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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Multi-analysis of potential and actual above ground biomass in a tropical deciduous forest in Mexico

Corona Núñez, Rogelio Omar January 2017 (has links)
Natural tropical deciduous forest (TDF) is considered with a medium to small height (< 15 m). Particularly, in Mexico TDF shows a remnant of 36.2% of primary forest driving changes in the structure and species composition. This vegetation in Mexico is mainly transformed into grassland for cattle raising, and agriculture, primarily for self-consumption. More information about the ecology and the social pressures on this vegetation can be seen in Chapter I. The general methods, including sampling allocation and collection, characteristics of the study site, as well the procedure of the research proposal is presented in Chapter II. The main aim of this thesis is to improve the accuracy of predictions of net carbon emissions and the spatial distribution of AGB in the Tropical Deciduous Forest of Mexico. To address this aim, it is important to take into consideration the forest structure, spatial patterns and processes in a natural forest in a multi-scale analysis; also, it is necessary to characterize the spatial socio-economic drivers that influence current AGB losses. With the understanding of such elements, it is possible to reconstruct the potential carbon stocks and estimate the allocation of net carbon emissions due to deforestation and forest degradation. This study shows that it is possible to count net carbon emissions caused by deforestation and forest degradation at a landscape scale. To come to such estimates, it was necessary to reduce the different sources of uncertainty. Chapter III explores different elements that drive the AGB allocation in a mature forest. The AGB in the mature forest was considered as the potential AGB that the forest could get assuming that it has reached its steady state. Different field sampling strategies and allometric equations were evaluated to account for uncertainty in the AGB estimations. The results showed that small sampling design (300-400 m2) and large-sized plots (4 ha) produce the same tree distribution for trees: ≥30 cm in DBH as well as in AGB. These results contradict what has been reported for others (Chave et al., 2004 and 2005) when they refer to the general definition of tropical forest. However, those other studies referred to forests with a much higher precipitation and which can be classified as tropical rain (perennial) forest (Chave et al., 2004). In the tropical deciduous forest, the kind considered in this study, AGB tends to be allocated in small-sized trees. Diverse biophysical characteristics that may drive AGB allocation were considered over different spatial scales. Water stress was the main driver for AGB density at different spatial scales. Nutrients showed little significance to explain AGB as other studies have suggested in secondary forests and/or chronosequences. With this understanding, Chapter IV shows the use of different multi-variable models. Parsimonious models were the result of the variables selection and sensitivity test. Most of the methodologies showed a better performance to explain AGB allocation than a null-model. However, when they were contrasted with independent observations over different spatial resolutions, it was possible to conclude that only GLM was capable of reproducing the spatial patterns, and its estimations were close to observations. Nevertheless, some observations with very large AGB densities were underestimated by the model. This underestimation was related to the presence of few very large-sized trees. These two chapters depict the possibility of accounting for the potential AGB, and the uncertainty, namely whether the landscape could reach it with the absence of human disturbance. Once the potential AGB map was built and validated, it was transformed to carbon stock, using a local carbon concentration estimate. This potential carbon stock map was contrasted to the different available maps of current carbon stocks. Consequently, it was possible to estimate net carbon emissions due to deforestation and forest degradation (Chapter V), suggesting that the general models tend to agree in the total carbon loss. However, there are some spatial discrepancies in the magnitudes of change. Main differences between maps can be reduced by diverse socio-ecological constraints that dominate the landscape. This is important because it may be possible to make future adjustments that would reduce variability, enabling more accurate AGB estimations. However, to individually account for deforestation and forest degradation, more detailed sources of local information are necessary, such as socio-economic variables. Therefore models with a bottom-up perspective would lead to a better understanding and representation of the landscape. Finally, the growing rural population will have larger demands for wood and food, so while remote or protected areas may have the potential for storing high AGB, forest close to settlements and access routes are likely to continue being disturbed, unless affordable alternatives are available for the sustainable use of the forest. In conclusion, the estimation of spatial heterogeneity of AGB in the landscape is of great importance when measuring carbon stocks and ecological dynamics. Various elements influence the AGB allocation in the mature forest. Among all of them, water availability played the most decisive part of various spatial scales. My models support the hypothesis that water availability plays the major role in explaining AGB in Mexico on a local, sub-regional and landscape scale. Model selection produced contrasting AGB estimates and patterns. Moreover, the results of this study tell us that there is not a clear consensus among various current AGB maps. However, they also show that with a multi-model comparison it is possible to identify carbon emissions drivers and calculate total carbon emissions due to forest disturbances. Socio-economic variables played the major role in explaining AGB losses. Therefore, future studies should look into a bottom-up approach for a better understanding and representation of current AGB.
172

Avaliação do processo de dry-hopping durante a maturação de cervejas artesanais / Evaluation of the dry-hopping process during the maturation of craft beers

Quelhas, João Olavo Figueiredo [UNESP] 17 March 2017 (has links)
Submitted by JOÃO OLAVO FIGUEIREDO QUELHAS null (olavofq@gmail.com) on 2017-03-29T23:13:49Z No. of bitstreams: 1 João Olavo Quelhas.pdf: 2589215 bytes, checksum: 6917db55e488c1ded8443d00719d55c9 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-30T18:36:37Z (GMT) No. of bitstreams: 1 quelhas_jof_me_sjrp.pdf: 2589215 bytes, checksum: 6917db55e488c1ded8443d00719d55c9 (MD5) / Made available in DSpace on 2017-03-30T18:36:37Z (GMT). No. of bitstreams: 1 quelhas_jof_me_sjrp.pdf: 2589215 bytes, checksum: 6917db55e488c1ded8443d00719d55c9 (MD5) Previous issue date: 2017-03-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O crescimento da produção de cerveja artesanal no Brasil e a consequente utilização de antigas técnicas de produção, como a lupulagem a frio (dry-hopping), esquecida pelas grandes empresas e pouco estudadas, abrem espaço para estudos sobre o melhoramento destas técnicas. Considerando a importância do lúpulo na produção de cerveja, principalmente seu alto teor de compostos considerados bioativos, por exemplo as procianidinas, a lupulagem a frio pode ser uma notável fonte de melhoramento nos aspectos sensoriais da cerveja, assim como no conteúdo de compostos com possíveis benefícios à saúde. Primeiramente, foi analisada a atividade antioxidante, pelos métodos de DPPH e ABTS, de sete variedades de lúpulo (Cascade, Fuggle, Tradition, Saaz, Centennial, Herkules e Magnum), com a finalidade de escolher uma para ser utilizada na lupulagem a frio. O Cascade foi selecionado para utilização na lupulagem a frio, principalmente por ser o atualmente o lúpulo mais produzido e consumido mundialmente. A produção das cervejas se diferenciou apenas na etapa da maturação, onde ela foi dividida em 17 recipientes. Cada cerveja maturou sob diferentes temperaturas (de 0 a 10°C), tempos de contato do lúpulo com a cerveja (de 0 a 20 dias) e concentrações de lúpulo (de 1,5 a 3 gL-1), seguindo um delineamento composto central rotacional, com três repetições do ponto central. As 17 cervejas foram analisadas físico-quimicamente em relação ao extrato original/primitivo, extrato aparente, atenuação aparente, teor alcoólico, amargor, cor, pH, turbidez, compostos fenólicos totais e atividade antioxidante (DPPH e ABTS). Foi realizada também uma análise sensorial, avaliando aceitação pela cor, aroma, sabor e amargor, além da aceitação global. As variáveis analisadas durante a lupulagem a frio não apresentaram influência no produto final em relação as analises físico-químicas e a aceitação sensorial. / The growth of craft beer production in Brazil and the consequent use of old production techniques, such as dry-hopping, forgotten by the large companies and little studied, open space for studies to improve these techniques. Considering the importance of hops in beer production, especially their high content of compounds considered bioactive, for example procyanidins, dry-hopping might be a notable source of improvement in the sensorial aspects of beer, as well as in the content of possible healthy compounds. Firstly, the antioxidant activity of seven hop varieties (Cascade, Fuggle, Tradition, Saaz, Centennial, Herkules e Magnum) was analized by DPPH e ABTS, in order to choose one to be used in the dry-hopping. Among the analyzed hops, the Cascade type was selected and, therefore, used during the dry-hopping process, mainly because it is currently the most produced and consumed hop worldwide. The brewing process was the same until the maturation, when the beer was divided into 17 containers. Each beer matured under different temperatures (from 0 to 10°C), time of contact between beer and hop (from 0 to 20 days) and hop concentration (from 1,5 to 3 gL-1), following a central rotational design, with three replicates of the central point. The 17 beers submitted to physicochemical analysis as original/primitive extract, apparent extract, apparent attenuation, alcohol content, bitterness, color, pH, turbidity, total phenolic compounds and antioxidant activity (DPPH and ABTS). A sensory analysis was also implemented, evaluating the attributes: color, aroma, flavor, bitterness and global acceptance. The variables analyzed during dry-hopping did not show any influence on the final product in the physical-chemical analysis and sensory acceptance.
173

Comportamento das fibras de vidro convencionais em matriz de cimento Portland modificada com látex e adição de sílica ativa. / Behavior of conventional glass fibers in matrix of Portland cement modified with latex and with the addition of silica fume.

Antônio de Paulo Peruzzi 22 July 2002 (has links)
As argamassas e concretos de cimento Portland são materiais de construção duráveis, relativamente baratos que, embora apresentem boa rigidez e adequada resistência à compressão, têm outras propriedades deficientes, tais como: resistência à tração, ao impacto, à fadiga, além de baixa tenacidade e ductilidade. Uma considerável melhora destas propriedades pode ser obtida com adição de fibras, em quantidades adequadas, na composição destes materiais. A utilização de fibra de vidro convencional (tipo E) no reforço das argamassas de cimento Portland, pode ser viável uma vez contornado o ataque do meio alcalino à fibra, principalmente o hidróxido de cálcio Ca(OH)2, produzido na hidratação do cimento. No presente trabalho foi obtida uma menor intensidade de ataque alcalino às fibras de vidro E, por meio da modificação com látex Estireno Butadieno, da adição de sílica ativa em substituição ao cimento Portland e da utilização de ambos concomitantemente. Outro procedimento utilizado, visando uma maior durabilidade das fibras de vidro, foi a proteção da superfície desta fibra com uma película de látex Estireno Butadieno e de uma mistura deste látex e sílica ativa. A eficiência de um e outro procedimento foi verificada por meio da comparação dos resultados de ensaio à tração e flexão, em amostras submetidas a processo de hidratação convencional e acelerado e observações pro meio de microscopia óptica. / Portland cement mortar and concrete are durable building materials, relatively cheap and, despite they display a good rigidity and an adequate compressive strength, they have other deficient properties such as tensile strength, impact, fatigue, beyond low toughness and ductility. A considerable improvement of these properties can be obtained adding fibers, in adequate quantities, in the composition of the materials. The use of conventional glass fiber (E-glass) in the reinforcement of Portland cement mortar can be possible if the attack of the alkaline environment, produced by cement hydration (chiefly by calcium hydroxide), to the fiber is controlled. In this work, a lesser intensity of alkaline attack on the E-glass fibers was succeded through the modification of the Portland cement matrix by styrene butadiene latex, the addition of silica fume or through the utilization of both additives at the same time. Another proceeding, aiming at a greater durability of the E-glass, has been the protection of the fiber surface with a styrene butadiene latex coating or with a mixture of this same latex and silica fume. The efficiency of each proceeding was verified by the comparison of tensile strength and flexural strength in samples submitted to accelerate and conventional hydration processes and by the observation of the interface glass/matrix with optical microscopy.
174

Seismic Analysis of and Provisions for Dry-Stack Concrete Masonry Wall Systems with Surface Bond in Low-Rise Buildings

Eixenberger, Joseph G. 01 April 2017 (has links)
Masonry is one of the oldest forms of construction materials that is still in use today. However, construction practices in the modern age demand faster and more economical practices. Dry-stack masonry, or masonry that doesn't use mortar to bind the blocks together, is a unique system to make masonry more economical. Though several systems of dry-stack masonry have been suggested little to no data exists as most of these systems are patented. This research used dry-stacked normal weight concrete masonry units with an eccentrically placed reinforcement. The wall system is connected through a surface bond and lacks any geometric connection. Previously, research has been conducted on the wall system for its axial compressive capacity, but little information is known about its ability to withstand lateral forces such as earthquakes. Research was conducted on the wall system in order to determine the seismic parameters, including the force reduction factor, overstrength factor, and the displacement amplification factor. To determine these factors the guidelines from the Federal Emergency Management Agency (FEMA) Quantification of Building Seismic Performance Factors 2009 were followed. The guidelines are explicit that both experimental data and computer modeling are needed to quantify these parameters. Experimental data was obtained from a diagonal tension test, and an in-plane shear test. The diagonal tensions test provided preliminary values on the shear modulus and shear resistance. The in-plane shear test was of primary interest and what would be used to verify the computer model. Computer modeling of the wall system was accomplished with Vector 2. Initially the computer modeling was done to reproduce experimental data. Then, a parametric study was performed using the model to see what component of the wall most effected its capacity. This analysis showed that the surface bond was the component of the wall that most affects its capacity. Finally, the computer model was run through the FEMA Far-Field earthquake suite to gather data on the strength and ductility. Values of the force reduction factor, overstrength factor, and displacement amplification factor were determined based on the time history analysis and pushover analysis on the computer model.
175

Factores que influyen en la exportación de Paprika seca (090421.10.90) respecto a la relación comercial entre Perú – México durante el periodo del 2008 - 2018

Pérez Segovia, Jesús Alejandro, Villafuerte Zamora, Ruth Briggitte 04 July 2019 (has links)
El presente estudio de investigación se basa en el análisis de tres variables que influyen en la exportación de paprika seca proveniente de Perú hacia el mercado de México durante el periodo 2008 al 2018. En ese sentido, se consideró necesario analizar las cuotas arancelarias, debido al alto grado de aplicación por parte de México para la importación de paprika seca desde la vigencia del Acuerdo de Integración Comercial en el año 2012. Por otra parte, otra variable que se consideró dentro de la investigación fueron las medidas sanitarias y fitosanitarias, ya que muchas veces estas suelen ejercer como una desviación hacia el comercio, sobre todo en productos agrícolas. Así mismo, como última variable se tuvo en consideración la competencia internacional. Dicha variable fue analizada con el apoyo de entrevistas y la realización de estadística que permitió ver la correlación directa entre los competidores y las exportaciones. Para el análisis de estas variables fue necesario un enfoque mixto, el cual se basó en un análisis estadístico de las exportaciones antes y después de la vigencia del AIC y de la competencia internacional. Además, también se usó las entrevistas especializadas para el estudio de la influencia de las medidas sanitarias y fitosanitarias para las exportaciones de paprika. En cuanto a los resultados, se pudo obtener que la variable más influyente fue la competencia internacional, las medidas sanitarias y fitosanitarias, y en menor medida las cuotas arancelarias de importación. / This research study is based on the analysis of three variables that influence the export of dried paprika from Peru to the Mexican market during the period 2008 to 2018. In that sense, it was considered necessary to analyze the tariff rate quotas, due to the high degree of application by Mexico for the importation of dried paprika since the Trade Integration Agreement entered into force in 2012. On the other hand, another variable that was considered within the investigation was the sanitary and phytosanitary measures, since often these tend to exert as a deviation towards trade, especially in agricultural products. Likewise, international competition was taken into account as the last variable. This variable was analyzed with the support of interviews and the realization of statistics that allowed seeing the direct correlation between competitors and exports. For the analysis of these variables, a mixed approach was necessary, which was based on a statistical analysis of exports before and after the validity of the AIC and international competition. In addition, specialized interviews were also used to study the influence of sanitary and phytosanitary measures for paprika exports. As for the results, it was possible to obtain that the most influential variable was international competition, sanitary and phytosanitary measures and, to a lesser extent, import tariff rate quotas. / Tesis
176

Transpiration and Dry Matter Response to Atmospheric Humidity, Matric Suction, and Fertility

Warrington, Gordon Edgar 01 May 1970 (has links)
Growth chamber studies showed that a relationship exists between transpiration and dry matter production of spring wheat (Tritiaum Aestivum L. var . Thatcher). A temperature of 27 C for a 16-hour day,and 21 C at night were used throughout the experiment. Relative humidities (RH) of 12, 25, 71, and 83 percent and matric suctions of 1, 3, and 9 bars were used a l ong with six fertility levels and a 20-day growing period. An equation was developed from previous equations by De Wit and Arkley to describe the transpiration ratio (Tr = mass of water transpired/mass of dry matter produced) as it relates to evaporative demand conditions measured by humidity and pan evaporation. Time and fertility effects were not included because of insufficient data. As humidity both increases and decreases from 25 percent, the transpiration ratio decreases. Increasing levels of matric suction had an effect on Tr only at 25 percent RH. As fertility increased, Tr decreased toward some minimum level. Tr seems to reach a stable maximum as plants mature under steady state conditions.
177

The Effect of Dry Heating on Alfalfa Seed and Adulterants

Staker, Ernest V. 01 May 1924 (has links)
The relationship of artificial heating to the germination of seeds has been a subject of more or less interest for the last 75 years. Like other research work, experimenters first had their attention called to the problem largely as the result of innate curiosity. They were interested in the result as measured by germinative power, of the application to seeds of different amounts of heat for varying periods of time, consequently many divergent and sundry experiments were carried out. Seeds of a large number of plants have been subjected to tests and the results recorded. The investigations include the effect of heating seeds in soil, in water, in atmospheres of different relative humidities, in carbon dioxid, in ether, in carbon disulphid and in dry air. Each specific experiment has been associated with various temperatures and with various periods of tiem. It is of interest to note that the actual methods used in determining results are about as diversified as the time and temperature. This thesis presents data showing only the effects of dry heating seed at high temperatures. Therefore in discussion of the literature only that material will be considered which has a direct bearing upon that phase of the heating problem.
178

Hydraulic Performance and Vulnerability on Sanitary Sewer Overflow in Southern Pinellas County, FL

Akabogu, Uchechi O. 25 June 2018 (has links)
Rain-induced sanitary sewer overflow due to high infiltration is a significant challenge for many utilities, including Pinellas County utilities. The main aim of this study is to develop a hydraulic model to analyze the performance of the existing sanitary sewer system, especially during intense rainfall events. To calculate the flow inputs for the model, a times series analysis was performed to separate the inflow and infiltration from the actual sewer flow. Using the Stevens-Schutzbach method, daily Base Infiltration (BI) was calculated and was subtracted from the total observed flow to give the Dry Weather Flow (DWF). Adjusting the DWF by the diurnal pattern, residual flows were calculated to test the flow variability in the system and compare to rain events (> 0.5 inches); the residual flow help deduced if there is a significant surface inflow into the system. Using PC SWMM as the hydraulic model, the average DWF was simulated using the average value and the diurnal daily and weekend pattern during the dry weather periods. The calculated BI was added to the model as a direct contribution from the statistical model. Both the average value of DWF and BI were distributed throughout the system for simulation. The simulated flow shows that few downstream manholes surcharges during extreme rainfall events and remained surcharge for over 48 hours. Cross-correlation analysis suggests the rainfall of the past seven days still impacts the BI, with the highest impact on days 1, 4 and 5. The correlogram results were used to develop a regression model, to predict the BI for different rainfall depths, which in turn was used for hydraulic performance analysis. Increasing the rainfall depths and routing the flow using PC SWMM, showed that the hydraulic grade line, number and hours of the surcharged manholes increases as total rainfall depths increases, but no sanitary sewer overflow. Sanitary sewer overflow occurred at the lift station with a design capacity of 200 GPM for all increased rainfall depths. Furthermore, the analysis results can help locate areas where overflow is more likely to occur, and can also help plan and implement a cost-effective rehabilitation program for the existing sewer network.
179

The loss of grain freshness : indicators or storage induced quality loss in dry barley and canola grain

Reuss, Rainer, n/a January 1999 (has links)
The work presented here explores the effect of storage on chemical and other characteristics of dry, free of added chemicals and pest-free barley and canola grain. This was achieved by measuring the changes in a number of variables of grain stored at different temperatures under laboratory conditions and in commercial storage. The following measurements were carried out: Viability, moisture contents (mc), oil contents (oc), whole grain colour, spectrophotometry of grain extracts, hydroxy methyl furaldehyde (HMF), changes in storage atmospheres, organic sulphide levels, tocol concentrations (vitamin E), Iodine Value (IV), Thiocyanogen Value (TV), Peroxide Value (PV), p-Anisidine Value (p-AV) and Acid Value (AV). The mc of canola and barley were within the range considered safe for storage. Oil content of canola did not change significantly with storage. Viability of canola stored at 4 and 25 °C did not change noticeably, but higher storage temperatures resulted in seed death. Barley maintained high viabilities at low temperatures, but was more susceptible to high temperatures than canola. Colour changes of whole barley grain in storage were pronounced and temperature dependent. Colorimetry of whole barley grain showed potential as a tool for monitoring quality changes in storage. Absorption spectra of grain extracts reflected chemical and physiological changes in storage. HMF, an indicator of Maillard browning, accumulated in short to medium term storage at 45°C and in long term storage at 25 and 35°C. Measurement of HMF was considered useful for monitoring quality changes of stored cereal grain. In a study of storage atmospheres, changes in the concentrations of carbon dioxide, carbon monoxide, oxygen, carbon disulphide and carbonyl sulphide were shown to be useful indicators of quality loss of grain in storage. Gas concentrations usually depended on storage temperature and time and reflected the storage history of the commodity. They indicated loss of carbohydrates and lipids by respiration, oxidative damage and deterioration of sulphur containing amino acids and other compounds. Oil quality indicators were consistent with oxidative damage to canola lipids in storage. IV, TV, and p-AV of canola oil did not correlate with quality of commercial samples. However, a relationship between increases in PV and high storage temperatures in canola was shown and AV increased in storage dependent on storage temperature and time. In barley and canola, the concentration of anti-oxidant tocol species (vitamin E) decreased at 35 and 45°C storage dependent on storage time. The overall tocol content as well as vitamin E activity decreased with storage decreasing the nutritional value of the commodities and indicating oxidative damage to lipids. It was concluded that the storage of dry, pest-free whole barley and canola grain at moderate temperatures (25-45°C) resulted in chemical and other changes. The consequence of these changes was a measurable reduction in the freshness of grain relevant to the nutritional, food technological and commercial quality of grain.
180

Sustainability of dryland cropping systems in the Wimmera region of Victoria / y Yvonne L. Postlethwaite.

Postlethwaite, Yvonne L., (Yvonne Lynette). January 1998 (has links)
Bibliography: p. 283-313. / xxxii, 313 p. : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Two systems of dryland cropping, one conventional and one conservation, were studied on the same farm over a period of 10 and 14 years respectively. The conventional cropping system was based on cultivated fallow which served to manage and conserve water, nitrified organic matter and controlled weeds. Stubble was burnt prior to cultivation for the fallow phase, with pasture and cropping phases rotated. The conservation farming system was based on the absence of soil tillage, stubble retention, rotation of a variety of crops and chemical control of weeds. Water conservation was achieved through increased infiltration by improved soil structure, avoidance of compaction, reduced water runoff and reduced evaporation by stubble retention. Overall, the conventional farming system was proven to be unsustainable. The conservation system was sustainable in terms of productivity, profitability and effect on the environmental resources of soil and water. The growing of sorghum as a summer grass in the Wimmera was also found to be an opportunity for improving productivity, profitability and sustainability by controlling winter weeds. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 1998

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