Processing Parameters for Selective Laser Melting (SLM) of Gold

Research into laser processing of different metals has enabled Solid Freeform Fabrication (SFF) processes to produce parts for a wide variety of applications. However, less focus has been made on the processing of precious metals. Currently little research has been reported on the processing of precious metals and alloys using the Selective Laser Melting (SLM) process. Here we present an initial investigation into the processing of 24 carat gold (Au) powder using a SLM system. Gold powder was tested for apparent density, tap density, particle shape and size distribution. A quality check of the specimen was carried out using a Scanning Electron Microscope (SEM) for sinterability and occurrence of porosity. Significant processing parameters were also identified.Mechanical Engineerin

Influence of temperature on the performance of a full-scale activated sludge process operated at varying solids retention times whilst treating municipal sewage

In this study, the solid retention time (SRT) was varied with the ambient temperature for a full-scale municipal activated sludge plant with capacity of 200,000 PE (Population Equivalent) located in a humid sub-tropical environment. The effects of ambient temperature on treatment performance were investigated. Off-line samples were collected and analyzed from the treatment plant. The actual temperature variation during the study period was divided into three overlapping ranges and the SRT was adjusted accordingly with temperature in order to achieve the desired effluent quality. The plant’s observed effluent quality and thereby its overall removal efficiency was evaluated in terms of measuring standard biochemical parameters. The results indicate that significant improvement in effluent quality can be obtained by applying the variable SRT (5–7 days) dependent on temperature variation

Design of coupled mace filters for optical pattern recognition using practical spatial light modulators

Spatial light modulators (SLMs) are being used in correlation-based optical pattern recognition systems to implement the Fourier domain filters. Currently available SLMs have certain limitations with respect to the realizability of these filters. Therefore, it is necessary to incorporate the SLM constraints in the design of the filters. The design of a SLM-constrained minimum average correlation energy (SLM-MACE) filter using the simulated annealing-based optimization technique was investigated. The SLM-MACE filter was synthesized for three different types of constraints. The performance of the filter was evaluated in terms of its recognition (discrimination) capabilities using computer simulations. The correlation plane characteristics of the SLM-MACE filter were found to be reasonably good. The SLM-MACE filter yielded far better results than the analytical MACE filter implemented on practical SLMs using the constrained magnitude technique. Further, the filter performance was evaluated in the presence of noise in the input test images. This work demonstrated the need to include the SLM constraints in the filter design. Finally, a method is suggested to reduce the computation time required for the synthesis of the SLM-MACE filter