<p>Tanzania has a characteristic developing economy, which is dependent on agricultural productivity.  About 90% of the total primary energy consumption of the country is from biomass.  Since the biomass is mostly consumed at the household level in form of wood fuel, it is marginally contributing to the commercial energy supply.  However, the country has abundant energy resources from hydro, biomass, natural gas, coal, uranium, solar, wind and geothermal.  Due to reasons that include the limited technological capacity, most of these resources have not received satisfactory harnessing.  For instance: out of the estimated 4.7GW macro hydro potential only 561MW have been developed; and none of the 650MW geothermal potential is being harnessed.  Furthermore, besides the huge potential of biomass (12 million tons of oil equivalent), natural gas (45 million cubic metres), coal (1,200 million tones), high solar insolation (4.5 – 6.5 kWh/m²), 1,424km of coastal strip, and availability of good wind regime (> 4 m/s wind speed), they are marginally contributing to the production of commercial energy.  Ongoing exploration work also reveals that the country has an active system of petroleum and uranium.  On the other hand, after commissioning the 229km natural gas pipeline from SongoSongo Island to Dar es Salaam, there are efforts to ensure a wider application in electricity generation, households, automotive and industry.</p><p> </p><p>Due to existing environmental concerns, biomass resource is an attractive future energy for the world, Tanzania inclusive.  This calls for putting in place sustainable energy technologies, like gasification, for their harnessing.  The high temperature gasification (HTAG) of biomass is a candidate technology since it has shown to produce improved syngas quality in terms of gas heating value that has less tar.</p><p> </p><p>This work was therefore initiated in order to contribute to efforts on realizing a commercial application of biomass in Tanzania.  Particularly, the work aimed at establishing characteristic properties of selected biomass feedstock from Tanzania.  The characteristic properties are necessary input to thermochemical process designers and researchers.  Furthermore, since the properties are origin-specific, this will provide baseline data for technology transfer from north to south.  The characteristic properties that were established were chemical composition, and thermal degradation behaviour.  Furthermore, laboratory scale high temperature gasification of the biomasses was undertaken.</p><p> </p><p>Chemical composition characteristics was established to palm waste, coffee husks, cashew nut shells (CNS), rice husks and bran, bagasse, sisal waste, jatropha seeds, and mango stem.  Results showed that the oxygen content ranged from 27.40 to 42.70% where as that of carbon and hydrogen ranged from 35.60 to 56.90% and 4.50 to 7.50% respectively.  On the other hand, the elemental composition of nitrogen, sulphur and chlorine was marginal.  These properties are comparable to findings from other researchers.  Based on the results of thermal degradation characteristics, it was evident that the cashew nut shells (CNS) was the most reactive amongst the analyzed materials since during the devolatilization stage the first derivative TG (DTG) peak due to hemicellulose degradation reached (-5.52%/minute) compared palm stem whose first peak was -4.81%/minute.  DTG first peak for the remaining materials was indistinct.</p><p> </p><p>Results from the laboratory gasification experiments that were done to the coffee husks showed that gasification at higher temperature (900°C) had an overall higher gasification rate.  For instance, during the inert nitrogen condition, 7% of coffee husk remained for the case of 900°C whereas the residue mass for the gasification at 800 and 700°C was 10 and 17% respectively.  Steam injection to the biomass under high temperature gasification evolved the highest volumetric concentration of carbon monoxide.  The CO peak evolution at 900°C steam only was 23.47 vol. % CO whereas that at 700°C was 21.25 vol. % CO.  Comparatively, the CO peaks for cases without steam at 900°C and 2, 3, and 4% oxygen concentrations were 4.59, 5.93, and 5.63% respectively.  The reaction mechanism of coffee husks gasification was highly correlated to zero reaction order exhibiting apparent activation energy and the frequency factor 161 kJ/mol and 3.89x10⁴/minute respectively.</p> / QC 20100923

The Tonle Sap is the largest and most important natural wetland in Southeast Asia. It covers an area of more than 15,000 km2 with a unique mosaic of natural and agricultural floodplain habitats that coexist with the largest fishery in the Mekong Basin. Accelerating hydropower development and climate change, however, are altering the Mekong’s hydrology, which could negatively affect downstream ecosystems. The Tonle Sap is facing a two-fold problem. First, the link between its hydrology and ecosystem properties is not well understood. Second, potential ecological changes caused by future hydrological disruptions related to hydropower and climate change are unknown. Thus, the main objective of this thesis was to quantify how alterations to the Mekong hydrology could affect the Tonle Sap ecosystem. The following studies were performed to addressed the objective: (1) an assessment of landscape patterns using geographical information and remote sensing tools; (2) an assessment of habitat patterns based on field surveys of water, vegetation, and soils; (3) ecosystem function modelling to simulate net primary production (NPP) as a function of water quantity, sediments, and habitat type; and (4) fauna habitat modelling linking the results from the assessment of landscape patterns to fauna species. The assessment of landscape patterns revealed a distinct relationship between inundation and vegetation. Habitats in the Tonle Sap were divided into five groups based on annual flood duration, as well as physiognomic factors and human activity: (1) open water, (2) gallery forest, (3) seasonally flooded habitats, (4) transitional habitats, and (5) rainfed habitats. Large habitat shifts could occur as a result of hydropower development scenarios by the 2030s; areas optimal for gallery forest could decrease by 82% from baseline conditions, whereas areas of rainfed habitats could increase by 10-13 % (813-1061 km2). The assessment of habitat patterns demonstrated that despite the complexity and intense human use of this ecosystem, the flood-pulse is the underlying driver of habitat characteristics by (1) determining inundation depth and duration; (2) creating the main soils gradient; (3) limiting the area cleared for agriculture; (4) influencing vegetation structure and water quality; and (5) shaping the composition of plant species. The ecosystem function model was used to estimate a reduction of 9-39% in annual NPP caused by different scenarios of hydropower development and/or climate change during 2032-2042. Cumulative impacts from hydropower would disrupt NPP to a greater extent than climate change. The fauna habitat model revealed that species richness was greatest in the gallery forests and seasonally flooded habitats. Animals that permanently reside in or that rely on these habitats to complete essential life-history stages would be the most affected by future changes. This thesis provides the first quantitative formulation that directly links fundamental components of the Tonle Sap ecosystem to its flood-pulse hydrology. It also provides a comprehensive assessment of the impacts of expected hydrological alterations. Hydropower is expected to bring more abrupt and distinct ecological alterations than climate change in future decades. Relative aerial changes to the gallery forests are expected to be greater than in other habitats. A decline of the Tonle Sap’s ecosystem services will occur if appropriate measures are not implemented. These measures include mitigating hydropower alterations, conserving natural habitats in areas that are likely to remain hydrologically undisturbed, restoring natural habitats in projected areas for optimal growth, and optimizing agricultural practices in the floodplain. Research findings from this thesis focused on the Tonle Sap, but given the fundamental commonalities between this system and other large floodplains, the information presented is highly informative to other large flood-pulse driven systems around the globe.

The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters. Their majesty evolves from the significant range of spatial scales they operate over: from the mesoscale, to the larger synoptic-scale. Their associated violent winds and seas, however, are often the cause of damage and destruction for settlements in their path. Between 10/11/07 and 16/11/07, tropical cyclone Sidr formed and intensified into a category 5 hurricane over the southeast tropical waters of the northern Indian Ocean. Sidr tracked west, then north, during the course of its life, and eventually made landfall on 15/11/07, as a category 4 cyclone near the settlement of Barguna, Bangladesh. The storm affected approximately 2.7 million people in Bangladesh, and of that number 4234 were killed. In this study, the dynamics of tropical cyclone Sidr are simulated using version 2.2.1 of Advanced Weather Research and Forecasting — a non-hydrostatic, two-way interactive, triply-nested-grid mesoscale model. Three experiments were developed examining model sensitivity to ocean-atmosphere interaction; initialisation time; and choice of convective parameterisation scheme. All experiments were verified against analysed synoptic data. The ocean-atmosphere experiment involved one simulation of a cold sea surface temperature, fixed at 10 °C; and simulated using a 15 km grid resolution. The initialisation experiment involved three simulations of different model start time: 108-, 72-, and 48-hours before landfall respectively. These were simulated using a 15 km grid resolution. The convective experiment consisted of four simulations, with three of these using a different implicit convective scheme. The three schemes used were, the Kain-Fritsch, Betts-Miller-Janjic, and Grell-Devenyi ensemble. The fourth case simulated convection explicitly. A nested domain of 5km grid spacing was used in the convective experiment, for high resolution modelling. In all experiments, the Eta-Ferrier microphysics scheme, and the Mellor-Yamada-Janjic planetary boundary layer scheme were used. As verified against available observations, the model showed considerable sensitivity in each of the experiments. The model was found to be well suited for combining ocean-atmosphere interactions: a cool sea surface caused cyclone Sidr to dissipate within 24 hours. The initialisation simulations indicated moderate model sensitivity to initialisation time: variations were found for both cyclone track and intensity. Of the three simulations, an initialisation time 108 hours prior to landfall, was found to most accurately represent cyclone Sidr’s track and intensity. Finally, the convective simulations showed that considerable differences were found in cyclone track, intensity, and structure, when using different convective schemes. The Kain-Fritsch scheme produced the most accurate cyclone track and structure, but the rainfall rate was spurious on the sub-grid-scale. The Betts-Miller-Janjic scheme resolved realistic rainfall on both domains, but cyclone intensity was poor. Of particular significance, was that explicit convection produced a similar result to the Grell-Devenyi ensemble for both model domain resolutions. Overall, the results suggest that the modelled cyclone is highly sensitive to changes in initial conditions. In particular, in the context of other studies, it appears that the combination of convective scheme, microphysics scheme, and boundary layer scheme, are most significant for accurate track and intensity prediction.

The eastern North Pacific Ocean has the highest density of tropical cyclone genesis events of any tropical basin in the world, and many of these systems form near land before moving westward. However, despite the level of tropical cyclone activity in this basin, and the proximity of the main genesis region to land, tropical cyclone behavior in the eastern North Pacific has been relatively unexplored. When synoptic conditions are favorable, moisture from northward-moving tropical cyclones can be advected into northern Mexico and the southwestern United States, often leading to the development of summertime thunderstorms during the North American monsoon season. An interaction with a mid-latitude trough produces the most rainfall, and the spatial variability of precipitation is greatly affected by the complex topography of the region. Moisture can be advected from a tropical cyclone around the subtropical ridge in place for much of the eastern North Pacific hurricane season and contribute to precipitation. This ridge, when it extends westward over the Pacific Ocean, can also prevent tropical cyclone moisture from impacting the southwestern United States. Northward-moving tropical cyclones often enter an environment with decreasing sea surface temperatures, increasing vertical wind shear, and meridional air temperature and moisture gradients. These key ingredients for extratropical transition are generally present in the eastern North Pacific, but the subtropical ridge prevents many named systems from moving northward, and only 9% of eastern North Pacific tropical cyclones from 1970 to 2011 complete ET according to cyclone phase space. However, over half of the systems that do not complete ET dissipate as cold core cyclones, a structural change that has yet to be explored in other tropical basins. It is difficult to estimate tropical cyclone intensity in a vast ocean area with few direct measurements available. The deviation angle variance technique, an objective method independent of the current techniques widely used today, was successfully applied to seven years of eastern North Pacific tropical cyclones. The RMS error of 13.5 kt for all seven years is comparable to the RMS errors found for other basins.

熱帶曲線(tropical curves) 是定義在熱帶半環(tropical semiring) 上的代數曲線。熱帶曲線是古典代數曲線經由某些賦值(valuation) 的映像，所以許多重要的代數曲線性質也同樣發生在熱帶曲線上。本篇論文我們試著將熱帶曲線圖形化。 首先，我們根據熱帶曲線的理論發展出幾個繪出熱帶曲線的演算法。再者，我們以電腦程式語言Python 去實現這些算演算法。我們發展的是跨平台的程式碼，可以在Linux, Mac OS X, Windows 等作業系統執行。 / Tropical curves are algebraic curves dened over the tropical semiring. They are the images of classical algebraic curves under some valuation maps, so reect many important properties of classical algebraic curves. In this thesis, we try to visualize tropical curves. We study the theory of tropical curves and develop several algorithms to draw the graphs of tropical curves. Furthermore, we implement these algorithms in Python programming language. These codes are cross-platform, running on Linux, Mac OS X, and Windows.

Tropical montane cloud forests (TMCF) are one of the most fascinating, but least understood ecosystems in the world, and the interest in the carbon (C) cycle of TMCFs with regard to carbon sequestration and storage practices has increased rapidly in recent years. One feature that prevails in all TMCFs is a decrease in aboveground net primary productivity (ANPP) and standing biomass and leaf area index (LAI) with increasing altitude, together with the stunted growth form of the trees. This thesis focuses on the input part of the TMCF C-cycle, and investigates the controlling factors on photosynthesis on a leaf, canopy, and ecosystem level in the Kosñipata valley in south east Peru, on the eastern slope of the Andes (13º11’28’’S / 71º35’24’’W). Leaf traits are known to relate to foliar C-exchange, and compared with other altitudinal transect studies of TMCFs, the studied sites had similar altitudinal trends for foliar nitrogen (N) content (though not for phosphorus) and leaf mass per area (LMA), with N content decreasing and LMA increasing with altitude. N concentrations were relatively high and LMA values relatively low, but this observed relationship was consistent with those found in global leaf trait surveys. Examining plant stoichiometry (i.e. N:P ratios), the data suggests that unlike the general hypothesis, the Kosñipata forests are not N limited, except for the study site at 2990 m a.s.l. At the 2990 m a.s.l. site, which is the focal study site of the thesis, photosynthetic parameters Vcmax (the carboxylation efficiency of the Rubisco protein) and Jmax (the electron transport efficiency) proved to be similar to those found in lowland tropical rainforest leaves when expressed on an area basis and standardised to 25 °C (55.6 ± 2.6 and 106.5 ± 5.2 mmol m-2 s-1, for Vcmax and Jmax, respectively). However, when standardised to the mean ambient TMCF temperature of 12.5 °C, both photosynthetic parameters were much lower than ambient tropical rainforest Vcmax and Jmax values. The TMCF Jmax -Vcmax relationships were steeper than found in other tropical biomes, indicating a possible adaptation to the lower light availability in TMCFs because of frequent cloud cover, or a consequence of little atmospheric evaporative demand, which is also due to the humid conditions in this forest type. Although N-Vcmax relationships were significant (P<0.05), the fit was not very strong and the relationship between nitrogen use efficiency (NUE) and Vcmax indicates that TMCF species can be regarded as a different plant functional type compared with other tropical forest types. Diurnal measurements of net photosynthesis (A), stomatal conductance (gs) and leaf water potential (Yleaf) showed that different TMCF species experienced non-contrasting diurnal patterns of Yleaf and gs in the dry season. The observed patterns suggest that some TMCF species can be classified as isohydric species, while others behave anisohydrically. Additionally, in situ gs was not very responsive to these to the range of experienced photosynthetically active radiation (PAR), vapour pressure deficit (VPD) or soil water content (SWC), leading to the conclusion that in the studied TMCF, drought stress does not play a role in C-uptake. When using the measured photosynthetic parameters for up-scaling C-uptake to stand scale with a Soil-Plant-Atmosphere model, simulated annual gross primary productivity (GPP) was 16.24 ±1.6 T C ha-1 yr-1, which is about half the GPP observed in neotropical lowland rainforests. Analyses of the modelled results showed that GPP in this TMCF is mostly controlled by temperature, PAR and leaf area index (LAI) and when increasing these three factors to values found in tropical lowland forest, GPP increased up to 75%. In addition, the modelled results indicate that hydraulic limitations on TMCF C-uptake are very unlikely under current climatic conditions. The modelled results also showed that increases in radiation as a result of less cloud cover do not translate to straightforward increases of GPP. The cloudy conditions of TMCFs, which reduced incident PAR in TMCFs, should therefore not be regarded simply as a negative control on TMCF GPP. Instead, the increase in fraction of diffuse radiation partially offsets the decrease in GPP following the reduction in PAR. Overall, the results of this study show that leaves of Andean TMCF forests have similar C-uptake capacity to tropical lowland rainforests when standardized to similar temperatures, but that for in situ C-uptake temperature, radiation and LAI are the key controls.

At present there is uncertainty over the response of neotropical ecosystems to the climatic changes of the Quaternary. The majority of vegetation reconstructions from the region are derived from fossil pollen records extracted from lake sediments. However, the interpretation of these records is restricted by limited knowledge of the contemporary relationships between the vegetation and pollen rain of neotropical ecosystems, especially for more open vegetation such as savanna and dry forest. This research aims to improve the interpretation of these records by investigating the relationship between the vegetation and modern pollen rain of different savanna and seasonally dry tropical forest (SDTF) ecosystems in Bolivia using artificial pollen traps and surface lake sediments to analyse the modern pollen rain. Vegetation data is used to identify taxa that are floristically important within the different ecosystems and to allow modern pollen/vegetation ratios to be calculated. The modern pollen rain from the upland savanna is dominated by Moraceae/Urticaceae (35.1%), Poaceae (29.6%), Alchornea (6.1%) and Cecropia (4.1%), whilst the seasonally-inundated savanna sites are dominated by Moraceae/Urticaceae (30.7%), Poaceae (19.5%), Cyperaceae (14.0%) and Cecropia (7.9%). These two different savanna ecosystems are only slightly differentiated by their modern pollen rain. The main taxa in the modern pollen rain of the upland SDTF are Moraceae/Urticaceae (25.8%), Cecropia (10.5%), Acalypha (7.6%) and Combretaceae/Melastomataceae (6.7%). Seasonally-inundated SDTF is dominated by Cecropia pollen to the extent that it was removed from the pollen sum and the main non-Cecropia pollen types are Moraceae/Urticaceae (39.0%), unknown type df 61 (6.4%), Asteraceae (6.3%), Celtis (6.0%) and Physocalymma scaberrimum (4.9%). These two SDTF ecosystems are well differentiated by their modern pollen rain, implying that they may be defined in fossil pollen records. The modern pollen rain obtained from the surface lake samples is generally complementary to that obtained from the artificial pollen traps for a given ecosystem. All sites have a high Moraceae/Urticaceae pollen signal due to effective dispersal of this pollen type from areas of evergreen forest in close proximity to the study sites. The savanna sites show lower Poaceae percentages than have been previously reported in the literature by some authors and this raises the possibility than the extent of this ecosystem in the past may have been underestimated. Modern pollen/vegetation ratios show that many key vegetation types are absent/under-represented within the modern pollen rain.

When a tropical cyclone (TC) is within 360 nautical miles of Kadena AB, the Air Force's Typhoon Determination (TYDET) program is used to estimate TC-induced winds expected at the base. Best-track data and Joint Typhoon Warning Center (JTWC) forecasts are used to evaluate systematic errors in TYDET. The largest contributors to errors in TYDET are a systematic error by which wind speeds are too large and the lack of size and symmetry parameters. To examine these parameters, best-track and forecasts are used to classify TCs as small or large and symmetric or asymmetric. A linear regression technique is then used to adjust TYDET forecasts based on the best-track and forecast position, size, and symmetry categories. Using independent data, over 65 percent of the overall cross-wind forecasts were improved and more than 60 percent of the cross-wind forecasts were improved when verifying conditions noted a cross-wind of 20 knots or greater. The effectiveness of the corrections and implications for TYDET forecasts are examined in relation to errors in forecast data used to initialize TYDET. A similar approach as developed here for the TYDET model at Kadena AB is proposed for other bases within the Pacific theater.

The cohomology of moduli spaces of curves has been extensively studied in classical algebraic geometry. The emergent field of tropical geometry gives new views and combinatorial tools for treating these classical problems. In particular, we study the cohomology of heavy/light Hassett spaces, moduli spaces of heavy/light weighted stable curves, denoted as $\calm_{g, w}$ for a particular genus $g$ and a weight vector $w \in (0, 1]^n$ using tropical geometry. We survey and build on the work of \citet{Cavalieri2014}, which proved that tropical compactification is a \textit{wonderful} compactification of the complement of hyperplane arrangement for these heavy/light Hassett spaces. For $g = 0$, we want to find the tropicalization of $\calm_{0, w}$, a polyhedral complex parametrizing leaf-labeled metric trees that can be thought of as Bergman fan, which furthermore creates a toric variety $X_{\Sigma}$. We use the presentation of $\overline{\calm}_{0,w}$ as a tropical compactification associated to an explicit Bergman fan, to give a concrete presentation of the cohomology.

No description available.