Influence of thermal phenomena on dc characteristics of the IGBT

The paper concerns the study of the effect of thermal phenomena on characteristics of the IGBT. The used measurement set-ups and the results of measurements of dc characteristics of the selected transistor obtained under different cooling conditions are presented. The influence of the ambient temperature and the applied cooling system on the shape of these characteristics is discussed. In particular, attention has been paid to the untypical shape of non-isothermal characteristics of this element in the sub-threshold range

Application of the averaged model of the diode-transistor switch for modelling characteristics of a boost converter with an IGBT

DC-DC converters are popular switch-mode electronic circuits used in power supply systems of many electronic devices. Designing such converters requires reliable computation methods and models of components contained in these converters, allowing for accurate and fast computations of their characteristics. In the paper, a new averaged model of a diode-transistor switch containing an IGBTis proposed. The form of the developed model is presented. Its accuracy is verified by comparing the computed characteristics of the boost converter with the characteristics computed in SPICE using a transient analysis and literature models of a diode and an IGBT. The obtained results of computations proved the usefulness of the proposed model

Compact thermal models of semiconductor devices – a review

In the paper the problem of modelling thermal properties of semiconductor devices with the use of compact models is presented. This class of models is defined and their development over the past dozens of years is described. Possibilities of modelling thermal phenomena both in discrete semiconductor devices, monolithic integrated circuits, power modules and selected electronic circuits are presented. The problem of the usefulness range of compact thermal models in the analysis of electronic elements and circuits is discussed on the basis of investigations performed in Gdynia Maritime University

An Experimental Evaluation of Time Series Classification Using Various Distance Measures

In recent years a vast number of distance measures for time series classification has been proposed. Obviously, the definition of a distance measure is crucial to further data mining tasks, thus there is a need to decide which measure should we choose for a particular dataset. The objective of this study is to provide a comprehensive comparison of 26 distance measures enriched with extensive statistical analysis. We compare different kinds of distance measures: shape-based, edit-based, feature-based and structure-based. Experimental results carried out on 34 benchmark datasets from UCR Time Series Classification Archive are provided. We use an one nearest neighbour (1NN) classifier to compare the efficiency of the examined measures. Computation times were taken into consideration as well

The modified Peyton approach in the teaching of cardiac auscultation

Background: The aim of the study was to evaluate the usefulness of the modified Peyton’s four-step approach in the teaching of cardiac auscultation and to determine students’ perception of Peyton’s four-step approach. Methods: The opinion of the participants on the usefulness of the modifi ed four-step approach was attained through the use of anonymous questionnaires, voluntarily completed by students, and on the basis of semi-structured interviews conducted with a subset of students. 187 second-year students of our 6-year long curriculum were enrolled. They attended an obligatory Laboratory Training of Clinical Skills course. The average group size was 16 students. Results: The survey findings identified that 88.1% of participants found it helpful in developing their understanding of cardiac auscultation. 89.8% of all participants claimed that the new modified four-step approach facilitated memorization. The modified Peyton’s four-step method allows for better organization of classes in the opinion of 87.6% students. The advantages of the method were noticed by the majority of students. Conclusions: The modified Peyton’s four-step approach in the teaching of cardiac auscultation under laboratory conditions was perceived by students to be a comprehensible method that facilitates understanding and memorization. This approach allows for improved organization of classes. From the student’s perspective this method allows one to master the technique of cardiac auscultation in the classroom, through the increased demand of the participants’ attention, activity and involvement

The modified Peyton's approach and students' learning style

Background: The aim of the study was to determine the predominant learning style and type of intelligence based on the VARK questionnaire and Multiple Intelligences Questionnaire respectively in second year medical students. Determining the relationship between individual preferences of students, based on their learning style and predominant type of intelligence and the perception of the modified Peyton’s four-step approach used to teach cardiac auscultation. Methods: The opinion of participants 236 of the modified four-step approach was attained through the use of anonymous questionnaires. Using the VARK questionnaire, the participants’ learning style was defined. The predominant type of intelligence was determined by the Multiple Intelligences Question-naire. Results: The kinesthetic style was the predominant unimodal learning style in second year medical students (in Polish and international students). The most predominant type of intelligence in Polish students was visual-spatial and mathematical and logical, while in international students the predominant types were visual-spatial and mixed type of intelligence. Quantitative analysis indicated that the modified Peyton’s approach is a valuable learning and teaching method for most students, independent of their predominant learning style or intelligence type. The exception was a small group of students with lin-guistic intelligence predominance according to the Multiple Intelligence Questionnaire, for which the Peyton method was more difficult. Conclusions: This study proves that the modified Peyton’s approach is useful and effective didactic tool and can be successfully applied to most students. This is a new learning strategy for teaching cardiac auscultation in laboratory conditions in classes for a significant majority. Due to the fact that a group of students with a predominance of linguistic intelligence more often perceived the Peyton method to be difficult, it is worth combining traditional methods with new ones in class so that all students, regardless of unimodal learning style or prevailing type of intelligence, are taught satisfactorily

Wstępne wyniki pierwszego w Polsce programu przesiewowego w tętniaku aorty brzusznej w województwie kujawsko-pomorskim

Background. Abdominal aortic aneurysm (AAA) is called a widening of the aorta below the renal arteries with a diameter more than 3 cm. The prevalence of AAA is estimated at 4–8% in men aged 65 years or more. The mortality rate for patients with ruptured AAA is 65%, while the mortality rate for aortic aneurysm repair surgery in elective patients undergoing pre-screened is 3%. The aim of this study was to determine the prevalence of AAA among men aged 60 years and older undergoing targeted ultrasonography of abdominal aorta. The additional aim was to determine the relationship between specific risk factors and the AAA, and to determine the prevalence of AAA in patients subgroups specified by the criteria for the screening programmes for AAA. Material and methods. Based on available data from the literature, study populations was defined as men aged 60 years and older. Applied research methods were as follow: 1) the questionnaire; 2) measurement of physical characteristics of aorta (diameter of abdominal aorta by ultrasound scan). The questionnaire consisted of two parts: 1) identification and demographic data; 2) the presence of risk factors. Analysis of data from the questionnaire determined the relationship between the risk factors and the AAA, whereas ultrasonography of the aorta, detected the disease (abdominal aortic aneurysm) and its prevelance. Statistical analysis of the data was performed using the software STATISTICA 9 (StatSoft, Inc., 2009). Results. Based on 1556 ultrasound scans, the abdominal aortic aneurysm was diagnosed in 94 men aged 60 years and older. The prevalence of AAA in the study group was 6.0%. Risk factors associated with the AAA were analyzed in two groups: I — AAA (n = 94) and II — normal aorta (n = 1464). The three risk factors were significantly associated with the AAA: age, smoking and family history, whereas the incidence of AAA in males at 65 years old was 4.0%, and a group of men between 65 and 75 years of age, smoking cigarettes ever, was 7.4%. Conclusions. In the obtained data the prevalence of AAA was similar to that of literature. Additionally, the positive relationship between age, smoking, and AAA was detected. Acta Angiol 2012; 18, 1: 9–17Wstęp. Tętniakiem aorty brzusznej (TAB) określa się poszerzenie aorty poniżej odejścia tętnic nerkowych o średnicy powyżej 3 cm. Częstość występowania TAB szacuje się na 4–8% u mężczyzn w wieku 65 lat i więcej. Współczynnik umieralności dla pacjentów z pękniętym TAB wynosi 65%, natomiast śmiertelność pooperacyjna dla operacji naprawczych tętniaka aorty w trybie planowym wśród pacjentów poddanych wcześniej badaniu przesiewowemu wynosi 3%. Podstawowym celem pracy było określenie częstości występowania (chorobowość, prevalence) TAB wśród mężczyzn w wieku 60 lat i starszych poddanych ukierunkowanemu badaniu ultrasonograficznemu aorty w odcinku brzusznym. Dodatkowo zbadano zależności między określonymi czynnikami ryzyka a TAB oraz częstość występowania TAB w subgrupach pacjentów określonych według kryteriów programów badań przesiewowych w kierunku TAB. Materiał i metody. Na podstawie dostępnego piśmiennictwa zdefiniowano populację narażoną, tj. mężczyzn w wieku 60 lat i starszych. Zastosowano następujące metody badawcze: 1) metodę kwestionariuszową; 2) pomiar cechy fizycznej (badanie ultrasonograficzne średnicy aorty w odcinku brzusznym). Kwestionariusz składał się z dwóch części: 1) dotyczącej danych identyfikacyjnych i demograficznych; 2) dotyczącej występowania czynników ryzyka. Analiza danych z kwestionariusza umożliwiła określenie zależności między badanymi czynnikami ryzyka a TAB, natomiast poddanie zdefiniowanej części populacji badaniu ultrasonograficznemu aorty umożliwiło wykrycie choroby (tętniak aorty brzusznej) i określenie częstość jej występowania. Analizę statystyczną uzyskanych danych przeprowadzono z wykorzystaniem oprogramowania STATISTICA 9 (StatSoft, Inc. 2009). Wyniki. Na podstawie wykonanych 1556 badań ultrasonograficznych aorty brzusznej tętniak zdiagnozowano u 94 mężczyzn w wieku 60 lat i starszych. Częstość występowania (prevalence) TAB w badanej grupie wyniosła 6,0%. Czynniki ryzyka związane z TAB analizowano, wyodrębniając dwie grupy: I — TAB (n = 94) i II — aorta prawidłowa (n = 1464). Istotny statystycznie związek z TAB miały 3 czynniki ryzyka: wiek, palenie tytoniu i występowanie rodzinne TAB. Częstość występowania TAB w grupie mężczyzn w 65. roku życia wyniosła 4,0%, natomiast w grupie mężczyzn między 65. a 75. rokiem życia, palących kiedykolwiek tytoń, wyniosła 7,4%. Wnioski. Na podstawie uzyskanych danych stwierdzono częstość występowania TAB podobną do tej z piśmiennictwa. Dodatkowo stwierdzono także zależności między wiekiem, paleniem tytoniu i występowaniem rodzinnym TAB a zachorowaniem na TAB. Acta Angiol 2012; 18, 1: 9–1

P2RX7 Purinoceptor: A Therapeutic Target for Ameliorating the Symptoms of Duchenne Muscular Dystrophy

open access articleDuchenne muscular dystrophy (DMD) is the most common inherited muscle disease, leading to severe disability and death in young men. Death is caused by the progressive degeneration of striated muscles aggravated by sterile inflammation. The pleiotropic effects of the mutant gene also include cognitive and behavioral impairments and low bone density. Current interventions in DMD are palliative only as no treatment improves the long-term outcome. Therefore, approaches with a translational potential should be investigated, and key abnormalities downstream from the absence of the DMD product, dystrophin, appear to be strong therapeutic targets. We and others have demonstrated that DMD mutations alter ATP signaling and have identified P2RX7 purinoceptor up-regulation as being responsible for the death of muscles in the mdx mouse model of DMD and human DMD lymphoblasts. Moreover, the ATP–P2RX7 axis, being a crucial activator of innate immune responses, can contribute to DMD pathology by stimulating chronic inflammation. We investigated whether ablation of P2RX7 attenuates the DMD model mouse phenotype to assess receptor suitability as a therapeutic target

Methods of Fast Analysis of DC–DC Converters—A Review

The paper discusses the methods of fast analysis of DC–DC converters dedicated to computer programmes. Literature methods of such an analysis are presented, which enable determination of the characteristics of the considered converters in the steady state and in the transient states. The simplifications adopted at the stage of developing these methods are discussed, and their influence on the accuracy of computations is indicated. Particular attention is paid to the methods of fast analysis of DC–DC converters, taking into account thermal phenomena in semiconductor devices. The sample results of computations of the DC–DC boost type converter obtained with the use of the selected methods are presented. The scope of application of particular computation methods and their duration times are discussed. Computations were performed with the use of SPICE and PLECS

The Analysis Of Accuracy Of Selected Methods Of Measuring The Thermal Resistance Of IGBTs

In the paper selected methods of measuring the thermal resistance of an IGBT (Insulated Gate Bipolar Transistor) are presented and the accuracy of these methods is analysed. The analysis of the measurement error is performed and operating conditions of the considered device, at which each measurement method assures the least measuring error, are pointed out. Theoretical considerations are illustrated with some results of measurements and calculations