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Search Results: 1 - 10 of 3583 matches for " Ulrich Brosa "
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Diffraction of Electromagnetic Waves
Ulrich Brosa
Physics , 2009,
Abstract: The general method to obtain solutions of the Maxwellian equations from scalar representatives is developed and applied to the diffraction of electromagnetic waves. Kirchhoff's integral is modified to provide explicit expressions for these representatives. The respective integrals are then evaluated using the method of stationary phase in two dimensions. Hitherto unknown formulae for the polarization appear as well as for imaging by diffraction. Ready-to-use formulae describing Fresnel diffraction behind a round stop are presented.
Electromagnetic Waves in Variable Media
Ulrich Brosa
Physics , 2011, DOI: 10.5560/ZNA.2011-0069
Abstract: Two methods are explained to exactly solve Maxwell's equations where permittivity, permeability and conductivity may vary in space. In the constitutive relations, retardation is regarded. If the material properties depend but on one coordinate, general solutions are derived. If the properties depend on two coordinates, geometrically restricted solutions are obtained. Applications to graded reflectors, especially to dielectric mirrors, to filters, polarizers and to waveguides, plain and cylindrical, are indicated. New foundations for the design of optical instruments, which are centered around an axis, and for the design of invisibility cloaks, plain and spherical, are proposed. The variability of material properties makes possible effects which cannot happen in constant media, e.g. stopping the flux of electromagnetic energy without loss. As a consequence, spherical devices can be constructed which bind electromagnetic waves.
Distribución del presupuesto sanitario público de Catalu?a del a?o 2005 entre las 17 categorías CIE-9-MC
Gisbert,Ramón; Brosa,Max; Bohigas,Lluís;
Gaceta Sanitaria , 2007, DOI: 10.1590/S0213-91112007000200006
Abstract: objectives: to describe the distribution of the catalan public healthcare budget for 2005 among the 17 icd-9-cm (international classification of diseases, ninth revision, clinical modification) categories. material and method: the methodology comprised 2 phases: an initial phase in which the global budget was distributed by type of healthcare (hospital, outpatient or pharmacological care), and a second phase in which the expenditure was distributed by the type of care among the icd-9-cm categories. in the first phase, this distribution was based on information enabling the various budget items to be assigned to the different types of care. various elements were used for the distribution by categories, depending on each type of care: hospital stay, outpatient visit or consumption by therapeutic subgroup. results: distribution of the budget was as follows: 46.6% for specialized care, 27.5% for pharmacological care, and 20.0% for primary care; 5.9% was not distributed. of the 17 categories, that accounting for the largest percentage (17.3%) was ?diseases of the circulatory system? (vii), followed by category viii, ?diseases of the respiratory system? which totaled 10.9%. the budget was concentrated in 5 categories, the 2 mentioned above plus category v ?mental disorders? (9.4%), category ii ?tumors? (9.1%) and category ix ?disorders of the digestive system? (7.7%), which accounted for 54.4% of the total budget. the internal composition of each category showed major variations. conclusion: the distribution of the budget offers a point of reference for health planning and management.
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.
Análisis de coste-efectividad de la vacunación antineumocócica en Espa?a
Morano,Raúl; Pérez,Ferrán; Brosa,Max; Pérez Escolano,Isabel;
Gaceta Sanitaria , 2011, DOI: 10.1590/S0213-91112011000400002
Abstract: objective: to perform a cost-effectiveness analysis of pediatric pneumococcal vaccination in spain. methods: a deterministic population-based model in the form of a decision-tree with a 1-year time horizon was used to estimate the impact of vaccination with synflorix? or prevenar13? in children aged less than 2 years in spain from the perspective of the national health system. epidemiological data were obtained from the hospital discharge minimum data set (mds) and the literature. data on costs were obtained from national health costs databases. the main outcomes measured were the number of cases avoided of invasive pneumococcal disease, acute otitis media (aom) and myringotomies, and hospital admissions for pneumonia. all costs were expressed in 2010 euros. effectiveness was measured as the number of quality-adjusted life years (qalys) gained. results: the efficacy of synflorix? in preventing episodes of aom caused by non-typeable haemophilus influenzae could lead to additional prevention of 41,513 episodes of aom, 36,324 antibiotic prescriptions and 382 myringotomy procedures and 143 qalys gained compared with prevenar13?. the total vaccination cost with synflorix? would result in savings of 22 million euros. conclusions: pneumococcal vaccination with synflorix? in comparison with prevenar13? in children aged less than 2 years old in spain could achieve a higher number of qalys and a substantial cost offset. vaccination with synflorix? would be a dominant strategy in terms of cost-effectiveness.
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.

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