REACTION SYNTHESIS MECHANISM IN DYNAMICALLY DENSIFIED Ti + C POWDER COMPACTS

Elemental titanium and carbon powder mixtures were statically and dynamically densified to make 88–90% dense compacts for subsequent reaction synthesis in an induction-heated hot press at 1100°–1400°C, with 60 minutes constant hold time and a nominal pressure of 34.5 MPa (5000 psi). The reaction behavior of the dynamically (shock) densified powder compacts was observed to be dominated by defect-enhanced solid-state diffusion. Measurements of titanium carbide formation rates revealed that the otherwise-sluggish diffusion of Ti or C through the initial C-deficient TiC_x layer is significantly altered in the dynamically compressed powders with activation energies for diffusion reduced by 4–6 times. The reacted dynamically densified compacts are 85% dense, and have a 5μm grain size. In contrast, statically pressed Ti + C compacts were observed to react via a combustion-type process (following initial solid-state reaction) resulting in porous reaction products with>30% retained porosity. © 1997 Acta Metallurgica Inc.     

A Highly Secured QoS Aware Routing Algorithm for Software Defined Vehicle Ad-Hoc Networks Using Optimal Trust Management Scheme

Wireless Personal Communications - Recent reports show that the millions of people killed each year in the road accidents are due to high density vehicles and traffic environment. The road traffic...     

Total System Energy Minimization for Wireless Image Transmission

In this paper, we focus on the total-system-energy minimization of a wireless image transmission system including both digital and analog components. Traditionally, digital power consumption has been ignored in system design, since transmit power has been the most significant component. However, as we move to an era of pico-cell environments and as more complex signal processing algorithms are being used at higher data rates, the digital power consumption of these systems becomes an issue. We present an energy-optimized image transmission system for indoor wireless applications which exploits the variabilities in the image data and the wireless multipath channel by employing dynamic algorithm transformations and joint source-channel coding. The variability in the image data is characterized by the rate-distortion curve, and the variability in the channel characteristics is characterized by the path-loss and impulse response of the channel. The system hardware configuration space is characterized by the error-correction capability of the channel encoder/decoder, number of powered-up fingers in the RAKE receiver, and transmit power of the power amplifier. An optimization algorithm is utilized to obtain energy-optimal configurations subject to end-to-end performance constraints. The proposed design is tested over QCIF images, IMT-2000 channels and 0.18m, 2.5 V CMOS technology parameters. Simulation results over various images, various distances, two different channels, and two different rates show that the average energy savings in utilizing a total-system-energy minimization over a fixed system (designed for the worst image, the worst channel and the maximum distance) are 53.6% and 67.3%, respectively, for short-range (under 20 m) and long-range (over 20 m) systems.     

Mechanical properties of injection molded long fiber polypropylene composites,Part 1: Tensile and flexural properties

Innovative polymers and composites are broadening the range of applications and commercial production of thermoplastics. Long fiber‐reinforced thermoplastics have received much attention due to their processability by conventional technologies. This study describes the development of long fiber reinforced polypropylene (LFPP) composites and the effect of fiber length and compatibilizer content on their mechanical properties. LFPP pellets of different sizes were prepared by extrusion process using a specially designed radial impregnation die and these pellets were injection molded to develop LFPP composites. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer and its content was optimized by determining the interfacial properties through fiber pullout test. Critical fiber length was calculated using interfacial shear strength. Fiber length distributions were analyzed using profile projector and image analyzer software system. Fiber aspect ratio of more than 100 was achieved after injection molding. The results of the tensile and flexural properties of injection molded long glass fiber reinforced polypropylene with a glass fiber volume fraction of 0.18 are presented. It was found that the differences in pellet sizes improve the mechanical properties by 3–8%. Efforts are made to theoretically predict the tensile strength and modulus using the Kelly‐Tyson and Halpin‐Tsai model, respectively. POLYM. COMPOS., 28:259–266, 2007. © 2007 Society of Plastic Engineers     

Sourcing Organic Materials for Pit Lake Bioremediation in Remote Mining Regions

Pit lakes formed by open-cut mining may have poor water quality as a result of Acidic and Metalliferous Drainage (AMD). Water quality remediation treatments that enhance naturally occurring alkalinity-generating processes (bioremediation) can be used to remediate these water quality problems. Microbially-mediated sulfate reduction using carbon as an electron donor is one approach that shows promise. Carbon amendment can be bulk organic materials, which are often cheap or free. This study investigated a process for determining what organic materials were best for in situ pit lake AMD bioremediation in a remote mining region. Following a literature review identifying how different organic materials facilitated sulfate reduction in AMD waters, we evaluated availability and costs of acquiring and transporting these materials to a typical remote mine pit lake. We found that those sourcing organic materials should focus on a mixture of sewage sludge and green waste, which are commonly available from mining camps/service towns and from land clearing operations.