• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 323
  • 256
  • 72
  • 53
  • 47
  • 40
  • 32
  • 30
  • 20
  • 11
  • 9
  • 7
  • 6
  • 4
  • 4
  • Tagged with
  • 944
  • 150
  • 125
  • 97
  • 86
  • 72
  • 61
  • 59
  • 58
  • 56
  • 56
  • 56
  • 55
  • 54
  • 52
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Efeito da adubação foliar e condicionadores de solo no enraizamento, crescimento e rustificação de mudas clonais de Pinus spp. / Effect of foliar fertilizer and soil conditioner on rooting, growth and hardening of cuttings of Pinus sp.

Santos, Kaline Gomes dos 18 September 2015 (has links)
A produção de mudas via propagação vegetativa é fundamental para se obter os ganhos desejados nos programas de melhoramento genético, bem como garantir o sucesso da implantação florestal. No entanto, existem muitos fatores que impedem a sua utilização de forma abrangente na produção de mudas para algumas espécies florestais, principalmente em relação à baixa taxa de enraizamento. Para atender a essa necessidade, pesquisas com o uso de substâncias que promovam maior taxa de enraizamento de miniestacas e crescimento de mudas vem sendo desenvolvidas, como o uso de reguladores de crescimento e de bioestimulantes à base de substâncias húmicas. Dessa forma o objetivo do presente trabalho é avaliar o efeito de adubos foliares e condicionadores de solo na produção de mudas clonais de híbridos de Pinus caribaea var. hondurensis vs. elliottii var. elliottii e de Pinus tecunumanii vs. caribaea var. hondurensis. Os experimentos foram desenvolvidos em viveiro florestal na cidade de Paranapanema-SP, com delineamento de blocos ao acaso, em arranjo fatorial 4x2, com duração de seis meses. Foram utilizados dois condicionadores de solo, sendo o C1 à base de pescados marinhos e o C2 à base de ácidos húmicos e quatro adubos foliares, sendo AF1 à base de quitosana, AF2 à base de pescados marinhos, AF3 à base de ácido húmico e AF4 extrato da alga Ascoplhyllum nodosum, além da mistura dos adubos M1AF (AF2+AF3+AF4) e o M2AF (AF1+AF3+AF4). Foram instalados dois experimentos: 1) híbrido de P. caribaea var. hondurensis vs. elliottii var. elliottii, testando a combinação dos dois condicionadores de solo e os adubos AF2, AF3, AF4 e M1AF e 2) híbrido de P. tecunumanii vs. carearia var. hondurensis em que a única alteração nos tratamentos foi o AF2 por AF1 e o M1AF por M2AF. As mudas foram avaliadas nas três fases da seguinte forma: 1) casa de vegetação: taxa de enraizamento; 2) casa de sombra: altura, massa seca e verde da parte aérea e radicial e a relação entre elas; e 3) rustificação: avaliadas as mesmas variáveis da casa de sombra, além do estado nutricional das acículas. Para o experimento 1, a taxa de enraizamento com C2 + AF3 foi 46,67% maior quando comparada à testemunha, comprovando o efeito positivo das substâncias húmicas no enraizamento. Já na fase de rustificação, a interação C1 + AF3 promoveu maior crescimento das mudas. Para o experimento 2, não houve diferença nas taxas de enraizamento na casa de vegetação, devido a característica de rápido crescimento do P. tecunumanii. E, na fase de rustificação, o adubo foliar AF4 promoveu maior crescimento somente em altura. Na casa de sombra, os tratamentos testados não promoveram crescimento significativo para ambos os híbridos. Os teores nutricionais analisados nas acículas estão dentro dos níveis adequados para ambos os experimentos. Somente o Mn apresentou baixo teor, mas sem sintomas de deficiência no experimento 2. Os híbridos obtiveram respostas diferentes quando submetidos a tratamentos semelhantes e a determinação do tratamento adequado vai depender do gargalo na produção de mudas, podendo este ser o enraizamento ou o crescimento. / The production of cuttings by vegetative propagation is essential to obtain the desired accomplishment in genetic improvement programs and ensure the success of forest establishment. However there are many factors that prevent their use in a comprehensive manner considering the production of cuttings for some forest species especially in low rooting rate. In order to meet this need research on the use of substances that promote greater rooting rates of minicuttings and growth of cuttings have been developed with the use of growth regulators and biostimulants based on humic substances. Thus the purpose of this study is to evaluate the effect of foliar fertilizers and soil conditioners in the production of Pinus caribaea var. hondurensis vs. elliottii var. elliottii and Pinus tecunumanii vs. caribaea var. hondurensis hybrids cuttings. The experiment was conducted in the city of Paranapanema-SP using cutting nursery with delineation of randomized blocks in a factorial arrangement 4x2, lasting six months. It used two soil conditioners, the C1 based on marine fish and C2 based on humic acids and 4 foliar fertilizers, the AF1 chitosan base, AF2 based on marine fish, AF3 based on humic acid and AF4 by Ascoplhyllum nodosum seaweed extract, besides the mixture of fertilizers M1AF (AF2;AF3;AF4) and M2AF (AF1;AF3;AF4). Two experiments were implemented: 1) hybrid of P. caribaea var. hondurensis vs. elliottii var. elliottii, testing the combination of two soil conditioners as well as fertilizers AF2, AF3, AF4 and M1AF and 2) hybrid of P. tecunumanii vs. caribaea var. hondurensis in which the only change in treatment was the AF2 by AF1 and M1AF by M2AF. Cuttings were evaluated in three phases as follows: 1) greenhouse: rooting rate; 2) shade house: higher, aerial drywet mass and radicial part as well as the relationship between them; 3) hardening: the shade house had the same variables evaluated, in addition with the nutritional status of needles. For the experiment 1, the rooting rate with C2 + AF3 were 46.67% higher compared with the control, this stated the positive effect of humic substances on rooting. Considering the hardening phase C1 + AF3 interaction promoted greater seedling growth. For the experiment 2 there was no difference in rooting rates at greenhouse, because the characteristic of fast growth of P. tecunumanii. In hardening phase, the foliar fertilizer AF4 promoted greater growth only in height. In the shade house treatments did not promote significant growth for both hybrids. Nutritional contents analyzed the needles leaves are within appropriate levels for both experiments. Mn showed only low level, but without deficiency symptoms in the experiment 2. Different answers were obtained on hybrids when subjected to similar treatment and to determine the appropriate treatment will depend on the obstaclecuttings production, which may either rooting or growth.
32

Efeito da adubação foliar e condicionadores de solo no enraizamento, crescimento e rustificação de mudas clonais de Pinus spp. / Effect of foliar fertilizer and soil conditioner on rooting, growth and hardening of cuttings of Pinus sp.

Kaline Gomes dos Santos 18 September 2015 (has links)
A produção de mudas via propagação vegetativa é fundamental para se obter os ganhos desejados nos programas de melhoramento genético, bem como garantir o sucesso da implantação florestal. No entanto, existem muitos fatores que impedem a sua utilização de forma abrangente na produção de mudas para algumas espécies florestais, principalmente em relação à baixa taxa de enraizamento. Para atender a essa necessidade, pesquisas com o uso de substâncias que promovam maior taxa de enraizamento de miniestacas e crescimento de mudas vem sendo desenvolvidas, como o uso de reguladores de crescimento e de bioestimulantes à base de substâncias húmicas. Dessa forma o objetivo do presente trabalho é avaliar o efeito de adubos foliares e condicionadores de solo na produção de mudas clonais de híbridos de Pinus caribaea var. hondurensis vs. elliottii var. elliottii e de Pinus tecunumanii vs. caribaea var. hondurensis. Os experimentos foram desenvolvidos em viveiro florestal na cidade de Paranapanema-SP, com delineamento de blocos ao acaso, em arranjo fatorial 4x2, com duração de seis meses. Foram utilizados dois condicionadores de solo, sendo o C1 à base de pescados marinhos e o C2 à base de ácidos húmicos e quatro adubos foliares, sendo AF1 à base de quitosana, AF2 à base de pescados marinhos, AF3 à base de ácido húmico e AF4 extrato da alga Ascoplhyllum nodosum, além da mistura dos adubos M1AF (AF2+AF3+AF4) e o M2AF (AF1+AF3+AF4). Foram instalados dois experimentos: 1) híbrido de P. caribaea var. hondurensis vs. elliottii var. elliottii, testando a combinação dos dois condicionadores de solo e os adubos AF2, AF3, AF4 e M1AF e 2) híbrido de P. tecunumanii vs. carearia var. hondurensis em que a única alteração nos tratamentos foi o AF2 por AF1 e o M1AF por M2AF. As mudas foram avaliadas nas três fases da seguinte forma: 1) casa de vegetação: taxa de enraizamento; 2) casa de sombra: altura, massa seca e verde da parte aérea e radicial e a relação entre elas; e 3) rustificação: avaliadas as mesmas variáveis da casa de sombra, além do estado nutricional das acículas. Para o experimento 1, a taxa de enraizamento com C2 + AF3 foi 46,67% maior quando comparada à testemunha, comprovando o efeito positivo das substâncias húmicas no enraizamento. Já na fase de rustificação, a interação C1 + AF3 promoveu maior crescimento das mudas. Para o experimento 2, não houve diferença nas taxas de enraizamento na casa de vegetação, devido a característica de rápido crescimento do P. tecunumanii. E, na fase de rustificação, o adubo foliar AF4 promoveu maior crescimento somente em altura. Na casa de sombra, os tratamentos testados não promoveram crescimento significativo para ambos os híbridos. Os teores nutricionais analisados nas acículas estão dentro dos níveis adequados para ambos os experimentos. Somente o Mn apresentou baixo teor, mas sem sintomas de deficiência no experimento 2. Os híbridos obtiveram respostas diferentes quando submetidos a tratamentos semelhantes e a determinação do tratamento adequado vai depender do gargalo na produção de mudas, podendo este ser o enraizamento ou o crescimento. / The production of cuttings by vegetative propagation is essential to obtain the desired accomplishment in genetic improvement programs and ensure the success of forest establishment. However there are many factors that prevent their use in a comprehensive manner considering the production of cuttings for some forest species especially in low rooting rate. In order to meet this need research on the use of substances that promote greater rooting rates of minicuttings and growth of cuttings have been developed with the use of growth regulators and biostimulants based on humic substances. Thus the purpose of this study is to evaluate the effect of foliar fertilizers and soil conditioners in the production of Pinus caribaea var. hondurensis vs. elliottii var. elliottii and Pinus tecunumanii vs. caribaea var. hondurensis hybrids cuttings. The experiment was conducted in the city of Paranapanema-SP using cutting nursery with delineation of randomized blocks in a factorial arrangement 4x2, lasting six months. It used two soil conditioners, the C1 based on marine fish and C2 based on humic acids and 4 foliar fertilizers, the AF1 chitosan base, AF2 based on marine fish, AF3 based on humic acid and AF4 by Ascoplhyllum nodosum seaweed extract, besides the mixture of fertilizers M1AF (AF2;AF3;AF4) and M2AF (AF1;AF3;AF4). Two experiments were implemented: 1) hybrid of P. caribaea var. hondurensis vs. elliottii var. elliottii, testing the combination of two soil conditioners as well as fertilizers AF2, AF3, AF4 and M1AF and 2) hybrid of P. tecunumanii vs. caribaea var. hondurensis in which the only change in treatment was the AF2 by AF1 and M1AF by M2AF. Cuttings were evaluated in three phases as follows: 1) greenhouse: rooting rate; 2) shade house: higher, aerial drywet mass and radicial part as well as the relationship between them; 3) hardening: the shade house had the same variables evaluated, in addition with the nutritional status of needles. For the experiment 1, the rooting rate with C2 + AF3 were 46.67% higher compared with the control, this stated the positive effect of humic substances on rooting. Considering the hardening phase C1 + AF3 interaction promoted greater seedling growth. For the experiment 2 there was no difference in rooting rates at greenhouse, because the characteristic of fast growth of P. tecunumanii. In hardening phase, the foliar fertilizer AF4 promoted greater growth only in height. In the shade house treatments did not promote significant growth for both hybrids. Nutritional contents analyzed the needles leaves are within appropriate levels for both experiments. Mn showed only low level, but without deficiency symptoms in the experiment 2. Different answers were obtained on hybrids when subjected to similar treatment and to determine the appropriate treatment will depend on the obstaclecuttings production, which may either rooting or growth.
33

Placement and control of static compensators for power system stability

Silva, Aguinaldo Silveira e. January 1990 (has links)
No description available.
34

INFLUÊNCIA DA NUTRIÇÃO MINERAL COM NITROGÊNIO E BORO NA PRODUTIVIDADE E PRESENÇA DE COMPOSTOS SECUNDÁRIOS POLARES EM Brassica oleracea var. capitata

CASTELUBER, I. P. 25 April 2014 (has links)
Made available in DSpace on 2018-08-01T23:26:44Z (GMT). No. of bitstreams: 1 tese_7392_37 - Dissertação - Ivana20150903-153147.pdf: 528640 bytes, checksum: 7c9c1018c02447ef374e533ce8807566 (MD5) Previous issue date: 2014-04-25 / A família botânica com o maior número de hortaliças são as Brassicaceas. No Brasil, o repolho é a brássica mais consumida e no Espírito Santo é a terceira cultura olerícola de maior expressão. A adubação correta favorece a qualidade do produto final, proporcionando respostas positivas na produtividade com aplicações crescentes. O objetivo deste trabalho foi verificar a influência da adubação nitrogenada e boratada na produtividade do repolho e na produção de metabólitos secundários no norte do Espírito Santo. O experimento foi conduzido na fazenda experimental do curso de agronomia do CEUNES/UFES. Foram usadas sementes do híbrido Astrus plus e as mudas mantidas por cerca de 30 dias na casa de vegetação. Utilizou-se o delineamento de blocos casualizados (DBC) com 5 tratamentos e 4 repetições e as adubações de plantio e cobertura seguiram as normas para o estado do Espírito Santo. Os tratamentos consistiam em 0,75,150,225 e 300 Kg de N.ha-1 e 0, 2, 4, 6 e 8 Kg de B.ha-1 feitas aos 15, 40 e 60 dias após o transplante. As características analisadas foram produtividade, massa fresca da cabeça, diâmetro da cabeça, número de folhas externas, índice de formato, relação altura do coração sobre diâmetro da cabeça, teor de massa seca, de nitrogênio total e de boro da cabeça e das folhas externas e metabólitos secundários. A extração e caracterização cromatográfica das amostras foram feitas na Universidade Federal de Santa Maria. A análise dos resultados mostrou que para ambos os nutrientes as respostas foram significativas para a maior parte dos parâmetros estudados. Os dados de produtividade e qualidade das plantas formadas se mostraram compatíveis com as exigências do mercado consumidor e os metabólitos secundários encontrados apresentaram maior concentração nas folhas externas.
35

Softwarové možnosti pro analýzu finančních časových řad / Software products for financial time series analysis

Vlasáková, Romana January 2012 (has links)
The present work deals with selected methods suitable to work with financial time series. Firstly, univariate linear models ARMA are introduced, followed by the description of volatility models ARCH and their generalization to GARCH models. There are many modifications of standard GARCH models designed with respect to the nature of financial data, some of which are presented. Another part of the work dealing with multiple time series focuses on VAR models and bivariate GARCH models. The most important part of the work are practical examples of building the theoretically described models in various types of software with built-in procedures for time series analysis. We apply five different types of commercial and non-commercial software, namely EViews, Mathematica, R, S-PLUS and XploRe. The used software products are presented and compared in terms of their capabilities and the results obtained for particular methods.
36

Making the business case for process safety using value-at-risk concepts

Fang, Jayming Sha 30 October 2006 (has links)
An increasing emphasis on chemical process safety over the last two decades has led to the development and application of powerful risk assessment tools. Hazard analysis and risk evaluation techniques have developed to the point where quantitatively meaningful risks can be calculated for processes and plants. However, the results are typically presented in semi-quantitative “ranked list” or “categorical matrix” formats, which are certainly useful but not optimal for making business decisions. A relatively new technique for performing valuation under uncertainty, Value at Risk (VaR), has been developed in the financial world. VaR is a method of evaluating the probability of a gain or loss by a complex venture, by examining the stochastic behavior of its components. We believe that combining quantitative risk assessment techniques with VaR concepts will bridge the gap between engineers and scientists who determine process risk and business leaders and policy makers who evaluate, manage, or regulate risk. We present a few basic examples of the application of VaR to hazard analysis in the chemical process industry. We discover that by using the VaR tool we are able to present data that allows management to make better informed decisions.
37

Essays in financial economics and risk management

Zou, Lin 15 May 2009 (has links)
No description available.
38

Government spending and unemployment : An empirical study on Sweden, 1994-2012

Olofsson, Mattias January 2013 (has links)
The aim of the study was to see if any relationship between government spending andunemployment could be empirically found. To test if government spending affectsunemployment, a statistical model was applied on data from Sweden. The data was quarterlydata from the year 1994 until 2012, unit-root test were conducted and the variables wheretransformed to its first-difference so ensure stationarity. This transformation changed thevariables to growth rates. This meant that the interpretation deviated a little from the originalgoal. Other studies reviewed indicate that when government spending increases and/or taxesdecreases output increases. Studies show that unemployment decreases when governmentspending/GDP ratio increases. Some studies also indicated that with an already largegovernment sector increasing the spending it could have negative effect on output. The modelwas a VAR-model with unemployment, output, interest rate, taxes and government spending.Also included in the model were a linear and three quarterly dummies. The model used 7lags. The result was not statistically significant for most lags but indicated that as governmentspending growth rate increases holding everything else constant unemployment growth rateincreases. The result for taxes was even less statistically significant and indicates norelationship with unemployment. Post-estimation test indicates that there were problems withnon-normality in the model. So the results should be interpreted with some scepticism.
39

A Gradual Non-Convexation Penalty Method for Minimizing VaR

Xi, Jiong January 2012 (has links)
This thesis investigates the portfolio optimization problem using Value-at-Risk (VaR) as a risk measure, when m sample scenarios are given. Minimizing VaR of a portfolio is computationally difficult: it is non-convex, non-smooth, and has many local minima. Recently Gaivoronski and Pflug define a quantile-based smoothed VaR function to approximate the original VaR; this smoothed VaR function is then minimized to obtain the minimal VaR portfolio. Unfortunately this method suffers two problems. Firstly, computational cost of minimization is high since each function evaluation requires O(m^3) work, where m is the number of scenarios. Secondly, it is difficult to determine the smooth parameter. We propose a new gradual non-convexation penalty method which can efficiently solve a VaR minimization problem. We first introduce an auxiliary variable and formulate the VaR minimization problem as an optimization problem with a probabilistic constraint, which involves a sum of step functions. A continuously differentiable piecewise quadratic function is used to approximate the step function. An exact penalty method is used to solve the constrained optimization problem. In an attempt to reach the global minimize, we also use a gradual non-convexation process with the initial problem close to a convex problem. The solution of the kth optimization problem is used as the starting point of the k+1th problem. As the indexing parameter increases, the problem becomes non-convex. Our new method has three advantages. Firstly, our formulation is structurally simpler. Secondly, our method has three computationally more efficient since each function evaluation requires O(m) work. Thirdly, we use a gradual non-convexation process in an attempt to track the global minimum; this also avoids the difficulty in choosing the smooth parameter. Both historical and synthetic data are used to test our VaR minimization method. We compare our method with both Uryasev and Rockafellar’s CVaR minimization method and Gaivoronski and Pflug’s quantile-based smoothed VaR method in terms of VaR, CPU time, and efficient frontiers. We show that our gradual non-convexation penalty method yields better minimal VaR portfolio than the other two methods. In addition, we show that the proposed gradual non-convexation penalty method is computationally much more efficient than Gaivoronski and Pflug’s quantile-based smoothed VaR method, especially when the number of scenarios is large.
40

Estimating and Analyzing Exchange Rates at Different Risk Levels

Hung, Te-Yuan 17 February 2011 (has links)
none

Page generated in 0.024 seconds