Practical Open-Loop Optimistic Planning

We consider the problem of online planning in a Markov Decision Process when given only access to a generative model, restricted to open-loop policies - i.e. sequences of actions - and under budget constraint. In this setting, the Open-Loop Optimistic Planning (OLOP) algorithm enjoys good theoretical guarantees but is overly conservative in practice, as we show in numerical experiments. We propose a modified version of the algorithm with tighter upper-confidence bounds, KLOLOP, that leads to better practical performances while retaining the sample complexity bound. Finally, we propose an efficient implementation that significantly improves the time complexity of both algorithms

Smanjenje gubitaka istitravanja kod neizravnog istosmjernog pretvarača s transformatorom uporabom RC-RCD prigušnog člana

Flyback converter is one of the most popular DC-DC converters for low power supply. Due to the transformer leakage inductance the converter suffers from the voltage spikes, which can be »controlled« by the dissipative RCD or non-dissipative LCD clamp circuits. Both of the clamp circuits consist of the diode. The diode reverse recovery charge causes the oscillation, which results in additional dissipation of the clamp circuitry. This paper describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp-diode\u27s oscillation. This clamp circuit is capable for improving a flyback converter\u27s power ratio.Neizravni istosmjerni pretvarač s transformatorom jedan je od najpopularnijih istosmjernih pretvarača za izvore napajanja malih snaga. Zbog rasipnog induktiviteta transformatora tijekom rada pretvarača dolazi do pojave prenapona, koji se mogu ograničiti pomoću disipativnih RCD ili nedisipativnih LCD prigušnih sklopova. Oba prigušna sklopa sadrže diodu. Reverzni naboj oporavljanja diode uzrokuje oscilacije koje uzrokuju dodatne gubitke u prigušnom sklopu. Članak opisuje pojavu istitravanja i uporabu RC-RCD prigušnog sklopa za prigušenje oscilacija uzrokovanih prigušnom diodom. Opisani prigušni sklop omogućava povećanje djelotvornosti neizravnog istosmjernog pretvarača s transformatorom

Likert scales: how to (ab)use them?

No abstract available

Knowledge and attitudes about health research amongst a group of Pakistani medical students

Background Health research training is an important part of medical education. This study was conducted to assess the level of knowledge and attitudes regarding health research in a group of Pakistani medical students at Aga Khan University, Karachi. Methods It was a cross-sectional pilot study conducted among a group of Pakistani medical students. Through stratified random sampling, a pre-tested, structured and validated questionnaire was administered to 220 medical students. Knowledge and attitudes were recorded on a scale (graduated in percentages). Results Mean scores of students were 49.0% on knowledge scale and 53.7% on attitude scale. Both knowledge and attitudes improved significantly with increasing years of study in medical college [Regression coefficient 4.10 (p-value; 0.019) and 6.67 (p-value; \u3c 0.001) for knowledge and attitudes, respectively]. Conclusion Medical students demonstrate moderate level of knowledge and attitude towards health research. Intensive training in this regard is associated with significant improvement in knowledge and attitudes of students towards health research

Individual characteristics and student's engagement in scientific research : a cross-sectional study

Background: In light of the increasing recognition of the importance of physician scientists, and given the association between undergraduate research experiences with future scientific activity, it is important to identify and understand variables related to undergraduate student’s decision to engage in scientific research activities. The present study assessed the influence of individual characteristics, including personality traits and socio-demographic characteristics, on voluntary engagement in scientific research of undergraduate medical students. Methods: For this study, all undergraduate students and alumni of the School of Health Sciences in Minho, Portugal were invited to participate in a survey about voluntary engagement in scientific research activities. Data were available on socio-demographic, personality and university admission variables, as part of an ongoing longitudinal study. A regression model was used to compare (1) engaged with (2) not engaged students. A classification and regression tree model was used to compare students engaged in (3) elective curricular research (4) and extra-curricular research. Results: A total of 466 students (88%) answered the survey. A complete set of data was available for 435 students (83%).Higher scores in admission grade point average and the personality dimensions of “openness to experience” and “conscientiousness” increased chances of engagement. Higher “extraversion” scores had the opposite effect. Male undergraduate students were two times more likely than females to engage in curricular elective scientific research and were also more likely to engage in extra-curricular research activities. Conclusions: This study demonstrated that student’s grade point average and individual characteristics, like gender, openness and consciousness have a unique and statistically significant contribution to student’s involvement in undergraduate scientific research activities.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/ESC/65116/200

Imagine Being a Nice Guy: A Note on Hypothetical vs. Incentivized Social Preferences

We conducted an experimental study on social preferences using dictator games similar to Fehr et al. (2008). We show that social preferences differ between participants who receive low-stakes monetary rewards for their decisions and participants who consider hypothetical stakes. The results are robust when we control for socio-demographic characteristics and par-ticipants' risk attitudes. Besides incentives, gender plays an important role for the categoriza-tion of different social preferences