Optimum process parameters to produce green ceramic complex parts

The fragility of green ceramic compacts introduces considerable difficulties during green or bisque machining. This paper demonstrates methods developed to manufacture thin wall-thin floor, complex green ceramic parts to close tolerance. Hybrid finite element (FE)/mechanistic models were utilized in the development of the green machining process. An FE model was used to define cutting edge geometry and machining parameters that would reliably produce crack free parts. Mechanistic model was used to direct cutter path generation of a 5-axis milling machine having a large axial depth of cut, and to prevent edge chipping. The optimized cutter path eliminated any need for hand work before densifying the machined part.     

A dynamic manifestation approach for providing universal access todigital library objects

Digital libraries are concerned with the creation and management of information sources, the movement of information across global networks, and the effective use of this information by a wide range of users. A digital library is a vast collection of objects that are of multimedia nature, e.g. text, video, images, and audio. Users wishing to access the digital library objects may possess varying capabilities, preferences, domain expertise, and may use different information appliances. Facilitating access to complex multimedia digital library objects that suits the users' requirements is known as universal access. We present an object manifestation approach in which digital library objects automatically manifest themselves to cater to the users' capabilities and characteristics. We provide a formal framework, based on Petri nets, to represent the various components of the digital library objects, their modality and fidelity, and the playback synchronization relationships among them. We develop methodologies for object delivery without any deadtime under network delays     

The impact of media on how positive,negative, and neutral communicated affect influence unilateral concessions during negotiations

In the online environment, audio and instant messaging (IM) media are quite commonly used by people to communicate with each other and make offers as they negotiate. While we know much about how IM and audio differ, we know very little about how offers that are favorable to the recipient (termed unilateral concessions) are affected by what and how people communicate over these media. The purpose of this study is twofold – (1) to examine how such concessions are influenced by communication that is either neutral, or positive, or negative in affect; and (2) to determine how the use of IM, relative to the use of audio, influences the effects of these types of communication on unilateral concessions. We develop a research model based on prosocial theory, which suggests that negotiators using audio are predisposed to interpret their partners’ motivations and behaviors in a positive (prosocial) light while negotiators using IM are predisposed to interpret their partners’ motivations and behaviors in a negative (competitive) light. We manipulate the use of IM and audio in anexperiment designed to test predictions based on this theory. Our work provides theoretical and empirical support for the idea that communications other than concessions (such as positive, neutral, and negative affect) can lead to more or less self-sacrifice depending on the medium employed, and thereby motivate negotiators to make greater or fewer unilateral concessions. Specifically, we found that (1) positive affect comments can increase unilateral concession independent of the medium used by negotiators; (2) neutral affect comments can increase unilateral concession when negotiators use audio, but have little impact when they use IM; and (3) negative affect comments can decrease unilateral concession when negotiators use audio, but can increase unilateral concession when they use IM. These results provide insights to researchers and practical guidance for negotiators.     

Digital Library Task Force

In 1995, the IEEE Computer Society established the Task Force on Digital Libraries as a first step leading to a full-fledged Technical Committee. The task force is to promote research in the theory and practice of all aspects of digital libraries. The task force sponsors activities that benefit its members and profession. Such activities include sponsoring and co-sponsoring symposia, sessions in large conferences, tutorials, and a newsletter. The task force co-sponsored the Forum on Research and Technology Advances in Digital Libraries and is co-sponsoring the International Journal of Digital Libraries, published by Springer-Verlag. Membership in the Task Force on Digital Libraries is free     

Poxvirus DNA. I. Studies on the structure of the vaccinia genome

We have studied the levels of hepatic GSH in animals intoxicated with bromobenzene. A marked decrease of hepatic GSH was observed in poisoned rats. Such decrease was prevented by previous administration of lead nitrate, an inhibitor of DMES. In the rats treated with lead nitrate alone a rise in hepatic GSH was observed. Such protection was further observed by histological examination. The mechanism of protection exerted by lead nitrate against bromobenzene intoxication is discussed.     

Engineering improvement of NaAlH4 system

The significant engineering challenges associated with developing lower-pressure, materials-based, hydrogen storage systems for hydrogen fuel cell light-duty vehicles are being addressed by focusing on the role that powder consolidation can play. NaAlH₄ with 4 mol % TiCl₃ was selected as the model material. We focused on the changes in the physical (density and thermal conductivity) and mechanical properties (biaxial flexure strength) and on how these impacted the volumetric capacity of the hydrogen storage system. Both the thermal conductivity and the density of the ball milled material improved with applied pressure in a uniaxial press over the range of 14 MPa–281 MPa. The thermal conductivity reached a value of (1.64 ± 0.02) W/m/K, which was a factor seven higher than that of the unconsolidated powder. The volume of the material was reduced by 42% at the highest applied pressure. A method was developed for determining the strength of NaAlH₄ pellets before and after hydrogen absorption and desorption cycles. It is based on a biaxial flexure test that was originally designed for determining the strength of green ceramic materials. The tests showed that the pellets were strong with biaxial flexure strength of 1.4 kpsi which was unaltered over three studied hydrogen absorption/desorption cycles. The increased materials density did not affect the hydrogen absorption and desorption kinetics, which is important in order to benefit from the improved volumetric capacity. The new material properties of the compacted NaAlH₄ were used in finite element modeling of a hydrogen storage system that targeted a fast refueling time. The results clearly show an improvement of the volumetric capacity of the system by powder consolidation but the gravimetric capacity remains below target, as expected. A system level study of a light-duty vehicle with such a hydrogen storage system is required in order to determine whether the amount of hydrogen stored in the pore volume of the sodium alanate will still be enough to enable one cold start from room temperature to its operating temperature (120–140 °C) or that a buffer volume needs to be installed. While it is recognized that a sodium alanate based hydrogen storage system has its limitations, it has been demonstrated that powder consolidation can address some of those limitations by improving the thermal conductivity and volumetric capacity.     

Strength Measurements of Monolithic SiC and A12O3/SiC Composites after Exposure to Coal Slag

Four Si-based ceramics—siliconized SiC (Si-SiC), sintered α-SiC, and two grades of SiC-particulate-reinforced A1₂O₃—were exposed to a typical western coal ash with high calcium content (Wyodak) and a typical eastern coal ash rich in iron (Illinois #6) at two temperatures for 300 h in a muffle furnace. After exposure, the coupons were cut into flexure bars and remaining strength was measured in four-point flexure at room temperature. The residual strength was compared to the as-received strength, and the fracture originating flaws were identified. The standard grade of the particulate-reinforced A1₂O₃ showed no corrosive attack under any of the exposure conditions, and a slight strength reduction was attributed to aging effects. The three other materials showed varying degrees of strength reduction, with corresponding fracture-initiating flaws being pits produced during the exposure. A general trend was that the eastern coal seemed to cause more corrosion than the western, and that 1260°C was a harsher exposure condition than 1093°C.