Development of temperature-heating rate diagrams for the pyrolytic removal of binder used for powder injection moulding

A polypropylene-based binder system was used to injection mould test bars containing 65 vol% aluminium powder. Specimens, 3 and 6 mm thick, made from these bars were used for pyrolytic binder removal experiments in static air and nitrogen. The development of a carefully defined experimental procedure for the determination of the heating rate at which binder removal can be carried out at a given temperature without the creation of macro defects is fully described. The use of isothermal heat treatments during pyrolysis are also considered and results are presented as temperature-heating rate diagrams for each atmosphere and thickness investigated. These diagrams show a lower and an upper boundary. Defect formation occurs if the temperature-heating rate relationship lies between the boundaries. Near optimum binder removal schedules deduced from each diagram have been experimentally verified.     

Comprehension of arithmetic word problems: A comparison of successful and unsuccessful problem solvers.

It is proposed that when solving an arithmetic word problem, unsuccessful problem solvers base their solution plan on numbers and keywords that they select from the problem (the direct translation strategy), whereas successful problem solvers construct a model of the situation described in the problem and base their solution plan on this model (the problem-model strategy). Evidence for this hypothesis was obtained in 2 experiments. In Experiment 1, the eye fixations of successful and unsuccessful problem solvers on words and numbers in the problem statement were compared. In Experiment 2, the degree to which successful and unsuccessful problem solvers remember the meaning and exact wording of word problems was examined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Large-scale quantum mechanical simulations of high- Z metals

High-Z metals constitute a particular challenge for large-scale ab initio electronic-structure calculations, as they require high resolution due to the presence of strongly localized states and require many eigenstates to be computed due to the large number of electrons and need to accurately resolve the Fermi surface. Here, we report recent findings on high-Z metals, using an efficient massively parallel planewave implementation on some of the largest computational architectures currently available. We discuss the particular architectures employed and methodological advances required to harness them effectively. We present a pair-correlation function for U, calculated using quantum molecular dynamics, and discuss relaxations of Pu atoms in the vicinity of defects in aged and alloyed Pu. We find that the self-irradiation associated with aging has a negligible effect on the compressibility of Pu relative to other factors such as alloying. The US Goverment’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Effect of low temperature and environment on the kinetics of fatigue crack growth in VT5-1kt titanium alloy with different microstructures

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 27, No. 6, pp. 69–71, November–December, 1991.     

Long-chain fatty ammonium quaternaries in papermaking

A series of long-chain quaternary ammonium halogen esters (UKK-chemicals), quaternary dimethyl tallow epoxypropyl ammonium halogens (EPK1), quaternary ditallow methyl epoxypropyl ammonium halogens (EPK2), and EPK2 oligomers (EPK2P) were synthesized. At acidic, neutral, or slightly basic conditions, EPK1-, EPK2-, EPK2P-, and UKK-chemicals operate as cationic chemicals. They can be used, for example, as stock sizings, surface sizings, or fixatives. Stock sizing, surface sizing, and fixative experiments indicate that EPK1-, EPK2-, EPK2P-, and UKK-chemicals function at least as well as or better than the corresponding synthetic chemicals used in papermaking.     

Electrophysical Characteristics of a Posistor Block

The influence of the parameters of posistor elements and the conditions of their heat exchange on the electrical and dynamic characteristics of a posistor block have been investigated. Good agreement between calculation results and experimental data has been established.