Passivity-Based Output-Feedback Control of Turbulent Channel Flow

This paper describes a robust linear time-invariant output-feedback control strategy to reduce turbulent fluctuations, and therefore skin-friction drag, in wall-bounded turbulent fluid flows, that nonetheless gives performance guarantees in the nonlinear turbulent regime. The novel strategy is effective in reducing the supply of available energy to feed the turbulent fluctuations, expressed as reducing a bound on the supply rate to a quadratic storage function. The nonlinearity present in the equations that govern the dynamics of the flow is known to be passive and can be considered as a feedback forcing to the linearised dynamics (a Lur’e decomposition). Therefore, one is only required to control the linear dynamics in order to make the system close to passive. The ten most energy-producing spatial modes of a turbulent channel flow were identified. Passivity-based controllers were then generated to control these modes. The controllers require measurements of streamwise and spanwise wall-shear stress, and they actuate via wall transpiration. Nonlinear direct numerical simulations demonstrated that these controllers were capable of significantly reducing the turbulent energy and skin-friction drag of the flow

Strain Localisation, Fracturing and Hydrothermal Mineralisation: Numerical Models of the Mount Isa Copper Deposit, Australia

There is substantial need in mineral exploration to understand the structural controls on ore deposition for these types of deposits in order to predict the localities of new ones. Application of basic principles of rock mechanics, and numerical simulations of deformation and fluid flow processes provide fundamental insights to Proterozoic hydrothermal mineralization atMount Isa, Australia. The rheology of layered meta-sedimentary rocks, and the orientation and position of these layered rocks relative to major fault systems were the key controls on ore deposition...conferenc

Process mapping and scripting in the Accounting Information Systems (AIS) curriculum

The ability to understand, document, and suggest improvements for a business process is an important skill for an accounting student for the following reasons: (1) efficient business processes give businesses a competitive advantage; (2) business process analysis provides auditors with an assessment of business risk; and (3) successful enterprise resource planning implementation depends on understanding and improving existing business processes. It is suggested that students be introduced to process mapping and scripting in an accounting information systems (AIS) course to facilitate their understanding of business processes and help them visualize the interaction between functional areas. The specifics of process mapping are covered and advantages of incorporating process mapping into the AIS curriculum discussed. It is also proposed that scripting, which is used to facilitate configuration, testing of ERP software and communication between the accountant and the programmer, be included in the AIS course. Finally, suggestions for classroom activities are included

The Sub-Saharan Africa Challenge Program: An experiment in mainstreaming institutional learning and change

The Sub-Saharan Africa Challenge Program (SSA CP) shows how the principles of institutional learning and change (ILAC) can be applied. This Brief outlines the basic components of the SSA CP and highlights various ILAC features of the Program. These include an innovation systems orientation; an approach to ‘thinking globally and acting locally’; the location of research within a broader context of policy, market and institutional change; and an emphasis on collaboration and learning among program participants and with other agencies involved in agricultural research and development in Africa

Promoting the adoption of innovations through participatory approaches: example from northern Nigeria

Open Access JournalParticipatory research and development approaches involving all stakeholders along the value chain have recently been hypothesized to produce quicker outcomes than the linear technology transfer model. This paper analyzed the crop yield obtained by farmers and their uptake of improved technologies in a 2009 survey, one year after the completion of project field activities. It was a multi-stakeholder project involving research, extension, farmer groups, marketers and policymakers, that operated for 4 years (2005-2008) in Borno state of Nigeria. Survey results indicated that farmers who participated in project activities’ have been successful in increasing crop yields. Both yields and per capita production of major crops were statistically significantly higher (ρ≤ 0.05) in project communities compared to non-project ones. It is also estimated that there was a decline in percentage of households in food insecurity situation in project communities. Probit regression revealed that participation in project activities had a positive and significant effect on household food security (ρ≤ 0.05). It is then concluded that development interventions that involve multiple stakeholder partnership, use of participatory research and extension approach can help increase technology uptake among resourcepoor farmers as well as increase food production and food security in a region

A Simplified Improvement on the Design of QO-STBC Based on Hadamard Matrices

yesIn this paper, a simplified approach for implementing QO-STBC is presented. It is based on the Hadamard matrix, in which the scheme exploits the Hadamard property to attain full diversity. Hadamard matrix has the characteristic that diagonalizes a quasi-cyclic matrix and decoding matrix that are diagonal matrix permit linear decoding. Using quasi-cyclic matrices in designing QO-STBC systems require that the codes should be rotated to reasonably separate one code from another such that error floor in the design can be minimized. It will be shown that, orthogonalizing the secondary codes and then imposing the Hadamard criteria that the scheme can be well diagonalized. The results of this simplified approach demonstrate full diversity and better performance than the interference-free QO-STBC. Results show about 4 dB gain with respect to the traditional QO-STBC scheme and performs alike with the earlier Hadamard based QO-STBC designed with rotation. These results achieve the consequent mathematical proposition of the Hadamard matrix and its property also shown in this study

Directed assembly of defined oligomeric photosynthetic reaction centres through adaptation with programmable extra-membrane coiled-coil interfaces

A challenge associated with the utilisation of bioenergetic proteins in new, synthetic energy transducing systems is achieving efficient and predictable self-assembly of individual components, both natural and man-made, into a functioning macromolecular system. Despite progress with water-soluble proteins, the challenge of programming self-assembly of integral membrane proteins into non-native macromolecular architectures remains largely unexplored. In this work it is shown that the assembly of dimers, trimers or tetramers of the naturally monomeric purple bacterial reaction centre can be directed by augmentation with an α-helical peptide that self-associates into extra-membrane coiled-coil bundle. Despite this induced oligomerisation the assembled reaction centres displayed normal spectroscopic properties, implying preserved structural and functional integrity. Mixing of two reaction centres modified with mutually complementary α-helical peptides enabled the assembly of heterodimers in vitro, pointing to a generic strategy for assembling hetero-oligomeric complexes from diverse modified or synthetic components. Addition of two coiled-coil peptides per reaction centre monomer was also tolerated despite the challenge presented to the pigment-protein assembly machinery of introducing multiple self-associating sequences. These findings point to a generalised approach where oligomers or longer range assemblies of multiple light harvesting and/or redox proteins can be constructed in a manner that can be genetically-encoded, enabling the construction of new, designed bioenergetic systems in vivo or in vitro