Volumen 26, Números 1 y 2
URI permanente para esta colecciónhttps://hdl.handle.net/10669/14635
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Ítem On the classification of constrained extrema(2011-07-18 00:00:00) Proti, Orieta; Figueroa González, HéctorUsing simple arguments, accessible to students of advanced calculus with an interest in Mathematics, we show the equivalence of several criteria, scattered in the literature, to classify the critical points of functions of two or three variables when restricted to side conditios.Ítem Evaluación de las aguas de drenaje del sector de riego de Tamarindo y su influencia sobre el Parque Nacional Palo Verde(2011-07-18 00:00:00) Pérez Castillo, Ana GabrielaThe following physicochemical parameters were measured to determine the quality of the drainage water of Tamarindo Irrigation Sector, at the Arenal-Tempisque Irrigation District: temperature, pH, dissolved oxygen saturation percentage, electrical conductivity, chemical oxygen demand, concentration of suspended solids, nitrates and total phosphorous, as well as the concentration of zinc, fats and oils. The measurements were taken when it was estimated that drainage water had received the highest pollution loads from the surrounding paddy fields, during the second half of 2002 and the year 2003. The results were evaluated using the water quality index for the management of floodplain lakes (ICA-L). The water from Tamarindo Irrigation Sector, which entered the Palo Verde National Park (PNPV) through La Bocana lagoon, got an average value of ICA-Lp of 70. Relevant increases in total phosphorous concentration were found. Zinc generated a punctual pollution problem in the area of irrigation when it was applied to the rice during the dry season. The Chilo Campo sampling point and the La Bocana lagoon showed a continuous contamination with fats and oils, which would prevent its use in floodplain lagoons of PNPV. Comparison between the results obtained at the sampling points of Chilo Ocampo and La Bocana showed that the buffer zone exerts a beneficial effect, particularly regarding suspended solids, nitrates and total phosphorous (rainy season of 2002), but not enough to control the influence of polluting discharges from the irrigation system.Ítem Determinación de un modelo para el consumo de energía con suspensión total de sólidos en fluidos newtonianos(2011-07-18 00:00:00) Ulate Brenes, Adolfo Mauricio; Vásquez, AlexanderThe development of a model for the power consumption in a mixing process for the suspension solids in a Newtonian liquid is proposed in this study. As a first step of this research, the critical variables were determined using an alternative method: the kind and size of the impellers (propeller and turbine, Da/Dt 0,333 and 0,433), the kind, size and quantity of solid (sand, volcanic stone and silica, 1,68x10-3 m and 7,07x10‑4 m in diameters); and the fluid. Two equations were developed to fix the experimental data, both using the same dimensionless numbers (One for Reynolds numbers lower than 60 000 and the other for Reynolds numbers between 60 000 and 150 000). These equations have similarities with the reported in the literature.Ítem Evaluación y desarrollo de la metacognición en la enseñanza de la química(2011-07-18 00:00:00) Sandí Ureña, Santiago; Cooper, Melanie M.Metacognition may be defined as the knowledge and regulation of one’s own cognitive system, the capacity to reflect about one’s actions and thoughts. Current views on metacognition pose it as a fundamental factor in achieving autonomy in learning, and promoting deep understanding and problem-solving skills. This relevance has in turn led to interest in creating learning experiences conducive to developing the use of metacognition, especially in science education. Despite this increasing interest, progress has been hindered by the inherent difficulties associated with developing assessment methods for metacognition. Consequently, evidence for the efficacy and effectiveness of learning environments in promoting metacognition has been scarce. In this article we present some of the work that our research group has done to contribute in addressing this problem. We report the development and validation of an automated and rapid multi-methods strategy to assess regulatory metacognition in chemistry problem solving from large numbers of participants. This strategy combines two separate instruments: one prospective, the Metacognitive Activities Inventory (MCAi) and one concurrent, the Interactive MultiMedia Exercises (IMMEX). Additionally, we describe two interventions that by using the multi- methods assessment strategy have been demonstrated to enhance metacognition use and problem solving ability. The first intervention is a cooperative problem-based general chemistry laboratory; this study presents evidence that links participation in the laboratory with development of higher order skills. The second instantiation is a two-week collaborative problem solving activity. Findings from a phenomenological approach nested within a mixed-methods design suggest that meaningful, purposeful social interaction and reflective prompting act as promoters of metacognition development in both learning environments. These factors are not exclusive to the interventions and we maintain that they are transferable and may be embedded by practitioners in their instruction. This report presents the development and validation of metacognition assessment methods and studies of the efficacy of learning experiences in developing metacognition.Ítem Polymers of unidimentional coordination [M(sac)2(H2O)(pyz)]n, (M= Ni2+, Cu2+ and Zn2+, sac =saccharinate, pyz= pyrazine), spectroscopy and magnetic properties(2011-07-18 00:00:00) Valle Bourrouet, Grettel; Weyhermüller, ThomasCoordination polymers have been prepared by the hydrothermal reaction of M2+saccharinates (M = Ni, Cu and Zn) and pyrazine, pyz, in a ratio 1:1. The complexes of formula [M(sac)2(H2O)2pyz]n, M = Ni2+ and Zn2+ and [Cu(sac)2(H2O)pyz]n were characterized by spectroscopic methods and elemental analysis, magnetic measurements, single and powder x-ray diffraction. The compounds crystallize in the triclinic space group p-1. The zinc ion is octahedrally coordinated by two sac ions, two water and two pyrazine molecules. The copper ion is penta-coordinated in a distorted square pyramidal geometry with the pyrazine molecules in the axial position. The metal atoms are connected via pyrazine μ-N,N’-coordination and form linear chains, containing a network of hydrogen bonds between the chains, that build a 2D sheet structure.Ítem Desórdenes del sistema musculoesquelético por trauma acumulativo en estudiantes universitarios de computación e informática(2011-07-18 00:00:00) Fonseca Barrantes, MelissaThe main objective of this research was to establish the correlation of Musculoskeletal Disorders (MSD ́s) by accumulative damage, among university ́s students from the computer science school (ECCI) at the Universidad de Costa Rica (UCR). The study group included 129 computer users with an average age of 21,9 years old. Neck pain was the most commonly reported symptom (81 cases), followed by lumbar region (71 cases) and wrist pain (63 cases). The women perceived the higher stress, and the computer laboratory, followed by home environment, seem to have the higher risk factor associated with the symptoms. At least 90 % of students use the computer 6 or 7 days per week and 31 % report to use the computer 8 or more hours per day. In general, the symptoms increased according to the time of exposition. The level of perception of computer-‐‑related health risks among the students was low.Ítem Soluciones interiores exactas a las ecuaciones de Einstein para un líquido ideal con simetría axial(2011-07-18 00:00:00) Alvarado Marín, Rodrigo EduardoExact interior solutions of Einstein equations were obtained, using the ideal fluid model with axial symmetry (Weyl-Lewis-Papapetrou or Weyl-Papapetrou).