• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 58
  • 10
  • 10
  • 6
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 133
  • 22
  • 17
  • 17
  • 15
  • 15
  • 14
  • 14
  • 13
  • 12
  • 12
  • 11
  • 10
  • 10
  • 10
  • 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.
51

Improving the bioconversion of lignocellulosic feedstock to bio-fuels and chemicals

Kumi, Philemon James January 2015 (has links)
This study investigated the fate of lignocellulosic biomass (wheat-feed and perennial rye grass) in different anaerobic digestion systems, evaluating the role of substrate specificity on the pattern of degradation. The two-stage (biohydrogen-biomethane) anaerobic system was found to be more effective in the degradation of lignocellulose, when compared to the conventional single-stage system. The perennial rye grass substrate possessed about 21% higher holocellulose concentration when compared to the wheat-feed; its exploitation in the acidogenic digestion was however poor, resulting in a 2.9% lower biogas yield in a equivalent two-stage system. The study therefore developed a treatment technique involving the use of cellulase and ferulic acid esterase enzyme combinations for the treatment of perennial rye grass. The enzyme cocktail at 0.202 ml enzyme/g VS added resulted in efficient bioconversion of the complex polymers to soluble carbohydrates, evident in the yield increase of soluble COD, to 321.0±10.9 mg/gVS, a 393.2% yield increase, when compared to the no enzyme added control. The yield of bio-hydrogen after enzymatic addition was 48ml/gVS, 335% higher when compared to the alkaline treatment; and more than seven fold higher than the yield obtained from the fermentation with no pre-treatment. The acetate to butyrate ratio varied from 4:1, when no pre-treatment was used, to 2:1when alkaline pre-treatment was used, then to 1:1 after the enzymatic treatment. The downstream effect of the prior hydrolysis on the subsequent processes to acidogenic fermentation like biomethane and PHA production and lignin recovery were also investigated. The hydrogenic/acidogenic fermentation resulted in methane yield improvement of 45.7%. The study shows that the more effective a hydrolysis procedure is in the depolymerisation of complex polymers, the greater the accumulation of PHA in the PHA biosynthesis operations. The enhanced hydrogenic /acidogenic fermentation having effectively degraded the holocellulose component of the perennial rye grass substrate ensured that relatively high quality lignin was obtained in an Organosolv lignin-extraction procedure. FT-IR profile show less contamination of polysaccharides and proteins in the lignin extracted from the enzymatically enhanced acidogenic fermentation. An evaluation of the economic viability of the investigated secondary processes showed that direct integrations of those processes to the biohydrogen process may not be as economically advantageous, when compared to a 2nd -stage biomethanation system.
52

Variabilidade genética para caracteres de crescimento em progênies de pinhão manso Jatropha curcas /

Fernandes, Kairo Henrique Pereira, 1985- January 2010 (has links)
Orientador: Edson Seizo Mori / Banca: Edson Seizo Mori / Banca: Mauricio Dutra Zanotto / Banca: Léo Zimback / Resumo: O pinhão manso (Jatropha curcas L.) é uma espécie perene com grande potencial para produção de biodiesel, pois apresenta rápido crescimento é de fácil cultivo e com capacidade de adaptação às diversas condições edafoclimáticas. O presente trabalho tem como objetivo avaliar, por meio de teste de progênies, a variabilidade genética de progênies de pinhão manso para as características de crescimento: altura, diâmetro do colo e número de ramos. Foi implantado um teste de progênies na Fazenda São Manuel, localizada no município de São Manuel - SP, pertencente à Faculdade de Ciências Agronômicas, UNESP, Campus de Botucatu. O espaçamento utilizado foi de 4,0 x 2,5 m, em blocos casualizados. Foram analisadas altura, diâmetro da base e número de ramos das plantas de 28 progênies, procedentes principalmente da EPAMIG, e obtidas às estimativas de parâmetros genéticos. As médias de altura e diâmetro foram aos seis meses de 52,38 e 2,91, aos 12 meses 68,87 e 3,98, aos 18 meses 82,31 e 4,23 e aos 24 meses 108,78 e 5,04, respectivamente. Detectou-se diferença estatística pelo Teste F, em nível de 5% de probabilidade, indicando haver variabilidade entre as progênies. As estimativas dos coeficientes de variação genética individual (CVgi) e coeficiente de variação genética de progênies (CVgp) aos 24 meses foram de 26,7 e 13,4% para altura; 15,1 e 7,5% para diâmetro e 21,2 e 10,6% para número de ramos, respectivamente. As estimativas de herdabilidade média de progênies () aos 24 meses foi de 0,36 para altura; 0,35 e para diâmetro e 0,42 para número de ramos, respectivamente. Os resultados obtidos indicam que as progênies de pinhão manso apresentam variabilidade genética para os caracteres avaliados, mostrando potencial para serem utilizadas em programas de melhoramento genético / Abstract: The jatropha (Jatropha curcas L.) is a perennial species with a great potential for biodiesel production, as it offers rapid growth, moreover it is easy to be cultivated and it has a high capacity of adaptability to various soil and climatic conditions. The objective of this research is to evaluate, by progeny test, the genetic variability for the following characteristics of jatropha's progenies; growth, height diameter and number of branches. It has been implanted a progeny test, at São Manoel's farm, located in São Manoel - São Paulo, belonging to the Faculdade de Ciencias Agronomicas, UNESP, Botucatu. The experimental design was random blocs 4,0 x 2,5 m. The project analyzed height, diameter, number of branches of 28 progenies of plants, coming mainly from EPAMIG, and as a result the project obtained estimates of genetic parameters. The average height and diameter in the first six months were 52.38 and 2.91, at twelfth month were 68,87 and 3,98, at eighteenth month were 82,21 and 4,23 and at twenty-fourth month were 108,78 and 5,04. Statistical difference was detected by a F test at 5% level of probability, it indicates variability among the progenies. The coefficient estimates of individual genetic variation and genetic variation of progenies at twenty-fourth months were 26.7 and 13.4% for height, 15,1 and 7,5% for diameter 21.2 and 10.6% for number of branches, respectively. Estimates of heritability at twenty-fourth months were 0.36 for height, 0.35 for diameter and 0.42 for number of branches, respectively. The results obtained indicate that the progenies of jatropha present genetic variability for traits showing potential to be used in breedind programs / Mestre
53

Zjištění a vyčíslení nákladů na výrobu sena v jednotlivých alternativních uspořádáních technologických linek. / The location and exppressing in number costs on production of hay in single alternate of ordering technological line

ŠVARC, Miroslav January 2009 (has links)
The graduation thesis is described economical valuation of production hey. There is described methods and condition of measure consumption a fuel of energetic vehicle and working set and demand of time for provide sinlge technologic operation of harvest. The measure value was used for assesment a general straight cost on the produciton of hey. In the next point is described technologic procedure of pruduction hey and structure technologic line. The one part of graueted thesis is analysis of using areas of perennial grass stands and their characteristic.
54

The development of methods to assess the ecological integrity of Perennial Pans

Ferreira, Martin 30 May 2012 (has links)
Ph.D. / Wetlands play an integral role in the hydrological cycle and biodiversity. Despite this, wetlands have been neglected in terms of research and monitoring in South Africa. This lack of research has become even more insufficient when it comes to endorheic wetlands. Endorheic wetlands in South Africa are known as pans. Pans are isolated depressions that for through wind erosion are generally shallow and lack an integrated drainage. Water gain is depended on rainfall and surface runoff and water loss is largely due to evaporation. Pans can be either ephemeral in nature or can remain inundated for long periods of time. There are close to 5000 pans in the study area of the Mpumalanga province of South Africa. An estimated 40% of these pans are perennial in nature. The little information on the ecology of pans is all focussed on those systems that are ephemeral. The lack of knowledge is, however, not restricted to the ecology of perennial pans but also the management tools available for these ecosystems. Whereas a variety of methods are available to determine the quantity and quality of water needed to sustain riverine systems (and wetlands connected to rivers), there are no such methods for pans. Especially important is the lack in standardised methods to assess the ecological integrity of perennial pans. This is important as perennial pan ecosystems are increasingly under threat from an increase in coal mining and agricultural activities in Mpumalanga. Coal mining activities have increased in the study area due to both an increase in energy demands and the ease of mining coal deposits in the study area. The lack in standardised methods could be as a direct result of the lack in knowledge of the ecology of the perennial pans. The aim of this study was thus to develop standardised methods for assessing the ecological integrity of perennial pans in Mpumalanga by studying the ecology of the pans. The study thus uses a fundamental approach to reach certain applied goals. To achieve the aim, a total of nine pans were included in the study of which seven were surveyed seasonally for two years and two were sampled on a single occasion. Five of these pans were located in the Mpumalanga Lake District (MLD) and were in a relatively pristine condition. The other four pans were impacted either by agricultural activities, mining activities or both. During these surveys, various components of the ecosystem were studied. These components included the spatial and temporal variations in the abiotic components like the physico-chemical characteristics, habitat quality and quantity, and the sediment characteristics. It also included the spatial and temporal variations in the vegetation communities surrounding the pans and the aquatic invertebrate communities within the pans. The aquatic invertebrate communities were assessed based on a taxonomic approach (diversity) and functional approach (biological traits).
55

Philosophia perennis / Perennial philosophy

Šotola, Jan January 2017 (has links)
My diploma thesis researches the concept of perennial philosophy (philosophia perennis, theologia prisca) and its development in the history of different cultures of the World. As I claim, the concept of Perennialism presents a useful means of understanding of different cultures distanced from us in time and space, including the history of the culture of ours. Perennialism shows, that Wisdom is not an exclusive property of just one civilization, but a common heritage of the Humankind as a whole. Further, it points to mutually beneficial influence of different cultures of the Globe. Throughout the paper, my focus lies on the development of philosophia perennis in the Islamic civilization, particularly on Sufism. Before being demolished by the rise of nationalism, the Sufist philosophy enabled a peaceful coexistence and dialog between different cultures and religions. The development of Perennialism is further studied in the philosophy of european Renaissance, where it was first tolerated by the Catholic Church, later to be abandoned, unfortunately (with few exceptions), during the Reformation and the Thirty Years' War. In the current pedagogical practice, the conception of philosophia perennis may become means of highlighting the common grounds of different cultures in the times of culminating...
56

Evaluation of different temperature winter fodder species (Festulolium hybrids, dactylis species, lolium hybrids) and grass-legume mixtures in the warmer summer rainfall areas of South Africa

Kabine, Ezekiel Simon January 2016 (has links)
Thesis (MSc. (Pasture Science)) -- University of Limpopo, 2016 / South Africa is regarded as a semi-arid area; only 28% of the country receives more than 600 mm rainfall recorded annually. Sustainable utilization of cool season fodder grasses in summer rainfall areas to produce winter animal feed remains a major problem. Farmers are affected by a shortage of adequate, good quality herbage for livestock during winter and dry periods on commercial farms. The study aimed to evaluate and compare the production potential of six Festulolium hybrids, three Dactylis species, and five Lolium hybrids and three grass-legume mixtures in the summer rainfall area. A total of 17 cultivars were evaluated for their DM production under the treatment of different fertilizer levels on three planting dates (16 March 2011, 21 April 2011 and 4 April 2012). The study was carried out at Hygrotech Seed Company (Experimental site), Dewagensdrift in Moloto Village outside Pretoria in the Gauteng Province. Data was collected on a monthly basis from sub-plots of 1 m x 1 m (m2) in 51 plots of 1.5 m x 6 m (9 m2), with nine rows that were 10 cm apart arranged under RCBD with three replicates per cultivar. Harvested fresh samples were taken, weighed, dried at 60ºC until they reached a constant dry weight and weighed to determine DM content. A Fischer’s protected LSD at the 5 % level was performed to compare the treatment means. Over a period of three years of study, it shows that the low fertilizer level resulted in the lowest DM production, with no significant difference occurring between medium and high fertilizer levels. To achieve optimum DM production with minimum cost medium fertilizer is recommended. The cultivars responded differently to the three different planting dates. The time of planting had an effect on DM production in winter. It is recommended that Festulolium hybrids and Lolium hybrids be planted earlier (March) for better DM production in winter. / National Research Foundation (NRF)
57

A Net Plankton Survey of a Small Perennial Pond

Legett, Jesse Harrison 08 1900 (has links)
This thesis resulted from an examination of Lake Worth plankton in comparison to plankton found in similar bodies of water throughout the United States.
58

A Comparative Analysis of the Nutrient Composition and Digestibility of California Perennial and Annual Grasses at Four Stages of Growth

Cromer, Elaina 01 July 2017 (has links)
Beef products represent the fourth largest agricultural commodity in the state of California, valuing more than $3 billion from 2013 to 2015 (CDFA, 2016) and procure 90% of the income for the range livestock industry (FRAP, 2003). Forages found on California’s coastal, desert, foothill, and mountain ranges are the basis of the state’s beef cattle industry. Understanding their nutritional quality of these forages is important for their effective use (George et al., 2001a; Waterman et al., 2014). The objectives of this research were to investigate the nutritional characteristics, and in situ digestbilities in Angus beef cattle, of common California annual and perennial grasses: wild oats (Avena barbata and Avena fatua), soft chess (Bromus hordeaceous), filaree (Erodium botrys), Italian ryegrass (Lolium multiflorum), blue wildrye (Elymus glaucus), creeping wildrye (Leymus tritichoides), melic (Melica californica, Melica imperfecta, Melica torreyana), foothill needlegrass (Nasella lepida), purple needlegrass (Nasella pulchra). Nutritional composition as a percentage of dry matter (crude protein, CP; neutral detergent fiber, NDF; acid detergent fiber, ADF; and acid detergent lignin, ADL) and digestibilities were compared at four growth stages: late vegetative (LV), early reproductive (ER), late reproductive (LR), and dry (D). Plant samples were collected in San Luis Obispo County, CA. Crude protein concentrations decreased, and fiber concentrations increased, with maturity (P ≤ 0.05). Perennial grasses contained more NDF and ADF than annual grasses, across all growth stages (P ≤ 0.05). Annual grasses were significantly higher than perennials in dry matter digestibility (%DMD) at the 48 h incubation, when averaged across all growth stages (P ≤ 0.05); and at the LR and D stages, when averaged across all incubation periods (P ≤ 0.05). Within the annual grasses, %DMD was similar between ER, LR, and D stages. Within the perennial grasses, %DMD was similar between the LR and D stages (P ≤ 0.05).
59

Multifunctional production systems in Brazil : Opportunities, barriers, and implementation

Jonson, Sofia January 2020 (has links)
As populations grow and the call for renewable energy increases, so does the demand for biomass. However, the sustainability of biomass production has been debated. Concerns involve both negative environmental impacts from agricultural production, as well as the effects of increased bioenergy use on food security. Multifunctional production systems are a potential solution to these issues where environmental benefits are promoted in addition to maintained or enhanced biomass output. This study investigates multifunctional production systems in Brazil, as well as incentives and barriers for implementation within the Brazilian context. A systematic literature review was used to identify previous research on multifunctional production systems in Brazil. The review was then complemented by semi-structured open-ended interviews with local experts. The study found that even though common terminology from the field of multifunctional production systems was not frequently used in the Brazilian context, the systems were both studied and implemented. It was also concluded that economic feasibility is a prerequisite for successful implementation. However, factors like environmental circumstances, farmers perceptions, knowledge, and traditions are also important. Thus, effective adoption requires strategies combining economic incentives, policy incentives as well as educational tools. / <p>2020-06-13</p>
60

Oberlin's Experimental Hazelnut Orchard: Exploring Woody Agriculture's Potential for Climate Change Mitigation and Food System Resilience

Fireman, Naomi January 2019 (has links)
No description available.

Page generated in 0.071 seconds