Thermodynamic predictions for material processing in a plasma reactor using solid oxide feed materials

Thermodynamic calculations, based on a free energy minimization (FEM) program, are presented for a number of material synthesis systems pertinent to plasma processing. Thermo-dynamic analysis gives general guidelines for the expected reactions and equilibrium compo-sition of species at different temperatures and pressures. Thermodynamics also allows the preliminary screening of possible synthesis reactions. These predictions should be used along with kinetic considerations for any proposed reaction system. Experimental results are presented to elucidate these thermodynamic predictions.     

A novel drag test to evaluate media tribology design on head wear

 By changing the head's Z-height, a new accelerated drag test has been developed to characterize head wear under high interference conditions. Compared to contact start stop (CSS) and other drag tests, heads wear faster in our approach, due to the stressed condition at the tilted trailing edge. The optimized Z-height has been chosen so that the head-disk interference and acoustic emission are maximized. The wear volume can be estimated by optical microscopy. The influence of lube bonded ratio and X1P additive amount on head wear has been studied for AM3001 lubricant. Lower bonded ratio and higher X1P additive were found to give rise to less head wear, which is in agreement with the existing results of contact start-stop and other drag tests. In media manufacturing, tape burnish processes were found to significantly affect the bonded ratio in the AM3001/X1P lubricant system, which consequently affects head wear. Short tape burnish times were found to reduce the media's head wear. Received: 16 July 2002/Accepted: 23 October 2002 The authors would like to thank Dr. Ken E. Johnson for his extensive support in this project. Paper presented at the 13th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 17–18 June, 2002     

Mechanochemical processing of nanocrystalline Ti-6Al-4V alloy

Synthesis of nanocrystalline Ti-6Al-4V was explored using mechanochemical processing. The reaction mixture was comprised of CaH₂, Mg powder, anhydrous AlCl₃, anhydrous VCl₃, and TiCl₄. The milled powder (reaction product) primarily consisted of nanocrystalline alloy hydride having a composition (Ti-6Al-4V)H_1.942, along with MgCl₂ and CaCl₂ as by-products. Aqueous solutions of nitric acid, sulfuric acid, and 1 pct sodium sulfite were found to be very effective in leaching of the chlorides from the milled powder. The (Ti-6Al-4V)H_1.942 on dehydrogenation at 375°C resulted in nanocrystalline Ti-6Al-4V alloy powder.     

Water‐Resistant Poly(vinyl alcohol)‐Silica Hybrids through Sol‐Gel Processing

Poly(vinyl alcohol) (PVA)‐silica hybrids with exceptionally reduced solubility in water were synthesized. The hybrid xerogels were fabricated through sol‐gel processing of a mixture of PVA and the acid‐catalyzed silica precursor tetraethoxysilane. The effects of varying ratios of PVA and silica precursor on the surface structure, thermal properties, crystallinity, and solubility of the hybrids were investigated. Unlike the highly water‐soluble nature of PVA, all the hybrids displayed considerably reduced solubility in water. This anomalous behavior of PVA in the hybrids can be attributed to the unavailability of its pendant –OH groups. Water‐resistant PVA‐silica hybrids can find applications in various technologies requiring biocompatible systems that are stable in aqueous environments.     

Trust Establishment In Pure Ad-hoc Networks

An ad-hoc network is a set of limited range wireless nodes that function in a cooperative manner so as to increase the overall range of the network. Each node in the network pledges to help its neighbours by passing packets to and fro, in return of a similar assurance from them. All is well if all participating nodes uphold such an altruistic behaviour. However, this is not always the case and often nodes are subjected to a variety of attacks by other nodes. These attacks range from naive passive eavesdropping to vicious battery draining attacks. Routing protocols, data, battery power and bandwidth are the common targets of these attacks. In order to overcome such attacks a number of routing protocols have been devised that use cryptographic algorithms to secure the routing mechanism, which in turn protects the other likely targets. A limiting requirement regarding these protocols is the reliance on an omnipresent, and often omniscient, trust authority. In our opinion, this reliance on a central entity is against the very nature of ad-hoc networks, which are supposed to be improvised and spontaneous. We present in this paper, a trust-based model for communication in ad-hoc networks that is based on individual experience rather than on a third party advocating trust levels. The model introduces the notion of belief and provides a dynamic measure of reliability and trustworthiness in pure ad-hoc networks. Asad Amir Pirzada is presently doing his Ph.D. on trust and security issues in ad-hoc wireless networks at The University of Western Australia. His current research interests include wireless communications, networking, cryptography, real-time programming and data acquisition systems. He holds a BE Avionics from NED University Pakistan, a MSc Computer Science from Preston University USA and a MS Information Security from the National University of Sciences and Technology Pakistan. Chris McDonald holds a B.Sc(Hons) and Ph.D. in Computer Science from The University of Western Australia, and currently holds the appointments of senior lecturer in the School of Computer Science & Software Engineering at UWA and adjunct professor in the Department of Computer Science at Dartmouth College, New Hampshire. Chris has recently taught in the areas of computer networking, operating systems, computer & network security, computer architecture, distributed systems programming and, together with these areas, his research interests include network simulation, ad-hoc & mobile networking, programming language implementation, open-source software.     

CERAMIC CARBIDE POWDER SYNTHESIS IN A NON-TRANSFERRED ARC PLASMA FLOW REACTOR

A method for the synthesis of fine, pure ceramic carbide powders such as silicon carbide, boron carbide and titanium carbide has been developed involving the thermal dissociation of silica, boron oxide or titanium oxide and methane in a thermal plasma, followed by the formation of the carbides in flight and rapid quenching. A non-transferred arc thermal plasma reactor has been designed, engineered, constructed and operated for this synthesis. The powders have been characterized chemically and physically. Thermodynamic calculations were performed to identify the appropriate experimental conditions and confirm the interpretations of the observed experimental results. A reaction mechanism is proposed based upon the experimental observations and results     

Sargassum swartzii extracts ameliorate memory functions by neurochemical modulation in a rat model

Food Science and Biotechnology - Recently, considerable attention has been paid to drug exploration from natural sources for treating memory loss, a major manifestation of various neurodegenerative...     

SafeMesh: A wireless mesh network routing protocol for incident area communications

Reliable broadband communication is becoming increasingly important during disaster recovery and emergency response operations. In situations where infrastructure-based communication is not available or has been disrupted, an Incident Area Network needs to be dynamically deployed, i.e. a temporary network that provides communication services for efficient crisis management at an incident site. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with self-healing and self-configuring capabilities. These features, combined with the ability to provide wireless broadband connectivity at a comparably low cost, make WMNs a promising technology for incident management communications. This paper specifically focuses on hybrid WMNs, which allow both mobile client devices as well as dedicated infrastructure nodes to form the network and provide routing and forwarding functionality. Hybrid WMNs are the most generic and most flexible type of mesh networks and are ideally suited to meet the requirements of incident area communications. However, current wireless mesh and ad-hoc routing protocols do not perform well in hybrid WMN, and are not able to establish stable and high throughput communication paths. One of the key reasons for this is their inability to exploit the typical high degree of heterogeneity in hybrid WMNs. SafeMesh, the routing protocol presented in this paper, addresses the limitations of current mesh and ad-hoc routing protocols in the context of hybrid WMNs. SafeMesh is based on the well-known AODV routing protocol, and implements a number of modifications and extensions that significantly improve its performance in hybrid WMNs. This is demonstrated via an extensive set of simulation results. We further show the practicality of the protocol through a prototype implementation and provide performance results obtained from a small-scale testbed deployment.     

Thermal plasma processing of materials: A review

The use of thermal plasma in materials processing industries is becoming an increasingly active and attractive field for the development of new technology. The potential applications of thermal plasma processing technology cover a wide range of activities, such as: the extraction of metals, the refining/alloying of metals/alloys, the synthesis of fine ceramic powders, spray coatings, and the consolidation and destruction of hazardous wastes. A review of thermal plasma applications in materials processing is presented.