Learning kinds for students of technical high school : An analysis from the David Ausubel's theory

This article presents the findings of a field research, not experimental, observational, correlating, basic, of mixed data, micro sociologic, leading to a study of surveys.The object of study is to find learning kinds, and the unit of analysis were 529 high school students between 16 and 21 years old. Its purpose is to understand the impact of learning by rote, guided, self learned and meaningful learning and its achievement degree besides the learning outcomes of differentiated curriculum based on David Ausubel's thoughts, associated with different economic specialties (MINEDUC, 1998) where the population of the study is trained. To collect data, the test TADA - DO2 was used, this test has a reliability index of 0.911 according to Cronbach. From the hits it can be stated from the null hypothesis that there is a significant association (a = 0,05) between the learning kinds and the learning expected of differentiated training plan for both, male and female. It is complex to state that the training of the middle-level technicians leads to a successful employment.

Learning kinds for students of technical high school : An analysis from the David Ausubel's theory

This article presents the findings of a field research, not experimental, observational, correlating, basic, of mixed data, micro sociologic, leading to a study of surveys.The object of study is to find learning kinds, and the unit of analysis were 529 high school students between 16 and 21 years old. Its purpose is to understand the impact of learning by rote, guided, self learned and meaningful learning and its achievement degree besides the learning outcomes of differentiated curriculum based on David Ausubel's thoughts, associated with different economic specialties (MINEDUC, 1998) where the population of the study is trained. To collect data, the test TADA - DO2 was used, this test has a reliability index of 0.911 according to Cronbach. From the hits it can be stated from the null hypothesis that there is a significant association (a = 0,05) between the learning kinds and the learning expected of differentiated training plan for both, male and female. It is complex to state that the training of the middle-level technicians leads to a successful employment.

Planktic foraminiferal populations and test flux in the eastern North Atlantic Ocean

Planktic foraminiferal assemblages vary in response to seasonal fluctuations of hydrographic properties, between water masses, and after periodical changes and episodic events (e.g. reproduction, storms). Distinct annual variability of the planktic foraminiferal flux is also known from sediment trap data. In this paper we discuss the short-term impacts on interannual flux rates based on data from opening-closing net hauls obtained between the ocean surface and 500 m water depth. Data were recorded during April, May, June, and August at around 47°N, 20°W (BIOTRANS) in 1988, 1989, 1990, 1992, 1993, and during May 1989 and 1992 at 57°N, 20-22°W. Species assemblages closely resemble each other when comparing the mixed layer fauna with the fauna of the upper 100 m and the upper 500 m of the water column. In addition, species assemblages >100 µm are almost indistinguishable from assemblages that are >125 µm in test size. The standing stock of planktic foraminifers at BIOTRANS can vary by more than one order of magnitude over different years; however, species assemblages may be similar when comparing corresponding seasons. Early summer assemblages (June) are distinctly different from late summer assemblages (August). Significant variations in the species composition during spring (April/May) are independent of the mixed layer depth. Spring assemblages are characterized by high numbers of Globigerinita glutinata. In particular, day-to-day variations of the number of specimens and in species composition may have the same order of magnitude as interannual variations. This appears to be independent of the reproduction cycle. Species assemblages at 47°N and 57°N are similar during spring, although surface water temperatures and salinities differ by up to 10°C and 0.7 (PSU). We suggest that the main factors controlling the planktic foraminiferal fauna are the trophic properties in the upper ocean productive layer. Planktic foraminiferal carbonate flux as calculated from assemblages reveals large seasonal variations, a quasi-annual periodicity in flux levels, and substantial differences in timing and magnitude of peak fluxes. At the BIOTRANS station, the average annual planktic foraminiferal CaCO3 fluxes at 100 and 500 m depth are estimated to be 22.4 and 10.0 g/m**2/yr, respectively.

Studying the effect of CO2-induced acidification on sediment toxicity using acute amphipod toxicity test

Carbon capture and storage is increasingly being considered one of the most efficient approaches to mitigate the increase of CO2 in the atmosphere associated with anthropogenic emissions. However, the environmental effects of potential CO2 leaks remain largely unknown. The amphipod Ampelisca brevicornis was exposed to environmental sediments collected in different areas of the Gulf of Cádiz and subjected to several pH treatments to study the effects of CO2-induced acidification on sediment toxicity. After 10 days of exposure, the results obtained indicated that high lethal effects were associated with the lowest pH treatments, except for the Ría of Huelva sediment test. The mobility of metals from sediment to the overlying seawater was correlated to a pH decrease. The data obtained revealed that CO2-related acidification would lead to lethal effects on amphipods as well as the mobility of metals, which could increase sediment toxicity.

The O2, pH and Ca2+ Microenvironment of Benthic Foraminifera in a High CO2 World

Ocean acidification (OA) can have adverse effects on marine calcifiers. Yet, phototrophic marine calcifiers elevate their external oxygen and pH microenvironment in daylight, through the uptake of dissolved inorganic carbon (DIC) by photosynthesis. We studied to which extent pH elevation within their microenvironments in daylight can counteract ambient seawater pH reductions, i.e. OA conditions. We measured the O2 and pH microenvironment of four photosymbiotic and two symbiont-free benthic tropical foraminiferal species at three different OA treatments (~432, 1141 and 2151 µatm pCO2). The O2 concentration difference between the seawater and the test surface (delta O2) was taken as a measure for the photosynthetic rate. Our results showed that O2 and pH levels were significantly higher on photosymbiotic foraminiferal surfaces in light than in dark conditions, and than on surfaces of symbiont-free foraminifera. Rates of photosynthesis at saturated light conditions did not change significantly between OA treatments (except in individuals that exhibited symbiont loss, i.e. bleaching, at elevated pCO2). The pH at the cell surface decreased during incubations at elevated pCO2, also during light incubations. Photosynthesis increased the surface pH but this increase was insufficient to compensate for ambient seawater pH decreases. We thus conclude that photosynthesis does only partly protect symbiont bearing foraminifera against OA.

Wave height (regular and irregular waves) reduction in 2m water depth over a 40-m-long salt marsh test section in a large scale laboratory flume

Coastal communities around the world face increasing risk from flooding as a result of rising sea level, increasing storminess, and land subsidence. Salt marshes can act as natural buffer zones, providing protection from waves during storms. However, the effectiveness of marshes in protecting the coastline during extreme events when water levels and waves are highest is poorly understood. Here, we experimentally assess wave dissipation under storm surge conditions in a 300-m-long wave flume that contains a transplanted section of natural salt marsh. We find that the presence of marsh vegetation causes considerable wave attenuation, even when water levels and waves are high. From a comparison with experiments without vegetation, we estimate that up to 60% of observed wave reduction is attributed to vegetation. We also find that although waves progressively flatten and break vegetation stems and thereby reduce dissipation, the marsh substrate remained remarkably stable and resistant to surface erosion under all conditions.The effectiveness of storm wave dissipation and the resilience of tidal marshes even at extreme conditions suggest that salt marsh ecosystems can be a valuable component of coastal protection schemes.

Seawater carbonate chemistry, thickness and carbonate elemental composition of the test of juvenile sea urchins in a laboratory experiment

Continuous anthropogenic CO2 emissions to the atmosphere and uptake by the oceans will cause a reduction of seawater pH and saturation state (Omega) of CaCO3 minerals from which marine calcifiers build their shells and skeletons. Sea urchins use the most soluble form of calcium carbonate, high-magnesium calcite, to build their skeleton, spines and grazing apparatus. In order to highlight the effects of increased pCO2 on the test thickness and carbonate elemental composition of juvenile sea urchins and potential differences in their responses linked to the diet, we performed a laboratory experiment on juvenile Paracentrotus lividus, grazing on calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea, Dictyota dichotoma) macroalgae, under different pH (corresponding to pCO2 values of 390, 550, 750 and 1000 µatm). Results highlighted the importance of the diet in determining sea urchin size irrespectively of the pCO2 level, and the relevance of macroalgal diet in modulating urchin Mg/Ca ratio. The present study provides relevant clues both in terms of the mechanism of mineral incorporation and in terms of bottom-up processes (algal diet) affecting top-down ones (fish predation) in rocky subtidal communities

Perseveration in a guessing task by laying hens selected for high or low levels of feather pecking does not support classification of feather pecking as a stereotypy.

Feather pecking is a behaviour by which birds damage or destroy the feathers of themselves (self-pecking) or other birds (allo feather pecking), in some cases even plucking out feathers and eating these. The self-pecking is rarely seen in domestic laying hens but is not uncommon in parrots. Feather pecking in laying hens has been described as being stereotypic, i.e. a repetitive invariant motor pattern without an obvious function, and indeed the amount of self-pecking in parrots was found to correlate positively with the amount of recurrent perseveration (RP), the tendency to repeat responses inappropriately, which in humans and other animals was found to correlate with stereotypic behaviour. In the present experiment we set out to investigate the correlation between allo feather pecking and RP in laying hens. We used birds (N = 92) from the 10th and 11th generation (G10 and G11) of lines selectively bred for high feather pecking (HFP) and low feather pecking (LFP), and from an unselected control line (CON) with intermediate levels of feather pecking. We hypothesised that levels of RP would be higher, and the time taken (standardised latency) to repeat a response lower, in HFP compared to LFP hens, with CON hens in between. Using a two-choice guessing task, we found that lines differed significantly in their levels of RP, with HFP unexpectedly showing lower levels of RP than CON and LFP. Latency to make a repeat did not differ between lines. Latency to make a switch differed between lines with a shorter latency in HFP compared to LFP (in G10), or CON (in G11). Latency to peck for repeats vs. latency to peck for switches did not differ between lines. Total time to complete the test was significantly shorter in HFP compared to CON and LFP. Thus, our hypotheses were not supported by the data. In contrast, selection for feather pecking seems to induce the opposite effects than would be expected from stereotyping animals: pecking was less sequenced and reaction to make a switch and to complete the test was lower in HFP. This supports the hyperactivity-model of feather pecking, suggesting that feather pecking is related to a higher general activity, possibly due to changes in the dopaminergic system.

Trade Credits under Imperfect Enforcement: A Theory with a Test on Chinese Experience

It is widely recognized that trade credit is an important financial mechanism, particularly in developing economies and transition economies where institutions are weak. This paper documents theoretical analysis and empirical accounts on what facilitates an effective supply of trade credit based on original surveys conducted in P.R. of China. Our theory predicts that trade volume and trade credit are increasing function of cash held by the buyer and enforcement technology of the seller. Furthermore, if the state sector’s enforcement technology is high, it has positive external effect to expand the volumes of trade credit and trades in the whole economy. From the data, we found that government made active commitment in enforcement of trade credit contract and the government owned firms are main supplier and receivers of trade credit, which suggest that enforcement by government and state sector were effective against presumptions in the previous literatures.

Contribution to the Analysis, Design and Assessment of Compact Antenna Test Ranges At Millimeter Wavelengths - Contribución al Análisis, Diseño y Caracterización de Sistemas de Medida de Antenas en Rango Compacto para Frecuencias Milimétricas

This Doctoral Thesis entitled Contribution to the analysis, design and assessment of compact antenna test ranges at millimeter wavelengths aims to deepen the knowledge of a particular antenna measurement system: the compact range, operating in the frequency bands of millimeter wavelengths. The thesis has been developed at Radiation Group (GR), an antenna laboratory which belongs to the Signals, Systems and Radiocommunications department (SSR), from Technical University of Madrid (UPM). The Radiation Group owns an extensive experience on antenna measurements, running at present four facilities which operate in different configurations: Gregorian compact antenna test range, spherical near field, planar near field and semianechoic arch system. The research work performed in line with this thesis contributes the knowledge of the first measurement configuration at higher frequencies, beyond the microwaves region where Radiation Group features customer-level performance. To reach this high level purpose, a set of scientific tasks were sequentially carried out. Those are succinctly described in the subsequent paragraphs. A first step dealed with the State of Art review. The study of scientific literature dealed with the analysis of measurement practices in compact antenna test ranges in addition with the particularities of millimeter wavelength technologies. Joint study of both fields of knowledge converged, when this measurement facilities are of interest, in a series of technological challenges which become serious bottlenecks at different stages: analysis, design and assessment. Thirdly after the overview study, focus was set on Electromagnetic analysis algorithms. These formulations allow to approach certain electromagnetic features of interest, such as field distribution phase or stray signal analysis of particular structures when they interact with electromagnetic waves sources. Properly operated, a CATR facility features electromagnetic waves collimation optics which are large, in terms of wavelengths. Accordingly, the electromagnetic analysis tasks introduce an extense number of mathematic unknowns which grow with frequency, following different polynomic order laws depending on the used algorithmia. In particular, the optics configuration which was of our interest consisted on the reflection type serrated edge collimator. The analysis of these devices requires a flexible handling of almost arbitrary scattering geometries, becoming this flexibility the nucleus of the algorithmia’s ability to perform the subsequent design tasks. This thesis’ contribution to this field of knowledge consisted on reaching a formulation which was powerful at the same time when dealing with various analysis geometries and computationally speaking. Two algorithmia were developed. While based on the same principle of hybridization, they reached different order Physics performance at the cost of the computational efficiency. Inter-comparison of their CATR design capabilities was performed, reaching both qualitative as well as quantitative conclusions on their scope. In third place, interest was shifted from analysis - design tasks towards range assessment. Millimetre wavelengths imply strict mechanical tolerances and fine setup adjustment. In addition, the large number of unknowns issue already faced in the analysis stage appears as well in the on chamber field probing stage. Natural decrease of dynamic range available by semiconductor millimeter waves sources requires in addition larger integration times at each probing point. These peculiarities increase exponentially the difficulty of performing assessment processes in CATR facilities beyond microwaves. The bottleneck becomes so tight that it compromises the range characterization beyond a certain limit frequency which typically lies on the lowest segment of millimeter wavelength frequencies. However the value of range assessment moves, on the contrary, towards the highest segment. This thesis contributes this technological scenario developing quiet zone probing techniques which achieves substantial data reduction ratii. Collaterally, it increases the robustness of the results to noise, which is a virtual rise of the setup’s available dynamic range. In fourth place, the environmental sensitivity of millimeter wavelengths issue was approached. It is well known the drifts of electromagnetic experiments due to the dependance of the re sults with respect to the surrounding environment. This feature relegates many industrial practices of microwave frequencies to the experimental stage, at millimeter wavelengths. In particular, evolution of the atmosphere within acceptable conditioning bounds redounds in drift phenomena which completely mask the experimental results. The contribution of this thesis on this aspect consists on modeling electrically the indoor atmosphere existing in a CATR, as a function of environmental variables which affect the range’s performance. A simple model was developed, being able to handle high level phenomena, such as feed - probe phase drift as a function of low level magnitudes easy to be sampled: relative humidity and temperature. With this model, environmental compensation can be performed and chamber conditioning is automatically extended towards higher frequencies. Therefore, the purpose of this thesis is to go further into the knowledge of millimetre wavelengths involving compact antenna test ranges. This knowledge is dosified through the sequential stages of a CATR conception, form early low level electromagnetic analysis towards the assessment of an operative facility, stages for each one of which nowadays bottleneck phenomena exist and seriously compromise the antenna measurement practices at millimeter wavelengths.

Accident Management Actions In An Upper-Head Small-Break Loss-Of-Coolant Accident With High-Pressure Safety Injection Failed

Since the Three Mile Island accident, an important focus of pressurized water reactor (PWR) transient analyses has been a small-break loss-of-coolant accident (SBLOCA). In 2002, the discovery of thinning of the vessel head wall at the Davis Besse nuclear power plant reactor indicated the possibility of an SBLOCA in the upper head of the reactor vessel as a result of circumferential cracking of a control rod drive mechanism penetration nozzle - which has cast even greater importance on the study of SBLOCAs. Several experimental tests have been performed at the Large Scale Test Facility to simulate the behavior of a PWR during an upper-head SBLOCA. The last of these tests, Organisation for Economic Co-operation and Development Nuclear Energy Agency Rig of Safety Assessment (OECD/NEA ROSA) Test 6.1, was performed in 2005. This test was simulated with the TRACE 5.0 code, and good agreement with the experimental results was obtained. Additionally, a broad analysis of an upper-head SBLOCA with high-pressure safety injection failed in a Westinghouse PWR was performed taking into account different accident management actions and conditions in order to check their suitability. This issue has been analyzed also in the framework of the OECD/NEA ROSA project and the Code Applications and Maintenance Program (CAMP). The main conclusion is that the current emergency operating procedures for Westinghouse reactor design are adequate for these kinds of sequences, and they do not need to be modified.

Isotopic prediction simulations applied to high burnup samples irradiated in VANDELLÓS-II Reactor core

Isotopic content assessment has a paramount importance for safety and storage reasons. During the latest years, a great variety of codes have been developed to perform transport and decay calculations, but only those that couple both in an iterative manner achieve an accurate prediction of the final isotopic content of irradiated fuels. Needless to say, them all are supposed to pass the test of the comparison of their predictions against the corresponding experimental measures.

Tools in Spanish Universities to facilitate the transmission from High School to University and their assessment.

Incoming students in the University have education deficiencies, so universities studies require a sound basis of scientific knowledge. In this project are analysed instruments to reinforcing knowledge in those areas related to the studies that students are about to embark on public Spanish universities. There are important differences among universities and, in each university there are great differences among titles. Initial courses (cursos cero) are widespread (in 50% of universities) that selfevaluation instruments (14 % of universities). It is necessary to improve diffusion of those instruments because it is not possible to evaluate them. So are proposed the next actuations: to make regular standard surveys for professors and students; to publish results of surveys; public universities should institutionalize their basic training offer and improve the dissemination of this offer especially through the web. This paper presents a questionnaire to assess student opinion about these tools. To analyze the effectiveness, and make an initial estimate of the evaluation of these tools, we conducted a pilot test of the questionnaire with 68 students at the University of Extremadura. The results of preliminary statistical analysis conducted on the pilot test indicate that the survey results are reliable. A global evaluation of both tools, with a scale of 1 to 5, gave an average score of 3.29 for initial courses and 3.41 for selfevaluation. The 72.9% of the students consider the "self assessment" more effective than the "initial course"

Full scale test for explosion water barriers in small cross-section galleries

Underground coal mines explosions generally arise from the inflammation of a methane/air mixture. This explosion can also generate a subsequent coal dust explosion. Traditionally such explosions have being fought eliminating one or several of the factors needed by the explosion to take place. Although several preventive measures are taken to prevent explosions, other measures should be considered to reduce the effects or even to extinguish the flame front. Unlike other protection methods that remove one or two of the explosion triangle elements, namely; the ignition source, the oxidizing agent and the fuel, explosion barriers removes all of them: reduces the quantity of coal in suspension, cools the flame front and the steam generated by vaporization removes the oxygen present in the flame. Passive water barriers are autonomous protection systems against explosions that reduce to a satisfactory safety level the effects of methane and/or flammable dust explosions. The barriers are activated by the pressure wave provoked in the explosion destroying the barrier troughs and producing a uniform dispersion of the extinguishing agent throughout the gallery section in quantity enough to extinguish the explosion flame. Full scale tests have been carried out in Polish Barbara experimental mine at GIG Central Mining Institute in order to determine the requirements and the optimal installation conditions of these devices for small sections galleries which are very frequent in the Spanish coal mines. Full scale tests results have been analyzed to understand the explosion timing and development, in order to assess on the use of water barriers in the typical small crosssection Spanish galleries. Several arrangements of water barriers have been designed and tested to verify the effectiveness of the explosion suppression in each case. The results obtained demonstrate the efficiency of the water barriers in stopping the flame front even with smaller amounts of water than those established by the European standard. According to the tests realized, water barriers activation times are between 0.52 s and 0.78 s and the flame propagation speed are between 75 m/s and 80 m/s. The maximum pressures (Pmax) obtained in the full scale tests have varied between 0.2 bar and 1.8 bar. Passive barriers protect effectively against the spread of the flame but cannot be used as a safeguard of the gallery between the ignition source and the first row of water troughs or bags, or even after them, as the pressure could remain high after them even if the flame front has been extinguished.