Computer monitor recycling: a case study

The total number of computer monitors being scrapped per year worldwide is predicted to rise to 30 million units by the year 2005. Monitors contain significant quantities of lead (in the solder and CRT glass) and polybrominated flame retardants, which are potentially hazardous if released to the environment. A recent study investigated the possibility of cost-effectively recycling monitors     

Mathematical and Scientific Foundations for an Integrative Engineering Curriculum

All fields of engineering, whether chemical, civil, electrical, materials, mechanical, etc., encompass a common body of essential mathematics and science. In the freshman year of Drexels E⁴ program, this common mathematical and scientific foundation is cultivated in the Mathematical and Scientific Foundations of Engineering I, II and III (MSFE I, MSFE II, MSFE III). In an integrated fashion, MSFE I presents the essential calculus, physics and engineering mechanics vital to the freshman engineering student. In the first two quarters, MSFE II presents chemistry with clearly defined engineering applications and significance: in the third quarter, MSFE II presents living systems with the same thrust. Also in the third quarter, MSFE III presents basic circuits and circuit elements, and a brief introduction to electromagnetic theory.     

Development of a new 304L austenitic welding consumable containing tungsten

The transformation behaviour and kinetics of a duplex weld metal, in which tungsten was substituted for molybdenum, have been studied at 600, 700 and 800 C. Despite a low carbon level (0.037wt%), the material exhibited exceptional resistance against intermetallic formation during ageing. The Charpy impact toughness at room temperature was consistently superior compared to a standard molybdenum containing 316 weld metal. The results suggest that suitable development of the tungsten-bearing 304 consumable could lead to significant improvements in weld-metal properties.     

Computed tomographic imaging of the coronary arterial tree-use of local tomography

It has been demonstrated previously (see E.L. Ritman and A.A. Bove, in State of the Art in Quantitative Coronary Arteriography, p.67-78, 1986) that coronary artery anatomy can be visualized using high-speed, volume-scanning X-ray CT (computed tomography). In the current study it is demonstrated that local image reconstruction (i.e. the reconstruction kernel is ~2(+) mm long), as distinct from more conventional global image reconstruction (i.e. 200(+) mm kernel length), has the advantage of reducing the need for operator interactive image processing. In addition, the local reconstruction algorithm eliminates the need for recording the X-ray projection data over the full transaxial extent of the thorax because it requires only the X-ray attenuation data over the region of the heart. This latter aspect reduces the dynamic range requirements for the sensors and could reduce total X-ray exposure.     

A theoretical and experimental study of low-loss SAW filters with interdigitated interdigital transducers

A study of low-loss surface-acoustic-wave (SAW) interdigitated interdigital transducer (IIDT) structures is presented. A model based on mixed scattering matrices was used in the analysis. It is shown that the inherent comb frequency response of the IIDT can be smoothed by slanting the transducers in the structure. Alternatively, the combs can be enhanced to produce a compact low-loss feedback element for potential application in multimode oscillators. Experimental verification of the analysis is provided by a 3:2 slanted-finger IIDT filter with a 10% relative bandwidth of 5.9-dB insertion loss, and a comb filter with 13.4-dB insertion loss and comb spacing of about 3 MHz. The measured responses agree quite well with the theory.     

Is fluoridation a fraud?

During the past 15 years tooth decay rates have declined markedly amongst children in many parts of the industrialised world. Over the same period, however, decay rates have increased dramatically in children in developing countries. For many years it has been claimed that water fluoridation is the most important and cost-effective method for controlling dental caries. A series of recent papers in the scientific literature have challenged the 'fluoridation hypothesis', since the decline in decay reported in the developed countries has occurred in both fluoridated and unfluoridated areas. In some countries of the developing world, tooth decay is now reaching crisis proportions, hence it is important to know whether fluoridation really can "reduce tooth decay by about 60 per cent", or if the dental profession has been promoting a 'flawed' hypothesis for more than 40 years.