of the radiated and incident long waves suggests significant modification of the incident bound wave in the inner surf zone and, the dominance of long waves generated by the breaking process. It is proposed that these conditions occur when the primary short waves and bound wave are not shallow water waves at the breakpoint. A simple criterion is given to determine these conditions, which generally occur for the important case of storm waves.

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A key purpose of this study is to explore the lessons learned from international retail divestment and market withdrawal experiences. Drawing on 33 in-depth interviews with leading investment banks and key retail executives at Tesco, the study investigates the company's international restructuring and divestment activities in Ireland and France during the mid -1980s and 1990s. It has been demonstrated that, despite the progressive merger and acquisition wave sweeping through the corporate retail landscape recently, international retail divestment is quite widespread. The main conclusion from this study is that Tesco originally did not envisage divestment or de-internationalisation as part of the original internationalisation strategy process in either the acquisition of Three Guys in Ireland or Catteau in France. There was no appreciation from Tesco during their early period of expansion of the fact that exit pressures might arise during the course of market entry. In this regard, the case study provides insights into the relationship between investment and divestment within the context of international retail restructuring. The case evidence also demonstrates the positive impact of the Three Guys and Catteau divestments which helped management to refocus and rejuvenate the company's internationalisation process.

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The Q parameter scales differently with the noise power for the signal-noise and the noise-noise beating terms in scalar and vector models. Some procedures for including noise in the scalar model largely under-estimate the Q parameter. We propose a simple method for including noise within a scalar model which will allow both the noise-noise dominated limit and the signal-noise dominated limit to be treated consistently. © 2005 Elsevier B.V. All rights reserved.

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We have proposed and demonstrated a nonlinear polarization-rotation-based fiber laser with two different operation states: passive mode-locking and multiwavelength emission. The intensity-dependent transmission or loss induced by nonlinear polarization rotation accounts for the distinct operation regimes. Our experiment results indicate that both passively mode-locked pulses and continuous-wave multiwavelength can be generated from the same fiber laser just through adjusting polarizations. Another characteristic of the current multiwavelength laser is that the used periodic filter is a birefringence fiber filter, which facilitates all-fiber integration of the fiber laser, so it is a potential multifunction laser source with all-fiber configuration and convenient manipulation. © 2008 IEEE.

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We have proposed and demonstrated a nonlinear polarization-rotation-based fiber laser with two different operation states: passive mode-locking and multiwavelength emission. The intensity-dependent transmission or loss induced by nonlinear polarization rotation accounts for the distinct operation regimes. Our experiment results indicate that both passively mode-locked pulses and continuous-wave multiwavelength can be generated from the same fiber laser just through adjusting polarizations. Another characteristic of the current multiwavelength laser is that the used periodic filter is a birefringence fiber filter, which facilitates all-fiber integration of the fiber laser, so it is a potential multifunction laser source with all-fiber configuration and convenient manipulation. © 2008 IEEE.

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A hybrid passive-active damping solution with improved system stability margin and enhanced dynamic performance is proposed for high power grid interactive converters. In grid connected active rectifier/inverter application, line side LCL filter improves the high frequency attenuation and makes the converter compatible with the stringent grid power quality regulations. Passive damping though offers a simple and reliable solution but it reduces overall converter efficiency. Active damping solutions do not increase the system losses but can guarantee the stable operation up to a certain speed of dynamic response which is limited by the maximum bandwidth of the current controller. This paper examines this limit and introduces a concept of hybrid passive-active damping solution with improved stability margin and high dynamic performance for line side LCL filter based active rectifier/inverter applications. A detailed design, analysis of the hybrid approach and trade-off between system losses and dynamic performance in grid connected applications are reported. Simulation and experimental results from a 10 kVA prototype demonstrate the effectiveness of the proposed solution. An analytical study on system stability and dynamic response with the variations of various controller and passive filter parameters is presented.

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A vállalkozóvá válás meghatározó tényezőinek kutatása szakmai berkekben leginkább a Szent Grál keresésére emlékeztet: már lassan azt sem tudjuk, hogy egyáltalán léteznek-e ilyen tényezők. A kutatást nehezítik a többnyire önbevallásos kérdésekre adott torzított válaszok, a szóba jöhető tényezők számossága és a vállalkozói motivációk heterogenitása a különböző demográfiai karakterisztikákkal rendelkező népesség körében. Az egyetemi hallgatók körében némileg egyszerűbb a vizsgálat, hiszen ez egy relatíve homogén minta. Ugyanakkor itt a leginkább áttételesek a hatások, és ráadásul nem a tényleges vállalkozóvá válás, hanem többnyire csak a szándékok tesztelhetők. A vállalkozóvá válás szándékát Bandura társadalmi megismerés-elmélete, Shapero elmozduláselmélete és az Ajzen-féle tervezett magatartás elmélet alapján felállított koncepcionális modell keretén belül vizsgálják és elemzik a szerzők. Arra keresik a választ, hogy az egyes vállalkozói tulajdonságok, az egyetemi környezeti tényezők és a családi háttér hogyan hatnak a vállalkozóvá válásra. A teszteléshez a 21 országra kiterjedő 2011-es GUESSS-felmérésből a magyar egyetemi/ főiskolai hallgatók 5224-es erősségű mintáját használták fel. A multimoniális regressziós vizsgálat eredményei megerősítik, hogy a vállalkozói tulajdonságok és a családban levő vállalkozó megléte mellett a vállalkozói oktatás is pozitívan befolyásolják a vállalkozásindítási szándékot. A klaszterelemzés rámutatott arra, hogy a vállalkozói szándékok, az erre ható tényezők, továbbá a választott szak és más demográfiai tényezők szempontjából a hallgatók meglehetősen heterogének. _______ The search for the determining factors to become an entrepreneur is something like searching for the Holy Grail: After many decades we do not even know if these factors exist or not. The research is difficult because the questionnaires are self esteem, the potential influential factors are numerous, and the motivations do vary across the different cohorts of population. It is easier to conduct a survey amongst university students since this sample is relatively homogenous. At the same times, the determining factors to become an entrepreneur cannot be really tested; the authors can examine mostly the attitudes and the intentions. The conceptual model of entrepreneurial intentions, developed in the paper, based on Bandura, Shaper and Ajzen. The paper is testing eight hypotheses about the influential factors of entrepreneurial intentions such as entrepreneurial traits, the university environment, and the family background. For testing the hypothesis they use a sample of 5224 Hungarian students from the GUESSS 2011 survey. According to the multinomial regression, entrepreneurial intentions are positively influenced by certain entrepreneurial traits, entrepreneur in the family, and entrepreneurship courses at the higher education institutions. The cluster analysis results underline the heterogeneity of the students in terms of entrepreneurial intentions, gender, and the major field of studies

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The composition of atmospheric particles is an important factor in determining their impact on climate and health. In this study, an aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure the chemical composition of ambient single particles at two contrasting locations – an industrial site in Dunkirk, France and a regional background site in Corsica. The ATOFMS data were combined with meteorological information and other particle measurements to determine the various sources of the particles observed at the sites. The particle classes detected in Dunkirk included carbonaceous species from fossil fuel combustion and biomass burning, metal-containing types from local industries and seasalt. Highest particle number concentrations and mass concentrations of PM2.5, black carbon, organics, nitrate, ammonium and several metallic species (Fe, Mn, Pb, Zn) were found during periods heavily influenced by local industry. Particles from a ferromanganese alloy manufacturing facility were identified by comparing ambient ATOFMS data with single particle mass spectra from industrial chimney filters and ores. Particles from a steelworks were identified based on comparison of the ambient data with previous studies. Based on these comparisons, the steelworks was identified as the dominant emitter of Fe-rich particles, while the ferromanganese alloy facility emitted Mn-rich particles. In Corsica, regional transport of carbonaceous particles from biomass burning and fossil fuel combustion was identified as the major source of particles in the Mediterranean background aerosol. Throughout the campaign the site was influenced by air masses altering the composition of particles detected. During North Atlantic air masses the site was heavily influenced by fresh sea salt. Regional stagnation was the most common type of air mass regime throughout the campaign and resulted in the accumulation of carbonaceous particles during certain periods. Mass concentrations were estimated for ATOFMS particle classes, and good agreement was found between the major carbonaceous classes and other quantitative measurements. Overall the results of this work serve to highlight the excellent ability of the ATOFMS technique in providing source-specific composition and mixing state information on atmospheric particles at high time resolution.

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The distribution, abundance, behaviour, and morphology of marine species is affected by spatial variability in the wave environment. Maps of wave metrics (e.g. significant wave height Hs, peak energy wave period Tp, and benthic wave orbital velocity URMS) are therefore useful for predictive ecological models of marine species and ecosystems. A number of techniques are available to generate maps of wave metrics, with varying levels of complexity in terms of input data requirements, operator knowledge, and computation time. Relatively simple "fetch-based" models are generated using geographic information system (GIS) layers of bathymetry and dominant wind speed and direction. More complex, but computationally expensive, "process-based" models are generated using numerical models such as the Simulating Waves Nearshore (SWAN) model. We generated maps of wave metrics based on both fetch-based and process-based models and asked whether predictive performance in models of benthic marine habitats differed. Predictive models of seagrass distribution for Moreton Bay, Southeast Queensland, and Lizard Island, Great Barrier Reef, Australia, were generated using maps based on each type of wave model. For Lizard Island, performance of the process-based wave maps was significantly better for describing the presence of seagrass, based on Hs, Tp, and URMS. Conversely, for the predictive model of seagrass in Moreton Bay, based on benthic light availability and Hs, there was no difference in performance using the maps of the different wave metrics. For predictive models where wave metrics are the dominant factor determining ecological processes it is recommended that process-based models be used. Our results suggest that for models where wave metrics provide secondarily useful information, either fetch- or process-based models may be equally useful.

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Hurricane Sandy was the largest storm on historical record in the Atlantic Ocean basin with extensive coastal damage caused by large waves and high storm surge. The primary objectives of this thesis are to compare and evaluate three different spatially-varying surface wind fields of Hurricane Sandy to investigate the impact of the differences between the complex wind fields on predictions of the sea surface evolution, and to evaluate the impact of the storm on the hydrodynamics in Great South Bay (GSB) and the discharge of ocean water into the back-barrier bay from overwash over Fire Island. Three different spatially-varying surface wind fields were evaluated and compared to wind observations, including the parametric Holland (1980) model (H80), the parametric Generalized Asymmetric Holland Model (GAHM), and results from the WeatherFlow Regional Atmospheric Modelling System (WRAMS). The winds were used to drive the coupled Delft3D-SWAN hydrodynamic and ocean wave models on a regional grid. The results indicate that the WRAMS wind field produces wave model predictions in the best agreement with significant wave height observations, followed by the GAHM and H80 wind fields and that a regional atmospheric wind model is best for hindcasting hurricane waves and water levels when detailed observations are available, while a parametric vortex model is best for forecasting hurricane sea surface conditions. Using a series of four connected Delft3D-SWAN grids to achieve finer resolution over Fire Island and GSB, a higher resolution WRAMS was used to predict waves and storm surge. The results indicate that strong local winds have the largest influence on water level fluctuations in GSB. Three numerical solutions were conducted with varying extents of barrier island overwash. The simulations allowing for minor and major overwash indicated good agreement with observations in the east end of GSB and suggest that island overwash provided a significant contribution of ocean water to GSB during the storm. Limiting the overwash in the numerical model directly impacts the total discharge into GSB from the ocean through existing inlets. The results of this study indicate that barrier island overwash had a significant impact on the water levels in eastern GSB.

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The chemical compositions, modal mineralogy, and textural variability of interstitial minerals in sandstones of the Athabasca Group strata in the vicinity of the McArthur River unconformity-related uranium deposit were characterized using a combination of short wave infrared spectroscopy (SWIR), lithogeochemistry, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and laser ablation mass spectrometry (LA-ICP-MS) to determine the residence sites of pathfinder trace elements. The importance of integrating in-situ mineral chemistry with whole-rock analyses resides in the possibility to establish the mineralogical and paragenetic context of geochemical signatures in defining the footprint of the deposit. Located in the Athabasca Basin, Saskatchewan, Canada, the deposit is situated below ~550 m of quartz arenitic sandstones that are strongly silicified between depths of approximately 200-400 m. The silicified layer exhibits significant control on the distribution of alteration minerals, and appears to have restricted both the primary and secondary dispersion of pathfinder trace elements, which include U, radiogenic Pb isotopes, V, Ni, Co, Cu, Mo, As, Zn, and REEs. Diagenetic background sandstones contain assemblages of illite, dickite, aluminum-phosphate-sulfate (APS) minerals, apatite, and Fe-Ti oxide minerals. Altered sandstones contain assemblages of Al-Mg chlorite (sudoite), alkali-deficient dravite, APS minerals, kaolinite, illite, and oxide minerals. Throughout the sandstones, APS minerals account for the majority of the Sr and LREE concentrations, whereas late pre-ore chlorite, containing up to 0.1 wt.% Ni, accounts for the majority of Ni concentrations. Cobalt, Cu, Mo, and Zn occur predominantly in cryptic sub-micron sulfide and sulfarsenide inclusions in clay mineral aggregates and in association with paragenetically-late Fe-Ti oxides. Uranium occurs predominantly in cryptic micro-inclusions associated with pyrite in late-stage quartz overgrowths, and with paragenetically late Fe-Ti oxide micro-inclusions in kaolinite. Additionally, up to 0.2 wt.% U is cryptically distributed in post-ore Fe-oxide veins. Early diagenetic apatite, monazite and apatite inclusions in detrital quartz, and detrital zircon also contribute significant U and HREE to samples analyzed with an aggressive leach such as Aqua Regia. Detailed LA-ICP-MS chemical mapping of interstitial assemblages, detrital grains, and cements provides new insights into the distribution and inventory of pathfinder elements in the footprint of the McArthur River uranium deposit.

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The objective of this paper is to conceptualize Supply Chain Resilience (SCRes) and identify which supply chain capabilities can support the containment of disruptions and how these capabilities affect SCRes. Through a systematic and structured review of literature, this paper provides insights into the conceptualization and research methodological background of the SCM field. A total of one hundred and thirty four carefully selected refereed journal articles were systematically analyzed leading to the introduction of a novel definition for SCRes, which the authors view as the as “the ability to proactively plan and design the Supply Chain network for anticipating unexpected disruptive (negative) events, respond adaptively to disruptions while maintaining control over structure and function and transcending to a post-event robust state of operations, if possible, more favorable than the one prior to the event, thus gaining competitive advantage”. Finally, a critical examination of existing conceptual frameworks for understanding the relationships between the SCRes concept and its identified formative elements, is taking place.

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In Sudanese women with (n = 60) and without (n = 65) pre-eclampsia, circulating lipids, plasma and red cell saturated and monounsaturated fatty (MUFA) acids and dimethyl acetals (DMAs) were investigated. DMAs are an indirect marker of levels of plasmalogens, endogenous antioxidants, which play a critical role in oxidative protection, and cholesterol homeostasis. The pre-eclamptics had higher C18:1n-9 (p < 0.001) and ΣMUFA (p < 0.01) in plasma free fatty acids, C16:1n-7, C18:1n-9, ΣMUFA; 16:0/16:1n-7 (p < 0.01) in erythrocyte choline phosphoglycerides (ePC) and 16:1n-7, 18:1n-7 and 16:0/16:1n-7 (p < 0.01) in erythrocyte ethanolamine phosphoglycerides (ePE). In contrast, the DMAs 18:0, 18:1 and ΣDMAs in ePE, and 16:0, 18:0 and ΣDMAs in ePC were reduced (p < 0.001) in the pre-eclamptic women. This study of pregnant women with high carbohydrate and low fat background diet suggests pre-eclampsia is associated with oxidative stress and enhanced activity of the microsomal enzyme stearyl-CoA desaturase (delta 9 desaturase), as assessed by palmitic/palmitoleic (C16:0/C16:n-1) and stearic/oleic (C18/C18:1n-9) ratios.

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Philip Pullman, author of the His Dark Materials trilogy, has acquired an impressive critical reputation and acquired a favored role in British culture as a social commentator. This essay attempts to link the pleasures associated with the trilogy with the politics inscribed in them, and consider both in the context of Pullman’s role in the civil society. The essay suggests that The Northern Lights offers pleasures in fantastical and metaphysical possibilities, and social confederacies that potentially offset the affective privations of neoliberalism. These possibilities are set in the context of recent theories of the “enterprise society.” The essay draws attention to a number of discontinuities that unfold as the trilogy progresses, and suggests that these undermine the possibilities inherent in the first novel. These disconti - nuities throw the role of fantasy and alternative universes into question, and reveal the limitations of Pullman’s fiction. The essay considers the limit and scope of Pullman’s political vision, both as a function of his fiction and his public engagement with social issues, and suggests that he exemplifies Raymond Williams’s concept of “bourgeois dissent” in which political critique and a continuing investment in traditional institutions and class hierarchy can be mutually reinforcing.

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Aims and objectives. To explore the psychosocial needs of patients discharged from intensive care, the extent to which they are captured using existing theory on transitions in care and the potential role development of critical care outreach, follow-up and liaison services. Background. Intensive care patients are at an increased risk of adverse events, deterioration or death following ward transfer. Nurse-led critical care outreach, follow-up or liaison services have been adopted internationally to prevent these potentially avoidable sequelae. The need to provide patients with psychosocial support during the transition to ward-based care has also been identified, but the evidence base for role development is currently limited. Design and methods. Twenty participants were invited to discuss their experiences of ward-based care as part of a broader study on recovery following prolonged critical illness. Psychosocial distress was a prominent feature of their accounts, prompting secondary data analysis using Meleis et al.’s mid-range theory on experiencing transitions. Results. Participants described a sense of disconnection in relation to profound debilitation and dependency and were often distressed by a perceived lack of understanding, indifference or insensitivity among ward staff to their basic care needs. Negotiating the transition between dependence and independence was identified as a significant source of distress following ward transfer. Participants varied in the extent to which they were able to express their needs and negotiate recovery within professionally mediated boundaries. Conclusion. These data provide new insights into the putative origins of the psychosocial distress that patients experience following ward transfer. Relevance to clinical practice. Meleis et al.’s work has resonance in terms of explicating intensive care patients’ experiences of psychosocial distress throughout the transition to general ward–based care, such that the future role development of critical care outreach, follow-up and liaison services may be more theoretically informed.