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

Description of inclusive scattering of 4.045 GeV electrons from D

We exploit a relationship between the Structure Functions of nucleons, the physical deuteron and of a deuteron, composed of point-nucleons to compute angular distributions of inclusive cross sections of 4.05 GeV electrons. We report general agreement with data and interpret the remaining discrepancies. We discuss the potential of the data for information on neutron structure functions $F_k^n(x,Q^2)$ and the static form factor $G_M^n(Q^2)$.Comment: 9 pages,1 Fig., PS fil

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

Efficient measurements, purification, and bounds on the mutual information

When a measurement is made on a quantum system in which classical information is encoded, the measurement reduces the observers average Shannon entropy for the encoding ensemble. This reduction, being the {\em mutual information}, is always non-negative. For efficient measurements the state is also purified; that is, on average, the observers von Neumann entropy for the state of the system is also reduced by a non-negative amount. Here we point out that by re-writing a bound derived by Hall [Phys. Rev. A {\bf 55}, 100 (1997)], which is dual to the Holevo bound, one finds that for efficient measurements, the mutual information is bounded by the reduction in the von Neumann entropy. We also show that this result, which provides a physical interpretation for Hall's bound, may be derived directly from the Schumacher-Westmoreland-Wootters theorem [Phys. Rev. Lett. {\bf 76}, 3452 (1996)]. We discuss these bounds, and their relationship to another bound, valid for efficient measurements on pure state ensembles, which involves the subentropy.Comment: 4 pages, Revtex4. v3: rewritten and reinterpreted somewha

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