Figures of Merit

Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for a continuation of this trend. For identifying and quantifying such technological barriers this paper investigates the volume of the cooling system and of the main passive components for the basic forms of power electronics energy conversion in dependency of the switching frequency and determines switching frequencies minimizing the total volume. The analysis is for 5 kW rated output power, high performance air cooling, advanced power semiconductors, and single systems in all cases. A power density limit of 28 kW/dm3@300 kHz is calculated for an isolated DC-DC converter considering only transformer, output inductor and heat sink volume. For single-phase AC-DC conversion a general limit of 35 kW/dm3 results from the DC link capacitor required for buffering the power fluctuating with twice the mains frequency. For a three-phase unity power factor PWM rectifier the limit is 45 kW/dm3@810 kHz just taking into account EMI filter and cooling system. For the sparse matrix converter the limiting components are the input EMI filter and the common mode output inductor; the power density limit is 71 kW/dm3@50 kHz when not considering the cooling system. The calculated power density limits highlight the major importance of broadening the scope of research in power electronics from traditional areas like converter topologies, and modulation and control concepts to cooling systems, high frequency electromagnetics, interconnection technology, multi-functional integration, packaging and multi-domain modeling and simu- lation to ensure further advancement of the field along the power density trajectory.

The object of the current research manuscript is to analyze the valley-spin thermoelectric properties and Nernst coefficient at two different temperatures for ferromagnetic silicene superlattice. Photon-assisted tunneling probability is used to identify the resolved thermoelectric parameters including (valley, spin, and charge) electronic thermal conductance, Seebeck coefficient, figure of merit, and also electrical conductance and Nernst coefficient. The results show oscillatory behavior to all investigated parameters. The improved data of Seebeck coefficient (valley, spin, and charge) could be because of quantum confinement effect of the present investigated nanodevice. The figure of merit (valley, spin, and charge) attains quite high values with good high thermoelectric efficiency. The enhancement of Nernst coefficient (valley, spin, and charge) might consider Nernst effect is suitable for thermoelectric heat energy conversion system of the present flexible ferromagnetic silicene superlattice. The ferromagnetic silicene superlattice nanodevices are good candidates for flexible renewable energy generation as demonstrated by this analysis.

According to the latest recommendation of the International Union of Pure and Applied Chemistry, “selectivity refers to the extent to which the method can be used to determine particular analytes in mixtures or matrices without interferences from other components of similar behavior”. Because of the prime importance of selectivity as an analytical figure of merit, numerous proposals have been published on how to quantify it in spectrophotometric multicomponent analysis. We show that the criterion independently developed by Lorber [11,12] and Bergmann, von Oepen and Zinn [13] is the most suitable, because it directly relates to prediction uncertainty and allows for a consistent generalization to more complex systems of chemical analysis.

Summary form only given. Although electro-optic polymers can exhibit large electro-optic coefficients which lead to >100 GHz bandwidth devices, their electrooptic effect degrades in time under continuous illumination. Figures of merit for predicting the device lifetimes have been defined and measured for over 40 polymers. Lifetimes varied from a few hours, to almost a year at 1320 nm. To improve photostability, it is necessary to understand the mechanisms (photo-oxidation, cis-trans isomerization, etc.) and number of pathways (in which excited states are involved) in the photodegradation process. Experiments were carried out in different atmospheres for two prototypical polymers DANS (4N,N'-dimethylamino-4' nitrostilbene) and DR1 (disperse red, 1,4-[N-ethyl-N-(2-hydroxyethyl)amino]-4'-nitroazobenzene). Multiple photodegradation pathways and mechanisms were found

Boron-doped strontium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by using a polymeric precursor technique. The powders were characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and physical properties measurement system (PPMS) techniques. The XRD results showed that these patterns have a two-phase mixture. The phases are face-centered cubic (fcc) and body-centered cubic (bcc). Values of the crystallite size, dislocation density, and microstrain were calculated by using the Scherrer equation. The lattice parameters were calculated for fcc and bcc phases. The SEM results showed that needle-like grains are formed in boron-undoped composite materials, but the needle-like grains changed to the plate-like grains with the addition of boron. The distribution of the nanofiber diameters was calculated and the average diameter of the boron-doped sample is smaller than the boron-undoped one. PPMS values showed that the electrical resistivity values decreased, but the thermal conductivity values, the Seebeck coefficients, and figure of merit (ZT) increased with increasing temperature for the two samples.