Sonographic probing of laser filaments in air

The acoustic wave emitted from the plasma channel associated with a filament induced by a femtosecond laser pulse in air was detected with a microphone. This sonographic detection provides a new method to determine the length and the spatial profile of the free-electron density of a filament. The acoustic wave is emitted owing to the expansion of the gas in the filament, which is heated through collisions with high-energy photoelectrons generated by multiphoton ionization. Compared with other methods, the acoustic detection is simpler, more sensitive, and with higher spatial resolution, making it suitable for field measurements over kilometer-range distances or laboratory-scale studies on the fine structure of a filament.     

ESR study of hydroxyl alkoxyamine (HMPAP) in DMF and tert‐butylbenzene

Hydroxyl alkoxyamine (HMPAP) in DMF and in tert‐butylbenzene with oxygen as a scavenger was studied with electron spin resonance spectroscopy. From kinetics studies performed at 120°C, it was found that the rate constant of C? O bond homolysis was smaller in DMF than in tert‐butylbenzene. The difference in the behavior could be related to the formation of an activated six‐membered intermediate formed through intramolecular H‐bonding in tert‐butylbenzene and the disruption of H‐bonding in the polar solvent DMF. This led to alteration of the equilibrium constant between the alkoxyamine and the corresponding nitroxide and C‐centered radical in DMF and decreased initiating efficiency for the controlled/living radical polymerization using HMPAP as initiator. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4116–4120, 2006     

Single flux-quantum memory cells

Detailed investigations have been carried out on two-junction interferometers. These devices have potential as memory elements. Information is stored as single-flux quanta (SFQ cells) in overlapping vortex modes and is destructively read out by switching from a vortex to the voltage state. The devices are fabricated with a lead alloy and the junction oxide is formed by rf oxidation. Most investigations have been done on devices with an area of about 1000 μm², but storage and reading have also been demonstrated in our smallest interferometers having a size of about 150 μm². Computer studies of cell properties, especially of the vortex transitions, have given good agreement with experiments. It has also been found that the cell behavior is little affected by loads such as would exist in an array environment.     

A novel approach for calculating the monthly average daily fraction of diffuse solar radiation

A novel approach for calculating the monthly average daily fraction of diffuse radiation has been developed. It is based upon the use of concurrent total solar radiation measurements for both a tilted surface and a horizontal surface. It divides the data into two categories, clear and cloudy day, on an hourly basis. The clear day data is analyzed by means of both Liu and Jordan's and Page's empirical equations. The cloudy day data is analyzed by Liu and Jordan's equation for determining the insolation ratio on a tilted to a horizontal surface. A monthly average value for the diffuse fraction is then determined by calculating a weighted average of the clear and cloudy day values.The monthly average values, for twelve months of Beer Sheva data, for the fraction of diffuse radiation have been calculated and compared to the empirical relationships derived by Liu and Jordan and Page. The agreement between the calculated values and empiriical relationship is somewhat better in the latter case.     

Microstructure and cooling conditions of steel solidified in the continuous casting mould

Importance of uniform shell growth and fine microstructure on breakout safety and strand surface quality. Analysis of heat flow and shell growth in the mould for a 0.62 wt% C-steel, and correlation with the microstructure by comparison of calculated with measured dendrite arm spacing. Proposal of metallographic standards for the subsurface microstructure in order to check the intensity and uniformity of solidification conditions in the mould.     

What is embedded computing?

An embedded system is any computer that is a component in a larger system and that relies on its own microprocessor. Evolving from a craft to an engineering discipline over the past decade, embedded computing continues to mature. The purpose of this article is to demonstrate that embedded computing is an established engineering discipline with principles and knowledge at its core