HEH-BMAC: hybrid polling MAC protocol for WBANs operated by human energy harvesting

This paper introduces human energy harvesting medium access control (MAC) protocol (HEH-BMAC), a hybrid polling MAC suitable for wireless body area networks powered by human energy harvesting. The proposed protocol combines two different medium access methods, namely polling (ID-polling) and probabilistic contention access, to adapt its operation to the different energy and state (active/inactive) changes that the network nodes may experience due to their random nature and the time variation of the energy harvesting sources. HEH-BMAC exploits the packet inter-arrival time and the energy harvesting rate information of each node to implement an efficient access scheme with different priority levels. In addition, our protocol can be applied dynamically in realistic networks, since it is adaptive to the topology changes, allowing the insertion/removal of wireless sensor nodes. Extensive simulations have been conducted in order to evaluate the protocol performance and study the throughput and energy tradeoffs.Peer ReviewedPostprint (author's final draft

Safety and Labor Health, Corporate Social Responsibility with Return of Economic Benefits

This article is a quantitative and qualitative case study of the Self- Management Program Occupational Safety and Health (P.A.S.S.T.) implemented in twenty-five Mexican companies. The analysis is based on the theories of business ethics, corporate governance and the concept of publicprivate partnerships to explain the achieved link by the Ministry of Labor and Social Prevision (S.T.P.S) and the Private Initiative to improve the safety conditions and health within the companies. After reviewing the results of the data obtained by the companies, it was found that there are financial benefits and quality in processes, derived from the good corporate governance

Magnetic ions-doped ZnO nanocrystals : study of the structural, electronic, optical and magnetic properties

Tese (doutorado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação em Física, 2018.Como conseqüência da miniaturização geral dos dispositivos, os materiais nanocristalinos atraíram muita atenção de pesquisadores em várias áreas para estudar o tamanho finito e os efeitos de superfície. Estes efeitos geram novos fenômenos físicos e propriedades aprimoradas em relação à sua forma em "bulk". Entre esses materiais, os nanocristais (NCs) de óxido de zinco (ZnO) têm sido um dos mais intensamente estudados devido à baixa temperatura de processamento e total compatibilidade com a fabricação de circuitos integrados de larga escala. Os NCs de ZnO são reconhecidos como um material promissor para aplicações em spintrônica e para melhorar os dispositivos optoeletrônicos em nanoescala, tais como células solares, diodos emissores de luz orgânicos, diodos laser ultravioleta, etc. Desde o ponto de vista fundamental, o envolvimento dos efeitos em nanoescala permitiu maior compreensão e melhoria das propriedades dos materiais magnéticos e ópticos avançados. Devido ao intenso foco neste material, a literatura do ZnO é vasta e muitas vezes contraditória; no entanto, hoje em dia, as técnicas de absorção de raios-X (i.e., XANES e EXAFS) disponíveis em todo o mundo são usadas para decifrar a verdadeira origem das diferentes propriedades estruturais; e interações ópticas e magnéticas em compostos a base de ZnO. Devido à alta seletividade no átomo absorvedor e sua dependência da estrutura local dos íons estudados, essas técnicas podem oferecer informações valiosas. Na presente tese de doutorado, foram sintetizados NCs de ZnO dopado com Ni, Co, e Tb, obtidos através do método sol-gel e caracterizados por técnicas convencionais, tais como difração de raios-X (XRD), microscopia de transmissão de alta resolução (HRTEM), espectroscopia fotoeletrônica de raios-X (XPS), fotoluminescência (PL), ressonância paramagnética eletrônica (EPR) e magnetometria baseada em SQUID; e técnicas avançadas com seletividade atômica, tais como espectroscopia de estrutura de absorção de raios-X próxima à borda (XANES) e espectroscopia da estrutura fina de absorção de raios-X estendida (XAFS). Análise detalhada dos padrões de XRD e imagens HRTEM indicam a formação de NCs de ZnO puro e dopado na estrutura wurtzita, com formas circulares e elípticas, e mudanças nos parâmetros de rede conforme o teor de dopante—em consistência com a análise de dados EXAFS. O sinal EXAFS medido na borda K do Co mostrou características consistentes com aquelas mostradas pela borda K do Zn nos NCs puros de ZnO, fornecendo evidência clara de que o Co apresenta uma coordenação tetraédrica. Os resultados do EXAFS na borda K do Ni e na borda L3 do Tb sugerem a modificação do ambiente local do Ni e Tb em comparação àquele observado para os sítios de Zn e Co. Além disso, os resultados de XPS e XANES indicaram que o Co e Ni assumem predominantemente o estado de valência 2+ e estão localizados principalmente em sítios tetraédricos e octaédricos, respectivamente. Estes resultados estão de acordo com a análise dos espectros de EPR e—no caso do Co—com as medições de PL que exibem uma banda de emissão no vermelho relacionada com a transição interna dos íons Co2+ em um campo de cristal tetraédrico. Para a dopagem com Tb foi determinado um estado de valência mista (3+/4+) e as medições de PL forneceram emissões estreitas de resolução bem definida características de transições intra-iônicas dos íons Tb3+. A correlação das técnicas de PL e EPR nos permitiu sugerir que o elétron preso em uma vacância de oxigênio participa na emissão no verde de amostras de ZnO dopadas com Co. Finalmente, as medições magnéticas confirmam os resultados obtidos com as outras técnicas, indicando que os momentos magnéticos são consistentes com a presença de íons Co2+, Ni2+ e Tb3+/Tb4+ nos NCs de ZnO dopados com Co, Ni e Tb, respectivamente. Além disso, os valores negativos da temperatura de Curie (θ) determinados para as amostras dopadas com Co e Tb indicaram a ocorrência de interações locais antiferromagnéticas e os valores positivos de θ nas amostras dopadas com Ni indicaram a ocorrência de interações locais ferromagnéticas.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).As a consequence of the general miniaturization of devices, nanocrystalline materials have attracted a great deal of attention from researchers in various areas to study finite-size and surface effects. These effects yield new physical phenomena and enhanced properties with respect to their bulk counterpart. Among these materials, Zinc Oxide (ZnO) nanocrystals (NCs) have been one of the most intensively studied owing to the low processing temperature and full compatibility with the large scale integrated circuit fabrication. ZnO NCs are recognized as a promising material for applications in spintronics and to improving nanoscale optoelectronic devices, such as bandgap engineered solar cells, organic light emitting diodes, ultraviolet laser diodes, etc. From the fundamental point of view, the involvement of nanoscale effects has allowed further understanding and improvement of the properties of advanced magnetic and optical materials. Because of the intense focus on this material, the ZnO literature is vast and often contradictory; nevertheless, nowadays, the X-ray absorption techniques (i.e., XANES and EXAFS) available around the world are being used to decipher the real origin of the different structural properties; and optical and magnetic interactions in ZnO-based compounds. Due to the high selectivity on the absorber atom and their dependence on the local structure of the studied ions these techniques can offer valuable information. In the present doctoral thesis, we have synthesized and performed a detailed study of Ni-, Co-, and Tb-doped ZnO NCs obtained via the sol-gel method. The NCs were characterized by conventional macroscopic techniques, such as X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), electronic paramagnetic resonance (EPR), SQUID-based magnetometry; and element-specific advanced tools, such as X-ray absorption near-edge spectroscopy (XANES) and X-ray absorption fine structure (XAFS). Detailed analysis of the XRD patterns and HRTEM images indicate the formation of pure and doped ZnO NCs in the wurtzite structure, with circular- and elliptical-like shapes, and changes in the structural parameters with the dopant content—in consistency with the EXAFS data analysis. The experimental EXAFS signal measured at the Co K-edge showed features consistent with those displayed by the Zn K-edge of pure ZnO NCs providing clear evidence that Co ions are present in tetrahedral coordination. The EXAFS results at the Ni K- and Tb L3-edge suggest the modification of the Ni and Tb local environment in comparison to that observed for Zn and Co sites. Besides, XPS and XANES results indicated that Co and Ni ions assume predominantly the 2+ valence state and are mostly located in tetrahedral and octahedral sites, respectively. These results are in agreement with the analysis of EPR spectra and—in the case of Co—with the PL measurements, which exhibit a red emission band related to the internal transition of Co 2+ ions in a tetrahedral crystal field. For Tb-doping was determined a mixed-valence state (3+/4+) and the PL measurements provided additional well-resolve narrow emissions characteristic of intra-ionic transitions of Tb3+ ions. The correlation of PL and EPR techniques permitted us to suggest that the electron trapped in an oxygen vacancy participate in the green emission of Co-doped ZnO samples. Finally, the magnetic measurements confirm the results obtained from the other techniques indicating that the magnetic moments are consistent with the presence of Co2+, Ni2+, and Tb3+/Tb4+ ions in the Co-, Ni-, and Tb-doped ZnO NCs, respectively. Moreover, the negative values of the Curie temperature (θ) determined for samples doped with Co and Tb indicate the occurrence of local antiferromagnetic interactions and the positive θ values in the Ni-doped samples suggests the occurrence of local ferromagnetic interactions

LP seismicity source models for the activity of the Galeras volcano 2004-2010 (Colombia)

ilustraciones, fotografías, gráficas, tablasEn este estudio se analiza la sismicidad tipo LP del volcán Galeras para el periodo 2004 – 2010, desde los aspectos relacionados con: 1) su distribución temporal, mediante la aplicación de la técnica de variación de la dimensión fractal, 2) la segmentación de la sismicidad en familias y grupos de familias, utilizando correlación cruzada y la caracterización de familias y grupos mediante información espectral, 3) los resultados generados en 1 y 2, sirven de apoyo contextual para la generación de modelos de resonancia de una columna de magma, dentro de la cual se aplica una perturbación que se propaga en forma de ondas sísmicas por la interfase de la columna y la corteza superficial, hasta alcanzar un receptor. La información para la parametrización de la corteza superficial y el magma, se obtuvo de estudios específicos preexistentes, y la solución de los sistemas de ecuaciones se realiza mediante el método de elementos finitos. Los resultados muestran un comportamiento anómalo en la dimensión fractal durante el emplazamiento de los domos de lava de 2006 y 2008. La caracterización sísmica evidencia la existencia de 9 familias de sismos LP que se distribuyeron en dos grupos G1 y G2, asociados respectivamente con el emplazamiento de los domos de lava en superficie y la sismicidad precedente a estos domos. Se parametrizaron modelos para los grupos, G1 y G2, los cuales tienen por diferencias principales: la longitud de la columna de magma y el tipo de acción de la fuente sísmica. Se propone la resonancia de una columna de magma de aproximadamente 2800 m de largo, cuyo tope casi alcanza la superficie, como posible causante de la sismicidad del grupo G1 y una columna cercana a los 2000 m como responsable de los sismos del grupo G2. Adicionalmente, los resultados de este estudio ponen en duda la efectividad de la localización de sismicidad de fluidos basda en el método de atenuación de amplitudes. (Texto tomado de la fuente).This study analyzes the Long Period-type seismicity (LP) registered in Galeras volcano in the 2004 – 2010 period, from aspects related to: 1) its temporal distribution by applying the technique of the variation in the fractal dimension, 2) the segmentation of the seismicity into families and groups of families, using cross-correlation method and the characterization of families and groups using spectral information, 3) the results generated in 1 and 2, serve as contextual support for the generation of resonance models of a magma column, within from which a disturbance is applied. This disturbance is propagated in the form of seismic waves through the interface between the column and the superficial crust until to reach a receptor. The reference information used for the parameterization of the superficial crust and magma properties was obtained from specific pre-existing studies, and the solution for the system of the equations is carried out using the finite element method (FEM). The results show anomalous behavior in the fractal dimension during the emplacement of the lava domes of 2006 and 2008. Seismic characterization reveals the existence of 9 families of LP earthquakes that were distributed into two groups, G1 and G2, associated with the seismicity preceding the lava domes (G2) and that associated with their emplacement on the surface (G1). Models for groups G1 and G2 were parameterized, which have as main differences: the length of the magma column and the form of action of the seismic source. The resonance of a magma column of approximately 2000 m long is proposed as a possible cause of the seismicity of G2 group, while a 2800 m long column, whose top almost reaches the surface, as responsible for the earthquakes of the G1 group. Additionally, the results of this study cast doubt on the effectiveness of locating fluids seismicity based on seismic waves amplitude attenuation method.Incluye anexosDoctoradoDoctor en GeocienciasSismología volcánic

Detección y clasificación automática de registros sísmicos en el observatorio vulcanológico y sismológico de pasto utilizando redes neuronales artificiales

En este trabajo se aplica una metodología que combina Análisis de predicción lineal (LPC) y Redes neuronales artificiales (RNA) con el objetivo de detectar y clasificar tres tipos de sismos volcánicos: volcano-tectónicos (VT) tipo A, largo periodo (LP) y tremor (TRE). Se construye una herramienta computacional orientada a la detección y clasificación automática de estas señales sísmicas, generando información en tiempo real. Segmentos cortos de la traza continua se representan utilizando la técnica LPC que también cumple la función de reducir la dimensión del vector que contiene los datos de la forma de onda. Para las fases de detección y clasificación se utilizan RNA tipo perceptrón multicapa con una capa oculta. Entre las ventajas de la metodología está la posibilidad de detectar sismos con arribos emergentes, de corta duración o de bajo nivel energético. La aplicación del método muestra cerca de 100% de acierto para la distinción entre ruido y señal sísmica (fase de detección), 92 % de acierto para la clasificación entre sismos LP y VT y cerca del 100% en la detección de sismos tipo TRE. / Abstract. In this work is applied a methodology that to combine Linear Prediction Coding (LPC) and Artificial Neural Networks (ANN) in order to detect and classify three types of volcanic seismic signals: Type A Volcano-Tectonic events (VT), Long Period (LP) and volcanic Tremor (TRE). It was built a software oriented to detection and automatic classification of these kinds signals, generating information in Real-Time. Short segments of the continuous streams are represented using the LPC technique, also carry out the reduction of the vector containing waveform data. For the detection and classification processing-phases are used ANN type Multi-Layer Perceptron (MLP). Among the advantages of this methodology are the possibility of detect seismic events with emergent arrives, short duration or low energetic level. The application of this method shows near to 100 % of good choices for to distinguish between signal and noise level (detection phase); 92% of good choices for classification between LP and VT events; and near to 100 % for TRE-type seismicity detection.Maestrí

Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains

The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. The first one is focussed on the basic and fundamental analysis of turbulence models. In the second part the know-how acquired in the first part is applied to the study of air curtains.Regarding to the first part, the principal difficulty of computing and modelling turbulent flows resides in the dominance of non-linear effects and the continuous and wide spectrum of time and length scales. Therefore, the use of turbulence modelling employing statistical techniques for high Reynolds numbers or complex geometries is still necessary. In general, this modelization is based on time averaging of the Navier-Stokes equations (this approach is known as Reynolds-Averaged Navier-Stokes Simulations, RANS). As consequence of the average new unknowns, so-called Reynolds stresses, arise. Different approaches to evaluate them are: i) Differentially Reynolds Stress Models (DRSM), ii) Explicit Algebraic Reynolds Stress Models (EARSM), and iii) Eddy Viscosity Models (EVM).Although EVM models assuming a linear relation between the turbulent stresses and the mean rate of strain tensor are extensively used, they present various limitations. In the last few years, with the even-increasing computational capacity, new proposals to overcome many of these deficiencies have started to find their way. Thus, algebraic or non-linear relations are used to determinate the Reynolds stress tensor without introducing any additional differential equation.Therefore, the first part of this thesis is devoted to the study of several EARSM and EVM models involving linear and higher order terms in the constitutive relation to evaluate turbulent stresses. Accuracy and numerical performance of these models is tested in different flow configurations such as plane channel, backward facing step, and both plane and round impinging jets. Special attention is paid to the verification of the code and numerical solutions, and the validation of the mathematical models used. In the impinging plane configuration, improvements of models using higher order terms in the constitutive relation are limited. Whereas, in the rest of studied cases these non-linear models show a reasonably good behaviour.Moreover, taken into account models convergence, robustness and predictive realism observed in the analysis of these benchmark flows, some of them are selected for the study of air curtains and their interaction with the environment where they are placed. Air curtains are generally one or a set of vertical or horizontal plane jets used as ambient separator of adjacent areas presenting different conditions. The jet acts as a screen against energy losses/gains, moisture or mass exchanges between the areas.As was indicated before, the main purpose of the second part of this thesis is to characterize in detail actual air curtains using both experimental and different numerical approaches. Semi-empirical models to design air curtains are presented. Then, an experimental set-up used to study air curtain discharge and jet downstream is explained. Experimental measurements of velocity and temperature are shown. As a result of the experiments carried out, an improved air curtain with a new design of the discharge nozzle is obtained. Furthermore, air curtain experiments are numerically reproduced and predictions validated against the experimental data acquired. Good agreement between numerical and experimental results is observed.Finally, systematic parametric studies of air curtains in heating and refrigeration applications are done. Global energetic balances are specially considered together with global parameters selected in order to evaluate air curtain performance. It is found that discharge velocity, discharge angle and turbulence intensity of the jet are the most sensitive parameters. Inadequate values for these variables can produce undesirable effects and contribute to increase energy gains/losses

Síntese e caracterização das propriedades vibracionais, estruturais e magnéticas de nanopartículas de ZnO dopadas com metais de transição

Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, 2013.Neste trabalho foram estudadas as propriedades magnéticas de nanopartículas de ZnO dopadas com metais de transição (Mn, Fe). As amostras foram sintetizadas pelo método de co-precipitação e suas propriedades vibracionais foram estudadas com espectroscopia infravermelha e espetroscopia Raman. A espetroscopia infravermelha mostrou a evolução da formação da fase desejada através do surgimento de bandas associadas com as ligações Zn - O durante a lavagem. A espetroscopia Raman mostrou a presença de modos vibracionais associados com a estrutura wurtzita do ZnO, após calcinar as amostras a 300ºC. No entanto, modos vibracionais adicionais foram determinados nas amostras dopadas com Mn e Fe, os que foram associados com a presença dos íons dopantes na estrutura. Através de medidas de difração de raios X se determinou a presença de uma única fase cristalina identificada como a estrutura wurtzita em todas as amostras estudadas. O Refinamento dos padrões de difração usando o método de Rietveld mostrou que nas nanopartículas dopadas com Mn os parâmetros de rede não têm uma tendência clara ao aumentar a concentração do dopante, o que sugere que os íons de Mn não substituem íons de Zn, mas provavelmente ocupam posições intersticiais da estrutura. Foram feitos também estudos de estabilidade cristalina da amostra dopada com 10mol% de Mn. Após tratamentos térmicos adicionais da amostra em 500 e 900ºC se determinou a formação de uma fase secundária que pode ser Mn3O4 ou Mn3O4 /ZnMnO3. Nas nanopartículas de ZnO dopadas com Fe, o aumento de volume da célula unitária com a concentração de Fe sugere que nestas amostras acontece a substituição de íons Fe2+ por íons Zn2+. Por outro lado, as medidas de magnetização em função do campo magnético aplicado nas nanopartículas de ZnO sem dopagem, revelam a ocorrência de um ordenamento magnético de intensidade fraca, cuja origem foi associada com o ordenamento de spins de elétrons desemparelhados e armadilhados em vacâncias de oxigênio localizadas na superfície das partículas. A densidade destas vacâncias de oxigênio é grande devido ao tamanho pequeno das partículas. A caracterização magnética das nanopartículas de ZnO dopadas com Mn revela a coexistência de duas fases magnéticas; uma fase paramagnética intensa, na qual os momentos magnéticos dos íons de Mn apresentam interações antiferromagnéticas e outra fase ferromagnética, a qual foi associada com a presença de fases adicionais como Mn3O4. A caracterização magnética das nanopartículas de ZnO dopadas com Fe revela a ocorrência de um comportamento ferromagnético. As curvas de magnetização (M) em função do campo magnético (H) obtidas a 5K mostram campos coercivos que crescem com a concentração do dopante. A 300 K, estes campos coercivos tendem a zero. Curvas de zero-field-cooled (ZFC) e field-cooled (FC) para as amostras dopadas com Fe, mostram características próprias de relaxação térmica de superspins ou de sistemas frustrados. A fim de determinar a origem foram feitas medidas de susceptibilidade AC variando a frequência do campo alternado. A parte real da susceptibilidade em função da temperatura mostra um máximo que se desloca para temperaturas maiores à medida que se aumenta a frequência. Assumindo que esse máximo representa a temperatura de congelamento do sistema, ficou determinado que as propriedades magnéticas das nanopartículas de ZnO dopadas com Fe correspondem a um sistema que mostra comportamento tipo vidro de spin. ______________________________________________________________________________ ABSTRACTIn this work, the magnetic properties of ZnO nanoparticles doped with transition metals (Mn; Fe) were studied. The samples were synthesized by the coprecipitation method and its vibrational properties were analyzed with infrared and Raman spectros-copy. The infrared spectroscopy showed the evolution of the wurtzite phase formation through the arising of the bands associated with Zn O bonds during the washing. The Raman spectroscopy showed the presence of vibrational modes associated with the wurtzite structure of ZnO, after annealing the powders at 300C. Additional vibratio- nal modes were determined in samples doped with Mn and Fe, which were associated with the presence of dopant ions in the structure.Through X-ray di raction measurements, it was determined the presence of a single crystalline phase identi ed as the wurtzite structure in all samples. The Rietveld re nement of di raction patterns showed that in nanoparticles doped with Mn the lattice parameters did not show a clear dependence on the dopant concentration. This result suggests that the Mn ions do not substitute Zn ions, but probably they occupy interstitial sites in the structure. It was also made crystalline stability studies of the sample doped with 10mol% Mn. After additional thermal treatments of the sample at 500 and 900C, it was determined the formation of a secondary phase such as Mn3O4 ou Mn3O4 /ZnMnO3 . For the ZnO nanoparticles doped with Fe, it was determined an increase in unit cell volume as the Fe concentration is increased, which suggests that in 2+ 2+these samples the Fe ions substitute Zn ions. On the other hand, magnetization measurements as a function of applied magnetic eld of undoped ZnO nanoparticles reveal the occurrence of a magnetic ordering which signal is weak and its origin was associated with the coupling of spins of unpaired electrons trapped in the oxygen vacancies located at the surface of the particles. The oxygen vacancy density is large due to the small size of the particles. The magnetic characterization of ZnO nanoparticles doped with Mn reveals the coexistence of two magnetic phases; an intense paramagnetic phase, in which the magnetic moments of Mn ions show antiferromagnetic interactions and another ferromagnetic phase, which was associated with the presence of additional phases such as Mn3O4. The magnetic characterization of ZnO nanoparticles doped with Fe reveals the occurrence of a ferromagnetic behavior. The curves of magnetization (M) vs. magnetic eld (H) obtained at 5K show coercive elds. These coercive elds show an increase with the dopant concentration. At 300K, these coercive elds tend to zero. Zero- eld-cooled (ZFC) and eld-cooled (FC) curves obtained for the Fe-doped ZnO nanoparticles show features of thermal relaxation of superspins or frustrated systems. In order to determine the origin of those relaxations, AC susceptibility measurements were made by varying the frequency of the alternating eld. The real part of the AC susceptibility as function of the temperature shows a maximum, which shifts to higher temperatures when the frequency is increased. Assuming that maximum as the freezing temperature of the system, it was determined that the magnetic properties of the Fe-doped ZnO nanoparticles correspond to a spin glass-like behavior

QoS-Aware energy management in body sensor nodes powered by human energy harvesting

Harvesting energy in the human environment has been identified as an effective way to charge the body sensor nodes in wireless body area networks (WBANs). In such networks, the capability of the nodes to detect events is of vital importance and complements the stringent quality of service (QoS) demands in terms of delay, throughput, and packet loss. However, the scarce energy collected by human motions, along with the strict requirements of vital health signals in terms of QoS, raises important challenges for WBANs and stresses the need for new integrated QoS-aware energy management schemes. In this paper, we propose a joint power-QoS (PEH-QoS) control scheme, composed of three modules that interact in order to make optimal use of energy and achieve the best possible QoS. The proposed scheme ensures that a sensor node is able to detect the medical events and transmit the respective data packets efficiently. Extensive simulations, conducted for different human activities (i.e., relaxing, walking, running, and cycling), have shown that the application of PEH-QoS in a medical node increases the detection efficiency, the throughput, and the energy efficiency of the system.Peer ReviewedPostprint (author's final draft

Efecto de diferentes niveles lipídicos y proteicos en la dieta sobre el desempeño productivo de juveniles del pez ángel o escalar (Pterophyllum scalare)

Antecedentes: Actualmente, en nuestro país los peces ornamentales son un segmento importante de la piscicultura nacional,siendo el pez ángel o escalar (Pterophyllum scalare), una de las especies cultivadas más popular y apetecida en el mundo de acuariofilia, gracias a su belleza, majestuosidad y forma estilizada. Sin embargo, son pocos los autores que han estudiado sus exigencias nutricionales en términos de niveles lipídicos y proteicos. Objetivo: La presente investigación evaluó seis dietas, conformadas por la combinación de dos niveles de extracto etéreo (EE) 9 y 11 % y de tres niveles de proteína bruta (PB) 32, 34 y 36 %, para determinar su efecto sobre el desempeño productivo y la sobrevivencia de juveniles de pez escalar (P. scalare). Metodología: Fueron usados 324 juveniles de P. scalare con peso promedio de 753,5 ± 0,14 mg, los cuales fueron distribuidos en 18 acuarios con volumen de 105L, a una densidad de 18 peces/acuario y alimentados al 6% de la biomasa. Resultados: los hallazgos mostraron que un nivel 32% de proteína bruta en la dieta no afecta la sobrevivencia, pero si el desempeño productivo (p<0,05), y que niveles de 34 ó 36% de PB lo mejoran. También se evidencio que no hubo diferencia estadística (P>0,05) entre los dos niveles (9 y 11%) de extracto etéreo utilizados en las dietas. Conclusión: Se concluye que dietas para juveniles de esta especie, que contengan 32% de PB pueden afectar el desempeño productivo en términos de baja ganancia de peso, alta conver- sión alimenticia y bajas tasas específicas de crecimiento y de eficiencia proteica.PALABRAS CLAVE: Acuariofilia, pez ornamental, requeri- miento nutricional, tasa especifica de crecimiento, tasa de eficiencia proteica.Background: Currently, ornamental fish are an important element of the pisciculture in our country, with Angelfish(Pterophyllum scalare), being one of the most popular and desired cultured species in the fishkeeping field, given its beauty, majesty and stylized form. However, few authors have studied their nutritional requirements in terms of lipid and protein levels. Objective: This research evaluated six diets, formed by the combination of two levels of crude fat (CF) 9 and 11% and three levels of crude protein (CP) 32, 34 and 36%, to determine its effect on productive performance and the survival of juvenile angelfish (P. scalare). Methodology: 324 juveniles of P. scalare with average weight of 753.5 ± 0.14 mg were randomized in 18 aquariums with volume of 105L, a density of 18 fish/aquarium and fed to 6% of the biomass. Results: We found that a 32% level of crude protein in the diet did not affect the survival, but affected the productive performance (p <0.05), and that levels of 34 or 36% of CP improve it. It was also evidenced that there was no statistical difference (P> 0.05) between the two levels (9 and 11%) of the crude fat used in the diets. Conclusion: It is concluded that diets for juveniles of this species, containing 32% PB can affect the productive performance in terms of low weight gain, high feed conversion and low specific growth rates and protein efficiency.KEYWORDS:Fishkeeping, ornamen- tal fish, nutritional requirement, specific growth rate, protein efficiency rat

Comparative-experimental study of different roof types in a tropical climate

Introduction: The implementation of green roofs in buildings has become increasingly common, because it is an ecological construction alternative that provides great benefits, which range from reducing air pollution to improving air conditioning inside of the buildings. Objective: This article aims to evaluate whether extensive green roofs are an energy-valuable option in a tropical climate compared to a thermoacoustic, clay tile, and concrete roof. Methodology: An experimental study was carried out in summer (December) in a tropical climate, where the internal temperature of two identical small buildings was compared except for the roof type. Both small buildings were built with a low construction standard according to buildings of families with low income in this region. Data of internal temperatures and other climatic conditions were analyzed to compare the influence of the roof type on the inner shelter temperature. Results: In these experiments, the average inner shelter temperature of green roofs was lower than the same temperature for thermoacoustic, clay tile and concrete roof and resulted in average temperature differences of 1.8 °C, 0.9 °C and 1.5 °C, respectively (depending on environmental conditions). Conclusions: It was possible to show that the green roof has a greater thermal inertia compared to the others. However, the temperature difference between the green roof and the other roof types was in the same range as in studies conducted in other climatic regions, therefore no special benefit of the green roof has been derived in a warm-tropical climate in this study. However, the low building standard can be of great interest for a final evaluation and the authors recommend to conduct further studies.Resumen Introducción: La implementación de techos verdes en las edificaciones se ha vuelto cada vez más común, debido a que es una alternativa de construcción ecológica que brinda grandes beneficios que van desde la reducción de la contaminación en el aire, hasta la mejora de la climatización dentro de los edificios. Objetivo: Este artículo tiene como objetivo evaluar si los techos verdes extensivos son una opción energéticamente valiosa en un clima tropical en comparación con un techo termoacústico, de tejas de barro y concreto.  Metodología: Se realizó un estudio experimental en verano (diciembre) en clima tropical donde se comparó la temperatura interna de dos cubículos idénticos excepto del tipo de techo. Los cubículos fueron construidos de bajo estándar de construcción como se construyen casas unifamiliares de personas de bajos ingresos. Los datos de temperaturas internas y demás condiciones climáticas se analizaron para comparar la influencia del tipo de techo en la temperatura interna del cubículo.  Resultados: En los experimentos realizados, la temperatura interna promedio en los techos verdes fue menor que la misma temperatura de los techos termoacústicos, de tejas de barro y concreto, con diferencias de 1.8 °C, 0.9 °C y 1.5 °C, respectivamente (dependiendo de las condiciones ambientales). Conclusiones: Se pudo evidenciar que el techo verde presenta una mayor inercia térmica con respecto a los demás. Sin embargo, la diferencia de temperatura entre el techo verde y los otros tipos de techo estuvo en el mismo rango que en los estudios realizados en otras regiones climáticas, por lo tanto, no se ha derivado ningún beneficio especial del techo verde en un clima cálido tropical en este estudio. Sin embargo, el bajo estándar de construcción puede ser de gran interés para una evaluación final y los autores recomiendan realizar más estudios