1,721,231 research outputs found
The Hot-Spot Phenomenon and its Countemeasures in Bipolar Power Transistors by Analytical Electro-Thermal Simulations
No full textThis communication deals with a theoretical study of the hot spot onset (HSO) in cellular bipolar power transistors. This well-known phenomenon consists of a current crowding within few cells occurring for high power conditions, which significantly decreases the forward safe operating area
(FSOA) of the device. The study was performed on a virtual sample by means of a fast, fully analytical electro-thermal simulator operating in the steady state regime and under the condition of imposed input base current. The purpose was to study the dependence of the phenomenon onseveral thermal and geometrical factors and to test suitable countermeasures able to impinge this phenomenon at higher biases or to completely eliminate it. The power threshold of HSO and its localization within the silicon die were observed as a function of the electrical bias conditions as for instance the collector voltage, the equivalent thermal resistance of the assembling structure underlying the silicon die, the value of the ballasting resistances purposely added in the emitter metal interconnections and the thickness of the copper heat spreader placed on the die top just to the aim of making more uniform the temperature of the silicon surface
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Diversity of mitochondrial DNA of the endangered white-clawed crayfish (Austropotamobius italicus) in the Po River catchment.
No full textPhylogeographic structure of vairone Telestes muticellus (Teleostei, Cyprinidae) within three European peri-Mediterranean districts.
No full textThe phylogeographic pattern of vairone (Telestes muticellus) populations was assessed to test the biogeographic distinction of three peri-Mediterranean ichthyogeographic districts: Padano-Venetian (PV), Tuscano-Latium (TL) and Southern France (SF), evaluating the role of Alpine and Apennine barriers in shaping distinct evolutionary lineages. A fragment of mitochondrial DNA cytochrome b was sequenced in 153 specimens from 14 northwestern Italian populations, collected in 10 tributaries of Po River and in 4 rivers on the Tyrrhenian slope of Ligury. 32 haplotypes were identified. The phylogenetic analyses confirmed the presence of two distinct clades, an “Italian clade” (T. muticellus) and a “French clade” (T. souffia), showing an average genetic distance of 12.9 % (±1.3 SD) and allopatric distribution. The NCA and AMOVA analyses revealed an isolated gene pool in eastern basins on the Tyrrhenian slope of Ligury. The phylogeographic findings suggest: i) the lack of permeability of Alpine barrier towards the dispersion across Italian and French hydrographical systems, ii) partial permeability of Mediterranean Alps and Apennines through river captures crossing lower watersheds
THE DJOSER THERMAL SIMULATOR FOR ELECTRONIC DEVICES AND SYSTEMS: DIDACTICAL FEATURES FOR IMPROVING RELIABILITY CULTURE IN ACADEMIC AND INDUSTRIAL ENVIRONMENTS
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VALIDATION OF THE DJOSER ANALYTICAL THERMAL SIMULATOR FOR ELECTRONIC POWER DEVICES AND ASSEMBLING STRUCTURES
No full textThe present communication deals with the tests for the validation of the DJOSER steady-state thermal simulation program, purposely
designed for power electronic assembling structures and which is based on the resolution of analytical relationships. The validation
experiments were carried out theoretically by comparing the thermal maps with those obtained using standard finite-elements programs
and yielding temperature accuracy below 1%. Experimental tests were also performed on purposely built multi-layer structures and
industrial circuits with power diodes mounted in naked-chip configuration. The simulated maps were compared with accurate thermographic
recordings and showed a good agreement, testifying the validity of the mathematical model
Study of Water Speed Sensitivity in a Multifunctional Thick-film Sensor by Analytical Thermal Simulations and Experiments
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