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Objective: Tissue electroporation is achieved by applying a series of electric pulses to destabilize cell membranes within the target tissue. The treatment volume is dictated by the electric field distribution, which depends on the pulse parameters and tissue type and can be readily predicted using numerical methods. These models require the relevant tissue properties to be known beforehand. This study aims to quantify electrical and thermal properties for three different tissue types relevant to current clinical electroporation. Methods: Pancreatic, brain, and liver tissue were harvested from pigs, then treated with IRE pulses in a parallel-plate configuration. Resulting current and temperature readings were used to calculate the conductivity and its temperature dependence for each tissue type. Finally, a computational model was constructed to examine the impact of differences between tissue types. Results: Baseline conductivity values (mean 0.11, 0.14, and 0.12 S/m) and temperature coefficients of conductivity (mean 2.0, 2.3, and 1.2 % per degree Celsius) were calculated for pancreas, brain, and liver, respectively. The accompanying computational models suggest field distribution and thermal damage volumes are dependent on tissue type. Conclusion: The three tissue types show similar electrical and thermal responses to IRE, though brain tissue exhibits the greatest differences. The results also show that tissue type plays a role in the expected ablation and thermal damage volumes. Significance: The conductivity and its changes due to heating are expected to have a marked impact on the ablation volume. Incorporating these tissue properties aids in the prediction and optimization of electroporation-based therapies. [ABSTRACT FROM AUTHOR]

In this paper, effects of ambient temperature and nanoparticles on surface charge and discharge behavior of epoxy/aluminum nitride (AlN) nanocomposites were investigated. With the rise of ambient temperature, the surface discharge strength of epoxy resin decreases and the conductivity shows significant increase. The charges obtain higher energy, their movement becomes more violent and makes it easier for secondary electron emission avalanche. Meanwhile, the specimen’s trap level increases and trap density decreases. 1, 3 and 5 wt% proportions of AlN nanoparticles were added to the epoxy resin to increase the surface discharge strength at different operation temperatures. With the rise of filler content, the trap level, trap density and surface discharge strength increase first and then decrease at 20 °C. The specimen with 5 wt% filler content shows the highest shallow trap density and the one with 1 wt% filler content shows the highest deep trap density at 80 °C. As shallow traps can handle the migration of charges while deep traps may mainly cause electric field distortion, the specimen with 1 wt% filler content shows the highest surface discharge strength at 20 °C while the one with 5 wt% filler content shows the highest at 80 °C. The conclusions can help with finding different formulas to increase epoxy resin’s surface discharge strength at different operation temperatures. [ABSTRACT FROM AUTHOR]

We report Lamb acoustic wave resonators that are suitable for RF applications and that exhibit high power handling at high frequencies above 1 GHz. Resonators use aluminum–nitride as acoustic layer and are fabricated in the Institute of Microelectronics (IME) Agency for Science, Technology and Research (A*STAR)'s in-house RF microelectromechanical system silicon-on-insulator platform. We focus the study on devices operating at their first symmetric Lamb-wave mode (S0) at 900 MHz and 1.5 GHz, although demonstrate 400 MHz and 1.2 GHz as well. All devices are realized in the same multi-frequency platform. Assessment of devices covers gain compression point (P1dB), third-order intermodulation intercept point (IIP3), thermal management, impedance matching, and quality factor. Devices exhibit P1dB above +\30 dBm, and IIP3 higher than +\50 dBm with low insertion losses less than 3 dB and 50-\Omega impedance matching. [ABSTRACT FROM AUTHOR]

This paper is devoted to the simulation of the thermal shock and the induced pressure-waves expansion, generated by a dc pin-to-plan corona discharge in the air at ambient temperatures and under atmospheric pressure. The positive dc voltage applied to the tip generates a monofilamentary streamer that crosses the gap from the tip toward the plan. The simulation models are based on the coupling of a 2-D dynamics streamer model with the hydrodynamics conservation equations of a compressible gas. The source term for the gas dynamics equations takes into account the fast-energy relaxation from excited molecules to the random thermal energy. The simulation shows that the streamers generate a thermal shock near the anodic tip, which induces high pressure gradients and finally the gas expansion. The thermal shock is located just in front of the anodic tip, where the injected energy density is the highest. After 0.3 \mus, the mean gas temperature increases up to around 800 K in a small volume just in front of the anodic tip while the maximum temperature reaches 1200 K. In addition, two pressure waves, a spherical and a cylindrical one, are induced with a propagation velocity of 370 m~s^-1 i.e., close to the speed of sound in air. [ABSTRACT FROM PUBLISHER]

The weldability of resistance spot welding affected by different thermal, physical, and metallurgical properties is extensively investigated by realistically computing transient mass, momentum, energy, species, and magnetic field intensity transport in the alloy workpieces and electrodes. The properties considered are the thickness, radius, equilibrium partition coefficient of workpieces, electrode-to-workpiece electrical conductivity ratio, thermal conductivity ratio, and a joule heat-to-enthalpy change parameter. Resistance spot welding has been widely used in joining thin workpieces in various electronic packaging and manufacturing industries. Understanding of physical mechanisms for easily manipulating and controlling weld qualities in advance is important. This paper accounts for electromagnetic force, heat generations due to contact resistances at the electrode–workpiece interface and faying surface between workpieces, and temperature-dependent bulk resistance of the workpiece. The contact resistances are functions of hardness, temperature, electrode force, and surface condition. The computed results in general dimensionless expressions show that the welding is feasible or onset time is shortened by decreasing thickness, radius, equilibrium partition coefficient of the workpiece, and electrode-to-workpiece electrical conductivity and thermal conductivity ratios, and increasing the joule heat-to-enthalpy change parameter. The corresponding heat transfer and species patterns are also presented. [ABSTRACT FROM AUTHOR]

The article describes thermal performance of a special heterojunction bipolar transistor (HBT) structure for mobile communication systems, called a collector-up HBT and calculates the thermal resistance between the HBT finders and the bottom surface of a GaAs substrate using a finite element method. An HBT is a bipolar transistor whose emitter/base junction consists of different materials. A GaAs HBT has a higher current gain, a higher breakdown voltage, and a superior RF performance when compared to Si bipolar transistors. Normal HBTs have an emitter-up configuration. Because of the extrinsic area underneath the base electrodes, emitter-up HBTs suffer from large collector capacitance that limits the RF performance.