49,416 research outputs found
Apocaligonellidus nom. nov. for Echinopsis Fan & Chen, 1996, preoccupied (Acari: Prostigmata: Raphignathoidea: Xenocaligonellididae)
No full textFAN, Q.-H., CHEN, Y. (2008): Apocaligonellidus nom. nov. for Echinopsis Fan & Chen, 1996, preoccupied (Acari: Prostigmata: Raphignathoidea: Xenocaligonellididae). Zootaxa 1717 (1): 68, DOI: 10.11646/zootaxa.1717.1.6, URL: http://dx.doi.org/10.11646/zootaxa.1717.1.
[Carta a Ignacio Hernando de Larramendi y Montiano]
No full textInformación adicional de autor de la carta: President, Chung Kuo Insurance Company, LimitedFotografía número: 97
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
[{HC(CMeNAr)(2)}(2)Al2P4] (Ar=2,6-iPr(2)C(6)H(3)): A reduction to a formal {P-4},4(-) charged species
No full textExperimental study of blade thickness effects on the global and local performances of a Controlled Vortex Designed axial-flow fan
No full textThe purpose of this work is to study the effects of blade thickness on the performances of an axial-flow fan. Two fans that differ only in the thickness of their blades were studied. The first fan was designed to be part of the cooling system of an automotive vehicle power unit and has very thin blades. The second fan has much thicker blades compatible with the rotomoulding conception process. The global performances of the fans were measured in a test bench designed according to the ISO-5801 standard. The curve of aerodynamics characteristics (pressure head versus ow-rate) is slightly steeper for the fan with thick blades, and the nominal point is shifted towards lower flow-rates. The efficiency of the thick blades fan is lower than the efficiency of the fan with thin blades but remains high on a wider flow-rate range. The mean velocity field downstream of the rotors are very similar at nominal points with less centrifugation for the thick blades fan. The thick blades fan moreover maintains an axial exit-flow on a wider range of flow-rates. The main dierences concern local properties of the flow: Phase-averaged velocities and wall pressure fluctuations strongly differ at the nominal flow-rates. The total level of fluctuations is lower for the thick blades fan that for the thin blades fan and the spectral decomposition of the wall fluctuations and velocity signals reveal more harmonics for the thick blades fan, with less correlation between the different signals. For this kind of turbomachinery, the use of thick blades could lead to a good compromise between aerodynamic and acoustic performances, on a wider operating range
Development of a Method for Enhanced Fan Representation in Gas Turbine Modeling
No full textA challenge in civil aviation future propulsion systems is expected to be the integration with the airframe, coming as a result of increasing bypass ratio or above wing installations for noise mitigation. The resulting highly distorted inlet flows to the engine, make a clear demand for advanced gas turbine performance prediction models. Since the dawn of jet engine several models have been proposed and the present work comes to add a model that combines two well established compressor performance methods in order to create a quasi three dimensional representation of the fan of a modern turbofan. A streamline curvature model is coupled to a parallel compressor method, covering radial and circumferential directions respectively. Model testing has shown a close agreement to experimental data, making it a good candidate for assessing the loss of surge margin on a high bypass ratio turbofan, semi-embedded on the upper surface of a broad wing airframe
Identificación y estrategias de control de Fasciola hepática en ovinos y caprinos de Boyacá
No full textEl grupo de Investigación en Medicina Veterinaria y Zootecnia (GIDIMEVETZ) de la UPTC ofrece una guía para los productores de la Asociación de Caprinos de Boavita, Boyacá, sobre la Fascioliasis en ovinos y caprinos. La cartilla presenta el estado actual de la enfermedad y estrategias para su mitigación, manejo y control en pequeños rumiantes. Este documento surge del proyecto “Identificación y estrategias de control de Fasciola hepatica en ovinos y caprinos de Boyacá”, financiado por MINCIENCIAS y el departamento de Boyacá. La guía busca apoyar el manejo sanitario y ofrecer prácticas de campo que faciliten el control de vectores e interrumpan el ciclo biológico del parásito, aumentando la productividad y reduciendo pérdidas económicas en la industria ovina y caprina de Boyacá.Bibliografía y Webgrafía : páginas 37-38Convocatoria 865 de 2019 MINCIENCIAS- Convocatoria para el cierre de brechas tecnológicas del sector agropecuario a través del fortalecimiento de capacidades I+D+I en el departamento de Boyacá (Segundo corte).80740- 828-2020Identificación y estrategias de control de Fasciola hepatica en ovinos y caprinos de BoyacáColcienciasPatrimonio Autónomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación Francisco José de Calda
Design of dry friction and piezoelectric hybrid ring dampers for integrally bladed disks based on complex nonlinear modes
No full textThis paper investigates a new passive damper coupling the energy dissipative mechanisms of dry friction and piezoelectric shunting circuit for Integrally Bladed Disks (blisks). The idea is to distribute piezoelectric material to the dry friction ring so that the elastic deformation of the dry friction ring is utilized to generate additional damping. Mounting piezoelectric material on the additional structure instead of the host structure is a more practical alternative to install piezoelectric damping devices to realistic mechanical systems. This improves the reliability and maintainability of both dampers and host structures. Based on the concept of Complex Nonlinear Modes (CNMs), the dry friction damping effect of the proposed damper is measured through the modal damping ratio for target modes. Modal Electromechanical Coupling Factor (MEMCF) is extended to nonlinear electromechanical coupling systems in order to quantify the additional piezoelectric damping ratio. The damping effect of the hybrid damper is also evaluated by the maximal response amplitude in the frequency domain by the forced response analysis. On one hand, it validates the results from the nonlinear modal analysis, on the other hand, it serves as a reference to choose the optimum design parameters of the hybrid damper. Steady-state response of the cyclic symmetric structure under engine-order excitation is calculated by the Multi-Harmonic Balance Method (MHBM). A phenomenological lumped parameter model representing a blisk with a hybrid ring damper is firstly studied to demonstrate the methodology. Then a blisk finite element model is used as a demonstrator to quantitatively verify the effectiveness of the idea. It is shown that for those modes that can be damped by the dry friction damper, the addition of piezoelectric material further enhances the damping effect
Different types of gravity-driven flow deposits and associated bedforms in the Upper Bengal Fan, offshore Myanmar
No full textThis study uses 3D reflection seismic data to investigate how sediment gravity flows contribute to the evolution of the lower continental slope of the Myanmar margin that is part of the Bengal Fan, the largest deep-water fan system in the world. Seafloor and subseafloor data show large sediment wave fields that developed on both flanks of an extensive submarine canyon. The sediment waves exhibit asymmetric stoss and lee sides, wave lengths and heights of 850–3000 m and 25–70 m, respectively, and an upslope direction of migration. Seismic data reveals the presence of multiple fields of vertically stacked sediment waves, interbedded with units characterised by a chaotic seismic facies that accumulate mainly in the troughs of the sediment waves and can be tracked laterally to the adjacent canyons. According to their seismic facies, geometry, and internal architecture these chaotic units are interpreted as debrites. Seismic attributes extracted from different horizons indicate that the sediment waves are dominated by fine-grained sediment, while the debrites are probably associated with coarser-grained deposits. The debrites fill the troughs of the sediment waves, as well as the downstream portions of canyon thalweg, thus flattening the paleo-seafloor. The sediment waves are interpreted as cyclic steps formed by low-density turbidity currents flowing across the slope down to the basin floor, where the change in gradient favours the formation of hydraulic jumps and the transition from supercritical to subcritical flow conditions. A conceptual model for the sediment wave evolution was proposed for the study area, in the transitional environment on the lower slope, with low-density gravity flow deposits and high-density debris flow deposits alternatively accumulating on the major gravity flow conduits
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