Effect of surface modification on single-walled carbon nanotube retention and transport in saturated and unsaturated porous media

This work investigated the effect of different surface modification methods, including oxidization, surfactant coating, and humic acid coating, on single-walled carbon nanotube (SWNT) stability and their mobility in granular porous media under various conditions. Characterization and stability studies demonstrated that the three surface modification methods were all effective in solubilizing and stabilizing the SWNTs in aqueous solutions. Packed sand column experiments showed that although the three surface medication methods showed different effect on the retention and transport of SWNTs in the columns, all the modified SWNTs were highly mobile. Compared with the other two surface modification methods, the humic acid coating method introduced the highest mobility to the SWNTs. While reductions in moisture content in the porous media could promote the retention of the surface modified SWNTs in some sand columns, results from bubble column experiment suggested that only oxidized SWNTs were retention in unsaturated porous media through attachment on air–water interfaces. Other mechanisms such as grain surface attachment and thin-water film straining could also be responsible for the retention of the SWNTs in unsaturated porous media. An advection–dispersion model was successfully applied to simulate the experimental data of surface modified SWNT retention and transport in porous media

SIMBA: scalable inversion in optical tomography using deep denoising priors

Two features desired in a three-dimensional (3D) optical tomographic image reconstruction algorithm are the ability to reduce imaging artifacts and to do fast processing of large data volumes. Traditional iterative inversion algorithms are impractical in this context due to their heavy computational and memory requirements. We propose and experimentally validate a novel scalable iterative mini-batch algorithm (SIMBA) for fast and high-quality optical tomographic imaging. SIMBA enables highquality imaging by combining two complementary information sources: the physics of the imaging system characterized by its forward model and the imaging prior characterized by a denoising deep neural net. SIMBA easily scales to very large 3D tomographic datasets by processing only a small subset of measurements at each iteration. We establish the theoretical fixedpoint convergence of SIMBA under nonexpansive denoisers for convex data-fidelity terms. We validate SIMBA on both simulated and experimentally collected intensity diffraction tomography (IDT) datasets. Our results show that SIMBA can significantly reduce the computational burden of 3D image formation without sacrificing the imaging quality.https://arxiv.org/abs/1911.13241First author draf

Regularized Fourier ptychography using an online plug-and-play algorithm

The plug-and-play priors (PnP) framework has been recently shown to achieve state-of-the-art results in regularized image reconstruction by leveraging a sophisticated denoiser within an iterative algorithm. In this paper, we propose a new online PnP algorithm for Fourier ptychographic microscopy (FPM) based on the accelerated proximal gradient method (APGM). Specifically, the proposed algorithm uses only a subset of measurements, which makes it scalable to a large set of measurements. We validate the algorithm by showing that it can lead to significant performance gains on both simulated and experimental data.https://arxiv.org/abs/1811.00120Published versio

Regularized Fourier ptychography using an online plug-and-play algorithm

The plug-and-play priors (PnP) framework has been recently shown to achieve state-of-the-art results in regularized image reconstruction by leveraging a sophisticated denoiser within an iterative algorithm. In this paper, we propose a new online PnP algorithm for Fourier ptychographic microscopy (FPM) based on the accelerated proximal gradient method (APGM). Specifically, the proposed algorithm uses only a subset of measurements, which makes it scalable to a large set of measurements. We validate the algorithm by showing that it can lead to significant performance gains on both simulated and experimental data.https://arxiv.org/abs/1811.00120Published versio

Simulation Technology for Hydrodynamic and Water Quality in the Main Canal

The hydrodynamic and water quality simulation technology can be used for predicting the pollutant diffusion process after a sudden water pollution accident, and for analyzing the effect of emergency operation measures. The MRP features a long route, a variety of buildings, etc.; therefore, a set of hydrodynamic and water quality models that are applicable to the main canal of the MRP was independently developed based on 1-D open canal hydrodynamic and water quality theory and with various types of buildings as inner boundaries. Through calibration and verification, these models can be applied to the simulation of hydraulic and water quality response process under any operation conditions in the main canal of the MRP

A Portable Random Key Predistribution Scheme for Distributed Sensor Network

A distributed sensor network (DSN) can be deployed to collect information for military or civilian applications. However, due to the characteristics of DSNs such as limited power, key distribution for a distributed sensor network is complex. In this paper, a neighbor-based path key establishing method and a seed-based algorithm are put forward to improve the original random key pre-distribution scheme. The new scheme is portable because it is independent of the routing protocol. Moreover, the connectivity of the entire network also approaches 1. In particular, the new scheme can keep high connectivity by setting a small amount of redundancy in parameter values when the number of neighbors drops because of the node dormancy or death. The resilience against node capture in our scheme is not lower than that in the l-path scheme and the basic schemes when the number of hops in a path is larger than 5, and the simulation result shows that the efficiency of our scheme is also slightly higher

Transport of titanium dioxide nanoparticles in saturated porous media under various solution chemistry conditions

Because of its wide applications, nanosized titanium dioxide may become a potential environmental risk to soil and groundwater system. It is therefore important to improve current understanding of the environmental fate and transport of titanium oxides nanoparticles (TONPs). In this work, the effect of solution chemistry (i.e., pH, ionic strength, and natural organic matter (NOM) concentration) on the deposition and transport of TONPs in saturated porous media was examined in detail. Laboratory columns packed with acid-cleaned quartz sand were used in the experiment as porous media. Transport experiments were conducted with various chemistry combinations, including four ionic strengths, three pH levels, and two NOM concentrations. The results showed that TONP mobility increased with increasing solution pH, but decreased with increasing solution ionic strength. It is also found that the presence of NOM in the system enhanced the mobility of TONPs in the saturated porous media. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to justify the mobility trends observed in the experimental data. Predictions from the theory agreed excellently with the experimental data

Sustained visual attention is more than seeing

Sustained visual attention is a well-studied cognitive capacity that is relevant to many developmental outcomes. The development of visual attention is often construed as an increased capacity to exert top-down internal control. We demonstrate that sustained visual attention, measured in terms of momentary eye gaze, emerges from and is tightly tied to sensory-motor coordination. Specifically, we examined whether and how changes in manual behavior alter toddlers’ eye gaze during toy play. We manipulated manual behavior by giving one group of children heavy toys that were hard to pick up and giving another group of children perceptually identical toys that were lighter and easy to pick up and hold. We found a tight temporal coupling of visual attention with the duration of manual activities on the objects, a relation that cannot be explained by interest alone. Toddlers in the heavy-object condition looked at objects as much as toddlers in the light-object condition but did so through many brief glances, whereas looks to the same objects were longer and sustained in the light-object condition. We explain the results based on the mechanism of hand–eye coordination and discuss its implications for the development of visual attention