Engineering

Reverse osmosis (RO) is the most preferable process for water recovery from secondary effluent (SE) because of its higher rejection of impurities with lower associated cost and higher quality of product. Fouling still is a major challenge during the water recovery due to higher contaminant loadings in SE and high rejection capability of this membrane. The presence of suspended solids, colloidal and organic matters, and high level of biological activities in SE further elevate fouling potentiality. This review was performed to identify major foulants causing hindrance in sustainable application of reverse osmosis and to present available pre-treatment options for these foulants. There are four fouling types present in RO namely; bio-fouling, inorganic/scaling, organic, and particulate fouling. Among them; bio-fouling is less understood but dominant since the pre-treatment options are not well developed. Other fouling mechanisms have been overcome by well developed pretreatments. The major foulants for RO are dissolved and macromolecular organic substances, sparingly soluble inorganic compounds, colloidal and suspended particles, and microorganisms. Some of these potential fouling water quality parameters (PFWQPs) are interrelated with each others such as electrical conductivity is a surrogate measure of total dissolved solids with established stable relationship. Most of these PFWQPs such as total suspended solids, turbidity, chemical oxygen demand can be removed by conventional pre-treatment; some such as colloidal particles and microorganisms by modern options and even others such as endocrine disrupting compounds, pharmaceutical and personal care products are still challenging for current pre-treatments. These foulants need to be identified properly to integrate appropriate pre-treatments for minimizing fouling potentiality to increase water recovery at minimal costs.

The paper presents a framework to design robust transmit power controllers in cellular radio systems. The robust controllers designed are able to guarantee the quality of service (QoS) by keeping the carrier-to-inference-plus-noise ratio (CIRN) above a desired level in face of network link gain variations. The controller design problem is solved by solving a noncooperative dynamic game between the controller and unknown link gain variations.

Vision based tracking of an object using the ideas of perspective projection inherently consists of nonlinearly modelled measurements although the underlying dynamic system that encompasses the object and the vision sensors can be linear. Based on a necessary stereo vision setting, we introduce an appropriate measurement conversion techniques which subsequently facilitate using a linear filter. Linear filter together with the aforementioned measurement conversion approach conforms a robust linear filter that is based on the set values state estimation ideas; a particularly rich area in the robust control literature. We provide a rigorously theoretical analysis to ensure bounded state estimation errors formulated in terms of an ellipsoidal set in which the actual state is guaranteed to be included to an arbitrary high probability. Using computer simulations as well as a practical implementation consisting of a robotic manipulator, we demonstrate our linear robust filter significantly outperforms the traditionally used extended Kalman filter under this stereo vision scenario.

Fully-connected mesh networks that can potentially be employed in a range of applications, are inherently associated with major deficiencies in interference management and network capacity improvement. The tree-connected (routing based) mesh networks used in today's applications have major deficiencies in routing delays and reconfiguration delays in the implementation stage. This paper introduces a CDMA based fully-connected mesh network, which controls the transmission powers of the nodes in order to ensure that the communication channels remain interference-free and minimizes the energy consumption. Moreover, the bounds for the number of nodes and the spatial configuration are provided to ensures that the communication link satisfies the QoS (Quality of Service) requirements at all times.

This paper focuses on the development of a hybrid phenomenological/inductive model to improve the current physical setup force model on a five stand industrial hot strip finishing mill. We approached the problem from two directions. In the first approach, the starting point was the output of the current setup force model. A feedforward multilayer perceptron (MLP) model was then used to estimate the true roll separating force using some other available variables as additional inputs to the model.

Variation in the incoming sheet material and fluctuations in the press setup is unavoidable in many stamping plants. The effect of these variations can have a large influence on the quality of the final stamping, in particular, unpredictable springback of the sheet when the tooling is removed. While stochastic simulation techniques have been developed to simulate this problem, there has been little research that connects the influence of the noise sources to springback. This paper characterises the effect of material and process variation on the robustness of springback for a semi-cylindrical channel forming operation, which shares a similar cross-section profile as many automotive structural components. The study was conducted using the specialised sheet metal forming package AutoForm TM Sigma, for which a series of stochastic simulations were performed with each of the noise sources incrementally introduced. The effective stress and effective strain scatter in a critical location of the part was examined and a response window, which indicates the respective process robustness, was defined. The incremental introduction of the noise sources allows the change in size of the stress-strain response window to be tracked. The results showed that changes to process variation parameters, such as BHP and friction coefficient, directly affect the strain component of the stress-strain response window by altering the magnitude of external work applied to forming system. Material variation, on the other hand, directly affected the stress component of the response window. A relationship between the effective stress-strain response window and the variation in springback was also established.

Compression and bend tests were performed on an annealed and aged carbon steel that had been prestrained by different amounts. A bending model was developed to analyse the bending response of the material. While the bending test results agreed well with some of the material trends found in previous studies focusing on the Bauschinger effect, an overly high reduction of the bending yield with pre-strain was observed. Calculation of the moment curvature diagram for the pre-strained material based on the tensile and compression test data using the analytical model did not fit the experimental curve. In the control of yield phenomena by the industrial processes of temper rolling, skin passing, tension levelling and roller levelling, the effectiveness of the treatment is usually judged from tensile testing after treatment. However, the present work shows that where the yield phenomena have been removed by pre-processing, that the tensile test will not predict the subsequent bending behaviour and that the bending test may provide greater insight. This may have important consequences in the study of cold roll forming where shape defects in the product are believed to originate from small strain forward and reverse bending deformations that will be strongly affected by the Bauschinger and yield effects.