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Search Results: 1 - 10 of 3577 matches for " Dioari Ulrich Combari "
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Modelling Study of Magnetic Field Effect on the Performance of a Silicon Photovoltaic Module  [PDF]
Dioari Ulrich Combari, Issa Zerbo, Martial Zoungrana, Emmanuel Wendsongre Ramde, Dieudonné Joseph Bathiebo
Energy and Power Engineering (EPE) , 2017, DOI: 10.4236/epe.2017.98028
Abstract: Solar Photovoltaic is a very promising solution that can greatly contribute in solving the increasing global energy demand. In both rural and urban areas, photovoltaic modules are in some instances installed close to telecommunication antennas or voltage transformers which generate important magnetic fields in their vicinity. The question is whether or not these magnetic fields affect the performances of the photovoltaic installations. This article presents a modelling study of external magnetic field effect on the electrical parameters of a photovoltaic module. The photocurrent, the photovoltage, the electric power, the series and the shunt resistances of the photovoltaic module, made up of ideal cells, are deduced from those of a silicon solar cell. Then, the I-V and P-V curves are plotted and the theoretical values of the electrical parameters of the photovoltaic module are deduced. The series and shunt resistances of the photovoltaic module are calculated using well known equations and the previous electrical parameters. The results show the negative effect of magnetic field on the performance of a solar photovoltaic module.
Effect of Incidence Angle of Magnetic Field on the Performance of a Polycrystalline Silicon Solar Cell under Multispectral Illumination  [PDF]
Idrissa Sourabié, Issa Zerbo, Martial Zoungrana, Dioari Ulrich Combari, Dieudonné Joseph Bathiebo
Smart Grid and Renewable Energy (SGRE) , 2017, DOI: 10.4236/sgre.2017.810021
Abstract: The aim of this work is to investigate, with a three-dimensional steady-state approach, the effect of the incidence angle of a magnetic field on the performance of a polycrystalline silicon solar cell under multispectral illumination. The magneto-transport and continuity equations of excess minority carriers are solved to find the expression of the density of excess minority carriers and the related electrical parameters, such as the photocurrent density, the photovoltage and the electric power, of a grain of the polycrystalline silicon solar cell. The influence of the incidence angle of the magnetic field on the diffusion coefficient, the short-circuit photocurrent density, the open-circuit photovoltage and the electric power-photovoltage is studied. Then, the curves of the electric power-photovoltage is used to find the maximum electric power allowing to calculate, according to the incidence angle of the magnetic field, the fill factor and the conversion efficiency. The study has shown that the increase of the incidence angle of the magnetic field from 0 rad to π/2 rad, can reduce the degradation of the performance of solar cells.
Mathematical Rotordynamic Model Regarding Excitation Due to Elliptical Shaft Journals in Electrical Motors Considering the Gyroscopic Effect  [PDF]
Ulrich Werner
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.48A009
Abstract:

The paper presents a mathematical rotordynamic model regarding excitation due to elliptical shaft journals in sleeve bearings of electrical motors also considering the gyroscopic effect. For this kind of excitation, a mathematical rotordynamic model was developed considering the influence of the oil film stiffness and damping of the sleeve bearings, the stiffness of the end-shields and bearing housings, the stiffness of the rotor, the electromagnetic stiffness in the air gap of the electrical motor and the mass moment of inertia of the rotor and therefore also considering the gyroscopic effect. The solution of the linear differential equation system leads to the mathematical description of the absolute orbits of the shaft centre, the shaft journals and the bearing housings and to the relative orbits between the shaft journals and the bearing housings. Additionally, the bearing housing velocities can also be derived with this mathematical rotordynamic model.

Mathematical Multibody Model of a Soft Mounted Induction Motor Regarding Forced Vibrations Due to Dynamic Rotor Eccentricities Considering Electromagnetic Field Damping  [PDF]
Ulrich Werner
Journal of Applied Mathematics and Physics (JAMP) , 2017, DOI: 10.4236/jamp.2017.52032
Abstract: The paper presents a mathematical multibody model of a soft mounted induction motor with sleeve bearings regarding forced vibrations caused by dynamic rotor eccentricities considering electromagnetic field damping. The multibody model contains the mass of the stator, rotor, shaft journals and bearing housings, the electromagnetic forces with respect of electromagnetic field damping, stiffness and internal (rotating) damping of the rotor, different kinds of dynamic rotor eccentricity, stiffness and damping of the bearing housings and end shields, stiffness and damping of the oil film of the sleeve bearings and stiffness and damping of the foundation. With this multibody model, the bearing housing vibrations and the relative shaft vibrations in the sleeve bearings can be derived.
Influence of the Foundation on the Threshold of Stability for Rotating Machines with Roller Bearings—A Theoretical Analysis  [PDF]
Ulrich Werner
Journal of Applied Mathematics and Physics (JAMP) , 2017, DOI: 10.4236/jamp.2017.56114
Abstract: The paper presents a mathematical model for analyzing the threshold of stability for rotating machines, where the rotor is linked to the stator by roller bearings, bearing housings and end-shields and where the stator feet are mounted on a soft foundation. The internal (rotating) damping of the rotor is the only source of instability, which is considered in the paper. After the mathematical coherences of the multibody model are described, a procedure is presented for deriving the threshold of stability. Additionally, a numerical example is shown, where the threshold of stability is calculated for different boundary conditions. It could be demonstrated, that the stiffness of the foundation—even if the foundation stiffness is isotropic—can help stabilizing this kind of vibration system in the same way as orthotropic bearing stiffness or orthotropic bearing housing and end-shield stiffness for a rigid foundation.
Analysis of Different Vibration Control Strategies for Soft Mounted Induction Motors with Sleeve Bearings Using Active Motor Foot Mounts  [PDF]
Ulrich Werner
Journal of Applied Mathematics and Physics (JAMP) , 2019, DOI: 10.4236/jamp.2019.73045
Abstract: The paper presents a theoretical analysis of different vibration control strategies of soft mounted induction motors with sleeve bearings, using active motor foot mounts. After the vibration model is presented, different controllers in combination with different feedback strategies are mathematically investigated. The focus is here on the forced vibrations, caused by dynamic rotor eccentricityrotor mass eccentricity, magnetic eccentricity and bent rotor deflection. After the mathematically coherences are described, a numerical example is shown, where the forced vibrations caused by bent rotor deflection are investigated, for different control strategies, where the mass matrix, the stiffness matrix and the damping matrix are influenced by different control parameters. The aim of the paper is to show the mathematically coherences and the possibility to influence the vibration behaviour, by different control strategies to optimize the vibration behaviour of soft mounted induction motors.
Effects of Mango Wastes-Based Diets on the Growing Parameters of Laying Hens and Biometric Parameters of the Eggs  [PDF]
Drissa Barry, Timbilfou Kiendrebeogo, Modou Sere, Alima Combari, Youssouf Mopaté Logténé, Chantal Yvette Kaboré-Zoungrana
Open Access Library Journal (OALib Journal) , 2019, DOI: 10.4236/oalib.1105868
Abstract:
Introduction: Poultry production has increased during the past half century throughout the world. In Burkina Faso modern poultry farming is becoming a necessity in view of the growing demand for eggs. Intensive poultry farming is developing rapidly, given that the productivity of local poultry remains very low Because of the low availability and high cost of food. Therefore, it becomes imperative to develop strategies to make modern poultry farming more productive, by finding alternative solutions for feeds. Objective: The study aims to evaluate the effects of diets incorporating mango waste-based feed on the growth parameters of laying hens and biometric parameters of first eggs. Methods: Two hundred and ten (10) hens of the Isa Brown breed were divided into 3 batches (70 chicks per set) and feed with three diets namely mango and maize diet (MMD = lot1), control maize diet (CMD = lot2) and absolute control diet (ACD = lot3) in a feed experiment at INERA research station in Farako-ba, Bobo Dioulasso. Results: The final average weight (FW) gained by the lot1 and lot3 using the diet CMD (1364 ± 114 g) and ACD (1364 ± 115 g), respectively was significantly higher than the lot 2 feed with the MMD diet (1265 ± 117 g) (p < 0.05). The average daily weight gain (ADG) of CMD and ACD was significantly (p < 0.05) higher than that of the MMD ration. The feed intake (FI) and consumption index (CI) of the MMD ration were significantly (p < 0.05) higher than those of CMD and ACD (p > 0.05). Average weight and egg density were similar (p > 0.05) for the three diets. The eggs on the MMD diet were larger (p < 0.05) than those in the ration’s CMD and ACD, but the two later were similar (p > 0.05). Conclusion: Maize can be substituted with mango feed in growing layer diets. Mango waste-based feed is predisposed for better preparation of growing layers for good laying performances. It is an alternative to increase the availability of feed for farm animals including the laying hen.
Dirac Hamiltonian with Imaginary Mass and Induced Helicity—Dependence by Indefinite Metric  [PDF]
Ulrich D. Jentschura
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.39116
Abstract: It is of general theoretical interest to investigate the properties of superluminal matter wave equations for spin one-half particles. One can either enforce superluminal propagation by an explicit substitution of the real mass term for an imaginary mass, or one can use a matrix representation of the imaginary unit that multiplies the mass term. The latter leads to the tachyonic Dirac equation, while the equation obtained by the substitution m im in the Dirac equation is naturally referred to as the imaginary-mass Dirac equation. Both the tachyonic as well as the imaginary-mass Dirac Hamiltonians commute with the helicity operator. Both Hamiltonians are pseudo-Hermitian and also possess additional modified pseudo-Hermitian properties, leading to constraints on the resonance eigenvalues. Here, by an explicit calculation, we show that specific sum rules over the The spectrum is found to consist of well-defined real energy eigenvalues and complex resonance and anti-resonance energies. In the quantized imaginary-mass Dirac field, one-particle states of right-handed helicity acquire a negative norm (“indefinite metric”) and can be excluded from the physical spectrum by a Gupta-Bleuler type condition.
Non-peptide ligands in the characterization of peptide receptors at the interface between neuroendocrine and mental diseases  [PDF]
Margit Pissarek, Ulrich Disko
World Journal of Neuroscience (WJNS) , 2013, DOI: 10.4236/wjns.2013.32014
Abstract:

Hypothalamic receptors for neuropeptide Y, melaninconcentrating hormone, melanocortins and orexins/ hypocretins as well as for the downstream signaling corticotrophic factor have been discussed broadly for their influence on food intake and reward but also on several psychiatric disorders. For the development of non-peptide ligands for the in vivo detection of alterations in density and affinity of such G-protein coupled (GPCRs) peptide receptors the requirements to affinity and pharmacokinetics have been shifted to thresholds markedly distict from classical GPCRs to dissociation constants < 0.5 nM, partition coefficients log P < 3.5 and transcellular transport ratios, e.g. for the permeability glycoprotein transporter, below 3. Nevertheless, a multitude of compounds has been reported originally as potential therapeutics in the treatment of obesity among which some are suitable candidates for labeling as PET or SPECT-tracers providing receptor affinities even below 0.1 nM. These could be unique tools not only for better understanding of the mechanism of obesity but also for investigations of extrahypothalamic role of “feeding receptors” at the interface between neuroendocrine and mental diseases.

Age of grassy strips influences biodiversity of ground beetles in organic agro-ecosystems  [PDF]
Mazhar Ranjha, Ulrich Irmler
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.45030
Abstract:

The following investigations were conducted to evaluate grassy strips of different age for organic arable fields. From September 2009 to October 2010, adult ground beetles were sampled by pitfall traps in three grassy strips (2, 4, and 9 years old), their adjacent cropping areas, their field edges, and a control field (age 0) in Schleswig-Holstein, northern Germany. Carabid assemblages were similar among the fields, strips and edges. Grassy strips and edges had higher species richness and lower activity density than the control field. Activity density increased with increasing distance from the field edge in grassy strips and in the adjacent fields. In cropping areas, species richness andShannon’s H increased with increasing age of strips, whereas evenness and activity density decreased with increasing distance from the field edges. Compared to carnivorous and phytophagous carbides, omnivorous species were affected less by age of strips and distance from field margins. In the strips, species richness of the dominant species increased with age and decreased with distance, but the effect of strip age on species richness was still found in more than150 mfrom the margin. A positive effect of the age of grassy strips on species richness was found for cropping fields, grassy strips and field edges. Old grassy strips also exerted greater influence on the species richness and biodiversity of the adjacent arable fields than the younger strips.

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