On-line characterisation techniques for manufacture of nanomaterials

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Non-negative differential evolution for particle sizing from ultrasonic attenuation spectroscopy

Ultrasonic attenuation spectroscopy (UAS) is a potentially characterising technique for nano-meter size materials. It is the inversion of the ultrasonic attenuation spectrum to particle size distribution (PSD) by using an optimisation technique. Because the particle size is non-negative number, the inversion has to be optimised in the non-negative real number domain. However, many optimisation techniques have traditionally added the non-negative constrain into a cost function as a result the function becoming complex. In this article, the modification of the differential evolution (DE) technique has been proposed to narrow the searching solution domain bounded in the non-negative real number domain. An absolute function has been added to a mutant vector of the DE technique to guarantee the solution is non-negative real number. This technique is called DE-Nonneg technique. The technique has been demonstrated by characterising size of silica suspension. The optimisation results show that the PSD predictions are comparatively to simulated annealing (SA) technique. Moreover, the performance of DE-Nonneg could be improved via adjusting the parameters (expanding factor, cross over, number of parameters and mutation type) following the guideline addressed here. In addition, it is also possible to predict the PSD without using the structural PSD model. With this advantage, DE-Nonneg could possibly be applied for other non-negative optimisation problems

Cryptosporidium and Giardia detection in environmental waters of southwest coastal areas of Thailand

The aim of this study was to investigate water samples collected in coastal areas of Southern Thailand in the years of 2005 and 2008 for their contamination by the protozoan parasites Cryptosporidium and Giardia. One hundred eighteen water samples of different origin were collected from six Tsunami affected southern provinces of Thailand in early 2005, and they have been analyzed using standardized methodology. Fifteen out of 118 samples (12.7%) were positive for Cryptosporidium spp. and nine (7.6%) positive for Giardia spp. Additional 42 samples from two same areas were examined 3 years later, in the early 2008. Five out of 42 (11.9%) samples were positive for Cryptosporidium spp., and three out of 42 (7.1%) were positive for Giardia spp.. Both protozoans were found in reservoir, river/canal, and pond waters. It appears no significant differences (p \u3c 0.05) between Cryptosporidium and Giardia (oo)cysts levels during the two monitoring periods; however, the number of the investigated areas and samples in the second period was significantly less than in the first period. This is the first description on Cryptosporidium and Giardia (oo)cysts in water sources of Thailand, and it suggests the need for water quality control in the interest of public health safety

Making Use of Process Tomography Data for Multivariate Statistical Process Control

This paper describes a novel strategy for making effective use of on-line process tomography measurements for process monitoring. The electrical resistance tomography (ERT) sensing system equipped with sixteen electrodes provides 104 conductivity measurements every 25 milliseconds. The data has traditionally been used for construction of images for display purpose. In this study, ERT data was used for multivariate statistical process control (MSPC). Data at pre-defined normal operational conditions was processed using principal component analysis. The compressed data was used to derive two statistics; Hotelling’s T2 and squared prediction error (SPE). The Hotelling’s T2 and SPE charts predict the probability that the process being monitored has undergone statistically significant changes from previous state or the so-called normal operational state, in terms of mixing quality. The methodology is illustrated by reference to a case study of a sunflower oil/water emulsion process