The present communication reports on the effect of the sprayed solution volume variation (as a thickness variation element) on the detailed Raman spectroscopy for WO₃ thin films with different thicknesses grown from precursor solutions with two different concentrations. Walls-like structured monoclinic WO₃ thin films were obtained by the spray deposition method for further integration in gas sensors. A detailed analysis of the two series of samples shows that the increase in thickness strongly affects the films’ morphology, while their crystalline structure is only slightly affected. The Raman analysis contributes to refining the structural feature clarifications. It was observed that, for 0.05 M precursor concentration series, thinner films (lower volume) show less intense peaks, indicating more defects and lower crystallinity, while thicker films (higher volume) exhibit sharper and more intense peaks, suggesting improved crystallinity and structural order. For higher precursor concentration 0.1 M series, films at higher precursor concentrations show overall more intense and sharper peaks across all thicknesses, indicating higher crystallinity and fewer defects. Differences in peak intensity and presence reflect variations in film morphology and structural properties due to increased precursor concentration. Further studies are ongoing.

It is an actual trend for electronic equipment to be used into growing range of working temperatures and at high level of the mechanical stress. As example, for the domains exempted by RoHS 2 EU Directive (it became law from January 2013) like aerospace, the standard maximum working temperature is 398.15K (125°C). The results of the comparative investigations regarding electrical and mechanical properties of the Lead/Lead-free solder joints function of working temperature and soldering thermal profile are presented in the paper. The experiments were designed based on previous work [1,2] having as starting point the “Homologous Temperature” concept [1,3,4], in order to respond to constrains imposed by the qualification processes of lead-free solder alloys for usage into exempted domains according to the RoHS 2 EU Directive [5,6].

Determination of the junction temperature of power LEDs is a great challenge. Indirect calculation of the junction temperature can be done by calculations, starting from the temperatures that could be measured with thermocouples in the accessible points and taking into consideration the thermal resistances of the materials included in the LED structure and in the mounting PCB used as heatsink. In this paper the authors proposed to use as temperature sensor the protection diode embedded in most of the power LED structures.

The complete understanding of the electromagnetic field characteristics in artificially created bulk or thin media is essential to the efficient harnessing of the multitude of linear and nonlinear effects resulting from it. Due to the fact that recently developed artificial metastructures exhibit controllable electric and magnetic properties that are completely different from natural ones, the spectrum of behavior resulting from subjecting such media to electromagnetic fields has to be revisited. In this paper, we introduce a k-surface framework that offers complete information on the dispersion properties of media with designer electric and magnetic responses with positive and negative values, as well as for the coupling between the two. The extension from the classic k-surface case resides in the consideration of magnetic and bianisotropic materials with positive and negative permittivity and permeability values, as well as the introduction of the chirality coefficient.To illustrate the applicability of our framework, we have investigated the conditions to obtain collinear second harmonic generation in the case of artificial media with positively and negatively valued electric and magnetic responses. As expected, the phase matching tuning curves, defined as the intersections between the k-surfaces at both frequencies, are significantly modified with respect to the classic ones.

Since the ancient times apiculture relies one hundred percent on the bee-keeper's skills and experience. He constantly checks the hives to perform the required activities at the right moment. The rising demand for apiculture products leads to larger and larger apiaries, and checking every hive by hand becomes costly and time consuming. This project suggests a durable solution for bee hive monitoring. The prototype can be used by unqualified personnel, with minimum maintenance.

To obtain maximum performance from a LED, it must be driven with a constant current. The maximum continuous current allowed is limited by the thermal characteristics of the package, but often the die supports higher peak currents. By driving the LED with high current pulses, the optical flux is greatly increased and more distant objects can be illuminated. This paper describes the design of such a driver and the results obtained from driving high power LEDs.