Heat transfer evaluation of industrial pneumatic cylinders

Automatic positioning devices are worldwide used in tasks like handling or assembly, making them key components of modern manufacturing systems. Pneumatic solutions are usually less expensive than their electrical counterparts, are more reliable and require less maintenance. However, the complex nonlinear nature and high model order of pneumatic systems lead to a very difficult control task. These problems make model order reductions and simplifications a common practice in servo pneumatics. The heat transfer between air inside the cylinder and its environment is usually neglected or only indirectly accounted, since it varies with pressure, temperature and speed of the actuator, which makes its experimental assessment difficult. In this work we present a simple yet accurate procedure, based on a thermal time constant, enabling its evaluation. The procedure is validated by simulation studies and furthermore the heat conductance of three industrial actuators is experimentally determined

Physical properties of the Schur complement of local covariance matrices

General properties of global covariance matrices representing bipartite Gaussian states can be decomposed into properties of local covariance matrices and their Schur complements. We demonstrate that given a bipartite Gaussian state $\rho_{12}$ described by a $4\times 4$ covariance matrix \textbf{V}, the Schur complement of a local covariance submatrix $\textbf{V}_1$ of it can be interpreted as a new covariance matrix representing a Gaussian operator of party 1 conditioned to local parity measurements on party 2. The connection with a partial parity measurement over a bipartite quantum state and the determination of the reduced Wigner function is given and an operational process of parity measurement is developed. Generalization of this procedure to a $n$-partite Gaussian state is given and it is demonstrated that the $n-1$ system state conditioned to a partial parity projection is given by a covariance matrix such as its $2 \times 2$ block elements are Schur complements of special local matrices.Comment: 10 pages. Replaced with final published versio

Diluted antiferromagnet in a ferromagnetic enviroment

The question of robustness of a network under random ``attacks'' is treated in the framework of critical phenomena. The persistence of spontaneous magnetization of a ferromagnetic system to the random inclusion of antiferromagnetic interactions is investigated. After examing the static properties of the quenched version (in respect to the random antiferromagnetic interactions) of the model, the persistence of the magnetization is analysed also in the annealed approximation, and the difference in the results are discussed

Spin-glass behaviour on random lattices

The ground-state phase diagram of an Ising spin-glass model on a random graph with an arbitrary fraction $w$ of ferromagnetic interactions is analysed in the presence of an external field. Using the replica method, and performing an analysis of stability of the replica-symmetric solution, it is shown that $w=1/2$, correponding to an unbiased spin glass, is a singular point in the phase diagram, separating a region with a spin-glass phase ($w<1/2$) from a region with spin-glass, ferromagnetic, mixed, and paramagnetic phases ($w>1/2$)

Decoherence of tripartite states - a trapped ion coupled to an optical cavity

We investigate the non-dissipative decoherence of three qubit system obtained by manipulating the state of a trapped two-level ion coupled to an optical cavity. Modelling the environment as a set of noninteracting harmonic oscillators, analytical expressions for the state operator of tripartite composite system, the probability of generating maximally entangled GHZ state, and the population inversion have been obtained. The pointer observable is the energy of the isolated quantum system. Coupling to environment results in exponential decay of off diagonal matrix elements of the state operator with time as well as a phase decoherence of the component states. Numerical calculations to examine the time evolution of GHZ state generation probability and population inversion for different system environment coupling strengths are performed. Using negativity as an entanglement measure and linear entropy as a measure of mixedness, the entanglement dynamics of the tripartite system in the presence of decoherence is analysed.Comment: Revised version, errors corrected and references added. 12 pages, 6 figures, Presented at ICSSUR May 2005, Besancon, Franc

Reduced-order thermodynamic models for servo-pneumatic actuator chambers

This paper discusses thermodynamic models of air inside pneumatic actuator chambers. In servopneumatics common practice, these models are simplified by neglecting the temperature dynamics. Classical models in literature assume temperature inside the pneumatic chamber to be either constant or to follow a polytropic law. Furthermore, the mixing process of air entering the chamber and heat transfer between air and cylinder walls is often neglected or only implicitly taken into account. This work evaluates the impact of these simplifications/order reductions in the prediction of pressure inside the actuator chamber. Classical models are compared with several others taking into account not only the mixing process but also explicitly including heat transfer between air and cylinder walls. Simulation studies show that the reduced order models proposed in this paper can lead to a mean square error in pressure prediction of only 10% of the one obtained using classical models

Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics

In this work we show how to engineer bilinear and quadratic Hamiltonians in cavity quantum electrodynamics (QED) through the interaction of a single driven two-level atom with cavity modes. The validity of the engineered Hamiltonians is numerically analyzed even considering the effects of both dissipative mechanisms, the cavity field and the atom. The present scheme can be used, in both optical and microwave regimes, for quantum state preparation, the implementation of quantum logical operations, and fundamental tests of quantum theory.Comment: 11 pages, 3 figure

Avaliação de hibridos triplóides de melancia no Vale do Sub-médio São Francisco.

O desempenho agronômico de doze híbridos de melancia sem sementes foi avaliado no município de Petrolina -PE. Foram utilizados os híbridos Tiffany (Asgrow), Nova, AF-180, AF-179, AF-178, AF-177, AF-176 (Sakata-Agroflora), W-691 (Sainoda), Ailet 1, Ailet 2, HLT- 02 e H L T -03 (Embrapa Semi-Árido). O experimento foi realizado no delineamento de blocos ao acaso com três repetições de dez plantas e espaçamento de 3,0 x 1,0 m. Foram avaliados o número de dias para o aparecimento da primeira flor feminina, número de frutos por planta, peso médio de frutos, teor de sólidos solúveis, espessura média da casca, percentual de frutos com sementes e percentual de frutos com ocamento. Todos os híbridos apresentaram produtividade e teor de sólidos solúveis em níveis satisfatórios, no entanto verificou-se elevada ocorrência de frutos com sementes verdadeiras e com problemas de ocamento na polpa. Os altos coeficientes de variação observados na análise de algumas variáveis sugerem a necessidade de realizar novos ensaios, utilizando-se parcelas maiores, a fim de aumentar a precisão do experimento.Suplemento 2. Edição do 42 Congresso Brasileiro de Olericultura; 11 Congresso Latino Americano de Horticultura, Uberlândia, jul. 2002