Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 157-169).

Tropical forests have been studied by community ecologists since the earliest days of the field because of their diversity and complexity and much of the theory behind community assembly has been developed in the tropics. However, the processes that act to assemble species in tropical forest across a very fine scale are still poorly understood. This study investigates community structure in 20ha area of hyper diverse tropical rainforest in Sabah, Malaysia. In order to examine community phylogenetic structure, I reconstructed a molecular phylogeny for all species in the study site using DNA barcoding loci. From this, I calculated phylogenetic diversity metrics for each community and then used a null model to compare observed phylogenetic diversity with that which would be expected if communities were randomly assembled with respect to phylogeny. The analyses showed that communities are more closely related than predicted by the null model. I also collected species functional trait data and showed that species assemblages and community weighted mean trait values correlate with environmental gradients on the plot. I also compared functional diversity to data simulated from null models. This showed that communities are on average more functionally similar than predicted at random. Finally, I performed a multivariate analysis with environmental, spatial, phylogenetic and trait data from communities across the plot. The analyses recovered an elevational and soil gradient that correlated strongly with community composition. Species occupying different ranges along this gradient had differing trait values and were phylogenetically distinct. These analyses demonstrate that even fine scale environmental variation is influential in assembling communities over a small area of forest. A soil nutrient gradient is consistently recovered that correlates with topography, suggesting that soil nutrient distribution is mediated by the downslope movement of water leaching soils on ridge tops and leading to accumulation of nutrients in valleys. This gradient is associated with species compositional variation and also with community weighted mean functional traits, indicating that the environment is influencing species distributions even over very small areas. Communities were both functionally and phylogenetically clustered, adding further support to this conclusion.

Although gas turbine engines are designed to use dry air as the working fluid, the great demand over the last decades for air travel at several altitudes and speeds has increased aircraft’s exposure to inclement weather conditions. Although, they are required to perform safely under the effect of various meteorological phenomena, in which air entering the engine contains water, several incidents have been reported to the aviation authorities about power loss during flight at inclement weather. It was understood that the rain ingestion into a gas turbine engine influences the performance of the engine and particular the compressor and the combustor. The effects of water ingestion on gas turbine engines are aerodynamic, thermodynamic and mechanical. These effects occur simultaneously and affect each other. Considering the above effects and the fact that they are timedependent, there are few gas turbine performance simulation tools, which take into account the water ingestion phenomenon. This study is a new research of investigating theoretically the water ingestion effects on a gas turbine performance. It focuses on the aerodynamic and mechanical effects of the phenomenon on the compressor and the combustor. The application of Computational Fluid Dynamics (CFD) is the basic methodology to examine the details of the flow in an axial compressor and how it is affected by the presence of water. The calculations of water film thickness, which is formed on the rotor blade, its motion (direction and speed) and the extra torque demand, are provided by a code created by the author using FORTRAN programming language. Considering the change in blade’s profile and the wavy characteristics of the liquid film, the compressor’s performance deterioration is calculated. The compressor and combustor’s deterioration data are imported to a gas turbine simulation code, which is upgraded to calculate overall engine’s performance deterioration. The results show a considerable alteration in engine’s performance parameters and arrive at the same conclusions with the relevant experimental observations.

No description available.

The objective of the thesis is to make a critical assessment of the performance of three relatively simple deterministic models of the rainfall-runoff process. The need to evaluate and compare deterministic models arises because of the large number of models which are available in the literature. A number of the available models would appear to be equally suitable for a given situation whereas many models are found to be valid only under the specific range of conditions for which they were developed. Therefore there is a need for guidelines to allow the most judicious selection of a model for a particular set of circumstances. The models used in the study will be tested in a semi-arid catchment to determine their applicability under ephemeral flow conditions

Three-way median polish is used to model the monthly concentrations of three kinds of ions in precipitation, namely sulphate, nitrate and hydrogen ions. In contrast to previous findings that the wet acid deposition had decreased from late 70's to early 80's, the results suggest that there is a V-shaped trend for wet acid deposition during the period of 1980 -1986 with the change point around 1983. Strong seasonality is also discovered by the analysis. Nonparametric monotone trend tests are performed on the data collected from 1980 to 1986 and on the data collected from 1983 to 1986 separately. The results are consistent with the findings from the median polish approach. A nonparametric slope estimate of the trend is obtained for each monitoring station. Based on these estimates, the slope estimate is obtained by Kriging interpolation for each integer degree grid point of longitude and latitude across the 48 conterminous states in the United States. Also, a geographical pattern in the data is suggested by hierarchical clustering and by median polishing. / Science, Faculty of / Statistics, Department of / Graduate

This study gives a phenomenologically based stochastic model of space -time rainfall. Specifically, two random variables on the spatial rainfall, e.g. the cumulative rainfall within a season and the maximum cumulative rainfall per rainfall event within a season are considered. An approach is given to determine the cumulative distribution function (c.d.f.) of the cumulative rainfall per event, based on a particular random structure of space -time rainfall. Then the first two moments of the cumulative seasonal rainfall are derived based on a stochastic dependence between the cumulative rainfall per event and the number of rainfall events within a season. This stochastic dependence is important in the context of the spatial rainfall process. A theorem is then proved on the rate of convergence of the exact c.d.f. of the seasonal cumulative rainfall up to the ith year, i > 1, to its limiting c.d.f. Use of the limiting c.d.f. of the maximum cumulative rainfall per rainfall event up to the ith year within a season is given in the context of determination of the 'design rainfall'. Such information is useful in the design of hydraulic structures. Special mathematical applications of the general theory are developed from a combination of empirical and phenomenological based assumptions. A numerical application of this approach is demonstrated on the Atterbury watershed in the Southwestern United States.

Includes bibliography. / The objective of this thesis is to review existing methods for estimating missing values in rainfall records and to propose a number of new procedures. Two classes of methods are considered. The first is based on the theory of variable selection in regression. Here the emphasis is on finding efficient methods to identify the set of control stations which are likely to yield the best regression estimates of the missing values in the target station. The second class of methods is based on the EM algorithm, proposed by Dempster, Laird and Rubin (1977). The emphasis here is to estimate the missing values directly without first making a detailed selection of control stations. All "relevant" stations are included. This method has not previously been applied in the context of estimating missing rainfall values.

No description available.

The concept of religion and its practice within ancient societies across the world is a subject that has fascinated scientists for centuries. The pre-Columbian Maya codices, first-hand Postclassic hieroglyphic documents, have been examined by hundreds of anthropologists. Analysis of these books has led scientist to hypothesize that these manuscripts were vitally connected to the Maya Postclassic belief system. Understanding the central focus of a civilization's religion and how, why and under what circumstances the religion is practiced truly distinguishes them as a culture. The intent of this thesis is to examine the role of rain in Maya Postclassic religious belief. Through an examination of Postclassic Maya ethnographies, archaeological evidence and the Maya Dresden, Paris and Madrid codices, this thesis evaluates the major theme of rain that is threaded throughout the culture and religion of the Maya people. By cross referencing ethnohistoric, ethnographic and archaeological evidence, it is revealed that rain was a fundamental-part of Maya religious practice as: 1) a symbol of fertility, 2) a phenomenon that people actively sought to control through religious practice and 3) as a fundamental building block of the Maya universe, construed broadly to encompass both the natural and divine elements of the universe.