여재익 교수

Categorized certified reference materials simulating metal, rock, soils, or dusts are used to demonstrate the standoff detection capability of laser-induced breakdown spectroscopy (LIBS) at severely low pressure conditions. A Q-switched Nd:YAG laser operating at 1064 nm with 17.2-50 mJ energy per pulse was used to obtain sample signals from a distance of 5.5 m; the detection sensitivity at pressures down to 0.01 torr was also analyzed. The signal intensity response to pressure changes is explain

We compare two-dimensional model results with measurements for the thermal, chemical, and mechanical behavior in a thermal explosion experiment. Confined high explosives (HEs) are heated at a rate of 1°C∕h until an explosion is observed. The heating, ignition, and deflagration phases are modeled using an Arbitrarily Lagrangian-Eulerian code (ALE3D) that can handle a wide range of time scales that vary from a structural to a dynamic hydrotime scale. During the preignition phase, quasistatic mecha

Ageing of pyrotechnic substance, primarily fuel oxidisation, can cause changes in composition that degrade their performance. This study investigates the effect of ageing on zirconium potassium perchlorate (ZPP), a widely used NASA Standard Initiator. Although prior studies have investigated the effects of accelerated ageing on ZPP, this is the first to conduct kinetic analyses at different relative humidity (RH) levels. Here, both thermal and kinetic analyses are conducted for a variety of hygr

In recent times, there is a growing interest in the development of electrically controlled solid propellants (ECSPs) because they offer various advantages over conventional solid propellants. However, the fundamental understanding on the complex reaction mechanism of decomposition/combustion of these ECSPs is still limited. The present study attempts to expand the knowledge on thermal decomposition mechanisms of ECSPs based on lithium perchlorate (LP) oxidizer and poly vinyl alcohol (PVA) binder

The interaction of a high-power pulsed-laser beam with metal targets in air from a 1.06 μm, 5 ns, 3 J/pulse, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported blast wave and multimaterial reactive Euler equations. The high-speed blast wave generated by the laser ablation of metal reaches a maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations of motio

Simultaneous laser ignition and spectroscopy is a scheme that enables rapid determination of the local equivalence ratio and condensed fuel concentration during a reaction in a two phase spray flame. In parallel with laser ignition, the equivalence ratio and droplet characteristics such as the concentration, size, and distribution of spray combustion are simultaneously obtained for a feedback control system. The plasma characteristics of fuel droplets are evaluated initially by shadowgraph, and