WIRELESS METHANE DETECTOR WITH TEMPERATURE MODULATED HEATING PROFILE

The results of development of an autonomous methane detector in a dynamic measurement mode are presented. Industrial catalytic sensor was used as a sensitive element. To prevent burnout of the catalytic sensor microheater which often occurs during pulsed heating, the special form of heating pulse has been developed. The proposed dynamic mode of the sensor heating provides the measurements with low power consumption and the required level of safety in the measurement range of pre-explosive methane concentrations from 0.1 to 2 vol.%. Based on the analysis of the obtained results, the estimation of autonomous operating time of the detector is given.

Towards temperature controlled retinal laser treatment with a single laser at 10 kHz repetition rate

Laser photocoagulation is one of the most frequently used treatment approaches in ophthalmology for a variety of retinal diseases. Depending on indication, treatment intensity varies from application of specific micro injuries down to gentle temperature increases without inducing cell damage. Especially for the latter, proper energy dosing is still a challenging issue, which mostly relies on the physician’s experience. Pulsed laser photoacoustic temperature measurement has already proven its ability for automated irradiation control during laser treatment but suffers from a comparatively high instrumental effort due to combination with a conventional continuous wave treatment laser. In this paper, a simplified setup with a single pulsed laser at 10 kHz repetition rate is presented. The setup combines the instrumentation for treatment as well as temperature measurement and control in a single device. In order to compare the solely pulsed heating with continuous wave (cw) tissue heating, pulse energies of 4 µJ were applied with a repetition rate of 1 kHz to probe the temperature rise, respectively. With the same average laser power of 60 mW an almost identical temporal temperature course was retrieved in both irradiation modes as expected. The ability to reach and maintain a chosen aim temperature of 41 °C is demonstrated by means of model predictive control (MPC) and extended Kalman filtering at a the measurement rate of 250 Hz with an accuracy of less than ±0.1 °C. A major advantage of optimization-based control techniques like MPC is their capability of rigorously ensuring constraints, e.g., temperature limits, and thus, realizing a more reliable and secure temperature control during retinal laser irradiation.

Ultrafast laser heating of non-plasmonic nanocylinders

We develop a model describing non-equilibrium processes under the excitation of resonant semiconductor nanostructures with ultrashort laser pulses with a duration of about 100 fs. We focus on the heating effects related to pulsed excitation with account on free carriers generation, thermalization, and relaxation. The heat exchange between the electron and phonon system is treated within the two-temperature model. We applied the developed model to describing pulsed heating of silicon nanocylinder on top of a dielectric substrate. We come up with estimations of the thermal damage threshold of the considered structures which provides the limits for the experimental conditions and ensures thermal stability of the samples.

Single Pulse Heating of Nanoparticle Array for Biological Applications

With the ability to convert external excitation into heat, nanomaterials play an essential role in many biomedical applications. Two modes of nanoparticle (NP) array heating, nanoscale-confined heating (NCH) and macroscale-collective heating (MCH), have been found and extensively studied. Despite this, the resulting biological response at protein level remains elusive. In this study, we developed a computational model to systematically investigate the single-pulsed heating of NP array and corresponding protein denaturation/activation. We found that NCH may lead to targeted protein denaturation, however, nanoparticle heating does not lead to nanoscale selective TRPV1 channel activation. The excitation duration and NP concentration are primary factors that determine a window for targeted protein denaturation, and together with heating power, we defined quantified boundaries for targeted protein denaturation. Our results boost our understandings in the NCH and MCH under realistic physical constraints and provide a robust guidance to customize biomedical platforms with desired NP heating.

Pulsed IR Heating of Thermoplastic Sheets for Thermoforming Applications

This study presents the pulsed heating strategy as an advancement of the current state of the art in industry towards the theoretically fastest method of heating a thermoplastic sheet. Experimental temperature measurements are combined with an explicit finite difference numerical model to describe the pulsed heating method and indicate its added value in IR heating of thermoplastic sheets. Different process settings are evaluated and indicate the effect of the applied heat flux and the time interval tOFF during pulsed heating. When switched off, the residual heating of the heater elements is able to partially compensate for the convective heat losses at the surface of the sheet. This results in a more uniform temperature distribution through thickness without slowing down the overall heating process. The study shows that this effect is lost when the time interval in which the heater element is switched off, increases. Applying pulsed heating opens up a large processing window to control the through-thickness temperature difference. When the total amount of applied thermal energy is taken into account, pulsed heating is able to increase the overall heating rate and simultaneously keep the temperature difference through thickness limited.

Theoretical Analysis for Using Pulsed Heating Power in Magnetic Hyperthermia Therapy of Breast Cancer

In magnetic hyperthermia, magnetic nanoparticles (MNPs) are used to generate heat in an alternating magnetic field to destroy cancerous cells. This field can be continuous or pulsed. Although a large amount of research has been devoted to studying the efficiency and side effects of continuous fields, little attention has been paid to the use of pulsed fields. In this simulation study, Fourier’s law and COMSOL software have been utilized to identify the heating power necessary for treating breast cancer under blood flow and metabolism to obtain the optimized condition among the pulsed powers for thermal ablation. The results showed that for small source diameters (not larger than 4 mm), pulsed powers with high duties were more effective than continuous power. Although by increasing the source domain the fraction of damage caused by continuous power reached the damage caused by the pulsed powers, it affected the healthy tissues more (at least two times greater) than the pulsed powers. Pulsed powers with high duty (0.8 and 0.9) showed the optimized condition and the results have been explained based on the Arrhenius equation. Utilizing the pulsed powers for breast cancer treatment can potentially be an efficient approach for treating breast tumors due to requiring lower heating power and minimizing side effects to the healthy tissues.

The problem of crack formation in thin sublayers of silicon oxide during pulsed heating of interconnects

It is well known that in modern micro- and nanoelectronics thin-film structures are actively used as a gate dielectric, passivating layers, membranes, etc. The research is devoted to the problem of crack formation in thin sublayers of silicon oxide during pulsed heating of interconnects on single-crystal silicon wafers. The purpose of the paper is to study the effect of surface sources of thermal shock on the cracks formation in films and aspects of crack formation in SO2 films have been studied in detail. Experimental verification of the estimates made was carried out on multilayer structures of a silicon substrate-silicon oxide sublayer-aluminum film (Si-SiO2-Al). As substrates, it was used phosphorus-doped silicon single-crystal wafers oriented in the (111) direction, with a resistivity in the range p = 0.1 Ω.сm. The authors studied the temperature fields in silicon wafers (Al-Si system) and silicon oxide wafers (Al-SiO2 system) heated by a surface metallization layer both for the case of a point heat source and for the case of a long rectangular metallization path (provided that the track length significantly exceeds its width). The calculation results showed that the temperature profile of the metallization path (width 75 μm) in the transverse direction is heterogeneous. It was also shown that, in contrast to SiO2 films, the level of appearing mechanical stresses in silicon is insufficient for the formation of cracks near the source of thermal shock. This is due to a higher tensile strength than that of oxide.

Спектроскопия барьерного разряда низкого давления. Послесвечение с ионами Ne-=SUP=-2+-=/SUP=-, Ne-=SUP=-+-=/SUP=- и Ne-=SUP=-2+-=/SUP=-

We present the results of modeling the radiation of a decaying plasma, formed by the processes of electron-ion recombination with the participation of three neon ions: the molecular ion Ne2+ and atomic ions Ne+ and Ne2+. Such a combination of ions, simultaneously participating in the formation of the plasma spectrum, was first discovered in the afterglow of a pulsed barrier discharge of a cylindrical geometry at neon pressures less than 1 Torr and an electron density[e] ≤ 4 × 1010 cm-3. The main attention is paid to the comparative analysis of the mechanisms of impact-radiation recombination of Ne+ and Ne2+ ions based on the numerical solution of the system of differential equations for the densities of ions and long-lived excited atoms in the afterglow, taking into account the main elementary processes in decaying plasma with pulsed "heating" of electrons. The regularities of electron temperature relaxation from discharge values of several electron volts to 300 K in the late afterglow are considered in particular details. Comparison of the model solutions with the spectral intensities measured by the multichannel photon counting method shows that, given their good agreement in the case of singly charged ions, an adequate description of the evolution of ionic lines requires expanding the available information on the recombination of Ne2+ ions.