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

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

Paleoelevation estimates for the northern and central proto–Basin and Range from carbonate clumped isotope thermometry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99057/1/tect20016.pd

Body Size Changes in Elite Junior Rowers: 1997 to 2007

The aim of this study was to determine whether elite international junior rowers in 2007 were heavier and taller than those evaluated in 1997, and to compare this change among finalists and non-finalists, and sweep rowers and scullers. Body weight and height data obtained by a questionnaire from a total of 398 rowers (42% female, 58% male) at the Junior World Rowing Championships in Beijing, People’s Republic of China, in 2007 (65.9% of all competitors), were compared with data from 603 rowers measured at the Junior World Rowing Championships in Hazewinkel, Belgium in 1997 (36.5% female, 63.5% male, representing 90% and 89% of all competitors, respectively, by gender). Male and female rowers in 2007 were significantly taller compared to those in 1997 (1.0 cm, p=0.009 and 2.1 cm, p<0.001, respectively; one-sample t-test). No statistically significant difference was found for body mass. The finalists and sweep rowers were taller and heavier compared to nonfinalists and scullers at both Championships respectively. The heights of elite level junior rowers increased significantly over the decade. The finalists at World Junior Rowing Championships were again taller and heavier compared to the nonfinalists

The Cenozoic Climatic and Topographic Evolution of the Western North American Cordillera

Herein we present oxygen isotope records from Cretaceous to Recent terrestrial sediments in the western North American Cordillera. The purpose of this analysis is to use oxygen isotope records to understand the coupled surface elevation and climate histories of this region through the Cenozoic. To do this we constructed δ¹⁸(O) maps of surface waters for time intervals that trace the development of topography of western North America. These maps are based on 4861 oxygen isotope analyses from both published (4478) and new (383) data. We determined the δ¹⁸(O) values of surface waters using paleotemperatures derived previously from floral assemblages and the appropriate isotope fractionation factors. These data suggest that in the late Cretaceous to early Eocene the Sevier hinterland formed a plateau of unknown height. Around 50 Ma, a topographic wave developed in British Columbia and eastern Washington that swept southward reaching northeastern Nevada at ~40 to 38 Ma, and southern Nevada ~23 Ma. This southward encroachment of an Eocene Plateau (SWEEP) caused reorganization of drainage patterns such that the intraforeland basins of Wyoming and Utah drainages extended deep within the Sevier hinterland as the wave swept southward. The landscape within the Sevier hinterland developed into a rugged and high mountain range with the hypsometric mean elevation of ~4 km and relief of ~1.5 km. This Eocene highland was bordered on the west by a high Sierra Nevada ramp and on the east by the intraforeland basins that captured water draining these growing highlands. The spatial and temporal evolution of this highland correlates with the timing of volcanism and extension. These observations support tectonic models that call for north to south removal of the Farallon slab or piecemeal removal of mantle lithosphere. The isotopic data show that prior to growth of this highland the North American Monsoon (NAM) penetrated much farther north in the Paleocene/Eocene than today. The combined effects of global cooling, increasing latitudinal temperature gradients, and the generation of the orographic barrier created by the growing north to south highland produced a southward migration of the NAM front. By the Oligocene the hydrologic regime that we observe today was in place. It has been modified since then as a result of Basin and Range extension and collapse of the highlands in the mid-Miocene. This collapse allowed the NAM to penetrate farther north into the Great Basin of Nevada and Utah

Less Work, Less Respect: Authors' Perceived Importance of Research Contributions and Their Declared Contributions to Research Articles

BACKGROUND: Attitudes towards authorship are connected with authors' research experience and with knowledge of authorship criteria of International Committee of Medical Journal Editors (ICMJE). The objective of this study was to assess association between authors' perceived importance of contributions for authorship qualification and their participation in manuscripts submitted to a journal. METHODS: Authors (n = 1181) of 265 manuscripts submitted to the Croatian Medical Journal were asked to identify and rate their contribution in the preparation of the submitted manuscript (0-none to 4-full for 11 listed contributions) and the importance of these contributions as authorship qualifications (0-none to 4-full). They were randomly allocated into 3 groups: the first (n = 90 manuscripts, n = 404 authors) first received the contribution disclosure form and then contribution importance-rating questionnaire; the second (n = 88 manuscripts, n = 382 authors) first received the rating questionnaire and then the contribution disclosure form, and the third group (n = 87 manuscripts, n = 395 authors) received both questionnaires at the same time. We compared authors' perception of importance of contribution categories. RESULTS: 1014 (85.9%) authors of 235 manuscripts responded. Authors who declared contribution to a specific category rated it as more important for authorship than those authors who did not contribute to the same category (P>0.005 for all contribution categories, Mann-Withney test). Authors qualifying for ICMJE authorship rated all contribution categories higher than non-qualifying authors. For all contributions, associations between perceived importance of contribution and actual author's contribution were statistically significant. CONCLUSIONS: Authorship seems to be not a normative issue subjective to categorization into criteria, but also a very personal view of the importance and value of one's contributions

Body Size Changes in Elite Junior Rowers: 1997 to 2007

The aim of this study was to determine whether elite international junior rowers in 2007 were heavier and taller than those evaluated in 1997, and to compare this change among finalists and non-finalists, and sweep rowers and scullers. Body weight and height data obtained by a questionnaire from a total of 398 rowers (42% female, 58% male) at the Junior World Rowing Championships in Beijing, People’s Republic of China, in 2007 (65.9% of all competitors), were compared with data from 603 rowers measured at the Junior World Rowing Championships in Hazewinkel, Belgium in 1997 (36.5% female, 63.5% male, representing 90% and 89% of all competitors, respectively, by gender). Male and female rowers in 2007 were significantly taller compared to those in 1997 (1.0 cm, p=0.009 and 2.1 cm, p<0.001, respectively; one-sample t-test). No statistically significant difference was found for body mass. The finalists and sweep rowers were taller and heavier compared to nonfinalists and scullers at both Championships respectively. The heights of elite level junior rowers increased significantly over the decade. The finalists at World Junior Rowing Championships were again taller and heavier compared to the nonfinalists

Late Holocene isotope hydrology of Lake Qinghai, NE Tibetan Plateau: effective moisture variability and atmospheric circulation changes

A sub-centennial-resolution record of lacustrine carbonate oxygen isotopes (δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;C&lt;/sub&gt;) from the closed-basin Lake Qinghai on the NE Tibetan Plateau shows pronounced variability over the past 1500 years. Changes in δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;C&lt;/sub&gt; in hydrologically closed lakes are often interpreted in terms of changing effective moisture. Under this interpretation our record would imply increasing effective moisture during the Little Ice Age (LIA) compared to the Medieval Warm Period (MWP). However, independent evidence from other archives strongly suggests the Asian summer monsoon was stronger during the MWP and weakened during the LIA. Controls other than effective moisture (the balance of water inputs over evaporative loss) must therefore have contributed to the δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;C&lt;/sub&gt; values. We propose the LIA signal in Lake Qinghai resulted from a reduction in evaporation caused by colder air temperatures, coupled with a decrease in oxygen isotope composition of input waters as a result of an increase in the relative importance of westerly-derived precipitation. Our results caution against simplistic interpretations of carbonate oxygen isotope records from hydrologically closed lakes and suggest all possible controlling factors must be taken into account in order to avoid misleading palaeoclimatic reconstructions

Medical theses as part of the scientific training in basic medical and dental education: experiences from Finland

<p>Abstract</p> <p>Background</p> <p>Teaching the principles of scientific research in a comprehensive way is important at medical and dental schools. In many countries medical and dental training is not complete until the candidate has presented a diploma thesis. The objective of this study was to evaluate the nature, quality, publication pattern and visibility of Finnish medical diploma theses.</p> <p>Methods</p> <p>A total of 256 diploma theses presented at the University of Oulu from 2001 to 2003 were analysed. Using a standardised questionnaire, we extracted several characteristics from each thesis. We used the name of the student to assess whether the thesis resulted in a scientific publication indexed in medical article databases. The number of citations received by each published thesis was also recorded.</p> <p>Results</p> <p>A high proportion of the theses (69.5%) were essentially statistical in character, often combined with an extensive literature review or the development of a laboratory method. Most of them were supervised by clinical departments (55.9%). Only 61 theses (23.8%) had been published in indexed scientific journals. Theses in the fields of biomedicine and diagnostics were published in more widely cited journals. The median number of citations received per year was 2.7 and the range from 0 to 14.7.</p> <p>Conclusion</p> <p>The theses were seldom written according to the principles of scientific communication and the proportion of actually published was small. The visibility of these theses and their dissemination to the scientific community should be improved.</p

Regression of Moral Reasoning during Medical Education: Combined Design Study to Evaluate the Effect of Clinical Study Years

BACKGROUND: Moral reasoning is important for developing medical professionalism but current evidence for the relationship between education and moral reasoning does not clearly apply to medical students. We used a combined study design to test the effect of clinical teaching on moral reasoning. METHODS: We used the Defining Issues Test-2 as a measure of moral judgment, with 3 general moral schemas: Personal Interest, Maintaining Norms, and Postconventional Schema. The test was applied to 3 consecutive cohorts of second year students in 2002 (n = 207), 2003 (n = 192), and 2004 (n = 139), and to 707 students of all 6 study years in 2004 cross-sectional study. We also tested 298 age-matched controls without university education. RESULTS: In the cross-sectional study, there was significant main effect of the study year for Postconventional (F(5,679) = 3.67, P = 0.003) and Personal Interest scores (F(5,679) = 3.38, P = 0.005). There was no effect of the study year for Maintaining Norms scores. 3(rd) year medical students scored higher on Postconventional schema score than all other study years (p<0.001). There were no statistically significant differences among 3 cohorts of 2(nd) year medical students, demonstrating the absence of cohort or point-of-measurement effects. Longitudinal study of 3 cohorts demonstrated that students regressed from Postconventional to Maintaining Norms schema-based reasoning after entering the clinical part of the curriculum. INTERPRETATION: Our study demonstrated direct causative relationship between the regression in moral reasoning development and clinical teaching during medical curriculum. The reasons may include hierarchical organization of clinical practice, specific nature of moral dilemmas faced by medical students, and hidden medical curriculum