Investigating the behaviour of fluid-filled polyethylene containers under base drop impact: A combined experimental/numerical approach

In this work, the behaviour of fluid-filled plastic containers under base drop impact is investigated using a combined experimental/numerical approach. In addition, theoretical predictions from two approaches, waterhammer theory and a mass-spring model, are also given. Experimental tests are conducted using a specially designed rig for testing plastic containers (bottles). Tested containers are fully instrumented with pressure transducers and strain gauges. The experiments are simulated using a two-system fluid-structure interaction procedure based on the Finite Volume Method. Good agreement is found between measured and predicted pressure and strain histories. Results obtained are in favour of waterhammer theory.     

Decomposition of phenol by hybrid gas/liquid electrical discharge reactors with zeolite catalysts

Application of hybrid gas/liquid electrical discharge reactors and a liquid phase direct electrical discharge reactor for degradation of phenol in the presence and absence of zeolites have been investigated. Hybrid gas/liquid electrical discharges involve simultaneous high voltage electrical discharges in water and in the gas phase above the water surface leading to the additional OH radicals in the liquid phase and ozone formation in the gas phase with subsequent dissolution into the liquid. The role of applied zeolites, namely NH4ZSM5, FeZSM5 and HY, were also studied. Phenol degradation and production of primary phenol by-products, catechol and hydroquinone, during the treatment were monitored by HPLC measurements. The highest phenol removal results, 89.4-93.6%, were achieved by electrical discharge in combination with FeZSM5 in all three configurations of corona reactors. These results indicate that the Fenton reaction has significant influence on overall phenol removal efficiency in the electrical discharge/FeZSM5 system due to the additional OH radical formation from hydrogen peroxide generated by the water phase discharge.     

A molecular switch based on current-driven rotation of an encapsulated cluster within a fullerene cage

By scanning tunneling microscopy imaging and electronic structure theory, we investigate a single-molecule switch based on tunneling electron-driven rotation of a triangular Sc3N cluster within an icosahedral C80 fullerene cage among three pairs of enantiomorphic configurations. Bias-dependent action spectra and modeling implicate the antisymmetric stretch vibration of Sc3N cluster as the gateway for energy transfer from the tunneling electrons into the cluster rotation. Hierarchical switching of conductivity among multiple stationary states while maintaining a constant molecular shape, offers an advantage for the integration of endohedral fullerene-based single-molecule switches into multiple logic state molecular devices.     

Characterization of the fracture behavior of polyethylene using measured cohesive curves. I: Effects of constraint and rate

The damage and failure mechanisms in polyethylene are investigated using a circumferentially notched tensile specimen subject to constant rate displacement conditions. The fracture process can be quantified, independent of the bulk deformation, using a local traction–separation relation. The study found that the mechanisms of deformation under quasi‐static test speeds depend on the degree of crack tip constraint in addition to rate. This dependency can lead to contrasting deformation‐failure behavior between different grades of polyethylene and hence the overall energy dissipation process. Based on this approach, both gross and subtle differences in the fracture behavior between the grades were readily detected and differentiated. In general, the damage mechanisms changed from a brittle mode under conditions of high constraint to a ductile mode as the level of constraint is reduced. POLYM. ENG. SCI., 46:763–777, 2006. © 2006 Society of Plastics Engineers     

Limiting crack speeds in dynamic tensile fracture tests

The spring mass model is used to determine a crack speed, crack length and loading relationship in terms of energy release rate. An essential feature of the analysis is the inclusion of the contact stiffness and a geometry dependent limiting speed. The analysis is used to describe crack speed data taken over a wide range of geometry changes. A good fit to the data is obtained but a low wave speed is predicted. This is rationalised on the basis of a low, local strain dependent modulus.     

Design of linear phase FIR notch filters

This paper investigates some approaches for designing one-dimensional linear phase finite-duration impulse-responses (FIR) notch filters, which are based on the modification of several established design techniques of linear phase FIR band-selective filters. Based on extensive design examples and theoretical analysis, formulae have been developed for estimating the length of a linear phase FIR notch filter meeting the given specifications. In addition, the design of two-dimensional linear phase FIR notch filters is briefly considered. Illustrative examples are included. This work was supported in part by a University of California MICRO grant with matching supports from Rockwell International and CES Inc.     

Compositional dependence of absorption coefficient and band-gap for Nb2O5-SiO2 mixture thin films

The absorption coefficient of composite films consisting of niobia (Nb₂O₅) and silica (SiO₂) mixtures is studied for photon energies around the band gap. The films were deposited by co-evaporation and their composition was varied by changing the ratio of deposition rates of the two materials. Both, as-deposited and thermally annealed films were characterized by different techniques: the absorption coefficient was determined by spectrophotometric measurements and the structural properties were investigated using infrared spectroscopy, transmission electron microscopy and X-ray diffraction. The correlation between the variations of absorption properties and film composition and structure is established. The absorption coefficients determined experimentally are compared with the results derived from effective medium theories in order to evaluate the suitability of these theories for the studied composites.     

Measurement uncertainty of adaptive Chirp-z transform

In this paper analysis of measurement uncertainty of Adaptive Chirp-z transform (ACT) algorithm for power frequency measurement is presented. ACT is a new algorithm developed for real time monitoring of power frequency. Every element (hardware and software) of measurement chain is contributing to the total measurement uncertainty. The analysis of passive voltage dividers, analog-to-digital converters, numeric algorithms and processors (word length and type of arithmetic) are also presented. Estimated values of each contributing part of measurement chain are calculated to the final expression of measurement uncertainty.