A Modified Kennard-Stone Algorithm for Optimal Division of Data for Developing Artificial Neural Network Models

This paper proposes a method, namely MDKS (Kennard-Stone algorithm based on Mahalanobis distance), to divide the data into training and testing subsets for developing artificial neural network (ANN) models. This method is a modified version of the Kennard-Stone (KS) algorithm. With this method, better data splitting, in terms of data representation and enhanced performance of developed ANN models, can be achieved. Compared with standard KS algorithm and another improved KS algorithm (data division based on joint x - y distances (SPXY) method), the proposed method has also shown a better performance. Therefore, the proposed technique can be used as an advantageous alternative to other existing methods of data splitting for developing ANN models. Care should be taken when dealing with large amount of dataset since they may increase the computational load for MDKS due to its variance-covariance matrix calculations

Ta/TiO2-and Nb/TiO2-Mixed Oxides as Efficient Solar Photocatalysts: Preparation, Characterization, and Photocatalytic Activity

Ta/TiO2- and Nb/TiO2-mixed oxides photocatalysts were prepared by simple impregnation method at different TiO2 : Nb or Ta mass ratios of 1 : 0.1, 1 : 0.5, and 1 : 1, followed by calcination at 500∘C. The prepared powders have been characterized by XRD, XPS, UV-Vis spectra, and SEM. The photocatalytic activity was evaluated under natural solar light for decolorization and mineralization of azo dye Orange II solution. The results showed that Nb/TiO2- and Ta/TiO2-mixed oxides have higher activity than the untreated TiO2 under natural solar light. The maximum activity was observed for Nb/TiO2 sample (at mass ratio of 1 : 0.1), which is characterized by the smallest crystalline size (17.79 nm). Comparing with the untreated TiO2, the solar decolorization and mineralization rates improved by about 140% and 237%, respectively, and the band gap reduced to 2.80 eV. The results suggest that the crystal lattices of TiO2 powder are locally distorted by incorporating Nb5+ species into TiO2, forming a new band energy structure, which is responsible for the absorption in the visible region. Unlike Ta/TiO2, the Nb/TiO2-mixed oxides can prevent the grain size growth of the treated TiO2, which is important to achieve high solar photoactivity

Modeling the Contribution of Gas Hydrate to Corrosion Rate Along the Subsea Pipelines

This study developed a corrosion predictive model along the deepwater gas pipelines with hydrate as the corroding agent. The model was developed and simulated with primary focus on the thermodynamic properties of each component of the gas mixture and a solution algorithm written with Matlab 6.5 (The MathWorks, Natick, MA) code. The model was validated by comparing the generated results with the outputs of already established laboratory and mathematical corrosion studies; the trends of the results obtained comparatively agreed with these studies to confirm its reliability. The model correctly predicted the relationships between corrosion rate and other thermodynamic parameters such as temperature, pressure, wall shear stress, velocity loss, and pH. This study showed that hydrates can initiate galvanic corrosion, stress cracking corrosion, and erosion-corrosion amongst others. Furthermore, the resulting corrosion rate from the hydrates could be as high as 174 mm/year (0.48 mm/day). This is extremely alarming compared to the industry’s aim to operate below 2 mm/year. At this rate, an underwater pipeline would be subjected to full bore rupture within some days if corrective measures are not quickly taken;hence, the need for further studies

PCA-based Method of Identification of Dominant Variables for Partial Control

Since the early use of automatic control, the Partial Control strategy has frequently been adopted in complex chemical processes having more process variables than manipulated variables. The key idea of Partial Control is to find the dominant variables which can be controlled to constant setpoints and in turn leads to acceptable variations in the operating objectives in the face of external disturbances occurrence. Although the idea seems simple to understand, the identification of the dominant variables can be a daunting task where presently this is largely done based on extensive process knowledge and experience. In this paper, we present a novel methodology to identify the dominant variables based on Principal Component Analysis. The method can greatly facilitate the implementation of Partial Control strategy because it does not require extensive process experience and knowledge. The effectiveness of the methodology is demonstrated based on its application to a complex extractive fermentation process

Fuzzy Feedback Scheduling of Resource-Constrained Embedded Control Systems

The quality of control (QoC) of a resource-constrained embedded control system may be jeopardized in dynamic environments with variable workload. This gives rise to the increasing demand of co-design of control and scheduling. To deal with uncertainties in resource availability, a fuzzy feedback scheduling (FFS) scheme is proposed in this paper. Within the framework of feedback scheduling, the sampling periods of control loops are dynamically adjusted using the fuzzy control technique. The feedback scheduler provides QoC guarantees in dynamic environments through maintaining the CPU utilization at a desired level. The framework and design methodology of the proposed FFS scheme are described in detail. A simplified mobile robot target tracking system is investigated as a case study to demonstrate the effectiveness of the proposed FFS scheme. The scheme is independent of task execution times, robust to measurement noises, and easy to implement, while incurring only a small overhead.Comment: To appear in International Journal of Innovative Computing, Information and Contro

CFD simulation of solid-liquid stirred tanks for low to dense solid loading systems

The hydrodynamics of suspension of solids in liquids are critical to the design and performance of stirred tanks as mixing systems. Modelling a multiphase stirred tank at a high solids concentration is complex owing to particle-particle and particle-wall interactions which are generally neglected at low concentrations. Most models do not consider such interactions and deviate significantly from experimental data. Furthermore, drag force, turbulence and turbulent dispersion play a crucial role and need to be precisely known in predicting local hydrodynamics. Therefore, critical factors such as the modelling approach, drag, dispersion, coefficient of restitution and turbulence are examined and discussed exhaustively in this paper. The Euler-Euler approach with kinetic theory of granular flow, Syamlal-O'Brien drag model and Reynolds stress turbulence model provide realistic predictions for such systems. The contribution of the turbulent dispersion force in improving the prediction is marginal but cannot be neglected at low solids volume fractions. Inferences drawn from the study and the finalised models will be instrumental in accurately simulating the solids suspension in stirred tanks for a wide range of conditions. These models can be used in simulations to obtain precise results needed for an in-depth understanding of hydrodynamics in stirred tanks

Composite table algorithm - a powerful hybrid pinch targeting method for various problems in water integration

Water management has become a very vital issue due to stringent environmental regulations and rising cost of water resources. Pinch analysis provides a conceptual approach for water network synthesis. Targeting is the first stage in most pinch analysis techniques to provide the baseline for detailed water network design. Although Water Cascade Analysis and Material Recovery Pinch Diagram methods have been developed to handle diverse water network problems, Composite Table Algorithm (CTA) is another water pinch targeting tool with its unique combination of both numerical and graphical characteristics. CTA was originally developed for fixed flow rate problems. In this work, the applicability of CTA for various water network problems such as fixed load, mixed fixed load and fixed flow rate, multiple pinch, and threshold problem is discussed. To facilitate, the approach has been programed in MATLAB and results obtained are validated by comparing with literature

Co3O4 nanocrystals with predominantly exposed facets: Synthesis, environmental and energy applications

Facet-dependent properties of novel metal or metal-oxide nanocrystals were discovered recently, and are attracting intensive interest owing to their great potential for various practical applications. Co3O4 as an important transition metal oxide shows electronic, magnetic, and redox properties which have found many applications in energy conversion and storage, magnetic separation, sensor devices and catalysis. This review summarizes the most recent research advances in synthesis and applications of nanosized Co3O4 with predominantly exposed facets, with emphasis on the enhanced performances in catalysis and electrochemical properties. The mechanism for improved selectivity and activity was discussed, and a panorama of the correlations between particle shape, crystal plane, surface atom arrangement, and active sites has been drawn. Insightful findings in this scope may be achieved by forthcoming research in theoretical calculations, rational synthesis, and emerging applications. Thus, researchers can manipulate the synthesis at the atomic level resulting in novel applications of the materials in a wide variety of areas

A case study: Application of energy and exergy analysis for enhancing the process efficiency of a three stage propane pre-cooling cycle of the cascade LNG process

The propane pre-cooling cycle has been widely used in most LNG plants as the first cooling cycle in the natural gas liquefaction process. As LNG plants consume high amounts of energy, enhancements in the process design and plant operation will minimize the overall energy consumption of the plant. The aim of this study is to enhance the process efficiency of a three stage propane pre-cooling cycle of the Cascade LNG process for the large-scale LNG train by determining the optimal operating conditions of the propane evaporator that will minimize the overall energy consumption. Energy and exergy analysis methods are adopted to evaluate the process efficiency of the propane pre-cooling cycle. Six case studies were presented to determine the optimal operating conditions of the propane evaporator that gives maximum energy reduction. The propane pre-cooling cycle is modelled and simulated using Aspen HYSYS with detailed thermodynamic information obtained to calculate the exergy loss. The results of the energy and exergy analysis indicate that Case 6 gives the highest coefficient of performance (COP) and the maximum exergy efficiency compared to the baseline case, which are 15.51% and 18.76% respectively. The results indicate that by reducing the cooling duty at the intermediate stages of propane evaporator about 13.5% energy saving can be achieved compared to the baseline case

The Engineering Pavilion – a learning space developing engineers for the global community

Of the many factors, formal and informal, that facilitate engineering students’ skills development and engineering identity, interactions with fellow students, teachers and industry are key. The Engineering Pavilion at Curtin facilitates these interactions in a building dedicated to students, providing a ‘home’ throughout their studies, a base for industry to engage with students, and stimulating concept understanding in a live (instrumented) building and learning space.To understand how students develop their learning, experience and behavior in this space, we need to understand the culture of the Pavilion. The theories of Pierre Bourdieu and the key concept of habitus, allow us to operationalize the concept of culture and understand the shifting mixtures of values and beliefs that underlie behavior. An ethnographic approach, studying a culture-shaping group at a single site, was employed.The Pavilion, recently opened, already supports student interactions. In moving from a habitus of student to graduate engineer, students’ perceptions and behavior are influenced by these interactions. The larger field of engineering education also changes through adoption or revaluing new forms of behavior through the curriculum. The Pavilion hosts the development of changing habitus and exemplifies how innovative learning spaces can influence the norms of long-established disciplines