To see the other types of publications on this topic, follow the link: Index of crop diversification.
Dissertations / Theses on the topic 'Index of crop diversification'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Index of crop diversification.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Traub, Peter. "Market-oriented crop diversification and regional development in northeast Thailand." Saarbrücken ; Fort Lauderdale : Breitenbach, 1989. http://catalog.hathitrust.org/api/volumes/oclc/22299074.html.
Full text
2
Bittinger, Alison Kay. "Crop diversification and technology adoption the role of market isolation in Ethiopia /." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/bittinger/BittingerA0510.pdf.
Full textAbstract:
The supply of basic necessities, primarily food, in developing countries is an ongoing concern. A crucial component to improving this situation is access to information on the decision environment and behavior of smallholders in these countries. One challenge facing agricultural households is the lack of effective access for input and output markets. The markets that do exist often fail to facilitate efficient trade between buyers and sellers. Smallholders are forced to adjust their production behavior to compensate for this lack of market access. The purpose of this paper is to examine the crop diversification and technology adoption decisions made by households, in relation to their distance and, by implication, lack of access to a market center. This thesis uses a dataset that contains information on the production systems of Ethiopian smallholders in 2000/2001. The focus of the analysis is on the determinants of chemical fertilizer adoption, crop diversification levels, and crop choices. A simultaneous equation model is used to obtain estimates for the decisions to adopt chemical fertilizer and diversify crop mix in which the endogenous variables are truncated. In addition, a system of five OLS equations is used to explain the shares of land devoted to major categories of crops (primary staple crops; cereals/pulses; oils/spices; fruits/vegetables; and cash crops). The empirical results indicate that Ethiopian smallholders do react to changes in the level of market access by altering their production behavior.
3
Cossel, Moritz von [Verfasser], and Iris [Akademischer Betreuer] Lewandowski. "Agricultural diversification of biogas crop cultivation / Moritz von Cossel ; Betreuer: Iris Lewandowski." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2019. http://d-nb.info/1183790309/34.
Full text
4
Mandal, Gopal Chandra. "The role of agricultural diversification in rural development: A case study of mountain livelihood systems in the himalayan region of West Bengal." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2802.
Full text
5
Silvertooth, J. C., S. W. Stedman, and J. Tollefson. "Interaction of Pima Cotton Defoliation and Crop Water Stress Index." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/208291.
Full textAbstract:
A single field experiment was conducted in 1989 to evaluate the relationship of crop water status on Pima cotton defoliation by use of a crop water stress index (CWSI) as estimated by infrared thermometry. The entire study area was given the last irrigation uniformly on 24 August, and 20 row plots were outlined for the arrangement of three treatments in a randomized complete block design with three replications. Treatments consisted of making defoliant chemical application at three different targeted CWSI levels (0.40, 0.60, and 0.85). All defoliant treatments consisted of Dropp plus Accelerate (0.4 lb. and 1.5 pt. of material/acre, respectively) applied with a ground rig applicator. Results indicated no distinct advantage in terms of percent defoliation as a function of lower CWSI levels at which defoliants were applied. The defoliations made at 0.40 CWSI did result in more regrowth after 14 and 21 days. It appears from this test that Pima plants will defoliate satisfactorily with proper chemical treatments up to CWSI levels of 0.80. Further desiccation of the crop results in very erratic CWSI readings, resulting in difficulties in applying this technique to defoliation management. It does appear, though, that Pima cotton defoliation can be accomplished when CWSI readings are between 0.5 and 0.8 without substantial regrowth problems, providing precipitation or irrigation events do not occur.
6
Ghaddab, Sarra. "Google Search Volume Index and portfolio diversification using Machine Learning techniques." Electronic Thesis or Diss., Lyon 1, 2025. http://www.theses.fr/2025LYO10003.
Full textAbstract:
Cette thèse vise à évaluer la pertinence de l’indice de volume de recherche Google (GSVI), en tant que mesure de l’attention des investisseurs, dans la prédiction du comportement des marchés boursiers et ses implications pour la prise de décision financière, notamment dans la gestion de portefeuille. Plus précisément, elle examine comment les fluctuations du GSVI affectent les rendements financiers et leurs schémas de corrélation. Dans un premier chapitre, nous explorons l’hypothèse d'efficience des marchés (HEM), un sujet qui reste débattu dans les cercles financiers. En effet, aucune preuve concluante n'a été apportée à ce jour concernant la relation entre le GSVI et l'HEM. Pour y remédier, nous nous appuyons sur les travaux de Škrinjarić (2019) en appliquant des tests de robustesse, en introduisant diverses améliorations économétriques et en incorporant des variables explicatives supplémentaires. En utilisant un modèle de panel dynamique sur un ensemble de données couvrant dix indices européens émergents, déjà étudiés par Škrinjarić (2019), nous réexaminons le rôle du GSVI dans la prédiction des rendements boursiers. Contrairement à l’approche de Škrinjarić, qui a modélisé les séries temporelles de chaque pays indépendamment, en négligeant les interdépendances potentielles entre les marchés, notre étude adopte une approche par les données de panel. Nos résultats suggèrent que le GSVI n’influence pas significativement les rendements boursiers, ce qui signifie qu'il n'offre pas d'opportunités d’arbitrage pour les investisseurs. Ces conclusions soutiennent l'HEM dans les marchés étudiés et mettent en évidence la fragilité des études antérieures face aux tests de robustesse. Le deuxième chapitre comble une lacune dans la théorie de l'attention des investisseurs en s’intéressant aux entreprises de taille moyenne, un segment souvent négligé dans la littérature. Nous avançons que les inefficacités des marchés de capitalisation moyenne seraient plus prononcées que pour les grandes capitalisations, les rendant plus prévisibles à travers l’analyse de l'attention des investisseurs. Ainsi, ce chapitre examine si le GSVI peut prédire efficacement les rendements boursiers des entreprises de taille moyenne. En utilisant des données à haute fréquence, avec des intervalles de 8 minutes, nous contribuons au corpus limité de recherches utilisant des données intra-journalières dans des applications financières. Dans ce cadre, un modèle de régression avec des termes d’erreurs hétéroscédastiques conditionnellement autorégressifs généralisés (GARCH) est utilisé comme modèle de référence pour la prédiction des rendements boursiers, et sa performance est ensuite comparée à celle de modèles de réseaux neuronaux. Nos résultats révèlent que le GSVI influence effectivement les rendements de certaines entreprises, soulignant l’importance d’étendre les études sur l’attention des investisseurs au-delà des grandes capitalisations et de porter davantage d’attention aux entreprises de taille plus modeste. Le troisième chapitre fait progresser la littérature existante sur l'impact de l'attention des investisseurs sur les corrélations de rendements boursiers. Alors que les recherches précédentes se sont principalement concentrées sur les effets directs des volumes de recherche, notre travail est le premier à explorer les effets croisés de l'activité de recherche en ligne sur l'interconnexion des rendements boursiers. En utilisant les corrélations de l'indice de volume de recherche Google (GSVI) comme prédicteurs des co-mouvements de rendements, notre approche représente une innovation majeure dans ce domaine. Nos résultats montrent que les interrelations du GSVI influencent significativement les corrélations des rendements, tant sur les marchés développés qu'émergents. Ainsi, ces interrelations peuvent anticiper des changements importants sur les marchés, ouvrant la voie à des stratégies de gestion de portefeuille plus réactives<br>This thesis aims to assess the significance of the Google Search Volume Index (GSVI), as a measure of investor attention, in predicting stock market behavior and its implications for financial decision-making, particularly within portfolio management. Specifically, it examines how fluctuations in GSVI affect financial returns and their correlation patterns. In a first chapter, we explore the Efficient Market Hypothesis (EMH), a topic that remains a subject of debate within financial circles. Notably, no conclusive evidence has yet been presented on the relationship between the GSVI and the EMH. To address this, we build upon the work of Škrinjarić (2019) by applying robustness tests, introducing various econometric improvements, and incorporating additional explanatory variables. Using a dynamic panel model on a dataset of ten emerging European stock indices, previously studied by Škrinjarić (2019), we re-examine the role of the GSVI in predicting stock market returns. Unlike Škrinjarić’s approach, which modeled time series for each country independently and overlooked potential interdependencies between markets, our study employs a panel data framework. Our findings, derived from a more robust estimation approach, suggest that the GSVI has no significant impact on stock market returns, indicating that internet search queries do not provide viable opportunities for investors to exploit arbitrage. These results support the EMH in the studied markets and highlight the susceptibility of earlier studies to robustness concerns. The second chapter addresses a gap in investor attention theory by examining mid-cap companies, a segment often neglected in the literature. However, we posit that inefficiencies in mid-cap markets are likely more pronounced than those in large-cap markets, making them more predictable through the lens of investor attention. Therefore, this chapter investigates whether the GSVI can effectively predict stock returns in mid-cap markets. Using high-frequency data at 8-minute intervals, we contribute to the limited body of research that employs intraday data for financial applications. Within this framework, a regression model with Generalized Autoregressive Conditional Heteroskedastic (GARCH) error terms is used as a benchmark for predicting stock returns, and its performance is subsequently compared to that of neural network models. Our results reveal that the GSVI does indeed influence the returns of certain mid-sized companies, underscoring the importance of extending investor attention studies beyond large-cap firms and increasing focus on smaller companies. The third chapter advances the existing literature on how investor attention affects stock return correlations. While previous research has largely concentrated on the direct effects of search volumes, our work is the first to explore the cross-effects of online search activity on the interconnectedness of stock returns. By leveraging Google Search Volume Index (GSVI) correlations as predictors of stock return co-movements, our approach represents a key innovation in this field. Our results indicate that GSVI interrelations significantly drive return correlations across both developed and emerging markets. Thus, these interrelations can serve as early warning signals for major market shifts, offering actionable insights for more dynamic portfolio management strategies
7
Garrot, Donald J. Jr, Delmar D. Fangmeier, and Stephen H. Husman. "Scheduling Irrigations on Cotton Based on the Crop Water Stress Index." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/204489.
Full textAbstract:
The Crop Water Stress Index (CWSI) was used to schedule irrigations on drip irrigated cotton research plots in Tucson and on eight acre furrow irrigated fields at the Marana and Maricopa Agricultural Centers. Scheduling irrigations when plots reached 0.30 CWSI units resulted in highest yields with 1403 lbs/acre cotton lint using 33.8 inches of water. The Marana and Maricopa fields yielded 1322 lb/acre on 28 inches and 1767 lb/acre on 58 inches of water, respectively.
8
Perez, Jose 1950. "WATER AND NITROGEN EFFECTS ON THE CROP WATER STRESS INDEX OF COTTON." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275339.
Full text
9
Alou, Abdourahamane 1959. "Vegetative physiology of cotton as related to the Crop Water Stress Index." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276939.
Full textAbstract:
This study was undertaken to investigate Gossypium hirsutum L. reproductive physiology and metabolic activities as they relate to the Crop Water Stress Index. Five treatments were established based on the CWSI. These were the maximum stress levels allowed for each treatment. The indices investigated were .16, .35, .36, .40, and .62. Daily tagging of opened flowers in each treatment was conducted throughout the season. Diffusive resistance, transpiration, apparent photosynthesis, and yield were measured. There was no significant difference in treatment yield. Plants irrigated at stress level either below .30 or above .40, tended to yield relatively low compared to plants maintained between .30 and .40. Floral production, abscission and boll retention were negatively correlated to CWSI. Negative relationships were also found between apparent photosynthesis, transpiration, leaf area and CWSI. A two day lag response was observed between a decrease in CWSI values resulting from irrigation, and daily flowering increase.
10
El-Zayadi, Fawzi. "A genetic analysis of harvest index in barley (Hordeum vulgare L. emend. Lam.) /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65362.
Full text
11
Abdullahi, Abdi Isamail. "Does Export Diversification Boosts Economic Growth in Sub SaharanAfrica Countries?" Thesis, Södertörns högskola, Nationalekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-33724.
Full textAbstract:
Growth induced export has become a major concern for policy makers to transform and upgrade the export composition to achieve economic growth objectives; in this respect, export diversification become at the heart of growth induced export narrative. Nevertheless, this study attempts to find relationship between export diversification and economic growth. To investigate this relationship, a cross-section method is used with averaged data from the period 1991 to 2009 of 41 sub Saharan Africa countries; moreover, diagnostic tests were conducted to ensure the robustness of the model. The empirical result of this study shows positive correlation between export diversification and economic growth which can be concluded that export diversification promotes economic growth.
12
Phillip, Jarryd. "Using international diversification to enhance predicted equity index performance: a South African perspective." Master's thesis, Faculty of Commerce, 2019. https://hdl.handle.net/11427/31830.
Full textAbstract:
In the weak form, the Efficient Market Hypothesis (EMH) states that it is not possible to forecast the future price of an asset based on the information contained in the historical prices of that same asset. Under this assumption, the market behaves as a random walk and as a result, price forecasting is impossible. Furthermore, financial forecasting is a difficult task due to the intrinsic complexities of any financial system. The purpose of this study is to examine the potential of developing an international investment strategy using future index price predictions and offsetting predicted price declines by investing in negatively correlated international markets. Therefore, the first objective of this study was to examine the feasibility and accuracy of using a machine learning technique to model and predict the future price of stock market indices of South Africa (All Share Index) and a variety of other developed and developing international markets, which included South Africa, Brazil, Russia, India and China of the BRIC countries and Italy, France, Netherlands, Switzerland, Germany, Nigeria, Australia, Hong Kong, Saudi Arabia, Japan, the U.S., Turkey and the U.K., which were identified as South Africa’s major trading partners. Secondly, an analysis of market correlation between each country’s equity index and South Africa’s ALSI was conducted to determine which of these international indices were positively and negatively correlated to the South African ALSI. This allowed an extrapolation of potential international diversification opportunities. By using machine learning to predict future price trends of the South African All Share Index (ALSI) within a specified time period, the market correlation aspect of this study was able to suggest possible negatively correlated safe haven markets to invest in to offset predicted losses in an expected declining local market. The study’s major limitations include a single method for regression analysis (GARCH(1, 1)) and a limited number of variables in the feature space when predicting future prices. Additional parameters could prove a more robust modelling technique. The data used was a series of past closing prices of each country’s major index. The data was split into five periods, where each period was assigned an overarching theme based on the prevailing market conditions at the time. The ALSI data set was subjected to a unit root test and found to be non-stationary. The analysis thereafter followed a two-step test, with the first being the determination of market correlation of the South African equity market with other markets, using a generalised autoregressive conditional heteroskedasticity (GARCH (1: 1)) approach given the non-stationary nature of the ALSI historic data. The results showed strong positive market correlations between South Africa and China, India, Nigeria, Russia and Saudi Arabia, and strong negative correlation between South Africa and Australia, Germany, the Netherlands, and the United Kingdom. Secondly, the specific area of machine learning employed in this study was support vector machines, as implemented using Python programming. The results compare the actual index price with those predicted by the model and showed that this technique has the ability to predict the future price of the Index within an acceptable accuracy. The accuracy measure used was the mean relative error which in most cases was calculated to be between 95 and 98 which is considered relatively high. However, the results of the investment approach described above was considered to be too inconsistent to consider this diversification strategy viable. From a South African perspective, this approach has not been documented previously.
13
Sirisup, Siriluck. "Government policy and farmers' decision making in Thailand : the agricultural diversification programme in rice farming areas of the Chao Phraya River Basin, 1993-2000." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/1595/.
Full text
14
Garrot, D. J. Jr, S. Stedman, D. D. Fangmeier, S. H. Husman, and B. Benedict. "Pima Cotton Irrigation Scheduling Using Infrared Thermometers and the Crop Water Stress Index." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/208265.
Full textAbstract:
The Crop Water Stress Index (CWSI) was used to schedule irrigations on Pima S-6 cotton on 12 four-acre furrow-irrigated test plots in Coolidge and 20 drip- irrigated test plots at the Campus Agricultural Center in Tucson. Scheduling irrigations between 0.30 and 0.50 CWSI units resulted in highest lint production and plant water use efficiency at both locations.
15
Husman, Stephen H., Donald J. Jr Garrot, Delmar D. Fangmeier, and Norman F. Oebker. "Sweet Corn Irrigation Scheduling Using Infrared Thermometers and the Crop Water Stress Index." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/214474.
Full textAbstract:
The Crop Water Stress Index (CWSI) was used to schedule irrigations on Jubilee sweet corn on 12 drip- irrigated plots at the Campus Agricultural Center in Tucson. Irrigations were to be scheduled at 0.15, 0.35, and 0.50 CWSI values to represent a wet, medium and a dry treatment. Actual average CWSI values at time of irrigation were for 0.14, 0.36, and 0.48. There were no significant yield or quality differences for the wet and medium treatments with exception of a greater ear diameter in the wet treatment. Yield and quality significantly decreased for the dry treatment scheduled at a CWSI value of 0.48. Irrigation application totals were 26.4, 24.2 and 18.3 inches for the wet, medium and dry treatments respectively.
16
Van, Dyk Francois. "Portfolio diversification index as a measure to improve investment portfolio performance / Francois van Dyk." Thesis, North-West University, 2008. http://hdl.handle.net/10394/4193.
Full textAbstract:
Diversification is one of the three most prominent elements of portfolio management with risk and return being the other two. In addition, diversification is a core objective for combining assets and is a central tenet of portfolio construction. It is also widely known that diversification is concerned with the number of unrelated sources of return and in essence the aim of diversification is to eliminate unsystematic risk from an investment portfolio while systematic risk will remain as it can not be diversified away. This study focuses on the concept of diversification in an investment portfolio setting, while specifically investigating a relatively "new" diversification measure, the Portfolio Diversification Index (PDI).
The objectives of this study are twofold. First, establishing whether or not the PDI is a good diversification measure compared to the conventional/traditional and widely used residual variance method. The traditional method of measuring diversification remains inexact as this method measures portfolio diversification relative to a market index. When the market index itself is, however, poorly or not appropriately diversified it becomes problematic as the diversification measurement of the residual variance method is influenced. The PDI is a diversification measurement concept which is essentially free from the influences of the overall market index. This relatively "new" measure of diversification, the PDI, is based on the number of independent factors observed in a portfolio. These independent factors are quantified using Principal Components Analysis (PCA). In ascertaining the first objective the PDI battles "head-to-head" against the residual variance method of diversification by comparing fund ranking results of five South African unit trusts. This method of testing is used as no suitable statistical method exists. The fund ranking results of the two diversification measures are compared to a number of risk performance measures, including the Sharpe- and Sortino ratios. Extensive use is also made of the Omega ratio in this study as the Omega emerges as the dominant risk performance measure.
The second objective of this study is to determine whether the PDI can be used as a tool by fund managers to assist in constructing funds (or changing the composition of existing fund) to reduce (or minimise) portfolio risk without a concomitant reduction in portfolio return. The PDI is used to determine the most independent factors of a South African unit trust where after' this fund is optimised, using the information of the independent factors, in order to reduce the risk of this fund. The Omega ratio is used to evaluate the results of the PDI while the marginal portfolio diversification concept is also investigated.
A thorough literature study also presents the most relevant and important concepts and topics of the theory, management and construction of portfolios. Throughout the literature study the concept of diversification along with the topics most relevant to diversification are extensively focused and elaborated on.
The method of testing used not only confirms that the PDI is a good diversification measure compared to the residual variance method, but that the PDI can also be used as a tool when constructing (or changing the composition of an existing portfolio) in order to reduce the portfolio risk without a concomitant reduction in portfolio return.<br>Thesis (M.Com. (Risk Management))--North-West University, Potchefstroom Campus, 2009.
17
Copeland, Stephen Mark 1955. "Soil water potential as related to the Crop Water Stress Index of irrigated cotton." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276940.
Full textAbstract:
The application of the crop water stress index (CWSI) method to irrigation scheduling is enhanced by knowledge of the relationship between CWSI and soil water potential (SWP) and how this relationship is affected by soil texture. A study using the same cultivar of cotton on three different soils was conducted in southern Arizona over a single growing season. Detailed data were collected of CWSI and soil moisture content for several treatments that scheduled irrigations at threshold CWSI values. CWSI was correlated with soil water potential values calculated from pressure plate determined moisture release curves. Spatial variability of soil characteristics necessitated use of average rather than plot specific moisture release curves. Analysis showed a linear CWSI-SWP relationship that varied greatly with soil depth and study site. The study concluded that soil profile average SWP alone does not normalize the CWSI between sites with different soil textures.
18
Garrot, D. J. Jr, M. J. Ottman, D. D. Fangmeier, S. H. Husman, and J. M. Harper. "Scheduling Wheat Irrigations Using Infrared Thermometers and the Crop Water Stress Index in Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/201349.
Full textAbstract:
Durum wheat (Triticum turgidum L. var. durum ) is grown as a winter annual crop, normally in rotation with cotton, and in 1989, comprised 121,500 acres in Arizona. Winter rainfall is insignificant, therefore water is supplied totally through surface irrigation. The relationship between the timing and amount of irrigation water applied and grain yields have not been well -defined Field plot studies were conducted in 1986 and 1987 to test the feasibility of using the Crop Water Stress Index (CWSI) to time wheat irrigations and also to determine the relationship among the CWSI, grain production, and water applied The study was repeated at the commercial production level with a grower cooperator in 1989 to determine the usefulness of CWSI scheduling on large farms. Highest grain production was attained when irrigations were scheduled when the CWSI averaged 0.37 and 0.30 units on small plots for 1986 and 1987, respectively. At the grower production level, highest yields were attained when irrigations were scheduled when the CWSI averaged 0.17 units. In 1986 and 1987 scheduling irrigations at lower CWSI values did not significantly increase grain production while requiring more applied water than the optimum CWSI values. Scheduling irrigations at CWSI's exceeding the optimum values did significantly reduce grain production from the optimum, but required less applied water in all three years.
19
Ye, Tao. "Inter-sectoral and Inter-temporal Diversification of Agricultural Disaster Risk : Equilibrium Analysis of Risk Sharing Puzzle and the Role of Government." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/88039.
Full textAbstract:
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(工学)<br>甲第15002号<br>工博第3176号<br>新制||工||1477(附属図書館)<br>27452<br>UT51-2009-R726<br>京都大学大学院工学研究科都市社会工学専攻<br>(主査)教授 岡田 憲夫, 教授 小林 潔司, 教授 多々納 裕一<br>学位規則第4条第1項該当
20
Paut, Raphael. "Analyse des compromis entre diversité cultivée et complexité de gestion à travers le cas d’étude du Verger-Maraîcher : Une approche combinant modélisation et méthodes qualitatives Reducing risk through crop diversification: an application of portfolio theory to diversified horticultural systems Modelling crop diversification and association effects in agricultural systems." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0724.
Full textAbstract:
Les vergers-maraichers sont des systèmes mixtes agroforestiers qui visent à optimiser l'utilisation des ressources spatiales et temporelles en produisant des fruits et des légumes sur la même parcelle. De ce point de vue, ces systèmes semblent en mesure de répondre au double enjeu productif et environnemental auquel l’agriculture est confrontée aujourd’hui. Néanmoins, les vergers-maraichers sont caractérisés par une grande complexité structurale et organisationnelle, car ils combinent deux ateliers très exigeants possédant des dynamiques contrastées. Dans cette optique, les conditions permettant d’obtenir un compromis entre résilience des performances et complexification de la gestion du système nécessitent d’être identifiées.L’objectif de ma thèse est donc de caractériser les compromis entre les bénéfices attendus de ces systèmes et les difficultés engendrées par leur complexité structurelle et organisationnelle. La démarche de recherche s’appuie sur le développement de plusieurs modèles qui mobilisent alternativement (i) la théorie du portefeuille ; (ii) le concept de Surface Equivalente Assolée ; (iii) la modélisation dynamique de type états-contrôles.Ces outils de modélisation sont complétés par une approche compréhensive au travers d’entretiens semi-directifs réalisés auprès de 15 agriculteurs du sud-est de la France. La combinaison de ces différentes approches met en évidence quatre résultats principaux. (i) Les effets de la diversification dans un contexte horticole peuvent permettre de réduire la variabilité de la production globale jusqu’à 77% ; (ii) l’association de cultures, en plus d’augmenter le rendement global, réduit davantage le risque ; (iii) la part relative de l’arboriculture et du maraichage dans l’assolement, couplée à l’allocation du temps de travail entre ces deux ateliers sont des éléments déterminants dans la gestion à long terme de la dynamique du système ; (iv) enfin, gérer la complexité liée à la diversité des cultures et à leur agencement agroforestier implique une reconfiguration des pratiques de gestion.L’ensemble de ces résultats met en évidence que la conduite de ces systèmes permet d’arbitrer entre les différentes dimensions étudiées : réduction des risques, synergies entre cultures, différences de dynamiques entre arboriculture et maraichage, mais également, impact de la configuration agroforestière sur les pratiques agricoles. Ces travaux de thèse permettent ainsi de mieux caractériser les compromis entre les bénéfices attendus des vergers-maraichers et la complexité de leur mise en oeuvre<br>The need to redesign more sustainable agricultural systems able of producing more, especially through intercropping or agroforestry, cannot be achieved without taking into account the essential aspect of production variability. Yet, although many studies have focused on the effect of intercropping on overall production, the particular issue of production variability in such systems remains relatively unstudied. The approach we propose, for a shift towards a sustainable intensification of agricultural systems, considers the dual dimensions of yield and risk in a combined framework for the assessment and the comparison of two diversification strategies: (i) a simple diversification strategy (SDS) considered as an increasing number of crops grown on separate plots within a farm and (ii) an intercropping strategy (IC) considered as a within-plot increased diversity, where more than one species is grown at the same time and place. The two perspectives examined here were Modern Portfolio Theory and Land Equivalent Ratio. The former quantifies the effect of diversification on risk, the latter measures the effect of association on production. This research merges both approaches in a combined framework in order to assess intercropping system performances. By applying our framework to cases selected from the literature, we explored and compared the potential benefits of these two strategies in terms of yield and risk. Results showed that intercropping, in addition to being interesting with regard to yield, can have an additional risk reduction effect compared to a simple diversification strategy. Conversely, some crop mixtures maintained or even increased yield variability. Our work contributes to a better understanding of the possible impacts of diversification strategies on trade-offs between yield and risk, but also underlines the importance of taking yield variability into account in further studies
21
Blomkvist, Oscar. "Smart Beta - index weighting." Thesis, KTH, Matematisk statistik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168745.
Full textAbstract:
This study is a thesis ending a 120 credit masters program in Mathematics with specialization Financial Mathematics and Mathematical Statistics at the Royal Institute of Technology (KTH). The subject of Smart beta is defined and studied in an index fund context. The portfolio weighting schemes tested are: equally weighting, maximum Sharpe ratio, maximum diversification, and fundamental weighting using P/E-ratios. The outcome of the strategies is measured in performance (accumulated return), risk, and cost of trading, along with measures of the proportions of different assets in the portfolio. The thesis goes through the steps of collecting, ordering, and ”cleaning” the data used in the process. A brief explanation of historical simulation used in estimation of stochastic variables such as expected return and covariance matrices is included, as well as analysis on the data’s distribution. The process of optimization and how rules for being UCITS compliant forms optimization programs with constraints is described. The results indicate that all, but the most diversified, portfolios tested outperform the market cap weighted portfolio. In all cases, the trading volumes and the market impact is increased, in comparison with the cap weighted portfolio. The Sharpe ratio maximizer yields a high level of return, while keeping the risk low. The fundamentally weighted portfolio performs best, but with higher risk. A combination of the two finds the portfolio with highest return and lowest risk.<br>Denna studie är ett examensarbete som avslutar ett 120 poängs mastersprogram i Matematik med inriktning mot Finansiell Matematik och Matematisk Statistik på Kungliga Tekniska Högskolan (KTH). Ämnet Smart beta studeras i kontexten av en indexfond, där de olika testade principerna för viktning i portföljerna är: likaviktad, maximerad Sharpe-kvot, maximerad diversifiering, och fundamental viktning användandes av P/E-tal. Utfallet i testerna utvärderas i ackumulerad avkastning, portföljrisk, kostnad att handla i portföljen, och ett antal mått på fördelningen av tillgångarna. Studien går stegvis igenom processen för att samla in, ordna, och ”tvätta” data. En kort förklaring av historisk simulering, metoden för att estimera stokastiska variabler såsom kovariansmatriser, är inkluderad, såväl som en analys av distributionen av data. Processen för att optimera portföljerna och hur regler för att vara en UCITS-fond kan omformas till optimeringsvillkor beskrivs. Resultaten indikerar att alla utom den mest diversifierade portföljen har högre ackumulerad avkastning än den marknadsviktade portföljen under testperioden. I alla testade fall ökar handelsvolymen liksom marknadspåverkan när en annan strategi än marknadsviktad används. Portföljen med maximerad Sharpe-kvot ger en hög avkastning med bibehållen låg risk. Den fundamentalt viktade portföljen ger bäst avkastning, men med en litet förhöjd risk. Kombinationen av de båda metoderna ger den portföljen med högst ackumulerad avkastning och samtidigt lägst risk under testperioden.
22
Fangmeier, D. D., S. H. Husman, and D. J. Jr Garrot. "Irrigation Scheduling Based on the Crop Water Stress Index and Precision Water Application for High Cotton Yield." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/219764.
Full textAbstract:
The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.<br>A modified, low- pressure linear move irrigation system was used to irrigate cotton at the Marana Agricultural Center, University of Arizona in 1985. Irrigations were scheduled using the Crop Water Stress Index (CWSI) for timing and a neutron probe to determine soil moisture deficits. Irrigations were applied when the CWSI reached 0.1 resulting in minimal seasonal water stress. Yields ranged from 3.14 bales /acre to 2.73 bales/acre from 2 acre plots. Total applied water ranged from 31.3 inches to 32.3. Total seasonal rainfall was 2.90 inches.
23
Mazumdar, Deepayan Dutta. "Multiangular crop differentiation and LAI estimation using PROSAIL model inversion." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, c2011, 2011. http://hdl.handle.net/10133/3103.
Full textAbstract:
Understanding variations in remote sensing data with illumination and sensor angle changes is important in agricultural crop monitoring. This research investigated field bidirectional reflectance factor (BRF) in crop differentiation and PROSAIL leaf area index (LAI) estimation. BRF and LAI data were collected for planophile and erectophile crops at three growth stages. In the solar principal plane, BRF differed optimally at 860 nm 60 days after planting (DAP) for canola and pea, at 860 nm 45 and 60 DAP for wheat and barley, and at 860 nm and 670 nm 45 and 60 DAP for planophiles versus erectophiles. The field BRF data helped better understand PROSAIL LAI estimation. NDVI was preferred for estimating LAI, however the MTVI2 vegetation index showed high sensitivity to view angles, particularly for erectophiles. The hotspot was important for crop differentiation and LAI. Availability of more along-track, off-nadir looking spaceborne sensors was recommended for agricultural crop monitoring.<br>xiii, 161 leaves : ill., map ; 29 cm
24
Ames, Santillán Juan Carlos. "Alternativas de diversificación internacional para portafolios de acciones de la Bolsa de Valores de Lima." Pontificia Universidad Católica del Perú, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/114747.
Full textAbstract:
This paper gives an estimation of efficient frontiers for investment portfolios, they include stocks from Lima Stock Exchange General Index, Dow Jones Industrial Average, Gold, Cooper, Fixed Income Instruments of Peruvian government and savings in Peruvian financial institutions. The paper concludes that risk of investment in local portfolio reduces as a consequence of diversification, gold is an important asset and contributes to reduce portfolio risk.<br>El presente trabajo estima la frontera eficiente, en portafolios de inversión diversificados en acciones que componen el Índice General de la Bolsa de Valores de Lima (IGBVL), acciones que componen el Dow Jones Industrial Average (DJIA), oro, cobre, instrumentos de renta fija del Gobierno peruano e instrumentos de ahorro bancario. Se concluye que el riesgo de portafolios de inversión de acciones que componen el IGVBL disminuye como consecuencia de la diversificación; un activo relevante es el oro que contribuye a disminuir significativamente el riesgo del portafolio.
25
Marambe, Kodippili Arachchilage Yahampath Anuruddha Marambe. "Monitoring Crop Evapotranspiration in the Western Lake Erie Basin Using Optical Sensors." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1535362877977252.
Full text
26
Prenger, Jessica J. "Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844.
Full text
27
Sneessens, Inès. "La complémentarité entre culture et élevage permet-elle d’améliorer la durabilité des systèmes de production agricole ? : Approche par modélisation appliquée aux systèmes de polyculture-élevage ovin allaitant." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22505/document.
Full textAbstract:
La spécialisation des systèmes agricoles et des territoires montre ses limites, principalement d’un point de vue environnemental mais aussi économique si les prix augmentent. La diversification et l’intégration de culture et d’élevage au sein des exploitations apparaît être une solution de production plus durable, mais leur fonctionnement n’est pas totalement appréhendé. Nous émettons les hypothèses qu’il existe des conditions d’intégration sous lesquelles les systèmes de polyculture-élevage (PCE) sont effectivement plus durables que les systèmes spécialisés et que les méthodes de caractérisation et d’évaluation des systèmes de polyculture-élevage ne permettent pas d’identifier ces conditions. Dans l’objectif de vérifier ces hypothèses, nous avons développé le modèle Sheep’n’Crop pour simuler des systèmes de polyculture-élevage ovin allaitant contrastés auxquels deux types d’analyses ont été effectuées : (i) analyses d’indicateurs économiques, de productivité et environnementaux (GES, MJ, bilan N) à l’échelle de l’exploitation agricole et des ateliers de production en vue d’évaluer la durabilité des systèmes, et (ii) analyse d’efficience énergétique à partir de la méthode de frontière de production DEA pour caractériser la complémentarité des ateliers de culture et d’élevage. Ces analyses ont été menées sur trois stratégies de production à possibilités d’interactions décroissantes – systèmes intégrés, non-intégrés, diversifiés fictifs – au sein desquels l’organisation culture-élevage (% culture) et la saisonnalité de la production ovine (printemps ou automne) varient. L’évaluation de la durabilité montre que les interactions culture-élevage et une mise-bas de printemps permettent d’améliorer tous les indicateurs de durabilité, mais un pourcentage de culture élevé réduit les performances pour la consommation d’énergie non-renouvelable et le bilan azoté. La caractérisation de l’intégration des systèmes PCE par leur gain d’efficience énergétique – la complémentarité - montre que les systèmes intégrés et non-intégrés simulés sont plus efficients que les systèmes diversifiés fictifs de +6.4% et +0.4%. Le lien entre l’indicateur de complémentarité et la durabilité des systèmes est néanmoins difficile à établir étant donné l’existence de trade-off. Nous recommandons de compléter ces résultats en améliorant la considération des contextes pédoclimatiques et socio-économique, de l’efficience d’échelle de production, du niveau d’intensification de l’atelier animal et des effets agronomiques et techniques des interactions culture-élevage<br>Specialization of farming systems and territories are not environmental-friendly, moreover those systems are threatened by the expected higher prices of inputs of production. Diversification and integration of crop and livestock at the farming system scale appears to be a valuable way to enhance farming system sustainability. We posit that they must be conditions of integration that permit mixed crop-livestock systems to be more sustainable than specialized systems and that existing methods of mixed crop-livestock systems characterization do not permit identifying those conditions. To test those hypothesis, we designed a whole-farm model – Sheep’n’Crop – that permits simulating contrasted mixed crop-livestock systems and evaluating (i) their sustainability through economic, productive and environmental (MJ, GHG, N balance) indicators and (ii) their energetic efficiency through a DEA production frontier analysis in order to characterize the complementarity that exists between crop and livestock subsystems. Those analyses were run on three contrasted farming system strategies, distinguished by a decreasing possibility of interactions between crop and livestock subsystems: integrated systems, non-integrated systems and virtual diversified systems. Those systems are also characterized by various crop-livestock organizations (% of crops) and lambing’s periods (spring or autumn). The analysis of sustainability indicates that crop-livestock interactions and spring seasonality permit enhancing each performance of sustainability. However, a high percentage of crops makes decrease the MJ consumption and N balance performances. The characterization of mixed crop-livestock systems through their energetic efficiency gains – the complementarity – show that integrated and non-integrated systems are respectively more efficient than virtual diversified systems by +6.4% and +0.4%. Comparing the complementarity index and indicators of sustainability of farming systems, we highlighted the existence of trade-off. Before analyzing and identifying the best trade-off compromise, we recommend completing our results by testing various pedoclimatic and socio-economic context, the effect of scale efficiencies, the effect of livestock intensification and increasing agronomic and technical effects of crop-livestock interactions
28
Almeida, Julio Augusto Pires 1958. "Use of infrared thermometry to measure canopy-air temperature difference at partial cover to assess crop water stress index." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/191890.
Full textAbstract:
A study on the potential for extracting canopy temperature from composite scenes of plant and soil background using infrared thermometry was carried out. Using field and laboratory data, Heilman's equation was tested for its sensitivity and ability to predict actual canopy temperature. Using Idso's approach, crop water stress index values were calculated for partial and full canopies. The study showed that under partial canopy situations calculated leaf temperature is very sensitive to soil background and composite scene temperatures and moderately sensitive to canopy emissivity and cover. Negative values as well as values greater than unity for crop water stress index were calculated for partial canopy conditions. Negative values were also reported for the full canopy cover conditions thus, establishing a need for better estimates of data used in calculation of crop water stress index values. Infrared thermometry does not show much promise as an irrigation scheduling technique for canopies under partial cover using the approach investigated in this study.
29
Zeywar, Nadim Shukry 1959. "Effect of sensor placement on the relationships of crop water stress index, soil moisture tension and soil moisture content." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/191981.
Full textAbstract:
A field experiment was conducted to investigate the feasibility of making one measurement of soil moisture tension/content or crop water stress index (CWSI), and from it determine when and how much to irrigate. Cotton (Gossvpium hirsutum C.V. DPL-90) was planted in a sandy loam soil prepared with an underground drip irrigation system. Measurements of soil moisture tension, soil moisture content, plant temperature, and wet- and dry-bulb temperatures were made. The results indicate that soil moisture tension above 0.30 m and soil moisture content above 0.50 m in the root zone can be used as good indicators for CWSI or vice versa. Further work is required using different irrigation systems and different crops in larger land areas.
30
Fortin, Marie-Noël. "La répartition territoriale des produits issus des créneaux du patrimoine québécois /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
Full text
31
Banet, Amanda Inez. "Evolutionary diversification of reproductive modes in livebearing fishes." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957301301&SrchMode=2&sid=4&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268858219&clientId=48051.
Full textAbstract:
Thesis (Ph. D.)--University of California, Riverside, 2009.<br>Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 17, 2010). Includes bibliographical references. Also issued in print.
32
Toureiro, Célia do Carmo. "Procedimentos e metodologias para uma gestão integrada da água em grandes áreas de regadio: modelação com técnicas de detecção remota." Doctoral thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/16047.
Full textAbstract:
Mediante a utilização de tecnologias de deteção remota, integram-se diferentes fontes de dados da
atmosfera e das culturas (imagens da superfície cultivada obtidas por satélite ou por plataforma aérea não
tripulada), com os quais se monitorizam, com elevada resolução espacial e temporal, as necessidades
hídricas das culturas, calculando a evapotranspiração cultural (ETc), indicadores biofísicos e índices de
stress hídrico da vegetação (NDVI, Kc*, Kcb*, CWSI), que indicam a oportunidade e a dotação da rega,
facilitando uma eficiente gestão da água, num regadio sustentável. A análise aplicou-se na área regional
do Perímetro de Rega do Divor, tendo utilizado 7 parcelas experimentais, que são áreas regadas por
rampas rotativas com a cultura do milho, cuja condução agrícola foi da responsabilidade dos respetivos
agricultores.
A tecnologia baseada nas imagens obtidas por satélite parece conjugar-se bem com a utilização de
sensores (ou câmaras fotográficas), em plataformas voadoras a baixa altitude, resolvendo estas os
problemas, inerentes à informação de satélite, nomeadamente à elevada periodicidade e à dependência da
nebulosidade.
Toda esta informação é georreferenciada, podendo servir de suporte à elaboração em SIG de mapas da
situação hídrica e da oportunidade de rega das culturas, que poderão servir de base a um sistema de avisos
de rega aos agricultores e gestão da rega no perímetro ou grande região de regadio; ABSTRACT:Through the use of remote sense technologies, data from different sources of the atmosphere and crops
are integrated (images of the cultivated surface obtained by satellite or by flying unmanned platform),
with which crop water requirements are monitored with high spatial and temporal resolution, by
calculating evapotranspiration (ETc), biophysical indicators and indices of water stress of vegetation
(NDVI, Kc, Kcb, CWSI), indicating the opportunity and the allocation of irrigation, facilitating an
efficient water management for a sustainable irrigated agriculture. The analysis applied to Irrigated
District of Divor, having used 7 experimental plots, which are areas watered by center-pivot systems,
cultivated to corn, the agricultural driving having been the responsibility of the respective farmers.
The technology based on satellite images seems to combine well with the use of sensors (or cameras),
located on low altitude flying platforms, by solving some problems inherent to satellite information, in
particular to the low frequency and the dependence of cloud cover.
All this information is referenced, and can support the preparation of maps with GIS technology,
describing water situation and opportunity of watering crops, which could serve as a basis for a farmers
irrigation advice system and the region or the large perimeter irrigation management.
33
Widodo. "The Effects of Spacings & Cultivars on Biological Yields, Yields, Component of Yield & Harvest Index of Green Bush Snap Bean (Phaseolus vulgaris L.)." TopSCHOLAR®, 1989. https://digitalcommons.wku.edu/theses/2967.
Full textAbstract:
The effects of cultivars and plant spacings on biological yield, seed yield, seeds per pod, average seed weight, and harvest index of beans (Phaseolus vulgaris L.) were studied in 1987 and 1988. Two cultivars, 'Blue Lake 27' and 'Kentucky Wonder 125' and four plant spacings -- 7, 14, 21, and 28 cm, constituted eight treatments that were arranged in a split-plot with four replications. Each experimental unit or hill consisted of five plants -- four in the corners and one in the center of a square. Spacings treatment were established by varying the distance between the center plant and the four corner plants. Corner plants provided competition; only the center plant was harvested for experimental data. The data were subjected to analysis of variance procedure for a split-plot design, assuming a fixed model.
The cultivars had similar biological yield curves during the 1987 growing season and did not differ significantly for biological yield at the final harvest either year. Kentucky Wonder 125 produced significantly higher average seed weight and harvest index, but fewer seeds per pod, than did Blue Lake 274. In 1987, seed yield per plant was higher for Blue Lake 274 than for Kentucky Wonder 125; however, the cultivars did not differ significantly for seed yield per plant in 1988.
Spacing treatment effects were not significant when expressed through seed yield per plant, seeds per pod, average seed weight, or harvest index. Spacings affected biological yield significantly in 1988, but not in 1987. The linear response of biological yield to spacing was positive and significant both years. The linear effect of spacings on pod yield was significant in 1988, but not in 1987.
Drought conditions in 1987 and 1988 adversely affected bean growth and seed production. The experimental error, as evidenced by large coefficients of variation for treatment means, was unusually high. Consequently, some true cultivar and spacing effects may not have been detected.
34
Jones, Brian Paul. "Determination and Manipulation of Leaf Area Index to Facilitate Site-Specific Management of Double-Crop Soybean in the Mid-Atlantic, U.S.A." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31566.
Full textAbstract:
Double cropping soybean after small grain harvest does not always allow sufficient canopy growth to maximize photosynthesis and seed yield. This is due to a shorter growing season and moisture deficits common to the Mid-Atlantic USA. Leaf area index (LAI) is the ratio of unit leaf area of a crop to unit ground area and is a reliable indicator of leaf area development and crop biomass. An LAI of 3.5 to 4.0 by flowering is required to maximize yield potential. Soybean LAI will vary within and between fields due to soil differences, cultivar selection, and other cultural practices. Site-specific management strategies such as varying plant population may be used to manipulate LAI and increase yield in leaf area-limited systems. Furthermore, methods to remotely sense leaf area are in order to facilitate such management strategies in large fields. The objectives of this research were to: i) determine the effect of plant population density on soybean LAI and yield; ii) determine the relationship between LAI measured at different reproductive stages and yield; iii) investigate and validate relationships between LAI and yield for two cultivars in three crop rotations across varying soil moisture regimes; iv) validate relationships found in previous work between soybean LAI and yield across soil moisture regimes in grower fields; and v) determine if normalized difference vegetation index (NDVI) values obtained from aerial infrared images can be used to estimate LAI and soybean yield variability. Increasing plant population increased LAI for cultivars at Suffolk in 2000 and 2001, but LAI increased with plant populations on soils with lower plant available water holding capacity (PAWHC) at Port Royal in 2001. In 2000 at Suffolk, seed yield increased quadratically with increasing population and cultivar did not affect the response. In 2001, no relationship occurred between yield and plant population at either Suffolk or Port Royal, but the relationship of yield and LAI depended on soybean development stage at both sites. However, this relationship was not consistent between sites or years. In another study, crop rotation affected LAI and yield one out of two years. However, LAI and yield in both study years were negatively impacted on soil types with lower PAWHC. Where significant, a linear relationship was observed between yield and LAI for all soil types. Studies on grower fields showed similar linear relationships between yield and LAI. Remote sensing techniques showed promise for estimation of LAI and yield. When obtained at an appropriate development stage, vegetation indices correlated to both LAI and yield, and were observed to be effective as a predictor of LAI until plants achieved LAI levels of 3.5 to 4.0.<br>Master of Science
35
Buwembo, Mark. "An investigation into the relevance of international portfolio diversification from a South African perspective." University of the Western Cape, 2020. http://hdl.handle.net/11394/7363.
Full textAbstract:
Magister Commercii - MCom<br>Diversification is one of the more familiar concepts in finance because of its ability
to curtail risk towards investors. However, for diversification to be efficient, the
assets combined should have inversely related price movements. In the same light,
previous research done on international portfolio diversification has consistently
found that having investments diversified across different global markets that have
low to medium correlations helps to get as close to an optimal portfolio as possible.
However, previous research also indicates that both global financial integration and
exogenous shocks increase correlations among international markets, hence
negating the benefits of international portfolio diversification to an extent.
Therefore, with global integration on the rise, coupled with economic and political
instability in some BRICS nations, the research examines these factors and gauges
the current viability of international portfolio diversification from the perspective
of a South African investor.
36
Collin, Constance. "Towards a working crop insurance market : an integrated strategy of systemic risk management." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100006.
Full textAbstract:
Les pertes de rendement dues au climat sont positivement corrélées. Cela va à l’encontre des principes d’assurance et expose l’assureur à des risques financiers qu’il ne peut supporter seul. Les réassureurs eux-mêmes peuvent être dépassés par les sommes en jeu. Les marchés financiers en revanche possèdent la capacité financière requise et l’effet diversifiant des risques climatiques pourraient intéresser les investisseurs. Une stratégie de gestion du risque systémique consistant pour l’assureur à isoler la partie corrélée du risque rendement et à la transférer aux marchés financiers via des obligations catastrophe est analysée en trois points. Tout d’abord, des modèles de tarification isolant la part systémique du risque sont présentés. Ensuite, la démonstration de la faible corrélation d’une obligation agricole est faite, ainsi que de ses rendements élevés, confirmant son potentiel pour les investisseurs. Enfin, l’évolution de la valeur de marché des compagnies émettrices d’obligations catastrophe est étudiée. Au global, aucun impact n’est détecté. En détail, des émissions répétées favorisent la hausse de la valeur de l’émetteur, et de grosses émissions en favorisent la baisse. Les assurances indicielles sont utilisées comme support de l’étude. Basées sur des proxys de rendement plutôt que sur des rendements réels, elles donnent accès à des bases de données complètes et fiables. Ces travaux contribuent à la littérature restreinte concernant les risques agricoles et leur transfert vers les marchés financiers. Ils fournissent aux assureurs une stratégie alternative de transfert de risque et ouvrent la voie vers des outils innovants d’investissement<br>Crop yield insurance comes with loss correlation, impeding the classical insurance risk pooling. Insurers alone cannot face the high exposure entailed by weather risks, which can even fall beyond the reinsurers’ financial capacity. Financial markets appear as a logical risk-transfer solution, investors being potentially interested by the diversifying effect of weather-linked risks. A systemic risk management strategy consisting for the insurer to isolate the correlated component of the crop yield risk and to transfer it to the financial markets through catastrophe bonds is investigated in three points. First, insurance pricing models separating the risk into a systemic and a non-systemic component are presented. Second, the interest for investors to take part in a cat bond based on agricultural risks is analyzed. The low correlation to financial markets of such bonds and their potentially high returns confirm the attractiveness of this new asset class for investors. Finally, the evolution of the market value of cat bonds issuers is studied. No general evolution is identified, but firms used to issue cat bonds may expect their market value to increase, while the firms issuing the largest bonds may expect their market value to decrease. The study is applied to the case of index insurance, based on yield proxys rather than real yields, which provides detailed data for accurate risk quantification. This work contributes to the still limited literature regarding agricultural risks and insurance by describing an integrated systemic risk management strategy providing insurers with alternative risk-sharing solutions and investors with innovative asset allocation opportunities
37
Narasimhan, Balaji. "Development of indices for agricultural drought monitoring using a spatially distributed hydrologic model." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2727.
Full textAbstract:
Farming communities in the United States and around the world lose billions of dollars every year due to drought. Drought Indices such as the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) are widely used by the government agencies to assess and respond to drought. These drought indices are currently monitored at a large spatial resolution (several thousand km2). Further, these drought indices are primarily based on precipitation deficits and are thus good indicators for monitoring large scale meteorological drought. However, agricultural drought depends on soil moisture and evapotranspiration deficits. Hence, two drought indices, the Evapotranspiration Deficit Index (ETDI) and Soil Moisture Deficit Index (SMDI), were developed in this study based on evapotranspiration and soil moisture deficits, respectively. A Geographical Information System (GIS) based approach was used to simulate the hydrology using soil and land use properties at a much finer spatial resolution (16km2) than the existing drought indices. The Soil and Water Assessment Tool (SWAT) was used to simulate the long-term hydrology of six watersheds located in various climatic zones of Texas. The simulated soil water was well-correlated with the Normalized Difference Vegetation Index NDVI (r ~ 0.6) for agriculture and pasture land use types, indicating that the model performed well in simulating the soil water. Using historical weather data from 1901-2002, long-term weekly normal soil moisture and evapotranspiration were estimated. This long-term weekly normal soil moisture and evapotranspiration data was used to calculate ETDI and SMDI at a spatial resolution of 4km ?? 4km. Analysis of the data showed that ETDI and SMDI compared well with wheat and sorghum yields (r > 0.75) suggesting that they are good indicators of agricultural drought. Rainfall is a highly variable input both spatially and temporally. Hence, the use of NEXRAD rainfall data was studied for simulating soil moisture and drought. Analysis of the data showed that raingages often miss small rainfall events that introduce considerable spatial variability among soil moisture simulated using raingage and NEXRAD rainfall data, especially during drought conditions. The study showed that the use of NEXRAD data could improve drought monitoring at a much better spatial resolution.
38
Odame, Emmanuel A. "Assessing Heat-Related Mortality and Morbidity Risks in Rural Populations and Sub-Populations." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3637.
Full textAbstract:
Heat stress is an environmental and occupational hazard exacerbated by climate change. Rural populations and sub-populations continue to experience disproportionate risks of heat-related impacts due to their low adaptive capacities in terms of infrastructure, information and other resources which are critical in dealing with heat. The study goals were to determine heat-related mortality risks in rural populations globally, explore the contribution of the outdoor work environment and other factors in association with occupational heat-related illnesses (HRI), and assess the risk of heat stress among crop workers using the Wet Bulb Globe Temperature (WBGT). Published peer-reviewed scientific literature on heat-related mortality in rural areas was used to assess heat-related risks among rural populations worldwide. Excess risks of both all-cause and cardiovascular mortalities were found although temperature had a stronger impact on cardiovascular deaths than for all-cause mortality. Also, using cross-sectional data from health screening clinics conducted during the summers of 2014, 2015, and 2016, a total of 425 patient encounters were analyzed using chi-square and logistic regression analyses to determine the role of the outdoor work environment and other factors associated with heat stress. As expected, the outdoor work environment was significantly associated with HRI. Out of the total of 67 HRI cases that were self-reported or diagnosed, 82% (55 cases) worked outdoors. There were nonsignificant elevations in HRI prevalence reported in males, workers below 40 years of age, individuals who have worked in agriculture for ten years or less, and those trained on heat safety. Further, a comprehensive evaluation of heat stress among crop workers was conducted using the four thermal climate factors-- air temperature, humidity, wind speed and solar radiation-- as well as work load and clothing factors. It found both acclimatized and non-acclimatized workers at risk of HRI. Regression analysis revealed that HRI prevalence was strongly correlated with the daily maximum WBGT (R2= 0.89; p= 0.03). Thus, effective heat safety precautions are needed, in addition to acclimatization, to protect vulnerable outdoor workers.
39
Makaudze, Ephias M. "Do seasonal climate forecasts and crop insurance really matter for smallholder farmers in Zimbabwe? Using contingent valuation method and remote sensing applications." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110389049.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xiii, 155 p.; also includes map, graphics (some col.) Includes bibliographical references (p. 149-155). Available online via OhioLINK's ETD Center
40
Cholez, Célia. "Structures de gouvernance des transactions et dynamique des connaissances inter-firmes dans la création de filière : application aux contrats de production dans le secteur des grandes cultures en France." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0075.
Full textAbstract:
La thèse a pour objectif d’analyser comment les structures de gouvernance des transactions impactent la création et la diffusion de connaissances entre firmes, tout particulièrement dans le contexte de nouvelles filières. Elle s’appuie sur plusieurs études de cas de filières de diversification (comme le lin oléagineux ou les légumineuses à graines) qui émergent dans le secteur des grandes cultures, et dont la structuration se base sur des contrats de production. Dans un contexte de transition agroécologique, le développement de ces filières implique des changements techniques et le renouvellement des connaissances des opérateurs. Afin de comprendre les liens entre la coordination contractuelle et les dynamiques de connaissances entre firmes, cette thèse mobilise l’économie néo-institutionnelle, plus particulièrement la théorie des coûts de transaction, ainsi que l’économie de l’innovation et le management stratégique avec un focus sur les théories de l’apprentissage organisationnel. La thèse explique la diversité organisationnelle rencontrée dans les filières selon un arbitrage dépendant du niveau d’incertitude technique dans la filière, i.e. du besoin de connaissances des opérateurs. Elle montre tout d’abord la validité du principe d’alignement de la théorie des coûts de transactions au regard des actifs humains spécifiques déployés dans ces nouvelles filières agricoles. Elle met ensuite en évidence que les structures de gouvernance hybride génèrent des apprentissages inter-firmes car la contractualisation agit comme un artefact cognitif au regard des interactions générées et des dispositifs de capitalisation de la connaissance mis en œuvre. In fine, cette thèse montre que le choix des structures de gouvernance relève d’un arbitrage entre économie des coûts de transaction à court terme et création de valeur à moyen terme via le développement de connaissances<br>This thesis analyses how transaction governance structures foster the creation and diffusion of knowledge between firms, in particular in the context of emerging supply chains. The analysisrelies on several cases studies on crop diversification supply chains (such as linseed, fababean, pea or lupin), based on production contracts in the French field crop sector. In a context of agroecological transition, supply-chain development involves technical changes and a need forrenewing stakeholder’s knowledge. In order to understand the link between contractualcoordination and inter-firms knowledge dynamics, this thesis draws on new institutional economics – especially transaction costs theory – and innovation economics and strategic management,especially organizational learning approaches. This thesis explains the supply-chain organizationaldiversity encountered in accordance with a trade-off that depends on the level of technicaluncertainty in the supply chain itself, i.e. depending on stakeholders’ need for new knowledge.Firstly, we examine the transaction costs theory alignment principle according to specific human assets in crop diversification supply-chains. Secondly, we show that hybrid governance structuresgenerate inter-firm learning. Indeed, contractualization acts as a cognitive artefact by enhancinginterfirm interactions and knowledge capitalization devices. Finally, the thesis shows thatgovernance structures choice depends on a trade-off between short-term transaction costseconomizing and medium-term value creation thanks to knowledge development
41
Hausler, Melanie. "Assessment of vegetation parameters in olive trees in the region of Alentejo. A comparison of direct and indirect methods." Master's thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/4004.
Full textAbstract:
Mestrado em Engenharia Agronómica - Instituto Superior de Agronomia<br>Vegetation parameters, as the leaf area index (LAI) and the ground cover (GC) are commonly related to biosphere processes, being used in models to estimate yield and crop water requirements. Several direct and indirect methods have been developed in the past decades to determine the LAI. However, a simple approach to assess this parameter is still missing. In this study we tested the operability and precision of different methods to calculate the LAI of 6 and 20 year old olive trees (Arbequina and Cobrançosa), under irrigated and non-irrigated conditions in the region of Alentejo. The average LAI on a projected area basis was estimated to be 5.88 and 2.75 m2 m-2 at the irrigated and non-irrigated sites, respectively, corresponding to 1.01 and 1.05 m2 m-2 on a total area basis. Furthermore, a tool was introduced to simplify the decision making between the use of the LAI and the GC. The determination of the GC is much easier than the LAI in practical uses. The average GC was 5.7 m2 under irrigated and 18.0 m2 under non-irrigated conditions. A detailed comparison between direct and indirect methods is given and the future prospective of the decision making tool is discussed.
42
Moot, Derrick J. "Harvest index variability within and between field pea (Pisum sativum L.) crops." Lincoln University, 1993. http://hdl.handle.net/10182/1285.
Full textAbstract:
The association between individual plant performance and seed yield variability within and between field pea crops was investigated. In 1988/89 six F8 genotypes with morphologically distinct characteristics were selected from a yield evaluation trial. Analysis of the individual plant performance within these crops indicated an association between low seed yields and the location and dispersion of plant harvest index (PHI) and plant weight (PWT) distributions. The analyses also showed there was a strong linear relationship between the seed weight (SWT) and PWT of the individual plants within each crop, and that the smallest plants tended to have the lowest PHI values. A series of 20 simulations was used to formalize the relationships between SWT, PWT and PHI values within a crop into a principal axis model (PAM). The PAM was based on a principal axis which represented the linear relationship between SWT and PWT, and an ellipse which represented the scatter of data points around this line. When the principal axis passed through the origin, the PHI of a plant was independent of its PWT and the mean PHI was equal to the gradient of the axis. However, when the principal axis had a negative intercept then the PHI was dependent on PWT and a MPW was calculated. In 1989/90 four genotypes were sown at five plant populations, ranging from 9 to 400 plants m⁻². Significant seed and biological yield differences were detected among genotypes at 225 and 400 plants m⁻². The plasticity of yield components was highlighted, with significant genotype by environment interactions detected for each yield component. No relationship was found between results for yield components from spaced plants and those found at higher plant populations. The two highest yielding genotypes (CLU and SLU) showed either greater stability or higher genotypic means for PHI than genotypes CVN and SVU. Despite significant skewness and kurtosis in the SWT, PWT, and PHI distributions from the crops in this experiment, the assumptions of the PAM held. The lower seed yield and increased variability in PHI values for genotype CVN were explained by its higher MPW and the positioning of the ellipse closer to the PWT axis intercept than in other genotypes. For genotype SVU, the lower seed yield and mean PHI values were explained by a lower slope for the principal axis. Both low yielding genotypes were originally classified as having vigorous seedling growth and this characteristic may be detrimental to crop yields. A method for selection of field pea genotypes based on the PAM is proposed. This method enables the identification of weak competitors as single plants, which may have an advantage over vigorous plants when grown in a crop situation.
43
Weber, Liane de Souza. "Integração de dados espectrais e indicadores meteorologicos por meio de redes neurais para a estimativa de produtividade de cana-de-açucar." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257009.
Full textAbstract:
Orientador: Jansle Vieira Rocha<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola<br>Made available in DSpace on 2018-08-11T14:29:10Z (GMT). No. of bitstreams: 1
Weber_LianedeSouza_D.pdf: 866084 bytes, checksum: 6f14fe14fef394e2bd299f45b7c98915 (MD5)
Previous issue date: 2005<br>Resumo: O presente trabalho descreve um estudo sobre estimativa de safras cujo principal objetivo foi criar uma metodologia de integração de dados de produção, dados espectrais e indicadores meteorológicos por meio de redes neurais artificiais, estabelecendo correlações entre índices de vegetação e de produtividade, com o propósito de estimar a produtividade de cana-de-açúcar. O estudo foi dividido em duas etapas: a primeira correspondeu à obtenção e organização dos dados em um banco de dados com padrões de entrada/saída; a segunda, à implementação e ajuste das redes neurais, por meio de ensembles. O estudo foi realizado em unidades amostrais de produção de uma usina sucroalcooleira no município de Araras-SP. A primeira etapa consistiu na obtenção dos coeficientes de produtividade (kp), por meio da inversão do modelo agrometeorológico de Doorenbos e Kassam (1979), a partir da determinação do balanço hídrico. O resultado deste procedimento mostrou a sensibilidade do coeficiente à variabilidade da produtividade nos talhões. Os dados espectrais das imagens Landsat 7 ¿ ETM+ foram obtidos de correlações descritas na literatura estabelecidas entre o Índice de Vegetação Greenness (GVI), a banda do infravermelho próximo (B4) e a produtividade da cana-de-açúcar. A estratégia para treinamento dos ensembles foi baseada no aprendizado supervisionado aplicado a uma arquitetura Multilayer Perceptron (MLP), com uma camada escondida, método de aprendizado de 2ª ordem e feedforward. Na etapa de treinamento e validação, as redes neurais tiveram como variáveis de entrada os valores de kp, GVI e B4, e como variável de saída a produtividade, que definiram os padrões de entrada/saída. A fase de teste consistiu em implementar a metodologia em um grupo de padrões de entrada não utilizados nos treinamentos. Os resultados mostraram valores de EQM entre 0,03 e 0,51 ton/ha, enquanto que a estimativa da usina errou em média 9,93 ton/ha, o que garantiu o correto ajuste da rede neural quanto à topologia, ao número de iterações e aos algoritmos de aprendizagem. Esta etapa mostrou a capacidade de generalização da rede neural, já que os treinamentos foram realizados a partir de unidades amostrais. O estudo ratificou a aplicação desta metodologia na determinação da estimativa de produtividade de cana-deaçúcar, empregando-a como técnica complementar aos atuais métodos de estimativa agrícola,
sugerindo a ampliação da escala de aplicação para o ambiente de produção da usina<br>Abstract: The present thesis describes a study on crop forecast. Its main purpose was to create a methodology for integrating production, spectral and meteorological data indicators through artificial neural networks, establishing correlations between vegetation index and yield coefficients, aiming at the estimate of sugarcane yield. The study was divided in two parts: the first corresponded to obtaining and organizing data in a database with input/output default; the second corresponded to the implementation and adjustment of the neural network. The study was carried out in sample production units (fields) of a sugarmill agricultural area located in the municipality of Araras-SP, Brazil. The first part consisted in obtaining yield coefficients (kp) through the inversion of the Doorenbos-Kassam (1979) agrometeorological model, based on the determination of the water balance. The result of this procedure showed the coefficient¿s sensitivity to the variability of yield within the sample fields. The spectral data of the Landsat 7 ¿ ETM+ images were obtained from correlations, available in scientific literature, between the Greenness Vegetation Index (GVI), near infrared band, and sugarcane yield. The strategy for training the neural network was based on supervised learning applied to a Multilayer Perceptron (MLP) architecture, with a hidden layer, second order learning method and feedforward. For the training and validation stage, the neural network had as input variables kp, GVI and B4 values, and as output variable the yield, both obtained in the input/output database. The test stage consisted of implementing the methodology in a set of input patterns not used for the trainings. The results showed Mean Square Error (MSE) values between 0,03 and 0,51 ton/ha, while the average error of the sugarmill estimates were 9,93 ton/ha, which showed the correct adjustment of the network concerning topology, number of iterations and learning algorithms. This showed the generalization capacity of the neural network once the trainings were carried out based on sample units. The study ratified the application of this methodology for determining sugarcane yield estimate, employing it as a complementary technique to the present methods of agricultural forecast, suggesting the increase of the application scale to a broader area of the sugarmill production environment<br>Doutorado<br>Planejamento e Desenvolvimento Rural Sustentável<br>Doutor em Engenharia Agrícola
44
Jovana, Bezdan. "PRISTUP MONITORINGU POLJOPRIVREDNE SUŠE NA PODRUČJU VOJVODINE BAZIRAN NA STANDARDIZOVANOM INDEKSU PADAVINA I EVAPOTRANSPIRACIJE." Phd thesis, Univerzitet u Novom Sadu, Poljoprivredni fakultet u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=111002&source=NDLTD&language=en.
Full textAbstract:
U ovoj disertaciji je definisan i predstavljen pristup monitoringu poljoprivredne suše (SPEI-based approach to agricultural drought monitoring - ADM-SPEI) u Vojvodini koji objedinjuje više poznatih i priznatih metoda i kritičko mišljenje eksperata zasnovano na njihovom znanju i iskustvu i pri tome uzima u obzir lokalne specifičnosti agroklimatskih uslova. Iako je kreiran za područje Vojvodine, predloženi pristup monitoringu poljoprivredne suše baziran na SPEI indeksu opisan je generalno kroz tri faze i pripadajuće korake koji su detaljno opisani i objašnjeni što omogućava da se ADM- SPEI pristup modifikuje i primeni u bilo kojim drugim agroklimatskim uslovima. Predstavljeni pristup baziran je na modifikovanom i široko prihvaćenom i korišćenom Standardizovanom Indeksu Padavina i Evapotranspiracije (SPEI). Ovom modifikacijom SPEI je povezan sa specifičnom kulturom što omogućava da se suša, odnosno uslovi vlažnosti analiziraju individualno za specifičnu ratarsku ili povrtarsku kulturu u agroklimatskim uslovima Vojvodine. Kreiranju pristupa monitoringu poljoprivredne suše prethodilo je istraživanje koje se tiče uticaja referentne evapotranspiracije (ET0) na rezultate SPEI indeksa kako bi se potvrdila polazna pretpostavka da različiti metodi za izračunavanje ET0 u okviru SPEI indeksa daju u nekim slučajevima značajno različite vrednosti indeksa na području Vojvodine. Iz navedenih razloga je važno koristiti metod koji najviše odgovara specifičnom području od interesa. Modifikacija SPEI indeksa, odnosno zamena ET0 sa ETc (potencijalnom evapotranspiracijom kulture) izvršena je uključivanjem ekspertskog mišljenja odnosno intervjuisanjem više stručnjaka različitih ekspertiza iz domena korišćenja i upravljanja vodama u poljoprivredi što je omogućilo da se dođe do grupne odluke koja u najvećoj meri reprezentuje lokalne agroklimatske prilike. U tu svrhu upotrebljen je Analitički Hijerarhijski Proces (AHP metod) kao podrška odlučivanju kako bi se dobile individualne odluke stručnjaka i da bi se u narednom koraku dobila jedna grupna odluka o najpogodnijem metodu za izračunavanje ET0, odnosno ETc. U narednoj fazi predloženog pristupa, prateći dalju proceduru originalnog SPEI indeksa izračunati su klimatski vodni bilansi kultura. Analizom su obuhvaćeni podaci sa devet meteoroloških stanica na području Vojvodine, kao i jedanaest ratarskih i povrtarskih kultura. Zatim je statističkim metodama odabrana odgovarajuća teorijska distribucija za koju je potvrđeno najbolje slaganje sa empirijskim vrednostima klimatskog vodnog bilansa kultura i u narednom koraku dobijen modifikovani SPEI povezan sa specifičnom kulturom (agricultural drought SPEI - AD-SPEIcrop). Pristup omogućava i direktnu transformaciju indeksa u vrednosti klimatskog vodnog bilansa kulture, odražavajući potrebe useva za vodom. Sagledavanjem suše i sa tog aspekta omogućava analizu mogućnosti sistema za navodnjavanje u borbi protiv suše. U sledećoj fazi izvršena je validacija predloženog pristupa sa više različitih aspekata koji podrazumevaju: ispitivanje povezanosti indeksa sa prinosima kultura, kako na lokalnom nivou opština tako i na nivou cele teritorije Vojvodine; poređenje stepena slaganja sa prinosima kultura u odnosu na originalni indeks SPEI; komparaciju sa opšte priznatim i prihvaćenim indeksima suše (SPI, SPEI i SC-PDSI); i povratnu informaciju od strane eksperata. Bazirajući se na dobijenim rezultatima u fazi validacije može se zaključiti da predloženi pristup monitoringu poljoprivredne suše na području Vojvodine baziran na SPEI indeksu može biti uspešno primenjen i sa dobrim performansama, odnosno da indeks AD-SPEIcrop, dobijen kao rezultat ovog pristupa, predstavlja adekvatan pokazatelj poljoprivredne suše na području Vojvodine.<br>In the doctoral dissertation, the SPEI-based approach to agricultural drought monitoring (ADM-SPEI) in Vojvodina has been defined and presented. While integrating several well-known and recognized methods and experts’ critical opinion based on their knowledge and experience, ADM-SPEI takes into account local specificities of agro-climatic conditions. Although it was created for the Vojvodina region, the proposed approach to agricultural drought monitoring based on the SPEI index has been described in three phases alongside the corresponding steps, for which a detailed description and explanation have also been provided. This allows for the ADM-SPEI approach to be modified and applied in any other agro-climatic conditions. The presented approach is based on the modified and widely accepted and used Standardized Precipitation and Evapotranspiration Index (SPEI). The modification enables relating the SPEI to a specific crop, thereby ensuring the possibility for the analysis of drought or moisture conditions separately for specific field or vegetable crops in the agro-climatic conditions of Vojvodina. The creation of the approach to agricultural drought monitoring was preceded by the research of the impact of reference evapotranspiration (ET0) on the results of the SPEI index. The aim of the research was to confirm the initial assumption that different methods for calculating ET0 within the SPEI index give in some cases significantly different index values in the Vojvodina region. For these reasons, it is important to use the most appropriate method for the specific area of interest. Carrying out the modification of the SPEI index, i.e., the replacement of the ET0 with the ETc (potential crop evapotranspiration) included the involvement of experts’ opinions by interviewing experts of various expertise in the domain of water use and water management in agriculture. This led to making a group decision representing the local agro-climatic conditions. For this purpose, the Analytical Hierarchy Process (AHP method) was used as a decision-making support in order to get experts’ individual decisions and, in the next step, to obtain a group decision on the most suitable method for calculating ET0 and ETc. In the next phase of the proposed approach, following the procedure of the original SPEI index, the cropspecific climate water balances were calculated. The analysis includes data from nine meteorological stations in the Vojvodina region, as well as eleven field and vegetable crops. Then, statistical methods were used to select the appropriate theoretical distribution which proved to best fit to the empirical values of the crop-specific climatic water balance. In the next step, the modified SPEI related to specific crops (agricultural drought SPEI - ADSPEIcrop) was obtained. The approach also enables the direct transformation of the index into the values of the climate water balance of crops reflecting the crop water needs. Examining drought from this perspective as well makes it possible to analyze the capabilities of irrigation systems to cope with drought. In the next phase, the validation of the proposed approach was carried out from several different perspectives including examining the correlation of the index with the crop yields, both at the local county level and at the level of the entire territory of Vojvodina; the comparison between the degree of the agreement of the AD-SPEIcrop and the original SPEI index with the crop yields, respectively; the comparison with the generally acknowledged and accepted drought indices (SPI, SPEI and SC-PDSI); and experts’ feedback. According to the obtained results in the validation phase, it can be concluded that the proposed approach to agricultural drought monitoring in the Vojvodina region based on the SPEI index can be applied successfully and with good performance, and that the ADSPEIcrop index obtained as a result of this approach is an adequate indicator of agricultural drought in the Vojvodina region.
45
Lima, Júlio César. "Ecofisiologia da oportunidade da rega no milho: princípios biofísicos." Master's thesis, Universidade de Évora, 1996. http://hdl.handle.net/10174/14773.
Full textAbstract:
Em programas de rega, a identificação da oportunidade da rega das culturas persiste como uma questão actual dado que os critérios são tão variados quanto os parâmetros existentes para esse objectivo. A oportunidade da rega é entendida como o momento em que o estado hídrico da planta, ou do solo, atinge um valor critico, a partir do qual se deve regar. O material vegetal foi a variedade LG 26.88, Índice FAO-600, de milho (Zea mays L.), regada por sulcos e instalada num aluviossol moderno, no microclima. de Alvalade-Sado (37 [° ] N, 8 [°] 24' W, 62 [m]; SW Portugal.) de elevada concentração térmica estival e elevado índice de aridez. Neste estudo, é proposta e explorada a possibilidade do critério de rega se basear na igualdade entre a temperatura da cultura (Tc) e a tempertatura do ar (Ta), i. e Tc-Ta = 0 [°C]. A escolha deste critério justifica-se pela evidência empírica de Tc ser consistentemente inferior a Ta (Tc-Ta < 0), em condições de intensa irradiância, acentuado défice de pressão vapor (DPV) de água no ar e regime de vento moderado a calmo, associados a regimes de boa disponibilidade hídrica na rizosfera. Após uma rega o teor de água no solo diminui devido à evapotranspiração da cultura e Tc aumenta em relação a Ta (Tc-Ta tende para valores nulos os positivos). A explicação concisa do facto de Tc-Ta assumir valores com sinais algébricos diferentes, consoante as condições hídricas, é enquadrada no âmbito da micrometeorologia agrícola em que as relações entre Tc e Ta definem as condições de estabilidade atmosférica para o fluxo de quantidade de movimento: Tc-Ta < 0 exprime estabilidade, Tc-Ta = 0, neutralidade e, Tc-Ta >0, instabilidade atmosférica. A condição de regar a Tc-Ta = 0 e a validação do critério proposto significou assumir, a priori, três condições: 1) Tc-Ta = 0 deveria ocorrer num lapso de tempo (após a última rega) compatível com um regime hídrico que evitasse a ocorrência de carência hídrica para a cultura, 2) que, também, não redundasse na intensificação da rega e 3) que não provocasse a diminuição do índice de colheita (IC). Os resultados mostram que as condições iniciais, para a aceitação do critério de rega, segundo Tc-Ta = 0 (tratamento Rtiv), foram satisfeitas! No tratamento testemunha, a rega acumulada. RA = 600 [mm] (R600), o intervalo (Ir) entre regas, de 7 [dia], foram fixados a priori; resultou o regime médio de Tc-Ta = -3.9 [°C], entre duas regas consecutivas; em Rtiv, a ocorrência de Tc-Ta = 0 teve periodicidade oca (dependendo de Ta) e o valor médio Tc-Ta = 0.4 [°C], foi observado imediatamente antes da rega, com Tc-Ta = -1.9 [°C], entre duas regas consecutivas; em média verificou-se Ir = 8 [dia] associado a RA = 500 [mm]. Isto representa uma diminuição da frequência de rega em 14.3 % e um aumento da eficiência de aplicação da água igual a 16.7 %, em relação a R600. Em relação a R600, a produção de grão em Rtiv diminuiu mas não significativamente (LSD0.05 = 4.54 [t ha-1. Estes resultados validam o critério proposto. Esta validação foi corroborada pelos balanços de energia e de água no fitossistema e no âmbito de uma detalhada análise de crescimento.
46
Музиченко, М. В. "Диферсифікація ринку природного газу ЄС в контексті забезпечення енергетичної безпеки (автореферат)". Thesis, ХНУ імені В. Н. Каразіна, 2018. http://dspace.univer.kharkov.ua/handle/123456789/14174.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата економічних наук за спеціальністю 08.00.02 – Світове господарство і міжнародні економічні відносини. – Харківський національний університет імені В.Н. Каразіна Міністерства освіти і науки України, Харків, 2018. Дисертація присвячена поглибленню теоретико-методичних засад дослідження диверсифікації ринку природного газу ЄС та обґрунтуванню перспективних напрямів підвищення енергетичної безпеки ЄС за рахунок диверсифікації ринку газу. У роботі запропоновано енергетичну безпеку трактувати як інтегральну категорію, яка охоплює соціальні, економічні, політичні, технологічні і екологічні фактори і характеризує стан забезпечення економіки енергоресурсами, за якого потреби у енергії задовольняються за стабільними та доступними цінами шляхом використання енергоресурсів з внутрішніх та зовнішніх джерел і стратегічних резервів через надійну та захищену внутрішню енергетичну інфраструктуру і диверсифіковані та стабільно доступні зовнішні джерела, не створюються загрози сталому розвитку та екологічній безпеці і впроваджені механізми мінімізації наявних і потенційних ризиків для енергетичної сфери. У ході дослідження з’ясовано, що в ЄС безпека постачання енергоресурсів визначається як стан забезпечення енергоресурсами, за якого основні енергетичні потреби мають бути задоволені завдяки спільному використанню внутрішніх енергетичних ресурсів та стратегічних резервів у прийнятних економічних умовах та з використанням диверсифікованих та доступних зовнішніх джерел. Проведено аналіз структури та особливостей сучасного ринку газу ЄС і встановлено, що цей ринок займає одне з ключових місць в загальній структурі виробництва первинної енергії в ЄС, а загальним вектором його розвитку є формування єдиного конкурентоспроможного ринку, ключовими елементами якого є вільна конкуренція та біржове ціноутворення на високоліквідних газових хабах. Виявлено, що концепція диверсифікації на основі довгострокових контрактів, яка останнім часом була традиційною в ЄС, на даний час не може повною мірою забезпечити отримання додаткових обсягів імпорту газу. Найбільш привабливою альтернативою є концепція диверсифікації на основі розвитку конкуренції. Запропоновано концептуально-методичний підхід до оцінки рівня диверсифікації ринку газу ЄС на основі індексу диверсифікації ринку, який дозволяє оцінити рівень диверсифікації ринку за основними його аспектами. Удосконалено інструментарій кількісної оцінки рівня диверсифікації зовнішніх джерел постачання, який дозволяє оцінити рівень їх диверсифікації з урахуванням політичної стабільності та економічної доцільності щодо держав-постачальників. Розроблено модель диверсифікації ринку газу, яка дозволяє оцінити як рівень диверсифікації ринку за основними аспектами, так і загальний рівень диверсифікації ринку газу в цілому. Здійснено оцінку рівня диверсифікації ринку газу ЄС і встановлено, що поточний рівень диверсифікації відповідає нормальному рівню диверсифікації. Обґрунтовано перспективні напрями підвищення енергетичної безпеки ЄС за рахунок диверсифікації ринку газу. Визначено пріоритетні шляхи підвищення рівня диверсифікації ринку природного газу України, реалізація комплексу завдань за якими забезпечить задовільний загальний рівень диверсифікації вітчизняного ринку природного газу та є передумовою успішної інтеграції до ринку природного газу ЄС. The thesis for the degree of Candidate of Economic Sciences, speciality 08.00.02 – World Economy and International Economic Relations. – V.N. Karazin Kharkiv National University of the Ministry of Education and Science of Ukraine, Kharkiv, 2018. The thesis is devoted to the in-depth study of the theoretical and methodological research principles of the EU natural gas market diversification as well as to the
substantiation of perspectives for the EU energy security increase due to the diversification of gas market. Various approaches to the interpretation of energy security by international organizations, individual countries and academic researchers have been explored in the thesis. It has been established that energy security can be explored either under a one-sided approach based on the security of energy supply or under a multi-faceted approach that takes into account a number of other important aspects of energy security, such as energy availability, energy efficiency and environmental safety. By generalizing the existing approaches to the definition of energy security it has been established that energy security in its broad sense is defined as the state of the Economy energy resources supply, with no threats to sustainable development, and where the mechanisms for compensating existing and potential risks, that may arise as a result of the negative influence of internal or external factors, are implemented. The paper proposes to treat energy security as an integral category that covers social, economic, political, technological and environmental factors and characterizes the state of the economy's energy supply, in which energy needs (in various forms and in sufficient quantities) are met at stable and affordable prices through the use of energy resources from internal and external sources and strategic reserves through a reliable and secure internal energy infrastructure and diversified and stable external energy supply sources, no threat to sustainable development and environmental safety, and mechanisms for minimizing existing and potential risks for the energy sector are introduced. It has been established that central component of the EU energy security is the energy supply security, which means the availability of continuous access to energy resources at affordable prices. The availability of energy resources is a multidimensional concept, the components of which are diversification of energy resources suppliers, spatial diversification of energy resources distribution, diversification of type energy resources and diversification of supply routes (pipelines). The study found that in the EU energy security supply is defined as a state of energy supply, in which the basic energy requirements should be covered through the joint use of internal energy resources and strategic reserves under acceptable economic conditions involving diversified and accessible external sources. Diversification encompasses three aspects: the diversification of supply sources, suppliers, and location of energy objects by spatial criterion. It has been discovered that in order to maintain the appropriate energy security level the energy sector should be characterized by the diversification of the complex of primary energy sources; diversification of electricity production at the expense of gas; diversification of the portfolio of energy resources suppliers; diversification of supply routes for imports; a tendency to reduce the energy intensity of GDP; reliable energy infrastructure; affordable prices. Evaluating the place and role of the diversification in the system of factors of ensuring the EU energy security as one of the largest importers of energy resources in the world, it was established that under the assurance of EU energy security is understood the process of reducing dependence on external energy suppliers through the development of own energy production, diversification of the internal energy portfolio and diversification of the energy resources supply from external sources, the formation of sufficient strategic energy resources reserves, energy efficiency, decarbonisation as a means to combat climate change and minimize pollution. The analysis of the structure and features of the modern EU gas market has proved that this market takes one of the key places in the overall structure of primary energy production in the EU, and its general development trend is the formation of a single competitive market by means of free competition and stock pricing in the most liquid gas hubs. It has been discovered that the concept of diversification on the basis of various longterm contracts can not at this time fully ensure the receipt of additional volumes of gas imports. The most attractive alternative for the coming years is the concept of supply diversification based on the development of competition. The conceptual-methodical approach to assessing the level of diversification of the EU gas market based on the market diversification index is proposed, which allows us to assess the level of market diversification in its main aspects. It is noted that the gas market diversification index is a quantitative measure of how much energy security is ensured in the aspect of diversifying gas supply. The tools for quantifying the level of diversification of external sources of supply have been improved, which allows us to assess the level of their diversification, taking into account political stability and economic expediency. The gas market diversification model is developed, which allows quantitatively and qualitatively to assess both the level of the gas market diversification in its main aspects and the overall level of the gas market diversification as a whole. The assessment of external and internal aspects of the EU gas market diversification has proved that the current level of diversification corresponds to the correct level of diversification according to the proposed scale of assessment. The analysis of the obtained assessments of the EU gas market diversification level has been carried out and promising directions of increasing EU energy security due to natural gas market diversification are provided. The program of diversification of the gas market of Ukraine is proposed on the basis of the analogue of the existing N-1 gas infrastructure standard in the EU. The priority directions of increasing the Ukraine natural gas market diversification level are identified, realization of the tasks complex on which proposed target indicators of Ukraine natural gas market diversification level on the main internal and external aspects inherent in the EU natural gas market, will provide a satisfactory overall level of the domestic natural gas market diversification and is a prerequisite for successful integration with the EU natural gas market. Obtained variants of target values of diversification as target parameters can then be based on the diversification programs and determine the main promising directions of Ukraine natural gas market development in terms of increasing energy efficiency, changing the structure of the energy mix, reduction of natural gas consumption, decreasing the dependence on imports, increasing the diversification level of the external supply sources and suppliers.
47
Stark, Caroline, and Emelie Nordell. "Diversifying in the Integrated Markets of ASEAN+3 : A Quantitative Study of Stock Market Correlation." Thesis, Umeå University, Umeå School of Business, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-34476.
Full textAbstract:
<p>There is evidence that globalization, economic assimilation and integration among countries and their financial markets have increased correlation among stock markets and the correlation may in turn impact investors’ allocation of their assets and economic policies. We have conducted a quantitative study with daily stock index quotes for the period January 2000 and December 2009 in order to measure the eventual correlation between the markets of ASEAN+3. This economic integration consists of; Indonesia, Malaysia, Philippines, Singapore, Thailand, China, Japan and South Korea. Our problem formulation is:Are the stock markets of ASEAN+3 correlated?Does the eventual correlation change under turbulent market conditions?In terms of the eventual correlation, discuss: is it possible to diversify an investment portfolio within this area?The purpose of the study is to conduct a research that will provide investors with information about stock market correlation within the chosen market. We have conducted the study with a positivistic view and a deductive approach with some theories as our starting point. The main theories discussed are; market efficiency, risk and return, Modern Portfolio Theory, correlation and international investments. By using the financial datatbase, DataStream, we have been able to collect the necessary data for our study. The data has been processed in the statistical program SPSS by using Pearson correlation.From the empirical findings and our analysis we were able to draw some main conclusions about our study. We found that most of the ASEAN+3 countries were strongly correlated with each other. Japan showed lower correlation with all of the other countries. Based on this we concluded that economic integration seems to increase correlation between stock markets. When looking at the economic downturn in 2007-2009, we found that the correlation between ASEAN+3 became stronger and positive for all of the countries. The results also showed that the correlation varies over time. We concluded that it is, to a small extent, possible to diversify an investment portfolio across these markets.</p>
48
Franch, Mattia, and Bahaa Shehabi. "The potential benefits of investing in commodities : A study of the properties related to the investment in several commodities and adding them to stock portfolios." Thesis, Umeå universitet, Företagsekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-127354.
Full textAbstract:
Investing in commodities may have important benefits for investors but only in the last few decades have they started to think more about this possibility. Furthermore, large investors are more inclined to change their own personal view. Therefore, understanding the benefits that commodities could give to an investment portfolio might alleviate investors’ concerns. Several previous studies, as Belousova and Dorfleitner (2012) suggest, that the commodities with higher benefits are precious metals and gold, in particular. The purpose of our work is to understand which possible benefits are for equity investors and if they are common for certain commodities with different physical characteristics. The first part of our empirical work focuses on the main descriptive statistics of the return distribution (mean, variance, volatility, skewness, kurtosis and correlation) for 8 stock indices and 7 commodity futures. The main goal of this is to understand the differences among the commodities and between the commodities and the stock indices. In the second part of the empirical work, we test the safe-haven and the hedge properties of these commodities on a weekly basis for all of them with stock indices, and we do the same on a daily and monthly basis for only commodities which are negatively correlated on average with the stock indices. In the last part of our work, we combine these 7 commodities, following the principles of Bloomberg Commodity Index (BCOM), in order to create a well-balanced and well-diversified commodity index. Additionally, we create some mixed portfolios using this index and a different stock index every time. After that we look at the volatilities and the returns of these mixed portfolios with different weight combinations. Our main goals in this section are to understand the characteristics of the commodity index in comparison with stock indices and then, finding which weight combinations give the mixed portfolios the optimal risk-return trade off. Understanding which are efficient weights, can lead to conclusions about the weight that commodities should have in a portfolio according to the risk tolerance of the investors. The research is done considering three time frequencies: daily, weekly and monthly; in line with the ones used by Baur and McDermott (2010). The sample size differs among these three different time basis. In fact, daily data started in January 2007 and the other two time frequencies data began with January 1997. All the time samples ended in March 2016. The results of the first part show that gold is the only commodity with a volatility similar to the stock indices (it also has a higher average return) and that on the daily, weekly and monthly basis. Whereas, the other commodities are much riskier than stock indices since they have higher volatility for all the three time-frequencies analyzed. The results of the second part suggest that only gold is both a safe-haven and hedging commodity in line with the methodology used by Baur and McDermott (2010), but only for DAX 30 on a weekly basis. Furthermore, our results also show that natural gas is strong hedge in some cases such as natural gas for STI (Singapore) on a monthly basis or gold for Nikkei 225 on daily, weekly and monthly basis. Other commodities are neither safe-haven nor hedge in any case, except for silver which is a safe-haven commodity for DAX 30 and Sensex which at its worst, 1% and 5%, declines in the market respectively. The results of the last part of our work show that all the minimum variance mixed portfolios (the ones with the weights give the lowest risk) - made on a weekly basis - reduce the portfolio volatility and make the portfolio returns higher than the stock indices returns in 5 cases out of 8. Additionally, the results show how investors, who add a well-balanced and well-diversified commodity index to their portfolios, are able to observe several weight combinations and choose the one which suits their risk tolerance. Moreover, our results show that the optimal-weight combinations for commodity weights are lower than 0,5 only for FTSE 100 and S&P 500 (both values are 0,49) and higher than 0,62 but lower than 0,7 for DAX 30, Nikkei 225, Hang Seng, Sensex, SSEC. Furthermore, the optimal weight for STI is 0,54.
49
Johnson, Bryan Fisher. "Influence of Several Herbicides on Visual Injury, Leaf Area Index, and Yield of Glyphosate-Tolerant Soybean (Glycine max)." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32295.
Full textAbstract:
The occasional failure of glyphosate to control all weeds throughout the entire growing season has prompted growers to sometimes use herbicides other than glyphosate on glyphosate-tolerant soybean. Field studies were conducted in 1999 and 2000 to investigate potential crop injury from several herbicides on glyphosate-tolerant soybean, and to determine the relationship between soybean maturity, planting date, and herbicide treatment on soybean injury, leaf area index (LAI), and yield. Three glyphosate-tolerant soybean cultivars representing maturity groups III, IV and V were planted at dates representing the full-season and double-crop soybean production systems used in Virginia. Within each cultivar and planting date, 15 herbicide treatments, in addition to a control receiving only metolachlor preemergence, were applied to cause multiple levels of crop injury. Results of this study indicate that glyphosate-tolerant soybean generally recovered from early-season herbicide injury and LAI reductions; however, reduced yield occurred with some treatments. Yield reductions were more common in double-crop soybean than in full-season soybean. In full-season soybean, most yield reductions occurred only in the early maturing RT-386 cultivar. These yield reductions may be attributed to the reduced developmental periods associated with early maturing cultivars and double-crop soybean that often lead to reduced vegetative growth and limited LAI. Additional reductions of LAI by some herbicide treatments on these soybean may have coincided with yield reductions; however, reduced LAI did not occur with all yield reducing treatments. Therefore, soybean LAI response to herbicide treatments does not always accurately indicate the potential detrimental effects of herbicides on soybean yield. Further, yield reductions associated with herbicide applications occurred, although soybean sometimes produced leaf area exceeding the critical LAI level of 3.5 to 4.0 which is the minimum LAI needed for soybean to achieve maximum yield.<br>Master of Science
50
Morel, Kevin. "Viabilité des microfermes maraîchères biologiques. Une étude inductive combinant méthodes qualitatives et modélisation." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLA023/document.
Full textAbstract:
Dans le contexte des défis environnementaux et sociaux de l’Anthropocène, les microfermes sont des fermes maraîchères biologiques qui questionnent les fondements de la modernisation agricole par leurs petites surfaces, leur grande diversité cultivée, leur faible niveau de motorisation, une approche écologique holiste et leur commercialisation en circuits courts. Cette thèse a examiné la viabilité de ces systèmes agricoles atypiques qui suscitent un intérêt croissant dans les pays industrialisés. Elle s’est basée sur une étude de 20 cas en milieu rural dans le nord de la France et 10 cas en milieu urbain à Londres. Une démarche inductive a été mise en œuvre combinant analyse qualitative d’entretiens avec des paysans et modélisation quantitative à partir de données de terrain. Un cadre conceptuel a été développé pour analyser les choix stratégiques des paysans au regard des multiples aspirations de leur projet de vie où des considérations éthiques et subjectives occupent une place centrale. La satisfaction de ces aspirations est primordiale pour la viabilité de ces fermes. Un modèle de simulation stochastique de revenu et de temps de travail a été créé pour explorer les chances de viabilité économique de scénarios contrastés de microfermes intégrant stratégies techniques, commerciales et d’investissement. Des simulations ont été réalisées pour le contexte français et londonien et ont été discutées avec des acteurs de terrain. Bien que les chances de viabilité varient selon les scénarios, ce travail montre que les microfermes peuvent être viables<br>In the context of the environmental and social challenges of the Anthropocene, microfarms are organic market gardens which are questioning the principles of agricultural modernisation. They are characterised by a high level of crop diversity on small acreages, low motorisation, holistic ecological approach and marketing through short supply chains. My PhD work examined the viability of these atypical farming systems which are raising an increasing interest in industrialised countries. It was based on the study of 20 cases in rural Northern France and 10 cases in the urban context of London. An inductive approach was carried out combining qualitative analysis of interviews with farmers and quantitative modelling based on field data.A conceptual framework was developed to analyse farmers’ strategic choices in the light of their life project embracing various aspirations where ethics and subjectivity played a central role. The fulfilment of these aspirations is determinant for the viability of these fams. A stochastic simulation model of income and workload was created to explore the chances of economic viability of contrasted microfarms scenarios integrating technical, commercial and investment strategies. Simulations were run for the French and London context and were discussed with stakeholders. Although viability chances vary among scenarios, this work shows that microfarms can be viable