Near-wall velocity of suspended particles in microchannel flow

This contribution investigates the characteristic reduction of the particle velocity with respect to the velocity profile of a pure liquid (water) in a pressure driven flow (PDF). It is shown by simulations and experiments that particles are slowed down once their local perturbation "cloud" of the velocity field hits the wall. We show that this effect scales with the ratio of the distance of sphere's surface from the wall, a, and the radius, a, of the sphere, i.e. delta/a

Sample-centred shimming enables independent parallel NMR detection

Two major technical challenges facing parallel nuclear magnetic resonance (NMR) spectroscopy, at the onset, include the need to achieve exceptional [Formula: see text] homogeneity, and good inter-detector radiofrequency signal decoupling, and have remained as technical obstacles that limit high throughput compound screening via NMR. In this contribution, we consider a compact detector system, consisting of two NMR ‘unit cell’ resonators that implement parallel [Formula: see text] shimming with parallel radiofrequency detection, as a prototype NMR environment, pointing the way towards achieving accelerated NMR analysis. The utility of our approach is established by achieving local field correction within the bore of a 1.05T permanent magnet MRI. Our forerunner platform suppresses signal cross-coupling in the range of [Formula: see text] dB to [Formula: see text] dB, under a geometrically decoupled scheme, leading to a halving of the necessary inter-coil separation. In this permanent magnet environment, two decoupled parallel NMR detector sites simultaneously achieve narrow spectral linewidth, overcoming the spatial inhomogeneity of the magnet from 400 to 28 Hz

Numerical Thermal Analysis and 2-D CFD Evaluation Model for An Ideal Cryogenic Regenerator

Regenerative cryocoolers such as Stirling, Gifford–McMahon, and pulse tube cryocoolers possess great merits such as small size, low cost, high reliability, and good cooling capacity. These merits led them to meet many IR and superconducting based application requirements. The regenerator is a vital element in these closed-cycle cryocoolers, but the overall performance depends strongly on the effectiveness of the regenerator. This paper presents a one-dimensional numerical analysis for the idealized thermal equations of the matrix and the working gas inside the regenerator. The algorithm predicts the temperature profiles for the gas during the heating and cooling periods, along with the matrix nodal temperatures. It examines the effect of the regenerator’s length and diameter, the matrix’s geometric parameters, the number of heat transfer units, and the volumetric flow rate, on the performance of an ideal regenerator. This paper proposes a 2D axisymmetric CFD model to evaluate the ideal regenerator model and to validate its findings

A field focusing butterfly stripline detects NMR at higher signal-to-noise ratio

We present a compact tuned magnetic resonance detector that merges the conductor topology of a butterfly coil with that of a stripline, thereby increasing the magnetic field intensity per unit current, which increases the detection signal-to-noise ratio for mass-limited samples by a factor of 2. The s-parameter measurements further reveal improved radiofrequency shielding through the suppression of outside the coil when operated within an array of similar detectors. Simulations additionally show a sharper fall-off for the butterfly stripline outside the sensitive sample region. Our design is compatible with 2D planar manufacturing procedures, such as printed circuit board technology, and surface micromachining