Maize is the third most important cereal crop in the world and many subsistence farmers are practicing intercropping of it with legumes due to land scarcity and in order to enhance production. Intercropping system is being practiced in may areas of South Africa mainly in the Limpopo province. The objective of the study was to evaluate the crop responses to intercropping maize with different growth length cowpea cultivars. The effects of intercropping on weed growth, maize and cowpea growth and yield components were investigated. The experiment was conducted during the 2005/06 and 2006/07 seasons at Bethlehem and Potchefstroom. Treatments were: maize sole, maize+PAN311 (short duration cowpea cultivar), maize+Glenda (medium duration cowpea cultivar), maize+Agrinawa (long duration cowpea cultivar) and sole plots of all cowpea varieties. Each plot was divided into two weed levels where all the plots were kept weed free for one month after planting, after which one half was left weedy and the other half weed free. Weed sampling was done within each weed treatment. Intercropping reduced maize LAI and plant height while time to physiological maturity was also reduced by weed infestation, especially under drier and warmer environments. Glenda and Agrinawa intercrops produced more nodules per plant under cooler and wetter conditions. Agrinawa produced the highest leaf and total DMY under sole crop conditions and this was significantly reduced by weed infestation. Different growth duration cultivars did not differ in their N2-binding abilities. Maize intercropping, especially with Glenda and Agrinawa, significantly reduced weed biomass. Maize sole crop under zero weeds had high grain yield compared to intercropping. PAN311 and Glenda sole crops under zero weeds produced higher yields under dry and warmer conditions, and cooler and wetter conditions, respectively, compared to intercropping. High cowpea grain yields were strongly correlated to more seeds per pod and larger pod lengths and number of pods per plant especially for Glenda. No intercropping advantage compared to sole cropping was observed (total LER < 1). This implies that maize and cowpeas must rather be planted as sole crops for better yields under wetter and cooler, and warmer and drier conditions. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

[pt] Coeficientes de queda de pressão e transferência de calor foram determinados experimentalmente para escoamento turbulento em dutos circulares e semi-circulares lisos e pinados. Pinos de seção transversal circular foram colocados na superfície interna dos dutos. As experiências foram realizadas utilizado-se vários tipos de trocadores de calor, eram ar e água. Para se atingir condições totalmente desenvolvidas, os trocadores de calor possuíam um cumprimento de entrada de 25 diâmetros . Os coeficientes médios de troca de calor foram determinados através da medida dos coeficientes globais de troca de calor dos trocadores de calor. Números de Nusselt e coeficientes de atrito são apresentados como funções do número de Reynolds do escoamento. A finalidade de tal comparação foi estudar a influência dos pinos de seção circular na queda de pressão e taxa de transferência de calor . Números de Nusselt e coeficientes de atrito são apresentados como funções do número de Reynolds do escoamento. Os resultados para dutos lisos e pinados foram comparados. A finalidade de tal comparação foi estudar a influência dos pinos da seção circular na queda de pressão e taxa de transferência de calor. O desempenho térmico global de superfícies pinadas depende principalmente do número de Nusselt e da eficiência da região. Assim, resultados para a eficiência do pino foram também apresentados. / [en] Pressure drop and heat transfer coeficients have been experimentally determined for turbulent flow in smoth and pin finned circular and semi-circular ducts. Spines of circular cross section were attached to the internal surface of the ducts. The experiments were perfomermed by utilizing several types of heat exchanges. The flowing fluids, in the heat exchangers, were air and water. In order to attain fully developed conditions, the heat exchangers had a starting longth of 25 diameters. The average heat tranfer coefficients were determined by measuring the overall heat tranfer coefficients of the heat exchangers. Nusselt numbers and friction factors are presented as fuctions of the flow Reynolds number . The purpose of such comporison was to study the influence of the spines of circular cross section on the pressure drop and heat transfer rate. The overall thermal performance of pin finned surfaces depends mainly on the Nusselt number ando n the region efficiency. Then, results for the pin fin efficienty were also presented.

[pt] Um estudo experimental é realizado para investigar o fenômeno de fratura num fluido não Newtoniano viscoplástico através de expansão abrupta com simetria axial. Uma visualização foi, então, efetuada usando uma técnica simples, com adição de pequenas partículas esféricas ao fluido de teste. Neste trabalho três soluções de Carbopol 676, que representou o fluido viscoplástico, foram preparadas e submetidas ao escoamento laminar e lento, com número de Reynolds no tubo a jusante abaixo de 0,1. Três razões de aspecto, a saber, de 2,0 6,0 e 12,5, foram estudadas nesta estreita faixa de regime laminar. Perdas de carga na expansão foram determinadas a partir de medidas experimentais de pressões diferenciais num determinado trecho (antes e após a expansão) para três vazões volumétricas diferentes. Um modelo de um fluido Newtoniano Generalizado foi emprego para descrever o comportamento mecânico do material, com a função da viscosidade de Herschel-Bulkley, que envolve três parâmetros reológicos: tensão limite de escoamento (T0), índice de consistência (K) e índice de comportamento (n). / [en] An experimental study is accomplished to investigate the fracture phenomenon in a non Newtonian viscoplastic material trhougth and abrupt expansion with axial symmetry. A visualization was then performed using a simple technique, with addition of small spherical particles to the test fluid. Aqueous solutions of carbopol 676 at three different concentrations were prepared and submited to creeping flow, with Reynolds number at the larger tube below than 0,1. Three expansion ratios, namely, 2,0 6,0 and 12,5, were studied in this narrow range of laminar flow. Pressure losses ar the expansion plane were determined from experimental measurement of everall pressure differentials along the tubing, for three different flow rates. The generalized Newtonian fluid model was used to describe the mechanical behavior of the material, with the viscosity of the Herschel-Bulkley type, which involves three rheological parameters the yield stress (T0), consistency index (K) and the behaviour index (n).

[pt] O presente trabalho analisa experimentalmente o escoamento estratificado gás-líquido (ar-água) em um duto de seção retangular. Obteve-se uma correlação empírica para a tensão de cisalhamento na interface. Verifica-se que tal tensão, além de ser função dos números de Reynolds de ambos os escoamentos, depende também de características inerentes à fase líquida. Um perfil teórico de velocidade do gás foi comparado com os dados experimentais obtidos por anemometria para a região logarítmica. Foi realizada uma análise de incertezas, que mostrou uma elevada confiabilidade nos resultados obtidos. / [en] Experiments were carried out to analyse a gás-liquid (air-water) stratified flow through a retangular duct. An empirical correlation was ontained for the shear stress at the interface. Such shear stress, that depends on the Reynolds numbers of both flows, is also a function of liquid specific parameters. A theoretical gas velocity profile was compared with experimental data using a hot-wire anemometry with good results in the logaritimic region. The uncertainly abalysis shows that this correlation presents a very low degree of uncertainly.

Agricultural production is highly sensitive to climate and weather perturbations. Maize is the main crop cultivated in South Africa and production is predominantly rain-fed. South Africa’s climate, especially rainfall, is extremely variable which influences the water available for agriculture and makes rain-fed cropping very risky. In the aim to reduce the uncertainty in the climate of the forthcoming season, this study investigates whether seasonal climate forecasts can be used to predict maize yields for South Africa with a usable level of skill. Maize yield, under rain-fed conditions, is simulated for each of the magisterial districts in the primary maize producing region of South Africa for the period from 1979 to 1999. The ability of the CERES-Maize model to simulate South African maize yields is established by forcing the CERES-Maize model with observed weather data. The simulated maize yields obtained by forcing the CERES-Maize model with observed weather data set the target skill level for the simulation systems that incorporate Global Circulation Models (GCMs). Two GCMs produced the simulated fields for this study, they are the Conformal Cubic Atmospheric Model (CCAM) and the ECHAM4.5 model. CCAM ran a 5 and ECHAM4.5 a 6- member ensemble of simulations on horizontal grids of 2.1° x 2.1° and 2.8° x 2.8° respectively. Both models were forced with observed sea-surface temperatures for the period 1979 to 2003. The CERES-Maize model is forced with each ensemble member of the CCAM-simulated fields and with each ensemble member of the ECHAM4.5-simulated fields. The CERES-CCAM simulated maize yields and CERES-ECHAM4.5 simulated maize yields are combined to form a Multi-Model maize yield ensemble system. The simulated yields are verified against actual maize yields. The CERES-Maize model shows significant skill in simulating South Africa maize yields. CERES-Maize model simulations using the CCAM-simulated fields produced skill levels comparable to the target skill, while the CERES-ECHAM4.5 simulation system illustrated poor skill. The Multi-Model system presented here could therefore not outscore the skill of the best single-model simulation system (CERES-CCAM). Notwithstanding, the CERES-Maize model has the potential to be used in an operational environment to predict South African maize yields, provided that the GCM forecast fields used to force the model are adequately skilful. Such a yield prediction system does not currently exist in South Africa. / Dissertation (MSc)--University of Pretoria, 2009. / Geography, Geoinformatics and Meteorology / Unrestricted

Water shortage is the most important factor constraining agricultural production all over the world. New irrigation strategies must be established to use the limited water resources more efficiently. This study was carried out in a completely randomized design with three replications under the greenhouse condition at Shahrekord University, Shahrekord, Iran. In this study, the physiological responses of pepper plant affected by irrigation water were investigated. Irrigation treatments included control (full irrigation level, FI) and three deficit irrigation levels, 80, 60 and 40% of the plant’s water requirement called DI80, DI60, and DI40, respectively. A no plant cover treatment with three replications was also used to measure evaporation from the soil surface. Daily measurements of volumetric soil moisture (VSM) were made at each 10 cm intervals of the soil column, considered as a layer. The differences between the measured VSM and the VSM in the next day and evaporation rate at the soil surface at the same layer of the no plant cover treatment were calculated. Eventually, by considering the applied and collected water in each treatment, evapotranspiration (ETC) and root water uptake (RWU) in each layer per day were estimated. Furthermore, fruit number per plant, fresh fruit weight/day, root fresh/dry weight, shoot fresh/dry weight, root zone volume, root length and density, crop yield, and water use efficiency (WUE) were measured under different water treatments. The results showed that the maximum and minimum of all the studied parameters were found in the FI and DI40 treatments, respectively. ETC in the DI80, DI60, and DI40 treatments were reduced by 14.2, 37.4, and 52.2%, respectively. Furthermore, applying 80, 60, and 40% of the plant’s water requirement led to crop yield reduction by 29.4, 52.7, and 69.5%, respectively. The averages of root water uptakes (ARWUs) in the DI80, DI60, and DI40 treatments reduced by 17.08, 48.72, and 68.25%, respectively. WUE and crop yield also showed no significant difference in the FI and DI80 treatments. Moreover, in the DI80 treatment the reduced rate of water uptake was less than the reduced rate of plant's applied water. According to these results, it can be concluded that 20% deficit irrigation had no significant reduction on the yield of pepper, but above this threshold, there was an adverse effect on the growth and yield. Therefore, for water management in the regions with limited water resources, plant's applied water can be decreased around 20%.

The main focus of this work is to investigate experimentally the transition to turbulence of a yield stress shear thinning fluid in Hagen-Poiseuille flow. By combining direct high speed imaging of the flow structures with Laser Doppler Velocimetry (LDV), we provide a systematic description of the different flow regimes from laminar to fully turbulent. Each flow regime is characterized by measurements of the radial velocity, velocity fluctuations, and turbulence intensity profiles. In addition we estimate the autocorrelation, the probability distribution, and the structure functions in an attempt to further characterize transition. For all cases tested, our results indicate that transition occurs only when the Reynolds stresses of the flow equals or exceeds the yield stress of the fluid, i.e. the plug is broken before transition commences. Once in transition and when turbulent, the behavior of the yield stress fluid is somewhat similar to a (simpler) shear thinning fluid. We have also observed the shape of slugs during transition and find that their leading edges to be highly elongated and located off the central axis of the pipe, for the non-Newtonian fluids examined. Finally we present a new phenomenological approach for quantifying laminar-turbulent transition in pipe flow. This criterion is based on averaging a local Reynolds number to give ReG. Our localised parameter shows strong radial variations that are maximal at approximately the radial positions where puffs first appear during the first stages of turbulent transition. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The thesis aims to determine the value of the company Mlékárna Hlinsko, a.s. at December 31st 2014 at the nett value. The theoretical part deals with the definition of basic concepts and practices in the field of business valuation. In the practical part follows the introduction of the company in terms of its operations, history and ownership. The strategic analysis describes the current development of the market, its prediction and competitive position. This part continues with financial analysis, which aims to determine financial health of the company. On that basis, it is decided about the infinite duration of the company. There has been chosen yield valuation method. It continues with analysis and forecast of value drivers and a financial plan. It is followed by valuation itself.

Paper concentrates on issues regarding Leveraged Buyout transactions. It briefly depicts most common structure of transactions and means of financing. Substantial space is dedicated to two main participants on leveraged buyouts; investment banks and private equity funds. Instead on focusing on thoroughly described financing of the acquisition via secured bank loans we dedicate space in the thesis to mezzanine finance and high yield bonds. Second part of the thesis analysis latest development in the two main and most active regions regarding mergers and acquisition activity (Europe and USA) and compares Central Europe with it. Although capital markets developed substantially over past decades they are still lagging significantly former.

Tourism trade as well as hotel industry plays an important role in the services sector of the national economy of many countries, including the Czech Republic. The success of the whole branch is significantly influenced by demand fluctuations which usually occur in seasonal terms. Nowadays, however, when the world economy is afflicted by economical crisis, the demand downturns are apparent even in the times of high season. That is why the companies search for methods which would help to soften the impact of the crisis. Yield management appeared in hotel industry more than 20 years ago and is now used in many hotel chains and even small independent hotels. Its goal is to eliminate the demand fluctuation through an effective use of the hotel capacity. In practice it means to ensure that the right rooms are sold to the right customer for the right price. The aim of this thesis is a presentation of an application of Yield management theory in practice, in case of Hilton Prague hotel and to find out the opportunities of the Yield management to reduce the impact of economical crisis. First, we will need to define the base and principals of Yield management. Then we will apply them in practice to the Hilton Prague hotel. Finally, for the use of this hotel, we will examine the methods of smoothing the stroke of the crises.