Simultaneous fitting of statistical-model parameters to symmetric and asymmetric fission cross sections

peer reviewe

Mode detection in turbofan inlets from acoustic pressure measurements in the radiated field

Knowledge of the modal content of the sound field radiated from a turbofan inlet is important for source characterisation and for helping to determine noise generation mechanisms in the engine. An inverse technique for determining the mode decomposition is proposed using pressure measurements from mode on the Turbulence Control Screen (TCS). The TCS offers a useful platform for locating microphones since they are often fitted to engines during ground testing to smooth the integrated flow. Array performance is tested on computer-generated data from modal radiation predictions using a model based on the Kirchhoff approximation for flanged ducts with no flow. An overdetermined system of linear equations that accounts for the radiation at the TCS due to all cut-on modes and nearly cut-on modes is constructed from this model and is inverted to determining mode amplitudes. The sensitivity of the reconstructed mode amplitudes to noise is determined by the condition number of the radiation matrix, containing modal directivity functions predicted at each sensor location. This paper discusses the number and configuration of microphones on the TCS needed for robust and accurate modal inversion. Finally, this paper discusses the use of constraining the solution by regularisation in order to improve inversion robustness to noise

TREATMENT OF INDUSTRIAL WASTE EFFLUENT USING TREATED BAGASSE.

This research work is aimed at the investigation of the reduction of concentration of heavy metals from industrial Effluent water using sulphuric and acetic acid treated Bagasse. This was achieved by varying the concentration of the acids between 0.3M - 0.6M. This report discusses the treatment of Bagasse and the methodology of treating the industrial effluent water using the treated Bagasse as an adsorbent. The treated water samples were analysed using the atomic absorption spectrophotometer to determine the concentration of heavy metals present after treatment. The results obtained shows that 0.3M-0.6M sulphuric and acetic treated Bagasse were successful in the reduction of the concentration of heavy metals, with 0.4M-0.5M sulphuric and acetic acid treated Bagasse been the most effective because it has the lowest concentration of heavy metals after treatment and this implies that more active sites were opened for adsorption at this concentration. This research work has proved that treated Bagasse is an effective adsorbent in the reduction of the concentration of heavy metals in industrial effluent water

An investigation into a treatment strategy for the Berg River water at the Voëlvlei water treatment plant

Since the demand for fresh potable water increases every year, it is important to have future water demand strategies in place. People expect a secure, high quality, water supply and the water supply industry is governed by increasingly stringent water quality guidelines and legislation. The Cape Metropolitan Area (CMA) faces the challenge of an increasing demand for fresh water in excess of the existing supply. The City is responsible for the planning and development of the local water supply resources as well as managing the water demand in the CMA and to supplement the water supply to the City of Cape Town from local sources. The ‘Voëlvlei Augmentation Scheme’ was identified as one of the options to augment the water supply to the CMA. This option would involve pumping winter water from the Berg River via a pipeline to the Voëlvlei water treatment plant (WTP). The Voëlvlei WTP was designed to treat water from the adjacent Voëlvlei Dam. This Voëlvlei WTP raw water has a higher turbidity and a lower colour in comparison to the Berg River water. The plant’s treatment conditions were optimized to remove this high turbidity. The Voëlvlei WTP raw water also contains a relatively high manganese concentration and coagulation therefore occurs at a high pH with ferric sulphate to remove the manganese during the initial stages of the water treatment process. As the quality of the Berg River water is different to that of the Voëlvlei WTP raw water, it might not be possible to treat the Berg River water at the Voëlvlei WTP using the plants current treatment parameters. The Berg River water could possibly be blended with the Voëlvlei WTP raw water before treatment at the WTP. If the Berg River water, or its blends, could not be treated at the Voëlvlei WTP using the plants current treatment parameters, then this water would have to be pre-treated before entering the plant. Various forms of pre-treatment could be used, e.g., conventional water treatment using either aluminium or ferric sulphate as primary coagulants or ion-exchange water treatment using the MIEX® resin or even a combination of both. The main objective of this study was to determine a treatment strategy for the Berg River water at the Voëlvlei WTP. It is therefore important to determine if the Berg River water could be treated at the Voëlvlei WTP using the current treatment regime. Also, if the Berg River water should be blended with the Voëlvlei WTP raw water, this study would determine which blend would be the most suited for treatment at the Voëlvlei WTP. If the Berg River water could not be treated directly at the Voëlvlei WTP, a pre-treatment strategy for this water should be determined. The cost of pretreatment of the Berg River water as compared to the cost of direct treatment at the Voëlvlei WTP should also be evaluated. In order to determine the best treatment strategy for the Berg River water at the Voëlvlei WTP, it was important to sample the Berg River water and the Voelvlei WTP raw water at regular intervals over a period of at least a year to determine its quality and the impact of seasonal changes. Various laboratory physical (e.g., turbidity) and chemical (e.g., total alkalinity) analyses were conducted on the Berg River water and Voëlvlei WTP raw water to determine its quality. The experimental procedure focused mainly on the Jar test which simulates the coagulation, flocculation and sedimentation processes at the Voëlvlei WTP. Jar tests were conducted on the Berg River water and the Voëlvlei WTP raw water using ferric sulphate and aluminium sulphate as coagulants to determine the optimum pH and optimum coagulant dosage concentration for each coagulant. The Berg River water was also blended with the Voëlvlei WTP raw water in three different proportions and Jar tests were conducted on these blends using ferric sulphate as the coagulant at a coagulation pH of 5.0 and a Fe3+ dosage of 5.0 mg/L. Jar tests were also conducted on these blends with the Voëlvlei WTP treatment parameters using ferric sulphate as the coagulant at a coagulation pH of 9.2 and a Fe3+ dosage of 3.5 mg/L. The analytical results showed a similar pattern for the characterization of the Berg River water and the Voëlvlei WTP raw water. The iron and aluminium concentrations were consistently low during the summer months with significant increases during the winter months. There were no significant seasonal impact on the UV absorbance and colour. The Jar test results of the Voëlvlei WTP raw water and the Berg River water with ferric sulphate as the coagulant showed an optimum Fe3+dosage of 3.0 to 4.0 mg/L and 4.0 to 6.0 mg/L, respectively, with an optimum coagulation pH range of 6.6 to 9.5 and 5.0 to 10.0, respectively. The Jar test results of the Voëlvlei WTP raw water and the Berg River water with aluminium sulphate as the coagulant showed an optimum Al3+ dosage of 2.5 to 3.0 mg/L and 4.0 to 5.0 mg/L, respectively, with an optimum coagulation pH of 6.0 to 7.0 and 6.0, respectively. The Jar test results obtained for all 3 blends were similar to each other. The UV absorbance of the treated water was consistently below the operational specification, while the turbidities were inconsistent and did not always comply with the SANS 241:2006 Specification (Class I) for drinking water. The iron of the treated water was also consistently above the specified value of pre-treatment with ferric sulphate and lime pre-treatment with ferric sulphate and lime in conjunction with MIEX® resin pre-treatment with MIEX® resin only Further research and investigation would be necessary to determine the best pretreatment strategy in terms of cost and efficiency. The pre-treated Berg River water would have to pass through the Voëlvlei WTP treatment process (i.e. high coagulation pH) to remove any manganese that might be present in the water. It is recommended that more samples should be taken at various points along the Berg River upstream of the Voëlvlei WTP over a longer period of time to compare the quality of water at these points in the river and also to monitor the effect of various run-off sites. Further research and investigation is necessary to determine the optimum treatment parameters for the Berg River water when blended with the Voëlvlei WTP raw water. Other blending ratios, different to those used in this study, should also be investigated. A more in-depth investigation is also necessary to determine the actual capital and operational costs for the pre-treatment of the Berg River water.Dissertation (MSc)--University of Pretoria, 2011.Chemical Engineeringunrestricte

Active Contour Based Segmentation Techniques for Medical Image Analysis

Image processing is a technique which is used to derive information from the images. Segmentation is a section of image processing for the separation or segregation of information from the required target region of the image. There are different techniques used for segmentation of pixels of interest from the image. Active contour is one of the active models in segmentation techniques, which makes use of the energy constraints and forces in the image for separation of region of interest. Active contour defines a separate boundary or curvature for the regions of target object for segmentation. The contour depends on various constraints based on which they are classified into different types such as gradient vector flow, balloon and geometric models. Active contour models are used in various image processing applications specifically in medical image processing. In medical imaging, active contours are used in segmentation of regions from different medical images such as brain CT images, MRI images of different organs, cardiac images and different images of regions in the human body. Active contours can also be used in motion tracking and stereo tracking. Thus, the active contour segmentation is used for the separation of pixels of interest for different image processing

Understanding the Observed Evolution of the Galaxy Luminosity Function from z=6-10 in the Context of Hierarchical Structure Formation

Recent observations of the Lyman-break galaxy (LBG) luminosity function (LF) from z~6-10 show a steep decline in abundance with increasing redshift. However, the LF is a convolution of the mass function of dark matter halos (HMF)--which also declines sharply over this redshift range--and the galaxy-formation physics that maps halo mass to galaxy luminosity. We consider the strong observed evolution in the LF from z~6-10 in this context and determine whether it can be explained solely by the behavior of the HMF. From z~6-8, we find a residual change in the physics of galaxy formation corresponding to a ~0.5 dex increase in the average luminosity of a halo of fixed mass. On the other hand, our analysis of recent LF measurements at z~10 shows that the paucity of detected galaxies is consistent with almost no change in the average luminosity at fixed halo mass from z~8. The LF slope also constrains the variation about this mean such that the luminosity of galaxies hosted by halos of the same mass are all within about an order-of-magnitude of each other. We show that these results are well-described by a simple model of galaxy formation in which cold-flow accretion is balanced by star formation and momentum-driven outflows. If galaxy formation proceeds in halos with masses down to 10^8 Msun, then such a model predicts that LBGs at z~10 should be able to maintain an ionized intergalactic medium as long as the ratio of the clumping factor to the ionizing escape fraction is C/f_esc < 10.Comment: 15 pages, 2 figures; results unchanged; accepted by JCA

One-loop β\beta functions of a translation-invariant renormalizable noncommutative scalar model

Recently, a new type of renormalizable $\phi^{\star 4}_{4}$ scalar model on the Moyal space was proved to be perturbatively renormalizable. It is translation-invariant and introduces in the action a $a/(\theta^2p^2)$ term. We calculate here the $\beta$ and $\gamma$ functions at one-loop level for this model. The coupling constant $\beta_\lambda$ function is proved to have the same behaviour as the one of the $\phi^4$ model on the commutative $\mathbb{R}^4$. The $\beta_a$ function of the new parameter $a$ is also calculated. Some interpretation of these results are done.Comment: 13 pages, 3 figure

Investigation into a treatment strategy for the Berg River water at the Voëlvlei water treatment plant

The main aim of this study was to determine a treatment strategy for the Berg River water at the Voëlvlei water treatment plant (WTP). Jar tests were conducted using ferric and aluminium sulphate as coagulants to determine the optimum treatment parameters of the Berg River water and the Voëlvlei WTP raw water. The results for the Voëlvlei WTP raw water and the Berg River water with ferric sulphate as the coagulant showed an optimum Fe3+ dosage of 3.0 to 4.0 mg/L and 4.0 to 6.0 mg/L, respectively, with and optimum coagulation pH range of 6.6 to 9.5 and 5.0 to 10.0, respectively. The results with aluminium sulphate as the coagulant showed and optimum AI3+ dosage of 2.5 to 3.0 mg/L and 4.0 to 5.0 mg/L, respectively, with an optimum coagulation pH of 6.0 to 7.0 and 6.0, respectively. This study concluded that the Berg River water cannot be effectively treated at the Voëlvlei WTP using the plants treatment parameters, even if it is blended with the Voëlvlei WTP raw water. The best treatment strategy for the Berg River water would be pre-treatment using either ferric sulphate or the MIEX ® resin on its own, or in conjunction with one another.http://www.iwaponline.com/ws

Asymptotes in SU(2) Recoupling Theory: Wigner Matrices, 3j3j Symbols, and Character Localization

In this paper we employ a novel technique combining the Euler Maclaurin formula with the saddle point approximation method to obtain the asymptotic behavior (in the limit of large representation index $J$) of generic Wigner matrix elements $D^{J}_{MM'}(g)$. We use this result to derive asymptotic formulae for the character $\chi^J(g)$ of an SU(2) group element and for Wigner's $3j$ symbol. Surprisingly, given that we perform five successive layers of approximations, the asymptotic formula we obtain for $\chi^J(g)$ is in fact exact. This result provides a non trivial example of a Duistermaat-Heckman like localization property for discrete sums.Comment: 36 pages, 3 figure