Several species of fishes have been used for cage culture in Taiwan, including cobia, brown croaker, red drum, grouper, red seabream, emperor and snapper. Roughly speaking, the main factors determining the choice of the target species are mainly the selling price deleting the production cost. Different species have different biological characteristics that affect the economical performance. Included were specific growth rates, death or survival within cultural period, and efficiency in food conversion, etc.. By employing and modified the so-called Biomass model used in fishery biology (Kings, 1995), this research integrates the above factors into one single spreadsheet for each individual species, allowing for systematic observation of the continuous change in level of production (in terms of biomass). Through the culturing period, degrade in number was gradually offset by the gain in averaged body weights until a maximum value is reached before going downhill. This gives rise to the optimal solution of yield with the respective culturing period thus required. The results for different species were further compared in terms of expected investment and return by the end of the production. Results from this study showed that cobia has more advantage (in terms of biomass, biovalue and return on investment) than others as the prior choice under the current situation. Basic information for this study included the value of natural mortality, length-and-weigh relationship and the growth equation of the target species. The system was programmed under the EXCEL-Spreadsheet system of the Microsoft Inc. In the future other species of fishes may also be tested as possible candidates for cage culture. The program could also expected to serve as an auxiliary tool in education and fishery extension services.

As a result of concern about the effects of CO2 emssions on the global warming, there is increasing pressure to reduce such emissions from power generation systems. The use of biomass co-firing with coal in conventional pulverised fuel power plants has provided the most immediate route to introduce a class of fuel that is regarded as both sustainable and carbon neutral as it produces less net CO2 emissions. In the future it is anticipated that increased levels of biomass will be required to use in such systems to accomplish the desired CO2 emissions targets. The use of biomass, however, is believed to result in severe fireside corrosion of superheater and reheater tubing and cause unexpected early failures of tubes, which can lead to significant economic penalties. Moreover, future pulverised fuel power systems will need to use much higher steam temeptures and pressures to increase the boiler efficiency. Higher operating temperatures and pressures will also increase the risk of fireside corrosion damage to the boiler tubing and lead to shorter component life. Predicting the remaining service life of superheater and reheater tubes in coal-biomass fired power plants is therefore an important aspect of managing such power plants. The path to this type of failure of heat exchangers involves five processes: combustion, deposition, fireside corrosion, steam-side oxidation, and creep. Various models or partial models each of these processes are available from existing research, but to fully understand the impact of new fuel mixtures (i.e. biomass and coal) and changing operating conditions on such failures, an integrated model of all of these processes is required. This work has produced an integrated set of models and so predicted the remaining service life of superheater/reheater tubes based on the three frameworks which have been developed by analysing those models used in depicting the five processes: one was conceptual and the other two were based on mathematical model. In addition, the outputs of the integrated mathematical models were compared with the laboratory generated data from Cranfield University as well as historical data from Central Electricity Research Laboratories. Furthermore, alternative models for each process were applied in the model and the results were compared with other models results as well as with the experimental data. Based on these comparisons and the availability of models constants the best models were chosen in the integrated model. Finally, a sensitivity analysis was performed to assess the effect of different model input values on the residual life superheater and reheater tubing. Mid-wall metal temperature of tubes was found to be the most important factor affecting the remaining service life of boiler tubing. Tubing wall thickness and outer diameter were another critical input in the model. Significant differences were observed between the residual life of thin-walled and thick-walled tubes.

With the increase in human demands for energy, purpose-grown woody crops could be part of the global renewable energy solution, especially in geographical regions where plantation forestry is feasible and economically significant. However, up to now, it is still a challenging task to accurately and rapidly estimate forest biomass. Various solutions have been developed for estimating forest biomass. As we know, the only way to measure forest biomass implies directly cutting and weighing the mass of all trees in a plot. Unfortunately, the measurements of national-wide forest biomass cannot be conducted now due to restrictions like labor cost, non-destructive measurement requirements, etc. Meanwhile, obtaining permission to fell trees only for scientific purposes in China is difficult. Therefore, in my study, biomass is defined as the aboveground volume of trees as well as stands. Collecting this information at a national scale has been difficult for China because the data are scarce. The forest biomass inventory in some regions of China was designed to use available inventory data, especially volume, to derive biomass estimates. So volume-derived biomass methods have been applied in estimating forest biomass conventionally. In many research sites of my study, only the volume-related information is available in the forest inventory, which requires the volume-based method to understand the biomass yield in practice. Also, many forest scientists use volume-based models and conversion factors (e. g. from a wood density database) to derive the actual forest biomass arithmetically. Therefore, the output of a volume-based model may support many other calculations relevant to the evaluation of tree growth, potential productivity, and carbon stock. There are relatively few studies on biomass models of Short Rotation Forest(SRF) in China, and there is a lack of a general SRF biomass model. Therefore, we carried out a broad survey and critical review of all data from the different regions in China and formed a normalized tree biomass dataset for China. Based on these reasons, the biomass simulation of poplar plantations was carried out. The growth mechanism of SRF was studied on the stand scale. The influence of climate conditions and stand density on tree growth was discussed to achieve a breakthrough in scientific research at the model level. A general SRF biomass model based on growth conditions and planting density was established based on the stand height growth equation. We can summarize the research objectives as follows： ◆To find the influencing factors on the growth of short rotation poplar plantations ◆To find the relationship between biomass and tree height in short rotation poplar plantations ◆Construction and validation of tree height model of short rotation poplar plantations ◆Construction and validation of biomass model of short rotation poplar plantations

When intraspecific individuals differ in resource intake, scramble competition occurs among inferior individuals growing food-dependently. Scramble can be released through predation mortality. As a consequence of this release, production rates in inferior individuals increase and biomass overcompensation in the subsequent life-stages may occur. When intraspecific individuals do not differ in their resource intakes biomass overcompensation does not occur. If an individual changes its resource intake over ontogeny, the balance of intake and losses, its energetics, will change over ontogeny. Furthermore, differences will arise between the energetics of different life-stages. The predominant volume of interspecific competition theory is based on studies assuming no stage-specific differences in energetics, neglecting the influence of ontogeny on community dynamics altogether. We study how an stage-specific differences in energetics affect expectations from conventional competition theory. We use a stage-structured biomass model consistently translating individual life history processes, in particular food-dependent growth in body size, to the population level. The stage-structured population can be reduced to an unstructured population, if the energetics of all individuals are assumed to be equal.  The stage-structured model, however can also describe population dynamics when this equality is broken. We use the stage-structured biomass model to contrast the stage-specific differences resulting in a stage-structured population model, with an unstructured population model assuming no differences between stages. We show that stage-specific differences in energetics can affect competition on various trophic levels. I: In stead of outcompeting each other, a predator can be facilitated by another preying a scrambling prey life-stage of the same prey population. II: In coexistence with their prey, omnivores with an ontogenetic diet shift, where juvenile omnivores feed on resource and adults on prey, affect community structure only as predators, not as competitors to their prey. We show coexistence of omnivore and prey is not possible if the dominating interaction is competition. Feeding on prey, however, alleviates competition with prey and facilitates the introduction of omnivores. III: An ontogenetic diet shift creates niche partitioning, where without it this would result in neutral coexistence of two consumers competing for two resources. IV: Furthermore, predators can change resource requirements of diet shifters such that diet shifters can reduce resources to lower equilibria and sustain higher predator biomass than consumers without stage-specific differences in energetics. / LEREC

There is a widespread distribution of possibly toxic heavy metals, such as zinc, in aquatic ecosystems. Simultaneously aquatic food webs are changing due to declining predatory fish stocks. In this study, I examine how such an alteration of the food chain, the disappearance of a top trophic level, can affect the uptake and transfer of pollutants in lower trophic levels. I investigate a tri-trophic food chain containing resources (zooplankton), consumer fish, and predatory fish and use zinc as an example pollutant. This is done by constructing and adding a pollutant module to a stage-structured biomass model. The combined model is based on a system of eight ordinary differential equations to study the zinc concentrations in the consumer fish population in two scenarios: in the presence or absence of predatory fish, i.e., the food chain consists of either three or two trophic levels. The results show that the removal of the predator affects the concentration of the pollutant in the consumer population. In the absence of predators, the uptake of zinc from food is smaller and the zinc concentration is lower in the consumer fish population. The results remain the same for different values of the pollutant-specific parameters, i.e., uptake rate from water, assimilation efficiency, and efflux rate. This could indicate that food chain dynamics have a strong influence on the uptake and transfer of pollutants. Furthermore, this means that even if the model is parametrized to zinc in this study, the modeling tool can also be used for other pollutants with similar biokinetics as zinc. The results from this study highlight the importance to include food chain structure and dynamics when studying the uptake and transfer of pollutants. The novel knowledge and the developed tool from this study could advantageously be included to a higher degree when discussing the impact of pollution on aquatic ecosystems and mitigation measures. / Det finns en utbredd spridning av potentiellt giftiga tungmetaller, som t.ex. zink, i akvatiska ekosystem. Samtidigt förändras akvatiska födovävar på grund av minskande rovfiskbestånd. I denna studie undersöker jag hur en sådan förändring av födoväven, ett försvinnande av en trofisk toppnivå, kan påverka upptaget och överföringen av föroreningari lägre trofinivåer. Jag undersöker en tritrofisk födokedja som innehåller resurser (zooplankton), konsumentfisk och rovfisk och använder zink som ett exempel på förorening. Detta görs genom att konstruera och addera en föroreningsmodul till en stegstrukturerad biomassamodell. Den kombinerade modellen bygger på ett system med åtta ordinära differentialekvationer för att studera zinkhalterna i konsumentfiskpopulationen i två scenarier: i närvaro eller frånvaro av predatorer, dvs. födokedjan innehåller antingen tre eller två trofiska nivåer. Resultaten visar att koncentrationen av föroreningen i konsumentpopulationen förändras när födokedjan ändras. När rovfiskar saknas i systemet är upptaget av zink från föda mindre och zinkkoncentrationen lägre i konsumentfiskpopulationen. Resultaten förblir detsamma för olika värden på de föroreningsspecifika parametrarna, d.v.s. upptagshastighet från vatten, assimileringseffektivitet och utflödeshastighet, vilket skulle kunna indikera att födokedjans dynamik har ett starkt inflytande på upptag och överföring av föroreningar. Vidare innebär detta att även om modellen har parametriserats till zink i denna studie, så kan modelleringsverktyget även användas för andra föroreningar som har en liknande biokinetik som zink. Resultaten från denna studie understryker vikten av att inkludera födokedjans struktur och dynamik när man studerar upptag och överföring av föroreningar. Den nya kunskapen och det utvecklade verktyget från denna studie skulle med fördel i högre grad inkluderas när man diskuterar föroreningars påverkan på akvatiska ekosystem och vilka åtgärder som bör sättas in för att minska problemen.