Transport and Deposition of Angular Fibers in Turbulent Channel Flows

Transport and deposition of angular fibrous particles in turbulent channel flows were studied. The instantaneous fluid velocity field was generated by the direct numerical simulation (DNS) of the Navier-Stokes equation via a pseudo-spectral method. An angular fibers was assumed to consist of two elongated ellipsoids attached at their tips. For a dilute suspension of fibers, a one-way coupling assumption was used in that the flow carries the fibers, but the coupling effect of the fiber on the flow was neglected. The particle equations of motion used included the hydrodynamic forces and torques, the shear-induced lift and the gravitational forces. The hydrodynamic interactions of the high aspect ratio linkage were assumed to be negligibly small. Euler's four parameters (quaternions) were used for describing the time evolution of fiber orientations. Ensembles of fiber trajectories and orientations in turbulent channel flows were generated and statistically analyzed. The results were compared with those for spherical particles and straight fibers and their differences were discussed. Effects of fiber size, aspect ratio, fiber angle, turbulence near wall eddies, and various forces were studied. The DNS predictions were compared with experimental data for straight fibers and a proposed empirical equation model.     

Health and safety aspects of irrigation of raw-eaten food crops with reused water

The Monterey Wastewater Reclamation Study for Agriculture (MWRSA) has Completed its first year of a five-year pilot effort to investigate and to demonstrate feasibility of food crop irrigation with reclaimed municipal effluent. The project comprises a 96-plot field trial for statistical comparison of three water treatments: an eight-hectare commercial scale farm for demonstration of water reclamation for growing lettuce, broccoli, cauliflower, celery, and artichokes; an aerosol study, a virus assay, market studies, and other ancillary investigations. First year results preliminarily indicate that the main hypothesis of the study will prove to be true, i.e. “raw-eaten food crops irrigated with properly treated municipal wastewater effluent are safe for human consumption”.     

Uplink Spectral Efficiency Analysis for a Massive MIMO Primary Network

Wireless Personal Communications - Faster development of smart electronic devices in recent years along with significant increase in demanding higher data rates has made cognitive radio networks...     

An efficient and stable method to cluster software modules using ant colony optimization algorithm

The Journal of Supercomputing - Software evolution is a natural phenomenon due to the changing requirements. Understanding the program structure is a significant and complicated factor in...     

Comparison between pulsed laser and frequency-domain photoacoustic modalities: signal-to-noise ratio, contrast, resolution, and maximum depth detectivity

In this work, a detailed theoretical and experimental comparison between various key parameters of the pulsed and frequency-domain (FD) photoacoustic (PA) imaging modalities is developed. The signal-to-noise ratios (SNRs) of these methods are theoretically calculated in terms of transducer bandwidth, PA signal generation physics, and laser pulse or chirp parameters. Large differences between maximum (peak) SNRs were predicted. However, it is shown that in practice the SNR differences are much smaller. Typical experimental SNRs were 23.2 dB and 26.1 dB for FD-PA and time-domain (TD)-PA peak responses, respectively, from a subsurface black absorber. The SNR of the pulsed PA can be significantly improved with proper high-pass filtering of the signal, which minimizes but does not eliminate baseline oscillations. On the other hand, the SNR of the FD method can be enhanced substantially by increasing laser power and decreasing chirp duration (exposure) correspondingly, so as to remain within the maximum permissible exposure guidelines. The SNR crossover chirp duration is calculated as a function of transducer bandwidth and the conditions yielding higher SNR for the FD mode are established. Furthermore, it was demonstrated that the FD axial resolution is affected by both signal amplitude and limited chirp bandwidth. The axial resolution of the pulse is, in principle, superior due to its larger bandwidth; however, the bipolar shape of the signal is a drawback in this regard. Along with the absence of baseline oscillation in cross-correlation FD-PA, the FD phase signal can be combined with the amplitude signal to yield better axial resolution than pulsed PA, and without artifacts. The contrast of both methods is compared both in depth-wise (delay-time) and fixed delay time images. It was shown that the FD method possesses higher contrast, even after contrast enhancement of the pulsed response through filtering.     

Deformation Tracking in 3D Point Clouds Via Statistical Sampling of Direct Cloud-to-Cloud Distances

Dense three-dimensional (3D) point clouds of infrastructure systems, generated from laser scanners or through multi-view photogrammetry, have significant potential as a source of nondestructive evaluation information. The growing maturity of these techniques make them capable of reconstructing photorealistic 3D models with accuracy on the millimeter scale, adequate for inspection and evaluation practices. Manual analysis of these point clouds is often time consuming and labor intensive and does not provide explicit information on structural performance and health conditions, highlighting the need for new techniques to efficiently analyze these models. This paper presents a new 3D point cloud change analysis approach for tracking small movements over time through localized spatial analytics. This technique uses a combination of a direct point-wise distance metric in conjunction with statistical sampling to extract structural deformations. By identifying and tracking these changes, mechanical deformations can be quantified along with the associated strains and stresses. These measurements can then be used to assess both service conditions and remaining system capacity. The results of a series of laboratory experiments designed to test the proposed approach are presented as well. The findings indicate measurement accuracy on the order of +/? 0.2 mm (95% confidence interval), making it suitable for accurate and automatic geometrical analyses and change detection in a variety of infrastructure inspection scenarios. Ongoing work seeks to connect this technique to automated finite element model updating, and to field test the measurement technique.