The regulative and semantic ‘distance’ of electronic conferencing may impede the topical alignment and the unambiguous interpretation of messages, hindering collaborative learning processes. Compared to a face-to-face environment, in electronic conferencing this distance may be caused by a reduced strength of online ‘context’. Explicitly defining the context of messages in an electronic environment may increase the writers’ co-intentionality and co-reference. An annotation tool is presented, strengthening the context by providing a document under discussion and enabling users to anchor their messages (...) in specific passages of the document. Preliminary results indicate that the tool does indeed reinforce the context, focusing the online discussion around a certain topic (increasing co-intentionality) and providing a frame of reference for single messages (increasing co-reference). (shrink)

Universities introduce intermediate assessment because it is understood to have positive effects on student behaviour and achievement. Yet, how intermediate assessment is perceived might be conditional for its success. The current study investigates both teachers’ and students’ perceptions of intermediate assessment. Teachers and students were interviewed and Student Evaluations of Teaching were examined. Results indicate that both teachers and students had generally positive perceptions of intermediate assessment. However, the two groups provided different reasons for their positive perceptions. Teachers and students (...) agreed that intermediate assessment helps students to keep up with their study work. Moreover, teachers mentioned that they could assess various knowledge and skills with intermediate assessment, whereas students preferred intermediate assessments to test the same knowledge and skills as the final exam. This finding suggests that teachers and students in our study had different goals... (shrink)

In [2] John Burgess describes predicative versions of Frege's logic and poses the problem of finding their exact arithmetical strength. I prove here that PV, the simplest such theory, is equivalent to Robinson's arithmetical theory Q.

Brad Mellon argues that persistent-vegetative-state cases, including the recent Terri Schiavo case, are ambiguous. By this he seems to mean that decisions about such cases are fraught with doubt and uncertainty and perhaps even that rational resolution of many such cases is impossible. Faced with such cases the most we can do is to live and cope with the ambiguity. I am more optimistic. With good will, and much clarification and discussion, rational agreement is possible in these cases, including the (...) Schiavo case. (shrink)

PVS may be a modern form of an ancient punishment, exile from human community.

Standard pedagogy treats topics in general relativity (GR) in terms of tensor formulations in curved space-time. An alternative approach based on treating the vacuum as a polarizable medium is presented here. The polarizable vacuum (PV) approach to GR, derived from a model by Dicke and related to the “THεμ” formalism used in comparative studies of gravitational theories, provides additional insight into what is meant by a curved metric. While reproducing the results predicted by GR for standard (weak-field) astrophysical conditions, for (...) strong fields a divergence of predictions in the two formalisms (GR vs. PV) provides fertile ground for both laboratory and astrophysical tests to compare the two approaches. (shrink)

In this paper, a stochastic simulation model for a standalone PV system sizing is replicated and extended to supply a dairy’s power demand. A detailed hourly-based simulation is conducted considering an hourly load profile and global solar radiation prediction model. The stochastic simulation model is based on a thorough statistical analysis of the solar radiation data and simulates the energy yield, the excess energy curtailed, and the state of charge of the batteries for the sizing month and the whole year, (...) providing the designer autonomy factor values d to properly size the PV system, finding the optimum combination of installed peak power P m and battery storage capacity C L that meets the application load requirements, considering a preset reliability level at minimum cost. The model makes use of the NASA’S Surface Meteorology and Solar Energy database to obtain solar radiation data. Results show a substantial reduction of 44% in installed peak power and battery storage capacity when compared to conventional methodologies, considering three days of autonomy, and an 85% reduction considering four days. Considering the goodness of fit test results, the Wakeby distribution best represents the behavior of historical solar radiation data for the site in almost half of the months. This article seeks to contribute to the literature gap in the application of methodologies for the multicomponent power supply in the dairy industry through the use of renewable energy. (shrink)

I had my accident on the rugby field on July 29, 2000 about 2.00 p.m. during a simple line - out, even before the ball was thrown in. I t just felt like another simple case of concussion , I staggered to the sideline, the coach asked me “what ’s wrong”? He said I told him I just felt sick and to put me back on the field in 10 minutes. Then I collapsed, eventually blacked out and then was rushed (...) to hospital unconscious in an ambulance with them struggling drastically to keep me alive. Af ter three days of being in there, they thought I was alright and were going to send me home. Then it star ted happening. First I nearly collapsed again tak ing a shower . For days the spe - cialists didn’t k now what was wrong with me. M y girlfriend at the time, who had rushed down from Wanak a when she had heard it had happened went mad at the specialists to do something. Af ter six days of going in and out of seizures, finally af ter what seemed like all the tests k nown to man, they said I had suffered several brain stem strokes then one massive major one, which altogether had lef t me diagnosed with the ex tremely rare and unk nown condition only k nown to a few as “ locked in syndrome”. (shrink)

This paper presents proof that Buss's S22 can prove the consistency of a fragment of Cook and Urquhart's PV from which induction has been removed but substitution has been retained. This result improves Beckmann's result, which proves the consistency of such a system without substitution in bounded arithmetic S12. Our proof relies on the notion of "computation" of the terms of PV. In our work, we first prove that, in the system under consideration, if an equation is proved and either (...) its left- or right-hand side is computed, then there is a corresponding computation for its right- or left-hand side, respectively. By carefully computing the bound of the size of the computation, the proof of this theorem inside a bounded arithmetic is obtained, from which the consistency of the system is readily proven. This result apparently implies the separation of bounded arithmetic because Buss and Ignjatović stated that it is not possible to prove the consistency of a fragment of PV without induction but with substitution in Buss's S12. However, their proof actually shows that it is not possible to prove the consistency of the system, which is obtained by the addition of propositional logic and other axioms to a system such as ours. On the other hand, the system that we have considered is strictly equational, which is a property on which our proof relies. (shrink)

The whale optimization algorithm is a powerful swarm intelligence method which has been widely used in various fields such as parameter identification of solar cells and PV modules. In order to better balance the exploration and exploitation of WOA, we propose a novel modified WOA in which both the mutation strategy based on Levy flight and a local search mechanism of pattern search are introduced. On the one hand, Levy flight can make the algorithm get rid of the local optimum (...) and avoid stagnation; thus, it is able to prevent the algorithm from losing diversity and to increase the global search capability. On the other hand, pattern search, a direct search method, has not only high convergence rate but also good stability, which can boost the local optimization ability of the WOA. Therefore, the combination of these two mechanisms can greatly improve the capability of WOA to obtain the best solution. In addition, MWOA may be employed to estimate parameters in single diode model, double diode model, and PV modules and to identify unknown parameters of two different types of PV modules under diverse light irradiance and temperature conditions. The analytical results demonstrate the validity and the practicality of MWOA for estimating parameters of solar cells and PV modules. (shrink)

Sub-Saharan emerging countries experience electrical shortages resulting in power rationing, which ends up hampering economic activities. This paper proposes an approach for very short-term blackout forecast in grid-tied PV systems operating in low reliability weak electric grids of emerging countries. A pilot project was implemented in Arusha-Tanzania; it mainly comprised of a PV-inverter and a lead-acid battery bank connected to the local electricity utility company, Tanzania Electric Supply Company Limited. A very short-term power outage prediction model framework based on a (...) hybrid random forest algorithm was developed using open-source Python machine learning libraries and using a dataset generated from the pilot project’s experimental microgrid. Input data sampled at a 15-minute interval included day of the month, weekday, hour, supply voltage, utility line frequency, and previous days’ blackout profiles. The model was composed of an adaptive similar day module that predicts 15 minutes ahead from a sliding window lookup table spanning 2 weeks prior to the prediction target day, after which ASD prediction was fused with RF prediction, giving a final optimised RF-ASD blackout prediction model. Furthermore, the efficacy analysis of the short-term blackout prediction of the formulated RF, ASD, and RF-ASD regression and classification algorithms was compared. Considering the stochastic nature of blackouts, their performance was found to be fair in short-term blackout predictions of the test site’s weak grid using limited input data from the point of coupling of the user. The models developed were only able to predict blackouts if they occurred frequently and contiguously, but they performed poorly if they were sparse or dispersed. (shrink)

This work presents a distributed generation system that combines system of a wind turbine and photovoltaic using a unified power quality conditioner. Along with providing active power to the utility grid, Wind-PV-UPQC improves PQ indicators, for example, voltage drops/surges, harmonics of grid voltages, and PF. Since Wind-PV-UPQC depends on dual compensation scheme, the parallel converter works as a sinusoidal voltage source, while the series converter works as a sinusoidal current source. In this way, a smooth transition from grid operation to (...) island operation and vice versa can be achieved without load voltage transitions. In addition, in order to overcome the problems through abrupt solar radiation or wind speed variations, a faster power balance is achieved between the wind turbines, the PV array, and the grid, as FFCL pursue the production of the current references of series converter. Consequently, the dynamic reactions of the converter currents and the voltage of dc bus are enhanced. A comprehensive analysis of flow of the AP through the converters is done to ensure a proper understanding of how Wind-PV-UPQC works. Finally, the simulation results are shown to estimate the dynamic and static performance of Wind-PV-UPQC in conjunction with the power distribution system. (shrink)

Definition of the problem: The report supplies the national part of a European survey in which doctors that are involved in the treatment of patients in `Persistent Vegetative State' (PVS) are being interviewed. The questions concern decision-situations the doctors are frequently confronted with in the treatment of PVS-patients. The questionnaire is designed as a decisiontree in order to bring about the exact delineations that govern the decisions. Therefore the result of the survey only portrays which delineations are in fact being (...) accepted (and does not allow any conclusion concerning which norms should guide the decisions). Whether these factual delineations correspond to ethical-normative criteria that derive from guiding principles – such as human dignity – is being discussed in the part reflecting on the survey. It is crucial to an adequate interpretation of the survey results to keep in mind that the doctors were not being asked about what they actually did in the situations described; the survey was designed to bring about what the doctors' basic attitudes towards the problems are.Arguments: The reason this methodological approach to the problem was chosen is that an ethical evaluation can only take place when the action-guiding convictions of the agents concerned are known. The goal of the survey was to make a provisional orientation concerning the basic attitudes possible. Compared to other countries taking part in, the survey result in Germany confirms the hypotheses that doctors from different European countries – concerning the decisions of withdrawing treatment or withholding treatment – are guided by different basic attitudes.Conclusion: As it has become apparent that important national differences concerning the action-guided attitudes of the doctors exist, it would not be advisable to recommend that European guidelines for all countries should be set up for such cases. The decisions taken depend on the guiding ethical assumptions; they can only be decisions for the very case they were derived at. (shrink)