Evidence of the self-heating effect on surface reactivity and gas sensing of metal oxide nanowire chemiresistors

The effect of Joule self-heating of the semiconducting metal oxide nanowire (here (and below unless specified), due to the generality of the effect, we use the term 'nanowire' without specification as to whether the nanobelt or other class of quasi-1D nanostructure is considered) conductometric gas sensor on its surface reactivity and kinetics is demonstrated. Due to small thermal capacitance and hampered thermal losses from the nanowire to its surroundings, the sensor was able to operate without a heater, consuming only a few microwatts of power. These results demonstrate the importance of the self-heating effect in nanowire electronics and its potential use in chemical and bio-sensing, where the ultra-small size of the active element and minimal power consumption are crucial.     

Predicting electron beam welding conditions in the manufacture of multi-seam structures

The problem of producing multi-seam components by electron beam welding is investigated. It is shown that if the variation of temperature after welding the first joints is not taken into account and subsequent welded joints are produced in the same conditions, the depth of penetration increases. This has been confirmed by experimental results. To ensure the same depth of penetration in producing several welded joints in the same component, the second and subsequent welded joints should be produced in the corrected conditions after equalizing the temperature throughout the entire volume of the component. A method is proposed for calculating the electron beam welding conditions of consecutively produced welded joints and the holding time of the component to ensure equalization of temperature.     

Localization of pulsed energy deposition in a transverse surface discharge initiated in a gas flow with shock wave

The localization of a nanosecond transverse surface discharge initiated in a plasma sheet sliding over a dielectric surface in a channel featuring gas flow with a plane shock wave has been studied by monitoring glow intensity distribution at the discharge-ionized channel surface in the presence of the shock wave. Judging from the glow pattern, the entire energy of discharge is usually localized in a low-pressure region in front of the propagating shock wave. The density of energy deposited in front of the shock wave can be varied (in particular, increased up to 12–15 eV per particle) by initiating the discharge at various positions of the shock wave. Transitions from the discharge with glow localized sharply in front of the shock wave to the regimes with glow extended behind the front or with a volume glow region ahead of the shock wave were observed for certain values of the Townsend parameter (E/P) and Mach number (M).     

Dynamics of the drawing zone of a lightguide blank for different drawing regimes with furnace and laser heating

The results of numerical modeling of the process of drawing a quartz blank into a lightguide with different mehtods of heating are presented. The optimal regions of the space of drawing parameters for obtaining a stable lightguide diameter are determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 3, pp. 491–497, September, 1988.