997 resultados para almost sure limits


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Families of linear connections are constructed on almost con- tact manifolds with Norden metric. An analogous connection to the symmetric Yano connection is obtained on a normal almost contact manifold with Norden metric and closed structural 1-form. The curvature properties of this connec- tion are studied on two basic classes of normal almost contact manifolds with Norden metric.

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We consider a 3-dimensional Riemannian manifold V with a metric g and an a±nor structure q. The local coordinates of these tensors are circulant matrices. In V we define an almost conformal transformation. Using that definition we construct an infinite series of circulant metrics which are successively almost conformaly related. In this case we get some properties.

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Curriculum innovation is challenging and, as several commentators have reported, moves to introduce communicative language teaching in many contexts internationally have resulted in mixed outcomes, or even failure. In an effort to shed some light on this complex problem, this article focuses on curriculum change through the introduction of new communicative textbooks in an engineering college (kosen) in Japan. First, three key factors that inhibit change are considered and then other factors that specifically hindered change in the kosen environment are identified. A study investigating the attitudes and classroom practices of four Japanese teachers of English highlighted a culture of pedagogical uncertainty and lack of professional support. Suggestions for supporting teachers to implement curriculum change more effectively, both in Japan and elsewhere, are drawn out.

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Л. И. Каранджулов, Н. Д. Сиракова - В работата се прилага методът на Поанкаре за решаване на почти регулярни нелинейни гранични задачи при общи гранични условия. Предполага се, че диференциалната система съдържа сингулярна функция по отношение на малкия параметър. При определени условия се доказва асимптотичност на решението на поставената задача.

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2000 Mathematics Subject Classification: 60J27.

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We extend the theory of parametric noise amplification to the case of transmission systems employing multiple optical phase conjugators, demonstrating that the excess noise due to this process may be reduced in direct proportion to the number of phase conjugation devices employed. We further identify that the optimum noise suppression is achieved for an odd number of phase conjugators, and that the noise may be further suppressed by up to 3dB by partial digital back propagation (or fractional spans at the ends of the links).

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2000 Mathematics Subject Classification: Primary 40C99, 46B99.

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In this talk we investigate the usage of spectrally shaped amplified spontaneous emission (ASE) in order to emulate highly dispersed wavelength division multiplexed (WDM) signals in an optical transmission system. Such a technique offers various simplifications to large scale WDM experiments. Not only does it offer a reduction in transmitter complexity, removing the need for multiple source lasers, it potentially reduces the test and measurement complexity by requiring only the centre channel of a WDM system to be measured in order to estimate WDM worst case performance. The use of ASE as a test and measurement tool is well established in optical communication systems and several measurement techniques will be discussed [1, 2]. One of the most prevalent uses of ASE is in the measurement of receiver sensitivity where ASE is introduced in order to degrade the optical signal to noise ratio (OSNR) and measure the resulting bit error rate (BER) at the receiver. From an analytical point of view noise has been used to emulate system performance, the Gaussian Noise model is used as an estimate of highly dispersed signals and has had consider- able interest [3]. The work to be presented here extends the use of ASE by using it as a metric to emulate highly dispersed WDM signals and in the process reduce WDM transmitter complexity and receiver measurement time in a lab environment. Results thus far have indicated [2] that such a transmitter configuration is consistent with an AWGN model for transmission, with modulation format complexity and nonlinearities playing a key role in estimating the performance of systems utilising the ASE channel emulation technique. We conclude this work by investigating techniques capable of characterising the nonlinear and damage limits of optical fibres and the resultant information capacity limits. REFERENCES McCarthy, M. E., N. Mac Suibhne, S. T. Le, P. Harper, and A. D. Ellis, “High spectral efficiency transmission emulation for non-linear transmission performance estimation for high order modulation formats," 2014 European Conference on IEEE Optical Communication (ECOC), 2014. 2. Ellis, A., N. Mac Suibhne, F. Gunning, and S. Sygletos, “Expressions for the nonlinear trans- mission performance of multi-mode optical fiber," Opt. Express, Vol. 21, 22834{22846, 2013. Vacondio, F., O. Rival, C. Simonneau, E. Grellier, A. Bononi, L. Lorcy, J. Antona, and S. Bigo, “On nonlinear distortions of highly dispersive optical coherent systems," Opt. Express, Vol. 20, 1022-1032, 2012.

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The objective of this project is to design a new desalination system with energy efficiency approaching the theoretical thermodynamic limit—even at high recovery ratio. The system uses reverse osmosis (RO) and a batch principle of operation to overcome the problem of concentration factor which prevents continuous-flow RO systems from ever reaching this limit and thus achieving the minimum possible specific energy consumption, SEC. Batch operation comprises a cycle in three phases: pressurisation, purge, and refill. Energy recovery is inherent to the design. Unlike in closed-circuit desalination (CCD), no feedwater is added to the pressure circuit during the pressurisation phase. The batch configuration is compared to standard configurations such as continuous single-stage RO (with energy recovery) and CCD. Theoretical analysis has shown that the new system is able to use 33% less energy than CCD at a recovery ratio of 80%. A prototype has been constructed using readily available parts and tested with feedwater salinities and recovery ratios ranging from 2,000 to 5,000 ppm and 17.2–70.6%, respectively. Results compare very well against the standard configurations. For example, with feedwater containing 5,000 ppm NaCl and recovery ratio of 69%, a hydraulic SEC of 0.31 kWh/m3 was obtained—better than the minimum theoretically possible with a single-stage continuous flow system with energy recovery device.

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This paper seeks to provide a conceptual framework in which to examine the social practices of contemporary austerity programmes in urban areas, including how these relate to different conceptions of crisis. Of current theoretical interest is the apparent ease with which these austerity measures have been accepted by urban governing agents. In order to advance these understandings we follow the recent post-structuralist discourse theory ‘logics’ approach of Glynos and Howarth (2007), focusing on the relationship between hegemony, political and social logics, and the subject whose identificatory practices are key to understanding the form, nature and stability of discursive settlements. In such thinking it is not only the formation of discourses and the mobilisation of rhetoric that are of interest, but also the manner in which the subjects of austerity identify with these. Through such an approach we examine the case of the regeneration/economic development and planning policy area in the city government of Birmingham (UK). In conclusion, we argue that the logics approach is a useful framework through which to examine how austerity has been uncontested in a city government, and the dynamics of acquiescence in relation to broader hegemonic discursive formations.

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The Cuban military involvement in Angola has often been seen as a response to the wishes of the former Soviet Union. Yet, Castro intervened in Angola following his theory of internationalism. Internationalism, as conceived by Castro, sent Cubans on a voluntary basis to serve abroad, either in the military or in the civilian sector. This thesis will illustrate that from its inception, Castro sent military troops to Angola to divert domestic concerns and to boost Cuba's alliances throughout the world. Angola is different from other internationalist missions, because in Angola--for the first time--regular combat troops were used. Castro intervened in Angola to prevent a collapse of the Moviemento Popular de Libertacao de Angola (MPLA) government, and stayed on to ensure the viability of the MPLA. The primary sources are interviews conducted by the author, of participants in the Angolan civil war. The secondary sources consulted are works on Cuba, Southern Africa, Portuguese colonialism and Angola. ^

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Homero Aridjis (b. 1940) is a major Mexican poet, novelist, essayist and ecological activist whose prolific body of work, ranging over forty years and including more than eleven volumes of poetry and thirteen novels, has yet to be studied as a coherent literary corpus in the context of recent Latin American fiction. The purpose of this dissertation was to analyze the narrative works of this author as both illustrative of the changes that have occurred in Latin American fiction since the 1960s when it first burst onto the world scene, as well as to study the uniqueness of this particular author's view of literature as it relates to historical discourse, apocalypticism. and social commitment. ^ Research showed that in the case of the narrative style of Aridjis, major trends in the contemporary Latin American novel were present in such a profuse and model manner as to confirm this author's importance as a prime example of what is commonly known as “Post-Boom” fiction. However, beyond the mere presence of literary elements, this study showed that the author's unique approach to narrative style has altered and expanded the aesthetic and thematic possibilities of the contemporary novel. The area where this is most clearly seen is in his experimentation with the historical genre. By manipulating the referential techniques of what has lately come to be known as the “new historical novel,” Aridjis has written both a cycle of purely historical novels and a cycle of futuristic ones that attempt to transcend the temporal limits traditionally imposed by these narrative forms, fusing them into one constant questioning of the nature of love, hate and identity. In this manner, he has developed a “simultaneist” narrative approach where distinct historical and imagined periods, places, people, things, and texts coexist and interact, widening almost to delirium the interpretative possibilities of the work. ^ This unique view of time and narrative, together with the author's political activism and millenarian view of history, make the novels of Homero Aridjis an important element in understanding the continuing development and evolution of Latin American fiction at the turn of the century. ^

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The implementation of term limits on state legislators has provided a wealth of data for study. Florida, the second largest state in the Union with term limits, has not been comprehensively studied. This research examines the effects of term limits on electoral competition, member composition, legislator career paths, legislative leadership, and intra- and inter-governmental influences on Florida's legislature. This study looks at the Florida legislature from 1992 when term limits were enacted through 2004, three electoral cycles in which term limits have been in effect. This study uses both quantitative and qualitative data where appropriate. Electoral data is used to assess electoral and demographic effects, as well as member career trajectories. Interview data with current and former legislators, lobbyists, and executive branch officials is used to analyze both changes in legislative organization and intra- and inter-governmental influences on the legislative process. Term limits has only created greater competition when a legislative seat opens and has actually created a greater advantage for incumbents. Women and minorities have only made minimal gains in winning seats post-term limits. Newly elected legislators are not political novices with a vast majority having previous elective experience. Leadership is more centralized under term limits and the Senate has gained an advantage over the more inexperienced House. Lastly, the influence of staff, lobbyists, and most importantly, the governor has greatly increased under term limits. This research finds that term limits have not produced the consequences that proponents had envisioned.^

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Current water management practices in South Florida have negatively impacted many species inhabiting Florida Bay. Variable and high salinity has been identified as a key stressor in these estuaries. The Comprehensive Everglades Restoration Plan (CERP) includes water redistribution projects that will restore natural freshwater flows to northeastern Florida Bay. My studies focused on the following central theme and hypotheses: Biological performance measures (i.e., growth, reproduction, survival), behavior (i.e., habitat preference and locomotor behavior) and diversity of estuarine fish will be controlled by changes in salinity and water quality that will occur as a result of the restoration of freshwater flow to the bay. A series of acute and subchronic physiological toxicity studies were conducted to determine the effects of salinity changes on the life stages (embryo/larval, juvenile, adult) and fecundity of four native estuarine fish (Cyprinodon variegatus, Floridichthys carpio, Poecilia latipinna, and Gambusia holbrooki). Fish were exposed to a range of salinity concentrations (freshwater to hypersaline) based on salinity profiles in the study areas. Growth (length, weight) and survival were measured. Salinity trials included both rapid and gradual change events. Results show negative effects of acute, abrupt salinity changes on fish survival, development and reproductive success as a result of salinity stress. Other studies targeted reproduction and critical embryo-larval/neonate development as key areas for detecting long-term population effects of salinity change in Florida Bay. Adults of C. variegates and P. latipinna were also examined for behavioral responses to pulsed salinity changes. These responses include changes in swimming performance, locomotor behavior and zone preference. Finally, an ecological risk assessment was conducted for adverse salinity conditions in northeastern Florida Bay. Using the U.S. EPA's framework, the risk to estuarine fish species diversity was assessed against regional salinity profiles from a 17-year database. Based on the risk assessment, target salinity profiles for these areas are recommended for managers.^

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Refuge habitats increase survival rate and recovery time of populations experiencing environmental disturbance, but limits on the ability of refuges to buffer communities are poorly understood. We hypothesized that importance of refuges in preventing population declines and alteration in community structure has a non-linear relationship with severity of disturbance. In the Florida Everglades, alligator ponds are used as refuge habitat by fishes during seasonal drying of marsh habitats. Using an 11-year record of hydrological conditions and fish abundance in 10 marshes and 34 alligator ponds from two regions of the Everglades, we sought to characterize patterns of refuge use and temporal dynamics of fish abundance and community structure across changing intensity, duration, and frequency of drought disturbance. Abundance in alligator ponds was positively related to refuge size, distance from alternative refugia (e.g. canals), and abundance in surrounding marsh prior to hydrologic disturbance. Variables negatively related to abundance in alligator ponds included water level in surrounding marsh and abundance of disturbance-tolerant species. Refuge community structure did not differ between regions because the same subset of species in both regions used alligator ponds during droughts. When time between disturbances was short, fish abundance declined in marshes, and in the region with the most spatially extensive pattern of disturbance, community structure was altered in both marshes and alligator ponds because of an increased proportion of species more resistant to disturbance. These changes in community structure were associated with increases in both duration and frequency of hydrologic disturbance. Use of refuge habitat had a modal relationship with severity of disturbance regime. Spatial patterns of response suggest that decline in refuge use was because of decreased effectiveness of refuge habitat in reducing mortality and providing sufficient time for recovery for fish communities experiencing reduced time between disturbance events.