1,509 research outputs found

    Quantum radiation pressure on a moving mirror at finite temperature

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    We compute the radiation pressure force on a moving mirror, in the nonrelativistic approximation, assuming the field to be at temperature T.T. At high temperature, the force has a dissipative component proportional to the mirror velocity, which results from Doppler shift of the reflected thermal photons. In the case of a scalar field, the force has also a dispersive component associated to a mass correction. In the electromagnetic case, the separate contributions to the mass correction from the two polarizations cancel. We also derive explicit results in the low temperature regime, and present numerical results for the general case. As an application, we compute the dissipation and decoherence rates for a mirror in a harmonic potential well.Comment: Figure 3 replaced, changes mainly in Sections IV and V, new appendix introduced. To appear in Physical Review

    Inertial forces in the Casimir effect with two moving plates

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    We combine linear response theory and dimensional regularization in order to derive the dynamical Casimir force in the low frequency regime. We consider two parallel plates moving along the normal direction in D−D-dimensional space. We assume the free-space values for the mass of each plate to be known, and obtain finite, separation-dependent mass corrections resulting from the combined effect of the two plates. The global mass correction is proportional to the static Casimir energy, in agreement with Einstein's law of equivalence between mass and energy for stressed rigid bodies.Comment: 9 pages, 1 figure; title and abstract changed; to appear in Physical Review

    Application of fractional algorithms in control of a quad rotor flight

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    This paper studies the application of fractional algorithms in the control of a quad-rotor rotorcraft machine. The main contribution of this paper focuses in the development a flight simulator to provide the evaluation model of the quad-rotor. Several basic maneuvers are investigated, namely the elevation and the position control.N/

    Application of fractional algorithms in the control of a twin rotor multiple input-multiple output system

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    This paper presents the modelling and control of a laboratory helicopter twin rotor MIMO system using the MatLab package. Firstly, we provide an overview of the system model, secondly, we compare the behaviour of fractional and integer order controllers used a PSO algorithm for the controller optimization in order to obtain the minimum error. Finally, we analyse the system performance and the results obtained with the real helicopter show that fractional algorithms are smoother than conventional PID. Both controllers reveal good output responses but the PID needs more energy to perform the same task.N/

    Aplication of fractional algoritms in the control of an helicopter system

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    This paper compares the application of fractional and integer order controllers for a laboratory helicopter twin rotor MIMO system using the MatLab package.N/

    The Differentiation and Promotion of Students’ Rights in Portugal

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    This investigation includes a differential study (Study 1) and a quasi-experimental research (Study 2). In Study 1, the objective was to establish to what extent students’ rights existed and analyse the differentiation between students’ rights with Portuguese and immigrant mothers, throughout school years. The sample consisted of 537 students with Portuguese and immigrant mothers, distributed by different school years (7th, 9th and 11th grades). The Children’s Rights Scale (Hart et al., 1996; Veiga, 2001) was used. In Study 2, the purpose was to analyse the effects on students’ rights of the use by teachers of a communicational intervention program, supervised by school psychologists. The sample involved 7th and 9th grade students, in a total of four classes, two forming the experimental groups (n = 36) and two the control groups (n = 43); as in Study 1, the Children’s Rights Scale was used. The results indicated the effectiveness of the communicational intervention program on students’ rights and are consistent with previous studies. An implication is that psychologists and teachers, working together and taking a human rights perspective, may develop an important role in projects to promote the students’ rights

    Helicopter system modelling and control with matlab

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    This paper presents the modelling and control of a laboratory helicopter system with MatLab. In this perspective, students are motivated to investigate the dynamics, trajectory planning and control. Based on this experience, further studies on helicopter system, using more sophisticated concepts, are, then, more attractive from the students point of view.N/

    Molecular Dynamics of Film Formation of Metal Tetrasulfonated Phthalocyanine and Poly Amidoamine Dendrimers

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    We performed molecular dynamics computer simulations to elucidate the behavior and properties of the metal tetrasulfonated phthalocyanine molecule and the poly(amidoamine) dendrimers in self-assembly depositions, respectively, on poly(allylamine hydrochloride) polymer and on film formed by metal tetrasulfonated phthalocyanine with poly(allylamine hydrochloride). Important physical properties of phthalocyanines were obtained such as the kinetic energy and temperature in situ. By the semiempirical model, we also obtained the UV-Vis absorption spectrum of the film formed by cobalt tetrasulfonated phthalocyanine deposited on poly(allylamine hydrochloride). We performed a study with poly(amidoamine) dendrimers on their deposition time on metal tetrasulfonated phthalocyanine, poly(allylamine hydrochloride) film, and we show the relationship of deposition time with the electrical charge and molecular mass of phthalocyanines. The deposition times of the dendrimers, as a function of their mass, were also elucidated

    Germinação de sementes de Passiflora spp.

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    A forma mais utilizada na propagação de plantas do gênero Passiflora é por meio de sementes, devido à praticidade deste método. Por outro lado, o tempo de germinação das sementes do maracujazeiro pode ocorrer de dez dias a três meses, dificultando a formação das mudas para etapas posteriores do cultivo, por não apresentarem desenvolvimento padronizado
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