[en] Different methods for micropore volume calculation in carbonaceous material s were studied. it was investigated a method which approximates the micropore volume calculated from high pressure methane adsorption isotherms by means of low pressure adsorption isotherms (N₂ and CO₂). the best fit was achieved for the Dubinin-Astakhov equation for carbon dioxide isotherms, CO₂ at 273 K

[en] The use of renewable energy such as photovoltaic is growing. According to IRENA, these systems are one of the most dynamic generation technologies. The global photovoltaic market has grown rapidly between 2000 and 2016 at an annual average compound rate of 44%, from 0.8 GW to 291 GW. In Colombia, regions with high solar irradiation levels have been identified as emerging markets. The Government's plan is to increase the share of non-conventional energies in the energy matrix from 2% to 8% - 10%. However, the uncertainties associated with technology and sites specific degradation rates make it difficult to calculate accurate electricity generation efficiencies and predicting future performance and material degradation rates, and thus business models exhibit considerable deviations related to the real electricity generation rates. This work studies the performance and early degradation of a 180.8 kWp rooftop on grid connected photovoltaic system, installed in Barranquilla, Colombia. Two methods were used: i) estimation of solar conversion efficiency, and ii) visual inspection. The first method includes a cross analysis of climatic conditions, irradiance levels, and the generated energy downstream the inverters. The second method consists of periodical visual inspections of installed modules to check: discoloration, delamination, busbar corrosion, cracking of solar cell, glass breakage, anti-reflection coating and solder bond.

[en] This paper, which has teaching and public-science aims, presents some examples, attained in the Southern Bays of Galicia (Spain) of inferior and superior mirages, including castles in the air, fata Morganas and towering. The explanation for the unusual atmospheric refraction is presented, and the different kinds of ray paths distortions that lead to each optical effect and the respective gradient indexes that generate these distortions are shown. In addition, the temperature differences required for each case are related to the successive oceanographic and climatic conditions that occur along the year in this coast.

[en] The present study aims to estimate the expansion of the dose due to the use of gold nanoparticles in the treatment of uterine cancer. It simulates the source of 192Ir high dose rate (HDR) widely used in brachytherapy treatment in our country at the National Oncology and Radiobiology (INOR) to treat cervical cancer. For the simulation of brachytherapy treatment with this source was used mathematical phantom of the uterus (Eckerman et al, 1996). The composition and density of the tumor in the uterus was altered by the levels of concentration of nanoparticles used in previous studies in vivo: 7 and 18 mg Au / g tumor. Was also used in this study a higher concentration of 30 mg Au / g tumor. Was studied In addition, the effect of the presence of nanoparticles outside the tumor to a concentration of 2 mg Au / g tissue. The calculation of dose deposited in the presence and absence of nanoparticles in the tumor were performed with the MCNP-X program, based on Monte Carlo techniques. Was obtained Increasing the dose up to 20% in the tumor with the introduction of 3% by weight of the gold nanoparticles. These results demonstrate that nanotechnology could be added to conventional treatments of cancer treatment for their promising results. (author)

No abstract available

[en] The rapid development of image processing systems has made possible the mapping of not only the distribution of activity (SPECT, PET), but also the density (CT, NRM) in the organ or tissue of the patient. There is evidence that the coregistration and image fusion of different modalities leads to greater diagnostic accuracy. To treat cancer is necessary to know the dose to the tumor and organs at risk. At present the Monte Carlo method is more accurate dosimetric method. The determination of the dose distribution is a tool for the development of systems planning treatments for cancer patients. One of the biggest obstacles in the development of improved methods for more accurate estimate of the absorbed dose in cancer therapy has been the difficulty of obtaining the 3D distribution of dose from medical imaging patient multimodal specific. A boot strapper (Milian and Gual, 2004) as an interface between SPECT and MCNP code was developed to determine the specific patient dose distribution. The aim of this is to determine the absorbed dose distribution in tumors from the acquired images coregistered SPECT TAC studies by Monte Carlo code MCNPX. The results of this study will serve as input to the planning system in nuclear medicine treatments. (author)

[en] The Very High Temperature Reactor is one of the main candidates for the next generation of nuclear power plants. In pebble bed reactors, the fuel is contained within graphite pebbles in the form of TRISO particles, which form a randomly packed bed inside a graphite-walled cylindrical cavity. In previous studies, the conceptual design of a Transmutation Advanced Device for Sustainable Energy Applications (TADSEA) has been made. The TADSEA is a pebble-bed ADS cooled by helium and moderated by graphite. In order to simulate the TADSEA correctly, the double heterogeneity of the system must be considered. It consists on randomly located pebbles into the core and randomly located TRISO particles into the fuel pebbles. These features are often neglected due to the difficulty to model with MCNP code. The main reason is that there is a limited number of cells and surfaces to be defined. In this paper a computational tool, which allows to get a new geometrical model for fuel pebble to neutronic calculation with MCNPX, was presented. The heterogeneity of system is considered, and also the randomly located TRISO particles inside the pebble. There are also compared several neutronic computational models for TADSEA's fuel pebbles in order to study heterogeneity effects. On the other hand the boundary effect given by the intersection between the pebble surface and the TRISO particles could be significative in the multiplicative properties. A model to study this e ect is also presented. (author)

No abstract available

[en] Control strategies for auto-ignition control in turbocharged internal combustion engines operating with gaseous fuels are presented. Ambient temperature and ambient pressure are considered as the disturbing variables. A thermodynamic model for predicting temperature at the ignition point is developed, adjusted and validated with a large experimental data-set from high power turbocharged engines. Based on this model, the performance of feedback and feedforward auto-ignition control strategies is explored. A robustness and fragility analysis for the Feedback control strategies is presented. The feedforward control strategy showed the best performance however its implementation entails adding a sensor and new control logic. The proposed control strategies and the proposed thermodynamic model are useful tools for increasing the range of application of gaseous fuels with low methane number while ensuring a safe running in internal combustion engines. - Highlights: • A model for predicting temperature at the ignition point. • Robust PID, modified PID, and feedforward strategies for auto-ignition control. • λ′ were the best set of tuning equations for calculating controller parameters. • Robust PID showed significant improvements in auto-ignition control. • Feedforward control showed the best performance

[en] At the microscale, C-S-H gels from alite, or neat Portland cements, has a Ca/Si ratio close to 1.80. At the nanoscale, C-S-H is described by a defective tobermorite structure which allows a maximum Ca/Si ratio close to 1.40. There is no agreement in the location of the extra 0.40 mol of Ca(OH)₂ at the nanoscale. Atomistic modelling studies reported Ca(OH)₂ species within the tobermorite interlayer space. Other works point toward a fine intermixing of defective tobermorite and nanoportlandite. Here, we have prepared a series of alite blended with silica fume and studied the pastes by several techniques including synchrotron pair distribution function (PDF). In the employed conditions, the C-S-H gel formed by the pozzolanic reaction has nearly the same local structure than the primary C-S-H gel. Furthermore, differential PDF points toward Ca(OH)₂ excess having a local structure compatible with few-layer thick nanoparticles stretched along the c-axis.