Plasmon band gap generated by intense ion acoustic waves

In the presence of an intense ion acoustic wave, the energy-momentum dispersion relation of plasmons is strongly modified to exhibit a band gap structure. The intensity of an ion acoustic wave might be measured from the band gap width. The plasmon band gap can be used to block the nonlinear cascading channel of Langmuir wave decayComment: 3 pages, 3 figures, published on Po

Joining of thirty three percent by weight random carbon fibre reinforced low density polyethylene using variable frequency microwave

[Abstract]: This paper extends the range of applications for Variable Frequency Microwave facilities (VFMF) (2 – 18 GHz) to joining thirty three percent by weight carbon fibre reinforced low density polyethylene composite [LDPE/CF (33%)]. With a given power level, the composite was exposed to various exposure times to microwave irradiation. The primer or coupling agent used was 5-minute two-part adhesive containing 100% liquid epoxy and 8% amine, ie Araldite. Bond strengths of the joints were lap shear tested and results were compared with those obtained using fixed frequency (2.45 GHz) microwave processing. The VFMF was operated under software control, which provided automatic data logging facilities. The maximum lap shear strength of joint was 230 N/cm2 using variable frequency microwave facility while that obtained by fixed frequency microwave configuration was only 150 N/cm2. The former was found to be 53% stronger than the latter

Thermal analysis comparison between two random glass fibre reinforced thermoplastic matrix composites bonded by adhesives using microwaves: preliminary results

[Abstract]: This paper compares the thermal analysis of two types of random glass fibre reinforced thermoplastic matrix composites joined by adhesives using microwave energy. Fixed frequency, 2.45 GHz, microwave facility is used to join thirty three percent by weight random glass fibre reinforced polystyrene composite [PS/GF (33%)] and thirty three percent by weight random glass fibre reinforced low density polyethylene composite [LDPE/GF (33%)]. The facility used is shown in Figure 1. With a given power level, the composites were exposed to various exposure times to microwave irradiation. The primer or coupling agent used was 5-minute two-part adhesive. The heat distribution of the samples of the two types of composites was analysed and compared. The relationship between the heat distribution and the lap shear strength of the samples was also compared and discussed

Prediction of crushing stress in composite materials

A simple mathematical model for predicting the crushing stress of composite materials was derived and presented in this paper. The present knowledge of fracture mechanics and strength of materials are used as the basis for the model. The fracture mechanics part of the analysis was based on energy release rate approach; the energy release rate, G, of the proposed model was determined by this approach. This energy release rate was based on the Mode I (opening or tensile mode) failure. As for the strength of materials part analysis, buckling theory was used to determine the critical load of the fibre beams. These two engineering concepts were combined to form the equation for the proposed model. The derived equation is a function of the materials properties, geometric and physical parameters of the composite materials. The calculated stresses from the derived equation were compared with experimental data from technical and research papers. Good agreements shown in the results are encouraging and recommendations for future analysis with different modes of failure were also presented. This paper enables engineering designers to predict crushing stress in composite materials with confidence and makes their work more efficient and reliable

Preliminary results on literature review skills of students doing capstone projects

[Abstract]: A survey was carried out to investigate literature review skills of students doing their final year research projects. This survey was given before intervention to their literature review skills. Their literature review skills revealed by this survey were compared with that of a post-intervention survey, which was in turn compared with the literature review skills revealed in their intermittent reports. From the pre- and post-intervention surveys, it seems that the intervention workshops work and the percentage of students understanding how to conduct a literature review has improved from 11% to 78%. However, the intervention was not so successful if the literature review knowledge revealed by the project appreciation was compared with that of pre-intervention survey

Backward Raman compression of x-rays in metals and warm dense matters

Experimentally observed decay rate of the long wavelength Langmuir wave in metals and dense plasmas is orders of magnitude larger than the prediction of the prevalent Landau damping theory. The discrepancy is explored, and the existence of a regime where the forward Raman scattering is stable and the backward Raman scattering is unstable is examined. The amplification of an x-ray pulse in this regime, via the backward Raman compression, is computationally demonstrated, and the optimal pulse duration and intensity is estimated.Comment: 4 pages, 3 figures, submitted to PR

A method of solving sets of nonlinear algebraic equations Progress report

Methods for solving nonlinear algebraic equations in computer programs for nuclear magnetic resonance spectroscop