dissertation com jan 2008 (6 Ergebnisse)

Taschenbuch. Zustand: Neu. Neuware - We present the results of a large-area survey for millisecond pulsars (MSPs) at moderately high galactic latitudes with the 64 m Parkes radio telescope, along with follow-up timing and optical studies of the newly-discovered pulsars and several others. Major results include the first precise measurement of the mass of a fully recycled pulsar and measurement of orbital period decay in a double neutron star binary system allowing a test of general relativity along with improved measurements of the neutron star masses.In a survey of approx. 4,150 square degrees, we discovered 26 previously unknown pulsars, including 7 'recycled' millisecond or binary pulsars. Several of these recycled pulsars are particularly interesting: PSR J1528-3146 is in a circular orbit with a companion of at least 0.94 solar masses; it is a member of the recently recognized class of intermediate mass binary pulsar (IMBP) systems with massive white dwarf companions. We have detected optical counterparts for this and one other IMBP system; taken together with optical detections and non-detections of several similar systems, our results indicate that the characteristic age consistently overestimates the time since the end of mass accretion in these recycled systems. This result implies that the pulsar spin period at the end of the accretion phase is not dramatically shorter than the observed period as is generally assumed. PSR J1600-3053 is among the best high-precision timing pulsars known and should be very useful as part of an ensemble of pulsars used to detect very low frequency gravitational waves. PSR J1738+0333 has an optical counterpart which, although not yet well-studied, has already allowed a preliminary measurement of the system's mass ratio. The most significant discovery of this survey is PSR J1909-3744, a 2.95 ms pulsar in an extremely circular 1.5 d orbit with a low-mass white dwarf companion. Though this system is a fairly typical low-mass binary pulsar (LMBP) system, it has several exceptional qualities: an extremely narrow pulse profile and stable rotation have enabled the most precise long-term timing ever reported, and a nearly edge-on orbit gives rise to a strong Shapiro delay signature in the pulse timing data which has allowed the most precise measurement of the mass of a millisecond pulsar: 1.438 ± 0.024 solar masses. Our accurate parallax distance measurement, d = 1.14 +0.08 / -0.07 kpc, combined with the mass of the optically-detected companion, 0.2038 ± 0.022 solar masses, will provide an important calibration for white dwarf models relevant to other LMBP companions. We have measured the decay of the binary period of the double neutron star system B2127+11C in the globular cluster M15. This has allowed an improved measurement of the mass of the pulsar, 1.3584 ± 0.0097 solar masses, and companion, 1.3544 ± 0.0097 solar masses, as well as a test of general relativity at the 3% level. We find that the proper motions of this pulsar as well as B2127+11A and B2127+11B are consistent with each other and with one published measurement of the cluster proper motion. We have discovered three binary millisecond pulsars in the globular cluster M62 using the 100-m Green Bank Telescope (GBT). These pulsars are the first objects discovered with the GBT. We briefly describe a wide-bandwidth coherent dedispersion backend used for some of the high precision pulsar timing observations presented here.

Taschenbuch. Zustand: Neu. Neuware - The style of leadership in an interdisciplinary collaboration is an existing gap in collaborative literature. Studying the leaders in an existing interdisciplinary collaboration provided a description of the leadership style of the collaborative leaders of three behavioral health teams in New York City. This qualitative phenomenological study used structured interviews of interdisciplinary disciplines to describe the leadership style of the collaborative leaders within a team environment. The data collection and analysis were conducted using codes to identify dominant themes. The themes presented perceptions and experiences of three teams interacting collaboratively. The coding process identified five major themes that are unique components of leadership that suggests new methods of building collaborative leadership within the interdisciplinary team dynamics.

Taschenbuch. Zustand: Neu. Neuware - This study examines suicide perceptions of police officers from two groups, east coast officers and west coast officers. To investigate this problem, the researcher conducted a quantitative analysis utilizing a previously validated instrument. Participants of this study voluntarily completed the Suicide Attitude Questionnaire (SUIATT), administered by the National Police Suicide Foundation. The participants consisted of 75 sworn officers from each group varying in age, education, experience, and job description. This study also examined various leadership styles and makes recommendations for leaders to improve upon or implement police suicide prevention training. Risks factors and warning signs were identified by participating officers, which may assist supervisors in identifying potential officers at risk.

Taschenbuch. Zustand: Neu. Neuware - The problem addressed in the current study was that disruptive student behavior is detrimental to learning because quality teacher-student interaction time is reduced. The purpose of this ethnographic research study was to explore relationship between disruptive behavior of students and leadership styles of teachers, parents and school leaders. Results indicated that in some cases, an individualized approach could help the K-6 elementary student by reducing their disruptive behavior. However, it was also confirmed that as part of this individualized approach, school-wide implementation might provide the level of support needed to prevent future disruptive behavioral problems as well as providing the positive role models for students to observe and emulate.

Taschenbuch. Zustand: Neu. Neuware - The famous Black-Scholes model was the starting point of a new financial industry and has been a very important pillar of all options trading since. One of its core assumptions is that the volatility of the underlying asset is constant. It was realised early that one has to specify a dynamic on the volatility itself to get closer to market behaviour. There are mainly two aspects making this fact apparent. Considering historical evolution of volatility by analysing time series data one observes erratic behaviour over time. Secondly, backing out implied volatility from daily traded plain vanilla options, the volatility changes with strike. The most common realisations of this phenomenon are the implied volatility smile or skew. The natural question arises how to extend the Black-Scholes model appropriately. Within this book the concept of stochastic volatility is analysed and discussed with special regard to the numerical problems occurring either in calibrating the model to the market implied volatility surface or in the numerical simulation of the two-dimensional system of stochastic differential equations required to price non-vanilla financial derivatives. We introduce a new stochastic volatility model, the so-called Hyp-Hyp model, and use Watanabe's calculus to find an analytical approximation to the model implied volatility. Further, the class of affine diffusion models, such as Heston, is analysed in view of using the characteristic function and Fourier inversion techniques to value European derivatives.

Taschenbuch. Zustand: Neu. Neuware - The problem of automatic toponym resolution, or computing the mapping from occurrences of names for places as found in a text to an unambiguous spatial footprint of the location referred to, such as a geographic latitude/longitude centroid is difficult to automate due to insufficient and error-prone geographic databases, and a large degree of place name ambiguity: common words need to be distinguished from proper names (geo/non-geo ambiguity), and the mapping between names and locations is ambiguous (London can refer to the capital of the UK or to London, Ontario, Canada, or to about forty other Londons on earth). This thesis investigates how referentially ambiguous spatial named entities can be grounded, or resolved, with respect to an extensional coordinate model robustly on open-domain news text by collecting a repertoire of linguistic heuristics and extra-linguistic knowledge sources such as population. I then investigate how to combine these sources of evidence to obtain a superior method. Noise effects introduced by the named entity tagging that toponym resolution relies on are also studied. While few attempts have been made to solve toponym resolution, these were either not evaluated, or evaluation was done by manual inspection of system output instead of creating a re-usable reference corpus. A systematic comparison leads to an inventory of heuristics and other sources of evidence. In order to carry out a comparative evaluation procedure, an evaluation resource is required, so a reference gazetteer and an associated novel reference corpus with human-labelled referent annotation were created for this thesis, to be used to benchmark a selection of the reconstructed algorithms and a novel re-combination of the heuristics catalogued in the inventory. Performance of the same resolution algorithms is compared under different conditions, namely applying it to the output of human named entity annotation and automatic annotation using an existing Maximum Entropy sequence tagging model.