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Here, we describe surface functionalized, superparamagnetic iron oxide nanocrystals (IONCs) for ultrahigh PFAS sorption and precise, low energy (magnetic) separation, considering perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). As a function of surface coating, sorption capacities described are considerably higher than previous studies using activated carbon, polymers, and unmodified metal/metal oxides, among others. In particular, positively charged polyethyleneimine (PEI) coated IONCs demonstrate extreme sorption capacities for both PFOA and PFOS due to electrostatic and hydrophobic interactions, along with high polymer grafting densities, while remaining stable in water, thus maintaining available surface area. Further, through a novel method using a quart crystal microbalance with dissipation (QCM-D), we present real-time, interfacial observations (e.g. sorption kinetics). Through this method, we explore underpinning mechanism(s) for differential PFAS (PFOA vs PFOS) sorption behavior(s), demonstrating that PFAS functional head group strongly influence molecular orientation on/at the sorbent interface. The effect of water chemistry, including pH, ionic composition of water, and natural organic matter on sorption behavior are also evaluated and along with material (treatment) demonstration via bench-scale column studies.

This study investigates cooperative inter-lighting interference cancellation (C-ILIC) in indoor multiple-input single-output (MISO) visible light communication (VLC) to overcome co-channel interference (CCI) and provide connectivity, even if there is link blockage. C-ILIC exhibits great improvement in the average bit error rate (BER) performance and the transmission capacity. VLC plays an important role in handling the increasing data traffic in indoor environments. When the transmitters simultaneously send unique data over the same frequency resources, and the receiver obtains the different signals, CCI occurs because the signals interfere with each other. C-ILIC employs cooperative transmission to forward a composite data, which consists of the high received power data and the low received power data, and ILIC to decode the high received power data and reduce CCI in the low received power data before decoding. Through computer simulations, the BER performance of C-ILIC overcomes the conventional ILIC in any position because the receiver power ratio always complies with the threshold. Despite the BER performance deteriorating in the presence of link blockage, the data connection is guaranteed when the obstruction is not severe. Therefore, C-ILIC can provide reliable communication and full connectivity within a room.

In this work, we develop and demonstrate highly stable organic-coated engineered superparamagnetic iron oxide nanoparticles (IONPs), which provide effective osmotic pressure without aggregation, reverse diffusion, or membrane blocking (by nanoparticles) for osmotically driven membrane systems, considering both forward osmosis (FO) and pressure-retarded osmosis (PRO). For this, we synthesized highly water stable, monodisperse 12 nm IONPs with a rational series of water stabilizing surface coatings, including sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG). We then compared the library of surface functionalized IONPs as draw solutes for osmotic pressure-driven membrane processes. As synthesized, surface (organic) coatings are compact, thin, and can have very similar surface charge as the membrane itself, which results in effective osmotic pressure in forward osmosis (FO) mode configuration. To increase the osmotic pressure further, on a per mass basis, we synthesized and demonstrated novel hollow IONPs with identical surface coatings. Finally, water flux was further enhanced for stable particle systems using an oscillating magnetic field, thus physically altering concentration gradients, as a function of particle magnetic properties.

Photoactive cetyltrimethylammonium bromide-oleic acid (CTAB-OA) bilayer coated iron oxide nanocrystals (IONCs) were precisely synthesized and demonstrated for photo-enhanced hexavalent chromium (Cr(VI)) treatment. For these materials, an outward facing, CTAB layer offers specific affinity for Cr(VI), while the core IONC (8 – 25 nm, as Fe3O4 single domain) surface participates in Fe(II)/Fe(III) redox cycling. Further, at the coating-particle interface, the OA layer alters material photoactive dynamics (near UV and visible light) via a ligand-to-metal charge transfer (LMCT) mechanism, significantly enhancing Cr(VI) reduction. To delineate process variables, we first quantified photo-catalytic Cr(VI) reduction rates under UVA irradiation (sunlight mimic intensities) as a function of IONC core size, which correlates with the amount of surface available ferrous ion (Fe(II)). It was observed that 25 nm CTAB functionalized IONC showed outstanding Cr(VI) sorption and photoreduction performance compared with other IONC explored and controls (i.e. TiO2 nanocrystals). We next systematically explored the photoreduction mechanism(s) through a matrix of control experiments, considering solution pH, dissolved gas (air, O2, and CO2), along with hydroxyl and superoxide radicals. Results indicate that Fe(II) (at the IONC interface) acts as the primary Cr(VI) reductant and that Fe(III) (oxidized from Fe(II)) (re)cycles via a photocatalyzed reaction. Taken together, this work presents a clear physical and mechanistic description of CTAB-OA bilayer IONCs which, when optimized, are highly effective for Cr(VI) treatment under UVA. In addition to potential broad application for other contaminant targets which are reactive with Fe(II), which are many, this work also highlights the need for precise interfacial understanding of nano composite materials towards process optimization.

Herein, we describe engineered superparamagnetic iron oxide nanoparticles (IONPs) as platform materials for enhanced uranyl (UO22+) sorption and separation processes under environmentally relevant conditions. Specifically, monodispersed 8–25 nm iron oxide (magnetite, Fe3O4) nanoparticles with tailored organic acid bilayered coatings have been systematically evaluated and optimized to bind, and thus remove, uranium from water. The combined nonhydrolytic synthesis and bilayer phase transfer material preparation methods yield highly uniform and surface tailorable IONPs, which allow for direct evaluation of the size-dependent and coating-dependent sorption capacities of IONPs. Optimized materials demonstrate ultrahigh sorption capacities (>50% by wt/wt) at pH 5.6 for 8 nm oleic acid (OA) bilayer and sodium monododecyl phosphate (SDP) surface-stabilized IONPs. Synchrotron-based X-ray absorption spectroscopy shows that iron oxide core particle size and stabilizing surface functional group(s) substantially affec...

The final design of the ITER TF, CS, CC and VS AC/DC converters has been completed to implement ITER requirements following the detailed design and refinements of the preliminary design. The number of parallel thyristors and the rating of fuses are coordinated to keep those devices within the explosion limit even under most severe fault conditions. The impedance of the converter transformer has been optimized taking into account the energization inrush current, short circuit current, reactive power consumption and the available DC voltage. To ensure system integrity, AC/DC converters are mechanically divided into transformers, AC busbars, 6-pulse bridges, DC interconnecting busbars and DC reactors, and then all subsystems are decoupled by flexible links. To provide stable real time network communication down to the converters, a one GbE link is deployed between master controllers and local controllers. IEEE 1588 is implemented to the embedded controllers for precision time synchronization. This paper describes the detailed solutions implemented in the final design for the ITER AC/DC converters with R&D results of converter prototypes.

Here, we evaluate H2 generation, via NaBH4 hydrolysis, for a rationally designed library of cobalt based metal oxide nanocrystals. Specifically, we developed highly surface active wusite cobalt oxide nanorods (wz-CoO-NRs) with varied dimensions through the thermal decomposition of cobalt oleate (Co-OL) and cobalt stearate (Co-ST) – yielding multiple ‘nail’ structures grown along (002) direction. The length of wz-CoO-NRs (from 30 to 200 nm) was controlled by the ratio of Co-OL to Co-ST, temperature ramp rate, and reaction time. Further, by adjusting oleic acid concentration (as a surfactant) and/or (other) metal co-precursors (e.g. iron oleate (Fe-OL) and nickel oleate (Ni-OL)), shape (e.g. nanorod to urchin-like, irregular cube, flower, or sphere), crystal structure(s), and composition (from wz-CoO to cubic type CoO (cu-CoO) or ferrite metal oxides (Fe3O4, CoFe2O4, and Co0.5Ni0.5Fe2O4)) were serially tuned. The library of cobalt based metal oxide nanocrystals was compared, as catalysts, for H2 generation via NaBH4 decomposition, and performance was observed to be a function of crystal length for wz-CoO-NRs. A maximum hydrogen production rate of 10,367 mL min−1 g−1 at 293 K with an activation energy of 27.4 kJ mol-1 was observed for 200 nm wz-CoO-NRs, which is among the lowest reported activation energies for this reaction. Enhanced reactivity is likely due to increased favorable surface chemistries (multiple catalytically active (002) sites on the edge of multiple nails) and lowered charge transfer energy for longer (e.g. 200 nm) wz-CoO-NRs.

Engineered, superparamagnetic, iron oxide nanoparticles (IONPs) have significant potential as platform materials for environmental sensing, imaging and remediation due to their unique size, physicochemical and magnetic properties. To this end, controlling the size and surface chemistry of the materials is crucial for such applications in the aqueous phase, and in particular, for porous matrixes with particle-surface interaction considerations. In this study, superparamagnetic, highly monodispersed 8 nm IONPs were synthesized and transferred into water as stable suspensions (remaining monodispersed) by way of an interfacial oleic acid bilayer surface. Once stabilized and characterized, particle-particle and model surface interactions (deposition and release) were quantitatively investigated and described systematically as a function of ionic strength (IS) and type with time-resolved dynamic light scattering (DLS), zeta potential, and real-time quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The critical coagulation concentration (CCC) for oleic acid bilayer coated iron oxide nanoparticles (OA-IONPs) were determined to be 710 mM for NaCl (matching DLVO predictions) and 10.6 mM for CaCl2, respectively. For all conditions tested, surface deposition kinetics showed stronger, more favorable interactions between OA-IONPs and polystyrene surfaces compared to silica, which is hypothesized to be due to increased particle-surface hydrophobic interactions (when compared to silica surfaces).

Cho, J.H., Cho, J.M., Yun, H.S., Kim, T.W., Kim, C.W., 2013. A Study of Shoreline Changes in Antarctica (Terra Nova Bay) Based on SAR Data Unlike optical imaging, Synthetic Aperture Radar imaging can produce images regardless of the weather and the time of day, which makes it a useful tool for collecting topographical data in tropical rainforests and in the North and South Poles, where traditional optical imaging is ineffective due to the rapidly changing weather. For this study, this researcher acquired SAR imagery of Terra Nova Bay, located near the South Pole, from October 8, 2011 to March 11, 2012 to observe the changes in its shoreline in summer. SAR imagery was captured once every 11th day to determine the exact time in summer when the glaciers and ice along the shore melt. The acquired stereo SAR imagery data were then processed by applying the radargrammetric method along the shoreline to reduce the speckles specific to the SAR data, and to ensure the accuracy of the coordinates and the s...

The physical and chemical factors affecting boron solute flux behavior and membrane transport mechanisms in forward osmosis (FO) have been systematically investigated. Boron solute flux behavior in FO was further compared with that in reverse osmosis (RO) by employing identical plate-and-frame cells and membranes under the same filtration conditions. The influence of draw solution pH, draw solution type, and membrane orientation on boron solute flux was examined for FO, and the effects of water flux, cross-flow velocity, feed water boron concentration, and solution pH on boron solute flux were examined for both FO and RO. Results show that reverse salt diffusion, a unique feature of FO, is a key mechanism governing boron solute flux in FO. Boron solute flux through the FO membrane was inversely proportional to the degree of reverse salt diffusion by draw solution. The higher boron rejection observed in FO compared to RO is also attributed to reverse salt diffusion in FO. It is also shown that membrane orientation in FO plays an important role, affecting boron solute flux due to different degrees of internal concentration polarization. In both FO and RO, boron solute flux increased with increasing water flux. However, the influence of water flux on boron solute flux was less significant in FO than RO. Furthermore, boron solute flux decreased with increasing feed water pH due to the conversion of the neutral boric acid to borate anions. The findings provide new insight into the mechanisms and factors controlling boron solute transport in FO. © 2012 Elsevier B.V.

Feasibility of osmotic backwashing for cleaning fouled membranes during forward osmosis (FO) process was investigated focusing on the mechanisms and factors involved. Alginate and humic acids were used as model organic foulants; and colloidal silica particles with different sizes were used as model inorganic particulate foulants. Results showed that noticeable flux recovery was achieved by osmotic backwashing through the instantaneous replacement of the draw solution with the dilute solution that has much less osmotic pressure than that of the feed solution. The switch of water flow direction through the membrane from feed-to-draw to draw-to-feed allows the effective detachment of foulants from the membrane surface. It was found that the efficiency of osmotic backwashing was affected by several factors including foulant type, membrane orientation and backwashing conditions (i.e. initial flux and duration). In addition, concentration polarization was found to play an important role in determining ...

This paper investigates occupational exposure to time-varying magnetic field generation in high-power rectifier systems. Two different kinds of high-power rectifier systems rated for 25 kA are modeled and analyzed. The performance is compared and evaluated on the basis of exposure guidelines from the International Commission on Non-Ionizing Radiation Protection (ICNIRP). In order to focus on the qualitative effect of rectifier operation, the mechanical structure of the current-carrying conductors is simplified as an infinite long busbar model and low-frequency harmonic contents up to 65 kHz are considered. A thyristor rectifier generates a significant amount of low-frequency magnetic field harmonic contents, both at the ac and dc sides of the rectifier, infringing the limit from ICNIRP. The multilevel IGCT-type rectifier has almost negligible field generation from the ac input side and smaller harmonic contents in the dc load side, complying with ICNIRP guidelines. This remarkable advantage of multilevel rectifier-IGCT type can lead to a simpler site layout design for installation and cost-effective compliance to the guidelines of occupational exposure against the magnetic field.