[en] In 1987 the Regional Autonomous Corporation of Risaralda, CARDER and the Risaralda Government, they signed a cooperation agreement, in order to endowing from sanitary landfill to the municipalities of the department. In the mark of this agreement it was carried out the design of Santa Rosa's sanitary landfill, that with near 50.000 inhabitants it is constituted in the third city of the department. This city generates some 25 tons/day of garbage that at the present time are heady directly to the waters of San Eugenio River. The present work contains the most important methodological aspects in the design of the sanitary landfill and some comments about the approaches ideal Vs real approaches of selection of places

[en] This paper analyses both theoretically and experimentally the problem of film boiling from a body embedded in a liquid saturated porous medium. Two body geometries are investigated thoroughly: a horizontal cylinder and a sphere. The theoretical model relies on the Brinkman-extended flow model to describe the flow field inside the thin vapor layer occupying the neighborhood near the heated surface. The theoretical model also includes an improved formulation of the effective conductivity in the vicinity of the heater as a function of the vapor layer thickness and the geometry of the porous medium material. Solutions are obtained for the vapor layer thickness and the local Nusselt number as a function of angular position. Numerical solutions are also obtained for the overall heat transfer rates from the heated surface to the fluid for a range of problem parameters. Experimental data for a 12.70 mm OD stainless steel cylindrical heater embedded in a 3-mm glass particles porous medium were obtained under steady state operation. The experimental data obtained are compared with the theoretical analysis. The comparison shows that there is a good agreement between theory and experiments. The theoretical model is also compared with the experimental data obtained by other investigators for a spherical geometry. Excellent results are obtained in such comparison

[en] This paper reports on an experimental investigation that was conducted to evaluate the effect of tube spacing and liquid temperature on the average and local heat transfer coefficients of tubes in a tube bundle. The dependency on these two parameters was found to be controlled by the flow field around the tubes

[en] Nowadays, the ball milling technique has become one of the most important owing to its ease of getting the combination of different materials in a short time thus obtaining nanostructures of different types. In the present work, the temporal evolution of the phase change of titanium dioxide from anatase to rutile is shown through the ball milling technique. The milling time was varied from 1 to 9 hours at a carbon dioxide atmosphere controlled at a pressure of 34.47 KPa and a ratio of 1:10 (gram of material: gram of balls). The results were analyzed through X-ray photoelectronic spectroscopy. A change from anatase to rutile of the titanium dioxide structure is shown for each range of the milling time. In the same way, through scanning electron microscopy, a 90% reduction in the initial size was shown, thus, getting nanostructures of approximately 20 nm. (paper)

[en] An Fe-Co-Mn catalysts series after hydrogenation of carbon monoxide has been characterized. The XRD analysis shows the magnetite as main crystalline phase after reaction, in addition of carbon and carbide phases. All these phases lead to hydrogen consumption and oxidation rate changes on Fe-Co-Mn catalysts. A phase transformation superficial diagram is analysed. (Author)

[en] We present tight-binding calculations of the hole level structure of δ-doped Field Effect Transistor in a Si matrix within the first neighbors sp³s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type δ-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p_2d) of the p-type δ-doped well and the contact voltage (V_c). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

[en] The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented

[en] In this work we use the standard T-matrix method to study the tunneling of Dirac electrons through graphene multilayers. A graphene sheet is deposited on top of slabs of Silicon-Oxide (SiO₂) and Silicon-Carbide (SiC) substrates, in which we applied the Cantor’s series. We calculate the transmittance as a function of energy for different incident angles and different generations of the Cantor’s series. Comparing the transmittance, we found three types of self-similarity: (a) local - into generations, (b) between incident angles and (c) between generations. We also compute the angular distribution of the transmittance for fixed energies finding a self-similar pattern between generations. To our knowledge is the first time that four different self-similar patterns are presented in Cantor-based multilayers

[en] This paper describes the thermal power calibration and neutron flux measurement performed in order to have an approach to the IAN-R1 reactor core characterization in the framework of the recently acquired operating license for five years. (author)

[en] In this work we present the results obtained from the calculation of the level structure of a n-type delta-doped well Field Effect Transistor when is subjected to hydrostatic pressure. We study the energy level structure as a function of hydrostatic pressure within the range of 0 to 6 kbar for different Schottky barrier height (SBH). We use an analytical expression for the effect of hydrostatic pressure on the SBH and the pressure dependence of the basic parameters of the system as the effective mass m(P) and the dielectric constant ε(P) of GaAs. We found that due to the effects of hydrostatic pressure, in addition to electronic level structure alteration, the profile of the differential capacitance per unit area C⁻² is affected