Implementing General Moment Equations for Parallel Closures in NIMROD

Understanding how magnetic fields impact plasma transport is essential for improving the efficiency of thermonuclear fusion power plants. To address the transport problem, both plasma fluid equations and Maxwell’s equations must be solved. To solve these equations, it is necessary to derive closure relations that allow the system to be closed. Previous closure models are useful for describing the behavior of high-collisionality plasma but are not effective at low collisionality. To obtain closure relations valid for low collisionality, the first-order drift kinetic equation must be solved. This study presents methods for numerically obtaining parallel closures for NIMROD code by deriving a system of parallel moment equations from the drift kinetic equation in an axisymmetric magnetic field. Two methods are introduced: one uses two-dimensional finite elements in the poloidal plane of a tokamak. The other is a hybrid method that reduces memory burden by using the Fourier method over the poloidal angle of the tokamak to obtain closures, and then converting them back to the finite element basis. The obtained closures show convergence with an increasing number of moments and accurately resolve the drift kinetic equation, making this approach effective for incorporating kinetic effects into fluid simulations for nuclear fusion devices

Ion Parallel Closures

Ion parallel closures are obtained for arbitrary atomic weights and charge numbers. For arbitrary collisionality, the heat flow and viscosity are expressed as kernel-weighted integrals of the temperature and flow-velocity gradients. Simple, fitted kernel functions are obtained from the 1600 parallel moment solution and the asymptotic behavior in the collisionless limit. The fitted kernel parameters are tabulated for various temperature ratios of ions to electrons. The closures can be used conveniently without solving the kinetic equation or higher order moment equations in closing ion fluid equations

Optimization of a Trachea Bioreactor Design and Cell Seeding Parameters for the Re-epithelialization of Tracheal Scaffolds: a CFD Approach

Successful re-epithelialization of de-epithelialized tracheal scaffolds remains a challenge for tracheal graft success. Currently, the lack of understanding of the bioreactor hydrodynamic environment, and its relation to cell seeding outcomes, serve as major obstacles to obtaining viable tracheal grafts. In this work, we used computational fluid dynamics to (a) re-design the fluid delivery system of a trachea bioreactor to promote a spatially uniform hydrodynamic environment, and (b) optimize the perfusion cell seeding protocol to promote a spatially uniform cell deposition. Results showed that the proposed design change achieves these design goals. Lagrangian particle-tracking simulations showed that low rotation rates provide more uniform circumferential and longitudinal patterns of cell deposition, while higher rotation rates only improve circumferential uniformity but bias cell deposition proximally. Validation experiments with BEAS-2B cells confirm that the model accurately predicts cell deposition but not cell attachment, suggesting the need for including biologically accurate cell-cell and cell-scaffold interaction mechanisms in the simulations.M.A.S

Effects of Organic Iron Supplementation on the Performance and Iron Content in the Egg Yolk of Laying Hens

An experiment was conducted to determine the efficacy of dietary iron-soy proteinate (Fe-SP) and iron-methionine chelate (Fe-Met) on the performance of laying hens and iron content in egg yolk. Eight hundred Hy-Line Brown laying hens of 68wk old were housed in 400 cages of 2 birds each. Two hundred birds (10 cages×10 replicates) were assigned to one of the following four treatments: Control; non supplementation with Fe-SP or Fe-Met, Fe-Met 100; 100ppm iron supplementation with Fe-Met, Fe-SP 100; 100ppm iron supplementation with Fe-SP, Fe-SP 200; 200ppm iron supplementation with Fe-SP. Results of 35d feeding trial showed that there were significant differences in egg production, egg weight, feed conversion ratio and Haugh unit among the treatments. Egg weight and Haugh unit of Fe-SP 200 were significantly higher than the control. Hen-day egg production and feed conversion ratio of Fe-SP 100 and Fe-SP 200 were not significantly different from those of the control. Eggshell color was significantly improved in the Fe supplementation treatments compared to the control. The iron content of egg-yolk was maximized 5wk after feeding supplemental Fe and that of Fe-SP 100 was highest being 16.6% higher than the control. There were no significant differences in iron content of egg-yolk between source and level of iron supplementation. Copper content in the egg-yolk was not significantly affected by treatments but zinc content was significantly increased in iron supplemented treatments at 5th week after feeding. In conclusion, Fe content of egg-yolk could be effectively increased by supplementing 100ppm iron as iron-soy proteinate for 5wks. No significant difference was found in Fe content of egg yolk between Fe-SP and Fe-Met

0.6 V, 116 nW Neural Spike Acquisition IC with Self-Biased Instrumentation Amplifier and Analog Spike Extraction

This paper presents an ultralow power 0.6 V 116 nW neural spike acquisition integrated circuit with analog spike extraction. To reduce power consumption, an ultralow power self-biased current-balanced instrumentation amplifier (IA) is proposed. The passive RC lowpass filter in the amplifier acts as both DC servo loop and self-bias circuit. The spike detector, based on an analog nonlinear energy operator consisting of a low-voltage open-loop differentiator and an open-loop gate-bulk input multiplier, is designed to emphasize the high frequency spike components nonlinearly. To reduce the spike detection error, the adjacent spike merger is also proposed. The proposed circuit achieves a low IA current consumption of 46.4 nA at 0.6 V, noise efficiency factor (NEF) of 1.81, the bandwidth from 102 Hz to 1.94 kHz, the input referred noise of 9.37 μVrms, and overall power consumption of 116 nW at 0.6 V. The proposed circuit can be used in the ultralow power spike pulses acquisition applications, including the neurofeedback systems on peripheral nerves with low neuron density

RF Transmitter Based on RFDAC

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