Analysis of Acoustic Emission Propagation in Metal-to-Metal Adhesively Bonded Joints

Acoustic emission (AE) monitoring shows promise as one of the most effective methods for condition monitoring of adhesively-bonded joints. Previous research has demonstrated its ability to detect, locate and classify adhesive joint failure, though in these studies little attention appears to have been paid to the differences in AE wave propagation through the bonded and un-bonded sections of the specimens tested, or to the effects of the wave modes excited or the propagation distances. This paper details an experimental study conducted on large aluminium sheet specimens to identify the effects of the presence of an adhesive layer on AE wave propagation. Three specimens are considered; a single aluminium sheet, two aluminium sheets placed together without adhesive, and an adhesively-bonded specimen. A pencil lead break (PLB) is used as a simulated AE source, and is applied to the three specimens at varying propagation distances and orientations. The acquired signals are processed using wavelet-transforms to explore time-frequency features, and compared with modified group-velocity curves based on the Rayleigh–Lamb equations to allow identification of wave-modes and edge-reflections. The effects of propagation distance and source orientation are investigated while comparison is made between the three specimens. It is concluded that while the wave propagation modes can be approximated as being constant throughout all three specimens, there is a significant change in the received waveforms due to the attenuation of high-frequency components exhibited by the bonded specimen. These findings may be utilised to provide a deeper understanding of acquired AE data, improving the current abilities to identify, locate and characterise damage mechanisms occurring within adhesive joints, ultimately improving safety in the use of adhesive bonding for critical applications.     

An Analysis of Reducing Communication Delay in Network-on-Chip Interconnect Architecture

This paper presents an Enhanced Clustered Mesh (EnMesh) topology for a Network-on-Chip architecture in order to reduce the communication delay between remote regions by considering the physical positions of remote nodes. EnMesh topology includes short paths between diagonal regions to ensure fast communication among remote nodes. The performance and silicon area overhead of EnMesh are analyzed and compared to those of state-of-the-art topologies such as Mesh, Torus, and Butterfly-Fat-Tree (BFT). Experimental results demonstrate that EnMesh outperforms other existing regular topologies in terms of throughput, latency, packet loss rate, and silicon area overhead.     

Assessment of the Actual Performance of an Industrial Solar Kiln for Drying Timber

The aim of this study was to assess the actual performance of an instrumented industrial solar kiln for drying Australian hardwood timber (Eucalyptus pilularis) boards (270 × 43 mm). Ambient temperature and humidity, air temperature and humidity in the kiln, and wood moisture contents were recorded on site (Heron's Creek, NSW, Australia) using sensors and an electronic data acquisition and logging system. The average increases in air temperatures in the kiln compared with ambient conditions were 17.3°C (May-June), 13.8°C (July-August), 10°C (September-October), 8.2°C (November-March), and 7.5°C (March-May) for five runs monitored. Drying times were 2-4 months from initial moisture contents of 43 to 62% (dry-basis) to final moisture contents of 12 to 22%. Overall, the solar kiln has been shown to be an acceptable alternative to air-drying for pre-drying of Australian hardwood timber.     

ANN based prediction model for fatigue crack growth in DP steel

An artificial neural network (ANN)-based model was developed to analyse high-cycle fatigue crack growth rates (d a /d N ) as a function of stress intensity ranges (Δ K ) for dual phase (DP) steel. The training data consisted of d a /d N at Δ K ranges between 5 and 16 MPa √ for DP steel with martensite contents in the range 32 to 76%. The ANN back-propagation model with Gaussian activation function exhibited excellent agreement with the experimental results. The fatigue crack growth rate predictions were made to demonstrate its practical significance in a given real-life situation. Because of the wide range of data points used during training of the model, it will provide a useful predictor for fatigue crack growth in DP steels.     

Titanium dioxide-mediated photocatalysed degradation of few selected organic pollutants in aqueous suspensions

The photocatalytic degradation of maleic hydrazide (1), propham (2), tebuthiuron (3), propachlor (4), chlortoluron (5), thiram (6), phenoxyacetic acid (7), 2,4,5-trichlorophenoxy acetic acid (8), 4-chlorophenoxy acetic acid (9), uracil (10), 5-bromouracil (11) and bromothymol blue (12) have been investigated in aqueous suspensions of titanium dioxide (TiO₂) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the compounds were investigated under different conditions, such as types of TiO₂, pH, catalyst concentration, substrate concentration, temperature and in the presence of different electron acceptors, such as hydrogen peroxide (H₂O₂), potassium persulphate (K₂S₂O₈), ammonium persulphate (NH₄)₂S₂O₈ and potassium bromate (KBrO₃) besides molecular oxygen. TiO₂ Degussa P25 was found to be more efficient photocatalyst for the degradation of the model compounds as compared with other photocatalysts. The degradation products were analysed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed.     

Nutritional and anti-nutritional components in Pachyrhizus erosus L. tuber

Tuber of Pachyrhizus erosus L., an underutilized crop, was analyzed to determine its proximate chemical composition, vitamin, mineral, and amino acid contents, and enzymatic activity. The anti-nutritional factors were also determined. The tuber had a high level of moisture, appreciable amounts of carbohydrate, crude fibre and protein and negligibly low amount of lipid. The total caloric value corresponded to 39 kcal/100 g. The amino acid profile was deficient compared to the [FAO/WHO (1973). Energy and Protein Requirements. Technical Report Series (Vol. 52, pp. 1–118). Switzerland, Geneva: WHO.] recommended pattern. The micro- and macro-nutrient analysis revealed the tuber to be potential source of potassium, sodium, phosphorus, calcium and magnesium. The tuber contained a significant amount of ascorbic acid. Thiamine, riboflavin, pyridoxine, niacin and folic acid were also detected. Very negligible contents of anti-nutrient components were observed. Comparison of these data to those of several other commonly consumed local tubers revealed that P. erosus tuber could be included in dietary formulae for man or monogastric animals, especially in those areas where carbohydrate is in short supply.     

Hafnium Diboride as a saturable absorber for Q-switched lasers

Hafnium diboride (HfB₂) is used in hypervelocity re-entry vehicles (such as intercontinental ballistic missile (ICBM) or ICBM heat shields), nuclear reactors and aerodynamic leading edges because of its strong tensile strength and high thermal resistance. HfB₂ is an ultra-high-temperature ceramic (UHTC) with a melting point of 3250°C. In this paper, we study the performance of HfB₂ as a saturable absorber in Q-switched lasers. HfB₂ has a non-saturable absorptance of 2.5?dB/µm, a saturable absorptance of 0.8?dB/µm and a saturation fluence of 12?µJ/cm². In addition, the saturation lifetime is estimated as 989.3?ps, while the recovery lifetimes are estimated as 254.9 and 22.1?ps. As a saturable absorber in our Q-switched laser, we observed pulses with durations between 880 and 2000?ns. With the addition of an acousto-optic modulator, we have observed Q-switching mode-locking, with pulses as low as 250?ns. HfB₂ can potentially work at very high power, since its damage fluence is no less than 361?mJ/cm².     

Interfacial properties of phosphate glass fibres/PLA composites: Effect of the end functionalities of oligomeric PLA coupling agents

Polylactic acid (PLA) oligomers as coupling agents have shown higher interfacial shear strength in phosphate based glass fibres/PLA composites. To influence bonding on the glass fibre surface, short chain PLA oligomers with different end groups were used as coupling agents. The low molecular weight PLA with a sodium salt terminal group, a carboxylic acid end group and also with one, two and five hydroxyl groups were produced and applied on the fibre surface through a condensation reaction. Mechanical properties of the sized fibres/PLA composites were found to be increased. XPS and TG analyses showed the presence of the coupling agents on the fibres surface. SEM analysis further confirms the presence of the agents.