Microstructural Analysis of Sintered Gradient Materials Based on Distaloy SE Powder

The study describes the microstructural analysis of cylindrically-shaped functionally graded products sintered from iron powder with scheduled graded structure on the cross-section running from the core to the surface layer of the sinter. Different types of structure were produced using Distaloy SE powder in two compositions - one without the addition of carbon, and another with 0.6wt% C. Two methods were used to fill the die cavity and shape the products. The first method involving a two-step compaction of individual layers. The second method using an original technique of die filling enabled the formation of transition zone between the outer layer and the core still at the stage of product shaping. As part of microstructural analysis, structural constituents were identified and voids morphology was examined. Studies covered the effect of the type of the applied method on properties of the graded zone obtained in the manufactured product

Microstructural Analysis of Sintered Gradient Materials Based on Distaloy SE Powder

The study describes the microstructural analysis of cylindrically-shaped functionally graded products sintered from iron powder with scheduled graded structure on the cross-section running from the core to the surface layer of the sinter. Different types of structure were produced using Distaloy SE powder in two compositions - one without the addition of carbon, and another with 0.6wt% C. Two methods were used to fill the die cavity and shape the products. The first method involving a two-step compaction of individual layers. The second method using an original technique of die filling enabled the formation of transition zone between the outer layer and the core still at the stage of product shaping. As part of microstructural analysis, structural constituents were identified and voids morphology was examined. Studies covered the effect of the type of the applied method on properties of the graded zone obtained in the manufactured products

Analisys of the influence of nonlinearity of the thermal model of power mosfet on characteristics of boost converter

W pracy przeanalizowano zasadność stosowania nieliniowego modelu termicznego tranzystora MOS mocy przy analizach charakterystyk przetwornicy boost. Przedstawiono postać rozważanego modelu termicznego oraz wyniki elektrotermicznej analizy stanów przejściowych badanego układu, uzyskane przy uwzględnieniu nieliniowości modelu termicznego oraz przy pominięciu tej nieliniowości. Badania przeprowadzono dla przetwornic zawierających dwa różne zestawy półprzewodnikowych elementów kluczujących.In the paper the necessity of using the non-linear thermal model of the power MOS transistor at computer analyses of the boost converter is considered. The form of considered thermal model are presented and results of the electrothermal transient analysis of considered converter, obtained at the nonlinearity of the thermal model taking into account and at the omission of this nonlinearity are shown. Investigations were performed for converters containing two different sets of switching semiconductor devices

Application of the pirometric methods for the thermal resistance of power transistors measurements

Praca dotyczy pomiarórw rezystancji termicznej wybranych tranzystorów mocy przy wykorzystaniu metod pirometrycznych. Zamieszczono szereg wyników pomiarów tego parametru w funkcji mocy wydzielanej w elemencie, uzyskanych przy zastosowaniu różnych radiatorów obudów i orientacji przestrzennej badanych tranzystorów. Zbadano również nierównomierność przestrzennego rozkładu temperatury w badanej strukturze.In this paper the problem of measurements of the thermal resistance (Rth) of the selected power transistors with the use of the pirometric method is considered. The measuremental results Rth of bipolar transistors 2N3055 and MOS transistors IRF840 for the dissipated power changing as well as for the various kinds of device cases the temperature distribution on the chip has been estimated

Rolling and burnishing of internal threads. Part 2, The technology

Przedstawiono główne zagadnienia technologii walcowania i nagniatania gwintów wewnętrznych za pomocą głowic rolkowych własnej konstrukcji (dobór warunków obróbki, wyniki badań doświadczalnych oraz przybliżoną ocenę obciążeń rolek i łożysk ślizgowych głowic).The key issues of the technology of rolling and burnishing of internal threads with the rolling heads of own design (selection of process parameters, results of the experimental studies and an approximate estimate of load acting on the rolls and sliding bearings in the rolling head) were describe

Tensile properties of austenitic cast iron with 17% and 23% of nickel

Vydáno chybně pod ISSN 1210-047

Examinations of Selected Thermal Properties of Packages of SiC Schottky Diodes

This paper describes the study of thermal properties of packages of silicon carbide Schottky diodes. In the paper the packaging process of Schottky diodes, the measuring method of thermal parameters, as well as the results of measurements are presented. The measured waveforms of transient thermal impedance of the examined diodes are compared with the waveforms of this parameter measured for commercially available Schottky diodes

Changes in honey bee nutrition after exposure to radiofrequency electromagnetic field

Urban beekeeping has gained interest in recent years. Bees placed in cities, on the roofs of buildings, are exposed to many different sources of electromagnetic fields of different frequencies and intensities. Knowledge about the impact of electromagnetic fields on the physiology and behavior of insects (including honey bees) is limited. Hence, one of the first steps was to check how radiofrequency electromagnetic fields affect honey bees’ nutrition. The level of total proteins, glucose, triglycerides, and TAS activity in bee hemolymph was analyzed. This is because they indicate the honey bee’s nutrition level. The experiment involved 2-day-old Carniolan worker honey bees (Apis mellifera carnica L.). The bees were exposed to fields of 12 V/m, 28 V/m, and 61 V/m for 0.25, 1 and 3 h. Hemolymph was taken from 40 alive worker honey bees from each group immediately after exposure, by removing the antennae with sterile tweezers. The activity of biochemical markers (total proteins, TAS, and triglycerides) in the bee hemolymph in 12 V/m and 28 V/m groups showed statistically significant differences compared to the control group in most cases. According to our own research, radiofrequency electromagnetic fields disturb honey bee nutrition. The changes in the analyzed indicators may have long-term effects