Gelcast Tooling: Net Shape Casting and Green Machining

Gelcasting is an advanced powder forming process. It is most commonly used to form ceramic or metal powders into complex, near-net shapes. Turbine rotors, gears, nozzles, and crucibles have been successfully gelcast in silicon nitride, alumina, nickel-based superalloy, and several steels. Gelcasting can also be used to make blanks that can be green machined to near-net shape and then high fired. Green machining has been successfully applied to both ceramic and metal gelcast blanks. Recently, we have used gelcasting to make toolinj; for metal casting applications. Most of the work has centered on H13 tool steel. We have demonstrated an ability to gelcast and sinter H13 to near net shape for metal casting tooling. We have also been successful in green machining gelcast blanks using a three-axis CNC milling machine.     

Aqueous ring-opening metathesis polymerization of exo-7-oxabicyclo [2.2.1] hept-5-ene-2,3-dicarboximide

The aqueous ring-opening metathesis polymerization of the exo-Diels-Alder adduct of furan and maleimide was accomplished using an “activated Ruthenium” catalyst present in the supernatant of a RuCl₃-catalyzed aqueous polymerization of furan-dimethylacetylene dicarboxylate adduct. The polymer was characterized by solution ¹H? and ¹³C-NMR, IR, DSC, and viscometry. Characterization revealed an intact imide group and the possibility of high-temperature applications. © 1993 John Wiley & Sons, Inc.     

Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

Time differential perturbed angular correlation (TDPAC) and positron life-time measurements on cold-worked and hydrogen chargedNbHf indicate a strong binding of hydrogen decorated vacancy clusters with Hf impurities. Both TDPAC and positron lifetime results are mutually consistent on this aspect. Transformation of H-vacancy clusters into H-bubbles is indicated by the positron lifetime behaviour at annealing temperatures beyond 900 K. Impurity effects like oxygen pickup and coating of voids cannot be ruled out at elevated temperatures.     

Effect of series compensation on the voltage instability of EHV long lines

In this paper, the effects of the operating conditions and dynamic performance on the voltage instability phenomena of EHV lines with series compensation is discussed. Exponential modelling of loads and exact long-line equations are used in the analysis. Graphs showing the variations of the receiving-end voltage and the transformer tap ratio with time for an assumed load variation are given. It is shown that when series compensation is provided, the chances of voltage instability occurring are less. The effect of switched series compensation on the voltage instability is also investigated. The error in using short-line equations for the analysis of voltage instability phenomena is highlighted. The random loading conditions of the system and the random load parameter variations are also considered for the first time in analysing the voltage instability phenomenon.     

Measurement of individual differences in preference for numerical information.

Develops and validates a measure of preference for numerical information, defined as a proclivity toward using numerical information and engaging in thinking involving numerical information, and assesses the relationship of this construct to several constructs. Although past research has focused on ability in using numerical information, a basic attitude or proclivity toward numerical information has not been isolated and studied. This construct is argued to have applications in settings that involve the use of numerical information and to be related to several interests, temperaments, and cognitive styles. A measure of preference for numerical information is developed and tested for reliability and validity, its relationship with several constructs is examined, and its applications in various settings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dilatometric technique for evaluation of the kinetics of solid-state transformation of maraging steel

Solid-state transformation kinetics of a 350 grade commercial maraging steel were investigated using a nonisothermal dilatometric technique. Two solid-state reactions—namely, precipitation of intermetallic phases from supersaturated martensite and reversion of martensite to austenite—were identified. Determination was made of the temperatures at which the rates of these reactions reached a maximum at different heating rates. The kinetics of the individual reactions in terms of activation energy were analyzed by simplified procedures based on the Kissinger equation. An estimated activation energy of 145 ± 4 kJ/mol for the precipitation of intermetallic phases was in good agreement with reported results based on the isothermal hardness measurement technique. Martensite to austenite reversion was associated with an activation energy of 224 ± 4 kJ/mol, which is very close to the activation energy for diffusion of substitutional elements in ferrite. Results were supplemented with microstructural analysis.     

Diversity combining in FH/BFSK systems to combat partial bandjamming

A combiner for a frequency-hopped binary frequency-shift keyed (FH/BFSK) system, called the product-combining receiver (PCR), is introduced. The performance of the PCR is evaluated for the cases of an on/off partial-band noise with optimum-jamming fraction, and worst-case, partial-band tone jamming. The performance of PCR is shown to be comparable to that of the clipper receiver. The effect of diversity combining, along with convolutional coding and ratio-threshold technique, is analyzed. Whereas the clipper requires the knowledge of signal-to-noise ratio for threshold adjustments, the PCR does not require this knowledge for this operation     

Superconductivity in irradiated A-15 compounds at low fluences. I. Neutron-irradiated V3Si

The behavior of the superconducting transition temperature T _c of singlecrystal and polycrystalline V₃Si was investigated as a function of low-fluence neutron irradiation. It is found that the initial degradation of T _c is sample-dependent, some specimens showing no degradation in T _c up to a fluence of 2 × 10¹⁸ n/cm². This and many other earlier observations on low-fluence behavior are explained in terms of a recently proposed model of radiation damage in A-15 compounds.Work performed under the auspices of the U.S. Energy Research and Development Administration.