Three-dimensional Numerical Modeling and Computational Fluid Dynamics Simulations to Analyze and Improve Oxygen Availability in the AMC Bioartificial Liver

A numerical model to investigate fluid flow and oxygen (O(2)) transport and consumption in the AMC-Bioartificial Liver (AMC-BAL) was developed and applied to two representative micro models of the AMC-BAL with two different gas capillary patterns, each combined with two proposed hepatocyte distributions. Parameter studies were performed on each configuration to gain insight in fluid flow, shear stress distribution and oxygen availability in the AMC-BAL. We assessed the function of the internal oxygenator, the effect of changes in hepatocyte oxygen consumption parameters in time and the effect of the change from an experimental to a clinical setting. In addition, different methodologies were studied to improve cellular oxygen availability, i.e. external oxygenation of culture medium, culture medium flow rate, culture gas oxygen content (pO(2)) and the number of oxygenation capillaries. Standard operating conditions did not adequately provide all hepatocytes in the AMC-BAL with sufficient oxygen to maintain O(2) consumption at minimally 90% of maximal uptake rate. Cellular oxygen availability was optimized by increasing the number of gas capillaries and pO(2) of the oxygenation gas by a factor two. Pressure drop over the AMC-BAL and maximal shear stresses were low and not considered to be harmful. This information can be used to increase cellular efficiency and may ultimately lead to a more productive AMC-BAL

implicit polynomial systems: a symbolic computation approach”

Discussion on: “Stabilizability and stability for explicit an

OUTPUT DEAD BEAT CONTROL FOR A CLASS OF PLANAR POLYNOMIAL SYSTEMS

Output dead beat control for a class of nonlinear discrete time systems, which are described by a single input-output (I-O) polynomial difference equation, is considered. The class of systems considered is restricted to systems with a two-dimensional state space description. It is assumed that the highest degree with which the present input appears in the equation is odd. Necessary and sufficient conditions for the existence of output dead beat control and for the stability of the zero output constrained dynamics are presented. We also design a minimum time output dead beat control algorithm (feedback controller) which yields stable zero dynamics, whenever this is feasible. A number of interesting phenomena are discussed and illustrated with examples

Control of large-scale irrigation networks

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Systems engineering for irrigation systems: Successes and challenges

C1 - Journal Articles RefereedIn Australia, gravity fed irrigation systems are critical infrastructure essential to agricultural production and export. By supplementing these large scale civil engineering systems with an appropriate information infrastructure, sensors, actuators and a communication network it is feasible to use systems engineering ideas to improve the exploitation of the irrigation system. This paper reports how classical ideas from system identification and control can be used to automate irrigation systems to deliver a near on-demand water supply with vastly improved overall distribution efficiency

Number Theoretic Solutions to Intercept Time Problems

We consider a number of problems concerning the overlaps or coincidences of two periodic pulse trains. We show that the first intercept time of two pulse trains started in phase is a homogeneous Diophantine approximation problem which can be solved using the convergents of the simple continued fraction (s.c.f.) expansion of the ratio of their pulse repetition intervals (PRIs). We find that the intercept time for arbitrary starting phases is an inhomogeneous Diophantine approximation problem which can be solved in a similar manner. We give a recurrence equation to determine the times at which subsequent coincidences occur. We then demonstrate how the convergents of the s.c.f. expansion can be used to determine the probability of intercept of the two pulse trains after a specified time when one or both of the initial phases are random. Finally, we discuss how the probability of intercept varies as a function of the PRIs and its dependence on the Farey points. Keywords---Pulse Train Anal..

Finding Best Simultaneous Diophantine Approximations Using Sequences Of Minimal Sets Of Lattice Points

A theory is presented for simultaneous Diophantine approximation by means of minimal sets of lattice points, defined in a certain sense. We show that successive minima can be used to find best simultaneous Diophantine approximations. We construct algorithms for producing these minima, and consequently best approximations, for lattices of the second degree and for lattices of the third degree. The latter algorithm is demonstrated with some numerical examples