Intelligent Sensors for Atomization Processing of Molten Metals and Alloys
ABSTRACT We briefly introduce the principles of atomization processing of molten metals and alloys, discuss potentially applicable instrumentation, and propose opportunities for developing intelligent sensors for monitoring and control of the process. Particle size and velocity are considered the two most important variables to monitor and control the atomization process. Several on-line sensors suitable for atomization of molten metals and alloys are compared: laser light scattering methods using small angle scattering analysis, moderate angle scattering analysis, and doppler analysis, electrical methods using surface ionization and triboelectric charging, and image analysis. The isokinetic sampling probe is introduced as a direct method to sample powders at the desired point in the atomized spray. Prospects and problems of integrating instruments based on these principles into intelligent processing of materials (IPM) scenarios are discussed.
High-speed imaging and computational modelling of close-coupled gas atomization
Gas atomization process, especially Closed Coupled Gas Atomization (CCGA) is a very efficient processing method to produce ultra fine, spherodised metal powders. In this process, the high-pressure gas jet is used to disintegrate the molten metal stream in to the spherical powders. Due to hydrodynamic and thermal interaction between high-pressure gas jet and molten metal stream especially near melt delivery nozzle, this technique is very complex and challenging for atomization industries. 
Melt delivery nozzle design is one of the key factors to control powders properties. The optical Schlieren technique and analogue water atomizer along with Computational Fluid Dynamics (CFD) numerical methods are practical methods for observing the single or two-phase flow of gas-metal interaction during CCGA. 
This research is focused on the optical Schlieren and numerical CFD techniques to observe single-phase gas flow behaviour with different melt nozzles tip design and gas dies profile. The CFD numerical results are validated by the experimental Schlieren test results. The effect of melt tip design on open to closed-wake condition near melt nozzle was investigated. Comparing the CFD velocity field and velocity streamlines of different nozzle design at different atomization gas pressure could help to propose a new hypothesis of how open to closed-wake condition occurs at different nozzle tip design. In addition, the flow separation problem around melt nozzle by two different gas die systems was investigated. The results showed there are two major mechanisms for this phenomenon, which depends on gas die system set-up, melt nozzle tip protrusion length and mis-match angle of external nozzle wall to the gas jet direction.
NMR characteristics of intracellular K in the rat salivary gland: a 39K NMR study using double-quantum filtering.
Intracellular K of the perfused rat mandibular salivary gland was measured by 39K NMR spectroscopy at 8.45 T. Multiple-quantum NMR arising from multiple-exponential decay was used to eliminate the resonance due to extracellular K in the perfused gland at 25 degrees C. The resonance due to intracellular K consisted of two Lorentzian signals stemming from the [spin 1/2 to -1/2] coherence (sharp resonance) and the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences (broad resonance). The transverse relaxation time (T2) corresponding to the [spin 1/2 to -1/2] coherence was ca. 2.5 ms, and that corresponding to the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences was ca. 0.4 ms. The relaxation time of the double-quantum coherence of rank 3 (originating from product operators like Ix2Iz) was determined to be ca. 0.2 ms. These results suggest the possibility of the presence of a single homogeneous population of intracellular K with a correlation time of ca. 2.5 x 10(-8) s and a quadrupolar coupling constant of ca. 1.4 MHz.