El enfriamiento evaporativo y las pozas de aspersión

La transferencia acoplada de calor y masa en una poza de enfriamiento por aspersión es descrita y calculada a través de las ecuaciones básicas de continuidad y energía. Se establecen las relaciones que describen el movimiento y distribución espacial de gotas, la interacción de éstas con el aire circundante y los coeficientes de transferencia de calor y masa. El sistema álgebro diferencial de ecuaciones modela los campos de temperatura y humedad absoluta, mientras que el campo de velocidad del aire es supuesto constante y se estima a partir de valores obtenidos de literatura. Esta simplificación permite desacoplar, en el cálculo numérico, las variables de velocidad y temperatura. El tratamiento acoplado de estas variables es reportado en otro trabajo de los autores [18]. El modelo obtenido se aplica a una poza circular de enfriamiento por aspersión con viento nulo. Los perfiles de velocidad del aire se proponen invariables y su magnitud y sentido se obtienen de otros trabajos de los autores. La solución simultánea de los campos térmicos y másico se obtiene por medio del método numérico de diferencias finitas. Las ecuaciones de transporte se resuelven usando el método matricial de dirección alternada implícita (ADI). La estabilidad numérica del sistema se alcanza utilizando un factor de amortiguamiento en los coeficientes de la matriz de coeficientes de las ecuaciones discretizadas. Se analizan los resultados que entrega el modelo al variar la viscosidad turbulenta del aire, puesto que influye en los valores de temperatura y humedad del aire, con el correspondiente impacto sobre las características de disipación de la poza

Inducing nonclassical lasing via periodic drivings in circuit quantum electrodynamics

We show how a pair of superconducting qubits coupled to a microwave cavity mode can be used to engineer a single-atom laser that emits light into a nonclassical state. Our scheme relies on the dressing of the qubit-field coupling by periodic modulations of the qubit energy. In the dressed basis, the radiative decay of the first qubit becomes an effective incoherent pumping mechanism that injects energy into the system, hence turning dissipation to our advantage. A second, auxiliary qubit is used to shape the decay within the cavity, in such a way that lasing occurs in a squeezed basis of the cavity mode. We characterize the system both by mean-field theory and exact calculations. Our work may find applications in the generation of squeezing and entanglement in circuit QED, as well as in the study of dissipative few- and many-body phase transitions

Retornos accionarios e informacion contable : un caso para el estudio de eventos. Analisis empirico: 4° trimestre periodo 1995-2004

85 p.El impacto que ha tenido la publicación de las Fichas Estadísticas Codificadas Uniformes (FECUs), es decir, la información contable sobre la riqueza de los accionistas chilenos, es un tema que escasamente ha sido discutido por la literatura especializada. La presente investigación, aplica la metodología de Estudio de Eventos para analizar como el mercado de capitales chileno ha incorporado la publicación de las FECUs. Utilizando tres modelos estadísticos, los resultados señalan que Ios precios incorporan en forma positiva y estadísticamente significativa la publicación de buenas noticias contables. En el caso de las malas noticias contables, los precios incorporan en forma negativa y estadísticamente significativa la publicación de estas malas noticias

Double Coil-Less Fluxgate in Bridge Configuration

In this paper, a new method for excitation of coil-less fluxgate is presented. The purpose of this method is to reduce the spurious component of the output voltage, allowing us to increase the amplification. The method is based on the employment of two coil-less fluxgates in a double bridge, which injects pulsing current in opposite direction in each wire. By taking the difference of the voltages on the two wires, we suppress the component of the voltages, which does not change under application of external measured field. The sensitive axes are in opposite direction, so the wire feels opposite field. As a result, we will obtain an output voltage with low peak value, including only the component of the voltage that changes when we apply external field. Finally, we propose an improved version of the double bridge to allow the employment of two sensing elements with difference characteristics. This is obtained by optimizing the suppression of the spurious voltages and, at the same time, setting independently chosen values of exciting current for each wire

Hacia un manejo integrado de la degeneracion de la semilla de papa en Ecuador.

Peer Revie

Quantum coherent control of highly multipartite continuous-variable entangled states by tailoring parametric interactions

The generation of continuous-variable multipartite entangled states is important for several protocols of quantum information processing and communication, such as one-way quantum computation or controlled dense coding. In this article we theoretically show that multimode optical parametric oscillators can produce a great variety of such states by an appropriate control of the parametric interaction, what we accomplish by tailoring either the spatio-temporal shape of the pump, or the geometry of the nonlinear medium. Specific examples involving currently available optical parametric oscillators are given, hence showing that our ideas are within reach of present technology.Comment: 14 pages, 5 figure

Simulating quantum-optical phenomena with cold atoms in optical lattices

We propose a scheme involving cold atoms trapped in optical lattices to observe different phenomena traditionally linked to quantum-optical systems. The basic idea consists of connecting the trapped atomic state to a non-trapped state through a Raman scheme. The coupling between these two types of atoms (trapped and free) turns out to be similar to that describing light-matter interaction within the rotating-wave approximation, the role of matter and photons being played by the trapped and free atoms, respectively. We explain in particular how to observe phenomena arising from the collective spontaneous emission of atomic and harmonic oscillator samples such as superradiance and directional emission. We also show how the same setup can simulate Bose-Hubbard Hamiltonians with extended hopping as well as Ising models with long-range interactions. We believe that this system can be realized with state of the art technology