Modeling of an Impact of Thin Insulating Film on the Electrode Surface on Discharge Ignition in Mercury Illuminating Lamps at Low Ambient Temperatures
In this work, a model of the low-current discharge in the argon–mercury mixture at the existence of a thin insulating film on the cathode surface is developed. It takes into account, besides of the ion-electron emission from the cathode surface, the field electron emission from the cathode metal substrate into the film, caused by the strong electric field generated in it in the discharge.
A theoretical model of the cathode sheath of a normal glow discharge for the cathode with a thin insulating film is developed. In addition to the ion-electron emission, the field emission of electrons from the metal cathode substrate into the film under the action of the strong electric field generated in the insulator is taken into account in the model. It is established that the influence of the field electron emission on the glow discharge characteristics is determined by the emission efficiency of the film, equal to the fraction of electrons going out of it into the discharge volume. It is demonstrated that the calculated normal cathode voltage drop in the discharge in argon for the cathode with a barium oxide film coincides with its measured value for the emission efficiency of the film of the order of 0.1, which is in agreement with its experimental estimations.
Mechanical performances of titanium biomedical implants manufactured by superplastic forming are strongly related to the process parameters: the thickness distribution along the formed sheet has a key role in the evaluation of post-forming characteristics of the prosthesis. In this work, a finite element model able to reliably predict the thickness distribution after the superplastic forming operation was developed and validated in a case study. The material model was built for the investigated titanium alloy (Ti6Al4V-ELI) upon results achieved through free inflation tests in different pressure regimes. Thus, a strain and strain rate dependent material behaviour was implemented in the numerical model. It was found that, especially for relatively low strain rates, the strain rate sensitivity index of the investigated titanium alloy significantly decreases during the deformation process. Results on the case study highlighted that the strain rate has a strong influence on the thickness profile, both on its minimum value and on the position in which such a minimum is found.
The ХХV International scientific – technical conference “Foundry 2018” was held of the 18-20 April 2018 at “Rostov” hotel in the city of Pleven, Bulgaria. Its aim is to provide a meeting place for scholars from different countries to present their scientific achievements and to discuss the problems of casting production.
The structural and spectroscopic features of the EuAl3(BO3)4 individual skeletal microcrystals synthesized by a melt solution method have been studied. Their infrared spectra taken from the as-grown microcrystal surfaces mainly contain the lines of the rhombohedral modification of EuAl3(BO3)4 and additional peaks of its monoclinic modification. TEM and X-ray diffraction studies confirm that these additional peaks in the IR spectra belong to the monoclinic C2/c polytype of the EuAl3(BO3)4 compound. We are the first to demonstrate the presence of coherent monoclinic domains in rhombohedral EuAl3(BO3)4 crystals by TEM. Cathodoluminance spectroscopy shows that the microcrystals generate strong emission lines in the range 580–630 nm, and their intensities are strongly influenced by the crystal orientation.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.